TiO_2-ZrO_2聚合溶胶形成过程的小角X射线散射研究

Study on formation of polymeric TiO_2-ZrO_2 sols by small angle X-ray scattering

由金属醇盐(M(OR)_4)水解制备溶胶的方法已广泛应用于溶胶-凝胶法制备纳米孔无机膜。通过控制异丙醇钛[Ti(i-OC_3H_7)_4]和正丙醇锆[Zr(n-OC_3H_7)_4]的混合物在异丙醇(i-C3H7OH)中水解制备聚合型TiO_2-ZrO_2溶胶,利用小角X射线散射方法(SAXS)研究了初始反应混合物Ti(i-OC_3H_7)_4:Zr(n-OC_3H_7)_4:H2O:i-C_3H_7OH=0.9:0.1:m:30(摩尔比,m=1.8,2.0,2.2)形成TiO_2-ZrO_2溶胶的过程,探讨了水与醇盐摩尔比H_2O/M(OR)_4(M=Ti+Zr)、反应温度和正丙醇锆对TiO_2-ZrO_2溶胶形成的影响。研究结果表明,H_2O/M(OR)_4=1.8时,只有少量胶粒形成;H_2O/M(OR)_4=2.0~2.2时,TiO_2-ZrO_2溶胶中胶粒具有质量分形结构,分形维数1.2≤Dm<1.4;随着H_2O/M(OR)_4增加,胶粒的形成时间缩短,胶粒大小和分形维数均增大,溶胶的稳定性显著下降。升高反应温度有利于胶粒形成。[Ti(i-OC_3H_7)_4+Zr(n-OC_3H_7)_4]混合物比Ti(i-OC_3H_7)_4水解快,H_2O/M(OR)_4相同时,TiO_2-ZrO_2溶胶比TiO_2溶胶稳定性差。

Metal oxide sols can be prepared from metal alkoxides M(OR)4 by hydrolyzation,which has been widely used in synthesis of nano-porous ceramic membranes by sol-gel method.Polymeric TiO2-ZrO2 sols were prepared by controlled hydrolyzation of the mixture of titanium isopropoxide and zirconium n-propoxide in isopropanol.The formation of TiO2-ZrO2 sols from the initial reactant mixtures with a molar ratio of Ti(i-OC3H7)4:Zr(n-OC3H7)4:H2O:i-C3H7OH=0.9:0.1:m:30(m=1.8,2.0,2.2)was investigated by small angle X-ray scattering(SAXS).The effects of the molar ratio of water to metal alkoxides H2O/M(OR)4(M=Ti+Zr)in the initial reactant mixture,reaction temperature and Zr(n-OC3H7)4 on formation of TiO2-ZrO2 sols were discussed.When the molar ratio of H2O/M(OR)4=1.8,a few colloidal particles form.When the molar ratio of H2O/M(OR)4 is in the range of 2.0-2.2,the colloidal particles in TiO2-ZrO2 sols have a mass fractal structure with a fractal dimension of 1.2≤Dm<1.4.As the molar ratio of H2O/M(OR)4 increases from 2.0 to 2.2,the duration of colloidal particle formation becomes shorter,the size and fractal dimension of colloidal particles increase,and the stability of TiO2-ZrO2 sol decreases.Furthermore,the mixture of[Ti(i-OC3H7)4+Zr(n-OC3H7)4]hydrolyzes faster than Ti(i-OC3H7)4.TiO2-ZrO2 sol has lower stability than TiO2 sol from the initial reactant mixtures with the same molar ratio of H2O/M(OR)4.