Pyroxene-based glass-ceramics as glazes for floor tiles

Crystallization of a glass with composition in the diopside primary crystallization field in the MgO–CaO–Al₂O₃–SiO₂ quaternary system was investigated. Also the action of some additives, nucleants and fluxes, in the pyroxene development was examined. Glasses were prepared by conventional melting of a mixture of raw materials and cooled by pouring in water. Pellets of glass powder specimens were thermally treated at several temperatures up to 1200 °C. The crystallization path was followed by X-ray diffraction powder (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX). The results proved that, in addition to the effect of B₂O₃ and TiO₂ in the development of the final pyroxene phase, some amount of alkaline oxides, Na₂O and/or K₂O, are required to obtain well-defined morphologies of pyroxene crystals. Fast fired under industrial conditions glass-ceramic glazes on to porcelain stoneware supports improved hardness of final products     

Hardness and microhardness of zircon glazes for tiles

Translated from Steklo i Keramika, No. 5, p. 17, May, 1988.     

Development of sapphirine opaque glazes for ceramic tiles

The purpose of this work is to produce more excellent opaque wall tile glazes by using sapphirine instead of zirconium silicate as an opacifier. In order to achieve it, the chemical compositions were precisely adjusted in the system of SiO₂-Al₂O₃-MgO-K₂O-Na₂O-B₂O₃. The morphological characteristics of the glaze were determined by differential scanning calorimetry (DSC), X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). And the optical properties of the glaze were characterized by a spectrophotometer and a gloss meter. The results reveal that well-shaped crystals of sapphirine (Mg₂Al₄SiO₁₀) with needle-like morphology were formed as only crystal phase. The glaze is provided with better opacity whiteness and gloss compared with commercial zircon-based glass-ceramic glazes, and it is mainly composed of cheap mineral raw materials. Those features make it as an alternative one for improving the properties of conventional opaque ceramic glazes.     

Development of spinel opaque glazes for ceramic tiles

The feasibility of developing fast-firing opaque wall tile glazes obtained from zircon-free frits was studied. The structural and morphological characteristics of the glazes were determined by differential scanning calorimetry, an optical dilatometer, X-ray diffraction and scanning electron microscopy. The studied glaze was characterized by a high whiteness value L* greater than 94, very low values of a* and b* which is about ?0.65 and 0.01, respectively, and a high gloss value above 98%. The opaque effect is due to the presence of spinel crystals with a size range of 0.2–1.0 μm, which is formed by devitrification during fast-firing. The Vickers micro-hardness of the studied glaze is higher than the one of the commercial zircon based glass-ceramic glazes. This type of frit can be an alternative one for fabricating opaque ceramic glazes.     

微晶玻璃装饰板材的析晶工艺研究

介绍了微晶玻璃装饰板材的核化机理和晶化过程，并利用差热分析和玻璃试样析晶量的显微镜观察等对压延法和烧结法微晶玻璃装饰板材的热处理工艺制度进行了探讨和制定。     

Development of TiO2 white glazes for ceramic tiles

The objective of this work was the use of titania polymorphs (rutile and anatase) in substitution of zirconia as the main component for producing white opacity in ceramic glazes for tile coatings. Initially, total zirconia (12% mass fraction) was replaced in the standard frit by rutile and by anatase in mass fractions of 5%, 10% and 15%, forming two frit groups processed as ceramic glazes. The glaze color was determined by spectrophotometry and the glaze microstructure by XRD and SEM. The results showed the frit containing 10% anatase formed a totally white glaze presenting excellent coating capacity. The frits containing rutile produced yellow opacity. The results of microscopy and X-rays diffraction revealed that opacity was caused by tiny rutile crystals in the anatase frits and by titanite crystals in the rutile frits.     

Cathode-Ray Tube panel glass replaces frit in transparent glazes for ceramic tiles

The disposal of Cathode Ray Tubes (CRT) from end-of-life personal computers and TV screens represents a serious problem in electronic-waste management. As an assembly of different materials, finding a use for each of a monitor's parts is a critical step forward a solution. However, the CRT panel is a silicate glass with a relatively high proportion of alkaline and alkaline-earth oxides, for which recycling is a natural task, and the replacement of frit in ceramic glazes arises as an interesting alternative. In this context, we investigated the effect of CRT panel glass in glazes for ceramic tiles based on a comparative analysis. We replaced up to 40?wt% of commercial transparent frit with CRT panel glass in the formulation of one reference slurry. Chemical analyses were conducted by X-ray fluorescence (XRF) and inductively coupled plasma optical emission (ICP-OES) spectrometry. The thermal expansion coefficient and the glass transition and dilatometric softening temperatures were characterized by dilatometry and compared to such properties calculated as a function of composition, using the SciGlass software and database. 20- and 30-min firing cycles were applied in a fast-firing roller kiln, replicating industrial conditions. The samples transparency was measured by spectrophotometry and compared to the colorimetric parameters of a standard glaze. The maximum content of panel glass possible to add in the transparent glaze formulation without affecting the expected properties was 20?wt%, above which transparency decreased due to heterogeneities. The reformulation of a ceramic glaze with waste CRT panel glass was successful, thus suggesting an interesting approach for disposal of other electronic wastes.     

Production of floor tiles in Czechoslovakia

Glass and Ceramics -