Showing papers in "Propellants, Explosives, Pyrotechnics in 2013"

Altering Reactivity of Aluminum with Selective Inclusion of Polytetrafluoroethylene through Mechanical Activation

Abstract: Micrometer-sized aluminum is widely used in energetics; however, performance of propellants, explosives, and pyrotechnics could be significantly improved if its ignition barriers could be disrupted. We report morphological, thermal, and chemical characterization of fuel rich aluminum-polytetrafluoroethylene (70–30 wt-%) reactive particles formed by high and low energy milling. Average particle sizes range from 15–78 μm; however, specific surface areas range from approx. 2–7 m2 g−1 due to milling induced voids and cleaved surfaces. Scanning electron microscopy and energy dispersive spectroscopy reveal uniform distribution of PTFE, providing nanoscale mixing within particles. The combustion enthalpy was found to be 20.2 kJ g−1, though a slight decrease (0.8 kJ g−1) results from extended high energy milling due to α-AlF3 formation. For high energy mechanically activated particles, differential scanning calorimetry in argon shows a strong, exothermic pre-ignition reaction that onsets near 440 °C and a second, more dominant exotherm that onsets around 510 °C. Scans in O2-Ar indicate that, unlike physical mixtures, more complete reaction occurs at higher heating rates and the reaction onset is drastically reduced (approx. 440 °C). Simple flame tests reveal that these altered Al-polytetrafluoroethylene particles light readily unlike micrometer-sized aluminum. Safety testing also shows these particles have high electrostatic discharge (89.9–108 mJ), impact (>213 cm), and friction (>360 N) ignition thresholds. These particles may be useful for reactive liners, thermobaric explosives, and pyrolants. In particular, the altered reactivity, large particle size and relatively low specific surface area of these fuel rich particles make them an interesting replacement for aluminum in solid propellants.

Preparation and Characterization of Insensitive HMX/Graphene Oxide Composites

Abstract: may be more suitable for application in the energetic field compared with other carbon material. Moreover, due to the oxygen-containing functional groups on their basal plane and edges, GO sheets are highly anisotropic and can be readily exfoliated to form a stable, single layer suspension in HMX solution without any surfactant. The resulting suspensions are far more stable than those of the graphite powders [20]. At the same time, GO can be viewed as an unconventional “soft material” as it carries the characteristics of polymers, colloids, membranes [21], which is better for binding the impact energy. Summarizing the observa

Review on Energetic Thermoplastic Elastomers (ETPEs) for Military Science

Abstract: Energetic thermoplastic elastomers (ETPE) are futuristic binders for propellant/explosive formulations. Various aspects of ETPEs are addressed in this review. Synthesis modes of different copolymers for ETPEs are discussed. Attention is also given to formulations and thermal studies of ETPE-based propellants and explosives. Processing methods and parameters of composition are included. As the cost and environmental concerns are prime factors of future generation propellants/explosives, the recovery and reprocessing methods are also briefly discussed.

Aging of HTPB/Al/AP Rocket Propellant Formulations Investigated by DMA Measurements

Abstract: Three HTPB-based rocket propellant formulations containing ammonium perchlorate and aluminum particles, with different aluminum content and particle size, have been manufactured. The study has focused on the change of mechanical properties with aging time by using dynamic mechanical analysis (DMA). Therefore, propellant formulations underwent an accelerated aging program, in air (RH<10 %), between 60 °C and 90 °C with aging time adjusted to a thermal equivalent load of 15 to 20 years at 25 °C. DMA investigations revealed distinct changes in the shape of the loss factor curve. These curves were modeled with three exponentially modified Gaussian (EMG) functions in order to get the molecular interpretation of the involved aging phenomena by separating the binder fractions with different mobility. Aging of propellant formulations can be followed by considering only two parameters: the areas of the second and third loss factor transition peaks (A2, A3), and the corresponding maximum temperature values of the assigned Gauss peaks (Tc2, Tc3).

Attractive Nitramines and Related PBXs

Abstract: At present, cis-1,3,4,6-tetranitro-octahydroimidazo-[4,5-d]imidazole (bicyclo-HMX, BCHMX) and e-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (e-HNIW, CL-20) are a topic of interest from the attractive and the potentially attainable nitramines. They were chosen to be studied in comparison with 1,3,5-trinitro-1,3,5-triazinane (RDX) and β-1,3,5,7-tetranitro-1,3,5-tetrazocane (β-HMX). Marginal attention is devoted also to 4,8,10,12-tetranitro-2,6-dioxa-tetraazawurtzitane (Aurora 5). BCHMX, e-HNIW, RDX, and HMX were studied as plastic bonded explosives (PBXs) with elastic properties based on Composition C4 and Semtex 10 matrices. Also they were studied as a highly pressed PBXs based on the Viton A binder. The detonation parameters and sensitivity aspects of these nitramines and their corresponding PBXs were determined. Relative explosive strengths (RS) of these compositions are mentioned with mutual relationships between the measured RS values and some detonation parameters. These relationships indicate a possibility of changes in detonation chemistry of these mixtures filled mainly by HNIW. A sensitivity of RS-CL20 (HNIW with reduced sensitivity) is reported and the new findings in the friction sensitivity are discussed.

Effect of Solids Loading on Resonant Mixed Al-Bi2O3 Nanothermite Powders

Abstract: Sensitive nanoenergetic powders, such as nanothermites, have traditionally been processed by ultrasonic mixing of very low solids loaded suspensions in organic solvents, which has restricted their use and application due to high solvent content and associated handling issues. In this work, we report on the performance and mixing quality of nanothermite mixtures prepared in a LabRAM resonant mixer at high solids loadings as compared to ultrasonic mixing. Specifically, the aluminum-bismuth(III) oxide (Al/Bi2O3) system processed in the polar solvent N,N-dimethylformamide (DMF) was investigated. It was found that the performance and overall quality of mixing was strongly correlated to the volumetric solids loading during processing; increasing volumetric solids loading decreases separation of particles, leading to more particle interaction and more intimate mixing. The measured performance of this system processed at 30 vol-% was similar to traditionally ultrasonicated mixtures. Increasing the solids loading above 30 vol-% yielded diminishing returns in performance and may introduce additional safety concerns since dry powders are very sensitive to electrostatic discharge. This mixing approach uses significantly less solvent than traditional ultrasonic mixing, results in a higher density final material, and is amenable to scaling. In addition, solvent wetted nanothermite mixed at 30 vol-% solids loading can be mixed and deposited from a single applicator and was observed to be over five orders of magnitude less sensitive to electrostatic discharge than dry powders. This relative insensitivity enables the safe deposition of high density nanothermite ink onto devices.

Preparation and Properties of An Insensitive Booster Explosive Based on LLM‐105

Abstract: A new insensitive booster explosive based on 2,6-diamino-3,5-dinitropyrazing-1-oxide (LLM-105) was prepared by a solvent-slurry process with ethylene propylene diene monomer (EPDM) as binder SEM (scanning electron microscopy) was employed to characterize the morphology and particle size of LLM-105 and molding powder The mechanical sensitivity, thermal sensitivity, shock wave sensitivity, and detonation velocity of the LLM-105/EPDM booster were also measured and analyzed The results show that both mechanical sensitivity and thermal sensitivity of LLM-105/EPDM are much lower than that of conventional boosters, such as PBXN-5 and A5 Its shock wave sensitivity is also lower than that of PBXN-5 and PBXN-7 When the density of charge is 95 % TMD, its theoretical and measured detonation velocities are 7858 m s−1 and 7640 m s−1, respectively These combined properties suggested that LLM-105/EPDM can be used as an insensitive booster

Isocyanate‐Free and Dual Curing of Smokeless Composite Rocket Propellants

Abstract: Landsem, Eva; Jensen, Tomas Lunde; Kristensen, Tor Erik Holt; Hansen, Finn Knut; Benneche, Tore; Unneberg, Erik. Isocyanate-Free and Dual Curing of Smokeless Composite Rocket Propellants. Propellants, explosives, pyrotechnics 2013 ;Volum 38.(1) s. 75-86

On AlO Emission Spectroscopy as a Diagnostic in Energetic Materials Testing

Abstract: The emission of AlO is commonly observed in tests involving aluminum combustion in propellants and explosives. Such emission has been used as a signature of combustion, as a tool for measuring ignition and reaction times, and as a thermometer. This paper provides a critical review of methodologies exploiting AlO emission spectroscopy as a quantitative tool in energetics testing. Controlled tests involving aluminized explosives, as well as those using added alumina, are conducted, in which AlO emission is quantified and compared to total oxidation in the final residue. Experimental parameters such as optical depth and fireball confinement are systematically varied to examine the effect on AlO emission. We find that thermometry using AlO remains valid, and a new approach to using low resolution spectra is proposed. However, AlO emission spectroscopy or photometry can be quantitatively correlated to ignition and burning time, or used to infer the presence or absence of aluminum combustion, only under a limited set of circumstances. Factors that limit the ability to use AlO emission quantitatively are discussed in depth.

Agglomeration Characteristics of Aluminum Particles in AP/AN Composite Propellants

Abstract: Most solid rockets are powered by ammonium perchlorate (AP) composite propellant including aluminum particles. As aluminized composite propellant burns, aluminum particles agglomerate as large as above 100 μm diameter on the burning surface, which in turn affects propellant combustion characteristics. The development of composite propellants has a long history. Many studies of aluminum particle combustion have been conducted. Optical observations indicate that aluminum particles form agglomerates on the burning surface of aluminized composite propellant. They ignite on leaving the burning surface. Because the temperature gradient in the reaction zone near a burning surface influences the burning rate of a composite propellant, details of aluminum particle agglomeration, agglomerate ignition, and their effects on the temperature gradient must be investigated. In our previous studies, we measured the aluminum particle agglomerate diameter by optical observation and collecting particles. We observed particles on the burning surface, the reaction zone, and the luminous flame zone of an ammonium perchlorate (AP)/ammonium nitrate (AN) composite propellant. We confirmed that agglomeration occurred in the reaction zone and that the agglomerate diameter decreased with increasing the burning rate. In this study, observing aluminum particles in the reaction zone near the burning surface, we investigated the relation between the agglomerates and the burning rate. A decreased burning rate and increased added amount of aluminum particles caused a larger agglomerate diameter. Defining the extent of the distributed aluminum particles before they agglomerate as an agglomerate range, we found that the agglomerate range was constant irrespective of the added amount of aluminum particles. Furthermore, the agglomerate diameter was ascertained from the density of the added amount of aluminum particles in the agglomerate range. We concluded from the heat balance around the burning surface that the product of the agglomerate range and the burning rate was nearly constant irrespective of the added amount of aluminum particles. Moreover, the reduced burning rate increased the agglomerate range.

Characterization of PAX‐21 Insensitive Munition Detonation Residues

Abstract: Insensitive high explosives are being used in military munitions to counteract unintended detonations during storage and transportation. These formulations contain compounds such as 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazol-5-one (NTO), which are less sensitive to shock and heat than conventional explosives. We conducted a series of four tests on snow-covered ice utilizing 60-mm mortar cartridges filled with 358 g of PAX-21, a mixture of RDX, DNAN, and ammonium perchlorate. Rounds were detonated high- and low-order using a fuze simulator to initiate detonation. Blow-in-place (BIP) operations were conducted on fuzed rounds using an external donor charge or a shaped-charge initiator. Results indicate that 0.001 % of the original mass of RDX and DNAN were deposited during high-order detonations, but up to 28 % of the perchlorate remained. For the donor block BIPs, 1 % of the RDX and DNAN remained. Residues masses for these operations were significantly higher than for conventional munitions. Low-order detonations deposited 10–15 % of their original explosive filler in friable chunks up to 5.2 g in mass. Shaped-charge BIPs scattered 15 % of the filler and produced chunks up to 15 g. Ammonium perchlorate residue masses were extremely high because of the presence of large AP crystals, up to 400 μm in the recovered particles.

Factors Influencing Triacetone Triperoxide (TATP) and Diacetone Diperoxide (DADP) Formation: Part I

Abstract: Conditions, which result in the formation of tria- cetone triperoxide (TATP) or diacetone diperoxide (DADP) from acetone and hydrogen peroxide (HP) were studied for the purposes of inhibiting the reaction. Reaction of HP with acetone precipitates either DADP or TATP, but the overall yield and amount of each was found to depend on (1) reac- tion temperature, (2) the molar ratio of acid to HP/acetone, (3) initial concentrations of reactants, and (4) length of reac- tion. Controlling molar ratios and concentrations of starting materials was complicated because both sulfuric acid and hydrogen peroxide were aqueous solutions. Temperature exercised great control over the reaction outcome. Holding all molar concentrations constant and raising the tempera- ture from 5 to 258C showed an increase of DADP over TATP formation and a decrease in overall yield. At 258C a good yield of TATP was obtained if the HP to acetone ratio was kept between 0.5-to-1 and 2-to-1. At constant temperature and HP-to-acetone held at one-to-one ratio, acid-to-HP molar ratios between 0.10 : 1 and 1.2 : 1 pro- duced good yield of TATP. Plotting the molality of HP vs. that of sulfuric acid revealed regions, in which relatively pure DADP or pure TATP could be obtained. In addition to varying reaction conditions, adulterants placed into ace- tone were tested to inhibit the formation of TATP. Because there is much speculation of the relative stability, sensitivity, including solvent wetting of crystals, and performance of DADP and TATP, standard tests (i.e. DSC, drop weight impact, and SSED) were performed.

Fractal Networks of Inter‐Granular Voids in Pressed TATB

Abstract: Small-angle neutron scattering techniques were used to study the evolution of void morphology with press- ed density of the insensitive high explosive, TATB. Samples were studied as a loose powder and as pressed pellets, ranging in density from approx. 1 to 1.804 g cm � 3 . Inter- granular voids in the loose powder were randomly ar- ranged (non-fractal) and had a surface defined mean size of 0.66 mm. Pressing was found to induce a fractal network of voids with fractally rough interfaces. The surface-defined mean void size of the pressed samples was between 0.21- 0.33 mm over the range of densities studied and was found to increase with pressed density up to 1.720 g cm � 3 ,d e- creasing thereafter. The volume fractal dimension, indica- tive of the void arrangement, mirrored the changes in the mean void size. No systematic change in the surface fractal dimension was found. Surface area analysis allowed the average TATB grain size within the pressed samples to be quantified. An initial decrease of the mean grain size fol- lowed by an increase with pressed density suggests that the TATB grains behave in a brittle fashion at low densities and ductile at higher pressed densities.

Study of Plastic Explosives based on Attractive Cyclic Nitramines, Part II. Detonation Characteristics of Explosives with Polyfluorinated Binders

Abstract: A series of plastic bonded explosives (PBXs) based on Viton A and Fluorel binders were prepared using four nitramines, namely RDX (1,3,5-trinitro-1,3,5-triazinane), β-HMX (β-1,3,5,7-tetranitro-1,3,5,7-tetrazocane), BCHMX (cis-1,3,4,6-tetranitro-octahydroimidazo-[4,5-d]imidazole), and e-HNIW (e-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane). The detonation velocities, D, were determined. Detonation parameters were also calculated by means of modified Kamlet & Jacobs method, CHEETAH and EXPLO5 codes. In accordance with our expectations BCHMX based PBXs performed better than RDX based ones. The Urizar coefficient for Fuorel binder was also calculated.

Combustion Characteristics of Ammonium Nitrate and Carbon Mixtures Based on a Thermal Decomposition Mechanism

Abstract: In order to obtain a better understanding of the combustion characteristics of ammonium nitrate (AN) and carbon (C) mixtures (AN/C), burning tests and differential scanning calorimetry (DSC) were performed. AN mixed with carbon that is oxidized by nitric acid (HNO3), such as activated carbon (AC), burned at 1 MPa. However, AN mixed with carbon that is not oxidized by HNO3, such as graphite, did not burn under 7 MPa. Compositions with more than stoichiometric amounts of activated carbon had higher burning rates. Heat characteristic examinations found a similar trend. The burning rate of AN/AC mixed with CuO as a combustion catalyst deteriorated faster than an additive-free one. From the DSC result, AN/AC/CuO had a higher onset temperature and a lower heat of reaction than AN/AC. These results suggested that, in the combustion wave of AN/C, a thermal decomposition zone is formed on the burning surface, and combustion performance was affected by the thermal decomposition of AN/C.

A New Computer Code for Assessment of Energetic Materials with Crystal density, Condensed Phase Enthalpy of Formation, and Activation Energy of Thermolysis

Abstract: Crystal density and enthalpy of formation of the condensed phase of energetic compounds are two important input parameters for the performance prediction in several computer codes for rapid hazard assessment of energetic materials. A novel easy-to-handle user-friendly computer code in Visual Basic is introduced to predict these parameters for various energetic compounds including nitroaliphatics, nitrate esters, nitramines, polynitroarenes, and polynitroheteroarenes. The calculated values can be used as inputs for other thermochemical/hydrodynamic computer codes. This computer code is also able to calculate the activation energies of thermal decomposition of polynitroarenes and nitramines in condensed state. The number of carbon, hydrogen, oxygen, and nitrogen atoms and specification of some molecular fragments are input parameters for this code without using any experimental data. The new algorithms on the base of easy-to-get input parameters are tested for some new energetic compounds, which provide more reliable results as compared to the best available methods.

Application of Azido Esters as Energetic Plasticizers for LOVA Propellant Formulations

Abstract: The study of a cyclotrimethylene trinitramine-based low vulnerable ammunition (LOVA) propellant having cellulose acetate (CA) and nitrocellulose (NC) combinations as binders is described herein. Two propellant compositions (1 and 2) were prepared by replacing the non energetic plasticizer triacetin (TA) with the novel tetraazido ester plasticizers tetraazido malonate and tetraazido glutarate, respectively, and their ballistic, mechanical, and thermal properties were studied. Both compositions 1 and 2 showed thermal stability up to 200 °C with a heat release of 1752.81 and 1774.34 J g−1, respectively. Both compositions have high impact insensitivity (h50: 39 cm), friction insensitivity up to 36 kg, and an ignition temperature greater than 250 °C. The flame temperatures of 1 and 2 are 3164 and 3243 K with linear burn rate coefficients of 0.117 and 0.122 cm s−1 MPa−1, respectively. Similar percentage elongations at three different temperatures (−20 °C, +27 °C, and +55 °C) conditions were recorded for both compositions.

Glycidyl Azide Polymer Crosslinked Through Triazoles by Click Chemistry: Curing, Mechanical and Thermal Properties

Abstract: Glycidyl azide polymer (GAP) was cured through click chemistry by reaction of the azide group with bispropargyl succinate (BPS) through a 1,3-dipolar cycloaddition reaction to form 1,2,3-triazole network. The properties of GAP-based triazole networks are compared with the urethane cured GAP-systems. The glass transition temperature (T-g), tensile strength, and modulus of the system increased with crosslink density, controlled by the azide to propargyl ratio. The triazole incorporation has a higher T-g in comparison to the GAP-urethane system (T-g-20 degrees C) and the networks exhibit biphasic transitions at 61 and 88 degrees C. The triazole curing was studied using Differential Scanning Calorimetry (DSC) and the related kinetic parameters were helpful for predicting the cure profile at a given temperature. Density functional theory (DFT)-based theoretical calculations implied marginal preference for 1,5-addition over 1,4-addition for the cycloaddition between azide and propargyl group. Thermogravimetic analysis (TG) showed better thermal stability for the GAP-triazole and the mechanism of decomposition was elucidated using pyrolysis GC-MS studies. The higher heat of exothermic decomposition of triazole adduct (418kJmol(-1)) against that of azide (317kJmol(-1)) and better mechanical properties of the GAP-triazole renders it a better propellant binder than the GAP-urethane system.

Burning Characteristics of Ammonium Nitrate‐based Composite Propellants Supplemented with MnO2

Abstract: Ammonium nitrate (AN)-based composite propellants have several major problems, namely, a low burning rate, poor ignitability, low energy, and high hygroscopicity. The addition of a burning catalyst proved to be effective in improving the burning characteristics of AN-based propellants. In this study, the burning characteristics of AN-based propellants supplemented with MnO2 as a burning catalyst were investigated. The addition of MnO2 is known to improve the ignitability at low pressure. The most effective amount of MnO2 added (ξ) for increasing the burning rate is found to be 4 %. The increasing ratio with ξ is virtually independent of the burning pressure and the AN content. However, the pressure exponent unfortunately increased by addition of MnO2. The apparent activation energy of the thermal decomposition for AN and the propellant is decreased by addition of MnO2. From thermal decomposition kinetics it was found that MnO2 could accelerate the thermal decomposition reaction of AN in the condensed phase, and therefore, the burning characteristics of the AN-based propellant are improved.

On the Reliability of Sensitivity Test Methods for Submicrometer-Sized RDX and HMX Particles

Abstract: Submicrometer-sized RDX and HMX crystals were produced by electrospray crystallization and submicrometer-sized RDX crystals were produced by plasma-assisted crystallization. Impact and friction sensitivity tests and ballistic impact chamber tests were performed to determine the product sensitivity. Rather than reflecting the quality of the particles, we found the sensitivity tests to be unreliable for submicrometer particles. The used impact test was not accurate enough, while in the friction and ballistic impact chamber tests the submicrometer-sized crystals were distributed among the grooves of the porcelain plate or among the grains of the sandpaper used in these tests. These observations stress the need for revisiting the current standards used for determining the hazardous properties like friction and impact sensitivity of energetic materials in the case, where the sample consists of submicrometer-sized crystals. Recommendations were suggested to develop new test methods that only use the interactions between the particles and therefore allow the application of sensitivity tests for submicrometer/nano-sized energetic materials. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Combustion of Nanoaluminum and Water Propellants: Effect of Equivalence Ratio and Safety/Aging Characterization

Abstract: The deflagration and combustion efficiency of 80 nm aluminum/ice (ALICE) mixtures with equivalence ratios of ϕ=1.0, 0.75, and 0.67 were experimentally investigated. We find that pressure exponent and burning rate vary little between these three mixtures, with the exponent varying only from 0.42 to 0.50 and burning rate at 6.9 MPa varying from 2.05 to 2.10 cm s−1. However, reducing the equivalence ratio from 1.0 to 0.67 surprisingly increases combustion efficiency from 70 % to 95 % with unburned aluminum agglomerates visible in electron microscopy photographs of 70 % combustion efficiency (ϕ=1.0) products. Our findings suggest that nanoaluminum/water combustion is diffusionally limited for all conditions considered. Aging tests on the propellant show that storage at −30 °C essentially stops the Al/H2O reaction such that little nanoaluminum degradation occurs after 200 days. Electrostatic discharge (ESD), shock initiation, and impact sensitivity tests indicate that the propellant is insensitive to ignition by these stimuli. Specifically, while neat nanoaluminum powders are highly ESD sensitive (ignition threshold 0.3–14 mJ), nAl/H2O mixtures are insensitive to ESD and have ignition thresholds in excess of 400 mJ. Likewise, nAl/H2O mixtures are insensitive to impact ignition, having an ignition threshold in excess of 2.2 m. Propellants containing 80 nm or larger average particle size aluminum were also found to be insensitive to shock initiation.

Modifying Aluminum Reactivity with Poly(Carbon Monofluoride) via Mechanical Activation

Abstract: Modification of the reactivity of micrometer-sized aluminum through inclusion of low levels of poly(carbon monofluoride) (PMF) using mechanical activation (MA) is reported. Resulting composite particle combustion enthalpy, average particle size, and specific surface area depend on MA intensity, duration, and inclusion level, and range from 18.9 to 28.5 kJ g−1, 23.0 to 67.5 μm, and 5.3 to 34.8 m2 g−1, respectively. Differential scanning calorimetry experiments in O2/Ar indicate that MA reduces the exotherm onset from 555 to 480 °C (70/30 wt-%). Particles are sensitive to electrostatic discharge stimulus (11.5–47.5 mJ) but not to impact (>213 cm) or friction (>360 N) and some low energy MA particles are ignitable by optical flash. With their altered reactivity and high combustion enthalpy, these nanofeatured, micrometer-sized particles may have use as replacements for aluminum in energetic applications.

X-Band Microwave Properties and Ignition Predictions of Neat Explosives

Abstract: Microwave frequency electromagnetic properties are critical for understanding and predicting the heating and ignition behavior of explosives subjected to microwave irradiation. In this work we report relative complex permittivity measurements in the X-band (8–12 GHz) for 13 neat explosives measured by the circular cavity technique. This data set was then used in conjunction with COMSOL 4.3 Multiphysics® finite element analysis software to design and simulate a low power (100 W), high electric field X-band microwave applicator. The role of the sample holder on our ability to directly study the response of explosives to electromagnetic energy is examined and shown to be critical. Times to ignition were predicted for PETN, TATB, and HMX and indicate that for the proposed applicator and considered properties ignition may occur in less than one second exposure. These predictions show that explosives can be effectively heated in short time scales through direct microwave heating without absorptive binders or inclusions.

Preparation and Properties of 2,6‐Diamino‐3,5‐dinitropyrazine‐1‐oxide based Nanocomposites

Abstract: With estane as binder, a new nanocomposite energetic material based on 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105) was successfully prepared by the spray drying method. Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), and X-ray diffraction (XRD) was employed to characterize the nanocomposite samples. The impact sensitivity and thermal decomposition properties of the nanocomposites were also measured and analyzed. The results show that the nanocomposite particles are spherical in shape and range from 1 μm to 10 μm in size. The composite is aggregated of many tiny granules with nucleus/shell structure, in which the shell thickness and crystal size of LLM-105 are about 20 nm and 50–100 nm. The crystal type of LLM-105 in the nanocomposite is similar to that of raw LLM-105, however, the diffraction peaks become weaker and wider mainly due to decreasing of particle size. The nanocomposite has lower impact sensitivity and better thermal stability.

Structural Characterization of RDX‐Based Explosive Nanocomposites

Abstract: Recently developed cyclotrimethylene trinitramine (RDX)-based nanostructured explosive compositions were shown to exhibit greatly reduced initiation sensitivity as compared to conventional compositions prepared with coarser, micrometer-scale RDX. In particular, improvements were shown in the sensitivity towards shock and impact stimuli, key sources of inadvertent initiation. Such an improved response to mechanical stimuli is believed to be largely a result of smaller crystal and void sizes. Characterization of these structural parameters is therefore necessary in order to construct a meaningful physical description of these novel explosive compositions. Herein, we report the results of a detailed structural characterization of these novel RDX-based nanocomposites. The analyzed specimens were in pellet form with nominally 10 % porosity. These results constitute an unprecedentedly complete structural picture of this new class of energetic materials.