Engineering Commons^™

Enhancement Of The Mechanical Behavior Of Nitinol Wire For Vascular Stent Applications By The Addition Of A Polymer Matrix Composite Coating, Baylie Phillips

Graduate Theses & Non-Theses

Several clinical studies since 2008 have reported stent failure through mechanical means from inadequate strength, fatigue failure, coating failure via delamination and cracking, and pathological failures. Enhancement of the mechanical performance and stability of the polymer coating has the potential to minimize coating failure, aiding in the prevention of the other failure modes. The present study fabricated a polymer matrix composite coating from poly(D,L-lactide-co-glycolic) acid (PLGA) and hydroxyapatite (HA) nanoparticles on nitinol wires. Five weight fractions of HA (1.0, 2.5, 5.0, 7.5, and 10.0 wt.% HA) were studied for their influence on the mechanical performance of nitinol. The coatings were …

Investigating The Impact Of Secondary Activation Time On The Adsorption Properties Of Activated Biochar For Arsenic Removal From Wastewater, Achyuth Bharadwaj Rayarao

Graduate Theses and Dissertations (2019 - present)

Biochar, a naturally occurring and renewable carbon material, becomes porous through activation. Activated biochar is an ideal candidate for use as an adsorbent. The objective of this study is to investigate whether activated biochar derived from Colorado soft pine serves as a better adsorbent and demonstrates enhanced adsorption capabilities after undergoing secondary physical activation at various activation times. The effect of secondary action time on physical adsorption properties drawn from the analysis of isotherm plots, surface areas and pore size patterns were examined by using a physisorption analyzer. Chemical structures were identified using both ultimate and proximate analyses, while porosity …

Study Of The Influence Of B2o3 Oxide On The Physical And Technical Properties Of Ground Enamel Obtained Based On Local Raw Material Components, Shoxrux B. Naimov, Mastura Kh. Aripova

CHEMISTRY AND CHEMICAL ENGINEERING

The purpose of the study was to obtain ground enamel based on local raw materials and to study the effect of boron oxide. The selection of local raw materials for producing ground enamel showed that the resulting glass compositions are in the SiO₂–Al₂O₃–Na₂O–K₂O–CaO–B₂O₃ system. To adjust the properties, additives of nickel oxide and cobalt oxide were used. The properties of the developed compositions of primer enamels meet the requirements of GOST 24405-80. It has been determined that the addition of boron and an increase in its amount …

Formation Of Luminescent Coatings With The Use Of Low Melting Glass, Eygeniy N. Poddenezhny, Ekaterina E. Trusova, Andrei A. Boiko, Ekaterina R. Kravcova, Olga V. Davydova

CHEMISTRY AND CHEMICAL ENGINEERING

The aim of the present research is to develop compounds and technologies for applying the luminous vitrocrystalline compounds to smooth and ribbed glass substrates in LED lamp structure with a remote photoconverter that contains oxide low melting glass as the base and nanostructured cerium–doped yttrium–aluminum garnet powder as the luminophore. The luminescent coatings based on nanostructured cerium doped yttrium-aluminum garnet powder and low melting glass of composition BaO-Bi₂O₃-B₂O₃-K₂O-SiO₂ where prepared. YAG:Ce³⁺ powder was synthesized by the method of thermochemical reaction. Silica glass powder was introduced into the composition …

Anomalous Of Resistance And Magnetic Susceptibility At 280-310 K And Ambient Pressure In Bismuth Cuprates Synthesized By Solar Energy, Dilbara Dj. Gulamova, Elyor B. Eshonkulov, Valeriya R. Li, Grigor I. Mamniashvili, Timur I. Gulamov

CHEMISTRY AND CHEMICAL ENGINEERING

In order to obtain the full content of high-temperature superconducting phases using the “Super Fast Alloys Quenching” technology in the Large Solar Furnace (Parkent), precursors of bismuth cuprates of the series Bi_1,7Pb_0,3Sr₂Ca_(n-1)Cu_nO_y, n=3-30 were synthesized. Methods for study the properties of precursors are presented. The oriented nano-sized microstructure and layered structure of nanocrystalline nuclei are shown. The phase composition of the precursors at the beginning of the series (n=3-5) is represented by X-ray amorphous and crystalline phases. An increase in the content of CaO and CuO destabilizes the …

Waste Utilization In Korean Cement Plants, Geun-Seong Lee, Zebo Abdullaevna Babakhanova, Mastura Khikmatovna Aripova

CHEMISTRY AND CHEMICAL ENGINEERING

The kiln process in cement plant has the advantage of completely and effectively destroying and burning all organic substances due to high temperature and long residence time, oxygen atmosphere and excellent mixing effect, alkaline conditions of raw materials, and incorporation of trace metals into clinker, and plays a role as a pollutant emission barrier during waste utilization. Waste utilization technology is now proven and successful in cement plants. The waste utilization in Korean cement plants are greatly expanding in the view of energy and material recoveries, and economics as well as environmental preservation. Research on waste utilization in the Korean …

High Temperature Validation Of A Line Heat Source Technique For In-Pile Thermal Conductivity Determination, Katelyn Wada, Allyssa Bateman, Tony Valayil Varghese, Austin Fleming, Brian J. Jaques, David Estrada

Materials Science and Engineering Faculty Publications and Presentations

In-pile instrumentation is critical for advancing operations and materials discovery in the nuclear industry. Ensuring optimal performance of sensors in high temperatures is the first step in demonstrating their viability in the harsh in-pile environment. This work demonstrates the high temperature capabilities of a line heat source and measurement technique previously shown to extract thermal conductivity of nuclear fuel sized samples within a laboratory environment at room temperature. This method uses a hybrid AC/DC measurement technique to obtain rapid measurements of the temperature dependent voltage change of a heater wire, which also acts as a resistance thermometer. Once the temperature …

A Comprehensive Investigation Of The Influence Of Geometric Structure On The Shape Memory Performance Of Nafion, Jade Thomas

Physics Undergraduate Honors Theses

While perfluorosulfonic acid (PFSA) membranes have primarily been used in fuel cells due to their chemical, thermal, and mechanical stability, one PFSA, Nafion, boasts two unique characteristics: a broad glass transition (~55 °C to 130 °C) and a temperature-persistent electrostatic network. The combination of these two characteristics endows Nafion with exceptional shape memory properties – the ability of a material to morph and transform into pre-programmed shapes when exposed to an external stimulus – with enhanced permanent shape memorization, and a potentially near-infinite number of temporary shape memorization. This study focused on expanding the base of knowledge surrounding Nafion’s shape …

The Analysis Of Mechanical Exfoliation Of Graphene For Various Fabrication And Automation Techniques, Lance Yarbrough

Physics Undergraduate Honors Theses

Mechanical Exfoliation

Micro-Mechanical Characterization Of Uhpc Stiffness Mechanisms: Towards A Better Understanding Of Concrete Elastic Modulus, Charissa N. Puttbach

Graduate Theses and Dissertations

Current design code equations for estimating the elastic modulus of specialty concretes like ultra-high performance concrete are not all suitable. Developing empirical curves from exhaustive experimental testing is challenging for concretes that may have high levels of cement replacement with mineral admixtures and fibers at varying volume contents. As such, an alternative approach is taken that seeks to understand the constituent microscale stiffness mechanisms and relate the results to the macroscale. Micropillars are fabricated on several cement paste phases using a focused ion beam. A modified pico-indenter is used to determine the linear and non-linear behavior under micro-compression loading. Micropillar …

Release Of Small Molecules From Rubber: Effects Of Materials Properties, Mechanical Loading And Molecular Interactions, Yongcan Du

All Dissertations

Release of small molecules from polymeric materials has wide applications in the delivery systems of active molecules such as drug, fragrance, and semiochemical. Rubber materials are good candidates for the excipients of those systems due to properties such as good flexibility, permeability, and biocompatibility. Factors like material properties, mechanical loading, and molecular interactions may affect the release of small molecules in those systems. Therefore, understanding how those factors affect the release is key to the formulation, design, and evaluation of those systems.

To study the effects of materials properties, vulcanized natural rubber sheets with different crosslink densities, loaded with small …

Free And Forced Vibrations Of Elastically Restrained Cantilever With Lumped Oscillator, Alireza Babaei, Johné Parker, Paria Moshaver

Earth and Environmental Sciences Faculty Publications

The efficiency assessment of cantilever-based energy harvesters relies on vibrational analysis, which necessitates modi- fications aimed at enhancing efficiency. These modifications involve manipulating the fundamental frequency to lower values and encompassing a wider range of resonances within a specified bandwidth. Consequently, this paper introduces an original analytical-numerical exploration into the vibratory response of a cantilever with a novel boundary condi- tion involving an elastically restrained oscillator-spring arrangement. At the microbeam’s tip, an oscillator is elastically confined by a linear spring, resulting in a novel set of coupled governing equations and a distinct shearing boundary condition. Microbeam equations is derived from …

A Comprehensive Materials Approach To Thermal Management In Fiber Lasers, Bailey Meehan

All Dissertations

Optical fiber-based amplifiers and lasers enable a great many useful devices and conveniences. Unfortunately, however, they can generate considerable heat during operation that drives the need for complex cooling solutions, thus reducing many of the size, weight, and power (SWAP) benefits for which fiber lasers are known. Additionally, at elevated temperatures, thermally-driven phenomena, such as Transverse Mode Instability (TMI), can be induced that limit the power-scaling of fiber lasers. The focus of this Dissertation is to explore novel approaches to thermal management in fiber lasers through judicious materials science and engineering to obviate the aforementioned limitations. Fibers studied in this …

Quasi-Static And Dynamic Deformation Of Aluminum Matrix Composites Reinforced By Core-Shell Al35ti15cu10mn20cr20 High-Entropy Alloy Particulates, Dezhi Zhu, Tingting Chen, Xiaoqiang Jin, Haiming Wen, Zhiqiang Fu, Shengguan Qu

Materials Science and Engineering Faculty Research & Creative Works

Core-Shell Structured Particles Are Potential Reinforcement Agents For Metal Matrix Composites. In This Work, Aluminum Matrix Composites Reinforced With Core-Shell Structured Al35Ti15Cu10Mn20Cr20 High-Entropy Alloy (HEA) Particles Were Fabricated By Spark Plasma Sintering (SPS) And High-Temperature Diffusion Post-Treatment. Dynamic Compression Behavior And Adiabatic Shear Failure Mechanism In The Composites Were Investigated By Split Hopkinson Pressure Bar (SHPB), Scanning Electron Microscopy And Transmission Electron Microscopy. Results Showed That The Shell Thickness Of The Core-Shell Particles Ranged From 0.4 To 1.6 Μm, Which Were Formed By Thermal Diffusion Between HEA Core And Aluminum Alloy. The 30 Vol% (Al35Ti15Cu10Mn20Cr20)p/2024Al Composite Showed A High Compressive …

Encapsulated 2d Materials And The Potential For 1d Electrical Contacts, Sarah Wittenburg

Physics Undergraduate Honors Theses

The utilization of two-dimensional materials and heterostructures, particularly graphene and hexagonal boron nitride, have garnered significant attention in the realm of nanoelectronics due to their unique properties and versatile functionalities. This study focuses on the synthesis and fabrication processes of monolayer graphene encapsulated between layers of hBN, aiming to explore the potential of these heterostructures for various electronic applications. The encapsulation of graphene within hBN layers not only enhances device performance but also shields graphene from environmental contaminants, ensuring long-term stability. Experimental techniques, including mechanical exfoliation and stamp-assisted transfer, are employed to construct three-layer stacks comprising hBN-graphene-hBN. The fabrication process …

Development Of A Multi-Use Modular Microfluidic Platform Using 3d Printing, Carson Emeigh

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

Microfluidic lab-on-a-chip (LoC) technology has driven numerous innovations due to their ability to perform laboratory-scale experiments on a single chip using microchannels. Although LoC technology has been innovative, it still suffers from limitations related to its fabrication and design flexibility. Typical LoC fabrication, with photolithography, is time consuming, expensive, and inflexible. To overcome the limitations of LoC devices, modular microfluidic platforms have been developed where multiple microfluidic modules, each with a specific function or group of functions, can be combined on a single platform. Modular microfluidics have overcome some of the limitations of LoC devices, but currently, their fabrication is …

Characterization Of Platinum On Carbon Nanoparticles Selectively Coated With Titanium Nitride (Tin), Matthew Maramo

Honors Scholar Theses

Proton exchange membrane fuel cells are a promising low-carbon technology that still face problems including low durability during their normal operation cycles. At the cathode, the carbon supports of the catalysts may corrode. Atomic layer deposition of titanium nitride is performed on prepared catalyst layer samples. The purpose of the deposition is to create a thin film over the carbon supports to reduce carbon support corrosion and improve the lifespan of the fuel cell. Sheet resistances and contact angles are measured for the samples before and after the deposition, although some samples did not receive the deposition and post-deposition characterization …

Investigation Of Domain Formation During Phase Separation In A Mixture Of Flexible And Rigid Biopolymers, Steven Huntley

All Theses

Complex fluids and heterogenous mixtures composed of multiple types of polymers are found throughout industrial and biological fluid systems. For example, extrusion based additive manufacturing systems pass dense mixtures of polymers through the extrusion heads to deposit composite polymeric materials. In cells, active and complex mixtures of biopolymers self-organize into assemblies that perform critical physiological functions.

Polymers in dense solutions undergo phase separation as a result of differences in physiochemical properties. A few examples of these properties include charge, structure, rigidity, and hydrophobicity. We observe the formation of polymer domains composed of rigid and a flexible biopolymer species that phase …

Improved Ballistic Impact Resistance Of Nanofibrillar Cellulose Films With Discontinuous Fibrous Bouligand Architecture, Colby Caviness

All Theses

Natural protective materials offer unparalleled solutions for impact-resistant material designs that are simultaneously lightweight, strong, and tough. Particularly, the dactyl club of mantis shrimp features chitin nanofibrils organized in a Bouligand structure, which has been shown to effectively dissipate high-impact energy during powerful strikes. The mollusk shells also achieve excellent mechanical strength, toughness, and impact resistance with a staggered, layer-by-layer structure. Previous studies have shown that hybrid designs, by combining different bioinspired microstructures, can lead to enhanced mechanical strength and energy dissipation capabilities. Nevertheless, it remains unknown whether combining Bouligand and staggered structures in nanofibrillar cellulose (NFC) films, forming a …

Environment And Response Of 3d-Encapsulated Mesenchymal Stem Cells To Mechanical Loading, Augustus Greenwood

McKelvey School of Engineering Graduate Student Theses & Dissertations

This thesis explores the micromechanical environment induced when cyclically compressing hydrogels via finite element modeling and experimentally on the impact of loading on mesenchymal stem cells (MSCs) when encapsulated withing 3D hydrogel matrices. Degenerative joint diseases, characterized by cartilage degradation, present significant challenges due to cartilage's limited self-repair capacity. Innovative approaches, including stem cell-based therapies and engineered biomaterials, have emerged as promising strategies for cartilage repair and regeneration. This work specifically investigates the calibration of a bioreactor, the uniformity of load response across the hydrogel constructs via finite element modeling (FEM), and the stress response of MSCs subjected to various …

Germanium-Tin On Silicon For Integrated Photonics And Integrated Quantum Materials, Shang Liu

Dartmouth College Ph.D Dissertations

Group IV GeSn alloys are attracting attention due to their compatibility with the complementary metal-oxide-semiconductor (CMOS) process. On one hand, Ge-rich GeSn alloys with a tunable direct bandgap are well-suited to infrared (IR) photonic applications such as image sensors. On the other hand, Sn-rich GeSn alloys in diamond cubic α phase are topological quantum materials (TQM) holding potential for important quantum applications. However, directly growing GeSn on Si remains challenging due to the lattice mismatch. Regular epitaxial GeSn grown on a Ge buffer layer is not applicable to many photonic applications including CMOS image sensors (CIS) because the buffer layer …

Green Chemistry Design Of Epoxies From Biomass For Circular Economy, Kavya Ganesan

All Dissertations

The commercial epoxies market in automobiles has been growing mainly in terms of usage as automotive coatings and lightweight composite structures manufacturing. Most of these commercial epoxies are bisphenol-based. Bisphenol-based epoxies are a class of high-performance polymer materials that, when cured, yield thermosets with high mechanical, thermal and chemical resistance properties. Roughly, North America produces around 123 billion pounds of these epoxies which are used in various industrial applications like coatings, composites, structural parts, automotive, electronics, construction etc. These epoxies are mainly manufactured from bisphenol-A (BPA) and epichlorohydrin (EPH). These raw materials are sourced from fossil fuel resources and are …

Numerical Simulation Of Laser Induced Elastic Waves In Response To Short And Ultrashort Laser Pulses., Alireza Zarei

All Dissertations

In an era of intensified market competition, the demand for cost-effective, high-quality, high-performance, and reliable products continues to rise. Meeting this demand necessitates the mass production of premium products through the integration of cutting-edge technologies and advanced materials while ensuring their integrity and safety. In this context, Nondestructive Testing (NDT) techniques emerge as indispensable tools for guaranteeing the integrity, reliability, and safety of products across diverse industries.

Various NDT techniques, including ultrasonic testing, computed tomography, thermography, and acoustic emissions, have long served as cornerstones for inspecting materials and structures. Among these, ultrasonic testing stands out as the most prevalent method, …

Design And Optimization Of A Novel Monolithic Spring For High-Frequency Press-Pack Sic Fet Modules, Bogac Canbaz

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

Silicon Carbide (SiC) Field-Effect Transistor (FET) modules lead the way in power electronics, being superior in efficiency and robustness for high-frequency applications. The shift towards SiC from traditional silicon (Si)-based devices is driven by its superior thermal conductivity, higher electric field strength, and operational efficiency at elevated temperatures. These features are critical for the development of next-generation, grid-oriented power converters aimed at enhancing the reliability and sustainability of power systems. This research focuses on high-frequency press-pack (HFPP) SiC FET modules, addressing the primary challenge of miniaturizing SiC FET dies without compromising performance, through an innovative press-contact design essential for increased …

Smart Manufacturing Of Cement: From Lab-Scale Simulation And Testing To Industry-Scale Deployment., Juan David Tabares Tamayo

Electronic Theses and Dissertations

Cement kilns are controlled by experienced process operators who follow experience-based industry guidelines using data collected and fundamental knowledge. The manufacturing process, which is equipped with sensors and equipment, transfers data/information to the operators to aid standardized decision-making operations. In contrast, companies have used such data to develop and implement digital solutions for predictive control systems; in effect, FLSmidth and Rockwell Automation. However, despite the availability of automated control systems and investigation in automation for process monitoring and optimization, opportunities to radically optimize cement manufacturing are still abundant and in need of implementation. Therefore, this research developed simulation models and …

Drag Reduction In Channel Flow Configurations For Laminar And Turbulent Flow Past Superhydrophobic Surfaces, Henry Louis Ems

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

In this work, we present friction drag reduction in minichannel laminar flow past superhydrophobic metallic surfaces. Femtosecond laser surface processing (FLSP), a one-step scalable method, was used to create permanent microscale and nanoscale structures on 316 stainless steel plates. The resulting superhydrophilic plates were covered by tall (215 μm) or short (27 μm) structures. The FLSP plates were then transitioned to superhydrophobic by evaporative deposition of a fluorinated silane, a low surface energy coating. Using purified water, the friction factor was obtained by measuring pressure drop along a minichannel with a rectangular cross section for flow rates corresponding …

The Analysis Of Mechanical Exfoliation Of Graphene For Various Fabrication And Automation Techniques, Lance Yarbrough

Mechanical Engineering Undergraduate Honors Theses

Mechanical Exfoliation of Graphene is an often-overlooked portion of the fabrication of quantum devices, and to create more devices quickly, optimizing this process to generate better flakes is critical. In addition, it would be valuable to simulate test pulls quickly, to gain insight on flake quality of various materials and exfoliation conditions. Physical pulls of graphene at various temperatures, pull forces, and pull repetitions were analyzed and compared to the results of ANSYS simulations, solved for similar results. Using ANSYS’ ability to predict trends in exfoliations, flake thickness and coverage using stress and deflection analyses were investigated. Generally, both strongly …

Effects Of Ferrite And Graphite Phases On Scratch Characteristics Of Nodular Cast Iron, Zhitong Xu, Ming Liu, Chenghui Gao, Fuqian Yang

Chemical and Materials Engineering Faculty Publications

In this work, we conduct micro-scratch tests of nodular cast iron with Vickers indenter under constant normal load and investigate the effects of individual phases (i.e., ferrite and graphite phases) on the scratch charac- teristics of nodular cast iron. Using a bimodal Gaussian model to fit the experimental data of penetration depth, residual depth, elastic recovery rate, and scratch hardness, we calculate the contribution percentages of indi- vidual phases to scratch variables. The scratch variables are independent of the scratch speed used in this work, while the penetration depth increases linearly with increasing the normal load. There exists a large …

A Mechanical Model For Stress Relaxation Of Polylactic Acid/Thermoplastic Polyurethane Blends, Yi-Sheng Jhao, Hao Ouyang, Chien-Chao Huang, Fuqian Yang, Sanboh Lee

Chemical and Materials Engineering Faculty Publications

Polylactic acid (PLA) is considered a promising biodegradable polymer alternative. Due to its high brittleness, composite materials made by melt blending thermoplastic polyurethane (TPU) with PLA can enhance the toughness of PLA. To understand the forced aging caused by stress relaxation in polymer materials, this study explains the stress relaxation experiments of PLA/TPU blends with different mass ratios under applied strain through mechanical model simulations. The Kelvin representation of the standard linear solid model (SLSM) is used to analyze the stress relaxation data of TPU/PLA blends, successfully explaining that the Young’s moduli (E1 and E2) of springs decrease with increasing …

Adipose Stem Cell Response To Borophosphate Bioactive Glass, Nada A. Abokefa, Bradley A. Bromet, Rebekah L. Blatt, Makenna S. Pickett, Richard K. Brow, Julie A. Semon

Materials Science and Engineering Faculty Research & Creative Works

Silicate and Borate Bioactive Glasses Have Been Reported to Create Alkaline Conditions by Rapidly Releasing Ions When Reacting in Aqueous Solution. at Certain Levels, This Alkaline Solution Can Negatively Affect Cell Viability. Adding Phosphate Ions to the Glass Composition Can Control the Degradation Rate of Bioactive Glasses and Create a Neutral PH Environment. This Study Evaluated a Series of Boro phosphate Bioactive Glasses (BPBGs) with Nominal Molar Compositions 16Na₂O_-24CaO-XB₂O₃-(60-X) P₂O₅, Where X = 0, 40, or 60. the Phosphate (X0) Glass (PBG) Produced an Acidic Solution When Dissolved …