Combustion analysis of three different thermites consisting of aluminum (Al) particles with and without surface functionalization combined with molybdenum trioxide (MoO3) was performed to study the effect of surface functionalization on flame propagation velocity (FPV). Two types of Al particles had self-assembled monolayers (SAMs) of perfluoro tetradecanoic (PFTD) and perfluoro sebacic (PFS) acids around the alumina shell, respectively; the other one did not. Flame speeds for Al with PFTD acid combined with MoO3 are 86% higher than Al/MoO3 whereas those for Al with PFS acid combined with MoO3 are almost half of Al/MoO3. The Al–PFTD structure is more sterically hindered and exhibits lower bond dissociation energy. This chemistry promotes increased flame speeds. Thermal equilibrium studies were performed using a differential scanning calorimeter and a thermogravimetric analyzer to determine activation energy (E a) of the thermites. Results are consistent with flame speed observations and showed an inverse relationship between flame speed and E a. This study shows that surface functionalization can be used as an approach to control the reactivity of Al particles.

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The inclusion of graphene into composite energetic materials to enhance their performance is a new area of interest. Studies have shown that the addition of graphene significantly enhances the thermal transport properties of an energetic composite, but how graphene influences the composite’s ignition sensitivity has not been studied. The objective of this study is to examine the influence of carbon additives in composite energetic material composed of aluminum and polytetrafluoroethylene (Teflon™) on ignition sensitivity due to low velocity, drop weight impact. Specifically, three forms of carbon additives were investigated and selected based on different physical and structural properties: spherically shaped amorphous nano particles of carbon, cylindrically shaped multi walled carbon nanotubes, and sheet like graphene flakes. Results show an interesting trend: composites consisting of carbon nanotubes are significantly more sensitive to impact ignition and require the lowest ignition energy. In contrast, graphene is least sensitive to ignition exhibiting negligible reduction in ignition energy with low concentrations of graphene additive. While graphene does not significantly sensitize the energetic composite to ignition, graphene does, however, result in greater overall reactivity as observed through images of the reaction. The enhanced thermal transport properties of graphene containing composites may promote greater energy transport once ignited, but those properties do not also increase ignition sensitivity. These results and the understanding of the structural arrangement of particles within a composite as a key parameter affecting impact ignition sensitivity will have an impact on the safe handling and use of composite energetic materials.

This paper reports investigations into coal's viability as an alternative filler to wood flour in wood plastic composites (WPCs)a class of materials used in building applications in lieu of pressure-treated wood coal plastic composites (CPCs) were fabricated with 15−60 wt % coal combined with high-density polyethylene and their physical (mechanical, water absorption, and metal leaching) and chemical (oxidative degradation and flammability) properties were compared with commercial WPCs. In addition, mass and energy balances (10 ton/h basis) and life cycle analyses (60 wt % filler and 1 ton basis) were conducted on CPCs and WPCs to assess environmental impact during manufacturing. At 60 wt %, CPCs had higher flexural strength, slower oxidative degradation and burn rate, and lower water absorption in comparison to commercial WPCs, suggesting better performance and stability in building applications. Furthermore, CPC manufacturing showed 44% lower greenhouse gas emissions and 62% less energy usage in comparison with WPC. These results indicate that the direct utilization of coal as a filler in construction composite applications may yield lower-cost products with lower associated emissions and energy demand compared to that of existing WPC materials, potentially yielding a more sustainable end use for coal than current uses such as power production.