Easy conversion process of titanium surface covered with passive film into functional surface
Easy conversion process of titanium surface covered with passive film into functional surface
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DOI：
10.1111/ijac.13309
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发表时间：
2019-09
影响因子：
2.1
通讯作者：
T. Ishikawa;Keiko Tsujikura;Masashi Deguchi;Akinobu Aoki
中科院分区：
文献类型：
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作者：
T. Ishikawa;Keiko Tsujikura;Masashi Deguchi;Akinobu Aoki
钛金属的表面功能化是非常感兴趣的，特别是因为表面钝化膜转化为目标功能膜可以广泛用于生物和环境应用。然而，由于表面钝化膜非常稳定，因此功能化（例如转化为光催化TiO 2）使用相对复杂的工艺进行，例如水热反应和阳极氧化。这是因为钛金属的直接氧化在整个温度范围内仅导致八面体-金红石-TiO 2的热力学形成，而使用前体的化学合成可以在600°C或更低的温度下容易地产生四面体-金红石-TiO 2。在我们的工艺的第一步中，用还原剂处理钛以产生表面氢化钛层。之后，将经过处理的钛表面覆盖上氢化钛，浸入二氧化硅水溶液中，然后在空气中于900°C（特定温度）下煅烧，有效地生成表面TiO 2层。这是因为被覆盖的四面体-二氧化硅稳定了形成的晶体结构。通过在水中淬火可以很容易地去除覆盖的二氧化硅，从而露出由TiO 2组成的光催化表面层。
Surface functionalization of titanium metal is of great interest, especially as the conversion of the surface passive film into objective functional film can be widely used in bio‐ and environmental applications. However, since the surface passive film is very stable, the functionalization (such as conversion into photocatalytic anatase‐TiO2) has been performed using relatively complicated processes, for example, hydrothermal reaction and anodic oxidation. This is because direct oxidation of titanium metal only leads to thermodynamic formation of octahedral‐rutile‐TiO2in the entire temperature region, while chemical synthesis using precursors can easily produce tetrahedral‐anatase‐TiO2at 600°C or less. Here, we report a simple process for the direct formation of photocatalytic anatase‐TiO2on titanium by simple oxidation. In the first step in our process, titanium is treated with a reducing agent to create a surface titaniumhydride layer. After that, the treated titanium covered with titaniumhydride is immerged in aqueous silica; subsequent calcination at 900°C (specific temperature) in air effectively generates the surface anatase‐TiO2layer. This is because the covered tetrahedral‐silica stabilizes the anatase structure that is formed. The covered silica is easily removed by quenching in water to reveal the photocatalytic surface layer composed of anatase‐TiO2.