Research Symposium-2013
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Browsing Research Symposium-2013 by Author "Amaraweera, T.H.N.G."
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Item Li2CO3-coated Sri Lankan Vein Graphite Electrode for Rechargeable Lithium- ion Battery(Uva Wellassa University of Sri Lanka, 2013) Manthirathna, M.A.N.C.; Wijayasinghe, H.W.M.A.C.; Amaraweera, T.H.N.G.High quality vein graphite, containing 95-99% of pure carbon in Sri Lanka has been identified as promising candidate as anode material in lithium ion rechargeable battery. Purification and mild oxidation have been widely used to enhance the property of the vein graphite as anode material (Balasooriya et al., 2007; Amaraweera et al., 2013). However, alkali carbonates coating which are identified as cost effective and nontoxic approach for the surface modification have not been investigated for vein graphite in Sri Lanka (Komaba et al., 2008; Zhang et al., 2003). Therefore, present work is aimed to develop low cost anode material based on Li2CO3 coating of purified vein graphite. Methodology Purified vein graphite powder less than 53µm (<53 µm) was used for this study (Amaraweera et al., 2013). Graphite powder were added into an agate motor and milled for about 2 hours by adding aqueous Li2CO3to ensurethat the graphite was completely witted. Then the surrey was dried in vacuum at 100 C. The modification of the graphite mixture was characterized by FTIR Spectroscopy D.C conductivity of graphite powder and sheet conductivity of graphite electrode was measured by four-probe and VanderPauw, methods respectively.Item Purification of Vein Graphite by Alkali Roasting for Anode Material in Lithium Ion Batteries(Uva Wellassa University of Sri Lanka, 2013) Wewegedara, W.G.C.N.; Amaraweera, T.H.N.G.; Wijayasinghe, H.W.M.A.C.Unique vein graphite deposits with highly crystallized and high purity graphite are present in the mineralization zone of the central highlands of Sri Lanka This graphite has been identified as a potential candidate for the lithium ion rechargeable batteries (Balasooriyaet al., 2007). Recent attention has been made towards the purification of vein graphite in order to prevent the anode ageing and decomposition of the electrolyte in lithium ion batteries (Amaraweera et al., 2013). Alkali roasting for purification of graphite has found to be a very effective method to remove sulfide and silicate impurities at low temperatures (Lu et al., 2002). Therefore, this study focused on studying the effectiveness of alkali roasting for the purification of vein graphite in Sri Lanka Methodology Graphite powder (<53 µm) from Needle Platy Graphite (NPG) and Shiny Slippery Fibrous (SSF) morphological types from Bogala and Kahatagaha mines were used for this study. The graphite was treated in aqueous solutions containing 5, 10, 15, 20, 25, 30 and 35 vol. % NaOH (Solid: liquid, 1:2) separately and roasted at 250 C under air for one hour. Then, the roasted sample was acid leached in 10 vol. % H2SO4. After that, the solid was filtered, washed to neutral and vacuum dried at 100 C for 15 hours. Minimum concentrations of NaOH for the purity enhancement were identified for each graphite type. Roasting treatments were repeated at 150 C, 200 C, and 300 C, using the data obtained previously to identify the effect of roasting temperature on purity enhancement. Carbon percentages of the treated graphite samples and untreated graphite samples were determined by heat treating at 950 C for 3 hours in Muffle Furnace, according to ASTM – C 561 and weighing the residues. Pellets of treated and untreated graphite powder (D =12 mm and L = 5 mm) prepared by cold uniaxial pressing at 100 Mpa were used to measure D.C conductivity by four-probe method at room temperature.Item Synthesis of Graphite Oxide from Kahatagaha Vein Graphite using a Localized Improved Hummers Method(Uva Wellassa University of Sri Lanka, 2013) Madusanka, Y.V.; Amaraweera, T.H.N.G.; Wijayasinghe, H.W.M.A.C.In modern world, materials, - regardless of their make, whether natural or synthetic – play a huge role. From all these materials, Graphite is taking a wide consideration of scientists as they are naturally occurring, cheap material with very interesting physical, chemical and mechanical properties. Within the range of applications of Graphite, Graphite Oxide (GO) and Graphene are more important as they are having many applications and very good potential in Nano scale materials and Nano Technology. GO has attracted much interest recently as a possible route for the large scale production and manipulation of Graphene, a material with extraordinary electrical properties. Sri Lanka has two major natural vein graphite deposits in Kahatagaha- Kolongaha and Bogala. Of the two Kahatagaha vein graphite has the highest purity that can be upgraded up to 99.97% Carbon by HCl leaching (Amaraweera et al, 2013). No researches and experiments have been conducted on Kahatagaha vein graphite which has been upgraded up to 99.97% Carbon in nano scale. The potential for value addition to Kahatagaha graphite has not yet been adequately explored. This study aims at synthesizing GO using a localized version of the Improved Hummers Method and characterization of GO to confirm the oxidation. Methodology Graphite sample, KNPG (Kahatagaha Needle-Platy Graphite) was first crushed using a hammer to obtain +10 mm chips and then the sample was milled in a disc mill for 15 minutes. The milled sample was sieved using a sieve shaker and <53 microns portion was taken for further treatments. 675 ml of 5% HCl was added to 50 g of graphite in 1000 ml beaker and it was vigorously stirred for 1.5 hours at 60 C. The solution was vacuum filtered and washed with distilled water (500 ml) and the same procedure was repeated once. Finally purified graphite was washed until the pH become neutral. KNPG achieved purity level of 99.97% Carbon. 9: 1 mixture of conc. H2SO4 (96% 360 ml) and conc. H3PO4 (85% 40 ml) were added to a mixture of 3 g of purified KNPG and 18 g of KMnO4. The mixture was stirred for 6 hours at 50 C. Then the solution was poured on to ice (200 ml) with 30% H 2O2 3 ml and then vacuum filtered through Fisherbrand filter paper. The brown product left on the filter paper was collected and washed with water (200 ml x 3) and left in a vacuum drier at 105 C for 2 hours. The hard black solid taken out from the vacuum drier was crushed using an agate mortar and pestle to obtain finer particles of 6.86 g of GO. A pellet for electrical conductivity measurements was made using 1g of GO and FTIR Spectrum for GO was taken. A tape was casted using GO for sheet resistance measurements and XRD spectrum was obtained for characterization of GO.