COATING OF CARBON MATERIALS WITH ZRO2 BY SOL-GEL METHOD

The optimum conditons for ZrO2 coating on carbon materials by using a 2-propanol solution of zirconium tetra butoxide(ZrBu) were studied. In order to avoid the formation of ZrO2 fine particles during the hydrolysis of ZrBu, the additon of diethylene glycol (DEG) into the solution was essential. A homogeneous film of ZrO2 gel without cracks was obtained by using the solution containing ZrBu of 0.05 M and with DEG/ZrBu ratio of 2. In the cases what the DEG/ZrBu ratio was above and below 2, the gel film obtained showed faults, such as cracking or peeling. From the results by weight and viscosity changes of the sol (solution) due to gelation (Fig. 4) and thermal analysis of gel film (Fig. 5), the gelation in air for 24 hours and stepwise heating at 90 and 200-degrees-C for 1 hour, respectively, were determined. Scanning electron microscopic observations of the cross section and the surface of ZrO2 coated carbon (Figs. 7 approximately 9) showed that the ZrO2 film thus prepared had a high homogeneity and adhered excellently to carbon substrate.