Usually, mechanochemical reactions between solid phases are either gradual (by deformation-induced mixing), or self-propagating (by exothermic chemical reaction). Here, by means of a systematic kinetic analysis of the Bi–Te system reacting to Bi2Te3, we establish a third possibility: if one or more of the powder reactants has a low melting point and low thermal effusivity, it is possible that local melting can occur from deformation-induced heating. The presence of hot liquid then triggers chemical mixing locally. The molten events are constrained to individual particles, making them distinct from self-propagating reactions, and occur much faster than conventional gradual reactions. We show that the mechanism is applicable to a broad variety of materials systems, many of which have important functional properties. This mechanistic picture offers a new perspective as compared to conventional, gradual mechanochemical synthesis, where thermal effects are generally ignored.

Melt-driven mechanochemical phase transformations in moderately exothermic powder mixtures

Delogu, Francesco;
2016

Abstract

Usually, mechanochemical reactions between solid phases are either gradual (by deformation-induced mixing), or self-propagating (by exothermic chemical reaction). Here, by means of a systematic kinetic analysis of the Bi–Te system reacting to Bi2Te3, we establish a third possibility: if one or more of the powder reactants has a low melting point and low thermal effusivity, it is possible that local melting can occur from deformation-induced heating. The presence of hot liquid then triggers chemical mixing locally. The molten events are constrained to individual particles, making them distinct from self-propagating reactions, and occur much faster than conventional gradual reactions. We show that the mechanism is applicable to a broad variety of materials systems, many of which have important functional properties. This mechanistic picture offers a new perspective as compared to conventional, gradual mechanochemical synthesis, where thermal effects are generally ignored.
Chemistry (all); Medicine (all); Materials Science (all); Condensed Matter Physics; Mechanics of Materials; Mechanical Engineering
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11584/196024
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