细晶莫来石陶瓷的研究

发布时间：2018-06-18 21:39

本文选题：莫来石 + SPS　；参考：《武汉理工大学》2015年硕士论文

【摘要】：莫来石是一种用途比较广泛的材料,化学稳定向好。在高温环境下,莫来石的抗蠕变性好,力学性能优异,同时,莫来石的抗氧化性和耐腐性也比较好,是理想的高级耐火材料,在传统的高温结构陶瓷中被广泛应用。此外,莫来石的介电常数较低,在高温环境中还具有良好的透中红外性能,因此在光学和电子等领域莫来石也受到了广泛关注。在工业上,应用较多的就是用普通的莫来石作为原材料,采用传统的烧结方法制备莫来石陶瓷。这种莫来石虽然成本相对来说比较低、应用范围也很广泛,但是却不能将莫来石陶瓷本身特有的优异性能完全显示出来,因此应用范围还有待扩展。利用化学合成法可以制备性能较好的莫来石前驱体粉,这种前驱体粉纯度较高,而且晶粒尺寸较小且均匀。采用先进的工艺可以烧结制备出晶粒细小、性能优异的莫来石陶瓷。本实验中利用溶胶-凝胶法制备出高纯超细的莫来石前驱体粉,具有较高的烧结活性,采用放电等离子烧结(SPS)技术,制备出致密度高,晶粒细小的莫来石陶瓷。并利用莫来石前驱体粉良好的烧结活性,添加到TiB2粉体中,烧结制备出mullite/TiB2复相陶瓷材料,既能提高TiB2的高温抗氧化性能,又不影响陶瓷本身良好的导热、导电性能。本文采用TEOS(正硅酸四乙酯)和Al(NO3)3·9H2O(九水硝酸铝)为原料,利用溶胶-凝胶法制备莫来石前驱体粉,通过SPS快速烧结技术烧结制备出高致密度、细晶的莫来石陶瓷。研究表明,在烧结中后期降低烧结的升温速率,减少直流电流诱导生成的缺陷,降低晶粒生长的驱动力,抑制晶粒生长,并通过增加保温时间来提高样品的致密度,能够制备出致密度高、晶粒细小的陶瓷。在本文中,通过实验研究确定,选择升温速率转折点为1300℃,即在1300℃以后降低烧结的升温速率。在SPS烧结过程中,优化后的烧结工艺为:烧结温度为1400℃,升温速率转折点之前的升温速率为100℃/min,升温速率转折点之后的升温速率为20℃/min,保温时间20min,烧结压力80MPa,加压温度1150℃。利用该烧结工艺,能够烧结制备出晶粒细小、致密度高的莫来石陶瓷,致密度达到99.55%,平均晶粒尺寸为98nm。本文还探索了莫来石/二硼化钛复相陶瓷材料的制备方法。将莫来石前驱体粉和Ti B2粉体以体积比为3:7的比例均匀混合,混合后的粉体在高温管式炉中Ar气氛下烧结到1400℃,研究发现两种粉体在高温下氩气气氛中不发生反应。将混合均匀的莫来石/二硼化钛粉体进行烧结,当烧结温度达到1600℃,升温速率100℃/min,保温时间3min,烧结压力30MPa时,烧结制备出的复相陶瓷材料的致密度为99.03%,说明莫来石前驱体粉能够提高TiB2的烧结活性。将烧结温度为1500℃、致密度为94.17%的莫来石/二硼化钛复相材料在500℃、800℃和1100℃下进行静态氧化实验,保温时间为4h。通过对比氧化前后样品的质量变化(精确到10-4g),并与纯的Ti B2陶瓷的氧化实验进行对比,发现添加莫来石后,复相材料的抗氧化性有明显提高,尤其是在高温下效果较为明显。
[Abstract]:Mullite is a widely used material with good chemical stability. Under high temperature, mullite has good creep resistance and excellent mechanical properties. At the same time, the oxidation resistance and corrosion resistance of mullite are also good. It is an ideal high refractory material. It is widely used in the traditional high temperature structure ceramics. In addition, the dielectric constant of mullite is the permittivity of mullite. In the high temperature environment, it also has good medium and infrared properties, so mullite in the field of Optics and electronics is also widely concerned. In industry, the use of common mullite as raw material is to prepare mullite ceramic porcelain by traditional sintering method. This mullite is relatively low in cost. The application scope is very wide, but the excellent properties of mullite ceramics can not be fully demonstrated, so the application scope remains to be expanded. The better performance of mullite precursor powder can be prepared by chemical synthesis. The purity of the precursor powder is high, and the grain size is smaller and even. The advanced technology can be used. The mullite ceramics with fine grain and excellent properties were prepared by sintering. In this experiment, high purity superfine mullite precursor powder was prepared by the sol-gel method, with high sintering activity. The mullite ceramics with high density and small grain were prepared by discharge plasma sintering (SPS) technology, and the precursor powder of mullite was good. The sintering activity was added to the TiB2 powder, and the mullite/TiB2 composite ceramics were prepared by sintering, which could not only improve the high temperature oxidation resistance of TiB2, but also did not affect the good heat conduction and conductivity of the ceramics itself. This paper used TEOS (four ethyl orthosilicate) and Al (NO3) 3. 9H2O (nine water nitrate aluminum nitrate) as raw materials to prepare mullite by sol-gel method. By SPS rapid sintering technology, the high density and fine grain mullite ceramics are prepared by rapid sintering technology. The study shows that the heating rate of the sintering is reduced, the defects of the direct current induced, the driving force of the grain growth and the grain growth are reduced, and the density of the samples can be increased by increasing the heat preservation time. In this paper, it is determined that the turning point of the heating rate is 1300 C, that is, the heating rate of the sintering is reduced after 1300 C. In the process of SPS sintering, the optimized sintering process is that the sintering temperature is 1400, and the heating rate is 100 /min before the turning point of the heating rate. The heating rate after the turning point of heating rate is 20 /min, the holding time is 20min, the sintering pressure is 80MPa, and the pressure temperature is 1150. By using this sintering process, the mullite ceramics with fine grain and high density can be sintered, the density is 99.55%, the average grain size is 98nm., and the mullite / titanium diboride complex ceramics are also explored. The preparation method of material is to mix mullite precursor powder and Ti B2 powder evenly with the ratio of volume to 3:7, and the mixed powders are sintered at 1400 C under a Ar atmosphere in a high temperature tube furnace. It is found that two kinds of powders do not react in argon atmosphere at high temperature. The mixed mullite / titanium boride powders are sintered and burned. When the temperature reaches 1600 C, the heating rate is 100 /min, the heat preservation time is 3min and the sintering pressure is 30MPa, the density of the sintered ceramic material is 99.03%. It shows that the mullite precursor powder can improve the sintering activity of TiB2. The mullite / titanium diboride composite material with the sintering temperature of 1500 and the density of 94.17% is at 500, 800. The static oxidation experiment was carried out at 1100 C. The heat preservation time was 4h. through the quality change of the samples before and after the contrast oxidation (accurate to 10-4g), and compared with the pure Ti B2 ceramic oxidation experiment. It was found that the oxidation resistance of the composite was obviously improved after adding mullite, especially at high temperature.
【学位授予单位】：武汉理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ174.7

【参考文献】