Open Access. Powered by Scholars. Published by Universities.®

Materials Science and Engineering Commons™

Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics

Institution
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 4831 - 4860 of 5380

Full-Text Articles in Materials Science and Engineering

Electroreduction Of Holmium Ion On Iron Electrde In Molten Cholorides, Qiqin Yang, Guankun Liu, Yuzhi Su Feb 1995

Electroreduction Of Holmium Ion On Iron Electrde In Molten Cholorides, Qiqin Yang, Guankun Liu, Yuzhi Su

Journal of Electrochemistry

The cyclic voltammetry, open circuit potential-time curve after poteritiostatic electrolysis, current-time curve at potential step, X-ray diffraction and electron probe microanalysiswere used to investigate the electrode process of Ho(Ⅲ) reduced on iron electrode in molten chloridesand the phases of surface alloy layer. The Ho-Fe alloys are formed at first, and then the metallic holmium is deposited when Ho(Ⅲ) is reduced on iron electrode. The charge transfer is reversible. The free energies of formation for the four inter metallic compounds of Ho-Fe system, the diffusion coefficients and diffusion activation energy of Ho in alloyed cathode are determined.

Go to article

The Study Of The Growth Processes Of The Oxides On Lead Electrodes In Sulfuric Acid Solution, Hesheng Zhai, Xuguang Chen, Jinkua You, Yong Yang, Zugeng Lin Feb 1995

The Study Of The Growth Processes Of The Oxides On Lead Electrodes In Sulfuric Acid Solution, Hesheng Zhai, Xuguang Chen, Jinkua You, Yong Yang, Zugeng Lin

Journal of Electrochemistry

The growth processes of PbO and PbO2 on lead electrodes have been investigatedby using in-situ methods that are combined with temporary AC resistance measurment technique and in-situ laser scanning photoelectrochemical microscopy. It is found that a linear relationship existsbetween the electrode resistance(R) and1/2 after the electrode is oxidized at +0.6 V(vs.Hg/H2SO4/35% H2SO4) for more than 5 min. This result suggests that the growth of PbO is well distributed during the early stage of oxidation. The study by using laser scanning photoelectrochemical microscopy has further proved this point. The results also …

Go to article

The Electrode Process Of Y(Ⅲ) On Copper Electrode And Its Surface Metallizing, Chungen Zhou, Shuzhen Duan Feb 1995

The Electrode Process Of Y(Ⅲ) On Copper Electrode And Its Surface Metallizing, Chungen Zhou, Shuzhen Duan

Journal of Electrochemistry

The reduction of yttrium ion on copper electrode in NaCl-KCl-YCl3 molten saltshas been investigated. The results indicate that the formation of intermetallic compounds is occuredbefore the metallic yttrium to be formed. The formation of intermetallic compounds is controlled bythe process of which yttrium atoms are diffusing into copper electrode. The kinetic characters todiffusion of yttrium atoms were also discussed.

Go to article

The Catalytic Behavior For Ni-W Electrode Modified By Carbon Ion Beam Implantion, Jishuang Zhang, Yaojiao Lv, Qinglian Li, Baoen Shen Feb 1995

The Catalytic Behavior For Ni-W Electrode Modified By Carbon Ion Beam Implantion, Jishuang Zhang, Yaojiao Lv, Qinglian Li, Baoen Shen

Journal of Electrochemistry

The hydrogen evolution activity in acidic and basic mediums for Ni-W electrodemodified by carbon ion bean implantation was investigated. The experimental results show thiselectrode has superior catalytic activity for the hydrogen evolution reaction than that of the unmodified Ni-electrode. Long period testing of electrolysis under high current density show that this electrode hasalonger useful life hence it is a practical electrode material. The temperature effect of electrocatalytic property was also inverstigated. The experimental regularities are explained on the basis of the formation of surface multialloys of Ni-W-WC.

Go to article

Electrocatalytic Oxidation Of Formaidehyde And Formic Acid On A Pt/SbAd Electrode, Hong Li, Lincai Jiang, Xiong Jiang Feb 1995

Electrocatalytic Oxidation Of Formaidehyde And Formic Acid On A Pt/SbAd Electrode, Hong Li, Lincai Jiang, Xiong Jiang

Journal of Electrochemistry

The electrocatalytic activity for the oxidation of formaldehyde and formic acid ona Sb-modified platinum (Pt/Sbad) was investigated. Results showed that the Pt/Sbad electrode was electrocatalytically more active than a Pt electrode in the anodic oxidation of formaldehyde and formicacid. In the case of formaldehyde, an oxidation peak appeared at a potential of ca. 0.7V. During the oxidation of formic acid, a 4-fold increase in the 1st peak current was observed. The Sb-modified platinum electrode was found to be most electrocatalytically active at a coverage of 0.75±0.05. The electrocatalytic activity of the Pt/Sbad electrode can be best …

Go to article

The Effect Of Some Ions On Cr2O72- Anodic Formation Process At Pt And Pbo2 Electrodes, Shixiong Jin, Zhigang Zhou, Lan Wang Feb 1995

The Effect Of Some Ions On Cr2O72- Anodic Formation Process At Pt And Pbo2 Electrodes, Shixiong Jin, Zhigang Zhou, Lan Wang

Journal of Electrochemistry

The influence of Ag2SO4, Li2SO4, Na2SO4, K2SO4, (NH4)2SO4,MgSO4 and KF on the evolution of O2 and the formation of Cr2O at Pt and PbO2 anodes was investigated in mixed H2SO4-Cr2(SO2)3 solutions. The kinetic data related respectively to Cr2O formation and O2 evolution at Pt and PbO2 anodes were measured by method of resolving the steady-state polarization curve. The Tafel slope …

Go to article

Semiempirical Model For The Electrical Properties Of La1-Xcaxcoo3, S. R. Sehlin, Harlan U. Anderson, Don M. Sparlin Jan 1995

Semiempirical Model For The Electrical Properties Of La1-Xcaxcoo3, S. R. Sehlin, Harlan U. Anderson, Don M. Sparlin

Materials Science and Engineering Faculty Research & Creative Works

A semiempirical model of the Seebeck coefficient for a small polaron hopping conductor is presented. The population of small polarons is allowed to change as a function of temperature via the mechanism of charge disproportionation. The energy required for polaron formation by the disproportionation mechanism is modeled as screened by a Coulomb interaction with nearby small polarons. The charge carrier site occupancies generated by the model are used to successfully predict the electrical conductivity and Seebeck coefficient for compositions in the La1-xCaxCoO3 system. Cobalt ion valence populations predicted by the model are used to calculate effective paramagnetic moments for LaCoO3, …

Go to article

Structure And Electrical Properties Of La1-Xsrxco1-Yfeyo3. Part 1. The System La0.8sr0.2co1-Yfeyo3, L. W. Tai, M. M. Nasrallah, Harlan U. Anderson, Don M. Sparlin, S. R. Sehlin Jan 1995

Structure And Electrical Properties Of La1-Xsrxco1-Yfeyo3. Part 1. The System La0.8sr0.2co1-Yfeyo3, L. W. Tai, M. M. Nasrallah, Harlan U. Anderson, Don M. Sparlin, S. R. Sehlin

Materials Science and Engineering Faculty Research & Creative Works

Crystal structure, thermal expansion, thermogravimetry, thermoelectricity, and electrical conductivity of compositions in the system La0.8Sr0.2Co1-yFeyO3 with 0 ≤ y ≤ 1 were studied as function of Co Fe ratio and temperature, in air. The electrical conduction mechanism is attributed to the adiabatic-hopping of p-type small polarons. At high temperatures, oxygen deficiency causes lattice expansion and a reduction in electrical conductivity. The observed temperature dependence of the Seebeck coefficient is attributed to changes in carrier concentration caused by a thermally excited charge disproportionation of Co3+ ions and by the ionic compensation of induced oxygen vacancies. The measured electrical conductivity and Seebeck …

Go to article

Structure And Electrical Properties Of La1 - Xsrxco1 - Yfeyo3. Part 2. The System La1 - Xsrxco0.2fe0.8o3, L. W. Tai, M. M. Nasrallah, Harlan U. Anderson, Don M. Sparlin, S. R. Sehlin Jan 1995

Structure And Electrical Properties Of La1 - Xsrxco1 - Yfeyo3. Part 2. The System La1 - Xsrxco0.2fe0.8o3, L. W. Tai, M. M. Nasrallah, Harlan U. Anderson, Don M. Sparlin, S. R. Sehlin

Materials Science and Engineering Faculty Research & Creative Works

Crystal structure, thermal expansion, oxygen stoichiometry, thermoelectricity, and electrical conductivity of compositions in the system La1 - xSrxCo0.2Fe0.8O3 with 0 ≤ x ≤ 0.6 were studied as function of temperature and Sr content, in air. The solubility of Sr in the sintered perovskite-type oxide (ABO3) was limited to x ≤ 0.4. The observed p-type electrical conduction appeared to occur via a small-polaron hopping mechanism. The thermally induced oxygen loss caused a lattice expansion plus decreases in both the carrier concentration and the carrier mobility. A semi-empirical model was developed which takes into account the thermally activated disproportionation of Co3+ ions …

Go to article

Electrical Characterization Of The (La,Ca) (Cr,Co)O3 System, S. R. Sehlin, Harlan U. Anderson, Don M. Sparlin Jan 1995

Electrical Characterization Of The (La,Ca) (Cr,Co)O3 System, S. R. Sehlin, Harlan U. Anderson, Don M. Sparlin

Materials Science and Engineering Faculty Research & Creative Works

The results of electrical conductivity and thermopower measurements are presented for selected (La,Ca)(Cr,Co)O3 compositions. The La1 - xCaxCrO3 compounds are typical p-type small polaron conductors. The La1 - xCaxCrO3 compounds are found to be small polaron conductors at room temperature for x ≤ 0.20 with a higher electrical conductivity than the corresponding chromite's. The electrical conductivity at room temperature is lower for Co-rich compositions than for Cr-rich compositions for compositions containing 10 mol% and 20 mol% Ca. This fact is attributed to the trapping of p-type small polarons at energetically lower Cr sites, resulting in a broad room temperature conductivity …

Go to article

Characterization Of Piezoceramic Crosses With Large Range Scanning Capability And Applications For Low Temperature Scanning Tunneling Microscopy, J. A. Helfrich, Shireen Adenwalla, J. B. Ketterson, G. A. Zhitomirsky Jan 1995

Characterization Of Piezoceramic Crosses With Large Range Scanning Capability And Applications For Low Temperature Scanning Tunneling Microscopy, J. A. Helfrich, Shireen Adenwalla, J. B. Ketterson, G. A. Zhitomirsky

Shireen Adenwalla Papers

We have developed a large amplitude piezoceramic scanner which should have numerous applications. Scanning tunneling microscopy (STM) and other scanning probe microscopies predominantly use piezoceramics for the scanning elements. Similarly adaptive optics, high resolution lithography, and micromanipulators are other examples of research which regularly utilize piezoceramic scanners. We present a new geometry for a piezoceramic scanner which allows for both high resolution (~nanometers) and large amplitude (~400 µm) displacements. The cross-shaped geometry makes it possible to produce extremely long pieces with very high tolerances. We have shown its effectiveness by using it as the major component of a low temperature …

Go to article

Compensation And Characterization Of Gallium Arsenide, Randy A. Roush Jan 1995

Compensation And Characterization Of Gallium Arsenide, Randy A. Roush

Electrical & Computer Engineering Theses & Dissertations

The properties of transition metals in gallium arsenide have been previously investigated extensively with respect to activation energies, but little effort has been made to correlate processing parameters with electronic characteristics. Diffusion of copper in gallium arsenide is of technological importance due to the development of GaAs:Cu bistable photoconductive devices. Several techniques are demonstrated in this work to develop and characterize compensated gallium arsenide wafers. The material is created by the thermal diffusion of copper into silicon-doped GaAs. Transition metals generally form deep and shallow acceptors in GaAs, and therefore compensation is possible by material processing such that the shallow …

Go to article

Sorption Of Chlorinated Organic Compounds By Sedimentary Rocks, Paul M. Mcginley, S. Kesaraju, Ronald D. Gruzesky Dec 1994

Sorption Of Chlorinated Organic Compounds By Sedimentary Rocks, Paul M. Mcginley, S. Kesaraju, Ronald D. Gruzesky

KWRRI Research Reports

The sorption of dichlorobenzene and trichlorobenzene on carbonate and shale rocks collected in Kentucky demonstrate that rock organic matter content is a good indicator of sorptive reactivity in rock systems. Although this is similar to soil systems, significant differences between sorption in rock and soil systems exist. Sorption isotherms on these rocks are nonlinear and sorption can be an order of magnitude higher than predicted using correlations from soils and their organic matter content. This sorption reaction could lead to significant concentration tailing during contaminant cleanup. Experimental elution of trichloroethylene from rock filled columns verified that cleanup times might be …

Go to article

The Current Voltage Characteristics Of Electron Beam Controlled Thin Film Diamond Switches, Christopher Anthony Molina Oct 1994

The Current Voltage Characteristics Of Electron Beam Controlled Thin Film Diamond Switches, Christopher Anthony Molina

Electrical & Computer Engineering Theses & Dissertations

The dark current of natural diamond thin films and the induced current due to electron-beam irradiation was measured up to a range of 7000Ncm'. The contact material was aluminum, annealed and unannealed. Switching experiments were performed with electron energies ranging from 70keV to 172keV. The switching results obtained are strongly dependent on the biasing polarity, incident electron energy, and whether the contact is blocking or Ohmic in nature. A simple model which takes traps into consideration allows us to explain the various switching responses. The range of electrons which define, in part, the switch mode was measured for one sample …

Go to article

36th Rocky Mountain Conference On Analytical Chemistry Jul 1994

36th Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Program, abstracts, and information about the 36th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, July 31 - August 5, 1994.

Go to article

The Excitation Mechanism Of Praseodymium-Doped Semiconductors, Paul L. Thee Jun 1994

The Excitation Mechanism Of Praseodymium-Doped Semiconductors, Paul L. Thee

Theses and Dissertations

This study on praseodymium Pr luminescence in AlxGa1-xAs was conducted to enhance the understanding of the excitation mechanism. Pr was implanted at 390 keV with doses from 5 x 1012 to 5 x 1013 cm2 into AlxGa1-xAs x0.0 to 0.50 wafers which were annealed using the rapid thermal annealing RTA method. Low temperature photoluminescence PL was conducted using an Ar-ion laser and Ge detector. PL emissions of Pr from all hosts include peaks near 1.3 and 1.6 µm which are assigned to the intra-4f transitions of 1G4 yielding 3H5 …

Go to article

Diamond Thin Film Sensors For Hypersonic Flow Studies, Bhaskar Kumar Bulusu Apr 1994

Diamond Thin Film Sensors For Hypersonic Flow Studies, Bhaskar Kumar Bulusu

Electrical & Computer Engineering Theses & Dissertations

Conventional metal film sensors can measure flow instabilities of the order of 60 kHz. The turbulence fluctuations in the hypersonic regime are of the order of 200- 400 kHz. To measure these fluctuations, sensors with an enhanced frequency response are required. Therefore, it is required to identify the parameters to enhance the frequency response. These include parameters such as the temperature sensitivity, the resistivity, the thermal conductivity, the diffusivity, specific heat capacity and the geometric size and shape of the film and the substrate. A selection of materials was then carried out to maximize the frequency response. Diamond was identified …

Go to article

The Corrosive Effects Of Salt Spray On Electrolytic Zinc Plated Mechanical Fasteners: The Case Of Clear Chromate And Yellow Dichromate Coatings On Medium Carbon Plated Bolts, Souleymane Boukari Jan 1994

The Corrosive Effects Of Salt Spray On Electrolytic Zinc Plated Mechanical Fasteners: The Case Of Clear Chromate And Yellow Dichromate Coatings On Medium Carbon Plated Bolts, Souleymane Boukari

Dissertations and Theses @ UNI

The purpose of this study was to evaluate the relationship between plating thickness and corrosion resistance of zinc coated medium carbon steel bolts under salt spray moisture conditions. Two types of zinc coatings were chosen for the study: the clear chromate zinc and the yellow dichromate zinc. One hundred and eighty 3/8-16 x 5 3/4 inch medium carbon steel bolts were selected for the test and divided into groups of 18. Two types of salt solution were used in the study: the low salt and the high salt. Bolts with various coatings tested with low salt concentration were composed of …

Go to article

Reaction Of Titanocene Dichloride With Acetylenedicarboxylate, Tanya L. Hagler, Mark Draganjac, Paul M. Nave, J. Ed Bennett, Farooq Kahn, Robert Engelken, Gerard Williams, Chris Poole, Kwok Fai Yu Jan 1994

Reaction Of Titanocene Dichloride With Acetylenedicarboxylate, Tanya L. Hagler, Mark Draganjac, Paul M. Nave, J. Ed Bennett, Farooq Kahn, Robert Engelken, Gerard Williams, Chris Poole, Kwok Fai Yu

Journal of the Arkansas Academy of Science

The reaction of Cp2TiCl2 with either the mono- or dipotassium salt of acetylenedicarboxylic acid (ADC) gives high yields of an insoluble orange product. The insoluble compound shows potential semiconductor behavior, as evidenced by an apparent bandgap in the orange region of the visible spectrum. Under N2 ,the compound decomposes at 238° C, eventually losing approximately 46% total mass up to 1350° C. The exothermic decomposition in air, beginning at 235° C, results in the formation of titanium oxides.

Go to article

Neutron-Scattering Study Of Librations And Intramolecular Phonons In Rb_{2.6}K_{0.4}C_{60}, D. Reznik, W. A. Kamitakahara, D. A. Neumann, J. R. D. Copley, J. E. Fischer, Robert M. Strongin, M. A. Cichy, Amos B. Smith Iii Jan 1994

Neutron-Scattering Study Of Librations And Intramolecular Phonons In Rb_{2.6}K_{0.4}C_{60}, D. Reznik, W. A. Kamitakahara, D. A. Neumann, J. R. D. Copley, J. E. Fischer, Robert M. Strongin, M. A. Cichy, Amos B. Smith Iii

Chemistry Faculty Publications and Presentations

We report the results of inelastic neutron-scattering measurements on Rb2.6K0.4C60. Librational modes were observed as broad peaks with maxima between 4.1 and 4.7 meV, as the temperature is lowered from 300 to 12 K. As in K3C60, no change in the width or position of the librational peak was observed when the sample was cooled through the superconducting transition. Thus any coupling of the librations to electronic states is small. The magnitude of the orientational potential barrier was estimated from the librational peak frequency. A flat background observed in the …

Go to article

The Effects Of Optical Feedback On Polarization Of Vertical Cavity Surface Emitting Lasers, Gregory J. Vansuch Dec 1993

The Effects Of Optical Feedback On Polarization Of Vertical Cavity Surface Emitting Lasers, Gregory J. Vansuch

Theses and Dissertations

Vertical Cavity Surface Emitting Lasers VCSELs are a type of semiconductor laser with a cavity oriented orthogonally to the planes of material growth. These lasers differ from conventional edge emitting lasers in several important ways. They have symmetric output beams and they are easily built into two dimensional arrays, making them very attractive as photonic components. The characteristic of interest in this thesis is polarization. While the asymmetric cavities of edge emitters exhibit a clear preference for light polarized in a particular direction, the cylindrically symmetric cavity of a VCSEL has no clear preference. Therefore, it should be relatively easy …

Go to article

Photoluminescence Spectroscopy Of Zinc Germanium Diphosphide (Zngep2), Jack E. Mccrae Sep 1993

Photoluminescence Spectroscopy Of Zinc Germanium Diphosphide (Zngep2), Jack E. Mccrae

Theses and Dissertations

Zinc germanium diphosphide (ZnGeP2) is a chalcopyrite semiconductor with strong nonlinear optical properties and potential application to Air Force interests. The characteristics of this material have been studied using photoluminescence (PL) spectroscopy. The PL spectrum is dominated by transitions from the conduction band to a deep acceptor level, and features in the spectrum suggest that more than one transition is being observed. The PL is partially polarized, and the degree of polarization appears to differ for each feature in the spectrum. The relative PL intensity of these features are seen to depend upon the wavelength of the excitation …

Go to article

35th Rocky Mountain Conference On Analytical Chemistry Jul 1993

35th Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Program, abstracts, and information about the 35th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, July 25-29, 1993.

Go to article

Study Of Single-Fiber Fiber Optic Lever Microphone, Trung Duc Nguyen Jul 1993

Study Of Single-Fiber Fiber Optic Lever Microphone, Trung Duc Nguyen

Electrical & Computer Engineering Theses & Dissertations

Fiber optic sensors are widely used in today's technological applications, providing many advantages that conventional sensors lack. In particular, there is a demand in hypersonic applications to develop microphones to measure acoustic pressure that performs in high temperature and noisy surroundings. This thesis analyzes fiber optic lever microphones (FOLM), since they perform at high temperatures. An FOLM system is an intensity modulated sensor, which is simple to implement and is small in size. Two models of the FOLM have been fabricated and calibrated. The first model uses a seven-element fiber array while the second uses a single-fiber to transmit and …

Go to article

Light Injection From An Active Cladding To The Core Of A Fiber Optic Fluorosensor, Alvin Leon Bryant Jul 1993

Light Injection From An Active Cladding To The Core Of A Fiber Optic Fluorosensor, Alvin Leon Bryant

Electrical & Computer Engineering Theses & Dissertations

A fluorosensor works on the basis of light injection from the clad into the core of an optical fiber. The sensitivity of such a sensor depends on the efficiency of light injection. Conditions necessary for a high injection efficiency are experimentally determined. The refractive index difference between the core and the clad,ncore -nclad, must be maximized to achieve a high injection efficiency. Since an air clad has the least refractive index, a bare core fiber will have a maximum efficiency. Standard optical fibers used for communication employ a minimum value for ncore -nclad, in order …

Go to article

Boundary Value Problems In Rectilinearly Anisotropic Thermoelastic Solids, Gilbert Kerr Jul 1993

Boundary Value Problems In Rectilinearly Anisotropic Thermoelastic Solids, Gilbert Kerr

Mathematics & Statistics Theses & Dissertations

The boundary value problems which are considered are the type that arise due to the presence of a Griffith crack (or cracks) in an anisotropic thermoelastic solid. The thermoelastic field, in such materials, when the infinitesimal theory is employed, is governed by a set of elliptic partial differential equations. The general solution of these equations is expressed in terms of arbitrary analytic functions whose real parts, in turn, are expressed in terms of Fourier type integrals or Fourier series. Integral transform techniques are then used to determine the stress intensity factors (and other pertinent information) for various crack geometries. In …

Go to article

The Effects Of Electron Radiation On The Glass Transition Temperature Of A Polyetherimide, Kristen Tulloch Kern Apr 1993

The Effects Of Electron Radiation On The Glass Transition Temperature Of A Polyetherimide, Kristen Tulloch Kern

Physics Theses & Dissertations

The effects of electron radiation on a polyetherimide (PEI), Ultem*, were investigated. In particular, the changes in the glass transition temperature (Tg) with absorbed radiation dose were studied. The polymer was exposed to mono-energetic beams of 100-keV electrons and 1.0-MeV electrons for doses up to 100 megagray (MGy). Dosimetry for the exposures was based on Monte-Carlo simulations of the transfer of energy from an energetic electron to the polymer and on comparison to Nylon standards. Dynamic mechanical analysis was used to determine the (Tg) for non-exposed PEI and the changes in (Tg) resulting from …

Go to article

Design And Performance Evaluation Of A Gas Chromatograph Micromachined In A Single Crystal Silicon Substrate, Rocky R. Reston Mar 1993

Design And Performance Evaluation Of A Gas Chromatograph Micromachined In A Single Crystal Silicon Substrate, Rocky R. Reston

Theses and Dissertations

This investigation designed and developed a miniature gas chromatograph (GC) using silicon micromachining techniques. The GC is composed of a miniature sample injector (10 µl sample loop); a 0.9 m long, rectangular-shaped (300 µm width and 10 micrometers height) capillary column coated with a 0.2 µm thick copper phthalocyanine (CuPc) stationary phase; and a dual-detector scheme incorporating a CuPc-coated chemiresistor and a 125 µm diameter thermal conductivity detector bead. Micromachining was employed to fabricate the sample injector interface, the GC column, and the dual-detector cavity. A novel processing technique was developed to sublime the CuPc stationary phase coating on the …

Go to article

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 …

Go to article

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 …

Go to article

First Prev Next Last