偏组成堇青石陶瓷材料结构与性能

Microstructure and Properties of Partial Stoichiometry Cordierite Ceramic Materials

堇青石陶瓷具有热膨胀系数低、抗热震性好、耐高温等特点,被广泛应用于高低温急剧变化的环境。如何进一步降低堇青石陶瓷的热膨胀系数,提升其使用性能,仍然是国内外研究的热点,以单层片状结构的苏州高岭土、滑石和γ-Al_(2)O_(3)为原料,设计了不同的配比组成并制备了堇青石低膨胀陶瓷样品。采用XRD、SEM、CTE和EPMA等测试技术对样品的结构和性能进行了表征。探究了偏化学计量不同配比组成对合成堇青石陶瓷的结构与性能的影响。结果表明:偏镁样品(Si/Al为1.34时)合成的是单一的纯相堇青石;样品的热膨胀系数为1.91×10^(-6)℃^(-1) (25℃~800℃),抗折强度为50 MPa,气孔率为20%,体积密度为1.90 g·cm^(-3)。风冷热震循环试验(25℃~1000℃) 30次后抗折强度损失率仅为2.66%。偏镁组成中的MgO促进了高温液相的生成,液相传质推动高温化学反应充分进行,提高了样品中的堇青石含量(达到了99 wt.%),生成的堇青石晶粒定向排列,降低了样品的热膨胀系数,提高了样品的抗热震性。

Due to their characteristics of low thermal expansion coefficient,strong thermal shock resistance and high temperature resistance,cordierite ceramics have been widely used in environments with rapid changes between high and low temperatures.How to further reduce the thermal expansion coefficient of cordierite ceramics to improve their mechanical strength is still a research hotspot.With Suzhou kaolin,talc and γ-Al_(2)O_(3) with single-layer sheet structure as raw materials,cordierite ceramic samples with different compositions were designed,in order to achieve low thermal expansion.The samples were characterized by using XRD,SEM,CTE and EPMA and so on.The effects of partial stoichiometry on microstructure and properties of the cordierite ceramics were studied.It is found that single phase cordierite ceramics could be derived from metamagnesium(Si/Al is 1.34),with thermal expansion coefficient of 1.91×10^(-6) ℃-1(25–800 ℃),flexural strength of 50 MPa,porosity of 20%,bulk density of 1.90 g·cm^(-3),while the loss rate of flexural strength is only 2.66% after 30 cycles of air-cooling and heat-shock cycle test(25–1000 ℃).MgO in the metamagnesium promoted the formation of liquid phase at high temperatures,which boosted the chemical reaction,leading to the content of cordierite to be 99 wt.%.In addition,because the cordierite grains are oriented,the thermal expansion coefficient of the samples are reduced.As a result,thermal shock resistance of the sample is improved.