JPH0780713B2 - Ceramic composite material manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a surface-treated inorganic fiber reinforced ceramic composite material.

(Prior art and its problems) Ceramics are used in fields where heat resistance and high strength are required. However, in general, ceramics are vulnerable to mechanical shock and have a drawback that their mechanical strength or corrosion resistance is reduced at high temperatures.

In order to compensate for these drawbacks, a continuous fiber made of alumina, carbon, etc., a short fiber made of silicon carbide, etc. or a composite of whiskers and ceramics has been proposed.

Japanese Unexamined Patent Publication (Kokai) No. 52-81309 describes a method for producing a heat resistant ceramic composite reinforced with continuous silicon carbide fibers obtained from an organosilicon polymer compound. in this way,
The adhesiveness between the reinforcing fiber and the ceramic that is the matrix is poor, and a composite having the desired mechanical strength cannot be obtained.

In JP-A-55-85644, polycarbosilane, polysilane, by coating an organosilicon polymer compound such as polycarbosiloxane on the surface of the carbon fiber, by inorganicizing the organosilicon polymer compound, A method of forming a ceramic material mainly composed of silicon carbide as a surface layer has been proposed. In this method, the adhesiveness between the center layer and the surface layer is poor, and the strain remains between both layers, so that the tensile strength or flexibility of the reinforcing fiber itself is low, and the mechanical strength of the obtained composite is also high. It is unsatisfactory.

Further, in JP-A-59-53782, after forming a glassy layer on the carbon fiber in advance, polycarbosilane, polysilane, an organosilicon polymer compound such as polycarbosiloxane is applied to the surface of the carbon fiber, Then, a method of forming the surface layer by mineralizing the above-mentioned polymer compound is disclosed. In this method, the mechanical strength of the obtained reinforcing fiber itself is good, but the wettability of the carbide forming the surface layer with the ceramics is insufficient, and the mechanical strength of the obtained composite is satisfactory. Not a thing.

(Technical Means for Solving Problems) It is an object of the present invention to use mechanical treatment such as fracture toughness and compressive strength by using a surface-treated inorganic fiber having good adhesion between a center layer and a surface layer and a matrix. It is to provide a method for manufacturing a ceramic composite having excellent strength.

According to the present invention, in a method for producing a ceramic composite material using a surface-treated inorganic fiber as a reinforcing material and a ceramic as a matrix, (i) an amorphous substance consisting essentially of Si, C and O, or (ii) An aggregate composed of crystalline ultrafine particles substantially composed of β-SiC having a particle size of 500 Å or less and amorphous SiO ₂ , or (iii) the amorphous substance of (i) and the amorphous substance of (ii) above. Inorganic fiber containing silicon, carbon and oxygen consisting of a mixed system of crystalline ultrafine particle aggregates, polycarbosilane which is a raw material of the inorganic fiber, polymetallocarbosilane having a metalloxane bond, silane coupling agent, phenol resin, and A solution of at least one surface-treating agent selected from the group consisting of petroleum pitch dissolved in an organic solvent is applied and dried, and the resulting surface-treated inorganic fiber for reinforcement is used as a matrix for the cellar. Click powder or the preparation of a ceramic composite material and firing by kneading or embedded in organic matter of the ceramic by heat treatment is provided.

The inorganic fiber used in the present invention is, for example,
It can be prepared by the method described in JP-A-57-26527.

In the present invention, polycarbosilane, which is one of the polymers applied to the surface of the inorganic fiber, is, for example, Japanese Patent Publication No. 58-385.
It can be produced by the method described in JP-A-34.

Similarly, a polymetallocarbosilane having a metalloxane bond, which is one of the polymers applied to the surface of the inorganic fiber, is disclosed in, for example, Japanese Patent Publication Nos. 61-49335 and 61-856.
62-60414, 63-37139, 63-49691, 62-37050, etc. can be prepared according to the method described therein. These polytitanocarbosilanes or polyzirconocarbosilanes preferably contain 10 to 80% by weight of siloxane polymer.

Similarly, the silane coupling agent applied to the surface of the inorganic fiber is represented by the formula YRSiX ₃ [wherein, X represents —OR, —Cl, —NR ₂ , —R, and Y represents CH ₂
= C (CH ₃₎ COO-, NH ₂ —, HS—, NH ₂ CH ₂ CH ₂ NH—, Cl—, R—, wherein R represents a divalent aliphatic or aromatic residue. The compound of [] is generally used.

Similarly, there is no particular limitation on the phenol resin applied to the surface of the inorganic fiber, those which are soluble in an organic solvent are preferable, and for example, a phenol resin having an average molecular weight M _W of 500 to 20,000 is preferably used, and specific examples thereof are given. ,
Resol-type or novolac-type phenolic resins, such as phenol-formalin resin, cresol-formalin resin, modified phenolic resin, phenol-furfural resin, resorcin resin and the like can be mentioned.

Similarly, as the petroleum pitch applied to the surface of the inorganic fiber, pitch which is a residue during petroleum refining, for example, pitch obtained as a bottom residue during fluid catalytic cracking of crude oil can be used.

Examples of the organic solvent used in the present invention include alcohol solvents such as methanol and ethanol, aromatic solvents such as benzene, toluene and xylene, and aliphatic solvents such as hexane and heptane.

When a ceramic composite is produced using inorganic fibers treated with the above surface treatment agent, the mineralization of the polymer that forms the surface layer of the inorganic fibers during the firing step proceeds, and the surface layer is an inorganic fiber having a central layer. To form a porous boundary layer which is integrated with or strongly adhered to. The formed porous boundary layer causes an anchor effect and the like with the ceramic that is the matrix, and thus the obtained ceramic composite has excellent mechanical strength such as compressive strength.

Next, a method for producing the surface-treated inorganic fiber used in the present invention will be described.

As a method of applying the surface treatment agent used in the present invention to the inorganic fiber, for example, after dissolving the surface treatment agent in a suitable stable solvent, this solution is applied to the inorganic fiber by a spray method, a brush coating method or a dipping method. Apply. This is dried to produce a surface-treated inorganic fiber having a surface layer with a uniform thickness. The thickness of the surface layer is preferably 0.1 to 50 μm, particularly preferably 0.2 to 10 μm. The diameter of the inorganic fiber is generally 5-20
μm, preferably 7 to 15 μm. The length of the surface-treated inorganic fiber is preferably 0.2 to 50 mm, and may be chopped.

The surface-treated inorganic fibers in the composite are, in addition to those arranged at random, sheet-like materials aligned in one direction, or plain weave, satin weave, simulated weave, twill weave, bag weave, leno weave, spiral weave, tertiary Various shapes such as a weave can be adopted as needed.

The matrix ceramics used in the present invention include silicon carbide, titanium carbide, zirconium carbide, vanadium carbide, niobium carbide, tantalum carbide, boron carbide, chromium carbide, tungsten carbide, molybdenum carbide, and other carbide ceramics; silicon nitride; Titanium nitride, zirconium nitride, vanadium nitride, niobium nitride,
Nitride ceramics such as tantalum nitride, boron nitride, aluminum nitride and hafnium nitride; oxide ceramics such as alumina, magnesia, mullite and cordierite; glass ceramics such as borosilicate glass, high silica content glass and aluminosilicate glass; Examples thereof include carbon such as coke, carbon black, earthy graphite, and scaly graphite. These ceramics may be a mixture of two or more kinds. In addition, metal powder such as Si and Al may be added to the matox, if necessary.

In the method for producing the surface-treated inorganic fiber-reinforced ceramic composite pair of the present invention, as a method for kneading or embedding the surface-treated inorganic fiber in the ceramic, a method known per se as exemplified below can be adopted.

A method of kneading or embedding the reinforcing fibers in the ceramic powder matrix or a mixture of the ceramic powder matrix and a binder, and the reinforcing fibers are arranged in advance,
A method of filling the gap with the above-mentioned ceramic powdery matrix or a mixture thereof, and the like.

As a method of firing the aggregate of the reinforcing inorganic fiber and the ceramics, a rubber press, a die press or the like is used to press-mold the above polymer at a pressure of 50 to 5,000 kg / cm ² , and then in a heating furnace. A method of firing in the temperature range of 600 to 2,400 ° C,
It is possible to employ a method such as hot press firing in a temperature range of 600 to 2,400 ° C. while applying a pressure of 50 to 5,000 kg / cm ² .

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

(Example) An example and a comparative example are shown below. In the following, "part" means "part by weight".

Reference Example 1 (Synthesis of polymethanocarbosilane) To 100 parts of polydimethylsilane synthesized by dechlorinating and condensing dimethyldichlorosilane with metallic sodium, 3 parts of polyborodiphenylsiloxane was added, and 350 parts of nitrogen were added.
It was thermally condensed at ° C. The resulting polycarbosilane having a main chain skeleton mainly composed of the carbosilane unit of the formula (Si-CH ₂ ) and having a hydrogen atom and a methyl group at the silicon atom of the carbosilane unit is added with a titanium alkoxide to obtain a nitrogen atom of 34
Cross-linking is polymerized at 0 ° C to obtain 100 parts of carbosilane units and the formula (Ti
A polytitanocarbosilane consisting of 10 parts of the titanoxane unit of O) was obtained. The number average molecular weight of this polytitanocarbosilane was about 2,500.

Examples 1 to 3 and Comparative Examples 1 and 2 Polycarbosilane obtained in the same manner as in Reference Example 1 above was melt-spun, then infusibilized at 180 ° C. in air, and further heat treated at 1,300 ° C. in nitrogen. An inorganic fiber was obtained.

Phenolic resin (Hitachi Kasei VP
-803) ethanol solution by spray method,
It dried and prepared the reinforcement fiber for composite materials. This reinforcing fiber had a diameter of about 8.5 μm, and the coating thickness of the phenol resin after drying was 0.9 μm.

The reinforcing fiber is cut into a length of about 2 mm, fused alumina,
The mixture was added to a matrix composed of a mixture of graphite, fused silica and a phenol resin binder, sufficiently kneaded, and then molded by a rubber press at a pressure of ² t / cm ² . The obtained molded body was heated to 1,200 ° C. at a rate of 300 ° C./hour in a nitrogen stream and baked at the same temperature for 3 hours.

In Comparative Example 1, a fired body containing no reinforcing fiber was used in Example 1.
Comparative Example 2 is a similar method to that of Example 1, except that no surface treatment is performed.

The results are shown in Table 1.

As can be seen from Table 1, the ceramic composite material obtained by the present invention has remarkably improved compressive strength and bending strength.

Examples 4 to 6 Instead of the phenol resin ethanol solution, an aqueous solution of γ-aminopropyltriethoxysilane (APTES) (Example 4), an ethanol solution of petroleum pitch (Example 5) or the poly obtained in Reference Example 1 was used. A fired body was obtained by repeating the same method as in Example 1 except that a xylene solution of titanocarbosilane (PTCS) (Example 6) was used. The results are shown in Table 2.

(Effect of the invention) As is clear from the above description, the ceramic composite material obtained in the present invention has good adhesion between the center layer and the surface layer of the surface-treated inorganic fiber and the surface layer and the matrix ceramics. Excellent in compressive strength and bending strength.

Claims (1)

[Claims] 1. A method for producing a ceramic composite material comprising a surface-treated inorganic fiber as a reinforcing material and a ceramic as a matrix, comprising (i) an amorphous substance consisting essentially of Si, C and O, or (ii) particles An aggregate composed of crystalline ultrafine particles substantially composed of β-SiC having a diameter of 500 Å or less and amorphous SiO ₂ , or (iii) the amorphous substance of (i) above and the crystal of (ii) above Made of a mixed system of fine ultrafine particle aggregates, to inorganic fibers containing carbon and oxygen, polycarbosilane which is a raw material of the inorganic fibers, polymetallocarbosilane having a metalloxane bond, a silane coupling agent, a phenol resin, And at least one surface-treating agent selected from the group consisting of petroleum pitch is dissolved in an organic solvent and dried, and the resulting surface-treated inorganic fiber for reinforcement is used as a matrix. A method for producing a ceramic composite material, which comprises kneading or embedding in an organic powder which is made into ceramic by heat treatment or heating and then firing.