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In the pseudobinary system Nb(Rh1−xPdx)3, as in other similar alloy systems, a series of polytypic phases occurs which have related, closepacked structures with systematically varying stacking sequences. After rapid quenching from the... more
In the pseudobinary system Nb(Rh1−xPdx)3, as in other similar alloy systems, a series of polytypic phases occurs which have related, closepacked structures with systematically varying stacking sequences. After rapid quenching from the melt, the stacking sequence of these polytypes is often changed.A phase m-Nb(Rh.75Pd.25)3 of the PuGa3 type with a 12-layer stacking sequence has been prepared by RSP; this phase is probably metastable and displaces an equilibrium phase of the VCo3 type with a 6-layer structure. Occurrence of the m phase can be rationalized in terms of the sequence of the Jagodzinski notation (fraction of h-like packing) and the variation of the diffraction pattern with composition.
Critical currents of powder-in-tube processed silver-clad Bi-2223 short tape samples and coils have been measured at liquid nitrogen (77 K), liquid neon (27 K) and liquid helium (4.2 K) temperatures. The short samples have been... more
Critical currents of powder-in-tube processed silver-clad Bi-2223 short tape samples and coils have been measured at liquid nitrogen (77 K), liquid neon (27 K) and liquid helium (4.2 K) temperatures. The short samples have been characterized in fields up to 20 T and indicate a large anisotropy at 27 K with resistive behavior above 15 T in the worst field direction. A test magnet consisting of pancake coils generated magnetic fields greater than 1.0, 0.7 and 0.11 T at 4.2 K, 27 K and 77 K respectively. The ctest magnet generates significant self-fields in background fields up to 14.5 T at 4.2 K and 27 K. Optimization of thermo-mechanical process parameters have yielded J{sub c}`s in the superconducting core > 4.0 {times} 10{sup 4} A/cm{sup 2} at 77 K, zero field and > 2.0 {times} 10{sup 5} A/cm{sup 2} at 4.2 K, zero field for short tape samples. Long lengths (>30 m) of silver-clad tape superconductors have also been fabricated and tested to carry significant amounts of curre...
ABSTRACT Bi-2223 high Tc superconductors have been fabricated by the powder-in-tube technique to yield long lengths of flexible silver clad composites. Short samples sectioned from the long lengths were characterized by measuring their... more
ABSTRACT Bi-2223 high Tc superconductors have been fabricated by the powder-in-tube technique to yield long lengths of flexible silver clad composites. Short samples sectioned from the long lengths were characterized by measuring their transport properties and evaluating their microstructure. The dc transport critical current densities measured on short monotape samples which were prepared using an optimum processing schedule were greater than 105 A/cm2 at zero field in liquid helium (4.2K) and liquid hydrogen (20.2K), and exceeded 3×104 A/cm2 at liquid nitrogen (77K) temperature. Measurements with applied magnetic fields up to 20 Tesla on tape samples are also reported. Problems associated with fabricating long lengths of both the monotape and multifilament wire are discussed.
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ABSTRACT Aluminum-doped zinc oxide (ZnO:Al) is a promising transparent conducting oxide (TCO) for the second generation, thin film based solar cells. Moderately large area, directly textured ZnO:Al films were successfully deposited by... more
ABSTRACT Aluminum-doped zinc oxide (ZnO:Al) is a promising transparent conducting oxide (TCO) for the second generation, thin film based solar cells. Moderately large area, directly textured ZnO:Al films were successfully deposited by reactive-environment, hollow cathode sputtering (RE-HCS) using metal targets. The morphology, structural, electrical, and optical properties of the films have been investigated and comparisons are made with the properties of commercially available textured SnO2:F. Higher haze and reduced absorption could be obtained with the textured ZnO:Al films. Besides the textured surface, these films (∼1030nm thick) also have a low sheet resistance of 2.8 ohms/square. Hall effect measurements on these films yielded a record high mobility of 49.5 cm2/V-s and carrier concentration of 4.42 × 1020 cm−3. The use of these textured ZnO:Al films as a TCO for single junction a-Si cells resulted in increased Voc, Jsc, and FF. The novel deposition method of RE-HCS provides a possible and promising pathway to a relatively low cost, large area production process for a textured ZnO TCO for thin-film PV manufacturing.
ABSTRACT Cadmium sulfide (CdS), indium sulfide (In2S3) and zinc sulfide (ZnS) thin films have been deposited by chemical bath deposition (CBD) for buffer layer applications in Cu–chalcopyrite-based thin film solar cells. Films were... more
ABSTRACT Cadmium sulfide (CdS), indium sulfide (In2S3) and zinc sulfide (ZnS) thin films have been deposited by chemical bath deposition (CBD) for buffer layer applications in Cu–chalcopyrite-based thin film solar cells. Films were characterized by scanning electron microscopy (SEM), UV–Vis transmission, X-ray photoelectron spectroscopy (XPS), grazing-incidence X-ray diffraction (GIXRD), and spectroscopic ellipsometry. Results indicate CdS can be deposited with low oxygen content and high light transmission over 245–1700 nm. CBD-ZnS and CBD-InS both exhibit 5–10% less light transmission than CdS in the same thickness range. In terms of light transmission and degree of impurities CdS appears to be a better buffer material than CBD-ZnS or CBD-InS.
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Considerable progress has been made in fabricating Bi-2223 high temperature superconductor (HTS) wires and tapes with high critical current densities that are attractive for electric power and high-field magnet applications.... more
Considerable progress has been made in fabricating Bi-2223 high temperature superconductor (HTS) wires and tapes with high critical current densities that are attractive for electric power and high-field magnet applications. Powder-in-tube processed silver-clad Bi-2223 short tape samples, small coils and test magnets have been fabricated and measured at liquid nitrogen (77K), pumped liquid nitrogen (64 K), liquid neon (27K) and
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Joining YBaâCuâO/sub 6.5 + delta/ (123 phase) and BiâSrâCaâCuâO/sub 16 + delta/ (4424 phase) as structurally characterized high-T/sub c/ superconductors, the thallium-containing superconductor (Tl/sub .75/Bi/sub .25/)/sub 1.33/Sr/sub... more
Joining YBaâCuâO/sub 6.5 + delta/ (123 phase) and BiâSrâCaâCuâO/sub 16 + delta/ (4424 phase) as structurally characterized high-T/sub c/ superconductors, the thallium-containing superconductor (Tl/sub .75/Bi/sub .25/)/sub 1.33/Sr/sub 1.33/Ca/sub 1.33/CuâO/sub 6.67 + delta/ with the ideal stoichiometry (Tl, Bi)âSrâCaâCuâO/sub 6.5 + delta/ (1212 phase) is reported here. As prepared from the component oxides, 1212 has an initial deviation from resistance linearity
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Fabricating long lengths of robust and high-quality conductors is imperative for various applications of high-{Tc} superconductors. Long lengths of mono- and multifilament Ag-clad Bi-Sr-Ca-Cu-0 conductors have been fabricated by the... more
Fabricating long lengths of robust and high-quality conductors is imperative for various applications of high-{Tc} superconductors. Long lengths of mono- and multifilament Ag-clad Bi-Sr-Ca-Cu-0 conductors have been fabricated by the powder-in-tube technique. High values for critical current density (J{sub c}) have been achieved in both short- and long-length conductors. J{sub c} values up to 12,000 A/cm² have been achieved in an 850-m-long multifilament conductor. Pancake-shaped coils and test magnets fabricated from long-length conductors were characterized at various temperatures and applied magnetic fields. A magnet containing 770 m of high-{Tc} conductor generated a record high field of â 1 T at 4.2 K in a background field of â 20 T. In-situ tensile and bending characteristics of both mono- and multifilament conductors have also been studied. Multifilament conductors exhibited better axial strain tolerance ({var_epsilon} â 1%) than that of monofilament conductor ({var_epsilon} ...
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ABSTRACT The transport current properties of Ag-sheathed BSCCO-2223 superconducting tapes were analysed as a function of cooling rate. Changing the cooling rate showed a pronounced effect on the transport current of the superconductor... more
ABSTRACT The transport current properties of Ag-sheathed BSCCO-2223 superconducting tapes were analysed as a function of cooling rate. Changing the cooling rate showed a pronounced effect on the transport current of the superconductor heat-treated at in a 7% atmosphere. Results indicated that, during fast cooling, the thin layer of BSCCO adjacent to the Ag sheath is under compression. The compressive stress causes microcracking and affects the alignment and interconnectivity of 2223 grains in the thin layer of BSCCO next to the silver sheath. This changes the current path through the high-critical-current-density region in the superconductor. A comparison between furnace-cooled tapes and slowly cooled tapes ( to and then to room temperature) showed that the latter attained two or three times higher values. Based on this observation, a cooling schedule that includes several intermediate cooling steps is suggested. The effect of the lattice parameter on was investigated. Behaviour analogous to that of the 2212 phase was found, was affected by changes in the c-axis of the 2223 phase. However, the effect was not as pronounced as it was in the 2212 phase.
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ABSTRACT
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... 272 (1996) 319325 PHYSICA Transport AC losses in multifilamentary Ag Bi2223 tapes in low external DC magnetic fields M. Ciszek a,,, SP Ashworth a, BA ... There is also no sign of losses due to eddy currents in the silver cladding,... more
... 272 (1996) 319325 PHYSICA Transport AC losses in multifilamentary Ag Bi2223 tapes in low external DC magnetic fields M. Ciszek a,,, SP Ashworth a, BA ... There is also no sign of losses due to eddy currents in the silver cladding, these would manifest as a change in frequency ...
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Recent developments in the powder-in-tube fabrication of (Bi,Pb)âSrâCaâCuâOâ tapes include identification of high current transport regions of the superconductor core, optimization of conductor design and processing to take advantage of... more
Recent developments in the powder-in-tube fabrication of (Bi,Pb)âSrâCaâCuâOâ tapes include identification of high current transport regions of the superconductor core, optimization of conductor design and processing to take advantage of these high current regions, optimization of superconductor powders and heat treatments, and incorporation of flux pinning defects into the superconductor grains. These developments are briefly discussed and their implications are assessed.
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This paper reports progress in the achievement of high transport Jc in 3–5 cm long melt processed polycrystalline Y1Ba2Cu3O7−δ samples. Optical and scanning electron micrographs show apparently clean platelet connection across high angle... more
This paper reports progress in the achievement of high transport Jc in 3–5 cm long melt processed polycrystalline Y1Ba2Cu3O7−δ samples. Optical and scanning electron micrographs show apparently clean platelet connection across high angle boundaries between grains (domains) composed of parallel ab platelets. Critical current densities determined by magnetization and transport methods are in agreement at over 103 A/cm3 at 77 K in fields above 1 T. Work is underway to more closely examine the condition of these grain boundaries and provide clearer evidence that transport current across them is weak-link-free. Large Y2Ba1Cu1O5 precipitates distributed throughout the matrix are found to produce a factor-of-two increase in critical current density.
The alignment and the formation of (Bi, Pb)2Sr2Ca2Cu3O10 inside an Ag sheath were investigated for tapes from four different precursor powders. Microstructural characterization along with in situ transmission x-ray diffraction experiments... more
The alignment and the formation of (Bi, Pb)2Sr2Ca2Cu3O10 inside an Ag sheath were investigated for tapes from four different precursor powders. Microstructural characterization along with in situ transmission x-ray diffraction experiments revealed that the kinetics depended strongly on the processing technique and the phase assemblage of the precursors. The alignment process was governed by the preferential grain growth of the Bi-cuprates along the a-b plane and the constraint applied by the sheath. The formation mechanism of (Bi, Pb)2Sr2Ca2Cu3O10 was either the intercalation or the nucleation and growth, depending on whether excessive liquid is adjacent to the platelets.
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The alignment and the formation of (Bi, Pb) 2 Sr 2 Ca 2 Cu 3 O 10 inside an Ag sheath were investigated for tapes from four different precursor powders. Microstructural characterization along with in situ transmission x-ray diffraction... more
The alignment and the formation of (Bi, Pb) 2 Sr 2 Ca 2 Cu 3 O 10 inside an Ag sheath were investigated for tapes from four different precursor powders. Microstructural characterization along with in situ transmission x-ray diffraction experiments revealed that ...
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A metal organic chemical vapor deposition (MOCVD) method has been developed to achieve high currents in Y–Ba–Cu–O (YBCO) superconducting films deposited on biaxially textured buffer layers on polycrystalline (untextured) flexible metal... more
A metal organic chemical vapor deposition (MOCVD) method has been developed to achieve high currents in Y–Ba–Cu–O (YBCO) superconducting films deposited on biaxially textured buffer layers on polycrystalline (untextured) flexible metal substrates. Optimization of the MOCVD process parameters has yielded critical currents (Ic) greater than 50 A and critical current densities (Jc) higher than 1 MA/cm2 at 77 K in
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High-temperature {ital in} {ital situ} x-ray measurements have been undertaken during the growth of BiâSrâCaâCuâO{sub 10+δ} in order to determine the sequence of phases that form and the kinetics of growth. With a Ag-coated thin pellet... more
High-temperature {ital in} {ital situ} x-ray measurements have been undertaken during the growth of BiâSrâCaâCuâO{sub 10+δ} in order to determine the sequence of phases that form and the kinetics of growth. With a Ag-coated thin pellet of the starting mixture of Pb-doped BiâSrâCaâCuâO{sub 8+δ}, Ca-cuprates, and CuO in an air atmosphere, major changes occur in the x-ray spectrum at temperatures as low as 790 °C. A triplet of lines associated with CaâPbOâ forms as soon as the pellet reaches 790 °C and then disappears after 20 or 30 minutes. The BiâSrâCaâCuâO{sub 10+δ} phase begins to grow at about 810 °C. For these rather porous pellets, about 20% of the sample transforms to BiâSrâCaâCuâO{sub 10+δ}, as indicated by both x-ray intensities and superconducting magnetization studies. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
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We report results on the critical current density J(sub c)(T,H) at various fields and temperatures of Bi-2223/Ag tapes and small coils. In field measurements on small coils were performed under ascending and descending fields to... more
We report results on the critical current density J(sub c)(T,H) at various fields and temperatures of Bi-2223/Ag tapes and small coils. In field measurements on small coils were performed under ascending and descending fields to investigate hysteretic behavior. Strain dependence of J(sub c) was obtained by bending heat treated tapes around mandrels of varying diameters. Microstructural results of these tapes by optical microscopy, SEM, EDS, WDS are also presented.
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The powder in tube method was used to produce silver sheathed tapes of Tl0.78Pb0.5Ba0.4Sr1.6Ca2Cu3Oy. A precursor powder of Pb0.5Ba0.4Sr1.6Ca2Ca3Oy (prepared via the hydroxycarbonate coprecipitation of the metal ions from a stoichiometric... more
The powder in tube method was used to produce silver sheathed tapes of Tl0.78Pb0.5Ba0.4Sr1.6Ca2Cu3Oy. A precursor powder of Pb0.5Ba0.4Sr1.6Ca2Ca3Oy (prepared via the hydroxycarbonate coprecipitation of the metal ions from a stoichiometric nitrate solution) was thallinated and packed into a silver tube and processed into tape. The tape was then heated (in 100% oxygen or air) from 840°C by 870°C for
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Cryogenic Power Electronics (CPE) provides promising benefits for power conditioning system compared to their room-temperature counterparts in terms of reduced size and weight (increased power density), improved efficiency, improved... more
Cryogenic Power Electronics (CPE) provides promising benefits for power conditioning system compared to their room-temperature counterparts in terms of reduced size and weight (increased power density), improved efficiency, improved switching speed, and improved reliability. Active devices such as semiconductor switches can exhibit performance improvements such as reduced conduction losses, higher switching speed, reduced diode reverse recovery, greater device gain, higher
Research Interests: Materials Engineering, Condensed Matter Physics, Cryogenics, Power Electronics, Comparative Study, and 13 moreSystem Design, Switching, Reliability, Superconductors, Performance Improvement, Room Temperature, Miniaturization, System performance, Electronics Packaging, Semiconductor Device, Electrical And Electronic Engineering, Inductor, and Power Density
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ABSTRACT
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Research Interests: Engineering, Corrosion, Proton Exchange Membrane Fuel Cells, Physical sciences, PEM fuel cell, and 11 moreTitanium nitride, CHEMICAL SCIENCES, XPS, Surface Area, Low Temperature, Carbon Black, Proton Exchange Membrane Fuel Cell, Electric Conductivity, Open Circuit Potential, Electrochemical Oxidation, and Electrocatalyst
Research Interests: Cryogenics, Power Electronics, Structure, Numerical Simulation, Computer Simulation, and 9 moreClassical Physics, Temperature Dependence, Room Temperature, Interdisciplinary Engineering, Low Temperature, Breakdown Voltage, Physics based Modeling, power MOSFET, and Metal Oxide Semiconductor Field Effect Transistor
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We report a series of measurements of I-V curves for a c-axis-oriented Bi 2 Sr 2 Ca 2 Cu 3 O 10 /Ag tape immersed in liquid oxygen. By applying the critical scaling analysis to the I-V characteristics measured in various magnetic fields,... more
We report a series of measurements of I-V curves for a c-axis-oriented Bi 2 Sr 2 Ca 2 Cu 3 O 10 /Ag tape immersed in liquid oxygen. By applying the critical scaling analysis to the I-V characteristics measured in various magnetic fields, a vortex-glassliquid phase-transition line was ...
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Improved strain sensitivity of critical currents Ic of the multicored over the monocored (Bi,Pb)2Sr2Ca2Cu3O10–Ag tapes is shown for bending strains, but not for axial tensile strains. The improved mechanical tolerance is due, in part, to... more
Improved strain sensitivity of critical currents Ic of the multicored over the monocored (Bi,Pb)2Sr2Ca2Cu3O10–Ag tapes is shown for bending strains, but not for axial tensile strains. The improved mechanical tolerance is due, in part, to a better alignment of the Bi-cuprate platelets achieved in the multicored tapes. Furthermore, the difference in the response to these tapes to axial tensile and bending strains is due to the difference in the precise manner in which the strains are applied to the tapes.
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In the growth of BiâSrâCaâCuâO{sub 10+δ} from mixed powders of Pb-doped BiâSrâCaâCuâO{sub 8+δ} and other oxides, it has been discovered that a dense array of hillocks or mesas grow at the interface between a Ag overlay and Pb-doped... more
In the growth of BiâSrâCaâCuâO{sub 10+δ} from mixed powders of Pb-doped BiâSrâCaâCuâO{sub 8+δ} and other oxides, it has been discovered that a dense array of hillocks or mesas grow at the interface between a Ag overlay and Pb-doped BiâSrâCaâCuâO{sub 8+δ} grains during the ramp up to the reaction temperature. As viewed in an environmental scanning electron microscope, the Ag coated grains develop a texture that looks like {open_quote}{open_quote}chicken pox{close_quote}{close_quote} growing on the grains at about 700°C. These hillocks are about 100 nm across and are spaced at about 500 to 1000 nm. If there is no Ag, this texture does not develop. Preliminary measurements indicate that the hillocks are a recrystallization of (Bi,Pb)âSrâCaâCuâO{sub 8+δ}, and are definitely not a Pb rich phase. {copyright} {ital 1996 American Institute of Physics.}
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(Bi,Pb),Sr,Ca,Cu,O, oxide-powder-in-silver-tube pro-cess [Bi2223/Ag) tapes are considered to be a potential can-didate for use in applications of the high T, cuprate super-conductors. Despite the large anisotropic physical properties of... more
(Bi,Pb),Sr,Ca,Cu,O, oxide-powder-in-silver-tube pro-cess [Bi2223/Ag) tapes are considered to be a potential can-didate for use in applications of the high T, cuprate super-conductors. Despite the large anisotropic physical properties of Bi2223/Ag tape, it is less subject to transport ...
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Research Interests: Engineering, Corrosion, Proton Exchange Membrane Fuel Cells, Physical sciences, PEM fuel cell, and 11 moreTitanium nitride, CHEMICAL SCIENCES, XPS, Surface Area, Low Temperature, Carbon Black, Proton Exchange Membrane Fuel Cell, Electric Conductivity, Open Circuit Potential, Electrochemical Oxidation, and Electrocatalyst
... 272 (1996) 319325 PHYSICA Transport AC losses in multifilamentary Ag Bi2223 tapes in low external DC magnetic fields M. Ciszek a,,, SP Ashworth a, BA ... There is also no sign of losses due to eddy currents in the silver cladding,... more
... 272 (1996) 319325 PHYSICA Transport AC losses in multifilamentary Ag Bi2223 tapes in low external DC magnetic fields M. Ciszek a,,, SP Ashworth a, BA ... There is also no sign of losses due to eddy currents in the silver cladding, these would manifest as a change in frequency ...
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(Bi,Pb),Sr,Ca,Cu,O, oxide-powder-in-silver-tube pro-cess [Bi2223/Ag) tapes are considered to be a potential can-didate for use in applications of the high T, cuprate super-conductors. Despite the large anisotropic physical properties of... more
(Bi,Pb),Sr,Ca,Cu,O, oxide-powder-in-silver-tube pro-cess [Bi2223/Ag) tapes are considered to be a potential can-didate for use in applications of the high T, cuprate super-conductors. Despite the large anisotropic physical properties of Bi2223/Ag tape, it is less subject to transport ...
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CHAPTER 2 Proton Exchange Membrane Fuel Cells Adam Z. Weber,* Sivagaminathan Balasubramanian, and Prodip K. Das Contents 1. Introduction 2. Fundamentals of Fuel Cells 2.1 Thermodynamics 2.2 Kinetics 2.3 Conservation and transport 3.... more
CHAPTER 2 Proton Exchange Membrane Fuel Cells Adam Z. Weber,* Sivagaminathan Balasubramanian, and Prodip K. Das Contents 1. Introduction 2. Fundamentals of Fuel Cells 2.1 Thermodynamics 2.2 Kinetics 2.3 Conservation and transport 3. Modeling Aspects of Fuel Cells 3.1 Membrane 3.2 Porous media 3.3 Catalyst layers 3.4 Gas flow channels and flowfields 3.5 Boundary conditions and summary 3.6 Impedance modeling 4. Optimization 4.1 Single-parameter optimization 4.2 Multiparameter optimization 5. Summary Acknowledgments References ...
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We report results on the critical current density J(sub c)(T,H) at various fields and temperatures of Bi-2223/Ag tapes and small coils. In field measurements on small coils were performed under ascending and descending fields to... more
We report results on the critical current density J(sub c)(T,H) at various fields and temperatures of Bi-2223/Ag tapes and small coils. In field measurements on small coils were performed under ascending and descending fields to investigate hysteretic behavior. Strain dependence of J(sub c) was obtained by bending heat treated tapes around mandrels of varying diameters. Microstructural results of these tapes by optical microscopy, SEM, EDS, WDS are also presented.
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Understanding how the structure of the unit-cell affects the cryogenic performance of a Si power Metal Oxide Semiconductor Field Effect Transistor (MOSFET) is an important step toward optimizing of the device for cryogenic operations. In... more
Understanding how the structure of the unit-cell affects the cryogenic performance of a Si power Metal Oxide Semiconductor Field Effect Transistor (MOSFET) is an important step toward optimizing of the device for cryogenic operations. In this paper, numerical simulations of the Si power Double Diffused MOSFET’ (DMOS) are performed at room temperature and cryogenic temperatures. Physically based models for temperature
Research Interests: Cryogenics, Power Electronics, Structure, Numerical Simulation, Computer Simulation, and 9 moreClassical Physics, Temperature Dependence, Room Temperature, Interdisciplinary Engineering, Low Temperature, Breakdown Voltage, Physics based Modeling, power MOSFET, and Metal Oxide Semiconductor Field Effect Transistor
A near term high-temperature superconductor (HTS) application is the fault current limiter (FCL). This paper describes the development and testing of a 2.4 kV, 2.2 kA(RMS) fault current, 150 A(RMS) continuous current, HTS FCL that uses a... more
A near term high-temperature superconductor (HTS) application is the fault current limiter (FCL). This paper describes the development and testing of a 2.4 kV, 2.2 kA(RMS) fault current, 150 A(RMS) continuous current, HTS FCL that uses a Bi-2223 Ag-based conductor. The Lockheed Martin team, which included Southern California Edison (SCE), American superconductor Corporation (ASC) and Los Alamos National Laboratory (LANL),
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ABSTRACTUsing the arc-furnace hammer-and-anvil method, metastable alloys in the Al-rich portions of four Al-RE systems (10-30 at. pct. RE; Re = Gd, Ho, Er and Y) were prepared and examined by XRD. The principal results are: all... more
ABSTRACTUsing the arc-furnace hammer-and-anvil method, metastable alloys in the Al-rich portions of four Al-RE systems (10-30 at. pct. RE; Re = Gd, Ho, Er and Y) were prepared and examined by XRD. The principal results are: all equilibrium alloy phases [Al4RE (T phase), Al3RE (CN12 close-packed phases) and Al2RE (Laves phase)] have substantial metastable solid solubilities for excess Al; e.g., in the Al-Y system, L phase is extended from 66.7 up to 86 at. pct. Al, suppressing any formation of the Al3RE phase in that system.For early RE elements up to and including Gd, T phase is favored; for alloy chemically intermediate RE elements such as Y, L phase is dominant and for late RE elements (after Ho), the CP phases are extended most. DSC work indicates the formation of additional metastable phases occurring during equilibration.
ABSTRACT The cycling stability and the surface passivation qualities of a heterogeneous polycrystalline NiSi 2/amorphous Ni x SiO y core-shell nanowires cycled in a Li ion half cell is reported. The nanowire morphology showed stable... more
ABSTRACT The cycling stability and the surface passivation qualities of a heterogeneous polycrystalline NiSi 2/amorphous Ni x SiO y core-shell nanowires cycled in a Li ion half cell is reported. The nanowire morphology showed stable cycling and excellent charge rate capability having a stable capacity above 1700 mAh/g when cycled in a coin cell at 1/2 C and retaining a capacity of 300 mAhr/g when cycled at a 10 C charge rate. It is shown that the stable cycling is due to the passivation qualities of the oxide components within the
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ABSTRACT After fabricating long lengths (30–100 m) of Ag-clad Bi-2223 tapes by the powder-in-tube process, we co-wound them into pancake-shaped coils by the “wind-and-react” approach. Test magnets were then fabricated by stacking and... more
ABSTRACT After fabricating long lengths (30–100 m) of Ag-clad Bi-2223 tapes by the powder-in-tube process, we co-wound them into pancake-shaped coils by the “wind-and-react” approach. Test magnets were then fabricated by stacking and connecting the coils in series. We then characterized the magnets at the temperatures of liquid helium (4.2 K), liquid neon (27 K), pumped liquid nitrogen (64 K.), and liquid nitrogen (77 K) and in background fields of up to 12 T. A test magnet containing 10 pancake coils generated magnetic fields as high as 2.6 T at 4.2 K. Multifilament conductors of BSCCO-2212 and BSCCO-2223 have also been fabricated in this study. A BSCCO-2212 multifilament conductor was fabricated with both pure silver and dispersion-strengthened silver (Ag-Al2O3) as the sheath materials. After final heat treatment, the yield strength of the Ag-Al2O3 matrix was twice that of the pure Ag matrix. At 4.2 K, critical current density of the Ag-Al2O3 multifilament conductor approached 5 × 104 A/cm2 at zero applied field and >2 × 104 A/cm2 at 12 T. This paper addresses certain issues concerning high-Tc magnets and long-length multifilament conductors.