he Ignition Behaviour of Energetic Materials Under Confined Cookoff

© Cranfield University 2018. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright ownerIn a series of experiments and theoretical work, the process of ignition in confined energetic materials has been explored and understanding gained. Early work focused on the direct observation of the cook-off process but was hampered by the available technology. In more recent work, dynamic measurements of the deformation of the confinement have been explored, and refinements to the direct observation method have been made that make use of recent advances in camera technology. We have observed, for the first time, complex melting and development of gas spaces within which the early stages of ignition take place, and propose a new mechanism by which violent cook-off responses might develop in certain explosivesPh

Optical sensitisation of energetic crystals with gold nanoparticles for laser ignition

The laser ignition of explosives is safer and more environmentally beneficial than electric ignition systems, but optical sensitisers must be present to facilitate heating by optical absorption. We investigated, for the first time, the optical sensitisation of cyclotrimethylenetrinitramine (RDX) crystals by doping them with gold nanoparticles to enhance laser ignitibility using a near-infrared diode laser. RDX crystals physically coated with gold nanoparticles or recrystallised from a solution containing gold nanoparticles were tested for optical sensitisation by micro-imaging with a scanning electron microscope, and high-speed video was used to experimentally observe the enhanced laser ignitibility. The gold nanoparticles achieved effective optical sensitisation and significantly enhanced the laser ignitibility of RDX, reducing the laser ignition threshold power from more than 45 W to as little as 1 W. Our results show that gold nanoparticles are effective as optical sensitisers for the ignition of energetic materials using a small, low-power diode laser

Pulsed laser irradiation of a nanoparticles sensitised RDX crystal

The laser initiation of secondary explosives presents tactical, safety and environmental advantages over traditional ignition systems utilising primary explosives. In this paper, direct ignition or initiation by pulsed laser was investigated of cyclotrimethylenetrinitramine (RDX) crystals doped with gold nanoparticles (GNPs) for the first time. A nano-seconds pulsed laser was used for direct irradiation of the crystals at the GNP's surface-plasmon-resonance wavelength of 532 nm. RDX crystals were recrystallised from a solution containing GNPs and characterised by visual microscopy for surface coating and subsurface doping. A high-speed camera was used to observe and capture the modes of interaction between the GNPs-doped RDX crystals and pulsed laser irradiation with a new classification method. Laser fluence thresholds for ignition and initiation were established. The GNPs sensitized RDX to pulsed laser irradiation at this selected wavelength is 3 orders of magnitude more sensitive than pure RDX. Direct initiation of the GNPs doped RDX crystal at laser fluence of 0.04 J/cm2 led to the total consumption of a crystal sample, which was unreproducible with pure RDX. The results show that GNPs are effective optical sensitizers for direct initiation of RDX crystal by low-power pulsed laser

Gas gun ramp loading of Kel-F 81 targets using a ceramic graded areal density flyer system

Kel-F 81 (PCTFE/Polychlorotrifluoroethylene) polymer targets were subjected to ramp loadings generated by a ceramic flyer accelerated into the targets by a gas gun in the plate impact configuration. This approach used a ceramic graded areal density flyer in conjunction with a ceramic buffer plate to induce a ramp loading in the target. The flyer was comprised of a rapid prototyped alumina ceramic. The loading was observed with embedded electromagnetic particle velocity gauges (PV gauges) with the results compared with ANSYS Autodyn™ hydrocode simulations. Experimental results show that ramp loadings of varying duration and magnitude were induced into the target. These loadings can be described as shockless compressions leading to shocked states within the material. In addition, numerical simulations provided further insight into the loading approach – with good agreement found with experimental data, opening the potential to design more complex loading systems in future

Chemical modification of β-cyclodextrins: balancing soft and rigid domains in complex structures

Crystalline polymers such as β‐cyclodextrin (βCD) can be modified with polyethylene glycol (PEG) diglycidyl ether cross‐linkers (262, 394, 500 Da). Here we show that the quantity and length of the PEG soft segments influence the solubility and malleability of the products, which are water‐soluble and easily converted to nitrated analogues under standard reaction conditions. Inert and nitrated derivatives containing longer PEG segments showed the ability to self‐heal. The degree of cross‐linking and decomposition temperatures and energies depended on the quantity and length of the soft segment. Nitrated cross‐linked βCD containing longer PEG segments did not ignite following an electrostatic discharge of 4.5 J. The chemical stability of βCD/PEG binders was tested by heat flow calorimetry at 80 °C. We found that the balanced incorporation of soft PEG and rigid βCD segments improved the processability of cross‐linked βCDs and desensitised their nitrated derivatives, offering new solutions for inert and energetic binders

Quality standards for the management of alcohol-related liver disease: consensus recommendations from the British Association for the Study of the Liver and British Society of Gastroenterology ARLD special interest group

Objective Alcohol-related liver disease (ALD) is the most common cause of liver-related ill health and liver-related deaths in the UK, and deaths from ALD have doubled in the last decade. The management of ALD requires treatment of both liver disease and alcohol use; this necessitates effective and constructive multidisciplinary working. To support this, we have developed quality standard recommendations for the management of ALD, based on evidence and consensus expert opinion, with the aim of improving patient care.Design A multidisciplinary group of experts from the British Association for the Study of the Liver and British Society of Gastroenterology ALD Special Interest Group developed the quality standards, with input from the British Liver Trust and patient representatives.Results The standards cover three broad themes: the recognition and diagnosis of people with ALD in primary care and the liver outpatient clinic; the management of acutely decompensated ALD including acute alcohol-related hepatitis and the posthospital care of people with advanced liver disease due to ALD. Draft quality standards were initially developed by smaller working groups and then an anonymous modified Delphi voting process was conducted by the entire group to assess the level of agreement with each statement. Statements were included when agreement was 85% or greater. Twenty-four quality standards were produced from this process which support best practice. From the final list of statements, a smaller number of auditable key performance indicators were selected to allow services to benchmark their practice and an audit tool provided.Conclusion It is hoped that services will review their practice against these recommendations and key performance indicators and institute service development where needed to improve the care of patients with ALD

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

Enhancement of laser ignitibility of insensitive energetic materials (FOX-7)

Experimental investigation into the feasibility of optically sensitising an insensitive explosive, FOX-7 (1,1-Diamino-2,2-dinitroethene) by the doping of gold nanoparticles (GNPs) has been conducted. The commercially available GNPs were specifically designed in their particle shape and size to strongly absorb at the wavelength of the igniting laser (808 nm). The laser ignitibility of FOX-7 was significantly increased as the GNPs efficiently converted the absorbed energy into the heat. The laser ignitibility of such optically sensitised FOX-7 and the detonation capability of the laser initiator devices designed for the study were evaluated. Based on the evaluation of the initiator’s output in term of impact pressure, it was shown that an GNPs doped FOX-7 based laser slapper initiator was able to detonate a secondary explosive

Detonation properties of additively manufactured RDX: Dry powder printed

Research into additive manufacturing (AM) has been steadily expanding over the past five decades. Where once only polymeric materials could be reliably printed, AM has been adapted to print with a range of materials such as biological, metallic, ceramic and even foodstuffs. The advantages of manufacturing in an additive manner include; a) a layer-by-layer approach allows the creation of architecturally complex structures, b) a reduction in weight, c) lessening of waste and d) the ability to create parts that that are otherwise difficult or too costly to produce. 1,3,5-Trinitro-1,3,5-triazinane (RDX) is regularly used in explosive systems. Its detonation properties when conventionally manufactured are widely researched and broadly understood. However, recent advances in additive manufacturing technologies have led to greater interest in utilising RDX in this manner. There is growing evidence that emerging formulations and printing methods are changing the detonation properties of RDX composites, the critical diameter among them.1 This study reports on beginning to understand the detonation properties of additively manufactured RDX via a dry powder printing method

Optical sensitisation of energetic crystals with gold nanoparticles for laser ignition

The laser ignition of explosives is safer and more environmentally beneficial than electric ignition systems, but optical sensitisers must be present to facilitate heating by optical absorption. We investigated, for the first time, the optical sensitisation of cyclotrimethylenetrinitramine (RDX) crystals by doping them with gold nanoparticles to enhance laser ignitibility using a near-infrared diode laser. RDX crystals physically coated with gold nanoparticles or recrystallised from a solution containing gold nanoparticles were tested for optical sensitisation by micro-imaging with a scanning electron microscope, and high-speed video was used to experimentally observe the enhanced laser ignitibility. The gold nanoparticles achieved effective optical sensitisation and significantly enhanced the laser ignitibility of RDX, reducing the laser ignition threshold power from more than 45 W to as little as 1 W. Our results show that gold nanoparticles are effective as optical sensitisers for the ignition of energetic materials using a small, low-power diode laser