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Unsymmetrical dimethylhydrazine (UDMH) is a common liquid propellant widely used in rocket engines and other applications. The safety of UDMH in service is affected by its slow oxidation during long-term storage to form impurities such as dimethylamine (DMA) and formaldehyde dimethylhydrazone (FDH). How these impurities affect combustion performance is not known, and in order to assess these effects, the present experiments investigated the combustion characteristics of self-igniting fuels and carried out ignition delay time measurements and flame propagation velocity measurements of pure UDMH and its denatured mixtures in a nitrogen tetroxide (NTO) atmosphere. This experiment was carried out to measure the delay time of hedge ignition of pure UDMH and qualitative analysis of its flame propagation properties under vacuum conditions at room temperature (T = 293 K). Ignition delay time measurements and flame propagation characterization were performed under the same experimental conditions for UDMH mixed with 1%, 5% and 10% FDH, UDMH mixed with 1%, 5% and 10% H2O, UDMH mixed with 1%, 5% and 10% DMA, as well as for UDMH mixed with the same proportions of the three substances (1%, 5% and 10%). The flame propagation characteristics were analyzed. The results showed that the incorporation of DMA, H2O and FDH in different proportions could inhibit the combustion of UDMH to varying degrees and prolong its ignition delay time. It is worth noting that the introduction of FDH had the least effect on it, and the least effect was observed at a concentration of 1%. In contrast, the effect of DMA on UDMH is more obvious, and the addition of H2O has the largest increase in the ignition delay time of UDMH. In the flame propagation experiment, the flame of the experimental group adding H2O can no longer fill the whole experimental window, while the other experimental groups can still make the window full of flame. Combined with the measurements of the ignition delay time, it can be seen that the moisture content has the greatest effect on the combustion characteristics. [ABSTRACT FROM AUTHOR]

[Display omitted] Calorimetric monitoring of the autoclave reaction N 2 O 4 + C 2 H 4 at –85 to +10 °C under argon pressure 10–30 bar revealed that the exothermic chemical reaction started at temperatures above –52 °C at 10 bar, whereas an intensive exothermic reaction started at –85 °C and pressure of 30 bar. IR study showed that oligo/polynitroethylene was formed at 30 bar, while carbonyl and hydroxy compound as well as nitrate R–ONO 2 formation occurred upon processing at 10 bar. [ABSTRACT FROM AUTHOR]

We report the first experimental gas-phase observation of an asymmetric, trans-N2O4 formed by the dimerization of NO2. In additional to the dominant 14N2 16O4 species, rotational transitions have been observed for all species with single 15N and 18O substitutions as well as several multiply substituted isotopologues. These transitions were used to determine a complete substitution structure as well as an r0 structure from the fitted zero-point averaged rotational constants. The determined structure is found to be that of an ON-O-NO2 linkage with the shared oxygen atom closer to the NO2 than the NO (1.42 vs 1.61 Å). The structure is found to be nearly planar with a trans O-N-O-N linkage. From the spectra of the 14N15NO4 species, we were able to determine the nuclear quadrupole coupling constants for each specific nitrogen atom. The equilibrium structure determined by ab initio quantum chemistry calculations is in excellent agreement with the experimentally determined structure. No spectral evidence of the predicted asymmetric, cis-N2O4 was found in the spectra. [ABSTRACT FROM AUTHOR]

The N[sub 2]O[sub 4]→2 NO[sub 2] dissociation reaction was investigated at a high level of theory using the couple cluster with all single and double excitations and connected triples [CCSD(T)] and complete active space self-consistent field approaches, and the cc-pVDZ, aug-cc-pVDZ, and cc-pVTZ basis sets. Only at the coupled cluster level a first-order saddle point was found connecting reactant and products. Collectively, structural, vibrational, and thermodynamic data for the three stationary points represent the best theoretical description of this reaction system to date, and are in good agreement with available experimental results. Unimolecular transition state theory rate constants (k[sub ∞]) were also evaluated at 250, 298.15, and 350 K. At the CCSD(T)/cc-pVTZ level of calculation these results are 0.62×10[sup 1], 1.90×10[sup 3], and 1.66×10[sup 5] s[sup -1], respectively. Known experimental results at 298 K vary from 1.7×10[sup 5] to 1.0×10[sup 6] s[sup -1]. Including an estimate for basis set superposition error, we predict ΔH[sub 298][sup 0] for the dissociation reaction to be 12.76 kcal/mol (Expt. 13.1–13.7 kcal/mol). © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Monomethylhydrazine (MMH) fuel and nitrogen tetroxide (NTO)-based oxidizers embody the state of the art for hypergolic propellants. Despite their wide use, a detailed understanding of the full reaction chemistry between MMH and NTO, from early liquid phase reactions to ignition in the gas phase, is lacking. The gas phase reactions are relatively well understood with several spectroscopic techniques well suited to probe gaseous reaction zones and numerous computational chemistry studies supporting the experimental data. The present paper focuses on the early liquid phase reactions with a method devoted to the determination of Arrhenius preexponential factors and activation energies for global, single-step liquid phase chemical reaction models for MMH-NTO and MMH-red fuming nitric acid (RFNA) systems. Using a temperature and atmosphere controlled droplet contact chamber, the liquid phase induction delay times of MMH-RFNA and MMH-NTO were examined by capturing drop on drop tests at frame rates from 100,000 to 500,000 fps. Results indicate induction delays on the order of 30–100 microseconds and 10–40 microseconds for MMH-RFNA and MMH-NTO, respectively, and distinct reaction rate parameters for both pairs of propellants. [ABSTRACT FROM AUTHOR]

Highlights • Pure N 2 O 4 and N 2 O 4 /CO 2 mixtures are investigated as working fluid in CSP plants. • Two simple regenerative cycles using pure N 2 O 4 and N 2 O 4 /CO 2 mixtures are designed. • The N 2 O 4 /CO 2 composition is optimised for the considered application. • Two solar fields with maximum temperatures of 565 °C and 715 °C are designed with dedicated tools. • The overall solar-to-electric efficiency is determined for all the studied cases. Abstract The competitiveness of concentrated solar power technology in the near-future electricity generation scenario, requires a substantial reduction of the Levelized Cost of Energy which can be achieved with an increase of the energy conversion efficiencies while maintaining or reducing the investment costs. This paper discusses the use of pure Dinitrogen tetroxide N 2 O 4 , and N 2 O 4 /CO 2 mixture, as working fluids in supercritical Brayton cycles applied to solar tower power plants. When N 2 O 4 is combined with CO 2 , the resulting mixture has a comparatively higher critical temperature than pure CO 2 , allowing a condensing cycle even at the fairly high ambient temperatures of desert areas, where solar power plants are typically installed. This allows the adoption of simpler cycle configurations than the one used in sCO 2 cycles (cost reduction) while achieving very high thermodynamic efficiency (47% at 700 °C). The N 2 O 4 /CO 2 mixture with optimized composition, integrated in a solar tower unit, increases the solar-electric efficiency by 1% with respect to commercial plants based on steam cycle with 550 °C maximum temperature (22.3% vs. 21.3%). At 700 °C, the overall solar-electric efficiency can reach 24.5% which is slightly higher than supercritical CO 2 cycles, yet with a foreseeable reduction of the investment costs as consequence of the simpler plant lay-out. [ABSTRACT FROM AUTHOR]

Abstract An experimental study of a Monomethylhydrazine (MMH)/nitrogen tetroxide (NTO) counterflow pool flame was conducted to obtain data that contributes to proposed detailed chemical reaction mechanisms. The flames were imaged through high-speed imaging of chemiluminescence of broad band light emission with Band Pass Filters (BPF) centered at 310 nm ± 5 nm and 430 nm ± 5 nm. To help explain the flame structures observed in the experiment, one-dimensional numerical simulations with detailed chemical kinetics were also performed, considering, along with the proposed reaction mechanisms, the MMH evaporation environment at the boundary conditions. The experimental results show a multi-layered flame structure of an MMH/NTO non-premixed flame composed of two orange flames and one weak blue/white flame. Results obtained in numerical simulations indicate that MMH/NTO forms the multi-layered flame structures of two orange flames due to NH 3 decomposition and NO 2 recombination, and the blue/white flame was newly found in the region between the two orange flames. [ABSTRACT FROM AUTHOR]

Nitro-oxidizers (nitric acid-27S, nitrogen tetroxide and mixed nitrogen oxide) are common liquid oxidants widely used in liquid rockets and missile weapons. How to deal with large quantities of scrapped nitro-oxidizers is a complex, costly and dangerous project. We pretreated it with hydrogen peroxide (H2O 2) and converted the active oxidant component of nitro-oxidizers into nitric acid, which can be used as oxidant source to prepare graphite oxide from natural graphite. The comprehensive oxidation ability of the reaction system can be effectively controlled by adding different volumes of H2O2, and the oxidation ability can be expressed by the redox potential of the system. Combined with FT-IR, Raman and XRD characterization analysis, the optimal redox potential interval, [1700, 1800] mV, has been determined for the synthesis of graphite oxide. With the help of data interpolation and function nonlinear fitting and the initial potential of rejected nitro-oxidants obtained, the composition ratio of nitric acid and nitrogen tetroxide (N2O 4) has been preliminarily determined with the optimum amount of H2O2. Furthermore, the optimum oxidizing atmosphere for the synthesis of graphite oxide can be formed in spite of a wide range of concentrations of oxidant components, and the resulting graphite oxide has been proven to be a qualified and effective product. The change of ORP value of three nitro-oxidants with a series of reaction temperatures after pretreatment was observed. When the temperature reached the preset value and maintained stable for 5 minutes, the ORP of this temperature was determined. [ABSTRACT FROM AUTHOR]

Monomethyl hydrazine (MMH) and nitrogen tetroxide (NTO) propellant is the most prevalent combination in hypergolic liquid rocket engines for space propulsion scenarios. However, limited work has been reported on its combustion characteristics, especially at high chamber pressure. This work, for the first time, experimentally investigated the flame characteristics of MMH/NTO impinging jets at chamber pressure p c up to 5.1 MPa and at different flow rate Q and mixture ratio O/F conditions. High speed OH* chemiluminescence imaging technique resolved the structure, location, and direction of the flame, as well as the local reactivity of this liquid and gas phase combustion event. Results show that the flame is a cone shaped one, and its dimensional parameters depend on the test conditions. Two regions representing liquid phase reaction and main flame are distinctly observed, respectively at the impingement point and a certain distance downstream. In addition, the conventional flame direction estimation approach based on combined momentum direction deviates from the current hot test measurements, and a new correlation for flame direction prediction is proposed by correcting the O/F dependence. Finally, the maximum OH* intensity at the impingement point I max, imp indicates that chamber pressure and flow rate weakly affect liquid phase reactivity, but more fuel injection favors it. However, in the main flame region, the maximum OH* intensity I max, main quickly rises with increasing p c , and both Q and O/F non-monotonically affect I max, main due to the competition between local mixing and chemical reaction. This work is believed to be of significant merit for injector and chamber design for future high performance engines. [ABSTRACT FROM AUTHOR]

The oxidation of hexane-2,3,4,5-tetraone tetraoxime with dinitrogen tetroxide was studied in different solvents. The primary furoxan ring closure was found to occur involving either two central or two terminal oxime groups to form 4,7-dimethyl[1,2,5]oxadiazolo[3,4-d]pyridazine 1,5,6-trioxide and the previously unknown 4,4′-dimethyl-[3,3′-bi(1,2,5-oxadiazole)] 5,5′-dioxide. The structure of the latter compound was established by X-ray diffraction. [ABSTRACT FROM AUTHOR]

Abstract: We have discovered, by high‐level quantum‐chemical calculations, a new and predominant isomerization mechanism for N2O4 → ONONO2 via a roaming‐like transition state occurring unimolecularly or bimolecularly during collision with H2O. The new mechanism allows N2O4 to react with H2O with a significantly lower barrier (< 13.1 kcal/mol) than the commonly known tight transition state (∼30‐45 kcal/mol) by concurrent stretching of the NN bond and rotation of one of the NO2 groups to form trans‐ONONO2, which then undergoes a rapid metathetical reaction with H2O in the gas phase and in aqueous solution. The results have a significant implication for the hydrolysis of N2O4 in water to produce HONO and HNO3. Rate constants for the isomerization and hydrolysis reactions have been predicted for atmospheric modeling applications. [ABSTRACT FROM AUTHOR]

Pt nanoparticles were successfully encapsulated in hollow ZSM-5 single crystals by tetrapropylammonium hydroxide (TPAOH) hydrothermal treatment with an “dissolution-recrystallization” process. The prepared Pt/hollow ZSM-5 (Pt/ h -ZSM-5 re ) sample exhibited the best activity and a maximum NO conversion of 84% can be achieved at 90 °C with N 2 selectivity of 92% (GHSV = 50,000 h −1 ). Meanwhile, Pt/ h -ZSM-5 re catalyst exhibited excellent SO 2 , H 2 O resistance and durability, which was related to the stabilization of Pt active sites by hollow structure during H 2 -SCR. It was found that the increase of NO 2 concentration in the feed gas mixture led to an activity decline. In addition, the H 2 -SCR reaction routes over Pt/hollow ZSM-5 catalyst at different temperature were investigated. [ABSTRACT FROM AUTHOR]

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Unsteady simulations of hydrazine (N2H4) sprays in nitrogen tetroxide (NTO, NO2-N2O4) streams were conducted to explore the hypergolic combustion in bipropellant thrusters. The Navier–Stokes equations were solved using a detailed chemical kinetics mechanism and dispersed droplets were modeled through direct numerical simulations. Auto-ignition occurred when the sum of the heat transfer from the ambient gas and the heat release from hydrogen abstraction reactions exceeded the latent heat of the droplets. Although the evaporation of the droplets was enhanced as the droplet size decreased, the ignition delay time increased due to the lower temperatures of the mixtures of the N2H4vapor and nitrogen tetroxide. After the flames reached a steady state, a double flame structure appeared, comprised of outer diffusion and inner decomposition flames. The inner decomposition flame and N2H4vapor flow exhibited a sinusoidal behavior at a certain droplet size. This behavior was initiated by the locally expanded decomposition gases and developed by the supply of N2H4droplets to the decomposition gases at relatively high temperatures. In cases of larger and smaller droplet sizes, the sinusoidal behavior was not significant due to less evaporation of the N2H4droplets and a lower temperature of the N2H4vapor, respectively. The sinusoidal behavior of the decomposition flames enhanced the mixing and reactions of the fuel components (i.e., N2H4, NH3, and H2). The present study demonstrated a large impact of droplet size on flame dynamics, suggesting that a fine spray is not always better for hypergolic propellant combustion to consume the fuel components quickly. [ABSTRACT FROM AUTHOR]

In this paper we will analyze the impact of Russian launch vehicles (LV) Proton and Soyuz on the terrestrial ecosystems of the Central Kazakhstan and Altai-Sayan region. All LV were launched from the Baikonur Cosmodrome in 2014–2016. The operation of the LV leads to local mechanical, chemical, and pyrogenic effects on the ecosystems of separating stages falling regions (FR). Mechanical disturbances of ecosystems on the Proton first stage falling sites (FS) took the form of soil and vegetation cover damage when the large fragments scattered over an area of 1229 m 2 and small fragments scattered over an area of 22,044 m 2 . The area of vegetation fire reached 245,588 m 2 , and the leakage of propellant components (nitrogen tetroxide (NT) and unsymmetrical dimethylhydrazine (UDMH)) – up to 737 m 2 . We detected UDMH mainly in the snow of the Proton first stage FS, where its content reached up to 2200 mg/dm 3 (the most common range of concentrations was 0.1–0.2 mg/dm 3 ) and in sporadic soil samples it was up to 1.5 mg/kg. In early spring the content of UDMH was 0.09–0.69 mg/kg in the soil, in summer it did not exceed 0.05 mg/kg. In the NT leakage areas content of NO 3 – increased up to 22.3 g/dm 3 in the snow and 24.8 g/kg in the soil. In the places of UDMH leakages, pH value in the snow and soil increased to 10.3 and 9.4, respectively, and the background values varied from 5.1 to 7.9 and from 6.6 to 8.3, respectively. The pollution of snow and soil by NT decreased in pH value to 0.9, and 2.3, respectively. In the cases of Soyuz side blocks, the scattering of FS of large and small fragments reached 325 and 43,627 m 2 , respectively, the area of vegetation fire – up to 8556 m 2 , and the leakage of propellant components – to 129 m 2 . The contents of total petroleum hydrocarbons in places of kerosene T-1 leakage increased to 4354 mg/dm 3 in the snow and to 45,167 mg/kg in the soil while background values were 0.03–0.05 mg/dm 3 and 5–84 mg/kg, respectively. The operation of the heavy vehicle during the evacuation of fragments of the LV first stage can expand the impact zone several times. In the FR of the Proton and Soyuz second stages the main impact is associated with the mechanical pollution of ecosystems with the fragments of fallen stages. We did not detect chemical transformation in the soil and snow during three years of observation. [ABSTRACT FROM AUTHOR]

Impinging liquid jets of monomethylhydrazine (MMH) and MON3 (i.e. dinitrogen tetroxide containing 3 wt% NO) were observed with high-speed cameras in order to explore fluid and flame behaviors in the impinging region. At the beginning of the impingement, a portion of the fluids that turned yellow in the impinging region was considered the NO 2 and N 2 O 4 vapors or chemical condensate, while the white fogs were regarded mainly as the spreading MMH vapor. Auto-ignition occurred less than 5 ms after impingement, followed by the propagation of orange flames. Due to hypergolicity, orange and blue–white flames were held near the rim of the liquid sheet of the impinging jets. The orange flames tended to exist near the MON3 jets, while the blue–white flames spread on the side of the MMH jets. When atomization was so weak that a long liquid sheet was formed, the MMH and MON3 jets were separated by the orange flames. The atomization performance significantly affected the ignition delay time, as well as combustion efficiency and stability. However, even under strong atomization conditions, the liquid MMH and MON3 jets at a steady state are regarded as the impinging immiscible fluid jets. [ABSTRACT FROM AUTHOR]

Activated carbon fabric (ACF) obtained from novolacs carbonization was used as substrate for N2O4adsorption. In one case the ACF was soaked and impregnated with liquid N2O4(ACF-liq-N2O4) reaching an adsorbate loading of about 1400 mg N2O4/g(ACF). Another ACF was prepared by adsorption of a gaseous stream of N2O4(ACF-gas-N2O4). This time the adsorbate loading was found at 757 mg N2O4/g(ACF). The two samples were studied with FT-IR spectroscopy before and after the desorption. The amount of N2O4in the ACF samples was determined gravimetrically, thermogravimetrically (TGA) and by wet chemical analysis after hydrolysis of the samples in water. The N2O4/NO2desorption from the ACF was studied by TGA-FTIR analytical technique and it was found that the NO2desorption starts at low temperatures and reaches a peak at 158–170°C. In the correspondence of the NO2release peak starts also the gasification of the oxygenated groups present in the ACF with a simultaneous peak in the emission of CO2and CO. From the DSC analysis of ACF-liq-N2O4and ACF-gas-N2O4the heat of adsorption of N2O4was determined and found at –21.8 kcal/mol for ACF-liq-N2O4and –16.2 kcal/mol for ACF-gas-N2O4. The electrical resistivity of the ACF before and after the N2O4adsorption was measured. [ABSTRACT FROM AUTHOR]

Ionic liquids that are stable toward oxidation and nitration and are based on the 1-n-butyl-3-methylimidazolium cation (BMIm+) can be used as solvents and reaction media for copper dissolution in liquid dinitrogen tetraoxide N2O4. The ionic liquid not only favors the dissociation of N2O4 into NO+ and NO3−, but also takes part in the formation of different crystalline products. Thus, NO[BF4], NO[Cu(NO3)3] and (BMIm)2[Cu2(CF3COO)6] were prepared using (BMIm)A, A− = [BF4]−, (CF3SO2)2N−, CF3COO−, respectively. The formation of a certain product is determined by the nature of the anion A− and the relative solubility of the reaction products in the ionic liquid. Crystals of NO[BF4] were also prepared directly from a mixture of N2O4 and BMImBF4. According to XRD single-crystal structure analysis, the structure of NO[BF4] consists of tetrahedral [BF4]− anions and nitrosonium NO+ cations; the formation of these ions prove the heterolytic dissociation of N2O4 dissolved in the ionic liquid. The crystal structure of the earlier unknown binuclear copper trifluoroacetate (BMIm)2[Cu2(CF3COO)6] were determined by X-ray diffraction. The peculiarity of this dimer compared to the majority of known dimeric copper(ii) carboxylates is the unusually long Cu…Cu distance (3.15 Å), with Cu(ii) ions demonstrating an atypical coordination of a distorted trigonal bipyramid formed by five O atoms of five trifluoroacetate groups. [ABSTRACT FROM AUTHOR]

The heat effects in the case of manufacture process of nitration 1,2,4-triazol-5-one (TO) in nitric acid solution were distinguished and determined using the calorimeters of DSC200F3, C80 and E856; the influence of these heats on the total exothermic effect during manufacture process was examined. Five kinds of thermal effects were differentiated and measured: the heat of process of dosing TO (Δ H ), the heat of dissolution TO (Δ H ), the heat of reaction (Δ H ), the heat of crystallization of NTO (Δ H ) and the heat ( $$\Delta H_{{{\text{HNO}}_{{\text{3}}} }}$$ ) caused by changes in concentration of nitric acid. The data on dissolution heats of TO and NTO in nitric acid with different concentrations in the 0-98.4 % range and isobaric heat capacity of TO over the temperature range of 0-90 °C are determined. The main results of examination showed: The Δ H was the main contribution to the total exothermic effect during synthesis processes in 66-96 % HNO; the contribution ability rank of other four thermal effects varied based on the concentration of HNO adopted. [ABSTRACT FROM AUTHOR]

It has been shown previously that, under acidic conditions, 3-nitro-1,2,4-triazol-5-one (NTO) and 2,4-dinitroanisole (DNAN) degrade in the presence of iron/copper bimetal particles; the reactions can be modeled by pseudo-first-order kinetics. This study investigates the reaction mechanisms of the degradation processes under different conditions. Batch studies were conducted using laboratory-prepared solutions and an industrial insensitive munition-laden (IMX) wastewater. The influence of parameters such as initial pH of the solution, copper/iron (Fe-Cu) contact, and solid/liquid ratio were systematically investigated to assess their impact on the reaction kinetics. These parameters were subsequently incorporated into pseudo-first-order decomposition models for NTO and DNAN. The activation energies for the degradation reactions were 27.40 and 30.57 kJ mol, respectively. Degradation intermediates and products were identified. A nitro-to-amino pathway, which ultimately may lead to partial mineralization, is postulated. The amino intermediate, aminonitroanisole, was detected during DNAN degradation, but for NTO, aminotiazolone is suggested. Additionally, urea was identified as a degradation product of NTO. [ABSTRACT FROM AUTHOR]

Insensitive munitions, such as 3-nitro-1,2,4-triazol-5-one (NTO), are being considered by the U.S. Army as replacements for conventional explosives. Environmental emissions of NTO are expected to increase as its use becomes widespread; but only a few studies have considered the remediation of NTO-contaminated sites. In this study, sequential anaerobic-aerobic biodegradation of NTO was investigated in bioreactors using soil as inoculum. Batch bioassays confirmed microbial reduction of NTO under anaerobic conditions to 3-amino-1,2,4-triazol-5-one (ATO) using pyruvate as electron-donating cosubstrate. However, ATO biodegradation was only observed after the redox condition was switched to aerobic. This study also demonstrated that the high-rate removal of NTO in contaminated water can be attained in a continuous-flow aerated bioreactor. The reactor was first fed ATO as sole energy and nitrogen source prior to NTO addition. After few days, ATO was removed in a sustained fashion by 100%. When NTO was introduced together with electron-donor (pyruvate), NTO degradation increased progressively, reaching a removal efficiency of 93.5%. Mineralization of NTO was evidenced by the partial release of inorganic nitrogen species in the effluent, and lack of ATO accumulation. A plausible hypothesis for these findings is that NTO reduction occurred in anaerobic zones of the biofilm whereas ATO was mineralized in the bulk aerobic zones of the reactor. [ABSTRACT FROM AUTHOR]

Snow cover contamination is assessed in the impact areas of the first stage of the expandable launch system Proton in Central Kazakhstan. It was revealed that the chemical effect ofpropellants on the snow cover is local. The increase in the content of the following high-toxic substances in the snow was registered: unsymmetrical dimethylhydrazine, nitrosodimethylamine, and nitrate and nitrite ions. The most part of the pollutants is localized in the upper 5-cm snow layer. Nitrogen tetroxide decreases the value of pH, and unsymmetrical dimethylhydrazine increases it. The inflow of calcareous soil particles to the atmosphere and their subsequent fallout result in the alkalization of snow and in the neutralization of acidification by nitrogen tetroxide accompanied by the formation ofthe salts of nitric acid and nitrous acid. [ABSTRACT FROM AUTHOR]

Meeting the requirements for insensitive munitions remains a complex route, where all the steps of the production process have to be addressed. NTO is a choice component, especially for large munitions. Various compositions have been optimized, which are now available, in pressed or cast PBX as well as melt cast formulations. Standard products such as RDX have been improved by the synthesis or crystallization methods, giving reduced sensitivity formulations. Some cast PBX can sustain severe shaped charge jet impacts, thanks to their large critical diameter, and are candidates as main filling of large munitions such as IM Mk82. The formulation step is addressing not only new binder principles, allowing an increase in the filler and thus energy contents, but also a bi-component innovative method to get a semi continuous filling process where the pot life is no longer an issue. Finally a partial toolset for designing IM features is proposed with a recent example of successful application. [ABSTRACT FROM AUTHOR]

This article presents three experiments that make use of a syringe - a cheap, easily available and normally discarded item - to carry out conventional experiments. They use a minimum of chemicals, little or no heating and reduce the need for costly equipment by reusing old syringes. [ABSTRACT FROM AUTHOR]

Device and process of oxidization, degassing, acidity adjustment of 1BP (The Pu production feed from U/Pu separation section) from APOR process (Advanced Purex Process based on Organic Reductants) were improved through rational design and experiments. The device was simplified and the process parameters, such as feed position and flow ratio, were determined by experiments. Based on this new device and process, the reductants N , N -dimethylhydroxylamine (DMHAN) and methylhydrazine (MMH) in 1BP solution could be oxidized with much less N 2 O 4 consumption. [ABSTRACT FROM AUTHOR]

A blue-emitting SrB 2 O 4 :Eu 2+ phosphor with high color purity was synthesized by conventional high-temperature solid state reaction method. Its crystal structure, luminescence properties and concentration quenching mechanism were investigated. This phosphor can be effectively excited within the broad near ultraviolet wavelength region from 270 to 350 nm and feature a satisfactory blue-emitting performance. In particular, the color purity of the as-synthesized SrB 2 O 4 :Eu 2+ phosphor is much better than that of the blue emitting, commercial compound BaMgAl 10 O 7 :Eu 2+ . The emission peaks located at 448 nm, which can be attributed to the transitions of 4f 6 5d 1 to 4f 7 of Eu 2+ ions. It is shown that the 6.0 mol% doping concentration of Eu 2+ ions in SrB 2 O 4 :Eu 2+ phosphor is optimum, and that the concentration quenching occurs when Eu 2+ concentration is beyond 6.0 mol%. The physical mechanism of concentration quenching mechanism can be explained by the dipole–dipole interaction of Eu 2+ ions, and the critical transfer distance was determined to be 13.98 Å. The present work suggests that the SrB 2 O 4 :Eu 2+ phosphor is a promising blue-emitting material for near-UV white light-emitting diodes. [ABSTRACT FROM AUTHOR]

2-Dimethyl amino ethyl azide (DMAZ) has attracted much attention as a suitable liquid fuel replacement for monomethyl hydrazine (MMH) and unsymmetrical dimethyl hydrazine (UDMH) in propellant systems because, in contrast to these fuels, it is nontoxic. In this article, performance and ignition delay of DMAZ were studied with common liquid oxidizers including inhibited red fuming nitric acid (IRFNA), anhydrous nitric acid, dinitrogen tetroxide (N2O4), hydrogen peroxide (H2O2), liquid oxygen (LOX), and mixed oxides of nitrogen (MON). Results showed that combustion of DMAZ and LOX provides the highest specific impulse (305.8 s) compared to the other mentioned oxidizers. Moreover, DMAZ and H2O2gave the highest density specific impulse (360.2 s) at an optimum oxidizer-to-fuel ratio due to the higher density of hydrogen peroxide. Furthermore, a mixture of DMAZ and N2O4had the minimum ignition delay time (68 ms). Therefore, it seems that the DMAZ-N2O4propellant combination is suitable for space systems. [ABSTRACT FROM AUTHOR]

The heterodinuclear complexes [CuLnL(NO3)2(H2O)3MeOH]NO3·MeOH (Ln?=?Ho (1), Tm (2), Yb (3), and Lu (4); L?=?N,N?-bis(5-bromo-3-methoxysalicylidene)propylene-1,3-diamine) have been synthesized and characterized by elemental analysis, FTIR, thermogravimetric (TG)/differential scanning calorimetry (DSC), TG-FTIR, single crystal X-ray diffraction studies, and magnetic measurements. The isostructural compounds crystallized in the monoclinic space groupP21/n. The rare earth(III) cation is nine coordinate, whereas the coordination number for copper(II) is six. The complexes were stable at room temperature. The thermal decomposition products were mainly CH3OH, H2O, CH3Br, NOx(x?=?1 or 2), CO2, and CO. The magnetic properties of1–3were dominated by the crystal field effect on the LnIIIsite, masking the magnetic interaction between the paramagnetic centers. The CuII–LuIIIpair in4showed no significant interaction, which is in accord with the diamagnetic nature of the ground state for lutetium(III). The heterodinuclear compounds [CuLn(L)(NO3)2(H2O)3MeOH]NO3·MeOH (where Ln?=?Ho (1), Tm (2), Yb (3), and Lu (4)) have been synthesized and characterized by elemental analysis, FTIR, TG/DSC, TG-FTIR, single crystal X-ray diffraction studies, and magnetic measurements. The complexes are isostructural and crystallize in the monoclinic space groupP21/n. The magnetic properties of1,2, and3are dominated by the crystal field effect on the LnIIIsite, masking the magnetic interaction between the paramagnetic centers. [ABSTRACT FROM AUTHOR]

Abstract: Ablation property of CVD-SiC coated PIP-C/SiC composites was investigated by using a hot-firing test in a liquid propellant rocket motor. The effect of the combustion temperature was studied; then ablation mechanisms of coated composites were discussed. The degradation of PIP-C/SiC composites was determined by analyzing surface variations. Two different ablation modes of C/SiC composites were discussed. The coupling effects (thermal–mechanical denudation and thermal–chemical erosion) worsened the degradation of the coated PIP-C/SiC composites. CVD-SiC coating provided better protection for the composites under the MMH/N2O4 bipropellants tests. [Copyright &y& Elsevier]

ABSTRACT To meet the demands of less-sludge deposit and longer-service life, turbine oils need to possess superior oxidation stability. Commercially available turbine oil nitrogen tetroxide (NTO) became green in an actual turbine, which was a risk of serious damage to turbine bearing and lubricating systems. By analysis of pH discoloration, infrared spectroscopy, it is found that the chromogenic materials in in-service oil of NTO (UTO) were the oxidation products of diphenylamine antioxidant at low temperatures. Then, a method utilising Fenton reagent was developed to accelerate oxidation process for assessment of discoloration of turbine oil in service. By screening of experimental conditions, the colour and structure of chromogenic materials in accelerated oxidation products from NTO are the same as those of in-service oil of NTO. Turbine oils in different formulation are oxidised by Fenton reagent in preceding condition. The colours of oxidation products are consistent with the results of ASTM D943 after 1000 h test. This study also provided a better understanding of the oxidation process affecting lubricants and the functional mode of the radical scavenger antioxidant. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Organic gel propellants are promising candidates for a variety of rocket motor and scramjet applications, since they are intrinsically safe and provide high performance. It is well known that organic gel fuel droplets exhibit distinct combustion characteristics compared with conventional liquid fuel droplets, and furthermore an understanding of the ignition delay and lifetime of these droplets is critical to the improvement of combustor design. In this work, investigations of the combustion of unsymmetrical dimethylhydrazine (UDMH) organic gel droplets in different nitrogen tetroxide (NTO) oxidizing atmospheres were conducted using two sets of experimental apparatus. The combustion characteristics under different conditions of temperature and pressure were compared and analyzed based on the flame shapes observed during experimentation. From these trials, an unsteady combustion model was developed and used for the numerical simulation of spray-sized UDMH organic gel droplet combustion in an NTO atmosphere. The hypergolic ignition and burning characteristics of the organic gel droplets under conditions simulating either engine startup or steady state combustion were compared, and changes in ignition delay and droplet lifetime with ambient temperature and pressure were analyzed. The experimental and numerical results show that the UDMH organic gel droplets exhibit periodic swell-burst behavior following the formation of an elastic film at the droplet surface. Each droplet burst results in fuel vapor ejection and flame distortion, the intensity of which declines with increasing ambient pressure. However, the swell-burst period is extended with increasing ambient pressure, which results in potential flameout. Under conditions of low temperature and pressure similar to those at engine startup, the ignition delay and lifetime of spray-sized gel droplets decrease with increasing temperature or pressure, although there is a sharp increase in droplet lifetime when the ambient pressure reaches a critical value associated with flameout. The ignition delay was found to be a rate-limited phenomenon linked to the droplet heating rate. The proportion of ignition delay and droplet lifetime due to droplet heating-up decreased with increasing temperature or decreasing pressure. Conversely, at high temperatures and pressures simulating the engine's steady state operating conditions, the droplets were observed to flameout after several swell-burst periods and both ignition delay and lifetime decreased monotonically with increasing temperature or pressure. The ignition delay time was determined to be rate-limited by gas phase chemical reactions and contributed very little to the overall droplet lifetime compared with the engine startup condition. [ABSTRACT FROM AUTHOR]

The propulsion of most of the operating satellites comprises monopropellant (hydrazine--NH) or bipropellant (monometilydrazine-MMH and nitrogen tetroxide) chemical systems. When some sample of the propellant tested fails, the entire sample lot shall be rejected, and this action has turned into a health problem due to the high toxicity of NH. Thus, it is interesting to know hydrazine thermal behavior in several storage conditions. The kinetic parameters for thermal decomposition of hydrazine in oxygen and nitrogen atmospheres were determined by Capela-Ribeiro nonlinear isoconversional method. From TG data at heating rates of 5, 10, and 20 °C min, kinetic parameters could be determined in nitrogen ( E = 47.3 ± 3.1 kJ mol, ln A = 14.2 ± 0.9 and T = 69 °C) and oxygen ( E = 64.9 ± 8.6 kJ mol, ln A = 20.7 ± 3.1 and T = 75 °C) atmospheres. It was not possible to identify a specific kinetic model for hydrazine thermal decomposition due to high heterogeneity in reaction; however, experimental f( α) g( α) master-plot curves were closed to F model. [ABSTRACT FROM AUTHOR]

Insensitive high explosives are being used in military munitions to counteract unintended detonations during storage and transportation. These formulations contain compounds such as 2,4-dinitroanisole (DNAN) and 3-nitro-1,2,4-triazol-5-one (NTO), which are less sensitive to shock and heat than conventional explosives. We conducted a series of four tests on snow-covered ice utilizing 60-mm mortar cartridges filled with 358 g of PAX-21, a mixture of RDX, DNAN, and ammonium perchlorate. Rounds were detonated high- and low-order using a fuze simulator to initiate detonation. Blow-in-place (BIP) operations were conducted on fuzed rounds using an external donor charge or a shaped-charge initiator. Results indicate that 0.001 % of the original mass of RDX and DNAN were deposited during high-order detonations, but up to 28 % of the perchlorate remained. For the donor block BIPs, 1 % of the RDX and DNAN remained. Residues masses for these operations were significantly higher than for conventional munitions. Low-order detonations deposited 10-15 % of their original explosive filler in friable chunks up to 5.2 g in mass. Shaped-charge BIPs scattered 15 % of the filler and produced chunks up to 15 g. Ammonium perchlorate residue masses were extremely high because of the presence of large AP crystals, up to 400 μm in the recovered particles. [ABSTRACT FROM AUTHOR]

Abstract: A new potentially hexadentate N2O4 Schiff base ligand, H2L derived from condensation reaction of an aromatic diamine and salicylaldehyde, and its metal complexes were characterized by elemental analyses, IR, UV–Vis, EI–MS, 1H and 13C NMR spectra, as well as conductance measurements. It has been originated that the Schiff base ligand with Cu(II), Ni(II), Co(II), Cd(II) and Zn(II) ions form mononuclear complexes on 1:1 (metal:ligand) stoichiometry. The conductivity data confirm the non-electrolytic nature of the complexes. Also the crystal structures of the complexes [ZnL] and [CoL] have also been determined by using X-ray crystallographic technique. The Zn(II) and Co(II) complexes show a tetrahedral configuration. Electronic absorption spectra of the Cu(II) and Ni(II) complexes suggest a square-planar geometry around the central metal ion. The synthesized compounds have antibacterial activity against the three Gram-positive bacteria: Bacillus cereus, Enterococcus faecalis and Listeria monocytogenes and also against the three Gram-negative bacteria: Salmonella paraB, Citrobacter freundii and Enterobacter aerogenes. The results showed that in some cases the antibacterial activity of complexes were more than nalidixic acid and amoxicillin as standards. [Copyright &y& Elsevier]

The detection of atmospheric NO3 radicals is still challenging owing to its low mixing ratios (≈1 to 300 pptv) in the troposphere. While long-path differential optical absorption spectroscopy (DOAS) is a well established NO3 detection approach for over 25 yr, newly sensitive techniques have been developed in the past decade. This publication outlines the results of the first comprehensive intercomparison of seven instruments developed for the spectroscopic detection of tropospheric NO3. Four instruments were based on cavity ring-down spectroscopy (CRDS), two utilised open-path cavity enhanced absorption spectroscopy (CEAS), and one applied "classical" long-path DOAS. The intercomparison campaign "NO3Comp" was held at the atmosphere simulation chamber SAPHIR in Jülich (Germany) in June 2007. Twelve experiments were performed in the well mixed chamber for variable concentrations of NO3, N2O5, NO2, hydrocarbons, and water vapour, in the absence and in the presence of inorganic or organic aerosol. The overall precision of the cavity instruments varied between 0.5 and 5 pptv for integration times of 1 s to 5min; that of the DOAS instrument was 9 pptv for an acquisition time of 1 min. The NO3 data of all instruments correlated excellently with the NOAA-CRDS instrument, which was selected as the common reference because of its superb sensitivity, high time resolution, and most comprehensive data coverage. The median of the coefficient of determination (r2) over all experiments of the campaign (60 correlations) is r2 =0.981 (25th/75th percentiles: 0.949/0.994; min/max: 0.540/0.999). The linear regression analysis of the campaign data set yielded very small intercepts (1.2±5.3 pptv) and the average slope of the regression lines was close to unity (1.02, min: 0.72, max: 1.36). The deviation of individual regression slopes from unity was always within the combined accuracies of each instrument pair. The very good correspondence between the NO3 measurements by all instruments for aerosol-free experiments indicates that the losses of NO3 in the inlet of the instruments were determined reliably by the participants for the corresponding conditions. In the presence of inorganic or organic aerosol, however, differences in the measured NO3 mixing ratios were detectable among the instruments. In individual experiments the discrepancies increased with time, pointing to additional NO3 radical losses by aerosol deposited onto the inlet walls of the instruments. Instruments using DOAS analyses showed no significant effect of aerosol on the detection of NO3. No hint of a cross interference of NO2 was found. The effect of non-Lambert-Beer behaviour of water vapour absorption lines on the accuracy of the NO3 detection by broadband techniques was small and well controlled. The NO3Comp campaign demonstrated the high quality, reliability and robustness of performance of current state-of-the-art instrumentation for NO3 detection. [ABSTRACT FROM AUTHOR]

To gain an atomistic-level understandingon physical and chemicalprocesses occurring at the interfaces of hypergolic propellants, wecarried out the first reactive dynamic (ReaxFF) simulations to studythe reactive hypergolic mixture of monomethylhydrazine (MMH) and dinitrogentetroxide (NTO), in comparison with the ethanol (EtOH) and NTO mixturethat is reactive but nonhypergolic. Our studies show that the MMH–NTOmixture releases energy more rapidly than the EtOH–NTO mixtureupon mixing the fuels and oxidizers. We found that the major earlychemical reactions between MMH and NTO are hydrogen abstractions andN–N bond scissions. The MMH–NTO mixture has more reactionchannels than EtOH–NTO based on statistical analyses of chemicalreaction events and channels at early stages of the dynamics. Analyzingthe evolution of product distribution over reaction time shows thatthe oxidizer (NO2) diffuses into the fuels (MMH or EtOH)for the occurrence of reactions, demonstrating the influence of physicalmixing on chemical reactions. Our simulations suggest that effectivehypergolic systems require fuels with low energy barriers of H abstractionsand/or bond scissions and oxidizers with large diffusion mobilityfor efficient physical mixing. [ABSTRACT FROM AUTHOR]

Abstract: 3-Nitro-1,2,4-triazol-3-one (NTO) is an insensitive but powerful explosive. In this paper, Ag nanofilm was used as the surface-enhanced Raman spectroscopy (SERS) substrate for analysis of explosive NTO. The detection limit of NTO in deionized water (DI) water and an aged tap water were 35μg/L (0.35ng) and 0.35mg/L (3.5ng), respectively. pH variation in the range from 4.7 to 9.1 did not affect the position of SERS NTO bands, but affected the band intensity. The effect of eight common ions in natural waters on the SERS of 3.5mg/L NTO was evaluated. K+, Na+, Ca2+ and Mg2+ at 100mg/L did not have significant negative effect on the SERS of 3.5mg/L NTO as NTO has a stronger affinity for Ag nanofilm than that for the cations. SO4 2−, CO3 2− and NO3 − (100mg/L) also did not have significant negative effect on the SERS of 3.5mg/L NTO. Cl− in the range of 1–50mg/L can activate the SERS of NTO. At the high concentration of 100mg/L Cl−, the activation and deactivation of the SERS of 3.5mg/L NTO were both observed, but the overall average effect of Cl− was not very negative. [Copyright &y& Elsevier]