Abstract:

Corundum-mullite materials were fabricated using electro-fused dense corundum,tabular alumina,electro-fused mullite and composite powder of silicon and aluminum sources as raw materials. Effects of electro-fused dense corundum and tabular alumina on structure and properties of corundum-mullite materials fired at 1 600 ℃ and 1 700 ℃ were studied.The results show that: (1) electro-fused dense corundum has low reactivity,and in-situ mullite generates slowly and continuously,with fewer grains and larger sizes;while tabular alumina has high reactivity,and in-situ mullite has more grains,smaller sizes and uniform distribution;(2) with the same firing temperature,compared with electro-fused dense corundum mullite material,tabular alumina mullite material has relatively higher apparent porosity,smaller linear expansion rate,lower elastic modulus,cold modulus of rupture and cold compressive strength,but better thermal shock resistance;(3) when the firing temperature is increased from 1 600 ℃ to 1 700 ℃,the sintering degree,pore coalescence,in-situ mullite grain growth and hot modulus of rupture of the two materials are improved,but the thermal expansion coefficient mismatch degree also increases,resulting in lower cold modulus of rupture compared with the hot modulus of rupture.The in-situ mullite growth is more obvious in the electro-fused dense corundum mullite material,decreasing the cold compressive strength and cold modulus of rupture.

Key words: electro-fused dense corundum, tabular alumina, sintering, mullite, corundum-mullite material

摘要：

以电熔致密刚玉、板状刚玉、电熔莫来石、可引入硅源和铝源的复合粉体为主要原料,研究了电熔致密刚玉和板状刚玉对烧后(1 600、1 700 ℃)刚玉-莫来石材料结构与性能的影响。结果表明:1)电熔致密刚玉的反应活性较低,原位莫来石缓慢持续生成,晶粒数量较少、尺寸较大,而板状刚玉的反应活性相对较高,原位莫来石晶粒数量较多、尺寸较小、分布均匀;2)同一温度烧后,板状刚玉-莫来石材料的显气孔率相对较高,烧后线变化率较小,弹性模量、常温抗折强度和耐压强度较低,抗热震性更优异;3)烧成温度由1 600 ℃提高到1 700 ℃,两种材料的烧结程度提高,气孔聚结,原位莫来石晶粒长大,高温抗折强度提高,但热膨胀系数失配程度也随之增大,导致常温抗折强度均低于高温抗折强度,其中电熔致密刚玉-莫来石材料中原位莫来石发育长大更为明显,因而常温耐压强度和抗折强度降低。

关键词: 电熔致密刚玉, 板状刚玉, 烧结, 莫来石, 刚玉-莫来石