JPH03159968A - Bonding of ceramics of boron nitride - 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] [Summary] Regarding a method for joining silicon nitride ceramics, the purpose of this method is to bond silicon nitride ceramics with excellent adhesive strength even at high temperatures. The method for joining silicon nitride ceramics is characterized in that a mixture with an organic silicon compound is applied and brought into contact, and heated in a nitrogen gas atmosphere at a temperature at which the metal silicon can be changed into silicon nitride.

[Industrial application field]

The present invention relates to a method for joining silicon nitride ceramics that has excellent adhesive strength even at high temperatures.

Silicon nitride (hereinafter referred to as SL3N4) exhibits high mechanical strength even at high temperatures exceeding 1,000°C, and is known as a lightweight material with excellent thermal shock resistance.

That is, Si3N. is stable even at high temperatures,
Although it has a light specific gravity of 3.185, it has a high Mohs hardness of 9, and has unique properties such as being uncorrupted by high-temperature molten metal.

For this reason, practical applications such as cutting tool blades and crucibles and nozzles that require high-temperature corrosion resistance are underway, but it is also expected to be used in a wide range of fields such as the construction of ceramic turbos and various structural members. has been done.

[Conventional technology]

Si. When N4 ceramics are used as structural members, it is often necessary to bond the ceramics that make up the structural members.

As you can see, mechanical shrink fitting is the method for joining ceramics. The adhesive method, active metal method, brazing method, etc. are known.

However, such a bonding method does not provide adhesion that exhibits high mechanical strength even at high temperatures such as 800 to 900°C.

The reason for this is that these joints are performed using a solder material or adhesive whose usable temperature is much lower than that of S+ 3N4 Ceraminox.

Therefore, S' exhibits excellent mechanical strength even at high temperatures.
It was not possible to take advantage of the characteristics of iJn ceramics.

[Problem to be solved by the invention]

When using Si3N4 ceramics as a structural member and using it at high temperatures by taking advantage of its heat resistance, it is often necessary to bond the ceramics together.

However, conventional bonding methods cannot withstand high temperatures, so the characteristics of SiJ4 ceramics cannot be utilized.

Therefore, the challenge is to put into practical use a bonding method with excellent heat resistance.

[Means to solve the problem]

The above problem was solved by applying a mixture of metal silicon and an organic silicon compound to the joint of a molded body made of Si3N + Cera5 sox and contacting the joint, and in a nitrogen gas atmosphere, the metal silicon was bonded to Si3Ng.
Si3N is characterized by being heated at a temperature that can change to
This problem can be solved by carefully considering the method of joining 4 ceramics.

[Effect]

Initially, the inventor used metallic silicon (Si) in a nitrogen (N2) gas atmosphere as a method for bonding Si3N4 ceramics together.
) We considered joining using powder as a binding material.

However, in this case only a weak bond is obtained.

The reason for this is that when Si is nitrided, the next exothermic reaction occurs rapidly.

4Si(s) + 2Nz(g) 1Si*Nn(s
) −{t+ΔGy =153.61 Kcal/m
(The nitriding reaction of Equation 11 occurs rapidly, so it is difficult to control the reaction rate, and many voids are created at the joint, making it impossible to obtain a strong bond.

Therefore, the inventor proposed (as a method to control the reaction of formula 11) that SiJ4 decomposes when heated in a N2 atmosphere.
The nitriding reaction can be controlled by adding an organic silicon compound to Si powder and using it as a binder.
It was discovered that there were no voids and a strong bond could be formed.

Note that organic compounds have thermoplasticity and are in a molten state at high temperatures, so they also have the advantage of functioning as a binder.

Note that some organosilicon compounds are solid at room temperature, but in that case, the organosilicon compound is dissolved in a solvent before use, or the organosilicon compound is heated and melted, and Si is added into the solution. It is sufficient to use powdered adhesive as an adhesive, and experimental results showed that the latter was more effective.

From this table, the organic silicon compounds useful in the practice of the present invention include polysilazane: lINcl+3 (SiHzNCl{
J+ all vorisilane: ((CH3) zs
i) 2112 polyporosiloxane: ((CJs)
zsiOB(0)z) Polycarbosilane: (-St
-C-).

For example, it is desirable to use a material that has a high rate of transformation into ceramics when heated.

In method 1 of the present invention, first, a composite consisting of an organosilicon compound that can be efficiently converted into ceramics by thermal decomposition at high temperatures and metal St powder is applied to both sides of the ceramics to be bonded.

Then, when both ceramics are pressed together and heated to 1200°C in an N2 atmosphere, the organic nitrogen compound decomposes and becomes nitrided to form amorphous S43N4, covering the Si powder, and the Si powder is also nitrided. Proceed to Si3
becomes Na.

Then, it is heated at this temperature to advance sintering, and after completion of the sintering, it is precipitated/crystallized and taken out.

〔Example〕

N
The mixture was melted by heating to 300°C in 2 atmospheres ψ, and the S1 powder having an average particle diameter of 1 μm was mixed without stirring to prepare adhesive A.

Next, a separately prepared circle with a diameter or loam of 30 degrees in length↑. ) shape with a relative density of 99% or more. Apply the above adhesive to the bottoms of the two sintered bodies using a spatula,
It was cooled while it was tightly fixed.

This was placed in a Hoso 1 press, heated to <1200°C under N2 atmosphere without pressurization, heat treated for 1 hour, and then a pressure of 50 MPa was applied for 30 minutes at the same temperature. Ta.

The solid line 1 in Figure 1 is the result of a high-temperature tensile test of the bonded body obtained in this way.
Cu-Ti) ゛7l! 60 using I type metal brazing material
The results of the high-temperature tensile test are shown by the broken line 2, which were bonded at 0°C.

As is clear from this figure, Si3N in which the present invention was implemented
4 Ceraminox has a tensile strength of about 160 MPa at room temperature, and no decrease in tensile strength is observed up to 1000'C, whereas the tensile strength of Si:lN4 Ceraminox bonded by the active metal method is 130 MF). It is small at a, and decreases rapidly from about 800'C.

〔Effect of the invention〕

Consisting of Si powder and an organic silicon compound according to the present invention, N
2 Bonding materials used in atmosphere siJ. Ceraminox is substantially bonded with Sj3N4, so it has excellent heat resistance and can be used in an expanded range of fields as a structural member.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the high temperature tensile test results.

Claims (1)

[Claims] A mixture of metal silicon and an organic silicon compound is applied to the joint of a molded body made of silicon nitride ceramics, the mixture is brought into contact with the joint, and the mixture is heated in a nitrogen gas atmosphere at a temperature at which the metal silicon changes to silicon nitride. A method for joining silicon nitride ceramics.