MICROSTRUCTURAL ANALYSIS OF CORE-SHELL STRUCTURED MgB2 SUPERCONDUCTING FIBERS FABRICATED BY HYBRID PHYSICAL CHEMICAL VAPOR DEPOSITION

Abstract

We have deposited MgB 2 thin films on the carbon fiber by hybrid physical–chemical vapor deposition (HPCVD) method which is known as the most effective technique for depositing MgB 2 thin films without pore formation. By adopting carbon fiber as substrate and gas phase reaction between diborane ( B 2 H 6) gas and Mg vapor for MgB 2 formation, core-shell structured MgB 2/ C composite fiber could be synthesized. The high quality of the prepared MgB 2 fibers was confirmed with scanning electron microscopy (SEM), and the critical temperature (T c ) of the sample deposited at 590°C and 12 sccm flow rate of B 2 H 6 was measured at ~40 K. The microstructures of MgB 2 layer was characterized using transmission electron microscopy (TEM). The bright-field TEM images showed MgB 2 with the grain size of several nanometers. The MgB 2 thin film showed highly dense microstructure without pore and well-connected to the carbon fiber interface. High-resolution TEM (HRTEM) images and scanning transmission electron microscopy (STEM) revealed the presence of interface phase between MgB 2 thin films and carbon fiber.