高性能堇青石陶瓷的制备及影响因素分析

发布时间：2018-05-07 22:10

  本文选题：堇青石 + 热膨胀系数　； 参考：《吉林大学》2017年硕士论文

【摘要】：堇青石(2MgO·2Al_2O_3·5SiO_2)具有低热膨胀系数的优良性能,还具有良好的高温性能和吸附性能,较大的比表面积,稳定的化学性能和良好的介电性能等。因此,堇青石陶瓷在汽车尾气处理、臭氧抑制催化、有毒气体净化、作为涡轮发动机的热交换机等领域发挥着很大的作用。由于堇青石的应用范围仍在扩大,对其性能,尤其是对热膨胀性能提出更高的要求。如何有效地降低堇青石陶瓷的热膨胀系数成为一个热门的研究课题。本实验采用高温固相反应合成法,用“滑石-高岭土-氧化铝”系统进行制备堇青石陶瓷。因此本实验所用的主要原料有滑石、高岭土、煅烧高岭土和氢氧化铝等。重点研究了原料化学组成、添加剂和造孔剂等对堇青石性能的影响。通过XRD、FT-IR和SEM分别对陶瓷的物相组成、晶体结构、表观形貌、孔形、孔径和孔分布等进行观察,通过比较堇青石陶瓷样品的热膨胀系数,吸水率、气孔率和抗压强度等性能参数,优化配比和制备工艺条件。得到的主要结论如下:优选制备堇青石陶瓷的最佳基础配方是富含铝的配方,其中铝镁比为1.05。该样品的热膨胀系数为1.619×10-6/℃;吸水率和气孔率分别为14.66%和25.12%。SEM图中可以看到分布有孔结构和裂纹,且其大小和分布比较均匀。从XRD谱图和FT-IR光谱图分析,当原料中含有较多的Al_2O_3,可以与MgO充分反应生成镁铝比尖晶石,再与SiO_2反应从而生成大量的堇青石,可以减少中间相的剩余,有利于堇青石的生成,减少其他杂相的生成。以五氧化二钒、熔融石英和二氧化锆为添加剂制备陶瓷,发现添加4%V_2O_5效果最佳。样品的热膨胀系数降至最低为0.866×10-6 ℃-1;吸水率和气孔率分别增至22.65%,33%。通过XRD和FT-IR分析,虽有少量的顽火辉石,但样品中的堇青石纯度依然较高;V_2O_5中V~(5+)离子具有较高的活性,在烧结过程中进入到六元大通道中从而引起六元环一定程度的畸变;并形成新键V-O-Si和V-O,取代Al-O-Si键和Mg-O键。堇青石结构便发生微小变形,这使得堇青石晶体结构在a轴更紧凑,c轴结构不受影响。使堇青石的热膨胀系数降低,同时,V_2O_5的分解可以在陶瓷样品产生许多均匀分布的微孔,使陶瓷的气孔率增大。以甲基纤维素、淀粉、碳粉和稻壳为造孔剂制备陶瓷,发现添加10%甲基纤维素效果最佳。可使陶瓷的吸水率和气孔率大幅提升,分别为29.87%和40.53%,同时可使陶瓷的热膨胀系数降低为1.029×10-6 ℃-1;XRD和FT-IR分析结果显示,样品中几乎为堇青石纯相,含少量顽火辉石;SEM测试显示,堇青石晶粒尺寸大小分布均匀,形成的气孔多,但形态不规则。
[Abstract]:Cordierite 2MgO 2Al_2O_3 5SiO2) has excellent properties of low thermal expansion coefficient, good high temperature properties and adsorption properties, large specific surface area, stable chemical properties and good dielectric properties. Therefore, cordierite ceramics play an important role in automobile exhaust treatment, ozone suppression catalysis, toxic gas purification, as a turbine engine heat exchanger and other fields. Because the application range of cordierite is still expanding, the performance of cordierite, especially the thermal expansion property, is required higher. How to effectively reduce the thermal expansion coefficient of cordierite ceramics has become a hot research topic. Cordierite ceramics were prepared by using "talc-kaolin-alumina" system. Therefore, the main materials used in this experiment are talc, kaolin, calcined kaolin and aluminum hydroxide. The effects of chemical composition of raw materials, additives and pore-making agents on the properties of cordierite were studied. The phase composition, crystal structure, apparent morphology, pore shape, pore size and pore distribution of cordierite ceramics were observed by XRDD-FT-IR and SEM, respectively. The thermal expansion coefficient, water absorption rate, porosity and compressive strength of cordierite ceramics were compared. Optimization of the ratio and preparation conditions. The main conclusions are as follows: the best base formula for the preparation of cordierite ceramics is the aluminum-rich formula, in which the ratio of aluminum to magnesium is 1.05. The thermal expansion coefficient of the sample is 1.619 脳 10 ~ (-6) / 鈩，

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