Fios supercondutores de Cu-Nb3Sn preparados pelo metodo sinterização na fase liquida do cobre, com o uso de Nb-H

AUTOR(ES)
DATA DE PUBLICAÇÃO

1985

RESUMO

We prepared sintered samples of Cu-30wt%Nb using the new method "Sinterization in a Copper Liquid Phase" introduced in 1981 by O.F. de Lima. This method was improved here with the substitution of Nb powder, used in the original method, by Nb-H powder. The advantages are: 1) the oxygen content adsorbed in Nb-H powders is less than that of Nb powders. 2) The hydrogen released during the sintering heat treatment works as a reducing atmosphere and also as an activation agent for the wetting between liquid copper and niobium, thus favoring the sintering process. 3} Elimination of the dehydriding step. In our work we obtained a high density material (8,2 g/cm3) with good mechanical properties, which was reduced to fine-wire, without any heat treatment. To prepare the Cu-Nb3Sn wire we followed two ways: 1) The external diffusion process, by tin plating the Cu-30wt%Nb wire; 2) the internal diffusion process, by using the Sn-8,5wt%Cu alloy, reduced to rods of 3,5 mm. These rods together with Cu-30wt%Nb rods were enclosed in a copper tube and vacuum sealed (arrays of 7 and 61 rods). Then the billet was reduced by swaging and drawing. During the drawing steps some wires were fractured. This problem is discussed in the text and correlated with the microstructure of the Sn-8,5wt%Cu alloy. External and internal diffusion samples were first heat treated below 500ºC, for tin diffusion, then at 700ºC for the reaction between Nb and Sn, leading to the Nb3Sn phase. We prepared samples with several reaction times, and its influence upon the critical parameters Tc and Jc, and normal resistivity (rN), are analyzed. Our best results for the overall critical current density vs. applied magnetic field are comparable with those obtained by the bronze method: Jc(H = 7T) ~ 6 x 104A/cm2 , for the external diffusion wire with reaction time of 260 hours

ASSUNTO(S)

fios de cobre supercondutores

ACESSO AO ARTIGO

Documentos Relacionados