Synthesis, characterization and catalytic activity of CdO nanocrystals

In this paper, we report the synthesis of nanocrystalline cadmium oxide (CdO) and its characterization by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Its catalytic activity was investigated on the thermal decomposition of 1,2,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), ammonium perchlorate (AP), hydroxyl terminated polybutadiene (HTPB) and composite solid propellants (CSPs) using thermogravimetric analysis (TG), simultaneous thermogravimerty and differential scanning calorimetry (TG-DSC) and ignition delay measurements. Kinetics of thermal decomposition of AP + CdO has also been investigated using model free (isoconversional) and model-fitting approaches which have been applied to data for isothermal TG decomposition. All these studies show enhancement in the rate of decomposition of AP, HTPB and CSPs but no effect on HMX. The burning rate of CSPs has also been found to be increased with CdO nanocrystals.     

Preparation,characterization and catalytic behavior of copper oxide nanoparticles on thermal decomposition of ammonium perchlorate particles

In this study, copper oxide nanoparticles (CuO NPs) with mean particle size of 43–32?nm were prepared by wet grinding of commercial micronized CuO powders in a high-energy wet ball-milling apparatus during 20 and 30?h, respectively. X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM) analyses were used to characterize the structure, mean particle size and morphology of the resulting CuO NPs. The results confirmed that the CuO NPs obtained at different milling times consist of nanostructures with nearly spherical morphology and by increasing the milling time, smaller particle size was obtained. The catalytic activities of the synthesized CuO NPs on the thermal decomposition of ammonium perchlorate (AP) particles were examined through differential scanning calorimetry and thermogravimetry (DSC/TG) analyses. Evaluation of the experimental results illustrated that the surfaces of CuO NPs were effectively coated with AP particles and by adding 5%CuO NPs with 32?nm, the thermal decomposition temperature of the treated particles reduced by 83.0°C and the heat of decomposition reached 1553.7?Jg^?1. Moreover, the kinetic and thermodynamic parameters of the thermal decomposition of pure and AP?+?5%CW30 nanocomposites have been investigated by using the Kissinger, Boswell and Ozawa methods.     

高速撞击下温压炸药的响应敏感性

采用自行设计的动态加载装置对HMX基、HMX/NTO基和HMX/FOX-7基3种温压炸药撞击响应规律进行了研究,获得炸药的临界点火速度,并通过密闭燃烧罐分析撞击后回收试样的燃烧特性。结果表明:3种温压炸药药柱在高速撞击下均经历了冲击、塑性变形、破碎飞散和点火反应阶段;HMX基、HMX/NTO基和HMX/FOX-7基温压炸药的临界点火速度分别为302.9、312.3 m/s和315.3 m/s,NTO和FOX-7能够提高温压炸药的临界点火速度;分析撞击后回收试样的燃烧特性发现,与HMX基温压炸药相比,HMX/NTO基和HMX/FOX-7基温压炸药升压时间分别增加了103.6%和103.3%,升压速率分别降低了17.3%和21.1%,且撞击后的燃烧速率显著降低。     

Dependence of particle morphology and size on the mechanical sensitivity and thermal stability of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine

Three kinds of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) samples with spherical (beta-phase), needle (gamma-phase) and polyhedral (beta-phase) shapes were fabricated by wet milling, solvent/non-solvent and riddling methods, respectively. By changing the technical conditions, HMX powders with different particle sizes were obtained for each kind of sample. All as-prepared samples were characterized by laser granularity measurement, scanning electron microscopy (SEM) and X-ray diffractometry (XRD). Taking advantage of mechanical sensitivity tests, slow cook-off tests and differential scanning calorimetry (DSC) analysis, the mechanical sensitivity and thermal stability of HMX samples were found to depend on particle size and morphology. Results indicated that particle size played a significant role in the safety of HMX, and that morphology regulated the experimental results, i.e., for each kind of HMX samples, the mechanical sensitivity and thermal stability of HMX changed if the particle size differed. However, the trends of these changes exhibit much variance if the microstructure of the HMX particles is altered. Consequently, the difference in safety for these kinds of samples has to do with their specific morphology.     

Barium hydroxyapatite nanoparticles synthesized by citric acid sol-gel combustion method

Barium hydroxyapatite (BaHAP) nanoparticles have been synthesized by citric acid sol-gel combustion method using citric acid as a reductant/fuel and nitrate as an oxidant at a relatively low temperature of 600 °C. The thermal decomposition of nitrate-citrate xerogel was investigated by thermogravimetric/differential thermal analysis (TG/DTA) technique. The yielding powders calcined at 600 °C have been characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), and transmission electron microscope (TEM). The possible combustion process was presented.     

含能增塑剂BDNPF/A与几种高能炸药相容性研究

采用差示扫描量热法(DSC)和X射线衍射法(XRD),研究了含能增塑剂双(2,2-二硝基丙基)缩甲(乙)醛(BDNPF/A)与6种高能炸药[1-氧-2,6-二氨基-3,5-二硝基吡嗪(LLM-105)、三氨基三硝基苯(TATB)、2,6-二氨基-3,5-二硝基吡啶-1-氧化物(ANPy O)、奥克托今(HMX)、六硝基六氮杂异伍兹烷(CL-20)和3-硝基-1,2,4-三唑-5-酮(NTO)]的相容性。DSC结果表明:BDNPF/A与TATB混合体系相容,与LLM-105混合体系轻微敏感,与ANPy O和HMX混合体系敏感,与CL-20和NTO混合体系危险。XRD结果表明:BDNPF/A与HMX、CL-20和NTO之间存在相互作用。上述试验研究表明,BDNPF/A与CL-20和NTO相容性差,不推荐一起使用。     

Synthesis and characterization of KNd2Ti3O9.5 nanocrystal and its catalytic effect on decomposition of ammonium perchlorate

A novel kind of perovskite type oxide KNd₂Ti₃O_9.5 nanocrystals with an average size of 12 nm were successfully fabricated by a stearic acid sol–gel method (SAM) using Ti(OBu)₄, KOH, Nd₂O₃ and stearic acid as the raw materials. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the products. The catalytic effect of the KNd₂Ti₃O_9.5 nanoparticles on thermal decomposition of ammonium perchlorate (AP) was investigated by differential thermal analysis (DTA) and thermal gravimetry (TG) experiments. Results indicated that the obtained KNd₂Ti₃O_9.5 nanocrystals took on cubic structure and presented both good dispersibility and uniform crystallite size. Also, they have an intense catalytic effect on the thermal decomposition of AP. Adding 2% of KNd₂Ti₃O_9.5 nanoparticles to AP can obviously decrease the thermal decomposition temperature of AP by 50 °C, increase the heat of decomposition from 590 J g⁻¹ to 1659 J g⁻¹ and obviously quicken the decomposition reaction rate.     

Synthesis, characterization and thermolysis studies on 3,7-dinitro-1,3,5,7-tetraazabicyclo[3,3,1]nonane (DPT): A key precursor in the synthesis of most powerful benchmark energetic materials (RDX/HMX) of today

This paper reports studies undertaken on 3,7-dinitro-1,3,5,7-tetraazabicyclo[3,3,1]nonane (DPT). The synthesis of DPT was carried out by the nitration of hexamine based on the lines of reported method with minor modification. DPT was characterized by elemental analysis, scanning electron microscopy (SEM), Fourier transform infrared (FTIR) and (1)H nuclear magnetic resonance (NMR) techniques. Thermal stability of DPT was studied using thermogravimetry (TG) and differential scanning calorimetry (DSC). The thermal analysis studies revealed that DPT undergoes decomposition at 211 degrees C. Decomposition of DPT using TG-FTIR indicated the evolution of carbon dioxide, water and oxides of nitrogen as main gaseous products. The electrochemical behavior of DPT was studied using cyclic voltammetric (CV) studies. The experimentally determined sensitivity parameters indicated the insensitive nature of DPT towards external stimuli. The performance parameters of DPT, RDX and HMX have been computed using Linear Output Thermodynamic User Friendly Software for Energetic Systems (LOTUSES) code. The predicted properties of DPT are interesting and important from the point of process technology and/or safety. The work reported in this paper enriches the existing scanty research and development data on one of the key precursor used for synthesis of important high energy materials (HEMs).     

PMOCOPV/TiO2纳米复合材料的微观结构与性能

采用原位聚合方法制备聚(2-甲氧基-5-辛氧基)对苯乙炔(PMOCOPV)/二氧化钛(TiO2)纳米复合材料。利用扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)和热失重(TG)等方法对纳米复合材料的微观结构与性能进行表征。结果显示,纳米复合材料中TiO2并不是简单地与PMOCOPV分子共混,而是被PMOCOPV分子链缠绕包裹;纳米复合材料为分散均匀的球形微粒,粒径尺寸为60nm～80nm左右;同PMOCOPV相比,纳米复合材料结晶性随着TiO2含量增加而增强,且热稳定性提高。     

预设升温速度对电场作用下Fe-Cu-Ti-C体系燃烧合成的影响

采用Gleeble-3500D热模拟机,研究了电场作用下预设升温速度对Fe-Cu-Ti-C体系燃烧合成的影响.结合X射线衍射分析(XRD)、扫描电镜(SEM)及金相显微镜分析了合成产物的相组成及显微组织,同时基于能量守恒定律对体系中TiC的转化率进行理论计算.结果表明:随着预设升温速度的提高(50～100℃/s),体系的点火温度相应下降(752～629.78℃);试样的致密度则相应地提高;合成产物TiC颗粒逐渐变细.同时转化率计算结果显示:Fe-Cu-Ti-C体系中TiC的转化率随着预设升温速度的提高而有所增加.     

膨化高氯酸铵的制备及其性能研究

使用膨化剂在减压条件下制备出膨化高氯酸铵（AP）。利用扫描电镜、粒度分析仪、傅里叶红外光谱仪、比表面积仪、差示扫描量热仪、热失重分析仪及感度仪分别对膨化AP进行形貌分析和性能测试。结果表明:膨化AP颗粒表面具有沟壑,内部具有孔洞结构,粒径D₅₀=22.559 μm;与未膨化的原料AP相比,膨化AP低温分解温度提高16.0 ℃,高温分解温度提高6.7 ℃,分解热提高322.3 J/g;比表面积增大92.2%,吸湿性增大;极限撞击能为10 J,撞击感度提高。制备AP/HTPB(端羟基聚丁二烯)和膨化AP/HTPB复合推进剂并测定其燃速,膨化AP/HTPB复合推进剂燃速提高4.1%。     

Preparation, characterization and thermolysis of phenylenediammonium dinitrate salts

Four phenylenediammonium dinitrate salts were prepared and characterized by elemental, Infrared spectroscopy (IR), Ultraviolet spectroscopy (UV) and gravimetric methods. These dinitrates find application in propellant, explosives and pyrotechnics. Their thermal decomposition has been studied using thermogravimetry (TG) and simultaneous thermogravimetry-differential scanning calorimetry (TG–DSC). Kinetics parameters were evaluated by model fitting and isoconversional methods. Their thermolytic pathways have also been suggested, which involves decomposition followed by ignition.     

氧化亚铜/碳纳米管超细复合球的合成及性能研究

采用溶液法原位制备了氧化亚铜/多壁碳纳米管(Cu₂O/MWNTs)超细复合球. 通过扫描隧道显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射仪(XRD)、紫外-可见分光光度计(UV-vis)和差热分析(DSC)等手段对产品进行了形貌分析和性能检测. 结果表明: 碳纳米管均匀嵌镶在Cu₂O球中; 相比于同粒径纯Cu₂O球, 复合球的特征吸收峰发生蓝移, 复合球使高氯酸铵(AP)的高温分解温度进一步降低了11.5℃. 另外, 对复合球的形貌影响因素及生长机理进行了探讨, 发现明胶是复合物成球的关键, 而聚乙二醇影响复合球粒径的均匀性.     

Synthesis, characterization, thermolysis and performance evaluation studies on alkali metal salts of TABA and NTO

The lithium (Li) and potassium (K) salts of 3-nitro-1,2,4-triazol-5-one (NTO) and 2,4,6-trinitroanilino benzoic acid (TABA) were prepared and characterized during this work. The synthesis was carried out by addition of a solution of lithium/potassium hydroxide to the aqueous solution of NTO and TABA, respectively. The products were characterized by elemental analysis, metal content determination and Fourier Transform Infrared (FTIR) Spectrum. Differential scanning calorimetry (DSC) profile indicated that Li and K salts of NTO and TABA undergo exothermic decomposition in the temperature range of 257-360 degrees C suggesting their energetic nature. The thermo gravimetric (TG) weight loss pattern revealed loss of water for Li/K salts of NTO and TABA in the temperature range of 115-155 degrees C. Sensitivity results revealed that the compounds are insensitive to impact and friction (impact sensitivity--height of 50% explosion>170 cm and friction insensitivity up to 36 kg) stimuli despite even the parent molecule of NTO salts (NTO) being HEM in the hazard category of 1.1. The FTIR spectra of the gaseous products evolved during TGA of NTO and TABA salts indicated the release of NO2. The formation of products such as LiNCO and KNCO was also observed in case of NTO salts, whereas that of CO2 and NH containing products was indicated in case of TABA salts during this study. In order to assess the performance as energetic ballistic modifiers (EBMs), NTO and TABA salts were incorporated in the ammonium perchlorate-hydroxyl terminated polybutadiene (AP-HTPB) composite propellants. The potassium salts enhanced the burning rate of the propellant. The best catalytic effect was obtained with K-TABA salt, which increased the burning rate to the extent of approximately 81% as well as brought down the n-value to 0.15 (pressure 2-9 MPa).     

Synthesis of stable spherical platinum diphosphide, PtP2/carbon nanocomposite by reacting Pt(PPh3)4 at elevated temperature under autogenic pressure

The synthesis of microsized carbon spheres supporting the semiconductor platinum diphosphide, PtP₂, was conducted by the thermal decomposition of an organometallic precursor. This novel reaction was carried out using the reaction under autogenic pressure at elevated temperature (RAPET) method by dissociating Pt(PPh₃)₄ at 1000 °C. The product was characterized using methods of electron microscopy (scanning electron microscope (SEM), transmission electron microscope (TEM), selected area energy dispersive spectroscopy (SAEDS), elemental analyzer (EA) and energy dispersive X-ray analysis (EDX)) and powder-XRD. Transmission electron microscope images indicate that the particle size of the nanoparticles of PtP₂ coated on the carbon spheres is 50 nm.     

Effects of carbon nanotubes additions on flash ignition characteristics of Fe and Al nanoparticles

The influences of carbon nanotubes (CNTs) additions on the flash ignition characteristics of Iron (Fe) and aluminum (Al) nanoparticles (NPs) were presented. CNTs can be used as the additive to these metal nanoparticles for improving the flash ignition and burning processes. Different mass fractions of CNTs additions were considered. The mixture of Al and CNTs could combust in air with obvious giant flame, whereas the mixture of Fe and CNTs combusted under a relative stable condition with slight red light. The temperature distributions were measured using non-contact optical method and showed that Al NPs mixed with CNTs were burning at a higher temperature level than Fe NPs. Although different mass fractions of CNTs cannot significantly change the overall flash ignition phenomenon, CNTs additions influenced the minimum ignition energy (MIE) of mixtures. The appropriate content of CNTs addition can decrease the Fe NPs MIE significantly. However, the Al NPs MIE decreased all along with the increase of CNTs content. The micro- and nano- structures of Fe and Al NPs with CNTs additions before and after ignitions were examined by scanning electron microscope and high-resolution transmission electron microscopy. It was found that the special thermal conductive characteristics of CNTs and the cross-connected features for metal particles with CNTs caused the enhancement of flash ignition.     

Effect of calcining temperature on particle size of hydroxyapatite synthesized by solid-state reaction at room temperature

Using diammonium phosphate, calcium nitrate tetrahydrate and sodium bicarbonate as raw materials, hydroxyapatite (HAP) was facilely synthesized by solid-state reaction at room temperature. The crystallinity, phase, morphology and particle size of the products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry/differential thermal analysis (TG–DTA) and particle size analyzer. The influence of calcining temperature on the crystallinity and composition of HAP phase was also investigated.     

Synthesis and photocatalytic activity of nano-sized iron oxides

Nano-sized iron oxide powder with average crystallite sizes 35, 100 and 150 nm was prepared by thermal evaporation and co-precipitation techniques. The synthesized powders were characterized by X-ray diffraction analysis technique, transmission electron microscope (TEM) and scanning electron microscope (SEM). The prepared powders were tested as catalysts for the photo catalytic decomposition of Congo red dye. The effect of crystal size of iron oxides on the rate of decomposition of Congo red dye was investigated in visible light as well as in the absence of light. The experimental results show that both iron oxides with crystallite size 35 and 150 nm cause complete decomposition of Congo red dye while iron oxide particles with crystallite size 100 nm were unable to decompose the dye.     

Transition metal oxide nanoparticles: Potential nano-modifier for rocket propellants

ABSTRACT

TiO₂, ZnO₂, and CrO₂ nanoparticles were prepared by novel quick precipitation method, where transition metal oxides were used as catalyst. All nanoparticles were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The average particle size for TiO₂, ZnO₂, and CrO₂ was 44.8, 13.4, and 77.6 nm, respectively. Catalytic properties of these nanomaterials were studied using ammonium perchlorate (AP)/hydroxy-terminated polybutadiene (HTPB) propellant by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Both experimental results reveal that there is an increase in the thermal decomposition of propellants in the presence of transition metal oxide nanoparticles. Activation energy of high-temperature decomposition (HTD) of propellant with transition metal oxide nanoparticles was calculated by Kissinger equation. Burning rates of propellants were also calculated.     

Copper loaded carbon aerogel from chitosan-precursor promotes thermal decomposition of ammonium perchlorate for solid propellants

Chitosan (CS) was used as a carrier, in which copper particles were loaded, and CS-Cu carbon aerogel was obtained by freeze-drying and high-temperature carbonization, which was characterized by scanning electron microscopy test, Fourier transform infrared spectroscopy test, X-ray diffraction test, X-ray photoelectron spectroscopy, and gas adsorption method. Results show that CS-Cu carbon aerogel is a 3D porous material, and its 3D porous structure provides more active sites for the copper nanoparticles, effectively preventing the agglomeration phenomenon caused by the large surface energy of copper nanoparticles. The CS-Cu carbon aerogel was introduced into the solid propellant system, and the catalytic performance of the CS-Cu carbon aerogel on ammonium perchlorate (AP) was investigated by differential thermal analysis. The results show that the CS-Cu carbon aerogel has good catalytic performance, the high temperature decomposition peak of AP is reduced by 92.4 K and the activation energy is reduced from 215.9 ± 1.3 kJ/mol to 173.7 ± 1.5 kJ/mol for pure AP.