Abstract:Starting from (1-tert-butyl-3-nitroazetidin-3-yl)methanol, a melt-cast explosive of 3-azido-1,3-dinitroazetidine (AzDNAZ) with novel gem-azidonitro energetic group was obtained through an improved azidation-salinization-nitration strategy with a total yield of 58.8%. Structures of the intermediates and AzDNAZ were characterized by ¹H NMR, ¹³C NMR, IR and element analysis. One of the intermediates, 1-t-butyl-3-azido-3-nitro-azetidinium nitrate (compound 2), was obtained for the first time with the single crystal determined by X-ray single crystal diffraction, which reveals that it crystallizes in monoclinic, space group P2(1)/n with a=0.8281(314) nm, b=0.8607(2) nm,c=1.7195(2) nm, α=90°, β=94.983(2)°,γ=90°,V=1.2210(6) nm³,Z=4, M_r=262, D_c=1.427 g·cm^-3, μ=0.174 mm^-1, F(000)=552, R=0.0418 and ωR=0.1168. Meanwhile, thermal behaviors of AzDNAZ were studied by subsequently differential scanning calorimetry (DSC) and thermal gravimetric analyzer (TG) methods. Based on the measured values of density and heat of formation, the detonation parameters were calculated by Gaussian 09 program and Kamlet-Jacobs equations. Results show that the melting point, decomposition point, density, heat of formation, detonation velocity and detonation pressure are 78.2 ℃, 180.7 ℃, 1.75 g·cm^-3,331.73 kJ·mol^-1, 8460 m·s^-1 and 31.83 GPa, respectively, indicating AzDNAZ can be applied as a promising melt-cast explosive or an energetic plasticizer with satisfactory performances.

Abstract:In accordance with increasing stringent ammunition safety requirements, the manufacture, transportation and applications of traditional 2,4,6-trinitrotoluene (TNT)-based melt-cast explosives will not fulfill those safety standards. Recently, the melt-cast explosives based on 2,4-Dinitroanisole (DNAN) as substitute for those of TNT has aroused great attentions. In this paper, the research progress of DNAN-based melt-cast explosives in the last ten years were summarized towards their synthesis, physicochemical properties, energetic and sensitive performance, mechanical and rheological performances. Furthermore, the main research hotspots about DNAN-based melt-casting explosives in the future were also prospected in this article.

Abstract:In order to compare the comprehensive properties of 2,4-dinitroanisole(DNAN)-based and 2,4,6-trinitrotoluene（TNT） -based melt-cast explosives, the suspension rheology, performance, safety and mechanical properties of typical TNT-based and DNAN-based explosives were systematically investigated by experiment tests. The viscosity of DNAN(6.87 mPa·s) was lower than that of TNT(9.05 mPa·s), which made the limit solid content of the DNAN/HMX melt-cast system (about 80%) higher than that of the TNT/HMX melt-cast system (about 75%). The detonation velocity and detonation pressure was 8336 m·s^-1 and 31.03 GPa, 8452 m·s^-1 and 31.44 GPa, for DNAN/HMX(20/80) and TNT/HMX(25/75), respectively. The response level of DNAN/HMX(20/80) and TNT/HMX(25/75) was burning and explosion, respectively under 1 K·min^-1 slow cook-off. Under 4.51 GPa incident shock wave pressure, TNT/HMX(25/75）achieved complete detonation within 8-12 mm, whereas DNAN/HMX(20/80) failed to achieve complete detonation within 12 mm; tensile and compressive strength of DNAN/HMX(20/80) was higher than that of TNT/HMX(25/75).With basically equal energy performance, DNAN/HMX(20/80) melt-cast explosives have better safety and mechanical properties than TNT/HMX（25/75） melt-cast explosives.

Abstract:In order to obtain castable explosive with high energy and high mechanical strength, CL-20/DNAN/TNT castable explosive was successfully prepared by casting process with 2,4-dinitroanisole (DNAN) and trinitrotoluene (TNT) as low eutectic carriers and hexanitrohexaazoisowurtziane (CL-20) as high energy component. The effects of micro-nano CL-20 particle grading and three functional assistants of N-methyl-4-nitroaniline, tris-(2-chloroethyl) phosphate and catechol on the properties of CL-20/DNAN/TNT castable explosives were investigated. The prepared CL-20-based castable explosives were characterized by SEM, viscosity, density, XRD, mechanical sensitivity, mechanical properties and detonation speed. When the mass ratio of bulk CL-20 to 100 nm CL-20 was 70:30 and 0.5% tri-(2-chloroethyl) phosphate was added, the castable explosive had smooth surface, no obvious internal defects and good density uniformity. Compared with the castable explosive with coarse CL-20, the impact and friction sensitivity was reduced by 32.7% and 57.1%, respectively. The compressive and tensile strength was increased from 7.93 MPa and 3.48 MPa to 33.74 MPa and 4.94 MPa, respectively. The detonation speed was increased by 37.0 m·s^-1 from 8188 m·s^-1 to 8225 m·s^-1.

Abstract:In order to investigate the micro-crystalline structural morphology in Melt-cast explosive and improve the quality of explosive column, the CAFE module of ProCAST casting simulation software was used to simulate the internal crystalline structure of TNT melt-cast explosive. Using cellular automata in CAFE module, the shape and size of grain in column under different technological conditions and TNT nucleation parameters were predicted. The improvement measures of grain refinement process were obtained by adjusting the nucleation undercooling degree, pouring temperature and cooling rate of melt. The results show that with the decrease of melt nucleation undercooling, the equiaxed grain area in the column gradually increases, and the average grain size decreases to 458.5 μm from 715.5 μm; with the decrease of melt surface nucleation undercooling, the grain morphology inside the column does not change significantly, and the average grain size increases to 719.2 μm from 715.5 μm; with the decrease of melt pouring temperature, the equiaxed grain area in the column gradually increases, and the average grain size decreases to 729.2 μm from 1114.5 μm; with the decrease of cooling rate, the central equiaxed grain area gradually enlarges, the outer equiaxed grain area gradually disappears, and the average grain size increases to 1149.1 μm from 719.4 μm. After process optimization, the column is composed of fine equiaxed grains with an average grain size of 516.9 μm, the size distribution is concentrated, and the micro-quality of the grain is greatly improved.

Abstract:To improve the mechanical property of 2, 4-dinitroanisole(DNAN)/RDX melt-cast explosives, the effect of functional additives, N-methyl -4-nitroaniline(MNA), Tween 60, tris-(β-chloroethyl)fosfat(CEF)and cellulose acetate butyrate(CAB) on the interfacial binding energy was simulated by molecular dynamics. The powder contact angle method and platinum plate method were used to measure the contact angle and surface tension, and the simulation results were verified by calculating the adhesion work. The experiments of adhesion work were verified from macroscopic and microscopic scales by Brazilian experiments and scanning electron microscopy(SEM), respectively. Results show that the order of change ability of functional additives on DNAN/ RDX interfacial binding energy from high to low is CAB>CEF>Tween 60>MNA, and the experimental results agree well with the numerical simulation ones. Functional additives, CAB, CEF, Tween 60 and MNA can make the tensile strength of DNAN/RDX explosive increase by 58.37%, 47.85%, 29.71% and 5.83%, respectively. With the increase of adhesion work, the fracture mode of grain is changed from transgranular/intergranular mixed fracture to pure transgranular fracture.

Abstract:To explore the influence rule of octogen (HMX) solid content, system temperature, HMX particle size, HMX particle gradation and functional additives etc.on the rheological properties of 2, 4-dinitroanisole (DNAN)/HMX suspensions, the apparent viscosity of DNAN/HMX suspensions under different material state conditions was investigated by a digital viscometer.Results show that the suspension presents Newtonian fluid characteristics when the solid content is 3%.Apparent viscosity of the suspension can be described with Ostwald-deWaele model when the HMX solid content is 12%-30%, and the value of nonNewton index n is decreased from 0.842 to 0.374.The influence of temperture on the apparent viscosity can be described by the Arrhenius equation when the temperture is in the range of 95-116℃, and the activation energy E_a increases from 25.97 kJ·mol^-1 to 30.17 kJ·mol^-1.The apparent viscosity decrases as the particle size increases.When the particle gradation ratio of 999.5 μm particle size to 132.6 μm is 2:1, the apparent viscosity reaches the minimum and the solid content is up to 80%.Functional additives N-methyl-4-nitroaniline (MNA) and tri (β chloroethyl) phosphate (CEF) make the apparent viscosity of the suspensions decrease, while dehydrated sorbitol monostearate polyoxyethylene ether (Tween 60), microcrystalline wax-80(MV80), cellulose acetate butyrate (CAB), and thermoplastic polyurethane-5720(TPU 5720) make the the apparent viscosity of the suspensions increase.