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  • 1
    Electronic Resource
    Electronic Resource
    The mobility of oxygen ions in CaF2 (1990)
    Springer
    Journal of applied electrochemistry 20 (1990), S. 294-300 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The a.c. conductivity of CaF2 samples containing a fine dispersion of CaO particles has been measured in the temperature range 630 to 1100 K. The conductivity of the dispersed solid electrolyte is two orders of magnitude higher than that for pure polycrystalline CaF2 in the middle of the temperature range. Transport measurements on pure single crystals of CaF2 and polycrystalline samples, with and without CaO dispersion, using Fe+FeO and pure Fe as electrodes, clearly indicate that fluorine ions are the only migrating ionic species with a transport number of almost unity, contrary to the suggestion of Chou and Rapp [1, 2]. The enhanced conductivity of the dispersed solid electrolyte probably arises from two effects. A small solubility of oxygen in CaF2 results in an increase in the fluorine vacancy concentration and conductivity. Adsorption of fluorine ions on the surface of the dispersed particles of CaO results in a space charge region around each particle with enhanced conductivity. Measurements on a galvanic cell incorporating CaF2 as the solid electrolyte and oxide electrodes show that the e.m.f. is a function of the activity of CaO at the electrode/electrolyte interface. The response to an oxygen potential gradient is, therefore, through an exchange reaction, which establishes an equivalent fluorine potential at the electrode/electrolyte interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01033608
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  • 2
    Electronic Resource
    Electronic Resource
    Use of the Nasicon/Na2SO4 couple in a solid state sensor for SO x (x=2,3) (1988)
    Springer
    Journal of applied electrochemistry 18 (1988), S. 245-251 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The e.m.f. of a concentration cell for SO x (x=2,3)-O2 incorporating Nasicon as the main solid electrolyte has been measured in the temperature range 720 to 1080 K. The cell arrangement can be represented as, $$Pt, O'_2 + SO'_2 + SO'_3 \left| {Na_2 SO_4 \left\| {\left. {Nasicon} \right\|} \right.} \right.\left. {Na_2 SO_4 } \right|SO''_3 + SO''_2 + O''_2 , Pt$$ The Na2SO4 acts both as an auxiliary electrode, converting chemical potentials of SO x and O2 to equivalent sodium potentials, and as an electrolyte. The presence of Na2SO4 provides partial protection of Nasicon from chemical reaction with gas mixtures containing SO x . The open circuit e.m.f. of the cell is in close agreement with values given by the Nernst equation. For certain fixed inlet gas compositions of SO2+O2, the e.m.f. varies non-linearly with temperature. The intrinsic response time of the cell to step changes in gas composition is estimated to vary from ∼2.0 ksec at 723K to ∼ 0.2 ksec at 1077K. The cell functions well for large differences in partial pressures of SO3(p″SO 3/p′SO 3≈104) at the electrodes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01009271
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  • 3
    Electronic Resource
    Electronic Resource
    Sulphur potential measurements with a two-phase sulphideoxide electrolyte (1983)
    Springer
    Journal of applied electrochemistry 13 (1983), S. 55-67 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The open circuit potentials of the galvanic cell,Pt (or Au)¦(Ar + H2S + H2)′∥CaS + ZrO2(CaO)∥ (Ar + H2S+ H2)″£t (or Au) has been measured in the temperature range 1000 to 1660 K and PH2S:PH 2 ratios from 1.73×10−5 to 2.65×10−1. The solid electrolyte consists of a dispersion of calcium sulphide in a matrix of calcia-stabilized zirconia. The surface of the electrolyte is coated with a thin layer of calcium sulphide to prevent the formation of water vapour by reaction of hydrogen sulphide with calcium oxide or zirconia present in the electrolyte. The use of a ‘point electrode’ with a catalytically active tip was necessary to obtain steady emfs. At low temperatures and high sulphur potentials the emfs agreed with the Nernst equation. Deviations were observed at high temperatures and low sulphur potentials, probably due to the onset of significant electronic conduction in the oxide matrix of the electrolyte. The values of oxygen and sulphur potentials at which the electronic conductivity is equal to ionic conductivity in the two-phase electrolyte have been evaluated from the emf response of the cell. The sulphide-oxide electrolyte is unsuitable for sulphur potential measurements in atmospheres with high oxygen potentials, where oxidation of calcium sulphide may be expected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00615887
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  • 4
    Electronic Resource
    Electronic Resource
    Decomposition of β-alumina in an oxygen potential gradient (1983)
    Springer
    Journal of applied electrochemistry 13 (1983), S. 469-472 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Single phase sodiumβ-alumina solid electrolyte was found to undergo isothermal phase separation in electrochemical cells, where a large oxygen potential gradient was imposed across the electrolyte and electrodes, not reversible to sodium ions, were short circuited. The experimental conditions and evidence of decomposition are outlined and a thermodynamic explanation for the phenomenon is given. This finding may lead to new methods for making multi-layered ceramic materials involving ionic conductors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617521
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  • 5
    Electronic Resource
    Electronic Resource
    Studies on nonisothermal solid state galvanic cells — effect of gradients on EMF (1989)
    Springer
    Journal of applied electrochemistry 19 (1989), S. 394-400 
    Details
    ISSN: 1572-8838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Notes: Abstract An expression for the EMF of a nonisothermal galvanic cell, with gradients in both temperature and chemical potential across a solid electrolyte, is derived based on the phenomenological equations of irreversible thermodynamics. The EMF of the nonisothermal cell can be written as a sum of the contributions from the chemical potential gradient and the EMF of a thermocell operating in the same temperature gradient but at unit activity of the neutral form of the migrating species. The validity of the derived equation is confirmed experimentally by imposing nonlinear gradients of temperature and chemical potential across galvanic cells constructed using fully stabilized zirconia as the electrolyte. The nature of the gradient has no effect on the EMF.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01015242
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  • 6
    Electronic Resource
    Electronic Resource
    Heterobimetallische Vanadium- und Thallium-2-(dimethylaminomethyl)ferrocenyl-Verbindungen (1997)
    Springer
    Monatshefte für Chemie 128 (1997), S. 337-351 
    Details
    ISSN: 1434-4475
    Keywords: Vanadium ; Thallium ; Heterobimetallic ; 2-(Dimethylaminomethyl)ferrocenyl ; Orthometallation ; Electron transfer ; Möβbauer spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Summary Syntheses and properties of 2-(dimethylaminomethyl)ferrocenylderivatives of the composition (FcN) n VCl3−n (FcN=2-(dimethylaminomethyl)ferrocenyl;n=1 (1), 2 (2), 3 (3)), which are formed from VCl3·3THF and (FcN) Li (I), are reported. WhereasCp 2VCl2 (Cp=C5H5) reacts withI under formation ofCp 2V(FcN) (4), VO(acac)2 (acac=anion of acetylacetonate, C5H7O2) can be transformed into the 2-(dimethylaminomethyl)-ferrocenyl compound of tetravalent vanadium (FcN)VO(acac),5). However, when VOCl2·2THF reacts withI, the organovanadium(III)-derivative Li[(FcN)2V(O)Cl] (6) is formed. Reactions of VCl4·2THF,Cp 2VCl2, VOCl3, andCpVOCl2 with (FcN)3Tl (II) lead to thermally instable vanadiumorganic compounds under formation of (FcN)2TlCl (7). A detailed characterization of1–7 was carried out by elementary analysis, determination of effective magnetic moments, IR, mass and1H NMR spectroscopy as well as — especially referring to the formation of possible chelate structures — by UV/Vis andMöβbauer spectroscopy.
    Notes: Zusammenfassung Synthesen und Eigenschaften von 2-(Dimethylaminomethyl)ferrocenyl-Derivaten der Formel (FcN) n VCl3−n (FcN=2-(Dimethylaminomethyl)ferrocenyl;n=1 (1), 2 (2), 3 (3)), die aus VCl3·3THF und (FcN) Li (I) entstehen, werden mitgeteilt. WährendCp 2VCl2 (Cp=C5H5) mitI unter Bildung vonCp 2 V(FcN) (4) reagiert, läßt sich VO (acac)2 (acac=Anion des Acetylacetonates, C5H7O2) in die 2-(Dimethylaminomethyl)ferrocenyl-Verbindung des vierwertigen Vanadiums (FcN)VO(acac),5) überführen. Dagegen entsteht bei Umsetzungen von VOCl2·2THF mitI das Organovanadium (III)-Derivat Li [(FcN)2V(O)Cl] (6). Reaktionen von VCl4·2THF,Cp 2VCl2, VOCl3 undCpVOCl2 mit (FcN)3Tl (II) führen unter Bildung von (FcN)2TlCl (7) zu thermisch instabilen vanadiumorganischen Verbindungen. Eine eingehende Charakterisierung von1–7 erfolgte durch Elementaranalysen, Ermittlung der effektiven magnetischen Momente, IR-, Massen- und NMR-Spektroskopie sowie, insbesondere hinsichtlich der Ausbildung möglicher Chelatstrukturen, durch UV/Vis und Mößbauer-Spektroskopie.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00810770
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  • 7
    Electronic Resource
    Electronic Resource
    Heterobimetallische [(2-Dimethylaminomethyl)ferrocenyl](pentamethylcyclopentadienyl)-Komplexe der Lanthanoide: Synthesen und Mößbauer-Untersuchungen (1997)
    Springer
    Monatshefte für Chemie 128 (1997), S. 165-175 
    Details
    ISSN: 1434-4475
    Keywords: Organolanthanides ; Heterobimetallic complexes ; Ferrocene ; Mößbauer spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Reactions of 2-(dimethylaminomethyl)ferrocenyl-lithium ((FcN)Li,1) with various cerium(IV) precursors lead to the formation of heterobimetallic organocerium(III) complexes. The compounds Li3[(FcN)2CeF4(THF)3] (2), (FcN)2CeF(DME)2 (3), Li4[(FcN)CeCl6] (4), and Li[(FcN)CeCl3(DME)] (5) have been isolated by redox reactions. Similar treatment of (C5Me5)2 Ce(μ-Cl)2K(THF)2 with one equivalent of1 affords the neutral species (C5Me5)Ce(FcN)Cl (6)via displacement of one C5Me5 ligand. Complexes of the type (C5Me5)Ln(FcN)Cl have also been isolated forLn=Pr (7), Nd (8), and Sm (9). These and related heterobimetallic lanthanideFcN complexes have been studied by Mößbauer spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00807305
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  • 8
    Electronic Resource
    Electronic Resource
    Berechnung der Potentialströmung um Profile mit Absaugung und Ausblasen (1963)
    Springer
    Archive of applied mechanics 32 (1963), S. 51-65 
    Details
    ISSN: 1432-0681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00536502
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  • 9
    Electronic Resource
    Electronic Resource
    Self-organization of recent rhythmic iron-manganese precipitations in underground mines in the Harz mountains (1996)
    Springer
    International journal of earth sciences 85 (1996), S. 29-37 
    Details
    ISSN: 1437-3262
    Keywords: Banded mineralization ; Harz mountains ; Self-organization ; Iron, manganese, ferrihydrite, birnessite ; Time-series analysis ; Aquatic systems ; Iron bacteria ; Ostwald ripening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract A recent early diagenetic banded iron-manganese mud has been forming underground in a closed lead-zinc mine for approximately 40 years. The processes leading to the banded structure of the precipitate were studied during a period of 2 years. Therefore, 19 physical and chemical parameters were measured regularly in short intervals. The resulting time series were analysed with respect to the data sets of the monthly chemical analyses of the descendent mine water, the daily rainfall and the mineral content. The results reveal that the precipitated material undergoes internal self-organization due to interaction of redox, colloid-chemical, microbial, electrical and ripening processes, and not exclusively produced by seasonal fluctuations of material input. Thus, the primary banding of the material, caused by externally forced fluctuations of the redox conditions within the mine water, is reorganized after a short time. The finally observed bands are controlled by non-linear coupling of reaction and transport processes within the mud. A genetic model for the banded mineralization was developed and verified by numerical simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192057
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  • 10
    Electronic Resource
    Electronic Resource
    Morphological instabilities in pattern formation by precipitation and crystallization processes (1996)
    Springer
    International journal of earth sciences 85 (1996), S. 19-28 
    Details
    ISSN: 1437-3262
    Keywords: Anastomoses ; Crystal zoning ; Snow bands ; Liesegang rings ; Ostwald ripening ; Self organization ; Siderite ; Supersaturation theory ; Zebra rock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Morphological instabilities in periodic patterns occurring both in precipitation and crystallization processes (Liesegang rings and crystal zoning) are investigated and compared with similar patterns in geological samples (zebra rocks and mud bands in snow sediments). In classical Liesegang systems, undisturbed parallel or concentric precipitation bands are emanated from even or concentric diffusion sources in homogeneous diffusion matrices of gelatine or other gels. In the case of superposing diffusion sources, sources with undulatory curvatures or local diffusion barriers there may occur several types of instabilities within the sequence of regular patterns: (a) gaps within the bands forming radial alleys free of precipitate, (b) transition from broken bands to speckled patterns and (c) apparent branching of bands linked together by so-called anastomoses. Calculations with a competitive particle growth (CPG) model show that lateral instabilities in Liesegang bands (gaps and radial alleys of gaps) are the result of Ostwald ripening effects taking place after precipitation. Apparent branching of bands or formation of anastomoses can be simulated with a prenucleation model according to Ostwald's supersaturation theory. Similar irregularities can be observed in zebra rocks (e.g. banded siderite) whose bandings are commonly explained by sequential sedimentation processes. A very different mechanism is assumed to be responsible for the origin of mud bands in snow sediments. An initially homogeneous distribution of intrinsic mud in snow sediments can be arranged into parallel bands according to a crystal zoning mechanism which is based on repeated thawing and freezing of the snow sediment due to the daily alternation of sun and darkness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192056
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