| With the development of modern medicine, tissue replacement and reconstruction has become the focus of attention, its key technology is the development of biomimetic materials. Ti alloy, hydroxyapatite(HA) and polylactide(PLA), etc are usual biomaterials. This paper developed biological piezoelectric ceramic composite coating on Ti alloy substrate by plasma spraying. Composite coating with hydroxyapatite(HA) and barium titanate(BaTi O3) has both piezoelectric properties and biological activity. Plasma spraying HA coating on Ti matrix has been widely studied, research shows that the coatings have certain biological and mechanical properties, but the biological activity is not obvious. In vivo the coating is easy to be peeled off. In order to further improve the performance of the coating, the authors added barium titanate piezoelectric ceramics on the basis of previous, hoped that the coating has certain piezoelectric properties. By the use of stress and electricity of bone, to improve biological activity of coating, by controlling the process parameters of plasma spraying, to improve the adhesion strength of coating.In order to determine the optimum process parameters, this paper designed reasonable process parameters of spraying HA by the orthogonal test, selected spraying distance, spraying voltage and current as variable factors, the adhesion strength as evaluation index, spraying distance at 80-120 mm, spray voltage at 60-70 V, spraying current at 500-700 A, and ultimately determine that the appropriate process parameters is spraying distance 80 mm, spray voltage 65 V, spray current 600 A, then the adhesion strength of Ti alloy and hydroxyapatite achieved the maximum value of 25 N. At 80-120 mm, along with the increase of spraying distance, the adhesion strength decreases; at 60-70 V, with the increase of spray voltage, the adhesion strength increases first and then decreases; at 500-700 A, with increasing of spraying current, the adhesion strength increases first and then decreases. In order to further improve the wettability of ceramic coating and the metal substrate interface, by adding titanium powder in hydroxyapatite, prepared Ti/HA coating with the optimal process parameters. Finally by adding barium titanate ceramic powder, prepared Ti/HA/Ba TiO3 coating with the same process parameters.The morphology and composition of the coating were characterized by SEM/EDS, the adhesion strength of coating and substrate was tested by scratch test, the porosity of coating was tested by Image J software. Finally the cell culture test of Ti, Ti/HA, Ti/HA/BaTi O3 was done, the cytotoxicity was evaluated by using the CCK-8 method, the adhesion of cell was observed under electron microscope. The SEM of coating shows that in the 80 mm, 65 V, 600 A, prepared three kinds of coatings have a microstructure with the laminated shape, melting of the coating is good, have the droplet spreading morphology. Porosity test results show that the coating has a microporous structure, porosity is about 2.6%-8.6%. Scratch test results show that, HA, Ti/HA, Ti/HA/BaTi O3 three kinds of coatings prepared under optimal process parameters have higher adhesion strength. is respectively 25 N, 35 N, 27 N. Spalling failure occurs at the interface of coating and substrate. The results of cytotoxicity test show that, The cytotoxicity grade of Ti, Ti/HA is 1, the level of Ti/HA/BaTiO3 tends to 0, can be used as a biomaterial. By observing SEM morphology of cells, cells adhere to the surface of coating, spread many long pseudopodia. By comparing cell proliferation rate, the cell proliferation rate of Ti/HA/BaTiO3 coating is higher than other two kinds of materials, this also shows that the addition of barium titanate improves the bioactivity of the coatings. The above results show that, Ti/HA/BaTiO3 composite coating with certain adhesive strength can be prepared by plasma spraying, By using the piezoelectric effect of piezoelectric ceramic, can improve induced activity of HA, and provides a reference for the further development of bioactive materials with high performance. |
