2008 Vol. 25, No. 6
2008, 25(6): 1-6.
Abstract:
A series of starch/PVA (SP) films with the thickness of 0.05 mm～0.10 mm were casted by the solvent method. The degradation behaviors of the SP films in simulated blood fluid (SBF) and simulated saliva fluid (SSF) were studied. Changes of their mechanical properties, mass loss, swelling degree, thermal properties and morphology of surface during degradation were tested. It is found that the films can keep the shape stability and certain mechanical properties during 30 days degradation. The biocompatibility of the SP film was investigated by cytotoxicity, hemolytic and cell culture tests. The results show that the SP films possess excellent cell and blood compatibility. All the results demonstrate that the SP films can be potentially applied as guide tissue regeneration films.
A series of starch/PVA (SP) films with the thickness of 0.05 mm～0.10 mm were casted by the solvent method. The degradation behaviors of the SP films in simulated blood fluid (SBF) and simulated saliva fluid (SSF) were studied. Changes of their mechanical properties, mass loss, swelling degree, thermal properties and morphology of surface during degradation were tested. It is found that the films can keep the shape stability and certain mechanical properties during 30 days degradation. The biocompatibility of the SP film was investigated by cytotoxicity, hemolytic and cell culture tests. The results show that the SP films possess excellent cell and blood compatibility. All the results demonstrate that the SP films can be potentially applied as guide tissue regeneration films.
2008, 25(6): 7-11.
Abstract:
Bacterial cellulose (BC) is a kind of biomedical scaffold with nano network. BC should be oxidized to 2, 3-dialdehyde bacterial cellulose (DABC) by sodium periodate to make BC degradable. By the biomimetic route，the degradable HA/DABC composites for bone tissue engineering were prepared. It was observed that the apatite mineralized on DABC via the biomimetic route together with degradation of DABC by SEM. The HA/DABC composites acquired were proved by SEM，EDS and XRD. There was apatite formation on the surface and inside of the DABC via 7 days biomimetic mineralization. The ratio of calcium phosphate to the apatite is 1.75 by EDS. It was proved to be hydroxyapatite mainly with a little carbonate hydroxyapatite by XRD. It is shown that the degradable HA/DABC composites for bone tissue engineering could be prepared via the biomimetic route.
Bacterial cellulose (BC) is a kind of biomedical scaffold with nano network. BC should be oxidized to 2, 3-dialdehyde bacterial cellulose (DABC) by sodium periodate to make BC degradable. By the biomimetic route，the degradable HA/DABC composites for bone tissue engineering were prepared. It was observed that the apatite mineralized on DABC via the biomimetic route together with degradation of DABC by SEM. The HA/DABC composites acquired were proved by SEM，EDS and XRD. There was apatite formation on the surface and inside of the DABC via 7 days biomimetic mineralization. The ratio of calcium phosphate to the apatite is 1.75 by EDS. It was proved to be hydroxyapatite mainly with a little carbonate hydroxyapatite by XRD. It is shown that the degradable HA/DABC composites for bone tissue engineering could be prepared via the biomimetic route.
2008, 25(6): 12-15.
Abstract:
Poly (acrylic acid) (PAA) and montmorillonite (MMT)/PAA superabsorbent resins were synthesized by partly neutralized acrylic acid (AA) and sodium type montmorillonite. The structure of the superabsorbents was characterized by FTIR, XRD and SEM, and its blood compatibility was measured by the hemolysis test, coagulation time test and recalcification time test. The results show that montmorillonite layers reacted with acrylic acid during polymerization. The layers exfoliated and scattered in the composite at nano size after the polymerization. Both of the superabsorbent resins have good blood compatibility.
Poly (acrylic acid) (PAA) and montmorillonite (MMT)/PAA superabsorbent resins were synthesized by partly neutralized acrylic acid (AA) and sodium type montmorillonite. The structure of the superabsorbents was characterized by FTIR, XRD and SEM, and its blood compatibility was measured by the hemolysis test, coagulation time test and recalcification time test. The results show that montmorillonite layers reacted with acrylic acid during polymerization. The layers exfoliated and scattered in the composite at nano size after the polymerization. Both of the superabsorbent resins have good blood compatibility.
2008, 25(6): 16-21.
Abstract:
A novel drug carrier based on alginate and poly-L-arginine was fabricated. The alginate/poly(L-arginine) microcapsules with good sphericity, smooth surface and well roportioned particle size were prepared by the high voltage electrostatic method. According to the standard for the biological evaluation of medical devices, the biocompatibility of alginate/poly(L-arginine) microcapsules was studied. The cytotoxicity studies show that the alginate/poly(L-arginine) microcapsules have no significant growth inhibition effect on L929 cells when they were used at 0.1, 0.5, 1.0 mg/mL. The extract productions of the alginate/poly(L-arginine) microcapsules do not show cytotoxic effect even at 10.0 mg/mL. The alginate/poly(L-arginine) microcapsules have no acute systemic toxicity and no hemolytic reaction. All results indicate that the alginate/poly(L-arginine) microcapsules, prepared by the high voltage electrostatic method, have acceptable biocompatibility and might be an appropriate candidate for macromolecule drug delivery, and it is worthy of a further research.
A novel drug carrier based on alginate and poly-L-arginine was fabricated. The alginate/poly(L-arginine) microcapsules with good sphericity, smooth surface and well roportioned particle size were prepared by the high voltage electrostatic method. According to the standard for the biological evaluation of medical devices, the biocompatibility of alginate/poly(L-arginine) microcapsules was studied. The cytotoxicity studies show that the alginate/poly(L-arginine) microcapsules have no significant growth inhibition effect on L929 cells when they were used at 0.1, 0.5, 1.0 mg/mL. The extract productions of the alginate/poly(L-arginine) microcapsules do not show cytotoxic effect even at 10.0 mg/mL. The alginate/poly(L-arginine) microcapsules have no acute systemic toxicity and no hemolytic reaction. All results indicate that the alginate/poly(L-arginine) microcapsules, prepared by the high voltage electrostatic method, have acceptable biocompatibility and might be an appropriate candidate for macromolecule drug delivery, and it is worthy of a further research.
2008, 25(6): 22-27.
Abstract:
SiO2/alginate gel composites derived from 3-aminopropyltrimethoxysilane and sodium alginate were prepared through covalent cross-linking reaction. The gel biocomposites were used as carriers for the immobilization of cellulase. The loading efficiency (%) of the immobilized cellulase exceeds 86%, and the SEM photographs show that the cellulase is distributed homogeneously in the carriers. The activities of the free cellulase and immobilized cellulase were determined by measuring the amount of the glucose made from carboxymethyl cellulase under the given conditions. The results show that the immobilized cellulase has a higher Michaelis constant( Km) than free cellulase. The immobilized cellulase has better stability with respect to pH and temperature than the free cellulose. The optimal pH of enzyme is 3.6 and the optimal temperature of enzyme is 50℃.The storage and recycling stability of the cellulase increase after immobilization, it also remains up to 50% relative activity after 10 cycles and remains 81% relative activity after being stored for 30 days.
SiO2/alginate gel composites derived from 3-aminopropyltrimethoxysilane and sodium alginate were prepared through covalent cross-linking reaction. The gel biocomposites were used as carriers for the immobilization of cellulase. The loading efficiency (%) of the immobilized cellulase exceeds 86%, and the SEM photographs show that the cellulase is distributed homogeneously in the carriers. The activities of the free cellulase and immobilized cellulase were determined by measuring the amount of the glucose made from carboxymethyl cellulase under the given conditions. The results show that the immobilized cellulase has a higher Michaelis constant( Km) than free cellulase. The immobilized cellulase has better stability with respect to pH and temperature than the free cellulose. The optimal pH of enzyme is 3.6 and the optimal temperature of enzyme is 50℃.The storage and recycling stability of the cellulase increase after immobilization, it also remains up to 50% relative activity after 10 cycles and remains 81% relative activity after being stored for 30 days.
2008, 25(6): 28-32.
Abstract:
The chitosan rods were prepared by in-situ precipitation, and then chitosan fibers were filled into the matrix to reinforce the chitosan composite rod. The mechanical properties of this composite rod were investigated, and the morphology of the fracture surfaces was observed by means of SEM. The results indicate that chitosan fiber can improve the mechanical properties of the chitosan composite rod obviously. It is shown that the flexural strength of the composite is improved firstly and then decreases with increasing the mass fraction of chitosan fiber. Compared with the chitosan rod without chitosam fiber, the flexural strength of the composite increases with increasing the length of chitosan fiber. The flexural strength of the composite increases by 55.7% when 5% mass fraction of chitosan fiber with the length 17 mm was filled. This kind of chitosan fiber/chitosan composite will be widely used in the field of internal fixation in surgery.
The chitosan rods were prepared by in-situ precipitation, and then chitosan fibers were filled into the matrix to reinforce the chitosan composite rod. The mechanical properties of this composite rod were investigated, and the morphology of the fracture surfaces was observed by means of SEM. The results indicate that chitosan fiber can improve the mechanical properties of the chitosan composite rod obviously. It is shown that the flexural strength of the composite is improved firstly and then decreases with increasing the mass fraction of chitosan fiber. Compared with the chitosan rod without chitosam fiber, the flexural strength of the composite increases with increasing the length of chitosan fiber. The flexural strength of the composite increases by 55.7% when 5% mass fraction of chitosan fiber with the length 17 mm was filled. This kind of chitosan fiber/chitosan composite will be widely used in the field of internal fixation in surgery.
2008, 25(6): 33-38.
Abstract:
The spheral and smooth calcium alginate beads whose average size was around 290 μm were obtained through the electronic droplet generator. With poly-L-arginine and poly-L-histidine, the novel ALG/(PLA-PLH) composite microcapsules were prepared by incubating the beads into the mixed solution of PLA and PLH for the polymeric membrane forming. In vitro release characteristics of the microcapsules were investigated and the feasibility of application as an oral protein delivery carrier was evaluated by choosing Hb as the protein drug model.The results show that during the first half hour, the cumulative amount of Hb release from the composite microcapsules is lower than 40% and then reaches more than 80% in the end. The ALG/(PLA-PLH) group and the ALG/PLH group possesses a slower release rate compared with the ALG/PLA group. Due to the highest drug loading and encapsulation ratio, the 10 min group is considered as the optimal one. The microcapsules made from the pH 4.6 HAc-NaAc buffer has an obvious capacity of longtime release and low amount of leftover compared with the ones made from distilled water. The cumulative release of Hb is less than 10% when the microcapsules are immersed in the pH 1.2 HCl at the end of the first two hours, while most Hb is released in the pH 6.8 PBS buffer. The release time could be prolonged to some extent through the introduction of chitosan. The composite microcapsules of poly amino acids are likely to become a potential carrier of oral drug delivery system due to their excellent performance.
The spheral and smooth calcium alginate beads whose average size was around 290 μm were obtained through the electronic droplet generator. With poly-L-arginine and poly-L-histidine, the novel ALG/(PLA-PLH) composite microcapsules were prepared by incubating the beads into the mixed solution of PLA and PLH for the polymeric membrane forming. In vitro release characteristics of the microcapsules were investigated and the feasibility of application as an oral protein delivery carrier was evaluated by choosing Hb as the protein drug model.The results show that during the first half hour, the cumulative amount of Hb release from the composite microcapsules is lower than 40% and then reaches more than 80% in the end. The ALG/(PLA-PLH) group and the ALG/PLH group possesses a slower release rate compared with the ALG/PLA group. Due to the highest drug loading and encapsulation ratio, the 10 min group is considered as the optimal one. The microcapsules made from the pH 4.6 HAc-NaAc buffer has an obvious capacity of longtime release and low amount of leftover compared with the ones made from distilled water. The cumulative release of Hb is less than 10% when the microcapsules are immersed in the pH 1.2 HCl at the end of the first two hours, while most Hb is released in the pH 6.8 PBS buffer. The release time could be prolonged to some extent through the introduction of chitosan. The composite microcapsules of poly amino acids are likely to become a potential carrier of oral drug delivery system due to their excellent performance.
2008, 25(6): 39-46.
Abstract:
To improve the mechanical property and the bioactivity of scaffold materials for bone tissue engineering, combining the advantages of natural and synthetic polymers, the polycaprolactone(PCL)-chitosan(CS) porous scaffold materials were prepared by the solution blend and the phase separation method, and the scaffold materials were enhanced by infilling with n-HA-polyvinyl-alcohol(n-HA-PVA) composite slurry to prepare n-HA-PVA/PCL-CS composite porous scaffold through a novel method—centrifugal slipcasting technique. The scaffold materials were characterized by scanning electron microscope, Fourier transform infrared spectroscope, elemental analysis, porosity and compressive strength. The results show that PCL-CS scaffold materials have the mutual transfixion porosity structure like a honeycomb. The porosity of the materials can attain 60%～80%. With increasing the content of CS, the porosity increases and the compressive strength decreases. After filling with HA-PVA composite slurry, the porosity of n-HA-PVA/PCL-CS composite scaffold materials decreases, but still greater than 60%, and its compression modulus cn increase to 25.71 MPa.
To improve the mechanical property and the bioactivity of scaffold materials for bone tissue engineering, combining the advantages of natural and synthetic polymers, the polycaprolactone(PCL)-chitosan(CS) porous scaffold materials were prepared by the solution blend and the phase separation method, and the scaffold materials were enhanced by infilling with n-HA-polyvinyl-alcohol(n-HA-PVA) composite slurry to prepare n-HA-PVA/PCL-CS composite porous scaffold through a novel method—centrifugal slipcasting technique. The scaffold materials were characterized by scanning electron microscope, Fourier transform infrared spectroscope, elemental analysis, porosity and compressive strength. The results show that PCL-CS scaffold materials have the mutual transfixion porosity structure like a honeycomb. The porosity of the materials can attain 60%～80%. With increasing the content of CS, the porosity increases and the compressive strength decreases. After filling with HA-PVA composite slurry, the porosity of n-HA-PVA/PCL-CS composite scaffold materials decreases, but still greater than 60%, and its compression modulus cn increase to 25.71 MPa.
2008, 25(6): 47-51.
Abstract:
The new resin root canal filling materials (NRCFM) were prepared by using thermoplastic elastomer (TPE) and ethylene-vinyl acetate copolymer (EVA) as matrix resin，BaSO4，fumed SiO2 and hydroxyapatite (HA) as inorganic fillers and its compositions were emphatically selected and optimized. The stability of NRCFM in artificial saliva with pH 7.0 and 9.5 was also investigated. The results show that the optimal composition of NRCFM is：TPE 30g，EVA 5 g，BaSO4 45 g，SiO2 10g，HA 10g. NRCFM prepared at this optimal composition has the appropriate mechanical property and excellent resistant-medium stability: Shore A hardness is 88.9, tensile strength is 1.99 MPa and elongation at break is 457%. After soaking 30 days in both pH 7.0 and pH 9.5 artificial saliva，mass change of NRCFM is less than 0.5%.
The new resin root canal filling materials (NRCFM) were prepared by using thermoplastic elastomer (TPE) and ethylene-vinyl acetate copolymer (EVA) as matrix resin，BaSO4，fumed SiO2 and hydroxyapatite (HA) as inorganic fillers and its compositions were emphatically selected and optimized. The stability of NRCFM in artificial saliva with pH 7.0 and 9.5 was also investigated. The results show that the optimal composition of NRCFM is：TPE 30g，EVA 5 g，BaSO4 45 g，SiO2 10g，HA 10g. NRCFM prepared at this optimal composition has the appropriate mechanical property and excellent resistant-medium stability: Shore A hardness is 88.9, tensile strength is 1.99 MPa and elongation at break is 457%. After soaking 30 days in both pH 7.0 and pH 9.5 artificial saliva，mass change of NRCFM is less than 0.5%.
2008, 25(6): 52-58.
Abstract:
3D braided fibers were treated through the composite surface treatment process， and the 3D hybrid epoxy composites reinforced by carbon fiber (CF) and UHMWPE fiber were prepared using the resin transfer molding (RTM) process. The mechanical properties and the hybrid effect were analyzed. The results show that， with the decrease of the hybrid ratio of UHMWPE fiber/CF， the flexural and longitudinal compressive performances of the 3D UHMWPE/CF/ER composites are improved， and their longitudinal shear strength and impact toughness decrease. The fracture mechanism of the 3D UHMWPE/CF/ER hybrid composites is determined by the properties of the two fibers and their hybrid ratio. The mechanical properties of the hybrid composites can be effectively adjusted by the hybrid ratio of the two fibers.
3D braided fibers were treated through the composite surface treatment process， and the 3D hybrid epoxy composites reinforced by carbon fiber (CF) and UHMWPE fiber were prepared using the resin transfer molding (RTM) process. The mechanical properties and the hybrid effect were analyzed. The results show that， with the decrease of the hybrid ratio of UHMWPE fiber/CF， the flexural and longitudinal compressive performances of the 3D UHMWPE/CF/ER composites are improved， and their longitudinal shear strength and impact toughness decrease. The fracture mechanism of the 3D UHMWPE/CF/ER hybrid composites is determined by the properties of the two fibers and their hybrid ratio. The mechanical properties of the hybrid composites can be effectively adjusted by the hybrid ratio of the two fibers.
2008, 25(6): 59-62.
Abstract:
To realize an efficient and targeted cancer therapy by the drug/gene carrier， cell penetrating peptide Tat decorated Au-Au2S nanoparticles were prepared by a redox method. Transmission electron microscopy (TEM)， surface enhanced Raman scattering (SERS) and UV-vis spectrometer were used for characterizing Tat/Au-Au2S nanoparticles， and confocal laser scanning microscope (CLSM) and flow cytometer (FACS) were used to investigate the mechanism of cellular uptake. The chemicophysical results indicate that Tat peptide could be conjugated onto Au Au2S nanoparticles via Au—S bonds， and Tat/Au-Au2S nanoparticles present as 50 nm-diameter sphericities with NIR sensitivity. Co-location and endocytosis inhibition experiments suggest that Tat/Au-Au2S nanoparticles may enter Hela cells via a lipid raft mediated endocytosis pathway， whereas via a combined endocytosis pathway of lipid raft-dependent and receptor-dependent into bone marrow stromal cells (BMSCs).
To realize an efficient and targeted cancer therapy by the drug/gene carrier， cell penetrating peptide Tat decorated Au-Au2S nanoparticles were prepared by a redox method. Transmission electron microscopy (TEM)， surface enhanced Raman scattering (SERS) and UV-vis spectrometer were used for characterizing Tat/Au-Au2S nanoparticles， and confocal laser scanning microscope (CLSM) and flow cytometer (FACS) were used to investigate the mechanism of cellular uptake. The chemicophysical results indicate that Tat peptide could be conjugated onto Au Au2S nanoparticles via Au—S bonds， and Tat/Au-Au2S nanoparticles present as 50 nm-diameter sphericities with NIR sensitivity. Co-location and endocytosis inhibition experiments suggest that Tat/Au-Au2S nanoparticles may enter Hela cells via a lipid raft mediated endocytosis pathway， whereas via a combined endocytosis pathway of lipid raft-dependent and receptor-dependent into bone marrow stromal cells (BMSCs).
2008, 25(6): 63-66.
Abstract:
The titanium surface was modified by triethyl phosphate (TEP) to decrease its hydrophilicity. The BSA adsorption on the surface was investigated at different initial concentrations， different temperatures and pH values. The adsorption dynamics was examined by the ultraviolet visible absorption spectrograph (UV). The reason shows that during adsorption the BSA concentration in the solution sharply decreases in the first 40 min and then tends to be constant. The isotherm and adsorbed quantity were obtained according to the Langmiur formula. The BSA can be adsorpted onto the surface as shown by the Fourier transformed infrared spectroscopy and X-ray photoelectron spectroscopy.
The titanium surface was modified by triethyl phosphate (TEP) to decrease its hydrophilicity. The BSA adsorption on the surface was investigated at different initial concentrations， different temperatures and pH values. The adsorption dynamics was examined by the ultraviolet visible absorption spectrograph (UV). The reason shows that during adsorption the BSA concentration in the solution sharply decreases in the first 40 min and then tends to be constant. The isotherm and adsorbed quantity were obtained according to the Langmiur formula. The BSA can be adsorpted onto the surface as shown by the Fourier transformed infrared spectroscopy and X-ray photoelectron spectroscopy.
2008, 25(6): 67-71.
Abstract:
The low temperature plasma polymerization was used to introduce carboxyl (—COOH) onto the titanium surface. Fibronectin was immobilized to the surface via —COOH. The surface components were characterized by X-ray photoelectron spectroscopy and Fourier transform infrared reflection spectroscopy. The MG63 cells were seeded on the surface of the modified samples and the pure titanium was used as control. The results indicate that fibronectin is immobilized on the titanium and the modified samples are beneficial for the growth and adherence of the cells. The osteogenic activity of the samples with immobilized fibronectin is better than that of the pure titanium.
The low temperature plasma polymerization was used to introduce carboxyl (—COOH) onto the titanium surface. Fibronectin was immobilized to the surface via —COOH. The surface components were characterized by X-ray photoelectron spectroscopy and Fourier transform infrared reflection spectroscopy. The MG63 cells were seeded on the surface of the modified samples and the pure titanium was used as control. The results indicate that fibronectin is immobilized on the titanium and the modified samples are beneficial for the growth and adherence of the cells. The osteogenic activity of the samples with immobilized fibronectin is better than that of the pure titanium.
2008, 25(6): 72-76.
Abstract:
Pressureless sintered SiC (SSiC) is an important high temperature structure material, and the joining technique is one of the key techniques to extend its application. Joining of SSiC was carried out by the reaction joining process using polysiloxane (SR355) with active additive Ni nanopowder as joining materials. The pyrolysis of SR355 with Ni nanopowder was studied. The effects of the content of active additive and joining temperature on the joining strength of joints were investigated. The results show that the active additive promotes the pyrolysis of SR355. The maximum joining strength of the joints is obtained at the joining temperature of 1050℃ with the Ni nanopowder mass fraction of 1% and three times of the reinforcement treatments. The microstructure and composition of the interfacial area were analyzed by SEM and EDX. The results indicate that the interlayer is densified. The micrographs show good contact at the interfaces. The diffusion of elements takes place at the interfaces. The active additive Ni nanopowder participates in the chemical reactions in the joining process， which contributes to the interfacial bonding，resulting in the increasing of joining strength of the joints.
Pressureless sintered SiC (SSiC) is an important high temperature structure material, and the joining technique is one of the key techniques to extend its application. Joining of SSiC was carried out by the reaction joining process using polysiloxane (SR355) with active additive Ni nanopowder as joining materials. The pyrolysis of SR355 with Ni nanopowder was studied. The effects of the content of active additive and joining temperature on the joining strength of joints were investigated. The results show that the active additive promotes the pyrolysis of SR355. The maximum joining strength of the joints is obtained at the joining temperature of 1050℃ with the Ni nanopowder mass fraction of 1% and three times of the reinforcement treatments. The microstructure and composition of the interfacial area were analyzed by SEM and EDX. The results indicate that the interlayer is densified. The micrographs show good contact at the interfaces. The diffusion of elements takes place at the interfaces. The active additive Ni nanopowder participates in the chemical reactions in the joining process， which contributes to the interfacial bonding，resulting in the increasing of joining strength of the joints.
2008, 25(6): 77-81.
Abstract:
The gelatin/calcium phosphate cement (CPC) composite scaffold with antibiotic release ability for bone tissue engineering was prepared by infiltration of gelatin solution containing the gentamicin sulphate (GS)-entrapped poly (lactic-co-glycolic acid) (PLGA) microspheres into the macropores of the CPC scaffold. The morphologies of the microspheres and scaffold were observed by an electron scanning microscope，and the compressive strength and drug release of the scaffold were determined with a universal testing machine and an ultraviolet-visible spectrophotometer，respectively. The results indicate that the composite scaffold is significantly enhanced by the gelatin infiltration and a satisfying compressive strength of 2.42 MPa is achieved. The release of GS from the scaffold lasted for over 30 days， indicating a good drug release ability. This composite scaffold is a novel tissue engineering scaffold providing dual functions of bone-repairing and infection-diminishing with promising application prospects.
The gelatin/calcium phosphate cement (CPC) composite scaffold with antibiotic release ability for bone tissue engineering was prepared by infiltration of gelatin solution containing the gentamicin sulphate (GS)-entrapped poly (lactic-co-glycolic acid) (PLGA) microspheres into the macropores of the CPC scaffold. The morphologies of the microspheres and scaffold were observed by an electron scanning microscope，and the compressive strength and drug release of the scaffold were determined with a universal testing machine and an ultraviolet-visible spectrophotometer，respectively. The results indicate that the composite scaffold is significantly enhanced by the gelatin infiltration and a satisfying compressive strength of 2.42 MPa is achieved. The release of GS from the scaffold lasted for over 30 days， indicating a good drug release ability. This composite scaffold is a novel tissue engineering scaffold providing dual functions of bone-repairing and infection-diminishing with promising application prospects.
2008, 25(6): 82-87.
Abstract:
The in vitro mechanical properties, the in vivo degradation rate, the phase composition, and microstructure of degradable polylactic-co-glycolic acid (PLGA) fibre/calcium phosphate cement (F-CPC) composite at various immersion (or implantation) stages were investigated by using in vitro physiological saline immersion and in vivo rabbit muscle implantation，respectively. The in vitro immersion results show that at the initial immersion stages，the addition of degradation fibres decreases the compressive strength of the composite but slightly improves its flexural strength and significantly increases its fracture toughness by two orders of magnitude. After being subjected to a long-time immersion，the compressive strength，flexural strength and fracture toughness of the composite decrease uniformly. The in vivo implant results show that the addition of the degradable fibres promotes the degradation of the composite and also the increase amplitude at the degradation rate is gradually enlarged by further extending the implant time. The variations in these properties of the composite have a strong relationship with the fibre degradation behaviour and composite microstructure.
The in vitro mechanical properties, the in vivo degradation rate, the phase composition, and microstructure of degradable polylactic-co-glycolic acid (PLGA) fibre/calcium phosphate cement (F-CPC) composite at various immersion (or implantation) stages were investigated by using in vitro physiological saline immersion and in vivo rabbit muscle implantation，respectively. The in vitro immersion results show that at the initial immersion stages，the addition of degradation fibres decreases the compressive strength of the composite but slightly improves its flexural strength and significantly increases its fracture toughness by two orders of magnitude. After being subjected to a long-time immersion，the compressive strength，flexural strength and fracture toughness of the composite decrease uniformly. The in vivo implant results show that the addition of the degradable fibres promotes the degradation of the composite and also the increase amplitude at the degradation rate is gradually enlarged by further extending the implant time. The variations in these properties of the composite have a strong relationship with the fibre degradation behaviour and composite microstructure.
2008, 25(6): 88-92.
Abstract:
To investigate the preparation and the biology security of the porous carboxymethyl chitosan/nano hydroxyapatite（CMCTS/n-HA）scaffold biocomposites，the porous biocomposites of CMCTS/n-HA were prepared by means of the porogen leaching method. In the process，anhydrous ethanol was the porogen leaching solvent and citric acid was the sticky solvent. CMCTS/n-HA were characterized by SEM, the porosity and compressive strength were also tested. At the same time，changes of the bone histology and the detecting function of liver and kidney were observed by implanting CMCTS/n-HA into the bone defects of rabbits. The porosity ratio of CMCTS/n-HA is about 75% and the compressive strength can exceed 21 MPa. The diameter of the pores is about from several microns to six hundred microns and most of them are circular, which profits the growth and extension of many tissues. The animal experiments show that CMCTS/n-HA did not result in inflammatory reaction and bone putrescence and toxicity of liver and kidney. It is suggested that CMCTS/n-HA might be desirable for bone tissue engineering. So, CMCTS/n-HA would be a potential scaffold biocomposites for the treatment of bone defects.
To investigate the preparation and the biology security of the porous carboxymethyl chitosan/nano hydroxyapatite（CMCTS/n-HA）scaffold biocomposites，the porous biocomposites of CMCTS/n-HA were prepared by means of the porogen leaching method. In the process，anhydrous ethanol was the porogen leaching solvent and citric acid was the sticky solvent. CMCTS/n-HA were characterized by SEM, the porosity and compressive strength were also tested. At the same time，changes of the bone histology and the detecting function of liver and kidney were observed by implanting CMCTS/n-HA into the bone defects of rabbits. The porosity ratio of CMCTS/n-HA is about 75% and the compressive strength can exceed 21 MPa. The diameter of the pores is about from several microns to six hundred microns and most of them are circular, which profits the growth and extension of many tissues. The animal experiments show that CMCTS/n-HA did not result in inflammatory reaction and bone putrescence and toxicity of liver and kidney. It is suggested that CMCTS/n-HA might be desirable for bone tissue engineering. So, CMCTS/n-HA would be a potential scaffold biocomposites for the treatment of bone defects.
2008, 25(6): 93-96.
Abstract:
The microstructures and nano-mechanical properties of dental dentin and dental enamel were studied by means of OM，SEM，HRTEM and nano indentation equipment. The results show that the dental dentin consists of dentinal tubules and dentinal matrix，while the dental enamel is built up by enamel prisms and enamel matrix，and there is an obvious interface between dentin and enamel. It is also found that the content of Ca and P in enamel is higher than that in the dentin，while the content of carbon in enamel is lower than that in the dentin. A large quantity of hydroxyapatite (HA) crystal is found in enamel compared with that in dentin. The nano-hardness and elastic modulus of the enamel are determined to be 4.4 GPa and 81 GPa, respectively，while the nano-hardness and elastic modulus of the dentin are determined to be 1.0 GPa and 26 GPa on the other hand. The higher hardness of enamel is related to the formation of crystal phase of HA structure，and Ca and P have a great contribution to the formation of this structure.
The microstructures and nano-mechanical properties of dental dentin and dental enamel were studied by means of OM，SEM，HRTEM and nano indentation equipment. The results show that the dental dentin consists of dentinal tubules and dentinal matrix，while the dental enamel is built up by enamel prisms and enamel matrix，and there is an obvious interface between dentin and enamel. It is also found that the content of Ca and P in enamel is higher than that in the dentin，while the content of carbon in enamel is lower than that in the dentin. A large quantity of hydroxyapatite (HA) crystal is found in enamel compared with that in dentin. The nano-hardness and elastic modulus of the enamel are determined to be 4.4 GPa and 81 GPa, respectively，while the nano-hardness and elastic modulus of the dentin are determined to be 1.0 GPa and 26 GPa on the other hand. The higher hardness of enamel is related to the formation of crystal phase of HA structure，and Ca and P have a great contribution to the formation of this structure.
2008, 25(6): 97-101.
Abstract:
Nano silicon carbide composites reinforced by carbon fibers have excellent mechanical property and biocompatibility，and can be used as a full scale human skeleton to take the place of titanium alloy. The purpose of this paper is to investigate the effects of 3D orthogonal plaiting textures of T300 and M30 carbon fibers on the preparation process and flexural strength. C/SiC composites were prepared by polymer infiltration pyrolysis using polycarbosilane as preceramic and divinylbenzene as solvent. The density and porosity of C/SiC composites were measured by the Archimedes method. The flexural strength was tested by the method of three points bending. The flexural strength of M30 C/SiC composites is about 6.7% greater than that of T300 C/SiC composites. The results indicate that the cracking strength of C/SiC composites is dramatically affected by the elastic modulus of carbon fibers. High flexural strength of M30 C/SiC composites resulted from the high radial strength and high load bearing ratio of fiber to matrix，which all resulted from the higher elastic modulus of M30 than that of T300 carbon fibers.
Nano silicon carbide composites reinforced by carbon fibers have excellent mechanical property and biocompatibility，and can be used as a full scale human skeleton to take the place of titanium alloy. The purpose of this paper is to investigate the effects of 3D orthogonal plaiting textures of T300 and M30 carbon fibers on the preparation process and flexural strength. C/SiC composites were prepared by polymer infiltration pyrolysis using polycarbosilane as preceramic and divinylbenzene as solvent. The density and porosity of C/SiC composites were measured by the Archimedes method. The flexural strength was tested by the method of three points bending. The flexural strength of M30 C/SiC composites is about 6.7% greater than that of T300 C/SiC composites. The results indicate that the cracking strength of C/SiC composites is dramatically affected by the elastic modulus of carbon fibers. High flexural strength of M30 C/SiC composites resulted from the high radial strength and high load bearing ratio of fiber to matrix，which all resulted from the higher elastic modulus of M30 than that of T300 carbon fibers.
2008, 25(6): 102-106.
Abstract:
The porcelain-fused to metal (PFM) based on nickel-chromium alloy with the composition gradient structure was prepared by adding Ni，Cr，NiO and Cr2O3 in different proportions to the porcelain powder mainly constituted by leucite. The bending strength and thermal expansion coefficient (TEC) of the different gradient compositions were tested. SEM and XRD were also employed to characterize the as-prepared gradient samples. The thermal stress of the samples was simulated using an elastic stress model. The results show that when m(NiO)∶m(Cr2O3)∶m(Ni)∶m(Cr)＝0∶50∶40∶10，the functional gradient material (FGM) with high bending strength（101.217 MPa）and comparatively low thermal stress is obtained. The thermal stress curves exhibit that FGM structure could relax the thermal stress of the samples in the cross-sectional direction. The study result also indicates that the smaller particle size of the porcelain powder could improve the performance of FGM and reduce the sintering temperature，and the bending strength of the gradient materials presents aeolotropism.
The porcelain-fused to metal (PFM) based on nickel-chromium alloy with the composition gradient structure was prepared by adding Ni，Cr，NiO and Cr2O3 in different proportions to the porcelain powder mainly constituted by leucite. The bending strength and thermal expansion coefficient (TEC) of the different gradient compositions were tested. SEM and XRD were also employed to characterize the as-prepared gradient samples. The thermal stress of the samples was simulated using an elastic stress model. The results show that when m(NiO)∶m(Cr2O3)∶m(Ni)∶m(Cr)＝0∶50∶40∶10，the functional gradient material (FGM) with high bending strength（101.217 MPa）and comparatively low thermal stress is obtained. The thermal stress curves exhibit that FGM structure could relax the thermal stress of the samples in the cross-sectional direction. The study result also indicates that the smaller particle size of the porcelain powder could improve the performance of FGM and reduce the sintering temperature，and the bending strength of the gradient materials presents aeolotropism.
2008, 25(6): 107-110.
Abstract:
The rare earth (RE: Gd, Y and Tb) complexes of 8-hydroxyquinoline (8-HQ) were synthesized. The organic/inorganic hybrid composites，RE-HQ/hydroxyapatite(HAP) were directly prepared via the wet methods. The composites were characterized by means of SEM，XRD and IR. At the same time， the antibacterial activities of all the complexes were tested by using minimum inhibitory concentration (MIC)and minimum bactericidal concentration(MBC). The results show that the three composites are 50 nm～60 nm in average size and exhibit stronger acteriostatic activities against Staphylococcus aureus ( S. aureus) and Escherichia coli (E. coli). They all show higher antibacterial activity against S. aureus than against E. coli. The antibacterial efficacies of the three composites are increased in the order： Tb-HQ/HAP < Y-HQ/HAP
The rare earth (RE: Gd, Y and Tb) complexes of 8-hydroxyquinoline (8-HQ) were synthesized. The organic/inorganic hybrid composites，RE-HQ/hydroxyapatite(HAP) were directly prepared via the wet methods. The composites were characterized by means of SEM，XRD and IR. At the same time， the antibacterial activities of all the complexes were tested by using minimum inhibitory concentration (MIC)and minimum bactericidal concentration(MBC). The results show that the three composites are 50 nm～60 nm in average size and exhibit stronger acteriostatic activities against Staphylococcus aureus ( S. aureus) and Escherichia coli (E. coli). They all show higher antibacterial activity against S. aureus than against E. coli. The antibacterial efficacies of the three composites are increased in the order： Tb-HQ/HAP < Y-HQ/HAP
2008, 25(6): 111-117.
Abstract:
By combining the enrichment technique of autologous bone marrow mesenchymal stem cells (MSCs) and the rapid hybrid technique with porous β-tricalcium phosphate (β-TCP)，the bioactive composite (MSCs/β-TCP) was constructed. And with randomization and control principles，the enriched MSCs/β-TCP was identified for its osteogenesis function in goat spinal fusion experiment with the control of β-TCP alone and the control of autograft. The change of the number of MSCs post-enrichment was estimated by counting the colony-forming units which express alkaline phosphatase (CFUs/ALP+). The early stage of cell-scaffold hybrid was observed by scanning electron microscope (SEM). By X-ray，CT scan and histologic analysis，the osteogenesis of three sorts of materials and their transformations in vivo were evaluated. The results show that the concentration of MSCs after enrichment technique increases about 3.9 times，and the MSCs adhere to the inside wall of porous β-TCP only with 2 h hybrid. X-ray identifies that the moderate density shadows can be found gradually in the fusion site of group MSCs/β-TCP and group autograft. CT scan shows the fusion rates of group MSCs/β-TCP and autograft were 92% and 100% respectively，which were higher than those of group β-TCP alone (58%). The undecalcified section confirms that the osteogenesis ability of bioactive composite (MSCs/β-TCP) can compare with autologous bone graft in goat spinal fusion，and is better than that of β-TCP alone.
By combining the enrichment technique of autologous bone marrow mesenchymal stem cells (MSCs) and the rapid hybrid technique with porous β-tricalcium phosphate (β-TCP)，the bioactive composite (MSCs/β-TCP) was constructed. And with randomization and control principles，the enriched MSCs/β-TCP was identified for its osteogenesis function in goat spinal fusion experiment with the control of β-TCP alone and the control of autograft. The change of the number of MSCs post-enrichment was estimated by counting the colony-forming units which express alkaline phosphatase (CFUs/ALP+). The early stage of cell-scaffold hybrid was observed by scanning electron microscope (SEM). By X-ray，CT scan and histologic analysis，the osteogenesis of three sorts of materials and their transformations in vivo were evaluated. The results show that the concentration of MSCs after enrichment technique increases about 3.9 times，and the MSCs adhere to the inside wall of porous β-TCP only with 2 h hybrid. X-ray identifies that the moderate density shadows can be found gradually in the fusion site of group MSCs/β-TCP and group autograft. CT scan shows the fusion rates of group MSCs/β-TCP and autograft were 92% and 100% respectively，which were higher than those of group β-TCP alone (58%). The undecalcified section confirms that the osteogenesis ability of bioactive composite (MSCs/β-TCP) can compare with autologous bone graft in goat spinal fusion，and is better than that of β-TCP alone.
2008, 25(6): 118-122.
Abstract:
Otolith is a typical biomaterial which is composed of calcium carbonate and organic matrix. In order to study the micro-morphology of otolith，SEM observation was taken under different water conditions and of several treatment method otoliths. The otolith samples included fresh otoliths，alkali treated otoliths，Na2EDTA treated otolith，and sliced otoliths under alkali and Na2EDTA treatment. The result shows the lapillus is composed of hexagon or sham-hexagon aragonite which formed sheet or cylindrical structure, while asteriscus is composed of ball or bean-shaped vaterite crystal. The polished otolith which was dealt with NaOH and Na2EDTA can be distinguished as the crystal structure. The width of the daily increment is 2 μm～3 μm. The crystal structure of otoliths in different conditions show little difference，and as could be preliminarily inferred，the element content in water makes little effects on the crystal structure of otolith.
Otolith is a typical biomaterial which is composed of calcium carbonate and organic matrix. In order to study the micro-morphology of otolith，SEM observation was taken under different water conditions and of several treatment method otoliths. The otolith samples included fresh otoliths，alkali treated otoliths，Na2EDTA treated otolith，and sliced otoliths under alkali and Na2EDTA treatment. The result shows the lapillus is composed of hexagon or sham-hexagon aragonite which formed sheet or cylindrical structure, while asteriscus is composed of ball or bean-shaped vaterite crystal. The polished otolith which was dealt with NaOH and Na2EDTA can be distinguished as the crystal structure. The width of the daily increment is 2 μm～3 μm. The crystal structure of otoliths in different conditions show little difference，and as could be preliminarily inferred，the element content in water makes little effects on the crystal structure of otolith.
2008, 25(6): 123-129.
Abstract:
The porous Zn-containing glass and glass-ceramic scaffolds were prepared by sintering a ceramic slip-coated polymer foam at 700℃ and 1200℃，and the PLGA (poly-lactic-glyoclic-acid) or PBS (poly (butylene succinate)) glass-ceramic composite scaffolds were obtained by coating a PLGA and PBS film on the framework of the glass-ceramic scaffolds. The obtained glass-ceramic scaffolds have a well-interconnected porous structure and show high porosity of 80.1%±0.6% and low compressive strength of 258.4 kPa±23.6 kPa. The coating of PLGA or PBS film on glass-ceramic scaffolds does not affect interconnection of the pores，but results in a decrease of porosity and a sharp increase of compressive strength. The porosity and compressive strength of the scaffolds were 75.9%±0.6% and 1509.4 kPa±162.8 kPa for 58S3Z-1200℃-PLGA，and 77.9%±0.9%，901.6 kPa±94.5 kPafor 58S3Z-1200℃-PBS. The in vitro degradation experiments show that the composite scaffolds are degradable，reaching up to 13.3% (58S3Z-1200℃-PLGA) and 2.1% (58S3Z-1200℃-PBS) after 28 days of soaking. The cellular responses were assessed by culturing mesenchymal stem cells (MSC) on the scaffolds，and SEM observations show that the cells are attached to and proliferate well on the scaffolds. The results suggest that the composite scaffold has porous structure，higher mechanical strength，good degradability and cell compatibility，and might be used for bone tissue engineering.
The porous Zn-containing glass and glass-ceramic scaffolds were prepared by sintering a ceramic slip-coated polymer foam at 700℃ and 1200℃，and the PLGA (poly-lactic-glyoclic-acid) or PBS (poly (butylene succinate)) glass-ceramic composite scaffolds were obtained by coating a PLGA and PBS film on the framework of the glass-ceramic scaffolds. The obtained glass-ceramic scaffolds have a well-interconnected porous structure and show high porosity of 80.1%±0.6% and low compressive strength of 258.4 kPa±23.6 kPa. The coating of PLGA or PBS film on glass-ceramic scaffolds does not affect interconnection of the pores，but results in a decrease of porosity and a sharp increase of compressive strength. The porosity and compressive strength of the scaffolds were 75.9%±0.6% and 1509.4 kPa±162.8 kPa for 58S3Z-1200℃-PLGA，and 77.9%±0.9%，901.6 kPa±94.5 kPafor 58S3Z-1200℃-PBS. The in vitro degradation experiments show that the composite scaffolds are degradable，reaching up to 13.3% (58S3Z-1200℃-PLGA) and 2.1% (58S3Z-1200℃-PBS) after 28 days of soaking. The cellular responses were assessed by culturing mesenchymal stem cells (MSC) on the scaffolds，and SEM observations show that the cells are attached to and proliferate well on the scaffolds. The results suggest that the composite scaffold has porous structure，higher mechanical strength，good degradability and cell compatibility，and might be used for bone tissue engineering.
2008, 25(6): 130-135.
Abstract:
The graphitization degrees of quasi-3D C/C composites were analyzed through X-ray diffractometer, and the element contents of hydrargyrum， arsenic，plumbum and cadmium in the materials were determined by the atomic fluorescence analyzer. For the C/C composites that have undergone 2400℃ 2 h graphitization heat treatment under the protection of argon，the content of the above-mentioned elements is relatively low. In this light，the heat-treated C/C composites are more applicable for surgery implantation. The compression fracture experiments on the graphitized C/C composites were carried out on the electronic mechanical test machine under the condition of different loading rates and different loading directions. Then the fracture morphologies were observed by means of SEM and the stereological optical microscope. All the results reveal that quasi-3D C/C composites have strain rate sensitivity and the reinforced fibers have remarkable effects in arresting propagating cracks and plasticizing. The compressive strength(28.30 MPa～83.25 MPa) and elastic modulus (257.56 MPa～397.06 MPa) could satisfy the mechanical demands of bone-repairing materials.
The graphitization degrees of quasi-3D C/C composites were analyzed through X-ray diffractometer, and the element contents of hydrargyrum， arsenic，plumbum and cadmium in the materials were determined by the atomic fluorescence analyzer. For the C/C composites that have undergone 2400℃ 2 h graphitization heat treatment under the protection of argon，the content of the above-mentioned elements is relatively low. In this light，the heat-treated C/C composites are more applicable for surgery implantation. The compression fracture experiments on the graphitized C/C composites were carried out on the electronic mechanical test machine under the condition of different loading rates and different loading directions. Then the fracture morphologies were observed by means of SEM and the stereological optical microscope. All the results reveal that quasi-3D C/C composites have strain rate sensitivity and the reinforced fibers have remarkable effects in arresting propagating cracks and plasticizing. The compressive strength(28.30 MPa～83.25 MPa) and elastic modulus (257.56 MPa～397.06 MPa) could satisfy the mechanical demands of bone-repairing materials.
2008, 25(6): 136-139.
Abstract:
On the basis of analyzing the preparation method of hydroxyapatite (HA) and the diffluence method of silk fibroin fibre (SF)，a “one-step” method that is used to prepare nano hydroxyapatite/silk fibroin biology composite (SF/HA) was put forward. The SF/HA composite was observed and tested by FTIR, TEM and XRD.The ratio of calcium to phosphorus in the SF/HA composite was tested by the chemical method.The results show that the ratio of calcium to phosphorus in the SF/HA composite is 1.6692, which is the same as 1.67 in HA.The function groups in both HA and SF were discovered in the SF/HA composite. The SF/HA composite crystal particle is of spiculate or column configuration. The crystal size of the SF/HA composite is less than 100 nm in the horizontal direction. The HA and SF composite can come into being. The HA/SF composite is hexahedron crystal.When the mass fraction of SF in SF/HA was 10%，the crystal cell parameter of the SF/HA composite crystal is a=b=90319 A，c=7.0148 A. The average crystal size of SF/HA along the c axes direction is 230.7645 A. So the “one-step” method is rational and feasible.
On the basis of analyzing the preparation method of hydroxyapatite (HA) and the diffluence method of silk fibroin fibre (SF)，a “one-step” method that is used to prepare nano hydroxyapatite/silk fibroin biology composite (SF/HA) was put forward. The SF/HA composite was observed and tested by FTIR, TEM and XRD.The ratio of calcium to phosphorus in the SF/HA composite was tested by the chemical method.The results show that the ratio of calcium to phosphorus in the SF/HA composite is 1.6692, which is the same as 1.67 in HA.The function groups in both HA and SF were discovered in the SF/HA composite. The SF/HA composite crystal particle is of spiculate or column configuration. The crystal size of the SF/HA composite is less than 100 nm in the horizontal direction. The HA and SF composite can come into being. The HA/SF composite is hexahedron crystal.When the mass fraction of SF in SF/HA was 10%，the crystal cell parameter of the SF/HA composite crystal is a=b=90319 A，c=7.0148 A. The average crystal size of SF/HA along the c axes direction is 230.7645 A. So the “one-step” method is rational and feasible.
2008, 25(6): 140-145.
Abstract:
By using natural fiber—bacterial cellulose (BC) as the reinforcement and unsaturated polyester resin (UPR) as the matrix，natural fiber BC/UPR composites were prepared by the RTM process. The mechanical properties，moisture absorption and degradation of the composites were studied. The results show that chemical bonds are formed at the interface of the BC/UPR composites through surface treatment of BC，which enhances the mechanical properties of the composites. With the increasing fiber volume fraction，the BC/UPR composites get an increase in tensile strength as well as a decrease in elongation at break. The best tensile strength of 152.9 MPa can be obtained for the composites with a fiber volume fraction of 20%. The processes of moisture absorption of the BC/UPR composites，which lower the mechanical properties，can be described by Fick’s Law. UV radiation tests were carried out on the BC/UPR composites. XPS results prove that an oxidative degradation takes place and the contents of oxygenic functional groups increase when the materials are exposed to ultraviolet radiation，which induces photodegradation in the BC/UPR composites.
By using natural fiber—bacterial cellulose (BC) as the reinforcement and unsaturated polyester resin (UPR) as the matrix，natural fiber BC/UPR composites were prepared by the RTM process. The mechanical properties，moisture absorption and degradation of the composites were studied. The results show that chemical bonds are formed at the interface of the BC/UPR composites through surface treatment of BC，which enhances the mechanical properties of the composites. With the increasing fiber volume fraction，the BC/UPR composites get an increase in tensile strength as well as a decrease in elongation at break. The best tensile strength of 152.9 MPa can be obtained for the composites with a fiber volume fraction of 20%. The processes of moisture absorption of the BC/UPR composites，which lower the mechanical properties，can be described by Fick’s Law. UV radiation tests were carried out on the BC/UPR composites. XPS results prove that an oxidative degradation takes place and the contents of oxygenic functional groups increase when the materials are exposed to ultraviolet radiation，which induces photodegradation in the BC/UPR composites.
2008, 25(6): 146-151.
Abstract:
Epoxy resin matrix composites with various contents of multi-wall carbon nanotubes(MWCNTs) and organophilic montmorillonite(oMMT) were prepared by means of shearing mixing and speed mixture. X-ray diffraction analysis shows that the exfoliated microstructure is formed when the mass fraction of oMMT was 2%. The fracture tests indicate that MWCNTs and oMMT exhibit synergistic effect on improving the critical stress intensity factor of the pure epoxy. When incorporating 2 wt% oMMT and 0.1 wt% MWCNTs into the epoxy resin at the same time，the fracture toughness of the composite is 1.77，1.45 and 1.39 times that of pure epoxy，2 wt% oMMT/epoxy and 0.1 wt% MWCNTs/epoxy composite， respectively. The scanning electronic microscope observations show that MWCNTs are dispersed well in the matrix and a certain degree of platelet interlocks structure is achieved. The fracture surface micrographs prove that micro-cracks，cavities and fiber pull-out are responsible for improving the toughness of MWCNTs-oMMT/epoxy resin composites.
Epoxy resin matrix composites with various contents of multi-wall carbon nanotubes(MWCNTs) and organophilic montmorillonite(oMMT) were prepared by means of shearing mixing and speed mixture. X-ray diffraction analysis shows that the exfoliated microstructure is formed when the mass fraction of oMMT was 2%. The fracture tests indicate that MWCNTs and oMMT exhibit synergistic effect on improving the critical stress intensity factor of the pure epoxy. When incorporating 2 wt% oMMT and 0.1 wt% MWCNTs into the epoxy resin at the same time，the fracture toughness of the composite is 1.77，1.45 and 1.39 times that of pure epoxy，2 wt% oMMT/epoxy and 0.1 wt% MWCNTs/epoxy composite， respectively. The scanning electronic microscope observations show that MWCNTs are dispersed well in the matrix and a certain degree of platelet interlocks structure is achieved. The fracture surface micrographs prove that micro-cracks，cavities and fiber pull-out are responsible for improving the toughness of MWCNTs-oMMT/epoxy resin composites.
2008, 25(6): 152-155.
Abstract:
The CVD kinetics of pyrocarbon was investigated via the in-situ magnetic suspending balance，and the gaseous products were analyzed via the out-line gas chromatography coupled with the mass spectrometry (GC/MS) during the pyrolysis of a propylene/argon mixture in the range of 800～1200℃. The kinetic results indicate that pyrocarbon is formed with an apparent activation energy of 137 kJ/mol±25 kJ/mol controlled by chemical kinetic reaction from 800℃ to 1000℃，Whereas，above 1000℃，the deposition behavior is representative of the mass transformation and gas phased nucleation. The dependences of pressure and residence time on deposition rate show that pyrocarbon is obtained after a series of gas phase reactions and solid surface reactions. The key carbon-formed species controled by each mechanism of the deposition process are different. A simplified reaction model describing the kinetic deposition process of pyrocarbon CVD is derived on the basis of the above considerations.
The CVD kinetics of pyrocarbon was investigated via the in-situ magnetic suspending balance，and the gaseous products were analyzed via the out-line gas chromatography coupled with the mass spectrometry (GC/MS) during the pyrolysis of a propylene/argon mixture in the range of 800～1200℃. The kinetic results indicate that pyrocarbon is formed with an apparent activation energy of 137 kJ/mol±25 kJ/mol controlled by chemical kinetic reaction from 800℃ to 1000℃，Whereas，above 1000℃，the deposition behavior is representative of the mass transformation and gas phased nucleation. The dependences of pressure and residence time on deposition rate show that pyrocarbon is obtained after a series of gas phase reactions and solid surface reactions. The key carbon-formed species controled by each mechanism of the deposition process are different. A simplified reaction model describing the kinetic deposition process of pyrocarbon CVD is derived on the basis of the above considerations.
2008, 25(6): 156-159.
Abstract:
The magnesium alloy matrix composite was fabricated by the squeeze cast with the preform made of crystallized aluminum silicate short fibers as the reinforcement and aluminum phosphate as the binder. The interface microstructure and reaction products were investigated by optical microscope，TEM and HREM. It is shown that the thickness of the interface of the metal matrix composite (MMC) is about 100 nm，and there are not only lots of MgO grains and a small quantity of Mg Al2O4 and Mg2Si nano grains，but also a small quantity of MgP4 nano grains on the interface. The stronger interface binding force and ideal interface structure are formed between the magnesium alloy matrix and the alumina silicate fibers. Compared with the properties of the AZ91D alloy，the tensile strength of the MMC increases by 18% at room-temperature，and the Young‘s modulus increases by 58%.
The magnesium alloy matrix composite was fabricated by the squeeze cast with the preform made of crystallized aluminum silicate short fibers as the reinforcement and aluminum phosphate as the binder. The interface microstructure and reaction products were investigated by optical microscope，TEM and HREM. It is shown that the thickness of the interface of the metal matrix composite (MMC) is about 100 nm，and there are not only lots of MgO grains and a small quantity of Mg Al2O4 and Mg2Si nano grains，but also a small quantity of MgP4 nano grains on the interface. The stronger interface binding force and ideal interface structure are formed between the magnesium alloy matrix and the alumina silicate fibers. Compared with the properties of the AZ91D alloy，the tensile strength of the MMC increases by 18% at room-temperature，and the Young‘s modulus increases by 58%.
2008, 25(6): 160-165.
Abstract:
Nano ZrO2 was first modified with the poly(ethylene terephalate) prepolymer via polycondensation to increase its compatibility with PC. The nano ZrO2 /PC composite was successfully prepared by blending extrusion. The modified nano ZrO2 particles were characterized by FTIR，XPS，TEM，TG and contact angle test. The results show that the PET can be successfully combined to the surface of nano ZrO2 by the chemical bond， the hydrophobic property is improved and a good dispersibility is obtained. The mechanical performance of nano ZrO2 /PC composite was tested， and the relationship with the content of nano ZrO2 was discussed. The results show that the mechanical performance of nano ZrO2 /PC composite is better than that of pure PC. The notch impact strength and the tensile strength of the composite first increase and then decrease with the addition of the nano ZrO2，and they reach the maximum respectively when the mass fraction of the nano ZrO2 is 1% and 0.3%. The flexural stress of the composite is increased in the experimental range，and the maximum is 2.54 MPa higher than that of pure PC.
Nano ZrO2 was first modified with the poly(ethylene terephalate) prepolymer via polycondensation to increase its compatibility with PC. The nano ZrO2 /PC composite was successfully prepared by blending extrusion. The modified nano ZrO2 particles were characterized by FTIR，XPS，TEM，TG and contact angle test. The results show that the PET can be successfully combined to the surface of nano ZrO2 by the chemical bond， the hydrophobic property is improved and a good dispersibility is obtained. The mechanical performance of nano ZrO2 /PC composite was tested， and the relationship with the content of nano ZrO2 was discussed. The results show that the mechanical performance of nano ZrO2 /PC composite is better than that of pure PC. The notch impact strength and the tensile strength of the composite first increase and then decrease with the addition of the nano ZrO2，and they reach the maximum respectively when the mass fraction of the nano ZrO2 is 1% and 0.3%. The flexural stress of the composite is increased in the experimental range，and the maximum is 2.54 MPa higher than that of pure PC.
2008, 25(6): 166-174.
Abstract:
Rheological behaviors of geopolymeric pastes incorporated with polyvinyl alcohol (PVA) short fiber and fly ash were investigated by using the specially designed ram rheometer. Based on the rheological testing results，the PVA short fiber reinforced fly ash-geopolymer composite (SFRGC) (width to height ratio=12.5∶1.0) manufactured by single-screw extrusion technique was successfully prepared with different the fiber volume fractions and fly ash contents. The flexural behaviors were studied on the SFRGC by using materials testing machine. The corresponding microstructure and the failure mechanism were also explored by SEM. The results show that PVA fiber addition greatly increases the ductility of SFRGC，especially in the case of high volume fraction of fibers，resulting in a change of the impact failure mode from brittle pattern to ductile one. Comparatively fly ash addition also exhibites obvious influence on the flexural properties. SFRGC without or with low percentage of fly ash (≤10%) has high flexural strength，but low ductility. SFRGC with high percentage of fly ash (≥30%) has a low flexural strength，but a large defection.
Rheological behaviors of geopolymeric pastes incorporated with polyvinyl alcohol (PVA) short fiber and fly ash were investigated by using the specially designed ram rheometer. Based on the rheological testing results，the PVA short fiber reinforced fly ash-geopolymer composite (SFRGC) (width to height ratio=12.5∶1.0) manufactured by single-screw extrusion technique was successfully prepared with different the fiber volume fractions and fly ash contents. The flexural behaviors were studied on the SFRGC by using materials testing machine. The corresponding microstructure and the failure mechanism were also explored by SEM. The results show that PVA fiber addition greatly increases the ductility of SFRGC，especially in the case of high volume fraction of fibers，resulting in a change of the impact failure mode from brittle pattern to ductile one. Comparatively fly ash addition also exhibites obvious influence on the flexural properties. SFRGC without or with low percentage of fly ash (≤10%) has high flexural strength，but low ductility. SFRGC with high percentage of fly ash (≥30%) has a low flexural strength，but a large defection.
2008, 25(6): 175-180.
Abstract:
The tensile and compressive experiments of the polyurethane syntactic foams filled by hollow glass micro-spheres with different densities and mass fractions of micro-spheres were carried out to investigate the influence of micro-spheres on the mechanical properties. The experimental results show that the features of the tensile curves for the filled syntactic foams are similar to those of the conventional foams. However，the compressive characteristics of stress-strain relation of the filled syntactic foams differ from those of the conventional foams. With increasing of the material density，the micro-spheres have better reinforced effect on the resin matrix. It is found that the micro-sphere cluster and bad bonding at the interface between the micro-spheres and the resin would probably lead to the decline of mechanical properties. According to the simulation results using the finite element method and the observation of the damaged samples，the deformation and failure mechanism of the material were discussed.
The tensile and compressive experiments of the polyurethane syntactic foams filled by hollow glass micro-spheres with different densities and mass fractions of micro-spheres were carried out to investigate the influence of micro-spheres on the mechanical properties. The experimental results show that the features of the tensile curves for the filled syntactic foams are similar to those of the conventional foams. However，the compressive characteristics of stress-strain relation of the filled syntactic foams differ from those of the conventional foams. With increasing of the material density，the micro-spheres have better reinforced effect on the resin matrix. It is found that the micro-sphere cluster and bad bonding at the interface between the micro-spheres and the resin would probably lead to the decline of mechanical properties. According to the simulation results using the finite element method and the observation of the damaged samples，the deformation and failure mechanism of the material were discussed.
2008, 25(6): 181-185.
Abstract:
For search of new lubricant materials，NbSe2 fibers with diameters range of 80～160 nm were synthesized by the thermal decomposition of NbSe3 obtained from the reaction of Se and Nb in the airtight vessel. The phase constitution and the morphology of the NbSe2 fibers were analyzed by means of X-ray diffraction，scan electron microscopy and transmission electron microscopy. The tribological behavior of NbSe2 fibers as lubricating oil additive was investigated by the UMT-2 multi-specimen test system. The results show that the oil with NbSe2 fibers has better tribological properties than the pure oil and the oil with common layered NbSe2 at atmosphere. This could be attributed to the steady structure of the NbSe2 fibers. The copper sintered material with NbSe2 fibers was prepared by the process of powder metallurgy. The incorporation of NbSe2 fibers leads to the great reduction of friction coefficients under all kinds of loads，which may be attributed to the lubricating film formed on the worn surface.
For search of new lubricant materials，NbSe2 fibers with diameters range of 80～160 nm were synthesized by the thermal decomposition of NbSe3 obtained from the reaction of Se and Nb in the airtight vessel. The phase constitution and the morphology of the NbSe2 fibers were analyzed by means of X-ray diffraction，scan electron microscopy and transmission electron microscopy. The tribological behavior of NbSe2 fibers as lubricating oil additive was investigated by the UMT-2 multi-specimen test system. The results show that the oil with NbSe2 fibers has better tribological properties than the pure oil and the oil with common layered NbSe2 at atmosphere. This could be attributed to the steady structure of the NbSe2 fibers. The copper sintered material with NbSe2 fibers was prepared by the process of powder metallurgy. The incorporation of NbSe2 fibers leads to the great reduction of friction coefficients under all kinds of loads，which may be attributed to the lubricating film formed on the worn surface.
2008, 25(6): 186-191.
Abstract:
Silica was coated on the surface of magnetite nanoparticles by the sol-gel method and alkali catalyzing hydrolysis of tetraethyl orthosilicate（TEOS）. Inversion biomicroscope，field emission transmission electron microscope，X-ray diffraction，laser particle size analyzer and vibrating sample magnetometry were used to characterize the appearance，size and size distribution，magnetic characteristics，crystal structure and chemical composition of the composite. The results show that the particles have good performances, the diameter is about 15 nm，and the magnetic property is 10.9 emu/g. The silica coated magnetite nanoparticles were used to isolate plasmid DNA and genomic DNA.
Silica was coated on the surface of magnetite nanoparticles by the sol-gel method and alkali catalyzing hydrolysis of tetraethyl orthosilicate（TEOS）. Inversion biomicroscope，field emission transmission electron microscope，X-ray diffraction，laser particle size analyzer and vibrating sample magnetometry were used to characterize the appearance，size and size distribution，magnetic characteristics，crystal structure and chemical composition of the composite. The results show that the particles have good performances, the diameter is about 15 nm，and the magnetic property is 10.9 emu/g. The silica coated magnetite nanoparticles were used to isolate plasmid DNA and genomic DNA.
2008, 25(6): 192-197.
Abstract:
Diamond/Al composites were fabricated by spark plasma sintering（SPS）. The thermal conductivity of the samples with different particle volumes and particle sizes was investigated，and the influence of the processing parameters on the thermal conductivity of the composites was also considered. The results show that diamond/Al composites with good thermal conductivity can be made by SPS，and the density is the most important factor which affects the thermal conductivity of the composites. The diamond/Al composite with the highest thermal conductivity can be obtained when the composite contains 50 vol% diamond particles of 70 μm sintered at 550℃，and its thermal conductivity is 182 W/(m·K)，which is 34.8% higher than that of the sample of the pure Al sintered under the same condition，showing that the diamond particle gives significant improvement of the thermal conductivity of Al matrix composites.
Diamond/Al composites were fabricated by spark plasma sintering（SPS）. The thermal conductivity of the samples with different particle volumes and particle sizes was investigated，and the influence of the processing parameters on the thermal conductivity of the composites was also considered. The results show that diamond/Al composites with good thermal conductivity can be made by SPS，and the density is the most important factor which affects the thermal conductivity of the composites. The diamond/Al composite with the highest thermal conductivity can be obtained when the composite contains 50 vol% diamond particles of 70 μm sintered at 550℃，and its thermal conductivity is 182 W/(m·K)，which is 34.8% higher than that of the sample of the pure Al sintered under the same condition，showing that the diamond particle gives significant improvement of the thermal conductivity of Al matrix composites.
