An alumina ceramic scaffold, its preparation method and application

Abstract

This invention relates to an alumina ceramic scaffold, its preparation method, and its applications, belonging to the field of new materials technology. The preparation method of the alumina ceramic scaffold includes: preparing powder, mixing, crushing, injection molding, debinding, and three-stage sintering. This preparation method utilizes a three-stage sintering process, resulting in an alumina ceramic scaffold with high surface smoothness, high hardness, and high density, eliminating the need for subsequent processing.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, and in particular to an alumina ceramic scaffold, its preparation method, and its application. Background Technology

[0002] Alumina (Al₂O₃) ceramics are the most widely used high-temperature structural ceramics, possessing many excellent properties such as high mechanical strength, wear resistance, corrosion resistance, high temperature resistance, and high thermal conductivity and resistivity. In recent years, alumina ceramics have seen increasingly widespread application in high-tech and cutting-edge industries such as microelectronics, nuclear reactors, magnetohydrodynamic power generation, and artificial joints due to their unique advantages. For alumina ceramic products with high dimensional accuracy and complex shapes, injection molding offers unique technological advantages compared to the higher machining costs of traditional molding processes.

[0003] Sintering is crucial for obtaining high-density ceramic products. Currently, alumina ceramics are often prepared using a single-step sintering process, but this process is prone to defects and has a low yield. Additionally, a few researchers have employed a two-step sintering method; however, this method is time-consuming and does not achieve sufficient density. Summary of the Invention

[0004] To address the above problems, this invention provides a method for preparing an alumina ceramic scaffold. This method utilizes a three-stage sintering process to achieve a high surface smoothness, high hardness, and high density in the alumina ceramic scaffold, eliminating the need for subsequent processing.

[0005] To achieve the above objectives, the present invention provides a method for preparing an alumina ceramic scaffold, comprising the following steps:

[0006] Preparation of powder: Sintering aid, alumina and surface modifier are mixed to obtain abrasive, ball milled and dried to obtain powder;

[0007] Mixing: Mixing powder with binder to obtain the material;

[0008] Crushing: Crushing materials to obtain feed;

[0009] Injection molding: The injection molding method is used to prepare injection preforms from the feed material;

[0010] Degreasing: The injection embryo is placed on the substrate and degreased to obtain the embryo material;

[0011] Three-stage sintering: The blank is placed on the substrate and sintered to obtain an alumina ceramic support; the sintering includes the following steps: sintering the blank at 800-900℃ for 1.5-2.5h, cooling, sintering at 1500-1600℃ for 0.4-0.6h, cooling, sintering at 1700-1800℃ for 1.5-2.5h, cooling.

[0012] The alumina ceramic support obtained by the above preparation method not only has high surface smoothness, high hardness and high density, requiring no further processing, but also has a support width of 7-9mm, overcoming the problem that supports of this width range are prone to deformation and breakage during the molding process due to their small width and numerous holes.

[0013] In one embodiment, the sintering includes the following steps: sintering the blank at 800-900°C for 2 hours, cooling, sintering at 1500-1600°C for 0.5 hours, cooling, sintering at 1700-1800°C for 2 hours, and cooling.

[0014] In one embodiment, the substrate material includes alumina powder; in the degreasing step, the alumina powder has a mesh size of 350-450 mesh; in the three-stage sintering step, the alumina powder has a mesh size of 150-250 mesh.

[0015] In one embodiment, the alumina powder used in the degreasing step has a mesh size of 400; and the alumina powder used in the three-stage sintering step has a mesh size of 200.

[0016] In one embodiment, the degreasing is performed using a stepped heating method, which includes: heating at 0.5-1.5℃ / min to 150-250℃ and holding for 0.8-1.2h; heating at 1.5-2.5℃ / min to 350-450℃ and holding for 0.8-1.2h; and heating at 4.5-5.5℃ / min to 450-550℃ and holding for 1.5-2.5h.

[0017] In one embodiment, the stepped heating includes: heating to 200°C at 1°C / min and holding for 1 hour; heating to 400°C at 2°C / min and holding for 1 hour; and heating to 500°C at 5°C / min and holding for 2 hours.

[0018] In one embodiment, during the degreasing step, the injection preform is placed upside down on the substrate; during the three-stage sintering step, the preform is placed upside down on the substrate.

[0019] Inverting the injection preform or preform onto the substrate can prevent deformation of the injection preform due to its own weight when the binder in the injection preform softens during the heating and degreasing process. On the other hand, the alumina powder in the substrate is movable, which can reduce the friction generated during sintering shrinkage and reduce the risk of sintering deformation and cracking.

[0020] In one embodiment, the ball milling in the powder preparation step is wet ball milling;

[0021] The mass ratio of the grinding balls, the abrasive, and the grinding media in the ball mill is (1.5-2.5):1:1;

[0022] The ball mill rotates at a speed of 200-300 r / min and the milling time is 2-4 h.

[0023] In one embodiment, the sintering aid includes at least one of calcium oxide, magnesium oxide, and silicon oxide; the surface modifier includes stearic acid; and the ball milling medium is alcohol.

[0024] In one embodiment, the sintering aid includes calcium oxide, magnesium oxide, and silicon oxide; the weight ratio of calcium oxide, magnesium oxide, silicon oxide, and aluminum oxide is (0.3-0.7 parts): (0.8-1.2 parts): (2.3-2.7 parts): (94-98 parts).

[0025] Using the above raw materials and proportions to form a sintering aid can reduce the sintering temperature required for alumina ceramics and improve their microstructure.

[0026] In one embodiment, the weight ratio of the surface modifier to the sum of the mass of the sintering aid and the alumina is (3-5):100.

[0027] In one embodiment, the binder comprises high-density polyethylene and paraffin wax; the mixing step comprises heating the high-density polyethylene to a molten state, adding powder, mixing, cooling, adding paraffin wax, kneading, and cooling.

[0028] In one embodiment, during the mixing step, the heating temperature is 150-170°C, the heating time is 0.5-1h, the mixing time is 3-7min, the temperature after cooling is 140-160°C, and the kneading time is 0.5-1h.

[0029] In one embodiment, the particle size of the feed is 1-2 mm.

[0030] In one embodiment, in the powder preparation step, the average particle size of the alumina is 0.45-0.55 μm, the drying temperature is 40-60°C, and the drying time is 24-48 h.

[0031] In one embodiment, the average particle size of the alumina in the powder preparation step is 0.5 μm.

[0032] In one embodiment, the solid content of the material is 55-65 vol%.

[0033] In one embodiment, the solid content of the material is 60 vol%.

[0034] In one embodiment, the mass ratio of the high-density polyethylene to the paraffin is 1:4.

[0035] In one embodiment, during the injection molding step, the injection temperature is 120-150℃, the injection pressure is 100-200MPa, the injection time is 1.8-2.2s, the holding pressure is 90-110MPa, and the holding time is 4-6s. In another embodiment, the injection time is 2s, the holding pressure is 100MPa, and the holding time is 5s.

[0036] The present invention also provides an alumina ceramic scaffold prepared by the aforementioned preparation method.

[0037] The present invention also provides the application of the alumina ceramic scaffold in the fabrication of microelectronic devices, nuclear reactor equipment, magnetohydrodynamic power generation equipment and / or artificial joints.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention relates to an alumina ceramic scaffold, its preparation method and application. The preparation method utilizes a three-stage sintering process to achieve a high surface smoothness, high hardness and high density of the alumina ceramic scaffold, eliminating the need for subsequent processing. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the ceramic support obtained in Example 1 placed upside down;

[0041] Figure 2 This is a schematic diagram of the ceramic support obtained in Example 2 placed upright;

[0042] Figure 3 This is an SEM image of the cross-section of the ceramic support obtained in Example 2. Detailed Implementation

[0043] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0045] source:

[0046] Unless otherwise specified, all reagents, materials, and equipment used in this embodiment are commercially available; unless otherwise specified, all experimental methods are conventional experimental methods in this field.

[0047] Example 1

[0048] An alumina ceramic scaffold and its preparation method.

[0049] I. This alumina ceramic scaffold is a high-temperature alumina ceramic scaffold, and the specific preparation method is as follows:

[0050] 1. Prepare powder.

[0051] A mixture of 0.5 wt% CaO, 1 wt% MgO, 2.5 wt% SiO2, and 96 wt% Al2O3 (i.e., the weight ratio of calcium oxide, magnesium oxide, silicon oxide, and aluminum oxide is 0.5 parts: 1 part: 2.5 parts: 96 parts) was wet-milled. CaO, MgO, and SiO2 were used as sintering aids. 3% stearic acid (SA), equal to the combined mass of the sintering aids and Al2O3, was added as a surface modifier. Alcohol was used as the milling medium, and alumina grinding balls were added. The mass ratio of balls, material, and medium was 2:1:1. The milling speed was 200 r / min, and the milling time was 2 h. The milled powder was then dried in a blower dryer at 40℃ for 24 h to obtain the final powder.

[0052] 2. Mixing.

[0053] The dried powder is mixed with a binder, which includes high-density polyethylene and paraffin wax. The specific mixing steps are as follows:

[0054] First, high-density polyethylene (HDPE) is heated at 150°C for 0.5 hours in a kneader until it melts. Then, powder is added and kneaded for 5 minutes. The temperature is lowered to 140°C, paraffin wax (PW) is added and kneaded for 0.5 hours. The mixture is then allowed to cool naturally to obtain the material. The solid content of the material is 60 vol%, and the mass ratio of PW to HDPE is 4:1.

[0055] 3. Broken.

[0056] The material is crushed into 1-2mm particles using a crusher and used as feed.

[0057] 4. Injection molding.

[0058] The feed material is added to the injection molding machine, and the injection molding machine is run to press the ceramic slurry into the mold. The injection molding method is used to obtain the injection green body. The injection process is as follows: injection temperature is 120℃, injection pressure is 100MPa, injection time is 2s, holding pressure is 100MPa, and holding time is 5s.

[0059] 5. Degreasing.

[0060] The injection blank is placed upside down on a flat surface of 400-mesh fine alumina powder and degreased using a box-type resistance furnace in an air atmosphere. The degreasing heating process is as follows: heat up to 200℃ at 1℃ / min, hold for 1 hour, then heat up to 400℃ at 2℃ / min, hold for 1 hour, and finally heat up to 500℃ at 5℃ / min, hold for 2 hours to obtain the blank.

[0061] 6. Three-stage sintering.

[0062] The blank was placed on a flat layer of 200-mesh alumina powder and sintered in a furnace. The first stage was sintering at 800℃ for 2 hours and then naturally cooled. The second stage was sintering at 1500℃ for 0.5 hours and then naturally cooled. The third stage was sintering at 1700℃ for 2 hours and then naturally cooled.

[0063] II. The high-temperature ceramic support obtained in this embodiment is as follows: Figure 1 As shown, the high-temperature ceramic support prepared in this embodiment exhibits high surface smoothness, high hardness, and high density after sintering, with a density of 3.75 g / cm³. 3 .

[0064] Example 2

[0065] An alumina ceramic scaffold and its preparation method.

[0066] I. This alumina ceramic scaffold is a high-temperature alumina ceramic scaffold, and the specific preparation method is as follows:

[0067] 1. Prepare powder.

[0068] A mixture of 0.5 wt% CaO, 1 wt% MgO, 2.5 wt% SiO2, and 96 wt% Al2O3 (i.e., the weight ratio of calcium oxide, magnesium oxide, silicon oxide, and aluminum oxide is 0.5 parts:1 part:2.5 parts:96 parts) was wet-milled. CaO, MgO, and SiO2 were used as sintering aids. 4% stearic acid (SA), equal to the combined mass of the sintering aids and Al2O3, was added as a surface modifier. Alcohol was used as the milling medium, and alumina grinding balls were added. The mass ratio of balls, material, and medium was 2:1:1. The milling speed was 250 r / min, and the milling time was 3 h. The milled powder was then dried in a blower dryer at 50℃ for 36 h to obtain the final powder.

[0069] 2. Mixing.

[0070] The dried powder is mixed with a binder, which includes high-density polyethylene and paraffin wax. The specific mixing steps are as follows:

[0071] First, high-density polyethylene (HDPE) is heated at 160°C for 0.8 hours in a kneader until it melts. Then, powder is added and kneaded for 5 minutes. The temperature is lowered to 150°C, paraffin wax (PW) is added and kneaded for 0.8 hours. After natural cooling, the material is obtained. The solid content of the material is 60 vol%, and the mass ratio of PW to HDPE is 4:1.

[0072] 3. Broken.

[0073] The material is crushed into 1-2mm particles using a crusher and used as feed.

[0074] 4. Injection molding.

[0075] The feed material is added to the injection molding machine, and the injection molding machine is run to press the ceramic slurry into the mold. The injection molding method is used to obtain the injection green body. The injection process is as follows: injection temperature is 140℃, injection pressure is 150MPa, injection time is 2s, holding pressure is 100MPa, and holding time is 5s.

[0076] 5. Degreasing.

[0077] The injection blank is placed upside down on a flat surface of 400-mesh fine alumina powder and degreased using a box-type resistance furnace in an air atmosphere. The degreasing heating process is as follows: heat up to 200℃ at 1℃ / min, hold for 1 hour, then heat up to 400℃ at 2℃ / min, hold for 1 hour, and finally heat up to 500℃ at 5℃ / min, hold for 2 hours to obtain the blank.

[0078] 6. Three-stage sintering.

[0079] The blank was placed on a flat layer of 200-mesh alumina powder and sintered in a furnace. The first stage was sintering at 850℃ for 2 hours and then naturally cooled. The second stage was sintering at 1550℃ for 0.5 hours and then naturally cooled. The third stage was sintering at 1750℃ for 2 hours and then naturally cooled.

[0080] II. The high-temperature ceramic support obtained in this embodiment is as follows: Figure 2 As shown, its density is 3.81 g / cm³. 3 The cross-sectional morphology of the high-temperature ceramic support prepared in this embodiment was observed using a scanning electron microscope. The test results are shown in [link to sample]. Figure 3 As can be seen from the figure, the sintered product has a very small number of pores, high density, and uniform grain size without abnormal growth. The high-temperature ceramic support prepared in this embodiment has a high surface smoothness, high hardness, and high density after sintering.

[0081] Example 3

[0082] An alumina ceramic scaffold and its preparation method.

[0083] I. This alumina ceramic scaffold is a high-temperature alumina ceramic scaffold, and the specific preparation method is as follows:

[0084] 1. Prepare powder.

[0085] A mixture of 0.5 wt% CaO, 1 wt% MgO, 2.5 wt% SiO2, and 96 wt% Al2O3 (i.e., the weight ratio of calcium oxide, magnesium oxide, silicon oxide, and aluminum oxide is 0.5 parts:1 part:2.5 parts:96 parts) was wet-milled. CaO, MgO, and SiO2 were used as sintering aids. 5% stearic acid (SA), equal to the combined mass of the sintering aids and Al2O3, was added as a surface modifier. Alcohol was used as the milling medium, and alumina grinding balls were added. The mass ratio of balls, material, and medium was 2:1:1. The milling speed was 300 r / min, and the milling time was 4 h. The milled powder was then dried in a blower dryer at 60℃ for 48 h to obtain the final powder.

[0086] 2. Mixing.

[0087] The dried powder is mixed with a binder, which includes high-density polyethylene and paraffin wax. The specific mixing steps are as follows:

[0088] First, heat high-density polyethylene (HDPE) at 170°C for 1 hour in a kneader until it melts. Then, add powder and knead for 5 minutes. Cool down to 160°C, add paraffin wax (PW), and knead for 1 hour. Allow it to cool naturally to obtain the material. The solid content of the material is 60 vol%, and the mass ratio of PW to HDPE is 4:1.

[0089] 3. Broken.

[0090] The material is crushed into 1-2mm particles using a crusher and used as feed.

[0091] 4. Injection molding.

[0092] The feed material is added to the injection molding machine, and the injection molding machine is run to press the ceramic slurry into the mold. The injection molding method is used to obtain the injection green body. The injection process is as follows: injection temperature is 150℃, injection pressure is 200MPa, injection time is 2s, holding pressure is 100MPa, and holding time is 5s.

[0093] 5. Degreasing.

[0094] The injection blank is placed upside down on a flat surface of 400-mesh fine alumina powder and degreased using a box-type resistance furnace in an air atmosphere. The degreasing heating process is as follows: heat up to 200℃ at 1℃ / min, hold for 1 hour, then heat up to 400℃ at 2℃ / min, hold for 1 hour, and finally heat up to 500℃ at 5℃ / min, hold for 2 hours to obtain the blank.

[0095] 6. Three-stage sintering.

[0096] The blank was placed on a flat layer of 200-mesh alumina powder and sintered in a furnace. The process was as follows: first stage: sintering at 900℃ for 2 hours, followed by natural cooling; second stage: sintering at 1600℃ for 0.5 hours, followed by natural cooling; third stage: sintering at 1800℃ for 2 hours, followed by natural cooling.

[0097] II. The high-temperature ceramic support prepared in this embodiment exhibits high surface smoothness, high hardness, and high density after sintering, with a density of 3.92 g / cm³. 3 .

[0098] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0099] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for producing an alumina ceramic scaffold, characterized by, The preparation method includes the following steps: Preparation of powder: Sintering aid, alumina, and surface modifier are mixed to obtain abrasive, ball-milled, and dried to obtain powder; the weight ratio of the surface modifier to the sum of the masses of the sintering aid and alumina is (3-5):100; the surface modifier includes stearic acid; the sintering aid includes calcium oxide, magnesium oxide, and silicon oxide; the weight ratio of calcium oxide, magnesium oxide, silicon oxide, and alumina is (0.3-0.7 parts): (0.8-1.2 parts): (2.3-2.7 parts): (94-98 parts); Mixing: Mixing powder with binder to obtain the material; Crushing: Crushing materials to obtain feed; Injection molding: The injection molding method is used to prepare injection preforms from the feed material; Degreasing: The injection-molded green body is placed upside down on a substrate and degreased to obtain a blank; the substrate includes alumina powder; the degreasing is performed using a stepped heating method, which includes: heating at 0.5-1.5℃ / min to 150-250℃ and holding for 0.8-1.2h, heating at 1.5-2.5℃ / min to 350-450℃ and holding for 0.8-1.2h, and heating at 4.5-5.5℃ / min to 450-550℃ and holding for 1.5-2.5h. Three-stage sintering: The blank is placed upside down on the substrate and sintered to obtain an alumina ceramic support; the sintering includes the following steps: sintering the blank at 800-900℃ for 1.5-2.5h, cooling, sintering at 1500-1600℃ for 0.4-0.6h, cooling, sintering at 1700-1800℃ for 1.5-2.5h, and cooling.

2. The preparation method according to claim 1, characterized in that, In the degreasing step, the alumina powder has a mesh size of 350-450.

3. The preparation method according to any one of claims 1-2, characterized in that, In the powder preparation step, the ball milling is a wet ball milling process; The mass ratio of the grinding balls, the abrasive, and the grinding media in the ball mill is (1.5-2.5):1:1; The ball mill rotates at a speed of 200-300 r / min and the milling time is 2-4 h.

4. The preparation method according to claim 3, characterized in that, The medium used in the ball milling process is alcohol.

5. The preparation method according to claim 3, characterized in that, The binder comprises high-density polyethylene and paraffin wax; the mixing step comprises: heating high-density polyethylene to a molten state, adding powder, mixing, cooling, adding paraffin wax, kneading, and cooling.

6. The preparation method according to claim 3, characterized in that, In the injection molding step, the injection temperature is 120-150℃, the injection pressure is 100-200MPa, the injection time is 1.8-2.2s, the holding pressure is 90-110MPa, and the holding time is 4-6s.

7. The alumina ceramic scaffold prepared by the preparation method according to any one of claims 1-6.

8. The application of the alumina ceramic scaffold according to claim 7 in the fabrication of microelectronic devices, nuclear reactor equipment, magnetohydrodynamic power generation equipment and / or artificial joints.

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