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Materials Science and Engineering Faculty Research & Creative Works

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Articles 811 - 840 of 1006

Full-Text Articles in Materials Science and Engineering

Liquid-Mix Synthesis Of Oxide Powders And Thin Films Using A Starch-Based Polymer, Lone Wen F. Tai, Harlan U. Anderson Jan 1994

Liquid-Mix Synthesis Of Oxide Powders And Thin Films Using A Starch-Based Polymer, Lone Wen F. Tai, Harlan U. Anderson

Materials Science and Engineering Faculty Research & Creative Works

A commercially available water-soluble starch derivative was used as the sole organic precursor in the Liquid-Mix synthesis of mixed-cation oxide powders and thin films. The acidified polymer (by nitric acid) was able to complex metal ions through the carboxylate ligands. Loosely agglomerated fine powders as well as dense thin films of complex oxides have been prepared using the same type of polymer. Oxide powders of Cr-doped lanthanum aluminate and yttrium aluminum garnet both crystallized in a single step, without forming any intermediate or second phases, when the amorphous resin intermediates were calcined at 650 °C and 750 °C for 2 …

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Synthesis And Characterization Of Ysz Thin Film Electrolytes, C. C. Chen, M. M. Nasrallah, Harlan U. Anderson Jan 1994

Synthesis And Characterization Of Ysz Thin Film Electrolytes, C. C. Chen, M. M. Nasrallah, Harlan U. Anderson

Materials Science and Engineering Faculty Research & Creative Works

Dense, homogeneous and crack-free thin films (0.2-2 microm in thickness) of (ZrO2)0.84(YO1.5)0.16 (YSZ) were deposited on porous or dense substrates, at temperatures not exceeding 600°C, using a solution-deposition technique. The structural evolution and microstructure of the deposited films were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Raman spectroscopy revealed the presence of fine-grain cubic YSZ at annealing temperatures as low as 600°C. Grain growth occurred at higher temperatures as detected by atomic force microscopy (AFM). ac impedance spectroscopy was used to study the electrical characteristics of the YSZ films as a function of temperature. The ionic conductivity …

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Positron Annihilation Determination Of Damage Caused By Fatigue Cycling In The Superalloy Haynes 188, D. Hoeckelman, Hollis P. Leighly Jan 1994

Positron Annihilation Determination Of Damage Caused By Fatigue Cycling In The Superalloy Haynes 188, D. Hoeckelman, Hollis P. Leighly

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

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Correlation Of Wettability And Interfacial Reaction To The Densification And Dielectric Properties Of Fluxed-Batio₃, Sea-Fue Wang, Wayne Huebner, Joseph P. Dougherty Jan 1994

Correlation Of Wettability And Interfacial Reaction To The Densification And Dielectric Properties Of Fluxed-Batio₃, Sea-Fue Wang, Wayne Huebner, Joseph P. Dougherty

Materials Science and Engineering Faculty Research & Creative Works

Reducing the sintering temperature of BaTiO3 has typically been achieved through the use of a fluxing agent to promote densification by liquid phase sintering. Liquid phase formation in these systems is due either to the melting of the flux or to the formation of a eutectic liquid between the flux and BaTiO3. In this paper, the correlation between the wettability and interfacial reactions between fluxes and BaTiO3 with respect to the densification behavior associated with liquid phase sintering, and the resulting dielectric properties is presented. Fluxes used in this study include 5ZnO*2B2O3, 5CdO*2SiO2, Pb5Ge3O11, CuO*TiO2, 3Bi2O3*B2O3, and LiF.

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A Study Of The Sintering Mechanism Of Pzt-Based Piezoceramics, Wayne Huebner, Pei Wen Lu, Wanrong Xue Jan 1994

A Study Of The Sintering Mechanism Of Pzt-Based Piezoceramics, Wayne Huebner, Pei Wen Lu, Wanrong Xue

Materials Science and Engineering Faculty Research & Creative Works

The densification behavior a PZT-based composition with additions of BiFeO3 as a flux was studied. Two different PZT powders were studied with varying initial particle sizes. Results clearly showed that BiFeO3 forms a low temperature liquid that aids in the densification behavior, with 3 mole% being optimum. Fine particle sizes substantially improved the density at low temperatures, with the net result that ceramics could be densified in air without the aid of a lead source. The corresponding electromechanical properties were typical of a hard PZT formulation.

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Processing And Characterization Of Samarium And Manganese Modified Lead Titanate Thin Film, Chen-Lung Fan, Wayne Huebner Jan 1994

Processing And Characterization Of Samarium And Manganese Modified Lead Titanate Thin Film, Chen-Lung Fan, Wayne Huebner

Materials Science and Engineering Faculty Research & Creative Works

Samarium and manganese modified lead titanate thin films were fabricated by spin-coating an amorphous citrate precursor. These films transformed into an oxide film upon heat treatment at 400 degrees Celcius or above. Relatively large area and crack-free thin films could be obtained by this process both easily and inexpensively. The rheological behavior of the precursor solution, as well as its thermal decomposition and phase development were studied by means of DSC/TGA and XRD. The thickness and grain size of the oxide film were examined by TEM and SEM.

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Method For Stripping Metals In Solvent Extraction, Thomas J. O'Keefe Jul 1993

Method For Stripping Metals In Solvent Extraction, Thomas J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

Aqueous solutions containing metal cations, that may include cations of both desired metal and impurity or secondary metal, are treated with an organic liquid extractant suitable for the extraction of cations of the desired metal, cations of at least one secondary metal being co-extracted. After phase disengagement, the loaded organic phase containing cations of either a desired metal or desired metal together with at least one secondary metal is contacted with a solid metal or solid metal alloy capable of reducing in the organic phase cations of either a desired metal or a secondary metal from a higher to a …

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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 Mar 1993

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.

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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 Mar 1993

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.

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A Study Of Fatigue Failure In Superalloys Using Positron Annihilation, D. Hoeckelman, Hollis P. Leighly Jan 1993

A Study Of Fatigue Failure In Superalloys Using Positron Annihilation, D. Hoeckelman, Hollis P. Leighly

Materials Science and Engineering Faculty Research & Creative Works

This study shows there are significant changes occurring in the open volume defect concentration during fatigue cycling as measured by the S parameter. These changes are dependent upon the stress ratio, R = σmin/σmax, the maximum stress, σmax, and the number of fatigue cycles. The decline in the S parameter is due to the elimination of the residual vacancies. This decline is followed by an increase due to the generation of dislocations and the formation of small microcracks. This is followed by a decline in the S parameter due to growth of the microcracks ultimately leading to failure. Copyright © …

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Defect Structure Of Y1-Ycaymno3 And La1-Ycaymno3. Ii. Oxidation-Reduction Behavior, J. W. Stevenson, M. M. Nasrallah, Harlan U. Anderson, Don M. Sparlin Jan 1993

Defect Structure Of Y1-Ycaymno3 And La1-Ycaymno3. Ii. Oxidation-Reduction Behavior, J. W. Stevenson, M. M. Nasrallah, Harlan U. Anderson, Don M. Sparlin

Materials Science and Engineering Faculty Research & Creative Works

Electrical conductivity, Seebeck coefficient, and thermogravimetric behavior of compositions in the systems Y1-yCayMnO3 and Y1-yCayMnO3 were studied as functions of temperature and ambient oxygen activity in order to determine the mechanism of electrical transport and defect structure. Compositions in Y1-yCayMnO3 exhibited very slight oxygen activity-dependent behavior as the ambient oxygen activity was reduced. A defect model which includes the thermally excited disproportionation of Mn3+ into Mn2+ and Mn4+ pairs was applied to the oxygen-activity-dependent data for La0.80Ca0.20MnO3 …

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The Influence Of Matrix Microstructure, G. M. Vyletel, J. E. Allison, David C. Van Aken Jan 1993

The Influence Of Matrix Microstructure, G. M. Vyletel, J. E. Allison, David C. Van Aken

Materials Science and Engineering Faculty Research & Creative Works

The low-cycle and high-cycle fatigue behavior and cyclic response of naturally aged and artificially aged 2219/TiC/15p and unreinforced 2219 Al were investigated utilizing plastic strain-controlled and stress-controlled testing. The cyclic response of both the reinforced and un-reinforced materials was similar for all plastic strain amplitudes tested except that the saturation stress level for the composite was always greater than that of the unreinforced material. The cyclic response of the naturally aged materials exhibited cyclic hardening and, in some cases, cyclic softening, while the cyclic response for the artificially aged materials showed no evidence of either cyclic hardening or softening. The …

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Defect Structure Of Y1-Ycaymno3 And La1-Ycaymno3. I. Electrical Properties, J. W. Stevenson, M. M. Nasrallah, Harlan U. Anderson, Don M. Sparlin Jan 1993

Defect Structure Of Y1-Ycaymno3 And La1-Ycaymno3. I. Electrical Properties, J. W. Stevenson, M. M. Nasrallah, Harlan U. Anderson, Don M. Sparlin

Materials Science and Engineering Faculty Research & Creative Works

Electrical conductivity and the Seebeck coefficient of compositions in the system Y1-yCayMnO3 and La1-yCayMnO3 were studied to determine the mechanism of electrical transport and defect structure. Electrical conduction appeared to occur via a small polaron hopping mechanism for compositions with 0.30 ≤ y ≤ 0.80. The Seebeck coefficient data did not support the assumption that Mn is present in Cadoped Mn perovskites only in the +3 and +4 valence states. A new defect model was developed which includes the thermally excited disproportion of Mn3+ and Mn4+ pairs. The …

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Solid-State Science And Technology: Synthesis And Characterization Of (Ceo2)0.8(Smo1.5)0.2 Thin Films From Polymeric Precursors, C. C. Chen, Harlan U. Anderson, M. M. Nasrallah Jan 1993

Solid-State Science And Technology: Synthesis And Characterization Of (Ceo2)0.8(Smo1.5)0.2 Thin Films From Polymeric Precursors, C. C. Chen, Harlan U. Anderson, M. M. Nasrallah

Materials Science and Engineering Faculty Research & Creative Works

(CeO2)0.8(CSO) has been suggested for solid oxide fuel cell (SOFC) applications, because of its higher electrical conductivity and chemical stability, compared to other ceria-based materials. However, CSO is difficult to densify under conditions compatible with other SOFC components. A thin film synthesis technique has been developed for the fabrication of dense CSO films from precursor solutions at relatively low temperatures. Dense, smooth, and homogeneous films were obtained on Pt, single-crystal Si, and La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) substrates by spin-coating a polymeric precursor and subsequent heat-treatment. Crystallization of the film …

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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 Jan 1993

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 …

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Electrochemical Evaluation Of The Adherence Of Zinc To Aluminum Cathodes, Jang Sop Han, Thomas J. O'Keefe Nov 1992

Electrochemical Evaluation Of The Adherence Of Zinc To Aluminum Cathodes, Jang Sop Han, Thomas J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

Excess fluoride ions in zinc electrolyte are known to cause problems with the removal of electrowon zinc from aluminum blanks. The mechanisms responsible for this undesirable adherence were studied. Acid zinc sulfate electrolyte similar to that employed in zinc electrowinning was used. Using electrolyte containing various fluoride ion concentrations, the initial nucleation and growth morphology of zinc and the aluminum electrode surface were examined using scanning electron microscopy. Electrochemical tests were also carried out in various solutions to obtain a better understanding of the polarization behavior of the system. © 1992.

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Investigation Of Strontium-Doped La(Cr, Mn)O3 For Solid Oxide Fuel Cells, Rasit Koc, Harlan U. Anderson Nov 1992

Investigation Of Strontium-Doped La(Cr, Mn)O3 For Solid Oxide Fuel Cells, Rasit Koc, Harlan U. Anderson

Materials Science and Engineering Faculty Research & Creative Works

The (La, Sr) (Cr, Mn)O3 system was investigated in an effort to develop an interconnect and cathode materials for solid oxide fuel cells. Sintering studies were done in air at temperatures below 1500°C. Significant improvements in densification were observed with substitution of 50 mol% Mn for chromium and a density of 95% theoretical was achieved with the substitution of 70 mol% Mn for chromium in the La(Cr, Mn)O3 system. Electrical conductivity (d.c.) measurements were made as a function of temperature and oxygen activity. At 1000°C and 1 atm oxygen, the electrical conductivity ranged from 2.2-20 S cm-1 …

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Structural Ceramic Incorporating Boron Carbide Whiskers For The Strengthening Thereof, P. D. Ownby, J. Liu Nov 1992

Structural Ceramic Incorporating Boron Carbide Whiskers For The Strengthening Thereof, P. D. Ownby, J. Liu

Materials Science and Engineering Faculty Research & Creative Works

Ceramic composites, and in particular structural ceramic composites, have enhanced strength, toughness and abrasion resistance due to the presence of up to about 40 volume percent of relatively large boron carbide whiskers. Although whiskers of various sizes were studied, those of particular interest are whiskers having an average diameter greater than about 3 micrometers, and particularly about 5 to about 8 micrometers, with an average aspect ratio of about 50. Due to the larger size, which had been predicted to be detrimental, there is less respiratory health risk when using these whiskers in the manufacturing of thse improved ceramic composites. …

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The Effect Of Additives On The Nucleation And Growth Of Copper Onto Stainless Steel Cathodes, M. Sun, Thomas J. O'Keefe Oct 1992

The Effect Of Additives On The Nucleation And Growth Of Copper Onto Stainless Steel Cathodes, M. Sun, Thomas J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

A potentiostatic technique has been used to study the effects of chloride ion, glue, and thiourea on the initial electrodeposition of copper. A stainless steel (AISI 304) rotating disc electrode (RDE) with an electrolyte containing 40 g/1 Cu2+ and 180 g/1 H2SO4 at 40 °C was employed. The current transients from the potential step measurements for the additive-free electrolyte could be fitted to a model that assumed progressive nucleation followed by growth of three-dimensional (3-D) centers under diffusion control. The growth mechanism and the type of nuclei were also confirmed by scanning electron microscopy (SEM) of …

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The Degradation Of Aluminium Cathodes By Fluoride Ion During Zinc Electrowinning, J. S. Han, Thomas J. O'Keefe Jul 1992

The Degradation Of Aluminium Cathodes By Fluoride Ion During Zinc Electrowinning, J. S. Han, Thomas J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

The influence of fluoride ions on aluminum cathode surface degradation during zinc electrowinning has been studied. Electrolyte with a composition similar to that employed in plant operations has been used. A direct correlation is shown between the electrolyte fluoride content and the number of deposition cycles possible before zinc removal becomes difficult. The role of initial nucleation and starting electrode morphology is discussed in terms of the degree of adherence observed. Electrochemical tests have also been made on the electrodes at various stages of the process in an attempt to gain a better fundamental understanding of the mechanisms responsible for …

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X‐Ray Powder Diffraction Structural Phase‐Transition Study Of La(Cr1‐Xmnx)O3 (X = 0 To 0.25) Using The Rietveld Method Of Analysis, Scott A. Howard, Jen‐Kuan ‐K Yau, Harlan U. Anderson Jan 1992

X‐Ray Powder Diffraction Structural Phase‐Transition Study Of La(Cr1‐Xmnx)O3 (X = 0 To 0.25) Using The Rietveld Method Of Analysis, Scott A. Howard, Jen‐Kuan ‐K Yau, Harlan U. Anderson

Materials Science and Engineering Faculty Research & Creative Works

The La(Cr1‐xMnx)O3 (x = 0 to 0.25) system exhibited a displacive phase transformation from an orthorhombic to a rhombohedral structure at temperatures ranging from about 256°C at x= 0 to 305°C at x= 0.25. The Rietveld method of X‐ray analysis was used to determine structural characteristics and to assay phase concentrations when multiple phases were present. Indications were that the Mn ions on the B site affected the transition temperature through an ionic size effect; i.e., Mn3+, with a larger ionic size than Cr3+, increased the transition temperature while the presence …

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Grain Size Effect On The Induced Piezoelectric Properties Of 0.9pmn-0.1pt Ceramic, U. Kumar, Wayne Huebner, P. Marsh, H. Kankul, S. F. Wang, Clyde G. Oakley Jan 1992

Grain Size Effect On The Induced Piezoelectric Properties Of 0.9pmn-0.1pt Ceramic, U. Kumar, Wayne Huebner, P. Marsh, H. Kankul, S. F. Wang, Clyde G. Oakley

Materials Science and Engineering Faculty Research & Creative Works

Lead magnesium niobate-lead titanate (Pb(Mg1/3Nb2/3)O3 - PbTiO3 (PT) solid solutions have been widely researched to produce devices that can be used in low- and high-electric-field applications. For some applications, such as medical ultrasonic transducers, it is necessary to prepare the ceramic with high density and small average grain size. The effect of grain size on the low- and high-field properties of 0.9-PMN-0.10-PT ceramics is described in the present work. To prepare highly dense ceramic, vibratory and attrition milled powders were sintered between 1000 and 1250 ⁰C. The average grain sizes of the sintered ceramics …

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Sme Annual Meeting. Phoenix, Usa. February 22-27, 1992, Johh L. Watson Jan 1992

Sme Annual Meeting. Phoenix, Usa. February 22-27, 1992, Johh L. Watson

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

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Mixed‐Cation Oxide Powders Via Resin Intermediates Derived From A Water‐Soluble Polymer, Lone‐Wen ‐W Tai, Harlan U. Anderson, Paul A. Lessing Jan 1992

Mixed‐Cation Oxide Powders Via Resin Intermediates Derived From A Water‐Soluble Polymer, Lone‐Wen ‐W Tai, Harlan U. Anderson, Paul A. Lessing

Materials Science and Engineering Faculty Research & Creative Works

Sub micrometer powders of complex oxides were prepared via resin intermediates based on a starch type of organic precursor. A commercially available water‐soluble starch derivative was (for the first time) used as the organic base for solution synthesis of ceramic powders. Calcination of the charred, fluffy, amorphous resins at a temperature below 600°C for 4 h yielded perovskite powders of Sr‐doped LaMnO3 and Sr‐doped La(Fe,Co)O3. Sr‐doped LaCrO3 needed to be calcined above 750°C to ensure phase purity and to remove organic residue. Due to the low cost of starch derivatives, the process has the potential of …

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Solvent Extraction Reagent Entrainment Effects On Zinc Electrowinning From Waste Oxide Leach Solutions, M. Neira, Thomas J. O'Keefe, Johh L. Watson Jan 1992

Solvent Extraction Reagent Entrainment Effects On Zinc Electrowinning From Waste Oxide Leach Solutions, M. Neira, Thomas J. O'Keefe, Johh L. Watson

Materials Science and Engineering Faculty Research & Creative Works

A considerable quantity of metal-containing waste oxide is generated by the primary metal industry, and under increased environmental regulation, treatment of these wastes has become viable. Hydrometallurgical processing is often appropriate and one potential treatment process for zinc oxide wastes involves leaching the oxide with an acid, purifying by a solvent extraction operation, and recovering metallic zinc by electrowinning the purified leach solution. The purification stage is frequently critical and the introduction of a solvent extraction organic reagent into the flowsheet can be detrimental to downstream processes. The object of this study was to determine the effect of organics, entrained …

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Review Of P-Type Doped Perovskite Materials For Sofc And Other Applications, Harlan U. Anderson Jan 1992

Review Of P-Type Doped Perovskite Materials For Sofc And Other Applications, Harlan U. Anderson

Materials Science and Engineering Faculty Research & Creative Works

p-type perovskite-type oxides are candidates for use as components of high temperature fuel cells and as oxygen separation membranes. The particular properties that these applications require are reviewed. The characteristics that these oxides have which allow them to satisfy many of these requirements are discussed and a defect model presented. The status of the utilization of these oxides and of the areas which need to be addressed such as thermal expansion and sintering characteristics are reviewed. © 1992.

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Effect Of Ultrasound On Acidified Brine Leaching Of Double-Kiln Treated Eaf Dust, J. A. Barrera-Godinez, Thomas J. O'Keefe, Johh L. Watson Jan 1992

Effect Of Ultrasound On Acidified Brine Leaching Of Double-Kiln Treated Eaf Dust, J. A. Barrera-Godinez, Thomas J. O'Keefe, Johh L. Watson

Materials Science and Engineering Faculty Research & Creative Works

The U.S. steel industry produces approximately 500,000 tons/year of electric arc furnace (EAF) dust, which is classified as a hazardous waste. Increasing disposal costs of these dusts have encouraged studies to investigate treatment processes to render the material non-hazardous, and to possibly recover metal values. This research project was designed to examine the hydrometallurgical recovery of zinc from EAF dusts that have been treated by a double kiln fuming process. The test work consisted essentially of acidified brine leaching of the pelletized calcine to determine the influence of traditional conditions, such as acid concentration, temperature and agitation, plus the application …

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Tensile Fatigue Behaviour Of Tightly Woven Carbon/Carbon Composites, A. Ozturk, Robert E. Moore Jan 1992

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 …

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Electrical Conductivity And Seebeck Coefficient Of (La, Ca) (Cr, Co)O3, R. Koc, Harlan U. Anderson Jan 1992

Electrical Conductivity And Seebeck Coefficient Of (La, Ca) (Cr, Co)O3, R. Koc, Harlan U. Anderson

Materials Science and Engineering Faculty Research & Creative Works

Electrical conductivity and Seebeck coefficients of (La, Ca) (Cr, Co)O3 were measured as a function of temperature. The electrical conductivity as measured in air from 100 to 1100 °C increased with increasing Co and Ca content. The Seebeck coefficients were positive, indicating p-type conductivity. The substitution of Co for Cr significantly decreased the Seebeck coefficients, indicating that the substitution resulted in an increase in site occupancy, associated with the Co. The additional Ca substitution for La resulted in further decrease in the Seebeck coefficients, then exhibited a temperature-independent behaviour, indicating that the carrier mobility, rather than carrier concentration, was …

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Effect Of Cation Substitution On The Thermal Expansion Coefficient Of Lacro3, R. Koc, Harlan U. Anderson Jan 1992

Effect Of Cation Substitution On The Thermal Expansion Coefficient Of Lacro3, R. Koc, Harlan U. Anderson

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

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