Showing papers in "Propellants, Explosives, Pyrotechnics in 2019"

Engineering of Al/CuO Reactive Multilayer Thin Films for Tunable Initiation and Actuation

Abstract: Sputter-deposited Al/CuO multilayers represent the state-of-the-art of energetic nanomaterials. As such, they offer an opportunity for tunable ignition and actuation because their theoretical energy densities are significantly higher than most conventional secondary explosives while being less sensitive to undesired initiation. Both the sensitivity and combustion properties (temperature, rate and products released) can be manipulated via the layering, reactant spacing and stoichiometry of the multilayer and, to a lesser extent, via interface engineering. In this article, we first describe the technology of deposition of Al/CuO multilayers focusing on direct current sputter deposition followed by a comprehensive review of the materials structural characteristics. Next, experimental and theoretical works performed on these reactive multilayered materials to date is presented in terms of methods used, the results acquired on ignition and combustion properties, and conclusions drawn. Emphasis is placed on several studies elucidating the fundamental processes that underlie propagating combustion reactions. We examine the influence of the « ceiling » temperature that traduces the multilayer disintegration when reaching high temperatures (e.g., vaporization temperatures). This paper provides a good support for engineers to safely propose Al/CuO multilayers structure to regulate the energy release rates and ignition threshold in order to manufacture high performance and tunable initiator devices.

Insensitive High Explosives: III. Nitroguanidine – Synthesis – Structure – Spectroscopy – Sensitiveness

Abstract: This paper reviews the production, synthesis, crystallography, particle morphology and spectroscopy of the insensitive high explosive nitroguanidine, (NGu, CH4N4O2), CAS-No: [556-88-7] and its isotopologues [ D4]NGu and [N4]-NGu]. When compared with standard insensitive high explosives such as 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), 1,1-diamino-2,2-dinitroethylene (FOX-7) and N-guanylurea dinitramide (FOX-12), Nitroguanidine proves to be the least sensitive. The review gives 170 references to the public domain. For Part II see ref. [1].

Review of Gasless Pyrotechnic Time Delays

Abstract: AEL Mining Services (AEL/UP‐4400021845) and by the National Research Foundation (NRF) of South Africa (Grant 83874).

ADN and HAN-Based Monopropellants – A Minireview on Compatibility and Chemical Stability in Aqueous Media

Abstract: This article gives a short review on compatibility and chemical stability of selected aqueous ADN and HAN‐based energetic formulations. A brief introduction will outline Energetic Ionic Liquids (EILs) as a new class of energetic materials with beneficial physical‐chemical properties which make them valuable for application in propulsion technologies. EILs combine the advantages of e. g. low toxicity, showing equal or superior propulsion power compared to the state‐of‐the‐art monopropellant hydrazine. Focus is set on open access ADN and HAN‐based monopropellant formulations that are e. g. realized in the advanced blends LMP‐103S, FLP‐106 or LGP 1845.

Detonation Velocity Measurement of a Hydrogen Peroxide Solvate of CL‐20

Abstract: Synthesis and development of new energetic molecules is a resource-intensive process, yielding materials with relatively unpredictable performance properties. Cocrystallization and crystalline solvate formation have been explored as possible routes towards developing new energetic materials that reduce the initial investment required for discovery and performance uncertainty because existing energetic molecules with known properties serve as the constituents. The formation of a hydrogen peroxide (HP) solvate of CL-20 was previously reported and has a density comparable to that of ε-CL-20, the densest and most stable polymorph of CL-20. CL-20/HP produces a second crystalline form, which was unexpected given the high density of the original CL20/HP solvate. Both forms were predicted to have improved detonation performance relative to that of ε-CL-20. In this work, the detonation velocity of a solvate of CL-20/HP is measured and compared to that of CL-20. Using the measured enthalpy of formation, the solvate was predicted to detonate 80 m/s faster at a powder density of 1.4 g/cm 3 ; however, experimentally, the solvate detonates 300 m/s faster than CL-20. Thermochemical predictions are also used to show that the solvate detonates 100 m/s faster than ε−CL-20 at the theoretical maximum density, making it the first energetic cocrystal or solvate of ε-CL-20 predicted to detonate faster than CL-20 at full density.

Exploring Rapid, Sensitive and Reliable Detection of Trace Explosives Using Paper Spray Mass Spectrometry (PS‐MS)

Abstract: In this publication we work towards providing fast, sensitive and selective analysis of explosive compounds collected on swabs using paper spray mass spectrometry. We have (a) increased the size of the paper spray substrate to 1.6×2.1 cm for compatibility with current practise in swabbing for explosive material; (b) developed a method for determining a successful extraction of analyte from the substrate to reduce false negative events; and (c) expanded the range of analytes that can be detected using paper spray to include the peroxide explosive HMTD, as well as nitroglycerine (NG), picric acid (PA) and tetryl. We report the development of a 30 s method for the simultaneous detection of 7 different explosive materials using PSMS with detection limits below 25 pg, as well as detection of HMTD at 2500 pg, showing an improvement on previously published work.

Thermal Ignition of ADN-Based Propellants

Abstract: Thermal igniters are attractive for ADN thrusters as they allow a more prompt ignition and are better suited for larger engines (100-500 N) compared to the currently used preheated catalysts. Two thermal ignition methods, resistive and laser, were tested with the ADN based propellants LMP-103S and FLP-106. In the tests conducted on resistive ignition, a current was discharged through a drop of propellant. Different electrodes types and voltages were tested. Laser ignition was tested by suspending a droplet in an acoustic levitator. A pulsed laser was focused so that a plasma inside the droplet was generated. Laser ignition tests were conducted with the baseline propellants as well as with variations of these propellants with increased water content.