Preparation of Bioactive Metals by Chemical Treatments

当纯钛,Ti-6Al-4V Ti-6Al-2Nb-Ta和Ta-15Mo-5Zr-3Al合金、SUS316L(不锈钢)和Co-Cr-Mo合金受到氢氧化钠水溶液和热处理600゚C与离子浓度浸泡在模拟体液几乎等于那些人类血浆(SBF),钛及其合金组成了一个密集的和统一的鱼骨磷灰石layr表面在短时间内,而SUS316L和Co-Cr-Mo合金从来没有。碱处理后钛及其合金上形成磷灰石的原因解释如下：在SBF中Ti及其合金表面形成的水合二氧化钛凝胶可以诱导磷灰石成核，而从表面层释放到SBF中的钠离子可以通过增加SBF相对于磷灰石的过饱和程度来增强磷灰石的成核。在不热处理的情况下，随着NaOH溶液浓度的增加，SBF中纯Ti的磷灰石形成诱导期缩短。假设随着NaOH浓度的增加，在凝胶层中掺入并释放到SBF中的钠离子数量增加，导致周围流体的过饱和程度迅速增加，可以解释这一结果。而未经热处理的表面凝胶层容易脱落。当naoh处理的Ti在600℃左右热处理时，机械弱的凝胶层转变为机械稳定的凝胶层，而不失去其高磷灰石形成能力。钽和锆金属也通过类似的碱液处理在短时间内在其表面形成磷灰石。综上所述，化学处理是一种非常简单有效的诱导各种金属材料生物活性的方法。

When pure Ti, Ti-6Al-4V,Ti-6Al-2Nb-Ta and Ta-15Mo-5Zr-3Al alloys, SUS316L (stainless) and Co-Cr-Mo alloy which were subjected to NaOH aqueous and heat treatments at 600ﾟC were soaked in simulated body fluid with ion concentrations nearly equal to those of human blood plasma (SBF), the Ti and its alloys formed a dense and uniform bonelike apatite layr on their surfaces in a short period, whereas the SUS316L and Co-Cr-Mo alloys never did. The reason for the apatite formation on the Ti and its alloys by the alkali treatment is interpreted as follows. The hydrated titania gel formed on the surfaces of the Ti and its alloys in SBF might induce the apatite nucleation and the sodium ions released from the surface layr into the SBF might enhance the apatite nucleation by increasing the degree of supersaturation of the SBF with respect to the apatite. The induction period for the apatite formation on the pure Ti in SBF decreased with increasing concentration of NaOH solution in the case without heat treatment. This result is explained by assuming that as NaOH concentration increases, the amount of sodium ions which were incorporated in the gel layr and then released into SBF increased, giving rise to a rapid increase in the degree of supersaturation of the surrounding fluid. The surface gel layr without heat treatment was, however, liable to be peeled off. When the NaOH-treated Ti was heat treated around 600ﾟC,the mechanically weak gel layr was converted to the mechanicallystable one without losing its high apatite-forming ability. Tantalum and zirconium metals also formed the apatite on their surfaces by the similar alkaline solution treatment in a short period. In conclusion, the present chemical treatment is a quite simple and effective method for inducing the bioactivity of various metallic materials.