Carbon Fibers Enhance the Propagation of High Loading Nanothermites: In Situ Observation of Microscopic Combustion

Abstract

A major challenge in formulating and manufacturing energetic materials lies in the balance between total energy density, energy release rate, and mechanical integrity. In this work, carbon fibers are embedded into ∼90 wt % loading Al/CuO nanothermite sticks through a simple extrusion direct writing technique. With only ∼2.5 wt % carbon fiber addition, the burn rate and heat flux were promoted >2×. In situ microscopic observation of combustion shows that the carbon fiber intercept ejected hot agglomerates near the burning surface and enhanced heat feedback to the unreacted material. This study outlines how these approaches may enhance the propagation and reduce the two-phase flow losses.

Direct Imaging and Simulation of the Interface Reaction of Metal/Metal Oxide Nanoparticle Laminates

“…As mentioned previously, Al/CuO sputter-deposited nanolaminates have attracted a considerable number of studies owing to their precisely adjustable reactivity through the bilayer thickness. ,− We now compare our particle laminates with those of prior studies. Figure summarizes the burn rate and energy release rate (normalized based on the burn rate × density × flame temperature) with different bilayer thicknesses ranging from 0.15 to 420 μm.…”

“…Figure a shows the direct writing approach, which is formulated based on our previous studies. ,− The only difference is that we used two syringes/nozzles to alternatively deposit Al or CuO on the preheated substrate. Inks in both the syringes contain 10 wt % polymer mixtures of HPMC and PVDF and 90 wt % nanoparticles of Al or CuO.…”

“…Finally, the pads are peeled off from the substrate and cut into ∼2 mm wide sticks for combustion characterization. The porosity of all laminates is estimated as ∼65% based on our previous studies. ,− …”

“…Energetic particulate composites have been extensively investigated through macroscopic characterization approaches to characterize temperature, burn rates, and thermal decomposition properties − However, characterization at the microscopic scale has been less readily available. Given that the composition of these composites consists of nano or micro-sized reactants, observation at smaller length scales is needed to better understand the role of mass and heat transfer. ,− Previously, we employed a recently developed microscopic dynamic imaging system to probe the reaction zone of sputter-deposited Al/CuO nanolaminates with μs and μm temporal and spatial resolution respectively, which is more comparable to the reactant dimensions and reaction timescales . Through this technique, we obtained detailed images and temperature profiles across the Al/CuO nanolaminates reaction front.…”

Sandwich-Structured Hybrid of NiCo Nanoparticles-Embedded Carbon Nanotubes Grafted on C3N4 Nanosheets for Efficient Photodehydrogenative Coupling Reactions

“…Due to limited earth reserves and the high cost of noble metals, great efforts have been made in transition metals (e.g., Co, Ni, and Cu) as potential alternatives to noble metals owing to their low cost and earth abundance. − Meanwhile, some perfect support materials, such as carbon materials (e.g., graphene and carbon fibers), organic polymers materials (e.g., C 3 N 4 and COFs), and so on, have been often used to stabilize transition metal nanoparticles and optimize the electronic environment of transition metal nanoparticles. − The synergetic effects between the support materials and transition metal nanoparticles can change the electronic character and charge distribution on the surface of transition metal nanoparticles, contributing to improving catalytic properties . For instance, the graphene nanosheets grafted with carbon nanotubes embedded with Co nanoparticles exhibited a remarkable electrocatalytic hydrogen evolution activity .…”