A method for forming ceramic thin plates

Abstract

This invention belongs to the field of ceramic manufacturing technology and relates to a method for forming ceramic thin plates. The forming method includes the following steps: alternately laying ceramic powder layers and spacer layers, and then pressing them to obtain a shaped preform; sintering the shaped preform, and then heat-treating it under an oxygen-containing atmosphere to oxidize and decompose the spacer layer, thereby obtaining a ceramic thin plate; the material of the spacer layer is stable under sintering conditions. This invention, through the setting of spacer layers, enables the stacking and pressing of multiple layers of ceramic powder into a thicker whole, resulting in higher strength and bending resistance during subsequent processing, reducing cracking and warping; subsequently, a simple heat treatment can oxidize and decompose the spacer layer, naturally separating the stacked whole into individual ceramic thin plates, overcoming the breakage or warping problems that easily occur in the preparation of ceramic thin plates using existing technologies.

Description

Technical Field

[0001] This invention belongs to the field of ceramic manufacturing technology, and relates to a ceramic forming method, and more particularly to a method for forming thin ceramic plates. Background Technology

[0002] Ceramic forming is a crucial step in ceramic manufacturing, largely determining the uniformity of the green body and the ability to produce complex-shaped parts, and directly affecting the reliability of the material and the cost of the final ceramic component.

[0003] Dry pressing, also known as die pressing, is a commonly used molding method. It involves loading granulated powder with good flowability and appropriate particle size distribution into a mold cavity, applying pressure through a press head, and transmitting pressure by moving the press head within the mold cavity. This causes the powder particles in the mold cavity to rearrange and deform, thus being compacted to form a ceramic blank with a certain strength and shape.

[0004] Dry pressing is a simple process with advantages such as convenient operation, short cycle time, and high efficiency, making it suitable for automated production. Because the ceramic green body produced by dry pressing has extremely low moisture content, it has high density, making it the optimal forming method for preparing high-density ceramics. However, the uniformity of dry pressing is relatively low. A two-stage forming method combining dry pressing and isostatic pressing can be used to produce high-density, highly uniform products. The dry pressing pressure during the second stage is generally less than 0.6 T / cm². 2 Then, it is pressed into shape by isostatic pressing to obtain a ceramic blank with high uniformity and high density.

[0005] Both dry pressing and secondary forming methods present challenges in the preparation of thin ceramic slabs, including susceptibility to breakage, deformation, and warping. Specifically, the thinner thickness results in lower strength of the preform, making it prone to cracking and breakage during handling, packaging, and secondary isostatic pressing. This problem is particularly pronounced during secondary forming due to the lower pre-pressing pressure in dry pressing. The bending resistance of a thin slab is directly proportional to the square of its thickness; a thinner thickness leads to lower bending resistance. Factors such as uneven powder distribution, uneven pressing force, external forces during handling / packaging, and fluctuations in sintering temperature further exacerbate warping and deformation.

[0006] In response to the problems existing in the preparation of ceramic thin plates, there is a need to provide a simple method for preparing ceramic thin plates that is less prone to breakage and warping. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method for forming ceramic thin plates. This method, through the setting of spacer layers, enables the stacking and pressing of multiple layers of ceramic powder into a single, thicker whole. This results in higher strength and bending resistance during subsequent processing, reducing cracking and warping. Furthermore, a simple heat treatment process can oxidize and decompose the spacer layers, naturally separating the stacked whole into individual ceramic thin plates. This overcomes the breakage or warping problems that easily occur when preparing ceramic thin plates using existing technologies.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] This invention provides a method for forming a ceramic thin plate, the method comprising the following steps:

[0010] Ceramic powder layers and spacer layers are alternately laid, and then pressed to form a preform; the preform is sintered, and then heat-treated under an oxygen-containing atmosphere to oxidize and decompose the spacer layer, thus obtaining a ceramic sheet;

[0011] The material of the spacer layer is stable under sintering conditions.

[0012] The molding method provided by this invention, through the setting of spacer layers, enables the stacking and pressing of multiple layers of ceramic powder into a molded body. The multi-layered molded body forms a thicker whole, which has higher strength and bending resistance in subsequent processing, reducing cracking and warping. Then, the spacer layers can be oxidized and decomposed through simple heat treatment, thereby naturally separating the stacked whole into individual ceramic thin plates, overcoming the breakage or warping problems that are easy to occur when preparing ceramic thin plates in the prior art.

[0013] Preferably, the surface roughness of the spacer layer is 0.3 μm or more.

[0014] Preferably, the thickness of the spacer layer is 0.1 mm to 3 mm, more preferably 0.1 mm to 0.5 mm.

[0015] Preferably, the spacer layer is made of graphite paper and / or carbon fiber cloth.

[0016] Preferably, the ceramic powder layer has an average particle size of 20 μm to 150 μm.

[0017] Preferably, the thickness of the ceramic powder layer is 0.5 mm or more.

[0018] Preferably, the lateral dimension of the ceramic powder layer is D, and the thickness is H, then H / D≤0.05; the dimensions of the lateral dimension and the thickness are mm.

[0019] Preferably, the total number of ceramic powder layers is 2 to 10.

[0020] Preferably, the total thickness of the alternating ceramic powder layer and spacer layer is less than 50 mm.

[0021] Preferably, the compression molding method includes one-time molding or two-time molding;

[0022] The one-time molding method includes a first dry pressing molding;

[0023] The secondary molding method includes sequentially performing a second dry pressing molding and an isostatic pressing molding.

[0024] Preferably, the sintering is carried out under an oxygen-free atmosphere.

[0025] Preferably, the sintering temperature is between 2000°C and 2200°C.

[0026] Preferably, the sintering time is 30 min to 100 min.

[0027] Preferably, the method for removing the spacer layer includes heat treatment under an oxygen-containing atmosphere.

[0028] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The molding method provided by this invention, through the setting of spacer layers, enables the stacking and pressing of multiple layers of ceramic powder into a molded body. The multi-layered molded body forms a thicker whole, which has higher strength and bending resistance in subsequent processing, reducing cracking and warping. Then, the spacer layers can be oxidized and decomposed through simple heat treatment, thereby naturally separating the stacked whole into individual ceramic thin plates, overcoming the breakage or warping problems that are easy to occur when preparing ceramic thin plates in the prior art. Attached Figure Description

[0031] Figure 1 This provides a schematic diagram of the alternating laying of the molding method for Example 1.

[0032] Among them: 1, ceramic powder layer; 2, spacer layer. Detailed Implementation

[0033] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0034] This invention provides a method for forming a ceramic thin plate, the method comprising the following steps:

[0035] Ceramic powder layers and spacer layers are alternately laid, and then pressed to form a preform; the preform is sintered, and then heat-treated under an oxygen-containing atmosphere to oxidize and decompose the spacer layer, thus obtaining a ceramic sheet;

[0036] The material of the spacer layer is stable under sintering conditions.

[0037] The molding method provided by this invention, through the setting of spacer layers, enables the stacking and pressing of multiple layers of ceramic powder into a molded body. The multi-layered molded body forms a thicker whole, which has higher strength and bending resistance in subsequent processing, reduces cracking and warping, and is less prone to breakage and deformation during subsequent processing. Then, the spacer layers can be oxidized and decomposed through simple heat treatment, thereby naturally separating the stacked whole into individual ceramic thin plates, overcoming the breakage or warping problems that are easy to occur when preparing ceramic thin plates in the prior art.

[0038] For example, the gas used in the oxygen-containing atmosphere includes oxygen and / or air.

[0039] In some embodiments, the heat treatment temperature under an oxygen-containing atmosphere is above 400°C, thereby decomposing the spacer layer under oxygen-containing conditions. For example, this temperature could be 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, or 1000°C, but is not limited to the listed values; other unlisted values ​​within the range are also applicable. Considering both the cost of heat treatment and the need to avoid oxidation of the ceramic sheet, the preferred heat treatment temperature is between 400°C and 800°C.

[0040] The spacer layer has a suitable surface roughness, which is beneficial for ensuring a certain bonding strength between the ceramic layer and the spacer layer during pressing.

[0041] In some embodiments, the surface roughness of the spacer layer is greater than 0.3 μm, for example, it may be 0.3 μm, 0.32 μm, 0.35 μm, 0.38 μm or 0.4 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] The present invention does not further limit the method for achieving the required surface roughness of the spacer layer. As long as the surface roughness is above 0.3 μm, the preferred technical effect of improving the density of the obtained ceramic thin plate can be achieved.

[0043] To avoid the adverse effects of spacer layer settings on the quality of ceramic sheets, the thickness of the spacer layer needs to be optimized. For example, if the spacer layer is too thin, oxygen will not easily penetrate between the ceramic blanks during heat treatment in an oxygen-containing atmosphere, leading to a longer spacer layer removal time. Moreover, an excessively thin spacer layer is prone to breakage and cannot effectively separate the upper and lower ceramic blanks, resulting in localized connections between the ceramic blanks after sintering. On the other hand, if the spacer layer is too thick, it will hinder the deformation of the ceramic blank in subsequent processes, affecting uniformity, density, and yield. Furthermore, an excessively thick spacer layer increases the volume of the spacer layer to be removed, which also increases the difficulty and cost of spacer layer removal.

[0044] In some embodiments, the thickness of the spacer layer is from 0.1 mm to 3 mm, for example, it can be 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm or 3 mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, and it is further preferred to be from 0.1 mm to 0.5 mm.

[0045] In some embodiments, the spacer layer is made of graphite paper and / or carbon fiber cloth, more preferably graphite paper.

[0046] Graphite paper can withstand temperatures above 2500℃ in an oxygen-free environment, but in an oxygen-containing atmosphere, it can be decomposed by heat treatment at a lower temperature, thus causing the stacked structure of the molded blank to naturally decompose into multiple single-layer ceramic plates.

[0047] In some embodiments, the average particle size of the ceramic powder in the ceramic powder layer is 20 μm to 150 μm, for example, it can be 20 μm, 40 μm, 50 μm, 60 μm, 80 μm, 100 μm, 120 μm or 150 μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0048] In some embodiments, the ceramic powder layer comprises any one or a combination of at least two of silicon carbide powder, boron carbide powder, boron nitride powder, or oxide ceramics; wherein the oxide ceramics are ceramics sintered under non-oxidizing atmosphere conditions, including but not limited to zirconium oxide ceramics.

[0049] This invention does not further limit the formulation and preparation method of ceramic powder, as long as the ceramic powder has an average particle size of 20μm to 150μm.

[0050] For example, taking silicon carbide powder as an example of ceramic powder, the raw materials for preparing the ceramic powder include, by weight, 100 parts of silicon carbide powder, 100 to 120 parts of deionized water, 2 to 5 parts of carbon powder, 0.6 to 1.5 parts of boron carbide, 0.8 to 2 parts of polyvinyl alcohol, 0.8 to 2 parts of polyethylene glycol, 0.5 to 2 parts of ammonia, 0.5 to 4 parts of glycerol, 0.5 to 1.5 parts of dispersant, 1 to 5 parts of polyacrylic acid, 0.5 to 1.5 parts of release agent, and 0.3 to 1 part of defoamer.

[0051] For example, taking ceramic powder including silicon carbide powder as an example, the method for preparing the ceramic powder includes:

[0052] (1) Add deionized water, carbon powder, boron carbide, dispersant, ammonia, polyethylene glycol, polyvinyl alcohol and glycerol to a ball mill according to the formula amount, and grind in a closed manner for at least 3 hours. Then add silicon carbide powder and continue grinding in a closed manner for 30 to 50 hours to obtain slurry.

[0053] (2) Add the formulated amount of polyacrylic acid and defoamer to the slurry obtained in step (1), stir for 4 to 8 hours to defoam;

[0054] (3) Spray granulation is performed on the defoamed slurry to obtain granulated powder; the inlet temperature of the spray granulation device is 200℃ to 250℃ and the outlet temperature is 93℃ to 99℃.

[0055] (4) The granulated powder is put into a V-type mixer for 1 to 2 hours of mixing. At the same time as mixing, the formula amount of release agent is sprayed in so that it is evenly attached to the surface of the granulated powder. After the mixing is completed, the ceramic powder is obtained.

[0056] The molding method provided by this invention is particularly suitable for the preparation of ceramic thin plates. Since it can alternately lay ceramic powder layers and spacer layers, there is no specific limitation on the lower limit of the thickness of a single ceramic layer. However, considering that an excessively thin single ceramic powder layer is not conducive to the flat laying of ceramic powder, in order to achieve better uniformity of the thickness of the single ceramic powder layer, in some embodiments, the thickness of the ceramic powder layer is 0.5 mm or more, for example, it can be 0.5 mm, 0.6 mm, 0.8 mm, 0.9 mm or 1 mm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0057] In some embodiments, the lateral dimension of the ceramic powder layer is D, and the thickness is H, then H / D ≤ 0.05, for example, it can be 0.01, 0.02, 0.03, 0.04 or 0.05, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable; the dimensions of the lateral dimension and thickness are mm.

[0058] For preparing ceramic thin plates with regular shapes, the lateral dimension of the ceramic powder layer refers to its diameter or side length; while for preparing ceramic thin plates with irregular shapes, the lateral dimension of the ceramic powder layer refers to the diameter of the smallest circumscribed circle.

[0059] In some embodiments, the total number of ceramic powder layers is 2 to 10 layers, for example, 2, 4, 5, 6, 8 or 10 layers, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0060] When the thickness of the alternating ceramic powder layer and the spacer layer is too thick, it is not conducive to the uniform stress distribution of the ceramic powder layer, thereby affecting the quality of the resulting ceramic sheet. As a preferred technical solution, in some embodiments, the total thickness of the alternating ceramic powder layer and the spacer layer is less than 50 mm, for example, it can be 1.2 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 45 mm or 50 mm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0061] In some embodiments, the compression molding method includes one-time molding or two-time molding;

[0062] The one-time molding method includes a first dry pressing molding;

[0063] The secondary molding method includes sequentially performing a second dry pressing molding and an isostatic pressing molding.

[0064] In some embodiments, during the one-time molding process, the maximum pressure of the first dry pressing is 1 T / cm. 2 Up to 1.8T / cm 2 For example, it could be 1T / cm 2 1.2T / cm 2 1.4T / cm 2 1.5T / cm 2 1.6T / cm 2 Or 1.8T / cm 2 However, this does not limit the listed values; any other unlisted values ​​within the range are also applicable.

[0065] In some embodiments, during the one-time molding process, the first dry pressing is performed by gradually increasing the pressure.

[0066] Gradual pressurization allows ceramic powder more time to rearrange and fill, thus improving the density uniformity of the formed green body. It also reduces the likelihood of internal cracks in the green body, improving the structural integrity of the ceramic ligands. Furthermore, it avoids deformation and cracking defects during subsequent sintering caused by excessive stress. In addition, gradual pressurization can also reduce cracking defects and increase pressing density by promoting gas expulsion.

[0067] For example, the gradual pressurization includes: pressurizing to a first pressure and holding it for a first time, then releasing the pressure; pressurizing to a second pressure and holding it for a second time, then releasing the pressure; pressurizing to a third pressure and holding it for a third time, then releasing the pressure; pressurizing to a fourth pressure and holding it for a fourth time, then releasing the pressure; and pressurizing to a fifth pressure and holding it for a fifth time, then releasing the pressure.

[0068] The pressures of the first pressure, the second pressure, the third pressure, the fourth pressure, and the fifth pressure increase sequentially, and the fifth pressure is the maximum pressure for dry pressing.

[0069] In some embodiments, the first pressure is 8% to 12% of the maximum pressure, for example, it can be 8%, 9%, 10%, 11% or 12%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0070] In some embodiments, the second pressure is 28% to 32% of the maximum pressure, for example, it can be 28%, 29%, 30%, 31% or 32%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0071] In some embodiments, the third pressure is 48% to 52% of the maximum pressure, for example, it can be 48%, 49%, 50%, 51% or 52%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0072] In some embodiments, the fourth pressure is 78% to 82% of the maximum pressure, for example, it can be 78%, 79%, 80%, 81% or 82%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0073] In some embodiments, the durations of the first, second, third, fourth, and fifth pressure holding periods are each independently 8 to 12 seconds, for example, 8, 9, 10, 11, or 12 seconds, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0074] In some embodiments, during the secondary molding process, the pressure of the second dry pressing is 0.2 T / cm. 2 Up to 1T / cm2 For example, it could be 0.2T / cm 2 0.3T / cm 2 0.4T / cm 2 0.5T / cm 2 0.6T / cm 2 0.8T / cm 2 Or 1T / cm 2 However, this does not limit the listed values; any unlisted values ​​within the range are also applicable, with 0.3 T / cm being the preferred value. 2 Up to 0.5T / cm 2 .

[0075] In some embodiments, during the secondary molding, the isostatic pressing method includes hot isostatic pressing and / or cold isostatic pressing; taking cold isostatic pressing as an example, the maximum pressure of the cold isostatic pressing is 120MPa to 180MPa, and the pressure is held at the maximum pressure for 150 seconds to 200 seconds.

[0076] In some embodiments, the cold isostatic pressing includes sequentially performing a first isostatic pressing, a first isostatic pressing holding, a second isostatic pressing, a second isostatic pressing holding, a third isostatic pressing, and a third isostatic pressing holding.

[0077] The pressure of the first isostatic pressure is 40 MPa to 60 MPa, for example, it can be 40 MPa, 45 MPa, 50 MPa, 55 MPa or 60 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0078] The pressure of the second isostatic pressure is 70MPa to 90MPa, for example, it can be 70MPa, 75MPa, 80MPa, 85MPa or 90MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0079] The pressure of the third isostatic pressing is the highest pressure for cold isostatic pressing, for example, it can be 120MPa, 140MPa, 150MPa, 160MPa or 180MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0080] The holding times for the first and second isostatic pressures are each independently between 10 and 30 seconds, for example, 10, 15, 20, 25, or 30 seconds, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0081] The holding time for the third isostatic pressure is 150 to 200 seconds, for example, it can be 150 seconds, 160 seconds, 180 seconds, 190 seconds or 200 seconds, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0082] In some embodiments, the sintering is carried out under an oxygen-free atmosphere.

[0083] In some embodiments, the sintering temperature is 2000°C to 2200°C, for example, 2000°C, 2050°C, 2100°C, 2150°C or 2200°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0084] In some embodiments, the sintering time is from 30 min to 100 min, for example, it can be 30 min, 50 min, 60 min, 80 min or 100 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0085] Preparation Example 1

[0086] This preparation example provides a method for preparing ceramic powder. The raw materials for preparing the ceramic powder, by weight, include: 100 parts silicon carbide powder, 110 parts deionized water, 4 parts carbon powder, 1 part boron carbide, 1.5 parts polyvinyl alcohol (PVA17-88), 1.5 parts polyethylene glycol (PEG400), 1 part ammonia, 2 parts glycerol, 1 part dispersant (sodium polyacrylate, PAAS-4000), 3 parts polyacrylic acid (BASF, Sokalan PA25CL), 1 part release agent (zinc stearate), and 0.6 parts defoamer (dimethyl silicone oil, DC-1520).

[0087] The method for preparing the ceramic powder includes:

[0088] (1) Add deionized water, carbon powder, boron carbide, dispersant, ammonia, polyethylene glycol, polyvinyl alcohol and glycerol to a ball mill according to the formula amount, and grind in a closed manner for 3 hours. Then add silicon carbide powder and continue grinding in a closed manner for 40 hours to obtain slurry.

[0089] (2) Add the formulated amount of polyacrylic acid and defoamer to the slurry obtained in step (1), stir for 6 hours, and defoam.

[0090] (3) Spray granulation is performed on the defoamed slurry to obtain granulated powder; the specific parameters of the spray granulation device are adjusted according to the average particle size of the ceramic powder.

[0091] (4) The granulated powder is put into a V-type mixer for mixing. At the same time as mixing, the formula amount of release agent is sprayed in so that it is evenly attached to the surface of the granulated powder. After mixing, the ceramic powder is obtained.

[0092] Example 1

[0093] This embodiment provides a method for forming a ceramic thin plate, the method comprising the following steps:

[0094] Alternating laying (e.g.) Figure 1 (As shown) Ceramic powder layer 1 and spacer layer 2, wherein the total number of ceramic powder layer 1 and spacer layer 2 is 5 layers respectively, and then they are pressed to form a molded body; the molded body is sintered at 2100℃ for 60 minutes in an argon atmosphere, and then heat-treated at 500℃ in an oxygen atmosphere to oxidize and decompose the spacer layer, and the stacked whole is separated into multiple ceramic thin plates.

[0095] The spacer layer is graphite paper with a surface roughness of 0.3 μm and a thickness of 0.3 mm;

[0096] The ceramic powder used in the ceramic powder layer was prepared according to the preparation method provided in Preparation Example 1, and its average particle size was 100 μm; the thickness H of the single-layer ceramic powder layer was 2 mm, and the transverse dimension (diameter) D of the single-layer ceramic powder was 100 mm.

[0097] The pressing and molding method is a one-time molding process, that is, only the maximum pressure of 1.5T / cm is applied. 2 Dry pressing: Apply pressure to the first pressure (10% of the maximum pressure) and hold for 10 seconds, then release the pressure; apply pressure to the second pressure (30% of the maximum pressure) and hold for 10 seconds, then release the pressure; apply pressure to the third pressure (50% of the maximum pressure) and hold for 10 seconds, then release the pressure; apply pressure to the fourth pressure (80% of the maximum pressure) and hold for 10 seconds, then release the pressure; apply pressure to the fifth pressure (100% of the maximum pressure) and hold for 10 seconds, then release the pressure.

[0098] In Examples 2 to 8, except for the changes in the thickness and surface roughness of the spacer layer as shown in Table 1, everything else was the same as in Example 1; that is, the number of ceramic powder layers and spacer layers remained unchanged compared to Example 1. The yield rate was defined as the percentage of ceramic sheets that, after five repeated molding processes, exhibited no cracking or splitting of the single-layer ceramic body, showed no adhesion between ceramic layers after sintering, and could be separated after heat treatment. The heat treatment time was defined as the time required for the spacer layer to oxidize and decompose.

[0099] Table 1

[0100]

[0101]

[0102] As shown in Table 1, the surface roughness of the graphite paper used in Example 5 was only 0.1 μm. After pressing, the spacer layer separated from the ceramic blank, so no further processing was performed. A comparison of Examples 6 and 7 with Example 1 shows that when the spacer layer is too thin, oxygen cannot easily penetrate between the ceramic blanks, leading to an increase in the heat treatment time for removing the spacer layer. When the thickness is further reduced, some of the spacer layer breaks, causing the two ceramic blanks to connect, resulting in a defective product. A comparison of Example 8 with Example 1 shows that when the spacer layer is too thick, the density, yield, and flatness of the resulting ceramic sheet decrease. In Examples 9 to 12, except for the maximum pressure of dry pressing, which varies as shown in Table 2, the rest are the same as in Example 1.

[0103] Table 2

[0104]

[0105] As shown in Table 2, when the maximum pressure for dry pressing is within the preferred range of 1 T / cm 2 Up to 1.8T / cm 2 When the obtained ceramic sheet has a density of 95.0% or higher, a yield of 91% or higher, and a flatness of 0.08 or lower, it can be seen from the comparison between Example 11 and Example 1 that when the maximum pressure of dry pressing is too low, the density of the obtained ceramic sheet decreases, and due to the high shrinkage rate during sintering, the flatness increases, resulting in a lower yield. When the comparison between Example 12 and Example 1 shows that when the maximum pressure of dry pressing is too high, the elastic aftereffect is obvious, leading to a lower yield.

[0106] Examples 13 and 14 are identical to Example 1, except for the total number of ceramic powder layers and spacer layers, as shown in Table 3. The yield rate is the percentage of ceramic sheets produced by repeating the molding process multiple times until all ceramic sheets are 100, where the single-layer ceramic body is free of cracks throughout the process, the ceramic layers are not adhered to each other after sintering, and the sheets can be separated after heat treatment.

[0107] Table 3

[0108]

[0109] As shown in Table 3, within the range of 2 to 10 layers of ceramic powder, the molding method provided by the present invention can obtain ceramic thin plates with good density and flatness, and have a yield rate of over 87%.

[0110] Example 15

[0111] This embodiment provides a method for forming a ceramic thin plate, the method comprising the following steps:

[0112] The ceramic powder layer and the spacer layer are alternately laid, with a total of 5 layers of ceramic powder layer and spacer layer respectively. Then, the mixture is pressed to form a preform. The preform is sintered at 2100℃ for 60 minutes in an argon atmosphere, and then heat-treated at 500℃ in an oxygen atmosphere to oxidize and decompose the spacer layer. The stacked preform is then separated into multiple ceramic plates.

[0113] The spacer layer is graphite paper with a surface roughness of 0.3 μm and a thickness of 0.3 mm;

[0114] The ceramic powder used in the ceramic powder layer was prepared according to the preparation method provided in Preparation Example 1, and its average particle size was 100 μm; the thickness H of the single-layer ceramic powder layer was 2 mm, and the transverse dimension (diameter) D of the single-layer ceramic powder was 100 mm.

[0115] The pressing and molding method is a two-stage molding process, namely, dry pressing and cold isostatic pressing performed sequentially. The pressure of dry pressing is 0.4 T / cm. 2 The holding time is 10 seconds; cold isostatic pressing includes: holding pressure at 50MPa for 20 seconds, then holding pressure at 80MPa for 20 seconds, and finally holding pressure at 150MPa for 180 seconds.

[0116] Examples 16 and 21 are identical to Example 15, except for the changes in pressure during dry pressing and cold isostatic pressing as shown in Table 4. The yield rate is the percentage of ceramic sheets that, after five repeated molding processes, exhibit no cracks or splitting of the single-layer ceramic body, show no adhesion between ceramic layers after sintering, and can be separated after heat treatment.

[0117] Table 4

[0118]

[0119]

[0120] Table 4 shows that, within the optimal parameter range for secondary molding, the resulting ceramic thin plate has a density of over 98.1%, a yield rate of over 88%, and a flatness of less than 0.08 mm; when the maximum pressure for dry pressing is 0.2 T / cm... 2 With 1T / cm 2 When the yield rate of the obtained ceramic thin plates is slightly reduced, ceramic thin plates with the required density and flatness can still be obtained. Similarly, when the maximum pressure of cold isostatic pressing is 120MPa and 180MPa, the yield rate of the obtained ceramic thin plates is slightly reduced, but ceramic thin plates with the required density and flatness can still be obtained.

[0121] In summary, the molding method provided by this invention, through the setting of spacer layers, enables the stacking and pressing of multiple layers of ceramic powder into a single, thicker whole. This results in higher strength and resistance to bending during subsequent processing, reducing cracking and warping. It also increases the pressing pressure, thereby improving the density of the molded body and making it less prone to breakage and deformation during subsequent processing. Furthermore, by simply removing the spacer layers, the stacked whole can be naturally separated into individual ceramic sheets, overcoming the breakage or warping problems that easily occur when preparing ceramic sheets using existing technologies.

[0122] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method of forming a ceramic sheet, characterized by, The forming method comprises the following steps: alternately laying ceramic powder layers and spacer layers, and then performing press forming to obtain a forming blank; the forming blank is sintered, and then heat treated in an oxygen-containing atmosphere to make the spacer layers oxidize and decompose to obtain a ceramic sheet; the material of the spacer layer is stable under sintering conditions; the thickness of the ceramic powder layer is greater than or equal to 0.5 mm; the ceramic powder comprises silicon carbide powder; the press forming method comprises one-step forming or two-step forming; the one-step forming method comprises first dry press forming, which is performed in a step-by-step pressurizing manner; the step-by-step pressurizing comprises: pressurizing to a first pressure and performing first pressure keeping, then releasing pressure; pressurizing to a second pressure and performing second pressure keeping, then releasing pressure; pressurizing to a third pressure and performing third pressure keeping, then releasing pressure; pressurizing to a fourth pressure and performing fourth pressure keeping, then releasing pressure; pressurizing to a fifth pressure and performing fifth pressure keeping, then releasing pressure; the first pressure, the second pressure, the third pressure, the fourth pressure and the fifth pressure are sequentially increased, and the fifth pressure is the maximum pressure of the dry press forming; the two-step forming method comprises sequentially performing second dry press forming and isostatic press forming; the isostatic press forming method comprises hot isostatic press forming and / or cold isostatic press forming; the cold isostatic press forming comprises sequentially performing first isostatic pressing, first isostatic pressure keeping, second isostatic pressing, second isostatic pressure keeping, third isostatic pressing and third isostatic pressure keeping.

2. The molding method according to claim 1, characterized by, The surface roughness of the spacer layer is greater than or equal to 0.3 μm.

3. The molding method according to claim 1, characterized by, The thickness of the spacer layer is 0.1 mm to 3 mm.

4. The molding method according to claim 1, characterized by, The thickness of the spacer layer is 0.1 mm to 0.5 mm.

5. The molding method according to claim 1, wherein The material of the spacer layer comprises graphite paper and / or carbon fiber cloth.

6. The molding method according to claim 1, wherein In the ceramic powder layer, the average particle size of the ceramic powder is 20 μm to 150 μm.

7. The molding method according to claim 1, wherein The transverse dimension of the ceramic powder layer is D, and the thickness is H, then H / D≤0.05; the dimensions of the transverse dimension and the thickness are mm.

8. The molding method according to claim 1, characterized by, The total number of the ceramic powder layers is 2 to 10 layers.

9. The molding method according to claim 1, characterized by, The total thickness of the alternately laid ceramic powder layers and spacer layers is less than or equal to 50 mm.

10. The molding method according to claim 1, characterized by, The sintering is performed in an oxygen-free atmosphere.

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