Dense Mosi2 produced by reactive flash sintering: Control of Mo/Si agglomerates prepared by high-energy ball milling

The objective of this work is to determine the influence of the agglomeration state of the MA mixture on the microstructure and the chemical composition of SPS end-products. In order to produce MoSi2 with a microstructure and a density perfectly controlled via reactive sintering implying an SHS reaction, the characteristics of Mo/Si mechanically activated (MA) powder mixtures were investigated. Indeed, the MA powders have been characterized in terms of their surface specific area, size, phase composition and microstructure. The high-energy milling allows the formation of agglomerates (0.8 to 800 μm) composed of nanometric crystallites of molybdenum and silicon, as a consequence of a continuous fracture-welding process. This enhances the reactivity of powder mixtures due to an increase of interface number. The simultaneous synthesis–consolidation in one step could be performed using the spark plasma sintering (SPS) process. This study was performed on three agglomerate sizes: ∅ < 125 μm, ≤125 μm < 250 μm and ≥ 250 μm.

Graphical AbstractSEM observations of MoSi2 prepared by SPS at the Si melting temperature (1414 °C), 400 °C/min, 100 MPa and without holding time at the sintering temperature for different granulometric classes: mixture, ϕ < 125 μm, 125 < ϕ < 250 μm and, ϕ > 250 μm. Black zones are relative to the porosity, grey zones correspond to the MoSi2 phase whereas the grey zone corresponds to the secondary phase Mo5Si3.Figure optionsDownload as PowerPoint slide