Infrared normal emissivity measurement of graphite by integrated blackbody method incorporating modified flight time variation

Abstract

The integrated blackbody method is an emissivity measurement method that does not require independent measurement of the true temperature of the sample surface. In this method, the sample flies rapidly from the bottom of the cavity to the mouth of the cavity, and this rapid flight will cause a temperature drop on the sample surface, which will produce a non-negligible negative deviation of the emissivity measurement. At present, the temperature drop and emissivity of sample 0 flight time cannot be measured by experiments. Therefore, to study the influence of surface temperature drop caused by sample flight, an experiment design that can change sample flight time is proposed in this paper, and a corresponding experimental system is established. By adjusting the pulse value of the linear motor, the sample flight time can be adjusted to (147–1604)ms when the flight distance is 180 mm. Then, taking graphite material as an example, the experiment of sample flight temperature drop was carried out with the wavelength of 0.65 μm and temperature of 1573 K. The result with 0 flight time was obtained by extrapolation, and the correction factor of sample temperature drop was calculated for different flight times, with the wavelength region of (0.65–13.00) μm. Finally, the emittance measurement experiment from 3.00 μm to 13.00 μm was carried out, and the temperature drop correction factor was applied to correct the results.