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

摘要： 在Al₂O₃-C复合材料中添加低熔点相,对其性能与结构改善具有重要意义。以棕刚玉、氧化铝粉、鳞片石墨为主要原料,酚醛树脂为结合剂,加入不同量的无水硼砂(加入质量分数分别为 0、1%、2%、3%和4%),采用高速逆流造粒机混合,得到的混合料在冷等静压机内成型,经250 ℃干燥、1 000 ℃埋碳烧成,制备了Al₂O₃-C复合材料,研究了无水硼砂加入量对Al₂O₃-C复合材料性能及显微结构的影响。结果表明:随着无水硼砂加入量的增多,试样显气孔率显著下降,体积密度有所增加,但增加幅度较小;添加了无水硼砂的试样,细粉颗粒边界变得模糊,细粉之间孔隙部分被熔化后的无水硼砂所填充,从而使得显气孔率显著降低,常温抗折明强度显提升,抗氧化性能显著改善;与未添加无水硼砂的试样相比,加入4%(w)无水硼砂试样的显气孔率下降幅度约为25%,常温抗折强度的升高幅度约为5.6倍,氧化层面积下降约为60%。

关键词: 无水硼砂, Al₂O₃-C复合材料, 性能, 显微结构