CH702520B1 - ceramic material for decorative applications. - Google Patents

Abstract

The invention relates to a ceramic material comprising: a composite matrix of zirconia; particles of at least one refractory carbide or nitride carbonitride compound, the content of said particles being between 5% and 20% by weight; characterized in that the size of said particles is generally between 100 μm and 500 μm. The ceramic material has patterns with good hue and / or aspect contrast and can be obtained by a manufacturing process similar to conventional ceramic manufacturing.

Description

Technical area

The present invention relates to a decorative ceramic material based on zirconia comprising a colored phase, and a method of manufacturing said decorative material.

State of the art

Ceramics such as zirconia (ZrO2) or alumina (Al2O3) are widely used in watchmaking for the production of scratch-resistant boxes and wristbands. The color of pure zirconia or pure alumina is a milky white that finds few applications in watchmaking.

[0003] Methods for coloring zirconia in its mass are already commonly used by ceramics manufacturers. They generally consist in introducing into the base mixture of zirconium oxide, prior to an injection step, a pigment or an oxide in the powdery state.

For example, EP 678 490 describes a method of manufacturing a black decorative article based on a mixture of zirconia containing 99 to 90% by weight of stabilized zirconia and the complement, ie 1 to 10 %, a mixture of cobalt oxide and iron oxide or a CoFe2O4 spinel powder. The mixture is then sintered at 140 ° C or 160 ° C in air to obtain the article.

In another example, the document JP-A-02-167 875 describes a method for modifying a zirconia-based ceramic in order to modify, on the one hand, the hardness thereof and on the other hand on the other hand, to give it a black or gray-black color. To do this, it is proposed to introduce a piece of zirconia previously heated in a chamber in which a plasma is created, preferably a microwave from a gas mixture comprising hydrogen and a hydrocarbon or of the CO so that the surface layer of the ceramic is transformed into a form of zirconium carbide (ZrC) of black or gray-black appearance. The modified ceramic is then used to make cutting tools and machine parts.

The use of titanium nitride (TiN) layers to obtain a golden appearance is known. For example, in US Pat. No. 4,556,607, a layer containing 80% of TiN is deposited on a tungsten wick comprising intermediate sub-layers in order to improve the adhesion of the TiN layer as well as its physical properties. The TiN layer gives the wick a sparkling golden appearance.

In the document EP 850 900, a zirconia-based article is processed over part of its thickness to give this article a surface having a metallic appearance. To this end, the article is placed in a chamber containing a plasma obtained from a mixture of hydrogen, a neutral gas and traces of carbon so as to form a surface layer containing zirconium carbide. The article is intended for the manufacture of a component for dressing wristwatches.

[0008] US 6,355,202 discloses a method for obtaining a zirconia-based article having a ZrC surface layer of gold metallic appearance. The method comprises the zirconia partial reduction steps, arranging the article in a plasma generated by an ammonia gas or a mixture of nitrogen and hydrogen at a temperature between 500 and 900 ° C.

The above processes produce a ceramic article with a colored or metallized appearance over the entire surface of the article and do not allow the production of patterns with a contrast of hue and / or appearance. EP 0 741 117 discloses a method for locally dyeing a zirconia ceramic by means of illumination of the surface. However, this approach which requires an additional manufacturing step of the article, allows to produce patterns on the surface of the article and offers only a very strong white and black unsightly contrast.

Brief summary of the invention

The invention proposes to provide a ceramic material having a pattern with a good contrast of hue and / or appearance throughout the volume of the material.

For this purpose, the subject of the invention is a ceramic material comprising: a matrix composed of zirconia; particles of at least one refractory carbide and / or nitride compound, the content of said particles being between 5% and 20% by mass; characterized in that the size of said particles is generally between 100 μm and 500 μm.

According to one embodiment, said at least one refractory compound comprises a compound of titanium carbide or titanium nitride.

In another embodiment, said particles are in the form of flakes.

In yet another embodiment, the material is used as a piece of construction of a bracelet or box for a timepiece.

The invention also relates to a process for obtaining the ceramic material comprising: shaping a composition containing: between 5% and 20% by weight of particles of the refractory compound and the remainder of a zirconia powder to obtain a compact; and sintering said compact at a temperature of between 1350 ° C and 1500 ° C.

The ceramic material of the invention comprises a colored and aspect pattern and metallized and can be obtained by a manufacturing method similar to the manufacture of conventional ceramics.

Brief description of the figures

Examples of implementation of the invention are indicated in the description illustrated in FIG. 1 which represents a polished surface of a ceramic material obtained according to the invention.

Example (s) of embodiment of the invention

According to one embodiment, a composition comprises a zirconia powder (ZrO 2), preferably partially stabilized in a conventional manner in the tetragonal phase with a known stabilizer such as yttrium oxide (Y 2 O 3), magnesium oxide. (MgO), cerium oxide (CeO2) and / or calcium oxide (CaO), dissolved in a solid solution. The amount of the stabilizer may be between 3 and 70% by weight relative to zirconia. The amount of partially stabilized zirconia is typically from 80% to 95% by weight, based on the weight of the sintered material.

The zirconia can be colored by the addition of coloring components dispersed homogeneously in the composition. For this purpose, the coloring components may be metal powders, metal oxide powders or their precursors which, during the sintering, become powders of metal oxides, or pigments or a mixture of these compounds. More particularly, the dye components are an oxide of one of the elements of the group Iva, Va, Vla, Vlla or VIIa of the periodic table, for example an oxide of Cr, Co, Fe, Ti, Mn, V and Ni. These oxides can be reduced to lower carbide or elemental metal oxides by reduction in a reducing atmosphere containing carbon. The coloring components can also be composed of metal salts or complexes, or crystalline structures such as hematite, corundum, rutile, or spinel. The salts and metal complexes give colored oxides during sintering. The composition may also include many of these different types of coloring components so as to obtain new colors. The coloring components are incorporated in the composition in a proportion typically between 0.1 and 10% by weight, calculated for the oxide. An amount smaller than 0.1% by weight produces insufficient and uneven coloring, while an amount greater than 10% may deteriorate mechanical properties of sintered material.

In addition to the dyeing components mentioned above, the composition may also contain zirconia carbide (ZrC), in an amount typically between 0.05 and 15% by weight, in order to blacken or darken the color generated by the coloring particles. For example, an iridescent or metallic shade can be obtained by adding ZrC to coloring particles composed of NiO or CoO.

According to one embodiment, between 5% and 20% by weight of particles of a refractory compound of carbide and / or nitride are incorporated homogeneously in the composition. Preferably, the refractory compound is composed of particles of titanium nitride (TiN) or tungsten carbide. The addition of particles of titanium carbide (TiC), tungsten nitride (WN2), or titanium carbonitride or tungsten is also possible. The use of particles of the refractory compound based on a metal other than titanium and tungsten is also part of the invention. In the case where the level of the refractory compound is higher than 20% by weight, the mechanical properties of the ceramic material can degrade.

In another embodiment, the composition comprises a combination of at least two refractory compounds of different kinds. For example, the composition may contain titanium nitride particles and tungsten carbide particles. In all cases, the particles of the refractory compound (s) are added to the composition in an amount of between 5% and 20% by weight.

According to the invention, the particles of the refractory compound generally have a size between 100 and 500 microns, that is to say their largest dimension is between 100 and 500 microns. For example, in another preferred embodiment, the particles of the refractory compound are in the form of flakes having a length generally between 100 and 500 microns. The particles may also have a more three-dimensional shape, for example spherical (in this case with a diameter generally between 100 and 500 microns) or other. A particle size equal to or greater than 100 microns makes it possible to produce a pattern on the surface of the ceramic material easily visible to the naked eye. However, particles larger than 500 μm begin to degrade the mechanical properties of the ceramic material significantly.

Such refractory particles are manufactured, inter alia, by the company Easyl, France. The refractory particles can be manufactured by a high temperature self-sustaining synthesis method, as described in the patent application FR-A-2 629 078 and allowing the rapid synthesis of refractory powders of very fine microstructures. The particles can also be produced by reacting the metal with carbon and / or nitrogen at temperatures between 1200 and 2000 ° C. The carbon may be in a solid form, such as graphite powder or in molecular form in a gas.

In yet another embodiment, the composition is shaped so as to obtain an unconsolidated compact. By shaping is meant any industrial shaping process similar to the methods used for shaping ceramic parts. For example, the shaping can be carried out by a method of cold compaction of casting, injection molding, tape casting. Cold compaction methods such as pressing, injection or extrusion pressing, or prototyping are also possible. When shaping, the composition may form a solid mixture or be put into a liquid solution, for example, a slip preparation or suspension comprising the different component of the composition. The composition may be premixed in a wet mill. The shaping method makes it possible to produce a compact in a desired geometry such as a massive piece.

In addition to the aforementioned components, such as zirconia powder, coloring particles and the refractory compound, additive elements, such as binders and / or plasticizers may be incorporated into the composition prior to shaping. These additives can be removed (debinding) during a heat treatment, possibly assisted by an overpressure or a reduced pressure or by microwaves, or by capillary migration, or by sublimation under vacuum.

The compact is sintered under a controlled atmosphere, for example, under air or under a gas such as O2, N2, Ar, H2, NH3, to consolidate the shaped particles, densify the material and impart a mechanical strength to the material. ceramic. Sintering can be facilitated by additives that accelerate the densification and / or form a vitreous or liquid phase at high temperature, or that form a new inorganic phase during sintering (reactive sintering). Sintering is typically performed in an oven at a temperature ranging from 1350 ° C to 1500 ° C.

In one embodiment, the ceramic material is sintered by a hot uniaxial pressing method (HP). In such a method, the cold pressed compact is fed into a press where it is sintered by hot uniaxial pressing between two dies. An apparatus adapted to such pressing is described, for example, in the patent application DE 2004 006 454. The sintering is carried out at a temperature typically between 1350 ° C and 1500 ° C and at a pressure between 20 and 100 bar. This method achieves a uniform sintering temperature and pressure and produces ceramic articles reproducibly in terms of size, hardness and density.

Sintering can also be performed by laser sintering, for example during the design of a part by rapid prototyping. Alternatively, a pre-sintering step at a temperature around 1000 ° C can be carried out in order to give the compact sufficient strength for easy machining with appropriate tools (tungsten carbide, or diamond).

The ceramic material obtained according to the embodiments contains between 5% and 20% by weight of a refractory compound of carbide and / or nitride and the complement by weight of zirconia, that is to say between 80% and 95% by weight. The ceramic material thus obtained can be machined and / or receive a surface treatment, such as polishing. Such a step of machining and / or surface treatment makes it possible to obtain a product that can be used commercially and industrially.

FIG. 1 represents a polished surface of the ceramic material obtained according to the invention, comprising a black colored zirconia matrix, shown by the number 2 in the figure, and comprising 15% by weight of titanium carbide particles, shown by the number 1 in the figure. Titanium carbide particles reflect light in a spectrum similar to the gold element, producing a yellow color and a golden appearance.

The ceramic material obtained according to the embodiments of the invention makes it possible advantageously to produce an article made of zirconia, the appearance and the mechanical properties of which are particularly suitable for the production of component parts of timepieces, such as wristwatches, or the making of any other decorative item. More particularly, the incorporation of the particles of the refractory compound having a large size (from 100 to 500 microns) makes it possible to produce a "starry" ceramic type decorative appearance pattern that can be used as part or all of an element of construction of clockwork or other watch parts. For example, the ceramic material of the invention can be advantageously used for the manufacture of a disk for displaying the phases of the moon, the titanium carbide particles then serving to simulate the stars.

Other decorative applications are also conceivable, such as the use of the ceramic material of the invention for the manufacture of components for jewelery, tools, or medical applications.

Other patterns may also be obtained depending on the type of particles of the refractory component used. For example, the titanium carbonitride particles will add a color pattern from gray to purple, depending on the particle manufacturing process. Gray tungsten carbide will give a pattern with a silvery appearance (like stainless steel).

In the case where several types of refractory compounds are added to the composition, patterns comprising several colors or aspects can be obtained. For example, a composition comprising titanium nitride and tungsten carbide particles will yield a ceramic material with a pattern of gold-yellow and silver-colored areas, respectively.

Reference numbers used in the figures

[0036] <tb> 1 <SEP> particles of titanium carbide <tb> 2 <SEP> zirconia matrix

Claims (12)

1. Ceramic material composed: a matrix composed of zirconia; particles of at least one refractory carbonitride, carbide or nitride compound, the content of said particles being between 5% and 20% by mass; characterized in that the size of said particles is between 100 μm and 500 μm. The ceramic material of claim 1, wherein said at least one refractory compound comprises a titanium carbide or titanium nitride compound. The ceramic material of claim 1, wherein said at least one refractory compound comprises a tungsten carbide or tungsten nitride compound. The ceramic material of claim 1, wherein said at least one refractory compound comprises a titanium carbonitride compound. The ceramic material of claim 1, wherein said at least one refractory compound comprises a titanium nitride and tungsten carbide compound. The ceramic material of claim 1, wherein said particles are in the form of flakes. The ceramic material of claim 1, wherein said matrix comprises coloring components so as to color said matrix. 8. Use of the ceramic material according to one of the preceding claims for the production of a decorative article. 9. Use according to the preceding claim for the realization of a bracelet construction element or box for a timepiece. 10. Use according to claim 8 for the manufacture of a disk for displaying the phases of the moon. 11. Process for obtaining the ceramic material according to one of claims 1 to 7, characterized in that it comprises shaping a composition containing: between 5% and 20% by weight of particles of the refractory compound and the remainder of a zirconia powder to obtain a compact; and sintering said compact at a temperature of between 1350 ° C and 1500 ° C. 12. Production process according to the preceding claim, wherein said sintering is performed by a hot uniaxial pressing method at a temperature between 1350 ° and 1500 ° C and at a pressure between 20 and 100 bar.