Mechanically activated combustion synthesis and shockwave consolidation of magnesium silicide

Abstract

Magnesium silicide (Mg 2 Si) is a promising intermetallic compound for applications such as light-weight composite materials and thermoelectricenergy conversion.It is difficult, however, to synthesize high-quality Mg 2 Si on a large scale. Self-propagating high-temperature synthesis (SHS) is an attractive pathway, but it is difficult to ignite the low-exothermic Mg/Si mixtureand achieve a self-sustained propagation of the combustion wave. In the present paper, mechanical activation was used to facilitate the ignition. Magnesium and silicon powders were mixed and then milled in a planetary ball mill in an argon environment. The mixtures were compacted into pellets and ignited at the top in a reaction chamber filled with argon. Depending on the pellet dimensions and diameter-to-height ratio, two modes of combustion synthesis, viz.,thermal explosion and SHS, were observed. In both modes, Mg 2 Si product was obtained. Thermocouple measurements have revealed that the exothermic reaction stages include two self-heating events separated by a long period of relatively slow interaction. To clarify the reaction mechanisms, differential scanning calorimetry was used, which also revealed two peaks of exothermic reaction in the milled Mg/Si mixture. The first peak is explained by the effect of mechanical activation. Explosive-based shockwave consolidation was used to increase the product density. Thermophysical properties of the obtained material were determined using a laser flash apparatus.

Mechanical Alloying: A Novel Technique to Synthesize Advanced Materials

“…Successful consolidation of MA powders has been achieved by electrodischarge compaction, plasma-activated sintering, shock (explosive) consolidation [70], HIP, hydrostatic extrusion, strained powder rolling, and sinter forging [71]. By utilizing the combination of high temperature and pressure, HIP can achieve a particular density at lower pressure when compared to cold isostatic pressing or at lower temperature when compared to sintering.…”

A Review on Doped/Composite Bismuth Chalcogenide Compounds for Thermoelectric Device Applications: Various Synthesis Techniques and Challenges

“…76,77 The current procedure can be adapted mainly for inorganic materials such as bismuth, indium, tellurium, and selenium. [78][79][80] SHS synthesis offers advantages including a one-step process, scalable nature, and maintenance of stoichiometry, making some of the thermoelectric materials very popular. 74,81 In the SHS process between binary reactants, the combustion reaction continues in the mode of diffusion, and the reaction rate is partly through the second reactant diffusion.…”

Self-propagating high-temperature synthesis of advanced materials and coatings

“…It is not surprise that approaches similar to those used for aluminides and nickelides, are also applied for SHS of silicides. Among them are production of monolith dense silicide materials by combination of SHS and HP [229,230] and MA by ball milling [231,232]. Shock-wave consolidation applied during SHS of magnesium silicide yielded product with 88% theoretical density [232].…”