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.