A method for producing a colored article, in particular an orange article, made of zirconia; colored decorative article made of zirconia obtained according to the method
By adding ceria powder to the sintered zirconia-based ceramics and controlling the oxygen partial pressure and temperature during the sintering and annealing, the problems of colorant instability and heavy metal components in the prior art are solved, and the stability of bright orange products is achieved Production and uniform coloring, with good mechanical properties and gloss.
Patent Information
- Application Number
- CN202411653880.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2013-05-03
- Filing Date
- 2014-05-05
- Publication Date
- 2025-02-18
AI Technical Summary
The prior art has problems such as instability, heavy metal composition, large particle size when combining colorants into sintered zirconia-based ceramics, which limits its use, and is difficult to achieve uniform mixing and stable color in particular when producing orange products.
Reduction of cerium oxide is achieved by combining the cerium oxide powder into the mixture to be sintered and controlling the oxygen partial pressure and temperature during the sintering and annealing process, thereby imparting a bright orange color to the product.
The stable production of bright orange sintered zirconia-based products at high temperatures is achieved, ensuring that the products are uniformly colored on the surface and inside, and have good mechanical properties and gloss, and are suitable for decorative products.
Abstract
Description
[0001] The present application is a divisional application of the invention patent application with application number 201480035281.2. The application date of the original application is May 5, 2014. The name of the invention is: a method for producing colored products made of zirconium oxide, especially orange products; and colored decorative products made of zirconium oxide obtained according to the method.
[0002] The present invention relates to the manufacture of colored zirconium oxide-based articles, in particular such articles showing a color comprised in the range from bright orange to copper brown and achieved by means of sintering. For convenience, the articles are referred to as "orange articles" in the following description.
[0003] The invention also relates to a decorative zirconium oxide-based orange article obtainable in particular according to the process described hereinafter.
[0004] It is known to incorporate colorants or pigments such as cadmium sulfide (CdSe), cadmium selenide and cadmium sulfoselenide into ceramic materials to give orange / red ceramic articles such as are used to produce enamels, glazes and containers for household or floor use.
[0005] The use of such colorants has a number of disadvantages when it is desired to incorporate such colorants into technical ceramics, particularly sintered zirconia-based ceramics.
[0006] In fact, these colorants are unstable at high temperatures and develop their coloring properties up to 1,000 or 2,000° C. This greatly limits the use of such colorants and, in particular, does not allow their use in the production of sintered zirconia articles, since the sintering temperature of zirconia is in any case above 1,100° C.
[0007] Furthermore, the use of such colorants containing heavy metals in objects intended to come into contact with the user's skin, such as watch cases, is at least strongly discouraged, if not prohibited by law.
[0008] Additionally, commercially available colorants of this type have a large particle size, which is incompatible with obtaining a homogeneous mixture with the zirconium oxide powder.
[0009] The main object of the present invention is therefore to provide, on the one hand, a method for producing a bright orange sintered zirconia-based article and, on the other hand, such an article obtained according to the method, which has satisfactory mechanical properties while exhibiting a bright orange color at a depth of at least 5 mm from the surface.
[0010] To this end, the present invention relates to a method for producing a bright orange zirconium oxide-based article, characterised in that it comprises a series of steps, namely:
[0011] A first mixture is produced comprising:
[0012] ●Zirconium oxide powder,
[0013] 3-20% by weight of at least one stabilizer selected from the group of oxides comprising yttrium oxide, magnesium oxide and calcium oxide, either alone or in combination,
[0014] 0.1% to 5% by weight of at least one element intended to produce a glassy phase and chosen, alone or in combination, from the group comprising silicon dioxide, aluminum oxide, lithium oxide and yttrium oxide,
[0015] 1% to 6% by weight of cerium oxide powder;
[0016] producing a second mixture comprising the first mixture and a binder,
[0017] producing a granulated mixture by granulating the second mixture;
[0018] forming a green body by giving the second granular mixture the shape of a desired article;
[0019] Air sintering at a temperature of 1,250-1,500°C for at least 30 minutes, and the desired product is placed in a 10 -6 Up to 10 -1 annealing at a temperature of 700°C to 1,350°C for a period of 30 minutes to 20 hours in a reducing atmosphere of atmospheric oxygen partial pressure, and
[0020] The sintered green body is polished.
[0021] The process of the invention makes it possible to reduce the sintering temperature by incorporating cerium oxide powder (CeO2) into the mixture to be sintered. Cerium oxide also serves as one of the determining elements that imparts the desired orange color to the article.
[0022] In fact, after the sintering operation in the presence of CeO2, the color of the article is ivory white. The presence of CeO2 (+4 oxidation state) is then used to reduce it to Ce2O3 (+3 oxidation state) during the subsequent step of the method of the invention, the so-called annealing step. After this annealing step, the article has a color ranging from yellow-orange to bright orange, depending on the respective amounts of cerium in the +4 and +3 oxidation states present at the grain boundaries. The color of cerium oxide (CeO2) in the +4 oxidation state is ivory white, and the color of cerium oxide (Ce2O3) in the +3 oxidation state is bright orange.
[0023] The amount of each of the +4 and +3 oxidation states of cerium oxide present on the grain boundaries is determined by the annealing conditions, more specifically, by varying the oxygen partial pressure in the oven environment in which the annealing is performed.
[0024] According to one embodiment, the first mixture comprises 0.1-1 wt % of oxide powder for the glass phase, preferably 4-5 wt % of cerium oxide powder (Ce +4 O2).
[0025] The present invention also relates to a decorative bright orange zirconium oxide-based article obtained according to the above method, characterized in that it is formed by a sintered part, which is made of a molded part, which essentially comprises a zirconium oxide matrix, 3-20% by weight of at least one stabilizer, which is selected from the group of oxides comprising yttrium oxide, magnesium oxide and calcium oxide, alone or in combination, 0.1% to 5% by weight of a glass phase, which comprises at least one element selected from the group comprising silicon dioxide, aluminum oxide, lithium oxide and yttrium oxide, alone or in combination, and 1% to 6% by weight of cerium oxide.
[0026] The articles have the advantage of showing a high gloss after polishing and are therefore particularly suitable for producing decorative articles, such as components of watch cases, jewellery, bracelets, brooches, tie pins, necklaces, handbags, telephones, furniture or household appliances.
[0027] Further features and advantages of the invention emerge from the following description of an exemplary implementation of the method of the invention.
[0028] The manufacturing method of the invention now described in detail is a method which allows to produce a bright orange sintered zirconia-based article whose appearance and mechanical properties are particularly suitable for making a component part of a watch or for making any other decorative article.
[0029] The bright orange zirconium oxide product obtained according to the method contains 89% to 98.9% by weight of stabilized zirconium oxide and the remainder, i.e., 0.1% to 5% by weight, of a glass phase formed by silicon dioxide, aluminum oxide, yttrium oxide and lithium oxide alone or in combination, and 1% to 6% by weight of cerium oxide.
[0030] Zirconia is generally stabilized in a tetragonal phase by at least one stabilizer selected from the oxide group comprising yttrium oxide, magnesium oxide and calcium oxide, alone or in combination, in an amount of 3% to 20% by weight relative to the zirconium oxide.
[0031] To prepare the article, according to an exemplary implementation of the method of the present invention, a method is performed as follows:
[0032] 943 g of stabilized zirconium powder with 3% by weight of yttria are weighed. The powder used has an average particle size in the micrometer range, typically 0.1-0.5 μm. The powder is sold under the reference TZ-3Y by the Tosoh Corporation, Japan.
[0033] Then 7 g of a mixture of silica, alumina and lithium oxide powders were weighed, which were expected to form a glassy phase during subsequent sintering.
[0034] Preferably, the glassy phase comprises a mixture or combination of 47%, 40% and 13% by weight, respectively, of silica, alumina and lithium oxide.
[0035] The silicon powder used has an average particle size of less than 1 μm, typically 40 nm, and is sold under the name Aerosil OX50 by Cerdec, Germany.
[0036] The aluminium powder used has an average particle size of the micron or submicron range, typically 0.5 μm, and is sold under the name CR30 by Baikowski, France.
[0037] The lithium powder used has an average particle size of micron or submicron size, typically 2.4 μm, and is sold by Sigma-Aldrich Chemicals, Switzerland, under the reference number 374725. If necessary, the powder is ground to achieve the desired particle size.
[0038] Finally, weigh 50g of cerium oxide (Ce 4+ O); the powder used has a particle size of micrometer or submicrometer order, typically 0.5 μm, and is sold under the reference number 202975 by Sigma-Aldrich Chemicals, Switzerland.
[0039] It should be noted that these powders should preferably all have a purity of more than 95%.
[0040] When the powders are weighed, all of them are mixed and homogenized in a wet medium. In the final stage of homogenization, about 50 g of a binder, such as polyvinyl alcohol, are added.
[0041] The mixture is then dried, for example in a customary atomizer.
[0042] The particles thus obtained were sieved to keep particles having a particle size of less than 200 μm.
[0043] The sieved particles are then pressed into a mold having the shape of the article desired by the technician to form a green body thereof.
[0044] The article, which is in its nearly final general shape, is placed in a sintering furnace. In this regard, it should be noted that sintering can be carried out in air. The article is then heated to about 1,000° C. at a rate of 30° / hour in a first stage and then to a temperature of 1,250° C. at a rate of 50° / hour in a second stage. The article is kept at this temperature for at least 30 minutes, preferably 1 hour.
[0045] It should be noted that sintering can of course be carried out at any other temperature higher than or equal to 1,100° and lower than 1,600°C.
[0046] During sintering, silica, alumina, yttrium oxide and lithium oxide form a condensed glass phase with cerium oxide in the +4 oxidation state at the grain boundaries, which gives the article an ivory color after sintering.
[0047] It should be noted that the presence of lithium oxide advantageously reduces the sintering temperature and limits the transition of the color of the cerium oxide, thus allowing a bright orange color to be obtained.
[0048] After this sintering step, the article is placed in an annealing furnace with a selectable atmosphere. The desired article is annealed in a hydrogen atmosphere (H2), or in an atmosphere containing a mixture of nitrogen and hydrogen (N2 / H2) or a mixture of argon and hydrogen.
[0049] During this annealing operation, the oxygen partial pressure in the furnace was 10 -6 Up to 10 -1 Atmospheric pressure, the annealing temperature is 700° C. to 1250° C., and the annealing time is generally 30 minutes to 20 hours.
[0050] According to the preferred implementation of the method of the present invention, the atmosphere in the annealing furnace is hydrogen with an oxygen partial pressure of 10 -4 Up to 10 -1 Atmospheric pressure, annealing temperature is 900-1,150°C and annealing time is 4-6 hours. It should be understood that the color depth inside the article changes in proportion to the annealing time.
[0051] The color of the article obtained after the annealing operation is bright orange or a hue between orange and copper-brown, depending on the annealing conditions.
[0052] The article is then cooled and machined to obtain a shape suitable for its final use. It should be noted that the coloring is deep inside the article so that machining the article does not in any way change its color.
[0053] Finally, the article is polished, for example using a diamond paste, so that the resulting article has a glossy appearance of bright orange or a hue comprised between the above-mentioned colors, depending on the annealing conditions, giving it an attractive and interesting aesthetic feature, in particular for use in the watchmaking sector.
[0054] According to another exemplary execution of the method of the invention, the above method of operation was carried out to produce a circular watch bezel of 45 mm in diameter and 4 mm thick. This example uses a combination of SiO2 (47%), Al2O3 (40%) and Li2O (13%), thereby forming a compound with a weight proportion of 0.7% of the total composition, the mixture forming a glass phase, 6% by weight CeO2, and the remainder, i.e., 93.3% by weight, stabilized ZrO2. When constructed in its desired final shape, the bezel is sintered at 1,450°C in air for 2 hours. These bezels are then annealed at 1,000°C for 12 hours in an atmosphere containing 5% hydrogen and 95% argon. The bezel is then cooled and mirror polished. The resulting bezel has a bright orange glossy appearance. After breaking the bezel, it is also observed that the coloring is achieved deep in the article.
Claims
1. A method for manufacturing a bright orange zirconium oxide-based product, characterized in that It consists of a series of steps, namely: A first mixture is produced comprising: ●Zirconium oxide powder, 3-20% by weight of at least one stabilizer selected from the group of oxides comprising yttrium oxide, magnesium oxide and calcium oxide, alone or in combination, 0.1% to 5% by weight of at least one element intended to produce a glassy phase and selected from the group comprising silicon dioxide, aluminum oxide, lithium oxide and yttrium oxide, alone or in combination, 1% to 6% by weight of cerium oxide powder; producing a second mixture comprising the first mixture and a binder, producing a granulated mixture by granulating the second mixture; forming a green body by giving the second granular mixture the shape of a desired article; Sintering in air at 1,250-1,500°C for at least 30 minutes, and annealing the desired article in a reducing atmosphere at a temperature of 700°C to 1,350°C for 30 minutes to 20 hours, and The sintered green body is polished.
2. The method according to claim 1, wherein the first mixture comprises 0.1% to 1% by weight of powder intended to form a glassy phase.
3. A method according to claim 1 or 2, wherein the powder intended to form a glassy phase comprises silicon dioxide, aluminum oxide, lithium oxide and yttrium oxide in decreasing order of weight.
4. A method according to claim 3, wherein the amounts of silicon dioxide, aluminum oxide and lithium oxide in decreasing order by weight are 47%, 40% and 13% respectively.
5. A method according to any one of claims 1 to 4, characterised in that The first mixture contains 1-6%, preferably 4-5% by weight of cerium oxide powder.
6. A method according to any one of the preceding claims, characterised in that The stabilizer is yttrium oxide.
7. The method according to any one of the preceding claims, characterized in that The annealing temperature is 700-1,350°C and the reducing atmosphere has 10 -6 Up to 10 -1 The partial pressure of oxygen at atmospheric pressure.
8. The decorative bright orange zirconium oxide-based product obtained according to the above method is characterized in that The article is formed from a sintered part made from a molded part, the molded part essentially comprising: Zirconia substrate, 3-20% by weight of at least one stabilizer selected from the group of oxides comprising yttrium oxide, magnesium oxide, cerium oxide and calcium oxide and mixtures thereof, 0.1% to 5% by weight of a glassy phase comprising silicon dioxide, aluminum oxide, lithium oxide and yttrium oxide and mixtures thereof, and 1% to 6% by weight of cerium oxide.
9. A decorative orange zirconium oxide-based article according to claim 8, characterised in that The product is obtainable according to any one of claims 1 to 6.