Abstract:

Abstract:Mechanically mixed and electrostatic sprayed RDX/NC/AP/Al composite explosive using nitrocellulost （NC） as binder， ammonium perchlorate （AP） as oxidant， cyclotrimethyltrnitramine （RDX） and nano aluminum powder （Al） as combustion agent were prepared based on zero oxygen balance. The morphology， structure， thermal properties， combustion process and mechanical sensitivity of the different samples were analyzed by the scanning electron microscopy （SEM）， the Fourier transform infrared spectroscopy（FT-IR）， thermogravimetric differential scanning calorimeter （TG-DSC）， mechanical sensitivity and high-speed photography. The component（NC， RDX， AP and Al） in RDX/NC/AP/Al composite explosives obtained by both method are physical composite. However， the microstructure of mechanically mixed RDX/NC/AP/Al demonstrated in spheres and the electrostatic sprayed samples are microspheres. The mass loss process of RDX/NC/AP/Al composite explosive obtained by two methods contained two stages （200-210 ℃ and 250-350 ℃）. The first stage is the decomposition of part of RDX and AP， while the second stage is the decomposition of the remaining RDX and NC. Compared with the mechanical mixed samples， the activation energy and the critical temperature of thermal explosion of electrostatic sprayed RDX/NC/AP/Al increased by 41.25 kJ·mol^-1 and 4.09 K， respectively. Besides， the mechanical sensitivity is reduced， and the combustion rate is also improved.

Abstract:To alleviate the aggregates of n-Al particles and improve its combustion performance， high-energy low-sensitivity nitrochitosan （NCh） with a honeycomb network structure was used as coating agent to prepare a binary nanocomposite with uniform structure through an acoustic resonance method. The morphology， structure and combustion performance of NCh/n-Al were investigated by XRD， SEM， TEM and laser ignition， and compared with that of NC/n-Al composite. The results show that the prepared NCh/n-Al has uniform morphology and good dispersion. Compared with pure n-Al and NC/n-Al， the ignition delay time of NCh/n-Al is shortened by 6 ms and 20 ms， respectively. The combustion of NCh/n-Al is more complete， the condensed combustion products are mainly Al₂O₃， a very small amount of unburned Al and carbon residue， and the particle size is significantly smaller.

Abstract:In order to meet the requirements of explosives， thermoplastic elastomers with different number-average molecular weight （M_n） were prepared. Controllable polymerization and application of glycidyl azide polymer （GAP）-based energetic thermoplastic elastomers （GETPE） were conducted. The influence of polymerization medium and solid content on controllable polymerization of GETPE was investigated， and on-line viscosity monitoring on M_n was explored. The results show that M_n of GETPE can be accurately controlled by on-line viscosity monitoring. The error of M_n in the range of 20000-50000 can be tuned within ±2000， and the error rate can be controlled within 5%. GETPE has excellent compatibility with commonly used explosives and good application potential in high solid content propellant and high energy polymer bonded explosives （PBXs）.

Abstract:The phase transition behavior of HMX-based polymer-bonded explosives （PBX） and pure HMX pellet， prepared by compression molding， was studied by variable temperature wide-angle X-ray scattering （WAXS） and differential scanning calorimetry （DSC）. The HMX-based PBX contained polyester polyurethane （HMX-Estane）， fluororubber （HMX-F₂₃₁₄）， as well as nitrocellulose （HMX-F₂₃₁₄-NC）. The initial β→δ phase transition temperatures （T_i）， as determined by WAXS， were found to be 186 ℃ for HMX-Estane（95∶5）， 188 ℃ for HMX pellet， 192 ℃ for HMX-F₂₃₁₄（95∶5）， and 198 ℃ for HMX-F₂₃₁₄-NC（95∶3∶2）. The addition of the small amount of nitrocellulose （2%） to the binder increased the T_i by about 10 ℃， compared with HMX pellet. All samples retained the δ-phase when cooled from the high temperature phase to 100 ℃ and kept in vacuum for 12 h， except HMX-Estane which went through a reversible phase transition and changed β phase completely after kept at 100 ℃ for 3.5 h. Among the three types of binders only Estane promoted the β→δ phase transition and the reversed δ→β transition of HMX. This result was attributed to the dissolution （on heating） and the precipitation （on cooling） of β-HMX at the HMX-Estane interface.

Abstract:In order to study the aluminum-water reaction characteristics of PVA-nAl/HTPB， the PVA-nAl/HTPB composites were prepared by dispersing nAl/HTPB in the polyvinyl alcohol （PVA）， which was obtained by physical cross-linking method. In order to explore the aluminum-water reaction mechanism， the aluminum-water reaction characteristics of the polyvinyl alcohol-nAl/HTPB with 0.1 mol·L^-1 NaOH solution at different temperatures （25， 40， 55， 70， 85 ℃ and 100 ℃））were investigated and the residue after the aluminum-water reaction were characterized. The results show that the maximum hydrogen production and rate of PVA-nAl/HTPB is 76 mL·g^-1 and 80 mL·g^-1·min^-1， respectively， which is higher than that of PVA-nAl. The product of the aluminum-water reaction is aluminium oxyhydroxide （AlO（OH））.

Abstract:To determine the purity of 1，3-dichloro-2，4，6-trinitrobenzene （DCTNB） product accurately， a high-performance liquid chromatography （HPLC） real-time （or in-situ）method for the determination of DCTNB and its impurities， 1，5-dichloro-2，4-dinitrobenzene （DCDNB） and 2，3，4-trichloro-1，5-dinitrobenzene （TCDNB） was established.. The effect of different mobile phase system， mobile phase ratio， flow rate and injection volume etc. conditions on the separation of high performance liquid chromatography for DCTNB was discussed. The quantitative analysis method was carried out by an external standard method. Results show that The optimal chromatographic conditions obtained are as follows： hypersil ODS2 chromatographic column （250 mm×4.6 mm， 5 μm）， UV detection wavelength 240 nm， acetonitrile /water with a volume ratio of 55∶45 as mobile phase， flow rate 1.2 mL·min^-1， column temperature 25 ℃， injection volume 10 μL. Under the above chromatographic conditions， the retention times of DCDNB， DCTNB and TCDNB are 9.20， 10.50， and 14.17 min in sequence with good resolution of all peaks（greater than 3.70）. DCDNB， DCTNB and TCDNB show a good linear relationships in the concentration ranges of 5-250， 5-500 and 5-250 mg·L^-1， respectively， and the linear correlation coefficient R² is greater than 0.999. The detection limits of DCDNB， DCTNB and TCDNB are 0.47， 0.68， 0.85 mg·L^-1， the quantification limits are 1.58， 2.28， 2.82 mg·L^-1， respectively， the relative standard deviation of 1.01%-1.27%， and the standard recovery rates are 98.82%-102.13%．

Abstract:As an energetic material， octogen（HMX） is widely used in solid propellants. While improving the energy performance of the propellant， it also changes the combustion process of the propellant. To study the effect of HMX content on the ignition， combustion， and agglomeration properties of propellant and its condensed phase combustion products （CCPs）， burning surface photography， laser ignition and collection of the CCPs were used for testing and studying typical AP/HTPB/Al/HMX propellants with HMX contents ranging 0%-10%. Results show that as the HMX content increases from 0 to 10%， the ignition delay time increases from 191 ms to 286 ms， and both the burning rate and pressure exponent of the propellent decreases. The volume average particle size of the CCPs increased from 48.1 μm to 138.3 μm. The propellent with 10% HMX has the highest agglomeration degree on the burning surface， while the propellent with 8% HMX has the highest active aluminum content in the CCPs.

Abstract:In order to improve the safety performance of potassium perchlorate （KClO₄）， KClO₄/ Silver （KClO₄/Ag） composite particles were prepared by chemical reaction of glucose and silver ammonia on the surface of KClO₄ particles. The particle morphology， phase composition， thermal decomposition temperature and mechanical sensitivity of the modified particles were analyzed by means of scanning electron microscope （SEM）， X-ray diffraction （XRD）， differential scanning calorimeter （DSC）， et al. The results show that KClO₄/Ag composite particles have obvious spherification effect， smooth surface and no obvious edges and corners. On the basis of retaining the original good stability and high decomposition temperature of KClO₄， it also has the characteristics of silver metal. Compared with the initial raw KClO₄， the mechanical sensitivity of KClO₄/Ag composite particles decreased significantly， the friction sensitivity explosion probability decreased from 90% to 50%， and the impact sensitivity explosion probability decreased from 70% to 40%. At the same time， the thermal decomposition performance of KClO₄/Ag composite particles is obviously different from that of raw KClO₄. The exothermic peak of KClO₄/Ag composite particles is 12 ℃ earlier and the decomposition efficiency is higher than that of raw KClO₄.

Abstract:To evaluate the aging performance of acrolein-pentaerythritol resins （123 resins）-RDX based casting polymer bonded explosive （PBX）， accelerated aging tests were performed according to MIL-STD-1751. The microstructure and aging mechanism of casting PBX during aging were investigated by in-situ Infrared Spectroscopy （IR）， 3D-Super Depth of Field Digital Microscope and Scanning Electron Microscope （SEM）. After aging 260 days at 65 ℃， the mass and size change rates of the casting PBX columns are both within 0.25%， which is better than the standards （<1%） of U.S. military standard MIL-STD-1751. The results indicate that PBX columns are stabilization at an acceptable level after aging tests. In addition， no obvious variations on both surface and corss-sectional morphology are observed， except for color changes. The interface between RDX particles and the binder is still well bonded， and the cross section is mainly transgranular fracture. The mechanical properties including both compressive strength and tensile strength of 123 resins-based casting PBX increases obviously with the increase of aging time. After aging 60 and 150 days at 65 ℃， the compressive strengths increase by 6.42 MPa and 13.69 MPa with the increasement of 8.46% and 18.05%， respectively. After aging 90 and 180 days at 65 ℃， the tensile strengths increase by 0.78 MPa and 1.13 MPa with the increasement of 6.34% and 9.19%， respectively. The mechanism of the mechanical properties’ increase was studied by in-situ IR method and the post-casting behavior during aging process was considered as the main reason.

Abstract:In order to increase the energy of the secondary reaction of composite explosives， the novel composite oxidant ammonium perchlorate （AP）-lithium perchlorate （LiP） was prepared by solvent evaporation method. Scanning electron microscope （SEM） and X-ray diffractometer （XRD） were used to test and characterize the morphology， and crystal structure of the sample. The thermal decomposition properties of the samples were analyzed by differential scanning calorimetry （DSC）. The underwater explosion power parameters of three polymer bonded explosives （PBXs） containing composite AP-LiP， mechanical mixture AP-LiP and AP were evaluated by electrometric method. The results show that， for composite AP-LiP， the crystal morphology is fairly regular， the crystal surface is smooth， the particle size distribution is fairly uniform， and no agglomeration is observed. Composite AP-LiP has a high degree of crystallization and a fairly complete crystal structure. The thermal decomposition performance of composite AP-LiP is better than that of mechanical mixture AP-LiP. The underwater explosion results show that， compared with the AP-containing PBX， the shock wave energy， bubble energy， and total energy of underwater explosion of PBX containing composite AP-LiP increase by 0.098-0.154， 0.254 MJ·kg^-1 and 0.352-0.408 MJ·kg^-1 respectively， and the energy decays slower as the distance increases.

Abstract:The crystallization process of 1，3，5-triamino-2，4，6-trinitrobenzene （TATB） will be affected by dioctyl sulfosuccinate sodium salt （AOT） and the molecular dynamics （MD） method was used to study this crystallization process in this work. The crystal morphologies of TATB crystal in vacuum were predicted by Bravis-Friedel-Donnary-Harker （BFDH） and attachment energy （AE） models. Seven important crystal planes of TATB were determined， which are （0 0 1）， （1 0 -1）， （1 -1 0）， （1 0 0）， （1 -1 1）， （0 1 -1） and （0 1 0）. The interface model for TATB with AOT was established and performed the molecular dynamics simulation. The modified AE model was used to analysis simulation data. After calculation， we found that the crystallization rate of TATB was improved under the influence of AOT solution. After analyzing the molecular structure and the intermolecular interaction of TATB， it is considered that because of the special plane structure， the intermolecular interaction between （0 0 1） plane and AOT is weak and the attachment energy （119.832 kJ·mol^-1） of （0 0 1） plane is low. So， the growth rate of （0 0 1） plane is relatively slow. The attachment energies of （1 0 -1）， （1 -1 0）， （1 0 0）， （1 -1 1）， （0 1 -1） and （0 1 0） planes are all higher than （0 0 1） and they all grow faster than （0 0 1）. Therefore， in the experimental process， a leaf-like TATB structure formed first. With the reaction time was further， the （0 0 1） plane gradually grows， the leaves become longer.

Abstract:In order to study the thermal decomposition properties of the characteristic groups of 3，4-Dinitrofurazanylfuroxan （DNTF）， differential scanning calorimetry （DSC） and fast scanning Fourier transform infrared spectroscopy （FTIR）were adopted to study the thermal decomposition properties of DNTF in condensed phase. The changes of characteristic groups of DNTF were studied by using FTIR technology at three different heating rates of 2.5， 5.0， 10 ℃·min^-1. The thermal decomposition kinetic parameters of C─NO₂， furazan ring， and furoxan ring of DNTF were calculated by the Coats-Redfern method. The thermal decomposition mechanism of DNTF was inferred based on the thermal decomposition properties of the characteristic group of DNTF. The results show that the thermal decomposition of DNTF is controlled by the three-dimensional diffusion mechanism. The reactivity of groups in DNTF molecule is nitro>furoxan ring>furazan ring. With the increase of heating rate， the reactivity of each group shows an increasing trend. It is speculated that the thermal decomposition process is that C─NO₂ breaks first， and then the C─C bond connecting furuzan and furoxan ring breaks， and finally the N─O bond in furazan ring and furoxan ring breaks. The furoxan ring decomposes faster than furazan ring.

Abstract:Rapid detection of unsymmetrical dimethylhydrazine （UDMH） and its transformation products in water is of great significance for its pollution control. This paper reviewsthe research progress of chromatographic methods （including gas chromatography， high performance liquid chromatography， and ion chromatography） and non-chromatographic methods （including the electrochemical method， spectrophotometry and chemiluminescence） in the detection of UDMH in water. Then， application of chromatography in in the detection of UDMH conversion products in water was briefly introduced. The advantages and disadvantages of different detection methods in the detection concentration range， sample pretreatment and anti-interference ability， etc.，were pointed out. It was suggested that the design of efficient automatic chromatographic pretreatment device and the combination of various separation and detection technologies would be the future development direction to solve the detection problem of UDMH and its transformation products in water.

Abstract:The safety performance and initiation process of explosives are closely related to their high-temperature and high-pressure behavior. Therefore， it is of great significance to study explosives under high-temperature and high-pressure thus understanding their safety and initiation performance in depth. The structural evolution of twelve explosives under high-temperature and high-pressure is reviewed， including common nitroamine-based explosives represented by RDX and HMX， common nitroester-based explosives represented by PETN，nitro-based explosives represented by TNT， and new high-energy and low-sensitivity explosives represented by LLM-105 and TKX-50. The phase transformation processes of these explosives under high-temperature and high-pressure are summarized in detail， and the similarities and differences of the research results from different research teams on the same material are compared. This review provides a strong basis for the studies of structural evolution of explosives under high-temperature and high-pressure.