JPS6020347B2 - Manufacturing method of silicon nitride sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a high-strength, dense silicon nitride competitive body.

Silicon nitride (Si3N4) composite has excellent thermal shock resistance due to its unique low coefficient of thermal expansion, and has excellent mechanical strength, hardness, and chemical stability, so it is attracting attention as a variety of high-strength heat-resistant materials. There is.

However, since silicon nitride itself has poor dryness and has the property of volatilizing and decomposing under atmospheric pressure at around 190,000 ℃, various studies have been conducted on methods for repelling it. Among these methods, the hot press method produces a dense compact with high strength, but it is difficult to produce products with complex shapes, and the normal press method and reactive sintering method volatilize during compaction in an atmosphere of 1 atmosphere. As a result, there were many pinholes and it was not possible to obtain a material with high strength. However, since the ordinary sintering method is the simplest sintering method, it would have great industrial significance if a silicon nitride compact with sufficient strength could be obtained by this method. In order to meet these demands, the present inventors conducted intensive research and found that by adding Mg0 and Zr02 in a specific ratio to Si3N4 and sintering it in a non-oxidizing atmosphere, a dense and high-strength sintered body can be obtained. The present invention was completed based on the discovery that the following could be obtained.

In other words, the gist of the present invention is that within the range surrounded by the quadrilateral area connecting points A, B, C, and D of the attached ternary composition diagram (including on the straight line connecting A, B, C, and D) in terms of weight percentage, S of the proportion of
i3N4, Mg○ and Zr02, but points A, B, C
and D is Si3N4 MgO Zr02
A 98.0% 1% 1%B 89
10% 1% 0 80% 10% D 80% 1% 19% D It's in the manufacturing method.

The present invention will be explained in detail below.

The reason why the method of the present invention binds in a non-oxidizing atmosphere is because silicon nitride is extremely easily oxidized.

Akatsuki is usually 1,600 to 185,000, preferably 165
It is carried out at a temperature of 0 to 180 qo, and if the temperature is lower than 1600 qo, the blinding may be insufficient, and 1850 qo
If the temperature is higher than that, the volatilization of Si4 becomes significant.
This will be explained in detail below using Examples.

*Example 1 Q-Si3N49 weight increase % and 8-Si3N41 weight %
Si3N4 powder with an average particle size of 1 and an average particle size of 2
Buddha's ZrQ powder with an average particle size of 0. Autumn Mg○ powder (all commercially available products) was blended in various proportions shown in Table 1 and ground to an average particle size of 14 or less using a ball mill.

Camphor was added as a binder to this powder in an amount of 5% by weight based on the total powder, and the mixture was 10 x 5 x
Press-formed to a size of 3 broadsides, and then heated to 600℃ in a nitrogen stream.
After heating to 0.degree. C. to dissipate the binder, the compact was competitively bonded in a graphite crucible under an N2 atmosphere.

Table 1 shows the results of measuring various properties of the obtained samples a to i.

Note that sample numbers a to i correspond to those in FIG.
Table 1 *1 Transverse rupture force measurement: Using a 4 x 8 x 25 rudder test piece. Measured according to JISB Mountain 4104.

*2 Pinhole measurement: Mirror polish the sample. Measured according to ASTM standard B-276-54.

*3 Tissue f... Fibrous tissue. g...Grain structure As is clear from Table 1, samples a to e of the present invention have no more than one (B rank) pinhole inside the sintered body compared to samples f to i which are outside the range. Because the tissue became fibrous, the anti-new power value could be significantly increased. In the above example, ``The reason why excellent properties such as heat resistance can be obtained by adding Mg○ and Z2 as subcomponents in a specific ratio to the main component Si3N4 is that Z2 reacts with Si3N4. ZrN, Si02, etc. are partially generated, and at the same time, they form an age-promoting phase with Mg○, which improves competitiveness and becomes denser, and a structure in which the developed fibrous crystal phase intersects. This is thought to be because.

However, in the method of the present invention, the Sj3N4 component is
98.0% by weight was determined from 80% by weight of Si3N4.
When the amount of components decreases, the transverse rupture strength value decreases, 98. weight% of
This is because if the amount exceeds 1, it becomes necessary to raise the competitive sintering temperature, and in this case, the amount of volatilization during sintering increases, making it impossible to obtain a dense and high-strength sintered body. The reason why the Mg0 component is set to 1 to 10% by weight is that if it is less than 1% by weight, no effect as a dawning accelerator is observed, and if it exceeds 1% by weight, the amount of volatilization during dawning increases and the binder component This is because the glass phase and the softening phase at high temperatures increase, reducing the high temperature strength properties of the sintered body. The reason why 2 of Z is set to 1 to 19% by weight is that when it is less than 1% by weight, the internal structure of the leech body becomes difficult to become fibrous and no improvement in strength can be obtained, and when it exceeds 20% by weight, the internal structure becomes fibrous. However, this is because the sinterability deteriorates and the strength decreases. Also, Mg○ and Z in Si3N4
When r02 is added so that Mg0:Zr02 is larger than 1/4 and molded by hot pressing, Z2 is not stabilized and therefore breaks due to fatigue when repeated stress is applied. Due to the result, part of Z2 is zirconia without metamorphosis. The remaining Zr02 becomes umnitride and is stabilized by Mg0, and all unstabilized Zr02 disappears, resulting in a sintered body that is resistant to fatigue.
It is known empirically that all of the unstabilized 2's of Z disappear. Note that Zr in the sintered body according to the present invention
Since 02 is Shintsu sintered, part of the zirconium nitride 1 after solidification is stabilized without transformation. In general, Mg0 has the effect of improving the streak resistance of Sj3N4, and Z2 has the effect of creating a fibrous structure in the compact, but the present invention combines the two to exhibit their synergistic effect. It is.

This is clear from the results of Example 2 below. Example 2 Molten molding was carried out in the same manner as in Example 1, except that 2 powders of Z and 2 powders of M were mixed in various proportions to 9% by weight of Sj3N4 powder.

The transverse rupture strength of the obtained sample was measured and the results are shown in FIG.
As is clear from Figure 2, the subcomponents are Mg0, Mg0,
The transverse rupture strength is larger when both Z are mixed than when both are used alone.

The mixing ratio of both is preferably 4/1 to 1/4 by weight, particularly preferably 3/2 to 2/3.
In addition, in the above Examples 1 and 2, Mg0, Zr02
However, as is known, Mg○, Zr
It goes without saying that Mg compounds such as Mg salts and Zr salts, and Zr compounds such as 02 may be used, and the present invention also includes such cases.

As detailed above, in the present invention, a high strength sintered body can be obtained by a simple Shintsu sintering method by blending Si3N4 with Mg0 and Z2 in a specific ratio, and its industrial value is great.

Of course, unlike the hot press method, it is possible to freely obtain sintered bodies with complicated shapes.

[Brief explanation of the drawing]

FIG. 1 is a ternary composition diagram showing the basic components of the present invention, and FIG. 2 is a graph showing the relationship between the amount of M and Z added and the transverse rupture strength. Figure 1 Figure 2

Claims (1)

[Claims] 1. Points A, B, and C in the ternary composition diagram in Figure 1 of the appendix in weight percentage.
and the proportion of S within the range surrounded by the quadrilateral area connecting D
i_3N_4, MgO and ZrO_2, but point A,
B, C and D are Si_3N_4 MgO ZrO_
2 A mixed powder consisting of 98.0% 1% 1% B 89% 10% 1% C 80% 10% 10% D 80% 1% 19% is molded, and the molded body is sintered in a non-oxidizing atmosphere. A method for producing a silicon nitride sintered body, characterized by: 2. The method for producing a silicon nitride sintered body according to claim 1, wherein the weight ratio of MgO and ZrO_2 is 1/4 or more.