水热法制备TiO2纳米纤维的最佳工艺条件

OPTIMAL PROCESS CONDITIONS OF HYDROTHERMALLY SYNTHESIZED TiO_2 NANOFIBERS

以锐钛矿型TiO2粉体为前驱体,与KOH溶液在高压釜中进行水热反应,制备的样品分别经HCl溶液和蒸馏水超声洗涤至中性,合成了H2Ti3O7纳米纤维,采用透射电镜、扫描电镜,X射线衍射和X射线光电子能谱,对纳米纤维的微观形貌及晶型结构进行了表征,探讨反应温度、时间和碱液浓度等对产物的化学成分和形貌的影响。结果表明:水热反应最佳条件为:KOH溶液浓度为10～12mol/L,反应温度为150℃,时间为72h。随着反应时间的延长,纳米H2Ti3O7纤维的产率和长度不断增加,72h后,前驱体完全转变为H2Ti3O7纤维,长度达到微米级,长径比为50～60。该产物经400℃煅烧后,主要衍射峰属锐钛矿相TiO2,且结晶完好,说明H2Ti3O7纳米纤维已转变为TiO2纳米纤维。

H2Ti3O7 nanofibers were successfully synthesized through two steps. First, a simple hydrothermal reaction was initiated between anatase powders and potassium hydroxide solution in a high-pressure autoclave. Then the products obtained were washed with dilute hydrochloric acid with a concentration of 0.5 mol/L and distilled water until their pH value reached about 7.0. The struc- ture and microcosmic morphology of the nanofibers were investigated by transmission electron microscopy, scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy, and the effects of the concentration of alkaline solution, reaction temperature and time on the structure and microcosmic morphology of the samples were also studied. The results show that the optimal reaction conditions are a concentration of alkaline solution of 10-12 mol/L and a reaction temperature and time of 150℃ and 72 h respectively. With the extension of the reaction time, the yield and length of the H2Ti3O7 nanofibers increase. After 72 h, the precursors become H2Ti3O7 nanofibers with micron-sized lengths and aspect ratios of 50-60. The nanofibers of H2Ti3O7 are transformed into TiO2 nanofibers after calcination at 400℃.