JPH0867563A - Production of composite material - Google Patents

Abstract

PURPOSE: To obtain a composite material which can withstand the application at elevated temperature because of its high heat resistance by impregnating woven fabric of a silicon carbide fiber with a polycarbosilane polymer and heating the resultant fabric at a prescribed temperature in a carbon monoxide gas atmosphere. CONSTITUTION: Woven fabric of a silicon carbide fiber is impregnated with a polycarbosilane polymer. As a polycarbosilane polymer, may be cited a polycarbosilane mainly comprising (Si-CH2 ) units or a polymetacarbosilane in which carbosilanes mutually bond to each other where at least a part of silicon atoms bonds directly to titanium of zirconium atoms or via oxygen atoms to form cross-links. Then, the impregnated product is heated in a temperature range from 200 to 1,500 deg.C in a carbon monoxide gas atmosphere to give this composite material. This composite material withstands the application under environments over 1,200 deg.C and can be used as parts of a gas turbine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a composite material which can be used in a high temperature environment of 1200 ° C or higher.

[0002]

In Japanese Patent Laid-Open No. 62-26078, a three-dimensional woven fabric of ceramic fibers is impregnated with a solution in which a precursor of ceramics such as polytitanocarbosilane is dissolved in an organic solvent. There is disclosed a method of producing a ceramic composite material reinforced with ceramic fibers by firing. However, this publication does not describe the atmosphere at the time of firing the impregnated material.

Japanese Unexamined Patent Publication (Kokai) No. 62-248636 describes a method for producing a composite material in which a molded body in which polymetallocarbosilane is coated or impregnated on a woven or non-woven fabric is heated and fired at a temperature in the range of 200 to 1500 ° C. Has been done. Then, in page 12, left upper column, lines 12 to 14 of this publication, there is no particular limitation on the atmosphere during heating and firing, and it may be an oxygen-containing atmosphere or an inert gas atmosphere.

JOURNAL OF MATERIALS SCIENCE 26 (1991)
970-976 describes the change in strength and the microstructure of a fiber when the silicon carbide fiber is heat-treated at a temperature of up to 1600 ° C. in a nitrogen atmosphere or a carbon monoxide atmosphere. Then, this document reports that heat treatment of fibers in a carbon monoxide atmosphere causes less reduction in fiber strength as compared with heat treatment of fibers in a nitrogen atmosphere. Although this document describes that the above-mentioned silicon carbide-based fiber is used in a ceramic composite material, there is no description about heat treating the composite material in the atmosphere.

[0005]

A composite material containing silicon carbide fiber as a reinforcing fiber and ceramics derived from a polycarbosilane polymer as a matrix is excellent in heat resistance and mechanical properties at high temperature. It is attracting attention as a composite material that can withstand use in the industry.

[0006] The properties required for composite materials, especially the thermal properties capable of withstanding actual use at high temperatures, are becoming increasingly severe. For example, a composite material used as a gas turbine member is required to have a heat resistance of 1200 ° C. or higher.

The composite material that can withstand use at such a high temperature needs to be fired at a temperature higher than the use temperature in the process of manufacturing the composite material. Because the matrix derived from the polycarbosilane-based polymer undergoes densification at high temperature, if it is not fired at a temperature higher than its use temperature during the preparation process of the composite material, pores are formed due to volume contraction, This is because the mechanical properties of the composite material deteriorate.

On the other hand, the silicon carbide fiber forming the composite material is 1200 ° C. in a gas atmosphere such as nitrogen or argon.
As described above, especially when heated at a temperature of 1300 ° C. or higher, the strength of the material sharply decreases.

In order to make a composite material having silicon carbide fibers as reinforcing fibers and ceramics derived from a polycarbosilane polymer as a matrix capable of withstanding practical use at a temperature of 1200 ° C. or higher, a composite material is used. In the process of preparing the material, the necessity of densifying the matrix by high temperature heat treatment and the need of preventing deterioration of the fiber by high temperature heat treatment must be satisfied at the same time.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a composite material that satisfies both of the above contradictory needs.

The above object of the present invention is to heat an impregnated product obtained by impregnating a woven fabric of silicon carbide fibers with a polycarbosilane polymer to a temperature in the range of 1200 to 1500 ° C. in an atmosphere of monoxide gas. To be achieved.

Specific examples of the silicon carbide fiber include a fiber mainly made of SiC, Si-C-Ti or Zr-O.
The fiber consisting of is raised. The former fiber is commercially available from Japan Carbon Co., Ltd. as Nicalon (registered trademark), and the latter fiber is commercially available from Ube Industries, Ltd. as Tyranno fiber (registered trademark).

It is not necessary for the silicon carbide based fibers to have a special surface coating layer. However, when firing an impregnated product in which a woven fabric of silicon carbide-based fibers is impregnated with a polycarbosilane-based polymer, when the fibers are severely deteriorated due to the reaction between the fibers and the polymer, carbon on the fiber surface is It is preferable to use fibers having a coating layer or fibers having a silicon carbide coating film separately formed on the fiber surface by a chemical vapor deposition method.

The silicon carbide fiber may be in the form of a fiber bundle, or may be in the form of a woven fabric such as plain weave, satin weave, imitation weave, twill weave, hollow weave, leno weave, three-dimensional weave, or non-woven fabric. Good.

As the polycarbosilane-based polymer used in the present invention, polycarbosilane mainly composed of (Si—CH ₂ ) units and polycarbosilane mutuals are such that at least a part of their silicon atoms are titanium atoms or An example is polymetallocarbosilane, which is crosslinked with a zirconium atom directly or through an oxygen atom. The polymetallocarbosilane can contain a (Si—O) unit as a constitutional unit, and the (Si—
Total number of CH ₂₎ relative to the total number of units (Si-O) units is usually 100: 0.4-100: 1.5.

Polymetallocarbosilane can be prepared by reacting polycarbosilane with a titanium or zirconium alkoxide usually at 200 to 350 ° C.

There is no particular limitation on the method of impregnating the woven fabric of silicon carbide based fibers with the polycarbosilane-based polymer, but in general, a method of immersing the woven fabric in an organic solvent solution of the polycarbosilane-based polymer is adopted. To be done. Specific examples of the organic solvent include benzene and xylene.

The proportion of the polycarbosilane-based polymer impregnated into the silicon carbide fiber woven fabric varies depending on the volume% of the fibers in the finally obtained composite material, but usually 10 to 70 fibers are contained in the composite material. It is the ratio of volume%.

Next, the impregnated material is heat-treated to mineralize the polycarbosilane polymer to form a matrix. In the present invention, the silicon carbide fiber woven fabric may be impregnated with the polycarbosilane polymer and the subsequent firing may be performed only once, but in general, in order to tightly integrate the matrix and the fiber, It is preferable that the above cycle is repeated at least twice.

The heat treatment temperature of the impregnated material in the present invention is 1
The temperature is in the range of 200 to 1500 ° C. The heat treatment temperature can be selected from the above temperature range depending on the environmental temperature at which the final product is actually used. That is, it is desirable to heat-treat the impregnated product at a temperature higher than the ambient temperature of the final product.

When the impregnation and heat treatment are repeated twice or more, it is not always necessary to heat to the above temperature range in the heat treatment before the final time, and the impregnated material is heat treated to a lower temperature. be able to. In the final heat treatment, it is necessary to heat the impregnated material within the above temperature range.

In the present invention, the heat treatment of the impregnated material is carried out in a carbon monoxide gas atmosphere. When a cycle of impregnating a silicon carbide-based fiber fabric with a polycarbosilane-based polymer and heat-treating the impregnated product is repeated twice or more, and the heat-treatment temperature before the final time is lower than 1200 ° C. The heat treatment of the impregnated material can also be performed in an atmosphere other than carbon monoxide gas, for example, a gas atmosphere such as nitrogen or argon. Of course, it goes without saying that all the impregnation and heat treatment cycles can be performed in a carbon monoxide gas atmosphere.

By the heat treatment of the impregnated material, the silicon carbide-based polymer becomes SiC, or Si-C-Ti or Zr-O.
It is converted into an inorganic substance consisting of to form a matrix, and a composite material composed of a silicon carbide type fiber and a silicon carbide type matrix is obtained.

[0024]

Examples are shown below. In the following, all "parts" mean "parts by weight".

Reference Example 1 To anhydrous xylene containing 400 g of sodium, 1 l of dimethyldichlorosilane was added dropwise while heating and refluxing xylene under a nitrogen gas stream, and then heated and refluxed for 10 hours to form a precipitate. The precipitate was filtered and washed with methanol.
And then washed with water to give white polydimethylsilane 4
20 g was obtained.

Separately from this, 750 g of diphenyldichlorosilane and 124 g of boric acid were added to n-type under a nitrogen gas atmosphere.
The phenyl group-containing polyborosiloxane 5 was heated in butyl ether at 100 to 120 ° C., and the resulting white resinous material was further heated in vacuum at 400 ° C. for 1 hour.
30 g was obtained.

To 250 g of the above polydimethylsilane, 8.27 g of the above polyborodiphenylsiloxane was added and mixed, and the mixture was mixed with nitrogen gas in a quartz tube equipped with a reflux tube under nitrogen gas flow.
The mixture was heated to 50 ° C. and polymerized at the same temperature for 6 hours to obtain polycarbosilane partially containing siloxane bond. After allowing the product to cool, xylene was added and taken out as a solution, filtered, and then xylene was evaporated to give a solid organosilicon polymer 14
0 g was obtained.

0.3 g of xylene was added to 40 g of the above organosilicon polymer and 7.3 g of titanium tetrabutoxide.
Was added, and a reflux reaction was carried out while stirring at 120 ° C. for 0.5 hour under a nitrogen gas stream. After removing xylene, the obtained intermediate product was further subjected to 1 at 300 ° C. under a nitrogen gas stream.
Polymerization was carried out for a period of time to obtain polytanocarbosilane.

Reference Example 2 The polytitanocarbosilane obtained in Reference Example 1 was heated at 210 ° C.
Melt-spun with a tension-free spun fiber in air from room temperature to 15
The temperature was raised to 190 ° C at a heating rate of
The infusible fiber was obtained by holding for a time. The infusible fiber was heated to 1300 at a temperature rising rate of 100 degrees / hour without tension in a nitrogen gas stream.
The temperature was raised to 0 ° C., the temperature was maintained for 1 hour, and firing was performed to obtain inorganic long fibers. Three-dimensional woven fabric from this inorganic long fiber [yarn density (bundle / 25 mm): X direction 16, Y direction 16, Z direction 1
6] was created.

Example 1 The three-dimensional woven fabric obtained in Reference Example 2 was dipped in a mixed solution of 100 parts of polytitanocarbosilane obtained in Reference Example 1 and 100 parts of xylene, and tertiary sterilization was carried out at 5 atm in an argon atmosphere. The original fabric was impregnated with the above mixed solution, and then heated to 150 ° C. in an argon stream to evaporate and remove xylene. Then, the impregnated material was inserted into an electric furnace and baked by heating.

The above-mentioned impregnation of polytitanocarbosilane, removal of xylene, and heating and firing were repeated 8 times. From the 1st to the 6th heating and firing, under argon flow, 200 ° C /
The temperature was raised to 1000 ° C. at a heating rate of 1 hour, and the temperature was maintained for 1 hour. The seventh time and the eighth time were performed under a carbon monoxide stream at a temperature rising rate of 200 ° C./hour to 1400 ° C. and holding at the same temperature for 1 hour.

The tensile strength of the resulting composite was 40 kg / mm ² , and the tensile strength after heat treatment in air at 1250 ° C. for 100 hours was 37 kg / mm ² .

Comparative Example 1 Same as Example 1 except that all eight firings were carried out by raising the temperature to 1000 ° C. at a heating rate of 200 ° C./hour under an argon stream and holding at the same temperature for 1 hour. A composite was manufactured by the method of. The tensile strength of the obtained composite was 36.
Although it was kg / mm ² , the tensile strength of the composite after heat treatment at 1250 ° C. for 100 hours in air was 5 kg / mm ² .

Comparative Example 2 The seventh and eighth heating and firing steps were performed under an argon stream at 20 times.
A composite was manufactured in the same manner as in Example 1 except that the temperature was raised to 1400 ° C. at a heating rate of 0 ° C./hour and the temperature was maintained for 1 hour. The tensile strength of the obtained composite was 6 kg / mm ² .

Claims (1)

[Claims] 1. An impregnated product obtained by impregnating a woven fabric of silicon carbide fibers with a polycarbosilane polymer is heated to a temperature in the range of 1200 to 1500 ° C. in a carbon monoxide gas atmosphere. Composite material manufacturing method.