JPH11171671A - Production of plate silicon carbide-silicon composite ceramic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing an SiC-Si composite ceramic plate having extremely high flatness and usable as a tray or cover of a furnace for the baking of electronic parts, ceramics and powder. SOLUTION: This SiC-Si composite ceramic plate is compound mainly of 75-85 wt.% of SiC and 25-15 wt.% of Si. The ceramic plate is produced by adding an additive and a solvent to SiC particles having particle size distribution extending from 200 μm (the maximum diameter) to submicron order, forming the obtained slurry to a plate by a solid casting method, forming a layer composed exclusively of fine powders having particle diameter of <=25 μm as the surface layer having a thickness of 50-200 μm, and heating the formed product at >=1500 deg.C in a non-oxidizing atmosphere to effect the impregnation of Si. The surface layer is relatively easily formable using a gypsum material having a porosity of >=40% as the forming mold.

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 plate-shaped SiC-Si composite ceramic used as a shelf or a lid in a heating furnace for firing electronic parts or ceramics.

[0002]

2. Description of the Related Art When firing electronic components and various ceramics, plate-like members such as shelf boards and lids of sheaths are often used. For these plate shapes, conventionally, SiC,
Ceramic materials such as Al ₂ O ₃ and mullite are manufactured by pressure press molding such as vibration molding and are widely used. In recent years, SiC-Si-based composite ceramics have been spotlighted from the viewpoint of high-temperature strength and oxidation resistance. When manufacturing a plate-like SiC-Si-based composite ceramic, generally, a pressure press molding method such as vibration molding is used.
In general, a method of molding SiC powder and impregnating pores with metallic Si is used. This molding method has a drawback in that it is necessary to add considerable coarse particles, and the surface has poor smoothness. It is difficult to use due to poor surface smoothness, such as when loading and firing the processed material or when sucking during transportation. In addition, even if a solid casting method, which is generally known as a molding method of ceramics, is employed, when using SiC slurry, mold release properties and cavities often occur in a molded body, It was a difficult situation for practical use.

[0003]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies in order to provide such a requirement, that is, to provide a plate-shaped SiC-Si-based composite ceramic having good smoothness. By forming such a layer, a method for producing the same has been established.

[0004]

That is, a method for producing a plate-like SiC-Si-based composite ceramic according to the present invention comprises:
In a plate-shaped SiC-Si-based composite ceramic mainly composed of 75 to 85% by weight of SiC and 25 to 15% by weight of Si, an additive and a solvent are added to a SiC particle having a maximum particle size of 200 μm to submicron, and a slurry is added. And then molded into a plate by the solid casting method.
A layer consisting of only fine powder having a particle size of 25 μm or less is formed at 0 to 200 μm, and the formed body is heated at 1500 ° C. in a non-oxidizing atmosphere.
It is characterized by being impregnated with Si at the above high temperature. Here, in the above-mentioned solid casting method, a gypsum mold having a porosity of 40% or more is employed as a mold, so that a particle diameter of 25 μm is obtained.
m or less can be easily formed. The formation of the surface layer can be controlled by adjusting the porosity of the gypsum mold and the pressure at the time of solid casting.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION In the SiC-Si based composite ceramics according to the present invention, the content of SiC is less than 75% by weight,
If i exceeds 25% by weight, the amount of Si impregnated is large, so that the creep resistance and wear resistance are reduced, and the SiC
Exceeds 85% by weight, and if the content of Si is less than 15% by weight, the number of remaining pores increases, leading to a decrease in strength characteristics and oxidation resistance. Further, if SiC and Si as main components are within the above range, even if the third component is contained, it does not interfere with the production method of the present invention. If SiC particles having a maximum particle size of more than 200 μm are employed, sedimentation occurs when the slurry is formed, and the dispersion becomes poor. When the SiC particle size of the surface layer exceeds 25 μm,
Poor smoothness. Regarding the thickness of the surface layer, 50 μm
When the value is less than 2, the smoothness is not improved and there is no effect.
When the thickness exceeds 00 μm, coarse particles are remarkably increased at the center, and a decrease in strength is observed. Even if the porosity of the gypsum mold is less than 40%, the surface layer can be formed, but the mold release property is deteriorated and workability is inferior. Therefore, it is desirable to use a gypsum mold of 40% or more.

[0006]

The present invention will be described below with reference to examples. A uniform slurry was prepared by dispersing and mixing SiC particles having an average particle diameter of 3 μm and a maximum particle diameter of 180 μm in water using methyl cellulose as an organic binder. The porosity of this slurry is 44
% Of using plaster mold, 1.0 Kg / by solid casting method while applying a pressure of cm ² 300mm × 300mm × 7m
m was formed. A fine powder layer having a thickness of 100 μm and a maximum particle size of 15 μm was formed on the surface of the molded body.
This compact is heated to 1800 ° C. in an N ₂ atmosphere to
i was melted and impregnated to obtain a plate-like SiC-Si-based composite ceramic. The plate-like ceramic was composed of 80% by weight of SiC and 20% by weight of Si, and had an apparent porosity of 0.1%.
1%, room temperature flexural strength of 300 MPa.
The surface smoothness of this plate-shaped ceramic has reached the level of Ra = 1 μm, and the surface is further polished to obtain Ra = 1 μm.
It became possible to 0.002 μm. The surface smoothness of a plate-shaped ceramic of the same material without a surface layer is Ra =
Since the particle size was 10 μm and coarse particles were present on the surface, the smoothness was not improved even if the surface was polished.

[0007]

As described above, the plate-like SiC-S of the present invention is used.
According to the method for producing an i-type composite ceramic, a SiC-Si-based material having excellent strength and oxidation resistance, which has been widely used in recent years, can be used as a plate-like ceramic having very good smoothness. It can be used for heat treatment processes in a wide range of fields such as firing of electronic parts and ceramic powder, and great effects can be expected.

Claims (2)

[Claims] 1. 75% to 85% by weight of SiC and 25% to 1% of Si
In a plate-shaped SiC-Si-based composite ceramic containing 5% by weight as a main component, an additive and a solvent are added to SiC particles having a maximum particle size of 200 μm to submicron to form a slurry, and then solid casting is performed. To form a layer consisting of only fine powder having a particle size of 25 μm or less on the surface layer of 50 to 200 μm, and impregnating the molded body with Si at a high temperature of 1500 ° C. or more in a non-oxidizing atmosphere. A method for producing a plate-shaped SiC-Si-based composite ceramics, characterized in that: 2. The method for producing a plate-like SiC-Si-based composite ceramic according to claim 1, wherein the gypsum material having a porosity of 40% or more is used as a mold in the solid casting method according to claim 1.