宽电压范围下阳极氧化制备TiO_2纳米管阵列及其热稳定性

Fabrication and Thermal Stability of TiO_2 Nanotube Arrays by Anodic Oxidation at Wide Range of Voltage

采用电化学阳极氧化技术，以含有NH4F和H2O的甘油溶液为电解液，在宽氧化电压范围（20～100V）下于纯钛表面制备了结构高度有序的TiO2纳米管阵列。利用扫描电子显微镜（SEM）考察了阳极氧化工艺（氧化电压、NH4F浓度、环境温度、水分含量等因素）及退火处理对纳米管形貌的影响；采用X射线衍射分析（XRD）表征了不同氧化电压和退火前后TiO2纳米管阵列的物相：并从电流-时间曲线出发简要地分析了纳米管阵列的形成机理。结果表明，纳米管的内外径和管长随氧化电压的增大而增大：NH4F浓度和环境温度对纳米管形貌有一定的影响；水分含量的多寡决定了能否在高电压下自组装形成纳米管阵列；TiO2纳米管阵列具有良好的热稳定性，管状形貌可以保持到700℃；直接制备的TiO2纳米管阵列均为无定型结构，经450℃退火处理后．无定型的TiO2纳米管转变为锐钛矿相，而600℃退火处理后，部分锐钛矿相转变为金红石相。

Anodic oxidation was adopted to prepare TiO2 nanotube arrays, which were prepared isobarically by the anodization of pure Ti in glycerol-based electrolyte containing NHnF and H2O at wide range of anodic voltage. The effect of anodic voltages, fluorine concentration, environmental temperature, the content of H2O and thermal annealing treatment on the morphology of TiO2 nanotube was studied. The titania nanotube arrays were characterized with SEM and XRD. Then, the formation mechanism of nanotube arrays based on the current-time curves was suggested. The results showed that inside and external diameter increased with the increase of voltage; fluorine concentration and environment temperature could effected the morphology of TiO2 nanotubes; the content of H2O effected the grown nanotube at high voltage. As-prepared TiO2 nanotube arrays has good thermal stability. Theirs tubular morphology can maintain higher than 700 ℃. After annealing at 450℃, the amorphous nanotubes changed into anatase type. After annealing at 600 ℃, part of anatase type changed into rutile,