块状菱镁矿烧结中期液相烧结行为

摘要

By using high temperature furnace to sinter block magnesite,the influence of liquid phase sintering performance at the middle stage of the sintered samples(1 400~1 600℃)is researched. The results show that the more uniformly liquid phase around the crystal distribute,the more extensive wetting grain surface area, the better the grain growing and the higher degree of crystallinity own. The densification coefficient is in-creased from 23.51%to 71.24%at 1 400~1 600℃. The middle stage of the block magnesite sintering can be divided into two stages under the action of liquid:stage 1:the method of mass transfer is flowing,the sinter-ing activation energy decreases with the increasing of temperature and the rate densification increases rapidly. stage 2:the method of mass transfer is"dissolving—precipitation",with the increasing of temperature,chemi-cal gradient on particles surface and the liquid phase mass transfer rate increase,the sintering activation energy is reduced and particles densify rapidly. It reveals the block magnesite mechanism of liquid phase sintering stage,and provides theoretical data for practical production.%采用高温电炉对块状菱镁矿进行煅烧，研究了菱镁矿试样在煅烧中期（1400~1600℃）液相对烧结性能的影响。结果表明，液相在晶体周围分布越均匀，润湿晶粒的表面积越广泛，晶粒的发育程度越好，方镁石结晶度越大；1400~1600℃致密化系数由23.51%增加到71.24%，在液相的作用下块状菱镁矿烧结中期可分为两个阶段进行：阶段1—烧结传质方式为流动传质，烧结激活能随温度升高而减小，致密化速率快速增加；阶段2—随着温度的升高，烧结传质方式为“溶解-沉淀”，颗粒对应面产生化学位梯度增加，液相传质速率增加，烧结激活能降低，颗粒迅速致密化。揭示了块状菱镁矿液相烧结阶段的机理，为实际生产提供理论数据。