Hazard Characterization of Aluminum Nanopowder Compositions

The thermal behaviour in air of two Al nanopowders, Alss and Alsstef, a Teflon coated version of Alss, was determined using DSC, TG‐DTA and accelerating rate calorimetry (ARC). Compared to two larger Al nanopowders, for which hazards results have been reported, Alss and Alsstef are less reactive in air, possibly due to the nature of the passivating and coating layers. The stability of Alss and Alsstef in a wet environment was also investigated using ARC. Alss is very reactive with water, which could lead to a problem of aging in a humid atmosphere. The ”coating” of Alsstef significantly reduces the reactivity of Alss with water. Outgassing behaviour of mixtures of ADN, GAP and various Al powders was investigated using TG‐DTA‐FTIR‐MS. No chemical interactions were observed between ADN/Al, GAP/Al and ADN/GAP. The effect of the addition of Al nanopowders on the thermal decomposition of ADN and GAP was studied using ARC. Al nanopowders had a minor effect on the thermal stability of ADN, while the addition of Alss and Alsstef lowered the onset temperature of GAP. The electrostatic discharge (ESD), impact and friction sensitivities of Al nanopowders and their mixtures with ADN and GAP were also determined. Al nanopowders appear to sensitize ADN to ESD, impact and friction.     

Investigation of Blast Performance and Solid Residues for Layered Thermobaric Charges

The confined explosion of an annular layered charge composed of a phlegmatized RDX (RDXph) core and an external layer consisting of aluminum powder (Al) or a mixture of ammonium perchlorate (AP) and Al was studied. Experiments were carried out in fully and partially closed structures, i.e., in the explosion chamber of 150 dm³ in volume and in the 40 m³ volume bunker with four small holes and a doorway. Two types of aluminum powder were used in the mixtures. Signals of overpressure from two piezoelectric gauges located at the chamber wall were recorded and the influence of aluminum contents and particle size on a quasi‐static pressure (QSP) was studied. Moreover, the solid residues from the chamber were analyzed by using SEM, TG/DTA and XRD techniques to determine their structure and composition. Pressure and light histories recorded in the bunker enable us to determine the blast wave characteristics and time‐duration of light output. The effect of the charge mass and aluminum particle size on blast wave parameters were investigated. For comparison, the test for RDXph and TNT charges were also carried out.     

Role of Additives in the Combustion of Ammonium Dinitramide

The thermal decomposition behavior and combustion characteristics of mixtures of ammonium dinitramide (ADN) with additives were studied. Micrometer‐sized particles of Al, Fe₂O₃, TiO₂, NiO, Cu(OH)NO₃, copper, CuO, and nanometer‐sized particles of aluminum (Alex) and CuO (nano‐CuO) were employed. The thermal decomposition was measured by TG‐DTA and DSC. The copper compounds and NiO lowered the onset temperature of ADN decomposition. The heat value of ADN with Alex was larger than that of pure ADN in closed conditions. The burning rates and temperature of the pure ADN and ADN/additives mixtures were measured. CuO and NiO enhance the burning rate, particularly at pressures lower than 1 MPa, because of the catalyzed decomposition in the condensed phase; the other additives lower the burning rate. This negative effect on the burning rate is explained based on the surface temperature measurements by a physicochemical mechanism, which involves a chemical reaction, a phase change of the ammonium nitrate, and the blown‐off droplets of the condensed phase.     

Analysis of Post Detonation Products of Different Explosive Charges

High explosive charges containing TNT, Comp. B, PBXN-106, TNT/TATB and the aluminium containing charges TNT/AN/Al, Comp. B/Al and a PBX high explosive with polyurethane binder, RDX, AP and Al have been initiated in a containment of 1.5 m³ in argon atmosphere. The gaseous and solid products were analyzed by mass spectrometry and other techniques. From the reaction products, the completeness of the Al reaction under different conditions was evaluated. The heat of detonation was calculated from the heat of formation of the products and the components of the explosive charges. The method described is suitable for studying the reaction behavior of components in composite explosives, especially of less sensitive high explosives.     

纳米级金属和金属复合物粉末对高氯酸铵和高氯酸铵/聚合丁二烯复合固体推进剂热分解特性的影响

Effects of metal (Ni, Cu, Al) and composite metal (NiB, NiCu, NiCuB) nanopowders on the thermal decomposition of ammonium perchlorate (AP) and composite solid propellant ammonium perchlorate/hydroxyterminated polybutadiene (AP/HTPB) were studied by thermal analysis (DTA). The results show that metal and composite metal nanopowders all have good catalytic effects on the thermal decomposition of AP and AP/HTPB composite solid propellant. The effects of metal nanopowders on the thermal decomposition of AP are less than those of the composite metal nanopowders. The effects of metal and composite metal nanopowders on the thermal decomposition of AP are different from those on the thermal decomposition of the AP/HTPB composite solid propellant.     

Combustion heat of the Al/B powder and its application in metallized explosives in underwater explosions

An underwater explosion test is used to determine the detonation properties of metallized explosives containing aluminum and boron powders. An oxygen bomb calorimeter (PARR 6200 calorimeter, Parr Instrument Company, USA) is used to obtain the heat of combustion of the metal mixtures. As the content of boron powders is increased, the heat of combustion of the metal mixtures increases, and the combustion efficiency of boron decreases. The highest value of the combustion heat is 38.2181 MJ/kg, with the boron content of 40%. All metallized explosive compositions (RDX/Al/B/AP) have higher detonation energy (including higher shock wave energy and bubble energy) in water than the TNT charge. The highest total useful energy is 6.821 MJ/kg, with the boron content of 10%. It is 3.4% higher than the total energy of the RDX/Al/AP composition, and it is 2.1 times higher than the TNT equivalent.     

Characterization of ADN and ADN‐Based Propellants

Ammonium dinitramide (ADN), NH₄N(NO₂)₂ is being considered as one of the potential new energetic oxidizers for composite propellants. In this study, ADN crystals, prills and two ADN‐based propellants having different relative amounts of ingredients were characterized. The concentration of the crystals and the prills samples was determined using ion chromatography. The thermal behavior of the crystals, prills and propellants was studied using DSC, simultaneous TG‐DTA‐FTIR‐MS, ARC (accelerating rate calorimeter), HFC (heat flux calorimeter) and INC (isothermal nanocalorimeter). Decomposition of ADN was observed from all of the samples at temperatures above the melting point of ADN (~ 92 °C). Formation of N₂O, NO₂, H₂O, CO₂, CO, N₂ and NO was detected during the ADN decomposition. The thermal stability of the ADN samples at temperatures below the melting point of ADN was studied. Early solid decomposition of ADN, which generates N₂O and H₂O, was observed at 60 °C. Electrostatic discharge (ESD) and impact sensitivity of the ADN samples were determined. The crystals and prills are sensitive to impact, while the two propellants are relatively less ESD and impact sensitive.     

老化对TNT基熔铸炸药性能的影响

为了研究老化对炸药性能的影响,对自然贮存的3种熔铸炸药TNT／RDX、TNT／RDX／Al和 TNT／HMX／Al进行了加速老化试验。通过扫描电镜、真空安定性试验研究了老化前后3种炸药的微观形貌和安全性能,并测试了老化前后3种炸药的感度和爆速。结果表明,老化后炸药颜色变深,体积膨胀,质量变轻。样品的放气量小于2 mL／g ,热感度变化也较小。机械感度的变化与炸药组分和老化方式有关。TNT／RDX的爆速随着贮存时间的增加而降低,与整体加速老化情况一致,TNT／RDX／Al和 TNT／HMX／Al的爆热随贮存时间的增加变化趋势相反,说明两者老化机理可能不同。     

Experimental Study of the Effect of Metal Nanopowders on the Decomposition of HMX,AP and AN

The effect of metal nanopowders (Al, Fe, W, Ni, Cu, and Cu‐Ni alloys) on the decomposition of energetic materials (HMX, AP, and AN) with DTA–TGA method was studied and it was found that the catalytic action appears in the case of Cu‐Ni nanopowders with the three studied energetic materials. The temperature of decomposition of energetic materials with the addition of metal nanopowders could be lowered by 82 °C for AN, 161 °C for AP, and 96 °C for HMX. The reaction mechanism of metal nanopowders enhancing the decomposition of energetic materials is discussed.     

Preparation and Properties of an AP/RDX/SiO2 Nanocomposite Energetic Material by the Sol‐Gel Method

A nanocomposite energetic material was prepared using sol‐gel processing. It was incorporated into the nano or submicrometer‐sized pores of the gel skeleton with a content up to 95 %. AP, RDX, and silica were chosen as the energetic crystal and gel skeleton, respectively. The structure and its properties were characterized by SEM, BET methods, XRD, TG/DSC, and impact sensitivity measurements. The structure of the AP/RDX/SiO₂ cryogel is of micrometer scale powder with numerous pores of nanometer scale and the mean crystal size of AP and RDX is approx. 200 nm. The specific surface area of the AP/RDX/SiO₂ cryogel is 36.6 m² g⁻¹. TG/DSC analyses indicate that SiO₂ cryogel can boost the decomposition of AP and enhance the interaction between AP and RDX. By comparison of the decomposition heats of AP/RDX/SiO₂ at different mass ratios, the optimal mass ratio was estimated to be 6.5/10/1 with a maximum decomposition heat of 2160.8 J g⁻¹. According to impact sensitivity tests, the sensitivity of the AP/RDX/SiO₂ cryogel is lower than that of the pure energetic ingredients and their mixture.     

Thermal Decomposition,Kinetics and Compatibility Studies of Poly(3‐difluoroaminomethyl‐3‐methyloxetane) (PDFAMO)

The thermal decomposition of poly(3‐difluoroaminomethyl‐3‐methyloxetane) (PDFAMO) with an average molecular weight of about 6000 was investigated using thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). The kinetics of thermolysis were studied by a model‐free method. The thermal decomposition of PDFAMO occurred in a two‐stage process. The first stage was mainly due to elimination of HF and had an activation energy of 110–120 kJ mol⁻¹. The second stage was due to degradation of the polymer chain. The Fourier transform infrared (FTIR) spectra of the degradation residues showed that the difluoroamino groups decomposed in a two‐step HF loss at different temperatures. The remaining monofluoroimino groups produced by the incomplete elimination of HF were responsible for the two‐stage thermolysis process. The compatibility of PDFAMO with some energetic components and inert materials used in polymer‐bonded explosives (PBXs) and solid propellants was studied by DSC. It was concluded that the binary systems of PDFAMO with cyclotrimethylenetrinitramine (RDX), 2,4,6‐trinitrotoluene (TNT), 2,4‐dinitroanisole (DNAN), pentaerythritol tetranitrate (PETN), ammonium perchlorate (AP), aluminum powder (Al), aluminum oxide (Al₂O₃) and 1,3‐diethyl‐1,3‐diphenyl urea (C₁) were compatible, whereas the systems of PDFAMO with lead carbonate (PbCO₃) and 2‐nitrodiphenylamine (NDPA) were slightly sensitized. The systems with cyclotetramethylenetetranitroamine (HMX), hexanitrohexaazaisowurtzitane (CL‐20), 3‐nitro‐1,2,4‐triazol‐5‐one (NTO), ammonium nitrate (AN), magnesium powder (Mg), boron powder (B), carbon black (C. B.), diphenylamine (DPA), and p‐nitro‐N‐methylamine (PNMA) were incompatible. The results of compatibility studies fully supported the suggested thermal decomposition mechanism of PDFAMO.     

Modification of W/O Emulsions by Demilitarized Composition B

A series of W/O emulsion explosives containing 30–50 wt‐% of the demilitarized mixture RDX/TNT (Composition B 50/50) was prepared. Detonation velocities and relative explosive strengths of these mixtures were determined and their detonation characteristics were calculated according to the EU standard methods for commercial explosives. Thermal reactivities of the most reactive components of these W/O mixtures were examined by means of differential thermal analysis and outputs were analyzed according to the Kissinger method. The reactivities, expressed as the E_a ⋅ R⁻¹ slopes of the Kissinger relationship, correlate with the squares of the detonation velocities of the corresponding explosive mixtures. It was found that fortification of the W/O emulsions by the demilitarized mixture RDX/TNT allows modification of detonation velocities of the resulting emulsion explosives within relatively broad limits. However, the effect of this admixture on the relative explosive strength is not well defined. Nevertheless, fortification in this sense can give rock‐blasting explosives with a performance on the level of industrial powdered amatols.     

Cohesive Hamaker Constants and Dispersive Surface Energies of RDX,PETN, TNT,and Ammonium Nitrate‐Based Explosives

Inverse gas chromatography (IGC) was used to characterize dispersive surface energies γ_S^D and cohesive Hamaker constants A_ii for RDX, PETN, TNT, ammonium nitrate (AN), and AN‐based explosives at 303 K. The γ_S^D for RDX at 303 K is compared to previous studies and generally found to be in good agreement, substantiating the use of NESTT training materials to characterize explosives via IGC. Additionally, the effect of the amount of fuel in the AN mixtures on γ_S^D is examined using simple linear regression. Finally, the IGC‐predicted A_ii values are compared to Lifshitz estimations for A_ii of RDX, PETN, TNT, and AN.     

Thermal and Sensitivity Study of Dihydroxyl Ammonium 5,5′‐Bistetrazole‐1,1′‐diolate (TKX‐50)‐based Melt Cast Explosive Formulations

Dihydroxyl ammonium 5,5′‐bistetrazole‐1,1′‐diolate (TKX‐50) is a promising energetic material with predicted performance similar to RDX as well as to CL‐20. In the present study, TKX‐50 was evaluated as a possible replacement for RDX in TNT‐based, aluminized as well as non‐aluminized melt cast formulations. Thermal analysis reveals the compatibility of TKX‐50 with benchmark explosives like RDX and TNT in explosive formulations. This paper describes the thermal and sensitivity study of TKX‐50 with RDX and TNT‐based melt cast explosives. The result indicated that TKX‐50 can be effectively used as a RDX replacement in melt cast explosive formulations. TKX‐50/TNT‐based aluminized composition shows more thermal stability than RDX/TNT based composition, which clearly indicated the usefulness of TKX‐50 in melt cast explosive formulations.     

Degradation of TNT,RDX, and HMX Explosive Wastewaters Using Zero‐Valent Iron Nanoparticles

The high‐energy explosives 2,4,6‐trinitrotoluene (TNT), hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX), and the high melting explosive octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX) are common groundwater contaminants at active and abandoned munitions production facilities causing serious environmental problems. A highly efficient and environmentally friendly method was developed for the treatment of the explosives‐contaminated wastewaters using zero‐valent iron nanoparticles (ZVINs). ZVINs with diameters of 20–50 nm and specific surface areas of 42.56 m² g⁻¹ were synthesized by the co‐precipitation method. The explosives degradation reaction is expressed to be of pseudo first‐order and the kinetic reaction parameters are calculated based on different initial concentrations of TNT, RDX, and HMX. In addition, by comparison of the field emission scanning electron microscopy (FE‐SEM) images for the fresh and reacted ZVINs, it was apparent that the ZVINs were oxidized and aggregated to form Fe₃O₄ nanoparticles as a result of the chemical reaction. The X‐ray diffraction (XRD) and X‐ray absorption near edge structure (XANES) measurements confirmed that the ZVINs corrosion primarily occurred due to the formation of Fe₃O₄. Furthermore, the postulated reaction kinetics in different concentrations of TNT, RDX, and HMX, showed that the rate of TNT removal was higher than RDX and HMX. Furthermore, by‐products obtained after degradation of TNT (long‐chain alkanes/methylamine) and RDX/HMX (formaldehyde/methanol/hydrazine/dimethyl hydrazine) were determined by LC/MS/MS, respectively. The high reaction rate and significant removal efficiencies suggest that ZVINs might be suitable and powerful materials for an in‐situ degradation of explosive polluted wastewaters.     

Effect of Zn Powders on the Thermal Decomposition of Ammonium Perchlorate

In this paper, the catalytic effect of Zn nanopowders on thermal decomposition of ammonium perchlorate (AP) as well as those of Zn micropowders has been investigated using differential thermal analysis (DTA). The results show that both nanometer and micrometer Zn powders show similar excellent catalytic effect on the decomposition of AP, while the total heat releases of AP added by Zn nanopowders are generally higher than those of AP added by Zn micropowders. In addition, an attempt has been made to explain the observed results with the help of theoretical considerations and data generated during this work.     

Synthesis,characterization, thermal stability,and compatibility properties of poly(vinyl p‐nitrobenzal acetal)‐g‐polyglycidylazides

A series of energetic polymers, poly(vinyl p‐nitrobenzal acetal)‐g‐polyglycidylazides (PVPNB‐g‐GAPs), are obtained via cross‐linking reactions of poly(vinyl p‐nitrobenzal acetal) (PVPNB) with four different molecular weights polyglycidylazides (GAPs) using toluene diisocyanate as cross‐linking agent. The structures of the energetic polymers are characterized by ultraviolet visible spectra (UV‐Vis), attenuated total reflectance‐Fourier transform‐infrared spectroscopy (ATR‐FT‐IR), ¹H nuclear magnetic resonance spectrometry (¹H NMR), and ¹³C nuclear magnetic resonance spectrometry (¹³C NMR). Differential scanning calorimetry (DSC) is applied to evaluate the glass‐transition temperature of the polymers. DSC traces illustrate that PVPNB‐g?2^#GAP, PVPNB‐g?3^#GAP, and PVPNB‐g?4^#GAP have two distinct glass‐transition temperatures, whereas PVPNB‐g?1^#GAP has one. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) are used to evaluate the thermal decomposition behavior of the four polymers and their compatibility with the main energetic components of TNT‐based melt‐cast explosives, such as cyclotetramethylene tetranitramine (HMX), cyclotrimethylene‐trinitramine (RDX), triaminotrinitrobenzene (TATB), and 2,4,6‐trinitrotoluene (TNT). The DTA and TGA curves obtained indicate that the polymers have excellent resistance to thermal decomposition up to 200°C. PVPNB‐g?4^#GAP also exhibits good compatibility and could be safely used with TNT, HMX, and TATB but not with RDX. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42126.     

Effects of MgH2/Mg(BH4)2 Powders on the Thermal Decomposition Behaviors of 2,4,6‐Trinitrotoluene (TNT)

The thermal properties of 2,4,6‐trinitrotoluene (TNT), TNT/MgH₂, and TNT/Mg(BH₄)₂ were investigated by differential scanning calorimetry (DSC) and accelerating rate calorimetry (ARC). The results show that addition of MgH₂ or Mg(BH₄)₂ to TNT has a great effect on the DSC decomposition process. The exothermic decomposition peak of TNT disappeared and was replaced by a slow exothermic trend in the curves of both TNT/MgH₂ and TNT/Mg(BH₄)₂. The kinetic triplet of TNT formulations were calculated by ARC data. The results show that TNT/MgH₂ and TNT/Mg(BH₄)₂ have lower onset temperatures, apparent activation energies (E) and frequency factors (A) than neat TNT. A change of the TNT decomposition mechanism is also discussed.     

Applying modified hyperbranched polyester in hydroxyl‐terminated polyether/ammonium perchlorate/aluminium/cyclotrimethylenetrinitramine (HTPE/AP/Al/RDX) composite solid propellant

Composite solid propellants demand fine and stable mechanical properties, creep resistance and stress relaxation performance during their long storage and usage time. In this study, modified hyperbranched polyester (MHBPE) was prepared and introduced into HTPE/AP/Al/RDX (HTPE, hydroxyl‐terminated polyether; AP, ammonium perchlorate; RDX, cyclotrimethylenetrinitramine) solid propellant as an effective additive. The static tensile and dynamic mechanical properties of this propellant before and after the introduction of MHBPE were evaluated. The elevated interfacial interaction by using MHBPE between the binder and RDX fillers improved the toughness and elasticity of the propellant. The enhancement mechanisms were also confirmed by the influence on the fracture surface morphology of the binder which was investigated by SEM. In addition, some influence on the dynamic mechanical properties of HTPE/AP/Al/RDX propellant caused by MHBPE was investigated by dynamic mechanical analysis. The creep behaviors of the HTPE/AP/Al/RDX propellants with and without MHBPE were also investigated at different stresses and temperatures. Reduced creep strain rate and strain were obtained for the modified propellant, implying enhanced creep resistance performance. The creep properties were quantitatively evaluated using a six‐element model and the long‐term creep performance of the propellant was predicted using the time–temperature superposition principle. A creep behavior of nearly 10⁶ s at 30 °C could be acquired in a short‐term experiment (800 s) at 30–70 °C. Moreover, the stress relaxation investigation of the propellants with and without MHBPE at ?40 °C, 20 °C and 70 °C suggested that MHBPE/HTPE/AP/Al/RDX propellant possessed better response ability to deformation. Thus, the application of MHBPE provides an efficient route of reinforcement to enhance the creep resistance and stress relaxation properties. © 2020 Society of Chemical Industry     

Synthesis of Single‐Phase Gd‐Doped Ceria Nanopowders by Radio Frequency Thermal Plasma Treatment

Gd‐doped ceria nanopowders were synthesized using Radio Frequency (RF) thermal plasma. The powders were prepared by ball‐milling Gd₂O₃ and CeO₂ powders of several tens of μm in size at the cation ratio of 8:2 and 9:1. The prepared precursors were treated by RF thermal plasma at a plate power level of ~140 kVA, and then, small‐sized powders (~50 nm) were retrieved by filtration. Transmission Electron Microscopy, Electron Energy Loss Spectroscopy, and Selected‐Area Electron‐Diffraction images of the as‐synthesized powders showed that Gd atoms were incorporated into the CeO₂ particles. In addition, no crystalline peak for Gd₂O₃ appeared in the X‐ray diffraction patterns of the as‐synthesized powders, which is attributed to the solid solution of Gd³⁺ into the CeO₂ lattices. Finally, Inductively Coupled Plasma‐Optical Emission Spectrometry analysis data revealed relatively small changes within 3 at.% in the cation composition between the ball milled powder mixtures and the nanoscale powders prepared from these mixtures.