Materials Science and Engineering Commons^™

Multi-Electron Redox Materials For High Energy Density Electrodes, Xin-Ping Ai, Han-Xi Yang

Journal of Electrochemistry

Various new energy technologies being developed require electrochemical energy batteries to have a real breakthrough in energy density and rate capability,which imposes a great challenge for electrochemists and materials chemists. Multi-electron redox reactions seem to open a promising avenue to create new batteries with dramatically enhanced energy densities. This paper describes simply our research works on the multi-electron redox systems,including metal boride anode,lithium alloying compounds and electrochemical conversion materials, and also discusses the problems hindering these systems for battery applications.

In Situ Surface-Enhanced Raman Scattering Spectroscopic Study Of Sulfur Adsorption On Polycrystalline Platinum Electrode Surface, Bolian Xu, In-Su Park, Ying Li, De-Jun Chen, Yuye J. Tong

Journal of Electrochemistry

The paper reports the first in situ surface enhanced Raman scattering (SERS) spectroelectrochemistry study of sulfur adsorption and electro-oxidation on highly roughened polycrystalline Pt surface in both acidic and basic supporting electrolytes. The SERS spectra were taken at a constant electrode potential after accumulative electro-oxidation CVs of the Pt electrode with pre-adsorbed sulfur species and at different electrode potentials that were varied stepwise of the Pt electrode immersed in sulfur-containing electrolytes without pre-adsorbed sulfur species. In both cases,a dominant vibrational band at 299 cm^-1 in acidic electrolyte but at 310 cm^-1 in basic electrolyte was observed,which was assigned …

Preliminary Investigation Of Iron Protoporphyrin Sams On Platinum Electrodes By Surface Enhanced Vibrational Spectroscopies, Min Ma, Yao-Yue Yang, Han-Xuan Zhang, Wen-Bin Cai

Journal of Electrochemistry

In situ SERS and ATR-SEIRAS were applied to investigate the electrochemical and structural properties of iron protoporphyrin IX (FePP) self-assembled monolayers (SAMs) on Pt electrodes in 0. 1 mol· L -1 HClO₄. The potential dependent SERS spectra of the FePP SAM on a roughened Pt electrode with the enhancement factor of ca. 40 were acquired with the excitation line of 514 nm. Analyses of SERS data over the potential region from 0. 5 to -0. 3 V enabled to obtain potential dependent adsorption isotherms,from which the formal redox potential could be estimated to be ca. -0. 2 V. …

Solid State Nmr Studies Of Lithium Manganese Silicate As Positive Electrode Materials For Li-Ion Batteries, Hu Cheng, Zi-Geng Liu, Yi-Xiao Li, Zhong Chen, Yong Yang

Journal of Electrochemistry

The Li₂MnSiO₄ cathode material for lithium ion batteries was synthesized by sol-gel assisted hydrothermal method. XRD,FTIR and SS-NMR were used to study the phase,structure and morphology of obtained samples. Electrochemical performance of cathode material was tested. The results show that the main phase of sample prepared was Li₂MnSiO₄,whereas a small amount of impurities (Li₂CO₃) were existed. The Li₂MnSiO₄ cathode material gave an initial discharging capacity of about 190 mAh·g ^-1. But this capacity faded rapidly during the cycling process due to the decomposition of Li …

Comparative Study Of Nanoporous Pt, Ptru And Ptruir Catalysts Using Electrochemical Ftir Spectroscopy, M. Amussen Robert, Holt-Hindle Peter, Nigro Samantha, Aicheng Chen

Journal of Electrochemistry

In recent years much effort has been put towards developing efficient Pt-based electrocatalysts for applications in fuel cells. With the rising cost of precious metals such as Pt,the need to enhance the activity and to decrease the load of catalysts is prominent. Herein we report on the synthesis and comparative study of nanoporous Pt,PtRu and PtRuIr electrocatalysts. The nanoporous electrodes were fabricated using a hydrothermal method and characterized by scanning electron microscopy (SEM) ,energy dispersive spectroscopy (EDS) ,X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) . The electrocatalytic activity of the fabricated nanopo- rous materials was evaluated using both CO …

Studies Of Oxidation Processes Of Adsorbed And Solution Co On Pt(110) Electrode By Cyclic Voltammetry And In Situ Ftirs, Li Tian, Jun-Tao Li, Jin-Yu Ye, Chun-Hua Zhen, Shi-Gang Sun

Journal of Electrochemistry

The oxidation processes of adsorbed CO (COad) and solution phase CO (COsol) on Pt(110) electrode were investigated by cyclic voltammetry and in-situ FTIR spectroscopy. It has revealed that in comparison with COad on Pt(110) in a CO-free solution,the oxidation current peak of COsol in a CO-saturated solution is positively shifted ca. 168 mV,and the peak current density has been increased by 6. 70 times. Linear adsorbed CO (COL) is determined by in-situ FTIR spectroscopy as the main species,which is uniformly distributed on Pt (110) surface. In a CO-free solution,the onset potential of COL is measured by in-situ FTIRS ca. 0. …

Ebc Development For Hot-Pressed Y2O3/Al2O3 Doped Silicon Nitride Ceramics, Sivakumar Ramasamy, Surendra N. Tewari, Kang N. Lee, Ramakrishna T. Bhatt, Dennis S. Fox

Chemical & Biomedical Engineering Faculty Publications

Multilayer EBCs of alcohol and sol-based slurries containing (a) 45% SiO₂-34% Y₂O₃-%Al₂O₃, (b) mullite/Gd₂SiO₅ (88/12wt.%) with and without B₂O₃ addition, (c) mullite/rare-earth silicates (94/6wt.%, (Gd₂SiO₅, Lu₂SiO₅, Er₂SiO₅, and HfSiO₄)), and (d) only mullite, were applied on hot pressed Y₂O₃/Al₂O₃ doped Si₃N₄ substrates. Of the four major EBC systems studied, only mullite/Gd₂SiO₅ (88/12wt.%) EBCs sintered in air at …

Computer Aided Contour Profiling Of High Strength Deposits, Sriram Praneeth Isanaka, Amar Bala Sridhar, Frank W. Liou, Joseph William Newkirk

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Additive manufacturing processes suffer from the effect of ripples, edge rounding and surface variations. To reduce their effect, ideal process parameters for the laser deposition process were investigated. Also, a new method was identified to analyze deposits by accurately plotting their contours. This was achieved through point cloud data of the deposits generated using coordinate measurement and 3D scanning. Curve fitting was performed on the data in Matlab to generate the contours of the deposit. The intercept values, heights, and contact angle of the curves give an indication of the uniformity of deposits and aid in reducing defects.

Freeze Extrusion Fabrication Of 13-93 Bioactive Glass Scaffolds For Bone Repair, Tieshu Huang, Nikhil D. Doiphode, M. N. Rahaman, Ming-Chuan Leu, B. Sonny Bal, D. E. Day

Materials Science and Engineering Faculty Research & Creative Works

There is an increasing demand for synthetic scaffolds with the requisite biocompatibility, internal architecture, and mechanical properties for the bone repair and regeneration. In this work, scaffolds of a silicate bioactive glass (13-93) were prepared by a freeze extrusion fabrication (FEF) method and evaluated in vitro for potential applications in bone repair and regeneration. The process parameters for FEF production of scaffolds with the requisite microstructural characteristics, as well as the mechanical and cell culture response of the scaffolds were evaluated. After binder burnout and sintering (60 min at 700°C), the scaffolds consisted of a dense glass network with interpenetrating …

Selective Laser Sintering Of 13-93 Bioactive Glass, Krishna C. R. Kolan, Ming-Chuan Leu, Greg Hilmas, Mariano Garcia Velez

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Bioactive glasses are more promising than biopolymers in fabricating scaffolds for bone tissue repair because they convert to hydroxyapatite, when implanted in vivo. Both direct and indirect selective laser sintering (SLS) methods of 13-93 bioactive glass were considered in this research to study the feasibility of fabricating scaffolds for bone repair applications. Stearic acid was used as the binder in the indirect method to fabricate the scaffolds. The green scaffolds underwent binder burnout and sintering at various soaking conditions between 675⁰C and 700⁰C, achieving a maximum compressive strength of 23.6 MPa, which is higher than that of the human cancellous …

Optimization Of Selective Laser Sintering Process For Fabrication Of Zirconium Diboride Parts, Ming-Chuan Leu, Shashwatashish Pattnaik, Greg Hilmas

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Selective Laser Sintering (SLS) was investigated to fabricate Zirconium Diboride (ZrB₂) parts for ultra-high temperature applications. Experiments were conducted to determine values of SLS process parameters (laser power, scan speed, line spacing, and layer thickness) that can be used to build ZrB₂ parts with high integrity and sharp geometrical features. A sacrificial plate with a proper number of layers (determined from experimentation) separated from the main part was built in order to reduce thermal gradients when building the main part. The sacrificial plate was found to assist in eliminating cracks in the bottom of the main part. …

Corrosion Dynamics Of Cobalt-Chromium Alloy F-75 Powder, Tedman Tong

Master's Theses

The increasing usage of metal-on-metal joint replacements consisting of a cobalt-chromium-molybdenum alloy requires increasing concern regarding the inevitable generation of metallic wear debris. Patients with these joint replacements exhibit elevated concentrations of cobalt and chromium ions within their serum, blood and urine. The presence of these metal ions suggests the potential for bodily damage and indicates corrosive processes are acting upon wear debris.

To understand the behavior of these corrosive processes, powders of cobalt-chromium-molybdenum alloy F-75 were studied. Four powder sizes (44, 74, 105, and 420 µm diameter) were subjected to Hank’s Balanced Salt Solution (HBSS) for a 42 day …

The Effects Of Applied Strain And Heat Treatment On The Properties Of Niti Wire During Shape Setting, Frank Zapoticla

Master's Theses

NiTi components are commonly subjected to thermo-mechanical heat treatments during production and fabrication. This study investigates the effects of applied strain of 0-10% and heat treatments of 300-600ºC for times of 2-30 minutes during shape-setting of Ti–50.8 at% Ni wire with a nominal diameter of 0.495 mm and an initial transition temperature, Af, of 12ºC. Strain was applied prior to heat treatments by coiling NiTi wire, essentially producing coiled springs, around different diameter steel mandrels to obtain different strain levels. The samples of NiTi wire under applied strain were heat treated in a salt bath, followed by a rapid quench. …

Microstructure Modification Of Cu0.2ag2.8sbsete2 Through, Sloan Lindsey

All Theses

Cu0.2Ag2.8SbSeTe2 is new potential thermoelectric compound that exhibits very low thermal conductivity and a region of glass-like thermal conductivity. The compound phase segregates into AgSbTe2 and Ag2Te phases with Se and Cu acting as isoelectronic dopants. Backscatter SEM imaging is used to study the resulting microstructure. Normally cast samples exhibit cracks forming near the interfaces of the two phases. In this work we show that the cracks are caused by a low temperature monoclinic to cubic phase transition that occurs in the Ag2Te phase. We demonstrate that through rapid quenching we can control the size and shape of the phase …

52nd Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 52nd annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-endorsed by the Colorado Section of the American Chemical Society and the Society for Applied Spectroscopy. Held in Snowmass, Colorado, August 1-5, 2010.

Processing And Characterization Of New Oxy-Sulfo-Telluride Glasses In The Ge-Sb-Te-S-O System, C. (Charmayne) Smith (Lonergan), J. Jackson, L. Petit, C. Rivero-Baleine, K. Richardson

Materials Science and Engineering Faculty Research & Creative Works

New oxy-sulfo-telluride glasses have been prepared in the GeSbTeSO system employing a two-step melting process which involves the processing of a chalcogenide glass (ChG) and subsequent melting with TeO₂ or Sb₂O₃. The progressive incorporation of O at the expense of S was found to increase the density and the glass transition temperature and to decrease the molar volume of the investigated oxy-sulfo-telluride glasses. We also observed a shift of the visNIR cut-off wavelength to longer wavelength probably due to changes in Sb coordination within the glass matrix and overall matrix polarizability. Using Raman spectroscopy, correlations …

Fabrication Of Fluorescent Nanoparticle-Polymer Composites For Photoactive-Based Materials, Brett Ellerbrock

All Theses

Nanocomposites of nanoparticles dispersed throughout a polymer matrix have been studied to great length to improve the overall polymer properties. These enhancements are observed in the thermal, physical, and/or optical characteristics. Being able to harness nanoparticles in such a way may help improve fiber technology into the 21st century.
This work was geared toward synthesizing rare earth doped lanthanum fluoride (LaF₃) nanoparticles because good separation in the absorption and emission bands of the material and it fluoresces in the visible to near-infrared range. Terbium ions were added to a LaF₃ crystal because of their distinct visible green …

Surface Characterization And Electrochemical Behavior Of Colloidal Particles, Cinta Pepin

All Theses

There is an ongoing interest in research focused on developing polymeric organic-light-emitting-devices (OLED) to replace inorganic devices. Compared to inorganic devices, OLEDs could present better properties such as higher efficiency, lower cost and simpler device fabrication. In an attempt to get a device with high efficiency, the hole transporting group and the electron transporting group were combined into a polymer to make an individual 'particle device'. The idea was to create a polymer particle containing both charge transporting moieties via emulsion polymerization. In this presentation, different techniques will be described that were used to determine the stability and the surface …

Influence Of Iso-Structural Substitutions On Properties Of Ge(As,Sb)(S,Se) Glasses, Guillaume Guery

All Theses

Chalcogenide glasses possess exceptional infrared transparency, large non-linear refractive indexes and low phonon energies, making them good candidates for infrared optical applications. Previous studies in the Ge-Sb-S glass system have shown an increase in the nonlinear refractive index with an iso-structural substitution of two- coordinated selenium (Se) for sulphur (S) and variation of other physical properties with substitution of other iso-structural species such as three-coordinated arsenic (As) for antimony (Sb). The role of such iso-structural exchange on properties important to the thermo-, visco- and mechanical attributes of glasses in the Ge-As/Sb-S/Se system has not been thoroughly evaluated and form the …

Removal Of Inclusions From Aluminum Through Filtration, Lucas Nana Wiredu Damoah, Lifeng Zhang

Materials Science and Engineering Faculty Research & Creative Works

Filtration experiments were carried out using both an AlF3 slurry-coated and an uncoated Al2O3 ceramic foam filter to study the removal of nonmetallic inclusions and impurity elements. the results showed that the 30-ppi ceramic foam filter removed up to 85 pct inclusions from aluminum. Several pictures of two- and three-dimensional morphologies of both nonmetallic and intermetallic inclusions also have been presented. the following contributing mechanisms for the removal of nonmetallic inclusions in the deep-bed filtration mode are proposed: (1) collision with walls and interception effect and (2) the formation of both intermetallic and nonmetallic inclusion bridges during filtration. Fluid dynamics …