Determination of the Ortho-Para Ratio in Gaseous Hydrogen Mixtures

With the large volume uses of liquid hydrogen expected in the near future, specifically for the propulsion of space vehicles and other energy requirements, there is a need to monitor and accurately control the ortho/para ratio in gaseous samples of hydrogen. A ratiometer based on the difference in the thermal conductivity of the two molecular species of hydrogen has been constructed and tested to determine the ortho-to-para hydrogen ratio in gaseous samples. The design has sought to produce a fast, high accuracy measurement in a simple compact cell. The ratiometer and electronic readout package is described, and data demonstrating the sensitivity, stability, and speed of response of the device is also presented.     

用工业V205直接制备钒基固溶体贮氢合金

研究了五氧化二钒直接制备钒基固溶体贮氢合金的方法.分析测试了合金的化学成分、组织结构和贮氢性能.结果表明,用工业五氧化二钒可以合成钒基固溶体贮氢合金V3TiN0.56Al0.2;PCT曲线表明该合金已具备平衡吸放氢的性能,吸放氢容量为1.8×10-4m3/g;合金中含有少量的氧化物夹杂,但通过真空感应精炼,可使夹杂含量降低.     

用工业V2O5直接制备钒基固溶体贮氢合金

研究了五氧化二钒直接制备钒基固溶体贮氢合金的方法.分析测试了合金的化学成分、组织结构和贮氢性能.结果表明,用工业五氧化二钒可以合成钒基固溶体贮氢合金V3TiN0.56Al0.2;PCT曲线表明该合金已具备平衡吸放氢的性能,吸放氢容量为1.8×10-4m3/g;合金中含有少量的氧化物夹杂,但通过真空感应精炼,可使夹杂含量降低.     

Solid Hydrogen for Nonlinear Optics

We recently developed a new method of preparing a parahydrogen crystal which is suitable for experiments on nonlinear optical processes. The crystal was grown slowly from pressurized liquid–phase in order to avoid internal stress from the thermal constriction, and was cooled down to 4.2 K. The obtained crystal was uncracked and perfectly transparent with a high damage threshold. To evaluate the quality, the vibrational coherence decay was measured using the time–resolved coherent anti–Stokes Raman spectroscopy (CARS) technique. The decay process showed a nonexponential behavior, with an asymptotic limit characterized by a single time constant of 2.6 s, which corresponds to a linewidth of less than 0.1 MHz. This decay time is extremely slow compared to the previously published work.     

Solid state reactions in the Fe2O3-CaCO3-In2O3 system

The kinetics of solid-state reactions of powdered reactants were investigated by X-ray and by differential thermogravimetry in a magnetic field. Measurements revealed mutual diffusion of the Fe³⁺ and In³⁺ ions in the Fe₂O₃-In₂O₃ system heat treated for 3 h at 700 to 1400° C. Diffusion of indium into the Fe₂O₃ lattice caused a shift of the Curie temperature of the antiferromagnetic iron oxide towards lower temperatures. Only Caln₂O₄ was found between CaCO₃ and In₂O₃ up to 1400° C. Also, in the Fe₂O₃-CaCO₃-In₂O₃in system, the reaction started with the mutual diffusion of iron and indium and the forming of CaFe₂O₄. End-products were the magnetic -Ca₄Fe₁₄O₂₅ and CaFe₄O₇, and the non-magnetic CaFe₅O₇, depending on the In³⁺ concentration. Indium stabilized the magnetic calcium-iron oxide structures, shifting their Curie temperatures towards lower values.     

Al2O3-Si系原材料在氮气气氛下的高温物理化学变化过程

以电熔刚玉和单质硅为原料压制成试样，分别在氮气气氛、1400—1600℃高温反应烧结，获得五个不同温度点合成的试样，采用XRD分析技术研究试样的物相演变过程，从而对Al2O3-Si原料在氮气气氛下反应过程中的物相变化和反应过程进行了研究。结果表明：在氮气气氛条件下，经高温反应，新产生的主要物相是β—Sialon和Si3N4。同时，新生成物相β—Sialon（Si6-ZAlZOZN8-Z，0〈Z〈4．2）中的Z值与温度和原料配比密切相关。     

Hydrogen substitutes for the in situ generation of H2O2: an application in the Fenton reaction

This study investigates the ability of formic acid, hydrazine and hydroxylamine to act as H₂ substitutes in conducting phenol degradation by Fenton reaction using in situ generated hydrogen peroxide. The processes were performed with semi-heterogeneous (Pd/Al₂O₃ + soluble Fe²⁺) and fully heterogeneous (FePd/Al₂O₃) catalytic systems under ambient conditions. In contrast to bulk H₂O₂ production conditions, hydrazine is able to produce H₂O₂in situ followed by phenol degradation using Pd/Al₂O₃ + Fe²⁺ at pH 3 without the need for halide ions. However, a degree of mineralization exceeding 37% could not be achieved. The significant production of in situ H₂O₂ at the inherent acidic pH of hydroxylammonium sulfate in the presence of Pd/Al₂O₃ + Fe²⁺ was also found to differ from the bulk production of H₂O₂, in which no H₂O₂ was detected. A remarkable degree of mineralization (ca. 65%) as well as fast phenol degradation during the reaction started at pH 7 over FePd/Al₂O₃ may be an advantage of using hydroxylamine. On the other hand, using formic acid, H₂O₂ was produced at a moderate rate, thereby achieving higher efficiency in the mineralization of phenol. Most importantly, the catalysts were more stable in the presence of formic acid than hydrazine or hydroxylamine.     

Desorption of Solid O2 Induced by Vibrational Excitations

Molecular dynamics calculations of the vibrationally induced desorption of a simple low cohesive energy molecular solid, O ₂ have been carried out. The calculations were extended up to 8 ns after the excitation. The desorption process has been found to have an evaporative character. Upon high excitation densities, guest molecules dissolved in the lattice were carried off by the matrix material. The evolution of the bulk of the irradiated material was examined. The transfer of vibrational energy into lattice heating evolves from a steady linear to rapid nonlinear regime. The efficiency of energy transfer to the lattice was found to depend nonlinearly on the density of excited molecules and on the anharmonicity of the intramolecular potential.     

Direct Measurements of Infrared Normal Spectral Emissivity of Solid Materials for High-Temperature Applications

A new facility for the measurement of the normal spectral emissivity of solid materials for high-temperature applications in the thermal steady state was developed at the Bundeswehr University of Munich. The measurements are performed under atmospheric conditions. The facility covers the temperature range between $500\,^{\circ }\hbox {C}$ and $1350\,^{\circ }\hbox {C}$ and wavelengths between $0.6\,\upmu \hbox {m}$ and $15\,\upmu \hbox {m}$ . The principle of operation involves the spectral comparison of a test sample with a reference blackbody and the sample surface temperature determination with a numerical spectral ratio calculation. The optical characteristics of the blackbody and the sample surface temperature determination are discussed in detail. Furthermore, measurement results of the quasi-reference material silicon-carbide under steady-state conditions are presented to validate the measurement method.     

Solid Ar, N2, CO, and O2 in Nanopores

Molecular solids enclosed in pores with diameters in the nm-range are a research field which attracts growing interest. The major questions asked in this context are: what is the structure and the dynamics? How are phase and glass transitions modified by the geometrical constraint? In this contribution we present structural information, by x-ray diffraction measurements, as well as thermodynamic characterization, by vapor pressure and heat capacity measurements, on Ar, which is usually considered the simplest of all condensates, and on the small diatomic molecules N₂, C0, O₂ in porous glasses with average pore diameters from 50 to 130Å.     

Low-Frequency Relaxation Rate in the Superconducting YBa2Cu3O6.7

The submillimeter-wave 3 cm ^–1 < < 40 cm ^–1 complex conductivity of the reduced YBa ₂ Cu ₃ O _6.7 film, (T _C =56.5 K) was investigated for temperatures 4 K < T < 300 K. The frequency dependence of the effective quasiparticle scattering rate 1/*() was extracted from the spectra. 1/* is shown to be frequency independent at low frequencies and high temperatures. On decreasing temperature the scattering rate increases with increasing frequencies. Finally, at 6 K it follows a power-law, 1/* ^1.75±0.3.     

SiO2-CaO-B2O3-Al2O3微晶玻璃在平板式ITSOFC中密封性能的研究

平板式中温固体氧化物燃料电池(ITSOFC)的密封材料在工作温度下,与其接触的电池材料应具备以下特性:(1)气密性;(2)尺寸稳定性;(3)热匹配性;(4)化学稳定性;(5)绝缘性.采用SiO₂-CaO-B₂O₃-Al₂O₃系统微晶玻璃制备出一种适用于850℃的密封材料.该材料在850℃保证一定尺寸的前提下,能够与8YSZ电解质和Ni-Cr双极板紧密黏附,热膨胀系数8.9×10^-6)/℃和8YSZ接近,电导率约为10^-8S/cm有良好的电绝缘性能,在O₂和H₂气氛下保温100h没有气体泄漏,且密封后的黏附界面边界分明,元素扩散层厚度<10μm.实验证明该材料适用于ITSOFC 850℃密封.     

Conversion of O(2) into CO(2) for High-Precision Oxygen Isotope Measurements

An improved procedure of (18)O/(16)O ratio measurements by means of oxygen conversion to CO(2) is developed, which allows one to obtain the true δ(18)O values with a precision of ±0.05‰ in oxygen samples down to 7 μmol. The isotopic exchange between quartz glass and oxygen gas was measured in the temperature range of 600-900 °C, and it was found to be less than 0.2%.     

Effective Pair Potential for Solid Molecular Hydrogen at High Pressures

An effective pair potential for molecular hydrogen in the solid phase is presented. It is able to reproduce the measured equation of state up to 120?GPa. At short intermolecular distances, this potential is softer than previously proposed potentials. The calculations of the equation of state at high pressures are performed by a simple method involving a single frequency as a variational parameter. The accuracy of the calculation is estimated by treating perturbatively the difference of the real Hamiltonian and the harmonic one.     

Acoustic Properties of Solid 4He in the Limit of Zero Impurity

We have studied the elasticity of solid ⁴He in relation with its possible supersolidity. For this we have measured acoustic resonance frequencies in a 1 cm³ cell filled either with polycrystals or with single crystals of ⁴He. We have observed a large stiffening at low temperature as first observed by Day and Beamish in polycrystals. The ³He impurity content has been varied from 300 ppb to 0.4 ppb. When kept in equilibrium with liquid helium, single crystals should be impurity free. In these crystals, a large stiffening is observed, which should not be the result of the pinning of dislocations by impurities.     

Rate of dibutylsulfide decomposition by ozonation and the O3/H2O2 advanced oxidation process

A process of dibutylsulfide (DBS) oxidation using advanced methods of oxidation with ozone and hydrogen peroxide was studied. It was demonstrated that depending on pH value there are two mechanisms of DBS oxidation present: ionic and radical. The ionic mechanism predominates in acidic environment and the radical mechanism predominates in alkaline environment. At high pH ozone stability decreases and hydrogen peroxide has a deciding effect on DBS oxidation rate. At pH 9, and at high concentration of hydrogen peroxide (ranging from 0.1 to 1 mol/L), a clear increase in DBS decomposition rate was observed. That was caused by production of hydroperoxide radicals in reaction of hydrogen peroxide and ozone. In solutions pH value of which is close to 2, the rate of DBS oxidation by ozone alone is slower than in a O(3)/H(2)O(2) system, regardless the H(2)O(2) concentration. For higher H(2)O(2) concentrations (ranging from 0.1 to 1 mol/L), regardless the pH value of the solution, oxidation in a O(3)/H(2)O(2) system is faster, compared to a situation in which ozone is a sole oxidizer. For H(2)O(2) concentrations below 0.1 mol/L and when pH>2DBS oxidation in O(3)/H(2)O(2) system is slower compared to the situation in which ozone was the only oxidizer.