Engineering Commons^™

Microelectrode Studies On The Pitting Corrosion Process Of Stainless Steel, Changjian Lin, Lijian Chen, Ronggui Du, Zude Feng, Jianguang Tang, Hongping Dai

Journal of Electrochemistry

Differing with the scanning microelectrode techniques, which scan microelctrode closely to the interface of electrode/electrolyte and make electrochemical imaging in a lateral spatial resolution, the technique of microelectrode with a micron diameter is of very high time-resolution and ratio of signal/noise in electrochemical measurements. The microelectrode technique allows double-layer capacitance and background current for a microelectrode to be drastically reduced due to the exposed area of a microelectrode is usually 6～8 orders of magnetite lower than that of a conventional electrode with large-scale exposed area. Microelectrode was recently developed as a new powerful electrochemical technique and widely used in the …

Gold Electrodeposition On Microelectrodes, Lihua Xiong, Caihui Shi, Xiaoqin Li, Bingwei Mao

Journal of Electrochemistry

The initial stage electrodeposition behaviors of gold onto glassy carbon and platinum microelectrodes are studied in an acid solution containing AuCl₃ using cyclic voltammetry and potential step techniques. The results suggest that gold nucleation on microelectrodes requires a higher driving force with high probability. Within the range of the microelectrode dimension that have been used in the present work, large amount of gold nucleus could be formed at short time scale at overpotentials higher than a threshole value. The I_t curves from the platinum microelectrode are in consistence with the continuous nucleation model. It has been found that …

Study On The Synthesis And Electrochemical Behavior Of Poly (Quinonoid-Disulfide), Xiaohui Tang, Xiuwu Sun, Yongfang Li, Shibi Fang

Journal of Electrochemistry

Organic polydisulfide containing quinonoid structure was synthesized by chloromethylation, oxidation by nitric acid, and condensation polymerization with sodium disulfide. The effect of quinonoid structure on the electrochemical behavior of organic polydisulfide was investigated with cyclic voltammetry and chargedischarge measurement. The result shows that quinonoid struture mainly affects the positions of redox peaks of organic polydisulfide, open circuit voltage and discharge platform voltage of cell with the organic polydisulfide as cathode.

The Investigations Of Surface Treatment Methods And Characterization Of Oxide Films On Ab5 Based Metal Hydride Electrodes Ⅰ. New NiRich Treatment Methods And Photoelectrochemical Characterization Of Oxide Films, Junmin Nan, Yong Yang, Jun Li, Zugeng Lin

Journal of Electrochemistry

Two simple and efficient surface treatment methods for AB₅ type hydrogen storage alloys were developed. The results of X-ray photoelectron spectroscopy (XPS) and cyclic voltammetric (CV) experiments showed that the hydrogen storage alloys treated by two different methods had Ni rich surface layer so that the performances of the electrodes were improved after treatment. The characterization of the oxide films which formed on the surface of electrodes through potentiodynamic oxidation with the help of photoelectrochemical microscopy (PEM) were done. The anodic photocurrent and the cathodic photocurrent related to the oxidation of hydrogen and the reduction of oxygen on the …

Spectroscopic Investigation Of Ion Transport Mechanisms In Polyacrylonitrile Based Electrolytes, Zhaoxiang Wang, Biying Huang, Rongjian Xue, Xuejie Huang, Liquan Chen

Journal of Electrochemistry

Raman, IR, X-ray photoelectron (XPS), and NMR spectra of components in polyacrylonitrile based electrolytes have been studied. It is found that there are strong interactions among the components though different systems show different interaction characteristics. A concept of competition is proposed between the polymer matrix and the plasticizer on associating with the Li⁺ ions. By analyzing the important functions of the plasticizer, a possible mechanism of the ions transport in the polymer electrolyte is suggested.

A Study Of Adsorption Kinetics Of Β-Phenylaminopropiophenone On Iron In Acid Solution, Dihua Wang, Xianzhang Bu, Jinyun Zou, Fuxing Gan

Journal of Electrochemistry

The adsorption kinetics of β-phenylaminopropiophenone (PAP) on iron electrode in 0.5 mol/L H₂SO₄ solution with or without Cl^- were investigated by chronoamperometry.

A Study On Heterogeneous Indirect Electrosynthesis Of Benzaldehyde, Daobao Chu, Changjian Lin, Huashui Lin, Jianguang Tan

Journal of Electrochemistry

Heterogeneous indirect electrosynthesis process of benzaldehyde has been investigated using cyclic voltammetry and polarization curves. An optimum condition for preparation of benzaldehyde by indirect electrooxidation of toluenc with redox Mn³⁺/Mn²⁺ is given in this paper. Electrolytic regeneration Mn³⁺ are made at Pt/Ti anode in “slurry” MnSO₄/H₂SO₄ medium. Current efficiency for electrolytic regeneration Mn³⁺  was maintained over 88% by “double cyclic way”.

Investigation Of Methanol Anode Electrooxidation Catalysts, Gangyao Wen, Ying Zhang, Zhenglong Yang, Changzhi Li

Journal of Electrochemistry

A series of catalysts, Pt-WO₃/C, Pt/Ru/C and Pt-Ru-WO₃/C were prepared by chemical reduction deposition. Electrocatalytic oxidation of methanolon different catalyst/Nafion membrane electrodes was studies by voltammetry and current-potential polarization. The results indicated that the catalytic activity order of different catalysts is as follows: Pt-Ru-WO₃/C > Pt-Ru/C > Pt-WO₃/C. At the same time, influences of methanol concentrations and catalyst proportion on performances of anodes were also studies.

Progresses In Surface Electrochemistry And Electrocatalysis ——A Review On The 1997 Joint International Meeting Of Electrochemistry And 97' International Meeting Of Surface Electrochemistry, Shigang Sun

Journal of Electrochemistry

The progresses in surface electrochemistry and electrocatalsis reported in the 1997 joint international meeting of electrochemistry and in the 97′ international meeting of surface electrochemistry were reviewed. The main trends described in this paper consisted of 7 aspects: 1) the studies employing single crystal electrodes, 2) the development of in situ methods of diverse spectroscpoy, 3) the innovation of new research techniques, 4) the preparaton of electrocatalyst of high performances, 5) the quantitative studies on kinetics of electrocatalytic reactions, 6) the investigation on the dynamic processes of surface by timeresolved methods, and 7) the theoretical modeling and simulation of surface …

Anchor Effect Of Iron And Cobalt To Platinum On Carbon Substrates, Zidong Wei, Hetong Guo, Zhiyuan Tan

Journal of Electrochemistry

The cathodic reduction of oxygen is studied on porous carbonbased electrodes carrying platinumiron and/or cobalt alloy catalysts. Electrodes using such electrocatalysts, particularly when used as cathodes in acidic electrolytes, remain stable for longer periods. The cathodic polarization of oxygen reduction on such electrodes is 20 mV to 40 mV lower than that on the conventional electrode on which only platinum alone is used as an electrocatalysts. An accelerated aging test (AAT) is used to evaluate the corrosion resistance and sintering resistance of each catalyst. The dissolution of the catalyst in the AAT filtrate is analysed and provides a measure of …

Study On Nano Electrode Material Of Lithium Ion Batteries, Jinkua You, Yong Yang, Dong Shu, Shenghui Wu, Yingchun Zhang, Zugeng Lin

Journal of Electrochemistry

In this paper, the structure and morphology of the nano phase electrode materials have been characterized with XRD and TEM. The performances of electrochemical intercalation and deintercalation of lithium ions have been studied by using cyclic voltammograms and galvanostatic charge discharge techniques. The results show that the nano materials posses advantage of micro structure and Li⁺ ions intercalation performances. The observed high capacity and large charge discharge current density of the nano phase materials seem to have resulted from three kinds of effects: 1) an increase in the space for Li⁺ ions intercalation; 2) a decrease in the …

The Migration Of Samarium(Ⅲ) Across Oil/Water Interface, Jun-Wei Di, Xiao-Xing Xu, Ying Wu, Rui-Xi Fan

Journal of Electrochemistry

The migration of Samarium(Ⅲ) across water/nitrobenzene (w/nb) interface facilitated by diantipyrylmethane (DAM) and the electrochemical behaviour affected by emulsifier OP in the nb phase have been studied by normal and convolute cyclic voltammetry. It is concluded that the formation of the complex occurs at w/nb interface and the mechanism of the samarium(Ⅲ)transfer across w/nb interface facilitated by DAM is E mechanism.

Electrochemical Impedance Of Molten Salts Induced Hot Corrosion, Chaoliu Zeng, Weitao Wu, Jianqing Zhang

Journal of Electrochemistry

Electrochemical impedance technique was employed to study corrosion behaviors of Ni-3Al, IN100 and IN738 alloys in molten (Na, K, Li)₂SO₄ at 700 ℃. The Nyquist plots for Ni-3Al and IN100 alloys have the characteristics of diffusion controlled reaction. But, the corrosion reaction for IN738 alloy is not controlled by the diffusion of oxidants. The equivalent circuits were proposed, and the parameters in circuits were also calculated. Ni-3Al and IN100 alloys suffer from catastrophic corrosion due to the formation of a porous corrosion layer. IN738 alloy has excellent corrosion resistance because of the formation of a protective oxide …

Two-Dimensional Ferroelectric Films, Alexander V. Bune, Vladimir M. Fridkin, Stephen Ducharme, Lev M. Blinov, Serguei P. Palto, Alexander V. Sorokin, S. G. Yudin, A. Zlatkin

Stephen Ducharme Publications

Ultrathin crystalline films offer the possibility of exploring phase transitions in the crossover region between two and three dimensions. Second- order ferromagnetic phase transitions have been observed in monolayer magnetic films [1,2], where surface anisotropy energy stabilizes the two-dimensional ferromagnetic state at finite temperature [3]. Similarly, a number of magnetic materials have magnetic surface layers that show a second-order ferromagnetic–paramagnetic phase transition with an increased Curie temperature [4]. Ferroelectricity is in many ways analogous to ferromagnetism, and bulk-like ferroelectricity and finite-size modifications of it have been seen in nanocrystals as small as 250 Å in diameter [5], in perovskite films …

Dai Et Al. Reply:, Pengcheng Dai, Mohana Yethiraj, Herbert A. Mook, Terrence B. Lindemer, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

No abstract provided.

Incommensurate Magnetic Fluctuations In Yba2⁢Cu3⁢O6.6, Pengcheng Dai, Herbert A. Mook, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

We use inelastic neutron scattering to demonstrate that the low-frequency magnetic fluctuations in YBa₂Cu₃O_6.6 (T_c= 62.7 K) change from commensurate to incommensurate on cooling with the incommensurability first appearing at temperatures above T_c. For the energies studied, the susceptibility at incommensurate positions increases on cooling below T_c, accompanied by a suppression of the spin fluctuations at the commensurate points. These results suggest that incommensurate spin fluctuations may be a common feature for all cuprate superconductors.

Incommensurate Magnetic Fluctuations In Yba2cu3o6.6, Pengcheng Dai, Hernert A. Mook, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

We use inelastic neutron scattering to demonstrate that the low-frequency magnetic fluctuations in YBa₂Cu ₃O_6.6 (T_c=62.7 K) change from commensurate to incommensurate on cooling with the incommensurability first appearing at temperatures above T_c. For the energies studied, the susceptibility at incommensurate positions increases on cooling below T_c, accompanied by a suppression of the spin fluctuations at the commensurate points. These results suggest that incommensurate spin fluctuations may be a common feature for all cuprate superconductors.

Phase Equilibria Of A Nematic And Smectic-A Mixture, Hao-Wen Chiu, Thein Kyu

College of Polymer Science and Polymer Engineering

A phase diagram of a mixture consisting of nematic and smectic liquid crystals has been calculated self-consistently by combining Flory-Huggins (FH) theory for isotropic mixing and Maier-Saupe-McMillan (MSM) theory for smectic-A ordering. However, the MSM theory can be deduced to the original Maier-Saupe (MS) theory for nematic ordering. To describe the phase transitions involving induced smectic phase and nematic + smectic equilibrium, two nematic and two smectic order parameters for the nematic/smectic mixtures have been coupled through the normalized partition function and the orientation distribution function. Self-consistent numerical solution has been sought in establishing nematic/smectic phase diagrams involving (i) phase …

Comments On Response Errors Of Non-Proportionally Lightly Damped Structures, W. Gawronski, Jerzy T. Sawicki

Mechanical Engineering Faculty Publications

Letters to the editor authors reply

Design, Performance, And Applications Of A Coherent Ultra-Wideband Random Noise Radar, Ram M. Narayanan, Yi Xu, Paul D. Hoffmeyer, John O. Curtis

Department of Electrical and Computer Engineering: Faculty Publications

A novel coherent ultra-wideband radar system operating in the 1- to 2-GHz frequency range has been developed recently at the University of Nebraska. The radar system transmits white Gaussian noise. Detection and localization of buried objects is accomplished by correlating the reflected waveform with a time-delayed replica of the transmitted waveform. Broadband dual-polarized log-periodic antennas are used for transmission and reception. A unique signal-processing scheme is used to inject coherence into the system by frequency translation of the ultrawideband signal by a coherent 160-MHz phase-locked source prior to performing heterodyne correlation. The system coherence allows the extraction of a target’s …

A Model For Calculating Acoustic Gravity Wave Energy And Momentum Flux In The Mesosphere From Oh Airglow, Gary R. Swenson, Alan Z. Liu

Physical Sciences - Daytona Beach

Acoustic gravity and tidal waves propagating in the mesosphere/lower thermosphere (80-110 km) perturb the airglow layer intensities. The OH airglow has recently been modeled to determine the relationship between the relative perturbed atmospheric density and temperature (ρ’/ ρ, T’/T) to the OH intensity ( I’_OH/I_OH ) at the OH emission altitudes [Swenson and Gardner, 1997]. A model is presented here which relates wave perturbed OH airglow to the wave energy and momentum flux as they propagate through the emission layer. The model is dependent on the wave horizontal and vertical wavelengths (or phase speed as related through …

Frontal Chromatography Of Proteins. Effect Of Axial Dispersion On Column Performance, G. A. Heeter, Athanasios I. Liapis

Chemical and Biochemical Engineering Faculty Research & Creative Works

A mathematical model describing the dynamic adsorption of proteins in columns packed with spherical porous adsorbent particles is used to study the effect of axial dispersion on the performance of chromatographic systems. The values of the axial dispersion coefficient, D(L), are estimated from a correlation based on a model describing axial dispersion in packed beds that provides satisfactory results when compared with experiment. Simulations of frontal chromatography in systems including axial dispersion and in systems without axial dispersion are made and compared to determine the effect of axial dispersion on the efficiency of the adsorption process; also, the system parameters …

Tractor Test Museum Committee February 10, 1998, Tractor Museum

Lester F. Larsen Tractor Museum: Planning and Development Documents

Heating Issues Handouts for visitors Big Red Club

Computer Simulations Of Branched Alkanes: The Effect Of Side Chain And Its Position On Rheological Behavior, Richard L. Rowley, Tapani A. Pakkanen, Maija Lahtela, Mikko Linnolahti

Faculty Publications

Nonequilibrium molecular dynamics simulations have been performed on model fluids representing eicosane isomers in order to investigate the effect of branching and side chain position on fluid rheology. A heterogeneous, united-atom model with 20 Lennard-Jones interaction sites located at carbon centers was used to model the fluids. Vibrations and bond rotations were frozen, but torsional rotation was included. It was found that viscosity increases significantly from the n-alkane structure to a branch on carbon 2, but the movement of the branch along the carbon backbone has a smaller increasing than decreasing effect. The size of the group in a branched …

Ccfss Technical Bulletin February 1998, Wei-Wen Yu Center For Cold-Formed Steel Structures

CCFSS Technical Bulletins (1993 - 2020)

No abstract provided.

Acuta Enews February 1998, Vol.27, No. 2

ACUTA Newsletters

In This Issue

Call for Nominations

ACUTA Board of Directors 1998-1999

Board Report

ACUTA 1998 EVENTS

International Project Aims to Determine What IT Services Really Cost

DC at a Glance

Positions Available

Welcome New Members

Encryption Algorithms Made (Somewhat) More Natural (A Pedagogical Remark), Misha Kosheleva, Vladik Kreinovich, Luc Longpre

Departmental Technical Reports (CS)

Modern cryptographic algorithms, such as DES, IDEA, etc., are very complex and therefore difficult to learn. Textbooks explain in detail how these algorithms work, but they usually do not explain why these algorithms were designed as they were. In this paper, we explain why, and thus, hopefully, make cryptographic algorithms easier to learn.

An Operationalistic Reformulation Of Einstein's Equivalence Principle, Vladik Kreinovich, R. R. Zapatrine

Departmental Technical Reports (CS)

No abstract provided.

Derivation Of An Analytical Model To Calculate Junction Depth In Hgcdte Photodiodes, Stacy H. Gleixner, H. G. Robinson, C. R. Helms

Faculty Publications

Presents an enhanced analytical model to calculate junction depth and Hg interstitial profile during n-on-p junction formation in HgCdTe photodiodes. Detailed information on the enhanced model; Function of the model; Information on HgCdTe; Detailed information on how the model was obtained.

Factors Affecting The Room-Temperature Mechanical Properties Of Ticr2-Base Laves Phase Alloys, Katherine C. Chen, Samuel M. Allen, James D. Livingston

Materials Engineering

Various effects on the room-temperature mechanical properties of TiCr₂-base alloys have been assessed in efforts to improve the toughness of Laves phase intermetallics (AB₂). Systematic studies were performed on: (i) single-phase stoichiometric and nonstoichiometric TiCr₂, (ii) TiCr₂-base ternary Laves phases, and (iii) two-phase binary alloys containing TiCr₂. In order to make quantitative comparisons among the different alloys, Vickers indentation was used to obtain hardness and fracture toughness values. Within the single-phase field, constitutional defects accounted for the compositional dependencies of properties, and may aid the synchroshear deformation process. Ternary Laves …