Development of flexible, free-standing, thin films for additive manufacturing and localized energy generation

Abstract

Film energetics are becoming increasingly popular because a variety of technologies are driving a need for localized energy generation in a stable, safe and flexible form. Aluminum (Al) and molybdenum trioxide (MoO3) composites were mixed into a silicon binder and extruded using a blade casting technique to form flexible free-standing films ideal for localized energy generation. Since this material can be extruded onto a surface it is well suited to additive manufacturing applications. This study examines the influence of 0-35% by mass potassium perchlorate (KClO4) additive on the combustion behavior of these energetic films. Without KClO4 the film exhibits thermal instabilities that produce unsteady energy propagation upon reaction. All films were cast at a thickness of 1 mm with constant volume percent solids to ensure consistent rheological properties. The films were ignited and flame propagation was measured. The results show that as the mass percent KClO4 increased, the flame speed increased and peaked at 0.43 cm/s and 30 wt% KClO4. Thermochemical equilibrium simulations show that the heat of combustion increases with increasing KClO4 concentration up to a maximum at 20 wt% when the heat of combustion plateaus, indicating that the increased chemical energy liberated by the additional KClO4 promotes stable energy propagation. Differential scanning calorimeter and thermogravimetric analysis show that the silicone binder participates as a fuel and reacts with KClO4 adding energy to the reaction and promoting propagation.

Progress in Additive Manufacturing of Energetic Materials: Creating the Reactive Microstructures with High Potential of Applications

“…lished a series of papers on the manufacturing of thermitebased films using this approach [42][43][44][45]. The influence of the polymer and solvent type on the structure and performance of Mg/MnO 2 deposits was established [43].…”

“…The authors reported an intimate relationship among the initial mixture properties, the thickness and density of the produced film, and the flame speed [42]. More complex compositions have been produced by blade casting, i. e., Al/ MoO 3 /KClO 4 in silicone polymer (Mold Max™ 30)/xylene [44] and acrylonitrile butadiene styrene plastic (ABS)/acetone [45]. The still images from the video of the combustion of compositions where the ABS content exceeds 40 wt.% reveal the noticeable flame standoff distance, which is a consequence of the slow oxidation rate of polymer destruction products.…”

Development and Characterization of 3D Printable Thermite Component Materials

“…[5] This has been applied to control mechanical, [6][7][8][9][10] optical, [11][12][13] and electronic [14][15][16] properties of materials, as well as enable new functional materials. [21][22][23][24][25] RMs are a subset of energetic materials and are composites that, upon ignition, give rise to the rapid liberation of energy in the form of heat and/or pressure. [21][22][23][24][25] RMs are a subset of energetic materials and are composites that, upon ignition, give rise to the rapid liberation of energy in the form of heat and/or pressure.…”

“…[17][18][19][20] While a large portion of studies focus on quasi-static applications, additive manufacturing (AM) has also shown promise as a means to tailor dynamic properties, such as the rate of chemical energy release in reactive materials (RMs). [21][22][23][24][25] RMs are a subset of energetic materials and are composites that, upon ignition, give rise to the rapid liberation of energy in the form of heat and/or pressure. Further within the subset of RMs, materials can be defined as either intermetallics (metal/metal) or thermites (metal/metal oxide).…”

“…One factor in the choice of these precursors was to pick two systems that could be formulated with similar rheological properties, as disparate rheological properties could lead to potential issues during mixing operations. [21][22][23][24][25] RMs are a subset of energetic materials and are composites that, upon ignition, give rise to the rapid liberation of energy in the form of heat and/or pressure. The rheology of these high solids loaded prethermite inks had to be such that the inks could be extruded through a nozzle (i.e., shear thinning) as wet filaments.…”