MESII - 2019

Permanent URI for this collectionhttp://192.248.9.226/handle/123/17182

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Browsing MESII - 2019 by Author "Amarasinghe, DAS"

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    item: Conference-Abstract
    Development of Graphene Oxide based capacitive gas sensor for NO2 detection
    (Department of Materials Science and Engineering, 2019-01) Deemantha, MBA; Gunasena, RGSP; Amarasinghe, DAS; Sivahar, V; Sitinamaluwa, HS
    Parallel plate capacitive gas sensor was assembled using Graphene Oxide (GO) as the transducer material. The sensor was tested with NO2 as the target gas. GO was synthesized according to the Improved Hummer's Method (Tours Method) in which vein graphite was sufficiently oxidized. Synthesized graphene oxide was characterized by Fourier Transform Inirared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA) ascertaining that products were well oxidized. Sensor was tested for capacitance variation in the fi^equency and time domains under the influence of constant temperature ramp. The results showed an average response time of about 2 minutes to reach the steady state signal and an equal time to reach the initial reference signal levels once the testing chamber was evacuated of the target gas.
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    item: Conference-Abstract
    Development of nano silver impregnated food packaging materials
    (Department of Materials Science and Engineering, 2019-01) Samarasekara, AMPB; Amarasinghe, DAS; Madhushan, WKP; Chathuranga, SN; Sivahar, V; Sitinamaluwa, HS
    The growing demand for increased shelf-hfe of food and the need for protection against foodbome diseases, fiiel the development of new food packaging materials. Silver-nanoparticle (AgNp) impregnated packaging materials are promising candidates for active food packaging. These active packaging materials are capable of extending the shelf-life of foods and reducing the risk of pathogens. The current research work is focused on the development of AgNp incorporated coating for polymer-based food packaging. AgNp dispersed in polyvinyl alcohol solution was prepared by in situ reduction method, in which silver nitrate and polyvinyl alcohol (PVA) acted as precursor and capping agent respectively. Presence of silver nanoparticles in the solution was confirmed by photoluminescence spectroscopy and UV-Vis spectroscopy. In order to reduce coating solubility PVA solution was cross-linked. The compatibility of the coating with the substrate was enhanced by plasma treatments. Contact angle measurements were employed to monitor the wettability changes. The solubility of the coating was examined by gravimetric methods. The effects of cross-linked temperature and cross-linked agents on solubility were studied. The presence of silver nanoparticles in the coating was confirmed by surface plasmon resonance and electron micrographs. The modified Kirby-Bauer (disk diffusion) method was employed to measure the anti-bacterial effect of the coating.
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    item: Conference-Abstract
    Extraction of nanocellulose from Sri Lankan agricultural waste
    (Department of Materials Science and Engineering, 2019-01) Wickramasinghe, WAWIC; Lasitha, DS; Samarasekara, AMPB; Amarasinghe, DAS; Sivahar, V; Sitinamaluwa, HS
    Polymers are widely used in domestic and industrial applications because of their diverse functionality, lightweight, low cost and excellent chemical stability. They are mainly classified into naturally occurring or bio-based polymers and synthetic polymers. Bio-based polymers have the potential to replace petroleum-based.synthetic polymers and solve some of the most urgent problems caused by the overuse of petroleum-based polymers, such as environmental pollution especially water and soil pollution and harmful influence to human health. Rice is the major agricultural food and it is cultivated in all parts of Sri Lanka today. Rice straw is the waste product of the rice harvest. Rice straws have a considerable amount of cellulose. Cellulose is the mostly used bio-polymer material for various applications today. Nanocellulose is a light solid substance obtained from agricultural waste which comprises of Nano-sized cellulose fibrils. In this research, rice straw of BG 352 variety was collected from Polgahawela paddy cultivation area in Sri Lanka. Cellulose and nanocellulose materials were extracted from rice straw of BG 352 rice variety. Cellulose was extracted from rice straw using de-waxing, delignification, hemicellulose and silica removal treatments. Extracted cellulose was characterized by Fourier Transform Infrared spectroscopic techniques (FTIR). SEM images indicated that isolated cellulose fibers showed diameters ranging from 2-8|^m. Approximately 21wt. % of cellulose was extracted from the rice straw. Nanocellulose was extracted from cellulose by subjecting to acid hydrolysis, quenching, centrifugation, dialysis, sonication and freeze-drying processes. SEM images showed that extracted nanocellulose materials having 5-70 nm diameters. Therefore, Sri Lankan agricultural waste can be used as a source to synthesis value-added product of nanocellulose
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    item: Conference-Abstract
    Investigation of self discharge mechanism of locally available activated carbon-based super capacitor
    (Department of Materials Science and Engineering, 2019-01) Gunarathna, RNP; Muhandiram, DI; Attygalle, D; Amarasinghe, DAS; Sivahar, V; Sitinamaluwa, HS
    Carbon materials in their various forms are the most used electrode materials in the fabrication of supercapacitors. Activated carbon is derived from a variety of organic parent sources such as lignite, peat, coal, synthetic resins and biomass resources. Sri Lanka holds a global reputation for supplying high quality activated carbon derived from coconut shell with low levels of contaminants, which makes it ideal for incorporating in supercapacitors as the electrode material. The capacitance of supercapacitors, fabricated from activated carbon and an aqueous electrolyte, arises from the charge stored in the electric double layer at the interface between the surface of porous carbon and the electrolyte. Hermann von Helmholtz first proposed the double layer theory for supercapacitors and Gouy, Chapman, Grahame, and Stem later developed it. In electric double layer capacitors, self-discharge has been an inevitable issue which results in the decay of cell voltage and thus loss of stored energy. Further, fast selfdischarge rates restrict practical applications of the supercapacitors. In this research, our major interest was to identify the self-discharge mechanism of the supercapacitor fabricated using locally developed activated carbon in a neutral aqueous electrolyte. The results indicate that self-discharge of the fabricated supercapacitor can be adequately modeled simulating to the diffusion based model.