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Metal-Dielectric Transition in Hydrogen

100%

Shvets V., Vlasenko A.

Acta Physica Polonica A

2008

vol. 114

issue 4

851-858

The electrical resistivity of liquid metallic hydrogen at a temperature of 3000 K and a density of 0.35 mol/cm^3 is calculated. Hydrogen is considered as a three-component system consisting of electrons, protons, and neutral hydrogen atoms. The second order of perturbation theory in electron-proton and electron-atom interactions is used to determine the inverse relaxation time for electric conductivity. The Coulomb electron-electron interaction is taken into account in the random phase approximation and the exchange interaction and correlation of conductivity electrons are included in the local-field approximation. The model of hard spheres is used for the proton and atomic subsystems. The concentration of the electrically neutral atomic component proved to be significantly lower than the value assumed by the discoverers of metallic hydrogen.

Nanostructural Superconducting Materials for Fault Current Limiters and Cryogenic Electrical Machines

27%

Prikhna T., Gawalek W., Savchuk Y., Sergienko N., Moshchil V., Sokolovsky V., Vajda J., Tkach V., Karau F., Weber H., Eisterer M., Joulain A., Rabier J., Chaud X., Wendt M., Dellith J., Danilenko N., Habisreuther T., Dub S., Meerovich V., Litzkendorf D., Nagorny P., Kovalev L., Schmidt C., Melnikov V., Shapovalov A., Kozyrev A., Sverdun V., Kosa J., Vlasenko A.

Acta Physica Polonica A

2010

vol. 117

issue 1

7-14

Materials of the Y-Ba-Cu-O (melt-textured YBa_{2}Cu_{3}O_{7-δ}-based materials or MT-YBCO) and Mg-B-O (MgB_{2}-based materials) systems with high superconducting performance, which can be attained due to the formation of regularly distributed nanostructural defects and inhomogeneities in their structure can be effectively used in cryogenic technique, in particular in fault current limiters and electrical machines (electromotors, generators, pumps for liquid gases, etc.). The developed processes of high-temperature (900-800°C) oxygenation under elevated pressure (16 MPa) of MT-YBCO and high-pressure (2 GPa) synthesis of MgB_{2}-based materials allowed us to attain high superconductive (critical current densities, upper critical fields, fields of irreversibility, trapped magnetic fields) and mechanical (hardness, fracture toughness, Young modulus) characteristics. It has been shown that the effect of materials properties improvement in the case of MT-YBCO was attained due to the formation of high twin density (20-22 μm^{-1}), prevention of macrocracking and reduction (by a factor of 4.5) of microcrack density, and in the case of MgB_{2}-based materials due to the formation of oxygen-enriched as compared to the matrix phase fine-dispersed Mg-B-O inhomogeneities as well as inclusions of higher borides with near-MgB_{12} stoichiometry in the Mg-B-O matrix (with 15-37 nm average grain sizes). The possibility is shown to obtain the rather high T_{c} (37 K) and critical current densities in materials with MgB_{12} matrix (with 95% of shielding fraction as calculated from the resistant curve).

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2 Acta Physica Polonica A

1 2010

1 2008

2 Vlasenko A.

1 Chaud X.

1 Danilenko N.

1 Dellith J.

1 Dub S.

1 Eisterer M.

1 Gawalek W.

1 Habisreuther T.

1 Joulain A.

1 Karau F.

1 Kosa J.

1 Kovalev L.

1 Kozyrev A.

1 Litzkendorf D.

1 Meerovich V.

1 Melnikov V.

1 Moshchil V.

1 Nagorny P.

1 Prikhna T.

1 Rabier J.

1 Savchuk Y.

1 Schmidt C.

1 Sergienko N.

1 Shapovalov A.

1 Shvets V.

1 Sokolovsky V.

1 Sverdun V.

1 Tkach V.

1 Vajda J.

1 Weber H.

1 Wendt M.

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Metal-Dielectric Transition in Hydrogen

Nanostructural Superconducting Materials for Fault Current Limiters and Cryogenic Electrical Machines