PIT Processed MgB2 Thin Wires Sheathed With Stainless Steel

MgB2 superconducting thin wires sheathed with stainless steel (SS) have been prepared by in-situ powder-in-tube (PIT) process. Using Magnesium hydride MgH2 and amorphous B powders, SS sheathed MgB2 thin wires have been fabricated through drawing to form the round wires of 0.20 mm similar to 0.10 mm in diameter. The SS sheath of 0.1 mm in diameter was hardened to be a Vickers hardness of around 600 HV through cold-working at room temperature without annealing. The heat treatment was performed at 630 degrees C for 5 h in Ar gas atmosphere. The SS sheath recovered the hardness of 400 HV after heat treatment. The MgB2 wires show the critical temperature (T-c) of around 35 K in onset and sharp transition of 2 K. The transport critical current (I-c) at 4.2 K and self-field are 40 A and 8 A for the MgB2 thin wires of 0.2 mm and 0.1 mm in diameter, respectively. The I-c values correspond to the critical current density (J(c)) of around 4,000-5,000 A/mm(2). The present MgB2 thin wires with low thermal conductivity are promising as level sensors for liquid hydrogen and current leads with small heat leakage.