KR20140044963A - Alumina-based sintered body and the preparation method thereof - Google Patents

Abstract

Provided is an alumina-based sintered body and a manufacturing method thereof, wherein the tissue of the sintered body is uniform and processability is improved, thereby the original color of the sintered body is maintained. The alumina-based sintered body is formed in a crystal lattice and a particle phase and includes 0.08-0.30 wt% of titanium or titanium compounds, inclusively, in terms of titanium oxide. Since titanium or titanium compounds exist in a crystal lattice, grain growth is promoted. Therefore, the tissue of the sintered body becomes uniform and processability is improved. Moreover, the generation of aluminum titanate and oxygen deficiency in titanium oxide is hard to occur.

Description

Alumina sintered compact and its manufacturing method {ALUMINA-BASED SINTERED BODY AND THE PREPARATION METHOD THEREOF}

FIELD OF THE INVENTION The present invention relates to the field of fine ceramics, in particular to alumina sintered bodies and methods for producing the same.

Fine ceramics have various characteristics and are used in various fields such as information communication, precision machinery, and medical care. Among them, alumina sintered bodies are typical. Aluminum oxide is often used as a structural member because it is relatively inexpensive, has high versatility, and has excellent mechanical strength, heat resistance, corrosion resistance, and the like. However, the alumina sintered body has a hard workability, a lot of processing is required when producing a large or complex structural member, the ratio of the processing cost in the manufacturing cost can be easily increased. Therefore, if workability can be improved, a significant reduction in manufacturing cost can be expected.

Some products made of titanium oxide and aluminum oxide utilize such characteristics as electrostatic chucks. For example, an electrostatic chuck base obtained by adding aluminum oxide as a main component and adding titanium oxide and calcining in a reducing atmosphere has been proposed (see Japanese Patent Application Laid-Open No. 06-97675).

Some materials have a characteristic structure in order to improve strength and fracture toughness. An alumina sintered compact in which isotropic aluminum oxide crystal particles having a diameter of 3 µm or less, an aspect ratio of 1.5 or less, and an anisotropic aluminum oxide crystal particle having a diameter of 10 µm or more, and an aspect ratio of 3 or more is mixed (a prior art is proposed). Document 2: See Japanese Patent Application Laid-Open No. 09-87008.

Some have pursued ease of workability. An aluminum-based composite material containing aluminum borate has been proposed, and an easy-processing composite material produced by pouring a molten aluminum alloy into an aluminum borate compact is cast (see Japanese Patent Application Laid-Open No. 2004-353049).

Japanese Patent Publication No. 06-97675 Japanese Patent Application Laid-Open No. 09-87008 Japanese Patent Laid-Open No. 2004-353049

However, the electrostatic chuck base described in the prior art document 1 has a titanium oxide added amount of 0.5 to 2. In consideration of the fact that it is 0wt% and that it is calcined in a reducing atmosphere, aluminum titanate is produced and oxygen in titanium oxide is depleted. Therefore, aluminum titanate may be formed to form fine particles, resulting in deterioration of workability due to non-uniformity of particles, or deteriorating the original milky appearance of aluminum oxide.

Since the alumina sintered compact of prior art document 2 mixes isotropic aluminum oxide crystal grain and anisotropic aluminum oxide crystal grain, there exists a possibility that a sintered compact structure may become nonuniform and it will become difficult to process. Since the easily processable composite material of the prior art document 3 is manufactured by casting, it takes time.

This invention is made | formed with reference to such a situation, and an object of this invention is to provide the alumina sintered compact which is uniform in structure, and excellent in workability, and its manufacturing method.

(1) In order to achieve the above object, the alumina sintered compact of the present invention is an alumina sintered compact composed of crystal grains and grain boundary phases, in which titanium or titanium compound is 0.08 wt% or more and 0.30 wt% or less in terms of titanium oxide. It is characterized by employing.

As described above, in the alumina sintered compact of the present invention, since titanium or a titanium compound is dissolved in the crystal lattice and particle size growth is promoted, the sintered compact structure becomes uniform and workability is improved. In addition, generation of aluminum titanate and oxygen deficiency of titanium oxide are unlikely to occur.

(2) The alumina sintered compact of the present invention is characterized in that the average major axis length of the crystal grains is 20 µm or more. By having such a particle shape, processing resistance can be made small.

(3) The method for producing an alumina sintered compact of the present invention is a method for producing an alumina sintered compact in which titanium oxide is dissolved in crystal grains, wherein the aluminum oxide powder and the titanium oxide powder are in a mass ratio of 99.95: 0.050 to 99.5: 0.50. And a firing step of raising the temperature of the molded product obtained by molding the mixed powder and forming the mixed powder at a temperature increase rate of 80 ° C / hr or less from the room temperature to the firing temperature and firing the same.

Since the temperature is raised from the room temperature to the firing temperature at a heating rate of 80 ° C./hr or less, the titanium or titanium compound is dissolved in aluminum oxide to promote particle size growth. Thereby, an alumina sintered compact with a uniform sintered compact structure and favorable workability can be manufactured. In addition, since it is fired in an atmospheric atmosphere, it is possible to prevent the production of aluminum titanate and the oxygen deficiency of titanium oxide.

According to the present invention, since titanium or a titanium compound enters the crystal lattice and particle size growth is promoted, the sintered compact structure is uniform and workability is good. In addition, generation of aluminum titanate and oxygen deficiency of titanium oxide are unlikely to occur.

(Configuration of Alumina Sintered Body)

The alumina sintered compact of this invention is comprised from the crystal grain of aluminum oxide, and a grain boundary phase. Titanium or a titanium compound is dissolved in the crystal grains in the amount of 0.008 wt% or more and 0.30 wt% or less in terms of titanium oxide. Titanium or a titanium compound is dissolved in the crystal lattice, so that grain growth is promoted, so that the sintered structure becomes uniform and workability is improved. In addition, generation of aluminum titanate and oxygen deficiency of titanium oxide do not occur, and the original color of the alumina sintered compact is maintained.

It is preferable that the average major axis length of an alumina sintered compact is 10 micrometers or more. Thus, since the particle size grows sufficiently, workability is high. However, when the grain growth becomes excessive, pores are likely to occur and the density may be impaired. Therefore, the average major axis length is preferably 50 µm or less.

Moreover, it is preferable that the average major axis length of aluminum oxide crystal grain is 20 micrometers or more. By having such a particle shape, processing resistance can be made small.

(Method for producing alumina sintered body)

Next, the manufacturing method of an alumina sintered compact is demonstrated. First, an aluminum oxide powder obtained by mixing a high purity aluminum oxide powder and a high purity titanium oxide powder in a mass ratio of 99.95: 0.050 to 99.5: 0.50 is preferably 99% or more, more preferably 99.9% or more. It is preferable. Moreover, it is preferable that the particle diameter of the aluminum oxide powder to be used is 1.0 micrometer or less. Moreover, it is more preferable if it is 0.1 micrometer or more and 0.5 micrometer or less.

The purity of the titanium oxide powder to be added is preferably 99% or more, and more preferably 99.9% or more. Moreover, it is preferable that the particle diameter of a titanium oxide powder is 0.5 micrometer or less. It is more preferable if it is 0.03 micrometer or less. Moreover, although it is preferable to add a titanium oxide powder, it is not limited to this, You may add in various forms, such as a chloride and an organic titanium compound which produce | generate an oxide after sintering in air | atmosphere. By using titanium oxide powder, the alumina sintered compact excellent in workability can be obtained.

The slurry of aluminum oxide powder and titanium oxide powder can be mixed using a ball mill. For example, it mixes and slurries using the resin pot which put the alumina ball. Add a suitable dispersant or binder and mix to make a raw powder.

The obtained raw material powder is dried and molded. For example, it forms by uniaxial press molding by a metal mold, and CIP. The raw material powder may be molded by any of a variety of methods such as uniaxial press molding, CIP molding, wet molding, press casting and injection molding. Among them, pressurized casting or discharge injection molding is preferable. It is preferable that the slurry used in that case be prepared by fully mixing. For example, the mixing time is 18 hours or more. By mixing sufficiently, a slurry with a uniform dispersion can be obtained.

The obtained molded object is heated at a temperature increase rate of 80 ° C / hr or less from room temperature to a firing temperature, and is fired at 1500 ° C or more and 1700 ° C or less. The firing temperature is set to a temperature at which the average major axis length of the alumina sintered compact becomes 20 µm or more and sufficiently densified.

It is preferable to perform baking at normal pressure in various atmospheres, such as air | atmosphere, a vacuum, or an inert gas. Among them, atmospheric pressure at atmospheric pressure is most suitable. When firing in a reducing atmosphere containing a substance having a reducing ability such as carbon or CO, the blue spots of the sintered body may become remarkable, but this can be prevented.

The temperature increase rate from room temperature to the firing temperature is preferably 80 ° C / hr or less. It is more preferable if it is 50 degrees C / hr or less. By reducing the temperature increase rate, titanium or a titanium compound is easily dissolved in aluminum oxide, and the grain size is made uniform. When the temperature increase rate is higher than 80 ° C / hr, it is difficult to dissolve the solid solution, staining occurs in the obtained material, and cracks and cracks are likely to occur during firing.

(Experiment result)

The experimental results are shown below. Table 1 has shown the manufacturing conditions and evaluation of Samples 1-18.

Mixed powder ratio
(Mass ratio) Titanium or Titanium Compound
Aluminum oxide particle size (average major axis length)
Grain Residue Titanium or Titanium Compound
Firing temperature
Temperature rise
density
Open porosity
Oxidation
aluminum Titanium oxide wt% ㎛ ppm ℃ ℃ / hr 10 × kg / ㎥ % Sample 1 99.90 0.10 0.085 22 15 1600 25 3.92 0.00 Sample 2 99.85 0.15 0.11 30 40 1600 25 3.91 0.00 Sample 3 99.80 0.20 0.14 40 60 1600 25 3.90 0.00 Sample 4 99.80 0.20 0.10 30 100 1500 25 3.92 0.10 Sample 5 99.90 0.10 0.08 25 20 1700 10 3.92 0.00 Sample 6 99.85 0.15 0.12 27 30 1700 30 3.90 0.03 Sample 7 99.90 0.10 0.085 20 15 1600 50 3.93 0.06 Sample 8 99.80 0.20 0.133 28.2 67 1600 50 3.91 0.04 Sample 9 99.60 0.40 0.20 25.5 200 1600 50 3.91 0.05 Sample 10 99.50 0.50 0.25 24.3 250 1600 80 3.90 0.06 Sample 11 99.90 0.10 0.015 2 85 1400 25 3.67 6.34 Sample 12 99.85 0.15 0.01 2.8 140 1400 25 3.80 0.30 Sample 13 99.80 0.20 0.015 3.7 185 1400 25 3.91 0.10 Sample 14 99.50 0.50 0.045 5 455 1400 25 3.91 0.15 Sample 15 99.40 0.60 0.20 18 400 1600 100 3.87 0.05 Sample 16 99.00 1.00 0.16 15 840 1700 95 3.86 0.03 Sample 17 99.30 0.70 0.17 14 530 1500 100 3.89 0.03 Sample 18 99.30 0.70 0.145 12 555 1600 85 3.88 0.06

(Samples 1-10)

An aluminum oxide powder having an average particle diameter of 0.5 µm, a purity of 99.5%, a titanium oxide powder having an average particle diameter of 0.02 µm, and a purity of 99.9% was used as a mixed powder in the mixing ratio shown in Table 1. Mixing of each powder was performed by mixing for 18 hours using the resin pot which put the alumina ball of phi 10 of arbitrary quantity, and slurrying. After drying, the slurry was molded by uniaxial press molding with a mold and CIP, and the molded body was fired.

Titanium oxide was mixed into the aluminum oxide powder so as to fall within a mass ratio of from 99.95: 0.050 to 99.5: 0.50, and the molded body of the mixed powder was heated to 1500 to 1700 ° C at a heating rate of 10 to 80 ° C / hr and held for 3 hours. Then, the sintered compact was obtained by naturally cooling. The preparation conditions and the result of the obtained sintered compact were shown in Table 1 as Samples 1-10. The average major axis length of the aluminum oxide particle diameter was 20 micrometers or more, and all were excellent in workability.

(Samples 11-18)

Titanium oxide is mixed with aluminum oxide powder in a mass ratio of 99.90: 0.1 to 99.0: 1.0, heated to a temperature of 25 to 100 ° C / hr to 1400 to 1700 ° C, held for 3 hours, and then cooled naturally. A sintered compact was obtained. The preparation conditions and the result of the obtained sintered compact were shown in Table 1 as Samples 11-18. Compared with Samples 1-10, the sintered compact showed blue unevenness in the sample containing much titanium oxide. In particular, in the sample having a low firing temperature, the average major axis length of the aluminum oxide particle diameter was 4 µm or less, and workability was deteriorated.

(Assessment Methods)

The liver evaluation method is explained about the said Example and a comparative example. First, about the obtained alumina sintered compact, the sintered compact density, the titanium oxide conversion high capacity, and average particle diameter of a titanium or a titanium compound were measured. The sintered compact density was measured by the Archimedes method. Titanium or a titanium compound was converted to titanium oxide in terms of high capacity and quantitatively measured by an inductively coupled plasma luminescence spectroscopy method using an inductively coupled plasma luminescence spectrometer (type SPS-3500, manufactured by SII Nanotechnology).

The total amount of titanium contained in the alumina sintered compact was obtained by dissolving a sample in sulfuric acid in a pressurized container and performing a quantitative analysis of titanium contained in the solution. The total titanium amount contained in the alumina sintered compact is the sum total of the titanium solid solution contained in the aluminum oxide crystal grains and the titanium present in the grain boundary without solid solution.

The amount of titanium contained in the grain boundary in the alumina sintered compact was separately obtained by heating the sample under hydrofluoric acid and aqua regia for 30 minutes under normal pressure, filtering insolubles, and performing quantitative analysis of titanium contained in the filtrate. Then, the amount of titanium to be dissolved in the aluminum oxide crystal grains was obtained by subtracting the amount of titanium contained in the grain boundaries from the total amount of titanium, and the oxide conversion was compared. The average particle diameter mirror-polished the surface of the sintered compact, and the SEM observed the polished surface which precipitated the grain boundary by thermal etching. The squares were approximated to each particle, the length was measured using the long side as the long axis, and the average value was obtained. In addition, the average value was calculated | required by the number of samples.

Claims (3)

An alumina sintered body composed of crystal grains and grain boundaries,
Alumina-like sintered compact characterized in that a titanium or titanium compound is dissolved in a crystal grain in terms of titanium oxide in an amount of 0.08 wt% or more and 0.30 wt% or less. The alumina sintered compact according to claim 1, wherein the average major axis length of the crystal grains is 20 µm or more. As a method for producing an alumina sintered compact in which titanium oxide is dissolved in crystal grains,
Mixing an aluminum oxide powder and a titanium oxide powder in a mass ratio of from 99.95: 0.050 to 99.5: 0.50;
And a firing step of heating the resulting molded article after molding the mixed powder at room temperature to a firing temperature at a heating rate of 80 ° C / hr or less, and firing the resulting alumina sintered compact.