Thermal conductivity of oxide scale thermally grown on iron substrate corrected by temperature-dependent interfacial thermal resistance in laser flash measurement

Thermal conductivities of iron oxide scales have been determined in a temperature range of room temperature to 1 176 K by the laser flash method, where the interfacial thermal resistance between FeO and iron has been corrected for each temperature. Two series of samples were prepared from iron plates with 99.99% purity. One was samples with FeO scale only and the other was samples with multi-layered scale of Fe₂O₃/Fe₃O₄/FeO. The laser flash method was applied to measure apparent thermal diffusivities, which were converted to apparent thermal conductivities. Apparent thermal conductivities obtained are contaminated by the interfacial thermal resistance between scale and iron, and are in linear proportion to scale thickness. Using apparent thermal conductivities at room temperature, thermal conductivities of scale have been derived from the slope of the linearity as 2.4 Wm⁻¹K⁻¹ for FeO scale and 1.8 Wm⁻¹K⁻¹ for multi-layered scale, and interfacial thermal resistances have been derived from the intercept as 7.3×10⁻⁶ m²KW⁻¹ for the interface at FeO/iron and 6.4 × 10⁻⁶ m²KW⁻¹ for the interface at multi-layered scale/iron. The interfacial thermal resistance between FeO and iron decreases with increasing temperature. Considering these temperature-dependent interfacial thermal resistances, thermal conductivity values of FeO scale have been determined as a function of temperature. The values are roughly 2.2 Wm⁻¹K⁻¹ up to 1 176 K except 6.9 Wm⁻¹K⁻¹ at 674 K where the decomposition of FeO tends to take place.