Study on the Obtaining of MnSi1.75 Intermetallic Compound by Mechanical Alloying

Thermoelectric higher manganese silicide (HMS) having the composition MnSi1.75 material was obtained by mechanical alloying after 18 hours of milling. As starting materials, manganese and silicon elemental powders were used. After 18 hours of milling beside the HMS in the powders, MnSi phase was obtained as well. After only 4 hours of milling, both binary MnSi phases are found in material besides a significant amount of non-reacted elements. Milling up to 10 hours leads to the silicon characteristic peaks disappearance and the HMS and MnSi phases amount increase. Subsequent annealing of the milled powders was performed in order to promote internal stresses removal. The 4 hours annealing of the powder at the temperature of 350 °C under high vacuum (10−6 Torr) leads to stress release and an increase in the MnSi phase quantity. The particle size analysis shows that the powder diameter is in 0.1-125 μm range. A large amount of powder is in the range of 15-125 μm, but there is also a small amount that is in the 0.1-15μm range. Scanning electron microscopy (SEM) was used to characterize the powders morphology.