The Research On Preparation Of Multifunctional Coating On Carbon Fiber (CF) Surface And CF Reinforcing Hydroxyapatite Composites

This paper is part of the work that derived from the Natural Science Foundation Research Project of Shaanxi Province,“Research on Carbon Fiber/In Situ Growth of Nano-HA Coating Synergistically Reinforce HA Composites(2014JM6233)” and “Academic Backbone Cultivation Plan Project of Shaanxi University of Science and Technology(XSGP201208)”.It is also the follow-up work of the National Natural Science Foundation of China(51072107).Hydroxyapatite(HA)is the main inorganic component of human hard tissues,which presents excellent biocompatibility and bioactivity and could be used as a bone graft repair material with great application prospects.However,the wide application of HA as load-bearing bones in human body is highly restricted because of the high brittleness and poor strength.Carbon fiber(CF)has low density and high strength,is one of the ideal reinforcing material to improve the mechanical properties of HA.But,due to the difference in thermal expansion coefficient between CF and HA,and serious oxidation damage to CF by O2-and H2 O during the decomposition of HA,resulting in the reinforcing effect of CF far from the theoretical forecast level.In order to realize the enhancing and toughening of the CF/HA composites,nano-HA bioactive coating,SiC sintering protective coating,and TiAl/nHA composite coating were constructed on CF surface.Moreover,the composites were prepared by different sintering processes.The main contents and conclusions are as follows:The roughness and specific surface area of CF treated with mixed acid/hydrogen peroxide solution(NHSH)increased.And some active oxygen-containing functional groups such as hydroxyl group and carboxyl group were grafted.Compared with the untreated CF,the number of hydroxyl group and carboxyl group on NHSH-CF increased nearly 8 and 12 times,respectively.In addition,the nHA coating with controllable morphology,structure and composition was prepared by electrochemical deposition(ECD)on the surface of NHSH-CF.The results revealed that nHA coating with a nano acicular structure gradually evolved into a hexagonal rod structure as the deposition time extended from 60 min to 180 min at the current density of 5.0mA/cm2.A certain thickness,morphology and structure of the SiC coating was deposited on the CF by LPCVD.Furthermore,the forming mechanism of SiC coating and the effects of SiC coating on the mechanical properties and sintering protection performance to CF were studied.It was found that the dense SiC coating with 1.0?m in thickness was uniformly and continuously coated on the CF when the deposition time reached 3h.In addition,Ti Al/nHA coating was prepared on the NHSH-CF by multi-arc ion plating and ECD.The effects of CF surface state and different process parameters on the morphology,composition and structure of TiAl/nHA coating were studied.Results showed that the ideal Ti Al coating with thickness at 0.2?m was obtained on the NHSH-CF by multi-arc ion plating deposition for 1h.And the nHA coating with thickness at 0.5?m that closely coated on the TiAl-CF surface was obtained by ECD for 3h.CF/nHA/HA,CF/SiC/HA and CF/TiAl-n HA/HA composites were prepared by hot pressing and pressureless sintering,respectively.The CF content,CF surface state,sintering process and interfacial bonding properties have a great influence on the mechanical properties and enhancing and toughening mechanism of the composites.When the coated CF is applied for preparation of CF/HA composites,the internal stress is significantly reduced due to the presence of the coating.The coated CF could act as a bridge to control the forming of interfacial gaps effectively,improve the interface bonding properties between CF and HA.The bending strength and fracture toughness of CF/nHA/HA and CF/SiC/HA composites are obviously improved compared with pure HA.The CF in CF/SiC/HA and CF/TiAl-nHA/HA composites is well protected during the pressureless sintering process.This work would lay a theoretical foundation for the preparation and clinical application of CF/HA composites with good biomechanical compatibility.