Energy potential of solid composite propellants based on 1,1-diamino-2,2-dinitroethylene

To obtain new formulations for solid composite propellants for creating composites with low sensitivity to mechanical stress and improved thermal stability, the energy potential of composites based on 1,1-diamino-2,2-dinitroethylene (FOX-7) and additionally containing a hydrocarbon or active binder, aluminum, and inorganic oxidant was studied. A formulation with 60% FOX-7 and 19 vol % active binder can be created which is characterized by a specific impulse I _sp ~ 251 s, density ~1.91 g/cm³, and T _c below 3600 K. The composites containing FOX-7 have smaller specific impulse values than the same formulations with HMX: by 10 s at 60% FOX-7 and by 4 s at 30% HMX.     

1-氯-1,1-二硝基-2-（N-氯脒基）乙烷的波谱解析

在酸性条件下,用高锰酸钾氧化1,1-二氨基-2,2-二硝基乙烯（FOX-7）时,得到一种非预期的新化合物。通过元素分析、红外、核磁和质谱等波谱分析数据,鉴定样品的结构为1-氯-1,1-二硝基-2-（N-氯脒基）乙烷,并对其裂解途径进行了推断。     

Theoretical study on the mechanism of the reaction of FOX-7 with OH and NO2 radicals: bimolecular reactions with low barrier during the decomposition of FOX-7

The decomposition of 1,1-diamino-2,2-dinitroethene (FOX-7) attracts great interests, while the studies on bimolecular reactions during the decomposition of FOX-7 are scarce. This study for the first time investigated the bimolecular reactions of OH and NO₂ radicals, which are pyrolysis products of ammonium perchlorate (an efficient oxidant usually used in solid propellant), with FOX-7 by computational chemistry methods. The molecular geometries and energies were calculated using the (U)B3LYP/6-31++G(d,p) method. The rate constants of the reactions were calculated by canonical variational transition state theory. We found three mechanisms (H-abstraction, OH addition to C and N atom) for the reaction of OH + FOX-7 and two mechanisms (O abstraction and H abstraction) for the reaction of NO₂ + FOX-7. OH radical can abstract H atom or add to C atom of FOX-7 with barriers near to zero, which means OH radical can effectively degrade FOX-7. The O abstraction channel of the reaction of NO₂ + FOX-7 results in the formation of NO₃ radical, which has never been detected experimentally during the decomposition of FOX-7.     

Adsorption and thermodynamics studies of U(VI) by composite adsorbent in a batch system

The adsorption of U(VI) from aqueous solutions onto composite adsorbent (algistar) has been studied using a batch adsorber. The parameters that affect the U(VI) sorption, such as contact time, solution pH, initial U(VI) concentration, and temperature, have been investigated and optimized conditions determined. Equilibrium isotherm studies were used to evaluate the maximum sorption capacity of composite adsorbent, and experimental results showed this to be 43.10 mg/g. The adsorption patterns of metal ions on composite adsorbent followed the Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherms. The Freundlich, Langmuir, and D–R models have been applied, and the data correlate well with Langmuir model, and that the sorption is physical in nature (the sorption energy E _ads = 12.90 kJ/mol). Thermodynamic parameters (∆H _ads^o = −41.08 kJ/mol, ∆S _ads^o = −68.00 J/mol K, ∆G _ads (298.15 K) = −20.81 kJ/mol) showed the exothermic heat of adsorption and the feasibility of the process. The results suggested that the composite adsorbent is suitable as a sorbent material for recovery and biosorption/adsorption of uranium ions from aqueous solutions.     

双(2,2-二硝基丙基)甲缩醛的结构和爆轰性能的量子化学研究

利用B3LYP/6-311+G(2d,p)方法对一种新型含能增塑剂双(2,2-二硝基丙基)甲缩醛进行几何优化,计算了其红外光谱、生成焓和爆轰特性. 分析了最弱键的键离解能和键级并预测了目标化合物的热稳定性. 结果表明双(2,2-二硝基丙基)甲缩醛中的四个N-NO₂键的键离解能都为164.38 kJ/mol. 表明目标化合物是一个热力学性能稳定的化合物. 以凝聚相生成焓和分子密度为基础,采用Kamlet-Jacobs方法预测其爆速和爆压. 目标化合物的晶体结构属于P21空间群.     

1,2-丙二醇辅助溶胶凝胶法制备NASICON型Li1.3Al0.3Ti1.7(PO4)3固体电解质

通过1,2-丙二醇辅助的溶胶凝胶方法制备了具有NASICON结构的固体锂离子导体Li_1.3Al_0.3Ti_1.7(PO₄)₃,并且通过热重/差热分析、X射线衍射分析、比表面观测、电化学阻抗谱以及计时电流法等对其各方面性能进行了表征. 通过使用1,2-丙二醇辅助方法,未额外添加络合剂,也未对pH值进行调整得到均匀的溶胶前驱体,并且通过在850～950oC不同高温段烧结得到无杂相的具有NASICON结构     

Oxygen adsorption on the kinked Pt(321) surface

Oxygen adsorption and desorption were characterized on the kinked Pt(321) surface using high resolution electron energy loss spectroscopy and thermal desorption spectroscopy. Molecular oxygen adsorbs mainly as a peroxo-like species at 100K with a heat of desorption of about 22 k^J/mol. Some of the molecular oxygen also adsorbs dissociatively at 100K. Atomic oxygen is adsorbed in three states. One state is due to adsorption on the terraces and another state is due to adsorption along the rough step sites. The heat of desorption of both of these states approximately equal and decreases from 290 k^J/mol to 195kJ/mol with increasing coverage. Atomic oxygen is also observed to adsorb in another state which is interpreted as adsorption at an on-top site.     

Characteristics and Kinetics of Thermal Degradation of Fluoroether Rubber

An advanced, heat-resistant fluoroether rubber (FM-20) was subjected to dynamic thermogravimetric analysis (TGA) in the air atmosphere. The results suggested that its thermal degradation process can be divided into two parts. As the heating rate increased, the initial decomposition temperature and degradation temperature would move to higher ranges. The apparent activation energy of thermal decomposition, calculated by the Kissinger, Friedman and Flynn-Wall-Ozawa methods were 209, 240, and 211kJ/mol, respectively. Furthermore, the probable thermal degradation mechanism was also analyzed by the Coats-Redfern method. As a result, the most reasonable thermal degradation mechanism of FM-20 was g (α) = α^3/2     

Studies of molecular motions in the three phases of 1,1′,2,2′-tetrachloroferrocene by Mössbauer and1H-NMR spectroscopy

The molecular motions in the three phases of 1,1′,2,2′-tetrachloroferrocene below m.p. were studied by using⁵⁷Fe-Mossbauer and¹H FT-NMR spectroscopy. In the plastic phase at the low temperature, a rotational mode around the pseudo C₅ molecular axis was found to be activated with activation energy of 15 kJ/mol and in the higher temperature phase the rotational mode of the pseudo C₅ axis itself was found to be activated with activation energy of 23 kJ/mol in addition to the rotational mode around the pseudo C₅ axis. On the⁵⁷Fe-Mossbauer spectra, a steep decrease of the areal intensity was observed above the first transition temperature. The areal intensity in the lower plastic phase was estimated to be less than a few percent relative to that at 298 K. The results were discussed in terms of different possibilities for the movement of the molecules.     

A re-evaluation of the heat capacity of cerium zirconate (Ce2Zr2O7)

The heat capacity of cerium zirconate pyrochlore, Ce₂Zr₂O₇, was measured from 0.4 to 305 K by hybrid adiabatic relaxation method for various magnetic field strengths. Magnetisation measurements were performed on the sample also. The results revealed a low-temperature anomaly that showed Schottky-type characteristics with increasing magnetic field strength. The estimated entropy due to the magnetic ordering of the two Ce³⁺ moments is 1.37R, close to the theoretical value for a doublet ground state (1.39R). The enthalpy increments relative to 298.15 K were measured by drop calorimetry from 531 to 1556 K. The obtained results significantly differ from those reported in the literature; the origin of the discrepancy is due to the probable oxidation of the pyrochlore structure into fluorite.     

Strategy of improving the stability and detonation performance for energetic material by introducing the boron atoms

A novel stable energetic compound (E)‐1,2‐diamino‐1,2‐dinitrodiboron (DANB) was theoretically designed based on the structure of 1,1‐diamino‐2,2‐dinitroethene (FOX‐7). Atomization method in combination with Hess' law was used to predict the heat of formation. The detonation velocity (D) and detonation pressure (P) of DANB were approximatively estimated by using Kamlet–Jacobs equations. As a result, DANB has huge heat of formation (2013.5 kJ/mol) and specific enthalpy of combustion (?26.4 kJ/g). Furthermore, DANB possesses high crystal density (1.85 g/cm³) and heat of detonation (5476.0 cal/g), which lead to surprising detonation performance (D = 10.72 km/s, P = 51.9 GPa) that is greater than those of FOX‐7 (D = 8.63 km/s, P = 34.0 GPa) and CL‐20 (D = 9.62 km/s, P = 44.1 GPa). More importantly, DANB is very stable because its bond dissociation energy of the weakest bond (BDE = 357.8 kJ/mol) is larger than those of the most common explosives, such as FOX‐7 (BDE = 200.4 kJ/mol), CL‐20(BDE = 209.2 kJ/mol), HMX(BDE = 165.7 kJ/mol), and RDX (BDE = 161.4 kJ/mol). Therefore, our results show that DANB is a promising candidate for stable and powerful energetic material.     

Developments in geothermal energy in Mexico—Part thirty-three. Simultaneous determination of the thermal properties of geothermal drill cores

Thermal conductivity, thermal diffusivity and specific heat capacity of five drill cores from the Los Humeros and La Primavera geothermal fields were obtained via parameter estimation. The data were obtained by fitting an analytical model to the transient temperature rise caused by a line source of heat of constant strength located along the axis of the samples. The model was obtained from the solution to the problem of an infinite region bounded internally by a hollow circular cylinder with thermal contact resistance at the cylinder surface (J. H. Blackwell, Transient heat flow problems in cylindrical geometry, Ph.D. Thesis, University of Western Ontario Canada, London, Canada, 1952). Results were obtained for fused quartz and a Berea sandstone for calibration purposes and the agreement with known properties for these samples showed maximum differences of 10%. Results obtained for a dry drill core from the Los Humeros field showed a thermal conductivity of 1.36 W m⁻¹ K⁻¹, a diffusivity of 0.54 × 10⁶ m² s⁻¹ and a specific heat capacity of 0.96 kJ kg⁻¹ K⁻¹. Results for dry drill cores from the La Primavera geothermal field showed thermal conductivities between 1.53 and 2.51 W m⁻¹ K⁻¹ while thermal diffusivity varied from 0.71 to 1.0 × 10⁻⁶ m² s⁻¹. Specific heat capacity varied from 0.73 to 1.03 kJ kg⁻¹ K⁻¹. Results obtained for these cores under water saturation conditions showed significant increases in all three properties with the degree of increase being a function of the pore volume occupied by the water.     

Crystal structure and thermochemical properties of phase change materials bis(1-octylammonium) tetrachlorochromate

A new crystalline complex (C₈H₁₇NH₃)₂CdCl₄(s) (abbreviated as C₈Cd(s)) is synthesized by liquid phase reaction. The crystal structure and composition of the complex are determined by single crystal X-ray diffraction, chemical analysis, and elementary analysis. It is triclinic, the space group is P-1 and Z = 2. The lattice potential energy of the title complex is calculated to be U_POT (C₈Cd(s))=978.83 kJ·mol^-1 from crystallographic data. Low-temperature heat capacities of the complex are measured by a precision automatic adiabatic calorimeter over a temperature range from 78 K to 384 K. The temperature, molar enthalpy, and entropy of the phase transition for the complex are determined to be 307.3± 0.15 K, 10.15± 0.23 kJ·mol^-1, and 33.05± 0.78 J·K^-1·mol^-1 respectively for the endothermic peak. Two polynomial equations of the heat capacities each as a function of temperature are fitted by the least-square method. Smoothed heat capacity and thermodynamic functions of the complex are calculated based on the fitted polynomials.     

PuO分子X5Σ-态的势能函数及热力学函数的量子力学计算

在Pu的相对论有效原子实势近似和O原子6-311G^*全电子基函数下,用quadratic configuration interaction of singlely and doublely substitution(QCISD)方法计算了PuO分子基态X⁵Σ^-的Murrell-Sorbie解析势能函数和热力学函数,得到R_e,D_e,B_e,α_e,ω_关键词：     

Surface Ostwald-ripening and evaporation of gold beaded films on sapphire

The kinetics of morphological evolutions of gold nanoparticles on alumina, resulting from evaporation and surface Ostwald-ripening coarsening, have been investigated by means of Auger electron spectroscopy. When the fraction of the covered area is small, the kinetics of evaporation can be related to the desorption of adatoms. In the temperature range 943–1043 K we obtained the evaporation flux J(m^-2s^-1)=4.8×10²⁷exp[-196±9 (kJ/mol)/RT]. The experimental activation energy of evaporation of gold from a sapphire surface, Q_evap=196±9 kJ/mol, is lower than the tabulated value of enthalpy of sublimation of gold, ΔH_subl=368 kJ/mol. At lower temperatures, in the range 623–778 K, Ostwald-ripening experiments, carried out on nanosized clusters, yield the mass transfer surface diffusion coefficients of gold on alumina, D_s(m²/s)=2.6×10^-14exp[-58±9 (kJ/mol)/RT]. These results, providing information on the evolution of granular gold films such as those used in catalysts or sensors, are compared to previous data on similar systems. PACS 68.47.Jn; 68.43.Jk; 68.55.-a     

Thermal analysis of precipitation reactions in a Ti–25Nb–3Mo–3Zr–2Sn alloy

A study was undertaken on a Ti–25Nb–3Mo–3Zr–2Sn alloy using differential scanning calorimetry (DSC) in order to improve understanding of the precipitation reactions occurring during aging heat treatments. The investigation showed that isothermal ω phase can be formed in the cast and solution treated alloy at low aging temperatures. An exothermic peak in the temperature range of 300 to 400°C was detected for precipitation of the ω phase, with approximate activation energy of 176 kJ/mol. The ω phase begins to dissolve at temperatures around 400°C and precipitation of the α phase is favoured at higher temperatures between 400°C and 600°C. An exothermic peak with activation energy of 197 kJ/mol was measured for precipitation of the α phase. Deformation resulting in the formation of the stress induced α″ phase altered the DSC heating profile for the solution treated alloy. The exothermic peak associated with precipitation of the ω phase was not detected during heating of the deformed material and increased endothermic heating associated with recovery and recrystallisation was observed.     

Thermal Degradation Kinetics of Plasticized Poly (Vinyl Chloride) with Six Different Plasticizers

Plasticized PVC formulated with different kinds of normally used plasticizers, including bis(2-ethylhexyl) phthalate (DOP), dioctyl terephthalate (DOTP), acetyl tri-n-butyl citrate (ATBC), acetyl trioctyl citrate (ATOC), trioctyl trimellitate (TOTM), and a new vegetable devived plasticizer, isosorbide ester (ID-37), were prepared by a melt blending method. The effect of plasticizer on the thermal degradation behavior of plasticized PVC was investigated by thermal gravimetric analysis (TGA). The activation energies were calculated by three well known methods, developed by Flynn-Wall-Ozawa (FWO), Friedman and Kissinger, respectively. The TGA conducted in N₂ atmosphere showed that the type of plasticizer had an obvious influence on the thermal stability of plasticized PVC. It was found that the peak temperatures (T_P) of the thermal degradation processes shifted to higher temperature with the increase of the heating rate, with two processes being shown. The activation energy of the first thermal decomposition process (E₁), calculated by the Kissinger method, was between 118 and 130 kJ/mol, while the activation energy of the second thermal decomposition process (E₂) was between 261 and 305 kJ/mol, except 499 kJ/mol for the PVC/TOTM formulation. The corresponding values of E₁ and E₂ obtained by the Flynn-Wall-Ozawa method were similar to the above data. E of the sample with TOTM also showed a higher value than the others; the results demonstrated that the PVC plasticized with TOTM was more thermally stable than with the others. The activation energies for certain conversion degrees were calculated by the Friedman method and the FWO method. The value of activation energy for 20%, 50%, and 80% conversion calculated by the Friedman method, exhibited an apparent difference from that calculated by the Flynn-Wall-Ozawa method; the results showed that the value of E obtained by the Friedman method was much more reasonable than that obtained by the Flynn-Wall-Ozawa method.     

Medium range ordering and its effect on plasticity of Fe–Mn–B–Y–Nb bulk metallic glass

Glass formation, thermal properties and mechanical behavior were investigated in a series of Fe_{65? x} Mn₁₃B₁₇Y₅Nb _x (x = 0, 3, 5 and 7) alloys. Appropriate partial substitution of Fe by Nb in a Fe₆₅Mn₁₃B₁₇Y₅ bulk glassy alloy simultaneously enhances the glass-forming ability and the mechanical properties of the alloys. The Nb-containing glassy alloys exhibit an additional exothermic event in the supercooled liquid region. This exothermic reaction is correlated with the formation of medium range ordered (MRO) clusters originated from the large difference in mixing enthalpy between constituent elements such as Nb–Y (+30 kJ/mol) and Nb–B (?39 kJ/mol). The presence of MRO clusters in the as-cast state is dependent on the cooling condition from the liquid state, and plays a crucial role in providing plasticity in as-cast Fe–Mn–B–Y–Nb bulk metallic glass.     

Intermediate electronic relaxation betweenS=3/2 andS=1/2 states in Fe(J-mph)NO with a jäger-type ligand J-mph

The incomplete spin transition between the low-spin (LS) (S=1/2) and the intermediate-spin (IS) (S=3/2) states in the iron (III) complex Fe(J-mph)NO (mph=4-methyl-o-phenylene), centered atT _c≈212 K, has been studied with⁵⁷Fe Mössbauer spectroscopy and magnetic susceptibility measurements between 80 K and 320 K. The lineshape of the Mössbauer spectra is well reproduced by a two state stochastic relaxation model resulting in values of about 2·10⁶ s^?1 to 7·10⁶ s^?1 for the IS→LS transition rate constantk _IL. The kinetics of this spin transition can be described by an Arrhenius equation yielding activation energiesE _IL=1.1 (2) kJ/mol andE _LI=6.1 (2) kJ/mol for the IS→LS and LS→IS conversion, respectively.     

Theoretical Study on Mechanism of Cycloadditional Reaction Between Dichloro-Germylidene and Formaldehyde

用MP2/6-31G^*方法研究了单线态二氯亚甲基锗烯与甲醛环加成反应的反应机理,该反应有两条相互竞争的主反应通道,同时伴随着两中间体(INT3和INT4)副产物的生成. 第一条主反应通道所生成的物种为三员环中间体(INT1)和Ge-O顺位的四员环产物(P1);第二条主反应通道所生成的物种为Ge-O对位的扭曲四员环中间体(INT2)和氯迁移产物(P2);P1和INT2分别与甲醛(R2)的进一步作用而导致了两副产物的生成.