Forming method of ceramic sheet

Abstract

The invention belongs to the technical field of ceramic manufacturing, and relates to a forming method of a ceramic sheet, which comprises the following steps: alternately laying ceramic powder layers and spacing layers, and then carrying out compression molding to obtain a molded blank; sintering the molded blank, and performing heat treatment under an oxygen-containing atmosphere condition to oxidize and decompose the spacing layer to obtain a ceramic thin plate; the material of the spacer layer is stable under a sintering condition. Through the arrangement of the spacing layers, multiple ceramic powder layers can be stacked and then subjected to compression molding, multiple stacked molded blanks form a thicker whole, higher strength and bending resistance are achieved in the subsequent treatment process, and cracking and warping are reduced; and then, the spacing layer can be oxidized and decomposed through simple heat treatment, so that the stacked whole body is naturally separated into independent ceramic thin plates, and the problem that the ceramic thin plates are easy to break or warp when being prepared in the prior art is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic manufacturing, and relates to a ceramic forming method, in particular to a ceramic thin plate forming method. Background Art

[0002] Ceramic forming is an important part of the ceramic preparation process. It largely determines the uniformity of the green body and the ability to prepare parts with complex shapes, and directly affects the reliability of the material and the cost of the final ceramic parts.

[0003] Dry pressing, also known as compression molding, is one of the commonly used molding methods. It loads granulated powder with good fluidity and appropriate particle size distribution into the membrane cavity, applies pressure through the pressure head, and the pressure head moves in the membrane cavity to transmit pressure, so that the powder particles in the membrane cavity are rearranged and deformed and compacted to form a ceramic blank with a certain strength and shape.

[0004] The dry pressing process is simple, easy to operate, short cycle and high efficiency, and is convenient for automated production. Since the ceramic blank after dry pressing has extremely low water content, it has a higher density and is the best molding method for preparing high-density ceramics, but the uniformity of dry pressing is relatively low. The dry pressing and isostatic pressing secondary molding method can be used to prepare high-density and high-uniformity products. The dry pressing pressure during secondary molding is generally less than 0.6T / cm 2 Then, it is molded by isostatic pressing to obtain a ceramic green body with high uniformity and high density.

[0005] Whether it is the dry pressing method or the secondary molding method, there are problems of easy breakage and warping when preparing ceramic thin plates. Specifically, the thin thickness makes the strength of the embryo low, and it is easy to crack and break during transportation, packaging, secondary isostatic pressing and other links. In particular, the cracking and breakage problems are particularly prominent in the secondary molding due to the low dry pressing pre-pressing pressure. The bending resistance of the thin plate is proportional to the square of the thickness. The thinner thickness makes the embryo low in bending resistance. The factors such as uneven powder, uneven pressing force, external forces in the transportation / packaging process, and fluctuations in sintering temperature make it more sensitive to warping deformation.

[0006] In view of this, in order to solve the problems existing in the preparation of ceramic thin plates, it is necessary to provide a forming method for ceramic thin plates which has a simple preparation method and is not prone to breakage and warping. Summary of the invention

[0007] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for forming a ceramic thin plate. The forming method can stack multiple layers of ceramic powder layers and then press them into shape by setting a spacer layer. The multiple stacked molded embryos form a thicker whole, which has higher strength and bending resistance in subsequent processing, and reduces cracking and warping. Then, the spacer layer can be oxidized and decomposed by simple heat treatment, thereby naturally separating the stacked whole into separate ceramic thin plates, thereby overcoming the problem of breakage or warping that is easy to occur when preparing ceramic thin plates with the prior art.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

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

[0010] Alternately laying ceramic powder layers and spacer layers, and then pressing and molding to obtain a molded embryo; sintering the molded embryo, and then heat-treating the molded embryo under oxygen-containing atmosphere conditions to oxidatively decompose the spacer layer to obtain a ceramic thin plate;

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

[0012] The molding method provided by the present invention can stack multiple layers of ceramic powder layers and then press them into shape by setting a spacer layer. The multiple stacked molded embryos form a thicker whole, which has higher strength and bending resistance in subsequent processing, and reduces cracking and warping. Then, the spacer layer can be oxidized and decomposed by simple heat treatment, thereby naturally separating the stacked whole into separate ceramic thin plates, overcoming the problem of breakage or warping that is easy to occur when preparing ceramic thin plates in the prior art.

[0013] Preferably, the surface roughness of the spacer layer is greater than 0.3 μm.

[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 material of the spacer layer includes graphite paper and / or carbon fiber cloth.

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

[0017] Preferably, the thickness of the ceramic powder layer is greater than 0.5 mm.

[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 thickness are mm.

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

[0020] Preferably, the total thickness of the alternately laid ceramic powder layers and the spacer layers is less than 50 mm.

[0021] Preferably, the compression molding method includes primary molding or secondary molding;

[0022] The one-step forming method comprises a first dry pressing forming;

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

[0024] Preferably, the sintering is performed in an oxygen-free atmosphere.

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

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

[0027] Preferably, the method of removing the spacer layer comprises performing a heat treatment in an oxygen-containing atmosphere.

[0028] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists 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 the present invention can stack multiple layers of ceramic powder layers and then press them into shape by setting a spacer layer. The multiple stacked molded embryos form a thicker whole, which has higher strength and bending resistance in subsequent processing, and reduces cracking and warping. Then, the spacer layer can be oxidized and decomposed by simple heat treatment, thereby naturally separating the stacked whole into separate ceramic thin plates, overcoming the problem of breakage or warping that is easy to occur when preparing ceramic thin plates in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of alternating laying of the molding method is provided for Example 1.

[0032] Among them: 1, ceramic powder layer; 2, spacer layer. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

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

[0035] Alternately laying ceramic powder layers and spacer layers, and then pressing and molding to obtain a molded embryo; sintering the molded embryo, and then heat-treating the molded embryo under oxygen-containing atmosphere conditions to oxidatively decompose the spacer layer to obtain a ceramic thin plate;

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

[0037] The molding method provided by the present invention can stack multiple layers of ceramic powder layers and then press them into shape by setting a spacer layer. The multi-layer stacked molded embryo forms a thicker whole, which has higher strength and bending resistance during subsequent processing, reduces cracking and warping, and is not easy to break or deform during subsequent processing; then, the spacer layer can be oxidized and decomposed by simple heat treatment, thereby naturally separating the stacked whole into separate ceramic thin plates, overcoming the problem of breakage or warping that is easy to occur when preparing ceramic thin plates in the prior art.

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

[0039] In some embodiments, the temperature of the heat treatment under oxygen-containing atmosphere is above 400°C, so that the spacer layer is decomposed under oxygen-containing atmosphere, for example, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C or 1000°C, but not limited to the listed values, and other values ​​not listed in the numerical range are also applicable. Considering the cost of heat treatment and avoiding oxidation of the components of the ceramic thin plate, the temperature of the heat treatment is preferably 400°C to 800°C.

[0040] The surface of the spacer layer has a suitable roughness, which is beneficial to ensure a certain bonding strength between the ceramic layer and the spacer layer during press molding.

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

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

[0043] In order to avoid the adverse effects of the spacing layer on the quality of the ceramic thin plate, the thickness of the spacing layer needs to be optimally set. For example, when the thickness of the spacing layer is too thin, oxygen is not easy to penetrate into the ceramic embryos during heat treatment under oxygen-containing atmosphere conditions, resulting in a longer removal time of the spacing layer; moreover, a spacing layer that is too thin is easily damaged and cannot well separate the upper and lower layers of the ceramic embryos. After sintering, the ceramic embryos are partially connected and cannot be separated; and when the thickness of the spacing layer is too thick, it hinders the deformation of the ceramic embryo in subsequent links, affecting uniformity, density and yield; moreover, the thickness of the spacing layer is too thick, which increases the volume of the spacing layer to be removed, and also increases the difficulty and cost of removing the spacing layer.

[0044] In some embodiments, the thickness of the spacer layer is 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 numerical range are also applicable, and more preferably 0.1 mm to 0.5 mm.

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

[0046] Graphite paper can withstand temperatures above 2500°C in an oxygen-free environment, while in an oxygen-containing atmosphere, heat treatment at a lower temperature can decompose the graphite paper, allowing the stacked structure of the molded body to naturally decompose into multiple single-layer ceramic sheets.

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

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

[0049] The present invention does not further limit the formula and preparation method of the ceramic powder, as long as the ceramic powder satisfies the average particle size of 20 μm to 150 μm.

[0050] Exemplarily, taking ceramic powder including silicon carbide powder as an example, the raw materials for preparing the ceramic powder include, in parts 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 water, 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 defoaming agent.

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

[0052] (1) adding deionized water, carbon powder, boron carbide, dispersant, ammonia water, polyethylene glycol, polyvinyl alcohol and glycerol in a ball mill according to the formula, grinding for at least 3 hours, and then adding silicon carbide powder and continuing to grind for 30 to 50 hours to obtain a slurry;

[0053] (2) adding a formulated amount of polyacrylic acid and a defoaming agent to the slurry obtained in step (1), stirring for 4 to 8 hours to defoam;

[0054] (3) spray granulating the defoamed slurry to obtain granulated powder; the inlet temperature of the spray granulation device is 200° C. to 250° C., and the outlet temperature is 93° C. to 99° C.;

[0055] (4) The granulated powder is placed in a V-type mixer for mixing for 1 to 2 hours. During the mixing, a formulated amount of release agent is sprayed 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 forming method provided by the present invention is particularly suitable for the preparation of ceramic thin plates. Since ceramic powder layers and spacer layers can be laid alternately, the lower limit of the thickness of a single ceramic layer is not specifically limited; but considering that the thickness of a single ceramic powder layer that is too thin is not conducive to the flattening of the ceramic powder, in order to achieve better thickness uniformity of the single ceramic powder layer, in some embodiments, the thickness of the ceramic powder layer is greater than 0.5 mm, 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, and the remaining values ​​not listed within the numerical 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 numerical range are also applicable; the dimensions of the lateral dimension and thickness are mm.

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

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

[0060] When the thickness of the alternately laid ceramic powder layer and the spacer layer is too thick, it is not conducive to the uniform force of the ceramic powder layer, thereby affecting the quality of the obtained ceramic thin plate. As a preferred technical solution, in some embodiments, the total thickness of the alternately laid 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 the remaining values ​​not listed in the numerical range are also applicable.

[0061] In certain embodiments, the compression molding method includes primary molding or secondary molding;

[0062] The one-step forming method comprises a first dry pressing forming;

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

[0064] In some embodiments, during the one-time forming, the maximum pressure of the first dry pressing forming is 1T / cm 2 Up to 1.8T / cm 2 , for example, it can 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 , but not limited to the listed values, the remaining values ​​not listed in the numerical range are also applicable.

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

[0066] The gradual pressurization method can give the ceramic powder more time to rearrange and fill, thereby improving the density uniformity of the molded body; it can also reduce the possibility of cracks inside the molded body and improve the structural integrity of the ceramic ligand; it can also avoid deformation and cracking defects caused by excessive stress during subsequent sintering. In addition, the gradual pressurization method can also promote gas discharge, reduce cracking defects, and increase pressing density.

[0067] Exemplarily, the gradual pressurization includes: pressurizing to a first pressure and performing a first pressure holding, and then releasing the pressure; pressurizing to a second pressure and performing a second pressure holding, and then releasing the pressure; pressurizing to a third pressure and performing a third pressure holding, and then releasing the pressure; pressurizing to a fourth pressure and performing a fourth pressure holding, and then releasing the pressure; pressurizing to a fifth pressure and performing a fifth pressure holding, and then releasing the pressure.

[0068] The pressures of the first pressure, the second pressure, the third pressure, the fourth pressure and the fifth pressure are increased in sequence, and the fifth pressure is the maximum pressure of dry pressing.

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

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

[0074] In some embodiments, during the secondary molding, the pressure of the second dry pressing molding is 0.2T / cm 2 Up to 1T / cm2 , for example, it can 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 , but not limited to the listed values, the other values ​​not listed in the numerical range are also applicable, preferably 0.3T / cm 2 Up to 0.5T / cm 2 .

[0075] In certain 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 120 MPa to 180 MPa, and the pressure is maintained at the maximum pressure for 150 seconds to 200 seconds.

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

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

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

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

[0080] The time of the first isostatic holding and the second isostatic holding are independently 10 seconds to 30 seconds, for example, 10 seconds, 15 seconds, 20 seconds, 25 seconds or 30 seconds, but are not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

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

[0082] In certain embodiments, the sintering is performed in 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, and other unlisted values ​​within the numerical range are also applicable.

[0084] In some embodiments, the sintering time is 30 min to 100 min, for example, 30 min, 50 min, 60 min, 80 min or 100 min, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0085] Preparation Example 1

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

[0087] The preparation method of the ceramic powder comprises:

[0088] (1) adding deionized water, carbon powder, boron carbide, dispersant, ammonia water, polyethylene glycol, polyvinyl alcohol and glycerol into a ball mill according to the formula, grinding for 3 hours, and then adding silicon carbide powder and grinding for 40 hours to obtain a slurry;

[0089] (2) adding the formulated amount of polyacrylic acid and defoaming agent to the slurry obtained in step (1), stirring for 6 hours to defoam;

[0090] (3) spray granulating 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 placed in a V-type mixer for mixing. During the mixing, a formulated amount of a release agent is sprayed in so that the release agent is evenly attached to the surface of the granulated powder. After the mixing is completed, 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] Alternate laying (such as Figure 1 The ceramic powder layer 1 and the spacer layer 2 are formed into a plurality of ceramic sheets; the ...

[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 is prepared according to the preparation method provided in Preparation Example 1, and its average particle size is 100 μm; the thickness H of a single-layer ceramic powder layer is 2 mm, and the lateral dimension (diameter) D of a single-layer ceramic powder is 100 mm;

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

[0098] In Examples 2 to 8, except that the thickness and surface roughness of the spacer layer are changed as shown in Table 1, the rest are the same as in Example 1, that is, the number of ceramic powder layers and the spacer layer is unchanged relative to Example 1. The yield rate is: the proportion of ceramic sheets that have no cracks in the single-layer ceramic embryo during the whole process, no adhesion between ceramic layers after sintering, and can be separated after heat treatment to all ceramic sheets after repeated molding for 5 times. The heat treatment time is the time for the spacer layer to be oxidized and decomposed.

[0099] Table 1

[0100]

[0101]

[0102] As can be seen from Table 1, the surface roughness of the graphite paper used in Example 5 is only 0.1 μm, and the separation of the spacer layer and the ceramic embryo occurs after press molding, so no subsequent operation is performed. From the comparison of Example 6 and Example 7 with Example 1, it can be seen that when the spacer layer is too thin, oxygen is not easy to penetrate between the ceramic embryos, resulting in an increase in the heat treatment time for removing the spacer layer. When the thickness is further reduced, part of the spacer layer is damaged, connecting the two layers of ceramic embryos, resulting in an unqualified product. From the comparison of Example 8 with Example 1, it can be seen that when the spacer layer is too thick, the density, yield and flatness of the obtained ceramic thin plate will be reduced. In Examples 9 to 12, except that the maximum pressure of dry pressing changes as shown in Table 2, the rest are the same as Example 1.

[0103] Table 2

[0104]

[0105] It can be seen from Table 2 that when the maximum pressure of dry pressing is in the preferred range of 1T / cm 2 Up to 1.8T / cm 2 When the maximum pressure of dry pressing is too small, the density of the obtained ceramic thin plate is above 95.0%, the yield rate is above 91%, and the flatness is below 0.08. As can be seen from the comparison between Example 11 and Example 1, when the maximum pressure of dry pressing is too small, the density of the obtained ceramic thin plate decreases, and due to the high shrinkage rate of sintering, the flatness increases and the yield rate decreases; as can be seen from the comparison between Example 12 and Example 1, when the maximum pressure of dry pressing is too large, the elastic aftereffect is obvious, resulting in a decrease in the yield rate.

[0106] Except that the total number of ceramic powder layers and spacer layers in Example 13 to Example 14 is changed as shown in Table 3, the rest are the same as Example 1. The yield rate is: the molding is repeated for multiple times, so that the number of all ceramic thin plates is 100, and the proportion of ceramic thin plates that have no cracks in the single-layer ceramic embryo during the whole process, no adhesion between ceramic layers after sintering, and can be separated after heat treatment accounts for all ceramic thin plates.

[0107] Table 3

[0108]

[0109] It can be seen from Table 3 that when the total number of ceramic powder layers is in the range of 2 to 10 layers, the molding method provided by the present invention can obtain a ceramic thin plate with good density and flatness and a yield rate of more than 87%.

[0110] Embodiment 15

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

[0112] Alternately laying ceramic powder layers and spacer layers, wherein the total number of ceramic powder layers and spacer layers is 5 layers respectively, and then pressing and molding to obtain a molded embryo; the molded embryo is sintered at 2100° C. for 60 minutes in an argon atmosphere, and then heat-treated at 500° C. in an oxygen atmosphere to oxidize and decompose the spacer layer, and the stacked whole is separated into a plurality of ceramic thin 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 is prepared according to the preparation method provided in Preparation Example 1, and its average particle size is 100 μm; the thickness H of a single-layer ceramic powder layer is 2 mm, and the lateral dimension (diameter) D of a single-layer ceramic powder is 100 mm;

[0115] The pressing method is a secondary pressing method, that is, dry pressing and cold isostatic pressing are performed in sequence, and the pressure of the dry pressing is 0.4T / 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] Example 16 Example 21 Except that the pressure of dry pressing and the pressure of cold isostatic pressing are changed as shown in Table 4, the rest are the same as Example 15. The yield rate is: the proportion of ceramic thin plates that have no cracks in the single-layer ceramic embryo body during the whole process, no adhesion between ceramic layers after sintering, and can be separated after heat treatment accounts for all ceramic thin plates after repeated molding for 5 times.

[0117] Table 4

[0118]

[0119]

[0120] It can be seen from Table 4 that within the preferred parameter range of secondary molding, the density of the obtained ceramic sheet is above 98.1%, the yield rate is above 88% and the flatness is below 0.08 mm; when the maximum pressure of dry pressing is 0.2 T / cm 2 With 1T / cm 2 When the maximum pressure of cold isostatic pressing is 120MPa and 180MPa respectively, the yield rate of the obtained ceramic thin plate is slightly reduced, but the ceramic thin plate with the density and flatness symbol requirements can still be obtained; similarly, when the maximum pressure of cold isostatic pressing is 120MPa and 180MPa respectively, the yield rate of the obtained ceramic thin plate is slightly reduced, but the ceramic thin plate with the density and flatness symbol requirements can also be obtained.

[0121] To sum up, the molding method provided by the present invention can stack multiple layers of ceramic powder layers and then perform press molding through the setting of the spacer layer. The multi-layer stacked embryo forms a thicker whole, which has higher strength and bending resistance in the subsequent processing process, reduces cracking and warping, and can increase the pressing molding pressure, which is beneficial to improve the density of the molded embryo, which is not easy to break or deform during subsequent processing; then, by simply removing the spacer layer, the stacked whole can be naturally separated into separate ceramic thin plates, overcoming the problem of breakage or warping that is easy to occur when preparing ceramic thin plates in the prior art.

[0122] The applicant declares that the above is only a specific implementation mode 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 thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for forming a ceramic thin plate, characterized in that: The molding method comprises the following steps: Alternately laying ceramic powder layers and spacer layers, and then pressing and molding to obtain a molded embryo; sintering the molded embryo, and then heat-treating the molded embryo under oxygen-containing atmosphere conditions to oxidatively decompose the spacer layer to obtain a ceramic thin plate; The material of the distance layer is stable under sintering conditions.

2. The molding method according to claim 1, characterized in that: The surface roughness of the spacer layer is greater than 0.3 μm.

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

4. The molding method according to claim 3, characterized in that: The thickness of the spacer layer is 0.1 mm to 0.5 mm.

5. The molding method according to any one of claims 1 to 4, characterized in that: The material of the spacer layer includes graphite paper and / or carbon fiber cloth.

6. The molding method according to claim 1, characterized in that: 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 6, characterized in that: The thickness of the ceramic powder layer is greater than 0.5 mm; And / or, the lateral dimension of the ceramic powder layer is D, and the thickness is H, then H / D≤0.05; the dimension of the lateral dimension and the thickness is mm; And / or, the total number of ceramic powder layers is 2 to 10; And / or, the total thickness of the alternately laid ceramic powder layers and the spacer layers is less than 50 mm.

8. The molding method according to claim 1, characterized in that: The compression molding method includes primary molding or secondary molding.

9. The molding method according to claim 8, characterized in that: The one-step forming method comprises a first dry pressing forming; And / or, the secondary molding method includes a second dry pressing molding and an isostatic pressing molding performed sequentially.

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

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