Materials Science and Engineering Commons^™

Effect Of Accelerated Aging On Mechanical Properties And Structure Of Nano-Scale Composite Systems, David Economy

All Theses

Nano-scale composites are being investigated by academic, industrial, and national laboratories for potential applications such as wear resistant coatings and high strength foils. These structures are of interest due to their as-fabricated mechanical properties, such as high strength for nanolaminates. However, there have only been limited studies of the long-term mechanical stability. A greater understanding of how these systems might respond to sustained use is needed before these systems transition from research laboratories into widespread application. It is the objective of this thesis to clarify the link between accelerated aging using elevated temperatures over time and mechanical properties of two …

Thermoelectric Properties Of Nickel And Titanium Co-Intercalated Titanium Diselenide, Timothy Holgate

All Dissertations

Thermoelectric materials are involved in the direct conversion between thermal and electrical energy. They may be used to generate power from a thermal gradient or to pump heat in or out of a system when driven with DC power. Much of the recent advances in thermoelectric research have been in materials whose thermoelectric efficiency has been optimized at temperatures above room temperature where power generation is the main application.
The question that I seek to answer in this dissertation is to use our standard experimental techniques in order to assess the possibility of a class of transition metal dichalcogenides bases …

Quantitative Analysis Of The Reaction Between Gliadin And Citric Acid Under Weak Acidic And Weak Alkaline Conditions, Wei Li

Department of Agricultural and Biological Systems Engineering: Dissertations, Theses, and Student Research

Gliadin was reacted with citric acid under weak acidic and weak alkaline conditions in both wet and dry states and the reaction mechanism was studied. The low morphological stability in an aqueous environment and inferior mechanical properties have restricted the applications of plant proteins, although these materials possess a unique structure, biocompatibility and biodegradability. Carboxylic acids such as citric acid are inexpensive and nontoxic chemicals and are preferred for crosslinking proteins and cellulose to improve the desired properties of the materials.

In this study, gliadin was chosen as a model of plant proteins to react with citric acid. However, previous …

53rd Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 53rd 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, July 24-28, 2011.

Mapping Mos2-Co Catalytic Nanostructures Using Hrtem And Tem Simulations, Eduan Martínez-Soto ^, Brenda Torres, Domingo Ferrer, Gilles Berhault, Russell Chianelli, Manuel Ramos *

COURI Symposium Abstracts, Summer 2011

No abstract provided.

Synthesis And Characterization Of Cdse-Zns Core-Shell Quantum Dots For Increased Quantum Yield, Joshua James Angell

Master's Theses

Quantum dots are semiconductor nanocrystals that have tunable emission through changes in their size. Producing bright, efficient quantum dots with stable fluorescence is important for using them in applications in lighting, photovoltaics, and biological imaging. This study aimed to optimize the process for coating CdSe quantum dots (which are colloidally suspended in octadecene) with a ZnS shell through the pyrolysis of organometallic precursors to increase their fluorescence and stability. This process was optimized by determining the ZnS shell thickness between 0.53 and 5.47 monolayers and the Zn:S ratio in the precursor solution between 0.23:1 and 1.6:1 that maximized the relative …

Chitosan And Trimethyl Chitosan Particles As Oral Vaccine Delivery Systems: Comparison Of The Potential To Initiate Immune Responses, S Boontha, H Ej Unginger, N Waranuch, A Polnok, T Pitaksuteepong

Journal of Metals, Materials and Minerals

In this study, particles having low MW (Chi-L), high MW (Chi-H) and their respective trimethyl chitosan (TMC) with a degree of quaternization (DQ) of about 40% (TMC-L-40 and TMC-H-40), and prepared by using chitosan, were used to compare their potentials for provoking immune responses to ovalbumin (OVA) following oral administration. The results showed that the Chi-L particles gave higher serum immunoglobulin G (IgG) responses to OVA than those induced with Chi-H, TMC-L-40 and TMC-H-40 particles. However, Chi-L and Chi-H particles gave similar secretory immunoglobulin A (sIgA) to OVA, and sIgA titers obtained from mice immunized with OVA-loaded TMC were negligible. …

Corrosion Prevention Of Rebar In Concrete Due To Chloride, Y Srimahajariyaphong, S Niltawach

Journal of Metals, Materials and Minerals

In coastal and brackish areas, black rebar in concrete structures suffers from chloride corrosion which leads to spalling of the concrete. The Half Cell Potential Measurement technique has been applied to study the corrosion behavior of both black and galvanized deformed rebar in different concretes. Additives in the concretes vary from pozzolan, calcium nitrite, to pozzolan plus calcium nitrite. Rebar which has higher half cell potential possesses better corrosion resistance. It has been found that concrete cover thickness has no significant effect on the half cell potential of either rebar; that for both types of rebar, the half cell potential …

Design And Construction Of Water Atomizer For Making Metal Powder, S Yenwiset, T Yenwiset

Journal of Metals, Materials and Minerals

Water Atomization for metal powder is an appropriate method for producing metal powder from different kinds of metal. Typically, a water atomizing machine is designed with a molten metal spraying chamber in a vertical or horizontal orientation depending on a nozzle design, a molten metal spraying chamber and related components. The main variables influencing the working condition of the water atomization process, which affect sizes, shapes and distribution of metal powder particles, are water pressure, water flow rate, a temperature higher than melting point of liquid metal and flow rate of liquid metal. The water atomizing machine in the study …

Applying Computer Simulation In Improving Heat Treating Condition Of Thin High-Carbon Steel Parts, T Korad, M Polboon, N Chumchery, J Pearce

Journal of Metals, Materials and Minerals

The study was carried out using COSMOSFlowWorks to predict heat treatment conditions for AISI 1085 high-carbon steel sheet that is used to produce automotive parts that require wear resistance and stiffness resulting from controlled moderately high hardness levels. To achieve such properties, flat high-carbon steel parts need to be hardened to produce acicular matrix structures, and the most suitable heat treatment process to harden thin parts without distortion is austempering. In producing hard and stiff thin section parts in this company study the austempering process was performed by soaking at 830C and then quenching in a NaCl salt bath at …

Self-Crack Closing Ability Of Mortar With Different Additives, D Jaroenratanapirom, R Sahamitmongkol

Journal of Metals, Materials and Minerals

Self-crack closing ability of cementitious materials has been studied in various aspects. However, most studies focus mainly on the cementitious material with only cement as a binder (without mineral additives), although many additives are commonly used at present. This research thus aims to investigate the effect of additives on this self-crack closing ability by observing and measuring crack width on the mortar specimens. Cracks were created on mortar specimens by splitting method at the age of 3 and 28 days. As most reports show that the best self-crack closing performance was achieved when a plenty of water was supplied, the …

Purification Of An Industrial Aluminum Alloy By Melt Stirring During Ohno Continuous Casting Process, S Fashu, L Jianguo, H Q. Dan

Journal of Metals, Materials and Minerals

With the purpose of upgrading the purity of a dilute industrial aluminum alloy during Ohno Continuous Casting (OCC) process through the use of forced melt stirring; the critical stirring intensity required under a casting speed of 2 mm/min was numerically determined. The determined critical stirring intensity induces convective velocity magnitudes into the melt which are effective in transporting solutes from the solute boundary layer into the bulk melt. It was found that, with adequate melt stirring, production of substantially long and high purity ingots during OCC is possible before their purity diminishes to lower than the initial alloy purity.

Effect Of Nitrogen Partial Pressure On Characteristic And Mechanical Properties Of Hard Coating Tialn Film, C Chokwatvikul, S Larpkiattaworn, S Surinphong, C Busabok, P Termsuksawad

Journal of Metals, Materials and Minerals

(Ti,Al)N coating has been serving for the industry as cutting and forming tools. Compared with TiN film, TiAlN film significantly increases tool lifetime. Therefore, it reduces machine downtime and increases productivity. In this work, (Ti,Al)N film was deposited on cold-work tool steel (SKD 11) using PVD cathodic arc system. The sintered Ti-Al target with composition of (at%) 50 Ti and 50 Al was used as a cathode. The deposition bias voltage, bias arc current and deposition time were set at 100 V, 70 A and 90 minutes, respectively. Nitrogen gas was purged into the system with the applied pressure of …

Modification Of Montmorillonite With A Cationic Softener For Finishing Cotton Fabric With Hand Builder Performance, S Kittinaovarat, N Jiratumnukul, N Koolpreechanan

Journal of Metals, Materials and Minerals

Montmorillonite (Mont) was modified by cationic exchange with the cationic softener TEGO 28 (Di-Palm carboxyethyl hydroxyethyl methyl ammonium methosulfate). XRD analysis suggested that intercalation occurred in the modified Mont (mMont). Softening finishing solutions composed of pure TEGO 28 with and without mMont were treated on cotton fabrics by the pad-dry method and then evaluated for stiffness, whiteness, tear strength and thermal stability. TEGO 28 treatment alone increased the stiffness property of the finished fabrics, and this was increased further by the co-inclusion of mMont at 3 and 5% (w/v), but higher or lower mMont concentrations led to a marked and …

Development Of Composition Modulated Multilayer Alloy Coatings And Their Corrosion Behavior, S Yogesha, A C. Hegde

Journal of Metals, Materials and Minerals

Multilayer Zn-Ni alloy coating was developed on mild steel from acid chloride bath containing thiamine hydrochloride, as additive. Composition modulated multilayer alloy (CMMA) coatings, or simply, multilayer coating with gradual change in composition were developed galvanostatically using triangular current pulses from single bath technique. CMMA coatings of Zn-Ni were developed under different conditions, such as cyclic cathode current densities (CCCDs) and a number of layers, and their corrosion behaviors were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy method. Optimal configuration, (Zn-Ni)2.0/4.0/600 was found to exhibit ~50 times better corrosion resistance compared to monolayer (Zn-Ni)3.0 alloy, deposited from the same …

Effect Of Postweld Heat Treatment On Microstructures And Hardness Of Tig Weldment Between P22 And P91 Steels With Inconel 625 Filler Metal, N Tammasophon, W Homhrajai, G Lothongkum

Journal of Metals, Materials and Minerals

This research aims at searching for the optimal postweld heat treatment condition of the TIG weld joint between P22 (2.25Cr) and P91 (9Cr) steels using Inconel 625 as filler metal. The postweld heat treatment at 750C for 2, 4 and 6 hours was applied in order to reach the proper microstructure and hardness for high performance in mechanical properties at elevated temperatures. It is recommended that postweld heat treatment at 750C for 2 hours is the proper condition to reduce the hardness of heat affected zone (HAZ) of P91 steel.

Separation Of Lycopene/Solvent Mixture By Chitosan Membranes, P Yodjun, K Soontarapa, C Eamchotchawalit

Journal of Metals, Materials and Minerals

Acetone in view of lower toxicity could be used as extracting solvent of lycopene in tomato paste instead of hexane. The studied chitosan membranes were uncrosslinked and crosslinked types. It was found that the membrane morphology could be changed from porous to dense structure by increasing evaporation temperature or time or by crosslinking. They showed hydrophilicity but not preferred to both acetone and lycopene. The lycopene/acetone mixture could be separated by using water swollen chitosan membrane in pervaporation process. It was found that all studied membranes; i.e., both uncrosslinked and ionically crosslinked membranes prepared at 40 to 60C for 2 …

Chevron Crack Initiation In Mullti-Pass Drawing Of Inclusion Copper Shaped-Wire, S Norasethasopon

Journal of Metals, Materials and Minerals

In the copper superfine wire drawing, the internal cracks such as chevron cracks and breakage of the wire were fatal to the success of quantitative drawing operations. This paper shows how the main process parameters, the drawing pass numbers, influence the plastic deformation, hydrostatic stress, maximum principal tensile stress and chevron cracks initiation investigated by FEM simulation. The effect of the lateral and longitudinal sizes of a central cylindrical inclusion in the multi-pass copper shaped-wire drawing was studied. The plastic deformation, plastic strain, hydrostatic stress and maximum principal tensile stress of the copper shaped-wire containing an inclusion were obtained from …

Determination Of Forming Limit Stress Diagram For Formability Prediction Of Spce 270 Steel Sheet, S Panich, V Uthaisangsuk, J Juntaratin, S Suranuntchai

Journal of Metals, Materials and Minerals

The aim of this research is to apply numerical Finite Element Method (FEM) for determining Forming Limit Stress Diagram (FLSD) of sheet steel of grade SPCE 270. As a failure criterion for formability prediction in sheet metal forming process, the conventional Forming Limit Diagram (FLD) is often used. The FLD is a strain based criterion, by which the principal strains at failure are evaluated. Many investigations showed that the FLD is dependent on forming history and strain path. However, the stress based criterion does not confirm this dependency. This criterion is more robust against any changes in the strain path …

The Change Of Surface Alloy Compositions And Corrosion Behavior After Wedm Machining Of Commercially Pure Titanium (Grade 4) And Ti-6al-4v (Grade 5), K Sriprasertying, S Rhaiphu

Journal of Metals, Materials and Minerals

Nowadays, titanium and its alloys are widely used in medical applications because of excellent corrosion resistance and a high strength-to-weight ratio. Nevertheless, titanium and its alloys are classified as difficult-to-machine metals by conventional machining methods. Therefore, unconventional machining processes are recommended. Wire-electrical discharge machining (WEDM) has become an important non-traditional machining process, as it provides an effective solution for machining components made from difficult-to-machine metals. However, WEDM could damage the surface layer and have an effect on the biocompatibility properties. This research was focused on the effect of WEDM on grade 4 commercially pure titanium and Ti-6Al-4V (Grade 5) after …