Browsing by Author "Pons, Jean-François"

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    ANFO vapour detection with conducting polymer percolation network sensors and GC/MS
    (Royal Society of Chemistry, 2021-02-15) Lefferts, Merel J.; Humphreys, Lisa H.; Mai, Nathalie; Murugappan, Krishnan; Armitage, Ben I.; Pons, Jean-François; Castell, Martin R.
    Ammonium nitrate mixed with fuel oil (ANFO) is commonly used in improvised explosive devices (IEDs). The development of ANFO vapour sensors that are small, inexpensive, and easy to use will enable widespread IED detection in the context of security and humanitarian demining. Because of concealment and the low vapour pressures of most explosive materials, achieving sufficiently high sensitivity and low limits of detection are some of the main challenges of explosives vapour detection. Here ANFO chemiresistive vapour sensors based on polypyrrole (PPy) percolation networks are presented and compared to gas chromatography-mass spectroscopy (GC/MS) results for ANFO. Improved sensitivities are achieved by using a polymer percolation network instead of a thin film for the gas sensors. Vapour concentrations are detected of 13–180 ppb of ammonia emitted by a variety of different ammonium nitrate-containing fertilisers and fertiliser-diesel mixtures.
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    Complexities associated with nucleation of water and ice from jet fuel in aircraft fuel systems: A critical review
    (Elsevier, 2021-10-29) Ugbeh-Johnson, Judith; Carpenter, Mark; Williams, Colleen; Pons, Jean-François; McLaren, Dan
    The contamination and behaviour of water in aircraft fuel systems remains a significant global research interest following several aircraft incidents. To engineer a solution to the problem of icing in jet fuel, it is crucial to precisely identify the conditions and features that may exacerbate this phenomenon. This review will aid prospective researchers to identify work that has been done and work that is yet to be available for future study. In this review, conclusive data integrating a wide range of literature and also providing an in-depth description of the factors that influence the behaviour of trace water, ice formation in jet fuels was carefully summarised. On investigational studies, it was discovered that to date, no work is available that studies the impact of sustainable jet fuel and its blends on ice formation, size and frequency distribution of dispersed water droplets in aircraft fuel systems. Findings from comparative studies also reveal that surfaces will have an essential role in the growth pattern of ice in aircraft fuel systems. Furthermore, findings show that supercooled water droplets with sizes greater than or equal to 5 µm can induce ice accretion. This review identified a common problem with the prominent methods of reporting results as a graphically fitted plot. Subsequently, it proposed that authors of any original technical work provide raw data as supplementary information to allow comprehensibility. The study further offers a system that could help manage the nature of ice in aircraft fuel tank systems—making it readily available and accessible.
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    Detonation performance of urea hydrogen peroxide
    (Unknown, 2022-04-06) Halleux, Francis; Pons, Jean-François; Wilson, Ian; Van Riet, Romuald; Simoens, Bart; Lefebvre, Michel
    Carbamide Peroxide is commonly used in the cosmetic and pharmaceutical industries as a solid source of hydrogen peroxide. This adduct of Urea and Hydrogen Peroxide (UHP) has explosive properties, which have been only recently studied, highlighting its behaviour of non-ideal tertiary explosive and detonability at large scale. Our work focussed on investigating UHP detonability in the 100 g-scale. A maximum of experimental data, collected from combining laboratory and underwater measurement campaigns, is required to evaluate the detonation performance of non-ideal explosives. Our lab results confirmed self-sustained detonation under heavy confinement, with observed detonation velocities consistent with literature values from large-scale field experiments. We further fired UHP charges underwater and quantified brisance and explosive power respectively from underwater shock pressure and bubble period. By comparing experimental results and numerical simulations, we could assess the level of agreement between lab and underwater detonation performance parameters.
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    Detonation performance of Urea-Hydrogen Peroxide (UHP)
    (Wiley, 2023-02-23) Halleux, Francis; Pons, Jean-François; Wilson, Ian; Simoens, Bart; Van Riet, Romuald; Lefebvre, Michel
    Carbamide Peroxide, an adduct of Urea and Hydrogen Peroxide, is commonly used in the cosmetic and pharmaceutical industries as a solid source of hydrogen peroxide. However, it exhibits explosive properties and can be easily manufactured from readily available household chemicals, making it a potential emerging threat. We carried out a detailed performance assessment, combining experiments, thermochemical calculations and numerical simulations and highlighted a good level of agreement between experimental data from lab, field and underwater firings. A maximum detonation velocity of 3.65 km/s was recorded for unconfined 25 kg UHP charges at 0.85 g/cm 3 (200 mm charge diameter). We determined in these conditions an infinite diameter detonation velocity of 3.94 km/s. These results are also consistent with previous results obtained at small scale under heavy confinement. Airblast measurements highlighted an average 40% TNT equivalence for impulse and 55% for peak overpressure at short distance, which are in good agreement with the 57% (Power Index) calculated from Explo5, while 50% for bubble energy (explosive power) and 20% for shock pressure (brisance) were obtained from underwater experiments. The use of different experimental approaches has proven useful to characterise the performances parameters of a non-ideal explosive for risk assessment purposes.
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    New explosive materials through covalent and non-covalent synthesis: Investigation of explosive properties of trinitrotoluene: Acridine and picric acid: Acridine
    (Elsevier, 2023-07-10) Şen, Nilgün; Pons, Jean-François; Kurtay, Gülbin; Yüksel, Bayram; Nazir, Hasan; Khumsri, Akachai; Atakol, Orhan
    Trinitrotoluene (TNT) and picric acid (PIC) suffer from suboptimal thermal and impact sensitivities, which severely hinder their real-world use. We here demonstrate how co-crystallization with acridine (ACR) can improve these properties of TNT and PIC without detrimentally affecting their explosive performance. Remarkably, while PIC:ACR formed readily, attempts to co-crystallise TNT with ACR led to formation of new covalent bonds between the co-formers, thereby creating a new molecular entity. The structure and energetic behaviour of both novel solid forms (PIC:ACR and TNT-ACR) were characterised using a range of experimental and computational tools, indicating that both materials have improved thermal and mechanical stability but explosive performance has decreased to some extent. These findings will increase the likelihood of rational energetic material design in the future and open a new chapter in this discipline.
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    Nitration of primary amines to form primary nitramines (Review)
    (2016-07-04) McAteer, D.; Pons, Jean-François; Wilson, I. I.; Cavaye, H.
    The nitration of primary amines to form primary nitramines is a rarely reported synthetic procedure which proceeds through a minimum of two steps. This is in stark contrast to the nitration of alcohols and secondary amines which is readily achievable by a number of methods in a single step. In general the primary amine must initially be activated to nitration as direct exposure to nitrating media tends to result in the formation of an ionic nitrate salt. This activation may be achieved through the use of a multitude of protecting groups that are stable to the nitrating conditions used thereafter. The review presented here is an attempt to bring together the published literature on this often overlooked synthetic procedure in energetic materials chemistry.
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    Practical colorimetry of 3-Nitro-1,2,4-Triazol-5-One
    (Wiley, 2018-10-30) Tennant, Mat; Chew, Siao Chien; Krämer, Tobias; Mai, Nathalie; McAteer, Daniel; Pons, Jean-François
    A field ready colorimetric method of quantifying the concentration of aqueous 3‐nitro‐1,2,4‐triazol‐5‐one (NTO), several orders of magnitude below its environmental toxicity level, has been developed. The test allows for the immediate evaluation of the level of contamination in aqueous solution without the need for analytical equipment such as high pressure liquid chromatography (HPLC). The observed colours have been explained by the different NTO species present over the range of pH; these observations are supported by modelling and experimental results.
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    Practical remediation of 3-nitro-1,2,4-triazol-5-one wastewater
    (Wiley, 2017-11-30) Chew, Siao Chien; Tennant, Mat; Mai, Nathalie; McAteer, Daniel; Pons, Jean-François
    Limiting environmental impact is a top priority for the chemical industry, and manufacturing practices need to be well controlled to avoid any potential contamination. In order to reduce waste streams during the processing of 3-nitro-1,2,4-triazol-5-one (NTO), potentially evironmental hazardous at concentrations of 1 g/l, we investigated the potential remediation and recycling of water using a wide range of commercial sorption media. We studied the effect of experimental conditions, including flow rate, initial contaminant concentration and temperature. This led to the selection of Amberlyst A26 OH in a batch process and Activated Carbon in continuous flow, as the most effective sorption methods. Using high performance liquid chromatography photodiode array detection (HPLC-PDA), NTO was quantified from solutions, before and after remediation, showing a complete removal from a 10 g/l NTO solution. Our purification method therefore appears to be suitable for the remediation of NTO-contaminated wastewater.
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    Small-scale characterisation of urea hydrogen peroxide explosive performance using heterodyne velocimetry
    (Royal Society of Chemistry, 2022-06-24) Halleux, Francis; Stennett, Christopher; Pons, Jean-François; Wilson, Ian; Lefebvre, Michel
    Urea Hydrogen Peroxide (UHP) is widely available in the cosmetic and pharmaceutical industries. UHP exhibits the behaviour of a tertiary explosive and previous research from the same authors has highlighted its detonability at small-scale under heavy confinement. In this work, UHP performance parameters are further investigated by heterodyne velocimetry. An average detonation pressure of 3.7 GPa for UHP at a mean density of 0.75 g/cm3 has been determined using the impedance window method, corresponding to a 20% TNT equivalence for brisance. This result is consistent with calculation from empirical correlations. An average 3200 m/s detonation velocity was recorded using contact probes, in excellent agreement with measurements from passive optical probes. This small-scale experimental campaign, which was complementary to and consistent with previous research, has proven useful to characterise the performances of non-ideal explosives for risk assessment purposes.
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    Small-scale detonation of industrial Urea-Hydrogen Peroxide (UHP)
    (Wiley, 2021-12-03) Halleux, Francis; Pons, Jean-François; Wilson, Ian; Van Riet, Romuald; Lefebvre, Michel
    The adduct of Urea and Hydrogen Peroxide (UHP), also called Carbamide Peroxide, is industrially produced as a solid source of hydrogen peroxide for bleaching, disinfection, and oxidation reactions. As a chemical combination of fuel and oxidiser, UHP has explosive potential but it is unclear whether it could sustain a detonation at small scale. In the configuration we tested, we succeeded in recording self-sustained detonation at relatively small scale under heavy confinement, measuring a maximum experimental velocity of detonation of 3860 m/s at an optimum 1.1 g/cm3 loading density. UHP can sustain a detonation, even at the 100 g scale, but this is strongly dependant on booster size, confinement material, loading density, charge length and diameter. According to our performance assessment, pure UHP exhibits the behaviour of a non-ideal tertiary explosive. Maximum calculated detonation pressures are below 10 GPa, the order of magnitude for commercial blasting explosives. Small-scale results are consistent with literature values from large-scale experiments, although literature on the matter is quite limited. The proposed experimental method can be used to quantify the detonability and performance of other industrial materials that may have energetic properties, or small samples of homemade explosive compositions, avoiding time-consuming, expensive and potentially hazardous large-scale experiments.
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    Synthesis, structure characterization, Hirshfeld surface analysis, and computational studies of 3-nitro-1,2,4-triazol-5-one (NTO):acridine
    (Springer, 2024-04-30) Şen, Nilgün; Pons, Jean-François; Zorlu, Yunus; Dossi, Eleftheria; Persico, Federica; Temple, Tracey; Aslan, Nazife; Khumsri, Akachai
    To modify the physical features and extend applications of the 3-nitro-1,2,4-triazol-5-one (NTO), we synthesized NTO with acridine (ACR) at a molar ratio of 1:1, a neutralization reaction. Through altering the chemical composition, it was possible to alter physical properties such as thermal stability, free space (voids), packing coefficient, crystal density, difference in pKa of co-formers, morphology, solubility, and impact sensitivity, and detonation parameters . It appears that physical attributes could be entirely altered. Single-crystal and powder X-ray diffraction methods, infrared spectroscopy, mass spectrometry, nuclear magnetic resonance spectroscopy (1H-NMR and 13C-NMR), and thermal analysis were utilized to comprehensively characterize and confirm the formation of the structure of NTO:ACR. The substantial hydrogen bond interactions and planar layered structures observed between the cations and anions generated a complex 3D network, providing insight into the structure–property interrelationship. One intriguing feature discovered is the layered structure present in NTO:ACR, which may be responsible for the low impact sensitivity. According to the experimental results, NTO:ACR showed good thermal stability (Td = 229 °C) and outstanding impact sensitivity (IS = 100 J). Detonation velocity and pressure were calculated using the EXPLO5 software program and found to be 7006 m·s−1 and 20.02 GPa, respectively.
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    Urea-Hydrogen Peroxide (UHP): comparative study on the experimental detonation pressure of a non-ideal explosive
    (Wiley, 2023-08-28) Halleux, Francis; Pons, Jean-François; Wilson, Ian; Stennett, Christopher; Van Riet, Romuald; Lefebvre, Michel
    Carbamide Peroxide, an adduct of Urea and Hydrogen Peroxide (UHP) industrially used as a solid source of hydrogen peroxide, exhibits the behaviour of a tertiary explosive but a detailed performance characterisation is still lacking in the literature. In this work, we calculated a 20% experimental TNT equivalence for brisance, i.e. the shattering effect from the shock wave transmitted from the detonating high explosive into adjacent materials, by experimental indirect measurement of UHP detonation pressure. We determined a 3.5 GPa detonation pressure for 5 kg unconfined UHP charges (0.87 g/cm3, 120 mm charge diameter) by measuring the attenuated shock wave velocity (ASV) in adjacent inert materials using passive optical probes. Particle velocity measurements at the interface of a PMMA impedance window carried out with Photonic Doppler Velocimetry on scaled-down charges of 90 g UHP under heavy confinement (0.85 g/cm3, 30 mm charge diameter, 4 mm thick steel) are consistent with ASV results in the PMMA acceptors but further investigations are required to determine the detonation pressure, using a small-scale experimental set-up. The ASV method has proven reliable to assess the brisance of a non-ideal explosive for risk assessment purposes.