Articles authored by UoM staff

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Browsing Articles authored by UoM staff by Author "Adikary, SU"

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    item: Article-Abstract
    Characterization of locally available Montmorillonite clay using FTIR technique
    Adikary, SU; Wanasinghe, DD
    Montmorillonite (MMT) is a layered silicate clay which belongs to the smectite clay group with a wide range of applications in medicine, polymer industry, ceramic industry and nano materials. This research is focused on the use of Fourier Transform Infrared Spectroscopy (FTIR) technique to identify and characterize Montmorillonite clay deposits available in the dry zone of Sri Lanka. Apart from identification, FTIR can be used to discover the family of minerals to which the specimen belongs, the nature of isomorphic substituent and the distinction of molecular water from constitutional hydroxyl. Clay samples obtained from several locations within the dry zone of Sri Lanka were purified, treated and subjected to FTIR, X-ray Diffraction (XRD) and Differential Thermal Analysis (DTA). To further strengthen the findings, specimens of commercially available MMT and Bentonite were subjected to the same tests. Peaks of the resultant spectrum were analyzed and compared with published literature. Results revealed that the specimens subjected to the tests contained MMT with kaolinite. In-depth study of absorbance level of each specimen was useful in identifying the exchangeable cations present in MMT. Further study of the spectrum could pave the way for quantitative analysis of these clay minerals.
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    Development of a high thermal shock resistant ceramic body suitable for cookware applications
    Pussepitiya, PPSS; Adikary, SU
    Development of a ceramic based cookware body with adequate thermal shock resistance was successfully developed using low cost raw materials. The objective of this work was to develop a ceramic body composition suitable for cookware to be used in direct flame cooking. To achieve this objective, cookware body should have low thermal expansion coefficient, high strength, low water absorption and high thermal shock resistance. In this study, ball clay, talc, alumina and zirconium silicate were used as starting raw materials and twenty five samples were investigated with different compositions. All samples were wet-mixed, shaped by slip casting, dried and fired to a temperature of 1250°C in an electric furnace. Modulus of Rupture was tested by the three point bending method, the thermal conductivity of each body was measured with Lee's disk method and the coefficient of thermal expansion was measured by thermo mechanical analyzer. The thermal shock resistance of each sample was calculated with Kingery's formula. Optimum thermal shock resistance of 0.74 kJm-VHvas achieved for a body composition of 45% of clay, 15% of talc, 15% of alumina and 25% of zirconium silicate which was fired to 1250°C. Further, modulus of rupture and coefficient of thermal expansion of the ceramic body were 74 MPa and 30.2*10-7 K-1, respectively. These results suggest that the ceramic body is suitable to be used in cookware applications.
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    Dielectric dispersion and tunability of sol-gel derived BaxSr1-xTiO3 thin films
    Adikary, SU; Chan, HLW
    Ba0.5Sr0.5TiO3, Ba0.6Sr0.4TiO3, Ba0.7Sr0.3TiO3 and Ba0.8Sr0.2TiO3 thin films were fabricated by a modified sol-gel technique on Pt(111)/Ti/SiO2/Si(100) substrates. All BaxSr1-xTiO3 films crystallized in the perovskite structure with a crack free microstructure and clear grain boundaries. Highest relative permittivity and dielectric tunability was observed in the Ba0.7Sr0.3TiO3 thin film. Ba0.7Sr0.3TiO3 and Ba0.8Sr0.2TiO3 compositions demonstrated ferroelectric hysteresis loops indicating the presence of ferroelectricity at room temperature. The paraelectric compositions of Ba0.5Sr0.5TiO3 and Ba0.6Sr0.4TiO3 showed significant tunability with negligible loss tangent. The tunability of Ba0.5Sr0.5TiO3 thin film decreased with the increase of frequency from 100 kHz to 100 MHz. As the frequency increases, especially above 10 MHz, the relative permittivity decreases while the loss tangent increases. Since Ba0.5Sr-.5TiO3 thin film is paraelectric at room temperature, relaxation due to ferroelectric domains cannot occur. Therefore this behaviour has originated from the contact resistance and finite sheet resistance of both the bottom and top electrodes. To analyse the thin film capacitor, the parallel plate capacitor structure can be modeled based on an equivalent circuit, which contain electrode and contact resistance.
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    Effects of Proton Irradiation on the Ferroelectric to Paraelectric Transition of Ba0.65Sr0.35TiO3/P(VDF-TrFE) 0–3 Composites
    Adikary, SU; Peng, Z; Chan, HLW
    (Ba0.65Sr0.35TiO3)/P(VDF-TrFE)70/30 composites were irradiated with different dosages of 3 MeV protons. The XRD (X-ray diffraction) patterns exhibit a gradual increase in inter-chain spacing and decrease of ferroelectric domain size with the increase in proton dosage. At higher proton dosages, a significant decrease in TSDC (thermally stimulated depolarization current) peak corresponds to ferroelectric to paraelectric (F-P) transition was observed and at a high dosage of 100 Mrad, the peak value is so low that only a straight line was observed. The DSC (differential scanning calorimetry) thermograms of irradiated composites show decreased peak temperatures and enthalpy with the increase of proton dosage. Due to proton irradiation, dielectric peaks have broadened and moved towards lower temperature with increasing frequency.
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    Extraction of montmorillonite nano particles from naturally occurring clay mixtures
    Wanasinghe, DD; Adikary, SU
    Montmorillonite (MMT) nano clay has attracted lot of attention due to its ability toimpart superior mechanical, thermal and gas-barrier properties to polymer-clay nano composites. Therefore, this clay has a huge demand in the nano-technology related industry mainly in the area of nanocomposites. However at present, all the extraction methods of Montmorillonite mainly concentrate on bentonite. This research is focused on extracting nano sized Montmorillonite clay particles from local clay deposits that can be used in the fabrication of nano composites. Clay samples used in this research work were obtained from the dry zone of the country. These clay specimens were then purified in several steps and subjected to clay isolation process and finally an extraction process was carried out. The purified and extracted clay were analysed using X-Ray diffraction (XRD), laser particle size analysis, and Scanning Electron Microscope (SEM) analysis techniques. The results from these analysis showed that the extracted clay contained high concentration of Montmorillonite clay. With further purification the extracted clay can be used in the fabrication of polymer-clay nano composites which would have a beneficial output as it would contribute for the value addition for the local clay deposits.
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    Mineralogical characterization of clay deposits in embilipitiya region to study the presence of Montmorillonite Nano Particles
    Adikary, SU; Jayasinghe, WGP; Soysa, WRM
    Montmorillonite (MMT) is a clay type which has wide range of applications in the traditional engineering fields. Recent development has increased attention to this clay since it can be used in the synthesis of polymer-clay nanocomposites which has enhanced physical and mechanical properties. In this research clay deposits located in Embilipitiya region were studied. A methodologysince it can be used in the synthesis of polymer-clay nanocomposites which has enhanced physical and mechanical properties. In this research clay deposits located in Embilipitiya region were studied. A methodology for sample preparation was carried out in order to remove non-clay material and enhance the clay content. A chosen clay sample was then subjected to a partial isolation process of ultrasonic treatment and sedimentation. For characterization purpose Fourier Transform Infrared Spectroscopy (FTIR), Xray diffraction (XRD) analysis, Differential Thermal Analysis (DTA) and Thermogravimetric Analysis (TGA) and Particle size distribution analysis by Hydrometer method as well as by laser method were used. To aid the analysis commercial MMT and kaolinite were also tested. Characterization by FTIR method revealed that MMT and kaolinite minerals are present and DTA and TGA aid this findings. XRD analysis also confirms the presence of MMT, Kaolinite, Quartz and Pyrophyllite in the clay samples and also many other types of clays and non-clay minerals. The ultrasonic treatment and sedimentation has enhanced the amount of nano particle as of 80%of particles are less than ljim and die Quartz intensity has declined, which was confirmed by the XRD analysis.
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    Study of Adsorption Characteristics of Cadmium into Chitosan biopolymer to be used for waste water treatments
    Adikary, SU; Unagolla, JM
    Pollution by heavy metals is a serious threat to aquatic ecosystems because some of these metals are potentially toxic even at very low concentrations. Chitosan, a biopolymer produced from crustacean shells, has applications in various areas, particularly in drinking water and wastewater treatment due to its ability to remove metallic ions from solutions. The purpose of this research work was to study the adsorption of cadmium on chitosan produced from shrimp shells at a laboratory level. Chitosan, with a degree of deacetylation of approximately 70%, was used in the experimental part and the flake sizes were smaller than 0.25mm. Experimental work involved the determination of the adsorption isotherms for each metallic ion in a batch system. The resulting isotherms were fitted using Langmuir model and the parameters of the equation were determined. Kinetic studies of adsorption for metallic ions at different concentrations and with different particle sizes were performed in batch system. Simplified models such as pseudo-first-order, pseudo-secondorder, and intra-particle diffusion equations were used to determine the rate controlling step. The results showed that the adsorption capacity depends strongly on pH and on the species of metallic ions in the solution. Batch adsorption experiments were performed at two differentdegrees of deacetylation (DD) values, time period ranging from 15 minutes to 3 hours and pH of solutions ranging from 3 to 7. The study showed that the solution pH strongly affects the adsorption capacity of chitosan.
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    Synthesis and characterization of Chitosan/Hydroxyapatite (70/30) Nano-Composites
    Adikary, SU
    In this research work, (70/30) nanocomposites of Chitosan biopolymer and Hydroxyapatite (HA) ceramic powder were synthesized by insitu co-precipitation technique combined with double step stirring. Initially medical grade chitosan was extracted in the laboratory using locally available shrimp specices Penaeus Monodon. Analytic grade acetic acid, H3PO4 and Ca(OH)2 were used as starting materials. At first, chitosan was dissolved in acetic acid and mixed with required amount of H3PO4 acid. Then the chitosan / H3PO4 solution was added drop wise into the highly alkaline Ca(OH)2 suspension. During the addition chitosan precipitated with hydroxyapatite by forming the chitosan/ hydroxyapatite composite. Finally, the suspension pH reached 6.0-6.5 range, after the complete addition of the solution. Synthesized composite was characterized using Fourier Transform Infrared Spectroscopy (FTIR), Xray diffraction (XRD), thermo-gravimetric analysis (TGA) and differential thermal analysis (DTA). The XRD spectrum demonstrated relevance peaks of chitosan and HA in composite. FTIR spectrum of composite showed the characteristics bond energies of chitosan sample and hydroxyapatite sample. Each characterization techniques confirm the existence of chitosan and FLA in the composite. The size of the HA crystals embedded in composite was calculated using Scherrer formula and it was found to be ~55 nm.
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    Synthesizing and characterization of natural biopolymer chitosan derived from shrimp type, penaeus monodon
    Sewvandi, GA; Adikary, SU
    In this study natural biopolymer "chitosan" was synthesized using locally available shrimp type of Penaeus monodon. Synthesis of chitosan involved four main stages: preconditioning, demineralization, deprotenisalion and deacetylation. The first stage, "preconditioning " process, is a new step introduced in this research. Effect of deacetylation conditions such as alkali concentration, number of limes deacetylation was performed and reaction temperature was investigated. Yields of chitin and chitosan from R monodon were calculated. Chitosan was characterized using Fourier Transform Infrared (FTIR) Spectroscopy and X-ray diffraction. Degree of deacetylation of synthesized powder was calculated using FTIR spectra. Both characterization techniques confirm the existence of chitosan.
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    Thermal compatibility studies of variable body and glaze compositions for glazed clay based cookware applications
    (2015-09-01) Adikary, SU; Jayawardane, ST
    This study was focused on the development of a glazed red clay cookware with adequate thermal shock resistance for open flame cooking applications. Thermal compatibility of different red clay and fritted glaze compositions were investigated using thermal expansion and thermal shock resistance. Coefficients of thermal expansion and thermal shock resistance values of red clay bodies with different proportions of quartz were investigated. Commercially available lead free glazes were selected to satisfy the coefficient of thermal expansion and thermal shock resistance requirements. Thermal conductivity, modulus of rupture, and modulus of elasticity of each body and glaze were measured.Based on the test results, suitable red clay body and glaze compositions were selected and actual size cookware samples were fabricated.The red clay body with 25% quartz having a coefficient of thermal expansion of 60.31×10-7 K-1 and a thermal shock resistance of 0.97 kJm-1s-1, and the glazes having a coefficient of thermal expansion in the range of (49-51)×10-7 K-1 and thermal shock resistance in the range of (1.10-1.20) kJm-1s-1 could be effectively used to manufacture a glazed red clay cookware product. Hence it could be concluded that a suitable body composition for glazed cookware could be formulated by incorporating quartz in a certain proportion to kaolinitic type red clay