Preparation method for large beryllium oxide structural member

Abstract

The invention discloses a preparation method for a large beryllium oxide structural member, and belongs to the technical field of production processes of electronic functional ceramic materials. According to the preparation method for the large beryllium oxide structural part, the large beryllium oxide structural part can be produced, the internal stress of a green body can be effectively reduced in the production process, and then the ceramic sintering cracking risk is reduced. The preparation method comprises the following steps: dispersing and slurrying beryllium oxide powder, granulating and screening beryllium oxide slurry, and preparing a large-scale beryllium oxide structural part blank from qualified beryllium oxide granules in a cold isostatic pressing manner; and the large beryllium oxide structural part blank is subjected to segmented sintering forming in a kiln at least in three heating temperature sections with the heating rates gradually reduced. Wherein the beryllium oxide powder is dispersed by adopting a UP circulating stirring mill, and 0.3% of a magnesium and silicon eutectic mixture is added before stirring. In the forming process, only particles screened by 60-40 meshes and 40-20 meshes are selected to be mixed with slurry according to the proportion of 1: (3-5) to serve as a forming raw material.

Description

Technical Field

[0001] The invention relates to a preparation method, in particular to a preparation method for a large-scale beryllium oxide structural component, and belongs to the technical field of production technology of electronic functional ceramic materials. Background Art

[0002] Traditionally, beryllium oxide ceramics used in the electronics industry are small ceramic parts. 90% of these electronic beryllium oxide ceramic parts are no larger than 100 mm in size and weigh no more than 100 g. The primary purpose of these products is to miniaturize electronic devices, so systematic research on large-scale beryllium oxide structural components has been lacking. However, with the rapid development of high-power electronic vacuum industries, new energy vehicles, semiconductors, and the nuclear power sector, beryllium oxide ceramics have become a crucial material in these fields. Applications in these fields require the production of large-scale ceramic structural components, typically with outline dimensions exceeding 200 mm and individual components weighing in the kilogram or even 10 kg range. Existing ceramic fabrication processes in the electronics industry are not suitable for the production of large-scale beryllium oxide ceramic structural components. A prominent characteristic is the tendency for large-scale beryllium oxide ceramics to crack severely during the forming and sintering processes, making the fabrication of complete large-scale beryllium oxide ceramic parts impossible. Therefore, systematic research on the fabrication process for large-scale beryllium oxide structural components is urgently needed to meet the supporting needs of related fields. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a preparation method for large beryllium oxide structural parts which can produce larger sizes, effectively reduce the internal stress of the green body during the production process, and thus reduce the risk of ceramic sintering cracking.

[0004] The technical solution adopted to solve the above technical problems is: a method for preparing large-scale beryllium oxide structural parts, which includes the following steps: dispersing and slurrying beryllium oxide powder, granulating and screening the beryllium oxide slurry, preparing beryllium oxide large-scale structural part blanks by cold isostatic pressing using qualified beryllium oxide granules, and sintering the beryllium oxide large-scale structural part blanks in a kiln in at least three heating temperature sections with gradually decreasing heating rates. Among them, when dispersing and slurrying the beryllium oxide powder, first, the sodium aminosulfonate dispersant is evenly mixed with deionized water in a stirring barrel according to the specified proportion, and then the beryllium oxide powder with a purity of ≥99.8% and D50=1.0-1.5μm is poured into the deionized water mixed with the dispersant for slurry treatment, and then the slurryed beryllium oxide slurry is poured into the UP circulating stirred mill and magnesium and silicon eutectic are added according to the specified proportion. After that, the beryllium oxide powder is directly circulated and stirred according to the specified requirements to complete the dispersion and slurrying of the beryllium oxide powder; When granulating and screening the beryllium oxide slurry, the qualified beryllium oxide slurry is first granulated by spray granulation, and then the 60-40 mesh and 40-20 mesh granules screened are mixed in a three-dimensional mixer at a ratio of 1:3-5 to complete the granulation and screening of the beryllium oxide slurry.

[0005] Furthermore, when preparing beryllium oxide slurry, beryllium oxide powder and deionized water are configured in a ratio of 1:1, sodium aminosulfonate dispersant is configured in an amount of 2-3% by mass of the beryllium oxide powder, and magnesium and silicon eutectic is configured in an amount of 0.3% by mass of the beryllium oxide powder.

[0006] A preferred embodiment of the above scheme is that when mixing the sodium sulfamate dispersant and deionized water, a stirring paddle is used in a stirring barrel for stirring for 3-5 minutes; when slurrying the beryllium oxide powder, deionized water and sodium sulfamate dispersant, a stirring paddle is used in a stirring barrel for stirring for 30-60 minutes or until all the added beryllium oxide powder is converted into slurry; when circulating and stirring in the UP circulating stirred mill, the agitator is first stirred at a speed of 40-60 rpm for 30 minutes and then the circulating pump is turned on for circulating and dispersing stirring. The stirring speed of the circulating and dispersing stirring is 120-140 rpm, and the circulating and dispersing stirring time is 6-10 hours.

[0007] Furthermore, before granulation, the beryllium oxide slurry that has passed the circulating dispersion stirring is first filtered using a 200-mesh nylon screen, and then the filtered slurry is placed in a slow stirring barrel and stearic acid emulsion and polyvinyl alcohol aqueous solution glue are added according to the specified proportions, followed by stirring at a slow stirring barrel speed of 20-30 rpm for 30 minutes, and finally spray granulation is performed.

[0008] A preferred embodiment of the above scheme is as follows: the addition ratio of the polyvinyl alcohol aqueous solution glue added to the filter slurry is controlled at 20-30% of the mass of the beryllium oxide powder, and the addition ratio of the stearic acid emulsion added to the filter slurry is controlled at 0.1% of the mass of the beryllium oxide powder; after the spraying is completed, the granulated powder is analyzed and sieved using 60-mesh, 40-mesh and 20-mesh nylon screens respectively to remove powder smaller than 60 mesh and larger than 20 mesh, and then the 60-40 mesh and 40-20 mesh granules are mixed in a three-dimensional mixer at a ratio of 1:3-5 for 30 minutes to prepare the beryllium oxide slurry for molding.

[0009] Furthermore, during cold isostatic pressing, the inner cavity of the mold should be vacuumed after the mold is loaded, with a vacuum degree of -0.1 to 0.2 MPa, the molding pressure controlled at 120-150 MPa, and the holding time controlled at 300-600 seconds.

[0010] The preferred embodiment of the above scheme is that the final sintering temperature of the kiln is not lower than 1720°C, and sintering is performed in four sections from room temperature to the final sintering temperature with gradually decreasing heating rates.

[0011] Furthermore, room temperature-600℃ is a section, the heating rate is 0.4-0.5℃ / min; 600-1200℃ is a section, the heating rate is 0.15-0.25℃ / min; 1200-1500℃ is a section, the heating rate is 0.0.08-0.15℃ / min; 1500-final sintering temperature is a section, the heating rate is 0.05-0.08℃ / min.

[0012] The beneficial effects of the present invention are as follows: the above-mentioned technical solution provided by the present application replaces the ball milling dispersion method with an UP circulating stirred mill, thereby reducing the need to add some low-melting materials when using ball milling dispersion, thereby causing the final ceramic purity to only reach 99%. Then, the particle size is controlled after granulation, the vacuum negative pressure is controlled during molding, and finally the lifting and lowering rate is controlled in stages during sintering, thereby effectively reducing or even eliminating the internal stress of the green body and the shrinkage stress generated by sintering, thereby ensuring that the surface of the sintered product is free of cracks and fractures, thereby achieving the purpose of producing larger-sized beryllium oxide ceramic electronic devices. DETAILED DESCRIPTION

[0013] In order to solve the above-mentioned technical problems existing in the prior art, the present invention provides a method for preparing large-scale beryllium oxide structural parts that can produce larger sizes, effectively reduce the internal stress of the green body during the production process, and thus reduce the risk of ceramic sintering cracking. The preparation method includes the steps of dispersing and slurrying beryllium oxide powder, granulating and screening the beryllium oxide slurry, preparing the beryllium oxide large-scale structural part blank by cold isostatic pressing using qualified beryllium oxide granules, and sintering the large-scale beryllium oxide structural part blank in a kiln in at least three heating temperature sections with gradually decreasing heating rates. Among them, when dispersing and slurrying the beryllium oxide powder, first, the sodium aminosulfonate dispersant is evenly mixed with deionized water in a stirring barrel according to the specified proportion, and then the beryllium oxide powder with a purity of ≥99.8% and D50=1.0-1.5μm is poured into the deionized water mixed with the dispersant for slurry treatment, and then the slurryed beryllium oxide slurry is poured into the UP circulating stirred mill and magnesium and silicon eutectic are added according to the specified proportion. After that, the beryllium oxide powder is directly circulated and stirred according to the specified requirements to complete the dispersion and slurrying of the beryllium oxide powder; During the granulation and screening of the beryllium oxide slurry, the qualified beryllium oxide slurry is first granulated using a spray granulation method. The sieved 60-40 mesh and 40-20 mesh granules are then mixed in a three-dimensional mixer at a ratio of 1:3-5 to complete the granulation and screening of the beryllium oxide slurry. Accordingly, based on the actual conditions of the production site, when preparing the beryllium oxide slurry, the beryllium oxide powder and deionized water are mixed in a ratio of 1:1, the sodium aminosulfonate dispersant is added at a ratio of 2-3% of the mass of the beryllium oxide powder, and the magnesium and silicon eutectic is added at a ratio of 0.3% of the mass of the beryllium oxide powder.

[0014] Furthermore, in order to improve the operability of each step of the technical solution of the present application and to maximize the production of the largest possible beryllium oxide ceramic equipment, the present application uses a stirring paddle in a stirring barrel when mixing the sodium aminosulfonate dispersant and deionized water, and the stirring time is 3-5 minutes; when slurrying the beryllium oxide powder, deionized water and sodium aminosulfonate dispersant, a stirring paddle is used in a stirring barrel, and the stirring time is 30-60 minutes or until all the added beryllium oxide powder is converted into slurry; when circulating and stirring in the UP circulating stirred mill, the agitator first stirs at a speed of 40-60rpm for 30 minutes and then starts the circulating pump for circulating dispersion stirring. The stirring speed of the circulating dispersion stirring is 120-140rpm, and the circulating dispersion time of the circulating dispersion stirring is 6-10h. Before granulation, the beryllium oxide slurry that has passed the circulating dispersion stirring is first filtered using a 200-mesh nylon screen. The filtered slurry is then placed in a slow stirring barrel and stearic acid emulsion and polyvinyl alcohol aqueous solution glue are added in a specified proportion. The slow stirring barrel is then stirred at a speed of 20-30 rpm for 30 minutes, and finally spray granulation is performed. At the same time, the addition ratio of polyvinyl alcohol aqueous solution glue to the filtered slurry is controlled at 20-30% of the mass of the beryllium oxide powder, and the addition ratio of stearic acid emulsion to the filtered slurry is controlled at 0.1% of the mass of the beryllium oxide powder. After the spray granulation is completed, the granulated powder is analyzed and sieved using 60-mesh, 40-mesh, and 20-mesh nylon screens respectively to remove powder smaller than 60 mesh and larger than 20 mesh. The 60-40 mesh and 40-20 mesh granules are then mixed in a three-dimensional mixer at a ratio of 1:3-5 for 30 minutes to prepare the beryllium oxide slurry for molding.

[0015] More specifically, to minimize internal stress and shrinkage stress generated during molding and sintering, during cold isostatic pressing, the mold cavity should be evacuated to a vacuum of -0.1 to 0.2 MPa after filling, with a molding pressure of 120-150 MPa and a holding time of 300-600 seconds. The final sintering temperature in the kiln should be no less than 1720°C, and sintering should be performed in four stages with gradually decreasing heating rates from room temperature to the final sintering temperature. Specifically, room temperature-600℃ is a section, and the heating rate is 0.4-0.5℃ / min; 600-1200℃ is a section, and the heating rate is 0.15-0.25℃ / min; 1200-1500℃ is a section, and the heating rate is 0.0.08-0.15℃ / min; 1500-final sintering temperature is a section, and the heating rate is 0.05-0.08℃ / min.

[0016] In summary, the technical solution provided by this application also has the following advantages: 1. The purity of beryllium oxide powder in China is usually around 99.8%. The doping of a small amount of eutectic (about 0.5%) and the use of ball milling dispersion will introduce certain impurities, resulting in the current situation where the purity of beryllium oxide ceramics after being formed is above 99%. The non-ball milling dispersion method provided in this application reduces the proportion of eutectic added in the formula and abandons the traditional ball milling dispersion method, so that the purity of the final ceramic after being formed reaches above 99.5%. 2. The granulation method provided by this application can increase the particle size of beryllium oxide ceramic granules by more than 10%, meeting the current demand for relatively coarse granules for large-size ceramic molding, and is conducive to reducing the powder compression ratio of the molding process, ensuring that the molding size is large enough; 3. The molding method and sintering method provided in this application can effectively reduce the internal stress of large-sized ceramic green bodies and reduce the risk of ceramic sintering cracking. After sintering, the product surface has no cracks or fractures, and the overall volume density reaches above 2.80g / cm3, meeting the requirements of related fields.

[0017] The technical solution of this application is further described below through specific embodiments: The present invention provides a method for producing large-scale beryllium oxide ceramic structural components. The technical problem addressed by the present invention is to modify the dispersion and granulation methods of existing beryllium oxide ceramic materials so that the beryllium oxide granules can meet the molding requirements of large-scale structural components. Furthermore, by optimizing the ceramic molding and sintering parameters, the large-scale beryllium oxide ceramic structural components are crack-free and defect-free during the sintering process, ultimately achieving the production of large-scale beryllium oxide ceramic structural components. The beryllium oxide ceramic structural components produced using the patented method can have a maximum outline size (ceramic) exceeding 300 mm and a length exceeding 800 mm. A single ceramic product weighs over 10 kg, meeting current demand for large-scale beryllium oxide ceramic structural components in related fields such as vacuum, radioactive source containers, nuclear, automotive, and semiconductors.

[0018] The method comprises the following steps A. Dispersion of beryllium oxide powder (a) Weigh beryllium oxide powder with a purity of ≥99.8% and a D50 of 1.0-1.5 μm and deionized water in a mass ratio of 1:1. Pour the deionized water into a mixing bucket. Then weigh 2-3% of the powder mass of a sodium aminosulfonate dispersant (such as SD-00) and pour it into the deionized water. Stir the deionized water with the dispersant using a stirring paddle for 3-5 minutes to ensure that the dispersant and deionized water are evenly mixed.

[0019] (b) Pour the weighed beryllium oxide powder into deionized water containing a dispersant, and stir with a stirring paddle for 30 minutes to 60 minutes until the added beryllium oxide powder is completely converted into a slurry.

[0020] (c) Pour the stirred beryllium oxide slurry into a UP circulating stirred mill. No ceramic balls or other grinding media are added to the mill. A magnesium-silicon eutectic solution (0.3% by weight of the beryllium oxide powder) is added to the slurry. The mill's agitator is turned on at a speed of 40-60 rpm. After stirring for 30 minutes, the circulating pump is turned on and the agitator speed is adjusted to 120-140 rpm to allow the slurry to circulate and disperse in the agitator. The circulating dispersion time is 6-10 hours.

[0021] (d) Filter the stirred slurry through a 200-mesh nylon screen and pour the filtered slurry into a slow stirring barrel.

[0022] B. Beryllium oxide slurry granulation (a) The speed of the slow stirring barrel is controlled at 20-30 rpm, and a polyvinyl alcohol aqueous solution glue is added to the slurry. The glue addition amount is 20-30% of the mass of the beryllium oxide powder; then 0.1% stearic acid emulsion is added to the powder mass. After stirring for 30 minutes, spray granulation is performed.

[0023] (b) The granulated powder was sieved using 60-mesh, 40-mesh, and 20-mesh nylon sieves for analysis.

[0024] (c) Powders with a mesh size smaller than 60 or larger than 20 cannot be used for molding. They are weighed and mixed in a mass ratio of 60-40 mesh to 40-20 mesh granulation powder of 1:3-5, and mixed in a three-dimensional mixer for 30 minutes to obtain the prepared material for molding.

[0025] C. Forming of large structural parts of beryllium oxide Beryllium oxide ceramic components are formed using cold isostatic pressing. After the mold is filled, a vacuum device with a negative pressure of -0.1-0.2 MPa should be used to extract the air from the gaps between the granulated powder in the mold. The molding pressure should be controlled at 120-150 MPa, and the holding time should be controlled at 300-600 seconds.

[0026] D. Sintering of large-scale structural parts of beryllium oxide Ceramic structural parts are sintered in a kiln with a final temperature of up to 1720°C. The sintering heating rate should be set according to the table below.

[0027]

[0028] In the aforementioned method for manufacturing large beryllium oxide ceramic components, in step B(a), a polyvinyl alcohol (PVA) aqueous solution is preferably used as the binder. The polyvinyl alcohol is preferably PVA217, dissolved in hot water to form a 10% aqueous solution, with the amount added being 20-30% by weight of the beryllium oxide powder. A stearic acid emulsion (0.1% by weight of the beryllium oxide powder) is added as a release agent. The mixture is stirred evenly in a slow-mixing drum at 20-30 rpm.

[0029] Example 1 (1) Weigh 10 kg each of beryllium oxide powder with a purity of ≥99.8% and D50=1.15 μm and deionized water for later use. First, put 10 kg of deionized water into a 50 L mixing barrel. Then weigh 200 g of sodium aminosulfonate dispersant (such as SD-00) and pour it into the deionized water. Stir the deionized water with the dispersant added with a stirring paddle for 5 minutes to ensure that the dispersant and deionized water are evenly mixed.

[0030] (2) Pour 10 kg of beryllium oxide powder into deionized water containing a dispersant, and stir with a stirring paddle for 60 minutes until the added beryllium oxide powder is completely converted into a slurry.

[0031] (3) Pour the stirred beryllium oxide slurry into the UP circulating stirred mill. Do not add any porcelain ball grinding media to the circulating stirred mill. Add 30g of magnesium and silicon eutectic with beryllium oxide powder to the slurry. Turn on the agitator of the circulating stirred mill and control the speed at 40-60rpm. After stirring for 30 minutes, turn on the circulating pump and adjust the stirring speed to 125rpm to allow the slurry to circulate and disperse in the agitator. The circulating dispersion time is 8 hours.

[0032] (4) Filter the stirred slurry with a 200-mesh nylon screen and pour the filtered slurry into a slow stirring barrel.

[0033] (5) The speed of the slow stirring barrel is controlled at 20 rpm, and PVA217 aqueous solution is added to the slurry, with a glue concentration of 10% and a glue addition amount of 2 kg; then 10 g of stearic acid emulsion is added, and after stirring for 30 minutes, spray granulation is performed.

[0034] (6) The granulated powder was sieved using 60-mesh, 40-mesh, and 20-mesh nylon sieves for analysis.

[0035] (7) Powders smaller than 60 mesh and larger than 20 mesh cannot be used for molding. Take 2 kg of 60-40 mesh granulation powder and 6 kg of 40-20 mesh granulation powder, mix them in a three-dimensional mixer for 30 minutes and mix them evenly to form the preparation material for molding.

[0036] (8) Beryllium oxide ceramic structural parts are formed by cold isostatic pressing. The molding size is φ300*100mm. After the rubber mold is filled, a negative pressure vacuum device of -0.1MPa should be used to extract the air in the gap of the granulated powder in the mold. The molding pressure should be controlled at 135Mpa and the holding time should be 300s.

[0037] (9) Ceramic structural parts are sintered in a kiln with a final temperature of 1720℃. The sintering heating rate should be set according to the table below.

[0038]

[0039] Finally, a relatively intact ceramic structure with no cracks on the surface was obtained. The bulk density test of Example 1 was performed to obtain the density data C1. Example 2 (1) Weigh 20 kg of beryllium oxide powder with a purity of ≥99.8% and D50=1.15 μm and deionized water respectively. First, put 20 kg of deionized water into a 50 L mixing barrel. Then weigh 600 g of sodium aminosulfonate dispersant (such as SD-00) and pour it into the deionized water. Stir the deionized water with the dispersant with a stirring paddle for 5 minutes to ensure that the dispersant and deionized water are evenly mixed.

[0040] (2) Pour 20 kg of weighed beryllium oxide powder into deionized water containing a dispersant, and stir with a stirring paddle for 60 minutes until all the added beryllium oxide powder is converted into a slurry.

[0041] (3) Pour the stirred beryllium oxide slurry into the UP circulating stirred mill. Do not add any porcelain ball grinding media to the circulating stirred mill. Add 60g of beryllium oxide powder and magnesium-silicon eutectic to the slurry. Turn on the agitator of the circulating stirred mill and control the speed at 40-60rpm. After stirring for 30 minutes, turn on the circulating pump and adjust the stirring speed to 130rpm to allow the slurry to circulate and disperse in the agitator. The circulating dispersion time is 10 hours.

[0042] (4) Filter the stirred slurry with a 200-mesh nylon screen and pour the filtered slurry into a slow stirring barrel.

[0043] (5) The speed of the slow stirring barrel is controlled at 20 rpm, and PVA217 aqueous solution is added to the slurry, with a glue concentration of 10% and a glue addition amount of 6 kg; then 20 g of stearic acid emulsion is added, and after stirring for 30 minutes, spray granulation is performed.

[0044] (6) The granulated powder was sieved using 60-mesh, 40-mesh, and 20-mesh nylon sieves for analysis.

[0045] (7) Powders smaller than 60 mesh and larger than 20 mesh cannot be used for molding. Take 2 kg of 60-40 mesh granulation powder and 10 kg of 40-20 mesh granulation powder, mix them in a three-dimensional mixer for 30 minutes and mix them evenly to form the preparation material for molding.

[0046] (8) Beryllium oxide ceramic components are formed by cold isostatic pressing. The molding size is φ300*100mm. After the rubber mold is filled, a negative pressure vacuum device of -0.2Mpa should be used to extract the air in the gaps between the granulated powder in the mold. The molding pressure should be controlled at 150Mpa and the holding time should be 600s.

[0047] (9) Ceramic structural parts are sintered in a kiln with a final temperature of 1750℃. The sintering heating rate should be set according to the following table.

[0048]

[0049] Finally, a ceramic structural component with a relatively intact surface and no surface cracks is obtained. A volume density test is performed on Implementation Case 2 to obtain density data C2.

[0050] Example 3 (1) Weigh 20 kg of beryllium oxide powder with a purity of ≥99.8% and D50=1.15 μm and deionized water respectively. First, put 20 kg of deionized water into a 50 L mixing barrel. Then weigh 600 g of sodium aminosulfonate dispersant (such as SD-00) and pour it into the deionized water. Stir the deionized water with the dispersant with a stirring paddle for 5 minutes to ensure that the dispersant and deionized water are evenly mixed.

[0051] (2) Pour 20 kg of weighed beryllium oxide powder into deionized water containing a dispersant, and stir with a stirring paddle for 60 minutes until all the added beryllium oxide powder is converted into a slurry.

[0052] (3) Pour the stirred beryllium oxide slurry into the UP circulating stirred mill. Do not add any porcelain ball grinding media to the circulating stirred mill. Add 60g of beryllium oxide powder and magnesium-silicon eutectic to the slurry. Turn on the agitator of the circulating stirred mill and control the speed at 40-60rpm. After stirring for 30 minutes, turn on the circulating pump and adjust the stirring speed to 130rpm to allow the slurry to circulate and disperse in the agitator. The circulating dispersion time is 10 hours.

[0053] (4) Filter the stirred slurry with a 200-mesh nylon screen and pour the filtered slurry into a slow stirring barrel.

[0054] (5) The speed of the slow stirring barrel is controlled at 20 rpm, and PVA217 aqueous solution is added to the slurry, with a glue concentration of 10% and a glue addition amount of 6 kg; then 20 g of stearic acid emulsion is added, and after stirring for 30 minutes, spray granulation is performed.

[0055] (6) The granulated powder was sieved using 60-mesh, 40-mesh, and 20-mesh nylon sieves for analysis.

[0056] (7) Powders smaller than 60 mesh and larger than 20 mesh cannot be used for molding. Take 2 kg of 60-40 mesh granulation powder and 10 kg of 40-20 mesh granulation powder, mix them in a three-dimensional mixer for 30 minutes and mix them evenly to form the preparation material for molding.

[0057] (8) Beryllium oxide ceramic components are formed by cold isostatic pressing. The molding size is φ300*100mm. After the rubber mold is filled, a negative pressure vacuum device of -0.2Mpa should be used to extract the air in the gaps between the granulated powder in the mold. The molding pressure should be controlled at 135Mpa, and the holding time should be 600s.

[0058] (9) Ceramic structural parts are sintered in a kiln with a final temperature of 1750℃. The sintering heating rate should be set according to the following table.

[0059]

[0060] The product cracked after sintering. A bulk density test was conducted on Example 3 to obtain density data C3. The sintering temperature and ceramic density of the example are shown in Table 2: Table 2. Surface cracking and density of different implementation cases .

Claims

1. A method for preparing large beryllium oxide structural parts, characterized in that: The preparation method includes the following steps: dispersing and slurrying beryllium oxide powder, granulating and screening the beryllium oxide slurry, preparing beryllium oxide large structural part blanks by cold isostatic pressing using qualified beryllium oxide granules, and sintering the beryllium oxide large structural part blanks in a kiln in at least three heating temperature sections with gradually decreasing heating rates. Among them, when dispersing and slurrying the beryllium oxide powder, first, the sodium aminosulfonate dispersant is evenly mixed with deionized water in a stirring barrel according to the specified proportion, and then the beryllium oxide powder with a purity of ≥99.8% and D50=1.0-1.5μm is poured into the deionized water mixed with the dispersant for slurry treatment, and then the slurryed beryllium oxide slurry is poured into the UP circulating stirred mill and magnesium and silicon eutectic are added according to the specified proportion. After that, the beryllium oxide powder is directly circulated and stirred according to the specified requirements to complete the dispersion and slurrying of the beryllium oxide powder; When granulating and screening the beryllium oxide slurry, the qualified beryllium oxide slurry is first granulated by spray granulation, and then the 60-40 mesh and 40-20 mesh granules screened are mixed in a three-dimensional mixer at a ratio of 1:3-5 to complete the granulation and screening of the beryllium oxide slurry.

2. The method for preparing large beryllium oxide structural parts according to claim 1, wherein: When preparing beryllium oxide slurry, beryllium oxide powder and deionized water are configured in a ratio of 1:1, sodium aminosulfonate dispersant is configured in an amount of 2-3% by mass of the beryllium oxide powder, and magnesium and silicon eutectic is configured in an amount of 0.3% by mass of the beryllium oxide powder.

3. The method for preparing large beryllium oxide structural parts according to claim 2, wherein: When mixing the sodium sulfamate dispersant and deionized water, a stirring paddle is used in a stirring barrel for 3-5 minutes. When slurrying the beryllium oxide powder, deionized water and sodium sulfamate dispersant, a stirring paddle is used in a stirring barrel for 30-60 minutes or until all the added beryllium oxide powder is converted into slurry. When circulating and stirring in the UP circulating stirred mill, the agitator is first stirred at a speed of 40-60 rpm for 30 minutes and then the circulating pump is turned on for circulating and dispersing stirring. The stirring speed of the circulating and dispersing stirring is 120-140 rpm, and the circulating and dispersing stirring time is 6-10 hours.

4. The method for preparing large beryllium oxide structural parts according to claim 2 or 3, characterized in that: Before granulation, the beryllium oxide slurry that has passed the circulating dispersion stirring is first filtered with a 200-mesh nylon screen. Then the filtered slurry is placed in a slow stirring barrel and stearic acid emulsion and polyvinyl alcohol aqueous solution glue are added according to the specified proportions. Then, the slow stirring barrel is stirred at a speed of 20-30rpm for 30 minutes, and finally spray granulation is performed.

5. The method for preparing large beryllium oxide structural parts according to claim 4, characterized in that: The addition ratio of the polyvinyl alcohol aqueous solution glue added to the filter slurry is controlled at 20-30% of the mass of the beryllium oxide powder, and the addition ratio of the stearic acid emulsion added to the filter slurry is controlled at 0.1% of the mass of the beryllium oxide powder. After the spraying material is completed, the granulated powder is analyzed and sieved using 60-mesh, 40-mesh and 20-mesh nylon screens respectively to remove powders smaller than 60 mesh and larger than 20 mesh. Then, the 60-40 mesh and 40-20 mesh granules are mixed in a three-dimensional mixer at a ratio of 1:3-5 for 30 minutes to prepare the beryllium oxide slurry for molding.

6. The method for preparing large beryllium oxide structural parts according to claim 1, wherein: During cold isostatic pressing, the inner cavity of the mold should be vacuumed after the mold is loaded, with a vacuum degree of -0.1 to 0.2 MPa, the molding pressure controlled at 120-150 MPa, and the holding time controlled at 300-600 seconds.

7. The method for preparing large beryllium oxide structural parts according to claim 1, characterized in that: The final sintering temperature of the kiln is not lower than 1720℃, and sintering is carried out in four sections with gradually decreasing heating rates from room temperature to the final sintering temperature.

8. The method for preparing large beryllium oxide structural parts according to claim 7, characterized in that: Room temperature-600℃ is a section, and the heating rate is 0.4-0.5℃ / min; 600-1200℃ is a section, and the heating rate is 0.15-0.25℃ / min; 1200-1500℃ is a section, and the heating rate is 0.0.08-0.15℃ / min; 1500-final sintering temperature is a section, and the heating rate is 0.05-0.08℃ / min.

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