Combustion Mechanisms of Complex Metal Particles

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The objective of this work is to establish the mechanisms of combustion of complex metal particles consisting of two different metals, typically an aluminum core covered by another metal such as nickel, titanium or zirconium, in inert or oxidizing atmospheres. The study includes the fundamental processes that control ignition and combustion of single particles and propagation of reaction waves in clouds of particles. Influences on combustion of chemistry, morphology (size and shape), and concentration of particles, as well as composition of the gas phase, are clarified on both the microscopic (single particle) and macroscopic (particle cloud) scales. To do this, advanced experimental techniques are developed based on electrodynamic levitation and electrodynamic fluidization. Also, computer-assisted electrothermography of complex metal wires is used to obtain kinetic data on metal-metal and metal-gas reactions. These data provide a basis for modeling combustion of complex metal particles, accounting for such characteristics as intermetallic reactions and cracking of solid shells.The results of this work are directly relevant for applications in both materials synthesis and propulsion. Combustion of particle suspensions in gas is an attractive method for continuous production of intermetallic compounds. Complex metal particles in rocket propellants offer reduced agglomeration and lower ignition temperature than pure aluminum.