JPS61236659A - Manufacture of electroconductive ceramics - 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 <Industrial Application Field> The present invention relates to a method for manufacturing a novel conductive ceramic having excellent electrical and thermal conductivity.

<Prior art> Conventionally known methods for producing conductive ceramics include (A) mixing ceramic raw materials and conductive material powder, molding the mixture, and then hot heating in a vacuum or inert gas atmosphere; (B) applying a conductive material coating solution containing a binder onto the ceramic sintered plate; or (C) applying a conductive material to the surface of the ceramic sintered plate. There are methods of attaching the material using methods such as vacuum deposition, plating, or printing.

Among these methods, method (A) tends to have insufficient electrical and thermal conductivity because the conductive material is blended in the form of powder, and if a large amount of conductive material is blended, the mechanical strength of the ceramic molded body decreases. descend. In addition, (B) has a problem with heat resistance because the coating layer contains an organic binder, and both (B) and (C) have poor adhesion or adhesion to the surface of the ceramic sintered body. This tends to cause problems and limits the range of applications.

Problems with conventional manufacturing methods are not limited to the above-mentioned problems with characteristics, but also in manufacturing, the equipment is expensive, continuous production is difficult, and productivity is extremely poor, which has become a major industrial issue. ing.

<Problems to be Solved by the Invention> The present invention has been made in view of the two circumstances. The present invention provides a method for manufacturing excellent ceramics.

<Means for solving the problems> The greatest feature of the present invention is that a fibrous metal,
That is, the use of metal fibers with a fiber diameter of 4 to 8 um and a fiber length of 3 to 6 mm, and the adoption of a wet papermaking method as a means of obtaining an intermediate sheet before sintering, thereby improving the electrical conductivity of the ceramic sintered body. It has become possible to uniformly disperse fibrous metal, which is effective for application, into ceramic powder.

That is, in the present invention, an aqueous slurry containing 5 to 15 parts by weight of pulp and 3 to 35 parts by weight of metal fibers to 100 parts by weight of ceramic powder is formed into a sheet by wet papermaking-3 = paper quality. Then, a plurality of these layers are laminated to the required thickness and then integrated by pressure treatment to form a molded body.Then, by calcining in an oxygen atmosphere of 60,000 or less, the internal properties of the molded body are removed. The present invention provides a method for producing a conductive ceramic, which comprises burning and removing organic matter, and further sintering it in a vacuum, an inert gas atmosphere, or a reducing active gas atmosphere to form a sintered body.

The ceramic powder referred to in the present invention may be any conventional ceramic material or fine ceramic material, but magnetic tile clay is particularly preferably used in the present invention.

In addition, the metal fibers referred to in the present invention are fibers made of materials such as stainless steel, brass, copper, and aluminum, and the reason is that stainless steel fibers in particular can produce fine wires and have excellent rust resistance, heat resistance, and paper-making properties. are preferably used in the present invention.

Further, the pulp constituting the present invention includes not only ordinary wood pulp made of cellulose, but also synthetic fiber pulp such as polyethylene, inorganic fiber, and artificial fiber. Although each of these pulps can be used alone, a blend of wood pulp and synthetic fiber pulp is preferred for the following reasons.

In other words, these pulps must function as a binder between ceramic and metal fibers during the sheet manufacturing process in the wet papermaking process, and have good combustibility during the sintering process. Therefore, focusing on the function of wood pulp as a binder and the advantages of synthetic pulp in combustibility, a blend system of both is preferably used in the present invention.

The method for manufacturing the conductive ceramic of the present invention using the above materials is as follows.

First, an aqueous slurry consisting of 5 to 15 parts by weight of pulp and 3 to 35 parts by weight of metal fibers is prepared based on 100 parts by weight of ceramic powder. The reason why the amount of pulp is specified to be 5 to 15 parts by weight is that if it is less than 5 parts by weight, wet paper paper strength that can be used for wet paper making cannot be obtained, and if it is more than 15 parts by weight, shrinkage may occur during baking or gas may be released. This may lead to a decrease in the mechanical strength of the sintered body. On the other hand, the blending ratio of metal fibers is 3~
The reason for using 35 parts by weight is that if it is less than 3 parts by weight, it is difficult to form contact between the metal fibers necessary for conductivity within the ceramic sintered body, and if it is more than 35 parts by weight, it will lead to a decrease in the mechanical strength of the sintered body. It depends.

The form of the metal fiber used in the present invention is not particularly limited,
Generally available fiber diameter 2-16U1 fiber length 2-12
Although fibers with a fiber diameter of 4 to 8 μm and a fiber length of 3 to 6 mm are preferably used, considering dispersibility in an aqueous slurry.

To make an aqueous slurry, the surface of the pulp is cationized in order to coagulate and fix the main component, ceramic, into the pulp with a good yield. Specifically, after a cationic resin is added to pulp dispersed in water, ceramic powder is mixed, and sulfate is added as a fixing agent. Thereafter, a polymer flocculant is added to the aqueous slurry obtained by mixing metal fibers immediately before paper making, and the paper is formed into flocs of an appropriate size to produce a sheet. In this case, the wet paper machine can be either a Fourdrinier type or a circular screen type.

A plurality of ceramic sheets containing metal fibers obtained in this manner are laminated to a desired thickness and then integrated by pressure treatment to produce a molded body. In this case, the molding is carried out using a press at a pressure of 500 kg 1b degrees, and in the case of continuous molding, the molded body can also be obtained using a roll press.

Next, the molded body is subjected to a firing process, but in this case, calcination is performed in an oxygen atmosphere at 6000 C or less before performing the main firing required for sintering. That is, it is necessary to burn and remove the organic pulp fibers present in the molded body by calcining. Thereafter, it is fired in a vacuum or in an atmosphere of an inert gas such as nitrogen or a reducing active gas such as hydrogen to obtain the conductive ceramic of the present invention. In this case, the vacuum sintering conditions are, for example, a vacuum degree of I C1''2 torr, a firing temperature of 1200°C, and a firing time of 2 hours.The reason why the firing conditions are specified as vacuum or in an inert gas atmosphere in the present invention is as follows. This is because when fired in the presence of oxygen, the surface of the metal fiber is oxidized, resulting in a decrease in electrical conductivity and a decrease in physical strength due to grain boundary corrosion becoming saturated.

<Examples> The present invention will be described in detail below with reference to Examples and Comparative Examples.

Example 1 6 parts by weight of polyethylene synthetic pulp (SWP E-400, manufactured by Mikata Petrochemical Co., Ltd.) and NBKP with a beating degree of 30°SR
A cationic resin solution (Polyfix 301, manufactured by Showa Kobunshi Co., Ltd.) was added to the aqueous slurry obtained by dispersing 4 parts by weight of wood bulbs in water to a solid content concentration of 0.05%. The pulp fibers were cationized by adding 3% in proportion.

Next, the following operation was performed to mix 90 parts by weight of ceramic powder with 10 parts by weight of pulp fibers made of the synthetic pulp and wood pulp.

That is, while stirring the slurry, the magnetic tile clay 221 <components 5I0273, 94, A I203
15.32, Fe2030.70, Ca0O,23, M
gO0,1? , K2O3,70, Na20 1,85
, each percentage) was added at the above mixing ratio to adsorb the ceramic to the pulp fibers, and then 5% of sulfate was added to the pulp to coagulate and fix the ceramic on the surface of the pulp. In this slurry, stainless steel fibers with a fiber diameter of 8 μg and a fiber length of 6 mm (Susmic, manufactured by Tokyo Seikosha Co., Ltd.) were added, and the total weight of pulp fibers on ceramic powder was 10
10 parts by weight were mixed to 0 parts by weight and uniformly dispersed.

Immediately before paper making, an anionic polymer flocculant (Sunfloc, manufactured by Sanyo Kasei Co., Ltd.) solution is added to this slurry to form an appropriate floc size, and the ceramic particles are coagulated and fixed on the pulp fibers. The paper is made with a weight of 1.3k.
A sheet of g/J was produced.

Four of the sheets were stacked together in a press at a pressure of 500 kg/C- to form a molded product. This molded body is calcined in a kiln at 600°C to first burn and remove pulp fibers made of organic matter in the molded body, and then placed in a vacuum incinerator to reduce the pressure to a degree of vacuum of 10-2 to 10-3 torr. The conductive ceramic of the present invention was obtained by sintering. The firing conditions in this case are that after firing at a temperature of 1200° C. for 2 hours, it is slowly cooled to room temperature, and a vacuum state is maintained throughout this time.

The volume resistivity of the obtained conductive ceramic is 1.2X
1'00 Ω·cm, and the thermal conductivity measured by the step heating method was 0.566 W/m-, confirming excellent electrical and thermal conductivity.

In this case, the relationship between the amount of stainless metal fiber mixed with the ceramic and the volume resistivity is as shown in Figure 1.
1 (13 to 10
The electrical resistance can be arbitrarily obtained within the range of -2 Ω·cm.

Example 2 The shape of the stainless steel fiber in Example 1 was changed to a fiber diameter of 4I7.
A conductive ceramic of the present invention was obtained in the same manner as in Example 1 except that the fiber length was changed to 4 mm. The electrical resistance of this ceramic was 3.1XlO-'Ω·Cl11, and the thermal conductivity was 0.610 W/m-, confirming excellent electrical and thermal conductivity.

Comparative Example The molded product obtained in Example 1 was heated for 12 hours in a normal atmospheric atmosphere.
Firing treatment was performed at 00°C for 20 minutes.

The physical strength of the obtained conductive ceramic was sufficient for practical use, but the electrical resistance was 3.6XIOIIΩ.
・It was ctn. This is the result of firing in an oxygen atmosphere.
This was due to the formation of an oxide film on the surface of the metal fibers and loss of conductivity.

<Effects of the Invention> As is clear from the above structure, the present invention achieves advantages that could not be obtained with the prior art by employing ultrafine metal fibers as a means of making ceramic conductive and by adopting a wet papermaking method for mixing the ceramic and metal fibers. We were able to obtain a high degree of electrical and thermal conductivity that was previously unavailable.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the volume resistivity of the conductive ceramic of the present invention and the blending amount of stainless fiber.

Claims (1)

[Claims] 5-15 parts of pulp per 100 parts by weight of ceramic powder
Aqueous slurry containing 3 to 35 parts by weight of metal fibers is made into a sheet using a wet paper-making method, and multiple sheets of this are laminated to the required thickness and then subjected to pressure treatment. The molded product is integrated into a molded product, and then calcined in an oxygen atmosphere at 600°C or lower to burn and remove the organic matter inherent in the molded product, and then heated in a vacuum, an inert gas atmosphere, or a reducing active gas atmosphere. A method for producing a conductive ceramic, the method comprising: firing the conductive ceramic to form a sintered body.