Effect of substitution and heat treatment route on polycrystalline FeSe0.5Te0.5 Superconductors

The effect of atomic substitution of Te in iron based superconductors FeSe (1:1 type), which exhibits the simplest crystal structure among the iron-based superconductors, has been investigated in terms of structural, electronic transport and magnetic properties. Polycrystalline samples with nominal Se:Te in FeSe1-xTex samples for x=0.5350{\deg}C, 0.5700{\deg}C, 0.6700{\deg}C and 0.75700{\deg}C were synthesized by the solid-state reaction method. It has been observed that the most superconducting properties seen in x=0.6700{\deg}C samples as dc magnetic susceptibility, ac susceptibility and resistivity measurements. Tc enhancement is well correlated with the Te substitution up to 75% and c lattice parameters monotonically increased with increasing Te concentration

The effect of excess Y2O3 addition on the mechanical properties of melt-processed YBCO superconductor

In this study, two kinds of melt-processed YBCO samples with Y2O3 addition were fabricated and their microstructures were defined by XRD analysis and polarized light optical microscopy. The mechanical properties of these compounds have been investigated by measuring the Vickers hardness. The superconducting transition temperature was determined by inductive measurements for oxygenated and non-oxygenated samples. The compacted powders were located on a crucible with a buffer layer of Y2O3 and a crucible with Y2O3 powder freely poured to avoid liquid to spread on the furnace plate. It was found that the sample located on crucible with freely poured Y2O3 powder has shown almost single crystal and indicated a very sharp transition curve

The Effect of Y2O3 on AC susceptibility measurements of MPMG YBCO superconductor

Meeting: 3rd International Conference on Superconductivity and Magnetism (ICSM) Location: Istanbul, TURKEY Date: APR 29-MAY 04, 2012In this study, two kinds of melt-powder-melt-growth (MPMG) YBCO sample grown on a buffer layer of Y2O3 addition were fabricated. The compacted powders were located on a crucible with Y2O3 powder freely poured and a buffer layer of pressed Y2O3. AC susceptibility measurements of the samples as a function of temperature was reported for several different AC magnetic-field amplitudes (H (ac) ) in the presence of static bias magnetic field (H (b) ) directed along H (ac) . The loss peaks are found to shift towards lower temperatures as the AC field strength is increased. The frequency effect on the AC susceptibility was also measured. As the frequency increases, the peak temperature shifts to higher temperature. This effect can be interpreted in terms of flux creep

Performance test of dual fuel engine using octagonal with algae biodiesel

237-241In comparison to internal combustion engines, diesel engines are high thermal-efficient. However, the application of diesel engines is still dependent on fossil fuels. This fuel has limited availability and the effects are also very dangerous, especially its emission. Octagonal has been used as an alternative fuel to replace fossil-based diesel fuel. The purpose of this work is to explore the performance of the dual fuel engine-octagonal diesel. The performance test has been carried out by running the indirect injection engine that is modified to direct injection at 1500 rpm using four types of like diesel fuel, and diesel mixed with octagonal 2.5, 5 and 10%. The results show that there was an increasing effect of engine-indicated mean effective pressure (IMEP) value and brake-specific fuel consumption (BSFC) reduction when the engine is operated using octagonal diesel fuel blends. The emission of hydrocarbon (HC) tended to increase, while the emission of smoke and carbon monoxide (CO) decreased when the engine is operated using dual fuel-octagonal diesel

Investigation of effect of x in Yb1-xGdxBa2Cu3O7-y superconducting structures on upper critical magnetic field and coherence length.

The resistivity measurements of the Yb1-xGdxBa2Cu3O7-y superconducting samples prepared by using the solid-state reaction technique for x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 were performed in QD-PPMS system under different magnetic fields up to 5T in zero field cooling regime. The upper magnetic field Hc2(T=0) for each sample was calculated from 50% of the normalized resistivity (Rn) by the extrapolation Hc2(T) to T=0K and the coherence lengths x(T=0) of the samples were calculated from the Hc2(0) values. The examination of the effects of x in the composition on Hc2(0) showed us that the upper critical magnetic field decreased from 186.31T for x=0.0 to 37.99T for x=1.0 with the increasing of content x from x=0.0 to 1.0. Using the content x in the composition, the upper critical magnetic field can be controlled and this can be used in superconducting application especially as a superconducting relays

Improvement of superconducting properties of MgB2 by changing the argon ambient pressure and sintering conditions

We have investigated various characteristic properties depending on sintering conditions of MgB2 samples prepared by the standard solid state reaction method. It is inferred from experimental results that the crystallinity of samples were improved when the pressure of the Ar ambient increased. Also, it was found that the sintering temperature above 850 ºC caused extremely high amount of decomposition of the superconductor phase. Finally, it was considered that the sintering process of MgB2 must be carried out under the pressure of Ar ambient higher than 8 bar to impede the volatility of Mg in the structure of MgB2. The Jc values of samples systematically enhanced with the increase of sintering time and in particular, the sample sintered for 180 min. exhibited the highest Jc (0) of 4.9 × 103 A cm−2 at 30 K. The obtained results demonstrate that the sintering conditions of MgB2 have a significant influence on Tc (onset) and Jc, which are directly related to practical applications of MgB2 based superconductor components

Environmental emission analysis of the engine using Botryococcus braunii marine algae with CeO2 nanoparticle additives

AbstractAs fossil fuel is depleted day by day, there is a vast gap in the market and supply of fuel to the different industries that consume oil. In order to improve fuel properties, performance, combustion, and emissions from diesel engines, microalgae oil biodiesels are used as fuel with 20% of diesel on a mass basis by volume and 50 and 100 ppm of CeO2 nanoparticles as additives in combinations of biodiesel/diesel blends. The engine configuration consists of a single-cylinder, four-stroke, 3.5 kW, 1500 rpm diesel engine. Experiments were performed at constant speed on experimental test fuels for various load conditions. The addition of cerium oxide (CeO2) in the added biodiesel diesel blends improved the brake thermal performance (45%) compared to engine output. With CeO2 in the B20 blends, better combustion properties were observed, such as increased length of combustion (36 CA°), ignition delay (16 CA°), and heat release rate (55 J/deg) in the cylinder. The enhanced and improved fuel characteristics and combustion characteristics of CeO2 in the added biodiesel diesel blends minimise HC (0.54 g/kWh) and CO (4.6 g/kWh) emissions and smoke (0.61%) while increasing NOx (10.2 g/kWh) emissions from the engine cylinder

The nanoscale structure and unoccupied valence electronic states in FeSe1-xTex chalcogenides probed by X-ray absorption measurements

HACISALIHOGLU, Muammer Yasin/0000-0002-0795-2931; HACISALIHOGLU, Muammer Yasin Yasin/0000-0002-0795-2931; Joseph, Boby/0000-0002-3334-7540; Joseph, Boby/0000-0002-3334-7540WOS: 000357809300072PubMed: 26099493We have studied the nanoscale structure and unoccupied electronic states in FeSe1-xTex by a combined analysis of Se K, Te L-1 and Fe K-edges X-ray absorption measurements. Extended X-ray absorption fine structure (EXAFS) results show that iron-chalcogen (Fe-Se and Fe-Te) distances in ternary FeSe1-xTex are similar to those measured for binary FeSe and FeTe. the local Fe-Se/Te distances determined by different absorption edges fit well in the characteristic Z-plot of random alloys, providing unambiguous support to the inhomogeneous nanoscale structure of the ternary FeSe1-xTex system. X-ray absorption near-edge structure (XANES) spectra reveal a gradual evolution of the unoccupied valence electronic states as a function of Te-substitution in FeSe1-xTex. the Fe 3d-Se 4p/Te 5p hybridization is found to decrease with Te-substitution, accompanied by an increase in unoccupied Se 4p states and a decrease in unoccupied Te 5p states. the results are discussed in the frame of local inhomogeneity in the FeSe1-xTex system driven by random alloying of Se/Te atoms.MIUR, ItalyMinistry of Education, Universities and Research (MIUR) [2012X3YFZ2]The authors acknowledge the support and help from the Elettra staff during the experimental runs. One of us (M.Y.H.) would like to thank Sapienza University of Rome for the hospitality. M.Y.H. also acknowledges Professor Bernd Buchner, Drs Sabine Wurmehl, Michael Schulze, Christian Blum and IFF12 group members for the help and encouragement during the stay at IFW, Dresden for the sample preparations and characterizations. the work at the Sapienza University of Rome is supported by the PRIN2012 (grant no. 2012X3YFZ2) of MIUR, Italy

The size effect on the magnetic levitation force of MgB2 bulk superconductors

GUNER, SAIT BARIS/0000-0001-7487-4817WOS: 000390726600012In this study, the size effect on the magnetic levitation performance of disk-shaped MgB2 bulk superconductors and permanent magnets was investigated. MgB2 samples with varying diameters of 13 mm, 15 mm and 18 mm, each of which were 2 g in mass, were prepared by two-step solid state reaction method. Vertical levitation force measurements under both zero-field-cooled (ZFC) and field-cooled (FC) regimes were carried out at different temperatures of 20, 24 and 28 K. It was determined that the levitation force of the MgB2 strongly depends on both the diameters of the sample and the permanent magnet. in ZFC regime, the maximum levitation force value for the permanent magnet and the sample 18 mm in diameters reached to the 8.41 N at 20 K. in addition, in FC regime, attractive and repulsive force increased with increasing diameters of the sample and the permanent magnet. in that, the sample with 18 mm in diameter showed the highest attractive force value -3.46 N at 20 K and FC regime. the results obtained in this study are very useful in magnetic levitation devices as there is no detailed study on the size of superconductors and permanent magnets. (C) 2016 Elsevier Ltd. All rights reserved.Turkish Science and Technology Council-TUBITAKTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [113T008, 110T622]This work was supported by Turkish Science and Technology Council-TUBITAK under the project numbers 113T008 and 110T622

Magnetic Properties of YBCO Single-Crystal Grown on Y2O3 Layer by a Cold Top-Seeding Method

This study was supported by the Turkish Scientific and Research Council (TUBITAK) research grant (TBAG-107T751) and Karadeniz Technical University research grant (BAP-2008.111.001.8). The authors are grateful to Ms. Kubra Karaoglu for technical assistance.In this work, single-crystal samples 20 mm in diameter were grown by a cold top-seeding method. In order to study the effect of an Y2O3 buffer layer, a compacted precursor was located in a crucible on a buffer layer of freely poured Y2O3 powder. The YBCO bulk samples were carefully prepared in the same chemical composition. In order to examine the homogeneity of the samples, rectangular specimens were cut from a sample. The structural orientation of the specimens was measured by a X-ray diffractrometer (XRD). The microstructure was observed with a Scanning Electron Microscope (SEM). The magnetic properties were measured using a Vibrating Sample Magnetometer (VSM) at 77 K with the applied magnetic field parallel to the c-axis. As a result only (00l) peaks were observed in X-ray diffraction data, indicating that all specimens are highly oriented with the c-axis perpendicular to the top surface. Also the cut samples exhibited very fine Y211 inclusion distributed in the bulk sample observed in SEM micrographs. The critical current density J (c) (A/cm(2)) has been estimated by the extended Bean model. The maximum value of the critical current density at 77 K is 5.2x10(4) A/cm(2) in a self-field. The trapped magnetic field measurements of the samples were performed by using Hall probe scanning device with static field of 0.5 T at 77 K. The single-domain sample exhibits a trapped field of 1140 G at 77 K