J.Ma. Rincón

Glass-ceramic glazes for ceramic tiles - a review

Glass–ceramics are ceramic materials produced through controlled crystallisation (nucleation and crystal growth) of a parent glass. The great variety of compositions and the possibility of developing special microstructures with specific technological properties have allowed glass–ceramic materials to be used in a wide range of applications. One field for which glass–ceramics have been developed over the past two decades is that of glazes for ceramic tiles. Ceramic tiles are the most common building material for floor and wall coverings in Mediterranean countries. Glazed tiles are produced from frits (glasses quenched in water) applied on the surface of green tiles and subjected to a firing process. In the 1990s, there was growing interest in the development of frits that are able to crystallise on firing because of the need for improvement in the mechanical and chemical properties of glazed tiles. This review offers an extensive evaluation of the research carried out on glass–ceramic glazes used for covering and pavement ceramic tile is accomplished. The main crystalline phases (silicates and oxides) developed in glass–ceramic glazes have been considered. In addition, a section focused on glazes with specific functionality (photocatalytic, antibacterial and antifungal activity, or aesthetic superficial effects) is also included.

Use of vitrified urban incinerator waste as raw material for production of sintered glass-ceramics

Abstract The crystallization behavior of vitrified industrial waste (fly ash from domiciliary solid waste incineration) was examined by differential thermal analysis, X-ray diffractometry and scanning electron microscopy. It was demonstrated that powder processing route was required to transform the vitrified industrial waste into glass-ceramics products. Time-Temperature-Transformation (TTT) diagrams were drawn for the two main crystalline phases, diopside and wollastonite. The wollastonite existed in both monoclinic and triclinic forms and an iron-rich phase was also observed at the boundaries between glass particles. The morphology of the crystalline phases and the development of microstructure were observed as a function of heat treatment time and temperature. The optimum heat treatment was 900°C for 40–50 minutes.

New porcelainized stoneware materials obtained by recycling of MSW incinerator fly ashes and granite sawing residues

Porcelainized stoneware is a flooring and covering material of the ceramic sector with versatile and modern characteristics similar to those of the natural stone. It is a compact product, extremely hard and homogeneous, generally not fully vitreous (unglazed) in its surface obtained by fast firing of the starting bodies, a mixture of kaolinitic clays, feldspars and quartz in an appropiate relationship. The final product is characterized by its almost zero porosity, being adequated to sustain heavy traffic intensity for interiors or for exteriors, both in modern or classic constructions with a wide range of aspects, designs and colors. According to the chemistry and mineralogical composition of the granite and incinerator wastes, this paper deals with the use of an incinerator fly ash of municipal solid wastes (MSW) and two different granite sawing residues in the obtaining of new types of porcelainized stoneware. By considering most of the physical and mechanical properties here determined, these modified porcelainized stoneware (MPS) materials are close to the conventional porcelainized stoneware and glass ceramics products.

Crystal nucleation and growth in glasses from inorganic wastes from urban incineration

Abstract This paper reports the results of a study of the feasibility of recycling the fly ashes from domiciliary waste incineration by producing glasses and glass–ceramics. The major components of the fly ashes, Tyseley (F+L) and Tyseley (F), which were from a British domiciliary incinerator, were CaO, SiO2 and Al2O3 but nucleating agents, such as TiO2, P2O5 and Fe2O3, were also present in reasonable amounts. Tyseley (F+L) was similar to a waste ( Tirme F + L ) studied previously by the authors and hence glass and glass-ceramic development concentrated on Tyseley (F). It was found that a glass (designated TYS100) of suitable viscosity could be obtained from the waste without the need for any additives. The properties of this glass were similar to those of other glasses made from incinerator waste. The heat treatment required to crystallise the TYS100 glass was nucleation at 560°C for 55 min followed by crystal growth at 1050°C for 15 min. The main crystalline phase in the resulting glass–ceramic was akermanite (Ca2MgSi2O7) with some TiO and TiSi2 forming in the later stages of heat treatment. The akermanite existed in a thin surface layer and also as spherulites in the bulk; the TiO and TiSi2 crystals were associated with the spherulites. The mechanical properties and erosion resistance were superior to the glass and acceptable for applications such as tiles for the building industry and those requiring erosion resistance.

Effect of iron oxide content on the crystallisation of a diopside glass–ceramic glaze

Abstract The effect of iron oxide content on the crystallisation of a diopside glass–ceramic glaze was investigated using a glass–ceramic frit in the K 2 O–ZnO–MgO–CaO–Al 2 O 3 –SiO 2 system and a granite waste glass. Measurements by X-ray diffraction (XRD) combined with scanning electron microscopy (SEM) and EDX microanalysis showed that the distribution of Fe 3+ ions among different crystalline phases such as franklinite (ZnFe 2 O 4 ) and hematite Fe 2 O 3 depends on the iron content in the original diopside mixture. Thus, the original glaze crystallises to franklinite or hematatite when iron content is greater than 2 and 15%, respectively.

Preparation and properties of high iron oxide content glasses obtained from industrial wastes

The formulation and preparation of new glasses has been carried out by the recycling of goethite (FeOOH) industrial wastes originating from zinc hydrometallurgy with glass cullet and dolomite as complementary raw materials. The mineralogic (XRD) and microstructural (SEM, TEM) characterization of the product has been determined and the thermal, mechanical and chemical properties of original glasses have been measured. The results indicate that glass production is an effective recycling method for this kind of waste, yielding black stable glasses with good mechanical and chemical properties.

Preparation and properties of glass-ceramic materials obtained by recycling goethite industrial waste

The recycling of toxic goethite waste, originated in the hydrometallurgy of zinc ores, in glass-ceramic matrices has been studied. Oxide compositions suitable to form glasses were prepared by mixing the goethite waste with granite scraps and glass cullet, yielding the following oxide composition (wt%): SiO2, 44.6; Al2O3, 3.3; Fe2O3, 25.5; MgO, 1.6; CaO, 4.5; Na2O, 5.9; PbO, 3.1; ZnO, 6.5; K2O, 1.0; TiO2, 2.0; other 2.0. By proper addition of carbon powder, the initial Fe3+/Fe2+ ratio (12) of glasses melted in air at 1450 °C was approximated to the stoichiometric value of magnetite (2) to obtain high nucleation and crystallization rates. The heat treatment of iron supersaturated goethite glasses above 630 °C led to the formation of magnetite nuclei with a high tendency to grow and coalesce with time. The crystallization of pyroxene, occurring on the magnetite crystals above 800 °C, was found to be influenced by the nucleation period, so that the highest crystalline volume fraction, Vf (0.80–0.85), was obtained for 90–120 min nucleation time at 670 °C and 120 min crystallization at 860 °C.

Utilisation of IGCC slag and clay steriles in soft mud bricks (by pressing) for use in building bricks manufacturing.

The subject of this study is the application to the construction of soft mud bricks (also known as pressed bricks), both green and heat-treated bodies, built from raw materials from Santa Cruz de Mudela, Ciudad Real, and IGCC slag from the power central of Puertollano (Ciudad Real, Spain). For this purpose, industrial level tests have been performed: the production of these kind of bricks from mixes of waste from ores of construction clays and to significant fraction of different ratios and clay granulometries mixed with IGCC slag. The results of this experimentation suggests that not only can IGCC slag be applied to a ceramic process, but also its use gives several advantages, as water and energy savings, as well as improvements on the final properties of products.

EXPERIMENTAL STUDY OF CU+-NA+ EXCHANGED GLASS WAVEGUIDES

Optical waveguides have been obtained by field-assisted Cu(+)-Na(+) exchanged on glass. The refractive index profiles of the waveguides are determined by means of the prism-coupling technique and Chiangs method [J. Lightwave Technol. LT-3, 385 (1985)], and they correlate with the index profile calculated as a function of the glass composition. The composition profile is examined with the aid of a scanning electron microscopy with energy-dispersive x-ray analysis, and the diffusion process is explained by the one-dimensional diffusion equation.

Some aspects of crystallization microstructure on new glass-ceramic glazes

The nucleation and crystallization of thin layers of glasses (glazes) over ceramic substrates during the fast firing of tiles for pavements and wall tiles has been a topic of great interest for tile and ceramic paving industries in recent years. Here a wide range of glass-ceramic compositions having different types of crystallization microstructure has been investigated. Based on observations by scanning electron microscopy and energy-dispersive X-ray microanalysis, several aspects of nucleation and crystallization of these new types of glass-ceramic glazes are presented and discussed.