研究了一种利用稳态红外热成像法实现自悬浮薄膜面内热导率测量的方法。从一维热传导方程出发, 建立了稳态时薄膜表面温度分布的理论模型, 利用稳态理论模型, 只需测量薄膜边缘温度及厚度, 便可同时得到面内热导率、发射率及热流, 无需测量薄膜对可见光的吸收率。仿真表明,当薄膜的温升不超过5K时, 可以保证拟合得到的面内热导率与理论值的误差低于3%, 薄膜样品x方向的最小尺寸为6mm。对厚度为900nm的自悬浮聚酰亚胺薄膜进行实验测量, 拟合得到的面内热导率为2.04W/mK、红外发射率为0.92、x=0处的热流为1.77×104W/m2。实验结果与查阅文献的测量值一致, 证明方法可以用来测量自悬浮薄膜的面内热导率。

A method for in-plane thermal conductivity measurement of free-standing thin films by steady-state infrared thermography is introduced. Based on the one-dimensional heat conduction equation, a theoretical model of temperature distribution on the film surface at steady state is established. By measuring the edge temperature and thickness of the film, the in-plane thermal conductivity, emissivity and heat flux can be obtained simultaneously without measuring the absorption of visible light by the film. The simulation results show that the error between in-plane thermal conductivity and theoretical value is less than 3% when the temperature rise of the film is less than 5K. Meanwhile, the minimum size of the film sample in the x-direction is 6mm. The polyimide film with the thickness of 900nm is experimentally investigated by this method. The results show that in-plane thermal conductivity is 2.04W/mK, infrared emissivity is 0.92 and heat flow is 1.77×104W/m2 at x=0 by fitting temperature distribution curves. These results are in very good agreement with literature values, validating the method developed.