Enhanced Flux Pinning Performance of Bulk MgB2 via Immersion of Synthetic Motor Oil

Abstract The present investigation focuses on the incorporation of synthetic motor oil as an inexpensive, rich carbon source in bulk MgB 2 superconductor and its effect on superconducting and flux pinning properties. A set of three MgB 2 bulk samples were prepared from commercial high-purity powders of Mg metal and amorphous B powder utilizing a conventional in situ solid-state reaction process. Before sintering, the MgB 2 samples were immersed in used and new synthetic motor oil for a standby time of 30 min and sintered in pure Ar atmosphere at 775 °C for 3 h. X-ray powder diffractometer (XRD) analysis confirmed that single-phase formation of MgB 2 with a small shift in X-ray diffraction peaks especially at (110) towards the peak position due to the effect of carbon substitution into the boron sites in lattice for samples immersed in new and used synthetic oil. The magnetization measurements indicated the T c (onset) value to somewhat decrease to 37.5 K as a result of carbon doping. Microstructural observations with scanning electron microscopy (SEM) suggested that fine nano-sized MgB 2 grains improved self-field critical current density around 3.8 × 10 5 A/cm 2 at 20 K for all samples studied. Further, the high-field critical current density ( J c ) was improved especially for the sample immersed in used synthetic motor oil with the value of 2.7 × 10 4 A/cm 2 , 6 × 10 3 A/cm 2 at 20 K, and at 3 T and 4 T, which is higher as compared to pure-MgB 2 sample. In essence, the results signify that the bulk MgB 2 samples immersed with used synthetic motor oil would improve the bulk performance at high magnetic fields indicating to be a viable option for industrial applications.