Superconducting composite production

Plasma-Chemical Production of Oxide Powders for Synthesis of High-Temperature Superconducting Composites... 

A series of three solid solutions La2 x(Ba,Sr,Ca)xCu04 g was then prepared (152) the superconducting transition temperatures of the resulting products were determined from a.c. susceptibility measurements. The three-component phase diagram for this chemical system was plotted as a function of Tc. The maximum transition temperature of 37.0 K was observed for the composition, La18Sr0 2-Cu04 g, an end-member in the phase diagram. 

Paul" Chu, and others at University of Houston, also reproduced Zurich s I.B.M. research results (156). Bell Lab s confirmation of Bednorz and Muller s discovery of high Tc superconductivity in copper oxide compounds was published (157) in the Jan. 1987 issue of Physical Review Letters. The electrical resistivity data from their work showing an onset of superconductivity at 36.5 K for the composition Lax gSr0 2Cu04 is plotted as Figure 28. This product also showed a 60-70% Meissner effect. 

The reported Meissner fraction was an important property to follow during the early days of superconductivity research. The magnitude of this diamagnetic effect, when properly measured, gives a good indication of the homogeneous nature of the materials being prepared in different laboratories. The first reported values were low, 2 to 15%, but as the composition, structure, and synthetic conditions became better known, the values increased to 70-80%— indicative of bulk superconductivity in an essentially pure product. 

All of these procedures involve heating T1203 in non-sealed systems, and all are typified by superconducting product stoichiometries far different from the starting compositions. Again, in addition to safety concerns, little control of superconducting-phase composition and reproducibility of synthetic conditions is afforded by use of non-hermetically sealed reaction containers. The problem appears to be more complex than simply thallium reactant loss factors related to reaction kinetics are most likely quite important for the preparation of these metastable phases. 

There s also the possibility that the silver mixture will allow the superconducting proximity effect to occur. (Superconductivity can occur between two superconductors that are physically separated so long as the barrier is a conducting metal.) That tunneling effect may be the key to developing materials that can be machined, drawn into wires, or cast into various production shapes. Preliminary experiments have shown that the new silver composite is quite strong and can be machined into several useful forms. 

Products Chemical Composition (wt%) Impurities (wt%) Particle Size and Specific Surface Area Other Properties Microhardness, H, and Transition Temperature to Superconducting State,... 

Electroanalytical methods have been used repeatedly in HTSC studies for the quantitative determination of the chemical composition of ceramics and films, their precursors, and also the degradation products. To analyze a multicomponent non-stoichiometric oxide it is necessary to determine independently with sufficient accuracy, the content of individual components that are simultaneously present in the samples [282]. The independent quantitative determination of oxygen is most essential (difference analysis introduces noticeable errors in the values of the important parameter 6). Also important is the determination of the valence of copper. Certain theories of superconductivity of cuprate systems consider Cu " as the principal essential component of HTSCs [9,10], which attracts special attention to this problem. 

The decomposition products of zirconium halides heated under ammonia arc a blue nitride with the rocksalt structure 6-Zi N (yellow at perfect stoichiometry) and a brown compound of composition Zr,N4 both are diamagnetic, but 6-ZrN is a metallic conductor (superconducting Tc -- 10 K). whereas Zr, N4 is an insulator [286, 287], Band structure calculations suggest ZrN Zr, N4 would form a good Josephson junction [288],... 

Easy speciation and isotope detection have been identified as playing important roles in optimizing the production of superconducting NbsSn wires by heating a composite of bronze and niobium filaments. Application of TOF-LMMS has provided evidence of the out-diffusion and accumulation of phosphorous, inhibiting Nb3Sn formation when tin diffuses inward. The preferential incorporation of the lower tin isotopes in the NbsSn layer has confirmed the process to be driven by diffusion. The semiconductor industry has used TOF-LMMS to verify the lateral diffusion of dopants, e.g., boron in tantalum and cobalt silicide ruimers only 3 pm wide. Another application is the identification of microscopic residues left on integrated circuits after removal of the photoresist. 

Two dimensional 2D ILT was applied in a study addressed to the composition and the physical behaviour of water and fat mixtures. Several dairy products (like milks, cheeses) were measured in the stray field of a superconducting magnet ( H Larmor frequency 5.034 MHz). At g = 0.545 T/m, the samples diffusion properties can be observed, characterized by sample-specific diffusion coefficient ( >) distributions. 

The perspective direction of development of electrical equipment is production of composite electroconductors, for example, low-temperature superconductors in which the effect of superconductivity is caused by effect of a pinning - fixing of whirlwinds of a magnetic field on the defects of crystal structure being objects of a nanolevel. Carriers of such defects is the fibrous structure received at plastic deformation with big extents of deformation. 

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