2. Aluminum-Based Nano-energetic Materials: State of the Art and Future Perspectives

Technological innovations are indeed driven by enhanced abilities to understand and manipulate matter at molecular and atomic scale. Engineering energetic nanocomposites with tailored and tunable combustion characteristics is indispensable for their deployment in both civilian and defense applications. Specifically, a heterogeneous mixture of fuel [aluminum (Al), boron, magnesium, silicon, etc.] and oxidizer [cupric oxide, bismuth trioxide (Bi₂O₃), ferric oxide, etc.] with both the constituents having nanoscale dimensions constitutes a class of energetic material known as nanothermites. Among various fuels employed in nano-energetic formulations, the number of theoretical and experimental investigations on the utilization of Al outweighs that of any other metallic fuel. Knowledge on the physical and chemical characteristics of the constituents and their impact on combustion performance are fundamental to accelerate the pace of research and development in nano-energetic composites. Efforts to develop comprehensive understanding of the oxidation behavior are discussed in this article. Furthermore, the organization, intimacy, and dimensions of discrete fuels and oxidizers apart from their chemistry largely dictate the combustion kinetics exhibited by nanothermites. For a given nanocomposite, increasing the interfacial contact area between fuel and oxidizer improves its reaction rate by 3–5 orders of magnitude as a result of drastic reduction in mass and heat transport lengths. The bottom-up self-assembly process offers the most realistic solution to enhance the interfacial contacts between nanoscale constituents employing different approaches. This review summarizes the key findings in this area of research and lists the key challenges and opportunities for furthering the application aspects. Enhancement of combustion characteristics of energetic liquids through the utilization of Al and metal oxide nanoparticles as additives is another area of related research that continues to receive increasing attention (Sundaram et al. 2017). Energetic liquids possess unique characteristics such as lower activation temperature, higher pressure, and better volume expansion. Experimental research efforts have demonstrated ample promise for overcoming the inherent problems such as lower energy density and slow burn kinetics associated with energetic liquids. In gist, the central theme of this chapter is devoted to highlight and analyze the recent advancements on aluminum-based nano-energetic materials besides presenting the challenges and opportunities in the domain of nano-energetic materials development.