盐酸后处理对水热合成纳米钛酸盐形貌及光限幅效应的影响

采用碱性水热合成法制备纳米钛酸盐, 研究盐酸后处理对纳米钛酸盐-二氧化钛形貌及光限幅效应的影响. 采用X射线衍射分析仪、透射电子显微镜和扫描电子显微镜对样品的晶型转变及形貌演变进行表征, 通过紫外-可见光谱与开孔Z扫描激光测试技术, 研究样品的线性光学与非线性光学效应. 结果表明, 当酸处理浓度介于0.10-0.55 mol·L^-1范围时, 水热产物由钛酸盐转变为钛酸盐/二氧化钛混合物; 当酸处理浓度高于0.78mol·L^-1时, 钛酸盐近乎完全转变为金红石型二氧化钛. 在酸处理过程中, 纳米钛酸盐晶型转变速率与盐酸的浓度直接相关. 随着盐酸浓度的增加, 钛酸盐体系中逐步分离出游离的TiO₆八面体, 进而发生TiO₆八面体重组, 使水热产物由钛酸盐纳米管转变成二氧化钛纳米片和纳米颗粒. 当盐酸浓度为0.55 mol·L^-1时, 样品表现出最强的光限幅效应.

Effect of HCl Post-Treatment on Morphology of Hydrothermally Prepared Titanate Nanomaterials with Optical Limiting Properties

The effect of post-treatment HCl concentration on titanate-titania transformation was investigated. Titanate was prepared by the alkaline hydrothermal treatment of TiO₂, and then transformed to titania/titanate upon subsequent washing with 0.10-0.55 mol·L^-1 HCl. The titanate almost completely transformed to rutile when treated with HCl concentrations>0.78 mol·L^-1. Accompanying this phase transformation, the morphology of the sample changed from nanotubes to nanosheets and nanoparticles. This was related to the rate of phase transformation, which depended on the HCl concentration. Titanate became resolved into detached TiO₆ octahedra during HCl treatment, and titanate-titania transformation occurred via rearrangement of the TiO₆ octahedra. The phase transformation and morphological evolution were studied by X- ray diffraction, and transmission and scanning electron microscopies. The linear and nonlinear optical properties of the products were investigated using ultraviolet-visible absorption spectroscopy and the open aperture Z-scan technique, respectively. The minimum transmittance at Z=0 and maximum optical limiting effect were obtained when the HCl concentration was 0.55 mol·L^-1. Different nonlinear optical effects were exhibited by different morphologies.