Thermal Diffusivity and Conductivity of Fe₃O₄Scale Provided by Oxidation of Iron

The thermal diffusivity and conductivity of Fe3O4 scale have been determined with the laser flash method. Fe3O4 scale was provided by oxidation of iron plates at 823 K in Ar containing 0.84%H2 and 15.6%H2O. The scale was characterized by scanning electron microscopy and X-ray diffraction analysis for high temperature use to identify the phase of the scale. The thermal diffusivity and conductivity derived for the Fe3O4 scale decrease from 1.1 × 10-6 m2s-1 to 4.1 × 10-7 m2s-1 and from 3.5 Wm-1K-1 to 1.7 Wm-1K-1, respectively, with increasing temperature from room temperature to 676 K. The effective thermal conductivity of iron oxide scale with Fe3O4 has been evaluated assuming that Fe3O4 occupies 30% of the total scale thickness, suggesting the impact of the presence of Fe3O4 is about ten percent.