PREPARATION OF TRANSLUCENT AND POLYCRYSTA LLINE TIO2 MONOLITH FROM METAL ALKOXIDE SOLUTION

Translucent and polycrystalline TiO2 monolith was prepared by heating a gel at 500-degrees-C. Clear TiO2 gel as a precursor was formed throu gh the controlled hydrolysis of a Ti-n-butoxide/cyclohexane solution i n a vessel covered with a plastic film having pin-holes. Upon heating, the amorphous gel crystallized to anatase at 200-degrees-C and conver ted into rutile at 600-degrees-C. In the temperature range from room t emperature to 600-degrees-C, a large volume change which may cause a c rack in the gel occurred with decomposition of residual organic materi als. Transparency of the gel was retained up to 550-degrees-C except i n the decomposition temperature range of organic materials (160-330-de grees-C). The TiO2 monolith obtained from a crak-free gel after heatin g to 500-degrees-C at a rate of 20-degrees-C/h was a translucent porou s material (apparent porosity: 42% and pore diameter : 7-30 nm) and co nsisted of fine anatase grains.