Fractal Networks of Inter‐Granular Voids in Pressed TATB

Small‐angle neutron scattering techniques were used to study the evolution of void morphology with pressed 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 arranged (non‐fractal) and had a surface defined mean size of 0.66 μm. 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 μm over the range of densities studied and was found to increase with pressed density up to 1.720 g cm⁻³, decreasing thereafter. The volume fractal dimension, indicative 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 followed 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.     

The Shock Initiation Threshold of HNS as a Function of its Density

The shock initiation threshold of hexanitrostilbene (HNS) pellets with different densities has been investigated by performing small‐scale gap tests. As the sensitivity of HNS strongly depends on the density of the pellet, the density was varied in a range that the pellet material can be expected to be insensitive by means of no initiation at pressure loads of 2.6 GPa. In the case of HNS we observed that the material became insensitive at densities larger than 1.65 g cm⁻³. Further, we found that the pressure loads can be increased from 2.6 GPa to 3.29 GPa for densities increasing from ϱ=1.65 g cm⁻³ to ϱ=1.70 g cm⁻³ (98% TMD) without detonation of the HNS pellet.     

A Novel Insensitive High Explosive 3,4‐Bis (Aminofurazano) Furoxan

A novel insensitive high explosive 3,4‐bis (aminofurazano) furoxan (BAFF) was prepared using 3‐amino‐4‐acylchloroximinofurazan (ACOF) as a precursor. The molecular and crystal structures of BAFF were characterized by IR, MS, ¹H NMR, ¹³C NMR, elemental analysis, and single crystal X‐ray diffraction. The single crystal structure of BAFF recrystallized from water is monoclinic, space group P 21/c, and ρ_c=1.745 g cm⁻³, and that recrystallized from ethanol is triclinic, space group P 1, and ρ_c=1.737 g cm⁻³. BAFF has multiple crystal forms. The calculated detonation velocity by BKW code is 8100 m s⁻¹ (ρ=1.795 g cm⁻³, theoretical density calculated by quantum chemistry) and the experimental value is 7177 m s⁻¹ (ρ=1.530 g cm⁻³, charge density). The tested values of impact, friction, and electrostatic spark sensitivity show that BAFF is insensitive.     

Voids and Density Distributions in 2,4,6,8,10,12‐Hexanitro‐2,4,6,8,10,12‐Hexaazaisowurtzitane (CL‐20) Prepared Under Various Conditions

The density distributions of six samples of CL‐20 were measured using the density gradient technique. This technique was used to determine which preparation procedure produced the highest average CL‐20 density. Assuming crystals with fewer flaws result in reduced sensitivity to shock initiation, higher average crystal density (closest to the theoretical maximum density) would imply the least number of voids or inclusions. Based on hot‐spot theory, better crystals, i.e., smaller number of flaws will reduce the shock sensitivity and perhaps other impact initiation mechanisms as well. Six samples from different synthesis and crystallization procedures gave average densities from 2.042 to 2.0230 g/cm³ as measured by density gradient. Assuming the voids have no density, the crystals were between 99.90 to 98.98% of the theoretical maximum density (TMD for ε‐CL‐20 is 2.044 g/cm³). An attempt was made to account for the density difference by identifying voids in the crystals using polarized light microscopy. This method also gave some insight into the different morphologies produced by different crystallization techniques. In 3 cases voids on the order of several micrometers could be resolved in large CL‐20 crystals.     

Thermal Expansion of LX‐17, PBX 9502, and Ultrafine TATB

A large quantity of linear strain and LCTE data from −55 °C to 75 °C on LX‐17, PBX 9502 and ultrafine TATB (ufTATB) is presented. Axial and diametral measurements are blended to give final densities, which agree with the liquid immersion values of Baytos et al. The nominal densities at 21, −55 and 75 °C in g ⋅ cm⁻³ are: LX‐17 1.90, 1.920, 1.874; PBX 9502 1.89, 1.907, 1.867; ufTATB 1.80, 1.822, 1.778. Data taken radially show more thermal expansion than that taken transversely in cut‐up parts; both must be combined to get the density. There is no difference between virgin and recycled TATB. Rachet growth data is presented, both at low pressure and at higher pressure, where the swelling is diminished. A Kel‐F strain curve is presented and the theoretical maximum densities are computed.     

Studies on Advanced RDX/TATB Based Low Vulnerable Sheet Explosives with HTPB Binder

Hydroxyl‐terminated polybutadiene (HTPB) based sheet explosives incorporating insensitive 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB) as a part replacement of cyclotrimethylene trinitramine (RDX) have been prepared during this work. The effect of incorporation of TATB on physical, thermal, and sensitivity behavior as well as initiation by small and high caliber shaped charges has been determined. Composition containing 85% dioctyl phthalate (DOP) coated RDX and 15% HTPB binder was taken as control. The incorporation of 10–20% TATB at the cost of RDX led to a remarkable increase in density (1.43→1.49 g cm⁻³) and tensile strength (10→15 kg cm⁻²) compared to the control composition RDX/HTPB(85/15). RDX/TATB/HTPB based compositions were found less vulnerable to shock stimuli. Shock sensitivity was found to be of the order of 20.0–29.2 GPa as against 18.0 GPa for control composition whereas their energetics in terms of velocity of detonation (VOD) were altered marginally. Differential scanning calorimeter (DSC) and thermogravimetry (TG) studies brought out that compositions undergo major decomposition in the temperature region of 170–240 °C.     

Tetrazolyl Triazolotriazine: A New Insensitive High Explosive

A triazolotriazine carbonitrile ( 1 ) was formed by diazotization of 3‐amino‐5‐cyano‐1,2,4‐triazole followed by treatment with nitroacetonitrile. Cyclization of the C≡N bond with sodium azide results in a tetrazolyl triazolotriazine ( 2 ). Formation of the sodium salt of 2 , followed by metathesis with [PPN][Cl] resulted in the organic salt 3 . Compounds 1 , 2 , and 3 were characterized by elemental analysis and infrared, ¹H, and ¹³C{¹H} NMR spectroscopy and 1 and 3 were characterized by single‐crystal X‐ray diffraction. Compound 2 has a density of 1.819 g cm⁻¹, is thermally stable up to 305 °C, and is insensitive to impact, friction, and electrical discharge. The detonation pressure and velocity of 2 are calculated to be 27.04 GPa and 8.312 km s⁻¹, respectively, making this a 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB) replacement candidate.     

Crystal Morphology Controlling of TATB by High Temperature Anti‐Solvent Recrystallization

The spheroidizing of TATB (1,3,5‐triamino‐2,4,6‐trinitrobenzene) can help to control preferred orientation and anisotropic expansion of TATB based PBXs, as well as to improve crystal quality, desensitizing efficiency, packing density, and even explosive energy. In this paper, TATB crystals with different morphology were obtained by high temperature recrystallization from anti‐solvents. TATB was dispersed into DMSO and heated to dissolve. Water as an anti‐solvent was added to the solution with different conrol parameters. We designed additional experiments to study the particular influence of these parameters. It was shown that the crystal morphology is strongly affected by the stirring rate and the amount of water added. The recrystallized TATB samples have similar thermal stability as starting TATB, but higher densities and purities, which indicates that the quality of TATB crystals was improved. By slowly adding an appropriate amount of water and cooling, regular crystals of TATB were obtained, which proves that water is a good morphology modifier for TATB.     

Synthesis and Characteristics of Bis(nitrofurazano)furazan (BNFF), an Insensitive Material with High Energy‐Density

The insensitive compound bis(nitrofurazano)furazan (BNFF) with high energy‐density was synthesized by three‐step reactions and fully characterized. The key reduction reaction was discussed. BNFF has a high crystal density (1.839 g cm⁻³) and a low melting point (82.6 °C). BNFF is insensitive to impact and friction and has similar detonation velocity (8680 m s⁻¹) and detonation pressure (36.1 GPa) compared to RDX.     

TATB在1-乙基-3-甲基咪唑醋酸盐/二甲亚砜混合溶剂中的溶解度及结晶

研究了1-乙基-3-甲基咪唑醋酸盐([Emim]Ac)与二甲亚砜(DMSO)的质量比和溶解温度等对TATB溶解度的影响,用红外光谱(FTIR)、X射线衍射(XRD)、扫描电镜(SEM)、高效液相色谱(HPLC)和差示扫描量热(DSC)对结晶TATB的结构、形貌和热性能进行了表征。结果表明,[Emim]Ac与DMSO质量比为3∶7、温度为90℃时,TATB的溶解度为9.8g/100g。通过改变反溶剂醋酸的滴加速率能够控制TATB晶体的大小,形成的小颗粒镶嵌在大颗粒之间的晶体结构具有更好的热稳定性。     

Detonation Measurements on Damaged LX‐04

We have applied thermal insults on LX‐04 at 185 °C and found that the material expanded significantly, resulting in a bulk density reduction of 12%. Subsequent detonation experiments (three cylinder tests) were conducted on the thermally damaged LX‐04 samples and pristine low‐density LX‐04 samples and the results showed that the fractions reacted were close to 1.0. The thermally damaged LX‐04 and pristine low‐density LX‐04 showed detonation velocities of 7.7–7.8 mm μs⁻¹, significantly lower than that (8.5 mm μs⁻¹) of pristine high‐density LX‐04. Detonation energy densities for the damaged LX‐04, low‐density pristine LX‐04, and hot cylinder shot of LX‐04 were 6.48, 6.62, and 6.58 kJ cm⁻³, respectively, lower than the detonation energy density of 8.11 kJ cm⁻³ for the high density pristine LX‐04. The break‐out curves for the detonation fronts showed that the damaged LX‐04 had longer edge lags than the high density pristine LX‐04, indicating that the damaged explosive is less ideal.     

Investigation on the Thermal Expansion and Theoretical Density of 1,3,5‐Trinitro‐1,3,5‐Triazacyclohexane

The CTE and the theoretical density are important properties for energetic materials. To obtain the CTE and the theoretical density of 1,3,5‐trinitro‐1,3,5‐triazacyclohexane (RDX), XRD, and Rietveld refinement are employed to estimate the dimensional changes, within the temperature range from 30 to 170 °C. The CTE of a, b, c axis and volume are obtained as 3.07×10⁻⁵ K⁻¹, 8.28×10⁻⁵ K⁻¹, 9.19×10⁻⁵ K⁻¹, and 20.7×10⁻⁵ K⁻¹, respectively. Calculated from the refined cell parameters, the theoretical density at the given temperature can be obtained. The theoretical density at 20 °C (1.7994 g cm⁻³) is in close match with the RDX single‐crystal density (1.7990 g cm⁻³) measured by density gradient method. It is suggested that the CTE measured by XRD could perfectly meet with the thermal expansion of RDX.     

A Fuel‐Flexible Alkaline Direct Liquid Fuel Cell

We constructed a fuel‐flexible fuel cell consisting of an alkaline anion exchange membrane, palladium anode, and platinum cathode. When an alcohol fuel was used with potassium hydroxide added to the fuel stream and oxygen was the oxidant, the following maximum power densities were achieved at 60 °C: ethanol (128 mW cm⁻²), 1‐propanol (101 mW cm⁻²), 2‐propanol (40 mW cm⁻²), ethylene glycol (117 mW cm⁻²), glycerol (78 mW cm⁻²), and propylene glycol (75 mW cm⁻²). We also observed a maximum power density of 302 mW cm⁻² when potassium formate was used as the fuel under the same conditions. However, when potassium hydroxide was removed from the fuel stream, the maximum power density with ethanol decreased to 9 mW cm⁻² (using oxygen as oxidant), while with formate it only decreased to 120 mW cm⁻² (using air as the oxidant). Variations in the performance of each fuel are discussed. This fuel‐flexible fuel cell configuration is promising for a number of alcohol fuels. It is especially promising with potassium formate, since it does not require hydroxide added to the fuel stream for efficient operation.     

Tungsten Carbide Synthesized by Polystyrene Sphere Template Method Promoting Pd Electrocatalyst for Alcohol Oxidation in Alkaline Media

Tungsten carbide (WC) particles loading on hollow carbon spheres (HCS) have been synthesized by using ammonium metatungstate as W source, glucose as carbon source, P123 as dispersant and polystyrene sphere as template. The typical WC‐HCS composite has the WC particle sizes of 5–20 nm, specific surface area of 445 m² g⁻¹, pore volume of 0.24 cm³ g⁻¹ and hollow spherical structure. The above structures of WC‐HCS favor dispersion of Pd particles and mass transfer. Therefore, the Pd/WC‐HCS electrocatalyst has 4.6 times higher peak current density and 130 mV more negative onset potential than that of Pd/C for ethanol oxidation in alkaline solution. The mass transfer property of WC‐HCS (due to structure effect) and promotion effect of WC on Pd are believed to be the origins of the excellent performances.     

Studies into Laser Ignition of Unconfined Propellants

Prior to laser ignition tests, spectral absorption properties of three different solid motor propellants were analysed. The extruded double base (EDB) propellant exhibited >95 % absorption over the 250–550 nm wavelength band whereas, the cast double base (CDB) showed similar absorption over a wider band extending between 375–800 nm. The composite sample (CP) showed a uniform spectral absorption at about 90 % over 250–800 nm band. Ignition tests using an average of 500 nm output from an Ar‐ion laser showed that the double base propellants undergo deflagration prior to ignition due to the presence of carbon black material. Within the laser power density range of 24–125 Wċcm⁻², the threshold laser energy densities for deflagration and ignition in the double base propellant were found to␣be between 2–2.5 Jċcm⁻², and 40–215 Jċcm⁻², respectively. No deflagration was observed for the composite propellant, and the threshold ignition energy was found to be within the range, 11–18 Jċcm⁻² for the same range of laser power densities. From the ignition map for this propellant, the threshold energy for ignition at this wavelength was found to be approximately 18 Jċcm⁻² and was practically independent of laser power density. In the near infrared wavelength (780 nm) the EDB propellant was not readily ignitable due to its comparatively much higher reflectance at this wavelength. The ignition threshold values were found to be between 19–23 Jċcm⁻² for a similar power density level. The results indicate that the ignitability of propellants is enhanced through the promotion of deflagration.     

Research on Perfusion Explosives from SF‐3 Double‐Base Propellants Using Supercritical CO2

Perfusion explosives were prepared using porous SF‐3 propellants, which were synthesized by a supercritical fluid foaming process. Scanning electron microscopy (SEM) was used to characterize the porous SF‐3 propellants. Massive holes were generated after the foaming process. The density of perfusion explosives using foamed SF‐3 propellants exceeds 1.3 g cm⁻³, and the detonation velocities exceed 6000 m s⁻¹. Underwater energy tests and high‐speed photography were carried out to investigate the detonation performance of perfusion explosives. The results showed that perfusion explosives using unfoamed SF‐3 propellants could not be detonated. However, perfusion explosives using their foamed analogs could be detonated herein.     

Study on the Azido‐Tetrazolo Tautomerizations of 3,6‐Bis(azido)‐1,2,4,5‐tetrazine

The azido‐tetrazolo tautomerizations of 3,6‐diazido‐1,2,4,5‐tetrazine (DIAT) in different solvents were investigated with HPLC and ¹³C NMR spectroscopy. 6‐Amino‐tetrazolo[1,5‐b]‐1,2,4,5‐tetrazine (ATTZ) was irreversibly formed as the final product by azido‐cyclization following N₂ elimination from one of the azido substituents at room temperature in DMSO. The structure of ATTZ was characterized by X‐ray crystallography; differential scanning calorimetry (DSC), mass spectrometry, as well as IR and ¹H NMR and ¹³C NMR spectroscopy. The crystal density was found to be 1.272 g cm⁻³. DSC result suggested that ATTZ with the melting point of 84 °C strongly decomposes with explosion at 198 °C, which can be regarded as a primary explosive.     

New Application of Hydroxyl Groups: Ligands for High Density Metal Organic Frameworks

Energetic metal organic frameworks (MOFs) with energetic anions as ligands can be used as new‐generation explosives. Many powerful anions have been introduced into energetic MOFs to improve the properties; however, the hydroxyl as a common group for energetic MOFs has rarely been studied. In this article, we present two examples of energetic MOFs ([Cu(atz)(NO₃)(OH)]_n) and [Zn(ata)(OH)] (atz=4‐amino‐1,2,4‐triazole; ata=5‐amino‐1H‐tetrazole) with the hydroxyl group as the ligand. Crystal structure analyses reveal that the two compounds possess compact two‐dimensional (2‐D) structures with densities up to 2.41 g cm⁻³ and 2.54 g cm⁻³, respectively. These two compounds have excellent physicochemical properties. The results demonstrate that a hydroxyl group as the ligands could commendably increase the densities of energetic MOFs, thereby enhancing the detonation performance. It is anticipated this work will open a new direction for the development of energetic MOFs.     

Anaerobic and aerobic treatment of a simulated textile effluent

A simulated textile effluent (STE) was generated for use in laboratory biotreatment studies; this effluent contained one reactive azo dye, PROCION Red H‐E7B (1.5 g dm⁻³); sizing agent, Tissalys 150 (1.9 g dm⁻³); sodium chloride (1.5 g dm⁻³) and acetic acid (0.53 g dm⁻³) together with nutrients and trace elements, giving a mean COD of 3480 mg dm⁻³. An inclined tubular anaerobic digester (ITD) was operated for 9 months on the STE and a UASB reactor for 3 months. For a 57 day period anaerobic effluent from two reactors, a UASB and an ITD, was mixed and treated in an aerobic stage. In days 77–247 68% of the true colour of PROCION Red H‐E7B was removed by anaerobic treatment with no colour removal aerobically and up to 37% COD was removed anaerobically, with a corresponding BOD removal of 71%. For combined anaerobic and aerobic treatment a mean COD removal of 57% and BOD removal of 86% was achieved. Operation of the ITD at a 2.8 day HRT (volumetric loading rate (B _v) 1.24 g COD dm⁻³day⁻¹) and the UASB at a 2 day HRT (B _v 1.74 g COD dm⁻³day⁻¹) gave comparable COD removals but the UASB gave better true colour removal. Effluent from the combined process operating on this simulated waste still contained an average 1500 mg COD dm⁻³, and further treatment would be required to meet consent standards. © 1999 Society of Chemical Industry     

Design and Synthesis of Hydrolytically Stable N‐Nitrourea Explosives

A series of high energy density compounds (HEDCs) based on N‐nitrourea were designed and their theoretical performances were calculated using the Gaussian programs. The predicted values of the energy density of these compounds are in the range 1.848–1.93 g cm⁻³, and their calculated VODs are in the range 6700–8305 m s⁻¹. Tetranitrodiglycoluril (TNDGU) ( 1 ) and tetranitrotriglycoluril (TNTGU) ( 2 ) were synthesized and characterized by NMR (¹H, ¹³C) and IR spectroscopy as well as elemental analyses. The structure of the aminolysis product ( 7 ) of TNDGU was further confirmed by single‐crystal X‐ray diffraction, which indicated that the structure belongs to P2₁/c space group in the monoclinic system.