Chapter 11 magnetic nanoparticles in oxide glasses

Dependence of the magnetic moment of square arrays of Josephson junctions on a dc magnetic field and temperature has been studied experimentally. The arrays had junctions of SIS and SNS type. In SIS arrays, magnetic flux avalanches were observed at low temperatures. Statistical size distribution of magnetic avalanches is a power function with a crossover (the exponent changes from ?0.7 for small sizes of avalanches to ?6 for large sizes). The spectrum of avalanches at a linear development of the field is a power function of frequency. Such a behavior of avalanches is interpreted as a manifestation of the self-organized criticality. In SNS arrays, no avalanches are developed because of the high dissipation in junctions, but a considerable asymmetry of magnetic dynamics was found.     

Superconductivity in single crystals of the nonperovskite-like cuprate Ba2Cu3O6−x

Spontaneous crystallization from a solution in a melt at a pressure of (0.8–1)×10⁻³ Pa was used to obtain single crystals of a new nonperovskite-like superconducting phase Ba₂Cu₃O_6−x space group P _ccm, a=13.065, b=20.654, and c=11.431 Å). The superconducting properties of the crystals were investigated by modulated microwave absorption. The superconducting transition temperatures were 5 K (sample No. 1), 7 K and 13 K (sample No. 2). The superconductivity in the Ba₂Cu₃O_6−x crystals is attributed to the presence of CuO₂ chains of edge-sharing copper-oxygen squares. Nonperovskite-like Ba₂Cu₃O_6−x crystals are a new class of one-dimensional (1D) superconductors. Pis’ma Zh. Tekh. Fiz. 23, 27–34 (December 26, 1997)     

Phase equilibrium of the Ag2O- TeO2- V2O5 system in the Ag2O rich region

Using DTA and X-ray phase analysis the phase equilibrium in the Ag₂O-TeO₂-V₂O₅ system has been studied in the region rich in Ag₂O. The section Ag₂O · V₂O₅ · 2TeO₂-Ag₂O · V₂O₅ was of simple quasibinary type with a eutectic point at about 60mol % Ag₂O·V₂O₅. The remaining sections showed a complex polythermal course. On the basis of the experiments carried out, the fields of initial crystallization of 12 crystal phases were outlined.     

Development of a Technology for the Production of Tubes from Ni ― Mo Alloy Powder

Technology for the production of tubes from mixtures of nickel and molybdenum powders by hot pressing and cold rolling was developed. The operational parameters for hot pressing were determined and the engineering and mechanical properties of the tubes studied. The effect of annealing temperature on the mechanical properties of the hot-pressed metal was investigated. Regimes for cold rolling the hot-pressed tubes in rolling mills were determined. The rolled tubes were tested in accordance with the accepted specifications for alloy ÉP982. All tubes passed the engineering tests; the mechanical properties of the tube metal are superior to those of alloy ÉP982. The proposed technology is quite economical, the yield of satisfactory product is 80-85%.     

On the preparation of Cr2O3 single crystals by a chemical transport reaction

The preparation of Cr₂O₃ single crystals by chemical transport has been investigated. On the basis of thermodynamic calculations chlorine was found to be one of the most suitable carriers of Cr₂O₃. The thermodynamic data show that when using chlorine as a carrier, the CrO₂Cl₂ formed in the gaseous phase during the reaction plays the most important part in the transport. The dependence of the transport rate on the temperature gradient, on the concentration of the carrier and the temperature of the crystallization zone, respectively, has been studied experimentally.