Antistatic Modification of Lead Styphnate and Lead Azide for Surfactant Applications

Lead styphnate (LS) and lead azide (LA) must be considered vulnerable to accumulation and discharge of static charge under all conditions. To reduce the risk aroused by static initination hazard in the processing and handling of LS and LA, antistatic modifations of LS and LA are necessary. In this paper, four surfactants were applied to improve the antistatic abilities of lead styphnate and lead azide. The results showed that lauryl dimethylamine betaine (BS‐12) is significantly able to reduce the electrostatic accumulation of LS and LA. In addition, possible correlations of electrostatic accumulation with assumption and approximation could be drawn from the surfactant surface concentration. The electrostatic sensitivities, the 5 s delay explosion temperatures, and the thermal decomposition profiles of the compounds were measured. Selected products were additionally investigated by scanning electron microscopy (SEM). For LS the performance of the products with additives was less affected, whereas for LA the sensitivity of the products in the presence of surfactants was distinctly reduced. The surfactants which are preferably compatible with LS and LA do not affect their thermal stability.     

Thermal Kinetic Parameters of Lead Azide and Lead Styphnate with Antistatic Additives

Three antistatic additives were applied to improve the antistatic abilities of lead styphnate and lead azide. It has been found that PVA and DEX are more effective antistatic additives for LA, whereas CMC and DEX are more appropriate for LS by electrostatic accumulation test. The dynamic vacuum stability test (DVST) method was used to investigate the thermal decomposition of LA/PVA, LA/DEX, LS/CMC, LS/DEX, thermal kinetic parameters are obtained. The results show that antistatic additives have influence on the thermal kinetic parameters that lead to the thermal decomposition reaction which requires more energy, thus increasing the thermal stability of primary explosive. However, the reaction mechanism function that insure the explosive properties remained unchanged.     

Synthesis,Structure, Molecular Orbital and Valence Bond Calculations for Tetrazole Azide,CHN7

The synthesis, NMR spectroscopic characterization and structure determination of highly explosive tetrazole azide, a very nitrogen‐rich material (88.3% N) is reported. Tetrazole azide was prepared in high yield from the diazotation reaction of aminotetrazole, followed by treatment of the formed diazonium salt with sodium azide. Synthesis in diethylether/methanol and recrystallization from diethylether afforded colorless cubes: CHN₇ ( 1 ): monoclinic, P1 2₁/n₁, a=1346.6(5), b=499.6(2), c=1360.9(5) pm, β=105.14(1)⁰, V=0.884(2) nm³, Z=8, ϱ=1.670 g cm⁻³. The observed structural parameters (X‐ray) are in good accordance with the results from molecular orbital (MO) calculations. The computed electrostatic potential (B3LYP) suggests a pronounced shock and friction sensitivity which was confirmed experimentally. Quantitative valence bond (VB) calculations were performed for the most important 21 VB structures in order to obtain the structural weights and to obtain an assessment for the importance of the various individual VB structures considered.     

DBX‐1 – A Lead Free Replacement for Lead Azide

Efforts directed towards creating new environmentally friendly replacements for existing primary explosives have resulted in development of copper(I) 5‐nitrotetrazolate (DBX‐1). The chemical and physical properties of this material have been extensively investigated and it appears that DBX‐1 is a suitable drop‐in replacement for lead azide in a variety of ordnance applications. DBX‐1 is easily prepared, has excellent thermal stability and has safety and performance properties which are equivalent to or exceed those for lead azide. A program to qualify DBX‐1 for military use per NAVSEAINST 8020.5C has recently been completed and data has been forwarded to NSWC‐IH for submission to Naval Sea Systems Command.     

Studies on structure property correlation of cross‐linked glycidyl azide polymer

Glycidyl azide polymer (GAP) has been evaluated for use as binder for solid propellants. The effects of various parameters like cross‐linking conditions, concentration of crosslinker, and the ratio of isocyanate to hydroxyl functional groups (NCO/OH ratio) on the mechanical properties were studied in detail. It was observed that the type of curing agent and the NCO/OH ratio have a strong influence on the gum‐stock properties. Similar impact was seen for cross‐linker concentration also. The swelling characteristics of the cross‐linked binder prepared with different NCO/OH ratios were evaluated with toluene and tetrahydrofuran (THF). The polarity and the solubility parameter of the solvents were found to influence the swelling of GAP. The NCO/OH ratio and cross‐linker concentration of the polymer were also found to affect the swelling characteristics. The sol fraction determined for the polymer was found to follow a similar pattern. The cross‐link density and average molecular weight between crosslinks (Mc) were determined from the swelling studies and also from the stress–strain relationship. The Mc values were found to be influenced by the NCO/OH ratio. Finally, the Mc values determined from the swelling data were correlated to the gum‐stock properties, and the model parameters were estimated. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

钼酸铅介质中声光相互作用的研究

根据声光相互作用类型的区分标准分析得出声子与光子在钼酸铅介质中相互作用后产生的是Na-man-Nath衍射,并由实验观测到了Naman-Nath衍射;用共焦球面扫描干涉仪观察经超声衍射后He-Ne激光器的模式频谱结构,求出相邻衍射级之间的频率差,确定了光子与声子相互作用后在钼酸铅介质中形成的是超声驻波。     

Studies on Lead Titanate Ceramics Containing Niobium or Tantalum

Dielectric, lattice constant, and thermal-expansion measurements have been made on solid solution ceramics in the systems PbTiO₃Pb_0.5NbO₃ and PbTiO₃-Pb_o.5TaO₃. The ferro-electric Curie temperature is lowered to 465OC. at the solubility limit (2 to 5% Nb or Ta). Replacement of Ti⁴⁺ by Nb⁵⁺ or Ta⁵⁺ in these perovskite-type solid solutions is accompanied by the creation of cation vacancies. These vacancies seem to facilitate material transport and aid sintering. Thus ceramics were obtained with up to 91% of theoretical density. These compositions have peak dielectric constants of the order of 10,000 with tan δ less than 0.1 in the interval 25° to 525°C.     

Cobalt Catalyst Doped with Cerium and Barium Obtained by Co-Precipitation Method for Ammonia Synthesis Process

Abstract  

Unsupported cobalt catalysts promoted with barium (symbol Co/Ba), cerium (Co/Ce) or both (Co/Ce/Ba) were synthesized and tested in ammonia synthesis at 6.3 MPa. The Ba-free Co and Co/Ce oxide forms of the catalysts were prepared by precipitation/co-precipitation and a subsequent calcination at 500 °C. The Co and Co/Ce powders were impregnated with an aqueous solution of barium nitrite. Nitrogen physisorption and H₂ chemisorption measurements revealed that cerium and barium play the role of structural promoters, which hinder the sintering of cobalt oxide during calcination and stabilize the surface of cobalt under reduction conditions. It seems that barium also modifies the surface of the active phase, i.e., cobalt. The kinetic studies of NH₃ synthesis have shown that the co-promoted material (Co/Ce/Ba) is about 2–3 times more active than the system doped with barium (Co/Ba) and more than ten times as active as that with Ce. At 400 °C and at low conversion (1% NH₃), the ammonia synthesis rate (TOF) over Co/Ce/Ba proved to be almost 60% as high as that obtained for the commercial iron catalyst (KMI, H. Tops?e) commonly used in ammonia plants all over the world. Moreover, at the same temperature and a high ammonia concentration (8%) the co-promoted cobalt catalyst is over two times more active than the fused iron catalyst. Another asset of the cobalt catalyst is its high thermal stability.     

含叠氮化钠气体发生剂热动力学试验研究

通过ＤＳＣ热分析方法对叠氮化钠气体发生剂的热分解动力学特性进行研究，揭示了叠氮化钠以及其他添加剂对化学反应的影响程度。     

采集废气中铅的玻璃纤维滤筒前处理方法研究

为了有效降低滤筒中铅的空白值,采用了在硝酸中加入硫酸和EDTA的方法。结果表明,硫酸和EDTA对去除滤筒中铅的空白值具有明显的作用,同时,确定了两种试剂的最佳加入量,并结合各种因素,建议实际工作中采用加入硫酸的方法。     

PbO_2为阳极Cr~(+3)电化学氧化伏安特性的研究

应用三电极体系对硫酸介质中以二氧化铅为阳极的Cr3+电化学氧化的伏安特性进行了研究和探讨。试验结果表明 ,Cr3+电化学氧化是间接的电化学氧化反应过程 ,阳极反应的本质是阳极上H2 O的电化学氧化     

Glasses with Lead Sulfide Nanoparticles for Laser Technologies

The formation of nanoparticles of semiconducting lead sulfide in silicate and borosilicate glasses matrices is investigated. The dependence of the size of PbS particles on the temperature-time heat-treatment conditions is identified. The effect of clarification arising in theses nanostructural glass materials is established. The glasses developed can be used as solid passive locks in lasers radiating in the short IR spectrum range.     

Compounding of Glycidyl Azide Polymer with Nitrocellulose and its Influence on the Properties of Propellants

Currently formulated propellants comprise RDX and polymeric binders, such as hydroxy‐terminated polybutadiene (HTPB) and cellulose‐acetate butyrate (CAB) as well as the energetic substances glycidyl azide polymer (GAP) and nitrocellulose (NC). Propellants based on GAP are often brittle if they are formulated with a high content of cyclotrimethylene trinitramine (RDX) and due to the usually insufficient mechanical properties of GAP. On the other hand formulations based on RDX and NC may exceed the tolerable burning temperature with increasing RDX concentration. Therefore, in this study propellants with a high force and with relatively low burning temperature has been formulated by using a compound of NC and GAP as energetic binder. According to thermodynamic calculations GAP/NC composite propellants can be formulated with up to 15 percent more specific energy than seminitramines at the same burning temperature. By choosing appropriate polymerization conditions chemical stable compositions can be produced. ARC experiments give evidence that at temperatures from 120°C to 160°C the binder decomposes similar to NC. At higher temperatures the behaviour switches from NC type to GAP type decomposition. In comparison to GAP bound propellants the compressive strength of propellants bound by the GAP/NC compound can be significantly increased by up to 420 percent at room temperature. Although the examined seminitramine propellants bound with NC show a compressive strength which is about 10 percent higher at room temperature, the GAP/NC compositions are quite superior at elevated temperature.     

A facile crosslinking method of polybenzimidazole with sulfonyl azide groups for proton conducting membranes

A facile crosslinking method of polybenzimidazole (PBI) with sulfonyl azide groups (sPBI-SA) for proton conducting membranes is proposed. Thermally crosslinkable sPBI-SA is synthesized from sulfonated PBI (sPBI) and sodium azide. The structures of sPBI, sPBI-SA, and crosslinked sPBI are confirmed by FTIR and ¹H NMR. Upon heating, sPBI-SA loses nitrogen and form nitrene, which reacts with CH-bond of the backbone of another chain of PBI via the reactions of hydrogen abstraction, recombination, or CH-bond insertion. The crosslinking structure of PBI membranes is thus formed. Compared with the uncrosslinked membranes, the crosslinked sPBI membranes exhibit improved tensile strength, migration stability of phosphoric acid (PA), dimensional stability, and chemical oxidative stability. Whereas, the doping ability of PA and the proton conductivity of the crosslinked membranes decrease a little.