Preparation method of SiC fiber surface rare earth silicate anti-oxidation interface phase

Abstract

The invention relates to a preparation method of a SiC fiber surface rare earth silicate anti-oxidation interface phase. The preparation method comprises the following steps: (1) carrying out pre-oxidation treatment on the surface of the SiC fiber; (2) carrying out hydroxylation on the surface of the pre-oxidized SiC fiber; (3) carrying out alkylation modification on the surface of the hydroxylated SiC fiber; (4) dipping the surface-modified SiC fiber in a precursor solution containing a soluble rare earth source, and heating to obtain the SiC fiber with a rare earth precursor deposited on the surface; and (5) carrying out heat treatment on the SiC fiber with the rare earth precursor deposited on the surface to obtain the SiC fiber surface rare earth silicate anti-oxidation interface phase.

Description

Technical Field

[0001] The present invention belongs to SiC f The present invention relates to the field of preparation of SiC / SiC interface phase materials, and relates to a method for preparing a rare earth silicate antioxidant interface phase on a fiber surface. Background Art

[0002] Aircraft engines are known as the "crown jewel of modern industry". They are difficult to manufacture and have harsh service environments. They often face harsh environmental challenges such as high load, high temperature and high pressure, high-speed gas scouring, cyclic thermal shock, CMAS corrosion, etc., which place extremely high demands on aircraft engine materials. In addition, the continuous improvement of the thrust-to-weight ratio of aircraft engines has also led to increasingly stringent service temperatures for hot end components such as engine combustion chambers, turbines, and tail nozzles. Traditional titanium-based and nickel-based high-temperature alloys can no longer meet the higher service temperature requirements of high thrust-to-weight ratio aircraft engines for hot end component materials, and silicon carbide fiber reinforced silicon carbide (SiC f / SiC) ceramic matrix composites have excellent properties such as high temperature stability, high specific strength, high specific modulus, low density, and oxidation resistance. They have become an important candidate material for the hot end components of the next generation of high thrust-to-weight ratio aircraft engines.

[0003] SiC f / SiC ceramic matrix composites are composed of SiC fibers, interface phase and SiC matrix. Among them, the interface phase plays the role of transferring load, protecting fibers and crack deflection, which is the key to improving SiC f / SiC composite materials are an important component for damage tolerance and non-catastrophic failure of composite materials. At present, the interface phase of ceramic matrix composites used in aircraft engines is mostly boron nitride (BN) interface, and its unique layered structure can give the composite material good mechanical properties. However, the BN interface is easily corroded by the high-temperature water-oxygen coupling environment during the service of the aircraft engine, forming volatile boric acid substances, which leads to material failure. For this reason, there is an urgent need to develop a new interface phase material resistant to high-temperature water-oxygen corrosion to meet the requirements of SiC f / SiC's working requirements in the actual service environment of aircraft engines.

[0004] Rare earth silicates have a high melting point, excellent high-temperature stability, and oxidation resistance. Their thermal expansion coefficient is close to that of SiC, and they remain chemically stable at high temperatures, making them a promising candidate for antioxidant interface phases. A Chinese patent (CN118619688A) discloses a method for preparing a rare earth silicate interface phase layer. This method utilizes a sol-gel and immersion-coating method to coat the fiber surface with a rare earth silicate interface phase, demonstrating excellent resistance to oxidative corrosion. However, the rare earth silicate phase introduced in this invention is prone to being distributed extensively between fiber bundles due to sol adhesion, hindering the deposition and densification of the matrix. Summary of the Invention

[0005] In response to the above problems, the present invention is directed to a method for uniformly preparing a rare earth silicate anti-oxidation interface phase on the surface of SiC fibers, wherein the rare earth silicate serves as the interface phase of the composite material and plays an anti-oxidation protective role.

[0006] In one aspect, the present invention provides a method for preparing a rare earth silicate anti-oxidation interface phase on the surface of SiC fiber, comprising the following steps: (1) Pre-oxidation treatment of the SiC fiber surface; (2) hydroxylating the pre-oxidized SiC fiber surface; (3) alkylation modification of the hydroxylated SiC fiber surface; (4) immersing the surface-modified SiC fiber in a precursor solution containing a soluble rare earth source, and heating the solution to obtain a SiC fiber with a rare earth precursor deposited on the surface; (5) The SiC fiber with the rare earth precursor deposited on the surface is heat-treated to obtain a rare earth silicate anti-oxidation interface phase on the surface of the SiC fiber.

[0007] Preferably, the SiC fiber surface is debonded before pre-oxidation treatment; the debonding treatment temperature is 500-800°C, the time is 0.5-3h, the heating rate is 1-10°C / min, and the atmosphere is a non-oxidizing atmosphere, preferably nitrogen or argon.

[0008] Preferably, in step (1), the pre-oxidation treatment conditions include: the pre-oxidation temperature is 600-1400°C, the time is 0.1-100h, the heating rate is 1-15°C / min, and the atmosphere is an oxidizing atmosphere, preferably air or oxygen atmosphere.

[0009] Preferably, in step (2), the conditions for hydroxylation of the SiC fiber surface include: immersing the pre-oxidized SiC fiber in an acid solution and treating it at 40-90°C for 0.5-48h; preferably, the acid solution is at least one of nitric acid, hydrochloric acid, hydrofluoric acid, and piranha solution; more preferably, the piranha solution is a mixed solution of 98% concentrated sulfuric acid and 30% hydrogen peroxide; further preferably, the volume ratio of concentrated sulfuric acid to hydrogen peroxide in the piranha solution is (3-7):(7-3).

[0010] Preferably, in step (3), the conditions for alkylation modification of the SiC fiber surface include: immersing the surface hydroxylated SiC fiber in a solution containing a silane coupling agent and treating it at 18-30°C for 3-48h; preferably, the silane coupling agent is at least one of 3-mercaptopropyltrimethoxysilane, hexadecyltrichlorosilane, 3-methacryloxypropyltrimethoxysilane, and 3-mercaptopropyltriethoxysilane; the solvent in the solution is ethanol and deionized water; more preferably, the mass ratio of the silane coupling agent, ethanol, and deionized water in the solution is 1:(10-30):(1-20).

[0011] Preferably, in step (4), the precursor solution comprises a soluble rare earth source, a precipitant and a solvent; wherein the soluble rare earth source is a soluble rare earth inorganic salt; preferably, the soluble rare earth inorganic salt is at least one of acetate, nitrate, phosphate and chloride; more preferably, the rare earth element in the soluble rare earth inorganic salt is at least one of scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu); The precipitant is urea; The solvent is at least one of anhydrous ethanol and deionized water; Preferably, the molar ratio of the rare earth source to the precipitant in the precursor solution is 1:(2-10); Preferably, the concentration of the rare earth source in the precursor solution is 0.05 to 0.8 mol / L; Preferably, the concentration of urea in the precursor solution is 0.1-2 mol / L.

[0012] Preferably, in step (4), the heating temperature is 70-90° C. and the heating time is 10-120 h.

[0013] Preferably, in step (5), the heat treatment conditions include: first keeping warm at 600-800°C for 1-3 hours, then keeping warm at 1200-1400°C for 5-10 hours, with a heating rate of 5-10°C / min, and the atmosphere is a non-oxidizing atmosphere, preferably nitrogen or argon.

[0014] On the other hand, the present invention provides a rare earth silicate antioxidant interface phase on the surface of SiC fiber prepared by the above-mentioned preparation method, wherein the composition of the rare earth silicate antioxidant interface phase on the surface of the SiC fiber includes monosilicate or pyrosilicate containing rare earth elements; preferably, the rare earth element is at least one of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.

[0015] Preferably, the thickness of the rare earth silicate anti-oxidation interface phase on the surface of the SiC fiber is 50 to 1000 nm.

[0016] Beneficial effects: This invention provides a method for preparing a rare earth silicate antioxidant interface phase on the surface of SiC fibers. By modifying the fiber surface, a rare earth silicate precursor is uniformly deposited on the SiC fiber surface. After heat treatment, the rare earth silicate interface phase is obtained. Compared with the sol-gel method, this method can produce a more uniform rare earth silicate interface, effectively achieving the antioxidant interface's protective effect on the fiber, and improving the composite material's service temperature and service life in oxidizing environments, thus showing great application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a SEM image of the cross-sectional morphology of SiC fiber coated with Yb2Si2O7 interface prepared in Example 1 of the present invention; Figure 2 This is a SEM image of the surface morphology of SiC fibers coated with Yb2Si2O7 interfaces prepared in Example 1 of the present invention; Figure 3 This is a SEM image of the cross-sectional morphology of SiC fiber coated with Yb2Si2O7 interface prepared in Example 2 of the present invention; Figure 4 The surface morphology SEM image of SiC fiber coated with Yb2Si2O7 interface prepared in Comparative Example 1 of the present invention; Figure 5 This is the XRD pattern of SiC fiber coated with Yb2Si2O7 interface prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0018] To further illustrate the content, features and practical effects of the present invention, the present invention is described in detail below in conjunction with the embodiments. It should be noted that the modification method of the design of the present invention is not limited to these specific embodiments. Without departing from the spirit and connotation of the design of the present invention, equivalent replacements and modifications made by those skilled in the art based on the content of the present invention are also within the scope of the present invention.

[0019] The present invention provides a method for preparing a rare earth silicate antioxidant interface phase on the surface of SiC fibers. Specifically, SiO2 is uniformly introduced onto the SiC fiber surface through surface pre-oxidation to serve as a reaction template for the rare earth silicate. A Yb2O3 precursor is simultaneously homogeneously deposited using urea, and a two-step heat treatment is performed to achieve the preparation of a Yb2Si2O7 interface. The purpose of the surface alkylation modification is to introduce an organic monolayer onto the pre-oxidized SiC fiber surface, enhancing the adsorption of the Yb2O3 precursor during the homogeneous urea deposition process, thereby achieving uniform Yb2O3 deposition.

[0020] The following is an exemplary description of the method for preparing the rare earth silicate anti-oxidation interface phase on the surface of SiC fiber provided by the present invention.

[0021] The SiC fiber is debonded.

[0022] In an optional embodiment, the SiC fibers may be in the form of a one-dimensional fiber bundle, a two-dimensional fiber cloth, a three-dimensional fiber braid, or a hybrid structure. The degumming treatment is performed at a temperature of 500 to 800°C, for a time of 0.5 to 3 hours, at a heating rate of 1 to 10°C / min, in a non-oxidizing atmosphere, preferably nitrogen or argon.

[0023] The fiber surface is pre-oxidized. The debonded SiC fiber is placed in an oxidizing atmosphere for oxidation, the purpose of which is to obtain a uniform silicon dioxide layer on the fiber surface for the subsequent preparation of the rare earth silicate interface.

[0024] In an optional embodiment, the pre-oxidation treatment conditions include: a pre-oxidation temperature of 600-1400°C, a time of 0.1-100h, a heating rate of 1-15°C / min, and an oxidizing atmosphere, preferably air or oxygen atmosphere.

[0025] The pre-oxidized SiC fiber surface is hydroxylated. The pre-oxidized fiber is immersed in an acidic solution and heated in a water bath to generate hydroxyl groups on the fiber surface. The fiber is then ultrasonically cleaned and dried. This allows the hydroxyl groups to be used to graft silane molecules onto the fiber surface, achieving surface alkylation modification.

[0026] In an optional embodiment, the acidic solution is at least one of nitric acid, hydrochloric acid, hydrofluoric acid, and piranha solution. More preferably, the piranha solution is a mixture of 98% concentrated sulfuric acid and 30% hydrogen peroxide. Further preferably, the volume ratio of concentrated sulfuric acid to hydrogen peroxide in the piranha solution is (3-7):(7-3), for example, the volume ratio of concentrated sulfuric acid to hydrogen peroxide in the piranha solution is 7:3, 5:5, or 3:7. The present invention uses piranha solution as the acidic solution for the purpose of cleaning the SiC fiber surface and increasing the number of surface hydroxyl groups, which facilitates subsequent alkylation modification.

[0027] In an optional embodiment, the water bath heating temperature is 40-90°C for a treatment time of 0.5-48 hours; the drying temperature is 60-80°C for a drying time of 0.5-2 hours. Excessively high water bath and drying temperatures or excessively long drying times may cause condensation of hydroxyl groups; while excessively low temperatures or short drying times may result in insufficient hydroxyl groups being generated, thereby affecting the effectiveness of subsequent surface alkylation modification.

[0028] The hydroxylated SiC fiber surface is then alkylated. The hydroxylated SiC fiber is immersed in a solution containing a silane coupling agent at 18-30°C for 3-48 hours, then ultrasonically cleaned and dried. This allows for the assembly of an organic monolayer on the SiC fiber surface to aid in the subsequent deposition of rare earth precursors.

[0029] In an optional embodiment, the silane coupling agent is at least one of 3-mercaptopropyltrimethoxysilane, hexadecyltrichlorosilane, 3-methacryloxypropyltrimethoxysilane, and 3-mercaptopropyltriethoxysilane; the solvent in the solution is ethanol and deionized water; more preferably, the mass ratio of the silane coupling agent, ethanol, and deionized water in the solution is 1:(10-30):(1-20). In the present invention, the silane coupling agent used is an anionic surface modifier (such as 3-mercaptopropyltrimethoxysilane) because the Zeta potential of the rare earth precursor in the solution is positive, and an anionic surface modifier is required to adjust the surface potential of the SiC fiber to a negative potential, thereby achieving the purpose of adsorbing the rare earth precursor.

[0030] Deposition of rare earth precursor. First, using a soluble rare earth source as raw material, urea as a precipitant, deionized water and anhydrous ethanol as solvents, the rare earth source and precipitant are dissolved in the solvent in turn and stirred to obtain a rare earth precursor solution; then, the surface alkylated SiC fiber is immersed in the precursor solution and allowed to stand at 70-90°C for 10-120h, then taken out for ultrasonic cleaning and drying to achieve the deposition of the rare earth precursor on the surface of the SiC fiber. The urea in the precursor solution will spontaneously decompose to produce OH in a solution above 60°C. - With CO3 2- , thereby promoting the precipitation of rare earth elements in the solution.

[0031] In an optional embodiment, the soluble rare earth source is a soluble rare earth inorganic salt; preferably, the soluble rare earth inorganic salt is at least one of acetate, nitrate, phosphate, and chloride; more preferably, the rare earth elements in the soluble rare earth inorganic salt are scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium At least one of rhenium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu); preferably, the molar ratio of the rare earth source to the precipitant in the precursor solution is 1:(2-10); the concentration of the rare earth source in the precursor solution is 0.05-0.8 mol / L; the concentration of urea in the precursor solution is 0.1-2 mol / L.

[0032] Interface phase heat treatment: The SiC fiber deposited with the rare earth silicate precursor is placed in a carbon tube furnace and subjected to high-temperature heat treatment in a non-oxidizing atmosphere to obtain an oxidation-resistant rare earth silicate interface phase.

[0033] In an optional embodiment, the conditions for the high-temperature heat treatment include: first keeping warm at 600-800°C for 1-3 hours, then keeping warm at 1200-1400°C for 5-10 hours, with a heating rate of 5-10°C / min, and the atmosphere is a non-oxidizing atmosphere, preferably nitrogen or argon.

[0034] In the present invention, the cleaning agent for ultrasonic cleaning is deionized water; the drying temperature is 60-80° C., and the drying time is 1-3 hours.

[0035] The rare earth silicate anti-oxidation interface phase on the SiC fiber surface produced by the present invention comprises a monosilicate or pyrosilicate containing a rare earth element. Preferably, the rare earth element is at least one of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. The thickness of the rare earth silicate anti-oxidation interface phase on the SiC fiber surface is 50 to 1000 nm.

[0036] The following examples are further given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all fall within the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples within a suitable range, that is, those skilled in the art can make selections within a suitable range through the description herein, and are not limited to the specific numerical values exemplified below.

[0037] Example 1

[0038] The method for preparing the rare earth silicate anti-oxidation interface phase on the surface of SiC fiber provided in this embodiment 1 includes the following steps: (1) Pre-oxidation treatment of SiC fiber: The SiC fiber was placed in a muffle furnace, heated to 600°C at a heating rate of 5°C / min in an argon atmosphere, and then naturally cooled after debonding treatment for 1 hour; the debonded SiC fiber was placed in a tube furnace, heated to 1000°C at a heating rate of 10°C / min in an air environment, and then naturally cooled after keeping the temperature for 10 hours; (2) Surface hydroxylation of SiC fibers: The pre-oxidized SiC fibers were immersed in a piranha solution consisting of 98% concentrated sulfuric acid and 30% hydrogen peroxide (volume ratio of 7:3) and heated to 80°C for 1 h. The fibers were then removed, ultrasonically cleaned in deionized water, and dried in a 70°C oven for 1 h. (3) Alkylation modification of SiC fiber surface: 3-mercaptopropyltrimethoxysilane, water, and ethanol were added to a beaker in a mass ratio of 1:5:15, and magnetically stirred at 700 r / min for 10 min. The SiC fiber with surface hydroxylation was then immersed in the solution and allowed to stand at room temperature for 12 h. (4) Deposition of rare earth precursor: Ytterbium nitrate pentahydrate and urea were added to deionized water in a molar ratio of 1:10, and magnetic stirring was carried out at 700 r / min for 10 min to obtain a precursor solution with a concentration of 0.05 mol / L of ytterbium nitrate pentahydrate and a concentration of 0.5 mol / L of urea; the surface alkylated SiC fiber was immersed in the precursor solution and placed in an 80°C oven for 40 h. The SiC fiber was then taken out and ultrasonically cleaned with deionized water, and then placed in an 80°C constant temperature oven for 1 h to obtain a SiC fiber with rare earth precursor deposited on the surface; (5) Heat treatment of the Yb2Si2O7 interface phase. The SiC fiber with the rare earth precursor deposited on its surface was placed in a reaction chamber. In an argon atmosphere, the temperature was raised to 700°C at a rate of 10°C / min and kept at that temperature for 1 h. Then, the temperature was raised to 1250°C at a rate of 10°C / min and kept at that temperature for 10 h. SiC fibers with a Yb2Si2O7 interface phase of 400 nm in thickness were obtained.

[0039] Figure 1 and Figure 2 The cross-section and surface morphology of the SiC fiber with the Yb2Si2O7 interface phase prepared in Example 1 are shown. As can be seen from the figure, Yb2Si2O7 is evenly and densely coated on the fiber surface, and the interface layer is well bonded to the fiber.

[0040] Example 2

[0041] The method for preparing the rare earth silicate anti-oxidation interface phase on the surface of SiC fiber provided in Example 2 includes the following steps: (1) Pre-oxidation treatment of SiC fiber: The SiC fiber was placed in a muffle furnace, heated to 600°C at a heating rate of 5°C / min in an argon atmosphere, and then naturally cooled after debonding treatment for 1 hour; the debonded SiC fiber was placed in a tube furnace, heated to 1100°C at a heating rate of 10°C / min in an air environment, and then naturally cooled after keeping the temperature for 1 hour; (2) Surface hydroxylation of SiC fibers: The pre-oxidized SiC fibers were immersed in a piranha solution consisting of 98% concentrated sulfuric acid and 30% hydrogen peroxide (volume ratio of 7:3) and heated to 80°C for 1 h. The fibers were then removed, ultrasonically cleaned in deionized water, and dried in a 70°C oven for 1 h. (3) Alkylation modification of SiC fiber surface: 3-mercaptopropyltrimethoxysilane, water, and ethanol were added to a beaker in a mass ratio of 1:5:15, and magnetically stirred at 700 r / min for 10 min. The SiC fiber with surface hydroxylation was then immersed in the solution and allowed to stand at room temperature for 12 h. (4) Deposition of rare earth precursor: Ytterbium nitrate pentahydrate and urea were added to deionized water in a molar ratio of 1:10, and magnetic stirring was carried out at 700 r / min for 10 min to obtain a precursor solution with a concentration of 0.1 mol / L of ytterbium nitrate pentahydrate and a concentration of 1.0 mol / L of urea; the surface alkylated SiC fiber was immersed in the precursor solution and placed in an 80°C oven for 20 h. The SiC fiber was then taken out and ultrasonically cleaned with deionized water, and then placed in an 80°C constant temperature oven for 1 h to obtain a SiC fiber with rare earth precursor deposited on the surface; (5) Heat treatment of the Yb2Si2O7 interface phase. The SiC fiber with the rare earth precursor deposited on its surface was placed in a reaction chamber. In an argon atmosphere, the temperature was raised to 700°C at a rate of 10°C / min and kept at that temperature for 1 h. Then, the temperature was raised to 1250°C at a rate of 10°C / min and kept at that temperature for 10 h. SiC fibers with a Yb2Si2O7 interface phase of 50 nm in thickness were obtained.

[0042] Figure 3 This is a cross-sectional morphology of a SiC fiber with a Yb2Si2O7 interface phase prepared in Example 2. The figure shows that by adjusting the pre-oxidation and deposition conditions, the interface thickness can be controlled to approximately 50 nm, and the interface and the fiber are well bonded, demonstrating chemical compatibility.

[0043] Example 3

[0044] The method for preparing the rare earth silicate anti-oxidation interface phase on the surface of SiC fiber provided in Example 3 includes the following steps: (1) Pre-oxidation treatment of SiC fiber: The SiC fiber was placed in a muffle furnace, heated to 600°C at a heating rate of 5°C / min in an argon atmosphere, and then naturally cooled after debonding for 1 hour; the debonded SiC fiber was placed in a tube furnace, heated to 1200°C at a heating rate of 10°C / min in an air environment, and then naturally cooled after keeping the temperature for 5 hours; (2) Surface hydroxylation of SiC fibers: The pre-oxidized SiC fibers were immersed in a piranha solution consisting of 98% concentrated sulfuric acid and 30% hydrogen peroxide (volume ratio of 7:3) and heated to 80°C for 1 h. The fibers were then removed, ultrasonically cleaned in deionized water, and dried in a 70°C constant temperature oven for 1 h. (3) Alkylation modification of SiC fiber surface: 3-mercaptopropyltrimethoxysilane, water, and ethanol were added to a beaker in a mass ratio of 1:5:15, and magnetically stirred at 700 r / min for 10 min. The SiC fiber with surface hydroxylation was then immersed in the solution and allowed to stand at room temperature for 12 h. (4) Deposition of rare earth precursor: Ytterbium nitrate pentahydrate and urea were added to deionized water in a molar ratio of 1:10, and magnetic stirring was carried out at 700 r / min for 10 min to obtain a precursor solution with a concentration of 0.2 mol / L of ytterbium nitrate pentahydrate and a concentration of 2 mol / L of urea; the surface alkylated SiC fiber was immersed in the precursor solution and placed in an 80°C oven for 40 h. The fiber was then taken out and ultrasonically cleaned with deionized water, and placed in an 80°C constant temperature oven for 1 h to obtain SiC fiber with rare earth precursor deposited on the surface; (5) Heat treatment of the Yb2Si2O7 interface phase. The SiC fiber with the rare earth precursor deposited on its surface was placed in a reaction chamber. In an argon atmosphere, the temperature was raised to 600°C at a rate of 10°C / min and kept at that temperature for 1 h. Then, the temperature was raised to 1250°C at a rate of 10°C / min and kept at that temperature for 5 h. SiC fibers with a Yb2Si2O7 interface phase of 1000 nm in thickness were obtained.

[0045] Comparative Example 1

[0046] The preparation process of the rare earth silicate antioxidant interface phase on the SiC fiber surface in this comparative example 1 refers to that in Example 1, with the only difference being that in step (5), the conditions for the heat treatment of the Yb2Si2O7 interface phase are: in an argon atmosphere, heating to 700°C at 10°C / min and keeping warm for 1h, and then heating to 1100°C at 10°C / min and keeping warm for 10h.

[0047] Figure 4 、 5 The surface morphology and XRD patterns of SiC fibers with a Yb2Si2O7 interface phase prepared in Comparative Example 1 are shown. As can be seen from the figures, a too low final heat treatment temperature would result in incomplete reaction, and the interface phase formed would not be a single Yb2Si2O7.

Claims

1. A method for preparing a rare earth silicate anti-oxidation interface phase on the surface of SiC fiber, characterized in that: The following steps are involved: (1) Pre-oxidation treatment of the SiC fiber surface; (2) hydroxylating the surface of the pre-oxidized SiC fiber; (3) alkylation modification of the hydroxylated SiC fiber surface; (4) immersing the surface-modified SiC fiber in a precursor solution containing a soluble rare earth source, and heating the solution to obtain a SiC fiber with a rare earth precursor deposited on the surface; (5) The SiC fiber with the rare earth precursor deposited on the surface is heat-treated to obtain a rare earth silicate anti-oxidation interface phase on the surface of the SiC fiber.

2. The preparation method according to claim 1, characterized in that The SiC fiber surface is subjected to debonding treatment before pre-oxidation treatment; the debonding treatment temperature is 500-800°C, the time is 0.5-3h, the heating rate is 1-10°C / min, and the atmosphere is a non-oxidizing atmosphere, preferably nitrogen or argon.

3. The preparation method according to claim 1 or 2, characterized in that In step (1), the pre-oxidation treatment conditions include: the pre-oxidation temperature is 600-1400°C, the time is 0.1-100h, the heating rate is 1-15°C / min, and the atmosphere is an oxidizing atmosphere, preferably air or oxygen atmosphere.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step (2), the conditions for hydroxylation of the SiC fiber surface include: immersing the pre-oxidized SiC fiber in an acid solution and treating it at 40-90° C. for 0.5-48 hours; preferably, the acid solution is at least one of nitric acid, hydrochloric acid, hydrofluoric acid, and piranha solution; more preferably, the piranha solution is a mixed solution of 98% concentrated sulfuric acid and 30% hydrogen peroxide; further preferably, the volume ratio of concentrated sulfuric acid to hydrogen peroxide in the piranha solution is (3-7):(7-3).

5. The preparation method according to any one of claims 1 to 4, characterized in that In step (3), the conditions for alkylation modification of the SiC fiber surface include: immersing the surface hydroxylated SiC fiber in a solution containing a silane coupling agent and treating it at 18-30°C for 3-48 hours; preferably, the silane coupling agent is at least one of 3-mercaptopropyltrimethoxysilane, hexadecyltrichlorosilane, 3-methacryloxypropyltrimethoxysilane, and 3-mercaptopropyltriethoxysilane; the solvent in the solution is ethanol and deionized water; more preferably, the mass ratio of the silane coupling agent, ethanol, and deionized water in the solution is 1:(10-30):(1-20).

6. The preparation method according to any one of claims 1 to 5, characterized in that In step (4), the precursor solution includes a soluble rare earth source, a precipitant and a solvent; wherein, The soluble rare earth source is a soluble rare earth inorganic salt; preferably, the soluble rare earth inorganic salt is at least one of acetate, nitrate, phosphate, and chloride; more preferably, the rare earth element in the soluble rare earth inorganic salt is at least one of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium; further preferably, the concentration of the rare earth source in the precursor solution is 0.05 to 0.8 mol / L; The precipitant is urea; preferably, the concentration of urea in the precursor solution is 0.1 to 2 mol / L; The solvent is at least one of anhydrous ethanol and deionized water; Preferably, the molar ratio of the rare earth source to the precipitant in the precursor solution is 1:(2-10).

7. The preparation method according to any one of claims 1 to 6, characterized in that In step (4), the heating temperature is 70 to 90° C. and the heating time is 10 to 120 hours.

8. The preparation method according to any one of claims 1 to 7, characterized in that In step (5), the heat treatment conditions include: first keeping warm at 600-800°C for 1-3 hours, then keeping warm at 1200-1400°C for 5-10 hours, with a heating rate of 5-10°C / min, and the atmosphere is a non-oxidizing atmosphere, preferably nitrogen or argon.

9. A rare earth silicate anti-oxidation interface phase on the surface of SiC fiber prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The composition of the rare earth silicate anti-oxidation interface phase on the surface of the SiC fiber includes monosilicate or pyrosilicate containing rare earth elements; preferably, the rare earth element is at least one of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium.

10. The rare earth silicate anti-oxidation interface phase on the surface of SiC fiber according to claim 9, characterized in that: The thickness of the rare earth silicate anti-oxidation interface phase on the surface of the SiC fiber is 50 to 1000 nm.

Images