高纯度莫来石晶须的制备与分散

Preparation and Dispersion of Mullite Whisker with High Purity

莫来石晶须具有耐高温、抗氧化、热膨胀系数较小、高温强度较大、抗热震性能较好等优异性能,是一种优良的陶瓷基复合材料用补强剂。试验以γ-Al2O3和SiO2为主要原料,以氟化铝为助剂,采用原位反应法制备了莫来石晶须,并利用XRD和SEM分析了制备材料的物相组成及显微结构。实验表明:在原料粉自然堆积状态下,在特定氟化铝加入量下,影响莫来石晶须长径比的因素由主到次依次为保温时间、烧结温度和氟化铝形式;以粉质量10%的AlF3·3H2O为助剂,在1450℃温度下煅烧,保温6 h时,可以制备出高纯且长径比为20左右的莫来石晶须粉体;所制备得到的晶须的分散性因处于坩埚上、中、下部位的不同而有所差异;超声振动、极性溶剂及碱性环境有助于初步打开晶须间的团聚,达到晶须预分散的效果。

Mullite whisker is an excellent kind of reinforcments used in ceramic matrix composite,due to its’good properties such as high temperature resistance,good oxidation resistance,small coefficient of thermal expansion,good strength in high temperature,good thermal shock resistance and so on.Mullite whisker was prepared through solid reaction usingγ-Al2O3 and SiO2 as raw material,aluminum fluoride as additives.Phase composition of the as-prepared material was analyzed by XRD and microstructure was observed by SEM.The result shows that when the raw powder materials with a certain content of fluoride are naturally packing,the factors who affects aspect ratio of mullite whisker are proved to be holding time,calcining temperature and the kind of the aluminum fluoride.Using 10 wt.%Al F3·3H2O as additive,mullite whisker with high purity and aspect ratio of about 20 can be prepared after calcined at 1450℃for 6 hours.There are differences in the dispersibility of the whisker due to its situation in the crucible.The ultrasonic vibration,polar solvent and alkaline environment are helpful to the dispersion of the prepared mullite whiskers.