Architecture Can Significantly Alter the Energy Release Rate from Nanocomposite Energetics

With the advent of additive manufacturing methods combined with the increased interest in using nanoparticle components to formulate energetics materials, structure-function relationships and manufacturing methods have become intertwined. In this article, we explore three different approaches to formulate composites and evaluate the combustion properties. Here polyvinylidene fluoride (PVDF) was used to assemble both aluminum nanoparticles (Al NPs) and ammonium perchlorate (AP). Three different fabrication techniques, 3D-print, electrospray (E-spray), and electrospin (E-spin), were employed in this work. Composites of Al/PVDF and composites with a high oxidizer content, employing AP, were studied. The relationship between architecture and the burning rate of both Al/PVDF and Al/AP/PVDF was investigated by studying the thermal decomposition at high and low heating rates, and flame temperatures via the color camera pyrometry on microscale ignition/combustion events. By studying the release of HF, ignition temperatures, and the flame front, we propose a mechanism for the combustion of the multicomponent energetic films. Flame temperature, completeness of reaction, and a significant difference in ignition temperature appear to favor the E-spray material. However, the large difference in propagation velocity between E-spray and E-spun, given the minor difference in density, clearly points to the importance of microarchitecture on reaction properties. The relative energy release rate of E-spun AI/PVDF compared to the E-sprayed and 3-D printed case is an enhancement of similar to 6x and 18x, respectively, and the energy release rate of E-spun Al/AP/PVDF is similar to 19X higher than that of E-sprayed and 3D-printed samples. This implies that the lowest density spun material offers the highest mass energy release rate by far.