Browsing by Author "Moniruzzaman, Mohammed"

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    Azobenzene-based gel coated fibre Bragg grating sensor for moisture measurement
    (2016-08-23) Moniruzzaman, Mohammed; Rock, John
    A fibre Bragg grating sensor is coated with a novel polymer gel in order to investigate its suitability for nondestructive measurement of moisture in materials that can potentially lose their integrity due to moisture ingress. Absorption and desorption of moisture lead to swelling/shrinkage of an azobenzene-based gel, which induces a strain in the Bragg grating resulting in wavelength shifts. The results demonstrated that the amount of wavelength shift is linearly dependent on the amount of water ingress by the gel. The performance of the proposed optical fibre moisture sensor was found to be repeatable with no detectable hysteresis and has the potential to offer a low-cost route for monitoring moisture content.
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    Closed vessel burning behavior and ballistic properties of artificially-degraded spherical double-base propellants stabilized with diphenylamine
    (Elsevier, 2019-07-24) Tırak, Ergun; Moniruzzaman, Mohammed; Degirmenci, Ercan; Hameed, Amer
    The purpose of solid propellants is to generate gas, which expands to accelerate (and spin, in the case of rifled barrels) a gun projectile so that it achieves the desired launch velocity at the muzzle. Some of the important properties of a propellant are the burning rate and vivacity, both of which strongly influence gun performance and projectile range. However, nitrate ester propellants undergo physical and chemical degradation during storage and this can change the burning rate and/or vivacity, either reducing the propulsive efficiency or increasing the safety risk to the operator during transportation and handling. Here we report the effect of aging on the burning rate and vivacity of spherical double-base propellants containing diphenylamine (DPA) as the main stabilizer. We tested three sets of propellants that were artificially aged at 80 °C for 5.3, 10.6 and 21.6 days, equivalent to 5, 10 or 20 years of aging at 25 °C according to STANAG 4582. It was found that DPA was progressively lost from the propellants during aging, with the greatest loss observed in propellants aged for the longest time. The DPA was able to fulfil its stabilisation role of propellant when NG was up to 14%, however, failed to stabilize when the nitroglycerin content was nearer to 20%. Aging caused changes in the burning rate and vivacity compared to the unaged propellant batch. The burning rate of propellant containing ˜20% nitroglycerin exceeds the burning rates of samples containing 12–14% nitroglycerin. The limited role of DPA as a stabilizer for double-base propellants is discussed. The DPA stabilized double base propellant may undergo significant changes during storage, making them unsuitable for their designated use.
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    Interaction and thermal studies on graphene oxide in NC/DEGDN/GO nanocomposites
    (Royal Society of Chemistry, 2019-10-31) Yahya, Prima Kharisma Indra; Gill, Philip P.; Moniruzzaman, Mohammed
    Before considering the uses of graphene oxide (GO) in nitrate ester-based materials for performance and safety improvement, its interaction, compatibility and dispersion with the host matrices need to be well understood. This work addresses the interaction and dispersity of GO with nitrocellulose (NC)/diethylene glycol dinitrate (DEGDN)-based nanocomposites. The GO and DEGDN were successfully synthesised and characterised. The NC/DEGDN proved to be a good hosting matrix for the dispersion of GO nanosheets. Analysis of atomic force microscopy (AFM) showed that the thicknesses of dispersed GO were in the range of 1–4 nm suggesting that the GO in the nanocomposite consists of 1–2 layers for a 0.5% w/w GO containing nanocomposite and 2–4 layers for a 0.75% w/w nanocomposite. ATR-FTIR spectroscopy analysis established red-shifting of 744 to 752 cm−1 for the O–NO2 bond stretching vibrations, indicating bond stabilization by donor electron from the GO. The Raman spectra analysis showed GO peaks blue-shifting and broadening which is attributed to hydrogen bonding interaction between GO sheets and –NO2 groups. The activation energy of nitrate ester decomposition of NC/DEGDN/GO nanocomposites increases as a function of GO content from 167 kJ mol−1 and reaches a maximum of 214 kJ mol−1 for a 0.5% w/w GO loading. This suggests an improvement of the nitrate ester bond stability. These findings open a new direction to the application of GO in nitrate ester-based materials for increased stability, safety and shelf life.
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    Stability and hazard properties of improvised nitrocellulose
    (Taylor & Francis, 2023-02-12) Moniruzzaman, Mohammed; Houlihan, Emma; Parker, Matthew; Wilson, Ian
    Nitrocellulose is a vulnerable and sensitive energetic material that can easily be manufactured from ordinary household chemicals and used for illicit purposes. Hazards of this material can lead to incidents resulting from unplanned initiation in manufacturing, storage or handling. Thermal stability and hazard data for so-called improvised nitrocellulose (IN) are crucial to formulate guidance for storage and handling of such materials recovered from illegal possession. This study focused on the energy content, stability and safety properties of IN. The energy contents increase linearly with nitrogen contents of IN. Improvised nitrocellulose showed a similar sensitivity to impact and electrostatic discharge, but vacuum stability testing demonstrated more gas release (2.8–3.4 cm3 g−1) compared to commercial NC (1.7 cm3 g−1). Chemiluminescence analysis established activation energies for hydrolytic and thermolytic decomposition to be 36 and ~93 kJ mol-1, respectively. Results suggest that NC samples recovered from improvised devices or illegal possession should be handled with special care.
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    Ultrasonic studies of solid azobenzene decorated polymer thin films
    (American Chemical Society, 2018-12-19) Moniruzzaman, Mohammed; Christogianni, Paraskevi; Vrcelj, Ranko; Gill, Philip P.
    This work investigates the effect of ultrasound on switching of cis azobenzene isomers to their trans counterparts in solid films of methyl methacrylate and methacryloyloxyazobenzene copolymers [P(MMA/MOAB)]. UV/Vis and 1H NMR spectroscopy demonstrates that 46% of the cis isomer converts to the trans form purely by ultrasonic agitation and 46% converts to the trans isomer by localised ultrasound induced heating effects. Comparative studies of isomerisation by ultrasound wave, heat and visible irradiation shows that ultrasound exposure requires a longer time to switch the cis to trans conformation. The estimated activation energy for the cis to trans conversion in the solid polymer films is shown to be comparable to previous values of azobenzene isomerization, indicating that incorporation of the chromophore in a polymeric system affects the kinetics of transition, but not the barriers to conformational change.