Preparation and TG—DTA analysis of manganese silicon nitride

Manganese silicon nitride was prepared quantitatively as a precipitated phase by treating a Mn; Si-alloy (Mn: 1.84 w/o, Si: 1.12 w/o) in a mixture of 2% NH₃ and H₂ at 700°C. Nitriding was carried out in situ in a thermobalance and the nitrogen uptake was recorded as a function of time. The nitride phase was isolated and investigated by means of the combined TG-DTG-DTA technique both in an atmosphere of nitrogen at 25–1600°C and in a mixture of Ar+O₂ (p_O2 = 0.20 atm) at 25–1000°C. In the nitrogen atmosphere MnSiN₂ appears to be stable up to 1000°C. Oxidising the nitride in the Ar/O₂ mixture caused three distinct exothermic processes to occur at characteristic temperatures. The final oxidation products as identified by diffractometry and IR-spectroscopy are manganese oxide silicate (braunite) and silicon dioxide.