Porous ceramic as well as preparation method and application thereof

Abstract

The invention provides porous ceramic as well as a preparation method and application thereof, and relates to the technical field of ceramic materials. The preparation method of the porous ceramic adopts a pressure gel casting process, namely warm isostatic pressing is carried out in a gel forming process, so that slurry is cured in situ in a pressurizing process, and the advantage of uniform pore distribution of a traditional gel casting process is utilized; and the mechanical property of the porous ceramic is improved while the porous ceramic has enough porosity. Meanwhile, in the aspect of composition of the ceramic raw materials, the framework material, the binder and the colloid in a specific proportion are adopted, it is ensured that a large number of penetrating through holes are formed between stacking of the framework material, and the mechanical property of the porous ceramic is ensured through grain size grading combination of the binder and the framework material. The prepared porous ceramic has the advantages of high density, high strength, high hardness, uniform vent holes, good adsorption effect and the like; the prepared porous ceramic is used for preparing the vacuum suction cup, and the vacuum suction cup is not prone to deformation and powder falling in the using process and long in service life.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and in particular to a porous ceramic and a preparation method and application thereof. Background Art

[0002] Semiconductor integrated circuits (ICs) are a core technology in the electronics manufacturing industry. During IC production, silicon wafers, which serve as substrates, undergo multiple transfers and processing. Compared to traditional methods of clamping and transferring silicon wafers using mechanical clamping or wax bonding, using vacuum chucks to clamp and transfer silicon wafers prevents bending and warping, and is less likely to damage the wafers. This is particularly true during wafer thinning, where vacuum chucks are crucial components for adsorbing and securing the wafer, making them a popular choice.

[0003] A vacuum chuck uses a pressure differential to absorb objects. When used to absorb silicon wafers, air flows from the gap between the silicon wafer and the porous ceramic into the pores within the ceramic, creating a pressure differential across the gap. During the wafer thinning process, the vacuum chuck also needs to bear the weight of the wafer and its grinding head. If the vacuum chuck is not strong enough, it may deform during use, resulting in uncertainty in wafer processing accuracy. Insufficient hardness will result in insufficient bonding between the skeleton material and the binder, which will manifest as powder loss, contaminating the silicon wafer and affecting processing quality. Therefore, the porous ceramic used for vacuum chucks must possess both high adsorption and high mechanical properties (high strength and hardness): a pair of mutually exclusive properties.

[0004] In addition, during the operation of the ceramic vacuum suction cup, there will be blockage and it will be easily affected by the dust after grinding, which will lead to problems such as uneven suction and contamination of the clamped objects. Therefore, in normal use, the surface layer needs to be flat-ground before continued use. The traditional dry pressing process has the problem of pressure transmission attenuation, which leads to a low degree of densification inside the ceramic body, especially the large pore size in the core. In the subsequent flat grinding process, pits are easily formed, which in turn affects the thinning quality of the wafer. Therefore, the porous ceramics used for vacuum suction cups also need to have uniform vents. In addition, due to the limitation of colloid strength, the traditional gel injection molding process cannot achieve a high density, which will affect the strength and hardness of the porous ceramics. Summary of the Invention

[0005] In response to the shortcomings of the existing technology, the present invention provides a porous ceramic and its preparation method and application. The porous ceramic has high density, high strength, high hardness, uniform pore size distribution and good adsorption effect, which can meet the performance requirements of ceramic vacuum suction cups during wafer processing.

[0006] The present invention provides a method for preparing porous ceramics, comprising the following steps: S1. Adding a ceramic slurry comprising a skeleton material, a binder, a colloid, and water into a mold and performing warm isostatic gel pressing to obtain a ceramic green body; the binder is a high-temperature binder of 900-3000 mesh, the colloid comprises curdlan or gelatin, and the skeleton material comprises 90-400 mesh corundum sand; S2. The ceramic green body in step S1 is demoulded, dried, debinded and sintered to obtain porous ceramics.

[0007] In a possible embodiment, the warm isostatic pressing of the gel in step S2 is performed at a pressure of 2-30 MPa and a temperature of 50-100°C.

[0008] In a possible embodiment, the mass ratio of the skeleton material, the binder and the colloid in the ceramic slurry is (70-90):(10-30):(1-10).

[0009] In one possible embodiment, the method for preparing the ceramic slurry includes the following steps: D1. ball milling a solution containing a binder to form a first slurry; D2, adding the first slurry described in step D1 to the aqueous solution of the colloid and mixing to form a second slurry; D3. Add the skeleton material to the second slurry described in step D2 and mix to form a ceramic slurry.

[0010] Furthermore, the mass ratio of the colloid to water in the aqueous solution of the colloid in step D2 is 1:(5-20), and the solid content of the ceramic slurry in step D3 is 60-90 wt%.

[0011] In a possible implementation, the high-temperature adhesive in step S1 includes alumina powder or glass powder.

[0012] In a possible implementation manner, the sintering temperature in step S2 is 600-1650° C. and the sintering time is 1-4 hours.

[0013] In a possible implementation, the binder removal in step S2 is performed at a temperature of 50-600° C. and for a time of 1-8 h.

[0014] The present invention also provides a porous ceramic, which is prepared by the above-mentioned preparation method of the porous ceramic.

[0015] The present invention also provides the use of the porous ceramic in preparing a vacuum chuck.

[0016] The above embodiments can be combined arbitrarily based on the common knowledge in this field.

[0017] The reagents and raw materials used in the present invention are commercially available.

[0018] The positive progress effect of the present invention is: The preparation method of porous ceramics provided by the present invention is improved from two aspects: the composition of ceramic raw materials and the molding process. Through the graded combination of the binder and the skeleton material particle size, a large number of through holes are ensured to be formed between the skeleton material piles, and the mechanical properties of the porous ceramics are guaranteed. A pressure gel injection molding process is adopted, that is, warm isostatic pressing is performed simultaneously during the gel molding process, so that the slurry is solidified in situ during the pressurization process. It not only utilizes the advantage of the traditional gel injection molding process to achieve uniform pore distribution, but also improves its mechanical properties. The porous ceramics obtained have high density, high strength, high hardness, uniform air pores and good adsorption effect. The prepared porous ceramics are used to prepare vacuum suction cups. The vacuum suction cups have high strength and hardness, are not easy to deform or shed powder during use, and have a long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 : is the crystal phase diagram of the porous ceramic prepared in Example 1.

[0020] Figure 2 This is the surface SEM image of the porous ceramic prepared in Example 2.

[0021] Figure 3 Macroscopic morphology of the porous ceramic prepared in Example 3.

[0022] Figure 4 This is a macroscopic morphology of the porous ceramic prepared in Comparative Example 1. DETAILED DESCRIPTION

[0023] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only intended to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter ranges described in the present invention. Reasonable variations derived therefrom are still within the scope of protection of the claims of the present invention.

[0024] It should be noted that the endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed herein.

[0025] Unless otherwise defined, all terms, symbols and other scientific terms used herein are intended to have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. In some cases, terms with conventional meanings are defined herein for the purpose of clarification or ease of reference, and such definitions herein should not be construed as indicating significant differences from conventional understandings in the art. The technical methods described or cited herein are generally well understood by those skilled in the art and are adopted by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents and instruments was carried out in accordance with the protocols and parameters given by the manufacturers.

[0026] As mentioned in the Background section, porous ceramics with high adsorption performance, high mechanical properties, and uniform pore distribution are essential for vacuum chucks. On the one hand, high adsorption performance and high mechanical properties are mutually exclusive and difficult to achieve simultaneously; on the other hand, uniform pore distribution places high demands on the raw material selection and preparation process of the porous ceramic. This invention effectively solves these problems.

[0027] The present invention provides a method for preparing porous ceramics, comprising the following steps: S1. Adding a ceramic slurry comprising a skeleton material, a binder, a colloid, and water into a mold and performing warm isostatic gel pressing to obtain a ceramic green body; the binder is a high-temperature binder of 900-3000 mesh, the colloid comprises curdlan or gelatin, and the skeleton material comprises 90-400 mesh corundum sand; S2. The ceramic green body in step S1 is demoulded, dried, debinded and sintered to obtain porous ceramics.

[0028] The present invention discloses a porous ceramic used in a vacuum suction cup. In order to meet the use scenarios of the vacuum suction cup, the prepared porous ceramic needs to have good adsorption force (characterized by pore size and porosity) on the one hand, and good mechanical properties (such as strength, hardness, and no powder loss) on the other hand. At the same time, it needs to have sufficient lifespan and process effects (such as strength, hardness, processing flatness, etc.). Based on general technical knowledge, high porosity and strength are mutually exclusive characteristics. Specifically, the higher the porosity, the lower the strength (that is, the properties of existing porous ceramics are usually manifested as either high mechanical properties or high porosity).

[0029] In order to ensure uniform pore distribution without sacrificing strength and hardness, a warm isostatic gel pressing process was innovatively adopted. The traditional dry pressing process applies pressure from both the outside and the inside, gradually transferring pressure from the outside to the inside, making it impossible to guarantee uniform pressure. Even if the raw materials are evenly mixed, the green body will be compressed during the pressing process, resulting in uneven microstructures on the upper and lower surfaces and in the core. The gel casting process, due to its in-situ curing feature, ensures that the evenly mixed raw materials are cured and formed in situ, thus ensuring uniform pore size. Due to the low strength of the colloid, the traditional gel casting process cannot achieve a very high solid content. If the solid content is too high, the colloid content will be too low, resulting in insufficient strength and inability to form. If the solid content is too low, the colloid content will be too high, and this part of the colloid will be burned out during the debinding and sintering process, which is equivalent to introducing more pore-forming agents into the porous ceramic, resulting in excessively large pore size and porosity, reducing its strength. If a process of pressurizing after molding is selected, since the strength of the colloid is low after solidification, pressurizing the porous ceramic after molding is likely to cause cracking, resulting in its inability to sinter and mold. In order to solve the above problems, this patent selects a colloid that can be temperature-cured and has good affinity with the corundum sand skeleton material among different colloids, namely, gellan or gelatin, and cooperates with the warm isostatic pressing process to apply hydrostatic pressure at the same time during the colloid solidification process. The present invention fully utilizes the advantage of the gel injection molding process that can be in-situ solidified to ensure its uniform pore distribution, utilizes the property that the material can be further compressed under the hydrostatic pressure state, and can fully utilize the good liquid plasticity of the colloid before solidification, so that the whole system can withstand higher hydrostatic pressure, which in turn promotes its molding under higher solid content. In addition, the role of hydrostatic pressure in the molding process is to squeeze out the bubbles and excess water inside the slurry and rearrange the particles of the slurry. Higher hydrostatic pressure also helps the system to be formed at a higher solid content, so that the porous ceramics after sintering maintain the pore size and porosity constructed by the skeleton material while increasing its volume density, so that the porous ceramics have sufficient porosity while also improving the overall strength and hardness of the porous ceramics.

[0030] The preparation method of the porous ceramic provided by the present invention ensures the mechanical properties of the porous ceramic by selecting 90-400 mesh corundum sand and a 900-3000 mesh high-temperature binder and a graded combination of the skeleton material particle size. At the same time, it can ensure that the porosity of the prepared porous ceramic material is 30-60% and the average pore size is 5-100 μm, and can take into account both good adsorption and good mechanical properties.

[0031] The preparation method of the porous ceramic provided by the present invention cooperates with the composition of the ceramic raw materials and the preparation process. The prepared porous ceramic has the characteristics of high density, high strength, high hardness, uniform vents and good adsorption effect, and is suitable for vacuum suction cup application.

[0032] In one possible embodiment, the warm isostatic pressing of the gel in step S1 is performed at a pressure of 2-30 MPa and a temperature of 50-100°C. The warm isostatic pressing temperature of 50-100°C is consistent with the curing conditions of gelatin and curdlan colloids. Curing within this temperature range results in higher colloid strength, facilitating subsequent processing. Selecting an appropriate pressing pressure of 2-30 MPa helps reduce the presence of large bubbles and improves the uniformity of pore distribution within the ceramic green body.

[0033] In one possible embodiment, the mass ratio of the skeleton material, binder and colloid in the ceramic slurry is (70-90): (10-30): (1-10). A specific ratio of skeleton material corundum sand, binder and colloid is used to ensure that a large number of through holes are formed between the skeleton materials. The binder exists in the solid phase during the molding of porous ceramics. During sintering, the binder undergoes a solid-liquid-solid phase transition process. During the molding stage, the binder occupies space to form pores. Therefore, the content ratio of the binder to the skeleton material needs to be controlled. If the amount of binder is too little, the skeleton material cannot be evenly wrapped. After sintering, the hardness of the product is not high and it is easy to fall off. If the binder is too much, the binder will block the pores between the skeleton materials, resulting in its pore size and porosity not meeting the requirements; secondly, the strength of the binder itself is lower than that of the skeleton material. Too much binder will reduce the overall mechanical properties. Therefore, under the premise of ensuring that the binder evenly wraps the skeleton material, its proportion should be reduced as much as possible. When the binder is smaller than the size of the gap between the skeleton materials, it can wrap the skeleton materials as much as possible while minimizing its dosage. However, the binder size should not be too fine. When the binder is too fine, it is more likely to produce particle agglomeration and easily block holes, which increases the difficulty of the process. The ideal state is that during the molding process, the binder is evenly present in the gaps between the skeleton materials, just wrapping the skeleton materials while not gathering. This allows the position of the pores to be close to the skeleton material stacking structure, effectively improving the space utilization rate in the porous ceramic body. Therefore, the particle size ratio and weight ratio of the binder and the skeleton materials need to be within a suitable range.

[0034] In one possible embodiment, the method for preparing the ceramic slurry includes the following steps: D1. ball milling a solution containing a binder to form a first slurry; D2, adding the first slurry described in step D1 to the aqueous solution of the colloid and mixing to form a second slurry; D3. Add the skeleton material to the second slurry described in step D2 and mix to form a ceramic slurry.

[0035] Furthermore, the mass ratio of the colloid to water in the aqueous solution of the colloid described in step D2 is 1: (5-20), and the solid content of the ceramic slurry described in step D3 is 60-90 wt%. Limiting the mass ratio of the colloid to water in the aqueous solution of the colloid can reduce the entanglement of the polymer chains in the colloid, significantly reduce the viscosity of the slurry, and facilitate subsequent injection molding; limiting the solid content can ensure that the viscosity of the slurry is moderate, has sufficient fluidity for subsequent injection molding, and prevents particle sedimentation and stratification, ensuring slurry uniformity. The preferred solid content in the third slurry is preferably 70-85 wt%. Combined with the warm isostatic pressing gel casting molding process, this solid content can further improve the strength and hardness of the porous ceramic while taking into account the above advantages.

[0036] In a possible embodiment, the high-temperature adhesive in step S1 includes alumina powder or glass powder.

[0037] In one possible embodiment, the sintering temperature in step S2 is 600-1650°C and the time is 1-4h. According to the type of high-temperature binder selected, select an appropriate sintering temperature and sintering time. If the sintering temperature is too high and the sintering time is too long, the high-temperature binder may be lost, which will lead to a decrease in strength and hardness; if the sintering temperature is too low or the sintering time is too short, the ceramic will not be fully fired, affecting the strength and hardness. When the high-temperature binder used is alumina powder, the sintering temperature of the porous ceramic is preferably 1400-1600°C. Within this sintering temperature range, sufficient inter-particle diffusion and densification can be achieved, and the binder alumina powder melts and forms a strong grain boundary bond with the corundum sand skeleton particles, which helps to improve the strength and density of the porous ceramic. When the high-temperature binder used is glass powder, the sintering temperature of the porous ceramic is usually near the melting point of the glass powder used. Within this sintering temperature range, the glass powder can melt and partially fill the micropores between the skeleton particles, thereby enhancing the grain boundary bonding force while also achieving an optimal balance between the porosity and strength of the porous ceramic.

[0038] In one possible embodiment, the debinding process in step S2 is performed at a temperature of 50-600°C for 1-8 hours. To ensure that the porous ceramics after sintering have good overall performance, the debinding sintering process needs to be optimized. By controlling the debinding temperature and time, the density and pore size uniformity of the porous ceramics can be guaranteed.

[0039] In one possible embodiment, the ceramic slurry in step S1 further includes a defoamer and / or a colorant, the defoamer is n-butanol, and the mass ratio of the defoamer to the skeleton material is (0.01-0.1):(70-90), the colorant is cobalt trioxide, or a combination of manganese dioxide, titanium dioxide and magnesium oxide, or a combination of Fe-Co-Ni-Mn oxides, and the mass ratio of the colorant to the skeleton material is (5-20):(70-90). n-Butanol has high surface activity and can quickly adsorb on the surface of bubbles, reducing gas-liquid interfacial tension and promoting bubble merging or rupture. Furthermore, n-Butanol evaporates at room or low temperatures and is easily removed during subsequent drying or sintering stages, preventing it from remaining inside the porous ceramic and negatively impacting its mechanical properties and porosity. The mass ratio of the defoamer to the framework material is limited to 70-90:0.01-0.1. This low dose of defoamer is sufficient to suppress excessive bubble formation while also preventing excessive defoaming that could lead to insufficient porosity in the porous ceramic, thereby facilitating a uniform pore size distribution. The addition of a colorant imparts a darker color to the porous ceramic, preventing it from reflecting stray light and causing interference during photolithography of electronic components.

[0040] In order to improve its service life and process effect thereof, the present invention has been further improved, skeleton material described in step S1 is made up of 90 mesh corundum sands, 220 mesh corundum sands and 400 mesh corundum sands, and the mass ratio of described 90 mesh corundum sands, 220 mesh corundum sands and 400 mesh corundum sands is (120-150): (8-12): (2-5).By preferably 90 mesh corundum sands are external skeletons, the size and quantity of the gap inside of the external skeleton building composition are calculated, it is 220 mesh and 400 mesh corundum sands that are preferably selected to further fill the corundum sands in its hole, and by calculation and experimental verification, when 90 mesh corundum sands, 220 mesh corundum sands and 400 mesh corundum sands are than (120-150): (8-12): (2-5) interval time, the preferred gradation scheme, the porous ceramics with small aperture can be prepared.Due to corundum sand strength, hardness are higher than binding agent, the gradation scheme can further improve the strength and hardness of porous ceramics compared to the corundum sand scheme without gradation.

[0041] The present invention also provides a porous ceramic, which is prepared by the above-mentioned method for preparing the porous ceramic. The porous ceramic provided by the present invention has high density, high strength, high hardness, uniform vents and good adsorption effect.

[0042] The present invention also provides the use of the porous ceramic in preparing a vacuum chuck. When the porous ceramic is used to prepare a vacuum chuck, the vacuum chuck has high strength and hardness, is not easily deformed or shed during use, and has a long service life.

[0043] The above embodiments can be combined arbitrarily based on the common knowledge in this field.

[0044] The technical solutions of the present invention are further illustrated below with reference to specific examples and comparative examples. All reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment. The instruments used in the examples are commercially available.

[0045] Example 1

[0046] This embodiment provides a porous ceramic, which is prepared by the following steps: S1. Disperse 196 g of 3000 mesh alumina powder and 96 g of cobalt trioxide in 100 g of water at room temperature, and ball mill for 8 h to obtain an alumina slurry. S2. Disperse 16 g of curdlan in 160 g of water to form a curdlan aqueous solution; then add the alumina slurry prepared in step S1 to the curdlan aqueous solution while stirring and mix evenly; then add 486 g of 320-mesh corundum sand and stir at room temperature for 10 minutes to prepare a corundum mortar. The solid content of the corundum mortar is 75 wt %. S3, pouring the corundum slurry in step S2 into a silica gel mold, plastic-sealing, and placing it in a warm isostatic pressing device, pressing at 80° C. for 30 min at a pressure of 18 MPa to obtain a ceramic green body; S4. The ceramic wet body in step S3 is taken out, placed in an oven, and dried at 40°C for 24 hours to obtain a green body. The green body is then placed in a kiln, debinded at 600°C for 2 hours, and sintered at 1500°C for 2 hours to obtain a porous ceramic.

[0047] The crystalline morphology of the porous ceramics prepared in this embodiment is as follows: Figure 1 As shown, the porous ceramic is flat and dense, and the density of the ceramic is 2.68 g / cm 3 The pores are evenly distributed, the porosity is 40%, the hardness is 90 HRB, the flexural strength is 48 MPa, the surface does not fall off when abraded, and the gas permeability is 49 L·min at 100 kPa. -1 ·m -2 .

[0048] Example 2

[0049] This embodiment provides a porous ceramic, which is prepared by the following steps: S1. Disperse 246 g 3000 mesh glass powder (BL1241, Jinggu, Foshan) and 164 g cobalt trioxide in 150 g water at room temperature and ball mill for 16 h to obtain a glass powder slurry. S2. Dissolve 22 g of gelatin in 228 g of water until the gelatin is completely dissolved to form a gelatin aqueous solution; then add the glass powder slurry in step S1 to the gelatin aqueous solution while stirring, and then add 722 g of corundum sand formed by mixing 650 g of 90-mesh corundum sand, 52 g of 220-mesh corundum sand, and 22 g of 400-mesh corundum sand; stir at room temperature for 20 min to prepare a corundum sand slurry; the solid content of the slurry is 75 wt%; S3, pouring the corundum slurry in step S2 into a balloon mold, placing the mold in a warm isostatic pressing apparatus, and pressing the mold at 70° C. for 40 min at a pressure of 15 MPa to obtain a wet ceramic green body; S4. The ceramic wet body obtained in step S3 is taken out, placed in an oven, and dried at 40°C for 24 hours to obtain a green body. The green body is then debinded in a nitrogen atmosphere at 600°C for 3 hours, and then sintered in an air atmosphere at 800°C for 2 hours to obtain a porous ceramic.

[0050] The surface SEM morphology of the porous ceramics prepared in this embodiment is shown in FIG. Figure 2 As shown in FIG, the porous ceramics prepared in this embodiment have uniform pore distribution, a porosity of 40%, and a density of 2.78 g / cm 3 , hardness is 92HRB, flexural strength is 50MPa, surface does not fall off after grinding, gas permeability is 45 L·min at 100 kPa -1 ·m -2 .

[0051] Example 3

[0052] This embodiment provides a porous ceramic, which is prepared by the following steps: S1. Disperse 64 g of 2000 mesh alumina powder, 30 g of manganese dioxide, 22 g of titanium dioxide, and 12 g of magnesium oxide in 146 g of water at room temperature, and ball mill for 16 h to obtain an alumina slurry; S2. Dissolve 11 g of gelatin in 110 g of water until the gelatin is completely dissolved to form a gelatin aqueous solution; then add the alumina slurry prepared in step S1 to the gelatin aqueous solution while stirring and mix evenly; then add 448 g of 200 mesh corundum sand and stir at room temperature for 10 min to prepare a corundum sand slurry with a solid content of 70 wt %; S3, pouring the corundum slurry in step S2 into a silica gel mold, plastic-sealing, and placing it in a warm isostatic pressing device, pressing at 50° C. for 60 min and a pressure of 2 MPa to obtain a ceramic green body; S4. Take out the ceramic wet body in step S3, put it into an oven, and dry it at 40°C for 24 hours to obtain a green body. Then put the green body into a kiln, debind it at 300°C for 3 hours, and then sinter it at 1600°C for 2 hours to obtain a porous ceramic.

[0053] The macroscopic morphology of the porous ceramics prepared in this embodiment is as follows: Figure 3 As shown in the figure, it can be seen that the porous ceramics prepared in this embodiment have a smooth and dense surface, and the density of the ceramics is 2.64 g / cm 3 The pores are evenly distributed, the porosity is 45%, the hardness is 88 HRB, the flexural strength is 46 MPa, the surface does not fall off after grinding, and the gas permeability is 52 L·min at 100 kPa. -1 ·m -2 .

[0054] Example 4

[0055] This embodiment provides a porous ceramic, which is prepared by the following steps: S1. Disperse 82 g of 3000 mesh glass powder (BL1241, Jinggu, Foshan), 46 g of manganese dioxide, 26 g of titanium dioxide, and 10 g of magnesium oxide in 35 g of water at room temperature and ball mill for 15 h to obtain a glass powder slurry. S2. Dissolve 15 g of commercially available gelatin in 150 g of water until the gelatin is completely dissolved to form an aqueous solution of curdlan; then add the glass powder slurry prepared in step S1 to the aqueous solution while stirring and mix evenly; then add 574 g of corundum sand formed by mixing 515 g of 90-mesh corundum sand, 42 g of 220-mesh corundum sand, and 17 g of 400-mesh corundum sand; and stir at room temperature for 10 min to prepare a corundum mortar. The solid content of the corundum mortar is 80 wt %. S3, pouring the corundum slurry in step S2 into the balloon, and placing it in a warm isostatic pressing device, pressing it at 60° C. for 50 minutes at a pressure of 15 MPa to obtain a ceramic green body; S4. The ceramic wet body in step S4 is taken out, placed in an oven, and dried at 40°C for 24 hours to obtain a green body. The green body is then placed in a muffle furnace, debinded at 400°C for 4 hours, and then sintered at 700°C for 2 hours to obtain a porous ceramic.

[0056] The porous ceramics prepared in this embodiment have a smooth and dense surface and a density of 2.75 g / cm 3 The pores are evenly distributed, the porosity is 30%, the hardness is 88 HRB, the flexural strength is 47 MPa, the surface does not fall off due to grinding, and the gas permeability is 47 L·min at 100 kPa. -1 ·m -2 .

[0057] Example 5

[0058] This embodiment provides a porous ceramic, which is prepared by the following steps: S1. Disperse 102 g of 3000 mesh alumina powder and 76 g of cobalt trioxide in 335 g of water at room temperature, and ball mill for 12 h to obtain an alumina slurry. S2. Disperse 15 g of curdlan in 150 g of water to form a curdlan aqueous solution; then add the alumina slurry prepared in step S1 to the curdlan aqueous solution while stirring and mix well; then add 550 g of 320-mesh corundum sand and stir at room temperature for 10 minutes to prepare a corundum mortar; the solid content of the corundum mortar is 60 wt%; S3, pouring the corundum slurry in step S2 into a silica gel mold, plastic-sealing, and placing it in a warm isostatic pressing device, pressing it at 90° C. for 20 min at a pressure of 20 MPa to obtain a ceramic green body; S4. Take out the ceramic wet body in step S3, put it into an oven, and dry it at 40°C for 24 hours to obtain a green body. Then put the green body into a kiln, debind it at 400°C for 4 hours, and then sinter it at 1400°C for 2 hours to obtain a porous ceramic.

[0059] The porous ceramics prepared in this embodiment have a smooth and dense surface and a density of 2.7 g / cm 3 The pores are evenly distributed, the porosity is 35%, the hardness is 85 HRB, the flexural strength is 40 MPa, the surface does not fall off when ground, and the gas permeability is 46 L·min at 100 kPa. -1 ·m -2 .

[0060] Example 6

[0061] This embodiment provides a porous ceramic, which is prepared by the following steps: S1. Disperse 136 g of 3000 mesh glass powder and 58 g of cobalt trioxide in 47 g of water at room temperature, and ball mill for 11 h to obtain a glass powder slurry; S2, dispersing 17 g of curdlan in 170 g of water to form a curdlan solution; then adding the glass powder slurry in step S1 to the curdlan solution while stirring and mixing evenly, and then adding 677 g of corundum sand formed by mixing 625 g of 90-mesh corundum sand, 42 g of 220-mesh corundum sand and 10 g of 400-mesh corundum sand, and stirring at room temperature for 10 minutes to prepare a corundum mortar. The solid content of the corundum mortar is 80%; S3, pouring the corundum slurry in step S2 into a silica gel mold, plastic-sealing, and placing it in a warm isostatic pressing device, pressing at 90° C. for 30 min at a pressure of 30 MPa to obtain a ceramic green body; S4. The ceramic wet body obtained in step S3 is taken out, placed in an oven, and dried at 40°C for 24 hours to obtain a green body. The green body is then placed in an atmosphere furnace, debinded at 400°C in a nitrogen atmosphere for 2 hours, and then sintered in a muffle furnace at 900°C in an air atmosphere for 2 hours to obtain a porous ceramic.

[0062] The porous ceramics prepared in this embodiment have a smooth and dense surface and a density of 2.80 g / cm 3 The pores are evenly distributed, the porosity is 35%, the hardness is 90 HRB, the flexural strength is 48 MPa, the surface does not fall off when abraded, and the gas permeability is 46 L·min at 100 kPa. -1 ·m -2 .

[0063] Comparative Example 1 S1. Mix 192 g of 3000 mesh alumina powder, 44.8 g of manganese dioxide, 19.2 g of titanium dioxide, 8 g of magnesium oxide, and water, and then ball-mill for 16 h to obtain an alumina slurry. S2. Dissolve 2 g of gelatin gum in 10 g of water, disperse at room temperature, and then add the mixture to the alumina slurry in step S1 while stirring. Then, add 180 g of 200-mesh corundum sand while stirring to obtain a corundum sand slurry; S3, adding the corundum mortar material in step S2 into the mold, placing it in a 90° C. water bath to cure for 10 min without applying pressure during the process, and demoulding to obtain a wet blank; S4. The wet blank in step S3 is taken out, placed in an oven, and dried at 40°C for 24 hours to obtain a green blank. The green blank is then placed in a muffle furnace, debinded at 400°C for 4 hours, and sintered at 1400°C for 2 hours to obtain a ceramic.

[0064] The macroscopic morphology of the ceramic prepared in this comparative example is as follows Figure 4 As shown, there are excessive pore defects inside the ceramic, and the volume density of the ceramic is 2.42 g / cm 3 .

[0065] Comparative Example 2 S1. Mix 192 g of 3000 mesh alumina powder, 44.8 g of manganese dioxide, 19.2 g of titanium dioxide, 8 g of magnesium oxide, and water, and then ball-mill for 16 h to obtain an alumina slurry. S2. Dissolve 2 g of gelatin gum in 10 g of water, disperse at room temperature, and then add the mixture to the alumina slurry in step S1 while stirring. Then, add 180 g of 320 mesh corundum sand while stirring to form a corundum sand slurry; S3. Add the corundum slurry from step S2 to the mold, place it in a 90°C water bath to cure for 10 minutes, and then dry-press it at a pressure of 20 MPa. Remove the wet blank from the mold. S4. The wet blank in S3 was kept in an oven at 40 °C for 24 h to obtain a green blank; the green blank was then placed in a muffle furnace, debinded at 400 °C for 4 h, and sintered at 1400 °C for 2 h to obtain a porous ceramic.

[0066] The density of the ceramic prepared in this comparative example is 2.68 g / cm 3 , good air permeability, hardness of 82 HRB, but delamination was observed inside the ceramic, and the ceramic flexural strength was 11.1 MPa.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing porous ceramics, characterized in that: The following steps are involved: S1. Adding a ceramic slurry comprising a skeleton material, a binder, a colloid, and water into a mold and performing warm isostatic gel pressing to obtain a ceramic green body; the binder is a high-temperature binder of 900-3000 mesh, the colloid comprises curdlan or gelatin, and the skeleton material comprises 90-400 mesh corundum sand; S2. The ceramic green body in step S1 is demoulded, dried, debinded and sintered to obtain porous ceramics.

2. The method for preparing the porous ceramic according to claim 1, wherein: The warm isostatic pressing of the gel in step S1 is performed at a pressure of 2-30 MPa and a temperature of 50-100°C.

3. The method for preparing the porous ceramic according to claim 1, wherein: The mass ratio of the skeleton material, the binder and the colloid in the ceramic slurry is (70-90):(10-30):(1-10).

4. The method for preparing the porous ceramic according to claim 1, wherein: The preparation method of the ceramic slurry comprises the following steps: D1. ball milling a solution containing a binder to form a first slurry; D2, adding the first slurry described in step D1 to the aqueous solution of the colloid and mixing to form a second slurry; D3. Add the skeleton material to the second slurry described in step D2 and mix to form a ceramic slurry.

5. The method for preparing porous ceramics according to claim 4, characterized in that: The mass ratio of the colloid to water in the aqueous solution of the colloid in step D2 is 1:(5-20), and the solid content of the ceramic slurry in step D3 is 60-90 wt%.

6. The method for preparing porous ceramics according to claim 1, wherein: The high-temperature adhesive in step S1 includes alumina powder or glass powder.

7. The method for preparing porous ceramics according to claim 1, wherein: The sintering temperature in step S2 is 600-1650° C. and the sintering time is 1-4 h.

8. The method for preparing porous ceramics according to claim 1, wherein: The debinding process in step S2 is performed at a temperature of 50-600° C. and for a time of 1-8 h.

9. A porous ceramic, characterized in that: The porous ceramic is prepared by the preparation method of any one of claims 1 to 8.

10. Use of the porous ceramic according to claim 9 in preparing a vacuum chuck.

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