Institutional-Repository, University of Moratuwa
Welcome to the University of Moratuwa Digital Repository, which houses postgraduate theses and dissertations, research articles presented at conferences by faculties and departments, university-published journal articles and research publications authored by academic staff. This online repository stores, preserves and distributes the University's scholarly work. This service allows University members to share their research with a larger audience.
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Recent Submissions
item: Thesis-Abstract
Synthesis and characterization of multi-purpose emulsion polymer for paints and coatings using various monomer combinations
(2024) Rathnayaka, IM; Udayakumara , SV
Latex water-borne coatings are becoming increasingly popular due to their safety, environmental responsibility, and user-friendliness over solvent-base coatings. Most water borne coatings consist of acrylic as the binder resin. However, these water-borne coatings have drawbacks and show negative performance when exposed to certain weather conditions. Some of the detrimental effects, like blushing also known as water whitening, softening of the film ultimately lead to shorter lifespan of these water-borne products. Because of these unfavorable performances of the latex in the WB coatings; they have limitations in their use in exterior weather conditions, steel applications, and transparent wood coating applications. Considering all these factors, multi-purpose polymers are the new trend. As coatings and their raw material manufacturing is becoming increasingly competitive in the marketplace, polymers must possess innovative characteristics that set them apart. This research contributes to the advancement of multi-purpose resins those can be used not only in wall coatings but also in WB DTM and WB wood coatings those exhibit water resistance and related qualities, creating a product that is both more profitable and marketable for paint producers and the industry overall. This study explores various polymer compositions, synthesized by the emulsion polymerization process using selected monomers to address those common issues with water-borne acrylic resins and their usability as multi-purpose resins. Polymer samples are synthesized by varying monomers, and other conditions like surfactants, initiators are constant. Properties like particle size, blushing resistance, and rust inducement are examined in polymers. In the second phase, 3 types of coatings are produced and evaluated for their properties.
item: Thesis-Abstract
Numerical simulation of BiSI and BiSeI absorber material for peroveskite based solar cells using scaps 1-D
(2024) Wickramaarachchi, WAAS; Sewvandi, GA
The research is centered on numerically simulating lead-free bismuth Chalcohalide Solar Cells based on thin films of Bismuth Sulfur Iodide (BiSI) and Bismuth Selenium Iodide (BiSeI) through the Solar Cell Capacitance Simulator (SCAPS 1D). The cell architecture comprising with the titanium dioxide (TiO2) for the electron transport layer (ETM) and the Spiro-OMeTAD for the hole transport layer (HTM). Furthermore, we employed Bismuth Sulfur Iodide (BiSI) and Bismuth Selenium Iodide (BiSeI) as the absorbing layers, sandwiched between two electrode materials. Specifically, Fluorine-doped tin dioxide (FTO) served as the front electrode contact, and Gold (Au) was utilized as the back electrode contact.
During the research, the simulations were conducted using the SCAPS simulator to investigate the performances of the cell by varying thickness of the absorbing layer and the operating temperature. This straightforward cell architecture facilitated a comprehensive exploration of device parameters. The maximum power conversion efficiency (PCE) of 16.19% (open-circuit voltage Voc of 1.0066 V, short-circuit current Jsc of 28.255 mA/cm2 , and fill factor FF of 56.37%) is obtained at 1500 nm BiSI layer thickness for an optimized device with TiO2 as the ETL and Spiro- OMeTAD as the HTL for both materials. The maximum power conversion efficiency (PCE) of 22.59 % (open-circuit voltage Voc of 1.1819 V, short-circuit current Jsc of 31.989 mA/cm2, and fill factor FF of 59.15 %) is obtained at 1500 nm BiSI layer thickness for an optimized device with TiO2 as the ETL and Spiro-OMeTAD as the HTL for both materials of Bismuth Sulfur Iodide (BiSI) and Bismuth Selenium Iodide (BiSeI), and the optimized device temperature range was determined to be between 290K and 310K while determining 1500 nm as the optimum thickness of the absorbing layer.
item: Thesis-Abstract
A Cuboid chamber design for radiation-based SARS-COV-2 disinfection
(2024) Yalagama, WNI; Amarasinghe, DAS
Ultraviolet germicidal irradiation (UVGI) has long been recognized as a potent disinfection technology, but its prominence surged during the COVID-19 pandemic as an effective solution for air disinfection. This revival was fueled by its notable advantages over chemical and traditional disinfection methods. UVGI stands out for its residue-free nature and the absence of harmful substances, making it an environmentally friendly option. Additionally, UVGI effectively targets a broad spectrum of pathogens, including the resilient SARS-CoV-2 virus, without fostering microbial resistance. Thus, adequately designed UVGI irradiation systems hold immense promise for indoor air disinfection compared to conventional methods. Numerous studies affirm the effectiveness of UVGI radiation at ʹͷ͵Ǥ݊݉ in neutralizing the SARS-CoV-2 virus when administered at the appropriate dose, dependent on factors such as airflow and UV intensity. Our primary objective was to ensure that every air molecule passing through the disinfection system receives sufficient UV light to deactivate viruses, thereby ensuring system reliability. Design parameters were meticulously chosen based on the UV light photons required to deactivate 99.9% of the SARS-CoV-2 virus, with stringent precautions taken to mitigate UV light leakage, which poses risks to human health.
This study proposes a novel conceptual design of a cuboid chamber utilizing the Line Source Spherical Emission (LSSE) model to analyze irradiance variations based on a chosen coordinate system.
The selection of the 64T5 HO G5 Philips TUV T5 double-ended UV-C (germicidal) lamp was led by considerations of market availability and cost-effectiveness. Through simulations employing the LSSE model with varying point source numbers, we comprehensively examined irradiance variation at ʹͷ͵Ǥ݊݉ , producing informative graphs. The investigation unveiled that with an average airflow velocity of ݏ݉ܿ ʹͲǤʹͲʹ Τ, the proposed chamber geometry ensures that every bit of air passing through receives a UV dose sufficient for effectively deactivating ͻͻǤͻΨ of the SARS-CoV-2 virus. This finding highlights the usefulness of our design in delivering thorough disinfection to safeguard indoor environments.
item: Thesis-Abstract
Extraction and characterization of micro cellulose from Salvinia molesta
(2024) Abeyweera, AR; Samarasekara, AMPB
Salvinia molesta is an aquatic weed that is widely spread all over the world with an incredibly high growth rate. Because of its capacity to quickly cover the entire water body, it has historically provided a significant issue and currently poses a significant challenge. This plant has been managed and eliminated from water bodies using a number of biological, physical, and chemical strategies. Any of these techniques, however, revealed to be a long-term solution because it would be costly and time- consuming to implement. With its many remarkable features and wide range of possible uses, micro cellulose is a young and promising material that has attracted growing scientific interest over the decade.
The objective of this research was to extract cellulose from Salvinia molesta and make micro cellulose fibrils (MCFs) and micro cellulose crystals (MCCs) through the chemical treatments and physical processes. Cellulose isolation necessitated several pretreatment steps, including soxhlet extraction, alkaline treatment, and bleaching. Through the utilization of ultra-sonication, hydrolysis, and freeze-drying techniques, pure microcrystalline cellulose (MCC) and microcrystalline cellulose fibers (MCF) were obtained post-extraction. The raw Salvinia molesta, de-waxed, alkali-treated, bleached, and MCCs and MCFs samples underwent characterization using Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy
item: Thesis-Abstract
Synergistic advancements in sustainable coating technologies : polyurethane microencapsulation of soybean oil for autonomous self-healing and anticorrosive paints
(2025) Rikas, MFM; Udayakumara, SV
The objective of this thesis was to develop and characterize a sustainable, self- healing polyurethane (PU) coating containing microencapsulated soybean oil for improved anti-corrosion performance applicable particularly in automotive topcoats. Soyabean oil microcapsules were synthesized with phases of 100 µm to 7000 µm based on the interfacial polymerization and particle size was confirmed via scanning electron microscopy (SEM). Microencapsulation technique was successfully able to generate spherical microcapsules however the particle size was difficult to control. The largest of the microcapsules exceeded the required final dry film thickness of >250 µm, resulting in an uneven coating appearance. This made it visually unappealing and compromised the need for a smooth finish, which is critical in automotive applications. The self-healing capacity was tested by introducing microcapsules into PU-based paint at the content of 3, 5 and 7% wt of base pigmented PU composite on steel substrate. Optical microscopy assessments of X-shaped scratches at 1 and 7 days revealed that healing efficacy enhanced with higher concentration of microcapsules while excessive dosages caused surface roughness. The self-healing function and the surface properties of the coating were at odds with each other, showing that these properties need to be optimally dosed for high-finish applications. Corrosion resistance was assessed in a Neutral Salt Spray (NSS) test (ISO 9227) for 72, 168 and 240 hours, showing that increasing the dosage of microcapsules resulted in a significant decrease in the formation of rust and improved the corrosion resistance. Cross-hatch cross cut tape adhesion testing demonstrated consistent adhesion performance between all samples regardless of content, showing that incorporation of microcapsules does not appear to negatively impact adhesion. The results from this investigation highlight the utility of microencapsulated soybean oil for sustainable mitigation in PU coatings, which could lead to future self-healing automotive topcoats with potential corrosion protection properties. The results pave way for future efforts to focus on controlling the particle size and optimizing loading, which shall target simultaneous improvements in functional properties as well as aesthetic quality of protective coatings