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Abstract:Replacing traditional solid propellants with high-energy explosives (such as hexanitrohexaazaisowurtzitane (CL-20)) is an important way to achieve microthrusters with small size and large specific impulse. In order to realize the self-sustaining combustion of CL-20, a composite propellant system with CL-20 nano-microparticles hosted in the rGO three-dimensional network is designed. Ultrafine CL-20 spherical particles (diameter 300 nm-2 μm) have been prepared by a solvent-nonsolvent method firstly, then self-supporting rGO/CL-20 fiber propellant was prepared by a dimensionally confined hydrothermal strategy. Based on the analysis of thermal analysis kinetics and combustion characteristics, it is concluded that the positive feedback mechanism of the combustion heat release of rGO/CL-20 fiber propellant plays a key role in its combustion propagation. Due to the construction of rGO three-dimensional network, the thermal conductivity of the fiber propellant is improved, and the exothermic effect of rGO/KOH can serve as the initial ignition energy for rGO itself and CL-20 microparticles. Once ignited, the combustion of high-energy CL-20 releases more heat energy than rGO, thereby forming the positive feedback mechanism. The combustion propagation speed of the prepared self-supporting rGO/CL-20 fiber propellant is 20.66 mm·s^-1, moreover, the fibrous structure facilitates the rapid modular charge of the microthrusters.

Abstract:In order to improve the safety performance of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), nano CL-20/AP（ammonium perchlorate) energetic composite particles were readily prepared via a one-step ball milling method, a facile, clean, and continuous synthesized strategy. The prepared samples were studied by scanning electron microscopy(SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and impact sensitivity test. The SEM results show that the CL-20/AP composite particles are smooth on surface and nearly spherical with size of 300-500 nm. The XRD peak position of CL-20/AP is obviously deviated and some peaks are even disappeared, which means new crystalline phase may be formed. Due to the preferred orientation of the polycrystalline samples, the XRD peak intensity is reduced. The thermal decomposition peak of CL-20/AP decreases. The impact sensitivity result shows that the H₅₀ of the nano CL-20/AP composite particles is 26.07 cm, which increases by 13.10 cm compared with raw CL-20, indicating a better safety performance.

Abstract:To study the influence of particle size on critical detonation performance of hexanitrohexaazaisowurtzitane (CL-20)-based explosives ink by micro-flow direct writing technology, three different particle sizes of CL-20 explosives were prepared by mechanical ball grinding method and solvent-nonsolvent method, respectively. The CL-20-based explosive ink by micro-flow direct writing technology was prepared by a two-component adhesive dispersion system consisting of waterborne polyurethane (WPU) and ethyl cellulose (EC). The particle size distribution and morphology of the prepared CL-20 explosives and the corresponding ink samples were characterized by laser particle size analyzer and scanning electron microscope (SEM), respectively. The crystal type of the CL-20 in ink samples were measured by X-ray diffractometer (XRD). The critical detonation thickness of CL-20 explosive ink samples with different particle sizes were tested by wedge shaped charge test. The results show that the two CL-20 explosives prepared by mechanical ball grinding method have a nearly spherical shape and smooth surface, whose median size are 140 nm and 1.5 μm, respectively. The corresponding ink samples have a honeycomb shape, with good dispersing effect and uniform compact cross-section. The CL-20 explosive prepared by solvent-nonsolvent method has a fusiform shape with a median size of 15 μm. The corresponding ink sample has poor dispersing effect, and the explosive particles and adhesive system are difficult to form a composite structure. The XRD test results indicate that three crystal types of the CL-20 in ink samples are all ε form. The critical detonation thickness of CL-20 explosive ink samples with a charge width of 1 mm is as small as 69 μm, and decreases with the decrease of CL-20 particle size, indicating that reducing the particle size of the CL-20 can significantly enhance its critical detonation performance.

Abstract:To investigate the effect of carbon nanotubes(CNTs) on the combustion properties and mechanical properties of Al-CMDB propellant, the propellant samples were prepared through an absorption-extrusion method. The burning rate of propellants was measured by target line method and the pressure exponent was calculated. The tensile strength and ductility of propellant sample were tested at high, low and normal temperature. The reason of how CNTs effected the combustion performance of Al-CMDB propellant was analyzed by scanning electron microscopy(SEM), flame photo, combustion wave, morphology and element analysis of quenching surface and DSC analysis. The results show that the burning rate of propellant in the range of 6-20 MPa can be increased by adding 0.7% CNTs in Al-CMDB propellant, of which the burning rate at 6 MPa is increased most, which is 4.98 mm·s^-1, and the pressure exponent decreases from 0.57 to 0.45 at 6-20 MPa. CNTs with pipe diameter of 10-20 nm can enhance the tensile strength and ductility of Al-CMDB propellant at high, low and normal temperature. The effect of CNTs on the peak temperature of thermal decomposition of propellant is little but can make the exothermic quantity of propellant decomposition increase.

Abstract:To improve the combustion and ignition performances of ammonium perchlorate (AP)-based composite solid propellants, the manganese alginate film was prepared by an ion exchange method, and the nano-Mn₃O₄ composite catalyst was obtained after calcinations of the film. The effect of nano-Mn₃O₄ composite catalyst on the thermal decomposition performances of AP was studied. The morphology and structure of prepared nano-Mn₃O₄ composite catalyst were characterized by scanning electron microscopy(SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectrometer (XPS) and X-ray diffractometer(XRD). Results show that after the exchange of manganese ion, sodium alginate becomes manganese alginate, formed film surface is smooth and dense. After calcinations at 400 ℃, in situ-grown nano-Mn₃O₄ particle is loaded onto the carbonized alginate skeleton. The catalytic effect on AP enhances with increasing the content of nano-Mn₃O₄ composite catalyst and the exothermic rate also increases significantly. Compared with pure AP, the decomposition temperature of AP decreases by 89.1 ℃ when the content of nano-Mn₃O₄ composite catalyst is 3%.

Abstract:To improve the catalytic effect of nano-CuO, the CuO/PG nanocomposites of CuO morphology as flakes, lines, rods and spheres were prepared by complex precipitation method using porous graphene (PG) as carrier. The effect of CuO/PG nanocomposites on the thermal decomposition of ammonium perchlorate(AP) was investigated by DSC and its catalytic mechanism was analyzed. Results show that compared with the nano-CuO with the same morphology, the CuO/PG nanocomposites have larger specific surface area and better catalytic effect on the thermal decomposition of AP. Among four kinds of CuO/PG nanocomposites, the spherical copper oxide has the smallest particle size, about 4 nm and the specific surface area of the composite is the largest, about 115.25 m²·g^-1. Therefore, it has the most active catalytic sites and the best catalytic effect on the thermal decomposition of AP, so that the high temperature exothermic decomposition peak temperature of AP decreases to 310.1 ℃.

Abstract:To prepare nanocomposite energetic materials with homogeneous structure and excellent thermal properties, CuO/Al nanocomposite energetic materials were prepared by deoxyribonucleic acid (DNA) self-assembly method at room temperature and in water phase. The structures and thermal reaction properties of the nanocomposite energetic materials were characterized by Fourier transform infrared (FT-IR) spectroscopy, dynamic light scattering (DLS), transmission electron microscope (TEM), scanning electron microscope (SEM) and differential scanning calorimeter (DSC). Results show that CuO/Al nanocomposite energetic materials with more homogeneous structure are successfully prepared by DNA self-assembly. The reaction heat of DNA self-assembled CuO/Al nanocomposites is higher than that of physically mixed sample with the same proportion and at φ=1.6, the reaction heat of DNA self -assembled CuO/Al nanocomposites reaches 1520 J·g^-1，which is 52.15% higher than that of the physically mixed sample (999 J·g^-1).

Abstract:To study the thermal decomposition properties and combustion characteristics of nano-scale dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate(TKX-50), TKX-50 samples with network-like nanostructure were prepared by rapid freeze-drying method. Their morphologies and structures were characterized by scanning electron microscope（SEM）and X-ray diffractometer (XRD). Thermal decomposition properties was measured by thermogravimetric analysis-differential scanning calorimetry (TG-DSC). Combustion process was tested by camera. The effects of nano-sized structure on the thermal decomposition and combustion characteristics of TKX-50 were discussed. Results show that the nano-scale TKX-50 obtained by rapid freeze-drying method has a nano-level network-like connection structure and good crystal stability. The two-step thermal decomposition peak temperatures of nano-scaleTKX-50 are 238.0 ℃ and 267.7 ℃, compared with raw TKX-50, which are decreased by 12.1 ℃ and 5.6 ℃, respectively. The nano-scaleTKX-50 samples have lower ignition delay and higher burning rate, revealing that compared with raw TKX-50, the surface active atoms and groups of nano-scale TKX-50 samples prepared by rapid freeze-drying method are increased and samples are easily activated, which promotes the thermal decomposition and combustion of TKX-50.

Abstract:Aiming at the matching relationship between various parameters in the gas-solid in-situ synthesis of copper azide, we establish a two-dimensional shrinking core model to simulate the crystal growth mechanism of in-situ synthesis of copper azide and dynamic process. The relationship between the reaction rate of azide porous copper and the solid conversion rate and the diameter of precursor, porosity, charge height and reaction time have been obtained. At the same time, in order to verify the reliability of the model, a set of porous copper precursors with a porosity of approximately 80% and a height of 1mm and particle diameters of 50, 100, 200 and 500 nm are selected for the analysis of copper azide. Results show that the experimental data of the four different azide products are consistent with the simulated, and the maximum deviation is only 2.1%.

Abstract:Microstructure energy conversion components are the key components of micro-electro-mechanical-system (MEMS) initiating explosive device, its bridge area microstructure design has a significant effect on the output performance and energy utilization rate of MEMS initiating explosive device. To perfect the design theory of microstructure energy conversion components of MEMS initiating explosive device, 8 kinds of microstructure energy conversion components with different bridge shapes were designed and fabricated. The bridge-shaped structure optimization and microstructure effect of microstructure energy conversion components were studied by means of simulation research and infrared test Two kinds of energy conversion components with V-50 and L-1 optimization bridge-shaped structure were obtained, and the influence law of different bridge-shaped structure on the output performance of energy conversion components was revealed, in which, the average ignition voltage of V-50 bridge-shaped microstructure energy conversion components reaches 100 μF/3.5 V, and the energy utilization rate is 46.6%.

Abstract:Micro-nano energetic materials exhibit excellent properties and good application results due to their small size effect, crystal perfection effect, high surface energy and high surface activity. In this paper, the current advances in the recrystallization technologies and pulverization technologies used in the preparation of micro-nano energetic materials at present, and the drying technologies, characterization methods of particle size and morphology, mechanisms of sensitivity changed with particle size, application directions and effect etc. of micro-nano energetic materials were summarized based on the related research work of scholars both at home and abroad. It is pointed out that micro-nano energetic materials in the future should focus on the research work of strengthening basic theory, simulation, functional mechanism of application, engineering magnification and practical application etc. of micro-nano energetic materials, so that micro-nano energetic materials can be transferred into engineering applications as soon as possible, so as to accelerate the development of high-energy solid rocket propellants, composite explosives, gun propellants as well as pyrotechnics, and improve their performances.

Abstract:Due to numerous excellent properties of graphene, including large surface area, high conductivity, thermal conductivity, etc., graphene-based materials have been used as additive, catalyst carrier and component of energetic materials. Effects of graphene-based materials on thermal decomposition, combustion, mechanical and safety performances of energetic materials are systematically reviewed. Besides, researches of the application of doped graphene for explosive detection are also summarized. Graphene-based materials can significantly promote the thermal decomposition of energetic materials, reduce the thermal decomposition temperature of energetic components, and thus improve the combustion performance of propellants. Additionally, graphene-based materials are also used for enhancing thermal stability as well as reducing mechanical sensitivity of explosives. To sum up, graphene-based materials have wide application prospects in the field of energetic material. However, the interaction force between graphene-based-materials and nanometer metal catalyst, optimal component ratio and fabrication conditions of energetic composites are still needed to be further explored. Preparation of energetic graphene material by grafting energetic groups on functionalized graphene is also the focus of further research.

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