JPS60246254A - Manufacture of composite ceramic powder - 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 The present invention relates to a method for producing a bonded ceramic powder comprising a composite of several types of ceramic particles.

Ceramic sintered bodies, which are made by sintering a single type of ceramic powder at high temperatures, are high-performance materials, so various studies have been conducted, and various advantages have been revealed, such as high strength and high hardness. On the other hand, it has drawbacks such as requiring high temperatures for sintering, low toughness, and difficulty in processing and forming, and it is necessary to improve these.

Furthermore, it is a well-known improvement method to improve various physical properties by mixing one type of ceramic powder with another type of ceramic powder to form a composite ceramic. For example, fiber-reinforced ceramics made by mixing SIC whiskers with Si3N powder and sintering have improved electrical discharge machinability, and partially stabilized zirconia made by mixing zirconia with Inno 1 Rear has improved strong deformation compared to those without the mixture. .

The present inventors have discovered that multiple types of ceramic particles are uniformly distributed by +1
As a result of intensive research in order to obtain a composite ceramic powder with a + value, it was discovered that a composite ceramic powder with uniformly dispersed particles could be obtained by mixing the powder with other types of ceramic powder during powder synthesis. I was able to complete it.

That is, the present invention provides a composite ceramic powder characterized by mixing an aqueous dispersion in which ceramic particles and/or iskers are dispersed with a metal alkoxide, hydrolyzing the metal alkoxide, and further oxidizing it to a metal oxide. It provides a manufacturing method.

In the present invention, first, an aqueous dispersion in which ceramic powder and/or whiskers are dispersed and a metal alkoxyl
and hydrolyze the metal alkoxide. At this time, the metal hydroxide, which is a hydrolysis product, precipitates with the dispersed ceramic particles as nuclei, so even after the metal hydroxide is heated and dehydrated to form an oxide, the ceramic particles and the metal oxide are separated. This is predicted to be due to the existence of a physical bond between them.

That is, in the present invention, different types of ceramic particles are uniformly mixed and physical bonding exists between the different types of ceramic particles, resulting in a powder with good dispersibility.

The composite ceramic powder produced by the method of the present invention is
Even if the powder is handled in various ways during the manufacturing process of the ceramic sintered body, such as wet kneading and air transport, the powder remains uniform, so workability is good. Furthermore, the composite ceramic sintered body obtained from the powder of the present invention is characterized by no decrease in bending strength and significantly improved fracture toughness.

Hereinafter, the configuration of the present invention will be explained in more detail.

At least -f1 of the plurality or single types of ceramics/7xes constituting the composite ceramic powder obtained in the present invention is an oxidized type such as alumina, aluminosilicate, mullite, zirconia, titania, indium oxide, niobium oxide, boron oxide, etc. Ceramics and any mixture thereof.

Examples of the metal alkoxide of the present invention include aluminum isopropoxide, aluminum tetraethoxide, aluminum butoxide, I. Ethoxide, tetramethyl titanate, tetraisopropyl zirconate, zirconium tetrabutoxide, etc. can be used, but it is preferable to use aluminum isopropoxide or ethyl silicate, which are inexpensive and easily available.

Ceramic particles and/or whiskers to be dispersed in the aqueous dispersion include alumina, zirconia, titania,
Oxide ceramics such as hafnia, ittria, magnesia, lead oxide, lanthanum oxide, tin oxide, boron oxide, germanium oxide, tantalum oxide, silicon nitride,
Non-oxide ceramics such as silicon carbide and titanium carbide and any mixture thereof can be used, but zirconia or magnesia is preferably used.

When dispersing ceramic powder in an aqueous dispersion,
Dispersion can also be achieved by stirring, but it is preferable to use a small amount of dispersant. As a dispersant, a well-known surfactant or a salt of an organic acid can be used, but N
When it is necessary to avoid contamination with impurities such as a5K, Ca, S, etc., it is preferable to use an ammonium salt of a versatile organic acid, such as ammonium oxalate.

In the production method of the present invention, a small amount of ammonia water to promote hydrolysis, ceramic powder, a dispersant if necessary, and a water-soluble Add an organic solvent and stir thoroughly to obtain an ammonia aqueous solution in which ceramic particles are uniformly dispersed. The concentration at this time is preferably 5 to 50% by weight.

Then, the metal alkoxide is thermally decomposed into a water-soluble organic solvent such as ethanol, methanol, isopropanol, toluene, etc., and then cooled to room temperature to form a uniform alkoxide solution.

Preferably, the metal alkoxide solution has a solid content of 5 to 50% by weight.

The method of adding the alkoxide solution to the ammonia aqueous solution is not particularly limited, but it may be added gradually while stirring,
It is better to slowly hydrolyze the metal alkoxide.
At this time, a gel-like hydrolyzed product is precipitated using the ceramic particles dispersed in the aqueous solution as cores. After the reaction is completed, the gel-like material is washed twice, dried at 100 to 200°C, and then calcined at a high temperature, preferably 700 to 1500°C, to obtain a composite ceramic powder.

The composite ceramic powder obtained by the method described above has different particles mixed extremely uniformly, so the composite ceramic sintered body using the powder has improved physical properties such as bending strength and fracture toughness. . Therefore, the ceramics are extremely useful for use in mechanical parts such as engine parts, valve bodies, aggregates, bearings, gears, bolts, NANDs, cranks, and stirring blades.

The present invention will be specifically described below using Examples.

5- In the following examples, the test method for bending strength is JIS R
+601 Note that "part" in the text is based on weight.

Example 1 1 mole of aluminum isopropoxide was added to 5 moles of isopropanol while avoiding contact with moisture, and 80%
The mixture was heated and stirred at ℃ to completely melt it, and after dissolving, it was allowed to cool to room temperature to obtain a metal alkoxide solution. 51 flask, 500 g of ion-exchanged water, 5 mol of isopropanol, monoclinic zirconia powder (manufactured by Daiichi Kielement ■, RP) 14
g. Add 0.2 g of ammonium oxalate as a dispersant and 20 ml of ammonia water with an ammonia concentration of 28%, stir vigorously to uniformly disperse the zirconia powder, and then gradually add the alkoxide solution. At this time, the aluminum alkoxide becomes gel-like aluminum hydroxide due to hydrolysis, and the viscosity of the solution increases, so the solution is aged for 2 hours while being further vigorously stirred. After that, the product was filtered, thoroughly washed with isopropyl alcohol, and then
Heat to 0°C and dry. Next, the powder is heated to 1150°C to obtain a mixed powder of α-alumina and zirconia.

This powder is dry-pressed at It/- and sintered at 1600°C to produce zirconia-reinforced alumina. The critical stress intensity factor (Klc) and bending strength of this sintered body were measured.

The results are shown in Table-1.

Comparative Example 1 High purity alumina powder (manufactured by Sumitomo Chemical ■, AKP-30) 0
．． 5 mol, add 14 g of monoclinic zirconia powder with a surface area of 20 r//g, and add 400 g of alumina balls with an average surface of 41 cs to a ball mill with an inner diameter of +3C11 and a length of 13 as.
, charged with 200g of isopropanol, and the number of revolutions was 60.
After mixing for 96 hours at r, p, +n, it is dried at 90°C. After molding and sintering this powder in the same manner as in Example 1, the K/C and bending strength are measured. The results are shown in Table-1.

Comparative Example 2 The same alumina powder as in Comparative Example 1 was molded in the same manner as in Example 1.
Sintered. Table 1 shows the strength and bending strength of the sintered body.

The physical properties of the sintered body of Example 1, both Klc and bending strength, are significantly improved compared to Comparative Example 1.2.

Example 2 Instead of aluminum isopropoxide in Example 1, a mixture of 0.5 mol of ethyl silicate and 3 mol of aluminum isopropoxide was dissolved in the same manner as in Example 1, and 17 g of zirconia powder was dispersed. Examples I and 7--Dropped into the same ammonia aqueous solution to perform a hydrolysis reaction.

Thereafter, 1.5 L of the powder produced in the same manner as in Example 1 was added.
The critical stress intensity factor (Ic) and bending strength are measured for a zero-strand sintered body that is pressure-formed at Ic and d and sintered at 1700°C to produce zirconia-reinforced mullite. Display the results -
Shown in 2.

Comparative Example 3 To 0.5 mol of high-purity mullite produced in the same manner as in Example 2 without adding zirconia powder, 17
After mixing in the same manner as in Comparative Example 1, the resulting powder is molded and sintered in the same manner as in Example 2. K of sintered body
rc and bending strength are shown in Table-2.

Comparative Example 4 The same high-purity mullite as in Comparative Example 3 was molded and sintered under the same conditions as in Example 2. Table 2 shows the KJC and bending strength of the sintered body.
Shown below.

Example 3 The powders of Example 1 and Comparative Example 1 were passed through an 80-mesh sieve and subjected to high-speed elemental characterization using an X-ray microanalyzer. Table 3 shows the average and standard deviation of counter values for zirconium and aluminum elements. From Table 3, the powder of Example 1 has a small standard deviation, and the zirconia particles are clearly uniformly dispersed.

Table-1 Table-2 Table-3 (Electrical IF 15KV, sample current 10mA, average of 10 points) Agent: Katsutoshi Takahashi, patent attorney

Claims (1)

[Claims] 1. A composite ceramic characterized by mixing an aqueous dispersion in which ceramic particles and/or whiskers are dispersed with a metal alkoxide, hydrolyzing the metal alkoxide, and further oxidizing it to a metal oxide. Powder manufacturing method. 2. A method for producing a composite ceramic powder according to claim 1, in which zirconia particles are used as the ceramic particles.