JPS61117156A - Manufacture of zirconia black sintered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for manufacturing a zirconia black sintered body.

More specifically, the present invention relates to a method for producing a zirconia sintered body that exhibits high strength and a jet black color, and is particularly useful in the production of decorative items.

Conventional technology Zirconia ceramics have been used as high-temperature refractories for a long time. known to cause collapse. Therefore, oxides of metals such as Y, [:a, Mg, etc. are generally added as a stabilizer and used as stabilized zirconia ceramics (tetragonal lr O2) that do not cause volume changes. However, although this substance is stable up to quite high temperatures,
The strength was low, and it was difficult to obtain a dense sintered body.

By the way, later research revealed that by reducing the amount of stabilizer added, partially stabilized zirconia (PSZ)
Alternatively, a material called phase transformation strengthened zirconia (TTZ) has been developed, and has almost satisfactory physical properties such as strength, toughness, and thermal shock resistance.

This partially stabilized zirconia composition has attracted attention as a high-strength ceramic, and various applications are being developed, including applications for cutlery such as scissors and slitters.

By the way, it has traditionally been used as a decorative material for watch-related parts such as watch sides, cases, dials, and tie pins. Kui carbide tool materials were put into practical use. For example, gold colors include TaC, hNSTiN, etc., black colors include alumina ceramics with pigments added (Japanese Unexamined Patent Publication No. 56-59670), and natural or synthetic alumina-containing oxides such as ruby, sapphire, and emerald. Single crystals are also well known. These products are made into final products by cutting a single crystal material into a predetermined size using a diamond tool or the like, and going through various processes such as polishing and lapping.

However, these existing decorative ceramics are inferior in hardness, strength, and especially toughness, cannot be freely selected from a wide range of colors, and require advanced technology to create complex shapes, resulting in high costs. Becomes high. In addition, although the above-mentioned black alumina ceramics are satisfactory in terms of color tone, the strength of the sintered body is insufficient, so when applied to watch rings, for example, there are problems such as breakage. It is still insufficient for practical use as a decorative material.

Therefore, it is possible to use the above-mentioned partially stabilized zirconia, which is attracting attention as a high-strength ceramic, but since this partially stabilized zirconia is originally white, it is difficult to use it as a black decorative material. needs to be colored. Conventionally, this coloring method involves adding a stabilizer to a base material mainly composed of zirconia, molding the material, and then firing it in a non-oxidizing atmosphere (
(See Japanese Patent Application Laid-open No. 121165/1983).

Problems to be Solved by the Invention As detailed above, high-strength partially stabilized zirconia is attracting attention as a decorative black ceramic material, but as already mentioned, this material is originally white and cannot be used for black decoration. In order to give it a body, it was necessary to color it. As a method for blackening zirconia ceramics, the invention disclosed in JP-A-59-121165 is known, but with this method it is impossible to obtain products with a constant color tone with good reproducibility, and the color tone varies from lot to lot. There was a problem in that there were variations in the results.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for producing a zirconia sintered body having high strength, jet black color, and excellent decorative properties. Another object of the present invention is to provide a novel black zirconia sintered body having high strength and uniform color tone.

Means for Solving the Problems In view of the above-mentioned current state of the coloring method for zirconia ceramics, the present inventors conducted various studies in order to develop a new black decorative material that can express a jet black color tone with good reproduction. As a result, it was found that it is advantageous to use a certain amount of carbon as an additive.

The present invention is based on such new findings.

That is, the method for producing a zirconia black sintered body of the present invention is as follows:
Obtaining a powder mixture of tetragonal zirconia as a main component and an oxide of at least one element selected from the group consisting of IIIa group elements, Mg and Ca as a stabilizer,
It is characterized in that after adding 0.1 to 5.0% by weight of carbon, it is shaped and sintered in a non-oxidizing atmosphere.

In the method of the present invention, a powder mixture of zirconia and a stabilizer can be obtained from a predetermined stabilizer and zirconia by a coprecipitation method, or by simply uniformly mixing the stabilizer powder and zirconia powder. It can also be obtained by Furthermore, it is possible to use the metal alkoxide hydrolysis method, which has recently attracted attention as a method for synthesizing uniform powder with a strict composition ratio, and in this case, the alkyl group of the alkoxide group is one with a small number of carbon atoms. It is advantageous that Next, carbon powder in an amount within the above range is added and mixed to the powder mixture obtained as described above to obtain a raw material powder mixture. The mixture is processed using a ball mill or the like to form a uniform powder mixture. Further, it is preferable to add a small amount of a binder such as wax, vaseline, or liquid paraffin to ensure uniform mixing. In this case, the mixture can be directly sent to a sintering process after being formed, and wax or the like can be used as the carbon source. Therefore, it is also possible to obtain all the carbon from the binder.

Here, there is no particular restriction on the particle size of the zirconia powder and the stabilizing side powder, but in order to obtain a dense sintered body with few voids, it is advantageous to make it as small as possible. For example, it is desirable that the thickness be about 2.0 μm or less.

The powder mixture is then shaped, and this shaping can be carried out, for example, by known pressure forming means such as embossing. This shaping is advantageously carried out under conditions which reduce the voids in the shaped body as much as possible.

Sintering of the shaped raw material mixture is carried out at 1400-1700°C, preferably at 1,400°C in a non-oxidizing atmosphere, e.g. vacuum, reducing or inert gas atmosphere such as N2, Ar, N2, etc.
It is carried out at a temperature in the range of 450-1600°C.

That is, if the sintering temperature is 1,400°C or lower, the compact will not be sintered, and if the sintering temperature exceeds 1,700°C, the strength, especially the toughness, of the obtained sintered product will be poor, which is not preferable. . Therefore, it is desirable that the sintering operation be carried out at a temperature within the above range.

Further, in the present invention, the sintering time is not critical, and is not particularly limited as long as it is within a range in which sintering is sufficiently achieved.

In addition, in the method for producing a sintered body of the present invention, in addition to the essential components zirconia, stabilizer, and carbon, various known additives, such as sintering accelerators such as silica, alumina, and titania, are added. It is also possible to add it in an amount that does not impair the desired effect.

As the sintering method, any of the known ceramic sintering methods can be used, but the hot press method or HIP method is particularly suitable.
By using the hot isostatic pressure method, products with even better properties can be obtained.

In addition, as a carbon source, carbon black such as furnace black, lamp black, acetylene black,
Various other known materials such as channel black, roller black, disk black, and naphthalene black can be used, and the same effect can be obtained regardless of the shape of the material, whether carbonaceous, graphitic, or amorphous.

The sintered body thus obtained is then subjected to processing such as cutting, polishing, and lapping as described above to impart a predetermined shape and luster to the finished decorative article.

Ag-W is used for machining, such as hole machining and die engraving of various shapes.
Electric discharge machining using an electrode such as SCu-W, grinding using a diamond grindstone, etc., and mirror finishing, lapping using diamond abrasive grains (powder), etc. can be used.

The sintered body obtained by the method of the present invention is extremely suitable for use in various watch parts such as watch cases and dials, as well as decorative items such as tie pins.

Function: According to the method of the present invention, a predetermined amount of carbon powder is uniformly mixed into a powder mixture of tetragonal zirconia and a stabilizer, and after molding, sintering is performed in a non-oxidizing atmosphere. It has now become possible to easily and inexpensively produce a decorative black ceramic material with a uniform color, which has not been possible to obtain with good quality.

The amount of stabilizer is generally a percentage of the amount sufficient to stabilize the zirconia.

For example, when using Y 203, about 3 mol% (
2 to 9 mol %), the desired results can be obtained. This is because the sintered body has the highest strength when it has the highest tetragonal content. In either case, it is used in an amount sufficient to provide an 11 partially stabilized zirconia composition. Therefore,
For example, for the stabilizer CaO, 8 to 12 mol%, Mg
As for O, it is sufficient if it is within the range of 16 to 26 mol%.

Carbon as a coloring additive is used in a range of 0.1 to 5.0% by weight. This range is an essential requirement in the method of the present invention. That is, when the amount of carbon added is less than 0.1% by weight, jet blackness is insufficient due to the insufficient amount of carbon, the color tone is uneven, and the depth of the color is insufficient. On the other hand, when carbon is used in an amount exceeding 5% by weight, the densification of the resulting sintered body is inhibited, resulting in a porous sintered body, which is also unsatisfactory in terms of gloss and strength.

According to the present invention, processing to satisfy the above conditions is necessary in order to solve all the drawbacks of the conventional methods, thereby making it possible to provide an excellent decorative black ceramic material. .

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the scope of the present invention is not limited in any way by these Examples.

Example 1 A powder mixture having the composition shown in Table 1 below was hot press sintered at 1500°C under vacuum conditions to form a powder with dimensions 50x50.
A sintered sample with a size of 5 mm was obtained. The sample prepared in this way was first surface ground with a diamond grindstone, and then
When polished with μm diamond abrasive grains,
Both samples have Rockwell hardness (HRA) 92
As described above, it had excellent mechanical properties with a bending strength of 100 kg/mm2 or more, and the color tone was jet black and heavy. Although the same operation was repeated, a product with similar characteristics could be obtained with good reproducibility.

Table 1 Composition of powder mixture Example 2 Using the mixed powder of sample Nα3 shown in Example 1, it was pressed under a pressure of 20t/cut and then sintered at 1600°C for 2 hours under vacuum. . When the obtained sintered body was processed in the same manner as in Example 1, it had an HRA of 92.
5. It was found to be a jet black sintered body with a bending strength of 110 Kg/mm2.

Example 3 The unprocessed sintered body obtained in Example 2 was heated to 1600°C.
- When HIP sintering was performed in Ar at 1000 atm, it was found that the sintered density was further improved and the color tone was also deepened.

Reference Example 9 8% by weight of carbon powder was mixed into a mixture of 5% by weight of ZrO2 powder and 5% by weight of Y2O3 powder, and a sintered body was obtained under the same conditions as in Example 1. The sintered body thus obtained had a sintered density of 96%, and the gloss on the two surfaces of the borish was insufficient.

This result shows that if the amount of carbon added is too high, it is not possible to obtain the desired excellent sintered body.

Further, an example in which 0.05% by weight of carbon powder was added was treated in the same manner to obtain a sintered body, but this had a non-uniform color tone.

Effects of the Invention As described above, according to the method for producing a zirconia black sintered body of the present invention, carbon powder is added to a powder mixture of ZrO2 and a stabilizer in an amount within a predetermined range. , a black sintered body with high strength and stable color can be produced with good reproducibility.

Therefore, the black zirconia sintered body obtained by the method of the present invention has extremely high value as a decorative item compared to the conventional alumina sintered body and the partially stabilized zirconia sintered body without adding carbon. In addition, a wide range of applications other than decorative items can be considered.

Claims (3)

[Claims] (1) A powder mixture of tetragonal zirconia as a main component and an oxide of at least one element selected from the group consisting of Group IIIa elements, Mg and Ca as a stabilizer is obtained, and 0.1 After adding ~5.0 wt% carbon,
A method for producing a black zirconia sintered body, which comprises shaping and sintering in a non-oxidizing atmosphere. (2) The method according to claim 1, wherein the sintering is carried out by a hot pressing method or a hot isostatic pressing method. (3) The method according to claim 1 or 2, wherein the powder mixture is produced by a coprecipitation method or an alkoxide hydrolysis method.