Title :
Kinetics of MgB2 Formation Studied by in-situ Synchrotron X-Ray Powder Diffraction
Author :
Abrahamsen, Asger B. ; Grivel, J.C. ; Andersen, N.H. ; Homeyer, J. ; Saksl, K.
Author_Institution :
Ris Nat. Lab., Roskilde
fDate :
6/1/2007 12:00:00 AM
Abstract :
We have studied the kinetics of the formation of from a stoichiometric mixture of Mg and 2B in Fe tubes using in-situ synchrotron powder diffraction at photon energies between E = 76-100 keV. Reaction with the sheath was studied in Fe tubes holding only Mg or B. We here demonstrate the use of a Pb absorber ring or aperture to damp the signals from the sheath material and thereby increase the quality of the diffraction pattern from the superconductor considerably. The new method has revealed a slow reaction between Mg and B when the temperature is below the melting point of Mg and a dramatic increase in the reaction kinetics as the Mg is melted. The reaction is complete on a timescale of the order 15-20 minutes after the Mg is melted.
Keywords :
X-ray diffraction; magnesium compounds; melting point; stoichiometry; type II superconductors; MgB2 - Binary; absorber ring; diffraction pattern; electron volt energy 76 keV to 100 keV; melting point; photon energies; reaction kinetics; stoichiometric mixture; synchrotron X-ray powder diffraction; time 15 min to 20 min; Apertures; Iron; Kinetic theory; Niobium compounds; Powders; Superconducting filaments and wires; Superconducting materials; Superconductivity; Synchrotrons; X-ray diffraction; Formation kinetics; magnesium diboride; powder in tube; superconductivity;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
DOI :
10.1109/TASC.2007.900049