水热法制备过程中TiO2纳米纤维成形机理研究

采用水热法制备出φ20～30nm, 长度达微米级的TiO2纳米纤维, 以XRD、TEM、IR等手段对不同工艺条件下获得的产物晶型结构、微观形貌以及化学组成进行了表征, 对TiO₂纳米纤维成形机理进行探讨, 并就洗涤过程中pH值对纤维结构的影响进行分析. 结果表明, TiO₂纳米纤维的形成机理可能是锐钛矿型TiO₂纳米颗粒在强碱作用下生成K₂Ti₆O₁₃颗粒, 小颗粒沿一定晶轴生长, 遵循溶解-生长机理, 逐渐长成纳米纤维. 清洗溶液的pH值对产物的成分和结构有较大影响, 通过控制清洗溶液的pH值和热处理温度, 可以获得组成分别为K₂Ti₆O₁₃、H₂Ti₃O₇和TiO₂的纳米纤维. 在pH=7、80℃烘干条件下得到的主要是H₂Ti₃O₇纳米纤维, 400℃煅烧后转变为TiO₂纳米纤维.

Forming Mechanism of TiO2 Nanofibres Prepared by Hydrothermal Method

The TiO₂ nanofibres with the diameter of φ20-30nm and the length of micron-dimension were successfully synthesized by hydrothermal method. Their crystalline structure, morphology and chemical composition were characterized by the transmission electron microscope (TEM), X-ray diffraction patterns (XRD), infrared spectrum (IR), etc. The forming mechanism of the TiO₂ nanofibres and the effects of pH value in the process of washing on the nanofibres structure were investigated and analyzed, respectively. The results indicate that the forming mechanism of the TiO₂ nanofibres can be described as following: K₂Ti₆O₁₃ nanoparticles are initially formed in alkaline solution using anatase nanoparticles as raw materials, and then gradually grown to nanofibres along a certain crystalline axis obeyed the dissolution-growth mechanism. The pH value of washing solution has a significant influence on the structure and composition of the products. The nanofibres of K₂Ti₆O₁₃, H₂Ti₃O₇ and TiO₂ can be obtained by the controlling of the pH value of washing solutions and heat-treatment temperature. The products, washed in solution with pH=7 and dried at 80℃, form the nanofibres of H₂Ti₃O₇, which is subsequently calcined to form TiO₂ nanofibres at 400℃.