Study On Oxidation Resistance Of Graphite-silicon Carbide Crucible

In this thesis, on the basis of the comprehensive analysis to the importedgraphite-silicon carbide crucible sample, graphite-silicon carbide crucible sampleswere prepared, taking graphite, silicon carbide, clay and silicon powder as main rawmaterials. The effects of the composition, sintering temperature, forming method, andsurface coating on the oxidation resistance were investigated. The experimental resultsare as follows:(1) The sintering temperature of graphite-silicon carbide crucible sample has asignificant impact on the density. It was found that graphite-silicon carbide cruciblesample has a lower porosity and a higher density when the sintering temperature at1150℃.(2) The content of the silicon carbide has a great influence on the oxidationresistance of the graphite-silicon carbide crucible sample. With the increasing ofsilicon carbide, the porosity and weight loss rate of the sample decrease and theoxidation resistance increases. The porosity and weight loss decrease greatly when thecontent of silicon carbide is in the range of35%-50%. Moreover, the bulk density ofthe sample is the maximum, whereas the porosity and weight loss rate are theminimum when the content of silicon carbide increases to50%. At the meantime, theoxidation resistance of the sample is optimum.(3) Silicon powder can improve the oxidation resistance of graphite-siliconcarbide crucible. With the increasing of silicon powder, the porosity and weight lossrate of the sample decrease and the oxidation resistance increases. When the content ofsilicon powder increases to15%, the weight loss rate of the sample is the lowest andthe oxidation resistance is the optimum. (4) The effects of isostatic pressing and pressure molding on the oxidationresistance of sample were compared and analyzed. It was found that graphite-siliconcarbide crucible sample has a higher density and a lower weight loss rate when usingisostatic pressing method. The weight loss rate increases slowly with the increasing ofoxidation time, which indicates the oxidation resistance and service life can be increaseeffectively by using isostatic pressing method.(5) The composition and thickness of surface coating influence the oxidationresistance of crucible to some extent. The final results indicate that the surface coatingby adding silicon powder and B2O3are able to reduce the weight loss rate of thecrucible and thereby improve the oxidation resistance. When the coating compositionis the same, multilayer coating, comparing single layer coating, can further reduce theporosity and weight loss rate and then increase the oxidation resistance of sample.