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Sample records for ii ybco ceramic

  1. Test Status for Proposed Coupling of a Gravitational Force to Extreme Type II YBCO Ceramic Superconductors

    NASA Technical Reports Server (NTRS)

    Noever, David; Li, Ning; Robertson, Tony; Koczor, Ron; Brantley, Whitt

    1999-01-01

    As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair electron density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (about 10-6 g/cu cm). Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating Type II, YBCO superconductor, with the percentage change (0.05-2.1%) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 10(exp 4) was reported above a stationary (non-rotating) superconductor. In the present experiments reported using a sensitive gravimeter (resolution <10(exp -9) unit gravity or variation of 10(exp -6) cm/sq s in accelerations), bulk YBCO superconductors were stably levitated in a DC magnetic field (0.6 Tesla) subject to lateral AC fields (60 Gauss at 60 Hz) and rotation. With magnetic shielding, thermal control and buoyancy compensation, changes in acceleration were measured to be less than 2 parts in 10(exp 8) of the normal gravitational acceleration. This result puts new limits on the strength and range of the proposed coupling between high-Tc superconductors and gravity. Latest test results will be reported, along with status for future improvements and prospects.

  2. A hybrid phenomenological model for ferroelectroelastic ceramics. Part II: Morphotropic PZT ceramics

    NASA Astrophysics Data System (ADS)

    Stark, S.; Neumeister, P.; Balke, H.

    2016-10-01

    In this part II of a two part series, the rate-independent hybrid phenomenological constitutive model introduced in part I is modified to account for the material behavior of morphotropic lead zirconate titanate ceramics (PZT ceramics). The modifications are based on a discussion of the available literature results regarding the micro-structure of these materials. In particular, a monoclinic phase and a highly simplified representation of the hierarchical structure of micro-domains and nano-domains observed experimentally are incorporated into the model. It is shown that experimental data for the commercially available morphotropic PZT material PIC151 (PI Ceramic GmbH, Lederhose, Germany) can be reproduced and predicted based on the modified hybrid model.

  3. Continuous fiber ceramic composites. Phase II - Final report

    SciTech Connect

    Bird, James

    1997-10-31

    This report documents Atlantic Research Corporation's (ARC) Phase 11 effort on the Department of Energy's (DOE) Continuous Fiber Ceramic Composite (CFCC) program. This project is supported by the DOE cooperative agreement DE-FCO2-92CE40998. Such DOE support does not constitute an endorsement of the views expressed in this report. ARC'S CFCC Phase II effort began during October 1993 and was suspended in March of 1997 when, for business considerations, ARC closed the Amercom operation. This report covers progress from Phase II program inception through Amercom closure. ARC'S Phase II effort built upon the results of the Phase I Applications Assessment and Process Engineering developments to produce CFCC test components for end-user evaluation. Initially, the Phase 11 effort planned to develop and produce three CFCC components: CFCC compression rings for stationary diesel engines, CFCC hot gas fans for industrial furnace applications, and CFCC hot gas filters for current and advanced coal fired power cycles. As the program progressed, the development effort for the diesel engine piston rings was suspended. This decision was based on technical issues, cost factors and reduced program funding; the status of CFCC diesel engine piston ring development will be discussed in detail in section 2.2.1.

  4. Thermal cycling distortion of metal ceramics: Part II--Etiology.

    PubMed

    Campbell, S D; Pelletier, L B

    1992-08-01

    The three-dimensional geometry of conventional fixed prostheses complicates the study of the thermal cycling distortion in metal ceramic alloys. Any explanation of the etiology of thermal cycling distortion in metal ceramic restorations must account for the observed magnitude, timing, and direction of the deformation. The simplified experimental geometry developed in Part I was applied to elucidate the etiologic factors involved in metal ceramic deformation. Techniques to minimize the thermal cycling distortion were also studied. It was found that all of the significant distortion occurred during the first thermal cycling of the alloy (oxidation) and that no distortion resulted from the application of body porcelain. The specimens that were cold worked and then oxidized had significantly more distortion than any other group. A significant reduction in distortion was observed when the initial thermal cycling was completed before the specimens were cold worked. It was determined that the release of casting- and cold working-induced stresses had a synergistic effect. PMID:1501176

  5. Microstructural effects on fracture toughness of polycrystalline ceramics in combined mode I and mode II loading

    NASA Technical Reports Server (NTRS)

    Singh, D.; Shetty, D. K.

    1988-01-01

    Fracture toughness of polycrystalline alumina and ceria partially-stabilized tetragonal zirconia (CeO2-TZP) ceramics were assessed in combined mode I and mode II loading using precracked disk specimens in diametral compression. Stress states ranging from pure mode I, combined mode I and mode II, and pure mode II were obtained by aligning the center crack at specific angles relative to the loading diameter. The resulting mixed-mode fracture toughness envelope showed significant deviation to higher fracture toughness in mode II relative to the predictions of the linear elastic fracture mechanics theory. Critical comparison with corresponding results on soda-lime glass and fracture surface observations showed that crack surface resistance arising from grain interlocking and abrasion was the main source of the increased fracture toughness in mode II loading of the polycrystalline ceramics. The normalized fracture toughness for pure mode II loading, (KII/KIc), increased with increasing grain size for the CeO2-TZP ceramics. Quantitative fractography confirmed an increased percentage of transgranular fracture of the grains in mode II loading.

  6. Class II direct composite resin restorations with beta-quartz glass-ceramic inserts.

    PubMed

    Rada, R E

    1993-11-01

    With the increasing demand for esthetic posterior restorations, numerous techniques have been developed. The direct resin restoration has probably been used most extensively in Class II situations. Problems with Class II direct resin restorations include difficulty in developing proximal contact, occlusal wear, and polymerization shrinkage. Beta-quartz glass-ceramic inserts have been developed in an attempt to reduce the incidence of these potential problems. They can be placed in a one-appointment technique, are relatively inexpensive, and can readily be utilized by the clinician adept in placing Class II composite resin restorations.

  7. Magnesium oxide-impregnated tuff soil-derived ceramic: a novel cadmium(II) adsorbing media

    NASA Astrophysics Data System (ADS)

    Salim, Md; Bhakta, Jatindra N.; Maneesh, Namburath; Munekage, Yukihiro; Motomura, Kevin

    2015-07-01

    The contamination of cadmium (Cd) in the aquatic environment is one of the serious environmental and human health's risks. The present study attempted to develop the potential magnesium oxide (MgO)-impregnated tuff soil-derived ceramic (MITDC)-based novel adsorbent media for adsorbing higher rate of cadmium [Cd(II)] from water phase. A potential MITDC adsorbent media was developed using volcanic raw tuff soil and its Cd(II) adsorption capacity from water phase was evaluated comparing with the raw tuff soil. A series of studies were carried out in an agitated batch method at 20 ± 2 °C to characterize the adsorption capacity of MITDC under different conditions of factors, such as contact time (0-360 min), initial pH (3-11) of solution, dose of MITDC (2, 5, 7.5 and 10 g/L), and initial concentration of Cd(II) (5, 10, 20, 30, and 40 mg/L), influencing the adsorption mechanism. MITDC exhibited the equilibrium state of maximum Cd(II) adsorption at the contact time 120 min and pH 4.7 (removed 98.2 % Cd) when initial Cd(II) concentration was 10 mg/L in the present study. The dose of 7.5 g MITDC/L showed maximum removal of Cd(II) from water. Experimental data were described by the Freundlich and the Langmuir isotherms and equilibrium data fitted well with the Langmuir model (R 2 = 0.996). The Cd(II) adsorption capacity of MITDC was 31.25 mg/g. The high Cd(II) adsorption capacity indicated that novel MITDC could be used as a potential ceramic adsorbent media to remove high rate of Cd(II) from aqueous phase.

  8. Epitaxial growth and thermal dynamics of CeO II buffer layer on textured Ni-W substrates for YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Pan, C. Y.; Cai, C. B.; Ying, L. L.; Lu, Y. M.; Liu, Z. Y.; Gao, B.; Liu, J. L.

    2008-02-01

    In present study, the biaxially textured CeO II buffer layers on Ni-W substrates have been prepared by chemical solution deposition (CSD) with cerium acetate as the starting precursor, mixed with solvents of Propionic acid, Isopropanol and Acetylacetone. Typical XRD θ-2θ scans and the pole figure display well out-of-plane and in-plane textures of CeO II films. SEM and AFM results suggest that the buffer layer have uniform and smooth surface. Meanwhile, the effects of heating rate on CeO II formation starting from the precursor solution have been studied using differential thermal analysis (DTA). And the further analysis is given by XRD results for precursor xrogel at the corresponding temperature. Detailed high temperature optical microscope (HTOM) photographs investigate the surface characteristics evolved with temperature.

  9. Electrospinning of superconducting YBCO nanowires

    NASA Astrophysics Data System (ADS)

    Duarte, Edgar A.; Rudawski, Nicholas G.; Quintero, Pedro A.; Meisel, Mark W.; Nino, Juan C.

    2015-01-01

    YBa2Cu3O7-δ (YBCO) nanowires with critical transition temperature Tc = 91.7 K were synthesized by an electrospinning process with the use of sol-gel precursors. A homogeneous polymeric solution containing Y, Ba, and Cu acetates was electrospun, resulting in collections of randomly oriented nanowires as well as bundles of aligned nanowires. Fully crystallized YBCO nanowires were obtained after calcination at temperatures as low as 820 °C. The morphology, microstructure, and crystal structure were investigated, and the diameters of the polycrystalline nanowires varied between 120 and 550 nm depending on the viscosity of the precursors. Thinner individual wires, with diameters in the 50-80 nm range, were synthesized with a single grain structure across the entire wire cross-section.

  10. SCALE UP OF CERAMIC WASTE FORMS FOR THE EBR-II SPENT FUEL TREATMENT PROCESS

    SciTech Connect

    Matthew C. Morrison; Kenneth J. Bateman; Michael F. Simpson

    2010-11-01

    ABSTRACT SCALE UP OF CERAMIC WASTE FORMS FOR THE EBR-II SPENT FUEL TREATMENT PROCESS Matthew C. Morrison, Kenneth J. Bateman, Michael F. Simpson Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415 The ceramic waste process is the intended method for disposing of waste salt electrolyte, which contains fission products from the fuel-processing electrorefiners (ER) at the INL. When mixed and processed with other materials, the waste salt can be stored in a durable ceramic waste form (CWF). The development of the CWF has recently progressed from small-scale testing and characterization to full-scale implementation and experimentation using surrogate materials in lieu of the ER electrolyte. Two full-scale (378 kg and 383 kg) CWF test runs have been successfully completed with final densities of 2.2 g/cm3 and 2.1 g/cm3, respectively. The purpose of the first CWF was to establish material preparation parameters. The emphasis of the second pre-qualification test run was to evaluate a preliminary multi-section CWF container design. Other considerations were to finalize material preparation parameters, measure the material height as it consolidates in the furnace, and identify when cracking occurs during the CWF cooldown process.

  11. Origin of photovoltaic effect in superconducting YBa2Cu3O6.96 ceramics

    PubMed Central

    Yang, F.; Han, M. Y.; Chang, F. G.

    2015-01-01

    We report remarkable photovoltaic effect in YBa2Cu3O6.96 (YBCO) ceramic between 50 and 300 K induced by blue-laser illumination, which is directly related to the superconductivity of YBCO and the YBCO-metallic electrode interface. There is a polarity reversal for the open circuit voltage Voc and short circuit current Isc when YBCO undergoes a transition from superconducting to resistive state. We show that there exists an electrical potential across the superconductor-normal metal interface, which provides the separation force for the photo-induced electron-hole pairs. This interface potential directs from YBCO to the metal electrode when YBCO is superconducting and switches to the opposite direction when YBCO becomes nonsuperconducting. The origin of the potential may be readily associated with the proximity effect at metal-superconductor interface when YBCO is superconducting and its value is estimated to be ~10–8 mV at 50 K with a laser intensity of 502 mW/cm2. Combination of a p-type material YBCO at normal state with an n-type material Ag-paste forms a quasi-pn junction which is responsible for the photovoltaic behavior of YBCO ceramics at high temperatures. Our findings may pave the way to new applications of photon-electronic devices and shed further light on the proximity effect at the superconductor-metal interface. PMID:26099727

  12. Ceramics reinforced metal base composite coatings produced by CO II laser cladding

    NASA Astrophysics Data System (ADS)

    Yang, Xichen; Wang, Yu; Yang, Nan

    2008-03-01

    Due to the excellent performance in high strength, anti-temperature and anti-wear, ceramics reinforced metal base composite material was used in some important fields of aircraft, aerospace, automobile and defense. The traditional bulk metal base composite materials are the expensive cost, which is limited in its industrial application. Development of laser coating of ceramics reinforced metal base composite is very interesting in economy. This paper is focused on three laser cladding ceramics coatings of SiC particle /Al matrix , Al IIO 3 powder/ Al matrix and WC + Co/mild steel matrix. Powder particle sizes are of 10-60μm. Chemical contents of aluminum matrix are of 3.8-4.0% Cu, 1.2-1.8% Mg, 0.3-0.99% Mn and balance Al. 5KW CO II laser, 5 axes CNC table, JKF-6 type powder feeder and co-axis feeder nozzle are used in laser cladding. Microstructure and performance of laser composite coatings have been respectively examined with OM,SEM and X-ray diffraction. Its results are as follows : Microstructures of 3C-,6H- and 5H- SiC particles + Al + Al 4SiC 4 + Si in SiC/Al composite, hexagonal α-Al IIO 3 + cubic γ-Al IIO 3 + f.c.c Al in Al IIO 3 powder/ Al composite and original WC particles + separated WC particles + eutectic WC + γ-Co solid solution + W IIC particles in WC + Co/steel coatings are respectively recognized. New microstructures of 5H-SiC in SiC/Al composite, cubic γ-Al IIO 3 in Al IIO 3 composite and W IIC in WC + Co/ steel composite by laser cladding have been respectively observed.

  13. Cryolubricity of YBCO powder deposits

    NASA Astrophysics Data System (ADS)

    Stevens, Keeley M.; Krim, Jacqueline

    2010-03-01

    Motivated by recent reports of superconductivity-dependent friction [1] in macroscopic pin-on-disk measurements of steel on YBCO, [2] we have investigated the tribological properties of YBCO powder deposits on metal electrodes of a quartz crystal microbalance (QCM). Measurements are performed as a function of temperature over the range 80 - 300K, by monitoring the frequency and amplitude of the QCM both in the presence and absence of adsorbed nitrogen film layers. A pulsed magnetic field was applied to isolate the effect of superconductivity at and around the transition temperature. The powder deposits produce negative shifts in the QCM fundamental frequency, an indication of the strength of their attachment to the surface. The shifts exhibit structure as the temperature passes through the superconducting transition temperature, but the presumed drop in friction is not so large as to produce a decoupling effect which would lead to positive shifts. [3] Measurements on alternate QCM electrodes in the presence of adsorbed film layers are ongoing and will be reported on. Funding provided by NSF DMR. [4pt] [1] Highland, M. and Krim, J. Phys. Rev. Lett. 2006, 96, 226107.[0pt] [2] Ding, Q. et al. Wear 2008, 265, 1136.[0pt] [3] Dybwad, G.L. J. Appl. Phys. 1985, 58, 2789.

  14. Investigation of Radiation Affected High Temperature Superconductors - YBCO

    NASA Astrophysics Data System (ADS)

    Veterníková, J.; Chudý, M.; Slugeň, V.; Sojak, S.; Degmová, J.; Snopek, J.

    In this paper, high temperature superconductors are studied in terms of radiation stability, which is necessary for application in fusion reactors. Perspective superconducting materials based on YBCO (Perkovskite structure) were measured by positron annihilation lifetime spectroscopy. Measurements were performed for samples prior to and after fast neutron irradiation in TRIGA MARK II reactor in Vienna. The samples demonstrated accumulation of Cu-O di-vacancies due to the irradiation. Nevertheless, the structure showed regeneration during thermal treatment by defects recombination. Positron spectroscopy results were complemented with values of critical temperature, which also showed changes of superconducting properties after the irradiation and the annealing.

  15. High speed low damage grinding of advanced ceramics, Phase II final report

    SciTech Connect

    Kovach, J.A.; Malkin, S.

    2000-05-01

    In the manufacture of structural ceramic components, grinding costs can comprise up to 80% of the entire manufacturing cost. As a result, one of the most challenging tasks faced by manufacturing process engineers is the development of a ceramic finishing process to maximize part throughput while minimizing costs associated scrap levels.

  16. A comparative study on in situ grown superconducting YBCO and YBCO-Ag thin films by PLD on polycrystalline SmBa2NbO6 substrate

    NASA Astrophysics Data System (ADS)

    Kurian, J.; John, Asha M.; Wariar, P. R. S.; Sajith, P. K.; Koshy, J.; Pai, S. P.; Pinto, R.

    2000-02-01

    The development and characterization of SmBa2NbO6, which is a new ceramic substrate material for the YBa2Cu3O7-icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> superconductor, are reported. SmBa2NbO6 has a complex cubic perovskite structure with lattice constant a = 8.524 Å. The dielectric properties of SmBa2NbO6 are in a range suitable for its use as a substrate for microwave applications. SmBa2NbO6 was found to have a thermal conductivity of 77 W m-1 K-1 and a thermal expansion coefficient of 7.8 × 10-6 °C-1 at room temperature. Superconducting YBa2 Cu3O7-icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> and YBa2Cu3O7-icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> -Ag thin films have been grown in situ on polycrystalline SmBa2NbO6 by the pulsed laser ablation technique. The films exhibited (00l) orientation of an orthorhombic YBa2 Cu3O7-icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> phase and gave a zero resistivity superconducting transition (TC(0)) at 90 K with a transition width of ~1.5 K. The critical current density of YBCO-Ag thin films grown on polycrystalline SmBa2NbO6 substrate was ~3 × 105 A cm-2 at 77 K. A comparative study of YBCO and YBCO-Ag thin films developed on polycrystalline SmBa2NbO6 substrate by PLD based on the crystallinity, orientation and critical current density of the YBCO film is discussed in detail.

  17. Comparative evaluation of microleakage in class II cavities restored with Ceram X and Filtek P-90: An in vitro study

    PubMed Central

    Bogra, Poonam; Gupta, Saurabh; Kumar, Saru

    2012-01-01

    Context: Polymerization shrinkage in composite resins is responsible for microleakage. Methacrylate-based composite resins have linear reactive groups resulting in high polymerization shrinkage. A recently introduced composite resin Filtek P90 is based on siloxanes and oxiranes which polymerize by cationic “ring opening” polymerization resulting in reduced polymerization shrinkage. Objectives: Aim of this study was to compare microleakage in class II cavities restored with a nanoceramic restorative (Ceram X) and a silorane composite (Filtek P90). Materials and Methods: Standardized class II box type cavities were prepared on mesial (Groups Ia and IIa) and distal (Groups Ib and IIb) surfaces of twenty extracted permanent molar teeth with gingival floor ending 1 mm coronal and apical to the cementoenamel junction, respectively. The teeth in Group Ia and Ib were restored with Ceram X and Group IIa and IIb with Filtek P90. The specimens were thermocycled and microleakage evaluated. Statistical Analysis Used: The data were statistically analyzed using Wilcoxon Signed-Rank test at the 0.05 level of significance. Results: Mean microleakage score of group la and lb was 1 ± 2.260 and 2.8 ± 1.229, respectively. And that of group Ila and llb was 0.2 ± .869 and 0.3 ± .588, respectively. When groups I and II were compared, results were statistically significant (P<0.05). Conclusion: It was concluded that silorane-based composite may be a better substitute for methacrylate-based composites. PMID:22557890

  18. Photocatalytic decolouration of Orange II by ZnO active layers screen-printed on ceramic tiles.

    PubMed

    Marto, J; São Marcos, P; Trindade, T; Labrincha, J A

    2009-04-15

    In this work ZnO layers have been deposited by screen-printing in common ceramic tiles. These layers were characterized and tested for the photocatalytic degradation of the organic dye Orange II in aqueous solutions, using a batch photoreactor either under visible light provided by a Philips ML-160 W lamp or under direct exposure to sunlight. For sake of comparison, ZnO suspensions have also been evaluated for similar reacting conditions. The influence of experimental parameters such as (i) firing temperature of the printed layer; (ii) layer thickness; and (iii) operation time have been investigated. Screen-printed ZnO layers obtained in optimal processing conditions showed photocatalytic activity comparable to aqueous ZnO suspensions. The maximal attenuation degree is over 70% and decolourisation rate, assuming that reaction kinetics follows a pseudo-first order rate law, is over 0.015 min(-1). Thus these ZnO-layered ceramic tiles can be regarded as an alternative to photocatalytic suspensions of the same material with the advantage of avoiding the removal of the photocatalyst.

  19. Epitaxial growth of biaxially oriented YBCO films on silver

    NASA Astrophysics Data System (ADS)

    Liu, Danmin; Zhou, Meiling; Wang, Xue; Suo, Hongli; Zuo, Tieyong; Schindl, Michael; Flükiger, René

    2001-09-01

    YBCO films were deposited on (100), (110) and (111) oriented silver single crystals and { 100} <100>, { 110} <211> and { 012} <100> biaxially textured Ag substrates by pulsed laser deposition. It is shown that the (100) and (110) orientated single crystals and the { 110} biaxially textured Ag tape are all suitable for the deposition of YBCO thin films with c-axis in-plane alignment. The Jc of YBCO film deposited on { 110} <211> biaxially textured Ag foil is 7×105A cm-2 at 77 K, 0 T. A scheme for the regular growth of YBCO on silver was put forward.

  20. High speed low damage grinding of advanced ceramics - Phase II Final Report

    SciTech Connect

    Kovach, J.A.; Malkin, S.

    2000-02-01

    In the manufacture of structural ceramic components, grinding costs can comprise up to 80% of the entire manufacturing cost. As a result, one of the most challenging tasks faced by manufacturing process engineers is the development of a ceramic finishing process to maximize part throughput while minimizing costs and associated scrap levels. The efforts summarized in this report represent the second phase of a program whose overall objective was to develop a single-step, roughing-finishing process suitable for producing high-quality silicon nitride parts at high material removal rates and at substantially lower cost than traditional, multi-stage grinding processes. More specifically, this report provides a technical overview of High-Speed, Low-Damage (HSLD) ceramic grinding which employs elevated wheel speeds to achieve the small grain depths of cut necessary for low-damage grinding while operating at relatively high material removal rates. The study employed the combined use of laboratory grinding tests, mathematical grinding models, and characterization of the resultant surface condition. A single-step, roughing-finishing process operating at high removal rates was developed and demonstrated.

  1. Static Test for a Gravitational Force Coupled to Type 2 YBCO Superconductors

    NASA Technical Reports Server (NTRS)

    Li, Ning; Noever, David; Robertson, Tony; Koczor, Ron; Brantley, Whitt

    1997-01-01

    As a Bose condensate, superconductors provide novel conditions for revisiting previously proposed couplings between electromagnetism and gravity. Strong variations in Cooper pair density, large conductivity and low magnetic permeability define superconductive and degenerate condensates without the traditional density limits imposed by the Fermi energy (approx. 10(exp -6) g cc. Recent experiments have reported anomalous weight loss for a test mass suspended above a rotating type II, YBCO superconductor, with the percentage change (0.05 - 2.1 %) independent of the test mass' chemical composition and diamagnetic properties. A variation of 5 parts per 10' was reported above a stationary (non-rotating) superconductor. In experiments using a sensitive gravimeter, bulk YBCO superconductors were stably levitated in a DC magnetic field. Changes in acceleration were measured to be less than 2 parts in 108 of the normal gravitational acceleration. This result puts new limits on the strength and range of the proposed coupling between static superconductors and gravity.

  2. Ceramic Thermal Protection Materials - How Far Can We Go? (Part II)

    NASA Astrophysics Data System (ADS)

    Hilfer, G.

    2002-01-01

    A space vehicle re-entering the earth's atmosphere is exposed to severe environmental conditions. In particular, certain surface areas of the vehicle such as the stagnation point area or exposed control surfaces have to withstand extraordinary thermal and oxidative loads. These loads that have to be taken by a thermal protection system (TPS) are driven mainly by the geometry of the vehicle, its mass and its re-entry path. As a consequence, small vehicles like the X-38 demonstrator of a re-usable crew return vehicle (CRV) need TPS components capable of withstanding temperatures of 1800°C accompanied by severe aerodynamic and chemical loads. Currently, the only promising materials having the potential of re-usability in such an environment are Si-based ceramics and related derivatives such as C-C/SiC. These materials have an extended oxidation regime leading to the formation of an oxidation-inhibiting SiO2-layer. Nevertheless, a number of parameters may turn this so-called passive oxidation mode into a different oxidation mode which can be characterized by the release of gaseous SiO. This is the so-called active oxidation mode which induces massive degradation of the material. Based on a long-term experimental and theoretical investigation performed on the constituents of SiC and its most important derivatives and oxidation products, a mechanism was proposed describing the relevant parameters which govern the transition from passive to active oxidation of SiC in a re-entry type environment. The crucial reaction process related to this transition was found to be the interaction of SiO and SiO2 with atomic and molecular oxygen, i.e. In a previous publication this mechanism was derived by a thorough study of a large number of related elementary reaction steps and the analysis of experimental findings [1]. In the course of the investigation, however, many other results have been obtained which could not be published within the frame of the above publication. Therefore

  3. Fast infrared response of YBCO thin films

    NASA Technical Reports Server (NTRS)

    Ballentine, P. H.; Kadin, A. M.; Donaldson, W. R.; Scofield, J. H.; Bajuk, L.

    1990-01-01

    The response to short infrared pulses of some epitaxial YBCO films prepared by sputter deposition and by electron-beam evaporation is reported. The response is found to be essentially bolometric on the ns timescale, with some indirect hints of nonequilibrium electron transport on the ps scale. Fast switching could be obtained either by biasing the switch close to the critical current or by cooling the film below about 20 K. These results are encouraging for potential application to a high-current optically-triggered opening switch.

  4. Flux pinning effect in a melt textured YBCO bulk evaluated by using tension measurements

    NASA Astrophysics Data System (ADS)

    Lee, Joon Ho; Ahmad, Dawood; Kim, Byoung Joo; Cha, Myoungsik; Yang, Ho Soon; Kim, Young Cheol; Ko, Rock Kil; Jeong, Dae Young

    2013-01-01

    Research on the flux pinning effect in type-II superconductors has usually been focused on microor nanosize pinning centers, and mm-sized pinning centers have been relatively less studied. In order to investigate the flux pinning effect caused by mm-sized pinning centers, we introduce a tension measurement method in this research. A cm-sized melt-textured YBCO bulk, in which holes with a 2 mm diameter are made, is prepared. The YBCO bulk is field-cooled by using a strong magnet in liquid nitrogen, and the bulk and the magnet are separated from each other. Then, an attractive force ( f a ) between them is generated, and f a is detected by using a tension measuring device. As the distance ( d) between them is increased, f a increases at short distance and decreases at long distance, showing a maximum value, f am , at a specific distance. The measurement of f a is stopped when d reaches a value defined as the breaking distance ( d bk ), as if a `string' between the magnet and the YBCO bulk is broken. As the number of holes ( n) made in the YBCO bulk increases from 1 to 6, f am and d bk increase, in spite of the superconducting volume loss. f am and d bk for n ≥ 7 converge to nearly constant values, which are smaller than the values for n = 6. This means that the critical current density can be calculated by using f am or d bk for a sufficient number of holes.

  5. Maximum permissible voltage of YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Wen, J.; Lin, B.; Sheng, J.; Xu, J.; Jin, Z.; Hong, Z.; Wang, D.; Zhou, H.; Shen, X.; Shen, C.

    2014-06-01

    Superconducting fault current limiter (SFCL) could reduce short circuit currents in electrical power system. One of the most important thing in developing SFCL is to find out the maximum permissible voltage of each limiting element. The maximum permissible voltage is defined as the maximum voltage per unit length at which the YBCO coated conductors (CC) do not suffer from critical current (Ic) degradation or burnout. In this research, the time of quenching process is changed and voltage is raised until the Ic degradation or burnout happens. YBCO coated conductors test in the experiment are from American superconductor (AMSC) and Shanghai Jiao Tong University (SJTU). Along with the quenching duration increasing, the maximum permissible voltage of CC decreases. When quenching duration is 100 ms, the maximum permissible of SJTU CC, 12 mm AMSC CC and 4 mm AMSC CC are 0.72 V/cm, 0.52 V/cm and 1.2 V/cm respectively. Based on the results of samples, the whole length of CCs used in the design of a SFCL can be determined.

  6. Remarkable weakness against cleavage stress for YBCO-coated conductors and its effect on the YBCO coil performance

    NASA Astrophysics Data System (ADS)

    Yanagisawa, Y.; Nakagome, H.; Takematsu, T.; Takao, T.; Sato, N.; Takahashi, M.; Maeda, H.

    2011-08-01

    Cleavage strength for an YBCO-coated conductor at 77 K was investigated with a model experiment. The nominal cleavage strength for an YBCO-coated conductor is extremely low, typically 0.5 MPa. This low nominal cleavage strength is due to stress concentration on a small part of the YBCO-coated conductor in cleavage fracture. Debonding by the cleavage stress occurs at the interface between the buffer layer and the Hastelloy substrate. The nominal cleavage strength for a slit edge of the conductor is 2.5-times lower than that for the original edge of the conductor; cracks and micro-peel existing over the slit edge reduce the cleavage strength for the slit edge. Cleavage stress and peel stress should be avoided in coil winding, as they easily delaminate the YBCO-coated conductor, resulting in substantial degradation of coil performance. These problems are especially important for epoxy impregnated YBCO-coated conductor coils. It appears that effect of cleavage stress and peel stress are mostly negligible for paraffin impregnated YBCO-coated conductor coils or dry wound YBCO-coated conductor coils.

  7. Modified Lanthanum Zirconium Oxide buffer layers for low-cost, high performance YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Parans Paranthaman, M.; Sathyamurthy, S.; Li, Xiaoping; Specht, E. D.; Wee, S. H.; Cantoni, C.; Goyal, A.; Rupich, M. W.

    2010-03-01

    The pyrochlore Lanthanum Zirconium Oxide, La 2Zr 2O 7 (LZO), has been developed as a potential replacement barrier layer in the standard RABiTS three-layer architecture of physical vapor deposited CeO 2 cap/YSZ barrier/Y 2O 3 seed on Ni-5%W metal tape. The main focus of this research is to ascertain whether: (i) we can further improve the barrier properties of LZO; (ii) we can modify the LZO cation ratio and still achieve a high level of performance; and (iii) it is possible to reduce the number of buffer layers. We report a systematic investigation of the LZO film growth with varying compositions of La:Zr ratio in the La 2O 3-ZrO 2 system. Using a metal-organic deposition (MOD) process, we have grown smooth, crack-free, epitaxial thin films of La xZr 1-xO y ( x = 0.2-0.6) on standard Y 2O 3 buffered Ni-5W substrates in short lengths. Detailed XRD studies indicate that a single epitaxial LZO phase with only (0 0 1) texture can be achieved in a broad compositional range of x = 0.2-0.6 in La xZr 1-xO y. Both CeO 2 cap layers and MOD-YBCO films were grown epitaxially on these modified LZO barriers. High critical currents per unit width, Ic of 274-292 A/cm at 77 K and self-field were achieved for MOD-YBCO films grown on La xZr 1-xO y ( x = 0.4-0.6) films. These results indicate that LZO films can be grown with a broad compositional range and still support high performance YBCO coated conductors. In addition, epitaxial MOD La xZr 1-xO y ( x = 0.25) films were grown directly on biaxially textured Ni-3W substrates. About 3 μm thick YBCO films grown on a single MOD-LZO buffered Ni-3W substrates using pulsed laser deposition show a critical current density, Jc, of 0.55 MA/cm 2 ( Ic of 169 A/cm) at 77 K and 0.01 T. This work holds promise for a route for producing simplified buffer architecture for RABiTS based YBCO coated conductors.

  8. Modified Lanthanum Zirconium Oxide Buffer for Low-Cost, High Performance YBCO Coated Conductors

    SciTech Connect

    Paranthaman, Mariappan Parans; Sathyamurthy, Srivatsan; Li, Xiaoping; Specht, Eliot D; Wee, Sung Hun; Cantoni, Claudia; Goyal, Amit; Rupich, M. W.

    2010-01-01

    Lanthanum Zirconium Oxide, La2Zr2O7 (LZO) has been developed as a potential replacement barrier layer in the standard RABiTS three-layer architecture of physical vapor deposited CeO2 cap/YSZ barrier/Y2O3 seed/Ni-5W. The main focus of this research is to see (i) whether we can improve further the barrier properties of LZO; (ii) can we widen the LZO composition and still achieve the high performance?; and (iii) is it possible to reduce the number of buffer layers? We report a systematic investigation of the LZO film growth with varying compositions of La:Zr ratio in the La2O3-ZrO2 system. Using metal-organic deposition (MOD) process, we have grown smooth, crack-free, epitaxial thin films of LaxZr1-xOy (x = 0.2-0.6) on standard Y2O3 buffered Ni-5W substrates in short lengths. Detailed XRD studies indicate that a single epitaxial LZO phase without the (111) texture can be achieved in a wider compositional window of x = 0.2-0.6 in LaxZr1-xOy. Both CeO2 cap layers and MOD-YBCO films were grown 2 epitaxially on these modified LZO barriers. Transport property measurements indicate that we can achieve a higher critical current, Ic of 274-292 A/cm at 77 K and self-field on MOD-YBCO films grown on LaxZr1-xOy (x = 0.4-0.6) films. These results indicate that LZO films can be grown with a wider compositional window and still achieve high performance YBCO coated conductors. In addition, epitaxial MOD LaxZr1-xOy (x = 0.25) films were grown directly on biaxially textured Ni-3W substrates. About 3 m thick YBCO films with a Jc of 0.55 MA/cm2 at 77 K and 0.01 T were grown on a single MOD LZO buffered Ni-3W substrate using pulsed laser deposition. This work promises a route for producing simplified buffer architecture for RABiTS based YBCO coated conductors.

  9. Fabrication of Filamentary YBCO Coated Conductor by Inkjet Printing

    SciTech Connect

    List III, Frederick Alyious; Kodenkandath, Thomas; Rupich, Marty

    2007-01-01

    Inkjet printing is a potentially low cost, high rate method for depositing precursors for filamentary YBCO coated conductors. The method offers considerable flexibility of filament pattern, width, and thickness. Using standard solution precursors and RABiTSTM substrates, the printing, processing, and properties of some inkjet-derived filamentary YBCO coated conductors for Second Generation (2G) wire are demonstrated on a laboratory scale. Some systematic variations of growth rate and critical transport current with filament width are observed and discussed.

  10. Obtention and characterization of YBCO/Ag/YBCO welds at different misorientation angles

    NASA Astrophysics Data System (ADS)

    Bozzo, B.; Bartolomé, E.; Granados, X.; Puig, T.; Obradors, X.

    2006-06-01

    The microstructural and magnetic properties of YBa2Cu3O7 (YBCO) welds with different crystallographic [001]-tilt misorientation, prepared by the Ag surface melting induced welding technique, have been studied. The inter- and intra-grain critical current densities have been simultaneously obtained by solving the Inverse Problem from the remanent local magnetization magnetic field maps measured by Hall Probe imaging. The obtained dependence of the inter-grain current density with the angle, JcGB(θ), is compared to previous results for thin-film bicrystals and bulk boundaries.

  11. Portfolio: Ceramics.

    ERIC Educational Resources Information Center

    Hardy, Jane; And Others

    1982-01-01

    Describes eight art activities using ceramics. Elementary students created ceramic tiles to depict ancient Egyptian and medieval European art, made ceramic cookie stamps, traced bisque plates on sketch paper, constructed clay room-tableaus, and designed clay relief masks. Secondary students pit-fired ceramic pots and designed ceramic Victorian…

  12. AC and DC transport currents in melt-grown YBCO

    SciTech Connect

    Yi, Z.; Ashworth, S.; Becluz, C.; Scurlock, R.G. )

    1991-03-01

    It has been suggested that the transport J{sub c} in multi-grain samples of bulk YBCO are limited by the intergrain links. This paper reports on preliminary measurements of intergrain currents. The intergrain critical currents in melt grown YBCO do not appear to be as sensitive to the precise crystallographic alignment of adjacent grains a has been reported for thin films. The measured critical current of similar grain boundaries varies widely, between 15000 A/cm{sup 2} and 200A/Cm{sub 2} for adjacent boundaries in the same sample.

  13. Sealing glass-ceramics with near-linear thermal strain, Part II: Sequence of crystallization and phase stability

    DOE PAGESBeta

    Rodriguez, Mark A.; Griego, James J. M.; Dai, Steve

    2016-08-22

    The sequence of crystallization in a recrystallizable lithium silicate sealing glass-ceramic Li2O–SiO2–Al2O3–K2O–B2O3–P2O5–ZnO was analyzed by in situ high-temperature X-ray diffraction (HTXRD). Glass-ceramic specimens have been subjected to a two-stage heat-treatment schedule, including rapid cooling from sealing temperature to a first hold temperature 650°C, followed by heating to a second hold temperature of 810°C. Notable growth and saturation of Quartz was observed at 650°C (first hold). Cristobalite crystallized at the second hold temperature of 810°C, growing from the residual glass rather than converting from the Quartz. The coexistence of quartz and cristobalite resulted in a glass-ceramic having a near-linear thermal strain,more » as opposed to the highly nonlinear glass-ceramic where the cristobalite is the dominant silica crystalline phase. HTXRD was also performed to analyze the inversion and phase stability of the two types of fully crystallized glass-ceramics. While the inversion in cristobalite resembles the character of a first-order displacive phase transformation, i.e., step changes in lattice parameters and thermal hysteresis in the transition temperature, the inversion in quartz appears more diffuse and occurs over a much broader temperature range. Furthermore, localized tensile stresses on quartz and possible solid-solution effects have been attributed to the transition behavior of quartz crystals embedded in the glass-ceramics.« less

  14. High Tc YBCO superconductor deposited on biaxially textured Ni substrate

    DOEpatents

    Budai, John D.; Christen, David K.; Goyal, Amit; He, Qing; Kroeger, Donald M.; Lee, Dominic F.; List, III, Frederick A.; Norton, David P.; Paranthaman, Mariappan; Sales, Brian C.; Specht, Eliot D.

    1999-01-01

    A superconducting article includes a biaxially-textured Ni substrate, and epitaxial buffer layers of Pd (optional), CeO.sub.2 and YSZ, and a top layer of in-plane aligned, c-axis oriented YBCO having a critical current density (J.sub.c) in the range of at least 100,000 A/cm.sup.2 at 77 K.

  15. Superconductivity of YBCO Thick Films Prepared by Spark Plasma Sintering

    NASA Astrophysics Data System (ADS)

    Kim, Youngha; Lee, Kyong H.; Sung, Tae-Hyun; Han, Sang-Chul; Han, Young-Hee; Jeong, Nyeon-Ho; No, Kwangsoo

    2007-10-01

    YBa2Cu3O x (YBCO) superconducting thick films have been fabricated on Cu substrates, using a simple screen-printing method from Cu-free powders (Y2O3 and BaCO3). However, such films have poor superconducting properties such as critical current density ( J c) due to the low film density. In this work, we investigate the effect of uniaxial c-axis pressure on the superconducting properties of these YBCO films using a spark plasma sintering (SPS) technique. The film screen-printed on Cu substrates was heat-treated at 850°C for 5 min in vacuum varying the pressure (15, 30, and 45 MPa). To form a superconducting YBCO phase, the film was reheat-treated at 930°C for 30 s in air followed by oxygen annealing at 450°C for 1 h. For heat-treatments performed under pressure, lower film porosity was obtained, and a higher crack density was also observed compared to films prepared without pressure. The densification of the YBCO thick films using the SPS technique was very effective in improving the superconducting properties of the films.

  16. Pulsed laser deposition of YBCO thin films on IBAD-YSZ substrates

    NASA Astrophysics Data System (ADS)

    Li, M.; Ma, B.; Koritala, R. E.; Fisher, B. L.; Venkataraman, K.; Balachandran, U.

    2003-01-01

    High-quality YBa2Cu3O7-x (YBCO) films were fabricated on yttria-stabilized zirconia (YSZ)-buffered Hastelloy C276 substrates by pulsed laser deposition. YSZ was grown by ion-beam-assisted deposition. A thin (approx10 nm) CeO2 layer was deposited before the deposition of YBCO. The crystalline structure and biaxial texture of the YBCO film and the buffer layer were examined by x-ray diffraction 2theta-scan, phi-scan and pole-figure analysis. Epitaxial growth of the YBCO film on the buffer layer was observed. Full width at half maximum (FWHM) value of 7.4° was measured from the phi-scan of YBCO(103). Raman spectroscopy showed compositional uniformity and phase integrity in the YBCO films. Surface morphologies of the YBCO films were examined by scanning electron microscopy. Comparative studies indicated that the CeO2 buffer layer significantly improves the structural alignment and superconducting properties of YBCO films. Tc = 90 K, with sharp transition, and transport Jc = 2.2 × 106 A cm-2 at 77 K in zero-external field were obtained on the 0.5 mum thick YBCO films. The dependence of Jc on the FWHM of the YBCO(103) phi-scan indicated that high Jc is associated with low FWHM.

  17. Sealing glass-ceramics with near linear thermal strain, Part II: Sequence of crystallization and phase stability

    DOE PAGESBeta

    Dai, Steve Xunhu; Rodriguez, Mark A.; Griego, James M.

    2016-06-01

    Here, the sequence of crystallization in a re-crystallizable lithium silicate sealing glass-ceramic Li2O-SiO2-Al2O3-K2O-B2O3-P2O5-ZnO was analyzed by in situ high temperature X-ray diffraction (HTXRD). Glass-ceramic specimens have been subjected to a 2-stage heat treatment schedule, including rapid cooling from sealing temperature to a 1st hold temperature 650 °C, following by heating to a 2nd hold temperature of 810 °C. Notable growth and saturation of Quartz was observed at 650 °C (1st hold).

  18. Evaluation of ceramic fiber filters for hot gas cleanup in pressurized fluidized-bed combustion power plants. Addendum 1. Phase II results

    SciTech Connect

    Lippert, T.E.; Ciliberti, D.F.

    1984-01-01

    This report is an addendum to an earlier published EPRI contract report (EPRI CS-1846) on the evaluation of Ceramic Fiber Filters for Pressurized Fluidized-Bed Combustion (PFBC), Hot Gas Cleanup. The work presented is the result of a second test series (Test Phase II) that was conducted on the five-bag, felted-ceramic filter unit in a simulated PFBC environment. The filter was operated at higher than conventional filter air-to-cloth ratios, 10 ft/min (3 m/min), and was designed for off-line cleaning by a pulse-jet method. Results of tests are reported that suggest a decreasing performance level for the filter with continued operation and ineffective cleaning with the pulse-jet method. These results are partially attributable to insufficient capacity in the pulse-jet air supply system. Test data and results are described and discussed that reflect on both the filter bag test unit operation and the nature and evaluation of the problems encountered with the pulse-jet cleaning.

  19. Reel-to-reel fabrication of meter-long YBCO coated conductor

    NASA Astrophysics Data System (ADS)

    Yang, J.; Zhang, H.; Wang, S. M.; Lin, C. G.; Shi, D. Q.; Dou, S. X.

    2011-04-01

    YBa 2Cu 3O 7-δ (YBCO) superconductors were coated on the CeO 2/YSZ/Y 2O 3 buffered Ni-5at%W tapes by a reel-to-reel pulsed laser deposition (PLD). The process of a multi-layer deposition of YBCO film was explored. X-ray diffraction texture measurements showed good both in-plane and out of plane crystalline orientations in YBCO films. The average values calculated at a full width at half maximum (FWHM) of the peaks from phi-scans ( φ) and omega ( ω) scans for one meter-long YBCO tape were 7.49° and 4.71°, respectively. The critical current ( Ic) was over 200 A/cm-width at 77 K and under self-field for meter-long YBCO tape. The critical transition temperature of the YBCO tape was typically as 90.1 K with 0.5 K transition widths.

  20. Doping Effect of Nano-Ybco Additive on MgB2

    NASA Astrophysics Data System (ADS)

    Rui, X. F.; Sun, X. F.; Xu, X. L.; Zhang, L.; Zhang, H.

    The effect of YBCO nanoparticles added into MgB2 on Tc, Jc, and flux pinning was studied for MgB2(YBCO)x with x=0, 5, 10, 15 wt%. Phase analysis shows that none of elements are doped into the MgB2 lattice in the samples with YBCO addition. For the samples with YBCO addition, the Jc-H characteristics behave poorly in comparison with the pure sample. Our experimental results show that the nanoscale size of addition dosen't comprise the only condition for its effectiveness as pinning centers.

  1. Influence of oxygen partial pressure and silver additions on microstructure and related properties of YBCO superconductors

    SciTech Connect

    Singh, J.P.; Joo, J.; Guttschow, R.; Poeppel, R.B.

    1992-02-01

    Microstructure has a great influence on the mechanical and superconducting properties of YBCO. Mechanical properties of YBCO can be improved by both modifying the monolithic microstructure and developing composites of YBCO with silver (Ag). When monolithic YBCO was sintered to high densities ({approx} 91%) at a relatively low temperature ({approx} 910{degrees}C) by controlling oxygen partial pressure during sintering, the result was a small-grain microstructure (average grain size {approx} 5 {mu}m) and hence a high strength of 191 {plus_minus} 7 MPa. Addition of Ag as a second phase further improved the strength of YBCO. Composites of YBCO with 10 to 15 vol % Ag has a strength of 225 {plus_minus} 6 MPa and a fracture toughness of 3.3 {plus_minus} 0.2 MPa{radical}m. These improvements are believed to be due to compressive stresses in the YBCO matrix as a result of thermal mismatch between the YBCO and Ag phases. Furthermore, the Ag particles may provide increased resistance to crack propagation by pinning the crack. On the other hand, addition of Ag as a dopant to substitute for Cu sites in YBCO has a profound but nonmonotonic effect on grain microstructure and the resulting critical current density.

  2. Influence of oxygen partial pressure and silver additions on microstructure and related properties of YBCO superconductors

    SciTech Connect

    Singh, J.P.; Joo, J.; Guttschow, R.; Poeppel, R.B.

    1992-02-01

    Microstructure has a great influence on the mechanical and superconducting properties of YBCO. Mechanical properties of YBCO can be improved by both modifying the monolithic microstructure and developing composites of YBCO with silver (Ag). When monolithic YBCO was sintered to high densities ({approx} 91%) at a relatively low temperature ({approx} 910{degrees}C) by controlling oxygen partial pressure during sintering, the result was a small-grain microstructure (average grain size {approx} 5 {mu}m) and hence a high strength of 191 {plus minus} 7 MPa. Addition of Ag as a second phase further improved the strength of YBCO. Composites of YBCO with 10 to 15 vol % Ag has a strength of 225 {plus minus} 6 MPa and a fracture toughness of 3.3 {plus minus} 0.2 MPa{radical}m. These improvements are believed to be due to compressive stresses in the YBCO matrix as a result of thermal mismatch between the YBCO and Ag phases. Furthermore, the Ag particles may provide increased resistance to crack propagation by pinning the crack. On the other hand, addition of Ag as a dopant to substitute for Cu sites in YBCO has a profound but nonmonotonic effect on grain microstructure and the resulting critical current density.

  3. Unique magnetic structure of YbCo2Si2

    NASA Astrophysics Data System (ADS)

    Mufti, N.; Kaneko, K.; Hoser, A.; Gutmann, M.; Geibel, C.; Krellner, C.; Stockert, O.

    2016-07-01

    We report on the results of powder and single-crystal neutron diffraction to investigate the magnetic order in YbCo2Si2 below the Néel temperature TN=1.7 K in detail. Two different magnetically ordered phases can clearly be distinguished. At lowest temperatures a commensurate magnetic structure with a propagation vector k1=(0.25 0.25 1 ) is found, while the intermediate phase (T >0.9 K) is characterized by an incommensurate magnetic structure with k2=(0.25 0.086 1 ) . The magnetic structure in YbCo2Si2 is in marked contrast to all other known R Co2Si2 compounds (R = rare earth element) likely due to some itineracy of the Yb 4 f states being responsible for the magnetism.

  4. High frequency properties of YBCO bridges fabricated by MOCVD

    SciTech Connect

    Chen, J.; Yamoshita, T. ); Suzuki, H.; Kurosawa, H. ); Yamane, H.; Hirai, T. . Inst. for Materials Research)

    1991-03-01

    This paper reports on the high frequency properties of YBCO bridges at 4.2% and 77K. The YBCO films were prepared by MOCVD. For small bridges with the width(w) of about 1 {mu}m and thickness(t) of less than 0.5{mu}m, the constant voltage steps at integral multiples of {phi}{sub 0}fr = 20 {mu}V were observed up to 1 mV, which is much higher than the IcR{sub N} ({lt}0.13 mV) product of these bridges at 77K. The magnitudes of the current steps as functions of the rf current at 4.2K and 77K were in quantitative agreement with the theoretical results based on the RSJ model.

  5. Temperature dependence of nanoscale friction for Fe on YBCO

    NASA Astrophysics Data System (ADS)

    Altfeder, Igor; Krim, Jacqueline

    2012-05-01

    A magnetic probe microscopy study of levitation and atomic-scale friction is reported for Fe on YBCO (Tc = 92.5 K) in the temperature range 65-293 K. Below Tc, the friction coefficient is constant and exhibits no correlation with the strength of superconducting levitation forces. Above Tc, the friction coefficient increases progressively, and nearly doubles between Tc and room temperature. The results are discussed within the context of the underlying atomic-scale electronic and phononic mechanisms that give rise to friction, and it is concluded that contact electrification and static electricity may play a significant role in the non-superconducting phase. Given that the properties of YBCO can be finely tuned, the results point the way to a variety of interesting studies of friction and superconductors.

  6. Zone refining of sintered, microwave-derived YBCO superconductors

    SciTech Connect

    Warrier, K.G.K.; Varma, H.K.; Mani, T.V.; Damodaran, A.D.; Balachandran, U.

    1993-07-01

    Post-sintering treatments such as zone melting under thermal gradient has been conducted on sintered YBCO tape cast films. YBCO precursor powder was derived through decomposition of a mixture of nitrates of cations in a microwave oven for {approx}4 min. The resulting powder was characterized and made into thin sheets by tape casting and then sintered at 945 C for 5 h. The sintered tapes were subjected to repeated zone refining operations at relatively high speeds of {approx}30 mm/h. A microstructure having uniformly oriented grains in the a-b plane throughout the bulk of the sample was obtained by three repeated zone refining operations. Details of precursor preparation, microwave processing and its advantages, zone refining conditions, and microstructural features are presented in this paper.

  7. Vortex creep in TFA-YBCO nanocomposite films

    NASA Astrophysics Data System (ADS)

    Rouco, V.; Bartolomé, E.; Maiorov, B.; Palau, A.; Civale, L.; Obradors, X.; Puig, T.

    2014-11-01

    Vortex creep in YBa2Cu3O7 - x (YBCO) films grown from the trifluoracetate (TFA) chemical route with BaZrO3 and Ba2YTaO6 second-phase nanoparticles (NPs) has been investigated by magnetic relaxation measurements. We observe that in YBCO nanocomposites the phenomenological crossover line from the elastic to the plastic creep regime is shifted to higher magnetic fields and temperatures. The origin of this shift lies on the new isotropic-strong vortex pinning contribution appearing in these nanocomposites, induced by local lattice distortions. As a consequence, we demonstrate that the addition of non-coherent NPs produces a decrease in the creep rate S in most of the phase diagram, particularly, in the range of fields and temperatures (T\\gt 60 K, {{μ }0}H\\gt 0.5 T) relevant for large scale applications.

  8. Deposition of YBCO films by high temperature spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Shields, T. C.; Abell, J. S.; Button, T. W.; Chakalov, R. A.; Chakalova, R. I.; Cai, C.; Haessler, W.; Eickemeyer, J.; de Boer, B.

    2002-08-01

    The fabrication of YBCO coated conductors on flexible textured metallic substrates requires the deposition of biaxially textured buffer layers and superconducting films. In this study we have prepared YBCO thin films on single crystal SrTiO 3 substrates and cube textured Ni substrates by spray pyrolysis. The Ni substrates have been pre-buffered with CeO 2/YSZ/CeO 2, layers deposited by pulsed laser deposition. Spray pyrolysis of nitrate solutions has been performed directly on heated substrates at temperatures between 800 and 900 °C without need for a subsequent annealing step. YBCO films deposited on both types of substrate are biaxially textured. Full width half maximum values determined from φ-scans are 8° and 20° for films on SrTiO 3 and buffered Ni substrates respectively. A transport Jc value of 1.2×10 5 A/cm 2 at 77 K and zero field has been achieved on SrTiO 3 ( T c onset=91 K, ΔTc=6 K). χ ac susceptibility measurements of films on buffered Ni substrates show Tc onsets of 88 K with ΔTc=18 K.

  9. The Effect of Axial Stress on YBCO Coils

    SciTech Connect

    Sampson, W.; Anerella, M.; Cozzolino, J.P.; Gupta, R.C.; Shiroyanagi, Y.; Evangelou, E.

    2011-03-28

    The large aspect ratio of typical YBCO conductors makes them ideal for constructing solenoids from pancake style coils. An advantage of this method is that each subunit can be tested before assembly into the finished magnet. The fact that conductors are available in relatively short lengths is another reason for using such a fabrication technique. The principal drawback is the large number of joints required to connect the coils together. When very high field solenoids such as those contemplated for the muon collider are built in this way the magnetic forces between pancakes can be very large. Extensive measurements have been made on the effect of stress on short lengths of conductor, but there is little or no data on the effect of intercoil loading. The experiment described in this paper was designed to test the ability of YBCO coils to withstand these forces. A spiral wound 'pancake' coil made from YBCO coated conductor has been stressed to a pressure of 100MPa in the axial direction at 77K. In this case axial refers to the coil so that the force is applied to the edge of the conductor. The effect on the critical current was small and completely reversible. Repeatedly cycling the pressure had no measureable permanent effect on the coil. The small current change observed exhibited a slight hysteretic behaviour during the loading cycle.

  10. Oxidation and Corrosion of Ceramics and Ceramic Matrix Composites

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Opila, Elizabeth J.; Lee, Kang N.

    2000-01-01

    Ceramics and ceramic matrix composites are candidates for numerous applications in high temperature environments with aggressive gases and possible corrosive deposits. There is a growing realization that high temperature oxidation and corrosion issues must be considered. There are many facets to these studies, which have been extensively covered in some recent reviews. The focus of this paper is on current research, over the past two years. In the authors' view, the most important oxidation and corrosion studies have focused on four major areas during this time frame. These are; (I) Oxidation of precursor-based ceramics; (II) Studies of the interphase material in ceramic matrix composites; (III) Water vapor interactions with ceramics, particularly in combustion environments; and (IV) Development of refractory oxide coatings for silicon-based ceramics. In this paper, we shall explore the most current work in each of these areas.

  11. On Ceramics.

    ERIC Educational Resources Information Center

    School Arts, 1982

    1982-01-01

    Presents four ceramics activities for secondary-level art classes. Included are directions for primitive kiln construction and glaze making. Two ceramics design activities are described in which students make bizarrely-shaped lidded jars, feet, and footwear. (AM)

  12. Structural Ceramics

    NASA Technical Reports Server (NTRS)

    1986-01-01

    This publication is a compilation of abstracts and slides of papers presented at the NASA Lewis Structural Ceramics Workshop. Collectively, these papers depict the scope of NASA Lewis' structural ceramics program. The technical areas include monolithic SiC and Si3N4 development, ceramic matrix composites, tribology, design methodology, nondestructive evaluation (NDE), fracture mechanics, and corrosion.

  13. YBCO coated conductors on highly textured Pd-buffered Ni-W tape

    NASA Astrophysics Data System (ADS)

    Celentano, G.; Galluzzi, V.; Mancini, A.; Rufoloni, A.; Vannozzi, A.; Augieri, A.; Petrisor, T.; Ciontea, L.; Gambardella, U.

    2006-06-01

    High critical current density YBa2Cu3O7-x (YBCO) coated conductors were obtained on cube textured Ni-W. The use of a Pd transient layer as a first buffer led to a sharp out-of-plane grains alignment of the CeO2/YSZ/CeO2 buffer layer. YBCO films grown on this template exhibit an out-of-plane orientation with a full width at half maximum of about 3°, less than 50% of the respective starting Ni-W value. Despite the complete interdiffusion between Ni-W and Pd after the YBCO film deposition, the coated conductors exhibit good film adherence as well as a crack free and smooth surface of the YBCO film. YBCO thin films show critical temperature values above than 88 K and a critical current density of 2.1 MA/cm2 at 77 K and self field.

  14. Interactions of Y2BaCuO5 particles and the YBCO matrix within melt-textured YBCO samples studied by means of electron backscatter diffraction

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Mücklich, F.; Ogasawara, K.; Murakami, M.

    2005-02-01

    By means of automated electron backscatter diffraction (EBSD) analysis, we studied the local orientations of embedded Y2BaCuO5(211) particles within melt-textured YBa2Cu3Ox (YBCO) samples. On both components, we obtained high-quality Kikuchi patterns, thus allowing the automated mapping of the crystal orientations and a two-phase analysis of the samples. Investigations were performed on a variety of melt-textured YBCO samples. In melt-textured YBCO with (001) orientation, we find that the embedded 211 particles do not have any preferred orientation. The EBSD maps also reveal that at certain orientations of the 211 particles the YBCO growth is not altered. From the obtained EBSD mappings, we can conclude that the formation of small 211 particles will not disturb the YBCO matrix growth, whereas the presence of large 211 particles causes severe changes in the YBCO growth, leading to the formation of subgrains. The EBSD results are presented in the form of local orientation maps and local pole figures.

  15. All MOD buffer/YBCO approach to coated conductors

    NASA Astrophysics Data System (ADS)

    Parans Paranthaman, M.; Sathyamurthy, S.; Heatherly, L.; Martin, P. M.; Goyal, A.; Kodenkandath, T.; Li, X.; Thieme, C. L. H.; Rupich, M. W.

    2006-10-01

    RABiTS based metal-organic deposition (MOD) buffer/YBa2Cu3O7-δ (YBCO) approach has been considered as one of the potential, low-cost approaches to fabricate high performance second generation coated conductors. The most commonly used RABiTS architectures consisting of a starting template of biaxially textured Ni-W (5 at.%) substrate with a seed layer of Y2O3, a barrier layer of YSZ, and a CeO2 cap. In this three layer architecture, all the buffers are deposited using physical vapor deposition (PVD) techniques. Using these PVD deposited templates, 0.8-μm thick MOD-YBCO films with an Ic (critical current) of 250 A/cm have been achieved routinely in short lengths. We have developed a low-cost, non-vacuum, MOD process to grow epitaxial buffer layers on textured Ni-5W substrates. The main challenge in this effort is to match the performance of MOD templates to that of PVD templates. We have recently shown that the properties of MOD-La2Zr2O7 (LZO) layers can be improved by inserting a thin Y2O3 seed layer. Using MOD-CeO2 cap layers, we have demonstrated the growth of high performance MOD-YBCO films with an Ic of 200 A/cm-width on MOD-La2Zr2O7/Y2O3/Ni-5W substrates. This approach could potentially decrease the overall cost of the coated conductor fabrication.

  16. All MOD Buffer/YBCO Approach to Coated Conductors

    SciTech Connect

    Paranthaman, Mariappan Parans; Sathyamurthy, Srivatsan; Heatherly Jr, Lee; Martin, Patrick M; Goyal, Amit; Kodenkandath, Thomas; Li, Xiaoping; Thieme, C. L. H.; Rupich, Marty

    2006-01-01

    RABiTS based metal-organic deposition (MOD) buffer/YBa2Cu3O7-d (YBCO) approach has been considered as one of the potential, low-cost approaches to fabricate high performance second generation coated conductors. The most commonly used RABiTS architectures consisting of a starting template of biaxially textured Ni-W (5 at.%) substrate with a seed layer of Y2O3, a barrier layer of YSZ, and a CeO2 cap. In this three layer architecture, all the buffers are deposited using physical vapor deposition (PVD) techniques. Using these PVD deposited templates, 0.8-{mu}m thick MOD-YBCO films with an Ic (critical current) of 250 A/cm have been achieved routinely in short lengths. We have developed a low-cost, non-vacuum, MOD process to grow epitaxial buffer layers on textured Ni-5W substrates. The main challenge in this effort is to match the performance of MOD templates to that of PVD templates. We have recently shown that the properties of MOD-La2Zr2O7 (LZO) layers can be improved by inserting a thin Y2O3 seed layer. Using MOD-CeO2 cap layers, we have demonstrated the growth of high performance MOD-YBCO films with an Ic of 200 A/cm-width on MOD-La2Zr2O7/Y2O3/Ni-5W substrates. This approach could potentially decrease the overall cost of the coated conductor fabrication.

  17. The use of monolithic YBCO in electromagnetic launchers

    NASA Astrophysics Data System (ADS)

    Putman, Philip T.

    One of the fundamental barriers to the use of electromagnetic launchers is the high power required to reach launch speed in a reasonable distance. It has been proposed that large external power supplies can be avoided by using superconducting persistent currents in the barrel of the launcher to store energy. This study examines the use of monolithic YBCO for these persistent current magnets. Monolithic magnets, unlike wound magnets, can have a nonuniform current distribution, which causes energy transfer between the stationary energy storage magnets and the accelerated magnet to be inefficient. This problem can be overcome by optimization of the magnet shape. This requires a model for computation of current distribution, force vs. distance, and efficiency. A model is presented for calculating the current distribution and magnetic force for two YBCO rings, each with a trapped field such that an attractive force is developed between them. Two different methods were used to find current as a function of time. The first is a system of differential equations for the time dependence of the current distribution, which is solved using the 4-step vector Runge-Kutta method. The second is a speed-independent approximation that is less computationally intensive. The integral equation for force at each time step is solved using the finite sum method. After verifying the speed-dependent model by comparing computations to measured force vs. distance curves for twenty-eight pairs of YBCO magnets, the model was used to examine behavior at speeds up to 10,000 m/s. It was found that energy transfer is almost independent of speed for a properly designed launcher. Also, heating due to flux flow was found to be minimal. The fact that energy transfer did not depend on speed allowed the speed-independent model to be used with an optimizer to find a more efficient shape for the accelerated YBCO magnet. A magnet of this shape was fabricated, and efficiency was measured to be 84%, compared

  18. Ceramic joining

    SciTech Connect

    Loehman, R.E.

    1996-04-01

    This paper describes the relation between reactions at ceramic-metal interfaces and the development of strong interfacial bonds in ceramic joining. Studies on a number of systems are described, including silicon nitrides, aluminium nitrides, mullite, and aluminium oxides. Joints can be weakened by stresses such as thermal expansion mismatch. Ceramic joining is used in a variety of applications such as solid oxide fuel cells.

  19. Ceramic burner

    SciTech Connect

    Laux, W.; Hebel, R.; Artelt, P.; Esfeld, G.; Jacob, A.

    1981-03-31

    Improvements in the mixing body and supporting structure of a molded-ceramic-brick burner enable the burner to withstand the vibrations induced during its operation. Designed for the combustion chambers of air heaters, the burner has a mixing body composed of layers of shaped ceramic bricks that interlock and are held together vertically by a ceramic holding bar. The mixing body is shaped like a mushroom - the upper layers have a larger radius than the lower ones.

  20. Ceramic Processing

    SciTech Connect

    EWSUK,KEVIN G.

    1999-11-24

    Ceramics represent a unique class of materials that are distinguished from common metals and plastics by their: (1) high hardness, stiffness, and good wear properties (i.e., abrasion resistance); (2) ability to withstand high temperatures (i.e., refractoriness); (3) chemical durability; and (4) electrical properties that allow them to be electrical insulators, semiconductors, or ionic conductors. Ceramics can be broken down into two general categories, traditional and advanced ceramics. Traditional ceramics include common household products such as clay pots, tiles, pipe, and bricks, porcelain china, sinks, and electrical insulators, and thermally insulating refractory bricks for ovens and fireplaces. Advanced ceramics, also referred to as ''high-tech'' ceramics, include products such as spark plug bodies, piston rings, catalyst supports, and water pump seals for automobiles, thermally insulating tiles for the space shuttle, sodium vapor lamp tubes in streetlights, and the capacitors, resistors, transducers, and varistors in the solid-state electronics we use daily. The major differences between traditional and advanced ceramics are in the processing tolerances and cost. Traditional ceramics are manufactured with inexpensive raw materials, are relatively tolerant of minor process deviations, and are relatively inexpensive. Advanced ceramics are typically made with more refined raw materials and processing to optimize a given property or combination of properties (e.g., mechanical, electrical, dielectric, optical, thermal, physical, and/or magnetic) for a given application. Advanced ceramics generally have improved performance and reliability over traditional ceramics, but are typically more expensive. Additionally, advanced ceramics are typically more sensitive to the chemical and physical defects present in the starting raw materials, or those that are introduced during manufacturing.

  1. Ceramic filters

    SciTech Connect

    Holmes, B.L.; Janney, M.A.

    1995-12-31

    Filters were formed from ceramic fibers, organic fibers, and a ceramic bond phase using a papermaking technique. The distribution of particulate ceramic bond phase was determined using a model silicon carbide system. As the ceramic fiber increased in length and diameter the distance between particles decreased. The calculated number of particles per area showed good agreement with the observed value. After firing, the papers were characterized using a biaxial load test. The strength of papers was proportional to the amount of bond phase included in the paper. All samples exhibited strain-tolerant behavior.

  2. Comparative Evaluation of the Antibacterial Efficacy of Type II Glass lonomer Cement, Type IX Glass lonomer Cement, and AMALGOMER™ Ceramic Reinforcement by Modified “Direct Contact Test”: An in vitro Study

    PubMed Central

    Assudani, Harsha G; Patil, Vidyavathi; Kukreja, Pratibha; Uppin, Chaitanya; Thakkar, Prachi

    2016-01-01

    ABSTRACT Background: Streptococcus mutans (ATCC25175) has a profound effect on the incidence of dental decay in the human population. Many studies have been performed to assess the antimicrobial activity of different cements. However, little or no information is available about the antibacterial properties of Type II glass ionomer cement (GIC), Type IX GIC, and AMALGOMER™ ceramic reinforcement (CR). Aim: To comparatively evaluate the antibacterial activity of Type II GIC, Type IX GIC, and AMALGOMER™ CR by modified direct contact test. Materials and methods: The total sample size was 72 which was divided into four study groups. Six wells were coated by each: Type II GIC, Type IX GIC, AMALGOMER™ CR, and control group (only S. mutans). Statistical analysis was done using analysis of variance and the intergroup comparison was done using post hoc Tukey test. Results: AMALGOMER™ CR was found to have a better antibacterial effect as compared with Type II and IX GIC. Conclusion: AMALGOMER™ CR can serve as a valuable cement in pediatric dentistry due to its anticariogenic property. How to cite this article: Hugar SM, Assudani HG, Patil V, Kukreja P, Uppin C, Thakkar P. Comparative Evaluation of the Antibacterial Efficacy of Type II Glass lonomer Cement, Type IX Glass Ionomer Cement, and AMALGOMER™ Ceramic Reinforcement by Modified “Direct Contact Test”: An in vitro Study. Int J Clin Pediatr Dent 2016;9(2):114-117. PMID:27365930

  3. Thermal stability of NdBCO/YBCO/MgO thin film seeds

    NASA Astrophysics Data System (ADS)

    Volochová, D.; Kavečanský, V.; Antal, V.; Diko, P.; Yao, X.

    2016-04-01

    Thermal stability of the Nd1+x Ba2-x Cu3O7-δ (Nd-123 or NdBCO) thin films deposited on MgO substrate, with YBa2Cu3O7-δ (Y-123 or YBCO) buffer layer (NdBCO/YBCO/MgO thin film), has been experimentally studied in order to determine the optimal film thickness acting as seed for bulk YBCO growth. YBCO bulk superconductors with Y2BaCuO5 (Y-211) and CeO2 addition were prepared by the top seeded melt growth process in a chamber furnace using NdBCO/YBCO/MgO thin film seeds of different thicknesses (200-700 nm with 20 nm YBCO buffer layer) and different maximum temperatures, T max. The maximum temperatures varied in the range of 1040 °C-1125 °C. The highest thermal stability 1118 °C was observed in the case of NdBCO/YBCO/MgO thin film of 300 nm thickness. These results are corroborated with differential scanning calorimetry and high temperature x-ray diffraction measurements, as well as microstructure observations.

  4. Study on Quench Protection of HTS Coil Wound of YBCO Conductor

    NASA Astrophysics Data System (ADS)

    Fu, Youkun; Tsukamoto, Osami; Furuse, Mitsuho

    Recent progress of long YBCO coated conductors is remarkable and coils wound of YBCO conductors will be developed in near future. YBCO coated conductors that are made by deposition of thin YBCO film on high resistance metal substrates such as Hastelloy and nickel tapes are highly resistive when they are quenched. Therefore, measures for stabilization and quench protection are more important for YBCO conductors than for Bi/Ag sheathed tapes which have low resistive silver matrix. Though HTS conductors working at liquid nitrogen temperature are hard to be quenched, the conductors still have possibilities of quenches due to local defects for example. We studied necessary amount of copper stabilizer to protect the YBCO conductors in coils from damages caused by hot spots due to quenches. In the work we numerically calculated maximum hot spot temperature of a YBCO conductor quenched by a local disturbance during the sequence of quench detection and energy dump. In the analysis, necessary amounts of copper to keep the maximum hot spot temperature below a threshold are calculated. Based on the analysis, optimum conductor design is discussed to obtain safe and high current density conductors.

  5. A YBCO RF-SQUID magnetometer and its applications

    NASA Technical Reports Server (NTRS)

    Luwei, Zhou; Jingwu, Qiu; Xienfeng, Zhang; Zhiming, Tank; Yongjia, Qian

    1990-01-01

    An applicable RF-superconducting quantum interference detector (SQUID) magnetometer was made using a bulk sintered yttrium barium copper oxide (YBCO). The temperature range of the magnetometer is 77 to 300 K and the field range 0 to 0.1T. At 77 K, the equivalent flux noise of the SQUID is 5 x 10 to minus 4 power theta sub o/square root of Hz at the frequency range of 20 to 200 Hz. The experiments show that the SQUID noise at low-frequency end is mainly from 1/f noise. A coil test shows that the magnetic moment sensitivity delta m is 10 to the minus 6th power emu. The RF-SQUID is shielded in a YBCO cylinder with a shielding ability B sub in/B sub ex of about 10 to the minus 6th power when external dc magnetic field is about a few Oe. The magnetometer is successfully used in characterizing superconducting thin films.

  6. Formation of superconducting junctions in MT-YBCO

    NASA Astrophysics Data System (ADS)

    Prikhna, T. A.; Gawalek, W.; Novikov, N. V.; Moshchil, V. E.; Sverdun, V. B.; Sergienko, N. V.; Surzhenko, A. B.; Uspenskaya, L. S.; Viznichenko, R.; Kordyuk, A. A.; Litzkendorf, D.; Habisreuther, T.; Krachunovska, S.; Vlasenko, A. V.

    2005-02-01

    The formation of superconducting junctions between MT-YBCO using TmBa2Cu3O7-δ powder as a solder has been studied. The method proposed excludes the step of a very slow cooling (at a rate of several degrees per hour) during seam formation. The heating and cooling rate for joining parts produced from single-domain material without visible cracks (macrocracks) can be rather high (500-1000 K h-1) and a holding time at the highest temperature (1010 °C) of several minutes (0.05 h) is enough to form a reliable junction. Reasonable rates of heating and cooling are however around 100 K h-1 if crack propagation is to be avoided in joined blocks used for practical application. Modelling experiments on rings and studies of the ring properties by vibrating sample magnetometer (VSM), field mapping with a Hall probe and magneto-optical microscopy have shown that superconducting properties of the junction were not lower than that of the joined material (jc of about 30 kA cm-2 was observed in zero field at 77 K) and that the proposed process of joining did not adversely affect the properties of the material. The structure of the resulting junction was in good agreement with the structure of MT-YBCO.

  7. Limitations for the trapped field in large grain YBCO superconductors

    NASA Astrophysics Data System (ADS)

    Eisterer, M.; Haindl, S.; Zehetmayer, M.; Gonzalez-Arrabal, R.; Weber, H. W.; Litzkendorf, D.; Zeisberger, M.; Habisreuther, T.; Gawalek, W.; Shlyk, L.; Krabbes, G.

    2006-07-01

    The actual limitations for the trapped field in YBa2Cu3O7-δ (YBCO) monoliths are discussed. The influence of the sample geometry and of the critical current density on the trapped field is investigated by numerical calculations. The field dependence of the critical current density strongly influences the trapped field. A nonlinear relationship between the sample size, the critical current density and the resulting trapped field is derived. The maximum achievable trapped field in YBCO at 77 K is found to be around 2.5 T. This limit is obtained for reasonable geometries and high but realistic critical current densities. Such high fields have not been reached experimentally so far, due to non-optimized flux pinning and material inhomogeneities. These inhomogeneities can be directly assessed by the magnetoscan technique, and their influence is discussed. Significant differences between the a- and the c-growth sectors were found. Limitations due to cracks and non-superconducting inclusions (e.g. 211 particles) are estimated and found to be candidates for variations of Jc on a millimetre length scale, as observed in experiments.

  8. Grain morphology of YBCO coated superconductors prepared by spin process on Ni substrate

    NASA Astrophysics Data System (ADS)

    Liu, C. F.; Du, S. J.; Yan, G.; Xi, W.; Wu, X.; Pang, Y.; Wang, F. Y.; Liu, X. H.; Feng, Y.; Zhang, P. X.; Wu, X. Z.; Zhou, L.

    2003-04-01

    The YBCO thick films with c-axis preferred orientation were prepared by spin and printing processes on Ni substrates (including cold rolling Ni, cube textured Ni, and cube textured Ni+ self-oxided NiO ). The results show that the chrysanthemum (or spherulite) and polygon morphology grains dominate the microstructure of YBCO films. The chrysanthemum size is about 0.2-0.5 mm range, some reaches 1 mm, and polygon grains normally are placed in the center of the chrysanthemum grains. No chrysanthemum grains appear in the thick films prepared on the substrate with Ag or YBCO intermediate layers.

  9. Preparation and characterization of YBCO coating on metallic RABiT substrates by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Gonal, M. R.; Prajapat, C. L.; Igalwar, P. S.; Maji, B. C.; Singh, M. R.; Krishnan, M.

    2016-05-01

    Superconducting YBCO films are coated on metallic Rolling Assisted Bi-axially Textured Substrates (RABiTS) Ni-5wt % W (NiW) (002) substrate using pulsed laser deposition (PLD) system. Targets of YBa2Cu3O7-δ (YBCO) and buffer layers of Ceria and 8 mole % Yttria Stabilized Zirconia (YSZ) of high density are synthesized. At each stage of deposition coatings are characterized by XRD. Transport studies show superconducting nature of YBCO only when two successive buffer layers of YSZ and CeO2 are used.

  10. Nonvacuum Deposition of Silver Doped YBCO Coated Conductor on %100 Lattice Match Buffered Ni Tapes

    NASA Astrophysics Data System (ADS)

    Arda, L.; Cakiroglu, O.; Keskin, S.; Sacli, O. A.

    2007-04-01

    Silver doped YBa2Cu3O7-δ (YBCO) coated conductors were fabricated on Gd1.624Ho0.376O3 (100 % lattice match with YBCO) textured buffer layers on Ni tape by reel-to-reel sol-gel dip coating system. Sample were prepared with different wt(1-5) % Ag doped ratio. The surface morphologies and microstructure of all sample were characterized by ESEM, EDS and XRD. Pole figure texture analyses have been done to characterize texture of buffer layer and YBCO superconducting film . The critical current Ic measurement was performed using four wire method with the 1 μV/cm criterion. The critical current density, Jc was measured to be 2.2 × 104 A/cm2 at 77 K self field for 1 wt % Ag doped YBCO sample.

  11. Properties of large-scale melt-processed YBCO samples

    NASA Astrophysics Data System (ADS)

    Gauss, S.; Elschner, S.; Bestgen, H.

    Magnetic bearings and superconducting permanent magnets are some of the first possible applications of bulk high Tc superconductors. Large samples were prepared by a new melt process starting from reacted YBCO 123 and 211 powders. The addition of PtO 2 to the mixture led to reduced 211 inclusion size and better homogeneity. Simultaneously the density of microcracks dividing the a- b basal plane was reduced. For testing the overall magnetic properties of these samples magnetization and levitation force measurements were performed. In comparison to samples without PtO 2 addition a strong increase in the magnetization M and the repulsion force from a magnet were observed. The maximum in the field dependence of M increased to more than 1000 G. According to the time dependence of the trapped field after a field cooling experiment an acceptable flux creep at 77 K for a long-term application was achieved.

  12. Magnetic coupling by using levitation characteristics of YBCO superconductors

    NASA Astrophysics Data System (ADS)

    Ishigaki, H.; Ito, H.; Itoh, M.; Hida, A.; Takahata, R.

    1993-03-01

    A mechanical system which uses high lateral restoring forces of high-Tc materials as the driving force for a magnetic coupling is proposed. As the basic study of the superconducting magnetic coupling, the relationship between the lateral restoring force and levitation force, transmitted torque characteristics as a function of a twisting angle and clearance, and damping characteristics of the coupling were examined. Superiorities of the coupling such as high damping coefficients and high stability against time and twisting angle were revealed. A magnetic force sensor system was used to evaluate the superconducting characteristics of materials, and nonuniform distribution of repulsive force was observed for the YBCO pellet fabricated by the melt-powder-melt-growth process. The improvement of the homogeneity was achieved by compensating for the composition rate which had changed during the quenching process.

  13. Texture analysis of melt-textured YBCO superconductors

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Simon, P.; Ogasawara, K.; Murakami, M.

    2003-10-01

    We compare the results of an X-ray based pole figure texture analysis with the local texture analysis by means of electron-backscatter diffraction (EBSD) analysis. As samples, we employ two different melt-textured YBCO samples; one fully processed and one without oxygen treatment. To enable the direct comparison of the two techniques, we employ the [1 0 3] pole figures. We find a clear coincidence between the results obtained by the two measurement techniques on our samples, however, the EBSD results are much more detailed, yielding the local grain orientation distribution and quantitative results of the grain or subgrain misorientation angles. Therefore, the EBSD measurements give information not accessible to the X-ray pole figure analysis. The surface preparation procedure is essential to enable the automated EBSD mapping as high image quality Kikuchi patterns are required. The polishing procedures are discussed in detail.

  14. On-line characterization of YBCO coated conductors using Raman spectroscopy methods.

    SciTech Connect

    Maroni, V. A.; Reeves, J. L.; Schwab, G.; Chemical Engineering; SuperPower, Inc.

    2007-04-01

    The use of Raman spectroscopy for on-line monitoring of the production of superconducting YBa2Cu3O6+X (YBCO) thin films on long-length metal tapes coated with textured buffer layers is reported for the first time. A methodology is described for obtaining Raman spectra of YBCO on moving tape exiting a metal-organic-chemical-vapor-deposition (MOCVD) enclosure. After baseline correction, the spectra recorded in this way show the expected phonons of the specific YBCO crystal orientation required for high supercurrent transport, as well as phonons of non-superconducting second-phase impurities when present. It is also possible to distinguish YBCO films that are properly textured from films having domains of misoriented YBCO grains. An investigation of the need for focus control on moving tape indicated that focusing of the laser on the surface of the highly reflective YBCO films exiting the MOCVD enclosure tends to produce aberrant photon bursts that swamp the Raman spectrum. These photon bursts are very likely a consequence of optical speckle effects induced by a combination of surface roughness, crystallographic texture, and/or local strain within the small grain microstructure of the YBCO film. Maintaining a slightly out-of-focus condition provides the best signal-to-noise ratio in terms of the obtained Raman spectra. In addition to examining moving tape at the post-MOCVD stage, Raman spectra of the film surface can also be recorded after the oxygen anneal performed to bring the YBCO to the optimum superconducting state. Consideration is given to data processing methods that could be adapted to the on-line Raman spectra to allow the tagging of out-of-specification tape segments and, at a more advanced level, feedback control to the MOCVD process.

  15. Voltage-ampere characteristics of YBCO coated conductor under inhomogeneous oscillating magnetic field

    NASA Astrophysics Data System (ADS)

    Geng, J.; Shen, B.; Li, C.; Zhang, H.; Matsuda, K.; Li, J.; Zhang, X.; Coombs, T. A.

    2016-06-01

    Direct current carrying type II superconductors present a dynamic resistance when subjected to an oscillating magnetic field perpendicular to the current direction. If a superconductor is under a homogeneous field with high magnitude, the dynamic resistance value is nearly independent of transport current. Hoffmann and coworkers [Hoffmann et al., IEEE Trans. Appl. Supercond. 21, 1628 (2011)] discovered, however, flux pumping effect when a superconducting tape is under an inhomogeneous field orthogonal to the tape surface generated by rotating magnets. Following their work, we report the whole Voltage-Ampere (V-I) curves of an YBCO coated conductor under permanent magnets rotating with different frequencies and directions. We discovered that the two curves under opposite rotating directions differ from each other constantly when the transport current is less than the critical current, whereas the difference gradually reduces after the transport current exceeds the critical value. We also find that for different field frequencies, the difference between the two curves decreases faster with lower field frequency. The result indicates that the transport loss is dependent on the relative direction of the transport current and field travelling, which is distinct from traditional dynamic resistance model. The work may be instructive for the design of superconducting motors.

  16. Superconducting properties of experimental YBCO coils for FFAG accelerator magnets

    NASA Astrophysics Data System (ADS)

    Takayama, S.; Koyanagi, K.; Tosaka, T.; Tasaki, K.; Kurusu, T.; Ishii, Y.; Amemiya, N.; Ogitsu, T.

    2014-05-01

    A project to develop fundamental technologies for accelerator magnets using high-Tc coated conductors is currently in progress. The primary applications of this project are fixed field alternating gradient (FFAG) accelerators for carbon cancer therapy systems and accelerator-driven subcritical reactors. Several types of superconducting coils for FFAG accelerators have been conceptually designed. These coils have complicated shapes, including a negative-bend part or a three-dimensional bent part. One of the aims of the project is to establish winding technologies for complicated coil shapes using coated conductors. To demonstrate winding technologies for YBa2Cu3O7-x (YBCO) coils, small test coils having a negative-bend part or a three-dimensional bent part were designed and fabricated according to the present design of the FFAG magnet. The outside dimensions of the negative-bend test coil were 460 mm long and 190 mm wide, and the radius of curvature of the negative-bend part was 442 mm. The outside dimensions of the three-dimensional test coil were 380 mm long and 280 mm wide, and the radius of curvature of the mandrel of the three-dimensional coil was 700 mm. The test coils were wound using YBCO coated conductors with a length of about 100 m and were then impregnated with epoxy resin. The coils were placed in liquid nitrogen and excited to measure their V-I characteristics. From the V-I characteristics throughout a voltage range down to 10-9 V/cm, the V-I characteristics before and after impregnation were approximately the same, demonstrating that the superconducting properties were not degraded.

  17. Metallization and interconnection of HTS YBCO thin film devices and circuits

    NASA Astrophysics Data System (ADS)

    Du, J.; Lam, S. K. H.; Tilbrook, D. L.

    2001-10-01

    A comprehensive study of specific contact resistivity and ultrasonic wire bonding yield and strength was carried out on noble metal-YBa2Cu3O7-x (YBCO) thin film contacts prepared by a variety of methods and with different YBCO surface conditions. The metallization techniques investigated include in situ and ex situ deposition of gold or silver on YBCO films. The ex situ contacts were made with and without lithographic processes. Contact resistivities of less than 5×10-8 Ω cm2 at 77 K were achieved for contacts made by the rapid ex situ deposition of gold or silver on fresh YBCO films with smooth surfaces. These contacts also gave a high wire bonding yield and strength of 10-19 g. High contact resistivities in excess of 5×10-4 Ω cm2 and poor wire bonding yield and strength were observed for the contacts made by standard lithographic lift-off processes on old YBCO films. Surface treatments using either argon ion beam etching or rf O2 plasma cleaning prior to metallization were found to be useful in reducing the contact resistivity and improving the wire bonding results for the lift-off contacts. The influence of YBCO film morphology on the contact resistance and wire bonding yield and strength was also studied.

  18. Direct deposition of YBCO on polished Ag substrates by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Ma, B.; Li, M.; Koritala, R. E.; Fisher, B. L.; Dorris, S. E.; Maroni, V. A.; Miller, D. J.; Balachandran, U.

    2002-09-01

    YBCO thin films were directly deposited on mechanically polished nontextured silver (Ag) substrates at elevated temperature by pulsed laser deposition with various inclination angles of 35°, 55°, and 72°. Strong fiber texture, with the c-axis parallel to the substrate normal was detected by X-ray diffraction pole figure analysis. Atomic force microscopy and scanning electron microscopy images revealed that a few a-axis-oriented grains were dispersed on the top surface of the YBCO films. Transmission electron microscopy revealed dense amorphous layer at the interface between the YBCO film and the Ag substrate. Energy dispersive spectrum analysis indicates that the YBCO film deposited on the Ag substrate is slightly Cu-deficient. A YBCO film deposited at 755 °C and an inclination angle of 55° exhibited Tc=90 K. Transport critical current density measured by the four-probe method at 77 K in self-field was ≈2.7×10 5 A/cm 2. This work demonstrated a simple and inexpensive method to fabricate YBCO-coated conductors with high critical current density.

  19. High-Pressure Oxygenation of Mt-Ybco the way to Reduce the Oxygenation Time, to Prevent Macrocracking, and to Obtain Materials with High Critical Currents.

    NASA Astrophysics Data System (ADS)

    Prikhna, T. A.; Chaud, X.; Gawalek, W.; Joulain, A.; Rabier, J.; Moshchil, V. E.; Savchuk, Ya. M.; Sergienko, N. V.; Dub, S. N.; Melnikov, V. S.; Habisreuther, T.; Litzkendorf, D.; Bierlich, J.

    2008-03-01

    The oxygenation of MT-YBCO under isostatic oxygen pressure (up to 16 MPa) at 900-800 °C allowed reduced process time, lower macrocracking, and reduced microcracks. Additionally higher critical currents, trapped fields and mechanical characteristics can be attained. At 77 K thin-walled MT-YBCO had a jc in the ab plane of 85 kA/cm2 at 0 T and higher than 10 kA/cm2 in fields up to 5 T and the irreversibility field was 9.8 T. In the c-direction jc was 34 kA/cm2 in 0 T and higher than 2.5 kA/cm2 in a 10 T field. At 4.9 N-load the micohardness, Hv, was 8.7±0.3 GPa in the ab-plane and 7.6±0.3 GPa in the c-direction. The fracture toughness, K1C, was 2.5±0.1 MPaṡm0.5 (ab-plane) and 2.8±0.24 MPaṡm0.5 (c-direction). The samples with a higher twin density demonstrated a higher jc, especially in applied magnetic field. The twin density correlates with the sizes and distribution of Y211 grains in Y123. The thin-walled ceramics that demonstrated the highest jc contained about 22 twins in 1 μm and were practically free from dislocations and stacking faults. The maximal trapped field of the block of thin-walled ceramic oxygenated at 900-800 °C and 16 MPa was doubled as compared to that oxygenated at low temperature under ambient pressure.

  20. Structural ceramics

    NASA Technical Reports Server (NTRS)

    Craig, Douglas F.

    1992-01-01

    This presentation gives a brief history of the field of materials sciences and goes on to expound the advantages of the fastest growing area in that field, namely ceramics. Since ceramics are moving to fill the demand for lighter, stronger, more corrosion resistant materials, advancements will rely more on processing and modeling from the atomic scale up which is made possible by advanced analytical, computer, and processing techniques. All information is presented in viewgraph format.

  1. Deposition of YBCO thin films on silver substrate via a fluorine-free sol-gel synthesis

    NASA Astrophysics Data System (ADS)

    Xu, Yongli; Shi, Donglu; Lian, L.; Wang, M.; McClellan, Shaun M.

    2002-05-01

    To further develop grain-textured YBCO thin films for conductor development, we deposited, via a fluorine-free sol-gel synthesis, YBCO thin films on non-textured silver substrate. The interface structures were studied by both x-ray diffraction (XRD) and transmission electron microscopy (HRTEM). XRD data indicated that the YBCO films on silver substrate exhibited c-axis grain orientations. Experimental details are reported on the sol-gel synthesis chemistry and XRD and HRTEM characterization of the YBCO thin films.

  2. Superconductor-Mediated Modification of Gravity? AC Motor Experiments with Bulk YBCO Disks in Rotating Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Noever, David A.; Koczor, Ronald J.; Roberson, Rick

    1998-01-01

    We have previously reported results using a high precision gravimeter to probe local gravity changes in the neighborhood of large bulk-processed high-temperature superconductors. Podkietnov, et al (Podkietnov, E. and Nieminen, R. (1992) A Possibility of Gravitational Force Shielding by Bulk YBa2 Cu3 O7-x Superconductor, Physica C, C203:441-444.) have indicated that rotating AC fields play an essential role in their observed distortion of combined gravity and barometric pressure readings. We report experiments on large (15 cm diameter) bulk YBCO ceramic superconductors placed in the core of a three-phase, AC motor stator. The applied rotating field produces up to a 12,000 revolutions per minute magnetic field. The field intensity decays rapidly from the maximum at the outer diameter of the superconducting disk (less than 60 Gauss) to the center (less than 10 Gauss). This configuration was applied with and without a permanent DC magnetic field levitating the superconducting disk, with corresponding gravity readings indicating an apparent increase in observed gravity of less than 1 x 10(exp -6)/sq cm, measured above the superconductor. No effect of the rotating magnetic field or thermal environment on the gravimeter readings or on rotating the superconducting disk was noted within the high precision of the observation. Implications for propulsion initiatives and power storage flywheel technologies for high temperature superconductors will be discussed for various spacecraft and satellite applications.

  3. Structural Ceramics Database

    National Institute of Standards and Technology Data Gateway

    SRD 30 NIST Structural Ceramics Database (Web, free access)   The NIST Structural Ceramics Database (WebSCD) provides evaluated materials property data for a wide range of advanced ceramics known variously as structural ceramics, engineering ceramics, and fine ceramics.

  4. Passivation of Flexible YBCO Superconducting Current Lead With Amorphous SiO2 Layer

    NASA Technical Reports Server (NTRS)

    Johannes, Daniel; Webber, Robert

    2013-01-01

    Adiabatic demagnetization refrigerators (ADR) are operated in space to cool detectors of cosmic radiation to a few 10s of mK. A key element of the ADR is a superconducting magnet operating at about 0.3 K that is continually energized and de-energized in synchronism with a thermal switch, such that a piece of paramagnetic salt is alternately warm in a high magnetic field and cold in zero magnetic field. This causes the salt pill or refrigerant to cool, and it is able to suck heat from an object, e.g., the sensor, to be cooled. Current has to be fed into and out of the magnets from a dissipative power supply at the ambient temperature of the spacecraft. The current leads that link the magnets to the power supply inevitably conduct a significant amount of heat into the colder regions of the supporting cryostat, resulting in the need for larger, heavier, and more powerful supporting refrigerators. The aim of this project was to design and construct high-temperature superconductor (HTS) leads from YBCO (yttrium barium copper oxide) composite conductors to reduce the heat load significantly in the temperature regime below the critical temperature of YBCO. The magnet lead does not have to support current in the event that the YBCO ceases to be superconducting. Cus - tomarily, a normal metal conductor in parallel with the YBCO is a necessary part of the lead structure to allow for this upset condition; however, for this application, the normal metal can be dispensed with. Amorphous silicon dioxide is deposited directly onto the surface of YBCO, which resides on a flexible substrate. The silicon dioxide protects the YBCO from chemically reacting with atmospheric water and carbon dioxide, thus preserving the superconducting properties of the YBCO. The customary protective coating for flexible YBCO conductors is silver or a silver/gold alloy, which conducts heat many orders of magnitude better than SiO2 and so limits the use of such a composite conductor for passing current

  5. ME-μSR study in YBCO vortex states.

    NASA Astrophysics Data System (ADS)

    Le, T. H.; Boekema, C.

    2007-03-01

    We are analyzing μSR vortex data of YBa2Cu3O7-δ (Tc = 91 K). The average superconducting grain size is ˜20 μm. The μSR data are recorded in a transverse 1 kOe field and at temperatures below 10 K. The μSR technique is used to probe the magnetic fields in the cuprate vortex state. The μSR signals show an oscillatory time dependence. To determine the frequency-dependent signals, we use the Maximum Entropy (ME) transform technique. [2] The ME-Burg algorithm removes noise, and does not suffer from Fourier-like truncation effects. The frequency signals are better fit with Lorentzians than static Gaussians. This Lorentzian behavior indicates the existence of dynamic magnetism in and around the vortex cores. This is consistent with earlier YBCO vortex ME-μSR results [3] and the SO(5) modeling [4] of cuprate superconductivity, predicting the existence of antiferromagnetism in the vortex states. Research is supported by NSF-REU and WiSE at SJSU. [1] C. Boekema et al, Physica C282-287 (1997) 2069. [2] J Lee et al, J Appl Phys 95 (2004) 6906 and ref therein; AIP www: Virtual J Appl of Superconductivity 2004 V6 Iss11. [3] C. Boekema et al, 8th Int M2S-HTSC Conf, Physica C in press. [4] H-D Chen et al, Phys Rev B70 (2004) 024516; SC Zhang, Science 275 (1997) 1089.

  6. AC Loss Measurements on a 2G YBCO Coil

    SciTech Connect

    Rey, Christopher M; Duckworth, Robert C; Schwenterly, S W

    2011-01-01

    The Oak Ridge National Laboratory (ORNL) is collaborating with Waukesha Electric Systems (WES) to continue development of HTS power transformers. For compatibility with the existing power grid, a commercially viable HTS transformer will have to operate at high voltages in the range of 138 kV and above, and will have to withstand 550-kV impulse voltages as well. Second-generation (2G) YBCO coated conductors will be required for an economically-competitive design. In order to adequately size the refrigeration system for these transformers, the ac loss of these HTS coils must be characterized. Electrical AC loss measurements were conducted on a prototype high voltage (HV) coil with co-wound stainless steel at 60 Hz in a liquid nitrogen bath using a lock-in amplifier technique. The prototype HV coil consisted of 26 continuous (without splice) single pancake coils concentrically centered on a stainless steel former. For ac loss measurement purposes, voltage tap pairs were soldered across each set of two single pancake coils so that a total of 13 separate voltage measurements could be made across the entire length of the coil. AC loss measurements were taken as a function of ac excitation current. Results show that the loss is primarily concentrated at the ends of the coil where the operating fraction of critical current is the highest and show a distinct difference in current scaling of the losses between low current and high current regimes.

  7. Nanoscale inhomogeneities in yttrium-barium-copper-oxide (YBCO) superconductors

    NASA Astrophysics Data System (ADS)

    Islam, Zahirul; Sinha, S. K.; Lang, J. C.; Liu, X.; Haskel, D.; Moss, S. C.; Srajer, G.; Veal, B. W.; Wermeille, D.; Lee, D. R.; Haeffner, D. R.; Welp, U.; Wochner, P.

    2004-03-01

    X-ray diffraction studies at the Advanced Photon Source reveal that nanoscale inhomogeneities, electronic or structural in origin, form in yttrium-barium-copper-oxide (YBa_2Cu_3O_6+x) superconductors and coexist with the superconducting (SC) state. Diffuse scattering from these inhomogeneous superstructures is due to atomic displacements with respect to equilibrium lattice sites (Z. Islam et al. Phys. Rev. B 66, 92501 (2002)), that are characterized by a wavevector of the form q=(q_x,0,0), where qx varies with hole doping from 2 unit cells (along shorter Cu-O-Cu direction) for very low doping to 4 unit cells at optimal doping. Interestingly, while these superstructures are 3-dimensionally ordered when the SC state is weakened (e.g., at x=0.4), as the doping increases, they become quasi 1D with correlation lengths comparable to SC coherence lengths in these cuprates. Recent first-principles calculations (D. de Fontaine et al., to be published) for the x=0.63 compound show that atomic displacements consistent with experimental data can be the result of ordering of O vacancies in YBCO. Models for various superstructures and their role in the phase diagram will be discussed.

  8. Propagation characteristics of the magnetostatic surface wave in the YBCO-YIG film-layered structure

    SciTech Connect

    Tsutsumi, M.; Fukusako, T.; Yoshida, S.

    1996-08-01

    Propagation characteristics of the magnetostatic surface wave (MSSW) in a YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} (YBCO)-yttrium iron garnet (YIG) multilayered structure are investigated. Effects of the superconductor on the MSSW are discussed with regard to the dispersion characteristics of both the phase and attenuation constants as a function of the air gap between YIG and YBCO, taking into consideration the magnetic line-width of the YIG film. It was found that the nonreciprocity of MSSW is enhanced significantly by the superconductivity and depends on the magnetic line-width of the YIG film. To examine the effect of a YBCO on the MSSW propagation, experiments are carried out using a commercially available YIG film. Magnetic losses at low temperature are briefly discussed with experimentally observed nonreciprocity.

  9. Structural and electrical properties of epitaxial YBCO films on Si (Abstract Only).

    NASA Astrophysics Data System (ADS)

    Fork, David K.; Barrera, A.; Phillips, Julia M.; Newman, N.; Fenner, David B.; Geballe, Theodore H.; Connell, G. A. N.; Boyce, James B.

    1991-03-01

    Efforts to grow high quality films of YBCO on Si have been complicated by factors discussed in Ref. 1, chief among them being the reaction between YBCO and Si, which is damaging even at 550 C. This is well below the customary temperatures for YBCO film growth. To avoid the reaction problem, epitaxial YBCO films were grown on Si (100) using an intermediate buffer layer of yttria-stabilized zirconia (YSZ).2 Both layers are grown via an entirely in situ process by pulsed laser deposition (PLD). Although the buffer layer prevents reaction, another problem arises; the large difference in thermal expansion coefficients between silicon and YBCO causes strain at room temperature. Thin (<500 A) YBCO films are unrelaxed and under tensile strain with a distorted unit cell. Thicker films are cracked and have poorer electrical properties. The thermal strain may be reduced by growing on silicon-on-sapphire (SOS) rather than silicon.3 This allows the growth of films of arbitrary thickness. Ion channeling reveals a high degree of crystalline perfection with a channeling minimum yield for Ba as low as 12% on either silicon or SOS. The normal state resistivity is 250-300 i-cm at 300 K; the critical temperature, Tc (R=0), is 86-88 K with a transition width (ATc) of I K. Critical current densities (J)°f 2x107 A/cm2 at 4.2 K and >2x106 A/cm2 at 77 K have been achieved. In addition, the surface resistance of a YBCO film on SOS was measured against Nb at 4.2 K. At 10 GHz, a value of 45 was obtained. This compares favorably to values reported for LaAlO3. Application of this technology to produce reaction patterned microstrip lines has been tested.4 This was done by ion milling away portions of the YSZ buffer layer prior to the YBCO deposition. YBCO landing on regions of exposed Si reacts to form an insulator. This technique was used to make 3 micron lines 1.5 mm long. The resulting structure had a Jc of l.6xl06 A/cm2 at 77 K. Isolation of separate structures exceeded 20 M. Several

  10. YBCO thin films on CeO2 buffered silver substrates

    NASA Astrophysics Data System (ADS)

    Gallistl, B.; Gritzner, G.

    2008-02-01

    CeO2 was deposited on silver substrates by the chemical solution deposition method. Silver was dipped into a 0.05 M Ce(NO3)3 solution, dried in air and then annealed in air at 900 °C for 30 minutes. The CeO2 buffer layer was characterized by X-ray diffraction and scanning electron microscopy. YBCO was deposited onto the buffered substrate via screen printing. The YBCO films where sintered at temperatures of 880 °C and 890 °C. Dense and crack free YBCO layers were obtained with transition temperatures (Tc0) up to 83 K. Characterization of the superconducting film was performed by X-ray diffraction and SEM.

  11. AC over-current characteristics of YBCO coated conductor with copper stabilizer layer considering insulation layer

    NASA Astrophysics Data System (ADS)

    Du, H.-I.; Kim, M.-J.; Kim, Y.-J.; Lee, D.-H.; Han, B.-S.; Song, S.-S.

    2010-11-01

    Compared with the first-generation BSCCO wire, the YBCO thin-film wire boasts low material costs and high Jc and superior magnetic-field properties, among other strengths. Meanwhile, the previous BSCCO wire material for superconducting cables has been researched on considerably with regard to its post-wire quenching characteristics during the application of an alternating over-current. In this regard, the promising YBCO thin-film wire has yet to be further researched on. Moreover, still lacking is research on the YBCO thin-film wire with insulating layers, which is essential in the manufacture of superconducting cables, along with the testing of the application of an alternating over-current to the wire. In this study, YBCO thin-film wires with copper-stabilizing layers were used in testing alternating over-current application according to the presence or absence of insulating layers and to the thickness of such layers, to examine the post-quenching wire resistance increase and quenching trends. The YBCO thin-film wire with copper-stabilizing layers has a critical temperature of 90 K and a critical current of 85 A rms. Moreover, its current application cycle is 5.5 cycles, and its applied currents are 354, 517, 712, and 915 A peak. These figures enabled the YBCO thin-film wires with copper-stabilizing layers to reach 90, 180, 250, and 300 K, respectively, in this study. These temperatures serve as a relative reference to examine the post-quenching wire properties following the application of an alternating over-current.

  12. YBCO thin film evaporation on as-deposited silver film on MgO

    NASA Astrophysics Data System (ADS)

    Azoulay, J.

    1999-11-01

    YBa 2Cu 3O 7- δ (YBCO) thin film was evaporated on as-deposited Ag buffer layer on MgO substrate. A simple, inexpensive vacuum system equipped with one resistively heated source was used. The subsequent heat treatment was carried out under low oxygen partial pressure at a relatively low temperature and short dwelling time. The films thus obtained were characterized for electrical properties using DC four-probe electrical measurements and inspected for structural properties and chemical composition by scanning electron microscopy (SEM). It is shown that YBCO thin film can grow on as-deposited thin silver layer on MgO substrate.

  13. Transient Electromagnetic Phenomena during Current Limiting Process in YBCO Thin Film

    NASA Astrophysics Data System (ADS)

    Ichiki, Y.; Ohsaki, H.

    2006-06-01

    In order to design a reliable and high-performance fault current limiter, it is necessary to estimate the influences of the inhomogeneous superconducting properties on the current limiting process and S-N transition. This paper describes the measurements of transient electromagnetic phenomena in YBCO thin film using pick-up coils to observe current-sharing process and change of current distribution. At first current distribution in a steady state was measured. And then transient phenomena caused by applying an overcurrent to YBCO thin film covered with a silver layer were measured.

  14. Levitation forces of a bulk YBCO superconductor in gradient varying magnetic fields

    NASA Astrophysics Data System (ADS)

    Jiang, J.; Gong, Y. M.; Wang, G.; Zhou, D. J.; Zhao, L. F.; Zhang, Y.; Zhao, Y.

    2015-09-01

    The levitation forces of a bulk YBCO superconductor in gradient varying high and low magnetic fields generated from a superconducting magnet were investigated. The magnetic field intensity of the superconducting magnet was measured when the exciting current was 90 A. The magnetic field gradient and magnetic force field were both calculated. The YBCO bulk was cooled by liquid nitrogen in field-cooling (FC) and zero-field-cooling (ZFC) condition. The results showed that the levitation forces increased with increasing the magnetic field intensity. Moreover, the levitation forces were more dependent on magnetic field gradient and magnetic force field than magnetic field intensity.

  15. First Solar and Stellar Paintings in the Epipaleolithic and Neolithic Rock Art of the Iberian Peninsula (II): new Shelters and Ceramic Pieces decorated with Astral Paintings

    NASA Astrophysics Data System (ADS)

    Quintano, J. F.

    2009-08-01

    This paper is a continuation of the research into the astronomical reasons behind prehistoric rock and mobiliary art in the Iberian Peninsula, the first part of which was presented in the previous SEAC Congress celebrated in 2007 in Klaipeda (Lithuania). It proposes that all heavenly objects painted as rock art and on ceramic pieces be given the name of astraliformes [=solar and stellar paintings]. The six astraliformes from the two shelters visited, and the ceramic pieces on which astraliformes appear in the Prehistoric Museum of Granada are presented. Astraliformes appear in schematic art in a sudden manner and on a large scale, and are included in the panel because of their function as a means of regulating and promoting the agrarian cycle.

  16. Solderability Study of RABiTS-Based YBCO Coated Conductors

    SciTech Connect

    Zhang, Yifei; Duckworth, Robert C; Ha, Tam T; Gouge, Michael J

    2011-01-01

    The solderability of commercially available YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) coated conductors that were made from Rolling Assisted Biaxially Textured Substrates (RABiTS)-based templates was studied. The coated conductors, also known as second-generation (2G) high temperature superconductor (HTS) wires (in the geometry of flat tapes about 4 mm wide), were laminated with copper, brass, or stainless steel strips as stabilizers. To understand the factors that influence their solderability, surface profilometry and scanning electron microscopy were used to characterize the wire surfaces. The solderability of three solders, 52In48Sn, 67Bi33In, and 100In (wt.%), was evaluated using a standard test (IPC/ECA J-STD-002) and with two different commercial fluxes. It was found that the solderability varied with the solder and flux but the three different wires showed similar solderability for a fixed combination of solder and flux. Solder joints of the 2G wires were fabricated using the tools and the procedures recommended by the HTS wire manufacturer. The solder joints were made in a lap-joint geometry and with the superconducting sides of the two wires face-to-face. The electrical resistances of the solder joints were measured at 77 K, and the results were analyzed to qualify the soldering materials and evaluate the soldering process. It was concluded that although the selection of soldering materials affected the resistance of a solder joint, the resistivity of the stabilizer was the dominant factor.

  17. Process for making ceramic insulation

    SciTech Connect

    Akash, Akash; Balakrishnan, G. Nair

    2009-12-08

    A method is provided for producing insulation materials and insulation for high temperature applications using novel castable and powder-based ceramics. The ceramic components produced using the proposed process offers (i) a fine porosity (from nano-to micro scale); (ii) a superior strength-to-weight ratio; and (iii) flexibility in designing multilayered features offering multifunctionality which will increase the service lifetime of insulation and refractory components used in the solid oxide fuel cell, direct carbon fuel cell, furnace, metal melting, glass, chemical, paper/pulp, automobile, industrial heating, coal, and power generation industries. Further, the ceramic components made using this method may have net-shape and/or net-size advantages with minimum post machining requirements.

  18. Effects of thickness on superconducting properties and structures of Y2O3/BZO-doped MOD-YBCO films

    NASA Astrophysics Data System (ADS)

    Ding, Fa-Zhu; Gu, Hong-Wei; Wang, Hong-Yan; Zhang, Hui-Liang; Zhang, Teng; Qu, Fei; Dong, Ze-Bin; Zhou, Wei-Wei

    2015-05-01

    We report the thickness dependence of critical current density (Jc) in YBa2Cu3O7-x (YBCO) films with BaZrO3 (BZO) and Y2O3 additions grown on single crystal LaAlO3 substrates by metalorganic deposition using trifluoroacetates (TFA-MOD). Comparing with pure YBCO films, the Jc of BZO/Y2O3-doped YBCO films was significantly enhanced. It was also found that with the increase of the thickness of YBCO film from 0.25 μm to 1.5 μm, the Ic of BZO/Y2O3-doped YBCO film increased from 130 A/cm to 250 A/cm and yet Jc of YBCO film decreased from 6.5 MA/cm2 to 2.5 M A/cm2. The thick BZO/Y2O3-doped MOD-YBCO film showed lower Jc, which is mainly attributed to the formation of a-axis grains and pores. Project supported by the National Natural Science Foundation of China (Grant No. 51272250), the National Basic Research Program of China (Grant No. 2011CBA00105), the National High Technology Research and Development Program of China (Grant No. 2014AA032702), and the Beijing Natural Science Foundation, China (Grant No. 2152035).

  19. Mixed-mode fracture of ceramics

    SciTech Connect

    Petrovic, J.J.

    1985-01-01

    The mixed-mode fracture behavior of ceramic materials is of importance for monolithic ceramics in order to predict the onset of fracture under generalized loading conditions and for ceramic composites to describe crack deflection toughening mechanisms. Experimental data on surface flaw mixed-mode fracture in various ceramics indicate that the flaw-plane normal stress at fracture decreases with increasing in-flaw-plane shear stress, although present data exhibit a fairly wide range in details of this sigma - tau relationship. Fracture from large cracks suggests that Mode II has a greater effect on Mode I fracture than Mode III. A comparison of surface flaw and large crack mixed-mode I-II fracture responses indicated that surface flaw behavior is influenced by shear resistance effects.

  20. Long length oxide template for YBCO coated conductor prepared by surface-oxidation epitaxy method

    NASA Astrophysics Data System (ADS)

    Watanabe, Tomonori; Matsumoto, Kaname; Maeda, Toshihiko; Tanigawa, Toru; Hirabayashi, Izumi

    2001-08-01

    A 50 m long, biaxially textured NiO buffer layer for epitaxial growth ofYBa 2Cu 3O 7- δ (YBCO) film has been fabricated on the long cube textured nickel tape using surface-oxidation epitaxy (SOE) method. The SOE-NiO layers were highly {1 0 0} <0 0 1> textured. The full width at half maximum of 10-14.5° from X-ray φ-scan ( Δφ) was in the range of 10-14.5° through the whole length. The critical current density ( Jc) values exceeding 0.3 MA/cm 2 (77 K, 0 T) have been obtained in short samples of YBCO films on NiO/Ni tapes, by using thin MgO cap layer. Thirty meters long Ni-clad Ni-20wt.%Cr (Ni/NiCr) and Ni-clad austenitic stainless steel (Ni/SS) tapes were also prepared for YBCO coated conductors with higher strength and lower magnetism than those of pure nickel tape. Highly {1 0 0} <0 0 1> textured NiO layers were formed on those textured composite tapes by SOE method as same as on cube textured pure nickel tapes. YBCO films with Jc of 0.1 MA/cm 2 (77 K, 0 T) have been obtained on MgO/SOE-NiO layer of short Ni/NiCr composite tape.

  1. Effect of Interim Annealing on Mechanical Strength of TFA-MOD Derived YBCO Coated Conductors

    NASA Astrophysics Data System (ADS)

    Takagi, Y.; Nakaoka, K.; Nakamura, T.; Yoshizumi, M.; Kiss, T.; Izumi, T.; Shiohara, Y.

    TFA-MOD derived YBCO tapes are expected for many applications due to cost-efficiency. In some applications, uniformity and mechanical strength are required for tapes. A 205 m-long YBCO tape was fabricated with high and uniform Ic performance throughout the tape by adopting the interim annealing before the conversion process. The effect of the interim annealing on the crystal growth mechanism of YBCO has been studied focusing on the relationship between the interim annealing conditions and delamination, in this work. Delamination strength was evaluated in the samples prepared with and without interim annealing by the stud pull method. Measurements were carried out on 50 different points for each sample and the results were analyzed statistically. The difference between the two samples was remarkably seen in the delamination strength below 60 MPa. The conventionally annealed sample had more points with low delamination strength below 60 MPa than the interim annealed one. The cross sectional images of both samples observed by SEM showed that there were few pores within the interim annealed superconducting layer, although conventional superconducting layer had many pores. These results suggest that the pores within YBCO layer might be origins to be propagated for delamination at low strength.

  2. Development of Modified MOD-TFA Approach for YBCO Film Growth

    SciTech Connect

    Bhuiyan, Md S; Paranthaman, Mariappan Parans; Sathyamurthy, Srivatsan; Hunt, Rodney Dale; List III, Frederick Alyious; Duckworth, Robert C

    2007-01-01

    Low-cost coated-conductor fabrication methods are essential for various electric-power applications. Metal-organic-deposition (MOD) approach to grow both YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) and buffer layers on textured metal substrates is very promising towards fabrication of lower-cost second generation wires. YBCO coated conductors (CC) are being developed with high critical currents that should be sufficient for their extensive use in power applications. However, the present CC has high energy losses in ac magnetic field that are unacceptable. We have developed a modified MOD precursor route to deposit {approx} 0.8 {micro}m thick YBCO films in a single coat that requires less than one-fifth of the pyrolysis time compared to the traditional MOD approach. We have also developed a filamentization technique of CC using ink-jet printing to reduce ac losses due to applied ac fields. The preliminary results of YBCO films deposited on standard RABiTS template yielded an of 140 A/cm at 77 K and self- field. A modest reduction of ac loss was observed for the solution ink-jet printed filamentary conductor.

  3. New method for introducing nanometer flux pinning centers into single domain YBCO bulk superconductors

    NASA Astrophysics Data System (ADS)

    Yang, W. M.; Wang, Miao

    2013-10-01

    Single domain YBCO superconductors with different additions of Bi2O3 have been fabricated by top seeded infiltration and growth process (TSIG). The effect of Bi2O3 additions on the growth morphology, microstructure and levitation force of the YBCO bulk superconductor has been investigated. The results indicate that single domain YBCO superconductors can be fabricated with the additions of Bi2O3 less than 2 wt%; Bi2O3 can be reacted with Y2BaCuO5 and liquid phase and finally form Y2Ba4CuBiOx(YBi2411) nanoscale particles; the size of the YBi2411 particles is about 100 nm, which can act as effective flux pinning centers. It is also found that the levitation force of single domain YBCO bulks is increasing from 13 N to 34 N and decreasing to 11 N with the increasing of Bi2O3 addition from 0.1 wt% to 0.7 wt% and 2 wt%. This result is helpful for us to improve the physical properties of REBCO bulk superconductors.

  4. Experimental studies of helical solenoid model based on YBCO tape-bridge joints

    SciTech Connect

    Yu, M.; Lombardo, V.; Turrioni, D.; Zlobin, A.V.; Flangan, G.; Lopes, M.L.; Johnson, R.P.; /Fermilab

    2011-06-01

    Helical solenoids that provide solenoid, helical dipole and helical gradient field components are designed for a helical cooling channel (HCC) proposed for cooling of muon beams in a muon collider. The high temperature superconductor (HTS), 12 mm wide and 0.1 mm thick YBCO tape, is used as the conductor for the highest-field section of HCC due to certain advantages, such as its electrical and mechanical properties. To study and address the design, and technological and performance issues related to magnets based on YBCO tapes, a short helical solenoid model based on double-pancake coils was designed, fabricated and tested at Fermilab. Splicing joints were made with Sn-Pb solder as the power leads and the connection between coils, which is the most critical element in the magnet that can limit the performance significantly. This paper summarizes the test results of YBCO tape and double-pancake coils in liquid nitrogen and liquid helium, and then focuses on the study of YBCO splices, including the soldering temperatures and pressures, and splice bending test.

  5. Thermal stability of YBCO coated conductor with different Cu stabilizer thickness

    NASA Astrophysics Data System (ADS)

    Bae, J. H.; Park, H. Y.; Eom, B. Y.; Seong, K. C.; Baik, S. K.

    2010-11-01

    The studies on the conduction-cooled superconducting magnets are actively underway with rapid advancement in refrigeration technology recently. YBCO coated conductor (CC) is one of the promising conductors for a conduction-cooled superconducting magnet because of increasing the operation temperature of magnets and being able to have cost collectiveness with conventional copper conductor in the future. However, it is known that quench propagation velocity in high-temperature superconductor (HTS) is two or three orders of magnitude slower than that in low-temperature superconductor because of its large heat capacity and the high operating temperature. The hot spot will emerge in local region if a critical current is non-uniform along the length of HTS tape and eventually, it causes permanent destroy for the whole HTS tape. Based on the protection of YBCO CC, it is necessary to determine a suitable stabilizer thickness for YBCO CC so that the temperature of hot spot in local area does not exceed the permissible temperature. In this study, we have established a suitable thermal analysis model, and analyzed minimum quench energy and thermal properties for three kinds of YBCO CC samples with different stabilizer thickness, which are fabricated by Superpower Incorporated, using finite element method.

  6. Microstructural studies of K 2CO 3 and Rb 2CO 3 doped YBCO HTSC

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.

    2003-10-01

    The influence of Me 2CO 3 (Me=K or Rb) additions on the microstructural morphology of YBa 2Cu 3O x (YBCO) HTSC with nominal composition Y (1-0.2 x) Ba (2-0.2 x) M xCu 3O y ( x=0-2.0) were investigated by means of orientation imaging microscopy which provides a method for measuring a large number of individual grain orientations and relating them directly to the microstructural features by means of evaluating electron backscatter Kikuchi patterns in scanning electron microscopy. We investigated the influence of the alkali additions on the grain orientation distributions of YBCO. The samples are characterized by grain orientation maps, and pole and inverse pole figures. Finally, the grain orientation distribution functions are obtained from the measured data. Within a certain range of doping (up to 5 wt.% in the initial batch), the grain sizes are found to increase as compared to pure YBCO, accompanied by an improvement of the superconducting properties ( Tc). It is shown that the additions of alkali carbonates do not introduce any preferred grain orientations in YBCO HTSC in the entire doping range.

  7. Enhanced pinning in YBCO films with BaZrO.sub.3 nanoparticles

    DOEpatents

    Driscoll, Judith L.; Foltyn, Stephen R.

    2010-06-15

    A process and composition of matter are provided and involve flux pinning in thin films of high temperature superconductive oxides such as YBCO by inclusion of particles including barium and a group 4 or group 5 metal, such as zirconium, in the thin film.

  8. The role of Ag in the pulsed laser growth of YBCO thin films

    NASA Astrophysics Data System (ADS)

    Kalyanaraman, R.; Oktyabrsky, S.; Narayan, J.

    1999-05-01

    We have studied systematically the role of silver in improving microstructure and properties of Y1Ba2Cu3O7-δ (YBCO) thin films. We have more than doubled the grain size to nearly 1.8 μm and reduced processing temperatures by incorporating Ag in the YBCO films, which is accomplished by using a composite target containing 15% by weight of Ag. These films show approximately four times higher Jc than the best films obtained on MgO(001) substrates deposited from stoichiometric Y1Ba2Cu3O7-δ targets. Study of the silver content in the film as a function of the deposition temperature shows clearly a decreasing concentration with increasing temperature and a segregation of the Ag to the surface. The increased oxygen content in the films is also observed at lower processing temperatures, providing strong support for the efficient oxygenation of YBCO via the presence of silver. A qualitative model suggests that the formation of silver oxide, rapid surface diffusion of Ag on MgO surfaces, and the nonreactivity of Ag with YBCO are the key aspects to the improvement in microstructure. The possibility of extending these ideas to the growth of oxides is also discussed, along with the fabrication of in-situ superconducting-metal junctions with 3D geometries.

  9. Nickel-copper alloy tapes as textured substrates for YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Vannozzi, A.; Celentano, G.; Angrisani, A.; Augieri, A.; Ciontea, L.; Colantoni, I.; Galluzzi, V.; Gambardella, U.; Mancini, A.; Petrisor, T.; Rufoloni, A.; Thalmaier, G.

    2008-02-01

    NiCuCo alloy tape was studied as textured substrates for YBCO coated conductors application. The addition of a small amount of cobalt was pursued in order to enhance the microstructure of the NiCu alloy. The use of different thermal treatments during the recrystallization process permitted to obtain area densities of cube orientation as high as 95%. The substrate was thoroughly characterized by means of x-ray diffraction, EBSD and SEM analyses. Further, the mechanical properties and the magnetic behaviour of this substrate have been investigated and compared with those exhibited by Ni, NiW and NiCu tapes. The suitability of this alloy substrate for YBCO coated conductors has been tested through the deposition of a conventional CeO2/YSZ/CeO2 buffer layer architecture using a Pd transient layer. Apart from passivating Ni-Cu-Co substrate, the use of a Pd transient layer produces a relevant texture sharpening in the out-of-plane orientation and the full width at half maximum of the ?-scan drops from about 9° of NiCuCo to 2° of Pd layer. This sharp texture is transferred to the YBCO film and the results indicate that NiCuCo alloy is a promising alternative substrate for the realization of YBCO coated conductors.

  10. Trapped Field Characteristics of Stacked YBCO Thin Plates for Compact NMR Magnets: Spatial Field Distribution and Temporal Stability

    PubMed Central

    Hahn, Seungyong; Kim, Seok Beom; Ahn, Min Cheol; Voccio, John; Bascuñán, Juan; Iwasa, Yukikazu

    2010-01-01

    This paper presents experimental and analytical results of trapped field characteristics of a stack of square YBCO thin film plates for compact NMR magnets. Each YBCO plate, 40 mm × 40 mm × 0.08 mm, has a 25-mm diameter hole at its center. A total of 500 stacked plates were used to build a 40-mm long magnet. Its trapped field, in a bath of liquid nitrogen, was measured for spatial field distribution and temporal stability. Comparison of measured and analytical results is presented: the effects on trapped field characteristics of the unsaturated nickel substrate and the non-uniform current distribution in the YBCO plate are discussed. PMID:20585463

  11. Trapped Field Characteristics of Stacked YBCO Thin Plates for Compact NMR Magnets: Spatial Field Distribution and Temporal Stability.

    PubMed

    Hahn, Seungyong; Kim, Seok Beom; Ahn, Min Cheol; Voccio, John; Bascuñán, Juan; Iwasa, Yukikazu

    2010-06-01

    This paper presents experimental and analytical results of trapped field characteristics of a stack of square YBCO thin film plates for compact NMR magnets. Each YBCO plate, 40 mm × 40 mm × 0.08 mm, has a 25-mm diameter hole at its center. A total of 500 stacked plates were used to build a 40-mm long magnet. Its trapped field, in a bath of liquid nitrogen, was measured for spatial field distribution and temporal stability. Comparison of measured and analytical results is presented: the effects on trapped field characteristics of the unsaturated nickel substrate and the non-uniform current distribution in the YBCO plate are discussed.

  12. Pd layer on cube-textured substrates for MOD-TFA and PLD YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Mancini, A.; Celentano, G.; Galluzzi, V.; Rufoloni, A.; Vannozzi, A.; Augieri, A.; Ciontea, L.; Petrisor, T.; Gambardella, U.; Longo, G.; Cricenti, A.

    2008-01-01

    Pd films were deposited on rolling assisted biaxially textured substrate (RABiTS) Ni-5 at.% W in order to exploit the Pd effect of the texture sharpening with respect to that of the substrate, for the development of YBa2Cu3O7-x (YBCO) coated conductors. The Pd sharpening effect was relevant in the out-of-plane direction where the reduction for the ω-scans' full width at half maximum (FWHM) ranged from 55 to 65%, depending on the substrate roughness. The obtained minimum values of the FWHM in the transverse rolling direction of the (002) Pd ω-scan and in the (111) Pd phi-scan were of about 2.5° and 5°, respectively. The CeO2/YSZ/CeO2 (YSZ is Y2O3-stabilised ZrO2) heterostructure of the buffer layer was developed by pulsed laser deposition (PLD). In order to transfer the sharp orientation of the Pd film, both the seed CeO2 layer and the YSZ layer were deposited at low temperatures (450 °C), low enough to avoid Pd/Ni-W interdiffusion. The YBCO, films deposited by both PLD and metal-organic deposition (MOD) using metal trifluoroacetate acid (TFA), exhibited rolling direction (005) ω-scan and the (113) phi-scan FWHM values of about 2° and 5°, respectively. In spite of the complete interdiffusion between Ni and Pd during the YBCO film deposition, the coated conductors exhibit good adherence, as well as a smooth and crack-free surface. A zero-resistance critical temperature (TC0) of 90.8 K for the MOD-TFA YBCO films and critical current-density (JC) up to 2.2 MA cm-2 at 77 K and self-field for PLD YBCO films have been obtained.

  13. Fabrication and Characterization of YBCO Coated Conductors by Inclined Substrate Deposition

    NASA Astrophysics Data System (ADS)

    Ma, B.; Balachandran, U.; Xu, Y.; Bhattacharya, R.

    2006-03-01

    Inclined substrate deposition (ISD) is an effective method for rapid fabrication of high-quality template layers for YBCO-coated conductors. We have deposited biaxially textured ISD-MgO films on flexible metallic tapes in a reel-to-reel system by electron-beam evaporation at rapid deposition rates, 2-10 nmṡs-1. Strontium ruthenium oxide (SRO) buffer and YBCO films were grown by pulsed laser deposition (PLD). Pole figure analysis of a meter-long ISD-MgO tape was carried out by X-ray diffraction using a Bruker's D8 DISCOVER equipped with GADDS (general area detection diffraction system). The c-axis of the ISD-MgO film was tilted away from substrate normal. A full-width at half maximum (FWHM) of ≈10° was observed from the φ-scan of the MgO (002) diffraction measured on samples deposited with 35° inclination angle. Surface morphology measured by atomic force microscopy revealed a roof-tile shaped structure for the ISD-MgO films. Through the use of the SRO buffer, biaxial alignment in the YBCO film deposited on the ISD-MgO template was improved. The φ-scan FWHM was 5.8° for the YBCO (005) diffraction. We have measured the critical transition temperature Tc = 91 K and transport critical current density Jc >1.6×106 Aṡcm-2 at 77 K in self-field on a SRO-buffered YBCO film grown with ISD-MgO architecture.

  14. Monolithic ceramics

    NASA Technical Reports Server (NTRS)

    Herbell, Thomas P.; Sanders, William A.

    1992-01-01

    A development history and current development status evaluation are presented for SiC and Si3N4 monolithic ceramics. In the absence of widely sought improvements in these materials' toughness, and associated reliability in structural applications, uses will remain restricted to components in noncritical, nonman-rated aerospace applications such as cruise missile and drone gas turbine engine components. In such high temperature engine-section components, projected costs lie below those associated with superalloy-based short-life/expendable engines. Advancements are required in processing technology for the sake of fewer and smaller microstructural flaws.

  15. Development of YBCO Superconductor for Electric Systems: Cooperative Research and Development Final Report, CRADA Number CRD-04-150

    SciTech Connect

    Bhattacharya, R.

    2013-03-01

    The proposed project will be collaborative in exploration of high temperature superconductor oxide films between SuperPower, Inc. and the National Renewable Energy Laboratory. This CRADA will attempt to develop YBCO based high temperature oxide technology.

  16. Growth and properties of YBCO thin films on polycrystalline Ag substrates by inclined substrate pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Li, M.; Ma, B.; Koritala, R. E.; Fisher, B. L.; Dorris, S. E.; Venkataraman, K.; Balachandran, U.

    2002-06-01

    Fully c-axis-oriented YBCO films were directly deposited on polycrystalline silver substrates by inclined substrate pulsed laser ablation. The orientation and microstructure of the YBCO films were characterized by x-ray diffraction 2θ-scans, Ω-scans and pole figure analysis. Surface morphology was examined by scanning electron microscopy. Irregular-mosaic-shaped supergrains were observed in the films. Raman spectroscopy was used to evaluate the quality of the YBCO films. The superconducting transition temperature (Tc) and the critical current density (Jc) of the films were determined by inductive and transport measurements, respectively. Tc = 91 K with sharp transition and Jc = 2.7 × 105 A cm-2 at 77 K in zero field were obtained on a film that was 0.14 μm thick, 5 mm wide and 10 mm long. This work demonstrated a promising approach to obtain high-Jc YBCO films on nontextured polycrystalline silver substrate.

  17. Environmental durability of ceramics and ceramic composites

    NASA Technical Reports Server (NTRS)

    Fox, Dennis S.

    1992-01-01

    An account is given of the current understanding of the environmental durability of both monolithic ceramics and ceramic-matrix composites, with a view to the prospective development of methods for the characterization, prediction, and improvement of ceramics' environmental durability. Attention is given to the environmental degradation behaviors of SiC, Si3N4, Al2O3, and glass-ceramic matrix compositions. The focus of corrosion prevention in Si-based ceramics such as SiC and Si3N4 is on the high and low sulfur fuel combustion-product effects encountered in heat engine applications of these ceramics; sintering additives and raw material impurities are noted to play a decisive role in ceramics' high temperature environmental response.

  18. Critical current anisotropy and pinning in (103) YBCO superconducting thin films on SrTiO3(110) substrates

    NASA Astrophysics Data System (ADS)

    Wu, K. H.; Huang, S. J.; Wang, S. J.; Chen, S. P.; Juang, J. Y.; Uen, T. M.; Gou, Y. S.

    1996-03-01

    High quality (103) oriented YBCO superconducting thin films with T c ≈89 K have been prepared by pulsed laser deposition on SrTiO3(110) substrates. The grain morphology of the films, as revealed by both scanning electron microscopy and atomic force microscopy, shows distinct brick wall structure. The critical current densities measured along (001) direction of the substrates are about an order of magnitude higher than that measured on the other in-plane direction with no apparent weak- link behavior observed. The critical current densities in both directions, however, show a similar linear temperature dependence over a wide temperature range, indicative of a flux-creep limited mechanism. The creep rate in both cases, as fit to the Anderson-Kim creep model, is of order of 1 which is about an order of magnitude higher than that of conventional type-II superconductors. Samples co-ablated with silver were also studied. Detail mechanisms of pinning as wall as grain morphology evolutions are discussed.

  19. Tailoring the vortex pinning strength of YBCO thin films by systematic incorporation of hybrid artificial pinning centers

    NASA Astrophysics Data System (ADS)

    Jha, Alok K.; Matsumoto, Kaname; Horide, Tomoya; Saini, Shrikant; Mele, Paolo; Ichinose, Ataru; Yoshida, Yutaka; Awaji, Satoshi

    2015-11-01

    The effect of hybrid (columnar and spherical together) artificial pinning centers (APCs) on the vortex pinning properties of YBa2Cu3O7-δ (YBCO) thin films is investigated in detail on the basis of variation of critical current density (J C ) with applied magnetic field and also with the orientation of the applied magnetic field at 65 K and 77 K. Premixed YBCO + BaSnO3 composite targets are used for the deposition of the YBCO films which consist of self-assembled BaSnO3 nanocolumns (1D APCs); on the other hand, for the deposition of the YBCO films with hybrid APCs (BaSnO3 nanocolumns together with Y2O3 nanoparticles), the surface of the premixed YBCO + BaSnO3 composite targets are modified by putting a thin Y2O3 sectored piece on the premixed YBCO + BaSnO3 composite targets by means of silver paste. F pmax value increases systematically with incorporation of 1D and 1D and 3D APCs and it also shifts towards higher applied magnetic fields. Films with 1D APCs exhibit a strong J C peak at Θ = 0° (H//c-axis) whereas films consisting of hybrid APCs exhibit enhanced J C at all the investigated angular regimes. A possible mechanism of vortex pinning in samples with hybrid APCs is also discussed suggesting the role of 1D and 3D APCs.

  20. The mechanism of thermal runaway due to continuous local disturbances in the YBCO-coated conductor coil winding

    NASA Astrophysics Data System (ADS)

    Yanagisawa, Y.; Okuyama, E.; Nakagome, H.; Takematsu, T.; Takao, T.; Hamada, M.; Matsumoto, S.; Kiyoshi, T.; Takizawa, A.; Takahashi, M.; Maeda, H.

    2012-07-01

    Though YBCO coils are stable against transient disturbances such as conductor motion, they suffer from thermal runaway at a current below the coil critical current due to continuous local disturbances attributed to partial degradation of the conductor in the coil winding. Continuous heat generation in the degraded layer induces thermal runaway in adjacent layers; thermal runaway does not occur in the degraded layer spontaneously due to the small n index of the degraded YBCO-coated conductor. The thermal runaway current depends on the cooling conditions of the winding. For a paraffin-impregnated YBCO coil under quasi-adiabatic conditions, the thermal runaway current is far below the coil critical current, while it is close to the coil critical current in the case of a dry-wound coil. The permissible temperature rise following a thermal runaway for YBCO conductors in the degraded layer is demonstrated to be 340 K. If the YBCO coils are operated at a temperature below 20 K, the current density, typically 600-800 A mm-2, is much higher than that at 77 K. Therefore, the time interval between thermal runaway initiation and the melting temperature becomes less than 0.5 s, posing a difficult problem for protection; i.e., thermal runaway due to continuous local disturbances is hazardous to the safe operation of high current density YBCO coils.

  1. Gas Separations using Ceramic Membranes

    SciTech Connect

    Paul KT Liu

    2005-01-13

    This project has been oriented toward the development of a commercially viable ceramic membrane for high temperature gas separations. A technically and commercially viable high temperature gas separation membrane and process has been developed under this project. The lab and field tests have demonstrated the operational stability, both performance and material, of the gas separation thin film, deposited upon the ceramic membrane developed. This performance reliability is built upon the ceramic membrane developed under this project as a substrate for elevated temperature operation. A comprehensive product development approach has been taken to produce an economically viable ceramic substrate, gas selective thin film and the module required to house the innovative membranes for the elevated temperature operation. Field tests have been performed to demonstrate the technical and commercial viability for (i) energy and water recovery from boiler flue gases, and (ii) hydrogen recovery from refinery waste streams using the membrane/module product developed under this project. Active commercializations effort teaming with key industrial OEMs and end users is currently underway for these applications. In addition, the gas separation membrane developed under this project has demonstrated its economical viability for the CO2 removal from subquality natural gas and landfill gas, although performance stability at the elevated temperature remains to be confirmed in the field.

  2. The mechanism of sputter-induced orientation change in YBCO films on MgO (001)

    SciTech Connect

    Huang, Y.; Vuchic, B.V.; Baldo, P.; Merkle, K.L.; Buchholz, D.B.; Mahajan, S.; Lei, J.S.; Markworth, P.R.; Chang, R.P.H.

    1996-12-01

    The mechanisms of the sputter-induced orientation change in YBa{sub 2}Cu{sub 3}O{sub 7{minus}x}(YBCO) films grown on MgO (001) substrates by pulsed organometallic beam epitaxy (POMBE) are investigated by x-ray diffraction. Rutherford backscatter spectroscopy (RBS), cross-section TEM (XTEM) and microanalysis. It is found that the W atom implantation concurring with the ion sputtering plays an important role in effecting the orientation change. This implantation changes the surface structure of the substrate and induces an intermediate layer in the initial growth of the YBCO film, which in turn acts as a template that induces the orientation change. It seems that the surface morphology change caused by ion sputtering has only a minor effect on the orientation change.

  3. Study of microstructure and electrical properties of bulk YBCO prepared by melt textured growth technique

    SciTech Connect

    Gonal, M. R.; Krishnan, Madangopal; Tewari, R.; Tyagi, A. K.; Gyore, A.; Vajda, I.

    2015-06-24

    Bulk YBCO components were prepared using Melt Texture Growth (MTG) technique. Components were fabricated using MTG by addition of Y{sub 2}BaCuO{sub 5} (Y211) and Ag to YBCO, which leads to improved grain size without affecting superconducting properties. Green compacts prepared by cold isostatic pressing were pre-sintered at 930°C before subjecting melt texturing. Cooling rates lower than 1 °C.h{sup −1} was used, in between (peritectic) temperature of about 995 and 1025°C, to obtain large grained components. Microstructure studies in details were carried out by Scanning Electron Microscope (SEM), Electron Probe Micro Analysis (EPMA), Orientation Imaging Microscope (OIM) and TEM correlated with electrical properties like Critical current density (J{sub c})

  4. T /B scaling without quasiparticle mass divergence: YbCo2Ge4

    NASA Astrophysics Data System (ADS)

    Sakai, Akito; Kitagawa, Kentaro; Matsubayashi, Kazuyuki; Iwatani, Makoto; Gegenwart, Philipp

    2016-07-01

    YbCo2Ge4 is a clean paramagnetic Kondo lattice which displays non-Fermi-liquid behavior. We report a detailed investigation of the specific heat, magnetic Grüneisen parameter (Γmag), and temperature derivative of the magnetization (M ) on a high-quality single crystal at temperatures down to 0.1 K and magnetic fields up to 7 T. Γmag and d M /d T display a divergence upon cooling and obey T /B scaling. Similar behavior has previously been found in several other Yb-based Kondo lattices and related to a zero-field quantum critical point without fine tuning of pressure or composition. However, in the approach of B →0 the electronic heat capacity coefficient of YbCo2Ge4 saturates at low T , excluding ferromagnetic quantum criticality. This indicates that T /B scaling is insufficient to prove a zero-field quantum critical point.

  5. Versatility of metalorganic chemical vapor deposition process for fabrication of high quality YBCO superconducting thin films

    NASA Astrophysics Data System (ADS)

    Chern, C. S.; Kear, B. H.; Zhao, J.; Norris, P. E.; Li, Y. Q.

    1991-03-01

    YBCO films, having critical current densities in excess of 10 to the 6th A/sq cm at 77 K and transition temperatures of about 89 K, successfully deposited on close lattice matched substrate materials at substrate temperature in the range from 720 to 740 C, are presented. The critical current densities are 10,000 A/sq cm at 70 K and the critical temperatures are 82 K for the films deposited on sapphire substrates. Successful deposition of c-axis oriented YBCO films with a transition temperature of 85 K was also achieved on silver substrates. Detailed analyses of the films were carried out by X-ray diffraction, EDS, SEM, resistivity measurements, critical current density measurements, and magnetization susceptibility measurements.

  6. Hybrid quantum systems with YBCO coplanar resonators and spin ensembles of organic radicals

    NASA Astrophysics Data System (ADS)

    Ghirri, Alberto; Bonizzoni, Claudio; Troiani, Filippo; Cassinese, Antonio; D'Arienzo, Massimiliano; Beverina, Luca; Affronte, Marco

    We have studied the coherent coupling of microwave photons in a superconducting coplanar resonator with a spin ensemble of stable open-shell organic radicals. We fabricated YBCO/sapphire coplanar resonators that show quality factors ~= 3*104 at 1.8 K, that remain remarkably stable in high magnetic field applied parallel to the YBCO film [QL (7 T) = 90% QL (0 T)]. Spin ensembles of (3,5-Dichloro-4-pyridyl)bis(2,4,6-trichlorophenyl)methyl organic radical (PyBTM) show sharp EPR linewidth (8 MHz) due to the effect of the exchange narrowing. The frequency of the spin transition is tuned by means of the external magnetic field. We show the achievement of the strong collective coupling with the resonant photons with coupling rates exceeding 90 MHz at 1.8 K.

  7. Pinning features of the magnetic flux trapped by YBCO single crystals in weak constant magnetic fields

    NASA Astrophysics Data System (ADS)

    Monarkha, V. Yu.; Paschenko, V. A.; Timofeev, V. P.

    2013-02-01

    The dynamics of Abrikosov vortices and their bundles was experimentally investigated in weak constant magnetic fields, in the range of Earth's magnetic field. Characteristics of the isothermal magnetization relaxation in YBCO single-crystal samples with strong pinning centers were studied for different sample-field orientation. The obtained values of normalized relaxation rate S allowed us to estimate the effective pinning potential U in the bulk of the YBCO sample and its temperature dependence, as well as the critical current density Jc. A comparison between the data obtained and the results of similar measurements in significantly higher magnetic fields was performed. To compare different techniques for evaluation of Jc, the magnetization loop measurements M(H), which relate the loop width to the critical current, were carried out. These measurements provided important parameters of the samples under study (penetration field Hp and first critical field Hc1), which involve the geometrical configuration of the samples.

  8. Proximity effect induced by Kondo interaction in a network composed of YBCO and spin density wave

    NASA Astrophysics Data System (ADS)

    Maity, S.; Ghosh, Ajay Kumar

    2015-10-01

    The possibility of the proximity effect mediated by Kondo interaction in YBCO embedded in system of diluted magnetic spin ordering has been studied. An YBCO sample is selected in which both metal to insulator transition and superconducting state exist in the different ranges of temperature. The intergranular network of the bulk Y-123 has been modified by the inclusion of YMnO3 which has a well defined magnetic structure depending on temperature. The current-voltage measurements have been carried out in pure Y-123 at several temperatures. At the same set of temperatures the current-voltage curves in presence of YMnO3 have been studied. The role of the diluted spin magnetic ordering in tuning proximity effect and conduction property in binary systems is associated with reduced coherence length in the normal region.

  9. Ceramic Inlays: Effect of Mechanical Cycling and Ceramic Type on Restoration-dentin Bond Strength.

    PubMed

    Trindade, F Z; Kleverlaan, C J; da Silva, L H; Feilzer, A J; Cesar, P F; Bottino, M A; Valandro, L F

    2016-01-01

    This study aimed to evaluate the bond strength between dentin and five different ceramic inlays in permanent maxillary premolars, with and without mechanical cycling. One hundred permanent maxillary premolars were prepared and divided into 10 groups (n=10) according to the ceramic system (IPS e.Max Press; IPS e.Max CAD; Vita PM9; Vita Mark II; and Vita VM7) and the mechanical cycling factor (with and without [100 N, 2 Hz, 1.2×10(6) cycles]). The inlays were adhesively cemented, and all of the specimens were cut into microbars (1×1 mm, nontrimming method), which were tested under microtensile loading. The failure mode was classified and contact angle, roughness, and microtopographic analyses were performed on each ceramic surface. The mechanical cycling had a significant effect (p=0.0087) on the bond strength between dentin and IPS e.max Press. The Vita Mark II group had the highest bond strength values under both conditions, with mechanical cycling (9.7±1.8 MPa) and without (8.2±1.9 MPa), while IPS e.Max CAD had the lowest values (2.6±1.6 and 2.2±1.4, respectively). The adhesive failure mode at the ceramic/cement interface was the most frequent. Vita Mark II showed the highest value of average roughness. IPS e.max Press and Vita Mark II ceramics presented the lowest contact angles. In conclusion, the composition and manufacturing process of ceramics seem to have an influence on the ceramic surface and resin cement bond strength. Mechanical cycling did not cause significant degradation on the dentin and ceramic bond strength under the configuration used. PMID:27455117

  10. Dental ceramics: An update.

    PubMed

    Shenoy, Arvind; Shenoy, Nina

    2010-10-01

    In the last few decades, there have been tremendous advances in the mechanical properties and methods of fabrication of ceramic materials. While porcelain-based materials are still a major component of the market, there have been moves to replace metal ceramics systems with all ceramic systems. Advances in bonding techniques have increased the range and scope for use of ceramics in dentistry. In this brief review, we will discuss advances in ceramic materials and fabrication techniques. Examples of the microstructure property relationships for these ceramic materials will also be addressed.

  11. Epitaxial growth of YBCO films on metallic substrates buffered with yttria-stabilized zirconia

    NASA Astrophysics Data System (ADS)

    Ma, B.; Li, M.; Fisher, B. L.; Koritala, R. E.; Balachandran, U.

    2002-05-01

    Biaxially textured yttria-stabilized zirconia (YSZ) films were grown on polished Hastelloy C (HC) substrates by ion-beam-assisted deposition (IBAD) and electron-beam evaporation. A water-cooled sample stage was used to dissipate heat generated by the Kaufman ion source and to maintain the substrate temperature below 100 °C during deposition. X-ray pole figures were used for texture analysis. In-plane texture measured from the YSZ (111) φ-scan full-width-at-half-maximum (FWHM) was 13.2° and out-of-plane texture from the YSZ (002) ω-scan FWHM was 7.7°. In-plane texture improved with lowered substrate temperature during IBAD deposition. RMS surface roughness of 3.3 nm was measured by atomic force microscopy. A thin CeO2 buffer layer (≈10 nm) was deposited to improve the lattice match between the YSZ and YBCO films and to enhance the biaxial alignment of YBCO films. YBCO films were epitaxially grown on IBAD-YSZ buffered HC substrates with and without CeO2 buffer layers by pulsed laser deposition (PLD). In-plane texture FWHMs of 12° and 9° were observed for CeO2 (111) and YBCO (103), respectively. Tc=90 K, with sharp transition, and Jc values of ≈2×106 A/cm2 at 77 K in zero field were observed on 0.5-μm-thick, 5-mm-wide, and 1-cm-long samples.

  12. MOD Buffer/YBCO Approach to Fabricate Low-Cost Second Generation HTS Wires

    SciTech Connect

    Paranthaman, Mariappan Parans; Sathyamurthy, Srivatsan; Bhuiyan, Md S; Martin, Patrick M; Aytug, Tolga; Kim, Kyunghoon; Fayek, Mostafa; Leonard, Keith J; Li, Jing; Zhang, W.; Rupich, Marty

    2007-01-01

    The metal organic deposition (MOD) of buffer layers on RABiTS substrates is considered a potential, low-cost approach to manufacturing high performance Second Generation (2G) high temperature superconducting (HTS) wires. The typical architecture used by American Superconductor in their 2G HTS wire consists of a Ni-W (5 at.%) substrate with a reactively sputtered Y2O3 seed layer, YSZ barrier layer and a CeO2 cap layer. This architecture supports critical currents of over 300 A/cm-width (77 K, self-field) with 0.8 mum YBCO films deposited by the TFA-MOD process. The main challenge in the development of the MOD buffers is to match or exceed the performance of the standard vacuum deposited buffer architecture. We have recently shown that the texture and properties of MOD - La2Zr2Ogamma (LZO) barrier layers can be improved by inserting a thin sputtered Y2O3 seed layer and prepared MOD deposited LZO layers followed by MOD or RF sputtered CeO2 cap layers that support MOD-YBCO films with Ic's of 200 and 255 A/cm-width, respectively. Detailed X-ray and microstructural characterizations indicated that MOD - CeO2 cap reacted completely with MOD YBCO to form BaCeOs. However, sputtered CeO2 cap/MOD YBCO interface remains clean. By further optimizing the coating conditions and reducing the heat-treatment temperatures, we have demonstrated an Ic of 336 A/cm with improved LZO layers and sputtered CeO2 cap and exceeded the performance of that of standard vacuum deposited buffers.

  13. Design of a Cryogen Free Cryo-flipper using a High Tc YBCO Film

    NASA Astrophysics Data System (ADS)

    Parnell, S. R.; Kaiser, H.; Washington, A. L.; Li, F.; Wang, T.; Baxter, D. V.; Pynn, R.

    It is well-known that the Meissner effect in superconducting materials can be used to provide a well-defined non- adiabatic magnetic field transition that can be utilised to produce an efficient white beam neutron spin flipper. Typically these devices utilise niobium and hence require continuous use of liquid helium in order to maintain the device tem- perature. The use of high Tc materials removes the need for cryogens and has been explored previously and shown to provide efficient flipping of the neutron spin. Improvements in thin high Tc films over the past few years make these materials even more attractive. Here we present a design using a 350-nm-thick YBCO film capped with 100 nm of gold on a 78 x 100 x 0.5 mm sapphire substrate (Theva, Germany). The apparatus is compact (200 mm in length along the neutron beam), consisting of an oxygen-free high-conductivity copper frame, which holds the YBCO film and is mounted to the cold finger of a closed-cycle refrigerator. The part of the vacuum chamber, where the YBCO film is located, is ≈ 50 mm wide, which allows us to minimise the distance from the film to the external magnets. This distance is 26 mm on each side. The details of the guide field design are also discussed. In this design, the maximum neutron beam size that can be used is 40 × 40 mm2 and we can easily switch from a vertical to a horizontal guide field on either side of the YBCO film.

  14. Development of Solution Buffer Layers for RABiTS Based YBCO Coated Conductors

    SciTech Connect

    Paranthaman, Mariappan Parans; Qiu, Xiaofeng; Kim, Kyunghoon; Shi, D.; Zhang, Yifei; Li, Xiaoping; Sathyamurthy, Srivatsan; Thieme, C. L. H.; Rupich, M. W.

    2010-01-01

    The main objective of this research is to find a suitable alternate solution based seed layer for the standard RABiTS three-layer architecture of physical vapor deposited CeO2 cap/YSZ barrier/Y2O3 seed on Ni-5%W metal tape. In the present work, we have identified CeO2 buffer layer as a potential replacement for Y2O3 seeds. Using a metal-organic deposition (MOD) process, we have grown smooth, crack-free, epitaxial thin films of CeO2 (both pure and Zr, Cu and Gd-doped) directly on biaxially textured Ni-5W substrates in short lengths. Detailed XRD studies indicate that a single epitaxial CeO2 phase with slightly improved out-of-plane texture compared to the texture of underlying Ni-W substrates can be achieved in pure, undoped CeO2 samples. We have also demonstrated the growth of YSZ barrier layers on pure CeO2 seeds using sputtering. Both sputtered CeO2 cap layers and MOD-YBCO films were grown epitaxially on these YSZ-buffered MOD-CeO2/Ni-5W substrates. High critical currents per unit width, Ic of 264 A/cm (critical current density, Jc of 3.3 MA/cm2) at 77 K and 0.01 T was achieved for 0.8 m thick MOD-YBCO films grown on MOD-CeO2 seeds. These results indicate that CeO2 films can be grown directly on Ni-5W substrates and still support high performance YBCO coated conductors. This work holds promise for a route for producing low-cost buffer architecture for RABiTS based YBCO coated conductors.

  15. Enhancing critical current in YBCO thick films: Substrate decoration and quasi-superlattice approach

    NASA Astrophysics Data System (ADS)

    Sarkar, A.; Mikheenko, P.; Dang, V. S.; Abell, J. S.; Crisan, A.

    2009-10-01

    For power applications of superconducting films, the critical current density ( J c) and the thickness of the film ( d) should be as high as possible. Since J c decreases with both thickness and magnetic field, artificial pinning centres in addition to natural ones are required to keep J c high. The earliest cost-effective method used for introducing artificial pinning centres was the so-called substrate decoration, i.e., growing nano-scale islands (nano-dots) of certain materials on the substrate prior to the deposition of the superconducting thin film. Later on another version of this approach proved to be successful: building up a layered distribution of a second phase using a multilayer deposition (quasi-superlattices). Several materials have been used for the creation of artificial pinning centres. Here we report on the artificial pinning centres induced in YBCO thick films by substrate decoration and quasi-superlattice approaches using nano-dots of Pd and non-superconducting YBCO. The cross-sectional AFM images show evidence of c-axis correlated columnar defects. These defects significantly contribute to the pinning of magnetic flux and increase critical current in the films. We observed an important shift of the position of the maximum in the thickness dependence of J c( B) towards higher thicknesses compared with pure YBCO films by both approaches. A high J c( B) in our quite thick films provides a very high total critical current per cm of the film width. Critical current as high as 800 A/cm width was achieved in a 2.4 μm thick quasi-superlattice film with non-superconducting YBCO nano-dots.

  16. Development of Solution Buffer Layers for RABiTS Based YBCO Coated Conductors

    SciTech Connect

    Paranthaman, Mariappan Parans; Qiu, Xiaofeng; List III, Frederick Alyious; Zhang, Yifei; Li, Xiaoping; Sathyamurthy, Srivatsan; Thieme, C. L. H.; Rupich, M. W.

    2011-01-01

    Abstract The main objective of this research is to find a suitable alternate solution based seed layer for the standard RABiTS three-layer architecture of physical vapor deposited CeO cap/YSZ barrier/Y O seed on Ni-5%W metal tape. In the present work, we have identified CeO buffer layer as a potential replacement for Y O seeds. Using a metal-organic deposition (MOD) process, we have grown smooth, crack-free, epitaxial thin films of CeO (pure and Zr, Cu and Gd-doped) directly on biaxially textured Ni-5W substrates in short lengths. Detailed XRD studies indicate that a single epitaxial CeO phase with slightly improved out-of-plane texture compared to the texture of the underlying Ni-W substrates can be achieved in pure, undoped CeO samples. We have also demonstrated the growth of YSZ barrier layers on pure CeO seeds using sputtering. Both sputtered CeO cap layers and MOD-YBCO films were grown epitaxially on these YSZ-buffered MOD-CeO /Ni-5W substrates. High critical currents per unit width, of 264 A/cm (critical current density, of 3.3 MA/cm ) at 77 K and 0.01 T was achieved for 0.8 m thick MOD-YBCO films grown on MOD-CeO seeds. These results indicate that CeO films can be grown directly on Ni-5W substrates and still support high performance YBCO coated conductors. This work holds promise for a route for producing low-cost buffer architecture for RABiTS based YBCO coated conductors.

  17. High-material yield fabrication of YBCO coated conductors by Nd:YAG-PLD system

    NASA Astrophysics Data System (ADS)

    Ono, I.; Ichino, Y.; Yoshida, Y.; Yoshizumi, M.; Izumi, T.; Shiohara, Y.

    In order to fabricate superconducting coated conductors with lower cost, fabrication processes are required high material yield. We report an improvement of the material yield of YBCO films prepared by inside-plume Nd:YAG pulsed laser deposition method on metal substrates with an architecture of CeO2/LMO/IBAD-MgO/GZO/HastelloyTM. In this study, we shortened a distance from the target to the substrate (dT-S) in order to improve the material yield. Additionally, we have used Nd:YAG laser because initial and running costs are anticipated to be lower than those of excimer laser. As a result, by shorting the dT-S from 40 mm to 20 mm, the material yield increased on 10 mm×10 mm substrates. Additionally, by changing the O2 pressure (PO2) from 40 Pa to 400 Pa at dT-S = 20 mm, the material yield had a local maximal value of 18.6% at PO2=200 Pa. On multi-turn (MT) metal substrates, the material yield reached 56.0%. However, the critical current density (Jc) of the YBCO film which was deposited at dT-S = 20 mm and PO2=200 Pa on the 10 mm×10 mm substrate was 1.2 MA/cm2 at the edges and 0.2 MA/cm2 at the center at 77 K in self-field, although the YBCO films showed good aligned crystal textures. In order to improve this non-uniformity, we tilted the surface normal of the target 15 degree from a line connecting target and substrate. As a result, we achieved the uniformity in deposition rate. Then, we prepared YBa1.78Cu2.9Oy target to fabricate YBCO films with stoichiometric composition and obtained the uniform-high Jc.

  18. Effect of Au nano-particles doping on polycrystalline YBCO high temperature superconductor

    NASA Astrophysics Data System (ADS)

    Dadras, Sedigheh; Gharehgazloo, Zahra

    2016-07-01

    In this research, we prepared different Au nanoparticles (0.1-2 wt%) doped YBCO high temperature superconductor samples by sol-gel method. To characterize the samples, we used X-Ray diffraction (XRD) and scanning electron microscope (SEM) analysis. Results show the formation of orthorhombic phase of superconductivity for all prepared samples. We observed that by adding Au nanoparticles, the grains' size of the samples reduces from 76 nm to 47 nm as well. The critical current density (Jc) and transition temperature (Tc) were determined using current versus voltage (I-V) and resistivity versus temperature (ρ-T) measurements, respectively. We found that by increasing Au nanoparticles in the compound, in comparison to the pure YBCO sample, the transition temperature, pinning energy and critical current density will increase. Also, the highest Jc is for 1 wt% Au doped YBCO compound that its critical current density is about 8 times more than the Jc of pure one in 0.7 T magnetic field.

  19. High speed production of YBCO precursor films by advanced TFA-MOD process

    NASA Astrophysics Data System (ADS)

    Ichikawa, H.; Nakaoka, K.; Miura, M.; Sutoh, Y.; Nakanishi, T.; Nakai, A.; Yoshizumi, M.; Izumi, T.; Shiohara, Y.

    2009-10-01

    YBa 2Cu 3O 7-y (YBCO) long tapes derived from the metal-organic deposition (MOD) method using the starting solution containing trifluoroacetate (TFA) have been developed with high critical currents ( I c) over 200 A/cm-width. However, high speed production of YBCO films is simultaneously necessary to satisfy the requirements of electric power device applications in terms of cost and the amounts of the tapes. In this work, we developed a new TFA-MOD starting solution using F-free salt of Y, TFA salt of Ba and Cu-Octylate for application to the coating/calcination process and discussed several issues by using the Multi-turn (MT) Reel-to-Reel (RTR) system calcination furnace for the purpose of high throughput without degradation of the properties. The coating system was improved for uniform deposition qualities in both longitudinal and transversal directions. YBCO films using the new starting solution at the traveling rate of 10 m/h in coating/calcination by the MT-RTR calcination furnace showed the values of the critical current density of 1.6 MA/cm 2 as thick as 1.5 μm at 77 K under the self fields after firing at the high heating rate in the crystallization.

  20. Study of the Nucleation and Growth of YBCO on Oxide Buffered Metallic Tapes

    SciTech Connect

    Solovyov, Vyacheslav

    2009-04-10

    The CRADA collaboration concentrated on developing the scientific understanding of the factors necessary for commercialization of high temperature superconductors (HTS) based on the YBCO coated conductor technology for electric power applications. The project pursued the following objectives: 1. Establish the correlations between the YBCO nuclei density and the properties of the CeO{sub 2} layer of the RABiTS{trademark} template; 2. Compare the nucleation and growth of e-beam and MOD based precursors on the buffered RABiTS{trademark} templates and clarify the materials science behind the difference; and 3. Explore routes for the optimization of the nucleation and growth of thick film MOD precursors in order to achieve high critical current densities in thick films. The CRADA work proceeded in two steps: 1. Detailed characterization of epitaxial ceria layers on “model” substrates, such as (001) YSZ and on RABiTS tapes; and 2. Study of YBCO nucleation on well-defined substrates and on long-length RABiTS.

  1. Biaxially aligned template films fabricated by inclined-substrate deposition for YBCO-coated conductor applications.

    SciTech Connect

    Ma, B.; Li, M.; Koritala, R. E.; Fisher, B. L.; Erck, R. A.; Dorris, S. E.; Miller, D. J.; Balachandran, U.

    2002-08-12

    Inclined substrate deposition (ISD) has the potential for rapid production of high-quality biaxially textured buffer layers, which are important for YBCO-coated conductor applications. We have grown biaxially textured MgO films by ISD at deposition rates of 20-100 {angstrom}/sec. Columnar grains with a roof-tile surface structure were observed in the ISD-MgO films. X-ray pole figure analysis revealed that the (002) planes of the ISD-MgO films are tilted at an angle from the substrate normal. A small {phi}-scan full-width at half maximum (FWHM) of {approx}9{sup o} was observed on MgO films deposited at an inclination angle of 55{sup o}. In-plane texture in the ISD MgO films developed in the first 0.5 {micro}m from the interface, then stabilized with further increases in film thickness. YBCO films deposited by pulsed laser deposition on ISD-MgO buffered Hastelloy C276 substrates were biaxially aligned with the c-axis parallel to the substrate normal. T{sub c} of 91 K with a sharp transition and transport J{sub c} of 5.5 x 10{sup 5} A/cm{sup 2} at 77 K in self-field were measured on a YBCO film that was 0.46-{micro}m thick, 4-mm wide, 10-mm long.

  2. Bulk YBCO seeded with 45°-45° bridge-seeds of different lengths

    NASA Astrophysics Data System (ADS)

    Shi, Y.-H.; Durrell, J. H.; Dennis, A. R.; Cardwell, D. A.

    2013-01-01

    Single grain, (RE)BCO (rare earth-barium-copper oxide) bulk superconductors in large or complicated geometries are required for a variety of potential applications, such as in motors and generators and magnetic shielding devices. As a result, top, multi-seeded, melt growth has been investigated over the past 15 years in an attempt to enlarge the size of (RE)BCO single grains specifically for such applications. Of these multi-seeding techniques, so-called bridge-seeding provides the best alignment of two seeds in a single grain growth process. Here we report, for the first time, the successful growth of YBCO (yttrium-barium-copper oxide) using a special, 45°-45°, arrangement of bridge-seeds. The superconducting properties, including trapped field, of the multi-seeded YBCO grains have been measured for different bridge lengths of the 45°-45° bridge-seeds. The boundaries at the impinging growth front and the growth features of the top, multi-seeded surface and cross-section of the multi-seeded, samples have been analysed using optical microscopy. The results suggest that an impurity-free boundary between the two seeds of each leg of the bridge-seed can form when 45°-45° bridge-seeds are used to enlarge the size of YBCO grains.

  3. Method for adhesion of metal films to ceramics

    DOEpatents

    Lowndes, D.H.; Pedraza, A.J.; DeSilva, M.J.; Kumar, R.A.

    1997-12-30

    Methods for making strongly bonded metal-ceramic materials are disclosed. The methods include irradiating a portion of the surface of the ceramic material with a pulsed ultraviolet laser having an energy density sufficient to effect activation of the irradiated surface of the ceramic material so that adhesion of metals subsequently deposited onto the irradiated surface is substantially increased. Advantages of the invention include (i) the need for only a small number of laser pulses at relatively low focused energy density, (ii) a smoother substrate surface, (iii) activation of the laser-treated surface which provides a chemical bond between the surface and a metal deposited thereon, (iv) only low temperature annealing is required to produce the strong metal-ceramic bond; (v) the ability to obtain strong adhesion between ceramic materials and oxidation resistant metals; (vi) ability to store the laser treated ceramic materials for later deposition of metals thereon. 7 figs.

  4. Method for adhesion of metal films to ceramics

    DOEpatents

    Lowndes, Douglas H.; Pedraza, Anthony J.; DeSilva, Melvin J.; Kumar, Rajagopalan A.

    1997-01-01

    Methods for making strongly bonded metal-ceramic materials. The methods include irradiating a portion of the surface of the ceramic material with a pulsed ultraviolet laser having an energy density sufficient to effect activation of the irradiated surface of the ceramic material so that adhesion of metals subsequently deposited onto the irradiated surface is substantially increased. Advantages of the invention include (i) the need for only a small number of laser pulses at relatively low focused energy density, (ii) a smoother substrate surface, (iii) activation of the laser-treated surface which provides a chemical bond between the surface and a metal deposited thereon, (iv) only low temperature annealing is required to produce the strong metal-ceramic bond; (v) the ability to obtain strong adhesion between ceramic materials and oxidation resistant metals; (vi) ability to store the laser treated ceramic materials for later deposition of metals thereon.

  5. Ceramic electrolyte coating methods

    DOEpatents

    Seabaugh, Matthew M.; Swartz, Scott L.; Dawson, William J.; McCormick, Buddy E.

    2004-10-12

    Processes for preparing aqueous suspensions of a nanoscale ceramic electrolyte material such as yttrium-stabilized zirconia. The invention also includes a process for preparing an aqueous coating slurry of a nanoscale ceramic electrolyte material. The invention further includes a process for depositing an aqueous spray coating slurry including a ceramic electrolyte material on pre-sintered, partially sintered, and unsintered ceramic substrates and products made by this process.

  6. Rapid and semi-analytical design and simulation of a toroidal magnet made with YBCO and MgB2 superconductors

    DOE PAGESBeta

    Dimitrov, I. K.; Zhang, X.; Solovyov, V. F.; Chubar, O.; Li, Qiang

    2015-07-07

    Recent advances in second-generation (YBCO) high-temperature superconducting wire could potentially enable the design of super high performance energy storage devices that combine the high energy density of chemical storage with the high power of superconducting magnetic storage. However, the high aspect ratio and the considerable filament size of these wires require the concomitant development of dedicated optimization methods that account for the critical current density in type-II superconductors. In this study, we report on the novel application and results of a CPU-efficient semianalytical computer code based on the Radia 3-D magnetostatics software package. Our algorithm is used to simulate andmore » optimize the energy density of a superconducting magnetic energy storage device model, based on design constraints, such as overall size and number of coils. The rapid performance of the code is pivoted on analytical calculations of the magnetic field based on an efficient implementation of the Biot-Savart law for a large variety of 3-D “base” geometries in the Radia package. The significantly reduced CPU time and simple data input in conjunction with the consideration of realistic input variables, such as material-specific, temperature, and magnetic-field-dependent critical current densities, have enabled the Radia-based algorithm to outperform finite-element approaches in CPU time at the same accuracy levels. Comparative simulations of MgB2 and YBCO-based devices are performed at 4.2 K, in order to ascertain the realistic efficiency of the design configurations.« less

  7. Rapid and semi-analytical design and simulation of a toroidal magnet made with YBCO and MgB2 superconductors

    SciTech Connect

    Dimitrov, I. K.; Zhang, X.; Solovyov, V. F.; Chubar, O.; Li, Qiang

    2015-07-07

    Recent advances in second-generation (YBCO) high-temperature superconducting wire could potentially enable the design of super high performance energy storage devices that combine the high energy density of chemical storage with the high power of superconducting magnetic storage. However, the high aspect ratio and the considerable filament size of these wires require the concomitant development of dedicated optimization methods that account for the critical current density in type-II superconductors. In this study, we report on the novel application and results of a CPU-efficient semianalytical computer code based on the Radia 3-D magnetostatics software package. Our algorithm is used to simulate and optimize the energy density of a superconducting magnetic energy storage device model, based on design constraints, such as overall size and number of coils. The rapid performance of the code is pivoted on analytical calculations of the magnetic field based on an efficient implementation of the Biot-Savart law for a large variety of 3-D “base” geometries in the Radia package. The significantly reduced CPU time and simple data input in conjunction with the consideration of realistic input variables, such as material-specific, temperature, and magnetic-field-dependent critical current densities, have enabled the Radia-based algorithm to outperform finite-element approaches in CPU time at the same accuracy levels. Comparative simulations of MgB2 and YBCO-based devices are performed at 4.2 K, in order to ascertain the realistic efficiency of the design configurations.

  8. Ceramic to metal seal

    DOEpatents

    Snow, Gary S.; Wilcox, Paul D.

    1976-01-01

    Providing a high strength, hermetic ceramic to metal seal by essentially heating a wire-like metal gasket and a ceramic member, which have been chemically cleaned, while simultaneously deforming from about 50 to 95 percent the metal gasket against the ceramic member at a temperature of about 30 to 75 percent of the melting temperature of the metal gasket.

  9. Brittleness of ceramics

    NASA Technical Reports Server (NTRS)

    Kroupa, F.

    1984-01-01

    The main characteristics of mechanical properties of ceramics are summarized and the causes of their brittleness, especially the limited mobility of dislocations, are discussed. The possibility of improving the fracture toughness of ceramics and the basic research needs relating to technology, structure and mechanical properties of ceramics are stressed in connection with their possible applications in engineering at high temperature.

  10. Microstructural analysis on growth and crystallization mechanism of YBCO films deposited by advanced TFA-MOD process

    NASA Astrophysics Data System (ADS)

    Matsuda, J.; Nakaoka, K.; Sutoh, Y.; Nakanishi, T.; Yoshizumi, M.; Yamada, Y.; Izumi, T.; Shiohara, Y.

    2007-10-01

    We have investigated effects of the heating rate in the crystallization process on Ic values and microstructures of YBa2Cu3O7-δ (YBCO) films, which were fabricated by the advanced metalorganic deposition (MOD) method using trifluoroacetates. As a result, it was found that the slow heating rate less than 2 °C/min in the crystallization process increases the volume of randomly oriented YBCO crystals, which results in a low Ic value of the YBCO film. TEM observations of quenched samples prepared by cooling rapidly during the crystallization process revealed that unreacted phase particles such as CuO, Y2Cu2O5 and Ba-O-F crystallize and coarsen to large crystals before the nucleation and growth of YBCO crystals in the case of slow heating. We conclude that it is important to control the size and distributions of the unreacted phase particles in the crystallization process, in order to fabricate the YBCO coated conductor with high Ic.

  11. Thin film ceramic thermocouples

    NASA Technical Reports Server (NTRS)

    Gregory, Otto (Inventor); Fralick, Gustave (Inventor); Wrbanek, John (Inventor); You, Tao (Inventor)

    2011-01-01

    A thin film ceramic thermocouple (10) having two ceramic thermocouple (12, 14) that are in contact with each other in at least on point to form a junction, and wherein each element was prepared in a different oxygen/nitrogen/argon plasma. Since each element is prepared under different plasma conditions, they have different electrical conductivity and different charge carrier concentration. The thin film thermocouple (10) can be transparent. A versatile ceramic sensor system having an RTD heat flux sensor can be combined with a thermocouple and a strain sensor to yield a multifunctional ceramic sensor array. The transparent ceramic temperature sensor that could ultimately be used for calibration of optical sensors.

  12. Ceramic gas turbine shroud

    DOEpatents

    Shi, Jun; Green, Kevin E.

    2014-07-22

    An example gas turbine engine shroud includes a first annular ceramic wall having an inner side for resisting high temperature turbine engine gasses and an outer side with a plurality of radial slots. A second annular metallic wall is positioned radially outwardly of and enclosing the first annular ceramic wall and has a plurality of tabs in communication with the slot of the first annular ceramic wall. The tabs of the second annular metallic wall and slots of the first annular ceramic wall are in communication such that the first annular ceramic wall and second annular metallic wall are affixed.

  13. Forming of superplastic ceramics

    SciTech Connect

    Lesuer, D.R.; Wadsworth, J.; Nieh, T.G.

    1994-05-01

    Superplasticity in ceramics has now advanced to the stage that technologically viable superplastic deformation processing can be performed. In this paper, examples of superplastic forming and diffusion bonding of ceramic components are given. Recent work in biaxial gas-pressure forming of several ceramics is provided. These include yttria-stabilized, tetragonal zirconia (YTZP), a 20% alumina/YTZP composite, and silicon. In addition, the concurrent superplastic forming and diffusion bonding of a hybrid ceramic-metal structure are presented. These forming processes offer technological advantages of greater dimensional control and increased variety and complexity of shapes than is possible with conventional ceramic shaping technology.

  14. Orientations of Y 2BaCuO 5 and YBCO within melt-textured and directional solidified samples studied by EBSD

    NASA Astrophysics Data System (ADS)

    Koblischka, M. R.; Koblischka-Veneva, A.; Reddy, E. S.; Schmitz, G. J.; Ogasawara, K.; Murakami, M.

    2003-10-01

    By means of automated electron backscatter diffraction (EBSD) analysis, we studied the local orientations of embedded Y 2BaCuO 5 (2 1 1) particles within melt-textured YBCO samples, and also the orientations of embedded YBCO particles in directional solidified 211 samples. On both systems, we obtained high-quality Kikuchi patterns, allowing the automated mapping of the crystal orientations and a multi-phase analysis. In melt-textured YBCO with (0 0 1) orientation, we find that the embedded 211 particles do not have any preferred orientation, but the maps also reveal that at certain orientations of the 211 particles the YBCO growth is not altered. In directional solidified 211 samples, where the 211 is mainly oriented in (0 0 1) direction, the embedded YBCO particles show only some specific orientations.

  15. Electronic Properties of Layered Oxides:. Pulsed Laser Deposition of YBCO Films for In-Situ Studies by Photoemission Spectroscopy

    NASA Astrophysics Data System (ADS)

    Pavuna, D.; Ariosa, D.; Berger, H.; Christensen, S.; Frazer, B.; Gatt, R.; Grioni, M.; Margaritondo, G.; Misra, S.; Onellion, M.; Schmauder, T.; Vobornik, I.; Xi, X.; Zacchigna, M.; Zwick, F.

    Due to imperfect surfaces of most cuprate samples, almost all Photoemission studies in the past decade were performed on Bi2Sr2CaCu2O8+x, even though a large fraction of other studies and electronic applications was reported for YBa2Cu3O7-δ (YBCO) family of superconducting compounds. In order to systematically study the gap parameter and the Fermi surface variation in high symmetry directions of YBCO and related oxide films we have constructed a new facility at the Wisconsin Synchrotron Radiation Center. We use the pulsed laser ablation (PLD) system that is directly linked to the photoemission chamber. In our unique approach, the samples never leave the controlled ambient and we oxidize our films, either by molecular oxygen or by ozone. In this paper, we, summarize some of the most relevant recent results on electronic properties of layered oxides and describe our new facility for the study of YBCO and related oxide films.

  16. YBCO High-Temperature Superconducting Filters on M-Plane Sapphire Substrates

    NASA Technical Reports Server (NTRS)

    Sabataitis, J. C.; Mueller, C. H.; Miranda, F. A.; Warner, J.; Bhasin, K. B.

    1996-01-01

    Since the discovery of High Temperature Superconductors (HTS) in 1986, microwave circuits have been demonstrated using HTS films on various substrates. These HTS-based circuits have proven to operate with less power loss than their metallic film counterparts at 77 K. This translates into smaller and lighter microwave circuits for space communication systems such as multiplexer filter banks. High quality HTS films have conventionally been deposited on lanthanum aluminate (LaAlO3) substrates. However, LaAlO3 has a relative dielectric constant (epsilon(sub r)) of 24. With a epsilon(sub r) approx. 9.4-11.6, sapphire (Al2O3) would be a preferable substrate for the fabrication of HTS-based components since the lower dielectric constant would permit wider microstrip lines to be used in filter design, since the lower dielectric constant would permit wider microstrip lines to be used for a given characteristic impedance (Z(sub 0)), thus lowering the insertion losses and increasing the power handling capabilities of the devices. We report on the fabrication and characterization of YBa2Cu3O(7-delta) (YBCO) on M-plane sapphire bandpass filters at 4.0 GHz. For a YBCO 'hairpin' filter, a minimum insertion loss of 0.5 dB was measured at 77 K as compared with 1.4 dB for its gold counterpart. In an 'edge-coupled' configuration, the insertion loss went down from 0.9 dB for the gold film to 0.8 dB for the YBCO film at the same temperature.

  17. Fracture Toughness Prediction for MWCNT Reinforced Ceramics

    SciTech Connect

    Henager, Charles H.; Nguyen, Ba Nghiep

    2013-09-01

    This report describes the development of a micromechanics model to predict fracture toughness of multiwall carbon nanotube (MWCNT) reinforced ceramic composites to guide future experimental work for this project. The modeling work described in this report includes (i) prediction of elastic properties, (ii) development of a mechanistic damage model accounting for matrix cracking to predict the composite nonlinear stress/strain response to tensile loading to failure, and (iii) application of this damage model in a modified boundary layer (MBL) analysis using ABAQUS to predict fracture toughness and crack resistance behavior (R-curves) for ceramic materials containing MWCNTs at various volume fractions.

  18. Microstructure of artificial 45{sup degree} [001] tilt grain boundaries in YBCO films grown on (001) MgO

    SciTech Connect

    Huang, Y.; Vuchic, B.V.; Merkle, K.L.; Buchholz, D.B.; Chang, R.P.H.

    1996-03-01

    High-angle grain boundaries in YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) show weak-link effects and behave as Josephson junctions. This kind of grain boundary junction (GBJs) has potential applications in magnetic field measurement and electronic devices. This work studies the microstructure of artificially made GBJs in YBCO films on (001) MgO and the mechanism of boundary formation, with the goal to improve GBJ quality and obtain a better understanding of the junctions` transport properties.

  19. Centre seeded infiltration and growth process for fabrication of large grain bulk YBCO/Ag superconducting composites

    NASA Astrophysics Data System (ADS)

    Parthasarathy, R.; Seshubai, V.

    2012-06-01

    We report the fabrication of a large grain bulk YBCO/Ag superconductor using a novel technique which we call Centre Seeded Infiltration and Growth Process (CSIGP). Using this technique, it has been made possible to get bulk YBCO/Ag composite sample with uniform grain growth textured along the c-axis. The resulting large grain sample has been found to have high critical current densities up to large magnetic fields. We correlate the improved superconducting and magnetic properties to the modified grain growth conditions employed in this fabrication technique.

  20. The peculiarities of local structure of YbNi2 and YbCo2 intermetallics synthesized at high pressure.

    NASA Astrophysics Data System (ADS)

    Chernysheva, O. V.; Menushenkov, A. P.; Tsvyashchenko, A. V.; Fomicheva, L. N.; Ivanov, A. A.; Kuznetsov, A. V.

    2016-09-01

    Local structure of YbCo2 and YbNi2 was investigated by EXAFS and XANES spectroscopy. It was found that the bond Yb-Co(Ni) has the highest static disorder and its length increases with temperature decrease, while all other bonds remain almost unchanged. This phenomenon may be caused by short-range magnetic ordering at temperatures above the phase transition. XANES measurements above ZIII-Yb absorption edge in YbCo2 and YbNi2 revealed that both compounds have almost the same density of free 5d-states

  1. Performance of a polarised neutron cryo-flipper using a high TcYBCO film

    NASA Astrophysics Data System (ADS)

    Parnell, S. R.; Washington, A. L.; Kaiser, H.; Li, F.; Wang, T.; Hamilton, W. A.; Baxter, D. V.; Pynn, R.

    2013-09-01

    It is well-known that the Meissner effect in superconducting materials can be used to provide a well-defined, non-adiabatic, magnetic-field transition. This can be utilised to produce a highly efficient neutron spin flipper that is suitable for use with neutrons of multiple wavelengths. Devices of this type using superconducting niobium have been deployed on neutron diffractometers for several decades but have required liquid helium to maintain the correct temperature. The use of high Tc materials, which removes the need for cryogens and simplifies the device, was first explored by Fitzsimmons et al. in [1]. In this communication, we describe a π flipper which uses commercially available films consisting of a 350-nm-thick YBCO film capped with 100 nm of gold on a 78×100×0.5 mm sapphire substrate. We discuss the design and performance of this device. The apparatus is compact (≈200 mm in length along the neutron beam), consisting of an oxygen-free high-conductivity copper frame, which holds the YBCO film and is mounted to the cold finger of a closed-cycle He refrigerator. The part of the vacuum chamber, where the YBCO film is located, is 5 cm wide, which allows us to minimise the distance from the film to the magnetic guide fields. Negligible small angle neutron scattering is observed from the flipper and its transmission is measured to be greater than 98.5% over a wide band of neutron wavelengths. In this design, the maximum neutron beam size that can be used is 42×42 mm2 and we can easily switch from a vertical to a horizontal guide field (both perpendicular to the neutron beam) on either side of the YBCO film. Data are reported for neutron wavelengths between 4 and 8.5 Å and flipping efficiencies under a variety of conditions are discussed. Under optimum conditions an efficiency of 99.5±0.3% was achieved for 4-8 Å neutrons on a pulsed source and 99.4±0.5% was achieved at a monochromatic source using a neutron wavelength of 4.2 Å.

  2. Direct observation of surface plasmons in YBCO by attenuated total reflection of light in the infrared

    NASA Astrophysics Data System (ADS)

    Walmsley, D. G.; Smyth, C. C.; Sellai, A.; McCafferty, P. G.; Dawson, P.; Morrow, T.; Graham, W. G.

    1994-02-01

    Surface plasmons have been observed directly in YBCO films in an Otto-geometry attenuated total reflection measurement at a wavelength of 3.392 μm. The laser deposited films are c-axis oriented on an MgO substrate. This observation confirms theoretical deductions from complex dielectric function data. Measured data have been fitted to a theoretical model and are compared with the optical constants determined by Bozovic [1]. The investigations have been extended to films with other orientations to investigate whether material anisotropy is reflected in the results and non-metallic behaviour is found.

  3. HTS current lead units prepared by the TFA-MOD processed YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Shiohara, K.; Sakai, S.; Ishii, Y.; Yamada, Y.; Tachikawa, K.; Koizumi, T.; Aoki, Y.; Hasegawa, T.; Tamura, H.; Mito, T.

    2010-11-01

    Two superconducting current lead units have been prepared using ten coated conductors of the Tri-Fluoro-Acetate - Metal Organic Deposition (TFA-MOD) processed Y 1Ba 2Cu 3O 7-δ (YBCO) coated conductors with critical current ( Ic) of about 170 A at 77 K in self-field. The coated conductors are 5 mm in width, 190 mm in length and about 120 μm in overall thickness. The 1.5 μm thick superconducting YBCO layer was synthesized through the TFA-MOD process on Hastelloy™ C-276 substrate tape with two buffer oxide layers of Gd 2Zr 2O 7 and CeO 2. The five YBCO coated conductors are attached on a 1 mm thick Glass Fiber Reinforced Plastics (GFRP) board and soldered to Cu caps at the both ends. We prepared two 500 A-class current lead units. The DC transport current of 800 A was stably applied at 77 K without any voltage generation in all coated conductors. The voltage between both Cu caps linearly increased with increasing the applied current, and was about 350 μV at 500 A in both current lead units. According to the estimated values of the heat leakage from 77 K to 4.2 K, the heat leakage for the current lead unit was 46.5 mW. We successfully attained reduction of the heat leakage because of improvement of the transport current performance ( I c), a thinner Ag layer of YBCO coated conductor and usage of the GFRP board for reinforcement instead of a stainless steel board used in the previous study. The DC transport current of 1400 A was stably applied when the two current lead units were joined in parallel. The sum of the heat leakages from 77 K to 4.2 K for the combined the current lead units was 93 mW. In comparison with the conventional Cu current leads by gas-cooling, it could be noted that the heat leakage of the current lead is about one order of magnitude smaller than that of the Cu current lead.

  4. Co-doping effects of Gd and Ag on YBCO films derived by metalorganic deposition

    NASA Astrophysics Data System (ADS)

    Sun, Meijuan; Liu, Zhiyong; Bai, Chuanyi; Guo, Yanqun; Lu, Yuming; Fan, Feng; Cai, Chuanbing

    2015-12-01

    Y1-xGdxBa2Cu3O7-δ-Ag (x = 0, 0.25, 0.5, 0.75, 1) thin films were prepared on oxide buffered Hastelloy substrates by low fluorine metalorganic depostion (MOD) process. The effects of co-doping of Ag and Gd on the microstructures and superconducting properties of YBCO thin films are investigated with respect to improvement on texture and superconducting performance in case of optimized doping content. It is found that optimum addition of Ag and Gd may lead to better c-axis orientation, superior surface microstructure and finally give rise to much improvement of superconducting performance.

  5. Switching of YBCO thin films into the dissipative state at high current densities

    NASA Astrophysics Data System (ADS)

    Villard, Catherine; Devismes, Marie-Françoise; Carbone, Laurent; Bourgault, Daniel

    We report on the switching properties at high current densities of YBCO thin films shunted by an Ag layer. These experiments are performed either in liquid nitrogen or liquid argon (87.3K). Different transition regimes associated to specific electric field thresholds are observed. The nature of the thermal exchange with the bath and the role of the silver shunt and substrate are discussed. While only two regimes in the current-voltage characteristics are observed in liquid nitrogen, successively reversible and hysteretic, an intermediate behaviour appears at 87.3K associated with a total current diversion by the silver layer.

  6. Study on Quench Protection of Coil Wound of Copper or Silver Stabilized YBCO Conductors

    NASA Astrophysics Data System (ADS)

    Tsukamoto, O.; Fu, Y.; Yoshida, H.; Furuse, M.

    2004-06-01

    We investigated necessary amount of copper or silver stabilizer added to YBCO conductor by numerical calculation to protect the conductor in a coil of dry windings from damages caused by quenches. The coil is assumed to be operated at 20K, 40K and 77K and hot-spot temperature of the conductor during energy dump sequence is calculated. The necessary amount of the stabilizer and overall conductor current density of the conductor including the stabilizer were calculated to suppress the hot spot temperature below a certain threshold depending on the operation temperature.

  7. Fabrication and test of short helical solenoid model based on YBCO tape

    SciTech Connect

    Yu, M.; Lombardo, V.; Lopes, M.L.; Turrioni, D.; Zlobin, A.V.; Flanagan, G.; Johnson, R.P.; /MUONS Inc., Batavia

    2011-03-01

    A helical cooling channel (HCC) is a new technique proposed for six-dimensional (6D) cooling of muon beams. To achieve the optimal cooling rate, the high field section of HCC need to be developed, which suggests using High Temperature Superconductors (HTS). This paper updates the parameters of a YBCO based helical solenoid (HS) model, describes the fabrication of HS segments (double-pancake units) and the assembly of six-coil short HS model with two dummy cavity insertions. Three HS segments and the six-coil short model were tested. The results are presented and discussed.

  8. Development of improved processing and evaluation methods for high reliability structural ceramics for advanced heat engine applications Phase II. Final report

    SciTech Connect

    Pujari, V.J.; Tracey, D.M.; Foley, M.R.

    1996-02-01

    The research program had as goals the development and demonstration of significant improvements in processing methods, process controls, and nondestructive evaluation (NDE) which can be commercially implemented to produce high reliability silicon nitride components for advanced heat engine applications at temperatures to 1370{degrees}C. In Phase I of the program a process was developed that resulted in a silicon nitride - 4 w% yttria HIP`ed material (NCX 5102) that displayed unprecedented strength and reliability. An average tensile strength of 1 GPa and a strength distribution following a 3-parameter Weibull distribution were demonstrated by testing several hundred buttonhead tensile specimens. The Phase II program focused on the development of methodology for colloidal consolidation producing green microstructure which minimizes downstream process problems such as drying, shrinkage, cracking, and part distortion during densification. Furthermore, the program focused on the extension of the process to gas pressure sinterable (GPS) compositions. Excellent results were obtained for the HIP composition processed for minimal density gradients, both with respect to room-temperature strength and high-temperature creep resistance. Complex component fabricability of this material was demonstrated by producing engine-vane prototypes. Strength data for the GPS material (NCX-5400) suggest that it ranks very high relative to other silicon nitride materials in terms of tensile/flexure strength ratio, a measure of volume quality. This high quality was derived from the closed-loop colloidal process employed in the program.

  9. The friction and wear of ceramic/ceramic and ceramic/metal combinations in sliding contact

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.; Dellacorte, Christopher

    1993-01-01

    The tribological characteristics of ceramics sliding on ceramics are compared to those of ceramics sliding on a nickel based turbine alloy. The friction and wear of oxide ceramics and silicon-based ceramics in air at temperatures from room ambient to 900 C (in a few cases to 1200 C) were measured for a hemispherically-tipped pin on a flat sliding contact geometry. In general, especially at high temperature, friction and wear were lower for ceramic/metal combinations than for ceramic/ceramic combinations. The better tribological performance for ceramic/metal combinations is attributed primarily to the lubricious nature of the oxidized surface of the metal.

  10. Analyses of fine paste ceramics

    SciTech Connect

    Sabloff, J A

    1980-01-01

    Four chapters are included: history of Brookhaven fine paste ceramics project, chemical and mathematical procedures employed in Mayan fine paste ceramics project, and compositional and archaeological perspectives on the Mayan fine paste ceramics. (DLC)

  11. Ceramic tamper-revealing seals

    DOEpatents

    Kupperman, David S.; Raptis, Apostolos C.; Sheen, Shuh-Haw

    1992-01-01

    A flexible metal or ceramic cable with composite ceramic ends, or a u-shaped ceramic connecting element attached to a binding element plate or block cast from alumina or zirconium, and connected to the connecting element by shrink fitting.

  12. Continuous Fiber Ceramic Composites

    SciTech Connect

    2002-09-01

    Fiber-reinforced ceramic composites demonstrate the high-temperature stability of ceramics--with an increased fracture toughness resulting from the fiber reinforcement of the composite. The material optimization performed under the continuous fiber ceramic composites (CFCC) included a series of systematic optimizations. The overall goals were to define the processing window, to increase the robustinous of the process, to increase process yield while reducing costs, and to define the complexity of parts that could be fabricated.

  13. Method of sintering ceramic materials

    DOEpatents

    Holcombe, Cressie E.; Dykes, Norman L.

    1992-01-01

    A method for sintering ceramic materials is described. A ceramic article is coated with layers of protective coatings such as boron nitride, graphite foil, and niobium. The coated ceramic article is embedded in a container containing refractory metal oxide granules and placed within a microwave oven. The ceramic article is heated by microwave energy to a temperature sufficient to sinter the ceramic article to form a densified ceramic article having a density equal to or greater than 90% of theoretical density.

  14. Method of sintering ceramic materials

    DOEpatents

    Holcombe, C.E.; Dykes, N.L.

    1992-11-17

    A method for sintering ceramic materials is described. A ceramic article is coated with layers of protective coatings such as boron nitride, graphite foil, and niobium. The coated ceramic article is embedded in a container containing refractory metal oxide granules and placed within a microwave oven. The ceramic article is heated by microwave energy to a temperature sufficient to sinter the ceramic article to form a densified ceramic article having a density equal to or greater than 90% of theoretical density. 2 figs.

  15. Alumina-based ceramic composite

    DOEpatents

    Alexander, Kathleen B.; Tiegs, Terry N.; Becher, Paul F.; Waters, Shirley B.

    1996-01-01

    An improved ceramic composite comprising oxide ceramic particulates, nonoxide ceramic particulates selected from the group consisting of carbides, borides, nitrides of silicon and transition metals and mixtures thereof, and a ductile binder selected from the group consisting of metallic, intermetallic alloys and mixtures thereof is described. The ceramic composite is made by blending powders of the ceramic particulates and the ductile to form a mixture and consolidating the mixture of under conditions of temperature and pressure sufficient to produce a densified ceramic composite.

  16. Measuring Fracture Times Of Ceramics

    NASA Technical Reports Server (NTRS)

    Shlichta, Paul J.; Bister, Leo; Bickler, Donald G.

    1989-01-01

    Electrical measurements complement or replace fast cinematography. Electronic system measures microsecond time intervals between impacts of projectiles on ceramic tiles and fracture tiles. Used in research on ceramics and ceramic-based composite materials such as armor. Hardness and low density of ceramics enable them to disintegrate projectiles more efficiently than metals. Projectile approaches ceramic tile specimen. Penetrating foil squares of triggering device activate display and recording instruments. As ceramic and resistive film break oscilloscope plots increase in electrical resistance of film.

  17. Ceramic brush seals development

    NASA Technical Reports Server (NTRS)

    Howe, Harold

    1994-01-01

    The following topics are discussed in this viewgraph presentation: ceramic brush seals, research and development, manufacturing, brazed assembly development, controlling braze flow, fiber selection, and braze results.

  18. Corrosion of Ceramic Materials

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Jacobson, Nathan S.

    1999-01-01

    Non-oxide ceramics are promising materials for a range of high temperature applications. Selected current and future applications are listed. In all such applications, the ceramics are exposed to high temperature gases. Therefore it is critical to understand the response of these materials to their environment. The variables to be considered here include both the type of ceramic and the environment to which it is exposed. Non-oxide ceramics include borides, nitrides, and carbides. Most high temperature corrosion environments contain oxygen and hence the emphasis of this chapter will be on oxidation processes.

  19. Defect production in ceramics

    SciTech Connect

    Zinkle, S.J.; Kinoshita, C.

    1997-08-01

    A review is given of several important defect production and accumulation parameters for irradiated ceramics. Materials covered in this review include alumina, magnesia, spinel silicon carbide, silicon nitride, aluminum nitride and diamond. Whereas threshold displacement energies for many ceramics are known within a reasonable level of uncertainty (with notable exceptions being AIN and Si{sub 3}N{sub 4}), relatively little information exists on the equally important parameters of surviving defect fraction (defect production efficiency) and point defect migration energies for most ceramics. Very little fundamental displacement damage information is available for nitride ceramics. The role of subthreshold irradiation on defect migration and microstructural evolution is also briefly discussed.

  20. Applications of the electron backscatter diffraction technique to ceramic materials

    NASA Astrophysics Data System (ADS)

    Koblischka, M. R.; Koblischka-Veneva, A.

    2013-07-01

    A technique with a relatively high spatial resolution is required for an effective analysis of the microstructure of ceramic materials. The recently developed electron backscatter diffraction (EBSD) technique, which works within a scanning electron microscope, enables a spatially highly resolved study of crystallographic orientations while recording Kikuchi patterns on a user-defined grid. However, such an EBSD texture analysis was until now not often performed on ceramic materials - in contrary, the technique is widely employed in the analysis of metallic materials, including the investigation of various types of steels. The use of ceramics possesses a variety of problems for EBSD investigations like: (i) complicated crystal structure, (ii) difficult surface preparation, and (iii) problems arising from a low conductivity of the ceramic materials. Here, we discuss these problems and present solutions in order to obtain high-quality Kikuchi patterns from such ceramics.

  1. Preparation of YBCO single-crystal surfaces for angularly resolved planar tunneling studies

    NASA Astrophysics Data System (ADS)

    Lussier, Benoit; Charalambous, M.; Guillou, H.; Chaussy, J.; Lejay, P.; Pissas, M.

    1998-03-01

    For BCS superconductors, tunneling has proven to be a valuable tool. Indeed, using multiple recrystallisation techniques, planar junctions could be prepared along various crystalline directions enabling a direct mapping of the superconducting gap. For various reasons, such techniques are difficult (if not impossible) to apply to high-Tc materials. Furthermore, due to the small thickness of the single crystals, very few planar tunneling results into the basal plane are availlable. We present a new sample preparation technique which enables us to prepare surfaces for planar tunneling in any direction in the basal plane. After proper orientation of the high-Tc single crystal, the surface is mechanically polished using fine diamond paste. Such process routinely yields samples with rms surface roughness as low as 15ÅThe sample is then ion-polished with normal incidence xenon atoms and the tunneling barrier and counter-electrode are evaporated in-situ. Preliminary tunneling results for Au/YBCO and Nb/YBCO will be presented for twinned single crystals with tunneling in the (100) and (110) directions.

  2. Transport AC loss characteristics of a nine strand YBCO Roebel cable

    NASA Astrophysics Data System (ADS)

    Jiang, Zhenan; Badcock, R. A.; Long, N. J.; Staines, Mike; Thakur, K. P.; Lakshmi, L. S.; Wright, A.; Hamilton, K.; Sidorov, G. N.; Buckley, R. G.; Amemiya, Naoyuki; Caplin, A. D.

    2010-02-01

    Transport AC loss in a short length of 9/2 YBCO Roebel cable (nine 2 mm wide strands) is measured. The AC loss data are compared with those in a 5/2 YBCO Roebel cable (five 2 mm wide strands) as well as that in a single strand. All the strands composing the cables and the single strand are insulated and cut from the same stock material. The validity of the measurement method was reconfirmed by results at a range of frequencies. At a wide range of It/Ic, the normalized AC losses in the Roebel cable were around 6.2-6.7 times of those in the single strand. This is less than the nine times predicted for a tight bundle of nine conductors. The normalized transport AC losses in the 5/2 Roebel cable are much smaller than those in the 9/2 Roebel. This should be due to larger superposition of magnetic field in the 9/2 Roebel. The Ic of the 9/2 and 5/2 Roebel cables is determined by serial connection of the strands. This eliminates the effect where differing resistances in the current terminations cause uneven current sharing between strands when the strands are connected in parallel.

  3. VOLTAGE DISTRIBUTION AND MECHANICAL STRENGTH IN SPLICE JOINTS MADE FROM AS-MANUFACTURED YBCO COATED CONDUCTORS

    SciTech Connect

    Duckworth, Robert C; Zhang, Yifei; Gouge, Michael J; Rey, Christopher M; Van der Laan, Danko; Clickner, Cam

    2010-01-01

    With recommendations from wire manufacturers as a starting point, a series of solder joints were fabricated and characterized to determine the best method to produce repeatable, low-resistance and high-mechanical-strength splices in as-manufactured, stabilized YBCO coated conductors. From the 2.54 cm long splice joints that were fabricated, parameters such as solder material, stabilization material, fabrication method, and conductor geometry were varied to determine the impact of each on splice joint properties. Results indicate that the lowest resistance splice joints were influenced primarily by the tape orientation in the joint and the stabilization material. The lowest resistances were between 2 10-8 and 1.0 10-7 in 4-mm wide tapes and were obtained from pure copper stabilized tapes oriented with the YBCO layers in closest proximity. The voltage drop along the splice length indicated that only a fraction of the splice length contributes to the splice joint resistance. Mechanical characterization of splice joints showed that the joint resistance remained unchanged under axial stress up to a stress level at which the critical current of the tapes forming the joint degrades irreversibly.

  4. Position-dependent texture analysis of melt-textured YBCO by means of electron backscatter diffraction

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Ogasawara, K.; Murakami, M.

    2003-10-01

    The texture and phase distribution of melt-textured YBa 2Cu 3O x (YBCO) was studied by means of automated electron backscatter diffraction (EBSD) analysis as a function of the position in the bulk pellet of 4 cm diameter. A total of five samples was cut from the pellet; four samples from the surface of the bulk with different distances to the seed crystal, and one cut in vertical direction in the middle of the pellet. The melt-textured YBCO samples require a two-phase analysis to be performed, so a high surface quality is necessary to enable an automated EBSD scan. Good quality Kikuchi patterns are obtained from both the 1 2 3 and 2 1 1 phases. We found an inhomogeneous distribution of the 2 1 1 particles. Whereas the samples cut from the surface contain a large amount of 2 1 1 particles, in the samples of the vertical direction only traces of 2 1 1 particles are found. Furthermore, we measured the misorientation angle distribution of all samples. The data are presented in form of phase mappings, misorientation distribution functions and pole figures.

  5. The influence of magnetic nano metal oxides doping on structure and electrical properties of YBCO superconductor

    NASA Astrophysics Data System (ADS)

    Salama, A. H.; El-Hofy, M.; Rammah, Y. S.; Elkhatib, M.

    2016-03-01

    Superconductor samples of YBa2Cu3O7-δ (YBCO) + x where x = 0.1, 0.2, 0.3, 0.4 and 0.5 wt% of nano metal oxides namely Cr2O3, Co3O4 and Mn3O4 namely are synthesized by the solid-state reaction route. Both x-ray diffraction and electron microscopy have been employed to study the phase identification and the microstructure of these samples. Transition temperature of the samples has been determined by four probe resistivity measurements. The x-ray diffraction patterns indicate that the gross structure of YBCO does not change with the substitution of three types of nano metal oxides with different doping level. The critical transition temperature (Tc) is found to decrease with the increases of doping level. Mn3O4 has highest Tc value which may be due to flux pinning from some defects and the rapid suppression in Tc with increasing concentration of Mn3O4 may be due to the cooper pair breaking and the hole filling in the CuO2 planes.

  6. Inclined-substrate deposition of biaxially textured magnesium oxide thin films for YBCO coated conductors.

    SciTech Connect

    Ma, B.; Li, M.; Jee, Y. A.; Koritala, R. E.; Fisher, B. L.; Balachandran, U.; Energy Technology

    2002-02-01

    Highly textured MgO films were grown by the inclined-substrate deposition (ISD) technique at a high deposition rate. A columnar grain with a roofing-tile-shaped surface was observed in these MgO films. X-ray pole figure, and {phi}- and {omega}-scan were used to characterize in-plane and out-of-plane textures. MgO films deposited when the incline angle {alpha} was 55 and 30 degrees exhibited the best in-plane and out-of-plane texture, respectively. High-quality YBCO films were epitaxially grown on ISD-MgO-buffered Hastelloy C substrates by pulsed laser deposition. {Tc}=88 K, with sharp transition, and j{sub c} values of {approx}2x10{sup 5} A/cm{sup 2} at 77 K in zero field were observed on films 5 mm wide and 1 cm long. This work has demonstrated that biaxially textured ISD MgO buffer layers deposited on metal substrates are excellent candidates for fabrication of high-quality YBCO coated conductors.

  7. Microstructural, transport, and RF properties of multilayer-deposited YBCO films

    NASA Astrophysics Data System (ADS)

    Madhavrao, L. R.; Track, E. K.; Drake, R. E.; Patt, R.; Hohenwarter, G. K. G.

    1991-03-01

    Thin films of Y1Ba2Cu3O(7-x) (YBCO) have been fabricated by sequential multilayer RF magnetron sputter-deposition from Y2O3, BaCo3, and CuO targets and postannealing in oxygen. This approach readily allows precise control of the film stoichiometry and is promising for applications that require deposition over large areas. Films on different substrates-including SrTiO3, LaAlO3, MgO and sapphire-are found to be c-axis oriented for film thicknesses between 300 A and 10,000 A. Transport current densities in the range of 106 A/sq cm are obtained on SrTiO3 and LaAlO3 substrates and in the range of 105 A/sq cm on MgO and sapphire. Transition temperatures of 89 K (resistive) and 87 K (inductive) are obtained repeatably with LaAlO3 substrates. Copper cavity end wall measurements at 77 K and 35.6 GHz set an upper limit for the surface resistance of the YBCO films on LaAlO3 that is equal to the surface resistance of high-quality silver films. The fabrication and properties of these films are discussed.

  8. On the use of copper-based substrates for YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Vannozzi, A.; Fabbri, F.; Augieri, A.; Angrisani Armenio, A.; Galluzzi, V.; Mancini, A.; Rizzo, F.; Rufoloni, A.; Padilla, J. A.; Xuriguera, E.; De Felicis, D.; Bemporad, E.; Celentano, G.

    2014-05-01

    It is well known that the recrystallization texture of heavily cold-rolled pure copper is almost completely cubic. However, one of the main drawbacks concerning the use of pure copper cube-textured substrates for YBCO coated conductor is the reduced secondary recrystallization temperature. The onset of secondary recrystallization (i.e., the occurrence of abnormal grains with unpredictable orientation) in pure copper substrate was observed within the typical temperature range required for buffer layer and YBCO processing (600-850 °C). To avoid the formation of abnormal grains the effect of both grain size adjustment (GSA) and recrystallization annealing was analyzed. The combined use of a small initial grain size and a recrystallization two-step annealing (TSA) drastically reduced the presence of abnormal grains in pure copper tapes. Another way to overcome the limitation imposed by the formation of abnormal grains is to deposit a buffer layer at temperatures where secondary recrystallization does not occur. For example, La2Zr2O7 (LZO) film with a high degree of epitaxy was grown by metal-organic decomposition (MOD) at 1000 °C on pure copper substrate. In several samples the substrate underwent secondary recrystallization. Our experiments indicate that the motion of grain boundaries occurring during secondary recrystallization process does not affect the quality of LZO film.

  9. Inkjet printing of multifilamentary YBCO for low AC loss coated conductors

    NASA Astrophysics Data System (ADS)

    Hopkins, S. C.; Joseph, D.; Mitchell-Williams, T. B.; Calleja, A.; Vlad, V. R.; Vilardell, M.; Ricart, S.; Granados, X.; Puig, T.; Obradors, X.; Usoskin, A.; Falter, M.; Bäcker, M.; Glowacki, B. A.

    2014-05-01

    Considerable progress has been made with the development of REBCO coated conductors in recent years, and high performance conductors are available commercially. For many applications, however, the cost remains prohibitive, and AC losses discourage their selection for higher frequency applications. Chemical solution deposition (CSD) methods are attractive for low-cost, scalable preparation of buffer and superconductor layers, and in many respects inkjet printing is the method of choice, permitting non-contact deposition with minimal materials wastage and excellent control of coating thickness. Highly textured coatings of YBCO and Gd-doped CeO2 have previously been reported on buffered metal substrates. Inkjet printing also introduces the possibility of patterning - directly depositing two and three dimensional structures without subtractive processing - offering a low-cost route to coated conductors with reduced AC losses. In this contribution, the inkjet deposition of superconducting YBCO tracks is reported on industrially relevant buffered metal substrates both by direct printing and an inverse patterning approach. In the latter approach, ceria tracks were printed reported, which are a candidate both for resistive filament spacers and buffer layers. TFA-based precursor solutions have been printed on SS/ABAD-YSZ/CeO2 and Ni-W/LZO/CeO2 RABiTS substrates, and the resulting multifilamentary samples characterised by microscopy and scanning Hall probe measurements. The prospects for future inkjet-printed low AC loss coated conductors are discussed, including control of interfilamentary resistivity and bridging, transposed filamentary structures and stabilisation material.

  10. Estimation of magnetic relaxation property for CVD processed YBCO-coated conductors

    NASA Astrophysics Data System (ADS)

    Takahashi, Y.; Kiuchi, M.; Otabe, E. S.; Matsushita, T.; Shikimachi, K.; Watanabe, T.; Kashima, N.; Nagaya, S.

    2010-11-01

    Ion Beam Assist Deposition/Chemical Vapor Deposition(IBAD/CVD)-processed YBCO-coated conductors with high critical current density Jc at high magnetic fields are expected to be applied to superconducting equipments such as superconducting magnetic energy storage (SMES). For application to superconducting magnet in SMES one of the most important properties for superconductors is the relaxation property of superconducting current. In this paper, the relaxation property is investigated for IBAD/CVD-processed YBCO-coated conductors of the superconducting layer in the range of 0.18-0.90 μm. This property can be quantitatively characterized by the apparent pinning potential, U0∗. It is found that U0∗ takes a smaller value due to the two-dimensional pinning mechanism at high magnetic fields for conductor with thinner superconducting layer. Although U0∗ decreases with increasing thickness at low magnetic fields at 20 K, it increases at high magnetic fields. The results are theoretically explained by the model of the flux creep and flow based on the dimensionality of flux pinning. Scaling analysis is examined for the dependence of U0∗ on the magnetic field, temperature and the layer thickness.

  11. YBCO grain boundary Josephson junction coupled with a slot dipole antenna for terahertz wave detectors

    NASA Astrophysics Data System (ADS)

    Yamada, H.; Hayasaka, T.; Toya, G.; Saito, A.; Ohshima, S.; Nakajima, K.

    2014-05-01

    We examined terahertz wave detectors that used YBa2Cu3O7-δ (YBCO) grain boundary Josephson junctions (GBJJs) coupled with a slot dipole antenna (SDA). The detectors consisted of a 220-GHz full-wavelength SDA patterned on a Au layer and a GBJJ patterned on an YBCO/bicrystal MgO film, which were separated by an insulating benzocyclobutene layer. The microbridge of the fabricated junction was 5-μm wide and was trimmed to 2 μm using an ultraviolet laser cutter to modify the junction parameters. The critical current IC, normal resistance RN, and ICRN product after the trimming at 30 K were 0.62 mA, 1.42 Ω, and 0.88 mV, respectively. The current-voltage characteristics and radio frequency (RF) wave responses of these detectors for a millimeter wave of 180-240 GHz were measured at 30 K. The coupling efficiency between the GBJJ and the SDA and the system sensitivity were obtained as -19.0 dB and 630 V/W, respectively, at 193 GHz. For the RF wave response of 180-240 GHz, the coupling efficiency was relatively flat.

  12. Influence of Both Cooling Rate and TeO2 Addition on the Properties of YBCO Superconductor

    NASA Astrophysics Data System (ADS)

    Ahmed, Yasser Momtaz Zaki; Hassan, Mervat Said; Abd-Elatif, Hassan

    2016-08-01

    Composite of superconducting system YBCO-TeO2 was synthesized utilizing solid-state reaction technique. Different weight percentages of TeO2 were mixed with a basic mixture [YBCO] for the synthesis of [YBa2Cu3O7-y ]1-x (TeO2) x composites. These mixtures were sintered at 1213 K (940 °C) for 24 hours and the samples cooled down by two different ways. The first way carried out via slowly cooling in furnace with the rate of 274 K/min to 275 K/min (1 °C/min to 2 °C/min) and the second one is quenching in oxygen gas. The XRD analysis showed that YBCO orthorhombic phase is the major phase appeared in all samples with different TeO2 content regardless of the cooling way. Additionally, minor unknown secondary phases appeared and enlarged with increasing TeO2 addition. Although quenched samples showed a phase difference between the sample's outer surface (orthorhombic) and its interior (tetragonal), the slowly cooled one did not clearly show such distinction. Moreover, doping YBCO with TeO2 leads to increase in the sample bulk density and reduction in their degradation degree in the wet atmosphere.

  13. Some ceramic options

    SciTech Connect

    Zievers, J.F.; Eggerstedt, P.M.; Aguilar, P.C.; Zievers, E.C.

    1993-06-01

    Ceramic candle filters have proven to be an effective means of removing particulates to levels exceeding New Source Performance Standards (NSPS) in high temperature applications. The traditional {open_quotes}hard{close_quotes} ceramic filter elements, typically formed form granules however, have shown to be susceptible to failure from physical shock, thermal stress, and chemical attack. Additionally, these hard, dense candles can be costly and present internal filter design problems due to their relatively high weight. A good deal has been written about to use to porous ceramics in the filtration of high temperature gases for removal of particulate matter. Unlike the dense, granular ceramic filter elements, vacuum formed chopped ceramic fiber (VFCF) filters represent an attractive alternative. Composed of commercially available chopped ceramic fibers and utilizing existing vacuum forming technology, low cost filter elements with excellent physical and thermal shock resistance are now available. The ceramic fiber filter {open_quotes}skeleton{close_quotes} can be {open_quotes}post-treated{close_quotes} with refractory materials to enhance strength and chemical resistance, as well as to change permeability to suit a particular application. Also, because the ceramic fiber skeleton has greater porosity and is composed of low density materials, the final product is significantly lighter in weight than the traditional dense ceramic elements, making overall filter design an easier task. The use of ceramics extends beyond that of filter elements, however. Ceramics in the form of refractory have long been used to protect metal structures from high temperature and abrasion, and an extensive body of literature deals with this subject.

  14. Ceramic Technology Project

    SciTech Connect

    Not Available

    1992-03-01

    The Ceramic Technology Project was developed by the USDOE Office of Transportation Systems (OTS) in Conservation and Renewable Energy. This project, part of the OTS's Materials Development Program, was developed to meet the ceramic technology requirements of the OTS's automotive technology programs. Significant accomplishments in fabricating ceramic components for the USDOE and NASA advanced heat engine programs have provided evidence that the operation of ceramic parts in high-temperature engine environments is feasible. These programs have also demonstrated that additional research is needed in materials and processing development, design methodology, and data base and life prediction before industry will have a sufficient technology base from which to produce reliable cost-effective ceramic engine components commercially. A five-year project plan was developed with extensive input from private industry. In July 1990 the original plan was updated through the estimated completion of development in 1993. The objective is to develop the industrial technology base required for reliable ceramics for application in advanced automotive heat engines. The project approach includes determining the mechanisms controlling reliability, improving processes for fabricating existing ceramics, developing new materials with increased reliability, and testing these materials in simulated engine environments to confirm reliability. Although this is a generic materials project, the focus is on the structural ceramics for advanced gas turbine and diesel engines, ceramic bearings and attachments, and ceramic coatings for thermal barrier and wear applications in these engines. To facilitate the rapid transfer of this technology to US industry, the major portion of the work is being done in the ceramic industry, with technological support from government laboratories, other industrial laboratories, and universities.

  15. In-plane aligned YBCO film on textured YSZ buffer layer deposited on NiCr alloy tape by laser ablation with only O+ ion beam assistance

    NASA Astrophysics Data System (ADS)

    Tang Huang, Xin; Qing Wang, You; Wang, Qiu Liang; Chen, Qing Ming

    2000-02-01

    High critical current density and in-plane aligned YBa2 Cu3 O7-x (YBCO) film on a textured yttria-stabilized zirconia (YSZ) buffer layer deposited on NiCr alloy (Hastelloy c-275) tape by laser ablation with only O+ ion beam assistance was fabricated. The values of the x-ray phi-scan full width at half-maximum (FWHM) for YSZ(202) and YBCO(103) are 18° and 11°, respectively. The critical current density of YBCO film is 7.9 × 105 A cm-2 at liquid nitrogen temperature and zero field, and its critical temperature is 90 K.

  16. Industrial Ceramics: Secondary Schools.

    ERIC Educational Resources Information Center

    New York City Board of Education, Brooklyn, NY. Bureau of Curriculum Development.

    The expanding use of ceramic products in today's world can be seen in the areas of communications, construction, aerospace, textiles, metallurgy, atomic energy, and electronics. The demands of science have brought ceramics from an art to an industry using mass production and automated processes which requires the services of great numbers as the…

  17. Method of making a modified ceramic-ceramic composite

    DOEpatents

    Weaver, Billy L.; McLaughlin, Jerry C.; Stinton, David P.

    1995-01-01

    The present invention provides a method of making a shaped ceramic-ceramic composite articles, such as gas-fired radiant heat burner tubes, heat exchangers, flame dispersers, and other furnace elements, having a formed-on ceramic-ceramic composite thereon.

  18. Two-year evaluation of a new nano-ceramic restorative material.

    PubMed

    Schirrmeister, J F; Huber, K; Hellwig, E; Hahn, P

    2006-09-01

    The purpose of this prospective study was to evaluate the clinical performance of a new restorative material (Ceram.X) in combination with a new primer-adhesive (K-0127). One operator placed two Class I or II restorations in molars of 43 patients. One molar was restored with Ceram.X/K-0127, the other one with Tetric Ceram/Syntac Classic. At baseline, after 1 and 2 years, the restorations were evaluated by one evaluator using modified Ryge's criteria. After 2 years, 31 patients were examined. One Ceram.X-restoration had to be removed for root canal treatment due to pulpitis. Thus, failure rate of Ceram.X was 3.2% and of Tetric Ceram, 0%. In both groups, no sensitivity, no recurrent caries, and no changes in surface texture were recorded after 2 years. One restoration in each group showed slight changes in color stability (score B). Marginal discoloration (score B) was found concerning three Ceram.X-restorations (10.0%) and two Tetric Ceram-restoration (6.5%). Marginal integrity was score B for four Ceram.X-restorations (13.3%) and for four Tetric Ceram-restorations (12.9%). No statistically significant differences were found (p>0.05). After 2 years of clinical service, 96.8% of Ceram.X/K-0127 and 100% of Tetric Ceram/Syntac Classic restorations were in place and performed clinically well.

  19. Mounting for ceramic scroll

    DOEpatents

    Petty, Jack D.

    1993-01-01

    A mounting for a ceramic scroll on a metal engine block of a gas turbine engine includes a first ceramic ring and a pair of cross key connections between the first ceramic ring, the ceramic scroll, and the engine block. The cross key connections support the scroll on the engine block independent of relative radial thermal growth and for bodily movement toward an annular mounting shoulder on the engine. The scroll has an uninterrupted annular shoulder facing the mounting shoulder on the engine block. A second ceramic ring is captured between mounting shoulder and the uninterrupted shoulder on the scroll when the latter is bodily shifted toward the mouting shoulder to define a gas seal between the scroll and the engine block.

  20. Ceramic heat exchanger

    DOEpatents

    LaHaye, P.G.; Rahman, F.H.; Lebeau, T.P.; Severin, B.K.

    1998-06-16

    A tube containment system is disclosed. The tube containment system does not significantly reduce heat transfer through the tube wall. The contained tube is internally pressurized, and is formed from a ceramic material having high strength, high thermal conductivity, and good thermal shock resistance. The tube containment system includes at least one ceramic fiber braid material disposed about the internally pressurized tube. The material is disposed about the tube in a predetermined axial spacing arrangement. The ceramic fiber braid is present in an amount sufficient to contain the tube if the tube becomes fractured. The tube containment system can also include a plurality of ceramic ring-shaped structures, in contact with the outer surface of the tube, and positioned between the tube and the ceramic fiber braid material, and/or at least one transducer positioned within tube for reducing the internal volume and, therefore, the energy of any shrapnel resulting from a tube fracture. 6 figs.

  1. Ceramic heat exchanger

    DOEpatents

    LaHaye, Paul G.; Rahman, Faress H.; Lebeau, Thomas P. E.; Severin, Barbara K.

    1998-01-01

    A tube containment system. The tube containment system does not significantly reduce heat transfer through the tube wall. The contained tube is internally pressurized, and is formed from a ceramic material having high strength, high thermal conductivity, and good thermal shock resistance. The tube containment system includes at least one ceramic fiber braid material disposed about the internally pressurized tube. The material is disposed about the tube in a predetermined axial spacing arrangement. The ceramic fiber braid is present in an amount sufficient to contain the tube if the tube becomes fractured. The tube containment system can also include a plurality of ceramic ring-shaped structures, in contact with the outer surface of the tube, and positioned between the tube and the ceramic fiber braid material, and/or at least one transducer positioned within tube for reducing the internal volume and, therefore, the energy of any shrapnel resulting from a tube fracture.

  2. Recycling failed bulk YBCO superconductors using the NdBCO/YBCO/MgO film-seeded top-seeded melt growth method

    NASA Astrophysics Data System (ADS)

    Xu, H. H.; Cheng, L.; Yan, S. B.; Yu, D. J.; Guo, L. S.; Yao, X.

    2012-05-01

    REBa2Cu3Oy (RE123 or REBCO, RE = rare earth elements) bulk high-temperature superconductors have a potential perspective for large-scale engineering applications. However, the cost of REBCO bulk production is rather high, considering high failure rates, expensive RE materials, and Pt or Ag addition. Using the cold-seeding in the top-seeded melt growth, a simple and feasible process, we succeeded in recycling the failed REBCO (RE = Y) bulks. The distinctive feature of this recycling process is the use of YBCO-buffered NdBCO films as seeds, which have high thermal stability and can endure a maximum processing temperature (Tmax) up to 1120 °C to enable full decomposition of solid REBCO. Three typical microstructures were recognized in the failed samples attributed to the inherent differences in the non-optimized growth heating profiles. Preferential recycling procedures were chosen according to the difficulty of the failed-samples decomposition, which has a certain connection with the microstructures of the failed bulks. Finally, after oxygenation, the recycled bulks demonstrate good superconducting properties.

  3. High pressure ceramic joint

    DOEpatents

    Ward, M.E.; Harkins, B.D.

    1993-11-30

    Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present joint when used with recuperators increases the use of ceramic components which do not react to highly corrosive gases. Thus, the present joint used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present joint is comprised of a first ceramic member, a second ceramic member, a mechanical locking device having a groove defined in one of the first ceramic member and the second ceramic member. The joint and the mechanical locking device is further comprised of a refractory material disposed in the groove and contacting the first ceramic member and the second ceramic member. The present joint mechanically provides a high strength load bearing joint having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures. 4 figures.

  4. High pressure ceramic joint

    DOEpatents

    Ward, Michael E.; Harkins, Bruce D.

    1993-01-01

    Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present joint when used with recuperators increases the use of ceramic components which do not react to highly corrosive gases. Thus, the present joint used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present joint is comprised of a first ceramic member, a second ceramic member, a mechanical locking device having a groove defined in one of the first ceramic member and the second ceramic member. The joint and the mechanical locking device is further comprised of a refractory material disposed in the groove and contacting the first ceramic member and the second ceramic member. The present joint mechanically provides a high strength load bearing joint having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures.

  5. Ceramics for engines

    NASA Technical Reports Server (NTRS)

    Kiser, James D.; Levine, Stanley R.; Dicarlo, James A.

    1987-01-01

    Structural ceramics were under nearly continuous development for various heat engine applications since the early 1970s. These efforts were sustained by the properties that ceramics offer in the areas of high-temperature strength, environmental resistance, and low density and the large benefits in system efficiency and performance that can result. The promise of ceramics was not realized because their brittle nature results in high sensitivity to microscopic flaws and catastrophic fracture behavior. This translated into low reliability for ceramic components and thus limited their application in engines. For structural ceramics to successfully make inroads into the terrestrial heat engine market requires further advances in low cost, net shape fabrication of high reliability components, and improvements in properties such as toughness, and strength. These advances will lead to very limited use of ceramics in noncritical applications in aerospace engines. For critical aerospace applications, an additional requirement is that the components display markedly improved toughness and noncatastrophic or graceful fracture. Thus the major emphasis is on fiber-reinforced ceramics.

  6. Factors associated with biaxial texturing of Cu tapes for YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Kim, Y. H.; Sung, T. H.; Han, S. C.; Han, Y. H.; Jeong, N. H.; Kim, C. J.; Jun, B. H.; Oh, S. S.; Kim, H. S.; Kim, T. H.; No, K. S.

    2007-10-01

    A biaxially textured Cu(2 0 0) tape was used as a substrate for YBCO coated conductors by cold rolling followed by recrystallization heat treatment. In this work, we studied the influence of annealing conditions and final tape thickness on the recrystallization process. Phi (ϕ) scan and omega (ω) scan XRD revealed that the best in-plane and out-of-plane alignment of the Cu tape (thickness 100 μm), measured in terms of full width half maximum (FWHM) values of 6.64° and 4.49°, were obtained by annealing at 800 °C for 30 min. The texture of CeO2 buffer layer thermally-evaporated on the Cu tape was also analyzed.

  7. Engineered oxide thin films as 100% lattice match buffer layers for YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Akin, Y.; Heiba, Z. K.; Sigmund, W.; Hascicek, Y. S.

    2003-12-01

    One of the most important qualities of buffer layers for RE-BCO coated conductors' growth is close lattice match with RE-BCO. However, there is no natural material with a 100% lattice match with RE-BCO. In this study mixtures of europium oxide (Eu 2O 3) and ytterbium oxide (Yb 2O 3), (Eu 1- uYb u) 2O 3 (0.0⩽ u⩽1.0), were investigated as a candidate buffer layer that could have same lattice parameter as YBa 2Cu 3O 7- δ(YBCO). Because the pseudocubic lattice parameter of Eu 2O 3 is bigger, and that of Yb 2O 3 is smaller than lattice parameter of YBCO, and the mixed oxides with appropriate ratio would have same lattice parameter of YBCO. The mixtures were prepared using metal-organic precursor by sol-gel process, and it was found that all mixed samples are single phase, complete solid solutions, and have same crystal system over the whole range of " u". Lattice parameters of mixed (Eu 1- uYb u) 2O 3 oxide powders were changed between 10.86831 and 10.42828 Å which are lattice parameter of Eu 2O 3 and Yb 2O 3, respectively by changing the ratio of Eu/Yb in the mixture. Phase and lattice parameter analysis revealed that pseudocubic lattice parameter of (Eu 0.893Yb 0.107) 2O 3 is 3.82 Å which is same as the lattice parameter of YBCO. Textured (Eu 0.893Yb 0.107) 2O 3 buffer layers were grown on biaxially textured-Ni (1 0 0) substrates. The solution was prepared from Europium and Ytterbium 2,4-pentadioanate, and was deposited on the Ni substrates using a reel-to-reel sol-gel dip coating system. The textured films were annealed at 1150 °C for 10 min under 4% H 2-Ar gas flow. Extensive texture analysis has been done to characterize the texture of (Eu 0.893Yb 0.107) 2O 3 buffer layers. X-ray diffraction (XRD) of the buffer layer showed strong out-of-plane orientation on Ni tape. The (Eu 0.893Yb 0.107) 2O 3 (2 2 2) pole figure indicated a single cube-on-cube textured structure. The omega and phi scans revealed good out-of-plane and in-plane alignments. The full

  8. Calibration of Hall sensor array for critical current measurement of YBCO tape with ferromagnetic substrate

    NASA Astrophysics Data System (ADS)

    Zhu, Yunpeng; Wang, Gang; Liu, Liyuan; Yang, Xinsheng; Zhao, Yong

    2015-12-01

    HAS (Hall sensor array) is a powerful tool to detect the uniformity of HTS (high temperature superconductor) tape through mapping the distribution of remanent or shielding field along the surface of the tape. However, measurement of HTS tape with ferromagnetic parts by HSA is still an issue because the ferromagnetic substrate has influence on the magnetic field around the HTS layer. In this work, a continuous HSA system has been designed to measure the critical current of the YBCO tape with ferromagnetic substrate. The relationship between the remanent field and critical current was calibrated by the finite element method. The result showed that the HSA is an effective method for evaluating the critical current of the HTS tape with ferromagnetic substrate.

  9. 2D SQIF arrays using 20 000 YBCO high R n Josephson junctions

    NASA Astrophysics Data System (ADS)

    Mitchell, E. E.; Hannam, K. E.; Lazar, J.; Leslie, K. E.; Lewis, C. J.; Grancea, A.; Keenan, S. T.; Lam, S. K. H.; Foley, C. P.

    2016-06-01

    Superconducting quantum interference filters (SQIFs) have been created using two dimensional arrays of YBCO step-edge Josephson junctions connected together in series and parallel configurations via superconducting loops with a range of loop areas and loop inductances. A SQIF response, as evidenced by a single large anti-peak at zero applied flux, is reported at 77 K for step-edge junction arrays with the junction number N = 1 000 up to 20 000. The SQIF sensitivity (slope of peak) increased linearly with N up to a maximum of 1530 V T-1. Array parameters related to geometry and average junction characteristics are investigated in order to understand and improve the SQIF performance in high temperature superconducting arrays. Initial investigations also focus on the effect of the SQUID inductance factor on the SQIF sensitivity by varying both the mean critical current and the mean inductance of the loops in the array. The RF response to a 30 MHz signal is demonstrated.

  10. Experimental and numerical study of a YBCO pancake coil with a magnetic substrate

    NASA Astrophysics Data System (ADS)

    Zhang, Min; Kvitkovic, J.; Pamidi, S. V.; Coombs, T. A.

    2012-12-01

    A finite element model for a YBCO pancake coil with a magnetic substrate is developed in this paper. An axial symmetrical H formulation and the E-J power law are used to construct the model, with the magnetic substrate considered by introducing an extra time-dependent term in the formula. A pancake coil is made and tested. The measurement of critical current and transport loss is compared to the model result, showing good consistency. The influence of magnetic substrate in the condition of AC and DC current is studied. The AC loss decreases without a magnetic substrate. It is observed that when the applied DC current approaches the critical current the coil turn loss profile changes completely in the presence of magnetic substrate due to the change of magnetic field distribution.

  11. 2D SQIF arrays using 20 000 YBCO high R n Josephson junctions

    NASA Astrophysics Data System (ADS)

    Mitchell, E. E.; Hannam, K. E.; Lazar, J.; Leslie, K. E.; Lewis, C. J.; Grancea, A.; Keenan, S. T.; Lam, S. K. H.; Foley, C. P.

    2016-06-01

    Superconducting quantum interference filters (SQIFs) have been created using two dimensional arrays of YBCO step-edge Josephson junctions connected together in series and parallel configurations via superconducting loops with a range of loop areas and loop inductances. A SQIF response, as evidenced by a single large anti-peak at zero applied flux, is reported at 77 K for step-edge junction arrays with the junction number N = 1 000 up to 20 000. The SQIF sensitivity (slope of peak) increased linearly with N up to a maximum of 1530 V T‑1. Array parameters related to geometry and average junction characteristics are investigated in order to understand and improve the SQIF performance in high temperature superconducting arrays. Initial investigations also focus on the effect of the SQUID inductance factor on the SQIF sensitivity by varying both the mean critical current and the mean inductance of the loops in the array. The RF response to a 30 MHz signal is demonstrated.

  12. BIG films fabricated by PLD for magnetic flux visualisation of YBCO

    NASA Astrophysics Data System (ADS)

    Kawano, K.; Chakalov, R. A.; Kong, G.; Abell, J. S.; Kahl, S.; Grishin, A. M.

    2002-08-01

    Bi 3Fe 5O 12 (BIG) magneto-optic (MO) films have been grown onto (1 1 1) and (1 0 0) gadolinium gallium garnet substrates by pulsed laser deposition (PLD). X-ray and transmission electron microscopy measurements have confirmed the epitaxial growth of the BIG films on both substrate orientations. Faraday rotation angles of both films showed linear field dependence from -1600 to +1600 G and the saturated Faraday rotation angle values were ∼5 deg/μm and ∼7.8 deg/μm for the (1 1 1) and (1 0 0) oriented films, respectively. A change in the MO contrast of both films in applied magnetic field has been observed and magnetic flux distributions have been visualised in YBa 2Cu 3O 7- x (YBCO) bulk superconductor using the (0 0 1) oriented BIG film.

  13. Critical currents of YBCO tapes and Bi-2212 wires at different temperatures and magnetic fields

    SciTech Connect

    Lombardo, V.; Barzi, e.; Turrioni, D.; Zlobin, A.V.; /Fermilab

    2010-08-01

    Design studies for the cooling channel of a Muon Collider call for straight and helical solenoids generating field well in excess of the critical fields of state of the art Low Temperature Superconductors (LTS) such as Nb{sub 3}Sn or NbTi. Therefore, High Temperature Superconductors (HTS) will need to be used for the manufacturing of all or certain sections of such magnets to be able to generate and withstand the field levels at the cryogenic temperatures required by the new machine. In this work, two major High Temperature Superconductors - Bi2212 round wires and YBCO coated conductor tapes - are investigated to understand how critical current density of such conductors scales as a function of external field and operating temperature. This is vital information to make conductor choices depending on the application and to proceed with the design of such magnets.

  14. High-Tc Coated Conductors - Performance of Meter-Long YBCO/IBAD Flexible Tapes

    SciTech Connect

    Foltyn, S.R.; Arendt, P.N.; Dowden, P.C.; DePaula, R.F.; Groves J.R.; Coulter, J.Y.; Jia, Q.; Maley, M.P.; Peterson, D.E.

    1998-09-13

    One meter long tapes based on 50-100 {micro}m thick by 1 cm wide nickel alloy substrates have been coated in a continuous process with a textured yttria-stabilized zirconia layer by ion beam-assisted deposition, followed by a 1-2 {micro}m thick layer of YBCO by pulsed laser deposition. The best result to date is a tape with a critical current (I{sub c}) at 75 K of 96 A over an 87 cm measurement length. The overall critical current density and engineering current density are 1 MA/cm{sup 2} and 10 kA/cm{sup 2}, respectively. Using a special probe, individual I-V curves were generated for each centimeter of tape length in order to investigate longitudinal uniformity of the transport properties: the highest and lowest I{sub c} values fall within a range of {+-}25%.

  15. Radiation induced modifications on microstructure and related properties of high temperature superconductor YBCO

    NASA Astrophysics Data System (ADS)

    Marhas, Manmeet Kaur; Balakrishnan, K.; Saravanan, P.; Ganesan, V.; Srinivasan, R.; Kanjilal, D.; Mehta, G. K.; Vedwyas, M.; Ogale, S. B.; Pai, S. P.; Ramachandra Rao, M. S.; Pinto, R.; Mohan Rao, G.; Senthilnathan, S.; Mohan, S.

    Role of swift heavy ion irradiation on the modification of transport and structural properties of high temperature superconductors is studied. Good quality YBCO thin films prepared by high pressure oxygen sputtering and laser ablation were used in this investigation. Resistivity and atomic force microscopy (AFM) were mainly used to probe superconducting and microstructural modifications resulted from the irradiation of high energy and heavy ions like 100 MeV oxygen and 200 MeV silver. Radiation induced sputtering or erosion is likely to be a major disastrous component of such high energy irradiation that could be powerful in masking phase coherence effects, atleast in grain boundaries. The extent of damage/nature of defects other than columnar defects produced by swift heavy ions is discussed in the light of AFM measurements. The effect of high energy oxygen ion irradiation is anomalous. A clear annealing effect at higher doses is seen.

  16. Investigation of the bulk pinning force in YBCO superconducting films with nano-engineered pinning centres

    NASA Astrophysics Data System (ADS)

    Crisan, A.; Dang, V. S.; Yearwood, G.; Mikheenko, P.; Huhtinen, H.; Paturi, P.

    2014-08-01

    For practical applications of superconducting materials in applied magnetic fields, artificial pinning centres in addition to natural ones are required to oppose the Lorentz force. These pinning centres are actually various types of defects in the superconductor matrix. The pinning centres can be categorised on their dimension (volume, surface, or point) and on their character (normal cores or Δκ cores). We have used the Dew Hughes approach to determine the types of pinning centres present in various samples, with various thicknesses, temperatures and nanostructured additions to the superconducting matrix. Results show that normal surface pinning centres are present throughout almost all the samples, as dominant pinning mechanism. Such 2D extended pinning centres are mainly due to dislocations, grain boundaries, nanorods. Strong normal point pinning centres were found to be common in BZO doped YBCO samples. Other types of pinning centres, in various (minor) concentrations were also found in some of the samples.

  17. Magnetic levitation and its application for education devices based on YBCO bulk superconductors

    NASA Astrophysics Data System (ADS)

    Yang, W. M.; Chao, X. X.; Guo, F. X.; Li, J. W.; Chen, S. L.

    2013-10-01

    A small superconducting maglev propeller system, a small spacecraft model suspending and moving around a terrestrial globe, several small maglev vehicle models and a magnetic circuit converter have been designed and constructed. The track was paved by NdFeB magnets, the arrangement of the magnets made us easy to get a uniform distribution of magnetic field along the length direction of the track and a high magnetic field gradient in the lateral direction. When the YBCO bulks mounted inside the vehicle models or spacecraft model was field cooled to LN2 temperature at a certain distance away from the track, they could be automatically floating over and moving along the track without any obvious friction. The models can be used as experimental or demonstration devices for the magnetic levitation applications.

  18. (abstract) All Epitaxial Edge-geometry SNS Devices with Doped PBCO and YBCO Normal Layers

    NASA Technical Reports Server (NTRS)

    Barner, J. B.; Hunt, B. D.; Foote, M. C.

    1995-01-01

    We will present our results on tapered-edge-geometry SNS weak link fabricated from c-axis oriented base-, counterelectrode and normal layers using a variety of processing conditions. To date, we have employed a variety of different normal materials (Co-doped YBCO, Y-doped PBCO, Ca-doped PBCO). We have been examining the junction fabrication process in detail and we will present our methods. In particular, we have been examining both epitaxial and non-epitaxial milling mask overlayers and we will present a comparison of both methods. These devices behave similar to the expectations of the resisively shunted junction model and conventional SNS proximity effect models but with some differences which will be discussed. We will present the detailed systematics of our junctions including device parameters versus temperature, rf and dc magnetic response for the various processing conditions.

  19. Magnetization losses in superconducting YBCO conductor-on-round-core (CORC) cables

    NASA Astrophysics Data System (ADS)

    Majoros, M.; Sumption, M. D.; Collings, E. W.; van der Laan, D. C.

    2014-12-01

    Described are the results of magnetization loss measurements made at 77 K on several YBCO conductor-on-round-core (CORC) cables in ac magnetic fields of up to 80 mT in amplitude and frequencies of 50 to 200 Hz, applied perpendicular to the cable axis. The cables contained up to 40 tapes that were wound in as many as 13 layers. Measurements on the cables with different configurations were made as functions of applied ac field amplitude and frequency to determine the effects of their layout on ac loss. In large scale devices such as e.g. Superconducting Magnetic Energy Storage (SMES) magnets, the observed ac losses represent less than 0.1% of their stored energy.

  20. Numerical simulation and analysis of single grain YBCO processed from graded precursor powders

    NASA Astrophysics Data System (ADS)

    Zou, J.; Ainslie, M. D.; Hu, D.; Zhai, W.; Devendra Kumar, N.; Durrell, J. H.; Shi, Y.-H.; Cardwell, D. A.

    2015-03-01

    Large single-grain bulk high-temperature superconducting materials can trap high magnetic fields in comparison with conventional permanent magnets, making them ideal candidates to develop more compact and efficient devices, such as actuators, magnetic levitation systems, flywheel energy storage systems and electric machines. However, macro-segregation of Y-211 inclusions in melt processed Y-Ba-Cu-O (YBCO) limits the macroscopic critical current density Jc of such bulk superconductors, and hence, the potential trapped field. Recently, a new fabrication technique with graded precursor powders has been developed, which results in a more uniform distribution of Y-211 particles, in order to further improve the superconducting properties of such materials. In order to develop this graded fabrication technique further, a 3D finite-element numerical simulation based on the H-formulation is performed in this paper. The trapped field characteristics of a graded YBCO sample magnetized by the field cooling method are simulated to validate the model, and the simulation results are consistent with the experimental measurements. In addition, the influence of the graded technique and various graded Jc distributions for pulsed field magnetization, recognized widely as a practical route for magnetizing samples in bulk superconductor applications, is also investigated, with respect to the trapped field and temperature profiles of graded samples. This modelling framework provides a new technique for assessing the performance of various sizes and geometries of graded bulk superconductors, and by adjusting the Y-211, and hence Jc, distribution, samples can be fabricated based on this concept to provide application-specific trapped field profiles, such as the generation of either a high magnetic field gradient or a high level of uniformity for the traditionally conical, trapped field profile.

  1. Planar tunneling into Zn and Ni-doped YBCO thin films

    NASA Astrophysics Data System (ADS)

    Badica, E.; Greene, L. H.

    2001-03-01

    Superconducting thin films of Y_1Ba_2Cu_3-xM_xO_7-delta (M = Zn, Ni; x = 0, 0.01, 0.02, 0.08, and 0, 0.01, 0.02, 0.24 respectively) are grown in different crystallographic orientations, classified into c-axis and ab-oriented. The critical temperatures of the films are 90, 84, 81, 60K, and 90, 81 77K, for Zn and Ni doping, respectively. Planar tunneling spectroscopy into the ab-planes, using Pb and Bi counter-electrodes, shows that the gap-like feature scales with the critical temperature, and the magnitude of the surface-induced Andreev bound states (ABS) seen at zero bias decreases with increasing doping concentration. In the case of Zn-doping, the surface-induced ABS are quenched for the highest doping concentration used, consistent with previous measurements on ion-irradiated (1) and Pr-doped (2) YBCO thin films. A detailed comparison (3) of the influence of doping and disorder on the low-energy density of states of YBCO, as a function of temperature and externally applied magnetic field, will be presented. We acknowledge support from NSF (DMR 94-21957) and NSF (DMR 99-72087). 1. M. Aprili, M. Covington, E. Paraoanu, B. Niedermeier, and L. H. Greene, Phys. Rev. B 57, R8139 (1998); 2. M. Covington, and L. H. Greene, Phys. Rev. B 62, 12 440 (2000); 3. E. Badica, M. Aprili, M. Covington, and L. H. Greene, Proceedings for the SPIE 2000 Aerosense Symposium, 'Oxide Superconductors: Physics and Nano-engineering IV', April 24-28, 2000, Orlando, Florida.

  2. STANFORD IN-SITU HIGH RATE YBCO PROCESS: TRANSFER TO METAL TAPES AND PROCESS SCALE UP

    SciTech Connect

    Malcolm R. Beasley; Robert H.Hammond

    2009-04-14

    Executive Summary The materials science understanding of high rate low cost processes for Coated Conductor will benefit the application to power utilities for low loss energy transportation and power generation as well for DOD applications. The research in this program investigated several materials processing approaches that are new and original, and are not being investigated elsewhere. This work added to the understanding of the material science of high rate PVD growth of HTSC YBCO assisted by a liquid phase. A new process discovered uses amorphous glassy precursors which can be made at high rate under flexible conditions of temperature and oxygen, and later brought to conditions of oxygen partial pressure and temperature for rapid conversion to YBCO superconductor. Good critical current densities were found, but further effort is needed to optimize the vortex pinning using known artificial inclusions. A new discovery of the physics and materials science of vortex pinning in the HTSC system using Sm in place of Y came at growth at unusually low oxygen pressure resulting in clusters of a low or non superconducting phase within the nominal high temperature phase. The driving force for this during growth is new physics, perhaps due to the low oxygen. This has the potential for high current in large magnetic fields at low cost, applicable to motors, generators and transformers. The technical demands of this project were the motivation for the development of instrumentation that could be essential to eventual process scale up. These include atomic absorption based on tunable diode lasers for remote monitoring and control of evaporation sources (developed under DARPA support), and the utility of Fourier Transform Infrared Reflectivity (FTIR) for aid in the synthesis of complex thin film materials (purchased by a DURIP-AFOSR grant).

  3. Magnetic moment of single vortices in YBCO nano-superconducting particle: Eilenberger approach

    NASA Astrophysics Data System (ADS)

    Zakharchuk, I.; Sharafeev, A.; Belova, P.; Safonchik, M.; Traito, K. B.; Lähderanta, E.

    2013-12-01

    Temperature dependence of single vortex magnetic moment in nanosize superconducting particles is investigated in the framework of quasiclassical Eilenberger approach. Such nanoparticles can be used for preparation of high-quality superconducting thin films with high critical current density. In contrast to bulk materials where the vortex magnetic moment is totally determined by flux quantum, in nano-sized specimens (with characteristic size, D, much less than effective penetration depth, λeff) the quantization rule is violated and magnetic moment is proportional to D2/λ2eff(T). Due to strong repulsion between vortices in nanoparticles only a single vortex can be trapped in them. Because of small size of particles the screening current of the vortex is located near the vortex core where the current is quite high and comparable to depairing currents. Therefore, the superconducting electron density, ns, depends on the current value and the distance from the vortex core. This effect is especially important for superconductors having gap nodes, such as YBCO. The current dependence of ns in nanoparticles is analogous to the Volovik effect in flux-line lattice in bulk samples. The magnitude of the effect can be obtained by comparing the temperature dependence of magnetic moment in the vortex and in the Meissner states. In the last case the value of screening current is small and superconducting response to the external field is determined by London penetration depth. Because of importance of nonlinear and nonlocal effects, the quantum mechanical Eilenberger approach is applied for description of the vortex in nanoparticles. The flattening of 1/λ2eff(T) dependence has been found. A comparison of the theoretical results with experimental magnetization data in Meissner and mixed states of YBCO nanopowders has been done. The presence of nonlinear and nonlocal effects in vortex current distribution is clearly visible. The obtained results are important for the description

  4. Size effects of nano-scale pinning centers on the superconducting properties of YBCO single grains

    NASA Astrophysics Data System (ADS)

    Moutalbi, Nahed; Noudem, Jacques G.; M'chirgui, Ali

    2014-08-01

    High pinning superconductors are the most promising materials for power engineering. Their superconducting properties are governed by the microstructure quality and the vortex pinning behavior. We report on a study of the vortex pinning in YBa2Cu3O7-x (YBCO) single grain with defects induced through the addition of insulating nano-particles. In order to improve the critical current density, YBCO textured bulk superconductors were elaborated using the Top Seeded Melt Texture and Growth process with different addition amounts of Al2O3 nano-particles. Serving as strong pinning centers, 0.05% excess of Al2O3 causes a significant enhancement of the critical current density Jc under self field and in magnetic fields at 77 K. The enhanced flux pinning achieved with the low level of alumina nano-particles endorses the effectiveness of insulating nano-inclusions to induce effectives pinning sites within the superconducting matrix. On the other side, we focused on the effect of the size of pinning centers on the critical current density. This work was carried out using two batches of alumina nano-particles characterized by two different particle size distributions with mean diameters PSD1 = 20 nm and PSD2 = 2.27 μm. The matching effects of the observed pinning force density have been compared. The obtained results have shown that the flux pinning is closely dependent on the size of the artificial pinning centers. Our results suggest that the optimization of the size of the artificial pinning centers is crucial to a much better understanding of the pinning mechanisms and therefore to insure high superconducting performance for the practical application of superconducting materials.

  5. Properties of YBCO on LaMnO3-capped IBAD MgO-templates without Homo-epitaxial MgO layer.

    SciTech Connect

    Aytug, Tolga; Paranthaman, Mariappan Parans; Kim, Kyunghoon; Zhang, Yifei; Cantoni, Claudia; Zuev, Yuri L; Goyal, Amit; Thompson, James R; Christen, David K

    2009-01-01

    Previously, it has been well established that in an IBAD architecture for coated conductors, (1) LaMnO3 (LMO) buffer layers are structurally and chemically compatible with an underlying homo-epitaxial MgO layer and (2) high current density YBCO films can be grown on these LMO templates. In the present work, the homo-epi MgO layer has been successfully eliminated and a LMO cap layer was grown directly on the IBAD (MgO) template. The performance of the LMO/IBAD (MgO) samples has been qualified by depositing 1 m-thick YBCO coatings by pulsed laser deposition. Electrical transport measurements of YBCO films on the standard (with homo-epi MgO) and simplified (without homo-epi MgO) IBAD architectures were carried out. The angular dependencies of critical current density (Jc) are similar for both IBAD architectures. XRD measurements indicate good, c-axis aligned YBCO films. Transmission electron microscopy (TEM) images reveal that microstructures of YBCO/LMO/IBAD (MgO) and YBCO/LMO/homo-epi MgO/IBAD (MgO) templates are similar. These results demonstrate the strong potential of using LMO as a single cap layer directly on IBAD (MgO) for the development of a simplified IBAD architecture.

  6. Ceramic Stationary Gas Turbine Development. Technical progress report, April 1, 1993--October 31, 1994

    SciTech Connect

    1994-12-01

    This report summarizes work performed by Solar Technologies Inc. and its subcontractors, during the period April 1, 1993 through October 31, 1994 under Phase II of the DOE Ceramic Stationary Gas Turbine Development program. The objective of the program is to improve the performance of stationary gas turbines in cogeneration through the implementation of selected ceramic components.

  7. Magnetic and magnetotransport characterization of La0.7Sr0.3MnO3/YBCO/La0.7Sr0.3MnO3/YBCO spin valve

    NASA Astrophysics Data System (ADS)

    Dybko, K.; Aleshkevych, P.; Sawicki, M.; Przyslupski, P.

    2015-01-01

    We present magnetoresistance measurements on La0.7Sr0.3MnO3/YBCO/La0.7Sr0.3MnO3/YBCO (L1/Y1/L2/Y) heterostructure. The Ll/Y1/L2/Y spin valve shows large magnetoresistance peaks in coercive field at temperatures below the onset of the superconducting transition. The rotation in parallel magnetic field demonstrates a change of magnetoresistance; simultaneously the transition temperature to superconducting state Tc0(H=450 Oe, β) exhibits nonmonotonic dependence due to change of noncolinearity of magnetic moments of LSMO layers. Nonmonotonic change of the transition temperature as a function of angle is interpreted as a signature of generation of the triplet component superconducting phase in the Ll/Y1/L2/Y heterostructure.

  8. Making Ceramic Cameras

    ERIC Educational Resources Information Center

    Squibb, Matt

    2009-01-01

    This article describes how to make a clay camera. This idea of creating functional cameras from clay allows students to experience ceramics, photography, and painting all in one unit. (Contains 1 resource and 3 online resources.)

  9. Corrosion resistant ceramic materials

    DOEpatents

    Kaun, T.D.

    1996-07-23

    Ceramic materials are disclosed which exhibit stability in severely-corrosive environments having high alkali-metal activity, high sulfur/sulfide activity and/or molten halides at temperatures of 200--550 C or organic salt (including SO{sub 2} and SO{sub 2}Cl{sub 2}) at temperatures of 25--200 C. These sulfide ceramics form stoichiometric (single-phase) compounds with sulfides of Ca, Li, Na, K, Al, Mg, Si, Y, La, Ce, Ga, Ba, Zr and Sr and show melting-points that are sufficiently low and have excellent wettability with many metals (Fe, Ni, Mo) to easily form metal/ceramic seals. Ceramic compositions are also formulated to adequately match thermal expansion coefficient of adjacent metal components. 1 fig.

  10. Corrosion resistant ceramic materials

    DOEpatents

    Kaun, Thomas D.

    1996-01-01

    Ceramic materials which exhibit stability in severely-corrosive environments having high alkali-metal activity, high sulfur/sulfide activity and/or molten halides at temperatures of 200.degree.-550.degree. C. or organic salt (including SO.sub.2 and SO.sub.2 Cl.sub.2) at temperatures of 25.degree.-200.degree. C. These sulfide ceramics form stoichiometric (single-phase) compounds with sulfides of Ca, Li, Na, K, Al, Mg, Si, Y, La, Ce, Ga, Ba, Zr and Sr and show melting-points that are sufficiently low and have excellent wettability with many metals (Fe, Ni, Mo) to easily form metal/ceramic seals. Ceramic compositions are also formulated to adequately match thermal expansion coefficient of adjacent metal components.

  11. Corrosion resistant ceramic materials

    DOEpatents

    Kaun, Thomas D.

    1995-01-01

    Ceramic materials which exhibit stability in severely-corrosive environments having high alkali-metal activity, high sulfur/sulfide activity and/or molten halides at temperatures of 200.degree.-550.degree. C. or organic salt (including SO.sub.2 and SO.sub.2 Cl.sub.2) at temperatures of 25.degree.-200.degree. C. These sulfide ceramics form stoichiometric (single-phase) compounds with sulfides of Ca, Li, Na, K, Al, Mg, Si, Y, La, Ce, Ga, Ba, Zr and Sr and show melting-points that are sufficiently low and have excellent wettability with many metals (Fe, Ni, Mo) to easily form metal/ceramic seals. Ceramic compositions are also formulated to adequately match thermal expansion coefficient of adjacent metal components.

  12. Experiments with ceramic coatings

    NASA Technical Reports Server (NTRS)

    Lynn, E. K.; Rollins, C. T.

    1968-01-01

    Report describes the procedures and techniques used in the application of a ceramic coating and the evaluation of test parts through observation of the cracks that occur in this coating due to loading.

  13. Ceramic breeder materials

    SciTech Connect

    Johnson, C.E.

    1990-01-01

    The breeding blanket is a key component of the fusion reactor because it directly involves tritium breeding and energy extraction, both of which are critical to development of fusion power. The lithium ceramics continue to show promise as candidate breeder materials. This promise was recognized by the International Thermonuclear Reactor (ITER) design team in its selection of ceramics as the first option for the ITER breeder material. Blanket design studies have indicated properties in the candidate materials data base that need further investigation. Current studies are focusing on tritium release behavior at high burnup, changes in thermophysical properties with burnup, compatibility between the ceramic breeder and beryllium multiplier, and phase changes with burnup. Laboratory and in-reactor tests, some as part of an international collaboration for development of ceramic breeder materials, are underway. 32 refs., 1 fig., 1 tab.

  14. Ceramic heat pipe development

    NASA Astrophysics Data System (ADS)

    Merrigan, M.

    1980-09-01

    Ceramic materials used in conventional brickwork heat exchanger configurations increase allowable temperatures; however, joint leakage problems limit use of these designs. Ceramic tube heat exchanger designs reduce these problems but still require sliding joints and compliant tube end seals. Ceramic heat pipe based recuperator designs eliminate the sealing problems that limited the high temperature heat recovery installations. Heat pipe recuperators offer high corrosion and abrasion resistance, high temperature capability, reduced leakage, element redundancy, and simplified replacement and cleaning. The development of ceramic heat pipe recuperator elements involves the selection and test of materials and fabrication techniques having production potential, evaluation of technology in subscale tests, design and test of components for full scale recuperator applications, and demonstration of heat pipes in subscale and full scale recuperator installation.

  15. Super Thin Ceramic Coatings

    NASA Video Gallery

    New technology being developed at NASA's Glenn Research Center creates super thin ceramic coatings on engine components. The Plasma Spray – Physical Vapor Deposition (PS-PVD) rig uses a powerful ...

  16. Light emitting ceramic device

    DOEpatents

    Valentine, Paul; Edwards, Doreen D.; Walker, Jr., William John; Slack, Lyle H.; Brown, Wayne Douglas; Osborne, Cathy; Norton, Michael; Begley, Richard

    2010-05-18

    A light-emitting ceramic based panel, hereafter termed "electroceramescent" panel, is herein claimed. The electroceramescent panel is formed on a substrate providing mechanical support as well as serving as the base electrode for the device. One or more semiconductive ceramic layers directly overlay the substrate, and electrical conductivity and ionic diffusion are controlled. Light emitting regions overlay the semiconductive ceramic layers, and said regions consist sequentially of a layer of a ceramic insulation layer and an electroluminescent layer, comprised of doped phosphors or the equivalent. One or more conductive top electrode layers having optically transmissive areas overlay the light emitting regions, and a multi-layered top barrier cover comprising one or more optically transmissive non-combustible insulation layers overlay said top electrode regions.

  17. Advanced Ceramics Property Measurements

    NASA Technical Reports Server (NTRS)

    Salem, Jonathan; Helfinstine, John; Quinn, George; Gonczy, Stephen

    2013-01-01

    Mechanical and physical properties of ceramic bodies can be difficult to measure correctly unless the proper techniques are used. The Advanced Ceramics Committee of ASTM, C-28, has developed dozens of consensus test standards and practices to measure various properties of a ceramic monolith, composite, or coating. The standards give the "what, how, how not, and why" for measurement of many mechanical, physical, thermal, and performance properties. Using these standards will provide accurate, reliable, and complete data for rigorous comparisons with other test results from your test lab, or another. The C-28 Committee has involved academics, producers, and users of ceramics to write and continually update more than 45 standards since the committee's inception in 1986. Included in this poster is a pictogram of the C-28 standards and information on how to obtain individual copies with full details or the complete collection of standards in one volume.

  18. Ceramic fiber filter technology

    SciTech Connect

    Holmes, B.L.; Janney, M.A.

    1996-06-01

    Fibrous filters have been used for centuries to protect individuals from dust, disease, smoke, and other gases or particulates. In the 1970s and 1980s ceramic filters were developed for filtration of hot exhaust gases from diesel engines. Tubular, or candle, filters have been made to remove particles from gases in pressurized fluidized-bed combustion and gasification-combined-cycle power plants. Very efficient filtration is necessary in power plants to protect the turbine blades. The limited lifespan of ceramic candle filters has been a major obstacle in their development. The present work is focused on forming fibrous ceramic filters using a papermaking technique. These filters are highly porous and therefore very lightweight. The papermaking process consists of filtering a slurry of ceramic fibers through a steel screen to form paper. Papermaking and the selection of materials will be discussed, as well as preliminary results describing the geometry of papers and relative strengths.

  19. Fibrous ceramic insulation

    NASA Technical Reports Server (NTRS)

    Goldstein, H. E.

    1982-01-01

    Some of the reusable heat shielding materials used to protect the Space Shuttles, their manufacturing processes, properties, and applications are discussed. Emphases is upon ceramic materials. Space Shuttle Orbiter tiles are discussed.

  20. Fibrous ceramic insulation

    SciTech Connect

    Goldstein, H.E.

    1982-11-01

    Some of the reusable heat shielding materials used to protect the Space Shuttles, their manufacturing processes, properties, and applications are discussed. Emphasis is upon ceramic materials. Space Shuttle Orbiter tiles are discussed.

  1. Battery utilizing ceramic membranes

    DOEpatents

    Yahnke, Mark S.; Shlomo, Golan; Anderson, Marc A.

    1994-01-01

    A thin film battery is disclosed based on the use of ceramic membrane technology. The battery includes a pair of conductive collectors on which the materials for the anode and the cathode may be spin coated. The separator is formed of a porous metal oxide ceramic membrane impregnated with electrolyte so that electrical separation is maintained while ion mobility is also maintained. The entire battery can be made less than 10 microns thick while generating a potential in the 1 volt range.

  2. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2000-07-01

    This is the fourth quarterly report on a new study to develop a ceramic membrane/metal joint. The first experiments using the La-Sr-Fe-O ceramic are reported. Some of the analysis performed on the samples obtained are commented upon. A set of experiments to characterize the mechanical strength and thermal fatigue properties of the joints has been designed and begun. Finite element models of joints used to model residual stresses are described.

  3. Letter report on PCT/Monolith glass ceramic corrosion tests

    SciTech Connect

    Crawford, Charles L.

    2015-09-24

    The Savannah River National Laboratory (SRNL) is collaborating with personnel from Pacific Northwest National Laboratory (PNNL) to study advanced waste form glass ceramics for immobilization of waste from Used Nuclear Fuel (UNF) separations processes. The glass ceramic waste forms take advantage of both crystalline and glassy phases where ‘troublesome’ elements (e.g., low solubility in glass or very long-lived) partition to highly durable ceramic phases with the remainder of elements residing in the glassy phase. The ceramic phases are tailored to create certain minerals or unique crystalline structures that can host the radionuclides by binding them in their specific crystalline network while not adversely impacting the residual glass network (Crum et al., 2011). Glass ceramics have been demonstrated using a scaled melter test performed in a pilot scale (1/4 scale) cold crucible induction melter (CCIM) (Crum et al., 2014; Maio et al., 2015). This report summarizes recent results from both Phase I and Phase II bench scale tests involving crucible fabrication and corrosion testing of glass ceramics using the Product Consistency Test (PCT). Preliminary results from both Phase I and Phase II bench scale tests involving statistically designed matrices have previously been reported (Crawford, 2013; Crawford, 2014).

  4. High Jc YBCO coated conductors on non-magnetic metallic substrate using YSZ-based buffer layer architecture

    NASA Astrophysics Data System (ADS)

    Celentano, G.; Boffa, V.; Ciontea, L.; Fabbri, F.; Galluzzi, V.; Gambardella, U.; Mancini, A.; Petrisor, T.; Rogai, R.; Rufoloni, A.; Varesi, E.

    2002-08-01

    Biaxially aligned YBa 2Cu 3O 7- δ (YBCO) thick films were deposited by pulsed laser ablation technique on cube textured non-magnetic Ni 89V 11 (Ni-V) substrate, using CeO 2/YSZ/CeO 2/NiO buffer layer architecture. The first NiO seed layer was formed by epitaxial oxidation of the Ni-V substrate. Structural analyses show typical full width at half maximum values of φ- and ω-scans less than 10° and 8°, respectively. The highest value obtained for the critical current density at 77 K and zero magnetic field was 6×10 5 A cm -2, which is close to that obtained for YBCO films grown on CeO 2/NiO buffer layer architecture.

  5. Crystalline phase transition information induced by high temperature susceptibility transformations in bulk PMP-YBCO superconductor growth in-situ

    NASA Astrophysics Data System (ADS)

    Zhang, C. P.; Chaud, X.; Beaugnon, E.; Zhou, L.

    2015-01-01

    The dynamic susceptibility transformations of bulk HTSC PMP-YBCO growth have been investigated from 200 °C up to 1060 °C by the Faraday Balance in-situ. It revealed that the crystalline phase transitions of bulk PMP-YBCO growth in process. A new discovery of Y123 phase pre-formed then melted in heating stage has been found. It also discovered that Y123 crystal solidification started at 1004 °C in cooling stage. Before Y123 solidification the liquid phase CuO change to Cu2O reciprocally as well as the copper ion valence changed between divalent Cu2+ and trivalent Cu1+ each other. It was essential to keep quantities of CuO phase instead of the Cu2O for Y123 crystal solidification.

  6. Strong vortex matching effects in YBCO films with periodic modulations of the superconducting order parameter fabricated by masked ion irradiation

    NASA Astrophysics Data System (ADS)

    Haag, L. T.; Zechner, G.; Lang, W.; Dosmailov, M.; Bodea, M. A.; Pedarnig, J. D.

    2014-08-01

    We report on measurements of the magnetoresistance and of the critical current in thin films of the high-temperature superconductor YBa2Cu3O7-δ (YBCO). A square array of regions with suppressed superconducting order parameter has been created in these films by introducing point defects via irradiation with He+ ions through a silicon stencil mask. In such a structure distinct peaks of the critical current can be observed at commensurate arrangements of magnetic flux quanta with the artificial defect lattice. Concurrently, the magnetoresistance shows pronounced minima. Both observations demonstrate that the strong intrinsic pinning in YBCO can be overcome by a periodic array of ion-damage columns with 300 nm spacing.

  7. EBSD characterisation of Y2Ba4CuUOx phase in melttextured YBCO with addition of depleted uranium oxide

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Mücklich, F.; Koblischka, M. R.; Babu, N. Hari; Cardwell, D. A.

    2006-06-01

    Melt-textured YBCO samples processed with added Y2O3 and depleted uranium oxide (DU) contain nano-particles, which have been identified previously as Y2Ba4CuUOx (U-411). This phase has a cubic unit cell, which is clearly distinct from the orthorhombic Y-123 and Y-211 phases within the YBCO system. In samples with a high amount of DU addition (0.8 wt-% DU), U-2411 particles have sizes between 200 nm and several µm, so identification of the Kikuchi patterns of this phase becomes possible. Together with a parallel EDX analysis, the particles embedded in the Y-123 matrix can be identified unambiguously. In this way, a three-phase EBSD scan becomes possible, allowing also the identification of nanometre-sized particles in the sample microstructure.

  8. A simple multi-seeding approach to growth of large YBCO bulk with a diameter above 53 mm

    NASA Astrophysics Data System (ADS)

    Tang, Tian-wei; Wu, Dong-jie; Wu, Xing-da; Xu, Ke-Xi

    2015-12-01

    A successful simple multi-seeding approach to growing large size Y-Ba-C-O (YBCO) bulks is reported. Compared with the common single seeding method, our multi-seeding method is more efficient. By using four SmBa2Cu3O7-δ (Sm-123) seeds cut from a large size Sm-Ba-C-O (SmBCO) single domain, large YBCO samples up to 53 mm in diameter could be produced successfully and 100 mm diameter samples can also be grown. Experimental results show that the processing time can be shortened greatly by using this new approach, and the superconducting properties can also be improved. The Hall probe mapping shows that the trapped field distribution of 53 mm diameter multi-seeded sample is homogeneous and the peak value is up to 0.53 T. The magnetic levitation force density reaches to 14.7 N/cm2 (77 K, 0.5 T).

  9. Ceramic electrolyte coating and methods

    SciTech Connect

    Seabaugh, Matthew M.; Swartz, Scott L.; Dawson, William J.; McCormick, Buddy E.

    2007-08-28

    Aqueous coating slurries useful in depositing a dense coating of a ceramic electrolyte material (e.g., yttrium-stabilized zirconia) onto a porous substrate of a ceramic electrode material (e.g., lanthanum strontium manganite or nickel/zirconia) and processes for preparing an aqueous suspension of a ceramic electrolyte material and an aqueous spray coating slurry including a ceramic electrolyte material. The invention also includes processes for depositing an aqueous spray coating slurry including a ceramic electrolyte material onto pre-sintered, partially sintered, and unsintered ceramic substrates and products made by this process.

  10. Industry turns to ceramic composites

    SciTech Connect

    Constance, J.

    1990-03-01

    Developments in the area of ceramic composites, which can be used to construct stronger, lighter weight, and more fuel-efficient aircraft, are examined. Ceramic composites are applicable aircraft braking systems, hypersonic fuselage skins, engine parts, and missile guidance fins. The production and testing of new ceramic composites are discussed. Consideration is given to the production of ceramic composites of an alumina or aluminum nitride matrix; developing glass ceramic matrix composites and silicon nitride matrix composites; and improving synthesis and processing technology to enhance the reliability of ceramic composites.

  11. Clinical application of bio ceramics

    NASA Astrophysics Data System (ADS)

    Anu, Sharma; Gayatri, Sharma

    2016-05-01

    Ceramics are the inorganic crystalline material. These are used in various field such as biomedical, electrical, electronics, aerospace, automotive and optical etc. Bio ceramics are the one of the most active areas of research. Bio ceramics are the ceramics which are biocompatible. The unique properties of bio ceramics make them an attractive option for medical applications and offer some potential advantages over other materials. During the past three decades, a number of major advances have been made in the field of bio ceramics. This review focuses on the use of these materials in variety of clinical scenarios.

  12. Alumina-based ceramic composite

    DOEpatents

    Alexander, K.B.; Tiegs, T.N.; Becher, P.F.; Waters, S.B.

    1996-07-23

    An improved ceramic composite comprising oxide ceramic particulates, nonoxide ceramic particulates selected from the group consisting of carbides, borides, nitrides of silicon and transition metals and mixtures thereof, and a ductile binder selected from the group consisting of metallic, intermetallic alloys and mixtures thereof is described. The ceramic composite is made by blending powders of the ceramic particulates and the ductile to form a mixture and consolidating the mixture of under conditions of temperature and pressure sufficient to produce a densified ceramic composite. 5 figs.

  13. Development of a 20 GHz scanned beam microstrip antenna array with a proximity coupled YBCO feed network

    SciTech Connect

    Mittleman, S.D.; Herd, J.S.; Kenny, J.P.; Poles, L.D.; Champion, M.H.; Rainville, P.J.; Silva, J.H.

    1994-12-31

    A superconducting antenna array with a proximity coupled feed network operating at 20 GHz has been developed. The antenna is a 4x4 array and its performance was measured from 18 GHz to 22 GHz. At temperatures below 80 K, there was a 15 dBi gain measured at several frequencies in this range. The design of a low loss superconducting phase shifter monolithically incorporated into the YBCO feed network is indicated.

  14. Manufacture of YBCO Superconducting Flexible Tapes from Nanoparticle Films Derived from Sedimentation and by Flame Deposition of Nanoparticles from Solution

    SciTech Connect

    Wiesmann, Harold

    2008-02-24

    The objective of this CRADA was to develop the experimental and theoretical basis of a technology to produce yttrium barium copper oxide (YBCO) superconducting flexible tapes derived from nanoparticle metal oxide sols. The CRADA was a joint effort between Oxford Superconducting Technology, Brookhaven National Laboratory and Karpov Institute of Physical Chemistry. The effort was divided into three main tasks, the synthesis of a heteroepitaxial oxide buffer layer, and the manufacture of a flexible biaxially textured metallic substrate and the synthesis of a heteroepitaxial crystalline YBCO layer. The formation of a heteroepitaxial buffer layer was implemented using technology developed at the Karpov Institute of Physical Chemistry for the synthesis, stabilization and deposition of polymer stabilized nanoparticle metal oxide sols. Using this technology, flexible oriented RABiTS nickel tapes, manufactured and supplied by the CRADA partner, Oxford Superconducting Technology, Carteret, New Jersey, were coated with a film of metal oxide nanoparticles. After coating the RABiTS nickel tapes with the nanoparticle sols the nickel tape/nanoparticle composite structure was sintered in order to form a dense crystalline heteroepitaxial oxide layer on the surface of the tape, also known as a ‘buffer’ layer. The final phase of the research was the formation of a heteroepitaxial YBCO layer, grown on top of the metal oxide buffer layer. This work was scheduled to follow the development of the heteroepitaxial oxide buffer layer as described above. Three different polymer stabilized sols, yttrium hydroxide, Y(OH){sub 3}, copper hydroxide, Cu(OH){sub 2}, and barium fluoride, BaF{sub 2}, were synthesized and combined in the appropriate stoichiometric ratio. This metal oxide sol was then be deposited onto the buffer layer and reacted to form a crystalline heteroepitaxial YBCO film ranging from 1–5 microns thick.

  15. All-ceramic alternatives to conventional metal-ceramic restorations.

    PubMed

    McLaren, E A

    1998-03-01

    In the search for the ultimate esthetic restorative material, many new all-ceramic systems have been introduced to the market. One such system, In-Ceram, is primarily crystalline in nature, whereas all other forms of ceramics used in dentistry consist primarily of a glass matrix with a crystalline phase as a filler. In-Cream can be used to make all-ceramic crowns and fixed partial denture frameworks. Three forms of In-Ceram, based on alumina, spinal (a mixture of alumina and magnesia), or zirconia, make it possible to fabricate frameworks of various translucencies by using different processing techniques. This article discusses clinical indications and contraindications for the use of In-Ceram Alumina and In-Ceram Spinell all-ceramic restorations. Particular attention is given to cement considerations using several clinical examples.

  16. Improvements in Crystal Structure of Two Inch Double-Sided YBCO Thin Films by Preseeded Self-Template Layer

    NASA Astrophysics Data System (ADS)

    Li, Yanrong; Liu, Xingzhao; Tao, Bowan; Zhang, Ying; Deng, Xinwu

    2003-03-01

    A self-template layer was employed to improve the crystal structure and microwave properties of large-area double-sided YBCO thin films. Two-inch double-sided YBCO thin films with excellent out-of-plane orientation and lateral homogeneity of microwave surface resistance were prepared by using a preseeded self-template layer. The full width at half maximum (FWHM) value of the rocking curve as low as 0.15° was achieved. The electronic channeling pattern was very sharp, clear and symmetric. The values of microwave surface resistance Rs (75 K, 145 GHz, 0 T) below 55 mΩ were obtained over the entire YBCO thin films on 2-inch LaAlO3 wafers. The majority of the wafer area given in percent has Rs (75 K, 145 GHz, 0 T) values in the range from 15 mΩ to 40 mΩ. The high frequency (HF) power handling capability was demonstrated by a breakdown field higher than 6 mT at 8.5 GHz and 77 K.

  17. Peculiarities of the current-voltage characteristics of a Josephson medium in a YBCO high-temperature superconductor

    NASA Astrophysics Data System (ADS)

    Vasyutin, M. A.

    2013-12-01

    The influence of a weak magnetic field ( H < 150 Oe) on the current-voltage ( I- U) characteristic of a YBa2Cu3O7 - x (YBCO) high-temperature superconductor (HTSC) near the superconducting transition temperature has been studied. It is established that there exist narrow (<0.2 K) temperature regions where the I- U curve exhibits sharp bending for H < 30 Oe and the ohmic behavior changes to a quadratic dependence of the voltage on current in a region of several milliamperes. At higher temperatures, the I- U curve bending exhibits smearing. This behavior is observed at a temperature below that corresponding to a zero critical current. Above a certain current, the temperature and magnetic field exhibit equivalent effects on the I- U curve of YBCO. Experimental results are explained by a sharp decrease in the critical currents of intergranular Josephson junctions under the action of magnetic field and by the current-induced formation of uncoupled (with respect to the order parameter) superconducting grains. Characteristic currents for the transition of the intergranular Josephson medium into an incoherent state are determined and the first critical fields in YBCO are evaluated.

  18. An electron backscatter diffraction investigation of crystallographic orientations of embedded nanoparticles within melt-textured YBCO high temperature superconductors

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Babu, N. Hari; Cardwell, D. A.; Shlyk, L.; Krabbes, G.

    2006-07-01

    Microstructures of melt-textured YBCO samples with embedded nanosized particles of Y2BaCuO5 (Y-211) and Y2Ba4CuMOx (M-2411 with M = U,Zr) are analysed by means of electron backscatter diffraction (EBSD). With the recent developments of the EBSD technique, we can directly measure the crystallographic orientation of the embedded nanoparticles, employing a spatial resolution of about 40 nm. The high image quality of the Kikuchi patterns allows true three-phase (YBCO, Y-211 and M-2411) scans to be performed. The Y-211 particles do not exhibit any preferred orientation, even if their size is considerably reduced, to the 100 nm range. The size reduction reduces the negative influence of the Y-211 particles on the YBCO matrix, however. U-2411 particles, which are formed during the processing stage, do not show any orientation, and with increasing concentration, some texture develops. In contrast to this, embedded Zr-2411 particles are fully oriented in the (001) orientation according to the surrounding superconducting matrix.

  19. Field Performance of an Optimized Stack of YBCO Square “Annuli” for a Compact NMR Magnet

    PubMed Central

    Hahn, Seungyong; Voccio, John; Bermond, Stéphane; Park, Dong-Keun; Bascuñán, Juan; Kim, Seok-Beom; Masaru, Tomita; Iwasa, Yukikazu

    2011-01-01

    The spatial field homogeneity and time stability of a trapped field generated by a stack of YBCO square plates with a center hole (square “annuli”) was investigated. By optimizing stacking of magnetized square annuli, we aim to construct a compact NMR magnet. The stacked magnet consists of 750 thin YBCO plates, each 40-mm square and 80- μm thick with a 25-mm bore, and has a Ø10 mm room-temperature access for NMR measurement. To improve spatial field homogeneity of the 750-plate stack (YP750) a three-step optimization was performed: 1) statistical selection of best plates from supply plates; 2) field homogeneity measurement of multi-plate modules; and 3) optimal assembly of the modules to maximize field homogeneity. In this paper, we present analytical and experimental results of field homogeneity and temporal stability at 77 K, performed on YP750 and those of a hybrid stack, YPB750, in which two YBCO bulk annuli, each Ø46 mm and 16-mm thick with a 25-mm bore, are added to YP750, one at the top and the other at the bottom. PMID:22081753

  20. Effect of addition of BaTiO3 nano particles on the electrical transport properties of YBCO superconductor

    NASA Astrophysics Data System (ADS)

    Rejith, P. P.; Vidya, S.; Thomas, J. K.

    2015-02-01

    The flux pinning properties of YBCO bulk superconductors synthesized by conventional solid state route and are added with different weight% (x=0, 0.5, 1, 2, 3, 5) of nano BaTiO3 which are prepared by a modified combustion route are studied systematically. The phase analysis of the samples was done by using X-ray diffraction and scanning electron microscopy. Temperature-resistivity measurements, magnetic field dependence of critical current density (Jc-B Characteristics) and flux pinning force calculations were done at 77 K. From the SEM images the microstructure of the sample showed a relative uniform distribution of the nano-particles within the specimen. We found that, even though the transition temperature (Tc) does not change considerably with the BaTiO3 addition, both the critical current density (Jc) and flux pinning force (Fp) increased systematically up to 2 wt% BaTiO3 in the composite, in the presence of magnetic field ranging between 0 and 0.6 T. The Jc value in 2 wt% BaTiO3 added sample showed at least 250% larger than that of the pure YBCO. Also the flux pinning force calculated for the 2 wt% BaTiO3 added is found to be enhanced more than 9 times that of pure YBCO. These observations suggest that the BaTiO3 addition to the Y-123- compounds improve the electrical connection between superconducting grains to result in the increase in Jc.

  1. Pulsed laser deposition of c-axis untilted YBCO films on c-axis tilted ISD MgO-buffered metallic substrates

    NASA Astrophysics Data System (ADS)

    Li, M.; Ma, B.; Koritala, R. E.; Fisher, B. L.; Venkataraman, K.; Maroni, V. A.; Vlasko-Vlasov, V.; Berghuis, P.; Welp, U.; Gray, K. E.; Balachandran, U.

    2003-05-01

    Biaxially textured MgO template layer was deposited on nontextured metal substrates by inclined-substrate deposition (ISD) at a deposition rate of 24-600 nm/min. c-axis untilted YBa 2Cu 3O 7- x (YBCO) films were deposited on these MgO-buffered substrates by pulsed laser deposition. The crystalline structures of the YBCO films and MgO layers were examined by X-ray pole figure analysis, X-ray φ-scans, and χ-scans. A tilt angle of 33° of the MgO[0 0 1] with respect to the substrate normal and c-axis untilted YBCO films were observed, respectively. Good biaxial texture of these films with full-width-at-half-maximum values of 13.8° and 10.6° for the φ-scans of YBCO(1 0 3) and MgO(2 2 0), respectively, were obtained. Morphologies were examined by scanning electron microscopy, which revealed a unique roof-tile feature and columnar grain growth for the ISD MgO layer. Raman spectroscopy and magneto-optical image technique were also used to evaluate the quality of the YBCO film. An angular dependence of Jc on the direction of an applied magnetic field confirmed the c-axis untilted orientation of the YBCO films. Tc=90 K with sharp transition and Jc=3.0×10 5 A/cm 2 at 77 K in zero field were obtained on 0.4-μm-thick YBCO films.

  2. Fundamental tribological properties of ceramics

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.; Miyoshi, K.

    1985-01-01

    When a ceramic is brought into contact with itself, another ceramic, or a metal, strong bond forces can develop between the materials. Adhesion between a ceramic and itself or another solid are discussed from a theoretical consideration of the nature of the surfaces and experimentally by relating bond forces to the interface resulting from solid state contact. Elastic, plastic, and fracture behavior of ceramics in solid-state contact are discussed as they relate to friction and wear. The contact load necessary to initiate fracture in ceramics is shown to be appreciably reduced with tangential motion. Both friction and wear of ceramics are anisotropic and relate to crystal structure as with metals. Both free energy of oxide formation and the d valence bond character of metals are related to the friction and wear characteristics for metals in contact with ceramics. Lubrication is found to increase the critical load necessary to initiate fracture of ceramics with sliding or rubbing contact.

  3. Piezoelectric Ceramics and Their Applications

    ERIC Educational Resources Information Center

    Flinn, I.

    1975-01-01

    Describes the piezoelectric effect in ceramics and presents a quantitative representation of this effect. Explains the processes involved in the manufacture of piezoelectric ceramics, the materials used, and the situations in which they are applied. (GS)

  4. Microstructure and properties of ceramics

    NASA Technical Reports Server (NTRS)

    Hamano, K.

    1984-01-01

    The history of research into the microstructure and properties of ceramic ware is discussed; methods of producing ceramics with particular characteristics are investigated. Bubbles, sintering, cracks, and electron microscopy are discussed.

  5. Genotoxicity test of self-renovated ceramics in primary human peripheral lymphocytes.

    PubMed

    Hua, Nan; Zhu, Huifang; Zhuang, Jing; Chen, Liping

    2014-12-01

    Zirconia-based ceramics is widely used in dentistry. Different compositions of ceramics have different features. Our self-renovated ceramics become more machinable without scarifying its dental restoration properties after adjusting ratio of lanthanum phosphate (LaPO4)/yttrium oxide (Y2O3). In order to evaluate its safety, here, we tested its genotoxicity in primary human peripheral lymphocytes. The human lymphocytes cultured on three groups of different ratios of LaPO4/Y2O3 diphase ceramics for 6 days showed little effect of growth inhibition and similar effect of growth trend to the negative control. Furthermore, single-cell gel electrophoresis (comet assay) indicated that there was no significant difference of the value of tail moment between the tested ceramics and negative control, the IPS Empress II (P > 0.05). Our findings implicate that our self-renovated ceramics do not induce DNA damages in human peripheral lymphocytes and support their future clinic application.

  6. Ceramic microstructure and adhesion

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1985-01-01

    When a ceramic is brought into contact with a ceramic, a polymer, or a metal, strong bond forces can develop between the materials. The bonding forces will depend upon the state of the surfaces, cleanliness and the fundamental properties of the two solids, both surface and bulk. Adhesion between a ceramic and another solid are discussed from a theoretical consideration of the nature of the surfaces and experimentally by relating bond forces to interface resulting from solid state contact. Surface properties of ceramics correlated with adhesion include, orientation, reconstruction and diffusion as well as the chemistry of the surface specie. Where a ceramic is in contact with a metal their interactive chemistry and bond strength is considered. Bulk properties examined include elastic and plastic behavior in the surficial regions, cohesive binding energies, crystal structures and crystallographic orientation. Materials examined with respect to interfacial adhesive interactions include silicon carbide, nickel zinc ferrite, manganese zinc ferrite, and aluminum oxide. The surfaces of the contacting solids are studied both in the atomic or molecularly clean state and in the presence of selected surface contaminants.

  7. Ceramic combustor mounting

    DOEpatents

    Hoffman, Melvin G.; Janneck, Frank W.

    1982-01-01

    A combustor for a gas turbine engine includes a metal engine block including a wall portion defining a housing for a combustor having ceramic liner components. A ceramic outlet duct is supported by a compliant seal on the metal block and a reaction chamber liner is stacked thereon and partly closed at one end by a ceramic bypass swirl plate which is spring loaded by a plurality of circumferentially spaced, spring loaded guide rods and wherein each of the guide rods has one end thereof directed exteriorly of a metal cover plate on the engine block to react against externally located biasing springs cooled by ambient air and wherein the rod spring support arrangement maintains the stacked ceramic components together so that a normal force is maintained on the seal between the outlet duct and the engine block under all operating conditions. The support arrangement also is operative to accommodate a substantial difference in thermal expansion between the ceramic liner components of the combustor and the metal material of the engine block.

  8. FATIGUE OF DENTAL CERAMICS

    PubMed Central

    Zhang, Yu; Sailer, Irena; Lawn, Brian R

    2013-01-01

    Objectives Clinical data on survival rates reveal that all-ceramic dental prostheses are susceptible to fracture from repetitive occlusal loading. The objective of this review is to examine the underlying mechanisms of fatigue in current and future dental ceramics. Data/sources The nature of various fatigue modes is elucidated using fracture test data on ceramic layer specimens from the dental and biomechanics literature. Conclusions Failure modes can change over a lifetime, depending on restoration geometry, loading conditions and material properties. Modes that operate in single-cycle loading may be dominated by alternative modes in multi-cycle loading. While post-mortem examination of failed prostheses can determine the sources of certain fractures, the evolution of these fractures en route to failure remains poorly understood. Whereas it is commonly held that loss of load-bearing capacity of dental ceramics in repetitive loading is attributable to chemically-assisted 'slow crack growth' in the presence of water, we demonstrate the existence of more deleterious fatigue mechanisms, mechanical rather than chemical in nature. Neglecting to account for mechanical fatigue can lead to gross overestimates in predicted survival rates. Clinical significance Strategies for prolonging the clinical lifetimes of ceramic restorations are proposed based on a crack-containment philosophy. PMID:24135295

  9. Ceramic microstructure and adhesion

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1984-01-01

    When a ceramic is brought into contact with a ceramic, a polymer, or a metal, strong bond forces can develop between the materials. The bonding forces will depend upon the state of the surfaces, cleanliness and the fundamental properties of the two solids, both surface and bulk. Adhesion between a ceramic and another solid are discussed from a theoretical consideration of the nature of the surfaces and experimentally by relating bond forces to interface resulting from solid state contact. Surface properties of ceramics correlated with adhesion include, orientation, reconstruction and diffusion as well as the chemistry of the surface specie. Where a ceramic is in contact with a metal their interactive chemistry and bond strength is considered. Bulk properties examined include elastic and plastic behavior in the surficial regions, cohesive binding energies, crystal structures and crystallographic orientation. Materials examined with respect to interfacial adhesive interactions include silicon carbide, nickel zinc ferrite, manganese zinc ferrite, and aluminum oxide. The surfaces of the contacting solids are studied both in the atomic or molecularly clean state and in the presence of selected surface contaminants.

  10. Ceramic impregnated superabrasives

    DOEpatents

    Radtke, Robert P.; Sherman, Andrew

    2009-02-10

    A superabrasive fracture resistant compact is formed by depositing successive layers of ceramic throughout the network of open pores in a thermally stable self-bonded polycrystalline diamond or cubic boron nitride preform. The void volume in the preform is from approximately 2 to 10 percent of the volume of the preform, and the average pore size is below approximately 3000 nanometers. The preform is evacuated and infiltrated under at least about 1500 pounds per square inch pressure with a liquid pre-ceramic polymerizable precursor. The precursor is infiltrated into the preform at or below the boiling point of the precursor. The precursor is polymerized into a solid phase material. The excess is removed from the outside of the preform, and the polymer is pyrolized to form a ceramic. The process is repeated at least once more so as to achieve upwards of 90 percent filling of the original void volume. When the remaining void volume drops below about 1 percent the physical properties of the compact, such as fracture resistance, improve substantially. Multiple infiltration cycles result in the deposition of sufficient ceramic to reduce the void volume to below 0.5 percent. The fracture resistance of the compacts in which the pores are lined with formed in situ ceramic is generally at least one and one-half times that of the starting preforms.

  11. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2000-10-01

    This is the third quarterly report on oxygen Transport Ceramic Membranes. In the following, the report describes the progress made by our university partners in Tasks 1 through 6, experimental apparatus that was designed and built for various tasks of this project, thermodynamic calculations, where applicable and work planned for the future. (Task 1) Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. (Task 2) Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. (Task 3) Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. (Task 4) Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. (Task 5) Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. (Task 6) Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

  12. Thermal diffusion and quench propagation in YBCO pancake coils wound with ZnO and Mylar insulations

    NASA Astrophysics Data System (ADS)

    Sumption, M. D.; Majoros, M.; Susner, M.; Lyons, D.; Peng, X.; Clark, C. F.; Lawless, W. N.; Collings, E. W.

    2010-07-01

    The thermal diffusion properties of several different kinds of YBCO (yttrium barium copper oxide) insulations and the quench properties of pancake coils made using these insulations were studied. Insulations investigated include Nomex, Kapton, and Mylar, as well as insulations based on ZnO, Zn2GeO4, and ZnO-Cu. Nomex, Kapton, and Mylar, chosen for their availability and ease of use, were obtained as thin ribbons, while the ZnO based insulations were chosen for their high thermal conductivity and were applied by a thin film technique. Initially, short stacks of YBCO conductors with interlayer insulation, epoxy, and a central heater strip were made and later measured as regards their thermal conductivity in liquid nitrogen. Subsequently, three different pancake coils were made. The first two were smaller, each using one meter total of YBCO tape present as four turns around a G-10 former. One of these smaller coils used Mylar insulation co-wound with the YBCO tape, the other used YBCO tape onto which ZnO based insulation had been deposited. One larger coil was made which used 12 total meters of ZnO insulated tape and had 45 turns. Temperature gradients were measured and thermal conductivities were estimated from these coils; the results obtained were compared to those for the short stacks. Quench propagation velocity measurements were performed on the coils (77 K, self-field) by applying a DC current and then using a heater pulse to initiate a quench. Radial NZP (normal zone propagation velocity) values (0.02-1 mm s - 1) were two orders of magnitude lower than axial values (~10-20 mm s - 1). Nevertheless, the quenches were generally seen to propagate radially within the coils, in the sense that any given turn in the coil is driven normal by the turn underneath it. This was due to the fact that while the radial NZP is much lower than the NZP along the conductor (~100 ×) the distance by which the normal zone must expand longitudinally is much larger than the distance

  13. Lightweight ceramic insulation and method

    NASA Technical Reports Server (NTRS)

    Green, David J. (Inventor)

    1990-01-01

    A process is disclosed for manufacturing a low density ceramic powder which can be formed to make a lightweight material for insulation or other construction. The ceramic product made from the process has a final density of less than 25 to about 1 percent of the theoretical weight of the ceramic powder. The ceramic product is lightweight and can be made to withstand high temperatures greater than 1400 C.

  14. Ceramic automotive Stirling engine program

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The Ceramic Automotive Stirling Engine Program evaluated the application of advanced ceramic materials to an automotive Stirling engine. The objective of the program was to evaluate the technical feasibility of utilizing advanced ceramics to increase peak engine operating temperature, and to evaluate the performance benefits of such an increase. Manufacturing cost estimates were also developed for various ceramic engine components and compared with conventional metallic engine component costs.

  15. Ceramic Automotive Stirling Engine Program

    SciTech Connect

    Not Available

    1986-08-01

    The Ceramic Automotive Stirling Engine Program evaluated the application of advanced ceramic materials to an automotive Stirling engine. The objective of the program was to evaluate the technical feasibility of utilizing advanced ceramics to increase peak engine operating temperature, and to evaluate the performance benefits of such an increase. Manufacturing cost estimates were also developed for various ceramic engine components and compared with conventional metallic engine component costs.

  16. Nondestructive evaluation of advanced ceramics

    NASA Technical Reports Server (NTRS)

    Klima, Stanley J.; Kautz, Harold E.

    1988-01-01

    A review is presented of Lewis Research Center efforts to develop nondestructive evaluation techniques for characterizing advanced ceramic materials. Various approaches involved the use of analytical ultrasonics to characterize monolythic ceramic microstructures, acousto-ultrasonics for characterizing ceramic matrix composites, damage monitoring in impact specimens by microfocus X-ray radiography and scanning ultrasonics, and high resolution computed X-ray tomography to identify structural features in fiber reinforced ceramics.

  17. Ceramic tamper-revealing seals

    DOEpatents

    Kupperman, D.S.; Raptis, A.C.; Sheen, S.H.

    1992-12-08

    A flexible metal or ceramic cable is described with composite ceramic ends, or a U-shaped ceramic connecting element attached to a binding element plate or block cast from alumina or zirconium, and connected to the connecting element by shrink fitting. 7 figs.

  18. Assessment of ceramic membrane filters

    SciTech Connect

    Ahluwalia, R.K.; Geyer, H.K.; Im, K.H.

    1995-08-01

    The objectives of this project include the development of analytical models for evaluating the fluid mechanics of membrane coated, dead-end ceramic filters, and to determine the effects of thermal and thermo-chemical aging on the material properties of emerging ceramic hot gas filters. A honeycomb cordierite monolith with a thin ceramic coating and a rigid candle filter were evaluated.

  19. Ceramic coatings on smooth surfaces

    NASA Technical Reports Server (NTRS)

    Miller, R. A. (Inventor); Brindley, W. J. (Inventor); Rouge, C. J. (Inventor)

    1991-01-01

    A metallic coating is plasma sprayed onto a smooth surface of a metal alloy substitute or on a bond coating. An initial thin ceramic layer is low pressure sprayed onto the smooth surface of the substrate or bond coating. Another ceramic layer is atmospheric plasma sprayed onto the initial ceramic layer.

  20. Innovative grinding wheel design for cost-effective machining of advanced ceramics

    SciTech Connect

    Licht, R.H.; Kuo, P.; Liu, S.; Murphy, D.; Picone, J.W.; Ramanath, S.

    2000-05-01

    This Final Report covers the Phase II Innovative Grinding Wheel (IGW) program in which Norton Company successfully developed a novel grinding wheel for cost-effective cylindrical grinding of advanced ceramics. In 1995, Norton Company successfully completed the 16-month Phase I technical effort to define requirements, design, develop, and evaluate a next-generation grinding wheel for cost-effective cylindrical grinding of advanced ceramics using small prototype wheels. The Phase II program was initiated to scale-up the new superabrasive wheel specification to larger diameters, 305-mm to 406-mm, required for most production grinding of cylindrical ceramic parts, and to perform in-house and independent validation grinding tests.

  1. Ceramic regenerator program

    NASA Technical Reports Server (NTRS)

    Franklin, Jerrold E.

    1991-01-01

    The feasibility of fabricating an Air Turbo Ramjet (ATR) regenerator containing intricate hydraulic passages from a ceramic material in order to allow operation with high temperature combustion gas and to reduce weight as compared with metallic materials was demonstrated. Platelet technology, ceramic tape casting, and multilayer ceramic packaging techniques were used in this fabrication of subscale silicon nitride components. Proof-of-concept demonstrations were performed to simulate a methane cooled regenerator for an ATR engine. The regenerator vane was designed to operate at realistic service conditions, i.e., 600 psi in a 3500 R (3040 F), 500 fps combustion gas environment. A total of six regenerators were fabricated and tested. The regenerators were shown to be able to withstand internal pressurization to 1575 psi. They were subjected to testing in 500 fps, 3560 R (3100 F) air/propane combustion products and were operated satisfactorily for an excess of 100 hr and 40 thermal cycles which exceeded 2460 R (2000 F).

  2. Erosion of composite ceramics

    SciTech Connect

    Routbort, J.L.

    1992-08-01

    The theoretical basis to describe solid-particle erosion of monolithic ceramics is well developed. In many cases, the models can account for the impact velocity, impact angle and erodent-size dependencies of the steady-state erosion rate. In addition, the models account for effects of materials parameters such as fracture toughness and hardness. Steady-state erosion measurements on a wide variety of composite ceramics, including SiC whisker-reinforced Al[sub 2]O[sub 3], Si[sub 3]N[sub 4] containing Si[sub 3]N[sub 4] or SiC whiskers, Y[sub 2]O[sub 3]-stabilized ZrO[sub 2] reinforced with SiC whiskers, and duplex-microstructure Si[sub 3]N[sub 4] have been reported. The theories developed for monolithic ceramics are, however, less successful in describing the results for composites.

  3. Erosion of composite ceramics

    SciTech Connect

    Routbort, J.L.

    1992-08-01

    The theoretical basis to describe solid-particle erosion of monolithic ceramics is well developed. In many cases, the models can account for the impact velocity, impact angle and erodent-size dependencies of the steady-state erosion rate. In addition, the models account for effects of materials parameters such as fracture toughness and hardness. Steady-state erosion measurements on a wide variety of composite ceramics, including SiC whisker-reinforced Al{sub 2}O{sub 3}, Si{sub 3}N{sub 4} containing Si{sub 3}N{sub 4} or SiC whiskers, Y{sub 2}O{sub 3}-stabilized ZrO{sub 2} reinforced with SiC whiskers, and duplex-microstructure Si{sub 3}N{sub 4} have been reported. The theories developed for monolithic ceramics are, however, less successful in describing the results for composites.

  4. Whisker reinforced glass ceramic

    SciTech Connect

    Hirschfeld, D.A.; Brown, J.J. Jr.

    1996-06-03

    The process for making an in-situ whisker reinforced glass-ceramic that is up to 1.5 times as strong as conventional glass-ceramics was developed at Virginia Tech and patented in 1993. This technology has been identified as having commercial potential for use in high temperature heat exchanger applications for the electric power generation field by the National Center for Appropriate Technology (NCAT). This technology was licensed by MATVA, Inc., a small Virginia business, for further development. In particular, the goal of this project was to develop a property database and conduct initial testing of heat exchanger prototypes to demonstrate its potential application. This final report describes how the glass precursor was formed, physical properties of the glass-ceramic, techniques for making heat exchanger prototypes.

  5. Ceramic vane drive joint

    DOEpatents

    Smale, Charles H.

    1981-01-01

    A variable geometry gas turbine has an array of ceramic composition vanes positioned by an actuating ring coupled through a plurality of circumferentially spaced turbine vane levers to the outer end of a metallic vane drive shaft at each of the ceramic vanes. Each of the ceramic vanes has an end slot of bow tie configuration including flared end segments and a center slot therebetween. Each of the vane drive shafts has a cross head with ends thereof spaced with respect to the sides of the end slot to define clearance for free expansion of the cross head with respect to the vane and the cross head being configured to uniformly distribute drive loads across bearing surfaces of the vane slot.

  6. Verification of Ceramic Structures

    NASA Astrophysics Data System (ADS)

    Behar-Lafenetre, Stephanie; Cornillon, Laurence; Rancurel, Michael; De Graaf, Dennis; Hartmann, Peter; Coe, Graham; Laine, Benoit

    2012-07-01

    In the framework of the “Mechanical Design and Verification Methodologies for Ceramic Structures” contract [1] awarded by ESA, Thales Alenia Space has investigated literature and practices in affiliated industries to propose a methodological guideline for verification of ceramic spacecraft and instrument structures. It has been written in order to be applicable to most types of ceramic or glass-ceramic materials - typically Cesic®, HBCesic®, Silicon Nitride, Silicon Carbide and ZERODUR®. The proposed guideline describes the activities to be performed at material level in order to cover all the specific aspects of ceramics (Weibull distribution, brittle behaviour, sub-critical crack growth). Elementary tests and their post-processing methods are described, and recommendations for optimization of the test plan are given in order to have a consistent database. The application of this method is shown on an example in a dedicated article [7]. Then the verification activities to be performed at system level are described. This includes classical verification activities based on relevant standard (ECSS Verification [4]), plus specific analytical, testing and inspection features. The analysis methodology takes into account the specific behaviour of ceramic materials, especially the statistical distribution of failures (Weibull) and the method to transfer it from elementary data to a full-scale structure. The demonstration of the efficiency of this method is described in a dedicated article [8]. The verification is completed by classical full-scale testing activities. Indications about proof testing, case of use and implementation are given and specific inspection and protection measures are described. These additional activities are necessary to ensure the required reliability. The aim of the guideline is to describe how to reach the same reliability level as for structures made of more classical materials (metals, composites).

  7. Wear of 36-mm BIOLOX(R) delta ceramic-on-ceramic bearing in total hip replacements under edge loading conditions.

    PubMed

    Al-Hajjar, Mazen; Fisher, John; Tipper, Joanne L; Williams, Sophie; Jennings, Louise M

    2013-05-01

    Ceramic-on-ceramic bearings have become of great interest due to the substantial improvements in the manufacturing techniques and material properties and due to polyethylene wear debris-induced osteolysis and the issues with metal wear debris and ion release by metal-on-metal bearings. Edge loading conditions due to translational malpositioning (microseparation conditions) have been shown to replicate clinically relevant wear mechanisms and increase the wear of ceramic-on-ceramic bearings; thus, it was necessary to test new bearing materials and designs under these adverse conditions. The aim of this study was to assess the effect of increasing head size on the wear of BIOLOX(®) delta ceramic-on-ceramic bearings under edge loading conditions due to rotational (steep cup inclination angle) and translational (microseparation) malpositioning. In this study, six 36-mm ceramic-on-ceramic bearings (BIOLOX delta, CeramTec, Germany) were tested under standard and edge loading conditions using the Leeds II hip simulator and compared to the 28-mm bearings tested and published previously under identical conditions. The mean wear rate under standard gait conditions was below 0.1 mm(3)/million cycles for both the 28-mm and the 36-mm ceramic-on-ceramic bearings, and increasing the inclination angle did not affect the wear rates. The introduction of microseparation to the gait cycle increased the wear rate of ceramic-on-ceramic bearing and resulted in stripe wear on the femoral heads. Under microseparation conditions, the wear rate of size 36-mm bearings (0.22 mm(3)/million cycles) was significantly higher (p = 0.004) than that for size 28-mm bearings (0.13 mm(3)/million cycles). This was due to the larger contact area for the larger bearings and deprived lubrication under edge loading conditions. The wear rate of BIOLOX delta ceramic-on-ceramic bearings under microseparation conditions was still very low (<0.25 mm(3)/million cycles) compared to earlier generation

  8. An In Vitro Study on Effect of Ceramic Thickness and Multiple Firings on Colour of Metal Ceramic Restorations.

    PubMed

    Hasssija, Jyoti; Hegde, Veena; Sridhar, N

    2014-12-01

    Preparation of porcelain restorations that match the natural dentition has been a subject of great concern for many years. An understanding of the process by which the colour and translucency of fixed restorations are planned and obtained so as to replicate the colour of its adjacent teeth is important for achieving an esthetic restoration. This study was done to study the effect of fabrication procedures such as ceramic thickness and number of firing cycles on the colour of metal ceramic restorations. Metal ceramic samples with three different ceramic thicknesses; 0.5, 1 and 1.5 mm (N = 30, n = 10 per group) were fabricated. A3 shade of [VMK 95, VITA Zahnfabrik, Bad Sackingen, Germany] ceramic was used for the fabrication of samples. Samples were subject to multiple firing cycles and colour was measured after 2nd, 3rd, 4th, 6th, 8th and 10th firing cycle. Colour measurement was done objectively using spectrolino (Gretag Macbeth Inc., Germany) spectrophotometer. 'Repeated measures ANOVA' test was used for doing statistical analysis. No significant change was noticed in any of the four colour parameters between the baseline reading after second firing uptil the tenth firing for any of the three groups with different ceramic thicknesses. There was a consistent rise in L* or lightness of colour as the thickness of ceramic increased. Between group I and group III there was a consistent shift of a* axis towards the blue green side and there was a consistent shift in b* axis towards purple-blue with an increase in ceramic thickness. It was observed that there was a change in ΔE with a change in ceramic thickness. There was a change of about two units between group I and group II and a change of about one unit between group II and group III. Change in ΔE between group I and group III was the most significant, being about three units. It was concluded from the study that multiple firing cycles during fabrication of metal ceramic restorations do not have any effect

  9. Environment Conscious Ceramics (Ecoceramics)

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay; Levine, Stanley R. (Technical Monitor)

    2000-01-01

    Environment conscious ceramics (Ecoceramics) are a new class of materials, which can be produced with renewable natural resources (wood) or wood wastes (wood sawdust). Silicon carbide-based ecoceramics have been fabricated by reactive infiltration of carbonaceous preforms by molten silicon or silicon-refractory metal alloys. These carbonaceous preforms have been fabricated by pyrolysis of solid wood bodies at 1000 C. The fabrication approach, microstructure, and mechanical properties of SiC-based ecoceramics are presented. Ecoceramics have tailorable properties and behave like ceramic materials manufactured by conventional approaches.

  10. Supported microporous ceramic membranes

    DOEpatents

    Webster, Elizabeth; Anderson, Marc

    1993-01-01

    A method for permformation of microporous ceramic membranes onto a porous support includes placing a colloidal suspension of metal or metal oxide particles on one side of the porous support and exposing the other side of the porous support to a drying stream of gas or a reactive gas stream so that the particles are deposited on the drying side of the support as a gel. The gel so deposited can be sintered to form a supported ceramic membrane useful for ultrafiltration, reverse osmosis, or molecular sieving having mean pore sizes less than 100 Angstroms.

  11. Supported microporous ceramic membranes

    DOEpatents

    Webster, E.; Anderson, M.

    1993-12-14

    A method for the formation of microporous ceramic membranes onto a porous support includes placing a colloidal suspension of metal or metal oxide particles on one side of the porous support and exposing the other side of the porous support to a drying stream of gas or a reactive gas stream so that the particles are deposited on the drying side of the support as a gel. The gel so deposited can be sintered to form a supported ceramic membrane useful for ultrafiltration, reverse osmosis, or molecular sieving having mean pore sizes less than 100 Angstroms. 4 figures.

  12. Ceramic component for electrodes

    DOEpatents

    Marchant, David D.

    1979-01-01

    A ceramic component suitable for preparing MHD generator electrodes consists of HfO.sub.2 and sufficient Tb.sub.4 O.sub.7 to stabilize at least 60 volume percent of the HfO.sub.2 into the cubic structure. The ceramic component may also contain a small amount of PrO.sub.2, Yb.sub.2 O.sub.3 or a mixture of both to improve stability and electronic conductivity of the electrode. The component is highly resistant to corrosion by molten potassium seed and molten coal slag in the MHD fluid and exhibits both ionic and electronic conductivity.

  13. Ceramic powder compaction

    SciTech Connect

    Glass, S.J.; Ewsuk, K.G.; Mahoney, F.M.

    1995-12-31

    With the objective of developing a predictive model for ceramic powder compaction we have investigated methods for characterizing density gradients in ceramic powder compacts, reviewed and compared existing compaction models, conducted compaction experiments on a spray dried alumina powder, and conducted mechanical tests and compaction experiments on model granular materials. Die filling and particle packing, and the behavior of individual granules play an important role in determining compaction behavior and should be incorporated into realistic compaction models. These results support the use of discrete element modeling techniques and statistical mechanics principals to develop a comprehensive model for compaction, something that should be achievable with computers with parallel processing capabilities.

  14. Microwave sintering of ceramics

    SciTech Connect

    Snyder, W.B.

    1989-01-01

    Successful adaptation of microwave heating to the densification of ceramic materials require a marriage of microwave and materials technologies. Using an interdisciplinary team of microwave and materials engineers, we have successfully demonstrated the ability to density ceramic materials over a wide range of temperatures. Microstructural evolution during microwave sintering has been found to be significantly different from that observed in conventional sintering. Our results and those of others indicate that microwave sintering has the potential to fabricate components to near net shape with mechanical properties equivalent to hot pressed or hot isostatically pressed material. 6 refs., 11 figs.

  15. Why ceramic engines?

    NASA Technical Reports Server (NTRS)

    Stadler, H. L.

    1984-01-01

    Oil is still a problem for the U.S. and its allies. Transportation uses 61 percent of U.S. oil and its share is increasing, so more efficient technology should be concentrated there. Trucks' share of oil use is increasing because they are already much more efficient than autos. The primary truck opportunities are streamlining, more efficient engines, and shifting freight to railroads. More efficient engines are possible using ceramics to allow elimination of cooling systems and better use of waste exhaust heat. A 60 percent improvement seems possible if ceramics can be made tough enough and durable enough.

  16. Performance of Dental Ceramics

    PubMed Central

    Rekow, E.D.; Silva, N.R.F.A.; Coelho, P.G.; Zhang, Y.; Guess, P.; Thompson, V.P.

    2011-01-01

    The clinical success of modern dental ceramics depends on an array of factors, ranging from initial physical properties of the material itself, to the fabrication and clinical procedures that inevitably damage these brittle materials, and the oral environment. Understanding the influence of these factors on clinical performance has engaged the dental, ceramics, and engineering communities alike. The objective of this review is to first summarize clinical, experimental, and analytic results reported in the recent literature. Additionally, it seeks to address how this new information adds insight into predictive test procedures and reveals challenges for future improvements. PMID:21224408

  17. Battery utilizing ceramic membranes

    DOEpatents

    Yahnke, M.S.; Shlomo, G.; Anderson, M.A.

    1994-08-30

    A thin film battery is disclosed based on the use of ceramic membrane technology. The battery includes a pair of conductive collectors on which the materials for the anode and the cathode may be spin coated. The separator is formed of a porous metal oxide ceramic membrane impregnated with electrolyte so that electrical separation is maintained while ion mobility is also maintained. The entire battery can be made less than 10 microns thick while generating a potential in the 1 volt range. 2 figs.

  18. Orientation of embedded Y2BaCuO5 particles within the YBa2Cu3Ox matrix in melt-textured YBCO superconductors

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Koblischka, M. R.; Babu, N. Hari; Cardwell, D. A.; Mücklich, F.; Murakami, M.

    2005-03-01

    Automated electron backscatter diffraction (EBSD) was employed to study the local orientations of embedded Y2BaCuO5 (Y-211) particles within the YBa2Cu3Ox (Y-123) superconducting matrix of large grain, melt-textured Y-Ba-Cu-O (YBCO) samples. High-quality Kikuchi patterns were obtained, enabling automated mapping of the individual crystal orientations and a two-phase analysis of the samples. Investigations were performed on a variety of melt-textured YBCO samples, including samples with different element additions. We observe from the maps that the embedded Y-211 particles do not have any preferred orientation in melt-textured YBCO with (001) orientation, and that the YBCO growth is not altered for certain orientations of the Y-211 particles. In samples with (100) orientation, on the other hand, we observe only a small misorientation within the YBCO matrix, and the embedded Y-211 particles do not exhibit any texture. We can conclude from the EBSD maps obtained that the formation of small Y-211 particles does not disturb the Y-123 matrix growth, whereas the presence of large Y-211 particles leads, significantly, to the formation of subgrains.

  19. Fabrication of YSZ buffer layer by single source MOCVD technique for YBCO coated conductor

    NASA Astrophysics Data System (ADS)

    Jun, Byung-Hyuk; Sun, Jong-Won; Kim, Ho-Jin; Lee, Dong-Wook; Jung, Choong-Hwan; Park, Soon-Dong; Kim, Chan-Joong

    2003-10-01

    Yttria stabilized zirconia (YSZ) buffer layers were deposited by a metal organic chemical vapor deposition technique using a single liquid source for the application of YBa 2Cu 3O 7- δ (YBCO) coated conductor. Y:Zr mole ratio was 0.2:0.8, and tetrahydrofuran (THF) was used as a solvent. The (1 0 0) single crystal MgO substrate was used for searching the deposition conditions. Bi-axially oriented CeO 2 and NiO films were fabricated on {1 0 0} <0 0 1> textured Ni substrate by the same method and used as templates. At a constant working pressure of 10 Torr, the deposition temperatures (660-800 °C) and oxygen flow rates (100-500 sccm) were changed to find the optimum deposition condition. The best (1 0 0) oriented YSZ film on MgO was obtained at 740 °C and O 2 flow rate of 300 sccm. For a YSZ buffer layer with this deposition condition on a CeO 2/Ni template, full width half maximum values of the in-plane ( ϕ-scan) and out-of-plane ( ω-scan) alignments were 10.6° and 9.8°, respectively. The SEM image of YSZ film on CeO 2/Ni showed surface morphologies without microcracks. The film deposition rate was about 100 nm/min.

  20. Evaluation of the invasion heat for the HTS current lead using YBCO

    NASA Astrophysics Data System (ADS)

    Endoh, R.; Kato, H.; Izumi, T.; Shiohara, Y.

    2003-10-01

    Current leads using high- TC superconductors (HTS current leads) are one of cryogenic key devices to assemble compact superconducting magnets such as applied for maglev trains etc. It is essential to evaluate effective thermal conductance through a HTS current lead package together with evaluating Joule heat and critical current for efficient design that has high current capacity and low heat invasion. We have designed the 500 A class HTS current lead package using a YBCO rod whose size is ∅ 3 × 30 mm, and developed an apparatus to measure its heat invasion. Temperature drop as a function of heat flow between the two ends of the package was measured by a conventional steady heat flow method. The quantity of heat invasion of the package under typical practical conditions, from 80 K hot end to 20 K cold end, was 163 mW. This value was simulated to the total value of 158 mW by counting contributions of all the component materials.

  1. The effect of disorder on the critical points in the vortex phase diagram of YBCO

    SciTech Connect

    Crabtree, G. W.; Kwok, W. K.; Paulius, L. M.; Petrean, A. M.; Olsson, R. J.; Karapetrov, G.; Tobos, V.; Moulton, W. G.

    2000-01-19

    The effect of line disorder induced by heavy ion irradiation and of point disorder induced by proton and electron irradiation on the upper and lower critical points in the vortex phase diagram of YBCO is presented. The authors find that dilute line disorder induces a Bose glass transition at low fields which is replaced at the lower critical point by first order melting at higher fields. Strong pinning point defects raise the lower critical point, while weak pinning point defects have little or no effect on the lower critical point. The upper critical point is lowered by point disorder, but raised by line disorder. First order melting is suppressed by point disorder in two ways, by lowering of the upper critical point only for weak point pins, or by merging of the upper and lower critical points for strong point pins. The differing responses of the upper and lower critical points to line and point disorder can be understood in a picture of transverse and longitudinal spatial fluctuations.

  2. C-axis critical current density of second-generation YBCO tapes.

    SciTech Connect

    Jia, Y.; Hua, J.; Crabtree, G. W.; Kwok, W. K.; Welp, U.; Malozemoff, A. P.; Rupich, M.; Fleshler, S.; Materials Science Division; American Superconductor Corp.

    2010-10-01

    We report on measurements of the temperature and field dependence of the c-axis critical current density (J{sub c}{sup c}) obtained on mesa structures that were patterned into the YBCO layer of second-generation HTS tapes. We find the J{sub c}{sup c}-values of {approx}4 kA cm{sup -2} at 77 K and self-field, corresponding to an unexpectedly high anisotropy in the critical current density J{sub c}{sup ab}/J{sub c}{sup c} of 500-600. C-axis current flow is expected to arise in applications such as the helically wound wires in HTS cables. A simple estimate is given of the fraction of tape width for such a c-axis flow; while in our samples this fraction is approximately 5% for a typical geometry, the fraction will grow linearly with increasing current density anisotropy and could affect the current-carrying ability of the tape.

  3. Progress of 275 kV-3 kA YBCO HTS cable

    NASA Astrophysics Data System (ADS)

    Yagi, M.; Mukoyama, S.; Amemiya, N.; Ishiyama, A.; Wang, X.; Aoki, Y.; Saito, T.; Ohkuma, T.; Maruyama, O.

    2011-11-01

    A 275 kV-3 kA high temperature superconducting (HTS) cable has been developed in the Materials & Power Applications of Coated Conductors (M-PACC) project. AC loss reduction of a two-layer HTS conductor was undertaken by removing the edges of YBCO tapes with low critical current density. The HTS conductor using these tapes was fabricated, and low loss of 0.235 W/m at 3 kA rms was achieved. The 275 kV-3 kA cable was designed, and the 2 m model cables were fabricated. This cable had 325 mm 2 copper stranded former inside the HTS conductor and a 310 mm 2 copper shield layer on the HTS shield layer for over-current protection. These cables withstood an over-current of 63.0 kA for 0.6 s, which is the worst situation for 275 kV systems. The partial discharge (PD) and V- t characteristics of a liquid nitrogen (LN 2)/polypropylene (PP) laminated paper composite insulation system have been integrated into the design of the insulation for the 275 kV cable. The results revealed that the PD inception stress (PDIE) did not depend on the insulation thickness, and that lifetime indices of V- t characteristics at PD inception were as high as about 80-100.

  4. Doubling of the Critical Current Density of 2G-YBCO Coated Conductors through proton irradiation

    NASA Astrophysics Data System (ADS)

    Welp, Ulrich; Jia, Ying; Kwok, Wai-Kwong; Rupich, Marty; Fleshler, Steven; Kayani, Asfghar

    2013-03-01

    We report on magnetization and transport measurements of the critical current density of commercial 2G YBCO coated conductors before and after proton irradiation. The samples were irradiated along the c-axis with 4 MeV protons to a fluence of 1.5x1016 p/cm2. We find that at temperatures below 50 K, proton irradiation increases Jc by a factor of 2 in low fields and increases up to 2.5 in fields of 7 T. At 77 K, proton irradiation is less effective in enhancing the critical current. Doubling of Jc in fields of several Tesla and at temperatures below 50 K will be highly beneficial for applications of coated conductors in rotating machinery, generators and magnet coils. - Work supported by the US DoE-BES funded Energy Frontier Research Center (YJ), and by Department of Energy, Office of Science, Office of Basic Energy Sciences (UW, WKK), under Contract No. DE-AC02-06CH11357.

  5. Self-assembled artificial pinning centres in thick YBCO superconducting films

    NASA Astrophysics Data System (ADS)

    Mikheenko, P.; Abell, J. S.; Sarkar, A.; Dang, V. S.; Awang Kechik, M. M.; Tanner, J. L.; Paturi, P.; Huhtinen, H.; Babu, N. Hari; Cardwell, D. A.; Crisan, A.

    2010-06-01

    Strong, artificial pinning centres are required in superconducting films of large thickness for power applications in high magnetic fields. One of the methods for the introduction of pinning centres in such films is substrate decoration, i.e., growing nanoscale islands of certain materials on the substrate prior to the deposition of the superconducting film. Two other methods are building up a layered distribution of a second phase and homogeneous incorporation of second phase inclusions from a compositional target. In this paper, we compare the effectiveness of these methods in terms of the type of the self-assembly of nanoparticles. The comparison is made over a large set of YBa2Cu3O7 films of thickness up to 6.6 μm deposited with Au, Ag, Pd, LaNiO3, PrBa2Cu3O7, YBCO, BaZrO3 and Gd2Ba4CuWOy nanoparticles. It is found that substrate-decoration self-assembly is able to provide higher critical current in low magnetic field than the incorporation of homogeneous second phase in the sample microstructure. By specific modification of substrate decoration we achieved the self-field critical current per centimetre of width of 896 A/cm at 77.3 K and 1620 A/cm at 65 K in a film of thickness of 4.8 μm.

  6. Vortex dynamics of 250 MeV Ag ions irradiated YBCO films

    NASA Astrophysics Data System (ADS)

    Khatua, Sanghamitra; Kumar, Ravi; Mishra, P. K.; Sahni, V. C.; Pinto, R.

    YBCO thin films with c-axis orientation were grown in-situ by KrF laser on LaAIO 3 substrate. The films were irradiated with 250 MeV Ag ions at doses equivalent to B φ ranging from 1 T to 4 T. Critical currents were measured using SQUID magnetometer with field parallel to columnar defects. There is a marked enhancement of vortice pinning due to generation of additional pinning centres. There seems to be an upper limit to the irradiation doses beyond which there is a 'smearing effect' on Jc. We also find a shift in Irreversibility Line towards higher field which is attributed to better pinning induced by columnar defects. Defect production is examined in the framework of "Coulomb explosion" model and the consequences are analysed in terms of defect-induced behaviour within the purview of models such as "Bean model", 'Exponential model' and "Vortex Glass" model. We point out that the 'stress model' provides a qualitative explanation for the reduced Tc and a broad transition at high fluence.

  7. Irreversible properties of YBCO thick films deposited by liquid phase epitaxy on single crystalline substrates

    NASA Astrophysics Data System (ADS)

    Vostner, A.; Tönies, S.; Weber, H. W.; Cheng, Y. S.; Kurumovic, A.; Evetts, J. E.; Mennema, S. H.; Zandbergen, H. W.

    2003-10-01

    We report on the field and temperature dependence of the critical transport current density Jc, the angular dependence of the transport current at various external magnetic fields and the irreversibility fields in YBa2Cu3O7-delta (Y-123) thick films prepared by liquid phase epitaxy (LPE). A comparison of the irreversible properties between specimens produced with and without silver additions to the melt is also presented. Transmission electron microscopy (TEM) was employed to obtain information on the correlation between the transport properties and the microstructure. The samples were deposited either directly on NdGaO3 (NGO) or on seeded (100) MgO substrates, where a 200 nm thin YBCO film deposited by pulsed laser deposition (PLD) acts as seed layer for the LPE process. The final thickness of the Y-123 layer is of the order of 1 µm for the NGO and between 2 and 10 µm for the MgO samples. The critical current densities reach 3 × 109 A m-2 at zero field and 77 K in the best case.

  8. Superconducting YBCO thin film on multicrystalline Ag film evaporated on MgO substrate

    NASA Astrophysics Data System (ADS)

    Azoulay, Jacob; Verdyan, Armen; Lapsker, Igor

    Superconducting YBa 2Cu 3O 7-δ films were grown by resistive evaporation on multicrystalline silver film which was evaporated on MgO substrate. A simple inexpensive vacuum system equipped with resistively heated boat was used for the whole process. Silver film was first evaporated on MgO substrate kept at 400°C during the evaporation after which with no further annealing a precursor mixture of yttrium small grains and Cu and BaF2 in powder form weighed in the atomic proportion to yield stoichiometric YBa 2Cu 3O 7 was evaporated. The films thus obtained were annealed at 740°C under low oxygen partial pressure of about 1Pa for 30 minutes to form the superconducting phase. X-ray diffraction and scanning electron microscopy techniques were used for texture and surface analysis. Electrical properties were determined using a standard dc four-probe for electrical measurements. The physical and electrical properties of the YBCO films are discussed in light of the fact that X-ray diffraction measurements done on the silver film have revealed a multicrystalline structure

  9. Ceramics: rationale for material selection.

    PubMed

    McLaren, Edward A; Whiteman, Yair Y

    2010-01-01

    All imaginable types of materials and techniques, from very conservative ceramic restorations to very complex restorations of either metal or high-strength crystalline ceramics veneered with porcelain, have been introduced and tried throughout the years, with varying levels of success. However, there is considerable misinformation and a general lack of published rational treatment planning guidelines about when to use the ceramics available in dentistry. This article provides a systematic process for treatment planning with ceramic materials. Specific guidelines are outlined for the appropriate clinical conditions for using the various ceramic materials.

  10. Influence of resin cement shade on the color and translucency of ceramic veneers

    PubMed Central

    HERNANDES, Daiana Kelly Lopes; ARRAIS, Cesar Augusto Galvão; de LIMA, Erick; CESAR, Paulo Francisco; RODRIGUES, José Augusto

    2016-01-01

    ABSTRACT Objective This in vitro study evaluated the effect of two different shades of resin cement (RC- A1 and A3) layer on color change, translucency parameter (TP), and chroma of low (LT) and high (HT) translucent reinforced lithium disilicate ceramic laminates. Material and Methods One dual-cured RC (Variolink II, A1- and A3-shade, Ivoclar Vivadent) was applied to 1-mm thick ceramic discs to create thin RC films (100 µm thick) under the ceramics. The RC was exposed to light from a LED curing unit. Color change (ΔE) of ceramic discs was measured according to CIEL*a*b* system with a standard illuminant D65 in reflectance mode in a spectrophotometer, operating in the light range of 360-740 nm, equipped with an integrating sphere. The color difference between black (B) and white (W) background readings was used for TP analysis, while chroma was calculated by the formula C* ab=(a*2+b*2)½. ΔE of 3.3 was set as the threshold of clinically unacceptable. The results were evaluated by two-way ANOVA followed by Tukey's post hoc test. Results HT ceramics showed higher ΔE and higher TP than LT ceramics. A3-shade RC promoted higher ΔE than A1-shade cement, regardless of the ceramic translucency. No significant difference in TP was noted between ceramic discs with A1- and those with A3-shade cement. Ceramic with underlying RC showed lower TP than discs without RC. HT ceramics showed lower chroma than LT ceramics, regardless of the resin cement shade. The presence of A3-shade RC resulted in higher chroma than the presence of A1-shade RC. Conclusions Darker underlying RC layer promoted more pronounced changes in ceramic translucency, chroma, and shade of high translucent ceramic veneers. These differences may not be clinically differentiable. PMID:27556211

  11. Tribological properties of structural ceramics

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.; Miyoshi, K.

    1985-01-01

    The tribological and lubricated behavior of both oxide and nonoxide ceramics are reviewed in this chapter. Ceramics are examined in contact with themselves, other harder materials and metals. Elastic, plastic and fracture behavior of ceramics in solid state contact is discussed. The contact load necessary to initiate fracture in ceramics is shown to be appreciably reduced with tangential motion. Both friction and wear of ceramics are anisotropic and relate to crystal structure as has been observed with metals. Grit size effects in two and three body abrasive wear are observed for ceramics. Both free energy of oxide formation and the d valence bond character of metals are related to the friction and wear characteristics for metals in contact with ceramics. Surface contaminants affect friction and adhesive wear. For example, carbon on silicon carbide and chlorine on aluminum oxide reduce friction while oxygen on metal surfaces in contact with ceramics increases friction. Lubrication increases the critical load necessary to initiate fracture of ceramics both in indentation and with sliding or rubbing. Ceramics compositions both as coatings and in composites are described for the high temperature lubrication of both alloys and ceramics.

  12. Ceramic transactions: Ceramic joining. Volume 77

    SciTech Connect

    Reimanis, I.E.; Henager, C.H. Jr.; Tomsia, A.P.

    1997-11-01

    The advent of new materials for engineering applications almost always brings a new challenge: how will these new materials be joined to a larger engineering structure? New ceramic materials are being developed for a wide variety of applications in areas such as power generation, energy conversion, automotive and aerospace, with specific applications including heat exchangers, fuel cells, turbocharger rotors, combustor liners, and for many other applications. Typically the new materials will be exposed to more hostile environments with respect to temperature, corrosion, and stress than materials in the past, and thus, many of the conventional joining techniques developed for less hostile environments do not work. Understanding fundamental issues in joining enables the development of new techniques to be able to utilize new materials. A previous DOE workshop defined fundamental and critical issues in ceramic joining and classified them into four general areas: joining techniques; joint failure; residual stress; and characterization and testing. The present international symposium is an effort to discuss some of these fundamental issues and to define areas for future research. Separate abstracts have been indexed into the energy database for articles from this symposium.

  13. Light-weight ceramic insulation

    NASA Technical Reports Server (NTRS)

    Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

    2002-01-01

    Ultra-high temperature, light-weight, ceramic insulation such as ceramic tile is obtained by pyrolyzing a siloxane gel derived from the reaction of at least one organo dialkoxy silane and at least one tetralkoxy silane in an acid or base liquid medium. The reaction mixture of the tetra- and dialkoxy silanes may contain also an effective amount of a mono- or trialkoxy silane to obtain the siloxane gel. The siloxane gel is dried at ambient pressures to form a siloxane ceramic precursor without significant shrinkage. The siloxane ceramic precursor is subsequently pyrolyzed, in an inert atmosphere, to form the black ceramic insulation comprising atoms of silicon, carbon and oxygen. The ceramic insulation, can be characterized as a porous, uniform ceramic tile resistant to oxidation at temperatures ranging as high as 1700.degree. C. and is particularly useful as lightweight tiles for spacecraft and other high-temperature insulation applications.

  14. Metal to ceramic sealed joint

    DOEpatents

    Lasecki, J.V.; Novak, R.F.; McBride, J.R.

    1991-08-27

    A metal to ceramic sealed joint which can withstand wide variations in temperature and maintain a good seal is provided for use in a device adapted to withstand thermal cycling from about 20 to about 1000 degrees C. The sealed joint includes a metal member, a ceramic member having an end portion, and an active metal braze forming a joint to seal the metal member to the ceramic member. The joint is positioned remote from the end portion of the ceramic member to avoid stresses at the ends or edges of the ceramic member. The sealed joint is particularly suited for use to form sealed metal to ceramic joints in a thermoelectric generator such as a sodium heat engine where a solid ceramic electrolyte is joined to metal parts in the system. 11 figures.

  15. Metal to ceramic sealed joint

    DOEpatents

    Lasecki, John V.; Novak, Robert F.; McBride, James R.

    1991-01-01

    A metal to ceramic sealed joint which can withstand wide variations in temperature and maintain a good seal is provided for use in a device adapted to withstand thermal cycling from about 20 to about 1000 degrees C. The sealed joint includes a metal member, a ceramic member having an end portion, and an active metal braze forming a joint to seal the metal member to the ceramic member. The joint is positioned remote from the end portion of the ceramic member to avoid stresses at the ends or edges of the ceramic member. The sealed joint is particularly suited for use to form sealed metal to ceramic joints in a thermoelectric generator such as a sodium heat engine where a solid ceramic electrolyte is joined to metal parts in the system.

  16. Refractory ceramic fibers

    Integrated Risk Information System (IRIS)

    Refractory ceramic fibers ; CASRN Not found Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcino

  17. Microporous alumina ceramic membranes

    DOEpatents

    Anderson, Marc A.; Sheng, Guangyao

    1993-01-01

    Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

  18. Coated ceramic breeder materials

    DOEpatents

    Tam, Shiu-Wing; Johnson, Carl E.

    1987-04-07

    A breeder material for use in a breeder blanket of a nuclear reactor is disclosed. The breeder material comprises a core material of lithium containing ceramic particles which has been coated with a neutron multiplier such as Be or BeO, which coating has a higher thermal conductivity than the core material.

  19. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendfra Nagabhushana

    2001-07-01

    The mechanical properties of model systems were analyzed. A reasonably accurate finite element model was implemented and a rational metric to predict the strength of ceramic/metal concentrical joints was developed. The mode of failure of the ceramic/metal joints was determined and the importance of the mechanical properties of the braze material was assessed. Thermal cycling experiments were performed on the model systems and the results were discussed. Additionally, experiments using the concept of placing diffusion barriers on the ceramic surface to limit the extent of the reaction with the braze were performed. It was also observed that the nature and morphology of the reaction zone depends greatly on the nature of the perovskite structure being used. From the experiments, it is observed that the presence of Cr in the Fe-occupied sites decreases the tendency of Fe to segregate and to precipitate out of the lattice. In these new experiments, Ni was observed to play a major role in the decomposition of the ceramic substrate.

  20. Silicon carbide ceramic production

    NASA Technical Reports Server (NTRS)

    Suzuki, K.; Shinohara, N.

    1984-01-01

    A method to produce sintered silicon carbide ceramics in which powdery carbonaceous components with a dispersant are mixed with silicon carbide powder, shaped as required with or without drying, and fired in nonoxidation atmosphere is described. Carbon black is used as the carbonaceous component.

  1. Microporous alumina ceramic membranes

    DOEpatents

    Anderson, M.A.; Guangyao Sheng.

    1993-05-04

    Several methods are disclosed for the preparation microporous alumina ceramic membranes. For the first time, porous alumina membranes are made which have mean pore sizes less than 100 Angstroms and substantially no pores larger than that size. The methods are based on improved sol-gel techniques.

  2. Coated ceramic breeder materials

    DOEpatents

    Tam, Shiu-Wing; Johnson, Carl E.

    1987-01-01

    A breeder material for use in a breeder blanket of a nuclear reactor is disclosed. The breeder material comprises a core material of lithium containing ceramic particles which has been coated with a neutron multiplier such as Be or BeO, which coating has a higher thermal conductivity than the core material.

  3. Microwave processing of ceramics

    SciTech Connect

    Katz, J.D.

    1993-01-01

    Recent work in the areas of microwave processing and joining of ceramics is briefly reviewed. Advantages and disadvantages of microwave processing as well as some of the current issues in the field are discussed. Current state and potential for future commercialization of this technology is also addressed.

  4. Microwave processing of ceramics

    SciTech Connect

    Katz, J.D.

    1993-04-01

    Recent work in the areas of microwave processing and joining of ceramics is briefly reviewed. Advantages and disadvantages of microwave processing as well as some of the current issues in the field are discussed. Current state and potential for future commercialization of this technology is also addressed.

  5. Temperature Rise during Resin Composite Polymerization under Different Ceramic Restorations

    PubMed Central

    Yondem, Isa; Altintas, Subutay Han; Usumez, Aslihan

    2011-01-01

    Objectives: The purpose of this study was to measure temperature increase induced by various light polymerizing units during resin composite polymerization beneath one of three types of ceramic restorations. Methods: The resin composite (Variolink II) was polymerized between one of three different ceramic specimens (zirconium oxide, lithium disilicate, feldspathic) (diameter 5 mm, height 2 mm) and a dentin disc (diameter 5 mm, height 1 mm) with a conventional halogen light, a high intensity halogen light, or an LED unit. The temperature rise was measured under the dentin disc with a J-type thermocouple wire connected to a data logger. Ten measurements were carried out for each group. The difference between the initial and highest temperature readings was taken and the 10 calculated temperature changes were averaged to determine the mean value in temperature rise. Two way analysis of variance (ANOVA) was used to analyze the data (polymerizing unit, ceramic brand) for significant differences. The Tukey HSD test was used to perform multiple comparisons (α=.05). Results: Temperature rise did not vary significantly depending on the light polymerizing unit used (P=.16), however, the type of ceramic system showed a significant effect on temperature increases (P<.01). There were no statistically significant differences between lithium disilicate and feldspathic ceramic systems (P >.05); in comparison, the resin composite polymerized under the zirconium oxide ceramic system induced a significantly lower temperature increase than the other ceramic systems tested (P<.05) Conclusions: The resin composite polymerized beneath zirconium oxide ceramic system induced significantly smaller temperature changes. The maximal temperature increase detected in all groups in this study was not viewed as critical for pulpal health. PMID:21769272

  6. Ceramic Laser Materials

    SciTech Connect

    Soules, T F; Clapsaddle, B J; Landingham, R L; Schaffers, K I

    2005-02-15

    Transparent ceramic materials have several major advantages over single crystals in laser applications, not the least of which is the ability to make large aperture parts in a robust manufacturing process. After more than a decade of working on making transparent YAG:Nd, Japanese workers have recently succeeded in demonstrating samples that performed as laser gain media as well as their single crystal counterparts. Since then several laser materials have been made and evaluated. For these reasons, developing ceramic laser materials is the most exciting and futuristic materials topic in today's major solid-state laser conferences. We have established a good working relationship with Konoshima Ltd., the Japanese producer of the best ceramic laser materials, and have procured and evaluated slabs designed by us for use in our high-powered SSHCL. Our measurements indicate that these materials will work in the SSHCL, and we have nearly completed retrofitting the SSHCL with four of the largest transparent ceramic YAG:Nd slabs in existence. We have also begun our own effort to make this material and have produced samples with various degrees of transparency/translucency. We are in the process of carrying out an extensive design-of-experiments to establish the significant process variables for making transparent YAG. Finally because transparent ceramics afford much greater flexibility in the design of lasers, we have been exploring the potential for much larger apertures, new materials, for example for the Mercury laser, other designs for SSHL, such as, edge pumping designs, slabs with built in ASE suppression, etc. This work has just beginning.

  7. Ceramic tubesheet design analysis

    SciTech Connect

    Mallett, R.H.; Swindeman, R.W.

    1996-06-01

    A transport combustor is being commissioned at the Southern Services facility in Wilsonville, Alabama to provide a gaseous product for the assessment of hot-gas filtering systems. One of the barrier filters incorporates a ceramic tubesheet to support candle filters. The ceramic tubesheet, designed and manufactured by Industrial Filter and Pump Manufacturing Company (EF&PM), is unique and offers distinct advantages over metallic systems in terms of density, resistance to corrosion, and resistance to creep at operating temperatures above 815{degrees}C (1500{degrees}F). Nevertheless, the operational requirements of the ceramic tubesheet are severe. The tubesheet is almost 1.5 m in (55 in.) in diameter, has many penetrations, and must support the weight of the ceramic filters, coal ash accumulation, and a pressure drop (one atmosphere). Further, thermal stresses related to steady state and transient conditions will occur. To gain a better understanding of the structural performance limitations, a contract was placed with Mallett Technology, Inc. to perform a thermal and structural analysis of the tubesheet design. The design analysis specification and a preliminary design analysis were completed in the early part of 1995. The analyses indicated that modifications to the design were necessary to reduce thermal stress, and it was necessary to complete the redesign before the final thermal/mechanical analysis could be undertaken. The preliminary analysis identified the need to confirm that the physical and mechanical properties data used in the design were representative of the material in the tubesheet. Subsequently, few exploratory tests were performed at ORNL to evaluate the ceramic structural material.

  8. Retrospective clinical investigation and survival analysis on ceramic inlays and partial ceramic crowns: results up to 7 years.

    PubMed

    Felden, A; Schmalz, G; Federlin, M; Hiller, K A

    1998-12-01

    This study retrospectively evaluated the clinical performance of 287 all-ceramic restorations placed during routine patient care in the University setting in the past 7 years. All patients (n = 106) with ceramic inlays or partial ceramic crowns (PCC), placed during 1988-1994 (n = 327) by five experienced dentists were asked to take part in a clinical investigation, and 92 patients with 287 restorations (232 inlays, 55 PCC) agreed to do so. The following ceramics were used: 44 (15.3%) Dicor (Dentsply), 126 (43.9%) IPS-Empress (Ivoclar), 82 (28.7%) Mirage II, 33 (11.5%) Cerec-Vita-Mark 1 (Vita), and 2 (0.7%) Duceram LFC (Ducera) restorations. The restorations were placed using the following luting composites: 73 (25.4%) Dual Cure Luting Cement (Optec), 81 (28.3%) Variolink high viscosity (Ivoclar), 32 (11.1%) Microfill Pontic C (Kulzer), 51 (17.8%) Dual Zement (Ivoclar), 40 (13.9%) Dicor Light Activated Cement (Dentsply), and 10 (3.5%) Vita Cerec Duo Cement (Vita). Restorations were evaluated according to the modified USPHS criteria. Kaplan-Meier analysis was used to calculate the probability of survival. Of the 287 restorations 270 (94.2%) were still in function without any need of intervention. Fourteen restorations (4.8%) had failed before starting the clinical investigation, and in three a fracture was found during the investigation. These 17 failed restorations consisted of 14 PCC and 3 ceramic inlays. The results of the clinical investigation revealed 59.2% Alpha-ratings for marginal adaptation. Only one restored tooth showed recurrent caries. The probability of survival (95% confidence interval) for 7 years was 98% (97.99-98.01%) for ceramic inlays and 56% (46-66%) for PCC. Our findings show that ceramic inlays can be regarded as an acceptable alternative to cast gold restorations within the methodological limitations of the present study. For PCC further experience with more recent ceramics is warranted.

  9. Ceramic oxide powders and the formation thereof

    DOEpatents

    Katz, J.L.; Chenghung Hung.

    1993-12-07

    Ceramic oxide powders and a method for their preparation. Ceramic oxide powders are obtained using a flame process whereby two or more precursors of ceramic oxides are introduced into a counterflow diffusion flame burner wherein said precursors are converted into ceramic oxide powders. The morphology, particle size, and crystalline form of the ceramic oxide powders are determined by process conditions. 14 figures.

  10. Ceramic oxide powders and the formation thereof

    DOEpatents

    Katz, Joseph L.; Hung, Cheng-Hung

    1993-01-01

    Ceramic oxide powders and a method for their preparation. Ceramic oxide powders are obtained using a flame process whereby two or more precursors of ceramic oxides are introduced into a counterflow diffusion flame burner wherein said precursors are converted into ceramic oxide powders. The morphology, particle size, and crystalline form of the ceramic oxide powders are determined by process conditions.

  11. Hydrogen defects in α-Al2O3 and water weakening of sapphire and alumina ceramics between 600°C and 1000°C: II. Mechanical properties

    USGS Publications Warehouse

    Castaing, J.; Kronenberg, A.K.; Kirby, S.H.; Mitchell, T.E.

    2000-01-01

    Hydrogen impurities in alumina have been introduced by hydrothermal annealing (see part I). In this paper, we report on reductions in the flow strength of α-Al2O3 single crystals and polycrystals associated with hydrogen incorporation. Prior to deformation, α-Al2O3 single crystal and ceramic specimens were annealed in the presence of supercritical water at 850° or 900°C, under 1500 MPa pressure. Sapphire and alumina ceramics were plastically deformed between 600° and 1000°C under 1500 MPa pressure, by the addition of a uniaxial stress. Flow stresses are reduced by a factor of two, due to the presence of water, for sapphire and large grain (30–50 μm) polycrystals, as a result of enhanced dislocation mobility. Flow stresses of fine-grained (3–5 μm) polycrystals are reduced by water by a factor of six. This large reduction in strength is attributed to a change in mechanism from dislocation glide under dry conditions to grain boundary sliding under hydrothermal conditions.

  12. In-situ deposition of YBCO high-Tc superconducting thin films by MOCVD and PE-MOCVD

    NASA Technical Reports Server (NTRS)

    Zhao, J.; Noh, D. W.; Chern, C.; Li, Y. Q.; Norris, P. E.; Kear, B.; Gallois, B.

    1991-01-01

    Metal-Organic Chemical Vapor Deposition (MOCVD) offers the advantages of a high degree of compositional control, adaptability for large scale production, and the potential for low temperature fabrication. The capability of operating at high oxygen partial pressure is particularly suitable for in situ formation of high temperature superconducting (HTSC) films. Yttrium barium copper oxide (YBCO) thin films having a sharp zero-resistance transition with T(sub c) greater than 90 K and J(sub c) of approximately 10(exp 4) A on YSZ have been prepared, in situ, at a substrate temperature of about 800 C. Moreover, the ability to form oxide films at low temperature is very desirable for device applications of HTSC materials. Such a process would permit the deposition of high quality HTSC films with a smooth surface on a variety of substrates. Highly c-axis oriented, dense, scratch resistant, superconducting YBCO thin films with mirror-like surfaces have been prepared, in situ, at a reduced substrate temperature as low as 570 C by a remote microwave-plasma enhanced metal-organic chemical vapor deposition (PE-MOCVD) process. Nitrous oxide was used as a reactant gas to generate active oxidizing species. This process, for the first time, allows the formation of YBCO thin films with the orthorhombic superconducting phase in the as-deposited state. The as-deposited films grown by PE-MOCVD show attainment of zero resistance at 72 K with a transition width of about 5 K. MOCVD was carried out in a commercial production scale reactor with the capability of uniform deposition over 100 sq cm per growth run. Preliminary results indicate that PE-MOCVD is a very attractive thin film deposition process for superconducting device technology.

  13. In Situ deposition of YBCO high-T(sub c) superconducting thin films by MOCVD and PE-MOCVD

    NASA Technical Reports Server (NTRS)

    Zhao, J.; Noh, D. W.; Chern, C.; Li, Y. Q.; Norris, P.; Gallois, B.; Kear, B.

    1990-01-01

    Metalorganic Chemical Vapor Deposition (MOCVD) offers the advantages of a high degree of compositional control, adaptability for large scale production, and the potential for low temperature fabrication. The capability of operating at high oxygen partial pressure is particularly suitable for in situ formation of high temperature superconducting (HTSC) films. Yttrium barium copper oxide (YBCO) thin films having a sharp zero-resistance transition with T( sub c) greater than 90 K and Jc approx. 10 to the 4th power A on YSZ have been prepared, in situ, at a substrate temperature of about 800 C. Moreover, the ability to form oxide films at low temperature is very desirable for device applications of HTSC materials. Such a process would permit the deposition of high quality HTSC films with a smooth surface on a variety of substrates. Highly c-axis oriented, dense, scratch resistant, superconducting YBCO thin films with mirror-like surfaces have been prepared, in situ, at a reduced substrate temperature as low as 570 C by a remote microwave-plasma enhanced metalorganic chemical vapor deposition (PE-MOCVD) process. Nitrous oxide was used as a reactant gas to generate active oxidizing species. This process, for the first time, allows the formation of YBCO thin films with the orthorhombic superconducting phase in the as-deposited state. The as-deposited films grown by PE-MOCVD show attainment of zero resistance at 72 K with a transition width of about 5 K. MOCVD was carried out in a commercial production scale reactor with the capability of uniform deposition over 100 sq cm per growth run. Preliminary results indicate that PE-MOCVD is a very attractive thin film deposition process for superconducting device technology.

  14. Effect of copper content in precursor solution on the superconducting properties of YBCO films derived from low-fluorine solution

    NASA Astrophysics Data System (ADS)

    Zhao, Gaoyang; Lei, Li; Liu, Xiaomei; Chen, Yuanqing

    2008-12-01

    Four low-fluorine solutions with different stoichiometry of Y:Ba:Cu = 1:2: ξ ( ξ = 3, 3.5, 4, 4.5) were prepared using Ba-TFA, yttrium and copper acetate as precursors. YBa 2Cu 3O 7-δ (YBCO) films derived from these low-fluorine solutions were coated on LaAlO 3 (LAO) single crystal substrates by dip-coating process. The effect of copper stoichiometry in precursor solution on the microstructure and superconductivity of YBCO films was studied. The growth orientation and microstructure of the films were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The results show that there are large volume fraction of a-axis oriented YBCO grains in the films derived from precursor solutions with stoichiometry of Y:Ba:Cu = 1:2: ξ ( ξ = 3, 3.5, 4.5), while the films from the solution with stoichiometry of Y:Ba:Cu = 1:2:4 mainly grow along c-axis orientation and the volume fraction of c-axis oriented grains is 96.33%. Superconductivity test indicate that the film derived from the precursor solution with stoichiometry of Y:Ba:Cu = 1:2:4 exhibits excellent superconducting properties with the critical transition temperature Tc approximate 90 K, the sharp transition temperature Δ T below 1 K and the critical current density Jc over 1 MA/cm 2 (77 K, 0 T).

  15. BaHfO3 artificial pinning centres in TFA-MOD-derived YBCO and GdBCO thin films

    NASA Astrophysics Data System (ADS)

    Erbe, M.; Hänisch, J.; Hühne, R.; Freudenberg, T.; Kirchner, A.; Molina-Luna, L.; Damm, C.; Van Tendeloo, G.; Kaskel, S.; Schultz, L.; Holzapfel, B.

    2015-11-01

    Chemical solution deposition (CSD) is a promising way to realize REBa2Cu3O7-x (REBCO; RE = rare earth (here Y, Gd))-coated conductors with high performance in applied magnetic fields. However, the preparation process contains numerous parameters which need to be tuned to achieve high-quality films. Therefore, we investigated the growth of REBCO thin films containing nanometre-scale BaHfO3 (BHO) particles as pinning centres for magnetic flux lines, with emphasis on the influence of crystallization temperature and substrate on the microstructure and superconductivity. Conductivity, microscopy and x-ray investigations show an enhanced performance of BHO nano-composites in comparison to pristine REBCO. Further, those measurements reveal the superiority of GdBCO to YBCO—e.g. by inductive critical current densities, J c, at self-field and 77 K. YBCO is outperformed by more than 1 MA cm-2 with J c values of up to 5.0 MA cm-2 for 265 nm thick layers of GdBCO(BHO) on lanthanum aluminate. Transport in-field J c measurements demonstrate high pinning force maxima of around 4 GN m-3 for YBCO(BHO) and GdBCO(BHO). However, the irreversibility fields are appreciably higher for GdBCO. The critical temperature was not significantly reduced upon BHO addition to both YBCO and GdBCO, indicating a low tendency for Hf diffusion into the REBCO matrix. Angular-dependent J c measurements show a reduction of the anisotropy in the same order of magnitude for both REBCO compounds. Theoretical models suggest that more than one sort of pinning centre is active in all CSD films.

  16. Noise measurements in a composite niobium/YBCO SQUID and determination of the magnetic noise by direct measurement

    SciTech Connect

    Harrop, S.P.; Keene, M.N.; Muirhead, C.M.; Gough, C.E. )

    1991-03-01

    We have measured the noise performance of a composite niobium/YBCO point contact 2-hole SQUID, at 4.2 K in both rf and dc bias modes. The noise was measured by a technique which allowed the component which was flux noise to be measured. The flux noise was found to be the same in both bias modes. A direct measurement of the noise in a single hole in the same sample was made as a function of temperature and was found to display two peaks. Possible causes are discussed in this paper.

  17. Integrally cored ceramic investment casting mold fabricated by ceramic stereolithography

    NASA Astrophysics Data System (ADS)

    Bae, Chang-Jun

    Superalloy airfoils are produced by investment casting (IC), which uses ceramic cores and wax patterns with ceramic shell molds. Hollow cored superalloy airfoils in a gas turbine engine are an example of complex IC parts. The complex internal hollow cavities of the airfoil are designed to conduct cooling air through one or more passageways. These complex internal passageways have been fabricated by a lost wax process requiring several processing steps; core preparation, injection molding for wax pattern, and dipping process for ceramic shell molds. Several steps generate problems such as high cost and decreased accuracy of the ceramic mold. For example, costly tooling and production delay are required to produce mold dies for complex cores and wax patterns used in injection molding, resulting in a big obstacle for prototypes and smaller production runs. Rather than using separate cores, patterns, and shell molds, it would be advantageous to directly produce a mold that has the casting cavity and the ceramic core by one process. Ceramic stereolithography (CerSLA) can be used to directly fabricate the integrally cored ceramic casting mold (ICCM). CerSLA builds ceramic green objects from CAD files from many thin liquid layers of powder in monomer, which are solidified by polymerization with a UV laser, thereby "writing" the design for each slice. This dissertation addresses the integrally cored casting ceramic mold (ICCM), the ceramic core with a ceramic mold shell in a single patternless construction, fabricated by ceramic stereolithography (CerSLA). CerSLA is considered as an alternative method to replace lost wax processes, for small production runs or designs too complex for conventional cores and patterns. The main topic is the development of methods to successfully fabricate an ICCM by CerSLA from refractory silica, as well as related issues. The related issues are the segregation of coarse fused silica powders in a layer, the degree of segregation parameter to

  18. Ceramic Stereolithography: Additive Manufacturing for Ceramics by Photopolymerization

    NASA Astrophysics Data System (ADS)

    Halloran, John W.

    2016-07-01

    Ceramic stereolithography and related additive manufacturing methods involving photopolymerization of ceramic powder suspensions are reviewed in terms of the capabilities of current devices. The practical fundamentals of the cure depth, cure width, and cure profile are related to the optical properties of the monomer, ceramic, and photo-active components. Postpolymerization steps, including harvesting and cleaning the objects, binder burnout, and sintering, are discussed and compared with conventional methods. The prospects for practical manufacturing are discussed.

  19. Characterization of MgO substrates for growth of epitaxial YBCO thin films

    NASA Astrophysics Data System (ADS)

    Du, J.; Gnanarajan, S.; Bendavid, A.

    2005-08-01

    YBCO films were grown on magnesium oxide (MgO) substrates for fabricating step-edge junction SQUIDs and other Josephson junction-based devices. In-plane 45° grain misorientation was frequently observed in films grown on degraded or contaminated MgO substrates. The appearance of these misoriented grains results in a decrease of the thin-film critical-current density and reduces the device yield. In this work, we investigated the chemical properties of MgO substrates with various surface conditions due to different substrate preparation methods and environmental degradation, by using x-ray photoelectron spectroscopy (XPS). The XPS characteristics of the surface are compared before and after a thermal annealing at 760 °C resembling the thin-film deposition heating cycle. The MgO substrates, after lithographic processing or only weeks of exposure to the laboratory environment, showed surface degradation characterized by the presence of hydroxyl groups, carbonate, and other possible carbon compounds such as bicarbonate, alcohols and carboxyl. Heating of the substrates to 760 °C improves the surface quality to a certain degree with the removal of some of the above contaminants, but is not sufficient to recover the MgO surfaces. A final Ar ion-beam etch cleaning process at low ion energy proved to be very effective in refreshing the MgO substrate surface that had been degraded due to lithographic processing or storage. Films grown on MgO with this pre-treatment showed perfect grain alignment and high critical-current densities.

  20. Aspects of passive magnetic levitation based on high-T(sub c) superconducting YBCO thin films

    NASA Astrophysics Data System (ADS)

    Schoenhuber, P.; Moon, F. C.

    1995-04-01

    Passive magnetic levitation systems reported in the past were mostly confined to bulk superconducting materials. Here we present fundamental studies on magnetic levitation employing cylindrical permanent magnets floating above high-T(sub c) superconducting YBCO thin films (thickness about 0.3 mu m). Experiments included free floating rotating magnets as well as well-established flexible beam methods. By means of the latter, we investigated levitation and drag force hysteresis as well as magnetic stiffness properties of the superconductor-magnet arrangement. In the case of vertical motion of the magnet, characteristic high symmetry of repulsive (approaching) and attractive (withdrawing) branches of the pronounced force-displacement hysteresis could be detected. Achievable force levels were low as expected but sufficient for levitation of permanent magnets. With regard to magnetic stiffness, thin films proved to show stiffness-force ratios about one order of magnitude higher than bulk materials. Phenomenological models support the measurements. Regarding the magnetic hysteresis of the superconductor, the Irie-Yamafuji model was used for solving the equation of force balance in cylindrical coordinates allowing for a macroscopic description of the superconductor magnetization. This procedure provided good agreement with experimental levitation force and stiffness data during vertical motion. For the case of (lateral) drag force basic qualitative characteristics could be recovered, too. It is shown that models, based on simple asymmetric magnetization of the superconductor, describe well asymptotic transition of drag forces after the change of the magnet motion direction. Virgin curves (starting from equilibrium, i.e. symmetric magnetization) are approximated by a linear approach already reported in literature only. This paper shows that basic properties of superconducting thin films allow for their application to magnetic levitation or - without need of levitation

  1. Magnetism in EuBCO and YBCO vortex states near and below Tc

    NASA Astrophysics Data System (ADS)

    Schwartz, R.; Browne, M. C.; Boekema, C.

    2012-02-01

    By means of MaxEnt-μSR [1] analysis, we investigate transverse field μSR data [2] of EuBa2Cu3O7-δgEuBCO; Tc = 93 K). Our focus is on a temperature interval near Tc to search for precursor effects, [3] and for predicted [4a] pseudogap loop currents above and below Tc, already observed [4b] above Tc for GdBCO. Further, we continue to study the field-direction dependence of the predicted [5a] and observed [5b] antiferromagnetism (AF) below 0.5Tc for the vortex states in c-axis-oriented YBCO. This AF in and near the vortex cores is likely three-dimensional. In sum, magnetic roots of cuprate superconductivity are well plausible. Research is supported by LANL-DOE, REU-NSF and AFC. [4pt] [1] C Boekema and MC Browne, AIP Conf Proc #1073 (2008) 260.[0pt] [2] DW Cooke et al, Phys Rev B 39 (1989) 2748.[0pt] [3] B Aguilar, C Boekema et al, Bull Am Phys Soc 37 (1992).[0pt] [4a] CM Varma, Phys Rev Lett 83 (1999) 3538.[0pt] [4b] T Songatikamas et al, J Supercond & Novel Magn 23 (2010) 793.[0pt] [5a] S-C Zhang, Science 275 (1997) 1089; H-D Chen et al, Phys Rev B70 (2004) 024516.[0pt] [5b] C. Boekema et al, J Phys Conf Series, 150 (2009) 052022. http://jpcs.iop.org/LT25

  2. Aspects of passive magnetic levitation based on high-T(sub c) superconducting YBCO thin films

    NASA Technical Reports Server (NTRS)

    Schoenhuber, P.; Moon, F. C.

    1995-01-01

    Passive magnetic levitation systems reported in the past were mostly confined to bulk superconducting materials. Here we present fundamental studies on magnetic levitation employing cylindrical permanent magnets floating above high-T(sub c) superconducting YBCO thin films (thickness about 0.3 mu m). Experiments included free floating rotating magnets as well as well-established flexible beam methods. By means of the latter, we investigated levitation and drag force hysteresis as well as magnetic stiffness properties of the superconductor-magnet arrangement. In the case of vertical motion of the magnet, characteristic high symmetry of repulsive (approaching) and attractive (withdrawing) branches of the pronounced force-displacement hysteresis could be detected. Achievable force levels were low as expected but sufficient for levitation of permanent magnets. With regard to magnetic stiffness, thin films proved to show stiffness-force ratios about one order of magnitude higher than bulk materials. Phenomenological models support the measurements. Regarding the magnetic hysteresis of the superconductor, the Irie-Yamafuji model was used for solving the equation of force balance in cylindrical coordinates allowing for a macroscopic description of the superconductor magnetization. This procedure provided good agreement with experimental levitation force and stiffness data during vertical motion. For the case of (lateral) drag force basic qualitative characteristics could be recovered, too. It is shown that models, based on simple asymmetric magnetization of the superconductor, describe well asymptotic transition of drag forces after the change of the magnet motion direction. Virgin curves (starting from equilibrium, i.e. symmetric magnetization) are approximated by a linear approach already reported in literature only. This paper shows that basic properties of superconducting thin films allow for their application to magnetic levitation or - without need of levitation

  3. Onset of Superconductivity in YBCO in Very High Fields from ^17O and ^63Cu NMR

    NASA Astrophysics Data System (ADS)

    Halperin, William

    2000-03-01

    We have used NMR to study the onset of superconductivity in near optimally doped YBCO in fields from 1 to 27 T. We have compared Knight shift(^17O), spin-spin relaxation measurements(^17O), and spin lattice relaxation measurements (^63Cu and ^17O). The measurements have been performed as a function of temperature above and below the transition region. The Knight shift can be measured with considerable precision directly giving the Pauli spin susceptibility. We show that the onset of superconductivity in a magnetic field is really a crossover region from normal state behavior to a vortex liquid for which we determine a H-T phase diagram up to high field. The relaxation measurements show clear evidence for the opening of a pseudo gap near 100 K in the transition region. The different NMR experiments are sensitive to the susceptibility dependence on wave vector from different regions of the Brillouin zone indicating possible origins of such a gap including superconducting fluctuations or a gap in the spin excitation spectrum. Magnetic field dependence of the data allows discrimination. Intercomparison between samples near optimal doping as well as the work from other laboratories will be made. This work was performed in collaboration with V. F. Mitović, H. N. Bachman, E. E. Sigmund, M. Eschrig, J. A. Sauls, A. P. Reyes, P. Kuhns, and W. G. Moulton. Work at Northwestern University is supported by the NSF (DMR 91-20000) through the Science and Technology Center for Superconductivity. The NHMFL is supported through the NSF and the state of Florida.

  4. Comparative characterization of a novel cad-cam polymer-infiltrated-ceramic-network

    PubMed Central

    Pascual, Agustín; Camps, Isabel; Grau-Benitez, María

    2015-01-01

    Background The field of dental ceramics for CAD-CAM is enriched with a new innovative material composition having a porous three-dimensional structure of feldspathic ceramic infiltrated with acrylic resins.The aim of this study is to determine the mechanical properties of Polymer-Infiltrated-Ceramic-Network (PICN) and compare its performance with other ceramics and a nano-ceramic resin available for CAD-CAM systems. Material and Methods In this study a total of five different materials for CAD-CAM were investigated. A polymer-infiltrated ceramic (Vita Enamic), a nano-ceramic resin (Lava Ultimate), a feldspathic ceramic (Mark II), a lithium disilicate ceramic (IPS-e max CAD) and finally a Leucite based ceramic (Empress - CAD). From CAD-CAM blocks, 120 bars (30 for each material cited above) were cut to measure the flexural strength with a three-point-bending test. Strain at failure, fracture stress and Weibull modulus was calculated. Vickers hardness of each material was also measured. Results IPS-EMAX presents mechanical properties significantly better from the other materials studied. Its strain at failure, flexural strength and hardness exhibited significantly higher values in comparison with the others. VITA ENAMIC and LAVA ULTIMATE stand out as the next most resistant materials. Conclusions The flexural strength, elastic modulus similar to a tooth as well as having less hardness than ceramics make PICN materials an option to consider as a restorative material. Key words:Ceramic infiltrated with resin, CAD-CAM, Weibull modulus, flexural strength, micro hardness. PMID:26535096

  5. Positron annihilation in transparent ceramics

    NASA Astrophysics Data System (ADS)

    Husband, P.; Bartošová, I.; Slugeň, V.; Selim, F. A.

    2016-01-01

    Transparent ceramics are emerging as excellent candidates for many photonic applications including laser, scintillation and illumination. However achieving perfect transparency is essential in these applications and requires high technology processing and complete understanding for the ceramic microstructure and its effect on the optical properties. Positron annihilation spectroscopy (PAS) is the perfect tool to study porosity and defects. It has been applied to investigate many ceramic structures; and transparent ceramics field may be greatly advanced by applying PAS. In this work positron lifetime (PLT) measurements were carried out in parallel with optical studies on yttrium aluminum garnet transparent ceramics in order to gain an understanding for their structure at the atomic level and its effect on the transparency and light scattering. The study confirmed that PAS can provide useful information on their microstructure and guide the technology of manufacturing and advancing transparent ceramics.

  6. Ceramic hot-gas filter

    DOEpatents

    Connolly, E.S.; Forsythe, G.D.; Domanski, D.M.; Chambers, J.A.; Rajendran, G.P.

    1999-05-11

    A ceramic hot-gas candle filter is described having a porous support of filament-wound oxide ceramic yarn at least partially surrounded by a porous refractory oxide ceramic matrix, and a membrane layer on at least one surface thereof. The membrane layer may be on the outer surface, the inner surface, or both the outer and inner surface of the porous support. The membrane layer may be formed of an ordered arrangement of circularly wound, continuous filament oxide ceramic yarn, a ceramic filler material which is less permeable than the filament-wound support structure, or some combination of continuous filament and filler material. A particularly effective membrane layer features circularly wound filament with gaps intentionally placed between adjacent windings, and a filler material of ceramic particulates uniformly distributed throughout the gap region. The filter can withstand thermal cycling during back pulse cleaning and is resistant to chemical degradation at high temperatures.

  7. Ceramic hot-gas filter

    DOEpatents

    Connolly, Elizabeth Sokolinski; Forsythe, George Daniel; Domanski, Daniel Matthew; Chambers, Jeffrey Allen; Rajendran, Govindasamy Paramasivam

    1999-01-01

    A ceramic hot-gas candle filter having a porous support of filament-wound oxide ceramic yarn at least partially surrounded by a porous refractory oxide ceramic matrix, and a membrane layer on at least one surface thereof. The membrane layer may be on the outer surface, the inner surface, or both the outer and inner surface of the porous support. The membrane layer may be formed of an ordered arrangement of circularly wound, continuous filament oxide ceramic yarn, a ceramic filler material which is less permeable than the filament-wound support structure, or some combination of continuous filament and filler material. A particularly effective membrane layer features circularly wound filament with gaps intentionally placed between adjacent windings, and a filler material of ceramic particulates uniformly distributed throughout the gap region. The filter can withstand thermal cycling during backpulse cleaning and is resistant to chemical degradation at high temperatures.

  8. Seal between metal and ceramic conduits

    DOEpatents

    Underwood, Richard Paul; Tentarelli, Stephen Clyde

    2015-02-03

    A seal between a ceramic conduit and a metal conduit of an ion transport membrane device consisting of a sealing surface of ceramic conduit, a sealing surface of ceramic conduit, a single gasket body, and a single compliant interlayer.

  9. Ceramics for fusion applications

    SciTech Connect

    Clinard, F.W. Jr.

    1986-01-01

    Ceramics are required for a variety of uses in both near-term fusion devices and in commercial powerplants. These materials must retain adequate structural and electrical properties under conditions of neutron, particle, and ionizing irradiation; thermal and applied stresses; and physical and chemical sputtering. Ceramics such as Al/sub 2/O/sub 3/, MgAl/sub 2/O/sub 4/, BeO, Si/sub 3/N/sub 4/ and SiC are currently under study for fusion applications, and results to date show widely-varying response to the fusion environment. Materials can be identified today which will meet initial operating requirements, but improvements in physical properties are needed to achieve satisfactory lifetimes for critical applications.

  10. Ceramic composite coating

    DOEpatents

    Wicks, George G.

    1997-01-01

    A thin, room-temperature-curing, ceramic composite for coating and patching etal substrates comprises a sol gel silica glass matrix filled with finely ground particles or fibers, preferably alumina. The sol gel glass is made by adding ethanol to water to form a first mixture, then separately adding ethanol to tetraethyl orthosilicate to form a second mixture, then slowly adding the first to the second mixture to make a third mixture, and making a slurry by adding the finely ground particles or fibers to the third mixture. The composite can be applied by spraying, brushing or trowelling. If applied to patch fine cracks, densification of the ceramic composite may be obtained to enhance sealing by applying heat during curing.

  11. Ceramic composite coating

    DOEpatents

    Wicks, G.G.

    1997-01-21

    A thin, room-temperature-curing, ceramic composite for coating and patching metal substrates comprises a sol gel silica glass matrix filled with finely ground particles or fibers, preferably alumina. The sol gel glass is made by adding ethanol to water to form a first mixture, then separately adding ethanol to tetraethyl orthosilicate to form a second mixture, then slowly adding the first to the second mixture to make a third mixture, and making a slurry by adding the finely ground particles or fibers to the third mixture. The composite can be applied by spraying, brushing or trowelling. If applied to patch fine cracks, densification of the ceramic composite may be obtained to enhance sealing by applying heat during curing.

  12. Ceramic Composite Thin Films

    NASA Technical Reports Server (NTRS)

    Ruoff, Rodney S. (Inventor); Stankovich, Sasha (Inventor); Dikin, Dmitriy A. (Inventor); Nguyen, SonBinh T. (Inventor)

    2013-01-01

    A ceramic composite thin film or layer includes individual graphene oxide and/or electrically conductive graphene sheets dispersed in a ceramic (e.g. silica) matrix. The thin film or layer can be electrically conductive film or layer depending the amount of graphene sheets present. The composite films or layers are transparent, chemically inert and compatible with both glass and hydrophilic SiOx/silicon substrates. The composite film or layer can be produced by making a suspension of graphene oxide sheet fragments, introducing a silica-precursor or silica to the suspension to form a sol, depositing the sol on a substrate as thin film or layer, at least partially reducing the graphene oxide sheets to conductive graphene sheets, and thermally consolidating the thin film or layer to form a silica matrix in which the graphene oxide and/or graphene sheets are dispersed.

  13. Laser in Ceramics Processing

    NASA Astrophysics Data System (ADS)

    Lal, Bajrang; Jain, Pankaj

    LASER, an acronym for Light Amplification by Stimulated Emission of Radiation have unique properties, Which make it differ from ordinary light such as it is highly coherent, monochromatic, negligible divergence and scattering loss and a intense beam of electromagnetic radiation or light. It also occur in a wide range of wavelength/frequency (from Ultraviolet to Infrared), energy/power and beam-mode/configurations ; Due to these unique properties, it have use in wide application of ceramic processing for industrial manufacturing, fabrication of electronic circuit such as marking, serializing, engraving, cutting, micro-structuring because laser only produces localized heating, without any contact and thermal stress on the any part during processing. So there is no risk of fracturing that occurs during mechanical sawing and also reduce Cost of processing. The discussion in this paper highlight the application of laser in ceramics processing.

  14. Laser machining of ceramic

    SciTech Connect

    Laudel, A.

    1980-01-01

    The Kansas City Division of The Bendix Corporation manufactures hybrid microcircuits (HMCs) using both thin film and thick film technologies. Laser machining is used to contour the ceramic substrates and to drill holes in the ceramic for frontside-backside interconnections (vias) and holes for mounting components. A 1000 W CO/sub 2/ type laser is used. The laser machining process, and methods used for removing protruding debris and debris from holes, for cleaning the machined surfaces, and for refiring are described. The laser machining process described consistently produces vias, component holes and contours with acceptable surface quality, hole locations, diameter, flatness and metallization adhesion. There are no cracks indicated by dipping in fluorescent dye penetrant and the substances are resistant to repeated thermal shock.

  15. Ceramic composite coatings

    SciTech Connect

    Wicks, G.G.

    1991-12-31

    A thin, room-temperature-curing, ceramic composite for coating and patching metal substrates comprises a sol gel silica glass matrix filled with finely ground particles or fibers, preferably alumina. The sol gel glass is made by adding ethanol to water to form a first mixture, then separately adding ethanol to tetraethyl orthosilicate to form a second mixture, then slowly adding the first to the second mixture to make a third mixture, and making a slurry by adding the finely ground particles or fibers to the third mixture. The composite can be applied by spraying, brushing or trowelling. If applied to patch fine cracks, densification of the ceramic composite may be obtained to enhance sealing by applying heat during curing.

  16. Ceramic fabrication R D

    SciTech Connect

    Not Available

    1990-01-01

    This project is separated into three tasks. The first task is a design and modeling effort to be carried out by MSE, Inc. The purpose of this task is to develop and analyze designs for various cohesive ceramic fabrication (CCF) components, including an MHD electrode for strategic defense initiative (SDI) applications and a high stress, low cost, reinforced ceramic component for armor applications. The MHD electrode design is substantially completed. A layered structure composed of molybdenum disilicide graded with quartz glass has been designed and analyzed using finite element methods. The design demonstrates the fabrication capabilities of the CCF process. The high stress, armor application component will be silicon carbide reinforced alumina in thick plates. 2 refs., 4 figs., 1 tab.

  17. Testing Ceramics for Diesel Engines

    NASA Technical Reports Server (NTRS)

    Schneider, H. W.

    1985-01-01

    Adaptation of diesel engine allows prestressed ceramic materials evaluated under realistic pressure, temperature, and stress without introducing extraneous stress. Ceramic specimen part of prechamber of research engine. Specimen held in place by clamp, introduces required axial compressive stress. Specimen -- cylindrical shell -- surrounded by chamber vented or pressurized to introduce requisite radial stress in ceramic. Pressure chamber also serves as safety shield in case speimen disintegrates. Materials under consideration as cylinder liners for diesel engines.

  18. Tailored Ceramics for Laser Applications

    SciTech Connect

    Hollingsworth, Joel

    2007-12-10

    Transparent ceramics match or exceed the performance of single-crystal materials in laser applications, with a more-robust fabrication process. Controlling the distribution of optical dopants in transparent ceramics would allow qualitative improvements in amplifier slab design by allowing gain and loss to be varied within the material. My work aims to achieve a controlled pattern or gradient of dopant prior to sintering, in order to produce tailored ceramics.

  19. Processing method for superconducting ceramics

    DOEpatents

    Bloom, Ira D.; Poeppel, Roger B.; Flandermeyer, Brian K.

    1993-02-02

    A process for preparing a superconducting ceramic and particularly YBa.sub.2 Cu.sub.3 O.sub.7-.delta., where .delta. is in the order of about 0.1-0.4, is carried out using a polymeric binder which decomposes below its ignition point to reduce carbon residue between the grains of the sintered ceramic and a nonhydroxylic organic solvent to limit the problems with water or certain alcohols on the ceramic composition.

  20. Processing method for superconducting ceramics

    DOEpatents

    Bloom, Ira D.; Poeppel, Roger B.; Flandermeyer, Brian K.

    1993-01-01

    A process for preparing a superconducting ceramic and particularly YBa.sub.2 Cu.sub.3 O.sub.7-.delta., where .delta. is in the order of about 0.1-0.4, is carried out using a polymeric binder which decomposes below its ignition point to reduce carbon residue between the grains of the sintered ceramic and a nonhydroxylic organic solvent to limit the problems with water or certain alcohols on the ceramic composition.

  1. Miniature ceramic fuel cell

    DOEpatents

    Lessing, Paul A.; Zuppero, Anthony C.

    1997-06-24

    A miniature power source assembly capable of providing portable electricity is provided. A preferred embodiment of the power source assembly employing a fuel tank, fuel pump and control, air pump, heat management system, power chamber, power conditioning and power storage. The power chamber utilizes a ceramic fuel cell to produce the electricity. Incoming hydro carbon fuel is automatically reformed within the power chamber. Electrochemical combustion of hydrogen then produces electricity.

  2. Superplastic forging nitride ceramics

    DOEpatents

    Panda, Prakash C.; Seydel, Edgar R.; Raj, Rishi

    1988-03-22

    The invention relates to producing relatively flaw free silicon nitride ceramic shapes requiring little or no machining by superplastic forging This invention herein was made in part under Department of Energy Grant DE-AC01-84ER80167, creating certain rights in the United States Government. The invention was also made in part under New York State Science and Technology Grant SB1R 1985-10.

  3. Joined ceramic product

    DOEpatents

    Henager, Jr., Charles W [Kennewick, WA; Brimhall, John L [West Richland, WA

    2001-08-21

    According to the present invention, a joined product is at least two ceramic parts, specifically bi-element carbide parts with a bond joint therebetween, wherein the bond joint has a metal silicon phase. The bi-element carbide refers to compounds of MC, M.sub.2 C, M.sub.4 C and combinations thereof, where M is a first element and C is carbon. The metal silicon phase may be a metal silicon carbide ternary phase, or a metal silicide.

  4. Microprobes aluminosilicate ceramic membranes

    DOEpatents

    Anderson, Marc A.; Sheng, Guangyao

    1993-01-01

    Methods have been developed to make mixed alumina-silicate and aluminosilicate particulate microporous ceramic membranes. One method involves the making of separate alumina and silica sols which are then mixed. Another method involves the creation of a combined sol with aluminosilicate particles. The resulting combined alumina and silica membranes have high surface area, a very small pore size, and a very good temperature stability.

  5. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2001-12-01

    Conversion of natural gas to liquid fuels and chemicals is a major goal for the Nation as it enters the 21st Century. Technically robust and economically viable processes are needed to capture the value of the vast reserves of natural gas on Alaska's North Slope, and wean the Nation from dependence on foreign petroleum sources. Technologies that are emerging to fulfill this need are all based syngas as an intermediate. Syngas (a mixture of hydrogen and carbon monoxide) is a fundamental building block from which chemicals and fuels can be derived. Lower cost syngas translates directly into more cost-competitive fuels and chemicals. The currently practiced commercial technology for making syngas is either steam methane reforming (SMR) or a two-step process involving cryogenic oxygen separation followed by natural gas partial oxidation (POX). These high-energy, capital-intensive processes do not always produce syngas at a cost that makes its derivatives competitive with current petroleum-based fuels and chemicals. This project has the following 6 main tasks: Task 1--Design, fabricate and evaluate ceramic to metal seals based on graded ceramic powder/metal braze joints. Task 2--Evaluate the effect of defect configuration on ceramic membrane conductivity and long term chemical and structural stability. Task 3--Determine materials mechanical properties under conditions of high temperatures and reactive atmospheres. Task 4--Evaluate phase stability and thermal expansion of candidate perovskite membranes and develop techniques to support these materials on porous metal structures. Task 5--Assess the microstructure of membrane materials to evaluate the effects of vacancy-impurity association, defect clusters, and vacancy-dopant association on the membrane performance and stability. Task 6--Measure kinetics of oxygen uptake and transport in ceramic membrane materials under commercially relevant conditions using isotope labeling techniques.

  6. [Pharmaceutical ceramics by Buthaud].

    PubMed

    Devaux, G; Arléry, S

    1977-01-01

    In 1928 in Bordeaux, the ceramics manufacturer René Buthaud (1886-1986) created, in the neo-classical style that is typical of his work, four large pharmacists' jars, for display in a city dispensary. These pieces are presented here, each one decorated differently, with the back showing variations on the theme of the serpent and the front the design of tall, unclothed women holding objects Symbolic of the pharmceutical art.

  7. Multifracture of ceramic composites

    SciTech Connect

    Weitsman, Y.J.; Zhu, H.

    1992-03-01

    This work presents a mechanistic model for the multifracture process of uniaxially reinforced fibrous ceramic composites under monotonically increasing tension parallel to the fiber direction. The model employs an energy criterion to account for the progression of matrix cracks, bridged by intact fibers, and Weibull failure statistics to relate the failure of the fibers. Consideration is given to the interactions between the foregoing failure processes as well as to the effects of various material parameters on the response of the composite.

  8. Hot isostatic pressing of ceramic waste from spent nuclear fuel.

    SciTech Connect

    Bateman, K.J.; Rigg, R.H.; Wiest, J.D.

    2002-03-08

    Argonne National Laboratory has developed a process to immobilize waste salt containing fission products, uranium, and transuranic elements as chlorides in a glass-bonded ceramic waste form. This salt was generated in the electrorefining operation used in electrometallurgical treatment of spent Experimental Breeder Reactor-II fuel. The ceramic waste process culminated with a hot isostatic pressing operation. This paper reviews the installation and operation of a hot isostatic press in a radioactive environment. Processing conditions for the hot isostatic press are presented for non-irradiated material and irradiated material. Sufficient testing was performed to demonstrate that a hot isostatic press could be used as the final step of the processing of ceramic waste for the electrometallurgical spent fuel treatment process.

  9. Challenges in Modeling the Degradation of Ceramic Waste Forms

    SciTech Connect

    Devanathan, Ramaswami; Gao, Fei; Sun, Xin

    2011-09-01

    We identify the state of the art, gaps in current understanding, and key research needs in the area of modeling the long-term degradation of ceramic waste forms for nuclear waste disposition. The directed purpose of this report is to define a roadmap for Waste IPSC needs to extend capabilities of waste degradation to ceramic waste forms, which overlaps with the needs of the subconsinuum scale of FMM interests. The key knowledge gaps are in the areas of (i) methodology for developing reliable interatomic potentials to model the complex atomic-level interactions in waste forms; (ii) characterization of water interactions at ceramic surfaces and interfaces; and (iii) extension of atomic-level insights to the long time and distance scales relevant to the problem of actinide and fission product immobilization.

  10. Ceramic stationary gas turbine

    SciTech Connect

    Roode, M. van

    1995-10-01

    The performance of current industrial gas turbines is limited by the temperature and strength capabilities of the metallic structural materials in the engine hot section. Because of their superior high-temperature strength and durability, ceramics can be used as structural materials for hot section components (blades, nozzles, combustor liners) in innovative designs at increased turbine firing temperatures. The benefits include the ability to increase the turbine inlet temperature (TIT) to about 1200{degrees}C ({approx}2200{degrees}F) or more with uncooled ceramics. It has been projected that fully optimized stationary gas turbines would have a {approx}20 percent gain in thermal efficiency and {approx}40 percent gain in output power in simple cycle compared to all metal-engines with air-cooled components. Annual fuel savings in cogeneration in the U.S. would be on the order of 0.2 Quad by 2010. Emissions reductions to under 10 ppmv NO{sub x} are also forecast. This paper describes the progress on a three-phase, 6-year program sponsored by the U.S. Department of Energy, Office of Industrial Technologies, to achieve significant performance improvements and emissions reductions in stationary gas turbines by replacing metallic hot section components with ceramic parts. Progress is being reported for the period September 1, 1994, through September 30, 1995.

  11. Ceramic stationary gas turbine

    SciTech Connect

    Roode, M. van

    1995-12-31

    The performance of current industrial gas turbines is limited by the temperature and strength capabilities of the metallic structural materials in the engine hot section. Because of their superior high-temperature strength and durability, ceramics can be used as structural materials for hot section components (blades, nozzles, combustor liners) in innovative designs at increased turbine firing temperatures. The benefits include the ability to increase the turbine inlet temperature (TIT) to about 1200{degrees}C ({approx}2200{degrees}F) or more with uncooled ceramics. It has been projected that fully optimized stationary gas turbines would have a {approx}20 percent gain in thermal efficiency and {approx}40 percent gain in output power in simple cycle compared to all metal-engines with air-cooled components. Annual fuel savings in cogeneration in the U.S. would be on the order of 0.2 Quad by 2010. Emissions reductions to under 10 ppmv NO{sub x} are also forecast. This paper describes the progress on a three-phase, 6-year program sponsored by the U.S. Department of Energy, Office of Industrial Technologies, to achieve significant performance improvements and emissions reductions in stationary gas turbines by replacing metallic hot section components with ceramic parts. Progress is being reported for the period September 1, 1994, through September 30, 1995.

  12. Dental ceramics: a current review.

    PubMed

    Lawson, Nathaniel C; Burgess, John O

    2014-03-01

    Ceramics are used for many dental applications and are characterized in various ways, including by their hardness, brittleness, thermal and electrical insulation, and biocompatibility. The ceramics most commonly used in dentistry are oxides, particularly silicon dioxide (SiO2), or silica; aluminum oxide (Al2O3), or alumina; and zirconium dioxide (ZrO2), or zirconia. This article reviews the microstructure of current dental ceramic materials and how it relates to their mechanical properties, clinical techniques, and optical properties. Typical ceramics currently in use are described, and their clinically relevant properties such as strength, fracture, polishability, and wear are compared. Cementation methods are also discussed.

  13. Studies of Solution Deposited Cerium Oxide Thin Films on Textured Ni-Alloy Substractes for YBCO Superconductor

    SciTech Connect

    Stewart, Erin L; Bhuiyan, Md S; Sathyamurthy, Srivatsan; Paranthaman, Mariappan Parans

    2006-01-01

    Cerium oxide (CeO2) buffer layers play an important role for the development of YBa2Cu3O7-x (YBCO) based superconducting tapes using the rolling assisted biaxially textured substrates (RABiTS) approach. The chemical solution deposition (CSD) approach has been used to grow epitaxial CeO2 films on textured Ni-3 a 4% W alloy substrates with various starting precursors of ceria. Precursors such as cerium acetate, cerium acetylacetonate, cerium 2-ethylhexanoate, cerium nitrate, and cerium trifluoroacetate were prepared in suitable solvents. The optimum growth conditions for these cerium precursors were Ar-4% H2 gas processing atmosphere, solution concentration levels of 0.2-0.5 M, a dwell time of 15 min, and a process temperature range of 1050-1150 degrees C. X-ray diffraction, AFM, SEM, and optical microscopy were used to characterize the CeO2 films. Highly textured CeO2 layers were obtained on Ni-W substrates with both cerium acetate and cerium acetylacetonate as starting precursors. YBCO films with a Jc of 1.5 MA/cm2 were obtained on cerium acetylacetonate-based CeO2 films with sputtered YSZ and CeO2 cap layers.

  14. Temperature and Magnetic Field Dependence of Critical Currents in YBCO Coated Conductors with Processing-Induced Variations in Pinning Properties

    SciTech Connect

    Gapud, Albert Agcaoili; Feenstra, Roeland; Christen, David K; Thompson, James R; Holesinger, T. G.

    2005-01-01

    Several applications of high-temperature super-conducting wire require high currents at intermediate magnetic fields B and over a range of orientations; however, such conditions are at present achievable only at low temperatures (-30 K). The goal of this study is to determine the feasibility of higher operating temperatures for these applications by investigating temperature dependent, low- and high-field pinning properties of YBCO coated conductor samples. The YBCO films were grown on RABiTS templates by a PVD ex situ BaF{sub 2} process. Variations in pinning properties were induced by introducing excess yttrium (Y) in the precursor and controllably increasing the growth rate. The main result is a more uniform dependence of J{sub c} over all orientations of B, along with high irreversibility field B{sub irr} and high critical current densities J{sub c}. Results also show that for films with various pinning properties and processed under different conditions the self-field J{sub c} at 77 K is an effective indicator of performance in the temperatures and fields of interest.

  15. The mechanism of sputter-induced epitaxy modification in YBCO (001) films grown on MgO (001) substrates

    SciTech Connect

    Huang, Y.; Vuchic, B.V.; Carmody, M.; Baldo, P.M.; Merkle, K.L.; Buchholz, D.B.; Mahajan, S.; Lei, J.S.; Markworth, P.R.; Chang, R.P.; Marks, L.D.

    1998-12-01

    The sputter-induced epitaxy change of in-plane orientation occurring in YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} (001) thin films grown on MgO (001) substrates by pulsed organo-metallic beam epitaxy (POMBE) is investigated by a series of film growth and characterization experiments, including RBS and TEM. The factors influencing the orientation change are systematically studied. The experimental results suggest that the substrate surface morphology change caused by the ion sputtering and the Ar ion implantation in the substrate surface layer are not the major factors that affect the orientation change. Instead, the implantation of W ions, which come from the hot filament of the ion gun, and the initial Ba deposition layer in the YBCO film growth play the most important roles in controlling the epitaxy orientation change. Microstructure studies show that a Ba{sub x}Mg{sub 1{minus}x}O buffer layer is formed on top of the sputtered substrate surface due to Ba diffusion into the W implanted layer. It is believed that the formation of this buffer layer relieves the large lattice mismatch and changes the YBCO film from the 45{degree} oriented growth to the 0{degree} oriented growth. {copyright} {ital 1998 Materials Research Society.}

  16. Design of a cryogenic system for a 20m direct current superconducting MgB2 and YBCO power cable

    NASA Astrophysics Data System (ADS)

    Cheadle, Michael J.; Bromberg, Leslie; Jiang, Xiaohua; Glowacki, Bartek; Zeng, Rong; Minervini, Joseph; Brisson, John

    2014-01-01

    The Massachusetts Institute of Technology, the University of Cambridge in the United Kingdom, and Tsinghua University in Beijing, China, are collaborating to design, construct, and test a 20 m, direct current, superconducting MgB2 and YBCO power cable. The cable will be installed in the State Key Laboratory of Power Systems at Tsinghua University in Beijing beginning in 2013. In a previous paper [1], the cryogenic system was briefly discussed, focusing on the cryogenic issues for the superconducting cable. The current paper provides a detailed discussion of the design, construction, and assembly of the cryogenic system and its components. The two-stage system operates at nominally 80 K and 20 K with the primary cryogen being helium gas. The secondary cryogen, liquid nitrogen, is used to cool the warm stage of binary current leads. The helium gas provides cooling to both warm and cold stages of the rigid cryostat housing the MgB2 and YBCO conductors, as well as the terminations of the superconductors at the end of the current leads. A single cryofan drives the helium gas in both stages, which are thermally isolated with a high effectiveness recuperator. Refrigeration for the helium circuit is provided by a Sumitomo RDK415 cryocooler. This paper focuses on the design, construction, and assembly of the cryostat, the recuperator, and the current leads with associated superconducting cable terminations.

  17. Thickness-Dependent Properties of YBCO Films Grown on GZO/CLO-Buffered NiW Substrates

    NASA Astrophysics Data System (ADS)

    Malmivirta, M.; Huhtinen, H.; Zhao, Y.; Grivel, J.-C.; Paturi, P.

    2016-07-01

    To study the role of novel Gd_2 Zr_2 O_7 /Ce_{0.9} La_{0.1} O_2 buffer layer structure on a biaxially textured NiW substrate, a set of YBa_2 Cu_3 O_{7-δ } (YBCO) films with different thicknesses were prepared by pulsed laser deposition (PLD). Interface imperfections as well as thickness-dependent structural properties were observed in the YBCO thin films. The structure is also reflected into the improved superconducting properties with the highest critical current densities in films with intermediate thicknesses. Therefore, it can be concluded that the existing buffer layers need more optimization before they can be successfully used for films with various thicknesses. This issue is linked to the extremely susceptible growth method of PLD when compared to the commonly used chemical deposition methods. Nevertheless, PLD-grown films can give a hint on what to concentrate to be able to further improve the buffer layer structures for future coated conductor technologies.

  18. Effect of magnetic and nonmagnetic nano metal oxides doping on the critical temperature of a YBCO superconductor

    NASA Astrophysics Data System (ADS)

    Salama, A. H.; El-Hofy, M.; Rammah, Y. S.; Elkhatib, M.

    2015-12-01

    Bulk superconductor samples of YBa2Cu3O7-δ (YBCO) doped with nano metal oxides of Mn3O4, Co3O4, Cr2O3, CuO and SnO2 respectively with 0.2 wt% are synthesized by a solid-state reaction route. The structural characterization of all samples has been carried out by x-ray diffraction (XRD) and scanning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. The XRD patterns indicate that the magnetic doping of nano metal oxides ≤ft({{{Mn}}}{{3}}{{{O}}}{{4}}, {{{Co}}}{{3}}{{{O}}}{{4}}, {{{Cr}}}{{2}}{{{O}}}{{3}}\\right) gives a high value of orthorhombicity of the YBCO samples which is the result of high oxygen content, and consequently could give better superconducting properties contrary to the non magnetic nano oxides (CuO, SnO2). The critical temperature (Tc) of the studied samples was found to improve by nano magnetic doping and lower with nano nonmagnetic doping. The superconducting transition temperature Tc determined from electrical resistivity measurements was found to increase for Mn3O4 (5.27 μB) doping and decrease for other metal oxides doping.

  19. Preparation and microstructures of high-current density YBCO films by no-water post-annealing of precursor films including BaF 2

    NASA Astrophysics Data System (ADS)

    Ichinose, Ataru; Kikuchi, Akihiro; Kiss, Takanobu; Tachikawa, Kyoji; Akita, Shirabe; Inoue, Kiyoshi

    2003-10-01

    Precursor films are deposited on SrTiO 3 single crystals at room temperature by the co-evaporation technique using Y, BaF 2 and Cu as evaporation sources. Then, the precursor films are annealed in a low-pressure oxygen atmosphere without introduction of water vapor. A sample with a reflection high-energy electron diffraction (RHEED) pattern exhibiting some streaks, Kikuchi lines and Kikuchi zone, which resembles that of a single crystal, is successfully prepared. According to the cross-sectional TEM observation results, epitaxial growth of this YBCO film is achieved for the entire film thickness. The transport properties are measured using a small bridge with a width of 0.1 mm and a length of 1 mm by a standard four-probe method. The obtained YBCO film has a high Jc of over 1 MA/cm 2 at 77 K and a self-field. Furthermore, we discuss the relationship between the epitaxial YBCO layer thickness and the annealing conditions. Approximately 300- and 400-nm-thick epitaxial YBCO films are successfully prepared.

  20. Braze material for joining ceramic to metal and ceramic to ceramic surfaces and joined ceramic to metal and ceramic to ceramic article

    DOEpatents

    Hunt, Thomas K.; Novak, Robert F.

    1991-01-01

    An improved active metal braze filler material is provided in which the coefficient of thermal expansion of the braze filler is more closely matched with that of the ceramic and metal, or two ceramics, to provide ceramic to metal, or ceramic to ceramic, sealed joints and articles which can withstand both high temperatures and repeated thermal cycling without failing. The braze filler material comprises a mixture of a material, preferably in the form of a powder, selected from the group consisting of molybdenum, tungsten, silicon carbide and mixtures thereof, and an active metal filler material selected from the group consisting of alloys or mixtures of nickel and titanium, alloys or mixtures of nickel and zirconium, alloys or mixtures of nickel, titanium, and copper, alloys or mixtures of nickel, titanium, and zirconium, alloys or mixtures of niobium and nickel, alloys or mixtures of niobium and zirconium, alloys or mixtures of niobium and titanium, alloys or mixtures of niobium, titanium, and nickel, alloys or mixtures of niobium, zirconium, and nickel, and alloys or mixtures of niobium, titanium, zirconium, and nickel. The powder component is selected such that its coefficient of thermal expansion will effect the overall coefficient of thermal expansion of the braze material so that it more closely matches the coefficients of thermal expansion of the ceramic and metal parts to be joined.

  1. Braze material for joining ceramic to metal and ceramic to ceramic surfaces and joined ceramic to metal and ceramic to ceramic article

    DOEpatents

    Hunt, T.K.; Novak, R.F.

    1991-05-07

    An improved active metal braze filler material is provided in which the coefficient of thermal expansion of the braze filler is more closely matched with that of the ceramic and metal, or two ceramics, to provide ceramic to metal, or ceramic to ceramic, sealed joints and articles which can withstand both high temperatures and repeated thermal cycling without failing. The braze filler material comprises a mixture of a material, preferably in the form of a powder, selected from the group consisting of molybdenum, tungsten, silicon carbide and mixtures thereof, and an active metal filler material selected from the group consisting of alloys or mixtures of nickel and titanium, alloys or mixtures of nickel and zirconium, alloys or mixtures of nickel, titanium, and copper, alloys or mixtures of nickel, titanium, and zirconium, alloys or mixtures of niobium and nickel, alloys or mixtures of niobium and zirconium, alloys or mixtures of niobium and titanium, alloys or mixtures of niobium, titanium, and nickel, alloys or mixtures of niobium, zirconium, and nickel, and alloys or mixtures of niobium, titanium, zirconium, and nickel. The powder component is selected such that its coefficient of thermal expansion will effect the overall coefficient of thermal expansion of the braze material so that it more closely matches the coefficients of thermal expansion of the ceramic and metal parts to be joined. 3 figures.

  2. Life prediction methodology for ceramic components of advanced heat engines. Phase 1: Volume 2, Appendices

    SciTech Connect

    1995-03-01

    This volume presents the following appendices: ceramic test specimen drawings and schematics, mixed-mode and biaxial stress fracture of structural ceramics for advanced vehicular heat engines (U. Utah), mode I/mode II fracture toughness and tension/torsion fracture strength of NT154 Si nitride (Brown U.), summary of strength test results and fractography, fractography photographs, derivations of statistical models, Weibull strength plots for fast fracture test specimens, and size functions.

  3. Lightweight high performance ceramic material

    DOEpatents

    Nunn, Stephen D [Knoxville, TN

    2008-09-02

    A sintered ceramic composition includes at least 50 wt. % boron carbide and at least 0.01 wt. % of at least one element selected from the group consisting of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy Ho, Er, Tm, Yb, and Lu, the sintered ceramic composition being characterized by a density of at least 90% of theoretical density.

  4. Method of forming ceramic bricks

    DOEpatents

    Poeppel, R.B.; Claar, T.D.; Silkowski, P.

    1987-04-22

    A method for forming free standing ceramic bricks for use as tritium breeder material is disclosed. Aqueous solutions of sodium carbonate and potassium carbonate are mixed with an organic hydrocolloid dispersion and powdered lithium carbonate, spray dried, and ceramic bricks formed by molding in a die and firing.

  5. Method of forming ceramic bricks

    DOEpatents

    Poeppel, Roger B.; Claar, Terry D.; Silkowski, Peter

    1988-09-06

    A method for forming free standing ceramic bricks for use as tritium breeder material is disclosed. Aqueous solutions of sodium carbonate and potassium carbonate are mixed with an organic hydrocolloid dispersion and powdered lithium carbonate, spray dried, and ceramic bricks formed by molding in a die and firing.

  6. Method of forming ceramic bricks

    DOEpatents

    Poeppel, Roger B.; Claar, Terry D.; Silkowski, Peter

    1988-01-01

    A method for forming free standing ceramic bricks for use as tritium breeder material is disclosed. Aqueous solutions of sodium carbonate and potassium carbonate are mixed with an organic hydrocolloid dispersion and powdered lithium carbonate, spray dried, and ceramic bricks formed by molding in a die and firing.

  7. Ceramic applications in turbine engines

    NASA Technical Reports Server (NTRS)

    Byrd, J. A.; Janovicz, M. A.; Thrasher, S. R.

    1981-01-01

    Development testing activities on the 1900 F-configuration ceramic parts were completed, 2070 F-configuration ceramic component rig and engine testing was initiated, and the conceptual design for the 2265 F-configuration engine was identified. Fabrication of the 2070 F-configuration ceramic parts continued, along with burner rig development testing of the 2070 F-configuration metal combustor in preparation for 1132 C (2070 F) qualification test conditions. Shakedown testing of the hot engine simulator (HES) rig was also completed in preparation for testing of a spin rig-qualified ceramic-bladed rotor assembly at 1132 C (2070 F) test conditions. Concurrently, ceramics from new sources and alternate materials continued to be evaluated, and fabrication of 2070 F-configuration ceramic component from these new sources continued. Cold spin testing of the critical 2070 F-configuration blade continued in the spin test rig to qualify a set of ceramic blades at 117% engine speed for the gasifier turbine rotor. Rig testing of the ceramic-bladed gasifier turbine rotor assembly at 108% engine speed was also performed, which resulted in the failure of one blade. The new three-piece hot seal with the nickel oxide/calcium fluoride wearface composition was qualified in the regenerator rig and introduced to engine operation wiwth marginal success.

  8. Ceramic membrane development in NGK

    NASA Astrophysics Data System (ADS)

    Araki, Kiyoshi; Sakai, Hitoshi

    2011-05-01

    NGK Insulators, Ltd. was established in 1919 to manufacture the electric porcelain insulators for power transmission lines. Since then, our business has grown as one of the world-leading ceramics manufacturing companies and currently supply with the various environmentally-benign ceramic products to worldwide. In this paper, ceramic membrane development in NGK is described in detail. We have been selling ceramic microfiltration (MF) membranes and ultra-filtration (UF) membranes for many years to be used for solid/liquid separation in various fields such as pharmaceutical, chemical, food and semiconductor industries. In Corporate R&D, new ceramic membranes with sub-nanometer sized pores, which are fabricated on top of the membrane filters as support, are under development for gas and liquid/liquid separation processes.

  9. Protective coating for ceramic materials

    NASA Technical Reports Server (NTRS)

    Kourtides, Demetrius A. (Inventor); Churchward, Rex A. (Inventor); Lowe, David M. (Inventor)

    1994-01-01

    A protective coating for ceramic materials such as those made of silicon carbide, aluminum oxide, zirconium oxide, aluminoborosilicate and silicon dioxide, and a thermal control structure comprising a ceramic material having coated thereon the protective coating. The protective coating contains, in admixture, silicon dioxide powder, colloidal silicon dioxide, water, and one or more emittance agents selected from silicon tetraboride, silicon hexaboride, silicon carbide, molybdenum disilicide, tungsten disilicide and zirconium diboride. In another aspect, the protective coating is coated on a flexible ceramic fabric which is the outer cover of a composite insulation. In yet another aspect, a metallic foil is bonded to the outer surface of a ceramic fabric outer cover of a composite insulation via the protective coating. A primary application of this invention is as a protective coating for ceramic materials used in a heat shield for space vehicles subjected to very high aero-convective heating environments.

  10. Ceramic applications in turbine engines

    NASA Technical Reports Server (NTRS)

    Helms, H. E.; Heitman, P. W.; Lindgren, L. C.; Thrasher, S. R.

    1984-01-01

    The application of ceramic components to demonstrate improved cycle efficiency by raising the operating temperature of the existing Allison IGI 404 vehicular gas turbine engine is discussed. This effort was called the Ceramic Applications in Turbine Engines (CATE) program and has successfully demonstrated ceramic components. Among these components are two design configurations featuring stationary and rotating caramic components in the IGT 404 engine. A complete discussion of all phases of the program, design, materials development, fabrication of ceramic components, and testing-including rig, engine, and vehicle demonstation test are presented. During the CATE program, a ceramic technology base was established that is now being applied to automotive and other gas turbine engine programs. This technology base is outlined and also provides a description of the CATE program accomplishments.

  11. Interfacial shear bond strength between different base metal alloys and five low fusing feldspathic ceramic systems.

    PubMed

    Sipahi, Cumhur; Ozcan, Mutlu

    2012-01-01

    This study compared the bond strength between metal alloys and 5 ceramic systems. Ceramic systems (Vita VMK68, Ivoclar IPSd. SIGN, Ceramco II, Matchmaker and Finesse) were fired onto either Ni-Cr or Co-Cr base metal alloy. Metal-ceramic interfaces were subjected to shear loading until failure. The ceramic type significantly affected the bond strength results (p<0.05). For Ni-Cr alloy, the results ranged between 15.4-25.3 MPa and for Co-Cr alloy between 13.3-19.0 MPa. The highest mean bond strength value was obtained with the combination of Ni-Cr alloy-Ceramco II (25.3 MPa), the lowest bond strength was received from the combination of Co-Cr alloy-Ivoclar IPS d.SIGN ceramic (13.3 MPa). Adhesive failures between metal and ceramic were significantly more frequent with Ni-Cr alloy (31 out of 50) than with Co-Cr (20 out of 50) (p<0.05). Ceramco II presented the highest bond strength with both Ni-Cr and Co-Cr being significantly different from one another.

  12. Ceramic component for electrodes

    DOEpatents

    Marchant, David D.; Bates, J. Lambert

    1980-01-01

    A ceramic component suitable for preparing MHD generator electrodes having the compositional formula: Y.sub.x (Mg.sub.y Cr.sub.z).sub.w Al.sub.(1-w) O.sub.3 where x=0.9 to 1.05, y=0.02 to 0.2, z=0.8 to 1.05 and w=1.0 to 0.5. The component is resistant to the formation of hydration products in an MHD environment, has good electrical conductivity and exhibits a lower electrochemical corrosion rate than do comparable compositions of lanthanum chromite.

  13. TRANSFORMATION TOUGHENING IN CERAMICS

    SciTech Connect

    Evans, A. G.; Marshall, D. B.; Burlingame, N. H.

    1980-12-01

    The origin of transformation toughening in ceramics is examined using two separate approaches: one based on the stress field ahead of the crack and the other on the changes in thermodynamic potential during a crack increment. Both approaches yield essentially similar predictions of trends in toughness with particle size, temperature, composition, etc. The stress intensity analysis provides fully quantitative predictions of the toughness. These indicate that the shielding of the crack by the transformation zone only develops in the presence of a transformed wake, leading to R-curve behavior.

  14. Ceramic heat pipe wick

    NASA Technical Reports Server (NTRS)

    Seidenberg, Benjamin (Inventor); Swanson, Theodore (Inventor)

    1989-01-01

    A wick for use in a capillary loop pump heat pipe is disclosed. The wick material is an essentially uniformly porous, permeable, open-cell, silicon dioxide/aluminum oxide inorganic ceramic foam having a silica fiber ratio, by weight, of about 78 to 22, respectively, a density of 6 lbs/cu ft, and an average pore size of less than 5 microns. A representative material having these characteristics is Lockheed Missile and Space Company, Inc.'s HTP 6-22. This material is fully compatible with the freons and anhydrous ammonia and allows for the use of these very efficient working fluids, and others, in capillary loops.

  15. Recent advances in the field of ceramic fibers and ceramic matrix composites

    NASA Astrophysics Data System (ADS)

    Naslain, R.

    2005-03-01

    Progress achieved during the last decade in the field of ceramic fibers and related ceramic matrix composites is reviewed. Both SiC-based and alumina-based fine fibers have been improved in terms of thermal stability and creep resistance with temperature limit of about 1400 and 1200 ° C, respectively. Two concepts for achieving damage-tolerant ceramic matrix composites have been identified : (i) that of non-oxide composites with a dense matrix in which matrix cracks formed under load are deflected and arrested in a weak fiber coating referred to as the interphase and (ii) that of all-oxide composites with a highly porous matrix with no need of any fiber coating. The lifetime under load of non-oxide composites in oxidizing atmospheres, is improved through the use of multilayered self-healing interphases and matrices deposited from gaseous precursors by chemical vapor infiltration (CVI). Lifetime ranging from 1000 to 10,000 hours at 1200 ° C under cyclic loading in air are foreseen. Alumina-based composites although attractive for long term exposures in oxidizing atmospheres up to ≈1200 ° C, are still experimental materials.

  16. A new RE + 011 TSIG method for the fabrication of high quality and large size single domain YBCO bulk superconductors

    NASA Astrophysics Data System (ADS)

    Yang, W. M.; Chen, L. P.; Wang, X. J.

    2016-02-01

    High quality single domain YBCO bulk superconductors, 20 mm in diameter, have been fabricated using a new top seeded infiltration and growth method (called the RE + 011 TSIG method), with a new solid phase (Y2O3 + xBaCuO2) instead of the conventional Y2BaCuO5 solid phase, x = 0, 0.5, 1.0, 1.2, 1.5, 1.8, 2.0, 2.5, 3.0. The effects of different BaCuO2 contents x on the growth morphology, microstructure, and levitation force have been investigated. The results show that the levitation force of the YBCO bulks first increases and then decreases with increasing x, and reaches maximum levitation forces of about 49.2 N (77 K, 0.5 T, with the traditional liquid phase of YBa2Cu3O y + 3 BaCuO2 + 2 CuO) and 47 N (77.3 K, 0.5 T, with the new liquid phase of Y2O3 + 10 BaCuO2 + 6 CuO) when x = 1.2, which is much higher than that of the samples fabricated with the conventional solid phases (23 N). The average Y2BaCuO5 particle size is about 1 μm, which is much smaller than the 3.4 μm in the samples prepared with the conventional Y2BaCuO5 solid phase; this means that the flux pinning force of the sample can be improved by using the new solid phase. Based on this method, single domain YBCO bulks 40 mm, 59 mm, and 93 mm in diameter have also been fabricated using the TSIG process with the new solid phases (Y2O3 + 1.2BaCuO2). These results indicate that the new TSIG process developed by our lab is a very important and practical method for the fabrication of low cost, large size, and high quality single domain REBCO bulk superconductors.

  17. High-temperature corrosion resistance of ceramics and ceramic coatings

    SciTech Connect

    Tortorelli, P.F.

    1996-06-01

    Ceramics and ceramic composites offer the potential to operate fossil energy systems at the higher temperatures necessary for improved energy efficiency and better environmental control. However, because many fossil fuel-derived processes contain sulfur, chlorine, and carbon, as well as oxygen, degradation from high-temperature corrosion and environmental effects arising from reactions of solids with gases and condensable products is a common life-determining factor in operating systems. Ceramic-based products are not immune to such degradation; adequate corrosion resistance must be assured to exploit the technical and economic potential of such materials. This is normally accomplished by using stable, sound oxides that exist in their bulk form, that naturally grow as surface layers upon exposure to an oxidizing environment, or that are deposited as a coating on a susceptible material. It is therefore important to examine the critical issues with respect to more environmental stability of ceramics that have the potential to be corrosion resistant in particular fossil environments. Key aspects include not only chemical compatibility, but the influence of the environment on the mechanical behavior of the ceramic materials. In addition, for coatings, the mechanical reliability of the ceramic is a key issue in that an otherwise corrosion-resistant surface layer must remain sound and adherent in order to provide protection to the underlying substrate. The purpose of this work is to support the development of advanced ceramics and ceramic composites for applications in fossil environments by examining critical issues related to high-temperature corrosion resistance. More specifically, the overall objective of this task is to examine the chemical compatibility and reliability of potentially corrosion-resistant ceramics being developed as protective overcoats and/or structural materials as parts of other work elements funded by the AR&TD Program.

  18. Mixed-mode fracture toughness of ceramic materials

    SciTech Connect

    Suresh, S.; Shih, C.F.; O'Dowd, N.P. . Div. of Engineering); Morrone, A. . Dept. of Materials Science and Engineering)

    1990-05-01

    An experimental technique whereby pure mode I, mode II, and combined mode I-mode II fracture toughness values of ceramic materials can be determined using four-point bend specimens containing sharp, through-thickness precracks is discussed. In this method, notched and fatigue-precracked specimens of brittle solids are subjected to combined mode I-mode II and pure mode II fracture under asymmetric four point bend loading and to pure mode I under symmetric bend loading. A detailed finite element analysis of the test specimen is performed to obtain stress intensity factor calibrations for a wide range of loading states. The effectiveness of this method to provide reproducible combined mode I- mode II fracture toughness values is demonstrated with experimental results obtained for a polycrystalline Al{sub 2}O{sub 3}.

  19. Joining of ceramics for high temperature applications

    NASA Technical Reports Server (NTRS)

    Vilpas, Martti

    1987-01-01

    Summarized is a literature survey of the methods for joining ceramics to ceramics or ceramics to metals for high temperature applications. Also mechanical properties and potential applications of the joints are considered. The joining of ceramics is usually carried out by brazing or diffusion bonding. Especially the latter has been found useful, increasing the application of bonded ceramics. The possibility of using electron beam and laser beam welding for joining ceramics has also recently been investigated. The bonding of ceramics has found numerous applications typical for high operating temperatures, i.e., sensors and thermocouples.

  20. Ceramic fiber reinforced filter

    DOEpatents

    Stinton, David P.; McLaughlin, Jerry C.; Lowden, Richard A.

    1991-01-01

    A filter for removing particulate matter from high temperature flowing fluids, and in particular gases, that is reinforced with ceramic fibers. The filter has a ceramic base fiber material in the form of a fabric, felt, paper of the like, with the refractory fibers thereof coated with a thin layer of a protective and bonding refractory applied by chemical vapor deposition techniques. This coating causes each fiber to be physically joined to adjoining fibers so as to prevent movement of the fibers during use and to increase the strength and toughness of the composite filter. Further, the coating can be selected to minimize any reactions between the constituents of the fluids and the fibers. A description is given of the formation of a composite filter using a felt preform of commercial silicon carbide fibers together with the coating of these fibers with pure silicon carbide. Filter efficiency approaching 100% has been demonstrated with these filters. The fiber base material is alternately made from aluminosilicate fibers, zirconia fibers and alumina fibers. Coating with Al.sub.2 O.sub.3 is also described. Advanced configurations for the composite filter are suggested.

  1. Integral Textile Ceramic Structures

    NASA Astrophysics Data System (ADS)

    Marshall, David B.; Cox, Brian N.

    2008-08-01

    A new paradigm for ceramic composite structural components enables functionality in heat exchange, transpiration, detailed shape, and thermal strain management that significantly exceeds the prior art. The paradigm is based on the use of three-dimensional fiber reinforcement that is tailored to the specific shape, stress, and thermal requirements of a structural application and therefore generally requires innovative textile methods for each realization. Key features include the attainment of thin skins (less than 1 mm) that are nevertheless structurally robust, transpiration holes formed without cutting fibers, double curvature, compliant integral attachment to other structures that avoids thermal stress buildup, and microcomposite ceramic matrices that minimize spalling and allow the formation of smooth surfaces. All these features can be combined into structures of very varied gross shape and function, using a wide range of materials such as all-oxide systems and SiC and carbon fibers in SiC matrices. Illustrations are drawn from rocket nozzles, thermal protection systems, and gas turbine engines. The new design challenges that arise for such material/structure systems are being met by specialized computational modeling that departs significantly in the representation of materials behavior from that used in conventional finite element methods.

  2. Ceramic fabrication R D

    SciTech Connect

    Not Available

    1990-01-01

    This project is separated into three tasks. The first task is a design and modelling effort to be carried out by MSE, Inc. The purpose of this task is to develop and analyze designs for various cohesive ceramic fabrication (CCF) components, principally an MHD electrode for strategic defense initiative (SDI) applications. A high stress, low cost, ceramic component is to be selected, designed and, if possible, analyzed. The final design for the MHD electrode comprised a layered structure of molybdenum disilicide graded with quartz glass. The design demonstrates the fabrication capabilities of the CCF process. The high stress component was targeted at armor applications and will be thick alumina plate. Silicon carbide reinforcement of the alumina will be explored. Task 2 is directed at establishing a mechanical properties data base for monolithic and laminated alumina fabricated using the CCF process. Task 3 involved production of a solid oxide fuel cell model electrode; however, work ceased when it became apparent that successful integration of the electrode modules would require additional time. Currently, work is principally focused on the production of thick CCF alumina plates; three test plates were ballistically tested and showed a very satisfactory performance. Silicon carbide reinforcement of the CCF alumina is being explored. Effort on the CCF processing of molybdenum disilicide (a nonoxide material) continued at a reduced level. Sinter aids were explored, and densities of 87% theoretical density on pressureless sintered dry pressed pellets were achieved. 1 ref., 9 figs., 4 tabs.

  3. Ceramic fabrication R D

    SciTech Connect

    Not Available

    1990-01-01

    This project is separated into three tasks. The first task is a design and modeling effort to be carried out by MSE, Inc. The purpose of this task is to develop and analyze designs for various cohesive ceramic fabrication (CCF) components. This quarter, the advanced molybdenum disicilide MHD electrode design was essentially completed. Final refinements will be made after molybdenum disilicide processing results are available and the final layer compositions are established. Work involving whisker incorporation was initiated on the high stress component. It is unlikely that whiskers will become low cost, so particulate reinforcement will be pursued. Modeling work will resume once a suitable aluminum oxide/silicon carbide composition is selected that can be fired to acceptable densities by pressureless sintering. Task 2, subcontracted to Applied Technology Laboratories (ATL), is principally directed at establishing a property data base for monolithic and laminated alumina fabricated using the CCF process. This quarter, ATL demonstrated that the CCF process does not compromise the flexure strength of alumina. Task 3, subcontracted to Ceramics Binder Systems, Inc., focused on CCF silicon carbide particulate reinforced alumina and on the development of processing procedures for nonoxide molybdenum disilicide. Preliminary results indicate that achieving high densities in silicon carbide particulate reinforced aluminum oxide will be difficult. Molybdenum disilicide results are encouraging, and it is clear that the CCF process will work with this nonoxide material. 3 refs., 18 figs., 4 tabs.

  4. Ceramic-glass-ceramic seal by microwave heating

    DOEpatents

    Meek, T.T.; Blake, R.D.

    1983-10-04

    A method for producing a ceramic-glass-ceramic seal by microwaving, mixes a slurry of glass sealing material and coupling agent and applies same to ceramic workpieces. The slurry and workpieces are placed together, insulated and then microwaved at a power, time and frequency sufficient to cause a liquid phase reaction in the slurry. The reaction of the glass sealing material forms a chemically different seal than that which would be formed by conventional heating because it is formed by a diffusion rather than by wetting of the reactants.

  5. Ceramic-glass-ceramic seal by microwave heating

    DOEpatents

    Meek, Thomas T.; Blake, Rodger D.

    1985-01-01

    A method for producing a ceramic-glass-ceramic seal by microwaving, mixes a slurry of glass sealing material and coupling agent and applies same to ceramic workpieces. The slurry and workpieces are placed together, insulated and then microwaved at a power, time and frequency sufficient to cause a liquid phase reaction in the slurry. The reaction of the glass sealing material forms a chemically different seal than that which would be formed by conventional heating because it is formed by a diffusion rather than by wetting of the reactants.

  6. High pressure ceramic heat exchanger

    DOEpatents

    Harkins, B.D.; Ward, M.E.

    1998-09-22

    Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present header assembly when used with recuperators reduces the brittle effect of a portion of the ceramic components. Thus, the present header assembly used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present header assembly is comprised of a first ceramic member, a second ceramic member, a strengthening reinforcing member being in spaced relationship to the first ceramic member and the second ceramic member. The header assembly is further comprised of a refractory material disposed in contacting relationship with the first ceramic member, the second ceramic member and the strengthening reinforcing member. The present header assembly provides a high strength load bearing header assembly having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures. 5 figs.

  7. High pressure ceramic heat exchanger

    DOEpatents

    Harkins, Bruce D.; Ward, Michael E.

    1999-01-01

    Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present header assembly when used with recuperators reduces the brittle effect of a portion of the ceramic components. Thus, the present header assembly used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present header assembly is comprised of a first ceramic member, a second ceramic member, a reinforcing member being in spaced relationship to the first ceramic member and the second ceramic member. The header assembly is further comprised of a refractory material disposed in contacting relationship with the first ceramic member, the second ceramic member and the reinforcing member and having a strengthening member wrapped around the refractory material. The present header assembly provides a high strength load bearing header assembly having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures.

  8. High pressure ceramic heat exchanger

    DOEpatents

    Harkins, Bruce D.; Ward, Michael E.

    1998-01-01

    Many recuperators have components which react to corrosive gases and are used in applications where the donor fluid includes highly corrosive gases. These recuperators have suffered reduced life, increased service or maintenance, and resulted in increased cost. The present header assembly when used with recuperators reduces the brittle effect of a portion of the ceramic components. Thus, the present header assembly used with the present recuperator increases the life, reduces the service and maintenance, and reduces the increased cost associated with corrosive action of components used to manufacture recuperators. The present header assembly is comprised of a first ceramic member, a second ceramic member, a strengthening reinforcing member being in spaced relationship to the first ceramic member and the second ceramic member. The header assembly is further comprised of a refractory material disposed in contacting relationship with the first ceramic member, the second ceramic member and the strengthening reinforcing member. The present header assembly provides a high strength load bearing header assembly having good thermal cycling characteristics, good resistance to a corrosive environment and good steady state strength at elevated temperatures.

  9. Characterization of alpha-cordierite glass-ceramics from fly ash.

    PubMed

    He, Yong; Cheng, Weimin; Cai, Hesheng

    2005-04-11

    Batches of alpha-cordierite glass-ceramics, designated as GC-I and GC-II, containing 68 and 64 wt.% fly ash, respectively, were crystallized in the temperature range of 1125-1320 degrees C. The XRD (X-ray powder diffractometer) of the glass-ceramics show that alpha-cordierite became the dominant phase in GC-I and GC-II at 1200 degrees C. GC-I and GC-II, whose solid parts contain 74 and 78 vol.% alpha-cordierite and whose compressive strengths are 35 and 50 MPa, respectively, have the respective linear thermal expansion coefficients of 1.51x10(-6) and 1.43x10(-6)/ degrees C. The fly ash alpha-cordierite glass-ceramics can be employed as kiln furniture, honeycomb substrates for catalysts, and heat exchangers. PMID:15811690

  10. Dental ceramics: current thinking and trends.

    PubMed

    Kelly, J Robert

    2004-04-01

    Dental ceramics are presented within a simplifying framework allowing for understanding of their composition and development. The meaning of strength and details of the fracture process are explored, and recommendations are given regarding making structural comparisons among ceramics. Assessment of clinical survival data is dealt with, and literature is reviewed on the clinical behavior of metal-ceramic and all-ceramic systems. Practical aspects are presented regarding the choice and use of dental ceramics.

  11. Quantitative magneto-optical analysis of the role of finite temperatures on the critical state in YBCO thin films

    NASA Astrophysics Data System (ADS)

    Albrecht, Joachim; Brück, Sebastian; Stahl, Claudia; Ruoß, Stephen

    2016-11-01

    We use quantitative magneto-optical microscopy to investigate the influence of finite temperatures on the critical state of thin YBCO films. In particular, temperature and time dependence of supercurrents in inhomogeneous and anisotropic films are analyzed to extract the role of temperature on the supercurrents themselves and the influence of thermally activated relaxation. We find that inhomogeneities and anisotropies of the current density distribution correspond to a different temperature dependence of local supercurrents. In addition, the thermally activated decay of supercurrents can be used to extract local vortex pinning energies. With these results the modification of vortex pinning introduced by substrate structures is studied. In summary the local investigation of supercurrent densities allows the full description of the vortex pinning landscape with respect to pinning forces and energies in superconducting films with complex properties under the influence of finite temperatures.

  12. Dependence of levitation force on frequency of an oscillating magnetic levitation field in a bulk YBCO superconductor

    NASA Astrophysics Data System (ADS)

    Carter, Hamilton; Pate, Stephen; Goedecke, George

    2013-02-01

    The dependence of the magnetic field strength required for levitation of a melt textured, single domain YBCO superconductor disk on the frequency of the current generating the levitating magnetic field has been investigated. The magnetic field strength is found to be independent of frequency between 10 and 300 Hz. This required field strength is found to be in good experimental and theoretical agreement with the field strength required to levitate the same superconductor with a non-oscillating magnetic field. Hysteretic losses within the superconductor predicted by Bean’s critical-state model were also calculated. The measured data rules out any significant Bean’s model effects on the required levitation field strength within the measured frequency range.

  13. Hardness of ion implanted ceramics

    SciTech Connect

    Oliver, W.C.; McHargue, C.J.; Farlow, G.C.; White, C.W.

    1985-01-01

    It has been established that the wear behavior of ceramic materials can be modified through ion implantation. Studies have been done to characterize the effect of implantation on the structure and composition of ceramic surfaces. To understand how these changes affect the wear properties of the ceramic, other mechanical properties must be measured. To accomplish this, a commercially available ultra low load hardness tester has been used to characterize Al/sub 2/O/sub 3/ with different implanted species and doses. The hardness of the base material is compared with the highly damaged crystalline state as well as the amorphous material.

  14. The growth of the complex oxide YBCO by pulsed organo-metallic beam epitaxy

    NASA Astrophysics Data System (ADS)

    Buchholz, Donald Bruce

    To address the problems associated with the thin film heteroepitaxial growth of complex oxides a deposition technique, called pulsed organo-metallic beam epitaxy (POMBE), is developed. POMBE is designed to grow films layer-by-layer. Organo-metallics are delivered to the substrate as a series of discrete pulses via a set of computer-controlled valves. The precursor sequence and the amount of precursor in each pulse is programmed as the computer. Quartz crystal microbalances monitor the precursor transport rates. Computer feedback control maintains the precursor pulses at their programmed values. The ability to grow films layer-by-layer and to control the amount of material in each layer is demonstrated by the growth of YBasb2CUsb3Osb{7-delta}/PrBasb2CUsb3Osb{7-delta} superlattices. This is the first report of a high temperature superconductor superlattice grown by a chemical vapor deposition technique. The ability to grow films layer-by-layer is used to investigate the effect of changing the type and amount of precursor used to start the film growth. The correct choice of these parameters allows the growth of (001) YBasb2Cusb3Osb{7-delta} with a single in-plane orientation and Jsb{c}(77 K,0T) = 1-2× 10sp6amp/cmsp2 on (100) LaAlOsb3, (100) NdGaOsb3, (100) MgO, and (100) YSZ. The ability to control the initial film layer provides a means to control the in-plane orientation of (001) YBasb2Cusb3Osb{7-delta} (YBCO) grown on (100) MgO. Depositions started with thin BaO layers ({}{≈}1.1× 10sp{15}Ba/cmsp2) grow lbrack 100rbrack YBCOVertlbrack 100rbrack MgO. A mechanism that relates the change of in-plane orientation to a structural change of the initial BaO layer is described. The in-plane orientation of (001) YBasb2Cusb3Osb{7-delta} grown on (100) MgO can also be controlled by the ex situ, low energy Arsp+ sputtering of the MgO surface prior to film growth. To simultaneously grow lbrack 110rbrack YBCOVertlbrack 100rbrack MgO on non-sputtered MgO and lbrack 100rbrack

  15. Effects of ambient background gases on YBCO plume propagation under film growth conditions: Spectroscopic, ion probe, and fast photographic studies

    SciTech Connect

    Geohegan, D.B.

    1991-09-01

    The formation, composition, and propagation of KrF laser-produced plasmas from Y{sub 1}Ba{sub 2}Cu{sub 3}O{sub 7-x} have been studied with emphasis on topics relevant to film growth by pulsed-laser deposition. Spatially and temporally resolved, high-resolution optical absorption and emission spectroscopy, fast ion probes, and fast photography (obtained with a gated, image-intensified CCD array detector (ICCD)) are employed to investigate both emitting and non-emitting species in the laser plume as well as the overall shape and propagation of the laser plasma in background gases of oxygen and xenon. Transient optical absorption spectroscopy is applied to study the composition of the plume of ejected material from the dense layer near the target surface to distances of several centimeters. Optical absorption persists long after the decay of plasma fluorescence, indicating a slower component to plume transport. The absorption of YO formed by YBCO ablation in vacuum and by-yttrium ablation in oxygen is presented. Fast electric ion probes are utilized to measure velocities and total collected charge of the positive ions in the expanding YBCO laser plasma from near-threshold, vacuum conditions into the high fluence, background gas conditions utilized for thin-film growth. The exponential attenuation of the positive ion flux transmitted through 50--300 mTorr background oxygen is measured and used to define an attenuation coefficient. The showing of the laser plasma and formation of shock structures due to gas collisions is studied by ion probe measurements and fast ICCD photography. A comparison between shock wave propagation and drag models is presented to describe the arrival time and shape of the ion probe current waveform with distance. 11 refs, 11 figs.

  16. The magnetisation profiles and ac magnetisation losses in a single layer YBCO thin film caused by travelling magnetic field waves

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Coombs, Timothy

    2015-05-01

    This paper studies the magnetisation and ac magnetisation losses caused by a travelling magnetic wave on a single-layer YBCO thin film. This work provides thorough investigations on how the critical magnetic field gradient has been changed by the application of a travelling wave. Several conditions were studied such as zero-field cooling (ZFC), field cooling (FC) and a delta-shaped trapped field. It was found that the travelling wave tends to attenuate the existing critical magnetic field gradients in all these conditions. This interesting magnetic behaviour can be well predicted by the finite element (FEM) software with the E-J power law and Maxwell’s equations. The numerical simulations show that the existing critical current density has been compromised after applying the travelling wave. The magnetisation profile caused by the travelling wave is very different from the standing wave, while the magnetisation based on the standing wave can be interpreted by the Bean model and constant current density assumption. Based on the numerical method, which has reliability that has been solidly proven in the study, we have extended the study to the ac magnetisation losses. Comparisons were made between the travelling wave and the standing wave for this specific YBCO sample. It was found that by applying the magnetic wave of the same amplitude, the ac magnetisation loss caused by the travelling wave is about 1/3 of that caused by the standing wave. These results are helpful in understanding the general magnetism problems and ac magnetisation loss in the travelling magnetic wave conditions such as inside a high temperature superconducting (HTS) rotating machine, etc.

  17. Fracture resistance of teeth restored with all-ceramic inlays and onlays: an in vitro study.

    PubMed

    Saridag, S; Sevimay, M; Pekkan, G

    2013-01-01

    Fracture resistance of inlays and onlays may be influenced by the quantity of the dental structure removed and the restorative materials used. The purpose of this in vitro study was to evaluate the effects of two different cavity preparation designs and all-ceramic restorative materials on the fracture resistance of the tooth-restoration complex. Fifty mandibular third molar teeth were randomly divided into the following five groups: group 1: intact teeth (control); group 2: inlay preparations, lithium-disilicate glass-ceramic (IPS e.max Press, Ivoclar Vivadent AG, Schaan, Liechtenstein); group 3: inlay preparations, zirconia ceramic (ICE Zirkon, Zirkonzahn SRL, Gais, Italy); group 4: onlay preparations, lithium-disilicate glass-ceramic (IPS e.max Press); and group 5: onlay preparations, zirconia ceramic (ICE Zirkon). The inlay and onlay restorations were adhesively cemented with dual polymerizing resin cement (Variolink II, Ivoclar Vivadent AG). After thermal cycling (5° to 55°C × 5000 cycles), specimens were subjected to a compressive load until fracture at a crosshead speed of 0.5 mm/min. Statistical analyses were performed using one-way analysis of variance and Tukey HSD tests. The fracture strength values were significantly higher in the inlay group (2646.7 ± 360.4) restored with lithium-disilicate glass-ceramic than those of the onlay group (1673.6 ± 677) restored with lithium-disilicate glass-ceramic. The fracture strength values of teeth restored with inlays using zirconia ceramic (2849 ± 328) and onlays with zirconia ceramic (2796.3 ± 337.3) were similar to those of the intact teeth (2905.3 ± 398.8). In the IPS e.max Press groups, as the preparation amount was increased (from inlay to onlay preparation), the fracture resistance was decreased. In the ICE Zirkon ceramic groups, the preparation type did not affect the fracture resistance results.

  18. Demonstration of High Current Density YBCO Coated Conductors on RE2O3-Buffered Ni Substrates with Two New Alternative Architectures

    SciTech Connect

    Beach, D.B.; Chirayil, T.G.; Christen, D.K.; Cui, X.; Feenstra, R.; Goyal, A.; Kroeger, D.M.; Lee, D.F.; Martin, P.M.; Mathis, J.E.; Morrell, J.S.; Norton, D.P.; Paranthaman, M.; Specht, E.D.; Verebelyi, D.T.

    1999-07-12

    In continuation of our effort to develop single buffer layer architectures for YBCO (YBa2Cu3O7-g) coated tape conductors, we have studied RE2O3 (RE = Y, and rare earths) as candidate materials. Three types of crystal structures including the preferred cubic phase are known for the rare earth oxides. High quality simple cubic RE2O3 buffer layers were grown epitaxiahy on {100}<001> textured Ni substrates using both reactive evaporation and sol-gel processing. Detailed X-ray studies have shown that the Y2O3, Eu2O3, Gd2O3, and Yb2O3 were grown with a single epitaxial orientation. SEM micrographs indicated that both e-beam and sol-gel grown films were dense, continuous and crack free. High Jc YBCO films were grown on RE2O3-buffered Ni substrates with sputtered cap layers. Two new alternative buffer layer architectures were developed. A high Jc of 1.8 MA/cm2 at 77 K and self-field was obtained on YBCO films with a layer sequence of YBCO (pulsed laser deposition)/Yb2O3 (sputtered)/Y2O3 (e-beam)/Ni. Also, a high Jc of over 1 MA/cm2 at 77 K and self-field was obtained on YBCO films with a layer sequence of YBCO (ex-situ BaF2 process)/CeO2 (sputtered)YSZ sputtered)/RE2O3 (sol-gel or e-beam)Ni. The performance of sol-gel grown buffers approached the quality of e-beam grown buffers.

  19. Dynamic crack arrest in ceramics and ceramic composites

    NASA Technical Reports Server (NTRS)

    Kobayashi, A. S.; Yang, K. H.

    1989-01-01

    The results of past dynamic crack arrest experiments involving structural ceramics and ceramic composites are reviewed and analyzed. The lack of dynamic crack arrest in very brittle materials is discussed and contrasted with dynamic crack arrest in somewhat brittle metallic and polymeric materials. Numerical analyses show that the lack of crack arrest is due to reduced dynamic fracture resistance of the material and is not due to the kinetic energy.

  20. Evaluation of the marginal fit of full ceramic crowns by the microcomputed tomography (micro-CT) technique

    PubMed Central

    Demir, Necla; Ozturk, Atiye Nilgun; Malkoc, Meral Arslan

    2014-01-01

    Objective: To evaluate the marginal gap (MG) and absolute marginal discrepancy (MD) of full ceramic crowns with two finish line designs, shoulder and chamfer, using microcomputed tomography (micro-CT) before and after cementation. Materials and Methods: Sixty extracted human maxillary premolar teeth were divided into two groups based on the finish line design: Group I: 90° shoulder and Group II: 135° chamfer. The specimens were further grouped based on the type of full ceramic crown they received: Group A: Feldspathic Cerec inLab ceramic system, Group B: Cerec inLab aluminum oxide ceramic system and Group C: Lithium disilicate press ceramic system. Before cementation, five crowns from each group were scanned using micro-CT in two sections, sagittal and coronal, to determine the MG and MD values for four regions of the crown (sagittal buccal, sagittal lingual, coronal mesial and coronal distal). After cementation and thermal cycling, the scanning was repeated. Measurements were obtained from 10 points for each region, 80 points totally, to evaluate the MG and MD values. Files were processed using NRecon and CTAn software. Results were statistically analyzed using one- and two-way ANOVA and Tukey HSD tests (P = 0.05). Results: Full ceramic systems showed clinically acceptable marginal adaptation values. The Feldspathic Cerec inLab ceramic system generally presented the lowest variance, except in the MG values of the coronal mesial region. The MG and MD values of all ceramics increased significantly after cementation, except in the shoulder preparation design (sagittal buccal region) for MG and in the chamfer preparation design (sagittal lingual region) for MD values. Conclusions: Full-ceramic crowns showed clinically acceptable marginal adaptation values. The Feldspathic Cerec inLab ceramic system (Vitablocs Mark II) generally presented the lowest variance when compared with the other ceramics, except for the MG values on the mesial surface of the coronal section

  1. Dispersed metal-toughened ceramics and ceramic brazing

    SciTech Connect

    Moorhead, A.J.; Tiegs, T.N.; Lauf, R.J.

    1983-01-01

    An alumina (Al/sub 2/O/sub 3/) based material that contains approximately 1 vol % finely dispersed platinum or chromium was developed for use in high temperature thermal-shock resistant electrical insulators. The work at ORNL is divided into two areas: (1) development of DMT ceramics; and (2) development of brazing filler metals suitable for making ceramic-to-ceramic and ceramic-to-metal brazements. The DMT ceramics and brazements are intended for service at elevated temperatures and at high stress levels in the dirty environments of advanced heat engines. The development and characterization of DMT ceramics includes processing (powder preparation, densification and heat treatment) and detailed measurement of mechanical and physical properties (strength, fracture toughness, and thermal conductivity). The brazing work includes: (1) the formulation and melting of small quantities of experimental brazing filler metals; (2) evaluation of the wetting and bonding behavior of these filler metals on Al/sub 2/O/sub 3/, partially stabilized zirconia and ..cap alpha..-SiC in a sessile drop apparatus; and (3) determine the short-term strength and fracture toughness of brazements.

  2. Ceramic formation on metallic surfaces (ceramization) for medical applications.

    PubMed

    Rieu, J

    1993-01-01

    Surface transformations can be performed on metals in order to combine their load-bearing properties to the inertness and wear resistance of ceramics. In a joint prosthesis, metals are useful for their high fatigue strength and ductility, but they are more sensitive to superficial corrosion and wear than ceramics. Coating a ceramic on metal surface will improve the qualities of the metallic component. The various ways of transforming a metallic surface into a ceramic one are described. First, the surface treatments to improve the friction and wear properties are analysed. Coatings and surface transformations give superficial inert compounds. Many techniques are used to create hard, corrosion resistant layers on the surface. The processes may involve heating of the treated parts. But some metals cannot be heated without an alteration of their mechanical properties. The adhesion strength--and thus, the lifetime--of the ceramic layers depend on the binding forces and on the structure of the interfaces between the bulk metal and the outermost ceramic. Coatings generally have a lower adhesion strength than in-situ formed phases and the risk of peeling is higher. Second, the plasma-sprayed coatings performed to improve the bone anchorage are described. This review does not deal with bioactive materials. So, only the alumina coatings and their mechanical compatibility advantage are present.

  3. Lead zirconate titanate ceramics

    SciTech Connect

    Walker, B.E. Jr.

    1986-12-02

    This patent describes a lead zirconate titanate (PZT) piezoelectric ceramic composition which, based on total composition weight, consists essentially of a solid solution of lead zirconate and lead titanate in a PbZrO/sub 3/:PbTiO/sub 3/ ratio from about 0.505:0.495 to about 0.54:0.46; a halide salt selected from the group consisting of fluorides and chlorides of alkali metal and alkaline earth elements and mixtures thereof except for francium and radium in an amount from about 0.5 to 2 weight percent; and an oxide selected from the group consisting of magnesium, barium, scandium, aluminum, lanthanum, praesodynium, neodymium, samarium, and mixtures thereof in an amount from about 0.5 to about 6 weight percent, the relative amount of oxide being from about 1 to about 4 times that of the halide.

  4. Creep in electronic ceramics

    SciTech Connect

    Routbort, J. L.; Goretta, K. C.; Arellano-Lopez, A. R.

    2000-04-27

    High-temperature creep measurements combined with microstructural investigations can be used to elucidate deformation mechanisms that can be related to the diffusion kinetics and defect chemistry of the minority species. This paper will review the theoretical basis for this correlation and illustrate it with examples from some important electronic ceramics having a perovskite structure. Recent results on BaTiO{sub 3}, (La{sub 1{minus}x}Sr){sub 1{minus}y}MnO{sub 3+{delta}}, YBa{sub 2}Cu{sub 3}O{sub x}, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x}, (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} and Sr(Fe,Co){sub 1.5}O{sub x} will be presented.

  5. Lightweight Ceramic Insulation

    NASA Technical Reports Server (NTRS)

    Wheeler, W. H.; Creedon, J. F.

    1986-01-01

    Fiber burnout process yields low densities. Low density attained by process of sacrificial burnout. Graphite or carbon fibers mixed into slurry of silica, alumina, and boron-compound fibers in amounts ranging from 25 to 75 percent of total fiber content by weight. Mixture formed into blocks and dried. Blocks placed in kiln and heated to 1,600 degrees F(870 degrees C) for several hours. Graphite or carbon fibers slowly oxidize away, leaving voids and reducing block density. Finally, blocks heated to 2,350 degrees F (1,290 degrees C) for 90 minutes to bond remaining ceramic fibers together. Developed for use on Space Shuttle and other spacecraft, rigid insulation machined to requisite shape and bonded in place.

  6. Ceramic turbine nozzle

    DOEpatents

    Shaffer, J.E.; Norton, P.F.

    1996-12-17

    A turbine nozzle and shroud assembly having a preestablished rate of thermal expansion is positioned in a gas turbine engine and being attached to conventional metallic components. The metallic components have a preestablished rate of thermal expansion greater than the preestablished rate of thermal expansion of the turbine nozzle vane assembly. The turbine nozzle vane assembly includes a plurality of segmented vane defining a first vane segment and a second vane segment, each of the first and second vane segments having a vertical portion, and each of the first vane segments and the second vane segments being positioned in functional relationship one to another within a recess formed within an outer shroud and an inner shroud. The turbine nozzle and shroud assembly provides an economical, reliable and effective ceramic component having a preestablished rate of thermal expansion being less than the preestablished rate of thermal expansion of the other component. 4 figs.

  7. Ceramic turbine nozzle

    DOEpatents

    Shaffer, James E.; Norton, Paul F.

    1996-01-01

    A turbine nozzle and shroud assembly having a preestablished rate of thermal expansion is positioned in a gas turbine engine and being attached to conventional metallic components. The metallic components having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the turbine nozzle vane assembly. The turbine nozzle vane assembly includes a plurality of segmented vane defining a first vane segment and a second vane segment. Each of the first and second vane segments having a vertical portion. Each of the first vane segments and the second vane segments being positioned in functional relationship one to another within a recess formed within an outer shroud and an inner shroud. The turbine nozzle and shroud assembly provides an economical, reliable and effective ceramic component having a preestablished rate of thermal expansion being less than the preestablished rate of thermal expansion of the other component.

  8. OXYGEN TRANSPORT CERAMIC MEMBRANES

    SciTech Connect

    Dr. Sukumar Bandopadhyay; Dr. Nagendra Nagabhushana

    2003-01-01

    In the present quarter, experiments are presented on ceramic/metal interactions of Zirconia/Ni-B-Si system and with a thin Ti coating deposited on zirconia surface. Processing of perovskites of LSC, LSF and LSCF composition for evaluation of mechanical properties as a function of environment are begun. The studies are to be in parallel with LSFCO composition to characterize the segregation of cations and slow crack growth in environmental conditions. La{sub 1-x}Sr{sub x}FeO{sub 3-d} has also been characterized for paramagnetic ordering at room temperature and the evolution of magnetic moments as a function of temperature are investigated. Investigation on the thermodynamic properties of the membrane materials are continued to develop a complete model for the membrane transport.

  9. Ceramic Cerami Turbine Nozzle

    DOEpatents

    Boyd, Gary L.

    1997-04-01

    A turbine nozzle vane assembly having a preestablished rate of thermal expansion is positioned in a gas turbine engine and being attached to conventional metallic components. The metallic components having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the turbine nozzle vane assembly. The turbine nozzle vane assembly includes an outer shroud and an inner shroud having a plurality of horizontally segmented vanes therebetween being positioned by a connecting member positioning segmented vanes in functional relationship one to another. The turbine nozzle vane assembly provides an economical, reliable and effective ceramic component having a preestablished rate of thermal expansion being greater than the preestablished rate of thermal expansion of the other component.

  10. Creation of a ceramics handbook

    NASA Technical Reports Server (NTRS)

    Craft, W. J.; Filatovs, G. J.

    1974-01-01

    A study was conducted to develop a ceramics handbook defining properties and parameters necessary for thermostructural design. Continuing efforts toward this goal, and in particular toward the evolution of a reliable predictor of fracture from current literature, are described.

  11. Ceramic powder for sintering materials

    NASA Technical Reports Server (NTRS)

    Akiya, H.; Saito, A.

    1984-01-01

    Surface activity of ceramic powders such as MgO and Al2O3, for use in sintering with sp. emphasis on their particle size, shape, particle size distribution, packing, and coexisting additives and impurities are reviewed.

  12. Ceramic regenerator systems development program

    NASA Technical Reports Server (NTRS)

    Fucinari, C. A.; Rahnke, C. J.; Rao, V. D. N.; Vallance, J. K.

    1980-01-01

    The DOE/NASA Ceramic Regenerator Design and Reliability Program aims to develop ceramic regenerator cores that can be used in passenger car and industrial/truck gas turbine engines. The major cause of failure of early gas turbine regenerators was found to be chemical attack of the ceramic material. Improved materials and design concepts aimed at reducing or eliminating chemical attack were placed on durability test in Ford 707 industrial gas turbine engines late in 1974. Results of 53,065 hours of turbine engine durability testing are described. Two materials, aluminum silicate and magnesium aluminum silicate, show promise. Five aluminum silicate cores attained the durability objective of 10,000 hours at 800 C (1472 F). Another aluminum silicate core shows minimal evidence of chemical attack after 8071 hours at 982 C (1800 F). Results obtained in ceramic material screening tests, aerothermodynamic performance tests, stress analysis, cost studies, and material specifications are included.

  13. Recent progress in ceramic joining

    SciTech Connect

    Loehman, R.E.

    1998-09-01

    Both fundamental and practical aspects of ceramic joining are understood well enough for many, if not most, applications requiring moderate strengths at room temperature. This paper argues that the two greatest needs in ceramic joining are for techniques to join buried interfaces by selective heating, and methods for joining ceramics for use at temperatures of 800 to 1,200 C. Heating with microwave radiation or with high-energy electron beams has been used to join buried ceramic interfaces, for example SiC to SiC. Joints with varying levels of strength at temperatures of 600 to 1,000 C have been made using four techniques: (1) transient liquid phase bonding; (2) joining with refractory braze alloys; (3) joining with refractory glass compositions; and (4) joining using preceramic polymers. Joint strengths as high as 550 MPa at 1,000 C have been reported for silicon nitride-silicon nitride bonds tested in four-point flexure.

  14. Inorganic glass ceramic slip rings

    NASA Technical Reports Server (NTRS)

    Glossbrenner, E. W.; Cole, S. R.

    1972-01-01

    Prototypes of slip rings have been fabricated from ceramic glass, a material which is highly resistant to deterioration due to high temperature. Slip ring assemblies were not structurally damaged by mechanical tests and performed statisfactorily for 200 hours.

  15. Process for producing advanced ceramics

    DOEpatents

    Kwong, Kyei-Sing

    1996-01-01

    A process for the synthesis of homogeneous advanced ceramics such as SiC+AlN, SiAlON, SiC+Al.sub.2 O.sub.3, and Si.sub.3 N.sub.4 +AlN from natural clays such as kaolin, halloysite and montmorillonite by an intercalation and heat treatment method. Included are the steps of refining clays, intercalating organic compounds into the layered structure of clays, drying the intercalated mixture, firing the treated atmospheres and grinding the loosely agglomerated structure. Advanced ceramics produced by this procedure have the advantages of homogeneity, cost effectiveness, simplicity of manufacture, ease of grind and a short process time. Advanced ceramics produced by this process can be used for refractory, wear part and structure ceramics.

  16. Ceramic automotive Stirling engine study

    NASA Technical Reports Server (NTRS)

    Musikant, S.; Chiu, W.; Darooka, D.; Mullings, D. M.; Johnson, C. A.

    1985-01-01

    A conceptual design study for a Ceramic Automotive Stirling Engine (CASE) is performed. Year 1990 structural ceramic technology is assumed. Structural and performance analyses of the conceptual design are performed as well as a manufacturing and cost analysis. The general conclusions from this study are that such an engine would be 10-26% more efficient over its performance map than the current metal Automotive Stirling Reference Engine (ASRE). Cost of such a ceramic engine is likely to be somewhat higher than that of the ASRE but engine cost is very sensitive to the ultimate cost of the high purity, ceramic powder raw materials required to fabricate high performance parts. When the design study is projected to the year 2000 technology, substantinal net efficiency improvements, on the order of 25 to 46% over the ASRE, are computed.

  17. Abstracted model for ceramic coating

    SciTech Connect

    Farmer, J C; Stockman, C

    1998-11-14

    Engineers are exploring several mechanisms to delay corrosive attack of the CAM (corrosion allowance material) by dripping water, including drip shields and ceramic coatings. Ceramic coatings deposited with high-velocity oxyfuels (HVOF's) have exhibited a porosity of only 2% at a thickness of 0.15 cm. The primary goal of this document is to provide a detailed description of an abstracted process-level model for Total System Performance Assessment (TSPA) that has been developed to account for the inhibition of corrosion by protective ceramic coatings. A second goal was to address as many of the issues raised during a recent peer review as possible (direct reaction of liquid water with carbon steel, stress corrosion cracking of the ceramic coating, bending stresses in coatings of finite thickness, limitations of simple correction factors, etc.). During the periods of dry oxidation (T ≥ 100°C) and humid-air corrosion (T ≤ 100°C & RH < 8O%), it is assumed that the growth rate of oxide on the surface is diminished in proportion to the surface covered by solid ceramic. The mass transfer impedance imposed by a ceramic coating with gas-filled pores is assumed to be negligible. During the period of aqueous phase corrosion (T ≤ 100°C & RH ≥ 80%), it is assumed that the overall mass transfer resistance governing the corrosion rate is due to the combined resistance of ceramic coating & interfacial corrosion products. Two porosity models (simple cylinder & cylinder-sphere chain) are considered in estimation of the mass transfer resistance of the ceramic coating. It is evident that substantial impedance to 0₂ transport is encountered if pores are filled with liquid water. It may be possible to use a sealant to eliminate porosity. Spallation (rupture) of the ceramic coating is assumed to occur if the stress introduced by the expanding corrosion products at the ceramic- CAM interface exceeds fracture stress. Since this model does not account for the possibility of

  18. Metal-ceramic joint assembly

    DOEpatents

    Li, Jian

    2002-01-01

    A metal-ceramic joint assembly in which a brazing alloy is situated between metallic and ceramic members. The metallic member is either an aluminum-containing stainless steel, a high chromium-content ferritic stainless steel or an iron nickel alloy with a corrosion protection coating. The brazing alloy, in turn, is either an Au-based or Ni-based alloy with a brazing temperature in the range of 9500 to 1200.degree. C.

  19. Glass and ceramics. [lunar resources

    NASA Technical Reports Server (NTRS)

    Haskin, Larry A.

    1992-01-01

    A variety of glasses and ceramics can be produced from bulk lunar materials or from separated components. Glassy products include sintered regolith, quenched molten basalt, and transparent glass formed from fused plagioclase. No research has been carried out on lunar material or close simulants, so properties are not known in detail; however, common glass technologies such as molding and spinning seem feasible. Possible methods for producing glass and ceramic materials are discussed along with some potential uses of the resulting products.

  20. Extruded ceramic honeycomb and method

    DOEpatents

    Day, J. Paul

    1995-04-04

    Extruded low-expansion ceramic honeycombs comprising beta-spodumene solid solution as the principal crystal phase and with less than 7 weight percent of included mullite are produced by compounding an extrusion batch comprising a lithium aluminosilicate glass powder and a clay additive, extruding a green honeycomb body from the batch, and drying and firing the green extruded cellular honeycomb to crystallize the glass and clay into a low-expansion spodumene ceramic honeycomb body.

  1. Batch compositions for cordierite ceramics

    DOEpatents

    Hickman, David L.

    1994-07-26

    Ceramic products consisting principally of cordierite and a method for making them are provided, the method employing batches comprising a mineral component and a chemical component, the mineral component comprising clay and talc and the chemical component consisting essentially of a combination of the powdered oxides, hydroxides, or hydrous oxides of magnesium, aluminum and silicon. Ceramics made by extrusion and firing of the batches can exhibit low porosity, high strength and low thermal expansion coefficients.

  2. Casting Of Multilayer Ceramic Tapes

    NASA Technical Reports Server (NTRS)

    Collins, Earl R., Jr.

    1991-01-01

    Procedure for casting thin, multilayer ceramic membranes, commonly called tapes, involves centrifugal casting at accelerations of 1,800 to 2,000 times normal gravitational acceleration. Layers of tape cast one at a time on top of any previous layer or layers. Each layer cast from slurry of ground ceramic suspended in mixture of solvents, binders, and other components. Used in capacitors, fuel cells, and electrolytic separation of oxygen from air.

  3. High-temperature ceramic receivers

    SciTech Connect

    Jarvinen, P. O.

    1980-01-01

    An advanced ceramic dome cavity receiver is discussed which heats pressurized gas to temperatures above 1800/sup 0/F (1000/sup 0/C) for use in solar Brayton power systems of the dispersed receiver/dish or central receiver type. Optical, heat transfer, structural, and ceramic material design aspects of the receiver are reported and the development and experimental demonstration of a high-temperature seal between the pressurized gas and the high-temperature silicon carbide dome material is described.

  4. Heat distribution ceramic processing method

    DOEpatents

    Tiegs, Terry N.; Kiggans, Jr., James O.

    2001-01-01

    A multi-layered heat distributor system is provided for use in a microwave process. The multi-layered heat distributors includes a first inner layer of a high thermal conductivity heat distributor material, a middle insulating layer and an optional third insulating outer layer. The multi-layered heat distributor system is placed around the ceramic composition or article to be processed and located in a microwave heating system. Sufficient microwave energy is applied to provide a high density, unflawed ceramic product.

  5. Method for preparing ceramic composite

    DOEpatents

    Alexander, Kathleen B.; Tiegs, Terry N.; Becher, Paul F.; Waters, Shirley B.

    1996-01-01

    A process for preparing ceramic composite comprising blending TiC particulates, Al.sub.2 O.sub.3 particulates and nickle aluminide and consolidating the mixture at a temperature and pressure sufficient to produce a densified ceramic composite having fracture toughness equal to or greater than 7 MPa m.sup.1/2, a hardness equal to or greater than 18 GPa.

  6. Method for preparing ceramic composite

    DOEpatents

    Alexander, K.B.; Tiegs, T.N.; Becher, P.F.; Waters, S.B.

    1996-01-09

    A process is disclosed for preparing ceramic composite comprising blending TiC particulates, Al{sub 2}O{sub 3} particulates and nickel aluminide and consolidating the mixture at a temperature and pressure sufficient to produce a densified ceramic composite having fracture toughness equal to or greater than 7 MPa m{sup 1/2}, a hardness equal to or greater than 18 GPa. 5 figs.

  7. Nonlinear fracture of concrete and ceramics

    NASA Technical Reports Server (NTRS)

    Kobayashi, Albert S.; Du, Jia-Ji; Hawkins, Niel M.; Bradt, Richard C.

    1989-01-01

    The nonlinear fracture process zones in an impacted unnotched concrete bend specimen, a prenotched ceramic bend specimen, and an unnotched ceramic/ceramic composite bend specimen were estimated through hybrid experimental numerical analysis. Aggregate bridging in concrete, particulate bridging in ceramics, and fiber bridging in ceramic/ceramic composite are modeled by Barenblatt-type cohesive zones which are incorporated into the finite-element models of the bend specimens. Both generation and propagation analyses are used to estimate the distribution of crack closure stresses in the nonlinear fracture process zones. The finite-element models are then used to simulate fracture tests consisting of rapid crack propagation in an impacted concrete bend specimen, and stable crack growth and strain softening in a ceramic and ceramic/ceramic composite bend specimens.

  8. Wedge edge ceramic combustor tile

    DOEpatents

    Shaffer, J.E.; Holsapple, A.C.

    1997-06-10

    A multipiece combustor has a portion thereof being made of a plurality of ceramic segments. Each of the plurality of ceramic segments have an outer surface and an inner surface. Each of the plurality of ceramic segments have a generally cylindrical configuration and including a plurality of joints. The joints define joint portions, a first portion defining a surface being skewed to the outer surface and the inner surface. The joint portions have a second portion defining a surface being skewed to the outer surface and the inner surface. The joint portions further include a shoulder formed intermediate the first portion and the second portion. The joints provide a sealing interlocking joint between corresponding ones of the plurality of ceramic segments. Thus, the multipiece combustor having the plurality of ceramic segment with the plurality of joints reduces the physical size of the individual components and the degradation of the surface of the ceramic components in a tensile stress zone is generally eliminated reducing the possibility of catastrophic failures. 7 figs.

  9. Wedge edge ceramic combustor tile

    DOEpatents

    Shaffer, James E.; Holsapple, Allan C.

    1997-01-01

    A multipiece combustor has a portion thereof being made of a plurality of ceramic segments. Each of the plurality of ceramic segments have an outer surface and an inner surface. Each of the plurality of ceramic segments have a generally cylindrical configuration and including a plurality of joints. The joints define joint portions, a first portion defining a surface being skewed to the outer surface and the inner surface. The joint portions have a second portion defining a surface being skewed to the outer surface and the inner surface. The joint portions further include a shoulder formed intermediate the first portion and the second portion. The joints provide a sealing interlocking joint between corresponding ones of the plurality of ceramic segments. Thus, the multipiece combustor having the plurality of ceramic segment with the plurality of joints reduces the physical size of the individual components and the degradation of the surface of the ceramic components in a tensile stress zone is generally eliminated reducing the possibility of catastrophic failures.

  10. Method for Waterproofing Ceramic Materials

    NASA Technical Reports Server (NTRS)

    Cagliostro, Domenick E. (Inventor); Hsu, Ming-Ta S. (Inventor)

    1998-01-01

    Hygroscopic ceramic materials which are difficult to waterproof with a silane, substituted silane or silazane waterproofing agent, such as an alumina containing fibrous, flexible and porous, fibrous ceramic insulation used on a reentry space vehicle, are rendered easy to waterproof if the interior porous surface of the ceramic is first coated with a thin coating of silica. The silica coating is achieved by coating the interior surface of the ceramic with a silica precursor converting the precursor to silica either in-situ or by oxidative pyrolysis and then applying the waterproofing agent to the silica coated ceramic. The silica precursor comprises almost any suitable silicon containing material such as a silane, silicone, siloxane, silazane and the like applied by solution, vapor deposition and the like. If the waterproofing is removed by e.g., burning, the silica remains and the ceramic is easily rewaterproofed. An alumina containing TABI insulation which absorbs more that five times its weight of water, absorbs less than 10 wt. % water after being waterproofed according to the method of the invention.

  11. Failure Analysis of Ceramic Components

    SciTech Connect

    B.W. Morris

    2000-06-29

    Ceramics are being considered for a wide range of structural applications due to their low density and their ability to retain strength at high temperatures. The inherent brittleness of monolithic ceramics requires a departure from the deterministic design philosophy utilized to analyze metallic structural components. The design program ''Ceramic Analysis and Reliability Evaluation of Structures Life'' (CARES/LIFE) developed by NASA Lewis Research Center uses a probabilistic approach to predict the reliability of monolithic components under operational loading. The objective of this study was to develop an understanding of the theories used by CARES/LIFE to predict the reliability of ceramic components and to assess the ability of CARES/LIFE to accurately predict the fast fracture behavior of monolithic ceramic components. A finite element analysis was performed to determine the temperature and stress distribution of a silicon carbide O-ring under diametral compression. The results of the finite element analysis were supplied as input into CARES/LIFE to determine the fast fracture reliability of the O-ring. Statistical material strength parameters were calculated from four-point flexure bar test data. The predicted reliability showed excellent correlation with O-ring compression test data indicating that the CARES/LIFE program can be used to predict the reliability of ceramic components subjected to complicated stress states using material properties determined from simple uniaxial tensile tests.

  12. Surface roughness of a dental ceramic after polishing with different vehicles and diamond pastes.

    PubMed

    Camacho, Guilherme Brião; Vinha, Dionísio; Panzeri, Heitor; Nonaka, Tomio; Gonçalves, Mariane

    2006-01-01

    During fabrication of bonded ceramic restorations, cervical adaptation, occlusal adjustment and final finishing/polishing are procedures to be performed at the dental office after adhesive cementation. Final adjustments may result in loss of ceramic glaze, which requires new polishing of the ceramic surface, with special attention for selection of adequate materials and instruments. The purpose of this study was to evaluate the efficiency of different vehicles associated with diamond pastes indicated for dental ceramic polishing. Two polishing pastes (Crystar Paste and Diamond Excell) associated with four vehicles (rubber cup, Robinson bristle brush, felt wheel and buff disc) were evaluated. Disc-shaped specimens were fabricated from Ceramco II dental ceramic. Surface roughness means (Ra) of the ceramic specimens were determined with a rugosimeter. Data were analyzed statistically by two-way ANOVA and Tukey's test at 5% significance level. There was no statistically significant difference (p>0.01) between the polishing pastes. However, there were statistically significant differences (p<0.01) among the tested vehicles. Vehicle-paste interaction showed statistically significant difference (p<0.05) as well. It may be concluded that: 1) Robinson bristle brush, felt wheel and buff disc were efficient vehicles to be used in association with a diamond polishing paste; 2) The use of rubber cup as a vehicle showed poor efficiency for mechanical polishing of the ceramic surfaces; 3) Both pastes provided similar and efficient polishing and may be recommended for use with an appropriated vehicle. PMID:17262123

  13. Grain orientations and distribution of Y2Ba4CuUOx phase in melt-textured YBCO with addition of depleted uranium oxide studied by EBSD

    NASA Astrophysics Data System (ADS)

    Koblischka-Veneva, A.; Mücklich, F.; Koblischka, M. R.; Babu, N. Hari; Cardwell, D. A.; Murakami, M.

    2006-07-01

    The local grain orientations and the distribution of Y2Ba4CuUOx (U-2411) phase are measured within melt-textured YBCO samples by means of electron backscatter diffraction (EBSD). In this work, several samples with varying addition (0.1-0.8 wt%) of depleted uranium oxide (DU) were analysed by means of EBSD. The embedded U-2411 particles were found to have sizes around 200 nm, some large particles being present in the samples with a high DU concentration. Combined EBSD and EDX analysis enabled the identification of the Kikuchi patterns of the U-2411 phase, so that a true three-phase EBSD scan (YBCO, Y2BaCuO5 and U-2411) becomes possible.

  14. Spectrophotometric Determination of the Hole Concentration in the Superconductor YBa2Cu3O(sub 7-x)

    ERIC Educational Resources Information Center

    Hoppe, Jack I.; Malati, Mounir A.

    2005-01-01

    An experimental study of ceramic superconductors namely YBa2Cu3O(sub 7-x), which illustrates the use of spectrophotometry, based on the electronic spectra of complexes of Fe(II), Fe(III) and Cu(II) to better understand the stoichiometry of YBCO is described. The results from this experiment are in good agreement with those obtained by the…

  15. FOREWORD: Focus on Advanced Ceramics Focus on Advanced Ceramics

    NASA Astrophysics Data System (ADS)

    Ohashi, Naoki

    2011-06-01

    Much research has been devoted recently to developing technologies for renewable energy and improving the efficiency of the processes and devices used in industry and everyday life. Efficient solutions have been found using novel materials such as platinum and palladium-based catalysts for car exhaust systems, samarium-cobalt and neodymium-iron-boron permanent magnets for electrical motors, and so on. However, their realization has resulted in an increasing demand for rare elements and in their deficit, the development of new materials based on more abundant elements and new functionalities of traditional materials. Moreover, increasing environmental and health concerns demand substitution of toxic or hazardous substances with nature-friendly alternatives. In this context, this focus issue on advanced ceramics aims to review current trends in ceramics science and technology. It is related to the International Conference on Science and Technology of Advanced Ceramics (STAC) held annually to discuss the emerging issues in the field of ceramics. An important direction of ceramic science is the collaboration between experimental and theoretical sciences. Recent developments in density functional theory and computer technology have enabled the prediction of physical and chemical properties of ceramics, thereby assisting the design of new materials. Therefore, this focus issue includes articles devoted to theory and advanced characterization techniques. As mentioned above, the potential shortage of rare elements is becoming critical to the industry and has resulted in a Japanese government initiative called the 'Ubiquitous Element Strategy'. This focus issue also includes articles related to this strategy and to the associated topics of energy conversion, such as phosphors for high-efficiency lighting and photocatalysts for solar-energy harvesting. We hope that this focus issue will provide a timely overview of current trends and problems in ceramics science and

  16. Ferroelectric ceramics in a pyroelectric accelerator

    SciTech Connect

    Shchagin, A. V.; Miroshnik, V. S.; Volkov, V. I.; Oleinik, A. N.

    2015-12-07

    The applicability of polarized ferroelectric ceramics as a pyroelectric in a pyroelectric accelerator is shown by experiments. The spectra of X-ray radiation of energy up to tens of keV, generated by accelerated electrons, have been measured on heating and cooling of the ceramics in vacuum. It is suggested that curved layers of polarized ferroelectric ceramics be used as elements of ceramic pyroelectric accelerators. Besides, nanotubes and nanowires manufactured from ferroelectric ceramics are proposed for the use in nanometer-scale ceramic pyroelectric nanoaccelerators for future applications in nanotechnologies.

  17. Progress in fabrication of large magnetic sheilds by using extended YBCO thick films sprayed on stainless steel with the HVOF technique

    SciTech Connect

    Pavese, F.; Bergadano, E.; Ferri, D.

    1997-06-01

    Fabricating a full box-type magnetic shield, by spraying a thick film of commercial YBCO powder on stainless steel with the oxygen-fuel high-velocity technique (HVOF, also referred to as {open_quotes}continuous detonation spray{close_quotes} (CDS)), requires the solution of several specific problems since the design stage of the project. The design problems of this type of shield are examined and the results obtained in the early stages of the realization are discussed.

  18. Nano-Ceramic Coated Plastics

    NASA Technical Reports Server (NTRS)

    Cho, Junghyun

    2013-01-01

    Plastic products, due to their durability, safety, and low manufacturing cost, are now rapidly replacing cookware items traditionally made of glass and ceramics. Despite this trend, some still prefer relatively expensive and more fragile ceramic/glassware because plastics can deteriorate over time after exposure to foods, which can generate odors, bad appearance, and/or color change. Nano-ceramic coatings can eliminate these drawbacks while still retaining the advantages of the plastic, since the coating only alters the surface of the plastic. The surface coating adds functionality to the plastics such as self-cleaning and disinfectant capabilities that result from a photocatalytic effect of certain ceramic systems. These ceramic coatings can also provide non-stick surfaces and higher temperature capabilities for the base plastics without resorting to ceramic or glass materials. Titanium dioxide (TiO2) and zinc oxide (ZnO) are the candidates for a nano-ceramic coating to deposit on the plastics or plastic films used in cookware and kitchenware. Both are wide-bandgap semiconductors (3.0 to 3.2 eV for TiO2 and 3.2 to 3.3 eV for ZnO), so they exhibit a photocatalytic property under ultraviolet (UV) light. This will lead to decomposition of organic compounds. Decomposed products can be easily washed off by water, so the use of detergents will be minimal. High-crystalline film with large surface area for the reaction is essential to guarantee good photocatalytic performance of these oxides. Low-temperature processing (<100 C) is also a key to generating these ceramic coatings on the plastics. One possible way of processing nanoceramic coatings at low temperatures (< 90 C) is to take advantage of in-situ precipitated nanoparticles and nanostructures grown from aqueous solution. These nanostructures can be tailored to ceramic film formation and the subsequent microstructure development. In addition, the process provides environment- friendly processing because of the

  19. Growth of epitaxial Y 2O 3 buffer layers on biaxially textured Ni-W substrates for YBCO coated conductors by MOD approach

    NASA Astrophysics Data System (ADS)

    Bhuiyan, M. S.; Paranthaman, M.; Kang, S.; Lee, D. F.; Salama, K.

    2005-06-01

    We have grown epitaxial Y 2O 3 buffer layers on biaxially textured Ni-W substrates for YBCO coated conductors using a newly developed metal organic decomposition (MOD) approach. Y 2O 3 precursor solution of 0.25 M concentration was spin coated on short samples of Ni-3 at.%W (Ni-W) substrates and heat-treated at 1150 °C in a gas mixture of Ar-4% H 2 for an hour. Detailed X-ray studies indicate that Y 2O 3 films have good out-of-plane and in-plane textures with full-width-half-maximum values of 6.22° and 7.51°, respectively. SEM and AFM investigations of Y 2O 3 films reveal a fairly dense and smooth microstructure without cracks and porosity. Highly textured YSZ barrier layers and CeO 2 cap layers were deposited on MOD Y 2O 3-buffered Ni-W substrates using rf-magnetron sputtering. Pulsed laser deposition was used to grow YBCO films on these substrates. A critical current, Jc, of about 1.21 MA/cm 2 at 77 K and self-field was obtained on YBCO (PLD)/CeO 2 (sputtered)/YSZ (sputtered)/Y 2O 3 (spin-coated)/Ni-W.

  20. MOD approach for the growth of epitaxial CeO2 buffer layers on biaxially textured Ni W substrates for YBCO coated conductors

    NASA Astrophysics Data System (ADS)

    Bhuiyan, M. S.; Paranthaman, M.; Sathyamurthy, S.; Aytug, T.; Kang, S.; Lee, D. F.; Goyal, A.; Payzant, E. A.; Salama, K.

    2003-11-01

    We have grown epitaxial CeO2 buffer layers on biaxially textured Ni-W substrates for YBCO coated conductors using a newly developed metal organic decomposition (MOD) approach. Precursor solution of 0.25 M concentration was spin coated on short samples of Ni-3 at%W (Ni-W) substrates and heat-treated at 1100 °C in a gas mixture of Ar-4%H2 for 15 min. Detailed x-ray studies indicate that CeO2 films have good out-of-plane and in-plane textures with full-width-half-maximum values of 5.8° and 7.5°, respectively. High temperature in situ XRD studies show that the nucleation of CeO2 films starts at 600 °C and the growth completes within 5 min when heated at 1100 °C. SEM and AFM investigations of CeO2 films reveal a fairly dense microstructure without cracks and porosity. Highly textured YSZ barrier layers and CeO2 cap layers were deposited on MOD CeO2-buffered Ni-W substrates using rf-magnetron sputtering. Pulsed laser deposition (PLD) was used to grow YBCO films on these substrates. A critical current, Jc, of about 1.5 MA cm-2 at 77 K and self-field was obtained on YBCO (PLD)/CeO2 (sputtered)/YSZ (sputtered)/CeO2 (spin-coated)/Ni-W.

  1. A 5.9 tesla conduction-cooled coil composed of a stack of four single pancakes wound with YBCO wide tapes

    NASA Astrophysics Data System (ADS)

    Iwai, Sadanori; Miyazaki, Hiroshi; Tosaka, Taizo; Tasaki, Kenji; Urata, Masami; Ioka, Shigeru; Ishii, Yusuke

    2013-11-01

    We have been developing a conduction-cooled coil wound with YBCO-coated conductors for HTS applications. Previously, we have fabricated a coil composed of a stack of 12 single pancakes wound with 4 mm-wide YBCO tapes. This coil had a central magnetic field as high as 5.1 T at 10 K under conduction-cooled conditions. In the present study, we fabricated and tested a coil composed of a stack of four single pancakes wound with 12 mm-wide YBCO tapes. The total size of the coil and the Jc value of the tapes were almost the same as those of the former coil. At 77 K, the voltage-current characteristics showed a high n-value of 24, confirming that the coil had no degradation. Furthermore, in a conduction-cooled configuration at 20 K to 60 K, the coil showed a high n-value of over 20. At 20 K, the central magnetic field reached 5.9 T at 903 A, which is 1.3-times higher than that of the former coil.

  2. Performance of Ceramics in Severe Environments

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Fox, Dennis S.; Smialek, James L.; Deliacorte, Christopher; Lee, Kang N.

    2005-01-01

    Ceramics are generally stable to higher temperatures than most metals and alloys. Thus the development of high temperature structural ceramics has been an area of active research for many years. While the dream of a ceramic heat engine still faces many challenges, niche markets are developing for these materials at high temperatures. In these applications, ceramics are exposed not only to high temperatures but also aggressive gases and deposits. In this chapter we review the response of ceramic materials to these environments. We discuss corrosion mechanisms, the relative importance of a particular corrodent, and, where available, corrosion rates. Most of the available corrosion information is on silicon carbide (SIC) and silicon nitride (Si3N4) monolithic ceramics. These materials form a stable film of silica (SO2) in an oxidizing environment. We begin with a discussion of oxidation of these materials and proceed to the effects of other corrodents such as water vapor and salt deposits. We also discuss oxidation and corrosion of other ceramics: precurser derived ceramics, ceramic matrix composites (CMCs), ceramics which form oxide scales other than silica, and oxide ceramics. Many of the corrosion issues discussed can be mitigated with refractory oxide coatings and we discuss the current status of this active area of research. Ultimately, the concern of corrosion is loss of load bearing capability. We discuss the effects of corrosive environments on the strength of ceramics, both monolithic and composite. We conclude with a discussion of high temperature wear of ceramics, another important form of degradation at high temperatures.

  3. Glass Ceramic Formulation Data Package

    SciTech Connect

    Crum, Jarrod V.; Rodriguez, Carmen P.; McCloy, John S.; Vienna, John D.; Chung, Chul-Woo

    2012-06-17

    A glass ceramic waste form is being developed for treatment of secondary waste streams generated by aqueous reprocessing of commercial used nuclear fuel (Crum et al. 2012b). The waste stream contains a mixture of transition metals, alkali, alkaline earths, and lanthanides, several of which exceed the solubility limits of a single phase borosilicate glass (Crum et al. 2009; Caurant et al. 2007). A multi-phase glass ceramic waste form allows incorporation of insoluble components of the waste by designed crystallization into durable heat tolerant phases. The glass ceramic formulation and processing targets the formation of the following three stable crystalline phases: (1) powellite (XMoO4) where X can be (Ca, Sr, Ba, and/or Ln), (2) oxyapatite Yx,Z(10-x)Si6O26 where Y is alkaline earth, Z is Ln, and (3) lanthanide borosilicate (Ln5BSi2O13). These three phases incorporate the waste components that are above the solubility limit of a single-phase borosilicate glass. The glass ceramic is designed to be a single phase melt, just like a borosilicate glass, and then crystallize upon slow cooling to form the targeted phases. The slow cooling schedule is based on the centerline cooling profile of a 2 foot diameter canister such as the Hanford High-Level Waste canister. Up to this point, crucible testing has been used for glass ceramic development, with cold crucible induction melter (CCIM) targeted as the ultimate processing technology for the waste form. Idaho National Laboratory (INL) will conduct a scaled CCIM test in FY2012 with a glass ceramic to demonstrate the processing behavior. This Data Package documents the laboratory studies of the glass ceramic composition to support the CCIM test. Pacific Northwest National Laboratory (PNNL) measured melt viscosity, electrical conductivity, and crystallization behavior upon cooling to identify a processing window (temperature range) for melter operation and cooling profiles necessary to crystallize the targeted phases in the

  4. A novel HTS magnetometer, exploiting the low jc of bulk YBCO

    SciTech Connect

    Gallop, J.C.; Lilleyman, S.; Langham, C.D.; Radcliffe, W.J.; Stewart, M.

    1989-03-01

    The authors report here a novel of magnetometer which is based on the low critical magnetic field H/sub cl/ of sintered samples of the high temperature ceramic superconductor YBa/sub 2/Cu/sub 3/O/sub y/. By driving a sample of the superconductor around a magnetization hysteresis loop, at a frequency of --100 kHz, and detecting the induced voltage in a coil coupled to the sample, at the second harmonic of the drive frequency, the authors find that this voltage is linearly dependent on the aplied d.c. magnetic field in which the sample is situated. They present a model which explains the operation of this magnetometer. This device, while not as sensitive as a SQUID, has the advantage of a wider dynamic range and direct measurement of flux density, unlike a SQUID which is only capable of sensing flux density changes. When operated at 77K the prototype magnetometer has already demonstrated a sensitivity at least 10 times better than that of a commercial fluxgate magnetometer. The system also appears to provide a simple method for investigation of flux flow in these materials.

  5. Ceramic HEPA Filter Program

    SciTech Connect

    Mitchell, M A; Bergman, W; Haslam, J; Brown, E P; Sawyer, S; Beaulieu, R; Althouse, P; Meike, A

    2012-04-30

    Potential benefits of ceramic filters in nuclear facilities: (1) Short term benefit for DOE, NRC, and industry - (a) CalPoly HTTU provides unique testing capability to answer questions for DOE - High temperature testing of materials, components, filter, (b) Several DNFSB correspondences and presentations by DNFSB members have highlighted the need for HEPA filter R and D - DNFSB Recommendation 2009-2 highlighted a nuclear facility response to an evaluation basis earthquake followed by a fire (aka shake-n-bake) and CalPoly has capability for a shake-n-bake test; (2) Intermediate term benefit for DOE and industry - (a) Filtration for specialty applications, e.g., explosive applications at Nevada, (b) Spin-off technologies applicable to other commercial industries; and (3) Long term benefit for DOE, NRC, and industry - (a) Across industry, strong desire for better performance filter, (b) Engineering solution to safety problem will improve facility safety and decrease dependence on associated support systems, (c) Large potential life-cycle cost savings, and (d) Facilitates development and deployment of LLNL process innovations to allow continuous ventilation system operation during a fire.

  6. Ordered ceramic membranes

    SciTech Connect

    Anderson, M.A.; Hill, C.G. Jr.; Zeltner, W.A.

    1991-10-01

    Ceramic membranes have been formed from colloidal sols coated on porous clay supports. These supported membranes have been characterized in terms of their permeabilities and permselectivities to various aqueous test solutions. The thermal stabilities and pore structures of these membranes have been characterized by preparing unsupported membranes of the correpsonding material and performing N{sub 2} adsorption-desorption and X-ray diffraction studies on these membranes. To date, membranes have been prepared from a variety of oxides, including TiO{sub 2}, SiO{sub 2}, ZrO{sub 2}, and Al{sub 2}O{sub 3}, as well as Zr-, Fe-, and Nb-doped TiO{sub 2}. In many of these membranes pore diameters are less than 2 nm, while in others the pore diameters are between 3 and 5 nm. Procedures for fabricating porous clay supports with reproducible permeabilities for pure water are also discussed. 30 refs., 59 figs., 22 tabs.

  7. Disc piezoelectric ceramic transformers.

    PubMed

    Erhart, Jirií; Půlpán, Petr; Doleček, Roman; Psota, Pavel; Lédl, Vít

    2013-08-01

    In this contribution, we present our study on disc-shaped and homogeneously poled piezoelectric ceramic transformers working in planar-extensional vibration modes. Transformers are designed with electrodes divided into wedge, axisymmetrical ring-dot, moonie, smile, or yin-yang segments. Transformation ratio, efficiency, and input and output impedances were measured for low-power signals. Transformer efficiency and transformation ratio were measured as a function of frequency and impedance load in the secondary circuit. Optimum impedance for the maximum efficiency has been found. Maximum efficiency and no-load transformation ratio can reach almost 100% and 52 for the fundamental resonance of ring-dot transformers and 98% and 67 for the second resonance of 2-segment wedge transformers. Maximum efficiency was reached at optimum impedance, which is in the range from 500 Ω to 10 kΩ, depending on the electrode pattern and size. Fundamental vibration mode and its overtones were further studied using frequency-modulated digital holographic interferometry and by the finite element method. Complementary information has been obtained by the infrared camera visualization of surface temperature profiles at higher driving power. PMID:25004532

  8. Bar piezoelectric ceramic transformers.

    PubMed

    Erhart, Jiří; Pulpan, Půlpán; Rusin, Luboš

    2013-07-01

    Bar-shaped piezoelectric ceramic transformers (PTs) working in the longitudinal vibration mode (k31 mode) were studied. Two types of the transformer were designed--one with the electrode divided into two segments of different length, and one with the electrodes divided into three symmetrical segments. Parameters of studied transformers such as efficiency, transformation ratio, and input and output impedances were measured. An analytical model was developed for PT parameter calculation for both two- and three-segment PTs. Neither type of bar PT exhibited very high efficiency (maximum 72% for three-segment PT design) at a relatively high transformation ratio (it is 4 for two-segment PT and 2 for three-segment PT at the fundamental resonance mode). The optimum resistive loads were 20 and 10 kΩ for two- and three-segment PT designs for the fundamental resonance, respectively, and about one order of magnitude smaller for the higher overtone (i.e., 2 kΩ and 500 Ω, respectively). The no-load transformation ratio was less than 27 (maximum for two-segment electrode PT design). The optimum input electrode aspect ratios (0.48 for three-segment PT and 0.63 for two-segment PT) were calculated numerically under no-load conditions.

  9. Disc piezoelectric ceramic transformers.

    PubMed

    Erhart, Jirií; Půlpán, Petr; Doleček, Roman; Psota, Pavel; Lédl, Vít

    2013-08-01

    In this contribution, we present our study on disc-shaped and homogeneously poled piezoelectric ceramic transformers working in planar-extensional vibration modes. Transformers are designed with electrodes divided into wedge, axisymmetrical ring-dot, moonie, smile, or yin-yang segments. Transformation ratio, efficiency, and input and output impedances were measured for low-power signals. Transformer efficiency and transformation ratio were measured as a function of frequency and impedance load in the secondary circuit. Optimum impedance for the maximum efficiency has been found. Maximum efficiency and no-load transformation ratio can reach almost 100% and 52 for the fundamental resonance of ring-dot transformers and 98% and 67 for the second resonance of 2-segment wedge transformers. Maximum efficiency was reached at optimum impedance, which is in the range from 500 Ω to 10 kΩ, depending on the electrode pattern and size. Fundamental vibration mode and its overtones were further studied using frequency-modulated digital holographic interferometry and by the finite element method. Complementary information has been obtained by the infrared camera visualization of surface temperature profiles at higher driving power.

  10. Reliability of ceramics for heat engine applications

    NASA Technical Reports Server (NTRS)

    1980-01-01

    The advantages and disadvantages associated with the use of monolithic ceramics in heat engines are discussed. The principle gaps in the state of understanding of ceramic material, failure origins, nondestructive tests as well as life prediction are included.

  11. Thermally induced micromechanical stresses in ceramic/ceramic composites

    SciTech Connect

    Li, Zhuang; Bradt, R.C.

    1992-11-01

    The internal micromechanical stresses which develop in ceramic-ceramic composites as a consequence of temperature changes and thermoelastic property differences between the reinforcing and matrix phases are addressed by the Eshelby method. Results for two whisker reinforced ceramic matrix composites and for quartz particles in porcelain are discussed. It is concluded that the stresses which develop in the second phase reinforcing inclusions are quite substantial (GPa-levels) and may be highly anisotropic in character. These stresses are additive to the macroscopic thermal stresses from temperature gradients which are encountered during heating and cooling, and also to externally apphed mechanical stresses (loads). These micromechanical stresses are expected to be highly significant for thermal cycling fatigue and other failure processes.

  12. Catastrophic failure of ceramic-on-ceramic total hip arthroplasty presenting as squeaking hip

    PubMed Central

    Malem, David; Nagy, Mathias Thomas; Ghosh, Sabyasachi; Shah, Bhavik

    2013-01-01

    A 68-year-old woman with osteoarthritis had a ceramic-on-ceramic left total hip arthroplasty, including ceramic femoral head and acetabular liner. At 5 years after surgery, the patient developed onset of a very loud squeaking noise, which could be heard 25 m from her, associated with limited hip movement. Findings at revision surgery included a broken ceramic femoral head component, complete wear of the ceramic acetabular component, and black wear debris. Squeaking hip after ceramic-on-ceramic total hip arthroplasty may be associated with catastrophic failure of the arthroplasty components. PMID:23429031

  13. Protein adsorption onto ceramic surfaces.

    PubMed

    Takami, Y; Yamane, S; Makinouchi, K; Otsuka, G; Glueck, J; Benkowski, R; Nosé, Y

    1998-04-01

    Ceramics seldom have been used as blood-contacting materials. However, alumina ceramic (Al2O3) and polyethylene are incorporated into the pivot bearings of the Gyro centrifugal blood pump. This material combination was chosen based on the high durability of the materials. Due to the stagnant flow that often occurs in a continuous flow condition inside a centrifugal pump, pivot bearing system is extremely critical. To evaluate the thombogenicity of pivot bearings in the Gyro pump, this study sought to investigate protein adsorption, particularly albumin, IgG, fibrinogen, and fibronectin onto ceramic surfaces. Al2O3 and silicon carbide ceramic (SiC) were compared with polyethylene (PE) and polyvinylchloride (PVC). Bicinchoninic acid (BCA) protein assay revealed that the amount of adsorbed proteins onto Al2O3 and SiC was significantly less than that on PVC. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) indicated that numerous proteins adsorbed onto PVC compared to PE, Al2O3, and SiC. Identification of adsorbed proteins by Western immunoblotting revealed that the adsorption of albumin was similar on all four materials tested. Western immunoblotting also indicated lesser amounts of IgG, fibrinogen, and fibronectin on Al2O3 and SiC than on PE and PVC. In conclusion, ceramics (Al2O3 and SiC) are expected to be thromboresistant from the viewpoint of protein adsorption. PMID:9511095

  14. Transient liquid phase ceramic bonding

    DOEpatents

    Glaeser, Andreas M.

    1994-01-01

    Ceramics are joined to themselves or to metals using a transient liquid phase method employing three layers, one of which is a refractory metal, ceramic or alloy. The refractory layer is placed between two metal layers, each of which has a lower melting point than the refractory layer. The three layers are pressed between the two articles to be bonded to form an assembly. The assembly is heated to a bonding temperature at which the refractory layer remains solid, but the two metal layers melt to form a liquid. The refractory layer reacts with the surrounding liquid and a single solid bonding layer is eventually formed. The layers may be designed to react completely with each other and form refractory intermetallic bonding layers. Impurities incorporated into the refractory metal may react with the metal layers to form refractory compounds. Another method for joining ceramic articles employs a ceramic interlayer sandwiched between two metal layers. In alternative embodiments, the metal layers may include sublayers. A method is also provided for joining two ceramic articles using a single interlayer. An alternate bonding method provides a refractory-metal oxide interlayer placed adjacent to a strong oxide former. Aluminum or aluminum alloys are joined together using metal interlayers.

  15. Shock compression profiles in ceramics

    SciTech Connect

    Grady, D.E.; Moody, R.L.

    1996-03-01

    An investigation of the shock compression properties of high-strength ceramics has been performed using controlled planar impact techniques. In a typical experimental configuration, a ceramic target disc is held stationary, and it is struck by plates of either a similar ceramic or by plates of a well-characterized metal. All tests were performed using either a single-stage propellant gun or a two-stage light-gas gun. Particle velocity histories were measured with laser velocity interferometry (VISAR) at the interface between the back of the target ceramic and a calibrated VISAR window material. Peak impact stresses achieved in these experiments range from about 3 to 70 GPa. Ceramics tested under shock impact loading include: Al{sub 2}O{sub 3}, AlN, B{sub 4}C, SiC, Si{sub 3}N{sub 4}, TiB{sub 2}, WC and ZrO{sub 2}. This report compiles the VISAR wave profiles and experimental impact parameters within a database-useful for response model development, computational model validation studies, and independent assessment of the physics of dynamic deformation on high-strength, brittle solids.

  16. Ceramic tile expansion engine housing

    DOEpatents

    Myers, B.

    1995-04-11

    An expandable ceramic tile housing for a high temperature engine is disclosed wherein each tile is independently supported in place in an interlocking matrix by retention mechanisms which mechanically couple the individual ceramic tiles to an outer metal support housing while maintaining thermal isolation of the metal housing from the ceramic tiles. The ceramic tiles are formed with either an octagonal front face portion and a square shank portion or a square front face portion with an octagonal shank portion. The length of the sides of the octagonal front face portion on one tile is equal to the length of the sides of the square front face portion of adjoining tiles to permit formation of an interlocking matrix. Fibrous ceramic sealing material may be placed between radial and tangential facing surfaces of adjacent tiles to limit radial gas flow there between. Labyrinth-sealed pressure-controlled compartments may be established between the tile housing and the outer metal support housing to control radial gas flow. 8 figures.

  17. Transparent ceramic lamp envelope materials

    NASA Astrophysics Data System (ADS)

    Wei, G. C.

    2005-09-01

    Transparent ceramic materials with optical qualities comparable to single crystals of similar compositions have been developed in recent years, as a result of the improved understanding of powder-processing-fabrication- sintering-property inter-relationships. These high-temperature materials with a range of thermal and mechanical properties are candidate envelopes for focused-beam, short-arc lamps containing various fills operating at temperatures higher than quartz. This paper reviews the composition, structure and properties of transparent ceramic lamp envelope materials including sapphire, small-grained polycrystalline alumina, aluminium oxynitride, yttrium aluminate garnet, magnesium aluminate spinel and yttria-lanthana. A satisfactory thermal shock resistance is required for the ceramic tube to withstand the rapid heating and cooling cycles encountered in lamps. Thermophysical properties, along with the geometry, size and thickness of a transparent ceramic tube, are important parameters in the assessment of its resistance to fracture arising from thermal stresses in lamps during service. The corrosive nature of lamp-fill liquid and vapour at high temperatures requires that all lamp components be carefully chosen to meet the target life. The wide range of new transparent ceramics represents flexibility in pushing the limit of envelope materials for improved beamer lamps.

  18. Ceramic tile expansion engine housing

    DOEpatents

    Myers, Blake

    1995-01-01

    An expandable ceramic tile housing for a high temperature engine is disclosed wherein each tile is independently supported in place in an interlocking matrix by retention mechanisms which mechanically couple the individual ceramic tiles to an outer metal support housing while maintaining thermal isolation of the metal housing from the ceramic tiles. The ceramic tiles are formed with either an octagonal front face portion and a square shank portion or a square front face portion with an octagonal shank portion. The length of the sides of the octagonal front face portion on one tile is equal to the length of the sides of the square front face portion of adjoining tiles to permit formation of an interlocking matrix. Fibrous ceramic sealing material may be placed between radial and tangential facing surfaces of adjacent tiles to limit radial gas flow therebetween. Labyrinth-sealed pressure-controlled compartments may be established between the tile housing and the outer metal support housing to control radial gas flow.

  19. Dynamic properties of ceramic materials

    SciTech Connect

    Grady, D.E.; Wise, J.L.

    1993-09-01

    Controlled impact methods have been employed to obtain dynamic response properties of armor materials. Experimental data have been obtained for high-strength ceramics. Continued analysis of time-resolved velocity interferometer measurements has produced systematic material-property data for Hugoniot and release response, initial and post-yield strength, pressure-induced phase transformation, and dynamic fracture strength. A new technique has been developed to measure hydrodynamic properties of ceramic through shock-wave experiments on metal-ceramic composites and data obtained for silicon carbide. Additional data on several titanium diboride ceramics and high-quality aluminum oxide ceramic have been acquired, and issues regarding the influence of microstructure on dynamic properties have emerged. Comparison of dynamic (Hugoniot elastic limit) strength and indentation hardness data has been performed and important correlations revealed. Innovative impact experiments on confined and unconfined alumina rods using axial and transverse VISAR diagnostics have been demonstrated which permit acquisition of multiaxial dynamic response data. Dynamic failure properties of a high-density aluminosilicate glass, similar in composition to the intergranular glassy phase of some aluminas, have been investigated with regard to yield, spall, and failure-wave propagation.

  20. Ceramic inserts do not generally improve resin composite margins.

    PubMed

    Strobel, W O; Petschelt, A; Kemmoona, M; Frankenberger, R

    2005-08-01

    summary Ceramic inserts are reported to possibly reduce polymerization shrinkage for posterior resin composite fillings. The aim of the present investigation was to evaluate the effect of different insert systems before and after thermomechanical loading. Sixty sound human third molars received occlusomesial Class II cavities, 40 with proximal margins 2 mm above and 20 with proximal margins 1 mm below the cementum-enamel junction. The specimens were randomly assigned to one of the six experimental groups (n = 10). The enamel-bordered cavities were restored with Syntac classic and Tetric Ceram (ST), Syntac classic, Tetric Ceram and beta-quartz inserts (TB), Syntac classic, Tetric Ceram and Cerana inserts (TC), Syntac classic, Tetric flow and SonicSys approx inserts (TS). The dentin-limited cavities were filled with Syntac classic and Tetic Ceram (DT), Syntac classic, Tetric flow and SonicSys approx inserts (DS). Before and after thermomechanical loading (100 000 x 50 N, 2500 x 5 degrees C/55 degrees C), replicas were made and both interfaces tooth/composite and insert/composite were examined under a scanning electron microscope at 200x. The Cerana and SonicSys insert groups showed significantly less gaps in enamel (P < 0.05). With beta-quartz inserts, no reduction of gaps was found (P > 0.05). Marginal integrity in dentine-bordered specimens could not be improved with SonicSys inserts (P > 0.05). The bonding performance insert/composite was promising for all IPS Empress inserts (Cerana, SonicSys enamel) but worse for beta-quartz inserts. Regarding gap formation between resin composite and tooth, Cerana and SonicSys inserts significantly reduced gaps. The use of SonicSys inserts in deep proximal cavities cannot be recommended. PMID:16011640

  1. Organopolysiloxane Waterproofing Treatment for Porous Ceramics

    NASA Technical Reports Server (NTRS)

    Leiser, Daniel B. (Inventor); Cagliostro, Domenick E. (Inventor); Hsu, Ming-ta S. (Inventor); Chen, Timothy S. (Inventor)

    1998-01-01

    Rigid and flexible porous ceramics, including thermal insulation of a type used on space vehicles, are waterproofed by a treatment which comprises applying an aqueous solution of an organopolysiloxane water-proofing agent having reactive silanol groups to the surface of the ceramic and then heating the treated ceramic to form a waterproofed ceramic. The organopolysiloxane is formed by the hydrolysis and partial condensation of di- and trialkoxyfunctional alkylalkoxysilanes having 1-10 carbon atom hydrocarbyl groups.

  2. Hydridosiloxanes as precursors to ceramic products

    DOEpatents

    Blum, Yigal D.; Johnson, Sylvia M.; Gusman, Michael I.

    1997-01-01

    A method is provided for preparing ceramic precursors from hydridosiloxane starting materials and then pyrolyzing these precursors to give rise to silicious ceramic materials. Si--H bonds present in the hydridosiloxane starting materials are catalytically activated, and the activated hydrogen atoms may then be replaced with nonhydrogen substituents. These preceramic materials are pyrolyzed in a selected atmosphere to give the desired ceramic product. Ceramic products which may be prepared by this technique include silica, silicon oxynitride, silicon carbide, metal silicates, and mullite.

  3. Hydridosiloxanes as precursors to ceramic products

    DOEpatents

    Blum, Y.D.; Johnson, S.M.; Gusman, M.I.

    1997-06-03

    A method is provided for preparing ceramic precursors from hydridosiloxane starting materials and then pyrolyzing these precursors to give rise to silicious ceramic materials. Si-H bonds present in the hydridosiloxane starting materials are catalytically activated, and the activated hydrogen atoms may then be replaced with nonhydrogen substituents. These preceramic materials are pyrolyzed in a selected atmosphere to give the desired ceramic product. Ceramic products which may be prepared by this technique include silica, silicon oxynitride, silicon carbide, metal silicates, and mullite.

  4. Emerging Ceramic-based Materials for Dentistry

    PubMed Central

    Denry, I.; Kelly, J.R.

    2014-01-01

    Our goal is to give an overview of a selection of emerging ceramics and issues for dental or biomedical applications, with emphasis on specific challenges associated with full-contour zirconia ceramics, and a brief synopsis on new machinable glass-ceramics and ceramic-based interpenetrating phase composites. Selected fabrication techniques relevant to dental or biomedical applications such as microwave sintering, spark plasma sintering, and additive manufacturing are also reviewed. Where appropriate, the authors have added their opinions and guidance. PMID:25274751

  5. Process for strengthening silicon based ceramics

    DOEpatents

    Kim, Hyoun-Ee; Moorhead, A. J.

    1993-01-01

    A process for strengthening silicon based ceramic monolithic materials and omposite materials that contain silicon based ceramic reinforcing phases that requires that the ceramic be exposed to a wet hydrogen atmosphere at about 1400.degree. C. The process results in a dense, tightly adherent silicon containing oxide layer that heals, blunts , or otherwise negates the detrimental effect of strength limiting flaws on the surface of the ceramic body.

  6. Process for strengthening silicon based ceramics

    DOEpatents

    Kim, Hyoun-Ee; Moorhead, A. J.

    1993-04-06

    A process for strengthening silicon based ceramic monolithic materials and omposite materials that contain silicon based ceramic reinforcing phases that requires that the ceramic be exposed to a wet hydrogen atmosphere at about 1400.degree. C. The process results in a dense, tightly adherent silicon containing oxide layer that heals, blunts , or otherwise negates the detrimental effect of strength limiting flaws on the surface of the ceramic body.

  7. Crystalline ceramics: Waste forms for the disposal of weapons plutonium

    SciTech Connect

    Ewing, R.C.; Lutze, W.; Weber, W.J.

    1995-05-01

    At present, there are three seriously considered options for the disposition of excess weapons plutonium: (i) incorporation, partial burn-up and direct disposal of MOX-fuel; (ii) vitrification with defense waste and disposal as glass ``logs``; (iii) deep borehole disposal (National Academy of Sciences Report, 1994). The first two options provide a safeguard due to the high activity of fission products in the irradiated fuel and the defense waste. The latter option has only been examined in a preliminary manner, and the exact form of the plutonium has not been identified. In this paper, we review the potential for the immobilization of plutonium in highly durable crystalline ceramics apatite, pyrochlore, monazite and zircon. Based on available data, we propose zircon as the preferred crystalline ceramic for the permanent disposition of excess weapons plutonium.

  8. Microscribing of ceramics by Nd:YLF laser

    NASA Astrophysics Data System (ADS)

    Iwai, Y.; Arai, T.; Honda, T.; Tanaka, Ryuzo; Takaoka, T.

    2003-02-01

    We studied the microscribing of Al2O3 ceramics by a diode-pumped Nd:YLF laser. The third harmonic of a Nd:YLF laser (λ=349nm) was used. The scribing characteristics such as groove width, groove depth and debris height were measured. By varying the focal position of the beam at fixed laser power, we observed three regions characterized by the color and the profile of the irradiated area. Region I was marked by high debris and black color due to thermal effects at the focusing position, Region II showed brown color and good scribing properties with low debris height at a slightly defocused position, and finally Region III was unchanged color (original white) but little scribing due to low power density at the defocused position. These results show that an optimum energy for scribing ceramics exists. Finally good scribing without color change may be possible by adjusting the irradiation energy.

  9. Patches for Repairing Ceramics and Ceramic-Matrix Composites

    NASA Technical Reports Server (NTRS)

    Hogenson, Peter A.; Toombs, Gordon R.; Adam, Steven; Tompkins, James V.

    2006-01-01

    Patches consisting mostly of ceramic fabrics impregnated with partially cured polymers and ceramic particles are being developed as means of repairing ceramics and ceramic-matrix composites (CMCs) that must withstand temperatures above the melting points of refractory metal alloys. These patches were conceived for use by space-suited, space-walking astronauts in repairing damaged space-shuttle leading edges: as such, these patches could be applied in the field, in relatively simple procedures, and with minimal requirements for specialized tools. These design characteristics also make the patches useful for repairing ceramics and CMCs in terrestrial settings. In a typical patch as supplied to an astronaut or repair technician, the polymer would be in a tacky condition, denoted as an A stage, produced by partial polymerization of a monomeric liquid. The patch would be pressed against the ceramic or CMC object to be repaired, relying on the tackiness for temporary adhesion. The patch would then be bonded to the workpiece and cured by using a portable device to heat the polymer to a curing temperature above ambient temperature but well below the maximum operating temperature to which the workpiece is expected to be exposed. The patch would subsequently become pyrolized to a ceramic/glass condition upon initial exposure to the high operating temperature. In the original space-shuttle application, this exposure would be Earth-atmosphere-reentry heating to about 3,000 F (about 1,600 C). Patch formulations for space-shuttle applications include SiC and ZrO2 fabrics, a commercial SiC-based pre-ceramic polymer, and suitable proportions of both SiC and ZrO2 particles having sizes of the order of 1 m. These formulations have been tailored for the space-shuttle leading-edge material, atmospheric composition, and reentry temperature profile so as to enable repairs to survive re-entry heating with expected margin. Other formulations could be tailored for specific terrestrial

  10. Fabrication of large ceramic electrolyte disks

    NASA Technical Reports Server (NTRS)

    Ring, S. A.

    1972-01-01

    Process for sintering compressed ceramic powders produces large ceramic disks for use as electrolytes in high-temperature electrolytic cells. Thin, strain-free uniformly dense disks as large as 30 cm squared have been fabricated by slicing ceramic slugs produced by this technique.

  11. Reliability and Lifetime Prediction for Ceramic Components

    SciTech Connect

    Vedula, V.R.; Glass, S.J.; Monroe, S.L.; Neilsen, M.K.; Newton, C.

    1999-01-11

    Ceramic materials are used extensively in non-nuclear components in the weapons stockpile including neutron tubes, stronglinks, weaklinks, batteries, and current/voltage stacks. Ceramics also perform critical functions in electronics, passively as insulators and actively as resistors and capacitors, Glass and ceramic seals also provide hermetic electrical feedthrus in connectors for many weapons components.

  12. Dense high temperature ceramic oxide superconductors

    DOEpatents

    Landingham, Richard L.

    1993-01-01

    Dense superconducting ceramic oxide articles of manufacture and methods for producing these articles are described. Generally these articles are produced by first processing these superconducting oxides by ceramic processing techniques to optimize materials properties, followed by reestablishing the superconducting state in a desired portion of the ceramic oxide composite.

  13. Dense high temperature ceramic oxide superconductors

    DOEpatents

    Landingham, R.L.

    1993-10-12

    Dense superconducting ceramic oxide articles of manufacture and methods for producing these articles are described. Generally these articles are produced by first processing these superconducting oxides by ceramic processing techniques to optimize materials properties, followed by reestablishing the superconducting state in a desired portion of the ceramic oxide composite.

  14. Lubrication And Wear Of Hot Ceramics

    NASA Technical Reports Server (NTRS)

    Sliney, H. E.; Jacobson, T. P.; Deadmore, D.; Miyoshi, K.

    1988-01-01

    Report presents results of experiments on tribological properties of ceramics. Describes friction and wear characteristics of some ceramics under consideration for use in gas turbines, diesel engines, and Stirling engines. Discusses formulation of composite plasma-sprayed ceramics containing solid lubricant additives, and data for carbide- and oxide-based composite coatings for use at temperatures up to at least 900 degree C.

  15. Ablation Resistant Zirconium and Hafnium Ceramics

    NASA Technical Reports Server (NTRS)

    Bull, Jeffrey (Inventor); White, Michael J. (Inventor); Kaufman, Larry (Inventor)

    1998-01-01

    High temperature ablation resistant ceramic composites have been made. These ceramics are composites of zirconium diboride and zirconium carbide with silicon carbide, hafnium diboride and hafnium carbide with silicon carbide and ceramic composites which contain mixed diborides and/or carbides of zirconium and hafnium. along with silicon carbide.

  16. Instructional Resources. The Significance of Form: Ceramics.

    ERIC Educational Resources Information Center

    Zawatsky, Carole; And Others

    1989-01-01

    Presents four lesson plans designed to teach K-12 students about ceramics and the artists using the medium. Each lesson is centered around one ceramic piece: (1) "Wall Clock," by the Chantilly Porcelain Factory; (2) "Poppy Vase," by Adelaide Robineau; (3) "Laughing Eyes," by Pablo Picasso; and (4) "Ceramic Drum Jar," by Tsayutitsa. (GEA)

  17. Uses of ceramics in microelectronics: A survey

    NASA Technical Reports Server (NTRS)

    Bratschun, W. R.; Mountvala, A. J.; Pincus, A. G.

    1971-01-01

    The properties and behavior of ceramic materials used in components for electronic circuitry are examined to appraise the present and future directions for microelectronics, and to suggest further product development, and how innovations may be useful in other technologies. Ceramic and glass insulators, resistors, capacitors, and the use of ceramics and glasses in microcircuitry are discussed along with technology transfer to nonaerospace uses.

  18. Preparation of a dense, polycrystalline ceramic structure

    DOEpatents

    Cooley, Jason; Chen, Ching-Fong; Alexander, David

    2010-12-07

    Ceramic nanopowder was sealed inside a metal container under a vacuum. The sealed evacuated container was forced through a severe deformation channel at an elevated temperature below the melting point of the ceramic nanopowder. The result was a dense nanocrystalline ceramic structure inside the metal container.

  19. High impact resistant ceramic composite

    DOEpatents

    Derkacy, James A.

    1991-07-16

    A ceramic material and a method of forming a ceramic material which possesses a high impact resistance. The material comprises: (a) a first continuous phase of .beta.-SiC; and (b) a second phase of about 25-40 vol % TiB.sub.2. Al.sub.2 O.sub.3 is preferably used as a densification aid. The material is formed by hot-pressing the mixture at a temperature from greater than about 1800.degree. C. to less than the transition temperature of .beta.-SiC to .alpha.-SiC. The hot-pressing is performed at a pressure of about 2000 psi to about 4000 psi in an inert atmosphere for several hours and results in the formation of a two phase sintered ceramic composite material.

  20. Surface treatment of ceramic articles

    DOEpatents

    Komvopoulos, K.; Brown, I.G.; Wei, B.; Anders, S.; Anders, A.; Bhatia, C.S.

    1998-12-22

    A process is disclosed for producing an article with improved ceramic surface properties including providing an article having a ceramic surface, and placing the article onto a conductive substrate holder in a hermetic enclosure. Thereafter a low pressure ambient is provided in the hermetic enclosure. A plasma including ions of solid materials is produced the ceramic surface of the article being at least partially immersed in a macroparticle free region of the plasma. While the article is immersed in the macroparticle free region, a bias of the substrate holder is biased between a low voltage at which material from the plasma condenses on the surface of the article and a high negative voltage at which ions from the plasma are implanted into the article. 15 figs.