Materials Science and Engineering Commons^™

Effects Of Nickel Content And Simulated Heat Affected Zone Of 2205 Duplex Stainless Steel On Pitting Corrosion, Horng-Yih Liou, Ju-Tung Lee, Wen-Ta Tsai, Rong-Iuan Hsieh, Yeongtsuen Pan

Journal of Electrochemistry

The effects of nickel content and Gleeble simulated heat affected zone (HAZ) of 2205 stainless steel on pitting corrosion were investigated in this paper. The results showed that nickel content, ranging from 4.5 wt% to 6.5 wt% in base metal, had only a minor effect on the electrochemical polarization curves, with all E_np's and E_pp's falling in the rang of 1100~1200 mV. Comparing with the base metal, the simulated HAZ microstructure caused an increase in the anodic current density, a distinct decrease in both E_np and E_pp , and a reduction in the passive …

Investigation Of Solution Chemistry In Crevice Of Carbon Steel And Its Anodic Polarization Behavior, Zhuo Chen, Cui-Wei Du, Bei Cao, Yin-Shun Wu, Hai Yang, Zheng-Rong Zhang

Journal of Electrochemistry

A self-made wedge-shaped simulated crevice apparatus was designed to investigate the solution chemistry in crevice of carbon steel and its anodic polarization behavior. For carbon steel with 3.5%(wt) NaCl, the change and the distribution of electrode potential, concentration of Cl^- and pH value of solution in the crevice, and the current density of metal in the crevice were measured respectively under various conditions of anodic polarization. The results showed that without polarization the metal about 2 cm away from the opening of the crevice was attacked preferentially because of its lowest free corrosion potential. The anodic polarization promoted the …

The Behaviors Of Capacity Loss Of Limn2O4 Cathodeat Elevated Temperatures, Xiao-Hong Hu, Han-Xi Yang, Xin-Ping Ai, Sheng-Xian Li, Xin-Lin Hong

Journal of Electrochemistry

The capacity loss of spinel LiMn₂O₄ cathode at elevated temperatures was evaluated by constant current charge-discharge methods and it was found that serious capacity loss and cycleability decrease occured at above 50, especially for the charged cells. The mechanisms for this phenomena were examined by atomic emission and infrared spectrometry of the electrolyte, XRD measurment of the cycled elecrode and microelectrode voltammetry of LiMn₂O₄ at room and elevated temperatures. The results showed that with increasing temperature, Mn and Li ions tended to redistribute partly in the spinel framework due to the disproportion of Mn …

Effect Of Inhibitor On Electrochemical Behavior Of 1cr18 Stainless Steel In Acidic Solution Under Friction, Jin-Ping Xiong

Journal of Electrochemistry

The electrochemical behavior of 1Cr18 stainless steel had been studied using a reciprocating triboelectrochemical equipment under friction in 0.2 mol/L H₂SO₄ solution with and without addition of thiourea, the frictionized surface of 1Cr18 stainless steel had been examined by the SEM, XPS and IR. The results showed that the loss rate of 1Cr18 stainless steel in the solution could be reduced by addition of thiourea. The adsorption of thiourea on the surface of 1Cr18 stainless steel prohibited the oxidization of Cr³⁺ to form Cr(Ⅵ) and formation of passive film consisting of CrO₄^2- or/and Cr(Ⅵ), …

Electrochemical Behavior Of Riboflavin On Glassy Carbon Electrode, Hong Li, Lin-Cai Jiang, Liang-Nian Ji

Journal of Electrochemistry

The electrochemical behavior of riboflavin(RF) on glassy carbon has been investigated by using potential sweep, rotating ring-disc electrode and the measurement of differential capacitance. It is shown that a single well-behaved oxidation-reduction wave corresponding to a reversible two-electrons reaction apears in medium of pH<6, and the adsorption of RFH₂ formed by electro-reduction is weak and hence its solubility is good. In medium of pH>6, there are two separating but overlapping partly oxidation-reduction waves corresponding to two-step one-electron reaction. The adsorptions of RFH and RFH₂ produced by reduction reactions in medium of 6

Study On The Microband Array Electrode-Based Glucose Microsensor, Neng-Qin Jia, Chui-Jue Sun, Lin Gao, Zong-Rang Zhang, Jian-Zhong Zhu, Guo-Xiong Zhang

Journal of Electrochemistry

The microband array electrode (MAE) consisting of 11 Pt microband of 5 m in wide, 2000 m long and 85 m gap was fabricated with a thin film techology. The MAE was characterized by means of cyclic voltammetry in a solution of K₃Fe(CN)₆ and H₂O₂. The results showed higher current density on MAE than on conventional Pt eletrode due to the strong edge effect of the former. A glucose microsensor was constructed with the substrate electrode of microband array. Microband array electrode was modified by Nafion followed by the immobilization of ferrocene onto …

Oxidation And Adsorption Of Deoxyribonucleic Acid At Highly Ordered Pyrolytic Graphite And Glass Carbon Electrode, Jian-Zhang Zhou, Ling-Ling Wu, Jin Luo, Zhong-Hua Lin

Journal of Electrochemistry

It is shown that calf thymus DNA (CT DNA) can be adsorbed at highly ordered pyrolytic graphite (HOPG) electrode and detected by differential pulse voltammetry (DPV) and electrochemical atomic force microscopy (ECAFM). It is found that controlled potential pre-polarization influences largely the adsorption of dsDNA while it has little influence on ssDNA. It is demonstrated that ECAFM is useful to exploit adsorption of DNA at HOPGE. The pattern of adsorption of DNA at HOPG electrode that fits best with the experimental data is proposed. The results aslo shows that UV/Vis reflection spectroscopy, which has not been used in studying electrochemical …

Study On The Hydrogen Permeation Through Zinc Electrodeposit, Jiang-Li Cao, Ji-Xun Wu, Yan-Ping Lu, Jie Shi

Journal of Electrochemistry

The electrochemical hydrogen-permeation technique was used to study hydrogen permeation through zinc electrodeposit with bilayer specimens of Fe substrate/zinc electrodeposit. The effect of coating thickness on hydrogen diffusion coefficient and hydrogen steady-state flux was studied. The results showed that hydrogen diffusion coefficient was approximately in the range of 10-11 cm²·s^-1 rank and zinc coating could retard hydrogen permeation. Accordingly, hydrogen steady-state flux and effective diffusion coefficient declined while the coating thickness increased.

In Situ Ftir Spectroelectrochemical Study Of Palladium Hexacyanoferrate Thin Film Deposited On Glassy Carbon Electrode, Ai-Li Bo, Xiang-Qin Lin

Journal of Electrochemistry

The electrochemically deposited Palladium hexacyanoferrate thin film on Glassy Carbon electrode (PdHCF|GC) has been studied in HCl, KCl and NaCl solutions by in-situ external reflection FTIR spectroelectrochemical technique. It is found that the behavior of the electroactive PdHCF film can be understood in terms of two states: Pd₂Fe(II)(CN)₆ formed in the inner layer and (M⁺)2Fe(II)(CN)₆ (M⁺: electrolyte cation) formed in the outer layer. The inner layer is oxidized at E_m=0.87 V in 1 mol/L KCl, while for the outer layer Em=0.77 V(vs. Ag/AgCl). In 1 mol/L NaCl or HCl solutions, …

Influence Of Ptfe And Nafion On The Utilization Efficiency Of Pt/C Catalyst In Pemfc, Xiao-Liang Cheng, Bao-Lian Yi, Jing-Xin Zhang, Ming Han, Ya-Guang Qiao

Journal of Electrochemistry

With cycling voltammetry curve(C-V), TEM and SEM photographs, the influence of PTFE and Nafion on the platinum utilization in catalyst layer of PEMFC was investigated. The results show that in gas diffusion electrode, the blocking effect of PTFE in the platinum utilization is not pronunced. In the thin-film catalyst layer, the electron conduct of the catalyst was blocked by the nafion solid and this caused the decrease of platinum utilization. With the increase of the nafion content in the catalyst layer, both platinum utilization and the electron conductivity decreased in the catalyst layer. Because the molecule size of nafion is …

Preparation And Application Of Gold-Film On The Surface Of Bacterial-Modified Carbon Paste Electrode, Rong-Zong Hu, Yan-Ping Ruan, Hao Xu, Jin-Kun Fu, Wei-De Zhang, Wen-Yun Hu

Journal of Electrochemistry

A novel method for preparation of gold-film composed of ultra-fine gold particles was reported in this paper. The gold-film was prepared by electrochemical method on the surface of the paste electrode modified with the strain Bacillus sp. D01 which has strong ability to absorb and reduce Au³⁺. In addition, this paper reported an experimental method of determining trace amount of Cu²⁺ in water solution using cathodic stripping analysis to estimate the performances of the obtained gold-film. The experimental results indicated that this new method for preparation of gold-film is simple. The obtained gold-film electrode is stable and …

The Magnetic Excitation Spectrum And Thermodynamics Of High-Tc Superconductors, Pengcheng Dai, Herbert A. Mook, Stephen M. Hayden, Toby G. Perring, Gabriel Aeppli, Rodney Dale Hunt, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

Inelastic neutron scattering was used to study the wave vector– and frequency dependent magnetic fluctuations in single crystals of superconducting YBa₂Cu₃O_6+x. The spectra contain several important features, including a gap in the superconducting state, a pseudo gap in the normal state, and the much-discussed resonance peak. The appearance of the pseudo gap determined from transport and nuclear resonance coincides with formation of the resonance in the magnetic excitations. The exchange energy associated with the resonance has the temperature and doping dependences as well as the magnitude to describe approximately the electronic specific heat near …

The Magnetic Excitation Spectrum And Thermodynamics Of High-Tc Superconductors, Pengcheng Dai, Herbert A. Mook, Stephen M. Hayden, Gabriel Aeppli, Toby G. Perring, Rodney Dale Hunt, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

Inelastic neutron scattering was used to study the wave vector– and frequency dependent magnetic fluctuations in single crystals of superconducting YBa₂Cu₃O_6+x. The spectra contain several important features, including a gap in the superconducting state, a pseudo gap in the normal state, and the much-discussed resonance peak. The appearance of the pseudo gap determined from transport and nuclear resonance coincides with formation of the resonance in the magnetic excitations. The exchange energy associated with the resonance has the temperature and doping dependences as well as the magnitude to describe approximately the electronic specific heat near …

Structural Disorder And The Origin Of High-Tc Suppression In La1.875ba0.125cuo4−Δ, Daniel Haskins, Edward A. Sterns, Fatih Dogan, Arnie R. Moodenbaugh

Materials Science and Engineering Faculty Research & Creative Works

Polarized x-ray absorption fine structure (XAFS) measurements at all La, Ba and Cu sites were used to study local structural features that accompany the strong T_c suppression at x ~ 1/8 in La_2-xBa_xCuO₄. Two critical parameters regulating the strength of hole-lattice coupling in this material were determined, i.e., the di- rection and magnitude of CuO₆ octahedra local tilts. Our findings include the existence of large disorder in the magnitude of the tilt angle about its average value < 0>, with a rms (formula presented) ≈2< 0>. We suggest that this large disorder strongly …

Why Does Ni Suppress Superconductivity In La1.85sr0.15cu1−Yniyo4?, Daniel Haskel, Edward A. Stern, V. Polinger, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

The role played by Ni impurities in destroying the superconducting state of La_2-xSr_xCuO₄ is still unclear. This is partly due to the lack of clear experimental evidence on the effect of Ni substitution upon the atomic and electronic structure of this cuprate. To provide this information, we performed Ni /(-edge polarized XAFS measure-ments on oriented powder. A special magnetic alignment geometry allowed us to measure pure ~ and aAb-polarized XAFS in identical experimental conditions. We found that the NiO6 octahedra are contracted along the t-axis by 0.16(A) relative to the CuO₆ octahedra in Lal.~sSro.~sCuO4, …

Numerical Assessment Of The Effects Of Grout Characteristics On Settlement Measurements In Borehole Extensometers, Ahmed Abdel-Wahab Mohamed Bayoumi

Archived Theses and Dissertations

No abstract provided.

Impact Of Aggregate Fines On Short Term Properties Of Concrete Incorporating Water-Reducing Admixtures, Maged Maher Fakhry

Archived Theses and Dissertations

No abstract provided.

Low-Temperature Molecular Beam Epitaxy Of Gaas: A Theoretical Investigation Of Antisite Incorporation And Reflection High-Energy Diffraction Oscillations, K. Natarajan, Rama Venkat, Donald L. Dorsey

Electrical & Computer Engineering Faculty Research

Surface dynamics dominate the incorporation of charged, As+Ga, and neutral, As0Ga, antisite arsenic, and the temporal variation of reflection high-energy electron diffraction(RHEED) intensity in the low-temperature molecular beam epitaxy of (100) gallium arsenide(GaAs). A rate equation model is proposed which includes the presence and dynamics of a physisorbed arsenic (PA) layer riding the growth surface. The PA layer dictates the incorporation and concentration of As+Ga and As0Ga. Additionally, it influences the RHEED oscillations (ROs) behavior and the RO’s dependence on its coverage through its contribution to the reflected intensity. The model results for the dependence of As+Ga and As0Ga concentrations …

Output Control Of Vertical Microcavity Light Emitting Device, James A. Lott

AFIT Patents

An improved intracavity sensor based output power control for microcavity light emitting devices. An improved phototransistor transducer is both configured and physically disposed so that it passively transmits the spurious optical energy output of the microcavity light emitting device while simultaneously generating a light determined electrical signal of easily used large magnitude that is nearly free of error. The base-collector region of the transistor is disposed with a quantum well absorbing layer and produces a signal responsive to a selected emission wavelength. The configuration of the optical energy communicating transducer is arranged so that it is improved in sensitivity and …

Cracking In Cycloaliphatic Epoxy/Aluminum Composite Electrical Bushings, Keith Alan Parker

Doctoral Dissertations

The problem of cracking in electrical apparatus bushings as a result of thermal stresses was investigated. The bushings were composed of cycloaliphatic epoxy insulators with embedded aluminum conductors. The problem is due to the difference in coefficients of thermal expansion of the two materials. A solution to the problem had been to coat the conductors before they were formed together with the epoxy insulators. The coating was assumed to prevent cracking by allowing movement between the two materials as their dimensions changed during thermal expansion and contraction. The contribution of the coating was to be established.

The hypothesis was that …

Evaluation Of Lead Anode Reactions In Acid Sulfate Electrolytes. I. Lead Alloys With Cobalt Additives, Pu Yu, Thomas J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

Lead alloys, such as lead-calcium-tin and lead-silver, are the primary insoluble anodes used in the electrowinning of metals. While some difficulties are encountered in their use, there is no obvious replacement that is economically and technically competitive. Two of the specific problems with lead include decreased cathode purity due to incorporation from corrosion products and the relatively high overpotential which increases cell voltage. To gain an improved understanding of the fundamental behavior of lead anodes, the polarization behavior of six different alloys in sulfuric acid was evaluated. Some tests were also made with Co(II) in the acid sulfate electrolyte. Notable …

Magnetic And Mössbauer Spectral Study Of Mixed Valent La₀.₂Sr₀.₈Cu₀.₂Fe₀.₈O2.68 And Related Perovskites, Gary J. Long, Dimitri Hautot, Amitabh Mohan, Ingeborg Kaus, Harlan U. Anderson, Fernande Grandjean

Chemistry Faculty Research & Creative Works

The La_0.2Sr_0.8Cu_1-xFe_xO _3-δ perovskites are important because they are mixed electron and oxygen anion conductors and thus are able to serve as dense oxygen separation membranes. In order to better understand the mechanism for this separation a Mössbauer spectral study has been carried out to determine the ratio of iron(III) to iron(IV) in these mixed valent compounds. The Mössbauer spectra of La_0.2Sr_0.8Cu_0.2Fe_0.8O _3-δ obtained between 4.2 and 78 K reveal that its Néel temperature is ~75 K and the two well-resolved magnetic sextets observed …

Relationship Between Cost Of Technical Training And Cost Reduction Of Internal Defects At John Deere Waterloo Foundry, John Brackin

Graduate Research Papers

Can the cost of technical training at John Deere Waterloo Foundry pay for itself in the reduction of internal defects? This research compared training costs to the savings from reduced internal defects on Molding Unit 801 located in the John Deere Waterloo Foundry. Training was the independent variable of this research. The results of this research identified a correlation between training costs ( operational definition on page 10) and defect reduction costs. A correlation between these two established a break even point for training dollars spent.

The dependent variable was the dollar savings based on reduction of internal defects. There …

Preparation And Surface Studies Of Negative Electron Affinity Semiconductors Photocathodes, Khaled A. Elamrawi

Electrical & Computer Engineering Theses & Dissertations

Fabrication of high quantum efficiency, long lifetime negative electron affinity photocathodes is important for applications such as photomultipliers, image intensifiers, electron beam lithography, electron microscopy, and polarized electron sources. The surface cleanliness of the III-V semiconductor photocathode is crucial in obtaining high photosensitivity.

GaAs(100) and InP(100) photocathodes are prepared by atomic hydrogen cleaning. The cleaning effect on the photocathode performance is discussed. The surface degradation mechanisms which reduce the photocathode lifetime are presented. The photocathode surface cleanliness, structure, and morphology are studied using reflection high-energy electron diffraction (RHEED).

Quantum efficiencies of ∼14% and 8% are obtained for GaAs and InP, …

Preparation Of A Zro₂-Al₂O₃ Nanocomposite By High-Pressure Sintering Of Spray-Pyrolyzed Powders, Rajiv S. Mishra, V. Jayaram, B. Majumdar, C. E. Lesher, A. K. Mukherjee

Materials Science and Engineering Faculty Research & Creative Works

ZrO2-Al2O3 powders were synthesized by spray pyrolysis. These powders were sintered at 1 GPa in the temperature range of 700Ç1100 ÉC. The microstructural evolution and densification are reported in this paper. The application of 1 GPa pressure lowers the crystallization temperature from ~850 to 700 ÉC. Similarly, the transformation temperature under 1 GPa pressure for <>g ê a Al2O3 reduces from ~1100 to 700Ç800 ÉC range, and that for t <>ê m ZrO2 reduces from ~1050 to 700Ç800 ÉC range. It was possible to ob-tain highly-dense nanocrystalline ZrO2-Al2O3 composite at temperatures as low as 700 ÉC. The effect of high …

Electrical Characterization Of Ion-Implanted 4h-Silicon Carbide, Christian P. Morath

Theses and Dissertations

Electrical characterization has been performed on ion-implanted p-type 4H-SiC to assess the activation efficiency and implantation-related damage recrystallization with the intention of developing an implantation/annealing scheme. Low doped (Na - Nd = 5x10(exp 15)/cu cm) epitaxial p-type layers grown by MOCVD were implanted with Al or B at doses ranging from 1x10(exp 13) to 1x10(exp 14)/sq cm at room temperature or 500 deg. C. The electrical technique of Temperature Dependent Hall Effect (TDHE) indicated that Al and B act as shallow acceptors 4H-SiC with ionization energies of ^252 and ^285 meV, respectively. The highest activation efficiency for Al and B …

A New Cell Structure For Proton Exchange Membrane Fuel Cell, Ming Han, Hong-Feng Xu, Bao-Lian Yi

Journal of Electrochemistry

Separating the functions of current collection and gas flow distribution and then to design two separate elements to achieve the desired performance characteristics, a nonconventional cell structure for proton exchange membrane fuel cells bave been developed. The current collector is achieved using a thin stain steel sheet, the gas flow distribution is achieved using a carbon paper that has the desired chemical durabiliy when in contact with the proton exchange membrane. Combining these two separate elements into a single divice yields a bifunctional device that performs as a bipolar separator plate. The advantages of this alternative appproach to making biplar …

Kinetic Study Of Electrooxidation Of Benzene, Xin-Sheng Zhang, Ping Ding, Ying-Chun Dai, Wei-Kang Yuan

Journal of Electrochemistry

A reaction kinetic study for electrochemical oxidation of benzene was performed on a PbO₂ rotating disk electrode in 1 mol/L H₂SO₄ aqueous solution. The reaction orders, the activation energies and transfer coefficient were measured, and the kinetic expression was obtained.

Oxidation Mechanism Of Hypophosphite, Dong-Bai Sun, Ying Jin, Hong-Ying Yu, De-Jun Yang

Journal of Electrochemistry

There exist two oxidation current peaks on the anodic polarization curve between -0.7 V and 0 V (SCE) in Na-hypophosphite solution. Peak Ⅰ (-0.55 V, SCE) , which represents the oxidation process from H₂PO₂^- to H₂PO₃^-, has been studied previously. Peak Ⅱ, which is located at the potential about -0.4 V (SCE), is investigated emphatically in this paper. The results show that, peak Ⅰ and Ⅱ are corresponding to two successive steps in oxidation process of H₂PO₂^-, i.e. peak Ⅱ corresponds to the oxidation process of …

Synthesis And Application Of Polymeric Corrosion Inhibitor For Reinforced Concrete, Wei-Wei Lin, Sheng-Xian Wang, Jian-Qing Zhang, Jun Yuan, Zhen-Guo Ji

Journal of Electrochemistry

A new polymer E-T was synthesized and used as a corrosion inhibitor for reinforced concrete. The inhibitive behavior and mechanism were studied with linear polarization, Tafel polarization, EIS and XPS method in simulated pore solution system with concrete samples. The result showed that the polymer was a mixing type inhibitor. A 1% dosage was sufficient to imhibit the corrosion of steel in simulated pore solution system. The salt endurance was enhanced from 0.02 mol/L to 0.10 mol/L. The result also showed the good synergetic effect of NaNO₂, especially in low NaNO₂ concentration. The EIS showed that E-T …