Porcelain Stoneware Research Articles

Role of iron-rich clays on sintering of porcelain stoneware tiles

Porcelain stoneware traditionally contains low Fe2O3 (<1 wt%), limiting research on iron's effects beyond coloration to date. However, recent changes in the supply chain induced a shift towards resource efficiency and circular economy, which led to body formulations with Fe2O3 up to 2.5 wt%. This study investigates the impact of iron-rich clays on the firing behaviour of porcelain stoneware, focusing on sintering processes, Fe speciation, and physical properties of the vitreous phase. Results show that red clays influence vitrification paths and maximum densification temperature, as well as composition and properties of the melt. This occurs not only because the relatively high iron percentage (up to 1.7 wt%), but for a set of factors, like the overall mineralogical and chemical composition of batches. Iron turns to be crucial for the stability of ceramic bodies at high temperatures, since Fe3+ can partially reduce to Fe2+, releasing gases and contributing to bloating phenomena.

Characterization and processing of kaolin from southern Brazil for potential strategic application in the porcelain stoneware tiles manufacturing

The ceramic industry in the productive hub of Santa Catarina needs some raw materials with specific characteristics such as kaolin to manufacture its products. This clay mineral with a naturally variable chemical composition in relation to its geolocation (in extraction area composed by rock and combined with sediment materials), attributes significant increases in transport costs due to its distance from the main productive areas in southern Brazil. Thus, as a strategic alternative, the improvement of kaolin with a high quartz content (69.9%) from the northern region of the state of Santa Catarina (∼400 km from ceramic hub in the south of the state), more precisely from the municipality of Garuva, was sought. Unit processing operations by classifying this mineral for suitability for use in industry, resulted in an increase in the concentration of kaolinite. The results indicated that the proposed method reduced the amount of quartz and consequently increased the kaolinite content, resulting in an aluminum oxide content of approximately 28.20%, a value higher than the normal natural content of ∼19%.

Influence of variable valence metal oxides on physico-chemical and antibacterial properties of semi-coated glazes

The paper presents the results of studies on the production of semi-coated glazes with antibacterial activity by introducing variable valence oxides CeO2, WO3, Bi2O3, Fe2O3, MnO2 and MoO3 into their composition. The raw polycomponent compositions were comprised of aluminosilicate multi-calcium glass frit, dolomite powder, feldspar, alumina, quartz sand, wet-enriched kaolin and refractory clay. The coatings were obtained by single firing on a ceramic-based porcelain stoneware at a temperature of 1 200 ± 5 °C in a high-speed mode for 60 ± 2 minutes. The study focused on the processes of glaze formation of coatings and the influence of the components of glaze charges on decorative and aesthetic characteristics of coatings (color, texture, gloss and whiteness). Parameters of physical and chemical properties were determined in accordance with the existing specification for the products, i. e. temperature coefficient of linear expansion, heat resistance, chemical resistance, microhardness, frost resistance, wear resistance, etc. Antibacterial activity of the coatings towards Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 6538 test strains was studied.

Residues from beneficiation of granite in porcelain stoneware: Effects on technological properties

Granite extraction waste represents an interesting alternative material for porcelain stoneware production, but information on its influence presents several gaps. For this reason, two different wastes were selected: a coarser iron-rich material from magnetic separation and a finer one from conveyance and abatement systems. Both were physically and chemically characterized. Batches were formulated by partial substitution of feldspar and technological behaviour of bodies was assessed by simulating the industrial manufacture at laboratory scale. Tiles were shaped by uniaxial pressure and fired by fast firing in electric roller kiln. The effect of waste addition was evaluated during the whole production process. Fired samples were characterized in terms of technological properties, mineralogical composition and microstructure evolution. The formulation optimization reduces firing temperature getting commercial technological constraints. A further increase of finer waste content affects compaction and mechanical strength. The presence of micaceous particles after the firing process may act as cracks initiation.

Content of crystalline silica phases in porcelain stoneware

Kitchen and bathroom countertop is a demanding application, where high aesthetic standards must combine with durability, ease of maintenance, and resistance to heat, stain, scratch and chipping. The hard materials and composites used for high-end countertops usually contain crystalline silica phases that can be inhaled by workers during drilling and cutting operations. The occurrence of silicosis and other respiratory diseases in machining workers makes it important to know exactly how much crystalline silica is present in countertop materials. This paper collects over 300 quantitative determinations of quartz and cristobalite in porcelain stoneware products and compare these contents with other countertop materials. The sum of crystalline silica phases in porcelain stoneware is on average 21 ± 5 % by weight (mostly quartz). This content is lower than granite (∼30 %) and much lower than engineered stone (∼90 %). Possible ways to reduce the amount of crystalline silica phases in ceramic slabs are overviewed and critically discussed.

Phenomenological model of moisture redistribution in porcelain stoneware spray-dried powder stored in silo

Porcelain stoneware powder requires at least 24 h of silo storage to stabilize temperature and moisture content after spray-drying. Homogeneity is crucial to produce dimensionally stable tiles. The objective was to model moisture redistribution in granules of different sizes using phenomenological formulation. An original multiscale approach incorporated segregation into the coupled mass/heat transfer equations. Finite element method numerically solved and accurately estimated moisture content in fines, intermediate, and coarse granules in accordance with industrial data. The starting moisture content difference of 3.19% between coarse and fine granules was reduced to 1.62% and 0.88% for 24 h and 48 h storage times, respectively. Output temperature estimates agreed with measurements (maximum error of 17%). Higher thermal gradients evidenced the cooling effect as moisture content increased in all granules at the wall, observed as condensed water in the actual system. This model could be applied to any material in storage within a center-filled silo.

Using of wastes from the enrichment of quartz-feldspar raw materials in the production of porcelain stoneware

Using of wastes from the enrichment of quartz-feldspar raw materials in the production of porcelain stoneware

Enhanced Skorohod–Olevsky viscous model incorporating microstructure evolution for finite element analysis of ceramic sintering

Skorohod and Olevsky’s constitutive relation for viscous sintering (SOVS) is employed to simulate the shrinkage and relative density evolution of ceramics during the sintering process. While this model effectively simulates shrinkage and density evolution, the original formulation of the SOVS model does not explicitly incorporate grain growth or microstructural evolution. This paper introduces an enhanced version of the SOVS model, incorporating a novel calibration method to obtain the temperature dependence of the viscosity parameter. It considers grain growth as well as the evolution of the microstructure by adding new parameters. Simulations were conducted using Code_Aster, an open-source finite element software, in conjunction with MFront, a tool for formulating material behaviour equations. Dilatometer tests were performed with probes of porcelain stoneware composition to calibrate the model. The predictions of dimensional shrinkage and relative density evolution showed a high accuracy of the model (>95%), enabling its use in the manufacturing process.

Comparative life cycle analysis between commercial porcelain stoneware and new ones designed by using volcanic scraps

To achieve carbon neutrality by 2050, many companies have started implementing sustainability policies. The aim of this work, as result of collaboration between Universities and companies, is to assess the environmental impacts associated with the production of alternative formulations of porcelain stoneware. The proposed formulations contain extraction scraps and chamotte and have promising technological properties. A comparative analysis of the life cycle in three different scenarios was carried out to assess the environmental footprint of the final products. The analyzed scenarios were a glazed porcelain stoneware (which was taken as a reference and is commercially available), a porcelain stoneware containing pumice scraps, and one containing volcanic lapillus scraps. It was observed that the transportation of raw materials has the largest environmental impact, followed by the production and extraction of the raw materials themselves. From the performed analysis, it was possible to observe that by replacing the currently used materials by the ones hereby studied, environmental benefits can be obtained. In particular, depending on the considered pollutant, the environmental impact can be reduced between a minimum of about 8 % (Freshwater Aquatic Ecotoxicity category) to a maximum of 48 % (Acidification category). In a time when raw materials supply is difficult, the use of scraps, which would otherwise be disposed of, is particularly interesting and can lead to the production of an environmentally friendly product.

Effect of milling and compaction on sintering of porcelain stoneware tiles

The present study aims to provide a deeper understanding of how different particle size distributions and degrees of powder compaction affect the densification process of porcelain stoneware tiles. For this purpose, three different batches underwent a laboratory simulation of the industrial tilemaking process, at growing grinding time or increasing forming pressure, with technological characterization of both unfired and fired products. Sintering behaviour was determined by hot-stage microscopy. Phase composition was determined by XRD-Rietveld allowing the estimation of the chemical composition and physical properties of the liquid phase. The results illustrate the impact of too fine (or too coarse) grain size on powder compaction, firing shrinkage, water absorption, efficiency of densification, sintering rate, stability at high temperature, and risk of anticipated overfiring (and similarly for too high or too low forming pressure). Simultaneous variation of particle size and forming pressure beyond usual standards induced changes in technological behaviour that in most cases compensate each other. Phase composition is moderately influenced by particle size and little by powder compaction. The vitreous phase mainly suffered from a decreasing degree of polymerization as the particle size became finer or the dry bulk density decreased. In case of insufficient grinding, too much residual feldspars caused improper composition and properties of the glassy phase, which resulted in lower efficiency of densification and slower sintering rate. Both the sintering kinetics and degree of densification depend on the timescale, i.e. the ratio of surface tension to viscosity (melt) and median particle size. Nevertheless, a low powder compaction can trigger a microstructural effect on sintering (improving both densification rate and efficiency) that may outweigh the timescale effect.

Frit-Free solar reflective porcelain stoneware ceramic tiles using recycled granite Waste: An investigation on its engobe and glaze formulations

The design of tiles can accelerate the transition of urban environments towards sustainability when building materials are prepared with sustainable, indigenous, renewable or recycled resources and additionally, present solar reflective properties for mitigating the Urban Heat Island (UHI) phenomenon. Here, an innovative approach to develop frit-free ceramics having solar reflectance property using locally sourced recycled granite waste was explored. The investigation unfolds in three parts: (i), the formulations were tailored for the engobe or glaze by varying raw material proportions; (ii), the solar reflectance was improved using whitening agents; and (iii), the selected formulations were subjected to an industrial trial casting of porcelain stoneware tiles. The full replacement of nepheline and feldspar with recycled granite powder offered properties suitable for the engobe such as a matte surface with high roughness and low gloss, while the same was identified to be less suitable in the glaze. The glaze formulation without any industrial frits was achieved by altering the proportions of nepheline and feldspar in the matrix. The solar reflectance of the engobe was enhanced by adding 10% of fine-grained zircon. The industrial trial showed that the developed formulation retained its conventional characteristics and superior functional performance in stain and chemical resistance.

Оценка скорости старения битумного вяжущего в асфальтобетонах на основе отхода производства керамогранита

The results of studies on the design of the composition of asphalt concrete mixture B1 and the physical and mechanical properties of asphalt concrete when replacing its finely crushed mineral part with waste from the production of porcelain stoneware are presented. A method has been proposed for assessing the aging rate of bitumen binder when using technogenic material, which consists of testing the strength of asphalt concrete and extracted organic binder after heating at a temperature of 160 ºC for 1 to 7 hours, which allows us to evaluate the possibility of obtaining asphalt concrete with increased performance properties, in particular in as a result of using porcelain stoneware production waste as a fine aggregate.

Porcelain Stoneware Tiles Based on Clays Mixture and Recycled Waste Glass Powder: Effect of Soaking Time

The effect of soaking time on the properties of porcelain stoneware tiles based on clay mixture and recycled waste glass powder was studied. Mixture was prepared and fired at 1150°C. During firing, raw mixture was subjected to various soaking times: 30, 60, 90 and 120 min. The by-products were characterized by their linear shrinkage, water absorption, bulk density, flexural strength, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results were modelled by using different mathematical expressions. The results demonstrated that physico-mechanical properties of ceramic probe are significantly affected by soaking time. After 30 min, products satisfied the ISO 13006 standard condition for porcelain stoneware wall and floor tiles: water absorption value was lowest (0.07%) and mechanical strength value was 44.4 MPa. Prolonged soaking time was undesirable due to its negative effect (bloating) on the products’ physical and mechanical performance. The XRD patterns indicated the presence of mullite, cristobalite, enstatite, anorthite, hematite and quartz as the main crystalline phases. SEM images of the tiles fired at 1150°C for 30 min display a very close texture and dense microstructure.

ОПРЕДЕЛЕНИЕ ВЗАИМОСВЯЗИ СВОЙСТВ ВЫСОКОПРОЧНЫХ КЕРАМИЧЕСКИХ ИЗДЕЛИЙ С МИКРОСТРУКТУРОЙ И ФАЗОВЫМ СОСТАВОМ

The article investigates interconnection of high physical and mechanical characteristics of highstrength building ceramics and phase composition of ceramic shard. The authors identify phase composition and microstructure of clinker brick and porcelain stoneware samples by powder X-ray diffraction and using a scanning electron microscope. The shard structure affects many properties of products, including strength, water absorption, frost resistance, etc. The article considers components of building ceramics microstructure, which give high physical and mechanical characteristics to product. High physical and mechanical properties of clinker bricks are achieved due to the content of needle-shaped mullite. The microstructure of clinker bricks is represented by fused quartz grains and mullite crystals with glass interlayers between them. In porcelain stoneware, fine-crystalline mullite is distributed in the X-ray amorphous phase. Porcelain stoneware has a welldeveloped X-ray amorphous phase due to intensive liquid-phase sintering. In samples of high-strength building ceramics the study establishes leucite crystals formation, having reinforcing effect on structure of a ceramic shard.

Fired electrical porcelain scrap (chamotte waste) recycling and reuse as an alternative raw material for sustainable porcelain stoneware production

The development of new sustainable ceramic formulations that incorporate industrial waste is a practice that meets the efficiency and sustainability criteria that today's society demands for an industry with high energy and non-renewable mineral sources consumption. In this research, fired electrical porcelain scrap (chamotte waste) was recycled and reused in the porcelain stoneware manufacture, partially replacing the quartz and feldspar from the triaxial system at 5, 10, 15, 20, and 30 wt%. The experimental samples were obtained after uniaxial pressing of ceramic mixture powders at 30 MPa and firing at 1260 °C following a fast-firing process (90 min cold to cold). The technological properties were studied by bulk density, apparent porosity, linear shrinkage, water absorption, cold crushing strength, and Vickers microhardness. The microstructural aspects and the amount of crystalline and amorphous phases in the ceramic bodies were analyzed by scanning electron microscope and X-ray diffraction, respectively. The best technical characteristics were achieved with the incorporation of 15 wt% of chamotte in the new ceramic formulations, yielding a density value of 2.41 g/cm3, and percentages of linear shrinkage and water absorption of 11.2 and 0.08 %, respectively, as well as mechanical resistance of 314.94 MPa and microhardness of 7.07 GPa. The mechanical resistance achieved by the experimental sample containing 15 wt% of chamotte waste means six times the value obtained by the control sample (0 wt% of chamotte addition) and was attributed to a higher mullite phase content and well-dispersed crystals (primary and secondary mullite) in the ceramic body. The results suggest and advance in the design and development of a best-performance porcelain stoneware materials elaborated by a sustainable and ecological route.

Technological prospects of domestic alkaline metasomatites using in the production of technical porcelain stoneware

Achieving the highest degree of sintering of porcelain stoneware (W &lt; 0.5%) is the main condition of obtaining high­quality products with high resistance to the simultaneous action of mechanical and abrasive loads, aggressive reagents and sign­changing temperature fluctuations. The main impact in this case is dependent upon quartz­feldspathic natural material. Unfortunately, domestic Ukraine’s deposits of feldspathes are almost exhausted, while the impact of alternative fluxes is not researched on the level of technological practice. For the stable functioning of domestic industry in the market economy it is crucial to expand raw materials base and solve energy­saving problems. To solve the mentioned issues, it is required to find alternative fluxing materials, which should ensure the highest degree of sintering, and therefore complex high operational product properties, in conditions of energy­saving quick sintering of technical porcelain stoneware.&#x0D; This study justifies the forecast estimate methodology of quartz­feldspathic materials’ usage efficiency taking into the account products’ sintering conditions. A set of theoretical and experimental studies was carried out, the results of which helped to determine the usage expediency of a range of domestic alkaline metasomatites in the production of technical porcelain stoneware tiles. The used approach to predicting the behavior of alternative raw materials made it possible to obtain data on their technological properties, in particular the characteristics of the melts formed under conditions of high­speed products firing at a temperature of 1200 °C: η = 102.05 ÷ 3.07 Pa·s, s = 0.304 ÷ 314 mN/m. The results of theoretical and experimental studies of the chemical­mineral composition and properties of six different occurrences of alkaline metasomatic rocks indicate the advisability of their use as an alternative to albite concentrates imported from Turkey. Obtained new data allowed to outline the transition ways from costly feldspathic concentrates to domestic substitutes, thus allowing to eliminate of import dependence of domestic producers of porcelain stoneware tiles and large format slabs.

Optimizing raw material composition to increase sustainability in porcelain tile production: A simulation‐based approach

AbstractReducing the environmental impact of porcelain tile production while maintaining cost‐effectiveness is challenging. This work introduced a novel modeling approach for optimizing a standard composition range comprising kaolinite (15–38 wt.%), illite (0–20 wt.%), quartz (20–40 wt.%), and feldspar (20–45 wt.%) to establish a robust composition interval for porcelain stoneware tiles. The proposed study considers several factors, such as composition impact on the manufacturing sequence, production costs, and CO2 emission. A flowsheet simulation database was generated by coupling the Dyssol framework with MATLAB. This study investigated the influence of raw material composition within the process sequence, the total CO2 emissions, and production costs within the contexts of Spain and Brazil, two of the top five global producers. Granules with a higher proportion of talc and illite exhibit reduced moisture content after spray drying, and these combinations have lower green body porosity after compaction. The addition of talc allowed for decreased porosity content after compaction reduced firing temperature, and lowered costs and CO2 emissions despite the higher prices associated with talc. The proposed simulation methodology offers a powerful decision‐making tool for optimizing raw material composition to minimize cost and CO2 emissions in the porcelain tile production. This methodology represents an early stride toward integrating digital twin methodologies within the ceramic tile sector, facilitating improved process regulation, and promoting the adoption of digital technologies.

Development of the composition of matte glaze with usage of pharmaceutical glass waste for the production of porcelain stoneware

The paper shows the prospects of using pharmaceutical glass waste for partial replacement of high-value frits in the glazes composition. According to the results of X-ray fluorescence spectroscopy, the glass wastes belong to the group of alkali-containing aluminoborosilicate glasses. The results of thermomicroscopic and dilatometry studies showed that the combination of industrial waste frits and glass waste allows obtaining coatings that, according to their technological characteristics, meet the conditions of porcelain stoneware high-speed firing. The conditions for the resource-valued glass waste use as part of porcelain stoneware tiles glazes have been established. This allowed to use their potential as efficiently as possible and to partially replace (within 15–30%) high-value frits. Combinations of waste glass and industrial boron-free frits with high crystallization ability due to the increased content of alkaline earth oxides (RO=22–34 wt.%) were studied to prepare opaque matte coatings. Glazes compositions have been developed, which under conditions of high-speed firing, form matte coatings due to the directed crystallization of phase’s complex (ZnAl2O4, Zn2SiO4 and CaAl2Si2O8). Ceramic granite with white color coating (brightness coefficient of 80–83%) that differs by "silky" mattness (mirror reflection coefficient of 31–42%), high heat resistance (10 or more heat changes) and abrasion resistance of III–IV class was obtained. The best results were observed when using matte glazes in a complex with engobe, which includes the same glass waste in the amount of up to 30 wt.%. This is in general ensures a high level of their utilization, a significant high-value raw materials saving and an energy costs reduction for fritting.

Moisture sorption isotherm and effective diffusion coefficient of porcelain stoneware spray-dried powder

Moisture sorption isotherm and effective diffusion coefficient of porcelain stoneware spray-dried powder

Pumice and lapillus scraps: New national environmental-friendly chance for the production of ceramic tiles

Italian pumice and volcanic lapillus scraps have been used in different percentages as alternative raw materials to foreign feldspars in porcelain stoneware mixtures. The aim of this work was to create naturally colored support to limit the use of artificial dyes while maintaining the technical properties of the reference product. For this purpose, the significant presence of chromophores (Fe and Ti in particular) in by-products from extraction of Italian volcanic pumice and lapillus was exploited. The work was carried out in collaboration with a company: the products were made on a laboratory scale and then they were glazed and fired within the industrial production cycle (48 min, 1210 °C).The resulting slip and the fired samples were characterized by measuring the efflux time, density, linear shrinkage, water absorption and tensile strength to evaluate the technological performance. In addition, thermogravimetric analysis (TG), differential thermal analysis (DTA), and optical and mechanical dilatometry were performed to study the thermal behavior of the formulations.The obtained products could be classified as porcelain stoneware and belong to the BIa group (WA 0.5%, B.S.>35 MPa) in accordance with UNI EN 14411 ISO 13006.