Diffusion triggered synthesis of Mg2Si based on infiltrated silicon structures in a molten Mg alloyThursday (08.10.2020) 15:50 - 16:10
The intermetallic compound Mg2Si is of great interest due to its potential applications in lithium-ion batteries, infrared sensors, solar cells, and especially thermoelectric devices. Mg2Si-based compounds are also interesting because of their non-toxicity, low cost constituents, good mechanical and chemical properties, as well as low density.
One possible manufacturing method for magnesium silicides is melting metallurgy. However, it is associated with some challenges: In particular, the difference between the melting temperature of silicon (θkf ≈ 1414 °C) and the boiling temperature of magnesium (θfg ≈ 1090 °C) needs to be mentioned in this context. Hence, common melting metallurgical methods result in large evaporation losses and oxidation of magnesium. In this study, this problem is addressed by splitting the processing route into several successive steps. Firstly, an open-pore cellular Si structure is fabricated by investment casting. In a further step, the cellular Si structure is infiltrated by a molten Mg alloy, followed by a subsequent thermal treatment. The attractive aspects in this context are the open-pore structure, which ensures a fluid exchange between the individual cells and, thus, the infiltration with molten metal, and the very large specific surface area, which promotes the diffusion process between the cellular structure and the infiltrated Mg alloys. Based on recent results, we study the formation of Mg2Si following from annealing experiments at high temperatures. SEM is used for observing the microstructure of the composites and EDX to determine the phase compositions of the diffusion layers.
PS: This work is part of the InSeL project