Ceramic sintered body, electrode for plasma generation, and heat-resistant member

Abstract

A ceramic sintered body according to the present invention comprises: a plurality of carbide crystal particles containing carbides of first specific elements constituted by five or six elements selected from titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (Ta), and tungsten (W); and a plurality of oxide crystal particles containing an oxide of aluminum (Al). The carbide crystal particles constitute a solid solution containing 45 at% to 55 at% of carbon. In a cross section of the ceramic sintered body, the ratio of the cross-sectional area of the oxide crystal particles to the cross-sectional area of the ceramic sintered body is 5% to 60%.

Description

Ceramic sintered body, plasma generation electrode, and heat-resistant component

[0001] This invention relates to a ceramic sintered body, a plasma generating electrode, and a heat-resistant member.

[0002] Conventional ceramic sintered bodies have been known (for example, Patent Documents 1 and 2, and Non-Patent Document 1).

[0003] Patent No. 6929755 Patent No. 4177493

[0004] Shiro Shimada, Michio Inagaki, Kunihito Matsui, "Oxidation Kinetics of Hafnium Carbide in the Temperature Range of 480° to 600°C", Journal of the American Ceramic Society, Volume 75, Issue 10, October 1992, Pages 2671-2678, [Retrieved March 10, 2025], Internet <https: / / doi.org / 10.1111 / j.1151-2916.1992.tb05487.x>

[0005] However, even with prior art such as Patent Documents 1 and 2 and Non-Patent Document 1, there was still room for improvement in techniques for increasing the strength of ceramic sintered bodies.

[0006] The present invention aims to provide a technique for improving the strength of ceramic sintered bodies.

[0007] The present invention has been made to solve at least some of the above-mentioned problems and can be realized in the following forms.

[0008] (1) According to one embodiment of the present invention, a ceramic sintered body is provided. This ceramic sintered body comprises a plurality of carbide crystal particles containing a carbide of a first specific element consisting of five or six elements selected from titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (Ta), and tungsten (W), and a plurality of oxide crystal particles containing an oxide of aluminum (Al), wherein the carbide crystal particles are a solid solution containing 45 at% to 55 at% carbon, and in the cross-section of the ceramic sintered body, the ratio of the cross-sectional area of ​​the oxide crystal particles to the cross-sectional area of ​​the ceramic sintered body is 5% to 60%.

[0009] With this configuration, the ceramic sintered body has a structure in which carbide crystal particles and oxide crystal particles are combined, which suppresses the grain growth of each crystal particle. As a result, the ceramic sintered body has dense and fine crystal particles. In addition, since the carbide crystal particles are a solid solution containing 45 at% to 55 at% carbon, the generation of free carbon at the grain boundaries can be suppressed. These factors improve the strength of the ceramic sintered body.

[0010] (2) In the above-described form of ceramic sintered body, the amount of iron (Fe) contained in the ceramic sintered body may be 1000 at ppm or less. With this configuration, since the amount of iron contained in the ceramic sintered body is 1000 at ppm or less, the precipitation of iron-based particles with relatively low melting points is suppressed. This makes it possible to suppress the decrease in strength of the ceramic sintered body in a high-temperature environment.

[0011] (3) In the ceramic sintered body of the above form, each of the carbide crystal particles and the oxide crystal particles contains chromium (Cr), and the atomic percentage of chromium in the carbide crystal particles is A Cr The atomic percentage of chromium in the oxide crystal particles is set to B. Cr Therefore, the following equation (1) is satisfied: 0.05 ≤ B Cr / A Cr≤0.5 ... (1) With this configuration, since chromium is contained in both the carbide crystal particles and the oxide crystal particles, the bonding at the interface between the carbide crystal particles and the oxide crystal particles becomes relatively strong. This further improves the strength of the ceramic sintered body.

[0012] (4) In the ceramic sintered body of the above form, the ratio of the cross-sectional area of ​​the oxide crystal particles to the cross-sectional area of ​​the ceramic sintered body in the cross-section of the ceramic sintered body may be 5% or more and 40% or less. With this configuration, the ratio of the cross-sectional area of ​​the oxide crystal particles to the cross-sectional area of ​​the ceramic sintered body in the cross-section of the ceramic sintered body is within a certain range, so that the carbide crystal particles provide electrical conductivity while the oxide crystal particles improve the strength of the ceramic sintered body.

[0013] (5) According to another embodiment of the present invention, a plasma generating electrode is provided. This plasma generating electrode comprises a ceramic sintered body as described above. With this configuration, the plasma generating electrode comprises a ceramic sintered body having a structure in which carbide crystal particles and oxide crystal particles are combined, thereby improving its strength. Consequently, thermal shock resistance is improved, and the lifespan of the plasma generating electrode can be extended.

[0014] (6) According to yet another embodiment of the present invention, a heat-resistant member is provided. This heat-resistant member comprises a ceramic sintered body as described above. With this configuration, the heat-resistant member comprises a ceramic sintered body having a structure in which carbide crystal particles and oxide crystal particles are combined, thereby improving its strength. As a result, thermal shock resistance is improved, and the lifespan of the heat-resistant member can be extended.

[0015] Furthermore, the present invention can be realized in various forms, for example, in the form of a method for manufacturing a ceramic sintered body, a method for manufacturing an electrode for plasma generation, a method for manufacturing a heat-resistant member, an apparatus equipped with a ceramic sintered body, a method for controlling such apparatus, and so on.

[0016] This is a cross-sectional view of a plasma generating electrode comprising a ceramic sintered body according to the first embodiment. This is a schematic cross-sectional view of the ceramic sintered body according to the first embodiment. This is a diagram illustrating the manufacturing conditions for a sample of the ceramic sintered body. This is the first diagram illustrating the characteristics of a sample of the ceramic sintered body. This is the second diagram illustrating the characteristics of a sample of the ceramic sintered body. This is a perspective view of a heat-resistant member comprising a ceramic sintered body according to the second embodiment.

[0017] <First Embodiment> Figure 1 is a cross-sectional view of a plasma generating electrode 10 equipped with an electrode tip 1 (ceramic sintered body) according to this embodiment. The plasma generating electrode 10 of this embodiment is used, for example, to generate oxygen plasma in a cutting machine, surface treatment apparatus, thermal spray apparatus, etc. that uses plasma. The plasma generating electrode 10 comprises an electrode tip 1 as a plasma generating cathode and a tip support portion 11 that supports the electrode tip 1.

[0018] The electrode tip 1 is a ceramic sintered body comprising a plurality of carbide crystal particles containing carbides of a first specific element consisting of five or six elements selected from titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (Ta), and tungsten (W), and a plurality of oxide crystal particles containing aluminum (Al) oxide. The carbide crystal particles of the electrode tip 1 are a solid solution containing 45 at% to 55 at% carbon, and in the cross-section of the ceramic sintered body, the ratio of the cross-sectional area of ​​the oxide crystal particles to the cross-sectional area of ​​the ceramic sintered body is 5% to 60%.

[0019] Figure 2 is a schematic cross-sectional view of the ceramic sintered body of this embodiment. As shown in Figure 2, the electrode tip 1 of this embodiment comprises a plurality of carbide crystal particles Pcc and a plurality of oxide crystal particles Pco. The carbide crystal particles Pcc have a single-phase structure containing carbides of a first specified element consisting of five or six elements selected from titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten. The carbide crystal particles Pcc of the electrode tip 1 of this embodiment contain titanium, vanadium, chromium, niobium, and tantalum as the first specified element. The identification and concentration of the first specified element in the carbide crystal particles Pcc are performed by energy-dispersive X-ray spectroscopy (EDS) at a magnification of 500x. Whether or not the carbide crystal particles Pcc have a single-phase structure is determined by X-ray diffraction (XRD) using an X-ray diffractometer. Specifically, in the analysis of the crystal structure of electrode tip 1 by X-ray diffraction using CuKα1 rays, when 2θ is measured from 20° to 80°, if there is only one peak each at 30.0°–37.2°, 34.8°–43.1°, 50.2°–62.3°, 59.7°–74.4°, and 62.7°–78.5°, originating from the <111>, <200>, <220>, <311>, and <222> directions of the NaCl-type structure, then it is determined that electrode tip 1 has a single-phase structure. Furthermore, if two or three peaks are observed within any of the following ranges: 30.0°–37.2°, 34.8°–43.1°, 50.2°–62.3°, 59.7°–74.4°, or 62.7°–78.5°, it is determined that the tissue has a diphasic structure.

[0020] The oxide crystal particles Pco contain aluminum oxide. In this embodiment, whether or not the oxide crystal particles Pco contain aluminum oxide is determined by X-ray diffraction using an X-ray diffractometer.

[0021] The electrode tip 1 of this embodiment has a structure in which carbide crystal particles Pcc and oxide crystal particles Pco are combined, thus suppressing grain growth of the crystal grains. As a result, a ceramic sintered body with relatively high strength can be produced. Furthermore, since the ceramic sintered body of this embodiment contains elements with a lower melting point than hafnium carbide (HfC), a dense sintered body can be produced by sintering methods other than the current-driven sintering method, such as hot pressing, in the manufacturing method of the electrode tip 1 described later.

[0022] In this embodiment, the electrode tip 1 is a solid solution of carbide crystal particles Pcc containing 45 at% to 55 at% carbon. This suppresses the generation of free carbon at the grain boundaries, thereby improving the strength of the ceramic sintered body. The carbon concentration in the carbide crystal particles Pcc in this embodiment is 54.1 at%. In this embodiment, the carbon concentration in the carbide crystal particles Pcc is measured by energy-dispersive X-ray spectroscopy at a magnification of 500x.

[0023] In the electrode tip 1 of this embodiment, the ratio of the cross-sectional area of ​​oxide crystal particles to the cross-sectional area of ​​the ceramic sintered body is 5% or more and 60% or less. This allows the electrode tip 1 to have electrical conductivity as an electrode tip 1 while also having a certain level of strength or higher. In the electrode tip 1 of this embodiment, the ratio of the cross-sectional area of ​​oxide crystal particles to the cross-sectional area of ​​the ceramic sintered body is 33.8%. It is more desirable that the ratio of the cross-sectional area of ​​oxide crystal particles to the cross-sectional area of ​​the ceramic sintered body be 5% or more and 40% or less. In this embodiment, the ratio of the cross-sectional area of ​​oxide crystal particles Pco in the cross-section of the ceramic sintered body is calculated by performing binarization processing on the image of the cross-section of the ceramic sintered body captured by a scanning electron microscope (SEM) using the image analysis software WinROOF.

[0024] The electrode tip 1 of this embodiment contains iron (Fe) as an unavoidable impurity. In this embodiment, the amount of iron contained in the electrode tip 1 is 1000 at ppm or less. Since iron has a relatively low melting point, it may reduce the heat resistance of the electrode tip 1, and therefore it is preferable not to include it. Accordingly, the amount of iron contained in the electrode tip 1 may be 0 at ppm. The concentration of iron in the electrode tip 1 of this embodiment is 763 at ppm. In this embodiment, the concentration of iron in the ceramic sintered body is measured by inductively coupled plasma atomic emission spectroscopy (ICP-AES).

[0025] In this embodiment, the electrode tip 1 has few pores because each of the multiple carbide crystal particles Pcc is a single-phase structure, resulting in a so-called dense ceramic sintered body. In this embodiment, the density of the electrode tip 1 is calculated by determining the relative density using the specific gravity and open porosity measured according to JIS R1634:1998 "Method for measuring density and open porosity of sintered fine ceramics", and the specific gravity of the mixture of metal raw material powders used in the manufacture of the electrode tip 1. The specific gravity of the mixture of metal raw material powders used in the manufacture of the electrode tip 1 is calculated using the specific gravity of each metal raw material powder weighed during the manufacture of the electrode tip 1 and the mixing ratio. The electrode tip 1 in this embodiment has a relative density of 98.5%.

[0026] In this embodiment, the electrode tip 1 contains chromium (Cr) in both the carbide crystal particles Pcc and the oxide crystal particles Pco, and the atomic percentage of chromium in the carbide crystal particles Pcc is A Cr Let B be the atomic percentage of chromium in the oxide crystal grain Pco. Cr This satisfies equation (1) below. As a result, the bonding at the interface between the carbide crystal particles Pcc and the oxide crystal particles Pco in the electrode tip 1 becomes relatively strong, and the strength of the ceramic sintered body can be further improved. In the electrode tip 1 of this embodiment, the atomic percentage A of chromium in the carbide crystal particles Pcc Cr The atomic percentage B of chromium in oxide crystal grains Pco. CrThe ratio is 0.5. In this embodiment, the atomic percentage A of chromium in each of carbide crystal particles Pcc and oxide crystal particles Pco Cr , B Cr is calculated by energy dispersive X-ray spectroscopy at a magnification of 500 times. 0.05≦B Cr / A Cr ≦0.5 ......(1)

[0027] The tip support portion 11 is a bottomed cylindrical member, and is formed, for example, by processing a copper rod-shaped member. A hole 11b into which the electrode tip 1 is fitted is formed in a bottom portion 11a of the tip support portion 11. The plasma generating electrode 10 of the present embodiment is completed by fitting the electrode tip 1 into the hole 11b of the tip support portion 11.

[0028] Next, a method for manufacturing the electrode tip 1 will be described. As the method for manufacturing the electrode tip 1, first, weighed raw material powder is put into a ball mill together with an acetone solvent, and mixed pulverization is performed for 20 hours, thereby preparing a slurry. The types of the raw material powders to be weighed are, as carbide raw materials, titanium carbide powder (TiC, average particle diameter: 1.7 μm), vanadium carbide powder (VC, average particle diameter: 1.8 μm), chromium carbide powder (Cr₃C₂, average particle diameter: 4.5 μm), niobium carbide powder (NbC, average particle diameter: 1.1 μm), and tantalum carbide powder (TaC, average particle diameter: 1.0 μm), and as an oxide raw material, aluminum oxide powder (Al₂O₃, average particle diameter: 0.7 μm). Among these raw material powders, the carbide raw materials are weighed such that titanium carbide, vanadium carbide, niobium carbide, and tantalum carbide account for 23 mol% in total, and chromium carbide accounts for 8 mol%, and aluminum oxide in an amount corresponding to 20 wt% of the total weight of the carbide raw materials is added to the carbide raw materials. The mixture of the carbide raw materials and aluminum oxide is put into a ball mill together with an acetone solvent, and mixed pulverization is performed for 20 hours, thereby preparing a slurry. The prepared slurry is dried in a hot water bath at 60° C., and then passed through a sieve with an opening of 100 μm, thereby preparing granulated powder. The prepared granulated powder is put into a hot pressing mold, and fired by a hot pressing method (HP) in which pressure is applied at 30 MPa in a vacuum atmosphere at a temperature of 2000° C., thereby completing the electrode tip 1.

[0029] Next, an evaluation test on a ceramic sintered body used as an electrode tip of a plasma generating electrode will be described. In this evaluation test, a plurality of ceramic sintered bodies with different production conditions were produced, and the influence of the production conditions on the properties of the ceramic sintered body was evaluated.

[0030] FIG. 3 is a diagram illustrating production conditions for samples of the ceramic sintered body. In this evaluation test, 22 types of samples, Sample 1 to Sample 22, were produced as samples of the ceramic sintered body. In FIG. 3, as production conditions for each of Sample 1 to Sample 22, there are shown the type and molar percentage of each "carbide" as a "main raw material", the weight percentage of Al₂O₃, as well as the "firing method", "temperature" (unit: °C) and "pressure" (unit: MPa) as "firing conditions".

[0031] First, the "carbide" as the "main raw material" will be described. Among Samples 1 to 21, in the production of Samples 1 to 17, among titanium carbide (TiC), vanadium carbide (VC), chromium carbide (Cr₃C₂), zirconium carbide (ZrC), niobium carbide (NbC), molybdenum carbide (Mo₂C), hafnium carbide (HfC), tantalum carbide (TaC), and tungsten carbide (WC), as shown in FIG. 3, 5 to 6 types of materials were used as the "carbide". In the production of Samples 1 to 17, "carbide" powder having the average particle sizes shown below was used. Titanium carbide: 1.7 µm Vanadium carbide: 1.8 µm Chromium carbide: 4.5 µm Zirconium carbide: 2.4 µm Niobium carbide: 1.1 µm Molybdenum carbide: 1.8 µm Hafnium carbide: 0.7 µm Tantalum carbide: 1.0 µm Tungsten carbide: 1.1 µm

[0032] Next, "Al₂O₃" as the "main raw material" will be described. In the production of Samples 1 to 17, aluminum oxide (average particle size: 0.7 µm) was used.

[0033] In the production of Samples 1 to 17, a slurry was prepared in the same manner as in the production method for electrode tip 1. In the production of each slurry for Samples 1 to 17, for each "carbide" shown in FIG. 3, each "carbide" was weighed such that its mole percentage in the slurry matches the value shown in FIG. 3, and aluminum oxide was weighed such that the mass percentage thereof relative to the total weight of the "carbide(s)" matches the value shown in FIG. 3. The weighed "carbide(s)" and the weighed aluminum oxide were charged into a ball mill together with an acetone solvent, and mixed and pulverized for 20 hours. Next, after the prepared slurry was hot water bath dried at 60° C., it was passed through a sieve with an opening of 100 μm, whereby granulated powder was prepared.

[0034] In the production of Samples 1 to 17, firing was performed by a hot press method (HP), as shown in the "Firing method" under "Firing conditions" in FIG. 3. In the production of Samples 1 to 17, the obtained granulated powder was charged into a square hot press mold having dimensions of 35 mm × 35 mm such that the thickness of the sample after firing becomes 5 mm, and firing was performed in a vacuum atmosphere under the "Temperature" and "Pressure" conditions of the "Firing conditions" in FIG. 3.

[0035] Sample 18 is a sintered body of hafnium carbide, and was produced using hafnium carbide powder. In the production of Sample 18, firing was performed by a spark plasma sintering method (SPS) in which pressure is applied at 70 MPa in a vacuum atmosphere at a temperature of 1900° C. In the production of Sample 17, hafnium carbide powder was charged into a square spark plasma sintering mold having dimensions of 35 mm × 35 mm such that the thickness of the sample becomes 5 mm. Sample 17 is a reference sample used as a comparison object in the present evaluation test.

[0036] As shown in Figure 3, Sample 19 uses zirconium carbide, tantalum carbide, niobium carbide, and tungsten carbide as raw materials for the carbides, but does not use oxide raw materials. Sample 19 was prepared using the four types of carbides described above, in the same manner as the preparation of Samples 1 to 16. The firing process for Sample 18 was performed using a heat pump (HP) at a vacuum atmosphere at a temperature of 1800°C and a pressure of 30 MPa. Sample 19 is the reference sample for comparison in this evaluation test.

[0037] For Sample 20 and Sample 21, each metal oxide was weighed so that the composition ratios of titanium, tantalum, niobium, and chromium were the same. In addition, carbon was weighed so that the ratio of total metal element content (ME) to carbon (C) in the entire ceramic sintered body was ME:C = 0.6:0.4 for Sample 20 and ME:C = 0.4:0.6 for Sample 19. These metal oxides and carbon were mixed in a ball mill and heat-treated in a vacuum atmosphere at 1600°C for 3 hours. Next, in the preparation of Sample 20 and Sample 21, vanadium carbide was added to the heat-treated powder in the same molar amounts as titanium, tantalum, niobium, and chromium, and an amount of aluminum oxide equivalent to 20 wt% of the total weight of "carbides" was added and mixed in a ball mill. Using the mixed raw material powder, Sample 20 and Sample 21 were prepared in the same manner as in the preparation of Samples 1 to 17.

[0038] Sample 22 contains a higher amount of aluminum oxide than Samples 1 to 17. In the preparation of Sample 21, titanium carbide, vanadium carbide, niobium carbide, and tantalum carbide were weighed to 23.5 mol%, chromium carbide to 6 mol%, and aluminum oxide to 80 wt%. In the preparation of Sample 22, the weighed raw material powders were used and prepared in the same manner as in the preparation of Samples 1 to 17.

[0039] Figure 4 is the first diagram illustrating the characteristics of the ceramic sintered body samples. Figure 5 is the second diagram illustrating the characteristics of the ceramic sintered body samples. Figure 4 shows the items related to carbide crystal particles and items related to oxide crystal particles for each of Samples 1 to 22. Figure 5 shows the iron concentration and the ratio of the atomic percentage of chromium in oxide crystal particles to the atomic percentage of chromium in carbide crystal particles for each of Samples 1 to 22. Cr / A Cr Each of several items showing characteristics related to relative density and strength is shown. Here, the measurement or calculation methods for each item for the samples shown in Figures 4 and 5 will be explained. In this evaluation test, for the measurement or calculation methods for each item for the samples shown in Figures 4 and 5, each of the samples 1 to 22 prepared by the method described above was processed to a size of 3 mm × 4 mm × 35 mm. Note that for each item shown in Figures 4 and 5, items that were not measured are marked with "-".

[0040] Of the items listed under "Carbide Crystal Particles" in Figure 4, "Composition," "Crystal Phase" (indicating the degree of single-phase formation), and "C Concentration (at%)" (indicating the carbon concentration) were measured or calculated using the same methods as those used for measurement or calculation in the electrode tip 1 of this embodiment. The "Particle Size (μm)" of the "Carbide Crystal Particles" was calculated using the intercept method with a secondary electron image (magnification: 2000x) of the cross-section of the ceramic sintered body captured by a scanning electron microscope. The "Composition" of the "Carbide Crystal Particles" was measured on a sample that had undergone a strength test (described later), mirror-polished with diamond abrasives, and then thermal-etched for 5 minutes in a vacuum atmosphere at 1650°C.

[0041] In Figure 4, the "percentage (%)" of the "oxide crystal particles" item, which indicates the ratio of the cross-sectional area of ​​oxide crystal particles to the cross-sectional area of ​​the sample ceramic sintered body, was measured or calculated using the same method as the measurement or calculation method for electrode tip 1 in this embodiment. The "particle size (μm)" of the "oxide crystal particles" item was calculated using the same method as the "particle size (μm)" of the "carbide crystal particles" described above.

[0042] Figure 5 shows the iron concentration in the sample, "Fe concentration (at ppm)", "B Cr / A Cr The "(-)" and "relative density (%)" were measured or calculated using the same method as the measurement or calculation method for electrode tip 1 in this embodiment. Since sample 18 has a single composition, the "relative density (%)" was calculated using the specific gravity and open porosity measured according to JIS R1634:1998 "Method for measuring density and open porosity of sintered fine ceramics".

[0043] The "strength (MPa)" shown in Figure 5 was measured by a three-point bending strength test in accordance with JIS R1601:2008 "Test method for room temperature bending strength of fine ceramics". The "Young's modulus (GPa)" was measured using the ultrasonic pulse method on the sample used in the three-point bending test in accordance with JIS R1602:1995 "Test method for elastic modulus of fine ceramics".

[0044] The "high-temperature oxidation resistance" shown in Figure 5 indicates the resistance to oxidation in high-temperature environments. "High-temperature oxidation resistance" was calculated using an arc heating tester. Specifically, first, the weight of the sample to be evaluated was measured. Next, the sample was irradiated with an arc plasma generated using a nitrogen and oxygen mixture in a reduced-pressure atmosphere of 10 Pa or less, and the amount of sample loss was measured. In measuring the amount of sample loss using the arc heating tester, the sample temperature was adjusted to 1800°C, and the irradiation time was set to 3 minutes. Finally, the weight of the sample was measured, and the percentage change in weight before and after irradiation with the arc plasma was calculated. In this evaluation test, the ratio of the percentage change in weight of each sample, with the percentage change in weight of sample 18 set to 100, is defined as "high-temperature oxidation resistance" and is shown in Figure 5. That is, the smaller the value of "high-temperature oxidation resistance" shown in Figure 5, the better the oxidation resistance in high-temperature environments.

[0045] Figure 5 shows "Repeated Discharge," which indicates whether or not malfunctions occurred and the degree of malfunction when the sample was repeatedly discharged as a plasma generation electrode. "Wear Resistance" indicates the degree of wear when the sample was used as a plasma generation electrode. "Repeated Discharge" and "Wear Resistance" were calculated through tests simulating use as a plasma generation electrode. Specifically, an evaluation electrode was fabricated by processing the sample to a diameter of 1 mm and a length of 10 mm, used as the cathode, the anode was grounded and connected to a DC pulse power supply, and a plasma discharge with an energy of 400 W was performed in an atmosphere containing a mixed gas of nitrogen and oxygen, with one cycle consisting of a 1 minute discharge followed by a 10 second stop. For the determination of "Repeated Discharge," the sample was visually checked for malfunctions after the test, and the cumulative discharge time until a malfunction occurred was used as the evaluation index below: A: No malfunction occurred for 2 hours or more B: A malfunction occurred between 1 hour and less than 2 hours C: A malfunction occurred between 30 minutes and less than 1 hour D: A malfunction occurred in less than 30 minutes

[0046] In determining "wear resistance," the weight loss of the sample was measured after discharge, and the amount of sample consumed was calculated. In this evaluation test, the ratio of the weight loss of each sample to the weight loss of sample 19 (which was set to 100) was defined as "wear resistance," and is shown in Figure 5. In other words, the smaller the "wear resistance" value shown in Figure 5, the less likely the sample is to wear down.

[0047] Samples 1 to 17, shown in Figure 5, all comprise multiple carbide crystal particles containing a carbide of a first specified element selected from five elements chosen from titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten, and multiple oxide crystal particles containing aluminum oxide. The carbide crystal particles are solid solutions containing 45 at% to 55 at% carbon, and it was confirmed that the ratio of the cross-sectional area of ​​the oxide crystal particles to the cross-sectional area of ​​the sample is between 5% and 60%. All of these samples, from 1 to 17, exhibit strength above a certain value, and it was confirmed that they have relatively excellent resistance to high-temperature oxidation and abrasion.

[0048] As shown in Figure 4, Sample 19 contains four types of carbides of the first specified element contained in the carbide crystal particles: zirconium carbide, tantalum carbide, niobium carbide, and tungsten carbide. Furthermore, as shown in Figure 4, it was confirmed that Sample 19 does not contain oxide crystal particles. Therefore, in Sample 19, a composite structure of carbide crystal particles and oxide crystal particles is not formed, making it easier for grain growth of carbide crystal particles to progress (see "Particle size (μm)" for "Carbide crystal particles" in Figure 4). As a result, compared to Samples 1 to 16, Sample 19 has higher values ​​for both "High-temperature oxidation resistance" and "Wear resistance," confirming that oxidation progresses easily and wears down easily in high-temperature environments.

[0049] As shown in Figure 4, samples 20 and 21 have carbon concentrations in their carbide crystal particles that are less than 45 at% or greater than 55 at%. In ceramic sintered bodies, when the carbon concentration is between 45 at% and 55 at%, the carbide crystal particles form a single-phase structure containing the first specified element. However, when the carbon concentration is less than 45 at%, the metallic phase of the first specified element tends to precipitate. Since such a metallic phase has a lower melting point than the carbide, when used as a plasma generating electrode, for example, it may melt due to rising temperatures, and the lifespan of the plasma generating electrode tends to be shortened. Also, when the carbon concentration is greater than 55 at%, free carbon tends to precipitate. When free carbon precipitates, when used as a plasma generating electrode, the voltage required to start the discharge increases, making it prone to high temperatures and potentially melting. For this reason, the lifespan of the plasma generating electrode tends to be shortened. Samples 20 and 21, which had carbon concentrations lower than 45 at% or higher than 55 at%, showed higher values ​​for "high-temperature oxidation resistance" and "abrasion resistance" compared to samples 1 to 17. This confirmed that they were more susceptible to oxidation and abrasion in high-temperature environments.

[0050] As shown in Figure 4, in sample 22, the "percentage (%)" representing the ratio of the cross-sectional area of ​​oxide crystal particles to the cross-sectional area of ​​the ceramic sintered body sample is greater than 60%. When the ratio of the cross-sectional area of ​​oxide crystal particles to the cross-sectional area of ​​the ceramic sintered body is greater than 60%, there are more oxide crystal particles, which have relatively lower electrical conductivity than carbide crystal particles, making it difficult for electricity to flow. As a result, it becomes more prone to overheating and breakage, and the lifespan as a plasma generation electrode tends to be shortened. It was confirmed that sample 22, with a "percentage (%)" greater than 60%, is prone to breakage due to repeated discharge when used as a plasma generation electrode. Furthermore, when the ratio of the cross-sectional area of ​​oxide crystal particles to the cross-sectional area of ​​the ceramic sintered body is less than 5%, grain growth of carbide crystal particles progresses more easily, reducing the strength of the ceramic sintered body.

[0051] As described above, the electrode tip 1 of this embodiment is a ceramic sintered body, and because it has a structure in which carbide crystal particles Pcc and oxide crystal particles Pco are combined, grain growth of each crystal particle is easily suppressed. As a result, a dense and fine ceramic sintered body is formed. Furthermore, since the carbide crystal particles Pcc are a solid solution containing 45 at% to 55 at% carbon, the generation of free carbon at the grain boundaries can be suppressed. These factors improve the strength of the electrode tip 1.

[0052] Furthermore, in this embodiment, the electrode tip 1 contains less than 1000 at ppm of iron in the ceramic sintered body, thus suppressing the precipitation of iron-based particles with relatively low melting points. This makes it possible to suppress the decrease in strength of the electrode tip 1 in high-temperature environments.

[0053] Furthermore, the electrode tip 1 of this embodiment has an atomic percentage A of chromium in the carbide crystal particles Pcc. Cr And the atomic percentage B of chromium in oxide crystal grains Pco Cr The relationship satisfies equation (1). Thus, since chromium is contained in both the carbide crystal particles Pcc and the oxide crystal particles Pco of the ceramic sintered body, the bonding at the interface between the carbide crystal particles Pcc and the oxide crystal particles Pco becomes relatively strong. This further improves the strength of the electrode tip 1.

[0054] Furthermore, in the electrode tip 1 of this embodiment, the ratio of the cross-sectional area of ​​oxide crystal particles Pco to the cross-sectional area of ​​the ceramic sintered body is 33.8%, which is within the range of 5% to 40% in the cross-sectional area of ​​the ceramic sintered body. This makes it possible to improve the strength of the electrode tip 1 while maintaining its electrical conductivity with carbide crystal particles Pcc, and improving its strength with oxide crystal particles Pco.

[0055] Furthermore, the plasma generating electrode 10 of this embodiment is equipped with a ceramic sintered body having a structure in which carbide crystal particles Pcc and oxide crystal particles Pco are combined, thus improving its strength. Consequently, its thermal shock resistance is improved, and the lifespan of the plasma generating electrode 10 can be extended.

[0056] Furthermore, the electrode tip 1 of this embodiment is manufactured by hot pressing. As a result, the electrode tip 1 can have a complex shape while reducing equipment and manufacturing costs compared to plasma generation electrodes made of hafnium or hafnium carbide manufactured by electro-sintering. Therefore, it is possible to manufacture at a low cost and improve the degree of freedom in shape.

[0057] <Second Embodiment> Figure 6 is a perspective view of the heat-resistant member of the second embodiment. Compared to the electrode tip of the first embodiment (Figure 1), the heat-resistant member of the second embodiment is applied to a different field of ceramic sintered body.

[0058] The heat-resistant member 2 of this embodiment is a ceramic sintered body comprising a plurality of carbide crystal particles containing carbides of a first specific element consisting of five or six elements selected from titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten, and a plurality of oxide crystal particles containing aluminum oxide. The carbide crystal particles of the heat-resistant member 2 are a solid solution containing 45 at% to 55 at% carbon, and in the cross-section of the ceramic sintered body, the ratio of the cross-sectional area of ​​the oxide crystal particles to the cross-sectional area of ​​the ceramic sintered body is 5% to 60%. The heat-resistant member 2 of this embodiment is used, for example, in an oxidizing atmosphere in a high-temperature environment. Although the heat-resistant member 2 shown in Figure 6 has a flat plate shape, the shape of the heat-resistant member 2 is not limited thereto. The shape can be selected depending on the situation in which the heat-resistant member 2 is applied.

[0059] As described above, the heat-resistant member 2 of this embodiment is a ceramic sintered body comprising a plurality of carbide crystal particles containing carbides of a first specific element consisting of five or six elements selected from titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten, and a plurality of oxide crystal particles containing aluminum oxide. This makes it possible to improve the strength of the heat-resistant member 2.

[0060] Furthermore, since the heat-resistant member 2 of this embodiment comprises a ceramic sintered body having a structure in which carbide crystal particles Pcc and oxide crystal particles Pco are combined, its strength is improved. Therefore, its thermal shock resistance is improved, and the lifespan of the heat-resistant member 2 can be extended.

[0061] Furthermore, the heat-resistant member 2 of this embodiment is manufactured by hot pressing. As a result, the heat-resistant member 2 can have a complex shape while reducing equipment costs and manufacturing costs compared to heat-resistant members made of hafnium or hafnium carbide manufactured by electro-sintering. Therefore, it is possible to manufacture at a low cost and improve the degree of freedom in shape.

[0062] <Modifications of this Embodiment> The present invention is not limited to the above-described embodiments, and can be implemented in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0063] [Modification 1] In the above embodiment, the ceramic sintered body comprises a plurality of carbide crystal particles containing carbides of titanium, vanadium, chromium, niobium, and tantalum, and a plurality of oxide crystal particles containing aluminum oxide. The carbide crystal particles may include carbides of a first specific element consisting of five or six elements selected from titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, and tungsten.

[0064] [Modification 2] In the above embodiment, the ceramic sintered body had an iron concentration of 1000 at ppm or less. The iron concentration in the ceramic sintered body is not limited to this. However, when the iron concentration is 1000 at ppm or less, the precipitation of iron-based particles with relatively low melting points is suppressed, and thus the decrease in strength in high-temperature environments can be suppressed. Therefore, a lower iron concentration is desirable. The concentration of iron element may be below the detection limit when measured by inductively coupled plasma atomic emission spectrometry.

[0065] [Modification 3] In the above embodiment, the ceramic sintered body is the atomic percentage A of chromium in the carbide crystal particles Pcc.Cr And the atomic percentage B of chromium in oxide crystal grains Pco Cr The relationship was assumed to satisfy equation (1). Atomic percentage A of chromium in carbide crystal grains Pcc. Cr And the atomic percentage B of chromium in oxide crystal grains Pco Cr The relationship does not need to satisfy equation (1).

[0066] [Modification 4] In the above embodiment, the ceramic sintered body is provided by the plasma generating electrode 10 or the heat-resistant member 2. The technical field to which the ceramic sintered body is applied is not limited to this. It may be used in technical fields where high-temperature oxidation resistance and wear resistance are required.

[0067] The embodiments of this specification have been described above based on the embodiments and modifications described above. The embodiments described above are for the purpose of facilitating understanding of this specification and do not limit it. This specification may be modified and improved without departing from its spirit and the scope of the claims, and equivalents thereof are included in this specification. Furthermore, any technical features that are not described as essential in this specification may be deleted as appropriate.

[0068] <Application Example 1> A ceramic sintered body comprising: a plurality of carbide crystal particles containing a carbide of a first specific element consisting of five or six elements selected from titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (Ta), and tungsten (W); and a plurality of oxide crystal particles containing an oxide of aluminum (Al), wherein the carbide crystal particles are a solid solution containing 45 at% to 55 at% carbon, and in the cross-section of the ceramic sintered body, the ratio of the cross-sectional area of ​​the oxide crystal particles to the cross-sectional area of ​​the ceramic sintered body is 5% to 60%. <Application Example 2> The ceramic sintered body according to Application Example 1, wherein the amount of iron (Fe) contained in the ceramic sintered body is 1000 at ppm or less. <Application Example 3> A ceramic sintered body according to Application Example 1 or Application Example 2, wherein each of the carbide crystal particles and the oxide crystal particles contains chromium (Cr), and the atomic percentage of chromium in the carbide crystal particles is A Cr The atomic percentage of chromium in the oxide crystal particles is set to B. Cr Therefore, a ceramic sintered body characterized by satisfying the following equation (1): 0.05 ≤ B Cr / A Cr ≤0.5 ... (1) <Application Example 4> A ceramic sintered body according to any one of Application Examples 1 to 3, characterized in that, in the cross-section of the ceramic sintered body, the ratio of the cross-sectional area of ​​the oxide crystal particles to the cross-sectional area of ​​the ceramic sintered body is 5% or more and 40% or less. <Application Example 5> A heat-resistant member comprising a ceramic sintered body according to any one of Application Examples 1 to 4. <Application Example 6> A plasma generating electrode comprising a ceramic sintered body according to any one of Application Examples 1 to 4.

[0069] 1... Electrode tip 2... Heat-resistant material 10... Electrode for plasma generation Pcc... Carbide crystal particles Pco... Oxide crystal particles

Claims

1. A ceramic sintered body comprising: a plurality of carbide crystal particles containing carbides of a first specific element consisting of five or six elements selected from titanium (Ti), vanadium (V), chromium (Cr), zirconium (Zr), niobium (Nb), molybdenum (Mo), hafnium (Hf), tantalum (Ta), and tungsten (W); and a plurality of oxide crystal particles containing aluminum (Al) oxide, wherein the carbide crystal particles are a solid solution containing 45 at% to 55 at% carbon, and in the cross-section of the ceramic sintered body, the ratio of the cross-sectional area of ​​the oxide crystal particles to the cross-sectional area of ​​the ceramic sintered body is 5% to 60%.

2. A ceramic sintered body according to claim 1, characterized in that the amount of iron (Fe) contained in the ceramic sintered body is 1000 at ppm or less.

3. A ceramic sintered body according to claim 1 or claim 2, wherein each of the carbide crystal particles and the oxide crystal particles contains chromium (Cr), and the atomic percentage of chromium in the carbide crystal particles is A Cr The atomic percentage of chromium in the oxide crystal particles is set to B. Cr Therefore, a ceramic sintered body characterized by satisfying the following equation (1): 0.05 ≤ B Cr / A Cr ≤0.5 ... (1) 4. A ceramic sintered body according to claim 1 or claim 2, characterized in that, in the cross-section of the ceramic sintered body, the ratio of the cross-sectional area of ​​the oxide crystal particles to the cross-sectional area of ​​the ceramic sintered body is 5% or more and 40% or less.

5. A plasma generating electrode comprising a ceramic sintered body according to claim 1 or claim 2.

6. A heat-resistant member comprising a ceramic sintered body according to claim 1 or claim 2.

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