جستجوی مقالات مرتبط با کلیدواژه "ybco" در نشریات گروه "مواد و متالورژی"

In this study, the effect of of silver nanoparticles (Ag-NPs) inclusion on the AC magnetic susceptibility of high temperature YBa2Cu3O7-δ  (Y123) + x wt% Ag (x=0.00, 0.06, 0.10 and 0.30)  polycrystalline superconductors was investigated. The high temperature superconductors (Y123 + x wt% Ag) were fabricated by  the solid state reaction method. XRD analysis of the samples showed superconducting orthorhombic phase with symmetry of Pmmm space group. Analysis of scanning electron microscopy (SEM) images related to the surface morphology of the samples showed that increasing silver nanoparticles dopant causes a decrease in granule size of the compounds. Real magnetic susceptibility exhibited intrinsic diamagnetic behavior and grain boundary connections and imaginary components of magnetic susceptibility showed energy loss due to flux penetration and vortex movement at the grain boundary. The critical temperature of 92 K was obtained for pure Y123 by real component of magnetic susceptibility and complete diamagnetism was observed in all samples (x=0.00, 0.06, 0.10 and 0.30). Silver decreased the critical temperature and increased the critical current density. Based on the obtained values of maximum Josephson current and Josephson intergranular energy coupling, it can be concluded that x=0.10 is the best weight percentage for Ag among the Y123 doped samples. Indeed, the greater inter-granular Josephson coupling energy causes, the superior of the trapping force and consequently produces the better critical current density.

The conventional eddy current method for non-destructive inspection of welding joints has limitations that can examine defects to a certain depth below the surface of the sample and is not suitable for determining deep defects. This limitation can be overcome using the SQUID superconducting sensors. The nonstoichiometric composition of YBCO due to its superconducting temperature and desired critical current density is widely used including the use of highly sensitive SQUID sensors. The properties and temperature of the superconducting compound are related to producing pure and homogeneous with a precise ratio of this non-stoichiometric compound in phase Y:123. In this study, the production of this high-temperature superconductor was carried out using a sol gel self-combustion process with nitrate forming elements and then produced powder analyzed by TGA, XRD, scanning electron microscopy, and EDX method and optimum conditions for production of Y:123 superconducting nanopowder were obtained by sol gel self-combustion method. In these conditions, the superconducting phase Y:123 was produced and the impurities were removed and on the other hand, the need for further thermal treatment and the costly annealing process were removed. Finally, optimal conditions for deposition of this compound on the substrate for producing the SQUID sensor were investigated and an optimal condition was presented to produce thin layer YBCO deposited by pulsed laser deposition method and patterned to produce SQUID High temperature Superconductor SQUID sensor. Finally the SQUID based NDT test for detecting sub-surfaces defects was investigated.