Mendioroz Arantza, Fuente-Dacal Raquel, Apiñaniz Estibaliz, Salazar Agustín
Departamento de Física Aplicada I, Escuela Técnica Superior de Ingeniería, Universidad del País Vasco, Alameda Urquijo s/n, 48013 Bilbao, Spain.
Rev Sci Instrum. 2009 Jul;80(7):074904. doi: 10.1063/1.3176467.
Photothermal radiometry has been widely used to measure the thermal diffusivity of bulk materials. In the case of thin plates and filaments, a one-dimensional heat propagation model including heat losses has been developed, predicting that the thermal diffusivity can be obtained by recording both the surface temperature amplitude and phase profile slopes ("slope method"). However, this method has given highly overestimated values of the thermal diffusivity of poor-conducting films and filaments. In this paper we analyze the effect of the experimental factors affecting the thermal diffusivity measurements of thin plates and filaments using infrared thermography, in order to establish the experimental conditions needed to obtain accurate and reliable values of the diffusivity of any kind of material using the slope method. We present the calculations of the surface temperature of thin isotropic and anisotropic plates heated by a modulated and tightly focused laser beam, showing that the slope method is also valid for this kind of pointlike heating. Special attention is paid to the effect of surface heat losses (convective and radiative) on the diffusivity measurements of small-dimension and poor-conducting materials. Lock-in thermography measurements performed in the best experimental conditions on a wide set of samples of different thermal properties (thin isotropic and anisotropic plates and filaments) confirm the validity of the slope method to measure accurately the thermal diffusivity of samples of these shapes.
光热辐射测量法已被广泛用于测量块状材料的热扩散率。对于薄板和细丝的情况，已开发出一种包含热损失的一维热传播模型，该模型预测可通过记录表面温度幅值和相位分布斜率（“斜率法”）来获得热扩散率。然而，这种方法给出的低导热薄膜和细丝的热扩散率值被高估了很多。在本文中，我们使用红外热成像分析影响薄板和细丝热扩散率测量的实验因素的作用，以便确定使用斜率法获得任何材料准确可靠的扩散率值所需的实验条件。我们给出了由调制且紧密聚焦的激光束加热的各向同性和各向异性薄板表面温度的计算结果，表明斜率法对于这种点状加热也是有效的。特别关注表面热损失（对流和辐射）对小尺寸和低导热材料扩散率测量的影响。在最佳实验条件下对一系列具有不同热性质的样品（各向同性和各向异性薄板及细丝）进行的锁相热成像测量证实了斜率法准确测量这些形状样品热扩散率的有效性。
