The Properties Of The Carbon Materials Coated By Silicon Aluminum Oxide Coating Prepared By The Sol-gel Method

The Al2O3-SiO2 gel prepared by sol-gel method in this study which the the source material was isopropyl alcohol aluminum, aluminum nitrate and ethyl orthosilicate. The Al2O3-SiO2 gel became into the Al2O3-SiO2 coating on the surface of the diamonds and the carbon fibers through the heat treatment process which impacted on the thermal and mechanical properties of the carbon materials; and the study also showed the changes of the hardness, bending strength and grinding performance of the resin bond diamond grinding tool which was made by the diamonds with Al2O3-SiO2 coating. The experiment part was consisted by(1) the preparation process of the Al2O3-SiO2 gel;(2) the performance of the diamonds and the resin bond diamond grinding tool was impacted by the Al2O3-SiO2 coating;(3) the thermal performance of the carbon fibers impacted by the Al2O3-SiO2 coating.The pH of the gel system was controlled by the addition of the acetic acid through the preparation process of the Al2O3-SiO2 sol. It is showed that the solation time was the shortest about 8 hours when the pH≤3 which increased as the pH increases. The dry gel prepared by the drying process which cost about 12 hours in the incubator. The best heat treatment temperature of the dry gel was determined to be 450 ℃by the differential scanning calorimetry(DSC).The Al2O3-SiO2 coating was coated on the surface of the diamond by the dipping mixing method. It is showed that the thickness and integrity was affected by the stirring speed, and the best stirring speed was 400 rpm which could formed the compact coating on the surface of the diamonds; and the oxidation resistance, impact toughness and the single grain compressive strength of the diamonds with Al2O3-SiO2 coating were increased respectively 100℃, 11% and 100psi; the hardness and bending strength of the grinding tool which the diamonds with Al2O3-SiO2 coating was improved obviously and the grinding performance increased 12%.3Al2O3-2SiO2 gel prepared by the sol-gel method and the 3Al2O3-2SiO2 coating was obtained by the heat treatment process. It is showed that the 3Al2O3-2SiO2 coating had fewer defects when the concentration of the system was appropriate. the oxidation resistance of carbon fibers improved 40% under the condition of constant temperature and 200 ℃ under the condition of continuous heating because of the complete 3Al2O3-2SiO2 coating.