【摘要】：莫來石晶須具有耐高溫、抗氧化、熱膨脹系數(shù)較小、高溫強(qiáng)度較大、抗熱震性能較好等優(yōu)異性能,是一種優(yōu)異的陶瓷基復(fù)合材料用補(bǔ)強(qiáng)劑。本文從莫來石晶須的制備和莫來石晶須的分散兩大部分著手,旨在得到高純度、高長徑比、良好分散的莫來石晶須,為其將來工業(yè)化生產(chǎn)提供一些前期研究。本文以γ-Al2O3和SiO2為主要原料,以AlF3·3H2O或AlF3為助劑,采用固相反應(yīng)法制備了莫來石晶須,并利用XRD和SEM分析了制備材料的物相組成及顯微結(jié)構(gòu)。初步實(shí)驗(yàn)研究表明:在原料粉自然堆積狀態(tài)下,選用扁胖型坩堝,助劑選用AlF3·3H2O,加入量為10 wt%時(shí),可以制備出高純且長徑比較大的莫來石晶須粉體。進(jìn)而對影響莫來石晶須長徑比的主要因素(保溫時(shí)間、燒結(jié)溫度、氟化鋁含量)進(jìn)行了正交實(shí)驗(yàn)設(shè)計(jì),極差分析和方差分析表明:影響莫來石晶須長徑比的因素由主到次依次為:保溫時(shí)間、氟化鋁含量和燒結(jié)溫度;其中保溫時(shí)間為顯著影響因素,氟化鋁含量為較顯著影響因素,燒結(jié)溫度在1400-1480℃為不顯著影響因素。綜合兩分析結(jié)果得出最優(yōu)方案,實(shí)驗(yàn)驗(yàn)證發(fā)現(xiàn):以粉質(zhì)量10%的AlF3·3H20為助劑,在1450 ℃溫度下煅燒,保溫6h,可以制備出高純且長徑比為26左右的莫來石晶須粉體。對所制備得到的莫來石晶須的分散進(jìn)行了多方面的研究,通過測量最終沉降體積的方法表征其分散性。結(jié)果表明:所制備得到的晶須分散性因處于坩堝上、中、下部位的不同而有所差異,上層粉體分散效果最佳,而底部粉體的最差;超聲分散15分鐘分散效果明顯提升,但再延長時(shí)間分散效果不再明顯提高;pH值為3.5或9的條件下的分散效果要優(yōu)于6.5的;與聚丙烯酸銨相比,六偏磷酸鈉可以獲得更好的分散效果,且分散劑濃度對晶須的分散性有顯著影響;低濃度的氫氟酸的腐蝕效果明顯優(yōu)于鹽酸、硝酸和硫酸,腐蝕時(shí)間超過24小時(shí)會(huì)明顯影響制備晶須的長徑比。綜合研究結(jié)果獲得最優(yōu)分散工藝為:取坩堝中上層粉體,采用3 mol/L的氫氟酸溶液腐蝕晶須24小時(shí),多次清洗稀釋后調(diào)節(jié)極性溶液呈堿性,選用濃度為0.3 wt%的六偏磷酸鈉溶液作為分散劑,超聲分散15分鐘。采用最優(yōu)工藝對制備的莫來石晶須進(jìn)行分散實(shí)驗(yàn),獲得的平均最終沉降體積為0.7 ml,比初始合成晶須的沉降體積減小了近4倍,莫來石晶須間的團(tuán)聚現(xiàn)象得到明顯改善。
[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 緯 -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，

本文編號：2139305