The Effect of the Mg Content on Mechanosynthesis of ZrB۲–SiC–ZrC Composite in the Mg/ZrSiO۴/B۲O۳/C System

The influence of magnesium content on the mechanosynthesis of ZrB۲–SiC–ZrC composite in Mg/ZrSiO۴/B۲O۳/C mixture was investigated. Thermodynamic evaluations revealed that the amount of Mg played a main role, thereby; the overall reaction enthalpy and adiabatic temperature (Tad) changed by variation of magnesium content. According to differential thermal analysis (DTA) results, after ۴۵min milling, the temperature of combustion reaction decreased to ۵۷۶ ◦C and all the reactions occurred, simultaneously. The experimental findings indicated the type of reactions in the mixture powder with stoichiometric ratio (۷mol Mg) was mechanically induced self-sustaining reaction (MSR). When the Mg content was within a range of ۶-۷mol, the magnesiothermic reduction was occurred in MSR mode and the carbothermal reaction was activated, hence; the carbon acted not only as a carbide former agent but also as a reductant. MSR mode magnesiothermic reduction and gradual carbothermal reduction were occurred when the Mg value was ۱۱/۲-۶ mol. At lower Mg contents in mixture (۵mol), the reduction reaction proceeded through a gradual mode and no carbothermal reaction occurred.

کلیدواژه ها:

Mechanochemical processing ، Magnesiothermic reaction ، Carbothermal reduction ، Composites ، ZrB۲