SiC nanowire reinforced high-entropy porous ceramic as well as preparation method and application thereof

Abstract

The invention provides a SiC nanowire reinforced high-entropy porous ceramic and a preparation method thereof, the preparation method comprises the following steps: 1) dissolving TaCl5, NbCl5, TiCl4, ZrCl4, HfCl4 and tetraethoxysilane in ethanol to prepare a mixed alcohol solution; 2) reacting the mixed alcohol solution with polyol at a preset temperature and a preset pressure to obtain a solid-phase product; and 3) drying the solid-phase product, and performing high-temperature carbonization to obtain the SiC nanowire reinforced high-entropy porous ceramic. The introduction of the SiC nanowires not only improves the compressive strength of the high-entropy porous ceramic, but also realizes regulation and control of a hierarchical pore structure, effectively improves the compressive strength and heat conduction characteristics of the ultrahigh-temperature porous material, and realizes the structural and functional integrated design of the high-entropy porous ceramic. The existing technological process for preparing the SiC nanowire enhanced high-entropy porous ceramic is greatly simplified.

Description

Technical Field

[0001] The present invention relates to the field of thermal insulation ultra-high temperature ceramics, and particularly to a SiC nanowire-reinforced high-entropy porous ceramic, a preparation method thereof, and an application thereof. Background Art

[0002] High-entropy porous ceramics have the comprehensive properties of ultra-high temperature ceramics and porous ceramics, such as small bulk density, large specific surface area, good chemical and high-temperature stability, etc. These unique properties make high-entropy porous ceramics very potential candidate materials in application fields such as thermal insulation at extremely high temperatures and filtration of corrosive gases. However, due to the high porosity, high-entropy porous ceramics have relatively low mechanical properties. In order to achieve the integration of structure and function and improve the mechanical properties of high-entropy porous ceramics, using SiC nanowires to reinforce high-entropy porous ceramics can effectively adjust the relationship between thermal conductivity and compressive strength, and have ultra-high compressive strength while having a low thermal conductivity.

[0003] Currently, the methods for preparing SiC nanowire-reinforced porous ultra-high temperature ceramics are divided into chemical vapor deposition and in-situ reaction according to the different methods of introducing SiC nanowires. The paper "Fabrication and mechanical properties of carbon fibers / lithium aluminosilicate ceramic matrix composites reinforced by in-situ growth SiC nanowires" published by Wang et al. used chemical vapor reaction, precursor impregnation, and hot press sintering methods to continuously prepare Cf / LAS composites with in-situ grown SiC nanowires (SiCnw-Cf / LAS). Its flexural strength reached 597 MPa, which was 19% higher than that of the unreinforced Cf / LAS, and the maximum fracture toughness was 11.01 MPa·m -2 , which was increased by 46.4%. The paper "High strength aligned SiC nanowire reinforced SiC porous ceramics fabricated by 3D printing and chemical vapor infiltration" published by Zhu et al. used the direct ink printing method to prepare a SiC NWs skeleton, mixed SiC nanowires with a hydroxypropyl methylcellulose solution to prepare ink, and used chemical vapor deposition to prepare aligned SiC nanowire-reinforced SiC porous ceramics. The compressive strength reached 390 MPa, the porosity was about 41.3%, and the pore size was about 400 μm.

[0004] Chinese Patent Application CN202210386075.2 reported a SiC nanowire network-reinforced layered porous SiC ceramic and its preparation method. The SiC nanowire aerogel was hot-pressed to obtain a SiC nanowire network with a layered structure. The SiC nanowire network with a layered structure was subjected to interface modification treatment to deposit an interface layer. Using a ceramic precursor as the raw material, the SiC nanowire network with a layered structure deposited with the interface layer was subjected to several vacuum impregnation-crosslinking curing-high temperature pyrolysis treatments to obtain a SiC nanowire network-reinforced layered porous SiC ceramic. The bending strength of the SiC nanowire network-reinforced layered porous SiC ceramic is 40-210 MPa, and the compressive strength is 30-220 MPa.

[0005] In the above research, the preparation process of SiC nanowires is complex. Using a polymer precursor as the silicon source, the preparation of SiC nanowire-reinforced ceramic matrix composites requires multiple steps to complete, and the preparation cycle of the composites is long and the cost is high. Summary of the Invention

[0006] Aiming at the problems existing in the prior art, the present invention provides a SiC nanowire-reinforced high-entropy porous ceramic, its preparation method and application. The preparation method greatly simplifies the process flow of preparing SiC nanowire-reinforced high-entropy porous ceramics in the prior art.

[0007] The present invention is realized through the following technical solutions: In the first aspect, the present invention provides a preparation method of a SiC nanowire-reinforced high-entropy porous ceramic, including the following steps: 1) Dissolve TaCl 5 , NbCl 5 , TiCl 4 , ZrCl 4 , HfCl 4 and tetraethyl orthosilicate in ethanol to prepare a mixed alcohol solution; 2) React the mixed alcohol solution with a polyol at a preset temperature and a preset pressure to obtain a solid-phase product; 3) Dry the solid-phase product and then perform high-temperature carbonization to obtain a SiC nanowire-reinforced high-entropy porous ceramic.

[0008] Preferably, in step 1), the molar ratio of TaCl 5 , NbCl5, TiCl 4 , ZrCl 4 and HfCl 4 is 1:1:1:1:1.

[0009] Preferably, in step 1), TaCl 5 , NbCl 5 , TiCl 4, ZrCl 4 and HfCl 4 The ratio of the total molar amount of

[0010] Preferably, in step 2), the polyol is furfuryl alcohol.

[0011] Preferably, in step 2), TaCl 5 , NbCl 5 , TiCl 4 , ZrCl 4 and HfCl 4 The ratio of the total molar amount of

[0012] Preferably, in step 2), the preset temperature is 35 - 75 °C.

[0013] Preferably, in step 2), the preset pressure is 0.01 - 0.06 MPa.

[0014] Preferably, in step 3), the carbonization temperature is 1600 - 1900 °C, and the carbonization time is 2 - 4 h.

[0015] In a second aspect, the present invention provides an SiC nanowire - reinforced high - entropy porous ceramic obtained by the preparation method as described above.

[0016] In a third aspect, the present invention provides the application of the described SiC nanowire - reinforced high - entropy porous ceramic in the field of thermal protection.

[0017] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, using polyol as the carbon source, tetraethyl orthosilicate as the silicon source, TaCl 5 , NbCl 5 , TiCl 4 , ZrCl 4 , HfCl 4 as the metal source, reacting under heating and pressurization conditions, the polyol polycondensation exothermically releases gas, which has a pore - forming effect, so pores are generated inside the material. At the same time, tetraethyl orthosilicate reacts in situ with the polyol to grow SiC nanowires, forming an SiC nanowire - reinforced high - entropy porous ceramic. The introduction of SiC nanowires not only improves the compressive strength of the high - entropy porous ceramic, but also realizes the regulation of the hierarchical pore structure, effectively improves the compressive strength and heat conduction characteristics of the ultra - high - temperature porous material, realizes the integrated design of the structure and function of the high - entropy porous ceramic, and greatly simplifies the existing process flow for preparing SiC nanowire - reinforced high - entropy porous ceramics. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0019] Figure 1 is the XRD pattern of the SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramic material synthesized in Example 3 of the present invention; Figure 2 In (a) and (b) are SEM images of the SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramic material at different magnifications. Specific Embodiments

[0020] The following illustrates the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0021] It should be noted that the process equipment or devices not specifically specified in the following embodiments all adopt conventional equipment or devices in the art.

[0022] It should be noted that the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units does not necessarily have to be limited to those clearly listed steps or units, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or devices. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, rather than limiting the arrangement order of each method step or the scope in which the present invention can be implemented. The change or adjustment of their relative relationship, without substantial change in the technical content, should also be regarded as the scope in which the present invention can be implemented.

[0023] The present invention has developed a method for preparing SiC nanowire-reinforced high-entropy porous ceramics with a simple preparation process and in-situ growth of SiC nanowires.

[0024] Example 1 (1)Add TaCl 5 , NbCl 5 , TiCl 4 , ZrCl 4 and HfCl 4 to ethanol, then add tetraethyl orthosilicate, and stir and mix evenly at room temperature to prepare a mixed alcohol solution of metal salts and tetraethyl orthosilicate; among them, the molar ratio of TaCl 5 , NbCl 5 , TiCl 4 , ZrCl 4 and HfCl 4 is 1:1:1:1:1; the molar number of tetraethyl orthosilicate and the total molar number of TaCl 5 , NbCl 5 , TiCl 4 , ZrCl 4 and HfCl 4 is 1:2; (2)Take 24 mL of the mixed alcohol solution and 6 mL of furfuryl alcohol, add them to a reaction vessel, control the temperature in the reaction vessel at 35 °C, the pressure at 0.01 MPa, and the reaction time at 60 min to obtain a ceramic precursor; (3)Dry the ceramic precursor, then under the protection of Ar gas, heat it to 1600 °C at a rate of 2 °C / min and hold for 2 h, and cool it to room temperature with the furnace to obtain the SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramic material.

[0025] The porosity of the SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramic material prepared in this example is 46.22%, the compressive strength is 109.18 Mpa, and the room-temperature thermal conductivity is 0.36 W·m -1 K -1 .

[0026] Example 2 (1)Add TaCl 5 , NbCl 5 , TiCl 4 , ZrCl 4 and HfCl 4Add it to ethanol, then add tetraethyl orthosilicate, and stir and mix evenly at room temperature to prepare a mixed alcohol solution of metal salt and tetraethyl orthosilicate; among them, TaCl 5 、NbCl 5 、TiCl 4 、ZrCl 4 and HfCl 4 have a molar ratio of 1:1:1:1:1; the molar number of tetraethyl orthosilicate and TaCl 5 、NbCl 5 、TiCl 4 、ZrCl 4 and HfCl 4 has a ratio of 1:3 in terms of the total molar number; (2)Take 24 mL of the above-mentioned mixed alcohol solution and 6 mL of furfuryl alcohol, add them to a reaction vessel, control the temperature in the reaction vessel at 35 °C and the pressure at 0.03 MPa, and react for 50 min to obtain a ceramic precursor; (3)Dry the ceramic precursor, then under the protection of Ar gas, heat it to 1800 °C at a rate of 2 °C / min and keep it warm for 3 h, and cool it to room temperature with the furnace, then SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramic material is obtained.

[0027] The SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramic material prepared in this example has a porosity of 56.60%, a compressive strength of 126.16 MPa, and a room-temperature thermal conductivity of 0.25 W·m -1 K -1 .

[0028] Example 3 (1)Add TaCl 5 、NbCl 5 、TiCl 4 、ZrCl 4 and HfCl 4 to ethanol, then add tetraethyl orthosilicate, and stir and mix evenly at room temperature to prepare a mixed alcohol solution of metal salt and tetraethyl orthosilicate; among them, TaCl 5 、NbCl 5 、TiCl 4 、ZrCl 4 and HfCl4 The molar ratio is 1:1:1:1:1; the number of moles of tetraethyl orthosilicate and TaCl 5 , NbCl 5 , TiCl 4 , ZrCl 4 and HfCl 4 is in a proportion of 1:4 to the total number of moles; (2) Take 24 mL of the said mixed alcohol solution and 6 mL of furfuryl alcohol, add them into a reaction vessel, control the temperature in the reaction vessel at 35 °C, the pressure at 0.05 MPa, and the reaction time at 40 min to obtain a ceramic precursor; (3) Dry the ceramic precursor, then under the protection of Ar gas, heat it up to 1600 °C at a rate of 2 °C / min and hold for 4 h, and cool it down to room temperature with the furnace to obtain the SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramic material.

[0029] The SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramic material prepared in this example has a porosity of 50.24%, a compressive strength of 139.47 MPa, and a room-temperature thermal conductivity of 0.32 W·m -1 K -1 .

[0030] Example 4 (1) Add TaCl 5 , NbCl 5 , TiCl 4 , ZrCl 4 and HfCl 4 into ethanol, then add tetraethyl orthosilicate, and stir and mix evenly at room temperature to prepare a mixed alcohol solution of metal salts and tetraethyl orthosilicate; among them, the molar ratio of TaCl 5 , NbCl 5 , TiCl 4 , ZrCl 4 and HfCl 4 is 1:1:1:1:1; the number of moles of tetraethyl orthosilicate and TaCl 5 , NbCl 5 , TiCl 4 , ZrCl 4 and HfCl 4 is in a proportion of 1:5 to the total number of moles; (2) Take 24 mL of the mixed alcohol solution and 6 mL of furfuryl alcohol, add them into a reaction vessel, control the temperature in the reaction vessel at 55 °C, the pressure at 0.06 MPa, and the reaction time for 30 min to obtain a ceramic precursor; (3) Dry the ceramic precursor, and then under the protection of Ar gas, heat it to 1800 °C at a rate of 2 °C / min and hold for 4 h, and cool it to room temperature with the furnace to obtain SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramic material.

[0031] The porosity of the SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramic material prepared in this example is 62.76%, the compressive strength is 91.54 MPa, and the room-temperature thermal conductivity is 0.19 W·m -1 K -1 .

[0032] Example 5 (1) Add TaCl 5 , NbCl 5 , TiCl 4 , ZrCl 4 and HfCl 4 into ethanol, then add tetraethyl orthosilicate, and stir and mix evenly at room temperature to prepare a mixed alcohol solution of metal salts and tetraethyl orthosilicate; wherein, the molar ratio of TaCl 5 , NbCl 5 , TiCl 4 , ZrCl 4 and HfCl 4 is 1:1:1:1:1; the molar ratio of tetraethyl orthosilicate to the total molar amount of TaCl 5 , NbCl 5 , TiCl 4 , ZrCl 4 and HfCl 4 is 1:6; (2) Take 24 mL of the mixed alcohol solution and 6 mL of furfuryl alcohol, add them into a reaction vessel, control the temperature in the reaction vessel at 75 °C, the pressure at 0.03 MPa, and the reaction time for 20 min to obtain a ceramic precursor; (3) Dry the ceramic precursor, and then under the protection of Ar gas, heat it to 1600 °C at a rate of 2 °C / min and hold for 3 h, and then cool it to room temperature in the furnace to obtain the SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramic material.

[0033] The SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramic material prepared in this example has a porosity of 56.03%, a compressive strength of 99.97 MPa, and a room-temperature thermal conductivity of 0.28 W·m -1 K -1 .

[0034] Example 6 (1) Add TaCl 5 , NbCl 5 , TiCl 4 , ZrCl 4 and HfCl 4 to ethanol, and then add tetraethyl orthosilicate, and stir and mix evenly at room temperature to prepare a mixed alcohol solution of metal salts and tetraethyl orthosilicate; among them, the molar ratio of TaCl 5 , NbCl 5 , TiCl 4 , ZrCl 4 and HfCl 4 is 1:1:1:1:1; (2) Take 24 mL of the mixed alcohol solution and 6 mL of furfuryl alcohol, add them to a reaction vessel, control the temperature in the reaction vessel at 75 °C, the pressure at 0.06 MPa, and the reaction time at 10 min to obtain a ceramic precursor; (3) Dry the ceramic precursor, and then under the protection of Ar gas, heat it to 1800 °C at a rate of 2 °C / min and hold for 4 h, and then cool it to room temperature in the furnace to obtain the SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramic material.

[0035] The SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr0.2 Hf 0.2 ) The porosity of the SiC nanowire-reinforced (Ta -1 K -1 .

[0036] Comparative Example 1 It is basically the same as Example 3, except that tetraethyl orthosilicate is omitted.

[0037] The porosity of the high-entropy porous ceramic material obtained in this comparative example is 40.58%, and the compressive strength is 90.25 MPa.

[0038] The SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C ultra-high temperature porous ceramic material has a porosity of 46.22 - 62.76%, a compressive strength of 91.52 - 139.47 MPa, and a room temperature thermal conductivity of 0.19 - 0.36 W·m -1 K -1 .

[0039] Figure 1 is the XRD pattern of the SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramic material synthesized in Example 3. This pattern shows that the synthesized SiC nanowire-reinforced high-entropy porous ceramic material is composed of (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C phase and SiC phase, and has good crystallinity. Therefore, it is proved that the SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramic prepared by the method of the present invention has a high purity.

[0040] Figure 2 is the SEM image of the SiC nanowire-reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramic material synthesized in Example 3. Through Figure 2In (a), a porous structure was observed inside the material, indicating that the method of the present invention successfully prepared porous ceramics. A large number of SiC nanowires are distributed in the porous ceramics, and its pore size distribution presents a multi-level structure, laying a good structural foundation for subsequent thermal protection applications. By Figure 2 In (b), it was observed that SiC nanowires grew in-situ inside the material, and the SiC nanowires showed a uniform and network-like structure distribution, realizing the successful preparation of SiC nanowire reinforced (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramics.

[0041] By comparing Example 3 and Comparative Example 1, it can be seen that, compared with Comparative Example 1, the introduction of SiC nanowires in Example 3 significantly improved the compressive strength of the high-entropy porous ceramics.

[0042] The ultra-high temperature porous ceramics prepared by the present invention have at least the following advantages: The present invention realizes the in-situ growth of SiC nanowires in (Ta 0.2 Nb 0.2 Ti 0.2 Zr 0.2 Hf 0.2 )C high-entropy porous ceramics, which not only improves the compressive strength of the porous ceramics, but also realizes the regulation of the multi-level pore structure. In addition, selecting polyol as the carbon source reagent not only provides the carbon source required for the reaction, but also utilizes its spontaneous polycondensation characteristics in the precursor solution, eliminating the need to add a foaming agent separately, greatly simplifying the preparation process, saving time costs, having high repeatability, easily available raw materials, and low process costs. It is suitable for large-scale industrial production and is expected to realize the near-net shaping of complex-shaped parts in aerospace, playing a key role in the expanded application of ultra-high temperature porous ceramic materials in the field of aerospace thermal protection.

[0043] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing SiC nanowire-enhanced high-entropy porous ceramics, characterized in that: The following steps are involved: 1) Dissolve TaCl5, NbCl5, TiCl4, ZrCl4, HfCl4 and ethyl orthosilicate in ethanol to prepare a mixed alcohol solution; 2) reacting the mixed alcohol solution with the polyol at a preset temperature and a preset pressure to obtain a solid phase product; 3) The solid phase product is dried and then carbonized at high temperature to obtain SiC nanowire-reinforced high-entropy porous ceramics.

2. The method for preparing SiC nanowire-enhanced high-entropy porous ceramics according to claim 1, characterized in that: In step 1), the molar ratio of TaCl5, NbCl5, TiCl4, ZrCl4 and HfCl4 is 1:1:1:1:

1.

3. The method for preparing SiC nanowire-enhanced high-entropy porous ceramics according to claim 1, characterized in that: In step 1), the ratio of the total molar number of TaCl5, NbCl5, TiCl4, ZrCl4 and HfCl4 to the molar number of tetraethyl orthosilicate is (2-6):

1.

4. The method for preparing SiC nanowire-enhanced high-entropy porous ceramics according to claim 1, characterized in that: In step 2), the polyol is furfuryl alcohol.

5. The method for preparing SiC nanowire-enhanced high-entropy porous ceramics according to claim 1, characterized in that: In step 2), the ratio of the total mole number of TaCl5, NbCl5, TiCl4, ZrCl4 and HfCl4 to the mole number of the polyol is (1-5):

1.

6. The method for preparing SiC nanowire-enhanced high-entropy porous ceramics according to claim 1, characterized in that: In step 2), the preset temperature is 35-75°C.

7. The method for preparing SiC nanowire-enhanced high-entropy porous ceramics according to claim 1, characterized in that: In step 2), the preset pressure is 0.01-0.06 MPa.

8. The method for preparing SiC nanowire-enhanced high-entropy porous ceramics according to claim 1, characterized in that: In step 3), the carbonization temperature is 1600~1900 °C and the carbonization time is 2~4 h.

9. SiC nanowire-reinforced high-entropy porous ceramics obtained by the preparation method according to any one of claims 1 to 8.

10. Application of the SiC nanowire-enhanced high-entropy porous ceramics according to claim 9 in the field of thermal protection.

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