Browsing by Author "Wiik, Kjell"

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    Ceramic Properties of Pugu Kaolin Clays. Part 2: Effect of Phase Composition on Flexural Strength
    (2004-06) Akwilapo, Leonard D.; Wiik, Kjell
    Whiteware compositions prepared using Pugu kaolin and industrial grade quartz and feldspar were studied with respect to varying sintering temperatures. The strength developed was correlated to mullite (3Al 2 O 3 .2SiO 2) content and the microstructure. It was observed that within the vitrification temperature range, the strength mainly depended on the mullite content and the bulk density. Above the vitrification temperature range the deterioration of the strength is due to the coarsening of mullite needles and bloating.
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    Ceramic Properties of Pugu Kaolin Clays. Part I: Porosity And Modulus Of Rupture
    (2003-11) Akwilapo, Leonard D.; Wiik, Kjell
    The utilisation of Pugu kaolin clay as a raw material in porcelain has been tested by laboratory scale experiments. Physical characteristics of the clay have shown it to be of satisfactory quality and comparable to commercial clays found elsewhere. The chemical analysis has indicated the presence of high levels of iron oxide (~ 1.43%) which could adversely affect the translucency of whitewares. The ''as mined'' material could be suitable for ceramics that do not require high brightness specifications, such as stoneware and sanitary ware. The level of this oxide can, however, be reduced by appropriate means to give a relatively cleaner product that could be excellent for other types of whiteware products. Porcelain materials prepared using Pugu kaolin clay have shown to have similar properties as those prepared using other standard kaolin clays. The bulk density and flexural strength of the fired masses increase with firing temperature to a maximum at the soak temperature of 1200 o C. Beyond this soak temperature the flexural strength decreases. The decrease in strength is attributable to bloating which takes place as gasses are expelled from the matrix. Strictly firing procedures should be enforced in order to obtain a porcelain material of required strength.