Lightweight ablation-resistant metal-based thermal protection material and preparation method thereof

Abstract

The invention belongs to the technical field of thermal protection, and particularly relates to a light ablation-resistant metal-based thermal protection material and a preparation method thereof. The preparation method comprises the following steps: A, mixing LiOH powder and a metal matrix material; b, vacuum infiltration; and C, cooling and curing. The low-density hollow NiCr breathable porous material is subjected to LiOH inorganic salt composite modification, the high-temperature ablation resistance and heat insulation performance of the material are improved, meanwhile, light weight and engineering reliability are considered, and the material has good application prospects in the field of aerospace thermal protection.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal protection, and in particular relates to a lightweight, ablation-resistant metal-based thermal protection material and a preparation method thereof. Background Art

[0002] Spacecraft are subject to aerodynamic heating during flight. To ensure the proper functioning of electronic components within the spacecraft, thermal protection technologies must be employed in various locations to ensure safe operation. Thermal protection materials are a key component of thermal protection systems, making their research particularly important.

[0003] Existing thermal protection materials cannot meet the increasingly stringent requirements of high-speed aerospace vehicles for lightweight, integrated thermal insulation, and mechanical properties. For example, while porous SiO2 and Al2O3 aerogels offer good thermal insulation properties, their temperature resistance needs improvement, and their operating temperature generally does not exceed 1200°C. Ceramic fiber rigid insulation tiles offer good temperature resistance, but their brittleness and limited erosion resistance make them difficult to use in critical areas such as the nose cone and wing leading edge. Therefore, the need for lightweight, high-strength, integrated thermal insulation materials is a key factor hindering the development of high-speed aerospace vehicles.

[0004] In order to solve this problem, the inventor disclosed a hollow NiCr breathable porous material in the patent document CN119553191A previously applied for. This material has a low density and good permeability while ensuring strength, providing a new idea for the application of metal breathable materials in high-temperature sweating cooling in aerospace.

[0005] As a lightweight thermal protection material, the high porosity and fibrous structure of hollow NiCr breathable porous materials allow heat to travel farther within the material, making it easier to dissipate or even absorb heat. However, at higher service temperatures, hollow NiCr breathable porous materials struggle to withstand these conditions. Furthermore, relying solely on physical insulation through a porous structure is insufficient to meet thermal insulation requirements in higher temperature environments. Summary of the Invention

[0006] The purpose of the present invention is to provide a lightweight, ablation-resistant metal-based thermal protection material and a preparation method thereof. First, the preparation method of the hollow NiCr breathable porous material of CN119553191A is improved to reduce the final density of the rolling. Then, LiOH inorganic salt composite modification is performed to improve its high-temperature ablation resistance and thermal insulation performance, while taking into account lightweight and engineering reliability, so that it has good application prospects in the field of aerospace thermal protection.

[0007] Specifically, the present invention provides the following technical solutions:

[0008] A method for preparing a lightweight, ablation-resistant metal-based thermal protection material comprises the following steps:

[0009] A. Mixing LiOH powder and metal matrix material: Prepare LiOH powder and hollow NiCr gas permeable porous material. First, spread the LiOH powder in a crucible, and then place the hollow NiCr gas permeable porous material on the LiOH powder.

[0010] B. Vacuum Infiltration: Place the crucible in a vacuum infiltration furnace, evacuate the vacuum, and heat it up. Keep it at the infiltration temperature for a period of time. The high temperature melts the LiOH powder. Under vacuum conditions, the liquid inorganic salt penetrates into the fiber surface and pores of the hollow NiCr breathable porous material.

[0011] C. Cooling and solidification: Cooling in the furnace under vacuum conditions, the liquid inorganic salt solidifies to obtain a lightweight, ablation-resistant metal-based thermal protection material.

[0012] The preparation method provided by the present invention, step A is to place a hollow NiCr breathable porous material on a flat LiOH powder, and in step B vacuum infiltration, the molten inorganic salt (low viscosity liquid phase) penetrates the pores of the metal matrix from bottom to top under vacuum, relying on capillary force (rather than gravity) to achieve directional filling, thereby avoiding the uneven distribution caused by the sedimentation of salts due to density differences during direct mixing. In addition, when the molten salt infiltrates from below, the gas can be discharged upward along the unfilled pores of the metal matrix and drawn away by the vacuum system. If direct mixing is adopted, the salts may wrap the metal matrix and affect the internal infiltration effect, and the molten salt may be locally enriched to cause perforation of the metal matrix.

[0013] Preferably, in step A, the method for preparing the hollow NiCr breathable porous material comprises the following steps:

[0014] (1) Carbonization of absorbent cotton: The absorbent cotton is dried and then carbonized at a temperature of 600-1200°C for 4-8 hours to obtain curly and mutually entangled carbonized absorbent cotton fibers;

[0015] (2) Nickel plating: nickel plating the absorbent cotton carbonized fiber to obtain nickel-plated absorbent cotton carbonized fiber with a coating thickness of 1 to 3 μm;

[0016] (3) Dry process: Physically vibrate the nickel-plated absorbent cotton carbonized fiber to mix and distribute it evenly to obtain a blank;

[0017] (4) Wet hydrogen sintering: placing the green body into a wet hydrogen sintering furnace, and sintering at 750-1100° C. for 8-12 hours in a mixed atmosphere of hydrogen and water vapor to obtain a hollow porous nickel matrix composed of hollow nickel fibers;

[0018] (5) solid phase infiltration: placing the hollow porous nickel substrate into an infiltration furnace and performing Cr infiltration treatment to obtain a hollow NiCr porous material;

[0019] (6) Rolling: The hollow NiCr porous material is subjected to multiple rolling processes, and the final density of the rolled material is 1-2 g / cm 3 , and obtain the hollow NiCr breathable porous material.

[0020] The present invention is based on the preparation method of hollow NiCr breathable porous material disclosed in patent document CN119553191A, and reduces the final density of rolling. The density of the prepared hollow NiCr breathable porous material is 1-2g / cm 3 The reason is that the hollow NiCr breathable porous material in this density range has a higher porosity, which is convenient for further infiltration of inorganic salts for modification, and has a lower thermal conductivity, which is more in line with the requirements of thermal insulation materials.

[0021] Preferably, in step A, the mass ratio of the LiOH powder to the hollow NiCr breathable porous material is 1:1 to 1:5.

[0022] Preferably, before step A, the method further includes pre-treating the hollow NiCr gas-permeable porous material; the pre-treating comprises ultrasonically cleaning the hollow NiCr gas-permeable porous material and drying the material after cleaning. This pre-treating ensures that the pores of the hollow NiCr gas-permeable porous material are clean, thereby increasing permeability.

[0023] Preferably, in step B, the infiltration temperature is 500-800° C., and the holding time is 1-3 hours.

[0024] The present invention also provides a lightweight ablation-resistant metal-based thermal protection material, which is prepared by the above-mentioned preparation method. The matrix of the lightweight ablation-resistant metal-based thermal protection material has a density of 1-2 g / cm 3 The hollow NiCr porous material is a breathable, LiOH inorganic salt deposited on the fiber surface as a cooling medium, improving thermal protection efficiency. This lightweight, ablation-resistant metal-based thermal protection material has high specific strength, low density, excellent ablation resistance and thermal insulation, and can meet the increasingly stringent requirements of aerospace materials.

[0025] Preferably, the density of the lightweight ablation-resistant metal-based thermal protection material is 1.5-3 g / cm 3 .

[0026] The beneficial effects of the present invention are at least:

[0027] 1) The present invention provides a lightweight, ablation-resistant metal-based thermal protection material and its preparation method. This material utilizes a composite of LiOH inorganic salt and a low-density, hollow, and porous NiCr material to effectively avoid the problems of high density, poor ablation resistance, and poor thermal insulation properties faced by traditional metal thermal protection materials, providing a new approach to metal thermal protection.

[0028] 2) The present invention provides a lightweight, ablation-resistant metal-based thermal protection material and its preparation method. By adjusting the ratio of LiOH inorganic salt and low-density hollow NiCr breathable porous material, the heat protection temperature range of the composite material can be designed, enabling application in different temperature ranges and expanding the application range of the material in the field of thermal protection.

[0029] 3) The present invention provides a lightweight, ablation-resistant metal-based thermal protection material and its preparation method. During the vacuum infiltration process, the infiltration time and temperature are strictly controlled, effectively ensuring the uniform distribution of the LiOH inorganic salt in the hollow NiCr breathable porous material, thereby ensuring the thermal protection effect of the composite material.

[0030] 4) The present invention provides a lightweight, ablation-resistant metal-based thermal protection material and a preparation method thereof. The preparation process is simple, convenient for large-scale production, and can ensure the improvement of the performance of the metal thermal protection material, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the SEM image of the lightweight, ablation-resistant metal-based thermal protection material in Example 1.

[0032] Figure 2 These are the XRD patterns of the lightweight, ablation-resistant metal-based thermal protection material in Example 2 before and after oxyacetylene ablation; wherein (a) is the XRD pattern before oxyacetylene ablation, and (b) is the XRD pattern after oxyacetylene ablation.

[0033] Figure 3 This is the quartz lamp back temperature curve of the lightweight ablation-resistant metal-based thermal protection material in Example 3; wherein, the set temperature and the actual front temperature are 700°C, the heating time is 1154s, and the final temperature of the back of the composite material is 382.7°C. DETAILED DESCRIPTION

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions shall be followed.

[0035] In the following examples, the preparation method of the hollow NiCr breathable porous material is as follows:

[0036] (1) 200 g of absorbent cotton fiber was dried and placed in a muffle furnace, heated to 1200 °C and maintained for 4 h to obtain absorbent cotton carbonized fiber.

[0037] (2) Plating the carbonized absorbent cotton fibers in a nickel plating apparatus for electroplating with an electrolyte consisting of 300 g / L nickel sulfate, 30 g / L nickel chloride, and 30 g / L boric acid. The electroplating voltage was adjusted to 20 V and the current to 60 A for 1 hour. After nickel plating, the fibers were washed and dried to obtain nickel-plated carbonized absorbent cotton fibers.

[0038] (3) 150 g of the nickel-plated absorbent cotton carbonized fiber was placed in a mold with a length of 80 mm, a width of 80 mm, and a height of 10 mm, and the mold was formed uniformly by physical vibration to obtain a green body.

[0039] (4) The green body was placed in a wet hydrogen sintering furnace at a sintering temperature of 1100°C for 8 hours, a hydrogen flow rate of 5 L / min, and a water vapor flow rate of 3 L / min to obtain a hollow porous nickel matrix composed of hollow nickel fibers with a density of 0.8 g / cm 3 .

[0040] (5) adding Cr powder and NHCl powder in a mass ratio of 7:1 into a ball mill, and mixing them uniformly by ball milling to form an impregnation mixture; placing the hollow porous nickel substrate into an impregnation furnace, and loading it into an impregnation bag with the impregnation mixture in a mass ratio of 3:1, and then placing it into a tubular furnace under an argon protective atmosphere for infiltration at a temperature of 1000°C for 14 hours to obtain a hollow NiCr porous material;

[0041] (6) The hollow NiCr porous material is rolled through a rolling mill, with a reduction of 0.5 mm per pass. By controlling the number of rolling passes, the final density is 1 g / cm 3 , 1.5g / cm 3 , 2g / cm 3 Hollow NiCr breathable porous material.

[0042] In the following examples, the LiOH powder used was sourced from Beijing Innochem Technology Co., Ltd., with the brand INNOCHEM and the product number A92997.

[0043] Example 1

[0044] (1) Pretreatment of hollow NiCr breathable porous material: density 1g / cm 3 The hollow NiCr breathable porous material is ultrasonically cleaned and dried after cleaning to ensure that the pores are clean and increase the permeability of the porous metal matrix.

[0045] (2) Mixing LiOH powder and metal matrix material: LiOH powder and hollow NiCr gas permeable porous material were prepared in a mass ratio of 1:1. First, LiOH powder was spread evenly in a crucible, and then the hollow NiCr gas permeable porous material was placed on the LiOH powder.

[0046] (3) Vacuum Infiltration: Place the crucible in a vacuum infiltration furnace and heat it to 500°C until the gauge pressure reaches -0.1 MPa. Maintain the temperature for 3 hours. The high temperature melts the LiOH powder. Under vacuum conditions, the liquid inorganic salt penetrates into the fiber surface and pores of the hollow NiCr porous material.

[0047] (4) Cooling and solidification: Cooling in the furnace under vacuum conditions, the liquid inorganic salt solidifies, and the temperature is reduced to 50°C to obtain a lightweight, ablation-resistant metal-based thermal protection material with a density of 1.5 g / cm 3 .

[0048] The obtained lightweight, ablation-resistant metal-based thermal protection material was subjected to an oxyacetylene ablation test at 1400°C. XRD results before and after the experiment showed that the material structure was stable and had good ablation resistance. The lightweight, ablation-resistant metal-based thermal protection material was heated by a quartz lamp at 700°C for more than 1000s, and the back temperature was stabilized at 310°C, showing excellent thermal insulation performance.

[0049] Figure 1 This is the SEM image of the lightweight, ablation-resistant metal-based thermal protection material in Example 1. It can be seen that the inorganic salt is evenly distributed on the fiber surface in the form of small spherical particles, and the infiltration effect is good.

[0050] Example 2

[0051] (1) Pretreatment of hollow NiCr breathable porous material: density 1.5g / cm 3 The NiCr hollow fiber porous material is ultrasonically cleaned and dried after cleaning to ensure that the pores are clean and increase the permeability of the porous metal matrix.

[0052] (2) Mixing LiOH powder and metal matrix material: LiOH powder and hollow NiCr gas permeable porous material were prepared in a mass ratio of 1:3. First, LiOH powder was spread evenly in a crucible, and then the hollow NiCr gas permeable porous material was placed on the LiOH powder.

[0053] (3) Vacuum Infiltration: Place the crucible in a vacuum infiltration furnace and heat it to 600°C until the gauge pressure reaches -0.1 MPa. Hold the temperature for 2 hours. The high temperature melts the LiOH powder. Under vacuum conditions, the liquid inorganic salt penetrates the fiber surface and pores of the hollow NiCr porous material.

[0054] (4) Cooling and solidification: Cooling in the furnace under vacuum conditions, the liquid inorganic salt solidifies, and the temperature is reduced to 50°C to obtain a lightweight, ablation-resistant metal-based thermal protection material with a density of 2g / cm 3 .

[0055] The obtained lightweight ablation-resistant metal-based thermal protection material was subjected to oxyacetylene ablation test at 1400°C. Figure 2 This is the XRD pattern of the lightweight ablation-resistant metal-based thermal protection material in Example 2 before and after oxyacetylene ablation. The results show that the material structure is stable and has good ablation resistance. The lightweight ablation-resistant metal-based thermal protection material is heated by a quartz lamp at 700°C for more than 1000s, and the back temperature is stabilized at 350°C, showing excellent thermal insulation performance.

[0056] Example 3

[0057] (1) Pretreatment of hollow NiCr breathable porous material: density 2g / cm 3 The hollow NiCr breathable porous material is ultrasonically cleaned and dried after cleaning to ensure that the pores are clean and increase the permeability of the porous metal matrix.

[0058] (2) Mixing LiOH powder and metal matrix material: LiOH powder and hollow NiCr gas permeable porous material were prepared in a mass ratio of 1:5. First, LiOH powder was spread evenly in a crucible, and then the hollow NiCr gas permeable porous material was placed on the LiOH powder.

[0059] (3) Vacuum Infiltration: Place the crucible in a vacuum infiltration furnace and heat it to 800°C until the gauge pressure reaches -0.1 MPa. Hold the temperature for 1 hour. The high temperature melts the LiOH powder. Under vacuum conditions, the liquid inorganic salt penetrates the fiber surface and pores of the hollow NiCr porous material.

[0060] (4) Cooling and solidification: Cooling in the furnace under vacuum conditions, the liquid inorganic salt solidifies, and the temperature is reduced to 50°C to obtain a lightweight, ablation-resistant metal-based thermal protection material with a density of 3g / cm 3 .

[0061] The obtained lightweight ablation-resistant metal-based thermal protection material was subjected to oxyacetylene ablation test at 1400°C. The XRD results before and after the experiment showed that the material structure was stable and the ablation resistance was good. The lightweight ablation-resistant metal-based thermal protection material was heated by a quartz lamp at 700°C for more than 1000s. Figure 3 The back temperature curve of the quartz lamp made of lightweight, ablation-resistant metal-based thermal protection material shows that the back temperature is stable at 380°C, demonstrating excellent thermal insulation performance.

[0062] Comparative Example 1

[0063] Compared with Example 1, the only difference is that the mass ratio of LiOH powder to the hollow NiCr breathable porous material is 1:10.

[0064] (1) Pretreatment of hollow NiCr breathable porous material: density 1g / cm 3 The hollow NiCr breathable porous material is ultrasonically cleaned and dried after cleaning to ensure that the pores are clean and increase the permeability of the porous metal matrix.

[0065] (2) Mixing LiOH powder and metal matrix material: LiOH powder and hollow NiCr gas permeable porous material were prepared in a mass ratio of 1:10. First, LiOH powder was spread evenly in a crucible, and then the hollow NiCr gas permeable porous material was placed on the LiOH powder.

[0066] (3) Vacuum Infiltration: Place the crucible in a vacuum infiltration furnace and heat it to 500°C until the gauge pressure reaches -0.1 MPa. Maintain the temperature for 3 hours. The high temperature melts the LiOH powder. Under vacuum conditions, the liquid inorganic salt penetrates into the fiber surface and pores of the hollow NiCr porous material.

[0067] (4) Cooling and solidification: Cooling in the furnace under vacuum conditions, the liquid inorganic salt solidifies, and the temperature is lowered to 50°C to obtain a lightweight, ablation-resistant metal-based thermal protection material with a density of 1.6 g / cm 3 .

[0068] The obtained lightweight, ablation-resistant metal-based thermal protection material was subjected to an oxyacetylene ablation test at 1400°C. After the experiment, a small pit appeared in the center of the material. The lightweight, ablation-resistant metal-based thermal protection material was heated by a quartz lamp at 700°C for more than 1000s, and the back temperature was stabilized at 510°C.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a lightweight, ablation-resistant metal-based thermal protection material, characterized in that: The following steps are involved: A. Mixing LiOH powder and metal matrix material: Prepare LiOH powder and hollow NiCr gas permeable porous material. First, spread the LiOH powder in a crucible, and then place the hollow NiCr gas permeable porous material on the LiOH powder. B. Vacuum Infiltration: Place the crucible in a vacuum infiltration furnace, evacuate the vacuum, and heat it up. Keep it at the infiltration temperature for a period of time. The high temperature melts the LiOH powder. Under vacuum conditions, the liquid inorganic salt penetrates into the fiber surface and pores of the hollow NiCr breathable porous material. C. Cooling and solidification: Cooling in the furnace under vacuum conditions, the liquid inorganic salt solidifies to obtain a lightweight, ablation-resistant metal-based thermal protection material.

2. The preparation method according to claim 1, characterized in that In step A, the method for preparing the hollow NiCr breathable porous material comprises the following steps: (1) Carbonization of absorbent cotton: The absorbent cotton is dried and then carbonized at a temperature of 600-1200°C for 4-8 hours to obtain curly and mutually entangled carbonized absorbent cotton fibers; (2) Nickel plating: nickel plating the absorbent cotton carbonized fiber to obtain nickel-plated absorbent cotton carbonized fiber with a coating thickness of 1 to 3 μm; (3) Dry process: Physically vibrate the nickel-plated absorbent cotton carbonized fiber to mix and distribute it evenly to obtain a blank; (4) Wet hydrogen sintering: placing the green body into a wet hydrogen sintering furnace, and sintering at 750-1100° C. for 8-12 hours in a mixed atmosphere of hydrogen and water vapor to obtain a hollow porous nickel matrix composed of hollow nickel fibers; (5) solid phase infiltration: placing the hollow porous nickel substrate into an infiltration furnace and performing Cr infiltration treatment to obtain a hollow NiCr porous material; (6) Rolling: The hollow NiCr porous material is subjected to multiple rolling processes, and the final density of the rolled material is 1-2 g / cm 3 , and obtain the hollow NiCr breathable porous material.

3. The preparation method according to claim 1 or 2, characterized in that In step A, the particle size of the LiOH powder is micron-sized, and the mass ratio of the LiOH powder to the hollow NiCr breathable porous material is 1:1 to 1:

5.

4. The preparation method according to claim 1 or 2, characterized in that Before step A, the method further includes a step of pre-treating the hollow NiCr breathable porous material; the pre-treatment includes ultrasonically cleaning the hollow NiCr breathable porous material and drying the material after cleaning.

5. The preparation method according to claim 1 or 2, characterized in that The infiltration temperature is 500-800° C., and the holding time is 1-3 hours.

6. A lightweight, ablation-resistant metal-based thermal protection material, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 5.

7. The lightweight ablation-resistant metal-based thermal protection material according to claim 6, characterized in that: The density of the lightweight ablation-resistant metal-based thermal protection material is 1.5-3 g / cm 3 .

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