Tuning the particle size and morphology of high energetic material nanocrystals

Morphology controlled synthesis of nanoparticles of powerful high energetic compounds(HECs) such as l,3,5-trinitro-l,3,5-triazinane(RDX) and 1,3,5,7-tetranitro-l,3,5,7-tetrazocane(HMX) were achieved by a simple solvent—antisolvent interaction(SAI) method at 70 ℃.The effects of different solvents on particle size and morphology of the prepared nano-HECs were studied systematically.Particle size and morphology of the nano-HECs was characterized using field emission scanning electron microscopy(FE-SEM) imaging.X-ray diffraction(XRD) and Fourier transform infrared(FTIR) spectroscopy studies revealed that RDX and HMX were precipitated in their most stable polymorphic forms,i.e.a and P,respectively.Thermogravimetric analysis coupled with differential scanning calorimetry(TGA-DSC) studies showed that the thermal response of the nanoparticles was similar to the respective raw-HECs.HEC nanoparticles with spherical and rod shaped morphology were observed under different solvent conditions.The mean particle size also varied considerably with the use of different solvents.     

Combustion behavior and mechanism of molecular perovskite energetic material DAP-4-based composites with metal fuel Al

Combined with the oxidizer anions and fuel cations, molecular perovskite energetic materials show a good potential. In this work, the combustion behavior and mechanism of metal fuel aluminium(Al) with molecular perovskite energetic material(H₂dabco)[NH₄(ClO₄)₃](DAP-4) as a high-energy oxidant was investigated. The DAP-4 based composites with metal fuel Al were designed and fabricated by the different mass ratios. Results showed that DAP-4 exhibits a go...     

RDX crystals with high sphericity prepared by resonance acoustic mixing assisted solvent etching technology

In order to obtain high-quality spherical RDX crystal particles, the RDX crystals were suspended in a mixed solvent of cyclohexanone and cyclohexane, subsequently a solvent etching study was carried out under the action of vibration/acoustic flow coupled flow field, which generated by resonance acoustic mixing. The effects of solvent ratio, temperature, acceleration and experiment time on morphology as well as particle size of RDX crystals were studied. Not only were the morphology, particle siz...     

Trans-scale study on the thermal response and initiation of ternary fluoropolymer-matrix reactive materials under shock loading

To investigate the thermal response and initiation behavior of ternary fluoropolymer-matrix PTFE/Al/W reactive materials, a research combining shock loading tests and trans-scale modelling is conducted. On the basis of a good agreement of the numerically simulated and tested shock wave propagation, the significant impact of component ratios and particle sizes on the evolution of mesoscopic temperature,hot-spots and initiation is well characterized and analyzed. Results demonstrate that as the co...     

One-step rapid preparation of CL-20/TNT co-crystal assembly and spheroidized coating based on droplet microfluidic technology

Energetic materials pose challenges in preparation and handling due to their contradictory properties of high-energy and low-sensitivity. The emergence of co-crystal explosives is a new opportunity to change this situation. If the co-crystal explosive is coated into spherical particles with uniform particle size distribution, this contradiction can be further reduced. Therefore, binder-coated hexanitrohexaazaisowurtzitane/2,4,6-trinitrotoluene(CL-20/TNT) co-crystal microspheres were prepared by ...     

Shock response of cyclotetramethylene tetranitramine(HMX) single crystal at elevated temperatures

To investigate the shock response of cyclotetramethylene tetranitramine(HMX) single crystals at elevated temperatures(below the phase transition point), plate impact experiments at elevated temperatures were designed and conducted. The HMX/window interface particle velocities at temperatures of 300 K, 373 K, and 423 K were measured by the velocity interferometry system for any reflector(VISAR)technique. To further analyze the related mesoscale deformation mechanisms, a nonlinear thermoelastic-vi...     

Enhanced structural damage behavior of liquid-filled tank by reactive material projectile impact

A series of ballistic experiments were performed to investigate the damage behavior of high velocity reactive material projectiles(RMPs) impacting liquid-filled tanks, and the corresponding hydrodynamic ram(HRAM) was studied in detail. PTFE/Al/W RMPs with steel-like and aluminum-like densities were prepared by a pressing/sintering process. The projectiles impacted a liquid-filled steel tank with front aluminum panel at approximately 1250 m/s. The corresponding cavity evolution characteristics an...     

Study on Aging Precipitation Characteristic of High Strength Al-Zn-Mg-Cu Alloy

The precipitation of MgZn2 phase in aging process of Al-Zn-Mg-Cu alloy forging was characterized qualitatively after transmission electron microscope(TEM)observation,X-ray diffraction phase analysis and the exact measure of lattice parameter.And,the precipitation of the second-phase in aging process was simulated after test the resistivity of the alloy in a continuous heating process and delayed time processing.The results show that when heating in the same rate,the alloy resistivity increases with temperature first,a mutation point appears at 110℃,and the resistivity reaches its peak at 120℃.Then,the resistivity decreases and achieves a minimum at about 170℃.Afterwards,it increases again.The change of resistivity results from a combined effect of the temperature and phase transformation.The volume precipitation of η' phase dominates at about 120℃,and the resistivity of forgings decreases accordingly.When the specimen cools in a furnace at 240℃,the phase transformation finishes basically and the alloy content of Al-matix keeps stable,thus,the alloy resistivity depends on the temperature only.It decreases with temperature and time since the end of precipitation.The higher the temperature is,the bigger it will be.With a big descending rate of the resistivity curve,the time to reach the stable value becomes shorter.     

Tailoring conductive network Zn@NPC@MWCNTs nanocomposites derived from ZIF-8 as high-performance electromagnetic absorber for the whole X-Band

A porous 3D cross-linked conductive network pierced by multi-wall carbon nanotubes(MWCNTs) was successfully designed from zeolitic imidazolate framework-8(ZIF-8). Zn@NPC@MWCNTs composites were tailored by the facile regulating the mass ratios and thermal annealing treatment. Due to the combination of less eddy current loss and dielectric loss together with multiple reflection attenuation caused by a unique structure. With a 10 wt% filler loading, the Zn@NPC@MWCNTs composites carbonized at 800℃ s...     

Nano-silica modified lightweight and high-toughness carbon fiber/phenolic ablator with excellent thermal insulation and ablation performance

Lightweight and high-toughness carbon fiber/phenolic ablator(CFPA) is required as the Thermal Protection System(TPS) material of aerospace vehicles for next-generation space missions. To improve the ablative properties, silica sol with good particle size distribution prepared using tetramethoxysilane(TMOS) was blended with natural rubber latex and deposited onto carbon fiber felt, which was then integrated with phenolic aerogel matrix, introducing nano-silica into the framework of CFPA. The modi...     

The effect of Ti and Zr content on the structure,mechanics and energy-release characteristics of Ti—Zr—Ta alloys

Energetic structural materials(ESMs) are a new type of structural materials with bearing and damage characteristics.In this work the microstructure,mechanical properties and energy release characteristics of multi-element Ti-Zr-Ta alloys with good casting performance were studied.The microstructure of the Ti_xZrTa alloys gradually change from BCC+HCP to single BCC structure with the increase of Ti.While the Ti₂Zr_yTa alloys was still uniform and single BCC structur...     

Experimental study of polyurea-coated fiber-reinforced cement boards under gas explosions

Five types of polyurea elastomers were synthesized by changing the isocyanate component and the mechanical properties of polyurea materials were measured. Fiber-reinforced cement boards(FRCB)strengthened by polyurea with different formulations were processed, and a series of experiments were carried out on the specimens with gas explosion devices. The results showed that the conventional mechanical properties of different types of polyureas had their own advantages. Based on the gas explosion ov...     

Interfacial reinforcement of core-shell HMX@energetic polymer composites featuring enhanced thermal and safety performance

The weak interface interaction and solid-solid phase transition have long been a conundrum for 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane(HMX)-based polymer-bonded explosives(PBX). A two-step strategy that involves the pretreatment of HMX to endow —OH groups on the surface via polyalcohol bonding agent modification and in situ coating with nitrate ester-containing polymer, was proposed to address the problem. Two types of energetic polyether—glycidyl azide polymer(GAP) and nitrate modified G...     

Assessment of the ballistic response of honeycomb sandwich structures subjected to offset and normal impact

In the present study, experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb cores. The high velocity impact tests were carried out using a compressed air gun. A sharp conical nosed projectile was impacted normally and with some offset distance(20 mm and 40 mm). The deformation, failure mode and energy dissipation characteristics were obtained for both kinds of loading. Moreover, the explicit solver was run in Abaqus to create the fin...     

A new Ignition-Growth reaction rate model for shock initiation

Accurately predicting reactive flow is a challenge when characterizing an explosive under external shock stimuli as the shock initiation time is on the order of a microsecond. The present study constructs a new Ignition-Growth reaction rate model, which can describe the shock initiation processes of explosives with different initial densities, particle sizes and loading pressures by only one set of model parameters.Compared with the Lee-Tarver reaction rate model, the new Ignition-Growth reactio...     

Sagging damage characteristics of hull girder with trapezoidal cross-section subjected to near-field underwater explosion

To investigate the overall damage characteristics and failure modes of a warship subjected to an underwater non-contact near-field explosion, a hull girder with a trapezoidal cross-section was designed,manufactured, and tested. The design criteria and parameters were determined according to the similarity criterion. Dynamic responses of the girder freely floating on water were obtained under varying conditions, including stand-off distance, charge mass, and position of attack. Damage morphologie...     

Optimization of friction stir welding parameters for improved corrosion resistance of AA2219 aluminum alloy joints

The aluminium alloy AA2219(Al—Cu—Mg alloy) is widely used in the fabrication of lightweight structures with high strength-to-weight ratio and good corrosion resistance.Welding is main fabrication method of AA2219 alloy for manufacturing various engineering components.Friction stir welding(FSW) is a recently developed solid state welding process to overcome the problems encountered in fusion welding.This process uses a non-consumable tool to generate frictional heat on the abutting surfaces.The welding parameters,such as tool pin profile,rotational speed,welding speed and axial force,play major role in determining the microstructure and corrosion resistance of welded joint.The main objective of this work is to develop a mathematical model to predict the corrosion resistance of friction stir welded AA2219 aluminium alloy by incorporating FSW process parameters.In this work a central composite design with four factors and five levels has been used to minimize the experimental conditions.Dynamic polarization testing was carried out to determine critical pitting potential in millivolt,which is a criteria for measuring corrosion resistance and the data was used in model.Further the response surface method(RSM) was used to develop the model.The developed mathematical model was optimized using the simulated annealing algorithm optimizing technique to maximize the corrosion resistance of the friction stir welded AA2219 aluminium alloy joints.     

Damage of a large-scale reinforced concrete wall caused by an explosively formed projectile (EFP)

To quickly break through a reinforced concrete wall and meet the damage range requirements of rescuers entering the building, the combined damage characteristics of the reinforced concrete wall caused by EFP penetration and explosion shock wave were studied. Based on LS-DYNA finite element software and RHT model with modified parameters, a 3D large-scale numerical model was established for simulation analysis, and the rationality of the material model parameters and numerical simulation algorith...     

The role of physical properties in explosive welding of copper to stainless steel

This paper investigates the effects of the physical properties on the microstructure and weldability of explosive welding by joining two metals with a significant contrast in thermophysical properties:stainless steel and copper. Sound welds between stainless steel and copper were obtained, and the interfacial morphology was wavy, regardless of the position of the materials. The weldability of dissimilar pairs was found to be more dependent on the relationship between the physical properties of t...     

Explosion characteristics of aluminum-based activated fuels containing fluorine

Measuring the dust explosion characteristics of aluminum-based activated fuels was a prerequisite for developing effective prevention and control measures. In this paper, ignition sensitivity, flame propagation behaviors and explosion severity of aluminum/polytetrafluoroethylene(Al/PTFE) compositions including 2 PT(2.80 wt.% F), 4 PT(7.18 wt.% F) and 8 PT(11.90 wt.% F) were studied. When the content of F increased from 2.80 wt.% to 11.90 wt.%, the minimum explosive concentration MEC decreased fr...