CONTRIBUTION TO THE CLARIFYING OF THE ACTION OF THERMOCHEMICAL ADDITIVES ON THE MODIFICATION OF A MATRIX SILICON-CARBIDE USING SCANNING ELECTRON-MICROSCOPY AND ENERGY-DISPERSIVE X-RAY-ANALYSIS

Previous investigations have shown that the total evaporation of impur ities from silicon carbide powder can be achieved by its thermochemica l transformation to BaSiO3, BaF2 and CoSi (CoSi2) under the action of the modifier CoF2 + BaO, through in situ processing in an electrotherm ally heated graphite crucible [13]. The aim of the present work has be en to describe a methodology to perform a rational selection of variou s potential candidates for modifiers, to make successful combinations between various chemical additives, to understand the reason(s) for an effective/ineffective action of a particular additive, i.e. to find t he optimum conditions for each type of ceramic matrix chemical modifie r. A combination of scanning electron microscopy (SEM), energy dispers ive X-ray analyses (EDX) and X-ray diffraction analyses was used to co nfirm the identification of the alterations to the silicon carbide mat rix. Indirectly, the present work supports the view that ''the aim jus tifies the means'' particularly when the aim is to reach a complete ev aporation of the impurities from a carbide matrix, which as is well kn own is not an ordinary or easy task.