Thermal Diffusivity and Conductivity of Fe₃O₄ Scale Provided by Oxidation of Iron

抄録

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.