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2. A recycled natural resource as secondary raw material for versatile technological applications: the quarry waste from zeolite-rich tuffs

Author

Graziano, Sossio Fabio, Mercurio, Mariano, Izzo, Francesco, Langella, Alessio, Rispoli, Concetta, Santaniello, Nicola Davide, Di Benedetto, Claudia, Monetti, Vincenzo, Biondi, Marco, De Rosa, Giuseppe, Mayol, Laura, Villapiano, Fabrizio, Dondi, Michele, Zanelli, Chiara, Molinari, Chiara, Liguori, Barbara, Campanile, Assunta, and Cappelletti, Piergiulio

Published
2024
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37. Porcelain versus Porcelain Stoneware: So Close, So Different. Sintering Kinetics, Phase Evolution, and Vitrification Paths.

Author

Conte, Sonia, Molinari, Chiara, Ardit, Matteo, Cruciani, Giuseppe, Dondi, Michele, and Zanelli, Chiara

Subjects
STONEWARE, PORCELAIN, MANUFACTURING processes, VITRIFICATION, SINTERING, GLASS
Abstract

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]

Published
2023
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40. Phyllite as Feldspar Substitute in Porcelain Stoneware Tiles: Effect on Sintering Behaviour and Phase Composition

Author

Zanelli, Chiara, Conte, Sonia, Melchiades, Fábio G., Nastri, Suelen, Hernández-Sánchez, Miguel Y., Boschi, Anselmo O., and Dondi, Michele

Subjects
Porcelain stoneware, Brazilian phyllite, Ceramic tiles, Sintering behaviour
Abstract

The objective of this work was to report the preliminary results of substituting feldspar by phyllite in a typical Brazilian porcelain stoneware batch (i.e., sericite instead of K-feldspar as flux). Two bodies were prepared (50 % K-feldspar replaced by 50 % phyllite) and their behaviour during firing was compared after an industrial-like schedule and in isothermal conditions. Pyroplastic deformation and quantitative phase composition were determined, along with estimation of the chemical and physical properties of the vitreous phase at high temperature. The results show that the Substitution of feldspar by phyllite has important repercussions on the technological behaviour, with pros and cons, dictated by a different evolution of phase composition. The main drawback of the phyllitic batch is the higher firing temperature necessary to get a water absorption below 0,5 %. Clear advantages in the use of phyllite are an easier grindability and a lower pyroplastic deformation. Differences are not simply justified by the viscosity of the vitreous phase, but are likely linked to the relatively large amount of skeleton (and a proper shape of crystals dispersed in the melt).

Published
2020

43. Sericite instead of feldspar in porcelain stoneware: Effect on sintering and phase evolution.

Author

Tavares Brasileiro, Camila, de Almeida Filho, Humberto Dias, Santana, Geovana Lira, Lot, Ana Virgínia, Conte, Sonia, Zanelli, Chiara, Dondi, Michele, and Ortega Boschi, Anselmo

Subjects
STONEWARE, PORCELAIN, FELDSPAR, CERAMIC materials, X-ray powder diffraction, SCANNING electron microscopes
Abstract

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]

Published
2022
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44. Recycling Construction and Demolition Residues in Clay Bricks.

Author

Zanelli, Chiara, Marrocchino, Elena, Guarini, Guia, Toffano, Alice, Vaccaro, Carmela, and Dondi, Michele

Subjects
BRICKS, DEMOLITION, CONSTRUCTION management, RAW materials, CLAY, CONSTRUCTION industry
Abstract

In recent years, the management of construction and demolition residues (CDRs) has become a major challenge for the construction industry due to the increasing volume of waste produced and its associated environmental impact. The aim of this article is to assess the effect of fine-grained fractions (<0.125 mm–0.6–0.125 mm) of construction and demolition residues, obtained by industrial sorting in a CDR processing plant in Rovigo (Italy), on the technological behavior and technical performance of clay bricks. Simulating the brickmaking process on a laboratory scale, it was appraised whether the CDR additions determined any change in the main properties of both fired and unfired bricks, taking a CDR-free brick body as a reference. The results indicated that the use of CDR is technologically feasible. It is possible to obtain, through proper crushing and sorting operations, grain-sized fractions with quite homogenous chemical and mineralogical composition. The residues did affect the compositional properties, porosity and water absorption of the clay bricks. Nevertheless, the characterization of the residual-added semi-finished and fired products highlighted their good technological and mechanical properties, which allowed them to provide performances similar to those of standard bricks manufactured with raw natural materials. [ABSTRACT FROM AUTHOR]

Published
2021
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45. Exploring syenites from ring complexes in the eastern desert (Egypt) as ceramic raw materials

Author

Ismail, Ali I.M., Ghabrial, Doris Sadek, Wahab, Wael Abdel, Eissa, Mahmoud, Cazzaniga, Alberto, Zanelli, Chiara, and Dondi, Michele

Subjects
Ceramic flux, Ring complex, Beneficiation, Feldspar, Nepheline syenite
Abstract

The aim of this study is to assess the potential as ceramic flux of some feldspar sources in the Egyptian Eastern Desert, particularly syenites from Abu Khruq, which is the most promising ring complex, taking into account various issues, including the occurrence of nepheline syenites. This late Cretaceous ring complex shows zones of alkaline rocks arranged concentrically with quartz-syenite at the border and an inner zone of nepheline syenite. Both rock types are made up essentially of alkali feldspar with minor amounts of alkali pyroxene, amphibole and biotite, but the former contains interstitial quartz and the latter nepheline. The coexistence of silica-saturated and silica-undersaturated rocks is likely the result of crustal contamination. Geochemical data indicate that alumina (12-18%) and alkali (8-13%) contents are lower than nepheline syenites used in the ceramic manufacture and theFe2O3 content is high (4.1-6.4%). Thus, the investigated syenites must be beneficiated to be usable in the ceramic industry. Lab-scale mineralurgical treatments (comminution and magnetic separation) were carried out and the beneficiated samples were characterized from the chemical and technological view points. Abu Khruq syenites resulted to be suitable for the production of ceramic tiles.

Published
2018

47. Technological behavior of porcelain stoneware bodies with Egyptian syenites.

Author

Zanelli, Chiara, Soldati, Roberto, Conte, Sonia, Guarini, Guia, Ismail, Ali I. M., El‐Maghraby, Mohammed S., Cazzaniga, Alberto, and Dondi, Michele

Subjects
*SYENITE, *STONEWARE, *SINTERING, *GLASS structure, *MANUFACTURING processes
Abstract

The progressive depletion of the main feldspathic flux deposits in the World is forcing the ceramic industry to search for suitable substitutes. The aim of this study is to assess the potential of some feldspar sources in the Egyptian Eastern Desert, particularly syenites from Abu Khruq, in the manufacture of ceramic tiles. Beneficiated samples obtained by laboratory‐scale mineral processing were tested into porcelain stoneware batches (from 10% to 30% wt in replacement of feldspars) and compared with a reference body through a laboratory reproduction of the industrial processing. The technological behavior of unfired tiles does not suffer any significant alteration due to the use of syenites. On the other hand, syenite‐bearing bodies exhibit some changes in the phase composition and the chemistry of the melt, that turns richer in alkali, especially K2O. The consequently increased sintering rate depends mainly on the viscosity of the liquid phase formed during firing. In conclusion, syenites can be used without technological hindrances to manufacture porcelain stoneware tiles. The firing behavior of syenite‐bearing batches can be reasonably adjusted by setting key parameters (eg, the feldspar amount and the Na/K ratio), but the darker color of fired bodies requires to further lower the iron oxide. [ABSTRACT FROM AUTHOR]

Published
2019
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48. List of Contributors

Author

Aguzzi, Carola, Babu, Bathula, Borrego-Sánchez, Ana, Carazo, Esperanza, Cerezo, Pilar, Chang, Po-Hsiang, Chmielewská, Eva, Daković, Aleksandra, Datta, Samar C., de Gennaro, Bruno, Dondi, Michele, García-Villén, Fátima, Gatta, G. Diego, Gil, Antonio, Jiang, Wei-Teh, Krajišnik, Danina, Kumararaja, Periyamuthu, Li, Zhaohui, Lotti, Paolo, Manjaiah, Kanchikeri M., Marković, Marija, Milić, Jela, Misaelides, Panagiotis, Molinari, Chiara, Mukhopadhyay, Raj, Naveen, Shivalingegowda, Paul, Ranjan, Raghu, Anjanapura V., Ravindranadh, Koutavarapu, Reddy, Kakarla R., Rusmin, Ruhaida, Sánchez-Espejo, Rita, Sarkar, Binoy, Ugochukwu, Uzochukwu C., Venkata Reddy, Ch., Vicente, Miguel A., Viseras, César, and Zanelli, Chiara

Published
2019
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50. Alternative route for the synthesis of Lanthanum Strontium Titanate as SOFC Ni-free anode material

Author

Milandri, Lorena, Mercadelli, Elisa, Zanelli, Chiara, Albonetti, Stefania, and Sanson, Alessandra

Subjects
LST, Synthesis, SOFC anodes, Ni-free
Abstract

Among the perovskite structures, lanthanum-doped strontium titanates have attracted a lot of attention as possible candidates for SOFC Ni-free anodes. In particular the composition LaxSr1-(3x/2)TiO3 with x = 0.4 (LST) was recently considered for its tolerance to redox cycles and sufficiently high conductivities values. In this work an extensive study on the synthesis of LST powders with low-cost and easy-scalable methods is reported. The solid state and chemical synthesis as well as a combination of solution-solid state synthesis were considered. The influence of either the nature of the precursors (oxides, carbonates or nitrates) and the calcination temperature (from 500 to 1350°C) onto the perovskite formation was evaluated. The as-synthesized powders were morphologically, structurally and chemically characterized. The Pechini method leads to pure perovskite phase at 700°C for 1h, but it allows the production of only few grams of powder for each batch. On the other hand the solid state synthesis is a more up-scalable method but the phase can be obtained only at 1100°C for 1h. In addition the high reactivity of the lanthanum towards the humidity leads to a difficult control of the system stoichiometry and therefore of the final phase composition. An alternative solution-solid state synthesis was considered to produce batch of 100g of LST powders with good phase purity and in relatively mild conditions. The pure perovskite phase with the correct stoichiometry was obtained starting from the La and Sr nitrate aqueous solutions, highly reactive TiO2 followed by freeze-drying and calcination at 900°C for 1 h.

Published
2012

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