Preparation Of CF/Mg-nHA Coating/Mg-nHA Composite Under Low Sintering Temperature By Pressureless Method

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 the “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).The details are as follows:Hydroxyapatite(HA)is the main inorganic component of human bone tissue,with excellent biocompatibility and biological activity.It could effectively induce the growth of bone after implanting to form a good combination with human bone tissue.Accordingly HA is a greatly potential biological materials for bone repair and replacement.However,the mechanical properties of HA such as serious brittleness,poor toughness is poor.Carbon fiber(CF)can be used to improve the mechanical properties of HA as reinforcement materials.However,there are some problems such as oxidative damage of CF and mismatch of thermal expansion coefficient in the preparation of composites.Magnesium doped nano hydroxyapatite(Mg-nHA)with good sintering performance was synthetized by hydrothermal method.At the same time,Mg-nHA was coated on the surface of CF by electrochemical deposition,then Mg-nHA coated CF and Mg-nHA composite powder was prepared by hydrothermal method.Based on the thermal stability and sintering properties of Mg-n HA powder,CF/Mg-n HA coating/Mg-nHA composite with good interfacial adhesion was prepared by pressureless sintering under the lower sintering temperature than usually adopted in the reported literatures.This would protect the CF from oxidative damage during the preparation of the sintering process of composite.The research contents and results are as follows:(1)The influence of different hydrothermal condition such hydrothermal synthesis temperature,times,and additives on morphology and size of HA were discussed.The rod-like and long fibred HA with good crystallinity was synthetized at 160 ?.And the long fiber length of HA was prepared by using urea.In addition,the effects of sodium citrate on the growth of HA were investigated,the n HA morphology was transformed from flake to long rod as time passes.(2)The Mg-nHA was synthetized by hydrothermal synthesis method.The influence of pH,hydrothermal temperature on preparation of the product was studied.And the influence mechanism of sintering properties and thermal stability of Mg-nHA was analyzed.The doping of Mg2+ could improve the biological activity of nHA.With the increase of the doping content,the biological activity becomes better.The Mg-n HA had good thermal stability.It have good performance under low temperature by pressureless sintering.(3)The Mg-nHA coating was prepared on the surface of CF by electrochemical deposition method.The effects of electrolyte concentration and time on electrochemical deposition were investigated.The uniformly dense Mg-nHA coated on the CF surface was obtained after 3 h with the low concentration electrolyte.The composites were prepared by pressureless sintering under low temperature by using the Mg-nHA and Mg-nHA coated CF.The effects of sintering temperature,CF content and length of CF on the mechanical properties of composites were studied,and the mechanism of strengthening and toughening of CF composites was studied.The CF in the composites sintered at 700 ? had little oxidative damage.When the content of 6 mm CF was 1 wt%,the flexural strength of the composites was the highest,which was about 8.51 MPa.The Mg-nHA coating could alleviate the mismatch between CF and HA thermal expansion coefficient and improve the interfacial bonding.This study would provide a method which could realize potential reinforcing effect with low energy consumption to prepare CF/HA composites.And it would helo to promote the clinical application of HA.