镁橄榄石制备六方柱状堇青石及其晶相和性能研究

Crystal Phase and Properties of Hexagonal Columnar Cordierite Synthesized by Forsterite

我国天然镁橄榄石矿物资源丰富,但其成分复杂,导致高效利用率和产品附加值低。为拓展镁橄榄石高效利用技术,以镁橄榄石、工业氧化铝和石英砂为原料,在空气气氛下经800~1 380℃保温2~8 h制备得到堇青石材料,并研究了原料组成和烧成制度对合成六方柱状堇青石的影响。结果表明,合成堇青石的最佳烧成制度为1 380℃保温8 h,此时堇青石合成纯度最高,晶型发育良好且晶粒为六方柱状。当烧成温度为1 380℃,保温时间由2 h延长至8 h后,材料中石英砂对应衍射峰消失,堇青石析出量增多,材料的结晶度得到提高,堇青石晶体点缺陷类型可能由V″Mg转变为O″i。添加过量石英砂的试样经1 380℃保温8 h烧成后,堇青石晶粒被更多熔融相覆盖包裹,晶粒间间隔减小,堇青石材料更加致密,但堇青石材料的合成纯度并未得到提高。

Natural forsterite mineral resources are rich in China. Due to the complex composition of this material, it is underutilized and its products have low added value. Forsterite, industrial alumina and quartz sand were used as raw materials to prepare cordierite at 800 ℃ to 1 380 ℃ for 2 h to 8 h in air atmosphere in order to expand the technology of high-efficiency utilization of forsterite. The influences of raw material composition and firing schedule on the synthesis of hexagonal columnar cordierite were studied. The results show that the best sintering system for cordierite is synthesized at 1 380 ℃ for 8 h. At this time, the synthetic purity of cordierite is the highest, the crystal form of cordierite is well developed and the crystal grains are hexagonal columnar. When the sintering temperature is 1 380 ℃ and the holding time is extended from 2 h to 8 h, the corresponding diffraction peak of quartz sand disappeares while the amount of cordierite precipitation increases and the crystallinity of the material is improved. The type of point defects of cordierite crystal is transition from V″Mg to O″i. After the sample with excessive quartz sand is sintered at 1 380 ℃ for 8 h, the cordierite grains are covered and wrapped by glassy phase much more than before, the spacing between grains is reduced, and the density of cordierite increases, but the synthetic purity of cordierite is not improved.