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Solid-state reaction method was used to prepare superconductor samples with nominal composition of (SnO)(BiPb)SrCaCuO, (SnO)(Bi,Pb)-2223 composite, where 0.0 ≤ x ≤ 0.2 wt%. The prepared samples were characterized by X-ray diffraction (XRD) as well as scanning electron microscopy (SEM). XRD patterns proved that the addition of nano-SnO particles to (Bi,Pb)-2223 did not affect the tetragonal structure and the lattice parameters of this phase. Vickers microhardness measurements ( H ) for these samples were carried out at room temperature as a function of applied load, heating temperatures, and dwell time. However, to clarify the indentation size effect (ISE) behavior of these composite materials and to estimate the true microhardness values ( H ), different models including Meyer's law, Hays and Kendall (energy dissipation) model, elastic/plastic deformation model, as well as proportional specimen resistance model were applied. Some important mechanical parameters, such as Young's modulus ( E), yield strength ( Y), fracture toughness ( K), and brittleness index ( B), were estimated from the microhardness curves. It was found that the incorporation of a proper concentration of nano-SnO particles has proved their efficiency to enhance the mechanical properties of superconductors. Moreover, it was noted that dwell time and Vickers microhardness were inversely proportional. Indentation creep experiments showed that the operative creep mechanisms in the studied samples were dislocation creep in addition to dislocation interaction. [ABSTRACT FROM AUTHOR]

Superconductor samples of type (CoFeO)GdBaCuO, 0.0≤ x≤0.1 wt.%, were synthesized by the conventional solid-state reaction technique. The prepared samples were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), electrical resistivity, AC magnetic susceptibility, and Vickers microhardness. Phase examination by XRD indicated that the orthorhombic structure of Gd-123 is not affected by nanosized ferrite CoFeO addition, whereas the volume fraction of Gd-123 increased with x up to 0.01 wt.%. Morphological investigations by SEM revealed that the porosity among grains decreased as x increased from 0.0 to 0.1 wt.%. The superconducting transition temperature T was estimated from electrical resistivity and the AC magnetic susceptibility measurements. A reduction in T was observed as x increased from 0.0 to 0.1 wt.%, consisting with the effect of adding magnetic impurities to HTSCs. Room temperature microhardness measurements were carried out at different applied loads (0.5-10 N) for the study of the mechanical performance of the studied samples. The experimental results were analyzed using Meyer's law, Hays-Kendall approach, elastic/plastic deformation model, and proportional specimen resistance model. The results showed that all the samples exhibited normal indentation size effect, and Vickers microhardness values were increased as nanosized CoFeO addition increased. The analysis showed that the proportional specimen resistance model is the best model for computing the load-independent microhardness values of our samples. [ABSTRACT FROM AUTHOR]

Superconducting samples of type (nano-Ag) xCu 0.5Tl 0.5Ba 2Ca 2Cu 3O 10−δ, x=0.0,0.5,1.0,1.5,2.0, and 3.0 wt.% of the total sample’s mass were prepared by a single step solid-state reaction technique. The prepared samples were characterized using X-ray powder diffraction (XRD) and a scanning electron microscope (SEM). The electrical properties of the prepared samples were investigated using the electrical resistivity and I– V measurements. The Vickers microhardness ( Hv) was measured at different applied loads (0.25–3.0 N) for studying the mechanical performance of the prepared samples. All prepared samples exhibited normal indentation size effect (normal ISE) and the Hv number was load dependent. Hv number increases as nano-Ag addition increased. The experimental data of Hv was analyzed using different models; Mayer’s law, Hays–Kendall (H–K) approach, elastic/plastic deformation (EPD) model, proportional specimen resistance (PSR) model, and indentation induced cracking (IIC) model. In addition, the true microhardness ( Ho) values were evaluated through different models. The obtained data has good agreement with the PSR model. Also, Young’s modulus ( E), yield strength ( Y), fracture toughness ( Kf), and brittle index ( Bi) were calculated. [ABSTRACT FROM AUTHOR]

In this study, superconducting samples of type CuTlBaCaCuO,(CuTl)-1223, added by SnO and InO in nano-scale were prepared by a solid-state reaction technique. The concentrations of both SnO and InO were varied from 0.0 to 1.0 wt.% of the total sample's mass. The prepared samples were characterized using X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) for phase analysis and microstructure examination, respectively. The electrical resistivity of the prepared samples was measured by the conventional four-probe technique from room temperature down to the zero superconducting transition temperature ( T). An increase in T is observed up to x=0.6 wt.% for (SnO) CuTlBaCaCuO, followed by a systematic decrease with increasing nano-SnO addition for x>0.6 wt.%. While, for (InO) CuTlBaCaCuO the T is slightly changed with x. Room temperature Vickers microhardness measurements were carried out at different applied loads (0.49-2.94 N) for the study of the mechanical performance of the prepared samples and examination of the effect of different nano-oxides addition on the microhardness of (CuTl)-1223 phase. Furthermore, the true microhardness values ( H), for both additions, were evaluated through different models and their results were compared with those estimated from the experimental results in the plateau region. Also, some important mechanical parameters, such as Young's modulus ( E), yield strength ( Y), fracture toughness ( K) and brittleness index ( B), were calculated for both additions. The results clarified that these parameters are strongly dependent on both the applied loads and the nano-oxides addition. [ABSTRACT FROM AUTHOR]