Emissivity characteristics of boron and boric oxide at high temperatures

The spectral emissivity of boron at wavelengths λ = 0.45–6 μm during ignition and combustion was determined experimentally. The spatial resolution was not lower than 100 μm. Liquid boric oxide, boron filaments 100 μm in diameter, and artificially made agglomerates of amorphous boron particles 2 mm in size and ≈1.22 g/cm³ 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 μm, the absorption coefficient of liquid boric oxide was 2.2 ± 0.2 cm⁻¹.