Ceramic Materials Commons^™

Spin Dynamics Of Er3+ In Erba2cu3o7−Δ, Suntharalingam Skanthakumar, Jeffrey W. Lynn, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

Neutron scattering techniques are used to study the magnetic excitations of the Er ions in superconducting ErBa₂Cu₃O₇, a system where the Er ions order antiferromagnetically at T_N=0.62 K and the sublattice magnetization obeys the relation for a 2D S=1/2 Ising model. Our data, which were taken on a cold neutron triple axis spectrometer using a horizontally focusing analyzer, reveal that there is a large gap of about 0.20 meV in the excitation spectrum, about four times the thermal energy kT_N, as expected for an Ising system. However, we also observe …

Immobilization Of Radioactive Materials In Iron Phosphate Glass, Melissa G. Mesko

Doctoral Dissertations

"The current study investigates the feasibility of using iron phosphate glass for the immobilization of radioactive wastes considered incompatible with borosilicate glass. Wastes may be incompatible with borosilicate glass due to high phosphorus content (Hanford tank sludges), the presence of halides (CsCl and SrF₂ capsules), or large amounts of uranium (SNF).

Between 20 and 60 wt% Hanford tank sludge was vitrified with an iron phosphate glass at ≤ 1200°C in 1 hour. The chemical durability of iron phosphate glassy wasteforms was as good as, or better than a reference borosilicate glass (10^-9 g/cm²/min) in distilled water …

Evaluation Of Unified Interaction Parameter Model Parameters For Calculating Activities Of Ferromanganese Alloys: Mn-Fe-C, Mn-Fe-Si, Mn-C-Si, And Mn-Fe-C-Si Systems, L. I. Hongjie, Arthur E. Morris

Materials Science and Engineering Faculty Research & Creative Works

Interaction parameters for Mn-based alloys were evaluated using both carbon solubility and activity data for species in binary and ternary manganese alloys. The parameters at 1400 °C are the following εcc = -4.5; εccc = 58.8; εFeCC = 1.5; εFeCC = 2.5; In γC0 = -1.15 . εsisi = 15.5; εsisisi = 2.69; εFeSi = 2.5; εcsi = 12.4; εccsi = 27.5; In γSi0 = -7.46 The unified interaction parameter model (UIPM) was used to calculate the activity coefficients of species and the solubility of carbon in ferromanganese alloys (up to quaternary Mn-Fe-C-Si). The results were in good agreement with …

Chemical Durability Of Lead-Oxide-Based, Thick-Film Binder Glasses, Douglas M. Mattox, Joshua H. Robinson

Materials Science and Engineering Faculty Research & Creative Works

Lead-oxide-bearing glasses are incompatible with aluminum nitride metallization's, and federal legislation is recommending their replacement in thick-film electronics and labeling. To evaluate alternatives, the benchmark chemical durability's of the lead borosilicate and lead aluminate thick-film binder glasses have been determined. Aluminum oxide (Al2O3) benefits water durability moderately, acid durability substantially, and basic durability indistinguishably. The rate of attack in water is approximately two orders of magnitude greater than for soda-lime glass. The thermal contractions of the glasses are compatible. An apparent, spontaneous phase separation in the Al2O3-free glass is suppressed by Al2O3 that is included as a batch component.

Magnetic Dynamics In Underdoped Yba2⁢Cu3⁢O7−X: Direct Observation Of A Superconducting Gap, Pengcheng Dai, Mohana Yethiraj, Herbert A. Mook, Terrence B. Lindemer, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

Polarized and unpolarized triple-axis neutron measurements were performed on an underdoped crystal of YBa₂⁢Cu_3⁢O_7−x (x = 0.4 ±0.02, T_c = 62.7⁢K). Our results indicate, contrary to earlier evidence, that the spin excitations in the superconducting state are essentially the same as those in the fully doped material except that the unusual 41 meV resonance is observed at 34.8 meV. The normal state spin excitations are characterized by a weakly energy-dependent continuum whose temperature dependence shows the clear signature of a superconducting gap at T_c. The enhancement at the resonance is accompanied by …

Low Temperature Hydrothermal Synthesis Of Nanophase Batio3 And Bafe12019 Powders, Fatih Dogan, Shawn O'Rourke, Mao-Xu Qian, Mehmet Sarikaya

Materials Science and Engineering Faculty Research & Creative Works

Nanocrystalline powders with an average particle size of 50 nm have been synthesized in two materials systems under hydrothermal conditions below 100°C. Processing variables, such as temperature, concentration and molar ratio of reactants and reaction time were optimized to obtain particles of reduced size and stoichiometric compositions. Hydrothermal reaction takes place between Ba (OH)₂ solution and titanium/iron precursors in sealed polyethylene bottles in the BaTiO₃ and BaFe12019 systems, respectively. While crystalline BaTiO₃ forms relatively fast within a few hours, formation of fully crystalline and stoichiometric BaFe12019 require considerably longer reaction times up to several weeks and strongly …

Magnetic Dynamics In Underdoped Yba2cu3o72x: Direct Observation Of A Superconducting Gap, Pengcheng Dai, Mehmet Yethiraj, Herbert A. Mook, T. B. Lindemer, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

Polarized and unpolarized triple-axis neutron measurements were performed on an underdoped crystal of YBa₂Cu₃O_7-x (x 0.4 6 0.02, T_c 62.7 K). Our results indicate, contrary to earlier evidence, that the spin excitations in the superconducting state are essentially the same as those in the fully doped material except that the unusual 41 meV resonance is observed at 34.8 meV. The normal state spin excitations are characterized by a weakly energy-dependent continuum whose temperature dependence shows the clear signature of a superconducting gap at T_c. The enhancement at the resonance is accompanied by …

Recent Developments In Extrusion Freeform Fabrication (Eff) Utilizing Non-Aqueous Gel Casting Formulations, Greg Hilmas, John L. Lombardi, Robert A. Hoffman, Kevin Stuffle

Materials Science and Engineering Faculty Research & Creative Works

Extrusion Freeform Fabrication (EFF) was shown to be an extremely versatile method for fabricating Functionally Graded Materials (FGMs) The approach is inexpensive and potentially feasible for grading between any thermodynamically compatible ceramic-metal, ceramic-ceramic, or metal-metal material combination. Several material systems were investigated in this study including alumina-304 stainless steel, zirconia-304 stainless steel, alumina-Inconel 625, zirconiaInconel625, alumina-nickel aluminide, zirconia-nickel aluminide, titanium carbide-InconeI625, titanium diboride-nickel aluminide, and tungsten carbide-nickel aluminide. A controlled gradient was demonstrated between the end members for all of the above compositions. The FGMs were hot pressed to achieve near theoretical densities, providing flexural strengths as high as 1000 …

Incommensurate One-Dimensional Fluctuations In Yba2⁢Cu3⁢O6.93, Herbert A. Mook, Pengcheng Dai, Kamel Salama, Dominic Lee, Fatih Dogan, Gabriel Aeppli, Andrew T. Boothroyd, Mark E. Mostoller

Materials Science and Engineering Faculty Research & Creative Works

A novel neutron scattering technique has been utilized to discover one-dimensional fluctuations with a very sharply defined modulation period of 16.65⁢Å along the b⁡(a) direction in YBa₂⁢Cu_3⁢O_6.93. The fluctuations are found to be absent in the reduced oxygen compound YBa_2⁢Cu_3⁢O_6.15. The wave vector of the fluctuations is consistent with accepted values of 2⁢k_F for the Cu-O chains.

Incommensurate One-Dimensional Fluctuations In Yba2cu3o6.93, Herbert A. Mook, Pengcheng Dai, K. Salama, D. Lee, Fatih Dogan, G. Aeppli, A. T. Boothroyd, M. E. Mostoller

Materials Science and Engineering Faculty Research & Creative Works

A novel neutron scattering technique has been utilized to discover one-dimensional fluctuations with a very sharply defined modulation period of 16.65 Å along the ba direction in YBa₂Cu₃O_6.93. The fluctuations are found to be absent in the reduced oxygen compound YBa₂Cu₃O_6.15. The wave vector of the fluctuations is consistent with accepted values of 2kF for the Cu-O chains.

Q Dependence Of Self-Energy Effects Of The Plane Oxygen Vibration In Yba2cu3o7, D. Reznik, Bernard Keimer, Fatih Dogan, Ilhan A. Aksay

Materials Science and Engineering Faculty Research & Creative Works

We have measured the temperature dependence of the peak position and linewidth of the 42.5 meV phonon branch in a twinned single crystal of YBa₂Cu₃O₇ as a function of wave vector q. In the (100)/(010) direction in the Brillouin zone, considerable softening and broadening occur below the superconducting transition temperature T_c at some values of q. We observe an order of magnitude smaller softening and no linewidth broadening for q in the (110) / (1⁢1⁢0^-) direction. Possible implications of these findings for the symmetry of the superconducting order parameter are …

Phonon And Magnetic Neutron Scattering At 41 Mev In Yba2cu3o7, Hung Fai Fong, Bernard Keimer, Pw Anderson, D. Reznik, Fatih Dogan, Ilhan A. Aksay

Materials Science and Engineering Faculty Research & Creative Works

We report inelastic neutron scattering measurements at excitation energies ħ⁢w∼41 meV in YBa₂Cu₃O₇. We separate magnetic and phonon contributions to the scattering cross section by a detailed analysis of the momentum dependence of the scattered intensity. The previously reported broad peak around q = (π/a,π/a) in the normal state can be entirely accounted for by a phonon which primarily involves vibrations of the in-plane oxygen. Magnetic scattering centered around 41 meV and q = (π/a,π/a) appears in the superconducting state only. Theoretical implications of …

Radiolabeled Protein Composition And Method For Radiation Synovectomy, D. E. Day, Gary J. Ehrhardt, Kurt R. Zinn

Materials Science and Engineering Faculty Research & Creative Works

A radiolabeled protein composition adapted for radiation therapy which comprises a radioisotope and a protein material containing about 6 or more percent amino acids which have a sulfhydryl-containing side chain. A method for carrying out radiation synovectomy of arthritic joints. Rhenium radiolabeled protein micro- spheres are administered which contain cysteine and other amino acids. A method for radiolabeling a protein composition whereby the composition is treated with a reducing agent capable of reducing disulfides to sulfhydryls prior to radiolabeling.

Iron Phosphate Glasses As A Potential Nuclear Waste Disposal Medium, Melissa G. Mesko

Masters Theses

”Phosphate glasses containing large amounts of Fe₂O₃ (up to 43wt%) were studied to determine their potential suitability as nuclear waste disposal glasses for high level radioactive wastes containing large concentrations of iron oxide, phosphate, and fluoride compounds. Glass formation and chemical durability was the prime focus of this study, while properties such as density, thermal expansion, dilatometric softening temperature, and devitrification temperature were examined as well. It was found that large amounts of simulated nuclear waste material (up to 44.4wt% Cs₂O or 37.5wt% SrO) could be incorporated into the base iron phosphate glass while retaining …

Vortex Lattice Symmetry And Electronic Structure In Yba2cu3o7, Bernhard Keimer, Wan Y. Shih, Ross W. Erwin, Jeffrey W. Lynn, Fatih Dogan, Ilhan A. Aksay

Materials Science and Engineering Faculty Research & Creative Works

We report a small angle neutron scattering study of the vortex lattice in YBa₂Cu₃O₇ in magnetic fields of 0.5≤ H ≤5 T applied along and close to the c axis. Over the entire field range, the vortices form an oblique lattice with two nearly equal lattice constants and an angle of 73° between primitive vectors. Numerical calculations suggest that variations of the superconducting order parameter near the vortex core are important in stabilizing this structure. An analysis that accounts for the fourfold symmetry of the vortex core qualitatively explains both the symmetry and the orientation …

Nature Of The Ferroelectric Phase Transition In Pbtio3, Noam Sicron, B. Ravel, Y. Yacoby, Edward A. Stern, Fatih Dogan, John J. Rehr

Materials Science and Engineering Faculty Research & Creative Works

We have measured quantitatively the temperature dependence of the local distortions of PbTiO3 crystals below and above the structural ferroelectric phase transition, using x-ray absorption fine-structure (XAFS) measurements. Two probe atoms, Pb and Ti, were used. The results were analyzed by fitting parametrized theoretical XAFS spectra to the experimental results. These measurements provide quantitative ‘‘distortion parameters’’ defined as the difference between the distance of the probe to its nearest neighbor measured in the actual structure and that in a centrosymmetric structure with the same unit cell dimensions. At low temperatures the Pb-edge spectra were fit using four shells and included …

Microspheres For Radiation Therapy, D. E. Day, Gary J. Ehrhardt

Materials Science and Engineering Faculty Research & Creative Works

Microspheres for radiation therapy of a mammal which have a non-radioactive isotope which emits beta or gamma radiation of therapeutic intensity upon being irradiated. The microspheres also contain elements which do not become radioactive upon irradiation. The chemical durability of the microspheres is such that they do not release a significant amount of radiation emitting radioisotope into the mammal’s system upon administration. Microspheres containing phosphorus or yttrium; and carbon, nitrogen, fluorine, sodium, magnesium, aluminum, silicon, potassium, vanadium, manganese, gallium, niobium, iodine and/or lead.

Evaluation Of Yba,Cu,O,_, Bulk Superconductors For High Field Magnet Applications, K. Y. Blohowiak, D. F. Garrigus, T. S. Luhman, K. E. Mccrary, M. Strasik, I. A. Aksay, Fatih Dogan, W. B. Hicks, J. Liu, M. Sarikaya

Materials Science and Engineering Faculty Research & Creative Works

Processing of YBCO single crystals was carried out by solidification of semi-liquid YBCO composition using a seeding technique. Microstructural characterization of the pinning centers was investigated by transmission electron microscopy. Characterization of single crystals was carried out, relating grain size and shape to the corresponding flux profiles. Current densities were calculated based on measured trapped fields. Once circulating currents were established, flux pumping and quenching experiments were conducted. These large single crystals will be incorporated into electromagnetic forming devices for use in the military and commercial aircraft manufacturing and service industries.

Evaluation Of Yba2cu3o7-X Bulk Superconductors For High Field Magnet Applications, K. Y. Blohowiak, D. F. Garrigus, T. S. Luhman, K. E. Mccrary, M. Strasik, Ilhan A. Aksay, Fatih Dogan, W. B. Hicks, J. Liu, M. Sarikaya

Materials Science and Engineering Faculty Research & Creative Works

Processing of YBCO single crystals was carried out by solidification of semi-liquid YBCO composition using a seeding technique. Microstructural characterization of the pinning centers was investigated by transmission electron microscopy. Characterization of single crystals was carried out, relating grain size and shape to the corresponding flux profiles. Current densities were calculated based on measured trapped fields. Once circulating currents were established, flux pumping and quenching experiments were conducted. These large single crystals will be incorporated into electromagnetic forming devices for use in the military and commercial aircraft manufacturing and service industries.

Mechanical Properties Of Whisker-Reinforced Cordierite Glass Matrix Composites, John R. Dillingham

Opportunities for Undergraduate Research Experience Program (OURE)

The development of a whisker-reinforced ceramic matrix composite has been shown to be a reasonable method of achieving improved mechanical properties for ceramic materials. In this work a cordierite matrix was reinforced with 20vol% of silicon carbide whiskers. The mechanical properties of this composite were compared to those of the nonreinforced cordierite matrix. As would be expected, the whisker- reinforced matrix showed a significant improvement in mechanical properties.

The specimens used for testing were processed by hot-pressing in an argon atmosphere using a graphite die coated with boron nitride. Hot pressing was carried out at 950°C for the pure matrix …

Tape Casting For Lead Zirconate Titanate (Pzt) Multilayer Composites, Jane L. Cochran

Opportunities for Undergraduate Research Experience Program (OURE)

Tape casting is a process for making thin flat ceramic pieces by using a scraping blade or "doctor blade" to evenly coat a smooth surface with a slip[ 1 ]. The slip is a mixture of powder, solvent, binder, and other organics which result in a paint like consistency after they are mixed.

The tapes is cast into thicknesses ranging from 1 to 50 mils on a smooth surface , which is usually made of Mylar, and left to dry.

Once the tape has dried it can be cut into several different shapes and sizes, and then fired to form …

Inclined-Field Structure, Morphology, And Pinning Of The Vortex Lattice In Microtwinned Yba2cu3o7, B. Keimer, F. Doǧan, I. A. Aksay, R. W. Erwin, J. W. Lynn, M. Sarikaya

Materials Science and Engineering Faculty Research & Creative Works

A detailed small-angle neutron scattering study of the vortex lattice in a single crystal of YBa2Cu3O7 was made for a field of 0.5 tesla inclined at angles between 0 and 80 degrees to the crystalline c axis. The vortex lattice is triangular for all angles, and for angles less than or equal to 70 degrees its orientation adjusts itself to maximize the pinning energy to densely and highly regularly spaced twin planes. These observations have important implications for the microscopic flux-pinning mechanism, and hence for the critical current achievable in YBa2Cu3O7. For large angles (about 80 degrees) the vortex lattice …

Cyclodextrin Stationary Phases For The Gas-Solid Chromatographic Separation Of Hydrocarbons, Chris A. Monge

Opportunities for Undergraduate Research Experience Program (OURE)

Cyclodextrin, bonded to silica gel and used as a gas-solid chromatographic stationary phase provides a practical and efficient means for separating a wide variety of C₁-C₇ hydrocarbons at ambient to elevated temperatures. Conditioning the columns at high temperature (300°C) for several hours increased efficiency and resolution. The adsorption of these light hydrocarbons involves a multiple retention mechanism. Evaluation of the columns and an analogous silica gel column with hydrocarbon standards is reported. Capacity factors and chromatograms are presented for these GSC stationary phases.

Tensile Fatigue Behaviour Of Tightly Woven Carbon/Carbon Composites, A. Ozturk, Robert E. Moore

Materials Science and Engineering Faculty Research & Creative Works

The tensile fatigue behavior of a tightly woven carbon/carbon composite was investigated as a function of stress level. Load-controlled fatigue tests were performed in tension-tension mode with a stress ratio, R, of 0.1 under ambient laboratory conditions. Results of composite behavior are discussed in terms of the relationship of the stress/strain behavior to the fatigue life of these composites as well as the effects of applied stress levels. It is shown that these composites exhibit good resistance to cyclic loading. No fatigue failures were obtained after 106 cycles when the maximum tensile load in the fatigue cycle is less than …

Sol-Gel Derived, Air-Baked Indium And Tin Oxide Films, Douglas M. Mattox

Materials Science and Engineering Faculty Research & Creative Works

A sol-gel derived, transparent, electrically conducting tin-doped In₂O₃ film system has been developed which only requires air baking. The films approximate the properties of sputtered and hot-sprayed films but are simpler and less expensive to apply by dipping and spinning procedures. Substrate sodium interference was seen to be minimal. © 1991.

Composition And Method For Radiation Synovectomy Of Arthritic Joints, D. E. Day, Gary J. Ehrhardt

Materials Science and Engineering Faculty Research & Creative Works

A method for preparing nonradioactive microspheres adapted for radiation synovectomy of arthritic joints in a mammal involves forming the microspheres by doping a biodegradable glass material which may be lithium or potassium silicate, lithium or potassium aluminosilicate, lithium or potassium aluminoborate, lithium or potassium germanate or lithium or potassium alumino- germanate with an isotope which may be samarium, holmium, erbium, dysprosium, rhemium or yttrium so that the isotope is chemcially dissolved in and distributed uniformly throughout the glass material. The doped glass material is then treated with an acid wash to produce a thin layer on the surface thereof and …

Composition And Method For Radiation Synovectomy Of Arthritic Joints, D. E. Day, Gary J. Ehrhardt

Materials Science and Engineering Faculty Research & Creative Works

Radioactive microspheres for radiation synovectomy of arthritic joints in a mammal comprises a biodegradable glass material and a beta radiation emitting radioisotope chemically dissolved in and distributed substantially uniformly throughout the glass material. The biodegradable glass material may be lithium silicate, lithium aluminosilicate, lithium aluminoborate, lithium germa- nate, lithium aluminogermanate, potassium silicate, potassium aluminosilicate, potassium aluminoborate, potassium germanate or potassium aluminogermanate and the beta radiation emitting radioisotope may be samarium-153, holmium-166, erbium-169, dysprosium-165, rhenium-186, rhenium-188 or yttrium-90. Method for preparing such microspheres and for carrying out radiation synovectomy of arthritic joints utilizing such microspheres are also disclosed.

Radioactive Glass Microspheres, D. E. Day, Gary J. Ehrhardt

Materials Science and Engineering Faculty Research & Creative Works

A radioactive microsphere for radiation therapy of a mammal comprising a biologically compatible glass material containing a beta or gamma emitting radioisotope distributed substantially uniformly throughout the glass. Advantageously, the radioisotope is produced by irradiation of the microsphere.

Phase Separation In Glasses, N. J. Kreidl

Materials Science and Engineering Faculty Research & Creative Works

The detection, acceptance and further investigation of glass-glass phase separation was closely connected with the development of methods making detection possible, such as electron microscope technique pioneered and exploited by Werner Vogel, to whom this paper is dedicated on the occasion of his 65th birthday. Structures are not always found in agreement with rules derived from thermodynamic principles, and also depend on thermal history, as well as mode of preparation. The phenomenon is exemplified in many glass-forming systems. Among more recent applications are the control of crystallization by preceding phase separation as in glass-ceramics and semiconductor-doped glasses for non-linear optics. …

Toughening Mechanisms In Weak Matrix Ceramic Composites, Jowoong Ha

Doctoral Dissertations

"Tough behavior of ceramic matrix composites is closely related to the weak interface between fiber and matrix. The weak interfaces in composites have been provided by reducing the chemical bonding and the residual thermal stresses between constituents. A new way to introduce the weak interface by induced porosity or damaged zones, so called porosity toughening or damage toughening respectively, was proposed in this study to provide the rationale for guiding development of oxide/oxide composites. The existence of porosity toughening was examined by qualitative theoretical consideration and experiments. Porous oxide/oxide composites were fabricated using alumino-silicate fibers (Nextel 440) and magnesium alumino-silicate …