JPH08687B2 - Ceramics composition containing ultrafine metal particles - Google Patents

Description

TECHNICAL FIELD The present invention relates to a composite ceramic in which ultrafine particles of a metal are uniformly dispersed.

2. Description of the Related Art Ceramics have advantages such as being hard and having a high melting point, but have the drawback of being brittle. As a method of solving this drawback, it is possible to mix a highly elastic metal.

Further, since ceramics composed of silica / alumina has a drawback that it is brittle and inferior in heat resistance, a silica removal material, that is, high-purity alumina is mainly used as a ceramic raw material.

However, inferior heat resistance means that it is easy to sinter, which is excellent in workability and economical.

For composites of metals and ceramic materials, 40% by weight or more of sand iron and ceramic materials other than sand iron such as nickel oxide are used as heat storage materials for household heating appliances and industrial heat exchangers. The body is described (Japanese Patent Laid-Open No. 52-
65504 publication). However, with this method, the metal (sand iron) is mixed with coarse particles, so the resulting ceramic becomes microscopically non-uniform, and this method improves brittleness and it is not possible to obtain a homogeneous and tough ceramic. .

Furthermore, in the dispersion system of the metal particles as described above, a large amount of expensive metal is required until the properties of the metal are sufficiently exhibited, which causes an increase in cost.

Zeolite, one of the silica / alumina materials,
It is used as a raw material for catalysts, catalyst carriers, molecular sieves, adsorbents, and detergent builders, and can be obtained at low cost. The exchange of sodium ions in zeolite with metal salts is performed in the production of catalysts. For example
53-96999 discloses that a zeolite is exchanged with a salt or complex metal such as rhodium, the metal is reduced, and carbonylation is performed to obtain a metal carbonyl cluster heterogeneous catalyst retained in the crystal structure of the zeolite. Is disclosed. However, this utilizes zeolite as a support for metal carbonyl, and metal carbonyl is supported on the surface of zeolite, which is essentially different from the present invention. The present invention modifies the characteristics of the silica / alumina-based ceramics themselves, and the ultrafine metal particles are evenly distributed throughout the ceramics.

OBJECT OF THE INVENTION The present invention provides a metal-ceramic composite material which is tough and has little variation in quality.

Composition of the invention A ceramic composition containing ultrafine metal particles of the present invention is a ceramic composition mainly composed of silica, alumina, and metal, and silica and alumina: 40 to 95 wt% metal: 5 to 60 wt%, The metal is dispersed as fine particles having a particle diameter of 0.5 μm or less.

 Hereinafter, the present invention will be described in more detail.

In the ceramic composition of the present invention, the total amount of silica and alumina is 40 to 95% by weight, preferably 60 to 83% by weight.
included. If this amount is less than 40% by weight, the original advantages of ceramics will not be exhibited, while if it exceeds 95% by weight, the brittleness will not be improved. The ratio of silica to alumina is 0.
1 to 100 is suitable, and 0.5 to 20 is preferable.

Examples of silica / alumina materials include A type, X type
Type, Y type, etc. zeolite or mullite.

The ceramic composition of the present invention contains 5 to 60% by weight of metal. If the amount of metal is less than 5% by weight, the brittleness is not improved, while if it exceeds 60% by weight, the ultrafine metal particles agglomerate and coarsen, and the ceramic becomes brittle.

It is necessary that the metal is uniformly dispersed in the ceramic composition as ultrafine particles of 0.5 μm or less, preferably 0.05 μm or less. If the metal particles exceed 0.5 μm, the ceramics can no longer be said to be homogeneous, and a dramatic improvement in brittleness cannot be expected.

Specific examples of the metal include Ia to VIIa and Ib to V of the periodic table.
Metals belonging to the groups Ib and VIII are mentioned.

The ceramic composition of the present invention can be obtained by, for example, adsorbing a metal as an ion at an atomic level to a ceramic powder having a pore structure and then reducing the metal. Prior to the reduction, simultaneously with the reduction or after the reduction, the powder is sintered to obtain a ceramic compact containing ultrafine metal particles.

The silica / alumina ceramics having a pore structure is not particularly limited, but zeolite can be preferably used.

 Zeolites are represented by the general formula (I) below.
Minosilicate (shown as the anhydride)
A combination of a luminium atom, an oxygen atom and a silicon atom
Made a three-dimensional skeleton and charged it negativelyCharge of Me such as sodium ion Neutralize with. m
The values of and n depend on the type of zeolite
There are Na, K, etc.

mMeO: Al ₂ O ₃ .nSiO ₂ (I) Although various zeolites are used, A-type, X-type and Y-type having high metal ion exchange ability are preferable. Further, a hydrosodalite type can also be suitably used depending on the metal to be replaced.

An aqueous solution containing metal ions is brought into contact with powdery zeolite, and Ne ions and K ions in the zeolite are replaced with metal ions in the aqueous solution.

When zeolite and metal salt aqueous solution are contacted, Na and K
Exchange of ions with metal ions occurs, and metal ions are incorporated into the pores of the structural unit of zeolite at the atomic level by chemisorption. In order to realize a sufficiently high exchange of metal ions, it is important that the metal ions are incorporated into all the pores that are the structural units of the zeolite,
The particle size of zeolite is preferably 5 μm or less, more preferably 0.5 μm or less.

It is also possible to replace the Na and K ions in the zeolite with two or more metal ions in the aqueous solution. Further, by contacting the zeolite in which the metal ions are substituted with ammonia water, Na and K remaining in the zeolite
Ions can also be replaced with ammonium groups. The ammonia group is split and released during the heat treatment in the subsequent step.

The metal ion-substituted zeolite in which Na (K) ions are replaced with metal ions is solid-liquid separated into a cake, and then,
It is washed with water to remove Na ions and metal ions remaining in the aqueous solution in the pores, and dried to obtain metal ion-substituted zeolite powder.

The metal ion-substituted zeolite powder thus obtained is reduced to obtain a metal-containing powder in which ultrafine metal particles are uniformly dispersed. A zeolite compact is obtained by sintering this powder. Further, the reduction may be performed simultaneously with the sintering or after the sintering. The flow sheet of this manufacturing method is as follows.

First, the former flow will be described. The metal ion-substituted zeolite powder is 200-2000 in the presence of hydrogen gas.
Reduction is carried out by heating at ℃, preferably 300 to 1500 ℃.
If the temperature is too low, the reduction reaction will not proceed, and if it is too high, it will dissolve. By this reduction step, the metal ions taken into the zeolite at the atomic level are reduced to metals, and a metal-containing powder is obtained.

Next, if necessary, an inorganic or organic binder is added to the metal-containing powder, and the metal-containing powder is molded into a desired shape by compression molding or the like and sintered to obtain a metal ultrafine particle-containing ceramic. Sintering is carried out by heating at 200 to 2000 ° C, preferably 700 to 1600 ° C. If the temperature is too low, a dense sintered body cannot be obtained and the obtained ceramic becomes brittle. Further, if the temperature is too high, it will melt and a uniform ceramic cannot be obtained. In the obtained ultrafine metal particle-containing ceramics, the metal is uniformly dispersed at the atomic level, the hardness of the ceramics is maintained, and the brittleness is improved.

Then, without taking out once as a metal-containing powder,
Immediately after that, the flow of forming into ceramics will be described. In this case, the metal ion substituted zeolite powder,
Molded, then reduced and sintered. The details of each step are as already described. The reduction and sintering steps may be clearly distinguished by first reducing in a hydrogen gas atmosphere and then sintering in an air atmosphere.Also, consistently reducing and firing in a hydrogen gas atmosphere. A binding treatment may be applied.

EFFECTS OF THE INVENTION According to the present invention, the brittleness of silica / alumina-based ceramics is improved by containing silica, alumina and a metal in a fixed amount and by uniformly dispersing the metal as ultrafine particles of 0.5 μm or less. be able to.

Hereinafter, the present invention will be described more specifically with reference to examples. The measuring method of each evaluation item used in the examples is as follows.

(1) Bending strength The bending strength was measured according to JIS R1601 "Fine ceramics bending strength test method". However, the test atmosphere was air and the temperature was room temperature.

(2) Particle size of metal particles An electron micrograph (10,000 to 1,000,000 times) is taken, and the metal particles are analyzed by an X-ray microanalyzer (XM
Confirmed in A) and averaged from the particle size of those particles.

Examples 1-2 After 239 g of silver nitrate (AgNO ₃ ) was dissolved in 2 of water, 100 g of X-type zeolite of SiO ₂ / Al ₂ O ₃ = 3 (anhydrous equivalent) was added to this aqueous solution with stirring to obtain Ag. Substituting is carried out over a period of time until the ratio becomes the composition shown in Table-1. After that, the dispersion liquid is separated into solid and liquid by suction and washed with sufficient water. After drying the obtained cake, under a hydrogen gas atmosphere at 400 ° C for 5
Reduced in time. The obtained powder was pressure-molded at 5 t / cm ² to prepare a test piece, which was sintered in an electric furnace at 1000 ° C. to obtain the ceramic of the present invention. The composition and properties of this ceramic are shown in Table 1 below.

Comparative Example 1 370 g of silver nitrate (AgNO ₃ ) was dissolved in 2 of water, and then 100 g of X-type zeolite with SiO ₂ / AlO ₃ = 3 (anhydrous equivalent) was added to this aqueous solution with stirring. After standing overnight with stirring, the product is reduced with formaldehyde. The dispersion is solid-liquid separated by suction and washed with sufficient water. Almost no silver ions were observed in the mother liquor after the reduction and in the wash liquor. After the obtained cake was dried, a test piece was prepared by pressure molding at 5 t / cm ² , and this was sintered in an electric furnace at 1000 ° C. to obtain ceramics. The composition and properties of this ceramic are shown in Table 1.

Comparative Example 2 After thoroughly washing the zeolite X used in Example 1 with water,
It is dried and then left in a hydrogen atmosphere at 600 ° C. for 8 hours. Then, a test piece was prepared by pressure molding at a pressure of 5 t / cm ² , and this was sintered at 1000 ° C. to obtain a ceramic. The properties of this ceramic are shown in Table 1.

Example 3 After dissolving 156.8 g of silver nitrate (Cu (NO ₃ ) ₂ ) in 2 of water, sodium-substituted Y-type zeolite (Si
Add 100 g of O ₂ / AlO ₃ = 6) in terms of anhydride and stir.
Cu substitution is carried out until the proportion of copper in the zeolite reaches 15%, and then aqueous ammonia is added to replace the remaining sodium ions with ammonium ions. The dispersion is solid-liquid separated by suction and washed with sufficient water. The obtained cake was dried in a dryer at 105 ° C. for 2 hours to obtain Cu-substituted zeolite powder. After placing this Cu-substituted zeolite in an autoclave and replacing the internal air with hydrogen gas, the hydrogen pressure was 5 kg /
It was raised to cm ² and reduced at 430 ° C. for 10 hours. After cooling the autoclave to room temperature, the powder was taken out, a test piece was pressure-molded at 5 t / cm ² , and this was sintered in an electric furnace at 1000 ° C. for 5 hours to obtain a ceramic. The composition and properties of the obtained ceramics are shown in Table 2 below.

Comparative Example 3 135 g of the zeolite (anhydrous 73.9%) used in Example 3 was taken and dispersed in 20% aqueous ammonia 2 while stirring,
Leave overnight. Next, solid-liquid separation is performed by suction, and after sufficient washing, the cake obtained is dried. Take 109.0g of this powder (anhydrous 73.4%), add 12.5g of silver powder (silver 100%) of 2μm to it, and mix evenly in a mixer, then 5t
A test piece was pressure-molded at / cm ² and fired at 1000 ° C. to obtain a ceramic. The composition and properties of this ceramic are shown in Table 2.

Example 4 227.0 g of silver nitrate (AgNO ₃ 100%) was dissolved in 2000 g of pure water,
Phosphate zeolite (Na ₂ O = 20.7%, Al ₂ O
_{3 = 34.0%, SiO 2 =} 33.7%, P 2 O 5 = 11.5%) and to 100g added well dispersed stirred at variance terms anhydride. After stirring well, solid-liquid separation was performed, sufficient water washing was performed, and then drying was performed to obtain a silver-substituted phosphate zeolite powder. The components in the anhydrous zeolite are Ag ₂ O = 49.4%, Al ₂ O ₃ = 21.7%, SiO ₂ = 21.
5% and P ₂ O ₅ = 7.4%.

The obtained powder was reduced in a hydrogen gas atmosphere at 300 ° C. for 8 hours. After the reduction, a test piece was formed by pressure molding at 5 t / cm ² , and this was sintered in an electric furnace at 1000 ° C to obtain a ceramic. The composition and properties of this ceramic are shown in Table-3.

Comparative Example 4 Phosphate used in Example 4 Zeolite was thoroughly washed with water, dried and then left in a hydrogen atmosphere at 300 ° C. for 8 hours. Then, a test piece was prepared by pressure molding at a pressure of 5 t / cm ² , and this was sintered at 1000 ° C. to obtain a ceramic. The composition and properties of this ceramic are listed below.
3 is shown.

Claims (1)

[Claims] 1. Ceramics mainly composed of silica, alumina and metal, wherein silica and alumina: 40 to 95% by weight, metal: 5 to 60% by weight, and the metal is dispersed as fine particles having a particle size of 0.5 μm or less. A ceramics composition containing ultrafine metal particles.