Ceramic composition, silicon nitride and method for producing the same, ceramic article

Abstract

The application provides a ceramic composition, a silicon nitride and a preparation method thereof, and a ceramic product. According to mass parts, the ceramic composition comprises 80-100 parts of silicon nitride, 1-10 parts of a first sintering aid, 1-10 parts of a second sintering aid, 0.5-20 parts of a dispersing agent, 10-40 parts of a binder and 0.5-2 parts of an antifoaming agent. The first sintering aid is a non-oxidized magnesium-containing compound, and the second sintering aid is a rare earth silicide. When the raw material comprising the ceramic composition is used to prepare the silicon nitride ceramic, the thermal conductivity and the bending strength of the prepared silicon nitride ceramic can be simultaneously improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of functional ceramic materials, in particular to a ceramic composition, silicon nitride and a preparation method thereof, and a ceramic product. BACKGROUND

[0002] Silicon nitride ceramic substrate material has a wide application in the fields of aero-engine, mechanical industry, integrated circuit and metallurgy due to its good mechanical properties and thermal conductivity. For example, silicon nitride ceramic can be used as turbine blade, mechanical seal sheet, high-temperature bearing, high-speed cutter, permanent mold and the like in the mechanical industry, and can be used as electronic packaging substrate and substrate in the field of integrated circuit, and is an ideal packaging material for high-power electronic devices. In addition, silicon nitride ceramic can also be used as a component of hot work equipment such as crucible, burner and inner lining of aluminum electrolysis tank in the metallurgical industry.

[0003] The traditional forming methods of silicon nitride ceramic substrate mainly include tape casting, dry pressing and film rolling. The tape casting method is more suitable for large-scale industrial production due to its high production efficiency, continuous production and automation, and is an ideal ceramic substrate production technology. The basic process of tape casting forming process is to uniformly mix each component and solvent into slurry, form a smooth surface and uniform thickness film through a doctor blade, and then dry to obtain a green sheet with good toughness. However, the traditional tape casting method often uses low-boiling-point organic solvents, which pollutes the environment and increases the production cost, and the mechanical properties and thermal conductivity of the prepared silicon nitride ceramic cannot meet the increasing thermal conductivity requirement of silicon nitride ceramic material.

[0004] Therefore, the traditional technology still needs to be improved. SUMMARY

[0005] Based on this, the present application provides a ceramic composition, silicon nitride and a preparation method thereof, and a ceramic product. When the ceramic composition is used as raw material to prepare silicon nitride ceramic, the thermal conductivity and mechanical properties of the silicon nitride ceramic can be improved at the same time.

[0006] The technical scheme of the present application is as follows.

[0007] In a first aspect of the present application, a ceramic composition is provided, which comprises, in terms of mass fraction, 80-100 parts of silicon nitride, 1-10 parts of a first sintering aid, 1-10 parts of a second sintering aid, 0.5-20 parts of a dispersing agent, 10-40 parts of a binder and 0.5-2 parts of an antifoaming agent.

[0008] The first sintering aid is a non-oxidized magnesium-containing compound, and the second sintering aid is a rare earth silicide.

[0009] The ceramic composition contains specific components with specific mass fractions, wherein the first sintering aid is a non-oxidized magnesium-containing compound, and the second sintering aid is a rare earth silicide. On the one hand, the use of the two specific sintering aids can reduce the introduction of oxygen impurities. On the other hand, the two specific sintering aids and other specific components have a synergistic effect in the sintering process, further reducing the lattice oxygen content. The synergistic effect of the components can simultaneously improve the thermal conductivity and bending strength of the prepared silicon nitride ceramic.

[0010] Further, the ceramic composition contains components with specific proportions, so that the ceramic composition can generate a larger surface tension even in water, so that water can have good wettability to the components of the ceramic composition. When water is used as a solvent for casting, the deformation and cracking of the green body during preparation can be reduced, and the overall thermal conductivity and bending strength of the silicon nitride ceramic can be improved.

[0011] It can be understood that the "non-oxidized magnesium-containing compound" is a magnesium compound without oxygen elements.

[0012] In some embodiments, the mass fraction of the first sintering aid is 1 part to 5 parts.

[0013] In some embodiments, the mass fraction of the second sintering aid is 1 part to 5 parts.

[0014] The proportion of the sintering aid is adjusted to further reduce the probability of lattice oxygen in the silicon ceramic.

[0015] In some embodiments, the non-oxidized magnesium-containing compound includes at least one of silicon nitride magnesium, magnesium nitride, magnesium sulfide, and magnesium chloride.

[0016] In some embodiments, the rare earth silicide includes at least one of yttrium silicide, lanthanum silicide, gadolinium silicide, dysprosium silicide, and ytterbium silicide.

[0017] In some embodiments, the ceramic composition satisfies at least one of the following (1) to (2):

[0018] (1) The dispersant includes a silane-modified acrylic emulsion.

[0019] The silane-modified acrylic emulsion is selected as the dispersant. On one hand, the silane-modified acrylic emulsion contains hydrophilic carboxylate, which can further promote the uniform dispersion of the components in water. On the other hand, the silane-modified acrylic emulsion contains silicon elements. In the subsequent sintering process for preparing the silicon nitride ceramic from the ceramic composition, the silane-modified acrylic emulsion will undergo chemical reactions such as oxidation and cracking at high temperatures. The elements such as hydrogen are easy to form gas and volatilize. The chemical properties of silicon elements are relatively stable, so they remain in the silicon nitride ceramic. The silicon element is the main component and key element of the silicon nitride, so that the introduction of other impurity elements can be avoided, thereby further improving the purity of the key elements in the silicon nitride ceramic.

[0020] (2) The binder is a water-soluble binder.

[0021] The water-soluble binder can be dissolved in water, and when water is used as the solvent for the casting forming, the water can further improve the wettability of the water to the components of the ceramic composition.

[0022] In a second aspect of the present application, a silicon nitride ceramic is provided, which is prepared from the raw material including the ceramic composition of the first aspect.

[0023] The silicon nitride ceramic has excellent thermal conductivity and bending strength.

[0024] In a third aspect of the present application, a preparation method of a silicon nitride ceramic is provided, which includes the following steps:

[0025] Mixing the ceramic composition of the first aspect with water to prepare a ceramic composition slurry;

[0026] Sequentially performing forming treatment, degassing treatment and sintering treatment on the ceramic composition slurry to prepare a silicon nitride ceramic.

[0027] The ceramic composition contains specific components with specific mass fractions. The first sintering aid is a non-oxidized magnesium-containing compound, and the second sintering aid is a rare earth silicide. On one hand, the use of the two specific sintering aids can reduce the introduction of oxygen impurities. On the other hand, the two specific sintering aids and other specific components have a synergistic effect in the sintering process, further reducing the lattice oxygen content, and the components have a synergistic effect, thereby simultaneously improving the thermal conductivity and bending strength of the prepared silicon nitride ceramic. In addition, the ceramic composition can also generate a large surface tension in water, so that water can have good wettability to the components of the ceramic composition. When water is used as the solvent for the casting forming, the green body is also less likely to deform and crack during the preparation process.

[0028] In some embodiments, the preparation method satisfies at least one of the following conditions (1)-(5):

[0029] (1) before the step of the forming treatment, further comprising a step of performing a defoaming treatment on the ceramic composition slurry;

[0030] (2) the forming treatment is performed by using a tape casting method;

[0031] (3) the sintering treatment is performed in a protective atmosphere with a pressure of 0.1 MPa to 10 MPa;

[0032] (4) the sintering treatment is performed at a temperature of 1750℃ to 1950℃ for a time of 1h to 20h;

[0033] (5) the mass fraction of the water is 20 parts to 200 parts, based on the mass fraction of the silicon nitride.

[0034] In a fourth aspect of the present application, a ceramic product is provided, which comprises the silicon nitride ceramic of the second aspect or the silicon nitride ceramic prepared by the method of the third aspect. DETAILED DESCRIPTION

[0035] In order to facilitate the understanding of the present application, the present application will be described more fully below, and preferred embodiments of the present application will be given. However, the present application can be realized in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein only for the purpose of describing specific embodiments of the present application, and is not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0037] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0038] "RANGES" disclosed herein can be defined with both a lower and an upper limit to the range and the range is defined by selecting a lower limit and an upper limit, the selected lower limit and upper limit defining the boundaries of the particular range. Ranges defined in this manner can be either inclusive or exclusive of the endpoints, either endpoint can be independently included or excluded, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Further, if a minimum range value of 1 and 2 are listed, and if a maximum range value of 3, 4, and 5 are also listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, numerical ranges "a-b" are intended to indicate any and all subcombinations of the numerical values a and b, wherein a and b are both real numbers. For example, the numerical range "0-5" is intended to indicate that all real numbers between 0 and 5, such as 0, 1, 2, 3, 4, 5, etc. have been listed herein, and that "0-5" is merely a shorthand for listing each and every one of these values. Also, when a parameter is stated to be an integer ≥ 2, it is equivalent to listing the integer as, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For example, when a parameter is stated to be an integer selected from "2-10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0039] In this application, "optionally", "optional", "optional" means optional, i.e. selected from two parallel schemes of "have" or "no". If there are multiple "options" in a technical scheme, if there is no special instruction and no contradictory relationship or mutual restriction, each "option" is independent.

[0040] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive or alternative embodiments. It is expressly understood that the embodiments described herein are merely examples from among other embodiments that can be employed, and that the illustrative embodiments described herein in connection with the other embodiments can be interchanged therewith.

[0041] In this application, unless otherwise specified, the steps of the application are carried out at "room temperature" or "ambient temperature", which generally refers to 4-30°C, preferably 20±5°C.

[0042] In summary, the thermal conductivity of traditional silicon nitride ceramics cannot meet the increasingly high thermal conductivity requirements of packaging materials, especially when prepared by the tape casting method, which also produces organic solvent pollution of the environment and other problems.

[0043] In the prior art, the oxygen content in silicon nitride ceramics is reduced by optimizing sintering aids, and rare earth oxides are often used as sintering aids. However, it is found that the commonly used rare earth oxides and other oxygen-containing sintering aids contain oxygen elements, which means that oxygen is introduced during the sintering process, thereby increasing the probability of lattice oxygen formation in the silicon nitride ceramics during the sintering process, and limiting the improvement of the thermal conductivity of the silicon nitride ceramics.

[0044] After a large number of creative experiments, the ceramic composition capable of improving the thermal conductivity of the silicon nitride ceramics is obtained.

[0045] In an embodiment of the present application, a ceramic composition is provided, which comprises, in terms of mass fraction: 80-100 parts of silicon nitride, 1-10 parts of a first sintering aid, 1-10 parts of a second sintering aid, 0.5-20 parts of a dispersing agent, 10-40 parts of a binder, and 0.5-2 parts of an antifoaming agent.

[0046] The first sintering aid is a non-oxidized magnesium-containing compound, and the second sintering aid is a rare earth silicide.

[0047] The ceramic composition contains specific components with specific mass fractions. The first sintering aid is a non-oxidized magnesium-containing compound, and the second sintering aid is a rare earth silicide. On the one hand, the use of the two specific sintering aids can reduce the introduction of oxygen impurities. On the other hand, the two specific sintering aids and other specific components have a synergistic effect during the sintering process, further reducing the lattice oxygen content. The synergistic effect of the components can simultaneously improve the thermal conductivity and bending strength of the prepared silicon nitride ceramics.

[0048] Further, the ceramic composition contains components with specific proportions, so that the ceramic composition can produce a large surface tension even in water, and the water can have good wettability to the components of the ceramic composition. When water is used as a solvent for tape casting, the deformation and cracking of the green body during preparation can be reduced, and the overall thermal conductivity and bending strength of the silicon nitride ceramics can be improved.

[0049] It can be understood that the "non-oxidized magnesium-containing compound" refers to a magnesium compound without oxygen elements.

[0050] In the above “80 parts to 100 parts”, the mass fraction of silicon nitride takes values including the minimum and maximum values of the range, and every value between such minimum and maximum values, specific examples including but not limited to the point values in the embodiments and the following point values: 80 parts, 81 parts, 82 parts, 83 parts, 84 parts, 85 parts, 86 parts, 87 parts, 88 parts, 89 parts, 90 parts, 91 parts, 92 parts, 93 parts, 94 parts, 95 parts, 96 parts, 97 parts, 98 parts, 99 parts, 100 parts; or a range composed of any two numerical values.

[0051] In the above “1 part to 10 parts”, the mass fraction of the first sintering aid or the second sintering aid takes values including the minimum and maximum values of the range, and every value between such minimum and maximum values, specific examples including but not limited to the point values in the embodiments and the following point values: 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts; or a range composed of any two numerical values.

[0052] In the above “10 parts to 40 parts”, the mass fraction of the binder takes values including the minimum and maximum values of the range, and every value between such minimum and maximum values, specific examples including but not limited to the point values in the embodiments and the following point values: 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts; or a range composed of any two numerical values.

[0053] In the above “0.5 parts to 20 parts”, the mass fraction of the dispersant takes values including the minimum and maximum values of the range, and every value between such minimum and maximum values, specific examples including but not limited to the point values in the embodiments and the following point values: 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, 21 parts, 22 parts, 23 parts, 24 parts, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts, 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts; or a range composed of any two numerical values.

[0054] In the above-mentioned “0.5 parts to 2 parts”, the mass fraction of the defoaming agent takes values including the minimum value and the maximum value of the range, and every value between the minimum value and the maximum value, and specific examples include but are not limited to the following point values in the embodiments: 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts, 1 part, 1.1 parts, 1.2 parts, 1.3 parts, 1.4 parts, 1.5 parts, 1.6 parts, 1.7 parts, 1.8 parts, 1.9 parts, 2 parts; or a range composed of any two numerical values.

[0055] In some embodiments, the mass fraction of the first sintering aid is 1 part to 5 parts.

[0056] In some embodiments, the mass fraction of the second sintering aid is 1 part to 5 parts.

[0057] The ratio of the sintering aids is adjusted to further reduce the probability of lattice oxygen in the silicon ceramic.

[0058] In some embodiments, the non-oxidized magnesium-containing compound includes at least one of magnesium silicon nitride, magnesium nitride, magnesium sulfide, and magnesium chloride.

[0059] In some embodiments, the rare earth silicide includes at least one of yttrium silicide, lanthanum silicide, gadolinium silicide, dysprosium silicide, and ytterbium silicide.

[0060] The dispersant can be a dispersant commonly used in the art; including but not limited to: silane-modified acrylic emulsion.

[0061] The silane-modified acrylic emulsion is selected as the dispersant, on the one hand, the silane-modified acrylic emulsion contains hydrophilic carboxylate, which can further promote the uniformity of the dispersion of each component in water; on the other hand, the silane-modified acrylic emulsion contains silicon element, in the subsequent sintering of the ceramic composition to prepare silicon nitride ceramic, in the sintering process, the silane-modified acrylic emulsion will undergo chemical reactions such as oxidation and cracking at high temperatures, and hydrogen and other elements are easy to form gas volatilization, and the chemical properties of silicon element are relatively stable, so it remains in the silicon nitride ceramic, and silicon element is the main component and key element of silicon nitride, thereby avoiding the introduction of other impurity elements, and thus the purity of the key elements in the silicon nitride ceramic can be further improved.

[0062] In some embodiments, the binder is a water-soluble binder.

[0063] The water-soluble binder can be dissolved in water, and when water is used as the solvent for the casting forming, the wettability of water to each component of the ceramic composition can be further improved.

[0064] The defoaming agent can be a defoaming agent commonly used in the art, including but not limited to: silicone, surfactant, and organic acid defoaming agents.

[0065] In some embodiments, the silicon nitride is added in the form of a powder in the ceramic composition.

[0066] An embodiment of the present application provides a silicon nitride ceramic prepared from a raw material including the above ceramic composition.

[0067] The silicon nitride ceramic has excellent thermal conductivity and bending strength.

[0068] An embodiment of the present application provides a method for preparing a silicon nitride ceramic, including the following steps S10-S20.

[0069] Step S10: mixing the above ceramic composition with water to prepare a ceramic composition slurry.

[0070] Step S20: sequentially performing a forming treatment, a degassing treatment and a sintering treatment on the ceramic composition slurry to prepare a silicon nitride ceramic.

[0071] The ceramic composition contains specific components with specific mass fractions, wherein the first sintering aid is a non-oxidized magnesium-containing compound, and the second sintering aid is a rare earth silicide. On the one hand, the use of the two specific sintering aids can reduce the introduction of oxygen impurities. On the other hand, the two specific sintering aids and other specific components have a synergistic effect in the sintering process, further reducing the lattice oxygen content, and the synergistic effect of the components can simultaneously improve the thermal conductivity and bending strength of the prepared silicon nitride ceramic. In addition, the ceramic composition can also generate a large surface tension in water, so that water can have good wettability to the components of the ceramic composition. When water is used as a solvent for tape casting, the ceramic composition can also reduce the deformation and cracking of the green body during preparation.

[0072] In some embodiments, the mass fraction of water is 20-200 parts based on the mass fraction of silicon nitride.

[0073] In other words, the ceramic composition slurry includes 80-100 parts of silicon nitride, 1-10 parts of the first sintering aid, 1-10 parts of the second sintering aid, 0.5-20 parts of the dispersant, 10-40 parts of the binder, 0.5-2 parts of the defoaming agent, and 20-60 parts of water, in terms of mass fraction.

[0074] In some embodiments, the preparation steps of the ceramic composition slurry are as follows:

[0075] The silicon nitride, the first sintering aid, the second sintering aid, the dispersant and the water are subjected to a first mixing treatment to prepare a first mixture.

[0076] In some embodiments, the first mixing process is performed by ball milling. Further, the specific conditions include: the ball milling medium is a silicon nitride ball with a diameter of 10 mm, the ball milling speed is 200 r / min to 250 r / min, the ball milling time is 2 h to 4 h, and the mass ratio of the ball milling medium to the first mixture is (1.5-2.5):1.

[0077] The first mixture, the binder, and the defoaming agent are subjected to a second mixing process to prepare a ceramic composition slurry.

[0078] In some embodiments, the second mixing process is performed by ball milling. Further, the specific conditions include: the ball milling medium is a silicon nitride ball with a diameter of 5 mm, the ball milling speed is 120 r / min to 160 r / min, the ball milling time is 1 h to 3 h, and the mass ratio of the ball milling medium to the ceramic composition slurry is (1.5-2.5):1.

[0079] In some embodiments, the method further comprises a step of defoaming the ceramic composition slurry before the step of the forming process.

[0080] In some embodiments, the defoaming process is performed in a vacuum until the viscosity of the slurry reaches 3000 Pa·S to 10000 Pa·S.

[0081] In some embodiments, the forming process is performed by tape casting.

[0082] Further, the conditions of the tape casting include: the doctor blade height is 0.1 mm to 1.0 mm, and the casting speed is 50 cm / min to 100 cm / min.

[0083] The time of the tape casting process is determined by the shape of the desired silicon nitride ceramic product and is not particularly limited.

[0084] In some embodiments, the debinding process is performed in a vacuum at a temperature of 400°C to 600°C for 1 h to 10 h.

[0085] In the above "400°C to 600°C", the values include the minimum and maximum values of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the following point values in the embodiments: 400°C, 450°C, 500°C, 550°C, and 600°C.

[0086] In the above "1 h to 10 h", the values include the minimum and maximum values of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the following point values in the embodiments: 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, and 10 h.

[0087] In some embodiments, the sintering process is performed in a protective atmosphere with a pressure of 0.1 MPa to 10 MPa.

[0088] In some embodiments, the protective atmosphere comprises nitrogen.

[0089] In some embodiments, the sintering process is performed at a temperature of 1750°C to 1950°C for 1 h to 20 h.

[0090] In some embodiments, the sintering process is performed at a temperature of 1750°C to 1950°C for 1 h to 20 h.

[0091] The ceramic product has excellent heat conduction performance, and can be various products for packaging, including but not limited to packaging substrates for packaging electronic devices, and can also be turbine blades, mechanical sealing sheets, high-temperature bearings, high-speed cutters, permanent molds, or components of thermal equipment such as crucibles, burners, aluminum electrolysis tank linings, etc. in the metallurgical industry.

[0092] The application will be described in detail below with reference to specific embodiments, but the application is not limited to the following embodiments, and it should be understood that the appended claims generalize the scope of the application, and those skilled in the art should realize that certain changes to the embodiments of the application will be covered by the spirit and scope of the claims.

[0093] The following are specific embodiments.

[0094] Embodiment 1

[0095] (1) The first mixing process is performed on 100 g of silicon nitride powder, 5 g of a first sintering aid magnesium nitride, 5 g of a second sintering aid lanthanum silicide powder, 1 g of a dispersant (silane-modified acrylic emulsion), and 50 g of water, using a ball milling method with silicon nitride balls of 10 mm in diameter as the ball milling medium, a ball milling speed of 200 r / min to 250 r / min, a ball milling time of 2 h, and a mass ratio of the ball milling medium to the first mixture of 2:1.

[0096] The second mixing process is performed on the first mixture by adding 20 g of a bonding agent acrylic emulsion (PVB) and 1 g of a defoaming agent (silicone defoaming agent) using a ball milling method, to obtain a ceramic composition slurry. The second mixing process conditions include: the ball milling medium is silicon nitride balls of 5 mm in diameter, the ball milling speed is 120 r / min to 160 r / min, the ball milling time is 3 h, and the mass ratio of the ball milling medium to the ceramic composition slurry is 2.5:1.

[0097] (2) Pour the ceramic composition slurry into a container and place it in a vacuum defoaming machine for defoaming treatment. The defoaming treatment conditions include: defoaming at room temperature under vacuum, and stopping defoaming when the viscosity of the ceramic composition slurry reaches 6000 Pa·S.

[0098] (3) The ceramic composition slurry after defoaming treatment is prepared into a thin sheet-shaped green body by a casting method. The casting conditions include: a casting doctor blade height of 1.0 mm and a casting speed of 100 cm / min.

[0099] (4) The thin sheet-shaped green body is placed in a vacuum glue removal furnace for glue removal treatment. Specifically, the green body is placed in the furnace cavity, and the glue removal treatment is performed under vacuum at a temperature of 600°C for 5 hours to obtain a green body.

[0100] (5) The green body is placed in a high-temperature sintering furnace for sintering to obtain a silicon nitride ceramic. The high-temperature sintering is performed in a nitrogen atmosphere at 5 MPa at a temperature of 1750°C to 1950°C for 10 hours to obtain a silicon nitride ceramic.

[0101] (7) Performance testing, specifically as follows:

[0102] 1: The thermal conductivity of the prepared silicon nitride ceramic is tested by a laser flash method.

[0103] 2: The bending strength of the silicon nitride ceramic is tested by a 3-point method.

[0104] The component proportions of the ceramic composition slurry and the thermal conductivity test results of the silicon nitride ceramic are shown in Table 1.

[0105] Examples 2-6

[0106] Examples 2-6 are basically the same as Example 1, except that the component proportions of the ceramic composition slurry are different from those of Example 1. See Table 1 for details.

[0107] The other steps are the same as those of Example 1.

[0108] Examples 7-8

[0109] Examples 7-8 are basically the same as Example 1, except that the types of the first sintering aid and the second sintering aid are different from those of Example 1. See Table 1 for details.

[0110] The other steps are the same as those of Example 1.

[0111] Comparative Examples 1-3

[0112] Comparative Examples 1-3 are basically the same as Example 1, except that the component proportions of the ceramic composition slurry are different from those of Example 1. See Table 1 for details.

[0113] Other steps are the same as Example 1.

[0114] The components of the ceramic composition slurries and their proportions in each of the examples and each of the comparative examples, and the test results are shown in Table 1.

[0115] Table 1

[0116]

[0117] Note: " / " represents that the condition does not exist.

[0118] As can be seen from the data in Table 1, the silicon nitride ceramic prepared from the raw materials including the ceramic composition of the present application has both good mechanical properties and excellent thermal conductivity.

[0119] Any combination of the technical features of the above-described examples can be made, and in order to make the description simple, all possible combinations of each technical feature in the above-described examples are not described, however, as long as the combination of the technical features does not exist, it should be considered as the scope of the present disclosure.

[0120] The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent application. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the protection scope of the present patent should be subject to the appended claims.

Claims

1. A ceramic composition, characterized by, The ceramic composition comprises, in terms of mass fraction, 80-100 parts of silicon nitride, 1-10 parts of a first sintering aid, 1-10 parts of a second sintering aid, 0.5-20 parts of a dispersant, 10-40 parts of a binder, and 0.5-2 parts of an antifoaming agent; The first sintering aid is a non-oxidized magnesium-containing compound, and the second sintering aid is a rare earth silicide; The first sintering aid has a mass fraction of 1-5 parts, and the second sintering aid has a mass fraction of 1-5 parts. The non-oxidized magnesium-containing compound includes at least one of magnesium silicon nitride, magnesium nitride, magnesium sulfide, and magnesium chloride, and the rare earth silicide includes at least one of yttrium silicide, lanthanum silicide, gadolinium silicide, dysprosium silicide, and ytterbium silicide.

2. The ceramic composition of claim 1, wherein, The ceramic composition satisfies at least one of the following conditions (1) and (2): (1) The dispersant includes a silane-modified acrylic emulsion. (2) The binder is a water-soluble binder.

3. A silicon nitride ceramic, characterized by, The silicon nitride ceramic is prepared using raw materials including the ceramic composition according to any one of claims 1-2.

4. A method for producing a silicon nitride ceramic, characterized by, The method includes the following steps: Mixing the ceramic composition according to any one of claims 1-2 with water to prepare a ceramic composition slurry; The ceramic composition slurry is sequentially subjected to a forming treatment, a degassing treatment, and a sintering treatment to prepare a silicon nitride ceramic.

5. The method of producing silicon nitride ceramics according to claim 4, wherein The preparation method satisfies at least one of the following conditions (1)-(5): (1) Before the forming treatment, the ceramic composition slurry is further subjected to a degassing treatment; (2) The forming treatment is performed by tape casting; (3) The sintering treatment is performed in a protective atmosphere at a pressure of 0.1-10 MPa; (4) The sintering treatment is performed at a temperature of 1750-1950°C for 1-20 h; (5) The mass fraction of water is 20-200 parts based on the mass fraction of the silicon nitride.

6. The method of producing silicon nitride ceramics according to claim 4, wherein The ceramic composition is mixed with water to prepare a ceramic composition slurry, specifically including the following steps: Firstly mixing the silicon nitride, the first sintering aid, the second sintering aid, the dispersant, and water to prepare a first mixture; The first mixing treatment is performed by ball milling, the ball milling medium is silicon nitride balls with a diameter of 10 mm, the ball milling speed is 200-250 r / min, the ball milling time is 2-4 h, and the mass ratio of the ball milling medium to the first mixture is (1.5-2.5):1; Secondly mixing the first mixture, the binder, and the antifoaming agent to prepare the ceramic composition slurry; The second mixing treatment is performed by ball milling, the ball milling medium is silicon nitride balls with a diameter of 5 mm, the ball milling speed is 120-160 r / min, the ball milling time is 1-3 h, and the mass ratio of the ball milling medium to the ceramic composition slurry is (1.5-2.5):

1.

7. The method of producing silicon nitride ceramics according to claim 4, wherein The degassing treatment specifically includes the following steps: The degassing treatment is performed under vacuum at a temperature of 400-600°C for 1-10 h.

8. The method of producing silicon nitride ceramics according to claim 5, wherein The degassing treatment specifically includes the following steps: The defoaming treatment is performed in vacuum until the viscosity of the slurry reaches 3000 Pa·S~10000 Pa·S.

9. The method of producing silicon nitride ceramics according to claim 5, wherein The forming treatment is performed by using flow casting, and specifically includes the following steps: The conditions of the flow casting include: the doctor blade height of the flow casting is 0.1mm~1.0mm, the flow casting speed is 50 cm / min~100cm / min, and the time of the flow casting treatment is determined by the shape of the required silicon nitride ceramic product.

10. A ceramic article, characterized by, The ceramic product includes the silicon nitride ceramic as claimed in claim 3 or the silicon nitride ceramic prepared by the method as claimed in any one of claims 4~9.

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