JPWO2008018401A1 - SiC sintered body and manufacturing method thereof - Google Patents

Abstract

The present invention provides a SiC sintered body that is excellent in binder removal of a material to be fired and can obtain a material to be fired having a uniform composition, and a method for producing the same. The SiC sintered body of the present invention is an SiC sintered body containing at least SiC and Si as constituent components, and the sintered body has an average surface roughness of 5 μm to 100 μm, or the sintered body The surface porosity was 0.3% or more. The sintered body is formed by molding a molding raw material containing SiC powder, graphite powder, an organic binder, and water, and then sintered and cooled. At least one of the sintering step and the cooling step is nitrogen. It can be manufactured by introducing gas.

Description

  The present invention relates to a SiC-based sintered body used for firing an object to be fired, such as ceramics, tiles, and electronic parts, and a method for manufacturing the same.

A Si-SiC sintered body (also referred to as a SiC-based sintered body) containing SiC and Si as constituent components has industrially excellent heat resistance and fire resistance, and is covered with ceramics, tiles, electronic parts, and the like. It is used as a shelf board for firing fired products.
The Si-SiC sintered body is mainly formed by adding carbon (C) fine powder and an organic binder to SiC particles, and then molding them by casting, extrusion molding, press molding, etc., and then firing in an Si atmosphere. Manufactured.

Among the above production methods, press molding is optimal for mass production and industrialization, but there has been a problem that layer peeling easily occurs during molding, and breakage occurs during handling due to low retention.
In order to solve this problem, a SiC-based sintered body described in Patent Document 1 below has been developed.

Japanese Patent No. 2968882

  However, when the SiC sintered body described in Patent Document 1 is press-molded, the press pressure concentrates on the surface and becomes smooth, and the binder to be fired cannot be sufficiently removed. There was a problem that a product to be fired could not be obtained.

  In view of the above-mentioned problems, the present invention is to provide a SiC sintered body that is excellent in debinding of a fired product and can obtain a fired product having a uniform composition, and a method for producing the same.

The SiC sintered body of the present invention is an SiC sintered body containing at least SiC and Si as constituent components, and the average surface roughness of the sintered body is 5 μm to 100 μm.
By making this surface roughness, the binder of the fired product placed on the sintered body is easily removed, so that it is excellent in debinding, and a fired product with a uniform composition can be obtained. Become.

The present invention can also be a SiC sintered body containing at least SiC and Si as constituent components, and having a surface porosity of 0.3% or more.
Even with this surface porosity, since the binder of the fired product placed on the sintered body is easily removed, the binder is excellent in debinding, and a fired product having a uniform composition can be obtained. It will be a thing.

  The present invention combines the above characteristics, and the SiC sintered body in which the average surface roughness of the sintered body is 5 μm to 100 μm and the surface porosity of the sintered body is 0.3% or more, You can also

In the sintered body, the surface porosity is preferably larger than the internal porosity, and the ratio of the surface porosity to the internal porosity (surface porosity / internal porosity) is 1.3 or more. More preferred.
By doing in this way, it becomes a sintered body without a nest inside and becomes excellent in strength.

  The sintered body preferably has silicon nitride crystals on the surface.

The method for producing the sintered body is a method for producing a SiC sintered body in which a forming raw material containing SiC powder, graphite powder, an organic binder, and water is formed, and then sintered and cooled. Thus, a production method in which nitrogen gas is introduced into at least one of the sintering process and the cooling process can be mentioned.
By introducing nitrogen gas after forming and sintering or cooling, the nitrogen gas can remove Si from the surface of the sintered body, so that the surface can be appropriately roughened.

  In the above production method, the pressure of the nitrogen gas is 0.1 MPa to 1.0 MPa, the firing temperature is 1500 ° C. to 2500 ° C., the firing temperature holding time is 8 hours or more, and the heating rate is 120 ° C./hr or more. Is preferred.

  In addition, the surface porosity as used in the field of this invention means the porosity of the depth from both surfaces of about 30% with respect to thickness, and an internal porosity means the porosity of other center part. For example, when the thickness is 10 mm, the surface porosity is a porosity of 3 mm depth from both surfaces, and the internal porosity is a porosity of a depth of 3 mm to 7 mm from the surface.

Hereinafter, preferred embodiments of the present invention will be described.
In the present invention, the surface of a SiC sintered body containing SiC and Si as constituent components is roughened so that the average surface roughness is 5 μm to 100 μm and the surface porosity is 0.3% or more. . Of course, it is good also as a SiC sintered compact which satisfy | fills the range of both of these average surface roughness and surface porosity.
The SiC sintered body of the present invention can be manufactured by molding a molding raw material in which SiC powder, graphite powder, an organic binder, and water or an organic solvent are mixed and then sintering.

  As the SiC powder, SiC fine particles having an average particle diameter of 30 μm to 85 μm, preferably 55 μm to 75 μm can be used. Moreover, you may mix and use what differs in a particle size. When using particles having different particle diameters, SiC fine particles having an average particle diameter of 1 μm to 10 μm, preferably 2 μm to 8 μm, can be used as the SiC fine particles.

  The graphite powder having an average particle size of 3.0 μm to 8.5 μm, preferably 5.5 μm to 7.5 μm can be used. The graphite powder is contained in an amount of 1 to 15% by weight, preferably 3 to 10% by weight, based on the SiC powder.

  In the case of press molding to be described later, water or an organic solvent is preferably contained in an amount of 1 to 6% by weight with respect to the SiC powder. It is preferable to make it contain 20 to 20 weight%.

  As the organic binder, a lignin sulfonic acid organic binder, a polysaccharide organic binder, or an acrylic organic binder can be used, and 1 wt% to 5 wt%, preferably 2 wt% to 2.5 wt% with respect to the SiC powder. % Content.

SiC powder, graphite powder, an organic binder, and water or an organic solvent can be blended and mixed to obtain a raw material for molding. The mixing can be performed using a pulverizer such as a ball mill or a fret mill.
At this time, 90% by weight or more of the aggregated graphite particles are crushed. Here, the degree of crushing is determined by placing an appropriate amount of raw material before crushing into a 20 mm × 20 mm mold, measuring the number of graphite agglomerated powder on the press surface with a magnifying glass when press molding, and after crushing Similarly, the number of the raw materials can be measured by calculating the ratio of these numbers.

  Examples of the molding method include casting (casting) molding, extrusion molding, press molding, and the like, and a molded body can be created using these. Of these, press molding is preferable, and a hydraulic press and a vibration press are preferable.

  The SiC sintered body of the present invention can be manufactured by firing the molded body as follows.

Firing is performed at a firing temperature of 1500 ° C. to 2500 ° C., preferably 1800 ° C. to 1950 ° C. in a metal silicon atmosphere and an argon (Ar) gas atmosphere. Here, the metal silicon atmosphere means that, for example, a metal silicon reservoir is provided in a firing furnace, and the melted metal silicon is formed to be absorbed by the formed body by capillary action.
Thereafter, nitrogen (N ₂ ) gas is introduced at the time of firing at 1400 ° C. or higher, which is the melting point of silicon, or at the time of cooling. Thereby, it is possible to form irregularities due to SiN (silicon nitride) needle-like crystals on the surface of the SiC sintered body, which is excellent in safety and excellent in debinding of a sintered object such as an electronic component. A ligation can be obtained. The introduction of nitrogen gas is preferably performed at the end of the firing step or in the cooling step, since it does not interfere with the absorption of metallic silicon into the SiC sintered body.
When many SiN whiskers are formed immediately after firing, it is preferably removed by sandblasting.
In the firing, the pressure of nitrogen (N ₂ ) gas is preferably 0.1 MPa to 1.0 MPa, more preferably 0.4 MPa to 0.9 MPa.

  When the molded body has a substantially rectangular plate shape, it is preferable that the molded body is erected, that is, fired with one of the side end faces as the lower surface from the viewpoint of preventing warpage. At this time, the interval between the molded bodies is set to 2 mm or more, preferably 5 mm or more, whereby adhesion of the molded bodies due to leaching of Si can be prevented.

  In the sintered body, the surface porosity is preferably larger than the internal porosity. In particular, the ratio between the surface porosity and the internal porosity (surface porosity / internal porosity) is preferably 1.3 or more, more preferably 2.0 or more, and still more preferably 5.0 or more. Thereby, it becomes the SiC sintered compact excellent in the reactivity of a to-be-fired thing.

  Since the SiC sintered body of the present invention has an appropriate surface roughness with an average surface roughness of 5 μm to 100 μm, or a surface porosity of 0.3% or more, it is fired on the sintered body. The binder of the product is easily removed, and the fired product is not fused to the sintered body. In addition, the material to be fired has a uniform structure because the binder is sufficiently removed.

Examples of the present invention will be described below. However, the present invention is not limited to this.
In the following examples and comparative examples, the average surface roughness was measured at five points in accordance with JIS-B0601, and the average was obtained. Further, the surface porosity or the internal porosity was measured at four points by changing the location according to the boiling method described in JIS-R1634, and the average was obtained.

(Example 1)
2 parts by weight of a lignin sulfonic acid organic binder and 2 parts of a polysaccharide organic binder with respect to 100 parts by weight of a powder composed of 97% by weight of SiC particles having an average particle diameter of 70 μm and 3% by weight of graphite powder having an average particle diameter of 6 μm .5 parts by weight and 4.5 parts by weight of water were blended to obtain a raw material for molding. This raw material for molding was put into a mold and subjected to vibration pressing to obtain a molded body of 350 mm × 300 mm × 6 mm.
The obtained molded body was placed in a firing furnace having a silicon reservoir in the lower part, and the temperature was raised from room temperature to 700 ° C. for 3.5 hours in an Ar gas atmosphere (804.1 kPa (8.2 kg / cm ² )). The temperature was raised at a rate of about 200 ° C./hr) and held at 700 ° C. for 1 hour, and then raised from 700 ° C. to 1880 ° C. for 8 hours (temperature rise rate of about 150 ° C.). Hold for 5 hours. After that, nitrogen gas was introduced and fired at 1880 ° C. for 0.5 hour in a nitrogen gas atmosphere (804.1 kPa (8.2 kg / cm ² )) to obtain a SiC sintered body.
The obtained sintered compact had an average surface roughness of 9.8 μm and a surface porosity of 0.5%. The ratio (surface porosity / internal porosity) was 5.5. The bending strength, which is an index of strength, was 185 MPa.

(Example 2)
An acrylic organic binder with respect to 100 parts by weight of powder composed of 79% by weight of SiC fine particles having an average particle size of 55 μm, 19% by weight of SiC fine particles having an average particle size of 3 μm, and 2% by weight of graphite powder having an average particle size of 6 μm 1.2 parts by weight and 17 parts by weight of water were blended, and this was wet pulverized by a ball mill to obtain a forming raw material. This forming raw material was cast with a plaster mold to obtain a molded body of 250 mm × 120 mm × 6 mm.
The obtained molded body was placed in a firing furnace having a silicon reservoir in the lower part, and the temperature was raised from room temperature to 700 ° C. for 3.5 hours in an Ar gas atmosphere (804.1 kPa (8.2 kg / cm ² )). The temperature was raised at a rate of about 200 ° C./hr) and held at 700 ° C. for 1 hour, and then raised from 700 ° C. to 1880 ° C. for 8 hours (temperature rise rate of about 150 ° C.). Hold for 5 hours. After that, nitrogen gas was introduced and fired at 1880 ° C. for 0.5 hour in a nitrogen gas atmosphere (804.1 kPa (8.2 kg / cm ² )) to obtain a SiC sintered body.
The physical properties of the obtained sintered body were an average surface roughness of 6.9 μm and a surface porosity of 0.4%. The ratio (surface porosity / internal porosity) was 2.0. The bending strength, which is an index of strength, was 250 MPa.

(Comparative Example 1)
For 100 parts by weight of powder composed of 50% by weight of SiC fine powder having an average particle diameter of 1.0 μm and 50% by weight of SiC fine particles having an average particle diameter of 25 μm, 1.0 part by weight of graphite powder having an average particle diameter of 0.1 μm, An organic binder (methylcellulose) was blended in 0.1 part by weight and water in 3.0 part by weight, and this was pulverized by a ball mill to obtain a molding material. This forming raw material was put in a mold and hydraulically pressed at 300 kg / cm ² to obtain a molded body of 200 mm × 30 mm × 10 mm.
The obtained compact was obtained in the same manner as in Example 1 except that nitrogen gas was not introduced during firing to obtain a SiC sintered body.
The physical properties of the obtained sintered body were an average surface roughness of 3.7 μm and a surface porosity of 0.15%. The ratio (surface porosity / internal porosity) was 0.83.

(Evaluation)
Using the above Examples 1 and 2 and Comparative Example 1, the following fusing properties were evaluated.

(Fusability)
A material to be fired made of kaolin is placed on the SiC sintered body of Examples 1 and 2 or Comparative Example 1 and fired at 1200 ° C. for 12 hours. The material to be fired is fused to the SiC sintered body. I checked.

(result)
The above evaluation was performed using six SiC sintered bodies of Examples 1 and 2 and Comparative Example 1 each. ○ is evaluated as “no fusion”, Δ is “a little fusion”, and × is “fusing and cannot be taken out or the object to be fired is damaged”.
The results are shown in Table 1.

Claims (8)

  A SiC sintered body comprising at least SiC and Si as constituent components, wherein the sintered body has an average surface roughness of 5 μm to 100 μm.   A SiC sintered body comprising at least SiC and Si as constituent components, wherein the sintered body has a surface porosity of 0.3% or more.   A SiC sintered body containing at least SiC and Si as constituent components, the average surface roughness of the sintered body is 5 μm to 100 μm, and the surface porosity of the sintered body is 0.3% The SiC sintered body as described above.   The SiC sintered body according to claim 2 or 3, wherein the surface porosity is larger than the internal porosity.   The SiC sintered body according to claim 4, wherein a ratio of surface porosity to internal porosity (surface porosity / internal porosity) is 1.3 or more.   The SiC sintered body according to any one of claims 1 to 5, having a silicon nitride crystal on the surface.   A method for producing a SiC sintered body in which a raw material for molding comprising SiC powder, graphite powder, an organic binder, and water is molded, and then sintered and cooled, comprising at least a sintering process and a cooling process. A method for producing a SiC sintered body in which nitrogen gas is introduced into either one of them.   The method for producing a SiC sintered body according to claim 7, wherein the pressure of the nitrogen gas is 0.1 MPa to 1.0 MPa.