Chao Wang,Ying Liu,Mingze Wu,Jia Li,Ying Feng,Xianjin Ning,Hong Li,Ningfei Wang,Baolu Shi
A novel design of micro-aluminum ( μ Al) powder coated with bi-/tri-component alloy layer, such as: Ni–P and Ni–P–Cu (namely, Al@Ni–P, Al@Ni–P–Cu, respectively), as combustion catalysts, were introduced to release its huge energy inside Al-core and promote rapid pyrolysis of ammonium perchlorate (AP) at a lower temperature in aluminized propellants. The microstructure of Al@Ni–P–Cu demonstrates that a three-layer Ni–P–Cu shell, with the thickness of ∼100 nm, is uniformly supported by μ Al carrier (fuel unit), which has an amorphous surface with a thickness of ∼2.3 nm (catalytic unit). The peak temperature of AP with the addition of Al@Ni–P–Cu (3.5%) could significantly drop to 316.2 °C at high-temperature thermal decomposition, reduced by 124.3 °C, in comparison to that of pure AP with 440.5 °C. It illustrated that the introduction of Al@Ni–P–Cu could weaken or even eliminate the obstacle of AP pyrolysis due to its reduction of activation energy with 118.28 kJ/mol. The laser ignition results showed that the ignition delay time of Al@Ni–P–Cu/AP mixture with 78 ms in air is shorter than that of Al@Ni–P/AP (118 ms), decreased by 33.90%. Those astonishing breakthroughs were attributed to the synergistic effects of adequate active sites on amorphous surface and oxidation exothermic reactions (7597.7 J/g) of Al@Ni–P–Cu, resulting in accelerated mass and/or heat transfer rate to catalyze AP pyrolysis and combustion. Moreover, it is believed to provide an alternative Al-based combustion catalyst for propellant designer, to promote the development the propellants toward a higher energy.
Chao Wang,Ying Liu,Kang Niu,Jia Li,Qing Cao,Xiuchen Zhao,Hongyang Li,Ningfei Wang,Baolu Shi
To improve the combustion efficiency of widely used micro-aluminum (μAl) particle, enhancing its ignition and combustion performances is a critical issue via breaking through the intrinsic Al 2 O 3 layer covering the Al-core. This study proposed a facile in-situ ‘one-pot’ electroless plating method to functionalize the surface of μAl particles with ternary-shelled nickel-phosphorus-copper alloy coating and furthermore investigated the thermochemical and ignition/combustion behaviors of energetic core–shell composites (defined as Al@Ni-P-Cu). The microstructure characterization results of Al@Ni-P-Cu demonstrated that a spherically distributed triple-shell Ni-P-Cu alloy with the thickness of 129 nm was tightly coated on μAl particle surface. Through TG-DSC analysis, the Al@Ni-P-Cu composites exhibited improved heat release (7597.7 J/g) and decreased initial oxidation temperature (814.3 °C) in comparison to that of μAl particle with 949.2 J/g and 960.1 °C, respectively. The Al@Ni-P-Cu exhibited extremely shorter laser ignition delay time of 36.3 ms under 1 MPa O 2 atmosphere, reducing by 86.86% compared with that of raw μAl particles (276.3 ms); and its maximum flame temperature could reach up to 1588.93 °C, increasing by 243.36 °C compared with that of μAl (1345.57 °C). The drastic improving performances were attributed to the synergistic effects of surface/interfaces reactions along with heat release in the core–shell structure, resulting in enhanced mass and heat transfer to facilitate the combustion of internal Al-core.
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