Master of Science, University of Akron, 2014, Applied Mathematics

The distribution of the components in the dye-sensitized titanium dioxide solar cell (DSC) is investigated in the thesis. The transport and drift of the ions (iodide, triiodide and cathion) in the electrolyte and the electrons in the nanocrystalline titanium dioxide semiconductor were modeled in the operation of the cell. Homogenization is used to reduce the three dimensional solar cell into a one dimensional system along the thickness of the cell. The model includes both the porous semiconductor and the bulk electrolyte layer between the semiconductor and the cathode. The influence of the parameters of the cell on electron concentration profile is investigated. In particular, the influence of the electron lifetime and the thickness of the nanocrytalline semiconductor are investigated. We applied boundary layer techniques in the solution of the resulting system.

Committee: Dmitry Golovaty Dr. (Advisor); Gerald Young Dr. (Committee Member); Curtis Clemens Dr. (Committee Member) Subjects: Alternative Energy; Applied Mathematics; Energy

Master of Science, University of Akron, 2016, Polymer Science

Osteoarthritis (OA) is the most common articular disease and the most prevalent condition resulting in disability among the United States adult population. According to the U.S. Department of Health and Human Services, from 2010-2012, 52.5 million (22.7%) of adults aged > 18 years had self-reported doctor-diagnosed arthritis, and 22.7 million (9.8%) reported arthritis-attributable activity limitation, which indicates not only an ethical, but also economic importance of this disease. OA is characterized by progressive loss of articular cartilage and leads to chronic pain and functional restrictions in the affected joint. Although current treatments are successful in some aspects to provide short-term pain relief and recovered joint mobility, their long term benefits remain elusive and there is still no cure for the disease. The limited capacity for treatment is mainly due to the cartilage`s inability to repair itself. Regenerative medicine using tissue-engineered cartilage has the potential to address this issue, but a remaining challenge is the development of a feasible large scale cell expansion process, since during the expansion in monolayer cultures, chondrocytes undergo the process of dedifferentiation. Several surface-engineering approaches with bioactive factors and surface chemistry have been previously studied to look at increasing the interfacial interaction between the materials and cells. This project aimed to study the effects of various concentrations of surface functional groups on chondrocyte behavior. The cell proliferation and phenotype maintenance within continuously variable one-dimensional concentration gradients were examined. This method included fabrication of functionalized gradients by a vapor deposition technique that provided a fast, efficient, and reliable strategy by incorporating a series of concentrations in single substrates. Finally, human primary chondrocytes density and cellular survival were studied as response of amine and hydro (open full item for complete abstract)

Committee: Matthew Becker Dr. (Advisor); Abraham Joy Dr. (Committee Member) Subjects: Biomedical Research; Polymers

Master of Science, The Ohio State University, 2012, Mechanical Engineering

Solid oxide fuel cells (SOFCs) are electrochemical energy conversion devices capable of producing electrical power with high efficiency and low emissions. SOFCs are characterized by ceramic electrolyte membranes which transport oxide ions in the range of temperatures between 600°C and 1000°C. In order to facilitate efficient, low-range temperature operation the electrolyte is typically made very thin, on the order of 40 µm. SOFCs also employ porous electrodes on either side of the electrolyte which are then placed in contact with current collectors and seals. In the fuel cell environment, with high temperatures, substantial thermal gradients, mechanical loading between layers, as well as the desire to be able to thermally cycle the cell, one of the layers or components must provide mechanical support. It is typical for either the anode or electrolyte to provide the necessary mechanical support. This thesis focuses on an electrolyte that is used for electrolyte-supported SOFC configuration. To address the need for mechanically robust electrolytes, NexTech Materials has developed the FlexCellTM electrolyte. This electrolyte design incorporates 40 µm thick conducting regions in a honeycomb pattern, and surrounding 200 µm thick stability regions. Various experiments on and determinations about this material and design must be made to ensure sufficient mechanical stability during fuel cell operation. Thermal stresses from high temperatures, temporal and spatial temperature gradients, and differential thermal expansion of contacting materials, are critical issues within SOFCs. The critical property related to these issues, coefficient of thermal expansion (CTE), was measured in this work. An apparatus to measure the CTE of the FlexCellTM electrolyte material was designed and implemented. The average CTE of 3 mol% Y2O3-ZrO2 (yttria stabilized zirconia or 3YSZ) was found to increase from 9 µm•m-1•°C-1 between room temperature (RT) and 180°C to nearly 11.5 µm•m-1•°C-1 from R (open full item for complete abstract)

Committee: Dr. Mark E. Walter (Advisor); Dr. Brian D. Harper (Committee Member) Subjects: Materials Science; Mechanical Engineering