Ceramic material, preparation method thereof and ceramic product

Abstract

The invention relates to a ceramic material, a preparation method thereof and a ceramic product. The ceramic material is prepared from the following components in percentage by mass: 0.52 percent to 0.85 percent of CaO, 0.27 percent to 0.58 percent of MgO, 2.6 percent to 3.5 percent of SiO2, 94.7 percent to 96.31 percent of alpha-Al2O3 and impurities. On the basis of CaO, MgO, SiO2 and alpha-Al2O3, the dielectric loss and sealing strength of the ceramic material can be effectively improved by controlling the proportion of the components, especially the proportion of CaO; the D50 particle size and the D90 particle size of alpha-Al2O3 are controlled at the same time, so that the sealing strength of the ceramic material can be effectively improved; alpha-Al2O3 with a specific particle size is matched with CaO, MgO and SiO2 according to a specific ratio, so that the voltage-withstanding value of the ceramic material can be effectively improved, and the voltage-withstanding performance of the ceramic material is effectively improved.

Description

Technical Field

[0001] The present application relates to the field of material technology, and in particular to a ceramic material and a preparation method thereof, and a ceramic product. Background Art

[0002] As the shell of vacuum devices such as vacuum switches, high-power thyristors, vacuum relays, vacuum capacitors, and high-frequency high-power electron tubes, vacuum 95% Al2O3 ceramic tubes are widely used in radio stations, television stations, converters, switches and other systems. However, the pressure resistance of traditional Al2O3 ceramic tubes is relatively low.

[0003] Therefore, it is necessary to improve the traditional technology. Summary of the invention

[0004] Based on this, the present application provides a ceramic material with high pressure resistance and a preparation method and a ceramic product thereof.

[0005] The technical solution of this application to solve the above technical problems is as follows.

[0006] On the one hand, the present application provides a ceramic material, which comprises the following components by mass percentage:

[0007] CaO 0.52%~0.85%, MgO 0.27%~0.58%, SiO2 2.6%~3.5%, α-Al2O3 94.7%~96.31% and impurities, the D50 particle size of the α-Al2O3 is 1.8 μm~3.2 μm, and the D90 particle size of the α-Al2O3 is ≤5.5 μm.

[0008] In some embodiments, the ceramic material includes the following components by mass percentage:

[0009] CaO 0.6%~0.8%, MgO 0.3%~0.5%, SiO2 3%~3.5%, α-Al2O3 95.2%~96.1% and impurities.

[0010] In some of the embodiments, in the ceramic material, the maximum particle size of the α-Al2O3 is less than 12 μm.

[0011] In some of the embodiments, in the ceramic material, the impurities include Na2O and K2O, and the sum of the mass percentages of Na2O and K2O in the ceramic material is ≤0.1%.

[0012] In some of the embodiments, in the ceramic material, the raw materials for preparing the ceramic material include Al2O3 powder, talc, kaolin, calcium carbonate and quartz sand.

[0013] On the one hand, the present application provides a method for preparing a ceramic material, comprising the following steps:

[0014] Providing raw materials according to the composition of the above ceramic materials;

[0015] After the raw materials are mixed, isostatic pressing and sintering are performed in sequence to prepare a ceramic material.

[0016] In some of the embodiments, in the method for preparing the ceramic material, the isostatic pressing pressure is 120 MPa to 180 MPa.

[0017] In some of the embodiments, in the method for preparing the ceramic material, the sintering temperature is 1680° C. to 1700° C., and the sintering time is 2 h to 2.5 h.

[0018] In some of the embodiments, the method for preparing the ceramic material further includes the steps of wet ball milling and spray drying the mixture obtained by mixing the raw materials before the isostatic pressing step and after the raw materials are mixed.

[0019] In some of the embodiments, in the method for preparing ceramic materials, the spray drying parameters are: equipment pressure is -10 Pa~-50 Pa, inlet temperature is 250℃~310℃, outlet temperature is 115℃~118℃, and spray gun pressure is 2.5 MPa~3 MPa.

[0020] On one hand, the present application provides a ceramic product, including the above-mentioned ceramic material or the ceramic material prepared by the preparation method.

[0021] Compared with the prior art, the ceramic material of the present application has the following beneficial effects:

[0022] The ceramic material of the present application includes CaO, MgO, SiO2 and α-Al2O3. By controlling the proportion of each component, especially the proportion of CaO, the dielectric loss and sealing strength of the ceramic material can be effectively improved; by simultaneously controlling the D50 particle size and D90 particle size of α-Al2O3, the sealing strength of the ceramic material can be effectively improved; α-Al2O3 of a specific particle size cooperates with CaO, MgO and SiO2 in a specific proportion, which can effectively improve the pressure resistance value of the ceramic material, thereby effectively improving the pressure resistance performance of the ceramic material.

[0023] The ceramic material of the present application has high mechanical strength, volume resistivity and volume density, low dielectric loss and stable dielectric constant, and can meet the requirements for installation and use of ultra-high voltage 252 kV vacuum tube shells. DETAILED DESCRIPTION

[0024] The present application will be further described in detail below in conjunction with the embodiments and examples. It should be understood that these embodiments and examples are only used to illustrate the present application and are not used to limit the scope of the present application. The purpose of providing these embodiments and examples is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0025] It should also be understood that the present application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various changes or modifications without violating the connotation of the present application, and the equivalent forms obtained also fall within the scope of protection of the present application. For example, the features illustrated or described as part of one embodiment can be combined in another embodiment in a suitable manner to produce a new embodiment. In addition, in the description below, a large number of specific details are given in order to provide a more comprehensive understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing implementation modes and embodiments and are not intended to limit this application.

[0027] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0028] In the present application, "plurality", "multiple", "multiple times", etc., unless otherwise specified, refer to a quantity greater than 2 or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0029] As used herein, "combination thereof", "any combination thereof", "any combination thereof" etc. include all suitable combinations of any two or more of the listed items.

[0030] Herein, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc., shall be based on the ability to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0031] Herein, "preferred", "better", "more preferred", and "suitable" are only used to describe implementation methods or examples with better effects, and it should be understood that they do not constitute a limitation on the scope of protection of this application. If multiple "preferred" items appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "preferred" item is independent.

[0032] In the present application, "further", "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present application.

[0033] In this application, "optionally", "optional", and "optional" mean optional or dispensable, that is, any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0034] In the present application, the terms "first", "second", "third", "fourth", etc. in "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0035] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0036] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical range disclosed herein should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0037] The temperature parameters in this application, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0038] In this application, the term "room temperature" or "normal temperature" generally refers to 4°C to 35°C, for example, 20°C ± 5°C. In some embodiments of this application, "room temperature" or "normal temperature" refers to 10°C to 30°C. In some embodiments of this application, "room temperature" or "normal temperature" refers to 20°C to 30°C.

[0039] In this application, when referring to the unit of a data range, if there is a unit only after the right endpoint, it means that the units of the left and right endpoints are the same. For example, 3~5 h means that the units of the left endpoint "3" and the right endpoint "5" are both h (hours).

[0040] All documents mentioned in this application are cited as references in this application, just as each document is cited as reference separately. Unless they conflict with the invention purpose and / or technical solution of this application, the cited documents involved in this application are cited with all contents and all purposes. When the cited documents are involved in this application, the definitions of relevant technical features, terms, nouns, phrases, etc. in the cited documents are also cited. When the cited documents are involved in this application, the examples and preferred methods of the cited relevant technical features can also be incorporated into this application as references, but are limited to the implementation of this application. It should be understood that when the cited content conflicts with the description in this application, the present application shall prevail or be modified adaptively according to the description of this application.

[0041] The mass or weight of the relevant components mentioned in the specification of the embodiments of the present application may not only refer to the specific content of each component, but also indicate the proportional relationship of the mass or weight between the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the specification of the embodiments of the present application, it is within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass or weight described in the specification of the embodiments of the present application may be units known in the chemical industry such as μg, mg, g, and kg.

[0042] Traditional electric vacuum 95% Al2O3 ceramic tubes are used as medium and low voltage electric vacuum switch shells, and are only used in 72 kV electric vacuum switch shells, and cannot be used in high voltage 126 kV or even 252 kV electric vacuum switch shells.

[0043] The porcelain parts produced by the traditional ternary system formula (CaO-SiO2-Al2O3 system) used for the electric vacuum 95% alumina porcelain tube shell are prone to produce spots during metallization firing, and the porcelain parts have coarse grains, poor acid corrosion resistance, and unsatisfactory electromechanical properties. The porcelain parts produced by the traditional ternary system formula (MgO-SiO2-Al2O3 system) used for the electric vacuum 95% alumina porcelain tube shell have a whiter appearance, but the firing temperature of the porcelain parts is relatively high, which affects the control of production costs.

[0044] White porcelain pieces produced with traditional formulas have too strong glaze absorption during the metallization firing process, which is particularly prone to dry glaze and the entire product being scrapped. In addition, after metallization, the appearance of the porcelain pieces with this formula tends to be grayish and yellowish, which can easily lead to unqualified appearance color and lead to scrapping. Moreover, the traditional formula production has high requirements for the raw material high-temperature calcined Al2O3 powder, that is, the calcination conversion must be relatively complete, otherwise a large number of micro pores will be generated inside the porcelain pieces, causing the performance indicators of the ceramic products to be greatly reduced.

[0045] An embodiment of the present application provides a ceramic material, which comprises the following components by mass percentage:

[0046] CaO 0.52%~0.85%, MgO 0.27%~0.58%, SiO2 2.6%~3.5%, α-Al2O3 94.7%~96.31% and impurities, the D50 particle size of α-Al2O3 is 1.8 μm~3.2 μm, and the D90 particle size of α-Al2O3 is ≤5.5 μm.

[0047] The ceramic material of the present application includes CaO, MgO, SiO2 and α-Al2O3. By controlling the proportion of each component, especially the proportion of CaO, the dielectric loss and sealing strength of the ceramic material can be effectively improved; by simultaneously controlling the D50 particle size and D90 particle size of α-Al2O3, the sealing strength of the ceramic material can be effectively improved; α-Al2O3 of a specific particle size cooperates with CaO, MgO and SiO2 in a specific proportion, which can effectively improve the pressure resistance value of the ceramic material, thereby effectively improving the pressure resistance performance of the ceramic material.

[0048] The ceramic material of the present application has high mechanical strength, volume resistivity and volume density, low dielectric loss and stable dielectric constant, and can effectively improve the standard breakdown strength of ceramic products made of the ceramic material.

[0049] The ceramic material of the present application can meet the requirements for installation and use of ultra-high voltage 252 kV electric vacuum tube shells.

[0050] The ceramic material of the present application has a low firing temperature for producing ceramic parts, a compact organizational structure, good ceramic process performance, and good compatibility with existing metallization processes, thereby better ensuring the vacuum degree of the produced electric vacuum products.

[0051] When the CaO content is high, the ceramic material contains more calcium feldspar, which not only leads to a significant increase in the dielectric loss of the ceramic material and a significant decrease in the sealing strength, but also easily causes dark spots in the ceramic material, making the ceramic parts scrapped. When the MgO content exceeds 1 wt%, the density and performance of the ceramic parts will decrease.

[0052] It can be understood that in the ceramic material, the mass percentage of CaO includes, but is not limited to, 0.52%, 0.53%, 0.54%, 0.55%, 0.56%, 0.57%, 0.58%, 0.59%, 0.60%, 0.61%, 0.62%, 0.63%, 0.64%, 0.65%, 0.66%, 0.67%, 0.68%, 0.69%, 0.70%, 0.71%, 0.72%, 0.73%, 0.74%, 0.75%, 0.76%, 0.77%, 0.78%, 0.79%, 0.80%, 0.81%, 0.82%, 0.83%, 0.84%, 0.85%, 0.86%, 0.87%, 0.88%, 0.89%, 0.90%, 0.91%, 0.92%, 0.93%, 0.94%, 0.95%, 0.96%, 0.97%, 0.98%, 0.9 ...8%, 0.99%, 0.91%, 0.92%, 0.93%, 0.94%, 0.95%, 0.96%, 0.98%, .73%, 0.74%, 0.75%, 0.76%, 0.77%, 0.78%, 0.79%, 0.80%, 0.81%, 0.82%, 0.83%, 0.84%, 0.85%; the mass percentage of MgO includes but is not limited to 0.27%, 0.28%, 0.29%, 0.30%, 0.31%, 0.32%, 0.33%, 0.34%, 0.35%, 0.36%, 0.37%, 0.38 %, 0.39%, 0.40%, 0.41%, 0.42%, 0.43%, 0.44%, 0.45%, 0.46%, 0.47%, 0.48%, 0.49%, 0.50%, 0.51%, 0.52%, 0.53%, 0.54%, 0.55%, 0.56%, 0.57%, 0.58%; the mass percentage of SiO2 includes but is not limited to 2.6%, 2.7%, 2.8%, 2.9%, 3.0 %, 3.1%, 3.2%, 3.3%, 3.4%, 3.5%; the mass percentage of α-Al2O3 includes but is not limited to 94.7%, 94.8%, 94.9%, 95.0%, 95.07%, 95.1%, 95.2%, 95.3%, 95.4%, 95.5%, 95.6%, 95.7%, 95.8%, 95.9%, 96.0%, 96.1%, 96.2%, 96.3%, 96.31%. In some examples, any two of these point values ​​can be used as end values ​​in the range, the same below.

[0053] In some of these examples, the ceramic material includes the following components by mass percentage:

[0054] CaO 0.6%~0.8%, MgO 0.3%~0.5%, SiO2 3%~3.5%, α-Al2O3 95.2%~96.1% and impurities.

[0055] It can be understood that the D50 particle size refers to the particle size corresponding to when the cumulative particle size distribution percentage of a sample reaches 50%. Its physical meaning is that particles with a particle size larger than it account for 50%, and particles with a particle size smaller than it also account for 50%. The D50 particle size is also called the median diameter or median particle size. The D90 particle size means that in a certain particle group, 90% of the particles have a diameter less than or equal to this value.

[0056] It is further understood that the D50 particle size of α-Al2O3 includes but is not limited to 1.8μm, 1.9μm, 2.0μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm, 3.0μm, 3.1μm, and 3.2μm.

[0057] In some of these examples, the maximum particle size of α-Al2O3 in the ceramic material is less than 12 μm.

[0058] In some of the examples, in the ceramic material, the impurities include Na2O and K2O, and the sum of mass percentages of Na2O and K2O in the ceramic material is ≤0.1%.

[0059] By controlling the ratio of Na2O and K2O in ceramic materials, the volume resistivity of ceramic materials can be effectively improved.

[0060] In some of the examples, in the ceramic material, raw materials for preparing the ceramic material include Al2O3 powder, talc, kaolin, calcium carbonate and quartz sand.

[0061] The chemical compositions of Al2O3 powder, talc, kaolin, calcium carbonate and quartz sand are shown in Table 1 in terms of weight percentage.

[0062] Table 1

[0063]

[0064] In some of the examples, in the ceramic material, the raw materials for preparing the ceramic material include, by weight percentage:

[0065] Al2O3 powder 93%~94.8%, talc 0.8%~1.5%, kaolin 2.5%~3.8%, calcium carbonate 0.7%~1.8% and quartz sand 0.5%~1%.

[0066] The ceramic material of the present application effectively reduces the adsorption of glaze by ceramic products (white porcelain pieces) made of the ceramic material during metallization, greatly reducing product scrapping caused by dry glaze; in addition, it is well matched with metallization, improves the metallization sealing strength and other properties, especially improves the whiteness of the ceramic products, and the appearance color of the ceramic products after metallization is better, slightly bluish in white, and looks very beautiful; at the same time, it avoids the sensitivity of the original introduced formula to the conversion rate of the main raw material α-Al2O3, thereby improving product quality; it also avoids the shortcomings of the original introduced formula in producing porcelain pieces, such as poor toughness, strong rigidity, difficulty in cutting and grinding, and easy to cause gaps, and improves grinding efficiency.

[0067] An embodiment of the present application provides a method for preparing a ceramic material, comprising the following steps:

[0068] Providing raw materials according to the composition of the above ceramic materials;

[0069] After the raw materials are mixed, isostatic pressing and sintering are performed in sequence to prepare ceramic materials.

[0070] It can be understood that the preparation method of the ceramic material provided in the present application can produce the above-mentioned ceramic material, and thus has at least the same advantages as the above-mentioned ceramic material.

[0071] The quality of electric vacuum 95% Al2O3 ceramic tubes produced by hot die casting is unstable, the qualified rate is low, and only products with a tube diameter of less than 140 mm can be produced. Compared with the hot die casting process, the product quality of the cold isostatic pressing process is stable, the consistency is good, and the qualified rate can be as high as more than 92%. More importantly, compared with the hot die casting process, the ceramic performance index of the cold isostatic pressing process product is one order of magnitude higher, which greatly improves the physical and chemical properties of 95% Al2O3 ceramics and is the main development direction of electric vacuum ceramics.

[0072] In some of these examples, in the method for preparing ceramic materials, the isostatic pressing pressure is 120 MPa~180 MPa.

[0073] It will be appreciated that the isostatic pressing pressure includes but is not limited to 120 MPa, 125 MPa, 130 MPa, 135 MPa, 140 MPa, 145 MPa, 150 MPa, 155 MPa, 160 MPa, 165 MPa, 170 MPa, 175 MPa, and 180 MPa.

[0074] White porcelain parts produced by traditional cold isostatic pressing have poor toughness and strong rigidity, are difficult to cut and grind, and are prone to cracks during handling.

[0075] The present application subjects a mixture of specific ingredients to isostatic pressing and controls the isostatic pressing pressure to effectively control the grain size, thereby effectively improving the uniformity of the pressed green body, uniform density, good regularity, high strength, and good toughness; the pressed green body can be very conveniently machined and trimmed, shrinks evenly during firing, has small deformation of the porcelain parts, and has a high product qualification rate.

[0076] When the isostatic pressing pressure exceeds 200 MPa, the grains of the pressed samples are small, which is not conducive to metallization sealing. Analysis shows that the density of the green body under this pressure is high, the gap is small, the grains will meet quickly, and the grains must overcome the interface energy to continue to grow, resulting in a slower growth rate and smaller grains in the end.

[0077] In some of the examples, in the method for preparing the ceramic material, the isostatic pressing time is 10s~20s.

[0078] It can be understood that the time for isostatic pressing includes but is not limited to 10s, 11s, 12s, 13s, 14s, 15s, 16s, 17s, 18s, 19s, and 20s.

[0079] In some of the examples, in the method for preparing the ceramic material, the sintering temperature is 1680°C~1700°C, and the sintering time is 2 h~2.5 h.

[0080] It will be understood that the sintering temperature includes but is not limited to 1680°C, 1681°C, 1682°C, 1683°C, 1684°C, 1685°C, 1686°C, 1687°C, 1688°C, 1689°C, 1690°C, 1691°C, 1692°C, 1693°C, 1694°C, 1695°C, 1696°C, 1697°C, 1698°C, 1699°C, and 1700°C; and the sintering time includes but is not limited to 2h, 2.1h, 2.2h, 2.3h, 2.4h, and 2.5h.

[0081] By controlling the sintering temperature and time, the grain size can be effectively controlled.

[0082] If the firing temperature is too high, not only will the product deformation increase, but also the secondary crystal growth rate will be too fast, resulting in the generation of large grains with defects such as closures, which will not only affect the mechanical and electrical properties of the ceramic parts, but also reduce the sealing strength. When the firing temperature is low, the grains have not grown yet, which is not conducive to sealing.

[0083] In some of the examples, the method for preparing the ceramic material further includes the steps of wet ball milling and spray drying the mixture obtained by mixing the raw materials before the isostatic pressing step and after the raw materials are mixed.

[0084] In some of the examples, in the preparation method of ceramic materials, the spray drying parameters are: equipment pressure is -10Pa~-50 Pa, inlet temperature is 250℃~310℃, outlet temperature is 115℃~118℃, and spray gun pressure is 2.5 MPa~3MPa.

[0085] It will be understood that negative pressure includes but is not limited to 10Pa, 12Pa, 14Pa, 16Pa, 18Pa, 20Pa, 22Pa, 24Pa, 26Pa, 28Pa, 30Pa, 32Pa, 34Pa, 36Pa, 38Pa, 40Pa, 42Pa, 44Pa, 46Pa, 48Pa, 50Pa; inlet temperature includes but is not limited to 250℃, 255℃, 260℃, 265℃, 270℃, 275℃, 280℃, 285℃, 290℃, 295℃, 300℃, 305℃, 310℃; outlet temperature includes but is not limited to 115℃, 116℃, 117℃, 118℃; spray gun pressure includes but is not limited to 2.5MPa, 2.6MPa, 2.7MPa, 2.8MPa, 2.9MPa, 3MPa.

[0086] By using specific spray drying parameters, a powder with good fluidity and spherical particles can be obtained, with a particle size range of 110 μm~140 μm, which can further improve the pressure resistance of the ceramic material.

[0087] In some examples, the method for preparing the ceramic material includes the following steps:

[0088] The mixed material obtained by mixing the raw materials is successively subjected to ball milling (wet ball milling plus adhesive), spray drying, isostatic pressing, blanking (lathe), sintering, cold working, cleaning and inspection.

[0089] It can be understood that the adhesive includes but is not limited to at least one of polyvinyl alcohol and hydroxymethyl cellulose.

[0090] The preparation method of the ceramic material provided in the present application, through reasonable formula design and process optimization, produces products with stable quality and excellent performance.

[0091] One embodiment of the present application provides a ceramic product, including the above-mentioned ceramic material or the ceramic material prepared by the preparation method.

[0092] The ceramic product of the present application includes the above ceramic material or the ceramic material produced by the preparation method, and thus has at least the same advantages as the above ceramic material or the ceramic material produced by the preparation method.

[0093] In some of the examples, the ceramic products include but are not limited to electric vacuum devices; further, the electric vacuum devices include but are not limited to at least one of electric vacuum switches, electric vacuum relays, electric vacuum capacitors, high-frequency and high-power electron tubes, etc.

[0094] The present application is further described in detail below in conjunction with specific implementation methods, but the implementation methods of the present application are not limited thereto.

[0095] Example 1

[0096] Al2O3 powder (D50 particle size is 1.8 μm~3.2 μm, D90 particle size is ≤5.5 μm, and maximum particle size is <12 μm), talc, kaolin, calcium carbonate and quartz sand are used as raw materials, and the ingredients are prepared according to the following components: calculated by mass percentage, the following components are included: CaO 0.7%, MgO 0.4%, SiO2 3.2%, and the balance is α-Al2O3 and impurities, and the sum of the mass percentages of Na2O and K2O in the impurities is ≤0.1%.

[0097] The prepared Al2O3 powder, talc, kaolin, calcium carbonate and quartz sand are mixed, and a binder is added to stir and wet-mill for 5 hours to obtain a slurry; the obtained slurry is spray-dried (negative pressure 10 Pa~50 Pa, inlet temperature 250℃~310℃, outlet temperature 115℃~118℃, spray gun pressure 2.5 MPa~3 Mpa) to obtain a powder; the powder is isostatically pressed (pressure 120 Mpa, holding pressure 10 s~20 s) to obtain a green body; after being trimmed (lathe), it is fired (1680℃~1700℃ for 2 h~2.5 h), and then cold-processed, cleaned and inspected in sequence to obtain a ceramic material.

[0098] Example 2

[0099] Al2O3 powder (D50 particle size is 1.8 μm~3.2 μm, D90 particle size is ≤5.5 μm, and maximum particle size is <12 μm), talc, kaolin, calcium carbonate and quartz sand are used as raw materials, and the ingredients are prepared according to the following components: calculated by mass percentage, the following components are included: CaO 0.52%, MgO 0.58%, SiO2 2.9%, and the balance is α-Al2O3 and impurities, and the sum of the mass percentages of Na2O and K2O in the impurities is ≤0.1%.

[0100] The preparation steps are as in Example 1.

[0101] Example 3

[0102] Al2O3 powder (D50 particle size is 1.8 μm~3.2 μm, D90 particle size is ≤5.5 μm, and maximum particle size is <12 μm), talc, kaolin, calcium carbonate and quartz sand are used as raw materials, and the ingredients are prepared according to the following components: calculated by mass percentage, the following components are included: CaO 0.85%, MgO 0.58%, SiO2 2.9%, and the balance is α-Al2O3 and impurities, and the sum of the mass percentages of Na2O and K2O in the impurities is ≤0.1%.

[0103] The preparation steps are as in Example 1.

[0104] Example 4

[0105] It is basically the same as Example 1, except that the isostatic pressing pressure is 150 MPa.

[0106] Comparative Example 1

[0107] It is basically the same as Example 1, except that the ingredients are prepared according to the following components: in terms of mass percentage, the following components are included: CaO 1%, MgO 0.27%, SiO2 3.5%, and the balance is α-Al2O3 and impurities, and the sum of the mass percentages of Na2O and K2O in the impurities is ≤0.1%.

[0108] Comparative Example 2

[0109] The method is basically the same as Example 1, except that the sum of the mass percentages of Na2O and K2O in the impurities is 0.2%.

[0110] The properties of the prepared ceramic materials (flexural strength, bulk density, metallization tensile strength, breakdown strength, dielectric loss tangent, and dielectric constant) are shown in Table 2, and the test standard GB / T5593-2015 was followed.

[0111] Table 2

[0112]

[0113] The ceramic withstand voltage provided by each embodiment is relatively high, meeting the requirements for installation and use of ultra-high voltage 252 kV electric vacuum tube shells.

[0114] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0115] The above-described embodiments only express several implementation methods of the present application, which is convenient for understanding the technical solution of the present application in detail, but it cannot be understood as limiting the scope of protection of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the scope of protection of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the scope of protection of the claims attached to the present application. Therefore, the scope of protection of the patent of this application shall be based on the content of the attached claims, and the description can be used to interpret the content of the claims.

Claims

1. A ceramic material, characterized in that: Calculated by mass percentage, it includes the following components: CaO 0.52%~0.85%, MgO 0.27%~0.58%, SiO2 2.6%~3.5%, α-Al2O3 94.7%~96.61% and impurities, the D50 particle size of the α-Al2O3 is 1.8 μm~3.2 μm, and the D90 particle size of the α-Al2O3 is ≤5.5 μm.

2. The ceramic material according to claim 1, characterized in that Calculated by mass percentage, it includes the following components: CaO 0.6%~0.8%, MgO 0.3%~0.5%, SiO2 3%~3.5%, α-Al2O3 95.2%~96.1% and impurities.

3. The ceramic material according to claim 1, characterized in that The maximum particle size of the α-Al2O3 is less than 12 μm.

4. The ceramic material according to claim 1, characterized in that The impurities include Na2O and K2O, and the sum of the mass percentages of Na2O and K2O in the ceramic material is ≤0.1%.

5. The ceramic material according to any one of claims 1 to 4, characterized in that The raw materials for preparing the ceramic material include Al2O3 powder, talc, kaolin, calcium carbonate and quartz sand.

6. A method for preparing a ceramic material, characterized in that: The following steps are involved: Providing raw materials according to the components of the ceramic material according to any one of claims 1 to 5; After the raw materials are mixed, isostatic pressing and sintering are performed in sequence to prepare a ceramic material.

7. The method for preparing a ceramic material according to claim 6, characterized in that: The isostatic pressing pressure is 120 MPa to 180 MPa; and / or, The sintering temperature is 1680° C. to 1700° C., and the sintering time is 2 h to 2.5 h.

8. The method for preparing a ceramic material according to any one of claims 6 to 7, characterized in that: Before the isostatic pressing step is performed, after the raw materials are mixed, the method further includes the steps of wet ball milling and spray drying the mixed material obtained by mixing the raw materials.

9. The method for preparing a ceramic material according to claim 8, characterized in that: The spray drying parameters are: equipment pressure of -10 Pa~-50 Pa, inlet temperature of 250°C~310°C, outlet temperature of 115°C~118°C, and spray gun pressure of 2.5 MPa~3 MPa.

10. A ceramic product, characterized in that: The invention comprises the ceramic material as described in any one of claims 1 to 5 or the ceramic material prepared by the preparation method as described in any one of claims 6 to 9.

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