硅线石含量对轻质莫来石-刚玉耐火材料的显微结构与性能的影响

以多孔球形莫来石为骨料,板状刚玉细粉、硅线石和粘土为基质,经1400 ℃、1500 ℃和1600 ℃保温3 h烧成,制备了四组轻质莫来石-刚玉耐火材料.采用X-射线衍射仪(XRD)和扫描电子显微镜(SEM)对试样的物相组成和显微结构进行表征,研究了烧成温度及硅线石含量(4%、6%、8%和10%)对试样常温物理性能和显微结构的影响.结果表明:(1)当硅线石含量不变时,随着烧成温度的升高,试样的显气孔率逐渐减小,体积密度逐渐增大,线收缩率逐渐增加,常温耐压强度先降低后升高;(2)当硅线石的含量从4%增加到8%时,经1400 ℃烧后,试样的显气孔率和体积密度变化不大,当硅线石含量超过8%时耐压强度显著下降;经1600 ℃烧后,随硅线石含量的增加,试样的体积密度减小,强度降低,线收缩率也由2.5%减小到1.5%;(3)当硅线石含量为6%、烧成温度为1400 ℃时,试样的线收缩率为0.86%,耐压强度为36.1 MPa,热导率为0.249 W/(m·K)(300 ℃),试样基质中气孔的d50为46.7 μm.

Effect of Sillimanite Content on Microstructure and Properties of Lightweight Mullite-Corundum Refractories

Using porous spherical mullite as aggregate, tabular corundum as powder, sillimanite and clay as marix, four groups of lightweight mullite corundum specimens were prepared and sintered at 1400 ℃, 1500 ℃ and 1600 ℃ for 3 h.The phase composition and microstructure were investigated through X-ray diffractometry (XRD) and scanning electron microscopy (SEM).Effect of sintering temperature and sillimanite content on physical properties and microstructure of lightweight mullite-corundum refractories were studied.The results showed that: (1) When the sintering temperature increased from 1400 ℃ to 1600 ℃, the apparent porosity of specimens decreased, the bulk density increased, the linear shrinkage increased, the cold compressive strength first decreased and then increased.(2) When the sillimanite content increased from 4% to 8%, the apparent porosity and bulk density of the specimens remained constant which was sintered 1400 ℃.When the sillimanite content was more than 8%, the cold compressive strength decreased significantly;after sintered 1600 ℃, the bulk density of the specimen decreased, the cold compressive strength decreased, and the linear shrinkage decreased from 2.5% to 1.5% with the increase of sillimanite content.(3) The specimen with 6% sillimanite content which was sintered at 1400 ℃ has low linear shrinkage(0.86%), high cold compressive strength(36.1 MPa),low thermal conductivity(0.249 W/(m·K),300 ℃) and smaller average pore size in the matrix of specimen(d50=46.7 μm).