由于电解液成分、氧化条件和所制备纳米管尺寸等因素的影响,TiO2纳米管阵列在阳极氧化过程中容易形成纳米草结构,而利用两步阳极氧化法可制备出表面整洁的TiO2纳米环/纳米管分层结构.实验通过控制氧化时间得到了不同生长阶段的TiO2纳米环/纳米管分层结构,并对其生长机理及吸光特性展开研究.结果表明,在第二步阳极氧化过程中,钛箔表面的周期性六边形纳米洞结构可以使纳米管的生长过程局限于每个纳米洞内部,从而形成TiO2纳米环/纳米管分层结构.同时,存在的纳米环可以为其内部的纳米管提供支撑作用,防止纳米草结构的形成.TiO2纳米环/纳米管分层结构的吸收光谱在可见光区域呈现震荡形态,这是纳米环顶部反射的光与钛基底反射的光相互干涉导致的.根据震荡峰形状与样品厚度的关系,可以估算出入射光在TiO2纳米环/纳米管分层结构中的最大穿透深度为2μm左右.%On the top of TiO2 nanotube arrays, nanograss structure may be generated due to electrolyte composition, the oxidizing condition and the size of nanotube in anodic oxidation process. TiO2 nanoring/nanotube hierarchical structure with smooth surface was fabricated by two-step anodic oxidation. Growth mechanism and optical absorp-tion properties of the resulting TiO2 nanoring/nanotube hierarchical structure were investigated by controlling oxi-dation time of the anodic oxidation. The results show that the growth of nanotubes is limited by regular hexagonal nanocaves on the surface of Ti substrate during the second step of anodization resulting in formation of TiO2 nanoring/nanotube hierarchical structure. Meanwhile, the nanorings provide the support of their internal nanotubes to avoid formation of nanograss structure. Absorption spectrum of TiO2 nanoring/nanotube hierarchical structure exhibits oscillating peaks in visible light region, due to the interference between lights reflected from the top of nanorings and the bottom of Ti substrate. Based on the relationship between oscillation peaks shape and film thickness, the maximum optical penetration depth of TiO2 nanoring/nanotube hierarchical structure is estimated to be ~2μm.
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