高气孔率莫来石制备、性能及其非线性导热模型

Fabrication, Properties and Nonlinear Thermal Conductivity Model of Highly Porous Mullite Ceramics

以高铝矾土、硅灰为原料,玉米淀粉为造孔剂制备高气孔率莫来石,通过XRD、SEM等对产物物相、形貌进行表征,研究淀粉含量对显气孔率、体积密度和抗折强度的影响,及不同显气孔率的莫来石随温度变化的导热系数,建立体积密度、抗折强度与气孔率关系模型及非线性导热模型。结果表明:体积密度、抗折强度随气孔率增加而减小,并符合指数函数关系。导热系数随温度的升高而增大,实测值与非线性导热模型计算值吻合较好,非线性导热模型能够准确地反映高气孔率莫来石导热系数与温度、气孔率、平均孔径和热辐射等之间的关系。

Highly porous mullite ceramics were prepared by bauxite and silica fume as raw materials and corn starch as the pore-forming agent. The phase and morphology were characterized by XRD and SEM, respectively. The influ- ence of corn starch content on apparent porosity, bulk density and flexural strength were studied. Thermal conductivity of porous mullite was measured at 473-1273 K. A new nonlinear thermal conductivity model and several models be- tween bulk density, flexural strength and apparent porosity were established. The results indicate that, bulk density and flexural strength of porous mullite decrease with porosity increase and conform to the exponential fimction relation- ship. Thermal conductivity of porous mullite increases with the rise of temperature and the measured values are in good agreement with values calculated by nonlinear thermal conductivity model. The new model can accurately reflect the thermal conductivity correlations for temperature, porosity, radiation and mean pore size.