High-pressure synthesized nanostructural magnesium diboride-based materials for superconductive electromotors, generators and pumps
Additions of Zr can increase critical current density (jc) of high-pressure synthesized MgB2 (HPS-MgB2) in the same manner as additions of Ta or Ti, i.e. due to the absorption of impurity hydrogen (to form ZrH2). The formation in HPS-MgB2 of ZrB2phase at higher synthesis temperatures (about 950 °C) does not result in the jc increase. Some increase in jc of HPS-MgB2 at 10 K in the fields higher than 8 T was observed when nano-SiC was added. The additions of Zr, Ta or Ti can prevent the harmful MgH2 impurity phase from appearing and may prevent hydrogen from being introduced into the material structure and besides, their presence in HPS-MgB2 promotes the formation of a higher amount of MgB (most likely MgB2) inclusions in the MgBO material matrix that in turn leads to the increase of jc in magnetic fields. The high level of superconductive (SC) and mechanical characteristics attained for HPS-MgB2 and the possibility to manufacture large samples make its application in the superconductive electromotors, generators, pumps, etc., very promising.