Materials Science and Engineering Commons^™

Modeling, Fabrication, And Optimization Of Niobium Cavities – Phase I: Quarterly Progress Report May 15, 2001 - August 15, 2001, Robert A. Schill Jr., Mohamed Trabia

Transmutation Sciences Materials (TRP)

Multipacting is one of the major loss mechanisms in rf superconductivity cavities for accelerators. This loss mechanism limits the maximum amount of energy/power supported by the cavities. Optimal designs have been identified in others’ studies. In practice, these designs are not easily manufactured. Chemical etching processes used to polish the cavity walls result in a nonuniform surface etch compromising the optimal geometrical design. Past multipacting studies have not examined the impact of wall perturbations.

It is the purpose of this study to examine the chemical etching process in the design of niobium cavities so to maximize the surface quality of …

Performance Of Proton Exchange Membranefuel Cell With Co/H2 Fuel, Hong-Mei Yu, Zhong-Jun Hou, Bao-Lian Yi, Ke-Wan Bi, Jing-Xin Zhang, Zhi-Yin Lin, Ming Han

Journal of Electrochemistry

Fuel of proton exchange membrane fuel cell(PEMFC) mostly comes from reformatecontains CO which will poison the fuel cell electrocatalyst. The effect of CO on the performance of PEMFC was studied in this paper. The results of the experiment show that when CO is fed inPEMFC ,the cell voltage will be decreased violently,then it will become steady with some vibration. The poison will become more serious with higher CO content and weaker at higher temperature. The adsorption of CO on the electrocatalyst is reversible. The PtRu electrocatalyst is moresuitable for the electrocatalysis of CO/H₂ than Pt electrocatalyst.

Study Of The Oxidation Dynamics Of Tizro2 Metal-Ceramics, Wen-Chao Li, Li-Dong Teng

Journal of Electrochemistry

The oxidation dynamics of hot-pressed Ti-ZrO₂ metal-ceramics with the compositionof 50 vol.% Ti and 50 vol.% ZrO₂ has been studied.Thermodynamic analysis shows that Ticould react with O₂ but not with N₂ in the oxidizing process of TiZrO₂ composites at 0.1 MPa air. The oxidation dynamic behavior of Ti-ZrO₂ composites is analogous to that of pure Ti. Theactivation energy for the oxygen diffusion in Ti-ZrO₂ composites is higher than that in Ti solutions, for the presence of ZrO₂ restrains the oxygen diffusion in Ti-ZrO₂ composites. At early stagethe oxidation of Ti-ZrO_{2 …}

Preparation And Properties Of Separator For Lithium-Ion Battery, Xu-Mei Ren, Feng Wu, Chuan Wu, Han-Jun Li, Xue-Jie Huang

Journal of Electrochemistry

Lithium-ion batteries are well adapted to the new multimedia applications. PP/PE based microporous film is commonly used as separator in commercial lithium ion batteries. Herewe report a microporous film which is superior to the commercial available separator. The microporous PVDF polymer separators were prepared by the phase inversion process. The pore size of the separator is Φ 7 μm , and it's porosity is 75 %. The membrane in LiPF₆-EC/DEC showedhigh ionic conductivity (above 10^-3 S/cm at room temperature), and good mechanical properties(10³ kg/cm²). The half-cells consisted of Li/PVDF separator/MCMB showed excellent cyclingcharacteristics and …

Performance Of A Direct Methanol Fuel Cell, Zhao-Bin Wei, Jian-Guo Liu, Ya-Guang Jiao, Wei-Jiang Zhou, Wen-Zhen Li, Li-Kang Chen, Qin Xin, Bao-Lian Yi

Journal of Electrochemistry

A direct methanol fuel cell with 9cm² active area consists of Pt-Ru/C anode ,Pt/Ccathode and Nafion 115 membrane. The effect of operating conditions: methanol solution concentration, oxygen pressure and cell temperature on the cell performances was investigated. The results show that performance of single cell was enhanced by increasing oxygen pressure and celltemperature ,and a maximum power density 75 mW/cm² was obtained in the range of 250-300mA/cm² current density, 0.2 MPa oxygen pressure, 1.0 mol/L methanol concentration and 75 ℃ cell temperature. When cell operating at room temperature, a relatively low, but a stable performance of cell …

The Effect Of Preparation Condition On The Photoelectrochemical Performance Of Both The Pani Film And Tio2-Pani Composite Film On Au, Huai-Guo Huang, Hong-Ping Zhang, Zhi-Xin Zheng, Yan-Yan Xi, Ling-Ling Wu, Zhong-Hua Lin

Journal of Electrochemistry

Both the PANI (polyaniline) film and TiO₂-PANI composite film on the PATP(paminothiophenol)/Au substrate were obtained under different preparation condition by electrochemical methods, and their photoelectrochemical performances were alo studied. The resultsshowed that the photoelectrochemical performances of the films depend deeply on the comditionsof preparation. The self-assembling of PATP favors the adhesion of PANl. The partially-oxidizedPANI has a greater photoelectrochemical response than that of the reduced PANI and oxidized PANl. There is an optimum of film thickness for the photoelectrochemical performance of PANI film. Heat treating is in favor of the photoelectrochemical performance of TiO₂, but decreases …

New Progress In Studies Of Lithium Nickel Oxide As Positive Electrode Materials Of Lithium Ion Batteris, Han-San Liu, Yong Yang, Zhong-Ru Zhang, Zu-Geng Lin

Journal of Electrochemistry

Lithium nickel oxide as the positive electrode of lithium ion batteries has aroused more and more interests.This paper reviews the recent reserches on synthesis and element-substitution of LiNiO₂ cathode material,and summarizes the intrinsical relationship between properties and sturcture of the material.The developments of new synthesis methods and mutilsubstitution of the material are expecting to be studied in the future research.

Electrochemistry Characteristic Of Carbon Steel Under Biofilm And Sulfide Film, Ze-Hua Dong, Xing-Peng Guo, Jia-Shen Zheng, Li-Ming Xu

Journal of Electrochemistry

Wire Beam Electrode (WBE) made of Q235 carbon steel was applied to study theheterogeneous corrosion beneath biofilm formed by Sulfate Reducing Bacteria (SRB) in cultureand sulfide film in solution with 1% NaCl and 300 mg/L⋅S^2-. The potential, galvanic density mapping, as well as polarization curve and Electrochemical Impedance Spectrum (EIS) were measured to predict the localized corrosion under biofilm and sulfide film. As a result, the mappingshowed the potential fluctuation on the WBE suface decreased over time due to the conductivityof the biofilm and sulfide film. Therefore, the potential mapping could not be a criterion of localized corrosion …

Studies On The Formation Of Dna-Cationic Lipid Composite Films And Dna Hybridization In The Composites, Murali Sastry, Vidya Ramakrishnan, Mrunalini Pattarkine, Krishna N. Ganesh

Faculty Works

The formation of composite films of double-stranded DNA and cationic lipid molecules (octadecylamine, ODA) and the hybridization of complementary single-stranded DNA molecules in such composite films are demonstrated. The immobilization of DNA is accomplished by simple immersion of a thermally evaporated ODA film in the DNA solution at close to physiological pH. The entrapment of the DNA molecules in the cationic lipid film is dominated by attractive electrostatic interaction between the negatively charged phosphate backbone of the DNA molecules and the protonated amine molecules in the thermally evaporated film and has been quantified using quartz crystal microgravimetry (QCM). Fluorescence studies …

Time-Resolved Electron Diffraction Studies Of Phase Transitions At Low-Index Germanium Surfaces, Xinglin Zeng

Electrical & Computer Engineering Theses & Dissertations

The phase transitions at the low-index surfaces of germanium were investigated using conventional and 100-ps time-resolved reflection high-energy electron diffraction. For the time-resolved studies, the surface is heated by 100-ps laser pulse while a synchronized electron beam probes the structure. When heated by 100-ps laser pulse, Ge(111)-c(2x8) and Ge(100)-(2x1) reconstruction is seen to overheat above the onset temperatures for the disordering under thermodynamic equilibrium. Slow heating shows that the adatoms in the Ge(111)-c(2x8) reconstruction state start to disorder at ∼510 K and are converted to a totally disordered adatom arrangement at 573 K. For heating with 100-ps laser pulses, time-resolved …

Optical And Etching Studies Of Native Aluminum Oxide Layers For Use In Microcavity Photonic Devices, William L. Bernhard

Theses and Dissertations

Optical communication and computing systems are required to meet future information transfer and processing needs. Microcavity devices serve as an enabling technology to implement and integrate optoelectronic systems. It is important to understand the optical and mechanical properties of materials utilize within microcavity devices. Only then is it possible to accurately model and analyze structures. Microcavity structures incorporating a high aluminum content AlGaAs layers are designed, grown, processed, and measured. The processing of these devices includes the conversion of high aluminum-content AlGaAs layers to native aluminum oxide (AlO) layers through the process of thermal oxidation. This selective conversion of microcavity …

A Study On The Performance Of Matrix Prepared By Tape Cast And Its Molten Carbonate Fuel Cells (Mcfcs), Hua-Xin Lin, Bao-Lian Yi, Li Zhou, Chang-Qing He, Lian-Ying Kong, En-Jun Zhang

Journal of Electrochemistry

The matrix prepared with γ-LiAlO₂ powder and by tape cast displayed higher ability of preventing from gas cross over and lower ohmic polarization. The voltages of the stack (three cells, 122 cm²) stacked with the matrix were 2.02 and 1.78 V at 200 and 246 mA/cm², respectively, and the output power reached 53.4 W. The cell (28 cm ²) voltages were 0.85 and 0.75 V at 200 and 300 mA/cm², respectively, and the output power was about 6.6 W. Compensating the shrinkage of matrix in stacking cells promoted the enhancement of the …

How Can Direct Mthanol Fuel Cell Benefit From Carbonate Media, Lin Zhuang, Yang Wang, Jun-Tao Lu

Journal of Electrochemistry

The kinetics of methanol oxidation and oxygen reduction in 0.5 mol/L K₂CO₃ were compared with those in 0.5 mol/L H₂SO ₄. Experiments revealed that carbonate media could be more beneficial to direct methanol fuel cell(DMFC). Firstly, both electrode reactions show better performance in the carbonate than in the acid; secondly, materials other than noble metals become possible to be used as the anodic and cathodic catalysts; thirdly, the potential dectease caused by methanol crossover could be depressed by using metal oxide catalysts not stable in acid, such as MnO₂.

Synthesis Of Limn2O4-ΔClΔ Cathode Material By Like-Sol-Gel Methode, Zhao-Yong Chen, Yi He, Xing-Quan Liu, Zhi-Jie Li, Zuo-Long Yu

Journal of Electrochemistry

LiMn₂O_4-δCl_δ was synthesized by like sol gel methode, with calculated LiOH·H₂O, Mn(No₃)₂⋅6H₂O and LiCl·H₂O, and made electrochemical test with these compounds as positive materials. Result demostrated that LiMn₂O_4-δCl_δ cathode material has exellent stability and nearly no capacity loss after reaching stability.

Adsorption And Oxidation Of Ethanol On Nm-Pt/Gc Electrode Ii. Eqcm And In-Situ Ftir Spectroscopic Studies In Acid Media, Guo-Liang Chen, Sheng-Pei Chen, Zhi-You Zhou, Chun-Hua Zhen, Shi-Gang Sun

Journal of Electrochemistry

The adsorption and oxidation of ethanol on nm Pt/GC electrode in acid solutions containing 0.1 mol·L ^-1 H₂SO₄ +0.1 mol·L ^-1 CH₃CH₂OH was investigated by using cyclic voltammetry, EQCM and in situ FTIR spectroscopy. The experimental results demonstrated that the oxidation of CH₃CH₂OH is closely relaed to solution acidity and oxygen species on electrode surface; CH₃CH₂OH was oxidized on nm Pt/GC electrode in acidic media via a dual path reaction mechanism, i.e . CH₃CH₂OH may be oxidized into CO₂ through …

The Photoelectrochemistry Of Tio2-Polyaniline Composite Film, Huai-Guo Huang, Zhi-Xin Zheng, Jin Luo, Hong-Ping Zhang, Ling-Ling Wu, Zhong-Hua Lin

Journal of Electrochemistry

A TiO₂ and polyaniline (PANI) composite film was obtained by electrochemical methods. The SEM image of the composite film showed that the PANI film is almost completely covered with TiO₂ efficiency. The spectra of photocurrent for the TiO₂-PANI composite film were different from these of TiO₂ film photosensitized by PANI. The bandgap energy of TiO₂ film on partially oxidized PANI film was determined as 3.0 eV by the threshold energy of photocurrent band for TiO₂. The spectra of photocurrent for partially oxidized PANI film electrode suggested that it has the characteristics of …

Cationic Surfactant Mediated Hybridization And Hydrophobization Of Dna Molecules At The Liquid/Liquid Interface And Their Phase Transfer, Murali Sastry, Ashavani Kumar, Mrunalini Pattarkine, Vidya Ramakrishnan, Krishna N. Ganesh

Faculty Works

Hybridization of complementary oligonucleotides mediated by a cationic surfactant at the water/hexane interface leads to hydrophobic, double-helical DNA which may be readily phase transferred to the organic phase and cast into thin films on solid substrates.

Optical Properties Of Wide Band Gap Indium Sulphide Thin Films Obtained By Physical Vapor Deposition, N. Barreau, S. Marsillac, J. C. Bernède, T. Ben Nasrallah, S. Belgacem

Electrical & Computer Engineering Faculty Publications

Thin films of indium sulphide containing oxygen have been synthesized following a dry physical process. The constituents are deposited by thermal evaporation on glass substrates and then annealed under argon flow. Polycrystalline β-In₂S₃ containing oxygen thin films are obtained as soon as the temperature of annealing is between 623 and 723 K. In this paper, these β-In₂S₃ thin films have optically been studied. The optical band gap is direct. Its value is not dependent on the temperature of annealing. It is about 2.8 eV, which is higher than that of β-In₂S_{3 …}

Effects Of Argon Dilution Of Silane On The Optical Properties And Surface Morphology Of Hydrogenated Amorphous Silicon, Choon Kheam Lim

Student Works (2000-2009)

Hydrogenated amorphous silicon (a.Si:H) was prepared using the d.c plasma grow discharge system. Two sets of samples were prepared and studied. The first set of samples referred to as the high argon dilution films were prepared from the discharge of pure silane at flow-rate of 5sccm and silane at the same flow-rate diluted in argon at flow-rates of 5, 10 and 15sccm. Similarly, the second set of sample referred to as the low argon dilution films were prepared from the discharge of pure silane at flow-rate of20sccm and silane at the same flow-rate diluted in argon at the flow-rates mentioned …

Multimode Quantitative Scanning Microwave Microscopy Of In Situ Grown Epitaxial Ba1-XSrXTio3 Composition Spreads, K. S. Chang, M. Aronova, O. Famodu, I. Takeuchi, S. E. Lofland, Jason R. Hattrick-Simpers, H. Chang

Faculty Publications

We have performed variable-temperature multimode quantitative microwavemicroscopy of in situepitaxial Ba_1−xSr_xTiO₃ thin-film composition spreads fabricated on (100) LaA₁O₃ substrates. Dielectric properties were mapped as a function of continuously varying composition from BaTiO₃ to SrTiO₃. We have demonstrated nondestructive temperature-dependent dielectric characterization of local thin-film regions. Measurements are simultaneously taken at multiple resonant frequencies of the microscope cavity. The multimode measurements allow frequency dispersion studies. We observe strong composition-dependent dielectric relaxation in Ba_1−xSr_xTiO₃ at microwave frequencies.

Modeling, Fabrication, And Optimization Of Niobium Cavities: Phase I, Robert A. Schill Jr., Mohamed Trabia

Transmutation Sciences Materials (TRP)

Niobium cavities are important parts of the integrated NC/SC high-power linacs. Over the years, researchers in several countries have tested various cavity shapes. They concluded that elliptically shaped cells and buffered chemical polishing produce good performance. The objective of the proposed research is to maximize the performance of the niobium cavities through studying multipacting, studying the effect of chemical etching on the surface roughness, and redesigning the cavities.

The US Congress has recently authorized exploring an alternative way to deal with spent nuclear fuel: Accelerator Transmuting of Waste (ATW). In this approach, a particle accelerator produces protons that react with …

Hybridization Of Dna By Sequential Immobilization Of Oligonucleotides At The Air-Water Interface, Murali Sastry, Vidya Ramakrishnan, Mrunalini Pattarkine, Anand Gole, K. N. Ganesh

Faculty Works

The hybridization of DNA by sequential electrostatic and hydrogen-bonding immobilization of single-stranded complementary oligonucleotides at the air-water interface with cationic Langmuir monolayers is demonstrated. The complexation of the single-stranded DNA molecules with octadecylamine (ODA) Langmuir monolayers was followed in time by monitoring the pressure-area isotherms. A large (and slow) expansion of the ODA monolayer was observed during each stage of complexation in the following sequence: primary single-stranded DNA followed by complementary single-stranded DNA followed by the intercalator, ethidium bromide. Langmuir-Blodgett (LB) films of the ODA-DNA complex were formed on different substrates and characterized using quartz-crystal microgravimetry (QCM), Fourier transform infrared …

Template Synthesis Of Nano-Structured Electrode Materials And Its Electrochemical Performance, Jian Zhao, Quan-Yong Gao, Yong Yang, Zu-Geng Lin

Journal of Electrochemistry

In this letter, various nano structured materials such as spinel LiMn₂O₄ nanotubes/nanowires and carbon nanotubes have been prepared by using porous alumina template. The prepared template and materials have been characterized by AFM and TEM techniques. It is shown that size of the nanotubes can be conveniently controlled by using template method. Some preliminary results of cyclic voltammetry about nano structured LiMn₂O₄ are also reported.

Electrochemical Hydrogen Storage Properties Of Carbon Nanotubes, Xue Qin, Xue-Ping Gao, Feng Wu, Hong Liu, Ying Lan, Hua-Tang Yuan, De-Ying Song, Pan-Wen Shen

Journal of Electrochemistry

The electrochemical properties of carbon nanotubes (CNTs) electrode have been investigated in this paper. The high discharge capacity of 200 mAh·g^-1 was measured for the CNTs Ni electrode at a discharge density of 200 mAh·g^-1 . CNTs-Ni electrode, the high electrochemical activity and the long cycle life were observed. The electrochemical mechanism of hydrogen adsorption and oxidation at the CNTs Ni electrode was studied by cyclic voltammertry method.

The Memory Effect Of Mh-Ni Battery, De-Ming Xie, Jian-Ming Wang, Jian-Qing Zhang, Chu-Nan Cao

Journal of Electrochemistry

The memory effect of MH-Ni battery was investigated. The depth of discharge, discharge rate and cycle number influence the memory effect greatly. A few completely full charge/discharge cycles could eliminate it. The existence of the memory effect had nothing to do with zinc element. During the course of life cycling at low DOD (degree of discharge), the smaller the discharge current was, the lower was the maximum charge voltage. In addition, discharge voltage and discharge capacity drop fast at the beginning, gradually leveled off at about a value. If the discharge current was increased, the discharge capacity was obviously less …

The Development Of Carbon Monoxide Tolerant Catalysts For Proton-Exchange Membrane Fuel Cell, Zhong-Jun Hou, Hong-Mei Yu, Bao-Lian Yi, Ming Han

Journal of Electrochemistry

High over-potential of proton exchange membrane fuel cell (PEMFC) anode caused by carbon monnoxide poisoning when reformate or methanol is used as fuel is main obstacle to the high performance of PEMFCs. Using carbon monoxide tolerant catalysts is the most hopeful way to solve the CO problem. The CO poisoning problem is reviewed briefly in this paper, and the development of CO tolerant catalysts is introduced in details, including electrocatalysts activity, preparation method and mechanism of tolerance to CO.Mo and W can improve catalysts' CO tolerance. Multi-component catalysts are expected to be more tolerant to CO.

Effect Of High Concentration Lithium Bromide Solution On Electrochemical Behavior Of Low Alloy Steel At High Temperature, Jian-Wei Guo, Cheng-Hao Liang

Journal of Electrochemistry

By electrochemical measurements and weight loss experiments, the effect of MoO₄^2- on low alloy steel's electrochemical behaviors was investigated at high temperature in 55%LiBr+0.07 mol/L LiOH solution. The results showed that MoO₄^2-, as an anodic inhibitor, formed passive film rapidly and impeded both anodic and cathodic procedures. Moreover, Na₂MoO₄ prevented corrosion effectively in 55%LiBr+0.07 mol/L LiOH solution when its concentration is more than 200 mg/L. The pitting potential increased accompanying to the arising of Na₂MoO₄ concentration. Some elements of alloy strengthened resistance to corrosion, shch as chromium and nickel, …

Studies Of Adsorption And Oxidation Of Ethanol On Nm-Pt/Gc Electrode——I. Cyclic Voltammograms And In-Situ Ftir Spectroscopy In Alkaline Media, Guo-Lian Chen, Shi-Gang Sun, Sheng-Pei Chen, Zhi-You Zhou

Journal of Electrochemistry

The electro-oxidation of ethanol on nm-Pt/GC electrode in alkaline solutions containing 0.02 mol·L^-1 NaOH+0.1 mol·L^-1 CH₃CH₂OH was investigated by using cyclic voltammetry and in-situ FTIR spectroscopy. The experimental results demonstrated that the main product of ethanol oxidation is CH₃COO^-, only very small amount of CH ³CHO has been determined simultaneously. In contrast with the dual path reaction mechanism for the oxidation of ethanol in acid media, the oxidation of ethanol in alkaline media didn't pass through the dissociative adsorption, and no adsorbed species could be determined even using a …

Investigation Of A Complex Lithium Cobalt Nickel Oxide As Lithium Ion Battery Cathode Materials Prepared By A New Citrate Sol-Gel Method, Jing-Li Han, Qing-Guo Liu

Journal of Electrochemistry

The synthesis and electrochemical characteristics of lithium cobalt nickel oxide as cathode materials for rechargeable lithium batteries were investigated. It was clarified from these investigations that lithium cobalt nickel oxide has been produced from basic cobalt carbonate,basic nickel carbonate, lithium carbonate, and citrate. LiNi_0.8Co _0.2O₂ prepared under the stream of oxygen gas showed a higher cycling capacity of (～190 mAh·g^-1).

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.