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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]

The impact of adding the orthoferrite NdFeO3, at the nanoscale, on the (Cu0.5Tl0.5)Ba2Ca2Cu3O10–δ phase formation, microstructure, electrical and mechanical performance was studied. The nano-(NdFeO3)x/(CuTl)-1223 composites, with x = 0.00, 0.25, 0.50, 0.75, 1.00, and 2.00 wt.%, were prepared using the solid-state reaction technique. The X-ray diffraction (XRD) confirmed that supplementing the host (CuTl)-1223 phase with nano-NdFeO3 did not alter the unit cell parameters (a and c) and preserved the tetragonal structure. SEM micrographs suggested that the inclusion of nano-NdFeO3 reduced the number of voids and boosted the inter-grain connections. The energy-dispersive X-ray (EDX) spectra revealed the elemental compositions of the various superconductor composites. The superconducting transition temperature (Tc) and the critical current density (Jc) increased with the inclusion of nano-NdFeO3 up to x = 0.50 wt.%. X-ray photoelectron spectroscopy (XPS) spectra analysis revealed the elemental composition and oxidation state of all elements. The Vickers microhardness (Hv) measurements were analyzed and compared with five different theoretical models. According to Hv measurements, the modified proportional sample resistance (MPSR) model provided the best theoretical analysis of Hv within the plateau limit regions. Moreover, various mechanical parameters were estimated as a function of the inclusion of nano-NdFeO3. The indentation creep test showed that the composite samples with high nanoparticle concentration (x > 0.50 wt.%) have dislocation creep mechanism, while those with x ≤ 0.50 wt.% followed a dislocation climbs creep mechanism. A comparison between NdFeO3 nanoparticles and other magnetic ferrites and nano-magnetic oxides was reported. [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]

Superconducting samples of type (CuTl)-1223 added with nano-FeO ( x=0.0, 0.1, 0.2, 0.4, 0.6 and 1.0 wt.%) were prepared by solid-state reaction technique. The prepared samples were characterized using X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) for phase analysis and microstructure examination. The elemental content of the prepared samples was determined using particle induced X-ray emission (PIXE), whereas the Oxygen-content of these samples was obtained using non Rutherford backscattering spectroscopy at 3 MeV proton beam. It was found that the Oxygen-content of (CuTl)-1223 phase was not affected with the addition of nano-FeO. The electrical resistivity measurements showed that the superconducting transition temperature ( T) increases up to x=0.2 wt.%, followed by a systematic decrease for x>0.2 wt.%. In addition, room temperature Vickers microhardness ( H) measurements were carried out at different applied loads (0.49-2.94 N) to study the performance of the mechanical properties of samples. The experimental results of H were analyzed using different models such as elastic, energy dissipation, energy balance and modified energy balance models. It has been found that the energy dissipation model is in a good agreement with the microhardness data. [ABSTRACT FROM AUTHOR]

The influence of single wall carbon nanotubes SWCNTs and multi wall carbon nanotubes MWCNTs on Vickers microhardness of Gd-123 superconducting phase is studied. Samples of type (SWCNTs) x and (MWCNTs) x GdBa 2 Cu 3 O 7−δ , composite where, 0.0 ≤ x ≤ 0.1 wt.%, are prepared by solid-state reaction technique. The samples are characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM). Moreover the samples are examined by measuring electrical resistivity and Vickers microhardness. The obtained results showed an enhancement in the phase formation and grains connectivity up to 0.06 and 0.08 wt.% for SWCNTs and MWCNTs added samples, respectively. Likewise the superconducting transition temperature T c was improved at a low content of CNTs but it suppressed for higher concentrations. In addition, the analysis of Vickers microhardness measurements suggests that the most suitable model that describes the behavior of our sample is proportional specimen resistance PSR model. [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]