CN112876257B

CN112876257B - SiCfTwo-layer composite cladding tube made of/SiC composite material and preparation method thereof

Info

Publication number: CN112876257B
Application number: CN202110110002.6A
Authority: CN
Inventors: 张瑞谦; 李鸣; 何宗倍; 付道贵; 陈招科; 邱绍宇; 李志平
Original assignee: Nuclear Power Institute of China
Current assignee: Nuclear Power Institute of China
Priority date: 2021-01-27
Filing date: 2021-01-27
Publication date: 2022-05-17
Anticipated expiration: 2041-01-27
Also published as: CN112876257A

Abstract

The invention discloses a SiCf/SiC composite two-layer composite cladding tube and a preparation method thereof, which solves the problem of SiC prepared by the existing chemical vapor infiltration_fThe densification degree of the/SiC composite material is low, large holes are formed, the porosity is high, and the thermal conductivity is low. SiC of the invention_fa/SiC composite two-layer composite cladding tube comprising SiC_fA composite layer of SiC and a ceramic layer of SiC, the SiC_fthe/SiC composite layer comprises a SiC fiber layer, an interface layer and a SiC matrix, wherein the interface layer is prepared by adopting chemical vapor infiltration. SiC of the invention_fthe/SiC composite material two-layer composite cladding tube has the advantages of high density, low porosity, good air tightness, good heat conductivity and the like.

Description

SiCfTwo-layer composite cladding tube made of/SiC composite material and preparation method thereof

Technical Field

The invention relates to nuclear SiC_fThe technical field of/SiC composite materials, in particular to a SiCf/SiC composite material two-layer composite cladding tube and a preparation method thereof.

Background

The fuel element is a core component of the nuclear power reactor core, and is related to the safety and the economical efficiency of the operation of the nuclear reactor. In the prior art, Zr alloy is mostly adopted as a cladding material of a fuel element of a commercial nuclear power light water reactor. However, the Zr alloy as the cladding material has certain safety problems at high temperature, for example, the Zr alloy cladding reacts violently with high-temperature coolant water to release a large amount of heat and explosive gas hydrogen, which causes the mechanical property of the cladding material to be deteriorated, and nuclear disastrous results such as reactor hydrogen explosion and leakage of a large amount of radioactive products are generated. Therefore, compared with the existing Zr alloy cladding material for nuclear power, the cladding material for the fuel elements for the next generation and future advanced nuclear power pressurized water reactors has the advantages of better high-temperature steam oxidation resistance, high-temperature strength and high-temperature stability, capability of providing larger safety margin within a certain time and capability of avoiding potential serious reactor core melting accidents.

SiC_fThe SiC is used as a novel strategic structure ceramic material, the SiC fiber is used as a second reinforcing phase to reinforce the SiC matrix, and the SiC matrix has the characteristics of specific strength, high specific modulus, high temperature resistance, irradiation resistance, good high-temperature stability and the like, and simultaneously, the defects of insufficient toughness, high crack sensitivity and the like of the material are improved due to the introduction of the SiC fiber. SiC in high temperature environment_fThe mechanical property of the/SiC composite material is reduced slightly, the thermal expansion coefficient is small, and the composite material cannot deform seriously at high temperature, and is a new generation of nuclear reactor cladding material with huge potential. Compared with Zr alloy, the advantages of the Zr alloy used as the cladding material of the nuclear reactor are mainly that (1) the silicon carbide melting point is high, and SiC is high_fThe maximum working temperature of the/SiC composite material can reach 2000 ℃, and the occurrence of nuclear accidents caused by melting of cladding due to overhigh temperature can be avoided. (2) The high-temperature stability is good, and the hydrogen explosion event similar to the Fudao nuclear power station can not be caused by the reaction with water vapor. (3) SiC_fthe/SiC can bear higher working temperature, and the reaction can be carried out at higher temperature compared with Zr alloy, thereby improving the working efficiency. (4) High-temperature corrosion resistance is good, the service life can be greatly prolonged, and the cost of replacing materials is saved. (5) The neutron absorption interface is low, and the fuel is saved under the same condition. Thus SiC_fSiC composite materialIs a more excellent nuclear reactor cladding material and has very high application potential. For SiC by researchers_fThe problems of low thermal conductivity, molding technology, air tightness and the like of the/SiC composite material are researched in a series to obtain better performance.

At present, SiC is prepared_fThe process method of the/SiC composite material mainly comprises the following four steps: high temperature infiltration, polymer impregnation cracking (PIP), Chemical Vapor Infiltration (CVI), and Nano-impregnated-transient-eutectic (NITE) processes. Among the various methods, the CVI process is the preparation of nuclear SiC_fThe most common process for the matrix of the SiC composite material, the SiC matrix produced by the method is beta-SiC which has good radiation resistance, less impurities and nearly stoichiometric carbon-silicon ratio. So CVI is also the SiC for preparing the nucleus at present_fThe best method of the/SiC composite material.

However, the CVI process in application also has a series of problems, such as large porosity (15-20%) of the prepared composite material, low thermal conductivity, incapability of densification at fiber intersection, large holes and the like.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: SiC prepared by existing chemical vapor infiltration_fthe/SiC composite material has low densification degree, large pores, larger porosity and lower thermal conductivity.

The invention is realized by the following technical scheme:

SiC_fa/SiC composite two-layer composite cladding tube comprising SiC_fA composite layer of SiC and a ceramic layer of SiC, the SiC_fthe/SiC composite layer comprises a SiC fiber layer, an interface layer and a SiC matrix, wherein the interface layer is prepared by adopting chemical vapor infiltration.

The invention prepares SiC_fTwo-layer composite structure of/SiC composite layer and SiC ceramic layer, wherein SiC_fthe/SiC composite layer is used as a main body layer bearing load and a reinforcing and toughening layer of the cladding tube; the SiC ceramic layer on the outer layer is used as an anti-corrosion layer of the cladding tube and a functional layer for guaranteeing the air tightness of the cladding tube.

Prior art demonstration of fibersAnd interface layer between the substrate to SiC_fThe mechanical properties of the/SiC composite material have important influence. The interface layer can prevent the fiber from being corroded, and effectively transfer the load between the fiber and the matrix, so that the fiber plays a load bearing role. The appropriate interface layer can enable toughening mechanisms such as crack deflection, interface debonding, fiber pulling-out and the like to be exerted, and further the mechanical property of the composite material is improved.

The interface layer is prepared by a chemical codeposition method, so that a more compact interface layer can be obtained, and the mechanical property of the whole material is favorably improved.

The invention preferably selects a SiCf/SiC composite two-layer composite cladding tube, and the interface layer is a codeposition layer of a pyrolytic carbon layer and silicon carbide.

The method prepares the codeposition layer of the pyrolytic carbon layer and the silicon carbide by a chemical codeposition method, and is beneficial to obtaining a more compact interface layer, thereby improving the mechanical property of the whole material.

The invention preferably selects a SiCf/SiC composite two-layer composite cladding tube, a carbon nanotube layer is also arranged between the SiC fiber layer and the interface layer, and the carbon nanotubes used by the carbon nanotube layer are few-wall carbon nanotubes, preferably single-wall carbon nanotubes.

Preferably, a plurality of carbon nanotube layers are arranged between the SiC fiber layer and the interface layer, the number of the carbon nanotube layers is 3-5, and the thickness of each carbon nanotube layer is 100-200 nm.

The invention preferably selects a SiCf/SiC composite two-layer composite cladding tube, the outer diameter of the composite cladding tube is 6mm-20mm, the thickness of the tube wall is 0.7mm-1.2mm, and the SiC composite cladding tube is made of SiC_fThe thickness of the/SiC composite layer is 0.5 mm-1 mm, the thickness of the SiC ceramic layer is 200-500 mu m, and the SiC_fThe volume fraction of the/SiC composite layer is more than 50 percent.

Further, the SiC_fThe thickness of the/SiC composite layer is 0.5 mm-0.7 mm.

Further, the SiC_fThe density of the/SiC composite layer is 2.50-2.70 g/cm³The open porosity is about 3 to 10%.

Further, the thickness of the interface layer is 100-300 nm.

Further, the thickness of the SiC ceramic layer is 300-400 mu m.

Furthermore, the SiC fiber layer is prepared from high-purity high-crystalline III-generation SiC fibers.

Compared with a three-layer composite cladding with the same thickness, the composite cladding has better tensile mechanical property, and meanwhile, the thickness ratio of the composite material layer to the ceramic layer enables the stress distribution of the composite cladding to be more uniform and the deformation to be more coordinated when the composite cladding is subjected to internal pressure.

Preparation of SiC_fThe method for compounding the cladding tube with the two layers of the/SiC composite material comprises the following steps:

step 1: weaving of SiC fiber prefabricated part cladding tube

Winding or weaving SiC fibers on a graphite tube core mold to form a SiC cladding tube prefabricated part;

step 2: interfacial layer preparation

Depositing an interface layer on the surface of SiC fibers of the SiC cladding tube prefabricated part by using propylene as a precursor gas, hydrogen as a reducing gas and argon as a diluting gas by using a chemical vapor infiltration method to obtain the SiC cladding tube prefabricated part with the interface layer;

and step 3: densification of SiC fiber preforms with interface layers

Depositing a SiC matrix in the SiC cladding tube prefabricated part with the interface layer by using trichloromethylsilane as a precursor gas and utilizing a chemical vapor infiltration method to integrally compact the SiC fiber prefabricated part with the interface layer to obtain a densified SiC fiber prefabricated part;

and 4, step 4: preparing an outer SiC ceramic layer of the densified SiC fiber prefabricated part;

and 5: removing the graphite tube core mold;

and the step 4 and the step 5 are not separated in sequence.

Preferably, the SiC fiber weaving method in step 1 is: firstly winding and then weaving.

Specifically, at least 1 layer of SiC fiber is wound on the graphite core mold by a roller winding method, and then 1-2 layers of SiC fiber cloth are woven by a plain weave, twill weave or shallow zigzag combined weaving method.

According to the invention, the mechanical property of the obtained SiC fiber prefabricated part is better by the method of winding first and then weaving.

Preferred SiC of the present invention_fThe preparation method of the/SiC composite two-layer composite cladding tube comprises the step 2, wherein the interface layer is a codeposition layer of pyrolytic carbon and silicon carbide prepared by a chemical vapor infiltration method, and a precursor gas of the codeposition layer of the pyrolytic carbon layer and the silicon carbide is a mixed gas of propylene and trichloromethylsilane.

According to the invention, two kinds of precursor gases are mixed and codeposited to obtain a codeposited layer of pyrolytic carbon and silicon carbide, so that a more compact interface layer is obtained, fibers can be better protected, and better mechanical properties are realized.

Preferred SiC of the present invention_fThe preparation method of the/SiC composite two-layer composite cladding tube comprises the following steps between the step 1 and the step 2: and spraying the carbon nanotube suspension on the woven SiC fiber prefabricated part for multiple times to form a carbon nanotube layer.

Preferably, the preparation method of the carbon nanotube layer comprises the following steps: adopting an ethanol suspension system of carbon nano tubes with the average length of 100 mu m and the diameter of less than 100nm, wherein the content of the carbon nano tubes is 0.4-1g/ml, spraying the surface of the prefabricated member for 3-5 times, keeping the temperature of a constant temperature furnace at 40-60 ℃ for 5-10min under the protection of argon atmosphere after each spraying, and then spraying the carbon nano tubes for the next time, wherein the carbon nano tubes are double-wall carbon nano tubes or single-wall carbon nano tubes.

Preferably, the concentration of the carbon nanotube ethanol suspension is 0.8 g/ml.

Preferred SiC of the present invention_fThe preparation method of the/SiC composite two-layer composite cladding tube comprises the following steps of in the step 2, the deposition conditions of the interface layer are as follows: deposition temperature is 1000 ℃, deposition pressure is 200 +/-50 Pa, deposition time is 6h, and diluted Ar gas: 400ml/min, propane: 160 ml/min.

Preferred SiC of the present invention_fIn the step 4, before depositing the SiC outer coating, the surface of the densified SiC fiber prefabricated part is ground, and then nano SiC particles are adoptedCoating a coating at the position of the defect on the surface of the ground cladding tube by a slurry brush coating method, and directly entering a chemical vapor infiltration furnace to deposit an SiC outer coating after drying.

The outer SiC ceramic layer is prepared by a slurry brushing and chemical vapor deposition composite process and has the characteristics of high purity, high crystallinity, high compactness and the like.

Preferably, the preparation process flow of the slurry brush coating method is as follows: ball milling SiC nano powder → drying → preparing PVB adhesive → mixing and stirring the ball milling powder and the PVB adhesive → brushing → drying.

Preferably, the deposition process parameters of the SiC matrix in step 3 are as follows: the deposition temperature is 1000-1100 ℃, the deposition pressure is 200-2000 +/-50 Pa, the carrier gas hydrogen is 300-1600 ml/min, the diluted hydrogen is 450-2400 ml/min, and the deposition time is 200-400 h.

Preferably, the graphite pipe core mold is prepared by isostatic pressing high-purity graphite.

Preferably, step 5: the graphite pipe core mould removal step consists of mechanical deep hole digging and oxidation; the deep hole digging is finished by a machine tool, and the shell tube after cylindrical grinding is dug by utilizing a drill bit with the size of phi 8.5mm multiplied by 200mm, so that a graphite tube with the thickness of 1mm is remained in the SiC two-layer shell tube; the main purpose of the oxidation process is to remove the residual graphite tube with the thickness of 1mm after the deep hole digging process; the oxidation temperature is 600-800 ℃, and the oxidation time is 10-50 h.

The invention has the following advantages and beneficial effects:

1. the invention prepares SiC_fTwo-layer composite structure of/SiC composite layer and SiC ceramic layer, wherein SiC_fthe/SiC composite layer is used as a main body layer bearing load and a reinforcing and toughening layer of the cladding tube; the outer SiC ceramic layer is used as an anti-corrosion layer of the cladding tube and a functional layer for guaranteeing the air tightness of the cladding tube, and the interface layer is prepared by a chemical vapor infiltration method, so that the interface layer with better density is obtained, and the protection of the fiber layer and the improvement of the mechanical property of the composite cladding tube are facilitated.

2. According to the invention, the co-deposition layer of pyrolytic carbon and silicon carbide is co-deposited by adopting the mixed gas of propylene and trichloromethylsilane as the precursor gas and adopting a chemical vapor infiltration method, so that the density of the interface layer is further improved, and the silicon carbide is beneficial to improving the strength and the corrosion resistance of the interface layer, thereby better protecting the fiber layer and improving the mechanical property of the composite cladding tube

3. According to the invention, the carbon nanotube layer is sprayed on the SiC fiber layer, so that the good performance and the nanoscale of the carbon nanotubes can further improve the corrosion resistance, the thermal conductivity and the structural compactness of the composite cladding tube.

4. The invention adopts the method of winding firstly and then weaving on the weaving method of the SiC fiber, thereby improving the density of the SiC fiber.

5. When the core mold is removed, the mode of firstly deeply digging holes mechanically and then oxidizing is adopted, so that the removal effect is good.

6. The SiC fiber prefabricated part with the interface layer is densified and then ground on the surface, a nano SiC particle slurry brush coating method is adopted to coat a coating on the defect position on the surface of the ground cladding tube, and the SiC ceramic coating is directly deposited in a chemical vapor infiltration furnace after drying, so that a better SiC ceramic protective layer can be obtained.

7. The invention can obtain the density of 2.90g/cm³The two layers of cladding tubes have the porosity of less than 5.0%; the carbon-silicon ratio of the substrate is 1.0-1.1, the oxygen content is less than 1%, and the air tightness and the structural heat transfer performance are considered, wherein the air tightness can be less than 10^-9Pam³And/s, the radial thermal resistance of the structure is less than 80 ℃/W.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention. In the drawings:

fig. 1 is a picture of the appearance of the graphite tube core mold of the present invention.

FIG. 2 shows SiC of example 1 of the present invention_fAnd (3) pictures of the measurement states of the outer diameter, the inner diameter and the wall thickness of the sample of the/SiC composite cladding tube.

FIG. 3 shows SiC of example 1 of the present invention_fSample microstructure of/SiC composite cladding tubeAnd observing the microscope picture.

FIG. 4 shows SiC of example 2 of the present invention_fAnd (3) pictures of the measurement states of the outer diameter, the inner diameter and the wall thickness of the sample of the/SiC composite cladding tube.

FIG. 5 shows SiC of example 2 of the present invention_fAnd the microscopic picture of the microstructure observation of the sample of the/SiC composite cladding tube and the comparison pictures of the thickness measurement states of the composite material layer and the outer SiC ceramic layer.

FIG. 6 is a graph showing the variation of thermal resistance and air tightness according to the thickness of the ceramic coating layer in example 2 of the present invention.

FIG. 7 shows experimental data of oxidation in 1200 ℃ high temperature steam of example 2 and example 3 of the present invention,

FIG. 8 is experimental data of water corrosion performance at 360 ℃ in pure water environment for example 2 and example 3 of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not meant to limit the present invention.

Example 1

A method for preparing a SiCf/SiC composite two-layer composite cladding tube comprises the following steps:

step 1: weaving of SiC fiber prefabricated part cladding tube

Winding 1 layer of SiC fiber on a graphite core mold by adopting a winding method, wherein the outer diameter of the graphite core mold is 10.0mm, and weaving 2 layers of SiC fiber cloth on the graphite core mold wound with the SiC fiber by adopting a plain weaving method to form the SiC cladding tube prefabricated member with the outer diameter of 11.6 mm.

And 2, step: interfacial layer preparation

Using propylene as a precursor gas, hydrogen as a reducing gas and argon as a diluting gas, and depositing an interface layer on the surface of SiC fibers of the SiC cladding tube prefabricated part by using a chemical vapor infiltration method to obtain the SiC cladding tube prefabricated part with the interface layer, wherein the deposition conditions are as follows: the deposition temperature is 1000 ℃, the deposition pressure is 200 +/-50 Pa, the deposition time is 6h, and the flow of diluted Ar gas is as follows: 400ml/min, propylene flow rate: 160 ml/min.

And step 3: densification of SiC fiber preforms with interface layers

With trichloromethylsilane as a precursor gas, depositing a SiC matrix in the SiC cladding tube prefabricated part with the interface layer by using a chemical vapor infiltration method, and integrally compacting the SiC fiber prefabricated part with the interface layer to obtain a densified SiC fiber prefabricated part, wherein the deposition conditions of the SiC matrix are as follows: deposition temperature 1050 ℃, deposition pressure 400 +/-50 Pa and carrier gas H₂: 360ml/min, dilution H₂: 480ml/min, diluted Ar: 480ml/min, and the deposition time is 250 h;

after the cladding tube is discharged after deposition for 250 hours, the outer diameter of the cladding tube can reach 12-13 mm, surface grinding processing is carried out on the densified SiC fiber prefabricated part by using a coreless grinding machine so as to ensure the circularity, straightness and smoothness of the surface, the grinding processing is divided into 4 passes, the diameter of the outer circle of the cladding tube is gradually reduced from 13mm to 12.5mm, 12.2mm, 12.0mm and 11.6mm, a graphite tube core mold is removed by using a mechanical method and a low-temperature oxidation method, the mechanical method comprises deep hole digging and is completed by a machine tool, and the deep hole digging is carried out on the cladding tube subjected to the outer circle grinding by using a drill flower with the size of phi 8.5mm multiplied by 200mm, so that a graphite tube with the thickness of 1mm is remained in the two layers of cladding tube of SiC; the main purpose of the oxidation process is to remove the residual graphite tube with the thickness of 1mm after the deep hole digging process; the oxidation temperature is 700 ℃, the oxidation time is 20h, after the graphite core mold is removed, a SiC coating is coated on the surface defect position of the ground cladding tube by adopting a nano SiC particle slurry brush coating method, and the cladding tube is dried.

and (4) putting the SiC fiber prefabricated part dried in the step (3) into a coating layer at the surface defect position of the ground cladding tube by adopting a nano SiC particle slurry brushing method, wherein the preparation method of the nano SiC particle slurry comprises the following steps: ball-milling SiC nano powder to 200nm, drying at 100 ℃, adding 10% of polyvinyl butyral (PVB) binder for mixing, mixing and stirring the ball-milled powder and the PVB binder, then brushing, and drying at 100 ℃. After drying, directly entering a chemical vapor infiltration furnace to deposit the SiC ceramic coating, wherein the deposition conditions are as follows: the deposition temperature is 1250 ℃, the deposition pressure is 500 +/-50 Pa, the carrier gas hydrogen is 350ml/min, the diluted hydrogen is 500ml/min, the deposition time is 40h, and the SiC columnar crystal coating is deposited.

After the SiC ceramic layer is deposited, the surface is polished by using grinding and polishing equipment, the dimensional precision and the smoothness of the cladding tube are improved, and the final SiC ceramic layer is obtained_fthe/SiC composite material composite cladding tube.

Determination of SiC by Archimedes method_fThe density and the porosity of the/SiC composite material reach 2.83g/cm³The open porosity was only 5.8%.

Observing the microstructure by using an electron microscope, and measuring the outer diameter, the inner diameter and the wall thickness of the microstructure as shown in FIG. 2; as can be seen from FIG. 2, the obtained cladding tube has a good circularity, measured in three directions, with an outer diameter of 13.2mm, an inner diameter of 10.6mm and a wall thickness of 1.3 mm; the outer diameter, the inner diameter and the wall thickness of the pipe fitting are not deviated, but the wall thickness reaches 1.3 mm.

When the cross section of the cladding tube is observed in an enlarged manner, as shown in fig. 3, as can be seen from fig. 3, the cladding tube mainly consists of a composite material layer and an outer SiC ceramic layer, and is a typical two-layer composite cladding tube; meanwhile, the obvious SiC nanocrystalline slurry brush coating can be found and is discontinuously distributed between the CVD outer coating of the two-layer cladding tube and the SiCf/SiC composite material layer in a blocky manner.

Example 2

The difference between this example and example 1 is that the interface layer is formed by co-deposition of pyrolytic carbon and SiC, the mixed gas of propylene and trichloromethylsilane is used as the precursor gas for deposition, the volume ratio of propane to trichloromethylsilane is 1:1, and the deposition conditions are the same as example 1.

This example also differs from example 1 in that the carbon nanotube suspension is sprayed four times onto the woven SiC fiber preform to form a carbon nanotube layer, and then an interface layer is deposited on top of the carbon nanotube layer.

The preparation method of the carbon nanotube layer comprises the following steps: adopting an ethanol suspension system of carbon nano tubes with the average length of 100 mu m and the diameter of less than 100nm, wherein the content of the carbon nano tubes is 0.8g/ml, spraying the surface of the prefabricated member for 4 times, keeping the temperature of a constant temperature furnace at 50 ℃ for 8min under the protection of argon atmosphere after each spraying, and then spraying the prefabricated member for the next time, wherein the carbon nano tubes are single-walled carbon nano tubes.

Determination of SiC by Archimedes method_fThe density and the porosity of the/SiC composite material reach 2.95g/cm³The open porosity was only 4.8%. Observing the microstructure by using an electron microscope, and measuring the outer diameter, the inner diameter and the wall thickness of the microstructure as shown in FIG. 4; the obtained cladding tube has good circularity, the outer diameter of the cladding tube is 12.2mm, the inner diameter of the cladding tube is 10.3mm, and the wall thickness of the cladding tube is 0.991-1.060 mm measured from three directions; maximum and minimum difference of external diameters of same section of pipe fitting<0.1mm, maximum and minimum difference of inner diameter size<0.1 mm; the size difference of the wall thickness is less than 0.05 mm.

When the cross section of the cladding tube is observed in an enlarged manner, as shown in fig. 5, the cladding tube mainly consists of a composite material layer and an outer SiC ceramic coating layer, and is a typical two-layer composite cladding tube. Wherein the thickness of the intermediate composite material layer is about 651 mu m; the overcoat thickness was about 405 μm.

FIG. 6 shows the variation of thermal resistance and airtightness with the thickness of the coating layer in example 2, wherein the straight line represents the thermal resistance and the curve represents the helium leakage rate, and it can be seen from FIG. 6 that the nuclear leakage rate is reduced to 10 when the thickness of the SiC ceramic layer is 200-500 μm^-9Pam3/s, and in this thickness range, the thermal resistance is also small, less than 80 ℃/W.

Fig. 7 and 8 show the results of the corrosion resistance test of the test piece of example 2, and it can be seen from the oxidation experimental data of fig. 7 in high temperature steam of 1200 c that the mass change thereof is about 0.3mg and the initial mass thereof is 350mg, i.e., the mass change rate is less than 0.1%, at 14000S, i.e., about 4 hours. From fig. 8, the corrosion of the sample under the pure water environment condition of 360 ℃ is: when the corrosion is carried out for 45 days, the mass change is less than 1 percent, so that the sample has good corrosion resistance.

Comparing fig. 2 and 3 with fig. 4 and 5, it can be seen that the microstructure of example 2 is denser, both the density of the fibers and the density of the SiC ceramic layer are higher than those of example 1, and therefore, the density is higher and the porosity is lower, which indicates that the use of pyrolytic carbon and SiC coprecipitation and the carbon nanotube layer contributes significantly to the compactness of the whole structure.

Comparative example 1

This example differs from example 2 in that the SiC_fThe SiC ceramic layer is not prepared in the two-layer composite cladding tube of the/SiC composite material, and as can be seen from the comparison results of fig. 7 and fig. 8, the corrosion resistance of the composite cladding tube with the SiC ceramic layer is far better than that of the cladding tube without the SiC ceramic layer.

SiC of the invention_fthe/SiC composite material two-layer composite cladding tube has high density, small porosity and good thermal conductivity and air tightness, and can be used as a Light Water Reactor (LWR) fuel cladding tube and other working components in extreme irradiation environments.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. SiC_fthe/SiC composite material two-layer composite cladding tube is characterized by comprising SiC_fA composite layer of SiC and a ceramic layer of SiC_fthe/SiC composite layer comprises a SiC fiber layer, an interface layer and a SiC matrix, wherein the interface layer is prepared by adopting chemical vapor infiltration;

the outer diameter of the composite cladding tube is 6mm-20mm, the thickness of the tube wall is 0.7mm-1.2mm, and the SiC_fThe thickness of the/SiC composite layer is 0.5 mm-1 mm, and the thickness of the SiC ceramic layer is 200-500 mu m;

the interface layer is a codeposition layer of a pyrolytic carbon layer and silicon carbide;

and a carbon nanotube layer is also arranged between the SiC fiber layer and the interface layer, and carbon nanotubes used by the carbon nanotube layer are few-wall carbon nanotubes.

2. A method of producing the SiC of claim 1_fThe method for compounding the cladding tube with the/SiC composite material in two layers is characterized by comprising the following steps of:

step 1: SiC fiber prefabricated part cladding tube weaving

and 2, step: interfacial layer preparation

Depositing an interface layer on the surface of SiC fibers of the SiC cladding tube prefabricated part by using propylene and trichloromethylsilane as precursor gases, hydrogen as a reducing gas and argon as a diluting gas by using a chemical vapor permeation method to obtain the SiC cladding tube prefabricated part with the interface layer;

and step 3: densification of SiC fiber preforms with interface layers

and 5: removing the graphite tube core mold;

step 4 and step 5 are not sequenced;

the interface layer in the step 2 is a pyrolytic carbon layer and a silicon carbide codeposition layer prepared by a chemical vapor infiltration method.

3. SiC according to claim 2_fThe preparation method of the/SiC composite two-layer composite cladding tube is characterized by also comprising the following steps between the step 1 and the step 2: and spraying the carbon nanotube suspension on the woven SiC fiber prefabricated part for multiple times to form a carbon nanotube layer.

4. SiC according to claim 2_fThe preparation method of the/SiC composite two-layer composite cladding tube is characterized in that in the step 2, the deposition conditions of the interface layer are as follows: the deposition temperature is 1000℃,Deposition pressure 200 +/-50 Pa, deposition time 6h, diluted Ar gas: 400ml/min, C₃H₆：160ml/min。

5. SiC according to claim 2_fThe preparation method of the/SiC composite two-layer composite cladding tube is characterized in that in the step 4, before the SiC outer coating is deposited, the surface of the densified SiC fiber prefabricated part is ground, then a nano SiC particle slurry brush coating method is adopted to coat a coating at the position of the defect on the surface of the ground cladding tube, and after drying, the coating directly enters a chemical vapor infiltration furnace to deposit the SiC outer coating.

6. SiC of claim 3_fThe preparation method of the/SiC composite two-layer composite cladding tube is characterized in that the preparation method of the carbon nanotube layer comprises the following steps: adopting an ethanol suspension system of carbon nano tubes with the average length of 100 mu m and the diameter of less than 100nm, wherein the content of the carbon nano tubes is 0.4-1g/ml, spraying the surface of the prefabricated member for 3-5 times, keeping the temperature of a constant temperature furnace at 40-60 ℃ for 5-10min under the protection of argon atmosphere after each spraying, and then spraying the carbon nano tubes for the next time, wherein the carbon nano tubes are double-wall carbon nano tubes or single-wall carbon nano tubes.