CN107640976B - Three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material and preparation method thereof - Google Patents
Three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material, which comprises a three-dimensional silicon carbide fiber prefabricated part and yttrium silicate, wherein the yttrium silicate is Y2Si2O7And Y2SiO5Mixed crystal phase of (2), Y2Si2O7Crystalline phase or Y2SiO5And crystal phase, wherein yttrium silicate is uniformly filled in the pores of the three-dimensional silicon carbide fiber prefabricated part, and the porosity of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material is 10-16%. The preparation method comprises the following steps: (1) preparation of Y2O3‑SiO2Compounding sol; (2) dipping; (3) drying; (4) heat treatment; (5) and (4) repeating the dipping-drying-heat treatment process of the steps (2) to (4). The three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material has the advantages of low porosity, high density, high temperature resistance, oxidation resistance, excellent mechanical property and the like, the preparation method is high in preparation efficiency, and the density and the mechanical property of the prepared composite material are remarkably improved.
Description
Technical Field
The invention relates to the technical field of high-temperature-resistant fiber-reinforced ceramic matrix composite materials, in particular to a three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material and a preparation method thereof.
Background
Yttrium silicate consisting of Y2O3And SiO2Consisting of a material having a polycrystalline phase structure, essentially having three crystalline phase structures, i.e. Y2SiO5、Y2Si2O7And Y4Si3O12Of which the former two are most common. In addition to being useful as optical matrix materials and dielectric materials, yttrium silicate is an excellent refractory ceramicMaterial, its main crystal form Y2SiO5、Y2Si2O7And Y4Si3O12The melting points of (A) were 1980 ℃, 1775 ℃ and 1950 ℃ respectively. The yttrium silicate has a series of excellent physicochemical properties such as low thermal conductivity, low elastic modulus, low oxygen permeability, low high-temperature volatility, high chemical stability and the like while having a high melting point, so that the yttrium silicate becomes one of the best candidate materials of the high-temperature oxidation-resistant ceramic coating, and has been extensively and deeply researched.
However, as a monolithic ceramic, yttrium silicate has very low strength and toughness, and Y is2Si2O7The bending strength of the ceramic is only 135MPa, and the fracture toughness is only 2.12 MPa.m1/2，Y2SiO5The bending strength of the ceramic is only 116MPa, and the fracture toughness is only 1.85 MPa.m1/2. The low strength and toughness make the yttrium silicate monomer ceramic difficult to be practically used as structural ceramic, and particularly in the occasions with large mechanical load impact and thermal shock, the yttrium silicate monomer ceramic needs to be subjected to reinforcing and toughening treatment.
The introduction of fibers in ceramic matrices has proven to be the most effective method of reinforcement and toughening that can significantly improve fracture toughness and strength. In the reinforced fiber, the silicon carbide fiber has strong high temperature resistance, high tensile strength and modulus, and particularly good oxidation resistance, and the thermal expansion coefficient of the silicon carbide fiber is relatively close to that of yttrium silicate, so if the silicon carbide fiber and the yttrium silicate can be compounded together, the advantages of the silicon carbide fiber and the yttrium silicate are combined, and the fiber reinforced yttrium silicate composite material with high temperature resistance, oxidation resistance, high strength and high toughness is expected to be obtained theoretically.
The fiber preform reinforced composite material can be divided into one-dimensional, two-dimensional and three-dimensional preform reinforced composite materials according to the arrangement mode of fibers in the composite material, namely the structural form of the fiber preform. The one-dimensional composite material is prepared by winding fiber bundles into non-woven cloth through slurry prepared from ceramic matrix powder (the slurry contains a binder for adhering the ceramic powder to fibers), then laying the non-woven cloth in different directions and different angles, or directly winding the non-woven cloth into a required shape in different directions and different angles, and then sintering at high temperature and under no pressure or under hot pressure. The two-dimensional composite material is obtained by adhering a ceramic matrix on the surface of fiber cloth in a manner of coating, dip-coating and the like with slurry prepared from ceramic matrix powder, laminating the fiber cloth, and then sintering at high temperature and under no pressure or under hot pressure. The three-dimensional composite material is obtained by firstly manufacturing fibers into a three-dimensional prefabricated part and then introducing a ceramic matrix into the prefabricated part by means of a gas phase method, a liquid phase method and the like. In comparison, the three-dimensional composite material has better integrity (the in-plane and interlayer performance of the one-dimensional and two-dimensional composite materials is weaker), and the designability of the fiber content and the arrangement directionality is strong, so that the three-dimensional composite material is more suitable for preparing components with complex shapes.
However, densification of three-dimensional composites is difficult to handle in one-dimensional and two-dimensional composite manufacturing processes due to the different preform structures. For the structural features of three-dimensional preforms, two densification methods are currently commonly used: firstly, heating a prefabricated member to a required temperature, introducing gaseous raw materials, diffusing the raw materials into the prefabricated member, reacting and depositing under the action of high temperature to obtain a ceramic matrix, gradually filling pores in the prefabricated member with the ceramic matrix along with the prolonging of deposition time, and continuously increasing the density, namely a gas phase method; secondly, after the prefabricated member is soaked in the liquid raw material, the prefabricated member is dried to remove the solvent, then the prefabricated member is subjected to heat treatment at high temperature to obtain a ceramic matrix, the soaking, drying and heat treatment are repeated for a plurality of periods, the pores in the prefabricated member are gradually filled with the ceramic matrix, the density is continuously increased, and the method is called as a liquid phase method. In contrast, the liquid phase method has low requirements on equipment, is insensitive to a temperature field and a chemical field in the equipment during compounding, and has more obvious advantages in the preparation of complex shapes and batch components. And for fiber-reinforced yttrium silicate composites, are currently suitable for deposition of Y2O3And SiO2The gaseous raw material is too little, the deposition characteristic is not ideal enough, the liquid raw material is easy to obtain, and the performance is reliable.
For a liquid phase method, how to rapidly prepare a three-dimensional fiber preform reinforced yttrium silicate composite material with high density and high mechanical property is a key problem to be solved, and related key technical points comprise liquid raw material properties, an impregnation process and a heat treatment process. At present, no research report on the preparation of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material by a liquid phase method is found.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material with low porosity, high density, high temperature resistance, oxidation resistance and excellent mechanical properties and a preparation method thereof.
In order to solve the technical problems, the invention adopts the following technical scheme:
the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material comprises a three-dimensional silicon carbide fiber prefabricated part and yttrium silicate, wherein the yttrium silicate is Y2Si2O7And Y2SiO5Mixed crystal phase of (2), Y2Si2O7Crystalline phase or Y2SiO5And the crystal phase is uniformly filled in the pores of the three-dimensional silicon carbide fiber prefabricated part, and the porosity of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material is 10-16%.
Preferably, the three-dimensional silicon carbide fiber preform is one or more of a three-dimensional silicon carbide fiber preform obtained by laminating and sewing silicon carbide fiber cloth, a three-dimensional silicon carbide fiber preform obtained by alternately laminating and needling silicon carbide fiber cloth and a mesh, a three-dimensional silicon carbide fiber preform with a three-dimensional five-way woven structure, a three-dimensional silicon carbide fiber preform with a two-dimensional semi-woven structure and a three-dimensional silicon carbide fiber preform with a three-dimensional four-way woven structure; the volume fraction of the silicon carbide fiber in the three-dimensional silicon carbide fiber prefabricated part is 20-55%.
As a general inventive concept, the present invention also provides a method for preparing a three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material, comprising the steps of:
(1) preparation of Y2O3-SiO2Compounding sol: will Y2O3Sol and SiO2Mixing the sol, adding stabilizerTo obtain Y2O3-SiO2Compounding sol;
(2) dipping: placing the three-dimensional silicon carbide fiber prefabricated part into a container, vacuumizing and sucking Y obtained in the step (1)2O3-SiO2Compounding sol, vacuum impregnating to make Y2O3-SiO2Filling the composite sol in the three-dimensional silicon carbide fiber prefabricated part;
(3) and (3) drying: taking out the three-dimensional silicon carbide fiber prefabricated part and drying to remove Y2O3-SiO2A solvent in the composite sol;
(4) and (3) heat treatment: carrying out heat treatment under the protection of inert atmosphere to obtain a three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material intermediate;
(5) and (4) repeating the dipping-drying-heat treatment processes in the steps (2) to (4) until the weight of the intermediate of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material is increased by less than 1% compared with the weight of the intermediate of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material in the last dipping-drying-heat treatment process, so as to obtain the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material.
In the above method for preparing the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material, preferably, in the step (1), the stabilizer is strong acid, and the stabilizer and the Y are mixed2O3The mass ratio of the sol is 2-3: 10.
Preferably, in the preparation method of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material, the strong acid comprises HNO3HCl or H2SO4。
In the above method for preparing the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material, preferably, in the step (1), Y is2O3-SiO2In the composite sol, the solid content is 20-40 wt%; y is2O3With SiO2The molar ratio of (1: 1) - (2) and the size of colloidal particles of the composite sol is less than or equal to 30 nm.
Preferably, in the step (3), the drying temperature is 400-700 ℃ and the drying time is 1-6 hours.
In the above method for preparing the three-dimensional silicon carbide fiber preform-reinforced yttrium silicate composite material, preferably, in the step (2), after vacuum impregnation, air pressure auxiliary impregnation is further performed under a set pressure, so that Y is obtained2O3-SiO2The composite sol is further filled in the three-dimensional silicon carbide fiber prefabricated member.
In the above method for preparing the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material, preferably, in the step (2), the process conditions of vacuum impregnation are as follows: the vacuum degree is less than or equal to 500Pa, and the dipping time is 4-8 h; the technological conditions of the air pressure auxiliary impregnation are as follows: the set pressure is 2MPa to 10MPa, and the dipping time is 2h to 6 h.
In the above method for preparing the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material, preferably, in the step (4), the heat treatment process includes: under the protection of inert atmosphere, the temperature is raised to 1000-1600 ℃ at the speed of 10-20 ℃/min, and the temperature is kept for 0.5-2 h.
Preferably, the preparation method of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material further comprises a pretreatment step of the three-dimensional silicon carbide fiber preform before the step (2), specifically: and (3) placing the three-dimensional silicon carbide fiber prefabricated part in vacuum or inert atmosphere, heating to 600-1200 ℃ at the speed of 5-15 ℃/min, and preserving heat for 1-4 h.
Compared with the prior art, the invention has the advantages that:
1. the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material provided by the invention combines the advantages of silicon carbide fiber, yttrium silicate and a three-dimensional prefabricated part together for the first time, so that the high-temperature-resistant and antioxidant three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material with excellent mechanical properties is obtained. The mechanical property of the three-dimensional silicon carbide fiber prefabricated part is utilized to provide excellent mechanical property, particularly high fracture toughness, and the brittleness of monomer yttrium silicate ceramic is overcome; the excellent oxidation resistance of the composite material is provided by utilizing the excellent oxidation resistance of the yttrium silicate and the silicon carbide fiber; the high temperature resistance of the silicon carbide fiber and the high melting point of the yttrium silicate are utilized to provide the excellent high temperature resistance of the composite material.
2. The three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material has lower porosity (10-16%), namely, the yttrium silicate content and the density are high, so that the composite material has excellent mechanical property, high temperature resistance and oxidation resistance.
3. The invention relates to a preparation method of a three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material, which uses Y2O3-SiO2The composite sol is a liquid raw material, the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material is prepared by adopting a liquid phase method, and the sol with high solid content and nano scale can ensure that Y is2O3-SiO2The particles are quickly and uniformly filled into the gaps in the prefabricated member, and compared with a technical route starting from a solution, the densification efficiency is high; compared with the technical route of taking the slurry prepared from the ceramic powder as the raw material, Y2O3-SiO2The distribution uniformity of the particles is good, the temperature for generating yttrium silicate is low, and the damage to the fiber is small.
4. The invention relates to a preparation method of a three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material, which is characterized in that liquid raw material Y is adopted2O3-SiO2HNO is introduced into the composite sol3As a stabilizer, solve Y2O3Sol and SiO2The sol has poor compatibility due to the obvious difference of hydrolysis speed, and stable Y is obtained2O3-SiO2The composite sol provides reliable raw material guarantee for the preparation of the composite material. Applicant is preparing Y2O3-SiO2During compounding of the sol, Y is found2O3Sol and SiO2The sol is mixed and then precipitated, the precipitation destroys the monodisperse state of nano-sized colloidal particles in the sol, and the obtained particles are in a large-size agglomeration state, cannot be impregnated into pores of a fiber prefabricated member, and cannot be used as a raw material of a technical route of impregnation-drying-heat treatment. Previous attempts have been made to dilute by dilutionAnd adding chelating agent to stabilize Y (principle of increasing steric hindrance and reducing collision probability of colloidal particles)2O3-SiO2The composite sol has a less ideal stabilizing effect, and the solid content of the composite sol is reduced to a certain extent, so that the preparation efficiency of the composite material is reduced. To better stabilize Y2O3-SiO2Composite sol, Applicant company's on Y2O3Sol and SiO2The reason for generating the precipitation after the sol is mixed is deeply researched theoretically and explored practically, and the research result shows that: y is2O3Sol and SiO2The sols are all basic, but Y2O3The alkalinity of the sol is obviously stronger than that of SiO2When the sol and the sol are mixed, the pH value is mismatched, the sol is instable, and precipitation occurs. The invention reverses thinking according to Y2O3Sol and SiO2The hydrolysis mechanism in the sol synthesis process is that acid liquid is added to partially peptize hydrolyzed colloidal particles, so that the collision instability probability is reduced, and meanwhile, the pH values of the colloidal particles and the acid liquid are adjusted to the same level, so that the stability of the composite sol is obviously improved, and the solid content and the composite efficiency of the composite sol are not reduced. In addition, the viscosity of the composite sol can be reduced to a certain extent by adding the acid liquor, so that the impregnation into the fiber preform is facilitated. The acid liquid is preferably strong acid, strong acid is against Y2O3-SiO2The composite sol has a stabilizing effect superior to that of weak acid, wherein nitric acid is used for Y2O3-SiO2The composite sol has the best stabilizing effect.
5. The invention relates to a preparation method of a three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material, which is characterized in that Y is used for preparing the Y-shaped silicon carbide fiber prefabricated part reinforced yttrium silicate composite material2O3-SiO2The composite sol contains a stabilizer which can remain in the gel in the form of acid radicals, and if the stabilizer cannot be removed completely at a lower temperature, Y at a high temperature can be influenced2O3And SiO2And the silicon carbide fibers are also damaged by the reaction and sintering of (2). The invention chooses to remove the acid radicals in the drying stage by raising the drying temperature (400-700 ℃), in which the acid radicals are decomposed, for example nitrate radicals can be decomposedDecomposition to NOxAnd O2Thereby the Y is not affected by the volatilization of the gas at high temperature2O3And SiO2The reaction and sintering shrinkage of the silicon carbide fiber are avoided, and meanwhile, the silicon carbide fiber is not obviously damaged.
6. The preparation method of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material further comprises the step of adding Y into the sol used by the invention2O3-SiO2The composite material is amorphous and nano-scale, has high surface energy, thus having high sintering activity and providing high-quality raw material guarantee for high-temperature heat treatment of the composite material.
7. The preparation method of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material further adopts a mode of vacuum impregnation and air pressure auxiliary impregnation, and the air in the gaps in the prefabrication is firstly vacuumized to remove the air in the gaps so as to provide space for the infiltration of the sol, and because the sol is Y with uniformly dispersed nano-sized single particles2O3-SiO2The composite colloidal particles have good stability, so that the composite colloidal particles can quickly and uniformly enter gaps of the prefabricated member; then, the sol is promoted to further permeate into the interior of the prefabricated member through the action of external air pressure, enters some complex pore spaces of the pore channels, and even can destroy some closed pores to open pores, so that the impregnation efficiency and the filling degree are improved.
8. The preparation method of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material further adopts amorphous Y with small and stable particle size2O3-SiO2On the basis of using the composite sol as a matrix raw material, Y is added2O3-SiO2The research of sintering shrinkage behavior sets the heat treatment temperature to 1000-1600 ℃ in the invention, and in the temperature range, Y can be ensured2O3-SiO2Converted into yttrium silicate, can obtain higher density of a matrix (improving the load bearing and load transmission capacity of the matrix), and finally obtain the three-dimensional silicon carbide fiber prefabricated member reinforced yttrium silicate composite material with excellent comprehensive performance.
In a word, the invention starts from the aspects of liquid raw material characteristics, dipping process, drying process and heat treatment temperature, obviously improves the compactness of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material, not only enhances the bearing capacity of the matrix, but also enhances the load transfer capacity of the matrix, so that the prepared three-dimensional fiber prefabricated part reinforced aluminum oxide composite material has excellent mechanical property, high temperature resistance and oxidation resistance.
Drawings
FIG. 1 is a photomicrograph of a three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite prepared according to example 1 of the present invention.
Fig. 2 is a microstructure diagram of a three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material prepared in example 2 of the present invention.
FIG. 3 is a photomicrograph of a three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite prepared according to example 4 of the present invention.
FIG. 4 shows a base material Y of the present invention2O3-SiO2And drying the composite sol to obtain the gel powder with XRD pattern.
FIG. 5 shows a base material Y of the present invention2O3-SiO2Composite sol (corresponding to Y)2Si2O7Crystalline phase, Y2O3With SiO2Molar ratio of 1: 2) dried gel powder, pressing into blocks, and performing heat treatment at different temperatures to obtain linear shrinkage.
FIG. 6 shows a base material Y of the present invention2O3-SiO2Composite sol (corresponding to Y)2SiO5Crystalline phase, Y2O3With SiO21: 1) the linear shrinkage after heat treatment at different temperatures after pressing into blocks.
FIG. 7 shows a base material Y of the present invention2O3-SiO2Composite sol (corresponding to Y)2Si2O7Crystalline phase, Y2O3With SiO2Molar ratio of 1: 2) drying the gel powder, heating at different temperaturesXRD pattern after treatment.
FIG. 8 shows a base material Y of the present invention2O3-SiO2Composite sol (corresponding to Y)2SiO5Crystalline phase, Y2O3With SiO2Molar ratio of 1: 1) dried gel powder, XRD pattern after heat treatment at different temperatures.
Detailed Description
The invention is further described below with reference to the drawings and specific preferred embodiments of the description, without thereby limiting the scope of protection of the invention.
Example 1:
the invention relates to a three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material, which comprises a three-dimensional silicon carbide fiber prefabricated part and yttrium silicate, wherein the yttrium silicate is used as a matrix, the three-dimensional silicon carbide fiber prefabricated part is used as a reinforcing phase, the yttrium silicate is uniformly filled in gaps of the three-dimensional silicon carbide fiber prefabricated part, and the crystalline phase is Y2Si2O7In this embodiment, the porosity of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material is 13.6%.
In this embodiment, the three-dimensional silicon carbide fiber preform is obtained by sewing laminated silicon carbide fiber cloth, and the volume fraction of fibers in the three-dimensional silicon carbide fiber preform is 46%.
In this example, the bending strength of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material was 208MPa, and the fracture toughness was 10.6MPa · m1/2. After heat treatment for 1h in high-temperature inert atmosphere at 1400 ℃, the strength retention rate is 88.2 percent; after being oxidized by static air at 1400 ℃ for 0.5h, the strength retention rate is 92.4 percent.
The preparation method of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material comprises the following specific process steps:
(1) selecting sol: selecting Y with solid content of 25wt%2O3-SiO2The composite sol is used as raw material of yttrium silicate matrix, wherein Y2O3With SiO2In a molar ratio of 1: 2 in the above Y2O3-SiO2HNO is added into the composite sol3As stabilizer, HNO3Is added in an amount of Y2O325% by weight of the sol.
(2) Pre-treating a prefabricated part: selecting a three-dimensional silicon carbide fiber prefabricated part obtained by laminating and sewing silicon carbide fiber cloth as a reinforcing phase, wherein the volume fraction of fibers in the three-dimensional silicon carbide fiber prefabricated part is 46%. And (3) placing the selected three-dimensional silicon carbide fiber prefabricated member in vacuum, heating to 1000 ℃ at the speed of 10 ℃/min, preserving heat for 2 hours, and then cooling along with a furnace to finish the pretreatment of the prefabricated member.
(3) Vacuum impregnation: placing the pretreated three-dimensional silicon carbide fiber prefabricated part in a vacuum tank, vacuumizing until the vacuum degree reaches 300Pa, and sucking Y in the step (1)2O3-SiO2Compounding the sol with Y2O3-SiO2And submerging the three-dimensional silicon carbide fiber prefabricated part by the composite sol, and soaking for 6 hours.
(4) Air pressure assisted impregnation: and (4) moving the prefabricated member (still soaked in the sol) to a pressure kettle, inflating to 4MPa, carrying out air pressure assisted impregnation, and keeping for 4 h.
(5) And (3) drying: and taking the three-dimensional silicon carbide fiber prefabricated member out of the sol, and drying the three-dimensional silicon carbide fiber prefabricated member for 2 hours at 500 ℃ in an inert atmosphere.
(6) And (3) heat treatment: and (3) heating the dried three-dimensional silicon carbide fiber prefabricated part to 1400 ℃ at the speed of 15 ℃/min under the protection of high-purity inert gas, preserving heat for 1h, and then cooling along with a furnace to obtain the intermediate of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material.
(7) The process is repeated: and (4) repeating the steps (3) to (6) for 32 times, detecting, and after the final treatment, the weight gain ratio of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material intermediate is 0.93% compared with the weight gain ratio after the last treatment, and obtaining the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material after the completion of the compounding process.
Fig. 1 is a macro photograph of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material prepared in this example. Through detection, the three-dimensional silicon carbide fiber preform reinforced yttrium silicate obtained in the embodiment（Y2Si2O7) The porosity of the composite material is 13.6 percent, the bending strength is 208MPa, and the fracture toughness is 10.6 MPa.m1/2. After heat treatment for 1h in high-temperature inert atmosphere at 1400 ℃, the strength retention rate is 88.2 percent; after being oxidized by static air at 1400 ℃ for 0.5h, the strength retention rate is 92.4 percent.
Example 2:
the invention relates to a three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material, which comprises a three-dimensional silicon carbide fiber prefabricated part and yttrium silicate, wherein the yttrium silicate is used as a matrix, the three-dimensional silicon carbide fiber prefabricated part is used as a reinforcing phase, the yttrium silicate is uniformly filled in gaps of the three-dimensional silicon carbide fiber prefabricated part, and the crystalline phase is Y2SiO5In this embodiment, the porosity of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material is 10.8%.
In this embodiment, the three-dimensional silicon carbide fiber preform is a three-dimensional silicon carbide fiber preform with a three-dimensional four-way woven structure, and the volume fraction of fibers in the three-dimensional silicon carbide fiber preform is 51%.
In this example, the bending strength of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material was 367MPa, and the fracture toughness was 15.1MPa · m1/2. After heat treatment for 1h in high-temperature inert atmosphere at 1400 ℃, the strength retention rate is 98.5 percent; after being oxidized for 0.5h by static air at 1400 ℃, the strength retention rate is 99.4 percent.
The preparation method of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material comprises the following specific process steps:
(1) selecting sol: selecting Y with the solid phase content of 35wt%2O3-SiO2The composite sol is used as raw material of yttrium silicate matrix, wherein Y2O3With SiO2In a molar ratio of 1: 1, HNO3The addition amount is Y2O320% by weight of the sol.
(2) Pre-treating a prefabricated part: the three-dimensional silicon carbide fiber prefabricated part with a three-dimensional four-way weaving structure is selected as a reinforcing phase, and the volume fraction of fibers in the three-dimensional silicon carbide fiber prefabricated part is 51%. And (3) placing the selected three-dimensional silicon carbide fiber prefabricated member in a high-purity argon atmosphere, heating to 1200 ℃ at the speed of 15 ℃/min, preserving heat for 1h, and then cooling along with a furnace to finish the pretreatment of the prefabricated member.
(3) Vacuum impregnation: placing the pretreated three-dimensional silicon carbide fiber prefabricated part in a vacuum tank, vacuumizing until the vacuum degree reaches 100Pa, and sucking Y in the step (1)2O3-SiO2Compounding the sol with Y2O3-SiO2The three-dimensional silicon carbide fiber prefabricated part is submerged by the composite sol and is soaked for 4 hours.
(4) Air pressure assisted impregnation: and (4) moving the prefabricated member (still soaked in the sol) to a pressure kettle, inflating to 8MPa, carrying out air pressure assisted impregnation, and keeping for 6 hours.
(5) And (3) drying: the three-dimensional silicon carbide fiber preform was taken out of the sol and dried at 400 ℃ for 4h in an inert atmosphere.
(6) And (3) heat treatment: and (3) heating the dried three-dimensional silicon carbide fiber prefabricated part to 1600 ℃ at the speed of 15 ℃/min under the protection of high-purity inert gas, preserving heat for 0.5h, and then cooling along with a furnace to obtain the intermediate of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material.
(7) The process is repeated: and (4) repeating the steps (3) to (6) for 30 times, detecting, and after the final treatment, wherein the weight gain ratio of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material intermediate is 0.78% compared with that after the last treatment, and after the compounding process is finished, obtaining the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material.
Through detection, the three-dimensional silicon carbide fiber preform prepared in the embodiment enhances yttrium silicate (Y)2SiO5) The porosity of the composite material is 10.8 percent, the bending strength is 367MPa, and the fracture toughness is 15.1 MPa.m1/2. After heat treatment for 1h in high-temperature inert atmosphere at 1400 ℃, the strength retention rate is 98.5 percent; after being oxidized for 0.5h by static air at 1400 ℃, the strength retention rate is 99.4 percent. FIG. 2 shows the three-dimensional silicon carbide fiber preform reinforced yttrium silicate (Y) prepared in this example2SiO5) As can be seen from the microstructure of the composite material, the yttrium silicate particles are sintered into blocks and uniformly filled in the fiber bundle, i.e. the single fibersThe space between them.
Example 3:
the invention relates to a three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material, which comprises a three-dimensional silicon carbide fiber prefabricated part and yttrium silicate, wherein the yttrium silicate is used as a matrix, the three-dimensional silicon carbide fiber prefabricated part is used as a reinforcing phase, the yttrium silicate is uniformly filled in gaps of the three-dimensional silicon carbide fiber prefabricated part, and the crystalline phase is Y2Si2O7And Y2SiO5Mixed crystal phase of composition, wherein, Y2Si2O7And Y2SiO5The molar ratio of (1 to 1), and in the implementation, the porosity of the three-dimensional silicon carbide fiber prefabricated member reinforced yttrium silicate composite material is 15.2%.
In this example, the three-dimensional silicon carbide fiber preform is a two-dimensional silicon carbide fiber preform having a half-woven structure, and the volume fraction of the fibers in the three-dimensional silicon carbide fiber preform is 43%.
In this example, the bending strength of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material was 242MPa, and the fracture toughness was 12.3MPa · m1/2. After heat treatment for 1h in high-temperature inert atmosphere at 1400 ℃, the strength retention rate is 96.3 percent; after being oxidized for 0.5h by static air at 1400 ℃, the strength retention rate is 92.5 percent.
The preparation method of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material comprises the following specific process steps:
(1) selecting sol: selecting Y with solid phase content of 20wt%2O3-SiO2The composite sol is used as raw material of yttrium silicate matrix, wherein Y2O3With SiO2In a molar ratio of 1: 1.5, HNO3The addition amount is Y2O320% by weight of the sol.
(2) Pre-treating a prefabricated part: the three-dimensional silicon carbide fiber prefabricated part with the two-dimensional semi-woven structure is selected as a reinforcing phase, and the volume fraction of fibers in the three-dimensional silicon carbide fiber prefabricated part is 43%. And (3) placing the selected three-dimensional silicon carbide fiber prefabricated member in vacuum, heating to 800 ℃ at the speed of 10 ℃/min, preserving heat for 3 hours, and then cooling along with a furnace to finish the pretreatment of the prefabricated member.
(3) Vacuum impregnation: placing the pretreated three-dimensional silicon carbide fiber prefabricated part in a vacuum tank, vacuumizing until the vacuum degree reaches 200Pa, and sucking Y in the step (1)2O3-SiO2Compounding the sol with Y2O3-SiO2And submerging the three-dimensional silicon carbide fiber prefabricated part by the composite sol, and soaking for 8 hours.
(4) Air pressure assisted impregnation: and (4) moving the prefabricated member (still soaked in the sol) to a pressure kettle, inflating to 10MPa, carrying out air pressure assisted impregnation, and keeping for 2 h.
(5) And (3) drying: and taking the three-dimensional silicon carbide fiber prefabricated member out of the sol, and drying the three-dimensional silicon carbide fiber prefabricated member for 1h at 700 ℃ in an inert atmosphere.
(6) And (3) heat treatment: and (3) heating the dried three-dimensional silicon carbide fiber prefabricated part to 1200 ℃ at the speed of 10 ℃/min under the protection of high-purity inert gas, preserving heat for 2 hours, and then cooling along with a furnace to obtain the intermediate of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material.
(7) The process is repeated: and (4) repeating the steps (3) to (6) for 34 times, detecting, and after the final treatment, wherein the weight gain ratio of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material intermediate is 0.98% compared with that after the last treatment, and after the compounding process is finished, obtaining the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material.
Through detection, the three-dimensional silicon carbide fiber preform prepared in the embodiment enhances yttrium silicate (50 mol% Y)2SiO5+50mol%Y2Si2O7) The porosity of the composite material is 15.2 percent, the bending strength is 242MPa, and the fracture toughness is 12.3 MPa.m1/2. After heat treatment for 1h in high-temperature inert atmosphere at 1400 ℃, the strength retention rate is 96.3 percent; after being oxidized for 0.5h by static air at 1400 ℃, the strength retention rate is 92.5 percent.
Example 4:
the invention relates to a three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material, which comprises a three-dimensional silicon carbide fiber prefabricated part and yttrium silicate, wherein the yttrium silicate is used as a matrix, the three-dimensional silicon carbide fiber prefabricated part is used as a reinforcing phase, and the yttrium silicate is uniformly filledFilled in the gaps of the three-dimensional silicon carbide fiber prefabricated part and has a crystal phase of Y2SiO5In this embodiment, the porosity of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material is 12.0%.
In this embodiment, the three-dimensional silicon carbide fiber preform is obtained by alternately laminating silicon carbide fiber cloth and a mesh fabric and needling, and the volume fraction of fibers in the three-dimensional silicon carbide fiber preform is 24%.
In this example, the bending strength of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material was 97.8MPa, and the fracture toughness was 6.3MPa · m1/2. After heat treatment for 1h in an inert atmosphere at a high temperature of 1400 ℃, the strength retention rate is 94.8 percent; after being oxidized by static air at 1400 ℃ for 0.5h, the strength retention rate is 92.2 percent.
The preparation method of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material comprises the following specific process steps:
(1) selecting sol: selecting Y with solid phase content of 40wt%2O3-SiO2The composite sol is used as raw material of yttrium silicate matrix, wherein Y2O3With SiO2In a molar ratio of 1: 1, HNO3The addition amount is Y2O330% by weight of the sol.
(2) Pre-treating a prefabricated part: selecting a three-dimensional silicon carbide fiber prefabricated part obtained by alternately laminating and needling silicon carbide fiber cloth and a net blank as a reinforcing phase, wherein the volume fraction of fibers in the three-dimensional silicon carbide fiber prefabricated part is 24%. And (3) placing the selected three-dimensional silicon carbide fiber prefabricated member in vacuum, heating to 600 ℃ at the speed of 5 ℃/min, preserving heat for 4 hours, and then cooling along with a furnace to finish the pretreatment of the prefabricated member.
(3) Vacuum impregnation: placing the pretreated three-dimensional silicon carbide fiber prefabricated part in a vacuum tank, vacuumizing until the vacuum degree reaches 500Pa, and sucking Y in the step (1)2O3-SiO2Compounding the sol with Y2O3-SiO2And submerging the three-dimensional silicon carbide fiber prefabricated part by the composite sol, and soaking for 8 hours.
(4) Air pressure assisted impregnation: and (4) moving the prefabricated member (still soaked in the sol) to a pressure kettle, inflating to 2MPa, carrying out air pressure assisted impregnation, and keeping for 6 hours.
(5) And (3) drying: the three-dimensional silicon carbide fiber preform was taken out of the sol and dried at 400 ℃ for 6h in an inert atmosphere.
(6) And (3) heat treatment: and (3) heating the dried three-dimensional silicon carbide fiber prefabricated part to 1000 ℃ at the speed of 10 ℃/min under the protection of high-purity inert gas, preserving heat for 2 hours, and then cooling along with a furnace to obtain the intermediate of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material.
(7) The process is repeated: and (4) repeating the steps (3) to (6) for 38 times, detecting, and after the final treatment, the weight gain ratio of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material intermediate is 0.99% compared with the weight gain ratio after the last treatment, and obtaining the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material after the completion of the compounding process.
Fig. 3 is a macro photograph of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material prepared in this example. Through detection, the three-dimensional silicon carbide fiber preform obtained in the embodiment reinforces yttrium silicate (Y)2SiO5) The porosity of the composite material is 12.0 percent, the bending strength is 97.8MPa, and the fracture toughness is 6.3 MPa.m1/2. After heat treatment for 1h in an inert atmosphere at a high temperature of 1400 ℃, the strength retention rate is 94.8 percent; after being oxidized by static air at 1400 ℃ for 0.5h, the strength retention rate is 92.2 percent.
Example 5:
the invention relates to a three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material, which comprises a three-dimensional silicon carbide fiber prefabricated part and yttrium silicate, wherein the yttrium silicate is used as a matrix, the three-dimensional silicon carbide fiber prefabricated part is used as a reinforcing phase, the yttrium silicate is uniformly filled in gaps of the three-dimensional silicon carbide fiber prefabricated part, and the crystalline phase is Y2Si2O7In this embodiment, the porosity of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material is 11.3%.
In this embodiment, the three-dimensional silicon carbide fiber preform is a three-dimensional silicon carbide fiber preform with a three-dimensional five-way woven structure, and the volume fraction of fibers in the three-dimensional silicon carbide fiber preform is 50%.
In this example, the bending strength of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material is 387MPa, and the fracture toughness is 14.3MPa · m1/2. After heat treatment for 1h in high-temperature inert atmosphere at 1400 ℃, the strength retention rate is 98.1 percent; after being oxidized for 0.5h by static air at 1400 ℃, the strength retention rate is 97.3 percent.
The preparation method of the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material comprises the following specific process steps:
(1) selecting sol: selecting Y with solid phase content of 30wt%2O3-SiO2The composite sol is used as raw material of yttrium silicate matrix, wherein Y2O3With SiO2In a molar ratio of 1: 2, HNO3The addition amount is Y2O325% by weight of the sol.
(2) Pre-treating a prefabricated part: selecting a three-dimensional silicon carbide fiber prefabricated part with a three-dimensional five-direction woven structure as a reinforcing phase, wherein the volume fraction of fibers in the three-dimensional silicon carbide fiber prefabricated part is 50%. And (3) placing the selected three-dimensional silicon carbide fiber prefabricated member in a high-purity argon atmosphere, heating to 1000 ℃ at the speed of 10 ℃/min, preserving heat for 2 hours, and then cooling along with a furnace to finish the pretreatment of the prefabricated member.
(3) Vacuum impregnation: placing the pretreated three-dimensional silicon carbide fiber prefabricated part in a vacuum tank, vacuumizing until the vacuum degree reaches 400Pa, and sucking Y in the step (1)2O3-SiO2Compounding the sol with Y2O3-SiO2And submerging the three-dimensional silicon carbide fiber prefabricated part by the composite sol, and soaking for 6 hours.
(4) Air pressure assisted impregnation: and (4) moving the prefabricated member (still soaked in the sol) to a pressure kettle, inflating to 6MPa, carrying out air pressure assisted impregnation, and keeping for 4 hours.
(5) And (3) drying: the three-dimensional silicon carbide fiber preform was taken out of the sol and dried at 600 ℃ for 3 hours in an inert atmosphere.
(6) And (3) heat treatment: and (3) heating the dried three-dimensional silicon carbide fiber prefabricated part to 1200 ℃ at the speed of 20 ℃/min under the protection of high-purity inert gas, preserving the heat for 1.5h, and then cooling along with a furnace to obtain the intermediate of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material.
(7) The process is repeated: and (4) repeating the steps (3) to (6) for 31 times, detecting, and after the final treatment, the weight gain ratio of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material intermediate is 0.81% compared with the weight gain ratio after the last treatment, and obtaining the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material after the completion of the compounding process.
Through detection, the three-dimensional silicon carbide fiber preform prepared in the embodiment enhances yttrium silicate (Y)2Si2O7) The porosity of the composite material is 11.3 percent, the bending strength is 387MPa, and the fracture toughness is 14.3 MPa.m1/2. After heat treatment for 1h in high-temperature inert atmosphere at 1400 ℃, the strength retention rate is 98.1 percent; after being oxidized for 0.5h by static air at 1400 ℃, the strength retention rate is 97.3 percent.
From examples 1 to 5, it can be seen that the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material prepared by the preparation method provided by the invention has low porosity, high mechanical properties and excellent high-temperature oxidation resistance.
In conclusion, the invention provides a novel material system of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material by combining the advantages of the silicon carbide fiber, the yttrium silicate and the three-dimensional prefabricated part based on the characteristics, the current research situation and the existing problems of the yttrium silicate material, and forms a preparation method capable of obtaining excellent performance.
In the preparation method, HNO is firstly added3As an additive, stable Y is obtained2O3-SiO2The composite sol provides reliable raw material guarantee for the preparation of the composite material, and then adopts Y with the solid phase content of 20-40 wt%2O3-SiO2The composite sol (the particle size of the colloid is less than or equal to 30 nm) is used as a matrix raw material, and the prepared material has the porosity of about 10 percent, the bending strength of 367MPa and the fracture toughness of 15.1 MPa.m within a limited period (about 30 periods)1/2Three-dimensional four-way silicon carbide fiber reinforced Y2SiO5A composite material. Albeit not at allThree-dimensional four-way silicon carbide fiber reinforced Y prepared by other fully corresponding methods2SiO5The composite material can be compared, but compared with similar prior art: firstly, AlCl is adopted in the prior art3·6H2O or Al (NO)3)3·9H2Sol prepared from O inorganic salt is used as a matrix raw material, and three-dimensional four-way carbon fiber reinforced Al is prepared by 13 periods of' dipping-drying-1260 ℃ heat treatment2O3The composite material is found that the density is not increased when the subsequent compounding is continued, the porosity is about 30 percent, and the bending strength is only 100MPa to 150 MPa; secondly, preparing Y from organic salt containing Si and organic salt solution containing Y2SiO5The coating needs to remove a large amount of solvent and additive, the preparation efficiency is very low, and a typical parameter is that the thickness is 2 mu m after 20 times of dip-coating heat treatment. Thus, by comparison, it can be seen that a high solid content Y is used2O3-SiO2The composite sol is used as the yttrium silicate matrix raw material, and the advantage of the preparation efficiency is self-evident.
In addition, the microstructure of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material is observed by adopting a scanning electron microscope, as shown in figure 2, yttrium silicate particles are sintered to be blocky and are uniformly filled in the fiber bundle, namely gaps among single fibers, so that the problem of uneven distribution of slurry raw materials is avoided. Thus, Y used in the present invention2O3-SiO2The composite sol not only maintains the advantages of uniform filling of the inorganic salt or organic salt solution raw material and high-efficiency impregnation of the slurry raw material, but also overcomes the disadvantages of low densification efficiency of the inorganic salt or organic salt solution raw material and non-uniform filling of the slurry raw material.
Then, the invention adopts a mode of vacuum impregnation firstly and then air pressure auxiliary impregnation, firstly, the air in the gap in the prefabrication is removed by vacuum pumping, space is provided for the infiltration of the sol, and because the sol is Y with uniformly dispersed nano-sized single particles2O3-SiO2Composite colloidal particles having good stability and thus being able to enter the preform rapidly and uniformlyIn the gap; then, the sol is promoted to further permeate into the interior of the prefabricated member through the action of external air pressure, enters some complex pore spaces of the pore channels, and even can destroy some closed pores to open pores, so that the impregnation efficiency and the filling degree are improved.
Finally, in the sol used according to the invention, Y2O3-SiO2Both in an amorphous state (as shown in fig. 4) and in a nano-scale, have high surface energy and thus high sintering activity. On the basis of the above, by pairing Y2O3-SiO2The research of sintering shrinkage behavior sets the heat treatment temperature to 1000-1600 ℃ in the invention, and in the temperature range, Y can be ensured2O3-SiO2Converted into yttrium silicate, can obtain higher density of a matrix (improving the load bearing and load transmission capacity of the matrix), and finally obtain the three-dimensional silicon carbide fiber prefabricated member reinforced yttrium silicate composite material with excellent comprehensive performance.
For Y2O3-SiO2Carrying out XRD detection on gel powder obtained after the sol is dried:
the phase composition of the gel powder was analyzed by X-ray diffractometer model D8 Advance. The test conditions were: CuK alpha rays, tube current 40mA, tube voltage 40KV, 2 theta = 15-90 DEG, and scanning speed is 4 DEG/min.
The detection result is shown in fig. 4, and it can be seen from the figure that: the map shows the peak characteristic of the steamed bread, and no sharp Y appears2O3Or SiO2Characteristic diffraction peak showing Y after drying at 200 deg.C2O3-SiO2The gel powder is typically in an amorphous state, which has high surface energy and can promote sintering densification.
For Y2O3-SiO2And (3) pressing gel powder obtained by drying the sol into blocks, and detecting the linear shrinkage condition of the gel powder after heat treatment at different temperatures:
drying the Y2O3-SiO2Gel powder (corresponding to Y respectively)2Si2O7And Y2SiO5Two crystal phases, gel powderY2O3With SiO2In a molar ratio of 1: 2 and 1: 1, respectively) into a metal mould having a diameter of 40mm, and pressing the powder at 100MPa on a press into round pieces having a diameter of 40mm and a thickness of 5 mm. And (3) putting the round block into a heat treatment furnace, carrying out heat treatment for 1 hour at different temperatures, measuring the change rate of the diameter and the thickness before and after the heat treatment, and measuring 5 points to obtain an average value as a final result.
The results of the detection are shown in FIG. 5 (Y)2Si2O7Crystalline phase) and FIG. 6 (Y)2SiO5Crystal phase), as can be seen from the figure: after heat treatment at 1000-1600 ℃, the linear shrinkage rates of the two materials are gradually increased along with the temperature rise within the range of 10-17 percent, which shows that Y2O3-SiO2Has better sintering activity; wherein, when the temperature is increased from 1000 ℃ to 1200 ℃, the linear shrinkage rate is obviously increased, and after the temperature exceeds 1200 ℃, the increase is small. Based on the data of FIGS. 5 and 6, and considering the greater probability of the silicon carbide fiber grain growth resulting in a decrease in strength beyond 1600 deg.C, the present invention selects a heat treatment temperature in the range of 1000 deg.C to 1600 deg.C.
Y after heat treatment at different temperatures2O3-SiO2Carrying out XRD detection on the gel powder:
drying the obtained Y2O3-SiO2Gel powder (corresponding to Y respectively)2Si2O7And Y2SiO5Two crystalline phases, Y in gel powder2O3With SiO2In a molar ratio of 1: 2 and 1: 1 respectively) were subjected to heat treatment at different temperatures for 1h and then the phase composition of the powder was analyzed using an X-ray diffractometer model D8 Advance. The test conditions were: CuK alpha rays, tube current 40mA, tube voltage 40KV, 2 theta = 10-60 degrees and scanning speed 4 DEG/min.
The results of the detection are shown in FIG. 7 (Y)2Si2O7Crystalline phase) and FIG. 8 (Y)2SiO5Crystal phase), as can be seen from the figure: for Y2SiO5In contrast (FIG. 8, Y in gel powder)2O3With SiO2In a molar ratio of 1: 1), Y after heat treatment at 1000 deg.C2O3-SiO2Just in reverseX should be generated stable at low temperatures1-Y2SiO5Crystalline phase, still X with increasing temperature up to 1200 DEG C1-Y2SiO5Crystalline phase, but the intensity of diffraction peak became stronger, indicating X1-Y2SiO5The crystallization degree of the crystal phase is improved; when the temperature rises to 1400 ℃ and 1600 ℃, X1-Y2SiO5Conversion of the crystalline phase to X stable at high temperature2-Y2SiO5The crystal phase and the degree of crystallinity further increase from the diffraction peak intensity. For Y2Si2O7In contrast (FIG. 7, Y in gel powder)2O3With SiO2In a molar ratio of 1: 2) and Y after a heat treatment at 1000 deg.C2O3-SiO2First reacted to form X which is stable at low temperatures1-Y2SiO5Crystalline phase, continuing to react to form a-Y as the temperature rises to 1200 deg.C2Si2O7The intensity of diffraction peak is obviously strengthened, when the temperature is further increased to 1400 ℃, a-Y2Si2O7Conversion of the crystalline phase to b-Y2Si2O7The crystalline phase, with the enhancement of the intensity of the diffraction peak, produces the most stable g-Y up to 1600 ℃2Si2O7A crystalline phase. The results of FIGS. 7 and 8 illustrate that Y2SiO5The crystal phase can be generated at 1000 ℃, Y2Si2O7The crystalline phase is formed at 1200 c, with the degree of crystallization increasing with increasing temperature, both being present in the most stable form up to 1600 c. Based on this, the invention selects the heat treatment temperature range to be 1000-1600 ℃.
The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-described embodiments. All technical schemes belonging to the idea of the invention belong to the protection scope of the invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention, and such modifications and embellishments should also be considered as within the scope of the invention.
Claims (10)
1. The three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material comprises a three-dimensional silicon carbide fiber prefabricated part and yttrium silicate, and is characterized in that the yttrium silicate is Y2Si2O7And Y2SiO5Mixed crystal phase of (2), Y2Si2O7Crystalline phase or Y2SiO5The crystal phase is uniformly filled in the pores of the three-dimensional silicon carbide fiber prefabricated part, and the porosity of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material is 10-16%; the preparation method comprises the following steps:
(1) preparation of Y2O3-SiO2Compounding sol: will Y2O3Sol and SiO2Mixing the sol, adding a stabilizer which is strong acid to obtain Y2O3-SiO2Compounding sol;
(2) dipping: placing the three-dimensional silicon carbide fiber prefabricated part into a container, vacuumizing and sucking Y obtained in the step (1)2O3-SiO2Compounding sol, vacuum impregnating to make Y2O3-SiO2Filling the composite sol in the three-dimensional silicon carbide fiber prefabricated part;
(3) and (3) drying: taking out the three-dimensional silicon carbide fiber prefabricated part and drying to remove Y2O3-SiO2A solvent in the composite sol;
(4) and (3) heat treatment: carrying out heat treatment under the protection of inert atmosphere to obtain a three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material intermediate;
(5) and (4) repeating the dipping-drying-heat treatment processes in the steps (2) to (4) until the weight of the intermediate of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material is increased by less than 1% compared with the weight of the intermediate of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material in the last dipping-drying-heat treatment process, so as to obtain the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material.
2. The three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material according to claim 1, wherein the three-dimensional silicon carbide fiber preform is one or more of a three-dimensional silicon carbide fiber preform obtained by laminating and sewing silicon carbide fiber cloth, a three-dimensional silicon carbide fiber preform obtained by alternately laminating and needling silicon carbide fiber cloth and a mesh, a three-dimensional silicon carbide fiber preform with a three-dimensional five-way woven structure, a three-dimensional silicon carbide fiber preform with a two-dimensional semi-woven structure and a three-dimensional silicon carbide fiber preform with a three-dimensional four-way woven structure; the volume fraction of the silicon carbide fiber in the three-dimensional silicon carbide fiber prefabricated part is 20-55%.
3. A preparation method of a three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material comprises the following steps:
(1) preparation of Y2O3-SiO2Compounding sol: will Y2O3Sol and SiO2Mixing the sol, adding a stabilizer which is strong acid to obtain Y2O3-SiO2Compounding sol;
(2) dipping: placing the three-dimensional silicon carbide fiber prefabricated part into a container, vacuumizing and sucking Y obtained in the step (1)2O3-SiO2Compounding sol, vacuum impregnating to make Y2O3-SiO2Filling the composite sol in the three-dimensional silicon carbide fiber prefabricated part;
(3) and (3) drying: taking out the three-dimensional silicon carbide fiber prefabricated part and drying to remove Y2O3-SiO2A solvent in the composite sol;
(4) and (3) heat treatment: carrying out heat treatment under the protection of inert atmosphere to obtain a three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material intermediate;
(5) and (4) repeating the dipping-drying-heat treatment processes in the steps (2) to (4) until the weight of the intermediate of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material is increased by less than 1% compared with the weight of the intermediate of the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material in the last dipping-drying-heat treatment process, so as to obtain the three-dimensional silicon carbide fiber prefabricated part reinforced yttrium silicate composite material.
4. Three-dimensional silicon carbide fiber preform reinforcement according to claim 3A method for producing an yttrium silicate composite material, characterized in that in the step (1), the stabilizer and the Y2O3The mass ratio of the sol is 2-3: 10.
5. The method for preparing the three-dimensional silicon carbide fiber preform-reinforced yttrium silicate composite material according to claim 4, wherein the strong acid comprises HNO3HCl or H2SO4。
6. The method for preparing a three-dimensional silicon carbide fiber preform-reinforced yttrium silicate composite material according to claim 4, wherein in the step (1), Y is2O3-SiO2In the composite sol, the solid content is 20-40 wt%; y is2O3With SiO2The molar ratio of (1: 1) - (2) and the size of colloidal particles of the composite sol is less than or equal to 30 nm.
7. The method for preparing the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material according to claim 6, wherein in the step (3), the drying temperature is 400-700 ℃ and the drying time is 1-6 h.
8. The method for preparing the three-dimensional silicon carbide fiber preform-reinforced yttrium silicate composite material according to any one of claims 3 to 7, wherein in the step (2), after the vacuum impregnation, the method further comprises performing air pressure assisted impregnation under a set pressure to enable Y to be impregnated2O3-SiO2The composite sol is further filled in the three-dimensional silicon carbide fiber prefabricated member.
9. The method for preparing the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material according to claim 8, wherein in the step (2), the vacuum impregnation process conditions are as follows: the vacuum degree is less than or equal to 500Pa, and the dipping time is 4-8 h; the technological conditions of the air pressure auxiliary impregnation are as follows: the set pressure is 2MPa to 10MPa, and the dipping time is 2h to 6 h.
10. The method for preparing the three-dimensional silicon carbide fiber preform reinforced yttrium silicate composite material according to any one of claims 3 to 7, wherein in the step (4), the heat treatment process comprises: under the protection of inert atmosphere, the temperature is raised to 1000-1600 ℃ at the speed of 10-20 ℃/min, and the temperature is kept for 0.5-2 h.
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