Melt-driven mechanochemical phase transformations in moderately exothermic powder mixtures

• Main Authors: Garroni, Sebastiano (Author), Delogu, Francesco (Author), Humphry-Baker, Samuel A (Contributor), Schuh, Christopher A (Contributor)
• Other Authors: Massachusetts Institute of Technology. Department of Materials Science and Engineering (Contributor), Schuh, Christopher A. (Contributor)
• Format: Article
• Language: English
• Published: Springer Nature, 2017-12-08T15:15:07Z.
• Subjects: Article
• Online Access: Get fulltext

 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.