Browsing by Author "Attygalle, D"

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item: Conference-Full-text
Atmospheric cold plasma to improve printability of polyethylene terephthalate
(IEEE, 2021-07) Sandanuwan, T; Hendeniya, N; Attygalle, D; Amarasinghe, DAS; Weragoda, SC; Samarasekara, AMPB; ; Hemachandra, K; Adhikariwatte, W; Rathnayake, M
Though paper is still the most common substrate in the printing industry, polymeric substrates are becoming common by the day. Commercially available polymers such as polyethylene terephthalate (PET), polyvinyl chloride (PVC) and polypropylene (PP) surfaces have lower density of polar functional groups. Thus, the adhesion characteristics of these materials are naturally poor. Consequently, producing a quality print on such polymer substrates has become a challenge. Hence, surface modification has become a necessity for such surfaces. This study investigates the technical viability of cold plasma-based surface treatment technologies on polymeric materials. The effect of plasma pre-treatment, on the printability of PET substrates, was studied. The surfaces of these polymer substrates were subjected to different cold plasma treatments, using 80% N2 and 20% O2 as feed gas. The study covers the effect of the plasma dose and the plasma intensity on the printability and the degree of surface modification. The study determined the optimum plasma conditions for quality and durable prints.
item: Conference-Full-text
Atmospheric pressure plasma treatment as a cost-effective and eco-friendly pre-treatment method to enhance seed perfomance in germination and early seedling growth
(IEEE, 2021-07) Hendeniya, N; Sandanuwan, T; Amarasinghe, DAS; Attygalle, D; Weragoda, S; Ranaweera, B; Rathnayake, K; Lalanka, M; Adhikariwatte, W; Rathnayake, M; Hemachandra, K
Novel methods of improving the seed quality have gained a lot of attention recently, cold atmospheric pressure plasma being one of the most promising methods. The effects of cold atmospheric pressure plasma treatment of chili - MI 2 (Capsicum annuum L.) and snake gourd - MI short (Trichosanthes cucumerina) seeds have been compared with a conventional fungicide seed coating and a biological coating treatment. The plasma exposure times used were 4min, 6min and 10min. Cold atmospheric pressure plasma treatment has shown improved effects on seed germination for both Capsicum annuum L. and Trichosanthes cucumerina seeds. Both seed types showed the best germination results under 6 min treatment while displaying the best Seed Vigor Index through 4 min plasma treatment. Compared with the coating treatments, cold atmospheric pressure plasma has shown a significant stimulation in seed germination and early growth.
item: Conference-Abstract
Development of a method to measure contact angles of sessile droplets to analyze and enhance the surface wettability of nichrome
(Department of Materials Science and Engineering, 2020-02) Kumarasiri, AAAP; Amarasinghe, DAS; Attygalle, D; Abeygunawardane, AAGA
Nichrome (Ni/Cr) alloys are used in many industrial applications due to their better electrical properties and commercial availability. It is a known fact that these alloys are having a surface passivation layer of chromium oxide (Cr2O3). This oxide passivation layer changes the surface tension of the metal surface, therefore, decreases the surface wettability during soldering. This phenomenon is critically addressed in electronic applications because the wettability inhabitancy of nichrome thin films tends to reduce the solderability of the metal. The decrease in solderability will lead to many difficulties such as poor connecting strength of wires and fluctuations of resistance. In this study, two approaches were introduced to enhance the wettability of nichrome alloy surface. In the first approach a liquid salt solution was used in an acidic environment (ZnCl2/HCl) to remove the oxide passivation layer, thereby, to enhance the wettability of the nichrome alloy. Lead-free industrial solder alloy, SN100C (Sn / Cu 0.70% / Ni 0.06% / Ge 0.005%.) was used as the soldering material for this experiment. Solder drops were formed on the Nichrome thin film (With and without treatment of (ZnCl2/HCl) in 325-350°C temperature range. The second approach was an electroplating process to form a thin nickel coat (3 μm) on the nichrome surface. A two-step plating process was carried out. Various plating conditions such as pH- condition, thickness and current density were controlled of the watts bath to obtain the best wettability and adhesion. An experimental setup together with an image processing software was developed to process the image of the solder droplet and measure the contact angles of the nichrome-solder alloy interface. The contact angle measurements were based on the sessile droplet method. The polynomial and ellipse fitting methods were used to digitize the drop shape.The results of the study show that the contact angles of solder droplets were reduced by more than 50 percent after the ZnCl2/HCl treatment. Contact angles can be reduced by more than 60 percent by nickel electroplating. Therefore, the solderability of the nichrome alloy is significantly enhanced by both treatments.
item: Conference-Abstract
Development of a methodology to identify repairable photoreceptor drums
(Department of Materials Science and Engineering, 2020-02) Sampath, WGC; Senarath, GN; Attygalle, D; Abeygunawardane, AAGA
Toner cartridges are discarded due to the degradation of the organic photoconductor while the other parts of the cartridge are in usable condition. This research is focused on developing a method to identify repairable drums. Since the condition of the used drum is unknown, identifying the primary cause for the quality deterioration of xerographic prints is of great importance in repairing these drums.The print quality deterioration can happen due to deterioration of charge transport layer alone,degradation of charge generation layer alone, or occurance of both simultaneously.The damaged charge transport layer could lead to a higher residual potential due to trapped charges in the charge transport layer, and that finally affect the print quality. A locally fabricated setup was used to obtain dark decay curves and photoinduced discharge curves. These curves were then used to identify repairable drums successfully. Furthermore, the wear-out thickness of the charge transport layer was also estimated using the same data. This information was then used to develop a repair methodology for the damaged drums.
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.
item: Conference-Abstract
Development of a photosensor based on photo dielectric effect of cadmium sulphide
Kumari, TID; Jayasumana, MASD; Attygalle, D
A photosensor is an electronic component that detects the presence of visible light, infrared radiation, and/ or ultraviolet radiation. 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). A thin layer of CdS was deposited on Fluorine-doped Tin Oxide glass using chemical bath deposition technique. The optimum photo-dielectric behaviour was observed for chemical bath temperature between 40-45 ºC. After annealing the deposited film at 180-200 ºC, they have shown a band gap in the range of 2.30– 2.40 eV. Photo-capacitance and photoconductivity in dark and visible light illumination showed a significant change, indicating these films are suitable for photo sensing applications.
item: Conference-Abstract
Development of a piezoresistive pressure sensor using laser scribed graphene
(Department of Materials Science and Engineering, 2020-02) Prabhath, AAN; Perakotuwa, HPTS; Attygalle, D; Abeygunawardane, AAGA
Pressure sensors are often used in applications in the areas of direct pressure sensing in weather instrumentation, aircrafts, automobiles, machinery and Altitude sensing in aircraft, rockets, satellites. Development of piezo resistive commercial pressure sensors is currently restricted to Silicon, Polysilicon thin film, bonded metal foil and sputtered thin film. Properties of graphene shows the potential to develop more accurate and cheaper piezo resistive pressure sensors. This research is focused on the development of such a graphene based pressure sensor for commercial applications. Major steps towards the success of the research was to reduce graphene oxide to graphene from laser scribing method so that chemical reduction steps are omitted and then to design and fabricate a functional pressure sensor. In this research, graphene oxide was synthesized by modified hummers method. The prepared graphene oxide was characterized using FT-IR spectroscopy, XRD, TGA analysis and SEM. The sensors were fabricated using laser reduction of graphene oxide films that were coated on PET (polyethylene terephthalate) substrates. Sensor calibration was done and optimizing steps were taken for better functionality of the sensor. Uniform films of graphene oxide were prepared by drop casting method. Laser reduced graphene oxide has shown an electrical conductivity comparable to chemically reduced graphene oxide. Functionality of the sensor was analyzed after calibration and significant resistance change with applied pressure was observed. Response time of the sensor was coupled with the design of the apparatus used. Laser reduced graphene has shown the potential to design simple, low cost pressure/strain sensors.
item: Conference-Abstract
Development of a theoretical model to predict filtration efficiency of electret based masks
(Department of Materials Science and Engineering, University of Moratuwa., 2022-11) Wimalasinghe, BP; Siriwardhana, BM; Attygalle, D; Abeygunawardana, AAGA
In this study, a 2-Dimensional computational model to predict the filtration efficiency of the electret layer of N95 facemask was developed. The fiber packing density, fiber diameter and fiber layer thickness were included as the parameters defining the fiber structure for the model. Random 2-Dimensional fiber structure were designed using MATLAB and AUTOCAD software while COMSOL Multiphysics was used to simulate filtration mechanisms. The developed model was used to study the filtration mechanisms behavior with various surface charge densities and fiber packing densities. Also, the effect of sticking probabilities with the electrostatic and mechanical filtration were observed.
item: Conference-Abstract
development of CZTS based solar cell
(Society of Materials Engineering Students, Department of Materials Science and Engineering, University of Moratuwa, 2017-03) Dilshan, HADI; Weerasinghe, WDD; Attygalle, D; Sivahar, V
The two semiconductor layers Cu2ZnSnS4 (CZTS) and CdS were successfully fabricated using economical, solution-based fabrication techniques. CZTS thin film fabrication was done by spin coating technique onto soda-lime glass substrates at rotating speed of 2000 to 6000 rpm. It was found that the optimum precursor solution temperature is 38 o C-42 o C. The films dried at 140 o C-160 o C and annealed in air at 280 o C have shown a band gap in the range of 1.45 to 1.55eV. Cadmium Sulfide (CdS), the n-type semiconductor heterojunction partner for CZTS was also deposited with good thickness control and uniformity in the range of 50-100nm range. Chemical bath deposition method was utilized for CdS thin film fabrication and the CdS thin film with optimum properties was obtained at the conditions of 40 o C-45 o C temperature range and thickness variations were also apparent with the number of coatings applied and the fabrication time. The annealing temperature was found to be critical within the range of 180 o C-220 o C (30 mins) for the optimization of CdS bandgap. CdS thin film fabricated under optimum conditions has shown a bandgap range of 2.30eV-2.50eV. Successful deposition on Fluorine doped Tin Oxide (FTO) glass substrate, reveals a feasible route to fabricate superstrate type photovoltaic cell.
item: Conference-Abstract
Development of engine oil quality analyzer based on optical metrological techniques
(Department of Materials Science and Engineering, University of Moratuwa., 2023-07-28) Ishan, RLP; Heshan, MPN; Attygalle, D; Sivahar, V
With an annual global consumption of 36.3 million tons of engine oil and concerns about premature disposal, we propose an optical metrological approach to accurately assess engine oil quality. A side polished optical fiber in touch with oil, photo diode and a photo detector were used to build the sensor unit. To avoid damage to the core, cladding removal was performed meticulously, while minimizing wire bending reduced optical power loss. Utilizing a side-polished optical fiber, the refractive index changes in engine oil were measured, allowing real-time assessment. This method offers non-destructive, precise, and straightforward measurements. Theoretical validation was done by utilizing Fresnel's equations. Further a correlation between theoretical values and refractive indices of oils with mileage was established. For the oil type 10W-30, which is used as the engine oil for petrol engines, a change of refractive index of 1.4651 to 1.4689 was observed over a milage of 3140 km. the detector voltage ratio for that range was 0.5928 to 0.6748, which is well within the range the sensor can detect. Similarly, an experiment conducted for oil type 15W-40, which is an engine oil used in diesel engine showed a refractive index variation of 1.5966 to1.6015 over a milage of 3721 km, which corresponds to a change of sensor voltage ratio 0.5427 to 0.4571 was obtained. Both experimental data and theoretical predictions confirmed that the sensor is effective and sensitive to subtle change in oil quality. This research successfully developed optical metrology, offering potential for online oil quality monitors, and addressing environmental concerns linked to premature oil disposal.
item: Conference-Abstract
Development of graphene oxide based capacitive gas sensor for selective detection of NO2
Gunasena, RGSP; Deemantha, MBA; Amarasinghe, DAS; Attygalle, D
NO2 gas is a harmful vapor that, when present in large quantities, can impose severe threats on health and environment. Gas sensors for NO2 have been in development over the past few decades albeit selectivity towards the gas still remains somewhat unperfected. A method was suggested to improve selectivity towards NO2 by registering a unique and recurring feature of the signal behavior as the selection criterion i.e. gradient of sensor response. A parallel plate capacitive gas sensor was fabricated taking graphene oxide as the dielectric medium and was tested for NO2. Graphene oxide was synthesized adhering to the Improved Hummer’s Method (Tours Method) which produced sufficiently oxidized graphene with a yield of 193% with respect to the starting material. Synthesized graphene oxide was characterized by Fourier Transform Infrared Spectroscopy (FTIR), Thermo Gravimetric Analysis (TGA) and X-ray Diffractometry (XRD) techniques ascertaining that the products were well oxidized with acceptable d-spacing values. Sensor assembly was tested for capacitance variation in the frequency domain, time domain and under the influence of constant temperature ramp. The results showed an average response time of about 1 minute to reach the steady state signal and an equal time to go back to the initial reference signal level once the target gas was evacuated. Keywords— graphene oxide, capacitive sensor, selective sensing, FTIR
item: Conference-Abstract
Development of heterojunction CZTS based solar cell using solution based deposition methods
(2017) Dilshan, HADI; Weerasinghe, WDD; Attygalle, D
The superstrate configuration of heterojunction thinfilm solar cell deposition was investigated using low cost solution based techniques. Commercially available SnO2:F coated glass was used as the front contact and superstarte, Cadmium Sulfide (CdS) as the n-type semiconductor and Copper Zinc Tin Sulfide (CZTS) as the p-type absorber layer. Chemical bath deposition method was utilized for CdS thin film fabrication and the CdS thin film with optimum properties was obtained at the conditions of 40oC-45oC temperature range and thickness variations were also apparent with the number of coatings applied and the change of fabrication time. The annealing temperature was found to be critical within the range of 180oC-220oC for the optimization of CdS bandgap, and grain growth and grain refining effects were apparent at higher temperatures. CdS thin films fabricated under optimum conditions have given a bandgap range of 2.30eV-2.50eV. CZTS layer fabrication was done using spin coating method and optimum conditions for CZTS layer fabrication was found to be 2000rpm-6000rpm spinning speed with 30 seconds of spin time, 38oC-42oC precursor solution temperature, 140oC-160oC drying temperature, and 280oC annealing temperature that promotes the formation of CZTS. The obtained CZTS layers have shown a bandgap in the range of 1.45eV to 1.55eV.
item: Conference-Abstract
Development of metal oxide based solid state gas sensor platform
(Society of Materials Engineering Students, Department of Materials Science and Engineering, University of Moratuwa, 2017-03) Udaraka, MPSD; Nanayakkara, HATV; Attygalle, D; Amarasinghe, DAS; Sivahar, V
Gas sensors are chemical sensors which have a transducer and an active layer for converting the chemical information into another form of electronic signal. Gas detection and determining the composition of a gas in a mixture is necessary in many different fields. In this research, development of metal oxide based sensing material layer and design of sensor platform were on focus. SnO2 was selected as the main precursor of the sensing material and Mn as the dopant. Material deposition was done by spin coating method on soda lime glass substrate. The complete platform consists of sensor material, heating element, temperature monitoring and control unit, Arduino board for data acquisition and signal processing. The temperature dependence of resistivity of SnO2 film was studied in detail in the presence of different gases and gas mixtures. The results shows that the Mn doped spin coated SnO2 thin film is a promising method for the preparation of high quality ethanol sensor even in a mixture of ethanol and acetone. Optimum sensitivity for ethanol was obtained at 140 0 C - 160 0 C temperature range.
item: Conference-Abstract
Development of spark emission spectrometer to identify an alloy
(Society of Materials Engineering Students, Department of Materials Science and Engineering, University of Moratuwa, 2017-03) Gunerathne, MGGM; Karunasena, DBTK; Attygalle, D; Amarasinghe, DAS; Sivahar, V
Spark optical emission spectrometer (OES) is a widely used technique in identifying alloy compositions of metals. Based on the OES principle, a low-cost spark, portable and fully automated spark optical emission spectrometer was developed. A 1000kV ultra-high voltage arc generator coil module was used as the excitation source and a CMOS (complementary metal-oxide semiconductor) image sensor was used as the spectral detector in this spark OES. Data collection and interfacing was done through a Raspberry Pi Single-board Computer. Analysis of wavelength and intensity data were performed using an algorithm coded in python programming language. The program presents the alloy elements and their quantities. Three main factors that limits the precision and accuracy of results were identified as the excitation source, the resolving powers of the spectrometer and the electronic noise characteristics of the systems.
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.
item: Conference-Full-text
Direct current resistivity based in-situ cure monitoring technique for amine cured epoxy resins
(IEEE, 2022-07) Herath, HS; Janith, GI; Weragoda, VSC; Amarasinghe, DAS; Attygalle, D; Samarasekara, AMPB; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
The Epoxy resins and epoxy resins-based system usage in industrial applications such as composites and electronic materials keep growing. Thus, research focused on enhancing the properties of these resin-based systems is of importance for manufacturing quality controls. Especially monitoring of cure progression and chemo-rheological behavior of epoxy resins are essential for many industries. Commonly practiced cure monitoring methods such as DSC and DMA for the purpose are conducted in laboratories under specified conditions and are not practiced for real-time cure monitoring. However, in-situ cure monitoring techniques are essential for many industries as they provide more insight and thus more control over processing parameters. This study introduces a direct current resistivity-based cure monitoring method as it is simple, cost-effective, reliable, and more importantly, industry-friendly. The fast response of direct current measurements combined with the simplicity of the analysis makes this method suitable for real-time sensing applications. The strong correlation between the degree of cure and the viscosity allows us to take simultaneous measurements of both. The method's feasibility was analyzed using two amine cured epoxy resin systems.
item: Conference-Full-text
The effect of surface topology on the edl capacitance: 1_d case
(IEEE, 2022-07) Amarathunga, AAS; Malshan, LPJ; Amarasinghe, DAS; Attygalle, D; Rathnayake, M; Adhikariwatte, V; Hemachandra, K
An electrical capacitor is an energy storage device that generates an electric field between electrodes and produces potential that can be channeled through associated circuits. The Electrical Double Layer (EDL) capacitor is a unique capacitor with a remarkably higher capacity. The energy densities of these capacitors can range between 0.5 and 10 Wh/kg. This study develops a method to predict the dependence of the double-layer capacitance on the roughness profile of the electrode using the linear Poisson-Boltzmann theory, and the Gouy-Chapman theory for 1-D systems. The roughness dependence of diffuse layer differential capacitance is obtained for a defined roughness profile. The theory developed here helps to understand the Debye-length dependent on the roughness factor and profile. The variation of double-layer capacitance with roughness is analyzed based on a numerical solution obtained for the model roughness profile.
item: Conference-Full-text
Effects of current density on the solder wettability of nickel electrodeposited ni20cr alloy
(IEEE, 2021-07) Kumarasiri, A; Herath, HS; Amarasinghe, DAS; Attygalle, D; Adhikariwatte, W; Rathnayake, M; Hemachandra, K
Nickel-chromium alloys are in high demand in the electrical industry, as they have some favorable electrical properties. The formation of a thin chromium oxide layer on the alloy surface protects the alloy from further oxidation. The passivation layer formation is almost instantaneous when exposed to the ambient atmosphere. It prevents the strong bonding between the solder and the substrate due to the alteration of the substrate's surface energy by the passivation layer. Poor solderability could cause short-circuiting and resistance variations in electrical devices. This paper reviews the effect on solderability due to the passive layer formation and proposes solutions to overcome the problems caused by this layer. The introduction of solder-compatible metal layers such as Ni onto the substrate surface is a way to overcome this. However, solder-compatible metals such as Ni cannot be introduced with conventional electroplating baths due to the alloy's passive behavior. Therefore, a breakdown of the passivity is required before the nickel coating. A three-bath electrodeposition strategy comprising; pre-cleaning, activation, and electroplating, were used to achieve the task. The study examines the dependency of solder wettability on the current density, using an in-house fabricated contact-angle measuring device and analytical software.
item: Conference-Abstract
Fabrication and characterization of cu2znsns4 thin films by spin coating
(Engineering Research Unit, Faculty of Engiennring, University of Moratuwa, 2016-04) Wijewantha, NLW; Wijesinghe, DPS; Attygalle, D; Jayasekara, AGBP; Amarasinghe, YWR
This study reports the fabrication and characterization of Cu2ZnSnS4 (CZTS) thin films which is inexpensive and environmental friendly photovoltaic (PV) material using solution based method. The CZTS thin films were coated on soda lime glass substrates using spray pyrolysis and spin coating methods. The thickness variation, electrical properties and optical properties of the films were determined for different numbers of coatings. The optical band gap energy of the prepared films was within the range of 1.5eV to 2.07eV. A set of prepared CZTS films on glass substrates were subjected to an annealing process in a normal atmospheric environment to obtain better crystalline properties [2]
item: Conference-Full-text
Feasibility assessment of obtaining kinetic parameters for independent simultaneous first- order reactions using friedman isoconversion analysis
(IEEE, 2023-12-09) Panawala, PSS; Kanchana, PK; Amarasinghe, DAS; Attygalle, D; Samarasekara, AMPB; Weragoda, VSC; Abeysooriya, R; Adikariwattage, V; Hemachandra, K
This research investigates the effect of two independent first-order reactions occurring concurrently within a given temperature range. A theoretical simulation-based approach was employed to analyze the influence of these concurrent reactions on the kinetic parameters obtained using the Friedman isoconversion method. A novel technique for separating the kinetic parameters of two reactions is also discussed here. The results demonstrate that, in most cases, the disparity between the actual activation energies of the two reactions and the values obtained through the Friedman isoconversion method is minimal, with an error of less than 1%. However, when the two first-order reactions exhibit DTG peaks within the same temperature range, the error can escalate to as high as 15%. This investigation provides valuable insights into the errors associated with kinetic parameter estimations on multiple simultaneous reactions. The findings contribute to a more indepth understanding of reaction kinetics and offer important substances for experimental design and reaction optimization in various fields.