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Effect of vanadium doping on the electrical and structural properties of GdBa2Cu3-xVxO7-δ
, Article Physica Status Solidi (B) Basic Research ; Volume 245, Issue 8 , 21 July , 2008 , Pages 1611-1617 ; 03701972 (ISSN) ; Bazargan, S ; Akhavan, M ; Sharif University of Technology
2008
Abstract
The compounds with composition GdBa2Cu3-xV xO7-δ and x = 0.0, 0.05, 0.1, 0.15, 0.2 and 0.3 have been prepared by the solid-state reaction method. The XRD spectra indicate single-phase formation of the compounds. The transition temperature decreases considerably with vanadium concentration to Tc = 26.4 K for x = 0.3. The host sample is in the orthorhombic phase, but by increasing the V content the structure approaches the tetragonal phase, and for x = 0.3 the structure is nearly tetragonal. The normal state resistivity has been compared with 2D-VRH, 3D-VRH, and CG regimes, which shows that the 2D-VRH and CG are in better agreement for our samples. The localization length is calculated for the...
Structural aspects and the conduction mechanism of Ln(Ba 2-xPrx)Cu3O7+δ (Ln = Tm, Lu)
, Article Physica Status Solidi (B) Basic Research ; Volume 244, Issue 9 , 2007 , Pages 3211-3222 ; 03701972 (ISSN) ; Akhavan, M ; Sharif University of Technology
2007
Abstract
TmBa2_xPrxCu3O7+δ and LuBa2_xPrxCu3O7+δ samples with 0.0 < x ≤ 1.0 have been prepared by a solid-state reaction technique. The occurrence of the orthorhombic to tetragonal phase transition, increasing of oxygen content with the increase of Pr doping, and the existence of solubility limit in both systems confirm the correct substitution of Pr at Ba sites. The solubility limit for Pr in the Lu-based samples is less than 0.7, which is less than x = 0.90 for the Tm-based samples. The Tc depression versus doping content in both systems shows that depression of superconductivity by Pr at Ba sites is mostly due to the hole-filling/localization effects. Also, in the Tm-based system, the...
Interplay of magnetism and superconductivity
, Article Physica Status Solidi (A) Applications and Materials Science ; Volume 203, Issue 11 , 2006 , Pages 2956-2961 ; 18626300 (ISSN) ; Sharif University of Technology
2006
Abstract
After about two decades of intense research since the discovery of high-temperature superconductivity (HTSC) in cuprates, although many aspects of the physics and chemistry of these cuprate superconductors are now well understood, the underlying pairing mechanism remains elusive. Magnetism and superconductivity are usually thought as incompatible, but in number of special materials including HTSCs these two mutually excluding mechanisms are found to coexist. The presence in a system of superconductivity and magnetism, gives rise to a large number of interesting phenomenon. This article provides perspective on recent developments and their implications for our understanding of the interplay...
High-temperature deformation and structural restoration of a nanostructured Al alloy [electronic resource]
, Article Journal of Scripta Materialia (Pergamon) ; June 2012, Volume 66, Issue 11, Pages 911–914 ; Simchi, A. (Abdolreza) ; Kim, H. S ; Sharif University of Technology
Abstract
We studied the flow stress and microstructural changes of nanostructured Al-6063 alloy produced by mechanical alloying at various temperatures and strain rates. The analysis of flow curves was performed by a constitutive equation, and the stress exponent and activation energy were determined as functions of strain. The deformation mechanisms were elaborated through microstructural observations by electron backscattering diffraction and transmission electron microscopy. Coarsening of the subgrains and grain growth upon deformation was monitored and related to the Zener–Hollomon parameter
High temperature mechanical properties of triple phase steels
, Article Materials Letters ; Volume 61, Issue 4-5 , 2007 , Pages 1023-1026 ; 0167577X (ISSN) ; Sharif University of Technology
2007
Abstract
A 0.15% C-1.2% Si-1.7% Mn steel was intercritically annealed at 780 °C for 5 min and then isothermally held at 400 °C for 4 min followed by oil quenching to room temperature and the annealed microstructure consist of 75% ferrite, 15% bainite and 10% retained austenite was produced. Samples of this steel with triple phase structure were tensile tested at temperature range of 25-450 °C. Stress-strain curves showed serration flow at temperature range of 120-400 °C and smooth flow at the other temperatures. All of the stress-strain curves showed discontinuous yielding at all testing temperatures. Both yield and ultimate tensile strength decreased with increasing temperature, but there exists a...
Survey on high-temperature superconducting transformer windings design
, Article Journal of Superconductivity and Novel Magnetism ; Volume 33, Issue 9 , 8 June , 2020 , Pages 2581-2599 ; Ardeshiri, A ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
Springer
2020
Abstract
Utilization of superconducting equipment increases every day due to availability of the HTS tapes with reasonable prices, commercially. Since 1997, many high-temperature superconducting (HTS) transformers have been designed and fabricated. In this paper, all the different developments of HTS transformer windings since 1997 will be reviewed. Additionally, the advantages and disadvantages of the application of the two main winding types (the pancake and the layer) in the HTS transformer will be studied. © 2020, Springer Science+Business Media, LLC, part of Springer Nature
Design and Fabrication of Inductive High Temperature Superconducting Fault Current Limiter
,
Ph.D. Dissertation
Sharif University of Technology
;
Vakilian, Mehdi
(Supervisor)
;
Fardmanesh, Mehdi
(Supervisor)
Abstract
The continuous rise in electricity demand and the ever growing power generation in different power networks over the world have caused the short circuit level in the power systems to exceed the operational rating of the installed power devices (including cables, circuit breakers and buses). Replacing these devices with new higher rating devices is an expensive solution. From this point of view, utilizing fault current limiters is an economical solution. Superconducting fault current limiters form an efficient category of current limiters. This type is expected to be studied and used widely in future due to their advantages. In this thesis, the first chapter reviews the superconductivity...
Raman Study of Tb-doped YBCO and Ce-doped GdBCO
, Article Physica C: Superconductivity and its Applications ; Volume 468, Issue 13 , 2008 , Pages 985-990 ; 09214534 (ISSN) ; Akhavan, M ; Sharif University of Technology
2008
Abstract
The phase formation and the variation of the normal phonon frequencies of high temperature superconductors YBa2Cu3O7-δ and GdBa2Cu3O7-δ upon doping Tb and Ce for Y and Gd, respectively, have been investigated using XRD and Raman spectroscopy measurements. It is found that the increase of doping content causes the formation of impurity phases that can be detected in the XRD and Raman spectra, and results in the suppression of superconductivity. Moreover, analysis of the Raman peaks reveals that substitutions of Tb and Ce for Y and Gd in the parent structure are restricted to low concentrations in favor of impurity island formation. © 2008
Axiomatic design of a reflective multilayer high-temperature insulator
, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 233, Issue 2 , 2019 , Pages 457-471 ; 09544100 (ISSN) ; Abedian, A ; Farsi, M. A ; Kalantarinezhad, R ; Sharif University of Technology
SAGE Publications Ltd
2019
Abstract
High-temperature insulators protect structures against extreme thermal loads in various industries such as energy and space-related areas. For such insulations, radiation is the dominant mode of heat transfer. The intended multilayer high-temperature insulator utilizes reflection as the controlling mechanism for the radiative heat transfer. In the current study, the axiomatic design methodology is used to map the design process of a reflective multilayer high-temperature insulator. In addition, an analytical model is developed to simulate the combined radiation and conduction heat transfer in the reflective multilayer high-temperature insulator. The model was solved numerically and validated...
High temperature mechanical properties of dual phase steels
, Article Materials Letters ; Volume 59, Issue 16 , 2005 , Pages 2070-2074 ; 0167577X (ISSN) ; Sharif University of Technology
2005
Abstract
Dual phase steels with different martensite volume fraction and morphology were tensile tested at temperature range of 25-550 °C. Stress-strain curves of all steels showed serration flow at temperature range of 250-450 °C and smooth flow at the other temperatures. Both yield and ultimate tensile strengths increased with increasing testing temperature up to about 450 °C and then decreased at higher temperatures. At a given temperature, yield stress, tensile strength, and work hardening increased with increasing volume fraction of martensite. Similar behavior was observed by changing martensite morphology from network to fibrous martensite. The change in mechanical properties was related to...
Room-temperature mechanical properties of dual-phase steels deformed at high temperatures
, Article Materials Letters ; Volume 59, Issue 14-15 , 2005 , Pages 1828-1830 ; 0167577X (ISSN) ; Vahdani, H ; Sharif University of Technology
2005
Abstract
Dual-phase steels with different morphology and volume fraction of martensite were deformed between 2% and 8% at a high-temperature range of 150-450 °C. Room-temperature tensile properties showed that both yield and tensile stresses depend on the amount of pre-strain, deformation temperature, volume fraction and morphology of martensite. Results show that both YS and UTS increase with increasing the amount of pre-strain at a given temperature. © 2005 Elsevier B.V. All rights reserved
Effect of rare-earth element additions on high-temperature mechanical properties of AZ91 magnesium alloy
, Article Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science ; Volume 36, Issue 12 , 2005 , Pages 3489-3494 ; 10735623 (ISSN) ; Nami, B ; Khoshkhooei, S ; Sharif University of Technology
Minerals, Metals and Materials Society
2005
Abstract
The present article focuses on the high-temperature mechanical properties of the magnesium alloy AZ91. The addition of rare-earth (RE) elements up to 2 wt pct improves both yield and tensile strengths at 140 °C by replacing the Mg17Al12 phase with RE-containing intermetallic compounds. This intermetallic phase is thermally and metallurgically stable and is expected to boost the grain-boundary strengthening. It also increases the resistance of grain boundaries to flow at high temperatures. Further increases of RE additions reduce strength and ductility due to growth of the Al11RE3 brittle phase, which has sharp edges. Still, at a 3 wt pct RE addition, the strength of the alloy at high...
Effects of Spin- Orbit Coupling on the Phase Diagram of Doped Mott Insulator
, M.Sc. Thesis Sharif University of Technology ; Vaezi, Abolhassan (Supervisor) ; Ejtehadi, Mohammad Reza (Supervisor)
Abstract
In the past few years, topological insulators (TIs), topological superconductors and their experimental observation have been in the center of condensed maer physicists’ aention. Kane and Mele proposed the simplest and the first model exhibiting TI phase for non-interacting electrons on the two dimensional honeycomb laice. On the other hand, in the Hubbard model for nonzero doping and near the half filling, the high temperature superconductivity is predicted theoretically. In this thesis, we fist investigate the interacting topological insulators by adding the Hubbard interaction to the Kane-Mele model. en, in the strong correlation limit we find an effective spin model -the so called...
Vortex Dynamics in Magnetic Phase Diagram of High Tc Cuprate Oxides
, M.Sc. Thesis Sharif University of Technology ; Khosroabadi, Hossein (Supervisor) ; Akhavan, Mohammad (Supervisor)
Abstract
In the 1950s, Abrikosov predicted the mixed state in superconductors (type II superconductors) which lead to a Noble Prize in 2003 with the experimental verification by shubnikov. Mixed-state is a network of magnetic flux lines with quantized flux (vortices) in superconductors. High-temperature superconductors are of Type II which the existense of vortices in a significant part of the temperature-field phase diagram of them, is an obvious phenomenon. These superconductors provided a proper context for understanding physical phenomena related to vortices and access to experimental data to compare with those provided by statistical mechanics. Vortices can move inside the superconductor by the...
Analysis of nonlinearities in superconducting microstrip straight bends; FDTD method in comparison with nonlinear circuit modeling
, Article Journal of Superconductivity and Novel Magnetism ; 2012 , Pages 1-4 ; 15571939 (ISSN) ; Javadzadeh, S. M. H ; Shishegar, A. A ; Banai, A ; Farzaneh, F ; Fardmanesh, M ; Sharif University of Technology
2012
Abstract
This paper presents the prediction of nonlinearities in the superconducting microstrip straight bends in microwave frequencies based on two different methods; FDTD simulation as a numerical approach, and nonlinear circuit modeling as an analytical method. In the FDTD method, the superconducting microstrip structures are simulated with London's equations. In the simulation, the penetration depth and normal conducting coefficient are considered as functions of current density of superconductor. To simulate the thin strip of superconductor, a non-uniform mesh has been used. For the nonlinear circuit modeling, we use distributed RLGC parameters for superconducting microstrip transmission lines....
High temperature synthesis of SAPO-34: applying an L9 taguchi orthogonal design to investigate the effects of experimental parameters
, Article Powder Technology ; Volume 217 , February , 2012 , Pages 223-230 ; 00325910 (ISSN) ; Kazemian, H ; Soltanieh, M ; Hosseinpour, M ; Rohani, S ; Sharif University of Technology
Abstract
SAPO-34 zeolite-like particles were successfully synthesized at high temperature environment. An L9 orthogonal array of the Taguchi method was implemented to investigate the effects of experimental conditions to prepare SAPO-34 with respect to crystallinity of the final product phase. The results showed that the favorable phase crystallinity was improved by increasing the hydrothermal synthesis temperature and organic template content, whereas increasing the water content in synthesis mixture decreased the crystallinity. No significant changes in crystallinity of the final products were observed by increasing the synthesis duration. In addition, zeolite SAPO-5, which was formed as the...
The impact of multilayered flux diverters on critical current in HTS transformer windings
, Article 27th Iranian Conference on Electrical Engineering, ICEE 2019, 30 April 2019 through 2 May 2019 ; 2019 , Pages 481-485 ; 9781728115085 (ISBN) ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2019
Abstract
Growing interest in high-temperature superconducting (HTS) power devices is the result of commercial availability of the HTS tapes. One of the most promising applications of the HTS technology is HTS transformer. Flux diverters are used for critical current elevation in HTS transformer windings. In this paper multilayered flux diverter arrangements have been introduced to reduce weight and losses of conventional solid flux diverter arrangement. Horizontal and vertical multilayered arrangements have been investigated and compared with solid arrangement. Two dimensional (2D) finite element method (FEM) simulations have been used for comparison between different arrangements
Terahertz lensing effect in high-temperature superconductors
, Article Journal of the Optical Society of America B: Optical Physics ; Volume 36, Issue 5 , 2019 , Pages 1241-1245 ; 07403224 (ISSN) ; Tavakol, M. R ; Khavasi, A ; Rejaei, B ; Sharif University of Technology
OSA - The Optical Society
2019
Abstract
We show that high-temperature superconductors can be used to build a terahertz superlens. These materials exhibit hyperbolic behavior at frequencies between their two plasma frequencies corresponding to electric fields parallel and perpendicular to their c-axis. Due to the large component of permittivity perpendicular to the c-axis, the resolution of the proposed lens is much below the diffraction limit (λ/1000). In this paper we demonstrate this lensing phenomenon with a simple slab of a high-temperature superconductor. © 2019 Optical Society of America
Terahertz lensing effect in high-temperature superconductors
, Article Journal of the Optical Society of America B: Optical Physics ; Volume 36, Issue 5 , 2019 , Pages 1241-1245 ; 07403224 (ISSN) ; Tavakol, M. R ; Khavasi, A ; Rejaei, B ; Sharif University of Technology
OSA - The Optical Society
2019
Abstract
We show that high-temperature superconductors can be used to build a terahertz superlens. These materials exhibit hyperbolic behavior at frequencies between their two plasma frequencies corresponding to electric fields parallel and perpendicular to their c-axis. Due to the large component of permittivity perpendicular to the c-axis, the resolution of the proposed lens is much below the diffraction limit (λ/1000). In this paper we demonstrate this lensing phenomenon with a simple slab of a high-temperature superconductor. © 2019 Optical Society of America
Optimal design of flux diverter using genetic algorithm for axial short circuit force reduction in HTS transformers
, Article IEEE Transactions on Applied Superconductivity ; Volume 30, Issue 1 , January , 2020 ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
The appealing advantages of high-temperature superconducting (HTS) power transformers over conventional ones have attracted transformer manufacturing companies, power companies, research institutes, and universities worldwide to conduct research and development in this field. Unfortunately, HTS transformers are more vulnerable to mechanical stresses than conventional transformers. The results of the interaction between current carrying windings and leakage magnetic fluxes are the electromagnetic forces, which act on transformer windings. Under short circuit events, these forces are remarkable, and, therefore, catastrophic failure of transformer may arise. Flux-diverter applications have been...