In this paper, preparation of nano-biphasic calcium phosphate （nBCP）, mechanical behavior and load-bearing of poly （lactide-co-glycolide） （PLGA） and PLGA/nBCP are presented. The nBCP with composition of 63/37 （...In this paper, preparation of nano-biphasic calcium phosphate （nBCP）, mechanical behavior and load-bearing of poly （lactide-co-glycolide） （PLGA） and PLGA/nBCP are presented. The nBCP with composition of 63/37 （w/w） HA/-TCP （hydroxyapatite/fl-tricalcium phosphate） was produced by heating of bovine bone at 700℃. Composite scaffolds were made by using PLGA matrix and 10-50 wt% nBCP powders as reinforcement material. All scaffolds were prepared by thermally induced solid-liquid phase separation （TIPS） at -60~C under 4 Pa （0.04 mbar） vacuum. The results of elastic modulus testing were adjusted with Ishai-Cohen and Narkis models for rigid polymeric matrix and compared to each other. PLGA/nBCP scaffolds with 30 wt% nBCP showed the highest value of yield strength among the scaffolds. In addition, it was found that by increasing the nBCP in scaffolds to 50 wt%, the modulus of elasticity was highly enhanced. However, the optimum value of yield strength was obtained at 30 wt% nBCP, and the agglomeration of reinforcing particles at higher percentages caused a reduction in yield strength. It is clear that the elastic modulus of matrix has the significant role in elastic modulus of scaffolds, as also the size of the filler particles in the matrix.展开更多
The combination of micro-carriers and polymer scaffolds as promising bone grafts have attracted considerable interest in recent decades.The poly(L-lactic acid)/poly(lactic-co-glycolic acid)/polycaprolactone(PLLA/PLGA/...The combination of micro-carriers and polymer scaffolds as promising bone grafts have attracted considerable interest in recent decades.The poly(L-lactic acid)/poly(lactic-co-glycolic acid)/polycaprolactone(PLLA/PLGA/PCL)composite scaffold with porous structure was fabricated by thermally induced phase separation(TIPS).Dexamethasone(DEX)was incorporated into PLGA microspheres and then loaded on the PLLA/PLGA/PCL scaffoldtopreparethedesiredcompositescaffold.The physicochemical properties of the prepared composite scaffold were characterized.The morphology of rat bone marrow mesenchymal stem cells(BMSCs)grown on scaffolds was observed using scanning electron microscope(SEM)and fluorescence microscope.The resultsshowedthatthePLLA/PLGA/PCLscaffoldhad interconnected macropores and biomimetic nanofibrous structure.In addition,DEX can be released from scaffold in a sustained manner.More importantly,DEX loaded composite scaffold can effectively support the proliferation of BMSCs as indicated by fluorescence observation and cell proliferation assay.The results suggested that the prepared PLLA/PLGA/PCL composite scaffold incorporating drug-loaded PLGA microspheres could hold great potential for bone tissue engineering applications.展开更多
FeCrAl fiber-reinforced hydroxyapatite（HA） biocomposites（FeCrAl（f）/HA） were fabricated by the hot pressing technique.The metallographic microscopy,X-ray diffractometry,scanning electron microscopy（SEM） and ene...FeCrAl fiber-reinforced hydroxyapatite（HA） biocomposites（FeCrAl（f）/HA） were fabricated by the hot pressing technique.The metallographic microscopy,X-ray diffractometry,scanning electron microscopy（SEM） and energy dispersive spectroscopy（EDS） were used to observe and analyze the microstructure and composition of FeCrAl（f）/HA composites,respectively.The mechanical properties of FeCrAl（f）/HA composites were measured by the three-point-bending test.The results show that the composite can be reinforced by FeCrAl fiber and enhanced gradually,and then declined with the increase of the content of FeCrAl fiber（0-11%,volume fraction） in the whole range of experiments.Both the HA matrix and FeCrAl fiber integrate very tightly and bit into each other very deeply and counter-diffusion takes place to some extent at two-phase interface.The optimum parameters of FeCrAl（f）/HA composite are diameter of 22 μm,length of 1-2 mm and of volume faction of about 7% for FeCrAl fibers.展开更多
A novel, Ti-6 Al-4 V(Ti64)/Hydroxyapatite(HA at 5% by weight concentration) metal/ceramic composite has been fabricated using electron beam powder bed fusion(EPBF) additive manufacturing(AM): specifically, the commerc...A novel, Ti-6 Al-4 V(Ti64)/Hydroxyapatite(HA at 5% by weight concentration) metal/ceramic composite has been fabricated using electron beam powder bed fusion(EPBF) additive manufacturing(AM): specifically, the commercial electron beam melting(EBM?) process. In addition to solid Ti64 and Ti64/5% HA samples, four different unit cell(model) open-cellular mesh structures for the Ti64/5% HA composite were fabricated having densities ranging from 0.68 to 1.12 g/cm^3, and corresponding Young's moduli ranging from 2.9 to 8.0 GPa, and compressive strengths ranging from ~3 to 11 MPa. The solid Ti64/5%HA composite exhibited an optimal tensile strength of 123 MPa, and elongation of 5.5% in contrast to a maximum compressive strength of 875 MPa. Both the solid composite and mesh samples deformed primarily by brittle deformation, with the mesh samples exhibiting erratic, brittle crushing. Solid, EPBF-fabricated Ti64 samples had a Vickers microindentation hardness of 4.1 GPa while the Ti64/5%HA solid composite exhibited a Vickers microindentation hardness of 6.8 GPa. The lowest density Ti64/5%HA composite mesh strut sections had a Vickers microindentation hardness of 7.1 GPa. Optical metallography(OM) and scanning electron microscopy(SEM) analysis showed the HA dispersoids to be highly segregated along domain or grain boundaries, but homogeneously distributed along alpha(hcp) platelet boundaries within these domains in the Ti64 matrix for both the solid and mesh composites. The alpha platelet width varied from ~5 μm in the EPBF-fabricated Ti64 to ~1.1 m for the Ti64/5%HA mesh strut. The precursor HA powder diameter averaged 5 μm, in contrast to the dispersed HA particle diameters in the Ti64/5%HA composite which averaged 0.5 m. This work highlights the use of EPBF AM as a novel process for fabrication of a true composite structure, consisting of a Ti64 matrix and interspersed and exposed HA domains, which to the authors' knowledge has not been reported before. The results also illustrate the prospects not only for fabricating specialized, novel composite bone replacement scaffolds and implants, through the combination of Ti64 and HA, but also prospects for producing a variety of related metal/ceramic composites using EPBF AM.展开更多
Poly(vinyl alcohol)(PVA)/hydroxyapatite(HA)composite hydrogel specimens were prepared with 15%PVA and 1%,2%,3%,4%and 5%HA by repeated freezing-thawing.The tests of static and dynamic mechanical properties were carried...Poly(vinyl alcohol)(PVA)/hydroxyapatite(HA)composite hydrogel specimens were prepared with 15%PVA and 1%,2%,3%,4%and 5%HA by repeated freezing-thawing.The tests of static and dynamic mechanical properties were carried out todiscuss the influence of different contents of HA and freezing-thawing cycles on the mechanical properties of PVA/HA compositehydrogel.The results of static mechanical tests showed that the PVA/HA composite hydrogel with 3%HA and ninefreezing-thawing cycles had excellent stress relaxation properties,higher relaxation ratio,lower stress equilibrium value andpresented better properties of creep and recovery.The results of dynamic mechanical test showed that the PVA/HA compositehydrogel with nine freezing-thawing cycles had higher storage modulus and loss modulus,so was the PVA/HA compositehydrogel with 3%HA.展开更多
Hydroxyapatite-graft-poly(D-lactide)(HA-g-PDLA)was synthesized by ring-opening polymerization with HA as initiator and stannous octanoate(Sn(Oct)2)as catalyst.Thermogravimetric analysis(TGA)and Fourier transform infra...Hydroxyapatite-graft-poly(D-lactide)(HA-g-PDLA)was synthesized by ring-opening polymerization with HA as initiator and stannous octanoate(Sn(Oct)2)as catalyst.Thermogravimetric analysis(TGA)and Fourier transform infrared spectroscopy(FUR)results indicate that PDLA chains are successfully grafted onto HA particles by covalent bond.Under two different processing temperatures(190 and 230℃),the effect of the grafted PDLA chains on the crystallization behavior of poly(L-lactide)/HA-g-PDLA(PLLA/HA-g-PDLA)composite was investigated in the current study,comparing to neat PLLA and its four composites(PLLA/HA,PLLA/HA-g-PLLA,PLLA/PDLA,and PLLA/HA/PDLA).The crystallization rate of PLLA/HA-g-PDLA composite is highly enhanced comparing to PLLA,PLLA/HA and PLLA/HA-g-PLLA composites in which there are no stereocomplex(SC)crystallites.In addition,when the processing temperature rises from 190℃ to 230℃,the acceleration of PLLA crystallization in PLLA/HA-g-PDLA composite is not influenced so much as other composites containing SC crystallites,such as PLLA/HA/PDLA or PLLA/PDLA.The differential scanning calorimetry(DSC)results demonstrate that even without SC crystallites,the crystallization of PLLA can still be accelerated a lot in this composite.This may be related to the interaction between the grafted PDLA chains and the amorphous PLLA chains in PLLA/HA-g-PDLA composite.The isothermal crystallization kinetics studies indicate that the nature of nucleation and crystal growth of PLLA/HAg-PDLA composite are more likely 3D crystalline growth with heterogeneous nucleation mode,which are different from PLLA or other composites.This investigation could shed new light on the application of PLLA/HA composites.展开更多
The in vitro degradation characteristic of the poly D, L-lactic acid （ PDLIA ）/ hydroxyapatite （ HA ） compound were investigated. The compoundfibers were immersed in static phosphate buffer at 37℃ to degrade fo...The in vitro degradation characteristic of the poly D, L-lactic acid （ PDLIA ）/ hydroxyapatite （ HA ） compound were investigated. The compoundfibers were immersed in static phosphate buffer at 37℃ to degrade for 22 weeks. The changes in pH value of the buffer solution, the mechanical strength and morphological of inside and outside of composite fibers with degrurlation characteristic were observed. Results show that pH value of the buffer solution stabilized to aboat 7.0 before 12 weeks, however after 20 weeks that pH value quick declined. After 7 weeks that composite fibers of mechanical strength cannot mensuration. SEM observation revealed ttua bimodal degradation occurred in composite fibers.展开更多
The co-continuous(HA+β-TCP)/Zn−3Sn composite was fabricated via vacuum casting-infiltration method.The microstructure,mechanical properties,corrosion behaviors,and hemolysis ratio of the composite were studied by sca...The co-continuous(HA+β-TCP)/Zn−3Sn composite was fabricated via vacuum casting-infiltration method.The microstructure,mechanical properties,corrosion behaviors,and hemolysis ratio of the composite were studied by scanning electron microscope,X-ray diffractometer,mechanical testing,electrochemical test,immersion test,and ultraviolet spectrophotometry.The results indicate that Zn−3Sn alloy infiltrated into porous HA+β-TCP scaffold,which resulted in the formation of a compact(HA+β-TCP)/Zn−3Sn co-continuous composite,without any reaction layer between the Zn−3Sn alloy and the HA+β-TCP scaffold.The compressive strength of the composite was equal to about 3/4 that of Zn−3Sn alloy bulk.The corrosion rate of composite in simulated body fluid solution was slightly higher than that of Zn−3Sn alloy bulk.The main corrosion product on the composite surface was Zn(OH)2.The hemolysis rate of the composite was lower than that of Zn–3Sn alloy bulk and exhibited superior blood compatibility.展开更多
In order to overcome the poor mechanical properties of HA and the low bioactivity of Ti, HA/Ti composites with various compositions were prepared by mechanical milling. The effects of milling condition and the composi...In order to overcome the poor mechanical properties of HA and the low bioactivity of Ti, HA/Ti composites with various compositions were prepared by mechanical milling. The effects of milling condition and the composition on the microstructure, the density and the hardness of the composites were studied. The results show that during the ball milling process, Ti particles are refined and the homogeneity of the HA/Ti mixtures is improved; HA will partially decompose due to the existence of Ti and high sintering temperature. The microstructure of HA/Ti composites is highly dependent on the milling condition and the composition. In the microstructure, Ti phase connects to be a continuous network, and HA/Ti mixtures disperse in the network. The longer the milling time, the finer the network will be. The density of HA/Ti composites decreases with the content of HA increasing and the milling time prolonging, because HA deteriorates the sinterability of Ti.The hardness of HA/Ti composites increases firstly with the content of HA increasing, and then drops when the content of HA exceeds 30%. Addition of HA will strengthen the HA/Ti composite but will decrease the density of the composite, which accounts for the effect of HA on the hardness of the composites.展开更多
Nonporous and porous C/PLA/nano-HA composites were fabricated by the process of solvent blending and freeze-drying technique, and the effect of porous structure on the mechanical properties of C/PLA/nano-HA composites...Nonporous and porous C/PLA/nano-HA composites were fabricated by the process of solvent blending and freeze-drying technique, and the effect of porous structure on the mechanical properties of C/PLA/nano-HA composites scaffold was investigated and analyzed. The results show that the effects of porous structure on the bending strength, modulus and curves of stress and strain were obvious. Compared with nonporous sample, the curves of stress and strain of porous sample show more rough, and alternative phenomenon of stress increase and stress relaxation appears. It is strongly suggested that the fracture model of C/PLA/nano-HA composites scaffold transforms from the local to global load due to the porous structure.展开更多
A three-dimensional finite element analysis was conducted to evaluate the feasibility of predicting the flexural properties of hydroxyapatite-reinforced poly-L-lactide acid （HA/PLLA） biocomposite using three differe...A three-dimensional finite element analysis was conducted to evaluate the feasibility of predicting the flexural properties of hydroxyapatite-reinforced poly-L-lactide acid （HA/PLLA） biocomposite using three different schemes. The scheme 1, originated from a beam analysis, was used to determine the flexural modulus analytically while the scheme 2 and 3 were designed to have different loading and boundary conditions using a finite element cell modeling approach. An empirical approach using Chow＇s formula and experimental data were used for comparison with the predicted results. In order to reduce the computational time and save the storage space involved in determining the effect of varying particle volume fractions on the flexural properties of HA/PLLA, a superelement technique was applied. The results using the scheme 3 and the Chow＇s formula were found to be in reasonable agreement with experimental results over the range of particle volume fraction. In addition to the Chow＇s formula, local stress distribution and the failure processes in HA/PLLA were simulated using the finite element technique.展开更多
Nano-hydroxyapatite reinforced poly（vinyl alcohol） gel（nano-HA/PVA gel） composites has been proposed as a promising biomaterial,especially used as an articular cartilage repair biomaterial.In this paper,nano-HA/PV...Nano-hydroxyapatite reinforced poly（vinyl alcohol） gel（nano-HA/PVA gel） composites has been proposed as a promising biomaterial,especially used as an articular cartilage repair biomaterial.In this paper,nano-HA/PVA gel composite was prepared by in situ synthesis method and incorporation with freeze-thaw cycle process.The microstructure and morphology were investigated by X-ray diffraction,TEM,SEM and FTIR.The results showed that the size of HA particles synthesized in PVA solution was on the nanometer scale.Both the size and crystallinity of HA particles synthesized in PVA solution decreased compared with that of HA synthesized in distilled water.The nano-HA particles were distributed in PVA matrix uniformly due to the effect of PVA solution as a dispersant while low content of HA particles in the composites.On the contrary,with high content of nano-HA particles in the composites,the particles tended to aggregate.The result of FT-IR analysis indicated that the chemical bond between nano-HA particles and PVA matrix existed.The conformation and degree of tacticity of PVA molecule changed because of the addition of HA particles.Furthermore,the interfacial strength of the composites was improved due to the interaction between nano-HA particle and PVA matrix and this was beneficial to improving the mechanical properties of the composites.展开更多
基金supported by Isfahan University of Technology and Ministry of Sciences, Research & Technology in Iran and Materials Science & Engineering School of Nanyang Technological University in Singapore
文摘In this paper, preparation of nano-biphasic calcium phosphate （nBCP）, mechanical behavior and load-bearing of poly （lactide-co-glycolide） （PLGA） and PLGA/nBCP are presented. The nBCP with composition of 63/37 （w/w） HA/-TCP （hydroxyapatite/fl-tricalcium phosphate） was produced by heating of bovine bone at 700℃. Composite scaffolds were made by using PLGA matrix and 10-50 wt% nBCP powders as reinforcement material. All scaffolds were prepared by thermally induced solid-liquid phase separation （TIPS） at -60~C under 4 Pa （0.04 mbar） vacuum. The results of elastic modulus testing were adjusted with Ishai-Cohen and Narkis models for rigid polymeric matrix and compared to each other. PLGA/nBCP scaffolds with 30 wt% nBCP showed the highest value of yield strength among the scaffolds. In addition, it was found that by increasing the nBCP in scaffolds to 50 wt%, the modulus of elasticity was highly enhanced. However, the optimum value of yield strength was obtained at 30 wt% nBCP, and the agglomeration of reinforcing particles at higher percentages caused a reduction in yield strength. It is clear that the elastic modulus of matrix has the significant role in elastic modulus of scaffolds, as also the size of the filler particles in the matrix.
基金National Natural Science Foundations of China(Nos.31271028,31570984)Innovation Program of Shanghai Municipal Education Commission,China(No.13ZZ051)+2 种基金International Cooperation Fund of the Science and Technology Commission of Shanghai Municipality,China(No.15540723400)Open Foundation of State Key Laboratory for Modification of Chemical Fibers and Polymer Materials,China(No.LK1416)“111 Project” Biomedical Textile Materials Science and Technology,China(No.B07024)
文摘The combination of micro-carriers and polymer scaffolds as promising bone grafts have attracted considerable interest in recent decades.The poly(L-lactic acid)/poly(lactic-co-glycolic acid)/polycaprolactone(PLLA/PLGA/PCL)composite scaffold with porous structure was fabricated by thermally induced phase separation(TIPS).Dexamethasone(DEX)was incorporated into PLGA microspheres and then loaded on the PLLA/PLGA/PCL scaffoldtopreparethedesiredcompositescaffold.The physicochemical properties of the prepared composite scaffold were characterized.The morphology of rat bone marrow mesenchymal stem cells(BMSCs)grown on scaffolds was observed using scanning electron microscope(SEM)and fluorescence microscope.The resultsshowedthatthePLLA/PLGA/PCLscaffoldhad interconnected macropores and biomimetic nanofibrous structure.In addition,DEX can be released from scaffold in a sustained manner.More importantly,DEX loaded composite scaffold can effectively support the proliferation of BMSCs as indicated by fluorescence observation and cell proliferation assay.The results suggested that the prepared PLLA/PLGA/PCL composite scaffold incorporating drug-loaded PLGA microspheres could hold great potential for bone tissue engineering applications.
基金Project(50774096) supported by the National Natural Science Foundation of ChinaProject(2011QNZT046) supported by the Fundamental Research Funds of the Central South University,ChinaProject supported by the Postdoctoral Science Foundation of Central South University,China
文摘FeCrAl fiber-reinforced hydroxyapatite（HA） biocomposites（FeCrAl（f）/HA） were fabricated by the hot pressing technique.The metallographic microscopy,X-ray diffractometry,scanning electron microscopy（SEM） and energy dispersive spectroscopy（EDS） were used to observe and analyze the microstructure and composition of FeCrAl（f）/HA composites,respectively.The mechanical properties of FeCrAl（f）/HA composites were measured by the three-point-bending test.The results show that the composite can be reinforced by FeCrAl fiber and enhanced gradually,and then declined with the increase of the content of FeCrAl fiber（0-11%,volume fraction） in the whole range of experiments.Both the HA matrix and FeCrAl fiber integrate very tightly and bit into each other very deeply and counter-diffusion takes place to some extent at two-phase interface.The optimum parameters of FeCrAl（f）/HA composite are diameter of 22 μm,length of 1-2 mm and of volume faction of about 7% for FeCrAl fibers.
文摘A novel, Ti-6 Al-4 V(Ti64)/Hydroxyapatite(HA at 5% by weight concentration) metal/ceramic composite has been fabricated using electron beam powder bed fusion(EPBF) additive manufacturing(AM): specifically, the commercial electron beam melting(EBM?) process. In addition to solid Ti64 and Ti64/5% HA samples, four different unit cell(model) open-cellular mesh structures for the Ti64/5% HA composite were fabricated having densities ranging from 0.68 to 1.12 g/cm^3, and corresponding Young's moduli ranging from 2.9 to 8.0 GPa, and compressive strengths ranging from ~3 to 11 MPa. The solid Ti64/5%HA composite exhibited an optimal tensile strength of 123 MPa, and elongation of 5.5% in contrast to a maximum compressive strength of 875 MPa. Both the solid composite and mesh samples deformed primarily by brittle deformation, with the mesh samples exhibiting erratic, brittle crushing. Solid, EPBF-fabricated Ti64 samples had a Vickers microindentation hardness of 4.1 GPa while the Ti64/5%HA solid composite exhibited a Vickers microindentation hardness of 6.8 GPa. The lowest density Ti64/5%HA composite mesh strut sections had a Vickers microindentation hardness of 7.1 GPa. Optical metallography(OM) and scanning electron microscopy(SEM) analysis showed the HA dispersoids to be highly segregated along domain or grain boundaries, but homogeneously distributed along alpha(hcp) platelet boundaries within these domains in the Ti64 matrix for both the solid and mesh composites. The alpha platelet width varied from ~5 μm in the EPBF-fabricated Ti64 to ~1.1 m for the Ti64/5%HA mesh strut. The precursor HA powder diameter averaged 5 μm, in contrast to the dispersed HA particle diameters in the Ti64/5%HA composite which averaged 0.5 m. This work highlights the use of EPBF AM as a novel process for fabrication of a true composite structure, consisting of a Ti64 matrix and interspersed and exposed HA domains, which to the authors' knowledge has not been reported before. The results also illustrate the prospects not only for fabricating specialized, novel composite bone replacement scaffolds and implants, through the combination of Ti64 and HA, but also prospects for producing a variety of related metal/ceramic composites using EPBF AM.
基金supported by National Natural Science Foundation of China(Grant No.50875252)Program for New Century Excellent TaIents in University(Grant No.NCET-06-0479)Natural Science Foundation of Jiangsu Proyince(Grant No.BK2008005)
文摘Poly(vinyl alcohol)(PVA)/hydroxyapatite(HA)composite hydrogel specimens were prepared with 15%PVA and 1%,2%,3%,4%and 5%HA by repeated freezing-thawing.The tests of static and dynamic mechanical properties were carried out todiscuss the influence of different contents of HA and freezing-thawing cycles on the mechanical properties of PVA/HA compositehydrogel.The results of static mechanical tests showed that the PVA/HA composite hydrogel with 3%HA and ninefreezing-thawing cycles had excellent stress relaxation properties,higher relaxation ratio,lower stress equilibrium value andpresented better properties of creep and recovery.The results of dynamic mechanical test showed that the PVA/HA compositehydrogel with nine freezing-thawing cycles had higher storage modulus and loss modulus,so was the PVA/HA compositehydrogel with 3%HA.
基金the National Natural Science Foundation of China(Nos.51603005 and 51973010)Beijing Natural Science Foundation(No.2182052).
文摘Hydroxyapatite-graft-poly(D-lactide)(HA-g-PDLA)was synthesized by ring-opening polymerization with HA as initiator and stannous octanoate(Sn(Oct)2)as catalyst.Thermogravimetric analysis(TGA)and Fourier transform infrared spectroscopy(FUR)results indicate that PDLA chains are successfully grafted onto HA particles by covalent bond.Under two different processing temperatures(190 and 230℃),the effect of the grafted PDLA chains on the crystallization behavior of poly(L-lactide)/HA-g-PDLA(PLLA/HA-g-PDLA)composite was investigated in the current study,comparing to neat PLLA and its four composites(PLLA/HA,PLLA/HA-g-PLLA,PLLA/PDLA,and PLLA/HA/PDLA).The crystallization rate of PLLA/HA-g-PDLA composite is highly enhanced comparing to PLLA,PLLA/HA and PLLA/HA-g-PLLA composites in which there are no stereocomplex(SC)crystallites.In addition,when the processing temperature rises from 190℃ to 230℃,the acceleration of PLLA crystallization in PLLA/HA-g-PDLA composite is not influenced so much as other composites containing SC crystallites,such as PLLA/HA/PDLA or PLLA/PDLA.The differential scanning calorimetry(DSC)results demonstrate that even without SC crystallites,the crystallization of PLLA can still be accelerated a lot in this composite.This may be related to the interaction between the grafted PDLA chains and the amorphous PLLA chains in PLLA/HA-g-PDLA composite.The isothermal crystallization kinetics studies indicate that the nature of nucleation and crystal growth of PLLA/HAg-PDLA composite are more likely 3D crystalline growth with heterogeneous nucleation mode,which are different from PLLA or other composites.This investigation could shed new light on the application of PLLA/HA composites.
文摘The in vitro degradation characteristic of the poly D, L-lactic acid （ PDLIA ）/ hydroxyapatite （ HA ） compound were investigated. The compoundfibers were immersed in static phosphate buffer at 37℃ to degrade for 22 weeks. The changes in pH value of the buffer solution, the mechanical strength and morphological of inside and outside of composite fibers with degrurlation characteristic were observed. Results show that pH value of the buffer solution stabilized to aboat 7.0 before 12 weeks, however after 20 weeks that pH value quick declined. After 7 weeks that composite fibers of mechanical strength cannot mensuration. SEM observation revealed ttua bimodal degradation occurred in composite fibers.
基金the National Natural Science Foundation of China(No.51101039)the Fundamental Research Funds for the Central Universities,China(No.3072020CFT0702).
文摘The co-continuous(HA+β-TCP)/Zn−3Sn composite was fabricated via vacuum casting-infiltration method.The microstructure,mechanical properties,corrosion behaviors,and hemolysis ratio of the composite were studied by scanning electron microscope,X-ray diffractometer,mechanical testing,electrochemical test,immersion test,and ultraviolet spectrophotometry.The results indicate that Zn−3Sn alloy infiltrated into porous HA+β-TCP scaffold,which resulted in the formation of a compact(HA+β-TCP)/Zn−3Sn co-continuous composite,without any reaction layer between the Zn−3Sn alloy and the HA+β-TCP scaffold.The compressive strength of the composite was equal to about 3/4 that of Zn−3Sn alloy bulk.The corrosion rate of composite in simulated body fluid solution was slightly higher than that of Zn−3Sn alloy bulk.The main corrosion product on the composite surface was Zn(OH)2.The hemolysis rate of the composite was lower than that of Zn–3Sn alloy bulk and exhibited superior blood compatibility.
文摘In order to overcome the poor mechanical properties of HA and the low bioactivity of Ti, HA/Ti composites with various compositions were prepared by mechanical milling. The effects of milling condition and the composition on the microstructure, the density and the hardness of the composites were studied. The results show that during the ball milling process, Ti particles are refined and the homogeneity of the HA/Ti mixtures is improved; HA will partially decompose due to the existence of Ti and high sintering temperature. The microstructure of HA/Ti composites is highly dependent on the milling condition and the composition. In the microstructure, Ti phase connects to be a continuous network, and HA/Ti mixtures disperse in the network. The longer the milling time, the finer the network will be. The density of HA/Ti composites decreases with the content of HA increasing and the milling time prolonging, because HA deteriorates the sinterability of Ti.The hardness of HA/Ti composites increases firstly with the content of HA increasing, and then drops when the content of HA exceeds 30%. Addition of HA will strengthen the HA/Ti composite but will decrease the density of the composite, which accounts for the effect of HA on the hardness of the composites.
基金Project(30870609) supported by the National Natural Science Foundation of ChinaProjects(KJ081205 KJ091213) supported by the Natural Science Foundation of Chongqing Education Committee, China
文摘Nonporous and porous C/PLA/nano-HA composites were fabricated by the process of solvent blending and freeze-drying technique, and the effect of porous structure on the mechanical properties of C/PLA/nano-HA composites scaffold was investigated and analyzed. The results show that the effects of porous structure on the bending strength, modulus and curves of stress and strain were obvious. Compared with nonporous sample, the curves of stress and strain of porous sample show more rough, and alternative phenomenon of stress increase and stress relaxation appears. It is strongly suggested that the fracture model of C/PLA/nano-HA composites scaffold transforms from the local to global load due to the porous structure.
基金Project supported by the Research Committee of the Hong Kong Polytechnic University (No.G-YX34).
文摘A three-dimensional finite element analysis was conducted to evaluate the feasibility of predicting the flexural properties of hydroxyapatite-reinforced poly-L-lactide acid （HA/PLLA） biocomposite using three different schemes. The scheme 1, originated from a beam analysis, was used to determine the flexural modulus analytically while the scheme 2 and 3 were designed to have different loading and boundary conditions using a finite element cell modeling approach. An empirical approach using Chow＇s formula and experimental data were used for comparison with the predicted results. In order to reduce the computational time and save the storage space involved in determining the effect of varying particle volume fractions on the flexural properties of HA/PLLA, a superelement technique was applied. The results using the scheme 3 and the Chow＇s formula were found to be in reasonable agreement with experimental results over the range of particle volume fraction. In addition to the Chow＇s formula, local stress distribution and the failure processes in HA/PLLA were simulated using the finite element technique.
基金Funded by the Natural Science Research of Key Projects of Anhui Provincial Universities (No. KJ2010A099)
文摘Nano-hydroxyapatite reinforced poly（vinyl alcohol） gel（nano-HA/PVA gel） composites has been proposed as a promising biomaterial,especially used as an articular cartilage repair biomaterial.In this paper,nano-HA/PVA gel composite was prepared by in situ synthesis method and incorporation with freeze-thaw cycle process.The microstructure and morphology were investigated by X-ray diffraction,TEM,SEM and FTIR.The results showed that the size of HA particles synthesized in PVA solution was on the nanometer scale.Both the size and crystallinity of HA particles synthesized in PVA solution decreased compared with that of HA synthesized in distilled water.The nano-HA particles were distributed in PVA matrix uniformly due to the effect of PVA solution as a dispersant while low content of HA particles in the composites.On the contrary,with high content of nano-HA particles in the composites,the particles tended to aggregate.The result of FT-IR analysis indicated that the chemical bond between nano-HA particles and PVA matrix existed.The conformation and degree of tacticity of PVA molecule changed because of the addition of HA particles.Furthermore,the interfacial strength of the composites was improved due to the interaction between nano-HA particle and PVA matrix and this was beneficial to improving the mechanical properties of the composites.
