JPS62187170A - Method of mixing sintering aid into mixture of silicon nitride particle/silicon carbide whisker - 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 mixture consisting of silicon nitride particles (St, N, p') and silicon carbide whiskers (SiCw).

The present invention relates to a method for uniformly mixing a substance that acts as a sintering aid when this mixture is molded and then sintered to form a composite ceramic product. The sintering aid targeted by this invention is
It is an oxide of yttrium or lanthanum.

When constructing structural parts such as turbines and diesel engines that are used under harsh conditions in high-temperature gases, silicon nitride (Si, N, ) is seen as the material with the greatest potential. Furthermore, the inherent brittleness of ceramics, which is much greater than that of metal materials, is found in heat-resistant fiber materials.

In particular, it is expected that significant improvements will be made by incorporating SiCw. That is, Sl, N, pt-
By combining it with 8icw, its brittleness is greatly improved and the reliability of its mechanical properties is significantly improved, and furthermore, electrical discharge machining, which was impossible with a sintered product of 5i5N,P alone, is now possible. Become.

For such a combined effect on the whisker particles, it is fundamentally important that not only these two components are mixed uniformly, but also the sintering aid essential for sintering is uniformly mixed. I bowed my head. S i5 N B
The most effective sintering aid for sintering p/S t Cw composite ceramic material raw material mixture is yttrium oxide (
y2o, ) or lanthanum oxide (La 2
It is generally known that it is a mixture of 05). These oxides are supplied in powder form, so in order to uniformly mix them with the main raw materials Sl, N, p and SiCw, it is necessary to mix them with Si, N, p and SiCw. Similarly, many difficulties are involved in preventing the destruction of the whiskers, so usually before this mixing, i.e., Sl.
After sufficiently uniformly mixing only N and P using a method such as a ball mill, it is necessary to mix with the next whisker under mild conditions to avoid damage to the whiskers.

To avoid problems associated with homogeneous mixing of such solid particles with easily damaged whiskers, nitrates or sulfates (Y(NO3)3 or Y2(S
It has been proposed to soak water-soluble salts such as O, )5) in the mixture in the form of an aqueous solution to provide a uniform distribution. But in this case.

During the subsequent sintering of Si, N, and P, NOx and SOx gases are generated, and these gases are not only harmful to the human body, but also because of their oxidizing properties.
There is a risk of oxidizing and deteriorating Cw.

The purpose of this invention is to create a mixture of Sl, N4p, and SiCw without disturbing the uniform mixing state of the two, and without causing problems such as deterioration of the material components.
An object of the present invention is to provide an improved mixing method capable of uniformly mixing a sintering aid. According to the method of the present invention, Si, N, 4p and SICw, which are mixed in advance at a predetermined mixing ratio, are mixed together. For the mixture, Y(OH) hydroxide (Y(OH) −,
) or alkoxide (Y(OR), ) is impregnated. This solution also contains lanthanum hydroxide (La(O
H), ) or a) v oxide (La(OR)s) may be contained. The solvent for such solutions is generally water or alcohol, but other solvents may be used as long as they readily volatilize under the drying and sintering conditions and do not threaten to degrade the ceramic material through this process. It is often uniformly dispersed in colloidal form in water.

Impregnation with a solution can be accomplished in a variety of ways, but generally involves placing the ceramic material mixture in a liquid-permeable container;
This can be easily done by immersing the container in the solution, and ultrasonic imaging can also be used to help exchange the air in the minute spaces in the mixture with the solution. good. Yttrium hydroxide or alkoxide% or in addition to lanthanum hydroxide or alkoxide is present in the impregnated solution, but in order for these materials to have the ability as sintering aids, the oxidation It is necessary to be transformed into the form of a thing.

Conversion from hydroxide to oxide can be carried out by removing excess solution after impregnation, further drying if necessary, and then dehydrating the hydroxide. Preferably, this dehydration treatment is carried out at a relatively low temperature, for example below 200° C., in order to prevent the generated water from having an adverse effect on the ceramic material, such as oxidation. Conversion of alkoxides into oxides can be carried out by removing excess solution after impregnation and then easily hydrolyzing the alkoxides into oxides according to a conventional method.

Through the above treatment, a sintering aid consisting of 1M yttrium (y2o) or a mixture of yttrium oxide and lanthanum oxide (Laz05) is uniformly mixed into the mixture of Si, N, p, and SiCw, and therefore the obtained The resulting mixture is shaped and sintered according to conventional methods to give a ceramic product which is very homogeneous and has good physical and mechanical properties.

S i 3 N B p/ applied to this invention method
The S i Cw mixture consists of separately produced St, N, p
and SiCw may be mixed by any method. The most preferred mixture is st, N, p, 5to2. After uniformly mixing the particles and carbon using a ball mill or other means, the mixture is heated to a predetermined temperature in a non-oxidizing atmosphere to form 'C, S.
It was obtained by converting i 02 t's i Cw. The mixture obtained by this method is.

Because each ingredient is mixed very evenly.

It gives a sintered product with significantly better properties.

It is also possible to add a sintering aid such as indium oxide in powder form to the St, N, p/SiO Depending on the conditions during the heat treatment process for converting into yttrium oxide, S
It was found that i 5 NB aggregated with p to form macroscopic colonies (<J) and showed a tendency to separate from SiCw.

Example 1 st, N, p3 each prepared separately in the usual manner
6.02 and SiCw12. Of? 5.871 colloidal slurry liquid of yttrium hydroxide 215.9 f
(Y2O, equivalent to 3/17 mol of St, N) and 200 cc of water overnight. After this immersion, run the ultrasonic oscillator for 1 hour and then.

Mixing was performed using a mixer type agitator for only 20 seconds.

After that, the water was separated by P using a Buchner funnel and 20
A sample was obtained by heating at 0±5° C. for 10 hours to perform drying and dehydration reactions.

Example 2 st, N, 4p 30. Of, 30% S i O 2 colloid aqueous solution 30, Of and carbon blank 30.
Of, CoC2 21% aqueous solution 100 CC, NaCt
20.09 were thoroughly mixed, dried at 110°C, and ground, then placed in a graphite crucible and heated to 1600±lθ°C for 1 hour.

5102 was converted to SiCw, and unreacted carbon black was removed by oxidation at 600° C. for 3 hours in air.

The resulting mixture was treated under the same conditions as in Example 1 to obtain a sample in which yttrium oxide as a sintering aid was uniformly mixed.

Comparative Example In Example 2, raw materials 5i5N, 5i5N instead of p,
p 30. Of in advance Y2O, 8, 52t (S i
, N, equivalent to 3/17 mole) in a ball mill and 30% S10□ colloid aqueous solution 30. Or, carbon black 30. Of,
CoC221% aqueous solution lOOCC, NaC220,O
It was added to f' in the same manner, mixed, dried, and pulverized, and heated under the same conditions to convert it into 8102 tsicw, to obtain a sample from which unreacted carbon blank was removed.

The samples obtained in Example 1.2 and Comparative Example were used.

1800 in a graphite crucible whose inner wall was coated with boron nitride.
℃.

Three types of sintered products were obtained by hot pressing at 400 Kv'cm for 60 minutes. From each sintered product, a square bar-shaped test piece with dimensions of 3 x 3 x 40 m was cut out,
For each, the three-point bending strength was determined under the conditions of a lower span of 20 degrees and a crosshead speed of 0.54. The results obtained are shown in Table 1. Each sintered sample was tested three times under the same conditions, and the results are indicated by Q■■.

Next, in Example 2, 1 of the molar amount of y(oH) used
Strength test on test pieces obtained under similar conditions when using both in place of /2t-L a (OH)5 and using an ethanol solution as the ethoxide of equimolar 'k Y * La of both. The results are shown in Table 2.

(Note) In Table 1.2 above, only the bone specimen has adult homogeneous colonies scattered inside.

Patent applicant Patent attorney representing Industrial Development Research Institute Foundation 1) Hiroshi Sawa (2 others)
- Procedural amendment (spontaneous) To the Commissioner of the Japan Patent Office: 1. Indication of the case: Japanese Patent Application No. 61-29937 2. Title of the invention: Silicon nitride particles/silicon carbide Quisker mixture with sintering aid 3, ? Relationship with the case of how to mix the i-correction method
Patent Applicant Address Name Industrial Development Research Institute 4, Agent Postal Code 105 Address
1-4-10 Nishi-Shinbashi, Minato-ku, Tokyo, Column 6 of the detailed description of the invention in the specification subject to amendment, Contents of the amendment (1) Page 8, line 5 and page 8, line 19 of the specification Correct "Carbo/Black 30.OfJ" to "Rikiichibo/Black 10.OfJ" respectively.

121 “100” on page 8, line 6 and page 8, line 20
c, cJ f respectively "10. Correct as Oeel.

that's all

Claims (2)

[Claims] (1) A step of impregnating a mixture of silicon nitride particles and silicon carbide whiskers with a solvent solution of yttrium hydroxide or alkoxide, and a step of converting the impregnated hydroxide or alkoxide into yttrium oxide. Also, a method of mixing a sintering aid into the silicon nitride particle/silicon carbide whisker mixture. (2) The method according to claim 1, characterized in that in addition to the yttrium hydroxide or alkoxide, a lanthanum hydroxide or alkoxide is used.