Preparation method and forming die of low-defect and high-breakdown-strength ceramic sheet

Abstract

The invention relates to a preparation method of a ceramic sheet of a high-purity ozone generator, in particular to a preparation method and a forming die of a low-defect and high-breakdown-strength ceramic sheet. A preparation method of a low-defect and high-breakdown-strength ceramic sheet comprises the following steps: firstly, preparing a ceramic green body by adopting a gel casting method, then putting the obtained ceramic green body into a forming mold for continuous isostatic pressing to obtain a ceramic green body, and then sintering and processing the ceramic green body to obtain the low-defect and high-breakdown-strength ceramic sheet. According to the preparation method of the low-defect and high-breakdown-strength ceramic thin plate, the ceramic thin plate blank is prepared by adopting a direct gel casting method, so that the defects such as impurities and microcracks in the blank can be greatly reduced; according to the preparation method, a ceramic body with few microdefects and a compact structure can be obtained, the passing rate of 18KV breakdown strength of the prepared ceramic sheet can reach about 90%, and the percent of pass is increased.

Description

Technical Field

[0001] The invention relates to a method for preparing a ceramic thin plate of a high-purity ozone generator, in particular to a method for preparing a ceramic thin plate with low defects and high breakdown strength and a forming die. Background Art

[0002] High-purity ozone generators are mainly used in the semiconductor field. With the changes in the international situation and the improvement of domestic industrial level, related equipment manufacturers are in urgent need of finding suppliers of key components from China. Among them, the 99.5 alumina ceramic plate, which is a key core component, has always been a problem for equipment manufacturers due to its stability in use. The size of the ceramic plate is φ100mm×0.5mm, and its performance requirements are: a 0.5mm thick ceramic plate needs to withstand a high voltage of about 18KV for a long time, that is, the breakdown strength is greater than 36KV / mm.

[0003] The breakdown strength of 99.5 alumina ceramics is generally greater than 36KV / mm. The difficulty lies in that an area of ​​about 100mm in diameter needs to withstand the above voltage, and at a thickness of 0.5mm, the risk of breakdown is greatly increased. To ensure that 100 such thin plates are not broken down at the same time, it means that at 0.785m 2 The main reason for the breakdown of the ceramic plate is the appearance of microscopic defects such as cracks, pores, impurities, etc. in the material, which means that the area of ​​0.785m 2 The above defects are not allowed to appear in the area.

[0004] At present, ceramic thin plates are generally formed by direct isostatic pressing of granulated powder. This preparation method is very likely to introduce the above defects during the preparation of granulated powder, and the defects between granulated particles are also very likely to remain during the forming process. Therefore, the risk of ceramic thin plates prepared by this method being punctured is very high. According to feedback from domestic equipment manufacturers, the qualified rate of ceramic thin plates purchased from abroad in the breakdown strength test barely reaches about 70%. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a method for preparing a ceramic thin plate with low defects and high breakdown strength. The specific technical scheme is as follows:

[0006] A method for preparing a ceramic thin plate with low defects and high breakdown strength comprises the following steps: firstly preparing a ceramic green body by a gel injection molding method, then placing the obtained ceramic green body into a molding die for further isostatic pressing to obtain a ceramic green body, and then sintering and processing to obtain a ceramic thin plate with low defects and high breakdown strength.

[0007] Preferably, the gel casting method comprises preparing slurry by using 0.2-0.3%wt of ISOBAM104 as a gelling agent, 0.05-0.2%wt of gum arabic, and 0.1-0.3%wt of aluminum sol as a reinforcing agent.

[0008] Furthermore, the slurry is first sieved through a 200-mesh screen, then stirred in a vacuum for 5 to 10 minutes, and finally poured into a molding mold for drying and dehydration to obtain a ceramic body.

[0009] Furthermore, the ceramic body is dried to a moisture content of 1% to 3% by weight, then sealed and homogenized for 20 to 28 hours, and then isostatically pressed.

[0010] Preferably, the forming mold forms one or more ceramic thin plates at a time.

[0011] A molding die for a ceramic thin plate with low defects and high breakdown strength, used in the method for preparing the above-mentioned ceramic thin plate with low defects and high breakdown strength, comprises: a mold sleeve, provided with a molding cavity, the molding cavity is used to place a plurality of ceramic thin plates; a rubber plug, provided with two ends of the mold sleeve; a metal plate, provided at both ends of the molding cavity and located on one side of the rubber plug; and a rubber gasket, provided on both sides of the ceramic thin plate.

[0012] Furthermore, the number of the ceramic thin plates is 20.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] The invention provides a method for preparing a ceramic thin plate with low defects and high breakdown strength. The method adopts a direct gel injection molding method to prepare a ceramic thin plate blank, which can greatly reduce defects such as impurities and microcracks in the blank; a ceramic body with few microscopic defects and a dense structure can be obtained, and the pass rate of the prepared ceramic thin plate with a breakdown strength resistance of 18KV can reach about 90%, thereby improving the qualified rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram of molding in a molding die;

[0016] Figure 2 This is a micrograph of Example 3 after the 18KV high voltage test.

[0017] Figure 3 This is a micrograph of the comparative example after 18KV high voltage test. DETAILED DESCRIPTION

[0018] The present invention will be further described with reference to the accompanying drawings.

[0019] like Figure 1As shown, a method for preparing a ceramic thin plate with low defects and high breakdown strength comprises the following steps:

[0020] Firstly, a ceramic green body is prepared by gel injection molding, and then the ceramic green body is placed in a molding mold for isostatic pressing to obtain a ceramic green body, which is then sintered and processed to obtain a ceramic thin plate with low defects and high breakdown strength.

[0021] The gel injection molding method comprises the following steps: preparing slurry by using 0.2-0.3%wt of ISOBAM104 as a gelling agent, 0.05-0.2%wt of gum arabic and 0.1-0.3%wt of aluminum sol as a reinforcing agent.

[0022] The slurry is first sieved through a 200-mesh screen, then stirred in a vacuum for 5 to 10 minutes, and finally poured into a molding mold for drying and dehydration to obtain a ceramic body.

[0023] The ceramic body is dried to a moisture content of 1% to 3% by weight, then sealed and homogenized for 20 to 28 hours, and then isostatically pressed.

[0024] When a voltage of 18KV is applied to both sides of the obtained ceramic thin plate and maintained for 5 minutes, the non-breakdown rate of the ceramic plate is 83%-92%.

[0025] Specifically, a method for preparing a ceramic thin plate with low defects and high breakdown strength comprises the following steps:

[0026] Step 1, preparing alumina slurry with a certain solid content;

[0027] Step 2: Screening the prepared alumina slurry, evacuating the slurry, injecting it into a molding mold, drying it after the slurry is gelled, and demolding it to obtain a ceramic body with a certain moisture content;

[0028] Step 3, homogenizing the ceramic body;

[0029] Step 4: placing the homogenized ceramic body into an isostatic pressing mold for pressing;

[0030] Step 5: Dry, sinter, process and test the formed body.

[0031] Embodiment 1

[0032] Alumina powder was used to prepare a slurry with a solid content of 50%, and 0.2%wt of ISOBAM104, 0.3%wt of gum arabic, and 0.3%wt of aluminum sol were added. After ball milling and dispersion for 12 hours, the slurry was passed through a 200-mesh sieve, vacuumed and stirred, and then injected into a prefabricated molding mold (φ127mm) for gelation, drying, and demolding. The moisture content of the green body was controlled to be about 1%, and a φ125mm×3mm ceramic green body was obtained. After the obtained ceramic green body was sealed and homogenized for 24 hours, it was placed in an isostatic pressing mold for isostatic pressing. Each mold had 16 pieces of molding pieces and the molding pressure was 150MPa. The molded green body was dried, and after drying, it was sintered in a kiln at 1600℃ for 5 hours. The sintered body was ground and polished to obtain a φ100mm×0.5mm ceramic thin plate product. 100 ceramic sheets were prepared and subjected to breakdown strength test. The test method was to apply 18KV voltage on both sides of the ceramic sheet for 5 minutes. The ceramic sheet was deemed qualified if it was not broken down. The final qualified rate of the test was 83%.

[0033] Embodiment 2

[0034] Alumina powder was used to prepare a slurry with a solid content of 50%, and 0.25%wt of ISOBAM104, 0.2%wt of gum arabic, and 0.2%wt of aluminum sol were added. After ball milling and dispersion for 12 hours, the slurry was passed through a 200-mesh sieve, vacuumed and stirred, and then injected into a prefabricated mold (φ127mm) for gelation, drying, and demolding. The moisture content of the green body was controlled to be about 2%, and a φ125mm×3mm ceramic green body was obtained. After the obtained ceramic green body was sealed and homogenized for 24 hours, it was placed in an isostatic pressing mold for isostatic pressing. Each mold had 20 pieces of forming pieces and the forming pressure was 150MPa. The formed green body was dried, and after drying, it was sintered in a kiln at 1600℃ for 5 hours. The sintered body was ground and polished to obtain a φ100mm×0.5mm ceramic thin plate product. 100 ceramic sheets were prepared and subjected to breakdown strength test. The test method was to apply 18KV voltage on both sides of the ceramic sheet for 5 minutes. The ceramic sheet was deemed qualified if it was not broken down. The final qualified rate of the test was 87%.

[0035] Embodiment 3

[0036] Alumina powder was used to prepare a slurry with a solid content of 50%, and 0.3%wt of ISOBAM104, 0.1%wt of gum arabic, and 0.1%wt of aluminum sol were added. After ball milling and dispersion for 12 hours, the slurry was passed through a 200-mesh sieve, vacuumed and stirred, and then injected into a prefabricated mold (φ127mm) for gelation, drying, and demolding. The moisture content of the green body was controlled to be about 3%, and a φ125mm×3mm ceramic green body was obtained. After the obtained ceramic green body was sealed and homogenized for 24 hours, it was placed in an isostatic pressing mold for isostatic pressing. Each mold had 22 pieces of forming pieces and the forming pressure was 150MPa. The formed green body was dried, and after drying, it was sintered in a kiln at 1600℃ for 5 hours. The sintered body was ground and polished to obtain a φ100mm×0.5mm ceramic thin plate product. 100 ceramic sheets were prepared and subjected to breakdown strength test. The test method was to apply 18KV voltage on both sides of the ceramic sheet for 5 minutes. The ceramic sheet was deemed qualified if it was not broken down. The final qualified rate of the test was 92%.

[0037] Comparative Example

[0038] The same alumina powder was used for spray granulation, dry pressing, isostatic pressing at 150MPa to form a ceramic sheet blank, which was then sintered in a kiln at 1600℃ for 5h. The sintered body was ground and polished to obtain a φ100mm×0.5mm ceramic sheet product. 100 ceramic sheets were prepared and subjected to a breakdown strength test. The test method was to apply 18KV voltage on both sides of the ceramic sheet for 5 minutes. The ceramic sheet was considered qualified if it was not broken down. The final pass rate of the test was 67%.

[0039] By comparison, it can be seen that the use of gum arabic as a reinforcing agent can improve the strength and toughness of the gel-molded green blank, providing a basis for secondary isostatic pressing;

[0040] Secondary isostatic pressing of the ceramic thin plate blank prepared by gel molding can further improve the density and consistency of the blank.

[0041] like Figure 2 As shown, it is a micrograph of Example 3 after the 18KV high voltage test. Obviously, the ceramic sheet is not broken down and no cracks are generated on the surface.

[0042] like Figure 3 , which is a micrograph of a comparative example after 18KV high voltage test. As indicated by the arrows in the figure, the ceramic sheet is punctured and cracks are generated.

[0043] Embodiment 4

[0044] like Figure 1As shown, a molding die for a ceramic thin plate with low defects and high breakdown strength is used in a method for preparing a ceramic thin plate with low defects and high breakdown strength. The molding die includes a mold sleeve 2, a rubber plug, a metal plate and a rubber pad.

[0045] The mold sleeve 2 is cylindrical and has a molding cavity inside, which is used to place a number of ceramic thin plates 5; the rubber plugs are installed at both ends of the mold sleeve 2 and inserted at the top of the molding cavity; the metal plates are arranged at both ends of the molding cavity and on one side of the rubber plug; the rubber gaskets are arranged on both sides of the ceramic thin plates 5, 20 ceramic thin plates 5 are provided, and 22 rubber gaskets are provided.

[0046] The molding die can mold one or more ceramic thin plates 5 at a time.

[0047] The rubber plug is used for sealing to prevent the liquid medium in the isostatic pressing cylinder from penetrating into the interior of the molding die during the pressing process.

[0048] The metal plate is located on one side of the two rubber plugs and is used for shaping to prevent the rubber plugs from bending and deforming under pressure, thereby causing deformation of the ceramic body.

[0049] The rubber gasket is placed between the ceramic blanks to isolate the ceramic blanks and prevent the ceramic blanks from sticking together under pressure.

[0050] The isostatic pressing ceramic thin plate 5 forming die can form about 20 ceramic thin plates 5 at a time, and the forming quantity can be adjusted by changing the height of the die sleeve 2. And its structure can ensure that the thin plate does not warp and crack during the forming process, thereby improving production efficiency and yield.

[0051] The method is used to prepare a ceramic sheet 5 with a size of φ100mm×0.5mm. The alumina ceramic sheet 5 blank is prepared by gel injection molding combined with cold isostatic pressing. Compared with the original cold isostatic pressing molding, the prepared ceramic sheet 5 has fewer microscopic defects, higher density, and higher breakdown strength of 18KV. In the breakdown strength test of every 100 pieces, the test pass rate of the ceramic sheet 5 obtained by this method is increased from less than 70% to more than 90%, and has good stability in use.

[0052] The technical principle of the present invention is described above in conjunction with specific embodiments. These descriptions are only for explaining the principle of the present invention and cannot be interpreted as limiting the protection scope of the present invention in any way. Based on the explanations herein, those skilled in the art can associate other specific implementations of the present invention without paying creative labor, and these methods will fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a ceramic thin plate with low defects and high breakdown strength, characterized in that: The following steps are involved: Firstly, a ceramic green body is prepared by gel injection molding, and then the ceramic green body is placed in a molding mold for isostatic pressing to obtain a ceramic green body, which is then sintered and processed to obtain a ceramic thin plate with low defects and high breakdown strength.

2. The method for preparing a ceramic thin plate with low defects and high breakdown strength according to claim 1, characterized in that: The gel injection molding method comprises the following steps: using 0.2-0.3%wt of ISOBAM104 as a gelling agent, 0.05-0.2%wt of gum arabic, and 0.1-0.3%wt of aluminum sol as a reinforcing agent to prepare slurry.

3. The method for preparing a ceramic thin plate with low defects and high breakdown strength according to claim 2, characterized in that: The slurry is first sieved through a 200-mesh screen, then vacuum stirred for 5 to 10 minutes, and finally poured into a molding mold for drying and dehydration to obtain a ceramic body.

4. The method for preparing a ceramic thin plate with low defects and high breakdown strength according to claim 3, characterized in that: The ceramic green body is dried to a moisture content of 1% to 3% by weight, then sealed and homogenized for 20 to 28 hours, and then isostatically pressed.

5. The method for preparing a ceramic thin plate with low defects and high breakdown strength according to claim 1, characterized in that: The forming mold forms one or more ceramic thin plates at a time.

6. A molding die for a ceramic thin plate (5) with low defects and high breakdown strength, used in the method for preparing a ceramic thin plate with low defects and high breakdown strength as claimed in claim 1, characterized in that: include: The mold sleeve (2) is provided with a molding cavity, wherein the molding cavity is used to place a plurality of ceramic thin plates (5); A rubber plug head is provided with two ends of the mold sleeve (2); A metal plate is provided at both ends of the molding cavity and is located on one side of the rubber plug; and Rubber gaskets are arranged on both sides of the ceramic thin plate (5).

7. A forming die for a ceramic thin plate (5) with low defects and high breakdown strength according to claim 6, characterized in that: The ceramic thin plates (5) are provided with 20 pieces.

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