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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.
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.
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 for 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.%.
Ceramic materials were obtained from mixtures of aluminium sludge and slate powder (with different Al2O3:SiO2 molar proportions), which were dried, shaped by uniaxial pressing and sintered at temperatures in the range of 950 to 1300 oC, in order both to detoxify the sludge by fixing the metals in a leach-resistant ceramic matrix and to yield a new material from the reactions of the above compounds at high temperature. The most promising material was obtained from the 2:1 mixture sintered at 1300 oC, which was also found to be inert after leaching tests. The average Vickers hardness HV3 (683), bend strength (126 MPa),Young’s modulus (161GPa) and fracture toughness (3.35 MPa.m1/2) are significantly higher than those found for the as sintered slate powders, which is attributed to the increased fraction of a-alumina and reduced content of glassy phase in the microstructure of the material due to the sludge addition.
Chemically-bonded refractory ramming mixes from Egyptian quartz and quartzite raw materials were processed for application in lining induction furnaces for ductile iron production.Two Egyptian quartz samples and one quartzite sample as well as an imported quartz mix were used. Chemical and mineralogical composition as well as crystallite size of quartz mineral and grain-size distribution of the latter mix were determined, using wet-chemical, XRD and sieve analysis methods. The obtained data were applied to process similar mixes from the Egyptian quartz and quartzite samples. Densification and thermo-mechanical properties of all mixes were determined along with the rate of transformation of quartz to cristobalite after firing up to 1400°C.The results led to recommend the Egyptian Rod EL-Lekah quartz raw material for processing chemically-bonded ramming silica mixes similar to the imported types in lining induction furnaces for ductile iron production after adding 1.2% boric acid. This is based on its relatively higher purity, larger crystallite size and hence lower rate of quartz-cristobalite transformation as compared with the other Egyptian quartz and quartzite mixes. Hence, the recommended mix shows relatively lower percentage of thermal expansion at 100-300°C and higher rate of subsidence under load up to 1500°C with higher degree of densification after firing up to 1400°C.The increase of boric acid content up to 3.2% leads to excessive development of liquid phase on firing up to 1400°C at the expense of quartz and cristobalite. Accordingly, higher rate of vitrification occurs which deteriorates the thermo-mechanical properties of the fired mixes.
Main objective of this study is to recycle shell wastes from the investment casting industry, using powder technology to produce refractory parts. Refractory powders were recovered from bulk wastes using a ball-milling technique and injection-moulded to produce refractory parts. Many thousands of complex-shaped parts were injection-moulded by optimising the process parameters. Recycled powders and the parts were characterized by particle size analysis, scanning electron microscopy, thermogravimetric analysis, density, and size measurements. Performance of the injection-moulded products was tested in sampling operations at molten steel under industrial steelmaking practice.The results allow us to conclude that the shell wastes can be effectively milled and used to produce refractory parts by the injection moulding process.After injection moulding followed by sintering, the final products present a porous microstructure, which has a beneficial effect on their thermal shock resistance.
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.
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.
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