Highly Reactive Thermite Energetic Materials: Preparation, Characterization, and Applications: A Review

Abstract

As a promising kind of functional material, highly reactive thermite energetic materials (tEMs) with outstanding reactive activation can release heat quickly at a high reaction rate after low-energy stimulation, which is widely used in sensors, triggers, mining, propellants, demolition, ordnance or weapons, and space technology. Thus, this review aims to provide a holistic view of the recent progress in the development of multifunctional highly reactive tEMs with controllable micro/nano-structures for various engineering applications via different fabricated techniques, including the mechanical mixing method, vapor deposition method, assembly method, sol-gel method, electrospinning method, and so on. The systematic classification of novel structured tEMs in terms of nano-structural superiority and exothermic performance are clarified, based on which, suggestions regarding possible future research directions are proposed. Their potential applications within these rapidly expanding areas are further highlighted. Notably, the prospects or challenges of current works, as well as possible innovative research ideas, are discussed in detail, providing further valuable guidelines for future study.

Keywords: broad prospects; energetic materials; exothermic performance; nanostructures; systematic classification; thermites.

Figure 7

(a) The steps for preparing Al/Fe₂O₃ energetic nanocomposites [94] Copyright 2012, Journal of Applied Physics, SEM images ((b) top view and (c) cross-section view) of the Co₃O₄ nanorods; SEM images ((d) top view and (e) cross-section view) of the Al/Co₃O₄ nEMs [96] Copyright 2012, Combustion and Flame, and (f) the schematic of the synthesis procedure for 3D ordered macroporous (3DOM) R_XO_Y nanothermite films, (R = Fe, Co and Ni) [98] Copyright 2016, Materials and Design.

Figure 8

(a) Optical image of 3D printing process for channels (left) and hurdles (right) composed of silver nanoparticle ink, (b) schematic illustration of the electrophoretic assembly process of Al/CuO EMs onto the electrode surfaces, (c) optical images (top view) of a channel, (d) hurdle architectures after deposition of Al/CuO film, (e) optical image of four kinds of channel and hurdle structures, followed by the corresponding combustion process and the resultant pressurization region and expansion process illustration [104] Copyright 2016, Advanced Materials; (f) the schematic diagram of the fabrication of superhydrophobic Al/Bi₂O₃ films, the SEM images ((g) low resolution and (h) high resolution) of product, and (i) the thermal stability property of product after different exposure time. Inset, DSC and ignition tests reveal the exothermic performance of products before and after two years exposure [111], Copyright 2018, Chemical Engineering Journal.

Figure 1

The classification, application and preparation process of highly reactive tEMs.

Figure 2

Field emission scanning electron microscopy (FESEM) image (a,b) of Al/Fe₂O₃ nEMs by soft template self-assembly with sol-gel process [46] Copyright 2015, Journal of Solid State Chemistry, a comparative visual observation of laser melting method process on a thick layer of (c) Al powder and (d) Al/5 wt% Fe₂O₃ powder mixture [47] Copyright 2012, Advanced Engineering Materials, the (e) FESEM and (f) transmission electron microscope (TEM) image of self-assembled Al/Fe₂O₃ nEMs, and followed by the (g) and (h) TEM images of physically solvent-mixed Fe₂O₃ nanotubes-Al nanoparticles sample [48] Copyright 2010, Combustion and Flame.

Figure 3

Typical FESEM image (a,b) of Al/CuO EMs by electrochemical and magnetron sputtering method [22] Copyright 2021, Journal of Alloys and Compounds, typical FESEM images with low (c) and high (d) resolution of the superhydrophobic Al/CuO energetic films [54] Copyright 2018, Materials Letters, (e) the 3D porous CuO prepared bycolloidal crystal template of polystyrene microspheres [56], followed by (f) the 3D Al/CuO EMs after magnetron sputtering of Al with different thicknesses of (f) 200 nm, (g) 100 nm, and (h) 300 nm, respectively. Copyright 2020, Chemical Engineering Journal.

Figure 4

The schematic diagram of the synthesis process for 3D porous superhydrophobic Al/Ni EMs [69]. Copyright 2016, Applied Surface Science.

Figure 5

Schematic illustrations of the core-shell n-Al@EMOFs tEMs: (a) the polymerization of dopamine; (b) the formation of EMOFs; (c) metal-chelating reactions between PDA and metal ions; (d) the overall preparation procedure [75]. Copyright 2020, Chemical Engineering Journal.

Figure 6

Schematic illustration of (a) quaternary Al/CuO/PVDF/RDX microspheres [86] Copyright 2021, Chemical Engineering Science, and (b) quaternary NC/GO/Al/KClO₄ nEMs [87], respectively. Copyright 2021, Combustion and Flame.

Figure 9

(a) The optical and SEM image of pure NC, NC/Al (50 wt%) and NC/Al-CuO (50 wt%), followed by the respective burning static snapshot [120] Copyright 2012, ACS Applied Materials Interfaces, and (b) the general procedures for the preparation of n-Al@PVDF/EMOF (DHBT) [121] Copyright 2020, Chemical Engineering Journal.

Figure 10

(a) Possible mechanisms of the burning of Al/CuO/NC nEMs made from physical mixing and electrospray. Note: Al (red); CuO (green); nitrocellulose (light blue) [142] Copyright 2014, Combustion and Flame, (b) the schematic illustration showing an exaggerated perspective that demonstrates random versus ordered assembly [48] Copyright 2010, Combustion and Flame, (c) schematic illustration of Al/CuO thermite reaction steps. Condensation of gasified Cu species on Al NPs hamper’s reaction of Al NPs with neighboring CuO NPs [88] Copyright 2015, Combustion and Flame, and (d) combustion process of Al/NiO nEMs [131] Copyright 2020, Chemical Engineering Journal.