Papers by Keyword: Superconductor

Abstract: The structural and superconducting properties of iron sheathed mono-filamentary superconducting wires of MgB₂ with and without Fe addition processed at a relatively low temperature of 600 °C were investigated. The transport critical current density (J_C) of the superconducting composite wires is found to increase steadily with an increase in Fe content to an optimum of 10 wt.% is reached. The magnetic J_C and flux pinning analysis of the samples carried out up to a field of 9 T also show significant enhancements throughout the entire field of study. Another observation is that the T_C of the composites doesn’t vary much, indicating that the added Fe has not gone in to the MgB₂ lattice.

Abstract: This paper reports on the properties of YBa₂Cu₃O_d (Y123) and YCaBa₄Cu₆Oy (Y146) with non-porous and porous structures. The relationship between calcium doping and critical temperature (T_c) was studied to determine the optimal superconducting properties. A series of heating and grinding via solid state reaction method was used to fabricate the ceramic materials. The electrical properties were investigated via critical temperature, T_C and critical current density, J_C using the resistivity measurement system (RMS). Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD) were used to analyze the material morphology and structure, respectively. The orthorhombicity increased due to less porosity of the samples. The calcium presence partially replaced larger Ba(II) site and degraded orthorhombicity. The highest critical current density (J_C) was porous YCaBa₂Cu₃Oy which was 2.32 A/cm² compared to 0.75 A/cm² for porous YCaBa₄Cu₆Oy at 60 K. The critical temperature for porous structure was less than non porous structure for Ca doped Y146 system which was 69.9 K and 67.9 K. SEM micrograph unveiled that the Jc was induced significantly by continuity of grain formation via grain size. Pores homogenized the grains surface quality and connectivity due to strain release thus increasing effective cross section of the sample for current density (Jc) over the vast areas.

Abstract: Low density HTSC with nominal composition of Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_y filled with crystalline sucrose has been synthesized and its structucal and superconducting properties have been studied. The transport properties, morphology, density and structural identification were determined by using the standard four point probe, Field Emission Scanning Electron Microscope (FESEM), densitometer and X-ray diffraction (XRD) respectively. The critical current density (J_c) of optimized ratio of crystalline sucrose onto Bi-2223 powder used to produce low density Bi-based superconductor was found to be higher than the bulk polycrystalline sample. T_{C zero} obtained was varied between 93 and 101 K towards the increment ratio of crystalline sucrose with the highest T_{C zero} = 101 K for ratio of 0.050:1.950 and decrease gradually for further addition of cystalline sucrose. The crystallographic structures was found to be remained in tetragonal where a=b≠c. The grains with higher porosity resulting in decreasing of critical current density (J_c) as well as critical temperature (T_{c zero}) due to lack of effective area of current flows.

Abstract: It is still a difficult problem to solve for a suspension system simultaneously to hold the body of the car in comfort and to execute the requirements of other safety systems like ABS, ESP, steer-by-wire, etc systems. Passive suspension systems are unlikely to provide a solution, the introduction of semi-active suspensions in the practical use is necessary. A possible solution could be a permanent magnetic (PM) synchronous tube generator, which can operate as a controllable shock absorber parallel with energy recuperative operation. Designer software is realized, to calculate the geometrical and electrical parameters of permanent magnetic (PM) or high temperature superconductor (HTS) magnets for arbitrary vehicle suspension systems

Abstract: With sugar as an addition, the active carbon released from sugar can lead to the effective carbon doping in MgB2 superconductors only under the condition of high temperature sintering. However, this kind of carbon doping cannot occur at low temperature sintering condition. The reason is that the carbon released from the decomposition reaction of the sugar added in MgB2 has very low chemical activity during low temperature sintering process, which is similar with the results of elemental carbon or graphite doping directly. Thus, only the sintering temperature reaches a certain temperature or more (generally greater than 700oC), the carbon can possess sufficiently high chemical activity and go into the lattice of MgB2 to replace the B. In the condition of low temperature, it is difficult to form an effective carbon-doped.

Abstract: The addition of two compounds, calcium silicate and calcium zirconate was tested, in the preparation of Bi: 2212 silver sheathed wires by powder-in-tube method, which were successfully tested previously in processing chips. The wires were treated in an atmosphere of O₂/Ar using partial melting method. The characterizations were structural and on their electrical and magnetic properties. As the results, transition temperatures were higher than the expected for this stage, ranged from 105K (BSCCO880) to 116K (+Si883). The critical current densities encountered in transport and magnetization measurements were improved in comparison with the wires without addition.

Abstract: In this research, we synthesized Y123 superconductor and Y235 superconductor doped with fluorine by solid sate reaction with Y₂O₃, BaCO₃, CuO and CuF₂ as precursor. The physical properties of Y235+F_x (Y₂Ba₃Cu₅O_y-xF_x) and Y123+F_x (YBa₂Cu₃O_y-xF_x) superconductors were studied at x = 0,0.1, 0.2. The calcinations process was done twice in air at 810 °C for 24 hr and was increased to 925 °C for one hour. The sintering process was done at 925 °C for 24 hr and reduced to 500 °C for 24 hr. Our samples obtained were characterization by the four point probe technique, SEM and EDX, respectively. The surface of all samples were inhomogeneous and no impurity. The critical temperature onset of Y123+F_x and Y235+F_x were equal to 92 K, 95 K, 93 K and 92 K, 93 K, 92 K with x= 0, 0.1, 0.2, respectively.

Abstract: In this research, the Y123 (YBa₂Cu₃O_x) and Y134 (YBa₃Cu₄O_x) superconductors were synthesized by solid state reaction and melt process, respectively. The crystal structure of all the samples were then determined using the Rietveld full-profile analysis method to indicate orthorhombic structure. The resistivity measurements showing T_c onset of Y123 lower than Y134 for solid state reaction but higher than Y134 melt process. However, the critical temperature off-set of Y134 has lower than of Y123. The SEM and EDX show that all samples were inhomogeneous. The SEM micrograph for solid state reaction Y123 has many pores between the grain and the grain size clearly demonstrated and bigger than Y134. It was seen that these pores are party eliminated in melt process samples. FTIR spectra detected the trace of carbonate residue in all samples.

Abstract: This paper reports on the design cost and scaling model of a small scale superconducting wind turbine generator, where the levelized cost of energy (COE) was calculated. The proposed design of the wind turbine is based on the vertical axis wind turbine (VAWT) type that drives the superconducting generator. VAWT was chosen due to its ability to operate under low wind speed. Wind turbine using superconducting generator was proposed since it is able to enhance magnetic flux within the stator of the generator and consequently improve the performance of the generator. Once the design has been accomplished, all the cost of parts and components must be accounted and contributes to the overall cost of generating electrical energy from the superconducting wind turbine generator. The cost elements include the initial capital cost (ICC), balance of station (BOS), operation and maintenance (O&M), levelized replacement cost (LRC) and annual energy production (AEP). The calculated levelized COE shows that the cost of generating electricity using superconducting wind turbine generator is lower than generating electricity from conventional sources.

Abstract: We investigated transport characteristics of composite that consist of the superconductor MgB₂ and ferromagnetic half-metallic nanoparticles La_0.7Ca_0.3MnO₃ (LCMO). The experiments were carried out in a wide temperature range with different volume content of the magnetic impurity. It was found that over 25% of the impurity manganite breaches percolation paths of the diboride magnesium. This leads to a considerable broadening of the MgB₂ superconducting transition and the formation of the network of contacts through the ferromagnetic inclusions. This result shows the possibility of the spin - activated surface realization on the superconductor - manganite boundary. It's allowing the free transition of Cooper pairs with s wave symmetry of the order parameter in a ferromagnet with 100% spin-polarized carriers.