Time filter

Source Type

Wang X.,Beijing Institute of Technology | Li J.,Beijing Institute of Technology | Li J.,Academy of Ordnance Science | Luo Y.,Beijing Institute of Technology
Fuhe Cailiao Xuebao/Acta Materiae Compositae Sinica | Year: 2013

Graphene aerogel (GA) was prepared by sol-gel chemistry, and then GA/epoxy (EP) composites were prepared by sonicate-mixing method. The structure of GA was characterized by SEM, N2 nitrogen sorption tests, XPS and XRD. In addition, the effects of GA mass fraction on the thermal property and the conductivity property of the GA/EP composites were also investigated. The results indicate that the GA shows a three-dimensional network of randomly oriented graphene sheets with wrinkled texture, and is rich in pores. After thermal reduction, the specific surface area of GA increases to 731.84 m2·g-1, the interlayer spacing of the graphene decreases to 0.347 nm, and the oxygen-containing functional groups are almost all removed. DMA and electrical conductivity testing results show that with the increase of GA content, Tg of GA/EP composites increases first and then decreases, and the electrical conductivity increases with the percolation threshold of 0.05%-0.3%.


Wang X.-B.,Beijing Institute of Technology | Li J.-Q.,Beijing Institute of Technology | Li J.-Q.,Academy of Ordnance Science | Luo Y.-J.,Beijing Institute of Technology
Wuli Huaxue Xuebao/ Acta Physico - Chimica Sinica | Year: 2013

Graphene hydrogels were prepared by the sol-gel method, and then used to prepare ammonium perchlorate (AP)/graphene composites by the incorporation of AP. The composites were dried naturally in air, freeze-dried, or dried with supercritical CO2. Scanning electron microscopy (SEM), elemental analyses (EA), and X-ray diffraction (XRD) were used to characterize the structure of the AP/graphene composites dried using different methods. Furthermore, the thermal decomposition behavior of the AP/graphene composites was investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis/infrared spectroscopy (TG-FTIR). Drying method had an obvious influence on the morphology of the AP/graphene composites; only the AP/graphene composites dried with supercritical CO2 showed similar three-dimensional networks and porous structure to graphene aerogels. Elemental analyses revealed that the AP contents in the AP/graphene composites prepared by drying naturally, freeze-drying, and supercritical CO2 drying were 89.97%, 92.41%, and 94.40%, respectively. XRD results showed that AP was dispersed homogeneously on the nanoscale in the AP/graphene composites dried with supercritical CO2 and the average particle diameter of AP was about 69 nm. DSC and TG-FTIR analyses indicated that graphene could promote the thermal decomposition of AP, particularly for the sample dried with supercritical CO2. Independent of drying method, the low-temperature decomposition of the as-prepared AP/graphene composites was not observed and the high-temperature decomposition was accelerated. Compared to the other two drying methods, graphene in the AP/graphene composites dried with supercritical CO2 showed most obvious promoting effects. The high-temperature decomposition temperature of the AP/graphene composites dried with supercritical CO2 decreased by 83.7 °C compared with that of pure AP, and the total heat release reached 2110 J·g-1. Moreover, graphene also took part in the oxidation reactions with oxidizing products, which was confirmed by the generation of CO2. © Editorial office of Acta Physico-Chimica Sinica.


Wang X.-B.,Beijing Institute of Technology | Li J.-Q.,Beijing Institute of Technology | Li J.-Q.,Academy of Ordnance Science | Luo Y.-J.,Beijing Institute of Technology
Huozhayao Xuebao/Chinese Journal of Explosives and Propellants | Year: 2012

Ammonium perchlorate/graphene aerogels (AP/GA) nanocomposites were prepared by sol-gel method and characterized by scanning electron microscope(SEM), elemental analysis and X-ray diffraction(XRD). Their thermal decomposition behaviours were investigated by TG-DSC-IR. The results indicate that AP is presented in the AP/GA nanocomposites with an average particle size of 69.41nm and occupied 94.4% of total mass. GA shows an obvious catalytic effect on the thermal decomposition of AP/GA. Compared to pure AP, the low temperature decomposition peak of AP/GA nanocomposites disappears, the high temperature decomposition peak temperature decreases by 83.7°C, and the total heat release reaches 2110 J/g.


Zhang W.-Y.,Beijing Institute of Technology | Li J.-Q.,Academy of Ordnance Science | Luo Y.-J.,Beijing Institute of Technology
Huozhayao Xuebao/Chinese Journal of Explosives and Propellants | Year: 2010

A series of novel thermoplastic polyurethane elastomers(TPUE) containing side ester groups which can be used as propeliam binder were synthesized from polyethylene/polypropylene adipate diol ( PEPA ), tetrahydrofuran/ethylene oxide copolyether ( PET ), isophorone diisocyanate ( IPDI ) and diethyl bis (Hydroxymethyl) malonate (DBM) as primary substances by melt pre-polymerization method. FTIR, GPC, DSC and tensile test were employed to characterize the structures and properties of TPUE. Results show that the polyurethane elastomers present higher molecular weight (Mn>8×104), and have relatively lower glass transition temperature of soft segment (T, < -56 C) which indicate that they have good low temperature mechanical properties. The elastomers exhibit optimum mechanical properties (σ >18 MPa and ε>500%) when the hard segment concentration is controlled between 50% and 60%. When the TPUE is introduced into modified double base propellant, the mechanical properties at low temperature are remarkably improved and the tensile strength at high temperature are slightly lowered.


Liu W.J.,Beijing Institute of Technology | Xu Z.B.,Beijing Institute of Technology | Cui K.J.,Beijing Institute of Technology | Xue M.,Beijing Institute of Technology | And 5 more authors.
Propellants, Explosives, Pyrotechnics | Year: 2015

Two intermediates, 1,5-dinitroso-3,7-dinitro-1,3,5,7-tetraazacyclooctane (DNDS) and 1-nitroso-3,5,7-trinitro-1,3,5,7-tetraazacyclooctane (MNX), were isolated and characterized in the synthesis of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) from the nitrolysis of 3,7-dinitro-1,3,5,7-tetraazabicyclo[3,3,1]nonane (DPT) for the first time. When the nitrolysis of DPT was slowed down, two intermediates were detected with HPLC. It was proposed that electrophilic NO2 + and NO+ from HNO3 and N2O4 might attack nitrogen atoms at positions 3 and 7 of DPT to form the cations of the intermediates, then nucleophilic H2O attacked the bridge carbon atoms of DPT to produce the intermediates, which were oxidized to form HMX. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Wang X.,Beijing Institute of Technology | Li J.,Beijing Institute of Technology | Li J.,Academy of Ordnance Science | Luo Y.,Beijing Institute of Technology | Huang M.,Beijing Institute of Technology
Science of Advanced Materials | Year: 2014

A novel ammonium perchlorate (AP)/graphene aerogel (GA) nanostructured energetic composite was prepared by the sol-gel method. The structure was characterized by using scanning electron microscope (SEM), nitrogen sorption tests and X-ray diffraction (XRD). The thermal decomposition behavior was investigated by using thermogravimetric analysis/differential scanning calorimetric/infrared spectrometry (TG-DSC-FTIR). The results show that the as-prepared AP/GA nanostructured energetic composites have numerous nanoscale pores and the specific surface area is 49.18 m2 g-1. The XRD results show that AP homogeneously disperses in the energetic composites at nanometric scale. TG-DSC-FTIR analysis indicates that GAs exhibit high promoting effects in the thermal decomposition process of AP. After incorporating with GAs, the hightemperature decomposition of AP is accelerated and its total heat release is significantly increased which is caused by the oxidation reaction between GAs and the oxidizing products. This study provides a new choice of metastable intermolecular composites which may have great potential in use for the solid rocket propellants. © 2014 by American Scientific Publishers.


Wang X.,Beijing Institute of Technology | Li J.,Beijing Institute of Technology | Li J.,Academy of Ordnance Science | Luo Y.,Beijing Institute of Technology
Gaofenzi Cailiao Kexue Yu Gongcheng/Polymeric Materials Science and Engineering | Year: 2013

Graphene(GO)/epoxy composites were prepared by sonicate-mixing method and in situ reducing graphene oxide in the presence of the epoxy matrix. The structures of the as-prepared composites were characterized by X-ray photoelectron spectroscopy (XPS), XRD, optical microscopy and SEM. In addition, the mechanical properties of the composites were also investigated using mechanical testing machine. XPS results indicate that graphene oxide has been reduced to GO in epoxy matrix. X-ray diffraction patterns, optical microscopy and scanning electron microscope images indicate that that graphene are well-dispersed in the epoxy matrix. Compared to pristine epoxy, the tensile strength and flexural strength of graphene/epoxy composites prepared by sonicate-mixing method increase by 29.2% and 1.4% respectively with the addition of 0.3% graphene. While the graphene/epoxy composites prepared by in situ reduction method show 40.5% improvement in tensile strength and 9.4% improvement in flexural strength with only 0.3% of graphene.


Zhang W.,Beijing Institute of Technology | Li J.,Beijing Institute of Technology | Li J.,Academy of Ordnance Science | Luo Y.,Beijing Institute of Technology
Gaofenzi Cailiao Kexue Yu Gongcheng/Polymeric Materials Science and Engineering | Year: 2012

Inverse gas chromatography (IGC) was employed to investigate the dispersive component of the surface free energy and the surface acid-base properties of the thermoplastic polyurethane elastomer (DTPU), surface properties of which were then compared with those of the traditional thermoplastic polyurethane elastomer (BTPU) that can be used as the propellant binder. It is found that the dispersive component of the surface free energy of DTPU is close to that of BTPU and the dispersive component of the surface free energy decreases linearly with increasing temperature. The Lewis acidic number K a and the basic number K b of DTPU are 0.09 and 0.48 respectively. The surface Lewis base number and total acid-basic ability of DTPU are higher than those of BTPU, whose Lewis acidic number is 0.06 and basic number is 0.37. Therefore, DTPU has better interactions with high-energy solid fillings.


Liu S.-H.,Beijing Institute of Technology | Luo X.-L.,Beijing Institute of Technology | Wang L.-X.,Beijing Institute of Technology | Cai Y.,Beijing Institute of Technology | Cai Y.,Academy of ordnance science
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2015

Motion detection frequently employs Optic Flow to get the velocity of solid targets in imaging sequences. This paper suggests calculate the gas diffusion velocity in infrared gas leaking videos by optic flow algorithms. Gas target is significantly different from solid objects, which has variable margin and gray values in diffusion. A series of tests with various scenes and leakage rate were performed to compare the effect of main stream methods, such as Farneback algorithm, PyrLK and BM algorithm. Farneback algorithm seems to have the best result in those tests. Besides, the robustness of methods used in uncooled infrared imaging may decline seriously for the low resolution, big noise and poor contrast ratio. This research adopted a special foreground detection method (FDM) and spectral filtering technique to address this issue. FDM firstly computes corresponding sample sets of each pixel, and uses the background based on the sets to make a correlation analysis with the current frame. Spectral filtering technique means get two or three images in different spectrum by band pass filters, and show a better result by mixing those images. In addition, for Optic Flow methods have ability to precisely detect directional motion and to ignore the nondirectional one, these methods could be employed to highlight the gas area and reduce the background noise. This paper offers a credible way for obtaining the diffusion velocity and resolves the robust troubles in practical application. In the meanwhile, it is an exploration of optic flow in varied shape target detection. © 2015 SPIE.


Ge Z.-H.,Academy of Ordnance Science | Yu Y.-G.,Nanjing University of Science and Technology | Yuan W.,Academy of Ordnance Science | Cao L.-Z.,Academy of Ordnance Science
25th International Symposium on Ballistics, ISB 2010 | Year: 2010

A study method of assessing the effect of the bore-wear reducing additive is proposed by researching the temperature of the gun barrel interior wall. A special temperature sensor is designed to measure the temperature a certain position deep from the barrel bore interface, and then the bore surface temperature can be extrapolated according the rule of heat-transfer. So the requirements of highly dynamic characteristics in measuring the bore surface temperature of the gun barrel can be easily satisfied. By the proposed method, the material choices and prescription of a new bore-wear reducing additive have been tested in 14.5mm ballistic gun. The peak temperature of the bore surface is used to assess the effect of the bore-wear reducing additive. The new bore-wear reducing additive has been used in 105mm APFSDS with high-energy and high-explosion temperature nitramine propellants, and brings a significant effect to reduce gun barrel wear and erosion.

Loading Academy of Ordnance Science collaborators
Loading Academy of Ordnance Science collaborators