| Carbon/carbon (C/C) composite is a novel material developed in the new material field and has great prospect in bone repair field due to excellent mechanical properties, especially elastic modulus close to that of human bones. However, C/C composite is bionert, in order to endow it with osteoconductivity and osteoinductity, biomedical materials with bioactivity could be coated on it. In this paper, on the basis of the reviews on two respects: titanium-based bioactive modification and bone tissue response to carbon materials, the research work would be focused on new preparation technologies, mechanism and bone response behaviors in vitro and in vivo of hydroxyapatite (HAp) coating deposited on C/C composite, the main contents were as followings.Due to the super critical effect of the hydrothermal reaction, a novel method–hydrothermal electrodeposition for preparing HAp coating on C/C composites was put forward. The HAp coatings were successfully prepared on C/C composites by this method. The influences of [Ca2+] concentrations, Ca/P in molar ratio, pH value, hydrothermal temperature, deposition time, current density, deposition voltage on the microstructures and morphologies of HAp coatings were investigated; and the effect of ethanol to the coating adhesion strength was also particularly investigated.The as-prepared HAp coatings were characterised by X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses. The coating deposition amount was measured, and the adhesion strength between the coating and the substrate was surveyed by universal testing machine.The results show that the optimal values of [Ca2+] concentrations, Ca/P in molar ratio and pH should be 0.02 mol/L, 1.67, and 4.8, respectively. The HAp coatings on C/C composites can be preparedat 100~140℃, and hydrothermal temperature has a big influence on the coatings phase composition, microstructure. Density and homogenous of the prepared HAp coatings are obviously improved with the increase of hydrothermal temperature. The adhesion strength between the coating and the substrate also has some extent improvement. In addition, the peak intensity of HAp along (210) and (211) directions increase with the increase of hydrothermal temperature, indicating the over growth of HAp crystallites along (210) and (211) directions. With the increase of deposition time, density and surface homogenous of the prepared HAp coatings are obviously improved. The influence of current density on the microstructure and morphology of hydroxyapatite coatings was also investigated. The crystallization, density and homogenous of the coatings are improved with the increase of current density, and HAp crystallites are found growth along (211) directions in some extent. In addition, the HAp deposition rate increases linearly with the ncrease of current density. With the increases of deposition voltage, density, homogeneity, adhesion and deposition rate of the prepared HAp coatings are all markedly improved; and HAp crystallites are found growth along (211) directions in some extent.To enhance the as-prepared coatings property, especially the adhesion strength, the ethanol was added into the solution. The ethanol content in the deposition solution has a big influence on the coatings microstructures and adhesion property with the substrate though has little effects on the coatings crystallization. With the increase of ethanol content from 0vol% to 20vol%, the density and adhesion property of the prepared HAp coatings are obviously improved.In order to comprehend the essence of the formation of HAp coating on carbon/carbon composite by hydrothermal electrodeposition, a simplified deposition model was put forward. In this model, the deposition procedure of HAp coating consisted of two steps: the first was the movement of ions containing P and Ca elements towards the C/C cathode by means of diffusion, and the second was the HAp coating growth on the C/C surface. The relevant mathematical model and the experiments to identify the physical and mathematical models were given. It was confirmed that the models were reasonable and the procedure of HAp coating formation by hydrothermal electrodeposition was mainly controlled by ion diffusion in the electrolyte. In addition, kinetics of HAp deposition on C/C composite were studied, the deposition kinetics of HAp coatings indicates that deposition amount and deposition rate increases with the increase of hydrothermal temperature; and the corresponding deposition activation energy of HAp coating by the hydrothermal electrodeposition process is calculated to be 25.8 kJ/mol.
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