Kinetics and associated microstructure for reactive phase formation

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While solid-state reactions are employed for the processing of complex materials, the microstructural evolution that initiates from a compositionally inhomogeneous patterned structure has received little to no attention. For example, it has been recognized recently that it is possible to achieve such structures in systems having entropy-stabilized line compounds that are thermodynamically stable only above a certain critical temperature. To obtain a better understanding of the kinetics and product microstructures associated with reactions that initiate on a template, we employ here a reaction-diffusion formalism to model the microstructural evolution of the product phase produced via solid-state reaction from a starting, bi-phasic template. In particular, we connect the spatio-temporal evolution of the product phase with the geometry and chemistry of the starting duplex structure. The formalism employed here was developed for chemical systems and, in this context, we show that it enables an understanding of microstructural evolution associated with solid-state reactions. While we consider here idealized examples to highlight underlying processes, we also discuss how one can use the results to select judiciously templates to promote the formation of desirable microstructures and to quantify important experimental kinetic parameters that dictate observed patterns. Finally, we describe the use of our simulation methodology to extract important kinetic information from experimentally-generated product-phase microstructures resulting from solid-state reactions.