JPH03285877A - Fiber reinforced ceramic composite material and fiber for reinforcement - Google Patents

Abstract

PURPOSE:To control the reactivity of silicon nitride-based fibers for reinforcement with a matrix and the adhesive property of the fibers to the matrix and to produce a desired composite effect by forming inorg. coatings having a specified compsn. on the surfaces of the fibers having a specified compsn. CONSTITUTION:When a ceramic-contg. matrix is reinforced with silicon nitride- based fibers contg. N and Si as essential components and O, C, H and metals (M) as optional components in such atomic ratios as N/Si=0.05-3, O/Si<=15, C/Si<=7 and M/Si<=5, inorg. coatings of a compd. selected among the carbides, nitrides, borides, silicides and oxides of C and groups IIA-VIIA, VIII, IIIB and IVB metallic elements or a combination of such compds. are formed on the surfaces of the fibers. The resulting inorg. fiber reinforced ceramic composite material has high tensile strength, a high modulus of elasticity, superior heat and wear resistances.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a fiber-reinforced ceramic composite material exhibiting high strength, high elasticity, and high heat resistance, and reinforcing fibers therefor.

[Conventional technology]

Ceramics, particularly heat-resistant ceramics, have superior heat resistance compared to conventional ceramics, and are therefore widely used under harsh conditions such as ultra-high temperatures, ultra-high pressures, and corrosive environments.

However, these heat-resistant ceramics usually have the disadvantage that they are weak against mechanical shock and their mechanical strength decreases at high temperatures. To compensate for these drawbacks, we have developed cermet composite materials that combine metal and ceramics, or composite materials that combine ceramics with continuous fibers made of fused silica, alumina, carbon, etc., or short fibers or whiskers made of silicon carbide, etc. is being developed.

However, the metals that make up cermet composite materials are easily oxidized at high temperatures, and the softening temperature is lower than that of ceramics, so sufficient high-temperature strength cannot be obtained. severely limited. On the other hand, the biggest drawback of composite materials with continuous fibers made of fused silica, alumina, etc. is that the production cost of these fibers is extremely high, and in addition, fused silica has a low elastic modulus, and alumina has a low elastic modulus. However, its use as a composite material is limited due to its poor thermal shock resistance.

Furthermore, carbon fiber composite materials, which can be produced in large quantities and are relatively easy to use economically, still have the drawback that they cannot be used in high-temperature oxidizing environments.

In addition, composite materials with short fibers and whiskers made of carbides and nitrides such as silicon carbide exhibit excellent durability even in high-temperature oxidizing environments, but these fibers and whiskers have a uniform thickness. Moreover, it lacks homogeneity, and furthermore, it is difficult to uniformly disperse it in the matrix. For this reason, composite materials using these as reinforcing materials lack uniformity in properties such as strength.
The reliability of the materials is low, and these fibers and whiskers cannot be mass-produced, and the manufacturing costs are high, so there are still many disadvantages economically.

Furthermore, silicon carbide fibers obtained by spinning, infusible, and firing organosilicon polymer compounds have maximum mechanical strength at a firing temperature of 1200°C, and at temperatures above 1300°C, β-3iC microcrystals precipitate, resulting in increased strength. Ceramic composite materials using this material have not been put into practical use because of the rapid decrease in the value and high cost.

[Problem to be solved by the invention]

In order to solve the above problems, the present inventors have disclosed a ceramic composite material whose surface is reinforced with silicon nitride fibers doped with boron (Japanese Patent Application No. 19512/1999).

Although this fiber-reinforced ceramic composite material has the desired effect, depending on the matrix used, the fibers may react with the matrix and there may be problems with heat resistance.
It has been found that the adhesion between the fibers and the matrix may be too strong or too weak, resulting in poor mechanical properties of the composite material.

Therefore, an object of the present invention is to control the reactivity and adhesion between the reinforcing fibers and the matrix to achieve a desired composite effect, thereby solving the problems of the prior art.

[Means to solve the problem]

The present invention achieves the above object by reinforcing a ceramic-containing matrix with silicon nitride fibers, which silicon nitride fibers contain silicon and nitrogen as essential components, and optionally contain oxygen, carbon, hydrogen, and metals. The element has the following atomic ratio N/S
i = 0.05 to 3.0/Si = 15 or less, C/5j
= 7 or less, M/Si = 5 or less (where M represents a metal), and the surface of the silicon nitride fiber is coated with an inorganic material, and the inorganic coating is made of carbon or a compound of elements HA to 1 of the Periodic Table of Elements. This is achieved by providing a fiber-reinforced ceramic composite material characterized by being made of carbides, nitrides, borides, silicides, oxides, or composites of metal elements in groups A, IIIB, and IVB. .

According to the present invention, there is also provided a novel silicon nitride fiber for use in the fiber-reinforced ceramic composite material. That is, silicon and nitrogen are essential components, oxygen, carbon, hydrogen, and metals are optional components, and these elements have the following atomic ratio N/Si=0.05 to 3, ○/Si=15 or less, C /Si=7 or less, M/Si=5 or less (however, M represents metals), and the surface is coated with an inorganic surface, and the inorganic coating is carbon or elements mA to ■A of the periodic table, ■ , carbides of metal elements of groups IB and IVB,
Provided is a silicon nitride fiber characterized by being made of a nitride, a boride, a silicide, an oxide, or a composite thereof.

In short, the present invention provides an inorganic coating on the surface of silicon nitride fibers to (1) suppress the reaction between the fibers and the matrix at high temperatures, and (2) control the adhesive force between the fibers and the matrix. The aim is to improve the heat resistance and mechanical properties of composite materials. The inorganic fiber used as (a) reinforcing material of the inorganic fiber-reinforced ceramic composite material of the present invention is an inorganic fiber containing silicon and nitrogen as essential components and oxygen, carbon, and metals as optional components. Although it does not matter whether it is crystalline or amorphous, it is preferably substantially amorphous.

That is, it is amorphous by X-ray diffraction analysis or contains a microcrystalline phase with a crystallite size (measured using the X-ray diffraction half-width method (JONES method)) of 20008 or less in all directions. Preferably. A particularly preferred crystallite size is 1000 Å or less, and an even more preferred crystallite size is 500 Å or less.

Note 1) H, P, Klug and L, E, Alexa
nder, rX-Ray DIFFRACTION
PROCED [IRES (2nd Edition),
P618~Chapter9 (1974), Joh
n Wiley & 5ons.

Further, the proportion of the microcrystalline phase is set so that the small-angle X-ray scattering intensity does not exceed 20 times that of air.

The ratio of each element constituting the inorganic fiber used in the present invention, expressed as an atomic ratio, is N/Si O, 05 to 30/Si 15 or less C/Si 7 or less N/Si 5 or less, and the preferable atomic ratio is , N/Si 0.1 to 2.3 0/Si 10 or less C/Si 3.5 or less N/Si 2.5 or less. More preferable atomic ratios are: N/Si O, 5 to 2.0 0/Si 4 or less C/Si 3.5 or less N/Si 1 or less (M is a metal element of Groups 1 to 2 of the Periodic Table of Elements) (one or more selected from the group of Can not.

Furthermore, according to the studies of the present inventors, inorganic fibers used as reinforcing fibers for ceramic composite materials have a specific small-angle scattering intensity, and are extremely effective in achieving the above-mentioned purpose. It has been found.

The properties required of reinforcing fibers for ceramic composite materials are that the small-angle scattering intensity is in the range of 1 to 20 times the scattering intensity of air at 1° and 0.5°, respectively.

A preferable small-angle scattering intensity ratio is 1 to 10 times, and a more preferable intensity ratio is 1 to 5 times both at 1° and 0.5°.
This is twice the range.

The small-angle scattering intensity detects the presence of micropores, that is, voids, or holes inside the inorganic fiber. If micropores exist in the fiber, small-angle scattering occurs due to the uneven distribution of electron density in the system. is observed.

In Guyet's theory of small-angle scattering, the scattering intensity can be expressed by the following formula.

1(h)=(Δρ)2V2exp(-h2Rg2/3)
I (h); Scattering intensity Δρ in vector measurement between inverted characters; Difference in electron density between the scattering void and surroundings Rg: Radius of inertia V: Volume of scatterer h; 4πsinθ λ λ: Wavelength of X-ray θ; Scattering angle Therefore, the scattering intensity I (h) at a certain scattering angle θ is proportional to the volume of the void with the radius of inertia Rg, and if density correction is performed, it can be used as a measure of the amount of voids in the fiber.

The measurement of small-angle scattering intensity is generally carried out by the method described in Nippon Kagaku Complete Edition "Experimental Chemistry Course 4 Solid State Physics J" (1956), but in the measurement of inorganic fibers according to the present invention, the method shown below is used. will be adopted.

[Measurement method of X-ray small angle scattering intensity ratio]

RJ-200B model manufactured by Rigaku Denki Co., Ltd. is equipped with PSPC (Position Detection Proportional Counter)-5, tube voltage is 45 KV, tube current is 95 mA, and the first and second slits are each 0.2 Mφ.
, 0.15mm diameter is used, and 100° is used every 0.02°.
The scattering intensity was measured by integrating for 0 seconds. Length 15 as sample
Cut out 18 mm of fiber, stick it uniformly in a slit of 10 mm length x 4 width, and compare the air scattering intensity at 1° and 0.5° to obtain the intensity ratio CI (silicon nitride fiber) / I ' (air)] was calculated.

The reinforcing inorganic fiber according to the present invention has a repeating unit represented by the formula - and has a number average molecular weight of 100 to 500.0.
It can be obtained by spinning polysilazane in the range of 0.00 and firing the spun fiber.

In the above formula, R', R2 and R3 are each independently a substituent or skeleton consisting of a hydrogen atom, a nitrogen atom, an oxygen atom, a carbon atom, a silicon atom and a hydrocarbon group, and R', R2 and R3 are They may all be the same or at least one type may be different.

Examples of the hydrocarbon group include an alkyl group, an alkenyl group, a cycloalkyl group, and an aryl group.

In this case, the alkyl group includes a methyl group, an ethyl group,
Examples of the alkenyl group include a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group, etc. Examples of the alkenyl group include a vinyl group, an allyl group, a butenyl group, an octyl group, a decenyl group, etc. Examples of the ryl group include a phenyl group, tolyl group, xylyl group, and naphthyl group.

In addition, as the metal, at least one selected from the group of metal elements of Groups I to II of the Periodic Table of Elements is used,
More preferred metals are those from Groups 1a and 2 of the Periodic Table of Elements.
Examples include one or more metals selected from the group of metal elements of Group Ⅰ, and particularly preferred metals are aluminum, titanium, zirconium, and the like.

Specific examples of polysilazane preferably used as the above-mentioned polysilazane include - having a repeating unit of the formula and having a number average molecular weight of 100 to 50;
000 cyclic inorganic polysilazane, dehydrated inorganic polysilazane, or a mixture thereof.

Such polysilazane can be obtained, for example, by reacting a halosilane such as dichlorosilane with a base such as pyridine, and then reacting an adduct of dichlorosilane and a base with ammonia (Japanese Patent Application No. 145903/1988). reference).

In addition, in order to exhibit even higher performance as a reinforcing fiber, it is necessary to use the silazane high polymer already proposed by the present inventors, that is, the above-mentioned polysilazane or A, 5toc as a raw material.
k, Ber, 54. p740 (1921)
, W. MScantlin, Inorganic
Chemistry, IH1972), A.
5eyFerth, U.S. Patent No. 4.397.328
The silazane polymer disclosed in the specification etc. of No. 1 is prepared by using a tertiary amine such as trialkylamine, a secondary amine having a sterically hindered group, or a basic compound such as phosphine as a solvent. A non-basic solvent, for example, a number average molecular weight of 200 to 5 obtained by adding it to a hydrocarbon and heating it at -78°C to 300°C to carry out a dehydration condensation reaction.
00,000, preferably 500 to 10,000, are suitable.

Furthermore, crosslinking -(-NHh (
n = 1 or 2), the atomic ratio of nitrogen bonded to silicon atoms and silicon (N/Si) is 0.8 or more, and the number average molecular weight is 200 to 500,000, preferably 500 to 1.
A value of 0.000 is preferred. This modified polysilazane can be produced by carrying out a dehydrogenation condensation reaction using ammonia or hydrazine (Japanese patent application No. 6
2-202767).

In addition, polymetallosilazanes proposed by the present inventors in Japanese Patent Application No. 62-223790 etc. are mainly represented by the general formula (R', R'' and R3 are each independently a hydrogen atom, an alkyl group, an alkenyl group, cycloalkyl group, aryl group,
or a group other than these groups in which the group directly bonded to silicon is carbon, an alkylsilyl group, an alkylamino group, an alkoxy group, and at least one of R', R'' and R3 is a hydrogen atom). M (OR
').

(M is one or more metals selected from the group of metal elements of Groups Royal to Group II of the Periodic Table of the Elements and is capable of forming an alkoxide; R4 may be the same or different; a hydrogen atom; is an alkyl group or aryl group having 1 to 20 carbon atoms, and at least one R4 is the above alkyl group or aryl group.) The metal/silicon atomic ratio obtained by reacting with a metal alkoxide represented by 0.001 to 60, and the number average molecular weight is 200 to 500,000, preferably 500 to 60.
50,000 can also be used.

In addition, is the repeating unit +5I82NH? and 15IH
20+, and the degree of polymerization is 5 to 300, preferably 5 to 1.
Polysiloxane No. 00 (Japanese Unexamined Patent Publication No. 195024/1986) can also be preferably used.

Furthermore, polyborosilazane proposed by the present inventors in Japanese Patent Application No. 1-69169, which mainly has repeating units represented by the general formula and has a number average molecular weight of 10
It can be obtained by spinning a polyborosilazane obtained by reacting a boron compound with a polysilazane having a molecular weight of 0 to 500,000, and firing the spun fiber.

In the above formula, R', R2 and R3 are substituents or skeletons consisting of a hydrogen atom, a hydrocarbon group, a nitrogen atom, an oxygen atom, a carbon atom and a silicon atom, and all of RR2 and R3 are the same or at least one may be different.

Examples of the hydrocarbon group include an alkyl group, an alkenyl group, a cycloalkyl group, and an aryl group.

Boron compounds to be reacted with polysilazane include organic,
Any inorganic boron compound can be used.

Examples of organic boron compounds include alkoxides, alkylborons, alkenylborons, and alkylaminoborons, and examples of inorganic boron compounds include borane, boron halides, aminoborons, and the like.

Next, in the present invention, the polysilazane obtained above is made into a spinning solution, which is then spun and fired to produce the inorganic fiber which is the component (a).

As the solvent for the spinning solution used in the present invention, a solvent that does not show reactivity with the polysilazane is used,
As such a non-reactive solvent, hydrocarbons, halogenated hydrocarbons, ethenope sulfur compounds, etc. can be used.

A spinning solution containing polysilazane exhibits sufficient spinnability by itself to be suitable for dry spinning without the addition of an organic polymer. However, in some cases, a small amount of organic polymer may be added. The concentration of polysilazane in the spinning solution is sufficient as long as the spinning solution exhibits spinnability, and although it varies depending on the average molecular weight, molecular weight distribution, and molecular structure of the polysilazane that is the spinning raw material, good results are usually obtained within the range of 50% to 98%. is obtained. Adjustment of polysilazane concentration in the spinning solution is
This can be carried out by concentrating a solution containing polysilazane or by dissolving a predetermined amount of dried polysilazane in a solvent.

Prior to spinning, the spinning solution is subjected to treatments such as defoaming and filtration to remove substances contained in the solution that have a harmful effect on spinning, such as gel and impurities. Dry spinning is convenient for spinning, but centrifugal spinning, blow spinning, etc. can also be used. In dry spinning, fibers can be obtained continuously by discharging a spinning solution from a spinneret into a spinning tube to form fibers, and winding the fibers. In this case, the hole diameter, discharge speed, and winding speed of the spinneret vary depending on the target fiber thickness and the physical properties of the spinning solution.
5mm~0.5mm, preferably 0.05m+n~
0.3f11ff11 Winding speed: 300m/min ~ 50
00 m/min, preferably 60 m/min to 2500 m/min. The atmosphere inside the spinning cylinder is not particularly limited, and normal atmosphere can be used, but at least one atmosphere selected from the group of dry air, ammonia, and inert gas is used as the atmosphere.
It is preferable to use a seed gas or to coexist water vapor or at least one of the above-mentioned non-reactive solvents in the atmosphere, and by such a method, the fibers in the spinning tube are made infusible or solidified by drying. can be controlled.

Furthermore, it is advantageous to heat the atmosphere or to heat the spinning tube, and such heating operations can favorably control the solidification of the fibers in the spinning tube. The temperature of the spinning solution is usually 20°C to 300°C, preferably 30°C to 200°C.
℃, and the atmospheric temperature inside the spinning cylinder is usually 20℃ to 30℃.
0°C, preferably 40°C to 250°C.

Since the spinning solvent remains in the dry-spun and wound fibers, if necessary, the spinning solvent may be removed under normal atmosphere, vacuum conditions, dry air, ammonia, and at least one inert gas. Residual solvent can be removed by drying the fibers under a gaseous atmosphere. It is advantageous to use heating in combination in this drying because drying of the fibers is accelerated.

Good results are usually obtained when the heating temperature is within the range of 20°C to 500°C. Furthermore, by tensioning the fibers during this drying, it is possible to prevent warpage, twisting, and bending that occur in the fibers during solidification. The tension is usually 1g/ff1I [
It is within the range of 12 to 50 kg/InflI2.

The polysilazane spun fibers obtained as described above are white but have high strength even before firing, so the fibers are first processed into a form such as yarn or woven fabric, and then fired to form inorganic fibers. Yarns, woven fabrics, etc. can also be produced.

The above manufacturing method is suitable as a method for manufacturing continuous fibers, but it can also be applied not only to manufacturing long fibers (continuous fibers) but also to manufacturing short fibers. Such short fibers can be obtained by cutting the final continuous fiber obtained by firing, cutting the continuous S fibers of a precursor, that is, polysilazane, to make short fibers, and then firing them to make inorganic short fibers. It can be produced by directly spinning polysilazane (brecasa) into short fibers and firing them into short fibers.

Since polysilazane fibers are infusible to heat, they can be fired as they are to form inorganic fibers. In this case, the calcination is preferably carried out under vacuum conditions or in an atmosphere of an inert gas such as nitrogen or argon, or a gas consisting of ammonia, hydrogen or a mixture thereof. The firing temperature is usually 500°C to 1800°C, preferably 70°C.
The temperature is 0°C to 1600°C, and the firing time is 5 minutes to 10 hours. In this firing process, the volatile components in the fibers are 30
Most of it vaporizes in the temperature range from 0 t to 600 t, so the m-fibers contract, generally causing twists and bends.
This can be prevented by applying tension to the fibers during firing. In this case, the tension is usually 1 g/mm2 to 50 kg/mm"
Those within the range of are used.

As described above, the present invention applies an inorganic coating to the surface of the silicon nitride fibers described above to control the reaction between the fibers and the matrix at high temperatures, and to optimize the adhesion between the fibers and the matrix. Therefore, the aim is to improve the heat resistance and mechanical strength of the composite material. To control the fiber/matrix reaction, select a coating material that has low reactivity with the matrix. On the other hand, if the adhesive strength between fibers and matrix is too strong, shear strength, reactivity,
The strength can be weakened by coating with a material with low wettability, and if it is too weak, the strength can be increased by coating with a material with high shear strength, reactivity, and wettability, or by adding irregularities to the coating surface. Generally, the magnitude of adhesion can be controlled by coating composition, microstructure, surface shape, thickness, and number of coating layers.

The reason why there is an optimum value for the fiber/matrix interfacial strength is as follows.

If the interfacial strength is too weak, the load sharing by the fibers will be small and the strength and elastic modulus of the composite material will not improve.

If the interfacial strength is too strong, the fracture will become brittle, and if the fracture progresses partially, the whole will be destroyed at once.

On the other hand, when the interface strength is appropriate, partial destruction due to the following reasons stops and does not lead to total destruction.

(i) The crack tip branches along the fiber direction at the fiber/matrix interface. The branching consumes energy and the stress at the crack tip is relaxed, stopping the fracture.

(ii) Extra energy is required to pull the fibers out of the matrix after crack propagation along the fiber/matrix interface.

In the present invention, coating materials effective for the above purpose include carbon, elements nA to ■A, ■ of the periodic table;
It is a carbide, nitride, boride, silicide, oxide, or composite of a metal element of group IIIB or TVB. Among them, the most effective ones are BN, SIC, Al2O3
,2rO=, c, A1203-3ID2-based oxide,
It is an Mg0-Al, 03-based oxide.

The following methods can be used for surface coating the fibers.

(1) If the CVD method-treated fiber is a continuous fiber, the fiber is placed in a high-temperature furnace (reactor).
A thread is threaded inside, and raw material gas is passed through it.

A ceramic film is obtained by thermally decomposing the raw material gas on the fiber surface.

When the treated fibers are short fibers or fabrics, the raw material gas is thermally decomposed in a batch reactor to obtain a ceramic film.

First, the surface of the raw material fiber is cleaned by methods such as (1) heat treatment in a high-temperature furnace in an inert atmosphere, and (2) cleaning with a solvent.

As the raw material gas for the CVD reaction, metal halides, metal hydrogen halides, organic metals, hydrocarbons, nitrogen, ammonia, hydrogen, carbon oxide, water, etc. are used depending on the coating material. Raw materials that are liquid (solid) at room temperature are
■ Heating and vaporizing (vaporizing), ■ Bubbling to extract the vapor of the raw material by passing carrier gas such as hydrogen or inert gas into the raw material liquid, and ■ Bubbling the raw material vapor near the heated raw material solid. It is vaporized by a method such as baking and introduced into a high-temperature furnace (reactor).

The reaction temperature varies depending on the combination of raw material gases, and is
~1800°C.

The reaction pressure is 10-'torr to atmospheric pressure. The residence time of the yarn in the reactor is between 5 minutes and 10 hours.

In addition, if necessary, the raw material gas can be discharged with high frequency energy,
The reaction may be promoted by excitation with a laser or the like to generate plasma.

The thickness of the ceramic film depends on the raw material gas concentration, reaction temperature,
Control by reaction pressure and residence time.

The preferred coating thickness is 0.01 to 5 microns.

The structure of the ceramic film can also be controlled using the above parameters. Structures such as amorphous, microcrystalline, and polycrystalline (facet structure, columnar structure, cone structure) can be produced. The strength of the film depends on these differences in structure.
The interfacial strength between the film/fiber and between the film/composite matrix changes. In controlling the strength of the ceramic film/matrix interface, a facet structure is preferred when increasing the strength, and an amorphous or microcrystalline structure is preferred when decreasing the strength.

(2) Precursor coating and firing method A ceramic film is obtained by applying a precursor to a fiber, drying it, and then firing it at a high temperature.

The raw material fibers are cleaned in the same manner as in the CVD method.

The precursor used is selected from ceramic precursor polymers, metal salts, metal hydroxides, organic metals, metal oxide sol solutions, etc., depending on the coating material. If necessary, the precursor is diluted with a suitable solvent before application to the fibers.

Drying is performed under an atmosphere such as vacuum, inert gas, nitrogen, dry air, or ammonia. Heating temperature is usually 20-500℃
℃ range.

Firing is performed in a vacuum, inert gas, nitrogen, dry air, ammonia, or other atmosphere. Heating temperature is usually 500 to 180
It is 0°C.

The thickness of the coating film is controlled by the concentration of the precursor solution applied. The film can also be made thicker by drying or by coating again after baking. In particular, the latter method is effective in cases where increasing the concentration of the precursor to increase the thickness of the film causes cracks during firing.

In addition, coating methods other than the CVD method and the precursor coating and firing method may be used.

In addition, coating treatment is performed multiple times, or
A multilayer coating can be applied by continuously performing a coating process using a processing apparatus having a plurality of CVD reactors (or coating-firing furnaces). By applying a multilayer coating, the thermal stability and interfacial strength of the fiber/coating layer and matrix/coating layer can be further optimized than with a single layer coating.

Next, manufacturing of the composite material will be explained.

The inorganic fibers obtained above can be obtained by (1) arranging the fibers themselves in the axle direction or multi-axis direction; (2) weaving the fibers into three-dimensional fabrics such as hand weaving, satin weaving, twill weaving, mosaic weaving, mixed weaving, etc.; It is preferable to employ means such as the above-mentioned method for producing a multidimensional fabric (3) method of using it as chopped fiber to exhibit its preferable characteristics.

Further, in order to manufacture fiber-reinforced ceramic composite materials suitable for various uses and purposes, other inorganic fibers can be used in combination with the above-mentioned inorganic fibers. Such inorganic fibers that can be used in combination include glass fiber, carbon fiber, boron fiber, silicon carbide fiber, alumina fiber, silica-alumina fiber, boron nitride fiber, boron carbide fiber, silicon carbide-titanium carbide fiber, etc. can.

As the volume fraction of fibers in the composite increases, the mechanical properties of the composite improve. The theoretical maximum value of the volume percentage of fibers depends on the arrangement of fibers and the structure of the fabric, so in order to make a practical fiber-reinforced ceramic composite material, the volume percentage of fibers should be between 10% and 90% (preferably 10%). %～70
%) gives good results.

The ceramic as the matrix used in the present invention can be arbitrarily selected from at least one of the known ceramics used in fiber-reinforced ceramic composite materials.
High strength and high elasticity at high temperatures, which is the objective of the present invention.
In order to more effectively provide a high-temperature material that has properties such as corrosion resistance and thermal shock resistance that can withstand extreme conditions, it is advantageous to use carbides and nitrides as the ceramic base material. However, other ceramics, such as oxides, silicides, borides, etc., can be used as the base material if the material has a more moderate resistance.

Specific examples of ceramic matrices preferable for achieving the objects of the present invention are as follows.

(1) Carbide; silicon carbide, titanium carbide, zirconium carbide, vanadium carbide, chromium carbide, molybdenum carbide, tungsten carbide, beryllium carbide, boron carbide, and other carbon materials.

(2) Nitride; silicon nitride, titanium nitride, zirconium nitride, vanadium nitride, beryllium nitride, boron nitride and aluminum nitride, and other nitrides.

(3) Oxides: alumina, silica, magnesia, zirconia, titania, mullite, cordierite, doria, borosilicate glass, high silica glass, aluminosilicate glass, nitride glass, spinel, zircon, spodunone, acid Silicon nitride, sialon, and other oxides.

(4) Ni-iron silicide, -triboron silicide, -boron silicide, -dimagnesium silicide, -manganese silicide, molybdenum disilicide, titanium silicide, cobalt silicide, and -vanadium silicide, and other silicides.

(5) Borides: chromium boride, tungsten boride, titanium boride, molybdenum boride, dimolybdenum boride, ethangestene boride, tetraboron carbide, diboron trioxide, and other borides.

(6) Others: Carbon According to the present invention, one type or a mixture of two or more of the above ceramic matrix materials can be used.

As the matrix raw material, powder of the above-mentioned ceramics, organic metal polymer, oxide zonope metal (Si
, AI, Ti, B, C, etc.), metal halide gas,
One or more of metal hydride gas, organometallic compound gas, hydrocarbon gas, and N2-NH3 can be used.

When using ceramic powder as the main raw material, an auxiliary agent (sintering aid) for promoting sintering of the powder and a molding binder are added as necessary.

As the sintering aid, common aids used in sintering carbides, nitrides, and oxides can be used.

For example, as a sintering aid for silicon carbide, BAl, Fe
, C, Be alone or their compounds, and sintering aids for silicon nitride such as magnesium oxide, aluminum oxide,
Examples include yttrium oxide.

As the molding binder, at least one of organic polymers, organometallic polymers (particularly organosilicon polymers and inorganic silicon polymers), and oxide sol solutions can be used.

Examples of organic polymers include polystyrene, polyolefin, cellulose acetate, acrylic polymer polyvinylalcono-paraffin, diethyl phthalate, and wax.

Examples of organic and inorganic silicon polymers include diphenylsiloxane, dimethylsiloxane, polyborodiphenylsiloxane, polyborodimethylsiloxane, polycarbosilane,
Examples include polytitanocarbosilane, polysilazane, polyborosilazane, polytitanosilazane, and polyaluminosilazane.

Examples of the oxide sol solution include alumina zonopecilia, zonobetitania, and zirconia sol.

Among these binders, the organic polymer needs to be removed in a degreasing step before firing the molded body, and if it is fired while remaining, it will interfere with sintering.

On the other hand, organometallic polymers (organosilicon polymers, inorganic silicon polymers) and oxide sol can be heated to produce Si3N,
SiC, 5i2N, 0. Si[l, 5in2. A
It converts into ceramics such as 1□03, or reacts with ceramic powder to produce carbides, nitrides, and oxides. As a result, the ceramic powder is firmly bonded and sintering is promoted. Therefore, these additions are advantageous for producing high-density, high-strength composite materials.

Furthermore, it is advantageous to use a polymer that exhibits less weight loss after heating as the polymer used in such applications. Such polymers include polysilazane, polyborosilazane, polytitanosilazane, and polyaluminosilazane.

The amount of the above-mentioned binder added is not particularly limited, but it may be within a range that can sufficiently obtain the effect of its addition, and in the case of organic polymers, it is about 0.5 to 5Qvo1% in the mixture with ceramic powder. is preferred.

Similarly, in the case of binders that convert into ceramics after heating, such as organometallic polymers (organosilicon polymers, inorganic silicon polymers) and oxide sols, Q is preferably 5vol% or more.

If a large amount of binder is added, sintering will be hindered and defects such as pores will appear in the matrix, but densification can be achieved by impregnating the pores with the same type of material as the binder and re-firing. .

Methods for molding the fiber-reinforced ceramic composite material of the present invention when ceramic powder or organic metal is used as a matrix raw material include filament winding method, prepreg method, slurry (resin) injection method, injection molding method, etc. .

(1) Filament winding method Roving fibers are impregnated with a slurry consisting of a matrix material such as ceramic powder, a binder, and a solvent, and then wound around a mold.

(2) Prepreg method A slurry consisting of a matrix material such as ceramic powder, a binder, and a solvent is impregnated into roving fibers and cloth, then wound up and dried to produce a sheet consisting of inorganic fibers, a matrix material, and a binder, that is, a prepreg. Create an intermediate material called

A desired shape is obtained by laminating and press-molding prepregs.

(3) Slurry (resin) injection method A preform such as a multidimensional fabric, a laminate of woven fabrics, an aggregate of short fibers, etc. is placed in a mold, and slurry is injected into the mold.

(4) Injection molding method A slurry consisting of short fibers, ceramic powder, binder, and solvent is injected into a mold.

As a method for sintering these molded bodies, methods such as normal pressure sintering, hot pressing, gas pressure sintering, and HIP are employed. The firing temperature ranges from 700 to 2500°C.

The firing atmosphere is a vacuum or an atmosphere consisting of at least one selected from nitrogen gas, ammonia gas, hydrogen gas, inert gas, hydrocarbons, and air.

In addition, 800 to 200 fiber preforms (preforms)
Alternatively, a method may be adopted in which the matrix is produced by a CVI method in which the preform is heated to 00° C., a raw material gas is caused to flow therethrough, and the ceramic is deposited. As the raw material gas, gases such as metal hydrides, metal halides, organic metals, hydrocarbons, nitrogen, and ammonia are used.

By subjecting the composite material sintered body thus obtained to the series of treatments described below at least once or more, a sintered body with even higher density can be obtained.

That is, organometallic polymers similar to those used in molding binders, especially organosilicon polymers, inorganic silicon polymers,
Alternatively, an aqueous oxide sol solution is impregnated into the pores, cracks, etc. of the composite material sintered body, and then heated and fired.

A liquid organometallic polymer can be used as an impregnating liquid as it is, but if necessary, it can be dissolved in a solvent or heated to form a melt.

As the impregnation method, a coating method, a vacuum impregnation method, a pressure impregnation method, etc. can be used.

The firing temperature ranges from 700 to 2500°C. The firing atmosphere is vacuum, nitrogen gas, ammonia gas,
At least one selected from hydrogen gas and inert gas
It is an atmosphere made up of more than just seeds.

The organometallic polymer impregnated into the pores and cracks of the composite sintered body becomes ceramic by firing, and the sintered body becomes a ceramic material.
Because the IJ socks are firmly bonded, pores and cracks that can cause breakage are reduced and eliminated, and mechanical strength and elastic modulus are improved. Furthermore, since the surface area in contact with the atmosphere is reduced, chemical stability such as oxidation resistance and corrosion resistance is also improved.

Further, the series of densification treatments described above can be repeated as many times as possible as long as impregnation is possible.

〔Example〕

Reference Example 1 [Manufacture of silicon nitride inorganic fiber] A four-loaf flask with an internal volume of 101 cm was equipped with a gas blowing pipe, a mechanical stirrer, and a dewar condenser. After replacing the inside of the reactor with deoxygenated dry air, 4900 d of degassed dry pyridine was placed in a four-bottle flask and cooled on ice. Next, 744 g of dichlorosilane was added to form a white solid (SiH2C12.2CsHsN). While cooling the reaction mixture on ice and stirring, purified ammonia 735 was passed through a sodium hydroxide tube and an activated carbon tube.
After blowing in g, the mixture was heated to 100°C.

After the reaction is completed, the reaction mixture is centrifuged, washed with dry pyridine, and further filtered under nitrogen atmosphere to obtain filtrate 5.
I got 100rn1. Filtrate 5mj! When the solvent was distilled off under reduced pressure, 0.24 g of resinous solid perhydropolysilazane was obtained.

The number average molecular weight of the obtained polymer was 980 as measured by GPC.

Next, 5000 mj of the obtained 5% perhydropolysilazane pyridine solution! was placed in a 10β stainless steel autoclave, 100g of ammonia was added, and then heated at 80°C for 3
The mixture was stirred for hours to cause a polycondensation reaction. After cooling to room temperature,
The gas was replaced with nitrogen. This modified perhydropolysilazane has a number average molecular weight of 2.400 and a weight average molecular weight of 20000 (gel permeation chromatography method,
polystyrene standard).

5,000 mf of xylene was added to this solution, and the mixture was distilled off under reduced pressure using a rotary evaporator at 60°C until the volume of the solution reached 1,000 d. When this operation was repeated two more times, the amount of pyridine contained in the solution was 0.03% by weight (gas chromatography method).

Further, the solvent was removed using a rotary evaporator. Vacuum removal was discontinued when the solution became sufficiently stringy. This solution was transferred to a defoaming container of a dry spinning device to obtain a spinning solution. After standing at 60℃ for about 2 hours to defoam, 30℃
The fibers were discharged from a nozzle with a diameter of 0.1 mm into a spinning cylinder in an air atmosphere at 130°C, and wound at a speed of 300 m/min to obtain fibers with an average fiber diameter of 10/-.

Next, the spun fibers were heated at a rate of 200°C/hour from room temperature to 1300°C under a nitrogen atmosphere while applying a tension of 500 g/ml112 to obtain silicon nitride fibers.

This silicon nitride fiber had a tensile strength of 270 kg/mm2 and an elastic modulus of 25 ton/mm2. Elemental analysis of this silicon nitride fiber revealed that silicon was 58.1% by weight, nitrogen was 35.1% by weight, oxygen was 1.42% by weight, and carbon was 1.4% by weight.
It was 5% by weight.

Reference Example 2 [Manufacture of silicon nitride inorganic fiber] A four-bottle flask with an internal volume of 11 was equipped with a gas blowing tube, a mechanical stirrer, and a dewar condenser. After purging the inside of the reactor with deoxygenated dry nitrogen, 490 ml of degassed dry pyridine was placed in a four-bottle flask! and cooled it on ice. Next, 51.6 g of dichlorosilane was added to form a white solid adduct (SiH2C12.2C5H5N). The reaction mixture was cooled on ice, and while stirring, purified ammonia was passed through a sodium hydroxide tube and an activated carbon tube.
0 g was injected.

After the reaction is completed, the reaction mixture is centrifuged, washed with dry pyridine, and further filtered under nitrogen atmosphere to obtain filtrate 8.
I got 50-. The solvent was distilled off from 5 mf of the filtrate under reduced pressure to obtain 0.102 g of resinous solid perhydropolysilazane.

The number average molecular weight of the obtained polymer was 980 as measured by GPC. Also, the IR of this polymer
(Infrared absorption) spectrum (solvent: dry ao − + sil
/ton; Concentration of perhydropolysilazane: 10.2 g
/ I! ), the wave number (cm') is 335
0 (apparent extinction coefficient ε = 0.5571g-'Cm-
) and NH-based absorption of 1175, 2170 (ε
Absorption based on 5i) I of =3.14); 1020-8
It was confirmed that absorption based on 20 SiH and 5iNSi was exhibited. In addition, 'HNMR (proton nuclear magnetic resonance) spectrum (60M) Iz of this polymer, solvent CDCl
3/Reference material TMS), it was confirmed that all of them exhibited a wide range of absorption. That is, δ4.8 and 4
．． 4 (br, 5iH); 1.5 (br, N
Absorption of H) was confirmed.

A pyridine solution of perhydropolysilazane obtained by the above procedure (concentration of perhydropolysilazane: 5.50% by weight) and 800 mjl! ) Limethylborate 34,0c
c (0,301 mol) was placed in an autoclave with an internal volume of 11, and the reaction was carried out at 160° C. for 4 hours with stirring. After cooling to room temperature, add 500mf of dry 0-xylene,
When the solvent was removed at a pressure of 3 to 5 mmHg and a temperature of 50 to 70°C, 43 g of polyborosilazane having a number average molecular weight of 2200 in the form of a white solid was obtained.

After dissolving this polyborosilazane in 0-xylene, the solvent was removed using a rotary evaporator. When the solution became sufficiently stringable, the vacuum distillation was stopped.

This solution was transferred to a defoaming container of a dry spinning device to obtain a spinning solution. After standing at 60°C for approximately 4 hours to defoam, it was discharged at 40°C from a nozzle with a diameter of 0.1 mm into a spinning tube in an air atmosphere at 120°C, and wound at a speed of 100 m/min to obtain an average fiber. A fiber with a diameter of about 10 mm was obtained.

While applying an attractive force of 500 g/mm2 to this fiber,
180℃/from room temperature to 600℃ under ammonia atmosphere
The temperature was raised over time, the atmosphere was changed to nitrogen, and the temperature reached 1700°C.
The temperature was raised to 1,700° C. over 3 hours, and the mixture was held at 1,700° C. for 1 hour and fired to obtain black fibers. The diameter of this fiber is about 7 mm, the tensile strength is 200 kg/mm2, and the elastic modulus is 33 ton/f.
It was 11m2. X-ray diffraction measurements of the obtained fibers confirmed that the fibers were amorphous. The elemental analysis results of the obtained fibers were: Si: 43.1%, N: on a weight basis.
34.8%, C: 0.6%, ○: 11.8%, B
: 7.80%.

Furthermore, in the fiber obtained by firing at 1800°C, the X-ray diffraction pattern shows 2θ=20°, 23°265
° , 31° , 34.5° , 35° , 39° ,
There are broad peaks around 42° and 43.5° that are thought to be related to α-813N4, and 2θ=23.5°,
27°, 33.5°, 36°41.5°, β near
-3i3N appeared, and it was found that α-5i3N and β-3i3N microcrystals were formed.

Moreover, the X-ray scattering intensity ratio of the #a fiber obtained was 1° and 0.
It was 20 or less in all cases of 5°.

Reference Example 3 [Manufacture of binder for molding] A four-loop flask with an internal volume of 10β was equipped with a gas blowing pipe, a mechanical stirrer, and a dewar condenser. After replacing the inside of the reactor with deoxygenated dry air, 4900 mE of degassed dry pyridine was placed in a four-neck flask and cooled on ice. Next, 744 g of dichlorosilane was added to form a white solid Adak) (SiH, C12・2C9
85N) was generated. The reaction mixture was ice-cooled, and while stirring, 735 g of purified ammonia was blown into the reaction mixture through a sodium hydroxide tube and an activated carbon tube, and then heated to 100°C.

After the reaction is complete, the reaction mixture is centrifuged, washed with dry pyridine, and further filtered under nitrogen atmosphere to obtain filtrate 5.
100rr+f was obtained. The solvent was distilled off from the filtrate 5- under reduced pressure to obtain 0.24 g of resinous solid perhydropolysilazane.

The number average molecular weight of the obtained polymer was 980 as measured by GPC.

Next, the obtained 5% perhydropolysilazane-pyridine solution 5000- was placed in a 10f stainless steel autoclave and stirred at 80°C for 3 hours to cause a polycondensation reaction. After cooling to room temperature, the gas was removed and replaced with nitrogen. This modified perhydropolysilazane has a number average molecular weight of +15
00, weight average molecular weight: 7000 (gel permeation chromatography method, polystyrene standard).

Add 5000rd xylene to this solution and heat it on a rotary evaporator at 60℃ until the volume of the solution is 100100O.
It was distilled off under reduced pressure until it became . When this operation was repeated two more times, the amount of pyridine contained in the solution was 0.03% by weight (gas chromatography method).

Furthermore, the solvent was removed using a rotary evaporator, and the concentration was adjusted to 3Qwt%. Elemental analysis of this polymer showed S: 64. ht%1N: 24.2wt
%○: 1.2wt%, (::4.9wt%).

Example [Silicon nitride inorganic fiber reinforced glass] Silicon nitride inorganic fiber was produced by the method of Reference Example 1.

A silicon carbide coating was applied to this fiber by the following method.

Silicon nitride fibers were immersed in a toluene solution (1 wt %) of commercially available polysilastyrene (manufactured by Nippon Soda) and dried at 80° C. to remove the solvent toluene. This was passed through a tubular furnace (nitrogen atmosphere) heated to 1200℃, and the temperature was increased at a rate of 20℃/
The yarn was fed at a speed equivalent to min. A coating film with a thickness of 0.3μ was obtained.

When this fiber was subjected to X-ray diffraction, it was found to be amorphous.

The composite material was manufactured as follows.

As a matrix raw material, 100 borosilicate glass powder (code 7740 manufactured by Corning Corporation) with a particle size of 325 mesh was used.
2 g of polyvinyl alcohol as a molding binder and 200 g of water as a solvent. This was mixed in a ball mill for 36 hours to prepare a slurry.

Silicon nitride inorganic W4 with the above-mentioned surface coating was placed in a slurry bath that was stirred to prevent the glass powder from settling.
The fibers were dipped and wound around a drum while drying to produce a prepreg. At this time, the fiber directions were made to be parallel. The prepreg was removed from the drum, cut into 5 cm square pieces, and laminated to a thickness of 2 cm so that the fiber direction was aligned in one direction. Place this in a hot press mold, 110
Dry at °C.

The molding binder was removed by baking at 600° C. for 2 hours in a nitrogen atmosphere.

Sintering of the matrix was performed by hot pressing.

Press pressure 100kgf/c at 1300℃ under nitrogen atmosphere
It was fired at.

The fiber volume content of the obtained sintered body was 45vol%. A JIS bending test piece (3 x 4 x 36 mm) was prepared from the sintered body.
) was cut out and subjected to a three-point bending strength test. The bending strength at room temperature was 82 kgf/cIIt, and the bending strength at 700° C. in an inert atmosphere was 55 kgf/cfll. Moreover, the fracture morphology was non-brittle.

Comparative Example 1 A silicon nitride inorganic fiber was used without surface treatment. Other conditions for producing the composite material were the same as in Example 1.

The fiber volume content of the obtained sintered body was 49vol%. A JIS bending test piece (3 x 4 x 36 mm) was prepared from the sintered body.
) was cut out and subjected to a three-point bending strength test. The bending strength at room temperature was 71 kgf/cnf, and the bending strength at 700°C in an inert snow atmosphere was 46 kgf/cnf. Moreover, the fracture form was extremely brittle.

Example 2 [Production of silicon nitride inorganic fiber reinforced silicon nitride] A silicon nitride inorganic fiber was produced by the method of Reference Example 2.

The fiber surface coating was carried out using the CVD method as follows.

The silicon nitride inorganic fibers were passed through a tube furnace heated to 600° C. in a nitrogen atmosphere to burn off deposits such as sizing agents and clean the fiber surfaces.

This fiber was passed through a tubular furnace heated to 1300°C, and 5iC1,, CH,, H, and 5O
N1/min, 5ON1/min, 100ONI
/+nin flowed. The reaction pressure was adjusted to 100 Torr. The fibers were fed at a speed of Q, 5 m/min to obtain a coating film with a thickness of 0.8 μm.

When this fiber was subjected to X-ray diffraction, β-3iC was observed.

The composite material was manufactured as follows.

Silicon nitride powder (Ube Industries 5N-CCIA, average particle size: sintering aid Y20.5wt%, Al2O35wt% included) 1
50g, perhydropolysilazane 5 as molding binder
100 g of xylene was added as a solvent and mixed in a ball mill for 36 hours to prepare a slurry.

A molding binder was produced by the method of Reference Example 3.

The above-described surface-coated silicon nitride inorganic fibers were immersed in a slurry bath and wound around a drum while drying to produce a prepreg. At this time, it was wound up so that the fibers were parallel. Remove the prepreg from the drum,
Cut into 5 cm squares, making sure the fiber direction is aligned in one direction.
It was laminated to a thickness of 2 cm. This was placed in a hot press mold and dried at 110°C under a nitrogen atmosphere.

Sintering of the matrix was performed by hot pressing.

Under nitrogen atmosphere, 1700℃, press pressure 300kgf/c
It was fired in III.

The fiber volume content of the obtained sintered body was 43vol%. A JIS bending test piece (3 x 4 x 36 mm) was prepared from the sintered body.
) was cut out and subjected to a three-point bending strength test. The bending strength at room temperature was 71 kgf/cffl, and the bending strength at 1200° C. in an inert atmosphere was 65 kgf/aI11. Moreover, the fracture morphology was non-brittle.

Comparative Example 2 A silicon nitride inorganic fiber was used without surface treatment. The other conditions for manufacturing the composite material were the same as in Example 2.

The fiber volume content of the obtained sintered body was 45vol%. A JIS bending test piece (3 x 4 x 36 mm) was prepared from the sintered body.
) was cut out and subjected to a three-point bending strength test. Room temperature bending strength is 62kgf/c++! , the bending strength was 59 kgf/cat in an inert atmosphere at 1200°C. Moreover, the fracture form was brittle.

〔Effect of the invention〕

The inorganic fiber-reinforced ceramic composite material obtained by the present invention has high tensile strength, high elastic modulus, excellent heat resistance and abrasion resistance, and low manufacturing cost, so it can be used as a material for aircraft, space development, ships and marine structures. It can be used for land transportation equipment materials, construction and civil engineering materials, mechanical work materials, medical care and nursing care materials, etc.

Claims (2)

[Claims] 1. A ceramic-containing matrix is reinforced with silicon nitride fibers, the silicon nitride fibers have silicon and nitrogen as essential components, and oxygen, carbon, hydrogen, and metals as optional components,
These elements have the following atomic ratio N/Si=0.05~3,
O/Si=15 or less, C/Si=7 or less, M/Si=5
(where M represents a metal), and the surface of the silicon nitride fiber is inorganic coated, and the inorganic coating is carbon, or elements IIA to VIIA of the periodic table,
A fiber-reinforced ceramic composite material comprising a carbide, nitride, boride, silicide, oxide, or a composite thereof of a group VIII, IIIB, or IVB metal element. 2. Silicon and nitrogen are essential components, oxygen, carbon, hydrogen and metals are optional components, and these elements have the following atomic ratio N/Si=0.05 to 3, O/Si=15 or less, C/S
i = 7 or less, M / Si = 5 or less (however, M represents a metal), and the surface is coated with an inorganic surface,
The inorganic coating may contain carbon or elements IIA to IIA of the Periodic Table of the Elements.
A silicon nitride fiber comprising a carbide, nitride, boride, silicide, oxide, or a composite thereof of a group VIIA, VIII, IIIB, or IVB metal element.