SiO_2二维纳米链的导热系数尺寸效应数值模拟

Numerical simulation on size effect of thermal conductivity of 2D SiO_2 nanowire

纳米隔热材料具有优良的隔热性能,在高超声速飞行器热防护技术中有着广泛应用前景。针对纳米隔热材料固体构架导热系数的尺寸效应,基于声子辐射传输方程建立了声子导热的二维计算模型,采用离散坐标法进行数值计算,以SiO2二维纳米链为例,对其横向及纵向导热系数尺寸效应进行了数值模拟。模拟结果表明,SiO2纳米隔热材料的二维纳米链导热具有明显尺寸效应,导热系数主要受纳米链直径影响,对直径2～4nm的纳米链,其导热系数比块材的导热系数小15%以上,研究结果对认识纳米隔热材料内固体构架热量传递机理具有一定指导作用。

Nano insulations have excellent insulating performance and find wide application in hypersonic vehicle thermal protection technologies.In this study a two dimensional computational model based upon phonon radiative transfer equation for phonon transport in the solid of nano insulations was established.The discrete ordinate method was used to solve the transport equation numerically.The size effects in the longitudinal and transverse conductivity were numerically simulated for a 2D silica nanowire.Results showed that obvious size effect in the conductivity exists in the 2D nanowire and the conductivity was mainly influenced by the wire diameter.For the nanowire with the diameter between 2-4nm considered,its thermal conductivity was 15% less than the bulk material.Results obtained in this study may be useful in recognizing the heat transfer mechanism in solids of nano insulations.