Materials Science and Engineering Commons^™

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 …

The Epitaxial Growth Of Ge And Gesn Semiconductor Thin Films On C-Plane Sapphire, Emmanuel Wangila, Calbi Gunder, Petro M. Lytvyn, Mohammad Zamani-Alavijeh, Fernando Maia De Oliveira, Serhii Kryvyi, Hryhorii Stanchu, Aida Sheibani, Yuriy I. Mazur, Shui-Qing Yu, Gregory J. Salamo

Physics Faculty Publications and Presentations

Ge_1−xSn_x growth on a new sapphire platform has been demonstrated. This involved the growth of GeSn on Ge/GaAs layers using the algorithm developed. The resultant growths of Ge on GaAs/AlAs/sapphire and Ge_1−xSn_x on Ge/GaAs/AlAs/sapphire were investigated by in situ and ex situ characterization techniques to ascertain the surface morphology, crystal structure, and quality. The growth mode of Ge on GaAs was predominantly two-dimensional (2D), which signifies a layer-by-layer deposition, contributing to enhanced crystal quality in the Ge/GaAs system. The growth of Ge_1−xSn_x with 10% Sn on a graded profile for 30 …

Revealing The Three-Dimensional Arrangement Of Polar Topology In Nanoparticles, Chaewa Jeong, Juhyeok Lee, Hyesung Jo, Jaewhan Oh, Hionsuck Baik, Kyoung-June Go, Junwoo Son, Si-Young Choi, Sergey Prosandeev, Laurent Bellaiche, Yongsoo Yang

Physics Faculty Publications and Presentations

In the early 2000s, low dimensional ferroelectric systems were predicted to have topologically nontrivial polar structures, such as vortices or skyrmions, depending on mechanical or electrical boundary conditions. A few variants of these structures have been experimentally observed in thin film model systems, where they are engineered by balancing electrostatic charge and elastic distortion energies. However, the measurement and classification of topological textures for general ferroelectric nanostructures have remained elusive, as it requires mapping the local polarization at the atomic scale in three dimensions. Here we unveil topological polar structures in ferroelectric BaTiO₃ nanoparticles via atomic electron tomography, which …

Development, 3d Printing, And Sintering Of Aluminum-Magnesium Alloy Pastes For In-Space Manufacturing Applications, Fatou Ndiaye

Electronic Theses and Dissertations

This study explores the additive manufacturing process of paste printing, sintering, and de-binding for fabricating aluminum-magnesium alloy components. The paste formulation involved combining aluminum powder with varying magnesium concentrations, utilizing acrylic polyol, solvent, and plasticizer to create a homogeneous mixture. Printing parameters were optimized to ensure continuous pressure for improved extrusion. Sintering conditions involved incremental temperature increases with nitrogen flow to remove solvents. Density measurements, tensile tests, and shrinkage calculations were conducted to assess part quality post-sintering. The study revealed significant improvements in part quality with 5 wt.% magnesium incorporation within aluminum, although density and tensile strength fell short of …

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 …

Layered Structure Protonic Ceramic Conductors Of The Form Ba5in2+Xal2zr1-Xo13-Δ, Nathan Cretegny

All Theses

In this work, the hexagonal perovskite of targeted composition Ba₅In_2+xAl₂Zr_1-xO₁₃ (x=0, 0.1, 0.2) was synthesized via a solid-state synthesis route to study the impact of oxygen vacancy concentration in layered hexagonal perovskites. Precursor oxides were mixed in stoichiometric proportions, calcined between 800-1200℃ and sintered at 1475℃. The sintered pellets were crushed into fine powders to investigate the chemistry and structure through X-ray diffraction, neutron diffraction, inductively coupled plasma mass spectrometry, and nuclear magnetic resonance. Dense pellets were used to study conductivity properties using electrochemical impedance spectroscopy.

The synthesis approach produced 100% …

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 …

Stabilization Of Layered Transition Metal Oxide Positive Electrodes At High Potential For Sodium Ion Batteries, Eric Gabriel

Boise State University Theses and Dissertations

As global demand for energy storage rises in response to the proliferation of electric vehicles and intermittent renewable energy sources, the resources associated with popular energy storage systems are increasingly strained. Lithium ion batteries (LIBs) rely heavily on elements with low abundance and unstable supply chains, while sodium ion batteries (SIBs) are a promising alternative technology based on abundant, globally available elements such as iron and sodium. However, the electrochemical performance of SIBs must be improved to enable their commercial viability. In the class of layered transition metal oxide (LTMOs) materials that are strong candidates as positive electrode materials for …

Engineering Multifunctional Silicon Nanostructures From Biorenewable Cellulose Nanocrystals, Nancy Chen

All Dissertations

The imperative search for alternative materials to address the pressing demand for advance energy storage is underscored by the escalating environmental predicaments. Lithium-ion batteries (LIBs) with graphite anodes have become the benchmark in energy storage; however, they are approaching a saturation point in terms of energy density. Silicon emerges as a promising contender to supplant graphite, owing to its profuse availability, cost-effectiveness, and impressive specific capacity of 4200 mAh g^-1. By integrating silicon anodes, LIBs stand to undergo a radical transformation, markedly diminishing in weight and size, thus heralding a novel wave of compact, lightweight energy storage systems. …

Process-Structure-Property-Performance Modeling For Semicrystalline Thermoplastics And Composites, Tatiana Stepanova

All Dissertations

With a growing focus on reducing the adverse effects of transportation on the environment, industries are seeking fuel-efficient and sustainable solutions. Fuel efficiency can be improved in several ways, but structural lightweighting has demonstrated overall effectiveness. In this regard, thermoplastic composites and additive manufacturing (AM) thermoplastics have become viable candidates for use in the automotive industry, given the need for weight reduction and efficiency improvement.

The advantages of AM include simplifying supply chains, simplifying part geometry, and enabling mass customization. In order to design high-performance AM structures, extensive modeling and simulation are required. AM thermoplastics are similar to conventional manufacturing …

A Manufacturing-To-Response Pathway For Manufacturing Optimization Of Carbon Fiber Reinforced Polymer Composite Structures, Madhura Limaye

All Dissertations

Over the past decade, there has been an increased adoption of thermoplastic and thermoset based continuous carbon fiber reinforced polymer (CFRP) composites for structural applications in several industries. Among the different manufacturing methods, thermoforming process for thermoplastic based continuous CFRP’s offer a major advantage in reducing cycle times for large scale productions. Similarly, out-of-autoclave curing process for thermoset based continuous CFRP’s using heated tooling enables production of large composite structures. However, these manufacturing processes can have a significant impact on the structural performance of parts by inducing undesirable effects. These effects include inhomogeneous fiber orientations, thickness variations, and residual stresses …

Additive Manufacturing With Bioresorbable Polymers: Process-Structure-Property Relationships For Biomimetic Tissue Scaffolds, Clayton Joseph Culbreath

All Dissertations

Tissue engineering has a base requirement of scaffold structures to support cell growth, proliferation, and regeneration. However, attempts to use artificial scaffold structures have often fallen short of clinical needs to justify the change away from the established, biologic-based current standard of care. Based on the limited number of successful tissue scaffolds produced by material extrusion modes of additive manufacturing, fused filament 3d printing and electrospinning, critical design specifications for a tissue scaffold are six minimum requirements: 1) biocompatibility, 2) porosity, 3) mechanical properties, 4) bioresorbable medical grade materials, 5) bioactivity, and 6) appropriately scaled production methods compliant with medical …

Machine Learning Assisted Discovery Of High-Performance Perovskites For Hydrogen Production, Ximei Zhai

All Dissertations

Hydrogen has significantly contributed to the global energy transition as a clean energy carrier. However, traditional hydrogen production involves energy-intensive processes with heavy carbon emissions. High-temperature water splitting to generate hydrogen has become a promising route for clean hydrogen production. Directly utilizing concentrated solar heat to perform solar thermochemical hydrogen (STCH) production is considered one of the most eco-friendly hydrogen production options. At the same time, high-temperature electrolysis in protonic ceramic electrolysis cells (PCECs) can efficiently utilize intermittent and cost-effective renewable electricity to produce hydrogen. Perovskite oxides with good redox capability and tolerance for oxygen deficiency are considered the most …

Volatile Crystalline Semiconductor Core Fibers, Thomasina Zaengle

All Dissertations

Optical fibers play critical roles across many facets of everyday life from communications to e-commerce to sensing and security. The ubiquity of optical fibers arises from their intrinsic clarity and, as glasses, their ability to be thermally drawn at high speeds over long distances when suitably heated about their glass transition temperature. Sixteen years ago, the first thermally drawn crystalline core fibers were fabricated using the molten core method, whereby a melt is confined within a glass capillary tube that is then drawn to fiber. This opened the door to crystalline semiconductor core fibers, which are now the backbone of …

Tin-Silver As A Novel Biodegradable Metallic Biomaterial, Charley Goodwin

All Dissertations

The Essure device is a non-hormonal, minimally-invasive, permanent female sterilization implant, removed from the market due to an increase in adverse events, hypothesized to be caused by corrosion of the Sn-Ag component of the implant. The goals of this dissertation were to first develop implant retrieval methods for Essure devices and surrounding tissue, documenting signs of degradation and metallic degradation products, then to characterize the electrochemical behavior of Sn-Ag in biologically representative environments and finally, to assess the biological interaction of Sn-Ag. Retrieval analyses developed successful methods, qualifying the degree of corrosion, primarily of the Sn-Ag component and finding Sn …

Sliding Markov Decision Processes For Dynamic Task Planning On Uncrewed Aerial Vehicles, Trent Wiens

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

Mission and flight planning problems for uncrewed aircraft systems (UASs) are typically large and complex in space and computational requirements. With enough time and computing resources, some of these problems may be solvable offline and then executed during flight. In dynamic or uncertain environments, however, the mission may require online adaptation and replanning. In this work, we will discuss methods of creating MDPs for online applications, and a method of using a sliding resolution and receding horizon approach to build and solve Markov Decision Processes (MDPs) in practical planing applications for UASs. In this strategy, called a Sliding Markov Decision …

Dynamic Impact Testing And Numerical Analysis Of Non-Proprietary Astm F2656-20 M50 Anti-Ram Barrier Components, Weston Kelley

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

In a post-9/11 world, hostile actors are using vehicles as weapons to inflict civilian casualties. Pedestrians, vulnerable road users, military personnel, and police may be targeted using a vehicle as a weapon. The United States Department of Defense (DoD) also utilizes Entry Control Facilities (ECFs) which are carefully designed transportation corridors to manage how threat vehicles are able to access military facilities. In 2004, DoD started to upgrade all ECFs using both passive and active barriers. Many anti-ram vehicle barriers were evaluated according to the criteria established in ASTM F2656, but to date few options are available which are (1) …

Effects Of Bending And Re-Bending On Mechanical Properties Of Locally-Manufactured Steel Rebars, Patrick W. Waruhiu, Simon I. Marandu, Mussa I. Mgwatu

Tanzania Journal of Science

Steel rebars experience deformation when subjected to bending and re-bending operations. Subsequently, their microstructures are impaired thus affecting the mechanical properties and leading to failure. This study establishes the effects of bending and re-bending the steel rebars on the mechanical properties. Experiments were conducted to determine the effects of bending and re-bending of the steel rebars. Testing was conducted on Ten virgin and Thirty specimens which were bent and re-bent at 45º, 90º, and 180º, and followed by tensile tests. Yield strength, ultimate tensile strength, elongation, and ultimate tensile strength to yield strength ratio (Rm/Re), were recorded. Results showed the …

Study Of Reactive Distillation Equipment For Eterification Process, Abbos Elmanov, Abdulaziz Bakhtiyorov, Adham Norkobilov, Olimjon Maksudov, Zarif Oripov

CHEMISTRY AND CHEMICAL ENGINEERING

The purpose of this work is to study the chemical technological processes for eterification processes, and the reactive distillation unit, which carries out the reaction and separation process in one device, was chosen as the object of research. А reаctive distillаtion system is exаmined to produce for the production of Ethyl Acetate (EtAc) viа eterificаtion of acetic acid (HAc) with ethаnol. Optimizаtion methods using sensitivity analysis аre аlso conducted. Cаlculаtion of vаpor liquid equilibrium of the mixture system is done using UNIFАC model. Heat integration from the distillate stream of the column to the acid feed stream and from bottom …

Numerical Calculation Of The Flame Spreading Over A Methane Hydrate Surface, Otabek Nigmatov, Oksana Ismailova

CHEMISTRY AND CHEMICAL ENGINEERING

The Methane Hydrate is expected as an energy source and is being as a medium distance transport means of natural gas alternative of LNG (Liquefied Natural Gas). During the natural gas transportation, fire accidents are concerned. In the present study, the flame spreading over a methane hydrate surface has been studied numerically as a function of hydrate surface temperature, T_s. When T_s = 173 K (-100℃), lower than the dissociation temperature (T_d = 183 K (-90℃)), the flame spreading speed is around 6.5 mm/s, while the flame spreading speed at T_s = 193 K (-80℃), …

Dft Study Of Quantum Chemical Parameters Of 4-Amino-2-Mercaptobenzimidazole And Their Tautomeric Forms, Dilnoza Rahmonova, Alisher Eshimbetov, Lobar Gapurova, Zuhra Ch. Kadirova, Shakhnoza Kadirova

CHEMISTRY AND CHEMICAL ENGINEERING

Coordination competing donor centers, electronic and geometric structures of the 4-amino-2-mercaptobenzimidazole ligand molecule were studied using quantum chemical calculation by the DFT / 6-31G method (d, p). It was shown that during the formation of the metal complex, the ligand is coordinated through the localized nitrogen atom of the imidazole ring. In this study, the total energies (Etot) of 4-amino-2-mercaptobenzimidazole (1) and its tautomeric forms (2 and 3) were calculated. And also, the energies of boundary molecular orbitals, the energy gap between boundary MOs (ΔE) and the distribution of the total charge on atoms and boundary orbitals were determined. In …

The Effect Of Hydrogen Peroxide And Potassium Amylxanthate On The Surface Properties Of Chalcocite And Enargite, Berdakh T. Daniyarov, Hajime Miki, Daminbek A. Ziyatov, Shahlo Daminova

CHEMISTRY AND CHEMICAL ENGINEERING

The effect on the surface properties and floatability of chalcocite and enargite after oxidative treatment with hydrogen peroxide (H₂O₂) in the presence and absence of potassium amylxanthate (PAX) as a collector was studied. In this research, flotation tests were carried out on mixed and individual minerals. Oxidative treatment with hydrogen peroxide had a negative effect on the floatability of chalcocite and enargite. PAX adsorption analysis shows that enargite adsorbs PAX faster than chalcocite. Moreover, Fourier transform infrared spectroscopy analysis shows that PAX was adsorbed in the form of copper amylxanthate on chalcocite and enargite surfaces. In …

Influence Of The Amount Of Monoethanolamine On The Physicochemical Properties Of Aminolysis Products, Soxibjon A. Egamberdiyev, Muzaffar G. Alimukhamedov, Juraev Asror, Ravshan Adilov

CHEMISTRY AND CHEMICAL ENGINEERING

The purpose of this paper is to investigate the process of aminolysis of secondary polyethylene terephthalate with monoethanolamine at low ratio. The effect of the amount of monoethanolamine on the physical and chemical properties of the aminolysis product of secondary polyethylene terephthalate was studied. With an increase of 1-4 moles of monoethanolamine obtained for synthesis (without the presence of a catalyst), it was observed that the number of amines in the aminolysis product increased from 324 to 503 mgKON/g, and the number of hydroxyls increased from 298 to 491 mgKON/g. The structure of the resulting bis(2-hydroxyethylene)terephthalamide was studied using IR …

Study Of The Structure Of Glass Ionomer Cements Developed Based On Glass System Sio2-Al2o3-Cao-Zno-P2o5-Caf2, Tatyana O. Nam, Mastura X. Aripova, Ripsime V. Mkrtchyan

CHEMISTRY AND CHEMICAL ENGINEERING

The goal was to study the structure of glass ionomer cements (GIC) developed on the basis of glasses of the SiO₂-Al₂O₃-CaO-ZnO-P₂O5-CaF₂ system. Glass powders with sizes less than 50 μm were sealed with a 40% solution of polyacrylic acid and after 72 hours, electron microscopic examination was carried out on a JSM-IT200 scanning microscope (JEOL, Japan). All samples demonstrate a cellular structure consisting of glass particles surrounded by glass elements that have entered into an acid-ion interaction with polyacrylic acid in a polymer matrix. GIC-4 and GIC-6 show the most …

Impact Of Sulfurization On Sputtered Bivo4 Thin Films, Shukur P. Gofurov, Dilbar T. Bozorova, Zuhra Ch, Kadirova, Oksana Ismailova

CHEMISTRY AND CHEMICAL ENGINEERING

The sulfurization method has been used to decrease the band gap of the BiVO₄ structure, reduce the recombination of electrons and holes, and increase the photoelectrochemical performance of this material. It has been observed that incorporation of sulfur into stoichiometric and V_rich BiVO₄ is variously affected changing of properties of the structure. Sulfurization can modify V_rich BiVO₄ structure rather than stoichiometric BiVO₄.

Development Of Clinker And Portland Cement Composition Based On Surkhondaryo Raw Materials, Salohiddin Ramazanov, Abdumalik Nabiyev, Mastura Aripova

CHEMISTRY AND CHEMICAL ENGINEERING

The purpose of this research work is to develop clinker and Portland cement compositions based on Surkhandarya raw materials for the planned construction of a cement plant, as well as to study their physical and chemical properties. The compositions of clinkers, including limestone, clay from the Yolgizbulok deposit and slag from the Almalyk mining and metallurgical plant, were studied. The optimal clinker composition was selected, on the basis of which Portland cement was obtained. The optimal amount of gypsum addition was determined to achieve a cement stone strength of 43,5 MPa. The developed clinker composition will provide the planned enterprise …

Antibacterial Cerium-Containing Glazes For Ceramic Tiles, Ivan Levitskiy, Mastura Aripova, Mihail Dyadenko, Dar’Ya Kucherova, Artem Golub

CHEMISTRY AND CHEMICAL ENGINEERING

The results of research on the production of semi-fritted cerium-containing glazes used for ceramic tiles are presented.

A multicomponent raw material mixture based on dolomite, cerium dioxide CeO₂, aluminosilicate multicalcium frit and permanent components including feldspar, alumina and clay components (kaolin and refractory clay) is used to produce glazes.

The characteristics of the obtained coatings were studied: appearance, technological and physico-chemical properties, including antibacterial properties in relation to the strains of Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 6538. The influence of temperature parameters on the formation of glaze coatings, as well as their structure and phase …