Superior performance of quaternary NC/GO/Al/KClO4 nanothermite for high speed impulse small-scale propulsion applications

Nanothermites are considered promising energetic materials and a key to develop new technologies in the field of energetics and propulsion. However, relatively low peak pressure, smaller thrust output, and incomplete combustion represent some of the potential problems associated with nanothermites. In this study to improve the combustion performance of nanothermites, varying quantities of nitrocellulose (NC) were introduced to produce the quaternary NC/GO/Al/KClO4 nanothermite using facile electrospinning. The morphology of nanothermites was characterized by SEM-EDX which confirmed that the nanoparticles were homogeneously dispersed without agglomeration. The combustion behavior of the composites was evaluated by igniting the samples at different packing densities (%TMD) in open acrylic tubes within a reaction chamber and using a 3.5 W continuous wave laser. High speed imaging captured the flame propagation and differential scanning calorimetry (DSC) was used to assess thermal behavior and energy output. Finally, for propulsion characterization, a small-scale test motor (STM) with a converging/diverging nozzle was used to evaluate the combustion performance of the prepared samples. In general, thrust output, specific and volumetric impulses (ISP and ISV), and total heat released exhibit remarkable enhancement with the addition of NC. Specifically, the total impulse (IFT) and ISP peaked at 5% NC/GO/Al/KClO4 at ~ 50% TMD, with IFT of 19.9 mN.s and ISP of 203.2 s. These are improvements of over 50% compared to the sample without NC (13.4 mN.s and 137.4 s). The ignition delay time and the power required to ignite the NC-enriched mixture is increased, but a sufficiently fast response is maintained for practical applications. Thermal analysis implies that addition of NC introduced another step to the GO/Al/KClO4 reaction: a gas− solid phase and liquid−liquid phase diffusion reaction, with the liquid−liquid phase reaction increasing with NC percentage. These results suggest that electrospinning is a simple technique for preparation of quaternary nanothermites that results in enhanced combustion performance and an improved suitability for small-scale propulsion applications.