磷酸盐调控纳米TiO2微结构及其表面羟基密度

以冰乙酸作诱导剂,研究磷酸盐在溶胶-凝胶法合成纳米二氧化钛过程中对其微结构及其表面羟基密度的影响,并利用XRD、BET、EDS、SEM、FT-IR和TGA等方法对二氧化钛相变过程和表面结构变化进行表征.结果表明:合成过程中添加磷酸根可增加纳米二氧化钛的表面羟基密度,500℃、700℃煅烧6h,其表面羟基密度分别为10.74nm^-2、4.03nm^-2,而对照样在500℃煅烧条件下其表面羟基密度为4.95nm^-2;同时磷酸根的添加,有利于锐钛型晶相结构的热稳定性,锐钛型向金红石转变的相变温度达800℃.这可能是由于PO₄^3-与TiO₂晶相生长基元TiO₆]八面体易发生多齿螯合,不利于金红石相形成.

Phosphate regulate the microstructure and surface hydroxyl density of nano-titanium dioxide

Titanium dioxide was prepared by adding phosphate in the sol-gel process and acetic acid used as an inducer. The effect of phosphate on nano-titanium dioxide micro-structure and surface hydroxyl density were studied in this paper. The process of phase transition and surface structural change were investigated by powder X-ray diffraction(XRD),Brunauer–Emmett–Teller (BET),X-ray energy-dispersive (EDS),scanning electron microscope (SEM),fourier-transformed infrared (FT-IR) and thermogravimetric analysis (TGA). The results showed that the surface hydroxyl groups of nano-titanium dioxide were significantly increased with the adding amount of phosphate. The surface hydroxyl densities were 10.74nm^-2 and 4.03nm^-2 of the samples calcined at the temperature of 500℃ and 700℃,respectively. However,the control sample with none phosphate was 4.95 D_OH/nm² at 500℃. Moreover,the thermal stability of the phase transition was enhanced by adding phosphate in sol-gel process. Until the phase change temperature reached 800℃ did it have been begun to ransform anatase to rutile. The may be due to the bonding of PO₄^3- in these multidentate modes occupy one full face of TiO₆] octahedra and inhibit the growing of chain along the opposite edges and hence inhibit the formation of rutile.