Abstract:

The Al₂O₃-C materials with Mg powder addition were prepared using tabular corundum,α-Al₂O₃ micropowder,flake graphite and Mg powder as the starting materials,and phenolic resin as the binder.Effects of Mg powder on properties of unfired Al₂O₃-C materials carbon embedded treated at different temperatures (600-1 400 ℃) were investigated.The results show that metal Mg reacts with O₂,CO or CO₂ to form MgO ceramic phases at 600 ℃,avoiding the oxidation of phenolic resin and the in-situ formed MgO ceramic phases form a tight binding to enhance the medium and low temperature strength of unburned Al₂O₃-C materials;at 1 000-1 400 ℃,MgO reacts with Al₂O₃ to form MgAl₂O₄,and the amount and the crystal size of MgAl₂O₄ increase with the temperature rising,strengthening the material;however,the strength of the specimen greatly decreases after firing at 1 400 ℃ due to the micro-cracks resulting from the expansion caused by MgAl₂O₄ formation.

Key words: alumina-carbon material, magnesium, magnesia, magnesium aluminate, strength

摘要：

以板状刚玉、α-Al₂O₃微粉、鳞片石墨和Mg粉为原料,以酚醛树脂为结合剂,制备了添加Mg粉的Al₂O₃-C材料,研究了不同温度埋炭处理后(600~1 400 ℃)Mg粉对不烧Al₂O₃-C材料性能的影响。结果表明:金属Mg活性高,Mg在600 ℃即可与O₂、CO或CO₂反应生成MgO陶瓷相,保护树脂碳不被氧化,且原位形成的MgO陶瓷相形成了紧密结合,产生强化作用,使不烧Al₂O₃-C材料的中低温强度提高;在1 000~1400 ℃,MgO和Al₂O₃生成MgAl₂O₄,且MgAl₂O₄的晶粒尺寸和生成量随着温度的升高而增加,对材料有增强作用;但 1 400 ℃烧后试样的强度明显下降,这是由于生成MgAl₂O₄产生膨胀致使材料中产生了微裂纹。

关键词: Al₂O₃-C材料, Mg, MgO, MgAl₂O₄, 强度