Characterization of condensed phase beryllium species in the presence of aluminium and silicon matrices during electrothermal heating on graphite and tungsten platforms

Abstract

Condensed phase beryllium species occurring on graphite and tungsten platforms in the presence of aluminium and silicon matrices were characterised over a wide temperature range. The solid residue was viewed by scanning electron microscopy (SEM), while the chemical composition was probed by energy dispersive (ED) X-ray spectrometry (XRS), Fourier transform-infrared (FT-IR) spectrometry and Raman microanalysis. Beryllium oxide phases were found to be the predominant species over a wide temperature range, persisting up to about 1800 °C on the graphite platform. Beryllium metal species were also identified at high temperatures (1500 °C), but the transformation of beryllium oxide to beryllium was influenced by the amount and localised behaviour of concomitant species on the platform surface. For graphite platform atomisation, aluminium and silicon concomitants are present as metal oxides. Other silicon species, such as silicon carbide, were found mainly at temperatures above 900 °C. Little or no beryllium oxide was found on tungsten platforms up to 1800 °C, although there was evidence of some beryllium alloyed to tungsten. Tungsten from the platform supports some hydration forming different tungsten oxidation states (W⁶⁺, W⁵⁺, W⁴⁺). Also, at 900 °C, silicon was present as an oxide, but also as elemental silicon, silicon carbide, and silicon alloyed to tungsten forming tungsten disilicide at the surface interface. When tungsten platform atomisation was used for samples containing silicon, evidence of degradation of the graphite tube through formation of carbon clusters and nanostructures was more easily noticeable and evaluated by Raman spectrometry.