制备矾土基莫来石均质料加热过程变化的研究

STUDY ON PROCESS OF PREPARED BAUXITE-BASED HOMOGENIZED MULLITE GROGS

研究了矾土为原料,部分配以适量煤矸石及加入少量Al2O3,制备矾土基莫来石均质料的加热过程线收缩率、显气孔率、相组成和显微结构的变化。结果表明,其加热过程一般分为三个阶段:(1)1000℃～1200℃,一次莫来石已经形成,试样收缩、气孔率降低。(2)1200℃～1500℃,二次莫来石化阶段,液相已经出现。其中,1300℃～1400℃,二次莫来石大量生成,试样膨胀、气孔率增加。(3)1500℃～1700℃,液相烧结阶段,试样收缩和气孔率下降较快。根据XRD图谱可判断低温阶段(<1400℃)形成的莫来石的结晶度,而对高温阶段则较困难,原因为高温形成的莫来石衍射峰变化很小;显微结构观察表明,随温度升高,莫来石晶体发育不断完善,从片状晶体(1200℃)到发育较差的柱状(1500℃),直至发育完善长大柱状晶体(1700℃),并由其构成交错连续的网络结构。

The changes of linear shrinkage, apparent porosity, phase composition and microstructure of bauxit-based homogenized mullite grogs prepared by homogenization process and high temperature sintering using bauxite as starting material incorporated with appropriate amount of coal gangue and addition of a small quantity of Al2O3 during heating process have been investigated. The results show that changes of heating process are consistent and can be divided three stages： （1） primary mullite have formed at 1000℃-1200℃, specimen shrinkage and apparent decrease. （2） secondary mullitization stage at 1200℃-1500℃ ,liquid phase have appeared, specimen expanding and apparent decrease at 1300℃-1400℃, owing to formation of a great deal second mullite. （3） liquid phase sintering stage at 1500℃-1700℃, specimen shrinkage and apparent decrease obviously. According to XRD patterns, mullite crystal degree formed at below 1400℃ can be estimated, but will be very difficult at above 1400℃due to little change of diffaction patterns of mullite at high temperature. Mullite crystals growth perfectly with temperature increase, from flake piece at 1200℃ to poor prisimatic at 1500℃ and up to well-developed mullite at 1700℃, by observing microstructure of specimens, and form the continuous interlocking network structure of well-developed prisimatic mullite crystals.