Composite material and method for producing composite material

Abstract

To provide a novel composite material having superior heat resistance and a method for producing the composite material.SOLUTION: A composite material of the present disclosure contains a carbide including Zr and Hf, and an inorganic fiber including at least one of carbon fiber and ceramic fiber. A method for producing the composite material of the present disclosure includes: melting an alloy including Zr and Hf to produce a molten alloy; and attaching the molten alloy to an inorganic fiber including at least one of carbon fiber and ceramic fiber.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to composite materials and a method for manufacturing composite materials.

Background Art

[0002] High-speed moving objects such as supersonic aircraft and atmospheric reentry vehicles are exposed to a severe heating environment by experiencing aerodynamic heating. Therefore, a material that can withstand the temperature rise generated during aerodynamic heating is desired. As a material that can withstand the temperature rise due to aerodynamic heating, carbon fiber reinforced carbon composite material (C / C composite (Carbon Fiber Reinforced Carbon Composite)) is known (for example, see Patent Document 1). As other materials, composite materials of carbon fiber and zirconium diboride (ZrB2) or zirconium diboride-silicon carbide (ZrB2-SiC) composite are known (for example, see Non-Patent Document 1). Also, as other materials, composite materials of zirconium diboride or hafnium diboride (HfB2) and silicon carbide are known (for example, see Non-Patent Document 2). Furthermore, an ablator is known that uses a composite material containing fibers and resin, and utilizes the blocking effect of pyrolysis gas generated by thermal decomposition of the material itself and the cooling effect due to the endothermic reaction of thermal decomposition (for example, see Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Carbon fiber reinforced carbon composites and ablators are not suitable for repeated use. In addition, in a composite material containing zirconium diboride, zirconium diboride oxidizes upon heating in an environment where oxygen is present, producing zirconium oxide and boron oxide. Boron oxide is liquid near 1200°C, but gasifies when the temperature exceeds 1200°C. Therefore, a composite material containing zirconium diboride is prone to deterioration in a temperature range exceeding 1200°C. When using a composite material of zirconium diboride and silicon carbide, silicon oxide (glass) is generated by heating. The oxidation of zirconium diboride is suppressed by the silicon oxide generated by heating, and the heat resistance is improved. However, the heat-resistant temperature of silicon oxide is about 1800°C, and in a temperature range higher than this, the composite material of zirconium diboride and silicon carbide is prone to deterioration. In addition, hafnium diboride, like zirconium diboride, is prone to deterioration in a temperature range exceeding 1200°C, and the same is true for a composite material with silicon carbide, and deterioration is prone to occur. From the above, a new composite material with excellent heat resistance has been demanded.

[0006] The present disclosure has been made in view of the above-described conventional circumstances, and an object thereof is to provide a new composite material having excellent heat resistance and a method for producing the same.

Means for Solving the Problems

[0007] Specific means for achieving the above object are as follows. <1> A composite material containing a carbide containing Zr and Hf, and an inorganic fiber containing at least one of carbon fiber and ceramic fiber. <2> The composite material according to <1>, wherein the proportion of Zr in all the metals constituting the carbide is 60 atomic% to 90 atomic%. <3> The composite material according to <1> or <2>, wherein the proportion of Hf in all the metals constituting the carbide is 1 atomic% to 20 atomic%. <4> The composite material according to any one of <1> to <3>, wherein the carbide further contains Ti. <5> The proportion of Hf in all the metals constituting the carbide is 1 atomic% to 20 atomic%, the proportion of Ti in all the metals constituting the carbide is greater than 0 atomic% and 29 atomic% or less, and the balance of all the metals constituting the carbide is Zr and inevitable impurities. The composite material according to <4>. <6> The composite material according to any one of <1> to <5>, wherein the proportion of unreacted Zr in all the Zr elements contained in the composite material is 10% by mass or less. <7> The composite material according to any one of <1> to <6>, wherein the proportion of unreacted Hf in all the Hf elements contained in the composite material is 10% by mass or less. <8> The composite material according to <4> or <5>, wherein the proportion of unreacted Ti in all the Ti elements contained in the composite material is 10% by mass or less. <9> Melting an alloy containing Zr and Hf to obtain a molten alloy, and attaching the molten alloy to an inorganic fiber containing at least one of carbon fiber and ceramic fiber. A method for producing a composite material including the above steps. <10> The method for manufacturing the composite material according to <9>, wherein the alloy further contains Ti. <11> The method for manufacturing the composite material according to <9> or <10>, wherein attaching the alloy melt to the inorganic fiber includes impregnating the inorganic fiber with the alloy melt.

Advantages of the Invention

[0008] According to the present disclosure, it is possible to provide a new composite material having excellent heat resistance and a method for manufacturing the same.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments according to the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments. In the following embodiments, the components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values and their ranges, which do not limit the present disclosure.

[0011] In the present disclosure, the term "step" includes not only a step independent of other steps but also a step that cannot be clearly distinguished from other steps as long as the purpose of the step is achieved. In the numerical range indicated by "~" in the present disclosure, the numerical values described before and after "~" are included as the minimum value and the maximum value, respectively. In the numerical ranges described step by step in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other step-by-step descriptions. Also, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. In the present disclosure, the ratios of various elements contained in the carbide and the alloy can be determined by a method using an energy dispersive X-ray spectroscopy attached to a scanning electron microscope. After identifying the locations of the alloy or carbide from the contrast of the surface image of the measurement object, it is possible to measure the ratios of the constituent elements with the energy dispersive X-ray spectroscopy. Note that the content rate of the metal component constituting the carbide may vary depending on the measurement location. In the present disclosure, the average value of the content rates of the metal component at any five locations of the carbide is taken as the ratio (content rate) of each element. The ratios of the elements constituting the carbide can be distinguished by the contrast of the electron microscope image. In the same contrast, the element ratios are close, and in different contrasts, particularly the amount of the metal element is reflected. In the carbon fiber and the part close to carbon, the ratio of carbon is high, and as the distance increases, the ratio of carbon decreases and the ratio of the metal element increases. Therefore, when measuring the content rate of the metal component constituting the carbide, it is desirable to select locations away from the carbon fiber and carbon. Also, it is desirable to select locations showing different contrasts.

[0012] <Composite material> The composite material of the present disclosure contains a carbide containing Zr and Hf, and an inorganic fiber containing at least one of carbon fiber and ceramic fiber. The composite material of the present disclosure is excellent in heat resistance. The reason is not clear, but it is speculated as follows. The carbide contained in the composite material of the present disclosure contains Zr and Hf. When the carbide is oxidized by heating, hafnium oxide (HfO2) is produced. Hafnium oxide has the property of low oxygen permeability. Therefore, the oxidation of other components constituting the composite material is suppressed by the generation of hafnium oxide. In addition, the carbide contained in the composite material of the present disclosure is a high melting point material. From the above, it is presumed that the composite material of the present disclosure has excellent heat resistance.

[0013] Hereinafter, the details of the carbide and inorganic fiber contained in the composite material of the present disclosure will be described.

[0014] [Carbide] The composite material of the present disclosure contains a carbide containing Zr and Hf. The carbide contained in the composite material contains Zr and Hf, and may contain at least one of other metal elements and non-metal elements as necessary. The carbide contained in the composite material may be produced by carbonizing the alloy described later. Details of the alloy will be described later.

[0015] (Zr) The carbide contained in the composite material of the present disclosure contains Zr. By the carbide containing Zr, oxidation resistance can be imparted to the composite material of the present disclosure. The ratio of Zr in all the metals constituting the carbide is not particularly limited. From the viewpoint of oxidation resistance, the ratio of Zr in all the metals constituting the carbide is preferably 60 atomic% or more, more preferably 62 atomic% or more, and still more preferably 65 atomic% or more. Also, from the viewpoint of being able to actively form high melting point ZrO2 during deterioration, the ratio of Zr in all the metals constituting the carbide is preferably 90 atomic% or less, more preferably 85 atomic% or less, and still more preferably 82 atomic% or less. The ratio of Zr in all the metals constituting the carbide may be 60 atomic% to 90 atomic%.

[0016] (Hf) The carbide contained in the composite material of the present disclosure contains Hf. By including Hf in the carbide, the heat resistance of the composite material of the present disclosure can be improved. The ratio of Hf in all the metals constituting the carbide is not particularly limited. From the viewpoint of heat resistance, the ratio of Hf in all the metals constituting the carbide is preferably 1 atomic% or more. The ratio of Hf in all the metals constituting the carbide may be 2 atomic% or more, or may be 3 atomic% or more. Also, the ratio of Hf in all the metals constituting the carbide may be 20 atomic% or less, may be 15 atomic% or less, or may be 10 atomic% or less. The ratio of Hf in all the metals constituting the carbide may be 1 atomic% to 20 atomic%.

[0017] (Other metal elements) The carbide contained in the composite material of the present disclosure may contain other metal elements other than Zr and Hf. Examples of other metal elements include at least one selected from the group consisting of Ti, Ta, La, Mo, Y, Gd, and Ce. When the carbide contained in the composite material of the present disclosure contains other metal elements, the total ratio of the other metal elements in all the metals constituting the carbide is preferably greater than 0 atomic%, more preferably 5 atomic% or more, and still more preferably 10 atomic% or more. When the carbide contains other metal elements, the total ratio of the other metal elements in all the metals constituting the carbide is preferably 29 atomic% or less, more preferably 28 atomic% or less, and still more preferably 27 atomic% or less. When the carbide contains other metal elements, the total ratio of the other metal elements in all the metals constituting the carbide may be greater than 0 atomic% and 29 atomic% or less. Details of other metal elements constituting the carbide will be described below.

[0018] -Ti- The carbide contained in the composite material of the present disclosure preferably contains Ti together with Zr and Hf. When the carbide contains Ti, the proportion of Ti in all the metals constituting the carbide is not particularly limited. From the viewpoint of suppressing the reduction in heat resistance, the proportion of Ti in all the metals constituting the carbide is preferably 29 atomic % or less, more preferably 28 atomic % or less, and still more preferably 27 atomic % or less. The proportion of Ti in all the metals constituting the carbide may be more than 0 atomic % and 29 atomic % or less.

[0019] -Ta- The carbide contained in the composite material of the present disclosure may contain Ta together with Zr and Hf. When the carbide contains Ta, the proportion of Ta in all the metals constituting the carbide is not particularly limited. From the viewpoint of suppressing the reduction in heat resistance, the proportion of Ta in all the metals constituting the carbide is preferably 29 atomic % or less, more preferably 25 atomic % or less, and still more preferably 20 atomic %. The proportion of Ta in all the metals constituting the carbide may be more than 0 atomic % and 29 atomic % or less.

[0020] -La- The carbide contained in the composite material of the present disclosure may contain La together with Zr and Hf. When the carbide contains La, the proportion of La in all the metals constituting the carbide is not particularly limited. From the viewpoint of suppressing the reduction in heat resistance, the proportion of La in all the metals constituting the carbide is preferably 29 atomic % or less, more preferably 25 atomic % or less, and still more preferably 20 atomic %. The proportion of La in all the metals constituting the carbide may be more than 0 atomic % and 29 atomic % or less.

[0021] The carbide contained in the composite material of the present disclosure may contain non-metallic elements.

[0022] -Inevitable impurities- The carbide contained in the composite material of the present disclosure may contain inevitable impurities. Here, the inevitable impurities refer to impurities that are inevitably mixed in the manufacturing process of the alloy used in the manufacture of the composite material, or impurities that are inevitably mixed in the raw materials of the alloy. Examples of the inevitable impurities include Al, Ba, Cd, Co, Cu, Cr, Fe, Ir, Mg, Ni, Pb, Pd, Sn, etc. From the viewpoint of suppressing the reduction of heat resistance, the total proportion of the inevitable impurities in the carbide is preferably 1 atomic% or less.

[0023] In the composite material of the present disclosure, the proportion of Hf in all the metals constituting the carbide is 1 atomic% to 20 atomic%, the proportion of Ti in all the metals constituting the carbide is greater than 0 atomic% and 29 atomic% or less, and the balance of all the metals constituting the carbide is preferably Zr and inevitable impurities. More preferably, the proportion of Hf in all the metals constituting the carbide is 3 atomic% to 15 atomic%, the proportion of Ti in all the metals constituting the carbide is 5 atomic% to 28 atomic%, and the balance of all the metals constituting the carbide is Zr and inevitable impurities. Even more preferably, the proportion of Hf in all the metals constituting the carbide is 5 atomic% to 10 atomic%, the proportion of Ti in all the metals constituting the carbide is 10 atomic% to 27 atomic%, and the balance of all the metals constituting the carbide is Zr and inevitable impurities. In the composite material of the present disclosure, the total proportion of the inevitable impurities in all the metals constituting the carbide is preferably 1 atomic% or less.

[0024] In the carbide contained in the composite material of the present disclosure, from the viewpoint of heat resistance, it is preferable that the content of the uncarbided metal component is as small as possible. The proportion of unreacted Zr in all the Zr elements contained in the composite material is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less. Also, the proportion of unreacted Hf in all the Hf elements contained in the composite material is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less. When the carbide contains Ti, the ratio of unreacted Ti to all Ti elements contained in the composite material is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less. In the present disclosure, the metal element being in the "unreacted state" means that the metal element has not reacted with a non-metallic component to form a carbide, nitride, oxide, boride, halide, or the like. The ratio of the unreacted metal is measured by energy dispersive X-ray spectroscopy (SEM-EDX).

[0025] [Inorganic fiber] The composite material of the present disclosure contains an inorganic fiber including at least one of carbon fiber and ceramic fiber. As the carbon fiber, known carbon fibers can be used. Examples of the carbon fiber include carbon nanotubes such as single-walled carbon nanotubes and multi-walled carbon nanotubes, vapor-grown carbon fibers produced by a vapor phase method, PAN-based carbon fibers using polyacrylonitrile (PAN) as a raw material, and pitch-based carbon fibers using pitch as a raw material. Examples of the ceramic fiber include silicon carbide fiber and alumina fiber. As the inorganic fiber, at least one of carbon fiber and silicon carbide fiber is preferable. The total amount of carbon fiber and silicon carbide fiber in the inorganic fiber is preferably 90% by mass or more, more preferably 99% by mass or more. It is even more preferable that the inorganic fiber consists of at least one of carbon fiber and silicon carbide fiber. The fiber length of the inorganic fiber is not particularly limited, and from the viewpoint of strength, continuous fibers are preferable.

[0026] The inorganic fiber may be in the state of a woven fabric or a non-woven fabric. Further, the inorganic fiber may be taken out from a composite material containing an inorganic fiber and a resin (recycled inorganic fiber). From the viewpoint of strength, a woven fabric is preferable as the inorganic fiber.

[0027] Among the inorganic fibers, the carbon fibers may be a UD material in which fiber bundles are arranged in one direction, or may be a cross material in which UD materials are laminated, or an angle ply material.

[0028] The volume-based ratio of the inorganic fibers and carbides contained in the composite material of the present disclosure is not particularly limited. From the viewpoint of strength, the volume-based ratio of the inorganic fibers in the entire composite material is preferably 15% by volume to 60% by volume, more preferably 18% by volume to 55% by volume, and even more preferably 20% by volume to 40% by volume. The volume-based ratio of the inorganic fibers in the entire composite material can be calculated by continuously imaging and reconstructing the X-ray transmission image and performing image analysis.

[0029] <Manufacturing method of composite material> The composite material of the present disclosure may be manufactured through any process, and its manufacturing method is not particularly limited. The composite material of the present disclosure is preferably manufactured by a manufacturing method of the composite material of the present disclosure, which includes melting an alloy containing Zr and Hf to obtain a molten alloy, and attaching the molten alloy to inorganic fibers including at least one of carbon fibers and ceramic fibers. Specific examples and preferred embodiments of the inorganic fibers used in the manufacturing method of the composite material of the present disclosure are the same as those in the case of the composite material of the present disclosure. In the manufacturing method of the composite material of the present disclosure, attaching the molten alloy to the inorganic fibers may include impregnating the molten alloy into the inorganic fibers. By attaching the molten alloy to the inorganic fibers, it becomes easier to impregnate the molten alloy into the inorganic fibers due to capillary action.

[0030] (C / C composite) When carbon fibers are used as the inorganic fibers, a C / C composite may be used. The carbon component and the alloy constituting the C / C composite can react to generate carbides. Further, by using the C / C composite, the occurrence of a carbonization reaction between the carbon fibers and the alloy is suppressed, and a decrease in the strength of the C / C composite can be suppressed. The carbon fiber content of the C / C composite is preferably 15% by volume to 60% by volume, and more preferably 20% by volume to 50% by volume.

[0031] (alloy) In the method for manufacturing the composite material of the present disclosure, an alloy containing Zr and Hf is used. The alloy used in the present disclosure contains Zr and Hf, and may contain at least one of other metal elements and non-metal elements as required. Further, the alloy used in the present disclosure may contain inevitable impurities.

[0032] -Zr- The alloy used in the present disclosure contains Zr. The proportion of Zr in the alloy is not particularly limited. From the viewpoint of oxidation resistance, the proportion of Zr in the alloy is preferably 70 atomic% or more, more preferably 72 atomic% or more, and still more preferably 75 atomic% or more. Also, from the viewpoints of economy and improving workability by lowering the melting point, the proportion of Zr in the alloy is preferably 90 atomic% or less, more preferably 85 atomic% or less, and still more preferably 82 atomic% or less. The proportion of Zr in the alloy may be 70 atomic% to 90 atomic%.

[0033] -Hf- The alloy used in the present disclosure contains Hf. The proportion of Hf in the alloy is not particularly limited. From the viewpoint of heat resistance, the proportion of Hf in the alloy is preferably 1 atomic% or more, more preferably 2 atomic% or more, and still more preferably 3 atomic% or more. Also, from the viewpoint of improving workability by lowering the melting point, the proportion of Hf in the alloy is preferably 20 atomic% or less, more preferably 15 atomic% or less, and still more preferably 10 atomic% or less. The proportion of Hf in the alloy may be 1 atomic% to 20 atomic%.

[0034] -Other metal elements- The alloy used in the present disclosure may contain other metal elements other than Zr and Hf. Examples of the other metal elements include at least one selected from the group consisting of Ti, Ta, La, Mo, Y, Gd, and Ce. When the alloy used in the present disclosure contains other metal elements, the total proportion of the other metal elements in the alloy is preferably greater than 0 atomic %, more preferably 5 atomic % or more, and still more preferably 10 atomic % or more. When the alloy contains other metal elements, the total proportion of the other metal elements in the alloy is preferably 29 atomic % or less, more preferably 25 atomic % or less, and still more preferably 20 atomic %. When the alloy contains other metal elements, the total proportion of the other metal elements in the alloy may be greater than 0 atomic % and 29 atomic % or less. Details of other metal elements will be described below.

[0035] The alloy used in the present disclosure may contain Ti together with Zr and Hf. When the alloy contains Ti, the proportion of Ti in the alloy is not particularly limited. From the viewpoint of lowering the melting point and improving workability, the proportion of Ti in the alloy is preferably greater than 0 atomic %, more preferably 5 atomic % or more, and still more preferably 10 atomic % or more. Also, from the viewpoint of suppressing a decrease in heat resistance, the proportion of Ti in the alloy is preferably 29 atomic % or less, more preferably 25 atomic % or less, and still more preferably 20 atomic %. The proportion of Ti in the alloy may be greater than 0 atomic % and 29 atomic % or less.

[0036] The alloy used in the present disclosure may contain Ta together with Zr and Hf. When the alloy contains Ta, the proportion of Ta in the alloy is not particularly limited. From the viewpoint of lowering the melting point and improving workability, the proportion of Ta in the alloy is preferably greater than 0 atomic %, more preferably 5 atomic % or more, and still more preferably 10 atomic % or more. Also, from the viewpoint of suppressing a decrease in heat resistance, the proportion of Ta in the alloy is preferably 29 atomic % or less, more preferably 25 atomic % or less, and still more preferably 20 atomic %. The proportion of Ta in the alloy may be greater than 0 atomic % and 29 atomic % or less.

[0037] The alloy used in the present disclosure may contain La together with Zr and Hf. When the alloy contains La, the proportion of La in the alloy is not particularly limited. From the viewpoint of lowering the melting point and improving workability, the proportion of La in the alloy is preferably greater than 0 atomic %, more preferably 5 atomic % or more, and still more preferably 10 atomic % or more. Further, from the viewpoint of suppressing the reduction of heat resistance, the proportion of La in the alloy is preferably 29 atomic % or less, more preferably 25 atomic % or less, and still more preferably 20 atomic %. The proportion of La in the alloy may be greater than 0 atomic % and 29 atomic % or less.

[0038] The alloy used in the present disclosure may contain inevitable impurities. The details of the inevitable impurities are the same as those of the inevitable impurities in the case of carbides.

[0039] When the alloy of the present disclosure is composed of Zr, Ti, Hf, and inevitable impurities, the total proportion of the inevitable impurities in the alloy is preferably 1 atomic % or less from the viewpoint of reducing heat resistance. When the alloy of the present disclosure is composed of Zr, Ti, Hf, and inevitable impurities, from the viewpoints of economy and melting point reduction, the content of Ti in the alloy is preferably 5 atomic % to 29 atomic % or less, the content of Hf is preferably 1 atomic % to 20 atomic %, and the balance is Zr and inevitable impurities. More preferably, Ti is 10 atomic % to 25 atomic %, Hf is 2 atomic % to 10 atomic %, and the balance is Zr and inevitable impurities. Still more preferably, Ti is 12 atomic % to 20 atomic %, Hf is 3 atomic % to 8 atomic %, and the balance is Zr and inevitable impurities.

[0040] (Manufacture of alloy) The alloy used in the present disclosure may be manufactured by any method. The alloy can be manufactured by heating a mixed sample in which simple metals as raw materials of the alloy are mixed to a temperature equal to or higher than the melting point of the alloy and melting it. The mixing ratio of the simple metals as raw materials of the alloy is set according to the composition of the alloy. The purity of each simple metal is not particularly limited, and is preferably 97 mass % or more, more preferably 98 mass % or more, and still more preferably 99 mass % or more. Examples of the method for heating the raw materials of the alloy include the air melting method, the vacuum melting method, the arc melting method, the plasma melting method, the electron beam melting method, and the like. When arc melting the raw materials of the alloy, it may be performed in an inert atmosphere such as helium, argon, or nitrogen. Further, from the viewpoint of further preventing oxidation, after creating a vacuum atmosphere, arc melting may be performed in an argon inert atmosphere. Arc melting can be performed using a vacuum arc melting device. Specifically, arc melting can be performed by placing the raw materials of the alloy on a water-cooled copper hearth, evacuating to a predetermined pressure in advance, and applying a desired current value under an inert gas atmosphere. The pressure during arc melting is adjusted by evacuation to, for example, 1×10 -2 Pa or less, preferably in the range of 1×10 -3 Pa or less. For example, after evacuation, arc melting can be performed under an inert gas of, for example, 0.01 MPa to 0.1 MPa.

[0041] The current value applied during arc melting is preferably adjusted in the range of, for example, 20 A (ampere) to 100 A. The voltage application time may be appropriately selected according to the case, such as applying the voltage multiple times for, for example, 5 seconds to 30 seconds.

[0042] The production of the alloy may include steps other than the above steps (other steps) as necessary. Examples of other steps include a raw material preparation step and a purification step of the obtained alloy.

[0043] When manufacturing the composite material of the present disclosure using a C / C composite, the composite material of the present disclosure can be obtained, for example, by placing the C / C composite and the alloy in a graphite crucible, heating this crucible with a carbon heater to melt the alloy, and impregnating the molten alloy into the carbon fibers contained in the C / C composite. In this case, it is preferable to place the C / C composite above or below the alloy in terms of facilitating impregnation of the molten alloy with the carbon fibers. The heating temperature when melting the alloy by heating is not particularly limited, and it may be a temperature higher than the melting point of the alloy used. Specifically, the heating temperature may be 1700 °C or higher, 1750 °C or higher, or 2000 °C or higher. Note that from the viewpoint of improving productivity, the heating temperature is preferably equal to or lower than the melting point of the alloy + 50 °C. The heating time when melting the alloy by heating is not particularly limited, and it is appropriately set according to the thickness of the C / C composite. Note that the carbon fibers contained in the C / C composite may be long fibers, single fibers, woven fabrics, or non-woven fabrics. The heating time may be 5 minutes or longer, or 1 hour or longer. Note that from the viewpoint of improving productivity, the heating time may also be 2 hours or shorter.

Example

[0044] Hereinafter, the above-described embodiment will be specifically described by way of examples. However, the scope of the above-described embodiment is not limited to these examples.

[0045] <Example 1> (Manufacture of Zr-Ti-Hf alloy) As the Zr raw material, Zr grains (shape: chip-like, 5 mm, purity: 98%) manufactured by High Purity Chemical Co., Ltd. were prepared. As the Ti raw material, Ti grains (shape: sponge-like, 10 mm to 20 mm, purity: 99%) manufactured by High Purity Chemical Co., Ltd. were prepared. As the Hf raw material, Hf grains (shape: plate, purity: 99.7%) manufactured by Sigma-Aldrich Co., Ltd. were prepared. The Zr grains, Ti grains, and Hf grains were mixed so that the ratios of Zr, Ti, and Hf were 80 atomic%, 15 atomic%, and 5 atomic%, respectively, to obtain a mixed sample. Next, using an ultra-small vacuum arc melting device (NEV-AD03 type, manufactured by Nissin Kogyo Co., Ltd.), 50 g of the mixed sample weighed as described above was placed on a water-cooled copper hearth, and evacuated for about 2 hours until the pressure reached 3 × 10 -3 After reaching Pa, the mixed sample was arc melted by adjusting the current value to about 40 A to 80 A under an argon atmosphere. In addition, in order to uniformly dissolve the mixed sample, after irradiating the sample with an arc, the procedure of inverting the mixed sample using an inversion rod and irradiating it with an arc again was performed three times. After cooling, 50 g of the obtained Zr-Ti-Hf alloy (ZTH alloy) was taken out from the water-cooled copper hearth.

[0046] (Manufacture of composite material) As the C / C composite, FS320 (25 mm × 25 mm, carbon fiber content: 20 vol%) of CFC Design Co., Ltd. was used. 50 g of the ZTH alloy manufactured as described above was placed in a graphite crucible installed in a carbon heater furnace, and the C / C composite was placed thereon. In that state, it was heated at 1750 °C for 80 minutes in an argon atmosphere, and after cooling, the composite material was taken out from the graphite crucible. This was used as the composite material of Example 1.

[0047] (Evaluation) Three test pieces with a thickness of 10 mm and a diameter of 20 mm were cut out from the composite material of Example 1 using an NC lathe. Each test piece was attached to a holder, and this holder was placed in the test chamber of an arc wind tunnel. An arc jet (high enthalpy air flow) was generated in the test chamber under the conditions of an applied current of 350 - 550 A and an internal pressure of the heater of 0.5 MPa to 0.6 MPa, and each test piece was heated for 30 seconds. In this case, the distance (L) from the nozzle of the arc jet to the test piece was set to 150 mm (Test A), 100 mm (Test B), or 80 mm (Test C). The heat flux and dynamic pressure in the cases of Test A, Test B, and Test C were as described in FIG. 1. Also, the surface temperature of the test piece increased with the increase in the irradiation time of the arc jet. The relationship between the irradiation time of the arc jet and the surface temperature of the test piece is shown in FIG. 2. The surface temperature was measured by a radiation thermometer, the heat flux was measured by a Gardon gauge having the same diameter as the test piece, and the dynamic pressure was measured by a pressure probe. The heated test piece was cut by a diamond blade cutter, and an optical microscope image of the cross-section was taken using a digital microscope manufactured by Keyence Corporation. The obtained cross-section photograph is shown in Fig. 3. In Fig. 3, the portion above the dotted line attached to the cross-section photograph indicates the region where the oxide film was formed. Also, by performing cross-sectional analysis of the test piece using IMAGE-J (National Institutes of Health, NIH), the thickness A of the test piece after the heating test was determined. In this case, the thicknesses were determined at 20 locations on the test piece, and the arithmetic mean was taken as the thickness A of the test piece after the heating test. Separately, the thickness B of the test piece before the heating test was determined in the same manner. From the obtained thicknesses A and B, the thickness reduction rate (thickness A / thickness B × 100 (%)) for each test piece was determined. The obtained results are shown in Fig. 4. In Fig. 4, the thickness reduction rate is denoted as "Normalized thickness of specimen".

[0048] Also, one test piece of 20 mm × 20 mm × 10 mm was cut out from the composite material of Example 1 using a NC lathe. For the obtained test piece, using SEM-EDX, under the following measurement conditions, the ratios of Zr, Hf, and Ti in all metals constituting the carbide, and the ratio of unreacted metal in each metal element contained in the composite material were determined. Furthermore, the ratio of carbon in the composite material was determined. Fig. 5 shows the SEM photograph of the test piece. Also, the above ratios were determined at the locations of Spectrum1-5 in Fig. 5, and the average values were calculated. In the composite material of Example 1, the ratio of Zr in all metals constituting the carbide was 68.3 atomic %, the ratio of Ti in all metals constituting the carbide was 25.3 atomic %, and the ratio of Hf in all metals constituting the carbide was 6.4 atomic %. Also, the ratio of unreacted Zr in all Zr elements contained in the composite material of Example 1 was 5 mass %, the ratio of unreacted Ti in all Ti elements was 5 mass %, and the ratio of unreacted Hf in all Hf elements was 5 mass %. Also, the carbon ratio in Spectrum 1-3 was 80.8 atomic% to 86.7 atomic%, and the carbon ratio in Spectrum 4-5 was 88.0 atomic% to 88.2 atomic%. The volume-based ratio of the inorganic fibers in the entire composite material of Example 1 was 20% by volume.

[0049] <Comparative Example 1> (Production of Ti-Hf alloy) A Ti-Hf alloy (TH20 alloy) was obtained in the same manner as in Example 1, except that the Ti grains and Hf grains used in Example 1 were mixed so that the ratios of Ti and Hf were 80 atomic% and 20 atomic%, respectively, to obtain a mixed sample. Using the obtained TH20 alloy, a composite material of Comparative Example 1 was obtained in the same manner as in Example 1. The obtained composite material of Comparative Example 1 was evaluated in the same manner as in Example 1. The obtained results are shown in FIGS. 3 and 4.

[0050] <Comparative Example 2> (Production of Zr-Ti alloy) A Zr-Ti alloy (ZT20 alloy) was obtained in the same manner as in Example 1, except that the Zr grains and Ti grains used in Example 1 were mixed so that the ratios of Zr and Ti were 20 atomic% and 80 atomic%, respectively, to obtain a mixed sample. Using the obtained ZT20 alloy, a composite material of Comparative Example 2 was obtained in the same manner as in Example 1. The obtained composite material of Comparative Example 2 was evaluated in the same manner as in Example 1. The obtained results are shown in FIGS. 3 and 4.

[0051] <Comparative Example 3> (Production of Zr-Ti alloy) A Zr-Ti alloy (ZT80 alloy) was obtained in the same manner as in Example 1, except that the Zr grains and Ti grains used in Example 1 were mixed so that the ratios of Zr and Ti were 80 atomic% and 20 atomic%, respectively, to obtain a mixed sample. Using the obtained ZT80 alloy, a composite material of Comparative Example 3 was obtained in the same manner as in Example 1. The obtained composite material of Comparative Example 3 was evaluated in the same manner as in Example 1. The obtained results are shown in FIGS. 3 and 4.

[0052] <Comparative Example 4> Evaluation was carried out in the same manner as in Example 1, except that FS320 of CFC Design Co., Ltd. was used instead of the composite material obtained in Example 1. The results obtained are shown in Fig. 4.

[0053] <Discussion> From the cross-sectional photograph of Fig. 3, it can be seen that the formation of the white oxide layer on the surface suppresses the wear of the entire composite material. Furthermore, it is clear that the internal fibers and matrix remain without being worn even after exposure to an oxidizing atmosphere at 2000°C or higher. These results indicate that the material has a mechanism to suppress wear by forming an oxide layer in an oxidizing atmosphere at 2000°C, and it can be said that the material is extremely excellent in heat resistance. Also, as is clear from the evaluation results in Fig. 4, it can be seen that the composite material of Example 1 is superior in heat resistance compared to the composite materials of Comparative Examples 1-3 and the C / C composite used in Comparative Example 4.

Claims

1. A composite material containing a carbide containing Zr and Hf, and an inorganic fiber containing at least one of carbon fiber and ceramic fiber.

2. The composite material according to Claim 1, wherein the proportion of Zr in all the metals constituting the carbide is 60 atomic % to 90 atomic %.

3. The composite material according to Claim 1, wherein the proportion of Hf in all the metals constituting the carbide is 1 atomic % to 20 atomic %.

4. The composite material according to Claim 1, wherein the carbide further contains Ti.

5. The proportion of Hf in all the metals constituting the carbide is 1 atomic % to 20 atomic %, the proportion of Ti in all the metals constituting the carbide is greater than 0 atomic % and 29 atomic % or less, and the balance of all the metals constituting the carbide is Zr and inevitable impurities. The composite material according to Claim 4.

6. The composite material according to Claim 1, wherein the proportion of unreacted Zr in all the Zr elements contained in the composite material is 10 mass % or less.

7. The composite material according to Claim 1, wherein the proportion of unreacted Hf in all the Hf elements contained in the composite material is 10 mass % or less.

8. The composite material according to Claim 4, wherein the proportion of unreacted Ti in all the Ti elements contained in the composite material is 10 mass % or less.

9. Melting an alloy containing Zr and Hf to obtain a molten alloy, and attaching the molten alloy to an inorganic fiber containing at least one of carbon fiber and ceramic fiber. A method for producing a composite material including these steps.

10. The method for producing a composite material according to Claim 9, wherein the alloy further contains Ti.

11. The method for producing a composite material according to Claim 9, wherein attaching the molten alloy to the inorganic fiber includes impregnating the molten alloy into the inorganic fiber.

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