Semiconductor heterojunction silicon carbide nanofiber aerogel with stable high-temperature wave absorption

Abstract

The invention relates to semiconductor heterojunction silicon carbide nanofiber aerogel with stable high-temperature wave absorption, and belongs to the technical field of aerogel materials.SiC aerogel grown through a chemical vapor infiltration (CVI) method serves as a high-temperature-resistant matrix structure material, tin segregation and two-section temperature complete decomposition and oxidation of a Ti2SnC material are utilized, and high-temperature wave absorption stability is achieved; two kinds of N-type semiconductor TiO2 / SnO2 nano mixed particles are obtained and anchored on the surface of SiC / SiO2 nano fibers in situ, the semiconductor heterojunction silicon carbide nano fiber aerogel is obtained, and the semiconductor heterojunction silicon carbide nano fiber aerogel not only has excellent flexibility, compression cycle performance and heat insulation performance, but also has the advantages of high temperature resistance, high temperature resistance and the like. The material also has excellent broadband electromagnetic wave absorption performance at high temperature and multi-spectrum compatibility of infrared stealth, realizes stable wave absorption performance and durable and repeatable high-temperature application in practical application, and has wide application prospects in development of high-temperature wave absorption materials.

Description

Technical Field

[0001] The invention relates to the technical field of aerogel materials, and in particular to a semiconductor heterojunction silicon carbide nanofiber aerogel with high-temperature wave absorption stability. Background Art

[0002] The current research and application of high temperature absorbing materials is to maintain reliable radar stealth level of weapons and equipment under extremely harsh combat conditions;

[0003] The wave absorption performance is improved by changing the microstructure of SiC aerogel. For example, layered aerogel is prepared by in-situ growth of SiC nanowire arrays, and binary porous SiC aerogel is prepared in SiC whisker pressed samples.

[0004] Ti commonly used in MAX phase ceramic materials 3 AlC 2 and Ti 3 SiC 2 , in high temperature environment, a protective characteristic oxide film Al will be formed 2 O 3 or SiO 2 , which prevents the contact oxidation reaction between oxygen and the internal MAX phase. The degree of reaction is difficult to accurately control, resulting in unstable high-temperature absorbing performance.

[0005] In the research on developing flexible absorbing aerogel materials using intrinsically high temperature resistant silicon carbide nanofibers, two research ideas are mainly used to enhance the loss mechanism and improve the absorbing performance. One is to regulate the microstructure of SiC aerogel, and the other is to combine SiC aerogel with other absorbers. Therefore, the research strategy of combining other effective absorbers in aerogel structural materials with extremely large porosity and specific surface area and using them to provide different synergistic effects to improve material performance is very promising.

[0006] In order to achieve the requirements of high-temperature and high-performance wave absorption, the first thing to consider is to select suitable high-temperature resistant and effectively enhanced performance fillers from a large number of complex wave absorbing fillers. In addition, the loading state of the filler in the nanofiber aerogel needs to be improved to solve the simple solid-solid contact problem.

[0007] The MAX phase material of the new ceramic compound is used in the development of new high-temperature absorbing materials due to its advantages such as good electrical and thermal conductivity, high melting point, high-temperature oxidation resistance and thermal stability. When the common Ti3AlC2 and Ti3SiC2 are used as absorbers, the higher conductivity will cause interface reflection and affect the electromagnetic wave absorption performance. On the other hand, at high temperatures, Al or Si elements form a protective oxide film Al2O3 or SiO2, which prevents further oxidation of oxygen and the internal MAX phase. The degree of reaction is difficult to accurately control, resulting in instability in high-temperature absorbing performance.

[0008] Ti2SnC is rarely studied compared to other MAX phase compounds, especially due to the segregation of the Sn element itself, which produces spontaneously grown whiskers, causing reliability risks in the application of electronic components. Researchers have studied the segregation and oxidation mechanism of Ti2SnC, but there is still a lack of reasonable use. In particular, semiconductor TiO2 and SnO2 have shown complex and fascinating charge transfer mechanisms in the fields of photocatalysis, electrochemistry, and wave absorption. Summary of the invention

[0009] In view of the above problems, the present invention provides a semiconductor heterojunction silicon carbide nanofiber aerogel with high temperature absorption stability, wherein SiC aerogel grown by chemical vapor infiltration (CVI) is used as a high temperature resistant matrix structural material, and Ti 2 The SnC material is completely decomposed and oxidized by tin segregation and two-stage temperature, and the two N-type semiconductor TiO 2 / SnO 2 The nano-hybrid particles are in situ anchored in the SiC / SiO 2 The semiconductor heterojunction silicon carbide nanofiber aerogel is obtained on the surface of the nanofiber. The semiconductor heterojunction silicon carbide nanofiber aerogel not only has excellent flexibility, compression cycle performance, and thermal insulation performance, but also has excellent broadband electromagnetic wave absorption performance at high temperature and multi-spectrum compatibility of infrared stealth, and in actual applications, it realizes stable absorbing performance and durable and repeatable high-temperature application, and has broad application prospects in the development of high-temperature absorbing materials.

[0010] The present invention provides a method for preparing a semiconductor heterojunction silicon carbide nanofiber aerogel with high temperature wave absorption stability, comprising:

[0011] Step 1, preparing a silicone xerogel;

[0012] Preferably, the specific steps of preparing the silicone xerogel in step 1 include:

[0013] Methyltrimethoxysilane, dimethyldimethoxysilane, a hydrolyzing agent and a catalyst are mixed, cross-linked and dried to obtain a silicone xerogel;

[0014] Furthermore, the mass ratio of the methyltrimethoxysilane, dimethyldimethoxysilane, hydrolyzing agent and catalyst is: 4:1:2:0.77;

[0015] Furthermore, the cross-linking treatment time is: 2-3h;

[0016] Furthermore, the cross-linking treatment time is: 2h;

[0017] Furthermore, the hydrolyzing agent is deionized water; the catalyst is concentrated nitric acid;

[0018] Furthermore, the specific steps of obtaining the silicone xerogel in step 1 include:

[0019] Pour anhydrous ethanol into a container as a mixture solvent, and then pour methyltrimethoxysilane MTMS and dimethyldimethoxysilane DMDMS in sequence; after mixing and stirring for 5-6 minutes, slowly add deionized water for hydrolysis, and drop concentrated nitric acid, and continue stirring for 2 hours.

[0020] Step 2, selecting a foam material for carbonization to obtain pure carbon aerogel foam;

[0021] Preferably, the foam material in step 2 is melamine foam; the size of the melamine foam is selected according to the processing container; the processing container is a tube furnace or a high-temperature box furnace;

[0022] Preferably, the specific steps of obtaining pure carbon aerogel foam in step 2 include:

[0023] The foam material is placed in a tubular furnace, heated and kept warm in an argon atmosphere to undergo a full carbonization reaction to obtain pure carbon aerogel foam;

[0024] Furthermore, the argon gas flow rate is 10-20 mL / min;

[0025] The insulation time is 120-150 minutes.

[0026] Furthermore, the argon gas flow rate is 20 mL / min;

[0027] The insulation time is 120 minutes.

[0028] Step 3, placing the pure carbon aerogel foam on top of the silica xerogel and heating it to obtain silicon carbide SiC nanofibers;

[0029] Preferably, the specific steps of obtaining silicon carbide SiC nanofibers in step 3 include:

[0030] The pure carbon aerogel foam is placed on top of the silica xerogel and then placed together in a crucible of a tubular furnace and heated to obtain silicon carbide SiC nanofibers;

[0031] Further, the ratio of the heating temperature in step 2 to the heating temperature in step 3 is: 6-7:14-15;

[0032] Furthermore, the heating rate in step 2 is 4-6°C / min; the heating temperature is 600-700°C;

[0033] The heating temperature in step 3 is 1400-1500°C, and the heating rate is 3-6°C / min;

[0034] Exemplarily, the heating temperature is 600° C.; the heating rate is 4° C. / min;

[0035] Furthermore, the specific steps of obtaining the silicon carbide SiC nanofibers in step 3 include:

[0036] The pure carbon aerogel foam is placed on top of the silica xerogel and then placed together in a crucible of a tubular furnace and heated to 1450°C to obtain silicon carbide SiC nanofibers.

[0037] The heating rate is 5°C / min;

[0038] In the present invention, placing the pure carbon aerogel foam above the silicon oxide dry gel is conducive to the full entry of gas, and the reactant SiO and CO gases flow in from the bottom of the pure carbon aerogel to perform a chemical vapor infiltration reaction.

[0039] In the technical solution of the present invention, pure carbon aerogel foam is placed on top of silica dry gel and then heated to obtain silicon carbide SiC nanofibers, and SiC nanofiber aerogel is grown on the surface of the pure carbon aerogel foam by chemical vapor infiltration (CVI) method, wherein the silica dry gel decomposes at high temperature to generate SiO and CO high-temperature gases, which reach the surface of the carbon skeleton and combine with active graphite C to generate SiC nanocrystal nuclei. With the continuous supply of SiO and CO gases, the crystal nuclei further grow into SiC nanofibers, and continue to accumulate and become longer.

[0040] Step 4: MAX phase tin carbide Ti 2 SnC powder was added to ethanol solution and ultrasonically treated to obtain tin carbide Ti 2 SnC dispersion;

[0041] Preferably, the MAX phase tin titanium carbide Ti 2 The mass ratio of SnC powder to ethanol solution is 0.1-0.3wt%;

[0042] The ultrasonic treatment time is 30-60 min.

[0043] Furthermore, the MAX phase tin titanium carbide Ti 2 The mass ratio of SnC to ethanol solution is 0.1wt%;

[0044] The ultrasonic treatment time is 30 min.

[0045] Step 5: Add tin titanium carbide Ti to silicon carbide SiC nanofibers 2 SnC dispersion to obtain a flexible composite aerogel;

[0046] Preferably, the specific steps described in step 5 include:

[0047] Place the SiC nanofibers in a watch glass and use a dropper to absorb the tin titanium carbide Ti 2 SnC dispersion is added repeatedly to the upper and lower surfaces of silicon carbide SiC nanofibers until the tin carbide titanium Ti 2 The SnC dispersion completely covers the silicon carbide SiC nanofibers to obtain a flexible composite aerogel; further, the MAX phase tin titanium carbide Ti in the flexible composite aerogel 2 The mass ratio of SnC to silicon carbide SiC nanofiber aerogel is 3:10;

[0048] Furthermore, the mass of the SiC nanofiber is 20-30 mg; the tin titanium carbide Ti 2 The amount of SnC dispersion used is 2-6 mL;

[0049] Furthermore, the mass of the SiC nanofiber aerogel is 20 mg; the tin titanium carbide Ti 2 2 mL of SnC dispersion;

[0050] In the technical solution of the present invention, a dropper is used to absorb the dispersion liquid, and the dispersion liquid is dripped on the upper and lower surfaces of the silicon carbide SiC nanofibers for multiple times, so that the dispersion liquid is absorbed into the aerogel through capillary phenomenon, thereby ensuring uniform absorption. 2 The mass ratio of SnC to SiC nanofiber aerogel is 3:10, which absorbs the most powder while ensuring uniform absorption;

[0051] Step 6: subjecting the flexible composite aerogel to oxidation treatment, heating once and then keeping the temperature, heating twice and then keeping the temperature, to obtain semiconductor heterojunction silicon carbide nanofiber aerogel; the semiconductor heterojunction silicon carbide nanofiber aerogel is SiC / SiO 2 @TiO 2 / SnO 2 Composite aerogel;

[0052] Preferably, the specific steps of obtaining the semiconductor heterojunction silicon carbide nanofiber aerogel in step 6 include:

[0053] The flexible composite aerogel is placed in a tubular furnace, subjected to oxidation treatment in an air atmosphere, heated once and then kept warm; heated twice and then kept warm to obtain a semiconductor heterojunction silicon carbide nanofiber aerogel, i.e., SiC / SiO 2 @TiO 2 / SnO 2 Composite aerogel;

[0054] Furthermore, the temperature ratio of the first heating and the second heating is 1:2;

[0055] Furthermore, the rate of the first heating is 3-6°C / min, and the temperature of the first heating is 55-650°C; the rate of the second heating is 3-6°C / min; and the temperature of the second heating is 1100-1300°C;

[0056] Furthermore, the rate of the primary heating is 5°C / min; the heating temperature is 600°C;

[0057] The secondary heating rate is 5°C / min; the heating temperature is 1100°C;

[0058] Furthermore, the ratio of the holding time after the first heating to the holding time after the second heating is 2:1;

[0059] Furthermore, the heat preservation time after the first heating is: 1-2 hours;

[0060] The heat preservation time after the second heating is 0.5-1 hour.

[0061] The ratio of the holding time after the first heating to the holding time after the second heating is 2:1; the holding time after the first heating is longer than the holding time after the second heating, which fully ensures that Ti 2 The tin segregation of SnC is decomposed and then completely oxidized; the second insulation needs to be controlled at about 0.5 to 1h to avoid excessive oxidation of SiC nanofibers.

[0062] In the technical solution of the present invention, the composite aerogel is subjected to oxidation treatment, and the temperature is increased twice and then kept warm to complete the in-situ oxidation of the MAX derivative and the surface oxidation of the nanofibers to obtain SiC / SiO 2 @TiO 2 / SnO 2 Composite aerogel, wherein the flexible composite aerogel is loaded with Ti 2 After SnC powder, tin segregation and decomposition occurred at 600℃, and further oxidation generated TiO 2 / SnO 2 Nanohybrid particles, SiO anchored on the surface of SiC nanofiber aerogel 2 On the nano protective layer, TiO 2 / SnO 2 Nano-hybrid particles are present at the intersection of SiC nanofiber aerogel and SiO 2The nano-protective layer forms a new interface contact, tightly fuses and anchors the intersection of SiC nanofiber aerogel, and produces many new amorphous phase / crystalline phase contact interfaces. At the same time, at the intersection of SiC nanofiber aerogel, many simple stacks are connected by amorphous oxide layers SiO 2 Tightly fused to obtain SiC / SiO 2 @TiO 2 / SnO 2 Composite aerogel.

[0063] SiC / SiO prepared by the present invention 2 @TiO 2 / SnO 2 In the composite aerogel, a large number of charges are accumulated in the heterogeneous interface regions of crystalline phase / crystalline phase and amorphous phase / crystalline phase, and polarized electric dipoles are gathered, which enhances the interface polarization effect, realizes super-strong absorption of electromagnetic waves under ultra-thin matching thickness, and covers the entire radio wave X-band. It has super high-temperature stability and high-temperature absorbing ability, and still has excellent absorbing performance at 800°C. At the same time, its excellent thermal insulation ability gives it the potential to achieve infrared stealth.

[0064] Another object of the present invention is to provide a semiconductor heterojunction silicon carbide nanofiber aerogel, comprising SiC / SiO 2 Aerogel skeleton and oxidized TiO 2 and SnO 2 Particles, including SiC, SiO 2 、TiO 2 and SnO 2 The mass ratio is 10:10:3:3;

[0065] The semiconductor heterojunction silicon carbide nanofiber aerogel achieves stable wave absorption at a high temperature of 800°C, has multi-spectrum compatibility characteristics, and realizes the infrared stealth function at high temperatures, solving the difficulty of single-band stealth materials in practical applications. The third object of the present invention is to provide an application of semiconductor heterojunction silicon carbide nanofiber aerogel, wherein the electromagnetic wave frequency range of the semiconductor heterojunction silicon carbide nanofiber aerogel is 8.2 to 12.4 GHz;

[0066] The semiconductor heterojunction silicon carbide nanofiber aerogel has an application temperature range of 20 to 800° C. When the semiconductor heterojunction silicon carbide nanofiber aerogel is used for wave absorption under repeated high-temperature conditions, it exhibits stable wave absorption performance and durable and repeatable high-temperature application.

[0067] The semiconductor heterojunction silicon carbide nanofiber aerogel in the technical solution of the present invention has a large number of heterophase interfaces of crystalline phase / crystalline phase and amorphous phase / crystalline phase, realizing the imaginary part of the dielectric function dominated by polarization loss. There are multiple polarization relaxation mechanisms in the semiconductor heterojunction silicon carbide nanofiber aerogel: first, in the TiO 2 / SnO 2 In the above, the partial dislocations in the two crystals, the vacancies and lattice distortions at the heterophase interfaces of different crystal phases, and the point defects and line defects in the ultra-long SiC nanofiber crystals can all serve as dipole polarization centers. 2 In the amorphous phase, since the dipole moment is difficult to align with the changing external electric field, there is a directional polarization loss caused by a large number of defect sites; more is the amorphous phase SiO 2 and crystalline SiC, TiO 2 / SnO 2 There are a large number of interface lattice defects in the heterophase interface region between them, which cause the dipole polarization aggregation. Especially when an external electromagnetic field is applied, the heterophase interface traps affect the migration of induced carriers in several N-type semiconductors, causing the accumulation of free electrons, showing a large number of electric dipoles, and synergistically enhancing the interface polarization; in addition, there are a small number of SiC and TiO 2 / SnO 2 Direct contact makes it easier for valence band carriers to transition at the interface of the two N-type semiconductors, reducing the interface potential barrier. At the same time, the electric dipole moment is reduced, making it easier to respond to the alternating electromagnetic field in the high-frequency part. Therefore, through the study of the imaginary part of the dielectric constant, it is found that the imaginary part representing polarization loss occupies a larger proportion.

[0068] Compared with the prior art, the present invention has at least the following beneficial effects:

[0069] (1) The present invention adopts Ti 2 SnC converts TiO into oxide after tin segregation at lower temperature 2 / SnO 2 In-situ anchoring on nanofibers solves the problem of unreliability and instability of loaded fillers in aerogels, greatly improves the material preparation yield and structural stability, and improves the material preparation efficiency;

[0070] (2) The SiC / SiO2@TiO2 / SnO2 composite aerogel prepared by the present invention has a large number of crystalline phase / crystalline phase and amorphous phase / crystalline phase heterophase interfaces, realizing the imaginary part of the dielectric function dominated by polarization loss;

[0071] (3) The SiC / SiO2@TiO2 / SnO2 composite aerogel prepared by the present invention is a high-temperature absorbing material, which achieves stable absorbing at a high temperature of 800°C;

[0072] (4) The SiC / SiO2@TiO2 / SnO2 composite aerogel prepared by the present invention satisfies the stealth effect of both radar electromagnetic waves and infrared compatibility, solving the difficult problem of single-band stealth materials in practical applications;

[0073] (5) Preparation of SiC / SiO by the present invention 2 @TiO 2 / SnO 2 The method of composite aerogel is simple and conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] The drawings are only for the purpose of illustrating particular embodiments and are not to be construed as limiting the invention.

[0075] Figure 1 The SiC / SiO prepared in Example 1 of the present invention 2 @TiO 2 / SnO 2 Schematic diagram of the composite aerogel preparation process;

[0076] Figure 2 (a) is the SiC / SiO prepared in Example 1 of the present invention 2 @TiO 2 / SnO 2 Composite aerogel TiO 2 / SnO 2 Schematic diagram of nano-hybrid particles; (b) is SiC / SiO prepared in Example 1 of the present invention 2 @TiO 2 / SnO 2 SiC / SiO composite aerogel 2 Schematic diagram of the SEM image of the microscopic morphology of nanofibers; (c) is the SiC / SiO prepared in Example 1 of the present invention. 2 @TiO 2 / SnO 2 Schematic diagram of the TEM image of the microstructure of the nanofiber intersection of the composite aerogel;

[0077] Figure 3 (a) is the SiC / SiO prepared in Example 1 of the present invention. 2 @TiO 2 / SnO 2 Schematic diagram of the thermogravimetric curve of the composite aerogel at 1200°C; (b) is the SiC / SiO prepared in Example 1 of the present invention. 2 @TiO 2 / SnO 2 Schematic diagram of the mass change of composite aerogel under the actual application environment of 800℃ insulation time and high temperature cycle number;

[0078] Figure 4 (a) is the SiC / SiO prepared in Example 1 of the present invention 2 @TiO 2 / SnO 2 Schematic diagram of stress-strain curves of composite aerogels at different compression ratios; (b) is the SiC / SiO prepared in Example 1 of the present invention. 2 @TiO 2 / SnO 2 Schematic diagram of the cyclic compression curve of the composite aerogel under 40% strain; (c) is the SiC / SiO prepared in Example 1 of the present invention. 2 @TiO 2 / SnO 2 Schematic diagram of the stress-strain curve of the composite aerogel after compression testing at 800°C high temperature cycling;

[0079] FIG5(a) is a SiC / SiO prepared in Example 1 of the present invention. 2 @TiO 2 / SnO 2 Schematic diagram of the morphological structural characterization of the amorphous / crystalline interface of the composite aerogel;

[0080] FIG5(b) is a SiC / SiO prepared in Example 1 of the present invention. 2 @TiO 2 / SnO 2 SnO composite aerogel 2 Schematic diagram of the interface;

[0081] FIG5(c) is a SiC / SiO prepared in Example 1 of the present invention. 2 @TiO 2 / SnO 2 Composite aerogel SiO 2 Schematic diagram of the interface;

[0082] Figure 5(d) shows the SiC / SiO prepared in Example 1 of the present invention. 2 @TiO 2 / SnO 2 Composite aerogel TiO 2 Schematic diagram of the interface;

[0083] Figure 6 (a) is the SiC / SiO prepared in Example 1 of the present invention 2 @TiO 2 / SnO 2 Schematic diagram of the imaginary part of the dielectric constant of the composite aerogel at different temperatures; (b) is the SiC / SiO prepared in Example 1 of the present invention. 2 @TiO 2 / SnO2 Polarization imaginary part curves of composite aerogel at different temperatures;

[0084] Figure 7 (a) is the SiC / SiO prepared in Example 1 of the present invention 2 @TiO 2 / SnO 2 The wave absorption performance of the composite aerogel at 25°C; (b) is the SiC / SiO prepared in Example 1 of the present invention. 2 @TiO 2 / SnO 2 The microwave absorption performance of composite aerogel at 200°C;

[0085] Figure 8 (a) is the SiC / SiO prepared in Example 1 of the present invention 2 @TiO 2 / SnO 2 The microwave absorption performance of the composite aerogel at 400°C; (b) is the SiC / SiO prepared in Example 1 of the present invention 2 @TiO 2 / SnO 2 The microwave absorption performance of composite aerogel at 600°C;

[0086] Fig. 9 The SiC / SiO prepared in Example 1 of the present invention 2 @TiO 2 / SnO 2 The microwave absorption performance of composite aerogel at different temperatures of 800℃;

[0087] Fig.10 The SiC / SiO prepared in Example 1 of the present invention 2 @TiO 2 / SnO 2 Schematic diagram of composite aerogel using CST simulation to simulate real far-field radar scattering;

[0088] Fig.11 The SiC / SiO prepared in Example 1 of the present invention 2 @TiO 2 / SnO 2 Schematic diagram of the thermal insulation performance of the composite aerogel under the infrared thermal imager during bottom heating. DETAILED DESCRIPTION

[0089] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. In addition, the present invention can also be implemented in other ways different from those described herein, and therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0090] A specific embodiment of the present invention, as Figure 1-11 , discloses a semiconductor heterojunction silicon carbide nanofiber aerogel with high temperature wave absorption stability. In order to illustrate the effectiveness of the method proposed by the present invention, the above technical solution of the present invention is described in detail through a specific embodiment below. The specific implementation steps are as follows:

[0091] Step 1, preparing a silicone xerogel;

[0092] Step 2, selecting a foam material for carbonization to obtain pure carbon aerogel foam;

[0093] Step 3: Place the pure carbon aerogel foam on the silica xerogel and heat it to obtain silicon carbide SiC nanofibers; Step 4: MAX phase tin titanium carbide Ti 2 SnC powder was added to ethanol solution and ultrasonically treated to obtain tin carbide Ti 2 SnC dispersion;

[0094] Step 5: Adding tin carbide Ti to SiC nanofibers 2 SnC dispersion to obtain a flexible composite aerogel;

[0095] Step 6: The flexible composite aerogel is subjected to oxidation treatment, and then heated once and then kept warm, and then heated twice and then kept warm, to obtain SiC / SiO 2 @TiO 2 / SnO 2 Composite aerogel.

[0096] Embodiment 1:

[0097] Selecting silica xerogel;

[0098] Commercial melamine foam of 5 cm×3 cm×2 cm is carbonized into pure carbon aerogel foam, and the pure carbon aerogel foam is placed on top of the silica xerogel and then put into a crucible of a tubular furnace together;

[0099] The SiC nanofibers were grown by heating the SiC nanofibers in a tube furnace at a heating rate of 5°C / min to 1450°C.

[0100] MAX phase tin titanium carbide Ti 2SnC powder is dispersed in an ethanol solution; the MAX phase tin titanium carbide Ti 2 The mass ratio of SnC powder to ethanol solution was 0.1wt%, and then ultrasonication was performed for 30 minutes until uniform dispersion was obtained. 2 SnC dispersion;

[0101] 0.02 g of SiC nanofiber aerogel was placed in a watch glass, and 2 mL of tin-titanium carbide Ti was pipetted with a rubber-tipped dropper. 2 SnC dispersion is repeatedly dripped on the bottom and top of SiC nanofibers to allow it to be absorbed into the aerogel through capillary action, ensuring uniform absorption until the MAX phase tin titanium carbide Ti 2 The mass ratio of SnC powder to SiC nanofibers was 3:10, and a flexible composite aerogel was obtained;

[0102] The flexible composite aerogel was transferred to a tubular furnace and subjected to oxidation treatment in an air atmosphere. The temperature was raised to 600°C at a rate of 5°C / min and kept at this temperature for 2 hours. The temperature was then raised to 1100°C at a rate of 5°C / min and kept at this temperature for 1 hour to complete the in-situ oxidation of the MAX derivative and the surface oxidation of the nanofibers, thereby obtaining a SiC / SiO2@TiO2 / SnO2 composite aerogel. Figure 1 ;

[0103] SiC / SiO prepared in Example 1 2 @TiO 2 / SnO 2 The microstructure of the composite aerogel, in which TiO 2 / SnO 2 The mixed particles form an interface contact with the oxide layer of the SiC nanofibers, tightly fusing the intersections of the SiC nanofibers and generating many new interfaces. At the same time, at the intersections of the SiC nanofibers, many simple stacks are transformed into tightly fused ones by the amorphous oxide layer SiO2, which greatly affects the mechanical and dielectric properties of the aerogel; Figure 2 ;

[0104] The SiC / SiO prepared in Example 1 2 @TiO 2 / SnO 2 The thermal stability of the composite aerogel is that the quality is stable when heated to 800°C in the air atmosphere thermogravimetric test, and the quality of the material does not change significantly when kept at this high temperature for 24 hours or heated in a cycle for twenty times, which shows that the thermal stability of the microstructure is good; Figure 3 ;

[0105] The stress-strain curve of the SiC / SiO2@TiO2 / SnO2 composite aerogel prepared in Example 1 shows that it has good compressive strain capacity and stable compression cycle capacity at 40% strain. Figure 4 ;

[0106] SiC / SiO in Example 1 2 @TiO 2 / SnO 2 A large number of heterogeneous interfaces of crystalline phase / crystalline phase and amorphous phase / crystalline phase of composite aerogel are shown in Figure 5;

[0107] The dielectric constant of the SiC / SiO2@TiO2 / SnO2 composite aerogel prepared in Example 1 is as follows: Figure 6 , realizing the dielectric imaginary part dominated by polarization loss, in amorphous SiO 2 and crystalline SiC, TiO 2 / SnO 2 There are a large number of interface lattice defects in the heterophase interface region between them, where the dipole polarization caused by them is concentrated. When an external electromagnetic field is applied, the heterophase interface traps affect the migration of induced carriers in several N-type semiconductors, causing the accumulation of free electrons, showing a large number of electric dipoles, and synergistically enhancing the interface polarization;

[0108] The SiC / SiO prepared in Example 1 2 @TiO 2 / SnO 2 The wave absorption performance of the composite aerogel at different ambient temperatures can achieve an ultra-strong absorption of -67.9dB at a frequency of 10.80GHz with an ultra-thin matching thickness of 2mm at room temperature, covering the entire X-band (8.2-12.4GHz); and when heated to 800℃, the aerogel still has a strong absorption of -35.0dB (at 11.63GHz), demonstrating its good wave absorption performance in a wide temperature range up to high temperature; Figure 7-9 ;

[0109] The SiC / SiO prepared in Example 1 2 @TiO 2 / SnO 2 The composite aerogel was simulated by CST to simulate the real far-field radar scattering interface, indicating that in actual applications, the surface covered by the aerogel showed extremely weak radar wave scattering signals and had good attenuation ability; Fig.10 ;

[0110] SiC / SiO prepared in Example 1 2 @TiO 2 / SnO 2The thermal insulation performance of the composite aerogel under the infrared thermal imager, the temperature readings every five minutes are as follows Fig.11 As shown, the detected temperature of the surface of the present invention is from 18.5-30.1℃, showing good thermal insulation performance, which can effectively prevent the heat from the bottom from transferring upward. In addition, as time goes by, the rising trend of the surface temperature slows down and almost no longer changes, showing excellent temperature control stability; excellent thermal insulation performance is an important influencing condition of infrared stealth function, which reduces infrared radiation outward and achieves the effect of hiding the target.

[0111] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a semiconductor heterojunction silicon carbide nanofiber aerogel with high temperature absorption stability, characterized in that: include: Step 1, preparing silica xerogel; Step 2, selecting a foam material for carbonization to obtain a carbon aerogel foam; Step 3, placing the carbon aerogel foam on top of the silica xerogel and heating it to obtain silicon carbide SiC nanofibers; Step 4, adding MAX phase tin titanium carbide Ti2SnC powder into an ethanol solution, and ultrasonically treating the solution to obtain a tin titanium carbide Ti2SnC dispersion; Step 5, adding titanium tin carbide Ti2SnC dispersion to SiC nanofibers to obtain a flexible composite aerogel; Step 6: subjecting the flexible composite aerogel to oxidation treatment, heating it once and then keeping it warm, heating it twice and then keeping it warm, to obtain a semiconductor heterojunction silicon carbide nanofiber aerogel.

2. The method for preparing semiconductor heterojunction silicon carbide nanofiber aerogel according to claim 1, characterized in that: The specific steps of preparing the silicone xerogel in step 1 include: Methyltrimethoxysilane, dimethyldimethoxysilane, a hydrolyzing agent and a catalyst are mixed, cross-linked and dried to obtain a silicone xerogel.

3. The method for preparing semiconductor heterojunction silicon carbide nanofiber aerogel according to claim 1, characterized in that: Step 2 The specific steps of obtaining the carbon aerogel foam include: The foam material is placed in a tubular furnace, heated and kept warm in an argon atmosphere to undergo a full carbonization reaction, thereby obtaining a carbon aerogel foam.

4. The method for preparing semiconductor heterojunction silicon carbide nanofiber aerogel according to claim 3, characterized in that: The ratio of the heating temperature in step 2 to the heating temperature in step 3 is 6-7:14-15.

5. The method for preparing semiconductor heterojunction silicon carbide nanofiber aerogel according to claim 1, characterized in that: The mass ratio of the MAX phase tin titanium carbide Ti2SnC powder to the ethanol solution is 0.1-0.3wt%.

6. The method for preparing semiconductor heterojunction silicon carbide nanofiber aerogel according to claim 1, characterized in that: The mass ratio of MAX phase tin titanium carbide Ti2SnC to silicon carbide SiC nanofibers in the flexible composite aerogel is 3:

10.

7. The method for preparing semiconductor heterojunction silicon carbide nanofiber aerogel according to claim 6, characterized in that: The specific steps of obtaining the semiconductor heterojunction silicon carbide nanofiber aerogel in step 6 include: The flexible composite aerogel is placed in a tubular furnace, subjected to oxidation treatment in an air atmosphere, heated up once and then kept warm; heated up twice and then kept warm to obtain a semiconductor heterojunction silicon carbide nanofiber aerogel.

8. The method for preparing semiconductor heterojunction silicon carbide nanofiber aerogel according to claim 7, characterized in that: The temperature ratio between the first heating and the second heating is 1:

2.

9. A semiconductor heterojunction silicon carbide nanofiber aerogel, prepared according to the preparation method according to any one of claims 1 to 8, characterized in that: It includes a SiC / SiO2 aerogel skeleton and oxidized TiO2 and SnO2 particles; the semiconductor heterojunction silicon carbide nanofiber aerogel achieves stable wave absorption at a high temperature of 800°C, has multi-spectrum compatibility characteristics, and realizes the function of infrared stealth at high temperatures.

10. An application of semiconductor heterojunction silicon carbide nanofiber aerogel, characterized in that: The semiconductor heterojunction silicon carbide nanofiber aerogel according to claim 9 is used under the conditions of an electromagnetic wave frequency range of 8.2 to 12.4 GHz and a temperature range of 20 to 800°C.

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