Additive Manufacturing of Energetic Materials and Its Uses in Various Applications

The work discussed in this document seeks to utilize traditional additive manufacturing techniques to selectively deposit energetic materials. The goal was to gain a fundamental understanding of how to use commonplace 2D inkjet printing and 3D fused deposition technology to selectively deposit reactive materials. Doing so provides the ability to manipulate the geometry, as well as composition, of the energetic material during the manufacturing process. Achieving this level manipulation and control has shown to be nontrivial, if not impossible, using traditional manufacturing methods. The ability to change the geometry of the energetic material at will greatly increases the ability of these energetic materials to be integrated with a wide range of systems, such as transient electronics. To create a transient electronic device, a destruction mechanism and an initiation system need to be integrated with electronic components. Experiments in this document investigate nanothermites for their ability to serve as this destruction mechanism. Nanothermites were prepared at various equivalence ratios and syringe deposited onto silicon substrates. The resultant destruction was shown to vary with the equivalence ratio of the material. A wide range of substrate destruction was demonstrated, varying from disintegration to only charring the wafer. Materials prepared near stoichiometric conditions were shown to disintegrate the silicon substrates completely. As the equivalence ratio was raised, less severe destruction was observed. The ability inkjet print these nanothermites provides the geometric control necessary to incorporate them into electronic components. An ink formulation process was explored in an attempt to create a fuel and an oxidizer ink, which could be inkjet printed simultaneously to create a nanothermite. Separate inks allow for the equivalence ratio, and therefore the resultant destruction, to be selectively tuned during the additive manufacturing process. Additionally, this gives the advantage of only needing two largely inert, shelf stable inks, instead of having to develop a new ink for every desired destruction level. Various candidate inks were formulated using different loadings and combinations of surfactants. Polyvinylpyrrolidone was shown to be the surfactant best suited for holding both aluminum and copper (II) oxide nanoparticles in suspension over time. These inks both showed reasonable shelf stability as well as viable reactivity when stoichiometric nanothermite samples were prepared using on-chip mixing. With respect to 3D printed energetic materials, fused deposition methods were used to print a fluoropolymer based energetic material which could be used as a multifunctional reactive structure. A reactive filament comprising of a polyvinylidene fluoride (PVDF) binder with 20% mass loading of aluminum (Al) was prepared using a commercial filament extruder and printed using a Makerbot Replicator 2X. The printing performance of the energetic samples was compared with standard 3D printing materials using metrics such as bead-to-bead adhesion and the surface quality of the printed samples. The reactivity and burning rates of the filaments and the printed samples were shown to be comparable. This result is imperative for fused deposition modeling to be used as a viable manufacturing method of energetic materials. In total, this document lays some of the groundwork necessary for additive manufacturing to be adopted as a viable method for the selective deposition of energetic materials. Going forward these methods can be used to integrate energetic materials in a manner not possible using traditional manufacturing methods

Additive Manufacturing of Energetic Materials and Its Uses in Various Applications

The work discussed in this document seeks to utilize traditional additive manufacturing techniques to selectively deposit energetic materials. The goal was to gain a fundamental understanding of how to use commonplace 2D inkjet printing and 3D fused deposition technology to selectively deposit reactive materials. Doing so provides the ability to manipulate the geometry, as well as composition, of the energetic material during the manufacturing process. Achieving this level manipulation and control has shown to be nontrivial, if not impossible, using traditional manufacturing methods. The ability to change the geometry of the energetic material at will greatly increases the ability of these energetic materials to be integrated with a wide range of systems, such as transient electronics. To create a transient electronic device, a destruction mechanism and an initiation system need to be integrated with electronic components. Experiments in this document investigate nanothermites for their ability to serve as this destruction mechanism. Nanothermites were prepared at various equivalence ratios and syringe deposited onto silicon substrates. The resultant destruction was shown to vary with the equivalence ratio of the material. A wide range of substrate destruction was demonstrated, varying from disintegration to only charring the wafer. Materials prepared near stoichiometric conditions were shown to disintegrate the silicon substrates completely. As the equivalence ratio was raised, less severe destruction was observed. The ability inkjet print these nanothermites provides the geometric control necessary to incorporate them into electronic components. An ink formulation process was explored in an attempt to create a fuel and an oxidizer ink, which could be inkjet printed simultaneously to create a nanothermite. Separate inks allow for the equivalence ratio, and therefore the resultant destruction, to be selectively tuned during the additive manufacturing process. Additionally, this gives the advantage of only needing two largely inert, shelf stable inks, instead of having to develop a new ink for every desired destruction level. Various candidate inks were formulated using different loadings and combinations of surfactants. Polyvinylpyrrolidone was shown to be the surfactant best suited for holding both aluminum and copper (II) oxide nanoparticles in suspension over time. These inks both showed reasonable shelf stability as well as viable reactivity when stoichiometric nanothermite samples were prepared using on-chip mixing. With respect to 3D printed energetic materials, fused deposition methods were used to print a fluoropolymer based energetic material which could be used as a multifunctional reactive structure. A reactive filament comprising of a polyvinylidene fluoride (PVDF) binder with 20% mass loading of aluminum (Al) was prepared using a commercial filament extruder and printed using a Makerbot Replicator 2X. The printing performance of the energetic samples was compared with standard 3D printing materials using metrics such as bead-to-bead adhesion and the surface quality of the printed samples. The reactivity and burning rates of the filaments and the printed samples were shown to be comparable. This result is imperative for fused deposition modeling to be used as a viable manufacturing method of energetic materials. In total, this document lays some of the groundwork necessary for additive manufacturing to be adopted as a viable method for the selective deposition of energetic materials. Going forward these methods can be used to integrate energetic materials in a manner not possible using traditional manufacturing methods

Applications of Additive Manufacturing Techniques in Making Energetic Materials

Energetic materials are currently manufactured using methods such as casting, which can only produce certain geometries. Additive manufacturing enables more flexible fabrication and the potential for improved material consistency. Additive manufacturing has transformed many industries, but has only recently been applied to the manufacturing of energetic materials. This paper describes the development of two processes to apply additive manufacturing methods to energetic materials. Method one applies a fused deposition modelling approach (FDM). 5 µm aluminum powder and PVDF were mixed and made into filaments using a Filabot Original filament extruder. Energetic filaments were created composed of 90:10, 80:20, and 75:25 mixtures of PVDF:Al by mass. These filaments had reactive sections, but did not have consistent composition and could not sustain self-propagating reactions. The second method had the goal of mixing ammonium perchlorate (AP) into a curable polymer which solidifies under UV light. Powdered sugar was used in place of AP to simulate the viscosity while testing extrusion and printing capabilities. The powdered sugar and UV Cure mixture could be extruded using a syringe pump when the powdered sugar to UV Cure ratio was 3:1, but this mixture would not stick to the print bed. Both processes need refinement to produce functional energetic materials. This paper forms a foundation for further development of processes in which additive manufacturing can be safely used to produce energetic materials

SecureMEMS: Selective Deposition of Energetic Materials

There exists a pressing operational need to secure and control access to high-valued electromechanical systems, and in some cases render them inoperable. Developing a reliable method for depositing energetic materials will allow for the near-seamless integration of electromechanical systems and energetic material, and, in turn, provide the pathway for security and selective destruction that is needed. In this work, piezoelectric inkjet printing was used to selectively deposit energetic materials. Nanothermites, comprising of nanoscale aluminum and nanoscale copper oxide suspended in dimethyl-formamide (DMF), were printed onto silicon wafers, which enabled both thermal and thrust measurements of the decomposing energetic material. Various solids loadings were studied in order to optimize printing characteristics. Going forward, further studies will focus on the plausibility of inkjet printing other energetic materials for the purposes of the degradation of electromechanical systems

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements