JPH03242372A - Golden zirconia ceramics and production thereof - Google Patents

Abstract

PURPOSE:To obtain the title ceramics with improved toughness by incorporating ZrO2 with Y2O3, TiO2 and C followed by calcination in a N2 gas atmosphere. CONSTITUTION:(A) ZrO2 is incorporated with (B) 3-6 mol% of Y2O3 and (C) 10-30wt.%, based on a total of ZrO2 and Y2O3, of TiO2, and the resulting mixture is put to wet grinding followed by addition of a forming binder into a slurry, which is then dried and granulated into mixed powder. Thence, 10-25wt.%, based on the TiO2, of C is added to this powder followed by forming under a pressure of ca.1ton/cm<2>, and the resultant form is calcined in an N2 gas atmosphere at 1300-150 deg.C for 1 to several hours, thus obtaining the objective golden zirconia ceramics with part of the TiO2 reduced and nitrided.

Description

Detailed Description of the Invention "Field of Industrial Application" This invention is applicable to watch cases, watch bands, watch dials, handbag fittings, decorative members such as tie clips, tire spikes, shoe spikes, The present invention relates to a method for manufacturing gold-colored zirconia ceramics used for various ceramic members such as mechanical members such as various structural members, ferrules for optical fibers, ceramic electronic members such as substrates for electronic parts, etc.

"Prior Art and its Problems" Recently, various colored ceramics have been studied in order to apply color to ceramics and use them in new fields such as decoration.

Among these colored ceramics, a method for producing gold-colored ceramics is known as a method for producing titanium nitride, in which titanium oxide is fired in ammonia gas and further sintered in nitrogen gas.

However, the 100% titanium nitride obtained in this manner is difficult to mirror polish due to its high hardness, and is therefore not suitable as a material for decorative members.

On the other hand, as a gold-colored ceramic other than titanium nitride, a method has also been proposed in which zirconia is used as the main material and only the surface layer is made into zirconium nitride under high temperature and high pressure conditions to give it a gold color. However, as mentioned above, this method requires special equipment because the treatment must be carried out under high temperature and high pressure conditions, and as a result, the manufacturing cost naturally increases.

In addition, the obtained golden ceramic is colored gold only on the surface layer, and when it is cut or polished, the polished or cut surface does not turn gold, so the sintered body is cut and polished to achieve the desired color. There was a problem that it could not be used for producing a member having the shape of .

The present invention has been made in view of the above circumstances, and it is possible to easily perform mirror polishing and cutting, to perform sintering under relatively low temperature and low pressure conditions, and to achieve a uniform golden color over the entire sintered body. The purpose of the present invention is to provide gold-colored zirconia ceramics that can be colored and a method for producing the same.

"Means for Solving the Problems" In order to achieve the above object, the golden zirconia ceramic according to the present invention has 3 to 6 mol% of yttrium oxide added to zirconium oxide, and titanium oxide is the sum of zirconium oxide and yttrium oxide. 1 per weight
Titanium oxide is added in an amount of 0 to 30 wt%, and a portion of the titanium oxide is reduced and nitrided.

In addition, as a method for producing the above-mentioned golden zirconia ceramics, 3 to 6 m of yttrium oxide is added to zirconium oxide.
10 to 30 wt% of titanium oxide to the total weight of zirconium oxide and yttrium oxide,
A material containing 10 to 25 wt% of carbon to the weight of titanium oxide was heated in a nitrogen gas atmosphere at 1300 to 500 liters.
A method of firing under conditions of ℃ is desirable.

This invention will be explained in more detail below.

The golden zirconia ceramic of the present invention is made by adding yttrium oxide (hereinafter referred to as yttrium) and titanium oxide (hereinafter referred to as titania) to zirconium oxide (hereinafter referred to as zirconia), and a part of the titania is reduced and nitrided. Titanium nitride is uniformly dispersed in zirconia ceramics containing itria and titania.

The toughness of zirconia comes from the fact that the crystal system undergoes a martensitic phase transformation from a tetragonal system to a monoclinic system when stress is applied. Ittria is added to partially stabilize tetragonal/monoclinic mixed crystal zirconia. It is also estimated that the addition of titania has a partial stabilizing effect.

The amount of ittria added to this zirconia ceramic is 3 to 1%. If the amount of ittria added is less than 3 mo1%, the partial stabilizing effect of ittria will be weakened, resulting in cracks in the zirconia ceramic sintered body. Also, the amount added is 6+io
If it is 1% or more, segregation of yttrium zirconium oxide occurs, resulting in a decrease in the strength of zirconia ceramics.

Furthermore, titania is added to partially stabilize the zirconia ceramics mentioned above, and to make the entire zirconia ceramic sintered body golden by producing titanium nitride through reductive nitridation of titania. The amount is 10 to 10% based on the total weight of zirconia and titania.
It is assumed to be 30wt%. If the amount of titania added is less than 10 wt%, it becomes difficult to give the zirconia ceramic a golden color, and uniform golden coloration cannot be obtained. Also, the amount added is 30
If it is more than wt%, a large amount of reducing carbon is required as described below, and as a result, the amount of residual carbon increases, the sintered density of the sintered body decreases, and mirror polishing of the sintered body becomes difficult. turn into.

This titania raw material is desirably one that easily causes reductive nitridation, and anatase is more preferable than rutile. In particular, a commercially available titania material having an average particle size of about 500 particles dispersed in a sol solution is suitably used.

The method of adding these additive materials to zirconia to make zirconia ceramics and reducing and nitriding titania is to mix the various ceramic raw materials, further add carbon as a reducing agent, mold, and then heat in a nitrogen gas atmosphere at 1300~
A method of firing at 1500° C. is desirable.

Next, a method for manufacturing golden zirconia ceramics according to the present invention will be explained.

In this method, first, raw material powders of zirconia, yttria (3 to 6 mo1% based on zirconia), and titania (10 to 30 wt% based on the total weight of zirconia and ittria) are uniformly mixed.

An example of a preparation method that is preferably used in mixing these raw material powders is to put each raw material powder together with water or an organic solvent such as ethanol in a ball mill, wet-pulverize it, and then add a molding binder. The slurry is dried using a spray dryer and granulated.

Next, powdered carbon is added to the obtained mixed powder in an amount of 10 to 25 wt% based on the amount of titania added, and mixed.

If the amount of carbon added to the titania is less than 10 wt%, the titania cannot be sufficiently reduced and nitrided, and the color of the sintered body becomes black and cannot be gold-colored. Further, if the amount of carbon added is 25% or more, the color tone becomes black due to residual carbon and reduction of zirconia, and it is impossible to change the color to gold.

Next, the carbon-added mixed material is formed into a desired shape such as a plate, disk, ring, block, or cylinder.

In the molding operation of this mixed material, a dry molding method is preferably used in which the mixed powder is placed in a mold of a desired shape and molded under a pressure of about 1 ton/am''.

Further, depending on the case, a CIP (cold isostatic pressing) treatment may be performed after this dry molding.

Next, the molded body subjected to the binder removal treatment is placed in a reduction sintering furnace, the inside of the furnace is filled with nitrogen gas, and sintering is performed at 1300 to 1500° C. for 1 to several hours while nitrogen gas is further introduced.

If the firing temperature is less than 1300° C., the production of titanium nitride through reductive nitridation of titania will be poor, and sintering will not be promoted, leading to a decrease in the strength of the sintered body. Moreover, if the firing temperature is 1500° C. or higher, the crystal system of zirconia becomes cubic, and the above-mentioned toughness is lost.

By this firing, a golden zirconia ceramic which is entirely colored gold and has excellent mechanical strength without cracks or cracks is obtained. The obtained sintered body has golden titanium nitride uniformly dispersed in zirconia ceramics, and can be mirror-polished and cut in the same way as ordinary zirconia ceramic materials, and can be cut as needed. Decorative materials such as exterior parts for watches or electronics by polishing and cutting.

Used as various parts such as mechanical parts.

Furthermore, since titanium nitride is uniformly present in the zirconia ceramic, this material has a much lower specific resistance than conventional ceramic materials, and therefore can be easily machined into any shape by electrical discharge machining or the like.

"Example" Golden zirconia ceramics were produced based on the production method according to the present invention.

Zirconia (3Y) powder 2.8Kg, Ittria powder 0
．． 2 Kg, titania powder (manufactured by 6 Hara Sangyo Co., Ltd., trade name: CS
Sol) 1. OK, g, 25 g of dispersant and 4.4 kg of pure water were placed in a ball mill with a capacity of 10 Q, and after pulverization and mixing for 40 hours, 400 g of binder was added and further stirred to make a slurry, and this slurry was dried with a spray dryer. , granulated.

An appropriate amount of the obtained granulated powder was taken out, 0.2 Kg of powdered carbon was added so that the amount was 20 wt% with respect to the amount of titania added, and after dry mixing in a mortar, the mixture was mixed with a dry press at a pressure of 1 ton/ton. cm” and the diameter is 20ma+.

It was molded into a disk shape with a thickness of 4 mm.

The obtained compact was placed in a reduction furnace, the inside of the furnace was evacuated, nitrogen gas was introduced to replace the gas, and the mixture was held at a nitrogen gas flow rate of 1 f2/min and a firing temperature of 1400°C for 5 hours.
Fired.

When the surface of the obtained golden zirconia ceramic was mirror-polished and the color tone of all chromaticities was observed, it was found that the polished surface had sufficient luster and the color tone was gold, which is preferable as a decorative item. When we cut this and examined the state of coloring inside, we found that it was uniformly colored all the way to the inside.

In addition, changes in the color tone of the sintered body were investigated by varying the amount of carbon added as a reducing agent. As a result, the color tone changes by changing the weight ratio of added carbon, and the weight of added carbon required to obtain a golden color is 10 to 25 w relative to the amount of titania added.
t%, more preferably 18 to 20 wt%. Judging from the X-ray diffraction pattern, if the carbon content is less than 10 wt% of titania, titania cannot be reduced sufficiently, and if the carbon content is 25% or more, carbon will remain. The color tone of the sintered body also turned black.

Note that the content of the present invention is not limited to the above-described embodiments, and various modifications can be made. For example, in each of the above examples, the granulated powder of the mixed powder was molded using a dry press machine, but instead of this dry press molding method, a doctor blade method, an extrusion molding method, an injection molding method, a casting molding method, etc. It is also possible to use

"Effects of the Invention" As explained above, according to the present invention, it is possible to obtain a ceramic material in which titanium nitride is uniformly present in the zirconia ceramic, which is golden in color as a whole, and has toughness.

Moreover, it can be manufactured under conditions of relatively low temperature and low pressure, and manufacturing costs can be reduced.

Furthermore, since titanium nitride is uniformly present in zirconia ceramics, the resistivity is significantly lower than that of conventional ceramic materials, making it easier to process into arbitrary shapes using electric discharge machining, etc. It will be done.

Claims (2)

[Claims] (1) Zirconium oxide contains 3 to 6 yttrium oxides
mol% is added, and titanium oxide is 10 to 30 wt% based on the total weight of zirconium oxide and yttrium oxide.
Gold-colored zirconia ceramics in which a portion of titanium oxide is reduced and nitrided. (2) Add 3 to 6 yttrium oxide to zirconium oxide
A material prepared by adding 10 to 30 wt % of titanium oxide to the total weight of zirconium oxide and yttrium oxide and 10 to 25 wt % of carbon to the weight of titanium oxide was heated in a nitrogen gas atmosphere at 1300 mol %. ~150
A method for producing golden zirconia ceramics, characterized by firing at 0°C.