NOVEL THIN-FILMS OF TITANIUM-DIOXIDE PARTICLES SYNTHESIZED BY A SOL-GEL PROCESS

Novel thin films of ultrafine titanium dioxide particles dispersed in a matrix of hydroxypropylcellulose (HPC) polymer have been made on qua rtz and silicon substrate. The titanium dioxide particles were made by the hydrolysis and condensation of titanium tetraethoxide (TEOT) in s olutions of HPC in a mixture of ethanol and water. HPC controlled the particle size by adsorbing at the particle surface during the growth p rocess and generating repulsive steric forces. The TiO2/HPC composite films were transparent in the visible region and completely blocked ul traviolet radiation at 300 nm. These films were crack-free and uniform in composition and thickness. Transparent films of amorphous TiO2 wer e made by burning out the HPC at 500 degrees C. These films were highl y uniform and had no macroscopic cracks. X-ray diffraction revealed a transition to the anatase form upon sintering at 600 degrees C. A film sintered at 700 degrees C had a porosity of 38%. The crystalline film s remained transparent until they densified at 800 degrees C.