Browsing by Author "Manoratne, C.H."

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    The Incorporation of Layered Type Clay in Graphite-Clay Based Electrodes as a Property Enhancement for High-temperature Applications
    (Uva Wellassa University of Sri Lanka, 2019) Tharangani, L.W.N.; Rathnayake, D.T.; Karunadasa, K.S.P.; Manoratne, C.H.
    Although the recent developments in the field of graphite-clay based electrodes are mainly confined to kaolin type clays, the present study has been investigated the possibility of incorporating layered clay in the fabrication process. The fabrication of graphite-bentonite (layered clay) electrodes (cylindrical) was achieved by mixing raw materials in distilled water (graphite to bentonite ratio of 20:80, 40:60, 50:50, 60:40 and 80:20), stirring the content for 1h at 800 rpm and finally pressing the dry composite material (1.00 × 10-2 kg) under 1.03 × 104 N ram force to obtain the electrodes with 4.00 × 10-2 m longer and 1.00 × 10-2 m in diameter, respectively. The compressed electrodes were fired at around 823 K for 1 h. The resistivity of fired electrodes was calculated subsequent to the resistance measurements. Results indicate that the electrode with 80% graphite is accounted for lowest resistivity (1.00 × 10-3 Ω m) whereas the highest resistivity for electrode containing 20% of graphite (1.10 × 10-2 Ω m). The resistivity range between the electrode with the lowest and highest amount of graphite is narrower for graphite-bentonite electrodes, unlike other graphite-clay based electrodes. It is also evident that the resistivity is abruptly decreased with the increased amount of graphite. The fired electrodes are very stable in both molten salts and aqueous solutions. A very high affinity of bentonite towards graphite is observed that further ensures stronger and homogeneous electrode matrix. The uniform composite matrix with minimum defects is accounted for a substantial electrical continuity and low resistivity across the entire electrode. The working temperature range up to 1473 K, low resistivity, electrical and mechanical stability, lightweight and durability are the key attributes of the fabricated electrode. The application of modified bentonite (conductive nanocomposites of clay) in electrode fabrication is also possible and will be achieved in the future.
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    Mechanically Compressed Graphite-Clay Composite Electrode for High-Temperature Applications
    (Uva Wellassa University of Sri Lanka, 2019) Rathnayake, D.T.; Tharangani, L.W.N.; Karunadasa, K.S.P.; Manoratne, C.H.
    The graphite-clay based electrodes have been received escalating attention very recently. Graphite based electrodes typically use as an anode in high-temperature molten salt deoxidation of minerals. The major objective is to fabricate mechanically compressed electrodes using local graphite and kaolinite to improve electrical conductivity, mechanical strength, thermal stability and durability. The composites were prepared by mixing different ratios of graphite and kaolinite (20:80, 40:60, 50:50, 60:40 and 80:20) followed by continuous stirring of the content for 1 hr at the rate of 1100 rpm. The fabrication of rod-shaped electrodes (length and diameter are around 3.00 × 10-2 m and 1.00 × 10-2 m, respectively) was achieved by pressing 8.50 × 10-3 kg of composite material (under 1.03 × 104 N ram force) using a specially designed stainless steel mould. The resistivity of electrodes was measured before and after the firing of electrodes at around 823 K for 1 hr duration. Results indicate that the fabricated electrodes are very good electrical conductors with considerably low resistivity. The resistivity of fired electrodes is lower than the unfired electrodes. The electrode containing 80% of graphite (fired electrode) is attributed to the lowest resistivity (7.80 × 10-4 Ω m) and vice versa for the electrode containing 20% of graphite (5.80 × 10-2 Ω m). It is also evident that the resistivity of fabricated electrodes is somewhat decreased exponentially with the increased amount of graphite. The fired electrodes are very stable in both molten salts and aqueous solutions over unfired electrodes that eventually failed to endure in the aqueous medium at room temperature. The fired electrodes are capable of withstanding the temperatures up to 1473 K which ensures improved thermal stability. The low resistivity, uniform matrix, higher strength, superior thermal stability, and durability are the salient features of the newly fabricated compressed graphite-kaolinite composite electrode.