Quo Vadis, Nanothermite? A Review of Recent Progress

Abstract

One of the groups of pyrotechnic compositions is thermite compositions, so-called thermites, which consist of an oxidant, usually in the form of a metal oxide or salt, and a free metal, which is the fuel. A characteristic feature of termite combustion reactions, apart from their extremely high exothermicity, is that they proceed, for the most part, in liquid and solid phases. Nanothermites are compositions, which include at least one component whose particles size is on the order of nanometers. The properties of nanothermites, such as high linear burning velocities, high reaction heats, high sensitivity to stimuli, low ignition temperature, ability to create hybrid compositions with other high-energy materials allow for a wide range of applications. Among the applications of nanothermites, one should mention igniters, detonators, microdetonators, micromotors, detectors, elements of detonation chain or elements allowing self-destruction of systems (e.g., microchips). The aim of this work is to discuss the preparation methods, research methods, direction of the future development, eventual challenges or problems and to highlight the applications and emerging novel avenues of use of these compositions.

Keywords: energetic materials; high-energy materials; nanothermite; thermite.

Figure 1

Research stand for determination of laser radiation sensitivity of explosives. Reprinted from [58] with permission form Elsevier.

Figure 2

LASEM experimental setup with schlieren imaging and emission diagnostics. Reprinted from [75] with permission form Elsevier.

Figure 3

Schematic of ESD sensitivity tester. Reprinted from [93] with permission of John Wiley and Sons.

Figure 4

Schematic of T-Jump test idea and sequence of photos captured during the test. Reprinted from [105] with permission of John Wiley and Sons.

Figure 5

Flash ignition test idea and sequence of photos captured during the test: (a) Schematic; (b) optical images of the experimental setup; (c) Photographs of the combustion of an Al/CuO thermite. Reprinted from [121] with permission of Elsevier.

Figure 6

Sequence of photos captured during the flash ignition test. Photographs taken in 1 ms intervals, depicting the combustion of (A) Al/SnO₂–PAni-7.7 and (B) Al/SnO₂ thermites. Reprinted from [49] with permission of John Wiley and Sons.

Figure 7

Expanded view of the calorimeter assembly. Reprinted from [137] with permission of Springer Nature.

Figure 8

T-Jump/TOFMS probe. Reprinted with permission from [164]. Copyright 2010 American Chemical Society.

Figure 9

TOFMS time-resolved mass spectra obtained for Al/CuO nanothermite. Reprinted with permission from [164]. Copyright 2010 American Chemical Society.

Figure 10

Schematic of time integrated emission collection experiment using an unconfined pile of nano-thermite (a) and schematic of temporally resolved spectra and high speed camera data acquisition experiment using a thermite filled burn tube (b). Reprinted from [192] with permission of Elsevier.

Figure 11

High-speed microscopy images for the Al/I₂O₅: (a) high-speed microscopy images; (b) corresponding temperature maps as calculated by color ratio pyrometry. Reprinted from [196] with permission of Elsevier.

Figure 12

Schematic of the experimental setup. Reprinted from [198] with permission of Elsevier.

Figure 13

Schematic of the experimental setup for combustion wave speed measurement. Reprinted from [183] with permission of Elsevier.

Figure 14

Schematic of voltage divider circuit used for on-chip burn rate measurement. Reprinted from [215] with permission of Taylor & Francis.

Figure 15

Schematic of the experiment consisting of the pressure cell and attached diagnostics. Reprinted from [197] with permission of AIP Publishing.

Figure 16

Schematic of the experimental setup for pressure–time measurements (1) combustion chamber, (2) pressure sensor holder, (3) pressure sensor, (4) test material. (5) metal support, (6) hot wire. Reprinted from [183] with permission of Elsevier.

Figure 17

Schematic of the shock-tube setup used for the measurements. Reprinted from [16] with permission of AIP Publishing.

Figure 18

Schematic depiction of a DDT Tube; unit: inches. Reprinted from [229] with permission of Springer Nature.

Figure 19

Schematic depiction of the structure of the MEMS initiator. Reprinted from [247] with permission of AIP Publishing.