Designer Direct Ink Write 3D‐Printed Thermites with Tunable Energy Release Rates

Abstract

Breakthroughs in additive manufacturing (AM), particularly direct ink write 3D printing, have allowed for greater control of material performance by manipulation of architecture and/or spatial composition. Herein, the range of control over the dynamic energy release rate in 3D‐printed Al/CuO thermite is quantified by substituting random porous pathways present in powder beds or compacts with printed void channels to modulate the energy transport during a reaction. The thermite is produced via on‐the‐fly static mixing of constituent Al and CuO inks, which offers a safe way to handle these materials. By reducing the fundamental burn unit size (i.e., filament size) and introducing small amounts of engineered porosity for gas flow, it is shown that energy release rates can be increased by more than 100 times that of maximum print density strips. Unique channel structures, which display propagation velocities of over 100 m s−1 due to confinement of gas flow, are reported. Ashby plots that show the reactivity design space for 3D‐printed thermites are presented as a function of the effective print/energy density. Architecting with AM tailors an object to release its energy in a prescribed way, and this control adds much‐needed versatility by allowing a single formulation to satisfy multiple applications.