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

Mechanical Engineering Commons™

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

University of South Carolina

Discipline
Keyword
Publication Year
Publication
Publication Type

Articles 601 - 614 of 614

Full-Text Articles in Mechanical Engineering

Oxygen Permeation Through Composite Oxide-Ion And Electronic Conductors, Kevin Huang, Michael Schroeder, John B. Goodenough May 1999

Oxygen Permeation Through Composite Oxide-Ion And Electronic Conductors, Kevin Huang, Michael Schroeder, John B. Goodenough

Faculty Publications

Oxygen permeation through composites consisting of four well-known oxide-ion conductors and a noble metal, Pd or Ag, is reported. The oxides were Zr0.9Y0.1O1.95 (YSZ), (Bi1.75Y0.25O3)0.95(CeO2)0.05 (BYC5), Ce0.8Sm0.2O1.9 (SSC), and La0.8Sr0.2Ga0.83Mg0.17O2.815 (LSGM). The results show that (BYC5 + Ag) yields the highest oxygen permeation flux, but the composite deteriorates with time. The composites (SSC + Pd), (LSGM + Pd), and (YSZ + Pd) give stable, but relatively lower oxygen permeation flux …


Preparation Of Mesoporous Tin Oxide For Electrochemical Applications, Fanglin Chen, Meilin Liu Jan 1999

Preparation Of Mesoporous Tin Oxide For Electrochemical Applications, Fanglin Chen, Meilin Liu

Faculty Publications

Mesoporous tin oxide stable up to 500 °C has been prepared for the first time using both cationic and neutral surfactants.


Sr‐ And Ni‐Doped Lacoo3 And Lafeo3 Perovskites: New Cathode Materials For Solid‐Oxide Fuel Cells, Kevin Huang, Hee Y. Lee, John B. Goodenough Jan 1998

Sr‐ And Ni‐Doped Lacoo3 And Lafeo3 Perovskites: New Cathode Materials For Solid‐Oxide Fuel Cells, Kevin Huang, Hee Y. Lee, John B. Goodenough

Faculty Publications

An improved cathode material for a solid‐oxide fuel cell would be a mixed electronic and oxide‐ion conductor with a good catalytic activity for oxygen reduction at an operating temperature T op ≥ 700°C and a thermal expansion matched to that of the electrolyte and interconnect. We report on the properties of Sr‐ and Ni‐doped LaCoO3 and LaFeO3 perovskites that meet these criteria. Single‐phase regions were determined by X‐ray diffraction, and thermogravimetric analysis measurements were used to obtain the temperatures above which oxygen loss, and hence oxide‐ion conductivity, occurs. The conductivity and Seebeck measurements indicate the coexistence of both …


Electrode Performance Test On Single Ceramic Fuel Cells Using As Electrolyte Sr‐ And Mg‐Doped Lagao3, Kevin Huang, Man Feng, John B. Goodenough, Christopher Milliken Oct 1997

Electrode Performance Test On Single Ceramic Fuel Cells Using As Electrolyte Sr‐ And Mg‐Doped Lagao3, Kevin Huang, Man Feng, John B. Goodenough, Christopher Milliken

Faculty Publications

The electrode performance of a single solid oxide fuel cell was evaluated using a 500 μm thick La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM) as the electrolyte membrane. Comparison of La0.6Sr0.4CoO3-δ (LSCo) and La0.9Sr0.1MnO3 (LSM) as cathodes showed LSCo gave an exchange current density two orders of magnitude higher than that of LSM. Comparison of CeO2/Ni and LSGM/Ni as anodes showed a degradation of the latter with time, and studies of the anode‐electrolyte interface and the reactivity of NiO and LSGM suggest better anode …


Preparation Of Nd-Doped Baceo3 Proton-Conducting Ceramics By Homogeneous Oxalate Coprecipitation, Fanglin Chen, Ping Wang, O. Toft Sorensen, Guangyao Meng, Dingkum Peng Jan 1997

Preparation Of Nd-Doped Baceo3 Proton-Conducting Ceramics By Homogeneous Oxalate Coprecipitation, Fanglin Chen, Ping Wang, O. Toft Sorensen, Guangyao Meng, Dingkum Peng

Faculty Publications

Nd-doped BaCeO3 have been obtained from homogeneous coprecipitated oxalates when calcined at temperatures T≥1000 °C. Ball-milling of the calcined powders well disperses the agglomerates and consequently has a beneficial effect in the densification process. The calcination temperature has a major influence on the sintering process and powders calcined at 1100 °C possess good sinterabilities. The pressure applied to press the green pellets has no apparent influence on the sintered density at sintering temperatures of T≥1400 °C. By controlling the processing variables it was possible to obtain near fully dense Nd-doped BaCeO3 ceramics with homogeneous microstructure at a sintering …


Chemical Stability Study Of Bace0.9Nd0.1O3−Α High Temperature Proton-Conducting Ceramic, Fanglin Chen, O. Toft Sorensen, Guangyao Meng, Dingkum Peng Jan 1997

Chemical Stability Study Of Bace0.9Nd0.1O3−Α High Temperature Proton-Conducting Ceramic, Fanglin Chen, O. Toft Sorensen, Guangyao Meng, Dingkum Peng

Faculty Publications

BaCe0.9Nd0.1O3−a (BCN) ceramic is known to be an excellent high-temperature proton conductor and is a candidate electrolyte for use in solid oxide fuel cells, hydrogen or steam sensors and steam electrolysers. In this work, the chemical stability of BCN was investigated systematically by combining XRD and DTA–TG techniques to study its processing compatibility and its feasibility in potential applications. It was found that above 1200 °C, BCN reacted with alumina or zirconia, leading to the loss of barium and an excess of cerium. In cold water, both sintered BCN disks and powder samples had very …


Characterization Of Sr‐Doped Lamno3 And Lacoo3 As Cathode Materials For A Doped Lagao3 Ceramic Fuel Cell, Kevin Huang, Man Feng, John B. Goodenough, Michael Schmerling Nov 1996

Characterization Of Sr‐Doped Lamno3 And Lacoo3 As Cathode Materials For A Doped Lagao3 Ceramic Fuel Cell, Kevin Huang, Man Feng, John B. Goodenough, Michael Schmerling

Faculty Publications

Energy dispersive spectrometry line scan and ac impedance spectroscopy were used in this study to investigate the chemical reactions between two cathode materials, La0.84Sr0.16MnO3 (LSM), La0.5Sr0.5CoO3-δ (LSC), and the electrolyte La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM). Significant interdiffusions of Co into LSGM and Ga into LSC were found at an LSC/LSGM interface even at relatively low fabrication temperatures. In contrast, only small interdiffusions of Mn into LSGM and Ga into LSM were detected at the LSM/LSGM interface even though it was fired at 1470°C. The …


Characterization Of The Si/Sio2 Interface Formed By Remote Plasma Enhanced Chemical Vapor Deposition From Sih4/N2O With Or Without Chlorine Addition, Young-Bae Park, Xiaodong Li, Shi-Woo Rhee Jul 1996

Characterization Of The Si/Sio2 Interface Formed By Remote Plasma Enhanced Chemical Vapor Deposition From Sih4/N2O With Or Without Chlorine Addition, Young-Bae Park, Xiaodong Li, Shi-Woo Rhee

Faculty Publications

The Si/SiO2interface formed by remote plasma enhanced chemical vapor deposition (RPECVD) at low temperature with SiH4/N2O or SiH4/N2O/Cl2 was studied and compared with thermal oxidation. The interface of the CVD SiO2 without chlorine addition is rougher than that with chlorine addition. But the surface roughness of CVD SiO2 films increases with chlorine addition. The thermal oxidation induces strong interface strains, and the strains generated by the CVD SiO2 without chlorine addition are stronger and are distributed more nonuniformly than those by the chlorinated SiO2. …


Microstructure And Deposition Rate Of Aluminum Thin Films From Chemical Vapor Deposition With Dimethylethylamine Alane, Byoung-Youp Kim, Xiaodong Li, Shi-Woo Rhee Jun 1996

Microstructure And Deposition Rate Of Aluminum Thin Films From Chemical Vapor Deposition With Dimethylethylamine Alane, Byoung-Youp Kim, Xiaodong Li, Shi-Woo Rhee

Faculty Publications

Deposition of aluminumfilm from DMEAA in the temperature range of 100–300 °C has been studied. In this temperature range, there is a maximum deposition rate at around 150 °C. The film deposited at 190 °C has elongated blocklike grain shapes, which are ∼600 nm in width and 930 nm in length. Grains in the film deposited at 150 °C showed an equiaxed structure with grain size in the range of 100–300 nm in a film with 600 nm thickness. Aluminum oxide particle inclusion was observed especially at high deposition temperature. Plausible reaction pathways of DMEAA dissociation were suggested to explain …


Structural Characterization Of Aluminum Films Deposited On Sputtered-Titanium Nitride/ Silicon Substrate By Metalorganic Chemical Vapor Deposition From Dimethylethylamine Alane, Xiaodong Li, Byoung-Youp Kim, Shi-Woo Rhee Dec 1995

Structural Characterization Of Aluminum Films Deposited On Sputtered-Titanium Nitride/ Silicon Substrate By Metalorganic Chemical Vapor Deposition From Dimethylethylamine Alane, Xiaodong Li, Byoung-Youp Kim, Shi-Woo Rhee

Faculty Publications

Alfilmsdeposited on sputtered‐TiN/Si substrate by metalorganic chemical vapor deposition(MOCVD) from dimethylethylamine alane (DMEAA) were characterized using x‐ray diffraction(XRD),Auger electron spectroscopy(AES),atomic force microscopy(AFM), and transmission electron microscopy (TEM). The TiN filmsputtered on the Si has a preferred orientation along the growth direction with the 〈111〉 of the film parallel to the Si〈111〉. Sputtering of the TiN film on the Si induced strains at the interface. The TiN/Si interface is flat while the Al/TiN interface is rough. There exist many dislocations at the Al/TiN interface. The Al2O3 phase was formed at the Al/TiN interface during the early stages of …


The Asymptotic Structure Of Transient Elastodynamic Fields At The Tip Of A Stationary Crack, Xiaomin Deng Jul 1994

The Asymptotic Structure Of Transient Elastodynamic Fields At The Tip Of A Stationary Crack, Xiaomin Deng

Faculty Publications

The asymptotic structure of the transient elastodynamic near-tip fields around a stationary crack is investigated for all three fracture modes. The transient fields are obtained as the sum of their quasi-static counterparts and corresponding transient correction terms, in terms of variable-separable expansions. By allowing the coefficients of terms in the quasi-static expansion to deviate from their quasi-static restrictions, the correction terms are shown to be the particular solutions of a set of first order (for mixed mode I and II) or second order (for mode III) ordinary differential equations with constant coefficients and non-homogeneous terms involving only sine and cosine …


Development Of Strength Theories For Random Fiber Composites, Victor Giurgiutiu Jan 1994

Development Of Strength Theories For Random Fiber Composites, Victor Giurgiutiu

Faculty Publications

A ressessment of existing theories for calculating the strength of random and quasi-random fiber composites is presented. Fundamental aspects regarding the physical model, macromechanics analysis, fiber distribution functions, generalized failure criterion, and progressive versus sudden failure models are covered first. Progressive ductile failure, progressive brittle failure, and sudden brittle failure are treated in detail. In each case, the original theory is briefly reviewed, and then its extensions accompanied by numerical examples are presented. Several limitations originally imposed by Hahn, such as the monotonically nonincreasing requirement on the failure strain curve, are lifted and the mathematical formulations are generalized. Some common …


Several Considerations Regarding The Variable Length Blade Rotor, Bogdan Popescu, Victor Giurgiutiu Jan 1994

Several Considerations Regarding The Variable Length Blade Rotor, Bogdan Popescu, Victor Giurgiutiu

Faculty Publications

No abstract provided.


On Stationary And Moving Interface Cracks With Frictionless Contact In Anisotropic Bimaterials, Xiaomin Deng Dec 1993

On Stationary And Moving Interface Cracks With Frictionless Contact In Anisotropic Bimaterials, Xiaomin Deng

Faculty Publications

The asymptotic structure of near-tip fields around stationary and steadily growing interface cracks, with frictionless crack surface contact, and in anisotropic bimaterials, is analysed with the method of analytic continuation, and a complete representation of the asymptotic fields is obtained in terms of arbitrary entire functions. It is shown that when the symmetry, if any, and orientation of the anisotropic bimaterial is such that the in-plane and out-of-plane deformations can be separated from each other, the in-plane crack-tip fields will have a non-oscillatory, inverse-squared-root type stress singularity, with angular variations clearly resembling those for a classical mode II problem when …