Experimental investigations on thermal diffusivity of heterogeneous materials

Abstract

The paper presents alternative methods for determining thermal diffusivity of heterogeneous materials. In the study the thermal regular regime method and the step-heating technique were applied to measure the thermal diffusivity of graphene oxide/rubber composites characterized by different kinds of basic matrix and different weight concentrations of the reduced graphene oxide nanoparticles. Thermal diffusivity plays a relevant role in the analysis of transient heat transfer processes. It is an essential material property which may be a measure of the quality of different kinds of engineering materials. Therefore, the knowledge of thermal diffusivity is important, especially for what heterogeneous materials (composites) concerns. In the present study composites with three kinds of matrix - have been studied: FKM- fluoroelastomer, NBR- acrylonitrile butadiene rubber and HNBR- hydrogenated acrylonitrile butadiene rubber. The reduced graphene oxide rGO in the form of crumpled flakes was used as filler in order to significantly influence the thermophysical properties of the composites. In the two tested experimental methods, - thermal regular regime method and step-heating technique, relatively large material samples were used. Hence, the influence of the material heterogeneity on the investigation results immaterial. The obtained results, both from thermal regular regime method and step-heating technique, show an increase of the thermal diffusivity with increasing the graphene oxide content in the composite. An uncertainty analysis of the results of applied research methods has been carried out, as well as measurements of the heat capacity of the matrix of two composites using differential scanning calorimetry to validate the thermal diffusivity results from the values of thermal conductivity and density.