Materials Science and Engineering Commons^™

Preparation Of The Protic Ionic Liquid/Pvdf-Hfp Composite Membranes And Its Performance For Dmfc, Rui-Ying Miao, Jian-Ling Li, Yong Fang, Xin-Dong Wang

Journal of Electrochemistry

The protic ionic liquid(PIL) α-methyl pyridinium trifluoroacetate([α-MPyH]Tfa) was synthesized by acid & alkali neutralization.Then PIL/PVDF-HFP composite membranes were prepared by means of phase inversion method using acetone as solvent.The conductivities of the composite membrane increased with the temperature and reached 8×10^-3 S/cm,1×10^-2 S/cm and 3×10^-2 S/cm at room-temperature,30 ℃ and 80 ℃,respectively,by electrochemical impedance method.The properties of the methanol-rejecting of the membranes were measured by chronoamperometry as well.The results indicate that the properties of methanol-resistance of the membranes before and after IL combination were equivalent approximately.

Synthesis,Characteristics And Electrochemical Performance Of Nano-Sized Snco/Graphite Composites As Anode For Lithium Ion Batteries, Jin-Shu Cai, Ling Huang, Fu-Sheng Ke, Shi-Gang Sun

Journal of Electrochemistry

The nano-structural Sn-Co/graphite composites were prepared by chemical reduction of the alloy electroless deposition solution in graphite suspensions, and the composites were annealed at 500 ℃. The phase structure and surface morphology of the composites were measured by XRD, SEM and Raman. The results indicate that there were high dispersions and high loadings of Sn-Co nanoparticles on graphite by thermal treatment. Electrochemical lithium storage performance was studied preliminarily on the obtained samples. The graphite modified with the Sn-Co nanoparticles possessed a higher electrochemical reversible capacity than that of graphite during the charge and discharge process. The appetency between the Sn-Co …

Corrosion Research On Rock Bolts And Steel Sets For Sub-Surface Reinforcement Of The Yucca Mountain Repository, Dhanesh Chandra, Jaak J.K. Daemen

Publications (YM)

Underground nuclear waste storage repositories generally use steels and super alloys for various structural members and storage containers. These materials are susceptible to corrosion due to seepage of water. We studied rock bolt materials for reinforcing tunnels and containment materials for storing nuclear waste materials. In general, the design of underground support materials for tunnels are mainly based on mechanical behavior of the materials, but not much was known about the interaction of the seepage YM waters with the structural members under various conditions in the tunnels. The sources of water in the Yucca Mountain (YM) repository are due to …

Mesoporous Carbon For High Power Supercapacitors, Bin Xu, Lu Peng, Guo-Qing Wang, Gao-Ping Cao, Feng Wu, Yu-Sheng Yang

Journal of Electrochemistry

Mesoporous carbon for supercapacitors was prepared from sucrose using nano-CaCO₃ as template.The microstructure of the carbon was characterized with N₂ adsorption and transmission electron microscopy(TEM) observation.The electrochemical performances were evaluated in 6mol·L^-1 KOH aqueous electrolyte with galvanostatic charge/discharge,cyclic voltammetry,and ac impedance spectroscopy.The sucrose-based mesoporous carbon had a surface area of 606 m²/g and enriched mesopores in the range of 10～30 nm.The mesoporous carbon presented a specific capacitance of 125 F/g at a current density of 50 mA/g and outstanding excellent rate performance.As the current density increased to 20 000 mA/g,its capacitance remained at 88 F/g,much …

Preparation And Performance Of The Thin-Film Libpon Electrolyte, Feng Wu, Ya-Dong Liu, Ren-Jie Chen, Shi Chen

Journal of Electrochemistry

The LiBPON thin-film electrolyte was prepared by magnetron sputtering,and the relationship between the performance and the deposition condition was investigated.As seen in the SEM images,the thin films are dense and uniform without cracks,and according to the XRD patterns they have an amorphous structure.The electrochemical performance of the electrolyte was characterized by electrochemical impedance spectroscopy(EIS).The ionic conductivities of the thin film decreased with the RF power,but increased with the N₂ pressure.The an ionic conductivity of 3.5×10^-6 S/cm at room temperature was found from the electrochemical measurement.While the deposition rate increased with the RF power,but decreased with the N_{2 …}

Hydrothermal Preparation And Electrochemical Characterizations Of Vanadate Compound Nav2O5 Crystals, Fang Hu, Xing Ming, Fei Du, Ying-Jin Wei, Gang Chen, Chun-Zhong Wang

Journal of Electrochemistry

The NaV₂O₅ was prepared by a low temperature hydrothermal process. The material crystallized in the layered orthorhombic structure with space group Pmmn. X-ray diffraction confirmed that the material was pure and the scanning electron microscopy showed that the material was composed of needle crystals with 20 μm in length and 200 nm in width. X-ray photoelectron spectroscopy indicated the co-existence of V⁴⁺ and V⁵⁺ in the material,which results in an average V^4.5+ oxidation state of the material. The observed Raman bands were ascribed to different V-O vibrations. The first specific capacity about 120 mAh/g …

Photoelectrochemical Properties Of Tio2 Nanoparticles, Jie Qu, Ying Li, Qi-Wei Jiang, Xue-Ping Gao

Journal of Electrochemistry

The protonated titanate nanoparticles were obtained at room temperature and subsequently calcined at different temperatures(300 ℃,400 ℃,500 ℃,600 ℃ and 700 ℃) in air.The obtained products were characterized by XRD,TEM and UV-Vis.It is found that the grain sizes of TiO₂ nanoparticles calcined at 300 ℃ were about 20 nm,and increased gradually with the temperature rise.Photoelectric performance was measured with I～V curve and electrochemical impedance spectroscopy(EIS).The TiO₂ nanoparticles obtained at 500 ℃ showed the best photoelectrochemical properties with a photovoltaic conversion efficiency of 6.39%,which is much higher than those at other temperatures.In addition,it is also demonstrated that the charge …

Electrooxidation Behaviors Of Tib2 As High Capacity Anodic Material In Neutral Aqueous Electrolytes, Ya-Dong Wang, Xian-Yong Guang, Zhi-Xin Wang, Xin-Ping Ai, Han-Xi Yang

Journal of Electrochemistry

Titanium diborides were investigated as an anodic material for neutral aqueous batteries. It is revealed that this material shows superiorly high electrochemical activities in the neutral electrolytes. The discharge capacities observed for TiB₂ reached 1300 mAh/g at the constant current density of 50 mA/g, exceeding all the metal electrodes reported so far. The electrooxidation of this compound was found to proceed via the electrochemical dissolution of boron to form borofluoride, while titanium remained unchanged at the electrode. These results suggest a possible use of the boride compounds as a new material for constructing neutral aqueous batteries with high electrochemical …

The Electrochemical Performance Of Ncf-Sulfur Cathode, Chun-Rong Zhao, Zhong-Bao Yu, Wei-Kun Wang, Yu-Sheng Yang

Journal of Electrochemistry

The electrochemical performance of NCF-sulfur cathode, with different NCF contents, was investigated by constant current discharge, cyclic voltammetry and AC impedance methods. The morphologies of the cathodes were observed using scanning electron microscopy. The results indicate that the cycle life and rate capability of NCF-sulfur cathode increased. Better performance of sulfur cathode was obtained by 3% and 5% NCF conductive addition. When the current density was 0.4 mA/cm², the 3% NCF-sulfur cathode had an initial capacity of 880 mAh/g and a reversible capacity of 630 mAh/g after 20 cycles.

Preparation And Characterization Of Tin-Nickel Alloy Electromagnetic Shielding Fabric, Ke-Jing Chu, Wei Wang, Bin Sun, Mei-Fang Zhu

Journal of Electrochemistry

A soft electromagnetic shielding fabric was successfully prepared by electroplating tin-nickel alloy on the Cu-plated PET fabric in potassium pyrophosphate system. Results show that the different tin content and different colour can be obtained by changing the ratio of metals in bath. Better corrosion resistance and anti-tarnishing were achieved with the fabric consisting of 68.96% Sn. The tin-nickel alloy surface for the electromagnetic shielding fabric had excellent conductivity, softness, permeability and soft luster, non-sensitized to the human body. Thereby it has broad prospect in EMI field and shielding clothing.

Electrosynthesis Of 2,2-Dimethylolpropionic Acid, Hong-Yan Sun, Zhen-Hai Liang

Journal of Electrochemistry

The Ti/SnO₂+Sb₂O₄/PbO₂ electrode was prepared.The structure phase and valent state were characterized by means of XRD and XPS.The 2,2-dimethylolpropionic acid was synthesized on the Ti/SnO₂+Sb₂O₄/PbO₂ anode by direct electro-oxidation of 2,2-dimethylolpropionaldehyde.The product and crude material were analyzed by HPLC,the effects of the concentration of 2,2-dimethylolpropionaldehyde,pH,potential and reaction temperature were studied.The results showed that the optimum conditions were anode potential 1.8 V,pH=1,reaction temperature 15 ℃ and 2,2-dimethylolpropionaldehyde concentration 0.10mol/L.Under the optimum conditions,the selectivity of 36%,the current efficiency of 28% and the conversion of 58% were reached.The reported …

The Electrochemical Behavior And Determination Of Carbendazim On Iron Montmorillonite Modified Electrode, Xiao-Li Jiang, Rong Li, Xiao-Ying He, Jiang Li, Ying Li

Journal of Electrochemistry

The FeCl₃ modified clay electrode was made.The electrochemical behavior of carbendazim(BCM) on the modified electrode was studied by cyclic voltammetry.The impacts of pH,scan rate and dosages of modifier were discussed and the important kinetic parameters of the electrochemical process were determined.The results indicated that the process was controlled by diffusion.The effective area of FeMM-CMC/GCE(A)=0.027 cm²,the transfer electron numbers(n)=2 and the diffusion coefficient(D)=5.115×10^-6cm²/s.Under the optimized conditions,a good linearity was found between the first order derivative of peak current and concentration of BCM in the range of 2.00×10^-5～8.00×10^-4mol/L,with i′p=-8.045×10^-7-0.0237c,correlation …

On Stresses Induced In A Thermal Barrier Coating Due To Indentation Testing, Jin Yan, Anette M. Karlsson, Marion Bartsch, Xi Chen

Mechanical Engineering Faculty Publications

Instrumented indentation has been suggested as a method to determine interfacial fracture toughness of thermal barrier coatings. However, in a previous experimental study we showed that the results are ambiguous. In this work, we investigate the experimental results by numerical simulations incorporating the material microstructure. In the numerical simulations, based on finite element analyses, the stress fields that are associated with the loading and unloading of the indenter are investigated. By comparing these stress fields to the damage observed in the experimental study, including crack path and interfacial delaminations, we explain key findings from the experimental observations. Our results suggest …

Effect Of Synthesis Time And Treatment On Porosity Of Mesoporous Silica Materials, Asli Ertan, Pradeep Kodumuri, Orhan Talu, Surendra N. Tewari

Chemical & Biomedical Engineering Faculty Publications

Nitrogen adsorption at 77 K on mesoporous silica materials (MPS) with varying synthesis time and treatment conditions was investigated. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were also used to characterize the mesoporous materials. This study was performed at 6, 24 and 72-h synthesis times. It is shown that 6-h is not enough for complete formation of the MPS material and at least 24-h is necessary. The pore structure starts decaying for the 72-h synthesis time. The three-after-synthesis treatment conditions used were 1) washed, 2) washed and calcined and 3) directly calcined after synthesis. Ethanol/HCl …

Magnetic Ordering In The Rare Earth Intermetallic Compound Tb₂Ti₃Ge₄: Magnetization And Neutron Diffraction Studies, Satish K. Malik, Jagat Lamsal, R. L. De Almeida, S. Quezado, William B. Yelon, V. O. Garlea, A. V. Morozkin, R. Nirmala

Physics Faculty Research & Creative Works

Magnetization and neutron diffraction studies on a polycrystalline Tb2Ti3Ge4 sample (orthorhombic Sm5Ge4-type structure, space group Pnma, No. 62) have been carried out. This compound is found to order antiferromagnetically at ~18 K (TN). The magnetization (M) versus field (H) isotherms obtained at 2, 3, 5, and 10 K indicate a field-induced antiferromagnetic to ferromagnetic transition in fields of the order of 0.5 T. The saturation magnetization value at 2.5 K (M extrapolated to 1/H-->0) is only ~5.6µB/Tb3+, suggesting the possible presence of crystal field effects with or without a persisting antiferromagnetic component. Neutron powder diffraction data at 10 K …

Finite Element Model Updating Approach To Damage Identification In Beams, Mohamed Medhat Saada

Archived Theses and Dissertations

No abstract provided.

Surface And Bulk Passivation Of Multicrystalline Silicon Solar Cells By Silicon Nitride (H) Layer : Modeling And Experiments, Chuan Li

Dissertations

The objective of this dissertation is to study passivation effects and mechanisms in Si solar cells, specifically, the surface and bulk passivation by hydrogen-rich PECVD silicon nitride (SiN :H) antireflection layer on multicrystalline silicon (me-Si) solar cells.

The passivation of silicon surface can be achieved in two ways: by field-effect passivation and/or by neutralization of interface states. In other words, the deposition should result in a high value of fixed charge, Qf and /or a low value of interface state density, D1. The surface recombination velocity can be described by Shockley-Read-Hall (SRH) statistics.

Current SRH formalisms have failed to explain …

An Investigation Of Students’ Conceptual Understanding In Related Sophomore To Graduate-Level Engineering And Mechanics Courses, Devlin Montfort, Shane Brown, David Pollock

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

Interviews were conducted with students from a sophomore-level mechanics of materials class, a sophomore/junior-level structures class, a senior-level steel design class and a graduate-level advanced steel design class to investigate students’ conceptual understanding of bending and normal stress. The graduate students generally demonstrated higher computational skill and confidence but they were not significantly different from the sophomores in terms of conceptual understanding. Interestingly, the seniors showed markedly lower confidence in their ability to solve the problems posed in the interviews. Common difficulties include a conceptual definition of stress and reasoning involving the normal stresses developed under bending.

Characterization Of A Viscoelastic Response From Thin Metal Films Deposited On Silicon For Microsystem Applications, Steven L. Meredith

Master's Theses

Understanding the mechanisms that control the mechanical behavior of microscale actuators is necessary to design an actuator that responds to an applied actuation force with the desired behavior. Micro actuators which employ a diaphragm supported by torsional hinges which deform during actuation are used in many applications where device stability and reliability are critical. The material response to the stress developed within the hinge during actuation controls how the actuator will respond to the actuating force. A fully recoverable non-linear viscoelastic response has been observed in electrostatically driven micro actuators employing torsional hinges of silicon covered with thin metal films. …

Start The Presses, Stephen V. Ducharme, Alexei Gruverman

Stephen Ducharme Publications

A simple nanoimprinting method creates arrays of ferroelectric polymer structures suitable for low-cost, non-volatile memories. With the development of nanoimprinted high-quality ferroelectric nanomesa arrays, it seems that we now have all the necessary ingredients to print inexpensive, disposable organic memory chips.

Effectiveness Of Thermal Oxidation In Relation To Anterior Cervical Plates, Katherine A. Miyashiro

Master's Theses

Ti-6Al-4V anterior cervical plates (ACP) are used in spinal fusion surgeries to fixate cervical vertebrae during graft adhesion. However, documented cases of implant failure and the potential for ACP corrosion raise concerns regarding any degradation of material resulting from extended implantation. In addition, abrasion during implantation may damage a section of the protective oxide layer, potentially exposing surrounding tissues to the harmful effects of bare titanium, aluminum, and vanadium. Thermal oxidation has been shown to improve corrosion-resistance and wear-resistance, depending on temperature and time. To quantify the attributes of the thermally grown oxide layer, Ti-6Al-4V coupons underwent thermal oxidation treatments …

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Agegnehu Atena, Mikhail Khenner

Mathematics Faculty Publications

In this paper the lubrication-type dynamical model is developed of a molten, pulsed laser-irradiated metallic film. The heat transfer problem that incorporates the absorbed heat from a single beam or interfering beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the peak laser beam intensity, the film optical thickness, the Biot and …

Thermocapillary Effects In Driven Dewetting And Self-Assembly Of Pulsed Laser-Irradiated Metallic Films, Agegnehu Atena, Mikhail Khenner

Mathematics Faculty Publications

In this paper the lubrication-type dynamical model is developed of a molten, pulsed laser-irradiated metallic film. The heat transfer problem that incorporates the absorbed heat from a single beam or interfering beams is solved analytically. Using this temperature field, we derive the 3D long-wave evolution PDE for the film height. To get insights into dynamics of dewetting, we study the 2D version of the evolution equation by means of a linear stability analysis and by numerical simulations. The stabilizing and destabilizing effects of various system parameters, such as the peak laser beam intensity, the film optical thickness, the Biot and …

Synthesis And Dip-Pen Nanolithographical Patterning Of Ferrite Nanoparticles, Jingwen He

Material Science and Engineering Theses - Archive

Magnetic nanoparticles are of great interest for researchers from a wide range of disciplines, including magnetic fluids, catalysis, biotechnology/biomedicine, magnetic resonance imaging, data storage, and environmental remediation. Ferrites, a class of ferrimagnetic ceramic compounds with the chemical formula of MFe₂O₄, where M represents any one of several metallic elements such as Mg, Fe, Co, Ni, Cu and so on, are commonly used magnetic materials for nanoparticles. Magnetite (Fe3O₄) is the prototype of ferrites. Magnetite nanoparticles have been prepared through the co-precipitation of Fe²⁺ and Fe³⁺ aqueous salt solutions by addition of base. They exhibit a size distribution from 4 nm …

Synthesis And Tribological Properties Of Dlc Film By Rf Pacvd: Effect Of Processing Parameters, Pruthul Desai

Material Science and Engineering Theses - Archive

Diamond-like carbon (DLC) films, have gained grounds in many industries ranging from automobile and oil and gas to electronics and bio fields due to their low friction and wear rate, chemical inertness and high hardness. Radio Frequency (RF) plasma discharge has been widely used to produce amorphous carbon films, because this method can be applied not only for etching but also for deposition on insulators. The advantage of RF plasma discharge is the application for wide area and the stability as compared with direct current (DC) plasma. The properties of DLC films deposited by RF plasma-assisted chemical vapor deposition (PACVD) …

Tribological Behavior Of Nanocrystalline Metals Prepared By Surface Mechanical Attrition Treatment, Michael Frink

Material Science and Engineering Theses - Archive

Nanocrystalline materials have shown great promise for a number of engineering applications ranging from structural and electronics to biomaterials and drug delivery. Nanoscale grain structures can cause tremendous improvements in strength, hardness and other mechanical properties. This is partially due to the suppression of dislocations within nanocrystalline grains and the entirely different deformation modes active at that scale. In spite of anticipated benefits, very little work has been performed to explore nanoscale effects on the tribological behavior of materials. Surface Mechanical Attrition Treatment (SMAT) is an effective and economical method to produce nanostructured surface layers in bulk materials. The process …

Thioacetamide As A Sulfur Precursor For Chalcopyrite Thin Film Solar Cells, Alex Alphonse

Material Science and Engineering Theses - Archive

Chalcopyrite CuInS₂ (CIS) thin films have the potential to be used in low cost terrestrial photovoltaic applications. The band gap of CIS is around 1.5 eV [1] and it well matches with the solar spectrum. However, the power conversion efficiencies in CIS solar cells are presently limited to 13.2% [2]. CIS absorber layers can be produced in a simple two-stage process consisting of the physical vapor deposition of a Cu-In bilayer - generally with Cu-rich composition - and its subsequent sulfurization under sulfur atmosphere made by either sulfur vapor or H₂S. While sulfur vapor is a safer option than H₂S …

Effect Of Reflow Variables On The Nanoscale Mechanical Properties Of Lead Free Solders, Tonye Adeogba

Material Science and Engineering Theses - Archive

This study presents findings on the nano-mechanical properties of binary and ternary (Cu, Ag) - Sn Solders. Nanoindentation with a cube corner tip was used on Sn-Ag and SAC405 alloy compositions to investigate the effect of reflow process variables on the properties of hardness and reduced modulus on a nanoscale. The specimens tested were sandwich solder joints where Cu was the substrate. While the reflow variables of cooling rate and reflow time were found to cause changes in IMC morphology and solder matrix microstructure, the nano hardness and reduced modulus were independent of these variables. Low max loads coupled with …

Negative Differential Resistance In Hydrated Deoxyribonucleic Acid Thin Films Mediated By Diffusion-Limited Redox Reaction, Hou Kuan Lee

Material Science and Engineering Theses - Archive

The charge transport mechanisms in DNA proposed in the literature cover broad range of possibilities including molecular band conduction, superexchange, multistep hole hopping, and polaron hopping. The reason for the surprisingly diverse results is all the variables in the experiments - DNA sequence, DNA characteristic (single molecule or bundle, DNA length), the metal/DNA contacts, and the environmental dissimilarities in temperature, humidity, etc. In this study, the humidity effect on the electrical conduction in DNA was systematically investigated in a humidity chamber over the wide range of DC voltage. The exponential increase in conduction with increasing humidity was observed for the …

Mechanism Of Wear Protection Of Al-Alloys Using Xanes, Beibei Wang

Material Science and Engineering Theses - Archive

The mechanism of wear protection of Al-Si alloys in wear tests using lubricants containing Zinc dialkyl-dithiophosphate (ZDDP), Dialkyl dithiophosphate (DDP) , Amine phosphates, Thiadiazole, Antimony 0, 0-dialkylphosphorodithioate (SbDDP) was studied. Using techniques such as XANES this study examined the tribological behavior of these compounds and the characteristics of the tribofilms formed by them. High frequency reciprocating rig (HFRB) tests were conducted with lubricant containing these five antiwear additives were compared in both base oil and fully formulated oil. The tribofilms formed were then analyzed by a variety of techniques such as Scanning electron microscopy of the film and the composition …