GRK 2802: Influence of Sample Preparation and Processing Procedures on the Thermal Diffusivity of MgO-C Refractories

Abstract

Reliable measurement of thermal diffusivity of MgO-C refractories is impeded by diverse sample preparation and processing procedures. In this study, the impacts of coking sequence, machining conditions, microstructural inhomogeneity, and graphite coating on the results obtained using the laser flash apparatus at room temperature are systematically evaluated. Specifically, machining samples after coking prevents surface oxidation compared with machining before coking. Mechanical damage is reduced by water-assisted machining, resulting in increased thermal diffusivity. However, when applied before coking, water-assisted machining leads to brucite formation, and thermal diffusivity is consequently decreased. Furthermore, uniaxial pressing induces microstructural inhomogeneity, with finer grains on the surface, thereby lowering thermal diffusivity. Uncoated samples overestimate thermal diffusivity compared with graphite-coated ones due to MgO translucency. To clarify these mechanisms, complementary analyses including phase, microstructural, and compositional characterization were performed to support these findings. The results demonstrate that the optimal preparation of MgO-C samples for measurements using the laser flash apparatus involves coking first, followed by water-assisted machining, and subsequent graphite coating. Such a preparation procedure enhances measurement reliability, providing practical guidance for standardized thermophysical property evaluation of MgO-C refractories.