Engineering Commons^™

Turning An Organic Semiconductor Into A Low-Resistance Material By Ion Implantation, Beatrice Fraboni, Alessandra Scidà, Piero Cosseddu, Yongqiang Wang, Michael Nastasi, Silvia Milita, Annalisa Bonfiglio

Nebraska Center for Energy Sciences Research: Publications

We report on the effects of low energy ion implantation on thin films of pentacene, carried out to investigate the efficacy of this process in the fabrication of organic electronic devices. Two different ions, Ne and N, have been implanted and compared, to assess the effects of different reactivity within the hydrocarbon matrix. Strong modification of the electrical conductivity, stable in time, is observed following ion implantation. This effect is significantly larger for N implants (up to six orders of magnitude), which are shown to introduce stable charged species within the hydrocarbon matrix, not only damage as is the case …

Novel Iron-Based Ternary Amorphous Oxide Semiconductor With Very High Transparency, Electronic Conductivity, And Mobility, A. Malasi, H. Taz, M. Patel, B. Lawrie, R. Pooser, A. Baddorf, G. Duscher, Ramki Kalyanaraman

Faculty Publications and Other Works -- Materials Science & Engineering

Here we report that ternary metal oxides of type (Me)2O3 with the primary metal (Me) constituent being Fe (66 atomic (at.) %) along with the two Lanthanide elements Tb (10 at.%) and Dy (24 at.%) can show excellent semiconducting transport properties. Thin films prepared by pulsed laser deposition at room temperature followed by ambient oxidation showed very high electronic conductivity (>5 × 104 S/m) and Hall mobility (>30 cm2/V-s). These films had an amorphous microstructure which was stable to at least 500 °C and large optical transparency with a direct band gap of 2.85 ± 0.14 eV. This …

High Capacity Silicon Electrodes With Nafion As Binders For Lithium-Ion Batteries, Jiagang Xu, Qinglin Zhang, Yang-Tse Cheng

Chemical and Materials Engineering Faculty Publications

Silicon is capable of delivering a high theoretical specific capacity of 3579 mAh g⁻¹ which is about 10 times higher than that of the state-of-the-art graphite based negative electrodes for lithium-ion batteries. However, the poor cycle life of silicon electrodes, caused by the large volumetric strain during cycling, limits the commercialization of silicon electrodes. As one of the essential components, the polymeric binder is critical to the performance and durability of lithium-ion batteries as it keeps the integrity of electrodes, maintains conductive path and must be stable in the electrolyte. In this work, we demonstrate that electrodes consisting of …

Evolution Of Non-Metallic Inclusions In Foundry Steel Casting Processes, Marc Harris, Von Richards, Ronald J. O'Malley, Semen Naumovich Lekakh

Materials Science and Engineering Faculty Research & Creative Works

The evolution of nonmetallic inclusions was examined for 4320 steel at an industrial steel foundry. The steel was followed from electric arc furnace melting through ladle refining to final casting. Timed sampling was performed at all stages of the process. Samples were analyzed using an automated SEM/EDS system. The overall evolution of oxide inclusions in terms of nucleation, growth, and flotation during liquid processing was studied using area fraction and average diameter. Chemical composition evolution was observed using a joint ternary plotting tool developed under this program. It was found that the use of zirconium as an addition for nitrogen/oxygen …

Ellipsometric Characterization Of Silicon And Carbon Junctions For Advanced Electronics, Alexander G. Boosalis

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Ellipsometry has long been a valuable technique for the optical characterization of layered systems and thin films. While simple systems like epitaxial silicon dioxide are easily characterized, complex systems of silicon and carbon junctions have proven difficult to analyze. Traditional model dielectric functions for layered silicon homojunctions, a system with a similar structure to modern transistors, often have correlated parameters during ellipsometric data analysis. Similarly, epitaxial graphene as grown from thermal sublimation of silicon from silicon carbide or through chemical vapor deposition, tend to have model dielectric function parameters that correlate with the optical thickness of the graphene due to …

Modeling And Simulation Of Micro Electrical Discharge Machining Process, Bai Shao

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

Micro parts and systems are playing crucial roles in the area of semiconductor, biomedical device, micro fluid devices, automotive, aerospace and so forth. Micro manufacturing is one of the most important technologies in realizing miniaturization. Compared to other micro manufacturing methods, micro-EDM is drawing lots of attention due to its ability to machine complex 3D parts regardless of the hardness of the workpiece material.

Micro-EDM is the cumulative result of numerous single discharges; therefore, it is crucial to understand the single discharge material removal process in micro-EDM. However, due to the stochastic nature and complex process mechanism, micro-EDM, including its …

Fully Magnetic Printing By Generation Of Magnetic Droplets On Demand With A Coilgun, Vladislav Vekselman, Luke Sande, Konstantin G. Kornev

Publications

In this paper, we exhibit a coilgun-based approach to drop-on-demand printing of liquids laden with magnetic particles. In contrast to other drop-on-demand technologies designed to print droplets only in gaseous environments, this methodology allows one to print magnetic droplets inside any gaseous or liquid media using the same coilgun. Furthermore, we demonstrate the basic principles of magnetic drop-on-demand generation and show the physico-chemical parameters controlling the process.

Comparative Estimates Of Anthropogenic Heat Emission In Relation To Surface Energy Balance Of A Subtropical Urban Neighborhood, Changhyoun Park, Gunnar W. Schade, Nicholas D. Werner, David J. Sailor, Cheolhee Kim

Mechanical and Materials Engineering Faculty Publications and Presentations

Long-term eddy covariance measurements have been conducted in a subtropical urban area, an older neighborhood north of downtown Houston. The measured net radiation (Q*), sensible heat flux (H) and latent heat flux (LE) showed typical seasonal diurnal variations in urban areas: highest in summer; lowest in winter. From an analysis of a subset of the first two years of measurements, we find that approximately 42% of Q* is converted into H, and 22% into LE during daytime. The local anthropogenic heat emissions were estimated conventionally using the long-term residual method and the heat emission inventory approach. We also …

Microstructure Alone Induced Wetting Transition From Hydrophilic To Hydrophobic On Silicon And Graphene, Henry L. Ems

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

In the present work, transition from hydrophilic to hydrophobic wetting states for an intrinsically hydrophilic surface (contact angle less than 45 degrees) using only surface microstructuring is presented. The surface microstructures are re-entrant microcavities (inverted trapezoidal microstructures) which promote air entrapment below the water droplet causing a Cassie wetting state as opposed to a Wenzel state where the surface is completely wetted. The microstructures were fabricated on a Silicon-On-Insulator (SOI) wafer through steps of deposition, photolithography, etching, and bonding. Contact angle measurements demonstrated the ability of the microfabricated surfaces to sustain large contact angles above 100°, in comparison to a …

Experimental Investigation And Thermal Modeling On Electro Discharge Drilling Of Pcd, Farnaz Nourbakhsh

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

This study presents an experimental investigation and finite element simulation of Electro Discharge Drilling (ED-Drilling) of Polycrystalline Diamond (PCD). PCD has many outstanding properties including uniformly high hardness, high wear resistance and strong corrosion which are the main causes of widely using PCD. While PCD has many advantages and an important role in industrial applications, its high level of hardness and wear resistance cause this material to be difficult to form and machine by using traditional machining methods. EDM as a nontraditional machining process is an effective method among other non-traditional methods for PCDs due to its low cost and …

Effect Of Nano-Oxide Particle Size On Radiation Resistance Of Ironechromium Alloys, Weizong Xu, Lulu Li, James A. Valdez, Mostafa Saber, Yuntian Zhu, Carl C. Koch, Ronald O. Scattergood

Mechanical and Materials Engineering Faculty Publications and Presentations

Radiation resistance of Fe-14Cr alloys under 200 keV He irradiation at 500 ­*C was systematically investigated with varying sizes of nano oxide Zr, Hf and Cr particles. It is found that these nano oxide particles acted as effective sites for He bubble formation. By statistically analyzing 700-1500 He bubbles at the depth of about 150-700 nm from a series of HRTEM images for each sample, we established the variation of average He bubble size, He bubble density, and swelling percentage along the depth, and found them to be consistent with the He concentration profile calculated from the SIRM program. Oxide …

Evaluation Of Organic Protective Coatings As Corrosion Prevention For The Interior Of Subsea Pipelines In Sour Gas Service, Faris M. Alkordy

FIU Electronic Theses and Dissertations

The purpose of this study was to examine the performance of several generic types of organic protective coatings as a corrosion protection method for the interior of subsea pipelines in sour gas media. The sour gas environment was simulated in the laboratory by the use of an Autoclave and the performance of the organic coatings was studied via the use of Electrochemical Impedance Spectroscopy (EIS) and Linear Polarization Resistance (LPR) tests to determine the coatings resistance, capacitance and corrosion behavior before and after the exposure to sour gas environment. The coating degradation and the corrosion products formed were examined by …

Evaluation Of External Coating Performance On Buried Pipelines In The Oil And Gas Industry, Mohammed A. Alrudayni

FIU Electronic Theses and Dissertations

Protective coatings is used to enhance the corrosion resistance of buried pipelines. However, the effectiveness of epoxy-coatings may be compromised due to inadvertent presence of surface damage and coating disbondment. Additionally, the disbonded coated panels is expected to be less effective than that of scratched or un-defected panels. This research was designed to evaluate the coating performance of FBE and hybrid epoxy in simulated Arabian Gulf water and synthetic Sabkha. The influence of coating damage and disbondment on corrosion resistance was also investigated.

Results of this research indicated a reduction in the adhesion bond between the coatings and substrate. The …

Imaging Thermal Conductivity With Nanoscale Resolution Using A Scanning Spin Probe, Abdelghani Laraoui, Halley Aycock-Rizzo, Yang Gao, Xi Lu, Elisa Riedo, Carlos A. Meriles

Advanced Science Research Center

The ability to probe nanoscale heat flow in a material is often limited by lack of spatial resolution. Here, we use a diamond-nanocrystal-hosted nitrogen-vacancy centre attached to the apex of a silicon thermal tip as a local temperature sensor. We apply an electrical current to heat up the tip and rely on the nitrogen vacancy to monitor the thermal changes the tip experiences as it is brought into contact with surfaces of varying thermal conductivity. By combining atomic force and confocal microscopy, we image phantom microstructures with nanoscale resolution, and attain excellent agreement between the thermal conductivity and topographic maps. …

Volatile Condensible Material Deposition In Leo Simulated Environment, Jinya Pu

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Room Temperature Vulcanized (RTV) silicone and compounds are widely used in outer-space for bonding or potting spacecraft components. In geosynchronous equatorial orbit (GEO), the silicone may outgas species which can condense on optically sensitive surfaces and degrade their performance, therefore shortening the lifetime of spacecraft. In low-earth-orbit (LEO), the silicone rubber is subject to an energetic and corrosive environment. Atomic oxygen (AO) and ultraviolet radiation can cause abrasion and degradation of the silicone rubber, cause changes in existing condensed VCM films and affect the properties of VCM films condensing in this atmosphere. Experiments were performed to simulate GEO conditions. In …

The Development Of A Novel Polymer Based System For Gene Delivery, Anh Van Le

FIU Electronic Theses and Dissertations

Gene therapy involves the use of nucleic acids, either DNA or RNA for the treatment, cure, or prevention of human diseases. Synthetic cationic polymers are promising as a tool for gene delivery because of their high level of design flexibility for biomaterial construction and are capable of binding and condensing DNA through electrostatic interactions.

Our lab has developed a novel polymer (poly (polyethylene glycol-dodecanoate) (PEGD), a polyester of polyethylene glycol (PEG) and dodecanedioic acid (DDA). PEGD is a linear viscous polymer that self-assembles into a vesicle upon immersion in an aqueous solution. A copolymer of dodecanedioc acid and polyethylene glycol …

Cobalt Ferrite Nanoparticles Fabricated Via Co-Precipitation In Air: Overview Of Size Control And Magnetic Properties, Dennis Toledo

FIU Electronic Theses and Dissertations

Cobalt Ferrite has important, size-dependent magnetic properties. Consequently, an overview of particle size is important. Co-precipitation in air was the fabrication method used because it is comparatively simple and safe. The effects of three different reaction times including 1, 2, 3 hour(s) on particle size were compared. Also, the effectiveness of three different capping agents (Oleic Acid, Polyvinylpyrollidone (PVP), and Trisodium Citrate) in reducing aggregation and correspondingly particle size were examined. Using Welch’s analysis of variance (ANOVA) and the relevant post hoc tests, there was no significant difference (p=0.05) between reaction times of 1 hour and 2 hours, but there …

Augmented Finite Element Method For Virtual Testing Of High Temperature Cmcs, Qingda Yang, Jaedal Jung, Bao-Chan Do

Composites at Lake Louise (CALL 2015)

Ceramic matrix composites (CMCs) have been increasingly used in high heat flux applications due to their ultra-high temperature resisting capabilities. However, CMCs are prone to processing-induced or in-serve cracking due to the large thermal stresses. Thermally-induced cracking are dangerous because they provide pathways for further damaging processes such as oxidation and vapor-assisted corrosion, which may lead to catastrophic failure [1]. High-fidelity thermal-mechanical analyses to CMCs with consideration of arbitrary cracking are very challenging because the heterogeneous nature makes it impossible to know the cracking locations a priori. Yet correct and efficient treatment of crack coalescence and bifurcation is critical …

Novel Anti-Decay Self-Setting Paste Of Hydroxyapatite/Collagen Nanocomposite Utilizing Gptms, Masanori Kikuchi, Taira Sato, Mamoru Aizawa, Yuki Shirosaki

Composites at Lake Louise (CALL 2015)

Bone is a typical inorganic/ortganic nanocomposite mainly composed of hydroxyapatite (HAp) nanocrystals and collagen molecules. The composition and nanostructure is closely related to bone’s biomechanical and biochemical properties. One of the most important things for bone is a bone remodeling process that maintains mechanical strength of bone to allow walking and running as well as homeostasis of calcium in our body. In fact, sintered HAp composed of HAp crystals approximately 1 µm in particle size is considered as non-bioresorbable; however HAp nanocrystals easily resorbed by osteoclasts. A hydroxyapatite/collagen bone-like nanocomposite (HAp/Col) was successfully synthesized by the authors via self-organizing process. …

Physical Aging And Glass Transition Of Single Component Nanocomposites, Hilmar Koerner

Composites at Lake Louise (CALL 2015)

Matrix free assemblies of polymer-grafted, “hairy” nanoparticles (HNP) exhibit novel morphology, dielectric and mechanical properties, as well as providing means to overcome dispersion challenges ubiquitous to conventional polymer-inorganic blended nanocomposites. Physical aging of the amorphous polymer glass between the close-packed nanoparticles (NPs) will dominate long-term stability. However, the energetics of cooperative relaxation of tethered chains confined within the interstitial spaces in single component nanocomposites is unknown. Herein, we compare glass transition temperature (Tg) and physical aging behavior of matrix free assemblies of HNPs (aHNPs) to conventional NP-polymer blends, across different nano-silica loadings (0-50 v/v%) and brush architecture of grafted polystyrene …

Designing Fire Safe Composites, Maude Jimenez

Composites at Lake Louise (CALL 2015)

Composites are increasingly used in transportation (railway, aircrafts,…) and their applications are more and more oriented toward structural parts. However the fire risk linked to the use of such organic materials has to be strongly reduced to keep this attractiveness and hence flame retardant solutions have to be used to fire proof them. A classical way to achieve fire performance is to incorporate fire retardants (FRs) in the bulk of the polymeric matrix of the composites at loading between 15 and 40wt%. However with such an approach, flammability properties of the composites will be achieved at the expense of their …

Mechanisms And Models For Sic Fiber Strength Changes After Oxidation In Air And Steam, Randall Hay

Composites at Lake Louise (CALL 2015)

The strengths of Hi-Nicalon^TM-S SiC fibers were measured after oxidation in wet air, dry air, and Si(OH)₄ saturated steam between 600° and 1400°C. Amorphous and crystalline SiO₂ scale thickness was measured by TEM. Deal-Grove kinetics for oxidation and Kolmogorov-Johnson-Mehl-Avrami kinetics for crystallization were determined. Fibers oxidized in steam much more rapidly than in dry or wet air. Hi-Nicalon^TM-S fibers were completely oxidized to crystalline SiO₂ after 100h at 1100°C. The corresponding scale thickness for dry air was 1.3 mm. Fiber strength changes after oxidation in dry and wet air were similar, but with …

Thermally Conductive Composites, Oren Regev

Composites at Lake Louise (CALL 2015)

The rapidly increasing device densities in electronics calls for efficient thermal management. If successfully exploited, graphene, which possesses extraordinary thermal properties, can be commercially utilized in polymer composites with ultrahigh thermal conductivity (TC). The total potential of graphene to enhance TC, however, is restricted by the large interfacial thermal resistance between the polymer-mediated graphene boundaries. We report a facile and scalable dispersion of commercially available graphene nano platelets (GnPs) in a polymer matrix, which forms composite with ultra-high TC of 12.4 W/mK (vs. 0.2 W/mK for neat polymer). This ultra-high TC is achieved by applying high compression forces during the …

Controlling The Interfacial Properties Of One-Dimensional Nanostructures, Kirk Ziegler

Composites at Lake Louise (CALL 2015)

The high surface area of nanomaterials dictates that the interface with their surroundings is important in determining their properties or functionality. For example, all atoms in single-walled carbon nanotubes (SWCNTs) exist on the surface and, therefore, have excellent sensing capabilities. The interface of SWCNTs with their surroundings is also important to their application in polymer composites, devices, drug delivery, bioimaging and biosensing. Understanding and ultimately controlling these surface layers is important because of its influence on dispersion, reactivity, adsorption of pollutants, and interaction with biological materials. SWCNT interfaces are often altered with surfactants to improve their dispersion in aqueous suspensions. …

Bio-Inspired Hybrid Nanocomposites In Single Crystalline Hosts: From Structure To Function, Boaz Pokroy

Composites at Lake Louise (CALL 2015)

Often crystals in nature exhibit fascinating mechanical, optical, magnetic and other characteristics. Such natural single crystals are very different than man-made crystals: they are in fact hybrid nanocomposites due to the incorporation of organic molecules within heir crystalline lattice and often reveal intricate shapes and morphologies rather than clear facets.

In this talk I will show that we can emulate these two specific features demonstrated by organisms so as to form new structural materials with new properties and characteristics.

I will show that we can grow inorganic single crystals in which different organic molecules are incorporated on a nanometer scale. …

Multilayer Nanocoatings Capable Of Separating Gases, Killing Bacteria And Stopping Fire, Jaime Grunlan

Composites at Lake Louise (CALL 2015)

Layer-by-layer (LbL) assembly is a conformal coating “platform” technology capable of imparting a multiplicity of functionalities on nearly any type of surface in a relatively environmentally friendly way. At its core, LbL is a solution deposition technique in which layers of cationic and anionic materials (e.g. nanoparticles, polymers and even biological molecules) are built up via electrostatic attractions in an alternating fashion, while controlling process variables such as pH, coating time, and concentration. Here we are producing nanocomposite multilayers (50 – 1000 nm thick), having 10 – 96 wt% clay, that are completely transparent and exhibit oxygen transmission rates below …

Hard/Soft Composited Materials For Stretchable Electronics, Hyun-Joong Chung, Xinda Li, Yi Chen

Composites at Lake Louise (CALL 2015)

Convergence between scientific disciplines creates myriads of new opportunities to the problems that traditional approaches have not provided the answers. For example, researches on materials engineering and nanofabrication can shed a light to the current challenges in clinical biomedical science. Specifically, this presentation describes how materials science is employed to solve fundamental and practical problems in the intimate integration of the state-of-art inorganic devices onto living organs or skins for biomedical research. [1]

Firstly, bioresorbable elastomers make a basic building block for tissue scaffolds for soft, moving organs (such as heart, blood vessels, and smooth muscles) and for substrate material …

Magnetically Assisted Assembly Of Bioinspired Composites, Tobias Niebel, Hortense Le Ferrand, Florian Bouville, André Studart

Composites at Lake Louise (CALL 2015)

Heterogeneous composites with intricate microstructures can be found widely in nature fulfilling the functional demands imposed by their environment. Reaching this level of intricacy in synthetic composites remains a challenge due to the lack of suitable and easily available processing tools. We present a new method to produce bioinspired composites with a broad variety of locally controlled composition, texture and shape using low magnetic fields. Nacre-like all-ceramic, polymer-ceramic and metal-ceramic composites with volume fractions of ceramic phase spanning from 40 to values as high as 95 vol% are achieved. By mixing magnetically responsive alumina microplatelets with ceramic nanoparticles, we can …

Atomistic Structures And Transport Phenomena At Interfaces In Lithium Battery Materials, Akihide Kuwabara

Composites at Lake Louise (CALL 2015)

Lithium-ion batteries (LIBs) are widely used in mobile devices. Increasingly they are also being scaled up for use as energy-storage devices in hybrid vehicles and fully electric ones. All-solid-state LIBs are expected to be one of the candidates as next generation LIBs because the LIBs can realize higher energy density and safety without liquid electrolytes. In these devices, the solid-solid interfaces, specifically those between electrodes and an electrolyte and grain boundaries within each component, are thought to strongly affect the battery performance. Despite their clear scientific and technical importance, however, so far, few studies have focused on the internal interfaces …

Mica Platelet-Reinforced, Geopolymer Composites, Patrick Keane

Composites at Lake Louise (CALL 2015)

The mica flakes were obtained from the Cogebi Company as phlogopite mica paper type Cobebi P160 containing no organic or inorganic binder. Mica can withstand temperatures in excess of 1000°C. Phlogopite, of composition (KMg₃(AlSi₃O₁₀)(OH)₂ is flame-retardant, non-flammable, does not give off fumes. It conducts very little heat, especially perpendicular to its strata. Natural mica has a dielectric strength greater than 25 kV/mm (625 V/mil), has good resistance to arcing and electrical erosion, and is permeable to microwaves. Mica has good compressive strength. It behaves well in the presence of tensile and bending stresses. …