Coloring effect of iron oxide content on ceramic glazes and their comparison with the similar waste containing materials

The effects of adding iron oxide to ceramic glaze formulations were studied in this study. Iron oxide was added in different weight ratios into the reactive transparent glaze, reactive opaque glaze, and transparent glaze formulations. The iron oxide content in the glaze composition, the coloring mechanisms, the phase distributions, and surface properties at temperatures of 950–1000-1050-1200 °C in the oxidation firing medium were investigated. Scanning Electron Microscopy (SEM) to determine the microstructural and morphological characterizations of the test glazes, X-Ray Diffractometry (XRD) to determine the crystallographic properties and phases, and X-Ray Fluorescence (XRF) analyses to determine the elemental and chemical composition were performed. In addition to these, surface images were examined with Digital Microscope (DM) and Commission Internationale de l'Eclairage (CIE) L*a*b, and water absorption values were compared. In addition, taking into account environmental factors, a comparison of ceramic glazes with the same amount of waste iron oxide was also performed for same purpose. As a result of the studies, it was observed that the addition of iron oxide and/or waste iron oxide did not have a negative effect, and coloring effects on the glaze layer were observed at different rates and firing temperatures.     

Zircon-free frits suitable for single fast-firing opaque wall tile glazes and their industrial productions

Wall tile glazes with a smooth surface texture, high glossiness, and whiteness are usually based on zirconium containing frits. However, these frits are quite expensive and therefore, there have recently been certain attempts to lower the production cost such as taking suitable glass–ceramic glaze systems into an account. With the present work, the frit-based glaze compositions belonging to the K₂O–MgO–CaO–ZnO–Al₂O₃–B₂O₃–SiO₂ glass–ceramic system were studied to prepare newly synthesized wall tile glazes for industrial single fast-firing. The design of a glass–ceramic glaze for this type of tiles should ensure that the selected frit precursor is technically and commercially compatible with the manufacturing conditions generally used in the production of glazed ceramic wall tiles. The aim of the study is to develop zircon-free, frit-based, glossy opaque glass–ceramic glazes for wall tiles by optimizing the CaO/MgO and adjusting the Al₂O₃/alkali ratios in the starting frit compositions. Frit production, glaze preparation, application, and single fast-firing of wall tiles were, first of all, conducted under laboratory working conditions and then, successful recipes were adapted to the relevant industry. The frit crystallization capability and crystallization temperature range were determined by differential thermal analysis (DTA). Thermal expansion coefficient values of glazes were determined by a dilatometer. Characterization of single fast-fired glass–ceramic glazes was made by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques. Colour and gloss analyses of the final glazes were measured with a spectrophotometer and a gloss meter, respectively.     

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.     

Preparation and characterization of glazes from combinations of different industrial wastes

The work reported here involves the preparation and characterization of ceramic glazes made from combinations of different industrial wastes. The wastes were float glass, granite and lime shale (a raw material waste from the oil shale industry in São Mateus do Sul, state of Paraná, Brazil), which were used to replace natural raw materials in a proportion of up to 50% in weight. The compositions were formulated using the Seger method and prepared by conventional ceramic processing. The stabilized suspensions were applied in commercial wall tile and porcelain stoneware tile, which were sintered at temperatures of 1080 °C and 1150 °C, respectively, using two different heating cycle. Three compositions were developed, two of which yielded opaque glazes and one a transparent glaze. Linear thermal expansion coefficients (α) of 80.10^?7 °C^?1 to 100.10^?7 °C^?1, and glaze softening temperatures of 600–700 °C were characterized by dilatometric analysis. The glaze compositions showed chemical resistance against acid and alkaline attack after 96 h, showing a mass loss of less than 0.1% in weight. The surface hardness of the glazes determined by the Mohs scale, Vickers microhardness and abrasion resistance (PEI indices) were between 6–7, 3–3.7 GPa and 3–4, respectively. These properties are compatible with those of commercial glazes for wall tiles and porcelain stoneware ceramics.     

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.     

Evaluation of solid wastes in the manufacture of ceramic tableware glazes

The recovery and reuse of industrial wastes are of great importance to the environment. Today, a large amount of waste is produced due to marble production, and it is extremely important to bring such wastes to the ceramic industry, to solve the pollution problem and to provide cost-efficient ceramic production. In this study, marble waste was used for ceramic earthenware glaze and body formulations. Marble waste was used in two different formulations as glaze and body. Chemical analysis, morphological features, crystallographic information of different formulations were made with XRF, SEM and XRD, respectively. When the hardness test results of the ceramic body and glazed samples were examined, the hardness values of the marble waste added samples increased by 1.9% compared to the standard samples. According to the results obtained, it has been seen that using marble waste in the ceramic industry is very important for both economic and environmental reasons.     

Compositional modifications to floor tile glazes opacified with zircon

Abstract

In the ceramic tile industry opaque glazes with considerable zircon content are widely used. However, the high cost of zircon limits its wide use in relevant glaze compositions. In the present study, a model opaque glaze was modified by changing the alumina/silica ratio, adding potassium oxide, or using a higher content of opaque frit while gradually eliminating the zircon content in the glaze batch. After glaze preparation, application, and single firing of glazed floor tiles under industrial conditions glazes were characterised by XRD, SEM, and EDX. The optimum alumina/silica ratio was found to be 0·26. Colour parameters L, a, and b of starting and final glazes showed that an increase in opaque frit content gives more positive improvement in opacity and in dry abrasion resistance than potassium oxide addition. Removal of zircon from the glazes resulted in a decrease of ～13–18% in glaze cost without detrimental effect on opacity.     

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.     

Floor tile glass-ceramic glaze for improvement of glaze surface properties

Simultaneous improvement of surface hardness and glossiness of floor tile glaze, without changing its firing temperature, was the main purpose of the present paper. Thus, various glazes in the system of CaO–MgO–SiO₂–Al₂O₃–ZrO₂ were prepared and their crystallization behaviors within a fast firing cycle were investigated. With increasing amounts of calcium and magnesium oxides to base glass, the optimum glass-ceramic glaze was obtained. The results showed that with increasing of CaO and MgO part weights in frit, the crystallization peak temperature was gradually decreased and the intensities of diopside and zirconium silicate were increased. The comparison of micro hardness for the optimum glass ceramic glaze derived in this work with a traditional one used in floor tile industries indicates an improvement of 21%. It was found that the glaze hardness not only depend on the amount and type of crystalline phases, but also on the residual glass composition. Furthermore, it was observed that the glaze micro hardness is only slightly affected by thermal expansion mismatch of body and glaze.     

Anorthite-based transparent glass-ceramic glaze for ceramic tiles: Preparation and crystallization mechanism

A series of high hardness anorthite-based transparent glass-ceramic glaze was successfully developed for ceramic tiles. These glazes were prepared by mixing a high-calcium frit (denoted as HCa) that can crystallize anorthite with other fluxes. The effect of HCa content on the crystalline phase, microstructure and properties of the glaze was studied. In addition, the phase transformation, microstructure evolution and crystallization kinetics of anorthite from frit glaze were investigated in detail. The results revealed that when the HCa content was 45–55 wt%, the glazes had excellent transparency with a hardness of 6.4–7.3 GPa, which was higher than conventional glazes. The XRD and SEM tests showed the crystallization of single-phase lamellar-shaped anorthite crystals up to 20–40 μm in length. Anorthite was found to crystallize directly from the frit glaze at 850 °C. The laminated anorthite was composed of thinner lamellae, and cracks were observed inside the large crystals. The activation energy of anorthite crystallization was about 420 kJ/mol, and the Avrami index (n) was 2.03?2.36. The n value indicates that the crystal is grown in two dimensions, which explains the formation of lamellar-shaped anorthite in SEM.     

An environmentally friendly process for preparing commercial ceramic foam composites based on frit/glass wastes

Considering the size of the amount of energy consumption in ovens during the production of gas ceramic foam materials in the ceramic industry, it can be stated that natural gas is one of the highest energy resources. Natural gas consumption during the production has been evaluated and financial analyses were made for saving consumption amounts. Raw materials and glass/frit wastes obtained from different regions were investigated and their chemical compositions were determined by X-Rays fluorescence spectrometry (XRF) analysis. Compared to their current alternatives, glass foams with homogenous structure and low density were developed by adding frit/glass wastes in the amount of 80%-90%. X-Ray diffraction (XRD) analysis has been conducted for mineralogical investigation of the samples. Also, to analyze the pore sizes and examine the surface morphology of foams, SEM images were obtained. With the addition of glass/frit wastes, natural gas consumption decreased (ca. 20%-25%) in firing process.     

陶瓷砖装饰用釉料——微晶玻璃釉

近年来，微晶玻璃材料引起众多行业的关注，主要原因在于其具有一些特殊的性能，如良好的耐腐蚀性能、机械强度高、表面硬度高、热膨胀系数低以及适应性强等特性。微晶玻璃铀应用陶瓷行业的变化是，传统的二次烧成工艺逐渐被—次快速烧成替代和传统的铀料配方有了很大的改变。     

Influence of viscosity and composition of alkali borosilicate lead-free frit on its reaction with hematite,and the color control of red overglaze enamels

Inspired by the ion diffusion at the interface between the red glaze and glaze layers, which was confirmed by the study of overglaze painting on porcelain test pieces, we developed frits with compositions in which a lime glaze was systematically added to a lead-free multicomponent alkali borosilicate glass frit. When the mixed powder of the frit and hematite was heat-treated, the excessive reaction with hematite was suppressed as the lime glaze content increased, due to the increase of the frit viscosity. The dissolution of hematite was suppressed in the sample with the same viscosity at a higher heat treatment temperature, i.e., with a higher lime glaze content, confirming that the composition of the frit strongly affects the dissolution of hematite. We attempted to improve the chroma of lime-glaze-added samples, and the highest chroma in this system was achieved by adjusting the amount of initial hematite and heat treatment temperature.     

Influence of firing temperature on the color developed by a (Zr,V)SiO4 pigmented opaque ceramic glaze

The analysis of the physical interactions between pigments, opacifiers and glazes is fundamental to understand the optical behavior of ceramic glazes. Furthermore is important to verify if the glaze devitrifies because the crystallized phases can contribute to the optical properties of the system. The size and the quantity of the formed crystals can change significantly the glaze color. The mean goal of this study was to evaluate the influence of firing temperature on the color stability of an opaque ceramic glaze colored by a blue vanadium–zircon pigment taking into account all the optical components. Quantitative X-ray diffraction analysis was conducted in order to evaluate the pigment dissolution at the three studied temperature and the quantity of the in situ formed zircon crystals from the used frit. The reported study demonstrated the importance to consider all the components in a multicomponent optical system as a ceramic glaze.     

EARTHENWARE BODIES AND GLAZES1

Effect of body composition on crazing .—-Six bodies of each of 2 standard clay compositions were prepared with variable clay and flint content and after biscuiting at cone 8 were glazed with 21 earthenware glazes and glost fired at cones 4 and 6. The results indicated that the variability of the silica content of clays would not be great enough to produce crazing in a well-balanced glaze. Effect of proportion and composition of frit .—-A standard whiteware glaze was compounded in 6 different ways and several other glazes in 2 ways. It was found that the method of compounding had no effect on crazing but it affected the gloss and fusibility. Increase in the percentage of material fritted increased the gloss and fusibility. With the same percentage of frit the best glost and highest fusibility were obtained when the flint and part of the clay were included in the frit. Effect of some variations in glaze composition .—-Substitution of CaO by Na₂O, pound for pound, as well as direct addition of Na₂O, increased crazing, improved gloss and increased the fusibility. Direct addition of feldspar increased crazing slightly and diminished gloss, but did not noticeably affect the fusibility. Substitution of 1½1/2 parts of feldspar for one part of flint to maintain the same fusibility increased crazing and diminished gloss. Direct addition of CaO improved gloss, increased fusibility and slightly reduced crazing.     

微晶玻璃釉的研究

用不同组成的微晶玻璃水淬料,施于陶瓷坯上经核化、晶化,同时完成烧成,而获得微晶玻璃釉层.其工艺制度可以结合DTA分析,通过实验来确定.微晶玻璃釉要和坯料相匹配:釉和坯的膨胀系数相近,微晶玻璃的晶化温度和坯的烧成温度要相一致.     

R2O-RO-Al2O3-SiO2-P2O5系分相/析晶乳浊釉乳浊粒子的形成机理

在普通石灰碱釉的基础上引入骨粉和滑石,形成R2O-RO-Al2O3-SiO2-P2O5系统釉料,通过调整釉料的化学组成获得分相/析晶乳浊釉.利用XRD,SEM,EDS等测试技术,研究了SiO2与P2O5和SiO2与MgO的摩尔比与釉层显微结构的关系,分析了乳浊粒子(玻璃液滴和微晶)的形成机理.     

R_20-RO-Al_2O_3-SiO_2-P_2O_5系分相／析晶乳浊釉乳浊粒子的形成机理

在普通石灰碱釉的基础上引入骨粉和滑石,形成R2O-RO-Al2O3-SiO2-P2O5系统釉料,通过调整釉料的化学组成获得分相／析晶乳浊釉。利用XRD,SEM,EDS等测试技术,研究了SiO2与P2O5和SiO2与MgO的摩尔比与釉层显微结构的关系,分析了乳浊粒子(玻璃液滴和微晶)的形成机理。     

Life cycle assessment of a ceramic glaze containing copper slags and its application on ceramic tile

Even though copper slags have many possible applications, their disposal is still practiced, creating long-term waste management problems. This led to the investigation of new products for residential applications, taking advantages of the interesting chemical properties of copper slag. This study aims to assess the environmental impact of the use of copper slag as secondary raw material in a ceramic glaze composition and to compare it with a traditional glaze. A manufacturing process was designed, through an industrial scale up operation from experimental laboratory data and the entire life cycle of the products was analyzed using the Life-cycle assessment (LCA) methodology. Considering the production of a ceramic glaze containing copper slag, the most impacting process resulted the one related to frit production, due to the large amount of thermal energy necessary for the raw materials melting. The comparative LCA analysis carried out between the frit obtained from metallurgical slags and a traditional one, demonstrated that the innovative ceramic frit has a greater environmental advantage. The LCA analysis allowed to highlight the most impactful stages of an industrial process using copper slag as a secondary raw material for glaze production and to quantify the potential environmental advantages of this operation.     

Utilization of seashells in matte glaze preparation

In this study, the investigation of the optical properties and microstructural development of matte glaze compositions prepared with the addition of seashells was aimed. The seashells obtained from Black Sea beaches of Samsun, Turkey were characterized using XRF, XRD, FTIR, TG-DTA techniques, and heating microscope. The calcite-aragonite polymorphic transition was provided by heat treatment of seashell powders at 700°C for 1 hour and then, aragonite-based seashell powders were incorporated to matte glaze compositions up to 30 wt%. Firstly, four different types of fired body specimens (red clay, chamotte, white, and porcelain) were produced at 800ºC for 7 hour. Secondly, the prepared glazes were applied on surface of all fired bodies and then, all bodies were sintered at 1100ºC for 8 hour. Finally, coloring parameters and microstructural features of seashell added glazes were determined. The addition of seashells to glaze composition by 10 and 20 wt% resulted in higher transparency. The matte glaze was formed with increment of seashell content to 30 wt%. The more reduced fluidity of the glaze caused nonhomogenous matte appearance. As a result, it is possible to produce transparent glazes in eco-friendly and cost-effective way by addition of seashells into glaze composition in 20 wt%.