Materials Science and Engineering Commons^™

Effects Of The Tempering And High-Pressure Torsion Temperatures Onmicrostructure Of Ferritic/Martensitic Steel Grade 91, Artur Ganeev, Marina Nikitina, Vil Sitdikov, Rinat Islamgaliev, Andrew Hoffman, Haiming Wen

Materials Science and Engineering Faculty Research & Creative Works

Grade 91 (9Cr-1Mo) steel was subjected to various heat treatments and then to high-pressure torsion (HPT) at different temperatures. Its microstructure was studied using transmission electron microscopy (TEM) and X-ray diffraction (XRD). Effects of the tempering temperature and the HPT temperature on the microstructural features and microhardness in the ultrafine-grained (UFG) Grade 91 steel were researched. The study of the UFG structure formation takes into account two different microstructures observed: before HPT in both samples containing martensite and in fully ferritic samples.

Seismic Response Analysis Along The Coastal Area Of Bengkulu During The September 2007 Earthquake, Lindung Zalbuin Mase

Makara Journal of Technology

A strong earthquake of 8.4 Mw occurred at the Sumatra Subduction Zone in September 12, 2007. The area that underwent the impact of the earthquake was located along the coastal area of the Bengkulu Province. A seismic ground response study was then performed with reference to the event. Several site investigations, including standard penetration test and shear wave velocity tests, were conducted to understand the subsoil condition. The data were used to analyze a ground response during the earthquake. The amplification factor of each site was obtained, and a comparison of the spectral accelerations was performed. The results showed that …

Coax-Fed Dipole-Type Applicator For Hepatic Cancer Rf Ablation, Basari Basari, Aditya Rakhmadi, Kazuyuki Saito

Makara Journal of Technology

Cancer is the third leading cause of mortality in the world and is one of the most difficult diseases to detect and cure. This fact motivates us to investigate a treatment method by using radiofrequency (RF) ablation. RF ablation therapy kills cancer cells by electromagnetically heating them up. The treatment uses an applicator that is inserted into the body to heat the cells. The cancer cells are exposed to a temperature of more than 60 °C in short duration (a few seconds to a few minutes), thereby causing cell destruction locally. To ensure effective treatment, a minimally invasive method is …

Materials Design With Polylactic Acid-Polyethylene Glycol Blends Using 3d Printing And For Medical Applications., Jeremiah R. Bauer

Electronic Theses and Dissertations

This thesis is an examination of two material systems derived from polylactic acid (PLA) and polyethylene glycol (PEG). PLA is a polymer commonly sourced from renewable sources such as starches and sugars. It is a relatively strong, biodegradable polymer, making it ideal for use in the body. Even though it has a relative high strength, PLA is also brittle leading to the use of plasticizers to increase flexibility. One such plasticizer is PEG, which is a material that can exist at room temperature as either a thin liquid, or a hard waxy solid depending on the molecular weight. The first …

In Situ Extrinsic Doping Of Cdte Thin Films For Photovoltaic Applications, Imran Suhrid Khan

USF Tampa Graduate Theses and Dissertations

The Cadmium Telluride thin film solar cell is one of the leading photovoltaic technologies. Efficiency improvements in the past decade made it a very attractive and practical source of renewable energy. Considering the theoretical limit, there is still room for improvement, especially the cell’s open circuit voltage (VOC). To improve VOC, the p-type carrier concentration and minority carrier lifetime of the CdTe absorber needs to be improved. Both these parameters are directly related to the point defect distribution of the semiconductor, which is a function of deposition stoichiometry, dopant incorporation and post-deposition treatments.

CdTe films were deposited by the Elemental …

Modeling Of Nitihf Using Finite Difference Method, Nazanin Farjam, Reza Mehrabi, Haluk E. Karaca, Reza Mirzaeifar, Mohammad Elahinia

Mechanical Engineering Faculty Publications

NiTiHf is a high temperature and high strength shape memory alloy with transformation temperatures above 100oC. A constitutive model based on Gibbs free energy is developed to predict the behavior of this material. Two different irrecoverable strains including transformation induced plastic strain (TRIP) and viscoplastic strain (VP) are considered when using high temperature shape memory alloys (HTSMAs). The first one happens during transformation at high levels of stress and the second one is related to the creep which is rate-dependent. The developed model is implemented for NiTiHf under uniaxial loading. Finite difference method is utilized to solve the proposed equations. …

Manufacturing Process Simulation – On Its Way To Industrial Application, Dennis Otten, Tobias A. Weber, Jan-Christoph Arent

International Journal of Aviation, Aeronautics, and Aerospace

Manufacturing process simulation (MPS) has become more and more important for aviation and the automobile industry. A highly competitive market requires the use of high performance metals and composite materials in combination with reduced manufacturing cost and time as well as a minimization of the time to market for a new product. However, the use of such materials is expensive and requires sophisticated manufacturing processes. An experience based process and tooling design followed by a lengthy trial-and-error optimization is just not contemporary anymore. Instead, a tooling design process aided by simulation is used more often. This paper provides an overview …

Functionalized Nanoporous Carbon Scaffolds For Hydrogen Storage Applications, Christopher Carr

Dissertations

Recent efforts have demonstrated confinement in porous scaffolds at the nanoscale can alter the hydrogen sorption properties of metal hydrides, though not to an extent feasible for use in onboard hydrogen storage applications, proposing the need for a method allowing further modifications. The work presented here explores how the functionalization of nanoporous carbon scaffold surfaces with heteroatoms can modify the hydrogen sorption properties of confined metal hydrides in relation to non-functionalized scaffolds (FS). Investigations of nanoconfined LiBH₄and NaAlH₄indicate functionalizing the carbon scaffold surface with nitrogen can shift the activation energy of hydrogen desorption in excess of …

Tensile Properties And Fatigue Behavior Of Geopolymer Matrix Composites With Carbon Fiber Reinforcement At Elevated Temperature, Steffan M. L. Wilcox

Theses and Dissertations

The tensile stress-strain and tension-tension fatigue of geopolymer matrix composites reinforced with 0/90 carbon fibers was investigated at 23 and 300°C in laboratory air. Geopolymers are inorganic polymeric materials composed of alumina, silica, and alkali metal oxides. Because geopolymers are synthesized as a fluid mixture or particles and liquid, they can be cast into a desired shape, and cured at only slightly elevated temperatures. The relative ease of synthesis and low processing temperatures make geopolymers an attractive choice as a matrix material for composite materials. Geopolymers also offer resistance to heat and oxidizing environments. Currently, geopolymer matrix composites are being …

Direct Print Additive Manufacturing Of Optical Fiber Interconnects, Roger B. Tipton

USF Tampa Graduate Theses and Dissertations

High performance communications, sensing and computing systems are growing exponentially as modern life continues to rely more and more on technology. One of the factors that are currently limiting computing and transmission speeds are copper wire interconnects between devices. Optical fiber interconnects would greatly increase the speed of today’s electronic devices. In this study it has been demonstrated that by using a new Direct Print Additive Manufacturing (DPAM) process of Fused Deposition Modeling (FDM) of plastic and micro-dispensing of pastes and inks, we can 3D print single and multi-mode optical fibers in a controlled manner such that compact, 3-dimensional optical …

A System Dynamics Innovation Diffusion Model Applied To Carbon Nanotube Manufacturing, Frances G. Mackinnon

Theses and Dissertations

The transition of advanced technologies from their nascent state to viable commercial entities is a critical step in assuring the United States' national technological superiority and support is often required to incubate such technological developments. We propose a spiral development to investigate the possible scenarios, underlying economics, and risk associated with scaling up carbon nanotube (CNT) production to a commercially viable scale. As the first stage of this proposed effort, this study characterizes the potential scenarios by which a CNT manufacturing company can generate positive annual net revenue and potentially be considered a competitive manufacturer of CNT products on an …

Creep Of Hafnium Diboride -20 Vol% Silicon Carbide At 1500°C In Air, Glen E. Pry

Theses and Dissertations

Refractory metal borides, commonly referred to as Ultra High Temperature Ceramics (UHTCs), exhibit a number of unique properties, such as extremely high melting temperature and hardness, chemical stability, high electrical and thermal conductivity and corrosion resistance. It has been demonstrated that the addition of SiC improves the oxidation resistance of ZrB2- and HfB2-based UHTCs above 1200°C by modifying the composition of the oxide scale. Addition of SiC retards the oxidation rate of ZrB2 and HfB2 by forming a protective layer of borosilicate glass. Creep deformation is one of the critical criterion for structural application of ceramics at elevated temperatures. Compression …

Measuring The Creep Behaviour Of Corrugated Board By Cascade And Individual Test Rig, Viktoria Köstner, Jörg B. Ressel, Bernd Sadlowsky, Péter Böröcz

Journal of Applied Packaging Research

In this paper static and quasi-static test are conducted to determine the creep behaviour of corrugated board. This study shows a possible way to take the real loads occurring in container shipping into account. The aim of the measurements is to develop a new test option, which is in keeping with the loads occurring. Two test rigs have been developed and constructed for this purpose. These make it possible to measure the creep of corrugated board extremely precisely over a longer period in the aspect of climate chamber size and relative humidity (RH) distribution in the chamber. To increase the …

Selective Laser Melting Of Ni-Rich Niti: Selection Of Process Parameters And The Superelastic Response, Narges Shayesteh Moghaddam, Soheil Saedi, Amirhesam Amerinatanzi, Ehsan Saghaian, Ahmadreza Jahadakbar, Haluk E. Karaca, Mohammad Elahinia

Mechanical Engineering Faculty Publications

Material and mechanical properties of NiTi shape memory alloys strongly depend on the fabrication process parameters and the resulting microstructure. In selective laser melting, the combination of parameters such as laser power, scanning speed, and hatch spacing determine the microstructural defects, grain size and texture. Therefore, processing parameters can be adjusted to tailor the microstructure and mechanical response of the alloy. In this work, NiTi samples were fabricated using Ni_50.8Ti (at.%) powder via SLM PXM by Phenix/3D Systems and the effects of processing parameters were systematically studied. The relationship between the processing parameters and superelastic properties were investigated …

Influence Of Slm On Compressive Response Of Niti Scaffolds, Narges Shayesteh Moghaddam, Soheil Saedi, Amirhesam Amerinatanzi, Ahmadreza Jahadakbar, Sayed Ehsan Saghaian, Haluk E. Karaca, Mohammad Elahinia

Mechanical Engineering Faculty Publications

Porous Nickel-Titanium shape memory alloys (NiTi-SMAs) have attracted much attention in biomedical applications due to their high range of pure elastic deformability (i.e., superelasticity) as well as their bone-level modulus of elasticity (E≈12-20 GPa). In recent years, Selective Laser Melting (SLM) has been used to produce complex NiTi components. The focus of this study is to investigate the superelasticity and compressive properties of SLM NiTi-SMAs. To this aim, several NiTi components with different level of porosities (32- 58%) were fabricated from Ni_50.8Ti (at. %) powder via SLM PXM by Phenix/3D Systems, using optimum processing parameter (Laser power-P=250 W, …

Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 1000°C In Air And In Silicic Acid-Saturated Steam, Brian G. Kroeger

Theses and Dissertations

Advanced SiC/SiC ceramic matrix composites (CMCs) are being considered for a variety of applications. Of interest is their ability to withstand exposure to high temperature in an aggressive oxidizing environment. The presence of steam creates such an environment. As steam traverses across a SiC/SiC composite and through cracks in the SiC matrix, it becomes saturated with silicic acid, Si(OH)₄. It is essential to understand the long-term impacts and durability of SiC/SiC CMCs that have been exposed to such a demanding environment. The present research investigated creep of Hi-Nicalon™ S SiC fibers at 1000°C in air and in silicic …

Non-Precious Metal Catalysts For Oxygen Reduction Reaction In Alkaline Solutions, Zhewen Yin

USF Tampa Graduate Theses and Dissertations

Mesoporous WO3 powders were prepared via sol-gel processing synthesis using nonionic surfactant Pluronic (P-123) as the template. The influences of heating temperature on the pore structure and properties of WO3 powders were investigated. Three kinds of modifications were compared and evaluated after finding out the best heating condition. Different amount of lanthanum was doped into mesoporous WO3 to improve its Oxygen Reduction Reaction (ORR) activity. Several factors contributing to the increase of catalytic performance were discussed. Vulcan carbon powder was also used as a support to increase the catalysts’ electrical conductivity as well as dispersity. The component, microstructure and specific …

The Subject Librarian Newsletter, Engineering And Computer Science, Spring 2018, Buenaventura "Ven" Basco

Libraries' Newsletters

No abstract provided.

Communication And Biodegradable Packaging Relationship: A Paradigm For Final Disposal, Breno Luiz Ottoni, Rafael Mattos Deus, José Alcides Gobbo Junior, Ângela Maria Grossi De Carvalho, Rosane Aparecida Gomes Battistelle

Journal of Applied Packaging Research

Solid waste generation is estimated to increase from 1.3 billion to 2.2 billion tons by 2025, causing environmental, social, and consequently public health problems. The biggest problem in this regard involves the inadequate disposal of waste, and in emerging countries like Brazil, it is sorted less waste for recycling or composting. In this context, plastic packaging is more complex due to the high polymer composition, as well as low recycling rates. Bioplastics appear as alternatives because they are mostly biodegradable. Given the various functions of packaging and a systematic review of the literature, the aim of this study was to …

Synthesis And Characterization Of Polymer-Silica Composite Hydrogel Particles And Influence Of Hydrogel Composition On Cement Paste Microstructure, Matthew J. Krafcik, B Bose, Kendra Erk

School of Materials Engineering Faculty Publications

The objective of this research is to define the fundamental structure-property relationships of water-swollen polymer hydrogel particles that are employed as internal curing agents in cementitious mixtures, in addition to reporting a novel synthesis procedure for combining pozzolanic materials with hydrogel particles. Solution polymerization was performed to incorporate amorphous nanosilica particles within acrylic-based polymer hydrogel particles of varying chemical compositions (i.e., monomer ratio of acrylic acid (AA) to acrylamide (AM)). Experiments were designed to measure the absorption capacity and kinetics of hydrogel particles immersed in pure water and cementitious pore solution, as well as determine the impact of particles on …

Preparation, Modification, Characterization, And Biosensing Application Of Nanoporous Gold Using Electrochemical Techniques, Jay Bhattarai, Dharmendra Neupane, Bishal Nepal, Vasilii Mikhaylov, Alexei Demchenko, Keith Stine

Chemistry & Biochemistry Faculty Works

Nanoporous gold (np-Au), because of its high surface area-to-volume ratio, excellent conductivity, chemical inertness, physical stability, biocompatibility, easily tunable pores, and plasmonic properties, has attracted much interested in the field of nanotechnology. It has promising applications in the fields of catalysis, bio/chemical sensing, drug delivery, biomolecules separation and purification, fuel cell development, surface-chemistry-driven actuation, and supercapacitor design. Many chemical and electrochemical procedures are known for the preparation of np-Au. Recently, researchers are focusing on easier and controlled ways to tune the pores and ligaments size of np-Au for its use in different applications. Electrochemical methods have good control over fine-tuning …

Application Of Cross-Linked Polyborosiloxanes And Organically Modified Boron Silicate Binders In Silicon-Containing Anodes For Lithium-Ion Batteries, Darius A. Shariaty, Dali Qian, Yang-Tse Cheng, Susan A. Odom

Chemistry Faculty Publications

To determine the effect of cross-linking in polymer binders on gravimetric capacity and retention in charge/discharge cycling of lithium-ion batteries containing silicon anodes, polymers with a varied chemiophysical characters have been studied as electrode binders. Here we report the utilization of cross-linked polyborosiloxanes and a boron-modified organosilicate as binders for nanoparticulate silicon-containing anodes for lithium-ion batteries. We show that highly cross-linked binders enable a large degree of capacity to be accessed and that capacity retention is greater when the electrodes are cycled in half cells. More extensive analysis of the boron-modified organosilicate is further explored.

Applications Of Open Source Gmaw-Based Metal 3-D Printing, Yuenyong Nilsiam, Paul G. Sanders, Joshua M. Pearce

Department of Materials Science and Engineering Publications

The metal 3-D printing market is currently dominated by high-end applications, which make it inaccessible for small and medium enterprises, fab labs, and individual makers who are interested in the ability to prototype and additively manufacture final products in metal. Recent progress led to low-cost open-source metal 3-D printers using a gas metal arc welding (GMAW)-based print head. This reduced the cost of metal 3-D printers into the range of desktop prosumer polymer 3-D printers. Consequent research established good material properties of metal 3-D printed parts with readily-available weld filler wire, reusable substrates, thermal and stress properties, toolpath planning, bead-width …

Supported Perovskite-Type Oxides: Establishing A Foundation For Co2 Conversion Through Reverse Water-Gas Shift Chemical Looping, Bryan J. Hare

USF Tampa Graduate Theses and Dissertations

Perovskite-type oxides show irrefutable potential for feasible thermochemical solar-driven CO₂ conversion. These materials exhibit the exact characteristics required by the low temperature reverse water-gas shift chemical looping process. These properties include structural endurance and high oxygen redox capacity, which results in the formation of numerous oxygen vacancies, or active sites for CO₂ conversion. A major drawback is the decrease in oxygen self-diffusion with increasing perovskite particle size. In this study, the La_0.75Sr_0.25FeO₃ (LSF) perovskite oxide was combined with various supports including popular redox materials CeO₂ and ZrO₂ along with more abundant …

Orthogonal Photo-Switching Of Supramolecular Patterned Surfaces, Dongsheng Wang, Frank Schellenberger, Jonathan T. Pham, Hans-Jürgen Butt, Si Wu

Chemical and Materials Engineering Faculty Publications

We used Azo/α-CD and ipAzo/γ-CD host–guest complexes to demonstrate that four independent stable states can be orthogonally photo-switched by UV (365 nm), blue (470 nm), green (530 nm) and red light (625 nm). A supramolecular patterned surface was fabricated and orthogonally photo-switched by light with different wavelengths.

Development Of A Resilient 3-D Printer For Humanitarian Crisis Response, Benjamin L. Savonen, Tobias Mahan, Maxwell W. Curtis, Jared W. Schreier, John K. Greshonen, Joshua M. Pearce

Department of Materials Science and Engineering Publications

Rapid manufacturing using 3-D printing is a potential solution to some of the most pressing issues for humanitarian logistics. In this paper, findings are reported from a study that involved development of a new type of 3-D printer. In particular, a novel 3-D printer that is designed specifically for reliable rapid manufacturing at the sites of humanitarian crises. First, required capabilities are developed with design elements of a humanitarian 3-D printer, which include, (1) fused filament fabrication, (2) open source self-replicating rapid prototyper design, (3) modular, (4) separate frame, (5) protected electronics, (6) on-board computing, (7) flexible power supply, and …

Comparison Of Plume Dynamics For Laser Ablated Metals: Al And Ti, William A. Bauer, Glen P. Perram, Timothy J. Haugan

Faculty Publications

Emissive plumes from pulsed laser ablation of bulk Ti and Al from KrF laser irradiation at laser fluence up to 3.5 J/cm² and argon background pressures of 0–1 Torr have been observed using gated intensified charged-coupled device imagery. Mass loss for Ti increases from 0.1 to 0.8 μg/pulse as pulse energy increase from 174 to 282 mJ/pulse (35–170 photons/atom) and decreases by ∼30% as pressure increases from vacuum to 1 Torr. Early plume energies are described by the free expansion velocities of 1.57 ± 0.02 and of 1.81 ± 0.07 cm/μs for Ti and Al, respectively, …

Demonstration Of Versatile Whispering-Gallery Micro-Lasers For Remote Refractive Index Sensing, Lei Wan, Hengky Chandrahalim, Jian Zhou

Faculty Publications

We developed chip-scale remote refractive index sensors based on Rhodamine 6G (R6G)-doped polymer micro-ring lasers. The chemical, temperature, and mechanical sturdiness of the fused-silica host guaranteed a flexible deployment of dye-doped polymers for refractive index sensing. The introduction of the dye as gain medium demonstrated the feasibility of remote sensing based on the free-space optics measurement setup. Compared to the R6G-doped TZ-001, the lasing behavior of R6G-doped SU-8 polymer micro-ring laser under an aqueous environment had a narrower spectrum linewidth, producing the minimum detectable refractive index change of 4 x 10⁻⁴ RIU. The maximum bulk refractive index sensitivity (BRIS) …

A New Hybrid Decision Support Tool For Evaluating The Sustainability Of Mining Projects, S. Kamenopoulos, Zacharias Agioutantis, K. Komnitsas

Mining Engineering Faculty Publications

The integration of sustainable development challenges and opportunities into the decision making process during the design and/or implementation of multi-disciplinary mining projects is generally not supported by decision support systems (DSS). A new hybrid decision support tool, which features an integrated assessment of sustainable development issues as they apply to mining projects, is hereby proposed. The proposed DSS framework, named “Acropolis DSS”, can be used to assist involved stakeholders in critical decisions, especially when addressing issues such as stakeholder participation, transparency, and trade-offs. The proposed DSS is based on a multi-criteria decision analysis combined with the multi-attribute utility theory.

Understanding Homogeneous Nucleation In Solidification Of Aluminum By Molecular Dynamics Simulations, A. Mahata, Mohsen Asle Zaeem, M. I. Baskes

Materials Science and Engineering Faculty Research & Creative Works

Homogeneous nucleation from aluminum (Al) melt was investigated by million-atom molecular dynamics simulations utilizing the second nearest neighbor modified embedded atom method potentials. The natural spontaneous homogenous nucleation from the Al melt was produced without any influence of pressure, free surface effects and impurities. Initially isothermal crystal nucleation from undercooled melt was studied at different constant temperatures, and later superheated Al melt was quenched with different cooling rates. The crystal structure of nuclei, critical nucleus size, critical temperature for homogenous nucleation, induction time, and nucleation rate were determined. The quenching simulations clearly revealed three temperature regimes: sub-critical nucleation, super-critical nucleation, …