摘要:

AbstractThe kinetics of the competition between the anodic decomposition of the dark p‐GaAs electrode and the anodic oxidation of TMPD have been studied in aqueous and in mixed aqueous‐methanolic medium by rotating ring‐disk voltammetry. The results were found to be qualitatively and quantitatively in agreement with those, previously obtained from an analogous study on the n‐GaAs photoanode, and confirm the conclusion that the mechanism depends on the medium. The latter point is further supported by the relationships between anodic current density, potential and TMPD concentration, observed at p‐GaAs. The accepted competition mechanisms allow to propose structures for the surface decomposition intermediates of GaAs involved. The value of the rate constant for the first decomposition step of GaAs is determined from current density‐potential and impedance measurements on p‐type electrodes and

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930102

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThe excess enthalpy for a quasiternary system of type MkN(1‐k)XlY(1‐l)is derived by use of a model, which considers the interaction of clusters composed of four particles. The distribution of the lattice constituents is assumed to be random. Based on this model the excess enthalpy can be described by a cubic function of the mole fractionskandlwith the standard reaction enthalpy and 8 interaction parameters as constants. It is shown, that the ternary interaction parameters can be calculated from the interaction parameters of the subregular quasibinary subsystems, whereas the reaction enthalpy for the double conversion between the binary components can be derived from their standard enthalpies. Thus the phase diagrams of quasiternary systems with two mixed sublattices can be derived from the quasibinary data without introducing any special ternary interaction parameter. ‐ The influence of the interaction parameters on the shape of the phase diagram and especially the influence of the standard reaction enthalpy on the tie line field is demonstrated by some calculated phase dia

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930103

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThe temperature dependence of NQR frequencies of halogens in ammonium hexahalotellurates(IV) has been reinvestigated in a wide range of temperature. A second‐order phase transition was definitely located at 89 K for (NH4)2TeCl6,below which temperature the existence of multiplet structure was suggested The temperature of a first‐order phase transition was determined for (NH4)2TeBr6at 194 K in addition to the phase transition previously reported, which was located accurately at 212 K. The lowest‐frequency line among the three81Br resonance lines observed below 194 K exhibited a positive temperature coefficient whereas the remaining two lines showed normal negative temperature coefficients. Except for the highest‐frequencyv1andv2lines, the all four127I lines observed for (NH4)2TeI6showed anomalous temperature dependences. These temperature dependences could be interpreted by considering that the Te‐I…H type hydrogen bonds partially break due to the thermal activation of the motion of ammonium ions in crystals. A phase transition was located at 449 K by means of differential therm

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930104

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThermodynamic properties of liquid Na‐Te solutions were measured over the range 0–52 at.% Na at temperatures between 573 and 873 K by means of alloy concentration cells. Beta alumina was used as the solid electrolyte. The following properties were derived from the emf data: ΔG, ΔH, ΔS, the excess heat capacityCEpand the excess stability, ES. The Gibbs energy, enthalpy and entropy showed marked negative deviations. The plot of excess stability versus composition exhibits a rather flat shoulder between 10 and 20 at.% Na and a broad maximum or shoulder near 50% Na indicating maximum short‐range ordering near these compositions. Liquidus and invariant points on the phase diagram as well as the Gibbs energies of formation of the solid compounds NaTe3, NaTe and Na2Te have also been de

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930105

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractIn order to complement previous investigations on the demixing of one‐phase oxide solid solutions on oxygen potential gradients, solid solutions in two‐phase regions were exposed in an analogous way. The demixing under (quasi‐) steady state conditions is basically the same as found in the one‐phase mixtures. However, in the case of (Mn,Fe)O (wustite)‐(Mn,Fe)3O4(spinel) solid solutions, the phase boundary between the lower (w) and the higher (sp) oxidized solid solution was not stable morphologically. In fact, a zone of phase mixtures developed in which wustite and spinel with continuously changing composition coexisted locally. This unique behaviour can be explained theoretically in the framework of linear transpo

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930106

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThe intercalation reaction of Cu with n‐SnS2has been studied with a variety of techniques. Electrochemical and photoelectrochemical methods provided information about the energetics of the intercalation reaction and the band gap and carrier type of the new phase (p‐CuSnS2). X‐ray photoelectron spectroscopy (XPS) was used to characterize the stoichiometry of the new phase as prepared both electrochemically and in UHV. The thermal stability of CuSnS2was studied with XPS and transmission electron microscopy (TEM) and the diffusion of copper through the van der Waals planes of SnS2was demonstrated. A structure for the new phase is proposed which is consistent with the measured physical properties. The intercalation reaction is discussed with respect to its differences from the rigid band model of intercal

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930107

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThe local equilibrium assumption commonly employed for the transport through the interface of a charged membrane has been analysed from a simplified electric double layer model. This layer is characterized on the basis of a surface potential arising from a non‐zero surface charge density placed on the membrane surface. The dependence of deviations from local equilibrium on the characteristic parameters of the problem is shown. Connection with the classical treatment by Donnan is discussed. Although the complexity of the problem calls for a number of simplifications, the results obtained appears to be significative. Thus, the analysis carried out displays not only that deviations from equilibrium are small, but also that in the limit of small fluxes, omission of a detailed study of the electric double layer is probably justified when characterizing ionic transport through common synthetic membran

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930108

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThis paper deals with charge dislocation problems occuring during overcharge in sealed nickel‐cadmium‐accumulators. In the case of catalyst particle forming gas consumption electrodes, the model “point electrode over flat electrode” was used for the determination of the current distribution. It was solved for linear polarized electrodes. The solution integral is analyzed numerically. A test apparatus for experimental testing was designed and built. This enlarged model enables a measurement of the current distribution. The theoretically predicted results are confirmed experimentally. Additionally the current distribution in the model “point electrode between two ideal unpolarized electrodes” is

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930109

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThe Rayleigh ratio has been obtained for the following mixtures of non‐electrolytes that show “w‐shape” CEpvs.xcurves: Nitrobenzene + n‐Heptane, 1,4‐Dichlorobutane + n‐Heptane and Acetone + n‐Dodecane. From them, the concentration‐concentration correlation functionScc(0) has been calculated, as well as the excess Gibbs energy. It has been found that a clear tendency to homocoordination is present in all the mixtures studied. There is a rough correspondence between the concentration at which the maximum of theScc(0) curves occur and those at which the negative curvature regions exist in the CEpcurves. Also the larger the value of max.Scc(0) the more intense the “w‐shape” effect. Despite size differences between the components and specific interactions which complicate the connection betweenScc(0) and CEp, an analysis in terms of simple mean field models supports the view that the systems which show “w‐shape” CEpcurves still feel the effects of the more or less distant UCST. HenceScc(0) is proposed as an i

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930110

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY

摘要:

AbstractThe electrochemical behaviour of the rotating aluminium disc electrode in LiAlH4/tetrahydrofuran (THF)‐toluene solutions was studied. The kinetic parameters controlling the electrode process were investigated. The effect of concentration of LiAlH4, the speed of rotation of the rotating disc electrode, and the temperature on the current density‐potential behaviour of the aluminium electrode during the anodic and cathodic polarization was analyzed. The results were compared with those obtained for pur AlCl3or AlCl3+ LiAlH4/THF‐toluene solu

ISSN:0005-9021    

DOI:10.1002/bbpc.19890930111

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1989

数据来源: WILEY