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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Reaction of nonaqueous halogen solutions with YBa2Cu3O(7-x)

The reaction of the surfaces of the new high-temperature superconductor YBa2Cu3O(7-x) with nonaqueous halogen solutions is investigated, and the species formed in the reactions are identified. Treatment of films with HF/EtOH (EtOH = HI in absolute ethanol) results in the formation of an oxyfluoride with Y:Ba:Cu relative concentrations of 1:4:3. Results of X-ray photoelectron spectroscopy of HF-treated films are consistent with the formation of CuF, a compound which does not exist in bulk form. Treatment of films with HCl/EtOH results primarily in the formation of BaCl2, with smaller amounts of YCl3, CuCl, and CuCl2. Treatment with Br2/EtOH or HBr/EtOH results in the formation of YBr3, BaBr2, and CuBr with relative concentrations of 1:4:3.

Vasquez, R. P.↗
NASA NTRS1990

Phase separation in the t-J model

A detailed understanding of the motion of 'holes' in an antiferromagnet is of fundamental importance for the theory of high-temperature superconductors. It is shown here that, for the t-J model, dilute holes in an antiferromagnet are unstable against phase separation into a hole-rich and a no-hole phase. When the spin-exchange interaction J exceeds a critical value Jc, the hole-rich phase has no electrons. It is proposed that, for J slightly less than Jc, the hole-rich phase is a low-density superfluid of electron pairs. Phase separation in related models is briefly discussed.

Emery, V. J.↗
NASA NTRS1990

Electromagnetic axisymmetric finite elements based on a gauged four-potential variational principle

Electromagnetic finite elements are derived based on a variational principle that uses the electromagnetic four-potential as a primary variable. The Lorentz gage normalization is incorporated as a constraint condition through a Lagrange multiplier field to construct elements suitable for downstream coupling with mechanical and thermal finite elements for the analysis of high-temperature superconductor devices with aerospace applications. The main advantages are: jump discontinuities on interfaces are naturally handled; no a priori approximations are invoked; and the number of degrees of freedom per node remains modest as the problem dimensionality increases. The new elements are tested on two magnetostatic axisymmetric problems. The results are in excellent agreement with analytical solutions and previous solutions for the 1D problem of a conducting infinite wire, in which case the multiplier field has no effect. For materials of widely different permeability, jump conditions are naturally accommodated by the present formulation.

Schuler, J.↗
NASA NTRS1990

Superconductivity applications for infrared and microwave devices; Proceedings of the Meeting, Orlando, FL, Apr. 19, 20, 1990

Various papers on superconductivity applications for IR and microwave devices are presented. The individual topics addressed include: pulsed laser deposition of Tl-Ca-Ba-Cu-O films, patterning of high-Tc superconducting thin films on Si substrates, IR spectra and the energy gap in thin film YBa2Cu3O(7-delta), high-temperature superconducting thin film microwave circuits, novel filter implementation utilizing HTS materials, high-temperature superconductor antenna investigations, high-Tc superconducting IR detectors, high-Tc superconducting IR detectors from Y-Ba-Cu-O thin films, Y-Ba-Cu0-O thin films as high-speed IR detectors, fabrication of a high-Tc superconducting bolometer, transition-edge microbolometer, photoresponse of YBa2Cu3O(7-delta) granular and epitaxial superconducting thin films, fast IR response of YBCO thin films, kinetic inductance effects in high-Tc microstrip circuits at microwave frequencies.

Bhasin, Kul B.↗
NASA NTRS1987

U.S. commercial space policies - Implications for developing countries

Recent U.S. policy developments on the commercial use of space are summarized and their international implications are considered. Attention is given to successful applications of technology developed in space, including an implantable cancer medication system, an implantable defibrillator, an ultrasonic residual stress monitor, and aquaculture treatment techniques. NASA projects involving bioengineering and rehabilitation applications are summarized, and plans to investigate high-temperature superconductors in space are addressed. Recent agreements entred into by NASA for space commercial studies are reviewed.

Gillam, Isaac T., IV↗
NASA NTRS2026

A Review of Superconducting Electric Machines with On-Board Cryocoolers

This paper reviews the evolution and emerging direction of superconducting electric machines that employ onboard cryocoolers integrated directly into the rotor, eliminating the need for cryogenic fluid coupling and, in some cases, rotary seals. Traditional low-temperature superconducting (LTS) machines relied on external cryogenic systems and liquid helium transfer couplers, which introduced excessive complexity, poor reliability, and significant parasitic energy losses. The advent of high-temperature superconductors (HTS) has enabled compact, closed-cycle cryocoolers that support self-contained, fluid-free refrigeration architectures suitable for rotating applications. This paper examines the key technological challenges associated with on-board cryocooler integration and reviews three representative efforts by KAIST, NASA, and Hinetics, each illustrating distinct strategies and milestones toward practical implementation. KAIST demonstrated early proof-of-concept for rotating machines with on-board cryocoolers, NASA developed a shaft-integrated Stirling-type pulse tube cryocooler for a 1.4 MW hybrid-electric motor, and Hinetics achieved full-scale validation of a self-contained HTS rotor incorporating a commercial Stirling cryocooler and spoke-suspension torque tube. Collectively, these achievements confirm the technical feasibility of on-board cryogenic refrigeration and highlight steady progress toward compact and efficient superconducting rotating systems across various applications. Embedding cryocoolers directly within the rotor enables practical, efficient, and commercially viable superconducting propulsion technologies.

Cryogenics↗
NASA NTRS1988

High-temperature processing of oxide superconductors and superconducting oxide-silver oxide composite

High temperature processing was found to partially convert the green 211 phase oxide to 123 phase. High Tc superconductivity was observed in Bi-Sr-Cu-O and Y-Sr-Cu-O systems prepared using the same heat treatment process. High temperature processing presents an alternative synthetic route in the search for new high Tc superconductors. An unusual magnetic suspension with enhancement in critical current density was observed in the 123 and AgO composite.

Wu, M. K.↗
NASA NTRS1989

Ceramic problems/challenges in high temperature oxide superconductors - Hysteretic force measurements as a new analysis tool

A technique is presented for analyzing high-temperature oxide superconductors using hysteretic magnetic force/distance measurements. Emphasis is placed on developing low weight, highly robust superconducting materials for space applications. Bi-Ca-Sr-Cu superconductors are prepared and characterized by standard techniques. It is found that standard techniques such as XRD, SEM, and TEM are insufficient to completely characterize superconductors. The magnetic properties of the superconductors are studied with the new technique, based on measuring the force between a magnet and the superconductor as a function of their separation.

Morgan, P. E. D.↗
NASA NTRS1988

High-temperature processing of cuprate oxide superconductors

Superconducting Y1Ba2Cu3O7 ('123') films were fabricated on the Y2BaCuO5 ('211') phase substrate. The superconducting characteristics of these films, in terms of superconducting transition temperature (Tc) and width, are better than those using other oxide compounds as substrates. In addition, using high-temperature processing, the bulk 211 phase was converted into the 123 phase. A new high Tc copper oxide material with non-rare-earth elements (Bi-Sr-Cu-O) was prepared using similar high-temperature processing. High-temperature processing presents an alternative synthetic route in the search of new high Tc superconductors.

Wu, M. K.↗
NASA NTRS1988

Syntactic intergrowth problems with BCSCO and fabrication difficulties therefrom

EDXS performed on isolated particles of the Bi-Ca-Sr-Cu-O high-temperature ceramic superconductor has verified the presence of significant elemental exchange between the Ca and Sr, and, to a lesser extent, between Cu and Bi. Two primary preparations, identified as primarily 24.4 A and 30.6 A, respectively, are identified. The Cu:Bi ratio in the 30.6 A material is approximately 1:1 for most particles, although only a few particles of the nominally 24.4 A material have the expected 1:2 ratio. No unequivocal assignment of atomic composition to the predominantly 24.4 A or 30.6 A appears possible, if major syntactic problems are present.

Morgan, P. E. D.↗
NASA NTRS1988

Study of high temperature oxide superconductors

Experimental studies are reported whose results indicate that proper processing procedures are critical to the formation of high-temperature copper oxide superconductors. Superconducting 123 films can be fabricated using the green 211 phase as a substrate. The transition temperature and transition width characteristics of these films are better than those obtained when other oxide compounds are used as substrates. A compact or single-crystal 211 phase will be desirable as a substrate for high-quality thin films. A new high T(c) copper oxide compound with nonrare earth elements was prepared using high-temperature processing. A YBa2Cu3O7-Ag composite with improved electrical conductivity was also prepared.

Wu, M. K.↗
NASA NTRS1988

Use of high temperature superconductors in magnetoplasmadynamic systems

The use of Tesla-class high-temperature superconducting magnets may have an extremely large impact on critical development issues (erosion, heat transfer, and performance) related to magnetoplasmadynamic (MPD) thrusters and also may provide significant benefits in reducing the mass of magnetics used in the power processing system. These potential performance improvements, coupled with additional benefits of high-temperature superconductivity, provide a very strong motivation to develop high-temperature superconductivity (HTS) applied-field MPD thruster propulsion systems. The application of HTS to MPD thruster propulsion systems may produce an enabling technology for these electric propulsion systems. This paper summarizes the impact that HTS may have upon MPD propulsion systems.

Reed, C. B.↗
NASA NTRS1987

Study of some superconducting and magnetic materials on high T sub c oxide superconductors

On the basis of existing data it appears that the high-temperature superconductivity above 77 K reported here, occurs only in compound systems consisting of a phase other than the K2NiF4 phase. A narrow superconducting transition was obtained with T sub c0 = 98 K and T sub c1 = 94 K in Y-Ba-Cu-O (YBCO). Preliminary results indicate that YBCO is rather different from the layered LaBCO, LaSCO, and LaCCO. While electron-photon interaction cannot be absent from this compound system, nonconventional enhanced superconducting interactions due to interfaces, Resonating Valence Bond (RVB) states, or even a superconducting state beyond the BCS framework, may be required to account for the high T sub c in YBCO. It is believed that study of the possible subtle correlation between magnetism and superconductivity will definitely provide important insight into the superconducting mechanism in YBCO and other oxides.

Wu, M. K.↗
NASA NTRS1991

Permanent magnets composed of high temperature superconductors

A study of persistent, trapped magnetic field has been pursued with high-temperature superconducting (HTS) materials. The main effort is to study the feasibility of utilization of HTS to fabricate magnets for various devices. The trapped field, when not in saturation, is proportional to the applied field. Thus, it should be possible to replicate complicated field configurations with melt-textured YBa2Cu3O7 (MT-Y123) material, bypassing the need for HTS wires. Presently, materials have been developed from which magnets of 1.5 T, at 77 K, can be fabricated. Much higher field is available at lower operating temperature. Stability of a few percent per year is readily attainable. Results of studies on prototype motors and minimagnets are reported.

Weinstein, Roy↗
NASA NTRS1981

Superconductivity, cohesive energy density, and electron-atom ratio in metals

It is shown that superconductivity above 8 K occurs in alloys and metallic compounds within relatively narrow regions of cohesive energy density with a sharp peak which includes Nb3Ge, SiV3, Nb3Ga, and NbN. When cross-correlated with the electron-atom ratio, high-temperature superconductivity can be observed in only a few regions. This suggests a search for superconductors with high-transition temperatures and critical fields within these regions.

England, C.↗
NASA NTRS1988

Evidence for a common high-temperature superconducting effect in La(1.85)Sr(0.15)CuO4 and YBa2Cu3O7

The paper reports the positron-annihilation lifetime and Doppler-broadening energy spectra in La(1.85)Sr(0.15)CuO4 superconductors for T = 10-297 K. A strong temperature dependence in positron lifetime and momentum distribution parameters is observed for positron-electron annihilation data while the sample is in the superconducting state, but not while it is in the normal state. Experimental evidence is presented that the superconducting mechanisms in La(1.85)Sr(0.15)CuO4 and YBa2Cu3O7 are similar and it is suggested that this is a consequence of a common physics involving the delicate balance between localized- and itinerant-electron behavior.

Jean, Y. C.↗
NASA NTRS1990

AMSAHTS 1990: Advances in Materials Science and Applications of High Temperature Superconductors

This publication is comprised of abstracts for oral and poster presentations scheduled for AMSAHTS '90. The conference will focus on understanding high-temperature superconductivity with special emphases on materials issues and applications. AMSAHTS '90, will highlight the state of the art in fundamental understanding of the nature of high-Tc superconductivity (HTSC) as well as the chemistry, structure, properties, processing and stability of HTSC oxides. As a special feature of the conference, space applications of HTSC will be discussed by NASA and Navy specialists.

Flom, Yury↗