DC ARC SPECTROSCOPIC STUDY OF THERMOCHEMICAL REACTIONS OF MODIFIERS IN SIC CERAMICS

The aim of this work was to clarify the process of evaporation of impurity elements from silicon carbide powder of industrial purity under the action of thermochemical additives, as a step towards the development of a method for the direct determination of all impurities. Considering the influence of classical additives - (C2F4)n, AgCl, CuCl, PdCl2 on both evaporation and excitation processes, the idea was developed of a modification of the matrix itself to more easy volatile compounds, allowing the impurities to be released. A complex modifier CoF2 + Ba(NO3)2 was used for that purpose. The evidence for its effective action is a complete evaporation of the elements Al, Fe, Cu, Ti, Va, Mo and B during the first 10 - 20 s of arcing. The mechanism of the action of a modifier was studied using a thermodynamic evaluation of thermochemical processes that take place in the electrode crater. The mechanism supposed is supported by scanning electron microscopy images of residues in the crater.