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Abstract:To study the effect of RDX particle size on the mechanical property and combustion performance of nitramine gun propellant, three kinds of nitramine gun propellants containing 25.0% RDX with average particle sizes of 30, 50 μm and 150 μm were designed, their impact strength, crushing situation and combustion performance were studied by pendulum charpy impact machine, drop weight test apparatus and closed bomb, respectively. Results show that with the particle size of RDX decreasing from 150 μm to 30 μm, the impact strength of gun propellants at low temperature (-40 ℃) increases from 3.46 J·cm^-2 to 8.99 J·cm^-2, and the crushing degree under the action of drop hammer impact (hammer weight 5kg and drop height 80 cm) decreases from 96% to 18%. When the average particle size of RDX, D₅₀, is 30, 50 μm and 150 μm, the pressure exponent of burning rate is 0.985, 0.996 and 1.063, respectively. When the particle size of RDX is 30 μm or 50 μm, the u-p curve of gun propellant is smooth, its combustion is stable. When the particle size of RDX is 150 μm, in the pressure range of 100~150 MPa to 150 MPa~p_dpm, the pressure exponent of burning rate decreases from 1.125 to 0.612, revealing that there is a mutation in the pressure exponent of burning rate and the propellant combustion is unstable.

Abstract:To optimize the solvent ratio of the coating solution in spraying process of preparing the coating layer of gun propellant with local end-coating flame retardant, the coating solution was prepared using cellulose acetate butyrate (CAB) as desensitized agent, mixture composed of CAB and absorption propellant tablets TG-1 with main components of nitrocellulose and nitroglycerin as solute, ethanol/ acetone of V/V=1/1 as solvent, according to different solvent ratios. Applying the coating solution, the films of coating layers and coated propellants were produced by spraying coating technology. The mechanical strength of the films of coating layers was obtained by an universal material tester. The local amplification observation and analysis of 3D video for surface structure of coating layers before and after tension were performed.The coated propellants were tested by the closed bomb experiments. Results show that the mechanical strength and morphology of both surface and fracture of coating layers are significantly related to solvent ratios. The solvent ratios affect the uniformity and compactness of coating layer materials mainly and are important factor affecting the mechanical strength of coating layers. Thereby, the combustion progressivity of coated propellants is effected.When the solvent ratio is 8:1, the porosity rate is over 95%. At the meantime, the surface of the coating layer obtained is the best smooth, the tensile strength of its film is the maximum, its value is 49.75 MPa, the fracture is the most tidy and the change value in combustion gas dynamic activity for coated propellant achieves a maximum value of 0.0920 MPa^-1·s^-1 in all samples.

Abstract:A T-shaped micro-channel device with continuous phase of aqueous solution and dispersed phase of ethyl acetate solution was used to prepare the spherical propellants based on the microfluidic technology. The effects of flow rate ratios and nitrocellulose/solvent ratios on the preparation of spherical propellants were studied, respectively. Results showed that when the nitrocellulose/solvent ratio was fixed to 50:2.5 and the flow rate of continuous phase was fixed to 1000 μL·min^-1, the particle size was increased from 270 μm to 306 μm with the increase of the flow rate of dispersed phase from 30 μL·min^-1 to 100 μL·min^-1. When the flow rate ratio of the two phase was fixed to 1000 μL·min^-1:100 μL·min^-1 and the nitrocellulose/solvent ratio of the dispersed phase was from 50:2.0 to 50:3.0, the particle size was increased from 250 μm to 350 μm. The characterization results of SEM show that the nitrocellulose spheres prepared by the microfluidic technology had regular morphology, narrow size distribution and good monodispersity.

Abstract:A new seraph star-hole stick gun propellant with large web size was designed and prepared. The combustion characteristics of the star-hole stick gun propellants with different ratios of length to diameter(L/D=1, 2, 6) and different sealing layer thicknesses/gun propellant web size ratios (s/e₁=0, 0.05, 0.1) were studied by closed bome and combined with a large caliber gun, the experimental verification was performed. Results show that the combustion of the star-hole propellant is stable, revealing a parallel layer combustion. When the L/D increases from 1 to 6, the progressive combustion factor P_r increases by 56.8% from 0.285 to 0.447, and the maximum pressure point delays. The L-B curves of end plane plugging propellants display obvious low initial combustion activity and hole breaking combustion. When the s/e₁ increases from 0 to 0.05 and 0.1, the initial gas generaation quantity of the star-hole stick gun propellant were reduced by about 1/2, and the hole breaking times were between the burning time needed to burn 10% to 20%(burned fraction) propellants. Selecting appropriate thicknesses of the plugging layers can realize the controllable regulation of the gas generation law of the propellants.When the s/e₁ increases from 0 to 0.05 and 0.1, the maximum bore pressure p_m decreases by 1.39% and 3.59% respectively, however, the initial speed of projectile at 32.5 m from gun muzzle increases by 0.28% and 1.4%, respectively.

Abstract:The enthalpies of formation for energetic polyurethane binder using glycidyl azide polymer (GAP), poly glycidyl nitrate (PGN), poly bis-azidomethyl oxetane (PBAMO), poly (3-nitratomethyl-3-methoxetane (PNIMMO) as polyether glycol, diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), isophorone diisocyanate (IPDI) as polyisocyanate were calculated by group additivity method. The energy parameters of the designed propellant formulations based on hexogen(RDX), hexanitrohexaazaisowurtaitane(HNIW), 1, 3, 3-trinitroazetidine(TNAZ), 3, 4-dinitrofurazanofuroxan(DNTF) were calculated by inner energy method.Simutaneously, iso-force content triangular plot of 1250, 1300, 1350 kJ·kg^-1 for (MDI/GAP₁₀₀₀)/RDX/HNIW, (MDI/GAP₁₀₀₀)/RDX/TNAZ and (MDI/GAP₁₀₀₀)/RDX/DNTF formulations were drawn. Results show the enthalpies of formation of polyurethane binder can be calculated by structure units. The formulations containing solid filler and energetic binder have high force content. The force content of formulations with 30%~50% solid filler could exceed 1300 kJ·kg^-1. The force content presents linear cariation trend when replacing RDX using HNIW, TNAZ, but when adding DNTF in formulations, there is a transition point on the iso-force line. The calculation results of (MDI/GAP₁₀₀₀)/RDX/TNAZ formulations indicat that the formulations could reach the international advanced level (force content higher than 1300 kJ·kg^-1, explosion temperature lower than 3300 K).

Abstract:The main disadvantages of lead 2, 4, 6-trinitroresorecinate (LTNR)are too high electrostatic sensitivity and the harm to the human body and the environment caused by lead. In search of a replacement for LTNR, potassium 4, 6-dinitro-7-oxygen-benzofuroxan monohydrate (KDNP·H₂O) was synthesized by two-step method. The single crystal of the compoud was obtained by solvent evaporation method. Its structure was chracterized by elemental analysis, IR spectroscopy, ¹H NMR/¹³C NMR spectroscopy and X-ray single-crystal diffraction. Its sensitivities were measured according to the Chinese military standard test method GJB-5891. The heat of detonation was calculated. The detonation parameters of the compoud were calculated by Kamlet-Jacobs equations. Results show that the crystal is triclinic, space group P-1 with one crystal water. For this primary explosives, the impact sensitivity (H₅₀) is 21.3 cm, the electrostatic sensitivity (E₅₀) is 0.69 J, the friction sensitivity is 56%, the flame sensitivity is 24.7 cm, the heat of detonation is 3.50 kJ·g^-1, the detonation velocity is 6.77 km·s^-1 and detonation pressure is 21.25 GPa, revealing that KDNP·H₂O is a primary explosives with lead-free, safe and environmental protection.

Abstract:Direct writing technology has the advantages of safety, batch and precise graphics, and it is the trend of future development of precision and efficient charge forming for energetic micro devices. Based on hexanitrohexaazaisowurtzitane (CL-20) based explosive ink, the effect of driving pressure and outlet diameter on the extrusion rate was investigated by the combination method of the simulation using Ansys software and the direct writing deposition experiment. The direct writing deposition data were analyzed by Matlab software. The effective direct wring parameters were obtained by an interpolation analysis method. The mathematical model describing the direct writing deposition rule was established. Results show the prepared CL-20 based explosive ink is a non-Newtonian fluid with a viscosity range of 10 Pa·s to 350 Pa·s. When the shear stress is greater than 650 Pa, the loss modulus is larger than storage modulus gradually. When the driving pressure is greater than 350 kPa, the viscosity of the CL-20 baded explosive ink decreases, making the change rate of the extrusion rate increase. When the outlet diameter is bigger than 0.6 mm, decreasing the extrusion energy loss of the ink decreases makes the change rate of the extrusion rate increase. The established direct writing parameters relation formula is u₁=0.00047×d₁^0.6516×p^1.5291, which indicates that the driving pressure is greater than the effect of outlet diameter on the extrusion rate.

Abstract:In order to investigate the effect of hydrophile-lipophile balance (HLB) numbers on the rheological properties of explosive inks, two nonionic surfactants of Span-80 and Tween-80 were selected to obtain 5 kinds of mixed surfactants with different HLB number by adjusting mass percentage. Whereafter, the viscosity of explosive ink with mixed surfactants was tested by means of Brookfield (CPS) rheometer and non-Newtonian index, yield values and thixotropic index(TI) were calculated at same time. Results indicate that for the explosive ink without surfactant the non-ewtonian index is 0.024, yield value is 467.08 Pa and TI value is 36.82, respectively, and the rheological properties of explosive ink will be effectively improved with the addition of surfactants. With the increasing of HLB number, the apparent viscosity of explosive ink will keep up at first and then down with the shear rate ranging from 5 s^-1to 100 s^-1. Meanwhile, non-Newtonian index and TI values fluctuate while yield vales continuously decrease. When HLB number is 11, the non-Newtonian index reaches the maximum 0.56, while the yield value attains the optimum value 5.38 Pa with TI value being the minimum 8.26, which are 23.33 times, 1.15% and 21.53% respectively compared with those of the explosive ink without surfactants. The surfactant with whose HLB number is 11 performs best in improving rheological property of explosive ink.

Abstract:Based on the technique of magnetically driven ramp loading, the dynamic response of hydroxyl-terminated polybutadiene(HTPB) samples solidified by toluene diisocynate(TDI) were investigated under loading pressure up to 1.2 GPa. The velocity response curves of three HTPB samples with different thickness were obtained by Photonic Doppler Velocimeter(PDV). The sound velocity vs. particle velocity curve and stress vs. specific volume curve were obtained by Lagrange analysis method. Based on the relationships above and the loading history gained from experimental data, the experiments were validated by one dimensional hydrodynamic simulation. The simulation results are in good agreement with experimental results. Research shows that the Lagrange sound velocity vs. particle velocity behaves linear relationship. The loading strain rate ranges from 2×10⁵ s^-1 to 1×10⁶ s^-1 and the strain rate increases with the increasing of sample thickness, but no strain-rate effect is observed. All results agree with the shock loading results in reference.

Abstract:In order to study the characteristics of the low density materials liner forming particle jets, the Smoothed Particle Hydrodynamics (SPH) method was used to simulate the formation of the low-density material liner particle jets by AUTODYN finite element software, and experimental verifications were carried out. The material of the liner is (PTFE/Cu), which was obtained via modification of adding copper powder of mass fraction as 38.5% with a certain particle size and a density of 8.93 g·cm^-3 into PTFE matrix. Results show that SPH method can effectively simulate the explosion and the formation of particle jets, and during the numerical simulation, choosing the particle spacing of the explosive particles and the particle spacing of the liner material as 0.03 cm is more appropriate. Under the action of the detonation wave, the PTFE/Cu material liner does not form a condensed jet, but will form a scattered particle jet. Through X rays it can be observed that the jet is very fine particles and the optical density increases along the radial direction. In the former 40 μs, the simulation and the experiment have a high similarity of the formation of particle jets patterns, the simulation results are in good agreement with the actual situation, but the motion of the actual particle jets after 100 μs shows a strong uncertainty, there are spial, deviation and other phenomena.

Abstract:Two dimensional numerical simulation of the boundary effect in explosive cladding was carried out by using the LS-DYNA software and gridless Smoothed Particle Hydrodynamics (SPH) method. Results show that the phenomena of metal jet and boundary effect were consistent with the production practiof explosive cladding. The reason of causing the boundary effect in explosive cladding is not caused by the damage and cracking at the boundary when colliding of the base composite plate due to the excess impact energy of the boundary, before the base composite plate collision, the fracture has been generated. Considering that The generation of boundary effect in explosive cladding is due to the effect of rarefaction wave on the detonation products at the boundary, leading to the velocity difference is existed at the boundary and internal of composite plate, so that the collision angle at the boundary of composite plate becomes bigger, the frature occurs under the action of detonation pressure. In addition, the boundary effect can be effectively controlled by using honeycomb structure explosive and double sided detonation composite method.The preventive measures are proposed to against such a phenomenon.

Abstract:In order to study the detonation performance of propellant grains in different medium, the interspaces among the propellant grains were fully filled with water, oxidant solution and oxidant gel, respectively. The detonation performances of propellant charges with different filling medium were studied through the plate dent test and chronometer measurement test, which compared with no filler. The underwater output energies of propellant charges containing different oxygen balance of filling fluids were also measured by underwater blast test. The results show that with the addition of different filling medium such as water, oxidant solution in the charge of propellant grains, it is conducive to the growth and spread of detonation shock wave. The work capability of the charge is improved, and the detonation velocity is also increased. When the charge of propellant grains is filled with the dense medium which contains oxidant, it has excellent detonation velocity(about 6.4 km·s^-1).The underwater energies of propellant charges are increased with the increase of the oxygen balance, and there is a significant linear relationship between the total energy and the oxygen balance of the charge. Its shock wave energy is more than 1.0 kJ·g^-1 and the total energy is basic quite compared with the rock emulsion explosive and ammonium nitrate-fuel oil explosive.

Abstract:To investigate the interference factors affecting the spectrophotometric determination of cyclotrimethylene trinitramine (RDX) in wastewater following the oxidation of ozone (O₃), a series of exploring experiments were carried out. With the help of the Rank sum test and F test, the system error between the RDX data determined by spectrophotometry and high performance liquid chromatography (HPLC) was estimated. RDX data in wastewater and standard solution before and after oxidation of O₃ obtained by spectrophotometry and HPLC were compared. The possible interfering substances were detected by liquid chromatography/mass spectrometry (LC/MS) and gas chromatography/mass spectrometry (GC/MS). The cause of misludging the spectrophotometric results of RDX was analysed.Results show that the systematic error does not exist between the RDX data determined by two test methods under the given significance level α=0.05. The organic substances in wastewater of RDX are oxidized by O₃ to produce formaldehyde, which interferes with the analysis results, but this part of formaldehyde can be effectively removed by sample pretreatment.At the same time, RDX can not be completely mineralized during the oxidation of O₃, producing low-molecular-weight intermediates, methylenedinitramine, dihydroxy-nitramine and 6-nitro-2, 4, 6-triaza-3, 5-dioxo-hexanal and so on. Among them, the decomposition reaction of methylenedinitramine, dihydroxy-nitramine and other amine-intermediates can occur similar to RDX with concentrated sulfuric acid, formaldehyde formed by the reaction becomes the direct interferencing factors of interfering the determination of RDX by spectrophotometry.

Abstract:Aming at the problems of large emissions and difficult degradation for pollutant of phenol series contained in wastewater of propellants and explosives, the electrocatalytic oxidation of simulated wastewater of propellants and explosives with phenol was studied using RuO₂-IrO₂-SnO₂/Ti as anode and Ti as cathode, sodium chloride as elecctrolyte.The effects of sodium chloride concentration, current density, pH value and initial concentration of phenol wastewater on phenol removal efficiency were investigated. The change in total organic carbon(TOC) and chemical oxygen demand (COD) with time were studied under the conditions of the best removal efficiency of phenol. The intermediate products and process of degradation of phenol were speculated by high performance liquid chromatography. Results show that under the conditions of sodium chloride concentration as 13 g·L^-1, current density as 30 mA·cm^-2, pH value as 5, initial concentration of phenol wastewater as 500 mg·L^-1, when the reaction time is 60 min, the phenol removal efficiency is up to 99.85%. Under the conditions of the best removal efficiency of phenol, when the reaction time is 100 min, the removal efficiency of TOC and COD are 53.55% and 59.37%, respectively.The electrode is easy to catalyze the electrophilic addition reaction of ClO^-, · OH and other active groups with benzene ring to form aromatic compounds, which can be oxidized to aliphatic compounds CO₂ and H₂O.

Abstract:The traditional methods of detecting energetic materials are mainly based on chemical sensing and precise instrument measurement, but these two methods are usually difficult to achieve the detection of explosives rapidly.In the past more than 10 years, in the crossing field of supermolecular material and coordination chemistry, a new material-luminescent metal-organic frameworks (LMOFs) has emerged, due to the porous, high quantum yield and stability characteristics of this material, it is considered to be an excellent luminescent material. On the one hand, LMOFs combine the advantages of organic luminescent materials and metal luminescent materials, and improve the luminous efficiency of the system through energy transfer within the skeleton. On the other hand, LMOFs have orderly pore structure and large specific surface, which is beneficial to the selective recognition of different explosive molecules.Therefore, LMOFs display promising applications in the molecular fluorescence recognition and detection of explosives.The paper introduces the research progress of LMOFs in the field of recognition and detection of explosives systematically, the main research objects include three categories, nitro-explosives, nitro-geo hetercyclic explosives and explosives without nitrogen. The recognition mechanizm and recognition selectivity of LMOFs are mainly summarized. In the future, the research on the detection of explosives by LMOFs may pay more attention to the exploration of surface modification of materials, improvement of water stability and detection of nitro-geo hetercyclic explosives and other aspects.

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