Ceramic powder, ceramic shaped article made therefrom, and method for producing the same

Abstract

To provide ceramic powder suitably used for molding by a binder jet type 3D printer, a ceramic molded object made of the same and a manufacturing method for the same.SOLUTION: Ceramic powder is composed of particles with at least three different center diameter particle sizes. The ceramic powder is composed of silicon carbide, silicon nitride, alumina, silica, or zirconia. The ceramic powder contains 62% or more particles with a center diameter of 31 to 60 μm, 7% or more particles with a center diameter of 11 to 20 μm and 4% or more particles with a center diameter of 1.1 to 3.0 μm. The ceramic powder consists of 0.01 to 2.0% particles with a center diameter of 0.51 to 1.0 μm or 0.01 to 0.4% particles with a center diameter of 0.05 to 0.30 μm or 0.01 to 4.0% particles with a center diameter of 0.31 to 0.50 μm.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a ceramic powder used for forming by a binder jet type 3D printer, a ceramic shaped article thereby, and a method for manufacturing the same.

Background Art

[0002] In the conventional forming of ceramic powders by CIP (Cold Isostatic Pressing) or casting, a shape along a mold or a plaster mold can be formed, but a formed body reproducing a complex shape inside the formed body cannot be obtained. Moreover, in order to satisfy the final shape and dimensional accuracy of the required specifications, finishing by machining or the like is necessary after firing.

[0003] On the other hand, in the case of products that are difficult to process, time-consuming, and laborious to join parts in the conventional method, and products that are desired to be manufactured as inexpensively as possible for multi-variety and small-lot products, in recent years, a shaping method using a 3D printer has been effectively utilized. (Non-Patent Document 1) In the case of a 3D printer of a stereolithography method using a laser beam among various shaping methods using a 3D printer, a slurry prepared by adding a photocurable resin to a ceramic raw material is thinly spread and cured by a laser beam such as ultraviolet light to perform shaping. Therefore, a dense body with a complex shape can be formed, and a high-density fired body can be obtained by firing in a subsequent process.

[0004] However, when shaping with a 3D printer of the stereolithography method, it is necessary to remove the unexposed material after shaping (see Patent Document 1: two kinds of inorganic particle slurries having different particle sizes) and to perform a degreasing treatment on the resin used as a binder.

[0005] In addition, it is necessary to adjust the slurry containing ceramic powder used in the stereolithography method. If the particle size of the ceramic powder is too large, the stability in the slurry will decrease and it will be prone to sedimentation, so there is a risk that a uniform slurry cannot be obtained. Furthermore, if the particle size of the ceramic powder is large (exceeding 100 μm), it will be difficult to fabricate a stereolithographic object that requires precise dimensions. (Patent Document 2: Blending a silane compound with silica powder) Additionally, there is also a problem that cracks or deformations may occur during the process of removing the unexposed material after shaping and the debinding process of the resin used as a binder.

[0006] In addition, in the case of ceramics such as SiC (silicon carbide) that have a very high absorption rate for short-wavelength visible light and ultraviolet light used in stereolithography-type 3D printers, light is absorbed in the SiC slurry and it is difficult to pass through, making shaping difficult. Even in the case of oxide-based alumina with a low light absorption rate, in the case of the stereolithography method, it is difficult to fabricate a size with a pore diameter of about φ0.3 mm or less and a thickness of 6 mm or more, and there are also disadvantages such as it being impossible to fabricate a fully closed hollow space shape in terms of manufacturing method. (Non-Patent Document 1)

[0007] Regarding the above-mentioned technical problems of the stereolithography method, in the binder jet method, which is one of the shaping methods of 3D printers, without using light, a binder resin layer for shaping is sprayed and laminated on a thinly applied and spread layer of ceramic powder, and this is repeated for shaping. Therefore, it is possible to shape ceramics such as SiC that have a high absorption rate for short-wavelength visible light and ultraviolet light. Furthermore, it has features such as being suitable for manufacturing porous bodies with complex shapes and large-sized shaped products.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0009] [Non-Patent Document 1] The Ceramic Society of Japan, Ceramics 56 (2021) No.11 P747 - P750 [Summary of the Invention] [Problems to be Solved by the Invention]

[0010] As described above, in conventional molding methods such as CIP and casting molding, although a near-net shape along the mold can be molded, a molded body that reproduces a complex shape inside the molded body could not be obtained.

[0011] Also, in recent years, in the molding by a stereolithography-based 3D printer that is being developed, it is difficult to mold a thick and large-sized molded body. Among ceramics, for materials that absorb short-wavelength visible light such as silicon carbide and ultraviolet light and are difficult to reflect and transmit, the curing depth of the photocurable resin in the slurry such as silicon carbide is shallow, warping of the molded body occurs, and it has been difficult to mold thick-walled products.

[0012] On the other hand, when using a binder jet type 3D printer that does not use light during molding, although single-grain ceramic raw materials can be molded, there are problems such as low strength of the molded and fired products, and they are easily damaged just by touching, making handling difficult.

[0013] Also, when trying to increase the strength of the molded product for easy handling and increasing the amount of binder sprayed, the dimensional accuracy decreases. Furthermore, when compounding raw materials with different particle sizes to increase the bulk density and strength, the fluidity decreases, and it becomes difficult to perform recoating to uniformly and thinly sprinkle and apply the ceramic powder, presenting mutually contradictory problems.

[0014] The present invention has been made in view of the problems of the above background art, and an object thereof is to provide a ceramic powder suitably used for molding by a binder jet type 3D printer, a ceramic molded article thereby, and a manufacturing method thereof. [Means for Solving the Problems]

[0015] The present invention relates to a ceramic powder used for forming a ceramic shaped article by a binder jet type 3D printer, which is a ceramic powder composed of particles having at least three different median diameters. The ceramic powder is made of silicon carbide, silicon nitride, alumina, silica, or zirconia.

[0016] The ceramic powder contains at least 62% or more of particles having a median diameter of 31 to 60 μm (% in the present invention is mass%, hereinafter simply referred to as %), 7% or more of particles having a median diameter of 11 to 20 μm, and 4% or more of particles having a median diameter of 1.1 to 3.0 μm. Further, it is preferable that the ceramic powder is added with 0.01 to 2.0% of particles having a median diameter of 0.51 to 1.0 μm, or 0.01 to 0.4% of particles having a median diameter of 0.05 to 0.30 μm, or 0.01 to 4.0% of particles having a median diameter of 0.31 to 0.50 μm.

[0017] The present invention also relates to a ceramic shaped article fired from the above ceramic powder, wherein the ceramic is made of silicon carbide, and the three-point bending strength of the ceramic shaped article has a value of 170 MPa or more.

[0018] The present invention also relates to a method for manufacturing a ceramic shaped article formed by firing the above ceramic powder, wherein the ceramic is silicon carbide, and the step of recoating the ceramic powder on the portion where the binder material is ejected by the 3D printer is repeated to form a molded body of the ceramic shaped article with the binder material, and then the molded body is fired to form the ceramic shaped article. In particular, it is preferable to manufacture with the addition rate of the binder material being 30 to 40%.

Advantages of the Invention

[0019] The present invention provides a mixing ratio of ceramic powder raw materials suitable for a binder jet type 3D printer, a ceramic shaped article made of the ceramic powder, and a manufacturing method thereof. Thereby, it becomes possible to form complex shapes and thick shaped articles that could not be obtained by CIP, casting molding, and 3D printers of the stereolithography method. Furthermore, the present invention has developed a raw material formulation with good fluidity suitable for shaping by a binder jet type 3D printer, and it becomes possible to recoat the raw material uniformly without unevenness on the print bed of the job box.

[0020] In the present invention, it has been found that proper settings for improving the fluidity of the raw material powder, such as the management of temperature and humidity during shaping and the ultrasonic output in the application of the ceramic powder during recoating, are important, and thereby it has become possible to maintain a stable and constant recoating speed and uniformity.

[0021] The shaped articles and fired articles made of the ceramic powder according to the present invention have a handleable strength that was difficult for shaped articles of conventional formulations. For example, in the case of silicon carbide, the molding strength and firing strength are about 1.5 MPa, and handling is easily possible. The Si-impregnated product has very little dimensional change from the molded body and the fired body, so it has good processing accuracy, and it has also obtained strength (about 170 MPa or more) and heat resistance that can be used in applications where load resistance and heat resistance are required.

[0022] Also, in the present invention, not only has it become possible to produce a silicon carbide molded body by binder jet type 3D printer shaping, but by selecting the optimum conditions for firing (and Si impregnation), it has become possible to obtain a product having a strength equal to or higher than that of products used in conventional semiconductor manufacturing equipment jigs (170 MPa or more, preferably 200 MPa or more by adjusting the blending conditions) after Si impregnation.

[0023] Furthermore, in order to improve the fluidity, for example, in the case of a silicon carbide raw material, the blending of raw materials with center diameters of 3 to 6 types in a predetermined ratio 50) By adding a certain amount of those with a submicron size (0.05 μm to 1.0 μm in the present invention), the bulk density was improved and the fluidity was further enhanced. As a result, the fluidity of the powder required for recoating in the binder jet method was improved, segregation depending on the location was reduced, and stable and uniform recoating could be achieved.

[0024] Also, in the present invention, it has been found that by maintaining the addition rate of the binder within a certain range, it is possible to maintain the handling strength while maintaining the dimensional accuracy within ±10 mass% of the target value. For example, in the case of silicon carbide, an addition rate of 30 to 40% of the binder is suitable, and the dimensional accuracy can be maintained within ±10% of the target value, and the molding strength can also be maintained at a level that can be handled.

Brief Description of the Drawings

[0025]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0026] Hereinafter, the implementation of the present invention will be described. The present invention is a ceramic powder used for forming a ceramic shaped article by a binder jet type 3D printer, and is a ceramic powder composed of particles having at least three different particle sizes with central diameters.

[0027] The ceramic powder is made of silicon carbide, silicon nitride, alumina, silica, or zirconia. In particular, the ceramic powder contains at least 62% or more of particles with a central diameter of 31 to 60 μm, 7% or more of particles with a central diameter of 11 to 20 μm, and 4% or more of particles with a central diameter of 1.1 to 3.0 μm. Further, the ceramic powder is preferably formed by adding 0.01 to 2.0% of particles with a central diameter of 0.51 to 1.0 μm, or 0.01 to 0.4% of particles with a central diameter of 0.05 to 0.30 μm, or 0.01 to 4.0% of particles with a central diameter of 0.31 to 0.50 μm, and is composed of powders having at least 3 to 6 of the above central diameters.

[0028] The method for manufacturing a ceramic shaped article formed by firing the ceramic powder of the present invention is, for example, when the ceramic is silicon carbide, repeating the step of recoating the ceramic powder on the portion where the binder material is ejected by the 3D printer to form a molded body of the ceramic shaped article with the binder material, and then firing the molded body to form the ceramic shaped article. Here, the addition rate of the binder material is preferably 30 to 40%. In the binder jet method, recoating, binder injection, and heating are repeated to stack thin layers for shaping.

[0029] Next, embodiments of the ceramic shaped article formed by the ceramic powder of the present invention will be described based on the drawings.

[0030] FIG. 1 and FIG. 2 are examples of the ceramic shaped article 10 of a heat sink in which several drum-shaped columns are standing. The ceramic shaped article 10 cannot be molded by a molding method using a conventional mold because it cannot be demolded, but using the ceramic powder of the silicon carbide raw material adjusted in the formulation of the example of the present invention, the uneven portion 12 of the drum-shaped column can be formed by a 3D printer of the binder jet method. The shaping of the ceramic shaped article 10 of the heat sink has become possible.

[0031] Also, FIGS. 3 and 4 show examples of the formed body 20 of the turbine model and the ceramic formed body 30. As in the formed body 20 of FIG. 3, the turbine-shaped blades and the movable forming part 22 which is the shaft entering the window frame 24 can be integrally formed by a binder jet type 3D printer. Further, as shown in FIG. 4, Si impregnation can be carried out at a temperature equal to or higher than the temperature at which Si melts, and a ceramic formed body 30 subjected to surface grinding can be formed. This ceramic formed body 30 is obtained by also carrying out Si impregnation on the movable forming part 22 of the formed body 20, and a high-strength movable forming part 32 can be formed in the window frame 34.

[0032] The present invention provides a ceramic raw material powder, a formed body, and a manufacturing method thereof that are suitably used in a binder jet type 3D printer, and enables a formed body that reproduces a complex shape inside the formed body, which could not be achieved by conventional CIP or casting molding methods, to be formed by a binder jet type 3D printer. Further, the present invention provides a ceramic powder, a formed body thereby, and a manufacturing method thereof that can utilize a binder jet type 3D printer for a complex shape inside a formed body, a large-sized product with thickness, and a ceramic material that absorbs light used in the stereolithography method and generates warpage, which could not be achieved by conventional stereolithography type 3D printers. This enables the formation of large-sized products in near-net shape without warpage.

[0033] Furthermore, in the present invention, in order to improve the fluidity of the raw materials blended in a ratio of three to six types, a certain amount of submicron fine powder with a central diameter of 1 μm or less is added, thereby improving the bulk density and further improving the fluidity.

[0034] Also, in the present invention, by maintaining the addition rate of the injected binder within a predetermined range, for a formed body using a binder jet type 3D printer, it has become possible to maintain dimensional accuracy close to the dimensions designed in 3D CAD while maintaining a handlingable forming strength.

[0035] In addition, according to the present invention, a formulation of highly fluid ceramic powder suitable for shaping by a binder jet type 3D printer has been developed, enabling the ceramic powder to be recoated in a thin layer uniformly without unevenness on the print bed of the job box used during shaping.

[0036] Also, in the manufacturing method of the present invention, it has been found that proper control of the temperature and humidity during shaping and appropriate setting of the ultrasonic output during recoating corresponding to the fluidity of the raw material powder are important, thereby enabling the maintenance of a stable and constant recoating speed and uniformity.

[0037] Furthermore, in the present invention, not only is it possible to fabricate a shaped body of ceramics (such as silicon carbide) by binder jet type 3D printer shaping, but also by selecting the optimum conditions for the formulation of raw materials and firing (and Si impregnation) after shaping, a product having a strength equivalent to or higher than that of products used in conventional semiconductor manufacturing equipment jigs after Si impregnation can be obtained.

Examples

[0038] Next, examples of the ceramic powder of the present invention will be described below. The raw materials that are ceramic powders are, for example, silicon carbide, silicon nitride, alumina, zirconia, etc. As examples of raw material formulations, for example, examples and comparative examples of shaping a flat test piece (target value: 6.6 x 12 x 33 mm) with silicon carbide powder are shown in Tables 1 to 3.

[0039] (Examples 1 to 8) Regarding these raw material powders, fluidity evaluations were carried out by an external institution. For all of Examples 1 to 8, the overall fluidity evaluation was good (overall evaluation 56 points or more: ○ good). The overall evaluation was set as 56 points or more: ○ good, 46 - 55 points: △ fair, 45 points or less: × poor. (External institution evaluation: evaluated with a total score of 100 points with a maximum of 25 points each for shear force, stress transmission rate, stress relaxation rate, and compression rate)

[0040] In Examples 1 to 8 of the present invention, it is possible to uniformly recoat the raw material without unevenness on the print bed of the job box during shaping by a 3D printer, and the bulk density at a pressure of 41.3 kPa is 1.7 (x1000 kg / m 3 ) or higher. These shaped articles could withstand handling and retain their shape even when fired at 1500 °C or higher in a firing furnace. When these were further subjected to Si impregnation at a temperature above the temperature at which Si dissolves, surface grinding was performed, and a three-point bending test was carried out. As a result, the three-point bending strength was as high as 170 MPa or higher, and those of 200 MPa or higher were also obtained as in Example 3 and Example 4.

[0041] From the examples of the present invention shown in Tables 1 to 3, it was found that it is more preferable to add 0 to 2.0% of ceramic powder G (average particle diameter: 0.51 to 1.0 μm), 0 to 0.4% of ceramic powder H (average particle diameter: 0.05 to 0.30 μm), or 0 to 4.0% of ceramic powder I (average particle diameter: 0.31 to 0.50 μm) to improve the bulk density and fluidity.

[0042] (Comparative Example 1) The overall evaluation of the fluidity of the single particles (A 100%) in Comparative Example 1 in Table 1 was ○ (60 points), and shaping was possible, but handling was difficult, it was easily damaged, and even if the shaped article was not damaged, it was damaged after firing and handling was impossible.

[0043] (Comparative Example 2) In Example 2 of Table 1, 0.4% of powder H with an average particle diameter of 0.05 to 0.30 μm was added and blended with powders A, C, D, and F. In Comparative Example 2, while maintaining the ratio of powders A, C, D, and F at almost the same level as in Example 2, 5.0% of powder H was added and blended. The overall evaluation of the fluidity of the raw material of Comparative Example 2 by an external institution was △ (51 points), and the bulk density was 1.64 (x1000 kg / m 3 ). Regarding Comparative Example 2, 5.0% of powder H was added and blended, but since the overall evaluation of fluidity was not good, shaping was not carried out.

[0044] (Comparative Example 3) In Comparative Example 3, 5.0% of the silane agent S was added without adding the powders G and H of Example 1 and Example 2. The comprehensive evaluation of the fluidity of the raw materials in Comparative Example 3 was poor with an × (35 points), and moreover, it was impossible to form.

[0045] In Comparative Example 4, in the case of blending two types of powders A and C, the comprehensive evaluation of fluidity was good with a ○ (65 points), and the bulk density during pressurization was also 1.70 (x1000kg.m 3 ) and it could be formed. However, the strength after firing was as low as 1.73 MPa, making handling difficult.

[0046]

Table 1

[0047] (Examples 9 - 12) In Examples 9 - 12 of the present invention in Table 2, the binder addition rates were set to 30% or 40% respectively, and test pieces of 6.6x12mmx33mm were formed. When the addition rate of the binder increases, an increase in dimensions with respect to the target dimension value can be seen. However, when the addition rates of the binder of the present invention are 30% and 40%, the increase rate α can be suppressed to 10% or less.

[0048] (Comparative Examples 4 - 7) In Comparative Examples 4 - 7, the addition rates of the binder to be added were set to 55%, 60%, and 65% respectively. When the addition rate of the binder reached 55%, diffusion of the binder outside the target dimensions was observed during heat drying, and an increase in the dimensions of the formed test pieces was seen. As a result, the thickness increase rate α, which is an index of dimensional accuracy, exceeded 10%. In Comparative Examples 4 - 7, the respective thickness increase rates α were 11%, 32%, 41%, and 38%.

[0049]

Table 2

[0050] (Examples 13 - 32) For the five formulations consisting of A, C, D, E, and F, Table 3, Examples 13 to 32 show the transition of the JIS bulk density (without pressure, conforming to JIS K5101, average value of two measurements) of the powder when the addition rates of the ceramic raw material G (center diameter: 0.51 to 1.0 μm) and the raw material I (center diameter: 0.31 to 0.50 μm) with a center diameter of sub-micron are increased from 0% at a certain ratio.

[0051] In Example 13, there is no addition, and the JIS bulk density without addition is 1.24 (x1000 kg / m 3 ), which is higher than the JIS bulk density of Comparative Examples 8 to 11 1.20 ~1.23 (x1000 kg / m 3 ).

[0052] In contrast, in Examples 14 to 20, by adding the ceramic raw material G up to 0.01 to 2.0%, the JIS bulk density is improved to be equal to or higher than 1.24 to 1.30 (x1000 kg / m 3 ). Also, in Examples 21 to 29, by adding the ceramic raw material I up to 0.01 to 4.0%, the JIS bulk density is improved to be equal to or higher than 1.24 to 1.31 (x1000 kg / m 3 ). Furthermore, in Examples 30 to 32, by adding the raw material H of silicon carbide up to 0.01 to 0.4%, the JIS bulk density is improved to be equal to or higher than 1.24 to 1.31 (x1000 kg / m 3 ).

[0053] (Comparative Examples 8 to 11) Table 3, Comparative Examples 8 to 11 show the JIS bulk density values of the powder when the addition rate of the ceramic raw material G is 3.0 to 4.0%, or the addition rate of the ceramic raw material H is 0.001%, or the addition rate of the ceramic raw material I is 5.0%. In Comparative Examples 8 to 9 where the addition rate of the ceramic raw material G is 3.0 to 4.0%, the JIS bulk density was 1.21, 1.20 (x1000 kg / m 3 ).

[0054] On the other hand, in Comparative Example 10, the addition rate of the raw material I is as high as 5.0%, and the JIS bulk density is 1.23 (x1000 kg / m 3) and lower than 1.24 of Example 13, and the overall fluidity evaluation was △( 55 points), and it was not good enough with ordinary , and it was not suitable for shaping. In Comparative Example 11 where the addition rate of raw material H was 0.001%, the JIS bulk density was 1.23 (x1000 kg / m 3 ), which was lower than those of Examples 14 to 32, and was also lower than the 1.24 (x1000 kg / m 3 ) without addition in Example 13 with the lowest JIS bulk density.

[0055]

Table 3

Description of Symbols

[0056] 10, 30 Ceramic shaped article 12 Concavo-convex part 20 Green body 22, 32 Movable shaping part

Claims

1. A ceramic powder used for forming a ceramic shaped article by a 3D printer of a binder jet method, wherein the ceramic powder is made of silicon carbide, contains 62% or more of particles having a median diameter of 31 to 60 μm, 7% or more of particles having a median diameter of 11 to 20 μm, and 4% or more of particles having a median diameter of 1.1 to 3.0 μm, and is composed of particles having at least three different median diameters of particle sizes, furthermore, it is a powder obtained by adding 0.01 to 2.0% of particles having a median diameter of 0.51 to 1.0 μm, or 0.01 to 0.4% of particles having a median diameter of 0.05 to 0.30 μm, or 0.01 to 4.0% of particles having a median diameter of 0.31 to 0.50 μm, and the addition rate of the binder material by the 3D printer is 30 to 40%. The ceramic powder is characterized by this.

2. A ceramic shaped article fired with the ceramic powder according to Claim 1, wherein the three-point bending strength of the ceramic shaped article has a value of 170 MPa or more. The ceramic shaped article is characterized by this.

3. In a method for manufacturing a ceramic shaped article formed by firing the ceramic powder according to Claim 1, the step of injecting the binder material by the 3D printer and recoating the ceramic powder on the portion where the binder material is injected is repeated to form a molded body of the ceramic shaped article. The molded body is manufactured with the addition rate of the binder material being 30 to 40%, and then the molded body is fired to form the ceramic shaped article. The method for manufacturing a ceramic shaped article is characterized by this.

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