JP2673717B2 - Sintering method of silicon nitride ceramics - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for sintering and joining silicon nitride ceramics.

The present invention relates to a ceramic tube, rod,
It includes crucibles and furnace structure.

[Conventional technology]

When manufacturing various machines and structural parts using ceramics, the joining method is effective and used, avoiding cutting and molding which are expensive and difficult methods.
The conventional technique is to metalize the bonding surfaces of the ceramic objects or to use a metal brazing agent (insert) without metallizing (for example, JP-A-58-120578 and JP-A-62-263044). And a method of using oxide-based glass-forming ceramics as an adhesive. Although the present invention belongs to the latter, there is a method described in the following patent document as a conventional technique.

A method of obtaining a silicon nitride bonding member by using Al ₂ O ₃ —SiO ₂ —MnO-based glass that has been melted and crushed in advance as an adhesive and heating at 1400 ° C. This method produces a liquid phase,
This is a joining method which is characterized by wetting the objects to be joined, and a glassy joint is formed after cooling (Japanese Patent Laid-Open No. 34410/1972).
No.).

An adhesive powder consisting of one of silica and other oxides, cordierite, β-spodumene, aluminum titanate, and zirconia as a low thermal expansion coefficient bonding agent was formed into a lump and then applied to the bonded object at 1200 ° C. The method of applying heat treatment (Japanese Patent Application Laid-Open No. 55-94975).

SiC and silicon nitride ceramics can be used as Y, Zr, Si, Al, O, N
A method of joining with an adhesive based on a compound.

This method is characterized in that the adhesive forming the joint contains SiC or silicon nitride (Japanese Patent Laid-Open No. 58-91).
086 publication).

Bonding method using a _{MgO-Al 2 O 3 -SiO 2} -Si 3 N 4 based mixed powder as a bonding agent for silicon nitride ceramics.

This method is characterized by having a joint thickness of 20 to 100 μm (JP-A-62-148380).

However, each of the above techniques has the following drawbacks. First, it is necessary to preform a fine glass powder as an adhesive, which is expensive. Furthermore, a relatively thick joint having a thickness of 10 μm or more is likely to introduce residual stress due to thermal expansion to reduce the joint strength.
, Tries to overcome these problems by mixing low coefficient of thermal expansion materials or two layers of adhesive attachment,
A sufficiently high bonding strength has not been achieved yet. Is Mg
O-Al ₂ O ₃ -SiO ₂ powder is used, and the eutectic temperature of this system is low, so joining is easy, but on the contrary, the heat resistance of the joint tends to decrease.

[Problems to be solved by the invention]

The object of the present invention is to include silicon nitride (including sialon)
It is an object of the present invention to provide a joining method capable of increasing the joining strength and the heat resistance of a joined portion when joining ceramics.

[Means for solving the problem]

The gist of the present invention is that Y ₂ O ₃ , Al ₂ O ₃ and SiO ₂ and Si ₃ N ₄ powder having an average particle size of 1.0 μm or less are used, and their composition is
The critical composition points A, B, C, D, E shown in the equivalent percentage (e / o) of the following table shown in FIG. 1, which is a Y-Si-Al-ON system behavior diagram at 1600 ° C. An adhesive for sintering and joining silicon nitride-based ceramics, which is made to exist in a polygonal prism surrounded by points F, G, and H, is mixed with a solvent to form a slurry. By applying a thickness of 15 μm or less on the surface to be adhered, applying a pressure of 4 to 10 kgf / cm ² to the bonding surface, and heat-treating at 1500 to 1700 ° C in a nitrogen atmosphere, needles are put into the glass matrix. A sintered joining method of silicon nitride-based ceramics is characterized in that a joint structure in which the β-sialon crystals in the form of a mesh are mixed with each other in a meshed state is formed.

Next, the present invention will be described in detail.

The present invention is basically based on M-Si-Al-O- at high temperature.
It was completed by studying the behavior of N system. Here, Y is most preferable for M, but Li, Be, Be, Mg, C
One or a combination of two or more of a, Sc, Zr and Ce may be used.

The composition of the adhesive according to the present invention has a composition point A, B, C, D, E,
It exists in a polygonal solid body surrounded by points F, G, and H.

By the way, to display the composition in such a behavior diagram,
It is not possible to use atoms or weight percentages as in normal phase diagrams. Using the equivalent composition or equivalent percentage (e / o), such a behavior diagram is easy to understand. The value of equivalent composition is obtained by multiplying the number of atoms (or atomic percentage value) of each element in the compound by their respective ionic valencies, and the total of equivalent cations and equivalent anions must be equal. I have to.
That is, in the equivalent composition shown in Table 1, 3a + 4b + 3c = 2d
+ 3e is established. The composition of a compound in terms of equivalent percent is then determined by converting each cation and anion equivalent composition to a percentage separately. Table 2 shows each calculation example according to the actual example.

Now, the ratio of oxygen and nitrogen in the case of sintering using the adhesive of the present invention at 1500 to 1700 ° C. in a nitrogen atmosphere is 50 to 80 e / oN.
Is preferably within the range. The adhesive composition range on each cut surface is the area shown by the diagonal lines in FIGS. 2 (a) and 2 (b). Table 3 shows the equivalent percentage of each limit point (A to H) and the weight percentage of each compound obtained by converting the equivalent percentage. Therefore, when showing the adhesive composition range in weight _{percent, Si 3 N 4: 28.9~68.8,} Y 2 O 3: 13.7~55.8%, Al 2 O 3: 4.2~
40.5%, SiO ₂ : 0.7 to 28.5%. The reason why the silicon nitride powder having an average particle size of 1.0 μm or less is mixed is that the glass phase serves as a nucleus for crystallizing a part of the glass phase in the adhesive layer in the cooling process after melting during the bonding and sintering. . According to many experimental results, it is necessary for the silicon nitride powder to have an average particle size of 1.0 μm or less, and an appropriate addition amount is 28 to 70%.

 Next, the joining method of the present invention will be described in detail.

First, the above-mentioned adhesive powder is mixed with a solvent to prepare a slurry. The adhesive powder mixture is, for example, in n-hexane.
It is obtained by kneading for 24 hours in a ball mill and crushing a cake obtained by drying. Although ethanol is used as the solvent, the use of ethanol has the advantage that it can be applied directly to the surfaces of the members to be joined without the need for special drying to remove the binder and solvent. .
The viscosity of the slurry of powder and ethanol is adjusted so that coating can be completed, but a weight ratio of 4: 1 to 5.5: 1 is preferable.

It is necessary to polish the surfaces of the members to be bonded to R _max <1 μm. The slurry-like adhesive powder is applied to the surfaces of the members to be joined by a spray gun or the like connected to an air compressor. And the coating thickness at this time is 15 μm
Do the following. Many experimental results show a coating thickness of 15
When the thickness is less than or equal to μm, the thickness after bonding and sintering becomes 6 μm or less, and a bonded joint having high bonding strength and high heat resistance was obtained.

The objects to be bonded to which the adhesive is applied are bonded under a pressure of 4 to 10 kgf / cm ² .

The joint in the joined body obtained by the present invention has a structure in which acicular β-sialon crystals (crystals in which oxygen and aluminum are solid-dissolved in silicon nitride) are intermingled (interlocking) in the vitreous matrix. can get. Such a joint structure (including a microstructure) is suitable for avoiding a thermal expansion coefficient mismatch caused by a compositional concentration gradient in a thicker joint as shown in the conventional patent document or technology.

〔Example〕

Table 4 shows some examples of adhesive compositions used to bond various silicon nitride ceramics.

A2 to A6 are compositions within the scope of the present invention, and A1 is a composition outside the scope of the present invention as a comparative example.

Table 5 shows the adhesive composition and their effect on the bond strength when varying various process factors such as bond temperature and time.

In the range of the composition of the bonding agent of the present invention, the bonding is good, and most of them are broken except in the bonded portion. Further, even when the fracture occurred at the joint, the one having the composition range of the jointing agent of the present invention had a sufficient strength of 36.8 kgf / cm ² or more, showing a great improvement as compared with the comparative example.

[Effects of the Invention] In the joint portion of the joint body obtained by the bonding method of the present invention, needle-like β-sialon crystals (crystals in which oxygen and aluminum are solid-dissolved in silicon nitride) interlock with each other in the glassy matrix. Since the structures are mixed in the (rocking) state, a bonded body having high bonding strength and high heat resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is a Y-Si-Al-O-N system behavior diagram at 1600 [deg.] C., showing the composition range of the adhesive as a polygonal solid body. FIGS. 2 (a) and 2 (b) are 50e / oN and 80e / oN cross-sectional views of the Y-Si-Al--O-N system behavior diagram, and the respective adhesive composition ranges are ABCC- It is shown as a shaded area surrounded by D-E and F-G-H.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiro Kubo 1618 Ida, Nakahara-ku, Kawasaki-shi, Kanagawa Shin-Nippon Steel Corp. Technical Research Institute No. 1 (56) Reference JP 1-11363 (JP, A)

Claims (1)

(57) [Claims] 1. A composition comprising Y ₂ O ₃ , Al ₂ O ₃ , SiO ₂ and Si ₃ N ₄ powder having an average particle size of 1.0 μm or less, the composition of which is Y-Si-A.
The critical composition points A, B, C, D, E, shown in the equivalent percentage (e / o) of the following table shown in FIG.
An adhesive for sintering and joining silicon nitride-based ceramics, which is made to exist in a polygonal columnar body surrounded by points F, G, and H, is mixed with a solvent to form a slurry, which is coated with the silicon nitride-based ceramics. By applying a thickness of 15 μm or less on the adhesive surface, applying a pressure of 4 to 10 kgf / cm ² to the bonding surface, and heat-treating at 1500 to 1700 ° C in a nitrogen atmosphere, needle-like in the glassy matrix A method for sinter-bonding silicon nitride-based ceramics, which comprises forming a joint structure in which the β-sialon crystals of 1 are mixed with each other in a meshed state.