片状氧化铝制备与形成机理研究

发布时间：2018-07-21 18:00

【摘要】：α-Al_2O_3陶瓷作为一种重要的陶瓷材料,具有独特的化学、电学及力学性能,它属于刚玉结构,具有高硬度、高强度、耐磨损、耐高温、耐腐蚀、绝缘性好等特性。片状α-Al_2O_3粉体材料除了具备普通氧化铝材料的优良性能,还具有特殊的片状二维结构,并且表面活性适中,附着力比较好,对光线的反射能力和屏蔽效应高等。片状α-Al_2O_3在化妆品、珠光颜料、耐火材料以及增韧陶瓷等领域都有着广泛的应用前景。本研究结合溶胶凝胶法与熔盐法,将硫酸铝作为原料,硫酸钾、硫酸钠为熔盐,通过一系列液相和固相反应制备了粒径大、厚度薄的片状氧化铝材料。本文通过光学显微镜、扫描电子显微镜、X射线衍射仪、综合热分析仪及红外光谱仪等检测表征手段,考察了不同铝盐原料对合成的片状氧化铝形貌的影响,探索了溶胶凝胶和熔盐过程中的工艺参数包括反应终点pH、反应温度、陈化时间及烧结温度对终产物的影响,同时详细研究了二氧化钛、硫酸锌、硫酸亚锡或其混合物等添加剂对片状氧化铝的形貌与径厚比的影响,最后对氧化铝的生长机理进行了研究,探索片状氧化铝的形成的机理。研究结果表明:在铝源的选择上,选用硫酸铝可制备出尺寸大且分布均匀的片状α-Al_2O_3晶粒。在熔盐的选择上,铝源与熔盐摩尔比为1:4时,制备的片状α-Al_2O_3表面平整而有光泽。在溶胶凝胶过程中,随着陈化时间增长,形成的片状氧化铝的晶粒尺寸越大,粒径分布越窄。煅烧温度在1000~1200oC,终产物都能得到片状α-Al_2O_3晶体,但是1100oC下径厚比最大,随着烧结温度的升高,片状氧化铝的晶体粒径增大较缓,但厚度增加较明显,导致径厚比减小。另外选择合适的添加剂能显著促进α-Al_2O_3晶体的各向异性生长,并且可以减少细碎晶体的比例,使粒径分布更均匀。研究发现添加2 wt%硫酸锌和0.4 wt%硫酸亚锡,可以得到粒径为25~40μm、厚度为200~300 nm、径厚比大于100、表面光滑的片状氧化铝粉体。结合晶体生长的不连续性现象,氧化铝的生长过程可能是相变诱导取向聚结的过程。
[Abstract]:As an important ceramic material, 伪 -Al2O3 ceramic has unique chemical, electrical and mechanical properties. It belongs to corundum structure and has the characteristics of high hardness, high strength, wear resistance, high temperature resistance, corrosion resistance and good insulation. In addition to the excellent properties of ordinary alumina, the lamellar 伪 -Al _ 2O _ 3 powder also has a special two-dimensional flake structure with moderate surface activity, good adhesion, and high light reflection and shielding effect. Lamellar 伪 -Al2O3 is widely used in cosmetics, pearlescent pigments, refractories and toughened ceramics. In this study, aluminum sulfate was used as raw material, potassium sulfate and sodium sulfate as molten salt, and a series of liquid-phase and solid-state reactions were used to prepare flake alumina material with large particle size and thin thickness, combined with sol-gel method and molten salt method. By means of optical microscope, scanning electron microscope, X-ray diffractometer, comprehensive thermal analyzer and infrared spectrometer, the influence of different aluminum salt materials on the morphology of flake alumina was investigated. The effects of reaction terminal pH, reaction temperature, aging time and sintering temperature on the final product of sol-gel and molten salt were investigated. At the same time, titanium dioxide and zinc sulfate were studied in detail. The effect of additives such as tin sulfate or its mixture on the morphology and diameter to thickness ratio of flake alumina was studied. Finally, the growth mechanism of aluminum oxide was studied, and the formation mechanism of flake alumina was explored. The results show that the large size and uniform distribution of 伪 -Al _ 2O _ 3 grains can be prepared by using aluminum sulfate in the selection of aluminum source. When the molar ratio of aluminum source to molten salt is 1:4, the surface of 伪 -Al _ 2O _ 3 prepared is smooth and glossy. In the sol-gel process, the larger the grain size and the narrower the particle size distribution are, the longer the aging time is. When the calcination temperature is 1000 ~ 1200oC, the final products can obtain 伪 -Al _ 2O _ 3 crystal, but the diameter to thickness ratio at 1100oC is the largest. With the increase of sintering temperature, the particle size of flake alumina increases slowly, but the thickness increases obviously, which results in the decrease of diameter to thickness ratio. In addition, the selection of appropriate additives can significantly promote the anisotropic growth of 伪 -Al2O3 crystals, reduce the proportion of fine crystals, and make the particle size distribution more uniform. It is found that the flake alumina powder with a diameter of 25 渭 m, a thickness of 200 ~ 300 nm, a diameter ratio of more than 100 and a smooth surface can be obtained by adding 2 wt% zinc sulfate and 0.4 wt% stannous sulfate. In combination with the discontinuity of crystal growth, the growth process of alumina may be a phase transition induced orientation coalescence process.
【学位授予单位】：湖北工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TQ133.1

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