Browsing by Author "Wevitavidana, W.V.R.T."

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    Structural Characteristics of Natural Graphite and Synthetic Graphite
    (Uva Wellassa University of Sri Lanka, 2012) Wevitavidana, W.V.R.T.
    Sri Lanka is famous for highly crystalline natural vein graphite. Bogala and Kahatagaha — Kolongaha are main graphite mines which are situated in the central highlands. Sri Lanka graphite has high purity carbon (more than 99% pure carbon in Kahatagaha - Kolongaha and 98% pure carbon in Bogala mine).At present graphite industry in Sri Lanka is mainly limited for pencil productions. High labor cost, expensive deep mining methods and high mining cost are main problems to decay production of graphite. Therefore currently Sri Lankan graphite is unable to conflict in world market. Currently synthetic graphite is used instead of natural graphite to produce different kinds of products. In the main, synthetic graphite is used for electrodes in lithium ion batteries, coatings etc. But in Sri Lanka, there are limited work has been done to study structural characteristics of graphite. When the graphite pieces convert to powders, large grinding hours are wanted to milling. As a result rhombohedral content is increasing gradually. Certain applications need rhombohedral phases rather than hexagonal phase. Therefore consider the rhombohedral phase of powder natural graphite important for further studies. The amount of rhombohedral percentage of graphite was calculated from X-ray diffractogramme which were plotted (Excel 2007) using XRD data by measuring height of the peaks of hexagonal (101) and rhombohedral (1 01) reflections. Crystallographic parameters of the mechanical treated and untreated natural graphite are calculated using the hexagonal crystallographic formulae. The lengths of coherence (La and Lc) of graphite were calculated using XRD data. The Lc values were calculated on the basis of the d002 diffraction line, using the Sherrer's formula while the La values were calculated with the d100 diffraction line using the Warren's formula. ( Parthasarathy et. al, 2006) The different chemical impurities in Sri Lanka natural graphite were analyzed qualitatively. The average crystallographic parameter, 'c' is 6.732 A and 'a' is 2.465 A, for untreated natural graphite. According to the diffraction line of d100 the La average values of natural graphite vary between 63nm and 160nm. The Lc values of natural graphite vary between 40nm and 70 nm with respect to d002 diffraction line.
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    Structural Characteristics of Natural Graphite and Synthetic Graphite
    (Uva Wellassa University of Sri Lanka, 2012) Wevitavidana, W.V.R.T.; Amaraweera, T.H.N.G.; Balasooriya, N.W.B.
    Sri Lanka is famous for highly crystalline natural vein graphite. Bogala and Kahatagaha Kolongaha are main graphite mines which are situated in the central highlands. Sri Lankan natural graphite is found in various morphologies with different structural and physical characteristics such as flake, plate and fibrous graphite. Sri Lanka graphite has high purity carbon. At present graphite industry in Sri Lanka is mainly limited for pencil productions. But in other countries which are producing graphite with high quality, motivate to conduct worthy industries. China, Mexico, Canada, Brazil and Madagascar are other countries which produce graphite for world market. Sri Lanka was top of the leading supplier of natural graphite to the world market and fulfilled the 20%-35% of the total world production. High labor cost, expensive deep mining methods and high mining cost are main problems to decay production of graphite. Therefore currently Sri Lankan graphite is unable to conflict in world market. As well as the lack of modern skills are main detriments for graphite industry. Currently synthetic graphite is used instead of natural graphite to produce different kinds of products. The synthetic graphite is known as artificial, manufactured or electro graphite. A carbon product (100% pure carbon) has been subject to a further stage of heat treatment at a temperature about 2400°C. In the main, synthetic graphite is used for electrodes in lithium ion batteries, coatings, conductive fillers, rubber and plastic compounds, foundry etc. However, in Sri Lanka, there are limited work has been done to study structural characteristics of graphite. Therefore, Sri Lankan natural graphite is unable to use for some industries like electrochemical application industries. Most of graphite used for applications as powder form. As a result, rhombohedra content is increasing gradually. Certain applications need rhombohedra phases rather than hexagonal phase.