ME Theses and Dissertations
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Item Role of multifunctional 3D structured conductive nanofibers for flexible and wearable health monitoring systems(Wichita State University, 2024-07) Yeasmin, Farzana; Asmatulu, RamazanThis study aimed to synthesize and manufacture electrically conductive electrospun fibers for wearable health monitoring devices. Wearable health monitoring devices are essential for early and quick detection of diseases. High electrical conductivity is crucial for their performance and fast response. Electrically conductive nanofibers have the potential to enhance the performance of wearable biosensors. In this study, 18 different nanofibers were synthesized by electrospinning. PAN, SPEEK, PVDF, and polystyrene fibers were prepared, and different weight ratios of PEG and PVP inclusions were added with PVDF and PS to make fibers hydrophilic. It was observed that both PVDF and PS fibers showed hydrophilic characteristics after adding hydrophilic polymers into the solution at a certain amount. The measured water contact angle (WCA) for many fibers was 0°. The synthesized fibers were then dip-coated in an electrically conductive PEDOT: PSS solution under different conditions. Ultrasonication and desiccation effects were applied to enhance the impact of the dip coating procedure. It was found that ultrasonication and desiccation effect during the dip coating process has an impact on adsorbing the conductive solution and enhancing the electrical conductivity of the fibers. In this study, PAN fiber showed the highest electrical conductivity of 23.08 S/cm among all fibers. Polystyrene and PVDF-based fibers also showed good electrical conductivity of 17.52 S/cm and 6.72 S/cm, respectively. In this work, four-point probe test, WCA, FTIR, SEM, and EDS tests were performed to study fiber morphology. The conductive fibers prepared in this study have promising applications in wearable health monitoring devices and biosensors applications. This study may open novel opportunities for preparing electrically conductive fibers and their applications.Item PVDF and pan-based piezoelectric nanocomposite fibers integrated on fiber composites for improved vibration energy harvesting rates(Wichita State University, 2024-07) Todmal, Purva; Asmatulu, RamazanThis research explores the development and characterization of electrospun nanofibers integrated with fiber reinforced composites for effective vibration energy harvesting applications. Polyvinylidene fluoride (PVDF) and polyacrylonitrile (PAN) nanocomposite fibers were fabricated using electrospinning with piezoelectric inclusions such as lead zirconate titanate (PZT), barium titanate (BaTiO3), and zinc oxide (ZnO) to enhance their piezoelectric properties. The nanofibers were then integrated into 'open' and 'sandwich' composite configurations using glass, Kevlar, and carbon fiber prepregs. The energy harvesting tests showed that the PVDF+2 wt% BaTiO3 composite with glass prepregs in the open configuration exhibited the highest performance, achieving 22.4 V and 0.00853 W/m². PAN composites peaked at 13.6 V for PAN+2 wt% PZT with carbon prepregs, with a power density of 0.00315 W/m². Among the 'sandwich' composites, PVDF+4 wt% BaTiO3 with glass prepregs achieved 15.8 V and 0.00567 W/m², while PAN+4 wt% PZT with carbon prepregs reached 10.2 V and 0.00324 W/m². The 'sandwich' configuration generally showed lower performance due to reduced exposure of the piezoelectric fibers. Fourier Transform Infrared (FTIR) Spectroscopy confirmed the presence of the β-phase in PVDF, essential for piezoelectric properties, with significant peaks around 840 cm⁻¹, 1070 cm⁻¹, and 1170 cm⁻¹. FTIR also highlighted the structural integrity of PAN fibers, showing prominent nitrile stretching peaks at 2240-2260 cm⁻¹. PVDF nanofibers exhibited diameters ranging from 0.276 μm to 0.721 μm, while PVDF+4 wt% BaTiO3 fibers ranged from 0.377 μm to 2.456 μm, indicating substantial variability due to the inclusion aggregation. The PAN+4 wt% PZT fibers showed more uniform diameters ranging from 0.106 μm to 0.468 μm. This study provides valuable insights into optimizing nanofiber integrated composites for energy harvesting.Item Electrolytic reduction of carbon dioxide to formate/formic acid across various metallic electrodes utilizing high performance liquid chromatography for product analysis(Wichita State University, 2024-07) Egan, Connor; Gu, ShuangElectrolytic reduction of carbon dioxide is a unique reaction which can produce many different major products such as formate (HCOO−) and formic acid (HCOOH). The interactions between CO2 electrolytes and the metallic electrodes lead to formation of various unstable intermediates which cause the reaction mechanism branch into different pathways. Previous literature suggest that bismuth could be the best suited for forming formate/formic acid, however there are many other metals known for the same reaction. The research in this thesis specifically aims to 1) establish effective detection methods for low formate concentrations (at the level of mM) in the highly concentrated electrolyte (2 MKHCO3) by high-performance liquid chromatography (HPLC), and 2) to conduct the comparative study on the metallic wire electrodes in reducing CO2 to formate in a flow cell electrolyzer, based on the established HPLC methods. Two HPLC methods were established with very high coefficient of determination (R2 > 0.99) for two different HPLC columns: reversephase and anion-exchange. The comparative study on metal wire electrodes showed significant formate production from bismuth electrodes, however, other metals such as Sn-Bi alloy, Au, and Ag consistently provided higher formate production rates.Item Design and synthesis of hydrogenated carbon and explore its application in perovskite solar cells(Wichita State University, 2024-07) Syed, Tajamul Hussain; Wei, WeiRenewable energy is defined as the energy which is derived from sources that are self-replenished. Renewable energy sources produce none to very less greenhouse emissions in comparison with fossil fuels. Renewable energy sources consist of solar energy, wind energy, geothermal energy, hydropower, etc. Solar energy is a type of renewable energy which is derived from sun’s radiation, it is clean and sustainable source of energy that can be harnessed using photovoltaic (PV) systems. Perovskite solar cell is one of the latest PV technologies. Perovskite solar cells are one type of thin-film photovoltaic technology which uses organometal halide perovskite materials as the active layer to convert sunlight into electricity. Since its inception in 2009, the power conversion efficiency of PSCs reached 25%. Perovskites solar cells usually use costly noble materials such as gold and platinum as counter electrode. This research is focused on design and synthesis of hydrogenated carbon and use it as a counter electrode on PSCs which can be a cheaper alternative to the currently used costlier noble materials. Reaction and experimental setup were deigned to synthesize hydrogenated carbon, various qualitative analysis was conducted to study it’s the properties. It was also used as a counter electrode on PSCs and performance was tested and compared with the performance of other commercially available carbons. It was concluded that lab synthesized hydrogenated carbon can be used as a counter electrode. The performance of PSCs with hydrogenated carbon as counter electrode was comparable to the results obtained by other researchers in this topic.Item A table of thermodynamic properties of helium gas based on Beattie-Bridgemen equation-of-state(Wichita State University, 1961-06) Glaspie, Donald LeeA table of thermodynamic properties of helium gas was calculated from a virial equation for the range of pressures, 14,696 to 6000 psia, and the range of temperatures - 400 to 2000°F. The virial coefficients with the first and second derivatives were calculated from the Beattie-Bridgeman equation-of-state and are tabulated for the range of temperatures - 440 to 4000°F. The equations used in the calculations were derived in the usual way. These equations were programmed on an IBM-650 digital computer which accomplished the voluminous computations necessary for the table properties.