2022 Vol. 39, No. 5
2022, 39(5): 1847-1858.
doi: 10.13801/j.cnki.fhclxb.20220302.001
Abstract:
Solar energy is a clean and pollution-free renewable energy, and its efficient development and utilization can significantly promote national “dual carbon” work. Using photovoltaic cells to convert solar energy into electricity is one of the ways to use solar energy. In this review, the research progress, industry policies, business models and development and application prospects of photovoltaic cell materials were summarized. First of all, the efficiency, cost, advantages and disadvantages of various photovoltaic cells and the impact of material factors on application scenarios were clarified, and combined with the latest research progress, the future development direction of various photovoltaic cells was analyzed. Secondly, combined with the business model and supporting policies of the photovoltaic industry, the influence of policy driving mechanisms on the development of photovoltaic cell materials and industry was discussed. Finally, based on the research progress of photovoltaic cell materials and the development direction of the photovoltaic industry, this field was summarized and prospected. The way that photovoltaic industry contributes to the national "dual carbon" work under the "dual carbon" vision was analyzed.
Solar energy is a clean and pollution-free renewable energy, and its efficient development and utilization can significantly promote national “dual carbon” work. Using photovoltaic cells to convert solar energy into electricity is one of the ways to use solar energy. In this review, the research progress, industry policies, business models and development and application prospects of photovoltaic cell materials were summarized. First of all, the efficiency, cost, advantages and disadvantages of various photovoltaic cells and the impact of material factors on application scenarios were clarified, and combined with the latest research progress, the future development direction of various photovoltaic cells was analyzed. Secondly, combined with the business model and supporting policies of the photovoltaic industry, the influence of policy driving mechanisms on the development of photovoltaic cell materials and industry was discussed. Finally, based on the research progress of photovoltaic cell materials and the development direction of the photovoltaic industry, this field was summarized and prospected. The way that photovoltaic industry contributes to the national "dual carbon" work under the "dual carbon" vision was analyzed.
2022, 39(5): 1859-1869.
doi: 10.13801/j.cnki.fhclxb.20220120.003
Abstract:
In recent years, cesium based inorganic perovskites (CsPbX3) are of great interest due to their high thermal resistance, low cost and tunable bandgap, which have been used as absorbers to for the development of novel thin-film solar cells. Currently, the photovoltaic performance of inverted perovskite solar cells (PSC) still leg behind that of regular solar cells, though the inverted solar cells are more stable and more promising as top layer of tandem solar cells. Therefore, the device structure of inverted solar cell remains to be further optimized. To approach this aim, researchers have developed a series of organic and inorganic interfacial layers, including hole-transport-layer and electron-transport-layer, with the aim of optimizing the inverted inorganic perovskite solar cells. Herein, we address the recent progress of organic and inorganic interfacial layers from the perspective of materials and processing techniques. A variety of material systems are compared to summarize their features. This work also discuss their bottlenecks and try to provide potential solutions for achieving ideal interfacial layers.
In recent years, cesium based inorganic perovskites (CsPbX3) are of great interest due to their high thermal resistance, low cost and tunable bandgap, which have been used as absorbers to for the development of novel thin-film solar cells. Currently, the photovoltaic performance of inverted perovskite solar cells (PSC) still leg behind that of regular solar cells, though the inverted solar cells are more stable and more promising as top layer of tandem solar cells. Therefore, the device structure of inverted solar cell remains to be further optimized. To approach this aim, researchers have developed a series of organic and inorganic interfacial layers, including hole-transport-layer and electron-transport-layer, with the aim of optimizing the inverted inorganic perovskite solar cells. Herein, we address the recent progress of organic and inorganic interfacial layers from the perspective of materials and processing techniques. A variety of material systems are compared to summarize their features. This work also discuss their bottlenecks and try to provide potential solutions for achieving ideal interfacial layers.
2022, 39(5): 1870-1889.
doi: 10.13801/j.cnki.fhclxb.20220422.002
Abstract:
New-generation solar cells, including organic solar cells, perovskite solar cells and quantum dot solar cells, are pretty promising photovoltaic devices. At present, the energy conversion efficiency of organic solar cells and perovskite solar cells exceeds 19% and 25.6% respectively. Fullerenes are widely used in organic solar cells active layer and interface layer, perovskite solar cells active layer and intermediate layer due to their high electron mobility and good electronic properties. In organic solar cells, fullerenes act as the active layer receptors to improve the electron transport capacity of devices. As an interface modification layer, it can effectively reduce the contact resistance and inhibit the recombination of carriers. In perovskite solar cells, fullerene materials act as active layer additive to passivate perovskite defect and restrain hysteresis effect. As an intermediate layer, the interface morphology can be optimized and charge extraction and transport can be promoted. In this paper, the research progress of fullerene materials in each component is reviewed, and the development prospect of fullerene materials in each component is prospected, and the future research direction is proposed.
New-generation solar cells, including organic solar cells, perovskite solar cells and quantum dot solar cells, are pretty promising photovoltaic devices. At present, the energy conversion efficiency of organic solar cells and perovskite solar cells exceeds 19% and 25.6% respectively. Fullerenes are widely used in organic solar cells active layer and interface layer, perovskite solar cells active layer and intermediate layer due to their high electron mobility and good electronic properties. In organic solar cells, fullerenes act as the active layer receptors to improve the electron transport capacity of devices. As an interface modification layer, it can effectively reduce the contact resistance and inhibit the recombination of carriers. In perovskite solar cells, fullerene materials act as active layer additive to passivate perovskite defect and restrain hysteresis effect. As an intermediate layer, the interface morphology can be optimized and charge extraction and transport can be promoted. In this paper, the research progress of fullerene materials in each component is reviewed, and the development prospect of fullerene materials in each component is prospected, and the future research direction is proposed.
2022, 39(5): 1890-1906.
doi: 10.13801/j.cnki.fhclxb.20211118.001
Abstract:
To achieve green and sustainable development, reducing CO2 emissions, it is deemed necessary to continue to promote and develop clean energy technologies, such as photovoltaics solar cell technology. Among of photovoltaic technologies, the organic-inorganic hybrid perovskite solar cells have the characteristics of low-cost, light weight, and simple manufacturing, which are more suitable for the requirements of future development. Perovskite materials are direct bandgap semiconductors with adjustable bandgap, which have lower exciton binding energy, longer carrier lifetime and diffusion length, and higher defect tolerance. The current maximum efficiency has exceeded 25%. However, the inherent instability of the material and sensitivity to environmental factors, such as water, heat, oxygen, and ultraviolet light, have become the primary problems limiting its further development. Recently, two-dimensional (2D) halide perovskite has attracted the attention of researchers around the world due to its ultra-high humidity stability. However, the efficiency of two-dimensional halide perovskite cells is still far behind that of traditional three-dimensional halide perovskite cells. Therefore, improving the efficiency of solar cells while maintaining excellent stability is a key problem in the research of 2D perovskite solar cells. In this paper, we mainly focus on the 2D halide perovskite film preparation and device structure, as well as efficiency and stability, and other issues to provide guidance for the development of efficient and stable 2D halide perovskite solar cells.
To achieve green and sustainable development, reducing CO2 emissions, it is deemed necessary to continue to promote and develop clean energy technologies, such as photovoltaics solar cell technology. Among of photovoltaic technologies, the organic-inorganic hybrid perovskite solar cells have the characteristics of low-cost, light weight, and simple manufacturing, which are more suitable for the requirements of future development. Perovskite materials are direct bandgap semiconductors with adjustable bandgap, which have lower exciton binding energy, longer carrier lifetime and diffusion length, and higher defect tolerance. The current maximum efficiency has exceeded 25%. However, the inherent instability of the material and sensitivity to environmental factors, such as water, heat, oxygen, and ultraviolet light, have become the primary problems limiting its further development. Recently, two-dimensional (2D) halide perovskite has attracted the attention of researchers around the world due to its ultra-high humidity stability. However, the efficiency of two-dimensional halide perovskite cells is still far behind that of traditional three-dimensional halide perovskite cells. Therefore, improving the efficiency of solar cells while maintaining excellent stability is a key problem in the research of 2D perovskite solar cells. In this paper, we mainly focus on the 2D halide perovskite film preparation and device structure, as well as efficiency and stability, and other issues to provide guidance for the development of efficient and stable 2D halide perovskite solar cells.
2022, 39(5): 1907-1923.
doi: 10.13801/j.cnki.fhclxb.20210609.002
Abstract:
Integrating sustainable cellulose materials into electronic devices is a hot research topic in academic communities. Highly transparent cellulose film with high transmission haze is a kind of paper with special optical properties. In addition to the advantages (degradability, low cost, flexibility, light weight, etc.) of ordinary paper, it also presents high transparency and strong light scattering behavior (high transmission haze), and has the potential to use in solar cells as a green optical transparent material to improve the power conversion efficiency. In this review, the development process of highly hazy and transparent cellulose film was first introduced. Then, the preparation and properties (such as optical properties, mechanical properties, thermal stability and water resistance) of highly transparent and hazy cellulose films were summarized in detail. After that, the progress in the use of transparent and hazy cellulose film in solar cells was discussed. Finally, scientific and technical problems of highly transparent and hazy cellulose films for solar cells were summarized, and their challenges and future research direction were provided as well.
Integrating sustainable cellulose materials into electronic devices is a hot research topic in academic communities. Highly transparent cellulose film with high transmission haze is a kind of paper with special optical properties. In addition to the advantages (degradability, low cost, flexibility, light weight, etc.) of ordinary paper, it also presents high transparency and strong light scattering behavior (high transmission haze), and has the potential to use in solar cells as a green optical transparent material to improve the power conversion efficiency. In this review, the development process of highly hazy and transparent cellulose film was first introduced. Then, the preparation and properties (such as optical properties, mechanical properties, thermal stability and water resistance) of highly transparent and hazy cellulose films were summarized in detail. After that, the progress in the use of transparent and hazy cellulose film in solar cells was discussed. Finally, scientific and technical problems of highly transparent and hazy cellulose films for solar cells were summarized, and their challenges and future research direction were provided as well.
2022, 39(5): 1924-1936.
doi: 10.13801/j.cnki.fhclxb.20211215.001
Abstract:
Recent years, perovskite solar cells have been developing rapidly because of the high efficiency, ease of preparation and low cost. To the preparation and optimization of multilayer structures for perovskite devices, researchers always pay most attention on the perovskite light absorber and charge-transporting layers. While in the case of the top electrode, evaporated Au electrodes can work well as a standard method at the current laboratory stage. Therefore, the top electrode issue is easily overlooked by researchers. However, the high cost of equipments and raw materials for evaporated precious metal electrodes will not be ignored in the large-area devices manufacturing and large-scale applications of perovskite solar cells. Several non-evaporation processes such as conductive film transferring or conductive paste coating have been developed to solve these problems. Herein, we addresses the current progress of transfer methods top electrodes from the perspective of process techniques. A variety of material systems including metals, polymers and carbon are compared to summarize some general principles. Also, the shortcomings of the transfer method, and bottlenecks of materials and potential solutions for ideal transfer electrodes are discussed.
Recent years, perovskite solar cells have been developing rapidly because of the high efficiency, ease of preparation and low cost. To the preparation and optimization of multilayer structures for perovskite devices, researchers always pay most attention on the perovskite light absorber and charge-transporting layers. While in the case of the top electrode, evaporated Au electrodes can work well as a standard method at the current laboratory stage. Therefore, the top electrode issue is easily overlooked by researchers. However, the high cost of equipments and raw materials for evaporated precious metal electrodes will not be ignored in the large-area devices manufacturing and large-scale applications of perovskite solar cells. Several non-evaporation processes such as conductive film transferring or conductive paste coating have been developed to solve these problems. Herein, we addresses the current progress of transfer methods top electrodes from the perspective of process techniques. A variety of material systems including metals, polymers and carbon are compared to summarize some general principles. Also, the shortcomings of the transfer method, and bottlenecks of materials and potential solutions for ideal transfer electrodes are discussed.
2022, 39(5): 1937-1955.
doi: 10.13801/j.cnki.fhclxb.20220303.001
Abstract:
Lead halide perovskite solar cells have attracted extensive attention on account of their excellent photoelectric conversion efficiency and relatively low fabrication cost. However, the poor long-term stability becomes a barrier that hinders the commercialization of lead halide perovskite solar cells. It is reported that interfacial non-radiative recombination in lead halide perovskite solar cells is the main cause that leads to energy loss, affects device stability and then deteriorates the device performance. To solve this issue, interface engineering is applied as a valid strategy to suppress interfacial non-radiative recombination and fabricate efficient and stable lead halide perovskite solar cells, achieving tangible results. In this review, the working principle of lead halide perovskite solar cells and interfacial non-radiactive recombination process are explained in detail. The origin of interfacial non-radiative recombination is also analyzed, which highlights the important role of interface engineering for lead halide perovskite solar cells. Meanwhile, the recent research advances of interface engineering in lead halide perovskite solar cells with normal n-i-p structure are summarized with the discussion of the modification mechanism. What’s more, based on the development status of the interface engineering in lead halide perovskite solar cells, we prospect the development directions for the interface engineering in lead halide perovskite solar cells in the future.
Lead halide perovskite solar cells have attracted extensive attention on account of their excellent photoelectric conversion efficiency and relatively low fabrication cost. However, the poor long-term stability becomes a barrier that hinders the commercialization of lead halide perovskite solar cells. It is reported that interfacial non-radiative recombination in lead halide perovskite solar cells is the main cause that leads to energy loss, affects device stability and then deteriorates the device performance. To solve this issue, interface engineering is applied as a valid strategy to suppress interfacial non-radiative recombination and fabricate efficient and stable lead halide perovskite solar cells, achieving tangible results. In this review, the working principle of lead halide perovskite solar cells and interfacial non-radiactive recombination process are explained in detail. The origin of interfacial non-radiative recombination is also analyzed, which highlights the important role of interface engineering for lead halide perovskite solar cells. Meanwhile, the recent research advances of interface engineering in lead halide perovskite solar cells with normal n-i-p structure are summarized with the discussion of the modification mechanism. What’s more, based on the development status of the interface engineering in lead halide perovskite solar cells, we prospect the development directions for the interface engineering in lead halide perovskite solar cells in the future.
2022, 39(5): 1956-1966.
doi: 10.13801/j.cnki.fhclxb.20211209.001
Abstract:
The preparation of porous carbon materials by high-temperature pyrolysis/activation of biomass under the protection of inert gas has the advantages of low cost, simple process, etc., and is an effective way to use waste and reduce environmental pollution. In this study, three different biomass materials were prepared by high-tempe-rature pyrolysis/activation to prepare porous carbon materials, which were combined with commercially conduc-tive carbon paste to make composite carbon paste and applied to the counter electrodes of perovskite solar cells (PSCs). The morphology, structure and specific surface area of different biomass porous carbon materials affect the photoelectric performance of the device. The results show that the photoelectric performance of PSCs based on different biomass porous carbon materials depends on the morphology, crystallinity, specific surface area and morphology of the biomass porous carbon materials and the interface contact between the perovskite/carbon electrode. The carbon-based PSCs prepared by the composite carbon electrode based on biomass porous carbon combined with the grinding process can obtain the highest photoelectric conversion efficiency (PCE) of 10.18% due to its good interface performance (the PCE of the PSCs without composite biomass carbon is 6.39%). After the best device is stored in air conditions for 60 days, 96% of the initial PCE was still retained.
The preparation of porous carbon materials by high-temperature pyrolysis/activation of biomass under the protection of inert gas has the advantages of low cost, simple process, etc., and is an effective way to use waste and reduce environmental pollution. In this study, three different biomass materials were prepared by high-tempe-rature pyrolysis/activation to prepare porous carbon materials, which were combined with commercially conduc-tive carbon paste to make composite carbon paste and applied to the counter electrodes of perovskite solar cells (PSCs). The morphology, structure and specific surface area of different biomass porous carbon materials affect the photoelectric performance of the device. The results show that the photoelectric performance of PSCs based on different biomass porous carbon materials depends on the morphology, crystallinity, specific surface area and morphology of the biomass porous carbon materials and the interface contact between the perovskite/carbon electrode. The carbon-based PSCs prepared by the composite carbon electrode based on biomass porous carbon combined with the grinding process can obtain the highest photoelectric conversion efficiency (PCE) of 10.18% due to its good interface performance (the PCE of the PSCs without composite biomass carbon is 6.39%). After the best device is stored in air conditions for 60 days, 96% of the initial PCE was still retained.
2022, 39(5): 1967-1975.
doi: 10.13801/j.cnki.fhclxb.20210426.001
Abstract:
Functional inorganic material nickel oxide (NiOx) as one of the most promising hole transport materials in perovskite solar cells, it has the advantages of high hole mobility, good stability, easy processing and suitable Fermi level. However, due to the inherent low conductivity of NiOx itself, the ionization energy of Ni vacancies is quite large, and the hole density in undoped NiOx is greatly restricted. In addition, the accumulation of holes increases the possibility of carrier recombination, thereby reducing the effective charge collection. Therefore, opti-mizing the quality of NiOx film formation is the key to solving the above problems. In this paper, DME-NiOx, EA-NiOx and NCs-NiOx films were prepared by solution method using ethylene glycol methyl ether (MEA), ethanol (EA) and deionized water as solutions. And optimized the NiOx-based perovskite device within the concentration adjustment range. In the end, the best device with a photoelectric conversion efficiency (PCE) of 18.50%, an open circuit voltage (Voc) of 1.034 V, a short circuit current (Jsc) of 22.94 mA/cm2 and a fill factor (FF) of 78% is obtained.
Functional inorganic material nickel oxide (NiOx) as one of the most promising hole transport materials in perovskite solar cells, it has the advantages of high hole mobility, good stability, easy processing and suitable Fermi level. However, due to the inherent low conductivity of NiOx itself, the ionization energy of Ni vacancies is quite large, and the hole density in undoped NiOx is greatly restricted. In addition, the accumulation of holes increases the possibility of carrier recombination, thereby reducing the effective charge collection. Therefore, opti-mizing the quality of NiOx film formation is the key to solving the above problems. In this paper, DME-NiOx, EA-NiOx and NCs-NiOx films were prepared by solution method using ethylene glycol methyl ether (MEA), ethanol (EA) and deionized water as solutions. And optimized the NiOx-based perovskite device within the concentration adjustment range. In the end, the best device with a photoelectric conversion efficiency (PCE) of 18.50%, an open circuit voltage (Voc) of 1.034 V, a short circuit current (Jsc) of 22.94 mA/cm2 and a fill factor (FF) of 78% is obtained.
2022, 39(5): 1976-1985.
doi: 10.13801/j.cnki.fhclxb.20220428.001
Abstract:
The preparation of large-area organic solar cells through coating or printing is the key to realizing the industrialization of organic photovoltaics. In the organic solar cells, ZnO is a commonly used material as an electron transporting layer. However, the self-aggregation of ZnO nanoparticles and the uneven drying of films during printing cause large numbers of defects and poor uniformity in large-area films, which seriously affects the perfor-mance of large-area printed organic photovoltaic devices. In this work, a ZnO nanoink suitable for large-area slot-die coating was developed by regulating solvent and introducing an ink dispersion stabilizer. The rheological pro-perties of ZnO nanoink were regulated by using a mixed solvent, which solved the issue of edge effect in the coated film. The introduction of ethanolamine additives solves the problem of ink aggregation during storage and printing, allowing the ink to maintain long-term stability during 18 months of storage. With this nanoink, large-area films with a size of 100×100 mm2 were obtained by slot-die coating. Such a film shows excellent film uniformity. Using the printed large-area ZnO films as electron transporting layer, an efficiency of higher than 14% is obtained for 1 cm2 flexible organic solar cells.
The preparation of large-area organic solar cells through coating or printing is the key to realizing the industrialization of organic photovoltaics. In the organic solar cells, ZnO is a commonly used material as an electron transporting layer. However, the self-aggregation of ZnO nanoparticles and the uneven drying of films during printing cause large numbers of defects and poor uniformity in large-area films, which seriously affects the perfor-mance of large-area printed organic photovoltaic devices. In this work, a ZnO nanoink suitable for large-area slot-die coating was developed by regulating solvent and introducing an ink dispersion stabilizer. The rheological pro-perties of ZnO nanoink were regulated by using a mixed solvent, which solved the issue of edge effect in the coated film. The introduction of ethanolamine additives solves the problem of ink aggregation during storage and printing, allowing the ink to maintain long-term stability during 18 months of storage. With this nanoink, large-area films with a size of 100×100 mm2 were obtained by slot-die coating. Such a film shows excellent film uniformity. Using the printed large-area ZnO films as electron transporting layer, an efficiency of higher than 14% is obtained for 1 cm2 flexible organic solar cells.
2022, 39(5): 1986-1994.
doi: 10.13801/j.cnki.fhclxb.20220222.001
Abstract:
The morphology of the active layer has an important influence on the device efficiency of organic solar cells. Tuning the molecular orientation in the active layer is one of the ways to optimize its morphology. This paper aims to use a Layer-by-Layer (LbL) method to regulate the orientation of molecules in the active layer of organic solar cells, thereby improving the efficiency of cell devices. By adding different additives to the electron acceptor, the orientation of acceptor molecule (Y6) in the active layer is adjusted, and the energy conversion efficiency of the optimized device reaches 16.2%. The active layer films were characterized by ellipsometry and grazing incidence wide-angle X-ray scattering (GIWAXS). The results show that after adding 1,8-diiooctane (DIO) as an additive to the receptor, Y6 molecules in the active layer tend to be horizontally oriented, and after adding chloronaphthalene (CN) as an additive to the receptor, Y6 molecules tend to be vertically oriented. The electrical and optical characterization results show that the horizontal orientation of Y6 increases the exciton separation efficiency, and then improves the energy conversion efficiency of the device.
The morphology of the active layer has an important influence on the device efficiency of organic solar cells. Tuning the molecular orientation in the active layer is one of the ways to optimize its morphology. This paper aims to use a Layer-by-Layer (LbL) method to regulate the orientation of molecules in the active layer of organic solar cells, thereby improving the efficiency of cell devices. By adding different additives to the electron acceptor, the orientation of acceptor molecule (Y6) in the active layer is adjusted, and the energy conversion efficiency of the optimized device reaches 16.2%. The active layer films were characterized by ellipsometry and grazing incidence wide-angle X-ray scattering (GIWAXS). The results show that after adding 1,8-diiooctane (DIO) as an additive to the receptor, Y6 molecules in the active layer tend to be horizontally oriented, and after adding chloronaphthalene (CN) as an additive to the receptor, Y6 molecules tend to be vertically oriented. The electrical and optical characterization results show that the horizontal orientation of Y6 increases the exciton separation efficiency, and then improves the energy conversion efficiency of the device.
2022, 39(5): 1995-2013.
doi: 10.13801/j.cnki.fhclxb.20210922.001
Abstract:
The nickel-rich lithium transition metal oxide cathode is an ideal high-energy power battery material due to its high capacity and high working voltage. Its performance is mainly affected by the structure, morphology, particle size and other factors of its hydroxide precursor. The spherical hydroxide precursor with controllable morphology and size of primary grain and secondary particles is the key for the preparation of nickel-rich cathode materials with excellent electrochemical performance. During the precipitation and crystallization process of hydroxide precursor, the process parameters will affect the performance of the precursor, and its growth mecha-nism has guiding significance for regulating the precipitation and crystallization. This paper reviews the basic theories related to precipitation crystallization, then discusses the growth mechanism of precipitation crystallization for hydroxide precursors of nickel-rich cathode materials and the influence of precipitation reaction factors on the physical and chemical properties of hydroxide. At last, the precursors for the synthesis of nickel-rich cathode materials with special structures such as single crystal, radial and core-shell structures are introduced.
The nickel-rich lithium transition metal oxide cathode is an ideal high-energy power battery material due to its high capacity and high working voltage. Its performance is mainly affected by the structure, morphology, particle size and other factors of its hydroxide precursor. The spherical hydroxide precursor with controllable morphology and size of primary grain and secondary particles is the key for the preparation of nickel-rich cathode materials with excellent electrochemical performance. During the precipitation and crystallization process of hydroxide precursor, the process parameters will affect the performance of the precursor, and its growth mecha-nism has guiding significance for regulating the precipitation and crystallization. This paper reviews the basic theories related to precipitation crystallization, then discusses the growth mechanism of precipitation crystallization for hydroxide precursors of nickel-rich cathode materials and the influence of precipitation reaction factors on the physical and chemical properties of hydroxide. At last, the precursors for the synthesis of nickel-rich cathode materials with special structures such as single crystal, radial and core-shell structures are introduced.
Research and discussion on processing technology of carbon fiber reinforced carbon matrix composites
2022, 39(5): 2014-2033.
doi: 10.13801/j.cnki.fhclxb.20211106.001
Abstract:
Carbon fiber reinforced carbon matrix composites (C/C) have the characteristics of low thermal expansion coefficient, corrosion resistance, thermal shock resistance, and wear resistance, which are widely used in military equipment, aerospace, automobile manufacturing and other fields. But it is difficult to achieve high precision machining of C/C composites by traditional processing technology. Laser processing technology has low requirements for the size, material and shape. It is easy to combine with other advanced processing technologies and has the characteristics that other methods do not have. This paper mainly reviews the preparation, application and processing methods of C/C composites, elaborates the mechanism and process characteristics of laser processing of C/C composites and the selection strategy of processing technology in different applications. Through the comparison of traditional processing methods and special processing methods, the problems and challenges faced by the processing of C/C composites are summarized, and the development trend of the combination of laser processing of C/C composites and other advanced manufacturing technologies is proposed.
Carbon fiber reinforced carbon matrix composites (C/C) have the characteristics of low thermal expansion coefficient, corrosion resistance, thermal shock resistance, and wear resistance, which are widely used in military equipment, aerospace, automobile manufacturing and other fields. But it is difficult to achieve high precision machining of C/C composites by traditional processing technology. Laser processing technology has low requirements for the size, material and shape. It is easy to combine with other advanced processing technologies and has the characteristics that other methods do not have. This paper mainly reviews the preparation, application and processing methods of C/C composites, elaborates the mechanism and process characteristics of laser processing of C/C composites and the selection strategy of processing technology in different applications. Through the comparison of traditional processing methods and special processing methods, the problems and challenges faced by the processing of C/C composites are summarized, and the development trend of the combination of laser processing of C/C composites and other advanced manufacturing technologies is proposed.
2022, 39(5): 2034-2048.
doi: 10.13801/j.cnki.fhclxb.20210824.001
Abstract:
The rapid development of modern industry has caused a large number of refractory organic pollutants to enter the water body, there is an urgent need for economic and efficient pollution control and reduction technologies for refractory organic pollutants. In recent years, advanced oxidation technologies (SR-AOPs) based on sulfate radicals (SO4•–) have attracted much attention because of their strong oxidizing properties, wide pH tolerance, and ease of operation. Different types of metal oxygen/sulfide, carbon-based materials, metal-non-metal composite materials and organic metal materials are used to activate persulfate to generate active oxygen, thereby achieving oxidative degradation and further mineralization of organic pollutants. Among them, layered double hydroxides (LDHs) show excellent reactivity and catalytic advantages in activating persulfate due to their unique layered structure advantages, anion exchangeability and guest molecule adjustability. This article reviews the current research status of LDHs and their composites as heterogeneous catalysts to activate persulfate from the aspects of catalyst type, catalytic performance and mechanism, and degradation system influencing factors, and proposes relevant prospects for the continuous improvement of the catalytic system and future development.
The rapid development of modern industry has caused a large number of refractory organic pollutants to enter the water body, there is an urgent need for economic and efficient pollution control and reduction technologies for refractory organic pollutants. In recent years, advanced oxidation technologies (SR-AOPs) based on sulfate radicals (SO4•–) have attracted much attention because of their strong oxidizing properties, wide pH tolerance, and ease of operation. Different types of metal oxygen/sulfide, carbon-based materials, metal-non-metal composite materials and organic metal materials are used to activate persulfate to generate active oxygen, thereby achieving oxidative degradation and further mineralization of organic pollutants. Among them, layered double hydroxides (LDHs) show excellent reactivity and catalytic advantages in activating persulfate due to their unique layered structure advantages, anion exchangeability and guest molecule adjustability. This article reviews the current research status of LDHs and their composites as heterogeneous catalysts to activate persulfate from the aspects of catalyst type, catalytic performance and mechanism, and degradation system influencing factors, and proposes relevant prospects for the continuous improvement of the catalytic system and future development.
2022, 39(5): 2049-2059.
doi: 10.13801/j.cnki.fhclxb.20211009.001
Abstract:
Two-dimensional nanomaterials are the best choice for anticorrosive coatings because of their lamellar structure, dense hexagonal lattice, large specific surface area and excellent thermochemical stability. In this paper, the applications of two-dimensional nanomaterials in corrosion protection composite coatings are reviewed. The barrier protection, inhibition protection and sacrifice protection of two-dimensional nanomaterials in epoxy resin anticorrosive coatings are introduced firstly, and then the application ways and methods of common two-dimensional nanomaterials in epoxy resin anticorrosive coatings are expounded. In addition, the problems of dispersion, orientation and adhesion to metal substrate in the application of two-dimensional nanomaterials in anticorrosive coatings and their solutions are also summarized. Finally, the application of two-dimensional nanomaterials in epoxy anticorrosive coatings is summarized and prospected.
Two-dimensional nanomaterials are the best choice for anticorrosive coatings because of their lamellar structure, dense hexagonal lattice, large specific surface area and excellent thermochemical stability. In this paper, the applications of two-dimensional nanomaterials in corrosion protection composite coatings are reviewed. The barrier protection, inhibition protection and sacrifice protection of two-dimensional nanomaterials in epoxy resin anticorrosive coatings are introduced firstly, and then the application ways and methods of common two-dimensional nanomaterials in epoxy resin anticorrosive coatings are expounded. In addition, the problems of dispersion, orientation and adhesion to metal substrate in the application of two-dimensional nanomaterials in anticorrosive coatings and their solutions are also summarized. Finally, the application of two-dimensional nanomaterials in epoxy anticorrosive coatings is summarized and prospected.
2022, 39(5): 2060-2072.
doi: 10.13801/j.cnki.fhclxb.20210901.001
Abstract:
Difficulty in prompting heat dissipation has emerged as a critical issue and technical bottleneck restricting further miniaturization of microelectronic devices and electrical insulation equipment. Traditional heat conductive epoxy composites are not qualified for meeting the heat dissipation requirements of high-power, ultra-high-frequency and high-voltage insulating packaging because the thermal conductivity (k) and dielectric strength (Eb) cannot be regulated and improved synergistically. Intrinsically thermal conductive epoxy (ITCE), whose k can be enhanced by regulating ordered structure of cross-linked network containing liquid crystal epoxy (LCE) units, simultaneously exhibits high k and Eb. This paper analyzes the microstructure and intrinsic heat conduction mecha-nism of LCE, and summarizes the latest research progress in ITCE based on different LCE structures. The present work systematically analyzes the influencing factors on k of ITCE, such as structures of LCE and curing agent, temperature, LCE content, grain size, and external field-assisted processing, and expounds the way to improve the ordered structure of LCE and the intrinsic k. Finally, it summarizes the existing problems in current ITCE research and points to the future development direction. ITCE with excellent comprehensive performances represents the future development direction of ITCE, and the ITCE based composites has significant potential applications in high-density packaging microelectronics, high-voltage and high-power power equipment.
Difficulty in prompting heat dissipation has emerged as a critical issue and technical bottleneck restricting further miniaturization of microelectronic devices and electrical insulation equipment. Traditional heat conductive epoxy composites are not qualified for meeting the heat dissipation requirements of high-power, ultra-high-frequency and high-voltage insulating packaging because the thermal conductivity (k) and dielectric strength (Eb) cannot be regulated and improved synergistically. Intrinsically thermal conductive epoxy (ITCE), whose k can be enhanced by regulating ordered structure of cross-linked network containing liquid crystal epoxy (LCE) units, simultaneously exhibits high k and Eb. This paper analyzes the microstructure and intrinsic heat conduction mecha-nism of LCE, and summarizes the latest research progress in ITCE based on different LCE structures. The present work systematically analyzes the influencing factors on k of ITCE, such as structures of LCE and curing agent, temperature, LCE content, grain size, and external field-assisted processing, and expounds the way to improve the ordered structure of LCE and the intrinsic k. Finally, it summarizes the existing problems in current ITCE research and points to the future development direction. ITCE with excellent comprehensive performances represents the future development direction of ITCE, and the ITCE based composites has significant potential applications in high-density packaging microelectronics, high-voltage and high-power power equipment.
2022, 39(5): 2073-2088.
doi: 10.13801/j.cnki.fhclxb.20211011.001
Abstract:
The increasingly serious energy exhaustion and environmental pollution accelerates the development of clean hydrogen energy. Water splitting via photocatalysis technology provides an economical and clean way for the hydrogen production, converting solar energy into chemical energy through photocatalytic means is also a promising technical means. The rational selection of photocatalyst is the critical step for obtaining hydrogen energy in an efficient and economical way. Featuring the traits of large specific surface area, adjustable pore size, easy structure modification and abundant active sites, metal-organic frameworks (MOFs) are ideal candidates for photocatalytic hydrogen production scientists from domestic and foreign have carried out numerous researches on the water splitting with MOF-based photocatalysts. Currently, fruitful progresses have been achieved. In this paper, the state-of-the-art advances for the MOF-based materials as catalysts in the field of hydrogen production from splitting water was reviewed, and the advantages and limitations of MOFs as catalysts were summarized. The development prospect of MOFs and related materials in the field of photocatalytic hydrogen production was proposed, providing a valuable guideline for developing future photocatalysts.
The increasingly serious energy exhaustion and environmental pollution accelerates the development of clean hydrogen energy. Water splitting via photocatalysis technology provides an economical and clean way for the hydrogen production, converting solar energy into chemical energy through photocatalytic means is also a promising technical means. The rational selection of photocatalyst is the critical step for obtaining hydrogen energy in an efficient and economical way. Featuring the traits of large specific surface area, adjustable pore size, easy structure modification and abundant active sites, metal-organic frameworks (MOFs) are ideal candidates for photocatalytic hydrogen production scientists from domestic and foreign have carried out numerous researches on the water splitting with MOF-based photocatalysts. Currently, fruitful progresses have been achieved. In this paper, the state-of-the-art advances for the MOF-based materials as catalysts in the field of hydrogen production from splitting water was reviewed, and the advantages and limitations of MOFs as catalysts were summarized. The development prospect of MOFs and related materials in the field of photocatalytic hydrogen production was proposed, providing a valuable guideline for developing future photocatalysts.
2022, 39(5): 2089-2105.
doi: 10.13801/j.cnki.fhclxb.20211106.002
Abstract:
The composite materials prepared based on the titanium dioxide (TiO2) nanoparticles as additives have excellent heat resistance, aging resistance, etc. The TiO2 nanoparticles have special photocatalytic activity, such as, it has strong antibacterial and bactericidal ability after absorbing ultraviolet energy. Currently, TiO2 nanoparticles have a wide range of applications in various fields of coatings, cosmetics and medicine. However, affected by the nano-dimensional effect, the TiO2 nanoparticles in the polymer matrix have the disadvantages of being easy to agglomerate and difficult to disperse, which limits its application. Therefore, it is necessary to regulate the surface properties of nano-TiO2 by various surface modification methods to enhance its compatibility with the polymer matrix. This paper first described the preparation, surface modification method and mechanism of TiO2 nanoparticles in detail, subsequently, and the research progress on the TiO2 nanoparticles modified polymer compound composite material is reviewed in the recent years. Finally, this paper discussed the TiO2 nanoparticles exist problems in the research of polymer composites, and prospected its development direction in the future.
The composite materials prepared based on the titanium dioxide (TiO2) nanoparticles as additives have excellent heat resistance, aging resistance, etc. The TiO2 nanoparticles have special photocatalytic activity, such as, it has strong antibacterial and bactericidal ability after absorbing ultraviolet energy. Currently, TiO2 nanoparticles have a wide range of applications in various fields of coatings, cosmetics and medicine. However, affected by the nano-dimensional effect, the TiO2 nanoparticles in the polymer matrix have the disadvantages of being easy to agglomerate and difficult to disperse, which limits its application. Therefore, it is necessary to regulate the surface properties of nano-TiO2 by various surface modification methods to enhance its compatibility with the polymer matrix. This paper first described the preparation, surface modification method and mechanism of TiO2 nanoparticles in detail, subsequently, and the research progress on the TiO2 nanoparticles modified polymer compound composite material is reviewed in the recent years. Finally, this paper discussed the TiO2 nanoparticles exist problems in the research of polymer composites, and prospected its development direction in the future.
2022, 39(5): 2106-2120.
doi: 10.13801/j.cnki.fhclxb.20210701.002
Abstract:
With the widespread promotion of new energy electric vehicles for lithium batteries worldwide, the demand for lithium is surging. And the industry chain of lithium is in the process of technological transformation and upgrading, the extraction of lithium from salt lake brine is becoming the main source. Comprehensively compare the precipitation method, adsorption method, calcining leaching method, extraction method, and other processes used in the extraction of lithium from brine, membrane separation is a high-efficiency and energy-saving separation and purification technology without phase change at room temperature, and it has become the most promising energy-saving and environmentally-friendly new technology in the lithium extraction industry. At present, the research on membrane processes with lithium separation effect mainly includes membrane-adsorption, membrane-solvent extraction and membrane-electrodialysis, etc. And membrane-electrodialysis technology has been successfully applied to extract lithium from salt lake brine in industry. However, the existing shortcomings of organic membranes, such as membrane blockage, organic matter dissolution loss, and environmental pollution, limit the promotion of membrane-electrodialysis in the lithium extraction industry. Inorganic ceramic membranes are divided into microfiltration, ultrafiltration and nanofiltration according to the pore size. The separation process is mainly based on the “physical screening” theory, and the inorganic ceramic membrane material has stable chemical structure, good mechanical properties, simple preparation process, high temperature resistance, uniform pore size, It has many advantages such as narrow pore size distribution range and long life. Therefore, the development of new inorganic membrane materials has attracted widespread attention from the academic community and has become a hot issue in the study of lithium extraction by membrane methods.
With the widespread promotion of new energy electric vehicles for lithium batteries worldwide, the demand for lithium is surging. And the industry chain of lithium is in the process of technological transformation and upgrading, the extraction of lithium from salt lake brine is becoming the main source. Comprehensively compare the precipitation method, adsorption method, calcining leaching method, extraction method, and other processes used in the extraction of lithium from brine, membrane separation is a high-efficiency and energy-saving separation and purification technology without phase change at room temperature, and it has become the most promising energy-saving and environmentally-friendly new technology in the lithium extraction industry. At present, the research on membrane processes with lithium separation effect mainly includes membrane-adsorption, membrane-solvent extraction and membrane-electrodialysis, etc. And membrane-electrodialysis technology has been successfully applied to extract lithium from salt lake brine in industry. However, the existing shortcomings of organic membranes, such as membrane blockage, organic matter dissolution loss, and environmental pollution, limit the promotion of membrane-electrodialysis in the lithium extraction industry. Inorganic ceramic membranes are divided into microfiltration, ultrafiltration and nanofiltration according to the pore size. The separation process is mainly based on the “physical screening” theory, and the inorganic ceramic membrane material has stable chemical structure, good mechanical properties, simple preparation process, high temperature resistance, uniform pore size, It has many advantages such as narrow pore size distribution range and long life. Therefore, the development of new inorganic membrane materials has attracted widespread attention from the academic community and has become a hot issue in the study of lithium extraction by membrane methods.
2022, 39(5): 2121-2132.
doi: 10.13801/j.cnki.fhclxb.20210707.002
Abstract:
The development of polymer dielectric materials with low dielectric constant, low dielectric loss, temperature resistance and high mechanical strength is of great significance to meet the requirements of high performance dielectric materials in 5G field. The hollow SiO2 nanoparticles (HS) were modified by 1H, 2H, 2H-perfluorooctyltriethoxysilane (PTES), and two kinds of low dielectric poly (aryl ether nitrile) composites (HS@PTES/PEN-F) were prepared by solution casting and phase conversion methods based on fluorinated poly (aryl ether nitrile) copolymer (PEN-F). The successful synthesis of fluorinated poly (aryl ether nitrile) copolymer was confirmed by FTIR and 1H NMR; the structure and morphology of PTES modified HS were characterized by FTIR, TGA and XPS. At the same time, the dielectric properties, mechanical strength and thermal stability of the HS@PTES/PEN-F composites were studied. The results show that the HS modified by PTES exhibit good dispersion and interface compa-tibility in the PEN-F matrix resin. In terms of dielectric properties, when the content of modified SiO2 nanoparticles reaches 7wt%, the dielectric constant and the dielectric loss of the HS@PTES/PEN-F composite film prepared by solution casting method are 2.88 and 0.0198 at 1 kHz; the dielectric constant and dielectric loss of the HS@PTES/PEN-F composite film prepared by phase conversion method are 1.19 and 0.0043, respectively. In the aspect of mechanical properties, taking the phase conversion method as an example, when the content of modified SiO2 nanoparticles reaches 5wt%, the tensile strength and elasticity modulus increase to 10.34 MPa and 365.32 MPa, respectively. In addition, the glass transition temperature of HS@PTES/PEN-F composite film can reach 160℃, which shows good thermal stability.
The development of polymer dielectric materials with low dielectric constant, low dielectric loss, temperature resistance and high mechanical strength is of great significance to meet the requirements of high performance dielectric materials in 5G field. The hollow SiO2 nanoparticles (HS) were modified by 1H, 2H, 2H-perfluorooctyltriethoxysilane (PTES), and two kinds of low dielectric poly (aryl ether nitrile) composites (HS@PTES/PEN-F) were prepared by solution casting and phase conversion methods based on fluorinated poly (aryl ether nitrile) copolymer (PEN-F). The successful synthesis of fluorinated poly (aryl ether nitrile) copolymer was confirmed by FTIR and 1H NMR; the structure and morphology of PTES modified HS were characterized by FTIR, TGA and XPS. At the same time, the dielectric properties, mechanical strength and thermal stability of the HS@PTES/PEN-F composites were studied. The results show that the HS modified by PTES exhibit good dispersion and interface compa-tibility in the PEN-F matrix resin. In terms of dielectric properties, when the content of modified SiO2 nanoparticles reaches 7wt%, the dielectric constant and the dielectric loss of the HS@PTES/PEN-F composite film prepared by solution casting method are 2.88 and 0.0198 at 1 kHz; the dielectric constant and dielectric loss of the HS@PTES/PEN-F composite film prepared by phase conversion method are 1.19 and 0.0043, respectively. In the aspect of mechanical properties, taking the phase conversion method as an example, when the content of modified SiO2 nanoparticles reaches 5wt%, the tensile strength and elasticity modulus increase to 10.34 MPa and 365.32 MPa, respectively. In addition, the glass transition temperature of HS@PTES/PEN-F composite film can reach 160℃, which shows good thermal stability.
2022, 39(5): 2133-2140.
doi: 10.13801/j.cnki.fhclxb.20210812.001
Abstract:
Reduced graphene oxide(RGO) modified carbon fiber/polyphenylene sulfide composites (RGO-CF/PPS) were prepared by powder lamination methodand hot pressing process. Interlaminar shear properties and micromorphology of the RGO-CF/PPS composites at room temperature and hygrothermal environment were investi-gated. Meanwhile, the effect of RGO on the interface performance of the composites was analyzed. Results show that the interlaminar shear strength (ILSS) of the 0.1%RGO-CF/PPS composites in the dry state at room tempera-ture is 18.4% higher than that of the CF/PPS composites. After hygrothermal treatment, the ILSS of the RGO-CF/PPS composites are decreased and the ILSS strength retention rate of the RGO-CF/PPS composites is lower than that of the CF/PPS composites. Dynamic thermomechanical behavior results of the composites show that the RGO is helpful to enhance the interface bonding performance of the RGO-CF/PPS composites. Micromorphology shows that the RGO effectively improves the ILSS of the RGO-CF/PPS composites in the dry state at room temperature.
Reduced graphene oxide(RGO) modified carbon fiber/polyphenylene sulfide composites (RGO-CF/PPS) were prepared by powder lamination methodand hot pressing process. Interlaminar shear properties and micromorphology of the RGO-CF/PPS composites at room temperature and hygrothermal environment were investi-gated. Meanwhile, the effect of RGO on the interface performance of the composites was analyzed. Results show that the interlaminar shear strength (ILSS) of the 0.1%RGO-CF/PPS composites in the dry state at room tempera-ture is 18.4% higher than that of the CF/PPS composites. After hygrothermal treatment, the ILSS of the RGO-CF/PPS composites are decreased and the ILSS strength retention rate of the RGO-CF/PPS composites is lower than that of the CF/PPS composites. Dynamic thermomechanical behavior results of the composites show that the RGO is helpful to enhance the interface bonding performance of the RGO-CF/PPS composites. Micromorphology shows that the RGO effectively improves the ILSS of the RGO-CF/PPS composites in the dry state at room temperature.
2022, 39(5): 2141-2152.
doi: 10.13801/j.cnki.fhclxb.20210805.003
Abstract:
Polymer/inorganic nanocomposites have attracted extensive research interests due to their unique properties. In order to obtain SiC composite coating material with excellent hydrophobic and anticorrosive performance, silicon carbide (SiC) nanoparticles were ammoniated by silane coupling agent (KH-550), and then the covalently functionalized SiC-sulfonated polyaniline (SiC-NH2-SPANI) composites were synthesized by one-step oxidative polymerization of aniline, aminobenzenesulfonic acid and aminated SiC nanoparticles, the microstructure and morphology of the composites were characterizated by FT-IR, UV-vis, XRD and SEM. Finally, the SiC-NH2-SPANI epoxy coating was coated on the substrate by spraying method and the hydrophobic and anticorrosion performance of the prepared coating was studied. The effects of the amount of different SiC nanoparticle, ammonium persulfate and the amount of the composite materials on the covalently functionalized silicon carbide-sulfonated polyaniline/epoxy resin anticorrosive composite coating (SiC-NH2-SPANI/EP) was investigated. The results of hydrophobic property show that the contact angle value of the composite coating with 3wt%SiC-NH2-SPANI reaches 99.87°, which is higher than that of the composite coating that used the pristine SiC substituted for SiC-NH2. With regard to the influence of different reaction amount of SiC and ammonium persulfate, the anticorrosion performance of SiC-NH2-SPANI/EP is the best when the mass ratio of 15wt%SiC-NH2 to ammonium persulfate (APS) is 1 : 1. Among the composite coatings doped with different materials (SiC/EP, SiC-NH2/EP and SiC-NH2-SPANI/EP), the SiC-NH2/EP coating has the largest contact angle, the best hydrophobic performance and anticorrosion performance. It also shows that there is a relationship between hydrophobic property and anticorrosion pro-perty and the hydrophobic performance is directly proportional to anticorrosive performance. With regard to the influence of the content of composite coatings, the long-term stability and corrosion resistance are more excellent when the addition of SiC-NH2-SPANI/EP is 3wt%.
Polymer/inorganic nanocomposites have attracted extensive research interests due to their unique properties. In order to obtain SiC composite coating material with excellent hydrophobic and anticorrosive performance, silicon carbide (SiC) nanoparticles were ammoniated by silane coupling agent (KH-550), and then the covalently functionalized SiC-sulfonated polyaniline (SiC-NH2-SPANI) composites were synthesized by one-step oxidative polymerization of aniline, aminobenzenesulfonic acid and aminated SiC nanoparticles, the microstructure and morphology of the composites were characterizated by FT-IR, UV-vis, XRD and SEM. Finally, the SiC-NH2-SPANI epoxy coating was coated on the substrate by spraying method and the hydrophobic and anticorrosion performance of the prepared coating was studied. The effects of the amount of different SiC nanoparticle, ammonium persulfate and the amount of the composite materials on the covalently functionalized silicon carbide-sulfonated polyaniline/epoxy resin anticorrosive composite coating (SiC-NH2-SPANI/EP) was investigated. The results of hydrophobic property show that the contact angle value of the composite coating with 3wt%SiC-NH2-SPANI reaches 99.87°, which is higher than that of the composite coating that used the pristine SiC substituted for SiC-NH2. With regard to the influence of different reaction amount of SiC and ammonium persulfate, the anticorrosion performance of SiC-NH2-SPANI/EP is the best when the mass ratio of 15wt%SiC-NH2 to ammonium persulfate (APS) is 1 : 1. Among the composite coatings doped with different materials (SiC/EP, SiC-NH2/EP and SiC-NH2-SPANI/EP), the SiC-NH2/EP coating has the largest contact angle, the best hydrophobic performance and anticorrosion performance. It also shows that there is a relationship between hydrophobic property and anticorrosion pro-perty and the hydrophobic performance is directly proportional to anticorrosive performance. With regard to the influence of the content of composite coatings, the long-term stability and corrosion resistance are more excellent when the addition of SiC-NH2-SPANI/EP is 3wt%.
2022, 39(5): 2153-2160.
doi: 10.13801/j.cnki.fhclxb.20210716.002
Abstract:
Plant fiber reinforced composites are being applied to various fields of life. The interfacial incompatibility between hydrophilic reinforcement and hydrophobic matrix limits the mechanical properties of composites. In this paper, the kenaf fiber was modified by carboxylated carbon nanotubes (c-MWCNTs) to explore the interface improvement mechanism of kenaf fiber/epoxy resin composites. Firstly, the kenaf fiber was pretreated by water and NaOH. The effects of different pretreatment methods on the grafting of c-MWCNTs by kenaf fiber were investigated by observing the changes of fiber diameter, infrared spectrum and fiber bundle fracture strength. Then the kenaf fibers were modified with 0.5wt%, 1wt% and 3wt% c-MWCNTs, respectively. Interfacial shear strength (IFSS) of kenaf fiber/epoxy composites was investigated by single fiber pull-out test. The results show that the diameter variation, the removal of non-cellulose components and the decrease of fiber bundle fracture strength of kenaf fiber after alkali treatment are the smallest and the dimensional stability of composite is higher. Through single fiber pull-out test, IFSS of the kenaf fiber/epoxy resin composite increases gradually, but the effectiveness decreases gradually. When the mass fraction of c-MWCNTs is 0.5wt%, the effectiveness is the highest, and the improvement effect reaches 45.09%. The interfacial properties of kenaf fiber/epoxy resin composites modified by c-MWCNTs are improved. Due to the existence of c-MWCNTs, the mechanical lock between fiber and resin matrix is strengthened.
Plant fiber reinforced composites are being applied to various fields of life. The interfacial incompatibility between hydrophilic reinforcement and hydrophobic matrix limits the mechanical properties of composites. In this paper, the kenaf fiber was modified by carboxylated carbon nanotubes (c-MWCNTs) to explore the interface improvement mechanism of kenaf fiber/epoxy resin composites. Firstly, the kenaf fiber was pretreated by water and NaOH. The effects of different pretreatment methods on the grafting of c-MWCNTs by kenaf fiber were investigated by observing the changes of fiber diameter, infrared spectrum and fiber bundle fracture strength. Then the kenaf fibers were modified with 0.5wt%, 1wt% and 3wt% c-MWCNTs, respectively. Interfacial shear strength (IFSS) of kenaf fiber/epoxy composites was investigated by single fiber pull-out test. The results show that the diameter variation, the removal of non-cellulose components and the decrease of fiber bundle fracture strength of kenaf fiber after alkali treatment are the smallest and the dimensional stability of composite is higher. Through single fiber pull-out test, IFSS of the kenaf fiber/epoxy resin composite increases gradually, but the effectiveness decreases gradually. When the mass fraction of c-MWCNTs is 0.5wt%, the effectiveness is the highest, and the improvement effect reaches 45.09%. The interfacial properties of kenaf fiber/epoxy resin composites modified by c-MWCNTs are improved. Due to the existence of c-MWCNTs, the mechanical lock between fiber and resin matrix is strengthened.
2022, 39(5): 2161-2171.
doi: 10.13801/j.cnki.fhclxb.20210722.001
Abstract:
Negative stiffness honeycomb cell structures were fabricated by fused filament fabrication (FFF) based on chopped carbon fiber reinforced nylon composites (MarkForged Onyx). In order to analyze the printing properties and compression properties, compression tests for negative stiffness honeycomb cell structure specimens were carried out. The influence mechanism of three process parameters, including building directions, fill patterns and wall layers, on the printing properties and compression properties of the structure was analyzed. The results show that the combination of flat building directions, hexagonal fill pattern and one wall layer can effectively reduce the printing time and cost of the structure. The compression properties of the flat building directions are superior to that of the on-edge and up-right. Compared with quadrilateral and hexagonal fill pattern, triangular fill pattern improves the energy absorption capacity of the structure significantly. Two wall layers have a great impact on the compressive strength of the structure. Cell structures show pronounced negative stiffness behavior during the loading process with percent energy absorbed up to 70%, and force threshold of about 185 N. Through the cycle tests, there is only 6% of the compression deformation, realizing the recoverable energy absorption of negative stiffness honeycomb core structures based on Markforged Onyx chopped carbon fiber reinforced nylon composites.
Negative stiffness honeycomb cell structures were fabricated by fused filament fabrication (FFF) based on chopped carbon fiber reinforced nylon composites (MarkForged Onyx). In order to analyze the printing properties and compression properties, compression tests for negative stiffness honeycomb cell structure specimens were carried out. The influence mechanism of three process parameters, including building directions, fill patterns and wall layers, on the printing properties and compression properties of the structure was analyzed. The results show that the combination of flat building directions, hexagonal fill pattern and one wall layer can effectively reduce the printing time and cost of the structure. The compression properties of the flat building directions are superior to that of the on-edge and up-right. Compared with quadrilateral and hexagonal fill pattern, triangular fill pattern improves the energy absorption capacity of the structure significantly. Two wall layers have a great impact on the compressive strength of the structure. Cell structures show pronounced negative stiffness behavior during the loading process with percent energy absorbed up to 70%, and force threshold of about 185 N. Through the cycle tests, there is only 6% of the compression deformation, realizing the recoverable energy absorption of negative stiffness honeycomb core structures based on Markforged Onyx chopped carbon fiber reinforced nylon composites.
2022, 39(5): 2172-2182.
doi: 10.13801/j.cnki.fhclxb.20210615.001
Abstract:
Graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) are widely used in rubber fillers due to their good mechanical properties and thermal conductivity. In order to increase the vulcanization efficiency and improve the physical properties of natural rubber, a GO/MWCNTs rubber composite was prepared by mixing graphene oxide and multi-walled carbon nanotubes with rubber in different proportions. Through testing the phy-sical properties of the rubber compound and the vulcanized rubber, it is concluded that there is a synergistic effect between MWCNTs filler and GO filler, and different ratios of GO and MWCNTs have different effects on the performance of the rubber compound. When MWCNTs filler is added quantitatively at 6wt%, with the increase of GO content: the maximum torque MH of the vulcanized rubber and the crosslinking density ΔM value increased; the scorch time tc10 and the normal vulcanization time tc90 decreased first, and tc90 rose slightly after 3wt%. When the content of GO and MWCNTs are 3wt% and 6wt%, the improvement of vulcanization efficiency is most obvious; when the two are added at 6wt% at the same time, the thermal conductivity of the compound and the vulcanized rubber are increased by 25.1% and 23.3% respectively; the 100% of the vulcanized rubber is fixed. Tensile stress and 300% constant elongation stress have a rising trend, and slightly decrease after 3wt%. Taken together, when GO and MWCNTs are added at 3wt% and 6wt%, respectively, the filler particles have the best reinforcement effect on the rubber. Its good thermal conductivity enhances the uniformity of the vulcanization reaction and realizes energy saving and consumption reduction in the vulcanization process.
Graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) are widely used in rubber fillers due to their good mechanical properties and thermal conductivity. In order to increase the vulcanization efficiency and improve the physical properties of natural rubber, a GO/MWCNTs rubber composite was prepared by mixing graphene oxide and multi-walled carbon nanotubes with rubber in different proportions. Through testing the phy-sical properties of the rubber compound and the vulcanized rubber, it is concluded that there is a synergistic effect between MWCNTs filler and GO filler, and different ratios of GO and MWCNTs have different effects on the performance of the rubber compound. When MWCNTs filler is added quantitatively at 6wt%, with the increase of GO content: the maximum torque MH of the vulcanized rubber and the crosslinking density ΔM value increased; the scorch time tc10 and the normal vulcanization time tc90 decreased first, and tc90 rose slightly after 3wt%. When the content of GO and MWCNTs are 3wt% and 6wt%, the improvement of vulcanization efficiency is most obvious; when the two are added at 6wt% at the same time, the thermal conductivity of the compound and the vulcanized rubber are increased by 25.1% and 23.3% respectively; the 100% of the vulcanized rubber is fixed. Tensile stress and 300% constant elongation stress have a rising trend, and slightly decrease after 3wt%. Taken together, when GO and MWCNTs are added at 3wt% and 6wt%, respectively, the filler particles have the best reinforcement effect on the rubber. Its good thermal conductivity enhances the uniformity of the vulcanization reaction and realizes energy saving and consumption reduction in the vulcanization process.
2022, 39(5): 2183-2191.
doi: 10.13801/j.cnki.fhclxb.20210903.003
Abstract:
Phenolic epoxy resin (EP) is widely used in electronics because of its excellent electrical insulating pro-perties. The thermal conductivity of EP is low, and filling the highly conductive thermal inorganic fillers is an effec-tive way to construct the thermal conductive pathway of the thermal transport frame to improve the thermal conductivity of polymer composites. In this paper, the hexagonal boron nitride (h-BN)-four needle zinc oxide whisker (T-ZnOw)/EP composite was prepared by solution blended and hot-compaction process. The microstructures aspects, phase structures, thermal conductivity and electric insulating propertis of composites were systematically characterized and analyzed. The results show the h-BN-T-ZnOw/EP composite has good thermal conductivity and electrical insulating properties. When h-BN-T-ZnOw loading is 30wt%/5wt%, the thermal conductivity at 25℃ is 0.55 W/(m·K), which is 2.9 times higher than that of EP, and its volume resistivity is greater than 1015 Ω·m.
Phenolic epoxy resin (EP) is widely used in electronics because of its excellent electrical insulating pro-perties. The thermal conductivity of EP is low, and filling the highly conductive thermal inorganic fillers is an effec-tive way to construct the thermal conductive pathway of the thermal transport frame to improve the thermal conductivity of polymer composites. In this paper, the hexagonal boron nitride (h-BN)-four needle zinc oxide whisker (T-ZnOw)/EP composite was prepared by solution blended and hot-compaction process. The microstructures aspects, phase structures, thermal conductivity and electric insulating propertis of composites were systematically characterized and analyzed. The results show the h-BN-T-ZnOw/EP composite has good thermal conductivity and electrical insulating properties. When h-BN-T-ZnOw loading is 30wt%/5wt%, the thermal conductivity at 25℃ is 0.55 W/(m·K), which is 2.9 times higher than that of EP, and its volume resistivity is greater than 1015 Ω·m.
2022, 39(5): 2192-2200.
doi: 10.13801/j.cnki.fhclxb.20210726.002
Abstract:
Polybutylene terephthalate (PBT) is a semi-crystalline thermoplastic polymer with excellent dimensional stability, high stiffness and hardness, good chemical resistance, mechanical properties and processability. But its impact resistance is low and toughness is poor. PBT was melt blended with poly(butylene succinate-co-butylene diphenyl ether dicarboxylate) (PBSO), which has excellent toughness, to improve the toughness of PBT. Firstly, PBSO was synthesized by a two-step method of esterification and polycondensation, using diphenyl ether dicarboxylic acid (OBBA), succinic acid (SA) and butanediol (BDO) as monomers, and tetrabutyl titanate as catalyst. Then, PBSO/PBT with different mass ratios of PBSO and PBT were blended by melt-extrusion to study the toughening effect of PBSO on PBT. The mechanical toughness of blends, the compatibility of PBSO and PBT, crystallization behavior, thermal stability and rheological properties were studied. The structure of PBSO was characterized by FT-IR, 1H NMR and GPC. The mechanical performance test show that the tensile strength of the 20wt%PBSO/PBT composite material is 40.3 MPa, the elongation at break reach to 82.1%, the breaking energy increas to 24.70 MPa, and the impact strength is 23.2 kJ/m2, indicating a higher tensile strength and good toughness. Dynamic mechanical analysis (DMA) and SEM results indicate that PBSO has a compatibilizing effect on PBT, and PBSO/PBT is a partially compatible blend system. DSC and wide-angle X-ray diffraction (WAXD) results show that the addition of amorphous polymer PBSO reduce the crystallinity of PBT, but do not change the crystal structure of PBT. Thermogravimetric analysis (TGA) analysis demonstrated that the PBSO/PBT composite has a good processing thermal stability.
Polybutylene terephthalate (PBT) is a semi-crystalline thermoplastic polymer with excellent dimensional stability, high stiffness and hardness, good chemical resistance, mechanical properties and processability. But its impact resistance is low and toughness is poor. PBT was melt blended with poly(butylene succinate-co-butylene diphenyl ether dicarboxylate) (PBSO), which has excellent toughness, to improve the toughness of PBT. Firstly, PBSO was synthesized by a two-step method of esterification and polycondensation, using diphenyl ether dicarboxylic acid (OBBA), succinic acid (SA) and butanediol (BDO) as monomers, and tetrabutyl titanate as catalyst. Then, PBSO/PBT with different mass ratios of PBSO and PBT were blended by melt-extrusion to study the toughening effect of PBSO on PBT. The mechanical toughness of blends, the compatibility of PBSO and PBT, crystallization behavior, thermal stability and rheological properties were studied. The structure of PBSO was characterized by FT-IR, 1H NMR and GPC. The mechanical performance test show that the tensile strength of the 20wt%PBSO/PBT composite material is 40.3 MPa, the elongation at break reach to 82.1%, the breaking energy increas to 24.70 MPa, and the impact strength is 23.2 kJ/m2, indicating a higher tensile strength and good toughness. Dynamic mechanical analysis (DMA) and SEM results indicate that PBSO has a compatibilizing effect on PBT, and PBSO/PBT is a partially compatible blend system. DSC and wide-angle X-ray diffraction (WAXD) results show that the addition of amorphous polymer PBSO reduce the crystallinity of PBT, but do not change the crystal structure of PBT. Thermogravimetric analysis (TGA) analysis demonstrated that the PBSO/PBT composite has a good processing thermal stability.
2022, 39(5): 2201-2214.
doi: 10.13801/j.cnki.fhclxb.20210702.003
Abstract:
The purpose of this paper is to study and prepare a kind of renewable composite paperboard with both flame retardancy and hydrophobicity, and to explore its flame retardancy, hydrophobicity and mechanical properties. The intumescent flame retardant system (IFR) was constructed with ammonium polyphosphate (APP)-carrageenan (KC), tetraethylorthosilicate(TEOS)-methyltrimethoxysilane (MTMS)@magnesium aluminum hydro-xide(MAH) as synergistic flame retardant, silane coupling agent KH550 (AEMO)@SiO2 as hydrophobic filler. The flame retardant, hydrophobic and mechanical properties of APP-KC-[(TEOS-MTMS)@MAH]-(AEMO@SiO2) composite paperboard were tested. According to the national standard, the main physical properties of corrugated board were measured. The flame retardant effect of corrugated board was tested by vertical combustion test and limiting oxygen index (LOI). The microstructure was characterized by FE-SEM. FTIR was used to study the changes of functional groups before and after combustion. Its thermal stability was analyzed by thermogravimetry (TG). Contact angle (CA) test, rolling angle (SA) test and water absorption test were used to determine its hydrophobicity. The water absorption of composite paperboard is 1.78 g·m−2, the puncture strength is 6.4 J, the edge pressure strength is 8.3 kN·m−1, and the compressive strength is 360 kPa. The optimal formula is adopted (the mass ratio of APP, KC, MTH and ATH was 3∶2∶1∶1). The limiting oxygen index (LOI) reaches 32% at the same time. After the combustion experiment, the carbonization length is 19 mm, the flame duration is 0.5 s, and the ignition time is 3 s. TG results show that the carbon residue of APP-KC-[(TEOS-MTMS)@MAH]-[AEMO@SiO2] composite paperboard is 37.5%. SEM results show that there is a foamed carbon layer on the surface of the composite board after combustion, and the fiber is still intact. The contact angle is 110.2°. The moisture content is 232% lower than that of base paper. APP-KC-[(TEOS-MTMS)@MAH]-(AEMO@SiO2) composite paperboard has good flame retardancy, hydrophobicity and mechanical properties.
The purpose of this paper is to study and prepare a kind of renewable composite paperboard with both flame retardancy and hydrophobicity, and to explore its flame retardancy, hydrophobicity and mechanical properties. The intumescent flame retardant system (IFR) was constructed with ammonium polyphosphate (APP)-carrageenan (KC), tetraethylorthosilicate(TEOS)-methyltrimethoxysilane (MTMS)@magnesium aluminum hydro-xide(MAH) as synergistic flame retardant, silane coupling agent KH550 (AEMO)@SiO2 as hydrophobic filler. The flame retardant, hydrophobic and mechanical properties of APP-KC-[(TEOS-MTMS)@MAH]-(AEMO@SiO2) composite paperboard were tested. According to the national standard, the main physical properties of corrugated board were measured. The flame retardant effect of corrugated board was tested by vertical combustion test and limiting oxygen index (LOI). The microstructure was characterized by FE-SEM. FTIR was used to study the changes of functional groups before and after combustion. Its thermal stability was analyzed by thermogravimetry (TG). Contact angle (CA) test, rolling angle (SA) test and water absorption test were used to determine its hydrophobicity. The water absorption of composite paperboard is 1.78 g·m−2, the puncture strength is 6.4 J, the edge pressure strength is 8.3 kN·m−1, and the compressive strength is 360 kPa. The optimal formula is adopted (the mass ratio of APP, KC, MTH and ATH was 3∶2∶1∶1). The limiting oxygen index (LOI) reaches 32% at the same time. After the combustion experiment, the carbonization length is 19 mm, the flame duration is 0.5 s, and the ignition time is 3 s. TG results show that the carbon residue of APP-KC-[(TEOS-MTMS)@MAH]-[AEMO@SiO2] composite paperboard is 37.5%. SEM results show that there is a foamed carbon layer on the surface of the composite board after combustion, and the fiber is still intact. The contact angle is 110.2°. The moisture content is 232% lower than that of base paper. APP-KC-[(TEOS-MTMS)@MAH]-(AEMO@SiO2) composite paperboard has good flame retardancy, hydrophobicity and mechanical properties.
2022, 39(5): 2215-2225.
doi: 10.13801/j.cnki.fhclxb.20210730.001
Abstract:
In order to effectively remove dye from wastewater, sodium alginate/graphene oxide (SA/GO) compo-site hydrogel was prepared by one-step hydrothermal method using sodium alginate (SA) and graphene oxide (GO) as raw materials, and SA/GO composite aerogel was prepared by freeze drying. The synthesized products were characterized by FT-IR, XRD, SEM, TEM, N2 adsorption-desorption and contact angel. The results show that the SA/GO composite aerogel is a porous material with three-dimensional structure, the specific surface area is about 580.54 m2·g−1. The influence factors of SA/GO composite aerogel on the adsorption process of methylene blue (MB) solution are discussed. Under alkaline conditions, the adsorption effect is the best, the adsorption rate can reach 99.41%, the adsorption capacity can reach 248.53 mg·g−1, and show excellent cyclic regeneration.
In order to effectively remove dye from wastewater, sodium alginate/graphene oxide (SA/GO) compo-site hydrogel was prepared by one-step hydrothermal method using sodium alginate (SA) and graphene oxide (GO) as raw materials, and SA/GO composite aerogel was prepared by freeze drying. The synthesized products were characterized by FT-IR, XRD, SEM, TEM, N2 adsorption-desorption and contact angel. The results show that the SA/GO composite aerogel is a porous material with three-dimensional structure, the specific surface area is about 580.54 m2·g−1. The influence factors of SA/GO composite aerogel on the adsorption process of methylene blue (MB) solution are discussed. Under alkaline conditions, the adsorption effect is the best, the adsorption rate can reach 99.41%, the adsorption capacity can reach 248.53 mg·g−1, and show excellent cyclic regeneration.
2022, 39(5): 2226-2237.
doi: 10.13801/j.cnki.fhclxb.20210820.002
Abstract:
To develop a high performance, recyclable, low cost photocatalyst. In this work, MoS2 modified ZnO (MoS2-ZnO) nanocomposites were prepared by a hydrothermal method. The morphology and optical properties of the samples were characterized by XRD, SEM, photoluminescence spectroscopy (PL) and XPS. We find that the prepared MoS2-ZnO samples own a porous structure from SEM. And MoS2 can not only enhance the separation efficiency of photocarriers in MoS2-ZnO, but also increase the absorption of visible light region, resulting in improving the photo-catalytic and gas sensitive properties. Under simulated sunlight, the MoS2-ZnO nanocomposite exhibits high photo-catalytic degradation activity for high concentration (15 mg/L) methylene blue dye (MB). At the same time, the MoS2-ZnO-based gas sensor possesses a high sensitivity for NO2 concentration of 2.05 mg/m3. This work offers a simple strategy to prepare highly efficient visible light-driven photocatalysts and gas sensors.
To develop a high performance, recyclable, low cost photocatalyst. In this work, MoS2 modified ZnO (MoS2-ZnO) nanocomposites were prepared by a hydrothermal method. The morphology and optical properties of the samples were characterized by XRD, SEM, photoluminescence spectroscopy (PL) and XPS. We find that the prepared MoS2-ZnO samples own a porous structure from SEM. And MoS2 can not only enhance the separation efficiency of photocarriers in MoS2-ZnO, but also increase the absorption of visible light region, resulting in improving the photo-catalytic and gas sensitive properties. Under simulated sunlight, the MoS2-ZnO nanocomposite exhibits high photo-catalytic degradation activity for high concentration (15 mg/L) methylene blue dye (MB). At the same time, the MoS2-ZnO-based gas sensor possesses a high sensitivity for NO2 concentration of 2.05 mg/m3. This work offers a simple strategy to prepare highly efficient visible light-driven photocatalysts and gas sensors.
2022, 39(5): 2238-2248.
doi: 10.13801/j.cnki.fhclxb.20210715.001
Abstract:
In order to solve the problem of low conductivity of MoS2 absorbing material, the MoS2/biomass carbon (BC) composite material was prepared by using shaddock peel (SP) as the raw material, using one-pot hydro-thermal and high-temperature calcination methods. The content of MoS2 in the composite material was adjusted by adjusting the content of the initial Mo source and S source. The results of microscopic morphology, structure and electromagnetic parameters show that with the increase of the MoS2 content in the composite material, the scattered distribution of MoS2 on the BC surface changes from flakes to flower-like coatings, and the conductivity and complex permittivity of MoS2/BC composites gradually decrease. By adjusting the ratio of MoS2 to BC, the effective control of the electromagnetic parameters of the MoS2/BC composite material is realized, and its impedance matching characteristics are optimized. The flower-like structure of MoS2 facilitates the multiple reflection/scattering of electromagnetic waves. At the same time, there are abundant interfaces between flower-like MoS2 and BC, which is beneficial to promote interface polarization and enhance the attenuation ability of MoS2/BC composites to electromagnetic waves. The prepared MoS2/BC-0.8 has a minimum reflectance loss (RL) value of –40.1 dB, and an effective absorption bandwidth of up to 5.9 GHz (11.1-17.0 GHz).
In order to solve the problem of low conductivity of MoS2 absorbing material, the MoS2/biomass carbon (BC) composite material was prepared by using shaddock peel (SP) as the raw material, using one-pot hydro-thermal and high-temperature calcination methods. The content of MoS2 in the composite material was adjusted by adjusting the content of the initial Mo source and S source. The results of microscopic morphology, structure and electromagnetic parameters show that with the increase of the MoS2 content in the composite material, the scattered distribution of MoS2 on the BC surface changes from flakes to flower-like coatings, and the conductivity and complex permittivity of MoS2/BC composites gradually decrease. By adjusting the ratio of MoS2 to BC, the effective control of the electromagnetic parameters of the MoS2/BC composite material is realized, and its impedance matching characteristics are optimized. The flower-like structure of MoS2 facilitates the multiple reflection/scattering of electromagnetic waves. At the same time, there are abundant interfaces between flower-like MoS2 and BC, which is beneficial to promote interface polarization and enhance the attenuation ability of MoS2/BC composites to electromagnetic waves. The prepared MoS2/BC-0.8 has a minimum reflectance loss (RL) value of –40.1 dB, and an effective absorption bandwidth of up to 5.9 GHz (11.1-17.0 GHz).
2022, 39(5): 2249-2257.
doi: 10.13801/j.cnki.fhclxb.20210709.001
Abstract:
Homo heterojunction or hetero heterojunction will form at the surface of two kinds of different semiconductor due to the difference of electronic affinity and band gap width. The interface carrier mobility can be improved by means of Fermi level effect at interface of heterojunction, which improves the gas sensitivity perfor-mance of gas sensor. The coaxial heterocomposite In2O3/SnO2 nanofibers were fabricated by a self-designed multilayer coaxial electrospinning device. The bigger In2O3 nanoparticles on the outer layer of In2O3/SnO2 fibers grow on the surface of the SnO2 nanoparticles on the inner layer of In2O3/SnO2 fiber, which forms the hollow hierarchical fiber structure. N-N homo-heterojunctions interface between of In2O3 and SnO2 nanoparticles will enhance electron mobility, surface activity and the content of adsorption oxygen, which will improve the adsorption capacity of In2O3/SnO2 sensor to formaldehyde. The response of coaxial hetero-nanofiber In2O3/SnO2 sensor is 14.12×10-6 to 50 ×10-6 formaldehyde, are 3.22 times, 3.84 times and 1.51 times of that of SnO2, In2O3 and mixed hetero-nanofiber In2O3/SnO2 sensor at 250℃. The coaxial hetero-nanofiber In2O3/SnO2 sensor also shows excellent cross-selectivity to formaldehyde, ethanol, acetone, ammonia, toluene and methanol. The coaxial hetero composite synthesized by coaxial electrospinning has application potential and development prospect to improve semiconductor function device.
Homo heterojunction or hetero heterojunction will form at the surface of two kinds of different semiconductor due to the difference of electronic affinity and band gap width. The interface carrier mobility can be improved by means of Fermi level effect at interface of heterojunction, which improves the gas sensitivity perfor-mance of gas sensor. The coaxial heterocomposite In2O3/SnO2 nanofibers were fabricated by a self-designed multilayer coaxial electrospinning device. The bigger In2O3 nanoparticles on the outer layer of In2O3/SnO2 fibers grow on the surface of the SnO2 nanoparticles on the inner layer of In2O3/SnO2 fiber, which forms the hollow hierarchical fiber structure. N-N homo-heterojunctions interface between of In2O3 and SnO2 nanoparticles will enhance electron mobility, surface activity and the content of adsorption oxygen, which will improve the adsorption capacity of In2O3/SnO2 sensor to formaldehyde. The response of coaxial hetero-nanofiber In2O3/SnO2 sensor is 14.12×10-6 to 50 ×10-6 formaldehyde, are 3.22 times, 3.84 times and 1.51 times of that of SnO2, In2O3 and mixed hetero-nanofiber In2O3/SnO2 sensor at 250℃. The coaxial hetero-nanofiber In2O3/SnO2 sensor also shows excellent cross-selectivity to formaldehyde, ethanol, acetone, ammonia, toluene and methanol. The coaxial hetero composite synthesized by coaxial electrospinning has application potential and development prospect to improve semiconductor function device.
2022, 39(5): 2258-2268.
doi: 10.13801/j.cnki.fhclxb.20210701.003
Abstract:
Artemisia is a common Chinese herbal medicine. The essential oil of Artemisia is easy to volatilize and cannot maintain bacteriostasis for a long time, which has become a bottleneck restricting its industrial application. In order to solve the above problems, Artemisia/polyacrylonitrile composite nanofibers were prepared by electrospinning using water-soluble Artemisia powders. The composite filter materials with good stability and long-term bacteriostasis were prepared by on-line process with melt-blown and hot-air nonwovens. The wettability, antibacterial properties, air permeability, filtration efficiency and unidirectional moisture transport of the composites were tested and compared with those of Artemisia essential oil materials. The results show that the addition of Artemisia powder made the composites uper hydrophilic, and the wetting time of the composites is 126 times shorter than that of pure polyacrylonitrile nanofibers. When the mass ratio of Artemisia grass to polyacrylonitrile reaches 15∶15, the bacteriostatic rate of staphylococcus aureus reaches 99.5% after two months. While under the same conditions, Artemisia essential oil volatilized faster, antibacterial property and durability are lower. It can be seen that Artemisia composite nanofiber material has excellent antibacterial and barrier properties. The melt-blown material is compounded with Artemisia/polyacrylonitrile nanofiber material, and the unidirectional moisture conductivity index can be as high as 988.96%. It is expected to solve the problems of hot concentration in summer, damp-cold in winter and bacterial reproduction, and has a broad application prospect in masks, dressings and medical protective clothing.
Artemisia is a common Chinese herbal medicine. The essential oil of Artemisia is easy to volatilize and cannot maintain bacteriostasis for a long time, which has become a bottleneck restricting its industrial application. In order to solve the above problems, Artemisia/polyacrylonitrile composite nanofibers were prepared by electrospinning using water-soluble Artemisia powders. The composite filter materials with good stability and long-term bacteriostasis were prepared by on-line process with melt-blown and hot-air nonwovens. The wettability, antibacterial properties, air permeability, filtration efficiency and unidirectional moisture transport of the composites were tested and compared with those of Artemisia essential oil materials. The results show that the addition of Artemisia powder made the composites uper hydrophilic, and the wetting time of the composites is 126 times shorter than that of pure polyacrylonitrile nanofibers. When the mass ratio of Artemisia grass to polyacrylonitrile reaches 15∶15, the bacteriostatic rate of staphylococcus aureus reaches 99.5% after two months. While under the same conditions, Artemisia essential oil volatilized faster, antibacterial property and durability are lower. It can be seen that Artemisia composite nanofiber material has excellent antibacterial and barrier properties. The melt-blown material is compounded with Artemisia/polyacrylonitrile nanofiber material, and the unidirectional moisture conductivity index can be as high as 988.96%. It is expected to solve the problems of hot concentration in summer, damp-cold in winter and bacterial reproduction, and has a broad application prospect in masks, dressings and medical protective clothing.
2022, 39(5): 2269-2279.
doi: 10.13801/j.cnki.fhclxb.20210916.004
Abstract:
Transition metal oxide MnO2 has great potential in battery storage because of its simple preparation process, abundant reserves, environmental protection and high theoretical specific capacity. In this paper, MnO2 nanosheets were prepared by exfoliating the hydrothermally synthesized δ-MnO2 by the swelling method. The Ag/MnO2 composites were obtained by loading Ag nanoparticles on the surface of MnO2 nanosheets under UV irradiation and NaBH4 reduction. The structure and morphology of Ag/MnO2 composites were characterized and their electrochemical properties were tested. The results show that the electrochemical performance of Ag/MnO2 as anode material for lithium ion batteries is obviously better than that of the pure phase δ-MnO2. The first reversible specific capacity of Ag/MnO2 at the current density of 100 mA/g reaches 1001.1 mA·h/g, and the coulombic efficiency is 79.9%. At the current density of 0.1, 0.2, 0.5, 1.0 and 2.0 A/g, the average reversible specific capacity is 936.3, 607.5, 429.5, 351.1 and 278 mA·h/g, respectively. When the current density returns to 0.1 A/g, the average reversible specific capacity can still reach 658.7 mA·h/g. The improvement of the electrochemical performance of Ag/MnO2 is attributed to the fact that the uniformly loaded conductive Ag particles significantly enhance the electrical conductivity of the electrode material, which is conducive to the transport of charged particles. In addition, the nano-structure of Ag/MnO2 composites shortens the transport path of lithium ions in the solid phase, thus increasing the diffusion rate of lithium ions.
Transition metal oxide MnO2 has great potential in battery storage because of its simple preparation process, abundant reserves, environmental protection and high theoretical specific capacity. In this paper, MnO2 nanosheets were prepared by exfoliating the hydrothermally synthesized δ-MnO2 by the swelling method. The Ag/MnO2 composites were obtained by loading Ag nanoparticles on the surface of MnO2 nanosheets under UV irradiation and NaBH4 reduction. The structure and morphology of Ag/MnO2 composites were characterized and their electrochemical properties were tested. The results show that the electrochemical performance of Ag/MnO2 as anode material for lithium ion batteries is obviously better than that of the pure phase δ-MnO2. The first reversible specific capacity of Ag/MnO2 at the current density of 100 mA/g reaches 1001.1 mA·h/g, and the coulombic efficiency is 79.9%. At the current density of 0.1, 0.2, 0.5, 1.0 and 2.0 A/g, the average reversible specific capacity is 936.3, 607.5, 429.5, 351.1 and 278 mA·h/g, respectively. When the current density returns to 0.1 A/g, the average reversible specific capacity can still reach 658.7 mA·h/g. The improvement of the electrochemical performance of Ag/MnO2 is attributed to the fact that the uniformly loaded conductive Ag particles significantly enhance the electrical conductivity of the electrode material, which is conducive to the transport of charged particles. In addition, the nano-structure of Ag/MnO2 composites shortens the transport path of lithium ions in the solid phase, thus increasing the diffusion rate of lithium ions.
2022, 39(5): 2280-2287.
doi: 10.13801/j.cnki.fhclxb.20210721.001
Abstract:
In order to detect pesticide residues on the surface of fruits, the flexible and wipeable Ag/cotton swab surface enhanced Raman scattering (SERS) substrate was prepared by in-situ growth process. By adjusting the concentration of silver nitrate in the growth medium, plasmonic cotton swab composite with uniform and dense Ag nanoparticles was obtained. The scanning electron microscopy, transmission electron microscopy, fourier transform infrared and thermogravimetric analysis indicated that the Ag nanoparticles were decorated on the surface of cotton swab. Nile Blue was used as a probe molecule to evaluate the SERS performance of Ag/cotton swab, furthermore the composite was employed for detecting thiram. The results show that the Ag nanoparticles with size 50 to 70 nm are uniformly distributed on the surface of cotton fiber. The Ag/cotton swab composite exhibits excellent SERS uniformity, with a relative standard deviation of 3.72%. The detection limit for Nile Blue is lower than 10−7 mol/L. The plasmonic Ag/cotton swab presented excellent flexibility and adsorption capability, which enable to adsorb and detect pesticide residue from irregular surface of pear directly by simple swabbing process, the sensiti-vity could achieve 10−6 mol/L. The manufacturing method can be easily extended to other cellulosic compounds, such as absorbent cotton and paper. This research proposes a new method to manufacture cost-effective, environmentally friendly and flexible SERS substrates.
In order to detect pesticide residues on the surface of fruits, the flexible and wipeable Ag/cotton swab surface enhanced Raman scattering (SERS) substrate was prepared by in-situ growth process. By adjusting the concentration of silver nitrate in the growth medium, plasmonic cotton swab composite with uniform and dense Ag nanoparticles was obtained. The scanning electron microscopy, transmission electron microscopy, fourier transform infrared and thermogravimetric analysis indicated that the Ag nanoparticles were decorated on the surface of cotton swab. Nile Blue was used as a probe molecule to evaluate the SERS performance of Ag/cotton swab, furthermore the composite was employed for detecting thiram. The results show that the Ag nanoparticles with size 50 to 70 nm are uniformly distributed on the surface of cotton fiber. The Ag/cotton swab composite exhibits excellent SERS uniformity, with a relative standard deviation of 3.72%. The detection limit for Nile Blue is lower than 10−7 mol/L. The plasmonic Ag/cotton swab presented excellent flexibility and adsorption capability, which enable to adsorb and detect pesticide residue from irregular surface of pear directly by simple swabbing process, the sensiti-vity could achieve 10−6 mol/L. The manufacturing method can be easily extended to other cellulosic compounds, such as absorbent cotton and paper. This research proposes a new method to manufacture cost-effective, environmentally friendly and flexible SERS substrates.
2022, 39(5): 2288-2298.
doi: 10.13801/j.cnki.fhclxb.20210813.001
Abstract:
In order to solve the problem of difficult recovery of hydrotalcite (LDH) adsorbent in sewage treatment, Fe3O4@Ni-Mg-Al-LDH magnetic hydrotalcite composite adsorption material was synthesized by combining magnetic Fe3O4 particles with Ni-Mg-Al-LDH hydrotalcite via double-drop precipitation method. The morphology and structure of the as-prepared Fe3O4@Ni-Mg-Al-LDH samples were characterized by SEM, XRD, FT-IR and N2 adsorption-desorption technologies. And it was used as adsorbent to simulate the wastewater treatment performance of Eosin Y dye. The results show that the adsorption of Eosin Y dye on Fe3O4@Ni-Mg-Al-LDH is very quickly within 20 min, while the adsorption tends to balance after 120 min. In addition, with the increase of the initial concentration of Eosin Y dye, the adsorption capacity of Fe3O4@Ni-Mg-Al-LDH sample for Eosin Y dye increases gradually and the maximum adsorption capacity is 108.6 mg·g−1. Meanwhile, the adsorption process of Eosin Y dye on Fe3O4@Ni-Mg-Al-LDH conforms to the Langmuir isothermal model and pseudo second-order kinetic equation, indicating that the adsorption process is dominated by the chemisorption of molecular layer, and the adsorption rate is controlled by surface diffusion and intra particle diffusion. After five cycles, the removal rate of Eosin Y dye still keeps above 80%, and the adsorbent is easy to be separated by magnetic field, implying that Fe3O4@Ni-Mg-Al-LDH magnetic hydrotalcite composite is a good adsorbent for dye wastewater.
In order to solve the problem of difficult recovery of hydrotalcite (LDH) adsorbent in sewage treatment, Fe3O4@Ni-Mg-Al-LDH magnetic hydrotalcite composite adsorption material was synthesized by combining magnetic Fe3O4 particles with Ni-Mg-Al-LDH hydrotalcite via double-drop precipitation method. The morphology and structure of the as-prepared Fe3O4@Ni-Mg-Al-LDH samples were characterized by SEM, XRD, FT-IR and N2 adsorption-desorption technologies. And it was used as adsorbent to simulate the wastewater treatment performance of Eosin Y dye. The results show that the adsorption of Eosin Y dye on Fe3O4@Ni-Mg-Al-LDH is very quickly within 20 min, while the adsorption tends to balance after 120 min. In addition, with the increase of the initial concentration of Eosin Y dye, the adsorption capacity of Fe3O4@Ni-Mg-Al-LDH sample for Eosin Y dye increases gradually and the maximum adsorption capacity is 108.6 mg·g−1. Meanwhile, the adsorption process of Eosin Y dye on Fe3O4@Ni-Mg-Al-LDH conforms to the Langmuir isothermal model and pseudo second-order kinetic equation, indicating that the adsorption process is dominated by the chemisorption of molecular layer, and the adsorption rate is controlled by surface diffusion and intra particle diffusion. After five cycles, the removal rate of Eosin Y dye still keeps above 80%, and the adsorbent is easy to be separated by magnetic field, implying that Fe3O4@Ni-Mg-Al-LDH magnetic hydrotalcite composite is a good adsorbent for dye wastewater.
2022, 39(5): 2299-2307.
doi: 10.13801/j.cnki.fhclxb.20210804.002
Abstract:
In order to study the bonding performance of bamboo scrimber-concrete interface connected by adhesive and construct bond-slip constitutive model, single shear tests were carried out on 44 bamboo scrimber-concrete bonding specimens. Plus, the effects of bond lengths, widths and thicknesses of bamboo scrimber, concrete strengths, and adhesive layer thicknesses on the shear performances of bond interfaces were also taken into consideration. The results of the study show that the failure modes of the specimens are almost the same under different influencing factors. That is, debonding failure occurs on the concrete surfaces, and the cracks between the bond interfaces develop from the loading stage to the free end. The failure process can be divided into elastic stage, softening stage and debonding platform stage. With the thickness of bamboo scrimber, the strength of concrete, and the thickness of glue layer increasing, the peak shear stress of the interface also increases; however, the peak shear stress decreases with the increase of the bonding width. According to the experimental bond-slip curve, a bond-slip constitutive model of bamboo scrimber-concrete interface was established. Compared with the experimental results, this model can better reflect the relationship between the shear stress and slippage of bamboo scrimber-concrete interface.
In order to study the bonding performance of bamboo scrimber-concrete interface connected by adhesive and construct bond-slip constitutive model, single shear tests were carried out on 44 bamboo scrimber-concrete bonding specimens. Plus, the effects of bond lengths, widths and thicknesses of bamboo scrimber, concrete strengths, and adhesive layer thicknesses on the shear performances of bond interfaces were also taken into consideration. The results of the study show that the failure modes of the specimens are almost the same under different influencing factors. That is, debonding failure occurs on the concrete surfaces, and the cracks between the bond interfaces develop from the loading stage to the free end. The failure process can be divided into elastic stage, softening stage and debonding platform stage. With the thickness of bamboo scrimber, the strength of concrete, and the thickness of glue layer increasing, the peak shear stress of the interface also increases; however, the peak shear stress decreases with the increase of the bonding width. According to the experimental bond-slip curve, a bond-slip constitutive model of bamboo scrimber-concrete interface was established. Compared with the experimental results, this model can better reflect the relationship between the shear stress and slippage of bamboo scrimber-concrete interface.
2022, 39(5): 2308-2317.
doi: 10.13801/j.cnki.fhclxb.20210804.001
Abstract:
Based on the research of the mechanical property of the new composite material “high strength stainless steel wire mesh reinforced engineered cementitious composite (ECC) (referred to as HSME)” and compression performance of confined concrete with this material, the compressive behavior of reinforced concrete (RC) short columns strengthened with high strength stainless steel wire mesh reinforced ECC was studied. The test parameters contained the reinforcement ratio and concrete strength of RC short columns, the ECC strength of reinforcement layer and the reinforcement ratio of transverse steel strands. The results indicate that, compared with the unstrengthened RC short columns, the specimens of HSME-strengthened RC short columns not only greatly increase the bearing capacity, but also crack without breaking when they are damaged, exhibiting obvious ductile failure pattern. Meanwhile, the cracking load, peak load and peak displacement are significantly increased. When the applied load reaches about 80% of the peak load and peak load, the maximum crack widths on the surface of the specimen are only 0.09 mm and 0.25 mm, respectively, showing excellent multi-slit cracking ability and crack control capabilities. The load-displacement curve of the HSME-strengthened RC short column is drawn as a skewed single-peak curve, which includes four stages: Elasticity, crack development, maximum load and bearing capacity decline. With the increasing of ECC compressive strength and transverse stainless steel strands reinforcement ratio, the cracking load and peak load of HSME strengthened columns increase significantly. Increasing the reinforcement ratio and concrete strength of the RC column could increase the peak load and the ductility of the HSME strengthened column.
Based on the research of the mechanical property of the new composite material “high strength stainless steel wire mesh reinforced engineered cementitious composite (ECC) (referred to as HSME)” and compression performance of confined concrete with this material, the compressive behavior of reinforced concrete (RC) short columns strengthened with high strength stainless steel wire mesh reinforced ECC was studied. The test parameters contained the reinforcement ratio and concrete strength of RC short columns, the ECC strength of reinforcement layer and the reinforcement ratio of transverse steel strands. The results indicate that, compared with the unstrengthened RC short columns, the specimens of HSME-strengthened RC short columns not only greatly increase the bearing capacity, but also crack without breaking when they are damaged, exhibiting obvious ductile failure pattern. Meanwhile, the cracking load, peak load and peak displacement are significantly increased. When the applied load reaches about 80% of the peak load and peak load, the maximum crack widths on the surface of the specimen are only 0.09 mm and 0.25 mm, respectively, showing excellent multi-slit cracking ability and crack control capabilities. The load-displacement curve of the HSME-strengthened RC short column is drawn as a skewed single-peak curve, which includes four stages: Elasticity, crack development, maximum load and bearing capacity decline. With the increasing of ECC compressive strength and transverse stainless steel strands reinforcement ratio, the cracking load and peak load of HSME strengthened columns increase significantly. Increasing the reinforcement ratio and concrete strength of the RC column could increase the peak load and the ductility of the HSME strengthened column.
2022, 39(5): 2318-2328.
doi: 10.13801/j.cnki.fhclxb.20210809.001
Abstract:
Steel bars-glass fiber-reinforced polymer (GFRP) bars reinforced concrete (RC) beams combined the advantages of steel bars and GFRP bars. Flexural capacity was increased compared with RC beams and serviceability performance was improved compared with the pure fiber-reinforced polymer (FRP) reinforced concrete beams, however, the investigation of fatigue behaviors was limited. In this study, seven beams were fabricated for fatigue tests, and the test parameters were load amplitude, effective reinforcement ratio and area ratio of FRP to steel bars (Af/As). The test results show that fatigue failure of the steel bars-GFRP bars RC beams start with fatigue fracture of steel bars and the fracture surface is significantly different from that of static tensile failure modes. Plane section assumption is verified under fatigue. The fatigue load amplitude has significant effects on the fatigue life. With the increase of fatigue load amplitude, strains in steel bars, GFRP bars and concrete increases, and the fatigue life decrease. The increase of effective reinforcement ratio contribute to decreasing mid-span deflection and crack width, and improve the serviceability. The increase of area ratio of FRP to steel bars (Af/As) has negative effects on the fatigue behaviors of steel bars-GFRP bars RC beams. The fatigue life decrease from 366 thousand cycles to 83 thousand cycles with Af/As increasing from 0.25 to 2.0. Different theoretical models for the mid-span deflection of beams under fatigue load are compared and the CEB-FIP 2010 presented satisfactory prediction, and thus is recommended.
Steel bars-glass fiber-reinforced polymer (GFRP) bars reinforced concrete (RC) beams combined the advantages of steel bars and GFRP bars. Flexural capacity was increased compared with RC beams and serviceability performance was improved compared with the pure fiber-reinforced polymer (FRP) reinforced concrete beams, however, the investigation of fatigue behaviors was limited. In this study, seven beams were fabricated for fatigue tests, and the test parameters were load amplitude, effective reinforcement ratio and area ratio of FRP to steel bars (Af/As). The test results show that fatigue failure of the steel bars-GFRP bars RC beams start with fatigue fracture of steel bars and the fracture surface is significantly different from that of static tensile failure modes. Plane section assumption is verified under fatigue. The fatigue load amplitude has significant effects on the fatigue life. With the increase of fatigue load amplitude, strains in steel bars, GFRP bars and concrete increases, and the fatigue life decrease. The increase of effective reinforcement ratio contribute to decreasing mid-span deflection and crack width, and improve the serviceability. The increase of area ratio of FRP to steel bars (Af/As) has negative effects on the fatigue behaviors of steel bars-GFRP bars RC beams. The fatigue life decrease from 366 thousand cycles to 83 thousand cycles with Af/As increasing from 0.25 to 2.0. Different theoretical models for the mid-span deflection of beams under fatigue load are compared and the CEB-FIP 2010 presented satisfactory prediction, and thus is recommended.
2022, 39(5): 2329-2339.
doi: 10.13801/j.cnki.fhclxb.20210622.005
Abstract:
When carbon fiber reinforced polymer (CFRP) is used to strengthen steel plate, CFRP is usually only adhered to the local part of the steel plate, which is susceptible to the influence of the peeling stress caused by the eccentricity of the specimen and the stress concentration at the lap edge. However, the peeling stress can be greatly reduced by using the full covering bonding method. The axial tensile tests of 30 CFRP reinforced steel plates with defects were carried out, and the unidirectional anti-stripping clamp was set up. The effects of adhesive type, defect length and thickness of carbon fiber plate on the reinforcement effect and failure mode were studied. The results show that the reinforcement effect of CFRP plate is significant, and the tensile strength of the specimen is signifi-cantly improved. Different adhesives have a great influence on the failure mode of the specimen. The specimen made of HJY adhesive is mainly destroyed by the adhesive, while the debonding phenomenon of the adhesive/steel appears in both Sika30 adhesive and WSB adhesive. With the increase of the defect length, the failure mode changes from the failure of CFRP plate to the failure of CFRP plate, steel plate or adhesive/steel debonding. The tensile strength of the specimen is less affected by the type of adhesive, but more affected by the size of the defect. When the defect increases, the tensile strength of the specimen decreases significantly. Based on the cohesive force model, the static mechanical tests were numerically simulated. The finite element analysis shows that the damage of adhesive starts from near the defect and then extends to both ends. However, increasing the thickness of CFRP plate can significantly increase the tensile strength of the specimen.
When carbon fiber reinforced polymer (CFRP) is used to strengthen steel plate, CFRP is usually only adhered to the local part of the steel plate, which is susceptible to the influence of the peeling stress caused by the eccentricity of the specimen and the stress concentration at the lap edge. However, the peeling stress can be greatly reduced by using the full covering bonding method. The axial tensile tests of 30 CFRP reinforced steel plates with defects were carried out, and the unidirectional anti-stripping clamp was set up. The effects of adhesive type, defect length and thickness of carbon fiber plate on the reinforcement effect and failure mode were studied. The results show that the reinforcement effect of CFRP plate is significant, and the tensile strength of the specimen is signifi-cantly improved. Different adhesives have a great influence on the failure mode of the specimen. The specimen made of HJY adhesive is mainly destroyed by the adhesive, while the debonding phenomenon of the adhesive/steel appears in both Sika30 adhesive and WSB adhesive. With the increase of the defect length, the failure mode changes from the failure of CFRP plate to the failure of CFRP plate, steel plate or adhesive/steel debonding. The tensile strength of the specimen is less affected by the type of adhesive, but more affected by the size of the defect. When the defect increases, the tensile strength of the specimen decreases significantly. Based on the cohesive force model, the static mechanical tests were numerically simulated. The finite element analysis shows that the damage of adhesive starts from near the defect and then extends to both ends. However, increasing the thickness of CFRP plate can significantly increase the tensile strength of the specimen.
2022, 39(5): 2340-2355.
doi: 10.13801/j.cnki.fhclxb.20210716.005
Abstract:
Multi-walled carbon nanotubes (MWCNTs) can strengthen and toughen cement-based materials. However, MWCNTs tend to agglomerate in cement paste. Up to now, there are few reports about how to improve the dispersion of MWCNTs by graphene oxide (GO) in cement paste. The effect of GO on the dispersion of MWCNTs in saturated calcium hydroxide solution (CH) used for simulated cement pore solution in the presence of sodium lignosulfonate (MN) was investigated by absorbance test, and the effects of GO on the mechanical properties, electrothermal properties, resistivity and pressure sensitivity of mortars containing MWCNTs were studied. The absorbance test shows that when the mass ratio of MN, GO and MWCNTs is 3∶1∶9, the dispersion of MWCNTs reaches the best. The mechanical properties test shows that when the optimal contents of MWCNTs and GO are 0.45wt% and 0.05wt% by the cement mass respectively, the 28 days flexural and compressive strength of the specimens are increased by 27.3% and 20.9%, the resistivity is reduced by 18.2%, and the resistance change rate is increased by 72.6%. The microstructure test shows that GO could further promote the dispersion of MWCNTs in cement-based materials, accelerate the hydration process of cement, densify the structure of cement paste. The synergy of GO and MWCNT increases the mechanical and durability and self-sensing properties of the cement mortar. In this study, the method to disperse MWCNT assisted by GO can be further extended to other carbon-based nano-reinforcing agents, and provides a new way for the development of self-sensing and intelligent cement-based materials.
Multi-walled carbon nanotubes (MWCNTs) can strengthen and toughen cement-based materials. However, MWCNTs tend to agglomerate in cement paste. Up to now, there are few reports about how to improve the dispersion of MWCNTs by graphene oxide (GO) in cement paste. The effect of GO on the dispersion of MWCNTs in saturated calcium hydroxide solution (CH) used for simulated cement pore solution in the presence of sodium lignosulfonate (MN) was investigated by absorbance test, and the effects of GO on the mechanical properties, electrothermal properties, resistivity and pressure sensitivity of mortars containing MWCNTs were studied. The absorbance test shows that when the mass ratio of MN, GO and MWCNTs is 3∶1∶9, the dispersion of MWCNTs reaches the best. The mechanical properties test shows that when the optimal contents of MWCNTs and GO are 0.45wt% and 0.05wt% by the cement mass respectively, the 28 days flexural and compressive strength of the specimens are increased by 27.3% and 20.9%, the resistivity is reduced by 18.2%, and the resistance change rate is increased by 72.6%. The microstructure test shows that GO could further promote the dispersion of MWCNTs in cement-based materials, accelerate the hydration process of cement, densify the structure of cement paste. The synergy of GO and MWCNT increases the mechanical and durability and self-sensing properties of the cement mortar. In this study, the method to disperse MWCNT assisted by GO can be further extended to other carbon-based nano-reinforcing agents, and provides a new way for the development of self-sensing and intelligent cement-based materials.
2022, 39(5): 2356-2368.
doi: 10.13801/j.cnki.fhclxb.20210622.002
Abstract:
In order to study the compressive service of polyvinyl alcohol fiber/cement composites under freezing condition after freeze-thaw cycle, the compressive test of polyvinyl alcohol fiber/cement composites under freezing condition was designed. Firstly, the samples were subjected to 0-300 freeze-thaw cycles, and then the samples were subjected to compressive test at −18℃ under continuous low temperature. The relationship between compressive stress and strain and its influence mechanism were analyzed. On this basis, combined with the principle of equiva-lent stress and statistical damage theory, the compressive constitutive model of polyvinyl alcohol fiber reinforced cement composites in frozen state was established, and the evolution characteristics of damage variable with the number of freeze-thaw cycles were discussed. The results show that: with the increase of freeze-thaw cycles, the peak compressive strength of polyvinyl alcohol fiber/cement composite decreases, the peak strain increases, and the brittleness is obvious at ultimate destruction. The elastic modulus of the sample under high freeze-thaw cycles is mainly provided by the pore ice in the sample. The established model can predict the compressive stress-strain relationship of polyvinyl alcohol fiber reinforced cement composites under freeze-thaw cycles. The freeze-thaw damage variate and total damage variate have significant correlation with freeze-thaw times.
In order to study the compressive service of polyvinyl alcohol fiber/cement composites under freezing condition after freeze-thaw cycle, the compressive test of polyvinyl alcohol fiber/cement composites under freezing condition was designed. Firstly, the samples were subjected to 0-300 freeze-thaw cycles, and then the samples were subjected to compressive test at −18℃ under continuous low temperature. The relationship between compressive stress and strain and its influence mechanism were analyzed. On this basis, combined with the principle of equiva-lent stress and statistical damage theory, the compressive constitutive model of polyvinyl alcohol fiber reinforced cement composites in frozen state was established, and the evolution characteristics of damage variable with the number of freeze-thaw cycles were discussed. The results show that: with the increase of freeze-thaw cycles, the peak compressive strength of polyvinyl alcohol fiber/cement composite decreases, the peak strain increases, and the brittleness is obvious at ultimate destruction. The elastic modulus of the sample under high freeze-thaw cycles is mainly provided by the pore ice in the sample. The established model can predict the compressive stress-strain relationship of polyvinyl alcohol fiber reinforced cement composites under freeze-thaw cycles. The freeze-thaw damage variate and total damage variate have significant correlation with freeze-thaw times.
2022, 39(5): 2369-2377.
doi: 10.13801/j.cnki.fhclxb.20210608.002
Abstract:
The calcined water treatment plant sludge powder (CWTS) was used to replace part of the cement to prepare high-volume sludge concrete, and the effect of the high-volume CWTS on the mechanical properties and microstructure of concrete was studied. The results show that although the high-volume CWTS is detrimental to the development of the 28-days compressive strength of concrete, 20wt% and 40wt% of the CWTS can significantly improve the 90-days compressive strength of concrete. The CWTS has pozzolanic reactivity and filling effect, which makes the 90-days pore structure of concrete mixed with 20wt%‒40wt%CWTS significantly refined, and the harmful pore volume (>1 µm) is significantly reduced. Meanwhile, it is observed from the nanoscale characteristics that adding 20wt%CWTS can significantly reduce the content of pore phase and unhydrated phase in the matrix, and increase the volume fraction of C—S—H phase, especially the high-density C—S—H phase. In addition, the addition of 20wt%CWTS can reduce the width of the interface transition zone (ITZ) by 20%, the addition of 40wt%CWTS and the control group (0wt%CWTS) have similar ITZ width. Therefore, using a large amount (20wt%‒40wt%) of CWTS to replace cement to prepare concrete not only has better economic and environmental benefits, but also benefits the improvement of its 90-days mechanical properties and microstructure.
The calcined water treatment plant sludge powder (CWTS) was used to replace part of the cement to prepare high-volume sludge concrete, and the effect of the high-volume CWTS on the mechanical properties and microstructure of concrete was studied. The results show that although the high-volume CWTS is detrimental to the development of the 28-days compressive strength of concrete, 20wt% and 40wt% of the CWTS can significantly improve the 90-days compressive strength of concrete. The CWTS has pozzolanic reactivity and filling effect, which makes the 90-days pore structure of concrete mixed with 20wt%‒40wt%CWTS significantly refined, and the harmful pore volume (>1 µm) is significantly reduced. Meanwhile, it is observed from the nanoscale characteristics that adding 20wt%CWTS can significantly reduce the content of pore phase and unhydrated phase in the matrix, and increase the volume fraction of C—S—H phase, especially the high-density C—S—H phase. In addition, the addition of 20wt%CWTS can reduce the width of the interface transition zone (ITZ) by 20%, the addition of 40wt%CWTS and the control group (0wt%CWTS) have similar ITZ width. Therefore, using a large amount (20wt%‒40wt%) of CWTS to replace cement to prepare concrete not only has better economic and environmental benefits, but also benefits the improvement of its 90-days mechanical properties and microstructure.
2022, 39(5): 2378-2386.
doi: 10.13801/j.cnki.fhclxb.20210730.002
Abstract:
In the process of high-speed flight, the temperature of the aircraft rises rapidly. The sealing material between the aircraft cabin should not only have excellent high-temperature resistance, but also have a low thermal conductivity to assist in blocking the heat transfer between the cabin, and have excellent mechanical properties to prevent it from being damaged. Used hollow ceramic microspheres as aggregates, added phenolic resin and phosphate curing system to prepare organic/inorganic hybrid high-temperature resistant and tough composites. The composites were subjected to high-temperature treatment to study the changes of the composites before and after the high-temperature treatment. The compressive strength, compression deformation ability, microstructure and composition changes of the composites before and after the high-temperature treatment were characterized by mechanical performance test, SEM observation, XRD and FT-IR. In addition, the high-temperature resistance performance of the composites was tested by flame combustion. The overall results show that the prepared composites have high compressive strength and excellent toughness. The macro morphology of the composites is not affected by the high-temperature treatment at 1000℃ for 600 s, which indicates that the composites have high thermal stability. And the thermal conductivity test results show that the increase in the content of hollow ceramic microbeads, the addition of phenolic resin and the high-temperature treatment all cause the thermal conductivity to decrease, and the lowest thermal conductivity is as low as 0.16 W/(m·K).
In the process of high-speed flight, the temperature of the aircraft rises rapidly. The sealing material between the aircraft cabin should not only have excellent high-temperature resistance, but also have a low thermal conductivity to assist in blocking the heat transfer between the cabin, and have excellent mechanical properties to prevent it from being damaged. Used hollow ceramic microspheres as aggregates, added phenolic resin and phosphate curing system to prepare organic/inorganic hybrid high-temperature resistant and tough composites. The composites were subjected to high-temperature treatment to study the changes of the composites before and after the high-temperature treatment. The compressive strength, compression deformation ability, microstructure and composition changes of the composites before and after the high-temperature treatment were characterized by mechanical performance test, SEM observation, XRD and FT-IR. In addition, the high-temperature resistance performance of the composites was tested by flame combustion. The overall results show that the prepared composites have high compressive strength and excellent toughness. The macro morphology of the composites is not affected by the high-temperature treatment at 1000℃ for 600 s, which indicates that the composites have high thermal stability. And the thermal conductivity test results show that the increase in the content of hollow ceramic microbeads, the addition of phenolic resin and the high-temperature treatment all cause the thermal conductivity to decrease, and the lowest thermal conductivity is as low as 0.16 W/(m·K).
2022, 39(5): 2387-2397.
doi: 10.13801/j.cnki.fhclxb.20210629.003
Abstract:
The relationship between the damage and strain as well as the relationship between the maximum strain and fracture position were investigated by the quasi-static uniaxial tensile test of plain weave C/SiC composite using digital image correlation (DIC) technology analysis. The variation of material’s internal structure during the damage evolution has been explored by analyzing the material’s pore and fracture. The results show that the strain of the material under tensile load is not well-distributed. The damage difference between layers and their inter-action result in the constant variation of maximum strain position. With the accumulation of damage, fracture occurs first to the position of maximum strain and the fracture failure location of this material is often closely related to its structural weakness and the stress and strain level. At the moment of material fracture, the multiple pull-out mechanism and the structural difference in each of layers lead to different failure positions among layers, resulting in delamination failure.
The relationship between the damage and strain as well as the relationship between the maximum strain and fracture position were investigated by the quasi-static uniaxial tensile test of plain weave C/SiC composite using digital image correlation (DIC) technology analysis. The variation of material’s internal structure during the damage evolution has been explored by analyzing the material’s pore and fracture. The results show that the strain of the material under tensile load is not well-distributed. The damage difference between layers and their inter-action result in the constant variation of maximum strain position. With the accumulation of damage, fracture occurs first to the position of maximum strain and the fracture failure location of this material is often closely related to its structural weakness and the stress and strain level. At the moment of material fracture, the multiple pull-out mechanism and the structural difference in each of layers lead to different failure positions among layers, resulting in delamination failure.
2022, 39(5): 2398-2404.
doi: 10.13801/j.cnki.fhclxb.20210615.002
Abstract:
Glass fiber materials, a kind of filter medium, have advantages of high filtration accuracy and large holding capacity of pollution. It is usually composited with nonwoven materials to improve its processability and service life by overcoming the poor folding ability and pressure resistance. However, the air permeability of this kind of composites will be decreased caused by the hot melt adhesive coating method. In this paper, this issue is addressed by creating a melt-blown fibrous bonding layer of hot melt resin rather than just coating a compact film between glass fiber medium and spunbond nonwoven materials. By this approach, the loading amount of melt-blown fibrous layer plays a significant role in the filtration performance of this filter medium. The results show that a high peel strength can be achieved but without compromising the permeability when loading 8 g/m2 melt-blown fibers. And, considering the properties of the product and the production, a filter medium product with good mechanical properties and filtration performance can be fabricated when setting the loading amount of melt-blown fibers, gauge, temperature, and speed of hot calender at 8 g/m2, 0.3 mm, 120℃ and 15 m/min, respectively.
Glass fiber materials, a kind of filter medium, have advantages of high filtration accuracy and large holding capacity of pollution. It is usually composited with nonwoven materials to improve its processability and service life by overcoming the poor folding ability and pressure resistance. However, the air permeability of this kind of composites will be decreased caused by the hot melt adhesive coating method. In this paper, this issue is addressed by creating a melt-blown fibrous bonding layer of hot melt resin rather than just coating a compact film between glass fiber medium and spunbond nonwoven materials. By this approach, the loading amount of melt-blown fibrous layer plays a significant role in the filtration performance of this filter medium. The results show that a high peel strength can be achieved but without compromising the permeability when loading 8 g/m2 melt-blown fibers. And, considering the properties of the product and the production, a filter medium product with good mechanical properties and filtration performance can be fabricated when setting the loading amount of melt-blown fibers, gauge, temperature, and speed of hot calender at 8 g/m2, 0.3 mm, 120℃ and 15 m/min, respectively.
2022, 39(5): 2405-2411.
doi: 10.13801/j.cnki.fhclxb.20210805.004
Abstract:
In order to prepare high entropy boride ceramics with excellent performance, (Hf0.2Zr0.2Ta0.2Ti0.2Me0.2)B2(Me=V, W) high entropy boride ceramics were fabricated though boro/carbothermal reduction method combined with spark plasma sintering (SPS) in this paper. The effects of V and W on phase composition, morphology and mechanical properties of (Hf0.2Zr0.2Ta0.2Ti0.2Me0.2)B2(Me=V, W) high entropy boride ceramics were investigated. Results show that (Hf0.2Zr0.2Ta0.2Ti0.2Me0.2)B2(Me=V, W) high entropy boride powders are failed formed single-phase solid solution in 1600℃, but (Hf0.2Zr0.2Ta0.2V0.2Ti0.2)B2 is formed a complete solid solution after 2 000℃ sintering. However, WB phase is still detected in (Hf0.2Zr0.2Ta0.2W0.2Ti0.2)B2 sample. The density of (Hf0.2Zr0.2Ta0.2V0.2Ti0.2)B2(93.1%) is lower than that of (Hf0.2Zr0.2Ta0.2W0.2Ti0.2)B2(96.7%), but its grain size is smaller. The hardness of (Hf0.2Zr0.2Ta0.2W0.2Ti0.2)B2(24.0 GPa) is higher, but the fracture toughness is lower than that of (Hf0.2Zr0.2Ta0.2V0.2Ti0.2)B2 (3.32 MPa·m1/2).
In order to prepare high entropy boride ceramics with excellent performance, (Hf0.2Zr0.2Ta0.2Ti0.2Me0.2)B2(Me=V, W) high entropy boride ceramics were fabricated though boro/carbothermal reduction method combined with spark plasma sintering (SPS) in this paper. The effects of V and W on phase composition, morphology and mechanical properties of (Hf0.2Zr0.2Ta0.2Ti0.2Me0.2)B2(Me=V, W) high entropy boride ceramics were investigated. Results show that (Hf0.2Zr0.2Ta0.2Ti0.2Me0.2)B2(Me=V, W) high entropy boride powders are failed formed single-phase solid solution in 1600℃, but (Hf0.2Zr0.2Ta0.2V0.2Ti0.2)B2 is formed a complete solid solution after 2 000℃ sintering. However, WB phase is still detected in (Hf0.2Zr0.2Ta0.2W0.2Ti0.2)B2 sample. The density of (Hf0.2Zr0.2Ta0.2V0.2Ti0.2)B2(93.1%) is lower than that of (Hf0.2Zr0.2Ta0.2W0.2Ti0.2)B2(96.7%), but its grain size is smaller. The hardness of (Hf0.2Zr0.2Ta0.2W0.2Ti0.2)B2(24.0 GPa) is higher, but the fracture toughness is lower than that of (Hf0.2Zr0.2Ta0.2V0.2Ti0.2)B2 (3.32 MPa·m1/2).
2022, 39(5): 2412-2420.
doi: 10.13801/j.cnki.fhclxb.20210616.004
Abstract:
In order to obtain high performance ceramic cores for investment casting of superalloy single crystal blade. In this paper, the short carbon fibers (Csf) were uniformly dispersed in silica-based ceramic slurry though synergistic effect of ultrasonic vibration and mechanical stirring, and the green cores were prepared by injection molding method and sintered in air and N2 atmosphere, respectively. The microstructure evolution and phase transformation during heating process were thoroughly observed and analyzed, and further revealed the densification behavior of Csf reinforced silica-based ceramic cores under two sintering atmospheres. The results indicate that the Csf can increase the mass transfer distance between ceramic particles, and provide carbon source to grow in-situ SiC crystals and affect the crystallization of cristobalite in matrix. Therefore, the diffusion and migration of solid phases and viscous flow of liquid phase in ceramic cores are inhibited by the stereo interlocked network of Csf and the high melt point crystalline phases at high temperature. Moreover, the open porosity of silica-based ceramic cores sintered in both air and N2 atmosphere is increased with the increase of Csf content, while the shrinkage is gradually decreased. When the fiber content is 1.5vol%, as for samples sintered in air atmosphere, the highest open porosities in air and N2 sintering atmospheres are about 42.95% and 39.50%, while the least shrinkages are about 0.64% and 0.48%, respectively. It can prove that the Csf and high melting point crystals have significantly influence on the sintering densification behavior of silica-based ceramic cores.
In order to obtain high performance ceramic cores for investment casting of superalloy single crystal blade. In this paper, the short carbon fibers (Csf) were uniformly dispersed in silica-based ceramic slurry though synergistic effect of ultrasonic vibration and mechanical stirring, and the green cores were prepared by injection molding method and sintered in air and N2 atmosphere, respectively. The microstructure evolution and phase transformation during heating process were thoroughly observed and analyzed, and further revealed the densification behavior of Csf reinforced silica-based ceramic cores under two sintering atmospheres. The results indicate that the Csf can increase the mass transfer distance between ceramic particles, and provide carbon source to grow in-situ SiC crystals and affect the crystallization of cristobalite in matrix. Therefore, the diffusion and migration of solid phases and viscous flow of liquid phase in ceramic cores are inhibited by the stereo interlocked network of Csf and the high melt point crystalline phases at high temperature. Moreover, the open porosity of silica-based ceramic cores sintered in both air and N2 atmosphere is increased with the increase of Csf content, while the shrinkage is gradually decreased. When the fiber content is 1.5vol%, as for samples sintered in air atmosphere, the highest open porosities in air and N2 sintering atmospheres are about 42.95% and 39.50%, while the least shrinkages are about 0.64% and 0.48%, respectively. It can prove that the Csf and high melting point crystals have significantly influence on the sintering densification behavior of silica-based ceramic cores.
2022, 39(5): 2421-2429.
doi: 10.13801/j.cnki.fhclxb.20210609.005
Abstract:
The supercooling and phase separation of hydrated salt phase change heat storage materials are two key issues which affect its thermal stability and thermal performance. MgCl2∙6H2O (MCH) and MgSO4∙7H2O (MSH) are used as the research materials, which are the phase change heat storage materials at moderate and low tempera-tures, and activated carbon (ACC) is used as the additive, The MCH-MSH-ACC composite phase change system was prepared by the melt blending method, then, the MCH-MSH-ACC/PA composite phase change system is prepared with paraffin (PA) as the modifier. The effects of PA on the phase change enthalpy, phase change temperature, subcooling degree and phase separation phenomenon of the composite phase change materials were studied. The re-sults show that the addition of trace PA is beneficial to improve the phase change heat storage performance of the MSH-MCH-ACC/PA system. Compared with other PA content systems, the system with 0.5wt% PA perform the shortest time in the heat storage stage and the maximum heat release time in the exothermic phase, whose initial phase change enthalpy value reach 321.75 kJ/kg, and the stable enthalpy is 310.25 kJ/kg after the cycle tests. The prepared new blend MSH-MCH-3wt%ACC/0.5wt%PA composite material has good heat storage property and good thermal cycle stability.
The supercooling and phase separation of hydrated salt phase change heat storage materials are two key issues which affect its thermal stability and thermal performance. MgCl2∙6H2O (MCH) and MgSO4∙7H2O (MSH) are used as the research materials, which are the phase change heat storage materials at moderate and low tempera-tures, and activated carbon (ACC) is used as the additive, The MCH-MSH-ACC composite phase change system was prepared by the melt blending method, then, the MCH-MSH-ACC/PA composite phase change system is prepared with paraffin (PA) as the modifier. The effects of PA on the phase change enthalpy, phase change temperature, subcooling degree and phase separation phenomenon of the composite phase change materials were studied. The re-sults show that the addition of trace PA is beneficial to improve the phase change heat storage performance of the MSH-MCH-ACC/PA system. Compared with other PA content systems, the system with 0.5wt% PA perform the shortest time in the heat storage stage and the maximum heat release time in the exothermic phase, whose initial phase change enthalpy value reach 321.75 kJ/kg, and the stable enthalpy is 310.25 kJ/kg after the cycle tests. The prepared new blend MSH-MCH-3wt%ACC/0.5wt%PA composite material has good heat storage property and good thermal cycle stability.
2022, 39(5): 2430-2440.
doi: 10.13801/j.cnki.fhclxb.20210604.001
Abstract:
Compared with the traditional design method of composite cylindrical shells with straight fiber laminate, variable stiffness composite cylindrical shells can greatly increase the design space of composite material and thus achieve higher buckling loads by means of the curved fiber laminate. To describe the curved fiber path precisely, it is necessary to establish high-fidelity detailed finite element model for variable stiffness composite cylindrical shells. Therefore, it brings great challenges to the efficiency of buckling analysis and optimization of variable stiffness composite cylindrical shells. In this paper, a variable-fidelity transfer learning model was proposed for the fast prediction of linear buckling load and post-buckling load of variable stiffness composite cylindrical shells. Firstly, the appropriate high-fidelity model and low-fidelity model of variable stiffness composite cylindrical shells were constructed. Then, the deep neural network was established and trained with a large number of low-fidelity samples as the source dataset, and the pre-trained model was obtained. Finally, the last layer was retained by fine-tuning with a small number of high-fidelity samples as the target dataset, and the variable-fidelity transfer learning model was constructed after the retraining on the pre-trained model. The example results of linear buckling and post-buckling load prediction of variable stiffness composite cylindrical shells indicate that, the computational cost of variable-fidelity transfer learning model can reduce by 47.7% and 62.3% than surrogates built by the high-fidelity samples directly when achieving similar prediction accuracy, showing the advantage of high prediction efficiency of the proposed method. Besides, compared with the variable-fidelity surrogate models built by the bridge function and Co-Kriging, the proposed method shows the best prediction accuracy with different combinations of high-fidelity and low-fidelity samples, which demonstrates the advantage of high prediction accuracy of the proposed method.
Compared with the traditional design method of composite cylindrical shells with straight fiber laminate, variable stiffness composite cylindrical shells can greatly increase the design space of composite material and thus achieve higher buckling loads by means of the curved fiber laminate. To describe the curved fiber path precisely, it is necessary to establish high-fidelity detailed finite element model for variable stiffness composite cylindrical shells. Therefore, it brings great challenges to the efficiency of buckling analysis and optimization of variable stiffness composite cylindrical shells. In this paper, a variable-fidelity transfer learning model was proposed for the fast prediction of linear buckling load and post-buckling load of variable stiffness composite cylindrical shells. Firstly, the appropriate high-fidelity model and low-fidelity model of variable stiffness composite cylindrical shells were constructed. Then, the deep neural network was established and trained with a large number of low-fidelity samples as the source dataset, and the pre-trained model was obtained. Finally, the last layer was retained by fine-tuning with a small number of high-fidelity samples as the target dataset, and the variable-fidelity transfer learning model was constructed after the retraining on the pre-trained model. The example results of linear buckling and post-buckling load prediction of variable stiffness composite cylindrical shells indicate that, the computational cost of variable-fidelity transfer learning model can reduce by 47.7% and 62.3% than surrogates built by the high-fidelity samples directly when achieving similar prediction accuracy, showing the advantage of high prediction efficiency of the proposed method. Besides, compared with the variable-fidelity surrogate models built by the bridge function and Co-Kriging, the proposed method shows the best prediction accuracy with different combinations of high-fidelity and low-fidelity samples, which demonstrates the advantage of high prediction accuracy of the proposed method.
2022, 39(5): 2441-2448.
doi: 10.13801/j.cnki.fhclxb.20210604.003
Abstract:
The traditional physical model has poor interpretability and low prediction accuracy in evaluating remaining useful life of silicon foam materials. This paper presents a remaining useful life prediction method based on double exponential particle filter model. Based on the stress relaxation mechanism of silicon foam material, a more interpretability double exponential stress degradation model was established by selecting the load retention rate of silicon foam structure as the characteristic quantity. Firstly, the least square method was used to fit the observed data for initializing the model parameters and health state. Then, the Bayesian theory was used to track the state of historical samples, update the state transfer function, and realize the degradation trend prediction of load retention rate and remaining useful life assessment. The generalization applicability and accuracy of the double exponential particle filter model for predicting the residual life of silicon foam materials were verified by simulation and experiment. At the same time, the prediction results were compared with those of the traditional exponential model. The results show that the proposed method has better prediction accuracy and stability.
The traditional physical model has poor interpretability and low prediction accuracy in evaluating remaining useful life of silicon foam materials. This paper presents a remaining useful life prediction method based on double exponential particle filter model. Based on the stress relaxation mechanism of silicon foam material, a more interpretability double exponential stress degradation model was established by selecting the load retention rate of silicon foam structure as the characteristic quantity. Firstly, the least square method was used to fit the observed data for initializing the model parameters and health state. Then, the Bayesian theory was used to track the state of historical samples, update the state transfer function, and realize the degradation trend prediction of load retention rate and remaining useful life assessment. The generalization applicability and accuracy of the double exponential particle filter model for predicting the residual life of silicon foam materials were verified by simulation and experiment. At the same time, the prediction results were compared with those of the traditional exponential model. The results show that the proposed method has better prediction accuracy and stability.
2022, 39(5): 2449-2459.
doi: 10.13801/j.cnki.fhclxb.20210616.007
Abstract:
Composite interference fit joints have become an advanced joint form because they can significantly reduce the stress concentration around the holes and thus improve the bearing capacity and fatigue life of the structure. However, due to the low interlaminar strength of composite materials, unreasonable interference bolt structure style, dimension and installation method can easily cause hole wall delamination and reduce the structure bearing capacity. To solve this problem, an interference joint structure based on sleeve-type bolts was proposed, and the experiment and finite element analysis of the structure during installation were carried out. The changes of installation force and damage around hole were measured. A damage prediction model based on progressive damage and cohesive element of composite was established by taking into full account the factors of intralaminar damage and interlaminar delamination. Through the comparative analysis of the insertion force and damage of sleeving bolts with 2.2% interference, it is found that the finite element model fits well with the test results, which proves the accuracy of the model. The reason why sleeve-type bolt can improve the quality of hole wall is explained and the range of reliable interference is put forward through comparative analysis under different interference and critical interference percentage calculation.
Composite interference fit joints have become an advanced joint form because they can significantly reduce the stress concentration around the holes and thus improve the bearing capacity and fatigue life of the structure. However, due to the low interlaminar strength of composite materials, unreasonable interference bolt structure style, dimension and installation method can easily cause hole wall delamination and reduce the structure bearing capacity. To solve this problem, an interference joint structure based on sleeve-type bolts was proposed, and the experiment and finite element analysis of the structure during installation were carried out. The changes of installation force and damage around hole were measured. A damage prediction model based on progressive damage and cohesive element of composite was established by taking into full account the factors of intralaminar damage and interlaminar delamination. Through the comparative analysis of the insertion force and damage of sleeving bolts with 2.2% interference, it is found that the finite element model fits well with the test results, which proves the accuracy of the model. The reason why sleeve-type bolt can improve the quality of hole wall is explained and the range of reliable interference is put forward through comparative analysis under different interference and critical interference percentage calculation.
2022, 39(5): 2460-2469.
doi: 10.13801/j.cnki.fhclxb.20210617.005
Abstract:
Accurately predicting and controlling the process-induced deformation of a variable stiffness structure is a key to obtain a reasonable variable stiffness design, the process-induced deformation of a composite structure will not only affect the stiffness and strength of the structure, but also affect the assembly performance of the structure. Based on the automatic placement technology, a process-oriented tow-course-panel multi-level three-dimensional variable stiffness finite element model algorithm was proposed. Combining the Kamal autocatalytic reaction curing kinetic model and the generalized Maxwell viscoelastic constitutive model for thermo-chemical-mechanical multi-field coupling analysis, the changes in the internal temperature field, curing degree field and residual stress field of the structure during the curing process were calculated, and the curing deformation of the variable stiffness structure was finally obtained. The results show that: when T0=45°, T1<T0, the curing deformation of the variable stiffness structure increases with the increase of T1. When T1>T0, the curing deformation of the variable stiffness structure decreases with the increase of T1. The 100% coverage rule effectively reduces the curing deformation of the structure, while the 0% coverage rule increases the curing deformation. The method proposed in this paper can effectively predict the effect of process parameters on the process-induced deformation of variable stiffness structures.
Accurately predicting and controlling the process-induced deformation of a variable stiffness structure is a key to obtain a reasonable variable stiffness design, the process-induced deformation of a composite structure will not only affect the stiffness and strength of the structure, but also affect the assembly performance of the structure. Based on the automatic placement technology, a process-oriented tow-course-panel multi-level three-dimensional variable stiffness finite element model algorithm was proposed. Combining the Kamal autocatalytic reaction curing kinetic model and the generalized Maxwell viscoelastic constitutive model for thermo-chemical-mechanical multi-field coupling analysis, the changes in the internal temperature field, curing degree field and residual stress field of the structure during the curing process were calculated, and the curing deformation of the variable stiffness structure was finally obtained. The results show that: when T0=45°, T1<T0, the curing deformation of the variable stiffness structure increases with the increase of T1. When T1>T0, the curing deformation of the variable stiffness structure decreases with the increase of T1. The 100% coverage rule effectively reduces the curing deformation of the structure, while the 0% coverage rule increases the curing deformation. The method proposed in this paper can effectively predict the effect of process parameters on the process-induced deformation of variable stiffness structures.
2022, 39(5): 2470-2481.
doi: 10.13801/j.cnki.fhclxb.20210601.005
Abstract:
Using the non-isothermal differential scanning calorimetry method, the viscosity test and Fourier infrared spectrum scanning technique, the curing characteristics of epoxy resin system under ultrasonic vibration with different amplitudes were studied. Based on Flynn-Wall-Ozawa/FWO, Kissinger-Akahira-Sunose/KAS and Boswell integral kinetic models, the activation energy of resin system under various ultrasonic vibration conditions was calculated. Combined with the Malek most probable function method, the curing reaction kinetic equation of resin system under ultrasonic vibration was obtained, which was verified by experimentally recorded curing degree. Results show that the greater the ultrasonic vibration amplitude, the more obvious the reduction of viscosity of the epoxy resin system. The activation energy of resin system increases under ultrasonic vibration with smaller amplitude, and the activation energy decreases significantly when the amplitude increases. The infrared spectrum test of cured product shows that with the increase of the ultrasonic amplitude, the hydroxyl absorption peak drops, which probably due to the fact that the ultrasonic effect accelerates the amine group addition reaction or the hydroxyl etherification reaction. The resin curing reaction model under ultrasonic vibration is in agreement with the form of autocatalytic model, which shows that ultrasonic effect cannot change curing reaction mechanism of epoxy resin system. The above research results have certain guiding significance for the design and optimization of ultrasonic vibration assisted resin transfer molding (RTM) technique for manufacturing carbon fiber reinforced polymer composites.
Using the non-isothermal differential scanning calorimetry method, the viscosity test and Fourier infrared spectrum scanning technique, the curing characteristics of epoxy resin system under ultrasonic vibration with different amplitudes were studied. Based on Flynn-Wall-Ozawa/FWO, Kissinger-Akahira-Sunose/KAS and Boswell integral kinetic models, the activation energy of resin system under various ultrasonic vibration conditions was calculated. Combined with the Malek most probable function method, the curing reaction kinetic equation of resin system under ultrasonic vibration was obtained, which was verified by experimentally recorded curing degree. Results show that the greater the ultrasonic vibration amplitude, the more obvious the reduction of viscosity of the epoxy resin system. The activation energy of resin system increases under ultrasonic vibration with smaller amplitude, and the activation energy decreases significantly when the amplitude increases. The infrared spectrum test of cured product shows that with the increase of the ultrasonic amplitude, the hydroxyl absorption peak drops, which probably due to the fact that the ultrasonic effect accelerates the amine group addition reaction or the hydroxyl etherification reaction. The resin curing reaction model under ultrasonic vibration is in agreement with the form of autocatalytic model, which shows that ultrasonic effect cannot change curing reaction mechanism of epoxy resin system. The above research results have certain guiding significance for the design and optimization of ultrasonic vibration assisted resin transfer molding (RTM) technique for manufacturing carbon fiber reinforced polymer composites.
2022, 39(5): 2482-2494.
doi: 10.13801/j.cnki.fhclxb.20210630.001
Abstract:
A three-dimensional elastoplastic damage constitutive model which takes into account the nonlinear mechanical response, strain rate effects of composites, material properties degradation due to damage evolution was proposed. A modified plastic model was used to characterize the nonlinear mechanical response under dynamic load. To accurately describe the elastoplastic mechanical response of composite materials under dynamic load, the rate-dependent amplification factor was introduced to modify the plastic hardening law under static condition. In order to alleviate mesh sensitivity of finite element analysis results, the“Crack Band Theory”was applied to regularize the softening branch of the material constitutive model. The Selective Range Inverse Parabolic Interpolation algorithm was used to calculate the angle of the initial fracture plane of matrix damage and the angle of the fiber kinking/splitting plane. User-defined material subroutine VUMAT containing the numerical integration algorithm was coded and implemented in finite element procedure ABAQUS V6.14. The efficiency of the material constitutive model was demonstrated through progressive failure analysis of IM7/8552 carbon fiber/epoxy composite laminates, the mechanical behavior of which demonstrates significant nonlinear mechanical response. The numerical results agree well with the experimental data reported in the literature. It is shown that the rate-dependent three-dimensional elastoplastic damage constitutive model can predict the mechanical behavior of composites under dynamic loads with sufficient accuracy. The proposed approach provides an efficient method for the design of composite components and structures.
A three-dimensional elastoplastic damage constitutive model which takes into account the nonlinear mechanical response, strain rate effects of composites, material properties degradation due to damage evolution was proposed. A modified plastic model was used to characterize the nonlinear mechanical response under dynamic load. To accurately describe the elastoplastic mechanical response of composite materials under dynamic load, the rate-dependent amplification factor was introduced to modify the plastic hardening law under static condition. In order to alleviate mesh sensitivity of finite element analysis results, the“Crack Band Theory”was applied to regularize the softening branch of the material constitutive model. The Selective Range Inverse Parabolic Interpolation algorithm was used to calculate the angle of the initial fracture plane of matrix damage and the angle of the fiber kinking/splitting plane. User-defined material subroutine VUMAT containing the numerical integration algorithm was coded and implemented in finite element procedure ABAQUS V6.14. The efficiency of the material constitutive model was demonstrated through progressive failure analysis of IM7/8552 carbon fiber/epoxy composite laminates, the mechanical behavior of which demonstrates significant nonlinear mechanical response. The numerical results agree well with the experimental data reported in the literature. It is shown that the rate-dependent three-dimensional elastoplastic damage constitutive model can predict the mechanical behavior of composites under dynamic loads with sufficient accuracy. The proposed approach provides an efficient method for the design of composite components and structures.
2022, 39(5): 2495-2503.
doi: 10.13801/j.cnki.fhclxb.20210616.006
Abstract:
The effects of the graphene orientation on interfacial thermal conductivity of graphene/nitrate compo-sites with binary nitrate Solar salt(NaNO3/KNO3 mass ratio of 6∶4) as substrate and graphene as filler was investi-gated by non-equilibrium molecular dynamics (NEMD) method. It is shown that the interfacial thermal conductance can be considerably enhanced from 46.36 MW·m−2·K−1 to 80.03 MW·m−2·K−1 as the angle θ between the graphene surface and the heat flux direction (i.e., z direction) decreases from 90° to 0°. As the angle θ decreases, the effective projection of the graphene plane in the direction of heat flow is enhanced, and more heat will be transported along the graphene plane. The results of the vibrational density of state (DOS) clearly signify that heat flow at the interface changes from transport across the graphene plane to efficient transport along the graphene plane with the decrease of angle between graphene and heat flow. Moreover, the nitrates form a similar dense layer around the graphene for all different orientation angles, which would also promote the enhancement of the thermal conductance. Finally, the thermal conductivity of the graphene/nitrates composites with different orientations at the microscale is predicted by the effective medium theory. It is found that the thermal conductivity of the composite decreases with the orientation angle, but increases with the volume fraction and the length of the graphene.
The effects of the graphene orientation on interfacial thermal conductivity of graphene/nitrate compo-sites with binary nitrate Solar salt(NaNO3/KNO3 mass ratio of 6∶4) as substrate and graphene as filler was investi-gated by non-equilibrium molecular dynamics (NEMD) method. It is shown that the interfacial thermal conductance can be considerably enhanced from 46.36 MW·m−2·K−1 to 80.03 MW·m−2·K−1 as the angle θ between the graphene surface and the heat flux direction (i.e., z direction) decreases from 90° to 0°. As the angle θ decreases, the effective projection of the graphene plane in the direction of heat flow is enhanced, and more heat will be transported along the graphene plane. The results of the vibrational density of state (DOS) clearly signify that heat flow at the interface changes from transport across the graphene plane to efficient transport along the graphene plane with the decrease of angle between graphene and heat flow. Moreover, the nitrates form a similar dense layer around the graphene for all different orientation angles, which would also promote the enhancement of the thermal conductance. Finally, the thermal conductivity of the graphene/nitrates composites with different orientations at the microscale is predicted by the effective medium theory. It is found that the thermal conductivity of the composite decreases with the orientation angle, but increases with the volume fraction and the length of the graphene.
2022, 39(5): 2504-2514.
doi: 10.13801/j.cnki.fhclxb.20210622.004
Abstract:
Fiber reinforced composite laminates are susceptible to delamination damage due to relatively weak inter-laminar mechanical properties. The growth of delamination is always accompanied by fiber bridging, which can significantly increase the resistance of delamination propagation, especially in the case of multidirectional lami-nates. Compared with the traditional bilinear model, a trilinear cohesive zone model with fiber bridging effects can describe the “R curve” characteristic of the fracture toughness shown in the delamination test, and consequently better characterize the delamination propagation behavior of composite laminates. In order to evaluate the effects of fiber bridging on the behaviors of delamination growth and post-buckling in composite laminates, a trilinear cohesive zone model was built to investigate the compressive behavior of composite laminates with a circular delamination. The results demonstrate that, fiber bridging has little effect on the buckling load of the laminates. The relative deflection between the upper and lower sub-laminate predicted by the trilinear model is much smaller than that predicted by the bilinear model under mixed buckling mode. The buckling mode predicted by the trilinear model transits to global buckling earlier than that predicted by the bilinear model at identical delamination depth. The post-buckling modes change from local buckling mode to mix mode buckling and finally global buckling with the increase of delamination depth. For shallow delamination, mode I delamination is prominent. With the increase of delamination depth, the mode I delamination gradually disappears, while the mode II and III delamination propagation increases significantly. For delamination close to the mid-plane of the laminate, the delamination propagation is dominated by mode II and mode III, without mode I growth.
Fiber reinforced composite laminates are susceptible to delamination damage due to relatively weak inter-laminar mechanical properties. The growth of delamination is always accompanied by fiber bridging, which can significantly increase the resistance of delamination propagation, especially in the case of multidirectional lami-nates. Compared with the traditional bilinear model, a trilinear cohesive zone model with fiber bridging effects can describe the “R curve” characteristic of the fracture toughness shown in the delamination test, and consequently better characterize the delamination propagation behavior of composite laminates. In order to evaluate the effects of fiber bridging on the behaviors of delamination growth and post-buckling in composite laminates, a trilinear cohesive zone model was built to investigate the compressive behavior of composite laminates with a circular delamination. The results demonstrate that, fiber bridging has little effect on the buckling load of the laminates. The relative deflection between the upper and lower sub-laminate predicted by the trilinear model is much smaller than that predicted by the bilinear model under mixed buckling mode. The buckling mode predicted by the trilinear model transits to global buckling earlier than that predicted by the bilinear model at identical delamination depth. The post-buckling modes change from local buckling mode to mix mode buckling and finally global buckling with the increase of delamination depth. For shallow delamination, mode I delamination is prominent. With the increase of delamination depth, the mode I delamination gradually disappears, while the mode II and III delamination propagation increases significantly. For delamination close to the mid-plane of the laminate, the delamination propagation is dominated by mode II and mode III, without mode I growth.
