高气孔率莫来石制备、性能及其非线性导热模型

doi:10.15541/jim20140048

摘要/Abstract

摘要：

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。

关键词: 高气孔率莫来石, 制备, 导热模型, 非线性

Abstract:

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 influence 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 between 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 function relationship. 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.

Key words: highly porous mullite, fabrication, thermal conductivity model, nonlinear

中图分类号:

TQ175

罗学维, 栗海峰, 向武国, 袁惠, 程呈, 沈绪根, 严春杰. 高气孔率莫来石制备、性能及其非线性导热模型[J]. 无机材料学报, 2014, 29(11): 1179-1185.

LUO Xue-Wei, LI Hai-Feng, XIANG Wu-Guo, YUAN Hui, CHENG Cheng, SHEN Xu-Gen, YAN Chun-Jie. Fabrication, Properties and Nonlinear Thermal Conductivity Model of Highly Porous Mullite Ceramics[J]. Journal of Inorganic Materials, 2014, 29(11): 1179-1185.

图/表 10

图1 样品在不同温度下煅烧1 h的XRD图谱

Fig. 1 XRD patterns of the samples calcined at different temperatures for 1 h

图2 淀粉原料(a)与多孔莫来石(b,c)SEM照片及多孔莫来石MIP曲线(d)

Fig. 2 SEM images of starch (a) and porous mullite (b, c) and MIP pore size distribution curve (d)

图3 淀粉含量对显气孔率、体积密度和抗折强度的影响

Fig. 3 Influence of starch content on the apparent porosity, bulk density and flexural strength

图4 气孔率对抗折强度、体积密度影响及指数拟合曲线

Fig. 4 Influence porosity (P) on bulk density (D) and flexural strength (F) and exponential fitting curves of F-P and D-P

图5 五种模型对应导热系数与气孔率关系计算值及实测值

Fig. 5 Calculated values of the relationships between thermal conductivity and porosity by five basic models and the experimental values at 298 K

图6 Shimizu Model导热系数计算值与实测值比较

Fig. 6 Contrast of the calculated values according to Shimizu model and experimental values of this work

表1 零孔隙率莫来石[32]及空气导热系数[25]

Table 1 Typical values of the thermal conductivity for bulk mullite and air at different temperature

T / K	λ_air×10² / (W·m^-1·K^-1)	λ_m / (W·m^-1·K^-1)
273	2.05	-
473	3.35	-
673	4.47	1.45
873	5.34	1.52
1073	6.02	1.58
1273	6.55	1.63
1473	-	1.67

表2 ξ1、ξ2数学表达式中α1~α5参数值

Table 2 Parameter values of α1- α5

Parameters	Mathematical formula
Parameters	ξ₁/×10^-5	ξ₂/×10^-8
α₁	-1.69	-1.59
α₂	7.04	6.63
α₃	-6.24	-5.87
α₄	-0.13	-0.12
α₅	-0.14	-0.13

图7 新模型导热系数计算数值与实测值比较

Fig. 7 The contrast of the calculated values according to the new thermal conductivity model Eq.10 and experimental values

图8 新模型预测多孔莫来石导热系数与气孔率、温度关系

Fig. 8 Thermal conductivity correlations for temperature and porosity as predicted by Eq.10 for porous mullite

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