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This document is a description of the work of ceramic artist Mike Stumbras. Stumbras draws inspiration from European ceramics, particularly porcelain objects from the 18th and 19th centuries. He combines the design elements of factory production with the individuality of handcrafted work. Stumbras values the imperfections and the passage of time in his vessels, which he sees as heirloom objects that reflect the ebb and flow of civilizations. He has lectured on his work and is represented by several art galleries. Stumbras was born in Chicago and has Lithuanian ancestry. He currently works as an Assistant Professor of Art at Southern Illinois University. [Extracted from the article]

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. [ABSTRACT FROM AUTHOR]

Different mass fractions of nano iron oxide were added to Jun porcelain glaze, and analyzed changes in the color and microstructure of Jun porcelain after firing in reducing atmosphere (96% Ar/4% H2) and oxidizing atmosphere (air). The color change was studied by spectrophotometer, the phase composition of Jun porcelain was studied by X-ray diffractometer and Raman spectrometer, and microstructure of glaze layer was studied by SEM. The results show that with an increase in the gradient of nano iron oxide content, Jun porcelain specimens changes from light blue to blue, then to cyan gray under reducing atmosphere, and from white to yellow, and then to sauce black under oxidizing atmosphere. When nano iron oxide content in the glaze layer reaches 3.0% (mass fraction), the SiO2 crystal phase on the glaze completely disappears and the glaze appeares amorphous. With the increase of nano iron oxide content, the glaze exhibites a liquid-liquid phase separation structure, and the microstructure size of reducing atmosphere increases from 85 nm to 150 nm, with a relative increase in Fe2+ content. After the glaze of Jun porcelain reaches glass transition in an oxidizing atmosphere, the size of the phase separation structure increased from 217 nm to 307 nm. [ABSTRACT FROM AUTHOR]

Reducing 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.Aflowsheet simulation databasewas generated by coupling the Dyssol framework with MATLAB. This study investigated the influence of rawmaterial compositionwithin 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 tominimize 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. [ABSTRACT FROM AUTHOR]

A comparative "cradle to grave" Life Cycle Analysis between the production processes of ceramic stoneware products and geopolymeric materials obtained by valorizing ceramic wastes is reported. This study presents an effective eco-design approach to obtain sustainable materials through a low energy consumption manufacturing process, a feature that is essential in a historical period of high geopolitical instability which makes the supplying of fossil fuels difficult and particularly expensive. In particular, the possibility of lowering production costs (saving on the cost of waste disposal, using a raw-second material, and a low-temperature production process) could represent a strong contribution to the environmental and economic sustainability of the Italian ceramic industry, which is going through a time of severe financial crisis which due to the unprecedent high cost of raw materials and energy. Finally, the new geopolymeric systems proposed in this paper could be profitably used in the field of green building, art, eco-design, and technical-artistic value-added applications, such as restoration, conservation, and/or rehabilitation of historic monuments, or simply as materials for building revetments. [ABSTRACT FROM AUTHOR]

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Purpose. To study the dielectric properties of porcelain obtained from a mixture of sand, kaolin, and feldspar. The latter has been partially substituted with solid barite wastes (SBWs). Methodology. The study involves preparation of porcelain using conventional solid-state reaction methods, employing two firing temperatures (1200 and 1300 °C) and a soaking time of 3 hours. SBWs are progressively added to the mixtures at levels of 0, 10, 20 and 30 wt%, replacing feldspar content. Structural and dielectric characterizations are conducted to examine the influence of SBWs substitution on macroscopic dielectric properties. Microstructural observations reveal various crystalline phases and micropores, contributing to property effects. Following sintering at 1200 °C, primary mineralogical phases include mullite, anorthite, and quartz. At 1300 °C, the celsian phase emerges alongside anorthite and quartz phases. The technological attributes of the produced porcelain samples, encompassing dilatometric properties, apparent density, and porosity, are determined. Findings. Dielectric characterization, conducted within the frequency range of 102–105 Hz, demonstrates that the relative constant permittivity values rise from 4.3 to 7.4 for samples sintered at 1200 °C and from 5.1 to 9.9 for those fired at 1300 °C, specifically for samples containing 10 wt% SBWs. Additionally, the dielectric loss tangent decreases with increasing sintering temperature. The macroscopic permittivity of porcelains can be accurately calculated using a mixing rule, which aligns well with experimental results. Originality. The original contribution lies in the use of 10 wt% Solid Barite Wastes (SBWs) from the Boucaid mine in order to effectively create environmentally friendly porcelain insulators. The study showcases the potential of SBWs as a partial substitute, thus promoting sustainability in porcelain insulator production. Practical value. The results of this study hold practical significance for the ceramics and insulator manufacturing industries by providing insights into enhancing the dielectric properties of porcelain through the incorporation of SBWs. This approach contributes to the production of environmentally friendly insulators. [ABSTRACT FROM AUTHOR]

This paper begins with an introduction to porcelain tiles. A review of the major scientific and technological features of mullite-based porcelain tiles (MPTs) and anorthite-based porcelain tiles (APTs), focusing primarily on the raw material, processing, phase evolution and mechanical behavior, is then presented. Based on the porcelain tile firing behavior and a series of physical and chemical changes that can occur, a comprehensive comparison is described. In the last part, the prospects for further developments related to MPTs and APTs are discussed. [ABSTRACT FROM AUTHOR]

In this work, we have exploited FLASH sintering as an alternative sintering process in the production of porcelain stoneware. FLASH sintering of porcelain stoneware occurred at temperatures ∼ 1020 °C, for 500 V cm-1, 2 mA mm-2 in 30 s. These conditions are significantly less severe than those typically applied in its conventional sintering, 1150–1250 °C for 1 h. Despite the reduction of time and sintering temperature, FLASH sintered samples exhibit heterogeneous microstructure and elemental distribution, with localized glassy phase formed on the positive pole. By decreasing the feldspar content, less localized glassy phase and more uniform microstructures were obtained, being of relevance the highest density and microstructure uniformity attained in the composition without feldspar. These results extend the FLASH sintering applicability and illustrate its importance for the development of alternative sintering technologies in traditional ceramic industry, that in addition may benefit from the reduction of feldspar in the porcelain stoneware production. [ABSTRACT FROM AUTHOR]

The design of porcelain stoneware tile composition is a very complex and time-consuming task, in the industry. After the long way to accomplish the product, processing, and cost requirements, the microstructure is seldom analyzed. If it is checked, it is not adjusted. The raw materials' chemical composition is one of the most helpful information to design. However, it has certain limitations because the mineralogy information is hidden. The paper approach formulates and optimizes porcelain stoneware compositions regarding raw materials' microstructure and mineralogy. Meta-analysis was applied to build models for mullite formation, firing temperature, and pyroplastic deformation. Kaolinite, illite/muscovite, talc, quartz, and feldspar were used as regressors. The robust microstructure is formed with interconnected mullite crystals. This feature could be numerically correlated to the mullite content ranging from 14% to 17%. Optimization was performed with mullite constrained from 13.5% to 17.5%, firing temperature <1230 °C and pyroplastic deformation <4.8x10−5 cm−1. It was possible to find feasible compositions' intervals. For instance, kaolinite needs to be between 23% and 37%. The comparison with 34 industrial compositions found that 90% of them have kaolinite content below the robust interval. This means it has opportunities to improve product and process performance in terms of stability, quality, cost, productivity, waste material incorporation, and sustainability. [ABSTRACT FROM AUTHOR]

Ink-jet decoration is a technology suitable for designing ceramic tiles with solar reflectance (SR) properties. SR is the ratio between the solar energy reflected by a surface and the total incident energy. If incorporated into the cities' building envelope, solar reflective tiles mitigate the Urban Heat Island (UHI) phenomenon, which makes urban centres hotter than rural areas. Even if many efforts have been conducted to develop solar reflective surfaces, little research has been conducted for the development of coloured tiles suitable to be fabricated by ink-jet technology, where the inks tend to counteract the effect of the reflective engobes. To overcome such an issue, the fabrication of solar reflective ink-jet decorated tiles using a reflective engobe was investigated. The engobe was prepared using an industrial CZAS (CaO–ZrO 2 –Al 2 O 3 –SiO 2) frit and a ZrSiO 4 pigment. The engobe prepared with such frit presented a high SR value (0.918 ± 0.002) and was able to develop ink-jet printed coloured tiles (cool colors) using both white and red porcelain stoneware supports. Overall, it was found that using high engobe thicknesses, white porcelain stoneware supports, and light colour inks allows the fabrication of cool color ink-jet printed tiles. Most of those tiles present solar reflective properties higher than those reported in previous works, even for dark inks that usually tend to counteract the effect of solar reflective engobes. [ABSTRACT FROM AUTHOR]

The present work aims to prospect and study the plastic and superplastic clay deposits in the state of São Paulo, Brazil, as a source of raw materials for the ceramic tile industry and especially for the production of porcelain stoneware tiles. To achieve the proposed objectives, a geological study was carried out through the mapping and identification of the present lithologies, lithogeochemical characterization using X-ray diffraction, inductively coupled plasma optical emission spectrometry, cation-exchange capacity and organic carbon and characterization of the ceramic technological properties, including granulometric analysis by sedigraph and Brunauer–Emmett–Teller specific surface area. According to their geological characteristics, the studied deposits were classified into two types: a detrital sedimentary deposit, restricted to Quaternary alluvial sediments and Neogenic Tertiary formations and composed of silt-sandy clay and plastic, kaolinitic, refractory and silico-aluminous facies; and an alterite type, found in Permo-Carboniferous rocks of the Paraná Basin, composed of laminated/massive weathering siltstones, with the highly plastic, fluxing clay minerals illite, kaolinite and smectites. Among the targets studied in these deposits, argillaceous facies with plastic and superplastic characteristics were identified, which affect their applicability in compositions for producing porcelain stoneware tiles and stoneware. [ABSTRACT FROM AUTHOR]

This paper discusses the influence of aluminum–alkali sludge and chemical production waste on the phase composition of porcelain stoneware based on kaolin clay. Porcelain stoneware with high physical and mechanical properties was obtained at 1250°C. X-ray phase and IR-spectroscopic studies revealed the presence of quartz, cristobalite, mullite, corundum, and glass phase in the porcelain stoneware, with at least 50% of the overall content comprising glass phase. The presence of corundum, spinel, mullite, and anorthite in porcelain stoneware composition imparts high physical and mechanical parameters (strength, frost resistance, heat resistance, etc.). Patent RF 2768886 was obtained for the developed formulations. [ABSTRACT FROM AUTHOR]

Five porcelain and porcelain stoneware bodies were investigated to compare sintering mechanisms and kinetics, phase and microstructure evolution, and high temperature stability. All batches were designed with the same raw materials and processing conditions, and characterized by optical dilatometry, XRF, XRPD-Rietveld, FEG-SEM and technological properties. Porcelain and porcelain stoneware behave distinctly during sintering, with the convolution of completely different phase evolution and melt composition/structure. The firing behavior of porcelain is essentially controlled by microstructural features. Changes in mullitization create conditions for a relatively fast densification rate at lower temperature (depolymerized melt, lower solid load) then to contrast deformations at high temperature (enhanced effective viscosity by increasing solid load, mullite aspect ratio, and melt polymerization). In porcelain stoneware, the sintering behavior is basically governed by physical and chemical properties of the melt, which depend on the stability of quartz and mullite at high temperature. A buffering effect ensures adequate effective viscosity to counteract deformation, either by preserving a sufficient skeleton or by increasing melt viscosity if quartz is melted. When a large amount of soda–lime glass is used, no buffering effect occurs with melting of feldspars, as both solid load and melt viscosity decrease. In this batch, the persistence of a feldspathic skeleton plays a key role to control pyroplasticity. [ABSTRACT FROM AUTHOR]

The study concerns the characterisation of five porcelain stoneware slabs with thicknesses of 12 and 20 mm and different cutting responses. Two slabs showed a deviation from a linear cut, resulting in a poor response to the diamond disk, while the other three slabs reacted well. In order to highlight any differences between these slabs, mineralogical and microstructural analyses were carried out, including the determination of a sintering index, total porosity and pore size distribution. This approach is based on a "reverse engineering" concept whereby the cause of the cutting effect can be traced by analysing the finished product. Both the total porosity values and the sintering index can be considered as critical parameters to evaluate the cutting responses of ceramic slabs. The best compromise to obtain a good cutting response, in porcelain stoneware slabs, is reached when the total porosity is the maximum possible, pores are the smaller as possible and the sintering index is the minimum possible, without compromising the quality and technical performance of the porcelain stoneware. [ABSTRACT FROM AUTHOR]

In this study, the effects of different types of investment casting waste sand were investigated in porcelain tile production in place of clay and kaolin. Dry and firing shrinkages, water absorption, dry and firing strengths and densities of porcelain tile bodies were determined. In addition, color measurements, XRD analysis and SEM analyses of the relevant samples were also investigated. A1, A2, A3, B and C porcelain tiles had higher density, firing shrinkage and firing strength values. However, they had lower water absorption, dry shrinkage and dry strength values than those of the reference porcelain tile. Quartz, mullite and albite were found in all the bodies as main phases and, in addition, zircon phase was determined in bodies in which waste sand was incorporated. [ABSTRACT FROM AUTHOR]

As sustainable mineral waste resources, smoky quartz tailings are regarded as potential raw materials for ceramic, but they are not efficiently utilized in thin porcelain ceramic plates. To improve the utilization value, the smoky quartz tailings were innovatively used to prepare thin porcelain ceramic plates. The potential ceramic formulas were explored by a formula optimization method with a triangle ingredients diagram. Besides, the functions of key components to the properties of thin porcelain ceramic plates, such as bulk density, water absorption, apparent morphology, mechanical properties, and mechanical mechanisms were respectively investigated. It was found that the densification tendency could be accurately represented in a triangle ingredients diagram, and the contour lines of 0.5% water absorption value by regression equation fit well with experimental data. The densification behaviors and microstructure evolutions were synergistically influenced by driving forces, mass transfer carriers, and chemical components. The ceramic plates from optimized ceramic formulas reached the highest bulk density of 2.85 g/cm3 and bending strength of 132.24 MPa, respectively. In addition, the excellent mechanical properties were mainly attributed to the mechanical mechanisms of micro-crack deflections and particle diffusion enhancements. This formula optimization method narrowing from optimized region to accurate ceramic formulas was proved to be efficient in gaining potential ceramic formulas and fully compatible with standard stoneware processing. [ABSTRACT FROM AUTHOR]

The SiO 2 layer preferentially generated on the surface of silicon carbide abrasives in Polishing Porcelain stoneware tile Residues (PPR) is corroded by silicate liquid during firing, resulting in continuous oxidation and foaming of silicon carbide, which makes the PPR difficult to be reused. The PPR is fired to form a silicate liquid that wraps micron silicon carbide in it. In this work, it is possible to study the corrosion of silicate to silicon carbide at high temperature by using two (Ceramic-SiC) and three (Ceramic-SiO 2 -SiC) layer structure model to simulate the corrosion of silicate to silicon carbide. The corrosion mechanism of SiC in PPR by silicate liquid during firing is revealed that the corrosion rate at its two sides (interfaces) determines the ultimate change in the thickness of the corrosion layer between the ceramic and the SiO 2 layer. Importantly, the corrosion layer thickness with time on the silicate-SiO 2 cross-section periodically presents wave-like changes, which can be attributed to the ionic migration between layers and the rate at which cations cross the corrosion layer when studying the three-layer model. • A two-layer Silicate-SiC model and a three-layer Silicate-SiO 2 -SiC model were used to simulate the corrosion of SiC by silicate liquid during firing polishing porcelain residues. • The corrosion mechanism of SiC in the polishing porcelain residues by silicate liquid during firing is revealed when studying the three-layer model. • The migration of cations on the interface of corrosion layer causes the thickness of the corrosion layer to change periodically with time. [ABSTRACT FROM AUTHOR]

Pressed compacts of an industrial spray-dried porcelain stoneware powder, consisting mainly of albite, quartz, kaolinite, and illite, were thermally treated at different temperatures and times. Fired test piece bulk density and water absorption, in addition to phase content (using X-ray diffraction (XRD) data and Rietveld refinements) and microstructure (using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM–EDS)), were determined. The isothermal kinetics of densification, mullite precipitation, and feldspar and quartz dissolution were obtained. The evolution of the mullite, quartz, feldspar, and vitreous phase mass percentages with the dissolved feldspar fraction was independent of thermal treatment. The evolution of water absorption, linear shrinkage, and bulk density with vitreous phase content was also independent of thermal treatment. Water absorption decreased linearly as vitreous phase content increased, until it cancelled out at a vitreous phase content of 66% by weight. [ABSTRACT FROM AUTHOR]

• Foaming was well controlled after C, Al and Si powder were introduced into the simulated polishing porcelain residues. • The phenomenon of alumina crystal precipitation on the pore wall of foamed ceramics was discovered after sintering. • O 2 diffuses faster in silicate liquid than CO during sintering, resulting in foaming of the polishing porcelain residues. Polishing porcelain stoneware tile residues (PPR) is used to prepare foamed ceramic to solve the problem of solid waste discharge in ceramic industry. In this study, C, Al and Si powder were added to the simulated PPR to control foaming, and the mechanism of silicon carbide foaming in the PPR was discussed in detail. After these powders were introduced into the simulated PPR, the phenomenon of alumina crystallization on the pore wall of the foamed ceramic and the diffusion of gas in the foamed ceramic were discovered to be exciting. The foaming mechanism of PPR is detailed as follows: the diffusion rate of oxygen in silicate liquid is faster than that of CO during sintering, so the CO generated by incomplete oxidation of silicon carbide in PPR accumulates in the liquid, which makes the volume of ceramics expand and causes foaming. [ABSTRACT FROM AUTHOR]

In this study, the possibility of using calcined-colemanite as an alternative fluxing agent in a body mixture used for porcelain tile was investigated. For this aim, a part of industrial spray-dried powders was replaced with the colemanite calcined by microwave-assisted heating (MACC) in varying amounts (up to 3 wt. %). The tile compositions prepared with different proportions of MACC addition were pressed uniaxially at 15 MPa, and the shaped tiles were then fired at 1220 °C for 50 min in an industrial roller kiln. Physical and mechanical tests, X-ray diffractometer (XRD), and scanning electron microscopy (SEM) analyses were performed to examine the effects of MACC addition on porcelain tile's technical properties and phase development. The results revealed that the porcelain tiles having 0.5 wt. % of MACC had better technical properties, i.e., lower water absorption (0.09%) and porosity (0.22% for apparent porosity and 7.25% for closed porosity), and higher bending strength (66.04 MPa) than that of others. Consequently, the MACC addition promoted a low-viscosity liquid phase during firing, resulting in a significant microstructural improvement by decreasing the closed porosity and increasing the bulk density and flexural strength. [ABSTRACT FROM AUTHOR]

• Ink-jet printed porcelain stoneware tiles for UHI mitigation were prepared. • A zircon containing engobe with a good ability to reflect solar radiation was used. • Two printing modes, five printing intensities, and four colours were tested. • Some of the prepared tiles fall in the general definition of cool colors (ρ sol ≥ 0.50). • The solar reflectance depends on engobe's coverage (by inks) and inks' composition. Digital ink-jet printing is a decoration system for ceramic tiles that requires the application of engobes with high whiteness and opacity, characteristics that can be used to design solar reflective ink-jet decorated tiles. These materials can help to mitigate Urban Heat Island (UHI) phenomenon. Here, the fabrication of ink-jet printed solar reflective tiles using an engobe with high solar reflectance was investigated. Two printing modalities (binary (BIN) and grayscale (GS)), five printing intensities, and four colours were tested. It was found that some of the prepared tiles can be used for mitigating the UHI phenomenon. The solar reflective properties were mainly derived from the reflective engobe, and in some grade, from the mineral composition of the inks. The colour and roughness measurements revealed that the GS modality could prepare ink-jet decorated tiles with good solar reflective properties with a smaller quantity of inks and good soiling resistance. [ABSTRACT FROM AUTHOR]

The growing demand for fluxes, dictated by the shift toward porcelain stoneware, is urging the ceramic tile industry to find a viable alternative to feldspathic materials. Sericite, a microcrystalline form of muscovite, is present in many ceramic raw materials. It melts during firing and can be a suitable substitute for potassic feldspar. The aim of this study is to understand in depth the effects of replacing feldspar with sericite in porcelain stoneware batches with nearly the same chemical composition. Characterization includes phase composition (X-ray powder diffraction, XRPD Rietveld), melt chemical composition (calculated), sintering behavior (optical thermo-dilatometry), and microstructure (scanning electron microscope (SEM). The results indicate a different vitrification path, mostly in the early stage of sintering, related to the different mineralogical composition and particle size distribution of sericite for K-feldspar. Nevertheless, at temperatures higher than 1150°C, the bodies have similar phase composition, microstructure, melt chemical composition, and physical properties. Densification kinetics is faster in the batch with sericite, while the body with feldspar is able to reach a higher bulk density. [ABSTRACT FROM AUTHOR]

The production of ceramic tiles with larger sizes and reduced thickness has increased the challenge of producing high-quality ceramic tiles in short single-firing cycles. For porcelain tiles, the pressing step is of upmost importance for the microstructure of the green bodies. The particle size distribution, mineral composition of the pastes and porosity before firing define the water flow during the decoration process. Hydro deformation is the curvature of unfired ceramic tiles caused by water absorption during the decoration step before firing. In this work, the hydro deformation is studied in function of tile thickness, compaction, and clay composition according to a 2K factorial design. Two compositions of porcelain tiles (glazed and polished) were pressed at two thicknesses (3–6 mm) and pressing pressures (35.5–49.8 MPa) forming ceramic tiles with 55 × 110 mm² of surface area. Chemical (XRF), mineralogical (XRD), thermogravimetric (TG), specific surface area (BET), granulometric, bulk density, and porosity analyses were performed for the green tiles of both compositions. To simulate the hydro deformation during the decoration step, the curvature (mm) of the tiles was studied within a 0–180 min interval. The water absorption rate through the surface (g.m−2·s−1) of the tiles in an interval of 0–180 s was studied as a function of thickness, pressure and porcelain tile composition. As a result, the thickness of the tiles can change the curvatures from concave to convex. Pressing conditions and composition of the tiles can change the water absorption rates. Porcelain tiles with higher content of clay minerals develop convex curvatures. For tiles with lower content of clay minerals, concave curvatures were developed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Borates, wollastonite, diopside, spodumene and phonolite were used as strong fluxes. • Strong fluxes modify phase composition and liquid phase viscosity and surface tension. • Flux changes melt properties: polymerization degree, network modifiers, Al speciation. • Strong fluxes anticipate densification start affecting sintering kinetics differently. • Microstructure and physical properties of porcelain stoneware depend on the flux type. Strong fluxes are needed to fire vitrified ceramics at temperatures significantly lower than those usually reached in industrial firing cycles. This work is aimed at understanding the role of strong fluxes in the microstructural evolution during sintering. Six fluxes (colemanite, ulexite, wollastonite, diopside, spodumene and phonolite) were individually added to a porcelain stoneware batch and processed in standard conditions. Compacts and fired bodies were characterized by optical dilatometry, XRD-Rietveld, SEM and measuring technological properties. Strong fluxes change the firing behaviour with a complex interplay of sintering kinetics, microstructural features, and phase composition. Every flux has its own repercussion on the properties of the liquid phase (chemical composition, degree of polymerization, viscosity and surface tension) which are key points to explain the observed microstructure, densification rates, and stability at high temperature. Batches with phonolite, wollastonite or diopside exhibit characteristics closer to standard porcelain stoneware, while spodumene and borates suffer from unsatisfactory microstructures and lower densification efficiency. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Segregation in a center-filled silo was included through multiscale modeling. • Moisture difference between coarse and fine granules reduced from 3.3 to 0.9% in 48 h. • Moisture equilibrium of granules was not achieved for a practical timeframe, < 60 h. • High temperature gradient affected water migration among granules near the silo wall. • Temperature control of granules can improve moisture homogenization during storage. [ABSTRACT FROM AUTHOR]

The bleeding phenomenon, a persistent and widespread issue in the application of cobalt-bearing pigment during porcelain decoration, has spurred different civilisations to develop various response strategies to alleviate this problem. In this study, we challenge the prevailing hypotheses concerning the role of composition and viscosity in determining the bleeding effect on blue-and-white wares, proposing a novel physical model framing it as a diffusion process that occurs within vitreous silicate, where the severity can be qualitatively expressed using the diffusion distance. Drawing upon the phenomenological Fick's law and microscopic diffusion mechanism, we quantitatively discuss the primary physical parameters that influence the diffusion behaviour for the first time, clarifying that the diffusion of cobalt ions is not related to the medium viscosity. Moreover, compared with the microstructural features of blue decors with and without the bleeding effect, we reveal that domestic cobalt particles are all encapsulated by anorthite crystals, acting as a passivation shell to hinder the dissolution of cobalt particles. Significantly, our reinterpretation has broader archaeological implications for the bleeding effect associated with cobalt pigment in ceramics, elucidating the historical trajectories of responsive practices and the multifaceted interplay between resource form, artistic expression and technological advancement across varying environmental and cultural contexts. Overall, these responses to the bleeding effect exemplify the complexities of technological evolution, highlighting that technology is not merely an extension of technical knowledge but also functions as a form of social construction deeply intertwined with its local context. This comprehensive understanding contributes to our understanding of historical narratives in ceramics and the diversity of human ingenuity in ancient societies, with potential implications for contemporary pigment manufacture. • Novel diffusion model challenges prevailing viscosity theories on bleeding effect. • Core-shell structure is identified as decisive factor in preventing bleeding. • Responsive practices are shaped by natural resources and technical traditions. [ABSTRACT FROM AUTHOR]

This work focused on obtaining a porcelain stoneware body containing only Italian raw materials. The starting mixtures differed in the feldspathic fraction, one pumice-based and one lapillus-based. German ball clay was gradually replaced by Italian kaolinitic clay. The influence of Italian kaolinitic clay on the technical and aesthetic properties of the final product was analyzed by comparing it with the references. The work was carried out in collaboration with a ceramic company which allowed the tile production process to be simulated in the laboratory and fired in an industrial kiln using the production cycle (48 min, 1210 °C). Ceramic bodies were characterized in order to evaluate technological performance by measuring efflux time and density of slip, flexural strength on green, linear shrinkage and water absorption in vacuum on fired samples. Mineralogical, microstructural (ESEM) and colorimetric analyses were also performed on the fired samples. Efflux time and density are processing parameters; these were in line with the reference in the lapillus-based bodies with kaolinitic clay replacement rates of 100%; in the case of the pumice-based bodies, they were considered acceptable only for replacements of 25%. The lapillus-based body showed a microstructure similar to that of porcelain stoneware. Vacuum water absorption values were better in lapillus-based formulations than in pumice-based formulations but showed higher linear shrinkage values for 100% replacements. According to UNI EN 14411 ISO 13006, some of the products obtained can be classified as porcelain stoneware (group BIa). • Italian kaolinitic clay replaced German ball clay in a porcelain stoneware support. • Clays are similar in quartz and kaolinite content, but ball clays have more illite. • The Lapillus-based support permitted the total replacement of German ball clay. • The Pumice-based support permitted up to 25% replacement of German ball clay. • The closed porosity of the fired product is increased by adding kaolinitic clay. [ABSTRACT FROM AUTHOR]

The development of tiles possessing antimicrobial activity is of great technological and scientific interest to improve the functionality of a very widely used article. Also the current SARS-CoV-2 pandemic is drawing the attention towards materials or compounds able to inactivate the virus, silver being among all the most promising one. In the present work, field-assisted ion exchange process was used to functionalize porcelain stoneware by introducing silver into the material surface using a solid silver electrode. The application of a small direct electric current (10 mA cm−2) at 380 °C allowed to fasten silver diffusion. The penetration of silver into stoneware appears homogeneous and primarily involves an exchange between silver and sodium ions under the effect of the external electric current. Penetration depths approaching 120 μm can be obtained in only 5 min. Preliminary characterization revealed that the Ag-exchanged stoneware possesses a strong biocidal action against Staphylococcus aureus. [ABSTRACT FROM AUTHOR]

[Display omitted] Integrated simulation of manufacturing plants plays crucial role in development of sustainable processes and optimized products. However, no investigation has been reported for the whole process chain of porcelain stoneware manufacturing. In this contribution, semi-empirical models of porcelain stoneware processing steps have been developed and implemented into Dyssol framework. By validation based on industrial and lab-scale experiments, the simulation has been applied for modeling and sensitivity analysis of the entire process. The simulation results are in a good agreement with experiments showing that the proposed modeling strategy has high potential to be used for future digital transformation in this sector. [ABSTRACT FROM AUTHOR]

Limestone was used to modify the fluxing action of two potash feldspars (a pure potash feldspar and a soda-potash feldspar) labeled P and C, respectively, in the formulation of porcelain stoneware based on Cameroonian raw materials. The effect of limestone addition (0–10 mass%) was investigated in the range of sintering temperature between 1125 and 1300 °C. Characterization of sintered samples including thermal behavior (DTA, TG and dilatometry test), phase evolution, densification parameters, flexural strength, morphology as well as pores structure was investigated in details. The maximum flexural strength (138 MPa) was obtained at 1175 °C with P series (7 mass% addition of limestone) and at 1200 °C (122 MPa) for C series. The maximum density (≈ 3.1 g cm−3) and lower water absorption (≈ 0%) were obtained at 1200 °C. Mullite and anorthite were identified as main crystalline phases. Starting from 1175 °C and mostly at 1200 °C, the two series compositions (with 7 mass% addition) presented a self-glazing phenomenon which gave them significant brightness and high aesthetic quality; these properties were accomplished only at 1300 °C for reference samples with no lime addition (P0 and C0). A proper addition of limestone (3–7 mass%) with potash feldspar significantly reduced the sintering temperature (~ 150 °C) and permits the production of high strength (122–138 MPa), low energy and sustainable porcelain stoneware. [ABSTRACT FROM AUTHOR]

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• We developed high stain resistant polished stoneware tiles. • Surfaces were sealed by using suspension of three frits with solid contents ranging from 30 to 70 wt.%. • Focus height of 105 mm, scan speed of 2640 mm.min−1, and laser power of 750, 800, and 850 W were used. • Solid content of 70 wt.% reduced up tu 99 % of the stained area related to a regular polished porcelain stoneware tile. This study aims to develop a new approach for the permanent sealing of surface pores on polished porcelain stoneware tiles, using ceramic frits for the filling pores, followed by laser-sealing to ensure the fixation of the applied material. The laser-sealing parameters compatible with the ceramic substrate were focus height (z) of 105 mm, scan speed (v) of 2640 mm.min−1, and power values of 750, 800, and 850 W. In order to define the working parameters, three ceramic frits with 30, 50, and 70 wt.% solid contents were tested by sealing at the mentioned powers. High stain resistant polished stoneware tiles were obtained using frit 1 and frit 3 with 50 and 70 wt.% solid contents, respectively, and the proposed procedure. High ease of cleaning is obtained related to the current treatment, demonstrating its suitability for improving the stain resistance for meeting the ISO 13006:2012 requirements. [ABSTRACT FROM AUTHOR]

Porcelain stoneware is sintered by partial vitrification through viscous flow of a liquid phase formed at high temperature. This sintering process involves a complex evolution of both phase composition and chemistry of the liquid phase, according to the dynamic equilibrium established with the residual minerals and the new crystalline phases formed during firing. The present contribution overviews the evolution of phase composition and microstructure of seven body formulations during firing at different temperatures and dwell times. Each mixture was characterized from the chemical point of view and, once fired, by XRPD (quantitative phase composition), SEM and optical microscopy (microstructure). Moreover, the sintering behavior of the batches was investigated in isothermal conditions by optical thermo-dilatometric analysis. The results indicate that the continuous variation of the phase composition during the heating treatment affects the chemical composition of the liquid phase reflected on the densification kinetics and pyroplastic deformation of tiles. [ABSTRACT FROM AUTHOR]

The disruption of the supply chain of ball clays from Donetsk basin, Ukraine, has demonstrated that relying on domestic raw materials is strategic and vital for the ceramic tile production. However, the use of local raw materials has in most cases led to the increase in the impurities, namely iron, content of porcelain stoneware batches. A case-study is presented about the Italian tile district located in the Sassuolo area. In this work, we undertook the full characterization of two red clays from local quarries that are iron-rich (∼7% Fe 2 O 3), thus leading to well-known issues in the ceramic tile production. The features of these samples were compared with those of a German ball clay containing ∼3% Fe 2 O 3. The complex mineralogical composition of the Val Rossenna varicolored clays and on the Monte Piano marls was unravelled, revealing that they are rich in illite-smectite (I S) mixed layers and illite, and poor in chlorite, sulfates and organic matter. The effects of a partial substitution in a porcelain stoneware body of classic ball clays with the Italian and German red clays were investigated. The obtained bodies were fully characterized from milling to firing. The amount of the red clays was chosen to best evaluate the effect of iron on the technological properties of semifinished and finished products. The substitution of the classic ball clays with red clays did not introduce unsolvable bottlenecks in ceramic tile production. The addition of the German red clay resulted in a slight increase of the sintering temperature (compared to the benchmark), possibly related to the higher quartz content of this raw material. Conversely, the addition of the Italian red clay induced a reduction of the firing temperature (compared to the benchmark), likely due to the higher content of iron, feldspars and carbonates. The most significant variations concern the color of fired tiles, which results darker (compared to the benchmark) in all the tested bodies, for the presence of pyroxene, hematite, and iron dissolved in the vitreous phase. • Characterization of clay from Val Rossenna and Monte Piano Formation (Northern Apennines) is given. • The main mineralogical components are illite and I/Sm mixed layer phyllosilicates. • These clays can be employed in the industrial production of porcelain stoneware. • Their use in low percentages is possible without severe technological bottlenecks. • The strongest limitation observed in the final product is the color, turning darker. [ABSTRACT FROM AUTHOR]

Featured Application: The iridescent effect of ceramic provides excellent visual and perceptual characteristics, being able to control the chromatic ranges produced in the function of diverse layers of enamel. It also provides a harmonious integration into environments of great landscape value when applied to building façades. In recent years, the use of porcelain stoneware in building envelopes has opened new lines of research and innovation favoring energy efficiency and the reduction of environmental impacts. However, there has been little research on its relationship with light vibration and reflectivity, visual perception, and integration in the urban environment and landscape. In this study, an analysis was conducted on the production and application of crafted pieces of porcelain stoneware, shaped in spherical caps, at the headquarters of the Botín Foundation in Santander (Spain). Various enamels with an iridescent-nacreous finish and metallic reflection were applied to the stoneware to generate a vibrant skin that would constantly change with natural light and the environment. A vitrification and metal deposition process were designed through successive applications of enamels and firings. The physico-chemical properties of the enameling and the microcracking factors that produced the iridescent effect were characterized. A colorimetric characterization was performed evaluating the goniochromatic or iridescent colors, measuring the spectral radiance factor of the light, and comparing these results with other ceramic pieces. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • The higher mechanical strength was for 15 wt% chamotte containing samples. • The mechanical strength improvement was attributed to higher mullite concentrations. • Chamotte containing samples are highly attractive to produce sustainable tiles. • Chamotte containing tiles are an economic and environmental alternative. [ABSTRACT FROM AUTHOR]