分别采用轻质碳酸钙和活性氧化铝,或纯铝酸钙水泥和活性氧化铝为初始原料,反应烧结合成了六铝酸钙(CA6)材料,研究了原料和成型压力对合成材料的烧结性能和显微结构的影响,同时借助于XRD、TG-DSC、SEM和EDAX等测试手段对其反应过程、物相变化和显微结构进行了分析和观察.研究结果表明:(1)1300 ℃时,合成材料的主晶相为刚玉相和CA2,并开始有CA6形成;温度升至1400 ℃,CA6大量生成;1500 ℃时反应完成,产物全部为CA6相.1300～1500 ℃时,上述反应表现为体积膨胀过程,试样的体积密度和径向线收缩率随温度的变化不大;而高于1500 ℃时,试样明显趋向烧结,体积密度升高,线收缩率加大.采用纯铝酸钙水泥和活性氧化铝合成的试样的体积密度均高于采用轻质CaCO3和活性氧化铝的,尤其在烧成温度高于1500 ℃时.坯体的成型压力对这两种合成试样的烧结性能均没有显著影响.(2)合成六铝酸钙材料的晶粒形貌与合成工艺有关,制备片状晶粒的六铝酸钙材料需满足两个条件:一是晶核有足够的发育空间,二是从晶核生长形成片状结构需足够的物质扩散.采用纯铝酸钙水泥和活性氧化铝为原料的试样,其CA6晶核很容易发育成片状晶形,且随着坯体成型压力的增加,片状CA6有向等轴状发展的趋势;采用轻质CaCO3和活性氧化铝的试样,坯体成型压力为50 MPa时,CA6的片状晶形明显,但增至200 MPa时,CA6晶形又呈颗粒状,片状晶形不明显.
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