阳极氧化制备TiO_2纳米管阵列的生长特性

Growing characteristics of TiO_2 nanotube array prepared by anodization method

基于TiO_2纳米管薄膜的广泛应用前景,采用阳极氧化的方法制备高度规则排列的TiO_2纳米管阵列,研究外加电压、阳极氧化时间、电解液(NH_4F^+乙二醇)浓度、电解液体系对纳米管阵列生长特性的影响。结果表明:随着外加电压从10 V增大到30 V,纳米管的管径和管壁逐渐由22 nm和4.5 nm分别增至82 nm和10 nm,而纳米管密度由2240μm^(-2)降至200μm^(-2)。纳米管阵列出现的临界阳极氧化时间为5 min,且随着氧化时间延长,纳米管的长度随之增加,当氧化时间增至2 h时,纳米管长度增至4μm,此后,纳米管长度不再增长。在含F^-的有机电解液体系中可制备规则的纳米管阵列,当电解液(NH_4F+乙二醇)浓度增加到0.2 mol/L后,出现清晰的纳米管管状结构,这是由于F^-和乙二醇的存在对于TiO_2纳米管阵列的形成具有至关重要的作用,F^-与Ti^(4+)形成的[TiF_6]^(2-)能延缓钛箔阳极的氧化进程,促使钛箔表面形成微孔;而乙二醇则有助于提高电解液的黏度,降低F的扩散速率,保证TiO_2纳米管阵列的稳定生长。

Based on the wide promising application of TiO2 nanotube films, highly ordered TiO2 nanotube arrays were prepared by anodization method. The effects of applied voltages, anodization time, electrolyte （NH4F＋ethylene glycol） concentration, electrolyte system on the growing characteristics of TiO2 nanotube arrays were studied. The results show that the nanotube diameter and wall thickness increase from 22 nm and 4.5 nm to 82 nm and 10 rim, respectively, and the nanotube density decreases from 2240 to 200 um-2 as the applied voltage increasing from 10 V to 30 V. The critical oxidation time of appearance of nanotube array is 5 min. The length of nanotubes increases with the oxidation time, and when the oxidation time is 2 h, the length of nanotubes increases to 4 pin and no more longer. The clear nanotube interface appears when the electrolyte （NHgF＋ethylene glycol） concentration increases to 0.2 mol/L. The reason is that the existence of F-and ethylene glycol is very important for the formation of TiO2 nanotube. The formation of [TiF6]2- by the reaction of F- and Ti4＋ Can retard the oxidization process of Ti foil and help Ti foil produce micropores on its surface. The ethylene glycol is beneficial to increase the electrolyte viscosity and decrease the F- diffusion rate. Therefore, the uniform growth of TiO2 nanotube array can be guaranteed.