Thermal and Combustion Properties of Energetic Thin Films with Carbon Nanotubes

Abstract

The effect of varying carbon nanotube concentration on ignition delay, flame speed, and electrical and thermal conductivity of three-dimensional printable energetic thin films made of magnesium and manganese oxide was investigated. Polyvinylidene fluoride was used as the binder for depositing the stoichiometric Mg∕MnO 2 mixture into thin films with an average thickness of 200 μm using an extrusion-based blade-casting method. Four films with a 0, 0.5, 1.0, and 1.5 wt % carbon nanotube were prepared. The ignition delay and flame speed of the films were measured using high-speed imaging techniques. Electrical and thermal conductivities were also measured. Results show that the inclusion of a 1.5 wt % carbon nanotube in the Mg∕MnO 2 /polyvinylidene fluoride films improved their flame speed by 440% and electrical conductance by two orders of magnitude (from 4.23 to 655.33 nS) and decreased ignition delay by 87.2%. Interconnectivity of carbon nanotubes in the films was estimated using a basic percolation model. Films with a 1.5 wt % carbon nanotube demonstrated the highest interconnectivity, which aided improved thermal and electrical energy transport, thereby improving combustion performance. The development of three-dimensional extruded thin films with tailorable thermal and combustion parameters is a precursor for the additive manufacturing of energetic materials.

Elucidating the dominant mechanisms in burn rate increase of thermite nanolaminates incorporating nanoparticle inclusions

“…As the energy release rate is directly dependent on the equivalence ratio, size and morphology of the oxidizer and fuel, many research studies propose to manipulate the material formulation; however it requires expensive and time-consuming synthesis and characterization loops. Another empirical procedure reported in the literature consists in doping the energetic composite with additives featuring high thermal diffusivities like metals and carbon structures [19][20][21][22][23] to enhance the heat conduction in different areas of the energetic composite with the goal to accelerate the thermal front (flame) propagation. In [19] the authors show that inclusions of 1.5 wt% carbon nanotubes in the Mg/MnO 2 /polyvinylidene fluoride (PVDF) films improved the burn rate by a factor of 4.…”

“…Another empirical procedure reported in the literature consists in doping the energetic composite with additives featuring high thermal diffusivities like metals and carbon structures [19][20][21][22][23] to enhance the heat conduction in different areas of the energetic composite with the goal to accelerate the thermal front (flame) propagation. In [19] the authors show that inclusions of 1.5 wt% carbon nanotubes in the Mg/MnO 2 /polyvinylidene fluoride (PVDF) films improved the burn rate by a factor of 4. Recently, Julien et al showed that incorporation of gold nanoparticles into Al/CuO nanothermite increases the ignitability and enhances burning properties [24].…”