Effect of the green porous texture on porcelain tile properties

Porcelain tile is a product characterised by low water absorption (usually less than 0.1%) and excellent mechanical properties. To enhance tile aesthetic qualities, much of the porcelain tile production is polished to provide a high-gloss surface finish, in which certain closed pores in the tile body become visible. This apparent porosity of the polished tile, which had been closed porosity before polishing, sometimes lowers the product's stain resistance.Test pieces were formed from a porcelain tile composition prepared under different milling conditions, pressing variables being kept constant, and the pore size distribution of these pieces was determined. The effect of the porous texture of the green pieces on the evolution of porosity during sintering and on the residual porosity of the densified body was analysed. It was verified that the porous texture of the fired piece was conditioned by the porosity and size of the largest pores in the green piece. The effect of residual porosity on stain resistance was determined by two cleaning methods. The presence of large pores in the green body, stemming from insufficient milling of the raw materials mixture, led to tiles with greater residual porosity and worse stain resistance.     

章村土提高电瓷绝缘子高温荷重性能的研究

在坯体配方中利用章村土部分替代长石,以提高电瓷坯体的高温粘度,增加坯体高温荷重,从而较好地解决百万伏特高压产品烧制过程中存在的吸红和拉裂掉头问题。     

Dependence of surface porosity on the polishing depth of porcelain stoneware tiles

Porcelain stoneware tile polishing is a process that adds value to ceramic tiles due to the high gloss achieved upon reducing surface roughness. However, surface polishing removes a fine layer of the product, revealing numerous “closed” pores initially located inside the material, which may compromise some of its properties such as stain resistance. The literature indicates a possible orientation of pores on surfaces parallel to that of the use of the product. Based on this hypothesis, the present work aimed to evaluate how the thickness of the layer removed by polishing acts upon the profile of exposed surface pores, and hence, on the stain resistance of the product. The results of this study are novel and reveal that the staining tendency of porcelain stoneware tile can be altered significantly by varying the conditions of the surface wear produced by polishing.     

Cleaner production of porcelain tile powders. Fired compact properties

A new ceramic powder preparation process, the droplet-powder granulation process (DPGP), was recently proposed for the cleaner production of ceramic tiles. The DPGP granules and resulting pressed compacts were characterized and compared with the granules and compacts obtained by spray-drying (SD) and dry granulation (G) processes in a previous paper. The results showed the feasibility of using the DPGP in the pre-firing stage of porcelain tile manufacture.This study compares the firing behaviour and fired properties of compacts pressed from three different types of granulated powders: DPGP, SD, and G and from a non-granulated powder (NG) obtained by dry milling. The evolution of compact microstructure (porosity and pore size distribution) with firing temperature was monitored and the fired compact properties (bulk density, water absorption, and stain resistance) were determined.The study shows that the DPGP improved the sintering behaviour and final properties of the resulting porcelain tiles with respect to those obtained by the G process. However, the fired compacts prepared from the DPGP powder exhibited a higher porosity and pore size compared with those of the compacts obtained from the SD granules at the same pressing pressure. The results obtained open up the possibility of manufacturing glazed porcelain tiles with a more eco-friendly process. However, the results also indicate that polished porcelain tile manufacture by the DPGP requires further research in order to improve granule characteristics, in particular green granule deformability, which is the critical factor in porcelain tile densification and vitrification during firing.     

Porcelain tile microstructure: Implications for polished tile properties

The present study was undertaken to determine the influence of sintered porcelain tile microstructure on mechanical properties (fracture strength, modulus of elasticity and fracture toughness) and surface properties (gloss and stain resistance). To obtain sintered specimens with different microstructures the peak firing temperature was varied for bodies made with industrial spray-dried powder, and sets of test compositions were also made in which quartz content and quartz particle size were varied.Liquid-phase sintering is the typical densification mechanism involved in the achievement of minimum porosity, which is characterised by isolated round pores. Bloating occurred above the firing temperature for minimum porosity. Increases in quartz content and quartz particle size in the starting composition led to reduced body sinterability, and thus gave rise to higher porosity in the fired tile.Mechanical properties were adversely affected by an increase in fired tile porosity. For the same variation in porosity, mechanical properties were more sensitive to the change in quartz content than to changes in particle size. No toughening effect was observed with a rise in quartz content or a decrease in particle size: mechanical properties depended primarily on sintered specimen porosity.Gloss and stain resistance (which characterise polished surface quality) varied with surface porosity, both showing the highest values for lowest porosity. The relationship between porosity and gloss was close to linear.     

The role of viscosity on microstructure development and stain resistance in porcelain stoneware tiles

Effect of composition on viscosity of porcelain stoneware tiles and role of the viscosity on microstructure development and stain resistance in porcelain stoneware tiles were investigated. The viscosity of the tiles was successfully measured by a thermomechanical analyzer. Na₂O/K₂O ratio was used as a parameter to change the viscosity. As the Na₂O/K₂O ratio increases, the viscosity decreases. This reduction in the viscosity results in improvement of microstructure (i.e., spherical pore morphology and reduced closed porosity) and usually increases the stain resistance significantly. However, too low viscosity may also cause deformation of the tile during production. Therefore, the viscosity of the tiles should be carefully controlled and it should lie between a lower limit (in this study this value is between 10^7.93 and ～10^8.35 P) and an upper limit (in this study this value is 10^8.67 P) to achieve high stain resistant porcelain tiles with no deformation.     

Enhancement of hybrid sol–gel coating and industrial application on polished porcelain stoneware tiles and investigation of the performance

The aim of this study was to improve stain resistance and cleanability of polished porcelain tiles by sealing the micro-pores on the tile surface with hybrid sol–gel solution. For this purpose, solutions of a hybrid system based on sol–gel technology were prepared. The obtained solution were applied to polished unglazed tiles and subsequently spread with soft tissue thereon. To achieve complete sealing, both organic and inorganic particles of different sizes were mixed with obtained sol–gel hybrid systems. Coated surfaces were investigated by means of a scanning electron microscope. The stain resistance and the cleanability of the tile surface were tested according to ISO-10545-2014 standard. It has been shown that prepared sealing material permanently prevents formation of stains such as olive oil, green staining paste, iodine solution on the surface of polished porcelain tiles. The remains of stains on the surface can easily be removed from it with a cleaning agent.     

Influence of body composition on the technological properties and mineralogy of stoneware: A DOE and mineralogical-microstructural study

This paper reports a systematic and comprehensive investigation of the effects of the starting mixture composition on the mineralogy and properties of porcelain stoneware tiles using mixture design and full quantitative phase analyses by the Rietveld method. Functional relationships between properties and the raw material mixture proportions were obtained and related to the mineralogical composition of the fired product. Mullite crystallisation depended on the chemical environment. Dissolved quartz mounted to 10 wt% of the dry body regardless on initial amount, indicating saturation of the surrounding melt. The paramount role of the amorphous content on the stoneware properties was disclosed quantitatively. Open porosity decreased with increasing amount of amorphous content, and consequently both the stain and wear resistance increased. The CIE-Lab colour parameters a* and b* increased with increased amorphous content due to interaction with surface iron in hematite. The mullite content increased wear resistance, thus supporting the mullite strengthening theory.     

Effect of spray-dried powder granulometry on the porous microstructure of polished porcelain tile

The low porosity of porcelain tile is the result of strict control of the material's processing conditions (milling of raw materials, compaction and sintering) and the characteristics of the raw materials used in its formulation (formation of liquid phases). Sealed pores remaining after the manufacturing process are revealed at the surface after polishing and are the main factor responsible for staining the product. The porous microstructure of the sintered material depends on the characteristics of the porous microstructure of the green compact and on how the densification process evolves during sintering. The present work evaluated how the size distribution of spray-dried granules acts upon the porous microstructure of green compacts and of polished porcelain tile. The results revealed that minor adjustments in the granulometric distribution curve can reduce the visibility of stains on the polished surface, thus improving this property.     

Evaluation of durability and cleanability performances of protective treatments for lapped ceramic tiles—Part 1

The aim of this work was to evaluate the durability, in real pedestrian traffic condition, of lapped porcelain stonewares with surface protective treatments able to fill up pores opened by the lapping process. In recent years, the durability of ceramic surfaces has become a key factor during the design process. The knowledge of the material durability is important to define the behavior of tiles in use. Standard procedures for indirectly assessing durability are already available (ie, abrasion tests, staining resistance, chemical resistance), however, a standard method of aging in real condition is still lacking. In this study, a durability test was performed in real pedestrian traffic condition by fixing tiles on floors to evaluate the surface characteristics after 6 and 12 months. The surface characteristics were analyzed before and after the durability tests and in terms of microstructural observations and determination of surface porosity. In particular a durability index has been estimated as ratio of pores filled by dirtiness respect to the original surface porosity (before aging). Results of durability index showed good correlation between aging duration and kind of treatments (industrially applied and/or manually applied).     

The effect of particle size of body components on the processing parameters of semi transparent porcelain

The effect of the particle size of quartz and K- feldspar on the sintering behaviour and technical properties of semi transparent porcelain were investigated. This study was implemented by “the Factorial Experimental Design Method” to determine the effect of factors on semi vitreous porcelain production. The sintering behaviour of the samples were examined by using an optical dilatometer. The phases and their respective amounts in the microstructure were determined by way of Rietvelt X- ray diffraction (XRD) technique. Furthermore, the values such as shrinkage, water absorption, bulk density, porosity, thermal expansion, light transmission measurements were taken on the samples and the microstructures were studied by SEM. It was observed that as the particle size of quartz and K- feldspar decreased; the viscosity of the liquid phase fell down, the relative amount of secondary mullite crystals increased and the large pores were removed among the particles and the densification rate increased. Data were analysed by Minitab 13.20 software, and assessed in relation to the amount of glassy phase and its viscosity. The effect of K- feldspar particle size on the densification of porcelain is less than the change of heat treatment and quartz particle size.     

Quartz particle size and cooling rate effects on microstructural defects and mechanical properties of feldspar-based ceramic materials

Reinforcement or microstructural damage? What effect do quartz particles have on a feldspar-based ceramic material? To answer this question, this study investigates the impact of different cooling conditions on the generation of microstructural defects in a sodium feldspar matrix caused by quartz particles. Moreover, the study aims to analyze how these defects influence the mechanical properties of the final product. Therefore, high-purity sodium feldspar and varying-sized quartz particles were used. The materials was sintered and subjected to different cooling rates during the quartz allotropic transition (). The results showed that the addiction of coarse quartz particles significantly reduced the mechanical properties of the ceramic composition. Cooling types only had a noticeable impact when a material with a high percentage of coarse quartz was rapidly cooled during the quartz allotropic transition. In summary, no evidence of microstructural reinforcement was found when adding quartz particles to a sodium feldspar matrix.     

Model development for the description of silica particles dispersion in silicone polymer

In order to improve the mechanical characteristics of silicone polymer, silica particulate filler can be dispersed in the continuous phase. During the dispersion process, silicone is adsorbed on the particle surfaces, and at the same time, the particles are submitted to breakage and erosion phenomena, modifying therefore their particle size distribution (PSD). A numerical tool, that can simulate the evolution of the silica PSD in polydimethylsiloxane (PDMS) during dispersion, and allows an a priori knowledge of the evolution of the suspension properties, is developed. The comparison between experimental and calculated PSD as well as process viscosity values is presented.The advantage of such a modelization lies in the prediction of the final product properties, or in the design and optimization of a process for obtaining a desired product. This approach also shows the effect of the particle porosity on the product characteristics evolution during the dispersion process. The influence of parameters such as the filler quantity, the stirring speed or the number of silanols sites on the silica surface is also investigated.     

Evolution with Temperature of Crystalline and Amorphous Phases in Porcelain Stoneware

Porcelain stoneware tile is a ceramic building material characterized by high technological properties, especially regarding water absorption, chemical and frost resistance, bending strength and abrasion resistance. Because mineralogy is one of the main factors affecting the mechanical properties of porcelain stoneware, a complete determination and quantification of the mineral and amorphous phases is of special importance in the study of porcelain stoneware tiles. In the present work, a reference industrial composition (50% kaolinitic clay, 40% feldspar, and 10% quartz) of porcelain stoneware tiles fired at different temperatures (400°–1400°C) was characterized by X-ray powder diffraction combined with quantitative full-phase analysis using the Rietveld method, including amorphous content. The green composition contained albite, microcline, and muscovite as fluxing agents, which start to decompose at low temperatures (400°–800°C range) and are completely dissolved above 1200°C. The mullite phase is formed from 1100° to 1230°C and at the latter temperature, quartz particles start to dissolve. Studies of mineralogical evolution have revealed that the high heating rate (45°–50°C/min) required in ceramic tile manufacture leads to significant differences in comparisons with whiteware ceramics fired at a lower heating rate (10°C/min). Thus, the formation of mullite in porcelain stoneware occurs at higher temperatures (1100°C) whereas the transformation of β-quartz to β-cristobalite does not take place. The experimental results of this study show that qualitative mineralogical analysis, based on the intensity of a particular diffraction peak for each crystalline phase, is a suitable methodology to obtain preliminary knowledge of mineralogical changes with temperature.     

Effect of soda-lime glass on sintering and technological properties of porcelain stoneware tiles

The feasibility of waste glass recycling in ceramic tile production was assessed with special reference to fully vitrified products (porcelain stoneware). Soda-lime float or container glass was introduced, in replacement of sodic feldspar, in typical porcelain stoneware bodies (up to 10 wt.%) that underwent a laboratory simulation of tilemaking process, with a technological and compositional characterization of both fired and unfired tiles. Soda-lime glass had no significant effect on semi-finished products, but it influenced remarkably the firing behaviour, increasing shrinkage and closed porosity, decreasing open porosity and bulk density, and lowering mechanical and tribological performances. Waste glass promotes a more effective melting of quartz and a partial dissolution of mullite, leading to a more abundant and less viscous liquid phase, which accelerates the sintering kinetics. In conclusion, soda-lime glass can be used in small amounts (5% or less) with tolerable modifications of technological behaviour and performances of porcelain stoneware tiles.     

Reusing sanitaryware waste products in glazed porcelain tile production

Reusing the waste products generated in ceramic manufacturing is an environmentally responsible and sustainable approach. This study aims to protect natural resources, minimise raw material costs and manage waste-generated pollution by reusing the vitrified sanitaryware waste (VSW) products from Canakkale Kalebodur Seramik San. A. S. Six sample formulations were prepared under industrial conditions and compared with a standard tile body. The results indicated that using VSW in place of feldspar results in an increased firing shrinkage and decreased bending strength, whereas using VSW in place of pegmatite results in an increased bending strength and reduced thermal expansion coefficients. The reduction in the thermal expansion coefficients is an important finding that aids in meeting the dimensional and deformation requirements of porcelain tiles and also results in a slight lightening of the tile colour. This study shows that the fired VSW products can be used in glazed porcelain tile production as a sustainable and technologically, economically and environmentally suitable approach.     

用鄂东原料研制仿石砖

仿石砖是表面凸凹不平,酷似天然石材的瓷质外墙砖。用鄂东当地开采的风化长石、瓷石、瓷砂、瓷土等为原料,控制恰当的生产工艺,可制备具有良好性能的一次快烧仿石砖。     

USE OF SODA FELDSPAR IN WHITEWARE BODIES *

A comparative study is presented of a soda feldspar produced by a flotation process and of two potash feldspars when tested alone and made up in semivitreous and vitreous bodies. The investigation was divided into two parts, (1) a laboratory study and (2) plant trials on semivitreous dinnerware and on vitreous sanitary porcelain. From the results of the investigation, it was concluded that (1) it should be possible to substitute soda feldspar for North Carolina potash feldspar in semivitreous bodies containing not more than 12% feldspar, on an equal basis, with no significant change in properties except possibly crazing resistance; where crazing occurs, a slight modification of the regular glaze to give it a lower thermal expansion should correct the trouble; the formula of one modified glaze for this purpose is suggested; and (2) the substitution of soda feldspar for potash feldspar in sanitary porcelain and other similar vitreous whiteware bodies will doubtless require a reduction in amount in order to duplicate the vitrification and other properties of the potash-feldspar body in use; a modification of the regular glaze to fit the soda-feldspar body will probably be required; and the castability and control of casting slips should not be affected by the use of soda feldspar in place of potash feldspar.     

氧化铝含量对环保型轻质材料性能的影响

本文以陶瓷抛光废料为主要原料,辅以长石、球土、石英等,制备环保型轻质材料.在此基础上,利用XRD、体式显微镜、导热仪等详细研究了氧化铝含量对试样体积密度、抗压强度、物相组成、导热系数等性能的影响.研究结果表明:随氧化铝含量的增多,试样的体积密度、抗压强度逐渐增大,且导热系数随体积密度的增大呈线性增大.此外,少量的氧化铝有助于试样内堇青石相的生成,但过多的氧化铝导致堇青石峰强度减弱,并伴有少量的刚玉相和莫来石相出现.     

瓷石尾砂工艺玻璃制品的研制

在对瓷石尾砂工艺矿物特性研究的基础上,以瓷石尾砂为主要原料,取代石英砂和长石等原料,加以通用的玻璃辅助原料,成功地研制出透明和彩色尾砂工艺玻璃制品.配料中尾砂用量大,熔融温度低,成形性能好,成本低.研究结果表明,瓷石尾砂在玻璃工业中有着广阔的开发应用前景.