CH719635A2 - Yellow colored item and its manufacturing process. - Google Patents

Abstract

The invention relates to a yellow-colored article made from a ceramic comprising zirconium oxide stabilized with one or more stabilizers chosen from yttrium oxide, magnesium oxide and calcium oxide, aluminum oxide and vanadium pentoxide, with a weight content for: – stabilized zirconium oxide of between 92 and 99.85%, – aluminum oxide of between 0.1 and 6%, – vanadium pentoxide between 0.05 and 2%. – The present invention also relates to the method of manufacturing said article. This item may be a trim component such as a middle part (1)

Description

Technical field of the invention

[0001] The present invention relates to a yellow-colored article and in particular to a watch component covering or the movement made from a zirconia-based material. It also relates to the manufacturing process of said article.

Technology background

[0002] To obtain yellow colored ceramics, it is known to use praseodymium oxide. However, the color obtained by conventional sintering of the mixture comprising this oxide is often close to mustard yellow.

[0003] The present invention proposes to expand the color palette to shades of bright yellow.

Summary of the invention

[0004] The object of the present invention is thus to propose a new yellow-colored ceramic composition based on zirconia. Her challenge is to develop a composition to obtain an item with a bright yellow color, which can also be described as lemon yellow.

[0005] More specifically, the present invention relates to a yellow-colored article made from a ceramic comprising zirconium oxide stabilized with one or more stabilizers chosen from yttrium oxide, magnesium oxide and calcium oxide, and comprising aluminum oxide and vanadium pentoxide, with a weight content for: – stabilized zirconium oxide of between 92 and 99.85%, – aluminum oxide of between 0.1 and 6%, – vanadium pentoxide between 0.05 and 2%.

[0006] This ceramic may also contain possible impurities with a content less than or equal to 0.2% by weight, preferably 0.1% by weight.

[0007] The use of vanadium oxide (V2O5) in a very small proportion makes it possible to obtain the bright yellow color by conventional sintering in air. It is observed that the vanadium oxide content must be kept within a fairly restricted range of between 0.05% and 2%, preferably between 0.1% and 1% by weight. In fact, by increasing the vanadium oxide content, we lose the desired color with a color tending towards orange with inhomogeneities in the mass. The mechanical properties are also degraded with a reduction in hardness.

[0008] The addition of alumina (Al2O3) makes it possible to opacify the zirconia, which has a direct impact on the desired color. In addition, the addition of alumina improves the mechanical properties and helps with sintering.

The article thus obtained has a yellow to bright yellow color. The color is solid and uniform. More precisely, it has in the Lab colorimetric space an a* component between -1 and -6, preferably between -2 and -5 and a b* component between 25 and 50, preferably between 30 and 45.

It has an HV10 hardness of between 900 and 1400, preferably between 1000 and 1350, more preferably between 1150 and 1350.

[0011] It has a toughness KIC of between 4 and 9 MPa √m, preferably between 5 and 8.5 MPa √m, more preferably between 5.2 and 8 MPa √m.

[0012] The present invention also relates to the process for manufacturing said article comprising the following steps: – Production of a base mixture, also called first mixture, with stabilized zirconium oxide, aluminum oxide and vanadium pentoxide in the aforementioned contents, and possibly in a liquid medium, – Production of a second mixture comprising the first mixture and an organic binder system, – Granulation of said second mixture, – Formation of a blank having the shape of l article, – Sintering of the blank in air at a holding temperature of between 1300 and 1550°C, preferably between 1350 and 1475°C, for a period of between 20 minutes and 20 hours, preferably between 30 minutes and 150 minutes.

[0013] The sintering temperature is maintained in a tight range below 1550°C (limit included), preferably below 1475°C (limit included), an increase in temperature resulting in a change of color towards an orange or even brown color and obtaining a structure which becomes friable.

[0014] The process can also include a debinding step before sintering in order to eliminate the binders. This step can be overlapped with the sintering step and take place in the same oven during the temperature rise during sintering.

Other characteristics and advantages of the invention will appear on reading the detailed description which follows, with reference to the appended drawing.

Brief description of the figure

[0016] Figure 1 represents a timepiece comprising a middle made with the ceramic material according to the invention.

Detailed description of the invention

The present invention relates to an article made from a ceramic material based on zirconia. The article may be a decorative article such as a constituent element of watches, jewelry, bracelets, etc. or more generally an external part of a portable element such as a shell of a mobile telephone. In the watchmaking field, this article can be a trim component such as a caseband, a back, a bezel, a pusher, a bracelet link, a dial, a hand, a dial index, etc. As an illustration, a middle part made with the ceramic material according to the invention is shown in Figure 1. It can also be a component of the movement such as a plate or an oscillating mass.

[0018] The ceramic article according to the invention comprises zirconium oxide (ZrO2), also called zirconia, one or more zirconia stabilizers chosen from yttrium oxide, magnesium oxide and calcium oxide, and comprises aluminum oxide (Al2O3) and vanadium oxide, more precisely vanadium pentoxide (V2O5). The article may optionally contain impurities.

The zirconia with the stabilizer(s) is present in a weight content of between 92 and 99.85%, preferably between 94 and 99.8%, more preferably between 94.5 and 99.7%. Preferably, the total content of the stabilizer(s) within the zirconia is comprised in molar percentage, between 1 and 8%, preferably between 2 and 5%, more preferably between 2.5 and 3.5%. Preferably, the stabilizer is yttrium oxide. The aluminum oxide content by weight is between 0.1 and 6%, preferably between 0.15 and 5.5%, more preferably between 0.2 and 5.2%. The vanadium oxide content by weight is between 0.05 and 2%, preferably between 0.07 and 1.2%, more preferably between 0.1 and 1%. Any impurities have a content of between 0 and 0.2% by weight, preferably between 0 and 0.1% by weight. Preferably, the article is made from a ceramic having a weight content for stabilized zirconium oxide of between 98.7 and 99.5%, for aluminum oxide of between 0.2 and 0.3%, and for vanadium pentoxide of between 0.2 and 0.3%. between 0.2 and 0.8%.

[0020] Preferably, the article consists of zirconium oxide (ZrO2), also called zirconia, of zirconia stabilizer(s) chosen from yttrium oxide, magnesium oxide and zirconia calcium, and consisting of aluminum oxide (Al2O3), vanadium oxide, more precisely vanadium pentoxide (V2O5) and possible impurities in the aforementioned contents.

[0021] The ceramic article has a CIELAB color space (compliant with CIE standards n°15, ISO 7724/1, DIN 5033 Teil 7, ASTM E-1164) with an L* component of between 75 and 95, preferably between 80 and 95, an a* component between -1 and -6, preferably between -2 and -5, and a b* component between 25 and 50, preferably between 30 and 45. It has an HV10 hardness of between between 900 and 1400, preferably between 1000 and 1350, more preferably between 1150 and 1350. It has a KIC toughness of between 4 and 9 MPa √m, preferably between 5 and 8.5 MPa √m, more preferably between 5.2 and 8 MPa √ mr.

[0022] The article is manufactured by sintering with the process consisting of: – Making the basic mixture, also called first mixture, with the various aforementioned compounds and possibly in a liquid medium. – Make a second mixture comprising the first mixture and an organic binder system (paraffin, polyethylene, polyvinyl acetate, etc.). – Granulate and, if necessary, dry said second mixture, for example, in an atomizer. Preferably, the aggregates have a size d50 of between 10 and 100 µm, and, preferably, between 40 and 60 µm. – Form a blank by giving this second granulated mixture the shape of the desired article, for example, by injection or pressing. Preferably, the shaping is carried out by pressing. – Sinter the blank in air at a holding temperature of between 1300 and 1550°C, preferably between 1350 and 1475°C, for a period of between 20 minutes and 20 hours, preferably between 30 minutes and 150 minutes. This step can be preceded by a thermal debinding step in a temperature range between 200 and 800°C. It could also be a solvent debinding in the case of shaping by injection.

The blank thus obtained is cooled. It can then be machined, polished and decorated if necessary to obtain the desired item. The color being present in the mass of the blank, these finishing operations do not alter the final color of the article.

The articles thus obtained have a density of between 5 and 6.5g/cm<3>, preferably between 5.7 and 6.1g/cm<3>.

[0025] Tests were carried out for the compositions listed in Table 1 below. It should be noted that the compositions may contain impurities included in the basic compounds (ZrO2, Al2O3, V2O5) provided. Hardness measurements are HV10 hardnesses. The toughness was determined based on measurements of the lengths of the cracks at the four ends of the diagonals of the hardness imprint according to the formula: with P which is the applied load (N), a which is the half-diagonal (m) and / which is the length of the measured crack (m).

[0026] The Lab colorimetric values were measured on the polished samples with a KONICA MINOLTA CM-5 spectrophotometer under the following conditions: SCI measurements (specular reflection included) and SCE (specular reflection excluded), inclination of 8°, measurement area MAV of 8 mm diameter.

All the samples obtained have a yellow color but they may have nuances depending on the composition or the sintering temperature. A drop in hardness from 1250 HV10 to 1020 HV10 is observed with the decrease in the sintering temperature from 1450°C to 1380°C for samples 1 and 2 having an aluminum oxide content of 0.25% and aluminum oxide. vanadium of 0.5% by weight. Sample 2 has a paler color, in other words, less intense than that of sample 1.

[0028] An increase in the vanadium oxide content to 1.5% by weight in sample 3 results in a drop in hardness with a value of 990 HV10. This sample is a little more orange.

Sample 4 with a vanadium oxide content of 0.1% and alumina content of 0.25% by weight presents a good toughness - hardness compromise with a hardness of 1310 HV10 and a toughness of 5.5 MPa √m. It has a slightly darker color, approaching egg yolk.

[0030] An increase in the aluminum oxide content to 5% by weight in sample 5 results in a slight change in the color with a slightly lighter color tending discreetly towards green.

Table 1

[0031] 1 99.25 0.5 0.25 1450 89.2 -2.9 43.5 1250 5.3 5.97 2 99.25 0.5 0.25 1380 93.6 -4.5 33.7 1020 5.5 5, 95 3 98.25 1.5 0.25 1450 90.8 -2.5 40.4 990 7.9 5.75 4 99.65 0.1 0.25 1450 83.4 -2.5 43.2 1310 5.5 6.03 5 94.9 0.1 5 1450 91.2 -4.3 36.4 1270 5.6 5.82

Claims (17)

1. Yellow-colored article made from a ceramic comprising zirconium oxide stabilized with one or more stabilizers chosen from yttrium oxide, magnesium oxide and calcium oxide, and comprising oxide aluminum, vanadium pentoxide and possible impurities, with a content by weight of: – stabilized zirconium oxide between 92 and 99.85%, – aluminum oxide between 0.1 and 6%, – vanadium pentoxide between 0.05 and 2%, – any impurities between 0 and 0.2%. 2. Article according to the preceding claim, characterized in that the content by weight of the stabilized zirconium oxide is between 94 and 99.8%. 3. Article according to one of the preceding claims, characterized in that the content by weight of the stabilized zirconium oxide is between 94.5 and 99.7%. 4. Article according to one of the preceding claims, characterized in that the weight content of the aluminum oxide is between 0.15 and 5.5%. 5. Article according to one of the preceding claims, characterized in that the weight content of the aluminum oxide is between 0.2 and 5.2%. 6. Article according to one of the preceding claims, characterized in that the content by weight of vanadium pentoxide is between 0.07 and 1.2%. 7. Article according to one of the preceding claims, characterized in that the weight content of vanadium pentoxide is between 0.1 and 1%. 8. Article according to one of the preceding claims, characterized in that the total content of the stabilizer(s) within the stabilized zirconium oxide is comprised in molar percentage between 1 and 8%, preferably between 2 and 5%, more preferably between 2.5 and 3.5%. 9. Article according to one of the preceding claims, characterized in that the content by weight of the stabilized zirconium oxide is between 98.7 and 99.5%, of the aluminum oxide is between 0.2 and 0.3%, of the vanadium pentoxide is between 0.2 and 0.8%. 10. Article according to one of the preceding claims, characterized in that it consists of zirconium oxide stabilized with one or more of the stabilizers chosen from yttrium oxide, magnesium oxide and magnesium oxide. calcium, and consisting of aluminum oxide, vanadium pentoxide and possible impurities with the contents according to one of the preceding claims. 11. Article according to one of the preceding claims, characterized in that it has in the CIELAB colorimetric space a component a* between -1 and -6, preferably between -2 and -5 and a component b* between between 25 and 50, preferably between 30 and 45. 12. Article according to the preceding claim, characterized in that it has in the CIELAB colorimetric space a component L* of between 75 and 95, preferably between 80 and 95. 13. Article according to one of the preceding claims, characterized in that it has an HV10 hardness of between 900 and 1400, preferably between 1000 and 1350, more preferably between 1150 and 1350. 14. Article according to one of the preceding claims, characterized in that it has a toughness KiC of between 4 and 9 MPa √m, preferably between 5 and 8.5 MPa √m, more preferably between 5.2 and 8 MPa √m. 15. Article according to one of the preceding claims, characterized in that it is a covering component or a watch movement. 16. Method of manufacturing an article according to one of the preceding claims, comprising the following steps: – Production of a basic mixture, also called first mixture, with stabilized zirconium oxide, aluminum oxide and vanadium pentoxide in the contents according to one of claims 1 to 9, and this optionally in liquid medium, – Production of a second mixture comprising the first mixture and an organic binder system, – Granulation of said second mixture, – Formation of a draft having the shape of the article, – Sintering of the blank in air at a holding temperature of between 1300 and 1550°C for a period of between 20 minutes and 20 hours, preferably between 30 minutes and 150 minutes. 17. Manufacturing process according to the preceding claim, characterized in that the sintering is carried out at a holding temperature of between 1350 and 1475°C.