Master of Science, The Ohio State University, 2005, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2024, Food Science and Technology

As the global population is projected to rise to 9.7 billion by 2050, environmental, health, and ethical concerns are driving many consumers to reduce their meat consumption. This shift has spurred a significant market for plant-based products. Despite advancements, many consumers still find these alternatives lacking in taste and texture, which are crucial for acceptance. Hempseed protein, a sustainable and nutritious alternative, offers promising texturization properties for plant-based products. This work explores the potential of hempseed protein in a high moisture extrusion application, examines the texture, and investigates the correlation between instrumental measurements and sensory perceptions. Rheological testing revealed that formulations with pea protein had higher storage modulus (G') values, suggesting similar strain resistance as wheat gluten, and formulations with pea protein resulted in higher viscosities. Extrudate analysis demonstrated significant textural differences: wheat gluten-containing samples were denser and more fibrous, while gluten-free samples had larger pores and rougher texture. Texture profile analysis indicated hemp flour increased hardness and chewiness, and friction measurements suggested similar oral processing characteristics for pea protein and hemp flour formulations. Though instrumental-sensory correlations were limited, panelists determined 60HP-40WG had the highest perceived hardness and chewiness and the lowest intensity of graininess.

Committee: Osvaldo Campanella (Advisor); Christopher Simons (Committee Member); Luis Rodriguez-Saona (Committee Member) Subjects: Food Science

Master of Science, Miami University, 2024, Mechanical and Manufacturing Engineering

The friction and wear properties of bilayer graphene on silicon substrate with diamond atomic force microscope tip were investigated using molecular dynamic simulation with three independent variables of tip velocity, temperature, and normal load. Based on isolated experimental results, it is determined that graphene friction is velocity, temperature, and normal load dependent. Velocity and normal load increase lead to positive friction correlations while temperature increase leads to negative friction correlations, thus leaving the mechanism to be determined. Combined studies reveal similar results, with each variable maintaining its isolated effect in chorus with the other utilized. Upon obtaining the contact area from these experiments it is evident that velocity and temperature change do not hold direct bearing on the contact area, rather that it is the normal load and size of the sliding surfaces that can fluctuate both contact area and friction in tandem. Hence, the mechanism with respect to velocity and temperature dependence of graphene friction is determined to be variation in interatomic potentials associated with interatomic interactions. Varying the contact area can increase or decrease the quantity of atoms in contact, therefore also having an impact on graphene friction.

Committee: Justin Ye (Advisor); Mark Sidebottom (Committee Member); Andrew Paluch (Committee Member); Timothy Cameron (Committee Member) Subjects: Engineering; Materials Science; Mechanical Engineering

Doctor of Philosophy, University of Akron, 2024, Mechanical Engineering

The rise of electric vehicles (EVs) has led to new engineering challenges for electric motors and new design opportunities for lubricants and tribological elements like bearings and gears. High power density EV motors require dual fluids: a high heat capacity, low viscosity coolant fluid and a highly effective lubricant capable of protecting ultra-high-speed bearings and gears. This dual fluid practice requires two different fluid systems (sumps, pumps, pipes, and filters) adding cost, weight and complexity. Compared to combustion engines, EVs fluids (oils and coolants) do not require similarly extreme high temperature capabilities. Thus, the opportunity exists to consider new fluids (coolants/lubricants) to enhance EV system performance. Towards this end, low viscosity, high heat capacity fluids such as water-based lubricants (WBLs) have gained popularity, as they can cool electric components and lubricate moving parts fulfilling the single fluid approach. However, WBLs have limitations such as low viscosity, evaporation, freezing point, microbiological growth, oxidation, corrosion, and high electrical conductivity. To mitigate these limitations, different additives such as ionic liquids, bio-based oils, and nanoparticles have been incorporated into WBLs. This has resulted in significant improvements in coefficient of friction and wear reduction. Limited literature is available on the rheological and tribological behavior of WBLs in steels, and the wear mechanisms for these lubricants are not fully understood. The proposed work aims to test different WBLs by characterizing their rheological properties and conducting tribological tests such as fretting and sliding experiments. Posttest analyses will be performed via SEM/EDX, XRD, and AFM to characterize the tribofilms and surface morphology. The results will be compared with traditional lubricants to gain a better understanding of the mechanisms and propose adjustments to current modeling tools. The study unders (open full item for complete abstract)

Committee: Christopher DellaCorte (Advisor); Yalin Dong (Committee Member); Nicholas G. Garafolo (Committee Member); Manigandan Kannan (Committee Member); Weinan Xu (Committee Member); Richard L. Einsporn (Committee Member) Subjects: Mechanical Engineering

PhD, University of Cincinnati, 2023, Engineering and Applied Science: Mechanical Engineering

A human's interaction with the outside world begins with the human skin and therefore, contact mechanics of human skin is an important area of research. The applications are all-encompassing, from medical technology in the form of drug delivery mechanisms and prosthetics to the digital world in the form of touchscreens or even personal care. The variations in morphological and physiological features in combination with the properties of counter surfaces make human skin contact a complex problem. There are several aspects of this complex tribological system that need to be addressed. These include characterizing the surface topography of human skin, enhancing the predictability of contact parameters, and understanding the mechanics at the interface of such interactions. In this study, as the first specific aim, a method is developed to characterize the directionality of skin tension lines using statistical methods of characterizing rough surfaces. The method is able to capture the increasing anisotropy of human skin with aging. The method can be applied to the surface coordinates of the skin and the pixel intensity data from skin images. The second specific aim is to predict the coefficient of friction considering the changes in the skin's morphological and physiological features. To achieve this, a fractal-based finite element model in combination with an interfacial condition-enhanced empirical method is used. Results show that the proposed approach can replicate several experimental findings from the literature. Human skin in general is a soft material. Therefore, the recent understanding of contact mechanics of soft materials is applicable to skin. The third specific aim is to understand the contact mechanics at the interface of skin interactions. To this end, we use finite element models to first extend the current single asperity studies to three-dimensional soft materials. Specifically, we investigate the role of surface roughness and mate (open full item for complete abstract)

Committee: Kumar Vemaganti Ph.D. (Committee Chair); Bhargava Sista Ph.D. (Committee Member); Manish Kumar Ph.D. (Committee Member); Woo Kyun Kim Ph.D. (Committee Member) Subjects: Mechanical Engineering

Master of Science, Miami University, 2023, Mechanical Engineering

Unfilled PTFE has a low friction coefficient, but also a high wear rate (K~10-4-10-3 mm3/Nm). Different filler materials can reduce the wear rate of PTFE by ~104 against 304 SS. These ultra-low wear composites form a film between the sliding interfaces which lowers the wear rate. The film observed on the counterbody is known as transfer film. Recently three metal filler (Cr, Ti, Mn) particles were able to achieve ultra-low wear rate against Brass 260 but mixed performance against 304 SS. This discovery motivated to explore other countebodies such as Cu110 and Zn. The test showed high variation in friction coefficient and wear rate among different counterbodies. Hence the transfer film needed to be analyzed to find the relation between these fillers and counterbodies other than 304 SS. PTFE-Cr was chosen for this study as it showed the most variation among the counterbodies (~2× variation in μ and 1000× variation in wear rate). PTFE-Cr showed lowest wear rate against Brass 260 (K~7.1×10-9 mm3/Nm with desired transfer film properties: coverage (Lf~50 μm @ 50 m), thickness (~300 nm), surface energy (~35 mJ/m2), low friction coefficient(μ~0.2). Cu 110, 304 SS, and Zn coated steel showed abrasive wear resulted in high wear rate.

Committee: Mark Sidebottom (Advisor); Zhijiang Ye (Committee Member); Giancarlo Corti (Committee Member); Andrew Sommers (Committee Member) Subjects: Mechanical Engineering

Doctor of Philosophy, University of Toledo, 2022, Engineering

Solid lubricants are materials with a layered crystal structure that provide lubrication in conditions where conventional liquid lubricants are unstable. They are used in extreme environmental and working conditions processes such as high and vacuumed pressure, cryogenic and high temperatures, corrosive and radiative environments, high loads and sliding velocity. Such conditions are mainly encountered in aerospace and marine applications. Some commercially used solid lubricants include 2D materials such as graphite, MoS2, h-BN. However, these materials lack good anti-wear properties and manufacture of lubricating composites where the lubricant is dispersed in a wear resistant matrix is the widely used method for increasing their wear resistance. Heavy metal doping that facilitates grain boundary strengthening and restricts the motion of dislocations across the grain boundary is also employed for improved wear properties. Another challenge of solid lubricants is the narrow operating range. Their lubricating properties drastically deteriorate with changes from specified operating parameters. Adaptive lubrication, where the lubricating mechanism changes with operating parameters is employed to increase the working range of these lubricants. This dissertation work focusses on understanding and improving the tribological properties of sputter deposited ZnO films. ZnO possess some desirable properties compared with existing solid lubricants. It has high-temperature stability, corrosion resistance, and radiation stability. Presently, commercially used solid lubricants are greatly influenced by these environmental parameters. Hence ZnO is a suitable candidate for developing solid lubricants with broad operating range. In this work, the effect of humidity and annealing on the coefficient of friction and wear life are primarily investigated. Pin-on-Disk tribo-test were conducted on sub stoichiometric ZnO films with silver, aluminium and nitrogen doping to understand its eff (open full item for complete abstract)

Committee: Ahalapitiya H. Jayatissa (Committee Chair); Adam Schroeder (Committee Member); Sorin Cioc (Committee Member); Lesley Berhan (Committee Member); Champa A. Jayasuriya (Committee Member) Subjects: Materials Science; Mechanical Engineering; Mechanics

Master of Science, The Ohio State University, 2021, Mechanical Engineering

Gear teeth experience contact conditions that vary continuously as they pass through the meshing zone. Thus, not only the sizes but also the positions of surface defects become critical to their scuffing survivability. High-speed gearbox cost and reliability can be improved by quantifying these features and determining their impact on scuffing performance. Pursuant to this, representative defects in the form of scratches are applied in two batches to the contacting surfaces of high-quality spur gear specimens. These, along with an undamaged baseline gear pair, are then tested through a staged scuffing matrix incrementally increasing the operating load, speed, and lubricant temperature. Metrological procedures developed to quantify scratch parameters and track surface damage are used initially and throughout testing to document evolvement of the surfaces. It is concluded that (i) larger scratches generally decrease scuffing performance, (ii) the location of scratches is critical to scuffing performance; scuffing was never observed in areas where sliding velocities were low, (iii) increased wear and heat generation are observed on defects in high-sliding regions, and (iv) wear and tribo-film formation improve the scuffing performance of scratched gears. In addition, thermal elastohydrodynamic lubrication simulations are performed to confirm that increasing scratch width and surface sliding velocities have the most influence on increasing the lubricant flash temperatures.

Committee: Ahmet Kahraman (Advisor); David Talbot (Committee Member) Subjects: Mechanical Engineering

Master of Science, Miami University, 2021, Mechanical and Manufacturing Engineering

Polytetrafluoroethylene (PTFE) is commonly used as a solid lubricant due to its ultralow friction coefficient (µ=0.04~0.20). However, its high wear rate (K~10-4 mm3/Nm) motivated researchers to study its composites to reduce wear. While many fillers can produce up to 1000 times lower wear, certain α-alumina can lower its wear rate up to 10,000 times. Robust tribofilm generation due to tribochemistry is likely the cause of this ultralow wear behavior. The filler particle porosity along with the filler material is considered behind this enhanced tribofilm generation. This study evaluated the effect on composite wear rate due to the ratio of its filler and countersurface hardness. During this investigation,additional ultralow wear low friction PTFE composites were discovered. This study revealed the friction coefficient of PTFE-Cr against brass 260 countersample to be around half that of ultralow wear PTFE α-alumin's (µ=0.12 vs µ=0.2~0.25) while delivering similar wear properties as PTFE α-alumina. It has also revealed that, within the same fillers, a lower wear rate can be distributed around a certain region of hardness ratio of filler and countersamples.

Committee: Mark Sidebottom Dr. (Advisor); Timothy Cameron Dr. (Committee Member); Zhijiang Ye Dr. (Committee Member) Subjects: Mechanical Engineering

Master of Science, University of Akron, 2020, Mechanical Engineering

Gears and bearings play a critical role as machine elements in automotive and wind turbine applications. High-performance thermoplastics can replace metals for load-bearing applications such as gear teeth due to their exceptional thermal and mechanical properties. However, there is a general lack of micropitting performance data for high-performance thermoplastics. This study attempts to address this by evaluating and comparing the performance of several high-performance thermoplastic families of materials using a micropitting rig. Rolling element bearing components suffer from high Hertzian stresses in service that cause micropitting. The stresses experienced by these mechanical components depends on factors such as loading, the degree of sliding motion, material composition, lubricant chemistry, and lubricant water contamination. Premature failures of automotive and wind turbine gearboxes have been reported, and efforts have been made to prolong the reliable life of these machine elements. A review of literature suggests that a comprehensive study of how lubricant water contamination, lubricant chemistry, and base oil properties affect the micropitting and wear of the widely used 52100 bearing steel has not yet been performed. In addition to evaluating the micropitting performance of high-performance gear thermoplastics, this study also aims to establish an understanding of the micropitting phenomena in bearing steel and how it is influenced by tribological and lubrication conditions. A range of chemically active additives are formulated into mineral and synthetic oils to analyze their relative performance using techniques such as optical profilometry, ICP-MS, and SEM/EDS. The results show that polyamide-imides (PAI) have superior micropitting performance of the thermoplastics considered. This is due to their exceptional dimensional stability and mechanical strength at elevated temperatures. It is also seen that chemically active lubricant additives (open full item for complete abstract)

Committee: Gary L. Doll PhD (Advisor); Manigandan Kannan PhD (Committee Member) Subjects: Materials Science; Mechanical Engineering

Master of Science, Miami University, 2020, Mechanical and Manufacturing Engineering

Titanium alloy is a useful and widely used material, but it is particularly difficult to machine. Conventional flood cooling methods used to remove heat from and reduce friction in the work zone have many disadvantages. Minimum quantity lubrication (MQL) provides a quality alternative, but highly effective lubricants are needed for this method to be successfully used on titanium alloy. The two-dimensional material graphene has been proposed for use in nanolubricants. This study aims to investigate the tribological behaviors of graphene nanofluids and find the optimal concentration/base combination for MQL milling of titanium alloy.

Committee: Zhijiang Ye (Advisor); Mark Sidebottom (Committee Member); Muhammad Jahan (Committee Member) Subjects: Engineering; Mechanical Engineering

Doctor of Philosophy, University of Akron, 2019, Mechanical Engineering

Titanium is used in many applications due to its variety of desirable properties such as high specific strength and excellent corrosion resistance. However, titanium possesses poor tribological properties and many surface treatments either lower the corrosion resistance or experience an “egg-shell” effect. Titanium alloy Ti-6Al-4V was studied in untreated, nitrided, thermally oxidized (TO), supplementary duplex treated (SDT), and complementary duplex treated (CDT) conditions. Characterization, tribological, critical load, corrosion, and tribo-corrosion studies were performed on each surface. Characterization was performed using optical microscopy, x-ray diffraction (XRD), nanoindentation, scanning electron microscopy with energy dispersion spectroscopy (SEM/EDS), x-ray photoelectron spectroscopy (XPS), and transmission electron spectroscopy (TEM). SDT was determined to be a titanium nitride-doped titanium dioxide coating. Tribological testing was performed in dry and lubricated environments. In both environments, Ti-6Al-4V experienced severe wear with a high wear rate. Lubrication was not effective in stabilizing the coefficient of friction and could not prevent the `stick-slip' behavior of Ti-6Al-4V. All of the engineered surfaces tested showed improved tribological properties over untreated Ti-6Al-4V and were compatible with lubricants. The wear seen in Ti-6Al-4V with engineered surfaces was mild and was reduced by one and two orders of magnitude with single stage and duplex treatments, respectively. Nitrided and TO surfaces failed at 4 N and 3 N, respectively. Both duplex treatments were tested at 10 N without failure. Corrosion testing was performed using polarization and electrochemical impedance spectroscopy (EIS) in Ringer's and 3.5% NaCl solutions. TO showed lower corrosion resistance in 3.5% NaCl solution because of defects in the coating allowed the corrosion to penetrate the thick oxide layer. All surfaces showed an increase in impedance in Ringer's (open full item for complete abstract)

Committee: Gary Doll (Committee Chair); Gregory Morscher (Committee Member); Chang Ye (Committee Member); Hongbo Cong (Committee Member); Robert Mallik (Committee Member) Subjects: Chemical Engineering; Materials Science; Mechanical Engineering; Metallurgy

Doctor of Philosophy, Case Western Reserve University, 2019, Macromolecular Science and Engineering

Thermoplastic polyurethanes (TPUs) are among the most versatile engineering polymers. The presence of hard and soft segments on their backbone and specific hydrogen bond interactions between the hard segments, provide TPUs with outstanding engineering properties whilst rendering them as very complex systems to study. Knowledge of morphology – property relationship is essential for TPUs since their thermal and mechanical behavior are directly dictated by their complicated morphology. Having in mind the need to improve TPU applications at high temperatures, TPU was optimized to reach its top performance. Exceeding the neat TPU performance limitations is possible through incorporation of nanofillers and formation of strong 3D networks. Nanocomposites were obtained through in-situ polymerization of TPU and carbon nanofillers with different geometries (carbon nanotubes (CNTs), carbon nanostructures (CNS) and graphene nanoplatelets (GNP)). By investigating nanocomposites with different nanofiller geometries, it became apparent that CNT and CNS are suitable for mechanical reinforcement while GNP is potentially the best candidate for tribological properties. For mechanical reinforcement, the goal is to form a strong percolated nanofiller network at the lowest possible filler content. It was found that addition of 0.3wt% straight CNTs or 0.1wt% of CNS extended TPU application window for more than 20oC and decreased creep strain up to 60 and 40% at 100 and 120oC, respectively. Due to their branched morphology, CNS proved to be more efficient in mechanical reinforcement than CNTs. The design strategy for nanocomposites tailored for tribological properties is not based on GNP percolated networks. Crosslinked polyurethane systems were also investigated. By activating tansesterification and transcarbamoylation dynamic exchange reactions, dynamic crosslinked networks (vitrimers) could undergo reprocessing, reshaping and self healing. Furthermore a microwave assisted (open full item for complete abstract)

Committee: Ica Manas-Zloczower (Advisor); David Schiraldi (Committee Member); Donald Feke (Committee Member); Gary Wnek (Committee Member) Subjects: Engineering; Nanotechnology; Polymer Chemistry; Polymers

Master of Science in Engineering, Youngstown State University, 2018, Department of Mechanical, Industrial and Manufacturing Engineering

Bearing supporting shoes play an important role in manufacturing bearings. A bearing shoe is the part that supports the bearing as its outer surface is machined. The work presented in this thesis was focused on numerical modeling of the process that creates the scars and scuff marks (shining band) created by the contaminants that are carried into the gap between the bearings and the shoes that support them. This phenomenon creates a shining band around the bearing which affects its aesthetics. In addition, additively manufactured carbon fiber filament was studied and examined to replace Tungsten Carbide (commonly called Carbide) as the material used to fabricate the shoes. The experimental part of this research included mechanical testing of the strength and wear rate of the 3D printed material used to create the shoes. The numerical part of this thesis included modeling an improved shoe by inserting a channel for clean fluid flow (water and emulsified oil mix) through the shoe to deflect the particles and prevent them from slipping into the film between the bearing and the shoe. A Computational Fluid Dynamics (CFD) software package (ANSYS FLUENT) was used to track the particles distribution in two and three- dimensional models. The results from CFD confirmed that steel particles can indeed be deflected using the method presented in this thesis.

Committee: Stefan Moldovan PhD (Advisor); Kyosung Choo PhD (Committee Member); Jae Joong Ryu PhD (Committee Member) Subjects: Fluid Dynamics; Materials Science; Mechanical Engineering

MS, University of Cincinnati, 2018, Engineering and Applied Science: Mechanical Engineering

Squeeze-film dampers (SFDs) are used in high-speed turbomachinery to provide viscous damping, reduce vibrations and improve machine stability. However, often the presence of cavitation can significantly hinder the damping capability of the bearing, and also cause damage to the bearing surface. The purpose of this study is to numerically model cavitation in squeeze-film damper bearings, understand the resulting impact of cavitation on damper performance, and conduct a parametric study to determine the effect of varying parameters on the onset and extent of cavitation. A commercial Computational Fluid Dynamics (CFD) solver, ANSYS Fluent 18.2, is used to model lubricant flow in squeeze-film dampers using the moving reference frame formulation that renders this transient problem steady. The mixture multiphase model is used, in conjunction with the Schnerr-Sauer and Singhal et al. cavitation, to simulate vapor and gaseous cavitation, respectively. The numerical solution is verified using the half Sommerfeld solution. The comparison between CFD and analytical results shows a nominal 2.87% difference in the damping forces. Next, the cavitation model is validated using experimental results. Simulations are run for a partially sealed damper with varying amounts of air mixed with the lubricant. Vapor cavitation is modeled for the zero void fraction case using the Schnerr-Sauer cavitation model. Comparisons in the cavitated zone show 4.3% difference between experimental and computational peak pressures. For the gaseous cavitation case, computational peak pressures are compared with the average experimental peak pressures over consecutive whirl cycles. The computational peak-to-peak pressures for gaseous cavitation cases with low to moderate void fractions are in very good agreement with the experimental results. However, the experimental film pressures seem to be non-repetitive and unstable during successive whirl motions in higher void fraction cases. This leads to a high (open full item for complete abstract)

Committee: Urmila Ghia Ph.D. (Committee Chair); Jay Kim Ph.D. (Committee Member); Tod Steen MSME (Committee Member) Subjects: Mechanical Engineering

Master of Science in Engineering, University of Akron, 2017, Chemical Engineering

Motion under load between any two surfaces that are in contact with each other most likely will develop damage. Lubricants are used between two surfaces in contact to reduce the amount of damage which occurs. Within these lubricants, additives are included to further enhance the beneficial properties such as anti-wear. The overall goal of this project is to build reaction mechanisms and achieve activation energies for the surface reactions that take place. The analogs di-tert-octyl polysulfide (DTOPS) was used for the sulfur class, triphenyl phosphate (TPP) was used for the phosphorous class, and zinc dialkyldithiophosphate (ZDDP) was used for the SP class. Additionally, mineral oil (MO) and fully formulated (FF) oil provided additional information within the scope of this research. Temperature programmed desorption (TPD) was used to identify the reaction species as they desorb from the surface. These surfaces were then analyzed by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) analysis, Fourier transfer infrared (FTIR) spectroscopy, and Raman spectroscopy. Tribological tests such as high frequency reciprocating rig (HFRR) testing studied the wear between two surfaces. The HFRR testing was performed with neat additives, which resulted in the sulfur class to perform the worst, the phosphorous class next, and the SP class performed the best. The HFRR data are used to calculate activation energies in the tribological contact based on the time and temperature that the wear regime begins. The TPD data are used to calculate the activation energies in the bulk desorption inside of a vacuum chamber. The activation energies are compared to see how they change from tribological contact to the bulk desorption. Suggested reaction mechanisms that follow the results are presented.

Committee: Gary Doll Dr. (Committee Chair); Paul Shiller Dr. (Committee Member); Edward Evans Dr. (Committee Member) Subjects: Chemical Engineering; Engineering

Doctor of Philosophy, Case Western Reserve University, 2018, EMC - Mechanical Engineering

The Hamrock-Dowson expressions for theoretical minimum and central film thickness of non-conformal contacts in fully flooded elastohydrodynamic lubrication (EHL) predict film collapse in the case of zero entrainment velocity (ZEV); however, past experiments show that films exist and support appreciable loads under this condition. To explore this phenomenon further, as well as the intermediate sliding speeds between pure sliding (ZEV) and pure rolling, a previously established experimental tribometer was resurrected and returned to useful service. Through independent control of two servo motors and a variable pressure loading mechanism, the tribometer is able to generate sliding velocities up to 8.0 m/s, entrainment velocities up to 3.0 m/s, and contact pressures up to 1.5 GPa or 364 N between two spherical test specimens. Using polyalphaolefin (PAO) NYE 182 as the working lubricant, the fluid film generated under these varying conditions was measured by a capacitance method integral to the design of the tribometer. While the lubricant was subjected to zero entrainment speeds, separating films of 0.52 ± 0.22 µm and 0.46 ± 0.15 µm were recorded at contact pressures of 0.5 GPa and 0.6 GPa (13.5 N and 23.3 N), respectively. The experimental results acquired during the present study are used to empirically extend the theoretical film equations to predict film thickness over the entire range of sliding speeds, from pure rolling to pure sliding, including zero entrainment velocity.

Committee: Joseph Prahl Dr (Committee Chair); James T'ien Dr (Committee Member); Paul Barnhart Dr (Committee Member); Kenneth Loparo Dr (Committee Member) Subjects: Aerospace Engineering; Engineering; Fluid Dynamics; Mechanical Engineering

Doctor of Philosophy, University of Akron, 2017, Chemical Engineering

Corrosion is estimated to have cost the global economy over $2.2 trillion in 2010 (~3.5% global GDP); corrosion-resistant coatings are a multibillion-dollar market. None of the current industrial corrosion-resistant coatings provide significant wear resistance for mechanical applications such as, bearing and powertrains. Development of a single coating with high corrosion and wear resistance can fulfill this unmet need. Research in this project tests two primary hypotheses: (1) is it possible to use pulsed reverse current (PRC) electrodeposition processes to develop coatings with corrosion and a tribological performance comparable to industrial baseline standards? ; and (2) is it possible to use the PRC process to develop coatings that promote synergistic benefits with typical extreme pressure and anti-wear lubricant additives that should provide enhanced durability and friction-reduction to oil-lubricated mechanical systems?. Electrodeposited coatings were developed and analyzed using, Scanning Electron Microscope (SEM), Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy (AES), High Frequency Reciprocating Rig (HFRR), Pin on Disk (POD) and 3D Optical Profilometer. The corrosion and tribological performance of developed coatings was compared to the performance of baseline industrial materials such as, uncoated AISI 52100, Tungsten Carbide (WC) doped diamond like carbon (DLC) coatings, ZnNi and chromate coatings. Two types of Ni-W coatings i.e. millisecond and second range were developed via pulse reverse current (PRC) electrodeposition process. Effect of doping TiO2 nanoparticles in the millisecond range Ni-W matrix was also observed. Ni-P coatings were developed using fixed millisecond and second range parameter settings. Results showed that the second and millisecond range deposition processes had distinct effects on the (open full item for complete abstract)

Committee: Gary L. Doll (Advisor); Paul J. Shiller (Committee Member); Hongbo Cong (Committee Member); Rajeev K. Gupta (Committee Member); Gregory N. Morscher (Committee Member); Richard L. Einsporn (Committee Member) Subjects: Chemical Engineering; Materials Science

Master of Science, University of Toledo, 2017, Engineering

Surface coatings are widely used to improve properties of materials. Thin films are deposited based on the properties of the substrate material and applications. Titanium nitride is a hard ceramic material, which has excellent mechanical properties. The superior properties of titanium nitride can be utilized for coating soft materials (such as aluminum). Titanium nitride has various applications in machine tool coatings, fastener coatings and as protective coatings in corrosive environment. However, the friction coefficient of titanium nitride was rather high. To improve the coefficient of friction of the titanium nitride film, a thin layer of molybdenum disulfide was coated that acted as a solid lubricant. Molybdenum disulfide is known for its lubricating properties and it is commonly used to decrease friction. The titanium nitride films were coated by RF magnetron sputtering method and molybdenum disulfide films were coated by vacuum thermal evaporation technique. Aluminum alloy of grade 1100 was used as the substrate material as it is most commonly used material in industrial applications. The effect of film thickness, fabricating technique, operating temperature, substrate heating, post deposition annealing have been studied. The frictional properties and wear were studied using a pin on disc tribometer. The effect of applied normal loads, speed, and interface material were also studied. Zinc oxide thin films were studied for their tribological performance. Zinc oxide was deposited using radio frequency magnetron sputtering and sol-gel method. The substrates were heat treated (annealed) to further investigate the effect of annealing. The effect of film thickness, fabricating technique, operating temperature, substrate heating, post deposition annealing of zinc oxide were studied. The tribological properties were evaluated using a pin on disc tribometer setup. The surface coatings were also tested for Vickers Hardness. The change in coefficient of friction was (open full item for complete abstract)

Committee: Ahalapitiya Jayatissa (Committee Chair); Sorin Cioc (Committee Member); Sarit Bhaduri (Committee Member) Subjects: Engineering; Materials Science; Mechanical Engineering

Doctor of Philosophy, The Ohio State University, 2001, Graduate School

Committee: Not Provided (Other) Subjects: Engineering