C/C Composites And Their Modification Research For Artificial Joint

Due to the low density, good geometric stability, similar elastic modulus with human fragments, as well as excellent biocompatibility, C/C composites have great potential in biomedical applications. However, the radiopacity and wear resistance of C/C composite needs to be further improved. In the present work, some reinforced phases were added into C/C composites to enhance the radiopacity. Furthermore, SiC and hydroxyapatite(HA) layers were coated on the surface to improve the wear resistance and bioactivity.Firstly, C/C composites were synthesized by the liquid impregnation method. The influences of ultrasonic processing and carbonization temperature on the densification, morphology and bending strength C/C composites were studied. At low carbonized temperature of 800℃, the influence of ultrasonic treatment on the formation and properties of C/C composites is slight, whilethe porous structure appeared after ultrasonic treatment at high carbonized temperature of 1200℃ and the ultimate bending strength reached 105 MPa. The improved bending property of C/C composites may contribute to the porous structure, which could block the spread of crack.. In addition, the fracture mode of C/C composites changed from brittle fracture to pseudo plastic fracture.Secondly, the reinforced phases ofTaC, ZrO2, and Ta2O5 + SiC were added into C/C composites by liquid impregnation method combined with heat treatment. The influence of nitric acid and ultrasound treatments on the radiopacity and bending strength were investigated. The results showed that abundant organic functional groups formed on the surface of C/C composites after 50% nitric acid treatment, which could improve the wettability of C/C composites. More ZrO2 particles were added into C/C composites and the bending strength reached 95 MPa. Furthermore ZrO2- C/C composites could be distinguished clearly under X-ray. The radiopacity is related to the proportion and the concentration of the additions. When the impregnation liquid is 15% ethanol tantalum zirconium and 15% acetic acid, the preparation samples had best radiopacity, and their flexural strengthes are 90 MPa and 95 MPa, respectively.Thirdly, the SiC coating layers were fabricated on C/C composite to improve its wear resistance property by the low-temperature packing cementation. The influences of packing temperature, packing time and the proportion of the packing materials composition on the structure, surface morphology, and friction property of SiC coatings were investigated. The results showed that when the packing temperature was 1200 ℃, the obtained SiC coating with moderate graphite was the densest, and its friction coefficient was as low as 0.18. At the same time, SiC nanowires were formed within the SiC coating. When the ratio of Si: MgO: C was 2:1:1, the SiC coating exhibited compact microstructure, and its friction coefficient was about 0.18.Finally, the HA coating was prepared on C/C composite to improve its biological activity by the electrochemical deposition combined with NaOH treatment. The influence of the electrochemical deposition temperature, concentration of electrolyte solution, concentration of Na+ and NaOH on the composition, surface morphology, and solubility of HA coating were studied. The results showed that when the deposition temperature was 70℃, the HA coating was compact. After dealing with the different concentration of NaOH solution, Ca(OH)2 phase was generated in the coatings. The HA coatings became denser with the increase of NaOH solution concentrations, while the solubility of coatings reduced due to the change of surface morphology and the formation of Ca(OH)2.