JPS5891074A - Manufacture of silicon nitride 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 (Technology for investigation) The present invention relates to a method of manufacturing ζ1 of silicon nitride sintered body,
Kuma 1 will discuss the improvement of place names using the HIp (High Temperature Isostatic Press) method.

(Advanced technology and its problems) In general, silicon has a resonant bonding pattern, so it is characterized by heat resistance, cocoonability, and strength.

However, since 7-10,000 is a stable material and is difficult to sinter, it has been synthesized in a porous state or made into mW by using a sintering aid.

At this point, those who failed to develop the technology were busy researching σ, and using α-type silicon nitride powder, adding 111a of the Periodic Law, and adding oxides (yttrium oxide, etc.) and alumina as a base, they were able to create a necessary i.
He discovered a method to obtain a material with easy strength by sintering the same composition with aluminum nitride and other oxides as a starting material.
% Kosho 52-3649, etc.).

[7] There are many fields in which heat-resistant materials such as silicon nitride are expected to be used at higher temperatures. In particular, when used in commercial heat engines, heat resistance at temperatures as high as 1200° C. or higher is required, and in many cases, considerable thermal stress or mechanical stress is required. For that purpose, we need ceramics made of silica (two pairs [2 moyot)] which has strength at temperature A,
Improvements in properties are expected to maintain corrosion resistance. In order to overcome this problem, the city should: ■ Reduce the number of additives to give silicon nitride properties as much as possible; ■ Find additives to form undesirable grain boundaries or grain boundary phases; or ■ Process The above measures are being considered.

If the amount of additives decreases, the sinterability will deteriorate, so sintering is performed with the help of external pressure. For example, the above (
Hot press or Hp (Q hot isostatic press) is generally known as a knotting method. Present Invention 1 - The inventors selected yttrium oxide and alumina as additives to α-type silicon nitride powder, and investigated the changes in sintering properties depending on the amounts added. As a result, even though the M addition force is 11, a comparison of 1. I found out. This result is in contrast to the microstructure, and if the amount of additives is small, columnarization of crystal grains, which increases the degree of compensation of the sintered body, is unlikely to occur, and as a result, the α-β phase transition occurs. This is thought to be due to the fact that the granular crystals have braided lines.

Regarding this, the properties of the silicon nitride powder are also mild, and when we examined the process, we found that the sintering process of the σHIP sintering method of the present invention is particularly N-required. In order to make the crystals columnar, it is preferable to carry out the heat treatment under a very strict temperature condition H-, and it has been found that this makes the grain shape columnar and contributes to improving the strength.

(Objective of the Invention) The present invention is characterized by the above-mentioned method for manufacturing a silicon nitride sintered body that can easily be made Si dense in Cm and has a mechanical strength rating of 7-1.

(Summary of the invention) What is the first non-inventive method? Add 1f4s of silicon nitride powder containing a large amount of 7I (-α type oxides of the 1117 Z group in the Kyushu Period Table represented by yttrium dioxide and alumina, and add the necessary (
1) It is preferable to use substances containing other crabmides (aluminum nitride, etc.) and oxides (titanium oxide, magnesium oxide, etc.) as additives, and add each as shown below.○ Yttrium oxide 01~ 4 Commercially available Thialumina 0.01-3I Aluminum nitride <3 # Oxide <05> These mixtures are mixed uniformly, a binder is added thereto as a caking agent, and the mixture is molded. The binders, citron and rice, are appropriately selected depending on the molding method, and in ordinary mold molding, several strokes are used, and in injection molding, for example, multiple layers of heat-resistant handle fat are used. However, in any case, since this binder is removed after molding, it does not play a role in the 1u welding and sintering composition.

After removing the binder from the powder compact formed in this way, it is sintered through the following three heat treatment steps.

(2) Heat treatment at 1600-1750°C, normal pressure, non-oxidizing atmosphere or 1400-1650°C under reduced pressure.

■ Place the heat-treated body of ■ in a glass capsule and degas it.
2. Cover the molded body with a glass layer to insulate the molded cedar body from the external environment.

■ After that, HIP treatment at 1700-2000℃,
The densification is photonized by sintering at 1000-3000 atm.

The sintered body is recovered after removing the glass.

Conventionally, a method has been invented in which the grain boundary phase is crystallized by heat treatment before photo-freezing (Japanese Patent Publication No. 56-3SS). The purpose is not to process the heat treatment, but to make the grain shape columnar. Although it is not possible to provide a clear grain growth mechanism for this heat treatment effect at the +it stage, it is generally inferred as follows.

Cooling of IJium (originally an oxide) causes anisotropic grain growth in α-type silicon nitride due to an α→β phase transition. That is, it is recognized that it causes the growth of columnar crystal grains, but the situation is different when a small amount is added, and such grain growth is less likely to occur. This is due to the presence of silica on the surface or inside of silicon nitride (7), or due to the oxygen present in the structure, the composition of the grain boundary phase is relatively 1. As a result, the grain growth effect inherent to yttrium oxide is weakened, making it difficult to grow columnar grains due to the α→β phase transition.

By intervening the step of heat treatment in an atmosphere of atmospheric pressure or lower pressure according to the present invention, the existing oxygen escapes in some form, for example, in the form of silicon oxide, creating a grain boundary phase with a good yttrium concentration. It is presumed that the effect of IJum became significant and caused the grains to become columnar. It is believed that there were two cruelties that made this invention possible.

(Example of the invention) A more detailed explanation will be given below using examples.

Example 1 95% α-phase silicon nitride powder with an average particle size of 1 μm, 2 weights of reagent-grade oxide, and further added 0.3 μm reagent-grade alumina powder. After mixing, add 5 paraffin as a binder.
1 meal plus 500K for 37 x 37 x 8 am
It was molded using f/el and degreased to prepare a sample for sintering.

This was heated to 1,650 liters at normal pressure in a flow of nitrogen gas of 3,000 liters per hour.
Heat treated for 2 hours at 1850°C, degassed by placing it in a silica glass, heated to form a glassy core, and heated to 1850°C.
Sintering (HIP) was performed at 2000 atm for 2 hours. As a result, the sintering density fk3.22r/. .

The three-point curve showed an intensity of 88 to/-. When the same composition was used without heat treatment, the densification was the same, but the strength was 45Ky/-.In the microstructure examination, the growth of columnar grains was observed in the former stage, but the latter was insufficient. Met.

Example 2 Example 1 (2) Similar method (2, composition and conditions, b
Table 2 Example 6 813N4-〇, 5 using the raw materials of Example 1 and cerium oxide with a thickness of 7 μm instead of yttrium oxide.
3[, in%0e02 0.51', % % A2
Sintering was carried out using 20B series mixed powder under the same conditions as in the example, with a density of 3.20 r/cc and a three-point bend of 1 degree 72
g/- was obtained. Enemy #1 was also composed of columnar grains.

Claims (1)

[Scope of Claims] 1) In a method of sintering a yarn composition in which silicon nitride is added with a periodic α-radiation compound and alumina by H-P (high temperature isostatic pressing), H-P sintering is performed. A method for manufacturing a silicon nitride sintered body, which is characterized in that the crystal grains are formed into columnar shapes by heat treatment under normal pressure or reduced pressure beforehand.
A method for manufacturing a silicon nitride sintered body, characterized by using silicon nitride as a phase body. 3) In claim 1 or 2, periodic table +f1. Group oxidation emission, 1-4]jJ% alumina o, oi
A method for producing a silicon nitride sintered body characterized by a coulometric capacity of ~3 mils. 4) A method for producing a silicon nitride m-structure using ittria oxide as an oxide of group 1lla of the periodic table in item 1, 2 or 3 of claim F15. 5) Claims 1, 2, or 4 further include the addition of aluminum nitride <3 nitride, other oxide <0.5 molten metal, and at least one electrode as an additive. A method for manufacturing a silicon nitride sintered body. 6) Percentage range of 1st, 2nd and 3rd terms. In item 4 or Fi item 5 In, the intermediate heat treatment temperature is 1600 to 1750°C at normal pressure, or 1400 to 16°C under reduced pressure.
A method for producing a silicon nitride sintered body, characterized in that the temperature is 50°C. 7) Claims 1, 2, and 3. 17 H engineering P treatment in Section 4, Section 5 or Section 6 C2
A method for producing a silicon nitride sintered body, characterized in that the process is carried out at 1 to 2000°C and 1000 to 3000 atm.