Effect of heat-treatment temperatures on density and porosity in MgB2 superconductor

Superconducting and Microstructural Properties of (Mg+2B)+MgB2/Cu Wires Obtained by High Gas Pressure Technology

“…As it is well known, the large pores reduce overall transport current significantly [9]. To overcome the problem of pores existence with pure grains and agglomerates connectivity, and low density of the samples, which causes low I c , we decided to use several high pressure methods -cold isostatic pressing (CIP), hot isostatic pressing (HIP), and hydro extrusion (HE).…”

Effects of the size of Mg powder on the formation of MgB2and the superconducting properties

“…The apparent density of the heat treated pellets is less than 50% of the theoretical density(2.57 g/cm 3 [14]) of the MgB 2 . A density decrease after heat treatment was reported in an in-situ processed MgB 2 bulk superconductor, which used Mg and B powders as the starting materials [17,26].…”

“…The apparent density reported in the in situ processed MgB 2 was approximately one half of the theoretical density [14] owing to the presence of many pores. This means that the J c of the in situ processed MgB 2 can be improved if the pellet density is increased through pore elimination.…”

Effect of fabrication route on density and connectivity of MgB2filaments

“…The volume occupied by the MgB 2 phase is smaller than that of the unreacted Mg + B mixture and therefore the in situ wires are accompanied by porous cores, typically reaching only 50% [9] of the theoretical density of 2.62 g/cm 3 [8]. On the other hand, for the ex situ samples, the 'closest packing of spheres' model indicates that the highest density that can be obtained is 74% [9].…”