ENHANCING CERAMIC PROPERTIES WITH TUNISIAN KEF ABED CLAY AND SEDIMENTARY ROCK BLENDS

Portugal is well known for its facades decorated entirely with ornamented glazed ceramic wall tiles called azulejos. On ageing, the tiles may detach and fall off, or deteriorate to such an extent that it becomes necessary to replicate them. Hence tile replication is a common practice in Portugal for façade restoration, but very often these new tiles do not have the same physical and/or chemical properties as the original ones. Such differences might be a factor in differential deterioration of the façades after restoration. One step toward an improvement in compatibility is to make new ceramic bodies with the same characteristics as the original ones. This study focuses on two types of glazed ceramic wall tiles from the Oporto region in Portugal: ‘calcic faience’ and pó de pedra. A total of 25 samples from the late nineteenth to early twentieth centuries were studied systematically as an attempt to improve knowledge of these materials and to create a basis for their replication. All samples were collected from facades that were under conservation/restoration at the time when sampling was performed. The original traditional ceramic bodies were analyzed by X-ray diffraction and X-ray fluorescence. Total open porosity, capillary absorption coefficient, and mercury intrusion porosimetry were also measured in order to gain knowledge on their physical characteristics in addition to their chemical and mineralogical compositions. High-temperature crystalline phases such as diopside, gehlenite, and mullite were found in the calcic faience, suggesting that the firing temperature of calcic faience bodies was within the range of 1100–1150 °C. Calcination trials were also performed in order to determine the most probable firing temperatures of the ceramic bodies. Collected data led to the assumption that the raw materials used for the ceramic bodies were kaolinitic clay, quartz sand, limestone, and talc. The raw materials for pó de pedra tiles were found to include kaolinite clay and quartz with firing temperatures estimated within the temperature range of 1150–1360 °C. Technical replicas made on the basis of these investigations were found to have the same mineralogical and capillary properties as the original tiles.

Renaissance lustred majolica shards from Gubbio and Deruta (Central Italy) were investigated in order to point out differences in chemical and mineralogical composition between these two very similar Italian potteries and furthermore to find correlations with the local raw clay materials probably used for their production. Chemical and mineralogical analysis on the ceramic body were performed by ICP-OES (inductively coupled plasma optical emission spectroscopy) and XRD (X-ray diffraction), respectively. Investigation of the ceramic body revealed significant differences on calcium content indicating that it could be used as a marker for the two different productions. A separation of the ceramic shards in groups, on the base of their provenance, has been achieved applying to the data set formed by the chemical compositional data some multivariate techniques, such as PCA (principal component analysis) and HCA (hierarchical cluster analysis). Even the mineralogical composition of the groups shows very interesting features, differing Gubbio production from Deruta one for the presence of several mineralogical species. The investigations carried out on clays that were collected in the two geographical places have confirmed these differences. In fact, the clay materials have a chemical composition coherent with that one found in the shards. Firing tests performed by heating these clay in different conditions (temperature and soaking time) have shown a different behaviour as concerns the formation of the minerals and it is compatible with the shard composition found. From the comparison between the fired clay and the ceramic shards, some assumptions about the firing conditions applied by the ancient potters have been drawn.

The challenging issues in ceramic tiles are low mechanical strength, thermal discomfort and high production costs. And in most efforts to improve strength, emphasis has been placed on minimization of quartz content in the ceramic tiles formula. This is due to β-α phase inversion of quartz which occurs at 573°C during cooling resulting to the development of stresses which initiate fracture and affects the strength of the final body. The objective of this work was to evaluate the possibility of using vermiculite and rice husk ash (RHA) in the composition of ceramic tile body. Initially, a typical ceramic body composed of the mixture of vermiculite and RHA batched with clay, feldspar, quartz and kaolin was prepared. Ceramic bodies were then obtained from this ceramic mixture by pressing samples at a forming pressure of 35MPa. These bodies were then fired at 1180°C in a laboratory furnace and finally the changes in the physical and mechanical properties caused by the introduction of vermiculite and RHA were tested and evaluated. The chemical composition of the raw samples was analyzed by X-ray fluorescence (XRF) while the phase composition was investigated using X-ray diffraction (XRD). The morphology of the powdered samples was studied by using Scanning electron microscopy (SEM). The bulk density and open porosity of the sintered ceramic bodies were evaluated using Archimedes ‘principle while the flexural rupture strength was determined by the three point bending test method. The major chemical compounds in vermiculite raw sample were SiO2, Al2O3 and Fe2O3 while RHA sample was found to contain mainly SiO2. From the XRD analysis, vermiculite sample had crystalline vermiculite while RHA sample had amorphous silica at low temperature below 900°C and crystallized (tridymite) above 900°C. The results from physical and mechanical properties tests show that with addition of vermiculite and RHA, the percentage of porosity, water absorption and linear shrinkage were increasing while the bulk density and bending strength of the fired ceramic bodies decreased. Among the studied compositions tile bodies made from a blend containing 20% wt. vermiculite and 5% wt. RHA were found to have the best properties for ceramic tiles applications. For this combination the percentage of porosity, water absorption and linear shrinkage were 12.08%, 7.60% and 3.29% while the bulk density and bending strength were 1.88 g/cm3 and 18.84 MPa respectively. These values were close to the required standards of wall and floor tiles.

Reformulation of roofing tiles body with addition of granite waste from sawing operations

Relationship between the thermal behaviour of the clays and their mineralogical and chemical composition: Example of Ipoh, Kuala Rompin and Mersing (Malaysia)

The objective of performing transmission electron microscopy (TEM) tomography (TEMT) on poly (lactic acid) (PLA)/clay samples is to characterize their 3D microstructure by obtaining the dispersion distribution and orientation of the dimensions of the clays. This information cannot be elucidated from a qualitative TEM analysis or from conventional characterization techniques such as X-ray diffraction. The nanocomposites are obtained by mixing PLA with Cloisite 20A and 30B at different extrusion shear rates which have been analyzed in 3D. Quantitative TEMT is performed to all the nanocomposites and the resulting 3D quantitative characterization (geometry of clay particles misalignment degree and distribution) is used for a more realistic comprehension of the mechanical behavior of the nanocomposites.

This chapter describes the methods of magnetic and mineralogical analysis that can be used in the study of diamond-bearing rocks, specifically in the assessment of diamond potential. Picroilmenite (paramagnetic particles in rock-forming dolerites) and titanomagnetite with magnetite-ulvospinel exsolution structures were also thoroughly studied and the results are given in detail. Relationships between magnetic properties and mineralogical composition were defined for all studied samples along with their mineralogical and elemental compositions. Specific mathematical methods of magnetic and mineralogical data processing were developed for samples containing several ferrimagnetic minerals. The results were validated using mineralogical and elemental composition analysis.

Thermal behavior of clays strongly influences that of ceramic bodies made thereof and hence, its study is must for assessing its utility in ceramic products as well as to set the body composition. Irreversible dilatometry is an effective thermal analysis tool for evaluating thermal reactions as well as sintering behavior of clays or clay based ceramic bodies. In this study, irreversible dilatometry of four red clay samples (S, M, R and G) of Gujarat region, which vary in their chemical and mineralogical compositions was carried out using a Dilatometer and compared. Chemical analysis and XRD of red clays were carried out. XRD showed that major clay minerals in S, M and R clays are kaolinite. However, clay marked R and G showed presence of both kaolinite and illite and /muscovite. Presence of non-clay minerals such as hematite, quartz, anatase were also observed in all clays. XRD results were in agreement with chemical analyses results. Rational analyses showed variation in amount of clay and non-clay minerals in red clay samples. Evaluation of dilatometric curves showed that clay marked as S, M and R exhibit patterns typical for kaolinitic clays. Variation in linear expansion (up to 550°C) and shrinkage (above 550°C) between these three clays was found to be related to difference in amount of quartz and kaolinite respectively. However, dilatometric curve of G exhibit a pattern similar to that for an illitic clay. This study confirmed that sintering of investigated kaolinitic and illitic and / muscovitic red clays initiates at above 1060°C and 860°C respectively and this behaviour strongly depends upon type and amount of minerals and their chemical compositions.

Potential use of the lower cretaceous clay (Kef area, Northwestern Tunisia) as raw material to supply ceramic industry

Sintering behaviour of a clay containing pyrophyllite, sericite and kaolinite as ceramic raw materials: Looking for the optimum firing conditions

Exploitation of petroleum waste sludge with local bauxite raw material for producing high-quality refractory ceramics

Phase changes of ceramic whiteware slip-casting bodies studied by XRD and FTIR

Firing transformations of Chilean clays for the manufacture of ceramic tile bodies

The exploitation of the interaction between nanostructured matter and small molecules, such as H2O at interfaces via dynamic hydrogen bonding, is essentially the key for smart, responsive nanodevic...

Optical microscopy, X-ray diffraction, X-ray fluorescence and scanning electron microscopy analyses were carried out on a typical Sevres soft (frit) porcelain plate from 1781 in order to determine the chemical and mineralogical composition as well as the microstructure of its ceramic body, glaze, overglaze decoration and gilding. The body is rich in SiO 2 (73 mass%), CaO (16) and alkali oxide (8) and shows acicular wollastonite and tridymite crystals embedded in a glassy matrix consisting of SiO 2 (75), K 2 O (12) and CaO (9). The 50–90 µm thick, transparent lead glaze (40.9 PbO) contains 47.6 SiO 2 , 6.5 K 2 O and 3.5 CaO and shows a 35–75 µm thick reaction zone (50 SiO 2 , 30 PbO, 14 CaO) towards the body. The maximum thickness of the different paints is 50 µm, with 15 µm as mean thickness of the individual paint stroke. Two blue colours, for the dentil comb and the flower painting, are chemically distinct (colouring CoO in the dental rim 7, in the flower’s blue 2 mass%) and contain many As- and Pb-rich globules and dendrites. Pseudohexagonal shaped platelets of Pb–Sb–Sn triple oxide crystals, embedded in a colourless glassy matrix, generate the opacity and the colour of the yellow paints. Opaque olive green colours are created by the combination of such yellow crystals with a bluish, Cu and Co bearing glassy matrix. The opaque red overglaze enamel is a mechanical mix of yellow Pb–Sb oxide crystals with an iron-rich (16 Fe 2 O 3 ) Pb–silica glass. Purple is very homogeneous and shows tiny drops of pure gold (max. diam. 0.5 µm) in a glassy matrix (47 PbO, 46 SiO 2 , 5 K 2 O). Violet is a mechanical blend of flower’s blue and purple. The pure (99.5 Au, 0.5 Fe 2 O 3 ) gilt consists of several folded gold particles. The results of this study are only broadly consistent with the archival documented 18 th century technologies. The compositional dissimilarities of the studied enamels suggest that each colour was independently fritted. Consequently, the original colour recipes written down by Hellot in 1753 must have been modified in the 30 years since then.