Structural Characteristics and Decomposition Mechanism of 2,2′-Dimethyl-5,5′-Azotetrazole

The geometry and the potential curve of thermal decomposition for 2,2′dimethyl-5,5′-azotetraol (2-DMAT) are calculated by ab initio quantum chemistry method. The structural characteristics and decomposition mechanism are carefully studied. It is found that the terrazzo ring satisfies 4n+2 rule and it is a conjugated π-systems for 2-DMAT. The azotetrazol has aromaic characteristic and its thermal decomposition can proceed in two steps: ring opening and N2 separation. The activation energies of the two steps are 152.3kJ/mol and 44.67kJ/mol respectively. The ring opening is the rate-controlling step.     

Structural Characteristics and Decomposition Mechanism of 1, 1′-Dimethyl-5,5′-Azotetrazole

The geometry and the potential curve of thermal decomposition for 1,1′dimethyl-5,5′-azotetraol (1-DMAT) are calculated by ab initio quantum chemistry method. The structural characteristics and decomposition mechanism are carefully studied. It is found that the terrazzo ring satisfies 4n+2 rule and it is a conjugated π-system for 1-DMAT. The azotetrazol has aromatic characteristic and its thermal decomposition can proceed in two steps: ring opening and separation N2. The activation energies of the two steps are 243.5kJ/mol and 64.01kJ/mol, respectively. The ring opening is the rate-controlling step.     

Structural Characteristics and Decomposition Mechanism of 2, 2＂-Dimethyl-5, 5＇-Azotetrazole

The geometry and the potential curve of thermal decomposition for 2, 2＇ dimethyl-5, 5＇-azotetraol （2-DMAT） are calculated by ab initio quantum chemistry method. The structural characteristics and decomposition mechanism are carefully studied. It is found that the terrazzo ring satisfies 4n ＋ 2 rule and it is a conjugated π-systems for 2 DMAT, The azotetrazol has aromaic characteristic and its thermal decomposition can proceed in two steps： ring opening and N2 separation, The activation energies of the two steps are 152.3 kJ/mol and 44.67 kJ/mol respectively. The ring opening is the rate-controlling step.     

Structural Characteristics and Decomposition Mechanism of 1, l＇-Dimethyl-5, 5＇-Azotetrazole

The geometry and the potential curve of thermal decomposition for 1, l＇dimethyl-5, 5＇-azotetraol （1-DMAT） are calculated by ab initio quantum chemistry method. The structural characteristics and decomposition mechanism are carefully studied, It is found that the terrazzo ring satisfies 4n ＋ 2 rule and it is a conjugated π-system for 1-DMAT. The azotetrazol has aromatic characteristic and its thermal decomposition can proceed in two steps： ring opening and separation N2. The activation energies of the two steps are 243.5 kJ/mol and 64.01 kJ/mol, respectively. The ring opening is the rate-controlling step.     

Estimation of the kinetic parameters for thermal decomposition of HNIW and its adiabatic time-to-explosion by Kooij formula

A differential/integral method to estimate the kinetic parameters （apparent activation energy Ea and pre-exponential factor A） for thermal decomposition reaction of energetic materials based on Kooij formula are applied to study the nonisothermal decomposition reaction kinetics of hexanitrohexaazaisowurtzitane （HNIW） by analyzing nonisothermal DSC curve data. The apparent activation energy （Ea） obtained by the integral isoconversional non-isothermal method based on Kooij formula is used to check the constancy and validity of apparent activation energy by the differential/integral method based on Kooij formula. The most probable mechanism function of thermal decomposition reaction of HNIW is determined by a logical choice method. The equations for calculating the critical temperatures of thermal explosion （T_b） and adiabatic time-to- explosion （t_Tlad） based on Kooij formula are used to calculate the values of Tb and t_Tlad to evaluate the thermal safety and heat-resistant ability of HNIW. All the original data needed for analyzing the kinetic parameters are from nonisothermal DSC curves. The results show that the kinetic model function in differential form and the values of E_a and A of decomposition reaction of HNIW are 3（1 - α）[-ln（1 - α）]2/3, 152.73 kJ mol 1 and 10~11.97 S 1, respectively, and the values of self-accelerating decomposition temperature （T_SADT）, Tb and t_Tlad are 486.55 K, 493.11 K and 52.01 s, respectively.     

Kinetics of the Exothermic Decomposition Reaction of s-Tripicryaminotrinitrobenzene

The kinetic parameters of the exothermic decomposition reaction of s-Tripicryaminotrinitrobenzene under linear temperature rise condition are studied by means of DSC. The results show that the empirical kinetic model function in differential form, apparent activation energy and pre-exponential constant of the reaction are 225.4 kJ·mol-1 and 1 019.53 s-1, respectively. The critical temperature of thermal explosion of the compound is 267.36 ℃.     

A New Aspect of Relationships between Electric Spark Sensitivity and Thermal Stability of Some Polynitro Arenes（英）

An ESZ KTTV instrument of a new,relatively simple construction has been applied to determination of electric spark sensitivity of 29 polynitro arenes,expressed as spark energy,EES,required for 50-percent initiation probability.The thermal stability thresholds,Tmax,were calculated from the published Arrhenius parameters of monomolecular thermal decomposition of the studied compounds,predominantly obtained under the conditions of the Russian manometric method.An approximate relationship has been found between the ln EES values and threshold Tmax values.In the sense of this relationship,the compounds studied fall into several sub-groups.The reason of the said diversification lies in the decomposition reaction rate at the temperature of onset of their thermal decomposition.It has been found that in each sub-group increasing thermal stability of polynitro arenes is accompanied by increasing electric spark sensitivity of these substances.This fact must be taken into account if we deal with the problem of electric spark energy transfer into the reaction centre of the molecule.     

Research on the fracture behavior of PBX under static tension

The fracture behavior of polymer-bonded explosive （PBX） seriously affects the safety and reliability of weapon system. The effects of interface debonding and initial meso-damage on the fracture behavior of PBX under quasi-static tension are studied using numerical method. A two- dimensional representative volume element （RVE） is established based on Voronoi model in which the component contents could be regulated and the particles are randomly distributed. A nonlinear damage model of polymer matrix relative to matrix depth between particles is constructed. The results show that the simulated strain-stress relation is coincident with experiment data. It is found that interface debonding leads to the nucleation and propagation of meso-cracks, and a main crack approximately perpendicular to the loading direction is generated finally. The interface debonding tends to occur in the interface perpendicular to the loading direction. There seems to be a phenomenon that strain softening and hardening alternatively appear around peak stress of stress and strain curve. It is shown that the initial damages of intragranular and interfacial cracks both decrease the modulus and failure stress, and the main crack tends to propagate toward the initial meso-cracks.     

Density Functional Theoretical Study of 5 ,5 ’-Azotetrazolate Nonmetallic Salts

The structures, infrared spectra and cation stability of seven 5,5 ＇-azotetrazolate nonmetallic salts are investigated by using B3LYP method with 6-311 ＋ G （d） basis set. The salts are guanidinium （ GZT）, aminoguanidinium （AGZT）, diaminoguanidinium （DAGZT）, triaminoguanidinium （TAGZT）, azidoformamidinium （AFZT）, ammonium （AZT）, and hydrazinium （HZT）, respectively. The calculated results indicate that the carbon and nitrogen atoms of the cations in seven nonmetallic salts are characterized to be spa hybrid atoms, and the ranges of characteristic absorption peaks in IR spectra of the seven nonmetallic salts are approximative consistent. All their cations are stable and their stabilities decrease with the increase in their nitrogen contents.     

Influence of A1203 particles on the microstructure and mechanical properties of copper surface composites fabricated by friction stir processing

The influence of three factors, such as volume percentage of reinforcement particles （i.e. A1203）, tool tilt angle and concave angle of shoulder, on the mechanical properties of Cu-A1203 surface composites fabricated via friction stir processing was studied. Taguchi method was used to optimize these factors for maximizing the mechanical properties of surface composites. The fabricated surface composites were examined by optical microscope for dispersion of reinforcement particles. It was found that A1203 particles are uniformly dispersed in the stir zone. The tensile properties of the surface composites increased with the increase in the volume percentage of the A1203 reinforcement particles. This is due to the addition of the reinforcement particles which increases the temperature of recrystallization by pinning the grain boundaries of the copper matrix and blocking the movement of the dislocations. The observed mechanical properties are correlated with microstructure and fracture features.     

Scale-up synthesis and characterization of 2,6-diamino-3,5-dinitropyrazine- 1-oxide

2,6-diamino-3,5-dinitropyrazine-1-oxide （ANPZO）, as an insensitive high explosive, with a high yield and excellent purity has been prepared at pilot plant scale by an improved method. The synthesized ANPZO is characterized by IR, laser granularity measurement, SEM and HPLC. The particle analysis revealed that the improved method could offer desired product with average particle size of 40 gm and high purity （〉98.45%）. The experimental parameters exhibited that the detonation velocity of the formulation based on ANPZO was higher than that of the corresponding TATB formulation. The DSC curve showed that the exothermic decomposition of the product occurred at the temperature between 300.5℃ and 360.4℃. Furthermore, the sensitivity test suggests its safe nature towards mechanical stimulus.     

Study of nano-nitramine explosives： preparation,sensitivity and application

Nano-nitramine explosives （RDX, HMX, CL-20） are produced on a bi-directional grinding mill. The scanning electron microscope （SEM） observations show that the prepared particles are semi-spherical, and the narrow size distributions are characterized using the laser particle size analyzer. Compared with the micron-sized samples, the nano-products show obvious decrease in friction and impact sensitivities. In the case of shock sensitivities, nano-products have lower values by 59.9% （RDX）, 56.4% （HMX）, and 58.1% （CL-20）, respectively. When nano-RDX and nano-HMX are used in plastic bonded explosives （PBX） as alternative materials of micron-sized particles, their shock sensitivities are significantly decreased by 24.5% （RDX） and 22.9% （HMX）, and their detonation velocities are increased by about 1.7%. Therefore, it is ex- pected to promote the application of nano-nitramine explosives in PBXs and composite modified double-based propellants （CMDBs） so that some of their properties would be improved.     

Design of Uncooled Thermal Imaging Systems Operating at Multiple Temperatures

The reasons why thermal imaging systems consume power are analyzed, and a low power consumption design scheme is presented for the thermal imaging systems operating at multiple temperatures. The relation between the response performance of α-Si microbolometer detector and its operating temperature is studied by means of formulas of mierobolometer detector＇s noise equivalent temperature difference （NETD） and detectivity. Numerical analysis based on true parameters demonstrates that the detectivity decreases slightly and NETD increases slightly when operating temperature rises, which indicates that α-Si microbolometer detector has approximately uniform response in a wide operating temperature range. According to these analyses, a thermal imaging system operating at multiple temperatures is designed. The power of thermoelectric stabilizer （TEC） is less than 350 mW and NETD is less than 120 mK in the ambient temperature range of - 40℃- 60℃, which shows that this system not only outputs high-quality images but consumes low power.     

Research on Performance of U Separator in Sand and Dust Test System

Sand/dust test is one of the key projects to examine the environmental adaptability of ordnance equipment.In order to decrease the abrasion of test facility caused by the sand/dust particles,the particles contained in the airflowneed to be reclaimed effectively.Amathematical model of Useparator is established.The flowfield and the trajectories of particles inside the separator are obtained using a numerical simulation method,and the separation efficiency and pressure drop of separator with different rows of separate components are also obtained at various flowvelocities.The simulation results indicate that the efficiency of U inertia separator is affected by the flowvelocity evidently,and a reasonably designed separator can meet the requirement of the separation efficiency in particular situation.The results can be use as reference for the design and test of sand/dust separate systems.     

Friction Sensitivity of Nitramines. Part Ⅲ: Comparison with Detonation Performance（英）

The friction sensitivities (FS) of five linear and eight cyclic nitramines have been determined.These FS values were compared with the respective detonation velocities,D,and with the dimensionless ratio created by relating the heat of explosion,Qreal,to the activation energy,Ea,of non-autocatalyzed thermal decomposition of the explosives concerned.For the nitramaines studied,these comparisons show a general trend of FS decreasing with increasing energy content.     

The Dilution/Crystallization Kinetics of RDX and HMX（英）

Three thermokinetic equaions describing the crystal growth process and two relationships between the parameters and the constants of the kinetic equations are derived.The thermokinetic data of crystal growth processes of RDX and HMX are treated based on the derived equations and relationships.The results show that the exothermic dilution/crystallization processes of RDX and HMX are the first order reaction and accord with the dislocation theory.     

Research on Microcrack Extension Mechanism of SiCp/Al in the Machining Process

The generation and development of microcracks of SiCp/Al materials in the machining process were researched, and the forming causes and mechanism of the cut surface morphology for ap=0.2 mm or ap=0.4 mm and at 2 m/min～10 m/min were systematically analyzed. The supporting and "floor"roles of aluminum are wake at a shallower cutting depth and a lower speed, the SiC particles are shed under the role of cutting force, and the microcrack size of cut surface is larger. With the increase in the cutting depth and the cutting speed, the cutting temperature increases, the supporting and "floor" roles of aluminum are enhanced, the shedding and fracture of the reinforcement particles are flexible under the action of the cutting force, the fracture of cutting transforms from brittle to ductile, and the expansion of microcrack on the entire surface tends to balance with a smaller size. A curve between the cutting force and the cutting speed was plotted, a microcrack form of the cut surface was given, and some theoretical basis is provided for the mechanical processing and the surface quality.     

Performance characterization of Ni60-WC coating on steel processed with supersonic laser deposition

Ni60-WC particles are used to improve the wear resistance of hard-facing steel due to their high hardness. An emerging technology that combines laser with cold spraying to deposit the hard-facing coatings is known as supersonic laser deposition. In this study, Ni60-WC is deposited on low-carbon steel using SLD. The microstructure and performance of the coatings are investigated through SEM, optical microscopy, EDS, XRD, microhardness and pin-on-disc wear tests. The experimental results of the coating processed with the optimal parameters are compared to those of the coating deposited using laser cladding.     

Construction and Properties of Structure- and Size-controlled Micro/Nano-energetic Materials

The recent research progress of structure- and size-controlled micro/nano-energetic materials is reviewed, which properties are fundamentally different from those of their corresponding bulk materials. The development of the construction strategies for achieving zero-dimensional (0D), one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) micro/nanostructures from energetic molecules is introduced. Also, an overview of the unique properties induced by micro/nanostructures and size effects is provided. Special emphasis is focused on the size-dependent properties that are different from those of the conventional micro-sized energetic materials, such as thermal decomposition, sensitivity, combustion and detonation, and compaction behaviors. A conclusion and our view of the future development of micro/nano-energetic materials and devices are given.     

Modeling mechanical behaviors of composites with various ratios of matrixeinclusion properties using movable cellular automaton method

Two classes of composite materials are considered: classical metaleceramic composites with reinforcing hard inclusions as well as hard ceramics matrix with soft gel inclusions. Movable cellular automaton method is used for modeling the mechanical behaviors of such different heterogeneous materials. The method is based on particle approach and may be considered as a kind of discrete element method. The main feature of the method is the use of many-body forces of inter-element interaction within the formalism of simply deformable element approximation. It was shown that the strength of reinforcing particles and the width of particle-binder interphase boundaries had determining influence on the service characteristics of metaleceramic composite. In particular, the increasing of strength of carbide inclusions may lead to significant increase in the strength and ultimate strain of composite material. On the example of porous zirconia ceramics it was shown that the change in the mechanical properties of pore surface leads to the corresponding change in effective elastic modulus and strength limit of the ceramic sample. The less is the pore size, the more is this effect. The increase in the elastic properties of pore surface of ceramics may reduce its fracture energy.