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2002

Articles 1 - 14 of 14

Full-Text Articles in Ceramic Materials

Phase Diagram For Stripes In Yba2cu3o6+X Superconductors, Herbert A. Mook, Fatih Dogan Dec 2002

Phase Diagram For Stripes In Yba2cu3o6+X Superconductors, Herbert A. Mook, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

Neutron scattering has been used to measure the charge and spin structure in the YBa2Cu3O6+x superconductors. Incommensurate static charge ordering is found at low doping levels while only charge fluctuations are found at higher doping. The spin structure is complex with both a commensurate resonance and incommensurate structure observed at low temperatures. The scattering results are used to construct a phase diagram for stripes in the YBa2Cu3O6+x system.

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Magnetic Order In Yba2⁢Cu3⁢O6+X Superconductors, Herbert A. Mook, Pengcheng Dai, Stephen M. Hayden, Arno Hiess, Jw Lynn, S-H Lee, Fatih Dogan Oct 2002

Magnetic Order In Yba2⁢Cu3⁢O6+X Superconductors, Herbert A. Mook, Pengcheng Dai, Stephen M. Hayden, Arno Hiess, Jw Lynn, S-H Lee, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

Polarized and unpolarized neutron diffraction has been used to search for magnetic order in YBa2⁢Cu3⁢O6+x superconductors. Most of the measurements were made on a high-quality crystal of YBa2⁢Cu3⁢O6.6. It is shown that this crystal has highly ordered ortho-II chain order, and a sharp superconducting transition. Inelastic scattering measurements display a very clean spin-gap and pseudo gap with any intensity at 10 meV being 50 times smaller than the resonance intensity. The crystal shows a complicated magnetic order that appears to have three components. A magnetic phase is found at …

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Phonon Dispersion Measurements Of Yba2cu3o6.15 And Yba2cu3o6.95 By Time-Of-Flight Neutron Spectroscopy, J-H Chung, T. Egami, R. J. Mcqueeney, M. Yethiraj, M. Arai, T. Yokoo, Herbert A. Mook, Y. Endoh, S. Tajima, C. Frost, Fatih Dogan Oct 2002

Phonon Dispersion Measurements Of Yba2cu3o6.15 And Yba2cu3o6.95 By Time-Of-Flight Neutron Spectroscopy, J-H Chung, T. Egami, R. J. Mcqueeney, M. Yethiraj, M. Arai, T. Yokoo, Herbert A. Mook, Y. Endoh, S. Tajima, C. Frost, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

We measured the phonon dispersions of YBa2Cu3O6.15 and YBa2Cu3O6.95 by time-of-flight inelastic neutron scattering. The in-plane bond-stretching modes in the metallic phase showed a distinct a-b plane an isotropy beyond what is expected for structural origin. Such an isotropy in the longitudinal optical modes, which is absent in the TO, suggests strong in-plane anisotropy in the underlying electronic structure. Apical oxygen bond-stretching modes showed a large frequency change between the insulating and the metallic phases. This large softening also is beyond structural origin, and suggests the effect of local electronic …

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Method For Sintering Ceramic Tapes, Fatih Dogan, Jian-Huei Feng, Lucian G. Ferguson Sep 2002

Method For Sintering Ceramic Tapes, Fatih Dogan, Jian-Huei Feng, Lucian G. Ferguson

Materials Science and Engineering Faculty Research & Creative Works

Flexible Setter powder deposition sheets containing Setter powders were developed for Sintering of ceramic articles including tapes by an economical, fast and Simple method. The sheets provide for deposition of a thin and uniform layer of Setter powders on a green ceramic article after burnout of a binder in the sheet. Because of high Strength and low burnout temperature, hydroxypropyl methylcellulose binder is preferred for production of these sheets. Tape cast sheets with low Solids loading can be obtained by optimizing the wetting behavior of aqueous slurries on tape carrier. Setter, powder deposition sheets are of particular benefit in processing …

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Dopant Effect On Local Dielectric Properties In Barium Titanate Based Electroceramics Determined By Transmission Eels, Kalpana S. Katti, Maoxu Quian, Fatih Dogan, Mehmet Sarikaya Sep 2002

Dopant Effect On Local Dielectric Properties In Barium Titanate Based Electroceramics Determined By Transmission Eels, Kalpana S. Katti, Maoxu Quian, Fatih Dogan, Mehmet Sarikaya

Materials Science and Engineering Faculty Research & Creative Works

Investigates the local electronic excitations of barium titanate electro ceramic using low-loss electron energy loss spectroscopy. Process for monitoring of electronic structure of titanate; Changes in valence and conduction band states by valence state of barium; Shift of oscillator strengths of excitations in local regions.

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Electron–Phonon Interactions In Htsc Cuprates, Takeshi Egami, J-H Chung, Rj Mcqueeney, Mohana Yethiraj, Herbert A. Mook, C. Frost, Y. Petrov, Fatih Dogan, Yasuhiro Inamura, Masatoshi Arai, Setsuuko Tajima, Yasuo Endoh May 2002

Electron–Phonon Interactions In Htsc Cuprates, Takeshi Egami, J-H Chung, Rj Mcqueeney, Mohana Yethiraj, Herbert A. Mook, C. Frost, Y. Petrov, Fatih Dogan, Yasuhiro Inamura, Masatoshi Arai, Setsuuko Tajima, Yasuo Endoh

Materials Science and Engineering Faculty Research & Creative Works

Phonons have been generally considered to be irrelevant to the high-temperature superconductivity in the cuprates. However, such a bias is usually based upon the assumption of conventional electron–phonon coupling, while in the cuprates the coupling can be rather unconventional because of strong electron correlation. We present the results of our recent measurements of phonon dispersion in YBa2Cu3O6+x by inelastic neutron scattering. These suggest certain phonon modes interact strongly with electrons and are closely involved in the superconductivity phenomenon with possible contribution to pairing.

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Biodegradable Glass Compositions And Methods For Radiation Therapy, D. E. Day, James E. White Apr 2002

Biodegradable Glass Compositions And Methods For Radiation Therapy, D. E. Day, James E. White

Materials Science and Engineering Faculty Research & Creative Works

A nonradioactive glass in particulate form adapted for radiation therapy in a mammal comprise a biodegradable rare earth-lithium borate glass material of a specified composition which, upon being subjected to an effective amount of neutron irradiation, will produce a beta or gamma emitting radioisotope, the radioisotope being distributed throughout the glass material, the glass upon being introduced into a body fluid for radiation therapy being adapted to react therewith causing the radioisotope to form an insoluble compound on the surface of the glass material which is retained in the glass material and thereby prevented from escaping from the treatment site. …

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Spectral Analysis Of Transition Metal-Doped Mgo “Matched Emitters” For Thermophotovoltaic Energy Conversion, Lucian G. Ferguson, Fatih Dogan Apr 2002

Spectral Analysis Of Transition Metal-Doped Mgo “Matched Emitters” For Thermophotovoltaic Energy Conversion, Lucian G. Ferguson, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

A new, thermally excited Co/Ni-doped MgO ceramic emitter for TPV energy conversion is described in this work and termed the “matched emitter” because its emissive power spectrum is very efficiently matched with the portion of the electromagnetic spectrum that can be converted directly into electrical energy by infrared responding GaSb photovoltaic cells. Ligand Field Theory calculations are used to estimate the crystal field splitting energies at high temperatures for Co and Ni-doped MgO matched emitters. Experimental measurements of the high temperature (1300–1400◦C) emissive power spectrums for Co and Ni-doped MgO emitters are compared with predictions obtained from ligand field calculations …

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Synthesis Of Pmma-Ceramics Nanocomposites By Spray Process, X.-D. Zhou, H. C. Gu Apr 2002

Synthesis Of Pmma-Ceramics Nanocomposites By Spray Process, X.-D. Zhou, H. C. Gu

Materials Science and Engineering Faculty Research & Creative Works

PMMA-ceramics nanocomposites particles were synthesized by a spray process. PMMA-ZnO compositions showed a higher homogeneous than PMMA-SiO2. The surface of PMMA-SiO2 composites was SiO2 rich. Donut shape particles were formed at high gas flow rate, which was due to the competition between surface tension and dragging force. The Zeta potential dramatically changed in PMMA-ZnO composites whereas there was a slight change in PMMA-SiO2 system.

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Method For Preparing Porous Shells Or Gels From Glass Particles, D. E. Day, Samuel D. Conzone Mar 2002

Method For Preparing Porous Shells Or Gels From Glass Particles, D. E. Day, Samuel D. Conzone

Materials Science and Engineering Faculty Research & Creative Works

A method is provided for preparing shells, concentric shells or porous, homogenous gels from alkali borate glass particles at low temperatures (i.e. room temperature or less than above 100° C.). The alkali borate glass particles contain one or more cations such as aluminum which react with an aqueous solution containing an anion such as hydroxide to form an aqueous insoluble material having a solubility limit of less than about 0.01 wt. percent. TTie resulting shells or gels may be used in many different applications such as a filler in resins, as filters, precursors for nano-sized powders, as thin surface films …

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Charge And Spin Structure In Yba2cu3o6.35, Herbert A. Mook, Pengcheng Dai, Fatih Dogan Mar 2002

Charge And Spin Structure In Yba2cu3o6.35, Herbert A. Mook, Pengcheng Dai, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

Neutron scattering has been used to measure the charge and spin structure in the highly underdoped superconductor YBa2Cu3O6.35. Incommensurate static charge ordering is found that remains at high temperatures. The magnetic pattern is complex with a resonance and incommensurate structure observed at low temperatures. The results clarify the role of striped phases in YBa2Cu3O6+x superconductors.

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Charge And Spin Structure In Yba2⁢Cu3⁢O6.35, Herbert A. Mook, Pengcheng Dai, Fatih Dogan Feb 2002

Charge And Spin Structure In Yba2⁢Cu3⁢O6.35, Herbert A. Mook, Pengcheng Dai, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

Neutron scattering has been used to measure the charge and spin structure in the highly underdoped superconductor YBa2⁢Cu3⁢O6.35. Incommensurate static charge ordering is found that remains at high temperatures. The magnetic pattern is complex with a resonance and incommensurate structure observed at low temperatures. The results clarify the role of striped phases in YBa2⁢Cu3⁢O6+x superconductors.

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Iron Phosphate Glass For The Vitrification Of Ineel Sodium Bearing Waste And Hanford Low Activity Waste, Robert Douglas Leerssen Jan 2002

Iron Phosphate Glass For The Vitrification Of Ineel Sodium Bearing Waste And Hanford Low Activity Waste, Robert Douglas Leerssen

Masters Theses

"The current study investigates the feasibility of using iron phosphate glass for the immobilization of nuclear wastes that have limited solubility in the current borosilicate glass used for vitrification. These wastes contain elements such as sulfur and phosphorus, which have proven problematic (causing phase separation at >1 wt%) for vitrification in borosilicate glasses, as well as having a high soda content (50-75 wt%) which also limits wasteloading"--Abstract, page iv.

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Reactive Hot Pressing Of Alumina-Molybdenum Disilicide Composites, William Fahrenholtz, Ronald E. Loehman, Kevin G. Ewsuk Jan 2002

Reactive Hot Pressing Of Alumina-Molybdenum Disilicide Composites, William Fahrenholtz, Ronald E. Loehman, Kevin G. Ewsuk

Materials Science and Engineering Faculty Research & Creative Works

Al2O3-MoSi2 Composites Were Prepared by Reactive Hot Pressing using Molybdenum, Aluminum, and Mullite Powders as Precursors. the Gibbs Free Energy Was Highly Negative for the Composite-Forming Reaction, Which Indicated that the Products Were Stable Relative to the Reactants. after the Reaction, the Composites Had High Relative Density, ∼96%. based on the Composite-Forming Reaction, the Composites Should Have Contained 18 Vol% MoSi2 in an Al2O3 Matrix. Scanning Electron Microscopy Revealed that the MoSi2 Inclusions Were Elongated, with an Average Thickness of ∼5 Μm and Inclusion Lengths that Ranged from 5 to 50 …

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