CH710274A2 - A method of making a colored article; especially gray in color; based on zirconia and colored decorative article based on zirconia obtained by this process. - Google Patents

Abstract

The invention relates to a method for manufacturing a gray article based on zirconia characterized in that it comprises the successive steps of: a) producing a first mixture, comprising - a zirconia powder forming the basic constituent, - 4% to 15% by weight of at least one stabilizer chosen from the group of oxides comprising yttrium oxide, magnesium oxide, and calcium oxide alone or in combination, - 0.1 % to 1% by weight of a vanadium oxide powder (V 2 O 5); - 0.1% to 1% by weight of a chromium oxide powder (Cr 2 O 3); and - 0.1% to 1% by weight of a silicon oxide powder (SiO 2), b) making a second mixture comprising said first mixture and a binder; c) producing a granulated mixture by granulating said second mixture; d) forming a blank by imparting to said second granulated mixture the shape of the desired article; e) sintering said article for at least thirty minutes at a temperature of between 1250 and 1550 ° C. The invention also relates to a molding composition comprising zirconia powder, and a gray zirconia-based article, forming in particular a component of a timepiece.

Description

The invention relates to a method of manufacturing a colored article based on zirconia, in particular such an article having a color included in the gray range and produced by sintering. Such an article will be designated in the remainder of the description “gray article” for reasons of convenience.

[0002] The invention also relates to a gray decorative article based on zirconia in particular obtained according to the above process.

[0003] It is already known from document CN 102 659 401 to produce articles in gray ceramic materials by heat treatment of a zirconia in a vacuum graphite furnace which produces a surface black / gray oxidation of the article. This method has the particular drawback of not coloring the article in the mass so that it prevents any subsequent machining of the article after treatment to give it its final shape. Furthermore, the surface color obtained is not uniform but has unwanted grain and marbling.

[0004] The main aim of the invention is therefore to provide, on the one hand, a method of manufacturing a gray article based on sintered, colored zirconia and, on the other hand, such an article in particular obtained by this process, this article having mechanical properties comparable to those of uncoloured zirconia while exhibiting bulk coloration.

[0005] To this end, the invention relates to a method of manufacturing a gray article based on zirconia characterized in that it comprises the successive steps consisting in: a) making a first mixture comprising: - a zirconia powder forming the basic constituent, - 4% to 15% by weight of at least one stabilizer chosen from all the oxides comprising yttrium oxide, magnesium oxide, and calcium oxide alone or in combination, - 0.1% to 1% by weight of a powder of vanadium oxide (V205); - 0.1% to 1% by weight of a powder of silicon oxide (Si02), and - 0.1% to 1% by weight of a powder of chromium oxide (Cr203); b) producing a second mixture comprising said first mixture and a binder; c) producing a granulated mixture by performing a granulation of said second mixture; d) forming a blank by giving this second granulated mixture the shape of the desired article; e) sintering said blank in air for at least thirty minutes at a temperature between 1250 and 1550 DEG.C.

The method of the invention allows by the incorporation, in a stabilized zirconia powder, of a mixture of powders of vanadium oxide, of chromium oxide and of silicon oxide, to achieve after shaping and sintering a mass-colored ceramic article which exhibits a uniform color in the gray scale. The process of the invention makes it possible to produce gray ceramic articles whose aesthetic appearance is particularly attractive without otherwise altering the intrinsic mechanical properties of the uncolored zirconia.

[0007] According to one embodiment of the invention, the first mixture comprises: 0.4% to 0.7% by weight of a powder of vanadium oxide (V2O5); 0.2% to 0.3% by weight of a powder of chromium oxide (Cr2O3); 0.2% to 0.3% by weight of silicon oxide powder (SiO2)

[0008] Advantageously, the first mixture further comprises between 0.1% to 1% and preferably between 0.2% and 0.3% by weight of a manganese oxide powder (MnO2). In an alternative embodiment, the first mixture further comprises 0.1% to 1% by weight of an iron oxide powder (Fe2O3) and preferably the first mixture further comprises 0.1% to 5% by weight an aluminum oxide powder (Al2O3).

[0009] A subject of the invention is also an injection or pressing molding composition, commonly referred to as feedstock according to Anglo-Saxon terminology, intended for the manufacture of a decorative and / or functional article comprising 75% to 96% in weight of a mixture of inorganic powders and 4% to 25% by weight of a binder, said mixture of powders comprising: 82% to 95.7% by weight of a zirconia powder; 4% to 15% by weight of at least one stabilizer selected from the group of oxides including yttrium oxide, magnesium oxide, and calcium oxide alone or in combination; 0.1% to 1% by weight of a powder of vanadium oxide (V2O5); 0.1% to 1% by weight of a powder of chromium oxide (Cr2O3); and 0.1% to 1% by weight of silicon oxide powder (SiO2).

[0010] According to a preferred embodiment, the binder and the mixture of inorganic powders in the form of granules suitable for use as feedstock for injection into a mold or in the form of powders ready to press in a mold . Advantageously, the mixture of inorganic powders further comprises between 0.1% to 1% and preferably between 0.2% and 0.3% by weight of a manganese oxide (MnO2) powder. Even more preferably, the mixture of inorganic powders further comprises 0.1% to 5% by weight of an aluminum oxide powder (Al2O3). According to one variant, the mixture of inorganic powders further comprises 0.1% to 1% by weight of an iron oxide powder (Fe2O3).

The invention also relates to a decorative and / or functional gray article based on zirconia, characterized in that it consists of a sintered part from a molded part comprising in substance a matrix of zirconium oxide, 4% to 15% by weight of at least one stabilizer chosen from all the oxides comprising yttrium oxide, magnesium oxide, and calcium oxide and their mixtures, 0, 1% to 1% by weight of vanadium oxide (V2O5); 0.1% to 1% by weight of chromium oxide (Cr2O3), 0.1% to 1% by weight of silicon oxide (SiO2).

[0012] Such articles have the advantage of having an intense shine after polishing and are thus particularly suitable for the production of decorative articles such as components of watch cases, jewelry, bracelets, brooches, pins. tie, necklaces, handbags, phones, furniture, or household utensils.

[0013] According to an advantageous embodiment, the article comprises 0.4% to 0.7% by weight of vanadium oxide (V2O5), 0.2% to 0.3% by weight of chromium (Cr2O3) and 0.2% to 0.3% by weight of silicon oxide (SiO2).

[0014] In a first variant, the article further comprises between 0.1% to 1% and preferably between 0.2% and 0.3% by weight of manganese oxide (MnO2), 0.1% to 5% by weight of aluminum oxide (Al2O3) and 0.1% to 1% by weight of iron oxide (Fe2O3).

[0015] Other characteristics and advantages of the invention will become apparent in the light of the following description, which presents examples of implementation of the method of the invention which are not limiting and only given by way of illustration.

A first example of the manufacturing process of the invention which will now be described in detail makes it possible to produce an article based on gray sintered zirconia, the appearance and mechanical properties of which are particularly suited to the production of constituent parts of wrist watches or the production of any other decorative and / or functional article.

[0017] The gray zirconia article obtained according to this first example comprises 98.8% by weight of stabilized zirconia and the balance by weight of 0.5% by weight of a powder of vanadium oxide (V2O5); 0.2% by weight of silicon oxide powder (SiO2), and 0.5% by weight of chromium oxide powder (Cr2O3).

Zirconia is stabilized in a conventional manner in the tetragonal phase by at least one stabilizer chosen from all the oxides comprising yttrium oxide, magnesium oxide, and calcium oxide alone or in combination, this stabilizer being in an amount of 5% by weight relative to the zirconia.

To achieve this article, we proceed according to this example of implementation of the method of the invention as follows:

2470 grams of zirconia powder stabilized at 5% by weight of yttrium oxide are weighed. The powder used has an average particle size of the order of one micrometer or submicron, typically 0.5 microns. Such a powder is sold under the reference TZ-3Y by the company Tosoh Corporation, Japan.

Then weighed 30 grams of a mixture of powder of silicon oxide, vanadium oxide, and chromium oxide.

The silicon powder used has a particle size of 2 Micron APS and is sold under the reference No. 13 024 by the company Alfa Aesar, Germany. The vanadium oxide powder used has an average particle size of the order of magnitude of one micrometer or submicron, typically 22 mesh and is sold under the reference No. 10904 by the company Alfa Aesar, Germany.

[0023] The chromium oxide powder used has an average particle size of the order of magnitude of a micrometer or submicrometer, typically 2.4 microns and is sold under the reference No. 374 725 by the company Sigma Aldrich Chemie, Switzerland. Where appropriate, the powder is ground to achieve the desired particle size.

It will be noted that all of these powders should preferably have a purity greater than 95%.

[0025] Once the weighing of the powders is completed, all of these powders are mixed and homogenized in a humid environment. In the final homogenization phase, about 50 grams of a binder, for example polyvinyl alcohol, is added.

The mixture is then dried, for example in a conventional atomizer.

The granule obtained is sieved to keep the particles having a particle size of less than 200 micrometers.

[0028] The sieved granulate is then pressed into a mold having the configuration of the article that is desired to obtain in order to form a blank of the latter.

[0029] The article in its generally almost final form is placed in a sintering furnace. It should be noted in this connection that the sintering can be carried out in air. The article is then heated in a first phase at a rate of 30 DEG. per hour up to about 1000 DEG.G, then in a second phase at a rate of 50 DEG. per hour up to a temperature of 1450 DEG.C. The article is kept at this temperature for at least thirty minutes and preferably for an hour.

It will be noted that the sintering can of course be carried out at any other temperature greater than or equal to 1100 DEG. and less than 1600 DEG.C.

[0031] The color of the article obtained after the sintering operation is a solid gray.

[0032] The article is then cooled and then machined to obtain a shape suitable for its end use. It will be noted that the coloring is carried out in the mass so that a machining operation of the article does not alter its color in any way.

Finally, the article is polished for example using a diamond paste, the article thus obtained has a light gray shiny appearance so that it has attractive and interesting aesthetic characteristics, in particular for applications in the watchmaking field.

[0034] According to another exemplary embodiment of the method of the invention, the procedure described above was followed to produce circular watch glasses 45 mm in diameter and 4 mm in thickness. In this example we used a combination of V2O5 (0.63%), Cr2O3 (0.25%), SiO2 (0.25%), MnO2 (0.25%) and AI2O3 (0.25%) ) forming a compound in which the proportion by weight of the total composition is 1.63%, and the balance is 98.37% by weight of stabilized ZrO2. Once configured into their desired final shape, the bezels and watch cases were sintered in air for 2 hours at 1450 DEG.C. The glasses and watch cases were cooled and then mirror polished. The obtained glasses and watch cases had a dark gray shiny appearance. It was also found after breaking a box that the coloring was done in the mass.

[0035] According to yet another exemplary embodiment of the method of the invention, the procedure described above was followed to produce circular watch bezels of 45 mm in diameter and 4 mm in thickness. In this example we used a combination of V2O5 (0.75%), Cr2O3 (0.5%), SiO2 (0.30%), MnO2 (0.10%), AI2O3 (0.25 %) and Fe2O3 (0.25%) forming a compound in which the proportion by weight of the total composition is 2.15%, and the balance is 97.85% by weight of stabilized ZrO2. Once configured into their desired final shape, the glasses were sintered in air for 2 hours at 1450 DEG.C. The glasses were cooled and then mirror polished. The glasses obtained had a slightly brownish gray shiny appearance. It was also observed after breaking a telescope that the coloration was made in the mass.

[0036] The following table shows other examples of articles produced according to the invention with the colors obtained according to their composition.

Claims (18)

1. A method of manufacturing a gray article based on zirconia characterized in that it comprises the successive steps of: a) producing a first mixture comprising: A zirconia powder forming the basic constituent, 4% to 15% by weight of at least one stabilizer chosen from the group of oxides comprising yttrium oxide, magnesium oxide and calcium oxide, alone or in combination, 0.1% to 1% by weight of a vanadium oxide powder (V 2 O 5); 0.1% to 1% by weight of a chromium oxide powder (Cr 2 O 3); and 0.1% to 1% by weight of a silicon oxide (SiO 2) powder, b) forming a second mixture comprising said first mixture and a binder; c) producing a granulated mixture by granulating said second mixture; d) forming a blank by imparting to said second granulated mixture the shape of the desired article; e) sintering said blank for at least 30 minutes at a temperature of between 1250 and 1550 ° C. 2. Method according to claim 1, characterized in that the first mixture comprises: 0.4% to 0.7% by weight of a vanadium oxide powder (V 2 O 5); 0.2% to 0.3% by weight of a chromium oxide powder (Cr 2 O 3); and 0.2% to 0.3% by weight of a silicon oxide powder (SiO2). The process according to claim 1 or 2, wherein the first mixture further comprises between 0.1% to 1% and preferably between 0.2% and 0.3% by weight of a manganese oxide powder ( MnO2). 4. Method according to one of the preceding claims, wherein the first mixture further comprises 0.1% to 5% by weight of an aluminum oxide powder (Al2O3). 5. The process according to one of the preceding claims, wherein the first mixture further comprises 0.1% to 1% by weight of an iron oxide powder (Fe2O3). 6. Method according to any one of the preceding claims, characterized in that the stabilizer is yttrium oxide. 7. Method according to any one of the preceding claims, characterized in that it further comprises a step of polishing the article after step e). An injection molding or pressing composition for the manufacture of a decorative and / or functional article comprising 75 to 96% by weight of a mixture of inorganic powders and 4% to 25% by weight of a binder, said mixture of inorganic powders comprising: 82 to 95.7% by weight of zirconia powder 4% to 15% by weight of at least one stabilizer chosen from the group of oxides comprising yttrium oxide, magnesium oxide and calcium oxide, alone or in combination, 0.1% to 1% by weight of a vanadium oxide powder (V 2 O 5); 0.1% to 1% by weight of a chromium oxide powder (Cr 2 O 3); and 0.1% to 1% by weight of a silicon oxide powder (SiO 2). Molding composition according to claim 8, characterized in that said inorganic powder mixture comprises: 0.4% to 0.7% by weight of a vanadium oxide powder (V 2 O 5); 0.2% to 0.3% by weight of a chromium oxide powder (Cr 2 O 3); and 0.2% to 0.3% by weight of a silicon oxide powder (SiO2). The molding composition of claim 8 or 9, wherein the admixture of the inorganic powders further comprises from 0.1% to 1% and preferably from 0.2% to 0.3% by weight of a powder of manganese oxide (MnO2). The molding composition according to one of claims 8 to 10, wherein the inorganic powders mixture further comprises 0.1% to 5% by weight of an aluminum oxide powder (Al2O3). The molding composition according to one of claims 8 to 11, wherein the mixture further comprises 0.1% to 1% by weight of an iron oxide (Fe 2 O 3) powder. 13. Article decorative and / or functional gray zirconia based obtained in particular according to the process according to claims 1 to 7, characterized in that it consists of a sintered part from a molded part comprising in substance a matrix zirconium oxide, 4% to 15% by weight of at least one stabilizer selected from the group of oxides including yttrium oxide, magnesium oxide, and calcium oxide and mixtures thereof, 0.1% to 1% by weight of vanadium oxide (V 2 O 5); 0.1% to 1% by weight of chromium oxide (Cr 2 O 3), and 0.1% to 1% by weight of silicon oxide (SiO 2). 14. Article according to claim 13, characterized in that it comprises 0.4% to 0.7% by weight of vanadium oxide (V2O5), 0.2% to 0.3% by weight of oxide chromium (Cr2O3), and 0.2% to 0.3% by weight of silicon oxide (SiO2), 15. Article according to claim 13 or 14, characterized in that it further comprises between 0.1% to 1% and preferably between 0.2% and 0.3% by weight of manganese oxide (MnO2). 16. Article according to one of claims 13 to 15, characterized in that it further comprises 0.1% to 5% by weight of aluminum oxide (Al2O3). 17. Article according to one of claims 13 to 16, characterized in that it further comprises 0.1% to 1% by weight of iron oxide (Fe2O3). 18. Article according to one of claims 13 to 17, characterized in that it forms a constituent element of a timepiece.