【作者】 赵丹；

【导师】 武秀兰；

【作者基本信息】 陕西科技大学 ， 材料工程， 2012， 硕士

【摘要】 莫来石（3A1₂O₃·2SiO₂）晶须是针状结构的单晶，不但具有莫来石材料的特点，且力学性能、耐高温性能、抗氧化性和抗热震性等性能都优于多晶莫来石。此外，莫来石晶须还具有热膨胀系数小、高温强度较大和剪切模量高等特点。因此，莫来石晶须作为陶瓷基复合材料中一种优异的增韧补强剂，其开发和应用必将会引起材料界的广泛关注。粉煤灰和煤矸石是目前大量排放的工业固体废料，主要化学成分为A1₂O₃和SiO₂。其中，粉煤灰是燃煤电厂排出的主要固体废料，是从煤燃烧后的烟气中捕集下来的细灰。现阶段粉煤灰的年排放量已达3000万吨，并且排放量呈逐年增加的趋势。大量的粉煤灰如不加以利用或处理，不但会引起环境污染问题，还会对人体和生物带来危害。煤矸石是采煤和洗煤过程中排放的固体废料。历年来，我国已积存了约1000Mt的煤矸石，并且仍以每年约100Mt的速度继续排放，大量堆积的煤矸石不仅占用耕地，而且还容易自燃污染空气或引发火灾。因此，利用粉煤灰和煤矸石等工业废料制备高性能的材料必将引起材料科研工作者的广泛关注。目前，莫来石晶须的制备方法主要有粉末烧结法、凝胶-凝胶法、矿物分解法、氧化物掺杂法、原位生长法、熔盐法等。其中，溶胶-凝胶法制备过程复杂不利于工业化，粉末煅烧法、矿物分解法合成温度高、生产成本高，而熔盐法是一种简单、适用、成本低的合成方法。不仅如此，熔盐法制备莫来石晶须还结合了溶液合成法和固相合成法的优势，熔盐在熔融状态下粘度小，有利于晶须的成核和生长，且对特殊形貌的产物具有一定的可控性。本课题以粉煤灰或煤矸石为主要原料，硫酸铝为Al₂O₃的补充剂，分别采用Na₂（SO₄）、KCl或NaCl为熔盐，在低温下成功制备出了微观形貌较好的的莫来石晶须。运用差热分析（DSC）、X-射线衍射分析（XRD）、扫描电子显微镜分析（SEM）等测试手段详细地研究了制备工艺条件对产物的热效应、物相、微观形貌等的影响，并进一步探讨了制备莫来石晶须的反应机理。利用工业废料制备莫来石晶须的工艺研究结果表明：以粉煤灰为主要原料，在1000℃保温3h，Al₂O₃与SiO₂的摩尔比为1.5，熔盐为Na₂SO₄且用量为50wt%时，合成的莫来石晶须的各项指标达到最佳，其纯度最高，长径比大于15（直径为40⁷0nm）；以煤矸石为主要原料，在1100℃保温3h，Al₂O₃与SiO₂的摩尔比为1.5，熔盐为Na₂SO₄且用量为65wt%时，合成的莫来石晶须的各项指标达到最佳，其纯度最高，长径比大于30（直径为35⁶5nm）。更多还原

【Abstract】 Mullite （3A1₂O₃·2SiO₂） whisker is needle-like structure mullitemonocrystal, it possesses the performance of mullite, but has the bettermechanical property, the thermostability, the antioxidant, the thermal shockresistance, low thermal expansion, high strength at high temperature and highshear elasticity. For these reasons, as one of the excellent addition for theceramic, the development of mullite whiskers would be used in the field ofmachinery, electron and fuel.Fly ash and coal gangue are one massive solid discharge of industrial,the chemical composition are A1₂O₃and SiO₂. Fly ash is the fine ash fromexhaust gas of burned coal. Years slagging at present in China, the discharge offly ash had reached30million tons, and the slagging would increase. So muchfly ash would pollute the air, and it is harm to bodies. Coal gangue is solid wasteduring the coal mining and one of the black rock, who has low carbon content,the1000million tons has stored up so far. So much coal gangue would occupythe cultivated land, and cause fire hazard. Therefore, the recycling of industrialwaste to produce valuable materials attracts a great deal interest from scientistsalike.At present, the preparation methods of mullite whisker mainly containsfiring the powders, sol-gel, mineral decompose, dope the oxide, growing in situand molten-salt method. But the methods of sol-gel and mineral decompose areprejudice industrialization produce, because of complex process and highsynthesis temperature. However, the method of molten-salt possessessimpleness, applicability, low cost and others advantage. On the other side, themolten-salt combine the advantage of solution synthesis and solid synthesis, themolten-salt is mobile phase during the reaction, because of the low viscosity,these in favour of the growing of whiskers, and the morphology of the product.In this study, the industrial waste of fly ash and coal gangue are used asraw materials, aluminum sulfate as replenishers of Al₂O₃, Na₂（SO₄）, KCl andNaCl are used as molten-salt, the better micro-morphology of mullite whiskersare obtained. The phase formation and microstructure of the as synthesized whiskers were characterized via differential scanning calorimetry （DSC）, X-raypowder diffraction （XRD） and scanning electron microscopy （SEM）.The results indicate that the dispersed uniformly with high purity and aspectratio>15（40-70nm in diameter） mullite whiskers are synthesized via fly ash asraw materials at1000℃for3h, the molar ration of Al₂O₃and SiO₂is1.5with50wt%Na₂SO₄. When the coal gangue are used as raw materials, at1100℃for3h, the molar of Al₂O₃and SiO₂is1.5and the mass ratio of Na₂SO₄is65%, thehigh purity mullite whiskers were synthesized, the aspect ratio>30（35-65nm indiameter）.更多还原