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Peter Sutter - One of the best experts on this subject based on the ideXlab platform.

  • size dependent phase diagram of nanoscale alloy drops used in vapor liquid solid growth of semiconductor nanowires
    ACS Nano, 2010
    Co-Authors: Eli Sutter, Peter Sutter
    Abstract:

    We use in situ observations during high-temperature transmission electron microscopy to quantify the exchange of semiconductor material between Au−Ge vapor−liquid−solid seed drops and Ge nanowires (NWs). By performing simultaneous measurements under identical conditions on arrays with systematic variations in NW diameter, we establish the nanoscale size dependence of the temperature-dependent Equilibrium Composition of the Au−Ge binary alloy. We find a significantly enhanced Ge solubility for drops on thin NWs compared to thicker ones. The controlled modification of the surface of the NW by an ordered carbon shell leads to drastic changes in the solubility.

  • phase diagram of nanoscale alloy particles used for vapor liquid solid growth of semiconductor nanowires
    Nano Letters, 2008
    Co-Authors: Eli Sutter, Peter Sutter
    Abstract:

    We use transmission electron microscopy observations to establish the parts of the phase diagram of nanometer sized Au−Ge alloy drops at the tips of Ge nanowires (NWs) that determine their temperature-dependent Equilibrium Composition and, hence, their exchange of semiconductor material with the NWs. We find that the phase diagram of the nanoscale drop deviates significantly from that of the bulk alloy, which explains discrepancies between actual growth results and predictions on the basis of the bulk-phase equilibria. Our findings provide the basis for tailoring vapor−liquid−solid growth to achieve complex one-dimensional materials geometries.

Eli Sutter - One of the best experts on this subject based on the ideXlab platform.

  • size dependent phase diagram of nanoscale alloy drops used in vapor liquid solid growth of semiconductor nanowires
    ACS Nano, 2010
    Co-Authors: Eli Sutter, Peter Sutter
    Abstract:

    We use in situ observations during high-temperature transmission electron microscopy to quantify the exchange of semiconductor material between Au−Ge vapor−liquid−solid seed drops and Ge nanowires (NWs). By performing simultaneous measurements under identical conditions on arrays with systematic variations in NW diameter, we establish the nanoscale size dependence of the temperature-dependent Equilibrium Composition of the Au−Ge binary alloy. We find a significantly enhanced Ge solubility for drops on thin NWs compared to thicker ones. The controlled modification of the surface of the NW by an ordered carbon shell leads to drastic changes in the solubility.

  • phase diagram of nanoscale alloy particles used for vapor liquid solid growth of semiconductor nanowires
    Nano Letters, 2008
    Co-Authors: Eli Sutter, Peter Sutter
    Abstract:

    We use transmission electron microscopy observations to establish the parts of the phase diagram of nanometer sized Au−Ge alloy drops at the tips of Ge nanowires (NWs) that determine their temperature-dependent Equilibrium Composition and, hence, their exchange of semiconductor material with the NWs. We find that the phase diagram of the nanoscale drop deviates significantly from that of the bulk alloy, which explains discrepancies between actual growth results and predictions on the basis of the bulk-phase equilibria. Our findings provide the basis for tailoring vapor−liquid−solid growth to achieve complex one-dimensional materials geometries.

Gianni Carvoli - One of the best experts on this subject based on the ideXlab platform.

  • liquid liquid equilibria of the ternary systems water acetic acid ethyl acetate and water acetic acid isophorone 3 5 5 trimethyl 2 cyclohexen 1 one
    Journal of Chemical & Engineering Data, 1999
    Co-Authors: Andrea Colombo, Paolo Battilana, Vittorio Ragaini, C L Bianchi, Gianni Carvoli
    Abstract:

    Liquid-liquid equilibria for the ternary systems water + acetic acid + ethyl acetate and water + acetic acid + isophorone (3,5,5-trimethyl-2-cyclohexen-1-one) were measured over the temperature range (283 to 313) K. The results were used to estimate the interaction parameters between each of the three compounds of the systems studied for the NRTL and UNIQUAC models. The estimated interaction parameters were successfully used to predict the Equilibrium Compositions by the two models; experimental data were successfully reproduced. The UNIQUAC model was the most accurate in correlating the overall Equilibrium Composition of the studied systems. Also the NRTL model satisfactorily predicted the Equilibrium Composition. Isophorone experimentally resulted in a better extraction capacity for acetic acid and in a lower miscibility with water.

Christian Ruempler - One of the best experts on this subject based on the ideXlab platform.

  • Chemical Equilibrium Composition of air-copper-PA66 mixtures and their effects on dielectric breakdown for low-voltage circuit breaker post-current-zero
    2013 Abstracts IEEE International Conference on Plasma Science (ICOPS), 2013
    Co-Authors: Venkat R. T. Narayanan, Joachim V. R. Heberlein, Christian Ruempler
    Abstract:

    Summary form only given. Metallic vapor emanating from the electrodes and plastic vapor from wall ablation on or before current-zero in a low-voltage circuit breaker (LVCB) significantly affect the dielectric recovery characteristics of atmospheric pressure air in the contact gap after current-zero. When the net ionization coefficient becomes positive, dielectric breakdown is said to occur and the reduced electric field (E/N) of this occurrence is termed the critical reduced electric field ((E/N)crit) [1]. In this paper, we analyze the dielectric breakdown behavior for the case of copper being the electrode material and polyamide 6/6 (PA-66) being the plastic wall material. Firstly, the chemical Composition is calculated by the minimization of Gibbs free energy and the results are compared for two different methodologies (denoted as M1 [2] and M2 [3], for convenience). Unlike M2, M1 includes the condensed species of copper and carbon (graphite) and it will be shown that below 3500 K, the two methods provide widely different Composition results. Secondly, Boltzmann's EEDF equation is solved to obtain the generalized non-Maxwellian electron-energy distribution function (EEDF) [4], with the electron-impact collision cross-sections gathered from literature as input. Using the afore-mentioned inputs, (E/N)crit is calculated and plotted against temperature ranging between 300-6000 K, for different mass-fraction values of air, copper and PA-66. Additionally, it has been observed that the presence of vibrationally- and electronically-excited species enhances the dielectric breakdown by lowering (E/N)crit. This approach is part of an initial attempt towards addressing realistic chemical non-Equilibrium conditions involving finite-rate kinetics in an LVCB after current-zero and the numerical results will subsequently be utilized for comparisons with available experimental data.

  • chemical Equilibrium Composition of air copper pa66 mixtures and their effects on dielectric breakdown for low voltage circuit breaker post current zero
    International Conference on Plasma Science, 2013
    Co-Authors: Venkat R. T. Narayanan, J Heberlein, Christian Ruempler
    Abstract:

    Summary form only given. Metallic vapor emanating from the electrodes and plastic vapor from wall ablation on or before current-zero in a low-voltage circuit breaker (LVCB) significantly affect the dielectric recovery characteristics of atmospheric pressure air in the contact gap after current-zero. When the net ionization coefficient becomes positive, dielectric breakdown is said to occur and the reduced electric field (E/N) of this occurrence is termed the critical reduced electric field ((E/N)crit) [1]. In this paper, we analyze the dielectric breakdown behavior for the case of copper being the electrode material and polyamide 6/6 (PA-66) being the plastic wall material. Firstly, the chemical Composition is calculated by the minimization of Gibbs free energy and the results are compared for two different methodologies (denoted as M1 [2] and M2 [3], for convenience). Unlike M2, M1 includes the condensed species of copper and carbon (graphite) and it will be shown that below 3500 K, the two methods provide widely different Composition results. Secondly, Boltzmann's EEDF equation is solved to obtain the generalized non-Maxwellian electron-energy distribution function (EEDF) [4], with the electron-impact collision cross-sections gathered from literature as input. Using the afore-mentioned inputs, (E/N)crit is calculated and plotted against temperature ranging between 300-6000 K, for different mass-fraction values of air, copper and PA-66. Additionally, it has been observed that the presence of vibrationally- and electronically-excited species enhances the dielectric breakdown by lowering (E/N)crit. This approach is part of an initial attempt towards addressing realistic chemical non-Equilibrium conditions involving finite-rate kinetics in an LVCB after current-zero and the numerical results will subsequently be utilized for comparisons with available experimental data.

Anthony B. Murphy - One of the best experts on this subject based on the ideXlab platform.

  • dominant particles and reactions in a two temperature chemical kinetic model of a decaying sf 6 arc
    Journal of Physics D, 2016
    Co-Authors: Xiaohua Wang, Mingzhe Rong, Qingqing Gao, Aijun Yang, Chunping Niu, Anthony B. Murphy
    Abstract:

    This paper is devoted to the computation of the non-Equilibrium Composition of an SF6 plasma, and determination of the dominant particles and reactions, at conditions relevant to high-voltage circuit breakers after current zero (temperatures from 12 000 K to 1000 K and a pressure of 4 atm). The non-Equilibrium Composition is characterized by departures from both thermal and chemical Equilibrium. In thermal non-Equilibrium process, the electron temperature (T e) is not equal to the heavy-particle temperature (T h), while for chemical non-Equilibrium, a chemical kinetic model is adopted. In order to evaluate the reasonableness and reliability of the non-Equilibrium Composition, calculation methods for Equilibrium Composition based on Gibbs free energy minimization and kinetic Composition in a one-temperature kinetic model are first considered. Based on the one-temperature kinetic model, a two-temperature kinetic model with the ratio T e/T h varying as a function of the logarithm of electron density ratio (n e/) was established. In this model, T* is introduced to allow a smooth transition between T h and T e and to determine the temperatures for the rate constants. The initial Composition in the kinetic models is obtained from the asymptotic Composition as infinite time is approached at 12 000 K. The molar fractions of neutral particles and ions in the two-temperature kinetic model are consistent with the Equilibrium Composition and the Composition obtained from the one-temperature kinetic model above 10 000 K, while significant differences appear below 10 000 K. Based on the dependence of the particle distributions on temperature in the two-temperature kinetic model, three temperature ranges, and the dominant particles and reactions in the respective ranges, are determined. The full model is then simplified into three models and the accuracy of the simplified models is assessed. The simplified models reduce the number of species and reactions by a factor of about 2, while providing results that agree closely with the full model. Thus, the physicochemical processes of SF6 arc can be characterized by relatively few species and reactions in each temperature range. It is noted that the simplified models can also be applied to a wide range of pressures, 1–16 atm, conditions which cover most circuit breaker applications. The simplified species and reactions will allow the computing time of multi-dimensional models, taking into account departures from both thermal and chemical Equilibrium, to be decreased dramatically while capturing the main physicochemical processes in SF6 arcs.

  • thermophysical properties of high temperature reacting mixtures of carbon and water in the range 400 30 000 k and 0 1 10 atm part 1 Equilibrium Composition and thermodynamic properties
    Plasma Chemistry and Plasma Processing, 2012
    Co-Authors: Anthony B. Murphy, Weizong Wang, J D Yan, Mingzhe Rong, J W Spencer, M T C Fang
    Abstract:

    This paper is devoted to the calculation of the chemical Equilibrium Composition and thermodynamic properties of reacting mixtures of carbon and water at high temperature. Equilibrium particle concentrations and thermodynamic properties including mass density, molar weight, entropy, enthalpy and specific heat at constant pressure, sonic velocity, and heat capacity ratio are determined by the method of Gibbs free energy minimization, using species data from standard thermodynamic tables. The calculations, which assume local thermodynamic Equilibrium, are performed in the temperature range from 400 to 30,000 K for pressures of 0.10, 1.0, 3.0, 5.0 and 10.0 atm. The properties of the reacting mixture are affected by the possible occurrence of solid carbon formation at low temperature, and therefore attention is paid to the influence of the carbon phase transition by comparing the results obtained with and without considering solid carbon formation. The results presented here clarify some basic chemical process and are reliable reference data for use in the simulation of plasmas in reacting carbon and water mixtures together with the need of transport coefficients computation.

  • diffusion in Equilibrium mixtures of ionized gases
    Physical Review A, 1993
    Co-Authors: Anthony B. Murphy
    Abstract:

    Diffusion in a mixture of two nonreacting homonuclear gases with an arbitrary degree of ionisation is considered. It is shown that, provided that an Equilibrium Composition of the gas mixture can be defined as a function of temperature, pressure, and relative concentrations of the two gases, diffusive mixing of the gases can be fully described by three combined diffusion coefficients. These coefficients describe diffusion due to concentration, temperature, and pressure gradients, respectively, and replace the 1/2(q 2 +q-2) independent diffusion coefficients required in previous treatments to describe diffusion in a q-species gas mixture. Diffusion due to applied electric and gravitational fields is also considered