Kinetic Enhancement of Direct Hydrogenation of MgB2 to Mg(BH4 )2 upon Mechanical Milling with THF, MgH2 , and/or Mg

Modification of magnesium diboride, MgB₂ , by mechanical milling with THF, MgH₂ , and/or Mg results in a lowering of the conditions required for its direct, bulk hydrogenation to magnesium borohydride, Mg(BH₄ )₂ , by 300 bar and 100 °C. Following mechanical milling with MgH₂ or THF and Mg, MgB₂ can be hydrogenated to Mg(BH₄ )₂ at 300 °C under 700 bar of H₂ while achieving ∼54-71 % conversion to the borohydride. The discovery of a means of dramatically lowering the conditions required for the hydrogenation of MgB₂ is an important step towards the development of a practical onboard hydrogen storage system based on hydrogen cycling between Mg(BH₄ )₂ and MgB₂ . We suggest that mechano-milling with THF, Mg, and/or MgH₂ may possibly introduce defects in the MgB₂ structure which enhance hydrogenation. The ability to activate the MgB₂ through the introduction of structural defects transcends its relevance to hydrogen storage, as a method of overcoming its chemical inertness provides the key to harnessing other interesting properties of this material.

Direct Pen Writing of High-Tc, Flexible Magnesium Diboride Superconducting Arrays

High-Tc , flexible MgB2 -nanowire-based superconducting arrays are fabricated via a direct pen writing method on both copper foils and poly(dimethylsiloxane) (PDMS) substrates. Such superconducting arrays constitute a new approach for fabricating superconducting devices. The realization of a PDMS-based device demonstrates the potential for expanding this material into other high-Tc superconductor systems, which may lead to novel ways of driving the development of "real-life" applications.

Superconductivity and the periodic table: from elements to materials

Based on the normal-state electronic band structure, the necessary condition for a metal to become a superconductor is the simultaneous occurrence of flat and steep bands at the Fermi level. The sufficient condition at least for conventional superconductors is a strong enough coupling of the flat band states to the lattice, e.g. via phonons. Selected elements (Te) and compounds of the rare earth metals (RE(2)C(3), REC(2), RE(2)X(2)C(2) with X=halogen) and MgB(2) serve as examples to illustrate the idea.

Flexible, ultralight, porous superconducting yarns containing shell-core magnesium diboride-carbon nanotube nanofibers

Magnesium-diboride-coated carbon nanotube arrays are synthesized by templating carbon-nanotube aerogel sheets with boron and then converting the boron to MgB2. The resultant MgB2-CNT sheets are twisted into flexible, light-weight yarns that have a superconducting transition around 37.8 K and critical current and critical field comparable with those of existing MgB2 wires, but have about 20 times lower density than bulk MgB2.

Enhancement of the critical current density in FeO-coated MgB(2) thin films at high magnetic fields

The effect of depositing FeO nanoparticles with a diameter of 10 nm onto the surface of MgB(2) thin films on the critical current density was studied in comparison with the case of uncoated MgB(2) thin films. We calculated the superconducting critical current densities (J(c)) from the magnetization hysteresis (M-H) curves for both sets of samples and found that the J(c) value of FeO-coated films is higher at all fields and temperatures than the J(c) value for uncoated films, and that it decreases to ~10(5) A/cm(2) at B = 1 T and T = 20 K and remains approximately constant at higher fields up to 7 T.