包覆沉淀法制备氧化硅改性的纳米二氧化钛及其性质

Preparation and properties of silica-modified nano-titania by coating precipitation method

采用包覆沉淀法,以混晶纳米二氧化钛粉体为载体,硅酸钠为包覆剂,用硫酸调pH值,成功的在纳米二氧化钛表面包覆致密的二氧化硅膜。并用IR、XRD、EDS及TEM进行了表征,同时对包覆改性前后的纳米二氧化钛进行比表面积、光催化活性的测定。IR、EDS表明:该包覆方法可行,氧化硅以化学键合的方式沉积在纳米TiO2的表面,在包覆层和纳米TiO2颗粒之间的界面上形成了Ti—O—Si键。XRD证实氧化硅的添加提高了二氧化钛纳米颗粒的热稳定性能,有效地抑制纳米二氧化钛的晶型转化。TEM照片显示,包覆后的TiO2粒径减小,粒度分布均匀,表面光滑。比表面和光降解实验结果显示,改性后的TiO2具有高的比表面,而且随包SiO2含量的增大而减小。和未改性纳米TiO2相比,具有较高的光催化活性,且在煅烧温度为600℃时催化活性最好。

Titania nano-particles coated with silica were prepared by the coating precipitation method, which sodium silicate was used as the coating agent and sulfuric acid as the neutralization agent. The prepared samples were characterized by FT-IR, XRD, TEM and X-ray energy dispersive spectrum （EDS）. It was inferred that the Ti--O--Si bond was formed at the interface of the coating layer and TiO2 particles. The addition of silica in TiO2 particle could effectively decrease the formation of rutile phase. TEM images demonstrated that TiO2 coated with silica has smaller particle size, uniform size distribution and polished surface. The specific surface area experiment showed that the specific surface area of titania nano-particles coated with silica reduced with increasing of m（SiO2） ： m（TiO2）. When content of silica is 2.39%, the specific surface area become highest value. In comparison with pure TiO2 nanoparticles, the silica-modified TiO2 nanoparticles exhibited better photocatalytic activities, and the optimal activities were obtained as they were treated at the calcinations temperature of 600℃.