High-temperature interactions of transition-metal carbides with Na2SO4

Article abstract of DOI:10.1016/0022-5088(91)90325-X

The high-temperature (900-1200 K) interaction of transition-metal carbides namely Cr₇C₃, Fe₃C, TiC, ZrC, NbC, TaC, MoC, WC, VC and HfC with Na₂SO₄ has been studied in a stream of pure and dried oxygen gas. Thermogravimetric studies were carried out by measuring the weight change as a function of time and mole fraction of Na₂SO₄ in the reaction mixture. The presence of different constituents in the reaction products were identified by X-ray diffraction analysis and the morphologies of the reaction products were discussed on the basis of metallography, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). The quantitative determination of soluble metal species in the aqueous solutions of Na₂SO₄-transition-metal carbide products was carried out by atomic absorption spectroscopy. At high temperatures, transition-metal carbides interact with Na₂SO₄, forming metal oxides. The resulting metal oxide interacts with Na₂SO₄ forming a soluble sodium metal oxide or a metal sulphide depending upon the local condition prevailing during the reaction.