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Highly dense nanocrystalline MgB_2 bulk superconductors with distinctly improved pinning were prepared by mechanical alloying of Mg and B powders and hot compaction at ambient temperatures. The nanocrystalline samples reveal high critical…

Superconductivity · Physics 2009-11-07 A. Gümbel , J. Eckert , G. Fuchs , K. Nenkov , K. -H. Müller , L. Schultz

We present electrical transport, magnetization, and specific heat measurements on bulk MgB2 samples (T_{c} = 38.5 K) synthesized under 200 MPa pressure using a process based on hot isostatic pressing with cooling under pressure. The samples…

Superconductivity · Physics 2009-11-07 N. A. Frederick , Shi Li , M. B. Maple , V. F. Nesterenko , S. S. Indrakanti

Single crystals of MgB2 have been grown with a high-pressure cubic anvil technique. They grow via the peritectic decomposition of the MgNB9 ternary nitride. The crystals are of a size up to 2x1x0.1mm3 with a weight up to 230 micrograms.…

Superconductivity · Physics 2016-08-31 J. Karpinski , S. M. Kazakov , J. Jun , N. D. Zhigadlo , M. Angst , R. Puzniak , A. Wisniewski

We synthesized single crystalline and policrystalline MgB_2 under ambient pressures. The single crystals of MgB_2 were of good quality, where the crystal structure refinements were successfully converged with R = 0.020. The specific heat of…

Superconductivity · Physics 2009-11-07 Y. Machida , S. Sasaki , H. Fujii , M. Furuyama , I. Kakeya , K. Kadowaki

We have fabricated a series of ex situ copper sheathed powder-in-tube MgB2 wires with 20% by volume Ag, Pb, In, and Ga metal added to the MgB2 powder. We find the transport critical current of these wires increases significantly with the…

Superconductivity · Physics 2009-11-11 M. J. Holcomb

Low resistivity ("clean") MgB2 bulk samples annealed in Mg vapor show an increase in upper critical field Hc2(T) and irreversibility field Hirr(T) by a factor of 2 in both transport and magnetic measurements. The best sample displayed Hirr…

Superconductivity · Physics 2009-11-07 V. Braccini , L. D. Cooley , S. Patnaik , P. Manfrinetti , A. Palenzona , A. S. Siri , D. C. Larbalestier

In the present study, we report a systematic study of doping/ admixing of carbon nanotubes (CNTs) in different concentrations in MgB2. The composite material corresponding to MgB2+ x at.%CNTs (35 at.% > x > 0 at.%) have been prepared by…

Superconductivity · Physics 2007-05-23 Chandra Shekhar , Rajiv Giri , S. K. Malik* , O N Srivastava

The Powder-In-Tube process has been employed to fabricate tape-like conductors with a strong metallic sheath and based on the newly discovered MgB2 superconducting phase. Long superconducting tapes have been prepared by packing reacted MgB2…

Superconductivity · Physics 2009-11-07 G. Grasso , A. Malagoli , C. Ferdeghini , S. Roncallo , V. Braccini , M. R. Cimberle , A. S. Siri

Oxygen was systematically incorporated in MBE grown MgB2 films using in-situ post-growth anneals in an oxygen environment. Connectivity analysis in combination with measurements of the critical temperature and resistivity indicate that…

Superconductivity · Physics 2009-11-13 R. K. Singh , Y. Shen , R. Gandikota , C. Carvalho , J. M. Rowell , N. Newman

Current transport in polycrystalline magnesium diboride is highly non-uniform (percolative) due to the presence of secondary phases and also due to the intrinsic anisotropy of the material. The influence of secondary phases on the transport…

Superconductivity · Physics 2009-02-18 M. Eisterer , J. Emhofer , S. Sorta , M. Zehetmayer , H. W. Weber

Nanocarbon-doped Fe-sheathed MgB2 tapes with different doping levels were prepared by the in situ powder-in-tube method. Compared to the undoped tapes, Jc for all the C-doped samples was enhanced by more than an order of magnitude in…

Superconductivity · Physics 2009-11-11 Yanwei Ma , Xianping Zhang , G. Nishijima , K. Watanabe , Xuedong Bai

MgB2 tapes and wires were fabricated by the Powder-In-Tube method. Stainless steel and Cu-Ni tubes were used as sheath materials, and no heat treatment was applied. The tapes made of stainless steel showed transport critical current density…

Superconductivity · Physics 2009-11-07 H. Kumakura , A. Matsumoto , H. Fujii , K. Togano

Fe-sheathed MgB2 tapes with cheap stearic acid, Mg stearate and Zn stearate doping were prepared through the in situ powder-in-tube method. It is found that Jc, Hirr, and Hc2 were significantly enhanced by doping. Compared to the pure…

We study the effect of neutron irradiation on the critical current density Jc of isotopically pure polycrystalline Mg11B2 samples. For fluences in the range 1017-1018 cm-2, Jc is enhanced and its dependence on magnetic field is…

Transport measurements of critical current density, Jct, in monocore powder-in-tube MgB2 strands have been carried out at temperatures, T, of from 4.2 K to 40 K, and in transverse fields, B, of up to 14 T. Processing methods used were…

Superconductivity · Physics 2015-05-30 G Z Li , Y Yang , M A Susner , M D Sumption , E W Collings

The high-pressure synthesis is one of the most promising methods to produce MgB2 superconductive (SC) material. The available high-pressure apparatuses have working volume up to 100 cm3 which allows samples up to 60 mm in diameter to be…

Superconducting MgB2 thin films were prepared on Al2O3(0001) and MgO(100) substrates. Boron thin films were deposited by the electron-beam evaporation followed by post-annealing process with magnesium. Proper post annealing conditions were…

Superconductivity · Physics 2009-11-07 S. H. Moon , J. H. Yun , H. N. Lee , J. I. Kye , H. G. Kim , W. Chung , B. Oh

We report dc transport and magnetization measurements of Jc in MgB2 wires fabricated by the powder-in-tube method, using commercial MgB2 powder with 5 %at Mg powder added as an additional source of magnesium, and stainless steel as sheath…

Materials Science · Physics 2009-11-07 A. Serquis , L. Civale , D. L. Hammon , J. Y. Coulter , X. Z. Liao , Y. T. Zhu , D. E. Peterson , F. M. Mueller

We fabricated (Ba,Na)Fe2As2 superconducting wires using the powder-in-tube method and hot isostatic pressing. By improving powder synthesis processes compared with previous studies, highly pure raw materials for the wire fabrication were…

We review recent measurements of upper (Hc2) and lower (Hc1) critical fields in clean single crystals of MgB2, and their anisotropies between the two principal crystallographic directions. Such crystals are far into the "clean limit" of…

Superconductivity · Physics 2009-11-07 A. D. Caplin , Y. Bugoslavsky , L. F. Cohen , L. Cowey , J. Driscoll , J. Moore , G. K. Perkins