JPH0214883A - Fiber-reinforced mullite composite material dispersed and reinforced with granule and production of the same composite material - Google Patents

Abstract

PURPOSE:To obtain the title composite improved in breaking toughness by reinforcing mullite with a combination of fiber with granule dispersion. CONSTITUTION:The objective composite can be obtained by reinforcing mullite with a combination of fiber with granule dispersion, thus being made up of a mullite matrix, fiber and granules of the same or different kind as or from said fiber both dispersed in said matrix. To produce this composite, mullite granules to be the matrix are dispersed in a solution containing an organometallic polymer to prepare an impregnating solution. Thence, fiber is continuously passed through this solution to evenly impregnate the fiber with said solution. The resultant fiber is then made into a laminate and the organometallic polymer contained therein is insolubilized, the resulting laminate is sintered in an Ar or N2 gas under normal or higher pressure.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention further strengthens the fiber-reinforced mullite composite material by dispersing particles, and in particular, the fracture toughness value is surprisingly improved.
The present invention relates to a mullite complex α material that is expected to be applied to cylinder liners and piston rings of reciprocating engines, turbine rotor blades of gas turbine engines, etc., and a method for manufacturing the same.

[Prior Art] Ceramics have better heat resistance and oxidation resistance than metal materials, and also have better heat insulation properties, so they have attracted attention as heat-resistant structural materials that can replace metals. however,
Ceramics are composed of covalent bonds and ionic bonds, and cannot be deformed or stretched due to dislocations like metal materials, and stress concentrates on minute defects inside the material or scratches on the surface, causing it to break easily. Therefore, it has the disadvantage of being extremely brittle and having poor fracture toughness.

11 light (3A + 20.・2S io 2) also has heat resistance and 5 thermal shock resistance, exhibits uniform thermal expansion, and has little change in mechanical properties due to temperature, and can be heated to 1350℃.
It has almost the same strength as silicon carbide, but like other ceramics, it has inferior fracture toughness.

The resistance of a material to brittle fracture is generally determined by the fracture toughness fl
The KI of conventional mullite is denoted by l K +c.
O is 1.5 to 1.8 MN/m", and 34 MN/m of aluminum alloy, which is said to be relatively brittle among metal materials,
In order to apply ceramics as engineering ceramics to reciprocating engines or gas turbine engines, it is necessary to make the fracture toughness value as high as possible.

To this end, various methods have been researched to improve the brittleness of structural ceramics.Among these, a particle dispersion strengthening method in which various particles are mixed and dispersed in a ceramic matrix, and a method in which various types of fibers are added to a ceramic matrix have been studied. A method of reinforcing fibers by dispersing them in

Fibers for fiber-reinforced ceramics (hereinafter referred to as FRC) can be broadly divided into short fiber type and long fiber type.

Long fibers include glass-capped metal fibers, carbon fibers, and ceramic fibers. Carbon fibers have high strength and high elastic modulus, making them suitable for composite materials, but they have the disadvantage of being susceptible to oxidation. Ceramic fibers such as silicon carbide and alumina are spun and heat-treated from organic raw materials, have a high melting point, and are most commonly used. Short fibers refer to whiskers, which are acicular single crystals, or chopped long fibers, but whiskers are Fr? Although it shows ideal strength as a C fiber, it has the drawbacks that it is difficult to uniformly disperse it in 57 trix and is expensive.

Regarding the ceramics that serve as the matrix, A.I.
, Os, Mullite, ZrO2, S r z N-1Si
C.

Attempts have been made to combine many ceramics, from arsenic acids such as glass to non-oxides, with m t and i.

For patents on fiber-reinforced ceramic materials,
Sintered body of spinel (MgO-Al□0.) mixed with silicon carbide short fibers (JP-A-62-119175>, sintered body of alumina mixed with silicon carbide short fibers JP-A-62-1191)
74), carbon continuous fiber reinforced SiC composite (Unexamined Japanese Patent Publication No. 1986-2
47663), ceramic composites made by adding carbon fiber to metal oxides or metal carbides and sintering them simultaneously with pressure (
JP-A-50136306), silicon carbide fiber reinforced ceramic composite material (JP-A No. 62-35996), etc.

The mechanism by which fracture toughness of ceramics is improved by particle dispersion is as follows.
This is thought to be because the reinforcing particles somehow disperse or absorb the energy that causes the tip of the crack to advance further, causing a stress relaxation phenomenon. As an example of fracture toughness relaxation, there is an example in which TiC particles are dispersed in S i 3 N 4 .

[Problems to be Solved by the Invention] However, when creating the above-mentioned composite material, it is important to consider whether the fibers maintain the desired strength without reacting with the matrix at the sintering temperature, which is chemical compatibility, and the coefficient of expansion. Physical compatibility, such as whether or not differences damage the fibers, influences properties such as fracture toughness of composite materials, so the reality is that fiber reinforcement or particle dispersion reinforcement alone cannot provide the expected fracture toughness value. be. Fiber reinforcement of mullite has also been attempted, but satisfactory results have not been obtained.

The present invention has been made in view of the above-mentioned problems of fiber-reinforced mullite composite materials, and an object of the present invention is to provide a fiber-reinforced mullite composite material with excellent fracture toughness and a method for producing the same.

[Means for solving the problem] As a result of intensive research to solve the 1rI registration problem, the inventor has developed a reinforced tif that combines fiber reinforcement and particle dispersion reinforcement.
I came to think of 4.

Crack deflection is cited as a mechanism for improving fracture toughness due to particle dispersion. In other words, t) differences in various properties such as toughness and coefficient of thermal expansion between the matrix and the dispersed phase,
Due to the interfacial state between the two, the liquid moves around the dispersed phase in a zigzag manner. This consumes the energy necessary for crack propagation, improving fracture toughness.

In addition, fitiI, which improves fracture toughness due to fiber strength,
This is believed to be due to pullout and deflection. In other words, when whiskers are mixed as a dispersed phase, h
, when the crack passes through the location of the whisker, the whisker is pulled out of the matrix by the amount of gap created by the crack. The amount of work done to pull out the whiskers consumes energy and improves toughness.

We have come up with the idea that if the crack deflection and pullout mentioned above occur effectively at the same time, the fracture energy will increase tremendously and the fracture toughness value will increase significantly, and we have completed the present invention. It's arrived.

That is, the fiber-reinforced mullite composite material of the present invention is one in which fiber reinforcement and particle dispersion reinforcement are performed at the same time. The gist is that it consists of ceramic fine particles of the same or different types.

Further, the manufacturing method of the present invention includes a step of preparing an impregnating liquid by dispersing mullite particles serving as a matrix in a solution in which an organic metal polymer is dissolved, and a step of preparing an impregnating liquid by continuously passing the fiber through the impregnating liquid. A step of uniformly impregnating the fibers with the impregnating liquid, and laminating the fibers and applying the impregnating liquid to the fibers. a step of making the organic gold IX polymer in the laminate into a peripheral body, a step of making the organic gold IX polymer in the laminate infusible, and a step of sintering the laminate in argon gas or nitrogen gas under gas pressure or normal pressure. The gist is that.

The reinforcing fibers dispersed in the mullite matrix may be short fibers or long fibers. Glass fibers, metal fibers, carbon fibers, and ceramic fibers can be used as the long fibers.

In order to improve the oxidation resistance of these fibers or to control the interface α with the mullite matrix, it is preferable to coat the fiber surfaces with ceramics or the like by CVD.

The reinforcing fibers are dispersed in the mullite matrix by a known method. For example, in the case of long fibers, there is a method in which the fibers are immersed in a slurry of mullite powder and wound around a drum one after another (filament winding method), or a method in which the fibers are made into a sheet and matrix powder is alternately layered (laminated). For example, a method is used in which an unfired laminate is made using a method (method), and this laminate is molded in accordance with a pressing mold and hot-pressed.

FIG. 1 is a diagram demonstrating the filament winding method. Long fiber 1 unwound from spool 10
2 is immersed in an impregnating liquid 16 in the form of a slurry in which mullite powder contained in an impregnating liquid layer 14 is mixed and passed through it, and the impregnating liquid 16 is attracted to the surface of the long fibers 12 to form a winding drum 1.
Wind it up to 8.

The laminate 20 wound around the drum is removed from the drum 18 by cutting at an appropriate location, cut into a desired size,
Laminate to appropriate thickness. The stacked laminate 20 is degreased if necessary, then molded into a mold and hot pressed.

Additionally, CVD (chemical vapor deposition) is used to generate a ceramic matrix phase in the gaps between fiber preforms.
Alternatively, a sol-gel method in which fibers are impregnated with a gel polymer of metal alkoxide and then thermally decomposed to obtain metal oxides can be used. In the case of short fibers, a slip casting method is effective, in which the fibers are dispersed in a ceramic powder slurry, poured into a plaster mold, and a female mold that matches the mold is taken out and fired. The composite amount of fibers is suitably 30 to 40% by volume.

The fine particles dispersed in the mullite matrix may be particles of a different type or the same type as the mullite matrix. Strengthening of the matrix by particle dispersion is S i )
As T-measured from the knowledge of N-T i C, 20
The maximum effect is obtained at ~25 vol. 1%.

From the viewpoint of crack deflection, it is effective for the particle size of the particles to be dispersed to be uniformly present at the grain boundaries of the matrix in a fine state.

The most appropriate particle dispersion method is a method that utilizes thermal decomposition of organometallic polymers, since it is difficult to achieve uniform dispersion and create fine particles using the powder mixing method. That is, when an organometallic polymer containing a metal element such as silicon that forms a ceramic is thermally decomposed in an inert atmosphere, the organic component is separated and an arsenic or nitride is obtained. Examples of organometallic polymers include polysiloxane, polysilazane, polycarbosilane, and polysilastyrene. Polycarbosilane produces silicon carbide as shown in formula (1), and polysilazane produces silicon carbide as shown in formula (2). Silicon nitride is obtained in this way.

(SiH(CH*)・CH2)n-4sic
(1) (SiRR'NH□)n → Si, N,
(2) Organometallic polymer is coated on the surface of mullite particles that serve as a matrix, and then a thermochemical reaction is performed to form ceramics and fine particles are dispersed. Therefore, the organometallic polymer is dissolved in a solvent (toluene, xylene, etc.), mullite particles serving as a matrix are mixed therein, and the surfaces of the mullite particles are coated with the organometallic polymer.

In order to uniformly disperse Ia fibers in the matrix, an impregnating liquid is prepared by mixing matrix particles in a solution of the organometallic polymer, and the fibers are continuously passed through the impregnating liquid to coat the fiber surface with the impregnating liquid. By the filament winding method that evenly attaches the material. The amount of fibers dispersed in the mullite matrix can be adjusted by the viscosity of the impregnating liquid and the fiber passage speed, but the fiber content is
The most preferable range is about 30 to 40%.

The material wound using the filament winding method is heated with nitrogen gas or argon gas before being sintered.
Or in a mixed gas stream of nitrogen gas and ammonia gas 7
The organic gold H polymer is made infusible at a temperature of 00 to 800° C., and a vitrified ceramic layer, which is a precursor to fine particles, is generated on the surface of the mullite particles that serve as a matrix. After making the organometallic polymer infusible, the molded product is pressurized (~9 kg/c+i2G) in argon gas or nitrogen gas.
Alternatively, sintering is performed under an unpressurized air flow.

[Function] The particle-dispersion reinforced fiber-reinforced mullite composite of the present invention has the following properties:
Since fine particles of the same type as the matrix ceramic or 51Fl are dispersed in the grain boundaries, crack deflection occurs and fracture toughness is improved. In other words, cracks propagate in a zigzag manner around the dispersed phase due to differences in the toughness, thermal tensile strength, and various other properties of the dispersed phase between the matrix and fine particles, as well as the state of the interface between the two. Necessary energy is consumed, fracture energy increases, and fracture toughness improves.

Further, since the mullite composite of the present invention is reinforced by dispersing fibers, the fracture toughness is improved by fiber reinforcement. That is, when fibers are mixed as a dispersed phase, when the cracks pass through a location where the fibers are present, the fibers are pulled out from the matrix by the amount of gap created by the cracks. Energy is consumed by the amount of work done to pull out the fibers, increasing fracture energy and improving fracture toughness.

The most distinctive feature of the particle dispersion-strengthened fiber-reinforced mullite composite of the present invention is that the above-mentioned improvement in fracture toughness due to particle dispersion and improvement in fracture toughness due to fiber reinforcement occur simultaneously and effectively, resulting in improved fracture toughness. This is a significant increase.

In the manufacturing method of the present invention, mullite particles serving as a matrix are mixed into a solution containing an organometallic polymer to form an impregnating liquid, and the fibers are impregnated with this impregnating liquid.
After making the organometallic polymer infusible, when the fiber laminate is sintered in an inert atmosphere, the organic components are separated due to thermal decomposition of the organometallic polymer, and fine carbides or nitrides form at the mullite grain boundaries. A fiber-reinforced Murai 1-composite which is precipitated and strengthened by particle dispersion can be obtained.

[Examples] Preferred embodiments of the present invention will be described below to clarify the present invention more specifically, but the present invention should not be construed to be equally limited by the description of the embodiments described below.

(Example 1) 42 g of polysilastyrene (trade name, PSS-400) manufactured by Nippon Soda Co., Ltd. was dissolved in 110 g of l.luene as a solvent. This solution was prepared separately with an internal volume of 500cc.
into a polyethylene pot, and 98 g of mullite powder (trade name: KM Murai, manufactured by Kyoritsu Ceramic Materials Co., Ltd.) was added. Next, 300 g of high alumina cylinder-shaped cobblestones with a diameter of 12.5111 mm were placed in this, the pot lid was left open, and the pot was rotated at 50 rpm for 16 hours to prepare an impregnating solution.

This impregnation liquid was poured into the impregnation layer, and the carbon MIA fibers ((
Ltd.) Power VJ! (M-60,2 product, Bina type, or Toho Rayon IM40.6 product, Pan type) was attached to the spool stand, passed through the impregnating liquid of the impregnated layer at a winding speed of 3 cII/sec, Carbon fibers were uniformly impregnated with an impregnating liquid, and the carbon fibers holding the impregnating liquid were wound up on a winding drum.

In addition, before winding the carbon fiber onto the winding drum,
Hot air heated to 0 to 50° C. was supplied to volatilize toluene from the carbon fibers, and the polysilastyrene was wound up in a state in which it had adhesive properties. In addition, since adhesive carbon fibers are wound onto the winding drum, it is recommended that the parts that come into contact with the carbon fiber laminate be treated with fluorine, etc., so that the carbon fiber laminate can be easily removed. good.

The carbon fiber laminate removed from the winding drum is cut into any shape and then subjected to a biaxial pressure press, or a cold or warm isostatic press (C, Machining, P or W, ■,
The molded body was molded and pressurized at P), placed in an open chamber maintained at a temperature of 50° C., and left for 24 hours to completely volatilize the toluene.

Subsequently, the polysilastyrene contained in this molded article was treated to be infusible. In the infusibility treatment, the molded body was heated under N2 gas pressure (~5kg/cI112) under a temperature gradient of 3°5°C/hour.
G), it was treated up to 600°C to completely vitrify it.

In sintering this molded body, fine powder of nitrogen and boron was applied to the surface of the degreased molded body to perform masking. This molded body was heated under gas pressure (9 kg in the case of nitrogen gas).
/cm”G, argon gas field h2 kg/cm2G
) Sintering was performed under the conditions of heating at a temperature gradient of 200° C./hour and holding at a temperature of 1650° C. for 1 hour.

For comparison, an organometallic polymer was used as a conventional example.
Prepare an impregnating solution without using carbon fiber, and create a laminate impregnated with pitch-based and bread-based carbon fibers using the same method as above.
It was cut and pressure-molded in the same manner as above to obtain a molded body, which was made infusible under the same conditions as above and then sintered to obtain a sintered body.

The bending strength and fracture toughness of the obtained sintered bodies of the present invention example and the conventional example were measured at 1°, and the results are shown in Table 1.

As is clear from Table 1, in comparison with the conventional example, the bending strength and fracture toughness of the example of the present invention were improved by about 40% or more in the pitch system, and the bending strength and fracture toughness of the bread system were improved by more than 40%. High toughness values of approximately 40% or more were obtained in both cases, confirming the effectiveness of the present invention.

(The following is a blank space) (Example 2) In order to prevent surface oxidation of the same carbon fibers (pitch type and bread type) used in Example 1, silicon carbide was deposited on the fiber surface by chemical vapor deposition (CVD). Using this carbon fiber, a sintered body was obtained using the same impregnating liquid composition, winding conditions, degreasing and sintering conditions as in Example 1.

For comparison, the same carbon fiber was immersed in an impregnating liquid that did not dissolve the organometallic polymer, wound up, and degreased and sintered under the same conditions to obtain a conventional sintered body.

The bending strength and fracture toughness values of the obtained sintered bodies of the present invention example and the conventional example were measured and shown in Table 2.

(Left below) As is known from Table 2, the conventional example has a bending strength of 6 to 7 kHz/mm" in pitch systems, a fracture toughness of 2.5 MN/m", and a bending strength of 2.5 MN/m in bread systems. is 6°6
kgr/Tsuru m2, the fracture toughness value was 2.4 MN/-, whereas in the example of the present invention, the pitch system had a bending strength of 9, 6 kgf/Tsuru m2, and a fracture toughness value of 3.5 MN/-.
7. Bending strength of bread type is 9.4kgf/me+'
The fracture toughness value was 3.4 MN/m3'2, and the bending strength and fracture toughness values were both significantly improved, confirming the effect of the present invention.

- (Example 3) Polysilazane (trade name: NCP-200, product containing 652≦toluene solution) manufactured by Chisso Corporation 64.611 was dissolved in 87.4 g of toluene as a solvent.

This solution was placed in a separately prepared polyethylene bottle with an internal volume of 500 cc, and 98 g of mullite powder (manufactured by Kyoritsu Ceramic Materials Co., Ltd., trade name, KM Mullite) was added. Put 300 g of shaped stones, close the bottle lid, and close the pot.
An impregnating solution was prepared by mixing for 16 hours at rpi*.

This impregnating liquid is poured into the impregnated layer, and carbon fiber (Co., Ltd.)
Attach the belt and force (IM 60.2, pitch type, or Toho Rayon IM40.6, pan type) to the spool stand, and apply the impregnating liquid to the impregnated layer at a winding speed of 3 cm/sec. The carbon fibers having a width of JFFI L were uniformly impregnated with the impregnating liquid, and the carbon fibers holding the impregnating liquid were wound up on a winding drum.

Thereafter, the material was laminated, degreased, and sintered under the same conditions as in Example 1 to obtain a sintered body of an example of the present invention. For comparison, as a conventional example, an impregnating liquid that does not dissolve polysilazane was prepared in 71, and a sintered body of the conventional example was obtained in the same manner.

The bending strength and fracture toughness values of the obtained sintered bodies of the present invention example and the conventional example were measured and shown in Table 3.

Table 3 As is known from Table 3, the conventional example has a bending strength of 5.5 kgf/mm2 and a fracture toughness of 2.0 MN/s+'' in the pitch system, and a bending strength of 5.4 kgf/mm2 in the bread system. , the fracture toughness value was 1.9 MN/ram2, whereas in the example of the present invention, the pitch system had a bending strength of 7.8 kHr/ram2 and a fracture toughness value of 2.9 MN/ram2.
9MN/tread 7, bending strength in bread system 7, 7k
g/ram”, fracture toughness value is 2,7 MN/
vs.eta., high values of around 40% were obtained for both bending strength and fracture toughness, confirming the effects of the present invention.

(Implementation rI/44) In order to prevent surface oxidation of the same carbon fibers (pitch type and bread type) used in Example 1, silicon carbide was deposited on the fiber surface by chemical vapor deposition (CV D ). Using this carbon fiber, a sintered body was obtained under the same impregnation liquid composition as in Example 3 and the same winding conditions, degreasing and sintering conditions as in Example 1.

In addition, for comparison, the same carbon m-fiber was used as a conventional example, immersed in an impregnating liquid that did not dissolve the organometallic polymer, wound up, and degreased and sintered under the same conditions to obtain a sintered body. .

The bending strength and fracture toughness values of the obtained sintered bodies of the present invention example and the conventional example were measured and shown in Table 4.

As is clear from Table 4, No. 1k, in the example of the present invention, compared to the conventional example, the bending strength and fracture toughness values of both the pitch and bread systems were reduced by more than 40%, demonstrating the effect of the present invention. confirmed.

(Example 5) In Examples rIA1 to 4, test results were shown for composite materials using carbon fiber, but in this example, tungsten fiber was used, which has superior strength, elastic modulus, melting point, or decomposition point to carbon mtt. did.

When tungsten fibers are heated above 1300℃, grains grow and become easier to cut, so doria (Th02) is
．． Fibers doped with 5% and which do not cause grain growth upon heating were used.

The tungsten fibers used were manufactured by Nippon Tungsten Co., Ltd. and had a fiber diameter of 50 μm. Since it would take time to wind the fibers one by one using the filament winding method, 50 fibers were bundled and soaked in the impregnating liquid. It passed through the impregnated layer and was wound up on a winding drum.

Two formulations were used for the impregnating liquid: a system in which polysilastyrene was mixed with silicon nitride in Example 1, and a system in which silicon nitride was mixed in polysilazane in Example 3.6 The winding conditions, degreasing, and sintering conditions were as in Example 1. Alternatively, a sintered body was obtained in the same manner as in Example 3. In addition, for comparison, we used an impregnating liquid that did not dissolve the organometallic polymer as a conventional example, impregnated tungsten fibers, degreased and sintered them under the same conditions, and produced one sintered fiber in the conventional example. Prepared.

The bending strength and fracture toughness values of the obtained sintered bodies of the present invention example and the conventional example were measured and shown in Table 5.

Table 5 As is clear from Table 5, the example of the present invention obtained superior values of bending strength and fracture toughness of over 40% in the polysilastyrene system compared to the conventional example, and the polysilazane system In this test, excellent bending strength and fracture toughness values of over 40% were obtained, confirming the effects of the present invention.

[Effects of the Invention] As explained above, the fiber-reinforced mullite composite material reinforced by particle dispersion of the present invention comprises a mullite matrix, fibers dispersed in the mullite matrix, and ceramics of the same or different types dispersed in the ceramic matrix. The crack deflection occurs due to the fine particles dispersed in the matrix grain boundaries, improving fracture toughness, and the pull-out of the fibers dispersed in the matrix causes crack deflection. Since the fracture energy was increased, the fracture toughness value as well as the bending strength could be significantly improved.

Although conventional ceramics have various excellent properties, they are brittle materials that are susceptible to sudden changes in strength due to impact, and their applications are limited. A certain fracture toughness 1ilIK +c is significantly improved, and it becomes possible to apply it to cylinder liners, piston rings, etc. in reciprocating engines, and to turbine rotor blades in gas turbine engines.

In the manufacturing method of the present invention, mullite particles serving as a matrix are mixed into a solution containing an organometallic polymer to form an impregnating liquid, and the fibers are impregnated with this impregnating liquid.
After making the organometallic polymer infusible, when the fiber laminate is sintered in an inert atmosphere, the organic component is separated due to thermal decomposition of the Ii% metal polymer, and fine carbon particles or nitrides are formed. is precipitated at the matrix grain boundaries, and a fiber-reinforced ceramic N itself which is strengthened by particle dispersion can be obtained. In addition, when carbon fibers are used, they are coated with organic metal polymers, and a thin film of carbon, arsenic, and silicon nitride is applied through a thermochemical reaction, which improves the acid and arsenic resistance of carbon fibers. A positive effect can be expected.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing the filament winding method. - Spool, long fiber, impregnated layer, - impregnated liquid, winding drum, 20 - Laminated body.

Claims (2)

[Claims] (1) A fiber-reinforced mullite composite material reinforced by particle dispersion, characterized by comprising a mullite matrix, fibers dispersed in the mullite matrix, and fine ceramic particles of the same or different types dispersed in the mullite matrix. (2) A process of preparing an impregnating liquid by dispersing mullite particles as a matrix in a solution in which an organic metal polymer is dissolved, and passing the fibers continuously through the impregnating liquid to uniformly coat the fibers with the impregnating liquid. a step of laminating the fibers to form a laminate; a step of making the organometallic polymer in the laminate infusible; and a step of pressurizing the laminate in argon gas or nitrogen gas or A method for producing a fiber-reinforced mullite composite material reinforced by particle dispersion, characterized by comprising a step of sintering at normal pressure.