Engineering Commons^™

Pressureless Sintering Of Zirconium Diboride With Carbon And Boron Carbide Nanopowder, Eric W. Neuman, Gregory E. Hilmas, William Fahrenholtz

Materials Science and Engineering Faculty Research & Creative Works

Zirconium diboride ceramics with and without carbon and boron carbide nano powder additives were prepared by ball milling with ZrB2 grinding media and pressureless sintering. Additions of up to 1 wt% nano-B4C and 0.5 wt% C were made to the ZrB2 powder. The materials were then sintered between 1800 and 2300 °C for between 90 and 360 min in an Ar/10H2 atmosphere. After sintering at 2200 °C for 90 min, densities ranged from 88.3 to 90.7% for the ZrB2 with 0–1.0% nano-B4C addition. Carbon additions of 0.5 wt% and nano-B4C additions from 0 to 1.0 wt% resulted in densities ranging …

Crystal Structure Prediction Of Materials At Extreme Conditions, Ashley S. Williams

USF Tampa Graduate Theses and Dissertations

The prediction of the structure of a crystal given only the constituent elements is one of the greatest challenges in both materials science and computational science alike. If one were to try to predict a novel crystal by brute force, meaning by arranging the atoms in every possible position of the unit cell and optimizing the geometry to find the energy minima of the potential energy surface, the amount of computer resources required to complete the calculation on the timescale of a few years would vastly exceed the currently installed computational capacity of the entire world. Fortunately, several methods have …

Equations Of State For Warm Dense Carbon From Quantum Espresso, Derek J. Schauss

Theses and Dissertations

Warm dense plasma is the matter that exists, roughly, in the range of 10,000 to 10,000,000 Kelvin and has solid-like densities, typically between 0.1 and 10 grams per centimeter. Warm dense fluids like hydrogen, helium, and carbon are believed to make up the interiors of many planets, white dwarfs, and other stars in our universe. The existence of warm dense matter (WDM) on Earth, however, is very rare, as it can only be created with high-energy sources like a nuclear explosion. In such an event, theoretical and computational models that accurately predict the response of certain materials are thus very …

Jcati Pyrolysis System, Jack Dutton

All Undergraduate Projects

The Joint Center for Aerospace Technology Innovation (JCATI) project is designed to recycle carbon fiber pieces for use in manufacturing. Part of the system requires the removal of resin from the carbon fibers to facilitate the recycling of carbon fiber. To accomplish this task the pyrolysis process is implemented using a commercial grade oven with a conveyor system. Argon gas is injected into the shroud and over the oven to purge the interior of oxygen. The conveyor system enables this to be a batch process. A ramp is used to allow simple addition of material to the conveyor system and …

Carbon Oxidation At The Atomic Level: A Computational Study On Oxidative Graphene Etching And Pitting Of Graphitic Carbon Surfaces, Simon Schmitt

Theses and Dissertations--Mechanical Engineering

In order to understand the oxidation of solid carbon materials by oxygen-containing gases, carbon oxidation has to be studied on the atomic level where the surface reactions occur. Graphene and graphite are etched by oxygen to form characteristic pits that are scattered across the material surface, and pitting in turn leads to microstructural changes that determine the macroscopic oxidation behavior. While this is a well-documented phenomenon, it is heretofore poorly understood due to the notorious difficulty of experiments and a lack of comprehensive computational studies. The main objective of the present work is the development of a computational framework from …

Exploring The Electrical Properties Of Twisted Bilayer Graphene, William Shannon

Senior Theses

Two-dimensional materials exhibit properties unlike anything else seen in conventional substances. Electrons in these materials are confined to move only in the plane. In order to explore the effects of these materials, we have built apparatus and refined procedures with which to create two-dimensional structures. Two-dimensional devices have been made using exfoliated graphene and placed on gold contacts. Their topography has been observed using Atomic Force Microscopy (AFM) confirming samples with monolayer, bilayer, and twisted bilayer structure. Relative work functions of each have been measured using Kelvin Probe Force Microscopy (KPFM) showing that twisted bilayer graphene has a surface potential …

Acid Treated Carbon As Anodic Electrocatalysts Toward Direct Ascorbic Acid Alkaline Membrane Fuel Cells, He-Mu Chen, Chen-Xi Qiu, Yuan-Yuan Cong, Hui-Yuan Liu, Zi-Hui Zhai, Yu-Jiang Song

Journal of Electrochemistry

In order to improve the hydrophilicity and electrocatalytic activity, commercial carbon black (BP 2000) was subjected to acid treatment to obtain acid-treated carbon (ATC). The generation of rich oxygen-containing groups on the surface of the ATC was proved by X-ray photoelectron spectra (XPS), Fourier transform-infra red spectra (FTIR), thermogravimetric analysis (TG) and contact angle measurement. UV-vis spectra were firstly recorded to calculate activation energy (Ea) of ascorbic acid (AA) chemical oxidation in alkaline conditions by oxygen in air and the Ea value was determined to be 37.1 kJ·mol^-1. Additionally, electrochemical impedance spectra (EIS) were used to evaluate unprecedented …

First-Principles Study Of The Products Of Co2 Dissociation On Nickel-Based Alloys: Trends In Energetics With Alloying Element, Lynza H. Sprowl, Benjamin Adam, Julie D. Tucker, Líney Árnadóttir

Mechanical and Materials Engineering Faculty Publications and Presentations

Oxidation and corrosion of nickel and Ni-based alloys are a problem for many industrial applications, such as power plants that use supercritical CO2 as the working fluid. In supercritical CO2 environments, CO2 dissociates on the surface forming adsorbed CO and O, which can oxidize the surface. The adsorbed CO can further breakdown via direct CO dissociation or via the Boudouard reaction to form adsorbed C, which can in turn carburize the surface. Understanding how the adsorbed species interact with different Ni-based alloys can help guide the design of future alloys. The interactions of adsorbed O, C, and CO on the …

Development Of Low Cost, Environmentally Friendly And High Strength Carbon Foams From Bread And Cake, Laura Mountain-Tuller

Materials Engineering

Carbon foam is a high niche material that consists of a highly porous, three-dimensional cellular network that is characterized by extremely high strength-to-weight ratios and low thermal conductivity. Due to these properties, carbon foams excel in structural and thermal applications, especially in the aerospace industry. Typically, carbon foams are formed through a heating process called pyrolysis of polymer precursors with high carbon content. This process is done at high temperatures in an oxygen free environment. These precursors are expensive to make and use toxic chemicals to produce, therefore, there is a push to find an environmentally friendly and cost-effective method …

Photoluminescence From Gan Co-Doped With C And Si, Mykhailo Vorobiov

Theses and Dissertations

This thesis devoted to the experimental studies of yellow and blue luminescence (YL and BL relatively) bands in Gallium Nitride samples doped with C and Si. The band BL_C was at first observed in the steady-state photoluminescence spectrum under high excitation intensities and discerned from BL1 and BL2 bands appearing in the same region of the spectrum. Using the time-resolved photoluminescence spectrum, we were able to determine the shape of the BL_C and its position at 2.87 eV. Internal quantum efficiency of the YL band was estimated to be 90\%. The hole capture coefficient of the BL_{C …}

Bear Minimum: Ultralight Composite Bear Canister, Rama B. Adajian, Adam C. Eisenbarth

Mechanical Engineering

The ultralight backpacking community needs a strong, easy to use, safe bear canister that is lighter than current market products for trekking in the backcountry. A full design of the lid for the bear canister is to be completed. This includes the locking mechanism to ensure it is bear proof, the interface between the lid and the canister, and the structure of the lid so it passes the strength and weight specifications. The lid, along with the already designed canister body, is to be manufactured with formal documentation. The lid will initially be tested separately and then with the canister …

Preparation And Electrochemical Properties Of Attapulgite-Supported Nitrogen-Doped Carbon@Nico2O4Composites For Supercapacitors, Hui Wan, Zong-Rong Ying, Xin-Dong Liu, Jian-Jian Lu, Wen-Wen Zhang

Journal of Electrochemistry

In this work, the attapulgite-supported nitrogen-doped carbon (ANC) was prepared by in-situ chemically polymerizing polyaniline coating upon attapulgite, followed by high temperature heat treatment, and then NiCo₂O₄was reacted onto the surface of ANC by a combination of hydrothermal reaction and calcination to synthesize ANC@NiCo₂O₄ composites. The chemical composition and morphology of the samples were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N₂ adsorption/desorption. The electrochemical properties were evaluated by means of constant current charge discharge (GCD) and cyclic voltammetry (CV). …

Indentation Behavior Of Superelastic Hard Carbon, Olga Chernogorova, Ekaterina Drozdova, Iraida Ushakova, Evgenii Ekimov, Vicente Benavides, Aleksander Soldatov

Nanomechanical Testing in Materials Research and Development V

Supererlastic hard carbon particles up to 1 mmin size were produced by fullerene collapse upon high-pressure high-temperature treatment with simultaneous sintering of metal-matrix composite materials (CM) reinforced by such particles. The hardness of carbon particles can be varied in a wide range by changing the parameters of their structure, which consists of curved graphene planes or their packets of different sizes. Such carbon phase was called “nanoclusterd graphene phase” (NGP) [1]. The properties of the carbon particles were controlled by changing treatment pressure (5 and 8 GPa) and temperature (1100-1800 K), composition of parent fullerites (C60 or C60/70), and pre-treatment …

Lignin-Based Li-Ion Anode Materials Synthesized From Low-Cost Renewable Resources, Nicholas William Mcnutt

Doctoral Dissertations

In today’s world, the demand for novel methods of energy storage is increasing rapidly, particularly with the rise of portable electronic devices, electric vehicles, and the personal consumption and storage of solar energy. While other technologies have arguably improved at a rate that is exponential in accordance with Moore’s law, battery technology has lagged behind largely due to the difficulty in devising new electric storage systems that are simultaneously high performing, inexpensive, and safe.

In order to tackle these challenges, novel Li-ion battery anodes have been developed at Oak Ridge National Laboratory that are made from lignin, a low-cost, renewable …

Applications Of Carbon Materials In Electrochemical Energy Storage, Ji Liang, Lei Wen, Hui-Ming Cheng, Feng Li

Journal of Electrochemistry

An electrode material for electrochemical energy storage is one of the key components for high performance devices. In a variety of electrochemical energy storage systems, carbon materials, especially the lately emerged carbon nanomaterials including the carbon nanotube and graphene, have been playing a very important role and brought new vitality to the development and demonstration of the broad application prospects. In this review, we summarize the applications of various carbon materials in the typical electrochemical energy storage devices, namely lithium/sodium ion batteries, supercapacitors, and lithium-sulfur batteries, as well as flexible electrochemical energy storage and electrochemical catalysis. A perspective of novel …

Single Fiber Mechanical Properties Using Nano-Tensile Testing And Carbon Fiber Structure-Property Relationship, Matthew Erich Kant

Doctoral Dissertations

Single carbon fibers are studied using a nano-tensile testing system. This system has unprecedented load and displacement resolution, nN and nm respectively, and the ability to perform dynamic testing for storage and loss modulus during quasi-static tensile extension. Furthermore, improved fiber mounting and alignment procedures coupled with the precision of the nano-tensile testing system assist in unprecedented resolution in single fiber mechanical testing for axial modulus and strength. Hence, using these unique capabilities, the moduli and their statistical distribution of many high performance carbon fibers are reported here. From this, a simplified single parameter model describing the strain dependent modulus …

Mode I Fracture Toughness Of Eight-Harness-Satin Carbon Cloth Weaves For Co-Cured And Post-Bonded Laminates, Josh E. Smith

Master's Theses

Mode I interlaminar fracture of 3k 8-Harness-Satin Carbon cloth, with identical fill and weft yarns, pre-impregnated with Newport 307 resin was investigated through the DCB test (ASTM D5528). Crack propagations along both the fill and weft yarns were considered for both post-bonded (co-bonded) and co-cured laminates. A patent-pending delamination insertion method was compared to the standard Teflon film option to assess its applicability to mode I fracture testing. The Modified Beam Theory, Compliance Calibration method, and Modified Compliance Calibration method were used for comparative purposes for these investigations and to evaluate the validity of the proposed Equivalent Stiffness (EQS) method. …

On Electric Conduction Of Amorphous Silicon Carbonitride Derived From A Polymeric Precursor, Yaohan Chen, Fuqian Yang, Linan An

Chemical and Materials Engineering Faculty Publications

A long-existing problem that the conductivity of amorphous silicon carbonitrides derived from polymeric precursor increases significantly with pyrolysis temperature is investigated. We show that the conductivity exhibited an Arrhenius dependence on pyrolysis temperature, with the activation energy of ∼3.41 eV. Structural analysis using Raman spectroscopy reveals that the free carbon within the material undergoes a sp³-to-sp² transition as pyrolysis temperature increases, with the activation energy of ∼3.6 eV. We conclude that the pyrolysis-temperature induced increase in the conductivity is mainly due to the increase in the conductivity of the free carbon. A simple model is proposed to …

Evaluation Of The Transient Thermal Performance Of A Graphite Foam/Phase Change Material Composite, Michael Paul Trammell

Masters Theses

The thermal transient response of graphite foam infiltrated with paraffin wax as a thermal protection composite was investigated. Graphite foam is a rigid open-celled porous carbon material that exhibits high thermal conductivity along the ligaments. To increase the ability of graphite foam to store heat energy, it was infiltrated with a phase change material, paraffin wax. Filling the foam with a phase change material (PCM) creates a composite that transfers heat through an interconnected network of ligaments to a large surface area of PCM for absorption. Foams were made at various pressures to understand the effect of porosity, which also …

Parametric Study Of Reaxff Simulation Parameters For Molecular Dynamics Modeling Of Reactive Carbon Gases, Benjamin David Jensen

Dissertations, Master's Theses and Master's Reports - Open

Abstract

Wolfpack Gear Inc. Composite Frame Firefighter Backpack, Gabriel Mountjoy, Blair Ridings, Carl Drummond Buchenroth

Mechanical Engineering

No abstract provided.

Development Of Interatomic Potentials For Large Scale Molecular Dynamics Simulations Of Carbon Materials Under Extreme Conditions, Romain Perriot

USF Tampa Graduate Theses and Dissertations

The goal of this PhD research project is to devise a robust interatomic potential for large scale molecular dynamics simulations of carbon materials under extreme conditions. This screened-environment dependent reactive empirical bond order potential (SED-REBO) is specifically designed to describe carbon materials under extreme compressive or tensile stresses. Based on the original REBO potential by Brenner and co workers, SED-REBO includes reparametrized pairwise interaction terms and a new screening term, which serves the role of a variable cutoff. The SED-REBO potential overcomes the deficiencies found with the most commonly used interatomic potentials for carbon: the appearance of artificial forces due …

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 …

Mesophase Pitch-Based Carbon Fiber And Its Composites: Preparation And Characterization, Chang Liu

Masters Theses

The objective of this study is to investigate the relationship among process, structure, and property of the UTSI pitch-based carbon fibers and optimize carbon fiber’s mechanical properties through the stabilization process. Various analysis techniques were employed throughout these investigations which include the Scanning Electron Microscope (SEM), optical microscope, Dia-stron system, MTS, and ImageJ.

Several fiber process techniques including fiber spinning, stabilization, and carbonization were explored to determine the effect of the thermal process on the fiber yield, fiber diameter, the sheath-core structure of stabilized fibers, the pac-man and hollow core structures of carbonized fibers, and the resulting mechanical properties of …

Prevention Of Environmentally Induced Degradation In Carbon/Epoxy Composite Material Via Implementation Of A Polymer Based Coati, Bradford Tipton

Electronic Theses and Dissertations

As the use of fiber reinforced plastics increases in such industries as aerospace, wind energy, and sporting goods, factors effecting long-term durability, such as environmental exposure, are of increasing interest. The primary objectives of this study were to examine the effects of extensive environmental exposure (specifically UV radiation and moisture) on carbon/epoxy composite laminate structures and to determine the relative effectiveness of polymer-based coatings at mitigating degradation incurred due to such exposure. Carbon/epoxy composite specimens, both coated and uncoated, were subjected to accelerated weathering in which prolonged outdoor exposure was simulated by controlling the radiation wavelength (in the UV region), …

Catalytic Conversion Of Hydrocarbons To Hydrogen And High-Value Carbon, Naresh Shah, Devadas Panjala, Gerald P. Huffman

Chemical and Materials Engineering Faculty Patents

The present invention provides novel catalysts for accomplishing catalytic decomposition of undiluted light hydrocarbons to a hydrogen product, and methods for preparing such catalysts. In one aspect, a method is provided for preparing a catalyst by admixing an aqueous solution of an iron salt, at least one additional catalyst metal salt, and a suitable oxide substrate support, and precipitating metal oxyhydroxides onto the substrate support. An incipient wetness method, comprising addition of aqueous solutions of metal salts to a dry oxide substrate support, extruding the resulting paste to pellet form, and calcining the pellets in air is also discloses. In …

The Effects Of Patch Properties On The Debonding Behavior Of Patched Beam-Plates, Anette M. Karlsson

Mechanical Engineering Faculty Publications

The debonding characteristics of patched structures are investigated in this study by means of an analytical model. In particular, the effects the lay-up sequence and edge tapering of a carbon-reinforced epoxy patch, as well as the beveling of an aluminum patch, have on the initiation, stability, and extent of the debonding are considered. The results presented show that both the degree of edge-tapering and the patch properties must be carefully selected in order to optimize the patched structure. It is also shown that when designing a patched system, it is important to model the correct boundary and load conditions to …

Activated Carbon And Process For Making Same, Francis John Derbyshire, Marit Jagtoyen

Chemical and Materials Engineering Faculty Patents

A process is described for the manufacture of activated carbon in the form of a powder, as granules or as extrudates. The process includes treating a biomass feedstock, such as woods, coconut shells, fruit pits, peats, lignites and all ranks of coal with a processing agent and an activation agent. The processing agent may be a natural or synthetic monomer, oligomer, polymer or mixtures thereof capable of interacting or co-polymerizing with the biomass feedstock. The activation agent may be, for example, phosphoric acid, zinc chloride or mixtures thereof. A high surface area, high hardness extruded activated carbon may be produced …

Kinetics Of Laser Chemical Vapor Deposition Of Carbon And Refractory Metals, Feng Gao

Doctoral Dissertations

Three-dimensional laser chemical vapor deposition (3D-LCVD) has been used to grow rods of carbon, tungsten, titanium, and hafnium from a variety of hydrocarbons and metal halide-based precursors. A novel computerized 3D-LCVD system was designed and successfully used in the experiments. A focused Nd:Yag laser beam (λ = 1.06 μm) was utilized to locally heat up a substrate to deposition temperature. The rods, which grew along the axis of the laser beam, had a typical diameter of 30–80 μm and a length of about 1 mm. The precursors for carbon deposition were the alkynes: propyne, butyne, pentyne, hexyne, and octyne. Propyne …