JPH0218360A - Silicon nitride-base ceramics material - Google Patents

Abstract

PURPOSE:To obtain the titled ceramics material which has high strength and high reliability and is inexpensive by molding, degreasing and sintering a compsn. composed of Si3N4 powder, aluminum chelate compd., yttrium chelate compd., and specific org. material. CONSTITUTION:The compsn. is obtd. by mixing 40-70vol.% Si3N4 powder having <=1mum average grain size and >=10m<2>/g BET specific surface area, 0.5-10wt.% (in terms of metal) aluminum chelate compd. (e.g.: acetoalkoxy aluminum diisopropyrate), 0.5-10wt.% (in terms of metal) yttrium chelate compd. (e.g.: acetoyttrium diisopropyrate), and 10-30vol.% org. matter selected from resins and wax. This compsn. is then molded and after the molding is degreased by heating at <=800 deg.C in the atmosphere, the molding is sintered at 1,600-2,000 deg.C in a nonoxidative atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to silicon nitride matrix ceramic materials which are highly reliable and advantageous in terms of economy.

(Prior Art) Generally, the strength of ceramics is affected by porosity, crystal grain size, and surface condition. These factors also govern the strength of 513N4, which is attracting attention as a structural ceramic. Si3N4
In an attempt to improve the strength of sintered bodies, sintering aids and sintering methods are being developed. For example, for hot press sintering, AmsCeramv 5oc1Bull +
52 (+973), 5801 bending strength ~100kg/
w”, and for pressureless sintering, 1981 Ceramics Association Annual Conference Lecture Proceedings (1981), 178I ~I 00 kg/@II
In both cases, strength is improved by minimizing porosity.

Also, 5i3tJ+ using Y2O3 as the main sintering aid
-Y2O3-AQ20a-based silicon nitride sintered body manufacturing method is disclosed in Japanese Patent Publication No. 49-2109, Japanese Patent Publication No. 48-3844
It is disclosed in Publication No. 8. These are Y2O3, A(
Mainly using oxide powder such as Y2O3, after going through a grinding and mixing process with Si3N+ powder, shaping and sintering,
A sintered body is obtained through a predetermined process.

(Problem to be solved) In the conventional technology described above, the auxiliary agents are YzO3 and AQ203.
It is a hard material, and since each primary particle is fine and highly cohesive, there are limits to pulverization and mixing, and it is extremely difficult to pulverize and mix to a submicron size or smaller. Even uniform mixing has its limits.

Furthermore, impurities from the media used for pulverization are unavoidable, and these remain in the sintered body and cause defects and uneven structure of the sintered body, resulting in decreased strength and reliability. There was a problem in that it caused a decline in sexuality.

Furthermore, the above-mentioned method mainly involves molding the auxiliary mixed powder by die pressing or cold isostatic pressing, and is not suitable for mass production of complex-shaped products. On the other hand, injection molding is an excellent mass production molding method because the organic material and auxiliary powder are mixed and molded, but as it requires sufficient kneading, the above-mentioned pulverization and mixing and contamination of impurities cannot be avoided. Furthermore, since a large amount of organic material is required, there are problems such as cracking of the molded product during the degreasing process.

(Means for Solving the Problems) The present invention has high reliability by minimizing the non-uniformity and contamination of impurities when mixing the above-mentioned auxiliaries, and by adding moldability that is excellent in mass production. The purpose is to provide an inexpensive silicon nitride matrix ceramic material, which has the following characteristics: 40 to 70% by volume of silicon nitride powder, and 0.0% of each of aluminum chelate compound and yttrium chelate compound in terms of metal content.
It is obtained by molding, degreasing, and sintering a composition consisting of 5 to 10% by weight of an organic material selected from resins and waxes in an amount of Iθ to 30→n% by volume.

(Function) According to the ceramic material of the present invention, by adding an aluminum chelate compound and a yttrium chelate compound to the silicon nitride raw material powder, a uniform film is formed on the surface of the silicon nitride powder, and an organic material for molding is formed. improve compatibility with Additionally, this chelate compound forms a uniform film of aluminum and buttrium oxide required during sintering on the surface of the silicon nitride powder during the degreasing process, resulting in uneven mixing of the auxiliary agents, contamination of impurities when mixing the auxiliary agents, and It works to solve various problems such as the occurrence of cracks in the degreasing process due to the reduction in the amount of 11-material by improving the kneading properties of organic materials for molding.

In order to bring about the best effect of the ceramic material of the present invention, the average particle size of the silicon nitride raw material powder is 1 μm or less, preferably 0.5 μm or less, and the specific surface area (BET) is IO +
Use powder weighing more than //g. The amounts of the aluminum chelate compound and the yttrium chelate compound are each preferably 0.5 to 10% by weight in terms of gold am. 0
．． If it is less than 5% by weight, the sinterability and affinity with the organic material for molding will be insufficient, and if it exceeds 10% by weight, it will cause a decrease in the strength of the final sintered body, especially the high-temperature properties, and it will also cause problems in the finger removal process. This may cause cracking or blistering of the molded product. Each chelate compound can be used after being diluted with an appropriate amount of solvent, and an organic material for dispersion may be used together with the chelate compound to reduce agglomeration of the silicon nitride raw material powder.

After stirring the above mixture using a high-speed mixer or the like, 10 to 30% by volume of an organic material for molding is further added. In this case, if the filling is less than 10% fi, it is not possible to impart appropriate fluidity to the molding mixture, and if it exceeds 3G volume ffi%, the molded product will crack or bulge during the finger removal process.

Such a mixture is kneaded using, for example, a pressure kneader and used as a molding mixture for injection, extrusion, and the like. After molding, the molded body is detrl-removed by a known de-fingering method, but in particular the chelate compound is decomposed and AQ is added to the surface of the silicon nitride powder.
To form a film of oxides of zOa and Y2O3, it is heated in the atmosphere at ~800°C.

With the above effects, the time required to prepare a molding mixture is significantly shortened compared to conventional methods, and its uniformity is also improved. Mass production molding such as injection molding and extrusion molding is also possible.

The ceramic material of the present invention is obtained by sintering the thus obtained molded body after degreasing and oxide film treatment at a non-oxidizing atmosphere I of 800 to 2000°C. The ceramic material of the present invention has excellent sinterability because the oxide as an auxiliary agent is uniformly mixed therein, and there is very little non-uniformity introduced during sintering, so it has high reliability. It becomes a ceramic material.

(Example) Unidirectional particle diameter 0.37jm 1BET a 11.5n?
/g, tx condensation rate=! ls, o% of silicon nitride powder, 2% by weight of each of acetalkoxyaluminum diisopropylate and acetoytrium diimpropylate as chelate compounds in terms of metal content.
and 4.5% by weight diluted in n-propertool and heated at 80°C.
The mixture was stirred for 15 minutes at SOO rpm. Add 10% of the organic material for molding (Celna NE-511 manufactured by Middle East Yushi Co., Ltd.) to the above.
After adding % by weight and kneading in a pressure kneader at 120°C, injection molding (secondary injection pressure 750 kg/cJ), IO
15 molded bodies were made in 1 x IOX 50m.

This molded body was heated to 50℃ for 5 hours, to SOO℃ for 8 hours, and then to 800℃ for 5 hours, and then heated to 800℃.
It was kept in the atmosphere for 15 hours. After sintering the above molded body in a N2 atmosphere of 5 atm at 800°C for 6 hours, JISR1
After polishing into a 601 test piece and finishing the tensile strength with diamond paste, it was subjected to a JISRIGO 13-point bending test.

Result is Average bending strength　135　kg/explosion♂ Weibull series number 25 A ceramic material with high strength and high reliability was obtained.

(Effects of the Invention) As described above, the silicon nitride matrix ceramic material of the present invention has significantly higher strength than the conventional 5iaN4-based sintered body, and can be applied to various mechanical structural parts. Automobile d1 requires mass production, low cost, and high reliability.
It is extremely effective when applied to products, etc.

Claims (1)

[Claims] (1) Consisting of 40 to 70% by volume of silicon nitride powder, 0.5 to 10% by weight of aluminum chelate compound and yttrium chelate compound each in terms of metal content, and 10 to 30% by volume of organic material selected from resin and wax. A silicon nitride matrix ceramic material obtained by molding, degreasing and sintering the composition.