다공성 표면에 HA 코팅된 TI-25Nb-xTa 합금의 표면특성 및 생체적합성

Abstract

In this study, we developed a non-toxic titanium alloy with low elastic modulus in order to improve biocompatibility, and the surface characteristics of HA-coated Ti-25Nb-xTa alloys by various coating method after pore formation was investigated by using various experimental techniques. The Ti–25Nb–xTa ternary alloys having Ta contents (x) of 0, 3, 7, and 15 wt% were fabricated by using pure Ti. The applied voltage and treatment time of PEO (plasma electrolytic oxidation) were 280 V and 3 min, respectively. Calcium acetate monohydrate (Ca(CH3COO)2·H2O) + calcium glycerophosphate (C3H7CaO6P) and 1M H3PO4 were used as the electrolytes in the PEO. Subsequently, HA was coated on PEO-treated surface in H3PO4 solution by RF sputtering. The surface and mechanical properties of the Ti–25Nb–xTa alloys were analyzed by optical microscopy, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, nanoindentation, atomic force microscopy, and wettability measurements. Also, biocompatibility was analyzed by wettability test, SBF formation, and cell culture test. The results were as follows : 1. In the Ti-25Nb-xTa alloy, as the Ta content increased, grain size increased, and martensite structure decreased. The α "phase peak of martensite structure decreased mainly with increasing Ta content. The equiaxed β-phase peak increased with Ta content. Vickers hardness and elastic modulus decreased with increasing Ta content. 2. As a result of PEO treatment with various electrolytes in Ti-25Nb-xTa alloy, the surface morphology showed porous surface and irregular pores. The pore area, pore size, and pore number on the PEO-treated surface in 1M H3PO4 solution decreased compared to PEO-treated surfaces in electrolyte containing Ca and P. From the XRD results, PEO-treated surface showed the peaks of anatase in both electrolytes. 3. HA-coated Ti-25Nb-xTa alloy surface by RF-sputtering after PEO treatment in 1M H3PO4 electrolyte showed the structure of anatase, rutile, and HA peaks on the surface. 4. As a result of the wettability measurement, the contact angle of PEO-treated Ti-25Nb-xTa alloy in 1M H3PO4 electrolyte showed relatively lower than those of PEO-treated Ti-25Nb-xTa alloy in electrolyte containing Ca and P ions and HA-coated Ti-25Nb-xTa alloy by sputtering, and decreased slightly with increasing Ta content. Surface roughness of PEO-treated Ti-25Nb-xTa alloy in 1M H3PO4 electrolyte was higher than those of others. 5. The formation of hydroxyapatite on the PEO-treated Ti-25Nb-xTa alloy surface was initially formed inside the pores and grew around the surface with time, and formed well on the HA-coated surface after PEO treatment in 1M H3PO4 electrolyte. 6. From the cell culture results, cell were well grown and distributed as Ta content. Cell growth and proliferation showed on the HA-coated Ti-25Nb-xTa alloy after PEO treatment in 1M H3PO4 electrolyte. In conclusion, the Ti-25Nb-xTa alloy developed in this study was found to be nontoxic and have a low modulus of elasticity compared to the conventional Ti metal. After PEO treatment, the large surface area was obtained by formed a micro pore in the surface. Therefore, the HA-coated surface is expected to improve biocompatibility and shorten the bone healing time of the implant surface and surrounding bone tissue.