Symposium CN
Science and Technology for Silicate Ceramics

Session CN-1 - Functionalized Surfaces of Silicate Ceramics

CN-1:IL01  Multifunctional Inorganic Glazes: Surfaces Mimicking the Nature
J.J. REINOSA, A. DEL CAMPO, J.F. FERNÁNDEZ, Glass and Ceramics Institute (CSIC), Madrid, Spain

Glazed tiles were developed to exploit properties in a multifunctional way (all in one) by the addition of copper. The tiles were translated to industrial furnaces in the production of stoneware: air atmosphere and high temperature (1200 ºC). In order to obtain the concept of multifunctionality on glazes both the amount and the particle size of copper as a function of the glaze layer thickness were taken into account. The samples were characterized by XANES, RBS and Confocal Raman Spectroscopy to obtain chemical analysis with high spatial resolution. The study by SEM and AFM was also performed in order to correlate the structure with a cellular type micro-nanostructure.
Samples with different optical effects were obtained depending on the thickness of the glaze layer because of a mechanism of dissolution and precipitation of copper at the glassy matrix. A copper-gradient towards the surface of the samples was found. Benard currents mechanism was found as the origin of the surface cellular microstructure. Copper at the surface form a microstructure and in turn, a nanostructure is also presented. The combination of both structures and the presence of copper at the surface are responsible of the hydrophobic and bactericide properties which were observed in these inorganic coatings.


CN-1:IL02  Antibacterial and Self-cleaning Coatings for Silicate Ceramics
F. BONDIOLI, Department of Materials and Environmental Engineering, University of Modena and Reggio Emilia, Modena, Italy

The development of advanced materials is increasingly leading to integration of functions into materials and components. This drive in technological innovation is strongly felt in many traditional fields, like textiles or ceramics. Over the last twenty years, the so-called "traditional" ceramics industry for tile production has undergone a profound technological reorganization, both in production technologies and automation of the different production phases, but new products and possible new applications are still needed, thereby opening up new markets.
In this presentation a review of the state of art in the use of nanotechnology in the ceramic tile sector both from an industrial and scientific point of view will be presented. Special attention will be focused on novel smart and functional coating to obtain antibacteric, selfcleaning and photocatalytic tile surfaces.


CN-1:IL03  Nanocomposite Photrocatalyst Based on Layered Double Hydroxides (LDHs) Associated with TiO2
J. RANOGAJEC, O. RUDIC, S. VUCETIC, University of Novi Sad, Faculty of Technology, Novi Sad, Serbia

Surfaces of building materials are constantly exposed to the actions of environmental factors, pollutants of inorganic and organic origin as well as microorganisms, which are significantly contributing to corrosion phenomena.
The application of coatings could decrease the negative action of the pollutant minimizing their direct contact with the substrate. Different types of coatings with additional functions have been developed. A specific problem of these applications is the lack of compatibility of the photocatalysts with the surface of the building materials and the detachment of potentially toxic TiO2 nano-particles. This difficulty was solved by the proper immobilization of TiO2 nano-particles onto the photocatalyst support, layered double hydroxides (LDHs). The newly formed nanocomposite photrocatalyst prevented nanoparticle aggregation providing adequate porosity, improvement of photocatalytic activity, as well as compatibility with the mineral substrates. Different methods for the preparation of TiO2/LDH solution were studied in order to design suitable photocatalytic coatings on the surface of building materials (clay roofing tiles, mortars, renders, bricks, stones). The properties important for the evolution of self-cleaning effect, were analyzed. The positive effect of the coating deposition resulted in the development of photocatalytic activity, improvement of photo-induced hydrophilicity and in a decrease in surface roughness.


CN-1:IL04  Superhydrophobic and Superhydrophilic Surfaces: the Way for Self-cleaning Ceramics
M. RAIMONDO, CNR ISTEC, Faenza, Italy

Recently self-cleaning has been increasingly considered as a key property of ceramic surfaces for indoor and outdoor exposure. One of the possible ways to provide materials of self-cleaning ability is to modulate their wettability - introducing hydrophilicity or hydrophobicity so creating a situation in which it becomes very difficult for dirt to adhere to them - and/or to promote their ability to decompose contaminants particles. The present lecture is an overview of the potentiality offered by nanotechnologies into the development of innovative surfaces by low-cost manufacturing processes, easily scalable for large areas. Examples of chemical and microstructural modifications at nano-scale of different typologies of ceramic surfaces are highlighted by deposition of optically transparent, inorganic, or hybrid organic/inorganic coatings with a controlled nanostructure and chemistry. The hydrophilic behaviour and the attitude to the degradation of c ontaminants were assessed according to the current ISO standard, while the repellence to water was related to contact angle, surface energy and inorganic/organic ratio of coatings' components.
The main hindrances related to the production of industrial ceramic material, in terms of products and process parameters, have been reviewed as well the issues concerning the durability of functional performances over the time in working conditions.


CN-1:IL05  EasyDep - Photocatalytic Surfaces for Silicate Ceramics
D. TOBALDI, M.P. SEABRA, J.A. LABRINCHA, University of Aveiro & CICECO, Aveiro, Portugal

This presentation describes the production of TiO2 and ZnO photocatalytic layers on the surface of ceramic tiles, by using common deposition techniques (screen-printing and jet-spray). The pieces were then used in the discoloration of organic dyes, testing the effect of distinct variables. Amongst these, the irradiation conditions were found crucial to assure optimal performance. The preparation of TiO2-doped powders, attempting to improve their action under visible light irradiation, is also described.


CN-1:L06  Solar Reflectance of Glazed Tiles
T. SUGIYAMA, H. KAKIUCHIDA, K. KUSUMOTO, M. OHASHI, Materials Research Institute for Sustainable Development, National Institute of Advanced Industrial Science and Technology, Nagoya, Japan

Exterior wall tiles with high solar reflectance are effective in mitigating heat-island phenomenon. Such walls have also the potential to decrease the warming up of building interiors in mid-summer. For the purpose of increasing the solar reflectance of wall tiles, several kinds of glazes were prepared to measure their visible and infra-red spectral reflectance by the spectrophotometer. The incident angle of sunlight on vertical exterior wall is larger than 70 degrees at midday of the summer season in Japan. The reflectance theoretically increases with the increase of incident angle. It is important to examine the reflectance against the sunlight with varied incident angles. The practical solar reflectance of glazed tiles is calculated by measuring the hemi-spherical integrated spectral reflectance with an oblique incident light. Even the mat glaze showed larger reflectance when the incident angle was larger than 60 degree. The glazes of tiles having layered structure were also prepared and their spectral reflectance was investigated.

CN-1:L07  Photocatalytic Activity of External Self-cleaning Ceramic Tiles
A. SEVER SKAPIN¹, V. DUCMAN¹, L. ŠKRLEP¹, U. LAVRENČIČ ŠTANGAR², J. RANOGAJEC³, ¹Slovenian National Building and Civil Engineering Institute, Ljubljana, Slovenia; ²Laboratory for Environmental Research, University of Nova Gorica, Slovenia; ³University of Novi Sad, Faculty of Technology, Novi Sad, Serbia

Photocatalytically active materials can be successfully integrated into external surfaces of building materials such as tiles to prevent their ageing and degradation caused by various environmental influences. Nano-titania in anatase modification has been found as the most promising photocatalytically active materials [1]. The production of self-cleaning coatings on ceramic tiles requires introduction of special processing that gives the final product sufficient durability. In order to improve the adhesion of nanotitania coatings onto external tiles, either binders or high temperature process is applied [2]. During the process of firing, the nano TiO₂ layer is sintered and attached strongly to the tile surface. In this way self-cleaning coatings become more durable. On the other hand, firing of nano anatase causes the photocatalytic activity drops to low values. To ensure sufficient adhesion of nanoparticles onto the surface and, at the same time, a high photocatalytic activity the great efforts have been directed to increase the thermal stability of the anatase phase and prevent the growth of nano-particles at elevated temperatures and at the same time optimal temperature of firing has to be found.
We synthesized photocatalytic nano-titania in anatase modification in hierarchically structured spherical clusters consisted of smaller nano-sized subunits. For thermal stabilization of the anatase phase and slow-down the growth of nano-size particles, various dopants were incorporated into the anatase. In order to obtain ceramic tiles with required durability and, at the same time, considerable photocatalytic activity, the effect of firing temperature on durability of the self-cleaning effect was determined.
References
1. Fujishima A., Rao T.N. and Tryk D. A., Journal of Photochemistry and Photobiology C: Photochemistry Reviews, vol. 1, 1-21, 2000.
2. Shimohigoshi M. and Saeki Y., in Proceedings of International RILEM Symposium on Photocatalysis, Environment and Construction Materials, erited by P. Baglioni, L. Cassar, Florence, 2007, 291-297.

 
Session CN-2 - Sustainability of Silicate Ceramics Manufacturing

CN-2:IL01  Sustainability and Competitiveness in the Ceramic Tile Sector: an Overview
G. TIMELLINI, R. RESCA, Centro Ceramico Bologna, Bologna, Italy

A schematic review of the position of environmental sustainability of ceramic floor and wall tile in legislation and international standardization is developed. Starting from this reference framework, the following subjects are dealt with in this paper:
- the present level of performance of ceramic floor and wall tiles as regards environmental sustainability. A list of environmental data and criteria will be presented and discussed, suitable as an inventory for LCA;
- the evolution in the last years of the level of environmental performance of the Italian ceramic tile sector, based on systematic data collection activities involving a highly representative sample of ceramic tile factories. This knowledge is made possible by a data base designed and progressively completed in the framework of a research project (InProCer) funded by Emilia Romagna Region (Italy) and carried out by Confindustria Ceramica with the scientific support of Centro Ceramico Bologna;
- a critical analysis of the contribution of ceramic tiles, as construction products, to the sustainability of the building works;
- environmental sustainability as a competitiveness factor for ceramic tiles;
- the new ISO standard on sustainability of ceramic tiling, in preparation within the ISO TC 189 "Ceramic Tiles".


CN-2:IL02  Preparation of Flame Retardant Layered Silicate / Polyamide 66 Nanocomposite
K. TAMURA¹, S. OHYAMA^{1, 2}, K. UMEYAMA³, ¹National Institute for Materials Science, Tsukuba, Ibaraki, Japan; ²Department of Chemistry, Toho University, Funabashi, Chiba, Japan; ³Topy Industries LTD, Toyohashi, Aichi, Japan

Most of the previous research on nanocomposites has dealt with layered silicate-polymer nanocomposites that are based on smectite clays. Morphology controlling techniques provide effective alternatives to achieve further improvements in nanocomposite properties. Nanocomposites are also potential materials for the improvement of flame resistance performance without ordinary halogen based flame retardants. A flame retardant triazine compound modified mica was prepared to improve the flame retardant performance of polyamide 66 (PA 66). The melamine-modified ME (MME) was melt-kneaded with PA66 using a twin-screw kneader at 270ºC. XRD, TEM, thermal analysis, tensile tests and UL-94 vertical burning tests were used to examine the effects of MME on morphology, mechanical properties and flame resistance performance. TEM and XRD results confirmed the partial exfoliation of the MME in the PA 66 matrix. However, the PA 66/MME nanocomposite had no rating in the UL-94 vertical burning test because it did not extinguish until the entire polymer component was burnt. In this study, we found a correlation between the dispersion state of the silicate layers and the flame decadency in this system. Eventually, the PA 66/MME nanocomposite with 4.4wt% of melamine cyanurate demonstrated V0 class, which is the most flame retardant rating in the UL94 vertical burning test.


CN-2:L03  Development of a Semi-wet Process for Ceramic Floor Tile Granule Production
K. KAYACI, A. ALTINTAS, Y. YILDIRIM, M. KILIC, E. DURGUT, Kale Ceramic Research & Development Center, Can Canakkale, Turkey, H. ERGIN, Mining Engineering Department, Istanbul Technical University, Istanbul, Turkey

In ceramic tile manufacturing industry, the wet process, including wet grinding and spray drying, is widely used for preparing granule. However, energy consumption for the water evaporation in spray dryer has become a major problem in wet process. In recent years, there has been vast amount of research for developing the dry granulation process that consists of dry mills such as vertical roller mill or pendular mill and a granulator. The currently developed dry systems have various problems on the granule shapes and granule size distributions that cause some quality problems in the final products.
In this research, it is aimed to develop a new production system, called as Semi-Wet Process. The new system consists of a raw-material dryer, dry ball mill, separator and additional high speed mixture. The raw-materials having low humidity are ground to the required fineness in dry size reduction process. The other components of recipe, that are prepared in conventional wet process, are mixed with the dry prepared powder in the mixing slurry tank. The addition of dry powder reduces the water ratio of final suspension, in other words, the bulk density of the slurry increases. Hence, the natural gas consumption for water evaporation is decreased in the spray dryer as well as the grinding energy consumption.
The application of developed semi wet system has been carried out in Kaleseramik Factory, which is the largest ceramic manufacturer in Turkey. The sintered floor tile ceramic rejects were ground in the developed dry grinding system to the fineness of 3 % residue of 45 µm. The dry prepared powder was added by 20 % to the mixing tank provided that adjusting the body composition, the bulk density of the monocottura slip rises from 1660 g/l to 1750 g/l and glazed porcelain rises from 1670 g/l to 1750 g/l. The trials in the laboratory test and industrial process have shown that the produced granule performs at least as good as the conventional system products or even better. As a result, the costs of the natural gas consumption reduces from 18,03 US$/Ton to 13,97 US$/Ton for glazed porcelain and 17,81 US$/Ton to 13,66 US$/Ton for "monocottura". The use of developed semi wet system is able to provide profit around 25 % for natural gas consumption and 20 % for grinding energy consumption.


CN-2:L05  Energy and Material Efficiency during Firing of Silicate Ceramics
M. HERRERA, H. BRENDEL, F. RAETHER, Fraunhofer Institute for Silicate Research ISC - Center for High Temperature Materials and Design, Bayreuth, Bayern, Germany

Increasing demand for traditional silicate ceramics makes it necessary for the industry sector to aim for faster and reliable product and process optimization, while reducing energy consumption and CO2 emissions. Although empiricism is more common when dealing with optimization challenges within the silicate ceramic industry, computer simulations have a great potential for enabling sustainable innovation and technical progress in the sector.
Thermal parameters such as temperature profile, furnace atmosphere, heat flow, and temperature distribution at the product are essential for attaining high quality. In this work, such process parameters are approached via a Finite-Element-Model for a silicate ceramic process through the transient calculation of a temperature field in a continuous furnace.
As an advancement to previous approaches, this work focuses not only on the technical aspects of the furnaces, but also on the physic-chemical transformations that occur at the load, essential to understand the parameters that influence material behavior, product quality and emissions.
The simulation is to be validated against a real industrial process. It allows identifying decision criteria for a sustainable production in terms of manufacturing cycles, material and constructive innovation.


CN-2:IL06  Functional Glasses and Glass-ceramics Derived from Wastes
F. BERNARDO, Dipartimento di Ingegneria Industriale, Università degli Studi di Padova, Padova, Italy

The recycling of inorganic waste into new usable glass-based materials has been a key strategy for environmental protection for the last decades. Nevertheless, it must be acknowledged that some criticism remains, mainly concerning costs and energy use. Many efforts have been dedicated to the reduction of processing times and temperatures, especially for the conversion of waste-derived glasses into glass-ceramics. Direct sintering of wastes, combined with recycled glasses, has been proven as a valid low-cost alternative for glass-ceramic manufacturing, for wastes with limited hazardousness. Further improvements rely on the application of waste-derived glasses and glass-ceramics in rather unexplored fields, exploiting their functional properties. In particular, porous glass-ceramics have been increasingly considered, for thermal and acoustic insulations. These products are mainly due to gas release, at moderate temperature (generally <1000°C), in a pyroplastic mass determined by the viscous flow sintering of glass, operated by selected additives ("foaming agents"), both potentially waste-derived. Iron-rich wastes, besides providing cellular glass-based materials, are also useful for products with unusual catalytic activity, magnetic, optical and electrical properties.


CN-2:L07  Mixtures of Metallurgical Slags and Recycled Glasses Converted into Functional Glass-ceramics: Thermally Insulating Foams and Magnetic Monoliths for Induction Heating
I. PONSOT, M. MARANGONI, E. BERNARDO, Dipartimento di Ingegneria Industriale, Università di Padova, Padova, Italy

Several types of metallurgical slags have been stabilized by direct sintering with recycled glasses (common soda-lime glass and borosilicate glass from the pharmaceutical industry), at relatively low temperature (<1100 °C). The resulting glass-ceramic materials could constitute valuable products, due to the observed functional properties, mainly associated to significant content, in the mixtures, of iron oxide. C-containing slags, in particular, led to highly porous glass-ceramics, to be used for thermal insulation, starting from soda-lime glass, owing to the presence of an «oxidation couple»: carbon is homogenously oxidized, releasing gasses (in turn determining the foaming), by reduction of Fe2O3 into FeO. C-free slags, on the contrary, led to dense monoliths, combined with borosilicate glass; in this case, the sintering promoted a limited reduction, with Fe2O3 (hematite) passing to Fe3O4 (magnetite). Magnetic inclusions in the glass-ceramic monoliths, associated to magnetite formation, are particularly advantageous, since they allow the use of the products as efficient substrates for induction heating.


CN-2:L08  Determination of Dry Grinding Properties of Floor Tile Wastes
K. KAYACI, A. ALTINTAS, Y. YILDIRIM, M. KILIC, E. DURGUT, C. YIGIT PALA, Kale Ceramic Research & Development Center, Can Canakkale, Turkey; H. ERGIN, Mining Engineering Department, Istanbul Technical University, Istanbul, Turkey

In ceramic production, there are around 5-9 % of tile defects occurred due to unsuitable body compositions or process operations. The reuse of those fired products creates problems due to difficult grindability features. These kinds of wastes are stored near factories and create environmental problems. There are some attempts to utilize these waste materials by adding to the recipes at small amounts. However, the grinding efficiency of the system is detrimentally affected and the grinding costs increases sharply.
The aim of this work is to determine grinding properties of floor tile wastes in order to utilize more and economical manner in the process. This paper includes grinding experiments in the laboratory dry ball mill. It is cylindrical shape with the diameter of 37 cm and length of 57 cm. The mill is lined by flat shape alumina liners. It is driven by inverter and control panel that allows measuring the mill rotational speed, grinding time, frequency, current and energy consumption. Systematic grinding tests were carried out to observe the effect of feed particle size, feed rate, material moisture and mill rotational speed on the grinding efficiency. Electricity consumption and grinding time were measured to obtain the product having particle size of 45 micron sieve residue 4%. The optimum grinding condition was found to be feed size -1 mm, 49 rev/min mill speed, and ball to material ratio 6. Finally, the ground powder was added in dry form to the body composition. This gives advantages of both reducing the grinding energy costs and also drying costs of final slurry in the spray dryer. The use of dry ground floor tile waste indicated that there are no inconvenient results on the sintered body. The trials in the laboratory test and industrial process have shown that the produced granule with dry ground floor tiles perform at least as good as the conventional wet system products or even better.


CN-2:L09  The Development of Multi-purpose Ceramic Tile Bodies
A. KARA, Anadolu University, Department of Materials Science & Engineering, Eskisehir, Turkey; Ceramic Research Center INC, Eskisehir, Turkey; O.E. SAGLAM, M.F. OZER, Ceramic Research Center INC, Eskisehir, Turkey

This study was made in order to develop a multipurpose tile body using a single formulation. In order to achieve this, several wall and porcelain tile body recipes were prepared using local raw materials at same sieve residues. The most suitable formulations were determined and fired at different peak temperatures and fired regimes under laboratory conditions in order to determine their vitrification ranges and optimum firing temperatures. The tested peak firing temperatures were determined for multipurpose wall and porcelain tile bodies. The physical and thermal properties of the fired bodies such as water absorption, breaking strength, linear firing shrinkage, bulk density and linear thermal expansion coefficient were measured. The vitrification behaviour of the multipurpose bodies was also evaluated using optical dilatometer. Furthermore, the fired bodies were subjected to colour measurements and the phase and microstructural evolution of the developed tile bodies were investigated. X-ray diffraction (XRD) was used to analyse the phases formed before and after firing. Scanning electron microscopy (SEM) was further employed in order to observe the microstructural and microchemical characteristics of the fired bodies with respect to peak firing temperature. The experimental results showed that it was possible to obtain a multipurpose body with the properties in accordance with ISO-EN 10545.


CN-2:IL10  Recycling of Wastes in Ceramic Manufacturing
F. ANDREOLA, L. BARBIERI, I. LANCELLOTTI, Dept. of Engineering "Enzo Ferrari", University of Modena and Reggio Emilia, Modena, Italy

The continued increase in waste requires not only measures to reduce their generation, but also recycling and reuse. In this regard, the latest European Directives concerning waste, Directives 2006/12/CE and.2008/98/CE, are oriented to transforming the European Union into a "recycling society" that attempts to avoid generating waste and that uses it as a resource.
Inorganic waste in Europe, is estimated more than 1,500 million tonnes and traditionally they have been disposed off in landfills. Alternative ways of reuse or recycling of not hazardous inorganic waste should be investigated and implemented.
From the other hand, ceramic manufacturing requires massive amount of natural raw materials, which until few years was mainly based on the traditional system clay-silica-feldspar.
Besides, natural raw materials used show a wide range of compositional variations and the resulting products are very heterogeneous.
Nowadays, ceramic tile cycle works at zero emissions permitting to recycle within the manufacturing process all by-products and partially amounts of residues derived from depuration process.
The waste recovery is viable for all kind of ceramic products, in particular in this review will be described studies regarding both ceramic tiles and bricks manufacturing.


CN-2:L11  Effect of Alternative Materials Added to the Plaster Composition
M. SEYHAN¹, A.TAYCU¹, A. EKER¹, K. KAYACI¹, M. GULA¹, A. KARA², ¹Kaleseramik Canakkale Kalebodur Seramik San. A.S, Can-Canakkale, Turkey; ²Ceramic Research Center, Eskisehir, Turkey

In this study, the effect of alternative additives on the properties (bending strength, water absorption and bulk density) of sanitaryware plaster molds was investigated. For this reason, the alternative additives were partially replaced by plaster as experimental compositions. Perlite, diatomite, glass beads were used as alternative additives and substituted for partially plaster. Technological properties of alternative compositions such as initial setting time, spread, and drying time were measured. The phases present in the standart and experimental compositions were determined by X-ray diffraction (XRD) analyses and the distribution and shape of phases that has been formed in the microstructure were determined by scanning electron microscopy (SEM). It was found that perlite and diatomite decreased the bulk density and bending strength, and also increased water absorption. On the other hand the presence of glass beads decreased the bulk density but increased the bending strength and water absorption.


CN-2:L12  Glass and Glass-ceramics from Natural and Waste Raw Materials
M. MARANGONI, I. PONSOT, E. BERNARDO, P. COLOMBO, University of Padova, Italy; H. ALTALSI, M. BINMAJED, M. BINHUSSAIN, KACST, Saudi Arabia

Monolithic glass-ceramics were produced by a novel sintering approach starting from raw materials as well as industrial waste present in Saudi Arabia. The surface porosity of a glass-ceramic body, produced from direct sintering of selected mixtures of inorganic wastes, can be sealed by a dense sinter-crystallized glass-ceramic layer realized from the same starting raw materials. The investigated wastes consists of fly ash from thermal power plants, recycled soda-lime glass and mining residues, corresponding to both basalt extraction and purification of valuable boron containing minerals. For a mixture comprising boron waste, a substantial viscous flow, for the substrate, was observed even at a relatively low sintering temperature (850 °C).

 
Session CN-3 - New Products and Challenges for Silicate Ceramics

CN-3:IL01  Towards Rational Design of Porcelain Tile Glazes
J.L. AMOROS,  Instituto de Tecnología Cerámica (ITC), Asociación de Investigación de las Industrias Cerámicas (AICE), Universitat Jaume I, Castellón, Spain

The complexity of porcelain tile glaze compositions also translates into complex behaviour during firing in which, concurrently or in partially overlapping form, very different processes develop, such as the dissolution of crystalline phases, the crystallisation of new phases, and sintering phenomena. This complexity, and the scarcity of studies relating to the subject, make it extremely difficult to formulate such glaze compositions scientifically and efficiently. This study analyses the physico-chemical transformations that occur during the firing of these glazes, focusing in particular on the sintering process and its kinetics. A multi-step kinetic model was developed for this purpose, from which the effective viscosity of the glaze melt was obtained. This property was compared, on the one hand, with the effective viscosity obtained experimentally by hot stage microscopy (HSM) and, on the other, with that estimated theoretically from the chemical and mineralogical composition of the material, at different temperatures. The results obtained by the two methods exhibited very good agreement. The concept of effective viscosity provides a better understanding of the role played by the different glaze constituents and the firing conditions in sintering, enabling more rational design of these materials.


CN-3:IL02  New Ceramic Pigments for the Coloration of Ceramic Glazes
M. LLUSAR, G. MONRÓS, C. GARGORI, S. CERRO, J.A. BADENES, Department of Inorganic and Organic Chemistry, University Jaume I, Castellón, Spain

Research trends in the field of ceramic pigments are actually directed to find new host structures and chromophores, or also to develop new preparation routes and decoration strategies. Pigment formulations must be optimized to improve their functional performance and to reduce their toxicity or environmental impact and economic costs, including sustainability aspects. Moreover, they must fulfill the microstructure and rheological requirements of the emerging decoration strategies.
In this communication we provide a general overview of some of these research hot topics. The classical approach of finding new host lattices and chromophores is illustrated with examples of new formulations for red and yellow ceramic pigments, i.e. based on perovskites, pseudobrookites and related titanate structures. The development of environment-friendly pigments containing rare earths or other non-toxic chromophores will be also considered. Finally, we highlight the advantages of non-conventional preparation routes, and also the challenging aspects of emerging decoration strategies, such as the development of nano- or sub-micron pigments and ceramic inks for ink-jet printing technology, or the use of self-generating pigment formulations based on metal-organic or sol-gel precursors.


CN-3:L03  Ceramic Pigments: Prospects and Challenges
M. DONDI, CNR-ISTEC, Faenza, Italy; G. Cruciani, M. ARDIT, Dept. Physicas and Earth Sciences, University of Ferrara, Italy

Ceramic pigments are mostly oxides and silicates that bestow color on glazes and vitrified bodies by a heterogeneous mixture of crystals dispersed in the vitreous phase formed during firing. Ceramic pigments must fulfil strict requirements in terms of optical properties (color saturation and purity, refractive index >1.7), heat resistance (melting point >1400°C) and chemical resistance (in contact with aggressive liquid phases). Industrially-manufactured pigments pertain to a few crystal structures (the main being spinel, zircon, corundum, rutile) which were already in production 60 years ago. They passed practically untouched through technological revolutions, like fast single firing and porcelain stoneware, with their dramatic changes of firing schedules and composition of glazes and bodies. However, ceramic decoration has been drastically innovated only in the last decade with the advent of inkjet printing of ceramic tiles. The present contribution will shortly overview the current knowledge on the origin of color and the technological behavior of ceramic pigments, envisaging promising routes and prospects to develop novel colorants. The challenges to ceramic pigments stemming from the new technologies adopted in ceramic manufacturing will be outlined and discussed.


CN-3:L04  Thermally Comfortable Ceramic Floor Tiles
G.C. KORC, A. KARA, Ceramic Research Center, Anadolu University, Eskisehir, Turkey; F. KARA, Anadolu University, Department of Material Science and Engineering, Eskisehir, Turkey

The use of porcelain floor tile may be limited because of its uncomfortable sensation to walk on with bare feet. As lower is the thermal conductivity and density more comfortable is the ceramic floor tile.
The objective of this study is to develop thermally comfortable floor tiles with an appropriate mechanical properties and water absorption below 3%. For this aim, porcelain green bodies with silicon carbide as a foaming agent (0-0.3%) were prepared from a porcelain tile powder and SiC particle as an additive, and were sintered at industrial fast firing conditions in which the total firing program was 40 min. The effect of SiC content, particle size and sintering temperature on pore size and density were investigated. The sintering behaviour of the samples was studied by optical dilatometer. The microstructure of the porous samples was studied by scanning electron microscopy. The experimental results show that a small amount of SiC with a particles size below 10µm provides high amount of porosity due to the oxidation reaction of SiC particles. The closed pore size can be controlled by changing the sintering kinetics of the porcelain tile body and the mechanical properties were improved by designing the porcelain tile recipes.


CN-3:IL05  Ink Technology for Digital Decoration: An Overview
D. GARDINI, M. BLOSI, C. ZANELLI, M. DONDI, CNR-ISTEC, Faenza, Italy

The digital decoration of ceramic tiles by ink-jet printing has quickly become the leading decoration technology in the tilemaking sector. The reasons for such a success can be found in two key features: the lower costs with respect to the traditional decoration systems and the much higher flexibility into customizing the images. However, in order to get reliable jet cycles and high quality decoration, several technological aspects have to be carefully set up. The printability of the inks imposes constraints on the dimensionless numbers (Reynolds, Weber, Ohnesorge) governing the physics of ink jet printing, and consequently on the physical properties of the inks (viscosity, surface tension, density). Therefore ink formulation, in relation with the printing conditions, becomes critical to get printable inks. However, it is crucial also to have stable systems (both colloidally and over time) to avoid nozzle clogging, to have the proper chemico-physical interaction with the substrates and, finally, to fulfil the expected colouring performances after sintering. In this contribution a survey of the most important technological aspects involved in the ink-jet printing will be given on the basis of the scientific results from literature on this technology and of industrial practice.


CN-3:IL06  Vitrification and Sinter-crystallization of Iron-rich Industrial Wastes
A. KARAMANOV, Institute of Physical Chemistry, Bulgarian Academy of Sciences, Acad., Sofia, Bulgaria

Results about the vitrification of several hazardous iron-rich industrial wastes (from productions of Zn, Cu and Ni, as well as EAFD and MSWA) and the use of obtained glasses for sintered glass-ceramics are summarised. It is shown that the appropriate method of sinter-crystallization mainly depends on the crystallization trend of used glasses. When the parent composition is characterised by formation of a moderate amount of crystal phase, low temperature sintering with short crystallization step in the interval 800-900 °C can be used. In addition, attractive granite-like building glass-ceramic can be obtained by mixing fine and coarse glass frits and "free" sintering in refractory moulds at 1000-1050 °C. On the contrary, intensive phase formation inhibits sintering and this results in specimens with scarce degree of densification. However, in some cases a secondary densification process occurs at temperatures near to the eutectic ones, leading to well sintered samples with higher crystallinity and improved mechanical properties. It is also highlighted that preventing Fe2+oxidation by using an inert atmosphere during the heat-treatments leads to a decrease of sintering temperature, finer crystalline structure and additional enhancement of the mechanical properties.


CN-3:L07  Design of a Cool Color Glaze for a Solar Reflective Tile
C. FERRARI, A. LIBBRA, A. MUSCIO, C. SILIGARDI, EELab, Department of Engineering "Enzo Ferrari", University of Modena and Reggio Emilia, Modena, Italy

One of the most common materials-measures to counteract Urban Heat Island Effect can be identified in cool roof: white surface characterized by high solar reflectance and high thermal emissivity. One of the problems for the realization of cool roof is the difficult matching of white color with urban planning needs. In order to better integrate cool roofs into skylines cool colors were developed integrating pigments into cool roof surfaces. Cool roof market is actually dominated by organic based products with optimal solar performances but low durability against ageing. The use of ceramic based products is crucial in the design of a new durable cool roof thanks to their naturally high thermal emissivity (ε=0.90) and their high chemical durability. The development of a new ceramic based product made by a traditional porcelain stoneware tile as support, an inorganic engobe was started in the last years. In order to complete the product with a suitable glaze, eight different inorganic pigments were added to three different glaze, each one characterized by different surfaces features. Even if the addition of glazes, and pigments decrease the reflectance values of the solar reflective engobe, some promising results were achieved in this study especially regarding warm colored glazes.


CN-3:L08  Development of an Alternative Whitening System for Zirconium Silicate Substition in Porcelain Tile Bodies
N. TAMSU SELLI, A. VEDAT BAYRAK, Eczacibasi Building Product Co., Bilecik, Turkey

Zirconium silicate is generally used as a whitening agent in super white and ultra white porcelain tile compositions. Depending on the market speculation, this material's price fluctuated. To reduce this negative effect of the material on the our profitability, an alternative whitening compositions is developed.
The aim of the study is to prepare an alternative whitening composition with an innovative approach such as controlling the amount of the amorphous and crystalline phases in the porcelain tile body and to produce the new composition with the same property compared standard body such as water absorption, size, strength, color, and also ensure the sustainable production with the same quality.

 
Session CN-4 - Managing the Complexity of Silicate Ceramics

CN-4:IL01  The Complexities of Sustainable Slip Resistant Ceramic Surfaces
R. BOWMAN, Intertile Research, Brighton East, VIC, Australia

Consumers expect sustainably manufactured ceramic tile to retain their appearance and functional characteristics. The European Construction Product Regulations require products to be adequately slip resistant at the end of an economically reasonable working life. Since many ceramic tiles lose appreciable slip resistance in service, how can manufacturers make responsible slip resistance declarations, particularly where consumer laws expect merchants to recommend products that are fit for disclosed purposes? Current declarations of the initial slip resistance of ceramic tiles are often illusory. Consumers want a consistent level of cleanability and slip resistance throughout the product life cycle.
In order to engineer a sustainably slip resistant ceramic tile, one should understand how the surface and the slip resistance change due to wear, soiling and maintenance procedures. Prior knowledge of the limitations of certain test methods and any inadequacies of compliance criteria or test interpretation would be certainly help to ensure that any problems can be identified and addressed.
Managing the complexity of pedestrian slip resistance requirements is very much a global industry problem. Perhaps the ceramic tile industry should do more to retain its market competitiveness?


CN-4:IL02  Effect of Microstructure on the Technological Properties of Porcelain Stoneware
M. ROMERO, Eduardo Torroja Institute for Construction Sciences (IETcc-CSIC), Madrid, Spain

Porcelain stoneware is a vitrified product of mixtures of clay, quartz and feldspar. Porcelain microstructures are grain and bond type with large particles of filler (usually quartz) held together by a finer matrix, which is almost fully dense, composed by mullite crystals and a glassy phase. Porcelain stoneware tile is a building material characterized by a very compact microstructure and high technical characteristics, especially as regards water absorption, chemical and frost resistance, bending strength and abrasion resistance. The technological properties of porcelain stoneware depend on its microstructure. Therefore, the understanding of the relationship between the microstructure and the properties is of fundamental importance for the development and design of materials in accordance with application specific requirements. In this paper, a review will be given to some of the interesting results obtained elsewhere, and present our own new results on the effect of microstructure (aspect ratio of mullite crystals and proportion of crystalline and amorphous phases) as well as different physical features (bulk density, closed and open porosity and absolute density) on the technological properties of porcelain stoneware).


CN-4:IL05  Characterization of Silicate Ceramics Using Ultrasonics Test Method
S. KURAMA, E. EREN, Anadolu University, Department of Materials Science and Engineering, Eskisehir, Turkey

Nondestructive testing has been practiced for many decades, with initial rapid developments in instrumentation encouraged by the technological advances. During the earlier days, the primary purpose was the detection of defects. As a part of "safe life" design, it was intended that a structure should not develop macroscopic defects during its life. In response to this need, increasingly sophisticated techniques using ultrasonics, eddy currents, x-rays, dye penetrants etc. Ultrasonic NDT is better known in its more common applications for thickness gauging, flaw detection, and acoustic imaging, however high frequency sound waves can also be used to quantify basic mechanical properties of solids.
The knowledge of the density is of relevant importance in ceramic production in order to reduce cost. Therefore the aim of the ceramic producer reduce defect in the process. The reliability of ceramic materials can be enhanced by an accurate rejection of products that contain critical defects. Different defects currently found in ceramic works are cracks, porosity, and inclusions; density and structural variations may also greatly impair component performance in particular situations. Quality control of the sintered material can be achieved by ultrasonic images allowing defect detection.


CN-4:L07  Microstucture of Ceramic Brick Contaminated by Sulfate Salts
T. STRYSZEWSKA, S. KANKA, Cracow University of Technology, Cracow, Poland

Durability of building ceramics is determined by phase composition, the presence of various admixtures and porosity structure. Insertion of salts into the shard of ceramic bricks causes a gradual loss of the original properties of the material.
The studies presented in this paper relate to the impact of sulfate salts to the microstructure change of the ordinary ceramic brick treated with salt solutions such as MgSO4, K2SO4, Na2SO4 MgSO4. Two types of ceramic bricks were selected for the studies with significantly different properties of shard, which through capillary action were brought to full saturation by solutions.
Determination of changes in microstructure of the test materials by the process of crystallization of salts derived from solutions and the crystallization of the corrosion products, was carried out by observation of the microstructure in SEM. In selected places, chemical analysis was performed to determine the changes in the phase composition of the test materials.
As a very important factor that affects the stability of ceramic brick is its porosity, pore structure determination was performed by mercury porosimetry. Based on the received results, the categorization of pores was presented with the indication of priority place of accumulation of crystallizing salts.
 
 
Poster Presentations

CN:P04  Evaluation of Open Porosity of the Ceramic Proppants during Sintering
J. PARTYKA, M. BUCKO, M. GAJEK, E. WÓJCIK, Faculty of Materials Science and Ceramic, AGH University of Science and Technology, Kraków, Poland

Light ceramic proppant's are most commonly used as the aggregates for the pressurized fracturing of wells used to exploitation the gas resources of shell carbohydrates. One of the major proppant's parameters taken into consideration is their mechanical resistance in the gas fields and providing the high penetrability for gas. The gas permeability depends mainly on the proper position of the proppant's but can also be the porosity of the proppant's granules. The presented research shows the process of the sintering of the chosen ceramic materials that can create the internal porosity especially open porosity. Additional unquestioned factor is high mechanical resistance of the single granules as well as the group of them.


CN:P07  Preparation of Exfoliated the Melamine Modified Mica/polyamide-6 Nanocomposite and its Properties
S. OHYAMA^{1, 2}, K. TAMURA¹, T. KITAZAWA², A. YAMAGISHI², ¹National Institute for Materials Science, Tsukuba, Japan; ²Toho University, Japan

We have tried to prepare a high performance polymer composite using expandable mica (ME) modified with melamine. The expandable mica was modified with a melamine hydrochloride salt at 60ºC for three hours. The resulting melamine-modified ME (MME) was melt-kneaded with polyamide 6 (PA6) using a twin-screw kneader at 250ºC. The non-expandable potassium mica (MK) was used as reference sample. Loading with MME was 2.1 and 4.1 mass% (MME2.1/PA, MME4.1/PA) and loading with MK was 2.1 and 4.3 mass% (MK2.1/PA, MK4.3/PA), respectively. The extruded composite pellets were injection molded into ISO standard specimens at 250C. XRD, TEM and stress-strain analysis were used to examine the effect of the MME on morphology and mechanical properties. The addition of MME to the PA6 matrix resulted in a finer dispersion, as evidenced by the disappearance of the 00l reflections in the XRD patterns and TEM image. And the exfoliation of silicate layers favors the formation of the γ crystalline form. The tensile modulus of MME4.1/PA nanocomposite increased by about 1.8 times compared with that of the neat PA6, which can be attributed to the effective exfoliation of the silicate platelets present in the nanocomposites.


CN:P09  Study of the Variables that Lead to Hue Variations on Tiles Decoration Based on Silicon Cylinder Technique Laser Engraving Method
F. FERRACO, A.O. BOSCHI, Federal University of Sao Carlos, Sao Paulo, Brazil

One of the most recurrent problems on the ceramic tiles production is the hue variation. The determination of its origins within the entire production process and the minimization of this event are of fundamental importance. The hue variation problem has already been diagnosed as having its origins in each one of the steps on the production line of ceramic tiles, regardless of typology and process. The hue variation within the production line of ceramic tiles can be divided in two classes according to the time of its occurrence: hue variation within the same production and hue variation between different productions. The difficulty in maintaining the hue or tone between different lots are usually linked to the lack of standardizations regarding to raw materials, ink preparation methods, reuse of remaining batches of ink, equipment set-up (specially the decoration machines), variations regarding the decoration elements (cylinders or screens), methods of glaze application, temperature and superficial moisture of the tiles, among others. In this work it was investigated the variables inside the process of decoration step to minimize the hue variation within the same and between different lots of production.


CN:P11  The Effect of Lithium Alumina Silicate Phases on Elastic Modulus of Porcelain Tiles
T. AYDIN¹, A. KARA², ¹Kirikkale University, Faculty of Engineering, Department of Metallurgy and Materials Engineering, Kirikkale, Turkey; ²Material Science and Engineering Department, Anadolu University, Eskisehir, Turkey

Spodumene, which is a Lithium alumina silicate, has been used as a raw material in the production of thermal shock resistant whitewares and sanitarywares. The presence of spodumene results in enhancement of mullitization and imparts better physical and mechanical properties to ceramics. In this study, the influence of Lithium alumina silicate phases on the mechanical properties of standard porcelain stoneware body was investigated. Especially solid-solid reactions were observed between spodumene and quartz or spodumene and clay. these solid-solid reactions bring about a newly formed Lithium Alumina Silicate (LAS) phases Spodumene allows the development of a low viscosity liquid phase and results in a decrease in closed porosity, also with increase in bulk density, bending strength and elastic modulus.


CN:P12  Study of Processing Techniques for Use of Raw Material Rich in Nepheline
C. DEL ROVERI¹, A. ZANARDO², L, LUIS DA SILVA³, L. HIRATA GODOY², M.M. TORRES MORENO², F. CABANAS NAVARRO¹, S. CARVALHO MAESTRELLI¹, ¹UNIFAL - MG, Campus Avançado de Poços de Caldas, ICT, Brazil; ²UNESP - DPM; ³Endeka Ceramics

Lavrinhas, a city located 234 km northeast of Sao Paulo, presents occurrence of syenitic rocks with high content of nepheline, whose preliminary field assessment indicated potential use in the production of ceramics. This work aimed to study this raw flux and to determine the best methods of processing to be performed on the basis of mineralogy and texture, targeting the highest yield in the removal of nepheline. Petrographic characterization was carried out in two rock samples as well as the characterization of the particle size material without treatment, looking for the separation into fractions, for testing magnetic separation and the optical microscope observation of the products. In addition, tests were performed chemical analysis, particle size analysis and melting test. The latter aimed at assessing the color of melting the material before and after magnetic separation as well as their potential for use in glazes, when compared to a standard sample of nepheline, and inferences for use in bodies of porcelain. Preliminary tests showed that after removal of the residual iron oxide, the raw carrier nepheline could be used in the formulation of masses of porcelain, replacing other materials fluxes with higher added value.


CN:P15  Composition and Ceramic Characteristics of Cretaceous Clays from Morocco
C. SADIK¹, A. ALBIZANE¹, IZ-EDDINE EL AMRANI², ¹Department of Chemistry, Faculty of Science and Technology, University Hassan II, Mohammedia, Morocco; ²Department of Earth Sciences, University Mohammed V Agdal, Scientific Institute, Rabat, Morocco

Investigations were undertaken to assess the thermal modification in clay products from the Cretaceous deposit (Moroccan Meseta), in order to use them in ceramic products. That is why the study had recourse to several techniques of analysis; chemical analysis, a mineralogical study, thermal analyses and analyses of technological traits. The samples were dry pressed and sintered at temperatures ranging from 800 to 1200 °C. XRD and SEM were used to identify the phases present and the densification level. The relationship between water absorption, shrinkage and flexural strength as a function of the firing temperature was examined in order to enhance the quality of the final products and to optimize the production process. The results revealed that sintering is governed by different mechanisms according to the temperature. The neomineralization processes were investigated principally by X-ray diffraction. At the end of this study one can affirm that these clays have qualities necessary for the manufacture of ceramic products.