Browsing by Author "Medawela, S."

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    Development of Glassy Hard Wearing Glaze for Floor Tiles
    (Uva Wellassa University of Sri Lanka, 2016) Gamage, S. L.; Medawela, S.; Cooray, J.T.
    Glaze is a decorative layer on the tile surface and mainly there are three types, gloss, matt and rough. In Sri Lanka, most of people would like to use gloss tiles than matt or rough. Gloss glazes easily bounce the light and render adorable surface of the tile. However, gloss glazes can be easily scratched and wearable. Therefore, hard wearing gloss glazes are very important in Sri Lankan tile industry. However, Sri Lankan ceramic industry is not producing any glazes and all raw materials for production of glazes are importing. The main problem is lack oftechnology and high production cost. In this work, we developed a new glaze with increasing the surface hardness using TiO2, ZrO„ V20, and Al203/corundum as suitable additives without change the composition of frit, glossiness and firing temperature. In addition, fast firing cycle with single firing system was use for this research. The study was carried out changing the composition of above materials and checked the surface abrasion. In our results, Al203 was shown positive results for increasing wear resistance among other materials. Further, dry glazes made here used to remove unwanted organic materials and other impurities, and also reduced the surface defects on the tiles. In addition, we show that the abrasion class was increased by glaze when it add as in particle form, since it helped to reduce the contact area on the tile surface. Keywords: Glaze, Frit, Alumina, corundum, surface abrasion
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    Purification of Meetiyagoda Kaolin for boron free glaze manufacturing
    (Uva Wellassa University of Sri Lanka, 2015) Hussain, M.H.S.; Cooray, J.T.; Medawela, S.
    A tile is a manufactured piece of hard-wearing material such as ceramic, stone, metal, or even glass for covering of roofs, floors, walls, or other objects. Tiles are often made from ceramic with a hard glaze finish. But sometimes with other materials such as glass, marble, granite and slate are also used to produce tiles. Among them, floor tiles are commonly made of ceramic, porcelain and stones due to their attractiveness, durability, and easiness to clean. The main components of a tile are tile body, glaze layer, and printed layer. The raw materials used to form a tile consist of clay minerals, quartz, feldspar which is used to lower the firing temperature and chemical additives required for the shaping process. Tile decoration is mainly depending on the glaze layer. Sodium feldspar, potassium feldspar, quartz, wollastanite and kaolinite are abundantly used materials in glaze production. Even through Sri Lanka contains most of the above raw materials; at present all required glaze materials as imported to the country due to the cost, lack of technology and some quality problems of raw materials. So this research aims to manufacture a low cost glaze medium mainly using local mineral materials and few imported materials. Methodology The current study was carried out at Uva Wellassa University, Badulla, Sri Lanka and Lanka Tiles PLC, Jaltara, Sri Lanka. First, the raw materials were purified to make frit and glaze. The acid leach process was carried out for purification of kaolin and the magnetic process was carried out feldspar, wollastanite and quartz. The clay sample selected for investigation was kaolinite clay obtained from Meetiyagoda area. Then the clay sample was ground using a laboratory ball mill to –149 μm (100 meshes). The ground clay sample was placed on the sieve, and then mechanically shacken for 5 min. The oversize was further grounded followed by sieving with the same sieve. The procedures were repeated till the entire clay sample passed through the sieve. After that ground clay sample passing 100 mesh was subjected to calcination. The sample was heated at C ) to activate the clay before acid treatment (Al-Zaharani and Abdulmajid, 2009). Calcineated clay sample passing 100 mesh were leached using 3M hydrochloric acid for different periods of time (10-150 min) and at different leaching temperatures (25ºC to boiling temperature) using a constant temperature shaking water bath at a fixed shaking rate of 160 cycles/min and using boiling under reflux (Hulbert and Huff, 1970). At the end of leaching, the resulted slurry was filtered to separate undissolved materials and, washed in distilled water. The filtrate and washings were continued until ions were removed in the sample. The resulting sample was dried for 24 h in Laboratory oven. Likewise the feldspar and wollastanite were purified by magnets. The purity and quality of leached kaolinite were tested using common base (CS 100) in tile industry. After that the frit was made using 80g of sodium tetraborate pentahydrate (Na2B4O7.10H2O), 100g quartz, 160g of kaolin, 40g of wollastonite, 20g of zirconium silicate and 5g sodium chloride. The raw material was mixed in a pot mill. Water was added slowly step by step until the mixture forms in to a crumb. The crumb was heated at 100 C until it was completely dry. Then the dried product was transferred to porcelain cups and it was placed in a laboratory muffle kiln. The kiln was heated at a rate of 4 C per minute up to a 1050 C and kept at same temperature for 90 minutes (Simon et al, 2007). The furnace was switched off and the crucible was allowed to cool down to ambient temperature in the furnace. The product was removed, wrapped in a plastic film hammered to break in to small pieces. Then the base formula was generated by using it. Glass formation and formulation mechanisms (fluxes, vitrifying agent, opecifier), thermal expansion of the materials and melting point (softening temperature) were considered for base making. The materials in the base thermal expansion were adjusted according to frit thermal expansion. Frit (30g), kaolin (8g), sodium feldspar (30g), wollastanite (32g), zirconium silicate (10g), aluminium oxide (2.5g), zinc oxide(1.5g), C.M.C (0.2g) and S.T.P.P (0.2g) were added to the base formula and it was grind with 100 ml water in pot mill for about 20 minutes. Resulted base medium was sieved using a 100 µm sieve and it was sprayed by spray gun on to engobe green tile. Base density and base viscosity was measured before spraying. Based tile was fired in the kiln. Finally fired tile surface properties, thermal shock, abrasion, strain, cracking and acid resistance were checked to ensure the quality.