Fine-Tuning Combustion Behavior in Microscale Energetic Lines Fabricated by Direct Ink Writing Using Nano Thermite Microspheres for Applications in Pyro-MEMS

Energy-containing micro-electro-mechanical systems (MEMSs) present a promising avenue for the future advancement of pyrotechnic technology. The combination of high reaction energy and tunable reaction performance inherent to thermite agents renders them ideally suitable for use in energy-containing microelectromechanical systems within future pyrotechnic materials. In this study, nano-Al and nano-CuO-based aluminum thermite microspheres, denoted as nano-Al/CuO/NC (nAl/CuO/NC), were initially synthesized via spray-drying techniques. Subsequently, these microspheres were utilized to fabricate a microscale aluminum thermite energetic line through direct ink writing (DIW) using nAl/CuO/NC thermite ink. To compare, nano aluminum thermite inks composed of physically mixed nAl/CuO were also subjected to DIW processing, resulting in the creation of an nAl/CuO aluminum thermite energetic line. A comprehensive examination was undertaken to analyze the morphology, combustion velocity characteristics, combustion dynamics, ignition properties, and flame propagation behaviors of the 3D directly written aluminum thermite energetic lines. The experimental results demonstrate that 3D printing inks containing nAl/CuO/NC exhibit superior fluidity, leading to a more uniform and dense structure postcuring. Impressively, nAl/CuO/NC thermite ink can support 3D direct writing with a particle loading as high as 97 wt %. Remarkably, the combustion rate of the nAl/CuO/NC aluminum thermite energetic line remains relatively stable regardless of the number of layers directly written. During the combustion of nAl/CuO/NC thermite energetic lines, the microspheres tend to ignite and burn independently. This characteristic, along with the observation that the nAl/CuO/NC aluminum thermite energetic line possesses a higher explosion heat value and faster heating rate, highlights its improved performance. Notably, nAl/CuO/NC aluminum thermite inks have been proved to successfully ignite using Ni–Cr bridge ignition devices, further showing their compatibility and efficacy in MEMS applications.