Formation of Additive-Containing Nanothermites and Modifications to their Friction Sensitivity

Abstract

Nanothermites can provide high energy densities and reaction rates but can also display extreme friction sensitivities. Additives that provide friction modification offer the potential to reduce the friction sensitivity of nanothermites. In the present work, MoS 2 , graphene, and hexadecane additives were dispersed in MoO 3 prior to nanothermite formation with the aim of reducing friction sensitivity. Nanothermites were subsequently prepared using a palmitic acid-passivated nano-aluminum (L-Al) and additive-containing nano-MoO 3 by the resonant acoustic mixing of dry powders. In general, the incorporation of additives results in a reduction in friction sensitivity with the baseline minimum ignition friction rising from 10 to 120 N using 0.5% wt/wt micrometer-sized MoS 2 or 5% wt/wt hexadecane. However, the relationships between loading and performance are complex and vary by additive; for example, the friction sensitivity dependence using micrometer-diameter MoS 2 displays a maximum at 0.5% wt/wt and declines to 7 N using 5% MoS 2 .

Electrostatic Discharge Sensitivity and Resistivity Measurements of Al Nanothermites and their Fuel and Oxidant Precursors

“…Thermo-gravimetric analyses provided data suggestive of particle diameters smaller than 100 nm, based on consistent onset melting temperatures of 655 ± 1 °C and enthalpies of fusion of 304-310 J·g . SEM images corresponded to a 30-200 nm distribution, with occasional particles greater than 1 mm [19]. SEM images of CuO, Fe 2 O 3 and MoO 3 were consistent with their stated particle sizes.…”

“…The properties of nano aluminium are critical to performance and those of the nano aluminium common to this work and a series of studies are described elsewhere [19]. In brief, the nano aluminium fuels were of common origin and displayed active aluminium contents of 82.6%, 82.9% and 72.5% for O-Al, L-Al and V-Al, respectively.…”

Mechanical Desensitization of an Al/WO3 Nanothermite by Means of Carbonaceous Coatings Derived from Carbohydrates

“…Aluminium metal was systematically chosen as the fuel and was mixed with different oxide ceramics (CuO, WO 3 , MoO 3 and MnO 2 ) [16][17][18][19][20][21][22][23][24] or a polymer (polytetrafluoroethylene, PTFE) [25][26][27]. Desensitization can occur due to two different approaches: Either by modifying the aluminium particles (average particle size and passivizing alumina layer) [21,22] or by adding an additive in the traditional binary fuel/oxidizer energetic composites [16][17][18][19][20][23][24][25][26][27]. Regarding this second method, in a large majority of studies, synthetic carbons such as nanotubes, graphene and nanofibres were selected that provided more efficient electrostatic discharge desensitization [16,17,[24][25][26][27] without effect or mention regarding the friction sensitivity.…”

“…More recently, two papers have shown the beneficial use of non-carbonaceous additives to mitigate the sensitivities of nanothermites. The first one examined and demonstrated the efficiency of a lubricating molybdenum sulphide material (MoS 2 ) and hexadecane (C 16 H 34 ) as friction desensitizing additives in an Al/MoO 3 nanothermite, but no reactive properties were evaluated [23]. The second paper focused on the use of a polyaniline-conducting polymer in an Al/WO 3 nanothermite.…”

Ball Milling Produced FeF3‐Containing Nanothermites: Investigations of Its Thermal and Inflaming Properties

“…So far, various methods have been explored to manufacture nanothermites, which can be mainly classified into two categories: physical method and chemical method. Ultrasonic dispersion approach, as the most typical one of physical methods, possesses low cost and massive production characterizations. However, there exists severe agglomeration phenomenon because of extremely huge surface energy of corresponding products.…”