ES2310139A1 - Ceramic enamel with metallic brilliance, method for preparation and application - Google Patents

Abstract

The present invention concerns a ceramic enamel with metallic brilliance characterized in that it is constitued by: - A powder of micro/nanometric metal from the type of Cu, Ni, Cd, Ru, Fe, Pd, Au, Ag, Co, W, Mo, Pt, Rh and Ir, and possible alloys thereof with the former or other metals, and/or particles of various oxides having metallic character in the optical range (Fe3 O4,Co3 O 4, NbO, TaO, Mn3O4, Mox Oy and Wx Oy ) or precursors used for obtaining the previous conductive oxides - One frit and kaolin and smoke black. And also the method for preparation of said enamel.

Description

Ceramic enamel with metallic luster, procedure for obtaining and applying.

Technical sector

This patent has its scope in the  production of tiles, ceramic pavements, enamels and ceramic coatings.

State of the art

The metal enamels have been widely used for centuries in pottery as elements decorative due to metallic reflections and iridescence that produce [Caiger-Smith A., Luster Pottery: Technique, Tradition and Innovation in Islam and the Western World, Faber and Faber, London, 1985]. The examples of these enamels known as Lustres date from the Middle Ages and the Renaissance, these enamels have a high local concentration of metal nanoparticles that are perfectly dispersed in a vitreous melt. Obtaining metal lustres such as decorative elements were limited to temperatures that did not exceeded 700 [Pérez-Arantegui J., Molera J., Larrea A., Pradell T., Vendrell-Saz M, Luster Pottery from the thirteenth century to the sixteenth century: a nanostructured thin metallic fim. J. Am. Ceram. Soc. 84,2,442-446,2001]. Industrially, the lustres Metallic are based on noble metals that require cooking in third fire generally limited to temperatures below 1000ºC [Enamels and ceramic pigments, P. Escribano, J. B. Carda and E. Cordoncillo, Faenza Editrice S. L. Castellón 2001]. Recently, new technologies such as vapor phase deposition to obtain ceramic tiles, floor and wall tiles with metallic look [Alberdi A., Franch M., Belda A., Lucas F., Laucirca J., Bueno M., Method of producing ceramic tiles having a metallic finish and the tile tus produced, European patent EP1498402A1 01-13-2005]. These finishes are produced as a result of the deposition of a metallic layer of elements such as chrome, zirconium, tantalum, titanium and nitrides or carbides of said elements. The limitations of this technique they are based on the fact that previously prepared tiles are required and the difficulty of decorating the pieces beyond the metallic coating

The development of metallic effects in tiles Ceramics has been proposed from mixtures of oxides essentials such as SiO2, Al2O3, Fe2O3 and P_ {2} O_ {5} together with certain optional oxides, namely: CaO, MgO, Na2O and K2O [Cabrera M.J., Formulation and procedure for obtaining metallic effects in tiles Ceramics and their applications. Spanish Patent 2161193 of 16.11.2001]. This formulation is characterized by being exempt from noble metals, to be applied in ceramic tiles and baked in a industrial cooking oven between 1100-1250ºC and by have a high content of Fe 2 O 3 and P 2 O 5, 10-30% and 7-27% respectively. By on the other hand, phosphorus pentoxide is a vitreous network former and since phosphate glasses have a high solubility in aqueous medium [Fernández-Navarro J.M. Glass, Edits Higher Council of Scientific Research, Madrid 1991], its use in flooring and cladding strongly limits your application.

From the optical point of view, a metal is characterized by presenting a complex refractive index and by fully reflecting the incident radiation since it is an excellent conductor of electricity. On the other hand, a dielectric material has a real index of refraction, so, although it may have a certain degree of brightness, it is of lower intensity, and in general, it is linearly polarized [Born & Wolf, Principles of Optics, Pergamon press 7th ed ., 484-492, 1989]. However, most lustres cannot be classified as metals or dielectric, because they are electrical insulators, but they maintain a high reflective power. They are actually composite materials, insulating-metal, with metal concentrations close to the percolation threshold [Introduction to Percolation Theory, 2nd ed., Stauffer D., London 1994 (second printing)]. Under these conditions, and within a certain range of metal concentration between the high dilution limit, f 1c and the percolation threshold [Moya JS et al , Prog Mater Sci (2007), available online 10-05- 2007: [http://dx.doi.org/10.1016/j.pmatsci.2006.09.003], an enamel with an insulating behavior could be designed, although the average dielectric constant was high enough to generate a high reflective power .

In this invention, new enamels are proposed with  Metallic luster, the method of producing metallic enamels Applicable as coatings in the flooring industry ceramic or as decorative elements.

Description of the invention brief description

The metallic enamels object of the present invention, are based on the use of micro / nanometric particles of various metals, metal oxides and alloys, mixed homogeneously with ceramic frits, coal dust and others Typical additives such as surfactants, dyes, etc.

The procedure for obtaining enamels with Metallic luster comprises a series of stages:

to)

Preparation of homogeneous mixtures of precursors  of ceramic enamel (fried, kaolin, etc), metal particles of the type of Cu, Ni, Cd, Ru, Fe, Pd, Au, Ag, Co, W, Mo, Pt, Rh and Ir, and its possible alloys with these or other metals, as well as particles of different metal oxides that have a  component of the imaginary part of the index of refraction greater than 10-5, such as Fe3O4, Co3O4, NbO, TaO, Mn_ {3} O_ {4}, Mo_ {x} O_ {y} and W_ {x} O_ {y}, or precursors that allow obtaining the previous conductive oxides monodispersed on a matrix consisting of particles micro / nanometric of different oxides (silica, alumina, zirconia, magnesia, etc.), clays in general (kanditicas, montmorillonitic, illicit, etc.) or in particular, in clays specials (sepiolite, attapulgite and its isomorphs) [Mott C.J., Catal. Today, 2, 199, 1988] and a powder that allows obtaining a local and transient reducing atmosphere (e.g. coal dust). The proportion of this dust (e.g. carbon black) introduced into the mixture described in section a), shall be comprised between minimum amount necessary for the reducing atmosphere to be generated required (approximately 0.5% by weight) and the maximum limit that lead to the formation of unwanted porosity in the layer of enamel (approximately 20% by weight) being in any case subject to the nature of metals, oxides and alloys responsible for metallic luster.

b)

Industrial cycle firing of the enamel layer deposited from stable suspensions or inks containing the elements of the mixture in the required proportions, on the ceramic tile, in which a reducing atmosphere will be generated local and transient at a temperature above 400 ° C.

Detailed description

The invention is based on cycle cooking industrial (e.g. monocoction in a gas monostrate furnace fast cooking, for 40-120 minutes) of mixtures homogeneous ceramic frits, with particles of different nature (e.g. metallic, oxides and alloys), and agents reducers (e.g. coal dust) as well as other additives, such as surfactants, dyes, etc. This mixture will be processed following routes similar to those conventionally used in the ceramic flooring industry.

The procedure for obtaining enamels with Metallic luster comprises a series of stages:

to)

Preparation of homogeneous mixtures of ceramic enamel precursors (fried, kaolin, with a weight ratio between 30/1 and 4/1, preferably with a ratio of 9/1), metal particles of the type of Cu, Ni, Cd , Ru, Fe, Pd, Au, Ag, Co, W, Mo, Pt, Rh and Ir, and their possible alloys with these or other metals, as well as particles of different oxides with metallic character that have a component of the imaginary part of the refractive index greater than 10-5 such as Fe 3 O 4, Co 3 O 4, NbO, TaO, Mn_ {3 O 4, Mo_ {O} {y} and W_ {x} O_ {y}, or precursors that allow obtaining the previous conductive oxides. These particles with metallic character in the monodispersed micro / nanometric size optical range that can be dispersed in the ceramic frit directly, embedded, deposited or any of their possible combinations, on a matrix consisting of micro / nanometric particles of different oxides (eg silica , alumina, zirconia, magnesia, etc.), clays in general (eg kanditicas, montmorillonites, ilitics, etc.) or in particular, in special clays (sepiolite, attapulgite and its isomorphs) [Pecharromán C., J. Am. Ceram. Soc., 89, [10] 3043-3049, 2006] and a powder that allows obtaining a local and transient reducing atmosphere (eg coal dust). The concentration of metallic particles in the optical range in the final enamel should be between the high dilution limit, f 1c, and the percolation threshold. This range can be estimated as between 0.1 and 50% by volume, although these values can be altered in systems with poor homogenization or in those in which the morphology of the metallic particles is acicular, among others. The concentration of carbon (eg carbon black) in the original mixture will be between the minimum amount necessary to generate the required reducing atmosphere (value subject to the nature of metallic particles in the optical range used) and the limit maximum that results in the formation of unwanted porosity in the enamel layer (approximately 20% by weight).

b)

Cooking in industrial cycle e.g. 1100-1250 ° C for 40-120 minutes, of the enamel layer deposited from stable suspensions or inks containing the elements of the mixture in the required proportions, on the ceramic cake. During this stage a local and transient reducing atmosphere is generated at a temperature above 400 ° C. In this way, a fraction of particles with metallic character in the optical range Starting from total oxidation. Once the enamel formed, the vitreous layer constitutes a barrier to the diffusion of oxygen that prevents the oxidation process of particles with character metallic in the optical range during the rest of the cycle of cooking.

Another particular object of the invention is it constitutes the functional characteristics that the presence of these micro / nanometric particles of certain metals such as Cu, Ni, Cd, Ru, Fe, Pd, Au, Ag, Co, W, Mo, Pt, Rh and Ir, in the final product and its various applications.

Another particular object of the invention is it constitutes the procedure by which different ones can be obtained  enamels with glossy or matte metallic appearance varying both the metal, alloy or metal oxide content (figure 1) as the particle size and dispersion (figure 2).

Another particular object of the invention is It is the procedure by which enamels can be obtained With metallic luster with different color tones, varying the nature and content of the metallic particles that give place to enamel.

Another particular object of the invention is constitutes the procedure by which particles with character  metallic in the optical range form structures with a pattern determined, e.g. dendritic (figure 3) or cellular (figure 4).

Another particular object of the invention is constitutes the enamelling procedure by deposition on the ceramic cake in the form of enamel, granule, screen printing or micronized on ceramic tiles. and cooking in an oven rapid cooking (e.g. 1100-1250 ° C for 40-120 minutes).

Description of the figures

Figure 1.- Photographic image corresponding to ceramic glaze with matt or gloss metallic appearance varying the Cu / fried ratio (A: 30/70, B: 22/78 and C: 17/83).

Figure 2.- Photographic image corresponding to ceramic enamel constituted from a proportion of Cu / Fe 2 O 3 of 50% with a fried ratio of 30/70, with glossy or matte metallic appearance obtained by varying the thickness of the deposited enamel layer (A: 150 m, B: 350 m, C: 720 m and D: 950 m).

Figure 3.- Image of optical microscopy corresponding to the dendritic pattern that appears in the enamel ceramic obtained from a Cu / fried ratio of 22/78.

Figure 4.- Image of optical microscopy corresponding to the glaze enamel repeating pattern metallic obtained from a ratio of Cu / Fe 2 O 3 50% with a fried ratio of 30/70.

Figure 5.- Image of electron microscopy of scanning with field emission of size particles nanometric with metallic character in the optical range of the sample of Cu / frit in a weight ratio of 17/83 (A) and of the sample with Cu / Fe 2 O 3 nanoparticles supported on sepiolite with a ratio of 25/75 with respect to the frit (B).

Examples of embodiment of the invention Example 1 Procedure for obtaining metallic enamels from copper particles in ceramic pavements

The metallic enamel of the invention was obtained by homogenizing a mixture consisting of:

to)

A micrometric metal copper powder with a average particle size of \ sim3 \ mum.

b)

A crystalline and kaolin-type frit in one 9/1 ratio.

C)

10% additional weight of carbon black type Ivory Black-39.

The weight ratio of ceramic frit and copper  Metallic was 17/83.

A stable suspension of the powders was obtained above in an aqueous medium with a solid / liquid ratio of 3/2. The deposition of this suspension was made through a airbrush on the ceramic porcelain paste holder with a variable thickness from 50 µm to 1000 µm.

The enamel deposited on the support was treated thermally at a temperature of 1200 ° C in an oxidizing atmosphere in a fast-cooking monostrat oven. As a result, a vitreous coating of metallic appearance on the ceramic support (figure 1 C).

The enamels obtained were studied by optical microscopy, scanning electron microscopy with field emission. This enamel with metallic luster is characterized by the presence of dendritic patterns (figure 3), and for being nanostructured (figure 5 A).

Example 2 Procedure for obtaining metallic enamels from nanometric particles of copper and iron oxide (Fe 2 O 3) supported on a sepiolite matrix

The metallic enamel of the invention was obtained by homogenizing a mixture consisting of:

to)

A micrometric powder consisting of nanoparticles of iron oxide (hematite) and metallic copper chemically supported on a microfiber substrate of sepiolite with a metal concentration of 50% by weight of hematite and 70% by weight of copper in sepiolite following the detailed procedure in Spanish patent P 200302396/8. The ratio of Fe 2 O 3 with respect to metallic Cu in the Sepiolite was 50%.

b)

A crystalline and kaolin-type frit in one 9/1 ratio.

C)

10% additional weight of carbon black type Ivory Black-39.

The weight ratio of ceramic frit and copper and hematite particles supported on a matrix of sepiolite was variable according to the proportions 10/90, 15/85, 20/80 and 25/75.

A stable suspension of the powders was obtained above in an aqueous medium with a solid / liquid ratio of 3/2. The deposition of this suspension was made through a airbrush on the ceramic porcelain paste holder with a variable thickness from 50 µm to 1000 µm (Figure 2).

The enamel deposited on the support was treated thermally at a temperature of 1200 ° C in an oxidizing atmosphere in a fast-cooking monostrat oven. As a result, a vitreous coating of metallic appearance on the support ceramic.

The enamels obtained were studied by optical microscopy, scanning electron microscopy with field emission. This enamel with metallic luster is characterized by being nanostructured (figure 5 B).

Claims (9)

1. Ceramic enamel with metallic luster characterized in that it is constituted by:

-

\ vtcortauna A metal powder of micro / nanometric size of the type of Cu, Ni, Cd, Ru, Fe, Pd, Au, Ag, Co, W, Mo, Pt, Rh and Ir, and their possible alloys with these or other metals, and / or by particles of different oxides that have a metallic character in the optical range (Fe 3 O 4, Co 3 O 4, NbO, TaO, Mn_ {3} O 4, Mo_ { x} O_ {y} and W_ {x} O_ {y}) or precursors that allow obtaining the previous conductive oxides

-

\ vtcortauna A fried and kaolin

-

\ vtcortauna Carbon black

2. Ceramic enamel with metallic luster according to claim 1 characterized in that the weight ratio of these metals, alloys or oxides with respect to the ceramic frit will be between 0.1 and 50% by volume. 3. Ceramic enamel with metallic luster according to claim 1 characterized in that the ratio of weight of frit and kaolin is between 30/1 and 4/1, preferably with a ratio of 9/1. 4. Method for obtaining ceramic glazes with metallic gloss according to claims 1 to 3 further characterized in that the particles can be found:

to)

Scattered directly with the components of Typical items in the process of obtaining an enamel, e.g. fried, kaolin, surfactants, etc.

b)

Embedded in a matrix consisting of particles micro / nanometric of different oxides (silica, alumina, zirconia, magnesia, etc.), clays (of the kanditic, montmorillonitic type, illicit, etc.), or in special clays (of the type of sepiolite, attapulgite and its isomorphs).

C)

Supported on one of the matrices described in section b).

d)

As a combination of the cases described in the previous sections.

5. Procedure for obtaining ceramic glazes with metallic luster according to claims 1 to 4, characterized in that the amount of reducing agent eg coal dust, necessary for the local and transient reducing atmosphere to be generated during the homogenous mixture, is added to the homogeneous mixture obtained. cooking process, which will be between a minimum value of 0.5% by weight and a maximum of 20%. 6. Application of ceramic glazes with metallic luster according to claims 1 to 5, characterized in that it can be deposited in the form of enamel, granule, silkscreen or micronized on ceramic tiles. 7. Enameling procedure with ceramic glazes with metallic luster according to claims 1 to 6 further characterized in that once the homogeneous mixture is deposited on the ceramic support of porous or porcelain paste type, it is cooked in a typical industrial cycle in the manufacture of these ceramic products (eg 1100-1250 ° C for 40-120 minutes). 8. Use of ceramic glazes with metallic luster according to claims 1 to 7 as a decoration element on all kinds of materials compatible with enamel, with a wide range of color tones and brightness. 9. Use of ceramic glazes with metallic luster according to claims 1 to 7 as a decoration element in a ceramic tile, with a wide range of color tones and glitters.