Engineering Commons^™

Preparation, Structure And Electrochemical Hydrogenation Of Carbon Nanotubes Supported Platinum Catalysts, Qing-Gang He, Xiao-Zi Yuan, Xian-Xia Yuan, Zi-Feng Ma

Journal of Electrochemistry

In this paper, Pt/CNTs catalyst was prepared and its electrocatalytic property was studied by obtaining cycling voltammetry curves (C-V) and Tafel curves. In addition, the XRD,XPS and TEM tests were carried out to determine the structure and composition of the catalysts. It can be found that the platinum loading has been increased significantly using a carbon nanotubes support. Dispersion of Platinum was better and gave more active sites. The electrochemical characteristic of Pt/CNTs was also more desirable than that of Pt/C catalys t(Johnson Matthey). In conclusion, carbon nanotubes can played a conspicuous role in "electrogenerative" processes of PEMFC hydrogenation reactor.

Template Synthesis Of Highly Ordered Monocrystalline Metal Nanowire Arrays By A Two-Step Ac Electrodeposition, Juan Xiang, Jing-Hua Tian, Zi-Mian Ni, Zhi-Feng Huang, Bo Liu, Zhong-Qun Tian

Journal of Electrochemistry

The monocrystalline metal nanowire arrays were prepared by using a two-step AC electrodeposition in porous anodic aluminum oxide (AAO) template. The growth mechanism of nanowires was discussed. As a result, it has been found that the second voltage pulse has a considerable effect on the pore-filling ratio, the uniformity and the crystal structure, whereas the initial voltage pulse affects only the pore-filling ratio. Using the two-step AC electrodeposition, a highly ordered monocrystalline metal nanowire arrays with a pore-filling ration above 95% can be easily obtained.

The Interaction In Doping Lithium Of Carbonaneous Anode In Lithium Ion Battery, Chang-Guo Chen, Hong-Min Zhang, Jia Chen, Dan-Mei Yu

Journal of Electrochemistry

The quantum chemical DV-X_α method was used to calculate the lithium-doped models from one-Li-dopant to LiC₆ and LiC₂. It was found that Li⁺ has an tendency to attract electrons from the carbon plane through the C₆ hexagons lying above or below it by the graph of charge-density difference. It was shown that LiC₆ can exist steadily,while LiC₂ can not exist steadily.

Study On Determination Of Iodine Ion At Chitosan Modified Glassy Carbon Electrode, Bin Liu, Xiang-Ying Sun, Jin-Rui Xu

Journal of Electrochemistry

In this paper, a chitosan modified glassy carbon electrode was prepared by the method of covalent-bond reaction, and the anodic stripping voltammetric characteristics of iodine on the modified electrode was studied. The results showed that the modified electrode has higher adsorption and selectivity for I^- , and the sensitivity for I^-  has been much improved in 0.1 mol·L^-1 KH₂PO₄ solution (pH=4.0). The anodic stripping peak current of I^- on the modified electrode varied linearly with I^-  concentration in the range of 2.0×10^-6～2.0×10^-3 mol·L^-1, and the detection limit …

Formation And Characterization Of Water-Repellent Nano Tio2 Coating And Studying Its Anticorrosion Property, Guang-Xia Shen, Yi-Cong Chen, Chang-Jian Lin

Journal of Electrochemistry

Using ethyl acetoacetate (EAcAc) as a chelating agent, ultra fine TiO₂ sol is prepared. Nano-TiO₂ coatings are deposited on the 316L stainless steel by the dip-coating. Hydrothermal post-treatment leads to crack-free coatings. Meanwhile, the surface struture and properties was optimized. Self-assembly of Hetadecafluorodecyltrimethoxysilane (FSA-13) fabricates hydrophobic layers on the surface of the nano-TiO₂ coatings. Particle sizes of TiO₂ sol was analysed by zeta pals potential analysis, and surface morphology, structure and properties was characterized by contract angle instrument, XRD, and SEM technologies. The results have shown that the surface of coatings is porous, with approx. 375 …

Study Of Electrochemical Properties Of The Hydride Alloy Electrode Zrcr0.4Mn0.2V0.1Co0.1Ni1.2 At High Temperature, Song Li, Shi-Jun Ji, Jun-Cai Sun

Journal of Electrochemistry

Electrochemical properties of the hydride alloy electrode ZrCr_0.4Mn_0.2V_0.1Co_0.1Ni_1.2 at the different temperature have been investigated. The results showed that the alloy electrodes possessed the maximum discharge capacities 336 mAh/g and 298 mAh/g at 25 ℃ and 70 ℃ respectively. The activation process of the alloy at 70 ℃ became faster, and the alloy reached its maximum capacity in less than 4 cycles, while in 13 cycles at 25 ℃. The high rate capability increased from 55 % at 25 ℃ to 71% at 70 ℃ at 300 mA/g. It was worth …

Electrochemical Synthesis Of Ferrate(Vi) By Anodic Oxidation, Jia-Ju Xu, Jian-Ming Wang, Wei-Hua Yang, Cheng Chen, Jian-Qing Zhang

Journal of Electrochemistry

The ferrate(Ⅵ) was synthesized by electrochemical anodic oxidation. The effects of preparation conditions on the current yield of ferrate(VI) synthesis have been studied in this work. The experimental results showed that grey cast iron as an anodic material is suitable for electrochemical synthesis and NaOH solution as an electrolyte results in a higher current yield than KOH solution. The highest current yield was obtained at a current density (4.54) mA·cm^-2, temperature 20 ℃ and 14 mol·dm^-3 NaOH. In this case, a current yield of 68.5% was obtained by electrolysis for 1 h.

Substrates Made By Electrodeposition For Measuring Electrical Properties Of One Dimensional Nanomaterials, Jin-Xuan Liu, Juan Xiang, Zhong-Qun Tian, Bing-Wei Mao

Journal of Electrochemistry

A method to prepare alternating conducting/insulating substrates by electrodeposition-oxidation was established to facilitate I-E measurements of one-dimensional nanomaterial by CT-AFM. The prepared Au/CuO and HOPG/CuO substrates showed low roughness as well as high uniformity of the alternating conducting/insulating structure, Qualitative I-E measurements were performed on a single carbon nanotube attached to the two above-mentioned substrates, both showing metallic characteristics at room temperature and in air.

Studies On The Mechanism Of Electroreduction Of Oxalic Acid, Yu-Zhan Li, Xin Liu, Rui-Sheng Hu, Deng-Ping Gu

Journal of Electrochemistry

The electroreduction mechanism of oxalic acid on Pb electrode in Na₂SO₄ solution were investigated using high scan rate cyclic voltammetry and chronoamperometry. The dynamic parameters for the first step electron transter reaction of oxalic acid electroreduction by were determined. The corresponding reduction peak potentials of oxalic acid, glyoxylic acid and glycolic acid in the cyclic voltammogranis obtained in the same condition were compared, and the intermediate reduction products of oxalic acid were suggested. The results showed that oxalic acid is weakly absorbed on the lead electrode.

Electrochemical Character Of Water Containing Gel Electrolyte And Its Preliminary Examination In Lithium Water Cell, Jing-Dong Liu, Wen-Ji Wang, Xin-Zheng Yi

Journal of Electrochemistry

AC impedance technique has been used to characterize the system of poly(methyl acrylic acid)-poly(methyl acrylic lithiumate)-glycerol (referred to as GPE).The results showed that the conductivity of GPE increased with increasing both temperature and its water content.The glass transition temperature of GPE polymer could be lowered by water. Its conducting characteristic was just like liquid electrolyte,The electrolysis of GPE was almost the same as the electrolysis of water. Its composition voltage was about 1.50V. The GPE has been used to manufacture lithium water cell. When the graphite was used as cathode, the cell could discharge continuously for 2 hours under constant …

An Electrochemical Study Of The Effects Of Chelating Agents And Additives On Electroless Copper Plating, Xin Gu, Zhou-Cheng Wang, Chang-Jian Lin

Journal of Electrochemistry

In this study, ethylenediaminetetraacetic acid disodium salt (Na₂EDTA), triethanolamine(TEA), and 2,2′-dipyridine were adopted as chelating agents or additives in the electrolyte for electroless copper plating, and formaldehyde (HCHO) was as the reducting agent. Linear sweep voltammetry was applied to analyze the polarization behavior. The peak current of formaldehyde oxidation which increased by the addition of 2,2′-dipyridine is beneficial to formaldehyde oxidation in a specific range of concentration, While TEA decreased the peak current of formaldehyde oxidation. Two cathodic peaks due to copper(Ⅱ)reduction of TEA chelatation and copper(Ⅱ)reduction of EDTA chelatation were examined. EDTA increased the reduction peak current …

Electrodeposition Nanolaminated Growth Of Zinc, Ying Cao, Tian-Hui Shen, Jing-Yuan Yao, Gui-Fu Ding

Journal of Electrochemistry

Nanolaminated growth of the electrodeposition of zinc was studied. The structure and size of crystalline in zinc coatings were investigated by using FEG-TEM and XRD. The corrosion tests of the zinc deposition and the Coatings-Neutral salt spray test were performed, the capability in corrosion resistance of the nanolaminated growth was better than that of others.

Optical Characterization Of Ceramic Thin Films: Applications In Low-Temperature Solid Oxide Fuel-Cell Materials Research, Vladimir Petrovsky, Tatiana Petrovsky, Harlan U. Anderson, Brian P. Gorman

Materials Science and Engineering Faculty Research & Creative Works

Characterization of thin film solid oxide fuel-cell materials can be difficult due to the range of porosities in electrodes and electrolytes as well as the nano-sized pores and particles. In this study, optical characterization techniques such as ultraviolet-visible transmission and reflection spectrophotometry are illustrated as methods for achieving information about the film density from the film refractive index as well as the film thickness. These techniques were used to investigate the sintering process of colloidal CeO2 on sapphire substrates and polymeric precursor-derived ZrO2:16%Y (YSZ) thin films on silicon over the temperature range 400-1000 °C, and the results were compared with …

Durability And Stability Of Briquetting From Solid Agricultural Wastes, Ishaq Oladapo Adeleke

Archived Theses and Dissertations

This study is concerned with the transformation of agricultural wastes into useful solid form of energy known as briquettes. Being agricultural in nature, Egypt disposes huge quantities in adhoc manner resulting in economic loss and adverse environmental consequences. This improved form of agricultural waste eases utilization and storage. Two major parameters -residue size and processing conditions- were investigated. Bagasse-mudcake mixture, cotton stalk, rice straw and com stalk are the residues studied for briquetting. Since stable and durable briquettes are important qualities density and strength of the formed briquettes are calculated as measures of stability and durability. The problem is too …

A Micromachined Thermo-Optical Light Modulator Based On Semiconductor-To-Metal Phase Transition, Lijun Jiang

Dissertations

In this research, a micromachined thermo-optical light modulator was realized based on the semiconductor-to-metal phase transition of vanadium dioxide (VO₂) thin film. VO₂ undergoes a reversible phase transition at approximately 68 0C, which is accompanied with drastic changes in its electrical and optical properties. The sharp electrical resistivity change can be as great as five orders. Optically, VO₂ film will switch from a transparent semiconductor phase to a reflective metal phase upon the phase transition. The light modulator in this research exploits this phase transition related optical switching by using surface micromachined low-thermal-mass pixels to achieve …

Reactive Modification Of Polyesters And Their Blends, Chen Wan

Dissertations

As part of a broader research effort to investigate the chemical modification of polyesters by reactive processing a low molecular weight (MW) unsaturated polyester (UP) and a higher MW saturated polyester, polyethylene terephthalate (PET), alone or blended with polypropylene (PP) were melt processed in a batch mixer and continuous twin screw extruders. Modification was monitored by on-line rheology and the products were characterized primarily by off-line rheology, morphology and thermal analysis. Efforts were made to establish processing/property relationships and provide an insight of the accompanying structural changes. The overall response of the reactively modified systems was found to be strongly …

Fabrication And Characterization Of Microcrystalline Silicon Solar Cells, Liwei Li

Dissertations

In this study, single junction p-i-n μc-Si:H solar cells were prepared using plasma of silane diluted by hydrogen in a low-cost, single chamber, non-load-locked RF-PECVD system. Direct structural characterization of μc-Si:H solar cells, rather than stand-alone films, was conducted using Raman Spectroscopy, XRD, and AFM. Strong correlations among device deposition, i-layer structural properties, and device performance have been established. With such correlations, critical issues in fabricating low-cost, large-scale, high performance μc-Si:H solar cells were identified.

The critical importance of seeding processes in determining the microstructure of μc-Si:H i-layers and performance of μc-Si:H solar cells has been demonstrated. Using …

Simultaneous Heat And Mass Transfer To A Liquid Through Two Separated Interfaces, Ku-Il Park

Theses

The oxygenator is the main element of a heart-lung machine, which takes over the work of the lungs (adding oxygen to and removing carbon dioxide from the blood) during an operation. Oxygenators function by passing oxygen through a hollow fiber (straw-like fiber), where blood gases are exchanged via tiny pores in the fiber walls. In this study, a fiber-in-fiber technology was used to design a temperature controlled blood oxygenator membrane module. A Celgard® X-10 hollow fiber was put through the lumen of a polypropylene hollow fiber having a solid wall. Both fibers are made of polypropylene and are waterproof due …

Chemical Vapor Deposition Of Polymeric Films, Chi Yu

Theses

Poly-peri-naphthalene (PPN) is a one-dimensional (1 -D) graphite polymer with unique planar ladder-like conjugated molecular structure. PPN was predicted to be a good intrinsic conductor and have high thermal stability and high environmental stability.

In this project, chemical vapor deposition (CVD) and plasma enhanced chemical vapor deposition (PECVD) of carbon films with PPN structure using PTCDA as precursor were carried out under different conditions. There is only limited information in literature on the synthesis of PPN films by PECVD process, which may allow deposition at a higher rate with lower substrate temperature. In this work the influence of deposition parameters, …

High Temperature Heat Exchanger Project (Hthx) Project Quarterly Report, University Of Nevada, Las Vegas. Research Foundation

Publications (NSTD)

On October 24, 2003, the University of Nevada, Las Vegas (UNLV) hosted an all-day HTHX Kickoff Meeting attended by all participating institutional representatives and researchers. Objectives of this meeting were to identify near-term research objectives, coordinate collaborative activities, and identify required urgent action items.

Modeling, Fabrication, And Optimization Of Niobium Cavities: Phase Iii Second Quarterly Report, 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 are the most appropriate shape for superconducting cavities. The need for very clean surfaces lead to the use of a buffered chemical polishing produce for surface cleaning to get good performance of the cavities. The third phase concludes the experimental a fluid flow study and optimization study. The first quarter and second quarter of phase three also begins the experimental set-up of secondary emission studies from niobium in superconducting mode. This …

Mapping Surface Polarization In Thin Films Of The Ferroelectric Polymer P(Vdf-Trfe)., Bradley W. Peterson, Stephen Ducharme, Vladimir M. Fridkin, Timothy J. Reece

Stephen Ducharme Publications

Pyroelectric Scanning Microscopy (PSM) has been developed to enable mapping of surface polarization in ferroelectric thin films, in particular the copolymer polyvinylidene fluoride trifluororethylene, or P(VDF-TrFE). The Chynoweth method for dynamically measuring pyroelectric current is employed in conjunction with a micropositioning system to construct two-dimensional images of the film polarization. These images have revealed enhancement of the polarization near the edges of the film below the average coercive field, with the center's polarization increasing thereafter to meet the edge value at saturation.

Joining Challenges In The Packaging Of Biomems, Hans Herfurth, Reiner Witte, S. Heinemann, Golam Newaz, Ahsan Mian, Daniel Georgiev, Greg Auner

Mechanical and Materials Engineering Faculty Publications

Micro-joining and hermetic sealing of dissimilar and biocompatible materials is a critical issue for a broad spectrum of products such as micro -electronical, micro -optical and biomedical products and devices. Novel implantable microsystems currently under development will include functions such as localized sensing of temperature and pressure, electrical stimulation of neural tissue and the delivery of drugs. These devices are designed to be long-term implants that are remotely powered and controlled. The development of new, biocompatible materials and manufacturing processes that ensure long-lasting functionality and reliability are critical challenges. Important factors in the assembly of such systems are the small …

Processing, Microstructural And Mechanical Characterization Of Mechanically Alloyed Al-Al2o3 Nanocomposites, Pushkar Katiyar

Electronic Theses and Dissertations

Aluminum-alumina nanocomposites were synthesized using mechanical alloying of blended component powders of pure constituents. This study was performed on various powder mixtures with aluminum as the matrix and alumina as the reinforcement with volume fractions of 20, 30, and 50 % and Al2O3 particle sizes of 50 nm, 150 nm, and 5 µm. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used for the crystal structure and microstructural characterization of the powders at different stages of milling. Al2O3 powders with 50 nm and 150 nm particle size were predominantly of γ-type, while Al2O3 of 5 µm size was …

Cfd Analysis Of Unsteady Separated Transonic Oscillation Cascade Aerodynamics, Xuedong Zhou, J. Mitch Wolff

Mechanical and Materials Engineering Faculty Publications

With an improved algebraic mesh-deforming algorithm, STAR-CD, a commercial computational fluid dynamics (CFD) solver is employed for the numerical analysis of a transonic oscillating linear cascade of advanced design blades. The center blade oscillates 0.6-degrees about the middle cord. The numerical simulation is conducted for a frequency range from 200 Hz to 500 Hz. A hybrid grid, which utilizes a structured O-grid around the airfoil and an unstructured grid everywhere else is employed. The Spalart-Allmaras (S-A), one equation turbulence model, along with other two equation k-ε models, are also utilized for the steady state simulation. The S-A turbulence …

Microwave Induced Preparation Of A-Axis Oriented Double-Ended Needle-Shaped Zno Microparticles, Suresh Pillai, John Kelly, Graeme Watson, Deirdre Ledwith

Articles

Microwave irradiation of solutions of Zn(NO₃)₂ and urea provides a straightforward route to a-axis oriented crystals of needle-like morphology.

Low-Temperature Crystallization Of Sol–Gel Processed Pb0.5ba0.5tio3: Powders And Oriented Thin Films, Suresh Pillai, Stacey Boland, Sossina Haile

Articles

A novel sol– gel process suitable for depositing thin-film lead
barium titanate has been developed. X-ray diffraction analysis
showed perovskite phase crystallization to occur at a temperature
as low as 400°C with single-phase Pb0.5Ba0.5TiO3 (PBT)
resulting at a temperature as low as 500°C. Small concentrations
of barium carbonate were evident by X-ray diffraction at
400°C, and indications of minor, carbonate-containing phases
were evident by FTIR at 600°C. Deposition of the sol by spin
coating on single-crystal and thin-film MgO on silicon resulted
in highly oriented PBT films after calcination at 600°C. Mixed
(100)/(001) films were obtained on single-crystal MgO,
whereas …

Optical Characterization Of Ceramic Thin Films: Applications In Low-Temperature Solid Oxide Fuel-Cell Materials Research, B. P. Gorman, V. Petrovsky, Harlan U. Anderson, T. Petrovsky

Materials Science and Engineering Faculty Research & Creative Works

Characterization of thin film solid oxide fuel-cell materials can be difficult due to the range of porosities in electrodes and electrolytes as well as the nano-sized pores and particles. in this study, optical characterization techniques such as ultraviolet-visible transmission and reflection spectrophotometry are illustrated as methods for achieving information about the film density from the film refractive index as well as the film thickness. These techniques were used to investigate the sintering process of colloidal CeO₂ on sapphire substrates and polymeric precursor-derived ZrO₂:16%Y (YSZ) thin films on silicon over the temperature range 400-1000 °C, and the results …

Characterization And Modeling Of Local Electromechanical Response In Stress-Biased Piezoelectric Actuators, N. Navapan-Traiphol, Robert W. Schwartz, Daniel S. Stutts, J. Wood

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Numerous investigators have explored the factors that contribute to the high electromechanical performance of stress-biased actuators with particular attention being given to the importance of the extrinsic (domain wall translation) response mechanism. Based on the variation in lateral stress through the thickness of the piezoelectric layer within these devices, it has been suggested that the piezoelectric coefficient varies as a function of position within the layer, though no direct evidence has been previously presented. In this study, the results of Moire interferometry investigations of local strains within these devices are reviewed. The technique permits effective depth-profiling of local deformations at …

Preparation Of (Pb,Ba)Tio3 Powders And Highly Oriented Thin Films By A Sol-Gel Process, Stacey Boland, Suresh Pillai, Wein-Duo Yang, Sossina Haile

Articles

Solid solution Pb1-xBaxTiO3, with particular emphasis on Pb0.5Ba0.5TiO3, was prepared
using a sol-gel process incorporating lead acetate trihydrate, barium acetate, and
titanium isopropoxide as precursors, acetylacetone (2,4 pentanedione) as a chelating
agent, and ethylene glycol as a solvent. The synthesis procedure was optimized by
systematically varying acetylacetone: Ti and H2O:Ti molar ratios and calcination
temperature. The resulting effects on sol and powder properties were studied using
thermogravimetric analysis/differential scanning calorimetry, Fourier transform infrared
spectroscopy, Brunauer-Emmett-Teller analysis, and x-ray diffraction (XRD).
Crystallization of the perovskite structure occurred at a temperature as low as 450 °C.
Thin films were prepared by spin …