CN113087533A

CN113087533A - In-situ synthesis of Ti on SiC fiber surface by using SiC nano crystal particles3SiC2Method for preparing interface phase

Info

Publication number: CN113087533A
Application number: CN202110351928.4A
Authority: CN
Inventors: 成来飞; 杨劲松; 崔永静; 叶昉; 张立同
Original assignee: Northwestern Polytechnical University
Current assignee: Northwestern Polytechnical University
Priority date: 2021-03-31
Filing date: 2021-03-31
Publication date: 2021-07-09
Anticipated expiration: 2041-03-31
Also published as: CN113087533B

Abstract

The invention relates to an in-situ synthesis method of Ti on the surface of SiC fiber by using SiC nano crystal particles₃SiC₂Preparing pyrolytic carbon with a certain thickness on the surface of the SiC fiber by using a chemical vapor deposition method to change the chemical composition of the surface of the SiC fiber; then burying the titanium dioxide in a molten salt system containing Si and Ti elements; then carrying out heat treatment on the SiC nano-crystalline particles to synthesize Ti by utilizing the reaction of the SiC nano-crystalline particles in the SiC fibers, PyC on the surfaces of the fibers and Si and Ti in a molten salt environment₃SiC₂An interfacial phase. The invention adopts CVD combined with molten salt method for the first time, and utilizes SiC nano crystal particles to prepare Ti on the surface of SiC fiber in an in-situ synthesis mode₃SiC₂The interface phase, the obtained interface phase and the SiC fiber and the subsequent matrix can realize strongerBinding ability, and the Ti₃SiC₂The interface phase has a different toughening mechanism than the common PyC and boron nitride interface phases of SiC fiber reinforced ceramic matrix composites, and in contrast, the interface phase also has better oxidation resistance.

Description

In-situ synthesis of Ti on SiC fiber surface by using SiC nano crystal particles3SiC2Method for preparing interface phase

Technical Field

The invention belongs to the field of ceramic matrix composite materials, and relates to an in-situ synthesis method of Ti on the surface of SiC fibers by using SiC nano-crystalline grains₃SiC₂A method for preparing an interfacial phase.

Background

Silicon carbide continuous fiber reinforced silicon carbide composite material (herein abbreviated as SiC)_f/SiC) has the characteristics of high temperature resistance, high strength, high modulus, low density and the like, and is expected to replace high-temperature alloy to become a preferred material for advanced aeroengine hot-end parts. In SiC_fIn the preparation of SiC, it is generally necessary to prepare an interface phase between the SiC fiber and the SiC matrix. The existence of the interface phase connects the fiber and the matrix on one hand, and transmits the load borne by the matrix to the fiber through shearing; on the other hand, the interfacial phase also induces the cracks generated in the matrix to deflect in the interfacial region, so as not to allow the high concentrated stress at the crack tip to act directly on the fiber, resulting in fiber breakage.

At present, SiC_fThe interfacial phase material of/SiC is mainly divided into two types: one is pyrolytic carbon (herein abbreviated as PyC) having a turbostratic graphite structure; the other is hexagonal boron nitride (abbreviated as h-BN) with the structure similar to that of graphite. The two interface phases can cause weak bonding between the fiber and the matrix, when SiC is used_fAfter the stress borne by the SiC exceeds the cracking stress of the matrix, the matrix cracks can expand to the interface, and then the phenomena of fiber debonding, fiber pulling-out and the like can occur at the interface, so that the composite material is prevented from brittle fracture, and the composite material has good fracture toughness. However, such weakly bonded interphase inevitably results in the composite material being loaded with stresses that are difficult to transfer completely from the matrix to the fibers, causing premature cracking of the matrix and affecting the SiC_fthe/SiC is more widely applied to engineering. At the same time, SiC_fWhen the/SiC is applied to a thermal structural component, the working environment is a high-temperature aerobic condition, and the oxidation problem of the composite material is difficult to avoid. The oxidation resistance of PyC and h-BN interface phases is poor, and the obvious oxidation temperatures are respectively 450 ℃ and 900 ℃. The oxidized interface phase will lose its original valueStructure and function, directly resulting in SiC_fthe/SiC strength decreases. Therefore, for SiC_fThe increasingly stringent application requirements of/SiC require the development of new interface phase materials to make up for the deficiencies of PyC and h-BN.

With Ti₃SiC₂The MAX phase materials that are representative are a series of early transition metal carbonitrides with an atomic scale layered structure. The series of materials have the characteristics of metal and ceramic, namely high fracture toughness, high damage limit, good machinability, high strength, high modulus, high temperature resistance, oxidation resistance and corrosion resistance. The interphase of the continuous fiber reinforced ceramic matrix composite generally has a low shear strength, e.g., both PyC and h-BN exhibit anisotropy in the crystal structure. The MAX phase material has an atomic-level layered structure, good oxidation resistance (the obvious oxidation temperature is up to 1400 ℃) and corrosion resistance, so that the MAX phase material has great potential as a novel interface phase, and the problems of the current PyC and h-BN interface phase in application are solved.

At present, SiC has been reported_fPreparation of Ti in/SiC₃SiC₂The interface phase method mainly comprises an electrophoretic deposition method and a magnetron sputtering method. The interface phase prepared by the electrophoretic deposition method does not exchange with the fiber and the matrix, and Ti₃SiC₂Bonding between particles by electrostatic force, resulting in Ti₃SiC₂The interface phase is weakly bonded to the fiber and the matrix and is difficult to sufficiently carry. Such an interface phase prepared by adsorption by weak electrostatic force would be difficult to exert Ti₃SiC₂Intrinsic mechanical advantages such as high fracture toughness, high damage tolerance, etc. By magnetron sputtering on SiC_fPreparation of Ti in/SiC₃SiC₂The interface phase has been reported, but because of the characteristics of the process, the deposition base surface needs to be directly opposite to the target material during preparation, and has certain requirements on the distance from the target material to the deposition surface, and Ti is difficult to realize for parts with certain complex shapes, large-size and thick-wall parts₃SiC₂Uniform deposition of the interface phase.

The fused salt synthesis method is a common ceramic synthesis method, and in the past research, researchers used the fused salt synthesis method to prepare Ti on the surface of carbon fiberC/Ti₂AlC interphase (Li, M, Wang, K, Wang, J, et al. preparation of TiC/Ti)₂AlC coating on carbon fiber and activation of the oxidation resistance properties.J. Am ceramic Soc.2018; 101: 5269-5280. https:// doi.org/10.1111/jace.15784). In the research, Ti and Al elements dissolved in molten salt melt react with carbon fibers to form TiC/Ti₂AlC bilayer interface phase. The method is difficult to control the corrosion degree of Ti and Al elements in the molten salt to the carbon fiber, the preparation process generates irreversible damage to the carbon fiber, and the tensile strength of the material is only 78 MPa. Then, in order to solve the problem of fiber damage, the group proposed to prepare PyC (K.Wang et al, "Interface modification of carbon fibers with TiC/Ti) on the surface of carbon fibers₂AlC coating and its effect on the tension string, "Central. Int., vol.45, No.4, pp.4661-4666, Mar.2019, doi: 10.1016/J.CERAMINT.2018.11.156"). Although the method reduces the damage degree of the fiber to a certain degree, the prepared interface phase is PyC/TiC/Ti₂The first layer PyC weak bonding interface of the AlC three-layer structure enables C to exist_fThe fracture behavior of the/SiC composite material still takes debonding of PyC interface as the main part, and the third layer of Ti₂The AlC interface hardly exhibits its excellent mechanical properties characteristic as a MAX phase material.

Li and Wang et al work, although using a similar ceramic preparation process, were unable to use for reference to prepare Ti₃SiC₂The interface phase has the key points that: (1) first, the carbon fibers used in the study by Li et al are very different from the SiC fibers according to the present invention in both chemical environment and microstructure. Carbon fibers are skin-core structured fibers formed of surface graphite crystallites and internal amorphous carbon. The SiC fiber is mainly composed of SiC nanometer crystal grains, and the element ratio of carbon to silicon is close to 1: 1. The differences in composition and microstructure necessarily lead to large differences in both the chemical reaction path of the synthesis and the chemical stability between the phases. (2) Second, the interfacial phase of Li et al and Ti₃SiC₂While belonging to the MAX phase material, it is two completely different ternary systems. The chemical reaction mechanism of the Ti-Si-C system is different from that of the Ti-Al-C system, in which Ti₃SiC₂With Ti₂In the preparation process of two AlC interface phases, a control method of phase components and a removal method of impurity phases do not have references. (3) Finally, Ti₃SiC₂Preparation of the interphase, but it has different significance from the study by Li et al. In the study of Li et Al, the main role of PyC production is to protect the carbon fibers from corrosion by Ti and Al elements, as a result of which the produced interface phase overall exhibits PyC/TiC/Ti₂The AlC three-layer structure has no great difference with a pure PyC weak interface in mechanical behavior, and still realizes crack deflection by means of a weak bonding interface to toughen. In conclusion, the studies reported by Li et al and Ti₃SiC₂The preparation of the interface phase has large difference, and Ti preparation on the surface of SiC fiber is difficult to be easily obtained through research of Li and the like₃SiC₂Interface phase molten salt synthesis process.

Disclosure of Invention

Technical problem to be solved

In order to avoid the defects of the prior art, the invention provides a method for synthesizing Ti on the surface of SiC fiber in situ by using SiC nano crystal particles₃SiC₂A method for preparing an interfacial phase. In-situ synthesis of Ti on SiC fiber surface by using SiC nano crystal particles₃SiC₂A method for preparing an interphase, comprising the steps of: firstly, preparing PyC with the thickness of less than 200nm, especially 120nm on the surface of the SiC fiber by adopting a chemical vapor deposition method (CVD for short), and obtaining the SiC fiber with the surface carbon-rich characteristic; then burying the titanium alloy in a molten salt system containing Si and Ti elements; then, the fiber is heat treated, and SiC nanocrystalline grains in the area with the peripheral thickness of the SiC fiber being less than 1 mu m react with PyC on the surface of the fiber and Si and Ti in the molten salt to synthesize Ti₃SiC₂An interfacial phase.

Technical scheme

In-situ synthesis of Ti on SiC fiber surface by utilizing SiC nano crystal particles₃SiC₂The preparation method of the interface phase is characterized by comprising the following steps:

step 1: preparing PyC with the specified thickness of less than 200nm on the surface of the SiC fiber by adopting a CVD method to obtain the SiC fiber with the surface rich in carbon;

step 2: burying SiC fibers with the surface having the carbon-rich characteristic in a molten salt system, wherein the molten salt system comprises Ti-containing element powder, Si-containing element powder and halogen salt; wherein the molar ratio of the Ti element to the Si element is 3:1, and the addition amount of the halogen salt is 4-12 times of the total amount of the Ti element and the Si element in terms of the amount mol of the substance;

step 3, heat treatment: under the pressure of 1-101 kPa, heating to the melting point of the molten salt, preserving heat for 0.5h to realize full dissolution of Ti particles and full diffusion of melt in fiber bundle gaps, heating to 1100-1300 ℃, preserving heat for 0.5-2 h, and using Ar gas as a protective gas;

synthesizing Ti by utilizing SiC nano-crystalline grains with the peripheral thickness of less than 1 mu m of area of fiber in molten salt environment through reaction of SiC, C, Si and Ti₃SiC₂An interfacial phase.

The thickness of the PyC is 120 nm.

When the SiC fibers with the surface carbon-rich characteristic are buried in a molten salt system, the powder is kept in a natural dispersion state.

The powder containing Ti element is Ti powder or TiH₂Powder or TiO₂And (3) pulverizing.

The Si-containing powder is Si powder or SiO₂And (3) pulverizing.

The halogen salt comprises one or a mixture of two of NaCl, KCl, NaBr, KBr, NaF and KF.

Advantageous effects

The invention provides a method for in-situ synthesizing Ti on the surface of SiC fiber by using SiC nano crystal particles₃SiC₂Firstly, preparing pyrolytic carbon (PyC) with a certain thickness on the surface of the SiC fiber by using a Chemical Vapor Deposition (CVD) method so as to change the chemical composition of the surface of the SiC fiber; then burying the titanium dioxide in a molten salt system containing Si and Ti elements; then carrying out heat treatment on the SiC nano-crystalline particles to synthesize Ti by utilizing the reaction of the SiC nano-crystalline particles in the SiC fibers, PyC on the surfaces of the fibers and Si and Ti in a molten salt environment₃SiC₂An interfacial phase. The invention adopts CVD combined with molten salt method for the first time, and SiC nano crystal particles are used for preparing the SiC nano crystal particles on the surface of SiC fibers by an in-situ synthesis modePreparation of Ti₃SiC₂The interface phase, the obtained interface phase and SiC fiber and subsequent matrix can realize stronger binding capacity, and the Ti₃SiC₂The interface phase has a different toughening mechanism from the common PyC and boron nitride (h-BN) interface phase of the SiC fiber reinforced ceramic matrix composite, and in contrast, the SiC fiber reinforced ceramic matrix composite has better oxidation resistance.

Although the molten salt synthesis method is a common ceramic synthesis method, the present inventors still need to specifically solve the above problems in the prior art using the molten salt method. Firstly, complex chemical reaction exists in the synthetic process of the molten salt method, and the prepared Ti₃SiC₂The connection of chemical bonds can be realized between each crystal grain in the interface phase and between the interface phase and the fiber. Compared with a physical connection mode that an interface phase prepared by electrophoretic deposition depends on electrostatic force, Ti synthesized by a molten salt method₃SiC₂The interface phase has stronger bonding capacity with the fiber, and is helpful for the composite material to transmit the stress borne by the matrix to the fiber more fully when the composite material is loaded. On the other hand, in the implementation process of the molten salt method, the metal elements have higher dissolving and diffusing capacity in the molten salt fluid, the molten fluid can fully fill parts, and Ti is hopefully and uniformly prepared on parts with complicated shapes and large sizes₃SiC₂The interface phase solves the problem that the magnetron sputtering method is difficult to uniformly prepare Ti in large and complex structural components₃SiC₂The problem of interfacial phases.

In past studies, researchers have prepared TiC/Ti on the surface of carbon fibers by molten salt synthesis₂AlC interface phase, Ti and Al elements dissolved in molten salt melt react with carbon fiber to form TiC/Ti₂AlC bilayer interface phase. However, the existing method is difficult to control the corrosion degree of Ti and Al elements in the molten salt to the carbon fiber, the preparation process generates irreversible damage to the carbon fiber, and the tensile strength of the material is only 78 MPa. Then, in order to solve the problem of fiber damage, the group proposed to prepare PyC on the surface of carbon fiber, which reduces the damage degree of the fiber to some extent, but the prepared interface phase was PyC/TiC/Ti₂AlC three-layer structure, the first layer PyC weak bonding interfaceExist such that C_fThe fracture behavior of the/SiC composite material still takes debonding of PyC interface as the main part, and the third layer of Ti₂The AlC interface hardly exhibits its excellent mechanical properties characteristic as a MAX phase material.

The invention provides a method for synthesizing SiC by using molten salt_fPreparation of Ti between fiber and matrix of/SiC composite material₃SiC₂The interface phase adopts a similar ceramic preparation process as the work of Li and Wang, and the key points which are fundamentally different from the invention are as follows: (1) first, the carbon fibers used in the study by Li et al are very different from the SiC fibers according to the present invention in both chemical environment and microstructure. Carbon fibers are skin-core structured fibers formed of surface graphite crystallites and internal amorphous carbon. The SiC fiber is mainly composed of SiC nanometer crystal grains, and the element ratio of carbon to silicon is close to 1: 1. The differences in composition and microstructure necessarily lead to large differences in both the chemical reaction path of the synthesis and the chemical stability between the phases. (2) Second, the interfacial phase of Li et al synthesis and Ti of the present invention₃SiC₂While belonging to the MAX phase material, it is two completely different ternary systems. The chemical reaction mechanism of the Ti-Si-C system is different from that of the Ti-Al-C system, in which Ti₃SiC₂With Ti₂In the preparation process of two AlC interface phases, a control method of phase components and a removal method of impurity phases do not have references. (3) Finally, the invention relates to the preparation of the surface PyC of SiC fibers, which is of different significance than the study by Li et al. In the study of Li et Al, the main role of PyC production is to protect the carbon fibers from corrosion by Ti and Al elements, as a result of which the produced interface phase overall exhibits PyC/TiC/Ti₂The AlC three-layer structure has no great difference with a pure PyC weak interface in mechanical behavior, and still realizes crack deflection by means of a weak bonding interface to toughen. The PyC prepared by the method mainly aims to increase the content of the C element on the surface of the fiber and adjust the stoichiometric ratio of the Ti, Si and C elements at a reaction interface to be closer to 3:1:2 so as to avoid generation of Ti and C₃SiC₂Other than TiC, Ti₅Si₃And the like. In the prepared interphase, PyC was just consumedOnly Ti is generated₃SiC₂A strong bonding interface is formed. In the present invention, the addition of the Si-containing particles to the molten salt system is effective in participating in Ti as an Si source₃SiC₂Synthesis of the interphase, on the other hand by formation of water-washable Ti₅Si₃The particles reduce the concentration of Ti element in the melt, thereby achieving the purpose of controlling the synthesis of Ti on the surface of the fiber₃SiC₂The reaction rate is to avoid excessive reaction between Ti and SiC, resulting in strong corrosion of the fiber and loss of strength.

When the mixed powder containing Ti element powder, Si element powder and halogen salt is used for embedding SiC fibers, the natural dispersion state of the powder is maintained, the powder is not tamped, the distribution state of the Si element in a melt is maintained, more impurities on the fibers after heat treatment are avoided, and in-situ synthesis of Ti is reduced₃SiC₂The quality of the interface phase.

In the synthesis process, Ti element can be fully dissolved in the fused salt melt, Si element cannot be dissolved, and smaller particles of the Ti element and the melt form suspension which diffuses along with the flow of the melt. And the Si substance is added according to the molar ratio of the Ti element to the Si element of 3:1, so that the Si substance reacts with the dissolved Ti element to generate a plurality of Ti-Si compounds, and the reactivity of the Ti element in the melt is reduced. The problem that Ti-containing element melt with over-strong activity reacts violently with SiC fibers to generate a large amount of TiC impurities is solved. The addition of Si element is helpful to promote Ti₃SiC₂The amount of the generated SiC fibers is reduced, and simultaneously, the SiC fibers are protected from being corroded too strongly.

The PyC preparation of the invention leads the surface of the SiC fiber to be in a carbon-rich state, and the measure is beneficial to relieving Ti₃SiC₂The proportion of Si and C elements in the fiber is unbalanced in the synthesis process. The thickness of less than 200nmPyC supplements the C element for the chemical reaction, especially the PyC of about 120nm supplements the C element for the chemical reaction better, and can ensure that the C element is completely consumed after the reaction is finished. The thickness of PyC is more than 200nm, which can affect the synthesis process and lead to excessive impurity phases of PyC and TiC or Ti₃SiC₂The synthesis failed.

In the heat treatment process, the SiC nano-crystalline grains on the surface of the SiC fiber are subjected to chemical reaction with the raw material powder in the molten salt through PyC, and a large amount of substance exchange occurs in the near-surface area of the fiber, so that the fiber and the newly generated interface phase are strongly combined in a chemical reaction mode.

Has the advantages that: compared with the prior method for preparing TiC/Ti on the surface of the carbon fiber by utilizing a molten salt synthesis method₂The research of AlC, the invention adopts CVD combined with molten salt method for the first time to synthesize Ti with higher purity in situ on the surface of SiC fiber₃SiC₂An interfacial phase. SiC prepared by the interface phase_fthe/SiC realizes the strengthening and toughening effect and simultaneously shows a different strengthening and toughening mechanism from PyC or h-BN. In addition, compared to SiC prepared with PyC interphase_f/SiC of Ti₃SiC₂SiC of interface phase_fthe/SiC will have a stronger oxidation resistance.

Drawings

FIG. 1: preparing Ti₃SiC₂Morphology and element spectrum of SiC fibers of interface phase

FIG. 2: prepared Ti₃SiC₂Microstructural structure diagram and element analysis of interface phase

Detailed Description

The invention will now be further described with reference to the following examples and drawings:

example 1:

weighing Ti powder, Si powder, NaCl and KCl according to the molar ratio of 3:1:16:16, adding absolute ethyl alcohol, carrying out ball milling and mixing, drying, and then sieving with a 200-mesh sieve to obtain the required molten salt environment (powder state); putting the SiC fiber woven piece into a chemical vapor deposition furnace, and depositing PyC with the thickness of about 120nm on the surface of the SiC fiber by using propylene gas; placing SiC fibers with carbon-rich surfaces into an alumina crucible containing a molten salt system, placing the crucible into a tubular furnace protected by Ar atmosphere after covering, keeping the pressure in the furnace at 10kPa, raising the temperature to 660 ℃ at the rate of 5 ℃/min, preserving the heat for 0.5h, and raising the temperature to 1200 ℃ again, preserving the heat for 1 h; after cooling along with the furnace, taking out the crucible, cleaning the SiC fibers by deionized water, and drying the SiC fibers to obtain the SiC fibersTo obtain Ti₃SiC₂An interfacial phase.

FIG. 1 shows Ti produced in example 1 observed and detected by a scanning electron microscope and an energy dispersive spectrometer₃SiC₂Morphology photographs of the interface phase and elemental composition results. As can be seen from FIG. 1, Ti₃SiC₂The interface phase is uniformly distributed on the SiC fiber, the thickness of the interface phase is 1.5 mu m, the thickness of about 1 mu m outside the SiC fiber is changed due to participation in chemical reaction to cause microstructure change, and the area with the diameter of 11.6 mu m of the fiber main body is not influenced. The prepared interface phase is lamellar Ti₃SiC₂The crystal grains are lapped and have no preferred orientation, and the energy dispersion spectrometer proves that the proportion of three elements of Ti, Si and C in the interface phase is about 3:1: 2. FIG. 2 shows Ti prepared in example 1, which was observed and analyzed by a transmission electron microscope and an energy dispersion spectrometer after cutting a cross section by FIB₃SiC₂Microscopic structure photograph of interface phase and element analysis result. As can be seen from FIG. 2, the prepared interphase consisted only of Ti₃SiC₂The blue region in the energy dispersive spectrum mapping map is Ti₃SiC₂The yellow region is SiC, the green region is a Pt plating layer in the FIB processing, and no other impurity phase is found. High resolution photographs of the interface phase and fiber junctions show the large size of Ti in the interface phase and the nano-grains in SiC fibers₃SiC₂The grains are tightly combined. Confirmation example 1 successful preparation of Ti strongly bonded to SiC fibers₃SiC₂An interfacial phase.

Ti was prepared as in example 1₃SiC₂The SiC fiber woven part (two-dimensional layer) of the interface phase is densified by CVI-SiC to prepare Ti-containing₃SiC₂SiC of interface phase_f(iii) SiC, as example 1 group; the SiC fiber woven part (two-dimensional ply) deposited with the 120nm PyC interface phase is densified by CVI-SiC to prepare SiC containing the PyC interface phase_fAs a control group,/SiC. Three-point bending tests were performed on both groups (3 test specimens per group) to obtain the bending strengths thereof as shown in table 1. Then, to confirm Ti₃SiC₂The interphase had more excellent antioxidant properties, and the samples of example 1 and the control (3 samples each) were usedTest sample) was oxidized in static air at 800 c for 10 hours, and then a three-point bending test was performed to obtain the residual bending strength and strength retention rate after oxidation thereof, as shown in table 1. As can be seen from Table 1, Ti is contained₃SiC₂The composite material of the interface phase achieves the aim of strengthening and toughening, and the oxidation resistance of the composite material is obviously superior to that of the composite material containing the PyC interface phase.

TABLE 1 SiC_fBending strength of/SiC and residual bending strength after oxidation

Example 2:

TiH is weighed according to the molar ratio of 3:1:16:16₂Adding the powder, Si powder, NaCl and KCl into absolute ethyl alcohol, carrying out ball milling and mixing, drying, and then sieving by a 200-mesh sieve to obtain a required molten salt environment (powder state); putting the SiC fiber woven piece into a chemical vapor deposition furnace, and depositing PyC with the thickness of about 120nm on the surface of the SiC fiber by using propylene gas; placing SiC fibers with carbon-rich surfaces into an alumina crucible containing a molten salt system, placing the crucible into a tubular furnace protected by Ar atmosphere after covering, keeping the pressure in the furnace at 10kPa, raising the temperature to 800 ℃ at the rate of 5 ℃/min, preserving the heat for 0.5h, and raising the temperature to 1200 ℃ again, preserving the heat for 1 h; after cooling along with the furnace, taking out the crucible, cleaning the SiC fiber by deionized water, and drying to obtain Ti on the surface of the SiC fiber₃SiC₂An interfacial phase.

Example 3:

weighing Ti powder, Si powder, NaCl and KCl according to the molar ratio of 3:1:20:20, adding absolute ethyl alcohol, carrying out ball milling and mixing, drying, and then sieving with a 200-mesh sieve to obtain a required molten salt environment (powder state); putting the SiC fiber woven piece into a chemical vapor deposition furnace, and depositing PyC with the thickness of about 60nm on the surface of the SiC fiber by using propylene gas; placing SiC fibers with carbon-rich surfaces into an alumina crucible containing a molten salt system, placing the crucible into a tubular furnace protected by Ar atmosphere after covering, keeping the pressure in the furnace at 101kPa, raising the temperature to 660 ℃ at the rate of 5 ℃/min, preserving the temperature for 0.5h, and raising the temperature to 1200 ℃ again, preserving the temperature for 1 h; after cooling with the furnaceTaking out the crucible, washing the SiC fiber with deionized water, and drying to obtain Ti on the surface of the SiC fiber₃SiC₂An interfacial phase.

Claims

1. In-situ synthesis of Ti on SiC fiber surface by utilizing SiC nano crystal particles₃SiC₂The preparation method of the interface phase is characterized by comprising the following steps:

2. The in-situ synthesis of Ti on the surface of SiC fibers using SiC nanocrystals according to claim 1₃SiC₂The preparation method of the interface phase is characterized by comprising the following steps: the thickness of the PyC is 120 nm.

3. The in-situ synthesis of Ti on the surface of SiC fibers using SiC nanocrystals according to claim 1₃SiC₂The preparation method of the interface phase is characterized by comprising the following steps: when the SiC fibers with the surface carbon-rich characteristic are buried in a molten salt system, the powder is kept in a natural dispersion state.

4. The method of claim 1 using SiC nanocrystalsIn-situ synthesis of Ti on SiC fiber surface₃SiC₂The preparation method of the interface phase is characterized by comprising the following steps: the powder containing Ti element is Ti powder or TiH₂Powder or TiO₂And (3) pulverizing.

5. The in-situ synthesis of Ti on the surface of SiC fibers using SiC nanocrystals according to claim 1₃SiC₂The preparation method of the interface phase is characterized by comprising the following steps: the Si-containing powder is Si powder or SiO₂And (3) pulverizing.

6. The in-situ synthesis of Ti on the surface of SiC fibers using SiC nanocrystals according to claim 1₃SiC₂The preparation method of the interface phase is characterized by comprising the following steps: the halogen salt comprises one or a mixture of two of NaCl, KCl, NaBr, KBr, NaF and KF.