JPH07268646A - Production of three-dimensional network structure - Google Patents

Abstract

PURPOSE:To produce a three-dimensional network structure of a metal, ceramics, etc., in an arbitrary shape and with a high yield. CONSTITUTION:Adhesion is imparted to the surface of polyurethane foam by dipping the foam in an acrylic adhesive soln. and the foam is buried in carbonyl nickel powder and swung to stick the powder to the foam. The foam is then dipped in 1mol/l aq. nickel nitrate soln., dried and heated in the air. The foam as a substrate is decomposed and removed by burning and the remaining powder is sintered in a reducing atmosphere to obtain the objective block-shaped three- dimensional network structure of nickel having a shape transferred from that of the polyurethane foam. The dimensions of this structure is 80X80X50mm and the porosity is about 95%. The three-dimensional network structure having a cubic shape and high porosity is easily obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a three-dimensional network structure made of metal, ceramics or the like used for filters, catalyst carriers, battery current collectors and the like.

[0002]

2. Description of the Related Art A powder sintering method is known as a method for manufacturing a three-dimensional network structure. In this method, an adhesive is applied to a synthetic resin foam having a three-dimensional network structure such as urethane foam, which is a base material, to give adhesiveness to the surface of the resin foam, and then powder is adhered and fired. Thus, the base is removed and the powder is sintered to obtain a three-dimensional network structure in which the shape of the base is transferred. Since this powder sintering method uses the sintering of powder, it is possible to manufacture a three-dimensional network structure without limitation of materials such as metal and ceramics by appropriately selecting powder. Since the deposition of the powder occurs selectively on the part to which the adhesive is applied, a three-dimensional network structure having good breathability can be obtained without forming a part that blocks the network of the substrate. Further, since the powder is deposited only on the surface of the pressure-sensitive adhesive, it is possible to uniformly deposit a fixed amount of the powder on the substrate, and a three-dimensional network structure having high strength can be obtained. Furthermore, since powder sintering is used, the surface of the three-dimensional network structure skeleton has fine irregularities, and the specific surface area can be increased, so that it is suitable for catalyst carriers, battery current collectors, etc. To be

[0003]

However, since the powder sintering method includes a temperature region in which the strength is temporarily reduced during the heat treatment process, cracking and buckling are likely to occur during this process, resulting in a decrease in product yield. However, there is a drawback that the shape that can be manufactured is limited. This is because the decomposition temperature of the resin base is generally lower than the sintering temperature of the powder, so the resin base is decomposed and burned in the heat treatment process, and the sintering of the powder is not progressing, that is, the cohesive force of the powder. This is because there is a temperature region having a low strength that maintains the shape. For this reason, a three-dimensional shape such as a block shape cannot be maintained because the shape thereof cannot be maintained because it is buckled by its own weight due to insufficient strength. Further, the sheet-like material is apt to be cracked, and it is difficult to manufacture a large-sized material.

The present invention has been made in view of the above problems, and does not depend on the material, has a good air permeability, and has a high strength, a three-dimensional mesh structure made of metal or ceramics having an arbitrary shape and yield. It provides a method of manufacturing well.

[0005]

The present invention provides a substrate for a three-dimensional network structure by applying adhesion to the skeleton surface of the three-dimensional network structure as a substrate, applying powder, and then heat treating the powder. A method for producing a three-dimensional network structure, which comprises removing and subsequently performing heat treatment in a reducing, inert, or oxidizing atmosphere to sinter the powder, the method comprising: The method for producing a three-dimensional network structure is characterized in that the powder thus obtained is wetted with a solution containing a metal salt. That is, according to the present invention, a powder is deposited on the skeleton surface of a three-dimensional network structure as a substrate, which is then wetted with a solution containing a metal salt, and then a heat treatment is carried out to produce a three-dimensional network structure. Is the way.

The three-dimensional network structure serving as a substrate is a foaming resin having an open cell structure such as urethane foam, or a non-woven fabric or a woven fabric, and the shape is appropriately selected according to the purpose of use. Facilitates the deposition of powder on the surface of the base skeleton,
It is preferable to impart tackiness for the purpose of preventing peeling. The tackiness is imparted by applying an acrylic or rubber adhesive solution or an adhesive resin solution such as a phenol resin, an epoxy resin, or a furan resin. Further, it is possible to give tackiness to the substrate itself by plasma treatment or the like.

After imparting tackiness to the skeleton surface of the substrate, the powder is adhered to the skeleton surface by a method such as rocking the substrate in the powder or spraying the powder onto the substrate.
This allows the dry powder to be applied directly to the surface of the substrate. Also, powder deposition occurs on the substrate surface,
Since it does not depend on the thickness of the adhesive layer, the deposition amount of the powder is uniform over the entire substrate, and when a constant weight of powder is deposited, a three-dimensional network structure having high strength can be obtained. Furthermore, since the powder selectively adheres only to the portion to which tackiness is given and does not form the closed portion, it is possible to obtain a mesh structure having good air permeability. The powder material is metal, ceramics,
It is applicable without limitation of materials such as carbon, or may be a mixture thereof. The particle size of the powder may be in the range that can be adhered to the surface of the substrate, 0.01 micron to 100
It is desirable to be in the micron range. Further, the shape of the powder is not particularly limited.

After depositing the powder, the substrate is wetted with a liquid containing a metal salt and then dried. By carrying out this treatment, the strength after decomposition and burning of the resin base during the heat treatment step and before powder sintering is improved and buckling or cracking does not occur, so that the shape of the resin base can be maintained. Any metal salt may be used as long as it dissolves in a liquid, but a metal salt that forms an oxide near the temperature at which the resin substrate is decomposed and removed is preferable because it has a large effect of improving strength. For this reason, a general resin substrate is decomposed 500
Organic salts such as nitrates or acetates and formates which form oxides at a temperature of not higher than 0 ° C. are preferable. The type of metal salt may contain the same metal ion as that of the powder, or may contain different metal ions. When different kinds of metal ions are contained, a three-dimensional network structure composed of alloy or composite compound can be easily obtained.

The method for wetting the powder is carried out by immersing the substrate in a liquid containing a metal salt, spraying the liquid containing a metal salt onto the substrate, and the like. Any type of liquid may be used as long as it does not reduce the adhesive force between the substrate and the powder, but water is the most practical. The concentration of the metal salt solution is preferably 0.01 mol / l or more in order to obtain the effect. The upper limit of the concentration may be saturation. 0.
1-2 mol / l is particularly preferred. The amount of the metal salt added to the powder can be adjusted by the concentration of the metal salt solution and the number of times of immersion or spraying.

After depositing the powder on the substrate, heat treatment is performed. The heat treatment is intended to remove the substrate and sinter the powder. As the heat treatment conditions, the treatment temperature, time and atmosphere are appropriately selected depending on the substrate used and the properties of the powder. When using foamed resin for the base and metal for the powder,
It is preferable to change the atmosphere by burning the base material in an oxidizing atmosphere and by sintering the metal powder in a reducing atmosphere. When oxide ceramics or platinum powder is used for the powder, there is no problem of oxidation, so an oxidizing atmosphere Can be heat treated. Further, a three-dimensional network structure having an arbitrary skeleton thickness can be obtained by repeating the step of imparting tackiness, the step of applying powder and the step of wetting with a metal salt solution.

[0011]

By applying a treatment of wetting the substrate with a liquid containing a metal salt after the powder is adhered and then drying it, the strength after decomposition and burning of the resin substrate during the heat treatment process and before powder sintering is improved, and buckling and buckling Since no cracking occurs, the shape of the resin substrate can be maintained. By wetting the powder deposited on the surface of the substrate with a liquid containing a metal salt, the surface tension of the liquid causes the powder to agglomerate during the drying process, and the metal salt attached to the powder surface forms a binder between the powders. As a result, the strength of the base body, which has the smallest strength during the manufacturing process, is decomposed and burned and before the powder is sintered, and the force for maintaining the shape is increased. Therefore, it becomes possible to sinter without causing buckling in a base body having a thickness in the height direction such as a block shape, and to suppress the occurrence of cracks in a sheet base body. Become.

[0012]

【Example】

Example 1 As a substrate having a three-dimensional network structure, 100 × 100 × 7
0 mm polyurethane foam was used. The polyurethane foam was dipped in an acrylic pressure sensitive adhesive solution having a resin content of 5% using methyl ethyl ketone as a solvent, and then the excess solution was removed to impart tackiness to the surface of the substrate skeleton. After drying at 100 ° C. for 10 minutes to remove the solvent, the substrate was inserted into carbonyl nickel powder having an average particle size of 3 μm and rocked to deposit nickel powder. Then, it was immersed in a nickel nitrate aqueous solution having a concentration of 1 mol / l and dried at 100 ° C. for 30 minutes. 5 with 100 x 100 mm as the bottom
The substrate was kept at 00 ° C. for 10 minutes in the atmosphere to decompose and remove the polyurethane foam as the substrate. The base is 95 x 95 x 65 mm
Contracted to. Then, it was kept at 1200 ° C. for 20 minutes in a reducing atmosphere in which hydrogen gas was passed. As a result, a nickel block-shaped three-dimensional network structure having a shape in which the nickel powder was sintered and the polyurethane foam was transferred was obtained. The size of the obtained three-dimensional network structure was 80 × 80 × 50 mm and the porosity was 95%.

Comparative Example A Ni three-dimensional network structure was obtained in the same manner as in Example 1 except that the carbonyl Ni powder was applied and then immersed in a pure aqueous solution instead of the nickel nitrate aqueous solution. The size of the obtained three-dimensional network structure was 80 × 80 × 10 mm and the porosity was 75%. This is 95 × after disassembling and removing the polyurethane foam
This is because buckling occurred in the height direction of 95 × 13 mm and a large amount of contraction occurred.

Example 2 After deposition of carbonyl Ni powder, nickel was used as the main component in the same manner as in Example 1 except that it was immersed in a 0.5 mol / l cobalt nitrate aqueous solution instead of the nickel nitrate aqueous solution.
% To obtain a three-dimensional network structure made of an alloy.

Example 3 As a substrate having a three-dimensional network structure, 100 × 100 × 7
0 mm polyurethane foam was used. The polyurethane foam was dipped in an acrylic pressure sensitive adhesive solution having a resin content of 5% using methyl ethyl ketone as a solvent, and then the excess solution was removed to impart tackiness to the surface of the substrate skeleton. After drying at 100 ° C. for 10 minutes to remove the solvent, the substrate was inserted into aluminum oxide powder having an average particle size of 5 μm and rocked to deposit the aluminum oxide powder. Then, immerse in an aluminum acetate aqueous solution with a concentration of 1 mol / l,
It was dried at 100 ° C. for 30 minutes. Block-shaped tertiary aluminum oxide having a shape in which the polyurethane foam is transferred by decomposing and removing the polyurethane foam of the substrate by keeping the surface of 100 × 100 mm as the bottom surface at 1550 ° C. for 2 hours in the atmosphere, and sintering the aluminum oxide powder. An original mesh structure was obtained. The size of the obtained three-dimensional network structure was 75 × 75 × 50 mm and the porosity was 93%.

[0016]

According to the present invention, after the powder is deposited on the substrate,
A highly porous three-dimensional network structure having a three-dimensional shape can be stably obtained by a simple method of wetting with a solution containing a metal salt and heat treatment.

Claims (2)

[Claims] 1. A tackifier is applied to the surface of a skeleton of a three-dimensional network structure to be a substrate, a powder is applied to the skeleton surface, and heat treatment is performed to remove the substrate of the three-dimensional network structure. Inactive,
Alternatively, it is a method for producing a three-dimensional network structure in which heat treatment is performed in an oxidizing atmosphere to sinter the powder, and after the powder is applied and before the heat treatment, the applied powder is treated with a solution containing a metal salt. A method for producing a three-dimensional mesh structure characterized by being wet. 2. The method for producing a three-dimensional network structure according to claim 1, wherein the metal salt is at least one selected from nitrates and organic acid salts.