1600℃氮气气氛下Al对Al2O3–MgO材料中尖晶石物相演变的影响

Effect of Al on Spinel Phase Evolution of AlO–MgO Refractories at 1600℃ in Nitrogen

探究了在1 600℃氮气气氛下金属Al对Al2O3-MgO耐火材料中尖晶石物相演变的影响。结果表明,金属Al显著改变了尖晶石物相的组成、形貌和反应路径。未添加金属Al时,氧化镁与氧化铝反应生成镁铝尖晶石;镁铝尖晶石与其包裹的氧化铝颗粒发生固溶体反应形成一次富氧化铝的镁铝尖晶石。C-O2反应使体系氧分压持续降低,氧化镁分解产生的Mg(g)与周围的氧化铝和一次富氧化铝的镁铝尖晶石发生置换反应,形成二次富氧化铝的镁铝尖晶石和金属Al(l/g)。在高温氮气下,金属Al(l/g)氮化形成氮化铝后,与上述一次或二次富氧化铝的镁铝尖晶石反应形成镁阿隆尖晶石(MgAlON)尖晶石。将金属铝引入到Al2O3-MgO耐火材料后,含铝气相物质——Al(g)和Al2O(g),沿耐火材料中的气孔或孔隙扩散传质。一方面,Al(g)和Al2O(g)氮化反应形成氮化铝,固溶强化并提升MgAlON尖晶石中氮元素的含量;另一方面,Al(g)、Al2O(g)、Mg(g)、N2和O2发生气-气化学反应,形成片状形貌的MgAlON尖晶石。

Effect of Al on the spinel evolution within Al2O3-Mg O refractories in nitrogen at 1 600 ℃ was investigated. The results show that Al can markedly change the composition, morphology and reaction path of spinel phase within Al2O3-MgO refractories. Without Al addition, Mg O reacts with Al2O3 to form spinel, and then spinel reacts with Al2O3 encompassed by itself to form once-rich-Al2O3 spinel. When the oxygen partial pressure by C-O2 consumed oxygen reaction decreases, MgO becomes unstable and decomposes into Mg(g) and O2;Mg(g) diffuses and transfers along pores or gaps in the materials, reacting with rich-Al2O3 spinel to generate new rich-Al2O3 spinel and Al(g), Al(g) is nitrided as AlN and then AlN dissolves into rich-Al2O3 spinel to form MgAlON. Al(g) and Al2O(g) diffuse and transfer along pores or gaps in the materials after introduction of Al into Al2O3-MgO refractory. Al(g) and Al2O(g) change into AlN and further dissolve into rich-Al2O3 spinel, enhancing N content of MgAlON. Also, in the gas-gas reaction system, Al(g)/Al2O(g), Mg(g), N2 and O2 react with each other to form flake MgAlON.