Combustion of Environmentally Altered Molybdenum Trioxide Nanocomposites

Abstract

Nanocomposite thermite mixtures are currently under development for many primer applications due to their high energy densities, high ignition sensitivity, and low release of toxins into the environment. However, variability and inconsistencies in combustion performance have not been sufficiently investigated. Environmental interactions with the reactants are thought to be a contributing factor to these variabilities. Combustion velocity experiments were conducted on aluminum (Al) and molybdenum trioxide (MoO 3 ) mixtures to investigate the role of environmental interactions such as light exposure and humidity. While the Al particles were maintained in an ambient, constant environment, the MoO 3 particles were exposed to UV or fluorescent light, and highly humid environments. Results show that UV and fluorescent lighting over a period of days does not significantly contribute to performance deterioration. However, a humid environment severely decreases combustion performance if the oxidizer particles are not heat-treated. Heat treatment of the MoO 3 greatly increases the materials ability to resist water absorption, yielding more repeatable combustion performance. This work further quantifies the role of the environment in the decrease of combustion performance of nanocomposites over time.

Combustion Wave Speeds of Sol−Gel-Synthesized Tungsten Trioxide and Nano-Aluminum: The Effect of Impurities on Flame Propagation

“…It also should be noted that the bonded water (or chemisorbed water) is actually separated from the Al particles because it is bonded to the WO 3 particles (and inherent in the WO 3 synthesis process). In contrast, humidity-induced Al oxidation (which is a relatively slow process and usually associated with the degradation of the Al combustion performance with aging) is a completely different phenomenon because the water molecules that are derived from environmental humidity are “attached” to the Al particles. In this way, the oxidation processes are different because, for humidity-induced oxidation, the water is directly diffusing into Al particles through the alumina shell, whereas the bonded water must first separate molecularly from their WO 3 host prior to diffusing toward the Al particles.…”

Nanoenergetic Materials for MEMS: A Review

“…The easiest method is the physical powder mixing. In recent works, the ultrasonic mixing is mostly employed to combine nano-Al and oxidizer powder [40], [47]- [50], [54]- [56]. Typically, the nano-Al and oxidizer are dispersed in solvents (e.g., hexane) and mixed together with ultrasonic wave.…”

Highly Exothermic and Superhydrophobic Mg/Fluorocarbon Core/Shell Nanoenergetic Arrays

“…It was reported that after treating MoO 3 nanoparticles in 99% relative humidity atmosphere for 1 day, the Al/MoO 3 nanocomposite exhibited a reduction in burn velocity of over 99%. 41 The humidity of air differs according to locations and climates. Consequently, concerns arise in that while the freshly prepared nanocomposites are capable of superior properties, the performance can degrade significantly after long-distance transportation and/or long-term storage.…”

“…Some widely used oxidizers are hydrophilic (e.g., CuO) or even hygroscopic, which makes performance maintenance a big issue. It was reported that after treating MoO 3 nanoparticles in 99% relative humidity atmosphere for 1 day, the Al/MoO 3 nanocomposite exhibited a reduction in burn velocity of over 99% . The humidity of air differs according to locations and climates.…”