JPH03109269A - Sialon-based ceramics composite material reinforced with carbon fiber - Google Patents

Abstract

PURPOSE:To obtain carbon fiber-reinforced ceramic composite material having high strength at high temp. and high toughness by using carbon fiber as the reinforcement and Sialon ceramics as the matrix which comprises Yalpha-Sialon crystal of specified composition, beta-Sialon crystal and Y-contg. glass phase. CONSTITUTION:The carbon fiber-reinforced Sialon ceramic composite material consists of carbon fiber (preferable with 4-20mum diameter) as the reinforcement and Sialon ceramics as the matrix comprising Yalpha-SIALON crystal (A) expressed by formula I (0<x<=2) (preferably with 0.01-10mum major axis), beta-Sialon crystal (B) expressed by formula II (0<z<=4.2) preferably with 1-50mum major axis), and Y-contg. glass phase (C). The amt. of carbon fibers contained is 1-70vol.%, and proportion of each phase in the matrix is 0<A<50wt.%, 10<B<95wt.% and 1<C<20wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a carbon fiber-reinforced sialon-based ceramic composite material useful for manufacturing various engineering ceramics that require high-temperature high strength and high toughness.

(Prior art and its problems) Yα-Sialon is a substance in which Al is substituted in the Si position of α-type silicon nitride, 0 is substituted in the N position, and Y is interstitial solid solution, and has the formula Y-( S i, /Mri, □(0,N)16 N)
(In the formula, X is a number satisfying 0<x≦2.) This Yα-sialon has high hardness, low coefficient of thermal expansion,
It has properties as an engineering ceramic, such as excellent corrosion resistance.

However, since the sintered body of the single Yα-sialon phase has a granular crystal shape, it does not have sufficient properties such as strength and fracture toughness as an engineering ceramic. Therefore, in order to improve this drawback, Japanese Patent Application Laid-open No. 185484/1984 discloses a Yα-sialon crystal and a β-type silicon nitride S
Formula 5lb-zAlyoO,N,-,(n) (in the formula, 2 is O
The number satisfies <z≦4.2. ) A sialon-based sintered body has been proposed, which is a composite of acicular β-sialon crystals.

However, the mechanical properties of this sialon-based sintered body are not sufficient for practical use.

(Objective of the Invention) An object of the present invention is to solve the above-mentioned problems and provide a novel carbon fiber-reinforced sialon-based ceramic composite material with high high temperature strength and toughness.

(Summary of the Invention) According to the present invention, carbon fiber is used as a reinforcing material, and the formula (Il
A carbon fiber-reinforced sialon-based ceramic composite material is provided, which has a sialon-based ceramic matrix consisting of a Yα-sialon crystal represented by the formula (II), a β-sialon crystal represented by the formula (II), and a glass phase containing Y. Ru.

(Detailed Description of the Invention) In the present invention, as the carbon fiber which is a reinforcing material, PA
Both N-based and pitch-based materials can be used. The diameter of the carbon fibers is preferably in the range of 4 to 20 μm. Further, the proportion of carbon fiber in the composite material of the present invention is preferably 1 to 70% by volume. If the proportion of carbon fiber is less than 1% by volume, the reinforcing effect of the obtained composite material will not be so great, and if it is more than 70% by volume, sintering will not proceed sufficiently and the strength will decrease. So I don't like it.

In the present invention, the content ratio of each phase in the sialon-based ceramic that is the matrix is usually within the range shown below.

5<Yα-Crystalline phase of Sialon〈50% by weight10
Crystalline phase of sialon <95% by weight 1<20% by weight Glass phase containing Y
~10μm.

It is preferable that the major axis of the β-sialon crystal is 1 to 50 μm.

In addition, in the present invention, SiC and/or 5iiN are mainly used at the interface between the carbon fiber and the sialon group matrix.
Preferably, an interfacial bonded phase consisting of four phases is formed.

This interfacial bonding phase enhances the adhesion between the carbon fiber and the sialon group matrix. The content ratio of the interfacial bonding phase in the sialon group matrix is 0.1 <interfacial bonding phase 1
0% by weight is preferred.

Any method may be used to produce the carbon fiber-reinforced sialon-based ceramic composite material of the present invention as long as a composite material having the above structure can be obtained.

An example of a method for manufacturing the composite material of the present invention is shown below.

The composite material of the present invention has Yα-sialon represented by the above formula CI] as a main phase, and contains 8% by weight or less of excess oxygen with respect to the theoretical oxygen amount defined by formula (1).
It is obtained by compositing raw material powder consisting of 50% by weight or less of α-sialon powder and the balance consisting of α-silicon nitride powder and carbon fibers, and heating and sintering the composite at a maximum temperature in the range of 1600 to 2200°C.

Through such heating and sintering operation, the raw material Yαsialon and α-silicon nitride react, and the composition of the raw material Yα-sialon together with the β-sialon crystals and Y-containing glass phase transforms X in the formula A composite material reinforced with carbon fibers is obtained by generating slightly lower Yα-sialon crystals and forming a matrix.

In addition, when the raw materials Yα-sialon, α-silicon nitride, or their reaction products partially react with the carbon fibers, at the interface between the carbon fibers and the sialon group matrix,
An interfacial bonded phase is formed consisting primarily of SiC and/or Si, N, phase.

The Yα-sialon powder may be any powder containing Yα-sialon as a main phase represented by the formula (I), but it is possible to use any powder having the main phase of Yα-sialon represented by the formula (I).
Powders prepared according to the invention of No. 223009 are preferred. This proposed method consists of (a) amorphous silicon nitride powder, (b) metallic aluminum or aluminum nitride, (c)
A metal salt that produces an oxide of Y that forms an interstitial solid solution between the lattices of Yα-sialon, and, if necessary, (d) an oxygen-containing compound of aluminum or silicon, is mixed to obtain a desired Yα-sialon composition. This is a method for producing Yα-sialon powder by heating the mixture to a temperature in the range of 1300 to 1900° C. in a nitrogen-containing atmosphere. The Yα-sialon powder obtained by this method is a fine and uniform powder with a particle size of 0.2 to 2 μm, and contains almost no free carbon and metal impurities, so it does not have pores or abnormal grain growth. It is possible to provide a sintered body without

In order to improve the sinterability of the Yα-sialon powder and at the same time obtain a high-strength sintered body, the Yα-sialon powder as a sintering raw material must contain 8% by weight of the theoretical oxygen amount defined by formula (1). It is necessary to contain the following excess oxygen.

Examples of methods for containing excess oxygen in the Yα-sialon powder include a method of adding an excessive amount of an oxygen-containing compound of silicon or aluminum to amorphous silicon nitride in the preparation stage of the Yα-sialon powder; A method is adopted in which the material is heated in an oxygen-containing atmosphere. An example of the latter is a method in which Yα-sialon powder is heated to a temperature in the range of 800 to 1200° C. in an oxygen-containing atmosphere to cause the Yα-sialon powder to contain oxygen in excess of the theoretical amount. Heating time is usually 0.5 to 5 hours.

This treatment can be carried out, for example, by placing Yα-sialon powder thinly on a holding plate and leaving it in an oxygen-containing atmosphere, or by fluidizing α-sialon powder in an oxygen-containing atmosphere.

The amount of excess oxygen is 8% by weight or less, preferably 1 to 6.5% by weight, particularly preferably 2 to 4% by weight.

If the amount of excess oxygen is too large, many phases with low melting points remain in the sintered body, and mechanical properties at high temperatures are impaired.

The α-silicon nitride powder preferably has a particle size of 1 μm or less in terms of sinterability, and further contains impurities that impair the strength, corrosion resistance, and oxidation resistance of the resulting sintered body at high temperatures. It is preferable that the content is 1% by weight or less.

The blending ratio of α-silicon nitride powder in the mixture of Yα-sialon powder and α-silicon nitride powder is 30% by weight or more, preferably 50 to 95% by weight, more preferably 60 to 90% by weight.
Weight%. Within the above range, as the blending ratio of silicon nitride powder increases, the ratio of the β-sialon phase in the produced sialon group matrix increases. When the blending ratio of α~silicon nitride powder exceeds 95% by weight, the sinterability of the mixture decreases and densification of the sintered body does not proceed.

There are no particular restrictions on the method of mixing the Yα-sialon powder and the α-silicon nitride powder, and methods known per se may be used, such as a method of dry mixing the two, a method of wet mixing the two in an inert liquid, and then mixing the two with an inert liquid. A method for removing the above can be adopted as appropriate. As a mixing device, a type mixer, a ball mill, etc. are conveniently used.

In the present invention, a binder may be added to the raw material powder in order to further improve the adhesion between the sialon group matrix and the carbon fibers.

As a binder, organic silicon polymers such as diphenylsiloxane, polyborodiphenylsiloxane, polyborodimethylsiloxane, polycarbosilane, polydimethylsilazane, polytitanocarbosilane, polyzirconocarbosilane, diphenylsilanediol, hexamethyl Examples include organic silicon compounds such as disilazane.

This binder is mainly made of SiC or Si by heating.
Although converted to N4, these react on the surface of the sialon-based matrix to form new carbides, nitrides, or oxides, resulting in extremely excellent adhesion between the sialon-based matrix and carbon fibers.

The amount of the binder added may be within a range that provides the effect of the addition, but is usually 0.1 to 10% by weight based on the raw material powder.

Methods of compositing the raw material powder and carbon fibers include a method of embedding carbon fibers in the raw material powder, a method of alternately arranging carbon fibers and raw material powder, a method of placing carbon fibers in advance,
Examples include a method of filling the gap with raw material powder.

In this case, the carbon fibers may be oriented in a uniaxial or multiaxial direction, or may be used in various fabrics such as plain weave, satin weave, mock-satin weave, twill weave, spiral fabric, or three-dimensional fabric, or , can be used as chopped fiber.

The method for sintering the aggregate obtained by compositing the raw material powder and carbon fiber is to press-form the aggregate using a rubber press, mold press, etc. at a pressure of 50 to 5000 kg/ci, and then A method of sintering in a heating furnace under normal pressure or pressurized nitrogen-containing gas atmosphere, 50-5000 kg/
A method such as hot press sintering while pressurized at a pressure of ci can be adopted.

The sintering temperature is usually 1600 to 2200°C, and the sintering time is usually 0.5 to 10 hours. If the sintering temperature is too low, sintering will not proceed, and if the sintering temperature is too high, the composition will change due to thermal decomposition in the sintered body, which is not preferable.

In the present invention, a composite material with even higher density can be obtained by subjecting the composite material obtained as described above to at least one of the series of treatments described below. That is, the composite material is immersed under reduced pressure in a melt of the above-mentioned organosilicon compound or organosilicon polymer, or if necessary, a solution in which the compound or polymer is dissolved in an organic solvent, and the melt or solution is applied to the composite material. A higher density composite material can be obtained by a series of treatments in which grain boundaries and pores are impregnated and the impregnated composite material is heated. In this case, the impregnated organosilicon compound or organosilicon polymer is converted primarily into SiC or Si3N4 by heating. These are present in the grain boundaries and pores of the composite material, and at the same time reduce the pores and form strong bonds in the ceramic matrix, improving mechanical strength.

Alternatively, the above-mentioned organosilicon compound or organosilicon polymer may be applied as is or a solution diluted with an organic solvent if necessary to the composite material to eliminate open pores, or the surface may be coated and heat treated in the same manner as above. Mechanical strength can also be improved by doing so.

Examples of the organic solvent include solvents that dissolve the above-mentioned compounds, such as benzene, toluene, xylene, hexane, ether, tetrahydrofuran, dioxane chloroform, methylene chloride, ligroin, petroleum ether, petroleum benzine, DMSOlDMF, and the like. The above compounds can be dissolved in these organic solvents and used as less viscous solutions.

The heat treatment is performed at a temperature in the range of 800 to 2400°C in vacuum or in an inert gas atmosphere such as nitrogen, argon, carbon oxide, hydrogen, etc.

Further, the above series of impregnation or coating can be repeated as many times as possible.

(Effects of the Invention) The carbon fiber-reinforced sialon-based ceramic composite material obtained by the present invention has
Since mechanical properties such as high-temperature strength and fracture toughness are improved, it can be suitably used as a highly reliable structural material and heat-resistant material.

(Example) Examples and comparative examples are shown below.

Examples 1 to 5 and Comparative Example 1 Amorphous silicon nitride powder 479.2 g, Yz03 powder 59
, 4 g and 63 g of metal A2 powder were mixed in a vibrating mill under a nitrogen gas atmosphere for 1 hour. The mixed powder was filled into a carbon crucible, set in a resistance heating high temperature furnace, and heated at 1200°C from room temperature to 1200°C for 1 hour in a nitrogen gas atmosphere.
C to 1400'C for 4 hours, then 1400°C
The mixture was crystallized by heating from 1,600°C to 1,600°C on a 2-hour heating schedule to obtain Yα-sialon powder. The properties of the obtained Yα-sialon powder are shown below.

Theoretical composition Yo, 5siq, 5Alz, zso. ,
? 5NI5.25 Specific surface area 2.5bo/g Grain shape Equiaxed crystal formation phase α phase 290% Product composition (wtχ) Ynia, 2Si: 44.2 8l: 9.8
0:4.9 N:33.9 Excess oxygen amount 2.9% by weight The above Yα-sialon powder and α-silicon nitride powder (average diameter: 0.5 μm, specific surface area: 11 bo/g) are shown in Table 1. After milling for 48 hours using ethanol as a medium at the ratio shown, vacuum drying was performed at 80°C.

The obtained raw material powder and carbon fibers (T-300 manufactured by Toshi Co., Ltd., diameter 7 μm) uniformly arranged in one direction were alternately laminated so that the fiber content was as shown in Table 1. At this time, the carbon fibers were laminated in two axial directions of 0 degrees and 90 degrees, and then 1'? 50°C1250kg/e
It was held at 1M for 1 hour.

Table 1 shows the properties of the obtained carbon fiber-reinforced sialon-based ceramic composite material.

Claims (1)

[Claims] Carbon fiber is used as a reinforcing material, and the formula Y_x(Si,Al)_1_2(O,N)_1_6(
In the formula, x is a number satisfying 0<x≦2. ), a β-sialon crystal represented by the formula Si_6_-_zAl_zO_zN_8_-_z (where z is a number satisfying 0<z≦4.2), and Y A carbon fiber-reinforced sialon-based ceramic composite material with a matrix of sialon-based ceramics containing a glass phase.