Abstract
Anorthite is a rare compositional variety of plagioclase. This mineral is a type of calcium-rich plagioclase feldspar which has great properties such as low thermal expansion coefficient and high modulus of rupture. Therefore, physical properties of hard porcelain bodies will be improved by creating anorthite phase. According to limitation of anorthite natural sources, various sources were used to synthesis of anorthite. In this paper, white cement was introduced as a new calcium oxide source to reach anorthite phase. For this purpose, a standard composition for hard porcelain was prepared by addition of 50 wt% kaolin, 25 wt% potassium feldspar and 25 wt% quartz. Six additional body mixtures were formulated partially by replacing 0, 3, 4.5, 6, 7.5 and 9 wt% of potassium feldspar by white cement. The linear shrinkage, water adsorption, modulus of rapture (M.O.R), and bulk density of fired body were calculated. Phase characterization was accomplished by X-ray diffractometer (XRD) and scanning electron microscopes. By replacing potassium feldspar with white cement, anorthite was appearance in fired body at 1250 °C. This replacing decreases bulk density, linear shrinkage and modulus of rapture. Although, water adsorption and consequently firing temperature increase by replacing white cement but 1250 °C was a good temperature for firing replaced bodies.
Highlights
Porcelains are one of the most important glazed or unglazed vitrified whitewares which contain ternary compound of kaolin, feldspar and quartz [1]
White cement was used as a new CaO source for anorthite base porcelains and its influence on sintering behavior, M.O.R, thermal expansion coefficient (TEC), bulk density, and water adsorption were investigated
The raw materials used in this investigation were kaolin (Super Standard Porcelain, IMERYS Ceramics, UK), quartz (Morvarid–Iran), potassium feldspar (Quantum AP200F, Cibelco–India) and white cement
Summary
Porcelains are one of the most important glazed or unglazed vitrified whitewares which contain ternary compound of kaolin, feldspar and quartz [1]. Feldspar is used as flux in porcelain industries to reduce firing temperature and make glass phase and quartz is used as filler which is effective on the reduction of pyroplastic deformation through firing process [2]. Free quartz and mullite are formed and distributed in glassy matrix and fired body reach to maximum density between 1250 and 1300 °C [1,2,3,4]. Supplementary scientists investigate about various calcium sources to reach anorthite phase in porcelain bodies. They used Ca(OH), calcite, marble powder and gypsum mold waste [20], dolomite, wollastonite and calcite [21]. White cement was used as a new CaO source for anorthite base porcelains and its influence on sintering behavior, M.O.R, TEC, bulk density, and water adsorption were investigated
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