Development of anorthite based white porcelain glaze without ZrSiO4 content

The aim of this study was to develop new compositions of white glazes without the addition of ZrSiO₄designed for sanitary products obtained in a 12-h firing cycles at a maximum temperature of 1230 °C.Alternative glazes with a good opacity and a high degree of whiteness were obtained, composed primarily of raw materials available on the domestic market in Poland. The opaque effect was achieved due to crystallisation of anorthite, which was identified as a major crystalline phase in the system. The glazes were characterised by a high whiteness value L*, greater than 90 in the CIELAB colour space, and a gloss, measured with a 60° light incident angle on the glaze surface, above 50%.The microstructure and structure of the glazes were measured with the use of a Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD). The colour and gloss of glazes were measured with the use of a spectrophotometer and a gloss metre at a 60° angle of incidence. The topography of glazes surfaces, as well as the roughness level (Ra), were measured with the use of a confocal microscope.     

EFFECT OF COMPOSITION ON PROPERTIES OF CONE 11 ZIRCONIUM SILICATE-OPACIFIED GLAZES *

Studies were made of the effects of magnesium, calcium, barium, strontium, and zinc oxides on the gloss, texture, and opacity of one-fire, zirconium silicate-opacified glazes at cone 11. The opacity was determined with a Hunter multipurpose reflectometer and the gloss was observed visually. Limits for the various fluxes were determined and a practical base glaze formula was developed.     

无锆乳浊釉的研制

本文以粘土、钾长石、石英、硅灰石、氧化锌、滑石、硼钙石等为原料,形成K2O-CaO-MgO-ZnO-B2O3-Al2O3-SiO2系统釉料,运用四角配料的方法进行配制,获得釉面平整、白度和光泽度高的无锆乳浊釉。采用XRD、SEM等测试手段,研究了该釉的微观结构和乳浊机理。     

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.     

Adjustment of Thermal Expansion of Cone 8 Glazes

Shivering of cone 8 zirconium-opacifled glazes for use on one-fire pyrophyllite wall tile and warping of the tile body were corrected by increasing the thermal expansion of the glazes. This was accomplished by (1) increasing the alkali content, (2) substituting strontium oxide for zinc oxide, (3) substituting calcium oxide for magnesium oxide, and (4) decreasing the silica-alumina ratio. The last method appeared to be the most effective. It is shown that the calculated coefficient of cubic thermal expansion is often unreliable as a value for the actual expansion. Expansions were obtained with a quartz-rod dilatometer.     

Red mud as a substitute coloring agent for the hematite pigment

Red mud (RM), a highly alkaline iron oxide rich sludge obtained during the production of alumina, was treated to work as a coloring agent for ceramic glazes. The approach aims the valorization of this residue, adding environmental and economic value. RM was sintered at different temperatures (1100 °C, 1150 °C, 1200 °C, 1250 °C, 1300 °C and 1350 °C) to assess changes in its mineralogical composition. The obtained powders were characterized by XRD, UV–Vis and CIELab. The samples were added to glazes (transparent, opaque and matte) and their color stability analyzed by CIELab. RM sintered at 1300 °C was compared with commercial hematite producing lower coloring power but yielding better color stability on glazes for temperatures of 1100 °C ± 15 °C, thus presenting RM_1300C as a suitable substitute for the hematite pigment.     

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.     

铁系金属釉的制备与研究

本文采用廉价的铁系氧化物,研究了过渡金属氧化物的组成、气氛、晶核剂等因素对釉面金属光泽的影响。通过铁系金属釉的配方设计和工艺控制的优化,得到了有金属光泽艺术效果的制品。     

铁系金属釉的制备与研究

采用廉价的铁系氧化物,研究了正交设计的过度金属氧化物组成、气氛、晶核剂等因素对釉面金属光泽的影响。通过铁系金属釉配方设计和工艺控制的优化,使制品具有金属光泽的艺术效果。     

PRACTICAL PRODUCTION OF ONE-FIRE LUSTER GLAZED POTTERY*

Various metals in small quantities, singly and in various combinations, were ground in lead and leadless glazes. It was found that various colored lusters, transparent and opaque, could be reproduced under a fair degree of control in an ordinary downdraft gas-fired sagger kiln, which was fired from cones 010 to 1. After cooling to a dull red heat, the glazes were given a short reduction firing. Standard decorative processes were used with the luster glazes. Additional colors were produced by adding stains and metal oxides. Acid-resistant luster glazes were developed.     

Color Fading of Underglaze Decalcomania

A study was made of some possible causes of color fading of underglaze decalcomania used in the commercial production of semivitreous dinnerware, While the quality of the decalcomania employed is of primary importance, ware losses due to color fading can be minimized by careful control of glost firing procedures, adjustment of glaze composition, and proper fritting practice. Cone 2 dinnerware glazes identical in chemical composition but different in constituency were found to have widely different characteristics toward underglaze colors. Best results were obtained when lead oxide was fritted and 10% or more whiting was left unfritted and added as a mill addition. Low-melting frits did not produce so good results as did the more refractory frits. Strontia, as a lead replacement, was effective in reducing color fading. Barium oxide also showed characteristics favorable to underglaze colors, but tin oxide, zinc oxide, and magnesia, even in small amounts, were decidedly harmful to most colors. When alumina and silica were varied and other oxides were kept constant, increases in alumina were decidedly unfavorable to most colors, resulting in extreme fading at the higher alumina contents. The effect of raising the silica content was generally favorable. For best results, glazes should be compounded to prevent the formation of low-temperature melts. Adjustment of glaze composition to increase viscosity and lower surface tension of the molten glaze is suggested as a method of minimizing glaze attack on color.     

CLAY SEWER PIPE MANUFACTURE.—IV. THE INFLUENCE OF DIFFERENT SALT GLAZING TEMPERATURES UPON THE COLOR AND GLOSS OF GLAZES OBTAINED ON CLAYS WITH VARYING SILICA,ALUMINA, AND IRON OXIDE CONTENTS1

Object .—A study was made of the effects of different salt glazing temperatures upon the color and brightness of salt glazes produced upon clays with varying silica, alumina, and iron oxide contents. Results .—In tests conducted in commercial kilns operating under normal conditions, it was found that increasing the salt glazing temperatures has a tendency to produce duller and darker glazes on clays containing iron oxide. The brightness of the glazes produced may be approximately represented by the following formula: -1.00×₁+ 0.376×₂ - (1.885 + 0.385(1.01253)^(T-1110))×₃= 100G ×₁, ×₂ and ×₃ represent the percentages of silica, alumina and iron oxide, respectively. T is the salt glazing temperature in °C. When G was greater than 0, the glazes were bright; when between -0.1337 and 0 they were semi matt; and when less than -0.1337 they were matt. The color obtained may be approximately represented by the following formula: 10.3x₁ - 2.65x₂+ (14.6 + 54.1 (1.0066)^(T-1110))x₃= 100°C When C was between 0 and 2, white to tan glazes were produced; when between 2 and 3.5, light brown glazes were obtained; when between 3.5 and 4.75, brown glazes were produced; when between 4.75 and 8.2, mahogany colors were obtained; and when above 8.2, dark brown to black glazes were produced. Clays containing a high iron oxide content should be salt glazed at low temperatures while clays containing a low iron oxide content should be glazed at high temperatures to produce the best glazes. Decreasing the iron oxide and alumina contents will improve the brightness of the salt glazes. High alumina clays will produce darker colors than high silica clays with the same percentage of iron oxide.     

Study on the phase-separated opaque glaze in ancient China from Qionglai kiln

Qionglai kiln is a famous folk kiln site in China. Six pieces of opaque green-glazed porcelain shards with mild gloss and jade-like feel fired in the Tang dynasty (618–907 A.D.), were adopted as test samples. The correlation among composition, microstructure, firing technique and glaze appearance has been investigated by means of energy-dispersive X-ray fluorescence, field emission electron microscopy, direct transmission electron microscopy, X-ray diffraction and refiring experiment. The study has demonstrated that the opaque green glazes from Qionglai kiln site are high-temperature calcia–magnesia–silicate glazes and typical of phase-separated glazes. The liquid–liquid immiscibility structure plays a key role for the artistic appearance of the glazes.     

影响低温釉性质因素的探讨

由予能源的短缺和环保的要求，陶瓷行业的低温釉正成为研究的热点。但是含铅的低温釉不但其研磨硬度较差．而且铅含量高影响环保，因此应开发兼顾节能、耐磨和环保性能的新型陶瓷低温釉。本文使用硼和锶为添加剂．成功地制备了无铅低温釉，对釉的性质进行了测试与分析。     

Effects of cobalt,copper, manganese and titanium oxide additions on the microstructures of zinc containing soft porcelain glazes

Different types of glazes, which are nearly all based upon silicate compositions, are used to meet a wide range of requirements in service. Many artistic effects are achieved by departing from a clear, smooth, transparent system. Coloured glazes are produced by several means such as the inclusion of colouring oxides, addition of stains, dispersing finely divided particles and the use of precious metals, applied in the form of lines or bands, or even screen-printed patterns. Colouring oxides commonly used include iron, copper, cobalt, chromium, manganese, nickel, vanadium, cadmium and selenium. Zinc oxide has a beneficial effect in many coloured glazes amongst which crystalline ones are more noteworthy. With this paper the effects of CoO, CuO, MnO₂ and TiO₂ additions into zinc oxide containing crystal glazes differentially heat-treated are described on micro-scale appearances. Experimental techniques used were X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDX).     

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.     

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.     

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.     

Formation and surface properties of electron-emissive coatings IV. DTA,ETA and dilatometry studies on some alkaline–earth hydroxides

The decomposition under vacuum of the hydroxides of calcium, strontium and barium was investigated by differential thermal analysis (DTA), electrothermal analysis (ETA) and dilatometry. The results suggest that the rate of sintering of calcium oxide is initially governed by the formation of a pseudo-hydroxide lattice; rapid sintering occurs only after conversion of this to the true oxide. Compacts of the oxides of strontium and barium show a remarkable resistance to sintering at temperatures up to 1000°. It is proposed that the sintering may have been inhibited by the presence of trace amounts of calcium oxide and strontium oxide formed by decomposition of impurities present in the samples of strontium and barium hydroxides, respectively.     

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.