JPS6271555A - Production of silicon nitride sintered body using ball stone - 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 Field of Application) The present invention relates to a boulder used to obtain a uniform fine powder by crushing and mixing raw material powder, and the production of a silicon nitride sintered body using the boulder. It is about law.

(Prior Art) Ball mills, vibration mills, and the like used in the pulverization and mixing process during the manufacturing process of silicon nitride sintered bodies use cobblestones to pulverize and mix raw material powders to obtain uniform fine powders.

Conventionally known boulders include iron and tungsten carbide, and JP-A-54-88909 discloses a boulder for grinding silicon nitride raw materials made of sintered silicon nitride. Further, Japanese Patent Application Laid-open No. 54-97614 discloses a boulder made of an oxide or silicate of aluminum, zirconium, magnesium, beryllium, and/or yttrium.

(Problems to be Solved by the Invention) However, in the conventional cobblestones described above, the cobblestones are sometimes worn and cobblestone components are mixed into the raw material powder.

Therefore, the densification of the sintered body is inhibited and the properties deteriorate due to the action of the mixed cobblestone components, especially Pe, WC, and Z.
In the case of rO2 boulders, there was a drawback that the high temperature characteristics deteriorated.

Further, since excellent pulverization effects cannot be obtained with stones having a light specific gravity such as ^' zOs, Si, J, and cobblestone, only sintered bodies with low room temperature strength could be obtained.

The purpose of the present invention is to solve the above-mentioned problems, to obtain a fine powder by uniformly pulverizing the raw material powder, and even if cobblestone components are mixed into the raw material powder due to wear, it will not have an adverse effect on the sintered body. The present invention aims to provide a cobblestone and a method for manufacturing a silicon nitride sintered body using the cobblestone.

(Means for Solving the Problems) The boulder of the present invention is characterized by containing Ce01 as a main component, and the method for producing a silicon nitride sintered body of the present invention uses a silicon nitride starting material powder as a centrifugal powder. The main ingredient is cobblestone, which is crushed, mixed, shaped, and fired.

(Function) In the above-mentioned configuration, the cobblestone mainly composed of CeO□ has a high specific gravity (high pulverizing effect, and even if the Ce01 component is mixed into the raw material powder, it will not inhibit the densification of the sintered body. It is possible to obtain a sintered body with good properties because it does not deteriorate the properties, but rather helps promote densification and improve the properties.

Hereinafter, CeO2 boulders and a method for producing a silicon nitride sintered body using the same will be described in detail. First, a silicon nitride starting material powder is prepared. This silicon nitride starting raw material powder may be a single silicon nitride raw material powder, or may be a blended powder of silicon nitride raw material powder and a sintering aid. As a sintering aid, Yz03JgO+A1203° or the like is added as it is or as an aqueous solution.

Next, this silicon nitride starting material powder is pulverized and mixed using a pulverizer using CeO and cobblestones. As a crusher, wet type,
Either dry method can be used, for example, a ball mill, attritor mill, vibration mill, etc. Thereafter, the obtained molding powder is molded by dry pressing, injection molding, slip casting, etc., and the resulting molded body is subjected to pressureless sintering, pressure sintering,
A silicon nitride sintered body is obtained by firing by a method such as hot press (IP) or true isostain ink press (IIIP). Among these, the conditions for pressureless sintering are 1600℃~
It is preferable to perform the firing at a temperature of 2000° C. in a nitrogen gas atmosphere.

In addition, in the above-mentioned example, when using a blended powder of silicon nitride raw material powder and a sintering aid as the silicon nitride starting raw material powder, the silicon nitride raw material powder is crushed with CeO, a cobblestone, and then mixed with the sintering aid. A powder for molding can also be suitably obtained.

(Example) Su JlfL1 Purity 99.9% by weight, average particle size 0.4 #o++Ce0
Z powder raw material 98% by weight and sintering aid purity 99% by weight
, 0.5 each of MgO and Sing with an average particle size of 1 to 2 μ-
% by weight and 5% by weight of YtOs, pulverized and mixed using nylon resin-coated iron cobblestones, added with an organic binder, and dried and granulated to obtain a powder for molding. This is 10m+■φ
It was molded in a spherical mold and fired in air at 1500° C. for 5 hours to obtain the cobblestone of the present invention whose main component is CeO.

The bulk density of this cobblestone was 6.858/cm3.

1 Blood 1 Silicon nitride raw material powder with purity 97.1% by weight, average particle size 0.7 μm, BET specific surface area 20 m”/g and purity 98-99
weight%, average particle size 0.6-2μIII, BET specific surface area 8-30mt/g, 8l zoz+srO,Y
The raw material powders of gOz and MgO were mixed in the proportions listed in Table 1, and the raw materials were mixed using the cobblestones mainly composed of Ce01 described in Example 1 and a nylon resin container with an internal volume of 1.21. Things 200. 3kg of boulders and 500y of water
a1 was added and pulverized for 48 hours in a pot mill with a rotation speed of 20 times/min.

Thereafter, it was dried and granulated to a particle size of 100 μm to obtain a powder for molding. Next, it was hydrostatically pressed at a pressure of 3 ton/cm".
A molded body of 0×60×6 m+a was prepared and sintered without pressure in a nitrogen atmosphere at 1700° C. for 30 minutes each to obtain silicon nitride raw material powder 1, 6.11 of the present invention.

In addition, powders with the same formulation composition as these were used as ZrO, WC.

Aj! Comparative Examples 2 to 5.7 to 10.12 to 15 listed in Table 1 were obtained by mixing, pulverizing, drying, granulating, molding, and firing under the same conditions using cobblestones containing to* and Si3N4 as main components, respectively. . However, in these comparative examples, the boulders are ZrO.

Cobblestone 3kg, WC cobblestone 8kg, al, o, cobblestone 2.5
1.8 kg of 5iJ4 boulders were used.

The bulk density and four-point bending strength at room temperature and 1200° C. of these sintered bodies were measured, and the results are shown in Table 1.

The bulk density of the sintered body was measured by the Archimedes method. The four-point bending strength was measured according to JIS R-1601r Fine Ceramics Bending Strength Test Method.

As is clear from Table 1, the silicon nitride sintered body 11 of the present invention is formed by molding and firing raw materials crushed by CeO and cobblestones.
m1. Na6 and No.11 have higher room temperature strengths than Comparative Examples Na2-5, No.7-10, and -12-15 due to the crushing effect. Moreover, the silicon nitride sintered body of the present invention 11m1. l1h
In No. 6, even if CeO is mixed, the grain boundary phase does not deteriorate and the high temperature strength does not decrease compared to the room temperature strength. On the other hand, in Comparative Examples Nos. 2 to 5, 11 and 7 to 10, the strength decreased at high temperatures due to the inclusion of cobblestone components.

The same silicon nitride raw material powder as in Example 2 was used as C shown in Example 1.
Using cobblestones whose main component is eO
Milled in a minute bot mill for 100 hours. This pulverized product was prepared as All 103. as in Example 2. Each raw material powder of SrO, 'ttOx, and MgO was prepared in the proportions shown in Table 2, and mixed using a nylon-coated iron cobblestone and a nylon resin container. Subsequently, drying, granulation, molding, and firing were performed in the same manner as in Example 2 to obtain a silicon nitride sintered body Na16.22.28 according to the method for producing a silicon nitride sintered body of the present invention as shown in Table 2. . In addition, the same silicon nitride raw material powder is used as iron, Zr01JC
, A 41 gos, and 5isNa were crushed under the same conditions using the same container as the cobblestones whose main components were, respectively. However, in these comparative examples, the iron cobble weight was 4.5 kg.

3 kg of ZrO2 cobbles, 8 kg of WC cobbles, 2 AltOs cobbles, 5 kg + S i s Na cobbles 1.
8 kg was used. These pulverized materials were mixed, dried, and mixed as described in Table 2 in the same manner as for CeO and cobblestone.
After molding and firing, silicon nitride raw material powders 17 to 21 of Comparative Examples listed in Table 2 were prepared. Ni23-27. Obtained numbers 29-33.

The bulk density and four-point bending strength at room temperature and 1200° C. of these sintered bodies were measured using the same method as in Example 1, and the results are shown in Table 2.

As is clear from Table 2, the silicon nitride sintered body N of the present invention is formed by molding and firing the crushed raw material with CeO and cobblestones.
116. N122 and Arashi 28 are comparative examples Na17~21, Na23~27.1lh29~ due to the crushing effect.
The room temperature strength is higher than that of No. 33. Further, in the silicon nitride sintered body N116°11h22 of the present invention, even if CeO is mixed, the grain boundary phase does not deteriorate, and the high temperature strength does not decrease compared to the room temperature strength.

In contrast, comparative examples 11h17-21, l1h23-2
In No. 7, the strength decreased at high temperatures due to the inclusion of cobblestone components.

(Effects of the Invention) As is clear from the above detailed explanation, according to the cobblestone and the method for producing a silicon nitride sintered body using the cobblestone of the present invention, since the specific gravity of CeO□ cobblestone is high, ZrO□ ,W
Like C,Fe boulders, it has high pulverization efficiency, breaks aggregates of raw materials, and disperses additives well, making it possible to obtain uniform sintered bodies. Therefore, a sintered body with high density and room temperature strength can be obtained.

In addition, even if the CeO component in the cobblestone is mixed into the raw material powder, it does not deteriorate the properties of the grain boundary phase.For this reason, the presence of CeO will cause the grain boundary phase to crystallize, resulting in a matrix with high high-temperature strength ( For example, Yz(h -MgO series 6~10°-22~
27 and YtOs-Al tit system 11hl~5.
The high temperature strength of I'&L16-21) is not reduced relative to the room temperature strength.

Claims (1)

[Claims] 1. A cobblestone for grinding and mixing, characterized by containing CeO_2 as a main component. 2. A method for producing a silicon nitride sintered body, which comprises pulverizing and mixing a silicon nitride starting material powder using cobblestones containing CeO_2 as a main component, shaping and firing.