A method for synthesizing a Ti-Si-C composite interface phase in situ on the surface of a silicon carbide fiber

Abstract

The application discloses a method for synthesizing a Ti-Si-C composite interface phase on a silicon carbide fiber surface in situ, which comprises the following steps: using a carbon source and a silicon source as raw materials, and adopting a chemical vapor deposition method to alternately deposit PyC and SiC coatings on the silicon carbide fiber surface in sequence to obtain a PyC-SiC-PyC composite coating silicon carbide fiber; and embedding the PyC-SiC-PyC composite coating silicon carbide fiber in a Ti-containing molten salt powder and performing heat treatment to obtain the PyC-SiC-PyC composite coating silicon carbide fiber. The method improves the uniformity and controllability of the obtained composite coating, and the obtained composite material has excellent mechanical properties, and the bending strength retention after oxidation is more than 95%.

Description

Technical Field

[0001] This invention belongs to the fields of functional interface phase technology and composite material technology, and relates to a method for in-situ synthesis of Ti-Si-C composite interface phase on the surface of silicon carbide fiber. Technical Background

[0002] Third-generation SiC fibers are considered the most promising SiC for nuclear applications due to their superior radiation resistance. f Reinforcing materials for SiC composites. f In SiC composites, to achieve pseudo-plastic fracture characteristics and improve damage tolerance, an interfacial phase needs to be prepared on the fibers to adjust the bonding strength between the fibers and the matrix. However, existing interfacial phases (PyC, BN) do not perform satisfactorily under radiation. PyC (pyrolytic carbon) is prone to structural transformation under neutron radiation, leading to a rapid decline in the mechanical properties of the composite material. Because the BN phase contains the strongly absorbing neutron element boron, it cannot be used in core-shell materials. Although SiC has good radiation resistance, its interfacial strength is uncontrollable, resulting in poor mechanical properties of the composite material. Therefore, it needs to be used in combination with PyC or BN. Thus, a new coating material is needed to further improve the performance of SiC. f Radiation resistance of SiC.

[0003] Under neutron irradiation, TiC exhibits good structural stability due to its low neutron absorption cross section. Titanium silicon carbide (Ti3SiC2) is a novel ternary compound MAX phase. Due to its similar local atomic structure to TiC, it inherits the high neutron irradiation resistance of its carbides. It also possesses high intrinsic fracture toughness and damage tolerance, while exhibiting excellent high-temperature resistance, oxidation resistance, and corrosion resistance. Furthermore, compared to other MAX phases (such as Ti2AlC, Ti3AlC2, and Ti3Si(Al)C2), Ti3SiC2 shows superior chemical compatibility with SiC, making it a promising candidate for SiC MAX phase. f Interface phase in SiC.

[0004] Currently, the reported applications in SiC f The main methods for preparing the Ti3SiC2 interface phase in SiC include electrophoretic deposition, magnetron sputtering, chemical vapor deposition, dip coating, and molten salt method. Among these, the molten salt method involves preparing a mixture of salt and reactants in a specific ratio, then heating the mixture to a temperature above the salt's melting point to melt the salt. The molten salt provides a liquid medium for the reaction system, which not only promotes the reaction but also allows for control of the microstructure of the reaction products by adjusting the synthesis temperature, salt content, and type.

[0005] Patent CN113087533A discloses a method for in-situ synthesis of Ti3SiC2 interfacial phase on the surface of SiC fiber by CVD combined with molten salt method, and Ti3SiC2 is uniformly dense and tightly combined with the fiber. The technical solution is to use SiC nanocrystalline grains inside the SiC fiber and PyC deposited on the surface of the fiber to react with Si and Ti in the molten salt environment to synthesize Ti3SiC2 interfacial phase. On the one hand, the SiC nanocrystalline grains inside the SiC fiber and the PyC on the surface react with Si and Ti powder in the molten salt, and a large amount of material exchange occurs in the near-surface region of the fiber, so that the fiber and the newly generated interfacial phase produce strong bonding through chemical reaction. On the other hand, by adding Si-containing particles as Si source to participate in the synthesis of Ti3SiC2 interfacial phase, and the reaction of Si material with dissolved Ti element to generate various Ti-Si compounds, the reactivity of Ti-containing melt in the melt is reduced. The problem of violent reaction between the active Ti-containing melt and SiC fiber to generate a large amount of TiC impurities is reduced. However, the thermal expansion coefficient of Ti3SiC2 (9x10 -6 1 / K) in this scheme is quite different from the thermal expansion coefficient of SiC matrix (4.5x10 -6 1 / K), and the Ti3SiC2 prepared at high temperature will produce a very high thermal mismatch stress with the SiC matrix during the process of dropping to room temperature, resulting in delamination and peeling of the Ti3SiC2 coating. TiC can alleviate the thermal mismatch stress problem between the Ti3SiC2 layer and the SiC matrix, so the TiC-Ti3SiC2 composite layer is actually more conducive to the combination with the SiC matrix. In addition, the Si element in the form of particles is almost insoluble in the molten salt system, which will cause problems such as difficult dispersion and diffusion, and thus the Ti3SiC2 phase cannot be uniformly distributed.

[0006] Patent CN116836002 A discloses a Ti-Si-C composite coating for SiC f / SiC surface and a preparation method thereof. The composite coating has a three-layer structure of TiC layer, Ti3SiC2 layer and Ti5Si3Cx layer from the surface of SiC matrix to the outside, and the control of the carbon and silicon molar ratio of SiC matrix, the addition amount of silicon powder and the heat treatment temperature and time realizes the control of the total thickness of the coating and the thickness of each layer of TiC, Ti3SiC2 and Ti5Si3Cx. This technical solution also has problems such as difficulty in dispersing Si element and difficulty in achieving uniform distribution of the coating. SUMMARY

[0007] In view of the deficiencies in the prior art, the purpose of the present application is to provide a method for synthesizing Ti-Si-C composite interface phase in situ on the surface of silicon carbide fibers, which replaces the silicon powder particles in the prior art with a CVD-SiC coating, provides C source and Si source for the synthesis of TiC and Ti3SiC2 phases by preparing a PyC-SiC-PyC composite coating on the surface of silicon carbide fibers, realizes the uniform distribution of TiC-Ti3SiC2 phases, and avoids the excessive corrosion of silicon carbide fibers in the molten salt system, thereby avoiding irreversible loss. By the method, the synthesis temperature can be significantly reduced and the reaction time can be shortened, and the composite interface synthesized by the method has a significant toughening effect on the silicon carbide fibers, and the SiC f / SiC composite material prepared by densifying the composite interface phase containing TiC-Ti3SiC2 through CVI-SiC can retain more than 95% of the bending strength.

[0008] In order to achieve the above technical purpose, the present application provides a method for synthesizing Ti-Si-C composite interface phase in situ on the surface of silicon carbide fibers, which uses chemical vapor deposition method to alternately deposit PyC and SiC coatings on the surface of silicon carbide fibers with carbon source and silicon source as raw materials, to obtain PyC-SiC-PyC composite coating silicon carbide fibers; and the PyC-SiC-PyC composite coating silicon carbide fibers are embedded in Ti-containing molten salt powder and subjected to heat treatment.

[0009] The present application adopts chemical vapor deposition and molten salt method to prepare a method for synthesizing TiC-Ti3SiC2 composite interface phase on the surface of silicon carbide fibers. The key technical point of the present application is to first prepare a PyC-SiC-PyC coating on the surface of silicon carbide fibers, and to deposit PyC layer A, SiC layer and PyC layer B from outside to inside. Then, Ti ions are introduced into the molten salt, so that the Ti ions rapidly diffuse to the surface of the silicon carbide fibers and chemically react. The whole reaction mechanism is as follows: first, the Ti ions rapidly diffuse to the outer PyC layer A and react (1) to form a first layer of TiC; then, the Ti ions continue to diffuse to the middle SiC coating and react (2) to continue to form a second layer of TiC, while releasing a large amount of active Si; the remaining Ti continues to diffuse to the inner PyC layer B and reacts (1) to form a third layer of TiC; at the same time, part of the released active Si diffuses outward and inserts between the second and first layers of TiC, reacts (3) to form a layer of Ti3SiC2, and part of the active Si diffuses inward and inserts between the second and third layers of TiC, also reacts (3) to form a new layer of Ti3SiC2. Excess Si may also react with excess Ti while diffusing to produce soluble by-products such as Ti5Si3 and TiSi2, and the soluble by-products Ti5Si3 and TiSi2 can be further removed by cleaning.

[0010] PyC + Ti → TiC (1)

[0011] SiC + Ti → TiC + Si (2)

[0012]

[0013] 5Ti + 3Si → Ti5Si3 (4)

[0014] Ti + 2Si → TiSi2 (5)

[0015] As a preferred solution, the thickness of the PyC layer A is greater than the thickness of the SiC layer and greater than the thickness of the PyC layer B; the thickness of the SiC layer is greater than or equal to the thickness of the PyC layer B and less than half the sum of the thicknesses of the PyC layer A and the PyC layer B. The PyC-SiC-PyC coating on the surface of the silicon carbide fiber, the thickness of the PyC layer A is greater than the thickness of the SiC layer and greater than the thickness of the PyC layer B, so that the thickness of the first layer of TiC is greater than the second and third layers of TiC; the thickness of the SiC layer is greater than or equal to the thickness of the PyC layer B and less than half the sum of the thicknesses of the PyC layer A and the PyC layer B, so that the thickness of the second layer of TiC is greater than or equal to the third layer of TiC and provides an appropriate amount of active Si source for the formation of TiC-Ti3SiC2, so that the first layer of TiC partially inserts Si ions to generate a TiC-Ti3SiC2 double-layer structure, and the second and third layers of TiC are basically completely inserted into Si ions to generate a Ti3SiC2 single-layer structure, and finally a TiC-Ti3SiC2 composite layered structure is obtained. The thickness of each layer is related to the thickness of the other layers, which is derived as follows:

[0016] The distribution and thickness of the PyC layer A, the PyC layer B and the SiC layer determine the structure of the Ti-Si-C composite interface phase. As can be seen from equations (1) and (2), PyC and SiC both react with Ti ions to form TiC in a molar ratio of 1:1:1. The molar amount of the PyC, SiC and TiC layers is equivalent to their thicknesses. Assuming that the thickness of a unit of molar PyC layer A is a, the thickness of a unit of molar SiC layer is c, and the thickness of a unit of molar PyC layer B is b, the thickness of the generated TiC layer is a for the first layer, c for the second layer and b for the third layer, and a unit of molar active Si is released, as shown in reactions (6) to (8). Active Si reacts with TiC to form Ti3SiC2 in a molar ratio of 1:3:1, so 3c thickness of TiC layer is required to completely react with a unit of molar active Si to form Ti3SiC2, as shown in equation (9).

[0017] aPyC + Ti → aTiC (6)

[0018] cSiC + Ti → cTiC + Si (7)

[0019] bPyC + Ti → bTiC (8)

[0020] Si + 3cTiC → cTi3SiC2 + cC (9)

[0021] ① When a + b + c > 3c, i.e. a + b > 2c, TiC is in excess relative to active silicon, and a TiC-Ti3SiC2 composite layered structure is mainly generated. If a > c ≥ b, the first layer of TiC is in excess, and a TiC-Ti3SiC2 composite layered structure is generated from outside to inside. If b > c ≥ a, the third layer of TiC is in excess, and a Ti3SiC2-TiC composite layered structure is generated from outside to inside. If a > c and b > c, both the first and third layers of TiC are in excess, and a TiC-Ti3SiC2-TiC composite layered structure is generated from outside to inside.

[0022] ② When a + b + c = 3c, i.e. a + b = 2c, active silicon diffuses to the outside and the inside at the same time, and reacts completely with the first, second and third layers of TiC, generating Ti3SiC2, and a small amount of residual carbon is generated, which reacts with excess Ti to generate TiC. Finally, Ti3SiC2 structure is mainly obtained, accompanied by a small amount of TiC component.

[0023] ③ When a + b + c < 3c, i.e. a + b < 2c, TiC is insufficient relative to active silicon, and active silicon reacts with excess Ti to generate Ti5Si3, TiSi2 and other soluble by-products in addition to Ti3SiC2, and a Ti3SiC2-Ti5Si3-TiSi2 composite structure is finally obtained.

[0024] As a preferred scheme, the thickness of the PyC layer A is 100-500 nm, the thickness of the PyC layer B is 100-500 nm, and the thickness of the SiC layer is 100-500 nm. Further preferably, the thickness of the PyC layer A is 200-400 nm, the thickness of the PyC layer B is 100-300 nm (expanded range according to the data of Example 2), and the thickness of the SiC layer is 100-300 nm.

[0025] As a preferred scheme, during the deposition of the PyC layer A, the temperature is 950-1150°C, the deposition time is 6-30 h, and the deposition thickness is 200-400 nm; during the deposition of the PyC layer B, the temperature is 950-1150°C, the deposition time is 3-10 h, and the deposition thickness is 100-200 nm; and during the deposition of the SiC layer, the temperature is 1000-1200°C, the deposition time is 5-15 h, and the deposition thickness is 100-200 nm.

[0026] As a preferred scheme, the carbon source is at least one of methane, propylene and acetylene; and the silicon source is at least one of trichloromethylsilane, silicon tetrachloride and methylsilane.

[0027] As a preferred scheme, Ar or N2 is used as the dilution gas during the deposition of the PyC layer A and the PyC layer B, and methane, propylene, acetylene or other alkane is used as the carbon source gas.

[0028] As a preferred scheme, trichloromethylsilane (MTS), silicon tetrachloride and methylsilane or the like are used as the silicon source gas during the deposition of the SiC layer, H2 is used as the carrier gas and reaction gas, and Ar is used as the dilution gas.

[0029] As a preferred scheme, the Ti-containing molten salt powder is obtained by mixing Ti powder and a solution containing halogen salt and then wet ball milling, so that the Ti element is fully mixed and uniform in the molten salt. The Ti ion is introduced into the molten salt, and the Ti ion rapidly diffuses to the surface of silicon carbide to chemically react.

[0030] As a preferred scheme, the halogen salt is at least one of NaCl, KCl, NaBr, KBr, NaF and KF.

[0031] As a preferred scheme, the molar ratio of the Ti powder to the halogen salt is 1:(3-20), and further preferably 1:(8-15). The reaction of the Ti ion in the PyC-SiC-PyC composite coating is controlled by controlling the mass ratio of the Ti powder to the halogen salt, so as to obtain the silicon carbide TiC-Ti3SiC2 composite interface phase. Ti has a certain solubility in the molten salt and can exist in the ionic state. Therefore, the molten salt can provide a liquid reaction environment on the one hand, so that the Ti ion can rapidly and uniformly diffuse to the surface of the PyC-SiC-PyC coating to react; on the other hand, the strong polarization of the molten salt can reduce the reaction barrier and accelerate the reaction kinetics. The ratio of the Ti powder to the halogen salt determines the solubility of Ti in the molten salt and also determines the content of Ti that can participate in the reaction. The larger the ratio, the higher the content of Ti, the faster the reaction rate, and the more smoothly the reaction proceeds. However, if the ratio is too large and the content of Ti is too high, on the one hand, too much by-product Ti5Si3 and TiSi2 is produced, which reduces the effect of the interface phase; on the other hand, the silicon carbide fiber is also easily eroded.

[0032] As a preferred scheme, the wet ball milling is performed for 12-48 h with ethanol as the solvent. Zirconia grinding medium can be added during the ball milling to promote more sufficient ball milling.

[0033] As a preferred scheme, the heat treatment is performed at a heating rate of 4-10 ℃ / h, a heat treatment temperature of 1000-1200 ℃ and a holding time of 1-5 h. The heat treatment is performed in an argon protective atmosphere.

[0034] As a preferred scheme, the Ti-Si-C composite interface phase has a TiC-Ti3SiC2 composite structure of TiC and Ti3SiC2 from the outside to the inside of the silicon carbide fiber. The prior art commonly uses a single PyC coating, and mainly synthesizes Ti3SiC2, which limits its application in SiC f / SiC composites. The outer TiC layer of the composite interface of the present application is used to relieve the thermal mismatch stress of the Ti3SiC2 layer and the SiC matrix, and the inner Ti3SiC2 layer is used for toughening of the SiC f / SiC composite, and the multi-layer interface structure is more conducive to the mechanical properties of the composite material.

[0035] Compared with the prior art, the present application has the following beneficial effects:

[0036] 1) The present application provides C source and Si source for the synthesis of TiC and Ti3SiC2 phase by preparing a PyC-SiC-PyC composite coating on the surface of the silicon carbide fiber, and controls the composition of TiC-Ti3SiC2 by adjusting the thickness of the PyC and SiC coating, which is conducive to the control of uniform distribution of TiC-Ti3SiC2 phase, and further avoids the irreversible loss caused by excessive corrosion of the silicon carbide fiber in the molten salt system. The method can significantly reduce the synthesis temperature and shorten the reaction time, and the interface phase synthesized by the method has a significant toughening effect on the silicon carbide fiber. After CVI-SiC densification, SiC f / SiC composite material containing TiC-Ti3SiC2 interface phase can retain more than 95% of the maximum bending strength.

[0037] 2) The present application uses a deposited SiC coating as an active Si source, which has the advantages of relatively good uniformity, easier chemical reaction, and easier control of reaction products compared with difficult-to-dissolve Si particles.

[0038] 3) The molten salt in the present application simultaneously plays the role of flux and reaction medium. The reaction raw materials have a faster diffusion rate in the molten salt, and the surface energy is improved under the polarization effect of the molten salt, which makes it easier to break through the reaction barrier and react, significantly reducing the synthesis temperature and shortening the reaction time. DETAILED DESCRIPTION

[0039] The present application will be further described below in conjunction with specific embodiments, but the scope of protection of the present application is not limited to the following specific embodiments. Obviously, the following described embodiments are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative labor still belong to the scope of protection of the present application.

[0040] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0041] Example 1

[0042] A method for in-situ synthesis of Ti-Si-C composite interface phase on silicon carbide fiber surface, the specific steps of which are as follows:

[0043] 1) Using acetylene as the carbon source and trichloromethylsilane (MTS) as the silicon source, a PyC-SiC-PyC composite coating was deposited on the surface of silicon carbide fibers using chemical vapor deposition. The thickness of PyC layer A was 200 nm, PyC layer B was 100 nm, and the thickness of the intermediate SiC layer was 100 nm. Nitrogen was used as the dilution gas for PyC layer deposition, the furnace pressure was 5 kPa, the acetylene / nitrogen gas flow rate was 0.15 / 3 L / min, the deposition temperature of PyC layer A was 950℃, and the deposition time was 10 h, while the deposition temperature of PyC layer B was 950℃, and the deposition time was 4 h. For the intermediate SiC layer deposition, H2 was used as the carrier gas, and MTS was introduced into the reaction chamber by bubbling. Ar was used as the dilution gas and protective gas, the H2 / Ar gas flow rate was 0.25 / 0.25 L / min, the furnace pressure was 3 kPa, the deposition temperature was 1100℃, and the deposition time was 5 h.

[0044] 2) Weigh Ti powder, NaCl and KCl in a molar ratio of 1:5:5, mix them with zirconium oxide grinding media and an appropriate amount of ethanol in a horizontal ball mill, and then ball mill for 24 hours. After drying, pass the mixture through a 200-mesh sieve to obtain Ti-containing molten salt powder.

[0045] 3) Embed silicon carbide fibers with PyC-SiC-PyC on their surface in an alumina crucible containing Ti molten salt powder. Heat the crucible in a tube furnace, maintaining the furnace pressure at 5 kPa. Under Ar atmosphere protection, raise the temperature to 1200°C at 5°C / min and hold for 2 hours. After the furnace cools down, remove the crucible.

[0046] 4) Wash the reactants with deionized water to remove water-soluble byproducts. Dry to obtain silicon carbide fibers with a TiC-Ti3SiC2 composite interface structure on the surface.

[0047] Example 2

[0048] The only difference between this embodiment and Embodiment 1 is that the thickness of PyC layer A in step 1) is changed to 500 nm, and the deposition time is 30 h; the thickness of PyC layer B is changed to 300 nm, and the deposition time is 15 h; the thickness of the intermediate SiC layer is changed to 300 nm, and the deposition time is 20 h. All other steps and conditions are the same, resulting in silicon carbide fibers with a TiC-Ti3SiC2 composite interface structure on the surface.

[0049] Example 3

[0050] The only difference between this embodiment and Embodiment 1 is that the molar ratio of Ti powder, NaCl and KCl in step 2) is changed to 1:10:10, while the other steps and conditions are the same, resulting in silicon carbide fibers with a TiC-Ti3SiC2 composite interface structure on the surface.

[0051] Comparative Example 1

[0052] The steps in this comparative example are the same as those in Example 1, except that steps 2), 3), and 4) are not performed to obtain silicon carbide fibers with a PyC-SiC-PyC interface structure on the surface.

[0053] Comparative Example 2

[0054] The only difference between this comparative example and Example 1 is that the thickness of PyC layer B is greater than the thickness of SiC layer, and also greater than the thickness of PyC layer A; the thickness of SiC layer is equal to the thickness of PyC layer A, and less than half the sum of the thicknesses of PyC layer A and PyC layer B. In step 1), the thickness of PyC layer A was changed to 100 nm, and the deposition time was 4 h; the thickness of PyC layer B was changed to 200 nm, and the deposition time was 10 h; the thickness of the intermediate SiC layer was changed to 100 nm, and the deposition time was 5 h. All other steps and conditions remained the same, resulting in silicon carbide fibers with a Ti3SiC2-TiC surface structure.

[0055] Comparative Example 3

[0056] The only difference between this comparative example and Example 1 is that the thickness of the SiC layer is controlled to be half the sum of the thicknesses of PyC layer A and PyC layer B. In step 1), the thickness of PyC layer A is changed to 200 nm and the deposition time is 10 h; the thickness of PyC layer B is changed to 100 nm and the deposition time is 4 h; the thickness of the intermediate SiC layer is changed to 150 nm and the deposition time is 9 h. All other steps and conditions are the same, resulting in silicon carbide fibers with a surface mainly composed of Ti3SiC2 interface structure.

[0057] Comparative Example 4

[0058] The difference between this comparative example and Example 1 is that the molar ratio of Ti powder, NaCl and KCl in step 2) is changed to 1:1:1, while the other steps and conditions are the same, resulting in silicon carbide fibers with a surface mainly composed of TiC interface structure.

[0059] Comparative Example 5

[0060] The difference between this comparative example and Example 1 is that only a PyC coating is deposited on the surface of silicon carbide fibers, and Si particles are used as the Si source for subsequent molten salt treatment.

[0061] 1) Using acetylene as the carbon source, a PyC coating was deposited on the surface of silicon carbide fiber by chemical vapor deposition. Nitrogen was used as the dilution gas during deposition. The furnace pressure was 5 kPa, the acetylene / nitrogen flow rate was 0.15 / 3 L / min, the deposition temperature was 950℃, the deposition time was 15 h, and the PyC deposition thickness was 300 nm.

[0062] 2) Based on the stoichiometric ratio of Ti3SiC2, Ti powder and Si powder were uniformly mixed at a molar ratio of 3:1, while NaCl and KCl were uniformly mixed at a molar ratio of 1:1. Then, 1 mol of Ti-Si elemental powder was mixed with 10 mol of NaCl-KCl binary salt. The mixed powder containing Ti, Si, NaCl and KCl was then mixed with an appropriate amount of ethanol in a horizontal ball mill with zirconia grinding media for 24 hours. After drying, it was passed through a 200-mesh sieve to obtain Ti and Si molten salt powder.

[0063] The remaining steps and conditions were the same, resulting in silicon carbide fibers with a surface mainly composed of Ti3SiC2 interface structure.

[0064] The silicon carbide fiber braids obtained in Examples 1-3 and Comparative Examples 1-5 were densified with CVI-SiC to produce SiC containing an interface phase. f The bending strength of the SiC composite material was tested using the three-point bending method. The sample was then placed in a muffle furnace and oxidized at 1200℃ for 2 hours. The bending strength was then measured, and the bending strength and strength retention rate before and after oxidation are shown in Table 1.

[0065] Table 1. Test results of toughening and antioxidant capabilities.

[0066]

Claims

1. A method for in-situ synthesis of a Ti-Si-C composite interface phase on the surface of silicon carbide fibers, characterized in that: Using carbon and silicon sources as raw materials, PyC and SiC coatings are sequentially and alternately deposited on the surface of silicon carbide fibers by chemical vapor deposition to obtain PyC-SiC-PyC composite coated silicon carbide fibers; the PyC-SiC-PyC composite coated silicon carbide fibers are embedded in Ti-containing molten salt powder and subjected to heat treatment, washing, and drying to obtain the final product. The Ti-Si-C composite interface phase has a TiC-Ti3SiC2 composite structure with TiC and Ti3SiC2 sequentially arranged from the outside to the inside of the silicon carbide fiber.

2. The method for in-situ synthesis of Ti-Si-C composite interface phase on the surface of silicon carbide fiber according to claim 1, characterized in that: The silicon carbide fiber surface is deposited with PyC layer A, SiC layer and PyC layer B sequentially from the outside to the inside.

3. The method for in-situ synthesis of Ti-Si-C composite interface phase on the surface of silicon carbide fiber according to claim 2, characterized in that: The thickness of PyC layer A is greater than the thickness of SiC layer, and also greater than the thickness of PyC layer B; The thickness of the SiC layer is greater than or equal to the thickness of the PyC layer B, and less than half the sum of the thicknesses of the PyC layer A and the PyC layer B.

4. The method for in-situ synthesis of Ti-Si-C composite interface phase on the surface of silicon carbide fiber according to claim 3, characterized in that: The deposition conditions for the PyC layer A are: temperature 950~1150℃, time 6~30h; The deposition conditions for the PyC layer B are: temperature 950~1150℃, time 3~10h; The deposition conditions for the SiC layer are: temperature of 1000~1200℃ and time of 5~15h.

5. A method for in-situ synthesis of a Ti-Si-C composite interface phase on the surface of silicon carbide fibers according to any one of claims 1 to 4, characterized in that: The carbon source is at least one of methane, propylene, and acetylene; The silicon source is at least one of trichloromethylsilane, silicon tetrachloride, and methylsilane.

6. The method for in-situ synthesis of Ti-Si-C composite interface phase on the surface of silicon carbide fiber according to claim 5, characterized in that: The Ti-containing molten salt powder is obtained by mixing Ti powder and halogen salts and then wet ball milling.

7. The method for in-situ synthesis of a Ti-Si-C composite interface phase on the surface of silicon carbide fibers according to claim 6, characterized in that: The halogen salt is at least one selected from NaCl, KCl, NaBr, KBr, NaF, and KF; The molar ratio of Ti powder to halide salt is 1:(3~20).

8. The method for in-situ synthesis of Ti-Si-C composite interface phase on the surface of silicon carbide fiber according to claim 7, characterized in that: The conditions for wet ball milling are: time of 12-48 hours, and solvent of ethanol.

9. The method for in-situ synthesis of a Ti-Si-C composite interface phase on the surface of silicon carbide fibers according to claim 1, characterized in that: The heat treatment conditions are: temperature 1000~1200℃, time 1~5h.

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