New advanced in situ carbon monoxide sensor for the process application

Mixed potential solid electrolyte CO sensors with sensing electrodes based on composite with various semiconducting oxides were extensively studied in the temperature range 500–650 °C for sensitivity, stability and cross-sensitivity besides CO to other combustion components like CO₂, H₂O, O₂, and SO₂. The highest CO sensitivity was found for the CO sensor with composite electrode based on Au/Ga₂O₃ showing also good reproducibility and stability in hazardous combustion environment. CO sensor response behavior in non equilibrated oxygen containing gas mixtures is mainly determined by the catalytic activity of the measuring electrode and depends strongly on preparation and measuring conditions. Mixed oxides based on doped chromites show only a little sensitivity to CO. CO sensor based on Au/Ga₂O₃ composite electrodes was showing good CO selectivity in the presence of other combustion gas species and finally was tested in combustion environment at power plant. Paper presented at the 11th EuroConference on the Science and Technology of Ionics, Batz-sur-Mer, Sept. 9–15, 2007.     

Current–voltage characteristic of BaTiO3−δ in its mixed n/p regime under oxygen potential gradients

Current (I)–voltage (V) characteristic under oxygen potential gradients was experimentally examined on single crystal BaTiO_3−δ in its mixed ion/electron/hole regime at 1000 °C. The variation of I vs. V appears similar to that of an n/p junction, but with the limiting slope (dI/dV) approaching the maximum and minimum possible equilibrium conductances in the given oxygen potential gradient as increasing forward and reverse bias, respectively. This characteristic has been precisely traced theoretically by using the partial ionic and electronic conductivities of BaTiO_3−δ as measured against uniform oxygen chemical potential in equilibrium state. The nonlinear characteristic is attributed to the redistribution of oxygen chemical potential that is caused by a non-vanishing gradient of the ionic transference number of the oxide under the given oxygen potential gradient. It is demonstrated that the bulk transport properties of a mixed conductor may be tailored by terminal voltage in a chemical potential gradient.     

Impedance spectroscopy of undoped and Cr-doped ZnO gas sensors under different oxygen concentrations

Thin films of undoped and chromium (Cr)-doped zinc oxide (ZnO) were synthesized by RF reactive co-sputtering for oxygen gas sensing applications. The prepared films showed a highly c-axis oriented phase with a dominant (0 0 2) peak appeared at a Bragg angle of around 34.13 °, which was lower than that of the standard reference of ZnO powder (34.42 °). The peak shifted to a slightly higher angle with Cr doping. The operating temperature of the ZnO gas sensor was around 350 °C, which shifted to around 250 °C with Cr-doping. The response of the sensor to oxygen gas was enhanced by doping ZnO with 1 at.% Cr. Impedance spectroscopy analysis showed that the resistance due to grain boundaries significantly contributed to the characteristics of the gas sensor.     

Investigating the effect of gas absorption on the electromechanical and electrochemical behavior of graphene/ZnO structure,suitable for highly selective and sensitive gas sensors

Graphene/ZnO hybrid was used, for the first time, to fabricate a highly selective and sensitive graphene based gas sensor by a combination of electromechanical and electrochemical characteristics of the graphene. ZnO nanowires in our fabricated sensor have two important roles: as the reductant of graphene oxide to obtain graphene and as an efficient electromechanical actuator due to their piezoelectric properties. To investigate the operation of the fabricated sensor as a gas sensor, a selected set of chemical vapors were introduced to the structure. It was found that chemical vapors change the resonance frequency of the graphene/ZnO structure, as well as the electrical resistivity of the sensor. The observed variation of the mechanical and electrical characteristics of the graphene/ZnO in response to gas exposure entitles the graphene/ZnO based sensor as a highly selective/sensitive device for gas sensing applications with distinctive signatures for different gas species.     

超流Fermi气体在非简谐势阱中的集体激发

研究了非谐振势中超流Fermi气体的集体激发. 基于一维超流流体动力学模型, 采用变分法获得了体系从分子Bose-Einstein凝聚端渡越到Cooper对凝聚端时系统的两个低能激发模, 即偶极模和呼吸模. 分析发现: 在整个跨越区偶极模和呼吸模都发生了频移现象, 且在BCS端频移更加显著. 进一步研究发现在不同驱动振幅激发下超流Fermi气体质量中心和宽度变化呈现出了复杂动力学特性, 由于非谐振势的贡献,超流Fermi气体两低能模发生耦合, 使宽度变化产生量子拍频现象, 且拍频频率随着驱动振幅的增加而增大. 这种非线性耦合对外部驱动的响应在幺正区尤其显著. 关键词： 超流Fermi气体 非谐振势 集体激发     

Space charge effects on stopped projectile fragment drift in gas

The results from a particle-in-cell code developed to describe the drifting of ions in an ionized buffer gas are described. The rate of ionization was found to have a dramatic effect on the collection efficiency of the heavy ions and results of the calculations agree well with recent observations.      

Tailoring mixed proton-electronic conductivity of BaZrO3 by Y and Pr co-doping for cathode application in protonic SOFCs

BaZr_0.8 − xPr_xY_0.2O_3 − δ (BZPYx, 0.1 ≤ x ≤ 0.4) perovskite oxides were investigated for application as cathode materials for intermediate temperature solid oxide fuel cells based on proton conducting electrolytes (protonic-SOFCs). The BZPYx reactivity with CO₂ and water vapor was evaluated by thermogravimetric and X-ray diffraction analyses, and good chemical stability was observed for each BZPYx composition. Conductivity measurements of BZPYx sintered pellets were performed as a function of temperature and p_O2 in humidified atmospheres, corresponding to cathode operating condition in protonic-SOFCs. Different conductivity values and activation energies were measured depending on the Pr content, suggesting the presence of different charge carriers. For all the compositions, the partial electronic conductivity, calculated from conductivity measurements at different p_O2, increased with increasing the temperature from 500 to 700 °C. Furthermore, the larger the Pr content, the larger the electronic conductivity. BaZr_0.7Pr_0.1Y_0.2O_3 − δ and BaZr_0.4Pr_0.4Y_0.2O_3 − δ showed mostly pure proton and electron conductivity, respectively, whereas the intermediate compositions showed mixed proton/electronic conductivity. Among the two mixed proton/electronic conductors, BaZr_0.6Pr_0.3Y_0.2O_3 − δ presented the larger conductivity, which coupled with its good chemical stability, makes this perovskite oxide a candidate cathode materials for protonic-SOFCs.     

Calculation of spectroscopic parameters of diatomic van der waals molecules and ions: inert-gas atom-inert gas ion of the halogen-type in the ground state

Based on the effective-pneudopotential method with the use of a new form of the polarization-interaction potential, obtained on the basis of calculating the most important polarization diagrams of the perturbation theory in the Thomas—Fermi approximation, the authors calculated interatomic potentials in the inert-gas ion in the ground state-inert-gas atom system: Ne⁺, Kr⁺−Ne, Ar, Kr, Xe. The results of calculating on its basis quasi-molecular terms of the sought van der Waals systems that refine the available data are given; a part of the results is obtained for the first time. Odessa Hydrometeorological Institute, 15, L’vovskaya St., Odessa, 270016, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 6, pp. 935–938, November–December, 1998.     

纳米TiO2多孔薄膜电极平带电势的研究

采用光谱电化学方法研究了纳米TiO₂多孔薄膜电极的平带电势,获得了薄膜厚度以及TiCl₄处理对纳米TiO₂薄膜电极平带电势的影响情况,并研究了平带电势对染料敏化太阳电池光伏性能的影响.结果表明,可以通过检测纳米TiO₂电极平带电势的变化趋势来反映电池中TiO₂电极平带电势的变化趋势.随着TiO₂电极膜厚的增加,其平带电势将向正方向移动,导致对应电池的开路电压随之减小.另外,经 关键词： 平带电势 2')" href="#">纳米TiO₂ 染料敏化 太阳电池     

Enhancement of the electrochemical performance in MgO stabilized ZrO2 oxygen sensors by co-doping trivalent metal oxides

The present work looked at the co-doping effect of the typical trivalent metal oxides on the electrochemical performance of 8 mol% of MgO stabilized ZrO₂ (Mg-PSZ) electrolyte ceramics used for oxygen sensors. An appreciable increase in the ionic conductivity occurred on substituting MgO with trivalent metal oxides except La₂O₃ in the Mg-PSZ electrolyte ceramics across the measured temperature range. The conductivity was related to the co-dopant ionic radius and the ionic conductivity increased with the co-dopant ionic radius of the trivalent metal oxides, reached a maximum at about 1.02 Å, and thereafter decreased. Through comparison and analysis, the Y₂O₃ exhibited excellent superiority than other trivalent metal oxides and the oxygen sensor assembled by 1Y7Mg-PSZ electrolyte possessed more excellent response speed and stability.     

The number of electronic states in metallic nanowires as a function of the electrochemical potential

We derive a mathematical expression for the number of electronic states in metallic nanowires within the electrochemical environment as a function of the electrochemical potential so that the variation of the above number with respect to this potential is discussed within an electron energy range from zero energy up to Fermi energy.     

Analysis of gas flow dynamics in hollow core photonic crystal fibre based gas cell

Gas flow dynamics in hollow core photonic crystal fibre (HC-PCF) is a trivial problem to study the gas filling time in HC-PCF gas sensor and other gas filled HC-PCF devices. This article analyzes the pressure dependence of gas diffusion coefficient in core and cladding holes of HC-PCF under the same condition of temperature and pressure during filling of methane and acetylene gas. An analytical model has been proposed to study the gas flow dynamics in core and cladding of HC-PCF. Due to gas filling, as the pressure varies inside the HC-PCF, at each increment of time, this model computes the change in pressure and respective gas diffusion coefficient. Using incremental gas diffusion coefficient, this model computes the gas filling time in a process similar to practical scenario. The gas filling time inside the core and cladding holes of HC-PCF for both methane and acetylene gas has been analyzed in this article. The results obtained can be utilized for HC-PCF based gas cell design.     

Accurate determination of the relative concentrations of ammonia isotopologues in a cold,electrostatically guided molecular beam

Buffer-gas cooling and electrostatic velocity selection techniques are combined in this work to produce a continuous molecular beam with rotational and translational temperatures comparable to those in the interstellar medium (ISM). A number of different mixtures of the isotopologues of ammonia (ND₃, ND₂H, NH₂D and NH₃) in varying ratios are used as the source gas, and the molecular beam emanating from the quadrupole guide velocity selector is characterised using mass spectrometry and Monte Carlo trajectory simulations. The guiding of the mixed isotopologues ND₂H and NH₂D is demonstrated for the first time. This approach establishes both the relative concentrations of each species in the beam and the internal rotational state distributions after buffer-gas cooling and guiding. Such information is essential for experiments in which the beam is used in reaction rate measurements (e.g., for ion–molecule reactions) and facilitates the study of reactions relevant to deuterium fractionation in the ISM, such as the competition between H and D transfer with mixed species including ND₂H and NH₂D.     

Fermi气体在势阱中的最大囚禁范围与状态方程

在Thomas-Fermi近似条件下,研究了n维广义幂律势阱中Fermi原子气体的最大囚禁范围,给出了n维势阱中气体的实际囚禁体积,导出了状态方程.结果表明,最大囚禁范围和囚禁气体压强不仅与势阱性质有关,也与自由理想Fermi系统的化学势有关.对三维球对称简谐势阱进行了应用,表明在Thomas-Fermi近似有效的前提下,当系统满足条件((kT)/(hω))² ((16π²g)/ 关键词： Fermi气体 n维势阱')" href="#">n维势阱 最大囚禁范围 状态方程     

Isospin effects of the Skyrme potential and the momentum dependent interaction at intermediate energy heavy ion collisions

We improve the isospin dependent quantum molecular dynamical model by including isospin effects in the Skyrme potential and the momentum dependent interaction to obtain an isospin dependent Skyrme potential and an isospin dependent momentum interaction. We investigate the isospin effects of Skyrme potential and momentum dependent interaction on the isospin fractionation ratio and the dynamical mechanism in intermediate energy heavy ion collisions. It is found that the isospin dependent Skyrme potential and the isospin dependent momentum interaction produce some important isospin effects in the isospin fractionation ratio.     

General model for the functional dependence of defect concentration on oxygen potential in mixed conducting oxides

To understand and engineer applications for mixed conducting oxides, it is desirable to have explicit, analytical expressions for the functional dependence of defect concentration and transport properties on the partial pressure of the external gas phase. To fulfill this need, general expressions are derived for the functional dependence of defect concentration on the oxygen partial pressure () for the mixed ionic electronic conductors. The model presented in this paper differs from expressions obtained using the popular Brouwer approach because they are continuous across multiple Brouwer regions.

Mean field kinetic theory of a classical electron gas in a periodic potential. III. The high-temperature limit in two dimensions

The Vlasov-like mean field kinetic equation for a classical electron plasma in the periodic field of an ionic lattice is solved in the high-temperature limit in two dimensions. The predictions for the one-electron density, the static structure factor, and the long-wavelength charge fluctuation spectrum are compared to the results of extensive molecular dynamics simulations. The predicted shift and damping of the plasma oscillation mode are in reasonable agreement with the simulation data at intermediate couplings (=e ²/k _B T1), but the agreement deteriorates as the temperature or the density is lowered, because mean field theory does not lead to the expected Kosterlitz-Thouless transition to the dielectric phase where electrons are localized.     

等离子体中充入工作气体抑制电子逃逸行为分析

利用NaI闪烁体探测器组成的伽马射线探测系统和BF3 正比计数管、3He正比计数管和ZnS闪烁体探测器组成的中子探测系统,研究了欧姆放电平稳阶段充入工作气体后对逃逸电子产生过程的影响。实验结果表明：在欧姆放电平稳阶段充入工作气体严重影响了逃逸电子行为,充入的工作气体能有效抑制逃逸电子的产生。     

Electron interaction and ‘memory’ effects in the presence of mixed disorder

We have studied the effect of electron–electron interaction in the presence of mixed disorder on the conductivity and Hall effect of a high-mobility two-dimensional electron gas in a GaAs/AlGaAs heterostructure. A parabolic, negative, temperature-dependent magnetoresistance (MR) and temperature-dependent Hall effect are observed. We show that these effects can be explained in terms of the interaction theory. In addition, a temperature independent, positive MR is observed. This classical MR is also shown to be a consequence of the mixed disorder.