Abstract
M.Eng. (Mechanical Engineering Science)
With the recent global interest in developing sustainable energy sources that are not detrimental to human habituation, electricity producers are focused on exploring and improving renewable energy sources to meet this rising need. From the many renewable energy sources on Earth, solar energy is the most prevalent and can be tapped into electricity using photovoltaic panels, an aggregate of solar cells. Photovoltaic panels are designed and installed in the open for the absorption of solar energy. However, this outdoor placement of the solar panels causes dust and other contaminants to clog the surface. This shields the solar cells beneath from direct sun rays and causes their power conversion efficiency to drop. Thus, requiring cleaning maintenance from time to time for their sustainability. Self-cleaning is one of the technologies researchers are considering to help maintain the photovoltaic surfaces clean and reduce the cost associated with other cleaning methods. The idea has given rise to the growth of self-cleaning films and the engineering of suppositious surfaces to function as solar panel overlays to ease the elimination of dust to maintain or augment their energy absorption efficiency and light transmission. Titanium dioxide (TiO2) is among the materials researchers are studying for self-cleaning. The spin coating method offers great promise as a technique for fabricating thin TiO2 films for application as self-cleaning covers for photovoltaic panels. The dissertation synthesized, spin-coated, and characterized TiO2 thin films for self-cleaning applications. This research focused on the experimental synthesis and deposition of Titanium dioxide thin film via a novel sol-gel and spin coating approach. Two process parameters were optimized, viz, solution aging and heat treatment, to establish the best performing set by varying them differently during the synthesis and spin coating of the TiO2 thin film. A novel heat-assisted sol-gel approach was implemented to synthesize Titanium dioxide sol from which TiO2 thin films were spin-coated to examine these parameters. The TiO2 sol was synthesized from Titanium (IV) Isopropoxide. The effectiveness of the heat-assisted sol-gel process was confirmed by drying the synthesized solution in an oven to obtain Titanium dioxide nanoparticles that were further calcined at 600 0C and characterized for application on selfcleaning surfaces. Also, two parameters affecting the self-cleaning ability of Titanium dioxide were adequately investigated with the motive of improving on them for their final thin film performance. Titanium dioxide is a unique and adaptable substance with good physical and chemical properties widely used in engineering. However, how the selfv cleaning ability of TiO2 Sol is affected by aging in thin films has not been well researched and reported. Similarly, its self-cleaning behavior under annealing temperature variations has not been adequately studied and registered in the open literature. This research employed the spin coating technique to produce TiO2 thin films to evaluate its self-cleaning ability from 24, 48, and 72 hours aged Sol. Secondly, TiO2 thin films were created by the same technique to analyze the effect of annealing temperature variations on their self-cleaning ability. The TiO2 sol was made using a heat-assisted sol-gel synthesis method, and the gel was spuncoated on flat glass substrates before being annealed at 400, 600, and 800 ᴼC, respectively. Characterization of the films was done using X-ray diffraction for structure and phase composition, scanning electron microscope for morphology, Fourier transformed infrared spectroscopy for molecular bonding and absorption bands, and UV-vis spectrophotometer for optical properties, followed by wettability, durability, and self-cleaning test. The obtained TiO2 nanoparticles were further characterized for detailed morphology under the transmission electron microscope (TEM) and subjected to a photocatalytic test using methylene blue degradation. The TEM images of the TiO2 nanoparticles analyzed using ImageJ software gave a mean area value of 10.24nm-2. Structural analysis showed the particle size ranged from 6.69 nm to 15.4 nm, with the anatase being the most prominent, well crystallized, and pure phase. The self-cleaning test confirmed the prepared TiO2 nanoparticles to be a strong photodegradation catalyst. The TiO2 sol aging effect investigation found that all fabricated TiO2 thin sheets had snowflake-shaped particles, tightly packed at first but gradually dispersed in a chain-like pattern over the entire substrate as the aging period rose. With increasing sol aging time, the optical bandgap shrank. The study discovered that aging TiO2 sol increased the self-cleaning ability of TiO2 films but that the aging duration should be limited. The survey of annealing temperature variation on TiO2 thin films showed the TiO2 particles having snowflake structures, uniformly distributed but increasingly agglomerated over the substrate surface as annealing temperature increased. The particle size and crystallinity improved with an increase in annealing temperature. The optical bandgap decreased from 3.39 eV to 3.20 eV, indicating that increasing the annealing temperature improved the TiO2 thin films' self-cleaning characteristics. This research will significantly contribute to the corpus of knowledge in self-cleaning technology and TiO2 slim film design for self-cleaning applications. In photovoltaic, it will improve the power conversion efficiency of photovoltaic cells. TiO2 is readily available, the application of this study will help achieve the United Nations' goal of clean, affordable, and sustainable energy. Also, the findings of this study will go a long way to contribute to the broader field of Engineering.