Ink Formulation and Direct Ink Writing of Thermites

3D printing is a rapidly emerging technology involving the layer-by-layer deposition of material to form a final part. This technique has great potential for reactive materials, in that dynamic behavior may be controlled through the strategic placement of material into features within a part. Direct ink writing (DIW) is an extrusion-based method of 3D printing, involving the room temperature extrusion of custom inks through micronozzles. Since heating is not required, this technique is suitable to print reactive materials such as pyrotechnics or thermites. Here we investigate the formulation of both aluminum and copper oxide based inks for the direct printing of thermite. Choices of volume loading, surfactant concentration, and matrix solvent are all critical with regard to establishing an ink capable of shear thinning, but also rapidly setting upon extrusion. Without the latter behavior, the ink would sag upon printing and would not produce a quality part. The formulation and rheological properties of the inks are reported here. We demonstrate the ability of each material to be extruded for 3D printing and discuss several parameters important to the process. Additionally, the components are mixed with a custom mixing head for direct printing of the thermite composite.   This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-691141.