JPS59190268A - Silicon carbide sintered body - 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 The present invention relates to a silicon carbide sintered body which is made dense by a pressureless sintering method and has high strength even at high temperatures.

BACKGROUND ART Silicon carbide sintered bodies are considered to be promising along with silicon nitride sintered bodies as one of the encinaging ceramics, and many proposals have been made regarding silicon carbide sintered bodies and methods for producing the same. Regarding manufacturing methods, reaction sintering method,
Examples include hot press method and pressureless sintering method. In the reaction sintering method, for example, a carbonaceous molded body is impregnated with metallic silicon and the two are reacted at a reaction temperature to form a silicon carbide sintered body, which can be sintered into any complex shape with almost no firing shrinkage. Although there are advantages such as gaining a body, it is about 1400″
There is a drawback that the strength suddenly decreases in C.

The hot press method uses a boron compound, a carbon source material, and a fully bent aluminum l-. This method involves adding and mixing a small amount of aluminum sulfide to silicon carbide powder and subjecting it to high-temperature, high-pressure treatment.Compared to the reaction sintering method and Tsunetsuji sintering method, a high-strength, high-rich sintered body is generally produced. . However, these real press baked 16
The body also has high temperature stability and oxidation resistance of silicon pentoxide.
Heat-reducing German J? In order to make use of its excellent physical properties such as lactic properties and to utilize it as a gas-kuhin member or other high-temperature structural material, it is required to have high strength not only at room temperature but also at high temperatures. Hot-pressed sintered bodies that satisfy this requirement are finally being developed.

In other words, JP-A No. 55-47275 has a sintered body made of only carbide powder that has been specially treated, and JP-A No. 55-6757
No. 2 contains aluminum nitride and/or boron nitride additives, and JP-A-55-167179 and JP-A-56-9277 contain aluminum powder or aluminum phosphide additives.
JP-A-56-92168 discloses a magnesium source addition system,
Japanese Patent Publication No. 1983-. No. 92169 describes a silicon carbide sintered body which has a high strength even at high temperatures and is added with a chloride content, a boron content, or an aluminum content. However, all of these are based on the hot press method,
Because of the disadvantages of being limited to extremely simple shapes and having poor flexibility in shape, they are still not satisfactory as truly useful engineering ceramics.

The pressureless sintering method is a method in which a compact of silicon carbide powder, which is inherently difficult to sinter, is sintered at atmospheric pressure or near atmospheric pressure by adding an appropriate sintering aid. Although it is possible to obtain a high-density, high-strength sintered body of any shape, its strength, particularly its high-temperature strength, is still insufficient or it has other drawbacks. That is, Japanese Patent Publication No. 57-4257
No. 7 describes a silicon carbide pressureless sintered body to which a small amount of aluminum oxide is added, but its 1400°C bending strength is only 58 K g/ll1 m2 at most, and the Although the carbonaceous-added silicon carbide pressureless sintered body did not show a 1200° O+living strength of 71 Kg/mm2, it required an additional silicification treatment step after the split-pressure sintering R1, and the 14
It is thought that the strength suddenly decreases near 00°O.

The present inventor has conducted repeated experiments with the aim of finding a silicon carbide sintered body that has properties comparable to or better than that of hot-pressed bodies even when using the pressureless sintering method instead of using the real press method, and has already done so. We have made several proposals, and now we have discovered that a silicon carbide sintered body containing a specific amount of aluminum compound can be prepared by an atmospheric pressure sintering method. The present invention was based on the discovery that it is particularly excellent in physical properties such as strength and strength.

That is, the present invention provides aluminum nitride, aluminum oxynitride, and aluminum oxide carbide.
3-25 weight paper% (Hereinafter, unless otherwise specified, weight% is simply %)
(abbreviated as), l1la element resistance 0.2-15
% and the remainder silicon carbide.

The sintered body of the present invention has three essential components.

The first is silicon carbide, which is the main component. The silicon carbide in the sintered body of the present invention may be α-type, β-type, or a mixture of both.

Among these, those in which the α-type accounts for 50% or more, especially 80% or more are preferred, and among the α-type, those in which the macrogonal type, especially the 4H type, are predominant are preferred. These silicon carbides have a polycrystalline structure in the sintered body, and the individual crystal grain size is generally about 10 mm or less, preferably 5 μm.
It is below that level.

On the other hand, the crystal type of the silicon carbide powder used as a raw material may be α type, β type, or a mixture of both. In this case, 4. 'F constant crystal form is not preferable, but rather whether silicon carbide powder is α type, β type, hexagonal type, rhombohedral type, cubic type, 4H type,
6H type.

It is preferable that the purity of any of the 3CIQ and the like is 80% or more, especially 90% or more at least at any level. Furthermore, it is often preferable that the crystal type of silicon carbide in the sintered body is different from the crystal type of the raw material silicon carbide powder. The reason for this is thought to be that these crystalline particles grow with phase transition and form a fine structure consisting of interlaced plate-like particles. The particle size of the raw material silicon carbide powder is preferably about 5 lm or less, particularly about lm or less, but is not necessarily limited to this. The higher the purity of the raw material silicon carbide, the better it is, but impurities that are usually unavoidably mixed in, such as silicon, silicon dioxide, carbon, and gold, which are the ingredients for silicon carbide synthesis. etc., and handling of silicon carbide powder 17) There is no problem even if there is a small amount of silicon dioxide produced by liquefaction on the particle surface. It is a compound '11', specifically one or more selected from aluminum nitride, aluminum oxide, and aluminum oxide carbide (excluding cases where only aluminum nitride is used). This second component, in cooperation with the oxides of the l1la group elements described later, is greatly involved in the development of the high temperature and high strength of the special number Koyaki-shiki Kichiro.
I believe that Here, aluminum oxynitride (hereinafter abbreviated as A-○-N) is a compound consisting of oxygen, nitrogen, aluminum, and aluminum, and is expressed by the general formula %. This sentence A-〇-N was published by W, Rafanell O and others in the Journal Our American and Ceramic Society magazine (J,
Synthesis and identification are possible by the method described in Amer, Geram, Soc, October 11, 181, page G-128. Also, aluminum oxide carbide (hereinafter referred to as T A l
(abbreviated as -0-C) is a compound consisting of oxygen, carbon, and aluminum, and is expressed by the general formula (%). This A-0-C can also be synthesized and identified by the same method as in the case of Humanities-0-N. The second component of the present invention may be any of the above three types, or -0-C* alone, or a combination of two or more of the above three types, but A or -0-N alone, or Aluminum nitride and A
A combination of 4-0-N is preferred. The use of A-0-N Shikawa has the advantage that the sintering temperature can be lowered than when using only aluminum nitride.

Such a second component is 3 to 25% in the silicon carbide sintered body.
%, especially 4 to 20%, especially 5 to 15%. If it is less than 3%, the strength at high temperatures will not be sufficient, and if it is more than 25%, the characteristics of a silicon carbide sintered body will be insufficient.
The effect of the present invention is more prominently exhibited at 20%, particularly 5 to 15%.

The third component is an oxide of a group IIIa element. It is believed that this third component functions in conjunction with the aforementioned second component to impart sinterability to the silicon carbide particles in the scratches. Here, the IIIa group elements are scandium, yttrium,
It refers to at least one of the elements with atomic numbers 57 to 71 and 89 or higher. Therefore, in the present invention, the 111a-radiating element may be used alone or in combination of two or more. The acetide of the IITA element is preferably one or more selected from indium butyride, lanthanum oxide, and cerium liquefaction, particularly isotrium oxide. Furthermore, if we also take into account the second component, Afl-0-N
Particularly preferred is the combination of K1 and ibu-1lium oxide. This third component is present in the silicon carbide sintered body from 0.2 to
15%, especially 0.5-8% is important. If it is less than 0.2%, sinterability will be insufficient, and if it is more than 15%, the grain boundary phase components will be too large, both of which will result in insufficient strength of the sintered body. The effects of the invention are more clearly expressed.

In the sintered body of the present invention, the second component and the third component are mainly present in the silicon carbide grain boundaries, and it is preferable that they are, but conversely, they are mainly present in the silicon carbide crystals. I don't mind. It is also possible that the second component and the third component may exist as separate tissues, or that at least some of them may exist in a structure in which both components form a compound and fuse into one. A lot, and this is preferable. Among these, it is preferable that at least most of the second component and the third component form such a compound and are considered to exist as a fused and integrated structure. Further, the smaller the grain boundary phase in the sintered body, the more preferable it is from the viewpoint of high-temperature strength. In any case, it is important that the sintered body of the present invention has second and third components that can be assigned by elemental analysis.

As the raw material for the second component of the present invention, powders of aluminum nitride, A-0-N, and A-0-C produced by various manufacturing methods can be used, and are preferred.

It is desirable that these raw materials have high purity, or they may contain impurities such as metallic aluminum, aluminum oxide, aluminum carbide, and metals other than aluminum due to the manufacturing method or handling. Metal aluminum, aluminum oxide,
Even when using powder such as aluminum carbide, it can be crushed, mixed,
There is no problem as long as these are substantially converted into the second component in the sintered body through chemical changes during processes such as molding, pre-sintering, and sintering.

Similarly, the raw material for the third component is IIIa produced by various manufacturing methods.
Powders of group element infusions can be used and are preferred. It is desirable that these raw materials also have high purity, but there is no problem even if they contain metals other than Group IIIa as unavoidable impurities. In addition, even if powders such as hydroxides of group IIIa elements, group l1la elements, sulfuric acid, nitrates, organic acid salts, or other salts of group l1la elements are used as raw materials for the third component, pulverization, mixing, molding, preparatory There is no problem as long as these are substantially converted into the third component in the sintered body through a chemical change in the process such as sintering or sintering.

The particle size of the powder of these second component raw materials and third component raw materials is 5.
The thickness is preferably about μm, particularly about 1 μm or less per piece, but is not necessarily limited to this.

The sintered body of the present invention is produced by subjecting the powder mixture, which is the raw material for these essential components, to further ball milling as necessary.
It is conveniently obtained by molding into a desired shape and sintering the molded body under normal pressure.

For molding, any method commonly used for molding ceramics can be used. That is, press molding, pick-and-slip cast molding, injection molding, extrusion molding, etc. are suitable.

Pressureless sintering is a sintering method that does not actively use pressure as the driving force for sintering, and is a sintering method that does not actively use pressure as a driving force for sintering. The pressure of I may be approximately atmospheric pressure, or may be appropriately pressurized to maintain convenient atmospheric conditions, or may be under reduced pressure or vacuum to facilitate degassing during sintering. It's okay. ♂Environment l
A non-acid dead weight of 4 is preferable, and alkone, helium, nitrogen, hydrogen, carbon oxide, etc. can be used, and the first two are particularly convenient because they are generally inert.

On the other hand, on the sintered surface (Jl and aluminum nitride, A-0
A nitriding atmosphere may be desirable in order to generate -N or suppress their decomposition, and in this case nitrogen, ammonia, etc. can be used. In some cases, it may be desirable to use an atmosphere containing aluminum element or aluminum compound in order to promote the formation of the second component or to suppress the decomposition of the second component. It is appropriate that the lining of the sintering furnace be made of aluminum oxide, aluminum nitride, or the like. The sintering temperature in the pressureless sintering method is 1,900 to 230,000. 200 for wounds
0 to 2200'O is preferable. Also, the sintering time is usually
A suitable time is 1 to 24 hours, preferably 2 to 15 hours.

The sintered body of the present invention can be sintered by the above-mentioned pressureless sintering method, but is not limited to this method, and can also be obtained by a hot pressing method or a hot isostatic pressing method. In the Honto press method, the molded body is heated at 1950 to 2100°C for 1
It is preferable to hold it for 1 to 5 hours under the condition of 00-500 Kg/0 m2. In addition, in the hot isostatic pressing method, the molded body is heated at 1900-2100℃ and 1000-200℃
i-s B under the 0Kg/0m2 row Ino I! It is preferable to hold it for 4 hours. Thus, in the present invention, nitrogen, helium,
Regarding argon, J'1 to 2000 kg/cm' can be adopted.

Regarding the physical properties of the sintered body of the present invention, first, the theoretical density is 0.9
One example is that the density is 0 times or more higher. Second component 4
~20%, and when the third component is 05 to 8%, the density is 0.95 times or more higher than the theoretical density, and the second component is 5 to 8%.
15%, No. F: In the case of component 0.5 to 8%, the theoretical density is often 0.98 (i'9 or more -1-) high density. That is, the three-point bending strength is Go, Kg/'mm2 or more, and in particular, the second component is 4 to 20%, and the third component is 0.5 to 20%.
In the case of 8%, it is often 70Kg/mm2 or more. Another point is that it has high strength at high temperatures. In other words, the three-point bending strength at 1400°C is 55 kg/
mm2 or more, and in particular, when the second component is 5 to 15% and the third component is 0.5 to 8%, it is often 70 Kg or more. Regarding bodies, hot-pressed sintered bodies and hot isostatic pressed sintered bodies often exhibit physical property values that are generally equal to or higher than these.

The unexploded ψ will be explained below using an example.

(Example) In Table 1, Examples 1 to 5 are Examples, and Examples 6 to 10 are Comparative Examples. Unless otherwise specified, each side of Table 1 has a purity of 88
% or more, β-silicon carbide powder with an average particle size of 1 gm or less,
Mix the second component powder and third component powder shown in the column with a purity of 85% or more and an average particle size of about 2 gm, and
20X 20X by hydraulic forming at 000Kg/Cm2
The physical properties of a sintered body obtained by sintering a 40 mm compact under the conditions shown in the firing conditions column under the conditions shown in the sintering conditions column under the conditions shown in the sintering conditions column are shown. The bending strength is the average value of five measurements of the three-point bending strength at room temperature and 1400°C of test) 1 of 3 x 3 x 30 mm cut out from this sintered body.

In Examples 1, 2, 4, and 5, α-silicon carbide powder with a purity of 98% or more and an average particle size of 1 μm or less was used instead of β-silicon carbide powder. In Example 2, aluminum nitride powder cavities were used as filling powder, and the compact was buried in this filling powder and sintered. Example 5 was sintered by hot pressing method (200 Kg/cm2).

A-mon-〇-N used in Examples 1, 2, and 5 was prepared by mixing alumina and carbon powder at a ratio of 3:1, and firing the mixture in a nitrogen stream at 1700°C for 12 hours. 1 missing humanities-0-N minute JJ "Confession corresponds to formula A father 23027 NS. Sentence A-〇-C in Examples 3 and 4 is the above-mentioned sentence A-〇-
In the case of N, the mixed powder was heated to 1700°C in an argon stream.
, obtained by firing 2 poems 1jJl, and its analytical value is formula A sentence 2
Corresponds to 0G.

Claims (1)

[Claims] 3 to 25% by weight of one or more selected from aluminum nitride, aluminum oxynitride, and aluminum oxide carbide (excluding cases where only aluminum nitride is used), 0.2 to 15% by weight of oxides of l1la group elements, and the remainder of silicon carbide A silicon carbide sintered body.