A Novel Measurement Method for Material Emissivity Under High Temperature

Accurate material emissivity measurements play an important role in many thermal and optical applications. In this work, we propose a novel method for measuring emissivity under high temperature. Its distinguishing feature lies in the employment of an occlusion tube, utilizing it to achieve the measurement both blackbody radiation and intrinsic radiation by determining whether the occlusion tube blocks the thermal radiation emitted from the blackbody furnace toward the test sample located at the bottom of the blackbody furnace. By establishing equations related to blackbody radiation, intrinsic radiation, emissivity, and the surface temperature changes of the sample during the processes of the occlusion tube descending and ascending, the emissivity of the sample is calculated. The accuracy of this method is verified by measuring the emissivity of a reference sample (oxidized Inconel alloy). The results show that the average deviation of the emissivity measured in this study is only 0.001 compared to the standard values at approximately $620~^{\circ }$ C ( $0.820~\to ~0.821$ ) and $820~^{\circ }$ C ( $0.830~\to ~0.829$ ), with the total measurement deviation ranging from −0.002 to 0.002 and from −0.002 to 0.004, respectively. These results suggest that this method provides a new and straightforward approach for measuring emissivity.