Self-Propagating High-Temperature Synthesis as an Enabling Route for High-Entropy MAX Phases

Established methods for MAX phase synthesis face limitations in achieving high-entropy configurations. Thermodynamic stability windows for HE-MAX phases are narrow, complicating synthesis. Binary and ternary carbides often compete with HE-MAX phases during processing. Volatility of A-site elements under equilibrium conditions further hinders synthesis. Current approaches struggle with multicomponent diffusion and entropy-driven stabilization. Non-equilibrium methods may offer alternative routes to overcome these constraints. SHS has been explored in other materials systems but not fully applied to HE-MAX phases. This review addresses the need for scalable and energy-efficient synthesis of HE-MAX phases.

This review aims to evaluate SHS as a viable route for HE-MAX phase synthesis. The study addresses the challenge of stabilizing entropy-driven MAX phase chemistries. It proposes a thermodynamic-kinetic framework to guide SHS processing of HE-MAX phases. The goal is to delineate phase stability boundaries and reaction sustainability. The paper seeks to correlate adiabatic temperature predictions with experimental outcomes. It also aims to outline scalable design principles for SHS-based HE-MAX synthesis. The review includes strategies for exfoliation into high-entropy MXenes. Finally, it assesses the functional potential of HE-MAX phases in emerging applications.

The review integrates experimental SHS studies with thermodynamic modeling. A unified framework is developed to analyze reaction enthalpy and configurational entropy. The combustion wave sustainability is evaluated using adiabatic temperature predictions. Phase evolution is studied through correlations with experimental data. The roles of diluents and transient liquid formation are systematically analyzed. The study compares predicted and observed phase boundaries in HE-MAX systems. Stoichiometric sensitivity is assessed in the context of SHS processing. The review also incorporates critical assessments of functional applications.

SHS is shown to enable stabilization of entropy-driven MAX phase chemistries. Ultrafast thermal excursions and rapid quenching are key to phase stabilization. Adiabatic temperature predictions align with experimental phase stability boundaries. Binary and ternary carbides are less favored under SHS conditions. Diluents and transient liquid formation influence phase evolution in HE-MAX systems. Stoichiometric sensitivity is reduced under non-equilibrium processing. Scalable design principles for SHS synthesis of HE-MAX phases are outlined. Strategies for exfoliation into high-entropy MXenes are proposed.

SHS offers an energy-efficient route for HE-MAX phase synthesis. The review highlights the role of ultrafast thermal excursions in stabilizing HE-MAX phases. Combustion wave sustainability is critical for successful SHS processing. Adiabatic temperature predictions correlate with experimental phase boundaries. Diluents and transient liquid formation are important for phase evolution. The study outlines scalable design principles for SHS-based synthesis. Exfoliation into high-entropy MXenes is a promising application direction. The review provides a foundation for future work on functional HE-MAX applications.