In recent years, micron-sized Al-based binary alloys have received much attention. A low-density polyethylene coating was synthesized to modify and activate Al, shorten the residence time of particles on the propellant surface, induce the microexplosion, and reduce agglomeration. The iron coating of the Al-based alloy powder was used to improve its thermal properties and aging stability. An Fe-Al composite powder with an electroless coating was prepared to improve the energy release rate of fuel. For example, coating a layer of nickel on the surface of Al microparticles to replace the alumina layer can increase the active Al content by ~4%. Another feasible strategy is to activate the surface of micron-sized Al or adopt surface coating to increase the active Al content. However, the incorporated polymer chemically reacts with Al, which can cause safety concerns when in storage. By adding other substances, such as a nanopolymer, into Al powder, the microexplosion of Al can be induced on the propellant surface, reducing sintering and agglomeration. Nanometer Al powder was used to replace micron-sized Al in propellants however, agglomeration and sintering still occurred, and a low active Al content and incomplete combustion reduced the comprehensive performance of the propellants. Many new strategies have been proposed to solve these problems. The results suggest that the addition of Li promoted the combustion performance of Al by changing the surface structure of the oxide film and the combustion mode. Finally, the ignition and combustion mechanism of the Al-Li alloy in air was demonstrated by combining SEM, EDS, and XRD analyses of the material and residues. The Al-Li alloy burned in N 2, but no microexplosion was observed. The combustion temperature of the Al-Li alloy at atmospheric pressure was slightly higher than those at elevated pressures. The ambient pressure had a significant effect on the ignition and combustion characteristics of the Al-Li alloy, and the ignition delay time and burn time exponentially decreased as the ambient pressure enhanced. Moreover, during combustion, a microexplosion occurred, which increased the combustion rate and reduced the burn lifetime. The emission lines of AlO revealed the gas-phase combustion of the Al-Li alloy, and thus the Al-Li alloy exhibited a mixed combustion mode, including surface combustion and gas-phase combustion. The TG-DSC results demonstrated that, as compared to the counterpart Al, the Al-Li alloy had a lower ignition temperature. The ignition probability, ignition delay time, flame propagation rate, burn time, combustion temperature, flame radiation spectra, and microexplosion characteristics were obtained. Then, the ignition and combustion characteristics of single micron-sized Al-Li alloy particles were investigated in detail using a self-built experimental apparatus and multiple characterization methods. To solve the problems associated with micron-sized aluminum (Al), including sintering, agglomeration, and slag deposition during the combustion of aluminized propellants, aluminum–lithium (Al-Li) alloy, prepared by introducing a small amount of Li (1.0 wt.%) into Al, was used in place of Al.
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