关键词: 无水硼砂, Al₂O₃-C复合材料, 性能, 显微结构

Abstract: Adding low-melting point phases to Al₂O₃-C composites is of great significance for improving their properties and microstructure.Using brown corundum,alumina powder,and flake graphite as the main raw materials,phenolic resin as the binder,and adding different amounts (0,1%,2%,3%,4%,by mass) of anhydrous borax,the mixture was prepared by mixing with a high-speed counter-current granulator.The resulting mixture was shaped in a cold isostatic press,dried at 250 ℃,and then fired at 1 000 ℃ under a carbon-embedded atmosphere to prepare Al₂O₃-C composite samples.The effects of the anhydrous borax addition on the properties and microstructure of the Al₂O₃-C composites were investigated.The results show that:with the anhydrous borax addition increasing,the apparent porosity of the samples decreases significantly,while the bulk density increases slightly.For the samples containing anhydrous borax,the boundaries between fine powder particles become blurred,and part of the pores between fine powders are filled by the melted anhydrous borax,leading to the significant reduction in porosity,a notable enhancement of cold modulus of rupture,and a marked improvement in oxidation resistance.Compared with the sample without anhydrous borax,the sample with 4% anhydrous borax exhibits a decrease in apparent porosity by approximately 25%,an increase in cold modulus of rupture by about 5.6 times,and a reduction in the oxidized layer area by about 60%.

Key words: anhydrous borax, Al₂O₃-C composites, properties, microstructure