2022 Vol. 39, No. 6
2022, 39(6): 2515-2526.
doi: 10.13801/j.cnki.fhclxb.20220107.001
Abstract:
Water is necessary for organisms to survive in nature. In the animal and plant kingdoms, there are many interesting wetting phenomena. Recently, the research on the wettability of bio-inspired micro/nano-structured composites is an emerging and hot topic, which involves interdisciplinary and multidisciplinary subjects. This paper reviews the research progress of spider silk-like micro-composites with water collection for the field of bionic engineering. The micro/nano-structure and related mechanism for controlling wettability or liquid behaviours are briefly analysed. The fabricating and preparing methods of bio-inspired spider silk and integrated spider web are summarised, including dip-coating, electrospinning, micro-fluidics, 3D braiding, 3D printing, etc. The structure and fog harvesting ability of diverse micro/nano composites are displayed. This article also analyses and compares the bio-inspired structure design, fabricating and preparing technology, and water collection performance of diverse spider silk-like micro/nano composites. These composite materials which have water-harvesting function will have further or new applications in chips, weather forecast, seawater desalination, drug release, micro-reactor, energy storage and conversion, etc.
Water is necessary for organisms to survive in nature. In the animal and plant kingdoms, there are many interesting wetting phenomena. Recently, the research on the wettability of bio-inspired micro/nano-structured composites is an emerging and hot topic, which involves interdisciplinary and multidisciplinary subjects. This paper reviews the research progress of spider silk-like micro-composites with water collection for the field of bionic engineering. The micro/nano-structure and related mechanism for controlling wettability or liquid behaviours are briefly analysed. The fabricating and preparing methods of bio-inspired spider silk and integrated spider web are summarised, including dip-coating, electrospinning, micro-fluidics, 3D braiding, 3D printing, etc. The structure and fog harvesting ability of diverse micro/nano composites are displayed. This article also analyses and compares the bio-inspired structure design, fabricating and preparing technology, and water collection performance of diverse spider silk-like micro/nano composites. These composite materials which have water-harvesting function will have further or new applications in chips, weather forecast, seawater desalination, drug release, micro-reactor, energy storage and conversion, etc.
2022, 39(6): 2527-2542.
doi: 10.13801/j.cnki.fhclxb.20211129.005
Abstract:
Metal-organic framework (MOF) is a new type of nanomaterials with high porosity, specific surface area and high designability, which has been widely used in many fields such as adsorption separation and solid phase extraction. Ionic liquid (IL) have good stability and functional design, which have great application prospects as new green solvents. Loading ILs into the pores of MOFs to develop new IL/MOF composites can give full play to the advantages of the two materials. In this review, we discussed all the construction strategies of IL/MOF composites so far, as well as the application and advantages of CO2 capturing and separating in atmospheric environment and removing pollutants in water environment. We also summarized and prospected the application of IL/MOF compo-sites in environmental media in the future.
Metal-organic framework (MOF) is a new type of nanomaterials with high porosity, specific surface area and high designability, which has been widely used in many fields such as adsorption separation and solid phase extraction. Ionic liquid (IL) have good stability and functional design, which have great application prospects as new green solvents. Loading ILs into the pores of MOFs to develop new IL/MOF composites can give full play to the advantages of the two materials. In this review, we discussed all the construction strategies of IL/MOF composites so far, as well as the application and advantages of CO2 capturing and separating in atmospheric environment and removing pollutants in water environment. We also summarized and prospected the application of IL/MOF compo-sites in environmental media in the future.
2022, 39(6): 2543-2555.
doi: 10.13801/j.cnki.fhclxb.20211105.003
Abstract:
Magnetic chitosan microsphere (MCM) is a new type of adsorption material, which has unique magnetic response characteristics and good adsorption performance. With its outstanding environmental protection and controllability, it has attracted high attention in many fields such as biomedicine, food engineering, sewage treatment and so on. MCM prepared by traditional methods has some problems, such as nanoparticles are easy to dissolve in acidic solution and narrow application range. Therefore, researchers have carried out a lot of work in its optimization and modification. In this paper, the research progress of optimizing MCM was reviewed in detail from two aspects: magnetic nanoparticles modification and chitosan modification, including modification and replacement of magnetic nanoparticles, chitosan molecular imprinting modification, grafting modification, metal chelation modification, alkylation modification and so on. The adsorption and removal effects of modified MCM on heavy metal ions in wastewater and ionic dyes in printing and dyeing waste were summarized. Finally, the problems and challenges faced by modified MCM were discussed. Its future development trend was prospected, and the methods and ideas to further improve the application efficiency of modified MCM were put forward.
Magnetic chitosan microsphere (MCM) is a new type of adsorption material, which has unique magnetic response characteristics and good adsorption performance. With its outstanding environmental protection and controllability, it has attracted high attention in many fields such as biomedicine, food engineering, sewage treatment and so on. MCM prepared by traditional methods has some problems, such as nanoparticles are easy to dissolve in acidic solution and narrow application range. Therefore, researchers have carried out a lot of work in its optimization and modification. In this paper, the research progress of optimizing MCM was reviewed in detail from two aspects: magnetic nanoparticles modification and chitosan modification, including modification and replacement of magnetic nanoparticles, chitosan molecular imprinting modification, grafting modification, metal chelation modification, alkylation modification and so on. The adsorption and removal effects of modified MCM on heavy metal ions in wastewater and ionic dyes in printing and dyeing waste were summarized. Finally, the problems and challenges faced by modified MCM were discussed. Its future development trend was prospected, and the methods and ideas to further improve the application efficiency of modified MCM were put forward.
Research progress in preparation and application of functional films based on inverse opal structure
2022, 39(6): 2556-2570.
doi: 10.13801/j.cnki.fhclxb.20220120.002
Abstract:
As a representative structure of photonic crystals, films constructed with inverse opal (IO) structure exhibit a typical periodic arrangement. These films have some special optical properties in addition to the advantages of uniform micropores, high porosity and great flexibility of pore sizes. In recent years, films possessing an IO structure have attracted widespread attention from fields such as detection, anti-counterfeiting, drug delivery and filtration. In this article, the structural characteristics and optical properties of IO films were described, then the preparation methods of IO films were introduced and summarized into the three-step method and the two-step method. The applications of IO films in aspects of structural coloration, photocatalysis and medical carrier were depicted in details, and finally the prospects of films with IO structure in research direction and development trend in the future were given. The research work described in this article can provide strategic supports for the promotion and application of IO functional films.
As a representative structure of photonic crystals, films constructed with inverse opal (IO) structure exhibit a typical periodic arrangement. These films have some special optical properties in addition to the advantages of uniform micropores, high porosity and great flexibility of pore sizes. In recent years, films possessing an IO structure have attracted widespread attention from fields such as detection, anti-counterfeiting, drug delivery and filtration. In this article, the structural characteristics and optical properties of IO films were described, then the preparation methods of IO films were introduced and summarized into the three-step method and the two-step method. The applications of IO films in aspects of structural coloration, photocatalysis and medical carrier were depicted in details, and finally the prospects of films with IO structure in research direction and development trend in the future were given. The research work described in this article can provide strategic supports for the promotion and application of IO functional films.
2022, 39(6): 2571-2585.
doi: 10.13801/j.cnki.fhclxb.20220106.001
Abstract:
Due to the alloying/dealloying reaction mechanism in the low potential range, the theoretical discharge specific capacity of antimony sulfide (Sb2S3) material is as high as 946 mA·h·g−1, which is a promising anode mater-ial for lithium/sodium/potassium ion batteries. However, the aggregation and poor conductivity of Sb2S3 materials limit ion/electron transfer, resulting in poor electrochemical performance and severely hindering its practical application. It is necessary to summarize the structural design and lithium/sodium/potassium storage mechanism of Sb2S3-based anode materials and some important work in recent years. This article reviews the research progress of Sb2S3 based compound materials in recent years, mainly including reasonable structure design and/or combining with carbon-based materials and the electrochemical reaction mechanism involved, and puts forward the prospect of further improving Sb2S3 compound anode materials.
Due to the alloying/dealloying reaction mechanism in the low potential range, the theoretical discharge specific capacity of antimony sulfide (Sb2S3) material is as high as 946 mA·h·g−1, which is a promising anode mater-ial for lithium/sodium/potassium ion batteries. However, the aggregation and poor conductivity of Sb2S3 materials limit ion/electron transfer, resulting in poor electrochemical performance and severely hindering its practical application. It is necessary to summarize the structural design and lithium/sodium/potassium storage mechanism of Sb2S3-based anode materials and some important work in recent years. This article reviews the research progress of Sb2S3 based compound materials in recent years, mainly including reasonable structure design and/or combining with carbon-based materials and the electrochemical reaction mechanism involved, and puts forward the prospect of further improving Sb2S3 compound anode materials.
2022, 39(6): 2586-2598.
doi: 10.13801/j.cnki.fhclxb.20220120.009
Abstract:
Sodium ion batteries (SIBs) have attracted more and more attention because of their low cost and high safety. Due to the extremely high theoretical capacity, phosphorus-based material has been considered as one of the most promising anode materials for SIBs. However, phosphorus has shortcomings such as low conductivity and large volume expansion during sodiation-desodiation cycles, which significantly deteriorate its rate performance and cycle stability. Constructing metal phosphides by combining P with germanium, tin, copper or other metals can not only enhance their conductivity, but also significantly improve the reversibility and cycle performance of phosphorus-based anode materials. In this review, recent progress on metal phosphides and their composites with carbon nanotubes and graphene for SIBs anode materials were summarized. Furthermore, the current issues of metal phosphides anodes for SIBs were discussed, such as low practical capacity, poor cycle performance and so no. Meanwhile, various approaches and techniques to address these issues were proposed, including design and construction of composite materials, surface modification, regulation of size and morphology, advanced in-situ characterizations, etc. Finally, future perspectives of metal phosphides anode materials for SIBs were also presented.
Sodium ion batteries (SIBs) have attracted more and more attention because of their low cost and high safety. Due to the extremely high theoretical capacity, phosphorus-based material has been considered as one of the most promising anode materials for SIBs. However, phosphorus has shortcomings such as low conductivity and large volume expansion during sodiation-desodiation cycles, which significantly deteriorate its rate performance and cycle stability. Constructing metal phosphides by combining P with germanium, tin, copper or other metals can not only enhance their conductivity, but also significantly improve the reversibility and cycle performance of phosphorus-based anode materials. In this review, recent progress on metal phosphides and their composites with carbon nanotubes and graphene for SIBs anode materials were summarized. Furthermore, the current issues of metal phosphides anodes for SIBs were discussed, such as low practical capacity, poor cycle performance and so no. Meanwhile, various approaches and techniques to address these issues were proposed, including design and construction of composite materials, surface modification, regulation of size and morphology, advanced in-situ characterizations, etc. Finally, future perspectives of metal phosphides anode materials for SIBs were also presented.
2022, 39(6): 2599-2606.
doi: 10.13801/j.cnki.fhclxb.20210819.005
Abstract:
Epoxy resin (EP) has low thermal conductivity, and EP-based insulate equipments will failure due to their poor heat dissipation and heat re-sistance in long-term use. A composite insulating material with high heat resistance and high thermal conductivity was prepared by adding micron boron nitride (BN) to EP, and the thermal conductivity and heat resistance of the composite material were studied. The results show that when the mass fraction of hexagonal boron nitride (hBN) is 30wt%, the thermal conductivity of the composite is 0.444 W/(m·K), which is 2.3 times that of pure EP. When the filler mass fraction is 30wt%, the thermal conductivity of the composite mater-ial prepared by using KH560 modified hBN is 0.456 W/(m·K), which is slightly higher than that of the unmodified material. For the hBN-cBN/EP hot-pressed composite material, when the filler mass fraction is 30wt%, the in-plane thermal conductivity is 1.32 W/(m·K), which is much greater than the normal thermal conductivity. The hBN/EP composite materials with two particle sizes (1, 5-10 μm) were prepared by blending. The results show that filler blending can significantly improve the heat resistance of the material. Two cubic boron nitride (cBN) with two particle sizes (1, 5-10 μm) were added to prepare composite materials and their hot-pressed composite materials. The results show that the addition of cBN and hot-pressing can improve the heat resistance of the composite materials.
Epoxy resin (EP) has low thermal conductivity, and EP-based insulate equipments will failure due to their poor heat dissipation and heat re-sistance in long-term use. A composite insulating material with high heat resistance and high thermal conductivity was prepared by adding micron boron nitride (BN) to EP, and the thermal conductivity and heat resistance of the composite material were studied. The results show that when the mass fraction of hexagonal boron nitride (hBN) is 30wt%, the thermal conductivity of the composite is 0.444 W/(m·K), which is 2.3 times that of pure EP. When the filler mass fraction is 30wt%, the thermal conductivity of the composite mater-ial prepared by using KH560 modified hBN is 0.456 W/(m·K), which is slightly higher than that of the unmodified material. For the hBN-cBN/EP hot-pressed composite material, when the filler mass fraction is 30wt%, the in-plane thermal conductivity is 1.32 W/(m·K), which is much greater than the normal thermal conductivity. The hBN/EP composite materials with two particle sizes (1, 5-10 μm) were prepared by blending. The results show that filler blending can significantly improve the heat resistance of the material. Two cubic boron nitride (cBN) with two particle sizes (1, 5-10 μm) were added to prepare composite materials and their hot-pressed composite materials. The results show that the addition of cBN and hot-pressing can improve the heat resistance of the composite materials.
2022, 39(6): 2607-2618.
doi: 10.13801/j.cnki.fhclxb.20210716.003
Abstract:
Aircraft tires are used at high speeds and loads, and the wear resistance of tread rubber composites directly affects the service life of tires. Using a homemade rubber abrasion device to simulate the high speed (> 11 Hz) and high load (> 1.8 MPa) on the tire during the actual driving process, the effects of load, rotation speed and carbon black (CB) loading on the wear resistance of natural rubber-trans-polyisoprene (NR-TPI) composites were investigated, and the related influencing mechanisms were proposed by combining the morphology of rubber surface and the morphological characteristics of wear debris. The results show that the abrasion of rubber increases with the increase of load. The effect of rotation speed on the abrasion rate is less than that of load. When the rotation speed increases from 600 r/min to 800 r/min, the abrasion rate increases. However, the abrasion rate does not change significantly when the rotation speed is further increased. The abrasion rate of samples with 40 or 45 phr CB is similar, but when 50 phr CB is adopted, the wear resistance of sample is significantly improved. Observation on the abraded surface and the wear debris reveals that sticky degradation layers appear on the rubber surface, and micrometer sized fine-grained wear debris and large-sized crimped wear debris are simultaneously included in the wear debris, indicating that the abrasion resistance of NR-TPI composites mainly depends on the dynamic cycle of the two processes, the degradation of surface layer and the peeling of degradation layer. Particle wear mainly occurs when the former is dominant, while roll-up wear becomes the dominant wear mechanism when the latter is dominant. The effects of load and rotation speed on abrasion resistance are essentially achieved by affecting these two processes.
Aircraft tires are used at high speeds and loads, and the wear resistance of tread rubber composites directly affects the service life of tires. Using a homemade rubber abrasion device to simulate the high speed (> 11 Hz) and high load (> 1.8 MPa) on the tire during the actual driving process, the effects of load, rotation speed and carbon black (CB) loading on the wear resistance of natural rubber-trans-polyisoprene (NR-TPI) composites were investigated, and the related influencing mechanisms were proposed by combining the morphology of rubber surface and the morphological characteristics of wear debris. The results show that the abrasion of rubber increases with the increase of load. The effect of rotation speed on the abrasion rate is less than that of load. When the rotation speed increases from 600 r/min to 800 r/min, the abrasion rate increases. However, the abrasion rate does not change significantly when the rotation speed is further increased. The abrasion rate of samples with 40 or 45 phr CB is similar, but when 50 phr CB is adopted, the wear resistance of sample is significantly improved. Observation on the abraded surface and the wear debris reveals that sticky degradation layers appear on the rubber surface, and micrometer sized fine-grained wear debris and large-sized crimped wear debris are simultaneously included in the wear debris, indicating that the abrasion resistance of NR-TPI composites mainly depends on the dynamic cycle of the two processes, the degradation of surface layer and the peeling of degradation layer. Particle wear mainly occurs when the former is dominant, while roll-up wear becomes the dominant wear mechanism when the latter is dominant. The effects of load and rotation speed on abrasion resistance are essentially achieved by affecting these two processes.
2022, 39(6): 2619-2630.
doi: 10.13801/j.cnki.fhclxb.20210728.001
Abstract:
In order to explore the enhancement and improvement of porous polyimide (PI) material’s oil content and tribological properties, PI materials were prepared by using mesoporous carbon, graphene and rare earth as modifiers, respectively. The effects of different modifiers on the oil content property, tribological property and mechanical property of the materials were studied. The experimental results show that mesoporous carbon can greatly increase the oil content of porous PI. Compared with pure PI, the oil content of 2wt% mesoporous carbon increases by 55.6%, but the friction coefficient tends to increase, the mechanical property decreases obviously; a small amount of graphene can improve the oil content and frictional properties of porous PI, but with the increase of graphene content, the oil content friction coefficient of porous PI increases rapidly, and the impact strength decreases significantly; rare earth has greatly improved the oil content friction properties of porous PI. As the rare earth content increases from 0wt% to 5wt%, the friction coefficient decreases from 0.05 to 0.026. There is an inflection point after 5wt%. However, the oil friction coefficients of all samples are lower than the pure PI, and the oil content rate goes up. The mechanical property of rare earth modified porous PI doesn’t decrease significantly compared with mesoporous carbon and graphene, which shows the best enhancement effect on the comperhensive performance of porous PI.
In order to explore the enhancement and improvement of porous polyimide (PI) material’s oil content and tribological properties, PI materials were prepared by using mesoporous carbon, graphene and rare earth as modifiers, respectively. The effects of different modifiers on the oil content property, tribological property and mechanical property of the materials were studied. The experimental results show that mesoporous carbon can greatly increase the oil content of porous PI. Compared with pure PI, the oil content of 2wt% mesoporous carbon increases by 55.6%, but the friction coefficient tends to increase, the mechanical property decreases obviously; a small amount of graphene can improve the oil content and frictional properties of porous PI, but with the increase of graphene content, the oil content friction coefficient of porous PI increases rapidly, and the impact strength decreases significantly; rare earth has greatly improved the oil content friction properties of porous PI. As the rare earth content increases from 0wt% to 5wt%, the friction coefficient decreases from 0.05 to 0.026. There is an inflection point after 5wt%. However, the oil friction coefficients of all samples are lower than the pure PI, and the oil content rate goes up. The mechanical property of rare earth modified porous PI doesn’t decrease significantly compared with mesoporous carbon and graphene, which shows the best enhancement effect on the comperhensive performance of porous PI.
2022, 39(6): 2631-2638.
doi: 10.13801/j.cnki.fhclxb.20210816.002
Abstract:
In view of the structural deformation, weight and high-temperature requirements in the application of titanium engine compartment rear structure of a certain aircraft, composite structural design was carried out instead of titanium alloy for aircraft engine compartment rear structure, taking the AC729RTM polyimide composite with temperature resistance of 350℃ as design material. The finite element (FE) model of composite engine compartment rear structure was generated to perform parameter analysis and reasonable structural design parameters were obtained. The composite engine compartment rear structure was fabricated by resin transfer molding process (RTM). Finally, verification and evaluation were carried out from static strength test, structural deformation and weight. The results show that the internal quality and appearance of polyimide composite engine compartment rear structure are in good condition except for pores of small areas (porosity<2%) through non-destructive inspection. There are no obvious damages in engine compartment rear structure except for debonding of small areas through verification of static strength test, and satisfied the requirement of room temperament strength. The shape deviation of composite engine compartment rear structure is controlled in –0.808-0.664 mm and is better than titanium alloy structural. Compared with titanium alloy structural, the mass is reduced by 27.5%, achieving good benefits.
In view of the structural deformation, weight and high-temperature requirements in the application of titanium engine compartment rear structure of a certain aircraft, composite structural design was carried out instead of titanium alloy for aircraft engine compartment rear structure, taking the AC729RTM polyimide composite with temperature resistance of 350℃ as design material. The finite element (FE) model of composite engine compartment rear structure was generated to perform parameter analysis and reasonable structural design parameters were obtained. The composite engine compartment rear structure was fabricated by resin transfer molding process (RTM). Finally, verification and evaluation were carried out from static strength test, structural deformation and weight. The results show that the internal quality and appearance of polyimide composite engine compartment rear structure are in good condition except for pores of small areas (porosity<2%) through non-destructive inspection. There are no obvious damages in engine compartment rear structure except for debonding of small areas through verification of static strength test, and satisfied the requirement of room temperament strength. The shape deviation of composite engine compartment rear structure is controlled in –0.808-0.664 mm and is better than titanium alloy structural. Compared with titanium alloy structural, the mass is reduced by 27.5%, achieving good benefits.
2022, 39(6): 2639-2648.
doi: 10.13801/j.cnki.fhclxb.20210819.003
Abstract:
Cyanate ester (CE) resin, which has high glass transition temperature, low curing shrinkage and excellent dielectric properties, is commonly used as the material of high temperature resistant or microwave absorption in the aerospace field. However, after high temperature curing, the poor immigration adhesion between CE resin and carbon fiber (CF) would result in brittleness of its composite product. In addition, the preparation process of composites is complex, resulting in delamination damage. Therefore, the product quality and practical application are considerably affected. In this paper, polyether sulfone (PES) was used to modify CE resin and prepare prepreg. It prepares prepreg with good wettability and can apply to various dry forming composite preparation processes. The results show that the introduction of PES can significantly enhance the mechanical properties and thermal stability of CF/CE resin matrix composites. Compared with the CF/CE unidirectional plate, the flexural strength of 7.5wt%PES-CF/CE unidirectional plate is increased by 17%; the interlaminar shear strength is increased by 31%; the impact strength is increased by 39%; and the longitudinal thermal expansion coefficient is reduced from −2.07×10−8 K−1 to −10.7×10−8 K−1; the transverse thermal expansion coefficient is reduced by 20%. The modification effect is signifi-cant.
Cyanate ester (CE) resin, which has high glass transition temperature, low curing shrinkage and excellent dielectric properties, is commonly used as the material of high temperature resistant or microwave absorption in the aerospace field. However, after high temperature curing, the poor immigration adhesion between CE resin and carbon fiber (CF) would result in brittleness of its composite product. In addition, the preparation process of composites is complex, resulting in delamination damage. Therefore, the product quality and practical application are considerably affected. In this paper, polyether sulfone (PES) was used to modify CE resin and prepare prepreg. It prepares prepreg with good wettability and can apply to various dry forming composite preparation processes. The results show that the introduction of PES can significantly enhance the mechanical properties and thermal stability of CF/CE resin matrix composites. Compared with the CF/CE unidirectional plate, the flexural strength of 7.5wt%PES-CF/CE unidirectional plate is increased by 17%; the interlaminar shear strength is increased by 31%; the impact strength is increased by 39%; and the longitudinal thermal expansion coefficient is reduced from −2.07×10−8 K−1 to −10.7×10−8 K−1; the transverse thermal expansion coefficient is reduced by 20%. The modification effect is signifi-cant.
2022, 39(6): 2649-2660.
doi: 10.13801/j.cnki.fhclxb.20210720.001
Abstract:
In order to improve the friction and wear properties or ultrahigh molecular weight polyethylene (UHMWPE) under low speed and high normal loads conditions, composites consisting of hollow glass microspheres (HGM) treated with coupling agent and UHMWPE were prepared by hot pressing. The hardness and the crystallinity of composites were characterized, and the friction and wear properties of composites were measured by ball-disk reciprocating friction test in condition of high normal loads and dry friction. As the results, the hardness and the crystallinity of composites with a small amount of HGM added are higher than that of the pure UHMWPE. The friction coefficient of composites in a short time becomes higher to a certain extent as the content of HGM rising, and the wear rate decreases first and then increases. The composite with 1wt% HGM content has the lowest wear rate, the wear rate of which decreases by 44.7% and 48.4% in the friction tests under normal loads of 50 N and 100 N respectively compared with the wear rate of pure UHMWPE. With the increase of friction time, the friction coefficient and wear rate of the composites increase to varying degrees. The composite with 2wt% HGM has the lowest average friction coefficient during 120 min-friction-test, and the wear rates of pure UHMWPE and HGM/UHMWPE composites containing a small amount of HGM are close.
In order to improve the friction and wear properties or ultrahigh molecular weight polyethylene (UHMWPE) under low speed and high normal loads conditions, composites consisting of hollow glass microspheres (HGM) treated with coupling agent and UHMWPE were prepared by hot pressing. The hardness and the crystallinity of composites were characterized, and the friction and wear properties of composites were measured by ball-disk reciprocating friction test in condition of high normal loads and dry friction. As the results, the hardness and the crystallinity of composites with a small amount of HGM added are higher than that of the pure UHMWPE. The friction coefficient of composites in a short time becomes higher to a certain extent as the content of HGM rising, and the wear rate decreases first and then increases. The composite with 1wt% HGM content has the lowest wear rate, the wear rate of which decreases by 44.7% and 48.4% in the friction tests under normal loads of 50 N and 100 N respectively compared with the wear rate of pure UHMWPE. With the increase of friction time, the friction coefficient and wear rate of the composites increase to varying degrees. The composite with 2wt% HGM has the lowest average friction coefficient during 120 min-friction-test, and the wear rates of pure UHMWPE and HGM/UHMWPE composites containing a small amount of HGM are close.
2022, 39(6): 2661-2667.
doi: 10.13801/j.cnki.fhclxb.20210728.002
Abstract:
Owing to the incidental crosslinking reaction of monomer, the as-prepared poly(divinyldioxythiophene (PEDOT) always has poor electric conductivity and difficult subsequent processing. Thus, it is very important to develop appropriate polymerization method to synthesis PEDOT. Poly(divinyldioxythiophene has been synthesized via free radical oxidation polymerization in the one-dimensional channel of indium p-phthalic coordination polymer (In-BDC) metal organic framework material (MOF) as a reactive template to form PEDOT@In-BDC composite. The PEDOT@In-BDC composites were characterized by XRD, SEM, FTIR, TG and N2-sorption isotherm analysis. The results show that the monomer conversion of divinyldioxythiophene (EDOT) is higher than 91%. During the polymerization reaction, the framework of In-BDC template keeps constant. The specific surface area (BET) value of PEDOT@In-BDC composite is 45 m2/g. Compared with In-BDC template, PEDOT@In-BDC composites obtained by free radical oxidation polymerization of monomer divinyldioxythiophene in MOF are more stable. The result of current-voltage (I-V) linear scan test indicates that the PEDOT@In-BDC composite is novel semiconductor material and conductive based on PEDOT. The conductivity of PEDOT@In-BDC composite reaches 2.7×10−5 S/m. Compared with the functional porous material In-BDC (10−12 S/cm) , the PEDOT@In-BDC composite has higher electric conductivity and is at least six orders higher than that of In-BDC template.
Owing to the incidental crosslinking reaction of monomer, the as-prepared poly(divinyldioxythiophene (PEDOT) always has poor electric conductivity and difficult subsequent processing. Thus, it is very important to develop appropriate polymerization method to synthesis PEDOT. Poly(divinyldioxythiophene has been synthesized via free radical oxidation polymerization in the one-dimensional channel of indium p-phthalic coordination polymer (In-BDC) metal organic framework material (MOF) as a reactive template to form PEDOT@In-BDC composite. The PEDOT@In-BDC composites were characterized by XRD, SEM, FTIR, TG and N2-sorption isotherm analysis. The results show that the monomer conversion of divinyldioxythiophene (EDOT) is higher than 91%. During the polymerization reaction, the framework of In-BDC template keeps constant. The specific surface area (BET) value of PEDOT@In-BDC composite is 45 m2/g. Compared with In-BDC template, PEDOT@In-BDC composites obtained by free radical oxidation polymerization of monomer divinyldioxythiophene in MOF are more stable. The result of current-voltage (I-V) linear scan test indicates that the PEDOT@In-BDC composite is novel semiconductor material and conductive based on PEDOT. The conductivity of PEDOT@In-BDC composite reaches 2.7×10−5 S/m. Compared with the functional porous material In-BDC (10−12 S/cm) , the PEDOT@In-BDC composite has higher electric conductivity and is at least six orders higher than that of In-BDC template.
2022, 39(6): 2668-2678.
doi: 10.13801/j.cnki.fhclxb.20210916.003
Abstract:
Poly(lactic acid) (PLA) has the advantages of high mechanical properties, non-toxicity, renewablility, biodegradability and biocompatability. PLA has become one of the most widely used biobased plastics. However, PLA also has the disadvantages of high cost, high brittleness and low ductility, which hinders its further application in some fields. Thus, a series of bio-based poly(epoxidized palm oil) (PEPO)/PLA blends were prepared by twin-screw extrusion and injection molding techniques. The crystallization behavior, rheological properties, mechanical properties, thermal stability and micro-morphology of the blends were studied. The dynamic vulcanization mechanism of PEPO and PLA blends as well as the toughening mechanism of PEPO rubber phase in PLA were investigated. The results show that during the melt-blending of epoxidized palm oil (EPO) and PLA, EPO can self-polymerize with the help of the cationic initiator, thus forming PEPO rubber phase in PLA matrix. The formation of two-phase structure endows the blends plastic deformation under stress, leading to significant toughening efficiency on PLA. With an addition of 20wt% PEPO, the elongation at break and tensile toughness of the blend increase from 10% and 4.7 MJ/m3 (pure PLA) to 100% and 30.4 MJ/m3, respectively; but the tensile strength, tensile modulus, storage modulus and glass transition temperature of the blends decrease.
Poly(lactic acid) (PLA) has the advantages of high mechanical properties, non-toxicity, renewablility, biodegradability and biocompatability. PLA has become one of the most widely used biobased plastics. However, PLA also has the disadvantages of high cost, high brittleness and low ductility, which hinders its further application in some fields. Thus, a series of bio-based poly(epoxidized palm oil) (PEPO)/PLA blends were prepared by twin-screw extrusion and injection molding techniques. The crystallization behavior, rheological properties, mechanical properties, thermal stability and micro-morphology of the blends were studied. The dynamic vulcanization mechanism of PEPO and PLA blends as well as the toughening mechanism of PEPO rubber phase in PLA were investigated. The results show that during the melt-blending of epoxidized palm oil (EPO) and PLA, EPO can self-polymerize with the help of the cationic initiator, thus forming PEPO rubber phase in PLA matrix. The formation of two-phase structure endows the blends plastic deformation under stress, leading to significant toughening efficiency on PLA. With an addition of 20wt% PEPO, the elongation at break and tensile toughness of the blend increase from 10% and 4.7 MJ/m3 (pure PLA) to 100% and 30.4 MJ/m3, respectively; but the tensile strength, tensile modulus, storage modulus and glass transition temperature of the blends decrease.
2022, 39(6): 2679-2689.
doi: 10.13801/j.cnki.fhclxb.20210721.002
Abstract:
The organic phase change energy storage materials have high phase change latent heat, stable chemical properties, no supercooling and phase separation. Through thermodynamic analysis of decanoic acid, methyl laurate, 1 decanol, lauric acid and tetradecane, and compounding them in pairs, three binary organic compounds of decanoic acid-methyl laurate (molar ratio 30∶70), decanoic acid-1 decanol (molar ratio 36∶64), and lauric acid-tetradecane (molar ratio 21∶79) were obtained. Their phase transition temperature is all between 0-5℃ and corresponding latent heats of phase transition are higher. A kind of phase change energy storage material suitable for fruit packaging and logistics was acquired through the adsorption performance of poly(N-isopropylacrylamide) (PNIPAM) gel on binary organic compound, moreover the adding of polyethylene glycol 1000 (PEG1000) porogen during the gel preparation process can effectively improve the swelling ratio of the gel in the binary organic compound. The results show that, the phase change temperature of PNIPAM-40%PEG1000/decanoic acid-methyl laurate phase change energy storage material is 3.2℃, and the latent heat of phase change is 188.10 J/g, and the phase change temperature of PNIPAM-40%PEG1000/decanoic, acid-1 decanol phase change energy storage material is 1.2℃, and the latent heat of phase change is 177.74 J/g. The phase change temperature of PNIPAM-40%PEG1000/lauric acid-tetradecane phase change energy storage material is 4.2℃, and the latent heat of phase change is 206.17 J/g.
The organic phase change energy storage materials have high phase change latent heat, stable chemical properties, no supercooling and phase separation. Through thermodynamic analysis of decanoic acid, methyl laurate, 1 decanol, lauric acid and tetradecane, and compounding them in pairs, three binary organic compounds of decanoic acid-methyl laurate (molar ratio 30∶70), decanoic acid-1 decanol (molar ratio 36∶64), and lauric acid-tetradecane (molar ratio 21∶79) were obtained. Their phase transition temperature is all between 0-5℃ and corresponding latent heats of phase transition are higher. A kind of phase change energy storage material suitable for fruit packaging and logistics was acquired through the adsorption performance of poly(N-isopropylacrylamide) (PNIPAM) gel on binary organic compound, moreover the adding of polyethylene glycol 1000 (PEG1000) porogen during the gel preparation process can effectively improve the swelling ratio of the gel in the binary organic compound. The results show that, the phase change temperature of PNIPAM-40%PEG1000/decanoic acid-methyl laurate phase change energy storage material is 3.2℃, and the latent heat of phase change is 188.10 J/g, and the phase change temperature of PNIPAM-40%PEG1000/decanoic, acid-1 decanol phase change energy storage material is 1.2℃, and the latent heat of phase change is 177.74 J/g. The phase change temperature of PNIPAM-40%PEG1000/lauric acid-tetradecane phase change energy storage material is 4.2℃, and the latent heat of phase change is 206.17 J/g.
2022, 39(6): 2690-2697.
doi: 10.13801/j.cnki.fhclxb.20210819.002
Abstract:
The polyethylene grafted acrylic acid (PE-g-AAC) composite films with different grafting ratios were prepared by electron beam pre-irradiation. The study explored the effect of grafting ratio on the performance of composite membranes. The results show that the grafting ratio and water absorption ration of PE-g-AAc composite membrane increase with the increase of acrylic acid concentration. When the volume fraction of acrylic acid is 15vol%, the maximum grafting ratio is 263%, and the maximum water absorption ratio is 635%. The area resistance of PE-g-AAc composite membrane decreases with the increase of acrylic acid grafting ratio. When the grafting ratio is 30.4%, the area resistance of PE-g-AAc composite membrane decreases from 45000 mΩ·cm2 (without grafting) to 870.9 mΩ·cm2. When the grafting ratio is 263%, the area resistance is 70.1 mΩ·cm2. The tensile strength first decreases and then increases with the increase of grafting ratio. The maximum tensile strength reaches 45.6 MPa when the grafting ratio is 262%. The elongation at break decreases with the increase of grafting ratio. The grafting ratio result shows that under certain absorbed dose and reaction conditions, the higher the concentration of acrylic acid, the greater the ratio of chain growth rate to chain termination rate, and the greater the degree of acrylic acid polymerization. The results on water absorption and area resistance study show that, acrylic acid can effectively increase the surface energy of the polyethylene film, enhance the hydrophilicity, increase the ion conductivity, and reduce the area resistance of the polyethylene film. This study will provide direct reference value for the preparation of polyethylene grafted acrylic membrane for battery separator and ion exchange membrane.
The polyethylene grafted acrylic acid (PE-g-AAC) composite films with different grafting ratios were prepared by electron beam pre-irradiation. The study explored the effect of grafting ratio on the performance of composite membranes. The results show that the grafting ratio and water absorption ration of PE-g-AAc composite membrane increase with the increase of acrylic acid concentration. When the volume fraction of acrylic acid is 15vol%, the maximum grafting ratio is 263%, and the maximum water absorption ratio is 635%. The area resistance of PE-g-AAc composite membrane decreases with the increase of acrylic acid grafting ratio. When the grafting ratio is 30.4%, the area resistance of PE-g-AAc composite membrane decreases from 45000 mΩ·cm2 (without grafting) to 870.9 mΩ·cm2. When the grafting ratio is 263%, the area resistance is 70.1 mΩ·cm2. The tensile strength first decreases and then increases with the increase of grafting ratio. The maximum tensile strength reaches 45.6 MPa when the grafting ratio is 262%. The elongation at break decreases with the increase of grafting ratio. The grafting ratio result shows that under certain absorbed dose and reaction conditions, the higher the concentration of acrylic acid, the greater the ratio of chain growth rate to chain termination rate, and the greater the degree of acrylic acid polymerization. The results on water absorption and area resistance study show that, acrylic acid can effectively increase the surface energy of the polyethylene film, enhance the hydrophilicity, increase the ion conductivity, and reduce the area resistance of the polyethylene film. This study will provide direct reference value for the preparation of polyethylene grafted acrylic membrane for battery separator and ion exchange membrane.
2022, 39(6): 2698-2706.
doi: 10.13801/j.cnki.fhclxb.20210628.001
Abstract:
In view of the insufficient heat resistance and poor ablation resistance of fiber-reinforced phenolic resin composites, island silicate mineral-almandine micropowder (AM) was used as ceramicized filler to modify the boron phenolic resin (BPR), and the molding process was used to prepare different filler contents. AM/BPR ceramizable composite material and high silica glass fiber (HSF)-AM/BPR ceramizable composite material with different filler contents were prepared by molding process. The influence of AM on the heat resistance, ablation resistance and mechanical properties of the boron phenolic resin system, as well as the phase transition and microscopic morphology changes of the material at different temperatures were explored. The results show that as the content of AM increases, the heat resistance of AM/BPR composites increases. A liquid phase is formed above 800℃, and a denser ceramic layer is formed at 1100℃, which is important for the high-temperature performance and ablation resistance of the composite material. When the AM content is 50wt%, the linear ablation rate is 0.221 mm/s, and the mass ablation rate is 0.103 g/s, which is 44.05% and 43.6% lower than that of pure BPR. When the content of AM is 40wt%, the flexural strength of HSF-AM/BPR ceramic composites at room temperature and after high temperature treatment are increased by 29% and 47.97% compared with those without filler, respectively. Its excellent heat resistance, ablation resistance and mechanical properties are expected used as a thermal protection material in the aerospace field.
In view of the insufficient heat resistance and poor ablation resistance of fiber-reinforced phenolic resin composites, island silicate mineral-almandine micropowder (AM) was used as ceramicized filler to modify the boron phenolic resin (BPR), and the molding process was used to prepare different filler contents. AM/BPR ceramizable composite material and high silica glass fiber (HSF)-AM/BPR ceramizable composite material with different filler contents were prepared by molding process. The influence of AM on the heat resistance, ablation resistance and mechanical properties of the boron phenolic resin system, as well as the phase transition and microscopic morphology changes of the material at different temperatures were explored. The results show that as the content of AM increases, the heat resistance of AM/BPR composites increases. A liquid phase is formed above 800℃, and a denser ceramic layer is formed at 1100℃, which is important for the high-temperature performance and ablation resistance of the composite material. When the AM content is 50wt%, the linear ablation rate is 0.221 mm/s, and the mass ablation rate is 0.103 g/s, which is 44.05% and 43.6% lower than that of pure BPR. When the content of AM is 40wt%, the flexural strength of HSF-AM/BPR ceramic composites at room temperature and after high temperature treatment are increased by 29% and 47.97% compared with those without filler, respectively. Its excellent heat resistance, ablation resistance and mechanical properties are expected used as a thermal protection material in the aerospace field.
2022, 39(6): 2707-2715.
doi: 10.13801/j.cnki.fhclxb.20210625.001
Abstract:
Soft body amour has the advantages of good concealment and high comfortability. Recent studies demonstrate that soft body amours made up of layers of woven fabrics and unidirectional (UD) laminates show better ballistic performance. However, the mechanism behind has not been clarified. This work utilized three layers of woven fabrics (A) made by ultrahigh molecular weight polyethylene (UHMWPE) yarns and two layers of Dyneema® SB51 UD laminates (B) to compose two types of hybrid panels, viz. AAABB and BBAAA. Ballistic tests were carried out to evaluate their performance. The results show that the first type panel absorbs around 20% more energy than the second counterpart does. The finite element modelling is used to clarify the ballistic mechanism. The results illustrate that when the woven fabrics in front, they are not easier to be failed by shear, which results in more deformation of the fabric and therefore more deformation of the UD laminates behind, thereby giving rise to higher energy absorption. In contrast, when the UD laminates in front, they are easier to be damaged by the shear stress, failing to act on the followed layers. Moreover, when the woven fabrics at the rear, they tend to slip and meanwhile bring about more deformation in depth, which is detrimental to the protection. This study sheds light on the ballistic mechanism of hybrid panels with laying woven fabrics and UD laminates in different sequences. Such results, theoretically, pave the way for the design of the hybrid soft body amours.
Soft body amour has the advantages of good concealment and high comfortability. Recent studies demonstrate that soft body amours made up of layers of woven fabrics and unidirectional (UD) laminates show better ballistic performance. However, the mechanism behind has not been clarified. This work utilized three layers of woven fabrics (A) made by ultrahigh molecular weight polyethylene (UHMWPE) yarns and two layers of Dyneema® SB51 UD laminates (B) to compose two types of hybrid panels, viz. AAABB and BBAAA. Ballistic tests were carried out to evaluate their performance. The results show that the first type panel absorbs around 20% more energy than the second counterpart does. The finite element modelling is used to clarify the ballistic mechanism. The results illustrate that when the woven fabrics in front, they are not easier to be failed by shear, which results in more deformation of the fabric and therefore more deformation of the UD laminates behind, thereby giving rise to higher energy absorption. In contrast, when the UD laminates in front, they are easier to be damaged by the shear stress, failing to act on the followed layers. Moreover, when the woven fabrics at the rear, they tend to slip and meanwhile bring about more deformation in depth, which is detrimental to the protection. This study sheds light on the ballistic mechanism of hybrid panels with laying woven fabrics and UD laminates in different sequences. Such results, theoretically, pave the way for the design of the hybrid soft body amours.
2022, 39(6): 2716-2723.
doi: 10.13801/j.cnki.fhclxb.20220225.005
Abstract:
Flexible strain sensor has great potential in medical industry, health care and robotics, etc. However, most flexible strain sensors reported only output electrical signal (e.g. resistance, current and capacitance) in response to external strain, and lack direct notice of external loading, restricting their applications in early warning and health care, etc. In this work, we produced a flexible color-changeable strain sensor by using the silver nanowire (AgNW)/silicone composite film as the transparent electrode and polyacrylamide organogel as the electrochromic component. In addition to the excellent flexibility and moderate strain sensing performance (strain sensitivity of 0.07), the senor obtained has a reversible color transformation in response to external strain via the electrochromic effect. In virtue of these advantages mentioned above, the current sensor has broad applications in interactive wearable devices, electronic skin, anti-counterfeiting, artificial prosthetics and intelligent robots.
Flexible strain sensor has great potential in medical industry, health care and robotics, etc. However, most flexible strain sensors reported only output electrical signal (e.g. resistance, current and capacitance) in response to external strain, and lack direct notice of external loading, restricting their applications in early warning and health care, etc. In this work, we produced a flexible color-changeable strain sensor by using the silver nanowire (AgNW)/silicone composite film as the transparent electrode and polyacrylamide organogel as the electrochromic component. In addition to the excellent flexibility and moderate strain sensing performance (strain sensitivity of 0.07), the senor obtained has a reversible color transformation in response to external strain via the electrochromic effect. In virtue of these advantages mentioned above, the current sensor has broad applications in interactive wearable devices, electronic skin, anti-counterfeiting, artificial prosthetics and intelligent robots.
2022, 39(6): 2724-2733.
doi: 10.13801/j.cnki.fhclxb.20210805.002
Abstract:
Co Prussian blue analogue (CoPBA) has attracted much attentions as a promising anode material of supercapacitors due to its high capacity and long cycle life. But CoPBA suffers from poor electrical conductivity, leading to unsatisfied rate performance. A nanocomposite of Co Prussian blue analogue/multi-walled carbon nano-tubes (CoPBA/MWCNT) composite was synthesized using ZIF-67 as a precursor. The structure and morphology of CoPBA/MWCNT were characterized by XRD, SEM and TEM. In a three-electrode system, the specific capacitance of the CoPBA/MWCNT electrode reaches up to 312 F·g−1 at a current density of 1 A·g−1. The fabrication of CoPBA/MWCNT is beneficial for improving electronic conductivity and mechanical stability, resulting in high electrochemical performance. An asymmetric supercapacitor cell is assembled with CoPBA/MWCNT as cathode and activated carbon (AC) as anode. Its capacity retention rate is 83.1% after 5000 cycles, exhibiting excellent cycling stability.
Co Prussian blue analogue (CoPBA) has attracted much attentions as a promising anode material of supercapacitors due to its high capacity and long cycle life. But CoPBA suffers from poor electrical conductivity, leading to unsatisfied rate performance. A nanocomposite of Co Prussian blue analogue/multi-walled carbon nano-tubes (CoPBA/MWCNT) composite was synthesized using ZIF-67 as a precursor. The structure and morphology of CoPBA/MWCNT were characterized by XRD, SEM and TEM. In a three-electrode system, the specific capacitance of the CoPBA/MWCNT electrode reaches up to 312 F·g−1 at a current density of 1 A·g−1. The fabrication of CoPBA/MWCNT is beneficial for improving electronic conductivity and mechanical stability, resulting in high electrochemical performance. An asymmetric supercapacitor cell is assembled with CoPBA/MWCNT as cathode and activated carbon (AC) as anode. Its capacity retention rate is 83.1% after 5000 cycles, exhibiting excellent cycling stability.
2022, 39(6): 2734-2741.
doi: 10.13801/j.cnki.fhclxb.20210706.001
Abstract:
The application of WO3 materials has been attracted much attention in photoelectric catalysis, but its poor photo-generated electron hole separation ability and low utilization rate of sunlight have limited its photoelectric catalytic property. To solve this problem, WO3 nano-films were prepared on the conductive glass (FTO) by hydrothermal method, and WO3/Bi2MoO6 composite films with different reaction time (7 h, 9 h and 11 h) were synthesized on WO3 nano-films by solvothermal method. XRD and SEM tests proved the successful preparation of WO3/Bi2MoO6 composite films. The WO3/Bi2MoO6 composite film samples were subjected to absorption spectrum test, photocurrent test, photoelectric catalytic test and alternating current impedance test. The results show that the WO3/Bi2MoO6 composite film samples have better light absorption characteristics, more outstanding photocurrent characteristics and significantly improved photoelectrocatalysis activity compared with pure WO3 nano-films. And the WO3/Bi2MoO6 composite film samples with the hydrothermal reaction for 9 h have the highest photocurrent density and the best photoelectrocatalysis efficiency. The analysis suggests that the WO3/Bi2MoO6 composite film may constitute a heterojunction structure, which reduces the electronic impedance inside the composite film and increases the effective photoelectrochemical reaction sites; Meanwhile, the response range of the spectrum is expanded by increasing the utilization rate of sunlight. So the photoelectrochemical property can be significantly improved.
The application of WO3 materials has been attracted much attention in photoelectric catalysis, but its poor photo-generated electron hole separation ability and low utilization rate of sunlight have limited its photoelectric catalytic property. To solve this problem, WO3 nano-films were prepared on the conductive glass (FTO) by hydrothermal method, and WO3/Bi2MoO6 composite films with different reaction time (7 h, 9 h and 11 h) were synthesized on WO3 nano-films by solvothermal method. XRD and SEM tests proved the successful preparation of WO3/Bi2MoO6 composite films. The WO3/Bi2MoO6 composite film samples were subjected to absorption spectrum test, photocurrent test, photoelectric catalytic test and alternating current impedance test. The results show that the WO3/Bi2MoO6 composite film samples have better light absorption characteristics, more outstanding photocurrent characteristics and significantly improved photoelectrocatalysis activity compared with pure WO3 nano-films. And the WO3/Bi2MoO6 composite film samples with the hydrothermal reaction for 9 h have the highest photocurrent density and the best photoelectrocatalysis efficiency. The analysis suggests that the WO3/Bi2MoO6 composite film may constitute a heterojunction structure, which reduces the electronic impedance inside the composite film and increases the effective photoelectrochemical reaction sites; Meanwhile, the response range of the spectrum is expanded by increasing the utilization rate of sunlight. So the photoelectrochemical property can be significantly improved.
2022, 39(6): 2742-2749.
doi: 10.13801/j.cnki.fhclxb.20210726.003
Abstract:
In order to improve the problems of low porosity, low electrolyte uptake of commercial separators, poor heat resistance and thermal dimensional stability, Polybenzimidazole (PBI) was used to modify polyimide (PI). The PBI∶PI=0.3∶1.0 (mass ratio) composite fiber separator was prepared by the method of high-voltage electrostatic spinning. The microscopic morphology, porosity, electrolyte uptake, thermal performance, electrochemical performance and battery performance of the composite fiber separator were studied. The performance of composite fiber separator with mass ratio of PBI∶PI=0.3∶1.0, PI fiber separator and polypropylene (Celgard 2400, PP) separator were compared. The results show that the composite fiber separator with PBI∶PI=0.3∶1.0 has a porosity of 82% and electrolyte uptake of 618%; in an air atmosphere, there is no size shrinkage at 300℃; in a nitrogen atmosphere, the decomposition temperature is above 400℃, and the residual mass at 800℃ is more than 50%. The ionic conductivity reaches 1.29×10−3 S/cm, which is almost an order of magnitude higher than PP separatos; the interface impedance is 489.34 Ω, which is 17% lower than PP separator; the electrochemical stability window is increased to 5.05 V, which is 19% of the PP separator; CR 2032 battery assembled with PBI∶PI=0.3∶1.0 composite fiber separator shows excellent battery performance. After high current discharged, cells properties remain stable, initial discharge capacity is 130.01 mA·h/g, capacity retention rate is 98.91% after 100 cycles of 1 A/s, which is better than PP separator cells.
In order to improve the problems of low porosity, low electrolyte uptake of commercial separators, poor heat resistance and thermal dimensional stability, Polybenzimidazole (PBI) was used to modify polyimide (PI). The PBI∶PI=0.3∶1.0 (mass ratio) composite fiber separator was prepared by the method of high-voltage electrostatic spinning. The microscopic morphology, porosity, electrolyte uptake, thermal performance, electrochemical performance and battery performance of the composite fiber separator were studied. The performance of composite fiber separator with mass ratio of PBI∶PI=0.3∶1.0, PI fiber separator and polypropylene (Celgard 2400, PP) separator were compared. The results show that the composite fiber separator with PBI∶PI=0.3∶1.0 has a porosity of 82% and electrolyte uptake of 618%; in an air atmosphere, there is no size shrinkage at 300℃; in a nitrogen atmosphere, the decomposition temperature is above 400℃, and the residual mass at 800℃ is more than 50%. The ionic conductivity reaches 1.29×10−3 S/cm, which is almost an order of magnitude higher than PP separatos; the interface impedance is 489.34 Ω, which is 17% lower than PP separator; the electrochemical stability window is increased to 5.05 V, which is 19% of the PP separator; CR 2032 battery assembled with PBI∶PI=0.3∶1.0 composite fiber separator shows excellent battery performance. After high current discharged, cells properties remain stable, initial discharge capacity is 130.01 mA·h/g, capacity retention rate is 98.91% after 100 cycles of 1 A/s, which is better than PP separator cells.
2022, 39(6): 2750-2763.
doi: 10.13801/j.cnki.fhclxb.20210722.002
Abstract:
In order to remove ofloxacin (OFXL), which is difficult to biodegrade in water, and break through the bottleneck of solid-liquid separation and regeneration of adsorbents, Mn0.6Zn0.4Fe2O4 magnetic nanoparticles were modified by SiO2 and CeO2 to prepare Mn0.6Zn0.4Fe2O4@SiO2-CeO2 magnetic nanocompsite adsorbents. The as-prepared Mn0.6Zn0.4Fe2O4@SiO2-CeO2 were systematically characterized using XRD, FTIR, SEM, TEM, vibration sample magnetometer. The investigation results of three kinetic models (quasi-first-order kinetics, quasi-second-order kinetics, and intraparticle diffusion models), three isotherm models (Langmuir, Freundlich and D-R models) and adsorption thermodynamics show that the adsorption rate is controlled by multiple factors such as intra-particle diffusion and liquid film diffusion; the adsorption process is dominated by physical adsorption, and the chemical adsorption is the rate-controlling step; the adsorption process is spontaneously and exothermic with entropy increase. The characterization results of FTIR and XRD spectroscopy indicate that the interaction forces between Mn0.6Zn0.4Fe2O4@SiO2-CeO2 and OFLX include π-π conjugation, hydrogen bonding and coordination. After six cycles of adsorption-oxidation regeneration in situ, the equilibrium adsorption capacity of Mn0.6Zn0.4Fe2O4@SiO2-CeO2 for OFLX is 27.00 mg·g−1. The research results can provide basic theoretical data on the control technology of nonbiodegradable OFLX.
In order to remove ofloxacin (OFXL), which is difficult to biodegrade in water, and break through the bottleneck of solid-liquid separation and regeneration of adsorbents, Mn0.6Zn0.4Fe2O4 magnetic nanoparticles were modified by SiO2 and CeO2 to prepare Mn0.6Zn0.4Fe2O4@SiO2-CeO2 magnetic nanocompsite adsorbents. The as-prepared Mn0.6Zn0.4Fe2O4@SiO2-CeO2 were systematically characterized using XRD, FTIR, SEM, TEM, vibration sample magnetometer. The investigation results of three kinetic models (quasi-first-order kinetics, quasi-second-order kinetics, and intraparticle diffusion models), three isotherm models (Langmuir, Freundlich and D-R models) and adsorption thermodynamics show that the adsorption rate is controlled by multiple factors such as intra-particle diffusion and liquid film diffusion; the adsorption process is dominated by physical adsorption, and the chemical adsorption is the rate-controlling step; the adsorption process is spontaneously and exothermic with entropy increase. The characterization results of FTIR and XRD spectroscopy indicate that the interaction forces between Mn0.6Zn0.4Fe2O4@SiO2-CeO2 and OFLX include π-π conjugation, hydrogen bonding and coordination. After six cycles of adsorption-oxidation regeneration in situ, the equilibrium adsorption capacity of Mn0.6Zn0.4Fe2O4@SiO2-CeO2 for OFLX is 27.00 mg·g−1. The research results can provide basic theoretical data on the control technology of nonbiodegradable OFLX.
2022, 39(6): 2764-2773.
doi: 10.13801/j.cnki.fhclxb.20210708.003
Abstract:
To solve severe photocorrosion of Ag3PO4, which was used to prepare a core-shell Ag3PO4@polyaniline (PANI) composite photocatalyst by chemisorption, and graphene oxide (GO) was used as the carrier of Ag3PO4@PANI composite photocatalyst, reaching the superior carrier separation efficiency via synergetic effect of GO and PANI. The photocatalyst with mass ratio of GO to Ag3PO4@PANI of 4% shows visible light activity for the degradation of phenol, ciprofloxacin (CIP), tetracycline (TC) and dyes of 98.1%, 90.3%, 98.6% and 100% in 24 min, 18 min, 15 min and 5 min, respectively. Even after six repeat reactions, Ag3PO4@PANI/GO still maintain a high degradation rate. The trapping experiments confirm that •h+ and •O2 are the main active species in the photocatalytic degradation. The experimental results show that a core-shell structure is formed between PANI and Ag3PO4, the introduction of GO increases the electron transport rate, and the synergistic effect of PANI and GO on Ag3PO4 promotes the separation of photogenerated electrons and holes, thereby improving the stability of Ag3PO4 and photocatalytic activity.
To solve severe photocorrosion of Ag3PO4, which was used to prepare a core-shell Ag3PO4@polyaniline (PANI) composite photocatalyst by chemisorption, and graphene oxide (GO) was used as the carrier of Ag3PO4@PANI composite photocatalyst, reaching the superior carrier separation efficiency via synergetic effect of GO and PANI. The photocatalyst with mass ratio of GO to Ag3PO4@PANI of 4% shows visible light activity for the degradation of phenol, ciprofloxacin (CIP), tetracycline (TC) and dyes of 98.1%, 90.3%, 98.6% and 100% in 24 min, 18 min, 15 min and 5 min, respectively. Even after six repeat reactions, Ag3PO4@PANI/GO still maintain a high degradation rate. The trapping experiments confirm that •h+ and •O2 are the main active species in the photocatalytic degradation. The experimental results show that a core-shell structure is formed between PANI and Ag3PO4, the introduction of GO increases the electron transport rate, and the synergistic effect of PANI and GO on Ag3PO4 promotes the separation of photogenerated electrons and holes, thereby improving the stability of Ag3PO4 and photocatalytic activity.
2022, 39(6): 2774-2782.
doi: 10.13801/j.cnki.fhclxb.20210922.002
Abstract:
In order to realize waste recycling and remove pollutants from wastewater, two new Fenton-like compo-sites (SFM) with dual functions of removing ammonia nitrogen (NH4+-N) and permanganate index (IMn) were prepared. The two SFMs are made by mixing fly ash, dried sludge and oyster shell as basic raw materials (FDO) in a certain proportion and adding two bentonite based inorganic mineral materials, which are respectively recorded as activated clay type (ATC/FDO) and bentonite type (BT/FDO). The surface morphology and pore structure of SFM were characterized by SEM and BET. The adsorption and removal effects of IMn and NH4+-N in wastewater under the Fenton-like system of two kinds of SFM were comparatively studied, and the adsorption characteristics were analyzed by kinetics and adsorption isotherm models. The results show that the removal effect of ATC/FDO on IMn and NH4+-N is better than that of BT/FDO. After 5 days of treatment, the corresponding removal rate of ATC/FDO on IMn and NH4+-N is as high as 95.76% and 99.65% respectively. The optimum preparation conditions of ATC/FDO are as follows: the mass ratio of activated clay as basic raw material is 5∶5, calcination temperature is 400℃, calcination time is 120 min. The optimum conditions are 20℃, pH=6.5, and the dosage ratio of ATC/FDO to H2O2 is 5 g/L∶1 ml/L. The adsorption process of NH4+-N on the two SFMs conforms to the quasi-second-order kinetics and the Freundlich adsorption isotherm equation. The research results can provide new technologies and new materials for waste resource utilization and water treatment.
In order to realize waste recycling and remove pollutants from wastewater, two new Fenton-like compo-sites (SFM) with dual functions of removing ammonia nitrogen (NH4+-N) and permanganate index (IMn) were prepared. The two SFMs are made by mixing fly ash, dried sludge and oyster shell as basic raw materials (FDO) in a certain proportion and adding two bentonite based inorganic mineral materials, which are respectively recorded as activated clay type (ATC/FDO) and bentonite type (BT/FDO). The surface morphology and pore structure of SFM were characterized by SEM and BET. The adsorption and removal effects of IMn and NH4+-N in wastewater under the Fenton-like system of two kinds of SFM were comparatively studied, and the adsorption characteristics were analyzed by kinetics and adsorption isotherm models. The results show that the removal effect of ATC/FDO on IMn and NH4+-N is better than that of BT/FDO. After 5 days of treatment, the corresponding removal rate of ATC/FDO on IMn and NH4+-N is as high as 95.76% and 99.65% respectively. The optimum preparation conditions of ATC/FDO are as follows: the mass ratio of activated clay as basic raw material is 5∶5, calcination temperature is 400℃, calcination time is 120 min. The optimum conditions are 20℃, pH=6.5, and the dosage ratio of ATC/FDO to H2O2 is 5 g/L∶1 ml/L. The adsorption process of NH4+-N on the two SFMs conforms to the quasi-second-order kinetics and the Freundlich adsorption isotherm equation. The research results can provide new technologies and new materials for waste resource utilization and water treatment.
2022, 39(6): 2783-2791.
doi: 10.13801/j.cnki.fhclxb.20210909.006
Abstract:
How to prepare high-performance separation membranes with morphology controlled and well-dispersed nanoparticles, has been a hotspot and difficulty in the field of membrane separation. Mixed matrix membranes were prepared by crosslinking polyvinyl alcohol (PVA), maleic acid (MA) and SiO2 via an aqueous sol-gel route and solution casting method. The membrane was characterized by SEM, FTIR, XRD and tested for its perfor-mance in pervaporation separation of ethanol/water mixtures with feed ethanol concentration of 97wt% at 50℃. Membrane characterization results reveal that SiO2/crosslinked PVA membrane shows that elliptic leaves SiO2 nano-particles cover the surface and act as a water prescreening layer, are well disperse within the polymer matrix. It results in a significantly enhanced effect in both flux and selectivity. The membranes achieve high water flux of 0.072 kg·m−2·h−1 and separation factor of 12301 for separation of 97wt% ethanol aqueous solution. The enhanced membrane performance can be attributed to the surface prescreening ability and dense crosslinking membrane network. The research results would promote the study of SiO2/PVA composite materials, and their application in the field of membrane separation.
How to prepare high-performance separation membranes with morphology controlled and well-dispersed nanoparticles, has been a hotspot and difficulty in the field of membrane separation. Mixed matrix membranes were prepared by crosslinking polyvinyl alcohol (PVA), maleic acid (MA) and SiO2 via an aqueous sol-gel route and solution casting method. The membrane was characterized by SEM, FTIR, XRD and tested for its perfor-mance in pervaporation separation of ethanol/water mixtures with feed ethanol concentration of 97wt% at 50℃. Membrane characterization results reveal that SiO2/crosslinked PVA membrane shows that elliptic leaves SiO2 nano-particles cover the surface and act as a water prescreening layer, are well disperse within the polymer matrix. It results in a significantly enhanced effect in both flux and selectivity. The membranes achieve high water flux of 0.072 kg·m−2·h−1 and separation factor of 12301 for separation of 97wt% ethanol aqueous solution. The enhanced membrane performance can be attributed to the surface prescreening ability and dense crosslinking membrane network. The research results would promote the study of SiO2/PVA composite materials, and their application in the field of membrane separation.
2022, 39(6): 2792-2800.
doi: 10.13801/j.cnki.fhclxb.20220124.002
Abstract:
In recent years, bendable flexible electronic devices have attracted widespread attention, but the performance stability and bending stability of the devices have hindered their practical applications. In this paper, we focus on the changes of functional film and device performance before and after bending of flexible quantum dot light-emitting diodes (QLEDs) by applying bending force to QLEDs. The film parameters and device electrical properties were tested by regulating the bending radius of QLEDs. The polyethylene terephthalate-indium tin oxide (PET-ITO) composite transparent electrodes with different bending radii were analyzed by the finite element method, and the results show that as the bending radius decreases, the ITO electrode shows a more obvious stress concentration phenomenon. The morphological characterization and square resistance tests show that excessive bending will cause damage to the electrode material and increase the square resistance. Transient electroluminescence spectroscopy (TREL) was used to characterize the devices before and after bending. The results show that the decrease in the bending radius of curvature reduces the efficiency of charge transfer on the electrode, and the smaller bending radius of curvature leads to the increase of internal defects, which reduces the efficiency of carrier injection and transfer inside the device and affects the performance of the device.
In recent years, bendable flexible electronic devices have attracted widespread attention, but the performance stability and bending stability of the devices have hindered their practical applications. In this paper, we focus on the changes of functional film and device performance before and after bending of flexible quantum dot light-emitting diodes (QLEDs) by applying bending force to QLEDs. The film parameters and device electrical properties were tested by regulating the bending radius of QLEDs. The polyethylene terephthalate-indium tin oxide (PET-ITO) composite transparent electrodes with different bending radii were analyzed by the finite element method, and the results show that as the bending radius decreases, the ITO electrode shows a more obvious stress concentration phenomenon. The morphological characterization and square resistance tests show that excessive bending will cause damage to the electrode material and increase the square resistance. Transient electroluminescence spectroscopy (TREL) was used to characterize the devices before and after bending. The results show that the decrease in the bending radius of curvature reduces the efficiency of charge transfer on the electrode, and the smaller bending radius of curvature leads to the increase of internal defects, which reduces the efficiency of carrier injection and transfer inside the device and affects the performance of the device.
2022, 39(6): 2801-2809.
doi: 10.13801/j.cnki.fhclxb.20210708.004
Abstract:
To facilitate the practical application of fiber-reinforced polymer (FRP) strengthened seawater sea-sand concrete (SSC) structures in marine infrastructures and alleviate the brittleness of abrupt failure of FRP confined SSC columns, the mechanical performance of carbon fiber-reinforced polymer (CFRP) nonuniformly wrapped square SSC columns under axial compression was explored. Test results show that the failure pattern of nonuniformly CFRP confined square SSC columns exhibits less brittle since the rupture of thinner CFRP band between two adjacent strips can provide a warning sign due to the inequivalent number of CFRP layers at different locations along the height of the specimens. Compared to the specimens uniformly wrapped with CFRP sheets and strips under the same volumetric ratio of CFRP, CFRP nonuniformly wrapped SSC columns possess superior mechanical properties, especially for the specimens with a smaller clear spacing. Besides, with the decrease of clear spacing ratio and the increment of the thickness of external CFRP strips, the ultimate strengths and strains of confined specimens increase obviously. In specific, the enhancement of ultimate strengths ranges from 5.4%-18.5% as the decreasing of clear spacing ratio. Moreover, under the same clear spacing ratio, the maximum ultimate strength improvement and strain improvement are equal to 15.8% and 21.8% respectively when the thickness of external CFRP strips doubles. Finally, several representative stress-strain models were selected to examine their validity in predicting the ultimate conditions of FRP nonuniformly wrapped concrete and the accuracy and reliability of each model were also assessed.
To facilitate the practical application of fiber-reinforced polymer (FRP) strengthened seawater sea-sand concrete (SSC) structures in marine infrastructures and alleviate the brittleness of abrupt failure of FRP confined SSC columns, the mechanical performance of carbon fiber-reinforced polymer (CFRP) nonuniformly wrapped square SSC columns under axial compression was explored. Test results show that the failure pattern of nonuniformly CFRP confined square SSC columns exhibits less brittle since the rupture of thinner CFRP band between two adjacent strips can provide a warning sign due to the inequivalent number of CFRP layers at different locations along the height of the specimens. Compared to the specimens uniformly wrapped with CFRP sheets and strips under the same volumetric ratio of CFRP, CFRP nonuniformly wrapped SSC columns possess superior mechanical properties, especially for the specimens with a smaller clear spacing. Besides, with the decrease of clear spacing ratio and the increment of the thickness of external CFRP strips, the ultimate strengths and strains of confined specimens increase obviously. In specific, the enhancement of ultimate strengths ranges from 5.4%-18.5% as the decreasing of clear spacing ratio. Moreover, under the same clear spacing ratio, the maximum ultimate strength improvement and strain improvement are equal to 15.8% and 21.8% respectively when the thickness of external CFRP strips doubles. Finally, several representative stress-strain models were selected to examine their validity in predicting the ultimate conditions of FRP nonuniformly wrapped concrete and the accuracy and reliability of each model were also assessed.
2022, 39(6): 2810-2820.
doi: 10.13801/j.cnki.fhclxb.20210716.001
Abstract:
To solve the problems of CFRP plate being easy to peel off from concrete of concrete structure strengthened with carbon fiber reinforced polymer (CFRP) plate and the limited increase of bearing capacity of concrete structure strengthened with engineered cementitious composites (ECC), the CFRP plate-ECC-concrete composite interface was proposed to take full advantage of both the high tensile strength of CFRP plate and good durability of ECC with multiple cracking. 21 single-shear specimens with different ECC thickness and concrete/ECC strength were designed and tested. The distribution of interface load-carrying capacity, strain distribution and bond-slip curve of specimens were obtained. The results show that the failure pattern of all specimens with ECC layer is the debonding failure which occurs in the interface between the CFRP plate and ECC. It demonstrates that the ECC layer can obviously delay the debonding of CFRP plate, meanwhile, transfer the interfacial shear stress effectively. Compare with the specimens without ECC layer, the ultimate load-carrying capacity of specimens with ECC layer increases by 27.3%-59.6%. Based on the LU Xinzheng et al’ ultimate load-carrying capacity calculation model, a prediction model of the load-carrying capacity of single-shear specimens considering the thickness of ECC was proposed, and the calculated value is consistent with the experimental results. Different bond-slip models were adopted to analyse the test results and the comparison shows that: Ferracuti et al’ model considers more comprehensive factors and fits better with the test results than other models.
To solve the problems of CFRP plate being easy to peel off from concrete of concrete structure strengthened with carbon fiber reinforced polymer (CFRP) plate and the limited increase of bearing capacity of concrete structure strengthened with engineered cementitious composites (ECC), the CFRP plate-ECC-concrete composite interface was proposed to take full advantage of both the high tensile strength of CFRP plate and good durability of ECC with multiple cracking. 21 single-shear specimens with different ECC thickness and concrete/ECC strength were designed and tested. The distribution of interface load-carrying capacity, strain distribution and bond-slip curve of specimens were obtained. The results show that the failure pattern of all specimens with ECC layer is the debonding failure which occurs in the interface between the CFRP plate and ECC. It demonstrates that the ECC layer can obviously delay the debonding of CFRP plate, meanwhile, transfer the interfacial shear stress effectively. Compare with the specimens without ECC layer, the ultimate load-carrying capacity of specimens with ECC layer increases by 27.3%-59.6%. Based on the LU Xinzheng et al’ ultimate load-carrying capacity calculation model, a prediction model of the load-carrying capacity of single-shear specimens considering the thickness of ECC was proposed, and the calculated value is consistent with the experimental results. Different bond-slip models were adopted to analyse the test results and the comparison shows that: Ferracuti et al’ model considers more comprehensive factors and fits better with the test results than other models.
2022, 39(6): 2821-2828.
doi: 10.13801/j.cnki.fhclxb.20210816.005
Abstract:
Chemical composition design of raw materials is the basis of hydration reaction and mechanical strength formation of excess-sulfate phosphorgypsum slag cement (PPSC). Laboratory experiments and molecular dynamics simulation (MD) provide a multi-scale regulation and control design basis for chemical composition of PPSC raw materials. The structural model of the PPSC was established by Materials Studio (MS). The effect of the molar ratios of chemical components on the compressive strength of PPSC was studied by means of MD simulation and XRD. The results show that with the increase of the CaO/SO3 molar ratio and the decrease of SiO2/Al2O3, the compressive strength of PPSC shows an increasing trend. When the SiO2/Al2O3 molar ratio is 3.5-3.7 and the CaO/SO3 molar ratio is 1.8~2.0, the compressive strength of PPSC is higher. The MD simulation result of PPSC pore structure is contrary to the compressive strength test result, which proves the reliability of the simulation result. At the atomic scale, MD simulation shows that O, Ca, Al and S atoms exhibit high diffusion ability. In the alkaline environment, sulphate activation increases the bond length of S=O, Al—O and O=O, and the structure is unstable and hydrolyzed, resulting in more ettringite that promotes strength. By adjusting the raw materials SiO2/Al2O3 molar ratio and CaO/SO3 molar ratio, PPSC can form a more stable internal structure. The design of chemical composition molar ratio and MD simulation methods are of great significance for the composition design and application promotion of PPSC.
Chemical composition design of raw materials is the basis of hydration reaction and mechanical strength formation of excess-sulfate phosphorgypsum slag cement (PPSC). Laboratory experiments and molecular dynamics simulation (MD) provide a multi-scale regulation and control design basis for chemical composition of PPSC raw materials. The structural model of the PPSC was established by Materials Studio (MS). The effect of the molar ratios of chemical components on the compressive strength of PPSC was studied by means of MD simulation and XRD. The results show that with the increase of the CaO/SO3 molar ratio and the decrease of SiO2/Al2O3, the compressive strength of PPSC shows an increasing trend. When the SiO2/Al2O3 molar ratio is 3.5-3.7 and the CaO/SO3 molar ratio is 1.8~2.0, the compressive strength of PPSC is higher. The MD simulation result of PPSC pore structure is contrary to the compressive strength test result, which proves the reliability of the simulation result. At the atomic scale, MD simulation shows that O, Ca, Al and S atoms exhibit high diffusion ability. In the alkaline environment, sulphate activation increases the bond length of S=O, Al—O and O=O, and the structure is unstable and hydrolyzed, resulting in more ettringite that promotes strength. By adjusting the raw materials SiO2/Al2O3 molar ratio and CaO/SO3 molar ratio, PPSC can form a more stable internal structure. The design of chemical composition molar ratio and MD simulation methods are of great significance for the composition design and application promotion of PPSC.
2022, 39(6): 2829-2843.
doi: 10.13801/j.cnki.fhclxb.20210716.007
Abstract:
The occurrence of fire often leads to the damage and deterioration of the micro-meso-structure of concrete materials, which is reflected in the decomposition of hydrates, the coarsening of pore structure, thermal cracking, and the cracking induced by the increase of water vapor pressure, which in turn lead to the decline of the macroscopic mechanical properties and durability of materials. The meso-regulatory function of the lightweight, high-strength, internally porous, and highly thermally stable glazed hollow beads (GHB) can improve the high-temperature resistance of concrete. In order to study the characteristics of the internal meso-scale structure and crack evolution of recycled aggregate thermal insulation concrete (RATIC) subjected to high temperature, the cube compressive strength test and CT test were firstly carried out on RATIC after high temperature. Then the RATIC meso-scale model was established based on the real structure by the improved image segmentation algorithm based on the adaptive threshold method and the regional growth method (IISA). The process of initiation, development and coalescence of internal microcracks in RATIC with different GHB and recycled coarse aggregate (RCA) contents with temperature change were studied. Furthermore, the failure patterns of RATIC under simulated conditions and CT re-sults were analyzed by contrast, which show that GHB can significantly block the extension of cracks, provide a release channel for vapor pressure, alleviate cracks in the mortar area and pore boundaries, slow down the spread of heat in the concrete. It has a positive effect on improving the heat-induced damage resistance of concrete.
The occurrence of fire often leads to the damage and deterioration of the micro-meso-structure of concrete materials, which is reflected in the decomposition of hydrates, the coarsening of pore structure, thermal cracking, and the cracking induced by the increase of water vapor pressure, which in turn lead to the decline of the macroscopic mechanical properties and durability of materials. The meso-regulatory function of the lightweight, high-strength, internally porous, and highly thermally stable glazed hollow beads (GHB) can improve the high-temperature resistance of concrete. In order to study the characteristics of the internal meso-scale structure and crack evolution of recycled aggregate thermal insulation concrete (RATIC) subjected to high temperature, the cube compressive strength test and CT test were firstly carried out on RATIC after high temperature. Then the RATIC meso-scale model was established based on the real structure by the improved image segmentation algorithm based on the adaptive threshold method and the regional growth method (IISA). The process of initiation, development and coalescence of internal microcracks in RATIC with different GHB and recycled coarse aggregate (RCA) contents with temperature change were studied. Furthermore, the failure patterns of RATIC under simulated conditions and CT re-sults were analyzed by contrast, which show that GHB can significantly block the extension of cracks, provide a release channel for vapor pressure, alleviate cracks in the mortar area and pore boundaries, slow down the spread of heat in the concrete. It has a positive effect on improving the heat-induced damage resistance of concrete.
Effect of ultra-low temperature on flexural behavior of ultra-high toughness cementitious composites
2022, 39(6): 2844-2854.
doi: 10.13801/j.cnki.fhclxb.20210823.001
Abstract:
As a new type of composite material with good mechanical properties and durability, the flexural toughness of ultra-high toughness cementitious composites (UHTCC) is an important indicator to evaluate its mechanical properties. To explore the bending performance of UHTCC materials under an ultra-low temperature environment, five groups of UHTCC materials with different fiber contents were designed. After cryogenic treatment, four-point bending tests were carried out, and the equivalent strength was analyzed. A toughness evaluation method suitable for ultra-low temperature was proposed, which provided the theoretical basis and technical support for the wide application of UHTCC in the field of ultra-low temperature. The results show that the flexural strength of UHTCC increases significantly after ultra-low temperatures. When the temperature decreases to −160℃, the flexural strength of UHTCC increases by 67.67%, but it shows obvious brittleness. In an ultra-low temperature environment, the strength and toughness of UHTCC with 1.5vol% volume fraction are the best, but the performance of UHTCC is slightly reduced after exceeding the optimal volume fraction.
As a new type of composite material with good mechanical properties and durability, the flexural toughness of ultra-high toughness cementitious composites (UHTCC) is an important indicator to evaluate its mechanical properties. To explore the bending performance of UHTCC materials under an ultra-low temperature environment, five groups of UHTCC materials with different fiber contents were designed. After cryogenic treatment, four-point bending tests were carried out, and the equivalent strength was analyzed. A toughness evaluation method suitable for ultra-low temperature was proposed, which provided the theoretical basis and technical support for the wide application of UHTCC in the field of ultra-low temperature. The results show that the flexural strength of UHTCC increases significantly after ultra-low temperatures. When the temperature decreases to −160℃, the flexural strength of UHTCC increases by 67.67%, but it shows obvious brittleness. In an ultra-low temperature environment, the strength and toughness of UHTCC with 1.5vol% volume fraction are the best, but the performance of UHTCC is slightly reduced after exceeding the optimal volume fraction.
2022, 39(6): 2855-2863.
doi: 10.13801/j.cnki.fhclxb.20210902.001
Abstract:
The whole life cycle of carbon fiber reinforced polymer composite from production, service to retirement will produce huge amount of waste, bringing serious environmental pollution and resource waste. In this paper, the waste carbon fiber produced in the production process was added to the concrete to study its influence law and mechanism on the strength and conductivity of concrete. The results show that the recovery effect of carbon fiber on the strength of concrete is not obvious, because the coating on the surface of industrial carbon fiber makes it easier to gather into bundles and not easy to disperse in the process of concrete mixing. The incorporation of recycling carbon fiber can significantly improve the conductivity of concrete. When the content of recycling carbon fiber is 0wt%-0.3wt%, the drying/water absorption process changes the pore structure of concrete. And the C—S—H gel rearrangement, local shrinkage and partial irreversible characteristics make concrete produce a new conductive path. The resistivity increases first and then decreases with the decrease of water content. When the content is 0.4wt%-1.5wt%, a stable physical contact conductive network is formed in the concrete, and the age and moisture content have no obvious effect on the conductivity.
The whole life cycle of carbon fiber reinforced polymer composite from production, service to retirement will produce huge amount of waste, bringing serious environmental pollution and resource waste. In this paper, the waste carbon fiber produced in the production process was added to the concrete to study its influence law and mechanism on the strength and conductivity of concrete. The results show that the recovery effect of carbon fiber on the strength of concrete is not obvious, because the coating on the surface of industrial carbon fiber makes it easier to gather into bundles and not easy to disperse in the process of concrete mixing. The incorporation of recycling carbon fiber can significantly improve the conductivity of concrete. When the content of recycling carbon fiber is 0wt%-0.3wt%, the drying/water absorption process changes the pore structure of concrete. And the C—S—H gel rearrangement, local shrinkage and partial irreversible characteristics make concrete produce a new conductive path. The resistivity increases first and then decreases with the decrease of water content. When the content is 0.4wt%-1.5wt%, a stable physical contact conductive network is formed in the concrete, and the age and moisture content have no obvious effect on the conductivity.
2022, 39(6): 2864-2874.
doi: 10.13801/j.cnki.fhclxb.20211110.002
Abstract:
C14/EG composite phase change material was prepared by physical adsorption method with n-tetradecane (C14) as phase change material and expanded graphite (EG) as carrier. The micro-morphology, phase change temperature, phase change latent heat and chemical structure of C14/EG composite phase change material were tested by SEM, DSC and FTIR. The quick freeze-thaw cycle tests of phase change energy storage cement-based materials (PCESM) doped (mass ratio to cement) with 0%, 2%, 4% and 6% phase change materials were carried out. The effects of freeze-thaw cycle on the surface damage, mass loss, dynamic modulus loss, compressive strength and pore structure were analyzed, and the deterioration mechanism of PCESM during freeze-thaw cycle was revealed. The experimental results show that C14 can be well adsorbed in the pores of EG, and C14 has good compatibility with EG, and there is no chemical reaction between them. With the increase of C14/EG phase change material content, the porosity increases and the mechanical properties decrease, but the frost resistance increases first and then decreases. The frost resistance of PCESM with 4% C14/EG phase change material is the best.
C14/EG composite phase change material was prepared by physical adsorption method with n-tetradecane (C14) as phase change material and expanded graphite (EG) as carrier. The micro-morphology, phase change temperature, phase change latent heat and chemical structure of C14/EG composite phase change material were tested by SEM, DSC and FTIR. The quick freeze-thaw cycle tests of phase change energy storage cement-based materials (PCESM) doped (mass ratio to cement) with 0%, 2%, 4% and 6% phase change materials were carried out. The effects of freeze-thaw cycle on the surface damage, mass loss, dynamic modulus loss, compressive strength and pore structure were analyzed, and the deterioration mechanism of PCESM during freeze-thaw cycle was revealed. The experimental results show that C14 can be well adsorbed in the pores of EG, and C14 has good compatibility with EG, and there is no chemical reaction between them. With the increase of C14/EG phase change material content, the porosity increases and the mechanical properties decrease, but the frost resistance increases first and then decreases. The frost resistance of PCESM with 4% C14/EG phase change material is the best.
2022, 39(6): 2875-2884.
doi: 10.13801/j.cnki.fhclxb.20210622.006
Abstract:
In order to investigate the influence of high temperature and copper slag fine aggregate on corrosion mode of steel bar in concrete, high temperature test was carried out on concrete specimens with different copper slag replacing ratios, then the artificial accelerated chloride ion corrosion test was conducted on the specimens using dry-wet cycling immersion method, and the corrosion state of steel bars embedded in concrete was monitored by measuring the half-cell potential value using electrochemical method, the chloride ion content in concrete and corrosion rate of steel bar were also measured at last. The results show that the half-cell potential method well reflects the actual corrosion situation of steel bar in specimen. High temperature destroys the chloride ion penetration resistance performance of concrete, thus causing the corrosion degree of steel bar in concrete specimen increases with the increase of heating temperature. In addition, the combined effect of inherent larger expansion deformation of copper slag at high temperature and uncoordinated shrinkage between copper slag and cement paste after cooling furtherly destroys the microstructure of concrete, thus causing the corrosion rate of steel bar increases with the increase of copper slag replacing ratio. A fitting formula for corrosion depth of steel bar in copper slag concrete after exposure to high temperature under chloride attack was established at last.
In order to investigate the influence of high temperature and copper slag fine aggregate on corrosion mode of steel bar in concrete, high temperature test was carried out on concrete specimens with different copper slag replacing ratios, then the artificial accelerated chloride ion corrosion test was conducted on the specimens using dry-wet cycling immersion method, and the corrosion state of steel bars embedded in concrete was monitored by measuring the half-cell potential value using electrochemical method, the chloride ion content in concrete and corrosion rate of steel bar were also measured at last. The results show that the half-cell potential method well reflects the actual corrosion situation of steel bar in specimen. High temperature destroys the chloride ion penetration resistance performance of concrete, thus causing the corrosion degree of steel bar in concrete specimen increases with the increase of heating temperature. In addition, the combined effect of inherent larger expansion deformation of copper slag at high temperature and uncoordinated shrinkage between copper slag and cement paste after cooling furtherly destroys the microstructure of concrete, thus causing the corrosion rate of steel bar increases with the increase of copper slag replacing ratio. A fitting formula for corrosion depth of steel bar in copper slag concrete after exposure to high temperature under chloride attack was established at last.
2022, 39(6): 2885-2893.
doi: 10.13801/j.cnki.fhclxb.20210906.004
Abstract:
Low grade heat energy, such as solar radiation heat energy, is an important part of energy utilization and conversion. Due to the large amount and being not effectively used, it is emitted to the environment, resulting in waste and low energy efficiency. Phase change materials can absorb, store and release heat with its latent heat capacity, while their temperature fluctuation during phase changing is small. So combined the above two, the transformation of photo-thermal energy and heat storage based on phase change materials has become one of the important ways to utilize solar radiation energy. However, solid-liquid phase change materials are easy to leak. Therefore, in order to solve the problem of easy leakage of phase change materials, like polyethylene glycol, the waste biomass pomelo peel was focused, which was converted into a dual functional material of supporting skeleton and light absorption through a simple carbonization process, and further electro-deposition to enhance its light absorption performance. The shape stable phase change composites with the features of high loading capacity, high phase change enthalpy retention and excellent cycle stability were obtained by vacuum impregnation of polyethylene glycol. The maximum mass loss of 100 cycles is only 2.2%, and the heat storage efficiency of photo-thermal conversion is 87.5%. The shape stable phase change composites based on waste pomelo peel not only have low cost, simple preparation, but also realize waste utilization. The leakage free bio-based composites provide a new choice for further efficient and comprehensive utilization of low-grade heat energy.
Low grade heat energy, such as solar radiation heat energy, is an important part of energy utilization and conversion. Due to the large amount and being not effectively used, it is emitted to the environment, resulting in waste and low energy efficiency. Phase change materials can absorb, store and release heat with its latent heat capacity, while their temperature fluctuation during phase changing is small. So combined the above two, the transformation of photo-thermal energy and heat storage based on phase change materials has become one of the important ways to utilize solar radiation energy. However, solid-liquid phase change materials are easy to leak. Therefore, in order to solve the problem of easy leakage of phase change materials, like polyethylene glycol, the waste biomass pomelo peel was focused, which was converted into a dual functional material of supporting skeleton and light absorption through a simple carbonization process, and further electro-deposition to enhance its light absorption performance. The shape stable phase change composites with the features of high loading capacity, high phase change enthalpy retention and excellent cycle stability were obtained by vacuum impregnation of polyethylene glycol. The maximum mass loss of 100 cycles is only 2.2%, and the heat storage efficiency of photo-thermal conversion is 87.5%. The shape stable phase change composites based on waste pomelo peel not only have low cost, simple preparation, but also realize waste utilization. The leakage free bio-based composites provide a new choice for further efficient and comprehensive utilization of low-grade heat energy.
2022, 39(6): 2894-2906.
doi: 10.13801/j.cnki.fhclxb.20210803.001
Abstract:
In the process of emulsified asphalt demulsification, the hydrophilic group of the emulsifier molecule is adsorbed on the surface of the aggregate, and the lipophilic group pulls the asphalt droplets to aggregate on the surface of the aggregate to achieve complete demulsification. Therefore, in order to explore the influence of hydrophilic groups of emulsifier on demulsification process of emulsified asphalt, the adsorption of five kinds of anionic emulsifiers with different hydrophobic groups of dodecyl carbon chain and hydrophilic groups on the surface of the main chemical component (SiO2) of basalt was explored by molecular dynamics and electrical conductivity experiments. The simulation results show that the K+ in the hydrophilic group can enhance the van der Waals interaction between the dodecyl anionic emulsifier and water molecules more than Na+, and promote the aggregation and adsorption of the dodecyl anionic emulsifier on the SiO2 surface. The introduction of phenyl functional group into the hydrophilic group can improve the van der Waals interaction between dodecyl anion emulsifier and water molecules and the adsorption capacity of dodecyl anion emulsifier on the surface of SiO2. The higher the introduction rate of phenyl functional groups, the stronger the van der Waals interaction between the dodecyl anionic emulsifier and water molecules and the stronger the adsorption capacity of the dodecyl anionic emulsifier on the SiO2 surface. Because of the action of Coulomb force, the diffusion behavior of C atom at the tail end of hydrophobic group and S atom at the polar head of hydrophilic group on the surface of SiO2 is weaker than that of the five dodecyl anionic emulsifiers. The experimental results show that the adsorption capacity of five kinds of dodecyl anionic emulsifiers on SiO2 surface increases with the increase of emulsifier concentration and solid/liquid ratio. The order of the adsorption amount of the five anionic emulsifiers on the SiO2 surface is consistent with the results in molecular dynamics, which verifies the reliability of the conclusion.
In the process of emulsified asphalt demulsification, the hydrophilic group of the emulsifier molecule is adsorbed on the surface of the aggregate, and the lipophilic group pulls the asphalt droplets to aggregate on the surface of the aggregate to achieve complete demulsification. Therefore, in order to explore the influence of hydrophilic groups of emulsifier on demulsification process of emulsified asphalt, the adsorption of five kinds of anionic emulsifiers with different hydrophobic groups of dodecyl carbon chain and hydrophilic groups on the surface of the main chemical component (SiO2) of basalt was explored by molecular dynamics and electrical conductivity experiments. The simulation results show that the K+ in the hydrophilic group can enhance the van der Waals interaction between the dodecyl anionic emulsifier and water molecules more than Na+, and promote the aggregation and adsorption of the dodecyl anionic emulsifier on the SiO2 surface. The introduction of phenyl functional group into the hydrophilic group can improve the van der Waals interaction between dodecyl anion emulsifier and water molecules and the adsorption capacity of dodecyl anion emulsifier on the surface of SiO2. The higher the introduction rate of phenyl functional groups, the stronger the van der Waals interaction between the dodecyl anionic emulsifier and water molecules and the stronger the adsorption capacity of the dodecyl anionic emulsifier on the SiO2 surface. Because of the action of Coulomb force, the diffusion behavior of C atom at the tail end of hydrophobic group and S atom at the polar head of hydrophilic group on the surface of SiO2 is weaker than that of the five dodecyl anionic emulsifiers. The experimental results show that the adsorption capacity of five kinds of dodecyl anionic emulsifiers on SiO2 surface increases with the increase of emulsifier concentration and solid/liquid ratio. The order of the adsorption amount of the five anionic emulsifiers on the SiO2 surface is consistent with the results in molecular dynamics, which verifies the reliability of the conclusion.
2022, 39(6): 2907-2917.
doi: 10.13801/j.cnki.fhclxb.20210909.005
Abstract:
Aiming at the problems of traditional plastic products which are difficult to degrade and pollute the environment, this work selects environmentally friendly and degradable Jackfruit seeds starch (JFss), carboxymethyl cellulose (CMC) and sodium alginate (SA) as raw materials and prepares a biodegradable composite film by a coating process. The effects of the amount of JFss on the mechanical properties, water resistance, water solubility and moisture permeability of the composite membrane were investigated, as well as the changes of the wettability of the composite membrane with time, and the composite membrane was tested for soil burial degradability. SEM, FITR, XRD and TGA were used to characterize the morphology, structure and thermal stability of the composite films. The results show that the addition of JFss increases the tensile strength of the composite film by 35.8%, water resistance by 4.16%, water solubility by 7.8%, water vapor barrier by 153.7%, and has good wettability, moisture retention and biodegradability. In addition, each component of CMC, SA and JFss in the composite film forms intermolecular hydrogen bonds, which have good compatibility and thermal stability. The raw materials for the preparation of composite film by this method are inexpensive, simple to prepare, and can be produced on a large scale, which have potential applications in the field of biodegradable materials.
Aiming at the problems of traditional plastic products which are difficult to degrade and pollute the environment, this work selects environmentally friendly and degradable Jackfruit seeds starch (JFss), carboxymethyl cellulose (CMC) and sodium alginate (SA) as raw materials and prepares a biodegradable composite film by a coating process. The effects of the amount of JFss on the mechanical properties, water resistance, water solubility and moisture permeability of the composite membrane were investigated, as well as the changes of the wettability of the composite membrane with time, and the composite membrane was tested for soil burial degradability. SEM, FITR, XRD and TGA were used to characterize the morphology, structure and thermal stability of the composite films. The results show that the addition of JFss increases the tensile strength of the composite film by 35.8%, water resistance by 4.16%, water solubility by 7.8%, water vapor barrier by 153.7%, and has good wettability, moisture retention and biodegradability. In addition, each component of CMC, SA and JFss in the composite film forms intermolecular hydrogen bonds, which have good compatibility and thermal stability. The raw materials for the preparation of composite film by this method are inexpensive, simple to prepare, and can be produced on a large scale, which have potential applications in the field of biodegradable materials.
2022, 39(6): 2918-2929.
doi: 10.13801/j.cnki.fhclxb.20210906.007
Abstract:
3D nanofiber scaffold composites in bone tissue engineering are promising. Poly(L-lactic acid)-polycaprolactone-cellulose acetate 3D composite micro-nanofibrous porous scaffolds were prepared by low-temperature phase separation, without the assistance of additives. The effects of PCL-CA-PLLA ratio, quenching time, polymer concentration and quenching temperature on the morphology of fibrous scaffolds were investigated by SEM. The diameter of PCL-CA-PLLA (1∶1∶8) is (276±121) nm, which is similar to the size of the extracellular matrix (50-500 nm), and the porosity and specific surface area are 95.12% and 54.18 m2/g, respectively. It is indicated that PCL-CA-PLLA 3D micro-nanofibrous porous scaffold composites are 3D porous materials with high porosity and large specific surface area. Compared with pure PLLA fibrous scaffolds, the mechanical strength and hydrophilicity of PCL-CA-PLLA 3D micro-nanofibrous porous scaffold composites are improved. PLLA-PCL-CA 3D micro-nanofibrous are expected to be ideal tissue engineering scaffold materials.
3D nanofiber scaffold composites in bone tissue engineering are promising. Poly(L-lactic acid)-polycaprolactone-cellulose acetate 3D composite micro-nanofibrous porous scaffolds were prepared by low-temperature phase separation, without the assistance of additives. The effects of PCL-CA-PLLA ratio, quenching time, polymer concentration and quenching temperature on the morphology of fibrous scaffolds were investigated by SEM. The diameter of PCL-CA-PLLA (1∶1∶8) is (276±121) nm, which is similar to the size of the extracellular matrix (50-500 nm), and the porosity and specific surface area are 95.12% and 54.18 m2/g, respectively. It is indicated that PCL-CA-PLLA 3D micro-nanofibrous porous scaffold composites are 3D porous materials with high porosity and large specific surface area. Compared with pure PLLA fibrous scaffolds, the mechanical strength and hydrophilicity of PCL-CA-PLLA 3D micro-nanofibrous porous scaffold composites are improved. PLLA-PCL-CA 3D micro-nanofibrous are expected to be ideal tissue engineering scaffold materials.
2022, 39(6): 2930-2940.
doi: 10.13801/j.cnki.fhclxb.20210726.001
Abstract:
The aim of this research was to explore the effect of different morphologies of bamboo fiber (BF) on epoxy resin (EP) impregnation in vacuum-assisted resin transfer molding (VARTM) process and the properties of BF/EP composites. Three types of BF with different morphologies (BF-2, BF-3 and BF-4) were obtained by mechanical rolling with 2, 3 and 4 times, respectively. The BF were made into bamboo fiber mat (BFM) by wet layering process, and then produced into BF-2/EP, BF-3/EP and BF-4/EP composites with fiber content of 45wt% by VARTM. The properties of BF, BFMs and BF/EP composites were characterized with ESEM, ultra-depth-of-field microscope, mechanical testing machine, TG, DMA and micro-CT. The results show that the fluffy degree of BFMs by wet layering decreases and the difficulty of resin injection increases when the fiber length decreases and the fiber separation increases. The fiber accumulation occurs during resin injection of BFM-4, and BF-3/EP composite has the lowest water absorption. The BF-2 with longer length and lower dispersion can easily lead to poor interfacial bonding with resin, although it can maintain the structure and properties of BF. The mechanical properties of the composite prepared by BF-3 with moderate length and separation are the best, and the flexural strength, flexural modulus, shear strength and impact toughness are 97.90 MPa, 7.2 GPa, 17.01 MPa and 8.11 kJ/m2, respectively. BF accelerates the pyrolysis of BF/EP composites. The BF-4/EP composite has a higher pyrolysis temperature because BF-4 has lower hemicellulose content compared with other BF. BF can improve the rigidity of EP. The interface bonding between BF-3 and resin is the best, and the proportion of pores volume is only 0.04%. The maximum storage modulus of BF-3/EP composites is 5198 MPa. When BF/EP composites are prepared by VARTM, the appropriate BF size and separation degree are the key factors that affect the interfacial bonding and properties.
The aim of this research was to explore the effect of different morphologies of bamboo fiber (BF) on epoxy resin (EP) impregnation in vacuum-assisted resin transfer molding (VARTM) process and the properties of BF/EP composites. Three types of BF with different morphologies (BF-2, BF-3 and BF-4) were obtained by mechanical rolling with 2, 3 and 4 times, respectively. The BF were made into bamboo fiber mat (BFM) by wet layering process, and then produced into BF-2/EP, BF-3/EP and BF-4/EP composites with fiber content of 45wt% by VARTM. The properties of BF, BFMs and BF/EP composites were characterized with ESEM, ultra-depth-of-field microscope, mechanical testing machine, TG, DMA and micro-CT. The results show that the fluffy degree of BFMs by wet layering decreases and the difficulty of resin injection increases when the fiber length decreases and the fiber separation increases. The fiber accumulation occurs during resin injection of BFM-4, and BF-3/EP composite has the lowest water absorption. The BF-2 with longer length and lower dispersion can easily lead to poor interfacial bonding with resin, although it can maintain the structure and properties of BF. The mechanical properties of the composite prepared by BF-3 with moderate length and separation are the best, and the flexural strength, flexural modulus, shear strength and impact toughness are 97.90 MPa, 7.2 GPa, 17.01 MPa and 8.11 kJ/m2, respectively. BF accelerates the pyrolysis of BF/EP composites. The BF-4/EP composite has a higher pyrolysis temperature because BF-4 has lower hemicellulose content compared with other BF. BF can improve the rigidity of EP. The interface bonding between BF-3 and resin is the best, and the proportion of pores volume is only 0.04%. The maximum storage modulus of BF-3/EP composites is 5198 MPa. When BF/EP composites are prepared by VARTM, the appropriate BF size and separation degree are the key factors that affect the interfacial bonding and properties.
2022, 39(6): 2941-2948.
doi: 10.13801/j.cnki.fhclxb.20210707.005
Abstract:
The B4C/Al composites were prepared by stirring casting method. The method of experimental analysis combined with first-principles calculations was used to explore the influence mechanism of the interfacial reaction products Al3BC and TiB2 on the wettability of B4C/Al composite particles and the interfacial bonding strength. The results show that when the interface reaction product is Al3BC, the wettability of B4C particles has not been substantially improved, particle agglomeration still exists, and the interface bonding is poor. Excessive interface reaction makes the decomposition and loss of B4C particles serious, resulting in insignificant strengthening effect of B4C particles. When the interface reaction product is TiB2 by adding Ti element, the particle wettability is significantly improved, the agglomeration of B4C particles is significantly reduced, the interface bonding strength is higher, and the mechanical properties are significantly improved. The Al(111)/TiB2(0001) interface adhesion work of different terminals is greater than that of Al(111)/B4C(0001), indicating that the interface reaction product TiB2 can improve the wettability of B4C particles. The interface reaction product Al3BC is very limited in improving the wettability of B4C particles. A mixed covalent/metallic bond is formed on the interface of Al(111)/Al3BC(0001) and Al(111)/TiB2(0001). The chemical bonding strength on the Al(111)/TiB2(0001) interface is greater, and the interface bonding strength is correspondingly greater.
The B4C/Al composites were prepared by stirring casting method. The method of experimental analysis combined with first-principles calculations was used to explore the influence mechanism of the interfacial reaction products Al3BC and TiB2 on the wettability of B4C/Al composite particles and the interfacial bonding strength. The results show that when the interface reaction product is Al3BC, the wettability of B4C particles has not been substantially improved, particle agglomeration still exists, and the interface bonding is poor. Excessive interface reaction makes the decomposition and loss of B4C particles serious, resulting in insignificant strengthening effect of B4C particles. When the interface reaction product is TiB2 by adding Ti element, the particle wettability is significantly improved, the agglomeration of B4C particles is significantly reduced, the interface bonding strength is higher, and the mechanical properties are significantly improved. The Al(111)/TiB2(0001) interface adhesion work of different terminals is greater than that of Al(111)/B4C(0001), indicating that the interface reaction product TiB2 can improve the wettability of B4C particles. The interface reaction product Al3BC is very limited in improving the wettability of B4C particles. A mixed covalent/metallic bond is formed on the interface of Al(111)/Al3BC(0001) and Al(111)/TiB2(0001). The chemical bonding strength on the Al(111)/TiB2(0001) interface is greater, and the interface bonding strength is correspondingly greater.
2022, 39(6): 2949-2961.
doi: 10.13801/j.cnki.fhclxb.20210708.001
Abstract:
A computational representative volume element (RVE) framework considering interface, as well as particle morphology, was adopted to provide a better understanding and prediction of the existing links between the behaviors of contents, interface and the macroscopic mechanical responses of composite solid propellants. A cohesive zone model (CZM) was taken into account to study the significance of interface stiffness, strength and critical displacement, along with the relative contribution of particle morphology and interface, on the macroscopic mechanical properties of the propellant. Results indicate that the initial modulus of propellant increases from 0.67 MPa to 3.67 MPa as the interface stiffness varies between 0.004 MPa/mm and 400 MPa/mm, while the tensile strength of propellant increases from 0.15 MPa to 0.76 MPa when the interface strength changes from 0.05 MPa to 30 MPa, which implies that an increase in the interface stiffness has a limited improvement over the initial modulus of the propellant. In comparison, the interface strength improves its tensile strength remarkably. However, higher interfacial strength may lead to “damage localization” in the microstructure, thus reducing the elongation of propellant. The different behaviors observed on macroscopic view are rather due to interface than to the morphology of particles; all of the results exhibit that the interface is one of the major determining factors affecting the tensile properties of the propellant. Finally, based on the previous analyses, the creep behaviors of another propellant were predicted under various stress levels. It is found that the logarithm of creep rupture time is linear with constant stress.
A computational representative volume element (RVE) framework considering interface, as well as particle morphology, was adopted to provide a better understanding and prediction of the existing links between the behaviors of contents, interface and the macroscopic mechanical responses of composite solid propellants. A cohesive zone model (CZM) was taken into account to study the significance of interface stiffness, strength and critical displacement, along with the relative contribution of particle morphology and interface, on the macroscopic mechanical properties of the propellant. Results indicate that the initial modulus of propellant increases from 0.67 MPa to 3.67 MPa as the interface stiffness varies between 0.004 MPa/mm and 400 MPa/mm, while the tensile strength of propellant increases from 0.15 MPa to 0.76 MPa when the interface strength changes from 0.05 MPa to 30 MPa, which implies that an increase in the interface stiffness has a limited improvement over the initial modulus of the propellant. In comparison, the interface strength improves its tensile strength remarkably. However, higher interfacial strength may lead to “damage localization” in the microstructure, thus reducing the elongation of propellant. The different behaviors observed on macroscopic view are rather due to interface than to the morphology of particles; all of the results exhibit that the interface is one of the major determining factors affecting the tensile properties of the propellant. Finally, based on the previous analyses, the creep behaviors of another propellant were predicted under various stress levels. It is found that the logarithm of creep rupture time is linear with constant stress.
2022, 39(6): 2962-2973.
doi: 10.13801/j.cnki.fhclxb.20210707.004
Abstract:
Strength is a important factor to consider when designing high-performance composite materials. Inspired by the excellent mechanical properties and complex hierarchical structure of nacre, a nanocomposite was designed, in which the graphene layers were interlaced in the polymethyl methacrylate matrix. Coarse-grained molecular dynamics simulations were used to investigate the effect of various geometrical variations on the mechanical properties under tension loads, including the two-dimensional geometric shapes of graphene, the number of graphene layers, the interlayer distance of the graphene sheets and the overlap length of the graphene sheets. The simulation results show that the strengthening effects of different geometries of graphenes on composites are very different, among which, the rectangle and sawtooth shapes are close to each other and are stronger than the trapezoidal graphene. There is an optimal number of graphene layers to make the composite have the strongest overall mechanical properties. The mechanical properties of graphene can be improved by reducing the interlayer distance of the graphene sheets or increasing the overlap length of the graphene sheets. Overall, this paper systematically studies the influencing factors of graphene-reinforced polymer composites and reveals the influence rules and microscopic mechanisms of each factor. This study provides a useful guidance for the design of nanocompo-sites with targeted properties.
Strength is a important factor to consider when designing high-performance composite materials. Inspired by the excellent mechanical properties and complex hierarchical structure of nacre, a nanocomposite was designed, in which the graphene layers were interlaced in the polymethyl methacrylate matrix. Coarse-grained molecular dynamics simulations were used to investigate the effect of various geometrical variations on the mechanical properties under tension loads, including the two-dimensional geometric shapes of graphene, the number of graphene layers, the interlayer distance of the graphene sheets and the overlap length of the graphene sheets. The simulation results show that the strengthening effects of different geometries of graphenes on composites are very different, among which, the rectangle and sawtooth shapes are close to each other and are stronger than the trapezoidal graphene. There is an optimal number of graphene layers to make the composite have the strongest overall mechanical properties. The mechanical properties of graphene can be improved by reducing the interlayer distance of the graphene sheets or increasing the overlap length of the graphene sheets. Overall, this paper systematically studies the influencing factors of graphene-reinforced polymer composites and reveals the influence rules and microscopic mechanisms of each factor. This study provides a useful guidance for the design of nanocompo-sites with targeted properties.
2022, 39(6): 2974-2986.
doi: 10.13801/j.cnki.fhclxb.20210902.005
Abstract:
The delamination damage has significant influence on the bearing capacity and failure mode of open-hole laminates. By combining experiment and simulation, the compression bearing capacity and failure mode of composite open-hole laminates with single prefabricated laminated defects, two laminated coupling defects on the same side and double laminated coupling defects on the different side were studied. Through the embedded polytetrafluoroethylene (PTFE) membrane, the open-hole laminate containing single prefabricated delamination defects was prepared. By means of immersion ultrasonic C scan and digital image DIC technique, the damage evolution and normal deformation were characterized and monitored. The delamination propagation behavior and failure deformation characteristics of laminates with various defect sizes under compression loading were studied, and the influence mechanism of the size of the delamination defects on the bearing capacity of the laminates was revealed. A numerical model of open-hole laminate was established based on the cohesion element method. The damage propagation mechanism of open-hoe laminate with single prefabricated laminated defects was explored. Based on the optimized model, the numerical prediction and analysis of the buckling deformation, delamination expansion and bearing capacity of the open-hole laminate with two delaminated coupling defects were carried out. The experimental results show that the specimen with single delamination defect presents the initial compression, local buckling and overall buckling. The delamination size has significant impact on the compressive capability, which decreases with the increasing of delamination size. The numerical results of two delaminated defects show the second delaminated defect further reduces the compressive bearing capacity. The failure model of laminate with two coupling defects on the same sides is similar with that of laminates with single prefabricated defect; while, double-crack propagation occurs in the asymmetrical coupled laminated structure on the opposite side, which further weakens the compression bearing capacity of open-hole laminates.
The delamination damage has significant influence on the bearing capacity and failure mode of open-hole laminates. By combining experiment and simulation, the compression bearing capacity and failure mode of composite open-hole laminates with single prefabricated laminated defects, two laminated coupling defects on the same side and double laminated coupling defects on the different side were studied. Through the embedded polytetrafluoroethylene (PTFE) membrane, the open-hole laminate containing single prefabricated delamination defects was prepared. By means of immersion ultrasonic C scan and digital image DIC technique, the damage evolution and normal deformation were characterized and monitored. The delamination propagation behavior and failure deformation characteristics of laminates with various defect sizes under compression loading were studied, and the influence mechanism of the size of the delamination defects on the bearing capacity of the laminates was revealed. A numerical model of open-hole laminate was established based on the cohesion element method. The damage propagation mechanism of open-hoe laminate with single prefabricated laminated defects was explored. Based on the optimized model, the numerical prediction and analysis of the buckling deformation, delamination expansion and bearing capacity of the open-hole laminate with two delaminated coupling defects were carried out. The experimental results show that the specimen with single delamination defect presents the initial compression, local buckling and overall buckling. The delamination size has significant impact on the compressive capability, which decreases with the increasing of delamination size. The numerical results of two delaminated defects show the second delaminated defect further reduces the compressive bearing capacity. The failure model of laminate with two coupling defects on the same sides is similar with that of laminates with single prefabricated defect; while, double-crack propagation occurs in the asymmetrical coupled laminated structure on the opposite side, which further weakens the compression bearing capacity of open-hole laminates.
2022, 39(6): 2987-2996.
doi: 10.13801/j.cnki.fhclxb.20210707.003
Abstract:
Generalized mixed finite element method of pure elastomer was introduced into the static analysis of piezoelectric materials. Because the 8-node hexahedral noncompatible solid element was used to solve the whole structure discretely, many artificial assumptions in the theory of plate and shell were abandoned. The addition of noncompatible terms makes this method exhibit better numerical performance than the same kind of compatible elements. In this method, the stress boundary conditions and displacement boundary conditions were considered simultaneously, and the interlaminar stress and in-plane stress were treated separately in the solution process, and the in-plane stress was calculated according to the constitutive relation of each layer, so that the obtained interlaminar stress and in-plane stress are closer to the exact solution. The accuracy of the proposed method was illustrated by several representative numerical examples of laminates. Compared with the traditional analytical and numerical methods, the theoretical method presented in this paper has advantages in applicability and effectiveness.
Generalized mixed finite element method of pure elastomer was introduced into the static analysis of piezoelectric materials. Because the 8-node hexahedral noncompatible solid element was used to solve the whole structure discretely, many artificial assumptions in the theory of plate and shell were abandoned. The addition of noncompatible terms makes this method exhibit better numerical performance than the same kind of compatible elements. In this method, the stress boundary conditions and displacement boundary conditions were considered simultaneously, and the interlaminar stress and in-plane stress were treated separately in the solution process, and the in-plane stress was calculated according to the constitutive relation of each layer, so that the obtained interlaminar stress and in-plane stress are closer to the exact solution. The accuracy of the proposed method was illustrated by several representative numerical examples of laminates. Compared with the traditional analytical and numerical methods, the theoretical method presented in this paper has advantages in applicability and effectiveness.
2022, 39(6): 2997-3008.
doi: 10.13801/j.cnki.fhclxb.20210702.002
Abstract:
In order to predict and control the damage degree of carbon fiber reinforced polymer (CFRP) anti-collision beams in low speed collision, a finite element explicit dynamic collision model of CFRP anti-collision beams was established. Mechanical properties of CFRP anti-collision beams were simulated by solid composite materials, and the interlayer interaction of CFRP was simulated by cohesive element. A VUSDFLD subroutine based on Tsai-Wu tensor theory was developed to determine the damage of composite elements in six directions during the collision process. The stiffness of the failure elements was reduced according to the sudden degradation model. The Johnson-Cook constitutive model was used to simulate the impact damage of reinforced aluminum alloy layers. The stiffness reduction of the failure element was carried out by linear continuous degradation model. The collision results of two CFRP laminates ([±45°/45°/0°/0°/90°/45°/0°/0°/90°]s and [±45°/45°/0°/0°/0°/45°/90°/45°/0°/0°/90°]s) were compared with the collision results of CFRP anti-collision beam containing aluminum alloy reinforced layer. It can be seen that when the number of elements in the layer is the same, the number of failure elements decreases obviously by adding four layers of composite laminates to CFRP anti-collision beam. The number of failure elements of the multi-material hybrid anti-collision beam structure with reinforced aluminum alloy layer is significantly reduced under the condition that the mass of the beam is basically unchanged. The results show that the developed VUSDFLD subroutine can be used for the explicit dynamic collision damage simulation of composite anti-collision beams, and the results based on the collision damage simulation can provide a reference for the structural design of CFRP anti-collision beams.
In order to predict and control the damage degree of carbon fiber reinforced polymer (CFRP) anti-collision beams in low speed collision, a finite element explicit dynamic collision model of CFRP anti-collision beams was established. Mechanical properties of CFRP anti-collision beams were simulated by solid composite materials, and the interlayer interaction of CFRP was simulated by cohesive element. A VUSDFLD subroutine based on Tsai-Wu tensor theory was developed to determine the damage of composite elements in six directions during the collision process. The stiffness of the failure elements was reduced according to the sudden degradation model. The Johnson-Cook constitutive model was used to simulate the impact damage of reinforced aluminum alloy layers. The stiffness reduction of the failure element was carried out by linear continuous degradation model. The collision results of two CFRP laminates ([±45°/45°/0°/0°/90°/45°/0°/0°/90°]s and [±45°/45°/0°/0°/0°/45°/90°/45°/0°/0°/90°]s) were compared with the collision results of CFRP anti-collision beam containing aluminum alloy reinforced layer. It can be seen that when the number of elements in the layer is the same, the number of failure elements decreases obviously by adding four layers of composite laminates to CFRP anti-collision beam. The number of failure elements of the multi-material hybrid anti-collision beam structure with reinforced aluminum alloy layer is significantly reduced under the condition that the mass of the beam is basically unchanged. The results show that the developed VUSDFLD subroutine can be used for the explicit dynamic collision damage simulation of composite anti-collision beams, and the results based on the collision damage simulation can provide a reference for the structural design of CFRP anti-collision beams.
2022, 39(6): 3009-3019.
doi: 10.13801/j.cnki.fhclxb.20210616.003
Abstract:
The adhesive bonding strength enhancement of aluminum substrate and carbon fiber reinforced polymer (CFRP) at cryogenic temperature has attracted far-ranging attention with their application expanding to rocket booster. Aiming at the potential bonding interface defect of epoxy joint, we adopted the anodizing and sanding treatments to modify surface performance of Al substrate and CFRP panel respectively. The resin pre-coating (RPC) technique was used to eliminate the originally existing defect caused by macromolecular epoxy at the root of porous Al substrate. The carbon nanotubes were applied as additives to be impregnated into channels on Al substrate surface via RPC technique and construct the quasi-Z directional fiber bridging, which can further improve the adhesive bonding strength of epoxy joint. The three-point bending (3-P-B) results show the flexural strength of aluminum substrate-CFRP after treated has been enhanced by 14.6% at room temperature, and even higher 27.6% at liquid nitrogen temperature based on that of the one only cleaned by acetone. Failure mode exhibits the weaker adhesive failure on bonding interface has been transformed into main structure fracture failure of CFRP after combined surface treatments at both room temperature and liquid nitrogen temperature. Overall, the effective treatment methods can offer an alternative reference in industrial application of cryogenic liquid fuel tank.
The adhesive bonding strength enhancement of aluminum substrate and carbon fiber reinforced polymer (CFRP) at cryogenic temperature has attracted far-ranging attention with their application expanding to rocket booster. Aiming at the potential bonding interface defect of epoxy joint, we adopted the anodizing and sanding treatments to modify surface performance of Al substrate and CFRP panel respectively. The resin pre-coating (RPC) technique was used to eliminate the originally existing defect caused by macromolecular epoxy at the root of porous Al substrate. The carbon nanotubes were applied as additives to be impregnated into channels on Al substrate surface via RPC technique and construct the quasi-Z directional fiber bridging, which can further improve the adhesive bonding strength of epoxy joint. The three-point bending (3-P-B) results show the flexural strength of aluminum substrate-CFRP after treated has been enhanced by 14.6% at room temperature, and even higher 27.6% at liquid nitrogen temperature based on that of the one only cleaned by acetone. Failure mode exhibits the weaker adhesive failure on bonding interface has been transformed into main structure fracture failure of CFRP after combined surface treatments at both room temperature and liquid nitrogen temperature. Overall, the effective treatment methods can offer an alternative reference in industrial application of cryogenic liquid fuel tank.
2022, 39(6): 3020-3028.
doi: 10.13801/j.cnki.fhclxb.20210622.003
Abstract:
Based on cubic non-uniform rational B-splines (NURBS) curve, the design and bucking property of cylindrical shell produced by fiber variable angle placement were studied. Firstly, the reference trajectory of fiber variable angle placement was defined by cubic NURBS curve, and the parameterized expression of fiber variable angle placement was determine. Secondly, taking the fiber variable angle placements ±<25(0.4)(0.8)75> and ±<65(0.4)(0.8)10> as examples, the fiber angle distributions of the axial and circumferential shift placements of the cubic NURBS curve on the cylindrical shell were demonstrated. Then, the ±45° placement of constant stiffness cylindrical shell was replaced by the fiber variable angle placements. The linear buckling analysis of the variable stiffness cylindrical shell was carried out, and the axial translation cylindrical shell, circumferential translation cylindrical shell and constant stiffness cylindrical shell were compared. Finally, the influence of weight factors on the buckling property was studied under the constraint of curvature radius. The results show that the circumferential translation cylindrical shell has better buckling performance. Under the constraint of curvature radius, the variable stiffness cylindrical shell with excellent buckling performance can be obtained by determining initial angle, termination angle and control point parameter, and the buckling load of the variable stiffness cylindrical shell can be increased again by changing the weight factor.
Based on cubic non-uniform rational B-splines (NURBS) curve, the design and bucking property of cylindrical shell produced by fiber variable angle placement were studied. Firstly, the reference trajectory of fiber variable angle placement was defined by cubic NURBS curve, and the parameterized expression of fiber variable angle placement was determine. Secondly, taking the fiber variable angle placements ±<25(0.4)(0.8)75> and ±<65(0.4)(0.8)10> as examples, the fiber angle distributions of the axial and circumferential shift placements of the cubic NURBS curve on the cylindrical shell were demonstrated. Then, the ±45° placement of constant stiffness cylindrical shell was replaced by the fiber variable angle placements. The linear buckling analysis of the variable stiffness cylindrical shell was carried out, and the axial translation cylindrical shell, circumferential translation cylindrical shell and constant stiffness cylindrical shell were compared. Finally, the influence of weight factors on the buckling property was studied under the constraint of curvature radius. The results show that the circumferential translation cylindrical shell has better buckling performance. Under the constraint of curvature radius, the variable stiffness cylindrical shell with excellent buckling performance can be obtained by determining initial angle, termination angle and control point parameter, and the buckling load of the variable stiffness cylindrical shell can be increased again by changing the weight factor.
