Study On Al₂O₃-SiC_w Sintering Protective Composite Coating On Carbon Fiber Surface And Its Reinforcing Hydroxyapatite Composites

Carbon fiber?CF?reinforced hydroxyapatite?HA?composites?CF/HA?are widely used as biomaterials.However,during sintering process of CF/HA,the oxidative damage of CF caused by dehydroxylation of HA and difference in thermal expansion coefficients will reduce the reinforcing effect of CF on HA.First modified CF by several methods to determine reasonable parameters for improving wettability of CF.Further,Al₂O₃ and Al₂O₃ composite coating added with Si C_w?Al₂O₃-SiC_w?were prepared on CF surface by sol-dipping and sol-spraying.The protective effect of coatings on CF was studied.Finally,the composites were prepared by pressureless and hot-press sintering process.The effects of process on morphology,microstructure and mechanical properties of composites were investigated.Al₂O₃ coating was prepared on mixed acid-hydrogen peroxide modified carbon fiber?TCF?surface by sol-dipping?Al₂O₃-TCF?.The effects of dipping times and sol concentration on morphology,composition and oxidation resistance of coatings were investigated.In order to further optimize the anti-oxidation protection of Al₂O₃ coating,Al₂O₃-SiC_w protective composite coating was prepared on ultrasonic anodized carbon fiber(CF_U2)surface by sol-spraying.The effects of sintering process on morphology,structure and mechanical properties of Al₂O₃-SiC_w coated carbon fiber reinforced HA composites?CF/?Al₂O₃-Si C_w?/HA?were studied.The main conclusions are as follows.Contact angle of TCF was 31.7%lower than that of CF,the wettability was significantly improved.When TCF is secondarily coated in a 0.4 mol/L Al₂O₃ sol,a uniform and continuous Al₂O₃ coating can be obtained on TCF.Al₂O₃-TCF exhibited good anti-oxidation after oxidized at 700°C for 20 min,its mass loss and oxidation rate were both lower than that of CF.When using Al₂O₃-TCF reinforced HA composites prepared by pressureless sintering,due to protection of Al₂O₃ coating,the oxidative damage of CF caused by HA decomposition is effectively reduced,the difference in thermal expansion coefficient between CF and HA is mitigated.When content of Al₂O₃-TCF in composites was 0.5 wt%,the obtained density and hardness reached the maximum,which were 1.25 g/cm³ and422 HV,respectively.Surface energy of CF_U2 is 33.4%higher than that of unmodified CF,and roughness is increased by about 4 times.When Al₂O₃-SiC_w coating was prepared by sol-spraying,the coating prepared by three spraying times was uniform,dense and continuous.The coating reduced the mass loss of CF at 800°C for 30 minutes by 44.0%compared with uncoated CF.In composites preparation process,CF/?Al₂O₃-SiC_w?/HA composites sintered by pressless sintering at 1200°C for 60min are dense with high hardness.Compared with CF/HA composites,the compressive strength increased by 38.7%,bending strength and flexural modulus increased by 31%and 1.71 times,respectively.The CF/?Al₂O₃-SiC_w?/HA composites sintered by hot-press sintering at 1200°C for 60 min are highly dense with hardness of 552 HV and compressive strength of 74.45 MPa,which is 2.8%and 2.66 times higher than that of CF/HA.The simulated body fluid immersion experiment results show that compared with CF/?Al₂O₃-SiC_w?/HA composites prepared by hot-press sintering,the composites prepared by pressureless sintering are more conducive to the formation of apatite and have better biological activity.This article is based on advantages of easy control,simple operation,low cost and wide adaptability of Al₂O₃ coating prepared by sol-dipping.The Al₂O₃ sol with Si C_w was atomized by an optimized sol-spraying method to prepare a uniform,dense and continuous Al₂O₃-SiC_w coating.The sintering protective effect of Al₂O₃and Al₂O₃-SiC_w coatings on CF was fully exerted,which laid foundation for obtaining high-performance composites with potential clinical application value.