A Simple High-yield Synthesis of Pure MgB 2 Superconducting Nanowires

1. A Simple High-yield Synthesis of Pure MgB2 Superconducting Nanowires Manashi Nath and Bruce A. Parkinson, Colorado State University, DMR0107429 Magnesium boride (MgB2) has been an interesting material for study ever since the recent discovery of superconductivity in this compound. We have been successful in synthesizing MgB2 nanowires and some unusual open nanostructures by a combination of simple sol-gel chemistry and pyrolysis. The starting reactants are ethanolic solutions of MgBr2 and NaBH4 that forms a gel when left open to the atmosphere for several hours. Nanowires can be prepared either by heating the thickened gel under an atmosphere of N2 and diborane (B2H6) gas or by loading the gel into the pores of an alumina membrane before pyrolysis (Fig. 1). Fig. 1 SEM image of the as-synthesized MgB2 nanowires obtained from the raw gel; (inset shows a MgB2“nanovase” obtained by pyrolyzing the gel in the pores of anodic alumina membrane.

2. The diameter of the MgB2 nanowires obtained from the gel is in the range of 50-100 nm while the length exceeds several micrometers. The DC susceptibility measurement acquired on an ensemble of the MgB2 nanowires shows a strong Meissner effect indicating the onset of superconductivity at the bulk value of 39K (Fig. 2). The simple single source gel precursor and the purity and crystallinity of the obtained nanowires makes this technique promising for the continuous production of superconducting cables. Fig. 2 - The DC susceptibility measurement of the MgB2 nanowires showing the superconducting transition at 39K (Tc).