Method for regenerating sintered body

Abstract

Provided are at least one of: a method for recycling a zirconia sintered body, which is capable of regenerating a zirconia sintered body that is difficult to be pulverized by pulverizing; a powder obtained thereby; and a use thereof. A powder of zirconia comprising grains. Such a powder is preferably obtained by a production method comprising: a hydrothermal treatment step in which a sintered zirconia body is subjected to hydrothermal treatment at a hydrothermal treatment temperature of 150-400 DEG C (inclusive) with the mass ratio of water to the sintered body being 1.5 or less; and a crushing step in which the sintered body after the hydrothermal treatment is crushed.

Description

Technical Field

[0001] This disclosure relates to the regeneration of sintered zirconium oxide, and further, to the regenerated zirconium oxide obtained therefrom. Background Technology

[0002] From the perspective of Sustainable Development Goals (SDGs), the recycling and reuse of resources has been emphasized in recent years. However, ceramics, represented by zirconia (zirconia dioxide, ZrO2), have very high mechanical properties and chemical stability, making recycling extremely difficult. Therefore, only a portion of used ceramics (sintered bodies) is used as raw materials for cement, while the majority is discarded. On the other hand, the recycling of zirconia sintered bodies has been a long-standing research focus.

[0003] For example, Patent Document 1 discloses a method for recycling sintered zirconium oxide by pulverizing and micronizing the sintered body in the form of flakes. Furthermore, Patent Document 2 proposes a method for recycling the sintered body by heat-treating the sintered zirconium oxide with water to sol-gel the zirconium oxide.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2009-263157 Patent Document 2: Japanese Patent Application Publication No. 10-218662 Summary of the Invention The technical problem that the invention aims to solve Zirconia sintered bodies are typically dense, and due to their high mechanical strength, miniaturization by pulverization is extremely difficult. As disclosed in Patent Document 1, pulverizing three-dimensional sintered bodies with a size and thickness of 1 mm or more is energy inefficient, and impurities are introduced during pulverization. Therefore, the method in Patent Document 1 is only applicable to very thin zirconia sintered bodies with a thickness of less than 1 mm. Furthermore, the recycling specifically disclosed in Patent Document 1 is limited to sintered bodies with a thickness of less than 300 mm. μ The method involves the recycling of sintered cubic zirconia sheets with low mechanical strength. Patent Document 2 describes a process where the grains constituting the zirconia spheres dissolve to obtain a fine sol, which is then shaped and sintered. However, Patent Document 2 does not disclose specific data such as observation diagrams or X-ray diffraction patterns. Furthermore, the inventors conducted research and confirmed that the method in Patent Document 2 not only fails to produce a sol but also does not alter the properties of the zirconia spheres before and after treatment. Therefore, the method in Patent Document 2 cannot be used for the recycling of zirconia sintered bodies.

[0005] The purpose of this disclosure is to provide at least one of the following: a method for recycling sintered zirconium oxide, the resulting powder, and its use, wherein the recycling method enables the regeneration of sintered zirconium oxide that is difficult to pulverize by grinding.

[0006] Technical solutions for solving technical problems In this disclosure, the regeneration of sintered zirconium oxide bodies with a thickness of 1 mm or more that are difficult to pulverize by crushing was investigated. The results showed that by subjecting the sintered body to hydrothermal treatment under specific conditions, it can be crushed and pulverized. Furthermore, it was found that the resulting powder can be used as a raw material for the regeneration of the sintered body.

[0007] That is, the present invention is as described in the claims, and the gist of this disclosure is as follows.

[0008] [1] A zirconium oxide powder comprising grains.

[0009] [2] According to the powder described in [1] above, wherein the BET specific surface area of ​​the powder is 0.5 m². 2 / g or more and 10.5m 2 The particle size is below / g and the median particle size is 0.2. μ m or more and 2.0 μ Below m.

[0010] [3] The powder according to [1] or [2] above, wherein the zirconium oxide is zirconium oxide containing stabilizing elements.

[0011] [4] According to the powder described in [3] above, wherein the stabilizing element is selected from one or more of yttrium, magnesium, calcium, cerium, gadolinium and erbium.

[0012] [5] According to the powder described in [3] or [4] above, wherein the content of the stabilizing element is 1.5 mol% or more and 6 mol% or less.

[0013] [6] The powder according to any one of [1] to [5] above, wherein the monoclinic crystallization rate of the powder is 50% or more.

[0014] [7] The powder according to any one of [1] to [6] above, wherein the BET specific surface area is 12 m² relative to the median particle size. 2 / (g· μ (m) and below.

[0015] [8] The powder according to any one of [1] to [7] above, wherein the powder is a recycled powder.

[0016] [9] The method for manufacturing the powder described in any one of [1] to [8] above includes: a hydrothermal treatment step, wherein the sintered body of zirconium oxide is hydrothermally treated at a hydrothermal treatment temperature of 150°C or higher and 400°C or lower, wherein the mass ratio of water to the sintered body is set to 1.5 or lower; and a crushing step, wherein the sintered body after hydrothermal treatment is crushed.

[0017]

[10] According to the manufacturing method described above [9], the sintered body of zirconium oxide is a sintered body with tetragonal zirconium oxide as the main phase.

[0018]

[11] In the manufacturing method described in [9] or

[10] above, the proportion of monoclinic crystals in the crystalline phase of the sintered zirconium oxide is less than 5%.

[0019]

[12] The manufacturing method according to any one of [9] to

[11] above, wherein the three-point bending strength of the sintered zirconium oxide is 1000 MPa or more.

[0020]

[13] A method for regenerating a sintered body, comprising: a hydrothermal treatment step, wherein the sintered body of zirconium oxide is subjected to hydrothermal treatment at a hydrothermal treatment temperature of 150°C or higher and 400°C or lower, wherein the mass ratio of water to the sintered body is set to 1.5 or lower; and a crushing step, wherein the sintered body after hydrothermal treatment is crushed.

[0021] Invention Effects According to this disclosure, at least one of the following can be provided: a method for recycling sintered zirconium oxide, the resulting powder, and its use; said recycling method enables the regeneration of sintered zirconium oxide that is difficult to pulverize by grinding. Attached Figure Description

[0022] Figure 1 This is a SEM image of the sintered body of Synthesis Example 1 (scale bar is 1). μ m).

[0023] Figure 2 This is an optical microscope image of the sintered body sheet from Example 1 (scale bar is 1000). μ m).

[0024] Figure 3 This is a SEM image of the powder from Example 1 (scale bar is 1). μ m).

[0025] Figure 4 This is a SEM image of the powder from Example 2 (scale bar is 1). μ m). Detailed Implementation

[0026] Hereinafter, an example of an embodiment of the sintered body of this disclosure will be described. The terminology used in this embodiment is as follows. Furthermore, the various components and parameters disclosed in this specification include arbitrary combinations, and the upper and lower limits of the values ​​disclosed in this specification also include arbitrary combinations.

[0027] "Composition" refers to a substance having a certain composition, such as one or more selected from powders, granules, molded bodies, pre-fired bodies and sintered bodies.

[0028] "Powder" refers to an aggregate of powder particles and is a fluid composition. "Zirconium oxide powder" is a powder that essentially contains zirconium oxide and is a powder with zirconium oxide as its main component.

[0029] "Molded body" refers to a composition having a certain shape, consisting of powder particles agglomerated by physical force, especially a composition in a state where the shape has been imparted (e.g., after molding) but no heat treatment has been performed. "Zirconium oxide molded body" refers to a molded body that essentially contains zirconium oxide, and further refers to a molded body with zirconium oxide as the matrix (base material). In this embodiment, "molded body" and "powder compact" can be used interchangeably.

[0030] "Sintered body" refers to a composition having a certain shape and consisting of grains, which is a composition that has been heat-treated at a temperature above the sintering temperature. The shape of the sintered body in this embodiment can be, for example, selected from at least one of the following: spherical, substantially spherical, elliptical, plate-like, cylindrical, cubic, cuboid, polyhedral, and substantially polyhedral. Furthermore, it can be any shape for specific purposes such as achieving various uses. "Zirconium oxide sintered body" refers to a sintered body that essentially contains zirconium oxide, and further refers to a sintered body with zirconium oxide as the matrix (base material).

[0031] "Stabilizing element" refers to an element that has the function of stabilizing the crystalline phase of zirconium oxide by dissolving it in zirconium oxide.

[0032] The "BET specific surface area" is a value obtained by measuring the BET multi-point method (5 points) using nitrogen as the adsorbent gas, according to JIS R 1626. Specific conditions for measuring the BET specific surface area can be illustrated as follows.

[0033] Adsorption medium: N2 Adsorption temperature: -196℃ Pretreatment conditions: Degassing treatment at atmospheric temperature and 250°C for more than 1 hour. BET specific surface area can be measured using conventional equipment (e.g., TRISTAR II 3202, manufactured by Shimadzu Corporation).

[0034] "Median particle size" and "volume average particle size" are the particle sizes that correspond to the 50% cumulative frequency in the cumulative volumetric particle size distribution obtained by measuring the particle size distribution using a volumetric reference method via laser diffraction and scattering. 50 The cumulative volumetric particle size distribution includes the diameter (Dsize) and the average particle size. Additionally, the "standard deviation" is one indicator of the width of the particle size distribution; it is calculated by using the particle size distribution with a cumulative frequency equivalent to 16% of the total particle size distribution (Dsize). 16 ) and cumulative frequency equivalent to 84% of the particle size (D 84 The value is obtained by the following mathematical expression.

[0035] Standard deviation μ m] = (D 84 [ μ m]-D 16 [ μ m]) / 2 The particle size distribution determination using the volume reference method of laser diffraction and scattering can be performed under the following conditions using a conventional particle size distribution measuring device (e.g., device name: MT-3300EXII, manufactured by MicrotracBEL).

[0036] Measurement range: 0.01~2000 μ m Particle refractive index: 2.17 Particle permeability: Transmission Particle shape: Non-spherical Solvent refractive index: 1.333 Calculation mode: HRA Measurement time: 30 seconds Distribution: Volume "Monoclinic crystal ratio" refers to the proportion of monoclinic crystals in the crystalline phase, and is a value calculated from X-ray diffraction (hereinafter also called "XRD") patterns using the following mathematical formula.

[0037] f M =100×[I m (111) + I m (11-1)] / [I m (111) + I m (11-1)+I t (111) + I c (111)] In the above mathematical formula, f M I is the monoclinic crystallinity. t (111) represents the integral intensity of the (111) plane of the tetragonal crystal, I c (111) is the integral intensity of the (111) plane of the cubic crystal, I m(111) is the integrated intensity of the (111) plane of a monoclinic crystal, I m (11-1) represents the integral intensity of the (11-1) plane of a monoclinic crystal.

[0038] The integrated intensity of each crystal plane can be obtained by curve fitting of the smoothed and background-removed XRD patterns using a segmented pseudo-Voigt function. Analysis of the XRD patterns, including smoothing, background removal, and integral intensity calculation, can be performed using analysis programs included with the X-ray diffraction apparatus (e.g., PDXL Ver. 2.2, manufactured by RIGAKU).

[0039] In this embodiment, the XRD pattern is preferably obtained by XRD measurement based on the following conditions.

[0040] X-ray source: CuK α ray( λ =0.15418nm) Measurement mode: Continuous scan Scanning speed: 2° / minute Measurement range: 2 θ =26°~33° Accelerating voltage and current: 40mA·40kV Longitudinal diverging slit: 10mm Diverging / Incident Slit: 1° Light-receiving slit: open Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter Goniometer radius: 185mm XRD measurements can be performed using conventional X-ray diffraction equipment (e.g., Ultima IV, manufactured by RIGAKU). It should be noted that, in the case of a pre-fired or sintered composition, its surface should be ground to a surface roughness Ra ≤ 0.02. μ m, the surface can be measured by XRD.

[0041] Examples of XRD peaks corresponding to the various crystal planes of zirconium oxide measured in the above-mentioned XRD measurements can be found in the following two... θ The XRD peak has a apex.

[0042] Equivalent XRD peaks on the (111) plane of monoclinic crystal: 2 θ =31±0.5° Equivalent XRD peaks on the (11-1) plane of a monoclinic crystal: 2 θ =28±0.5° XRD peaks equivalent to the tetragonal (111) plane: 2θ =30±0.5° XRD peaks equivalent to the (111) plane of a cubic crystal: 2 θ =30±0.5° The XRD peaks corresponding to the tetragonal (111) plane and the XRD peaks corresponding to the cubic (111) plane are measured as an overlapping peak. Therefore, I in the above formula t (111) + I c (111) As long as it is based on 2 θ The integral intensity of the XRD peak with a apex at 30±0.5° can be obtained.

[0043] "Three-point bending strength" refers to the value obtained through a three-point bending test according to JIS R 1601. The test is conducted using a cylindrical sintered specimen with a width of 4 mm and a thickness of 3 mm, with the distance between the support points set to 30 mm. The average value of 10 measurements is taken as the three-point bending strength in this embodiment.

[0044] "Atmospheric pressure sintering" refers to a method of sintering by heating without applying external force to the sintered material (shaped body, pre-sintered body, etc.).

[0045] [powder] This embodiment describes zirconium oxide powder, specifically zirconium oxide powder containing grains. Grains are zirconium oxide particles obtained by heat treatment at temperatures above the sintering temperature; they are the zirconium oxide particles constituting a sintered body. The sintered body is composed of grains, and these grains form a composition with a specific shape by forming grain boundaries (interfaces) between them. In contrast, the powder of this embodiment is a powder in a state where the grains constituting the sintered body are dispersed. In other words, the powder of this embodiment is a powder obtained by peeling away the interfaces (grain boundaries) between the grains constituting the sintered body. It should be noted that even if the grain boundaries are not completely eliminated, the grains can still be dispersed. Therefore, the powder of this embodiment can contain particles with grain boundaries. The powder of this embodiment can be considered as a powder with grains as powder particles, or as a powder composed of sintered particles (sintered powder).

[0046] Another aspect of the powder in this embodiment is powder in a state where the sintered zirconia body is broken, and further, powder in a state where the sintered zirconia body is hydrothermally treated and broken. Even further, it is powder in a state obtained by the powder manufacturing method of this embodiment, which will be described later.

[0047] Such powder is obtained through the reprocessing of the sintered body, i.e., the regeneration (recycling) of the sintered body. Therefore, the powder in this embodiment can also be regarded as recycled powder (recycled zirconium oxide powder).

[0048] Zirconia powder used industrially is obtained through liquid-phase methods such as co-precipitation and hydrolysis (hereinafter, for convenience, it is also referred to as "synthetic powder"). Synthetic powder is synthesized without undergoing thermal processes above sintering temperature, and therefore contains fine primary particles or secondary particles as aggregates. Synthetic powder contains particles with a large number of voids, resulting in a larger specific surface area relative to particle size compared to the powder of this embodiment. For example, synthetic powder with a particle size similar to that of the powder of this embodiment has a high BET specific surface area; conversely, synthetic powder with a low specific surface area has a larger particle size. In contrast, the powder of this embodiment is a powder in a state of grain dispersion constituting a sintered body. Therefore, it is considered that the individual particles (grains) constituting the powder of this embodiment are dense, resulting in a smaller specific surface area relative to particle size. As a result, it is considered that the powder of this embodiment combines a large particle size and a low specific surface area compared to the synthetic powder. Furthermore, in contrast to synthetic powders that are generally spherical or other amorphous, the powder particles (crystals) constituting the powder of this embodiment sometimes also include polyhedral particles. Therefore, the powder of this embodiment may contain polyhedral powder particles (crystals), and may further be composed of polyhedral powder particles.

[0049] The powder used in this embodiment is zirconium oxide powder, specifically a powder with zirconium oxide as the main component (so-called zirconium oxide powder). Preferably, this zirconium oxide contains stabilizing elements (stabilized zirconium oxide).

[0050] The stabilizing element can be any element that stabilizes the crystalline phase of zirconia, and examples include one or more selected from yttrium (Y), magnesium (Mg), calcium (Ca), cerium (Ce), gadolinium (Gd), and erbium (Er). Preferably, examples include one or more selected from yttrium, magnesium, calcium, gadolinium, and erbium, and more preferably, at least one of yttrium and gadolinium. The powder of this embodiment is preferably obtained from a sintered body with tetragonal zirconia as the main phase, and the stabilizing element includes yttrium, and more preferably only yttrium.

[0051] The content of the stabilizing element (hereinafter also referred to as "amount of stabilizing element," and in the case of yttrium or the like, "yttrium content") is sufficient to stabilize the crystalline phase of zirconium oxide into at least one of tetragonal and cubic crystals. Examples include 1 mol% or more and 10 mol% or less, and more preferably 1.6 mol% or less and 4.5 mol% or less. For obtaining a sintered body with tetragonal crystal as the main phase, preferred yttrium contents include 1.5 mol% or more, 2 mol% or more, or 2.5 mol% or more, and less than 6 mol%, 5.5 mol% or less, or 3.8 mol% or less, preferably 1.5 mol% or more and less than 6 mol%, 2 mol% or more and 5.5 mol% or less, or 2.5 mol% or more and 3.8 mol% or less.

[0052] The amount of stabilizing element is the ratio [mol%] of the content of stabilizing element converted from oxides to the total content [mol] of zirconium oxide and the content of stabilizing element converted from oxides. In the oxide conversion, yttrium is Y₂O₃, magnesium is MgO, calcium is CaO, cerium is CeO₂, gadolinium is Gd₂O, and erbium is Er₂O₃.

[0053] The powder of this embodiment may contain one or more selected from alumina, silicon dioxide, and germanium oxide (hereinafter also referred to as "additives"). Alumina is preferred as the additive.

[0054] The content of the added ingredient (hereinafter also referred to as "amount of added ingredient," and in the case of the added ingredient such as alumina, it is also referred to as "alumina content," etc.) can be 0% or more by mass, more than 0% by mass, or more than 0.01% by mass. In addition, it can be 0.5% or less by mass, less than 0.3% by mass, less than 0.1% by mass, or less than 0.75% by mass. Examples include 0% or more by mass and less than 0.75% by mass, more than 0% by mass and less than 0.75% by mass, or more than 0.01% by mass and less than 0.5% by mass. In order to make it versatile and easy to mix with various synthetic powders, the powder of this embodiment preferably does not contain any added ingredient (the amount of added ingredient is 0% by mass). For the same reason, it is more preferable to at least not contain silicon dioxide. As for the amount of silicon dioxide in the powder of this embodiment, taking into account measurement errors, it can be 0% or more by mass and less than 0.01% by mass, and more preferably 0% or more by mass and less than 0.005% by mass. Examples of the amount of powder added in this embodiment include 0% or more by mass and 0.3% or less by mass, 0% or more by mass and 0.2% or less by mass, 0% or more by mass and 0.1% or less by mass, or 0% or more by mass and less than 0.05% by mass.

[0055] In this embodiment, the amount of added component is the ratio [mass %] of the content of the added component [g] converted from oxides to the total content of zirconium oxide and the content of the metal element [g] converted from oxides (hereinafter also referred to as "metal content"). In the oxide conversion, aluminum oxide is Al2O3, silicon dioxide is SiO2, and germanium oxide is Ge2O3.

[0056] The powder of this embodiment is preferably free of impurities, but may contain impurities to a extent that does not impair its effectiveness. In particular, the powder of this embodiment may contain hafnium oxide (HfO2), which is an unavoidable impurity of zirconium oxide. It should be noted that in this embodiment, the calculation of values ​​from composition such as density can be performed by treating hafnium oxide (HfO2) as zirconium oxide (ZrO2).

[0057] For example, in the case where the powder in this embodiment is a powder containing alumina and containing zirconium oxide grains stabilized by yttrium oxide, its composition is determined by the following.

[0058] Metal content [g] = ZrO2 + Y2O3 + Al2O3 Alumina content [mass %] = {Al2O3 / (ZrO2+Y2O3+Al2O3)} × 100 Stabilizing element amount (=yttrium amount) [mol%] = {Y₂O₃ / (ZrO₂+Y₂O₃)}×100 The powder in this embodiment is preferably a zirconium oxide powder whose crystalline phase includes monoclinic crystals, and more preferably a zirconium oxide powder with monoclinic crystals as the main phase. The monoclinic crystal content of the powder in this embodiment can be more than 50%, more than 70%, or more than 75%, and less than 100%, less than 98%, less than 85%, or less than 82%, preferably more than 50% and less than 100%, more than 70% and less than 98%, more than 75% and less than 85%, or more than 75% and less than 82%. On the other hand, the monoclinic crystal content can be more than 86% and less than 100%, or more than 90% and less than 99%. Cubic zirconium oxide does not undergo crystalline phase changes caused by external forces such as breakage, but tetragonal zirconium oxide undergoes a phase transformation caused by external forces such as breakage, generating monoclinic zirconium oxide. The monoclinic crystals in the powder of this embodiment are preferably crystalline phases generated through tetragonal phase transformation, and the powder of this embodiment is particularly preferably a zirconium oxide powder obtained from a sintered body of zirconium oxide containing tetragonal zirconium oxide.

[0059] In this embodiment, the median particle size of the powder is preferably 0.2. μ m or more and 2.0 μ Below 1 m. By making the median particle size 0.2. μ A particle size of 2.0 μm or larger can further suppress the aggregation of powder particles. On the other hand, if the median particle size is 2.0 μm... μ When the particle size is below a certain value (µm), the density of the resulting sintered body tends to be high. In this embodiment, the median particle size of the powder can be exemplified as exceeding 0.2 µm. μ m, 0.4 μ m or more, 0.5 μ m or more or 0.7 μ Above m, and also 1.5 μ Below m, 1.0 μ Below m or 0.8 μ For m and below, 0.2 is preferred. μ m or more and 1.5 μ Less than m, more than 0.2 μ m and 1.5 μ Below m, 0.4 μ m or more and 1.5 μBelow m, or 0.7 μ m or more and 0.8 μ Below m.

[0060] In this embodiment, the powder preferably has a uniformly distributed particle size relative to the median particle size. μ The volume average particle size [m] μ The particle size ratio (m) is preferably 0.9 or higher and 1.5 or lower, more preferably 0.95 or higher and 1.1 or lower. The volume average particle size is one of the indicators of the particle size of powder particles in a dispersed state. In this embodiment, as long as the powder satisfies the above-mentioned particle size ratio, its volume average particle size is preferably the same as the median particle size, for example, 0.2. μ m or more, exceeding 0.2 μ m and 0.4 μ m or more, 0.5 μ m or more or 0.7 μ m and above, also 2.0 μ Below m, 1.5 μ Below m, 1.0 μ Below m or 0.8 μ For m and below, 0.2 is preferred. μ m or more and 1.5 μ Less than m, more than 0.2 μ m and 1.5 μ Below m, 0.4 μ m or more and 1.5 μ Below m, or 0.7 μ m or more and 0.8 μ Below m. The volume average particle size is preferably greater than the median particle size.

[0061] In this embodiment, the particle size distribution width of the powder is preferably small, and the absolute value of the standard deviation is preferably 0.5. μ Below m, 0.25 μ Below m or 0.2 μ Below m. Preferably with a small standard deviation, ideally 0. μ m. However, in reality, due to the width of the distribution, the absolute value of the standard deviation can be found to be greater than 0. μ m or 0.05 μ m and above can be used to represent more than 0 μ m and 0.5 μ Below m, 0.05 μ m or more and 0.25 μ Less than m, or 0.05 μ m or more and 0.2 μ Below m.

[0062] The powder in this embodiment has a BET specific surface area of ​​0.5 m². 2 / g or more and 10.5m 2 / g or less, preferably 0.5m 2 / g or more and 10m 2 / g or less. Although the powder of this embodiment has a relatively large particle size, it has a low BET specific surface area. An example of the BET specific surface area of ​​the powder of this embodiment is 1m². 2 / g or more, 2m 2 / g or more or 3m 2 / g or more, in addition, 8m 2 / g or less, 5m 2 / g or less or 4m 2 / g or less, preferably 0.5m 2 / g or more and 8m 2 / g or less, 2m 2 / g or more and 8m 2 / g or less, or 2m 2 / g or more and 4m 2 / g or less.

[0063] The powder in this embodiment preferably has both a large particle size and a low specific surface area, with a BET specific surface area [m²]. 2 / g] relative to median particle size [ μ m] (hereinafter also referred to as "BET ratio"). Examples of 12m are given. 2 / (g· μ (m) and below, 9.5m 2 / (g· μ (m) or less or 5m 2 / (g· μ Below m), also, 0m 2 / (g· μ m or more, exceeding 0m 2 / (g· μ m) or 2m 2 / (g· μ m) or above, 0m can be exemplified 2 / (g· μ m or more and 12m 2 / (g· μ (m) or less, or more than 0m 2 / (g· μ (m) and 9.5m 2 / (g· μ (m) or less, or more than 2m 2 / (g· μ m) and 5m 2 / (g· μ (m) and below.

[0064] [Powder Composition] The powder of this embodiment can be directly supplied as a raw material for sintered bodies, and is suitable for preparing powder compositions (hereinafter also referred to as "powder compositions of this embodiment") containing the powder and synthetic powder. Furthermore, the powder compositions of this embodiment can also be supplied as raw materials for sintered bodies.

[0065] The powder composition of this embodiment only needs to include the powder of this embodiment and any synthetic powder. For example, as a powder composition of this embodiment, it can include two or more powders, at least the powder of this embodiment, and the BET specific surface area relative to the median particle size (BET ratio) exceeds 9.5 μm. 2 / (g· μ A powder composition comprising (m). As another embodiment, the powder composition of this embodiment may include the powder of this embodiment and a BET specific surface area relative to the median particle size exceeding 12 μm. 2 / (g· μ A powder composition of zirconium oxide powder (m), further examples include powders comprising the powder of this embodiment with a BET ratio exceeding 12m. 2 / (g· μ Zirconia powder with a BET ratio exceeding 9.5m (m) 2 / (g· μ A powder composition of m).

[0066] The powder composition of this embodiment only needs to have the same composition as the powder of this embodiment, and is a zirconium oxide powder composition, preferably zirconium oxide containing stabilizing elements.

[0067] The stabilizing element is any element that stabilizes the crystalline phase of zirconium oxide. Examples include one or more selected from yttrium, magnesium, calcium, cerium, gadolinium, and erbium. Preferably, it is selected from one or more selected from yttrium, magnesium, calcium, gadolinium, and erbium. More preferably, it is selected from at least one of gadolinium and yttrium. It is preferred to include yttrium, and even more preferably, it is only yttrium.

[0068] The amount of stabilizing element is sufficient to stabilize the crystalline phase of zirconia into at least one of tetragonal and cubic crystals, and examples include 1 mol% or more and 10 mol% or less, and more preferably 1.6 mol% or less and 4.5 mol% or less. For suitability as a raw material for sintered bodies with higher mechanical properties, preferred yttrium amounts include 1.5 mol% or more, 2 mol% or more, or 2.5 mol% or more, and less than 6 mol%, 5.5 mol% or less, or 3.8 mol% or less, preferably 1.5 mol% or more and less than 6 mol%, 2 mol% or more and 5.5 mol% or less, or 2.5 mol% or more and 3.8 mol% or less.

[0069] The powder composition of this embodiment may contain additives, preferably alumina. Examples of additive amounts include 0% by mass or more, more than 0% by mass, or 0.01% by mass or more; alternatively, 0.5% by mass or less, 0.1% by mass or less, or 0.75% by mass or less. Examples of additive amounts include 0% by mass and less than 0.75% by mass, more than 0% by mass and less than 0.75% by mass, or 0.01% by mass and less than 0.5% by mass.

[0070] The BET ratio of the powder composition in this embodiment varies depending on the amount of synthetic powder incorporated, and can be exemplified as exceeding 9.5m. 2 / (g· μ m), 9.5m 2 / (g· μ (m) or more and 15.0m 2 / (g· μ (m) and below, 9.5m 2 / (g· μ (m) or more and 13.5m 2 / (g· μ (m) or less, or 10.0m 2 / (g· μ (m) or more and 15.0m 2 / (g· μ (m) and below.

[0071] If the powder composition of this embodiment has the above-described BET ratio, it exhibits the same formability and sintering properties as the synthesized powder, and therefore can be supplied as a raw material for sintered bodies. Therefore, any value for particle size and specific surface area is acceptable.

[0072] The BET specific surface area of ​​the powder composition in this embodiment can be exemplified by 5m². 2 / g or more or 6m 2 / g or more, in addition, 10m 2 / g or less or 8m 2 Below / g, 5m can be cited as an example. 2 / g or more and 10m 2 / g or less, or 6m 2 / g or more and 8m 2 / g or less.

[0073] An example of the median particle size of the powder composition in this embodiment is 0.4. μ m or more, 0.5 μ m or more or 0.6 μ m and above, in addition, 1.0 μ Below m, 0.8 μ Below m or 0.7μ For values ​​below m, 0.4 can be cited as an example. μ m or more and 1.0 μ Below m, 0.5 μ m or more and 0.8 μ Less than m, or 0.6 μ m or more and 0.7 μ Below m.

[0074] Examples of particle size ratios for the powder composition of this embodiment include 0.9 or more and 1.5 or less, and more specifically 0.95 or more and 1.1 or less. The volume average particle size of the powder composition of this embodiment only needs to be similar to the median particle size; for example, 0.4 is acceptable. μ m or more or 0.5 μ m and above, in addition, 1.0 μ Below m or 0.8 μ For m and below, 0.4 is preferred. μ m or more and 1.0 μ Less than m, or 0.5 μ m or more and 0.8 μ Below m. It should be noted that the volume average particle size is preferably greater than the median particle size.

[0075] The absolute value of the standard deviation of the powder composition in this embodiment can be 0.2. μ Below m or 0.18 μ Below m, and above 0 μ m or 0.05 μ m and above can be used to represent more than 0 μ m and 0.2 μ Less than m, or 0.05 μ m or more and 0.18 μ Below m.

[0076] The monoclinic crystal ratio of the powder composition of this embodiment can be 25% or more or 40% or more, or 60% or less or 50% or less, and can be 25% or more and 60% or less, or 40% or more and 50% or less.

[0077] As long as the powder composition has these components, the ratio of powder to synthetic powder in this embodiment is arbitrary. The mass ratio of synthetic powder in the powder composition of this embodiment is preferably 0.2 or more, 0.3 or more, or 0.5 or more, and less than 1.0, 0.9 or less, or 0.8 or less. Examples of other ratios include 0.2 or more and less than 1.0, 0.3 or more and less than 0.9, 0.5 or more and less than 0.9, or 0.5 or more and less than 0.8.

[0078] The powder composition of this embodiment has a BET specific surface area exceeding 12 μm relative to the median particle size, which is achieved by the powder of this embodiment. 2 / (g· μ It is obtained by a manufacturing method that mixes zirconium oxide powder (m) in a mixing process. The BET ratio exceeds 12m. 2 / (g· μ The zirconium oxide powder (hereinafter also referred to as "added powder") is a synthetic powder, and may further be commercially available zirconium oxide powder.

[0079] The mass percentage of the powder in the powder composition of this embodiment is arbitrary. The total mass of the added powder and the powder of this embodiment is set to 100%. The powder of this embodiment can be 5% or more by mass, 10% or more by mass, 30% or more by mass, or 50% or more by mass.

[0080] The mixing process can be carried out by adding powder and making the powder of this embodiment uniform, and can be at least one of wet mixing and dry mixing, preferably wet mixing, more preferably one of stirred mill mixing or ball mill mixing, and even more preferably ball mill mixing.

[0081] [Powder Manufacturing Method] The powder of this embodiment can be obtained by a manufacturing method having the following steps (hereinafter also referred to as "the manufacturing method of this embodiment"): a hydrothermal treatment step, wherein the sintered body of zirconium oxide is hydrothermally treated at a hydrothermal treatment temperature of 150°C or higher and 400°C or lower, wherein the mass ratio of water to the sintered body is set to 1.5 or lower; and a crushing step, wherein the sintered body after hydrothermal treatment is crushed.

[0082] The manufacturing method of this embodiment includes a hydrothermal treatment step. Through the hydrothermal treatment step, the sintered body after hydrothermal treatment becomes a solid with reduced mechanical strength (hereinafter also referred to as "sintered body sheet" or simply "sheet"). As a result, compared with a highly fluid state such as gel, it can be supplied to the subsequent crushing process in a state that is easy to handle, and through crushing, the grains are easily dispersed while maintaining their shape.

[0083] The shape and size of the sintered body sheet vary depending on the shape and size of the sintered body (hereinafter also referred to as "raw material sintered body") supplied to the hydrothermal treatment process. The maximum length of the sintered body sheet can be 10 mm or less, and further examples include 5 mm or less. As for the shape of the sintered body sheet, it is a scaly sintered body sheet, and examples include at least one of polyhedral and amorphous shapes.

[0084] A sintered body of zirconium oxide is supplied in the hydrothermal treatment process. The shape of the raw material sintered body is arbitrary, and examples include one or more selected from spherical, substantially spherical, elliptical, plate-like, cylindrical, cubic, cuboid, polyhedral, and substantially polyhedral shapes. The sintered body supplied to the hydrothermal treatment process can be a sintered body with a thickness of 1 mm or more, more preferably a sintered body with a thickness of 3 mm or more, preferably a sintered body with a thickness of 1 mm or more and 10 mm or less, and more preferably a sintered body with a thickness of 3 mm or more and 5 mm or less. In the manufacturing method of this embodiment, even a sintered body with such a thickness can have its grains dispersed and be made into powder.

[0085] The manufacturing method of this embodiment is suitable for the regeneration of sintered bodies that are difficult to crush. Therefore, the three-point bending strength of the raw material sintered body can be 1000 MPa or more, more preferably 1100 MPa or more, and even more preferably 1200 MPa or more. The upper limit of the three-point bending strength of the raw material sintered body can be 1600 MPa or less or 1500 MPa or less. In addition, the three-point bending strength of the raw material sintered body can be 1000 MPa or more and 1600 MPa or less, 1100 MPa or more and 1500 MPa or less, or 1200 MPa or more and 1500 MPa or less.

[0086] The raw material sintered body is preferably a sintered body with tetragonal zirconia as the main phase. The proportion of monoclinic crystals in the crystalline phase (monoclinic crystal ratio) is preferably 5% or less, more preferably 3% or less. Examples of monoclinic crystal ratios include 0% or more and 5% or less, 0% or more and 3% or less, or 0% or more and 2% or less.

[0087] The composition of the raw material sintered body only needs to have the same composition as the powder in this embodiment described above, and it is a sintered body of zirconium oxide, preferably zirconium oxide containing stabilizing elements.

[0088] The stabilizing element is any element that stabilizes the crystalline phase of zirconium oxide. Examples include one or more selected from yttrium, magnesium, calcium, cerium, gadolinium and erbium. Preferably, it is selected from one or more selected from yttrium, magnesium, calcium, gadolinium and erbium. More preferably, it is selected from at least one of yttrium and gadolinium. It is more preferably yttrium is included, and even more preferably, it is only yttrium.

[0089] The amount of stabilizing element is sufficient to stabilize the crystalline phase of zirconium oxide into at least one of tetragonal and cubic crystals, and examples include 1 mol% or more and 10 mol% or less, and more preferably 1.6 mol% or less and 4.5 mol% or less. Preferred amounts of yttrium include 1.5 mol% or more, 2 mol% or more, or 2.5 mol% or more, and less than 6 mol%, 5.5 mol% or less, or 3.8 mol% or less, preferably 1.5 mol% or more and less than 6 mol%, 2 mol% or more and 5.5 mol% or less, or 2.5 mol% or more and 3.8 mol% or less.

[0090] The raw material sintered body may contain additives, preferably alumina. Examples of additive amounts include 0% by mass or more, more than 0% by mass, or 0.01% by mass or more; alternatively, 0.5% by mass or less, 0.1% by mass or less, or 0.75% by mass or less. Examples of additive amounts include 0% by mass and 0.75% by mass, more than 0% by mass and 0.75% by mass, or 0.01% by mass and 0.5% by mass or less. On the other hand, for the same reasons as above, the raw material sintered body preferably does not contain additives (additive amount is 0% by mass), and more preferably, it does not contain at least silicon dioxide. As for the amount of silicon dioxide in the raw material sintered body, taking into account measurement errors, examples include 0% by mass and 0.01% by mass or less, and more specifically, 0% by mass and 0.005% by mass or less. Examples of added components as raw material sintered body include 0% or more by mass and 0.3% or less by mass, 0% or more by mass and 0.2% or less by mass, 0% or more by mass and 0.1% or less by mass, or 0% or more by mass and less than 0.05% by mass.

[0091] The water used for hydrothermal treatment can be pure water.

[0092] In the hydrothermal treatment process, hydrothermal treatment is performed at a temperature of 150°C or higher and 400°C or lower. When the hydrothermal treatment temperature is below 150°C, the treatment requires a very long time, making it impractical to perform the treatment within a reasonable timeframe. On the other hand, if the hydrothermal treatment temperature exceeds 400°C, general-purpose hydrothermal treatment equipment cannot be used, and the grains themselves are prone to breakage or dissolution. In either case, its application as an industrial regeneration method becomes difficult. Examples of hydrothermal treatment temperatures include 150°C or higher, or 180°C or higher, and also 400°C or lower, 350°C or lower, or 300°C or lower, with 150°C or higher and 400°C or lower, or 180°C or higher and 300°C or lower being preferred.

[0093] Hydrothermal treatment is carried out in a closed system with the sintered body and water. Therefore, hydrothermal treatment is performed under autogenous pressure.

[0094] In the hydrothermal treatment process, the mass ratio of water to the sintered body (hereinafter also referred to as the "solid-liquid ratio") is set to 1.5 or less. In this process, water is heated in a closed system, and in a vaporized state, it comes into contact with the sintered body. Therefore, it is assumed that the changes in the sintered body proceed moderately, and the strength of the grain boundaries (interfaces) between grains decreases before the individual grains break down and dissolve. Thus, it is assumed that the grains become easily dispersed during the crushing process. If the solid-liquid ratio exceeds 1.5, the generation of water vapor and its contact with the sintered body become insufficient. As a result, the mechanical strength of the sintered body does not decrease, and the grains cannot be dispersed in the subsequent crushing process. To ensure a more uniform interfacial strength in the sintered body sheets obtained through hydrothermal treatment, the solid-liquid ratio is preferably 1.5 or less, 1.0 or less, or 0.75 or less. The solid-liquid ratio can be any range that allows sufficient contact between the sintered body and water vapor, and can be 0.1 or more or 0.25 or more, preferably 0.1 or more and 1.5 or less, 0.1 or more and 1.0 or less, or 0.25 or more and 0.57 or less.

[0095] Hydrothermal treatment can be performed either by stirring or by allowing the sintered zirconia body to stand. To improve the workability of the resulting sintered sheet, hydrothermal treatment is preferably performed while the sintered body is standing.

[0096] The hydrothermal treatment time can be adjusted appropriately according to the amount of sintered body supplied for hydrothermal treatment and the performance of the hydrothermal treatment device. The preferred time for industrial regeneration methods is, for example, 20 hours or more, 50 hours or more, or 70 hours or more. Alternatively, it can be 300 hours or less, 150 hours or less, 120 hours or less, or 100 hours or less. Examples include 20 hours or more and 300 hours or less, or 50 hours or more and 100 hours or less.

[0097] As needed, the hydrothermally treated sintered body (sintered body sheet) can be subjected to solid-liquid separation and recovery, and then dried. Unlike gels, sintered body sheets are millimeter-sized sintered body flakes, making solid-liquid separation easy; therefore, the solid-liquid separation and drying methods are arbitrary. As methods for solid-liquid separation, at least one of decantation and filtration can be cited, with filtration being preferred. As drying methods, drying in an atmospheric atmosphere at temperatures above 80°C and below 150°C can be cited.

[0098] The manufacturing method of this embodiment includes a crushing step of crushing the sintered body after hydrothermal treatment. Through the crushing step, the grains constituting the sintered body sheet are dispersed, and the powder of this embodiment containing grains is obtained.

[0099] The crushing method in the crushing process can be any method and condition capable of breaking the grain boundaries, and can be at least one of wet crushing and dry crushing, more preferably wet crushing. As a preferred wet crushing method, an example is a method of preparing sintered sheet sheets into a slurry and then crushing it. To improve the crushing strength, for example, zirconia balls with a diameter of 0.1 mm or more and 20 mm or less can be used for crushing. It should be noted that in this embodiment, "crushing" refers to a process of removing slowly accumulated particles, while "pulverizing" refers to a process of breaking down primary particles or grains themselves.

[0100] Furthermore, in the crushing process, the powder composition of this embodiment can also be obtained by adding synthetic powder during the crushing of the sintered sheet.

[0101] The manufacturing method of this embodiment can also be used as a method for regenerating sintered bodies, a method for recycling sintered bodies, and a method for regenerating zirconia sintered bodies. It can also be regarded as a method for regenerating sintered bodies having the following steps: a hydrothermal treatment step, wherein the zirconia sintered body is hydrothermally treated at a hydrothermal treatment temperature of 150°C or higher and 400°C or lower, wherein the mass ratio of water to sintered body is set to 1.5 or lower; and a crushing step, wherein the hydrothermally treated sintered body is crushed.

[0102] [Manufacturing method of sintered body] The powder and the powder composition of this embodiment (hereinafter also referred to as "the powder of this embodiment") can be used as raw materials for the sintered body. The sintered body can be manufactured by a known sintering method other than using the powder of this embodiment, and can be manufactured by a manufacturing method having a sintering step of sintering a molded body containing the powder of this embodiment.

[0103] The molded body supplied for the sintering process can be of any shape, and can be selected from one or more of the following: spherical, approximately spherical, elliptical, circular plate, cylindrical, cubic, cuboid, polyhedral, and approximately polyhedral, or any shape depending on the use and purpose.

[0104] The molded body can be formed from the powder or the like of this embodiment by any molding method. Examples of molding methods include one or more selected from uniaxial pressing, cold isostatic pressing, slip casting, and injection molding, and more specifically, at least one of uniaxial pressing and cold isostatic pressing.

[0105] The sintering method in the sintering process can be any sintering method, such as one or more selected from atmospheric pressure sintering, pressure sintering and vacuum sintering, with atmospheric pressure sintering being preferred.

[0106] The following conditions can be cited as preferred sintering conditions.

[0107] Sintering method: Atmospheric pressure sintering Sintering atmosphere: Oxidizing atmosphere, preferably atmospheric atmosphere Maintain a temperature above 1300℃, 1400℃, or 1450℃, and... Below 1700℃ or below 1600℃ The holding time can be appropriately varied according to the shape of the molded body supplied for sintering and the characteristics of the sintering furnace. For example, it can be more than 1 hour and less than 6 hours, and further examples can be more than 2 hours and less than 4 hours.

[0108] Through the sintering process, a sintered body using raw materials obtained from the sintered body is obtained, known as a recycled sintered body. Thus, the sintered body can be recycled.

[0109] Example The present disclosure will now be described using examples. However, the present disclosure is not limited to these examples.

[0110] (Crystallization phase, monoclinic crystal ratio) The XRD pattern of the sample was obtained by XRD measurement based on the following conditions using an X-ray diffraction apparatus (Ultima IV, manufactured by RIGAKU).

[0111] X-ray source: CuK α ray( μ =0.15418nm) Measurement mode: Continuous scan Scanning speed: 2° / minute Measurement range: 2 μ =26°~33° Accelerating voltage and current: 40mA·40kV Longitudinal diverging slit: 10mm Diverging / Incident Slit: 1° Light-receiving slit: open Detector: Semiconductor detector (D / teX Ultra) Filter: Ni filter Goniometer radius: 185mm The identification of the crystalline phase was performed as follows: smoothing and background removal were performed using the analysis program accompanying the X-ray diffraction apparatus (program name: Integrated Powder X-ray Analysis Software PDXL Ver.2.2, manufactured by RIGAKU Corporation), and the processed XRD pattern was profiled by the segmented pseudo-Voigt function.

[0112] The monoclinic crystallinity was calculated using the above mathematical formula based on the XRD patterns of the powder and sintered body samples. It should be noted that the sintered body sample used was 1.3 ± 0.1 mm thick, with a measured surface roughness Ra ≤ 0.02. μ Sintered body after single-sided mirror polishing using the m method.

[0113] (BET specific surface area) The BET specific surface area was measured using an automatic specific surface area measuring device (device name: TriStar II 320, manufactured by Shimadzu Corporation) according to JIS R 1626, by the BET multi-point method (5 points) based on the following conditions.

[0114] Adsorption medium: N2 Adsorption temperature: -196℃ Pretreatment conditions: Degassing at atmospheric temperature and 250°C for 1 hour. (Median particle size, volume average particle size and standard deviation) The median particle size, volume average particle size, and standard deviation were determined using a Microtrac particle size analyzer (device name: MT3300EXII, manufactured by MicrotracBEL) from the cumulative volumetric particle size distribution obtained by measuring the particle size distribution using a volumetric reference method via laser diffraction and scattering. The measurement conditions for the particle size distribution are shown below.

[0115] Measurement range: 0.01~2000 μ m Particle refractive index: 2.17 Particle permeability: Transmission Particle shape: Non-spherical Solvent refractive index: 1.333 Calculation mode: HRA Measurement time: 30 seconds Distribution: Volume The cumulative frequency in the cumulative volumetric particle size distribution is equivalent to 50% of the particle size (D). 50 (diameter) as median particle size [ μ m], the average particle size in the cumulative volumetric particle size distribution is taken as the volume average particle size[ μ In addition, in the cumulative volumetric particle size distribution, the particle size (D) with a cumulative frequency equivalent to 16% is used. 16 ) and cumulative frequency equivalent to 84% of the particle size (D 84 The value obtained by the following mathematical formula will be used as the standard deviation. μ m).

[0116] Standard deviation μ m] = (D 84 [μ m]-D 16 [ μ m]) / 2 As a pretreatment, the sample powder was suspended in distilled water to form a slurry, which was then dispersed using an ultrasonic homogenizer (device name: US-150T, manufactured by Nippon Seiki Co., Ltd.).

[0117] (Measured density and relative density) The measured density of the sintered body is expressed as the ratio of the mass determined by mass measurement to the volume determined by the Archimedes method (g / cm³). 3 The relative density is calculated as the ratio (%) of the measured density to the true density.

[0118] (Three-point bending strength) The three-point bending strength was determined according to the three-point bending test in accordance with JIS R 1601. Ten tests were performed, and the average value was taken as the three-point bending strength. A sintered cylindrical specimen with a width of 4 mm and a thickness of 3 mm was used, and the distance between the support points was set to 30 mm for the test.

[0119] (Hydrothermal deterioration test) The surface roughness Ra will be ≤0.02. λ The sintered body after mirror polishing in the m-method was used as the test sample. The hydrothermal degradation test was carried out by immersing it in hot water at 134°C. The monoclinic crystal ratio of the sintered body surface after immersion for 5 hours was calculated using the above mathematical formula.

[0120] <Preparation of Sintered Bodies> Synthesis example 1 25g of commercially available zirconia powder (product name: TZ-3YS, manufactured by Tosoh Corporation) was filled into a 57mm × 34mm mold and uniaxially pressed at 98MPa to obtain a molded body. The obtained molded body was sintered at atmospheric pressure at 1500°C for 2 hours to obtain a cuboid-shaped sintered body containing yttrium-stabilized zirconia with a thickness of 3.7mm and a yttrium content of 3.0mol%, which was used as the sintered body of this synthesis example.

[0121] Synthesis example 2 Using commercially available zirconia powder (product name: TZ-2Y, manufactured by Tosoh Corporation), except that a cuboid-shaped sintered body containing yttrium-stabilized zirconia with a thickness of 3.7 mm and a yttrium content of 2.0 mol% was obtained by the same method as in Example 1, thus obtaining a sintered zirconia body.

[0122] The results are shown in the table below, and the SEM images of the sintered body of Synthetic Example 1 are shown in the figure below. θ .

[0123] [Table 1] All sintered bodies had a monoclinic crystal ratio below the detection limit (below 1%), confirming that the crystalline phase was tetragonal zirconia as the main phase in the sintered body.

[0124] Example 1 100g (4 pieces) of sintered bodies obtained by the same method as in Synthesis Example 1 and 50mL of pure water were filled into a 100mL Teflon (registered trademark) container, sealed, and subjected to hydrothermal treatment under the following conditions.

[0125] Hydrothermal treatment temperature: 200℃ Hydrothermal treatment time: 72 hours Hydrothermal treatment atmosphere: static Solvent / sintered body mass ratio: 0.5 After hydrothermal treatment, the sample was cooled to room temperature. Upon cooling, the solid component was recovered through solid-liquid separation via filtration. The recovered solid component was dried in atmospheric conditions at 110℃±15℃ for 24 hours to obtain thin sheets. The thickness of the obtained thin sheets was less than 0.8 mm, and the monoclinic crystal content was 71%. An optical microscope image of the obtained thin sheets is shown below. μ The maximum length of the flakes was less than 3 mm, and they consisted of solids with scaly or amorphous shapes. The resulting flakes were mixed with pure water and wet-crushed to produce a slurry.

[0126] The obtained slurry was dried at atmospheric temperature and 110±15℃ for 24 hours, and then sieved using a 180 mesh screen. μ The powder is graded using a stainless steel sieve and recycled as the powder in this embodiment.

[0127] Example 2 The flakes obtained by the same method as in Example 1 were mixed with pure water and then crushed for 24 hours using a ball mill with zirconia balls of 2 mm in diameter. The processed slurry was dried and graded, and otherwise the powder of this example was obtained by the same method as in Example 1.

[0128] Example 3 Using the sintered body from Synthesis Example 2 and setting the hydrothermal treatment time to 48 hours, the powder of this embodiment was obtained by the same method as in Example 1. The thickness of the obtained sheet was less than 0.8 mm, and the monoclinic crystal content was 96%.

[0129] Comparative Example 1 Zirconia spheres with a diameter of 5 mm were subjected to hydrothermal treatment using the method described in Patent Document 2. Specifically, 100 g of spheres with a diameter of 5 mm containing partially stabilized zirconia and 200 mL of pure water were added to a 2000 mL autoclave, and the mixture was heated at 200°C for 96 hours while stirring. However, although cracking was observed in the spheres after heat treatment, they retained their shape before hydrothermal treatment. Therefore, it can be confirmed that regeneration is not possible using the method described in Patent Document 2.

[0130] The results are shown in the table below. The reference examples in the table are the test results for commercially available zirconium oxide powder (product name: TZ-3YS, manufactured by Tosoh Corporation).

[0131] [Table 2] In Examples 1-3, it was confirmed that the three-point bending strength was above 1000 MPa. Furthermore, the sintered body of zirconia, primarily comprising tetragonal zirconia, could be powdered. Additionally, a comparison between the reference example and Example 2 confirmed that the powders of the examples had a lower BET ratio and a higher monoclinic crystal ratio. Further, it was confirmed that the particle size of the powders in Examples 1 and 2 was the average crystal grain size of the raw material sintered body (0.51 MPa). μ The size of the grains is 1.14 to 1.37 times that of the grains in the same diameter (m), indicating a similar degree of grain dispersion.

[0132] Based on the SEM images of the powders from Examples 1 and 2 ( μ and 4 The powders of Examples 1 and 2 both contain polyhedral particles (grains). This confirms that the powders of these examples are grain-containing powders in which the grains of the sintered body are dispersed while maintaining their shape. Furthermore, it was confirmed that the powder of Example 1, compared to Example 2, mainly consists of particles containing multiple grains. Additionally, a comparison of Examples 1 and 2 confirms that, through ball milling, the median particle size is close to the average crystal grain size of the raw material sintered body, further dispersing the grains.

[0133] <Preparation of Powder Compositions> Example 4 The powder composition of this embodiment was obtained by crushing and mixing 10g of flakes obtained by the same method as in Example 1, 90g of commercially available zirconium oxide powder (product name: TZ-3YS, manufactured by Tosoh Corporation) and 122g of pure water.

[0134] Example 5 The powder composition of this embodiment was obtained by crushing and mixing 20g of flakes obtained by the same method as in Example 1, 80g of commercially available zirconium oxide powder (product name: TZ-3YS, manufactured by Tosoh Corporation) and 122g of pure water. Otherwise, the powder composition of this embodiment was obtained by the same method as in Example 1.

[0135] Example 6 The powder composition of this embodiment was obtained by crushing and mixing 50g of flakes obtained by the same method as in Example 1, 50g of commercially available zirconium oxide powder (product name: TZ-3YS, manufactured by Tosoh Corporation) and 122g of pure water.

[0136] Example 7 20g of powder obtained by the same method as in Example 2, 80g of commercially available zirconia powder (product name: TZ-3YS, manufactured by Tosoh Corporation), and 122g of pure water were mixed while being crushed to obtain a slurry. The obtained slurry was dried at atmospheric temperature and 110±15°C for 24 hours, and then sieved using a 180mm sieve. μ μ μ μ μ Figure 1 Figure 2 μ μ Figure 3 μ The powder is graded using a stainless steel sieve and recycled to prepare the powder composition of this embodiment.

[0137] Example 8 A slurry was obtained by crushing and mixing 50g of powder obtained by the same method as in Example 2, 50g of commercially available zirconia powder (product name: TZ-3YS, manufactured by Tosoh Corporation), and 122g of pure water. Otherwise, the powder composition of this example was obtained by the same method as in Example 7.

[0138] Comparative Example 2 A slurry was prepared by mixing 80g of flakes obtained by the same method as in Example 1, 20g of commercially available zirconium oxide powder (product name: TZ-3YS, manufactured by Tosoh Corporation), and 122g of pure water while crushing. Otherwise, the powder composition of this example was obtained by the same method as in Example 1.

[0139] The results are shown in the table below.

[0140] [Table 3] <Manufacturing of Sintered Bodies> 3g of the powder obtained in the examples and comparative examples was filled into a mold with a diameter of 25mm and uniaxially pressed at a pressure of 98MPa to obtain a molded body. The molded body was then sintered in a muffle furnace under the following conditions to obtain a sintered body.

[0141] Heating rate: 100℃ / hour Sintering temperature: 1500℃ Sintering time: 2 hours The results are shown in the table below.

[0142] [Table 4] It was confirmed that the obtained recycled powder could be used as a raw material for sintered bodies. In addition, in Comparative Example 2, although a sintered body was obtained, the density of the sintered body was low.

[0143] The entire contents of the description, claims, drawings and abstract of Japanese Patent Application No. 2023-164193, filed on September 27, 2023, are incorporated herein by reference and are incorporated herein by reference as a disclosure of this publication.

Claims

1. A zirconium oxide powder, characterized in that, It contains grains.

2. The powder according to claim 1, wherein, The powder has a BET specific surface area of ​​0.5 m². 2 / g or more and 10.5m 2 The particle size is below / g and the median particle size is 0.

2. μ m or more and 2.0 μ Below m.

3. The powder according to claim 1 or 2, wherein, The zirconium oxide is zirconium oxide containing stabilizing elements.

4. The powder according to claim 3, wherein, The stabilizing element is selected from one or more of yttrium, magnesium, calcium, cerium, gadolinium, and erbium.

5. The powder according to claim 3 or 4, wherein, The content of the stabilizing element is above 1.5 mol% and below 6 mol%.

6. The powder according to any one of claims 1 to 5, wherein, The monoclinic crystallization rate of the powder is above 50%.

7. The powder according to any one of claims 1 to 6, wherein, BET specific surface area relative to median particle size is 12 μm. 2 / (g· μ (m) and below.

8. The powder according to any one of claims 1 to 7, wherein, The powder is recycled powder.

9. A method for manufacturing the powder according to any one of claims 1 to 8, characterized in that, have: A hydrothermal treatment process, wherein the sintered zirconia body is hydrothermally treated at a hydrothermal treatment temperature above 150℃ and below 400℃, with the mass ratio of water to the sintered body set to 1.5 or less; and The crushing process involves crushing the sintered body after hydrothermal treatment.

10. The manufacturing method according to claim 9, wherein, The sintered zirconium oxide is a sintered body with tetragonal zirconium oxide as the main phase.

11. The manufacturing method according to claim 9 or 10, wherein, The proportion of monoclinic crystals in the crystalline phase of the sintered zirconium oxide is less than 5%.

12. The manufacturing method according to any one of claims 9 to 11, wherein, The sintered zirconium oxide has a three-point bending strength of over 1000 MPa.

13. A method for regenerating a sintered body, characterized in that, have: A hydrothermal treatment process, wherein the sintered zirconia body is hydrothermally treated at a hydrothermal treatment temperature above 150℃ and below 400℃, with the mass ratio of water to the sintered body set to 1.5 or less; and The crushing process involves crushing the sintered body after hydrothermal treatment.

Images