Doctor of Philosophy (Ph.D.), Bowling Green State University, 2022, Chemistry

Materials Chemistry is an extremely important area of science touching everything from solar energy conversion to medical implants. The work of this dissertation has focused on developing porous materials, especially related to functional and stimuli responsive materials, including photochemical, for a variety of applications such as environmental remediation, soft robotics, and self-healing materials. We aimed to create silicon-based materials to overcome many of the technological barriers including low thermal stability, low selectivity, and poor mechanical properties of the typical materials used in these types of applications. Chapter 1 gives an overview and background of the types of materials that will be investigated in this dissertation. We will first introduce silsesquioxane (RSiO1.5)n chemistry, including synthesis methodologies, synthetic challenges and the properties that give reasons for their use. The research detailed in chapters 2 and 3 of this dissertation set out to contribute a new synthetic method for silicon-based porous materials involving fluoride catalyzed polymerization of R-alkoxysilanes. We aimed to gain a fundamental understanding of the reaction parameters and their impact on structure-property relationships in porous silsesquioxane-based gel materials. In chapter 4, we explored the interaction of fluoride with a silica-based cage called octa(dimethylsiloxy)silsesquioxane (Q8M8H). While it was expected that little interaction would occur with Q8M8H it was found that the outer siloxane units undergo rapid self-polymerization in the presence of a fluoride anion catalyst to form complex 3D porous structural network materials with specific surface areas up to 650 m2g-1. In chapter 5, we demonstrate our approach to photoswitchable silicon-based network polymers using Q8M8H as a cubic building block and azobenzene as a photo-actuatable cross-linker. We found that these photoswitchable silsesquioxane/azobenzene hybrid 3D–polymer gels can be e (open full item for complete abstract)

Committee: Joseph Furgal Ph.D. (Advisor); Gary Oates Ph.D. (Other); Pavel Anzenbacher Ph.D. (Committee Member); Alexis Ostrowski Ph.D. (Committee Member) Subjects: Chemistry; Materials Science; Polymer Chemistry; Polymers

PhD, University of Cincinnati, 2019, Engineering and Applied Science: Environmental Engineering

Porous materials are ubiquitous in nature and widely employed in many products and devices. Examples range from soil, living tissues, filters, and absorbent materials to fuel cells and microfluidic devices, driving the need to better understand the structure and processes in these materials. Their distinct properties, however, present new challenges in experimental and numerical characterization. Computer simulation of single-phase and multi-phase flow (e.g. air-water or oil-water systems) in porous media has been an indispensable tool in better understanding of the multi-phase flow phenomenon in complex porous structures as well as in porous systems design. In order to simulate fluid flow in a porous system, several constitutive relations are required that relate pore scale processes to physics of flow in continuum scale; such as capillary pressure-saturation curve, relative permeability-saturation curve and absolute permeability, to name a few. These relations used to be derived experimentally, but in the last few decades micro-scale (i.e. pore-scale) modeling approaches has gradually replaced the expensive experiments. Despite the success in micro-scale modeling and characterization of traditional low-porosity media (e.g. soil), implementing similar micro-modeling approaches on non-traditional porous structures has faced serious challenges. The objective of this dissertation is to address some of the challenges. Specifically homogeneous materials on the opposite ends of the porosity spectrum, as well as heterogeneous, hierarchical materials with gradient of pore size. In the category of homogeneous materials, I consider highly porous fibrous materials with porosity of above 80% (Chapter 2) and coals with porosity of under 5% (Chapter 3). In the heterogeneous category, I consider block copolymer ultrafiltration membranes with asymmetric hierarchical microstructure (Chapter 4). In Chapter 2, I introduce and develop Pore Topology Method (PTM), which is a micro (open full item for complete abstract)

Committee: Lilit Yeghiazarian-Nistor Ph.D. (Committee Chair); James Comer, Jr Ph.D. (Committee Member); Drew McAvoy Ph.D. (Committee Member); Mohamad Reza Soltanian Pereshkafti (Committee Member) Subjects: Hydrology

PhD, University of Cincinnati, 2018, Engineering and Applied Science: Aerospace Engineering

A generic novel injector was designed for multi-Lean Direct Injection (M-LDI) combustors. One of the drawbacks of the conventional pressure swirl and prefilming type airblast atomizers is the difficulty of obtaining a uniform liquid sheet under all operating conditions. Micro-channels are needed inside the injector for uniformly distributing the fuel. The problem of non-uniformity is magnified in smaller sized injectors. The non-uniform liquid sheet causes local fuel rich/lean zones leading to higher NOx emissions. To overcome these problems, a novel fuel injector was designed to improve the fuel delivery by using a porous stainless-steel material with 30 µm porosity. The porous tube also acted as a prefilming surface. Liquid and gaseous fuels can be injected through the injector. The current study investigates the aerodynamics, spray quality, fuel-air mixing and emission characteristics of the novel injectors at 4% pressure drop and atmospheric conditions. The injectors have two configurations with different counter-rotating radial-radial swirlers. And the injector 1 has a SN of 0.75 and SN of injector 2 is 0.6. The characteristics of the novel injectors are also compared with a typical airblast injector having a peanut nozzle with flow number of 1. A Central Toroidal Recirculation Zone (CTRZ) and Corner Recirculation Zone (CRZ) are observed from the aerodynamics study. Spray measurements are carried out at various equivalence ratio conditions without a confinement. D10, D32 and D0.5 are investigated on Jet-A, GTL and blended fuels. There is no significant influence of fuel types on the spray behavior due to their similar physics properties. The porous injectors generate a fine spray with weighted SMD ~45 µm at equivalence ratio of 0.6. Gaseous Fuel-air mixing studies are carried out at different equivalence ratios with and without a confinement. A fully premixed mixing profile was obtained at 0.43” downstream of the injector exit. Flame characterization (open full item for complete abstract)

Committee: San-Mou Jeng Ph.D. (Committee Chair); Jun Cai Ph.D. (Committee Member); Jongguen Lee Ph.D. (Committee Member); Bassam Mohammad Abdelnabi Ph.D. (Committee Member) Subjects: Aerospace Materials

Doctor of Philosophy, University of Akron, 2018, Polymer Engineering

Temperature responsive membranes are widely used in several controlled transport applications such as drug delivery. The transport rate across such membranes is dependent upon the constraints introduced by the grafted network on the travelling solute molecules inside the porous support membranes. The solute flux is also affected by the non-uniformities in pore size, morphology, and the pore size distribution of the support membranes which arise due to fabrication processes. Conventionally, photo-grafting is widely used `grafting-from' approach to photo-polymerize a temperature responsive monomer inside the pores. This approach is usually slow and often leads to undesirable surface polymerization on the membranes. To overcome these limitations, we developed a novel dual-step approach for the fabrication of temperature responsive membranes using a 248 nm KrF excimer laser. In the first step, membranes with uniform, ordered, and well-defined pores were fabricated with different pore sizes by masked laser ablation of polyethylene terephthalate (PET) films. Ranges of laser fluence (energy/area) and number of pulses were determined for different PET film thicknesses and mesh sizes to obtain pores in the range of 600 nm to 25 µm. In the second step, we used the perforated support membranes to polymerize (N-isopropylyacrylamide) (NIPAM) inside the pores using the same KrF excimer laser. Thus, this study also establishes the versatility of 248 nm KrF excimer laser as a tool for combined laser ablation and polymerization during the same manufacturing process. The `bottom-up' pulsed laser polymerization approach used is extremely fast and it reduces the grafting time considerably from a few minutes to a few seconds. The grafting density of PNIPAM in the pores can be tuned by appropriately selecting the laser parameters resulting in room temperature water permeabilities varying by 6 orders of magnitude. Water permeabilities increased above the lower solution critical tempe (open full item for complete abstract)

Committee: Erol Sancaktar (Advisor); Sadhan C. Jana (Committee Chair); Kevin Cavicchi (Committee Member); Chrys Wesdemiotis (Committee Member); Bi-min Zhang Newby (Committee Member) Subjects: Materials Science; Polymer Chemistry; Polymers

Master of Science in Mechanical Engineering (MSME), Wright State University, 2017, Mechanical Engineering

Three-dimensional (3D) printing, a form of Additive manufacturing (AM), is currently being explored to design materials or structures with required Electro-Mechanical-Physical properties. Microstrip patch antennas with a tunable radio-frequency (RF) response are a great candidate for 3D printing process. Due to the nature of extrusion based layered fabrication; the processed parts are of three-layer construction having inherent heterogeneity that affects structural and functional response. The purpose of this study is to identify the relationship between the anisotropy in dielectric properties of AM fabricated acrylonitrile butadiene styrene (ABS) substrates in the RF domain and resonant frequencies of associated patch antennas and also to identify the response of the antenna before and after a low velocity impact. In this study, ANSYS high frequency structure simulator (HFSS) is utilized to analyze RF response of patch antenna and compared with the experimental work. First, a model with dimensions of 50 mm x 50 mm x 5 mm is designed in Solidworks and three separate sets of samples are fabricated at three different machine preset fill densities using an extrusion based 3D printer LulzBot TAZ 5. The actual solid volume fraction of each set of samples is measured using a 3D X-ray computed tomography microscope. The printed materials appeared to exhibit anisotropy such that the thickness direction dielectric properties are different from the planar properties. The experimental resonant frequency for one fill-density is combined with ANSYS-HFSS simulation results to estimate the bulk dielectric constant of ABS and the equivalent dielectric properties in planar and thickness directions. The bulk dielectric properties are then used in HFSS models for other two fill densities and the simulated results appear to match reasonably well with experimental findings. The similar HFSS modeling scheme was adopted to understand the effect of material heterogeneity on RF response. In (open full item for complete abstract)

Committee: Ahsan Mian Ph.D. (Advisor); Raghavan Srinivasan Ph.D. (Committee Member); Joy Gockel Ph.D. (Committee Member) Subjects: Aerospace Engineering; Automotive Engineering; Design; Electrical Engineering; Mechanical Engineering; Mechanics; Plastics; Technology

PhD, University of Cincinnati, 2001, Engineering : Mechanical Engineering

A new experimental method to identify damping characteristics of dynamic systems and unique analytical techniques to study sound transmission characteristics of various structures were developed in this dissertation work. The damping identification method developed in this work identifies damping characteristics of a dynamic system in matrix forms from measured frequency response functions. A theoretical example was used to validate the method and study the noise effect on the identification results. A unique set of experimental measurements was devised to verify the practicality of the method in real engineering applications. Some potential applications and possible improvements of the method were discussed. While sound transmission characteristics of structures are important basic information in noise control, the related analysis usually becomes a very difficult task because of the complicated interactions between the structures and acoustic media. Solution techniques were developed to study sound transmission characteristics of various cylindrical structures with a single wall, double walls, and double walls lined with porous material for the first time in this study. Generally the system was idealized as an infinitely long circular cylinder subjected to a plane incident wave. The solution technique was extended to solve the sound transmission problems of periodically stiffened panels and cylinders. For all cases, exact solutions were obtained by using the full shell vibration equations coupled with the acoustic wave equations using the mode superposition method. An approximate An technique was proposed to calculate sound transmission through cylindrical walls lined with porous material. Because the porous material has both solid and fluid phases, which makes the related analysis very complicated. The unique approximate method was developed as a two-step analysis allowing relatively easy calculation of the sound transmission in such structures. An analysis metho (open full item for complete abstract)

Committee: Dr. Jay Kim (Advisor) Subjects: Engineering, Mechanical

MS, University of Cincinnati, 2000, Engineering : Materials Science

A novel electroless plating method had been employed to coat a silver film onto the inner surface of porous alumina substrate. While the original substrate was a very good insulator, the coated substrate became highly conductive. One of the possible applications of this coated porous material is to serve as a novel electrical charged filter (ECF). An evenly distributed silver film with a thickness of a few tens of micrometers had been successfully produced by the electroless plating method. Silver growth process was investigated to analyze its kinetics. The change of overall conductivity of the coated substrate with time was studied. An empirical equation was developed to fit the experimental data. Based on the physical model of the coating kinetics, the process was simulated animatedly by computer simulation. The morphology and other properties of the film was investigated by using SEM, XRD and other means. The newly formed film was found to have very weak bonding strength with the substrate. Annealing treatment was adopted to enhance the bonding. Experiments showed that while higher annealing temperature gave rise to higher bonding strength, the conductivity decreased. An optimized annealing condition was determined based on experimental results. The change in conductivity caused by annealing was attributed to the morphology change of the film. Preliminary experiments on water treatment capability of Electrical Charged Filter were also carried out and the results supported the validity of the ECF concept.

Committee: Donglu Shi (Advisor) Subjects:

MS, University of Cincinnati, 2010, Engineering and Applied Science: Materials Science

An approach based on a combination of ultra small angle x-ray scattering (USAXS), ultra small neutron scattering (USANS), and static light scattering (SLS) is proposed to characterize microporous membrane filters. The porosity, pore size (average pore chord), sample density of MCE (a mixture of nitrocellulose and cellulose acetate with nominal pore sizes from 0.025 to 1.2 µm), PVDF (Polyvinylidene fluoride with nominal pore sizes from 0.1 to 1.2 µm), Nylon (pore size 0.1 µm) and Anopore Whatman (top 0.02 µm bottom 0.2 µm) membranes were obtained from the scattering data. The calculated pore sizes were three times larger than the rated pore size given by the manufacturer. The sample densities calculated from the scattering data are consistent with the densities reported elsewhere. Our approach also yields the average size (chord) of the skeletal strut of the membrane. Therefore, scattering techniques in conjunction with the approach elucidated provide detailed structural information on the microporous membranes with pore sizes from 0.025 to 1.2 µm.

Committee: Dale Schaefer PhD (Committee Chair); Rodney Roseman PhD (Committee Member); Donglu Shi PhD (Committee Member) Subjects: Materials Science