170 research outputs found
Simple technique for superconducting joints quality estimation in bulk melt-processed high temperature superconductors
We propose an empirical approach to estimate the quality of superconducting
joints (welds) between blocks of bulk high temperature superconductors (HTS).
As a measuring value, we introduce a joint's quality factor and show its
natural correlation with joint's critical current density. Being simple and
non-destructive, this approach is considered to be quite important to solve the
problem of utilization of HTS in large scale applications. The approach has
been applied to characterize the joint's quality of melt-processed Y-123 joined
by Tm-123 solder.Comment: 3 pages with 2 figures (revtex
Modern superconductive materials for electrical machines and devices working on the principle of levitation
The peculiarities of high-pressure synthesis of highly dense nanostructural MgB₂-based
superconductive materials, of thermobaric treatment of MT–YBCO (melt-textured YBa₂Cu₃O₇₋δ-
based superconductor), high-pressure sintering of YBa₂Cu₃O₇₋δ, oxygenation of MT–YBCO under
high isostatic pressure of oxygen and processes of formation of superconductive junctions between
MT-YBCO blocks are considered. The attained level of superconductive and mechanical properties
of such materials and junctions make them promising for application in cryogenic devices working
on the principle of levitation: electricmotors, generators, pumps for liquid-gas transfer, magnetic
bearings, flywheels, fault current limiters, maglev transport, etc. High-pressure synthesized MgB₂
(with Ti additions) blocks were for the first time tried in the superconductive electricmotor at 20 K
and demonstrated an efficiency similar to MT–YBCO (at the same working temperature)
Temperature dependence of trapped magnetic field in MgB2 bulk superconductor
Based on DC magnetization measurements, the temperature dependencies of the
trapped magnetic field have been calculated for two MgB2 samples prepared by
two different techniques: the high-pressure sintering and the hot pressing.
Experimentally measured trapped field values for the first sample coincide
remarkably well with calculated ones in the whole temperature range. This
proves, from one side, the validity of the introduced calculation approach, and
demonstrates, from another side, the great prospects of the hot pressing
technology for large scale superconducting applications of the MgB2.Comment: 3 pages, 3 figures, submitted to AP
Thermobaric Effect on Melt-Textured MBaCuO (M = Y, Nd)
The effect of a short (10-30 min) thermobaric action (in the 1-5 GPa pressure
and 700-1300C temperature range) on the structure, superconductive and
mechanical properties of melt-textured-MBaCuO (M=Y, Nd) or
MT-MBCO have been studied. The existence has been established of
pressure-temperature--time conditions (2 GPa, 800C for 30 min and
900-950C for 15 min for MT-YBCO; 5 GPa, 850-900C for 15 min for
MT-NdBCO) the treatment under which allows superconductive properties of the
materials (because of the contact with zirconia and high pressure) to be
preserved or improved, mechanical characteristics increased and the materials
condensed.Comment: 2 pages (tex), 2 figures (eps), to be presented at LT2
Substitution induced pinning in MgB_2 superconductor doped with SiC nano-particles
By doping MgB_2 superconductor with SiC nano-particles, we have successfully
introduced pinning sites directly into the crystal lattice of MgB_2 grains
(intra-grain pinning). It became possible due to the combination of
counter-balanced Si and C co-substitution for B, leading to a large number of
intra-granular dislocations and the dispersed nano-size impurities induced by
the substitution. The magnetic field dependence of the critical current density
was significantly improved in a wide temperature range, whereas the transition
temperature in the sample MgB_2(SiC)_x having x = 0.34, the highest doping
level prepared, dropped only by 2.6 K.Comment: 4 pages, 6 figure
Electroerosion dispersion-prepared nano-and submicrometre-sized aluminium and alumina powders as power-accumulating substances
Superconducting joining of melt-textured Y-Ba-Cu-O bulk material
The Tm-Ba-Cu-O solder can be successfully used to produce a superconductive
joint between MT-YBCO parts. The peculiarities of solidification, phase
formation, structure transformations and electromagnetic properties of MT-YBCO
soldered with TmBa2Cu3O7-d are discussed.Comment: PS of 6 pages text and 5 figures, presented at ICMC'2000, Brasi
Erratum to: “Structure and properties of superhard materials based on aluminum dodecaboride α-AlB₁₂”
- …