Thermite combustion: Current trends in modeling and future perspectives

Aluminum-based reactive composites, such as thermites, represent a unique class of energetic materials characterized by their high energy densities, tunability in combustion properties and safety. Prepared using techniques such as mechanical mixing, milling, and physical vapor deposition, these materials are promising for achieving energetic functions beyond the capabilities of traditional energetic materials. Applications include thermal plugging, smart initiation, pyro-fusing in civilian devices where the use of explosives is not feasible. Unfortunately, engineers and researchers face the lack of predictive combustion models to optimize the thermite materials to a given application. The reason is the insufficient knowledge and quantification of reaction and combustion mechanisms and the key variables governing them. That is why, over the past decades, several approaches and models ranging from atomic-scale modeling to macroscopic simulations using computational fluid dynamics, were developed and are reviewed in this article. These methods provided insights into key reaction pathways, ignition mechanisms, and flame propagation dynamics. Despite these advancements, substantial gaps remain, particularly in capturing multiphase flow dynamics and suboxides condensation/nucleation process during the combustion at high temperature. Boundary-resolved transient direct numerical simulation approach and particle-resolved numerical techniques will allow acquiring knowledge in gas–particle and particle–particle interaction. Recent breakthroughs in machine learning will further accelerate the design and optimization of thermites by enabling the establishment of predictive quantitative structure–property relationships in complement of heavy detailed physical models. This review highlights foundational theoretical developments for thermite materials, and emphasize the need for interdisciplinary efforts particularly between fluid dynamicists and condensed matter physicists to realize the full potential of these versatile energetic materials.