A wide-frequency wave-absorbing material for 25-1300 DEG C and a preparation method thereof

Abstract

The application discloses a wide-frequency wave-absorbing material for 25-1300 DEG C and a preparation method thereof, and relates to the technical field of wave-absorbing materials.The wave-absorbing material comprises silicon carbide nanowires which are connected with each other to form a material with a three-dimensional structure; and the surface of the silicon carbide nanowires is coated with an Al4SiC4 ternary compound.The Al4SiC4 is coated on the SiC NWs The electromagnetic parameters and conductivity of the material are improved, the electric conduction loss of the material is improved, and the special structure network of the material increases the electromagnetic wave transmission path, so that the wave-absorbing performance of the material is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wave-absorbing materials, and particularly relates to a wide-band wave-absorbing material for 25 DEG C to 1300 DEG C and a preparation method thereof. BACKGROUND

[0002] Wave-absorbing materials are used to dissipate the energy of incident electromagnetic waves in the form of Joule heat, so as to achieve the purpose of stealth. Meanwhile, people are committed to developing light weight, small thickness, high strength, low cost, strong and wide-band stealth materials. Porous silicon carbide structure has open porosity, low density, low thermal conductivity, high temperature resistance and excellent chemical inertness, and has great attraction in applications such as thermal insulators, filters, catalyst carriers and absorbers. If the microstructure and dielectric constant can be adjusted to have excellent wave-absorbing performance, it is very promising.

[0003] Replica template technology is one of the most commonly used methods for manufacturing porous silicon carbide. A porous template is immersed in a preceramic slurry, and then dried and pyrolyzed. During the high-temperature pyrolysis process, the template will be extracted by burning or decomposing, leaving a three-dimensional open structure template that imitates the original template. Polymeric sponges such as melamine foam (MF) have the advantages of high permeability, light weight, super elasticity and low cost, and are usually selected as templates.

[0004] Silicon carbide aluminum (Al4SiC4) is a very promising high-temperature ceramic and additive, which has attracted widespread attention due to its low density, high melting point and high oxidation resistance. However, synthesis of Al4SiC4 usually requires high temperature and long reaction time, which limits the synthesis and application of Al4SiC4. The use of sintering additives can reduce the sintering temperature. In recent years, yttrium carbide (Y3Si2C2) has been successfully used as a sintering additive for silicon carbide, and is predicted to be a very promising interphase material for SiC composite materials.

[0005] The prior art discloses a composite electromagnetic wave absorbing foam prepared from ZIF-67 / melamine, which is prepared from three-dimensional network melamine foam and dodecahedron metal organic framework material ZIF-67. The prepared composite electromagnetic wave absorbing foam has a three-dimensional network structure, the three-dimensional carbon-based skeleton generated by high-temperature burning improves the conductivity of the composite foam, enhances the multiple scattering ability of electromagnetic waves in the composite foam, and the magnetic material derived from ZIF-67 introduces a magnetic loss mechanism, thereby synergistically enhancing the absorbing ability of the composite foam to electromagnetic waves. However, the high-temperature absorbing performance of the composite foam still has certain limitations, and the magnetic material cannot be used above the Curie temperature point. The prior art also discloses a preparation method of a multifunctional melamine flexible composite wave absorbing foam, and the prepared melamine composite wave absorbing foam has the advantages of high stability, light weight, high flexibility, good heat insulation, good and adjustable wave absorbing performance. However, the melamine composite wave absorbing foam cannot be used at high temperatures, and has certain limitations. SUMMARY

[0006] In view of the deficiencies in the above background art, the technical problem to be solved by the present application is to provide a lightweight, high reflection loss, wide absorption band wave absorbing material, which also has the characteristics of high temperature resistance, oxidation resistance and stable wave absorbing performance at high temperatures, so as to meet the use requirements of key parts of some weapons and equipment in high temperature environments. The present application provides a wideband wave absorbing material for 25℃-1300℃ and a preparation method thereof. The wave absorbing material is prepared by coating Al4SiC4 on SiC NWs The electromagnetic parameters and conductivity of the material are improved, the electrical conductivity loss of the material is improved, and the special structure network of the material increases the electromagnetic wave transmission path, thereby improving the wave absorbing performance of the material.

[0007] The first object of the present application is to provide a wideband wave absorbing material for 25℃-1300℃, which comprises silicon carbide nanowires connected to each other to form a material with a three-dimensional structure.

[0008] The surface of the silicon carbide nanowires is coated with an Al4SiC4 ternary compound.

[0009] Preferably, the diameter of the silicon carbide nanowires is between 100-150 nm.

[0010] Preferably, the thickness of the Al4SiC4 ternary compound coating is between 5-20 nm.

[0011] Preferably, the mass ratio of the Al4SiC4 ternary compound to the silicon carbide nanowires is 1:100-200.

[0012] Preferably, the use temperature of the wave absorbing material in an air environment is between 25℃ and 1300℃, and the minimum absorption bandwidth is more than 6 GHz.

[0013] The second object of the present application is to provide a preparation method of a wide-frequency wave-absorbing material for 25-1300 DEG C, comprising the following steps:

[0014] The mixed slurry of the carbon-silicon precursor is prepared by using a silicon source, a carbon source and aluminum powder as raw materials and an ethanol solution as a solvent;

[0015] The precursor material is obtained by immersing the mixed slurry into a template in a vacuum environment, vacuum degassing, removing excess slurry and drying after vacuum degassing.

[0016] The wide-frequency wave-absorbing material for 25-1300 DEG C is prepared by the molten salt method.

[0017] Preferably, the mass ratio of the silicon source, the carbon source and the aluminum powder is (25-29):(65-69):(1-5); the silicon source is tetraethyl orthosilicate; the carbon source is a white sugar solution, an icing sugar solution or a glucose solution; and the particle size of the aluminum powder is less than or equal to 5 microns.

[0018] Preferably, in the preparation process of the precursor material by the molten salt method, the molten salt and a sintering aid are uniformly mixed, and then the precursor material is buried in the mixture, and then the mixture is treated at 1450-1600 DEG C for 2-4 hours in an inert atmosphere, and then treated at 600-800 DEG C for 2-4 hours, thereby obtaining the wide-frequency wave-absorbing material for 25-1300 DEG C.

[0019] Preferably, the sintering aid is yttrium silicon carbide, yttrium oxide or yttrium powder; and the content of the sintering aid is 3-5 wt%.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] The present application provides a wide-frequency wave-absorbing material for 25-1300 DEG C, a preparation method and application thereof. NWs The wave-absorbing material is mainly composed of Al4SiC4 / SiC NWs ) nanowires coated with Al4SiC4 ternary compounds, which are connected to form a material with a three-dimensional (3D) structure. NWsThe electromagnetic parameters and conductivity of the material are improved, when the electromagnetic wave enters, the Al4SiC4 on the surface can improve the electric conduction loss and polarization loss of the material, meanwhile, the special structure network of the material increases the electromagnetic wave reflection times and current transmission path, further improves the electric conduction loss of the material, so that the wave absorbing performance of the material is improved. DETAILED DESCRIPTION

[0022] In order to make the skilled in the art better understand the technical scheme of the present application can be implemented, the following specific embodiments of the present application is further described, but the examples are not as a limitation of the present application.

[0023] The first aspect of the present application provides a wide frequency wave absorbing material for 25℃-1300℃, the wave absorbing material comprises silicon carbide nanowires (SiC NWs ) are connected to each other to form a material with three-dimensional structure; the surface of the silicon carbide nanowires is coated with Al4SiC4 ternary compound.

[0024] The wave absorbing material provided by the present application mainly comprises Al4SiC4 / SiC NWs ; mainly using melamine foam as a template, sugar solution as a carbon source, tetraethyl orthosilicate solution as a silicon source and aluminum powder (Al) to prepare by molten salt method at high temperature; the sugar solution is preferably white granulated sugar, granulated sugar or glucose solution, and the particle size of Al powder is less than 5μm. The wave absorbing material is a material with three-dimensional (3D) structure formed by silicon carbide nanowires (SiC NWs ) connected to each other with Al4SiC4 ternary compound coated on the surface. The Al4SiC4 is coated on the SiC NWs The electromagnetic parameters and conductivity of the material are improved, when the electromagnetic wave enters, the Al4SiC4 on the surface can improve the electric conduction loss and polarization loss of the material, meanwhile, the special structure network of the material increases the electromagnetic wave reflection times and current transmission path, further improves the electric conduction loss of the material, so that the wave absorbing performance of the material is improved.

[0025] The diameter of the silicon carbide nanowires is 100-150nm. The thickness of the Al4SiC4 ternary compound coating is 5-20nm. The mass ratio of the Al4SiC4 ternary compound to the silicon carbide nanowires is 1:100-200.

[0026] The use temperature of the wave absorbing material in air environment is 25℃-1300℃, and the effective absorption bandwidth (≤-10dB) can be up to more than 6GHz.

[0027] The second aspect of the present application provides a preparation method of a wide frequency wave absorbing material for 25℃-1300℃, comprising the following steps:

[0028] A mixed slurry of carbon-silicon precursor is prepared by using silicon source, carbon source and aluminum powder as raw materials and ethanol solution as solvent.

[0029] The precursor material is prepared by a molten salt method to obtain a wide-frequency wave-absorbing material for 25℃-1300℃.

[0030] The precursor material is prepared by a molten salt method to obtain a wide-frequency wave-absorbing material for 25℃-1300℃.

[0031] The mass ratio of the silicon source, the carbon source and the aluminum powder is (25-29):(65-69):(1-5).

[0032] The silicon source is tetraethyl orthosilicate, the carbon source is white sugar solution, sugar solution or glucose solution, and the particle size of the aluminum powder is ≤5μm.

[0033] Specifically, in the preparation process of the precursor material by the molten salt method, the molten salt and the sintering aid are mixed uniformly, and then the precursor material is buried, and then the wide-frequency wave-absorbing material for 25℃-1300℃ is obtained by treating at 1450-1600℃ for 2-4h and then treating at 600-800℃ for 2-4h in an inert atmosphere.

[0034] The sintering aid is yttrium silicon carbide (Y3Si2C), yttrium oxide (Y2O3) or yttrium (Y), and the content of the sintering aid is 3-5wt%.

[0035] In an embodiment, a wide-frequency wave-absorbing material for 25℃-1300℃ is prepared by the steps of proportioning, impregnating, drying, sintering and decarburizing, and specifically includes the following steps:

[0036] In step one, three solutions of tetraethyl orthosilicate, ethanol and H2O are mixed in a volume ratio of 2:2:1, hydrochloric acid is used as a pH adjuster to adjust the pH value of the solution to about 3, and then the solution is magnetically stirred for 24 hours; then, a sugar solution containing 10wt% is added in a volume ratio of 1:1 to form a mixed solution containing a carbon-silicon precursor, and then 1-5wt% Al powder is added, and the mixed solution is magnetically stirred for 24 hours to obtain a premixed slurry;

[0037] In step two, the premixed slurry containing the carbon solution, the silicon solution and the Al powder is immersed into a melamine foam template in a vacuum environment, vacuum degassing is performed for 1-3h to make the slurry completely fill the pores, and then the excess slurry is removed after immersion, and the slurry is dried in an oven at 100℃ for 12-24h.

[0038] Step three, when sintering, the dried sample is put into a crucible, the molten salt and the sintering aid are mixed first, then the sample is buried, and then put into an atmosphere furnace; the sample is first heated to 700℃ at a temperature of 1℃ / min, then heated to 1500℃ at a temperature of 5℃ / min, and kept for 2-4 hours in an argon atmosphere; finally, heated in air at a temperature of 600-800℃ for 2-4 hours, so as to obtain a wide-frequency wave-absorbing material for 25℃-1300℃. In the synthesis process, yttrium silicon carbon (Y3Si2C), yttrium oxide (Y2O3) or yttrium (Y) powder is added as a sintering aid, and the content is 3-5wt%.

[0039] It should be noted that the experimental methods used in the present application are conventional methods unless otherwise specified; the reagents and materials used are commercially available unless otherwise specified.

[0040] Example 1

[0041] A preparation method of a wide-frequency wave-absorbing material for 25℃-1300℃, comprising the following steps:

[0042] Step one, three solutions are mixed according to the volume ratio of tetraethyl orthosilicate: ethanol: H2O = 2:2:1, hydrochloric acid is used as a pH adjuster, the pH value of the solution is adjusted to about 3, and magnetic stirring is performed for 24 hours; then, a 10wt% sugar solution is added according to a volume ratio of 1:1 to form a mixed solution containing a carbon-silicon precursor, and then 1wt% Al powder is added, and magnetic stirring is performed for 24 hours, so as to obtain a premixed slurry;

[0043] Step two, the premixed slurry containing the carbon solution, the silicon solution and the Al powder is immersed into melamine foam as a template in a vacuum environment, vacuum degassing is performed for 1.5h, so that the slurry is completely filled into the pores; after immersion, the excess slurry is removed by compression, and drying is performed in an oven at 100℃ for 15h;

[0044] Step three, when sintering, the dried sample is put into a crucible, the molten salt and the sintering aid are mixed first, then the sample is buried, and then put into an atmosphere furnace; the sample is first heated to 700℃ at a temperature of 1℃ / min, then heated to 1500℃ at a temperature of 5℃ / min, and kept for 2 hours in an argon atmosphere; finally, heated in air at a temperature of 650℃ for 2 hours, so as to obtain a wide-frequency wave-absorbing material for 25℃-1300℃. In the synthesis process, yttrium (Y) powder is added as a sintering aid, and the content is 3wt%.

[0045] Example 2

[0046] A preparation method of a wide-frequency wave-absorbing material for 25℃-1300℃, comprising the following steps:

[0047] Step one, mix the three solutions according to the volume ratio of tetraethyl orthosilicate: ethanol: H2O = 2:2:1, use hydrochloric acid as a pH regulator to adjust the pH value of the solution to about 3, and then magnetically stir for 24 hours. Then, add a 10wt% sugar solution to form a mixed solution containing carbon-silicon precursors, and then add 5wt% Al powder. After magnetic stirring for 24 hours, a premixed slurry is obtained.

[0048] Step two, immerse the premixed slurry containing carbon solution, silicon solution and Al powder into the melamine foam template in a vacuum environment, vacuum degassing for 1h to completely fill the pores with the slurry. After immersion, remove the excess slurry by compression, and dry in an oven at 100℃ for 12h.

[0049] Step three, during sintering, place the dried sample in a crucible, mix the molten salt and sintering aid uniformly, then bury the sample, and place it in an atmosphere furnace. First, heat the sample to 700℃ at a temperature of 1℃ / min, then increase the temperature to 1500℃ at a rate of 5℃ / min, and keep it in an argon atmosphere for 4 hours. Finally, heat treat it in air at a temperature of 600℃ for 4 hours to obtain a wide-frequency wave-absorbing material for 25℃-1300℃. During synthesis, yttrium silicon carbon (Y3Si2C) is added as a sintering aid, with a content of 5wt%.

[0050] Example 3

[0051] A method for preparing a wide-frequency wave-absorbing material for 25℃-1300℃, comprising the following steps:

[0052] Step one, mix the three solutions according to the volume ratio of tetraethyl orthosilicate: ethanol: H2O = 2:2:1, use hydrochloric acid as a pH regulator to adjust the pH value of the solution to about 3, and then magnetically stir for 24 hours. Then, add a 10wt% sugar solution to form a mixed solution containing carbon-silicon precursors, and then add 5wt% Al powder. After magnetic stirring for 24 hours, a premixed slurry is obtained.

[0053] Step two, immerse the premixed slurry containing carbon solution, silicon solution and Al powder into the melamine foam template in a vacuum environment, vacuum degassing for 1h to completely fill the pores with the slurry. After immersion, remove the excess slurry by compression, and dry in an oven at 100℃ for 12h.

[0054] Step three, during sintering, the dried sample is put into a crucible, the molten salt and sintering aid are mixed first, then the sample is buried, and then put into an atmosphere furnace; the sample is first heated to 700℃ at a temperature of 1℃ / min, then heated to 1500℃ at a temperature of 5℃ / min, and kept for 2-4 hours in an argon atmosphere; finally, heated in air at a temperature of 600℃ for 2 hours, and a wide frequency wave absorbing material for 25℃-1300℃ is obtained. In the synthesis process, yttrium oxide (Y2O3) is added as a sintering aid, and the content is 4wt%.

[0055] In order to illustrate the related properties of the wave absorbing material provided by the present application, only the wave absorbing performance of the wave absorbing material provided by Example 1 is tested.

[0056] Table 1 is the wave absorbing performance of the wave absorbing material provided by Example 1 at different temperatures

[0057] Example Test temperature (°C) Effective bandwidth (≤ -10 dB) Minimum loss (-dB) Thickness (mm) 1 Room temperature 6.8 36 4.0 1 500 7.1 42 4.0 1 800 7.6 45 4.0 1 1000 6.4 37 4.0 1 1300 6.1 33 4.0

[0058] As can be seen from Table 1, the wave absorbing material prepared by the above steps has a minimum absorption bandwidth of more than 6GHz at a thickness of 4.0mm after testing at different temperatures, and the reflection loss is generally greater than 30dB. Even at a temperature of 1300℃, it can still maintain excellent wave absorbing performance.

[0059] The present application describes preferred embodiments and their effects. However, once the basic creative concept is known to those skilled in the art, additional changes and modifications can be made to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0060] Although embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A wide frequency wave absorbing material for 25℃-1300℃, characterized in that, The wave-absorbing material comprises silicon carbide nanowires which are connected to each other to form a material with a three-dimensional structure; The silicon carbide nanowires are coated with an Al4SiC4 ternary compound; The diameter of the silicon carbide nanowires is 100-150 nm; The thickness of the Al4SiC4 ternary compound coating is 5-20 nm; The mass ratio of the Al4SiC4 ternary compound to the silicon carbide nanowires is 1:100-200; The wide-frequency wave-absorbing material for 25-1300 DEG C is prepared according to the following steps: A mixed slurry of a carbon-silicon precursor is prepared by using a silicon source, a carbon source and aluminum powder as raw materials and an ethanol solution as a solvent; The mixed slurry is immersed into a melamine foam template in a vacuum environment, vacuum degassed, and then dried after removing the excess slurry to obtain a precursor material; The precursor material is prepared into the wide-frequency wave-absorbing material for 25-1300 DEG C by a molten salt method; During the preparation of the precursor material by the molten salt method, the following steps are included: the molten salt and a sintering aid are uniformly mixed, then the precursor material is buried, and then the material is treated at 1450-1600 DEG C for 2-4 h in an inert atmosphere, and then treated at 600-800 DEG C for 2-4 h to obtain the wide-frequency wave-absorbing material for 25-1300 DEG C. 2.The wide-frequency wave-absorbing material for 25 ℃-1300 ℃ of claim 1, wherein, The wave-absorbing material has a use temperature of 25-1300 DEG C in an air environment, and the minimum absorption frequency width is more than 6 GHz.

3. The preparation method of the wide-frequency wave-absorbing material for 25℃-1300℃ according to claim 1 or 2, characterized in that, The following steps are included: A mixed slurry of a carbon-silicon precursor is prepared by using a silicon source, a carbon source and aluminum powder as raw materials and an ethanol solution as a solvent; The mixed slurry is immersed into a melamine foam template in a vacuum environment, vacuum degassed, and then dried after removing the excess slurry to obtain a precursor material; The precursor material is prepared into the wide-frequency wave-absorbing material for 25-1300 DEG C by a molten salt method; During the preparation of the precursor material by the molten salt method, the following steps are included: the molten salt and a sintering aid are uniformly mixed, then the precursor material is buried, and then the material is treated at 1450-1600 DEG C for 2-4 h in an inert atmosphere, and then treated at 600-800 DEG C for 2-4 h to obtain the wide-frequency wave-absorbing material for 25-1300 DEG C. 4.The method for preparing a wide-frequency wave-absorbing material for 25 ℃-1300 ℃ according to claim 3, characterized in that, The mass ratio of the silicon source, the carbon source and the aluminum powder is (25-29):(65-69):(1-5); The silicon source is tetraethyl orthosilicate; the carbon source is a white granulated sugar solution, a granulated sugar solution or a glucose solution; and the particle size of the aluminum powder is ≤5 μm. 5.The method for preparing a wide-frequency wave-absorbing material for 25 ℃-1300 ℃ according to claim 3, characterized in that, The sintering aid is yttrium silicon carbide, yttrium oxide or yttrium powder; and the content of the sintering aid is 3-5 wt%.