Ceramic Materials Commons^™

Characterization Of Fatigue Behavior Of 2-D Woven Fabric Reinforced Ceramic Matrix Composite At Elevated Temperature, Daniel J. Groner

Theses and Dissertations

This study investigated the fatigue behavior and associated damage mechanisms in notched and unnotched enhanced Sic-SiC ceramic matrix composite specimens at 1100°C. Stiffness degradation, strain variation, and hysteresis were evaluated to characterize material behavior. Microscopic examination was performed to characterize damage mechanisms. During high cycle-low stress fatigue tests, far less fiber-matrix interface debond was evident than in low cycle-high stress fatigue tests. Notched specimens exhibited minimal stress concentration during monotonic tensile testing and minimal notch sensitivity during fatigue testing. Damage mechanisms were also similar to unnotched.

Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite Subjected To Tension-Tension Cycling With Hold Time, Scott A. Grant

Theses and Dissertations

This study was carried out to investigate the elevated temperature behavior of the SiC-MAS5 cross- ply [0-90]_4S ceramic matrix composite manufactured by Corning Inc. to fatigue with loading waveforms that combine the characteristics of stress rupture and high cycle fatigue. The test results were compiled in the form of S-N (cycles to failure), S-T (exposure time versus cycles to failure), S-S (energy exposure versus cycles to failure), normalized modulus degradation, strain progression, and hysteresis loop progression. From the mechanical behavior demonstrated by these curves, relationships between the effect of the environment and loading waveform were developed. In addition, a …

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.

Static Fracture Behavior Of A Ceramic Matrix Composite At Elevated Temperatures, David M. Agins

Theses and Dissertations

This study investigated systematically the damage initiation damage progression, and failure modes of a ceramic matrix composite, Nicalon/CAS, when loaded in tension at elevated temperatures in the presence of air. A cross-ply lay-up, [0/90]_2s, was studied. The primary means of analysis were stress-strain data taken during monotonic and incremental load tests and crack density assessments. Testing was conducted at room temperature 700°C, and 850°C. The stress-strain response was consistent for monotonic and incremental loading, except for a decrease in failure load at the elevated temperatures. Initial damage progression was also consistent, but the damage leading to failure and …

Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite Under Strain Controlled Tension-Tension And Tension-Compression Loading, James J. Gudaitis

Theses and Dissertations

This stuidy investigates the fatigue response of a cross-ply [0/90]_2s Nicalon/Calcium Aluminosillicate (Nicalcc/CAS) ceramic matrix composite at room temperature under strain controlled tension-tension and tension-compression fatigue loading. The primary objectives were to determine strain fatigue limits for both loading cases and to complete a fatigue life diagram (Δe-N) for all tests. Failure mechanisms were also studied. The average initial modulus value for this lay-up was 120 GPa. The ultimate tensile strain was 0.00988 mn/mm (285 MPa). Eight tests were conducted with maximum strains that ranged from 0.00300 mm/mm to 0.00722 mm/mm. The tension-tension fatigue limit was found to be …

Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite At Elevated Temperatures Under Tension-Tension Loading, Richard J. Tuznik

Theses and Dissertations

A study was conducted which investigated the behavior of a Nicalon/ Calcium-Aluminosilicate (Nicalon/CAS) cross-ply [0/90]_2S ceramic matrix composite at elevated temperatures under tension-tension fatigue loading. Tension-tension fatigue tests were performed with a load ratio of R = 0.10 and a frequency of 10 Hertz at 700°C and 850°C. These results were compared to results from a previous study conducted at room temperature. Material behavior and damage was recorded by fatigue life curves, elastic modulus' maximum and minimum strain, acetate replication techniques, and post-mortem fractography. Analysis of these results showed identical matrix dominated damage behavior at RT and 700°C. Ultimate …

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 …

Behavior Of A Centrally Notched Cross-Ply And Unidirectional Ceramic Matrix Composite In Tension-Compression Fatigue, William A. Weidenaar

Theses and Dissertations

Centrally notched (hole), cross-ply, ((0/90)₂)_s, and unidirectional, (0)₈ laminates of Silicon Carbide fiber-reinforced Aluminosilicate glass, SiC/1723, were fatigue tested under tension-compression loading with a load ratio of -1. Damage accumulated continuously for both lay- ups, leading to eventual failure and a reduced fatigue life. Critical damage in the cross-ply consisted of longitudinal cracks in the 90° plies growing and combining with transverse cracks to effectively eliminate the 90° plies' load carrying capability and allowing the specimen to buckle. Critical damage in the unidirectional lay-up consisted of longitudinal cracks which initiated at the shear stress concentration …

Fatigue Behavior Of A Cross-Ply Ceramic Matrix Composite Under Tension-Tension And Tension-Compression Loading, Frank A. Opalski

Theses and Dissertations

A study was conducted which investigated the behavior of a cross-ply [0/90]_2S Nicalon/Calcium-Aluminosilicate (Nicalon/CAS) ceramic matrix composite at room temperature under tension-compression fatigue loading. Material behavior and damage was recorded by stress-strain curves, elastic modulus, hysteretic energy density, and acetate replication techniques. Tension-tension fatigue tests at a load ratio R of 0.1 (R = σ_min/σ_max) were completed which determined that 140 MPa was the maximum stress allowable in which cycle runout (1,000,000 cycles) would occur. Above this value, transverse crack density increased with respect to cycles and failure ultimately occurred. Tension-compression tests were then performed …

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 …

Failure Characterization Of A Fiber Reinforced Ceramic Matrix Composite With Circular Holes, Daniel E. Bullock

Theses and Dissertations

The purpose of this study was to investigate the performance of a fiber reinforced ceramic matrix composite with circular holes. The specific objectives were to (1) determine the relationship between tensile failure stress and the ratio of hole diameter to specimen width, and (2) to examine the initiation and progression of damage. The ceramic matrix composite used was SiC/ 1723, composed of continuous silicon titanium carbide fibers in an aluminosilicate glass ceramic matrix. Uniaxial tensile tests were performed at room temperature on two different layups; unidirectional [0]₈, and [0/90]_2s symmetric. Each layup was tested at three diameter-to-width …

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.

Q Improvement Of A 5.2 Ghz Te011 Cavity By Incorporating Y1Ba2Cu3O7-X, R. Joseph Leclear

Electrical & Computer Engineering Theses & Dissertations

Research is undertaken to apply high temperature superconducting material to improve the quality factor (Q) of a 5.2 GHz cylindrical resonant cavity. In particular, the approach is to electrophoretically deposit polycrystalline Y₁Ba₂Cu₃O_7-x (YBCO) on the conducting surface of the cavity cylinder. Spalling of the YBCO ceramic coating due to expansion and contraction of the cavity during sintering and testing is overcome by segmenting the cylinder. Results show that the Q of the cavity is increased over that of a copper cavity at temperatures below 60 K. At 20 K, improvement exceeds a factor …

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 …

Recent Applications Of Glass Science, Norbert J. Kreidl

Materials Science and Engineering Faculty Research & Creative Works

Recent, often exciting, applications of glass science include solid state batteries, electronic switches and memories, electrophotography, solar cells, microspheres for optical strengthening and medical uses, novel glass ceramics such as machinable and bioactive materials, solder glasses, composites, sol-gel glasses, gradient index optics, communication fibers, sensors, non-linear and active optics, and, perhaps, digital optics. The large field of special coatings is not covered in this review. © 1990.

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 arithmetic joints in a mammal comprise 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. Methods for preparing such microspheres and for carrying out radiation synovectomy of arthritic joints utilizing such microspheres are also disclosed.

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.

Glass Formation And Properties In The Sm₂O₃·Al₂O₃·Sio₂ System, Erik M. Erbe

Masters Theses

"The purpose of this investigation was to develop a samarium containing aluminosilicate glass with properties suitable for use in the treatment of rheumatoid arthritis. Microspheres made from these compositions would be neutron activated to produce radioactive Sm-153 which has beta-particle energies suitable for treating rheumatoid arthritis as well as appropriate gamma-ray emission for nuclear imaging. The properties of Sm₂O₃ · AI₂O₃ · SiO₂ glasses containing 10 to 25 mole% Sm₂O₃ were evaluated as a function of composition. The density, refractive index, thermal expansion coefficient, and microhardness increased with increasing Sm …

The Effect Of Phosphate Additives On Alumina, Alumina-Calcia, Alumina-Silica Refractory Castable Systems, Sukendro Widjaja

Masters Theses

The effects of the addition of phosphate chemicals to Al₂O₃, Al₂O₃-CaO, and Al₂O₃-SiO₂ systems have been studied concentrating on selected dry and fired properties. The various refractories evaluated were formulated from all alumina aggregate systems based on 1) a mix of tabular and calcined fine aluminas, 2) a combination of calcium aluminate cement bonded-tabular and calcined fine aluminas, and 3) an alumina aggregate-silica fume mixture. Specimens were vibration-cast, dried at 110°C and fired at 1450°C. It was found that each system has different property responses to different …

Sessile Drop Studies Of Aluminum On Sapphire, Ke Wen K. Li

Masters Theses

A sessile drop technique employing a drop placement method has been used to investigate the wetting behavior and interfacial phenomena between aluminum and single crystal α-alumina. Measurements were made under a flowing mixture of H₂ and He atomsphere from 1200°C to 1600°C. Acute contact angles decreased continuously in all cases during the 8-hour experimental time. Neither the oxygen partial pressure of the flowing gas nor the orientation of the single crystal alumina substrate affected the contact angles, but the shapes of crystals grown at the substrate-metal interfaces were dependent on the orientation of the substrate surface to some extent. …