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The physical and mechanical properties of triaxial compositions involving the rock-type porcellanite, clays and volcanic ash (as flux) have been investigated. Two systems composed of (i) porcellanite/ash/low-plasticity clay (P-A-V) and (ii) porcellanite/ash/high-plasticity clay (P-A-G) were studied. In both systems the ash and clay proportions were alternatively held constant at 10% while varying the other and the porcellanite content such that for any given composition the porcellanite constituted the major body composition by weight (50 - 80%). In the P-A-V system it was found that essentially the same degree of total linear shrinkage (drying plus firing) was acheiveable over a range of compositions by keeping the ash constant and appropriately varying the clay/porcellanite ratio. With clay content constant, increased amount of ash enhanced strength, decreased porosity and increased bulk density in both triaxial systems, but at the trade-off cost of increased firing shrinkage.
A multipurpose single body composition was utilized for producing tiles for various applications viz., wall, floor or high abrasion resistant vitrified product only by controlling the firing schedule. A body composition containing 90% pyrophyllite may be utilized for producing wall tiles at 1100 °C with 0.86% linear shrinkage, 14.2% water absorption and 16.2 MPa flexural strength while the same composition when fired at 1175 °C exhibited properties like 4.0% linear shrinkage, 4.0% water absorption and 38.7 MPa flexural strength which conform to the requirements of floor tiles. Similarly a composition containing 50% pyrophyllite on firing at 1175 °C exhibited 5.75% linear shrinkage, 0.23% water absorption and 60.0 MPa flexural strength which conform to the requirements of synthetic vitrified tiles. The same composition at 1125 °C may be utilized for producing floor tiles. XRD analysis of sintered samples confirms the presence of quartz and mullite. The latter phase increases with increasing pyrophyllite content. Presence of mullite in higher proportion was responsible for the development of higher flexural strength. Microstructural features were also observed through SEM.
The possible use of trachyte as an alternative fluxing agent in a commercial floor tile body was investigated. The experiments were carried out in two parts: In the first part, standard tests were applied to the products obtained from the experimental tile bodies modified with varying amounts (0-40 wt. %) of non-magnetic trachyte following single fast-firing under industrial conditions. The results indicated that 20 wt. % of trachyte (TRA2 formulation) as a substitute of albite completely and pegmatite partially in the standard formulation (STD) was satisfactory to carry out further experiments. In the second part, both STD and TRA2 formulations were further fired at different peak temperatures under laboratory conditions in order to establish their vitrification ranges and optimum firing temperatures. Consideration was also given to the phase and microstructural evolution of the tile bodies using x-ray diffraction (XRD) and scanning electron microscopy (SEM) in combination with energy dispersive x-ray spectroscopy (EDS), respectively. The preliminary results showed that it was possible to incorporate trachyte into a floor tile formulation as a fluxing agent and to obtain meaningful technological properties.
In the county of Campos dos Goytacazes, north of the State of Rio de Janeiro, Brazil, there is a large production of sugar, in which the sugar cane bagasse is used to generate power in boilers. This work has the objective to incorporate sugar cane bagasse ash into clay bricks, another important industrial activity of the county. Characterization of the ash was done by chemical composition, particle size distribution, X-ray diffraction and scanning electron microscopy. Ceramic mixtures with 0, 5, 10 and 20 wt % of ash were prepared. Specimens were fabricated by extrusion and then fired in an industrial furnace at 970 °C. Technological properties such as plasticity, water absorption, linear shrinkage and flexural strength were evaluated. Microstructural evaluation was also performed by X-ray diffraction and SEM. The results showed that the bagasse ash is predominantly composed of quartz. The ash addition made the workability easier and increased the porosity after firing. It was concluded that the incorporation of sugar cane bagasse ash into clay bricks fired at 970 °C can be done up to a limit of 5 wt %.
The most common method of controlling the variable parameters in the process of spray drying ceramic powders is based on heuristic rules which are known to very few people and are difficult to extrapolate to other spray-drying plants. In our research, the orthogonal experimental design was applied to determine the variable parameters that exert the greatest effect on the quality of the powder, which is expressed as being the smallest deviation away from the nominal maximum grain size. A preliminary analysis allowed us to select an initial set of independent parameters that consisted of the intake temperature, the outlet temperature, slip flow rate and the depression inside the spray dryer. Application of the Taguchi Approach made it possible to determine the relative importance of each of these parameters as well as the optimal operating conditions. The optimal operating conditions were confirmed by implementing them in an industrial plant.
The effect of zircon additions on cordierite stabilization, porosity and thermal shock resistance of mullite-cordierite refractories with different content of mullite and cordierite was examined. The results show that the cordierite peaks are more sharp in composites fired from 1250 ° to 1350 °C in presence of zircon addition, while in zircon-free composites cordierite decomposes at 1300 °C. The thermal shock of specimens increases by the addition of zircon, especially in the composites containing a lower cordierite phase.
Glass-making is a very sophisticated skill and the contribution given by the chemical analyses of glass materials is fundamental for the classification of glass types and for identifying compositional groups according to consistent characteristics that can be associated with chronological and geographical differentiations. The chemical composition of glasses is particularly complex: to a few basic constituents many components were added, either derived from impurities in the raw materials or intentionally incorporated into the glass mix. The field of study concerning the chemical composition and the technology of Byzantine mosaic glass production has not been dealt with in a systematic manner and certainly not exhaustively from the view point of classification according to the reconstruction of chronological and geographical development. Nevertheless, it is of great interest because it is probable that during the Byzantine period the production of mosaic glass was quantitatively comparable to those of glass for other common applications. In this paper we propose a methodology for classifying Byzantine mosaic glasses on the basis of treatment of the chemical composition data. Byzantine glasses are also compared to glasses of different epoch and provenance.
A short description of the kaolinite structure as well as metakaolinite structure is given. Different views on process of the transformation of kaolinite into metakaolinite are shortly presented.
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