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Mechanical Engineering

2017

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Articles 1 - 30 of 71

Full-Text Articles in Nanoscience and Nanotechnology

Investigating Scalable Manufacturing Of High-Conductivity Wires And Coatings From Ultra-Long Carbon Nanotubes, Pouria Khanbolouki Nov 2017

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 ...


Multiple Consecutive Recapture Of Rigid Nanoparticles Using A Solid-State Nanopore Sensor, Jungsoo Lee Nov 2017

Multiple Consecutive Recapture Of Rigid Nanoparticles Using A Solid-State Nanopore Sensor, Jungsoo Lee

Mechanical Engineering Research Theses and Dissertations

Solid‐state nanopore sensors have been used to measure the size of a nanoparticle by applying a resistive pulse sensing technique. Previously, the size distribution of the population pool could be investigated utilizing data from a single translocation, however, the accuracy of the distribution is limited due to the lack of repeated data. In this study, we characterized polystyrene nanobeads utilizing single particle recapture techniques, which provide a better statistical estimate of the size distribution than that of single sampling techniques. The pulses and translocation times of two different sized nanobeads (80 nm and 125 nm in diameter) were acquired ...


Rapid Characterization Of Local Shape Memory Properties Through Indentation, Peizhen Li, Haluk E. Karaca, Yang-Tse Cheng Nov 2017

Rapid Characterization Of Local Shape Memory Properties Through Indentation, Peizhen Li, Haluk E. Karaca, Yang-Tse Cheng

Mechanical Engineering Faculty Publications

Shape memory alloys (SMAs) have the ability to show large recoverable shape changes upon temperature, stress or magnetic field cycling. Their shape memory, material and magnetic properties (e.g. transformation temperatures, strain, saturation magnetization and strength) determine their prospects for applications from small-scale microelectromechanical systems to large scale aerospace and biomedical systems. It should be noted that properties of SMAs are highly temperature dependent. Generally, the conventional mechanical characterization methods (e.g, tension, compression, and torsion) are used on bulk samples of SMAs to determine those properties. In this article, it will be shown that indentation technique can be used ...


Oct-Based Three Dimensional Modeling Of Stent Deployment, Pengfei Dong, David Prabhu, David L. Wilson, Hiram G. Bezerra, Linxia Gu Nov 2017

Oct-Based Three Dimensional Modeling Of Stent Deployment, Pengfei Dong, David Prabhu, David L. Wilson, Hiram G. Bezerra, Linxia Gu

Mechanical & Materials Engineering Faculty Publications

Stent deployment has been widely used to treat narrowed coronary artery. Its acute outcome in terms of stent under expansion and malapposition depends on the extent and shape of calcifications. However, no clear understanding as to how to quantify or categorize the impact of calcification. We have conducted ex vivo stenting characterized by the optical coherence tomography (OCT). The goal of this work is to capture the ex vivo stent deployment and quantify the effect of calcium morphology on the stenting. A three dimensional model of calcified plaque was reconstructed from ex vivo OCT images. The crimping, balloon expansion and ...


Floating-Gate Transistor Photodetector, Jinsong Huang, Yongbo Yuan Oct 2017

Floating-Gate Transistor Photodetector, Jinsong Huang, Yongbo Yuan

Mechanical & Materials Engineering Faculty Publications

A field effect transistor photodetector that can operate in room temperature includes a source electrode , a drain electrode , a channel to allow an electric current to flow between the drain and source electrodes , and a gate electrode to receive a bias voltage for controlling the current in the channel . The photodetector includes a light - absorbing mate rial that absorbs light and traps electric charges . The light absorbing material is configured to generate one or more charges upon absorbing light having a wavelength within a specified range and to hold the one or more charges . The one or more charges held ...


Metal Sulfides As Anode For Lithium Ion And Sodium Ion Battery, Ali Abdulla Oct 2017

Metal Sulfides As Anode For Lithium Ion And Sodium Ion Battery, Ali Abdulla

Electronic Thesis and Dissertation Repository

Abstract

Nanomaterials have been studied intensively in the last decades due to their unique physical and chemical properties and their potential for applications in different domains. Among these applications, energy storage has become the center of focus by many research groups and companies to develop high efficiency and reliable energy devices such as the commercial lithium ion batteries (LIBs). However, LIBs has not yet met the growing requirements of the high demand for increasing energy density. More efforts are requested to improve the performance of the batteries by designing better electrode materials and increasing the battery safety. Another type of ...


Software For Extracting Deformation Gradient And Stress From Md Simulations: Simulations Using The Charmm Force Field, Mehrdad Negahban, Lili Zhang, Zesheng Zhang, John Jasa, Antoine Jérusalem Aug 2017

Software For Extracting Deformation Gradient And Stress From Md Simulations: Simulations Using The Charmm Force Field, Mehrdad Negahban, Lili Zhang, Zesheng Zhang, John Jasa, Antoine Jérusalem

Mechanical & Materials Engineering Faculty Publications

Software was developed, and is provided under a general use license, to calculate continuum level deformation gradient and stress for any group of atoms in an MD simulation that uses the Charmm force fields. This software can also calculate the interaction stress applied by one group of atoms on any other group. To obtain deformation gradient and stress, the user needs to provide the selected group(s) of atoms in an atom group identification file, and provide the associated LAMMPS format files and force field parameter file. An example is included to demonstrate the use of the software.


Shape-Adaptive Mechanism For Robotic Grasping, Carl A. Nelson Aug 2017

Shape-Adaptive Mechanism For Robotic Grasping, Carl A. Nelson

Mechanical & Materials Engineering Faculty Publications

A grapser can include a first pantograph cell and a second pantograph cell coupled with the first pantogrpah cell. The first and second pantograph cells can be coupled together at a first pivot and a second pivot. The grasper can also include a finger extendable in a direction extending between the first pivot and the second pivot. The grasper can include a support base, where one or more links of the first pantograph cell can be slidably coupled with the support base for extending the grasper. In some embodiment, the grasper can be configured to extend along a curved path ...


Modal Phonon Transport Across Interfaces By Non-Equilibrium Molecular Dynamics Simulation, Yang Zhong, Tianli Feng, Xiulin Ruan Aug 2017

Modal Phonon Transport Across Interfaces By Non-Equilibrium Molecular Dynamics Simulation, Yang Zhong, Tianli Feng, Xiulin Ruan

The Summer Undergraduate Research Fellowship (SURF) Symposium

Phonons represent the quantization of lattice vibration, responsible for heat transfer in semiconductors and dielectrics. Phonon heat conduction across interfaces is crucially important for the thermal management of real-life devices such as smartphones, electric vehicles, and satellites. Although recent studies have broadly investigated spectral phonon contribution to lattice thermal conductivity, the mechanism of phonon modal transport across interfaces is still not well-understood. Previous models, including the acoustic mismatch model (AMM) and diffuse mismatch model (DMM), only consider elastic process while neglecting inelastic phonon contributions. Herein, we employ spectral Non-Equilibrium Molecular Dynamics Simulation (NEMD) to probe the temperature and heat flux ...


Spectral Phonon Relaxation Time Calculation Tool Based On Molecular Dynamics, Divya Chalise, Tianli Feng, Xiulin Ruan Aug 2017

Spectral Phonon Relaxation Time Calculation Tool Based On Molecular Dynamics, Divya Chalise, Tianli Feng, Xiulin Ruan

The Summer Undergraduate Research Fellowship (SURF) Symposium

Thermal conductivity is an important material property which affects the performance of a wide range of devices from thermoelectrics to nanoelectronics. Information about phonon vibration modes and phonon relaxation time gives significant insight into understanding and engineering material’s thermal conductivity. Although different theoretical models have been developed for studying phonon modes and relaxation time, extensive knowledge of lattice dynamics and molecular dynamics is required to compute phonon modal frequencies and relaxation times. Therefore, a computational tool which can take simple inputs to calculate phonon mode frequencies and relaxation time will be beneficial. Through this research work, such computational tool ...


Deformation Behavior Of Al/A-Si Core-Shell Nanostructures, Robert Andrew Fleming Aug 2017

Deformation Behavior Of Al/A-Si Core-Shell Nanostructures, Robert Andrew Fleming

Theses and Dissertations

Al/a-Si core-shell nanostructures (CSNs), consisting of a hemispherical Al core surrounded by a hard shell of a-Si, have been shown to display unusual mechanical behavior in response to compression loading. Most notably, these nanostructures exhibit substantial deformation recovery, even when loaded much beyond the elastic limit. Nanoindentation measurements revealed a unique mechanical response characterized by discontinuous signatures in the load-displacement data. In conjunction with the indentation signatures, nearly complete deformation recovery is observed. This behavior is attributed to dislocation nucleation and annihilation events enabled by the 3-dimensional confinement of the Al core. As the core confinement is reduced, either ...


Fluid‐Induced Alignment Of Carbon Nanofibers In Polymer Fibers, Mingchang Lu, Farrokh Sharifi, Nicole N. Hashemi, Reza Montazami Jul 2017

Fluid‐Induced Alignment Of Carbon Nanofibers In Polymer Fibers, Mingchang Lu, Farrokh Sharifi, Nicole N. Hashemi, Reza Montazami

Mechanical Engineering Publications

Carbon nanofiber/polycaprolactone (CNF/PCL) composite fibers are fabricated using a microfluidic approach. The fibers are made with different content levels of CNFs and flow rate ratios between the core and sheath fluids. The electrical conductivity and tensile properties of these fibers are then investigated. It is found that at a CNF concentration of 3 wt%, the electrical conductivity of the composite fiber significantly increases to 1.11 S m−1. The yield strength, Young's modulus, and ultimate strength of the 3 wt% CNF increase relative to the pure PCL by factors of 1.72, 2.88, and 1 ...


Multiple Scattering Theory For Heterogeneous Elastic Continua With Strong Property Fluctuation: Theoretical Fundamentals And Applications, Huijing He Jun 2017

Multiple Scattering Theory For Heterogeneous Elastic Continua With Strong Property Fluctuation: Theoretical Fundamentals And Applications, Huijing He

Mechanical & Materials Engineering Faculty Publications

Scattering of elastic waves in heterogeneous media has become one of the most important problems in the field of wave propagation due to its broad applications in seismology, natural resource exploration, ultrasonic nondestructive evaluation and biomedical ultrasound. Nevertheless, it is one of the most challenging problems because of the complicated medium inhomogeneity and the complexity of the elastodynamic equations. A widely accepted model for the propagation and scattering of elastic waves, which properly incorporates the multiple scattering phenomenon and the statistical information of the inhomogeneities is still missing. In this work, the author developed a multiple scattering model for heterogeneous ...


A Strategy To Optimize Recovery In Orthopedic Sports Injuries, Michael P. Sealy, Ziye Liu, Chao Li, Yuebin Guo, Ben White, Mark Barkey, Brian Jordon J, Luke N. Brewer, Dale Feldman Jun 2017

A Strategy To Optimize Recovery In Orthopedic Sports Injuries, Michael P. Sealy, Ziye Liu, Chao Li, Yuebin Guo, Ben White, Mark Barkey, Brian Jordon J, Luke N. Brewer, Dale Feldman

Mechanical & Materials Engineering Faculty Publications

An important goal for treatment of sports injuries is to have as short a recovery time as possible. The critical problem with current orthopedic implants is that they are designed to be permanent and have a high complication rate (15%) that often requires removal and replacement with a second surgery; and subsequently a second rehabilitation cycle. This study was designed to test the feasibility of having a device that could provide the needed mechanical properties, while promoting healing, for a specified amount of time and then degrade away, to shorten the recovery time. The specific strategy was to create a ...


Enhanced Visible Light Photocatalytic Remediation Of Organics In Water Using Zinc Oxide And Titanium Oxide Nanostructures, Srikanth Gunti Jun 2017

Enhanced Visible Light Photocatalytic Remediation Of Organics In Water Using Zinc Oxide And Titanium Oxide Nanostructures, Srikanth Gunti

Graduate Theses and Dissertations

The techniques mostly used to decontaminate air as well as water pollutants have drawbacks in terms of higher costs, require secondary treatment, and some methods are very slow. So, emphasis has been given to water though the use of photocatalysts, which break organic pollutants to water and carbon dioxide and leave no trace of by-products at the end. Photocatalytic remediation aligns with the waste and wastewater industries’ zero waste schemes with lower cost, eco-friendly and sustainable treatment technology. The commonly used photocatalysts such as titanium oxide (TiO2), zinc oxide (ZnO), tungsten oxide (WO3) have band gap of nearly ...


Platinum Nanoparticle Decorated Sio2 Microfibers As Catalysts For Micro Unmanned Underwater Vehicle Propulsion, Bolin Chen, Nathaniel T. Garland, Jason Geder, Marius Pruessner, Eric Mootz, Allison Cargill, Anne Leners, Granit Vokshi, Jacob Davis, Wyatt Burns, Michael A. Daniele, Josh Kogot, Igor L. Medintz, Jonathan C. Claussen Jun 2017

Platinum Nanoparticle Decorated Sio2 Microfibers As Catalysts For Micro Unmanned Underwater Vehicle Propulsion, Bolin Chen, Nathaniel T. Garland, Jason Geder, Marius Pruessner, Eric Mootz, Allison Cargill, Anne Leners, Granit Vokshi, Jacob Davis, Wyatt Burns, Michael A. Daniele, Josh Kogot, Igor L. Medintz, Jonathan C. Claussen

Jonathan C. Claussen

Micro unmanned underwater vehicles (UUVs) need to house propulsion mechanisms that are small in size but sufficiently powerful to deliver on-demand acceleration for tight radius turns, burst-driven docking maneuvers, and low-speed course corrections. Recently, small-scale hydrogen peroxide (H2O2) propulsion mechanisms have shown great promise in delivering pulsatile thrust for such acceleration needs. However, the need for robust, high surface area nanocatalysts that can be manufactured on a large scale for integration into micro UUV reaction chambers is still needed. In this report, a thermal/electrical insulator, silicon oxide (SiO2) microfibers, is used as a support for platinum nanoparticle (PtNP) catalysts ...


Nanoscale Investigations Of Thermal And Momentum Transport In Graphene – Water Systems, Drew Champion Marable May 2017

Nanoscale Investigations Of Thermal And Momentum Transport In Graphene – Water Systems, Drew Champion Marable

Masters Theses

Demand for miniaturized electronic devices has given rise to new challenges in thermal management. Integration with graphene, a two-dimensional (2D) material with excellent thermal properties, allows for further reduced sizes and combats thermal management issues within novel devices. Moreover, due to its wide availability and adequate thermal properties, liquid water is commonly used within traditional thermal systems to enhance cooling performance; as such, water is expected to yield similar performance in smaller-scale applications. However, at reduced sizes descending to the nanoscale realm, system behaviors deviate from traditional macroscale-based theory as interfacial effects become amplified. Employing insight provided by molecular dynamics ...


Optimization Of Reduced Graphene Oxide Deposition For Hydrogen Sensing Technologies, Matthew Pocta May 2017

Optimization Of Reduced Graphene Oxide Deposition For Hydrogen Sensing Technologies, Matthew Pocta

Mechanical Engineering Undergraduate Honors Theses

Graphene is known to be a key material for improving the performance of hydrogen sensors. High electrical conductivity, maximum possible surface area with respect to volume, and high carrier mobility are a few of the properties that make graphene ideal for hydrogen sensing applications. The problem with utilizing graphene is the difficulty in depositing uniform, thin layers onto substrate surfaces. This study examines a new method of optimizing graphene deposition by utilizing an airbrush to deposit both graphene oxide (GO) and reduced graphene oxide (rGO) onto glass substrates. The number of depositions were varied among samples to study the effect ...


Fabrication And Study Of The Structure And Magnetism Of Rare-Earth Free Nanoclusters, Bhaskar Das Apr 2017

Fabrication And Study Of The Structure And Magnetism Of Rare-Earth Free Nanoclusters, Bhaskar Das

Theses, Dissertations, and Student Research: Department of Physics and Astronomy

No abstract provided.


Primary Blast Waves Induced Brain Dynamics Influenced By Head Orientations, Yi Hua, Yugang Wang, Linxia Gu Apr 2017

Primary Blast Waves Induced Brain Dynamics Influenced By Head Orientations, Yi Hua, Yugang Wang, Linxia Gu

Mechanical & Materials Engineering Faculty Publications

There is controversy regarding the directional dependence of head responses subjected to blast loading. The goal of this work is to characterize the role of head orientation in the mechanics of blast wave-head interactions as well as the load transmitting to the brain. A three-dimensional human head model with anatomical details was reconstructed from computed tomography images. Three different head orientations with respect to the oncoming blast wave, i.e., front-on with head facing blast, back-on with head facing away from blast, and side-on with right side exposed to blast, were considered. The reflected pressure at the blast wave-head interface ...


Increasing The Activity Of Immobilized Enzymes With Nanoparticle Conjugation, Shaowei Ding, Allison A. Cargill, Igor L. Medintz, Jonathan C. Claussen Mar 2017

Increasing The Activity Of Immobilized Enzymes With Nanoparticle Conjugation, Shaowei Ding, Allison A. Cargill, Igor L. Medintz, Jonathan C. Claussen

Jonathan C. Claussen

The efficiency and selectivity of enzymatic catalysis is useful to a plethora of industrial and manufacturing processes. Many of these processes require the immobilization of enzymes onto surfaces, which has traditionally reduced enzyme activity. However, recent research has shown that the integration of nanoparticles into enzyme carrier schemes has maintained or even enhanced immobilized enzyme performance. The nanoparticle size and surface chemistry as well as the orientation and density of immobilized enzymes all contribute to the enhanced performance of enzyme–nanoparticle conjugates. These improvements are noted in specific nanoparticles including those comprising carbon (e.g., graphene and carbon nanotubes), metal ...


Platinum Nanoparticle Decorated Sio2 Microfibers As Catalysts For Micro Unmanned Underwater Vehicle Propulsion, Bolin Chen, Nathaniel T. Garland, Jason Geder, Marius Pruessner, Eric Mootz, Allison Cargill, Anne Leners, Granit Vokshi, Jacob Davis, Wyatt Burns, Michael A. Daniele, Josh Kogot, Igor L. Medintz, Jonathan C. Claussen Mar 2017

Platinum Nanoparticle Decorated Sio2 Microfibers As Catalysts For Micro Unmanned Underwater Vehicle Propulsion, Bolin Chen, Nathaniel T. Garland, Jason Geder, Marius Pruessner, Eric Mootz, Allison Cargill, Anne Leners, Granit Vokshi, Jacob Davis, Wyatt Burns, Michael A. Daniele, Josh Kogot, Igor L. Medintz, Jonathan C. Claussen

Jonathan C. Claussen

Micro unmanned underwater vehicles (UUVs) need to house propulsion mechanisms that are small in size but sufficiently powerful to deliver on-demand acceleration for tight radius turns, burst-driven docking maneuvers, and low-speed course corrections. Recently, small-scale hydrogen peroxide (H2O2) propulsion mechanisms have shown great promise in delivering pulsatile thrust for such acceleration needs. However, the need for robust, high surface area nanocatalysts that can be manufactured on a large scale for integration into micro UUV reaction chambers is still needed. In this report, a thermal/electrical insulator, silicon oxide (SiO2) microfibers, is used as a support for platinum nanoparticle (PtNP) catalysts ...


Intracellular Nanoparticle Dynamics Affected By Cytoskeletal Integrity, Martha E. Grady, Emmabeth Parrish, Matthew A. Caporizzo, Sarah C. Seeger, Russell J. Composto, David M. Eckmann Mar 2017

Intracellular Nanoparticle Dynamics Affected By Cytoskeletal Integrity, Martha E. Grady, Emmabeth Parrish, Matthew A. Caporizzo, Sarah C. Seeger, Russell J. Composto, David M. Eckmann

Mechanical Engineering Faculty Publications

The cell interior is a crowded chemical space, which limits the diffusion of molecules and organelles within the cytoplasm, affecting the rates of chemical reactions. We provide insight into the relationship between non-specific intracellular diffusion and cytoskeletal integrity. Quantum dots entered the cell through microinjection and their spatial coordinates were captured by tracking their fluorescence signature as they diffused within the cell cytoplasm. Particle tracking revealed significant enhancement in the mobility of biocompatible quantum dots within fibrosarcoma cells versus their healthy counterparts, fibroblasts, as well as in actin destabilized fibroblasts versus untreated fibroblasts. Analyzing the displacement distributions provided insight into ...


Formation Of Mound-Like Multiscale Surface Structures On Titanium By Femtosecond Laser Processing, Edwin Peng, Alfred Tsubaki, Craig A. Zuhlke, Ryan Bell, Meiyu Wang, Dennis R. Alexander, George Gogos, Jeffrey E. Shield Mar 2017

Formation Of Mound-Like Multiscale Surface Structures On Titanium By Femtosecond Laser Processing, Edwin Peng, Alfred Tsubaki, Craig A. Zuhlke, Ryan Bell, Meiyu Wang, Dennis R. Alexander, George Gogos, Jeffrey E. Shield

Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research

Surface Functionalization Technique • Femtosecond Laser Surface Processing (FLSP) • Utilize high power, femtosecond (10-15 s) laser pulses • Produce self-organized, multiscale surface micro/nanostructures • Diverse range of applicable substrates: semiconductors, metals, polymers, & composites

Why? • What are the different types of FLSP structures on Ti? • Physical evidence needed for FLSP formation models • Optimize FLSP of Ti for biomedical & other applications

How? • Obtain evidence of mound growth processes by examining underlying microstructure • Utilize dual beam Scanning Electron Microscope-Focused Ion Beam instrument to cross section surface structures & fabricate transmission electron microscopy samples


Morphology Inherence From Hollow Mofs To Hollow Carbon Polyhedrons In Preparing Carbon-Based Electrocatalysts, Yuchen Pei, Zhiyuan Qi, Xinle Li, Raghu V. Maligal-Ganesh, Tian Wei Goh, Chaoxian Xiao, Tianyu Wang, Wenyu Huang Feb 2017

Morphology Inherence From Hollow Mofs To Hollow Carbon Polyhedrons In Preparing Carbon-Based Electrocatalysts, Yuchen Pei, Zhiyuan Qi, Xinle Li, Raghu V. Maligal-Ganesh, Tian Wei Goh, Chaoxian Xiao, Tianyu Wang, Wenyu Huang

Chemistry Publications

Hollow carbon nanostructures are emerging as advanced electrocatalysts for the oxygen reduction reaction (ORR) due to the effective usage of active sites and the reduced dependence on expensive noble metals. Conventional preparation of these hollow structures is achieved through templates (e.g. SiO2, CdS, and Ni3C), which serve to retain the void interiors during carbonization, leading to an essential template-removal procedure using hazardous chemical etchants. Herein, we demonstrate the direct carbonization of unique hollow zeolitic imidazolate frameworks (ZIFs) for the synthesis of hollow carbon polyhedrons (HCPs) with well-defined morphologies. The hollow ZIF particles behave bi-functionally as a carbon source and ...


Nanotextured Titanium Surfaces For Implants: Manufacturing And Packaging Aspects, Sachin Bhosle Jan 2017

Nanotextured Titanium Surfaces For Implants: Manufacturing And Packaging Aspects, Sachin Bhosle

Dissertations, Master's Theses and Master's Reports

It has been shown that nanotexturing the surface of otherwise smooth titanium orthopedic materials increases osteoblast proliferation in vitro, and the bone-implant contact area and pullout force in vivo. However, this prior work has not focused on the requirements for scale-up to industrial processes. This dissertation reports on titanium surface modifications by electrochemical anodization using a benign NH4F electrolyte, and a hybrid electrolyte also containing AgF, rather than hazardous hydrofluoric acid used elsewhere. Nanotube fabrication of Ti6Al4V foils, rods, thermal plasma sprayed commercial implants, and laser and e-beam melted powder materials was demonstrated.

It was found that the ...


Degradation Resistant Surface Enhanced Raman Spectroscopy Substrates, Ryan D. Scherzer Jan 2017

Degradation Resistant Surface Enhanced Raman Spectroscopy Substrates, Ryan D. Scherzer

UNF Graduate Theses and Dissertations

Raman spectroscopy is employed by NASA, and many others, to detect trace amounts of substances. Unfortunately, the Raman signal is generally too weak to detect when very small, but non-trivial, amounts of molecules are present. One way around this weak signal is to use surface enhanced Raman spectroscopy (SERS).

When used as substrates for SERS, metallic nanorods grown using physical vapor deposition (PVD) provide a large enhancement factor to the Raman signal, as much as 1012. However, Silver (Ag) nanorods that give high enhancement suffer from rapid degradation as a function of time and exposure to harsh environment. Exposure ...


Rapidly Solidified Rare-Earth Permanent Magnets: Processing, Properties, And Applications, Shampa Aich, Dillip K. Satapathy, Jeffrey E. Shield Jan 2017

Rapidly Solidified Rare-Earth Permanent Magnets: Processing, Properties, And Applications, Shampa Aich, Dillip K. Satapathy, Jeffrey E. Shield

Mechanical & Materials Engineering Faculty Publications

Rapidly solidified rare-earth-based permanent magnets are considered to have better potential as permanent magnets compared to the conventional bulk materials, which can be attributed to their improved microstructure and better magnetic properties compared to rare-earth magnets synthesized by the conventional (powder metallurgy) routes. The performance (quality) of these magnets depends on the thermodynamics and kinetics of the different processing routes, such as atomization, melt spinning, and melt extraction. Here, we review the various processing routes of rapidly solidified rare-earth permanent magnets and the related properties and applications. In the review, some specific alloy systems, such as Sm–Co-based alloys, Nd ...


Strained Hybrid Perovskite Thin Films And Their Impact On The Intrinsic Stability Of Perovskite Solar Cells, Jingjing Zhao, Yehao Deng, Haotong Wei, Xiaopeng Zheng, Zhenhua Yu, Yuchuan Shao, Jeffrey E. Shield, Jinsong Huang Jan 2017

Strained Hybrid Perovskite Thin Films And Their Impact On The Intrinsic Stability Of Perovskite Solar Cells, Jingjing Zhao, Yehao Deng, Haotong Wei, Xiaopeng Zheng, Zhenhua Yu, Yuchuan Shao, Jeffrey E. Shield, Jinsong Huang

Mechanical & Materials Engineering Faculty Publications

Organic-inorganic hybrid perovskite (OIHP) solar cells have achieved comparable efficiencies to those of commercial solar cells, although their instability hinders their commercialization. Although encapsulation techniques have been developed to protect OIHP solar cells from external stimuli such as moisture, oxygen, and ultraviolet light, understanding of the origin of the intrinsic instability of perovskite films is needed to improve their stability. We show that the OIHP films fabricated by existing methods are strained and that strain is caused by mismatched thermal expansion of perovskite films and substrates during the thermal annealing process. The polycrystalline films have compressive strain in the out-of-plane ...


Controllable Energy Absorption Of Double Sided Corrugated Tubes Under Axial Crushing, Hozhabr Mozafari, Shengmao Lin, Linxia Gu Jan 2017

Controllable Energy Absorption Of Double Sided Corrugated Tubes Under Axial Crushing, Hozhabr Mozafari, Shengmao Lin, Linxia Gu

Mechanical & Materials Engineering Faculty Publications

To maximize the controllable energy absorption of corrugation troughs as observed in the single sided corrugated (SSC) tube, we proposed and tested a new structure design, i.e., double-sided corrugated (DSC) tube made of Al 6060-T6 aluminum alloy or CF1263 carbon/epoxy composite. Finite element models were developed to test the mechanical advantage of the DSC tube in comparison with both SSC and classical straight (S) tubes under axial crushing. Results have shown that the total absorbed energy of the DSC aluminum tube with 14 corrugations was 330% and 32% higher than that of the SSC tube with 14 corrugations ...