Method for producing ceramic article, and ceramic article

Abstract

To provide a method for producing a ceramic article in which the improvement of mechanical strength, abrasion resistance and mechanical workability is realized using a direct molding system, and a ceramic article.SOLUTION: A method for producing a ceramic article comprises: a step (i) where powder essentially consisting of ceramic is arranged on a base stand; a step (ii) where a part or the whole of the arranged powder is irradiated with an energy beam, and the powder is melted and solidified to obtain an intermediate molding; a step (iii) where a metal component-containing liquid is absorbed and impregnated into the molding; and a step (iv) where the molding absorbed with the metal component-containing liquid is subjected to heating treatment.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to methods for manufacturing ceramic articles using additive manufacturing techniques, and to ceramic articles manufactured by such methods. [Background technology]

[0002] Additive manufacturing, a technology that irradiates a material powder with an energy beam based on three-dimensional data of the object to be manufactured, to bond the material powder and obtain the desired object, is becoming widespread for applications such as rapid prototyping and small-lot manufacturing. In metal powder manufacturing (metal manufacturing), powder bed laser direct manufacturing is widely used, resulting in dense and diverse metal objects. The high density of metal objects is achieved by effectively melting and solidifying the metal powder. Building on this success in metal manufacturing, the application of additive manufacturing technology to ceramic materials has been discussed, and many efforts have been reported. However, unlike metals, common ceramics such as aluminum oxide and zirconium oxide have low absorption of laser light. Therefore, in order to melt them in the same way as metals, more energy must be input, but the laser light diffuses, causing uneven melting, making it difficult to achieve the required molding precision.

[0003] Under these circumstances, for example, Non-Patent Document 1 discloses a technology that uses ceramics with an Al2O3-ZrO2 eutectic composition to lower the melting point, thereby reducing the energy required for melting and alleviating thermal stress, thereby suppressing the occurrence of cracks in the resulting shaped object. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Physics Procedia 5 (2010) 587-594 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in Non-Patent Document 1, the molded object has a phase separation structure specific to eutectic systems, and therefore has excellent mechanical strength such as three-point bending strength. However, when heated by a heater, part of the ceramic material powder around the molded object melts, resulting in extremely low molding accuracy. The present invention has been made to address such problems, and provides a method for manufacturing a ceramic article using a direct molding method, which achieves high molding accuracy while improving the mechanical strength of the molded product. [Means for solving the problem]

[0006] A method for manufacturing a ceramic article according to one aspect of the present invention includes: (i) placing a ceramic-based powder on a base; (ii) irradiating a part or all of the placed powder with an energy beam to melt and solidify the powder to obtain a shaped object; (iii) allowing the shaped object to absorb a metal component-containing liquid; and (iv) A step of heating the shaped object that has absorbed the metal component-containing liquid.

[0007] A ceramic article according to another aspect of the present invention is a ceramic shaped object having a phase-separated structure consisting of at least three phases, namely, an X phase, a Y phase, and a Z phase, wherein the materials constituting the three phases are in a eutectic relationship, and the average particle size x of the grains constituting the X phase, the average particle size y of the grains constituting the Y phase, and the average particle size z of the grains constituting the Z phase satisfy the relationships z / x<0.5 and z / y<0.5. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a method for producing a ceramic article having excellent mechanical strength with high molding accuracy using a direct molding method.

[0009] According to the present invention, it is possible to improve the mechanical strength of the object while still taking advantage of the characteristics of the direct fabrication method that allows for the fabrication of a precise and complex shape. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view showing an embodiment of a method for manufacturing a shaped object of the present invention. [Figure 2] 1 is a schematic cross-sectional view showing an embodiment of a method for manufacturing a shaped object of the present invention. [Figure 3] 1 is a schematic diagram illustrating a flow of steps in a method for manufacturing a shaped object according to the present invention. [Figure 4] 1 is a schematic cross-sectional view showing an embodiment of a method for manufacturing a shaped object of the present invention. [Figure 5] 1 is a schematic cross-sectional view showing an embodiment of a method for manufacturing a shaped object of the present invention. [Figure 6] 1 is a schematic perspective view showing a laser irradiation process in an embodiment of the present invention. [Figure 7] FIG. 1 is a schematic perspective view showing a shaped object according to an embodiment of the present invention. [Figure 8] 1 shows optical microscope images of a comparative object of Comparative Example 1 and an object of Example 1. [Figure 9] 1 is a cross-sectional view schematically showing an embodiment of a ceramic shaped article of the present invention and a comparative ceramic. FIG. [Figure 10] 1 is a phase diagram showing the relationship between the composition ratio and state of the X phase and the Y phase, which are in a eutectic relationship. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following specific examples.

[0012] As described above, the method for manufacturing a ceramic article according to the present invention includes the steps of: (i) placing a ceramic-based powder on a base; (ii) irradiating a part or all of the placed powder with an energy beam to melt and solidify the powder to obtain a shaped object; (iii) allowing the shaped object to absorb a metal component-containing liquid; and (iv) A step of heating the shaped object that has absorbed the metal component-containing liquid.

[0013] The manufacturing method of the present invention is suitable for producing three-dimensional objects by direct manufacturing methods, and by applying it to powder bed direct manufacturing methods and directed energy deposition methods (so-called cladding methods) in which a build-up of building material is performed, it is possible to achieve good manufacturing accuracy while significantly improving the mechanical strength, wear resistance, and machinability of the object.

[0014] The basic manufacturing process of the powder bed direct manufacturing method will be described with reference to Figures 1(a) to 1(h). First, powder 101 is placed on a base 130 mounted on a stage 151, and a powder layer 102 is formed using a roller 152 (Figures 1(a) and 1(b)). An energy beam emitted from an energy beam source 180 is irradiated onto the surface of the powder layer 102 in an irradiation area 182 corresponding to the desired shape while being scanned by a scanner unit 181. The powder melts and then solidifies, forming a molded object 100 (Figure 1(c)). Next, the stage 151 is lowered, and a new powder layer 102 is formed on the molded object 100 (Figure 1(d)). This series of steps is repeated to form a molded object 110 of the desired shape (Figures 1(e) and 1(f)). Finally, the unsolidified powder 103 is removed, and, if necessary, unnecessary portions of the intermediate object are removed or the object is separated from the base (Figures 1(g) and 1(h)).

[0015] Next, the cladding method will be explained using Figures 2(a) to 2(c). The cladding method is a technique in which powder is ejected from multiple powder supply holes 202 in a cladding nozzle 201, and an energy beam 203 is irradiated onto the area where the powder is focused, thereby additionally forming a molded object 100 at a desired location (Figure 2(a)). This process is repeated to obtain a molded object 110 of the desired shape (Figures 2(b) and 2(c)). Finally, unnecessary portions of the molded object are removed, and the molded object is separated from the base, as necessary.

[0016] In direct fabrication methods such as powder bed direct fabrication and cladding, powder melted by energy beam irradiation is cooled by the surroundings and solidifies to form a molded object. In the case of ceramics, the temperature difference between melting and solidification is large, resulting in the formation of many microcracks in the molded object. Microcracks are distributed throughout the entire molded object (surface and interior). When the cross section of the molded object is examined using a scanning electron microscope, the width of most microcracks is found to be several nanometers to several micrometers. Furthermore, the length of the microcracks varies from several micrometers to several millimeters. According to the present invention, by absorbing a metal-containing liquid into the microcracks of the molded object and then heating it, it is possible to selectively melt the area near the microcracks. This reduces the number of microcracks in the molded object while minimizing changes in the shape of the object, thereby improving the mechanical strength of the object.

[0017] The energy beam irradiated onto the powder layer is preferably controlled to have a gentle intensity profile on the surface of the powder layer. Irradiating a beam with a gentle intensity profile can reduce the impact on the shaped portion that exists below the irradiated portion and that has already been melted and solidified. This preserves microcracks in the shaped portion below, allowing the generation of microcracks to be controlled by the drawing direction, etc., and enabling microcracks to be generated uniformly throughout the entire intermediate object. For example, irradiating the powder layer with an energy beam in a defocused state is preferable because the intensity of the energy beam has a gentle profile on the surface of the powder layer.

[0018] The metal component-containing liquid absorbed into the microcracks is preferably one that changes into a metal compound, particularly a metal oxide, by a heat treatment performed after the metal component-containing liquid has been absorbed. This change into a metal oxide preferably occurs independently within the metal component-containing liquid itself, but it is also preferable that it also occurs through combination with, solid solution with, or diffusion into the material that constitutes the shaped object.

[0019] The metal oxide formed by the heat treatment is preferably a phase capable of forming a eutectic relationship with the phases constituting the shaped object. When the shaped object is composed of multiple phases, the phase may be capable of forming a eutectic relationship with any of the phases constituting the shaped object. As a result, in the vicinity of the microcracks into which the metal component has penetrated, the metal oxide phase formed by the heat treatment and the phase contained in the shaped object are in a eutectic relationship, melting at a temperature lower than the melting point of the shaped object, and the metal component diffuses into the shaped object. Then, as the heating is completed and the temperature drops, the crystals within the shaped object recrystallize with a composition containing the metal component. As a result, only the regions near the microcracks soften while maintaining the shape of the shaped object, thereby reducing or eliminating the microcracks. Furthermore, the bonding strength between crystalline components, such as at grain boundaries, of the shaped object is strengthened, improving the wear resistance of the shaped object. Here, "grain boundaries" refers to the boundaries between crystal grains. For ease of explanation, crystal grains may be referred to simply as "grains" below.

[0020] In order to generate this phenomenon, the temperature of the heat treatment performed after the metal component-containing liquid is absorbed into the microcracks of the molded object is also important. Figure 10 shows a phase diagram that shows the relationship between the composition ratio and state of the X phase and the Y phase when the X phase constituting the molded object and the metal oxide Y phase formed from the metal component-containing liquid are in a eutectic relationship. The melting point of the X phase is T m , the melting point of the Y phase is T i , the eutectic temperature of the X and Y phases is T E Then, the respective temperatures are T E <T m , T E <T iIn this case, the maximum temperature T S But, T E <T S <T m It is preferable to set it so that T E <T S <T m -(T m -T E ) / 2. This gives the melting point T m This makes it possible to selectively melt the vicinity of the microcracks at a temperature lower than the temperature at which the microcracks are formed, thereby reducing or eliminating the microcracks, and thus making it easier to maintain the shape of the shaped object.

[0021] The more times the process of absorbing the metal component-containing liquid into the molded object and then heating it is repeated, the greater the effect of reducing or eliminating microcracks. m <T i This means that a high effect can be achieved with fewer sessions. This is shown in Figure 10. m <T i By this, the eutectic composition of the X phase and the Y phase becomes rich in the X phase, and the vicinity of the microcracks can be melted at the eutectic temperature with a low proportion of the Y phase. m <T i is not a necessary condition.

[0022] For example, if the object is made of aluminum oxide (Al2O3; melting point T m In the case where the metal component is a liquid containing zirconium, the liquid containing zirconium is preferably used. Zirconium is then extracted from the liquid containing zirconium by heat treatment. i The eutectic temperature of Al2O3 and ZrO2 is about 1900°C. m <T i This is a preferable combination that satisfies the relationship. With this combination, the concentration of the ZrO2 component absorbed in the microcracks is adjusted to bring the ratio of Al2O3 and ZrO2 near the microcracks closer to the eutectic composition, thereby reducing the maximum temperature T S 1900℃ <T S <2070°C. Therefore, it is possible to melt Al2O3 at a temperature sufficiently lower than its melting point, thereby reducing or eliminating microcracks.

[0023] When the object is made up of two phases, Al2O3 and GdAlO3, the melting point of the object is determined by the composition ratio of the two phases. For example, if these two phases are a eutectic composition, the melting point will be approximately 1720°C. In this case, it is possible to select a liquid containing zirconium, which will produce a ZrO2 phase upon heat treatment, as the liquid containing the metal component. The melting point of the ZrO2 phase is 2715°C, but since the eutectic temperature of the three phases of Al2O3, GdAlO3, and ZrO2 is approximately 1662°C, the maximum temperature T during heat treatment will be sufficiently lower than the approximately 1720°C of the object. S This makes it possible to reduce or eliminate microcracks.

[0024] Even when a molded object consists of two phases, Al2O3 and ZrO2, the melting point of the object depends on the composition ratio of the two phases. For example, if these two phases are a eutectic composition, the melting point is approximately 1900°C. A liquid containing gadolinium and aluminum in a 1:1 ratio can be selected as the metal-containing liquid. In this case, heat treatment produces a GdAlO3 phase, whose melting point is 2050°C. However, as mentioned above, the eutectic temperature of the three phases of Al2O3, GdAlO3, and ZrO2 is approximately 1662°C. Therefore, it is possible to reduce or eliminate microcracks by performing heat treatment at a temperature well below the melting temperature of the molded object, approximately 1900°C.

[0025] As described above, there are countless other combinations of metal oxide phases obtained by heat treatment of at least one phase constituting the object and the metal component-containing liquid. For example, T m <T iExamples of combinations that satisfy this relationship are SiO2 and ZrO2, SiO2 and Al2O3, Al2O3 and MgO, Al2O3 and HfO2, [Al2O3 and ReAlO3 (Re is a rare earth)] and ZrO2, [Al2O3 and ReAl5O 12 (Re is a rare earth)] and ZrO2, [Al2O3 and ReAlO3 (Re is a rare earth)] and HfO2, [Al2O3 and ReAl5O 12 (Re is rare earth)] and HfO2, Mg2Al4Si5O 18 and Mg2SiO4, Mg2Al4Si5O 18 Examples of metal oxides that can be used include, but are not limited to, MgSiO3 and MgSiO3. In the above explanation, the brackets indicate the phases that make up the object, and the brackets indicate the metal oxide phases obtained by heat treatment of the metal component-containing liquid.

[0026] The shaped object is composed of crystalline and amorphous structures formed by the irradiation of the energy beam. Then, as described above, the heating process after absorbing the metal-containing liquid causes the metal components to diffuse into the crystalline and amorphous structures and recrystallize. Therefore, the grains that make up the phase originally contained in the shaped object before heating and the grains that make up the phase containing the metal components differ in grain size (e.g., average grain size) after heating. In this way, the shaped object is composed of a phase-separated structure consisting of multiple phases with different average grain sizes, which strengthens the bonding strength between the crystalline structures. As a result, the mechanical strength, wear resistance, and machinability of the resulting shaped object are improved, enabling precise finishing with minimal chipping.

[0027] As described above, the present invention is characterized by introducing a metal component into a molded object produced by melting and solidifying powder with an energy beam, and the metal component is subsequently absorbed into the microcracks in the powder before melting. Even if the metal component is already incorporated, the same effect as the present invention cannot be obtained. Even if the powder before melting contains a metal component that is subsequently absorbed into the microcracks, countless microcracks will form in the molded object due to thermal stress caused by the temperature difference between melting and solidification. By implementing the absorption process of the present invention, microcracks can be reduced, improving the mechanical strength of the molded object.

[0028] Furthermore, if the powder before melting contains 3 mol% or more of metal compounds generated when the metal component-containing liquid used in step (iii) is heated, it becomes difficult to locally melt only the vicinity of the microcracks during the heating step, which may result in deformation of the molded object. Therefore, the amount of the metal compounds pre-contained in the powder before melting is preferably less than 3 mol%, more preferably less than 2 mol%. Furthermore, in order to obtain a molded object that can be precisely machined with little chipping, it is preferable that the amount of the metal compounds pre-contained is less than 1 mol%. By keeping the amount of the metal compounds below 1 mol%, a molded object consisting of multiple phases with significantly different average particle diameters can be obtained, thereby ensuring the effect of improving the machinability of the molded object.

[0029] Next, a method for manufacturing a ceramic article according to the present invention will be described. The manufacturing method according to the present invention is characterized by comprising the following four steps: (i) A powder containing ceramic as a main component is placed on a base. (ii) An energy beam is irradiated onto a part or all of the placed powder to melt and solidify the powder, thereby obtaining a shaped object. (iii) Allowing the shaped object to absorb a liquid containing a metal component. (iv) heating the shaped object that has absorbed the metal component-containing liquid; Below, we will explain each step in detail, taking as an example a case where a powder containing aluminum oxide, a general-purpose structural ceramic, as its main component is used for shaping. By appropriately melting and solidifying aluminum oxide, a shaped object with high mechanical strength can be obtained.

[0030] <Process (i)> First, a powder containing aluminum oxide as a main component (hereinafter, sometimes referred to as raw material powder) is placed on a base.

[0031] In the present invention, among the objects (powders or shaped objects) discussed as components, the component that is contained in the largest amount, expressed in molar ratio, is called the main component, and "powder containing aluminum oxide as the main component" refers to powder in which aluminum oxide is contained in the largest amount, in terms of molar ratio.

[0032] In the present invention, the powder primarily composed of aluminum oxide preferably contains, as a secondary component, an oxide of a rare earth element that forms a eutectic composition with aluminum oxide. It is particularly preferable that the powder contains at least one selected from gadolinium oxide, terbium oxide, and praseodymium oxide. For example, when the raw material powder contains gadolinium oxide that forms a eutectic composition with aluminum oxide, the melting point is lower than that of aluminum oxide alone near the Al2O3-Gd2O3 eutectic composition. This allows the powder to melt with less heat, suppresses energy diffusion within the powder, and improves shaping accuracy. Furthermore, when the raw material powder contains gadolinium oxide, the shaped object has a phase-separated structure consisting of two or more phases. This suppresses crack propagation and improves the mechanical strength of the shaped object. Similar effects to those of gadolinium oxide can be obtained when other rare earth element oxides (excluding terbium and praseodymium), such as yttrium oxide, are contained in place of gadolinium oxide.

[0033] When the energy beam is a laser beam, sufficient energy absorption in the powder suppresses the spread of heat within the powder and makes it localized, reducing the thermal impact on non-printed areas, improving printing accuracy. For example, when using an Nd:YAG laser or fiber laser, terbium oxide (Tb4O7) or praseodymium oxide (Pr6O 11 It is more preferable that the powder contains terbium oxide (Tb4O7) or praseodymium oxide (Pr6O 11 It is also preferable that the rare earth element contains both a rare earth element that exhibits good energy absorption for a laser beam such as ), and another rare earth element.

[0034] From the above viewpoint, particularly suitable raw material powders are Al2O3-Gd2O3, Al2O3-Tb4O7, Al2O3-Gd2O3-Tb4O7, and Al2O3-Pr6O 11 , Al2O3-Gd2O3-Pr6O 11 etc.

[0035] The raw material powder preferably contains a composition that forms a eutectic in a ratio that forms the eutectic composition. The eutectic composition is the composition at the eutectic point shown in a eutectic phase diagram. However, in a molding process using an energy beam, heating and cooling are repeated very quickly, so a eutectic structure having a phase separation structure is formed even if the composition is off the eutectic point. Therefore, the eutectic composition in the present invention is preferably defined as the composition range in which a eutectic structure is formed, and includes a range of ±10 mol% of the eutectic composition in the eutectic phase diagram. Similarly, in the case of a powder whose main component is other than aluminum oxide, it is preferable that the composition that forms the eutectic is contained in a ratio that forms the eutectic composition.

[0036] In this specification, materials may be expressed using chemical formulas, such as Al2O3 and Tb4O7, but the composition ratio of the elements in the actual material does not need to strictly match the ratio in the chemical formula as long as the spirit of the present invention is met. In other words, the valence of the metal elements constituting a certain material may differ slightly from the valence expected from the chemical formula. For example, the valence of Tb expected from Tb4O7 is tetravalent, but terbinium oxide with a valence of 3.5 or more but less than 4.5 is included in Tb4O7.

[0037] The material of the base used in the present invention can be appropriately selected from materials commonly used in the production of three-dimensional objects, such as ceramics, metals, and glasses, taking into consideration the intended use of the object, the production conditions, etc. When the intermediate object integrated with the base is heated in step (iv), it is preferable to use a heat-resistant ceramic for the base.

[0038] There are no particular restrictions on the method for placing the powder on the base. In the case of powder bed direct fabrication, as shown in Figures 1(a) to 1(h), the powder is placed in layers on the base using rollers, blades, or the like. In the case of cladding, as shown in Figures 2(a) to 2(c), the powder is sprayed from a nozzle onto the energy beam irradiation position, and the powder is placed on the base or an intermediate object placed on the base in a pile-up manner, and at the same time, the powder is melted and solidified by energy beam irradiation to produce an intermediate object.

[0039] <Process (ii)> In the subsequent step (ii), an energy beam is irradiated onto some or all of the powder placed on the base in step (i) based on three-dimensional shape data of the article to be manufactured, and the powder located in the irradiated area is melted and solidified to obtain an intermediate shaped object. This step will be described below based on a preferred embodiment.

[0040] In the powder bed direct molding method, as shown in Figures 1(a) to 1(h), in step (i), a predetermined area on the surface of powder placed on a base is irradiated with an energy beam while scanning it, melting and then solidifying the powder. In the cladding method, as shown in Figures 2(a) to 2(c), in step (i), powder is sprayed and supplied to the base in a manner that selectively deposits the powder in the area to be molded, and at the same time, an energy beam is irradiated onto the powder to melt and solidify the powder. When the energy beam is irradiated onto the powder, the powder absorbs the energy, which is converted into heat, melting the powder. After the energy beam has passed and irradiation is completed, the molten powder is cooled by the atmosphere and its surroundings and solidifies, forming a molded object. During this process, the rapid cooling during the melting and solidification processes generates stress on the surface and interior of the molded object, forming countless microcracks.

[0041] The energy beam used should be selected from a light source with an appropriate wavelength, taking into account the absorption characteristics of the powder. For high-precision shaping, it is preferable to use a laser beam or electron beam with a narrow beam diameter and high directivity. Suitable energy beams for powders primarily composed of aluminum oxide include YAG lasers and fiber lasers in the 1 μm wavelength range, and CO2 lasers in the 10 μm wavelength range. When the powder contains terbium oxide or praseodymium oxide as a secondary component, YAG lasers and fiber lasers in the 1 μm wavelength range, which are highly absorbed by terbium oxide and praseodymium oxide, are particularly suitable.

[0042] The series of steps (i) and (ii) may be repeated. That is, new powder is placed in step (i) on the object obtained in step (ii). When the placed powder is irradiated with an energy beam based on slice data generated from the three-dimensional shape data of the article to be manufactured, the powder in the energy beam irradiated area melts and solidifies, forming a new object integrated with the previously formed object. By alternately repeating steps (i) and (ii), an object having a desired three-dimensional shape corresponding to the three-dimensional shape data can be obtained.

[0043] <Step (iii)> Next, the method includes a step of impregnating the shaped article obtained in the step (ii) with a liquid containing a zirconium component.

[0044] The zirconium component-containing liquid will now be described. The zirconium component-containing liquid is composed of a raw material for the zirconium component, an organic solvent, and a stabilizer.

[0045] Various zirconium compounds can be used as the raw material for the zirconium component. Examples of the raw material for the zirconium component include metal alkoxides of zirconium and salt compounds such as chlorides and nitrates. Among these, metal alkoxides are preferred because they allow the zirconium component-containing liquid to be uniformly impregnated into the microcracks of the shaped object. Specific examples of zirconium alkoxides include zirconium tetraethoxide, zirconium tetra-n-propoxide, zirconium tetraisopropoxide, zirconium tetra-n-butoxide, and zirconium tetra-t-butoxide.

[0046] First, zirconium alkoxide is dissolved in an organic solvent to prepare a zirconium alkoxide solution. The amount of organic solvent added to the zirconium alkoxide is preferably 5 to 30 in molar ratio relative to the compound. More preferably, it is 10 to 25 in molar ratio. In the present invention, a molar ratio of 5 to N indicates that the molar amount of M added is 5 times the molar amount of N. If the concentration of zirconium alkoxide in the solution is too low, a sufficient amount of zirconium component cannot be impregnated into the shaped object. On the other hand, if the concentration of zirconium alkoxide in the solution is too high, the zirconium component in the solution will aggregate, making it impossible to uniformly distribute the zirconium component in the microcracks of the shaped object.

[0047] The organic solvent may be an alcohol, a carboxylic acid, an aliphatic or alicyclic hydrocarbon, an aromatic hydrocarbon, an ester, a ketone, an ether, or a mixture of two or more of these. Examples of alcohols include methanol, ethanol, 2-propanol, butanol, 2-methoxyethanol, 2-ethoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-propoxy-2-propanol, 4-methyl-2-pentanol, 2-ethylbutanol, 3-methoxy-3-methylbutanol, ethylene glycol, diethylene glycol, and glycerin. Examples of aliphatic or alicyclic hydrocarbons include n-hexane, n-octane, cyclohexane, cyclopentane, and cyclooctane. Examples of aromatic hydrocarbons include toluene, xylene, and ethylbenzene. Preferred esters include ethyl formate, ethyl acetate, n-butyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, and ethylene glycol monobutyl ether acetate. Preferred ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Preferred ethers include dimethoxyethane, tetrahydrofuran, dioxane, and diisopropyl ether. When preparing the coating solution used in the present invention, it is preferable to use alcohols from the viewpoint of solution stability among the various solvents mentioned above.

[0048] Next, stabilizers will be described. Zirconium alkoxides are highly reactive with water, and therefore rapidly hydrolyze upon the addition of moisture from the air or water, resulting in cloudy solution and precipitation. To prevent this, it is preferable to add a stabilizer to stabilize the solution. Examples of stabilizers include β-diketone compounds such as acetylacetone, 3-methyl-2,4-pentanedione, 3-ethyl-2,4-pentanedione, and trifluoroacetylacetone; β-ketoester compounds such as methyl acetoacetate, ethyl acetoacetate, butyl acetoacetate, allyl acetoacetate, benzyl acetoacetate, isopropyl acetoacetate, tert-butyl acetoacetate, isobutyl acetoacetate, ethyl 3-oxohexanoate, ethyl 2-methylacetoacetate, ethyl 2-fluoroacetoacetate, and 2-methoxyethyl acetoacetate; and alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine. The amount of stabilizer added is preferably 0.1 to 3 in molar ratio relative to the zirconium alkoxide. More preferably, it is 0.5 to 2. The solution may be prepared by reacting at room temperature or refluxing.

[0049] In the above step (ii), the powder is melted by irradiating it with a scanning energy beam, and then cooled by the surroundings and solidified, forming a molded object. In the case of ceramics, the temperature difference between melting and solidifying is large, so many microcracks occur in the molded object due to the difference in expansion / contraction rates. Therefore, microcracks exist vertically and horizontally inside the molded object.

[0050] In step (iii), the zirconium component-containing liquid penetrates and distributes not only on the surface of the shaped object but also inside the shaped object via the microcracks. The method for absorbing the zirconium component-containing liquid into the shaped object is not particularly limited, as long as a sufficient amount of the zirconia component can be present in a sufficient area of ​​the microcracks of the shaped object. The shaped object may be immersed in the zirconium component-containing liquid to impregnate it, or the zirconium component-containing liquid may be atomized and sprayed onto the shaped object, or applied to the surface with a brush, etc., to allow absorption. These methods may be combined, or the same method may be repeated multiple times. When spraying or applying the zirconium component-containing liquid, it is preferable to spray or apply 5 to 20 volume % of the zirconium component-containing liquid onto the shaped object that has not absorbed the liquid. If the amount is less than 5 volume %, the amount of zirconium component disposed in the microcracks of the shaped object will be insufficient, and the microcracks may not melt. If the content is greater than 20% by volume, when step (i) is performed after step (iii), the zirconium component-containing liquid may have an effect on uniformly distributing the powder on the shaped object, making it difficult to achieve this. In the case of large-volume shaped objects obtained by repeating steps (i) and (ii) multiple times, it is preferable to immerse the shaped object in the zirconium component-containing liquid and degas it under reduced pressure in order to ensure that the zirconium component is sufficiently distributed throughout the shaped object. Alternatively, the shaped object may be placed in a sealed container, degassed under reduced pressure, and then immersed in the zirconium component-containing liquid. Alternatively, it is preferable to spray the zirconium component-containing liquid in a mist form during the repetition of steps (i) and (ii) so that the zirconium component is absorbed into the shaped object at each stage. That is, the order of steps is preferably "step (i) → step (ii) → step (iii) → step (i) → ...".

[0051] <Process (iv)> In the next step (iv), the shaped article impregnated with the zirconium component-containing liquid is heat-treated. In the above step (iii), the zirconium-containing liquid is distributed on the surface of the object and in the microcracks inside the object. The zirconium-containing liquid in the vicinity of the microcracks has a lower melting point than the portion of the object farther from the microcracks, because the zirconium content brings the vicinity of the microcracks closer to the eutectic composition. Taking advantage of this difference in melting point, the object that has undergone step (iii) is heated to a temperature above the eutectic point of the eutectic phase formed by the material constituting the object and zirconium oxide, but below the melting point of the material constituting the object. As a result, the portion of the object where the zirconium content is present, i.e., the portion of the object near the microcracks, is sintered or partially melted, while maintaining the shape of the object.

[0052] When the shaped object is composed of two-phase materials and these two phases and zirconium oxide form a three-phase eutectic, the three-phase eutectic point is lower than the two-phase eutectic point. This is preferable because step (iv) can be performed at an even lower temperature than when the shaped object is composed of a single phase, and temperature unevenness within the shaped object can be reduced even for relatively large objects. Furthermore, when the article to be manufactured is an oxide, step (iv) can be easily performed in an electric furnace or the like in an air atmosphere at a relatively low temperature. For example, Al2O3-Gd2O3 is a material that can form a three-phase eutectic with zirconium oxide. Therefore, by performing step (iii) on a shaped object formed from a powder mainly composed of Al2O3-Gd2O3 and adjusting the composition ratio to form a three-phase eutectic near the microcracks, the melting point can be significantly lowered locally. This difference in melting point can then be utilized to melt only the microcracks and their vicinity by heating the shaped object at a temperature above the three-phase eutectic point and below the melting point of the object. Specifically, by performing heat treatment so that the maximum temperature near the microcracks of the shaped object formed from a powder mainly composed of Al2O3-Gd2O3 and subjected to step (iii) is 1600°C or higher and 1710°C or lower, the microcracks can be reduced or eliminated.

[0053] The heating time is not critical as long as the vicinity of the microcracks reaches the maximum temperature. Specifically, the molded object can be heated to the temperature desired for the vicinity of the microcracks in step (iii). When the microcracks and their vicinity are molten, atomic diffusion occurs in the direction of decreasing surface energy, resulting in the reduction or disappearance of the microcracks. In other words, upon heating, the zirconium components distributed in the microcracks diffuse into the crystalline and amorphous interior of the molded object, resulting in the recrystallization of the crystals containing zirconium. Therefore, the grains constituting the aluminum oxide phase and the phase containing the rare earth element added as a minor component formed in the molded object in step (i) differ significantly in grain size (e.g., average grain size) from the grains constituting the phase containing zirconium. In addition to the reduction or disappearance of microcracks, a phase-separated structure consisting of multiple phases with different average grain sizes is formed, improving the machinability of the molded object and enabling precise finishing with minimal chipping.

[0054] To selectively melt only the vicinity of the portion where the zirconium component is present, it is advisable to adjust the heating temperature or the concentration of the zirconium component near the microcracks. By adjusting the temperature or the concentration of the zirconium component near the microcracks, the shape of the object is not distorted, the complex or precise shape formed by the direct molding method is maintained, and the object shape can be obtained substantially as designed, thereby realizing high-precision molding.

[0055] If a sufficient amount of zirconium is present in the microcracks, the vicinity of the microcracks will melt, reducing or eliminating the microcracks, as described above. The zirconium concentration in the microcracks can be adjusted by the concentration of the zirconium component in the zirconium component-containing liquid, the method of absorbing the zirconium component-containing liquid into the microcracks, and the number of times this is done. In particular, when the vicinity of the microcracks approaches a eutectic composition in which the aluminum oxide-based object contains approximately 78 mol % zirconium oxide and approximately 22 mol %, the vicinity of the microcracks will melt more easily. To selectively melt the vicinity of the microcracks and reduce or eliminate the microcracks, heating at a temperature of 1650°C or higher and 1710°C or lower is more preferable.

[0056] For example, a shaped object formed from a powder mainly composed of Al2O3-Gd2O3 contains a phase mainly composed of Al2O3 and a phase mainly composed of GdAlO3. When this shaped object is absorbed into a zirconium-containing liquid (step (iii)) and heated at a temperature of 1600°C to 1710°C (step (iv)), the zirconium component distributed in the microcracks diffuses into the crystals of the intermediate shaped object and recrystallizes, forming a three-phase eutectic consisting of a fluorite-structured ZrO2-based phase, an Al2O3-based phase, and a GdAlO3-based phase. The average grain size of the grains constituting the Al2O3-based phase and the GdAlO3-based phase, which were originally present in the shaped object immediately after formation in step (i), i.e., before step (iv) was performed on the shaped object, increases due to the heat treatment in step (iv). On the other hand, the average grain size of the grains constituting the fluorite-structured ZrO2-based phase formed by the diffusion and recrystallization of the zirconium components distributed in the microcracks is smaller than that of the other two phases. In this way, the formation of a ZrO2-based phase with a small average grain size in the molded product strengthens the bonding strength between the crystalline structure of the molded product, greatly improving the wear resistance of the molded product. In addition, the molded product has high machinability, allowing for precise finishing with little grain chipping.

[0057] In order to improve the wear resistance and machinability, it is necessary to sufficiently diffuse the zirconium component into the crystal interior of the shaped product. From this perspective, it is preferable to heat the shaped product for a long period of time. From the perspective of widely diffusing the zirconium component into the crystal interior, it is preferable to heat the shaped product for a long period of time at a relatively high temperature within a range in which the shaped product does not deform. For example, in the case of a three-phase eutectic material such as the one described above, it is preferable to heat it at a temperature of 1600°C or higher and 1710°C or lower, and more preferably at a temperature of 1650°C or higher and 1710°C or lower.

[0058] The heating method is not particularly limited. The intermediate object that has absorbed the zirconium component-containing liquid may be heated by irradiating it with an energy beam again, or by placing it in an electric furnace. When heating with an energy beam, it is necessary to determine in advance using a thermocouple or the like the relationship between the amount of heat input by the energy beam and the temperature of the object so that the object is heated to the desired temperature.

[0059] During the heating process, the surface layer of the molded object or the vicinity of microcracks may melt, causing the molded object to adhere to the setter. Therefore, when placing the molded object on a setter during the heating process, it is preferable that the setter be inert. Examples of inert setters include platinum in air and iridium in a low-oxygen atmosphere.

[0060] <Flowchart> The order of each step and an example of a repetition pattern will be described below with reference to the flowchart in FIG. The basic flow is a flow that proceeds in the order of flow lines (1), (2), and (3) in Figure 3. That is, the basic flow is to execute each step in the order of step (i) → step (ii) → step (iii) → step (iv). The effects of the present invention can be obtained by executing all steps from step (i) to step (iv) at least once.

[0061] As shown by flow lines (4), (5), (6), and (7) in FIG. 3, each step may be executed repeatedly.

[0062] Flow lines (1) and (4) are flow lines for repeatedly executing step (i) and step (ii). Repeating step (i) and step (ii) in order n times (n is a natural number) is called [step (i) → step (ii)]. n [Step (i) → Step (ii)] n The n in the formula corresponds to the number of slices n in the slice data generated from the three-dimensional shape data of the three-dimensional object to be manufactured, which is characteristically used in the method of manufacturing a three-dimensional object by direct fabrication. This allows a model of a desired shape based on the three-dimensional shape data to be obtained. For example, a model 110 as shown in FIG. 1(g) can be obtained by repeatedly performing steps (i) and (ii). In FIGS. 1(a) to 1(h), first, powder 101 is placed on a base 130, and a powder layer 102 is formed using a roller 152 (FIGS. 1(a) and 1(b)). This operation corresponds to step (i). Next, an energy beam emitted from an energy beam source 180 is irradiated onto the surface of the powder layer 102 while scanning it with a scanner unit 181 within an irradiation range 182 based on the slice data. The powder melts and then solidifies to form a model 100 for one layer (FIG. 1(c)). This operation corresponds to step (ii). The stage 151 is lowered to form a new powder layer 102 on the model 100 (FIG. 1(d)), and the object is irradiated with an energy beam (FIG. 1(e)). This series of steps is repeated to form a model 110 of the desired shape based on the three-dimensional shape data (FIG. 1(f)). This operation is [Step (i) → Step (ii)]. n Corresponds to.

[0063] Flow lines (3) and (6) are flow lines for repeatedly executing steps (iii) and (iv). Repeating steps (iii) and (iv) in sequence m times (m is a natural number) is called [step (iii) → step (iv)]. m [Step (i) → Step (ii)] n After obtaining an intermediate object of a desired shape by the above steps, the process proceeds to step (iii) followed by step (iv). mThe number of repetitions m of steps (iii) and (iv) is preferably determined so that the vicinity of the microcracks in the molded object approaches a eutectic composition in which the intermediate molded object is primarily composed of aluminum oxide at 78 mol % and zirconium oxide at approximately 22 mol %. This makes it easier for the vicinity of the microcracks to melt, improving the effect of reducing or eliminating microcracks. As a result, the three-point bending strength of the molded object is further increased, and more zirconium components are diffused and recrystallized inside the crystals of the molded object, thereby further improving the wear resistance and machinability of the surface of the molded object.

[0064] When steps (iii) and (iv) are repeatedly performed, the zirconium component diffuses into the shaped object with each repetition. This reduces the difference in zirconium component concentration between the microcracks and the non-microcracks. This reduces the difference in melting point (eutectic point) between the microcracks and the non-microcracks. From the viewpoint of melting only the microcracks, the difference in melting point is preferably 20°C or more, more preferably 30°C or more. For shaped objects formed from powders primarily composed of aluminum oxide, it is preferable for the zirconium component in the shaped object to be less than 3 mol %, since this allows for melting only the microcracks while suppressing deformation of the shaped object. It is more preferable for the zirconium component to be less than 2 mol %.

[0065] Furthermore, to obtain a shaped product with minimal chipping that can be precisely machined, it is preferable that the zirconium content of the raw material powder is less than 1 mol %. When the zirconium content is less than 1 mol %, the shaped product after step (iv) is composed of phases whose average grain sizes are significantly different from each other, ensuring the aforementioned effect of improving the machinability of the shaped product. If the raw material powder contains a zirconium content of 3 mol % or more (e.g., zirconium oxide), it becomes difficult to locally melt only the vicinity of the microcracks during the heating step, which may result in deformation of the shaped product.

[0066] Flow lines (1), (2), and (5) are flow lines for executing steps (i) and (ii) again after step (iii). Step (iii) is executed on an intermediate object in the middle of forming a model 110 having a desired shape. Steps (i), (ii), and (iii) are repeated p times (p is a natural number) in this order [step (i) → step (ii) → step (iii)]. p 4(a) to 4(h) show an example in which flow lines (1), (2), and (5) are applied to the powder bed direct manufacturing method. First, powder 101 is placed on a base 130, and a powder layer 102 is formed using a roller 152 (FIGS. 4(a) and 4(b)). This operation corresponds to step (i). Next, an energy beam emitted from an energy beam source 180 is irradiated onto the surface of the powder layer 102 while being scanned by a scanner unit 181, causing the powder to melt and then solidify, forming a model 100 (FIG. 4(c)). This operation corresponds to step (ii). Next, a zirconia component-containing liquid is sprayed onto the model 100 from a liquid injection nozzle 190 (FIG. 4(d)). This operation corresponds to step (iii). Subsequently, the stage 151 is lowered, and a new powder layer 102 is formed on the model 100 (FIG. 4(e)). This operation corresponds to step (i). This series of steps is repeated to form a molded object 110 of the desired shape impregnated with the zirconia component-containing liquid (FIGS. 4(g) and 4(h)). In this way, by performing step (iii) on a molded object in the middle of its formation, as shown by flow lines (1), (2), and (5), the zirconia component-containing liquid can be sufficiently distributed throughout the interior of the molded object, particularly when the final size of the molded object is large, thereby effectively reducing or eliminating microcracks.

[0067] Flow lines (1), (2), (3), and (7) are flow lines for repeating steps (i), (ii), and (iii) after step (iv). Step (iv) is performed on an intermediate object at a stage on the way to forming the final intermediate object. Steps (i), (ii), (iii), and (iv) are repeated in order q times (q is a natural number) [step (i) → step (ii) → step (iii) → step (iv)]. qThe flow chart is written as follows. Figures 5(a) to 5(i) show an example in which flow lines (1), (2), (3), and (7) are applied to the powder bed direct manufacturing method. First, powder 101 is placed on a base 130, and a powder layer 102 is formed using a roller 152 ( Figures 5(a) and 5(b)). This operation corresponds to step (i). Next, an energy beam emitted from an energy beam source 180 is irradiated onto the surface of the powder layer 102 while being scanned by a scanner unit 181, causing the powder to melt and then solidify, forming a molded object 100 ( Figure 5(c)). This operation corresponds to step (ii). Next, a zirconia-containing liquid is sprayed onto the intermediate object 100 from a liquid injection nozzle 190 ( Figure 5(d)). This operation corresponds to step (iii). Next, an energy beam is irradiated onto the molded object 100, which has been impregnated with the zirconia-containing liquid, to heat the molded object 100. This operation corresponds to step (iv) (FIG. 5(e)). Next, the stage 151 is lowered, and a new powder layer 102 is formed on the molded object 100 (FIG. 5(f)). This operation corresponds to step (i). This series of steps is repeated to form a molded object 110 of the desired shape (FIGS. 5(h) and (i)). In this way, according to the flow line (7), the effects of the present invention can be obtained even when step (iv) is performed on a molded object in the middle of its formation.

[0068] Each of steps (i) to (iv) can be repeatedly performed by adding flow lines (1), (2), (3) and optionally flow lines (4), (5), (6), and (7).

[0069] <Ceramics> The ceramic article of the present invention preferably has a phase-separated structure consisting of at least three phases, X, Y, and Z, and the materials constituting the three phases are in a eutectic relationship. In particular, the average grain size x of the X phase, the average grain size y of the Y phase, and the average grain size z of the Z phase preferably satisfy the relationships z / x<0.5 and z / y<0.5. In the present invention, the average grain size refers to the average circle-equivalent diameter of crystal grains observed in the cross section of the ceramic shaped article.

[0070] The ceramic shaped product of the present invention, which has a three-phase eutectic structure of X, Y, and Z phases, has excellent mechanical strength, for example, a three-point bending strength of 30 MPa or more, because the propagation of cracks is suppressed. In particular, if the Z phase, which has a smaller average grain size than the other two phases, is present in the shaped product at a rate above a certain value, the ceramic shaped product will have even better mechanical strength, for example, a three-point bending strength of 100 MPa or more.

[0071] In ceramic shaped articles where the particle sizes x and y of the X and Y phases and the particle size z of the Z phase are in the relationship z / x<0.5 and z / y<0.5, the Z phase, which has a relatively small particle size relative to the other phases, is thought to act as a link between the other phases, which have a relatively large particle size. As a result, the shaped article has high mechanical strength and excellent workability (toughness) with little chipping during machining. In addition, it has improved wear resistance. From this perspective, the more preferable relationship between x, y, and z is z / x<0.35 and z / y<0.35.

[0072] It is preferable that the particle sizes of the X and Y phases are relatively large, since this reduces the porosity of the shaped product and increases its density. From this perspective, x and y are preferably 3 μm or more, and more preferably 5 μm or more. On the other hand, in order to obtain sufficient mechanical strength, x and y are preferably 30 μm or less. Furthermore, when the particle sizes of x and y are within the above ranges, the ceramic shaped product of the present invention can have better processability. In order to obtain better processability, it is preferable that z is small, specifically, it is preferably less than 5 μm, and more preferably, z is less than 3 μm.

[0073] The ceramic shaped article of the present invention is preferably produced by applying the above-described production method of the present invention. The preferred combination of the three phases is a phase mainly composed of Al2O3, a phase mainly composed of rare earth aluminate, and a phase mainly composed of ZrO2. Al2O3, rare earth aluminate, and ZrO2 are in a eutectic relationship, which allows the stable formation of a complex phase-separated structure consisting of three phases.

[0074] Preferable rare earths constituting the rare earth aluminate include gadolinium, yttrium, and terbinium. Examples of rare earth aluminates include GdAlO3, Y3Al5O 12 The crystal structure of each phase varies slightly depending on the manufacturing process, but it is preferable that each of the three-phase eutectic has the crystal structure described above.

[0075] As a preferred embodiment, we will describe a method for manufacturing a ceramic article that is primarily composed of a three-phase eutectic consisting of a phase primarily composed of Al2O3 (corresponding to the X phase), a phase primarily composed of GdAlO3 (corresponding to the Y phase), and a phase primarily composed of ZrO2 with a fluorite structure (corresponding to the Z phase). Al2O3 powder and Gd2O3 powder are mixed, preferably to form a eutectic composition, to obtain a mixed powder. The mixed powder is placed on a base (corresponding to step (i)), and an energy beam is irradiated thereto to melt and solidify the mixed powder, thereby obtaining a shaped object (corresponding to step (ii)). Depending on the energy beam irradiation conditions, the shaped object thus formed may at least partially contain the Al2O3-GdAlO3 two-phase. Microcracks are also formed in the shaped object. The shaped object is then absorbed into a zirconium-containing liquid, distributing the zirconium component in the microcracks of the shaped object (corresponding to step (iii)). Next, the shaped object is preferably heated at a temperature equal to or higher than the Al2O3-GdAlO3-ZrO2 three-phase eutectic point but lower than the Al2O3-GdAlO3 two-phase eutectic point (corresponding to step (iv)). For example, in the case of this material system, heating is preferably performed at a temperature of approximately 1650°C to 1710°C. By heating within this temperature range, the microcracks melt and shrink while maintaining the shape of the object, and the zirconium component diffuses into the crystals of the object.The object then recrystallizes with the zirconium component incorporated, becoming a three-phase eutectic object consisting of a phase mainly composed of ZrO2 with a fluorite structure, a phase mainly composed of Al2O3, and a phase mainly composed of GdAlO3.

[0076] The average grain size of the Al2O3-based phase and the GdAlO3-based phase, which were originally present in the molded product before the heating step (iv), increases with heating. However, the average grain size of the ZrO2-based phase, which is formed for the first time in step (iv), is smaller than the average grain size of the other two phases. In this way, the formation of a ZrO2-based phase, which has a smaller average grain size than the other phases, in the molded product strengthens the bonding strength between the crystalline structure of the molded product, greatly improving the wear resistance of the molded product. Additionally, the molded product has high machinability, allowing for precise finishing with minimal grain chipping.

[0077] In contrast, conventional processes, such as mixing raw material powders of the materials that make up the object, molding them, and then heating and sintering them, make it difficult to create the clear grain size differences between the three phases described above in the dense state after molten and solidified. In other words, it is believed that conventional sintering processes cannot be used to manufacture ceramic articles such as those of the present invention. Furthermore, if an attempt is made to melt the powder that makes up the object in order to increase the density of an object produced by a conventional sintering process or to create a fine eutectic structure within the object, the entire object must be melted, which would dull the edges of the object and destroy its fine shape. From these perspectives, it is important to create a molded object with microcracks that connect to the interior by melting and solidifying the powder through the irradiation of an energy beam, and then to heat the microcracks by distributing components that form a eutectic with the constituent material of the molded object.

[0078] FIG. 9(a) is a diagram showing a schematic representation of the phase-separated structure and the size relationship of the crystal grains constituting each phase observed in the cross section of a ceramic article of the present invention. The article has a phase-separated structure consisting of three phases: X phase 801, Y phase 802, and Z phase 803. The crystal grains 811 constituting the X phase and the crystal grains 812 constituting the Y phase have larger average grain sizes than the crystal grains 813 constituting the Z phase. In contrast, FIG. 9(b) is a schematic representation of the cross section of a conventional ceramic article produced by mixing raw material powders, molding, and then heating and sintering. Although the article has a three-phase eutectic phase-separated structure, there is no significant difference in the grain sizes of the crystal grains constituting each phase. Ceramics with this structure have poor machinability and cannot achieve the effects of the present invention.

[0079] As described above, a ceramic shaped object composed of a three-phase eutectic consisting of a phase mainly composed of Al2O3, a phase mainly composed of a rare earth aluminate, and a phase mainly composed of ZrO2 is preferred because a complex phase-separated structure can be stably formed by the manufacturing method of the present invention. The most preferred ceramic shaped article is one in which the phase mainly composed of Al2O3 is the X phase, the phase mainly composed of rare earth aluminate is the Y phase, and the phase mainly composed of ZrO2 is the Z phase.

[0080] A shaped article having such a separation layer structure can be produced by first preparing a shaped article containing an Al2O3-rare earth aluminate two-phase eutectic, then dispersing zirconium components into the microcracks of the shaped article, and heating the article at a temperature equal to or higher than the Al2O3-rare earth aluminate-ZrO2 three-phase eutectic point but lower than the Al2O3-rare earth aluminate two-phase eutectic point.

[0081] A shaped object in which the phase primarily composed of Al2O3 is the X phase, the phase primarily composed of rare earth aluminates is the Y phase, and the phase primarily composed of ZrO2 is the Z phase has a three-phase eutectic point of 1600°C or higher and 1700°C or lower. When the three-phase eutectic point of a ceramic shaped object is 1700°C or lower, sufficient thermal uniformity is achieved within the shaped object during heating corresponding to step (iv). This allows for localized melting of only the microcracked portions throughout the shaped object, thereby improving the mechanical strength of the shaped object while maintaining its shape. Furthermore, a three-phase eutectic point of 1600°C or higher is preferable because it enables the production of ceramic articles that require heat resistance.

[0082] In the case of a ceramic object composed of a three-phase eutectic consisting of a phase mainly composed of Al2O3, a phase mainly composed of rare earth aluminate, and a phase mainly composed of ZrO2, there are no restrictions on the combination of materials corresponding to the X, Y, and Z phases of the ceramic object. For example, a shaped article may be fabricated to contain a rare earth aluminate-ZrO2 two-phase eutectic, and then aluminum components may be dispersed throughout the shaped article and heated. In this case, the rare earth aluminate-ZrO2 two-phase structure becomes the X and Y phases with relatively large grain sizes, while Al2O3 becomes the Z phase with a relatively small grain size, resulting in a ceramic article having the effects of the present invention.

[0083] Alternatively, a shaped article may be fabricated containing an Al2O3-ZrO2 two-phase eutectic, and then the rare earth component may be dispersed throughout the shaped article and heated. In this case, the Al2O3-ZrO2 two-phase structure becomes the X and Y phases with relatively large grain sizes, and the rare earth aluminate becomes the Z phase with a relatively small grain size, resulting in a ceramic article having the effects of the present invention.

[0084] The Z phase is preferably a metal oxide with a fluorite structure. This makes it easier to achieve the effects of improving the wear resistance and workability described above. Furthermore, it is preferable for the Z phase to contain a rare earth element, as this stabilizes the formation of the Z phase. It is more preferable for the ratio of the rare earth element contained in the Z phase to be 0.20 mol or more and 0.40 mol or less per mol of the other metal elements contained in the Z phase, as this will result in a Z phase with sufficient temperature stability. It is even more preferable for the ratio to be 0.25 mol or more and 0.35 mol or less.

[0085] The main component of the Z phase is preferably zirconium oxide or hafnium oxide. When the Z phase contains zirconium oxide or hafnium oxide, the resulting shaped product has high mechanical strength. When the Z phase is primarily composed of zirconium oxide or hafnium oxide, if the zirconium and hafnium elements are 0.2 mol % or more among the metal elements constituting the ceramic shaped product, a sufficient amount of Z phase is formed in the ceramic shaped product, resulting in improved wear resistance and processability. If the zirconium and hafnium elements are less than 3 mol % among the metal elements constituting the ceramic shaped product, this is preferable because it can suppress the expansion of the Z phase grain size.

[0086] The above has been described using examples of shaping using powder whose main component is aluminum oxide and three-dimensional objects whose main component is aluminum oxide, but the present invention is not limited to cases where the main component is aluminum oxide. Any ceramic material with a three-phase eutectic system can be used to produce the ceramic shaped object of the present invention. Specifically, a shaped object is first produced from powder of a material that forms a two-phase eutectic relationship. Then, the material that forms the two-phase eutectic relationship and a component that forms a three-phase eutectic relationship are dispersed into the microcracks of the shaped object, and the object is heated at a temperature equal to or higher than the three-phase eutectic point but lower than the eutectic points of the two phases originally contained in the shaped object.

[0087] <Evaluation method> The mechanical strength of the molded object can be evaluated by a three-point bending test based on R1601, the JIS standard for room temperature bending strength testing of fine ceramics. The three-point bending strength is calculated as 3×P×L / (2×w×t), where P [N] is the maximum load at which the test piece breaks, L [mm] is the distance between the external supports, w [mm] is the width of the test piece, and t [mm] is the thickness of the test piece. 2 ) (Equation 1) was used to calculate.

[0088] The wear resistance of a molded object can be evaluated by the wear rate of the molded object when it is ground under certain conditions. The wear rate D is the amount of wear per unit time, for example, D [mm 3 / min]. The smaller the wear rate D, the better the wear resistance. The machinability of a molded object can be evaluated by the number of chippings on the edge of the cut surface when the molded object is cut under certain conditions.

[0089] The relative density [%] was calculated by dividing the bulk density (weight divided by volume) of the shaped object by the theoretical density. The theoretical density was calculated from the crystal structure. The crystal structure was identified by X-ray diffraction measurement and Rietveld analysis.

[0090] The phases that make up ceramic objects can be investigated using X-ray diffraction, electron diffraction, etc. In particular, by combining an electron backscatter diffraction (EBSD) detector and an energy dispersive X-ray spectroscopy (EDX) detector attached to a scanning electron microscope (SEM), it is possible to analyze the phase separation structure and crystal grains. For small phases such as the Z phase, the composition and crystal structure can be analyzed using a transmission electron microscope (TEM). The grain size of the crystal grains that make up the phase can be obtained by observing more than 300 crystal grains in the same phase on the cross section of the molded object using EBSD or other methods, and calculating the average circle equivalent diameter of each crystal grain.

[0091] Furthermore, the amount of metal elements that make up powders and shaped objects can be measured using SEM-EDX, TEM-EDX, electron beam diffraction, inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), X-ray fluorescence spectrometry (XRF), etc. [Example]

[0092] The method for producing a shaped object according to the present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0093] Example 1 <Step (i) and Step (ii)> α-Al2O3 powder with an average particle size of approximately 20 μm, Gd2O3 powder with an average particle size of approximately 35 μm, and Tb2O powder with an average particle size of approximately 5 μm. 3.5 Prepare powder (Tb4O7 powder) with a molar ratio of Al2O3:Gd2O3:Tb2O 3.5 Each powder was weighed so that the ratio of the powders was 77.4:20.8:1.8. The weighed powders were mixed in a dry ball mill for 30 minutes to obtain a mixed powder (raw material powder). The average particle size in the present invention is the median size, and is the particle size (D 50 ) The composition of the raw material powder was analyzed by ICP emission spectrometry, and the content of zirconium oxide was found to be less than 1 mol %.

[0094] Next, the shaped object of Example 1 was fabricated through steps similar to those shown in FIGS. 1(a) to 1(h) described above. The object was formed using a ProX DMP 100 (product name) manufactured by 3D SYSTEMS, which is equipped with a 50 W fiber laser (beam diameter: 65 μm).

[0095] First, a 20 μm-thick first powder layer made of the raw material powder was formed on an alumina base using a roller (step (i)). Next, a 30 W laser beam was irradiated onto the powder layer to melt and solidify the material powder in a rectangular area of ​​5 mm × 42 mm. The drawing speed was 100 mm / s to 140 mm / s, and the drawing pitch was 100 μm. Furthermore, as shown in Figure 6(a), the drawing lines were positioned so that they were at a 45-degree angle to each side of the rectangle.

[0096] Under the above conditions, the powder layer was irradiated with a laser beam to melt and solidify the powder within a rectangular area measuring 5 mm × 42 mm (step (ii)). Next, a new 20 μm-thick powder layer was formed using a roller to cover the melted and solidified area (step (i)). As shown in Figure 6(b), the laser was irradiated onto the powder layer directly above the rectangular area, perpendicular to the first layer's drawing line, to melt and solidify the powder within a 5 mm × 42 mm area (step (ii)). This process was repeated to fabricate a prismatic object with a base measuring 5 mm × 42 mm and a height of 6 mm for use in a three-point bending strength test. A similar process was used to fabricate a prismatic object with a base measuring 6 mm square and a height of 6 mm for a wear resistance test. Observation of the surfaces of these objects with an optical microscope revealed that the surface irregularities were less than 30 μm. Each of the molded objects was separated from the alumina base and polished to obtain a molded object of W40mm x D4mm x H3mm for the three-point bending strength test (Figure 7(a)) and a molded object of W5mm x D5mm x H5mm for the wear resistance test (Figure 7(b)).

[0097] <Step (iii) and Step (iv)> The zirconium component-containing solution was prepared as follows. A solution of 85% by weight of zirconium butoxide (zirconium (IV) butoxide (hereinafter referred to as Zr(On-Bu)4)) in 1-butanol was prepared. The Zr(On-Bu)4 solution was dissolved in 2-propanol (IPA), and ethyl acetoacetate (EAcAc) was added as a stabilizer. The molar ratio of each component was Zr(On-Bu)4:IPA:EAcAc=1:15:2. The mixture was then stirred at room temperature for approximately 3 hours to prepare the zirconium component-containing solution. When the zirconium component-containing liquid is heated in the atmosphere, zirconium oxide is produced. The above-mentioned shaped article processed for testing was immersed in the zirconium component-containing liquid, degassed under reduced pressure for 1 minute to allow the liquid to penetrate deep into the shaped article, and then air-dried for 1 hour (step (iii)).

[0098] Next, the shaped object impregnated with the zirconium component-containing liquid was placed in an electric furnace and heated to 1670°C in an air atmosphere over 2.5 hours, and then held at 1670°C for 50 minutes. After that, the current was stopped and the object was cooled to 200°C or below over 1.5 hours (step (iv)).

[0099] In Example 1, the step of immersing the shaped object in a zirconium-containing liquid (step (iii)) and the step of heat treatment (step (iv)) were alternately repeated four times each. Three shaped objects measuring W40 mm x D4 mm x H3 mm were produced for a three-point bending strength test, one shaped object identical to the strength test for evaluating composition and structure, and one shaped object measuring W5 mm x D5 mm x H5 mm for an abrasion resistance test.

[0100] <Evaluation> The three-point bending test was performed using a compression testing machine manufactured by Instron Corp. Three shaped articles of Example 1, each measuring 40 mm wide x 4 mm deep x 3 mm high, were tested, and the average value of the three-point bending strength was 159.15 MPa.

[0101] The wear resistance was evaluated by the following method. The shaped object of Example 1, measuring W 5 mm x D 5 mm x H 5 mm, was placed on a #600 diamond grinding disc (manufactured by Musashino Electronics) rotating at 80 rpm, and was ground under a load of 0.5 kg. The wear rate was 1.03 mm 3 / min].

[0102] The machinability was evaluated by checking the number of chipped areas on the edge of the cut surface during the wear resistance evaluation. Specifically, an arbitrary 5 mm side of the cut surface was observed with an optical microscope, and the number of chipped areas on the side was counted. The number of chipped areas was counted when the maximum chipped width in the direction parallel to the side was 50 μm or more and the maximum chipped width in the direction perpendicular to the side was 50 μm or more. The machinability was evaluated as follows: A if there were no chipped areas, B if there were 1 to 3 chipped areas, and C if there were 4 or more chipped areas. Example 1 had 0 chipped areas, and the machinability was ranked as excellent, A.

[0103] Furthermore, the molded object was polished to a mirror finish, and the crystal structure and composition of the phases that make up the molded object were examined using X-ray diffraction, electron beam diffraction, SEM-EDX, and TEM-EDX. The phase separation structure and the average grain size of the crystal grains that make up each phase were analyzed using SEM-EBSD.

[0104] The shaped article of Example 1 was composed of three phases: an Al2O3 phase, a GdAlO3 phase, and a fluorite-structured zirconium oxide-based phase. The average grain sizes of the Al2O3 phase, the GdAlO3 phase, and the fluorite-structured zirconium oxide-based phase were 8.3 μm, 9.5 μm, and 1.6 μm, respectively. The main metal elements constituting the fluorite-structured zirconium oxide-based phase were Zr, Gd, and Tb, and the content of metal elements other than Zr, Gd, and Tb was less than 1 mol %. Furthermore, the proportion of rare earth elements among the metal elements contained in the fluorite-structured zirconium oxide-based phase was an average of 30 mol %.

[0105] The shaped article was subjected to ICP-AES analysis and ICP-MS analysis to determine the amount of Zr element contained in the shaped article. Of the metal elements constituting the shaped article of Example 1, the amount of Zr element was 0.9 mol %.

[0106] Examples 2 to 5 <Step (i) and Step (ii)> An intermediate object measuring W40 mm × D4 mm × H3 mm was prepared for the three-point bending strength test, and an intermediate object measuring W5 mm × D5 mm × H5 mm was prepared for the abrasion resistance test in the same manner as in Example 1. When the surfaces of the intermediate objects of Examples 2 to 5 were observed with an optical microscope, the irregularities on the surfaces of the objects were found to be 30 μm or less.

[0107] <Step (iii) and Step (iv)> In this step, the same zirconium component-containing solution as in Example 1 was used. The step of immersing the shaped object in the zirconium component-containing solution (step (iii)) and the step of heating the shaped object impregnated with the zirconium component-containing solution (step (iv)) were also carried out under the same conditions as in Example 1. In Example 2, steps (iii) and (iv) were carried out sequentially once each. In Example 3, steps (iii) and (iv) were repeated alternately twice each. In Example 4, steps (iii) and (iv) were repeated alternately three times each. In Example 5, steps (iii) and (iv) were repeated alternately five times each. In this manner, four shaped objects measuring 40 mm W × 4 mm D × 3 mm H and one shaped object measuring 5 mm W × 5 mm D × 5 mm H were obtained for each of Examples 2 to 5.

[0108] As in Example 1, the three-point bending strength, wear rate, relative density, and machinability of each of the molded objects of Examples 2 to 5 were evaluated, and the crystal structure and composition of the phases constituting the molded objects, the phase separation structure, and the average grain size of the crystal grains constituting each phase were analyzed. The results of measurement and evaluation of three-point bending strength, wear rate, relative density, and machinability for Examples 2 to 5 are shown in Table 1 together with the results for Example 1.

[0109] The shaped articles of Examples 2 to 5 were composed of three phases: an Al2O3 phase, a GdAlO3 phase, and a phase mainly composed of zirconium oxide with a fluorite structure. Hereinafter, the Al2O3 phase of the shaped articles of each Example will be referred to as the X1 phase, the GdAlO3 phase as the Y1 phase, and the fluorite-structured zirconium oxide phase as the Z1 phase. In each Example, the average grain sizes of the crystal grains constituting the X1 phase, Y1 phase, and Z1 phase will be denoted by x1, y1, and z1, respectively. The analysis results of the ratio of rare earth elements among the metal elements contained in the Z1 phase and the ratio of Zr among the metal elements constituting the shaped articles are shown in Table 2, along with the results of Example 1.

[0110] (Comparative Example 1) Four shaped objects measuring W 40 mm × D 4 mm × H 3 mm and one shaped object measuring W 5 mm × D 5 mm × H 5 mm were produced in the same manner as in Example 1, except that the step of immersing the shaped object in a zirconium component-containing liquid (step (iii)) and the step of heating the shaped object impregnated with the zirconium component-containing liquid (step (iv)) were not performed. As in Example 1, the shaped object of Comparative Example 1 was also evaluated for three-point bending strength, wear rate, relative density, and machinability, and the crystal structure and composition of the phases constituting the shaped object, the phase separation structure, and the average grain size of the crystal grains constituting each phase were analyzed. Table 1 shows the measurement and evaluation results for three-point bending strength, wear rate, relative density, and machinability. The shaped object of Comparative Example 1 was composed of an Al2O3 phase, a GdAlO3 phase, and an amorphous phase with compositional fluctuations. These phases were not in a three-phase eutectic relationship. Furthermore, no phase primarily composed of zirconium oxide with a fluorite structure was present.

[0111] (Comparative Example 2) A 40mm W × 4mm D × 3mm H molded object for a three-point bending strength test and a 5mm W × 5mm D × 5mm H molded object for an abrasion resistance test were prepared in the same manner as in Example 1, except that the step of immersing the molded object in a zirconium-containing liquid (step (iii)) was omitted. The molded object was placed in an electric furnace and subjected to a heat treatment. The temperature was raised to 1670°C in an air atmosphere over 2.5 hours, held at 1670°C for 50 minutes, and then the current was turned off and the object was cooled to below 200°C over 1.5 hours. This process was repeated three times to prepare four 40mm W × 4mm D × 3mm H molded objects and one 5mm W × 5mm D × 5mm H molded object for an abrasion resistance test. As in Example 1, the shaped object of Comparative Example 2 was also evaluated for three-point bending strength, wear rate, relative density, and machinability, and the crystalline structure and composition of the phases constituting the shaped object, the phase separation structure, and the average grain size of the crystal grains constituting each phase were analyzed. The measurement results of the three-point bending strength, depletion rate, and relative density are shown in Table 1. Analysis revealed that the molded product of Comparative Example 2 was composed of two phases: a phase consisting of Al2O3 and a phase consisting of GdAlO3. No phase consisting mainly of zirconium oxide with a fluorite structure was present.

[0112] (Comparative Example 3) α-Al2O3 powder with an average particle size of approximately 200 nm, Gd2O3 powder with an average particle size of approximately 200 nm, and ZrO2 powder with an average particle size of approximately 200 nm were prepared and weighed to a molar ratio of Al2O3:Gd2O3:ZrO2 = 75.7:20.3:4.0. The weighed powders were mixed in a dry ball mill for 30 minutes to obtain a mixed powder. Three parts by weight of PVA (polyvinyl alcohol) binder dissolved in pure water was added to the mixed powder, mixed in a mortar, and dried. The mixture was then ground and mixed in a dry ball mill for 10 hours to obtain a granulated powder. The granulated powder was placed in a mold and pressure-molded into a 3 mm thick, 1 cm diameter disk. The temperature was raised to 600°C in an air atmosphere over one hour, held at 600°C for three hours, then raised from 600°C to 1650°C over two hours and sintered at 1650°C for two hours. The fired comparative ceramics had large unevenness, like ripples of 100 to 300 μm, on the surface and sides. Because the unevenness of the sintered body was large, it was not possible to produce an evaluation object with a W40 mm × D4 mm × H3 mm shape using the manufacturing method of Comparative Example 3, and it was not possible to perform a three-point bending strength test. A block measuring W5 mm x D5 mm x H2 mm was cut out from the disk while avoiding any irregularities, and the same wear resistance test as in Example 1 was carried out on the W5 mm x D5 mm surface. The evaluation results of wear rate, relative density, and machinability are shown in Table 1.

[0113] The ceramic shaped article of Comparative Example 3 was composed of three phases: an Al2O3 phase, a GdAlO3 phase, and a zirconium oxide-based phase. Hereinafter, the Al2O3 phase of the comparative ceramic of Comparative Example 3 will be referred to as the X2 phase, the GdAlO3 phase as the Y2 phase, and the zirconium oxide-based phase as the Z2 phase. The average grain sizes x2, y2, and z2 of the crystal grains constituting the X2 phase, Y2 phase, and Z2 phase were 21 μm, 25 μm, and 15 μm, respectively. The ratios of the average grain size z2 of the crystal grains constituting the Z2 phase to the average grain sizes x2 and y2 of the crystal grains constituting the X2 phase and the Y2 phase were z2 / x2 = 0.71 and z2 / y2 = 0.60, respectively.

[0114] [Table 1]

[0115] [Table 2]

[0116] (Consideration) Fig. 8(a) is an optical microscope image of the object of Comparative Example 1, and Fig. 8(b) is an optical microscope image of the object of Example 1. The streaky microcracks seen in the object of Comparative Example 1 were hardly observed in the object of Example 1 formed by the manufacturing method of the present invention, indicating that the microcracks were reduced or eliminated by the manufacturing method of the present invention.

[0117] The results shown in Table 1 show that the three-point bending strength of each of the objects of Examples 1 to 5 produced by the manufacturing method of the present invention was significantly improved and the wear rate was significantly reduced compared to the object of Comparative Example 1. This shows that the manufacturing method of a shaped object of the present invention can significantly improve the mechanical strength and wear resistance of the object.

[0118] Comparing Examples 1 to 5, the more times steps (iii) and (iv) were repeated, the more the three-point bending strength of the shaped article improved and the rate of wear decreased, i.e., the more the mechanical strength and wear resistance were improved.

[0119] In Example 4, the three-point bending strength was significantly improved and the wear rate was significantly reduced compared to Comparative Example 2, which differed only in that impregnation with the zirconium-containing solution was not performed. These results demonstrate that the step (iii) of impregnating the intermediate shaped object with the zirconium-containing solution according to the present invention significantly contributes to improvements in mechanical strength and wear resistance. Examples 1 to 5, which satisfied z1 / x1<0.5 and z1 / y1<0.5, were superior in machinability and wear resistance compared to Comparative Example 3, which was produced by sintering raw material powders. In particular, Examples 1, 4, and 5, which satisfied z1 / x1<0.3 and z1 / y1<0.3, were ranked A in machinability, which was even better than Examples 2 and 3, which were ranked B.

[0120] In all examples, the surface irregularities of the shaped object were 30 μm or less. In contrast, in Comparative Example 3, firing was performed at a high temperature close to the eutectic point, resulting in partial melting, and although a high relative density was achieved, irregularities of 100 to 300 μm were observed on the surface and side of the ceramic shaped object. It was found that it is difficult to produce a structure that achieves both density and shape accuracy using the manufacturing method of Comparative Example 3 in a three-phase eutectic material system. Therefore, it was confirmed that the manufacturing method of the present invention enables manufacturing with higher manufacturing accuracy than the manufacturing method of the comparative examples.

[0121] As described above, the method for manufacturing a shaped article according to the present invention can improve the mechanical strength, wear resistance, and machinability of the shaped article while achieving high shaping accuracy. Furthermore, by adjusting the number of times that the step of absorbing the zirconium-containing solution and the heat treatment step are performed on the shaped article mainly composed of aluminum oxide, it is possible to obtain a ceramic article that has high shaping accuracy and improved mechanical strength, wear resistance, and machinability depending on the application. Next, mixed powder of silicon oxide and terbium oxide was used as the raw material powder to carry out molding in Examples 6 to 9, and evaluations were carried out.

[0122] (Examples 6 to 7) <Step (i) and Step (ii)> SiO2 powder with an average particle size of approximately 38 μm, Tb2O powder with an average particle size of 4 μm 3.5 Prepare powder (Tb4O7 powder) with a molar ratio of SiO2:Tb2O 3.5 The powders were weighed so that the ratio was 98.4:1.6. The weighed powders were mixed in a dry ball mill for 30 minutes to obtain a mixed powder (raw material powder). Next, the shaped objects of Examples 6 and 7 were produced using the same apparatus and process as in Example 1. However, the laser irradiation conditions were changed to a laser beam output of 47.5 W, a drawing speed of 60 mm / s, and a drawing pitch of 80 μm. Based on the slice data for forming a powder layer (step (i)) and creating a porous material with a porosity of 20%, a laser beam was irradiated within a rectangular area of ​​the powder layer measuring 5 mm x 42 mm to melt and solidify the powder (step (ii)). This process was repeated. A rectangular pillar-shaped object measuring 5 mm x 42 mm at the base and 6 mm in height was obtained, with a porous material with a porosity of approximately 20%. When the surface of the object was observed with an optical microscope, the irregularities on the surface were found to be less than 30 μm. The fabricated object was separated from the alumina base and polished to obtain a W40mm x D4mm x H3mm object (Figure 7(a)) for the three-point bending strength test.

[0123] <Step (iii) and Step (iv)> The zirconium component-containing liquid was prepared in the same manner as the zirconium component-containing liquid used in Example 1. The shaped article processed for testing was immersed in a zirconium component-containing liquid and air-dried in the same manner as in Example 1 (step (iii)). The shaped object impregnated with the zirconium component-containing liquid was placed in an electric furnace and heated. Specifically, the temperature was raised to 1685°C in an air atmosphere over 2.5 hours, and the temperature was maintained at 1685°C for 50 minutes. After that, the current was stopped and the object was cooled to 200°C or lower over 1.5 hours (step (iv)). In Example 6, the step of immersing the shaped object in a zirconium component-containing liquid (step (iii)) and the heat treatment step (step (iv)) were each performed once, to obtain one shaped object for a three-point bending strength test measuring W 40 mm × D 4 mm × H 3 mm. In Example 7, step (iii) and step (iv) were alternately repeated twice each to obtain one shaped object measuring W 40 mm x D 4 mm x H 3 mm.

[0124] (Examples 8 to 9) A shaped object was produced in the same manner as in Examples 6 and 7, except that an aluminum component-containing liquid was used in step (iii) and the conditions of step (iv) were changed accordingly. The aluminum component-containing solution was prepared by dissolving aluminum sec-butoxide in 2-propanol (IPA) and adding ethyl acetoacetate (EAcAc) as a stabilizer. The molar ratio of each component was aluminum sec-butoxide:IPA:EAcAc = 1:5:2. The solution was then stirred at room temperature for approximately 3 hours to prepare the aluminum component-containing solution. A shaped object processed for testing was immersed in the aluminum component-containing liquid, degassed under reduced pressure for 1 minute to allow the liquid to penetrate deep into the shaped object, and then air-dried for 1 hour (step (iii)). The intermediate shaped article impregnated with the aluminum component-containing liquid as described above was placed in an electric furnace and heated. Specifically, the temperature was raised to 1600°C in an air atmosphere over 2 hours, and the temperature was maintained at 1600°C for 30 minutes. After that, the current was stopped and the article was cooled to 200°C or lower over 1.5 hours (step (iv)). In Example 8, the process of immersing the molded object in an aluminum component-containing liquid (process (iii)) and the heat treatment process (process (iv)) were each performed once, and one molded object for three-point bending strength testing measuring W 40 mm × D 4 mm × H 3 mm was obtained. In Example 9, step (iii) and step (iv) were alternately repeated twice each to obtain one shaped object measuring W 40 mm x D 4 mm x H 3 mm.

[0125] Comparative Example 4 One molded object for the three-point bending test was produced in the same manner as in Example 6, except that the step of impregnating the molded object with a liquid containing zirconium or aluminum components (step (iii)) and the subsequent step of heating the molded object (step (iv)) were not performed.

[0126] <Evaluation> As in Example 1, the three-point bending strength was measured using a compression testing machine manufactured by Instron Corp. The three-point bending strength of one shaped object measuring W 40 mm × D 4 mm × H 3 mm for each of Examples 6 to 9 and Comparative Example 4 is shown in Table 3. [Table 3]

[0127] (Consideration) The shaped objects containing silicon oxide as the main component, according to Examples 6 to 9, which were produced by the manufacturing method of the present invention, had improved three-point bending strength compared to Comparative Example 4. This result indicates that microcracks can be reduced or eliminated by impregnating a shaped object produced by irradiating a powder containing silicon oxide as the main component with a laser with a liquid containing zirconium or aluminum, followed by heat treatment. Although the above has described shaping using powder whose main component is aluminum oxide or silicon oxide, the present invention is not limited to these. According to the manufacturing method of the present invention, it is possible to obtain a ceramic article with high shaping accuracy and enhanced mechanical strength according to the intended use. Furthermore, the ceramic article according to the present invention can achieve not only high mechanical strength according to the intended use, but also high wear resistance and machinability. [Industrial Applicability]

[0128] According to the present invention, it is possible to provide a method for manufacturing a molded object that utilizes the characteristics of direct molding, which allows for the production of objects with dense and complex shapes, while further improving the mechanical strength, wear resistance, and machinability of the object. Furthermore, it is possible to provide a ceramic molded object that has excellent mechanical strength, wear resistance, and machinability while maintaining shape accuracy. [Explanation of symbols]

[0129] 100 Sculptures 101 powder 102 Powder layer 103 Uncoagulated powder 110 Object of desired shape 130 Foundation 151 Stages 152 Roller 180 Energy Beam Source 181 Scanner section 190 Liquid injection nozzle 201 Cladding Nozzle 202 Powder supply hole 203 Energy Beam 801 X phase 802 Y phase 803 Z phase

Claims

[Claim 1] A method for manufacturing a ceramic article by repeatedly irradiating powder with an energy beam based on three-dimensional data of an object to be manufactured, thereby melting and solidifying the powder, the method comprising: A manufacturing method comprising a step of forming a phase separation structure including a three-phase eutectic of X, Y, and Z phases, wherein the average grain size of a plurality of crystal grains constituting the X phase is 5 μm or more, the average grain size of a plurality of crystal grains constituting the Y phase is 5 μm or more, and the average grain size of a plurality of crystal grains constituting the Z phase is less than 5 μm.

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