摘要:

AbstractThe substages of the oxidation of CoO have been investigated with the PAC method during isochronal and isothermal annealings at low oxygen activity (10−9atm). The successive trapping of cation vacancies at the111In probe atoms up to the formation of spinel‐like microclusters has been observed. The results of the PAC experiments are compared with those of X‐ray diffraction and RBS analyses and confirmed by a PAC experiment for111In in Co3O4. A quantitative analysis of the oxidation kinetics in terms of first order rate equations yields an activation enthalpy of ΔH= 0.27(4) eV. It is found that the absorption of oxygen and the formation of vacancies at the surface are the rate controlling processes in this expe

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940102

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

年代:1990

数据来源: WILEY

摘要:

AbstractSingle crystals of Cd4BSe6(B = Si, Ge) (ARGYRODITES) were grown by CVT method using a three zone furnace. As‐grown crystals were of n‐type and they have been characterized by photoelectrochemical (PEC) measurements in aqueous electrolytes. The current‐potential curves, Mott‐Schottky plots and action spectra were examined. From the analysis of spectral response measurements the band gaps (indirect) for Cd4SiSe6and Cd4GeSe6were found to be 1.68 and 1.5 eV, respectively. The opencircuit photopotentials for these semiconductor electrodes were as high as 1.1 V vs. SCE in some of the electrolyt

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940103

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe photochromic and electrochromic responses of MoO3thin films subjecting to UV irradiation were investigated in different environments. It was found that photochromic responses were different in different chemical environments. The presence of oxygen had a detrimental effect on the photochromic responses of the films. Additionally, the irradiated MoO3films, after biased negatively in 0.1 M LiClO4/propylene carbonate solution, showed enhancement in electrochromism when compared to the non‐irradiated samples treated in a similar fashion. The MoO3and WO3thin films showed significant differences in photochromic responses in HCOOH and C2H5OH vapor

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940104

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

年代:1990

数据来源: WILEY

摘要:

AbstractResults of measurements of the temperature dependence of the shear viscosity of critical mixtures of polystyrene/cyclohexane and polystyrene/cyclohexane‐d12using a capillary viscometer are reported. The polystyrene had a molar mass ofMw= 4.0 · 105g mol−1(Mw/Mn≤ 1.03). The data are analysed to determine the value of the critical exponent zηof the viscosity and the value of the system specific viscosity parameter Q0. It is found that zηhas a value of zη= 0.044 ± 0.005 which is smaller than the theoretically predicted value (zη(theoretically) = 0.054). The system specific viscosity parameterQ0has the same value for both systems:Q0= (1.2 ± 0.5) · 106cm−1. A Q0value of this order of magnitude leads to non‐critical contributions to the mutual diffusion coefficient near the critical point r

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940105

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

年代:1990

数据来源: WILEY

摘要:

AbstractAn experimental reinvestigation of the high‐temperature phase equilibria and critical curve of the water‐argon system was made for water mole fractionsxbetween 0.2 and 0.95 in the temperature range from 480 to 663 K and at pressures from 10 to 340 MPa. Molar volumes were measured at thepTx‐phase equilibrium surface. Contrary to the results of an earlier determination [3], the critical curve shows a temperature minimum at 637 K and 84 MPa and proceeds to 658 K at 261 MPa. Thus the curve belongs to the “type II”‐group. Phase equilibrium data are shown for pressures to 300 MPa. A calculation based on a rational equation of state confirms the cri

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940106

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

年代:1990

数据来源: WILEY

摘要:

AbstractAn equation of state, suggested previously, has been extended and applied to calculate phase equilibria and critical phenomena of ternary and quaternary fluid systems to high temperatures and pressures. The equation consists of a modified hard sphere repulsion term and an additive perturbation term based on a square well potential to account for molecular attraction. The procedure of calculation is described. It uses exclusively binary interaction parameters, derived from properties of the binary sub‐systems. — In order to compare the calculated results, phase diagrams have been experimentally determined for the system H2O—N2‐hexane to 679 K and 270 MPa. The experimental procedure is described. The comparison is made with isothermal and isobaric prismatic diagrams. The agreement is satisfactory above 500 K. Results of calculations are also shown for the ternary systems H2O—N2—CO2and H2O—CO2‐hexane as well as for the quaternary system H2

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940107

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe vaporization of the phases of the NaI — DyI3system present at a temperature of 1000 K, DyI3(s) + melt for 0

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940108

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe vaporization of liquid and solid alloys of the Al — Ni system in the rangexNi= 0.7 to 1 has been extensively investigated by the use of Knudsen effusion mass spectrometry in the temperature range between 1389 and 1734 K. 15 alloy samples of different compositions of the complete concentration range were studied in the course of 25 runs and their Al and Ni partial pressures determined. The vapour pressure measurements in the course of the individual runs were carried out over temperature ranges of up to about 300 K covering the solid and the liquid state for many of the alloys investigated. Chemical activities and chemical potentials for Al and Ni as well as Gibbs energies were evaluated at 1600 K for the solid and at 1728 K for the liquid state. Two independent methods were used for the determination of Ni activities of the solid alloys yielding consistent results. The large temperature range of the partial pressure measurement for the solid AlNi3phase withxNi= 0.750 rendered possible the determination of a complete set of partial and integral thermodynamic functions (ΔG, ΔH, ΔS) for the formation of this phase. The values obtained are discussed. The partial and integral enthalpies of formation are compared with the enthalpies of dissociation of the gaseous species Ni2(g), Al2(g), and AlNi(g). The integral enthalpy of formation, obtained for the first time by vapour pressure measurements, agrees well with the results of a recent calorimetric s

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940109

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

年代:1990

数据来源: WILEY

摘要:

AbstractThermodynamic investigations on liquid Au—Pd alloys have been performed by means of a computer‐aided mass spectrometer in combination with a high temperature Knudsen cell unit with improved temperature measurement. A further development of the “Algebraic Intensity‐Ratio”‐method (A.I.R.) has been applied for determining the thermodynamic excess functions. T.A.P.‐series (Thermodynamically adapted power series) with three adjustable parameters are used for the algebraic representation of the thermodynamic excess properties. At 1850 K the molar excess Gibbs energyGEis negative (minimum: — 1300 J/mol at 33.9 at.% Pd) nearly over the whole range of concentration, only the alloys with more than 85 at.% Pd show slight positiveGE‐values (maximum: 78 J/mol at 93.2 at.% Pd). The molar heats of mixingHE, and the molar excess entropiesSEshow at 1850 K a similar behaviour. These quantities are mainly negative; slightly positive values occur only for alloys with more than 70 at.% Pd. The minimumHE‐value is —8220 J/mol (28.7 at.% Pd), and the minimumSE‐value is —3.8 J/mol · K (28 at.% Pd). The maximumHE‐value is 1390 J/mol at 88.15 at.% Pd. and the maximumSE‐value is 0.7 J/mol · K (87.5 at.% Pd). At 1850 K the thermodynamic Au‐activitiesaAuare found to show slight negative deviations from ideality over the whole concentration range. The same behaviour is observed for the Pd‐activities for Pd‐concentrations less than 50 at.‐% Pd. The Pd‐activities of alloys with more than 50 at.‐% Pd show s

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940110

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

年代:1990

数据来源: WILEY

摘要:

AbstractTheoretical calculations of the second virial coefficients, self‐diffusion, viscosity and thermal conductivity of monatomic alkali metal vapours, lithium, sodium, potassium, cesium and rubidium are presented. The calculations have been carried out using reliable analytical two body interaction potential energy functions for the ground singlet1Σ+gand the excited triplet3Σ+gmolecular states of the alkali dimers. The results are compared with previously calculated values. — The interpretation of experimental data on the thermophysical properties of alkali metal vapours is complicated by the formation of dimers. It follows that theoretical calculations for the monatomic species should thus provide an independent information on the zero density limits for the experimental properties. Full utilization of this principle is tried in Part II of this paper where an assessment of the available experimental data is atte

ISSN:0005-9021    

DOI:10.1002/bbpc.19900940111

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

年代:1990

数据来源: WILEY