M. Pakdil

Decrement in metastability with Zr nanoparticles inserted in Bi-2223 superconducting system and working principle of hybridization mechanism

Abstract This exhaustive study experimentally deals with the role of Zr foreign impurities on the electrical, superconducting and flux pinning properties of the bulk Bi-2223 superconducting compounds by the typical experimental characterization methods such as dc resistivity (ρ–T), transport critical current density (Jc) and powder X-ray diffraction (XRD) surveys. All the experimental findings show that the curial characteristics, being in charge of the varied attractive and feasible applications, retrograde significantly with the enhancement of the Zr nanoparticles in the Bi-2223 superconducting system due to the presence of two trap levels for mobile holes. This leads to the degradation of the metastability of the superconducting materials. In more detail, based on the dc resistivity and transport critical current density measurements, the Zr additives give rise to the localization problem as a consequence of the change in the dynamics of electron–electron interaction. Thus, the room state conductivity,

Microstructural and mechanical characterization of laser beam welded AA6056 Al-alloy

T_{c}^{onset}

Examination of effective nucleation centers for flux pinning of vortices and optimum diffusion annealing temperature for Au-diffusion-doped Bi-2212 polycrystalline compound

Tconset,

Enhancement of local microstructural distortions, boundary weak-interactions and crucial defeats performed via Bi+3/La+3 partial substitution in the Bi-2212 matrix

T_{c}^{offset}

Degeneration of mechanical characteristics and performances with Zr nanoparticles inserted in Bi-2223 superconducting matrix and increment in dislocation movement and cracks propagation

Tcoffset and Jc values retrograde significantly. Similarly, the Zr foreign impurities embedded in the Bi-2223 crystal lattice make the artificial random defects, dislocations and grain boundary weak-interactions in the consecutively stacked layers enhance immediately, and the superconducting Cu–O2 layers distort especially. Moreover, the XRD investigations including the evidences about the decrement/increment in the c-axis/a-axis length verify the regression of the superconducting properties with the Zr dopant. The main differentiation of the lattice constant parameters stems from aliovalent substitutions (replacement of the divalent Cu by the tetravalent Zr impurties) along with the crystal structure. In other words, the reduction of the electronegativity leads to decrease the mobile hole concentration in the Cu–O2 consecutively stacked layers. Furthermore, all the decrement parameters are theoretically favored by hybridization mechanism.

Mechanical properties and uniformity of Fe-MgB 2 wires upon various wire drawing steps

In this study, a failure analysis of glass-epoxy laminated composite bolted-joints with bolt/hole clearance under various torques was carried out. To estimate the effects of joint geometry and fiber orientation on the failure strength and failure mode, parametric studies were conducted experimentally. The two different geometrical parameters were the edge distance-to-hole diameter ratio (E/D) and plate width-to-hole diameter ratio (W/D), E/D ratio was selected from 1 to 5, and W/D ratio was chosen from 2 to 5. The bolt preload torque was also carried out as 0, 3, and 6 Nm. To investigate the material parameters effect, laminated plates were oriented as three different stacking sequences [90o]8, [45o]8, and [0o] 8. The experiments were carried out with a clearance between the diameters of the bolt and the circular hole of 5 and 6 mm, respectively. According to experimental results, failure mode and bearing strength are strongly influenced by both material parameters and geometrical parameters. Additionally, when a torque is applied to the bolted-joints, the failure mechanism is affected by its increasing values.