Powder for ceramic molding, ceramic molded object, and manufacturing method thereof

Abstract

To provide: a powder for laser shaping that is capable of stable shaping and makes it possible to obtain a three-dimensional shaped article with ensured shaping precision; and a method for using the powder for laser shaping.SOLUTION: A powder for ceramic shaping is for obtaining a shaped article by repetition of successive sintering or melting and solidification of the powder by a laser light irradiation unit, wherein: the powder includes a plurality of compositions; at least one composition from among the compositions is an absorbent body that shows relatively higher absorption of the laser light than the other compositions; and at least part of the absorbent body is changed in response to irradiation with the laser light into another composition with a relatively lower rate of absorption of the laser light. A method for using the powder is also provided.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a powder used in forming a ceramic shaped object by laser irradiation and a manufacturing method using the powder. [Background technology]

[0002] In recent years, additive manufacturing technology has advanced, and particularly in the metals field, powder bed fusion has enabled the creation of dense and diverse objects. This denseness is due to the fact that the object is obtained as a solidified structure by effectively melting it. In this context, the possibility of applying this technology to ceramics manufacturing has also been discussed, and many efforts have been reported. To melt ceramics in the same way as metals, a corresponding amount of energy must be input, but unlike metals, light diffusion within the powder makes it difficult to achieve uniform melting, making it difficult to achieve manufacturing precision. Therefore, by limiting the process to sintering rather than melting, objects were formed with the aim of ensuring manufacturing precision, but they lacked density.

[0003] In light of this situation, for example, Non-Patent Document 1 proposes a method of using an Al2O3-ZrO2 eutectic system to lower the melting point and form a microstructure specific to eutectic systems when melted and solidified, thereby achieving high mechanical strength. However, although this method succeeded in improving the density of the molded object, numerous protrusions occurred on the surface of the molded object, and the molding precision was not sufficient. [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] The wavelength of the laser light is Nd:YAG (approximately 1 μm), and even if the melting point is reduced using a eutectic system, neither Al2O3 nor ZrO2 exhibits clear absorption, so a considerable amount of energy is required to melt and solidify the material system. In such a system, light diffusion occurs in the powder, which can cause issues such as uneven melting in the desired shaped area and the creation of wide, unevenly sintered areas around it.

[0006] Furthermore, there was a problem that areas where the process had already been completed, such as nearby areas during laser scanning or in the stacking direction, could be processed again due to the absorption of laser light, which could have a negative impact on modeling accuracy.

[0007] Therefore, in order to improve the molding accuracy, a material was needed that could suppress light diffusion in the powder, absorb the laser wavelength, and reduce or eliminate the absorption effect in areas that had already been molded so that the laser light would not be reabsorbed and affected. [Means for solving the problem]

[0008] The ceramic molding powder of the present invention is a ceramic molding powder for obtaining a molded object by repeatedly sequentially sintering or melting and solidifying the powder in the laser light irradiated area, characterized in that the powder contains multiple compositions, at least one of the compositions is an absorber that exhibits relatively higher absorption of the laser light than other compositions, and at least a portion of the absorber is changed to another composition that exhibits relatively lower absorption of the laser light upon irradiation with the laser light.

[0009] In addition, in the production of a ceramic shaped object in which a shaped object is obtained by repeatedly sequentially sintering or melting and solidifying powder in an irradiated area of ​​laser light, (i) placing the ceramic shaping powder in a laser irradiation area; (ii) a step of irradiating the powder for ceramics molding with a laser based on three-dimensional modeling data, thereby sintering or melting the powder for ceramics molding and then solidifying it; and (iii) repeating steps (i) and (ii) to produce a shaped object; The present invention is characterized by having the following. [Effects of the Invention]

[0010] When the ceramic molding powder of the present invention is used, a portion of the absorber changes to another composition with relatively low absorption of the laser light upon irradiation with laser light, making the sintered or melted region less susceptible to the effects of laser irradiation during subsequent molding. Furthermore, because the absorber has a relatively higher absorption of the laser light than the other compositions that make up the powder, light diffusion can also be reduced. As a result, it is possible to manufacture ceramic molded objects with high molding accuracy. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing an example of a molding apparatus to which the powder of the present invention can be applied. [Figure 2] FIG. 10 is a diagram showing another example of a molding apparatus to which the powder of the present invention can be applied. [Figure 3] FIG. 1 is a conceptual diagram showing the temperature rise process of a powder containing the absorbent of the present invention and a reference powder not containing the absorbent. [Figure 4] FIG. 10 is a diagram showing the measurement results of the amplitude of the contour of the boundary between the laser irradiated region and the non-irradiated region. [Figure 5] FIG. 2 is a diagram showing a process of irradiating the powders of Examples 8 to 25 of the present invention with laser light. [Figure 6] FIG. 1 shows shaped objects made using the powders of Examples 8 to 25 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, the powder, composition, and absorber of the present invention will be described. A powder is an aggregate of particles that can be recognized as isolated grains. A powder is composed of multiple compositions. A composition is composed of multiple components (elements or compounds). A powder composed of multiple compositions means that multiple types of particles composed of a single composition are mixed, or that one or multiple types of particles composed of multiple compositions are mixed. An absorber is defined as a composition that has a relatively high absorption capacity for the laser light used compared to the other compositions that make up the powder. In other words, an absorber has the highest absorption capacity for laser light among the compositions contained in the powder. At least one composition that makes up the powder of the present invention is an absorber that can absorb laser light. The absorber's absorption capacity is preferably 10% or more for laser light of the wavelength used. An absorption rate of 40% or more is more preferable, and an absorption rate of 60% or more is most preferable. The absorptance of a single absorber can be measured using a general spectrometer, and an integrating sphere is used to irradiate the absorber, which is placed in a sample dish, with light of the expected wavelength (near the laser wavelength used in manufacturing), and measurement is performed. The absorptance is calculated from the ratio of the reference data when there is no sample.

[0013] (powder) The powder of the present invention is composed of two or more types of compositions, and the compositions include at least one type of absorbent composition. Each particle constituting the powder may be composed of a single composition, or one particle may be composed of multiple compositions. The cases will be explained below in order.

[0014] First, there is the case where the powder is composed of particles of a single composition. For example, if the multiple compositions are composed of three types of materials, Al2O3, ZrO2, and Tb4O7 (absorber), the powder will be composed of a mixture of Al2O3 particles, ZrO2 particles, and Tb4O7 particles.

[0015] Next, there is a case where the powder contains particles composed of two or more types of compositions. As an example, if the composition is composed of three types of compositions, Al2O3, ZrO2, and Tb4O7 (absorber), it may be composed only of particles consisting of Al2O3-ZrO2-Tb4O7, or it may be composed of Al2O3-ZrO2 particles and Tb4O7 particles, where Al2O3-ZrO2 constitutes the same particles. In particular, when the absorber is composed by containing other compositions in the same particles, it is preferable to maintain the Tb4O7 state in the case of Tb4O7, which is an example of the absorber of the present invention. Furthermore, it is preferable that the absorber composition constitutes particles alone, regardless of the composition of the other compositions.

[0016] Furthermore, for the powder of the present invention, the fluidity of the powder is important when forming a powder bed layer using a recoater in powder bed fusion or when spraying powder from a nozzle in cladding. It is preferable to use a powder that satisfies a fluidity index of 40 [sec / 50 g] or less. To ensure fluidity, the particles are preferably spherical. However, spherical shape is not essential as long as the above fluidity index is satisfied.

[0017] Furthermore, it is preferable that the particle size of the composition constituting the absorbent body (the particle size is not that of a single particle but the median value of a group of particles having the same composition) is 1 / 5 or less of the particle size of the composition other than the absorbent body. Therefore, since it is preferable that the particle size of the particles constituting the absorbent body is 1 μm or more and 10 μm or less, it is important that the particle size of the composition other than the absorbent body is 5 μm or more, satisfying the above condition.

[0018] Furthermore, the powder of the present invention preferably does not contain a resin binder. If a resin binder is contained, it may be explosively burned away by laser irradiation, which may cause voids or the like to be present in the shaping region. Furthermore, if carbon is contained, it will combine with oxygen to form a gas, and the volume occupied by the carbon component may become voids, so it is preferable that the carbon content be low. Therefore, the carbon content is preferably 1000 ppm or less in molar ratio relative to the metal elements of the multiple compositions that make up the powder. Furthermore, if carbon is contained, it will oxidize and gasify upon laser irradiation, which will have a negative effect on the shaping process, so it is preferable that it is incorporated into the shaped object, as in the absorber of the present invention, by changing into a different composition upon laser irradiation.

[0019] So far, we have described the absorber, composition, and particles. However, the ceramic molding powder of the present invention can be crystalline, amorphous, or a mixture thereof. Furthermore, the composition of the powder and the molded object does not need to be completely identical; differences in the oxidation state or nitride state are acceptable. Therefore, it is also preferable to control the atmosphere during the molding process, not only in the air atmosphere, but also in an inert state such as nitrogen or other rare gas atmosphere, a state that is easily reduced by partial hydrogen content or reduced pressure, or even an oxygen atmosphere. Such atmospheric control does not preclude the inclusion of a partially metallic composition as the raw material powder.

[0020] Although the present invention relates to a powder for ceramic molding, the molded object is not limited to being composed of 100% crystalline ceramics. If the desired physical properties are obtained, the molded object may contain amorphous regions or regions that have been reduced to a metallic state or the like.

[0021] (absorber) The absorber suitable for the present invention absorbs laser light and converts the powder at the irradiated portion of the laser light into a solidified mass by sintering or melting it with the heat of the laser light, and the absorber itself remains in the shaped object. At this time, a portion of the absorber is converted into another composition with a relatively low absorption capacity for the laser light and is incorporated into the shaped object. Therefore, the region converted into the solidified mass has a lower absorption capacity for the laser light than the powder before the laser light irradiation.

[0022] The function and effect of the absorbent body of the present invention will now be described in detail. The first effect is that the material efficiently absorbs the laser light used during manufacturing and heats up, which then spreads to other compositions within the area equivalent to the focal size of the laser light, causing a temperature rise. This effectively achieves localized heating, which clarifies the interface between the processed area (area irradiated with laser light) and the non-processed area (area not irradiated with laser light), improving modeling accuracy.

[0023] The second effect is that because the area where the laser light has been irradiated and the modeling process has been completed has low absorption, it is possible to prevent adjacent areas or areas below the layer where the process is about to be performed from absorbing the laser light again and becoming altered.In addition, because the impact on adjacent areas and areas below that have already been modeled is reduced, a wide process margin can be set for the laser irradiation conditions, and the adverse impact on modeling accuracy due to fluctuations in the irradiation conditions can be reduced.

[0024] When the ceramic shaping powder of the present invention is used to perform shaping by selective irradiation with laser light, shaping with high precision can be achieved due to the first and second effects described above.

[0025] This situation will be explained with reference to the conceptual diagram of Figure 3. The horizontal axis represents the laser irradiation time, and the vertical axis represents the temperature in the laser irradiation area. In lines A and B in Figure 3, line A represents the characteristics of a powder that does not contain an absorber. In line A, the temperature begins to rise upon laser irradiation, and the powder melts linearly beyond the melting point, reaching the molding temperature indicated by the dashed line. On the other hand, line B represents the characteristics of a powder that contains the absorber of the present invention. In line B, the temperature begins to rise rapidly upon laser irradiation due to the light absorption effect of the absorber, and the effect of the absorber decreases just before melting, resulting in a temperature rise rate similar to that of line A when no absorber is contained.

[0026] Powders that exhibit the characteristics of line A have poor heating efficiency, and a wide, low-density sintered area is formed at the boundary between the powder and the melted and solidified part in the area irradiated with the laser light, which has a wide impact on adjacent powder areas and makes it impossible to achieve spatial modeling precision.

[0027] On the other hand, powders exhibiting the characteristics of line B have good heating efficiency and can achieve localized heating. Therefore, when a laser irradiation area is formed, a sufficient temperature difference is maintained between adjacent areas, resulting in only a narrow sintered area at the boundary between the molten and solidified area and the powder, resulting in good molding accuracy. Furthermore, since the completed molding area after laser irradiation does not absorb light and exhibits characteristics similar to line A, even if the process conditions change and the laser light affects the existing molding area, the temperature rise caused by the laser light is relatively small, and this impact can be avoided. Furthermore, the area currently being irradiated with the laser and the area already irradiated are fused by thermal conduction between the two areas, maintaining the connection and strength of the boundary between the laser-drawn lines. Thus, when the characteristics of line B of the present invention are present, the two aforementioned effects can be obtained.

[0028] The absorber of the present invention can be any material that changes at least partly into another composition with relatively low absorption upon laser irradiation, but is preferably selected from metal oxides. This is because some metal oxides change the valence of the metal element due to the release of oxygen as the temperature rises, and change into another metal oxide with relatively low absorption of laser light (for example, Tb4O7 → Tb2O3, Tb 3+ This is because there are some compounds that are prone to undergoing reactions such as substitution of the Gd (gadolinium) site in GdAlO3. They also have a high affinity with other components that make up ceramics, making it possible for them to be incorporated into shaped objects.

[0029] Metal oxides whose valence changes function as a change in absorptivity for various laser wavelengths are preferably oxides of metals selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Hf, Ta, W, In, Sn, Bi, Ce, Pr, Sm, Eu, Tb, and Yb. For the Nd:YAG laser (1070 nm), which is a typical laser used for modeling, oxides of Tb and Pr are preferably used, and their oxidation states are Tb4O7 and Pr6O. 11 However, the present invention is not limited to the above ratios (composition ratios) of the molecular formulas, and other ratios or mixtures thereof may be used as long as the desired absorption effect is obtained.

[0030] Next, the terbium oxide that is most preferable as the composition of the absorber of the present invention will be described in detail as an example. Terbium oxide can take various forms, typically Tb4O7 and Tb2O3. Although the molecular formula is expressed as Tb4O7, it is not limited to a strict 4:7 ratio. In this case, Tb4O7 is Tb 4+ and Tb 3+ In Tb2O3, the Tb 3+ The high infrared absorption rate of Tb4O7 is remarkable around 1070 nm of Nd:YAG laser, and sometimes exceeds 60% and reaches 70%. 4+As the value of Tb decreases, the absorption rate decreases. 3+ In the Tb2O3 state, which is composed only of Tb, the ratio is about 7%. 4+ It is clear that the absorption rate decreases with a decrease in the absorber, and therefore terbium oxide (Tb4O7) containing tetravalent terbium as an absorber is suitable as one composition for realizing the present invention.

[0031] In addition, to obtain an absorption rate of 10% (measured with the absorber alone), Tb 4+ is Tb 3+ and Tb 4+ It is sufficient if it is present at approximately 10% of the total amount. Here, X-ray Absorption Fine Structure (XAFS) can be applied as a method for evaluating the valence. Since the rising energy of the absorption edge differs for each valence, it can be evaluated from the ratio. In addition, evaluation can be performed using common evaluation methods such as X-ray photoelectron spectroscopy (XPS: X-ray Photoelectron Spectroscopy or ESCA: Electron Spectroscopy for Chemical Analysis) and electron spin resonance (ESR).

[0032] In oxides with a metal element to oxygen ratio of 2:3, the metal element is stabilized at a valence of 3+, so after conversion to a solid, it exists in a solid solution state in other compositions (for example, Y2O3, Gd2O3, or other R2O3 (R: metal element)). Therefore, the region converted to the solid after molding does not show significant absorption. Also, in multi-element oxides, R 3+ In compounds where Tb is stable, a similar state can be achieved by substituting Tb at the R site. Furthermore, in ZrO2, Tb contributes to the stabilization of the fluorite structure by forming a solid solution, and the valence is also 3+. Thus, the absorber of the present invention can also function as a material for constructing shaped objects.

[0033] Furthermore, to achieve the effects of the present invention, it is preferable that the difference in absorptance between before and after the laser light irradiation process be 1.2 times or more, and more preferably 2 times or more. Alternatively, it is preferable that the absorptance be 50% or more before the process and 40% or less after the process. Alternatively, it is preferable that the absorptance be 60% or more before the process and 20% or less after the process. Using Tb4O7, an example of an absorber, as a composition is preferable to achieve this situation. Note that this absorptance is for the absorber alone.

[0034] The absorber can be effective if it is contained in multiple compositions, but it is more preferable that the absorber composition be contained in the powder at 0.5 vol% to 53 vol%. Here, vol% is used because it is important to consider how much area the absorber occupies relative to the laser light irradiation size (focus size), and the mol% notation cannot be used when the composition that makes up the powder changes.

[0035] The above lower limit of the absorber content is determined by the necessity of containing at least one absorber particle within the laser focus size. The upper limit is determined by the effect on the main composition of the object. When the laser focus size is 10 μm, the laser melted region can be considered to be a hemisphere with a diameter of 10 μm, and the state in which one absorber particle with a diameter of 1 μm exists in that region is approximately 0.5 vol%. Therefore, the lower limit of the absorber composition is preferably 0.5 vol% or more.

[0036] Regarding the upper limit, when Tb4O7 is added to Al2O3, which is commonly used as a structural ceramic, the upper limit is Tb3Al5O 12 By utilizing the properties of Al2O3 ceramics, Tb3Al5O 12 To form a composite system with Tb4O7, the amount must be 53 vol% or less. In this case, Tb3Al5O 12 Since a state in which a small amount of Al2O3 is dispersed at the grain boundaries in the main phase is realized, the upper limit is preferably 53 vol%.

[0037] The particle size of the absorber is also important, and is preferably 10 μm or less, more preferably 1 μm to 10 μm, and most preferably 1 μm to 5 μm. Here, the particle size in the present invention defines the median range of the particle size distribution of particles made of the same composition, and does not mean that particles with particle sizes outside the range are excluded. Furthermore, particle size measurement applies not only to particles in a single crystal state, but also to particles in a polycrystalline state or an aggregated state. The absorber composition may be composed of particles in a single state.

[0038] When the absorber composition is composed of particles alone, if the absorber content is 0.5 vol%, the particle size is 1 μm, and the packed bulk density of the powder layer is 50% of the true density, a laser focal size of 10 μm corresponds to a state in which one particle is contained within the heated area (a hemispherical volume consisting of the focal size diameter), and the absorber effect is obtained. Also, when the particle size is 10 μm, a laser focal size of 100 μm corresponds to a state in which one particle is contained within the heated area, so it is important to select the particle size of the absorber to match the laser focal size.

[0039] From the viewpoint of uniformity, it is more preferable that at least two or more absorber particles are contained within the laser focus size. The particle spacing between each absorber is preferably 100 μm or less, and more preferably 50 μm or less. It is also preferable to adjust the laser focus size so that this situation can be achieved. As described above, assuming that the laser focus size has an upper limit of 100 μm from the viewpoint of modeling accuracy, it is preferable that the particle size of the absorber is 1 μm or more and 10 μm or less, as described above. However, the laser focus size may be 100 μm or more depending on the desired modeling accuracy.

[0040] On the other hand, from the viewpoint of ensuring the fluidity of the powder, it is desirable that the median particle size distribution of the particles of the composition that is the base material of the shaped object and that is not the absorbent be spherical and have a shape of 5 μm or more. Furthermore, the particle size of the absorbent is in the range of 1 μm to 10 μm, but it is preferable that the particle size be as small as possible. This is because of the viewpoints of the dispersibility of the absorbent in the powder and high packing density. Furthermore, in the present invention, it is preferable that the particle size of the absorbent be 1 / 5 or less of the particle size of the composition other than the absorbent.

[0041] (Composition other than absorbent) The composition other than the absorber includes the composition that forms the main component of the ceramic structure. Because such compositions significantly contribute to the strength and other properties of the final product, they should be selected appropriately depending on the application. Therefore, by determining the absorber for the wavelength of laser light used during manufacturing, it is preferable to select one or more main components from metal oxides with relatively low absorption effects, and it is also preferable to select compounds or mixtures of these. In particular, aluminum oxide and zirconium oxide (stabilized or metastable) can be used as general-purpose structural ceramics. Silicon oxide, silicon nitride, and aluminum nitride can also be used. While silicon nitride exhibits laser absorption effects, its absorption rate does not change before and after the process, so it does not function as an absorber in the present invention. Other ceramic materials that can be selected include cordierite (2MgO·2Al2O3·5SiO2), zircon (ZrO2·SiO2), mullite (3Al2O3·2SiO2), yttrium oxide, and aluminum titanate. Mixtures of the above materials are also acceptable.

[0042] The composition as the main component may further contain small-diameter silicon oxide particles having a particle size of less than 5 μm. The function of these silicon oxide particles will be described in detail below.

[0043] When ceramic molding powder is irradiated with laser light, the absorber in the irradiated area absorbs the energy and generates heat. Because small-diameter silicon oxide particles have a particle size of less than 5 μm and are easily melted, the heat from the absorber first melts the small-diameter silicon oxide particles around the absorber. The molten small-diameter silicon oxide particles then transfer heat to other relatively large-diameter particles, which then melt. The molten small-diameter silicon oxide particles in the laser irradiation area soften and deform, contacting the other relatively large-diameter particles over a wide area and efficiently transferring heat to their surfaces. This allows for more even heat transfer to the other relatively large-diameter particles than in a powder that does not contain small-diameter silicon oxide particles. As a result, the temperature distribution within the ceramic molding powder during melting is reduced, and the cooling rate during solidification is more uniform across different locations. This reduces thermal stress, suppresses the occurrence of microcracks during solidification, and results in ceramic molded products with fewer microcracks. Another effect is that when silicon oxide components are contained in the powder or form compounds with other main components during solidification, the thermal conductivity becomes relatively low, rapid cooling during solidification is mitigated, and the occurrence of microcracks is suppressed. Ceramic shaped products with few microcracks have high mechanical strength and low water absorption, making them suitable for use in components that require strength and low water absorption, such as vacuum equipment parts.

[0044] As mentioned above, the particle size of the small-diameter silicon oxide particles is smaller than that of particles of other compositions, preferably less than 5 μm. When the powder is composed of multiple types of particles, the particle size of the small-diameter silicon oxide particles is preferably smaller than that of each of the multiple types of particles. This is because a small particle size makes it easier to lead the melting together with the absorber, and the softened small-diameter silicon oxide particles are distributed more evenly than other particles, further reducing the temperature distribution within the powder for ceramic molding during melting. From the perspective of flowability, the small-diameter silicon oxide particles are preferably spherical, but they may also have anisotropic shapes such as amorphous, plate-like, or needle-like. It is preferable that the small-diameter silicon oxide particles have a narrow particle size distribution. Having a uniform particle size allows them to be dispersed uniformly throughout the powder for ceramic molding and, upon softening, to be distributed more uniformly on the surfaces of particles of other compositions.

[0045] The mass of small-diameter silicon oxide particles contained in the powder for ceramics manufacturing is preferably 0.04% or more and 5.0% or less of the mass of the absorber particles. By containing 0.04% or more SiO2 particles, the water absorption rate can be made 1.0% or less, which is desirable.

[0046] Furthermore, when the mass of the small-diameter silicon oxide particles is 5.0% or less of the mass of the absorber particles, almost all of the small-diameter silicon oxide particles present between particles of the main component composition, etc., are melted. This is more desirable because it prevents the formation of unmelted particles that could reduce the mechanical strength of the ceramic object. Furthermore, after the small-diameter silicon oxide particles melt upon irradiation with laser light and act as a heat transfer medium, some of them turn into glass and are distributed on the surface and inside of the ceramic object. If the powder for ceramic molding contains a large number of small-diameter silicon oxide particles during solidification, numerous glass regions originating from the small-diameter silicon oxide particles will form in the ceramic object, potentially reducing the mechanical strength of the ceramic object. Therefore, it is more preferable that the mass of the small-diameter silicon oxide particles be 1.0% or less of the mass of the particles consisting of the main component composition.

[0047] The powder of the present invention is composed of multiple compositions, and preferably contains at least one absorbent component and at least one of aluminum oxide, zirconium oxide, and silicon oxide as the main component forming the ceramic structure. Aluminum oxide, zirconium oxide, and silicon oxide are preferred because they have lower absorption capacity than the absorbent. They also form eutectic systems with many materials, and by expressing their microstructure, they can maintain high strength and also achieve a low melting point. For example, when aluminum oxide is mixed with Tb4O7, which is an absorbent, it changes from Tb4O7 to Tb3Al5O during molding. 12 On the other hand, in zirconium oxide, Tb 3+ In this state, the silicon dioxide plays a role in stabilizing zirconium oxide in a tetragonal crystal structure. It is also preferable that aluminum oxide and zirconium oxide are simultaneously included in the composition, resulting in a three-component structure together with the absorber. It is also possible to select not only a eutectic composition, but also Al2O3:ZrO2 = 85:15 wt% or 70:30 wt%. It is also preferable that silicon oxide be used as a shaped object, regardless of whether it is amorphous or crystalline. Furthermore, it is also preferable that silicon oxide be used as a two-component structure with the absorber, or a three-component or four-component structure containing zirconium oxide, aluminum oxide, or the like. Furthermore, the silicon oxide-containing shaped object may contain zircon, mullite, silicate with the absorber, or the like.

[0048] Although not limited in the present invention, it is preferable that the multiple compositions are contained in a relationship that forms a eutectic composition. The eutectic composition is the composition at the eutectic point shown in a eutectic phase diagram, but the laser beam-based shaping process of the present invention involves repeated heating and cooling at extremely high speeds, so the state is significantly different from the equilibrium state. Therefore, it is more preferable to define the eutectic composition as the composition range in which a eutectic structure is formed, and a range of ±10 mol% from the eutectic composition shown in the eutectic phase diagram is acceptable.

[0049] Next, preferably, at least one rare earth oxide that is not an absorber is included. The metal element of the rare earth oxide is preferably selected from Sc, Y, La, Ce, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu. In this case, depending on the composition, RAlO3 or R3Al5O may be used in place of R2O3 (or RO2 in some cases). 12 In some cases, it is also preferable that the composition is a eutectic composition. 3+ , Pr 3+ A material system consisting of the following is also applicable.

[0050] (Use of the ceramic molding powder of the present invention) The ceramics molding powder of the present invention is used in a manufacturing process (manufacturing method) of a shaped object by irradiation with laser light. The manufacturing process includes the steps of (i) placing the ceramics molding powder of the present invention in an irradiation area of ​​laser light, (ii) irradiating the ceramics molding powder with laser light based on three-dimensional modeling data to sinter or melt the ceramics molding powder and then solidifying it, and (iii) repeating the steps (i) and (ii) to form a shaped object.

[0051] The terms "sintering" or "melting and solidifying" used in this invention are not unique in that they refer to sintering when no powder is melted at all, or melting when no powder remains unmelted. Recently, the term "liquid phase sintering" has also been introduced, making the boundaries between these terms unclear. Therefore, the interpretation does not exclude sintering that only bonds the powder together, liquid phase sintering in which molten material surrounds the powder, or even melting in which some powder remains unmelted.

[0052] In the manufacturing process of the present invention, if necessary, it is also preferable to perform heat treatment after the step of forming the shaped object. In this case, there are no limitations on the heating means, and resistance heating, induction heating, infrared lamp, laser, electron beam, and other methods can be selected and used depending on the purpose. Heat treatment is also suitable for adjusting the crystal grain size of the shaped object in order to improve the density and strength of the shaped object. It is also preferable to impregnate or coat the shaped object with a glaze, regardless of whether it is organic or inorganic, during heat treatment.

[0053] In the above-described method of using the present invention, steps (i) and (ii) may be performed by spreading the powder of the present invention evenly and then irradiating the powder with laser light. Alternatively, steps (i) and (ii) may be performed by spraying the powder of the present invention at a predetermined location and then irradiating the predetermined location with laser light.

[0054] Specifically, the so-called powder bed fusion method and cladding method are techniques for obtaining a shaped object by repeatedly sintering or melting and solidifying the material in the irradiated area with laser light. While there are no limitations on the wavelength of the laser light used, it is preferable to use a laser with a desired focal size, such as 10 μm to 2 mm, adjusted using lenses or fibers. The focal size is one of the parameters that affects the shaping accuracy. To achieve a shaping accuracy of 0.1 mm, it is preferable that the line width is approximately the same, depending on the situation, and that the focal size be 100 μm or less. The laser light can be irradiated either continuously or in pulsed form. One example is an Nd:YAG laser with a wavelength of approximately 1070 nm.

[0055] The powder bed fusion method will be explained with reference to Figure 1. The equipment used for this method includes a powder container 11, a build stage 12, a recoater 13, a scanner 14, and a laser light source 15. The powder container 11 and build stage 12 move up and down as needed, while the recoater 13 manipulates the powder to spread it thinly and evenly over an area larger than the intended object. A cross-sectional shape of the object is then directly drawn onto the powder layer using a laser beam emitted from the laser light source 15 and the scanner 14. The drawn area is sintered or melted to solidify, and this process is repeated until the cross-section of the object is layered to form the final object.

[0056] The cladding method will be explained using Figure 2. This method involves spraying powder from multiple powder supply holes 22 in a cladding nozzle 21, irradiating the area where the powder is focused with laser light 23, and successively forming objects in desired locations. It is characterized by its ability to mold onto curved surfaces, etc.

[0057] The manufacturing process of the present invention as described above makes it possible to obtain a three-dimensional object that can be stably molded and has high molding accuracy. [Example]

[0058] [Example 1] This example demonstrates the improvement in molding accuracy achieved by incorporating the absorber of the present invention. To clarify the differences in molding accuracy, a 1.5 mm thick powder bed was melted and solidified by laser irradiation, and the boundary between the irradiated and unirradiated areas was observed. For Sample 1, a 1.5 mm thick powder bed was constructed using a mixture of Al2O3 powder, Gd2O3 powder, and Tb4O7 powder (composition ratio: Al2O3: 64.40 vol%, Gd2O3: 32.73 vol%, Tb4O7: 2.87 vol%). An Nd:YAG laser (1070 nm) with a focal diameter of 100 μm and a laser power of 30 W was used to irradiate 40 10 mm long lines at a 50 μm pitch at two laser irradiation speeds: 100 mm / sec and 250 mm / sec.

[0059] In addition, only Al2O3 powder was used as comparative sample 1, and a single crushed powder consisting of a (GdTb)AlO3-Al2O3 eutectic was used as comparative sample 2 (the raw material composition ratio for forming the eutectic was Al2O3: 64.40 vol%, Gd2O3: 32.73 vol%, Tb4O7: 2.87 vol%), and laser light was irradiated to these samples in the same manner as sample 1.

[0060] An example of the absorber used here is Tb4O7, which is 3+ Not only Tb 4+ In addition, the volume composition is calculated using a true density of Al2O3: 3.96 [g / cm 3 ], Gd2O3: 7.40 [g / cm 3 ], Tb4O7: 7.60 [g / cm 3 Even if this true density is a slightly different value, it does not affect the essence of the present invention.

[0061] Comparative sample 1 does not contain an absorber, and comparative sample 2 contains Gd in GdAlO3. 3+ It exists as a substitution at the Tb site. 4+ There is almost no absorption effect, and the absorption effect has disappeared. These two comparison samples without an absorber effect remained almost in a powder state under laser light irradiation conditions of 250 mm / sec, but melted at 100 mm / sec, and the solidified structure was clearly obtained. However, because there was no absorption effect, the heating state was largely non-uniform within the surface, and a two-dimensional solidified object was not obtained, and the solidified particles were in a state of rolling around after localized melting.

[0062] On the other hand, Sample 1 showed sufficient melting at 250 mm / sec, and it was confirmed that a two-dimensional object was formed in a planar shape. 3+Fluorescence observation under ultraviolet excitation confirmed that the tetravalent ions were incorporated into the powder, reaching a state of low absorption similar to that of comparative sample 2. In sample 1, the valence state of the absorber was such that the powder was mixed with the powder at an absorption rate of 60% or more, but after irradiation with laser light, fluorescence observation showed that there was almost no tetravalent ions present, resulting in an absorption rate of 30% or less. Furthermore, in comparative sample 2, fluorescence observation showed that the absorption rate was 30% or less from the powder state before molding, and there was no change after irradiation with laser light, remaining at 30% or less.

[0063] Figure 4 shows the results of calculating the deviation width of the boundary contours of a 3.83 mm wide image cut out from a micrograph of the boundary between the laser light irradiated area 42 and the unirradiated area 41. The width was 391 μm for Comparative Sample 1, 273 μm for Comparative Sample 2, and 85 μm for Sample 1. Furthermore, since the post-printing area of ​​Sample 1 and the powder of Comparative Sample 2 are in the same state in terms of the absorber effect, it was revealed that in Sample 1, the powder area where the absorber is functioning can be printed at 250 mm / sec, while the post-printing area has almost no effect at 250 mm / sec.

[0064] These results demonstrate that the inventive sample exhibited superior molding accuracy compared to the comparative sample, enabling the creation of a molded object without disturbing the processed area. Furthermore, the metal oxide Tb4O7, an example of an absorber, contains a 4+ valence, but the absorption characteristics changed in the molded area due to a decrease in the valence to 3+. The laser beam irradiation conditions vary depending on the ambient environment, material composition, powder layer thickness, and other factors, and are therefore not limited to the values ​​described in this example.

[0065] [Example 2] This example relates to the effect of adding Tb4O7, which is one candidate for an absorber. Tb4O7 has an absorption rate of 60% or more in the vicinity of 1070 nm, and is superior to Tb such as Tb2O3. 3+In Example 1, a mixed powder of Al2O3 powder, Gd2O3 powder, and Tb4O7 powder (composition ratio: Al2O3: 64.40 vol%, Gd2O3: 32.73 vol%, Tb4O7: 2.87 vol%) was used as Sample 1, and in addition, Samples 2, 3, 4, 5, and Comparative Sample 3 were compounded as shown in Table 1 below. In these cases, the particle size of the Tb4O7 powder used was approximately 2 μm.

[0066] These powders were spread evenly on an Al2O3 substrate to a thickness of approximately 20 μm and then irradiated with a Nd:YAG laser under the following conditions: focal spot size 20 μm, 10 W, 50 mm / sec, 12 lines of 4.5 mm length with a 50 μm pitch.

[0067] [Table 1]

[0068] For each sample, the width of the boundary between the irradiated and unirradiated areas was observed over a 2 mm range. The results are shown in Table 1. The table shows the amount of each composition (vol%), the width of the boundary (μm), and the effect of adding Tb4O7, as shown by the symbols: Excellent ◎, Good ○, and Unacceptable ×. The width of the boundary (fluctuation width) is an index essentially equivalent to the surface roughness of the side of the molded object; the larger the width, the rougher the surface of the molded object. The standard surface roughness of objects manufactured using metal powder is said to be around 10 μm. Therefore, cases with a roughness equivalent to this were evaluated as ◎. The same criteria were used for evaluation of other examples.

[0069] In comparative sample 3, which did not contain an absorber, many granular dissolved material was generated at the boundary, and the boundary width was the widest. On the other hand, it was found that the width of the boundary narrowed when an absorber was added (samples 1 to 5). In other words, it was found that the inclusion of the absorber of the present invention was effective. In particular, it was confirmed that the width was narrower in samples 1 to 3. Therefore, when Tb4O7, an example of an absorber of the present invention, was added, the evaluation results shown in Table 1 were obtained, and it was found that the effect of improving molding accuracy was obtained over a wide composition range compared to the case without any additives.

[0070] [Example 3] In this example, PrO, which is a candidate for the absorber, is used. 11 The effect of adding praseodymium oxide (PrO) 11 In addition, when the valence state is close to this, the absorption rate is 80% or more in the vicinity of 1070 nm, and Pr such as Pr2O3 3+ When the state is high, the absorption rate is less than 50%. Sample 6 is Al2O3 powder, Gd2O3 powder, Pr6O 11 Mixture of powders (composition ratio: Al2O3: 63.85 vol%, Gd2O3: 33.29 vol%, Pr6O 11 :2.86 vol%) was used. 11 The particle size of the powder used was approximately 2 μm. The true density of Al2O3 was 3.96 g / cm3. 3 ], Gd2O3: 7.40 [g / cm 3 ], PrO 11 :7.20[g / cm 3 Even if this true density is a slightly different value, it does not affect the essence of the present invention.

[0071] As in Example 2, these powders were spread evenly on an Al2O3 substrate to a thickness of approximately 20 μm, and then irradiated with an Nd:YAG laser under the following conditions: focal spot size 20 μm, 10 W, 50 mm / sec, 12 lines of 4.5 mm length at a 50 μm pitch.

[0072] [Table 2]

[0073] The width of the boundary between the irradiated and unirradiated areas was observed over a 2 mm range. The results are shown in Table 2. As shown in Table 2, the blending amounts (vol%) of each composition were as described above, and the width of the boundary was 42.7 μm, PrO 11 The effect of the addition was good.

[0074] The width of the boundary is narrower than that of Comparative Sample 3 in Example 2, and PrO 11 When added, the evaluation results shown in Table 2 were obtained, and it was found that the effect of improving the molding accuracy was obtained compared to when no additive was added.

[0075] [Example 4] This example relates to the effect of the absorber on compositions other than the absorber. The compositions examined are shown in Table 3. The volume composition was calculated using a true density of Al2O3: 3.96 [g / cm 3 ], ZrO2:5.68, Y2O3:5.01[g / cm 3 ], Tb4O7: 7.60 [g / cm 3 Even if this true density is a slightly different value, it does not affect the essence of the present invention. Powders containing these compositions were spread evenly on an Al2O3 substrate to a thickness of approximately 20 μm, and then irradiated with laser light. The conditions were a focal spot size of 100 μm, 30 W, and scanning speeds of 50, 100, 200, and 500 mm / sec to draw two 4.5 mm long lines at a 50 μm pitch, and the melting states were compared.

[0076] [Table 3]

[0077] Comparative Sample 4, which is pure Al2O3, was able to melt and solidify in a line shape up to 100 mm / sec, but Sample 7, which had an absorber added, was able to do so up to 500 mm / sec. Comparative Sample 5, which is pure ZrO2, was able to melt and solidify in a line shape up to 100 mm / sec, but Sample 8, which had an absorber added, was able to do so up to 500 mm / sec. Comparative Sample 6, which has a near-Al2O3-ZrO2 eutectic composition, was able to melt and solidify in a line shape up to 200 mm / sec, but Sample 9, which had an absorber added, was able to do so up to 500 mm / sec. Comparative Sample 7, which has a near-Al2O3-Y2O3 eutectic composition, was able to melt and solidify in a line shape up to 200 mm / sec, but Sample 10, which had an absorber added, was able to do so up to 500 mm / sec.

[0078] From the above results, it was confirmed that adding Tb4O7, an example of an absorber, to various systems enabled melting and solidification at higher scanning speeds. Therefore, this absorber contributes to improving the molding accuracy of objects regardless of the material system.

[0079] [Example 5] This example relates to the 3D printing property when an absorber is contained. The particle sizes of the compositions constituting the powder used in this example are shown in Tables 4 and 5. The particles of these compositions are also used as absorbers, such as Tb4O7 and Pr6O 11 All other samples were spherical.

[0080] [Table 4]

[0081] [Table 5]

[0082] Tables 6 and 7 show the volume compositions of the materials used. [Table 6]

[0083] [Table 7]

[0084] To calculate the volumetric composition, the true density was Al2O3: 3.96 [g / cm 3 ], ZrO2·Y2O3: 6.05 [g / cm 3 ], Gd2O3: 7.40 [g / cm 3 ], Y2O3: 5.01 [g / cm 3 ], SiO2: 2.20 [g / cm 3 ], Tb4O7: 7.60 [g / cm 3 ], PrO 11 :7.20[g / cm 3 ], Al2O3·ZrO2(85:15wt%):4.13[g / cm 3 ], Al2O3·ZrO2(70:30wt%):4.46[g / cm 3 ], 2MgO 2Al2O3 5SiO2:2.60[g / cm 3 Even if this true density is a slightly different value, it does not affect the essence of the present invention.

[0085] For this study, a 3D Systems ProX (trade name) series DMP100 modeling device was used. 6x6x6 mm models were fabricated using the fabrication conditions listed in Table 8 for Comparative Sample 8, which did not contain an absorbent, and Samples 11 to 24, which were composed of multiple compositions containing an absorbent. The modeling performance was evaluated as follows: no shape formed (×), slightly poor (◯), with rough surfaces and sides (◯), and models obtained according to the specified dimensions (◎). In all cases, the powder layer thickness was 20 μm, and an alumina plate was used as the substrate. The powder layer thickness refers to the value at which the fabrication stage 12 in Figure 1 is lowered. Because the powder layer melts and shrinks in the thickness direction upon laser light irradiation, the apparent powder layer thickness gradually increases with repeated layering, converging to a range of 67 to 133 μm. Therefore, although the average particle size of the compositions listed in Tables 4 and 5 is larger than the 20 μm powder layer used during fabrication, this does not pose a problem in use. For objects that could be printed, the surface roughness Ra was measured using Alpha-step (product name) manufactured by KLA Tencor to confirm the printing accuracy. Since the roughness was relatively greater on the side of the object than on the surface, the evaluation was performed on the side. The scan width during calculation was 1 mm.

[0086] [Table 8]

[0087] As shown in Table 8, in comparative sample 8, which does not contain the absorbent material of the present invention, although it partially dissolved like comparative sample 1 in Example 1, it was unable to maintain the shape of the object as a result of additive manufacturing. The other samples 11 to 24 were densely formed as additively manufactured objects, and it was possible to measure the surface roughness of the side surfaces. The absorber of the present invention improved the surface roughness, and in particular, it was possible to obtain objects with a roughness suppressed to around 10 μm, demonstrating that accurate manufacturing is possible.

[0088] [Example 6] This example relates to the case where the composition other than the absorber is individual particles and the case where it is the same particle. Sample 13 of Example 5 is compared with a sample in which Al2O3 and Gd2O3 are eutectic powders (a mixture of Al2O3 and GdAlO3) and Tb4O7 are mixed, and further, Sample 15 is compared with a sample in which Al2O3 and Y2O3 are eutectic powders (Al2O3 and Y3Al5O 12 The results were compared with a sample containing Tb4O7.

[0089] As in Example 5, a ProX (trade name) DMP100 from 3D Systems was used as the modeling device. A 6x6x6 mm model was produced under the modeling conditions in Table 11. The modeling properties were evaluated as follows: no shape was obtained: poor (×); roughness was observed on the surface or side: slightly poor (◯); and a model was obtained according to the specified dimensions: good (◎). In all cases, the powder layer thickness was 20 μm, and an alumina plate was used as the substrate.

[0090] [Table 9]

[0091] [Table 10]

[0092] [Table 11]

[0093] As shown in Table 11, both Samples 25 and 26 were rated as excellent in formability, with surface roughness of approximately 10 μm. Thus, it was confirmed that both Sample 25 compared to Sample 13 and Sample 26 compared to Sample 15 were excellent in formability when using a powder in which the composition constituted individual particles, and when using a powder in which the composition other than the absorbent was contained within the same particle, as in this example. This demonstrates that the effectiveness of the absorbent of the present invention is not dependent on the composition of the powder other than the absorbent.

[0094] [Example 7] This example relates to an example of tolerance to changes in laser light irradiation conditions when the absorber of the present invention is used. A mixed powder of Al2O3 powder, Gd2O3 powder, and Tb4O7 powder (composition ratio: Al2O3: 64.40 vol%, Gd2O3: 32.73 vol%, Tb4O7: 2.87 vol%), which is the powder composition of Sample 13 in Example 5, was used, and a ProX (trade name) DMP200 manufactured by 3D Systems was used as the modeling device.

[0095] The laser beam irradiation speed was fixed at 500 mm / s, and the laser beam irradiation line pitch was fixed at 130 μm. The laser power was changed to increase or decrease the energy density during modeling. The powder layer thickness was 25 μm, and an alumina plate was used as the substrate. A 6 x 6 x 6 mm model was created using the laser power shown in Table 12, and the modeling performance was evaluated as follows: no shape was obtained (poor ×); roughness occurred on the surface or side (slightly poor ◯); and a model was obtained according to the specified dimensions (good ◎).

[0096] [Table 12]

[0097] When the laser power was 65W, there was almost no melting and the shape of the printed object was distorted, resulting in a poor result (X). When the power was 75W and 84W, the energy required for melting was somewhat insufficient, resulting in the surface of the printed object becoming powdery and resulting in a slightly poor result (O). In the range of 95W to 140W, the surface of the printed object was flat and rated as good (◎). Furthermore, in the range of 146W to 154W, the amount of energy input was too high and the surface became wavy and tended to become uneven, resulting in a slightly poor result (O). At 160W, the energy input was too high and the shape of the printed object was distorted, resulting in a poor result (X).

[0098] From the above, it was confirmed that stable modeling was possible, at least in the range of 75 W to 154 W, with an energy density increase of approximately 2.0 times. This reflects the fact that the powder of the present invention has absorption ability only when in powder form, and after being incorporated into a model, it has low absorption rate and is less susceptible to the effects of laser light irradiation, so that even if the power of the laser light fluctuates, it is less likely to affect modeling.

[0099] [Example 8] This example is an example in which SiO2 particles were added. The powder for ceramic molding in this example was manufactured using the following procedure. As the main component, Al2O3 powder (purity 99.99% or more, particle size 20 μm) and Gd2O3 powder (purity 99.99% or more, particle size 20 μm) were mixed in a mass ratio of 1:1 and used. As the absorber, Tb4O7 powder (purity 99.9% or more, particle size 4 μm) was used. SiO2 particles with a purity of 99.9% or more and a particle size of 4 μm were used. The powders were weighed so that the mass ratio of the particles constituting the main component, the particles constituting the absorber, and the SiO2 particles was 96.4:3.5:0.14. The weighed powders were mixed in a dry ball mill for 30 minutes to obtain a mixed powder (powder for ceramics molding) (Sample 27).

[0100] The ceramic molding powder was dissolved by heating in dilute sulfuric acid, and its composition was analyzed by ICP atomic emission spectroscopy. The mass ratio of Al2O3, Gd2O3, Tb4O7, and SiO2 was 48.2:48.2:3.5:0.14, the same as the initial composition ratio. The content of other components was less than 0.2 mass% of the ceramic molding powder. From the composition ratio obtained by analysis, the mass α [%] of SiO2 particles relative to the mass of particles consisting of the composition other than the absorber (the main component constituting the ceramic structure) contained in the ceramic molding powder of Sample 27, i.e., α = SiO2 / (Al2O3 + Gd2O3 + ZrO2), was calculated to be α = 0.146 [%]. The mass β [%] of SiO2 particles relative to the mass of particles consisting of the composition constituting the absorber, i.e., β = SiO2 / (Tb4O7 + Pr6O 11) was calculated to be β = 4.03 [%]. The mass γ [%] of the particles that make up the main component and the particles that make up the absorber, that is, γ = (Tb4O7 + Pr6O 11 ) / (Al2O3+Gd2O3+ZrO2), the result was γ = 3.61%. When a portion of the powder for ceramic molding was analyzed using SEM-EDX (scanning electron microscope-energy dispersive X-ray spectroscopy), it was confirmed that SiO2 particles with a particle size of several μm were dispersed within the powder.

[0101] [Examples 9 to 25] Powders for ceramic molding of Samples 28 to 44 were produced as Examples 9 to 25 in the same manner as in Example 8, except that the raw material types and compounding ratios were changed according to Table 13. ZrO2 powder (purity 99.9% or more, particle size 15 μm) was used as zirconium oxide. Pr6O 11 The powder for ceramic molding of Samples 28 to 44 was analyzed for composition in the same manner as in Example 8, and the powder was found to contain Al2O3, Gd2O3, ZrO2, Tb4O7, Pr6O 11 The mass ratio of SiO2 and SiO2 was the same as the charged composition ratio. The contents of other components were less than 0.5 mass% of the powder for ceramics molding. From the composition ratio obtained by analysis, α, β, and γ were calculated in the same manner as in Example 8, and the results are summarized in Table 14. When a portion of the prepared powder for ceramics molding was analyzed by SEM-EDX, it was confirmed that SiO2 particles with a particle size of several μm were dispersed within the powder.

[0102] [Comparative Example] A comparative ceramic shaping powder was produced in the same manner as in Example 8, according to the blending ratios shown in Table 13. However, in this comparative example, SiO2 particles were not used, and the comparative ceramic shaping powder was composed only of Al2O3, Gd2O3, and Tb4O7 particles forming the absorber. When the composition of the comparative ceramic shaping powder was analyzed in the same manner as in Example 8, the mass ratio of Al2O3, Gd2O3, and Tb4O7 was the same as the charged composition ratio. SiO2 was less than 50 ppm relative to the comparative ceramic shaping powder. The content of other components was less than 0.2 mass% relative to the ceramic shaping powder.

[0103] [Table 13]

[0104] [Table 14]

[0105] Ceramic shaped objects were formed using the powders for ceramic shaping of Examples 8 to 25 and the Comparative Example. To form the molded object, a 3D SYSTEMS ProX (trade name) series DMP100 equipped with a 50 W Nd:YAG laser (beam diameter 65 μm) was used. As shown in Figure 5, ceramic molding powder was first spread evenly in the laser irradiation area on an alumina base 130, forming a 20 μm-thick first powder layer 102. Next, a 30 W laser beam 180 from a laser source 181 was irradiated onto the powder layer, melting and solidifying the powder in a rectangular area measuring 5 mm x 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 5(a), the drawing lines were angled 45 degrees relative to the sides of the rectangle. Next, a new 20 μm-thick powder layer was spread evenly to cover the melted and solidified area. As shown in Figure 5(b), a laser beam was irradiated onto the powder layer directly above the rectangular region, perpendicular to the drawing line of the first layer, to melt and solidify a 5 mm x 42 mm area. This additive manufacturing process was repeated to form a prismatic object with a 5 mm x 42 mm base and a height of 6 mm for use in three-point bending strength tests. A similar process was used to form a prismatic object with a 22 mm square base and a height of 12 mm for water absorption tests. Observation of the surfaces of Samples 27-44 and Comparative Sample 9 using an optical microscope revealed that the surface irregularities were 30 μm or less for Samples 27-39 and 42-44, and 40 μm or less for Samples 40, 41, and Comparative Sample 9. The shaped object was separated from the alumina base and polished to obtain a ceramic shaped object measuring W 40 mm × D 4 mm × H 3 mm (Fig. 6(a)) for the three-point bending strength test and a ceramic shaped object measuring W 20 mm × D 20 mm × H 10 mm (Fig. 6(b)) for the water absorption test. An Instron compression testing machine was used for the three-point bending test. The three-point bending strength of the ceramic shaped objects of each Example and Comparative Example 1 is shown in Table 15.

[0106] The water absorption rate is expressed as a percentage of the total amount of water contained in a ceramic object in a water-saturated state with its surface dry, relative to the amount of ceramic material in an absolutely dry state. If the mass of the ceramic object in an absolutely dry state is w1 and the mass of the ceramic object in a water-saturated state with its surface dry, the water absorption rate w [%] can be calculated as w = (w2 - w1) / w1 × 100.

[0107] First, the mass w1 [g] of the ceramics molded object in an absolutely dry state after drying at 80°C for 4 hours was measured. Next, the ceramics molded object was submerged under the water surface in a boiling bath and boiled for 30 minutes. After that, water was added and the object was cooled to room temperature to obtain a saturated sample. The water-exposed sample was removed from the water, and the surface was quickly wiped with wet gauze to remove water droplets. The mass w2 [g] of the ceramics molded object in a surface-dry saturated state was measured. The water absorption w [%] was calculated using w = (w2 - w1) / w1 × 100 and is summarized in Table 15.

[0108] [Table 15]

[0109] The ceramic objects produced using the ceramic molding powders of Examples 8 to 25 had high three-point bending strengths of 20 MPa or more and low water absorption of 1.0% or less. In particular, the ceramic objects of Samples 27, 28, 30 to 36, 38, 39, and 42 to 44, which satisfied the conditions α≦1.0, 0.04≦β≦5, and γ≦20, had high three-point bending strengths of 25 MPa or more. [Industrial Applicability]

[0110] The ceramic molding powder of the present invention can be used in powder bed fusion and cladding processes to obtain ceramic objects with high molding accuracy by adding an absorber, and can be used in the field of ceramic parts that require complex shapes. [Explanation of symbols]

[0111] 11 Powder volume 12 Modeling stage 13 Recoater section 14 Scanner unit 15, 181 Laser Source 21 Cladding Nozzle 22 Powder supply hole 23, 180 laser light 41 Unirradiated area 42 Laser light irradiation area 102 Powder bed 130 Foundation

Claims

1. A method for manufacturing a ceramic object by additive manufacturing, comprising: a step of heating the material by irradiating the material with laser light; the material includes a first composition and a second composition, the second composition having a higher absorption ability for the laser light than the first composition; the second composition absorbs the laser light and its temperature rises, whereby the second composition changes into a third composition having a lower absorption ability for the laser light than the second composition; The manufacturing method, wherein the first composition, the second composition, and the third composition are composed of compounds.

2. The manufacturing method according to claim 1 , wherein the change involves a change in the valence of an element that constitutes the second composition.

3. The manufacturing method according to claim 1 or 2, wherein the first composition is melted by the heating.

4. The method of claim 1 , wherein the second composition is an oxide and the third composition is an oxide, and the second composition and the third composition have different oxidation states.

5. 5. The manufacturing method according to claim 1, wherein the first composition is an oxide of a first element, the second composition is an oxide of a second element, the third composition is an oxide of the second element, and the second composition and the third composition have different valences of the second element.

6. The method according to claim 1 , wherein the second composition has an absorptance of 10% or more for the laser light.

7. The manufacturing method according to claim 1 , wherein the second composition has an absorptivity of 40% or more for the laser light.

8. The manufacturing method according to claim 1 , wherein the second composition has an absorptivity of 60% or more for the laser light.

9. The manufacturing method according to claim 1 , wherein the absorptance of the second composition to the laser beam is 1.2 times or more greater than the absorptance of the third composition to the laser beam.

10. The manufacturing method according to claim 1 , wherein the absorptance of the second composition to the laser light is at least twice as high as the absorptance of the third composition to the laser light.

11. The method according to claim 1 , wherein the third composition has an absorptivity of 40% or less for the laser light.

12. The method according to claim 1 , wherein the third composition has an absorptivity of 20% or less for the laser light.

13. The method of claim 1 , wherein the material is a powder.

14. The manufacturing method according to claim 1 , wherein the material includes a first group of particles containing the first composition and a second group of particles containing the second composition.

15. The manufacturing method according to claim 1 , wherein the material includes a first group of particles made of the first composition and a second group of particles made of the second composition.

16. The method according to claim 14 or 15, wherein the median particle size of the second particle group is ⅕ or less of the median particle size of the first particle group.

17. The method according to claim 14 , wherein the first particle group has a median particle size of 5 μm or more.

18. The method according to claim 14 , wherein the second particle group has a median particle size of 1 μm or more.

19. The method according to claim 14 , wherein the median particle size of the second particle group is 10 μm or less.

20. 20. The manufacturing method according to claim 14, wherein the material includes a third particle group made of a fourth composition, and the second composition has a higher absorption ability for the laser light than the fourth composition.

21. 21. The method of claim 20, wherein the material includes a fourth group of particles made of a fifth composition, and the second composition has a higher absorption ability for the laser light than the fifth composition.

22. The method of claim 1 , wherein the material includes a fourth composition that is an oxide of a metal element, and the third composition contains the oxide of the metal element.

23. 23. The method of claim 1, wherein the first composition is a compound selected from aluminum oxide, zirconium oxide, silicon oxide, silicon nitride, yttrium oxide, and aluminum titanate, or a mixture thereof.

24. 23. The method of any one of claims 1 to 22, wherein the material comprises an oxide of a metal element selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Hf, Ta, W, In, Sn, Bi, Ce, Pr, Sm, Eu, Tb, Yb.

25. 23. The method of claim 1, wherein the material comprises an oxide of a metal element selected from Sc, Y, La, Ce, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu.

26. 26. The method of claim 1, wherein the material comprises silicon oxide particles having a particle size of less than 5 μm.

27. 27. The method of claim 1, wherein the amount of the second composition in the material is 0.5% by volume or more and 53% by volume or less.

28. The method according to claim 1 , wherein the carbon content in the material is 1000 ppm or less relative to the metal elements in the material.

29. 29. The method of any one of claims 1 to 28, wherein the heating sinters or melts the material.

30. 30. The method of claim 1, wherein the ceramic object is formed by powder bed fusion.

31. placing the material; irradiating the material with the laser light based on modeling data; The method according to claim 1 , wherein the three-dimensional object is manufactured by repeating the steps of:

32. The method according to claim 31 , further comprising heat treating the three-dimensional structure.

33. The method according to claim 32 , wherein the three-dimensional structure is impregnated with or coated with a glaze during the heat treatment.

34. The manufacturing method according to any one of claims 1 to 33, wherein the laser power of the laser light is 10 W or more.

35. The manufacturing method according to any one of claims 1 to 34, wherein the focal size of the laser light is 10 µm to 2 mm.

36. 36. The method of any one of claims 1 to 35, wherein the irradiation is performed with a Nd:YAG laser.

37. 37. The method of any one of claims 1 to 36, wherein the heating raises the temperature of the first composition above the melting point of the first composition.

38. The method according to claim 1 , wherein the ceramic shaped object includes a crystal.

39. The method according to claim 1 , wherein the ceramic shaped object has a eutectic structure.

40. The method according to claim 1 , wherein the ceramic shaped object has an amorphous region.

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