Browsing by Author "Mai, Nathalie"
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Item Open Access 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.Item Open Access Characterization of water droplets size distribution in aviation turbine fuel: ultrasonic homogeniser vs high shear speed mixer(Elsevier, 2022-09-21) Ugbeh-Johnson, Judith; Carpenter, Mark; Okeke, Nonso Evaristus; Mai, NathaliePumps, pressure drops across fittings, and flight operations (such as turning manoeuvres, take-off, and landing) are some of the many sources of turbulence mixing and shearing in aircraft fuel systems, therefore, making it an inevitable condition. Literature established that shearing conditions would influence the droplets and droplets size distribution in an oil/water emulsion. So, low intensity shearing conditions could be beneficial as it promotes droplets coalescence, which could be a driving force for a weak emulsion. However, to date no experimental data has shown the influence homogenising intensity and total water content has on dispersed water droplets size distribution in aviation fuel. Therefore, to expand knowledge of quantification of measurements of dispersed water droplets in aviation fuel, this study characterizes dispersed water droplets in aviation turbine fuel, varying available laboratory homogenising devices and water content. Results presented show that droplets count increases with water concentration and shearing effect. To provide more statistical evidence, kurtosis and skew values were calculated from the extrapolated data and compared with data from a hexanol/water mixture given that hexanol is likely to form a stable emulsion. Experimental results show that the higher the homogenising intensity the more stable the emulsion is likely to be with a higher kurtosis and skew value close to that for the hexanol/water mixture. Therefore, observations show that mild shearing conditions (high shear mixing in this case) could help promote droplets coalescence, leading to a better separation ability.Item Open Access Chemical modification of β-cyclodextrins: balancing soft and rigid domains in complex structures(Wiley, 2019-09-19) Luppi, Federico; Mai, Nathalie; Kister, Guillaume; Gill, Philip P.; Gaulter, Sally; Stennett, Christopher; Dossi, EleftheriaCrystalline 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.Item Open Access Data for "Investigation into the environmental fate of the novel explosive 3-nitro-1,2,4-triazol-5-one (NTO): Acridine and its constituents"(Cranfield University, 2024-10-22) Persico, Federica; Temple, Tracey; Mai, Nathalie; Pons, Jean-Francois3-Nitro-l,2,4-triazol-5-one (NTO) is an Insensitive High Explosive (IHE) often considered as a safer alternative to traditional explosive 1,3,5-trinitroperhydro-1,3,5-triazine (RDX). NTO is highly soluble in water and previous studies have revealed that when transported through soil it has the potential to create an environmental challenge as it tends to easily reach groundwater systems. To combat some of these challenges recent work has shown that combining NTO in a co-crystal with Acridine (ACR) at a molar ratio of 1:1 has a positive effect on thermal stability and a reduction in solubility. This paper experimentally evaluates the fate and transport of this NTO:ACR co-crystal compared to its individual components, NTO and ACR, in a low-inorganic matrix. The findings of this study reveal that despite NTO maintaining its high solubility within the co-crystal structure , the quantity of NTO retained within the upper layers of the sand column is larger for NTO:ACR. The rate of transport of these materials through the soil was also considered. While the rate of transport of NTO was proportional to its concentration the presence ACR was shown to have an antagonistic effect on this activity. Therefore, consistent evidence is provided here of an interaction between NTO and ACR within the co-crystal structure which results in a lower solubility for NTO. Increasing the retention of a containment within soil could aid in environmental remediation of the area post-use.Item Open Access Dataset for "Environmental Fate of 2,4,6-trinitrotoluene (TNT) in Marine Environments - Dissolution and Remediation Strategies"(Cranfield University, 2024-09-16) Persico, Federica; Temple, Tracey; Mai, Nathalie; Kadansky, EvieItem Open Access DNAN behaviour during laboratory-scale explosiveness test(Cranfield University, 2018-03-19 08:49) Galante, Erick; Mai, Nathalie; Ladyman, Melissa; Gill, Philip; Temple, TraceyVideo recorded during a laboratory-scaled explosiveness test, in which a 10mg sample of DNAN was heated (43ºC/min) within a sealed 10mL headspace vialItem Open Access The effect of soil type on the extraction of insensitive high explosive constituents using four conventional methods(Elsevier, 2019-03-01) Temple, Tracey J.; Cipullo, S.; Galante, Erick; Ladyman, Melissa K.; Mai, Nathalie; Parry, T.Explosive contamination is commonly found at military and manufacturing sites (Hewitt et al., 2005; Clausen et al., 2004; Walsh et al., 2013). Under current environmental legislation the extent of the contamination must be characterized by soil sampling and subsequent separation of the explosive contaminants from the soil matrix by extraction to enable chemical analysis and quantification (Dean, 2009). It is essential that the extraction method can consistently recover explosive residue from a variety of soil types i.e. all materials that have not degraded or irreversibly bound to the matrix, so that any resultant risk is not underestimated. In this study, five different soil types with a range of organic content, particle size and pH, were spiked with a mixture of RDX, DNAN, NQ and NTO at 50 mg/kg and were extracted using one of four one-step extraction methods: stirring, shaking, sonication, and accelerated solvent extraction (ASE). Analysis of the extraction efficiencies of the four methods found that they were broadly successful for the extraction of all IHE constituents from all five soils (an average of 84% ± 14% recovery across 80 extractions). However, soils with high organic content (Total Organic Content (TOC) ≥ 2%) were found to significantly affect extraction efficiency and reproducibility. NTO and DNAN were the least consistent in extraction efficiency with poorest recovery of NTO as low as 37% ± 2%. Of the four tested methods shaking was found to be the most reproducible, though less efficient than stirring (64%–91%). ASE was found to have the most variable results for extraction of IHE constituents suggesting that ASE was the most affected by the different soil types. Therefore, it is recommended that the efficiency and reproducibility of the selected extraction method should be validated by extracting known concentrations of the IHE from the soil of interest and that any required correction factors are reported.Item Open Access Effects of Particulate Contamination and Jet Fuel Chemistry on the Nucleation of Water and Ice in Aircraft Fuel Systems(Cranfield University, 2022-04) Ugbeh-Johnson, Judith; Carpenter, Mark; Mai, Nathalie; Williams, MikeThe aviation industry is currently facing increasing environmental and energy challenges regarding its fuel use. Research is therefore currently under way to develop new sustainable aviation fuels. Understanding the properties of these fuels (along with the changing properties of existing fuel types) is required to understand their impact on aircraft fuel systems. Water solubility, water settling and ice formation in fuel are such properties of interest. The presence of water in jet fuel/fuel systems has been a long-standing issue in the aviation industry. Therefore, it is important to precisely identify the conditions and features that may exacerbate this phenomenon, understanding how fuel composition, temperature, water droplet sizes, flowrate and pipe surface affect ice formation and water solubility. Currently, there is relatively limited data regarding water solubility/settling rate and ice formation in sustainable fuels, specifically those specified in ASTM D7566. This work gives a comprehensive account of the recent advances and technologies in the literature indicating conditions that might lead to the nucleation of water and ice in aircraft fuel systems. These conditions have then been applied to characterizing dispersed water droplets in alternative fuels and conventional Jet A-1. Subsequently, the requirements have been applied to the design, set up, and effectiveness of an ice test rig to understand the types and amounts of ice that can be produced from different sustainable aviation fuel blends. In doing so, this work has helped shed light on the role of fuel composition in ice accretion and whether ice accumulation on a pump inlet strainer may impact pump performance. Furthermore, the results from this work will serve as a basis for design guidelines to minimise ice formation within an aircraft fuel system and help identify some potential/sustainable jet fuel candidates for ASTM D7566 certified jet fuels.Item Open Access Evaluation of small-scale combustion of an insensitive high explosive formulation containing 3-nitro-1,2,4-triazol-5-one (NTO), 2,4-dinitroanisole (DNAN), and 1,3,5-trinitroperhydro-1,3,5-triazine (RDX)(Taylor and Francis, 2020-05-25) Galante, Erick B. F.; Mai, Nathalie; Ladyman, Melissa K.; Gill, Philip P.; Temple, Tracey J.; Coulon, FredericEnergetic materials are often disposed by open-burning or open-detonation as it is a cost-effective and efficient means of destroying explosive material, and often minimizes the need to transport hazardous explosives to treatment facilities. This practice is often scrutinized for the negative environmental impact of the odorous and unsightly toxic gaseous emissions as well as the resulting deposition residues, which often contain unburned energetic materials. With the increasing use of Insensitive High Explosive compositions in munitions, it is essential that the potential environmental impact of their disposal is assessed before their extensive use to prevent the kind of contamination incidents experienced with legacy explosives. Therefore, the aim of this work was to develop a controlled laboratory experiment to identify the gaseous emissions and the energetic material residues that are generated through the combustion of the IHE components 3-nitro-1,2,4-triazol-5-one (NTO), 2,4-dinitroanisole (DNAN), and 1,3,5-trinitroperhydro-1,3,5-triazine (RDX). A sealed vial containing small (mg) quantities of energetic material was heated until the energetic material combusted. Gas chromatography/mass spectrometry (GCMS) was used to calculate the oxygen consumption and to identify the gases that were generated. The solid residues were analyzed by high-performance liquid chromatography (HPLC) to quantify unburned energetic material. Results showed that DNAN was the most resistant to burning, thus leaving significant quantities of unreacted starting material in the vial. An interesting observation for the IHE formulation was that DNAN also inhibited the combustion of NTO and RDX. The gases emitted during the open burning of IHE components and mixtures included CO, CO2, and N2O as expected, but the proportions differed when the components and mixture were compared, reflecting the influence of DNAN on the burning behavior. From our data, we concluded that open-burning DNAN-based formulations is an environmentally unfavorable waste-management practice for the disposal of IHEs mainly due to generation of solid residues as well as unburnt DNAN.Item Open Access Fate and transport of insensitive high explosives in the environment(2018-10) Temple, Tracey J.; Coulon, Frederic; Mai, NathalieThe research undertaken for this thesis has contributed to better understanding of the fate and transport on insensitive high explosives (IHE) formulations and suitable extraction methods from soil. Investigations into the dissolution behavior of hexahydro-1,3,5-triazine (RDX) from Polymer Bonded Explosives (PXB) showed that the polymer retained almost 97% of the explosive filling. This indicates that these formulations release their contents slowly although consistently suggesting that cumulative contamination may occur in the environment. Due to low release of RDX from the polymer it was necessary to validate the findings by ensuring all explosives were accounted for. As there was no existing extraction methods for PXB a novel Accelerated Solvent Extraction (ASE) method was successfully developed and optimized. To further understand IHE behaviours in the environment, fate and transport of IHE in soil was then considered. However, as RDX behaviour is well understood attention was then turned to IMX formulations in soil. Again suitable extraction for IHE in soil had not been reported, therefore a comparison of suitable extraction methods for IHE constituents in soil was undertaken. Results showed extraction of IHE is dependent on soil types, which highlighted the need to pre-determine extraction efficiency for soil type and targeted contamination. Therefore pre-testing extraction with known concentrations is recommended. This research was then applied to understanding the behaviour of the mixed constituents in soil, following column transportation studies. Results contributed to and supported work from the literature on the behaviour of individual IHE constituents suggesting that these explosives in combination did not adversely interact with each other when in soil. The novelty of this work was the investigation of IHE as mixtures rather than individually. This work has provided valuable insights into the behaviour of two different IHE (PBX and IMX) in the environment, and has communicated suitable extraction procedures to enable full quantification of contaminant concentrations.Item Open Access IHE1 behaviour during laboratory-scale explosiveness test(Cranfield University, 2018-03-15 13:50) Galante, Erick; Mai, Nathalie; Ladyman, Melissa; Gill, Philip; Temple, TraceyVideo recorded during a laboratory-scaled explosiveness test, in which a 20mg sample of NTO, DNAN and RDX was heated (43ºC/min) within a sealed 10mL headspace vialItem Open Access Influence of humidity on the decomposition process of double base rocket propellant(Elsevier, 2023-09-29) Romero Jabalquinto, Alonso; Mai, Nathalie; Mohammed, Yahaya; Gill, Philip P.The decomposition mechanisms of the polymer cellulose nitrate (NC) which is used in double base (DB) rocket propellants, have been extensively studied, and the influence of storage temperature on the lifetime of these energetic formulations is well known. However, the impact of humidity and water on the polymer decomposition process is poorly understood. This paper studies the influence of humidity on the decomposition chemistry of NC and its impact on shelf life. Stabiliser consumption was first analysed by ageing the propellant in sealed vials at different humidity levels for 7 days at an isothermal temperature of 90 °C. Samples were also analysed using heat flow calorimetry (HFC) at isothermal temperatures of 80 °C, 90 °C, and 100 °C. The results indicates that stabiliser depletion increases with increasing water content. Life assessment calculations (AOP 48 ed2) show that increasing the absolute humidity from 6 to 22 g m-3 will decrease the propellant life from 11 to 6 years (25 °C equivalents). The HFC results follow the same trend as the stabiliser depletion where greater absolute humidity increases the heat flow by up to 400 %. Unlike the pass/fail criteria for stabiliser depletion, the HFC samples passed the 10-year (25 °C equivalent) life criteria (STANAG 4582). A multi-temperature (80, 90, 100 °C) kinetic analysis of the initial heat flow showed that the heat flow rate increased with increasing humidity, but the activation energy for all humidity levels remained at 131 (± 3) kJ mol−1.Item Open Access Investigation into the environmental fate of the combined Insensitive High Explosive constituents 2, 4-dinitroanisole (DNAN), 1-nitroguanidine (NQ) and nitrotriazolone (NTO) in soil(Elsevier, 2018-01-12) Temple, Tracey J.; Ladyman, Melissa K.; Mai, Nathalie; Galante, Erick; Ricamora, M; Shirazi, R; Coulon, FredericContamination of military ranges by the use of explosives can lead to irreversible environmental damage, specifically to soil and groundwater. The fate and effects of traditional explosive residues are well understood, while less is known about the impact of Insensitive High Explosives (IHEs) that are currently being brought into military service. Current research has focussed on the investigation of individual constituents of IHE formulations, which may not be representative of real-world scenarios when explosive residues will be deposited together. Therefore, this study investigated the fate and transport of the combined IHE constituents 2,4-dinitroanisole (DNAN), 1-nitroguanidine (NQ) and 3-nitro-1,2,4-triazol-5-one (NTO) in two UK soil types. Static experiments ran for 9 weeks to determine the fate of the combined explosive constituents in soil by monitoring the rate of degradation. Transport was examined by running soil column experiments for 5 weeks, with a watering regime equivalent to the average yearly UK rainfall. Both static and soil column experiments confirmed that DNAN and NTO started to degrade within twenty-four hours in soil with high organic content, and were both completely degraded within sixty days. NQ was more stable, with 80% of the original material recovered after sixty days. The major degradation product of DNAN in the test soils was 2-amino-4-nitroanisole (2-ANAN), with trace amounts of 4-amino-2-nitroanisole. NTO was rapidly degraded in soil with high organic content, although no degradation products were identified. Results supported work from literature on the individual constituents DNAN, NQ and NTO suggesting that the three explosives in combination did not interact with each other when in soil. This study should provide a useful insight into the behaviour of three combined Insensitive High Explosive constituents for the predication of soil and water contamination during military training.Item Open Access Investigation of water droplet size distribution in conventional and sustainable aviation turbine fuels(Society of Automotive Engineers, 2022-05-17) Ugbeh Johnson, Judith; Carpenter, Mark; Okeke, Nonso Evaristus; Nnabuife, Somtochukwu Godfrey; Mai, NathalieWater droplet size variation has been established in the literature as an important variable that influences the behavior and characteristics of water in fuel emulsion. However, with the growing demand for sustainable aviation fuels (SAF), no data is available that shows how these fuels will affect the size of dispersed water droplets and their frequency distribution. To address this lack of knowledge, this study explores and presents experimental results on the characterization of dispersed water droplets in alternative fuels and Jet A-1 fuel under dynamic conditions. The alternative fuels comprised of two fully synthetic fuels, two fuels synthesized from bio-derived materials, and one bio-derived fuel. The data and statistics presented reveal that water droplet frequency and size distribution are sensitive to changes in fuel composition. Observations showed an evident transition of the droplet percentile over time in the cumulative frequency distribution; this could be attributed to droplet coalescence to form larger droplets. Mean droplet diameters between 3 and 6 μm were observed for all the fuels tested. With further analysis based on recommendations proposed in this work, the data may assist in providing insight to filter manufacturers.Item Open Access Low hazard small-scale synthesis and chemical analysis of high purity nitroglycerine (NG)(Royal Society of Chemistry, 2015-10-06) Contini, Alessandro E.; Flood, Nathan; McAteer, Daniel; Mai, Nathalie; Akhavan, JacquelineA previously reported two-phase (99.5% fuming nitric acid/dichloromethane) batch method to prepare high purity 1,2,3-propanetriyl trinitrate (nitroglycerine, NG) was evaluated, simplified and adapted specifically for low hazard small-scale synthesis. The purity of the product, as determined by NMR spectroscopy, HPLC and IR spectroscopic analysis was found to be greater than 99%. The quick synthetic method is highly recommended when small amounts of highly pure NG are required for analytical and related purposes in the absence of a microreactor.Item Open Access Modified Arrhenius kinetics for double base propellant decomposition: effect of water(Elsevier, 2024-05-31) Romero Jabalquinto, Alonso; Mai, Nathalie; Belghiche, Samira; Gill, Philip P.Numerous studies have been conducted on the decomposition mechanisms of cellulose nitrate (NC), a polymer employed in double base (DB) rocket propellants. It is well known that storage temperature affects the lifetime of these energetic formulations. However, less studies have been published on the influence of water. This research examined the role of water on the stabiliser consumption rate during accelerated ageing of a DB rocket propellant, as well as the impact on the shelf life prediction of the energetic formulation. Different volumes of water (0.8, 1.6, 2 and 4 µl/g) were added to the propellant in sealed vials, which were then isothermally aged (70, 80, 90, 100 °C). Analyses of the stabiliser consumption showed a faster decomposition kinetics in presence of water which is indirectly linked to the shortening of the storage life of the NC based propellant by 35 %. For the conditions, an activation energy of 133 ± 4 kJ/mol was reported for the water catalytic decomposition mechanism. A numerical model that included water as a variable was reported to reduce the uncertainty in the determination of the service life of NC based propellant. International standards such as Allied Ordnance Publication 48 should not overlook the effect of water/moisture on the safety of ammunition containing NC and should implement a modified Arrhenius equation.Item Open Access NTO behaviour during laboratory-scale low confinement test(Cranfield University, 2018-03-15 13:50) Galante, Erick; Mai, Nathalie; Ladyman, Melissa; Gill, Philip; Temple, TraceyVideo recorded during a laboratory-scaled explosiveness test, in which a 20mg sample of NTO was heated (43ºC/min) within a sealed 10mL headspace vialItem Open Access Optimised accelerated solvent extraction of hexahydro-1,3,5-trinitro-1,3,5 triazine (RDX) from polymer bonded explosives(Cranfield University, 2018-06-04 08:56) Ladyman, Melissa; Mai, Nathalie; Temple, Tracey; Coulon, FredericRaw HPLC data and calibration curves used to determine extraction efficiency of varying methods. The analysed data and produced graphs are also given. Numbers given are for % recovery of explosive (RDX or HMX) by extraction method/ optimized condition (ASE/ Sohxlet).Item Open Access Optimised accelerated solvent extraction of hexahydro‐1, 3, 5‐trinitro‐1, 3, 5 triazine (RDX) from polymer bonded explosives(Wiley, 2018-10-16) Temple, Tracey J.; Goodwin, Catherine; Ladyman, Melissa K.; Mai, Nathalie; Coulon, FredericAn Accelerated Solvent Extraction (ASE) method was developed and optimised to extract hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) from a polyurethane matrix. The ASE method development was benchmarked against Soxhlet extraction with a view to improving extraction efficiency in terms of time and solvent volume. Key parameters for the ASE method development involved selecting the most appropriate solvent, optimising static time, ensuring a safe oven temperature for explosives, determination of a sufficient number of rinse cycles and effective sample preparation. To achieve optimal extraction, cutting the PBX samples to maximise solvent exposure was essential. The use of acetone with a static time of 10 minutes at 100 °C with three rinse cycles achieved 97 %±10 % extraction of RDX from PBX in 40 minutes using 72 mL solvent. Extraction time was reduced from 48 hours and solvent use by half compared to the standard Soxhlet extraction. To validate the developed ASE method, two other PBX samples containing different quantities of explosive were also fully extracted using the same parameters. Overall, ASE efficiency was comparable to Soxhlet, which places the ASE as a good alternative and shows potential for implementation as a standard method for other polymer based explosives.Item Open Access PBX 110 behaviour during laboratory-scale explosiveness test(Cranfield University, 2018-03-15 13:50) Galante, Erick; Mai, Nathalie; Ladyman, Melissa; Gill, Philip; Temple, TraceyVideo recorded during a laboratory-scaled explosiveness test, in which a 20mg sample of PBXN-110 was heated (43ºC/min) within a sealed 10mL headspace vial