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2 Technical features Glazes A ceramic glaze is a vitreous material prepared from the milling of two types of constituents: mineral raw materials (non soluble in water) frits The frit/raw material ratio in a formula mainly depends on the firing temperature of the ceramic the glaze is applied on. The amount of frit can vary from 0 (ex. sanitaryware porcelain with a firing temperature > 250 C) to 95 (ex. earthenware fired at < 00 C). Glazes and engobes are made from raw materials with low Fe 2 O 3 content which bring the following chemical properties: - Glass former: SiO 2, B 2 O 3 - Stabilizer (to avoid a recrystallisation): Al 2 O 3 - Flux: CaO, MgO, Na 2 O, K 2 O, ZnO, BaO, PbO... Different techniques are used to apply the slurry onto the green or fired biscuit to make it impermeable after maturation. Engobes The engobe is an undercoat applied between the biscuit and the glaze. Its role is: to mask biscuit coloration to reduce glaze defects such as stains, spots and pitting to make the tile waterproof to prevent water rising to the surface after laying to limit the quantity of glaze necessary. To meet these requirements, the engobe must have: a maximum whiteness and high opacity a controlled fusibility to obtain a waterproof layer when the glaze is applied a thermal expansion coefficient adapted to the biscuit good rheological properties to facilitate application. functions for Glazes and Engobes: The main function of alumina in a glaze formulation is to increase the viscosity and limit the fluidity of the glaze, thus avoiding smudges. It also increases the mechanical resistance and scratch resistance. The glaze could be matt or glossy, transparent or opaque. Hard calcined alumina gives a shiny and transparent effect, while reactive alumina gives a matt and opaque effect. Special reactive alumina gives opacification and replaces totally or partially zircon sands in the formulation of engobes and glazes to give whiteness and opacification. Inks for Digital Printing The ink is made from a suspension of extra fine pigments, at the right temperature and with the right viscosity. Since the year 2000, new machines for inkjet decoration of tiles has been developed, able to decorate tiles 24 hours-a-day (000-0 m 2 /hour output). Inkjet decoration machines fit perfectly into glazing lines and improve efficiency. They can have up to 000 nozzles and work with 6 (or more) different inks. This machine uses inks having particles up to micron, which is the maximum size allowed by the process. The ink is shot from a connected nozzle (having an internal diameter of about 0.04 mm) to the target (whose distance can vary from a few millimeters to cm). The key parameter of the raw material used in the inks is particle size distribution. The pigments must be well dispersed and have particles sizes of less than micron. Pigments can lose their staining power when particles are too fine because the increased surface area exposes the crystal structure to chemical attack by glazes and bodies. functions: Super ground alumina has a very well controlled particle size distribution and top cut. Its high level of fineness allows it to be used in ink permitting distinctive and unique colour brightness, texture and surface effect. 02

3 Frits A frit could be considered as glass and is one of the components of the glaze. Surface reinforcement Frits are the result of the fusion (at C) between constituents sometimes soluble and toxic (lead, baryum, zinc salts, borax) and silica. There are three groups of oxides in the amorphous structure of the glass. Milled white fused alumina is added to the glaze to obtain a rough surface. Depending on its granulometry, this WFA is used for its abrasion resistance and anti-slip properties. Acids: Alkalis: Amphoterics: silicium, boron sodium, potassium, calcium aluminium functions: The Aluminium ion takes the place of the Si ion in the crystalline network. This enables the make up of the glaze to be varied without modifying the mechanical properties. 03

4 Porcelain Stoneware Glazed stoneware tiles are usually floor tiles defined according to the standard EN 44: 202. They may be classified in 2 sub-families, taking into account their porosity (water absorption): Group I porosity (WA) < 3 Group IIA porosity (WA) between 3 and 6 The function of these building materials is mainly aesthetic for floors and walls but a good abrasion resistance of the glazed surface is also required. Glazed floor tiles may be manufactured either from: * red bodies (natural stoneware made of ferruginous clays and no feldspars) or * light coloured bodies (feldspathic stoneware) Manufacturing: mainly single-fast firing in roller kilns (fast cycle of 30 to 45 mn) - at about 200 C. Standard formula () Ball clays Silica sand Feldspars > > > (or pitchers) (Soda or mixed) Fully vitrified tiles, also called PORCELLANATO, are products made from either white or coloured bodies with a porosity (water absorption) below 0.5. Here, the porosity has to be < 0. to ensure a good stain resistance (stains being the weak point of these products) Because of their mechanical resistance (wear, compression), these materials are well adapted to heavy duty applications (supermarkets, public buildings...). To achieve the aesthetic aspect, part of the production (0 to 25) is polished on continuous machines in order to give a gloss surface. Stain resistance is very delicate for fully vitrified tiles as polishing can remove the surface film from the fired tiles. This can open the internal pores of the material (closed micro-porosity). Fast firing in roller kilns at 200/230 C during 50 to 70 min cycles. Short cycles require the use of raw materials with little organic material content (organic carbon emphasizes black cores which originates from the reduction of iron contained in the clays). Polishing (for a part of the production only) Standard formula () Ball clays 30 > 40 Kaolins 3 > 7 Feldspars 45 > 57 Silica sand 3 > 5 Zircon,5 > 5 Other (flux) 0,5 2 > (or pegmatites) Note: raw materials for super white bodies (5 of the market) must have a Fe 2 O 3 + TiO 2 content <. Zircon and/or is added for whiteness. functions: The alumina binds with part of the silica to form mullite and this silicate is the bone of porcelain stoneware. It increases the mechanical resistance and avoids pyroclastic distortion (thermal expansion stabilization and vitreous phase viscosity increase). replaces completely zircon sands in the formulation to maintain the whiteness of the body. 04

5 Tableware Pigment Alumino porcelain, vitreous tableware for hotelware. A pigment is a mix of raw materials and oxides. functions: Ground calcined alumina may be used in ceramic bodies to adjust mineralogical composition and provide high performance which is required for the intensive use of hotelware. Improves thermal shock Improves scratch and abrasion resistance Improves mechanical resistance The development of a colour is obtained by the reaction between alumina and other oxides. The complex compounds that are obtained are aluminous spinels (Al 2 +++, M++, O 4 ), with the following colours: Al-Co (Cobalt) Al-Cr (Chrome) Al-Mn (Manganese) blue colour pink colour red colour functions: Precipitated micronic alumina trihydrate is used with cobalt to obtain the colour blue. Reactive alumina is used with manganese to obtain the colour red. The appropriate -based product by application Calcined Application Dry Hydrate Low calcined Medium calcined Hard calcined White Fused Frits Glaze Opaque Transparent Porcelain stoneware Tableware Pigment Surface reinforcement 05

6 for Glazes AR75, AC44, ATS Hard and medium calcined aluminas for glazes. The use of alumina in the composition of glazes is essential to provide high mechanical strength, wear resistance, thermal shock and chemical corrosion resistance. The glaze could be matt or glossy, transparent or opaque. Hard calcined alumina gives a shiny and transparent effect, while reactive alumina gives a matt Applications Surface Area BET Particle size distribution - Laser D50 < 5 <25 Loss on ignition Alpha content Al 2 O 3 Na 2 O total CaO SiO 2 Fe 2 O 3 Unit m 2 /g Reactive Very low calcined AR75 Frit, Glazes Physical properties Chemical analysis Calcined Hard calcined AC44/ AC45 Glazes, tableware AC44 for Inks for digital decoration P72SB Super ground alumina P72SB has a very well controlled particle size distribution and top cut. Its high level of fineness allows it to be used in Ink permetting distinctive and unique colour brightness, texture and surface effect. Applications Surface Area BET Particle size distribution - Sedigraph D50 D90 Loss on ignition Alpha content Al 2 O 3 Na 2 O total CaO SiO 2 Fe 2 O 3 Unit m 2 /g Super ground Calcined P72SB Inks Physical properties Chemical analysis P72SB 06

7 Applications Surface Area BET Particle size distribution - Laser D50 < 5 <25 Loss on ignition Alpha content Al 2 O 3 Na 2 O total CaO SiO 2 Fe 2 O 3 Unit m 2 /g Hydrate Reactive Very low calcined AR75 Frit, Glazes Physical properties Chemical analysis Semi-Reactive Calcined Calcined Hard calcined Dry SH500 ATS AC44/ AC45 Frit Frit Frit, Glazes, tableware for Frits AR75, AC44, SH500, ATS is one of the components of the amorphous glass network. Al 2 O 3 is used as a stabilizer in the glass network to avoid recrystallization. Depending on the fusion process reactive alumina, AR75, semi reactive alumina, ATS, hard calcined alumina, AC44, or hydrated alumina, SH500, can be used in this application. AR75 Chemical characteristics Al 2 O 3 Na 2 O SiO 2 Fe 2 O 3 CaO + MgO White fused alumina (WFA) for Surface Reinforcement CAC range Grain size Distribution CAC 90 CAC00 CAC20 CAC CAC80 CAC220 CAC This range of white fused aluminas, corundum CAC, with a massive shape are used for their abrasion resistance and anti slip properties. White fused 07

8 for opacification ARZ, AFRZ The light scattering properties and high refractive index of these intermediate calcined aluminas ARZ and AFRZ, make them ideal for opacifying in superwhite body, engobes and glazes. Special reactive alumina gives opacification and replaces, completely or partially, zircon sand in formulation to give whiteness and opacification. Ground alumina AFRZ can be used as a whitening agent when added after the milling of the body to obtain the best whiteness. Applications Surface Area BET Particle size distribution - Laser D50 D90 Loss on ignition Alpha content Al 2 O 3 Na 2 O total CaO SiO 2 Fe 2 O 3 Unit m 2 /g Ground Reactive Intermediate calcined AFRZ Physical properties Chemical analysis Reactive Intermediate calcined ARZ Tiles, engobes and glazes - Opacifier ARZ 08

9 Applications Surface Area BET Particle size distribution - Laser D50 Loss on ignition Alpha content Al 2 O 3 Na 2 O total CaO SiO 2 Fe 2 O 3 Unit m 2 /g Ground Calcined Hard calcined AC44B4 AC44B5 AC44B6 Tableware 4 98 < Physical properties 5 98 < Chemical analysis < Ground calcined alumina for tableware AC44B4, AC44B5, AC44B6 Ground calcined alumina may be used in ceramic bodies to adjust mineralogical composition and provide high performance which is required for the intensive use and thermal shock resistance of hotelware. Improves thermal shock Improves scratch and abrasion resistance Improves mechanical resistance Particle size distribution (Cilas 75) 00 () 50 AC44B4 AC44B5 AC44B6 TABLEWARE Applications Surface Area BET Particle size distribution - Laser D50 <25 Loss on ignition Alpha content Al 2 O 3 Na 2 O total CaO SiO 2 Fe 2 O 3 Unit m 2 /g Ground Hydrate Dry Dry Physical properties Chemical analysis Ground Reactive Low calcined Ground Calcined Hard calcined SH30 SH80 AR2B5 AC34B4 Pigments for pigments AR2B5, AC3B4, SH30, SH80 Various type of aluminas are used to enhance the colors, they build chemical complexes with metallic oxides and help the development of tints. From Gardanne s wide range of aluminas we have selected hydrates and ground calcined aluminas for this use. 09

10 ALTEO HAS ITS OWN R&D & ANALYTICAL LABORATORIES FOR CERAMICS IN GARDANNE Ongoing research and development projects include work on standard ceramics such as tiles, glazes and for technical ceramics such as spark plugs, electro ceramics, high temperature ceramics, porous materials and catalysis supports. Alteo has the experience and resources to seize opportunities for new applications for alumina and develop them in partnership with industry and university laboratories. To meet complex formulation demands and to move forward together, process and product development is carried out in the Gardanne R&D laboratories: Know-how studies to present the functions of alumina in a ceramic application (technical documentation, publications) Studies of the parameters of alumina: mineralogical and chemical composition, particle size, morphology - to measure their influence on the properties of ceramics and to define the product range. Confidential studies of formulation or technical service for customers: Technical-economic studies customised by the introduction of the alumina in the customer formula. 0

11 MAJOR EQUIPMENT: Raw material analysis CHEMICAL AND MINERALOGICAL ANALYSIS (XRF,ICP,FT-IR, TGA) CRYSTALLOGRAPHY (X-ray diffraction) PHYSICAL ANALYSIS (electronic microscopy) Ceramic synthesis GRINDING EQUIPMENT, SUSPENSION AND PASTE PREPARATION, GRANULATION, RHEOLOGY AND VISCOSITY MEASUREMENT, DEFLOCCULATION CURVE, ZETAMETER SHAPING (pressing, extrusion, glaze deposition, slip casting) FIRING (debinding, kilns, dilatometer) Final characterization COLOR AND GLOSS, HARDNESS, BENDING STRENGTH, STAIN RESISTANCE, DENSITY, WATER ABSORPTION, THERMAL EXPANSION

12 ALTEO AT A GLANCE World s largest supplier of specialty aluminas with tonnes of alumina based products (hydrate, calcined, tabular and fused aluminas) Headquartered in Gardanne (France) with 4 production facilities in Europe Global sales network Development centre in Europe Leading positions in Ceramics (technical and standard), Refractory, Abrasives, Specialty Glass, Chemicals, Feedstock ALTEO - Route de Biver B.P Gardanne Cedex France design: Your contact: Nathalie Martinez Ceramics Application Manager nathalie.martinez@alteo-alumina.com