MERCon - 2019

Permanent URI for this collectionhttp://192.248.9.226/handle/123/14700

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Now showing 1 - 9 of 9

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
Extraction and characterization of Nano Crystalline Cellulose (NCC) From Sri Lankan agricultural waste
Wickramasinghe, WAWIC; Lasitha, DS; Samarasekara, AMPB; Amarasinghe, DAS; Karunanayake, L
In this research synthesis and characterization of cellulose and nano cellulose and process run under several conditions to obtain parameters which are belongs to optimizing. Cellulose was extracted from BG 352 rice straw using de-waxing, delignification, hemicellulose and silica removal treatment. Extracted cellulose was characterized by Fourier transform infrared spectroscopic techniques (FTIR). SEM image showed that isolated cellulose fibers with diameter ranging from 2-8μm and yield of extracted cellulose are around 21%. Nanocellulose is the material at least one dimension in the nano meter range. The cellulose contains some amorphous regions as well as crystalline regions and by treating some strong acid such as sulfuric to broken up the cellulose from amorphous region. The resultant product is nanocellulose. Nano crystalline cellulose can be obtained from plant matter which comprises nano sized cellulose material. Nano crystalline cellulose synthesis was followed using cellulose by acid hydrolysis, quenching, centrifugation, dialysis, sonication, freeze drying process in this research. So locally available rice straw is a source to synthesize the nano crystalline cellulose.
item: Conference-Abstract
Fabrication and characterization of Polypropylene - microcrystalline cellulose based composites with enhanced compatibility
Rathnayake, WSM; Karunanayake, L; Samarasekara, AMPB; Amarasinghe, DAS
There is a heighten interest on natural fiber reinforced polymer composites to achieve superior, mechanical properties. However, such composites are limited due to the poor compatibility between natural-fiber reinforcement and polymer matrices. An enhanced fiber-polymer interface compatibility was achieved for microcrystalline Cellulose (MCC) and hydrophobic polymer, polypropylene (PP) system using sunflower oil biodiesel (SFEE) based surface treatments. Surface treated MCC was characterized based on their morphology, crystallinity, chemical structure and wettability. The influence of compositional variations of surface modified MCC on composite properties was also studied.
item: Conference-Abstract
Improvement of toner printing on polyethylene terephthalate based transparency sheets using atmospheric plasma
Sandanuwan, GAT; Somaweera, GD; Attygalle, D; Amarasinghe, DAS; Weragoda, VSC
The application of atmospheric plasma to improve printability on transparency sheets is presented in this paper. Printing on polymer substrates like Polyethylene, polyethylene terephthalate (PET), Poly propylene have become a challenge as the adhesion of ink, dyes or toner onto these surfaces are poor as they have low polar functional group densities on the surface. PET based transparency sheets were plasma treated using atmospheric plasma. The degree of surface modification was investigated by using contact angle measurements of water on the surface. The effect of plasma treatment on the printing quality was measured by image analysis techniques and tape tests. It was observed that there was a significant improvement in toner fixing after plasma treatments.
item: Conference-Abstract
Influence of surface modification of cellulose nanofibers (CNF) as the reinforcement of polypropylene based composite
Kahavita, KDHN; Samarasekara, AMPB; Amarasinghe, DAS; Karunanayake, L
Abstract—Improvement of the demand for materials with improved properties leads to acquiring the advancement of composite materials. Reinforcement of cellulose nanofibers with synthetic polymer materials is an interesting area in the polymerbased researches to enhance mechanical properties as well as to deplete environmental pollution. Polypropylene is one of the frequently used thermoplastic matrix materials in engineering composite applications. In nature, cellulose nanofiber is hydrophilic and polypropylene is hydrophobic. Therefore, surface modification of cellulose nanofibers is necessary to prepare a nanocomposite with better performance. In the present research discuss mechanical, water absorption, processability properties and morphological studies of polypropylene with up to 5 wt. % loading of unmodified and silane surface modified cellulose nanofiber reinforced composites. The results determined that there is a wide improvement of the mechanical properties of silylated cellulose nanofibers reinforced composite series than that of unmodified cellulose nanofiber reinforced series. Among that the best mechanical properties were given by the 3.5% silane surface modified cellulose nanofibers loaded polypropylene composite such as the hardness, tensile strength, and impact strength values higher than that of untreated cellulose nanofibers reinforced composite materials and pure polypropylene. The prepared nanocomposite material can be used for many engineering applications.
item: Conference-Abstract
Investigation on self-discharge mechanism of neutral aqueous electrolyte based electric double layer supercapacitor
Gunarathna, RNP; Muhandiram, DI; Attygalle, D; Amarasinghe, DAS
Supercapacitors are capable of holding electrical charges that are much larger than conventional dielectric capacitors. A supercapacitor was constructed using active carbon electrodes, deposited on metal current collectors and they were separated by a non-conducting membranes soaked in an electrolyte. An electrical double layer is developed at the interface between active carbon and the electrolyte. The electrical properties of constructed capacitors were investigated to identify the drawbacks of these systems. Self-discharge has been an inescapable issue of electrical double layer type super capacitors and it reduces cell voltage of the capacitor. The data collected from fabricated supercapacitor was used to model the self-discharge behaviour with the aim of understanding the discharge mechanism of these capacitors. It was found that in addition to ohmic leakage mechanism, there is another dominant mechanism.
item: Conference-Abstract
Lead free solder compatibility improvement on nichrome alloy through contact angle modification
Kumarasiri, A; Attygalle, D; Amarasinghe, DAS
Nichrome (Ni/Cr) alloys which are used in many industrial applications are known to have a surface passivation layer of chromium oxide (𝐂𝐫𝟐𝐎𝟑 ). This layer alters the surface tension and thereby decreases the surface wettability in the case of soldering. This phenomenon is critically addressing in electronic applications such as electronic industry because, if the wettability inhabitance of nichrome thin films tends to reduce the solderability. In this study, liquid salt solution used in an acidic environment (ZnCl2/HCl) to remove the oxide layer and enhance the wettability. Lead free industrial solder alloy SN100C (Sn / Cu 0.70% / Ni 0.06% / Ge 0.005%.) was used as soldering material for this experiment. Solder drops were formed in 325-350°C temperature range, on the ZnCl2/HCl treated nichrome thin films. In order to evaluate the wettability changes, an experimental setup was developed to measure the contact angles of solder droplets on the nichrome thin films. A computer software was developed to process the image and letting the user to measure the contact angles by polynomial and ellipse fitting methods. The results of the study revealed that contact angle values were reduced by more than 50% after the ZnCl2/HCl treatment. Limitations of this study were stated and future improvements to enhance the wettability on nichrome thin films were suggested.
item: Conference-Abstract
Microstructural rearrangements of 4,4′- methelenebis(phenyl isocyanate) (MDI) based polyurethanes in the presence of UV radiation
Amarasinghe, DAS; Senevirathna, MASR; Karunanayake, L
MDI based polyurethanes have vast variety of applications. Its applications will be broaden with an understanding of the microstructural changes in the polymer matrix due to UV exposure. In this study the fluorescence analysis has been used to uncover the microstructural changes of polymer matrix in a UV environment. When this polymer is exposed to UV radiation hard segments crystallize and the process is assisted localized melting. When the UV exposure was ceased molecules re-arrange back to their initial structure due to the tensile forces originating from softsegment crystallization. However, tensile forces are not strong enough for a complete recovery of the micro structure. Residual solvent molecules can also disturb the recovery.
item: Conference-Abstract
Structural analysis of cellulose fibers and rice straw ash derived from Sri Lankan rice straw
Ratnakumar, A; Samarasekara, AMPB; Amarasinghe, DAS; Karunanayake, L
Being an agricultural country, Sri Lanka generates over eight million metric tonnes of rice straw per annum as a byproduct of the paddy cultivation. Currently rice straw is burnt or ploughed into the field without being converted into a productive output. One such output can be isolating the cellulose fibers from this under-utilized waste material. The availability of rice straw is highly seasonal. In this study, cellulose fibers were extracted from rice straw via a three step chemical purification method straw which yeielded 33.4 ± 0.52 percent. The structure, chemical composition, morphology and thermal properties of rice straw, cellulose and rice straw ash were investigated using laser diffracted particle size analyzer, Fourier transform infrared (FTIR) spectroscopy, X-ray diffractometer, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). FTIR results and SEM images show the removal of lignin and hemicellulose and silica at each step of the isolation process. XRD results exhibit the increase in crystallinity of the fibers. This study reveals that thermal and structural properties have increased after the chemical isolation and purification treatment.

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Browsing MERCon - 2019 by Author "Amarasinghe, DAS"