Silicon carbide composite cladding connecting method and silicon carbide composite cladding

Abstract

The invention discloses a silicon carbide composite cladding connecting method and a silicon carbide composite cladding, and the connecting method comprises the following steps: S1, machining an end plug, and forming a T-shaped end at the first end of the end plug; s2, the T-shaped end of the end plug is matched with the inner-layer core mold; s3, arranging silicon carbide fibers on the outer surfaces of the inner-layer core mold and the end plugs to form a silicon carbide braid layer; s4, performing carbon deposition on the silicon carbide braid layer to form an interface layer on the surface of the silicon carbide fiber; s5, carrying out densification treatment on the silicon carbide braid layer; and S6, depositing a silicon carbide outer layer on the densified silicon carbide braid layer. According to the method, the inner core mold and the end plug are fixed preferentially, then the silicon carbide braid layer is arranged on the outer side and densified, and finally the cladding pipe is formed by matching with the silicon carbide outer layer, so that the connection reliability of the end plug and the cladding is improved, the air tightness and the corrosion resistance are improved, and the operation safety of the nuclear power station is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of cladding tubes, and in particular to a silicon carbide composite cladding connection method and a silicon carbide composite cladding. Background Art

[0002] Silicon carbide fiber reinforced silicon carbide (SiCf / SiC) composite materials have the characteristics of low neutron toxicity, neutron irradiation resistance and high temperature oxidation resistance, and have become important candidate structural materials for advanced nuclear energy systems. After the silicon carbide cladding tube is loaded with nuclear fuel, it needs to be sealed by an end plug. The reliability of the end plug-cladding connection has become one of the key technical issues restricting the final application of SiCf / SiC composite materials, and is directly related to the safety issues of the reactor, such as the leakage of highly radioactive fission products, the escape of fission gas, and the isolation of coolant and nuclear fuel.

[0003] At present, in order to improve the reliability of the connection between the end plug and the cladding, a lot of research has been carried out at home and abroad on the connection of SiC ceramics and SiCf / SiC composite materials. The more common connection methods include active metal brazing, diffusion bonding, glass ceramic bonding, Si-C reaction bonding, ceramic precursor bonding, transient eutectic phase bonding and MAX phase bonding. However, these research works mainly focus on improving the connection method, connection process, end plug processing, etc. The connection layer materials will directly contact the coolant, and there is a risk of damage to the end plug-cladding connection joint.

[0004] An existing method for welding and packaging SiCf / SiC cladding tubes uses a coating process to coat the surface of the cladding tube without changing the existing Zr alloy end plug design, combining thermal spray coating technology and electron beam welding technology to quickly achieve in-situ connection using SiCf / SiC cladding tubes. Another cladding tube packaging method is to provide a groove on the end of the SiC / SiC composite nuclear cladding tube, fix the cladding tube and the end plug by rivets, and use an end plug-cladding connector material with a similar thermal expansion coefficient and good wettability. However, the mechanical strength and air tightness of the end plug-cladding tube connection obtained by the current process are still difficult to guarantee, and the connection area is easily interacted with the coolant, resulting in a decrease in corrosion resistance. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide an improved silicon carbide composite cladding connection method and a silicon carbide composite cladding formed by the connection method.

[0006] The technical solution adopted by the present invention to solve the technical problem is: to provide a method for connecting a silicon carbide composite cladding, comprising the following steps:

[0007] S1, processing an end plug, wherein the first end of the end plug forms a T-shaped end;

[0008] S2, matching the T-shaped end of the end plug with the inner core mold;

[0009] S3, arranging silicon carbide fibers on the outer surfaces of the inner core mold and the end plug to form a silicon carbide braided layer;

[0010] S4, performing carbon deposition on the silicon carbide braided layer to form an interface layer on the surface of the silicon carbide fiber;

[0011] S5, performing densification treatment on the silicon carbide braided layer;

[0012] S6. Depositing a silicon carbide outer layer on the densified silicon carbide braided layer.

[0013] Preferably, step S1 further includes: processing the second end of the end plug to form an hourglass-shaped clamping end; and before step S6, it also includes cutting off part of the clamping end of the end plug.

[0014] Preferably, step S1 further comprises: machining a groove on the outer circumference of the end plug, wherein the groove is located between the first end and the second end of the end plug; and in step S3, the silicon carbide braided layer also covers the groove.

[0015] Preferably, the cross-sectional shape of the groove is conical or trapezoidal.

[0016] Preferably, in step S1, the maximum outer diameter of the end plug is the same as the outer diameter of the inner core mold.

[0017] Preferably, in step S2, the length of the T-shaped end of the end plug fitted into the inner core mold is 1 to 15 mm.

[0018] Preferably, in step S2, a connecting material is provided on the mating surfaces of the T-shaped end and the inner core mold; the connecting material is silicon carbide ceramic slurry or ceramic adhesive.

[0019] Preferably, in step S4, carbon deposition is performed on the silicon carbide braided layer by chemical vapor deposition.

[0020] Preferably, in step S5, the densification treatment method includes at least one of chemical vapor infiltration and impregnation cracking process; the densification temperature is 900° C. to 1300° C., and the densification time is 10 h to 600 h.

[0021] Preferably, step S5 comprises:

[0022] S5.1, performing fiber curing and shaping treatment on the silicon carbide braided layer;

[0023] S5.2, removing the inner core mold;

[0024] S5.3. Densification treatment is performed on the silicon carbide braided layer.

[0025] Preferably, in step S6, the inner core mold is retained inside the silicon carbide braided layer; and the inner core mold is formed by a silicon carbide tube.

[0026] The present invention also provides a silicon carbide composite cladding formed by any of the above silicon carbide composite cladding connection methods.

[0027] The beneficial effects of the present invention are as follows: by preferentially fixing the inner core mold and the end plug, then arranging the silicon carbide braided layer and densification on the outside, and finally combining the silicon carbide outer layer to form a cladding tube, this method is beneficial to improving the reliability of the connection between the end plug and the cladding, improving the air tightness and corrosion resistance, thereby improving the safety of nuclear power plant operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0029] Figure 1 It is a schematic diagram of the matching structure of the end plug and the inner core mold in the silicon carbide composite cladding connection method of the first embodiment of the present invention;

[0030] Figure 2 It is a schematic diagram of a part of the structure of the silicon carbide composite cladding obtained by the silicon carbide composite cladding connection method according to the first embodiment of the present invention;

[0031] Figure 3 It is a schematic diagram of the matching structure of the end plug and the inner core mold in the silicon carbide composite cladding connection method according to the second embodiment of the present invention;

[0032] Figure 4 is a schematic diagram of a portion of the structure of a silicon carbide composite cladding obtained by a method for connecting a silicon carbide composite cladding according to a second embodiment of the present invention;

[0033] Figure 5 It is a schematic diagram of the matching structure of the end plug and the inner core mold in the silicon carbide composite cladding connection method according to the third embodiment of the present invention;

[0034] Figure 6 It is a schematic diagram of a portion of the structure of a silicon carbide composite cladding obtained by a silicon carbide composite cladding connection method according to a third embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0036] like Figure 1-Figure 2 As shown, the silicon carbide composite cladding connection method of the first embodiment of the present invention at least comprises the following steps:

[0037] S1. Processing end plug 10.

[0038] The end plug 10 is a silicon carbide end plug having a first end and a second end opposite to each other. The first end of the end plug 10 is processed to form a T-shaped end 11, and the second end of the end plug 10 is used as a clamping end 12 for clamping the end plug with a clamping tool.

[0039] The overall length of the end plug 10 is greater than the length of the end plug of the silicon carbide composite cladding to provide a processing margin and a clamping positioning margin.

[0040] On the T-shaped end 11 of the end plug 10 , the end surface is the transverse part of the T shape, and the part protruding outward on the end surface is the vertical part of the T. The vertical part of the T-shaped end 11 is used to cooperate with the inner core mold 20 .

[0041] During the connection process, the second end of the end plug 10 is clamped by a clamping tool to fix the end plug. In order to facilitate clamping and subsequent cutting of the redundant part of the end plug, the clamping end 12 can be processed into an hourglass shape.

[0042] Further, as required, a groove 13 may be machined on the outer circumference of the end plug 10, and the groove 13 is located between the first end and the second end of the end plug. The cross-sectional shape of the groove 13 may be, but is not limited to, a cone or a trapezoid.

[0043] S2. Provide an inner core mold 20, match the T-shaped end 11 of the end plug 10 with the inner core mold 20, and fix the end plug 10 on the end of the inner core mold 20 to form a preform.

[0044] The maximum outer diameter of the end plug 10 is the same as the outer diameter of the inner core mold 20. The outer diameter of the inner core mold 20 is 7 mm to 9 mm.

[0045] The inner core mold 20 is preferably a core mold tube made of graphite or glass. When matched with the inner core mold 20, the T-shaped end 11 of the end plug 10 is matched with the end of the inner core mold 20 with the part protruding outward on the end surface. The length of the T-shaped end 11 matched in the inner core mold 20 is 1mm to 15mm.

[0046] The T-shaped end 11 of the end plug 10 and the inner core mold 20 can be further connected by at least one of mechanical connection, reaction connection, and adhesive connection. Among them, the mechanical connection includes riveting or taper matching. The reaction connection can be achieved by ceramic slurry connection. Adhesive bonding can be achieved by ceramic adhesives, and the ceramic adhesives further include ceramic organic adhesives and ceramic inorganic adhesives. The ceramic organic adhesives mainly include: epoxy system ceramic adhesives, silicone system adhesives, and acrylic system adhesives; ceramic inorganic adhesives mainly include: silicate adhesives, phosphate adhesives, aluminates, etc.

[0047] S3, disposing silicon carbide fibers on the outer surfaces of the inner core mold 20 and the end plug 10 to form a silicon carbide braided layer 30.

[0048] The silicon carbide braided layer 30 covers the inner core mold 20 and the outer surface of the end plug 10. On the outer surface of the end plug 10, the silicon carbide braided layer 30 mainly covers the T-shaped end 11 of the end plug 10, and also covers the groove 13, and can appropriately cover the clamping end 12 of the end plug 10 or part of the outer surface of the clamping end 12.

[0049] The groove 13 and the silicon carbide braided layer 30 are also arranged in the groove 13 to improve the stability of the end plug 10 and to prevent the end plug 10 from moving when the inner core mold 20 is subsequently removed.

[0050] The arrangement of the silicon carbide fibers is not limited, and may be at least one of weaving, braiding, and winding.

[0051] S4. Interface layer deposition.

[0052] In this step, carbon deposition is performed on the silicon carbide braided layer 30 by chemical vapor deposition to form an interface layer on the surface of the silicon carbide fiber, which also serves as a pretreatment for the subsequent densification treatment, and is beneficial to the coupling transfer of force, heat, electricity and other properties between the silicon carbide fiber and the subsequently deposited matrix material (silicon carbide).

[0053] In one embodiment, the preform with the silicon carbide braided layer 30 is placed in a reaction furnace, and propane (deposition carbon source) and argon are introduced. In the argon atmosphere, carbon is deposited on the surface of the silicon carbide fiber by pyrolysis carbon reaction to form an interface layer. The thickness of the interface layer is 100nm to 500nm.

[0054] S5. Densification treatment is performed on the silicon carbide braided layer 30.

[0055] After the interface layer is prepared, the silicon carbide braided layer 30 is densified by at least one of chemical vapor infiltration (CVI) and impregnation pyrolysis process (PIP), wherein the densification temperature is 900° C. to 1300° C. and the densification time is 10 hours to 600 hours.

[0056] For the chemical vapor infiltration method: the preform with the silicon carbide braided layer 30 is placed in the CVI reaction chamber, and the gaseous precursor of SiC is introduced. The precursor is directed to the silicon carbide braided layer, and diffuses through the pores of the silicon carbide braided layer 30 to the surface of the SiC fiber by diffusion, thereby chemically reacting to form a SiC matrix. The gaseous precursor of SiC is trichloromethylsilane (MTS, which enters the chamber with the carrier gas hydrogen through the bubbling method), and the gas atmosphere is hydrogen and argon.

[0057] For the impregnation cracking process: the precursor solution is impregnated into the silicon carbide braided layer 30 under vacuum conditions, and then the precursor is cross-linked and solidified in situ under certain conditions, and then cracked at high temperature to form a SiC ceramic matrix, and this is repeated to achieve the densification of the silicon carbide braided layer 30 through multiple impregnation / cracking processes. The raw material of the precursor solution is solid polycarbosilane (PCS), and the solvent is xylene. Argon is used as the cracking gas.

[0058] In this embodiment, before subsequently depositing the silicon carbide outer layer 40, the inner core mold 20 is removed. To this end, the step S5 may specifically include:

[0059] S5.1, performing fiber curing and shaping treatment on the silicon carbide braided layer 30;

[0060] S5.2, removing the inner core mold 20;

[0061] S5.3, densify the silicon carbide braided layer 30. The specific operation of the fiber curing and shaping treatment can refer to the densification treatment method (using CVI or PIP), or it can be the early stage of the densification treatment. For example, during the densification process, after the fibers in the silicon carbide braided layer 30 have reached the curing and shaping effect in the early treatment process, the inner core mold 20 is removed, and the silicon carbide braided layer 30 will not be deformed at this time. After removing the inner core mold 20, the densification post-treatment is continued.

[0062] S6. Part of the clamping end 12 of the end plug 10 is cut off, and a silicon carbide outer layer 40 is deposited on the densified silicon carbide braided layer 30 to obtain a silicon carbide composite cladding. The density of the silicon carbide composite cladding is greater than 2.7 g / cm 3 .

[0063] exist Figure 2 In the illustrated embodiment, the position where the clamping end 12 is cut off is located on the side of the funnel neck close to the T-shaped end 11 , and the end plug 10 after the cut off has the T-shaped end 11 , the section where the groove 13 is located, and part of the clamping end 12 .

[0064] The silicon carbide outer layer 40 may be deposited by chemical vapor infiltration. The silicon carbide outer layer 40 covers the silicon carbide braided layer 30 and the cut surface of the end plug 10 after removal. The thickness of the silicon carbide outer layer 40 is greater than 100 μm.

[0065] The silicon carbide composite cladding obtained by the above connection method has a two-layer structure of the cladding tube part, which is a dense silicon carbide braided layer and a silicon carbide outer layer from the inside to the outside. The end plug part of the silicon carbide composite cladding includes an end plug body and a silicon carbide braided layer and a silicon carbide outer layer formed on the outer surface of the end plug body.

[0066] like Figure 3-Figure 4As shown, the silicon carbide composite cladding connection method of the second embodiment of the present invention comprises at least the following steps:

[0067] S1. Processing end plug 10.

[0068] The end plug 10 is a silicon carbide end plug having a first end and a second end opposite to each other. The first end of the end plug is processed to form a T-shaped end 11, and the second end of the end plug 10 is used as a clamping end 12 for clamping the end plug with a clamping tool.

[0069] The overall length of the end plug 10 is greater than the length of the end plug of the silicon carbide composite cladding to provide a processing margin and a clamping positioning margin.

[0070] On the T-shaped end 11 of the end plug 10, the end surface is the transverse part of the T shape, and the part protruding outward on the end surface is the vertical part of the T. The vertical part of the T-shaped end 11 is used to cooperate with the inner core mold.

[0071] During the connection process, the second end of the end plug 10 is clamped by a clamping tool to fix the end plug 10. In order to facilitate clamping and subsequent cutting of the redundant part of the end plug, the clamping end 12 can be processed into an hourglass shape.

[0072] Further, as required, a groove 13 may be machined on the outer circumference of the end plug 10, and the groove 13 is located between the first end and the second end of the end plug 10. The cross-sectional shape of the groove 13 may be, but is not limited to, a cone or a trapezoid.

[0073] S2. Provide an inner core mold 20, match the T-shaped end 11 of the end plug 10 with the inner core mold 20, and fix the end plug 10 on the end of the inner core mold 20 to form a preform.

[0074] The maximum outer diameter of the end plug 10 is the same as the outer diameter of the inner core mold 20. The outer diameter of the inner core mold 20 is 7 mm to 9 mm.

[0075] In this embodiment, the inner core mold 20 is formed of a silicon carbide tube. When mating with the inner core mold 20, the T-shaped end 11 of the end plug 10 is mated with the outwardly protruding portion on the end surface into the end of the inner core mold 20. The length of the T-shaped end 11 mated in the inner core mold 20 is 1 mm to 15 mm.

[0076] The T-shaped end 11 of the end plug 10 and the inner core mold 20 can be further connected by at least one of mechanical connection, reaction connection, and adhesive connection. Among them, the mechanical connection includes riveting or taper matching. The reaction connection can be achieved by ceramic slurry connection. Adhesive bonding can be achieved by ceramic adhesives, and the ceramic adhesives further include ceramic organic adhesives and ceramic inorganic adhesives. The ceramic organic adhesives mainly include: epoxy system ceramic adhesives, silicone system adhesives, and acrylic system adhesives; ceramic inorganic adhesives mainly include: silicate adhesives, phosphate adhesives, aluminates, etc.

[0077] S3, disposing silicon carbide fibers on the outer surfaces of the inner core mold 20 and the end plug 10 to form a silicon carbide braided layer 30.

[0078] The silicon carbide braided layer 30 covers the inner core mold 20 and the outer surface of the end plug 10. On the outer surface of the end plug 10, the silicon carbide braided layer 30 mainly covers the T-shaped end 11 of the end plug 10, and also covers the groove 13, and can appropriately cover the clamping end 12 of the end plug 10 or part of the outer surface of the clamping end 12.

[0079] The groove 13 and the silicon carbide braided layer 30 are also arranged in the groove 13 to improve the stability of the end plug 10 at the end of the inner core mold 20.

[0080] The arrangement of the silicon carbide fibers is not limited, and may be at least one of weaving, braiding, and winding.

[0081] S4. Interface layer deposition.

[0082] In this step, carbon deposition is performed on the silicon carbide braided layer 30 by chemical vapor deposition to form an interface layer on the surface of the silicon carbide fiber, which also serves as a pretreatment for the subsequent densification treatment, and is beneficial to the coupling transfer of force, heat, electricity and other properties between the silicon carbide fiber and the subsequently deposited matrix material (silicon carbide).

[0083] In one embodiment, the preform with the silicon carbide braided layer 30 is placed in a reaction furnace, and propane (deposition carbon source) and argon are introduced. In the argon atmosphere, carbon is deposited on the surface of the silicon carbide fiber by pyrolysis carbon reaction to form an interface layer. The thickness of the interface layer is 100nm to 500nm.

[0084] S5. Densification treatment is performed on the silicon carbide braided layer 30.

[0085] After the interface layer is prepared, the silicon carbide braided layer 30 is densified by at least one of chemical vapor infiltration (CVI) and impregnation pyrolysis process (PIP), wherein the densification temperature is 900° C. to 1300° C. and the densification time is 10 hours to 600 hours.

[0086] For the chemical vapor infiltration method: the preform with the silicon carbide braided layer 30 is placed in the CVI reaction chamber, and the gaseous precursor of SiC is introduced. The precursor is directed to the silicon carbide braided layer, and diffuses through the pores of the silicon carbide braided layer 30 to the surface of the SiC fiber by diffusion, thereby chemically reacting to form a SiC matrix. The gaseous precursor of SiC is trichloromethylsilane (MTS, which enters the chamber with the carrier gas hydrogen through the bubbling method), and the gas atmosphere is hydrogen and argon.

[0087] For the impregnation cracking process: the precursor solution is impregnated into the silicon carbide braided layer 30 under vacuum conditions, and then the precursor is cross-linked and solidified in situ under certain conditions, and then cracked at high temperature to form a SiC ceramic matrix, and this is repeated to achieve the densification of the silicon carbide braided layer 30 through multiple impregnation / cracking processes. The raw material of the precursor solution is solid polycarbosilane (PCS), and the solvent is xylene. Argon is used as the cracking gas.

[0088] S6. Part of the clamping end 12 of the end plug 10 is cut off; on the basis of retaining the inner core mold 20, a silicon carbide outer layer 40 is deposited on the densified silicon carbide braided layer 30 to obtain a silicon carbide composite cladding. The density of the silicon carbide composite cladding is greater than 2.7g / cm 3 .

[0089] exist Figure 4 In the illustrated embodiment, the position where the clamping end 12 is cut off is located on the side of the funnel neck close to the T-shaped end. The end plug 10 after the cut off has the T-shaped end 11, the section where the groove 13 is located, and part of the clamping end 12.

[0090] The silicon carbide outer layer 40 may be deposited by chemical vapor infiltration. The silicon carbide outer layer 40 covers the silicon carbide braided layer 30 and the cut surface of the end plug 10 after removal. The thickness of the silicon carbide outer layer 40 is greater than 100 μm.

[0091] The silicon carbide composite cladding obtained by the above connection method has a three-layer structure of the cladding tube part, which includes a silicon carbide tube, a dense silicon carbide braided layer and a silicon carbide outer layer from the inside to the outside. The end plug part of the silicon carbide composite cladding includes an end plug body and a silicon carbide braided layer and a silicon carbide outer layer formed on the outer surface of the end plug body.

[0092] like Figure 5-Figure 6 As shown, the silicon carbide composite cladding connection method of the third embodiment of the present invention comprises at least the following steps:

[0093] S1. Processing end plug 10.

[0094] The end plug 10 is a silicon carbide end plug having a first end and a second end opposite to each other. The first end of the end plug is processed to form a T-shaped end 11, and the second end of the end plug 10 is used as a clamping end 12 for clamping the end plug with a clamping tool.

[0095] The overall length of the end plug 10 is greater than the length of the end plug of the silicon carbide composite cladding to provide a processing margin and a clamping positioning margin.

[0096] On the T-shaped end 11 of the end plug 10, the end surface is the transverse part of the T shape, and the part protruding outward on the end surface is the vertical part of the T. The vertical part of the T-shaped end 11 is used to cooperate with the inner core mold.

[0097] During the connection process, the second end of the end plug 10 is clamped by a clamping tool to fix the end plug. In order to facilitate clamping and subsequent cutting of the redundant part of the end plug, the clamping end 12 can be processed into an hourglass shape.

[0098] S2. Provide an inner core mold 20, match the T-shaped end 11 of the end plug 10 with the inner core mold 20, and fix the end plug 10 on the end of the inner core mold 20 to form a preform.

[0099] The maximum outer diameter of the end plug 10 is the same as the outer diameter of the inner core mold 20. The outer diameter of the inner core mold 20 is 7 mm to 9 mm.

[0100] In this embodiment, the inner core mold 20 is formed of a silicon carbide tube. When mating with the inner core mold 20, the T-shaped end 11 of the end plug 10 is mated with the outwardly protruding portion on the end surface into the end of the inner core mold 20. The length of the T-shaped end 11 mated in the inner core mold 20 is 1 mm to 15 mm.

[0101] The T-shaped end 11 of the end plug 10 and the inner core mold 20 can be further connected by at least one of mechanical connection, reaction connection, and adhesive connection. Among them, the mechanical connection includes riveting or taper matching. The reaction connection can be achieved by ceramic slurry connection. Adhesive bonding can be achieved by ceramic adhesives, and the ceramic adhesives further include ceramic organic adhesives and ceramic inorganic adhesives. The ceramic organic adhesives mainly include: epoxy system ceramic adhesives, silicone system adhesives, and acrylic system adhesives; ceramic inorganic adhesives mainly include: silicate adhesives, phosphate adhesives, aluminates, etc.

[0102] S3, disposing silicon carbide fibers on the outer surfaces of the inner core mold 20 and the end plug 10 to form a silicon carbide braided layer 30.

[0103] The silicon carbide braided layer 30 covers the outer surfaces of the inner core mold 20 and the end plug 10 .

[0104] The arrangement of the silicon carbide fibers is not limited, and may be at least one of weaving, braiding, and winding.

[0105] S4. Interface layer deposition.

[0106] In this step, carbon deposition is performed on the silicon carbide braided layer 30 by chemical vapor deposition to form an interface layer on the surface of the silicon carbide fiber, which also serves as a pretreatment for the subsequent densification process.

[0107] In one embodiment, the preform with the silicon carbide braided layer 30 is placed in a reaction furnace, and propane (deposition carbon source) and argon are introduced. In the argon atmosphere, carbon is deposited on the surface of the silicon carbide fiber by pyrolysis carbon reaction to form an interface layer. The thickness of the interface layer is 100nm to 500nm.

[0108] S5. Densification treatment is performed on the silicon carbide braided layer.

[0109] After the interface layer is prepared, the silicon carbide braided layer 30 is densified by at least one of chemical vapor infiltration (CVI) and impregnation pyrolysis process (PIP), wherein the densification temperature is 900° C. to 1300° C. and the densification time is 10 hours to 600 hours.

[0110] For the chemical vapor infiltration method: the preform with the silicon carbide braided layer 30 is placed in the CVI reaction chamber, and the gaseous precursor of SiC is introduced. The precursor is directed to the silicon carbide braided layer 30, and diffuses through the pores of the silicon carbide braided layer 30 to the surface of the SiC fiber by diffusion, thereby chemically reacting to form a SiC matrix. The gaseous precursor of SiC is trichloromethylsilane (MTS, which enters the chamber with the carrier gas hydrogen through the bubbling method), and the gas atmosphere is hydrogen and argon.

[0111] For the impregnation cracking process: the precursor solution is impregnated into the silicon carbide braided layer 30 under vacuum conditions, and then the precursor is cross-linked and solidified in situ under certain conditions, and then cracked at high temperature to form a SiC ceramic matrix, and this is repeated to achieve the densification of the silicon carbide braided layer through multiple impregnation / cracking processes. The raw material of the precursor solution is solid polycarbosilane (PCS), and the solvent is xylene. Argon is used as the cracking gas.

[0112] S6. Part of the clamping end 12 of the end plug 10 is cut off; on the basis of retaining the inner core mold 20, a silicon carbide outer layer 40 is deposited on the densified silicon carbide braided layer 30 to obtain a silicon carbide composite cladding. The density of the silicon carbide composite cladding is greater than 2.7g / cm 3 .

[0113] exist Figure 6 In the illustrated embodiment, the position where the clamping end 12 is cut off is located on the side of the funnel neck close to the T-shaped end. The end plug 10 after the cut off has a T-shaped end 11 and a part of the clamping end 12 .

[0114] The silicon carbide outer layer 40 may be deposited by chemical vapor infiltration. The silicon carbide outer layer 40 covers the silicon carbide braided layer 30 and the cut surface of the end plug 10 after removal. The thickness of the silicon carbide outer layer 40 is greater than 100 μm.

[0115] The silicon carbide composite cladding obtained by the above connection method has a three-layer structure of the cladding tube part, which includes a silicon carbide tube, a dense silicon carbide braided layer and a silicon carbide outer layer from the inside to the outside. The end plug part of the silicon carbide composite cladding includes an end plug body and a silicon carbide braided layer and a silicon carbide outer layer formed on the outer surface of the end plug body.

[0116] In addition, refer to Figure 4 and Figure 6 In combination with retaining the inner core mold 20 as the inner layer part of the cladding tube, when the inner core mold 20 is matched with the T-shaped end 11 of the end plug 10, the portion of the T-shaped end 11 that fits into the inner core mold 20 can be set as large as possible within a reasonable length range (1mm to 15mm) to increase the matching area between the end plug 10 and the inner core mold 20 and improve the connection stability between the two. For example, Figure 4 and Figure 6 In the embodiment, the length of the portion of the T-shaped end 11 of the end plug 10 that fits in the inner core mold 20 is greater than Figure 1 The T-shaped end 11 of the end plug 10 is shown to fit within the length of the portion of the inner core mold 20 .

[0117] The present invention will be further described below with reference to specific embodiments.

[0118] Embodiment 1:

[0119] Preparation of a three-layer silicon carbide composite cladding for the cladding tube portion, referring to the above Figure 3 to Figure 4 or Figures 5 and 6 The connection method of the embodiment shown in the figure, wherein the matching length between the T-shaped end of the end plug and the inner core mold is 10 mm, the matching surfaces of the two are sprayed with silicon carbide ceramic slurry, and after being butted together, they are placed in a vacuum furnace for curing.

[0120] The preform formed by connecting the end plug and the inner core mold is placed in a two-dimensional weaving device, and the third-generation SiC fiber is weaved on the surface to form a silicon carbide braided layer with two braided layers.

[0121] The silicon carbide braid is subjected to carbon deposition to form an interface layer.

[0122] Chemical vapor infiltration (CVI) densification: The preform with the silicon carbide braided layer is placed in a deposition furnace and infiltrated at 1000°C for 400 hours to obtain a densified silicon carbide braided layer.

[0123] Cut off part of the end plug and keep the T-shaped section and part of the hourglass section.

[0124] Coating deposition: Place in a deposition furnace and deposit at 1150° C. for 50 hours to obtain a silicon carbide composite cladding having a silicon carbide outer layer on the surface.

[0125] Embodiment 2:

[0126] Preparation of a silicon carbide composite cladding having a two-layer structure for the cladding tube portion, referring to the above Figure 1 to Figure 2 The connection method of the embodiment shown in the figure: wherein the matching length between the T-shaped end of the end plug and the inner core mold (graphite tube) is 2 mm, and a conical groove is machined on the end plug.

[0127] The preform formed by connecting the end plug and the inner core mold is placed in a two-dimensional weaving device, and the third-generation SiC fiber is weaved on the surface to form a silicon carbide braided layer with two braided layers.

[0128] The silicon carbide braided layer is subjected to pyrolytic carbon deposition at 900°C for 20 hours to obtain an interface layer.

[0129] Chemical vapor infiltration (CVI) densification: The preform with the silicon carbide braided layer is placed in a deposition furnace and infiltrated at 1000°C for 100 hours to fill the silicon carbide matrix in the silicon carbide fiber and solidify the silicon carbide fiber.

[0130] After removing the inner core mold, CVI densification was performed, and the preform with the silicon carbide braided layer was placed in a deposition furnace and infiltrated at 1000°C for 400h to obtain a densified silicon carbide braided layer.

[0131] Cut off part of the end plug and keep the T-shaped section and part of the hourglass section.

[0132] Silicon carbide outer layer deposition: put it into a deposition furnace and deposit it at 1150°C for 50 hours to obtain a silicon carbide composite cladding with a silicon carbide outer layer on the surface.

[0133] Comparative Example 1:

[0134] Referring to Example 1, the difference is that the silicon carbide braided layer, densification and coating are first arranged on the inner core mold, and finally the end plug is fitted onto the inner core mold.

[0135] The air tightness and corrosion performance of the silicon carbide composite cladding obtained in Example 1-Example 2 and Comparative Example 1 are shown in Table 1 below.

[0136] Table 1

[0137]

[0138] From the above results, it can be seen that the silicon carbide composite cladding obtained by the connection method of the embodiment of the present invention has better air tightness and corrosion resistance than that obtained by the comparative example.

[0139] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for connecting a silicon carbide composite cladding, characterized in that: The following steps are involved: S1, processing an end plug, wherein the first end of the end plug forms a T-shaped end; S2, matching the T-shaped end of the end plug with the inner core mold; S3, arranging silicon carbide fibers on the outer surfaces of the inner core mold and the end plug to form a silicon carbide braided layer; S4, performing carbon deposition on the silicon carbide braided layer to form an interface layer on the surface of the silicon carbide fiber; S5, performing densification treatment on the silicon carbide braided layer; S6. Depositing a silicon carbide outer layer on the densified silicon carbide braided layer.

2. The method for connecting silicon carbide composite cladding according to claim 1, characterized in that: Step S1 also includes: processing the second end of the end plug into an hourglass-shaped clamping end; Before step S6, the method further includes cutting off part of the clamping end of the end plug.

3. The method for connecting silicon carbide composite cladding according to claim 1, characterized in that: Step S1 further includes: machining a groove on the outer circumference of the end plug, wherein the groove is located between the first end and the second end of the end plug; In step S3, the silicon carbide braided layer also covers the groove.

4. The method for connecting silicon carbide composite cladding according to claim 3, characterized in that: The cross-sectional shape of the groove is conical or trapezoidal.

5. The method for connecting silicon carbide composite cladding according to claim 1, characterized in that: In step S1, the maximum outer diameter of the end plug is the same as the outer diameter of the inner core mold.

6. The method for connecting silicon carbide composite cladding according to claim 1, characterized in that: In step S2, the length of the T-shaped end of the end plug fitted into the inner core mold is 1 mm to 15 mm.

7. The method for connecting silicon carbide composite cladding according to claim 1, characterized in that: In step S2, a connecting material is provided on the mating surfaces of the T-shaped end and the inner core mold; the connecting material is silicon carbide ceramic slurry or ceramic adhesive.

8. The method for connecting silicon carbide composite cladding according to claim 1, characterized in that: In step S4, carbon deposition is performed on the silicon carbide braided layer by chemical vapor deposition.

9. The method for connecting silicon carbide composite cladding according to claim 1, characterized in that: In step S5, the densification treatment method includes at least one of chemical vapor infiltration and impregnation cracking process; The densification temperature is 900°C to 1300°C, and the densification time is 10h to 600h.

10. The method for connecting silicon carbide composite cladding according to any one of claims 1 to 9, characterized in that: Step S5 includes: S5.1, performing fiber curing and shaping treatment on the silicon carbide braided layer; S5.2, removing the inner core mold; S5.

3. Densification treatment is performed on the silicon carbide braided layer.

11. The method for connecting silicon carbide composite cladding according to any one of claims 1 to 9, characterized in that: In step S6, the inner core mold is retained inside the silicon carbide braided layer; the inner core mold is formed by a silicon carbide tube.

12. A silicon carbide composite cladding, characterized in that: It is formed by the silicon carbide composite cladding connection method described in any one of claims 1-11.

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