材料期刊网

着重分析了材料的显微结构对材料导热系数的影响:高孔隙率减弱固相传热作用从而使材料的导热系数减小,但是,高孔隙的也增大辐射传热作用.适当降低孔隙可减少辐射传热作用,这在高温时特别明显.尺寸<1 mm的孔隙中对流传热被制止,不再对传热起作用.在保持孔隙总量不变的前提下减小孔径可使孔隙数量增大,从而减小导热系数.小于100 nm的孔隙可以消除气体本身的热传导,从而极大地减小材料的导热系数.展示了几种不同显微结构的材料及其绝热性能.

Effect of microstructure of thermal insulation materials on their insulating property was studied. Increasing porosity leads decrease of thermal conductivity due to reduction of heat transfer through solid phase. However, high porosity enhances the heat radiation leading to increase of thermal conductivity. Therefore, decreasing properly the porosity results in decrease of thermal conductivity by reduction of heat radiation, especially at high temperature. Heat transfer by convection is eliminated in the pores with the size less than 1 mm. Thermal conductivity can be reduced, if the pore size is decreased; meanwhile the total volume of the pores remains constant. The pore size less than 100 nm eliminates the heat transfer through gas phase; therefore, the thermal conductivity of the material decreases considerably. Several insulation materials with deferent microstructure and their thermal insulating property are discussed.