BS ISO 19618:2017,Fine ceramics (advanced ceramics, advanced technical ceramics) – Measurement method for normal spectral emissivity using blackbody reference with an FTIR spectrometer.
ISO 19618:2017 specifies a method used for the determination of normal spectral emissivity and normal quasi-total emissivity of fine ceramics using blackbody reference with a Fourier transform infrared spectrometer (FTIR) at elevated temperatures. This method is applicable to fine ceramics, ceramic matrix composites, and continuous fibre-reinforced ceramic matrix composites which are opaque and highly non-reflective at wavelengths between 1,67 μm and 25 μm. The applicable temperature range is approximately 350 K to 1 100 K.
The infrared radiance spectrum data from a specimen surface and from a blackbody furnace are measured using an FTIR spectrometer. The normal spectrum emissivity of a specimen is determined by direct comparison to a blackbody reference data at the same temperature.
5 Apparatus
5.1 Measurement system
The measurement system consists of a Fourier transform infrared spectrometer(FTIR),specimen heating device, blackbody furnace, and temperature measuring devices as shown in Figure l.
5.2 Fourier transform infrared spectrometer (FTIR)
Infrared radiation from a specimen or a blackbody furnace is let into a Mickelson interferometer of an FTIR through an external optical path. Thereby, an interferogram of infrared radiation is obtained. The infrared radiance spectrum is obtained numerically by Fourier transformation processing from the interferogram.
The optical system including a Mickelson interferometer of an FTIR shall be filled with dry N2 or dry air of which the dew point is lower than 220 K to reduce the effect of H2O and CO2 in air. Vacuum may be used.
The measurement spot area at the sample position and at the blackbody furnace positions shall be measured preliminarily.