多孔矿物介质对有机相变材料导热性能的影响

通过对制备的基于膨胀多孔石墨和硅藻土两种多孔矿物介质与硬脂酸丁酯有机相变材料的相变蓄热复合材料,采用调制差示扫描量热方法(MDSC)测试复合材料的导热系数,并借助层状复合材料热传导模型分析多孔矿物介质内部结构特征对复合材料的导热性能的影响,其结果表明,采用膨胀多孔石墨制备的相变蓄热复合材料具有明显的层状结构,其压制方向的导热系数更接近层状复合材料热传导模型c轴方向导热系数预测结果;采用硅藻土制备的相变蓄热复合材料的导热系数符合层状复合材料热传导模型的a-b平面方向导热系数预测结果,说明该复合材料内部结构具有非常好的连通性。多孔矿物介质对相变材料导热系数的增强效果不仅受多孔矿物介质导热系数的影响,还会受到复合材料内部结构特征的明显影响,在热传导方向上形成连通性结构有利于增强效果,而形成与热传导方向垂直的层状结构则不利于导热系数的增强,即使多孔矿物介质具有很高的导热系数。

EFFECT OF POROUS MINERALS ON THE THERMAL CONDUCTIVITY OF ORGANIC PHASE CHANGE MATERIAL

The thermal conductivity of phase change composites made of expanded porous graphite,diatomite and butyl stearate was tested by means of temperature modulated differential scanning calorimetry(MDSC).The effect of the structure of porous minerals on the thermal conductivity of the composites was analyzed based on the model of thermal conductivity of layered composite.It was found that the composite made of expanded porous graphite has obvious multilayered structure,the thermal conductivity in the compression direction matched well with the prediction of the thermal conductivity of c-axis of the layered model.While the thermal conductivity made of diatomite coincided with the prediction of the thermal conductivity in the direction parallel to the a-b plane of the layered model,which means that the skeleton of the composite made of diatomite was well interconnected.The enhancement of the thermal conductivity of composite by porous minerals is not only controlled by the thermal conductivity of the porous minerals,but it is also influenced remarkably by the skeleton of composites,which results from the structures of the porous minerals.The interconnectivity is very helpful for the enhancement of the thermal conductivity of the composite in the same direction.In the condition of layered structure perpendicular to the direction of the thermal conductivity,the enhancement is very limited by the perpendicular layers,even if the thermal conductivity of the porous minerals is high.