JP7575876B2 - Articles made of inorganic compounds and methods for manufacturing articles made of inorganic compounds - Google Patents

Description

The present invention relates to an article made of an inorganic compound and a method for manufacturing an article made of an inorganic compound using a direct fabrication additive manufacturing technique.

Ceramic (inorganic compound) structures that have both porous and non-porous structures are used in suction plates used for transporting and fixing objects, and filters for removing specific substances from fluids. Patent Document 1 discloses a vacuum chuck member as a fixture for fixing semiconductor wafers used in semiconductor manufacturing equipment, in which a mounting part for placing a semiconductor wafer is provided in a recess in a support part made of non-porous ceramics. The mounting part is made of porous ceramics, and the semiconductor wafer can be fixed by suction on the mounting part by sucking air through an intake port and the mounting part provided in the support part.

Conventionally, such vacuum chuck members have been formed by bonding a support part made of a non-porous ceramic body and a mounting part made of prefabricated porous ceramics together using glass paste.

However, because the strength of the adhesive layer is relatively weak, there is a problem that the porous ceramics may peel off from the adhesive layer made of glass paste depending on the usage conditions. In addition, because the adhesive layer is formed by melting solid glass, it is difficult to control the thickness of the adhesive layer.

In recent years, additive manufacturing technology, which uses energy beams to bond material powders to obtain objects of desired shapes, has become popular for resin and metal materials in applications such as creating prototypes in a short time or manufacturing small quantities of parts, and its application to the manufacture of ceramic parts is being considered.

Patent document 2 describes a method for manufacturing an article using the so-called powder bed fusion method. In this method, a powder layer made of a powder of a material is formed on a substrate, and an energy beam is selectively irradiated onto the portion of the powder layer that corresponds to the article, to repeatedly perform a series of steps to sinter the powder. In the repetition of this series of steps, the previously sintered portion and the later sintered portion are bonded to each other to obtain an article of the desired shape.

Direct manufacturing methods such as powder bed fusion do not require the use of molds or cutting from ingots, and can produce objects directly from powder, making it possible to obtain objects with high precision in a short time. In addition, since objects can be created based on three-dimensional data created using design tools such as 3D CAD (three-dimensional computer-aided design) software, this method has the advantage of making it easy to make design changes and capable of producing three-dimensional objects with complex and intricate shapes.

JP 2010-205789 A Special Publication No. 1-502890

Consider the case where a ceramic object in which the porous structure portion (porous portion) and the non-porous structure portion (non-porous portion) described in Patent Document 1 are integrated is produced by the direct molding method described in Patent Document 2. When the direct molding method is applied to ceramic materials that are less malleable than metal materials, numerous cracks are formed inside the object due to the stress generated when the material powder melts and solidifies. Therefore, in order to obtain a high-strength object, a post-processing step is carried out after molding with an energy beam to reduce cracks inside the object.

The post-treatment process can be a heat treatment. However, in the case of a ceramic object in which a porous structure and a non-porous structure are integrated, the thermal behavior of the porous and non-porous parts differs greatly. This difference in thermal behavior causes large stresses at the boundary between the porous and non-porous parts during the heat treatment, resulting in problems such as the porous structure having weak mechanical strength and the boundary breaking.

The present invention was made to address these issues, and aims to provide a method for manufacturing an article made of a high-strength inorganic compound that integrates a porous structure and a non-porous structure, using a direct molding additive manufacturing technique.

An article made of an inorganic compound according to one embodiment of the present invention is characterized in that it comprises a porous portion and a non-porous frame surrounding the porous portion in a planar direction, and has a stress relaxation portion between the porous portion and the frame.
According to another aspect of the present invention, there is provided a method for manufacturing an article made of an inorganic compound, the article having a porous portion having a porous structure and a frame body having a non-porous structure surrounding the porous portion, and a stress relaxation portion between the porous portion and the frame body, the method comprising the steps of: forming a powder layer using a powder containing an inorganic compound powder; and irradiating the powder layer with an energy beam based on the three-dimensional shape of the article, to melt and solidify, or sinter, the powder.

According to the present invention, it is possible to obtain an article made of an inorganic compound that has a porous structure and a non-porous structure integrated using a direct molding additive manufacturing technique.

1 is a flowchart showing a process flow in an example of a method for manufacturing an article of the present invention. 1 is a schematic process diagram illustrating an embodiment of a method for producing an article of the present invention. FIG. 1A-1D are schematic top and cross-sectional views of several example embodiments of articles of the present invention. 1A and 1B are a top view and a cross-sectional view of an article according to an example of another embodiment of the present invention. FIG. 13 is a schematic diagram showing an overhang of a shaping portion. FIG. 1 is a schematic diagram for explaining the configuration of an additive manufacturing device. FIG. 2 is a schematic diagram showing a cross section of an adsorption platform prepared in an embodiment.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
(Additive manufacturing equipment)
First, the additive manufacturing apparatus 100 used in this embodiment will be described with reference to Fig. 6. Fig. 6 is a schematic diagram for explaining the configuration of the additive manufacturing apparatus 100. As shown in Fig. 6, the additive manufacturing apparatus 100 includes a modeling table 101, a plate 102, a modeling container 103, vertical movement mechanisms 104 and 105, a powder supply container 106, a roller 107, a movement guide 108, a laser light source 109, a scanner 110, a condenser lens 111, and a control unit 112.

The modeling table 101 is a table for mounting the plate 102, and also serves as the bottom surface of the modeling container 103. The modeling table 101 has pins (not shown), which are fitted into pin holes (not shown) in the plate 102 to position the plate 102. It is preferable that the plate 102 is fixed to the modeling table 101 by screws. The plate 102 does not necessarily have to be plate-shaped as long as it functions as a support base when forming a model made of an inorganic compound, and the method of positioning and fixing the plate 102 to the modeling table is not limited to this example. The modeling table 101 is supported by a vertical movement mechanism 104 so that it can be moved vertically. Here, in the present invention, the "modeled object" refers to an object in the state produced by additive manufacturing technology, and an object after some processing such as heat treatment is performed on the modeled object as necessary is called an article. However, if no processing is required for the modeled object, the modeled object and the article refer to the same thing.

The additive manufacturing apparatus 100 further includes a powder supply container 106 adjacent to the modeling table 101, a roller 107, a moving guide 108 for moving the roller 107, a laser light source 109, a scanner 110, and a condenser lens 111. The powder supply container 106 is a device for storing powder 113 for modeling and for adjusting the supply amount of powder 113 according to the thickness of the powder layer to be deposited in the modeling container 103. The supply amount of powder 113 can be adjusted by the lift amount of the vertical movement mechanism 105. The roller 107 is supported by the moving guide 108 so that it can move horizontally, and moves modeling powder from the powder supply container 106 to the modeling container 103, forming a powder layer of a predetermined thickness while leveling the surface.

The laser light source 109, the scanner 110 and the focusing lens 111 constitute an irradiation optical system for locally and selectively irradiating the desired area 114 of the powder layer with the laser light 115.

The control unit 112 is a computer for controlling the operation of the additive manufacturing device 100, and includes a CPU 1121, memory 1122, storage device 1123, and an I/O port (input/output unit) 1124.

Memory 1122 is a random access memory (RAM) or a read-only memory (ROM). Storage device 1123 is a hard disk drive, a disk drive, a magnetic tape drive, or the like, and stores programs that realize the processing of the flowcharts described below.

The I/O port 1124 is connected to external devices and networks, and can, for example, input and output data required for additive manufacturing between an external computer. Data required for additive manufacturing includes shape data for the ceramic object to be produced, information on the material used in the modeling, and shape data for each sintered layer, i.e., slice data. The slice data may be received from an external computer, or may be created by the CPU 1121 in the control unit 112 based on the shape data of the modeling model and stored in memory.

The CPU 1121 loads the program stored in the storage device into the memory 1122 and executes it, causing the additive manufacturing device 100 to perform the processes described below.

The control unit 112 is connected to each part such as the vertical movement mechanism 104, the vertical movement mechanism 105, the roller 107, the laser light source 109, the scanner 110, and the focusing lens 111, and controls the operation of these parts to perform the modeling-related processing.

Figure 1 is a flow chart showing the process flow in the method for manufacturing an article made of an inorganic compound of the present invention. Below, an embodiment of the present invention will be described according to the flow of Figure 1. However, the method for manufacturing an article made of an inorganic compound of the present invention is characterized by forming a stress relaxation part for relieving stress generated between a porous part and a non-porous frame surrounding the porous part, and other requirements are not limited to the specific examples below.

(Outline of the process)
The present invention is a method for producing an article made of an inorganic compound, which has a porous structure and a non-porous structure integrated therein.

With reference to FIG. 1, the entire method for manufacturing an article made of an inorganic compound will be described, and then the characteristic parts of the present invention will be described. Each step of the method for manufacturing an article made of an inorganic compound described below is realized by the CPU 1121 expanding a program (data generation program) stored in the storage device 1123 into the memory 1122 and executing it.

First, the CPU 1121 acquires three-dimensional shape data of the object to be modeled (modeling model) (step S1). The acquired three-dimensional shape data of the object is input from a 3D CAD or a three-dimensional scanner via the I/O port 1124 of the control unit 112 and stored in the memory 1122.

Next, the CPU 1121 divides the three-dimensional shape data of the article into multiple objects (step S2), and assigns information on the porous/non-porous structure to each object (step S3). Alternatively, multiple objects to which information on the porous/non-porous structure has been assigned using 3D CAD or the like may be prepared in advance, and the three-dimensional shape data may be formed by combining these objects.

Next, the additive manufacturing device 100 creates shape data for each layer required to layer-form the object, i.e., slice data for the three-dimensional object (step S4).

Steps S1 to S4 may be performed by the CPU 1121 of the control unit 112 creating data based on the molding model and three-dimensional shape data and storing the data in RAM, or these steps may be executed by an external computer and the created data may be received via the I/O port 1124. Furthermore, when three-dimensional shape data and slice data having a stress relaxation portion are available, each step may be omitted.

Next, the plate 102 is positioned and fixed on the additive manufacturing device 100. After supplying material powder onto the plate to form a powder layer of a predetermined thickness, the material powder is melted/solidified or sintered by irradiating it with an energy beam according to the slice data to form a solidified portion in the powder layer. The formation of the powder layer and the irradiation of the energy beam are repeated to perform additive manufacturing (step S5), thereby obtaining a molded object corresponding to the molded model.

2(a) to (g) are schematic cross-sectional views showing step S5 in the powder bed fusion method, which is a preferred embodiment of the method for manufacturing an article made of an inorganic compound of the present invention. A material powder 301 containing an inorganic compound powder is used for manufacturing. First, a roller 352 is used to form a powder layer 302 made of the material powder 301 and having a predetermined thickness on a substrate 320 (see FIGS. 2(a) and (b)). Based on the slice data, an energy beam 501 emitted from an energy beam source 500 is irradiated while scanning the surface of the powder layer 302 to selectively melt and solidify or sinter the material powder (see FIG. 2(c)). At this time, it is preferable to melt and solidify or sinter the area having the same energy beam irradiation conditions in the slice data with a continuous drawing line. For example, when the energy beam irradiation conditions of the frame body 304 and the stress relaxation portion 306 are the same, it is preferable to first mold the area corresponding to the porous portion 305, and then mold the frame body 304 and the stress relaxation portion 306 with a continuous drawing line. This allows the formation of a stronger molded part 300. Furthermore, it is preferable to start with the formation of the part with the most pores in terms of design. That is, in the present invention, it is preferable to start with the formation of the porous part 305. For example, when the frame body 304 and the stress relaxation part 306 are under the same irradiation conditions, the powder in the area corresponding to the porous part 305 in the slice data is first bonded, and then the area corresponding to the frame body 304 and the stress relaxation part 306 is formed. This strengthens the bond between the end of the porous part 305 and the adjacent part, and allows the formation of a stronger molded part 300. In the figure, the stress relaxation part 306 is marked separately from the frame body 304, but the stress relaxation part 306 may be part of the frame body 304.

Here, the overhang portion will be explained using Figure 5. When forming a modeling portion 300 having an overhang portion at an angle θ with respect to the modeling direction (stacking direction), an overhang portion with θ of 45° or less can be stably modeled. If there is an overhang portion with θ of more than 45°, stable modeling is possible by forming, for example, a columnar support (not shown) to support the overhang portion. The support is preferably formed under energy beam irradiation conditions that make it porous or amorphous so that it can be easily removed after the model is formed.

The above process forms an area (modeled area) 300 where the material powder 301 has melted and solidified or sintered, and an area (non-modeled area) 303 where the powder remains in a powder state. Next, the stage 351 is lowered to a position one powder layer below the upper end of the modeling container 353, and a new powder layer 302 is formed to cover the modeled area 300 and the non-modeled area 303 (see FIG. 2(d)). The process of forming the powder layer 302 and the process of selectively melting and solidifying or sintering the material powder by irradiating the energy beam 501 while scanning are repeated once or multiple times (see FIG. 2(e)). Then, a modeled area is formed in which the modeled areas formed from each powder layer are integrated in the stacked powder layers (see FIG. 2(f)).

Next, the area (non-shaped portion) 303 that remains in a powder state and the unbonded material powder contained within the porous portion are removed, and if necessary, the shaped portion is subjected to post-processing such as separation from the substrate 320 and removal of the support, to obtain a shaped object 307 (see FIG. 2(g)). Details will be described later, but in the figure, the filled pattern with reference numeral 304 indicates the frame (non-porous portion), the filled pattern with reference numeral 305 indicates the porous portion, and the filled pattern with reference numeral 306 indicates the stress relaxation portion.

(Material powder)
The material powder used in the present invention is a powder of an inorganic compound. Here, the inorganic compound refers to a solid inorganic compound excluding metals, and the solid bonding state (crystalline or amorphous) does not matter. In this specification, the inorganic compound refers to an oxide, nitride, oxynitride, carbide, or boride containing one or more elements selected from the group of elements from Groups 1 to 14 of the periodic table excluding hydrogen, plus antimony and bismuth. Examples of inorganic compound powders that can be used as material powders include metal oxides, nonmetallic oxides, nitrides, fluorides, borides, chlorides, and sulfides. The material powder may be composed of one type of inorganic compound, or may be a mixture of two or more types of inorganic compounds. In addition, the inorganic compound powder refers to a powder mainly composed of an inorganic compound, and does not exclude the inclusion of components other than inorganic compounds.

Objects made primarily of inorganic compounds (hereafter simply referred to as objects) have greater mechanical strength than resins or metals.

The main component of the inorganic compound powder is preferably an oxide. Compared to other inorganic compounds, oxides have fewer volatile components, making them suitable for additive manufacturing using direct molding methods, as they can be stably melted using an energy beam. Representative oxides include aluminum oxide, zirconium oxide, magnesium oxide, silicon oxide, and mixtures or compounds of these.

Furthermore, as the material powder for additive manufacturing technology, powder containing aluminum oxide and zirconium oxide, or powder containing aluminum oxide and rare earth oxide is more preferable. These powders have a lower melting point than powder consisting of one type of inorganic compound, so they can be melted even with a low-output energy beam. If the material powder is not melted sufficiently, a molded object cannot be formed, so there is a lower limit to the output of the energy beam. However, by using the above powder, the lower limit is reduced, and the range of output values can be expanded. As will be described later, the wide range of output values makes it easier to create porous and non-porous objects. In addition, since molding can be performed with a small output, unnecessary adhesion and bonding of material powder due to heat transfer from the energy beam irradiation part is suppressed, improving molding accuracy.

From the viewpoint of improving the strength of the molded object, a powder that forms a phase separation structure by melting and solidifying is preferable. For example, it is preferable to use a mixture of a eutectic composition of aluminum oxide and zirconium oxide, or a mixture of aluminum oxide and rare earth oxide as the powder of the inorganic compound. By using these powders, a molded object having a phase separation structure consisting of two or more phases can be obtained. The phase separation structure has the effect of suppressing the extension of cracks, and additionally exhibits functions such as improving the mechanical strength of the molded object. In the present invention, the eutectic composition refers to a range of ±10% of the composition at the eutectic point.

In addition, when the energy beam is a laser beam, sufficient energy absorption in the material powder suppresses the spread of heat in the powder layer and makes it local, thereby reducing the effect of heat on non-modeled parts, thereby improving modeling accuracy. For example, when a Nd:YAG laser is used, Tb ₄ O ₇ , Pr ₆ O _11, etc., which show good energy absorption for the YAG laser, may be added to the material powder. From the above viewpoints, more suitable material powders include _{Al2O3 -ZrO2 , Al2O3 - Gd2O3} , _{Al2O3 - Y2O3} , Al2O3- _{Tb4O7 , ZrO2} - _Tb4O7 , _{Y2O3 - Tb4O7 ,} and _Gd2O3 - _{Tb4O7 , and even} more suitable material powders _{include Al2O3 - Gd2O3 - Tb4O7 , Al2O3 - ZrO2 - Tb4O7 , and Al2O3 - Y2O3 - Tb4O7 , etc.}

In the present invention, the inorganic compound powder may contain a small amount (10 parts by weight or less per 100 parts by weight of the inorganic compound powder) of an organic substance such as a resin or an inorganic substance such as a metal in addition to the inorganic compound in order to adjust the fluidity of the powder and the performance of the final molded product.

(Formation of powder layer)
An example of a preferred embodiment of the powder layer forming step in the present invention will be described.

In the powder layer forming process, a powder layer is formed using a material powder containing an inorganic compound powder. In the process of forming the first powder layer on the substrate 320, a powder layer 302 having a predetermined thickness is formed as shown in FIG. 2(b). In the process of forming the second and subsequent powder layers, a new powder layer 302 is formed on the powder layer (non-modeled portion 303) and solidified portion (modeled portion) 300 formed in the previous process (see FIG. 2(d)). There is no particular limitation on the method of forming the powder layer 302. It is preferable to form the powder layer 302 while specifying the layer thickness with a roller 352 or a blade as shown in FIG. 2(a).

Although the powder bed fusion method has been described above, the modeling method according to the present invention is not limited to this, and directed energy deposition modeling (so-called cladding method) can also be used. Directed energy deposition modeling is a method in which a powder layer is not formed, but instead material powder 301 is sprayed from a nozzle to the irradiation position of the energy beam irradiated based on slice data, and modeling material is piled up on the substrate 320 or the modeling surface of the modeling unit 300.

(Melting and solidifying or sintering of material powder)
The process of irradiating a powder layer with an energy beam based on slice data of a model to melt and solidify or sinter the powder (hereinafter, abbreviated as the modeling process) in the present invention will be described based on a preferred embodiment.

In the modeling process, an energy beam is applied according to the slice data to melt and solidify or sinter the material powder.

When a powder layer is irradiated with an energy beam of sufficient heat, the material powder absorbs the energy, which is converted into heat and melts the material powder. When irradiation of the energy beam is terminated, the molten material powder is cooled by the surrounding area adjacent to the molten area and solidifies. The area formed by melting and solidification is non-porous with few voids. However, the non-porous area contains microcracks formed by stress.

On the other hand, if the amount of heat applied is reduced, there is not enough heat to melt the powder material, and the majority of the time, the surfaces of the particles in the powder melt and the particles bond together (a phenomenon called sintering). In the case of sintering, voids tend to form around the joints (necks) between the particles. Also, if the amount of heat input is controlled to reduce the degree of sintering, unsintered particles that have not been able to bond with the surrounding particles will be mixed in the laser irradiated area, and by removing the unsintered particles by subsequent cleaning, a porous material with random voids can be formed.

By adjusting the scanning pitch of the energy beam, the powder can be melted and solidified or sintered into a honeycomb shape. Subsequent cleaning to remove unsolidified/unsintered particles can form a porous structure with regular voids.

Here, the spaces contained within the molded object (inside the outer shape) are collectively called voids, and the spaces formed by unsolidified/unsintered powder are called holes. That is, voids include holes in the porous part and microcracks generated by stress during molding. In the porous part of the molded object, there are voids that are designed and intentionally formed so that the manufactured item has the desired function, such as an adsorption function for transporting or fixing objects, or a filter function for removing specific substances from a fluid. The porosity can be evaluated by the following method. A scanning electron microscope (SEM) is used to obtain an SEM image of the polished surface of the molded object, and the porosity is calculated from the SEM image to determine the percentage of voids in the porous part, frame, and stress relaxation part.

The porous structure of the present invention refers to a structure in which the porosity per unit area of its cross section (hereinafter simply referred to as porosity) is 15% or more. From the viewpoint of improving the adsorption function, it is more preferable that the porosity of the porous portion is 18% or more. On the other hand, from the viewpoint of the porous portion maintaining its shape as a structure, it is preferable that the porosity is 60% or less. More preferably, it is 50% or less.

In the present invention, a non-porous structure refers to a structure having a porosity of 10% or less per unit area of its cross section. When high mechanical strength is required, it is preferable for the non-porous structure to have a small porosity, and a porosity of 5% or less is preferable.

As will be described in detail later, it is preferable that the stress relief portion is formed under the same energy beam irradiation conditions as the frame body. In other words, it is preferable that the stress relief portion has a non-porous structure and its porosity is 10% or less.

2(c), when the surface of the powder layer 302 formed on the substrate 320 is irradiated with the energy beam 501 while scanning, the powders in the area irradiated with the energy beam 501 melt and solidify or sinter to form the modeling part 300. At this time, if the output of the energy beam 501 is adjusted so that the heat given to the modeling material reaches the interface between the substrate 320 and the powder layer 302, the substrate 320 and the modeling part 300 are bonded. Also, as shown in FIG. 2(d) and FIG. 2(e), when the energy beam 501 is irradiated to the powder layer 302 formed on the modeling part 300, a new modeling part 300 is formed. At this time, the heat given to the modeling material reaches the interface between the previously formed modeling part and the powder layer 302 formed later, so that the previously formed modeling part and the newly formed modeling part are bonded to each other, and the modeling part 300 is formed. By repeating this series of melting and solidifying or sintering processes, the shaped parts formed in each powder layer are bonded together to form an integrated shaped object 307 (see Figure 2 (g)).

As the energy beam to be used, a light source having an appropriate wavelength is selected in consideration of the absorption characteristics of the material powder. In order to perform high-precision modeling, it is preferable to adopt a laser beam or an electron beam with a narrow beam diameter and high directivity. When the material powder contains oxide powder, the laser beam can be a YAG laser or a fiber laser in the 1 μm wavelength band, or a _CO2 laser in the 10 μm wavelength band.

In the present invention, when irradiating an energy beam in the melting and solidifying or sintering process, at least one of the output of the energy beam, the scan pitch, and the scan speed can be switched depending on the irradiation area, thereby making it possible to create a porous structure or a non-porous structure. In other words, the slice data contains information on which areas are to be made into a porous structure and which areas are to be made into a non-porous structure.

When irradiating the energy beam, at least one of the output, focal position, scan pitch, and scan speed of the energy beam can be switched according to the irradiation area to change the degree of melting or sintering of the material and the porosity of the molded part. For conditions for forming a non-porous structure, increasing the scan speed of the energy beam, increasing the scan pitch, or decreasing the output will form a porous structure. Specifically, when the degree of melting is high, the molded part will have a region with low porosity, i.e., a non-porous structure. When the degree of melting is low and sintering is the main process, the molded part will have a region with high porosity, i.e., a porous structure. Also, even if the degree of melting is high, if the scan pitch is sufficiently large, honeycomb-shaped pores will be formed and the molded part will have a region with high porosity, i.e., a porous structure.

If the output of the energy beam is too low, there may not be enough heat and some material may remain unmelted. Conversely, if the output of the energy beam is too high, it may melt too much and not achieve the desired modeling precision. To create porous and non-porous materials while still achieving modeling precision, it is preferable to change either the scanning speed or scanning pitch of the energy beam, or both.

The scanning speed also affects the time required to form a model. When switching the scanning speed to form a non-porous structure, the scanning speed must be reduced, which may slow down the modeling speed. Therefore, it is particularly preferable to switch the scanning pitch to create porous and non-porous structures without switching the scanning speed, as this does not significantly affect the modeling speed.

In the case of directed energy deposition modeling, it is also possible to create non-porous and porous structures by changing the amount of heat input. Specifically, as with powder bed fusion, the desired conditions can be derived by changing at least one of the following depending on the region: the output of the energy beam, the relative position between the build surface and the focus of the energy beam, the scan pitch, and the scan speed.

In the molding method of the present invention, the porous portion, frame, and stress relaxation portion formed by irradiating the energy beam are made from the same powder, and therefore have approximately the same composition.

The material for the substrate used in the present invention can be appropriately selected from metals, inorganic compounds and other materials commonly used in the manufacture of articles, taking into consideration the use of the article, manufacturing conditions, and the like.
The method for producing an article made of an inorganic compound according to the present invention is a method for obtaining an article that does not break at the boundary between the porous portion and the frame even when subjected to the heat treatment described below. Specifically, a step of irradiating a material powder with an energy beam to melt and solidify or sinter the material powder (shaping step) is performed to produce an article having a stress relaxation portion for relieving stress occurring at the boundary between the porous portion and the frame.

(Heat Treatment)
The molded object obtained in the molding process is preferably heated after the molding process. Heat treatment has the effect of reducing stress and microcracks formed in various parts of the molded object in the molding process. A more effective process for reducing or eliminating microcracks is to have the molded object absorb a liquid containing a component that can form a eutectic with the main component of the molded object and then heat the molded object to fix it. When the main component of the molded object is aluminum oxide, a process of having the molded object absorb a liquid containing a zirconium component (hereinafter referred to as a zirconium component-containing liquid) and then heating the molded object can be mentioned. The reduction or elimination of microcracks dramatically improves the strength of the molded object.

Here, the zirconium component-containing liquid will be described.
A preferred example is a zirconium component-containing liquid that is composed of a raw material for the zirconium component, an organic solvent, and a stabilizer.

Various zirconium compounds can be used as the raw material for the zirconium component. When absorbing a zirconium component-containing liquid into an alumina-based shaped object, it is preferable to use raw materials that do not contain metal elements other than zirconium. Zirconium metal alkoxides and salt compounds such as chlorides and nitrates can be used as raw materials for the zirconium component. Among them, metal alkoxides are preferable because they can homogeneously absorb the zirconium component-containing liquid into the microcracks of the shaped object. Specific examples of zirconium alkoxides include zirconium tetraethoxide, zirconium tetra n-propoxide, zirconium tetraisopropoxide, zirconium tetra n-butoxide, and zirconium tetra t-butoxide.

First, a zirconium alkoxide is dissolved in an organic solvent to prepare a zirconium alkoxide solution. The amount of organic solvent added to the zirconium alkoxide is preferably 5 to 30 in molar ratio to the compound. More preferably, it is 10 to 25. In the present invention, the molar ratio of A to B is 5, which means that the molar amount of A added is 5 times the molar amount of B. If the concentration of zirconium alkoxide in the solution is too low, a sufficient amount of zirconium components cannot be absorbed into the molded product. On the other hand, if the concentration of zirconium alkoxide in the solution is too high, the zirconium components in the solution will aggregate, and the zirconium components will not be uniformly arranged in the microcracks of the molded product.

As the organic solvent, alcohols, carboxylic acids, aliphatic or alicyclic hydrocarbons, aromatic hydrocarbons, esters, ketones, ethers, or a mixture of two or more of these are used. As alcohols, for example, methanol, ethanol, 2-propanol, butanol, 2-methoxyethanol, 2-ethoxyethanol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-propoxy-2-propanol, 4-methyl-2-pentanol, 2-ethylbutanol, 3-methoxy-3-methylbutanol, ethylene glycol, diethylene glycol, glycerin, etc. are preferred. As aliphatic or alicyclic hydrocarbons, n-hexane, n-octane, cyclohexane, cyclopentane, cyclooctane, etc. are preferred. As aromatic hydrocarbons, toluene, xylene, ethylbenzene, etc. are preferred. Preferred esters include ethyl formate, ethyl acetate, n-butyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, and ethylene glycol monobutyl ether acetate. Preferred ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Preferred ethers include dimethoxyethane, tetrahydrofuran, dioxane, and diisopropyl ether. When preparing the zirconium component-containing liquid used in the present invention, it is preferable to use alcohols from the viewpoint of solution stability among the various solvents mentioned above.

Next, the stabilizer will be described. Zirconium alkoxide is highly reactive to water, so it is rapidly hydrolyzed by the addition of moisture in the air or water, causing the solution to become cloudy and precipitate. In order to prevent this, it is preferable to add a stabilizer to stabilize the solution. Examples of stabilizers include β-diketone compounds such as acetylacetone, 3-methyl-2,4-pentanedione, 3-ethyl-2,4-pentanedione, and trifluoroacetylacetone; β-ketoester compounds such as methyl acetoacetate, ethyl acetoacetate, butyl acetoacetate, allyl acetoacetate, benzyl acetoacetate, isopropyl acetoacetate, tert-butyl acetoacetate, isobutyl acetoacetate, ethyl 3-oxohexanoate, 2-methyl ethyl acetoacetate, 2-fluoro ethyl acetoacetate, and 2-methoxyethyl acetoacetate; and alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine. The amount of stabilizer added is preferably 0.1 to 3 in molar ratio to the zirconium alkoxide. More preferably, it is 0.5 to 2.

Another preferred example is a zirconium component-containing liquid that is composed of particles of a zirconium component, a dispersant, and a solvent.
As the particles of the zirconium component, zirconium particles or zirconia particles, which is an oxide of zirconium, can be used. The zirconium particles or zirconia particles can be produced by crushing the respective materials using a top-down method, or can be synthesized by a bottom-up method using a technique such as a hydrothermal reaction from metal salts, hydrates, hydroxides, carbonates, etc., or can be commercially available products.
The particle size is preferably 300 nm or less, more preferably 50 nm or less, in order to allow the particles to penetrate into microcracks.
The shape of the particles is not particularly limited, and may be spherical, granular, cylindrical, elliptical, cubic, rectangular, needle-like, columnar, plate-like, scaly, or pyramidal.

The dispersant preferably contains at least one of an organic acid, a silane coupling agent, and a surfactant. As the organic acid, for example, acrylic acid, 2-hydroxyethyl acrylate, 2-acryloxyethyl succinic acid, 2-acryloxyethyl hexahydrophthalic acid, 2-acryloxyethyl phthalic acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, 3-methylhexanoic acid, and 3-ethylhexanoic acid are preferable. As the silane coupling agent, for example, 3-acryloxypropyl trimethoxysilane, 3-methacryloxypropyl trimethoxysilane, hexyltrimethoxysilane, octyltriethoxysilane, and decyltrimethoxysilane are preferable. As the surfactant, for example, ionic surfactants such as sodium oleate, potassium fatty acid, sodium alkyl phosphate ester, alkylmethylammonium chloride, and alkylamino carboxylate, and nonionic surfactants such as polyoxyethylene laurin fatty acid ester and polyoxyethylene alkylphenyl ether are preferable.

As the solvent, alcohols, ketones, esters, ethers, ester-modified ethers, hydrocarbons, halogenated hydrocarbons, amides, water, oils, or a mixture of two or more of these solvents is used. As the alcohols, for example, methanol, ethanol, 2-propanol, isopropanol, 1-butanol, ethylene glycol, etc. are preferable. As the ketones, for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc. are preferable. As the esters, for example, ethyl acetate, propyl acetate, butyl acetate, 4-butyrolactone, propylene glycol monomethyl ether acetate, methyl 3-methoxypropionate, etc. are preferable. As the ethers, for example, ethylene glycol monomethyl ether, diethylene glycol monobutyl ether, butyl carbitol, 2-ethoxyethanol, 1-methoxy-2-propanol, 2-butoxyethanol, etc. are preferable. As the modified ethers, for example, propylene glycol monomethyl ether acetate is preferable. Preferred examples of hydrocarbons include benzene, toluene, xylene, ethylbenzene, trimethylbenzene, hexane, cyclohexane, and methylcyclohexane. Preferred examples of halogenated hydrocarbons include dichloromethane, dichloroethane, and chloroform. Preferred examples of amides include dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone. Preferred examples of oils include mineral oil, vegetable oil, wax oil, and silicone oil.

The zirconium component-containing liquid may be prepared by simultaneously mixing zirconium particles or zirconia particles, a dispersant, and a solvent, or by mixing zirconium particles or zirconia particles with a dispersant and then mixing a solvent, or by mixing the zirconium or zirconia fine particles with the solvent and then mixing the dispersant, or by mixing the dispersant with the solvent and then mixing the zirconium or zirconia fine particles.
The above-mentioned solution may be prepared by reacting at room temperature or by refluxing.
In the manufacturing process, in which an energy beam is irradiated onto a powder layer to melt and solidify or sinter the powder, there is a large temperature difference between the irradiated area and its surroundings, which causes many microcracks to occur in the object as it cools and solidifies.

The zirconium component-containing liquid penetrates and distributes not only on the surface of the molded object, but also inside the molded object through the microcracks. As long as a sufficient amount of zirconia component can be present in a sufficient range of the microcracks of the molded object, there is no particular limitation on the method for absorbing the zirconium component-containing liquid into the molded object. The molded object may be immersed in the zirconium component-containing liquid to impregnate it, the zirconium component-containing liquid may be sprayed onto the molded object in a mist form, droplets may be dripped onto the molded object, or the liquid may be applied with a brush or the like. Furthermore, a combination of these methods may be used, or the same method may be repeated multiple times.

Next, the process of heating the molded object that has absorbed the zirconium component-containing liquid will be described. When the molded object absorbs the zirconium component-containing liquid in the process of absorbing the zirconium component-containing liquid (hereinafter referred to as the absorption process), a certain amount of zirconium component will be present on the surface of the molded object facing the microcracks. When a heat treatment is performed in this state, an amount of alumina component that is in a eutectic composition or a composition ratio close to the eutectic composition with respect to the amount of zirconium component will melt at a temperature lower than the melting point of the molded object near the area where the zirconium component is present on the surface. It is believed that this will then recrystallize and contribute to repairing the microcracks. As a result, only the area near the microcracks will soften while maintaining the shape of the molded object, and the effect of reducing or eliminating the microcracks will be obtained.

At this time, it is believed that the zirconium components do not remain on the surface of the microcracks, but also diffuse into the solid phase into the molded object. As the heating is stopped and the temperature drops, the zirconium components melt near the microcracks, and the components contained in the molded object mix and recrystallize. For this reason, it is believed that the bonds between the tissues in the repaired areas are stronger than when cracks are filled using methods such as glass infiltration, resulting in a molded object with high mechanical strength.

When the molded object contains aluminum oxide, the part of the molded object where the zirconium component is present, i.e., the vicinity of the microcracks, is partially melted by heating the molded object at a maximum temperature of 1600°C to 1710°C. A more preferable maximum temperature is 1650°C to 1710°C. If the microcrack part reaches the maximum temperature of 1600°C to 1710°C, the microcrack part where the zirconium component is present will melt. Therefore, the heating time is not particularly limited. In addition, by controlling the heating temperature, it is possible to melt only the vicinity of the part where the zirconium component is present, so that the shape of the molded object does not collapse and the advantages of the direct molding method are guaranteed. Therefore, the shape of the molded object is maintained even if it is heated for a long time. After melting, the molded object solidifies and recrystallizes, and the mechanical strength is greatly improved due to the reduction and disappearance of microcracks. The heating method is not particularly limited, but the method of heating the molded object in a furnace is simple. The components of the metal elements contained in the liquid absorbed into the object obtained in the modeling process and the heating temperature are not limited to the above examples. It is preferable to change the components of the metal elements absorbed in the liquid and the heating temperature depending on the composition of the powder used for modeling.

(Articles made of inorganic compounds)
The article made of an inorganic compound of the present invention has a porous portion having a porous structure and a frame body having a non-porous structure surrounding the porous portion in a planar direction, and has a stress relaxation portion between the porous portion and the frame body.

In the present invention, the stress relief portion has the function of relieving stress occurring at the boundary between the porous portion and the frame. By having the stress relief portion, it is possible to suppress cracking and deformation caused by the above-mentioned stress, and it is possible to form an article made of an inorganic compound in which the porous portion and the frame are integrated. This type of structure is particularly suitable when forming a structure made of an inorganic compound in which a porous structure and a non-porous structure are integrated by a direct molding additive manufacturing method such as powder bed fusion.

Objects made of inorganic compounds formed by additive manufacturing using the direct molding method have many microcracks inside. For this reason, it is preferable to heat treat the object after additive manufacturing in order to obtain higher strength. The heat treatment melts or sinters a portion of the object made of inorganic compounds, reducing the microcracks and improving the mechanical strength. In particular, by carrying out the above-mentioned absorption treatment process and heat treatment process on the object, the microcracks in the object are significantly reduced, further improving the mechanical strength.

In the case of a molded object in which a porous structure and a non-porous structure are integrated, the thermal properties of the porous structure and the non-porous structure are different, so that a large stress is generated at the boundary between the porous structure and the non-porous structure during heat treatment. In the article made of an inorganic compound of the present invention, the stress relaxation section provided around the non-porous section deforms in accordance with the contraction or expansion of each section during heat treatment of the molded object, thereby relieving the stress generated at the boundary between the porous section and the frame. This makes it possible to prevent breakage of the porous section, which has relatively weak mechanical strength, and the boundary between the porous section and the frame, and to obtain an article made of an inorganic compound with high strength in which the porous section and the frame are integrated.

The stress relaxation portion is preferably configured to be flexibly deformable in accordance with the deformation of the porous portion and the frame during the heat treatment. FIG. 3 shows an example of an embodiment of the article of the present invention in a top view and a cross-sectional view. FIG. 3 shows a plate-shaped article made of an inorganic compound having a porous portion 305 and a frame 304 surrounding the porous portion 305 in the in-plane direction, and a stress relaxation portion 306 around the porous portion 305 in the in-plane direction. In FIG. 3, the article has a support portion 308 having a non-porous structure that covers the periphery (side surface) of the non-porous portion between the porous portion and the stress relaxation portion. This makes it possible to increase the strength of the side surface of the porous portion 305. The thickness of the support portion 308 in the in-plane direction is preferably 5 mm or less, more preferably 3 mm or less. The stress relaxation portion 306 is provided at a location adjacent to the support portion 308.

In the article according to the present invention, the stress relief portion 306 is a non-porous structure portion that surrounds the porous portion 305 and is thinner than the porous portion in the direction perpendicular to the plane direction. The stress relief portion 306 is provided in a region within 10 mm from the end of the porous portion 305. In Fig. 3(a), Fig. 3(c), and Fig. 3(d), as shown in the D-D' cross section, the average thickness of the stress relief portion 306 is thinner than the average thickness of the porous portion 305. It is more preferable that the stress relief portion 306 is not only thinner than the non-porous portion, but also has an oblique shape or a bellows shape as shown in Fig. 3(c) and Fig. 3(d). If the stress relief portion 306 has an oblique shape or a bellows shape, it is easier to follow the thermal deformation of the porous portion 305 and the frame body 304. As a result, the thin-walled stress relief portion 306 can deform in response to the thermal contraction or thermal expansion of the porous portion 305 and relieve stress. Here, the average thickness of each of the stress relief portion 306 and the porous portion 305 refers to the average thickness in the thickness direction of the plate-like article.

In the case of a plate-shaped article having a structure with porosity in the in-plane direction and non-porous portions surrounding it, as shown in Figures 3(a), (c), and (d), it is preferable that the average thickness of the stress relaxation portion is smaller than the average thickness of the non-porous portion. From the viewpoint of high stress relaxation ability, the average thickness of the thin portion is preferably 70% or less of the average thickness of the non-porous portion, and more preferably 60% or less, although this depends on the porosity of each portion. On the other hand, in order to obtain sufficient strength of the molded object, it is preferable that the average thickness of the stress relaxation portion is 20% or more of the average thickness of the frame body.

The stress relief section 306 may be divided into a plurality of discontinuous parts spaced apart from each other as shown in FIG. 3(b) and FIG. 3(f). The E-E' cross sections in FIG. 3(b) and FIG. 3(f) show cross sections passing through a portion where no parts are provided. In FIG. 3(b) and FIG. 3(f), the thickness (thickness in the surface direction, which corresponds to the width of each part in the top view) of each part constituting the stress relief section 306 is thinner than the average thickness (thickness in the plate thickness direction) of the porous section 305. Even in the case of such a structure, each part of the stress relief section can deform in response to the thermal contraction or thermal expansion of the porous section 305, thereby relieving stress. Although the plurality of parts can relieve stress even if they are not thinned in the plate thickness direction, it is preferable that they are thinned in the plate thickness direction as well, since the effect of stress relief is enhanced. When the stress relief portion is divided into multiple discontinuous parts as shown in Figures 3(b) and (f), the sum of the widths of the parts of the stress relief portion is preferably 70% or less of the circumferential length of the porous portion, and more preferably 60% or less. In addition, in order to obtain sufficient strength for the molded object, the sum of the widths of the parts of the stress relief portion is preferably 20% or more of the circumferential length of the porous portion. Here, the width of each part of the stress relief portion refers to the average length of each part in the circumferential direction of the porous portion in the plan view of Figure 3.

When using additive manufacturing equipment such as powder bed fusion to mold, stable molding is possible if the overhanging portion is at an angle of 45° or less to the molding direction (the direction in which the powder layers are stacked). Therefore, it is preferable to design the stress relief portion 306 so that it is inclined at an angle of 45° or less to the molding surface during molding.

It is also preferable that the stress relaxation section 306 is formed in a structure having a porosity C that is greater than the porosity A of the porous section 305 and less than the porosity B of the frame 304, as shown in FIG. 3(e). The stress relaxation section 306 having such a structure also exhibits the thermal properties between the porous section and the frame during heat treatment, and can disperse stress, making it possible to obtain an article made of an inorganic compound in which a porous structure and a non-porous structure are integrated.

It is preferable that the density of the stress relief portion is greater than that of the porous portion and less than that of the frame. However, it is most preferable that the stress relief portion has a low porosity comparable to that of the frame. That is, if the average porosity of the stress relief portion is A and the average porosity of the frame is B, then the ratio A/B is preferably 0.9 to 1.1, and more preferably 0.95 to 1.05. By making the stress relief portion have a low porosity comparable to that of the frame, it is possible to suppress variation in the flow rate of fluid flowing out or in from the article through the porous portion. In addition, it is possible to obtain a strength high enough to withstand practical use.

It is preferable that the porous portion, the frame, and the stress relaxation portion are made of substantially the same material. When a support portion is provided around the porous portion, it is preferable that the support portion is also made of substantially the same material as the other portions. Specifically, it is preferable that the first metal element that is most abundant in the molar ratio and the second metal element that is second most abundant in the molar ratio are common to the porous portion, the frame, the stress relaxation portion, and the support portion. This makes it easier to control the temperature in the heating process to increase the strength of the molded object, and when the molded object is processed by a polishing process or the like, a smooth surface with fewer irregularities can be obtained. It is more preferable that the first metal element is aluminum and the second metal element is a rare earth element. An oxide containing aluminum and a rare earth forms a phase separation structure consisting of two or more phases. The phase separation structure has the effect of suppressing the extension of cracks, and is more preferable because it exhibits additional functions such as improving the mechanical strength of the molded object.

Figure 4 shows a tubular article according to another embodiment of the present invention. Figure 4(a) shows a perspective view of an article 407 long in one direction, and Figure 4(b) shows a cross-sectional view of the article 407 cut in a direction perpendicular to the longitudinal direction. In the in-plane direction shown in Figure 4(b), the article has a porous portion 405 having a porous structure and a frame body 404 having a non-porous structure surrounding the porous portion 405, and a stress relaxation portion 406 is provided surrounding the periphery of the frame body 404. As in Figure 3, the side of the porous portion 405 is thinly covered with a support portion 408 having the same density (porosity) as the frame body 404 in order to maintain strength. The thickness of the support portion 408 is preferably 5 mm or less, more preferably 3 mm or less.

The stress relief section 406 in FIG. 4 is composed of multiple parts that are discontinuous with each other, and has a structure in which the plate-shaped article made of an inorganic compound shown in FIG. 3(f) is elongated in the plate thickness direction. The stress relief section 406 is not limited to the example shown in FIG. 4. It may be composed of multiple parts that are continuous in the cross-sectional direction and discontinuous in the length direction, or it is also preferable that the stress relief section 406 is formed in a structure having a porosity C that is greater than the porosity A of the porous section 405 and less than the porosity B of the frame body 404.

In the case of the structure shown in FIG. 4, the sum of the circumferential widths of the parts of the stress relief section 406 is preferably 70% or less of the circumferential length of the porous section 405, and more preferably 60% or less. This refers to the stress relief section.

In addition, when the stress relief section 406 is composed of multiple parts that are continuous in the circumferential direction but discontinuous in the longitudinal direction, the sum of the plate thicknesses (width in the longitudinal direction) of each part is preferably 70% or less of the longitudinal length of the article, and more preferably 60% or less. In order to obtain sufficient strength of the article, it is preferable that the sum of the plate thicknesses of the porous section 405 is 20% or more of the longitudinal length of the article. Here, the plate thickness of each part of the stress relief section 406 refers to the average length of each part in the longitudinal direction.

The article made of the inorganic compound of the present invention is suitable for use as an adsorption plate used when transporting or fixing objects. Inorganic compounds have a higher thermal resistance than metals. In addition, the thinned stress relief portion has a small cross-sectional area in the thickness direction of the plate, and therefore has a high thermal resistance. Therefore, by using the article made of the inorganic compound of the present invention as an adsorption plate, it is possible to suppress heat transfer to the porous portion (adsorption portion). For example, if it is used as a plate on which a chip is placed in a die bonder device for mounting semiconductors, it is possible to suppress the deterioration of the mounting adhesive tape attached to the chip due to heat.

The following examples are provided to explain in detail the article made of an inorganic compound according to the present invention and the method for producing an article made of an inorganic compound, but the present invention is not limited to these examples.

Example 1
This embodiment is an example in which a plate-shaped article having a frame body with a non-porous structure, a thinned stress relaxation portion, and a porous portion having a lattice pattern is produced under melting/solidification conditions and used as an adsorption plate.

First, a design drawing of a molded object having a porous portion, a frame body made of a non-porous structure, and a thin-walled stress relief portion was created using 3D CAD software. The outline of the desired molded object is shown in FIG. 3(d). The molded object is a square plate with a size of 4 cm on each side and a thickness of 8 mm. The outer periphery of the plate is formed of a non-porous structure, and in the center there is a square porous portion with a size of 1 cm on each side, made of a porous structure that is connected in the thickness direction of the plate. The corners of the square shape have an arc with a radius of 2 mm. As shown in the figure, the plate is thinned in the thickness direction and has a bellows-shaped stress relief portion made of a non-porous structure. The average plate thickness of the stress relief portion is 3 mm, which is 38% of the average plate thickness of the porous portion.

From the 3D CAD design drawing, slice data with a thickness of 20 μm was created in the thickness direction of the plate, and the slice data was imported into the additive manufacturing device.

Next, α-Al ₂ O ₃ powder, Gd ₂ O ₃ powder, and Tb ₂ O _3.5 powder (Tb ₄ O ₇ powder) were prepared, and each powder was weighed so that the molar ratio was Al ₂ O ₃ : Gd ₂ O ₃ : Tb ₂ O _3.5 = 77.4: 20.8: 1.8. The weighed powders were mixed in a dry ball mill for 30 minutes to obtain a mixed powder (material powder).

Through a process essentially similar to that shown in Figure 2 above, the object of Example 1 was formed based on the slice data.

To form the object, we used a 3D SYSTEMS ProX DMP 100 (product name) equipped with a 50 W Yb fiber laser (beam diameter 65 μm).

First, a roller was used to form a 20 μm-thick first powder layer of the above material powder on a pure alumina base. A 30 W laser beam was irradiated onto the powder layer at a scan speed of 140 mm/s and a scan pitch of 100 μm, filling the powder layer with the material powder in the area that forms the non-porous structure based on the slice data of the first layer, melting and solidifying the material powder in the area that forms the non-porous structure. Next, the 30 W laser beam was irradiated onto the powder layer at a scan speed of 180 mm/s and a scan pitch of 175 μm, solidifying the material powder in the area that forms the porous structure based on the slice data of the first layer. The drawing line was set to be at an angle of 45° to the square.

Next, a new powder layer 20 μm thick was formed with a roller so as to cover the above powder layer. Based on the slice data for the second layer, the powder in the area forming the non-porous structure was melted and solidified in a direction perpendicular to the drawing line of the first layer, and then the powder in the area forming the porous structure was solidified. This process was repeated based on the slice data for each layer to form the molded object of Example 1. The cut allowance for separating from the base was set to a thickness of 10 mm, which was the design value + 2 mm. The obtained molded object was separated from the base and unbound powder was removed to obtain a molded object (thickness 8 mm) in which the porous structure and non-porous structure parts were integrated.

Next, the shaped object was immersed in a zirconium component-containing liquid. The zirconium component-containing liquid was prepared as follows. A solution was prepared by dissolving 85% by weight of zirconium (IV) butoxide (hereinafter, referred to as Zr(O-n-Bu) ₄ ) in 1-butanol. The above-mentioned Zr(O-n-Bu) ₄ solution was dissolved in 2-propanol (IPA), and ethyl acetoacetate (EAcAc) was added as a stabilizer. The molar ratio of each component was Zr(O-n-Bu) ₄ :IPA:EAcAc=1:15:2. After that, the mixture was stirred at room temperature for about 3 hours to prepare a zirconium component-containing liquid. The weight concentration of the zirconia solid content in this liquid was 8%.

The above molded object was immersed in the zirconium component-containing liquid, degassed under reduced pressure for one minute, and the liquid was allowed to penetrate into the molded object, after which it was naturally dried for one hour.

The molded object impregnated with the zirconium component-containing liquid as described above was placed in an electric furnace and heated. Specifically, the sample was heated to 1670°C in an air atmosphere over 2.5 hours, held at 1670°C for 50 minutes, and then cooled to below 200°C over 5 hours.

In Example 1, the process of immersing the shaped object in a zirconium component-containing liquid and the process of heating were alternately repeated three times to obtain an article 707 made of an inorganic compound as shown in FIG. 7. The article 707 is a plate-like article in which a porous portion 705 and a non-porous portion 704, the sides of which are covered with a support portion 708, are connected in the in-plane direction via a stress relaxation portion 706, and are integrated together.

The porous portion 705 of the manufactured article 707 had open pores that communicated from one surface to the opposite surface. The manufactured article 707 was screwed to a main body portion 709 having a recess 711 and connected to an air vent 710 so as to close the recess 711, thereby manufacturing an adsorption table 700. When a Si wafer was placed on the article (adsorption plate) 707 and the air inside the main body 709 was discharged from the air vent 710 using a pump or the like, the recess 711 was reduced in pressure, and the Si wafer could be adsorbed. When air was introduced from the air vent 710 to remove the Si wafer that had been adsorbed, the pressure in the recess 711 increased, and the Si wafer could be easily removed from the adsorption plate.

The surface of the obtained article was polished and the porosity was calculated from the image observed under SEM. The porosity of the porous portion was 31%, and the porosity of the frame and stress relaxation portion was 2%.

To confirm the strength of the object, a similar object was created and subjected to a drop test. The plate-shaped object was allowed to freely drop onto lauan wood from heights of 30 cm, 60 cm, and 100 cm so that it would land on the side corner of the object, but no damage was observed.

Example 2
This example is an example in which heating was performed only once without performing zirconium impregnation after shaping. An article made of an inorganic compound was produced under the same conditions as in Example 1, except that there was no zirconium impregnation step and heating was performed only once.

Example 3
This embodiment is an example in which the open pores in the porous portion are randomly arranged.
In order to obtain a porous portion having randomly arranged open pores, an article made of an inorganic compound was produced under the same conditions as in Example 1, except that the drawing speed was set to 220 mm/s and the drawing pitch was set to 125 μm.

Example 4
This embodiment is an example in which an article having a shape different from that of the first embodiment was produced.
The outline shape of the target article is shown in FIG. 3(f). The article is a disk with a diameter of 4 cm and a thickness of 15 mm, the outer periphery of the disk is formed of a non-porous part, and there is a circular porous part with a diameter of 1 cm in the center that is connected in the thickness direction of the disk. Between the non-porous part and the porous part, there is a stress relaxation part having a shape thinned in the in-plane direction of the plate as shown in FIG. 3(f), which is divided into eight parts at equal intervals in a radial direction. The average width (16 mm) of the stress relaxation part, which is the sum of the average width (2 mm) of each part of the stress relaxation part, is about 51% of the circumferential length π of the circular porous part. An article made of an inorganic compound was produced under the same conditions as in Example 1 except for the shape.

Example 5
This example is an example of producing an article with a stress relaxation part having a different shape from that of Example 1. The outline shape of the target article is shown in FIG. 3(a). As shown in the figure, the molded object of this example has a stress relaxation part having a shape that is thinned parallel to the thickness direction of the plate. The thickness of the stress relaxation part is uniform at 5.6 mm, which is 70% of the thickness of the porous part, 8 mm. In this example, a support formed under the same conditions as the porous part was provided at the bottom of the stress relaxation part, which is an overhang part at 90° to the molding direction (lamination direction of the powder layer). A molded object with a support was formed by repeating the process of melting/solidifying or sintering the material powder by irradiating an energy beam in the same manner as in Example 1. After removing the support from the molded object, it was separated from the base and unbonded powder was washed and removed, and an article made of the inorganic compound of Example 5 was produced through the same manufacturing method as in Example 1.

Example 6
This example is an example in which an article was produced in which the average width of the stress relaxation parts was different from that in Example 4.
The article is a circular plate with a diameter of 4 cm and a thickness of 15 mm, the frame (the outer periphery of the circular plate) is formed of a non-porous structure, and there is a circular porous portion with a diameter of 1 cm in the center, which is made of a porous structure that is connected in the thickness direction of the circular plate. The stress relaxation portion, which is thinned in the in-plane direction of the plate, is divided into 10 parts at equal intervals in a radial direction. The average width (9 mm) of the stress relaxation portion, which is the sum of the average width (0.9 mm) of each part of the stress relaxation portion, is about 29% of the circumferential length π of the circular porous portion. An article made of an inorganic compound was produced under the same conditions as in Example 4, except for the average width of the stress relaxation portion and the number of parts.

(Comparative Example 1 and Comparative Example 2)
A comparative article was produced that did not have a stress relaxation section between the porous section and the frame. The comparative article was a square plate with a size of 4 cm on each side and a thickness of 8 mm, the frame (the outer periphery of the plate) was formed with a non-porous structure, and in the center was a square porous section with a size of 1 cm on each side and a porous structure that was continuous in the thickness direction of the plate. No stress relaxation section was provided between the porous section and the frame.

For the comparative article of Comparative Example 1, the process of impregnating the shaped object with a zirconium component-containing liquid was not carried out, and the heating process was carried out only once. For the article of Comparative Example 2, the shaped object produced under the same conditions as in Example 1 was impregnated with a zirconium component-containing liquid, and then the heating process was carried out once. Under both conditions, cracks appeared at the boundary between the porous portion of the article and the frame during the heating process.

The evaluation results of the examples and comparative examples are summarized in Table 1. Note that the drop test results in the table are marked as OK if no damage was observed on the item, and NG if even a small amount of damage was observed. Disc-shaped items were also dropped so that they landed on their side.

The functionality as an adsorption plate was also confirmed for the articles made of inorganic compounds from Examples 2 to 6. The adsorption table shown in FIG. 7 was produced by fixing the adsorption plates made of inorganic compounds from Examples 2 to 6 in order so as to cover the recess 711 of the main body, and the functionality as an adsorption table was confirmed in the same manner as in Example 1. The articles made of inorganic compounds from Examples 1 to 6 had open pores that communicated from one surface to the opposite surface, and for all of the molded objects, the Si wafer could be adsorbed by suctioning air.

The comparative objects in Comparative Examples 1 and 2 were unable to adsorb the Si wafer due to cracks that appeared during the heating process.

(Discussion)
The shaped objects of Examples 1 to 6 were able to form articles made of an inorganic compound in which the porous portion and the frame body were integrated even after the heating step. On the other hand, in the comparative example not having a stress relaxation portion, cracks occurred at the boundary between the porous portion and the frame body during the heating step, and an article in which the porous portion and the frame body were integrated could not be obtained.

Examples 1 and 3 to 6, which underwent the impregnation and heating process, had high strength and were able to withstand a 60 cm drop test.

Furthermore, when comparing objects of the same shape, the effect of stress relaxation was greater for objects with bellows-shaped stress relaxation sections, as in Examples 1 and 3, and the drop test results were better than for the flat plate-shaped object of Example 5. It is believed that Example 5 had some residual stress.

In addition, compared to Example 6, Examples 1, 3, and 4 have an appropriate average thickness of the stress relaxation portion relative to the average thickness of the porous portion, and therefore have high strength and good drop test results.

300... Modeled portion 301... Material powder 302... Powder layer 303... Non-modeled portion 304, 404, 704... Frame 305, 405, 705... Porous portion 306, 406, 706... Stress relaxation portion 307, 407, 707... Article 308, 408, 708... Support portion

Claims (20)

a first portion having a porous structure and a frame having a density greater than that of the first portion, the frame being disposed in an in-plane direction so as to surround the first portion;
a second portion which is a stress relaxation portion between the first portion and the frame body,
An article made of an inorganic compound, in which the first portion, the frame, and the second portion are integrated together ,
the second portion has at least one of a first structure, a second structure, and a third structure;
In the first structure, an average thickness of the second portion in a direction perpendicular to the in-plane direction is smaller than an average thickness of the first portion in a direction perpendicular to the in-plane direction,
In the second structure, the second portion is composed of a plurality of non-contiguous parts spaced apart from each other ,
An article characterized in that, in the third structure, the porosity of the second portion is greater than the porosity of the first portion and smaller than the porosity of the frame body. The article according to claim 1, further comprising a third portion between the first portion and the second portion and surrounding the first portion, the third portion having a structure in which the porosity per unit area of a cross section of the third portion is 10% or less . The article according to claim 2, characterized in that the thickness of the third portion in the in-plane direction is 5 mm or less. The article according to any one of claims 1 to 3, characterized in that the second portion is provided within a range of 10 mm from the end of the first portion. An article according to any one of claims 1 to 4, characterized in that the porosity per unit area in the cross section of the first portion is 15% or more, and the porosity per unit area in the cross section of the frame is 10% or less. The article according to any one of claims 1 to 5, characterized in that each of the frame and the second portion contains at least one of aluminum oxide or zirconium oxide. The article according to claim 6, characterized in that the ratio A/B of the porosity A of the second portion to the porosity B of the frame is 0.9 or more and 1.1 or less. The article according to any one of claims 1 to 7, characterized in that the first part, the frame and the second part each contain a first metal element, and the first part, the frame and the second part each contain a second metal element different from the first metal element. The article according to claim 8, wherein the first metal element is aluminum and the second metal element is a rare earth element. An article according to any one of claims 1 to 9, characterized in that the article is plate-shaped. a main body portion having a vent hole connected thereto and a recess;
a suction plate that covers the recess,
A suction platform, characterized in that the suction plate is an article according to any one of claims 1 to 10. The article according to any one of claims 1 to 10, characterized in that the weight concentration of the metal or resin contained in the first portion is 1/10 or less of the weight concentration of the common inorganic compound in the first portion. The article according to any one of claims 1 to 10 and 12, characterized in that the inorganic compound is at least one selected from the group consisting of oxides, nitrides, fluorides, borides, chlorides and sulfides. The article according to any one of claims 1 to 10, 12 and 13, characterized in that the frame includes a phase-separated structure consisting of two or more phases. The article according to any one of claims 1 to 10 and 12 to 14, characterized in that the first part and the frame are connected and integrated via the second part. The article according to any one of claims 1 to 10 and 12 to 14, wherein the second portion has the first structure. The article according to any one of claims 1 to 10 and 12 to 14, wherein the second portion has the second structure. The article according to any one of claims 1 to 10 and 12 to 14, wherein the second portion has the third structure. The method for manufacturing an article according to any one of claims 1 to 10 and 12 to 18, characterized in that an object including the first part, the frame body, and the second part is formed by a direct molding method. 19. The method of claim 1, wherein the article including the first portion, the frame, and the second portion is formed by powder bed fusion.

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