MESII - 2019

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

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Browsing MESII - 2019 by Author "Attygalle, D"

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    item: Conference-Abstract
    Development of a photosensor based on photo dielectric effect of cadmium sulphide
    (Department of Materials Science and Engineering, 2019-01) Kumari, TID; Jayasumana, MASD; Attygalle, D; Sivahar, V; Sitinamaluwa, HS
    A photosensor is an electronic component that detects the presence of visible light, infrared transmission (IR), and/or ultraviolet (UV) energy. A photosensor which changes its electrical capacitance in the presence of visible light was developed based on the photo-dielectric effect of Cadmium Sulphide (CdS). This photosensor was fabricated by depositing a CdS thin film on Fluorine-doped Tin Oxide glass (FTO glass). FTO acts as the front electrical contact and an aluminum sheet acts as the back contact, where a 2.0)im - 3.0)im thick CdS thin film acts as the photo-dielectric material. Chemical bath deposition method was used for CdS fabrication and the CdS thin film with optimum photovoltaic and micro structural properties was obtained at a bath temperature interval of 40 - 45 °C, annealing temperature of 180-220 °C. Film thickness was varied by adjusting deposition time and the number of coatings. Thickness variations were determined using a Scanning Electron Microscope (SEM). The transmittance and absorbance spectra are recorded in the range of 200 nm - 1100 nm. CdS thin film fabricated under optimum conditions resulted in a bandgap in the range of 2.30 eV-2.40 eV, which is closely agreeing to the theoretical value of 2.42eV. The photo-capacitance and photoconductivity were measured in a frequency range of 1 kHz to 5 MHz in dark and illuminated conditions. The Cole-Cole plots were analyzed to identify the most sensitive operational frequency for the device.
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    item: Conference-Abstract
    Development of thermal insulator based on phase change materials
    (Department of Materials Science and Engineering, 2019-01) Jayawardhana, SHP; Umayanga, PKA; Attygalle, D; Sivahar, V; Sitinamaluwa, HS
    Thermal Energy Insulation is very important, especially for energy saving purposes. The use of Phase change material (PCM) for Thermal Energy Insulation (TEI) is technique That is being studied extensively for building temperature regulation Phase change material (PCM) generally used for this purpose have low melting temperature and high latent heat of melting-solidification. Latent heat thermal energy insulates (LHTEI) with phase change materials (PCMs) deserves attention as it provides high energy density and small temperature change interval upon melting/solidifying and provide thermal regulation at particular phase change temperatures. This study aimed to modify thermal insulator based on commercially available paraffin with melting point (Tm) around 60 ? . A series of experimental data were collected irom a representative prototype construction, observing the temperature variation of enclosed system to identify the cutoff temperature. Using paraffin oil and coconut oil modified paraffin under different mass fi^actions of paraffin were studied to find the optimum combination. DSC/TGA and Lee's disc methods used to characterize the modified PCM to select better material for study.
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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.