Materials Science and Engineering Commons^™

Evolution Of The Pore Size Distribution In Sheared Binary Glasses, Nikolai V. Priezjev, Maxim A. Makeev

Mechanical and Materials Engineering Faculty Publications

Molecular dynamics simulations are carried out to investigate mechanical properties and porous structure of binary glasses subjected to steady shear. The model vitreous systems were prepared via thermal quench at constant volume to a temperature well below the glass transition. The quiescent samples are characterized by a relatively narrow pore size distribution whose mean size is larger at lower glass densities. We find that in the linear regime of deformation, the shear modulus is a strong function of porosity, and the individual pores become slightly stretched while their structural topology remains unaffected. By contrast, with further increasing strain, the shear …

Synthesis Of Graphene And Graphene-Based Composite Membrane, Yuanjun Fan

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Vibration membrane equipped for earphone requires high performance in both mechanical properties and electronic properties. With extraordinary properties on both, graphene and graphene-based composite materials appear as a promising candidate for this application. Chemical vapor deposition (CVD) is believed to be the most convenient way to synthesize a large area (on scale of square centimeters) as well as a homogeneous thickness for the membrane. The thesis focuses on applying control variable experiment method to analyze different effects on mechanical property of the two CVD setting parameters: cooling rate, and hydrocarbon precursor. For isolating the specimens efficiently, a modified electrochemical method …

Morphological, Thermal And Oxygen Barrier Properties Plasticized Film Polylactic Acid, Kurniawan Yuniarto, Bruce A. Welt, Foliatini -, Hanafi -, Candra Irawan

Journal of Applied Packaging Research

Introducing plasticizer poly(ethylene glycol) (PEG400) was applied into poly(lactic acid) (PLA) to produce film matrix packaging by direct casting. Non mechanical properties were carried out plasticized PLA including morphology, crystallinity structure and degree, thermal properties and oxygen barrier properties. Plasticized PLA revealed improving surface structure of PLA film matrix form fractures and homogenous film were achieved at 5% PEG 400. Chromatogram PLA and plasticized PLA were categorized crystal structure an α-form crystal. Intercalated and exfoliated structure did not occur significantly due to dispersion PEG 400 in the matrix but indicated dispersion structure. Thermal properties did not improve plasticized PLA significantly …

Nonlinear Optical Properties Of Gesbs Chalcogenide Waveguides, Ju Won Choi, Byoung Uk Sohn, George F.R. Chen, Dawn T.H. Tan, Zhaohong Han, Lionel C. Kimerling, Charmayne Smith (Lonergan), Kathleen A. Richardson, Anuradha M. Agarwal

Materials Science and Engineering Faculty Research & Creative Works

We characterize the nonlinear optical properties of GeSbS chalcogenide glasses with fiber-based experiments. A waveguide nonlinear parameter of 7 W-1/m and nonlinear refractive index of 3.71 x 10-18 m2/W are estimated by self-phase modulation. A GeSbS waveguide could also generate a supercontinuum from 1280 to 2120 nm at the -30 dB level for maximum coupled power of 340 W, showing a 14-fold spectral broadening of the input spectrum explained by cascaded stimulated Raman scattering.

Effective Mechanical Properties Of Multilayer Nano-Heterostructures, T Mukhopadhyay, A Mahata, S Adhikari, Mohsen Asle Zaeem

Materials Science and Engineering Faculty Research & Creative Works

Two-dimensional and quasi-two-dimensional materials are important nanostructures because of their exciting electronic, optical, thermal, chemical and mechanical properties. However, a single-layer nanomaterial may not possess a particular property adequately, or multiple desired properties simultaneously. Recently a new trend has emerged to develop nano-heterostructures by assembling multiple monolayers of different nanostructures to achieve various tunable desired properties simultaneously. For example, transition metal dichalcogenides such as MoS₂ show promising electronic and piezoelectric properties, but their low mechanical strength is a constraint for practical applications. This barrier can be mitigated by considering graphene-MoS₂ heterostructure, as graphene possesses strong mechanical properties. We …

Manipulating Electromagnetic Waves With Enhanced Functionalities Using Nonlinear And Chiral Metamaterials, Sinhara Rishi Malinda Silva

USF Tampa Graduate Theses and Dissertations

Metamaterials are artificial structures, which periodically arranged to exhibit fascinating electromagnetic properties, not existing in nature. A great deal of research in the field of metamaterial was conducted in a linear regime, where the electromagnetic responses are independent of the external electric or magnetic fields. Unfortunately, in linear regime the desired properties of metamaterials have only been achieved within a narrow bandwidth, around a fixed frequency. Therefore, nonlinearity is introduced into metamaterials by merging meta-atoms with well-known nonlinear materials. Nonlinear metamaterials are exploited in this dissertation to introduce and develop applications in microwave frequency with broadband responses. The nonlinearity was …

Investigating Scalable Manufacturing Of High-Conductivity Wires And Coatings From Ultra-Long Carbon Nanotubes, Pouria Khanbolouki

Mechanical Engineering ETDs

Carbon nanotubes (CNTs) are a promising candidate for next generation of electrical wirings and electromagnetic interference (EMI) shielding materials due to their exceptional mechanical and electrical properties. Wires and coatings from ultralong nanotubes that are highly crystalline, well-aligned and densely packed can achieve this goal. High-performance CNT conductors will be relatively lightweight and resistant to harsh conditions and therefore can potentially replace current conductors in many industries including aerospace, automotive, gas and oil.

This thesis investigates a new manufacturing approach, based on conventional solution coating and wire drawing methods, to fabricate high conductivity wires and coatings from ultra-long carbon nanotubes. …

Integration Of Thin Film Tpv Cells To Cvd Diamond Heat Spreaders, Emma J. Renteria

Electrical and Computer Engineering ETDs

In this work, techniques to isolate thermophotovoltaic (TPV) devices from the growth substrate and their subsequent integration with Chemical Vapor Deposition (CVD) diamond heat spreaders will be discussed, with the envisioned goal of fabricating thermally managed cells. CVD diamond heat spreaders are a great option for thermal management of TPV cells. The key requirement, however, is the bonding of the TPV cell directly onto the diamond wafer without the presence of thick (>350 μm) growth substrates, which can offer significant thermal resistance.

The first approach is to release GaSb epitaxial layers from GaSb substrates. However, this is challenging due …

Growth, Characterization, And Function Of Ferroelectric, Ferromagnetic Thin Films And Their Heterostructures, Mahesh Hordagoda

USF Tampa Graduate Theses and Dissertations

With recent trends in miniaturization in the electronics sector, ferroelectrics have gained popularity due to their applications in non-volatile RAM. Taking one step further researchers are now exploring multiferroic devices that overcome the drawbacks of ferroelectric (FE) and ferromagnetic (FM) RAM’s while retaining the advantages of both. The work presented in this dissertation focuses on the growth of FE and FM thin film structures. The primary goals of this work include, (1) optimization of the parameters in the pulsed laser deposition (PLD) of FE and FM films and their heterostructures, (2) development of a structure-property relation that leads to enhancements …

Organometal Halide Perovskite Solar Absorbers And Ferroelectric Nanocomposites For Harvesting Solar Energy, Chaminda Lakmal Hettiarachchi

USF Tampa Graduate Theses and Dissertations

Organometal halide perovskite absorbers such as methylammonium lead iodide chloride (CH₃NH₃PbI₃-_xCl_x), have emerged as an exciting new material family for photovoltaics due to its appealing features that include suitable direct bandgap with intense light absorbance, band gap tunability, ultra-fast charge carrier generation, slow electron-hole recombination rates, long electron and hole diffusion lengths, microsecond-long balanced carrier mobilities, and ambipolarity. The standard method of preparing CH₃NH₃PbI₃-_xCl_x perovskite precursors is a tedious process involving multiple synthesis steps and, the chemicals being used (hydroiodic acid …

Understanding Gas Sorption Mechanisms In Metal–Organic Materials Via Computational Experimentation, Katherine A. Forrest

USF Tampa Graduate Theses and Dissertations

Metal–organic materials (MOMs), a type of porous crystalline structure composed of organic ligands jointed with metal ions, have captured the interest of scientists as potentially useful in gas sorption applications. Some of the most crucial avenues of investigation are in H2 storage (for use as a clean burning fuel source) and CO2 capture and sequestration (to remove the greenhouse gas from the environment).

A major advantage of MOMs for such applications is their high variability in terms of physical dimensions and chemical moieties, based on composition and synthesis conditions, making them potentially customizable for specific application if necessary structural characteristics …

Comparing Laser Diffraction And Optical Microscopy For Characterizing Superabsorbent Polymer Particle Morphology, Size, And Swelling Capacity, Cole R. Davis, Stacey L. Kelly, Kendra Erk

School of Materials Engineering Faculty Publications

In this study, we determined the accuracy and practicality of using optical microscopy (OM) and laser diffraction (LD) to characterize hydrogel particle morphology, size, and swelling capacity (Q). Inverse-suspension-polymerized polyacrylamide particles were used as a model system. OM and LD showed that the average particle diameter varied with the mixing speed during synthesis for the dry (10–120 lm) and hydrated (34–240 lm) particles. The LD volume and number mean diameters showed that a few large particles were responsible for the majority of the water absorption. Excess water present in the gravimetric swelling measurements led to larger Qs (8.2 6 0.37 …

High Temperature Magneto-Structural Transition In Van Der Waals-Layered -Mocl3, Michael Mcguire, Jiaqiang Yan, Paula Lampen-Kelley, Andrew May, Valentino Cooper, Lucas Lindsay, Alexander Puretzky, Liangbo Liang, Santosh Kc, Ercan Cakmak, Stuart Calder, Brian Sales

Faculty Publications

The crystallographic and magnetic properties of the cleavable 4d3 transition metal compound α−MoCl3 are reported, with a focus on the behavior above room temperature. Crystals were grown by chemical vapor transport and characterized using temperature dependent x-ray diffraction, Raman spectroscopy, and magnetization measurements. A structural phase transition occurs near 585 K, at which the Mo-Mo dimers present at room temperature are broken. A nearly regular honeycomb net of Mo is observed above the transition, and an optical phonon associated with the dimerization instability is identified in the Raman data and in first-principles calculations. The crystals are diamagnetic at room temperature …

Friction Stir Welding Manufacturing Advancement By On-Line High Temperature Phased Array Ultrasonic Testing And Correlation Of Process Parameters To Joint Quality, Daniel James Huggett

LSU Doctoral Dissertations

Welding, a manufacturing process for joining, is widely employed in aerospace, aeronautical, maritime, nuclear, and automotive industries. Optimizing these techniques are paramount to continue the development of technologically advanced structures and vehicles. In this work, the manufacturing technique of friction stir welding (FSW) with aluminum alloy (AA) 2219-T87 is investigated to improve understanding of the process and advance manufacturing efficiency. AAs are widely employed in aerospace applications due to their notable strength and ductility. The extension of good strength and ductility to cryogenic temperatures make AAs suitable for rocket oxidizer and fuel tankage. AA-2219, a descendent of the original duralumin …

Computational Prediction Of Conductivities Of Disk-Shaped Particulate Composites, Jian Qiu

Electronic Theses and Dissertations

The effective conductivities are determined for randomly oriented disk-shaped particles using an efficient computational algorithm based on the finite element method. The pairwise intersection criteria of disks are developed using a set of vector operations. An element partition scheme has been implemented to connect the elements on different disks across the lines of intersection. The computed conductivity is expressed as a function of the density and the size of the circular disks or elliptical plates. It is further expressed in a power-law form with the key parameters determined from curve fittings. The particle number and the trial number of simulations …

Study Of Defect Coalescence In Heterogeneous Material Systems Using Broad Band Dielectric Spectroscopy., Vamsee Vadlamudi, Muthu Ram Prabhu Elenchezhian, Priyanshu Kumar Banerjee, Rassel Raihan, Kenneth Reifsnider

Institute of Predictive Performance Methodologies (IPPM-UTARI)-Archive

Composite materials are essential for many modern applications, including airplanes and cars, energy conversion and storage devices, medical prosthetics, and civil structures. Detecting the initiation, growth, accumulation, and coalescence of micro-damage in these heterogeneous materials and predicting the onset of component failure using conformal Broadband Dielectric Spectroscopy (BbDS) is a promising area of ongoing research. Recently, the authors have developed the critical path concept and Heterogeneous fracture mechanics concept that depicts the effect of defect nucleation, growth, coalescence, and fracture plane development and correlation of these damage mechanisms to change in dielectric response respectively. Current research applies those concepts to …

Superconductivity At Т≈200 K In Bismuth Cuprates Synthesized Using Solar Energy, J. Chigvinadze, Juana Acrivos, S. Ashimov, D. Gulamova, G. Donadze

Faculty Publications, Chemistry

When investigating low-frequency (0.1 Hz) oscillations of multiphase high-temperature cuprate superconductors (HTCS) Bi1,7Pb0,3Sr2Ca(n-1)CunOy (n=2-30), a wide attenuation peak (ΔT~100 К) with a maximum at Т≈200 К was detected. This peak was particularly pronounced in field cooling (FC) experiments, i.e. after abrupt cooling of the sample in the external magnetic field at the temperature Т<Тс with subsequent slow warming up to room temperature with invariance of the applied field. The attenuation peak height depended on the preliminaryorientation (before cooling) of the samples θ in the measured permanent magnetic field Н. On the one hand, it is well known that, after the FC procedure and subsequent slow warming up, at the temperatures close to the critical temperature Тс, the attenuation peak associated with “melting” of the Abrikosov frozen vortex structure and its disappearance at Т >Тс is detected in monophase samples. At the same time, in most multiphase bismuth HTCS samples, synthesized using solar energy and superfast quenching of the melt, the attenuation peak with the maximum at Т≈200 К was observed.Depending on the conditions of synthesis, the attenuation peak could …

Special Issue On Supercapacitors, Xiao-Gang Zhang

Journal of Electrochemistry

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Strategies To Enhance Energy Density For Supercapacitors, Jun-Wei Lang, Xu Zhang, Ru-Tao Wang, Xing-Bin Yan

Journal of Electrochemistry

The biggest advantage of supercapacitor lies in not only the excellent pulse and fast charging-discharging performance, but also the characteristics of long cycle life and wide operating temperature window with no pollution. However, the energy density of supercapacitor is low. In this paper, the working principle, the development status, defects and improvement method of supercapacitors are introduced. Based on the research workes of the supercapacitors with high energy density in our group, combined with the literature reports in recent years, the strategies to promote the energy density of supercarpacitors will be focused. The strategies for the enhancement of energy density …

Porous Carbon Materials Produced By Koh Activation For Supercapacitor Electrodes, Jiang-Lin Ye, Yan-Wu Zhu

Journal of Electrochemistry

Porous carbon materials with high specific surface area and excellent conductivity have wide applications in supercapacitor electrodes. Much effort has been made to synthesize and tailor the microstructures of porous carbon materials via various activation procedures (physical and chemical activations). In particular, the chemical activation using potassium hydroxide (KOH) as an activating reagent is promising because of the well-defined micropore size distribution and ultrahigh specific surface area up to 3000 m²·g^-1 of the resulting porous carbons. Based mainly on the previous works taken by the authors and collaborators in the field, we have summarized the activation mechanism …

Recent Advances On Carbon And Transition Metallic Compound Electrodes For High-Performance Supercapacitors, Dun Lin, Xi-Yue Zhang, Yin-Xiang Zeng, Ming-Hao Yu, Xi-Hong Lu, Ye-Xiang Tong

Journal of Electrochemistry

Supercapacitors (SCs) have stimulated intensive interests for their promising applications in electric vehicles and portable electronics, etc. Electrode material is the most important key component of SCs, which vastly determines the performance of SCs. Carbon and transition metallic compound materials have attracted considerable attention and been widely explored as electrode materials. However, the insufficient capacitance of carbon materials and unsatisfactory conductivity and cyclic stability of transition metallic compounds severely limit their implementation as robust SC electrodes. Herein, we highlight our recent efforts to boost the capacitive performance of carbon and metal oxide/nitride electrodes by rationally structural and componential design. The …

Lithium Ion Hybrid Capacitor With High Energy Density, Xian-Zhong Sun, Xiong Zhang, Kai Wang, Yan-Wei Ma

Journal of Electrochemistry

Lithium ion hybrid capacitors are electrochemical energy storage devices combining the advantages of both Li-ion battery and electrochemical capacitor. They can be extensively used in many fields. However, the commercialization of lithium ion hybrid capacitor has been encountered several problems, e.g., the device structure design, the screening of materials, the pre-lithiation process, and the interface between electrolyte and electrode, etc. This review summarizes the recent research advances in lithium ion hybrid capacitor with high energy density, including the selection of the active materials in cathode/anode and the separator, the pre-lithiation method using the three-electrode structure, the high- and low-temperature performances, …

Template Induced Fabrication Of Nitrogen Doped Carbon Sheets As Electrode Materials In Supercapacitors, Tao Huang, Guang-Zhi Tao, Chong-Qing Yang, Deng Lu, Lie Ma, Dong-Qing Wu

Journal of Electrochemistry

Due to the good electrical conductivity, high specific surface area, and excellent chemical/mechanical stability, carbon nanomaterials with two-dimensional morphology have gradually become the hot topic of the research on supercapacitors. Herein, we report for the first time the fabrication of nitrogen doped carbon sheets (NCSs). In our approach, the sheet-like magnisum aluminum (MgAl) layered double hydroxide was used as the hard template, which was mixed with o-phenylene diamine and iron chloride. The following thermal treatment could render the polymerization and carbonization of o-phenylene diamine. The NCSs with ordered hexagonal architectures were formed by final etching process of the thermally treated …

Preparation And Characterization Of Cellulose Acetate-Based Separator For Lithium-Ion Batteries, Hua-Feng Luo, Yuan-Dong Qiao

Journal of Electrochemistry

To improve the electrolyte wettability and thermal resistance of separators used for lithium-ion battery, a novel cellulose acetate (CA)-based separator is facilely prepared by non-solvent induced phase separation (NIPS) wet-process and investigated in lithium-ion batteries. Systematical investigations including morphological characterization, electrolyte wettability and thermal resistance testing were carried out. The results demonstrated that the CA-based separator exhibited well developed three-dimensional porous structures with porosity up to 65%, which is 1.5 times higher than that of PE separator. The CA separator also showed excellent electrolyte uptake (285%) and thermal stability at 150 ^oC for 30 min. Compared with the commercial …

Development Of Novel N-Isopropylacrylamide (Nipaam) Based Hydrogels With Varying Content Of Chrysin Multiacrylate, Shuo Tang, Martha Floy, Rohit Bhandari, Thomas D. Dziubla, J. Zach Hilt

Chemical and Materials Engineering Faculty Publications

A series of novel temperature responsive hydrogels were synthesized by free radical polymerization with varying content of chrysin multiacrylate (ChryMA). The goal was to study the impact of this novel polyphenolic-based multiacrylate on the properties of N-isopropylacrylamide (NIPAAm) hydrogels. The temperature responsive behavior of the copolymerized gels was characterized by swelling studies, and their lower critical solution temperature (LCST) was characterized through differential scanning calorimetry (DSC). It was shown that the incorporation of ChryMA decreased the swelling ratios of the hydrogels and shifted their LCSTs to a lower temperature. Gels with different ChryMA content showed different levels of response to …

Detection Of Methylation On Dsdna Using Nanopores In Mos2 Membrane, David Estrada

Materials Science and Engineering Faculty Publications and Presentations

Methylation at the 5-carbon position of the cytosine nucleotide base in DNA has been shown to be a reliable diagnostic biomarker for carcinogenesis. Early detection of methylation and intervention could drastically increase the effectiveness of therapy and reduce the cancer mortality rate. Current methods for detecting methylation involve bisulfite genomic sequencing, which are cumbersome and demand a large sample size of bodily fluids to yield accurate results. Hence, more efficient and cost effective methods are desired. Based on our previous work, we present a novel nanopore-based assay using a nanopore in a MoS₂ membrane, and the methyl-binding protein (MBP), …

Investigation Of Photo-Responsive Titania Surfaces, Evan Hyden, Matthew J. Beck

Commonwealth Computational Summit

Titania (TiO₂) is an oxide commonly used for photocatalysis. This proclivity to form free radicals when exposed to light has also prompted interest in applying porous TiO₂ as a reactive/responsive membrane. Surfaces of both main polymorphs of TiO₂ (especially rutile {110} and anatase {101}) have been shown to be stable and photo-active.

Polyacrylic acid (PAA) is a molecule of interest as changes in pH can cause the molecule to contract or expand, due to changes in the charge distribution relating to the carboxyl group. Due to TiO₂’s ability to generate photocarriers, we hypothesize that …

Computational Materials Characterization, Discovery, And Design With High Performance Computing, Qunfei Zhou, Xiaotao Liu, Tyler Maxwell, Thomas John Balk, Matthew J. Beck

Commonwealth Computational Summit

No abstract provided.

Spontaneous Jumping, Bouncing And Trampolining Of Hydrogel Drops On A Heated Plate, Jonathan T. Pham, Maxime Paven, Sanghyuk Wooh, Tadashi Kajiya, Hans-Jürgen Butt, Doris Vollmer

Chemical and Materials Engineering Faculty Publications

The contact between liquid drops and hot solid surfaces is of practical importance for industrial processes, such as thermal spraying and spray cooling. The contact and bouncing of solid spheres is also an important event encountered in ball milling, powder processing, and everyday activities, such as ball sports. Using high speed video microscopy, we demonstrate that hydrogel drops, initially at rest on a surface, spontaneously jump upon rapid heating and continue to bounce with increasing amplitudes. Jumping is governed by the surface wettability, surface temperature, hydrogel elasticity, and adhesion. A combination of low-adhesion impact behavior and fast water vapor formation …

Thermodynamics Of Concentrated Solid Solution Alloys, Michael C. Gao, Chuan Zhang, Pan Gao, Fan Zhang, Lizhi Ouyang, Michael Widom, Jeffrey A. Hawk

Mathematical Sciences Faculty Research

This paper reviews the three main approaches for predicting the formation of concentrated solid solution alloys (CSSA) and for modeling their thermodynamic properties, in particular, utilizing the methodologies of empirical thermo-physical parameters, CALPHAD method, and first-principles calculations combined with hybrid Monte Carlo/Molecular Dynamics (MC/MD) simulations. In order to speed up CSSA development, a variety of empirical parameters based on Hume-Rothery rules have been developed. Herein, these parameters have been systematically and critically evaluated for their efficiency in predicting solid solution formation. The phase stability of representative CSSA systems is then illustrated from the perspectives of phase diagrams and nucleation driving …