Emissivity characteristics of boron and boric oxide at high temperatures

The spectral emissivity of boron at wavelengths $\lambda$ = 0.45–6 $\mu$m during ignition and combustion was determined experimentally. The spatial resolution was not lower than 100 $\mu$m. Liquid boric oxide, boron filaments 100 $\mu$m in diameter, and artificially made agglomerates of amorphous boron particles 2 mm in size and $\approx$1.22 g/cm$^3$ in density served as radiation objects. It was determined that, as the surface temperature increased from 1 490 to 2 800 K, the emissivity of boron in the examined range of wavelength decreased almost linearly in an interval of 0.35–0.20. At temperatures of 1400–2100 and wavelength of 0.65 $\mu$m, the absorption coefficient of liquid boric oxide was 2.2 $\pm$ 0.2 cm$^{-1}$.