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183 results on '"Gritzner, Gerhard"'

67. Statistical Analysis of Gibbs Energies of Transfer of Cations and Soft Solvent Parameters.

Author

Gritzner, Gerhard and Auinger, Michael

Subjects
*STATISTICAL correlation, *GIBBS' free energy, *ENERGY transfer, *SOLVENTS, *ALKALI metals, *CATIONS
Abstract

Gibbs energies of transfer of the cations Li+, Na+, K+, Rb+, Cs+, Ag+, Tl+, Ba2+, Cu2+, Cd2+, Pb2+ and Hg2+ from water as reference into up to 42 non-aqueous solvents were analyzed by a statistical procedure based on the spectral theorem. The data set had to be separated into three groups. The first group included the alkali metal cations and Ba2+, the second Tl+, Cd2+ and Pb2+ and the third group Ag+ and Hg2+. Analysis of the respective subgroups yielded classification schemes for solvents versus the individual groups of cations. The respective solvent parameters derived from statistical analysis for the subgroups did not depend on each other. Correlations with solvent parameters claiming to account for "solvent softness" were only found for the parameters derived from the subgroup consisting of Ag+ and Hg2+. A mere separation into "hard and soft solvents" was found to be insufficient to account for the experimental data. [ABSTRACT FROM AUTHOR]

Published
2009

79. (Tl<SUB>0.5</SUB>Pb<SUB>0.5</SUB>)(Sr<SUB>0.8</SUB>Ba<SUB>0.2</SUB>)<SUB>2</SUB>Ca<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>y</SUB> superconducting thick films with high in-field critical current densities

Author

Heiml, Oliver, Gritzner, Gerhard, Tönies, Susanne, Weber, Harald W, Keckéš, Jozef, and Ortner, Balder

Abstract

Superconducting (Tl0.5Pb0.5)(Sr0.8Ba0.2)2Ca2Cu3Oy films with a thickness between 1 and 2 μm are prepared by screen printing the precursor material on monocrystalline lanthanum aluminate substrates followed by ex situ thallination. Texture analysis confirmed that highly c-axis oriented samples with critical temperatures Tc(0) between 117 and 119 K and with transition widths ΔT(90–10&percent;) of 1 K are achieved. The critical current densities in self-field are above 1.2 × 1010 A m−2 at 77 K, and the in-field behaviour is excellent, even without the introduction of artificial pinning centres. jc of 4 × 109 A m−2 at 77 K and 6 T (H || ab) and of 1 × 109 A m−2 at 1 T for H || c are observed.

Published
2002

80. Studies on cobalt-tris(bipyridyl) complexes in acetonitrile–water mixtures

Author

Benko, Ján, Vollárová, Ol'ga, and Gritzner, Gerhard

Abstract

The Gibbs energies of transfer, ΔtG°, for [Co(bipy)3]3+ and [Co(bipy)3]2+ in the full range of acetonitrile–water mixtures were derived from solubility measurements of the picrates and partitioned into single-ion contributions based on the tetraphenylarsonium tetraphenylborate assumption. The enthalpies of solution were obtained from calorimetry of the perchlorates of [Co(bipy)3]3+ and [Co(bipy)3]2+. The single-ion transfer entropies were calculated via the tetraphenylarsonium tetraphenylborate assumption. In addition polarography, cyclic voltammetry and UV–visible spectroscopy were also performed on these complexes in water–acetonitrile mixtures. Gibbs energies of transfer of [Co(bipy)3]+ were derived from the ΔtG° values for [Co(bipy)3]2+ and from electrochemical measurements. The TΔtS° values for [Co(bipy)3]3+ and[Co(bipy)3]2+ were calculated from the enthalpies and the Gibbs energies of transfer. The TΔtS° values of [Co(bipy)3]+ were obtained from the respective data for [Co(bipy)3]2+ and from the assumption of a negligible thermal diffusion potential. The Gibbs energies of transfer are accounted for in terms of hydrogen–hydrogen interactions between the methyl group of acetonitrile and the hydrogen atoms of the ligands of the studied complexes. The interpretations of TΔtS° values and the enthalpies of transfer were based on different regions for the structure of acetonitrile–water mixtures and on the possibility of the Co–bipy cations entering cavities in the water structure of water-rich mixtures.

Published
2001

81. High-resolution transmission electron microscopy analysis of the interface between a Tl-1223 (001) superconducting film and an untextured Ag substrate.

Author

Bong-Kun Kim, Matsui, Yoshio, Horiuchi, Shigeo, Dae-Yeong Jeong, Deinhofer, Christian, and Gritzner, Gerhard

Subjects
TRANSMISSION electron microscopy, ELECTRON microscopy, PARTICLES (Nuclear physics), OPTICS, SILVER
Abstract

The interface between a screen-printed (Tl0.5Pb0.5)(Sr0.85B0.15)2Ca2Cu3Oy (Tl-1223) superconducting film and an untextured Ag substrate is analyzed by transmission electron microscopy (TEM). Preferential orientation between the Tl-1223 grains and the Ag substrate is found. The (001) plane of TI-1223 grains is parallel to and the [113] plane of Ag is almost parallel to the interface. High-resolution TEM images show that CuO2, planes contact the faceted [113] planes of Ag substrate at the interface. A mechanism for the preferential growth of the Tl-1223 (001) film on untextured Ag substrate is proposed. [ABSTRACT FROM AUTHOR]

Published
2004
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82. MgB[sub 2] Thick Films via Screen Printing.

Author

Gritzner, Gerhard, Kühberger, Markus, Tönies, Susanne, and Weber, Harald W.

Subjects
*THICK films, *SUPERCONDUCTORS
Abstract

We report the fabrication of MgB[sub 2] thick films using a simple screen printing method. The substrates investigated were mono-crystalline Al[sub 2]O[sub 3], LaAlO[sub 3], MgO, ZrO, SrTiO[sub 3], Si as well as steel. The dense, polycrystalline MgB[sub 2] films consisted of crystallites with longest dimensions of about 100 nm. No texturing was observed. The transition temperatures T[sub c(0)] varied between 34 and 36 K with transition widths smaller than 2 K. The critical current densities depended only modestly on the external field. At 6 T critical current densities of 1 × 10[sup 8] A/m² could be measured a 10 K. [ABSTRACT FROM AUTHOR]

Published
2003
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83. TlxBa2Ca3Cu4Oysuperconductors from coprecipitated oxalate precursors

Author

Bernhard, Klaus and Gritzner, Gerhard

Abstract

Precursor material for Tl-Ba-Ca-Cu-O superconductors was prepared by coprecipitation of the cations as oxalates. Following calcination at 600°C, the powders were attrited, then uniaxially compacted at 7000 bar and converted into superconducting ceramics by sintering in the temperature range of 880°C to 915°C. The thallium content and the Tc(0) depended strongly on the sintering conditions. Best results were obtained for samples with the composition Tl1.4Ba2Ca3Cu4O11.4yielding superconductors with a Tc(0) of 118 K and a critical current density of 19.4 A cm−2at 77 K.

Published
1992
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87. A general description of ion-solvent interactions

Author

Gritzner, Gerhard and Gritzner, Gerhard

Abstract

The interactions of ions with solvent molecuies lead to changes of the thermodynamic properties of solutes. For neutral molecules and salts differences in the Gibbs energies, entropies and enthalpies in various solvents can be derived from measurements of solubilities and from heats of solution. A variety of models based on extrathermodynamic assumptions were proposed to obtain Gibbs energies, enthalpies and entropies for the cations and anions from the respective properties of the salt. Data for such single ion transfer properties from the reference solvent acetonitrile unto other solvents will be employed to develop a general description for the interactions of solvent molecuies with cations and with anions. This description treats ion-solvent interactions on a molecular level. It wiii be shown that the nature of the donor sites of the soivent molecules is responsible for the interaction of solvents with cations and that the nature of the acceptor sites of the solvent molecules is effective in the interaction with anions.

88. Single-ion transfer properties and solvent parameters

Author

Gritzner, Gerhard and Gritzner, Gerhard

Abstract

Studies on the temperature dependences of polarographic half-wave potentials and electrode potentials in nonisothermal cells allowed the estimation of entropies of transfer of cations from acetonitrile in up to 22 solvents. Gibbs energies of transfer were obtained from electrochemical measurements employing bis(biphenyl)chromium(I)/(0) as a reference redox system. Combining the Gibbs energies of transfer with the 298K $ \Delta \ _t$ S°-values resulted in enthalpies of transfer for cations. Transfer properties for anions are available from the tetraphenylarsonium tetraphenylborate assumption. Gibbs energies of transfer for cations and also for anions are accounted for in a donor-acceptor (coordination) model including the principle of hard and soft acids and bases. These values are also a suitable data base to abtain and to evaluate solvent parameters, which either reflect tha hard or soft donor properties or the acceptor properties of solvents. Since no solvent parameter for the transfer entropies of cations could be found, parameters for the transfer entropies are proposed.

89. Single-ion transfer properties and solvent parameters

Author

Gritzner, Gerhard and Gritzner, Gerhard

Abstract

Studies on the temperature dependences of polarographic half-wave potentials and electrode potentials in nonisothermal cells allowed the estimation of entropies of transfer of cations from acetonitrile in up to 22 solvents. Gibbs energies of transfer were obtained from electrochemical measurements employing bis(biphenyl)chromium(I)/(0) as a reference redox system. Combining the Gibbs energies of transfer with the 298K $ \Delta \ _t$ S°-values resulted in enthalpies of transfer for cations. Transfer properties for anions are available from the tetraphenylarsonium tetraphenylborate assumption. Gibbs energies of transfer for cations and also for anions are accounted for in a donor-acceptor (coordination) model including the principle of hard and soft acids and bases. These values are also a suitable data base to abtain and to evaluate solvent parameters, which either reflect tha hard or soft donor properties or the acceptor properties of solvents. Since no solvent parameter for the transfer entropies of cations could be found, parameters for the transfer entropies are proposed.

90. A general description of ion-solvent interactions

Author

Gritzner, Gerhard and Gritzner, Gerhard

Abstract

The interactions of ions with solvent molecuies lead to changes of the thermodynamic properties of solutes. For neutral molecules and salts differences in the Gibbs energies, entropies and enthalpies in various solvents can be derived from measurements of solubilities and from heats of solution. A variety of models based on extrathermodynamic assumptions were proposed to obtain Gibbs energies, enthalpies and entropies for the cations and anions from the respective properties of the salt. Data for such single ion transfer properties from the reference solvent acetonitrile unto other solvents will be employed to develop a general description for the interactions of solvent molecuies with cations and with anions. This description treats ion-solvent interactions on a molecular level. It wiii be shown that the nature of the donor sites of the soivent molecules is responsible for the interaction of solvents with cations and that the nature of the acceptor sites of the solvent molecules is effective in the interaction with anions.

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