JPH07172949A - Sintered material of inorganic fiber and its production - Google Patents

Abstract

PURPOSE:To produce the subject sintered material excellent in fracture toughness over the whole temperature range by preparing a sintered material composed of inorganic fibers and an inorganic substance filling gaps between the fibers and having a carbon layer in the boundary layer and further coating the uppermost surface with a layer of an oxide of the inorganic substance. CONSTITUTION:This sintered material is a sintered inorganic fiber composed of inorganic fibers made of (A) an amorphous material comprising Si, M (Ti or Zr), C and O, (B) an aggregate comprising a crystalline ultrafine particle of beta-SiC, MC, a solid solution of beta-SiC and MC and/or MC1-X. (X is >=0 or <1) and amorphous SiO2 and M03 or (C) a mixture of the component (A) and the aggregate (B) and an inorganic substance component composed of (D) an amorphous substance comprising Si, M and O, (E) a crystalline aggregate comprising crystalline SiO2 and MO2 or (F) a mixture of (D) and (E) as inorganic materials and filling gaps between the fibers. This sintered material has an amorphous (or crystalline) carbon layer of 1 to 200nm thickness on the boundary between the inorganic fiber and the inorganic substance component and an oxide layer composed of (D), (E) or (F) and having 20 to 500mum thickness on the uppermost surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inorganic fiber sintered body having high strength and toughness, and further showing excellent oxidation resistance in a wide temperature range, and a method for producing the same.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication (Kokai) No. 5-43338 discloses an inorganic fiber composed of the following (1), (2) or (3) and the following (4) existing at the interface of the inorganic fiber:
An inorganic fiber sintered body composed of an inorganic substance composed of (5) or (6) is disclosed.

(1) Substantially consisting of Si, M, C and O
An amorphous substance. (2) Substantially β-SiC, MC, β-SiC and MC
Solid solution and / or MC _1-xCrystalline ultrafine particles of
Amorphous SiO₂And MO₂An aggregate consisting of. (3) The amorphous substance of (1) above and the aggregate of (2) above
Mixture of. (4) An amorphous substance consisting essentially of Si, M and O. (5) crystalline SiO₂And MO₂Crystal set consisting of and
body. (6) The amorphous substance of (4) above and the crystal aggregate of (5) above
Mixture with the body. (In the formula, M represents Ti or Zr, and x represents
It is a number of 0 or more and less than 1. )

Further, in the above publication, as a method for producing the sintered body, an inorganic fiber comprising an inner surface layer and a surface layer,
The inner layer is composed of the above (1), (2) or (3),
A method is disclosed in which a laminate of inorganic fibers whose surface layer is composed of (4), (5), or (6) is heated and sintered at a temperature range of 1400 to 1900 ° C.

In the sintered body described in the above publication, the oxide layer existing at the interface of the inorganic fibers has a very good affinity with the inorganic fibers, and the propagation of fracture proceeds rapidly, so that the mechanical properties are high. Indicates. On the other hand, the above-mentioned sintered body tends to show a brittle fracture pattern, and there is room for improvement as a sintered body which is more resistant to cracking and has high fracture energy, that is, high fracture toughness.

The present inventor has proposed as a Japanese Patent Application No. 5-253550 a sintered body having higher fracture toughness as compared with the sintered body described in the above publication and a method for producing the same. The proposed sintered body is composed of the inorganic fiber composed of the above (1), (2) or (3) and the above (4), (5) or (6) existing at the interface of the inorganic fiber. An inorganic fiber sintered body composed of a constituent inorganic substance, which is 1 as a boundary layer between the inorganic fibers (1) to (3) and the inorganic substances (4) to (6).
There is a layer of ~ 200 nm of amorphous and / or crystalline carbon.

Further, the proposed method is an inorganic fiber comprising an inner surface layer and a surface layer, wherein the inner surface layer has the above-mentioned (1),
(2) or (3), wherein the surface layer is (4),
The first step of heating the laminate of the inorganic fibers composed of (5) or (6) from room temperature to 1400 ° C. under a pressure of 50 to 1000 kg / cm ² in an inert gas, 140
The temperature is raised to a temperature in the range of 0 to 1750 ° C.,
It consists of a second step of holding for 10 minutes to 10 hours, and a third step of heating and sintering the temperature from the holding temperature to a temperature in the range of 1900 ° C.

In the proposed sintered body, the carbon layer existing at the interface between the inorganic substance and the oxide layer serving as the matrix functions to appropriately weaken the bond between the two, so that the fracture progresses in a non-linear manner. However, it exhibits high fracture energy, in other words, high fracture toughness.

[0009]

As a result of further research by the present inventor, the proposed sintered body exhibits excellent mechanical properties in the temperature range of room temperature to 500 ° C. and 1000 to 1500 ° C. in air. On the other hand, the above sintered body is 500
When held in the medium temperature range of ~ 1000 ° C for a long time,
It was found that the carbon is pulled out before the oxide layer as the protective film is formed on the surface of the sintered body, so that the strength is reduced to a degree that cannot be ignored in practical use.

[0010]

The technical object of the present invention is to:
To solve the problem to be solved, that is, the oxidative deterioration in the medium temperature region of the sintered body previously proposed by the present inventors, and to provide an inorganic fiber sintered body having excellent fracture toughness over the entire temperature region from room temperature to high temperature. It is in. Another object of the present invention is to provide a method for producing an inorganic fiber sintered body that exhibits such excellent fracture toughness.

According to the present invention, the inorganic fiber composed of the following (a), (b) or (c) and the following (d) and (e) which are present so as to fill the gaps between the inorganic fibers. )
Or an inorganic substance composed of (f), which comprises (a) to
As a boundary layer between the inorganic fiber of (c) and the inorganic substance of (d) to (f), there is a layer of amorphous and / or crystalline carbon of 1 to 200 nm, and the outermost surface is 20-500 having the composition of (d), (e) or (f) of
Provided is an inorganic fiber sintered body covered with an oxide layer having a thickness of μm.

(A) Substantially consisting of Si, M, C and O
An amorphous substance. (B) Substantially β-SiC, MC, β-SiC and MC
Solid solution and / or MC _1-xCrystalline ultrafine particles of
Amorphous SiO₂And MO₂An aggregate consisting of. (C) The amorphous substance of (a) above and the aggregate of (b) above
Mixture of. (D) An amorphous substance consisting essentially of Si, M and O. (E) crystalline SiO₂And MO₂Crystal set consisting of and
body. (F) The amorphous substance of (d) above and the crystal aggregate of (e) above
Mixture with the body. (In the above formula, M is Ti or Zr
Here, x is a number of 0 or more and less than 1. )

Further, according to the present invention, the above (a),
An inner surface layer composed of (b) or (c) and the above (d),
A layered product of inorganic fibers comprising a surface layer composed of (e) or (f) in an inert gas at 50 to 1000 kg /
Under the pressure of cm ^2, a first step of raising the temperature from room temperature to 1400 ° C., a second step of raising the temperature to a temperature in the range of 1400 to 1750 ° C. and holding at the same temperature for 30 minutes to 10 hours, from the above holding temperature The sintered body obtained in the third step and the third step in which the temperature is raised to a temperature in the range of 1900 ° C.
Oxidation treatment is performed in an oxygen-containing gas at 000 to 1500 ° C. for 1 to 100 hours, and the above (d) and (e) are formed on the outermost surface of the sintered body.
Alternatively, there is provided a method for producing an inorganic fiber sintered body, which comprises a fourth step of forming an oxide layer having a composition of (f) and having a thickness of 20 to 500 μm.

First, the inorganic fiber sintered body of the present invention will be described. The ratio of each element constituting the inorganic fiber is usually S
i: 30 to 60% by weight, M: 0.5 to 35% by weight, preferably 1 to 10% by weight, C: 25 to 40% by weight, O:
It is 0.01 to 30% by weight. The equivalent diameter of the inorganic fiber is generally 5 to 20 μm.

On the surface of the inorganic fiber in the sintered body, 1-2
Amorphous and / or crystalline carbon in the range of 00 nm is unevenly distributed in layers. This carbon has been segregated from the inside of the inorganic fiber in the process of pressure sintering in the production method described later. The layered carbon on the surface of the inorganic fiber usually has a graded composition distribution in which the concentration decreases toward the inside of the inorganic fiber, and exists as a part of the fiber together with the inorganic fiber.

The above-mentioned (d), (e) or (f) is present so as to fill the gaps of the inorganic fibers. Depending on the location, the inorganic fibers and the inorganic fibers may be in contact with each other with amorphous and / or crystalline carbon in the range of 1 to 200 nm as a boundary layer.

The proportion of each element constituting the inorganic substance existing so as to fill the gaps of the inorganic fiber having the carbon layer on the surface is usually Si: 20 to 65% by weight, M: 0.3 to.
40% by weight, preferably 1 to 15% by weight, O: 30 to 5
It is 5% by weight and may contain 5% by weight or less of carbon in some cases.

The inorganic fiber sintered body of the present invention has an outermost surface having a composition of (d), (e) or (f) above from 20 to 20.
It is covered with a 500 μm thick oxide layer. This oxide layer is formed by, for example, an oxidation treatment which is the fourth step in the manufacturing method described later. Inside the oxide layer,
The composition and structure before the oxidation treatment are substantially completely retained. Then, this oxide layer acts as a protective layer inside the inorganic fiber sintered body. The boundary between the oxide layer and the inside of the sintered body generally has a composition distribution that is gradually inclined toward the inside.

The ratio of each element constituting the oxide layer existing on the outermost surface of the inorganic fiber sintered body is usually Si: 20 to 65.
% By weight, M: 0.3-40% by weight, preferably 1-15
% By weight, O: 30 to 55% by weight, and in some cases 5% by weight or less of carbon may be contained, and this carbon may partially exist as microcrystals of β-SiC.

The above oxide layer is formed by chemical vapor deposition (CV).
It is fundamentally different from the coating phase provided by D), etc., has a very uniform thickness, and it is possible to minimize residual stress in the vicinity of the interface. Further, this oxide layer exists as a layer for protecting the inside of the sintered body, as described above. As a result, the inorganic fiber sintered body of the present invention has excellent oxidation resistance and high mechanical properties in a wide temperature range from room temperature to 1500 ° C. in air.

Next, a method for manufacturing the inorganic fiber sintered body of the present invention will be described. The raw inorganic fiber used in the present invention,
For example, according to the method described in JP-A-62-289641, the inorganic fiber composed of the above (a), (b) or (c) is exposed to an oxidizing atmosphere, for example, 500 to 16
It can be prepared by heating at a temperature in the range of 00 ° C. Examples of the oxidizing atmosphere include air, pure oxygen, ozone, water vapor, and carbon dioxide gas. The inorganic fiber composed of the above (a), (b) or (c) is
It is commercially available from Ube Industries, Ltd. as Tyranno fiber (registered trademark).

By the above heat treatment, the surface of the inorganic fiber is oxidized to form a surface layer composed of the inorganic substance (d), (e) or (f). That is,
The inner surface layer is an inorganic fiber composed of the inorganic substance (a), (b) or (c), and the surface layer is an inorganic fiber composed of (d), (e) or (f).

The inorganic fibers used in the present invention may be in the form of continuous fibers or chopped short fibers obtained by cutting continuous fibers, and may be in the form of various woven fabrics woven from continuous fibers. It may be in the form of a sheet-like material in which continuous fibers are aligned in one direction.

In the present invention, a laminate of the above-mentioned various types of inorganic fibers is heated and sintered. As the sintering method, it is possible to employ a method in which the laminate is primarily molded and then sintered under pressure in an inert gas atmosphere, or a hot pressing method in which molding and sintering are simultaneously performed.

In the method in which the primary molding and the sintering are carried out separately, as the primary molding method, a die pressing method, a rubber pressing method, an extrusion molding method, and a sheet molding method are used.
A method of obtaining a sheet having a predetermined shape such as a sheet shape, a rod shape, or a spherical shape by pressurizing at a pressure of up to 5000 kg / cm ² . In the case of performing sintering by the hot pressing method, the laminate is put in a graphite pressing die sprayed with boron nitride as a release agent, pressed at a pressure of 50 to 1000 kg / cm ² and simultaneously heated to give a sintered body. Can be

In the present invention, it is necessary to raise the temperature in stages in order to form layered carbon on the surface of the inorganic fiber. There is no particular limitation on the temperature raising method up to 1400 ° C. in the first step, but 100 to 500 ° C.
It is preferable to raise the temperature at a rate of / hour.

In the second step, 1400 to 1750
After raising the temperature to the range of ℃, 30 minutes to 1
Hold for 0 hours. During this time, carbon of non-stoichiometric composition is segregated from the inside of the inorganic fibers to the surface, and at the same time, the oxide phase of the inorganic substance composed of the above (d), (e) or (f) between the inorganic fibers. Can be sufficiently filled with so that the number of voids in the molded body can be extremely reduced.

If the heating temperature in the second step is lower than 1400 ° C., the segregation rate of carbon becomes extremely slow, which is not effective. When the heating temperature exceeds 1750 ° C., the above oxide phase becomes an active molten state and reacts with the deposited carbon layer,
It is desorbed from the molded body as CO gas through the holes in the molded body.

In the third step, the temperature is raised to 1900 ° C. to obtain a sintered body having high fracture toughness. . Since there are very few voids in the molded body that has been subjected to the heat treatment in the second step, even in the temperature raising process up to 1900 ° C. in the third step,
The carbon deposited on the surface of the inorganic fiber is not desorbed as CO gas.

In the fourth step, the sintered body obtained in the third step was subjected to 1 at 1000 to 1500 ° C. in an oxygen-containing atmosphere.
Oxidize for ~ 100 hours. By this oxidation treatment, an oxide layer having a composition of (d), (e) or (f) described above and having a thickness of 20 to 500 μm is formed on the outermost surface of the sintered body. By this oxide layer, the inorganic fiber sintered body of the present invention has a high fracture toughness, and the oxidation resistance in a wide temperature range in air is significantly improved.

Specific examples of the oxygen-containing atmosphere include air,
Examples thereof include air or a mixed gas of oxygen and an inert gas such as nitrogen. When the oxidation treatment temperature is lower than 1000 ° C, it takes a long time to form the oxide layer on the outermost surface of the sintered body, which is not economical, and when the temperature exceeds 1500, an active (rapid) oxidation reaction occurs. Since it mainly occurs, SiO
Desorption as a gas progresses rapidly and the oxide layer is not effectively generated. In order to effectively form the oxide layer on the surface of the sintered body, the above-mentioned temperature range of 1000 to 1500 ° C. in which the passive (mild) oxidation reaction proceeds is necessary.

[0032]

EXAMPLES Examples and comparative examples will be shown below.

Example 1 Tyranno fiber (registered trademark) having a fiber diameter of 11 μm was heat-treated in air at 930 ° C. for 4 hours to obtain a raw inorganic fiber. A uniform oxide layer of about 150 nm was formed on the fiber surface.

A sheet-like laminate was prepared by laminating 100 sheets of unidirectional sheets each made of this raw material inorganic fiber and having a thickness of about 170 μm in the same fiber direction. This laminate was cut into 90 × 90 mm square pieces, set in a carbon die of a hot press, and 600 kg / cm under an argon stream.
The pressure of ² is applied, the temperature is raised to 1700 ° C. at a rate of 200 ° C./hour, and the temperature is maintained at 1700 ° C. for 2 hours.
The temperature was raised to 50 ° C at a rate of 200 ° C / hour to obtain a sintered body. About 32 nm around the inorganic fibers in this sintered body
A uniform carbon layer was formed, and the spaces between the inorganic fibers were uniformly filled with a phase mainly composed of crystalline SiO ₂ .
The presence of Ti atoms was confirmed in the phase mainly composed of SiO ₂ .

The above sintered body is 3 mm × 4 mm × 40 mm
After cutting the bending test piece of No. 1 to No. 3, it was oxidized in air at 1300 ° C. for 50 hours to form an oxide layer as a protective layer on the surface of the sintered body. The thickness of the oxide layer was about 80 μm.

The bending strength of the obtained inorganic fiber sintered body was 53 kg / mm ² at room temperature, and Fibrous as shown in FIG.
It showed a non-linear break pattern (not Brittle).
The bending strength after treating this inorganic fiber sintered body in air at each temperature of 600 ° C., 800 ° C. and 1500 ° C. for 100 hours was 50.7 kg / mm ² , 56.4, respectively.
a kg / mm ² and 50.9 kg / mm ^2, change in appearance of the sintered body even after the oxidation treatment was not observed at all.

Comparative Example 1 An inorganic fiber sintered body was obtained by repeating Example 1 except that the bending test piece was not oxidized in air. When this inorganic fiber sintered body was treated in air at 800 ° C. for 100 hours, it was significantly oxidized, and severe delamination was observed between the layers derived from the sheet-like laminate of the raw material fibers, and the bending strength was not measured. It was possible.

[Brief description of drawings]

FIG. 1 is a diagram showing a room temperature bending strength measurement result of an inorganic fiber sintered body obtained in Example 1.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiko Shintoku 5 Ube Kosan Co., Ltd., 5 1978 Kogushi, Ube City, Yamaguchi Prefecture

Claims (2)

[Claims] 1. (a) Substantially consisting of Si, M, C and O
Amorphous material, (b) substantially β-SiC, MC, β-
Solid solution of SiC and MC and / or MC _1-xSuper crystalline
Fine particles and amorphous SiO₂And MO₂Collection consisting of
Or (c) the amorphous substance of (a) above and (b) above
Inorganic fibers composed of a mixture with aggregates of
Exists so as to fill the gaps between the inorganic fibers, (d)
Amorphous substance consisting essentially of Si, M and O, (e) binding
Crystalline SiO₂And MO₂A crystal aggregate consisting of, or
(F) The amorphous substance of (d) above and the crystal aggregate of (e) above
Inorganic fiber composed of an inorganic substance composed of a mixture with the body
A sintered body (in the above formula, M is Ti or Zr
And x is a number of 0 or more and less than 1. ), (A) ~
The boundary between the inorganic fiber of (c) and the inorganic substance of (d) to (f)
1 to 200 nm of amorphous and crystalline carbon as a boundary layer
A layer consisting of
20 to 500 having the composition of (d), (e) or (f)
characterized by being coated with an oxide layer with a thickness of μm
Inorganic fiber sintered body. 2. An inorganic fiber comprising an inner surface layer and a surface layer
And the inner surface layer (a) consists essentially of Si, M, C and O.
Amorphous material, (b) substantially β-SiC, MC, β-
Solid solution of SiC and MC and / or MC _1-xSuper crystalline
Fine particles and amorphous SiO₂And MO₂Collection consisting of
Or (c) the amorphous substance of (a) above and (b) above
Inorganic chamber material consisting of a mixture with aggregates of
The surface layer is (d) amorphous consisting essentially of Si, M and O
Substance, (e) crystalline SiO₂And MO₂Crystal consisting of
An aggregate, or (f) the amorphous substance of (d) above and the above
Consists of an inorganic substance consisting of a mixture with the crystal aggregate of (e)
Inorganic fibers (in the above formula, M is Ti or Z
r is shown, and x is a number of 0 or more and less than 1. ) Laminate
In an inert gas of 50 to 1000 kg / cm²Pressure of
The first step of raising the temperature from room temperature to 1400 ° C., 140
Raise to a temperature in the range of 0 to 1750 ° C and keep at the same temperature for 3
Second step of holding for 0 minutes to 10 hours, from the above holding temperature to 1
The temperature is raised to a temperature in the range of up to 900 ° C and sintered by heating.
The sintered body obtained in the third step and the third step is 1000 to 150
Oxidation treatment in an oxygen-containing gas at 0 ° C. for 1 to 100 hours,
The composition of (d), (e) or (f) on the outermost surface of the sintered body
Forming an oxide layer having a thickness of 20 to 500 μm
Inorganic fiber sintered body characterized by comprising a fourth step
Manufacturing method.