Dinamització del sector ceràmic de Castelló. Taula rodona

Material addicional de la ponència presentada al III Congrés Obert i Virtual Castelló 2020. Castelló de la Plana, 2011-201

El sector cerámico de Castellón. Estrategias de futuro

Material addicional de la ponència presentada al I Congrés Obert i Virtual Castelló 2020. Castelló de la Plana, 201

Decoração Cerâmica com Tecnologias de Jato de Tinta (Inkjet)

Este artículo presenta una visión general de la tecnología de chorro de tinta de impresión digital aplicada al sector de la cerámica. Presenta un histórico de las principales tecnologías de inyección de tinta actualmente empleadas. El artículo también analiza los cambios que se produjeron en el sector del desarrollo producto de la tecnología del cabezal de impresión más adecuado para la impresión Tipo de tintas cerámicas y sus propiedades, y concluye comentando los retos tecnológicos que se deben superar para una aplicación generalizada de esta nueva tecnología de decoración cerámica.This article presents an overview of the digital inkjet printing technology applied to the ceramic sector. It presents a historical view of the main inkjet technologies currently employed. The article also discusses the changes that have come about in the areas of product development, the search for the printing head technology that was best suited to this kind of application, the different types of ceramic inks and their properties, and it concludes by commenting on the technological challenges that will have to be overcome before widespread application of this new technology can be accomplished

Mechanical properties obtained by nanoindentation of sintered zircon-glass matrix composites

This study was undertaken to determine the effect of zircon content and firing temperature on the hardness and indentation modulus of zircon–glass composites obtained by sintering. A standard non-devitrified borosilicate glass (SRM 717a) powder and an industrial micrometric zircon powder were used to prepare mixtures with a zircon volume/solids volume between 0 and 0.63, by the wet method. The values of these mechanical properties were determined by nanoindentation and related to the most important microstructural characteristics of the composites, such as porosity, zircon volume fraction, glass volume fraction, and average zircon grain size. Composite mechanical performance was interpreted and determined by statistically analysing the results of a large number of indentations using two maximum loads. An empirical model was developed that describes the effect of these microstructural characteristics on composite hardness and modulus of indentation. Composites of high hardness (11.3 ± 2.5 GPa) and low porosity (ε = 0.07) were obtained at 1100 °C from a mixture with a zircon volume/solids volume of 0.43

Non-isothermal sintering of powdered vitrified composites. A kinetic model

This report sets out the results obtained on studying the sintering process of glass–zircon composites, analysing the microstructural changes that developed on modifying zircon content. The sintering of composites with moderate zircon contents only developed via particle rearrangement by viscous flow. In contrast, at high zircon contents, the zircon solution–reprecipitation process was also required. A kinetic model was developed and validated that describes the effect of the heating rate and zircon volume fraction on the composite degree of non-isothermal sintering progress associated with particle rearrangement by viscous flow

Sinter-crystallisation kinetics of a SiO2–Al2O3–CaO–MgO–SrO glass-ceramic glaze

This paper examines the microstructural development and kinetics of the sintering and crystallisation processes of a SiO2–Al2O3–RO (R = Ca, Mg, Sr) glass-ceramic glaze. Crystallisation and sintering kinetics were studied by DTA and HSM, respectively, at different heating rates. The kinetic parameters of crystallisation were determined by the usual methods (Kissinger, Kissinger-Akahira-Sunose, Ozawa and Augis-Bennet methods), and the Johnson–Mehl–Avrami–Kolmogorov (JMAK) model, with an Avrami index of n = 3, characteristic of the surface crystallisation of very fine glass particles, was found to describe crystallisation kinetics very well. Sintering could also be described by the JMAK model, but with n < 1. Assuming the effect of temperature on the sintering rate to be the same as that of this variable on the inverse of glass matrix viscosity, a model was developed, based on the JMAK model, which only required a single fitting parameter. As the heating rate increased, the degree of overlap between the sintering and crystallisation processes was verified to decrease

Densification of irregular polydispersed glass particles described as a complex relaxation process

The sintering of compacts of irregular non-crystallising glass particles was studied by isothermal and constantrate heating experiments in a hot stage microscope. The resulting data fitted very well to kinetic equations developed in this study, in which sintering is assumed to be a complex relaxation process, described by the Kohlrausch–Williams–Watts (KWW) relaxation function. The effect of compact pressing pressure, heating rate, and particle size distribution on the sintering curve was determined. It was generally verified that the effect of temperature on the sintering rate could be described by the effect of temperature on the inverse of glass viscosity. For industrial particle size distributions, that the pre-exponential factor of the process rate constant (or inverse of relaxation time) increased with pressing pressure and decreased with the inverse of particle mean radius. For abnormally wide particle distributions a combination of KWW functions were required

Non-isothermal sinter-crystallisation of satin glazes: A kinetic model

Many materials of a glass-ceramic nature are obtained by glass particle sinter-crystallisation, whose process kinetics have been studied very little. The present study analyses the physico-chemical transformations that develop during the firing of a complex commercial satin glaze (containing more than five phases), with high frit content, particularly focusing on sinter-crystallisation kinetics. Glaze sintering and phase evolution were studied by hot stage microscopy (HSM) and X-ray diffraction (XRD). The glaze melting and crystallisation ranges and the kinetic parameters of the crystallisation process were determined by differential thermal analysis (DTA). Glaze sinter-crystallisation behaviour and the development of the crystal mass fractions, residual glass compositions, and effective viscosity, ηeff, during heating are discussed, based on Rietveld analysis of the XRD data. A new kinetic model was developed that describes the non-isothermal sinter-crystallisation of materials exhibiting three-stage sintering. A two-step kinetic model is involved: sintering with concurrent surface crystallisation (corresponding to sintering stages I and II) and sintering with simultaneous partial melting of crystalline phases (sintering stage III). The experimental data obtained by hot stage microscopy (HSM) at different heating rates were compared with those estimated by the model. The results obtained by the two methods exhibited very good agreement. The crystallisation kinetic parameters (activation energy, Ecr, and Avrami index, n, obtained by DTA, were consistent with the viscous flow activation energy, Q2, corresponding to the first sintering step (sintering stages I and II). The model was used to calculate the values of the effective sintering viscosity, ηs, of the glaze melt. These values were compared with the experimental effective viscosity, ηeff, data obtained by hot stage microscopy (HSM). Both sets of results exhibited good agreement. Effective sintering viscosity, ηs, which is readily measurable, helps better understand the role played by the different glaze constituents and by the firing conditions in sintering, enabling more rational design of these materials

Kinetic study of the thermal decomposition process of calcite particles in air and CO2 atmosphere

The thermal decomposition process of calcite particles (0.45–3.60 mm average diameter), made up of porous agglomerates of very small CaCO3 microcrystals, was studied in the 975–1216 K temperature range. The experiments were carried out under isothermal conditions in air atmosphere, in CO2 atmosphere, as well as in a gas stream comprising different concentrations of air and CO2. An equation is proposed that relates the calcite conversion degree to both reaction time and operating conditions. The equation satisfactorily fits to the experimental results obtained in the entire tested range of particle sizes and temperatures in all the studied carbon dioxide concentrations

Calcium carbonate decomposition in white-body tiles during firing in the presence of carbon dioxide

This study examines the thermal decomposition process of the calcium carbonate (calcite powder) contained in test pieces of porous ceramics, of the same composition as that used in manufacturing ceramic wall tile bodies, in the presence of carbon dioxide, in the temperature range 1123–1223 K. The experiments were carried out in a tubular reactor, under isothermal conditions, in a gas stream comprising different concentrations of air and carbon dioxide. Assuming that the relationship between the molar concentrations of CO2 on both sides of the gas–solid interface in the test pieces was conditioned by an equilibrium law of the form , the equation proposed in a previous paper was modified to correlate the results obtained when the experiments were conducted in the presence of carbon dioxide. The modified equation fitted well to the experimental data obtained in the temperature and carbon dioxide concentration ranges studied. The knowledge derived from this research has enabled the firing cycle used in the single-fire manufacture of this type of wall tile to be optimised