SGER: Superconducting MgB2/Metal Composites

Northwestern University, Evanston IL

Investigators

Abstract

The overall goal of this study is to demonstrate and investigate the reactive synthesis of superconducting composites consisting of two co-continuous phases, superconducting MgB2 and metallic Mg. The two routes to be studied (reactive liquid metal infiltration and reactive mechanical alloying) produce the MgB2 phase by reaction of B powders or fibers with liquid or solid Mg. The kinetics of the reaction and the formation of intermediate phases (e.g., MgB4) will be studied by metallography, x-ray diffraction using both traditional and synchrotron sources and surface techniques such as microprobe and SIMS. Superconducting and mechanical properties of the composites will also be assessed. The materials processed using the two routes will be characterized using metallography to determine porosity, connectivity and architecture of the MgB2 phase and other possible reaction products. These will further be investigated by XRD and SXRD, as well as surface science techniques such as microprobe and SIMS, the latter being highly sensitive to boron. The density of the mechanically alloyed powders as well as the infiltrated or densified composites will be determined by helium pycnometry. The hardness and compressive mechanical properties (modulus, strength and ductility) will also be measured. The electrical conductivity will be studied; both at ambient temperature and in the range of 2-50 K. Superconductivity properties will be measured with a computer-controlled magnetometer allowing SQUID measurements of temperature-dependence of magnetization up to fields of 55KG. This is a small grant exploratory project on the metallurgical/materials science study of the Mg-MgB2 system and may have significant importance in the eventual fabrication of tough, superconducting wires for magnets in energy storage devices, medical imaging systems, levitating devices and particle accelerators. Other applications include wires for power transmission and small SQUID systems. The proposed work is fundamental research and if successful may provide the impetus for further R&D and eventual commercialization of these superconducting composites.