Browsing by Author "Mintoff, Alice"

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    Not so crystal clear : Defects, hot spots and initiations in explosive crystals
    (Cranfield University, 2022-11-21T16:21:07Z) Mintoff, Alice
    Nitroamine explosives are a crystalline material used in munitions, as a charge or propellant in powder form. These crystalline powders are compounded into formulations with other materials that can be tuned to fit requirements and their sensitiveness to insult is well understood. The larger part of these formulations are the crystalline explosives, which currently have less tunability. Researchers are aware that different crystal structures result in different materials properties. This is seen in nitramine explosives, such as RDX, where sensitivity can be reduced by manufacturing RDX particles to be more spherical and reducing the crystalline defects. They also know that hot spot formation, spots within the structure that heat up faster than surrounding areas, a contributing factor to initiation, is caused by defects within the crystal structures of the explosives. The types of defects, point, line, surface, substitutional, or interstitial, are not unique to energetic crystalline materials and a material could have any combination of these. A better understanding of how thse defects effect the formation of hot spots and the subsequent sensitivity will enable researchers to develop techniques that can produce highly tuned crystalline explosives. This thesis will focus on the nitroamine explosive, HMX, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine. Large single crystals will be grown using temperature lowering methods and the subsequent defects will then be identified and mapped out using Xray topography. Once characterised, the single crystals will then be subject to a shockwave which will cause initiation. Correlations between this initiation and the mapped defects will be identified.
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    Using Inert Crystalline Materials as a Simulation for Energetic Materials
    (Cranfield University, 2023-01-04T10:29:32Z) Mintoff, Alice
    Researchers are aware that different crystal structures result in different materials properties. The understanding of a materials crystal structure is significant for materials development in multiple industries, from munitions to pharmaceuticals. The energetic material, HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) is a commonly used energetic material and is found as a by-product in some manufacturing processes for RDX. HMX exists in multiple polymorphs and also exhibits a phenomenon known as crystal twinning. Experimentation of the co-crystallisation of paracetamol and seven other isomers and analogues yielded initial results that shows similar crystalline properties between paracetamol and HMX. Making paracetamol and ideal starting point for the development of the experimental techniques required to grown single crystal HMX. Eight isomers of paracetamol and 26 combinations within 3 different ratios have been identified as a starting point for looking into co-crystallisation, the process of two or more entities aggregating together in a crystal structure with no covalent bonding, with optical microscopy, Powder Xray Diffraction and Differential Scanning Calorimetry being employed as methods of analysis of the resulting crystals. Research into the co-crystallisation of paracetamol and the various isomers and polymorphs has yielded initial results that indicate that some co-crystallisation has occurred.