Materials Science and Engineering Commons^™

Diamond Based-Materials: Synthesis, Characterization And Applications, Qiang Hu

USF Tampa Graduate Theses and Dissertations

The studies covered in this dissertation concentrate on the various forms of diamond films synthesized by chemical vapor deposition (CVD) method, including microwave CVD and hot filament CVD. According to crystallinity and grain size, a variety of diamond forms primarily including microcrystalline (most commonly referred to as polycrystalline) and nanocrystalline diamond films, diamond-like carbon (DLC) films were successfully synthesized. The as-grown diamond films were optimized by changing deposition pressure, volume of reactant gas hydrogen (H2) and carrier gas argon (Ar) in order to get high-quality diamond films with a smooth surface, low roughness, preferred growth orientation and high sp3 bond …

Oxygen Diffusion Characterization Of Frp Composites Used In Concrete Repair And Rehabilitation, Chandra K. Khoe

USF Tampa Graduate Theses and Dissertations

Many independent studies have conclusively demonstrated that fiber reinforced polymers (FRP) slow down chloride-induced corrosion of steel in concrete. The mechanism for this slow down is not well understood but it has been hypothesized that FRP serves as a barrier to the ingress of chloride, moisture, and oxygen that sustain electrochemical corrosion of steel.

This dissertation presents results from an experimental study that determined the oxygen permeation rates of materials used in infrastructure repair. In the study, the oxygen permeation constants for epoxy, carbon and glass fiber laminates, concrete, epoxy-concrete and FRP-concrete systems were determined and a method developed to …

Interface Engineered Diamond Coatings For Dry Machining Applications, Humberto Arturo Gomez Vega

USF Tampa Graduate Theses and Dissertations

Several studies have been propose to improve the adhesion of diamond films on cemented carbide tool materials, however a systematic study in identifying the role of the factors that affect the final diamond adhesion and the resulting machining performance of the tool under real manufacturing conditions is still unexplored. CVD diamond film's extraordinary qualities bring little benefit if the film fails to adhere sufficiently to the substrate. Inadequate adhesion undermines tool performance and longevity, causing unpredictable behavior under load and possibly leading to unexpected failure of the tool in the production line. This dissertation investigates the effects of different surface …

Novel Magnetic Materials For Sensing And Cooling Applications, Anurag Chaturvedi

USF Tampa Graduate Theses and Dissertations

The overall goals of the present PhD research are to explore the giant magnetoimpedance (GMI) and giant magnetocaloric (GMC) effects in functional magnetic materials and provide guidance on the optimization of the material properties for use in advanced magnetic sensor and refrigeration applications.

GMI has attracted growing interest due to its promising applications in high-performance magnetic sensors. Research in this field is focused on the development of new materials with properties appropriate for practical GMI sensor applications. In this project, we have successfully set up a new magneto-impedance measurement system in the Functional Materials Laboratory at USF. We have established, …

Growth And Characterization Of Nanoscale Thin Films, Erik Thomas Wolter

Honors Program Theses

Thin manganese films were grown by thermal evaporation in high vacuum. The growth rate was varied to determine how the growth rate affects the continuity of ultra-thin films. The resistance was measured with the two-point method in situ and the data was recorded digitally. The resistance was converted to resistivity and this was plotted against thickness. It was found that resistivity decreases exponentially as the film begins to form in islands. The film reaches a critical thickness as the islands coalesce and the data can then be fitted with Fuchs’ equation. The resistivity continues to decrease but the minimum resistivity …

Fabrication And Characterization Of Electrospun Cactus Mucilage Nanofibers, Yanay Pais

USF Tampa Graduate Theses and Dissertations

This work seeks to fabricate, optimize, and characterize nanofibers of cactus Opuntia ficus-indica mucilage and Poly (vinyl alcohol) (PVA) by electrospinning. Mucilage is a neutral mixture of sugars produced by cactus and PVA is a non-toxic, water-soluble, synthetic polymer, which is widely used as a co-spinning agent for polymers. Mucilage was extracted from the cactus pad and prepared for electrospinning by mixing with acetic acid. Two types of PVA were used differentiating in high and low molecular weights. Concentrations of PVA were varied to find an adequate threshold for fiber formation. Changing the ratio of PVA to cactus mucilage produced …

Stress Corrosion Cracking Evaluation Of Candidate High Strength Stainless Steels For Prestressed Concrete, Joseph Rogelio Fernandez

USF Tampa Graduate Theses and Dissertations

Prestressed concrete piles are commonly used to support over-water highway bridges in marine environments. The reinforcing steel within will ultimately be degraded via corrosion damage due to the penetration of chloride ions from sea water. The service life of these structures is, in part, dictated by the time required to diffuse chloride ions through the concrete cover and subsequently corrode the steel. Therefore, by slowing the rate of diffusion or increasing the chloride threshold of the steel (or both) an increased service life can be expected. This thesis focuses on the latter whereby stainless steel reinforcing alternatives were investigated to …

Precise Control Of Highly Ordered Arrays Of Nested Semiconductor/Metal Nanotubes, Diefeng Gu, Helmut Baumgart, Kandabara Tapily, Pragya Shrestha, Gon Namkoong, Xianyu Ao, Frank Müller

Electrical & Computer Engineering Faculty Publications

Lithographically defined microporous templates in conjunction with the atomic layer deposition (ALD) technique enable remarkable control of complex novel nested nanotube structures. So far three-dimensional control of physical process parameters has not been fully realized with high precision resolution, and requires optimization in order to achieve a wider range of potential applications. Furthermore, the combination of composite insulating oxide layers alternating with semiconducting layers and metals can provide various types of novel applications and eventually provide unique and advanced levels of multifunctional nanoscale devices. Semiconducting TiO₂ nanotubes have potential applications in photovoltaic devices. The combination of nanostructured semiconducting materials …

Purification Of Solar Grade Silicon Using Electromagnetic Field, Anping Dong, Lucas N.W. Damoah, Lifeng Zhang, Hui Zhu

Materials Science and Engineering Faculty Research & Creative Works

Non-metallic particles and the metallic impurity elements in the solar cell silicon have a strong detrimental effect on the conversion efficiency of the solar cell. Removing these impurities is one of the important tasks for silicon refining. the current paper proposed a new approach to purify silicon - electromagnetic (EM) separation. Since the non-metallic particles and the metallic impurity elements are non- or less conductive while the molten silicon is well conductive, under EM field, the Lorenz force will push the particles to the boundary layer, thus separate these inclusions. in the current study, a high frequency EM field was …

Non-Metallic Particles In Solar Grade Silicon (Sog-Si), Lucas Nana Wiredu Damoah, Anping Dong, Lifeng Zhang, Hui Zhu

Materials Science and Engineering Faculty Research & Creative Works

This study investigated the non-metallic inclusions in Solar 2rade Silicon (SoG-Si), especially the distribution of inclusions in the top 15mm layer of multicrystalline silicon ingot. the SoG-Si ingot produced from directional solidification process usually pushes the impurities to the top and finally cut off and discarded, which leads to material loss. the hard inclusions lead to wire breakages during the cutting of the ingot into wafers. the main kinds of inclusions found in top-cut silicon scraps from two manufacturers have been investigated using acid extraction, automated feature analysis techniques and SEM-EDS and optical Microscope: They are needle-like Si3N4 and lumpy …

Investigating Wood Welding Parameters Using A Prototype Welding Machine, Timothy R. Melin

Master's Theses

Understanding how different processing variables influence wood welded bonds is vital if the technique will ever be used to create engineered lumber without using adhesives. A variation of vibration welding, wood welding uses pressure and friction to bond materials together. During welding, heat causes a softening in the wood, a naturally occurring composite material. This softening leads to fiber entanglement and a bond forms upon cooling.

The goal of this research was to investigate several processing aspects of the wood welding procedure. A prototype wood welding machine, designed and fabricated from the ground up, was used to investigate the effects …

Versatile Route For Preparation Of Polydiacetylene/Zno Nanocomposites And Their Colorimetric Response To Ph And Ethanol, N Rungruangviriya, N Traiphol

Journal of Metals, Materials and Minerals

This contribution presents a simple method to prepare polydiacetylene(PDA)/ZnO nanocomposites, which can be utilized as active materials in sensing technology. The ZnO nanoparticles, which constitute of Zn-OH2 + , Zn-OH and Zn-O- groups at their surfaces, function as nano-substrates for self-assembling of diacetylene monomers, 10,12-pentacosadiynoic acid (PCDA), in aqueous medium. Photopolymerization of the assemblies yields poly(PCDA)/ZnO nanocomposites with core-shell structure. Strong interactions between the active groups at ZnO surface and carboxylic head groups of poly(PCDA) promote chain ordering and reduce segmental dynamics of poly(PCDA) in the nanocomposites. The existence of strong interfacial interaction drastically affects the colorimetric response behavior of …

Preparation And Properties Of Superhydrophobic Cotton Fabrics, P Kampeerapappun, K Visatchok, D Wangarsa

Journal of Metals, Materials and Minerals

In this study, superhydrophobic cotton fabric was prepared by coating maleic-anhydride grafted poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS-g-MA) triblock copolymer solutions containing calcium carbonate (CaCO3) particles. SEBS-g-MA solutions were prepared using single solvent (toluene and tetrahydrofuran (THF)) and mixed solvent (toluene: ethanol (EtOH) and THF: EtOH). Cotton fabrics were treated with the prepared solution using padding technique. All coated fabrics exhibited a water contact angle (WCA) of more than 100°. Optimum WCA values were observed when THF and 90:10 toluene: EtOH were employed. In case of CaCO3 particles addition, 6% W/V CaCO3 could impart the highest WCA value of 154°. However, the durability of …

Corrosion Assessment Of Carbon Steel In Thailand By Atmospheric Corrosion Monitoring (Acm) Sensors, W Pongsaksawad, E Viyanit, S Sorachot, T Shinohara

Journal of Metals, Materials and Minerals

Atmospheric corrosion of metal depends on material compositions, weather condition (dry, dew, and rain period), temperature, relative humidity, and airborne sea salt of specific location. General testing procedure to obtain the corrosion rate is by actual exposure test of the specimen panels based on time interval plan. In Japan, atmospheric corrosion monitoring (ACM) sensor, made of an iron-silver galvanic couple, has been developed and used to sense the corrosivity in terms of galvanic current. Under some atmospheric conditions, these data can be converted to time of wetness and related to the corrosion rate of carbon steel. With ACM sensors, it …

Preparation And Characteristics Of Galangal Essential Oil/Alginate Microcapsules, T Jiamrungraksa, S Charuchinda

Journal of Metals, Materials and Minerals

Galangal essential oil/alginate microcapsules were prepared by solidifying in liquid (orifice method) between sodium alginate and calcium chloride. The structure, morphology and also the thermal stability of the microcapsules were investigated by FT-IR, optical microscope, infrared moisture determination balance (IMDB) at 120°C for 2 hours. The galangal essential oil release content of microcapsules was estimated by measuring time course of weight of microcapsules determination by isothermal TGA at 37°C and 120°C. FT-IR spectral data confirmed the presence of galangal essential oil in the prepared microcapsules. An increase of sodium alginate concentration and oil content resulted in significantly higher average size …

Development Of An Aluminum Semi-Solid Extrusion Process, T Rattanochaikul, S Janudom, N Memongkol, J Wannasin

Journal of Metals, Materials and Minerals

Semi-solid extrusion process is a new forming process that is quite promising because the process requires lower forming pressure than conventional solid extrusion. In addition, semi-solid extrusion does not require large machines, which results in lower production costs. The aim of this article is to study the feasibility of an aluminum semi-solid extrusion process. The semi-solid technique selected for usage in this study was the Gas Induced Semi-Solid (GISS) process. The laboratory extrusion system was developed in this work. In the experiments, nitrogen gas was injected into aluminum melt for about 5 seconds. After that, the obtained semi-solid slurry was …

Hardness And Fracture Toughness Of Alumina-Based Particulate Composites With Zirconia And Strontia Additives, T Oungkulsolmongkol, P Salee-Art, W Buggakupta

Journal of Metals, Materials and Minerals

This project aims to study characteristics and mechanical properties i.e. hardness and fracture toughness of alumina matrix composite materials containing zirconia and strontium oxide. Two groups of composite specimen were fabricated: (i) Al2O3 matrix with 3 mol% Y2O3- ZrO2, varied from 10, 20, 30 and 40 vol%, and (ii) Al2O3 matrix with 2, 5, 10 and 15 vol% SrO added in the form of SrCO3. The powders were blended and then pressed into pellets. The compacts were pressureless sintered at 1600 o C for 2 hours in air. Density measurement of the sintered composites was carried out using liquid immersion. …

Development Of Layered Zn-Fe Coatings For Better Corrosion Protection, R S. Bhat, R Udupak, A C. Hegde

Journal of Metals, Materials and Minerals

In this research, the Zn-Fe coating having successive layers of alloys of two different compositions were developed alternatively on mild steel for better corrosion protection. The multilayer coatings, or alternatively, composition modulated alloy (CMA) coatings of different configurations have been developed, and their corrosion behaviors were evaluated by electrochemical DC and AC methods. The cyclic cathode current densities and numbers of layers have been optimised for peak corrosion stability of the coatings. Under optimal condition, the CMA coating having 300 layers, having about 67 nm average thickness was found to be approximately six times higher corrosion resistant than monolayer coating …

Microstructural Evolution Of Surface Layers During Electrolytic Plasma Processing, Cristian Cionea

Material Science and Engineering Dissertations - Archive

Electrolytic Plasma Processing is an emerging technology for surface modification. The EPP process is based on electrolysis of an aqueous electrolyte by application of an electrical potential between the workpiece and counter-electrode, and the production of plasma (micro-arc discharges on the workpiece surface). The plasma micro-arcs provide a heat source for surface modification via localized surface melting and rapid cooling (cleaning process) and, if desirable, enhance ion deposition on a given substrate (coating). Three substrates (low carbon steel, pure Al and pure Ti) were "cleaned" by EPP and their near surface layer microstructure was studied. It was found that the …

Bubble Template Synthesis Of Hollow Gold Nanoparticles And Their Applications As Theranostic Agents, Chienwen Huang

Material Science and Engineering Dissertations - Archive

Hollow gold nanoparticle with a sub-30nm polycrystalline shell and a 50 nm hollow core has been successfully synthesized through the reduction of sodium gold sulfite by electrochemically evolved hydrogen. Such hollow gold nanoparticles exhibit unique plasmonic properties. They strongly scatter and absorb near infrared light. In this thesis we seek to understand the formation mechanism of hollow gold nanoparticles in this new synthesis process and their plasmonic properties. Also, we explore their biomedical applications as theranostic agents (therapeutic and diagnostic imaging). A lithographically patterned electrode consisting of Ag stripes on a glass substrate was used to investigate the formation process …