高稳定性金红石型TiO_(2)-SiO_(2)载体的制备及表征

Preparation and characterization of thermally stable rutile TiO_(2)-SiO_(2) supports

采用均匀沉淀法制备金红石TiO_(2)纳米颗粒,再通过溶胶-凝胶法制备一系列不同TiO_(2)含量的金红石型TiO_(2)-SiO_(2)纳米复合物载体,利用比表面积及孔径分析仪、XRD、SEM、FT-IR、UV-vis DRS等对载体结构进行表征,考察TiO_(2)-SiO_(2)载体的高温稳定性。结果表明,TiO_(2)-SiO_(2)载体具有较大的比表面积和典型的SiO_(2)凝胶孔结构,其中的TiO_(2)晶型和晶粒尺寸与纯TiO_(2)相同。高温焙烧后,与纯TiO_(2)发生严重烧结相比,TiO_(2)-SiO_(2)载体表现出优异的高温稳定性,复合材料中的SiO_(2)发生轻微烧结,比表面积和孔容基本不变,其中的TiO_(2)仍保持高分散性,晶粒尺寸不变。TiO_(2)-SiO_(2)载体中未生成Ti-O-Si化学键,而且复合结构对金红石TiO_(2)的能带结构影响较小,TiO_(2)和SiO_(2)只是纳米尺度上的混合,所以SiO_(2)的空间结构是提高TiO_(2)颗粒高温稳定性的主要原因。

Rutile TiO_(2) nanoparticles were prepared by uniform precipitation method,and then a series of rutile TiO_(2)-SiO_(2) nanocomposite supports with different TiO_(2) content were prepared by sol-gel method.The structure of TiO_(2)-SiO_(2) supports were characterized by specific surface area and pore size analyzer,XRD,SEM,FT-IR,UV-vis DRS,etc..The high temperature stability of the TiO_(2)-SiO_(2) supports was further investigated.The results show that the TiO_(2)-SiO_(2) supports have a typical SiO_(2) gel pore structure,and uncalcined TiO_(2)-SiO_(2) supports have the same crystalline phase and crystallite size as TiO_(2) sample.After calcination of TiO_(2)-SiO_(2) supports at high temperature,the SiO_(2) in composites is slightly sintered,and the specific surface area and pore volume are reduced.Meanwhile,the TiO_(2) in the composites maintains high dispersibility and keeps the crystallite size unchanged.Compared with the severe sintering of pure TiO_(2) at high temperature,the TiO_(2)-SiO_(2) supports exhibit excellent high-temperature stability.By further analysis,we found that TiO_(2) and SiO_(2) in the TiO_(2)-SiO_(2) supports were mixed mechanically on the nanometer scale rather than the formation of Ti-O-Si chemical bonds.In addition,the composite structure had minor effect on the electronic structure of TiO_(2).As a result,the high temperature stability of TiO_(2) particles in TiO_(2)-SiO_(2) supports is mainly due to the steric hindrance of the SiO_(2) substrate.