莫来石晶须的制备与分散
发布时间：2018-07-23 11:43
【摘要】：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,是一种优异的陶瓷基复合材料用补强剂。本文从莫来石晶须的制备和莫来石晶须的分散两大部分着手,旨在得到高纯度、高长径比、良好分散的莫来石晶须,为其将来工业化生产提供一些前期研究。本文以γ-Al2O3和SiO2为主要原料,以AlF3·3H2O或AlF3为助剂,采用固相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。初步实验研究表明:在原料粉自然堆积状态下,选用扁胖型坩埚,助剂选用AlF3·3H2O,加入量为10 wt%时,可以制备出高纯且长径比较大的莫来石晶须粉体。进而对影响莫来石晶须长径比的主要因素(保温时间、烧结温度、氟化铝含量)进行了正交实验设计,极差分析和方差分析表明:影响莫来石晶须长径比的因素由主到次依次为:保温时间、氟化铝含量和烧结温度;其中保温时间为显著影响因素,氟化铝含量为较显著影响因素,烧结温度在1400-1480℃为不显著影响因素。综合两分析结果得出最优方案,实验验证发现:以粉质量10%的AlF3·3H20为助剂,在1450 ℃温度下煅烧,保温6h,可以制备出高纯且长径比为26左右的莫来石晶须粉体。对所制备得到的莫来石晶须的分散进行了多方面的研究,通过测量最终沉降体积的方法表征其分散性。结果表明:所制备得到的晶须分散性因处于坩埚上、中、下部位的不同而有所差异,上层粉体分散效果最佳,而底部粉体的最差;超声分散15分钟分散效果明显提升,但再延长时间分散效果不再明显提高;pH值为3.5或9的条件下的分散效果要优于6.5的;与聚丙烯酸铵相比,六偏磷酸钠可以获得更好的分散效果,且分散剂浓度对晶须的分散性有显著影响;低浓度的氢氟酸的腐蚀效果明显优于盐酸、硝酸和硫酸,腐蚀时间超过24小时会明显影响制备晶须的长径比。综合研究结果获得最优分散工艺为:取坩埚中上层粉体,采用3 mol/L的氢氟酸溶液腐蚀晶须24小时,多次清洗稀释后调节极性溶液呈碱性,选用浓度为0.3 wt%的六偏磷酸钠溶液作为分散剂,超声分散15分钟。采用最优工艺对制备的莫来石晶须进行分散实验,获得的平均最终沉降体积为0.7 ml,比初始合成晶须的沉降体积减小了近4倍,莫来石晶须间的团聚现象得到明显改善。
[Abstract]:Mullite whisker has excellent properties such as high temperature resistance, oxidation resistance, low coefficient of thermal expansion, high temperature strength, good thermal shock resistance and so on. It is an excellent reinforcing agent for ceramic matrix composites. In this paper, the preparation of mullite whiskers and the dispersion of mullite whiskers are discussed in order to obtain mullite whiskers with high purity, high aspect ratio and good dispersion. In this paper, mullite whiskers were prepared by solid state reaction with 纬 -Al _ 2O _ 3 and SiO2 as main raw materials and AlF3 3H2O or AlF3 as auxiliaries. The phase composition and microstructure of the prepared materials were analyzed by XRD and SEM. The preliminary experimental study shows that the mullite whisker powder with high purity and large length and diameter can be prepared by using flat and fat crucible, AlF3 _ 3H _ 2O as additive and 10 wt% as additive under the condition of natural stacking of raw material powder. Furthermore, the orthogonal experimental design was carried out on the main factors affecting the aspect ratio of mullite whiskers (holding time, sintering temperature, aluminum fluoride content). Range analysis and variance analysis showed that the main and secondary factors affecting the aspect ratio of mullite whiskers were: holding time, aluminum fluoride content and sintering temperature, in which holding time was a significant factor, and aluminum fluoride content was a more significant factor. The sintering temperature of 1400-1480 鈩，
本文编号：2139305
[Abstract]:Mullite whisker has excellent properties such as high temperature resistance, oxidation resistance, low coefficient of thermal expansion, high temperature strength, good thermal shock resistance and so on. It is an excellent reinforcing agent for ceramic matrix composites. In this paper, the preparation of mullite whiskers and the dispersion of mullite whiskers are discussed in order to obtain mullite whiskers with high purity, high aspect ratio and good dispersion. In this paper, mullite whiskers were prepared by solid state reaction with 纬 -Al _ 2O _ 3 and SiO2 as main raw materials and AlF3 3H2O or AlF3 as auxiliaries. The phase composition and microstructure of the prepared materials were analyzed by XRD and SEM. The preliminary experimental study shows that the mullite whisker powder with high purity and large length and diameter can be prepared by using flat and fat crucible, AlF3 _ 3H _ 2O as additive and 10 wt% as additive under the condition of natural stacking of raw material powder. Furthermore, the orthogonal experimental design was carried out on the main factors affecting the aspect ratio of mullite whiskers (holding time, sintering temperature, aluminum fluoride content). Range analysis and variance analysis showed that the main and secondary factors affecting the aspect ratio of mullite whiskers were: holding time, aluminum fluoride content and sintering temperature, in which holding time was a significant factor, and aluminum fluoride content was a more significant factor. The sintering temperature of 1400-1480 鈩，
本文编号：2139305
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