介孔复合材料内界面热阻及热导率

Interfacial thermal resistance in mesoporous composites and its thermal conductivity

界面广泛存在于复合材料中,对介孔复合材料热物性起着决定性的影响,研究界面的导热特性对于认识和理解介孔复合材料的导热机制十分重要。利用非平衡的分子动力学模拟方法计算介孔复合材料中基材与填充物间的界面热阻,考察界面热阻随温度、材料质量差异的变化,进一步用界面热阻修正介孔复合材料的有效热导率。结果表明,界面热阻的数量级为10^(-11) m^2·K·W^(-1),并随温度升高逐渐降低。界面两端材料质量差异越大,界面热阻越高。可通过减小孔径、减小纳米线长度、增大纳米线间距、降低纳米线填充率来降低介孔复合材料的有效热导率。界面热阻能降低材料的有效热导率。孔径越小、纳米线间距越小、纳米线长度越长、填充率越高,界面热阻降低热导率效果越显著。

The interface widely exists in composite material,and it plays a decisive impact on the thermal properties of mesoporous composite material.Study on the thermal conductivity of the interface is very important to know and understand the heat transfer mechanism of mesoporous composite material.In this paper,the simulation method of non-equilibrium molecular dynamics was used to calculate the interfacial thermal resistance between base material and filler in the mesoporous composite material,and the interfacial thermal resistance was analyzed with different temperature and different quality of material.Furthermore,the interfacial thermal resistance was used to modify the effective thermal conductivity of the mesoporous composite material.The results showed that the magnitude of the interfacial thermal resistance was 10^(-11) m^2·K·W^(-1) and it would gradually decrease with the temperature increasing.Since temperature increasing leads to the phonons' number increasing at the interface,the number and theenergy of phonons penetrating the interface will increase.The greater the difference of the interface material quality,the higher the interfacial thermal resistance.The effective thermal conductivity of the mesoporous composite material can be decreased by downsizing the pore diameter,reducing the length of nanowires,increasing the distance between the nanowires or reducing the filling rate of the nanowires.It can be seen that,with the increasing of the pore size,the effective thermal conductivity of the mesoporous composite of the Zdirection decreases,and those of X direction and Y direction have no obvious change.The effective thermal conductivity considering the interfacial thermal resistance is smaller than that without consideration,so it will be known that the interfacial thermal resistance can reduce the thermal conductivity,especially under the small pore diameter.The percentage of the interfacial thermal resistance is between 1%—7%,which will drop off gradually with the increasing of pore size.The effect of reducing the thermal conductivity through the interfacial thermal resistance will be more significant by decreasing the pore diameter and the distance between the nanowires,or increasing the length of nanowires and the filling rate.