为了在水相体系制备尺寸均一、形貌可控的锐钛矿型纳米TiO2颗粒,研究了钛源、溶液pH值、反应温度对TiO2晶体结构的影响.通过对样品进行XRD、TEM表征,发现形成锐钛矿型TiO2的最佳实验条件为:硫酸钛作为钛源、硝酸浓度为0.14 mol/L、反应温度60℃.硝酸浓度低、反应温度高有利于锐钛矿型TiO2的形成,反之则利于金红石的形成.通过在锐钛矿形成过程中施加外场作用,即紫外光和超声波,探究外场对其形貌的影响.结果表明:无外场作用时,生成的锐钛矿为纺锤状,尺寸为20~30 nm;施加紫外光4h之后,形状为近球状,尺寸约为10nm;施加超声波之后,形状仍为纺锤状,且尺寸无变化.造成TiO2形貌变化的主要原因是,在成核-长大过程中,紫外光可以抑制[001]晶向的生长速度,且时间越长,这种抑制作用越明显,当作用时间为4h时,[001]晶向的生长得到明显的抑制,使得纳米晶由纺锤状变为近似球形.因此,在TiO2的合成过程中可以通过施加外场作用对其形貌进行调控.
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