Thermal behaviour of glazed ceramic bodies
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Thermal behaviour of glazed ceramic bodies Mária Kolářová1 · Alexandra Kloužková1 · Jaroslav Kloužek2,3 · Jiří Schwarz4 Received: 30 August 2019 / Accepted: 21 February 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Thermal behaviour of glazed ceramic bodies was studied using three different thermal analysis techniques, dilatometry, thermomechanical analysis and differential thermal analysis. The data of relative expansions obtained through these analyses were used to calculate stress relations within two-component systems consisting of the glaze and ceramic body. The investigation also aimed to determine the long-term stability of glazed ceramic products and identify defect growth or degradation due to corrosive effects of the surrounding environment. The results of thermal analysis measurements showed that the values of thermal expansion coefficient, glass transition temperature Tg, set point Tn and deformation temperature Td increase slightly with growing heating rates. However, the measurements showed that heating rate does not affect stress relations within glaze–ceramic body systems. Keywords Ceramic glazes · Thermal analysis · Coefficient of thermal expansion (CTE) · Glass transition temperature Tg · Set point Tn · Deformation temperature Td
Introduction When preparing a glaze–ceramic body system, it is important to find a fusible glaze composition that fits in the narrow range of coefficients of thermal expansion (CTE) within which the system is stable [1, 2]. Stresses between the ceramic body and glaze occur immediately after the system has been fired and begins to cool down as a result of different CTE values. These stresses further develop as the ceramic product is being used. The formation of defects in the glaze layer depends on the extent and type of stress. Characterization of stress relations within the glaze–ceramic body system * Mária Kolářová [email protected] 1
Department of Glass and Ceramics, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague, Czech Republic
2
Laboratory of Inorganic Materials, University of Chemistry and Technology Prague, Technická 5, 166 28 Prague, Czech Republic
3
Institute of Rock Structure and Mechanics ASCR, Czech Academy of Sciences, V Holešovičkách 41, 182 09 Prague 8, Czech Republic
4
Department of General and Inorganic Chemistry, Faculty of Chemical Technology, University of Pardubice, Studentská 573, 532 10 Pardubice, Czech Republic
is important for contemporary ceramic production (e.g. roof tile production. etc.), but it can also be useful for determining the origin of defects in archaeological ceramic fragments and historical ceramics [2]. The occurrence of stresses depends on several factors. As mentioned above, the difference between the volume change in the ceramic body and the glaze is the crucial factor [3, 4]. A minute shift in the contact area (interface) between ceramic body and glaze during firing can cause undesirable stress relations. A stress exceeding the glaze strength leads to different
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