JPH0735314B2 - Heat and oxidation resistant high strength material - Google Patents

Description

Detailed Description of the Invention [Object of the Invention]

(Field of Industrial Application) The present invention is suitably used as a material for a structure part, a part and a product which are required to have high strength and excellent heat resistance and oxidation resistance. The present invention relates to heat-resistant and oxidation-resistant high-strength members. (Prior Art) In recent years, the required properties for the materials constituting the parts of structures, products, and products have become more severe, and conventional metal-based materials and resin-based materials cannot fully meet such required properties. Recently, ceramic-based materials have been actively developed, and fiber-reinforced metal (FRM), fiber-reinforced ceramics (FRC), and carbon fiber / carbon composite materials (C
/ C materials) and other composite materials have been developed and are being put to practical use. Since this C / C material is lightweight and has high strength, it is superior in terms of specific strength.Also, it has relatively good heat resistance and oxidation resistance, and wear and strength reduction due to heat are less than those of conventional metal-based materials. Since it is much less than the material, it can be said that it is suitable for applications exposed to harsh conditions such as members for aerospace equipment and members for nuclear facilities. As a method for producing this C / C material, carbon fiber / phenol, graphite fiber / phenol, carbon fiber) pitch, graphite fiber / pitch, etc. are carbonized or graphitized by primary firing, and pitch impregnation is performed to further increase the density. There is a resin char method that repeats firing and firing, and a vapor deposition method (CVD method) that vaporizes carbon generated by pyrolyzing hydrocarbons into aggregate woven with carbon fiber or graphite fiber. In addition to / C material,
Development of multi-dimensional C / C materials such as three-dimensional type and four-dimensional type, in which fibers are oriented in multiple dimensions, has also been made. As described above, the C / C material is lighter in weight and superior in strength as compared with the conventional metal-based material, and also has relatively good heat resistance and oxidation resistance, and it can be said that there is little wear or strength reduction due to heat. For example, in the case of re-entry into the atmosphere after activity in space, such as a space shuttle, the temperature becomes considerably high especially in the part subjected to aerodynamic heating, and at a temperature of about 800 ° C for C / C materials. Oxidation is consumed from the surface. Therefore, an oxidation-resistant surface treatment method has been developed to suppress the oxidative consumption on the surface of the C / C material. As this oxidation-resistant surface treatment method, for example, a powder made of 10% alumina (Al ₂ O ₃ ), 30% silicon (Si), and 60% silicon carbide (SiC) is used as a C / C material in a graphite retort. Pack it around and heat it at about 1650 ℃ in an argon atmosphere.
The surface of the C / C material is converted to SiC, and in the subsequent cooling process, C / C
Since a minute crack is generated due to the difference in thermal expansion between C material and SiC, there was an oxidation-resistant surface treatment method in which this minute crack was treated with tetraethyl orthosilicate (TEOS) and impregnated with SiO ₂ . . There is also an oxidation-resistant surface treatment method in which minute cracks generated in SiC are treated with a silicon modifier and impregnated with SiO ₂ (for example, TE
Regarding OS processing, CERAMIC BULLETIN VOL.60, No.11 (1
981). ). (Problems to be solved by the invention) When a TEOS-treated SiC coating layer is provided on the surface of such a C / C material, it is prevented that the C / C material undergoes aerodynamic heating and is oxidized and consumed. However, it becomes possible to use it at higher temperatures, but when it reaches about 1400 ° C, the surface SiC oxidizes to SiO ₂ , and this SiO ₂ melts at about 1700 ° C and scatters during navigation. Exhausted. Thus, for example, by undergoing aerodynamic heating, 17
If a material that can withstand even a temperature higher than 00 ° C is required, TEOS can be applied to the above surface.
The C / C material provided with the treated SiC coating layer has a problem that the requirement cannot be sufficiently satisfied. (Object of the Invention) The present invention has been made in view of such conventional problems, and has high strength required as a structural member and is also excellent in heat resistance and oxidation resistance. The object of the present invention is to provide a lightweight heat-resistant and oxidation-resistant high-strength member capable of withstanding a sufficient amount of oxidation consumption even when heated to a temperature exceeding 1800 ° C. by being subjected to aerodynamic heating. .

[Constitution of the invention]

(Means for Solving the Problems) The heat-resistant and oxidation-resistant high-strength member according to the first aspect of the present invention has a structure having an aluminum nitride layer on a part or all of the surface portion of the carbon fiber / carbon composite material. The heat-resistant and oxidation-resistant high-strength member according to the second aspect of the present invention has an aluminum nitride layer on part or all of the surface portion of the carbon fiber / carbon composite material, The heat and acid resistance according to the third aspect of the present invention is characterized in that a part or all of the surface portion of the aluminum nitride layer has a coating layer selected from hafnium oxide and zirconium oxide. The chemical-resistant high-strength member is characterized in that it has a yttrium nitride layer on a part or all of the surface portion of the carbon fiber / carbon composite material. Heat resistance
The oxidation-resistant high-strength member has a yttrium nitride layer on a part or all of the surface portion of the carbon fiber / carbon composite material, and among the hafnium oxide and zirconium oxide on a part or all of the surface portion of the yttrium nitride layer. It is characterized in that it has a coating layer selected from the above, and the above-mentioned structure of the heat-resistant and oxidation-resistant high-strength member is used as a means for solving the above-mentioned conventional problems. In the heat-resistant and oxidation-resistant high-strength member according to the present invention, the carbon fiber / carbon composite material (C / C material) serving as a base material is not particularly limited in its manufacturing method. A plain weave or a twill weave is used as the matrix binder, and a phenol-based, furan-based, or pitch-based one is used as the matrix binder. Carbon fiber / phenol, graphite fiber / phenol, carbon fiber / pitch, graphite fiber / pitch, etc. The material is carbonized or graphitized by primary firing, and the resin char method in which pitch impregnation and firing are repeated in order to further densify it, or hydrocarbon is pyrolyzed into aggregate woven with carbon fiber or graphite fiber to generate A method of manufacturing C / C materials is applied, which is manufactured by a vapor deposition method of vapor depositing carbon or a combination of these methods. It is not particularly limited. When the aluminum nitride (AlN) layer is provided on a part or all of the surface portion of the C / C material, in one embodiment, in a closed container, the base material made of the C / C material and AlN are used. A crucible accommodating the above is installed, the pressure inside the closed container is reduced to, for example, about 10 ⁻⁴ Torr, and an atmosphere in which Ar is ionized is performed to perform a pretreatment for cleaning the surface of the C / C substrate by sputtering. Then, the AlN in the crucible is irradiated with an electron beam by an EB gun to evaporate the AlN, and the AlN is vapor-deposited on a part or all of the surface portion of the C / C substrate in the sputter-cleaned and preheated state. For example, a method in which an aluminum nitride layer having a thickness of about 25 to 50 μm is coated can be adopted. Then, if necessary, hot isostatic pressing (HIP) using N ₂ gas as a pressure source is performed to pressurize at a high temperature of about 2000 ° C., for example, at a pressure of about 2000 Kgf / cm ² , and nitrogen. there are N ₂ was supplied to the aluminum nitride layer is pure aluminum parts which may be present are missing, thereby forming an aluminum nitride layer Al unreacted absent, nitride to C / C material Makes the aluminum layer more familiar. In this way, by having the aluminum nitride layer on the surface of the C / C material, it has the high strength required as a structural material, and also has excellent heat resistance and oxidation resistance. It becomes a strength member. In another embodiment in which the surface portion of the C / C material has an aluminum nitride layer, in the crucible in the closed container, Al is put in place of AlN, and N is set in the closed container. After ionizing the surface of the C / C material by sputter cleaning, irradiate the Al with an electron beam to form Al.
Can be evaporated to form an aluminum nitride layer in which this Al is combined with N in the atmosphere on the surface portion of the C / C material. In this case, since the atmosphere in the closed container is a reduced pressure atmosphere of, for example, 10 ⁻⁴ Torr, all evaporated Al is AlN.
Aluminum nitride layer containing metal Al that does not react with C
Although it may be formed on the surface of the material, in such a case, perform hot isostatic pressing using N ₂ gas as a pressure source in the same manner as described above to nitride all the metal Al. Therefore, it is also desirable to form an aluminum nitride layer having excellent heat resistance and oxidation resistance. Further, in another embodiment in which the surface of the C / C material has an aluminum nitride layer, A is formed on the required surface of the C / C material.
lN powder etc. are placed and the inside of the heating device is evacuated, Ar or N ₂ atmosphere, and the AlN powder is melted by induction heating up to about 2350 ° C.
The aluminum nitride layer may be formed on part or all of the surface portion of the / C material. in this case,
It is of course possible to adopt a form in which the aluminum nitride layer partially penetrates at least the surface portion of the C / C material. The atmosphere during the induction heating may be vacuum or Ar at the beginning, and an N ₂ atmosphere of, for example, about 1.5 atm may be formed in the middle to form an aluminum nitride layer without pure metal Al. Then, also in this case, after forming the aluminum nitride layer by induction heating, by performing hot isostatic pressing using N ₂ gas as a pressure source, the aluminum nitride layer
It is also desirable, if necessary, to make the conformability to the C / C substrate even better. Also, instead of AlN powder or the like, Al powder or the like should be placed on the required surface portion of the C / C base material, and the inside of the induction heating device should be in an N ₂ atmosphere of about 1.5 atm for induction heating. Melts Al and partially impregnates the surface portion of the C / C base material with Al and reacts with N ₂ as a result, whereby part or all of the surface portion of the C / C material is aluminum nitride. It can also be arranged so that layers are formed. In this case, the inside of the induction heating device is not set to N ₂ atmosphere, an Al layer is formed on the surface portion of the C / C material by induction heating, and then C ₂ is applied by hot isostatic pressing using N ₂ gas as a pressure source. An aluminum nitride layer may be formed on the surface of the / C material. Furthermore, in another embodiment in which the surface portion of the C / C material has an aluminum nitride layer, in the molten Al,
Nitrogen the surface of the C / C material by immersing the C / C material and then performing hot isostatic pressing using N ₂ gas as a pressure source or induction heating in an N ₂ atmosphere. It is also possible to form an aluminum layer. Furthermore, an Al layer is formed on the surface of the C / C material by ion plating, and then hot isostatic pressing using N ₂ gas as a pressure source is also performed, or induction heating is performed in an N ₂ atmosphere. It is also possible to form the aluminum nitride layer on the surface portion of the C / C material by performing the above. In this way, by having the aluminum nitride layer on the surface of the C / C material, the strength of the structure is maintained by the C / C material, and the heat resistance and oxidation resistance are good by the aluminum nitride. Becomes Then, for example, in an environment such as prolonged exposure of about 4 hours at a high temperature of about 1700 ° C., a part of the AlN is changed to Al ₂ O _3, a large Al of C / C thermal expansion coefficient than the material ₂ O ₃ may form and cause separation due to the difference in coefficient of thermal expansion, but in the case of a short time such as 10 minutes to 20 minutes as in the case of reentry of a space shuttle, a small amount of bearing is supported. Instead, it has sufficiently excellent heat resistance and oxidation resistance. Next, when providing a coating layer selected from hafnium oxide and zirconium oxide on a part or all of the surface portion of the aluminum nitride layer,
For example, by performing plasma spraying using the above-mentioned hafnium oxide (HfO ₂ ) and / or zirconium oxide (ZrO ₂ ) powder, for example, Hf having a thickness of about 0.1 to 0.2 mm can be obtained.
A coating layer made of O ₂ or ZrO ₂ is formed. Therefore, the melting point of hafnium oxide (HfO ₂ ) is about 2800.
℃, the melting point of zirconium oxide (ZrO ₂ ) is about 2700 ℃, it is extremely excellent in heat resistance and oxidation resistance, hafnium oxide when oxidative consumption occurs in the high temperature atmosphere containing oxygen. By again performing plasma spraying with powder and / or zirconium oxide powder,
It is possible to reuse the C / C material having the aluminum nitride layer on the surface portion. Next, in an embodiment in which a part or all of the surface portion of the C / C material has a yttrium nitride (YN) layer, the base material made of the C / C material and YN were housed in a closed container. Install a crucible, reduce the pressure in the closed container to, for example, about 10 ^-4 Torr and clean the substrate surface by sputter-cleaning the substrate surface in an atmosphere where Ar is ionized, then irradiate the YN in the crucible with an electron beam to remove the YN. It is possible to employ a method in which YN is evaporated and YN is vapor-deposited on a part or the whole of the surface portion of the base material, for example, a yttrium nitride layer having a thickness of about 25 to 50 μm is coated. Then, if necessary, hot isostatic pressing using N ₂ gas as a pressure source is performed, for example, at a high temperature of about 2000 ° C. and at a high temperature of about 2000 Kgf / cm ² to stabilize YN molecules. And improve the familiarity of the yttrium nitride layer with the C / C material. In this way, by having the yttrium nitride layer on the surface of the C / C material, it has the high strength required as a structural material, and also has excellent heat resistance and oxidation resistance. It becomes a strength member. In another embodiment in which the surface portion of the C / C material has an yttrium nitride layer, the crucible in the closed container contains Y instead of YN, and N in the closed container. After being formed in an ionized atmosphere, the surface of the C / C material is sputter-cleaned, and then Y is irradiated with an electron beam to evaporate Y, and this Y is combined with N in the atmosphere to form a yttrium nitride layer. It can also be formed on the surface of the / C material. And, in this case as well, by performing hot isostatic pressing using N ₂ gas as a pressure source as necessary, the YN molecular structure is stabilized and the familiar yttrium nitride C / C material is used. It is also desirable to be able to do good things. Further, in another embodiment in which the surface of the C / C material has an yttrium nitride layer, Y is formed on the required surface of the C / C material.
Place the N powder, etc., and evacuate the inside of the heating device.
It is also possible to melt YN by inductively heating it in an Ar or N ₂ atmosphere so that the yttrium nitride layer is formed on a part or all of the surface of the C / C material after solidification. it can. In this case, it is of course possible to adopt a form in which the yttrium nitride layer partially penetrates at least the surface portion of the C / C material. Further, if necessary, hot isostatic pressing using N ₂ gas as a pressure source may be performed to further improve the conformability of the yttrium nitride layer to the C / C material. In the case of the above embodiment, YN powder is used,
The Y powder is placed on the required surface of the C / C material, and the inside of the heating device is made to have an atmosphere of N _{2 of,} for example, about 1.5 atm, and induction heating is performed to melt the Y and C / C as necessary. C
It is also possible to partially impregnate the surface portion of the material with Y and react it with N ₂ so that the yttrium nitride layer is formed on part or all of the surface portion of the C / C material. In this case, the inside of the induction heating device is not made to be N ₂ atmosphere, a Y layer is formed on the surface portion of the C / C material by induction heating, and then hot isostatic pressing is performed using N ₂ gas as a pressure source. As a result, the yttrium nitride layer can be formed on the surface of the C / C material. Next, when providing a coating layer selected from hafnium oxide and zirconium oxide on a part or all of the surface portion of the yttrium nitride layer, for example, a powder of the above hafnium oxide (HfO ₂ ) or By performing plasma spraying using zirconium oxide (ZrO ₂ ) powder, for example, HfO _{2 having} a thickness of about 0.1 to 0.2 mm can be obtained.
And a coating layer of ZrO ₂ is formed. In the heat-resistant and oxidation-resistant high-strength member according to this embodiment, the melting point of hafnium oxide (HfO ₂ ) is about 2800.
℃, the melting point of zirconium oxide (ZrO ₂ ) is about 2700 ℃, which is extremely excellent in heat resistance and oxidation resistance. When it is placed in a high temperature oxidizing atmosphere, part of Y is oxidized and Y ₂ O ₃ , and this Y ₂ O ₃ contributes to the stabilization of ZrO ₂ . In addition, when the surface layer is consumed by oxidation, plasma spraying with hafnium oxide powder and / or zirconium oxide powder can be performed again to reuse the C / C material having the yttrium nitride layer on the surface. Become. (Operation of the Invention) The heat-resistant and oxidation-resistant high-strength member according to the present invention is made of carbon fiber /
Part or all of the surface of the carbon composite material (C / C material)
Since it has a nitride layer selected from aluminum nitride having a melting point of about 2300 ° C and a low thermal expansion coefficient and yttrium nitride having a melting point of about 2600 ° C and a low thermal expansion coefficient, a C / C material is used as a base material. Has a high strength due to the presence of a high melting point and a nitride layer with a high melting point and a low coefficient of thermal expansion on the surface portion, so that it has good heat resistance and oxidation resistance and has a surface layer portion. It is difficult to peel off. In addition, if necessary, on part or all of the surface portion of the nitride layer selected from the aluminum nitride layer and the yttrium nitride layer, hafnium oxide having a melting point of about 2800 ° C. and zirconium oxide having a melting point of about 2700 ° C. When it has a coating layer selected from the above, the heat resistance and the oxidation resistance are further excellent. Then, in this case, there is a difference between the coefficient of thermal expansion of the C / C material and the coefficient of thermal expansion of hafnium oxide and zirconium oxide, but between these there is a small coefficient of thermal expansion aluminum nitride or yttrium nitride. Since it is interposed, the risk of peeling due to the difference in thermal expansion coefficient at high temperature is
It will be extremely small. (Examples) Next, examples of heat-resistant and oxidation-resistant high-strength members according to the present invention will be described together with comparative examples. Example 1 A C / C material having a thickness of 1.5 mm and a crucible containing AlN were placed in a closed container, and the inside of the closed container was made into an Ar ionizing atmosphere of 10 ⁻⁴ Torr to prepare the surface of the C / C material. Was sputter-cleaned, and the AlN in the crucible was irradiated with an electron beam from an EB gun to evaporate the AlN and attach it to the surface of the C / C material preheated to 450 ° C with a thickness of 40 μm. Then, heat and pressure are applied by hot isostatic pressing under the conditions of a temperature of 2000 ° C. and a pressure of 2000 KgF / cm ^{2 to} obtain the heat and oxidation resistance of Example 1 having an aluminum nitride layer on the surface of the C / C material. A high-strength high-strength member was produced and subjected to the evaluation test described below. Example 2 Aluminum nitride was obtained by performing plasma spraying using hafnium oxide powder on the surface of the heat-resistant and oxidation-resistant high-strength member having the aluminum nitride layer on the surface of the C / C material produced in Example 1. The thickness of the surface of the layer is 0.
The heat-resistant and oxidation-resistant high-strength member of Example 2 having a hafnium oxide layer of 18 mm was prepared and subjected to the evaluation test described below. Example 3 Aluminum nitride was obtained by performing plasma spraying using zirconium oxide powder on the surface of a heat-resistant and oxidation-resistant high-strength member having an aluminum nitride layer on the surface of the C / C material produced in Example 1. Thickness on the surface part of the layer
Heat resistance of Example 3 having a 0.18 mm zirconium oxide layer
An oxidation resistant high-strength member was produced and subjected to the evaluation test described below. Example 4 A C / C material having a thickness of 1.5 mm and a crucible containing YN were placed in a closed container, and the inside of the closed container was made into an Ar ionizing atmosphere of 10 ⁻⁴ Torr to prepare the surface of the C / C material. Was sputter-cleaned and the YN in the crucible was irradiated with an electron beam from an EB gun to evaporate this YN and onto the surface of the C / C material preheated to 450 ° C.
YN is deposited to a thickness of 40 μm, and then hot isostatic pressing is performed to heat and pressurize at a temperature of 2000 ° C. and a pressure of 2000 Kgf / cm ² to form a yttrium nitride layer on the surface of the C / C material. The heat-resistant and oxidation-resistant high-strength member of Example 4 having the same was produced and subjected to the evaluation test described below. Example 5 Yttrium nitride was obtained by performing plasma spraying using hafnium oxide powder on the surface of a heat-resistant and oxidation-resistant high-strength member having a yttrium nitride layer on the surface of the C / C material produced in Example 4. The thickness of the surface of the layer is 0.
A heat-resistant and oxidation-resistant high-strength member of Example 5 having a hafnium oxide layer of 18 mm was produced and subjected to the evaluation test described below. Example 6 Yttrium nitride was obtained by performing plasma spraying using zirconium oxide powder on the surface of the heat-resistant and oxidation-resistant high-strength member having the yttrium nitride layer on the surface of the C / C material produced in Example 4. Thickness on the surface part of the layer
Heat resistance of Example 6 having a 0.18 mm zirconium oxide layer
An oxidation resistant high-strength member was produced and subjected to the evaluation test described below. Comparative Example 1 A C / C material having a thickness of 1.5 mm was subjected to an evaluation test described below as a test material of Comparative Example 1 without any surface coating. Comparative Example 2 10% Al ₂ O around a C / C material having a thickness of 1.5 mm in a closed container.
₃ filled with powder of -30% Si-60% SiC, in an Ar atmosphere
Comparison of heat treatment at 1650 ℃ to convert the surface of C / C material to SiC and treatment with tetraethylorthosilicate (TEOS) to impregnate SiO ₂ into cracks caused by the difference in coefficient of thermal expansion during cooling The test material of Example 2 was produced and subjected to the evaluation test described below. Comparative Example 3 A surface of a 1.5 mm thick C / C material was plasma sprayed with zirconium oxide powder to give a thickness of 0.18 mm.
Although the zirconium oxide layer of No. 1 was formed, it could not be used for the evaluation test described later because cracks were generated in the zirconium oxide layer during the cooling process and the zirconium oxide layer was peeled off. Evaluation Test Example Regarding the test materials prepared in Examples 1 to 6 and the test materials prepared in Comparative Examples 1 and 2, 1600 ° C. × 10 minutes in air plasma torch heating, 1700 ° C. × 10 minutes in air Plasma torch heating and plasma torch heating in the atmosphere at 2000 ° C. for 10 minutes were performed, and the heat consumption and oxidation resistance were evaluated by examining the amount of oxidative consumption after heating (weight reduction amount per square meter). The results are shown in Table 1. The numerical value in parentheses in Table 1 indicates the amount of reduction in plate thickness calculated from the amount of weight reduction. In addition, “unusable” indicates that the thickness reduction amount was 1 mm or more. As shown in Table 1, in the case of Example 1 having the aluminum nitride layer on the surface portion of the C / C material and Example 4 having the yttrium nitride layer, the C / C material itself without these layers was used. It is clear that the heat resistance and the oxidation resistance are considerably improved as compared with the case of a certain Comparative Example 1, and in the case of Example 1 having an aluminum nitride layer, SiC is formed on the surface of the C / C material.
It was found that the heat resistance and the oxidation resistance were superior to those of Comparative Example 2 in which the coating and the TEOS treatment were applied, and the surface portion of the aluminum nitride layer was further coated with a hafnium oxide layer and a zirconium oxide layer, respectively. In the case of Example 3 and in the case of Example 5 and Example 6 in which the surface portion of the yttrium nitride layer was further coated with a hafnium oxide layer and a zirconium oxide layer, respectively, heat resistance and oxidation resistance were further improved. It was confirmed that it was able to withstand a temperature rise of about 1900 to 1950 ℃ when the spacecraft reentry into the atmosphere.

【The invention's effect】

As described above, the heat / oxidation-resistant high-strength member according to the present invention has the aluminum nitride layer or the yttrium nitride layer on the surface portion of the carbon fiber / carbon composite material, and if necessary, on top of them. Furthermore, since it has a coating layer selected from hafnium oxide and zirconium oxide, high strength can be obtained by using a carbon fiber / carbon composite material as a base material, and the thermal expansion coefficient is Since aluminum nitride or yttrium nitride, which has a thermal expansion coefficient close to that of the fiber / carbon composite material, is provided on the surface, it prevents heat and oxidation resistance of the carbon fiber / carbon composite material in the high temperature oxidizing atmosphere. In addition to good performance, it also prevents cracking or peeling of the aluminum nitride layer and yttrium nitride layer due to the difference in thermal expansion coefficient. By further providing a coating layer selected from hafnium oxide and zirconium oxide on the surface portion of the aluminum nitride layer and the yttrium nitride layer, heat resistance and oxidation resistance can be further improved. Although there is a difference in the coefficient of thermal expansion between the carbon fiber / carbon composite material and hafnium oxide or zirconium oxide, the coefficient of thermal expansion between them is smaller than that of the hafnium oxide or zirconium oxide. Since the aluminum nitride layer and the yttrium nitride layer are intervened, it is possible to prevent the occurrence of cracks or peeling of the coating layer made of hafnium oxide or zirconium oxide. Even when it is heated to a temperature exceeding ℃ It results in a very excellent effect that it is capable of withstanding.

Claims (4)

[Claims] 1. A heat-resistant and oxidation-resistant high-strength member having an aluminum nitride layer on the surface of a carbon fiber / carbon composite material. 2. A heat-resistant material comprising an aluminum nitride layer on a surface portion of a carbon fiber / carbon composite material, and a coating layer selected from hafnium oxide and zirconium oxide on a surface portion of the aluminum nitride layer. -Oxidation resistant high strength material. 3. A heat-resistant / oxidation-resistant high-strength member having a yttrium nitride layer on a surface portion of a carbon fiber / carbon composite material. 4. A heat-resistant material comprising a yttrium nitride layer on a surface portion of a carbon fiber / carbon composite material, and a coating layer selected from hafnium oxide and zirconium oxide on a surface portion of the yttrium nitride layer. -Oxidation resistant high strength material.