A method for rapid low-temperature preparation of ultra-high temperature ceramic materials using polycarbosilane-modified binders

Abstract

This invention relates to a method for the rapid low-temperature preparation of ultra-high temperature ceramic materials using polycarbosilane-modified binders, belonging to the technical field of ceramic materials. The method uses polycarbosilane-modified phthalonitrile as a binder, and the ceramic material is obtained through curing, achieving rapid and controllable low-temperature molding of ultra-high temperature ceramic materials. The method utilizes hafnium carbide, hafnium boride, and silicon boride as ceramic powders, and polycarbosilane-modified phthalonitrile as a binder, bonding them into an organic / inorganic hybrid high-temperature resistant material. During high-temperature use, the polycarbosilane-modified phthalonitrile first generates carbon free radicals, some of which oxidize into carbon monoxide and volatilize. The remaining carbon free radicals, before oxidation, sinter with hafnium carbide and other materials to form carbon-based ultra-high temperature ceramics, constructing a continuous and dense carbide ablation layer, significantly improving the material's ablation resistance.

Description

Technical Field

[0001] This invention relates to a method for rapidly preparing ultra-high temperature ceramic materials at low temperatures using polycarbosilane-modified binders, which belongs to the technical field of ceramic materials. Background Technology

[0002] As the Mach number of high-speed aircraft continues to increase, the thermal barrier problem faced by thermal protection systems during service becomes particularly prominent. The surfaces of thermal protection structures such as the nose cone, wing leading edge, and combustion chamber and nozzle of scramjet engines are subjected to enormous aerodynamic heating, with surface temperatures reaching over 2000℃ in short periods. Furthermore, high-speed rail brake pads also experience significant thermo-coupling effects, all of which place increasingly stringent demands on the performance of high-temperature resistant materials. C / C composite materials, due to insufficient oxidation resistance, are mainly used in short-term reentry environments and cannot meet long-term heat resistance requirements. C / SiC composite materials, due to the high SiO2 content in their ablation products, have insufficient melting point and high-temperature stability, and can only be used in oxygen-rich environments below 1600℃. Moreover, the high manufacturing cost of both materials limits their widespread application.

[0003] Therefore, ultra-high temperature ceramics (UHTCs) have emerged. UHTCs refer to ceramics with melting points above 3000℃ and good ablation resistance in oxidizing atmospheres above 2000℃. They are a type of composite material that uses carbides, silicides, or borides of transition metals such as Zr, Hf, and Ta as the ceramic phase and carbon fibers as the toughening phase. They are the most promising ultra-high temperature thermal protection materials.

[0004] Currently, the main processes for preparing ultra-high temperature ceramics and their composites include: hot pressing sintering (HP, with sintering temperatures mostly above 1900 ℃), polymer precursor impregnation pyrolysis (PIP, with ultra-high temperature phase transformation temperatures mostly above 1700 ℃), and reactive infiltration (RMI, with temperatures mostly above 1800 ℃), etc., and the atmosphere used is argon, which is a scarce and expensive strategic resource. Existing molding processes for ultra-high temperature ceramics and their composites generally suffer from high preparation temperatures and long manufacturing cycles. Therefore, developing a low-temperature rapid preparation technology for ultra-high temperature ceramics using traditional resin-based composite materials is an urgent need for the development of this field. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for rapidly preparing ultra-high temperature ceramic materials at low temperatures using a polycarbosilane-modified binder. This method employs low-temperature rapid prototyping technology and utilizes the synergistic effect of multiple components to construct a continuous and dense ultra-high temperature ablation-resistant layer, thereby optimizing the ablation resistance of the material.

[0006] The technical solution adopted in this invention is: a method for rapidly preparing ultra-high temperature ceramic materials at low temperatures using a polycarbosilane-modified binder, comprising the following steps:

[0007] (1) Add 1 part of KH560 to 100 parts of phthalonitrile, then add 10 parts of polycarbosilane, heat to 160-180℃, stir for 20-40 minutes, cool to 110-120℃ and then add N,N-dimethylformamide solution to obtain polycarbosilane modified phthalonitrile adhesive solution.

[0008] (2) 100 parts of the polycarbosilane modified phthalonitrile binder solution, 50-150 parts of 1μm hafnium carbide, 100-500 parts of 5μm hafnium carbide, 50-150 parts of 1μm hafnium boride, and 50-150 parts of 1μm silicon boride are mixed evenly, then heated to remove the solvent, and pulverized into powder; then cured under pressure of 14-16MPa at room temperature and 220-250℃ for 0.3-1 hours to obtain ultra-high temperature ceramic material.

[0009] Furthermore, the polycarbosilane-modified phthalonitrile adhesive solution has a mass percentage of 30%.

[0010] Furthermore, in step (2), 100 parts of the polycarbosilane modified phthalonitrile binder solution, 50 parts of 1μm hafnium carbide, 300 parts of 5μm hafnium carbide, 150 parts of 1μm hafnium boride, and 100 parts of 1μm silicon boride are mixed evenly.

[0011] The ultra-high temperature ceramic material prepared by the above method was subjected to an oxyacetylene ablation test at a temperature of 2600℃ for 480s; the linear ablation rate was 0.188um / s and the mass loss rate was 2.04mg / s.

[0012] The specific steps of the above method are as follows: (1) Using 100 parts of phthalonitrile and 1 part of KH560 coupling agent as the mass standard, add different mass parts of solid polycarbosilane and mix, heat to 170°C, stir and keep warm for 30 min, then cool down to 120°C, add N,N-dimethylformamide, and prepare an adhesive with a concentration of 30%; the bonding test proved that when the polycarbosilane is 0-20 parts, the shear strength and peel strength are the best when the polycarbosilane is 10 parts.

[0013] (2) 100 parts of binder, 50-150 parts of 1μm hafnium carbide, 100-500 parts of 5μm hafnium carbide, 50-150 parts of 1μm hafnium boride, and 50-150 parts of 1μm silicon boride are added and mixed evenly. Then the solvent is removed by heating and the mixture is pulverized into powder. The powder is placed in a mold and pressed at 15MPa at room temperature and cured at 240℃ for 0.5 hours to obtain ultra-high temperature ceramic.

[0014] Furthermore, in step (1), KH560 coupling agent is added to the phthalonitrile.

[0015] Furthermore, in step (1), KH560 coupling agent is added to the phthalonitrile before polycarbosilane is added. Adhesion tests have shown that when the polycarbosilane content is 0-20 parts, optimization tests have shown that the shear strength and peel strength are optimal when the polycarbosilane content is 10 parts.

[0016] Furthermore, in step (1), the temperature is raised to 170°C, kept warm for 30 minutes, and stirred.

[0017] Further, in step (1), the temperature is raised to 170°C, kept at that temperature for 30 minutes and stirred, and then cooled to 120°C, and N,N-dimethylformamide is added as a solvent.

[0018] Furthermore, in step (1), the adhesive solution has a mass percentage of 30%.

[0019] Further, in step (2), N,N-dimethylformamide is used as a solvent, along with 100 parts of 30% polycarbosilane-modified phthalonitrile adhesive, 50 parts of 1μm hafnium carbide, 300 parts of 5μm hafnium carbide, 150 parts of 1μm hafnium boride, and 100 parts of 1μm silicon boride; all are mixed evenly.

[0020] The beneficial effects of this invention are as follows: This method uses polycarbosilane-modified phthalonitrile as a binder, and ultra-high temperature ceramics are obtained by curing and molding, realizing the low-temperature rapid and controllable molding of ultra-high temperature ceramic materials. That is, the molding temperature has been reduced from the original 1600℃ for several hours to 240℃ for 0.5 hours, which is a significant improvement.

[0021] This method uses polycarbosilane-modified phthalonitrile as a binder, and the ceramic material is obtained by curing and molding, realizing the low-temperature rapid and controllable molding of ultra-high temperature ceramic materials. The method utilizes hafnium carbide, hafnium boride, and silicon boride as ceramic powders, and polycarbosilane-modified phthalonitrile as a binder, bonding them into an organic / inorganic hybrid high-temperature resistant material. During high-temperature use, the polycarbosilane-modified phthalonitrile first generates carbon free radicals, some of which oxidize into carbon monoxide and volatilize, while the remaining carbon free radicals, before oxidation, sinter with hafnium carbide and other materials to form a carbon-based ultra-high temperature ceramic, constructing a continuous and dense carbide ablation layer, significantly improving the material's ablation resistance.

[0022] The obtained ultra-high temperature ceramic material was subjected to an ablation performance test at 2600℃ for 480 seconds, with a linear ablation rate of 0.188 μm / s and a mass loss rate of 2.04 mg / s. Attached Figure Description

[0023] Figure 1 This is a SEM image of the internal cross-section of an ultra-high temperature ceramic material after an oxyacetylene ablation test.

[0024] Figure 2These are SEM images of the surface of ultra-high temperature ceramic materials after an oxyacetylene ablation test. Detailed Implementation

[0025] The present invention will be specifically described below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention, but are not limited thereto, unless otherwise stated.

[0026] The specific embodiments of the present invention are described in detail below with reference to the technical solutions:

[0027] Solid polycarbosilane was purchased from Suzhou Saifei Group Co., Ltd., and KH560 coupling agent was purchased from Nanjing Chemical Reagent Co., Ltd.

[0028] Example 1

[0029] Using 100 parts of phthalonitrile and 1 part of KH560 coupling agent as the mass standard, different mass parts of solid polycarbosilane were added and mixed. The mixture was heated to 170℃, stirred and kept at that temperature for 30 min, and then cooled to 120℃. N,N-dimethylformamide was added to prepare a 30% adhesive solution. The curing conditions were 240℃ for 0.5 h. The tensile shear strength of the adhesive at different temperatures was tested according to GB7124, and the peel strength at room temperature was tested according to GB7122. The specific results are shown in Table 1.

[0030] Table 1 Mechanical properties of polycarbosilane-modified phthalonitrile adhesives

[0031]

[0032] The effect of different amounts of polycarbosilane on the tensile shear strength of the adhesive, using 100 parts of phthalonitrile as the standard (curing conditions: 240℃ for 0.5h).

[0033] As can be seen from Table 1, when the amount of polycarbosilane added is 10 parts, its adhesive performance is the best at different temperatures; and the peel strength at room temperature is also the best when the amount of polycarbosilane added is 10 parts.

[0034] Preparation of adhesive solution: Add 1 part KH560 to 100 parts phthalonitrile, then add 10 parts solid polycarbosilane, heat to 170℃, stir for 30 minutes, cool to 120℃ and then add N,N-dimethylformamide solution to obtain a polycarbosilane-modified phthalonitrile adhesive solution with a mass percentage of 30%.

[0035] Example 2

[0036] This method uses polycarbosilane-modified phthalonitrile as a binder and cures it at 240℃ for 0.5 hours to obtain a ceramicized sample. This method utilizes hafnium carbide and polycarbosilane-modified phthalonitrile binder to cure and bond them into an organic / inorganic hybrid high-temperature resistant material. During high-temperature use, the polycarbosilane-modified phthalonitrile decomposes to first generate carbon free radicals. Some of these free radicals are then oxidized to carbon monoxide and volatilized. Before oxidation, the other carbon free radicals sinter with hafnium carbide to form a carbon-based ultra-high temperature ceramic, constructing a continuous and dense ablation layer, which significantly improves the ablation resistance of the material. 100 parts of the polycarbosilane-modified phthalonitrile adhesive solution prepared in Example 1 were mixed with 50-150 parts of 1μm hafnium carbide, 100-500 parts of 5μm hafnium carbide, 50-150 parts of 1μm hafnium boride, and 50-150 parts of 1μm silicon boride. The mixture was heated at 140℃ for 50 min to remove N,N-dimethylformamide. After cooling to room temperature, the powder was ground. Equal weights of the powder were placed in a mold, and the mold was pressurized at 15 MPa at room temperature and cured under pressure at 240℃ for 0.5 hours to prepare an ultra-high temperature ceramic sample. Oxyacetylene ablation performance was tested (temperature controlled at 2600℃, held for 480 s).

[0037] Table 2 Factor Level Table

[0038]

[0039] Through orthogonal experiments, the above method was used to conduct experiments on the component contents listed in the table below, and the corresponding results were obtained:

[0040] Table 3 Orthogonal Experiment Table

[0041]

[0042] Rows I, II, and III represent the sum of the linear ablation rate / mass ablation rate of each factor at different levels, reflecting the overall performance of that factor at different levels. The range R measures the influence of each factor on the result; a larger R value indicates a greater influence of that factor on the experimental result. The final data is used to verify the sum, ensuring calculation accuracy, and can also be used to calculate the overall average performance. The optimal formulation mass ratio was ultimately determined to be 1μm hafnium carbide: 5μm hafnium carbide: 1μm hafnium boride: 1μm silicon boride at 50:300:150:100.

[0043] Through orthogonal experiments, the following composition was determined: 100 parts of polycarbosilane-modified phthalonitrile adhesive solution, 50 parts of 1μm hafnium carbide, 300 parts of 5μm hafnium carbide, 150 parts of 1μm hafnium boride, and 100 parts of 1μm silicon boride. After removing the solvent by heating at 140℃ for 50 min and cooling to room temperature, the powder was ground, pressurized at 15 MPa, and cured at 240℃ for 0.5 hours to obtain an ultra-high temperature ceramic material.

[0044] The ultra-high temperature ceramic material exhibits a room temperature compressive strength of 212 MPa and a thermal conductivity of 2.12 W / (m·K). After oxyacetylene ablation (temperature controlled at 2600℃ for 480 s), the compressive strength reaches 61 MPa, the linear ablation rate is 0.188 μm / s, and the mass loss on burn-off is 2.04 mg / s. SEM images of the internal cross-section after the oxyacetylene ablation test are shown below. Figure 1 As shown, the surface SEM image after the oxyacetylene ablation test is as follows: Figure 2 As shown.

[0045] The above embodiments are only used to illustrate the present invention. Any equivalent transformations and improvements made on the basis of the technical solutions of the present invention should not be excluded from the protection scope of the present invention.

Claims

1. A method for the rapid low-temperature preparation of ultra-high temperature ceramic materials using polycarbosilane-modified binders, characterized in that, Includes the following steps: (1) Add 1 part of KH560 to 100 parts of phthalonitrile, then add 10 parts of polycarbosilane, heat to 160-180℃, stir for 20-40 minutes, cool to 110-120℃ and then add N,N-dimethylformamide solution to obtain polycarbosilane modified phthalonitrile adhesive solution. (2) 100 parts of the polycarbosilane modified phthalonitrile binder solution, 50-150 parts of 1μm hafnium carbide, 100-500 parts of 5μm hafnium carbide, 50-150 parts of 1μm hafnium boride, and 50-150 parts of 1μm silicon boride are mixed evenly, then heated to remove the solvent, and pulverized into powder; then cured under pressure of 14-16MPa at room temperature and 220-250℃ for 0.3-1 hours to obtain ultra-high temperature ceramic material.

2. The method for rapid low-temperature preparation of ultra-high temperature ceramic materials using polycarbosilane-modified binders according to claim 1, characterized in that: The polycarbosilane-modified phthalonitrile adhesive solution has a mass percentage of 30%.

3. The method for rapid low-temperature preparation of ultra-high temperature ceramic materials using polycarbosilane-modified binders according to claim 2, characterized in that: In step (2), 100 parts of the polycarbosilane modified phthalonitrile binder solution, 50 parts of 1μm hafnium carbide, 300 parts of 5μm hafnium carbide, 150 parts of 1μm hafnium boride, and 100 parts of 1μm silicon boride are mixed evenly.

4. The method for rapid low-temperature preparation of ultra-high temperature ceramic materials using polycarbosilane-modified binders according to claim 3, characterized in that: The ultra-high temperature ceramic material prepared by this method was subjected to an oxyacetylene ablation test at a temperature of 2600℃ for 480s; the linear ablation rate was 0.188 μm / s and the mass loss rate was 2.04 mg / s.

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