Piotr Wyszomirski

Polish clayey raw materials for the production of ceramic tiles

Abstract Development of the Polish ceramic industry over the last ten years has resulted in a sharp increase in demand for basic raw materials, especially for ceramic clays - both white- and light-firing as well as red-firing varieties. Polish sources of white-firing clays are rather scarce. Their production is based on Santonian sandy-clayey sediments of the North-Sudetic Trough (Lower Silesia, SW Poland). Light-firing varieties occur mainly in Lower Jurassic sediments on the northern margin of the Holy Cross Mountains (central Poland). Red-firing well-sintering clays of Triassic age are known in the northern margin of the Holy Cross Mountains as well as in the Cracow-Silesian Monocline. The white-firing Santonian clays contain mainly highly-ordered kaolinite (~50%) and quartz (~30%) with minor amounts of illite. Their grain-size median ranges between 1.9 and 2.5 μm. They show moderate plasticity (bending strength after drying at 1.7-1.9 MPa) and weak sinterability (water absorption after firing ~12%), but greater lightness after firing (L parameter ~86%). The lightfiring Jurassic clays are kaolinitic-illitic in character, with a variable content of quartz. Kaolinite is represented by the low-ordered variety. The grain-size median is also variable, ranging between 1.1 and 3.4 μm. They show good plasticity (bending strength after drying 2.6-2.8 MPa), good or very good sinterability (water absorption after firing <6%) but moderate lightness (L ~79%). Triassic red clays are highly polymineralic, with illite, kaolinite, smectite, chlorite and mixedlayered minerals occurring in variable amounts. Their specific features are: large hematite content (5-12%), commonly small CaO content (<0.5 wt.%) and an extremely small organic matter content (≤0.1 wt.%). Their grain-size median usually varies between 2 and 3 μm. Using such clays, sintered ceramics (e.g. stoneware tiles) are obtained after firing in the temperature range 1150-1200°C.

Fly ash in Polish building ceramics : threat or proecology ?

Abstract Fly ash from the combustion of bituminous coals extracted in some Polish collieries (e.g. from “Wesola” colliery in the Upper Silesian Coal Basin) can be characterized by the moderate contents of subordinate and trace elements as well as by acceptable radioactivity. Hence, the fly ash can be used successfully for the production of building ceramic materials. The increase in the amount of fly ash (60–70 wt.% and more) in the raw materials for building ceramics can be considered as a proecologic solution. On the one hand it results in the utilization of this waste material and on the other it contributes to a decrease in the consumption of unrestorable clay raw materials.

Application of hot-stage microscopy to evaluating sample morphology changes on heating

Investigations of the thermal properties of a raw material or a ceramic product under a hot-stage microscope allow, among others, determining the characteristic temperatures corresponding to the changes of the shape and the cross-section area of samples being heated. They are based on observing and analysing images of the sample recorded with the growth of its temperature. The pictures of changes allow establishing—for the raw materials with the ability of thermal expansion—the technological temperatures of sintering, softening, thermal expansion, melting and flowing. Their knowledge is necessary in determining optimum ranges of manufacture conditions for a number of ceramic processes. Considering some difficulties with precise determination of these characteristic temperatures and with the problem of measuring the coefficient of thermal expansion S of clay raw materials, the authors have proposed hereby a new method of measuring a sample cross-section area on heating under a hot-stage microscope. It has been invented and implemented in the Matlab software environment on the basis of an image analysis of the expanding sample. The changes of its cross-section area (i.e. an outline area visible under a hot-stage microscope) are continuously recorded on the film and can be converted after digital processing into sample volume changes. The method is applicable to precise measuring the coefficient of thermal expansion S of clay raw materials, among others those used in the manufacture of lightweight ceramic aggregates.

The Characteristics of Organic Matter from the Triassic Clays of nw Margin of the Holy Cross Mts (Poland) — Preliminary Report

The Characteristics of Organic Matter from the Triassic Clays of nw Margin of the Holy Cross Mts (Poland) — Preliminary Report The molecular character of organic matter in Triassic clays on the NW border of the Holy Cross Mts was determined in apolar, aromatic and polar fractions of extractable organic matter (OM) using GC-MS analysis. The contribution of terrestrial higher plants to the kerogene is revealed by the dominant presence of odd long-chain n-alkanes and by the occurrence of retene. Benzophenone, fluorenone, cyclopenta(def)phenanthrenone, antracenone and benzanthrone were among the compounds identified in polar fractions of the soluble organic matter. These commonly originate during strong oxidation of sedimentary organic matter. The aromatic fraction is characterised by the presence of phenyl derivatives (PhPAC) such as phenylnaphthalenes, terphenyls, phenyldibenzofurans and phenylphenanthrenes that are also products of the abiotic oxidation of organic matter. The oxidation processes that occurred during sedimentation and during early diagenesis resulted in a very significant decrease in the organic matter content in the clays. This decrease considerably influences their technological properties.

EPR Study of Paramagnetic Defects in Clay Minerals

EPR Study of Paramagnetic Defects in Clay Minerals Radiation induced defects (RID-s) and transition metal ion impurities were revealed by EPR (Electron Paramagnetic Resonance) spectroscopy in kaolinites from a number of Polish deposits. Arelationship between the intensity of the EPR signals of the RID-s and quantity of radioactive elements was defined in these minerals. In one of the deposits of kaolinites (Wyszonowice) the EPR signal intensity depends on grain size. Other clay minerals studied (illites, montmorillonites) only show weak signals of the RID type. Badania paramagnetycznych defektów w minerałach ilastych metodą EPR Punktowe defekty strukturalne typu RID-s były badane metodą elektronowego rezonansu paramagnetycznego (EPR) w próbkach kaolinitu pochodzących z różnych złóż Polski. Stwierdzono w nich zależność między ilością defektów strukturalnych a zawartością pierwiastków promieniotwórczych. W przypadku kaolinitu pochodzącego z jednego ze złóż (Wyszonowice) sygnał EPR zależy też od uziarnienia minerału. Pozostałe badane minerały ilaste (illit, montmorillonit) ujawniają jedynie słabe sygnały typu RID.