Novel sol-gel process depositing α-Al2O3 for the improvement of graphite oxidation-resistance

Anhydrous Al2O3 sol was prepared from aluminum isopropoxide as the raw material and diethylene glycol monoethyl ether as the solvent. Peptization of the raw material in the organic solvent was accomplished using acetic acid, which produced a clear, viscous, and stable sol. The spinnable sol, prepared within 30 min, has remained stable for over a year, and crystallizes in the alpha -Al2O3 structure at 950 degreesC via a single transition phase, gamma -Al2O3. The deposited films synthesized using a modified dip-coating process, were uniform and crack-free, and provided an excellent oxidation resistance for graphite pre-coated with a silicon oxide layer. (C) 2001 Elsevier Science B.V. All rights reserved.