The microstructures and superconducting properties of MgB/sub 2/ tapes processed in-situ by a ball-milling method

We investigated the microstructures and superconducting properties of MgB/sub 2/ tapes fabricated by an in situ powder-in-tube method using ball-milled powders. The ball-milling technique was briefly applied to various powders, such as Mg, MgH/sub 2/, and B powder, and to powder mixtures of Mg and B, MgH/sub 2/ and B, and Mg+B+SiC. They were heat treated at the relatively lower temperature of 600/spl deg/C for 1 hour under an argon gas atmosphere. Though the ball-milling had almost no effect on the critical current density (J/sub c/) values when we used MgH/sub 2/ powder, we did observe a clear effect for Mg powder. Significant enhancements of the J/sub c/ values were obtained for the ball-milled powders of Mg+B and Mg+B+SiC. For the latter powder, we obtained a J/sub c/ value of 1.2/spl times/10/sup 4/ A/cm/sup 2/ at 4.2 K and 10 T. Those values are nearly equal to the excellent values of the in-situ processed tape of MgH/sub 2/+B+SiC powder that was not ball-milled. The high J/sub c/ values may be due to the fine B powder abrading Mg particles in the ball-milling processing, thereby producing fresh Mg and B surfaces.

[1]  H. Kitaguchi,et al.  Critical current densities of powder-in-tube MgB2 tapes fabricated with nanometer-size Mg powder , 2004 .

[2]  J. Eckert,et al.  Preparation of MgB2 tapes using a nanocrystalline partially reacted precursor , 2003 .

[3]  H. Hatakeyama,et al.  Effect of SiO2 and SiC doping on the powder-in-tube processed MgB2 tapes , 2003 .

[4]  K. Togano,et al.  Enhancement of critical current densities of powder-in-tube processed MgB2 tapes by using MgH2 as a precursor powder , 2002 .

[5]  H. Kitaguchi,et al.  The annealing effects of MgB2 superconducting tapes , 2002 .

[6]  Australia.,et al.  Enhancement of the critical current density and flux pinning of MgB2 superconductor by nanoparticle SiC doping , 2002, cond-mat/0207223.

[7]  Kevin Barraclough,et al.  I and i , 2001, BMJ : British Medical Journal.

[8]  Y. Takano,et al.  Critical current densities and irreversibility fields of MgB2 bulks , 2001 .

[9]  K. Togano,et al.  High transport critical current density obtained for powder-in-tube-processed MgB2 tapes and wires using stainless steel and Cu–Ni tubes , 2001, cond-mat/0106002.

[10]  R. V. Dover,et al.  High critical currents in iron-clad superconducting MgB2 wires , 2001, Nature.

[11]  S. Dou,et al.  High-transport critical current density above 30 K in pure Fe-clad MgB2 tape , 2001, cond-mat/0105152.

[12]  R. V. Dover,et al.  HIGH TRANSPORT CRITICAL CURRENTS IN DENSE, METAL- CLAD SUPERCONDUCTOR WIRES OF MgB2 , 2001, cond-mat/0104236.

[13]  Yunhua Shi,et al.  Superconductivity of powder-in-tube MgB2 wires , 2001 .

[14]  J. E. Cooper,et al.  RAPID COMMUNICATION: High intergranular critical currents in metallic MgB2 superconductor , 2001 .

[15]  A. Malagoli,et al.  Large transport critical currents in unsintered MgB2 superconducting tapes , 2001, cond-mat/0103563.

[16]  J. Nagamatsu,et al.  Superconductivity at 39 K in magnesium diboride , 2001, Nature.

[17]  R. Cava,et al.  Strongly linked current flow in polycrystalline forms of the superconductor MgB2 , 2001, Nature.