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In the production of ceramic tiles, composition of body and firing conditions determine the phase transformations and in turn affect the final properties of the product. Thus, selection of relevant raw materials and characterisation of their individual physico-mechanical and chemical characteristics are very important. In this study, sintering behaviour of a model double-fired ceramic wall tile body, mainly consisting of a sandy clay, was investigated. Further formulations were also prepared containing the sandy clay and increasing amount of calcite and were compared with a commercial formulation. Raw materials were characterized using XRF and XRD. In order to study the thermal properties of the developed formulations, TGA/DTG measurements were carried out. The sintering behaviour was evaluated using a double-beam optical non-contact dilatometer. XRD was also used to analyse the phases before and after firing. Microstructural and microchemical characteristics of the fired formulations were observed using scanning electron microscopy (SEM). Finally, the physical, mechanical and colour properties of the formulations, such as water absorption, linear firing shrinkage, bulk density, breaking strength and chromatic coordinates, were measured. The results showed that it was possible to develop wall tile formulations only by appropriate mixture of sandy clay and calcite and obtain suitable technological properties.
The aim of this study is to determine the properties of metarhyolites from Ilgin-Konya (Turkey) area and to decide whether or not metarhyolites are suitable as a flux agent for porcelain stoneware tile production. For this aim, the chemical and mineralogical properties of metarhyolite were determined by chemical analyses, XRD and SEM studies. Starting from the reference mix composition, different amounts 4, 8, 12 and 16 wt.% of potassium feldspar were replaced with the same amounts of metarhyolite. All the samples were fired under industrial conditions at 1200 °C for 49 min. The physical and mechanical properties of the fired porcelain stoneware bodies such as water absorption, linear shrinkage, bulk density and fired flexural strength were measured. Fired bodies were subjected to colour measurements and X-ray diffraction (XRD). The results indicate the possible use of metarhyolite as an effective fluxing agent in porcelain tile bodies.
Due to the growing production of boron wastes and the connected serious environmental problems, in the last years several scientific researches have been carried out with the aim to use them as new raw materials. The production of boron wastes and the new possible evaluation strategies are discussed with both economic and environmental aspects, on the bases of the reports and studies perfomed in recent years.
Cogeneration of heat and power is an energy efficiency technology still valid and worthy of dissemination in the ceramics industry. At present, around thirty ceramic plants produce approximately 140 MW electric power in Italy by this technology applied to spray driers. The main obstacle to a more widespread distribution of cogeneration consists in the investment costs, which in particular hinder its implementation by small and medium enterprises. In order to favour the application of a cogeneration plant to users with relatively limited consumption or, at least, make that cogeneration may be easily applied to single machines with only moderate heat energy demand, 100 kW electric power gas-microturbines are taken into consideration. Ceramica Mediterranea in Guspini (Sardinia), porcelain stoneware tile producer, and Turbec in Ferrara, microturbine producer, carried out an industrial R&D project with the support of the Italian Minstery of Industrial Productive Activities. The project consisted in the implementation of a cogeneration plant with four microturbines operated with LPG and applied to fluid-bed driers for granulated powders. The results obtained in operation, the advantages achieved and the profitability of the system are presented.
The rheological behaviour of ceramic suspensions (for slip casting, spray-drying, glazing, screen-printing, ink-jet printing) affects the quality of the products and the yield of the processes. Therefore, the importance of rheology control, either for Quality Control (QC) aims or for system formulation, is widely recognized. As the determination of the viscosity and its dependence on flow (flow behaviour) and on time are critical issues, the first part of this work is focused on the empirical instruments commonly used in many ceramic factories. Such instruments have the advantage to be simple and cheap, but the information they provide are limited and the optimization of the procedures is important to improve the reproducibility and precision. Therefore, in the second part of the paper, suggestions about simple tests and protocols applicable to such instruments are given. The protocol suggested try to minimize the influence of the factors that can affect the results, such as the thermo-mechanical history of the samples.
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