Engineering Commons^™

Nanoporous Sio2/Vycor Membranes For Air Separation, Mihir Tungare

Theses

Porous Vycor tubes with 40Å initial pore diameter were modified using low pressure chemical vapor deposition (LPCVD) of silicon dioxide N0₂). Diethylsilane (DES) in conjunction with nitrous oxide (N₂O) was used as a precursor to synthesize these SiO₂ films. The aim of this study was to obtain a considerable selectivity between species of comparable size and hence N₂O was used. The use of N₂O was believed to make the process self-limiting. DES was allowed to flow through the tube and N₂O on the outside in the chamber at 550°C …

Preparation And Properties Of Tantalum Silicide Films On Silicon Substrates, Lei Jin

Theses

Tantalum silicide (TaSi₂) thin films were sputter deposited on p- type and n- type silicon substrates using VARIAN 3125 magnetron DC sputtering system with TaSi₂ target. The thicknesses of TaSi₂ thin films considered in this study are 200Å, 600Å and 1000Å, respectively. The TaSi₂/Si wafers were annealed at temperatures in the range of 400 to 900°T. The sheet resistances of TaSi₂ thin films with various thicknesses were measured by four-point probe before and after annealing. The sheet resistance decreases with increase in annealing temperature and decreases with the increase in thickness of TaSi …

The Effect Of Cerium On The Anodic Behavior Of Pb-Ca-Sn Alloy In Sulfuric Acid Solution, Hou-Tian Liu, Jiong Yang, Hai-He Liang, Ji-Hua Zhuang, Wei-Fang Zhou

Journal of Electrochemistry

The cyclic voltammograms for Pb - 0.5 at% Ca - 1.5 at% Sn and Pb - 0.5 at% Ca - 1.5 at% Sn containing a certain amount of cerium in 4.5 mol·dm^-3 H₂SO₄ at 20℃ were measured between 0.6 V and 1.4 V(vs. Hg/Hg₂SO₄). The growth rate of the anodic Pb(Ⅱ) films formed on the mentioned alloy electrodes at 0.9 V in the same sulfuric acid medium was investigated using the Linear Sweep Voltammetry. The variation with electrode potential of the real part of the impedence (Z’) for the anodic Pb(Ⅱ) films …

The Lineal Polarization Method For Corrosion Rate Measurement Of Reinforcing Bar Of Concrete In Situ, Ai-Ling Du, Wen-Tao Hou, He-Ming Zhang, Jian-Qun Luo

Journal of Electrochemistry

A linear polarization method was applied to measure corrosion rate of reinforcing bar of concrete in situ. Generally in the experiment, the area and shape of the reinforcing bar as a working electrode can be changed and adjusted according to our needs. But polarization area cannot be defined when reinforcing bar is polarized in situ, so that a real R_p can't be obtained. Thus the purpose of present work is to improve the measurement system. We used the double-ring auxiliary electrodes made by ourselves. The size of the double-ring auxiliary electrodes was adjusted repeatedly until the real polarization area …

The Electro-Catalytic Oxidation Of Hcooh On Electrodeposited Pd Electrode, Quan Zhou, Cun-Zhong Zhang, Xiao-Lin Lu, Zhong-Da Wu

Journal of Electrochemistry

The coherent electroplates were prepared by electro depositing Pd on supporting materials glassy carbon. The surface morphology of the electrodes was examined by SEM. The electro oxidation of HCOOH in HClO₄ solution was investigated by using cyclic voltammetry. The results show that the deposited conditions in the preparation of electrodes by electro depositing Pd affect the electrodes electro catalytic activity to the oxidation of HCOOH. The platinized Pd electrode on GC substrates using large current density is of higher catalytic activity to the oxidation of HCOOH than Pd electrode. The electro catalytic activity of PdO formed on the Pd …

Electrochemical Characteristics Of Sb Irreversibly Adsorbed On Pt(100), Pt(110), Pt(111) And Pt(320) Electrodes, Yi-Yun Yang, Zhi-You Zhou, Qi-Hui Wu, Shi-Gang Sun

Journal of Electrochemistry

The electrochemical behaviors of irreversibly adsorbed antimony on Pt(100), Pt(110), Pt(111) and Pt(320) were studied by using cyclic voltammetry. The results revealeds that the Sb adatoms are stable on Pt(100), Pt(110), Pt(111) and on Pt(320) when electrode potentials are below 0.45 V(SCE) and 0.40 V, respectively. It was demonstrated that various coverages of Sb ad can be conveniently obtained by controlling the number of potential cycling and varying the upper limit of potential scan. The electrochemical behaviors of irreversibly adsorbed antimony varied with the surface atomic arrangement of Pt single crystal electrodes. Based on quantitative results of the relationship between …

A Study On Stochastic Resonance For The Process Of Active-Passive Transition Of Iron In Sulfuric Acid, Hong-Bo Ding, Bao-Yun Xia, Chun-Sheng Yin, Zhong-Xiao Pan, Renato Seeber

Journal of Electrochemistry

The bistable characteristics of the process of active passive transition of iron in sulfuric acid was described and the stochastic resonance phenomenon in the process was simulated.

Mechanisimic Study Of Fes Electrode Process, Cong-Sheng Guan, Shu-Zhen Duan

Journal of Electrochemistry

The mechanism of FeS electrode process has been investigated by using linear cyclic voltammetry. The electrode porcess of FeS is accompanied with the formation and dissolution of insoluble FeS and controlled by ohmic resistance. The peak currents and potentials on the cyclic voltammograms are dependent lineally on the square root of the scan rates. According to this, an ohmic resistance controlling model of FeS electrode has been put forward, and the relative functions between peak currents or potentials and scan rates have been deduced. The theoretical deduction is corresponding to the results of the experiments.

Electrochemical Evaluation On The Porosity Of Electroless Ni-P Alloy Coatings, Hong-Ying Yu, Dong-Bai Sun, Jing-Bing Huang, De-Jun Yang

Journal of Electrochemistry

By investigating the polarization curves of pure Ni-P alloy, Ni-P alloy coation and carbon steel in nitric acids with different concentrations, the sutable concentration of nitric acid for the evaluation of the porosity of Ni-P alloy coatings has been determined and the coatings with different thickness have been evaluated. The results indicated that the nitric acid with 10 wt% concentration is the most suitable solution for the porosity of the coating by using electrochemical method. The polarization curve of Ni-P alloy coating in 10% nitric acid can accurately reveal the porosity. With the decrease of the porosity of the coating, …

The Effect Of Anode Thickness In Sofcs With Anode Supported Ysz Film, Yi-Huang Zhang, Yi Jiang, Zi-Gui Lu, Yong-Lai Dong, Jing-Wang Yan

Journal of Electrochemistry

Solid oxide fuel cells with supported yttria stabilized zirconia electrolyte films on anode substrates of various thickness have been fabricated. The electrochemical performances of the SOFCs have been examined. The results showed that the cell performance was limited by the anodic overpotential, which is caused mainly by a concentration polarization when the anode substrate is thick. The anodic overpotential was reduced obviously as the thickness of anode substrate was decreased. As a result, the performance of the SOFC cell was improved. With a 0.5 mm anode substrate, a SOFC cell produced a power density about 0.19 W/cm² at 800 …

A New Method For The Preparation Of The Electrodes With Very Low Platinum Loading Used In Proton Exchange Membrane Fuel Cell, Zhi-Gang Shao, Bao-Lian Yi, Ming Han, Ya-Guang Qiao, Hao Liu, Jing-Rong Yu

Journal of Electrochemistry

Research and development on low platinum loading electrode is very important in reducing the cost of proton exchange membrane fuel cell(PEMFC) stack. This paper has put forward a new method to prepare the electrode of PEMFC. The pore forming substances were used in this methd. The low platinum loading electrodes (0.02 mg_Pt⋅cm^-2) have already been prepared with the method. Compared with the traditional method, the new method is simple, cheep, and easy to scale up. The superior composition of the electrodes is catalyst: pore forming substance: Nafion= 3:3:1. The performance of a single cell using this …

The Electrochemical Polymerization Of Erythrosin And The Fluorescence Spectra Of Polyerythrosin, Hong-Ping Zhu, Shao-Lin Mu

Journal of Electrochemistry

The solution used for the electrolysis consisted of 0.03 mol·dm^-3 erythrosin, 0.05 mol·dm^-3 sodium tetraborate and 0.5 mol·dm^-3 KCl with pH 8.50. Polyerythrosin film with red color has been electrochemically synthesized using repeated potential cycling between -0.20 and 1.10 V (vs.SCE). The film growth and the electrochemical property of polyerythrosin are affected by electrolytic conditions. Two main absorption peaks of polyerythrosin at 326 nm and 370 nm appear in the UV-visible spectrum, which are different from that of the monomer. Polyerythrosin in dimethyl sulfoxide or dimethylformamide has a strong fluorescence intensity and the fluorescence intensity of polyerythrosin …

Cathodic Indirect Oxidation Of Organic Compounds(Ⅱ)——Cathodic Indirect Epoxidation Of Olefine, Xue-Ying Zhang, Bao-Qiu Cui, Deng-Ping Gu, Wei Li

Journal of Electrochemistry

We described a novel cathodic indirect epoxidation system in which O₂ was first cathodically reduced to H₂O₂. Then VO(acac)₂ was oxidized by H₂O₂ homogeneously to VO(acac)₂OOH which was used to epoxidize some olefine such as maleic, fumaric and crotonic acids. Many affecting factors on the current efficiency were optimized. The research will contribute to the developments of organic electrosynthesis.

The Study On Lithiated Titanium Composite Oxides As Negative Electrode For Lithium-Ion Battery, Xiao-Yan Yang, Shou-Nan Hua, Shu-Yong Zhang

Journal of Electrochemistry

Lithiated titanium composite oxides Li₄Ti₅O₁₂ were prepared from Li₂CO₃ and TiO₂. The XRD results of this composite oxides indicated that the compound had a spinel structure. The electrochemical behavior of lithiated titanium composite oxides was examined. The results showed that this material had an excellent cyclic capability and reversibility for lithium insertion, and had high specific capacity: the initial discharge capacity was 300 mAh·g^-1 , and the reversible capacity was 100 mAh·g^-1 . The discharge plateau (about 1.5 V) and the charge plateau (about 1.6 V) were very …

Studies Of The LialYNi1-YO2 As Cathode Materials For Rechargeable Lithium Ion Batteries, Xiao-Gan Li, Wei-Hua Qiu, Chuan-Gang Lin, Qing-Guo Liu

Journal of Electrochemistry

In this paper, we have synthesized series of single-phase LiAl_yNi_1-yO₂ (differentive in value-y) by solid reaction. Through examining their electrothemical properties, found that, under a proper sintering condition, Li_xAl_0.25Ni_0.75O₂ solution for cathode materials of rechargeable lithium ion batteries showed more pleasing properties in overcharge-resist and cycling life (vs LiNiO₂). When x>1, the capacity can be kept 125mAh/g after 30 cycles under higher charged/discharged voltages ranging from 3.0 V to 4.8 V, whereas that of pure LiNiO₂ has only 61 nAh/g after 25 cycles. The …

Corrosion Behavior Of Reinforcing Steel In Concrete, Rong-Gui Du, Rong-Gang Hu, Zu-De Feng, Jiang-Guang Tan, Chang-Jian Lin

Journal of Electrochemistry

The corrosion behavior of reinforcing steel in concrete in chloride free and chloride contaminated simulated concrete solutions was studied by electrochemical technique. The results showed that the reinforcing steel exhitibted different corrosion characteristics in the different solutons. In general, the steel in concrete was protected in the test solutions with no salt or the lower concentration of NaCl. When the concentration of NaCl is larger than 70%, however, the corrosion behavior of the steel varied considerably, and the corrosion rate increased as pH fell and the concentration of Cl^- increased.

A Study On The Cylindrical Zinc-Air Battery, Sheng-Sian Li, Gui-Mao Zhou, Xin-Ping Ai, Han-Xi Yang

Journal of Electrochemistry

The zinc air battery has advantages of high specific energies and low cost, therefore attracts much interests. However, its application is limited only in prismatic and button type.This paper reported a novel design of cylindrical zinc air batteries and the performances of the batteries tested at various conditions. The results showed that when discharged at the current of 40 mA at 20 °C, the capacity of AA size and AAA size batteries reached 4000mAh and 1400mAh respectively, corresponding to the energy densities 280 Wh/kg and 200 Wh/kg. The effects of the discharge current, temperature and humidity on the performances of …

Synthesis Of Li1+XMn2O4 Cathode Material For Lithium-Ion Batteries With Solution Method, Pei-Song Liu, Sing-Quarn Liu, Qing Li, Zhao-Yong Chen, Bai-Lan Zhang, Zuo-Long Yu

Journal of Electrochemistry

The cathode materials Li_1+xMn₂O₄ were prepared with citric acid complexing and solution impregnating methods. Structure characterization and specific surface area test were performed by means of XRD, BET methods, the influences of calcination temperature, Li/Mn molar ratio and raw materials on the structure and electrochemical capacity of samples have beem examined. The results showed that the Li/Mn molar ratio and calcimation temperature were the key factors affecting the electrochemical capacity of cathode materias. The optimum conditions for synthesis of  Li_1+xMn₂O₄ cathode material were 0≤x≤0.05 and calcined at 750°C. The initial …

Membrane-Based Sorbent For Heavy Metal Sequestration, Dibakar Bhattacharyya, Leonidas G. Bachas, Lawrence Cullen, Jamie A. Hestekin, Subhas K. Sikdar

Chemical and Materials Engineering Faculty Patents

A process is provided for making membrane-based sorbents with enhanced binding activity that are particularly useful for heavy metal sequestration. The process includes the step of selectively hydrolyzing a polyacetylated membrane in order to deacetylate a surface layer of said membrane and expose free hydroxyl groups. This is followed by the oxidizing of the hydroxyl groups to aldehyde groups. This is then followed by the attaching of a polycarboxylic acid such as a polyamino acid, polyalkenoic acid or polypeptide to the membrane through the aldehyde groups. Preferably, the hydrolyzing step is completed under alkaline conditions and the oxidizing step is …

42nd Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Abstracts from the 42nd 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 Broomfield, Colorado, July 30 - August 3, 2000.

The Effect Of Impact Damage On The Room-Temperature Fatigue Behavior Of Γ-Tial, Trevor S. Harding, J. Wayne Jones

Materials Engineering

The relationship between impact damage and the fatigue behavior of γ-TiAl has been examined. Axial fatigue specimens fabricated from cast Ti-47.9Al-2.0Cr-1.9Nb (to be referred to as 48-2-2) and Ti-47.3Al-2.2Nb-0.5Mn-0.4W-0.4Mo-0.23Si (to be referred to as WMS) alloys were damaged by impact under controlled conditions with a 60 deg wedge-shaped indenter to simulate assembly-related damage in low-pressure turbine blades. The level of damage produced was quantified and found to correlate well with the peak load of the impact event. The WMS alloy exhibited a greater resistance to impact damage due to its higher yield strength and lamellar microstructure. A measure of the …

Effects Of Solvent Mixtures On Dispersion Of Lanthanum-Modified Lead Zirconate Titanate Tape Casting Slurries, Jian-Huei Feng, Fatih Dogan

Materials Science and Engineering Faculty Research & Creative Works

The effects of xylenes/ethanol solvent mixtures on lanthanum-modified lead zirconate titanate (PLZT) nonaqueous suspensions were investigated by measuring sediment height, viscosity, and adsorption of dispersant. Well-dispersed colloidal suspensions were obtained in xylene-rich solvents with a minimum amount of menhaden fish oil as a dispersant. It was also shown that adsorption of dispersant on particle surfaces strongly depends on selection of solvent(s). The ratio of solvent mixture affects PLZT solids content of unfired tapes, in which using insufficient as well as excess dispersant could decrease the packing density of particles. Solubility of other organic additives, such as binder, was also considered …

High Energy Density Dielectrics For Symmetric Blumleins, Wayne Huebner, Shi C. Zhang

Materials Science and Engineering Faculty Research & Creative Works

Multilayer, tape cast ceramics are being developed for use in large area, high voltage devices in order to achieve high specific energy densities (>10⁶ J/m³) and physical size reduction. In particular, symmetric Blumleins are desired with the following properties:

• High voltage hold off (≥ 300 kV)
• High, nondispersive permittivity: ≈100 to 900
• Ability to be fabricated into various shapes and sizes
• Surface flashover inhibition at the edge
• Ability to be triggered by surface flashover switching

The compositions being pursued are based on pure BaTiO₃ dielectrics. Our approach is to add glass phase additions which result …

Implementing An Engineering Teaching Development Program For Graduate Student Instructors, Sara Soderstrom, Christian Lorenz, Michael Keinath, Trevor S. Harding

Materials Engineering

The Engineering Teaching Development Project (ETDP), a pilot program started by the student chapter of ASEE at the University of Michigan, is a multi-component program designed to improve the long-term teaching skills of graduate student instructors (GSIs) in the College of Engineering. The first component of the ETDP is college-wide pedagogical workshop series. These workshops are conducted by nationally recognized engineering educators invited by the ASEE student chapter. The topics of these workshops include cooperative learning, diversity in the classroom, and classroom assessment techniques. These workshops offer a means of continual improvement for all of the educators in the university, …

Synthesis And Characterization Of Low Pressure Chemically Vapor Deposited Boron Nitride And Titanium Nitride Films, Narahari Ramanuja

Dissertations

This study has investigated the interrelationships governing the growth kinetics, resulting compositions, and properties of boron nitride (B-C-N-H) and titanium nitride (Ti-N-Cl) films synthesized by low pressure chemical vapor deposition (LPCVD) using ammonia (NH₃)/triethylamine-borane and NH₃/titanium tetrachloride as reactants, respectively.Several analytical methods such as the FTIR, UVNisible spectroscopy, XPS, AES, RBS, SEM, and XRD were used to study the stoichiometry and structure of the deposited films.

The B-N-C-H films were synthesized over a temperature range of 300 to 8500C at various flow rate ratios of the reactants and total pressure range of 50 to 150 mTorr. …

Electrocrystallization Mechanism And Grain Sizes Of Ni-W-B Alloy Eletrodeposits, Fang-Zu Yang, Gang-Min Cao, Xiao Hu, Shu-Kai Xu, Shao-Min Zhou

Journal of Electrochemistry

The electrodeposition characteristics and grain sizes of Ni-W-B alloy have been studied by cyclic voltammetry, potentiostatic step and X-ray diffraction (XRD). The results showed that Ni-W-B alloy electrodeposit obtained from the solution containing ammonium citrate as a complexing agent was presented in the lower electrochemical activity compared with Ni-W alloy. Based upon the i～t curves of potentiostatic step, it was revealed that electrocrystallization of Ni-W-B alloy on glassy carbon followed the mechanism of instantaneous nucleation and three dimensional growth with diffusion controlled. The crystal nucleus number on the surface of electrode was raised by the increase of overpotential. According to …

Study On The Effect Of Sodium Ion On Cycle Performance Of Lithium/Improved Graphite Lithium Ion Cell, Wen-Huang Huang, Yu-Shun Yan, Chun-Rong Wan, Chang-Yin Jiang

Journal of Electrochemistry

The different concentration of Na⁺ was introduced into the non-aqueous eletrolyte system EC/DEC/LiClO 4 with 4A molecular sieve and lithiated 4A molecular sieve, by which the trace amount of water was removed. The concentrations of Na⁺ and Li⁺ were determined by atomic adsorption spectrometry. The cycle performance of lithium/improved graphite cells was then examined by charging and discharging under the constant electric current. The results demonstrated that the cycle performance of the cells was destroyed by the high concentration of Na⁺ under the small electric current. With the increase of electric current the cell became less …

The Studies On Nanosized Materials For Lithium Ion Batteries, Hong Li, Jing-Ze Li, Li-Hong Shi, Guang-Yan Zhu, Qing Chen, Wei Lu, Xue-Jie Huang, Li-Quan Chen

Journal of Electrochemistry

Our recent works about nanosized materials for lithium ion batteries are reported, including the synthesis of nanosized Sb, SnSb, CuSn_x, Si and CuS, their electrochemical performance as anode or cathode active materials, the variation of crystal structure and morphology during discharge and charge cycling. In addition, the self-plasticization of lithium salt with nanosized anion ion in polymer electrolyte, the influence of the electrochemical Li-doping on the Raman spectra and photoluminescence of nano-Si are also introduced. Furthermore, the relationship between intrinsic properties of nanosized materials and their electrochemical behaviors are discussed. The prospect of nanosized materials for lithium ion …

Determination Of Kinetic Parameters Of Enzyme-Immunoelectrode For Sec Assay, Sa-Ying Dong, Xin-Miao Liu, Yuan-Zhi Wang, Guang-Zhang Chen, Ming-Xiang Lv, Bo-Yi Tian

Journal of Electrochemistry

Reaction mechanism of enzyme immunoelectrode is studied by potentiostatic. Rotating disk electrode is used to determine the controlling step of bioelectrode. Under different potentials and different modifying conditions, kinetic parameters of bioelectrodes were measured on the base of electrochemical impendance spectra. At the same time, these parameters are compared and discussed.

The Influence Of Surface Diffusion Of Adsorbed Intermediate On Hydrogen Evolution Reaction At Pt/Nafion Composite Electrodes, Wei-Yi Tu, Lei Su, Wen-Jun Liu, Bing-Liang Wu

Journal of Electrochemistry

The decrease of over-potential of hydrogen evolution reaction at Pt black powder/Nafion microelectrode, comparing that of the Pt microdisk/Nafion electrode, was evident from the polarization curves of the Pt microdisk/Nafion electrode, platinized Pt micrdisk/Nafion electrode and Pt black powder/Nafion microelectrode. It is also evidenced by a plane Pt electrode with an additional free Pt surface. The surface diffusion and the surface recombination reaction of the adsorbed intermediate at the free surface of the Pt particles were supposed. It is an additional reaction path that induced the decrease of the concentration of the adsorbed intermediate. Thereby, the over-potential decreased.