Engineering Commons^™

Electrocatalytic Oxidation Of Methanol At The Nano Ni-B Amorphous Alloy Powdermicroelectrode, Yi-Xiong Zheng, Shi-Bing Yao, Shao-Min Zhou

Journal of Electrochemistry

Electrocatalytic oxidation of methanol at the nano Ni-B amorphous alloy powder-microelectrode in alkaline media was studied by using cyclic voltammetry.Compared to the highly preferred orientation(220) nickel electrode,The onset potential of methanol electrooxidation at the nano Ni-B microelectrode is negatively shifted about 0.04V,and the current density is increased approximately by 2 orders of magnitude.Thus,the nano Ni-B microelectrode has very strong electrocatalytic activity for the oxidation of methanol.The kinetic parameters were determined with the steady polarization curves.The results show that the rate constants for both the oxidation of Ni(Ⅱ) to Ni(Ⅲ) and the reduction of Ni(Ⅲ) to Ni(Ⅱ) at the nano Ni-B …

Preparation Of Manganese/Chromium Hexacyanoferrate Modified Glassy Carbon Electrode And Its Electrochemical Behavior, Sheng-Tao Zhang, Xiao-Yan Han, Ming-Yue Xue

Journal of Electrochemistry

A film of poly(manganese/chromium hexacyanoferrate)(MnCrHCF)is formed on the glassy carbon electrode(GCE) by Cyclic Voltammetry scanning,and its electrochemical behavior was studied.Factors affecting the electro-deposition of the film such as pH values and sustaining electrolytes,were discussed.And mechanism of the reaction was investigated.

Morphology Of The Pb-Sn Alloy Thin-Layer Electrodeposition, Yan-Jun Du, Zhi-Gang Yin, Tong-Chi Xia

Journal of Electrochemistry

The morphology of Pb-Sn alloy thin-layer electrodeposition was studied.Experimental results showed that the morphology of deposit could vary as the concentration of Pb2+、 Sn2+ two kind metallic ion to be changed.The patterns of product appeared the dendritic,ramification,dense branch,fractal,and homogeneous structure and their morphological evolution was caused by the change in anisotropy of crystal growth and different stage of electrodeposits.

Laser-Assisted Synthesis And Optical Properties Of Bismuth Nanorods, Jason Reppert

All Theses

Bismuth in the bulk form is a semimetal with a rhombohedral structure. It has a small band overlap between the conduction and valence bands and a highly anisotropic electron effective-mass tensor. Thermoelectric materials, in which one of the three dimensions is in the nanometer regime, exhibit unique quantum confinement properties and have generated much interest in recent years. Theoretical investigations have suggested that nanowires with diameters <10 nm will possess a figure-of-merit ZT>2. Prior to this research, it has been shown by the Dresselhaus group at MIT that Bi nanowires with small enough diameters (~50 nm), prepared via the template-method, undergo a transition from a semimetal …

Experimental Investigation Of Effect Of Environment Temperature On Freeze-Form Extrusion Fabrication, Xiyue Zhao, Michael S. Mason, Tieshu Huang, Ming-Chuan Leu, Robert G. Landers, Greg Hilmas, Samuel J. Easley, Michael W. Hayes

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Freeze-form Extrusion Fabrication (FEF) is an additive manufacturing technique that extrudes ceramic loaded aqueous pastes layer by layer below the paste freezing temperature for component fabrication. A computer controlled 3-D gantry system has been developed for the FEF process. The system includes a temperature control subsystem that allows for fabrication of components below the paste freezing temperature. The low temperature environment allows for larger component fabrication. Comparisons in terms of layer thickness, self-sustaining ability, and system response were performed between 0⁰C and -20⁰C for alumina sample fabrications. The minimum deposition angles without use of support material have been determined for …

Modeling And Simulation Of A Laser Deposition Process, Frank W. Liou, Zhiqiang Fan, Heng Pan, Kevin P. Slattery, Mary Kinsella, Joseph William Newkirk, Hsin-Nan Chou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A laser deposition process involves the supply of metallic powders into a laser-heated spot where the powder is melted and forms a melt puddle which quickly solidifies into a bead. In order to design an effective system, the laser beam, the powder beam, and their interactions need to be fully understood. In this paper, the laser-material interaction within the melt pool is reported using a multi-scale model: A macroscopic model to model mass, heat, and momentum transfer. Experiments were also conducted to validate the simulation model.

Aqueous-Based Extrusion Fabrication Of Ceramics On Demand, Michael S. Mason, Tieshu Huang, Robert G. Landers, Ming-Chuan Leu, Greg Hilmas, Michael W. Hayes

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Aqueous-Based Extrusion Fabrication is an additive manufacturing technique that extrudes ceramic slurries of high solids loading layer by layer for part fabrication. The material reservoir in a previously developed system has been modified to allow for starting and stopping of extrusion process on demand. Design pros and cons are examined and a comparison between two material reservoir designs is made. Tests were conducted to determine the optimal deposition parameters for starting and stopping of the extrudate on demand. The collected test data is used to create a process model that describes the relationship between ram velocity and material extrusion rate. …

Numerical Simulation Of The Evolution Of Solidification Microstructure In Laser Deposition, Zhiqiang Fan, Todd E. Sparks, Frank W. Liou, Anand Jambunathan, Yaxin Bao, Jianzhong Ruan, Joseph William Newkirk

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A predictive model is developed to simulate the evolution of the solidification microstructure during the laser deposition process. The microstructure model is coupled with a comprehensive macroscopic thermodynamic model. This model simulates dendritic grain structures and morphological evolution in solidification. Based on the cellular automata approach, this microstructure model takes into account the heterogeneous nucleation both within the melt pool and at the substrate/melt interface, the growth kinetics, and preferential growth directions of dendrites. Both diffusion and convection effects are included. This model enables prediction and visualization of grain structures during and after the deposition process. This model is applied …

A Study Of Fabrication Of Ultra-High Resolution Nano Devices Through Electron Beam Lithography Process And Its Application To Electron – Optical Systems, Jihoon Kim

Doctoral Dissertations

Today’s semiconductor industry has been significantly changing in its techniques and processes for the fabrication of devices and accordingly, there has been dramatic increase in performance and a reduction in cost. To obtain still higher device performances and still further cost reduction, the dimensions of patterns in integrated circuits should be as small as possible and the 3-dimensional accuracy of multidimensional semiconductor structures should be also achieved as well. The manufacturing of smaller feature dimensions and 3-dimensional devices has been enabled by developments in lithography – the technology which transfers designed patterns onto the silicon wafer. Especially, electron beam lithography …

Determination Of Three-Dimensional Grain Boundary Connectivity From Two-Dimensional Microstructures, Megan Frary

Materials Science and Engineering Faculty Publications and Presentations

The connectivity of so-called "special" and "general" grain boundaries at a quadruple node is known to be nonrandom as a result of crystallographic constraints. Although a quadruple node is a three-dimensional feature, there exist two-dimensional features which are topologically identical. Therefore, the distribution of these two-dimensional features may be used to determine the three-dimensional connectivity. Computer simulations of a three-dimensional microstructure which is virtually serial sectioned are used to validate the proposed approach.

Quantum Ballistics, Andrei Sokolov

Materials Research Science and Engineering Center: Faculty Publications

For the last 40 years, computer-chip manufacturers have been constantly improving the performance of their products by shrinking the size of transistors—the building blocks of processors and memory chips. Having gone from dimensions of a few microns in the early 1970s to 45 nm in Intel’s latest prototypes, the number of transistors that can be etched on a given area of silicon has been doubling every 18 months. This exponential trend, which is known as Moore’s law, has been the driving force behind the relentless miniaturization of microelectronic devices. However, we are now approaching the physical limits of existing technology. …

High Temperature Heat Exchanger Project: Quarterly Progress Report April 1, 2007 Through June 30, 2007, Anthony Hechanova

Publications (NSTD)

• Ceramatec Sulfuric Acid Decomposer. Modeling with different reacting flow channel configurations (ribbed-surface channels, hexagonal channels, and diamond-shaped channels) was performed. The probability of failure for the one channel geometry with different reacting flow channel configurations was calculated to be zero in the three principal directions for all of the cases.

• Bayonet Heat Exchanger. The Matlab code for calculating the probability of failure using a two-dimensional axisymmetric model of the bayonet decomposer was developed. The probability of failure was calculated for the inner and outer SiC walls, and the intermediate quartz wall of the decomposer and found to be …

Guidelines For The Application Of Recycled Concrete Aggregate In The Egyptian Construction Industry, Ahmed Moustafa Essam Aly Kamel

Archived Theses and Dissertations

Construction industry is one of the most important fractions of economy worldwide. This industry consumes enormous amounts of raw materials and produces considerable waste. The optimization of construction material usage not only saves costs but also can significantly contribute towards sustainable development. The concept of recycling the construction and demolition rubble is being addressed in this study as a solution. The recycling of concrete, resulting from both the construction activities and the demolition activities, in order to be used as a source of aggregate is being focused upon in this study. Although the idea of using recycled concrete has been …

49th Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 49th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-endorsed by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Breckenridge, Colorado, July 22-26, 2007.

Mode-I Toughness And Curing Pressure Characterisitc Of Symmetrical Lay-Up Of Plain Weave Woven Gfrp Composites, Mohd Aidy Faizal Johari, Kiam Beng Yeo, Mohd Noh Dalimin

mohd aidy faizal johari

This study describes an experimental study on the interlaminar Mode-I fracture toughness behavior of hand lay-up plain-weave woven GFRP laminate by using a fracture energy method of evaluation. Mode-I double cantilever beam (DCB) tests were performed on woven GFRP unsaturated polyester composite, E-Glass EWR 600 NISER, specimens. The specimen design and test procedure are performed with reference to the BS ISO 15024 and ASTM D5528. Various curing uniform pressure distribution has been investigated at 35.8kg/m2, 70.1kg/m2, 104kg/m2 and 138.2kg/m2, with respect to the toughness value. The lay-up laminates designed with symmetrical arrangement at the center-plane of the composite are also …

Additive-Assisted, Cerium-Based, Corrosion-Resistant E-Coating, James O. Stoffer, Thomas J. O'Keefe, Eric L. Morris, Xuan Lin, Scott A. Hayes, Pu Yu

Chemistry Faculty Research & Creative Works

Corrosion resistance of metallic components such as stainless steel components of vehicles, and especially aluminum- based components of aircraft, is enhanced by application of an e-coat paint or primer which is enhanced by incorporation of cerium ions into the e-coat electrolytic bath. The resulting overall coating includes a cerium-based layer under a cerium-enhanced e-coat paint or primer layer.

Physisorption Of Nucleobases On Graphene: Density-Functional Calculations, Gowtham S, Ralph H. Scheicher, Rajeev Ahuja, Ravindra Pandey, Shashi P. Karna

Data Science Publications

We report the results of our first-principles investigation on the interaction of the nucleobases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) with graphene, carried out within the density-functional theory framework, with additional calculations utilizing Hartree-Fock plus second-order Møller-Plesset perturbation theory. The calculated binding energy of the nucleobases shows the following hierarchy: G>A≈T≈C>U, with the equilibrium configuration being rather similar for all five of them. Our results clearly demonstrate that the nucleobases exhibit significantly different interaction strengths when physisorbed on graphene. The stabilizing factor in the interaction between the base molecule and graphene sheet is …

Glass Transition In Metallic Glasses: A Microscopic Model Of Topological Fluctuations In The Bonding Network, T. Egami, S.J. Poon, Z. Zhang, Veerle Keppens

Faculty Publications and Other Works -- Materials Science & Engineering

Understanding of the structure and dynamics of liquids and glasses at an atomistic level lags well behind that of crystalline materials, even though they are important in many fields. Metallic liquids and glasses provide an opportunity to make significant advances because of its relative simplicity. We propose a microscopic model based on the concept of topological fluctuations in the bonding network. The predicted glass transition temperature, Tg, shows excellent agreement with experimental observations in metallic glasses. To our knowledge this is the first model to predict the glass transition temperature quantitatively from measurable macroscopic variables.

Control Of Porosity In Fluoride Thin Films Prepared By Vapor Deposition, Alexander H. King

Alexander H. King

We have measured the porosity in thin films of lithium fluoride (LiF), magnesium fluoride (MgF2), barium fluoride (BaF2), and calcium fluoride (CaF2) as a function of the substrate temperature for films deposited by thermal evaporation onto glass substrates. The amount of porosity in the thin films was measured using an atomic force microscope and a quartz crystal thickness monitor. The porosity was very sensitive to the substrate temperature and decreased as the substrate temperature increased. Consistent behavior was observed among all of the materials in this study.

Posterminaries: Full Circle, Alexander H. King

Alexander H. King

A few years ago, I was walking near the old Union Station in Pittsburgh with a colleague only slightly younger than myself, when we happened upon some large-scale relics of the steel industry displayed for public viewing. “You don’t see too many of those in public parking lots,” I offered. “Um… what is it?” was the response. I suppose I was just a little surprised that a prominent materials scientist did not recognize a Bessemer converter—arguably the principal source of wealth during the U.S. industrial revolution—but this conversation took place back when steel was in decline, and many university Materials …

Glass Transition In Metallic Glasses: A Microscopic Model Of Topological Fluctuations In The Bonding Network, T. Egami, S.J. Poon, Z. Zhang, Veerle Keppens

Veerle Keppens

Understanding of the structure and dynamics of liquids and glasses at an atomistic level lags well behind that of crystalline materials, even though they are important in many fields. Metallic liquids and glasses provide an opportunity to make significant advances because of its relative simplicity. We propose a microscopic model based on the concept of topological fluctuations in the bonding network. The predicted glass transition temperature, Tg, shows excellent agreement with experimental observations in metallic glasses. To our knowledge this is the first model to predict the glass transition temperature quantitatively from measurable macroscopic variables.

Rational Design And Investigation Of Polypeptide Multilayer Films And Capsules, Ling Zhang

Doctoral Dissertations

Three major concerns in the science of materials today are control over structure and function at the molecular level, biodegradability, and scalability of production. Polymeric materials, notably polyelectrolyte multilayer films, have shown considerable promise in all these areas, and for rational development of multifunctionality. Polypeptides constitute an especially interesting class of polyelectrolyte, given their inherent biodegradability, means of control over structure, methods of large-scale synthesis, and ability to encode biological information. Relatively little is known, however, about polypeptide multilayer films, despite recent advances in the general area.

In this dissertation, ten heteropolypeptides were designed and synthesized by Fmoc chemistry. These …

Glassification Of Electric Arc Furnace Dust By Using Fly Ash Or Bagasse Ash, S Polsilapa, P Wangyao

Journal of Metals, Materials and Minerals

Electric arc furnace (EAF) dusts contain significant quantities of iron and zinc found almost entirely as iron oxide, zinc oxide and zinc ferrite. The dust has been classified as a hazardous waste due to the relative high lead, cadmium and hexavalent chromium contents. An option for treating EAF dust with an economic and uncomplicated process is by using ashes. Silica in ashes has the ability to incorporate a variety of elements in a nonleachable form in the dust. In this study, the EAF dust was mixed with fly ash or bagasse ash in several ratios. All mixed samples were heated …

Effect Of Solution Annealing Temperature On Structure And Mechanical Properties Of En Aw 2024 Aluminium Alloy, M Fujda, R Mišičko, L Rusňáková, M Sojko

Journal of Metals, Materials and Minerals

The effect of solution annealing temperature on the change of microstructural and mechanical properties of EN AW 2024 aluminium alloy was investigated using a metallographic analysis, Vickers hardness measurement and tensile test. An intensive growth of solid solution grains was the result of the increase of solution annealing temperature by the finely dispersed particles dissolved during applied annealing process. The role of these finely dispersed particles was to inhibit the recrystallization process and grain growth of solid solution matrix through its pinning effect on the migrated solid solution grain boundaries. Observed changes of the microstructure involved the strength decline and …

Corrosion Stress Relaxation In Pure Magnesium And Die-Cast Mg Alloys, Y B. Unigovski, L Riber, E M. Gutman

Journal of Metals, Materials and Minerals

The effect of corrosive solutions on stress relaxation behavior of pure Mg and its alloys is studied. Pure magnesium shows a crucial corrosion stress relaxation in 3.5wt.% NaCl even at room temperature in comparison with tests in air. Die-cast Mg alloys AZ91D, AM50 and AS21 at room temperature show a relatively small stress decrease both in air and in different corrosive media. At elevated temperature, all studied die-cast Mg alloys show a strong stress relaxation in a 3.5 % NaCl corrosive solution. In a corrosive environment, the highest sensitivity to stress relaxation was observed both in the alloy with the …

Om Study Of Effect Of Hip And Heat Treatments On Microstructural Restoration In Cast Nickel-Based Superalloy, Gtd-111, P Wangyao, V Krongtong, W Homkrajai, N Panich, G Lothongkum

Journal of Metals, Materials and Minerals

The present work aims at studying and searching for the effect of repairing conditions on microstructural restoration. It also seeks to investigate into the most suitable and practicable repairing condition, which could provide the desired microstructural characteristics by rejuvenation method of hot isostatic pressing (HIP), followed by 12 heat treatment conditions for long-term serviced gas turbine blades, cast nickel-based superalloy grade GTD-111 operated by Electricity Generating Authority of Thailand (EGAT). During solution treatment, coarse carbides and over-exposed coarse gamma prime precipitates, which had formed previously during service, would dissolve into the matrix. Then specimens were processed through a series of …

Use Of Pp-G-Ma Prepared By Solution Process As Compatibilizerin Polypropylene/Polyamide 6 Blends, S Chongprakobkit, M Opaprakasit, S Chuayjuljit

Journal of Metals, Materials and Minerals

In this work, polypropylene grafted maleic anhydride (PP-g-MA) prepared by solution process was used as a compatibilizer for polypropylene (PP)/polyamide 6 (PA6) blends. PP with melt flow index (MFI) of 10 g/10 min was grafted with maleic anhydride (MA) using benzoyl peroxide (BPO) as an initiator and toluene as a solvent. The effects of BPO and MA concentration on the grafting degree of MA onto PP were studied. The grafting degree was determined by a back-titration procedure whereas the formation of graft copolymers was confirmed by FT-IR technique. It was found that the maximum extent of grafting achieved was 0.87%. …

Processing And Properties Of Palm Oil-Based Rigid Polyurethane Foam, S Chuayjuljit, T Sangpakdee, O Saravari

Journal of Metals, Materials and Minerals

Rigid polyurethane (PU) foam has been prepared from palm oil-derived polyol. The polyol was synthesized by transesterification reaction of palm oil and pentaerythritol using calcium oxide as a catalyst. The obtained palm oil-based polyol was reacted with commercial polymeric diphenylmethane diisocyanate in the presence of water (blowing agent), N,N-dimethylcyclohexylamine (catalyst) and polydimethylsiloxane (surfactant) to produce rigid PU foam. The effects of the amount of the catalyst and surfactant on foam properties (i.e. density, compressive strength and thermal behaviors) were studied. It was found that the density of the foams decreased whereas the compressive strength increased with the increasing amount of …

Analysis Of The Influence Of The Loading Rate On The Mechanical Properties Of Microalloyed Steel, M Mihalikova

Journal of Metals, Materials and Minerals

The aim of this paper is to analyse the influence of the loading rate in the range from 1 to 1000 mm/min, which corresponds to the tensile machine working range, on the strength properties and the formability characteristics obtained on standard and notched test bars made of steel strips. The combination of the loading rate and the test bar type made it possible to obtain the relationship of monitored variables in the strain rate interval from 10-4 to 10 s-1. In this interval, the strength properties of the tested strips thickness of 1, 1.5 and 1.8 mm increase exponentially, but …

Pvd Coatings Applied On The Tool Steels, M Hagarová, D Jakubéczyová, M Vojtko

Journal of Metals, Materials and Minerals

The paper deals with the properties of thin coatings deposited on the tool steels. The TiAlN coat was applied by PVD technology on the Vanadis steel produced by powder metallurgy. Development of a new technology of coat deposition is connected with adequate evaluation of coated parts. The quality of a thin coating - substrate system was determined by measuring properties.