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The MgB2 superconductor has already demonstrated its applicative potential, in particular for DC applications such as MRI magnets, thanks to the low costs of the raw materials and to its simple production process. However further efforts have still to be made in order to broaden its employment also towards the AC applications such as SFCL, motors, transformers. The main issues are related to the reduction of the AC losses. Some of these can be faced by obtaining multifilamentary conductors with a large number of very fine filaments and, in this context, the powders granulometry can play a crucial role. We have prepared MgB2 starting powders with different granulometries and by the ex-situ P.I.T method we have realized multifilamentary wires with a number of filaments up to 361 and an average size of each filament lowered down to 30 microns. In particular we have studied the relationship between grain and filament size in terms of transport properties and show that the optimization of this ratio is possible in order to obtain suitable conductors for AC industrial applications.
In DC and AC practical applications of MgB2 superconducting wires an important role is represented by the material sheath which has to provide, among other things, a suitable electrical and thermal stabilization. A way to obtain a large enough amount
Two types of MgB2 films were prepared by pulsed laser deposition (PLD) with in situ and ex situ annealing processes respectively. Significant differences in properties between the two types of films were found. The ex situ MgB2 film has a Tc of 38.1K
MgB2 monofilamentary nickel-sheated tapes and wires were fabricated by means of the ex-situ powder-in-tube method using either high-energy ball milled and low temperature synthesized powders. All sample were sintered at 920 C in Ar flow. The milling
We have fabricated a series of iron-sheathed superconducting wires prepared by the powder-in-tube technique from (MgB_2)_{1-x}:(Mg+2B)_x initial powder mixtures taken with different proportions, so that x varies from 0 to 1. It turned out that ex-sit
The two most common types of MgB2 conductor fabrication technique - in-situ and ex-situ - show increasing conflicts concerning the connectivity, an effective current-carrying cross-sectional area. An in-situ reaction yields a strong intergrain coupli