JPH0633187B2 - Inorganic fiber reinforced ceramic composite and method for producing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to an inorganic fiber reinforced ceramic composite (FRC) and a method for producing the same.

(Prior Art and its Problems) Heat-resistant ceramics are used under severe conditions such as ultra-high temperature, ultra-high pressure, or corrosive environment. In general, heat-resistant ceramics are generally vulnerable to mechanical shock, and have the drawback of lowering mechanical strength and corrosion resistance at high temperatures. In order to make up for these drawbacks, continuous fibers made of alumina, carbon, etc., or composites made by combining short fibers or whiskers with ceramics have been developed. For example, JP-A-52-81309 describes a method for producing a heat-resistant ceramic composite body reinforced with silicon carbide fibers obtained from an organosilicon polymer compound. However, according to this method, it is difficult to uniformly disperse the reinforcing fibers in the matrix ceramic, so that the resulting composite does not necessarily have sufficient strength and heat resistance.

(Technical Means for Solving Problems) It is an object of the present invention to provide a ceramic composite in which continuous fibers are uniformly dispersed in a ceramic serving as a matrix, and a method for producing the same.

The inorganic fiber reinforced ceramic composite of the present invention comprises (i) an amorphous substance consisting essentially of Si, M, C and O, or (ii) substantially β-SiC, MC, and β-SiC and MC. A solid solution and / or each crystalline ultrafine particle of MC _1-X having a particle size of 500 Å or less, and an aggregate composed of amorphous SiO ₂ and MO ₂ , or (iii) the amorphous substance of (i) above And a mixed system of the crystalline ultrafine particle aggregate of (ii) above (wherein M represents Ti or Zr in the above formula, and x is a number greater than 0 and less than 1), or titanium. Continuous inorganic fibers composed of zirconium, carbon and oxygen, and short fibers of a heat-resistant substance interposed between the continuous inorganic fibers,
The ceramic is reinforced with reinforcing fibers made of whiskers or powder.

The continuous inorganic fiber in the present invention can be prepared, for example, according to the following method described in European Patent Nos. 30145 and 37209.

(1) A number-average molecular weight of about 500 to 10,000 A polycarbosilane having a main chain skeleton composed of the structural unit of, wherein the silicon atom is essentially a hydrogen atom, a side alkyl group selected from the group consisting of a lower alkyl group, and a phenyl group. 2) A metalloxane bond unit having a number average molecular weight of about 500 to 10,000 (M: Ti or Zr) and siloxane bond unit Having a main chain skeleton consisting of, and the ratio of the total number of all-polysiloxane bond units of metalloxane bond units is from 30: 1 to
In the range of 1:30, most of the silicon atoms of the siloxane bond unit have one or two side chain groups selected from the group consisting of lower alkyl groups and phenyl groups, and the metalloxane bond unit. A polymetallosiloxane in which most of the metal atoms of the above have one or two lower alkyl groups as side groups, Of all structural units of the polymetallosiloxane Mixing in a quantity ratio such that the ratio of the total number of binding units is in the range of 100: 1 to 1: 100, and heating the resulting mixture in an organic solvent and under an atmosphere inert to the reaction, At least a part of silicon atoms of the polycarbosilane is bonded to at least a part of silicon atoms and / or metal atoms of the polymetallosiloxane via an oxygen atom to form a crosslinked polycarbosilane moiety and a polymetallosiloxane. Number average molecular weight consisting of parts and about 1000
A first step of producing ~ 50000 organometallic polymers, and a second step of making and spinning a spinning dope of the polymer
Third infusibilization of the spun fiber under tension or counter tension
From the step and the fourth step of firing the infusibilized spun fiber at a temperature in the range of 800 to 1800 ° C. in a vacuum or an inert gas atmosphere, substantially Si, Ti or Zr, C
It is possible to produce an inorganic fiber composed of O and O.

Alternatively, mainly (However, R in the formula represents a hydrogen atom, a lower alkyl group or a phenyl group.) Having a main chain skeleton represented by
0000 polycarbosilane, and formula MX ₄ (wherein M represents Ti or Zr, and X represents 1 carbon atom).
Represents an alkoxy group, a phenoxy group, or an acetylacetoxy group having ˜20. ) Is an organometallic compound represented by All structural units of the organometallic compound algae In addition to the quantity ratio in which the total number of structural units is within the range of 2: 1 to 200: 1, at least one of the silicon atoms of the polycarbosilane is reacted by heating in an atmosphere inert to the reaction. Part is bonded to the metal atom of the organometallic compound through an oxygen atom to give a number average molecular weight of about 700 to
The first step of producing 100,000 organometallic polymers, and the second step of producing a spinning solution of the above organometallic polymers and spinning them.
A step, a third step of infusibilizing the spun fiber under tension or no tension, and a fourth step of firing the infusibilized spun fiber at a temperature in the range of 800 to 1800 ° C. in a vacuum or an inert gas atmosphere From the process, substantially Si, Ti or Z
Inorganic fibers composed of r, C and can be produced.

The proportion of each element in the continuous inorganic fiber is Si: 30 to 60% by weight, Ti or Zr: 0.5 to 35.
% By weight, particularly preferably 1-10% by weight, C: 25-4
0% by weight and O: 0.01 to 30% by weight.

In the ceramic composite of the present invention, the continuous inorganic fiber is a method of orienting the fiber itself in a uniaxial direction or a polyaxial direction,
Alternatively, a method of using various kinds of fabrics such as plain weave, satin weave, imitation weave, twill weave, leno weave, spiral woven fabric, and three-dimensional woven fabric,
Alternatively, there is a method of using it as chopped fiber.

As the heat-resistant substance constituting the short fibers, whiskers or powder to be interposed in the fiber gap of the continuous inorganic fibers, silicon carbide, silicon nitride, alumina, silica, silica-alumina, zirconia, beryllia, boron carbide, titanium carbide, etc. Examples include ceramics, metals, and intermetallic compounds. The proportion of short fibers, whiskers or powder of the heat resistant material is preferably 0.5 to 500% by volume with respect to the continuous inorganic fibers.

As the ceramic in the present invention, a carbide ceramic, a nitride ceramic, an oxide ceramic, a glass ceramic or the like is used.

Examples of carbide ceramics include silicon carbide, titanium carbide, zirconium carbide, vanadium carbide, niobium carbide, tantalum carbide, boron carbide, chromium carbide, tungsten carbide, molybdenum carbide, graphite and the like.

Examples of the nitride ceramics include silicon nitride, titanium nitride, zirconium nitride, vanadium nitride, niobium nitride, tantalum nitride, boron nitride, aluminum nitride and hafnium nitride.

Examples of oxide ceramics include alumina, silica, magnesia, mullite, cordierite and the like.

Examples of glass ceramics include borosilicate glass,
Examples include a method of adhering short fibers, whiskers or powder to the surface of each of the fibers of high silica content glass, aluminosilicate glass or woven fabric.

In addition to the above, a ceramic having the same composition as the continuous inorganic fiber of the present invention can be used.

The reinforcing fiber comprising the continuous inorganic fiber and the short fiber of the heat-resistant substance, the whisker, or the powder interposed therebetween in the present invention can be suitably produced by the suspension dipping method.

As an example of the suspension dipping method, rewind a fiber bundle obtained by bundling continuous inorganic fibers or an appropriate number of continuous inorganic fibers wound around a bobbin or the like, or a woven fabric of continuous inorganic fibers, short fibers, whiskers or powder. Examples include a method of immersing in a suspended liquid and depositing short fibers, whiskers or powder on the surface of each of continuous inorganic fibers or fibers of a woven fabric.

When immersing a continuous inorganic fiber bundle or a woven fabric having a large number of fibers, it is preferable to vibrate with ultrasonic waves to uniformly attach the short fibers, whiskers or powder to each fiber. It is convenient that the frequency of ultrasonic waves is about 100 to 2000 KHz.

The suspension may be water, but an organic solvent such as ethanol,
Methanol and acetone are preferably used. When the above organic solvent is used as the suspension, when the inorganic fibers are sized, the sizing agent dissolves to easily attach the short fibers and the like, and the volatility is higher than that of water, so that the drying is quick. , There is an advantage that productivity is improved.

The concentration of the short fibers, whiskers or powder in the suspension is not particularly limited, but if it is too small, it does not uniformly adhere to the continuous inorganic fibers, and if it is too large, the adhesion amount becomes too large, so 0.5
It is preferably -30 g /.

In the present invention, as a binder optionally added during the production of the composite, a binder for sintering the ceramic base material at a high density, and for increasing the adhesion between the ceramic powder base material and the inorganic fibers. There is a binder. The former includes binders used in sintering carbides, nitrides and oxide glass ceramics, respectively. For example, silicon carbide binders include boron, carbon, and boron carbide,
The binder of silicon nitride includes alumina, magnesia, yttria, and aluminum nitride. Examples of the latter include organosilicon polymers such as diphenyldiloxane, dimethylsiloxane, polyborodiphenylsiloxane, polyborodimethylsiloxane, polycarbosilane, polydimethylsilazane, polytitanocarbosilane, and polyzirconocarbosilane, and diphenylsilane. Organosilicon compounds such as diel and hexatyldilysilazane may be mentioned.

The amount of these binders used is usually 0.5 to 20% by weight.

The inorganic fiber reinforced ceramic composite of the present invention can be produced by a method known per se as shown below.

There are various methods of obtaining an aggregate of the ceramic powder base material and the reinforced molten fiber, particularly, a method of burying the fiber in the ceramic powder base material or a mixture of the ceramic and the binder, the reinforcing fiber and the ceramic powder. It is comparatively easy to use the method of alternately arranging the matrix-like base material or the mixed wood mixture, or the method of installing reinforcing fibers in advance and filling the gap with the ceramic powder-like base material or the mixture The aggregate can be obtained. Next, as a method of sintering these aggregates,
50 by using a rubber press, a die press, etc.
After pressure molding at a pressure of up to 50,000 kg / cm ² , sintering in a temperature range of 800 to 2400 ° C in a heating furnace, or 5
800 ~ with pressure kept at 0 ~ 5000kg / cm ²
There is a method of hot press sintering in a temperature range of 2400 ° C.

The above-mentioned sintering can be performed in vacuum or under an atmosphere of an inert gas selected from nitrogen, argon, carbon monoxide, hydrogen and the like.

The inorganic fiber reinforced ceramic composite thus obtained can be made into a sintered body having a higher density by performing the series of treatments described below at least once. That is, the sintered body is immersed under reduced pressure in a melt of an organic silicon compound or an organic silicon polymer, or a solution of the compound or the polymer in an organic solvent, if necessary, to obtain the melt or the solution. A higher density sintered body can be obtained by a series of treatments in which the grain boundaries and pores of the sintered body are impregnated and the sintered body after the impregnation is heated. Heat treatment is 800-25
In the temperature range of 00 ° C, in vacuum or nitrogen, argon,
It is carried out in an atmosphere composed of an inert gas selected from carbon monoxide, hydrogen and the like.

(Example) Hereinafter, the present invention will be described with reference to an example.

Method for producing continuous inorganic fiber [I] 3 parts by weight of polyborosiloxane was added to 100 parts by weight of polydimethylsilane synthesized by dechlorinating and condensing dimethyldichlorosilane with sodium metal, and the mixture was heated to 350 in nitrogen.
Formula obtained by thermal condensation at ℃ Each of the main clavicle consisting mainly of carbosilane units of
Titanium alkoxide is added to polycarbosilane having a hydrogen atom and a methyl group in the silicon atom of the carbosilane unit, and crosslinked in nitrogen at 340 ° C. to give 100 parts of the carbosilane unit and the formula. Polytitanocarbosilane consisting of 10 parts of titanoxane was obtained. This polymer is melt-spun and heated in air at 190 ° C.
Infusibilization treatment, followed by firing in nitrogen at 1300 ° C., fiber diameter 13 μm, tensile strength 310 kg / mm ² ,
A continuous inorganic fiber [I] having a tensile elastic modulus of 16 t / mm ² and mainly composed of silicon, titanium, carbon and oxygen and having a titanium element content of 3% by weight was obtained. This fiber is composed of an amorphous substance composed of Si, Ti, C and O, a solid solution of β-SiC and TiC, and TiC _1-x (0 <x <1) crystalline ultrafine particles with a particle size of 50Å and non-crystalline particles. It was composed of a mixed system of crystalline SiO ₂ and an aggregate of TiO ₂ .

Method for producing continuous inorganic fiber [II] Polycozirconocarbosilane was prepared by the same method except that 10 g of zirconium ethoxide was added to 80 g of polycarbosilane obtained in the same manner as above. This polymer was dissolved in benzene, dry-spun, infusibilized at 170 ° C. in air, and subsequently in nitrogen.
Firing at 00 ℃, fiber diameter 10μ, tensile strength 350kg /
mm ^2, primarily silicon zirconium modulus 18t / mm ^2, the zirconium element content 4.5 consisting of carbon and oxygen
A wt% amorphous continuous inorganic fiber [II] was obtained.

Example 1 Silicon carbide whiskers (average diameter 0.2 μ, average length 100)
μ) 5 g was placed in a treatment tank containing ethanol 1.
A suspension was prepared by applying ultrasonic vibration and suspending.

The fiber bundle (800 yarns) of the inorganic fiber [I] is unwound from the bobbin, adjusted with a movable roll so that the immersion time is about 15 seconds, immersed in the suspension, and then pressed with a pressure roll. After that, it was wound on a bobbin and dried in the air at room temperature. 0.02g of whiskers per 10m of inorganic fiber bundle
It was attached.

A sheet-shaped product obtained by aligning the treated fiber bundle in the uniaxial direction,
Β-silicon carbide powder (average particle size: 0. 3%) mixed with 3% by weight of boron carbide and 10% by weight of polytitanocarbosilane.
2μ) and are alternately laminated, and a die press is used to
Press molding was performed at kg / mm ² . This molded body was heated to 1550 ° C. at a temperature rising rate of 200 ° C./min in an argon atmosphere to obtain a reinforced silicon carbide composite sintered body.

The fiber content of this composite sintered body was 40% by weight. When the cross section of the composite was examined with a scanning electron microscope, it was found that the reinforcing fibers were dispersed in the silicon carbide matrix without contacting each other. The room-temperature bending strength of the composite was 86 kg / mm ² , and the bending strength at 1400 ° C was 60 kg / mm ² .

The room-temperature bending strength of the composite obtained in the same manner as above except that no silicon carbide whiskers were attached was 61 kg /
It was mm ² .

Example 2 Example 1 except that a fiber bundle of continuous inorganic fibers [II] was used.
Silicon carbide whiskers were deposited in the same manner as in.

A sheet-shaped product obtained by aligning the treated fiber bundle in the uniaxial direction,
An α-silicon nitride powder (average particle size: 0.5 μ) in which 2% by weight of alumina, 3% by weight of yttria and 3% by weight of aluminum nitride are mixed is orthogonal to each other between layers in which the fibers of the fiber bundle are different from each other. Thus, the layers were alternately laminated. The laminated body is hot pressed at 1750 ° C, 300 kg / mm
^It was held at ² for 30 minutes to obtain an inorganic fiber reinforced silicon nitride composite sintered body.

In this case, the fiber content of the sintered body was 10% by weight. When the cross section of the composite was examined by a scanning electron microscope, it was found that the reinforcing fibers were dispersed in the matrix silicon nitride without contacting each other. The bending strength of the composite at room temperature was 143 kg / mm ² , and the bending strength at 1300 ° C. was 73 kg / mm ² .

The room-temperature bending strength of the composite obtained in the same manner as above except that no silicon carbide whiskers were attached was 110 kg.
/ Mm ² .

(Effects of the Invention) The composite of the present invention is capable of various combinations of continuous inorganic fibers, heat-resistant short fiber whiskers or powders, and matrix ceramics, and can satisfy a wide range of required properties. . Further, since the fibers are uniformly dispersed in the composite and the contact between the continuous fibers in the composite is extremely small, the strength of the continuous fibers in the direction perpendicular to the fiber axis is remarkably improved.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshihiro Ishikawa 5 1978, Ogushi, Ube, Yamaguchi Prefecture 5 1978, Ube Institute of Industrial Research, Ltd. Ube Institute Co., Ltd. Examiner Shunichi Nakagawa (56) References JP-A-55-85644 (JP, A)

Claims (4)

[Claims] 1. An (i) amorphous substance consisting essentially of Si, M, C and O, or (ii) a substantially β-SiC, MC, solid solution of β-SiC and MC and / or MC _{1. -X is} a crystalline ultrafine particle having a particle size of 500 Å or less, and an aggregate composed of amorphous SiO ₂ and MO ₂ , or (iii) the amorphous substance of (i) and the amorphous substance of (ii) above. From a mixed system of crystalline ultrafine particle aggregates (wherein M represents Ti or Zr and x is a number greater than 0 and less than 1), carbon, and oxygen. A continuous inorganic fiber, and a short fiber of a heat-resistant substance interposed between the continuous inorganic fibers,
An inorganic fiber reinforced ceramic composite reinforced with whisker or powder reinforcing fibers. 2. The inorganic fiber reinforced ceramic according to claim 1, wherein the volume ratio of the short fibers, whiskers or powder of the heat resistant material to the continuous inorganic fibers is 0.5 to 500%. Complex. 3. The inorganic fiber reinforced ceramic composite according to claim 1, wherein the blending ratio of the continuous inorganic fibers is 10 to 70% by volume based on the composite. 4. An (i) amorphous substance consisting essentially of Si, M, C and O, or (ii) a substantially β-SiC, MC, a solid solution of β-SiC and MC and / or MC _{1. -X is} a crystalline ultrafine particle having a particle size of 500 Å or less, and an aggregate composed of amorphous SiO ₂ and MO ₂ , or (iii) the amorphous substance of (i) and the amorphous substance of (ii) above. From a mixed system of crystalline ultrafine particle aggregates (wherein M represents Ti or Zr and x is a number greater than 0 and less than 1), carbon, and oxygen. With continuous inorganic fiber,
Inorganic fibers characterized in that short fibers of a heat-resistant substance intervening in the fiber gaps of the continuous inorganic fibers, reinforcing fibers consisting of whiskers or powder, or a woven fabric of the fibers are embedded in ceramic powder and fired. Manufacturing method of reinforced ceramic composites.