Study on Heat Treatment Process of Nano Titanium Dioxide

Titanium tetrachloride was used as raw material to prepare hydrated titanium dioxide by alkali neutralization method,and then anatase nano-TiO₂ and rutile nano-TiO₂ were prepared by heat treatment at different temperatures.The effects of heat treatment on the crystal structure,specific surface area,pore volume and UV absorption spectrum of the sample were analyzed by Raman spectroscopy,XRD and UV-visible spectroscopy,respectively.The experimental results show that the unheated samples have oxygen vacancy defects and have large lattice strain.With increase of the heat treatment temperature,the grain size of the samples grows from 6 nm to 70 nm with the specific surface area decreased from 186 m²·g^-1 to 5.6 m²·g^-1 and the total pore volume decreased from 0.085 cm³·g^-1 to 0.001 3 cm³·g^-1,respectively.Meanwhile,the crystal structure gradually transforms from amorphous phase into anatase and rutile phases accompanying gradual decrease of the lattice strain.The samples are composed of anatase phase with heat treatment temperature below 600 ℃,mixture of anatase and rutile phase at 600～650 ℃,and rutile phase with heat treatment temperature higher than 800 ℃.At 680～750 ℃,sodium hexatitanate is formed.