Double Layer Glaze Applications for the Vitrifies Glazes and Surface Properties

Sanitaryware glazes are of the raw type and have zirconium silicate as an opacifier. Glaze compounds affect glaze properties such as mechanical strength, surface properties etc. In this study, glazes were prepared in order to observe the effect of zircon presence in glaze and further alumina content. Melting behavior of glazes was determined by using hot stage microscope. Samples were prepared as once-fire and twice-fire with two layers. Surface smoothness, gloss, color and scratchiness of samples fired at approximately 1210 o C were investigated. Introduction Paralleling the improvements on the world ceramic industry, sanitarywares are becoming more open to new improvements and technologies as well. The majority of these studies have been aimed to expand the usage area and to enhance product’s overall properties. Additionally, to be able to produce environmental and user friendly products, many studies have been done. Another main expectation from sanitaryware is having smooth surfaces and as a result of this to achieve easy clean surfaces and products [1-4]. In this study, the achievement of smooth surface texture and easy-clean surfaces were aimed for the sanitarywares using two layers of glazing Experimental Studies In this study, regular zircon containing, zircon free and alumina added glazes were prepared and melting behavior of these glazes was investigated by Leica hot stage microscope. Samples were glazed and fired at 1210 o C under the 4 o C/min firing condition by using Protherm brand lab kiln. In Table 1, information about applied glazes can be seen. In Table 2, Seger formula of zircon free and zircon containing glazes were stated. To evaluate the surface texture and to take pictures of cross section of the fired samples, Olympus BX60M brand optic microscope was used. The microstructure of the samples was examined by using CamScan brand scanning electron microscope and the chemical analyses of crystals and bubbles in to the glazed body were made by EDX. Surface characteristics such as gloss and color were analyzed by using Minolta glossmeter and Minolta spectrophotometer. As a result, considering the final product’s surface smoothness and judging the easy-clean behavior, scratching test was done with HB type pencil. Results and Discussions In Figure 1, commercial glaze's cross-section scanning electron microscopy (SEM) picture can be seen. Considering chemical analyses (EDX) obtained from the bubbles in the glaze structure, it was concluded that zircon crystals were moving to surface by bubbles and due to that, surface was becoming uneven (Figure 2). Chemical analysis of this mentioned area is given in Table 3. Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 1673-1676 doi:10.4028/www.scientific.net/KEM.264-268.1673 © 2004 Trans Tech Publications Ltd, Switzerland All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications Ltd, www.scientific.net. (Semanticscholar.org-13/03/20,18:13:56) Table 1. Applied glazes and properties Firing cycle Glaze properties Fired Temp. ( o C) First layer Standard commercial glaze 1210 Twice fired Second layer Transparent glaze[4] 810 First layer Standard commercial glaze Once fired Second layer Zircon content taken standard sanitary ware glaze 1210 First layer Alumina added (5,10,15,20%) glaze in to standard Once fired Second layer Transparent glazes melting 900,1000,1100 o C 1210 First layer Standard commercial glaze Once fired Second layer Transparent glazes melting 1200 o C with different melting behavior 1210 Table 2. Seger formula of applied glazes Na2O 0,130 Al2O3 0,342 SiO2 3,755 K2O 0,054 Fe2O3 0,004 TiO2 0,002 CaO 0,679 ZrO2 0,203 MgO 0,100 ZnO 0,037 a. Seger formula of the regular vitrify glaze Na2O Al2O3 0,380 SiO2 3,287 K2O 0,261 CaO 0,417 MgO 0,164 BaO 0,069 ZnO 0,089 b. Seger formula of without zircon content glaze Table 3. Chemical analysis of bubble in to the glaze structure Oxides Na2O K2O CaO Al2O3 SiO2 ZrO2 Compound % 1,50 1,39 2,30 3,90 43,89 47,01 First, to observe the zircon crystal’s movements on the effect of unevenness, standard sanitaryware glaze was prepared and fired at 1210 o C. On top of this fired body, a transparent and zircon free glaze was applied and this glaze which has low melting point, fired at 810 o C. Even though the degree of gloss of the obtained body was a bit less than the standard, the color (L,a,b) was proven to be approximately the same as the standard. Additionally, it was established that this body had the easy-clean property and also scratching test was confirmed this result. Figure 1. Commercial sanitarywares cross-section SEM picture 200μm 1674 Euro Ceramics VIII