氮气保护下镁砂对Al–刚玉体系物相的影响

Phases of Al–Al2O3 Materials by High Purity Magnesia in Nitrogen Atmosphere

以烧结刚玉、α-Al2O3微粉、金属铝粉、高纯镁砂[加入量分别为3%（质量分数）、6%、15%]为原料,酚醛树脂为结合剂,制备Al–MgO–Al2O3系复合材料。样品成型后经过200℃烘干后在1 300℃氮气气氛下烧结。结果表明：添加金属铝粉后样品常规物理性能显著改善。样品中的主晶相为α-Al2O3和Mg Al2O4,有金属铝残留。镁砂对金属铝–烧结刚玉耐火材料物相组成影响大,当镁砂加入量为3%时形成Al4O4C相,镁砂加入量为6%或15%时,新相为Al4C3,未检测到Al4O4C相,镁砂添加量为15%时能检测到方镁石相。镁砂加入量大于或等于6%时,α-Al2O3颗粒或细粉表面形成的镁铝尖晶石包裹刚玉结构,将α-Al2O3表面包覆,阻断Al4C3与α-Al2O3反应生成Al4O4C。最后建立了该体系中新相形成机理的反应模型。

AI-MgO-AI203 composite was prepared with sintering alumina, 6t-A12O3 powder, aluminum powder and high-purity magnesia （i.e., 3%, 6%, and 15% （in mass fraction）, respectively） and phenolic resin as a binder. The samples were tempered at 200℃ and sintered at 1 300 ℃ in nitrogen atmosphere. The results show that the physical properties of the sample after the addition of aluminum powder are improved. The main crystalline phases in the sample are a-A12O3 and MgA12O4, with metallic aluminum residues. Magnesia has an influence on the phase composition of the alumina-sintered corundum refractories. When the content of magnesia is 3%, A14O4C phase is formed. When the content of magnesia is 6% or 15%, the phase is A14C3. The magnesia addition of 15% can detect a periclase phase. When the content of magnesia is more than or equal to 6%, the spinel is formed on the surface of a-A12O3 particles or fine powder, having a ring-shaped structure. The a-A12O3 surface is coated to restrict the reaction of A14C3 with A12O3 to form A1404C. In addition, a phase formation model in this system was also proposed.