Silicon carbide ceramic connecting agent, connecting method thereof and silicon carbide ceramic connecting joint

Abstract

The invention relates to the technical field of ceramic material connection, and particularly provides a silicon carbide ceramic connecting agent, a connecting method thereof and a silicon carbide ceramic connecting joint. The silicon carbide ceramic coupling agent comprises the following components in percentage by mass: 30%-80% of an organic silicon polymer precursor, 10%-60% of an inert filler and 1%-50% of an active filler. The organic silicon polymer precursor comprises vinyl hydrogen-based polycarbosilane, a cross-linking agent and an initiator, and in the organic silicon polymer precursor, the addition amount of the cross-linking agent is 0.1%-50% and the addition amount of the initiator is 0.1%-10% in terms of the mass of the vinyl hydrogen-based polycarbosilane being 100%. The invention aims to improve the compactness and the connection strength of the silicon carbide ceramic during connection.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic material connection, and more specifically, to a silicon carbide ceramic binder, a connection method thereof, and a silicon carbide ceramic connection joint. Background Art

[0002] Silicon carbide ceramic (SiC) is widely used in the fields of aerospace, nuclear energy, electronic packaging, etc. due to its high hardness, high temperature resistance, oxidation resistance, and excellent thermal conductivity. However, its high melting point, low toughness, and chemical inertness make the silicon carbide ceramic connection technology face many challenges.

[0003] Currently, the connection methods between silicon carbide ceramics of the same material and different materials include diffusion welding, brazing, transient eutectic connection, silicon-carbon reaction connection, and organosilicon polymer precursor connection, etc. Among them, the organosilicon polymer precursor connection method refers to the process of coating the interface with an organosilicon polymer precursor and pyrolyzing it at high temperature to generate silicon carbide. However, during the pyrolysis of the precursor, volume shrinkage is likely to occur, resulting in interfacial microcracks, which reduces the densification degree and connection strength of the silicon carbide ceramic connection joint. Summary of the Invention

[0004] The present invention aims to improve the densification degree and connection strength during the connection of silicon carbide ceramics.

[0005] To solve the above problems, the present invention provides a silicon carbide ceramic binder, a connection method thereof, and a silicon carbide ceramic connection joint. The specific technical solutions are as follows:

[0006] In the first aspect, the present invention provides a silicon carbide ceramic binder, which includes the following components by mass percentage: 30% to 80% of an organosilicon polymer precursor, 10% to 60% of an inert filler, and 1% to 50% of an active filler;

[0007] The components of the organosilicon polymer precursor include vinylhydridopolycarbosilane, a crosslinking agent, and an initiator. In the organosilicon polymer precursor, based on the mass of vinylhydridopolycarbosilane being 100%, the addition amount of the crosslinking agent is 0.1% to 50%, and the addition amount of the initiator is 0.1% to 10%;

[0008] Among them, the crosslinking agent includes any one or several of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 1,4-bis(ethenyldimethylsilyl)benzene, vinyl-POSS, and tris(isopropenyloxy)vinylsilane. The structural formula of vinylhydridopolycarbosilane is as shown in formula (Ⅰ):

[0009]

[0010] In formula (I), x ranges from 1 to 1000, and y ranges from 1 to 1000.

[0011] Optionally, the initiator includes any one or more of benzoyl peroxide, azobisisobutyronitrile, azobisisoheptonitrile, tert-butyl peroxybenzoate, methyl ethyl ketone peroxide, and diisopropyl peroxydicarbonate.

[0012] Optionally, the inert filler includes silicon carbide powder or silicon carbide fiber. The particle size of the silicon carbide powder is 50 nm to 100 μm, and the diameter of the silicon carbide fiber is 10 nm to 50 μm.

[0013] Optionally, the active filler includes any one or more of silicon powder, aluminum powder, zirconium powder, magnesium powder, titanium powder, aluminum oxide, silicon oxide, zirconium oxide, titanium oxide, yttrium oxide, boron carbide, and zirconium boride.

[0014] Optionally, the particle size of the active filler is 10 nm to 100 μm.

[0015] Optionally, the silicon carbide ceramic binder includes the following components by mass percentage: 55% to 70% of organosilicon polymer precursor, 10% to 20% of inert filler, and 15% to 30% of active filler; in the organosilicon polymer precursor, based on the mass of vinyl hydrogen polycarbosilane being 100%, the addition amount of the crosslinking agent is 6% to 12%, and the addition amount of the initiator is 1% to 3%.

[0016] In a second aspect, the present invention provides a method for joining silicon carbide ceramics. The joining method is based on the above-mentioned silicon carbide ceramic binder, and the joining method includes: after applying the silicon carbide ceramic binder on the surface of the silicon carbide ceramic, performing thermal curing and thermal cracking in sequence to obtain a silicon carbide ceramic joint.

[0017] Optionally, the temperature of the thermal curing is 50°C to 300°C, the time of the thermal curing is 10 min to 24 h, the temperature of the thermal cracking is 600°C to 1500°C, and the heat treatment time is 10 min to 5 h.

[0018] Optionally, the thermal curing includes: the first stage: raising the temperature from room temperature to 80 to 100°C at a heating rate of 20 to 25°C / min; the second stage: raising the temperature from 80 to 100°C to 150 to 200°C at a heating rate of 5 to 10°C / min; the third stage: raising the temperature from 150 to 200°C to 250 to 300°C at a heating rate of 15 to 20°C / min; the thermal cracking includes: raising the temperature from 250 to 300°C to 500 to 600°C at a heating rate of 3 to 5°C / min, and then raising the temperature from 500 to 600°C to 1200 to 1500°C at a heating rate of 25 to 50°C / min.

[0019] In a third aspect, the present invention provides a silicon carbide ceramic connection joint, which is prepared by using the above-mentioned connection method of silicon carbide ceramics.

[0020] The beneficial effects of the silicon carbide ceramic binder of the present invention are as follows:

[0021] The present invention prepares an organosilicon polymer precursor by selecting a specific cross-linking agent to carry out a cross-linking reaction with vinylhydrocarbyl polycarbosilane to promote the connection between polymer chains and form a high-density cross-linked network of organosilicon polymers. The cross-linked network of organosilicon polymers can pyrolyze in situ at high temperature to generate silicon carbide with a high yield, improve the compatibility between the connection interface of the silicon carbide base material and the connection layer, and at the same time reduce the stress between the connection layer and the base material. The inert filler serves as the support framework of the connection layer. By filling the pores and reducing the porosity, it is beneficial to improve the density and connection strength of the connection layer. And because its hardness and modulus are much higher than those of the ceramic matrix generated by the pyrolysis of the precursor, it can significantly improve the connection strength of the connection layer. The active filler can also form a glass phase at high temperature and fill the gaps in the connection layer, thereby improving the density and airtightness of the connection layer. Therefore, the present invention comprehensively promotes the connection density and connection strength of silicon carbide ceramics by preparing an organosilicon polymer precursor using the cross-linked network of organosilicon polymers and combining the filling and strengthening effects of inert fillers and active fillers. Description of the Drawings

[0022] Figure 1 It is the SEM diagram of the silicon carbide ceramic connection joint prepared in Example 1 of the present invention. Detailed Embodiments

[0023] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention is given.

[0024] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application;

[0025] As used herein, the term "comprising" and its variations are open-ended, i.e., "including but not limited to"; the term "based on" means "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiments". The relevant definitions of other terms will be given in the following description. It should be noted that the concepts of "first", "second", etc. mentioned in the present invention are used to distinguish different objects, rather than to describe a specific order or primary-secondary relationship. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present application, unless otherwise specified, the meaning of "a plurality" is two or more.

[0026] As a first aspect, an embodiment of the present invention provides a silicon carbide ceramic binder, and the silicon carbide ceramic binder comprises components in the following mass percentages: 30% to 80% of an organosilicon polymer precursor, 10% to 60% of an inert filler, and 1% to 50% of an active filler. The components of the organosilicon polymer precursor include vinylhydrogen polycarbosilane, a crosslinking agent, and an initiator. In the organosilicon polymer precursor, based on the mass of vinylhydrogen polycarbosilane being 100%, the addition amount of the crosslinking agent is 0.1% to 50%, and the addition amount of the initiator is 0.1% to 10%. Among them, the crosslinking agent includes any one or several of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 1,4-bis(ethenyldimethylsilyl)benzene, vinyl-POSS, and tris(isopropenyloxy)vinylsilane. The structural formula of vinylhydrogen polycarbosilane is as shown in formula (I):

[0027]

[0028] In formula (I), x is from 1 to 1000, and y is from 1 to 1000.

[0029] In the embodiments of the present invention, an organosilicon polymer precursor is prepared by selecting a specific crosslinking agent to carry out a crosslinking reaction with vinylhydrocarbyl polycarbosilane, so as to promote the connection between polymer chains and form a crosslinked network of high-density organosilicon polymer. The crosslinked network of organosilicon polymer can pyrolyze in situ at high temperature to generate silicon carbide with a high yield, improve the compatibility between the connection interface of silicon carbide base material and the connection layer, and simultaneously reduce the stress between the connection layer and the base material. The inert filler serves as the support framework of the connection layer. By filling pores and reducing the porosity, it is beneficial to improve the density and connection strength of the connection layer. And because its hardness and modulus are much higher than those of the ceramic matrix generated by the pyrolysis of the precursor, it can significantly improve the connection strength of the connection layer. The active filler can also form a glass phase at high temperature and fill the gaps in the connection layer, thereby improving the compactness and airtightness of the connection layer. Therefore, the present invention comprehensively promotes the connection compactness and connection strength of silicon carbide ceramics by preparing an organosilicon polymer precursor using the crosslinked network of organosilicon polymer and combining the filling and strengthening effects of inert filler and active filler.

[0030] In some alternative embodiments, in the organosilicon polymer precursor, the initiator includes any one or more of benzoyl peroxide, azobisisobutyronitrile, azobis(2,4-dimethylvaleronitrile), tert-butyl peroxybenzoate, methyl ethyl ketone peroxide, and diisopropyl peroxydicarbonate.

[0031] In the embodiments of the present invention, by selecting a specific initiator to control the progress of the crosslinking reaction, the crosslinking is made more uniform, avoiding the situations of local over-crosslinking or under-crosslinking, so that the silicon carbide generated by the pyrolysis of the crosslinked network of organosilicon polymer has a more uniform microstructure and improves the compatibility between the interface and the connection layer.

[0032] In some alternative embodiments, the inert filler includes silicon carbide powder or silicon carbide fiber. The particle size range of the silicon carbide powder is 50 nm to 100 μm, and the diameter range of the silicon carbide fiber is 10 nm to 50 μm.

[0033] In the embodiments of the present invention, the silicon carbide filler itself does not participate in chemical reactions. It mainly offsets the volume shrinkage during the pyrolysis of the precursor by physical filling, hinders crack propagation, and reduces the brittleness of the connection layer. The silicon carbide filler can also adjust the matching of the thermal expansion coefficients of the connection layer and the base material, reduce thermal stress, and improve the heat dissipation capacity of the connection layer. Specifically, silicon carbide fillers with different particle size dimensions can be added. The nano-scale silicon carbide filler is mainly used to fill micropores, and the micro-scale silicon carbide filler is mainly used to enhance mechanical properties.

[0034] In some alternative embodiments, the active filler includes any one or more of silicon powder, aluminum powder, zirconium powder, magnesium powder, titanium powder, alumina, silica, zirconia, titania, yttria, boron carbide, and zirconium boride. Among them, the particle size of the active filler is 10 nm to 100 μm.

[0035] In the embodiments of the present invention, the interfacial strengthening is achieved through in-situ chemical reactions by the active fillers. Among them, silicon powder can react with the products generated by the pyrolysis of the organosilicon polymer precursor at high temperature, such as silicon carbide, to fill the pores and improve the density. Meanwhile, in a nitrogen atmosphere, silicon nitride can also be generated. The introduction of silicon nitride can significantly enhance the high-temperature oxidation resistance and creep resistance of the bonding layer. For metal active fillers such as titanium powder and magnesium powder, titanium reacts with the free carbon generated by pyrolysis to form titanium carbide, thereby strengthening the interfacial bonding. Magnesium generates magnesium nitride in a nitrogen atmosphere and then hydrolyzes to form magnesium hydroxide, filling the pores. Moreover, the metal melt can wet the ceramic surface, promoting densification. For oxide active fillers, taking alumina as an example, alumina can react with the silica generated by the pyrolysis of the precursor to form mullite, enhancing the high-temperature oxidation resistance. At the same time, alumina can inhibit the oxidation of silicon carbide at high temperature, thereby delaying the degradation of its performance.

[0036] Further, as a preference, in the embodiments of the present invention, the components of the silicon carbide ceramic binder are formulated according to the following mass percentages: 55% to 70% of the organosilicon polymer precursor, 10% to 20% of the inert filler, and 15% to 30% of the active filler. Based on the mass of vinylhydrogen polysilane being 100%, the addition amount of the crosslinking agent is 6% to 12%, and the addition amount of the initiator is 1% to 3%.

[0037] The present invention finely regulates the addition amounts of the components in the silicon carbide ceramic binder, thereby facilitating the formation of a homogeneous joint with high densification and high joint strength. At the same time, based on the determined crosslinking agent and initiator, by finely regulating the addition amounts of the crosslinking agent and the initiator, it is beneficial for the organosilicon polymer precursor to pyrolyze at high temperature with a higher yield to generate silicon carbide ceramics with high density, low porosity, and high flexural strength, improving the compatibility between the bonding layer and the silicon carbide ceramic interface.

[0038] It should be noted that the preparation method of the silicon carbide ceramic binder in the embodiments of the present invention can be as follows: First, add the crosslinking agent and the initiator to the vinylhydrogen polysilane solution in sequence and mix evenly to obtain an organosilicon polymer precursor mixed solution; then add the inert filler and the active filler to the organosilicon polymer precursor mixed solution and mix evenly to obtain the silicon carbide ceramic binder.

[0039] Specifically, to promote the mixing effect, ultrasonic dispersion or ball milling-assisted dispersion can be used to promote the uniform distribution of the inert filler and the active filler in the organosilicon polymer precursor mixed solution.

[0040] As a second aspect, a bonding method for silicon carbide ceramics in the embodiments of the present invention includes: After coating the above-mentioned silicon carbide ceramic binder on the surface of the silicon carbide ceramic, thermal curing and thermal pyrolysis are carried out in sequence to obtain a silicon carbide ceramic bonded joint.

[0041] The silicon carbide ceramic binder in the embodiments of the present invention can be used for connecting two silicon carbide ceramic base materials. Specifically, the coating thickness of the silicon carbide ceramic binder can be 50 μm to 200 μm, which helps to avoid cracking caused by too thick a coating and insufficient connection strength caused by too thin a coating. In addition, in order to improve the coating effect and the penetration depth of the precursor, vacuum-assisted impregnation can be adopted.

[0042] In some alternative embodiments, the temperature for thermal curing is 50°C to 300°C, the time for thermal curing is 10 min to 24 h, the temperature for pyrolysis is 600°C to 1500°C, and the pyrolysis time is 10 min to 5 h.

[0043] In the embodiments of the present invention, both the thermal curing and pyrolysis processes can be carried out in an atmosphere such as air, nitrogen, argon, vacuum, etc., and the heating rate during the thermal curing and pyrolysis processes is 1 to 50°C / min. Specifically, the thermal curing operation in the embodiments of the present invention can include the following three stages: The first stage: First, raise the temperature from room temperature to 80 to 100°C at a heating rate of 20 to 25°C / min, and keep it at 80 to 100°C for 10 to 15 min; The second stage: Raise the temperature from 80 to 100°C to 150 to 200°C at a heating rate of 5 to 10°C / min, and keep it at 150 to 200°C for 5 to 10 min; The third stage: Raise the temperature from 150 to 200°C to 250 to 300°C at a heating rate of 15 to 20°C / min, and keep it at 250 to 300°C for 10 min to 24 h. By adopting stepwise heating, the bubbling phenomenon caused by rapid heating can be avoided.

[0044] Correspondingly, the pyrolysis operation in the embodiments of the present invention can include: The fourth stage: First, raise the temperature from 250 to 300°C to 500 to 600°C at a heating rate of 3 to 5°C / min, and keep it for 10 min to 30 min, so as to avoid cracks caused by the violent decomposition of the precursor in the initial stage of pyrolysis; The fifth stage: Raise the temperature from 500 to 600°C to 1200 to 1500°C at a heating rate of 25 to 50°C / min, and keep it for 2 h to 5 h to balance the heating efficiency and thermal stress.

[0045] In the embodiments of the present invention, by first promoting the occurrence of cross-linking reaction at a lower thermal curing temperature, the preliminary connection of silicon carbide ceramics can be achieved, and then by performing heat treatment at a higher temperature, the initially formed adhesive structure can be transformed into a dense and homogeneous joint, thereby obtaining a joint with higher connection strength.

[0046] As a third aspect, a silicon carbide ceramic connection joint in the embodiments of the present invention is prepared by using the above-mentioned connection method of silicon carbide ceramics.

[0047] The present invention will be described in detail below through specific embodiments:

[0048] Example 1

[0049] (1) Preparation of silicon carbide ceramic binder

[0050] S11: Add a crosslinking agent and an initiator to the vinylhydrocarbyl polycarbosilane solution in sequence. Among them, based on the mass of the vinylhydrocarbyl polycarbosilane solution being 100%, the addition amount of the crosslinking agent is 0.1%, and the addition amount of the initiator is 0.1%. Mix evenly to obtain a mixed solution of organosilicon polymer precursor.

[0051] S12: Add an inert filler and an active filler to the mixed solution of organosilicon polymer precursor, and perform ultrasonic-assisted dispersion to mix evenly to obtain a silicon carbide ceramic binder. Among them, the silicon carbide ceramic binder in this example includes the following components in mass percentage: 80% of organosilicon polymer precursor, 10% of inert filler, and 10% of active filler.

[0052] In this example, the crosslinking agent is 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, the initiator is benzoyl peroxide, the inert filler is silicon carbide powder, and the active filler is aluminum powder.

[0053] (2) Joining of silicon carbide ceramics

[0054] S21: Use vacuum-assisted impregnation to coat the silicon carbide ceramic binder prepared in this example on the surface of the silicon carbide ceramic.

[0055] S22: Under a nitrogen atmosphere, first increase the temperature from room temperature to 80°C at a heating rate of 20°C / min, and keep it at 80°C for 10 min; then increase the temperature from 80°C to 180°C at a heating rate of 10°C / min, and keep it at 180°C for 10 min; then increase the temperature from 180°C to 300°C at a heating rate of 20°C / min, and keep it at 300°C for 10 min to complete the thermal curing process.

[0056] S23: Continue under a nitrogen atmosphere. First increase the temperature from 300°C to 500°C at a heating rate of 5°C / min, keep it for 30 min, and then increase the temperature from 500°C to 1500°C at a heating rate of 30°C / min, keep it for 2 h to complete the thermal cracking process, and obtain a silicon carbide ceramic joined joint.

[0057] The SEM image of the silicon carbide ceramic joined joint obtained in this example is as shown in Figure 1 shown, Figure 1 in which, both base materials of the silicon carbide ceramic joined joint are silicon carbide ceramics, and between the base materials is a joining layer, and the joining layer is formed by curing and cracking of the silicon carbide ceramic binder. FromFigure 1 It can be visually reflected that the connection method of this embodiment can obtain a dense silicon carbide ceramic connection joint.

[0058] Example 2

[0059] The difference between this embodiment and Example 1 is as follows:

[0060] In the preparation process of the silicon carbide ceramic binder, based on the mass of the vinylhydrocarbyl polycarbosilane solution being 100%, the addition amount of the crosslinking agent is 4%, and the addition amount of the initiator is 0.8%. The silicon carbide ceramic binder in this embodiment comprises the following components by mass percentage: 55% of organosilicon polymer precursor, 30% of inert filler, and 15% of active filler. Among them, the crosslinking agent is 1,4-bis(ethenyldimethylsilyl)benzene, the initiator is azobisisobutyronitrile, the inert filler is silicon carbide fiber, and the active filler is silicon powder.

[0061] The connection process of the silicon carbide ceramic specifically includes:

[0062] S21: The silicon carbide ceramic binder prepared in this embodiment is coated on the surface of the silicon carbide ceramic by vacuum-assisted impregnation.

[0063] S22: Under a nitrogen atmosphere, first raise the temperature from room temperature to 100 °C at a heating rate of 25 °C / min and hold for 15 min at 100 °C; then raise the temperature from 100 °C to 200 °C at a heating rate of 5 °C / min and hold for 5 min at 200 °C; then raise the temperature from 200 °C to 250 °C at a heating rate of 15 °C / min and hold for 50 min at 250 °C to complete the thermal curing process.

[0064] S23: Continuing under a nitrogen atmosphere, first raise the temperature from 250 °C to 600 °C at a heating rate of 5 °C / min, hold for 10 min, and then raise the temperature from 600 °C to 1200 °C at a heating rate of 50 °C / min and hold for 4 h to complete the thermal cracking process, obtaining a silicon carbide ceramic connection joint.

[0065] Example 3

[0066] The difference between this embodiment and Example 1 is as follows:

[0067] In the preparation process of the silicon carbide ceramic binder, based on the mass of the vinylhydrocarbyl polycarbosilane solution being 100%, the addition amount of the crosslinking agent is 6%, and the addition amount of the initiator is 1%. The silicon carbide ceramic binder in this embodiment comprises the following components by mass percentage: 70% of organosilicon polymer precursor, 10% of inert filler, and 20% of active filler. Among them, the crosslinking agent is vinyl-POSS, the initiator is tris(isopropenyloxy)vinylsilane, and the active filler is titanium oxide.

[0068] Example 4

[0069] The difference between this example and Example 1 is that:

[0070] In the preparation process of the silicon carbide ceramic binder, based on the mass of the vinylhydridopolycarbosilane solution being 100%, the addition amount of the crosslinking agent is 10%, and the addition amount of the initiator is 1.8%. The silicon carbide ceramic binder in this example includes the following components by mass percentage: 65% of the organosilicon polymer precursor, 20% of the inert filler, and 15% of the active filler. Among them, the crosslinking agent is tris(isopropenyloxy)vinylsilane, the initiator is tert-butyl peroxybenzoate, the inert filler is silicon carbide fiber, and the active filler is boron carbide.

[0071] Example 5

[0072] The difference between this example and Example 1 is that:

[0073] In the preparation process of the silicon carbide ceramic binder, based on the mass of the vinylhydridopolycarbosilane solution being 100%, the addition amount of the crosslinking agent is 12%, and the addition amount of the initiator is 3%. The silicon carbide ceramic binder in this example includes the following components by mass percentage: 55% of the organosilicon polymer precursor, 15% of the inert filler, and 30% of the active filler. Among them, the crosslinking agent is tris(isopropenyloxy)vinylsilane, the initiator is tert-butyl peroxybenzoate, the inert filler is silicon carbide fiber, and the active filler is boron carbide.

[0074] Example 6

[0075] The difference between this example and Example 1 is that:

[0076] In the preparation process of the silicon carbide ceramic binder, based on the mass of the vinylhydridopolycarbosilane solution being 100%, the addition amount of the crosslinking agent is 25%, and the addition amount of the initiator is 5%. The silicon carbide ceramic binder in this example includes the following components by mass percentage: 30% of the organosilicon polymer precursor, 50% of the inert filler, and 20% of the active filler.

[0077] Example 7

[0078] The difference between this example and Example 1 is that:

[0079] In the preparation process of the silicon carbide ceramic binder, based on the mass of the vinylhydridopolycarbosilane solution being 100%, the addition amount of the crosslinking agent is 25%, and the addition amount of the initiator is 5%. The silicon carbide ceramic binder in this example includes the following components by mass percentage: 40% of the organosilicon polymer precursor, 10% of silicon carbide fiber, and 50% of the active filler.

[0080] Comparative Example 1

[0081] The difference between this comparative example and Example 1 is that no crosslinking agent and initiator are added to the silicon carbide ceramic binder in this comparative example. The silicon carbide ceramic binder comprises the following components in mass percentages: 80% of vinylhydridopolycarbosilane, 10% of silicon carbide powder, and 10% of aluminum powder.

[0082] Comparative Example 2

[0083] The difference between this comparative example and Example 1 is that no inert filler and active filler are added to the silicon carbide ceramic binder in this comparative example.

[0084] Comparative Example 3

[0085] The difference between this comparative example and Example 1 is that during the connection process of the silicon carbide ceramic, after the silicon carbide ceramic binder is coated on the surface of the silicon carbide ceramic, the silicon carbide ceramic is directly placed in a nitrogen atmosphere for pyrolysis. The pyrolysis temperature is 1500 °C, and the heat preservation time is 2 h.

[0086] The comparison data of the density and the shear strength at room temperature of the silicon carbide ceramic connection joints in Examples 1-7 and Comparative Examples 1-3 are shown in Table 1:

[0087] Table 1 Comparison data of the density and the shear strength at room temperature of the silicon carbide ceramic connection joints in Examples 1-7 and Comparative Examples 1-3

[0088]

[0089] In Table 1, the addition amounts of the crosslinking agent and the initiator refer to the addition amounts calculated based on the mass of the vinylhydridopolycarbosilane solution in the organosilicon polymer precursor being 100%, and " / " indicates that the addition amount is 0. As can be seen from Table 1, in Comparative Example 1, an uncrosslinked organosilicon polymer is used as the precursor, and the density and connection strength of the obtained connection joint are both poor; in Comparative Example 2, no inert filler and active filler are added to the binder, and the corresponding density and connection strength are at a relatively low level; in Comparative Example 3, the silicon carbide ceramic coated with the binder is directly heat-treated at a high temperature. Although the shear strength of the obtained connection joint reaches 78.4 MPa, the densification degree is still poor.

[0090] Furthermore, when the addition amount of the crosslinking agent in the organosilicon polymer precursor is 6%-12%, the addition amount of the initiator is 1%-3%, and the addition amounts of the inert filler and the active filler are 10%-20% and 15%-30% respectively, the density of the silicon carbide ceramic connection joint reaches more than 85%, and the shear strength also reaches more than 85 MPa, that is, the silicon carbide ceramic connection joint has more excellent density and connection strength.

[0091] Although the present invention is disclosed as above, the scope of protection of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will all fall within the scope of protection of the present invention.

Claims

1. A silicon carbide ceramic bonding agent, characterized in that: The invention comprises the following components in percentage by weight: 30% to 80% of an organosilicon polymer precursor, 10% to 60% of an inert filler and 1% to 50% of an active filler; The components of the organosilicon polymer precursor include vinyl hydrogen polycarbosilane, a crosslinking agent and an initiator. In the organosilicon polymer precursor, based on the mass of the vinyl hydrogen polycarbosilane as 100%, the added amount of the crosslinking agent is 0.1% to 50%, and the added amount of the initiator is 0.1% to 10%; Wherein, the crosslinking agent includes any one or more of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 1,4-bis(vinyldimethylsilyl)benzene, vinyl-POSS and tri(isoallyloxy)vinylsilane, and the structural formula of vinyl hydrogen polycarbosilane is shown in formula (I): In the formula (I), x is 1 to 1,000, and y is 1 to 1,000.

2. The silicon carbide ceramic bonding agent according to claim 1, characterized in that: The initiator includes any one or more of benzoyl peroxide, azobisisobutyronitrile, azobisisoheptanenitrile, tert-butyl perbenzoate, methyl ethyl ketone peroxide, and diisopropyl peroxydicarbonate.

3. The silicon carbide ceramic bonding agent according to claim 1, characterized in that: The inert filler includes silicon carbide powder or silicon carbide fiber. The particle size of the silicon carbide powder is 50 nm to 100 μm, and the diameter of the silicon carbide fiber is 10 nm to 50 μm.

4. The silicon carbide ceramic bonding agent according to claim 1, characterized in that: The active filler includes any one or more of silicon powder, aluminum powder, zirconium powder, magnesium powder, titanium powder, aluminum oxide, silicon oxide, zirconium oxide, titanium oxide, yttrium oxide, boron carbide, and boron zirconide.

5. The silicon carbide ceramic bonding agent according to claim 4, characterized in that: The particle size of the active filler is 10 nm to 100 μm.

6. The silicon carbide ceramic bonding agent according to claim 1, characterized in that: The silicon carbide ceramic connecting agent comprises the following components in percentage by mass: 55% to 70% of an organosilicon polymer precursor, 10% to 20% of an inert filler, and 15% to 30% of an active filler; In the organosilicon polymer precursor, based on 100% of the mass of the vinyl hydrogen polycarbosilane, the added amount of the crosslinking agent is 6% to 12%, and the added amount of the initiator is 1% to 3%.

7. A method for connecting silicon carbide ceramics, characterized in that: include: After the silicon carbide ceramic connecting agent according to any one of claims 1 to 6 is coated on the surface of the silicon carbide ceramic, thermal curing and thermal cracking are sequentially performed to obtain a silicon carbide ceramic connecting joint.

8. The method for connecting silicon carbide ceramics according to claim 7, characterized in that: The temperature of the thermal curing is 50°C to 300°C, the time of the thermal curing is 10 minutes to 24 hours, the temperature of the thermal cracking is 600°C to 1500°C, and the heat treatment time is 10 minutes to 5 hours.

9. The method for connecting silicon carbide ceramics according to claim 8, characterized in that: The thermal curing comprises: The first stage: the temperature is increased from room temperature to 80 to 100°C at a heating rate of 20 to 25°C / min; The second stage: the temperature is increased from 80 to 100°C to 150 to 200°C at a heating rate of 5 to 10°C / min; The third stage: the temperature is increased from 150 to 200°C to 250 to 300°C at a heating rate of 15 to 20°C / min; The thermal cracking comprises: The temperature was increased from 250 to 300°C to 500 to 600°C at a heating rate of 3 to 5°C / min; The temperature is then increased from 500 to 600°C to 1200 to 1500°C at a heating rate of 25 to 50°C / min.

10. A silicon carbide ceramic connection joint, characterized in that: The silicon carbide ceramic connection joint is prepared by the silicon carbide ceramic connection method described in any one of claims 7-9.

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