Ceramic molding powder, ceramic molded object, and method for manufacturing the same

Abstract

This invention provides a laser molding powder that enables stable molding and allows for the production of three-dimensional objects with guaranteed molding accuracy, as well as a method for using the same powder. [Solution] A powder for ceramic molding to obtain a molded object by repeatedly sequentially sintering or melting and solidifying powder in a laser light irradiation area, wherein the powder comprises a plurality of compositions, at least one of the compositions is an absorber that exhibits relatively higher absorption to the laser light than the other compositions, and at least a portion of the absorber changes to other compositions that exhibit relatively lower absorption to the laser light upon irradiation with the laser light, and a method for using the powder.

Description

[Technical Field]

[0001] The present invention relates to a powder used when forming ceramic objects by laser irradiation, and to a method for manufacturing such objects using the same powder. [Background technology]

[0002] In recent years, additive manufacturing technology has advanced, and particularly in the metal field, powder bed fusion (PBL) has enabled the creation of dense and diverse objects. This density stems from the effective melting and solidification of the material, resulting in a solidified structure. In this context, the potential for applying this technology to ceramics has been discussed, and many attempts have been reported. Melting ceramics in the same way as metals requires a considerable amount of energy, but unlike metals, light diffusion within the powder makes it difficult to achieve uniform melting and thus difficult to obtain manufacturing accuracy. Therefore, objects have been formed by limiting the process to sintering rather than melting, in order to ensure manufacturing accuracy, but this has resulted in a lack of density.

[0003] In this situation, for example, Non-Patent Document 1 proposes a method that uses an Al2O3-ZrO2 eutectic system to lower the melting point and, when melted and solidified, forms a microstructure characteristic of the eutectic system, thereby achieving high mechanical strength. However, while it succeeds in improving the density of the fabricated object, numerous protrusions appear on the surface of the fabricated object, and it has not achieved sufficient fabrication accuracy. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Physics Procedia 5 (2010) 587-594 [Overview of the project] [Problems that the invention aims to solve]

[0005] The wavelength of the laser light is Nd:YAG (about 1 μm). Even if eutectic systems are used to lower the melting point, neither Al2O3 nor ZrO2 shows distinct absorption. Therefore, in order to melt and solidify this material system, corresponding energy is required. In such a system, there are problems such as light diffusion in the powder, resulting in widespread non-uniform melting in the desired shaped part and non-uniform sintered regions around it.

[0006] Furthermore, there was a problem that parts that had already completed the process, such as in the proximity region or the stacking direction during laser scanning, might be processed again by absorption of the laser light, which had an adverse effect on the shaping accuracy.

[0007] Therefore, in order to improve the shaping accuracy, a material is required that can suppress light diffusion in the powder, shows absorption of the laser wavelength, and has a reduced or eliminated absorption effect in parts that have already been shaped so as not to be affected by re-absorption of the laser light.

Means for Solving the Problem

[0008] The powder for ceramic shaping of the present invention is a powder for ceramic shaping for obtaining a shaped object by repeatedly sintering or melting and solidifying the powder in the laser light irradiation part. The powder contains a plurality of compositions, and at least one of the compositions is an absorber that shows relatively higher absorption with respect to the laser light than other compositions. At least a part of the absorber changes to other compositions with relatively low absorption with respect to the laser light by irradiation with the laser light.

[0009] Also, in the production of a ceramic shaped object for obtaining a shaped object by repeatedly sintering or melting and solidifying the powder in the laser light irradiation part, (i) A step of arranging the above-mentioned powder for ceramic shaping in a laser irradiation part, (ii) A step of sintering or melting and then solidifying the powder for ceramic shaping by irradiating the powder for ceramic shaping with a laser based on three-dimensional shaping data, and (iii) A process of manufacturing a molded object by repeating steps (i) and (ii) above, It is characterized by having the following features. [Effects of the Invention]

[0010] By using the ceramic molding powder of the present invention, a portion of the absorber changes to another composition with relatively lower absorption of the laser light upon irradiation with laser light. As a result, the sintered or melted region becomes less susceptible to the effects of laser irradiation during subsequent molding. Furthermore, because the absorber has relatively higher absorption of the laser light than the other compositions constituting the powder, light diffusion can also be reduced. Consequently, it is possible to manufacture ceramic molded objects with high molding accuracy. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows an example of a molding apparatus to which the powder of the present invention can be applied. [Figure 2] This figure shows another example of a molding apparatus to which the powder of the present invention can be applied. [Figure 3] This is a conceptual diagram showing the temperature rise process of a powder containing the absorbent of the present invention and a reference powder that does not contain the absorbent. [Figure 4] This figure shows the measurement results of the amplitude of the contour at the boundary between the laser-irradiated area and the unirradiated area. [Figure 5] This figure shows the process of irradiating the powders of Examples 8 to 25 of the present invention with laser light. [Figure 6] This figure shows molded objects made using the powders of Examples 8 to 25 of the present invention. [Modes for carrying out the invention]

[0012] The embodiments for carrying out the present invention will be described below with reference to the drawings. First, the powder, composition, and absorber in the present invention will be described. A powder is an aggregate of particles that can be recognized as isolated particles. A powder also consists of multiple compositions. A composition is composed of multiple components (elements or compounds). When a powder consists of multiple compositions, it means that there are multiple types of particles made from one type of composition, or that there are one or multiple types of particles made from multiple types of compositions. An absorber is defined as a composition that has a relatively high absorption capacity for the laser light used compared to the other compositions constituting the powder. In other words, the absorber has the highest absorption capacity for laser light among the compositions contained in the powder. At least one of the compositions constituting the powder of the present invention is an absorber that has the ability to absorb laser light. The absorption capacity of the absorber is preferably 10% or more with respect to the laser light of the wavelength used. It is more preferable if the absorption rate is 40% or more, and most preferably 60% or more. To measure the absorptivity of a single absorber, a general spectrometer can be used. An integrating sphere is used to irradiate the absorber, packed in a sample dish, with a assumed wavelength (near the laser wavelength used in manufacturing), and the measurement is taken. The absorptivity is calculated from the ratio, using the case without a sample as reference data.

[0013] (powder) The powder of the present invention is composed of multiple compositions consisting of two or more types, and each of these multiple compositions includes at least one composition that is an absorbent. Each particle constituting the powder may consist of a single composition, or a single particle may consist of multiple compositions. The following will explain each case in turn.

[0014] First, there is the case where the powder is composed of particles made from a single composition. For example, if the multiple compositions consist of three types: Al2O3, ZrO2, and Tb4O7 (absorbent), then Al2O3 particles, ZrO2 particles, and Tb4O7 particles are present, and the powder is composed of a mixture of these particles.

[0015] Next, consider the case where the powder contains particles composed of two or more types of compositions. For example, if the composition consists of three types: Al2O3, ZrO2, and Tb4O7 (absorbent), the powder may consist only of particles made up of Al2O3-ZrO2-Tb4O7, or it may consist of Al2O3-ZrO2 particles and Tb4O7 particles, where Al2O3-ZrO2 constitutes the same particle. In particular, when the absorbent is contained in the same particles as the other compositions, it is preferable to maintain the Tb4O7 state in the case of Tb4O7, which is an example of the absorbent in the present invention. Furthermore, it is preferable that the absorbent composition constitutes the particles on its own, regardless of how the other compositions are composed.

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

[0017] Furthermore, it is preferable that the particle size of the particles constituting the absorbent (particle size refers to the median value of a group of particles having the same composition, not the particle size of a single particle) is 1 / 5 or less of the particle size of the particles of the non-absorbent composition. Therefore, since it is preferable that the particle size of the particles constituting the absorbent is 1 μm or more and 10 μm or less, it is important that the particle size of the non-absorbent composition is 5 μm or more to satisfy the above conditions.

[0018] Furthermore, it is preferable that the powder of the present invention does not contain a resin binder. If a resin binder is present, a process of explosive burning may occur upon laser irradiation, which may cause voids or other defects in the fabricated area. In addition, if carbon is present, it will combine with oxygen to become a gas, and the volume occupied by the carbon component may become voids, so it is preferable to have a small amount of carbon. Accordingly, it is preferable that the carbon content be 1000 ppm or less in molar ratio to the metal elements of the multiple compositions constituting the powder. Furthermore, if carbon is present, it will oxidize and gasify upon laser irradiation, negatively affecting the fabrication process. Therefore, it is preferable that the absorber, as in the present invention, undergoes a transformation into a different composition upon laser irradiation and is incorporated into the fabricated object.

[0019] Up to this point, we have described the absorber, composition, and particles, but the ceramic molding powder in this invention is not limited to being crystalline, amorphous, or a mixture thereof. Furthermore, the composition of the powder and the molded object do not need to be perfectly identical, and differences such as oxidation and nitridation states are acceptable. Therefore, it is also preferable to control the atmosphere during the molding process, and it is preferable to use not only an atmospheric atmosphere, but also an inert state such as a nitrogen or other noble gas atmosphere, a state that is easily reduced by partially containing hydrogen or under reduced pressure, and even an oxygen atmosphere. Such atmosphere control does not exclude the inclusion of a composition in a partially metallic state as the raw material powder.

[0020] The present invention relates to a powder for ceramic molding, but is not limited to a state in which the molded object is composed of 100% crystalline ceramics. If desired physical properties can be obtained, a part or more of the molded object may have regions in an amorphous state or regions that are reduced to a state close to a metallic state.

[0021] (Absorbent) An absorber suitable for the present invention absorbs laser light, and the heat generated causes the powder at the laser irradiation site to sinter or melt, converting it into a solidified body, while the absorber itself remains in the fabricated object. At that time, a portion of the absorber changes into another composition with relatively lower absorption capacity for the laser light and is incorporated into the fabricated object. Therefore, the region converted into the solidified body has lower absorption of laser light than the powder before laser irradiation.

[0022] The function and effects of the absorber of the present invention will be described in detail. The first effect is that, as an absorber, it efficiently absorbs the laser light used during manufacturing, and by becoming hot itself, the temperature rises to other compositions within a region equivalent to the focal size of the laser light, causing a temperature increase. This enables effective localized heating, clarifying the interface between the process area (the area irradiated with laser light) and the non-process area (the area not irradiated with laser light), and improving the accuracy of the fabrication.

[0023] The second effect is that, because the area where the shaping process is completed by irradiating with laser light has reduced absorption, it is possible to suppress the absorption and alteration of adjacent areas and lower layers within the layer where the process is about to be performed, by preventing them from absorbing the laser light again. In addition, because the impact on adjacent areas and lower layers where the shaping is complete is suppressed, a wider process margin can be taken for laser irradiation conditions, and the adverse effects on shaping accuracy due to fluctuations in irradiation conditions can also be reduced.

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

[0025] This situation will be explained with reference to Figure 3, a conceptual diagram. The horizontal axis represents the laser irradiation time, and the vertical axis represents the temperature of the laser irradiation region. In lines A and B in Figure 3, line A shows the characteristics of powder without the absorber. In line A, the temperature rise begins with laser irradiation, and the powder melts linearly beyond its melting point, reaching the molding temperature shown by the dashed line. On the other hand, line B shows the characteristics of powder containing the absorber of the present invention. In line B, the temperature rise begins rapidly with laser irradiation due to the light absorption effect of the absorber, and the absorber's effect decreases before melting, resulting in a temperature rise rate similar to line A when the absorber is not present.

[0026] In the case of powder exhibiting the characteristics of line A, the heating efficiency is poor, and a wide, low-density sintered area forms at the boundary between the molten and solidified portion and the powder within the area irradiated by the laser light. This widely affects the adjacent powder area, resulting in an inability to obtain spatial fabrication accuracy.

[0027] On the other hand, powders exhibiting the characteristics of line B have good heating efficiency and localized heating is achieved. Therefore, when a laser irradiation area is formed, a sufficient temperature difference is ensured with the adjacent area, resulting in only a narrow sintered area at the boundary between the molten and solidified portion and the powder, thus achieving good molding accuracy. Furthermore, since the completed molding area after laser irradiation does not show absorption and exhibits characteristics similar to line A, even if process conditions fluctuate and the laser light affects the existing molding area, the temperature rise due to the laser light is relatively small, and this effect can be avoided. Moreover, the area being irradiated with the laser and the irradiated area are joined by fusion due to heat conduction between the two areas, so the connection and strength of the boundary between laser drawing lines are maintained. Thus, when the characteristics of line B of the present invention are present, the two effects described above can be obtained.

[0028] The absorber of the present invention can be used without limitation as long as at least a portion of it changes into another composition with relatively lower absorption upon laser irradiation, but it is preferable to select from metal oxides. This is because, among metal oxides, the valence of the metal element changes due to the release of oxygen with increasing temperature, and it changes into another metal oxide with relatively lower absorption to laser light (for example, Tb4O7 → Tb2O3, Tb 3+ This is because some materials are prone to substitution of GdAlO3 at the Gd (gadolinium) site. Furthermore, they have high affinity with other components that make up ceramics, allowing them to be incorporated into the fabricated object.

[0029] For metal oxides where the valence state change functions as a change in absorption rate for various laser wavelengths, it is preferable to use 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), a typical laser used in fabrication, the use of Tb and Pr oxides is preferred, and their oxidation states are Tb4O7 and Pr6O 11 This is more preferable. However, it is not limited to the ratio (composition ratio) of the above molecular formula; other ratios or mixtures thereof can also be used if the desired absorption effect is obtained.

[0030] Next, the most preferred terbium oxide as the composition of the absorber of the present invention will be described in detail as an example. Terbium oxide can exist in various states, typically Tb4O7 and Tb2O3. The molecular formula is written as Tb4O7, but it is not strictly limited to a 4:7 ratio. In this case, Tb4O7 is Tb 4+ and Tb 3+ Although it is a substance composed of half and half, in Tb2O3 Tb 3+ It is composed of only this. The high infrared absorption rate of Tb4O7 is remarkable around 1070 nm in Nd:YAG lasers, sometimes exceeding 60% and reaching 70%. On the other hand, Tb 4+When it gradually decreases, the absorption rate decreases, and in the state of Tb2O3 composed only of Tb 3+ it becomes about 7%. Therefore, it is clear that the absorption rate decreases due to the decrease of Tb 4+ . Thus, terbium oxide (Tb4O7) containing tetravalent terbium in the absorber is suitable as one composition for realizing the present invention.

[0031] Also, in order to obtain an absorption rate of 10% (when measured with the absorber alone), Tb 4+ should be present at about 10% with respect to the total amount of Tb 3+ and Tb 4+ . Here, as a method for evaluating the valence, X-ray Absorption Fine Structure (XAFS) analysis can be applied. Since the rising energy of the absorption edge differs for each valence, it can be evaluated from the ratio. In addition, it can also be evaluated by making full use of general evaluation methods such as X-ray Photoelectron Spectroscopy (XPS) or Electron Spectroscopy for Chemical Analysis (ESCA), and Electron Spin Resonance (ESR).

[0032] In an oxide where the ratio of the metal element to oxygen is 2:3, the metal element is stabilized with a valence of 3+. Therefore, after conversion to a solidified body, it exists in a state of being dissolved in other compositions (for example, Y2O3, Gd2O3, and other R2O3 (R: metal element)). Therefore, the region converted to the solidified body after shaping does not show large absorption. Also, in multi-element oxides, etc., in a compound where R 3+ is stable, a similar state can be realized by substituting Tb for the R site. In addition, in ZrO2, it contributes to the stabilization of the fluorite structure by solid solution, and the valence also becomes 3+ at this time. Thus, the absorber of the present invention also functions as a material constituting the shaped article.

[0033] Furthermore, in order to obtain the effects of the present invention, it is preferable that there is a difference of 1.2 times or more in the absorption rate before and after the process by laser light irradiation, and more preferably 2 times or more. Alternatively, it is preferable that the absorption rate is 50% or more before the process and 40% or less after the process. Alternatively, it is preferable that the absorption rate is 60% or more before the process and 20% or less after the process. Using Tb4O7, an example of an absorber, as part of the composition is preferable for achieving this condition. Note that this absorption rate is for the absorber alone.

[0034] The absorbent's effect can be obtained by including it in multiple compositions, but it is more preferable that the absorbent composition is contained in the powder at a concentration of 0.5 vol% to 53 vol%. Here, vol% is used because it is important to know how much area the absorbent occupies relative to the laser beam irradiation size (focal size), and mol% is not applicable when the composition of the powder changes.

[0035] The lower limit of the absorber content is determined by the requirement that at least one absorber particle is contained within the laser focal size. The upper limit is determined by its effect on the main composition of the fabricated object. When the laser focal size is 10 μm, the laser melting region can be considered as a hemispherical shape with a diameter of 10 μm, and the presence of one absorber particle with a diameter of 1 μm in that region corresponds to approximately 0.5 Vol%, so it is preferable that the lower limit of the absorber composition be 0.5 vol% or more.

[0036] Furthermore, regarding the upper limit, when Tb4O7 is added to Al2O3, which is commonly used as a structural ceramic, Tb3Al5O 12 A Tb3Al5O is formed. Utilizing the properties of Al2O3 ceramics, 12 In order to form a composite system with Tb4O7, the amount must be 53 vol% or less, in which case Tb3Al5O 12 Since a situation is achieved in which a small amount of Al2O3 is dispersed at the grain boundaries in the main phase, the upper limit is preferably 53 vol%.

[0037] Furthermore, the particle size of the absorber is also important, preferably 10 μm or less, more preferably 1 μm to 10 μm, and most preferably 1 μm to 5 μm. Here, particle size in this invention refers to the range of the median particle size distribution of particles made from the same composition, and does not mean that particles with sizes outside this range are excluded. In addition, particle size measurement is applied not only to single-crystal particles, but also to polycrystalline and aggregated states. The absorber composition may consist of particles on its own.

[0038] When the absorbent composition consists of particles on its own, if the absorbent is contained at a concentration of 0.5 vol%, has a particle size of 1 μm, and the bulk density of the powder layer is 50% of the true density, then a single particle is contained within the region heated by a laser focal size of 10 μm (a hemispherical volume corresponding to the focal size diameter), and the absorbent effect is obtained. Furthermore, when the particle size is 10 μm, it corresponds to a single particle being contained within the region heated by a laser focal size of 100 μm, so selecting the particle size of the absorber to match the laser focal size is important.

[0039] From the viewpoint of uniformity, it is more preferable that at least two absorber particles are contained within the laser focal size. The spacing between each absorber particle is preferably 100 μm or less, and more preferably 50 μm or less. It is also preferable to adjust the laser focal size to achieve this condition. As described above, assuming that the laser focal size is limited to 100 μm from the viewpoint of fabrication accuracy, the particle size of the absorbers is preferably between 1 μm and 10 μm, as stated above. However, the laser focal size may be 100 μm or more depending on the desired fabrication 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 and shape of the particles of the composition that is the base material of the molded object and not the absorbent be spherical with a particle size of 5 μm or larger. Furthermore, the particle size of the absorbent is in the range of 1 μm to 10 μm, but it is preferable that it be as fine as possible. This is because of the dispersibility of the absorbent in the powder and the viewpoint of high packing density. In addition, in this 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] (Compositions other than the absorbent material) Other compositions besides the absorber include compositions that form the main components of the ceramic structure. Since such compositions greatly contribute to properties such as strength in the final fabricated product, they should be selected appropriately according to the application. Therefore, by determining the absorber for the wavelength of the laser light used during manufacturing, it is preferable to select one or more main component compositions 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 / meta-stabilized) can be used as general-purpose structural ceramics. Furthermore, silicon oxide, silicon nitride, and aluminum nitride can also be used. Although silicon nitride exhibits a laser absorption effect, its absorption rate does not change before and after the process, so it does not function as an absorber in this invention. Furthermore, ceramic materials such as cordierite (2MgO·2Al2O3·5SiO2), zircon (ZrO2·SiO2), mullite (3Al2O3·2SiO2), yttrium oxide, and aluminum titanate can also be selected. Mixtures of the above materials may also be used.

[0042] Furthermore, the above-mentioned main component composition may also contain small-diameter silicon oxide particles with a particle size of less than 5 μm. The function of these silicon oxide particles will be described in detail below.

[0043] When a laser beam is shone onto a ceramic molding powder, an absorber in the shone area absorbs the energy and generates heat. Small-diameter silicon oxide particles have a small particle size of less than 5 μm and are easily melted, so the heat from the absorber first melts the small-diameter silicon oxide particles surrounding the absorber. Then, the melted small-diameter silicon oxide particles transfer heat to other relatively larger particles, causing those particles to melt as well. The small-diameter silicon oxide particles that melt in the laser beam's irradiated area soften and deform, making contact with other relatively larger particles over a wide area and efficiently transferring heat to the particle surface. As a result, heat can be transferred more evenly to other relatively larger particles compared to cases without small-diameter silicon oxide particles. Consequently, the temperature distribution within the ceramic molding powder during melting is reduced, and the cooling rate during solidification becomes more uniform across locations. Therefore, thermal stress is reduced, the occurrence of microcracks during solidification is suppressed, and ceramic molded objects with fewer microcracks can be obtained. 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, mitigating rapid cooling during solidification and suppressing the occurrence of microcracks. Ceramic molded objects with fewer microcracks have high mechanical strength and low water absorption, making them suitable for applications such as vacuum equipment components where strength and low water absorption are required.

[0044] As mentioned above, the particle size of the small-diameter silicon oxide particles is smaller than the particle size of the other particles in the composition, preferably with a diameter of less than 5 μm. When the powder is composed of multiple types of particles, it is preferable that the particle size of the small-diameter silicon oxide particles is smaller than the particle size of each of the other particles. This is because the smaller particle size makes it easier for the small-diameter silicon oxide particles to lead the melting process together with the absorber, and the softened small-diameter silicon oxide particles are distributed more evenly than the other particles, thus further reducing the temperature distribution within the ceramic molding powder during melting. From the viewpoint of fluidity, 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. This is because uniform particle size allows for homogeneous dispersion in the ceramic molding powder and enables more homogeneous distribution on the surface of particles from other compositions when softened.

[0045] The mass of small-diameter silicon oxide particles contained in the ceramic molding powder is preferably 0.04% to 5.0% of the mass of the absorbent particles. It is desirable that the powder contains 0.04% or more SiO2 particles, as this allows the water absorption rate to be 1.0% or less.

[0046] Furthermore, if the mass of 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 the particles of the main component composition will melt. This is more desirable because it prevents the formation of unmelted material that could reduce the mechanical strength of the ceramic molded object. In addition, after the small-diameter silicon oxide particles melt upon irradiation with laser light and act as a heat transfer medium, some of them become glass and are distributed on the surface and inside the ceramic molded object. If a large amount of small-diameter silicon oxide particles are contained in the powder when the powder for ceramic molding solidifies, many glass regions originating from the small-diameter silicon oxide particles may be formed in the ceramic molded object, potentially reducing the mechanical strength of the ceramic molded object. Therefore, it is more preferable that the mass of small-diameter silicon oxide particles be 1.0% or less of the mass of the particles made up of the main component composition.

[0047] The powder of the present invention consists of multiple compositions, preferably containing at least one component as an absorber and at least one component of aluminum oxide, zirconium oxide, or 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 absorber, and they can form eutectic systems with many material systems, maintaining high strength through the manifestation of their microstructure and also achieving a lower melting point. For example, in the case of aluminum oxide, when it is a mixture of two types with the absorber Tb4O7, during molding, Tb4O7 changes into Tb3Al5O 12 Compositions related to TbAlO3 are generated. On the other hand, with zirconium oxide, Tb 3+ In this state, the zirconium oxide plays a role in stabilizing it into a tetragonal crystal. It is also preferable that aluminum oxide and zirconium oxide are included in the composition simultaneously, resulting in a three-component structure including the absorber. Not only eutectic compositions, but also Al2O3:ZrO2 = 85:15 wt% and 70:30 wt% can be selected. Furthermore, it is preferable that silicon oxide be incorporated into the fabricated object regardless of whether it is amorphous or crystalline. Moreover, it is preferable that the silicon oxide is composed of three or four components, including not only two compositions with the absorber, but also zirconium oxide, aluminum oxide, etc. Furthermore, the fabricated object containing silicon oxide may also contain zircon, mullite, silicate with the absorber, etc.

[0048] While not limiting, it is preferable that multiple compositions be contained in a relationship that forms a eutectic composition. Eutectic composition refers to the composition at the eutectic point shown in the eutectic phase diagram, but the laser light-based fabrication process of the present invention involves extremely rapid heating and cooling cycles, so it is far removed from the equilibrium state. Therefore, it is preferable to define the eutectic composition as the composition range in which the eutectic structure is formed, and a range of ±10 mol% from the eutectic composition as 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 instead of R2O3 (or RO2). 12 The following may be formed, and if it is possible to form a new composition with the compositions, it is also preferable to use that composition. In some cases, it is also preferable that the composition has a eutectic composition. Also, Tb 3+ , Pr 3+ A material system consisting of the above is also applicable.

[0050] (Use of the ceramic molding powder of the present invention) The ceramic molding powder of the present invention is used in a manufacturing process (manufacturing method) for a molded object by irradiation with laser light. The manufacturing process comprises: (i) placing the ceramic molding powder of the present invention described above in a laser light irradiation section; (ii) irradiating the ceramic molding powder with laser light based on three-dimensional molding data to sinter or melt and then solidify the ceramic molding powder; and (iii) repeating steps (i) and (ii) to form a molded object.

[0051] In this invention, the terms "sintering" or "melting and solidifying" are not strictly defined as meaning that sintering means no powder is melted at all, or that melting means there is no unmelted powder. Recently, the term "liquid-phase sintering" has also been used, and the scope of each term has become unclear. Therefore, in terms of interpretation, we do not exclude sintering that merely binds the powder particles together, liquid-phase sintering where molten material surrounds the powder, or even melting where some unmelted powder remains.

[0052] Furthermore, in the manufacturing process of the present invention, if necessary, it is preferable to perform heat treatment after the process of forming the molded object. In this case, there are no restrictions on the heating method, and resistance heating, induction heating, infrared lamp heating, laser heating, electron beam heating, etc., can be selected and used according to the purpose. Heat treatment is also suitable for adjusting the crystal grain size of the molded object, with the aim of improving the density and strength of the molded object. In addition, it is preferable to impregnate or coat the object with a glaze, whether organic or inorganic, during the 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 and then irradiating it with laser light. Alternatively, steps (i) and (ii) may be performed by ejecting the powder of the present invention to a predetermined location and then irradiating the predetermined location with laser light.

[0054] Specifically, the method of obtaining a fabricated object by repeatedly sequentially sintering or melting and solidifying the material in the laser irradiation area includes so-called powder bed fusion fusion and cladding methods. There are no restrictions on the wavelength of the laser light used, but it is preferable to use lenses or fibers that have been adjusted to a desired focal size, such as 10 μm to 2 mm. The focal size is one of the parameters that affects the fabrication accuracy, and in order to achieve a fabrication accuracy of 0.1 mm, it is preferable that the line widths are similar, depending on the situation, and that the focal size is 100 μm or less. It does not matter whether the laser light irradiation is continuous or pulsed. One example is an Nd:YAG laser with a wavelength of around 1070 nm.

[0055] The powder bed fusion method will be explained with reference to Figure 1. The apparatus used in this method includes a powder tray 11, a build stage 12, a recoater unit 13, a scanner unit 14, a laser light source 15, etc. In operation, the powder tray 11 and the build stage 12 move up and down as needed, while the recoater unit 13 manipulates the powder, spreading a thin layer of powder over an area wider than the intended object. Furthermore, the shape of one cross-section of the object is directly drawn onto the powder layer using laser light generated from the laser light source 15 and the scanner unit 14. The drawn area is sintered or melted and solidified, and this process is repeated to layer the cross-sections of the object and form the final object.

[0056] The cladding method will be explained using Figure 2. This method involves ejecting powder from multiple powder supply holes 22 in the cladding nozzle 21, and irradiating the area where the powder converges with laser light 23 to sequentially form a structure at the desired location. A key feature of this method is that it can also create structures on curved surfaces.

[0057] The manufacturing process of the present invention described above enables stable molding and ensures molding accuracy, thereby obtaining a three-dimensional object. [Examples]

[0058] [Example 1] This embodiment relates to the improvement of molding accuracy by incorporating the absorber of the present invention. To clarify the difference in molding accuracy, a 1.5 mm thick powder bed was melted and solidified by laser irradiation, and the state of the boundary between the irradiated and unirradiated areas was observed. As Sample 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 a 1.5 mm thick powder bed, and a Nd:YAG laser (1070 nm) with a focal diameter of 100 μm and laser power of 30 W was used to irradiate 40 lines of 10 mm length at 50 μm pitch using two laser irradiation speeds: 100 mm / sec and 250 mm / sec.

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

[0060] One example of the absorber used here is Tb4O7, which is Tb 3+ Not only Tb 4+ It also contains [something]. Furthermore, for calculating the volumetric composition, the true density of Al2O3 is 3.96 [g / cm³]. 3 ], Gd2O3:7.40[g / cm³ 3 ], Tb4O7:7.60[g / cm³ 3 The true density was used. Even if this true density is slightly different, it does not affect the essence of the present invention.

[0061] Comparative sample 1 does not contain an absorber, while comparative sample 2 has Tb as GdAlO3. 3+ It exists in a form that is replaced on the site, Tb 4+ The absorbent effect was almost nonexistent, effectively eliminating the absorption effect. In these two comparative samples lacking the absorbent effect, the material remained almost entirely in a powdery state under a laser irradiation condition of 250 mm / sec, and a clearly defined structure was obtained after dissolution at 100 mm / sec and subsequent solidification. However, due to the absence of the absorbent effect, the in-plane non-uniformity of the heating state was significant, and a two-dimensional object could not be obtained as a solidified body; instead, locally melted and solidified particles were scattered around.

[0062] On the other hand, in Sample 1, sufficient dissolution was observed from 250 mm / sec, and it was confirmed that the 2D fabricated object was formed in a planar manner. Furthermore, in the fabricated object in the irradiated area, Tb4O7 was found at the Gd site of GdAlO3. 3+Fluorescence observation under UV excitation confirmed that the absorber was incorporated as such, and it reached a low absorption effect similar to that of comparative sample 2. Based on the valency state of the absorber, sample 1 was mixed into the powder with an absorption rate of 60% or more, and after irradiation with laser light, fluorescence observation showed that there was almost no tetravalent absorber, resulting in an absorption rate of less than 30%. In comparative sample 2, fluorescence observation showed that the absorption rate was less than 30% in the powder state before fabrication, and there was no change after irradiation with laser light, remaining below 30%.

[0063] Figure 4 shows the results of calculating the amplitude of the boundary contour by cropping an image with a width of 3.83 mm from a micrograph of the boundary between the laser-irradiated area 42 and the unirradiated area 41. The amplitude for comparison sample 1 was 391 μm, for comparison sample 2 it was 273 μm, and for sample 1 it was 85 μm. Furthermore, since the fabricated area of ​​sample 1 and the powder of comparison sample 2 are in the same state in terms of the absorber's effect, it became clear that in sample 1, fabrication could be performed at 250 mm / sec in the powder area where the absorber was functioning, and the fabricated area was hardly affected at 250 mm / sec.

[0064] From the above results, it was found that the sample of the present invention exhibits superior fabrication accuracy compared to the comparative sample, and that fabricated objects can be obtained without disturbing the completed process area again. Furthermore, Tb4O7, a metal oxide that is an example of an absorber, contains 4+ in its valence state, but in the fabricated area, the absorption characteristics changed due to a decrease in valence to 3+. The laser irradiation conditions are varied depending on the surrounding environment, material composition, powder layer thickness, etc., so they are not limited to the values ​​described in this embodiment.

[0065] [Example 2] This example relates to the effect of adding Tb4O7, a candidate absorber. Tb4O7 has an absorption rate of 60% or more around 1070 nm, and Tb2O3 and other Tb 3+When considering only the state, the absorption rate is less than 30%. 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. In addition to this, Samples 2, 3, 4, 5, and comparative sample 3 were prepared as shown in Table 1 below. At this time, the particle size of the Tb4O7 powder used was approximately 2 μm.

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

[0067] [Table 1]

[0068] For each sample, the width of the boundary between the laser-irradiated and unirradiated areas was observed within a 2 mm width range. The results are shown in Table 1. In the table, the amount of each composition (vol%), the boundary width (μm), and the effect of Tb4O7 addition are indicated as Excellent (◎), Good (○), and Poor (×). Note that the boundary width (variability) is an index substantially equivalent to the surface roughness of the side surface of the fabricated object; the larger the width, the rougher the surface of the manufactured object. The standard surface roughness of objects manufactured using metal powder is said to be around 10-20 μm. Therefore, a value equivalent to this is evaluated as ◎. The same criteria are used to evaluate other examples.

[0069] In comparative sample 3, which did not contain the absorbent, numerous granular dissolved material was generated at the boundary, and the boundary width was the widest. On the other hand, it was found that the boundary width narrowed when the absorbent (samples 1-5) was added. In other words, it can be seen that the effect is obtained by including the absorbent of the present invention. In particular, it was confirmed that the width was narrower in samples 1-3. Therefore, when Tb4O7, an example of the absorbent of the present invention, was added, the judgment results shown in Table 1 were obtained, and it was found that the effect of improving molding accuracy over a wide range of compositions was obtained compared to the case without the additive.

[0070] [Example 3] This example uses Pr6O, one candidate absorber. 11 Regarding the effects of adding (praseodymium oxide). Pr6O 11 Furthermore, when in a valency state close to that, it has an absorption rate of 80% or more around 1070 nm, and Pr2O3 and other Pr 3+ When the conditions are numerous, the absorption rate is less than 50%. Sample 6 includes Al2O3 powder, Gd2O3 powder, and Pr6O 11 Powder mixture (composition ratio: Al2O3: 63.85 vol%, Gd2O3: 33.29 vol%, Pr6O 11 2.86 vol%) was used. At this time, Pr6O 11 Powder particles with a particle size of approximately 2 μm were used. For the volumetric composition calculation, the true density of Al2O3 was assumed to be 3.96 [g / cm³]. 3 ], Gd2O3:7.40[g / cm³ 3 ], Pr6O 11 :7.20[g / cm 3 The true density was used. Even if this true density is slightly different, it does not affect the essence of the present invention.

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

[0072] [Table 2]

[0073] The width of the boundary between the laser-irradiated and unirradiated areas was observed within a 2 mm width range. The results are shown in Table 2. As shown in Table 2, the amount (vol%) of each composition was as described above, and the boundary width was 42.7 μm, Pr6O 11 The effect of the additive was good.

[0074] Compared to comparative sample 3 of Example 2, the boundary width is shown to be narrower, and Pr6O is an example of an absorber of the present invention. 11 Adding the substance yielded the results shown in Table 2, revealing that it improved the molding accuracy compared to the case without the substance.

[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. For volume composition calculation, the true density of Al2O3 was used: 3.96 [g / cm³]. 3 ], ZrO2:5.68, Y2O3:5.01[g / cm 3 ], Tb4O7:7.60[g / cm³ 3 The true density was used. Even if this true density is slightly different, it does not affect the essence of the present invention. The powder containing these compositions was spread to a thickness of approximately 20 μm on an Al2O3 substrate, and then irradiated with laser light. The conditions were a focal size of 100 μm, 30 W, and two lines with a length of 4.5 mm were drawn at a 50 μm pitch at scan speeds of 50, 100, 200, and 500 mm / sec to compare the melting state.

[0076] [Table 3]

[0077] While pure Al2O3 in comparative sample 4 could melt and solidify in a linear fashion up to 100 mm / sec, sample 7, to which an absorber was added, could do so up to 500 mm / sec. Pure ZrO2 in comparative sample 5 could melt and solidify in a linear fashion up to 100 mm / sec, but sample 8, to which an absorber was added, could do so up to 500 mm / sec. Furthermore, comparative sample 6, near the eutectic composition of the Al2O3-ZrO2 system, could melt and solidify in a linear fashion up to 200 mm / sec, but sample 9, to which an absorber was added, could do so up to 500 mm / sec. In addition, comparative sample 7, near the eutectic composition of the Al2O3-Y2O3 system, could melt and solidify in a linear fashion up to 200 mm / sec, but sample 10, to which an absorber was added, could do so up to 500 mm / sec.

[0078] From these results, it was confirmed that adding Tb4O7, an example of an absorber, to various systems allowed for melting and solidification at higher scanning speeds. Therefore, this absorber is not limited to specific material systems and contributes to improving the accuracy of fabricated objects.

[0079] [Example 5] This example relates to 3D fabrication properties when an absorbent is included. The particle sizes of each component of the powder used in this example are shown in Tables 4 and 5. Furthermore, the particles of these compositions are Tb4O7 and Pr6O, which function as absorbents. 11 All other materials used were spherical.

[0080] [Table 4]

[0081] [Table 5]

[0082] The volume composition of the material systems used is shown in Tables 6 and 7. [Table 6]

[0083] [Table 7]

[0084] For calculating the volumetric composition, the true density is Al2O3: 3.96 [g / cm³]. 3 ], ZrO2·Y2O3: 6.05 [g / cm³] 3 ], Gd2O3:7.40[g / cm³ 3 ], Y2O3: 5.01 [g / cm³ 3 ], SiO2: 2.20 [g / cm³] 3 ], Tb4O7:7.60[g / cm³ 3 ], Pr6O 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 The true density was used. Even if this true density is slightly different, it does not affect the essence of the present invention.

[0085] For the study of this embodiment, a 3D Systems ProX (product name) series DMP100 was used as the 3D printing device. Comparative sample 8, which did not contain an absorber, and samples 11 to 24, which consisted of multiple compositions including an absorber, were fabricated as 6x6x6mm objects under the printing conditions shown in Table 8. The printability was judged as follows: No shape: Poor ×, Roughness on the surface or sides: Slightly poor ○, Object obtained to the specified dimensions: Good ◎. In all cases, the thickness of the powder layer was set to 20 μm, and an alumina plate was used as the substrate. The thickness of the powder layer is the value at which the printing stage 12 in Figure 1 is lowered. Since the powder layer melts and shrinks in the thickness direction due to laser irradiation, the apparent thickness of the powder layer gradually increases with repeated layering and converges 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 during printing, this does not pose a problem in use. For the successfully printed objects, the surface roughness Ra was measured using the Alpha-step (product name) from KLA Tencor to verify the printing accuracy. Since the roughness was relatively greater on the sides of the printed object than on the surface, the evaluation was performed on the sides. The scan width used for calculation was 1 mm.

[0086] [Table 8]

[0087] As shown in Table 8, in comparative sample 8, which does not contain the absorbent of the present invention, although it partially dissolved, as in comparative sample 1 of Example 1, it was unable to maintain the shape of the fabricated object as a result of additive manufacturing. Other samples 11-24 were densely formed as additively manufactured objects, and it was possible to measure the surface roughness of the sides. The absorber of the present invention improved the surface roughness, and in particular, it suppressed it to about 10-25 μm, demonstrating that accurate fabrication is possible.

[0088] [Example 6] This example relates to cases where the composition other than the absorber consists of individual particles and cases where the particles are the same. It compares Sample 13 from Example 5 with a sample in which Al2O3 and Gd2O3 are eutectic powder (a mixture of Al2O3 and GdAlO3) and Tb4O7 is mixed. Furthermore, it compares Sample 15 with a sample in which Al2O3 and Y2O3 are eutectic powder (Al2O3 and Y3Al5O 12 A comparison was made between the mixed state (of the sample) and a sample mixed with Tb4O7.

[0089] Similar to Example 5, a 3D Systems ProX (product name) DMP100 was used as the 3D printing device. A 6x6x6mm object was fabricated under the printing conditions shown in Table 11. The printability was judged as follows: No shape: Poor ×, Roughness on the surface or sides: Slightly poor ○, Object obtained to the specified dimensions: Good ◎. In all cases, the thickness of the powder layer was set to 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 Sample 25 and 26 exhibited excellent moldability (◎), and their surface roughness was approximately 10-20 μm. Thus, it was confirmed that both cases—using powders in which the composition constitutes individual particles (e.g., Sample 25 compared to Sample 13, and Sample 26 compared to Sample 15) and using powders in which the composition other than the absorber is contained within the same particle (as in this example)—showed good moldability. Therefore, it was demonstrated that the effect of the absorber of the present invention does not depend on the composition of the powder other than the absorber.

[0094] [Example 7] This example relates to an example of the tolerance to changes in laser light irradiation conditions when using the absorber of the present invention. The powder composition of Sample 13 in Example 5, 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, and a 3D Systems ProX (product name) DMP200 was used as the 3D printing device.

[0095] The laser beam irradiation speed was fixed at 500 mm / s and the laser beam irradiation line pitch at 130 μm. The laser power was varied to increase or decrease the energy density during fabrication. The powder layer thickness was 25 μm, and an alumina plate was used as the substrate. A 6x6x6 mm object was fabricated at the laser powers shown in Table 12, and its fabrication quality was judged as follows: No shape: Poor ×, Roughness on the surface or sides: Slightly poor ○, Object obtained to the specified dimensions: Good ◎.

[0096] [Table 12]

[0097] At a laser power of 65W, almost no melting occurred, resulting in a distorted shape of the printed object, which was deemed a failure (×). At 75W and 84W, there was insufficient energy for melting, resulting in a powdery surface on the printed object, which was deemed slightly poor (〇). In the range of 95W to 140W, the surface of the printed object was flat and was deemed good (◎). Furthermore, in the range of 146W to 154W, the energy input was too high, causing the surface to undulate and become uneven, which was deemed slightly poor (〇). At 160W, the energy input was too high, resulting in a distorted shape of the printed object, which was deemed a failure (×).

[0098] From the above, it was confirmed that stable fabrication is possible even with an energy density increase of approximately 2.0 times, at least in the range of 75W to 154W. This reflects the fact that the powder of the present invention has absorption capacity only when it is in powder form, and after being incorporated into the fabricated object, it has a low absorption rate and is less affected by laser irradiation, so even if the laser power fluctuates, it does not significantly affect the fabrication process.

[0099] [Example 8] This example shows the addition of SiO2 particles. The ceramic molding powder used in this example was manufactured by the following procedure. As the main component, a mixture of Al2O3 powder (purity 99.99% or higher, particle size 20 μm) and Gd2O3 powder (purity 99.99% or higher, particle size 20 μm) was used in a mass ratio of 1:1. As the absorbent, Tb4O7 powder (purity 99.9% or higher, particle size 4 μm) was used. SiO2 particles with a purity of 99.9% or higher and a particle size of 4 μm were used. Each powder was weighed so that the mass ratio of the main component particles, absorbent particles, and 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 ceramic molding) (Sample 27).

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

[0101] [Examples 9-25] Except for changing the raw material types and mixing ratios according to Table 13, ceramic molding powders for samples 28-44 were manufactured as Examples 9-25 in the same manner as Example 8. ZrO2 powder (purity 99.9% or higher, particle size 15 μm) was used as zirconium oxide. Pr6O was used as praseodymium oxide. 11 Powder (purity 99.9% or higher, particle size 4 μm) was used. The composition of the ceramic molding powders of samples 28-44 was analyzed in the same manner as in Example 8, and it was found to be Al2O3, Gd2O3, ZrO2, Tb4O7, Pr6O 11 The mass ratio of SiO2 was the same as the composition ratio of the initial preparation. The content of other components was less than 0.5% by mass relative to the ceramic molding powder. 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 ceramic molding powder 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 molding powder was prepared in the same manner as in Example 8, according to the mixing ratios shown in Table 13. However, in this comparative example, SiO2 particles were not used, and the comparative ceramic molding powder was composed only of Al2O3, Gd2O3, and Tb4O7, which are absorbent particles. When the composition of the comparative ceramic molding powder was analyzed in the same manner as in Example 8, the mass ratios of Al2O3, Gd2O3, and Tb4O7 were the same as the initial composition ratio. The SiO2 content was less than 50 ppm relative to the comparative ceramic molding powder. The content of other components was less than 0.2% by mass relative to the ceramic molding powder.

[0103] [Table 13]

[0104] [Table 14]

[0105] Ceramic molded objects were formed using the ceramic molding powders of Examples 8-25 and Comparative Examples. For the formation of the fabricated object, a 3D Systems ProX (product name) series DMP100, equipped with a 50W Nd:YAG laser (beam diameter 65μm), was used. As shown in the schematic of the main parts in Figure 5, first, ceramic fabrication powder was spread evenly on the laser irradiation area on the alumina base 130 to form a 20μm thick first powder layer 102. Next, a 30W laser beam 180 from the laser source 181 was irradiated onto the powder layer, melting and solidifying the powder in a rectangular area of ​​5mm × 42mm. The drawing speed was set to 100mm / s to 140mm / s, and the drawing pitch was 100μm. Also, as shown in Figure 5(a), the drawing lines were positioned at a 45-degree angle to the sides of the rectangle. Next, a new 20μm thick powder layer was spread 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 area in a manner perpendicular to the first layer drawing line, melting and solidifying a 5mm × 42mm area. This additive manufacturing process was repeated to form a prismatic object with a base of 5mm × 42mm and a height of 6mm for use in the three-point bending strength test. A similar prismatic object with a square base of 22mm and a height of 12mm was also formed through the same process for the water absorption test. When the surfaces of the printed objects of samples 27-44 and comparative sample 9 were observed with an optical microscope, the surface irregularities were 30μm or less for samples 27-39 and 42-44, and 40μm or less for samples 40, 41, and comparative sample 9. The aforementioned molded object was separated from the alumina base and polished to obtain a ceramic molded object measuring W40mm × D4mm × H3mm for the three-point bending strength test (Figure 6(a)) and a ceramic molded object measuring W20mm × D20mm × H10mm for the water absorption test (Figure 6(b)). An Instron compression testing machine was used for the three-point bending test. The three-point bending strength of the ceramic molded objects for each example and Comparative Example 1 is shown in Table 15.

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

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

[0108] [Table 15]

[0109] The ceramic objects fabricated using the ceramic molding powders of Examples 8-25 exhibited high three-point bending strengths of 20 MPa or higher, and low water absorption rates of 1.0% or less. In particular, the ceramic objects of samples 27, 28, 30-36, 38, 39, and 42-44, which satisfied α ≤ 1.0, 0.04 ≤ β ≤ 5, and γ ≤ 20, exhibited high three-point bending strengths of 25 MPa or higher. [Industrial applicability]

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

[0111] 11 Powder volume 12. Modeling Stage Section 13. Recoater Section 14. Scanner section 15, 181 Laser Sources 21 Cladding Nozzle 22 Powder supply hole 23,180 laser light 41 Unirradiated area 42 Laser beam irradiation area 102 Powder bed 130 base

Claims

1. A ceramic molding powder for obtaining a molded object by repeatedly sequentially sintering or melting and solidifying powder in a laser beam irradiation area, The powder comprises a plurality of compositions, wherein at least one of the compositions is an absorber that exhibits relatively higher absorption to the laser light than the other compositions, and at least a portion of the absorber changes to the other compositions that exhibit relatively lower absorption to the laser light upon irradiation with the laser light, characterized in that the powder is for ceramic molding.

2. The ceramic molding powder according to claim 1, characterized in that the absorbent is a metal oxide, and the other composition is a metal oxide different from the metal oxide.

3. The ceramic molding powder according to claim 1, characterized in that the absorbent is terbium oxide containing tetravalent terbium, or praseodymium oxide containing tetravalent praseodymium.

4. The ceramic molding powder according to claim 3, characterized in that the absorbent composition is contained in an amount of 0.5 vol% or more and 53 vol% or less.

5. The ceramic molding powder according to any one of claims 1 to 4, characterized in that the main composition of the plurality of compositions is at least one of silicon oxide, aluminum oxide, or zirconium oxide.

6. Furthermore, the ceramic molding powder according to claim 5, characterized in that at least one of the multiple compositions contains a rare earth oxide or a compound thereof.

7. The powder for ceramic molding according to claim 5 or 6, characterized in that the composition of the powder is a eutectic composition.

8. The powder for ceramic molding according to any one of claims 1 to 7, characterized in that the powder contains silicon oxide particles with a particle size of 5 μm or less.

9. The ceramic molding powder according to claim 8, characterized in that the mass of silicon oxide particles having a particle size of 5 μm or less is 0.04% or more and 5.0% or less of the mass of the absorbent.

10. A ceramic molding powder according to any one of claims 1 to 9, characterized in that it contains particles consisting of each individual composition.

11. A ceramic molding powder according to any one of claims 1 to 9, characterized by containing particles composed of two or more types of compositions.

12. The ceramic molding powder according to claim 11, characterized in that the absorbent composition constitutes particles on its own.

13. The ceramic molding powder according to any one of claims 10 to 12, characterized in that the particle size of the particles constituting the absorbent is 1 / 5 or less of the particle size of the particles of the composition that is not the absorbent.

14. The ceramic molding powder according to claim 13, characterized in that the particle size of the particles constituting the absorber is 10 μm or less.

15. A ceramic molding powder according to any one of claims 10 to 12, characterized in that it does not contain resin.

16. A ceramic molding powder according to any one of claims 10 to 15, characterized in that it satisfies a fluidity index of 40 [sec / 50g] or less.

17. A method for manufacturing ceramic molded objects, which involves repeatedly sequentially sintering or melting and solidifying powder in a laser light irradiation area to obtain a molded object, (i) A step of placing the ceramic molding powder according to any one of claims 1 to 16 into a laser irradiation section, (ii) A step of irradiating the ceramic molding powder with a laser to sinter or melt the ceramic molding powder and then solidify it, and (iii) A process of manufacturing a molded object by repeating steps (i) and (ii) above, A manufacturing method characterized by having the following features.

18. The manufacturing method according to claim 17, characterized in that steps (i) and (ii) are performed by irradiating the powder with a laser after it has been spread evenly.

19. The manufacturing method according to claim 17, characterized in that steps (i) and (ii) are performed by ejecting the powder to a predetermined location and irradiating the predetermined location with a laser.

20. A ceramic object made of an oxide containing aluminum, gadolinium, and terbium or praseodymium.

21. Furthermore, SiO ２ The ceramic molded product according to claim 20, characterized by containing particles.

22. A ceramic molding powder for obtaining a molded object by repeatedly sequentially sintering or melting and solidifying powder in a laser beam irradiation area, A powder for ceramic molding comprising at least one component selected from the group consisting of aluminum oxide, zirconium oxide, and silicon oxide; terbium oxide or praseodymium oxide; and at least one component selected from rare earth oxides other than terbium oxide and praseodymium oxide.

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