Multi-boride enhanced adjustable dielectric polymer conversion ceramic-based high-temperature wave-absorbing material as well as preparation method and application of multi-boride enhanced adjustable dielectric polymer conversion ceramic-based high-temperature wave-absorbing material

Abstract

The invention discloses a multi-boride enhanced adjustable dielectric polymer conversion ceramic-based high-temperature wave-absorbing material as well as a preparation method and application thereof, and belongs to the field of wave-absorbing materials. The method comprises the following steps: carrying out high-temperature pretreatment on five borides, namely zirconium boride, titanium boride, niobium boride, hafnium boride and tantalum boride, and then carrying out ball-milling mixing according to different mass proportions; the mixed powder is uniformly dispersed into liquid-phase polysiloxane (PSO), and the multi-boride enhanced adjustable dielectric polymer conversion ceramic-based high-temperature wave-absorbing material is prepared through low-temperature crosslinking and high-temperature cracking. The S-MB ceramic composite material prepared by the invention effectively regulates and controls the current situation that the PDC-SiOC ceramic is insufficient in dielectric frequency dispersion characteristic and insufficient in loss capability. The ceramic composite material can still keep good absorption performance at the high temperature of 1473 K, the absorption bandwidth can reach 7.54 GHz, and the wave absorption requirement of a high-speed aircraft in the high-temperature severe environment can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of absorbing materials, and in particular relates to a multi-component boride-enhanced adjustable dielectric polymer-converted ceramic-based high-temperature absorbing material, a preparation method and an application thereof. Background Art

[0002] As modern aircraft develop towards high Mach numbers and long flight times, their hot end parts such as aircraft engine tail nozzles, high-speed aircraft surfaces, and cruise missile nose cones will face extreme dynamic thermal environments with higher temperatures and more severe oxidation. This places stringent requirements on the ability of stealth materials to withstand harsh environments. There is an urgent need for materials that can withstand higher temperatures and absorb electromagnetic waves to meet the needs of high-temperature broadband stealth. Although traditional carbon-based and magnetic absorbing materials have strong loss capabilities, their application environments are severely restricted due to their shortcomings such as high-temperature demagnetization and easy oxidation. Ceramics or ceramic-based composites are potential candidates for solving the above problems due to their excellent oxidation resistance and chemical stability. Among them, polymer-converted ceramics (PDC) have received widespread attention due to their excellent oxidation resistance and adjustable dielectric properties. However, this type of material is usually used as a matrix material and cracked at low temperatures to obtain good impedance matching capabilities. Its disadvantages are insufficient dielectric dispersion characteristics and weak loss capabilities. Therefore, it is urgent to improve the dielectric properties of PDC-based ceramics and enhance the electromagnetic wave loss capability to meet the needs of high-temperature broadband stealth.

[0003] Reference 1 “Tang H, Wang K, Ren K, et al. Microstructural evolution and microwave transmission / absorption transition in polymer-derived SiOC ceramics[J]. Ceramics International, 2023, 49(12): 20406-20418.” This reference systematically studies the changes in the structure and electromagnetic properties of polymer-derived SiOC ceramics as the pyrolysis temperature increases. PDC-SiOC ceramics have excellent chemical stability, thermal stability and mechanical durability due to their unique anionic silica network. After pyrolysis at a temperature <1200 ℃, PDC-SiOC exhibits amorphous wave transmission characteristics, excellent impedance matching ability but poor dielectric loss ability. As the pyrolysis temperature increases, SiC nanocrystals appear in PDC-SiOC and exhibit wave absorption characteristics, but the impedance matching ability with free space becomes poor. Therefore, how to ensure excellent impedance matching ability while improving dielectric loss ability is a key issue that needs to be solved urgently.

[0004] The dielectric dispersion characteristic (the dielectric value rapidly decreases as the frequency increases) is an important condition for a material to achieve broadband absorption. The Debye relaxation formula elucidates that the polarization effect in the material is closely related to the change in the complex dielectric constant (ε r ). When the frequency of the external electric field increases, the polarizability of electrons and dipoles cannot be maintained, resulting in a decrease in the actual dielectric constant of the material with frequency. In addition, shortening the polarization relaxation time τ will cause an increase in ε r . However, this trend weakens as the electromagnetic wave frequency f increases, resulting in a lower ε r value at high frequencies than at low frequencies. Therefore, enhancing the polarization effect is a feasible strategy to improve the dielectric dispersion characteristics of materials.

[0005] Reference 2, "Ding J, Shi R, Gong C, et al. Defect engineering activates Schottky heterointerfaces of graphene / CoSe2 composites with ultrathin and lightweight design strategies to boost electromagnetic wave absorption[J]. Advanced Functional Materials, 2023, 33(48): 2305463.", shows that heterointerfacial engineering provides a direct and effective means to enhance the dielectric polarization effect of composites. The difference in work functions of the materials on both sides of the heterointerface causes the spontaneous transfer of electrons, forming a rapid electron transfer channel, resulting in an uneven charge distribution and strengthening the interfacial polarization effect.

[0006] Reference 3, "Wide-Band Tunable Microwave-Absorbing Ceramic Composites Made of Polymer-Derived SiOC Ceramic and in Situ Partially Surface-Oxidized Ultra-High-Temperature Ceramics[J]. ACS applied materials&interfaces, 2019, 11(49):45862-45874." discloses a preparation method of a nano-ZrB2 reinforced polymer-derived SiOC ceramic composite material, which exhibits excellent electromagnetic wave absorption ability. The effective absorption bandwidth reaches 13.5 GHz (26.5-40 GHz), covering the entire Ka band. The excellent absorption performance is attributed to the dielectric regulation of PDC-SiOC matrix by nano-ZrB2. The introduction of a large number of heterogeneous interfaces enhances the interfacial polarization loss effect of the composite material and improves the dielectric properties of the ceramic composite material.

[0007] Reference 4, "Yang X, Quan H, Wang K. SiC / Si–ZrSi2–ZrB2-HfB2 / SiC coating for oxidation protection of C / C composites prepared by three-step method[J]. Journal of Alloys and Compounds, 2020, 836: 155532." shows that ultra-high temperature boride ceramics (ZrB2, HfB2) have excellent oxidation resistance. The multi-component oxide layers such as ZrO2 and HfO2 generated by high-temperature oxidation can effectively prevent oxygen from entering the composite material matrix and prevent further oxidation.

[0008] According to the above references, ultra-high temperature boride ceramics have strong conductance loss ability, making them ideal electromagnetic wave absorbers in harsh high-temperature environments. Based on this, the present invention proposes a ceramic-based high-temperature wave-absorbing material incorporating multi-component borides to improve the dielectric characteristics of PDC-based ceramics and enhance the electromagnetic wave loss ability. Summary of the Invention

[0009] To solve the problems of insufficient dielectric dispersion characteristics and poor loss ability of low-temperature cracked PDC-SiOC ceramics, the present invention provides a multi-component boride-enhanced adjustable dielectric polymer-derived ceramic-based high-temperature microwave absorbing material, its preparation method and application. The dielectric dispersion characteristics of the S-MB ceramic composite material obtained by the present invention are effectively regulated, the absorption performance is significantly improved, and it has excellent broadband microwave absorbing ability.

[0010] To achieve the above object, the present invention provides the following technical solutions: The present invention provides a multi-component boride-enhanced adjustable dielectric polymer-derived ceramic-based high-temperature microwave absorbing material, wherein the ceramic-based high-temperature microwave absorbing material comprises a polymer-derived SiOC ceramic and a multi-component ultra-high temperature boride ceramic, and the ceramic-based high-temperature microwave absorbing material takes the polymer-derived SiOC ceramic as the matrix, and the multi-component ultra-high temperature boride ceramic is uniformly dispersed in the polymer-derived SiOC ceramic.

[0011] The multi-component ultra-high temperature boride ceramic comprises ZrB2, TiB2, NbB2, HfB2 and TaB2.

[0012] The present invention also provides a preparation method of the multi-component boride-enhanced adjustable dielectric polymer-derived ceramic-based high-temperature microwave absorbing material, comprising: Respectively placing the powders of ZrB2, TiB2, NbB2, HfB2 and TaB2 in an inert atmosphere for the first heat treatment; Mixing the ZrB2, TiB2, NbB2, HfB2 and TaB2 after the first heat treatment according to a preset mass ratio, and performing ball milling to obtain an MB mixed powder; Mixing the MB mixed powder and liquid polysiloxane evenly according to a preset mass ratio to obtain a blended slurry, and performing the second heat treatment on the blended slurry in an inert atmosphere to obtain a cross-linked material; Performing ball milling and sieving on the cross-linked material to obtain a ceramic composite material; Performing pressing on the ceramic composite material, and performing the third heat treatment on the pressed ceramic composite material in an inert atmosphere to prepare an S-MB ceramic composite material.

[0013] The mass ratio of the ZrB2, TiB2, NbB2, HfB2 and TaB2 powders is (1~10):(1~10):(1~10):(1~10):(1~10).

[0014] The mass ratio of the MB mixed powder and the liquid polysiloxane is (1~3):(1~3).

[0015] The first heat treatment is specifically: heating at a heating rate of 5 °C / min to 400~800 °C, holding for 1~4 h, and then naturally cooling to room temperature.

[0016] The specific second heat treatment is as follows: heating at a heating rate of 5 °C / min to 100 - 300 °C, holding for 0.5 - 2 h, and then naturally cooling to room temperature.

[0017] The specific third heat treatment is as follows: heating at a heating rate of 5 °C / min to 800 - 1000 °C, holding for 1 - 4 h, and then naturally cooling to room temperature.

[0018] The particle size of the ceramic composite material is less than 200 mesh.

[0019] The present invention also provides the application of the multi - boride - enhanced tunable dielectric polymer - converted ceramic - based high - temperature microwave absorbing material on an aircraft.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a preparation method and application of a multi - boride - enhanced tunable dielectric polymer - converted ceramic - based high - temperature microwave absorbing material. The preparation method of the present invention is to perform high - temperature pretreatment on five ultra - high - temperature boride ceramics, and then uniformly disperse them in the liquid - phase PSO according to a ratio. After low - temperature cross - linking, the S - MB ceramic composite material is prepared by a high - temperature pyrolysis process. By introducing a five - element boride absorber, a large number of heterogeneous interfaces are constructed inside the ceramic composite material, significantly enhancing the interfacial polarization loss effect. Compared with the single - boride - enhanced polymer - converted ceramic composite material, the multiple polarization loss mechanism of the S - MB ceramic composite material effectively regulates the dielectric properties, and its dielectric constant shows a rapid downward trend with the increase of the electromagnetic field frequency, showing excellent dispersion characteristics. The coaxial test results of the S - MB ceramic composite material prepared by the preparation method of the present invention show that, due to this characteristic, the S - MB ceramic composite material exhibits excellent absorption performance, with a minimum reflection loss of - 57.03 dB and a maximum effective absorption bandwidth (< - 10 dB) of 10.08 GHz. Through high - temperature reflectivity test verification, the S - MB ceramic composite material maintains stable microwave absorption performance in a wide temperature range from room temperature to high temperature of 1473 K. Specifically, the effective absorption bandwidth (EAB) in the temperature range of 298 K - 873 K is stable at 11.95 GHz - 12.03 GHz, and the wide - band absorption ability of 7.54 GHz - 7.70 GHz is still maintained in the high - temperature section of 1073 K - 1473 K.

[0021] The preparation method of the present invention has the advantages of low raw material cost, simple and controllable process, etc. The prepared S - MB ceramic composite material has wide - temperature - range adaptability and excellent wide - band electromagnetic wave absorption characteristics. Its wide - band absorption ability exceeds that of other reported high - temperature microwave absorbing materials at present, and has good application prospects. Description of the Drawings

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0023] Figure 1 This is the XRD pattern corresponding to the embodiment of the present invention; among them, (a) is the XRD pattern of the S-MB ceramic composite material in Example 1; (b) is the XRD pattern of the S-MB ceramic composite material in Example 2; (c) is the XRD pattern of the S-MB ceramic composite material in Example 3; (d) is the XRD pattern of the S-MB ceramic composite material in Example 4. Figure 2 This is the microscopic test diagram of Example 4; among them, (a) is the microscopic morphology diagram of the S-MB ceramic composite material in Example 4, (b) is the backscattered electron scanning photograph of the S-MB ceramic composite material in Example 4; (c)-(e) are respectively the elemental surface scanning analysis and point scanning analysis diagrams of the S-MB ceramic composite material in Example 4.

[0024] Figure 3 This is the dielectric constant test curve graph, where (a), (b), and (c) are respectively the real part, imaginary part, and tangent of the loss angle of the SiOC-unit boride ceramic composite material prepared in the comparative example; (d), (e), and (f) are respectively the real part and imaginary part values of the S-MB ceramic composite material prepared in Examples (1)-(4). Figure 4 This is the electromagnetic wave absorption performance test curve graph; among them, (a)-(d) respectively correspond to the electromagnetic wave absorption performance of the S-MB ceramic composite materials containing different proportions of multi-component borides in Examples (1)-(4); (e) is the minimum reflection loss value of the S-MB ceramic composite materials in Examples (1)-(4); (f)-(j) are respectively the electromagnetic wave absorption performance of the SiOC-unit boride ceramic composite materials with different single-component borides (content 40 wt.%) prepared in the comparative example; (k) is the minimum reflection loss value corresponding to the different SiOC-unit boride ceramic composite materials prepared in the comparative example.

[0025] Figure 5 This is the wave absorption curve graph of the S-MB ceramic composite material in Example 4; (a) is the room temperature absorption performance of the S-MB ceramic composite material prepared in Example 4 in the range of 2-40 GHz; (b) is the high temperature absorption performance of the S-MB ceramic composite material prepared in Example 4 from room temperature to high temperature 1473 K. Specific embodiments

[0026] In order to make the technical problems to be solved, technical solutions and beneficial effects of this application clearer and more understandable, the following further details this application in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0027] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Where A and B can be singular or plural. The character " / " generally represents an "or" relationship between the front and rear associated objects.

[0028] In this application, "at least one" means one or more, and "a plurality" means two or more. "At least one (item)" or its similar expression refers to any combination of these items, including any combination of single item (s) or plural items (s). For example, "at least one (item) of a, b, or c", or, "at least one (item) of a, b, and c" can both represent: a, b, c, a - b (that is, a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0029] It should be understood that in various embodiments of this application, the magnitude of the sequence numbers of the above - mentioned processes does not mean the sequence of execution. Some or all steps can be executed in parallel or successively. The execution sequence of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0030] The terms used in the embodiments of this application are only for the purpose of describing specific embodiments, and are not intended to limit this application. The singular forms of "a", "the", and "said" used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0031] The weights of the relevant components mentioned in the specification of the embodiments of this application can not only refer to the specific contents of each component, but also represent the proportional relationship of the weights between the components. Therefore, as long as the contents of the relevant components in the specification of the embodiments of this application are enlarged or reduced in proportion, they are within the scope disclosed in the specification of the embodiments of this application. Specifically, the mass described in the specification of the embodiments of this application can be mass units well - known in the chemical industry such as μg, mg, g, kg, etc.

[0032] The first object of this application is to provide a preparation method of a multi - boride - enhanced adjustable dielectric polymer - converted ceramic - based high - temperature microwave absorption material, including: The ZrB2, TiB2, NbB2, HfB2, and TaB2 powders are respectively placed in an inert atmosphere for the first heat treatment to obtain five pretreated powders; Take the five pretreated powders and perform ball milling to obtain an MB mixed powder; Mix the MB mixed powder and liquid polysiloxane evenly according to a preset mass ratio to obtain a blend slurry, and perform a second heat treatment on the blend slurry in an inert atmosphere to obtain a crosslinked material; The crosslinked material is ball milled and then sieved to obtain a ceramic composite material; The ceramic composite material is pressed, and the pressed ceramic composite material is subjected to a third heat treatment in an inert atmosphere to prepare a ceramic matrix high-temperature wave-absorbing material, namely a SiOC-multiple boride (S-MB) ceramic composite material.

[0033] The preparation method of the present invention introduces a quinary boride absorbent, constructs a large number of heterogeneous interfaces inside the ceramic composite material, and significantly enhances the interfacial polarization loss effect. Compared with the polymer-derived ceramic composite material enhanced by a single boride, the multiple polarization loss mechanism of the S-MB ceramic composite material effectively regulates the dielectric properties, and its dielectric constant shows a rapid downward trend with the increase of the electromagnetic field frequency, showing excellent dispersion characteristics.

[0034] The preparation method of the present invention for a multiple boride-enhanced tunable dielectric polymer-derived ceramic matrix high-temperature wave-absorbing material is specifically as follows: Step 1: Respectively place five kinds of nanoscale ultra-high temperature boride ceramic powders of zirconium boride (ZrB2), titanium boride (TiB2), niobium boride (NbB2), hafnium boride (HfB2), and tantalum boride (TaB2) in an alumina crucible, and then transfer them to a resistance wire heating type heat treatment furnace. In a flowing Ar atmosphere, heat from room temperature to 400-800 °C at a heating rate of 5 °C / min, keep warm for 1-4 h, then turn off the power, and then naturally cool to room temperature to obtain five single-phase ceramic powders of heat-treated ZrB2, TiB2, NbB2, HfB2, and TaB2.

[0035] Step 2: Weigh the heat-treated ZrB2, TiB2, NbB2, HfB2, and TaB2 in Step 1. The mass ratio of the ZrB2, TiB2, NbB2, HfB2, and TaB2 powders is (1-10):(1-10):(1-10):(1-10):(1-10). Then place them all in a ball mill and perform ball milling for 2-4 h to make the five boride ceramic powders evenly mixed to obtain an MB mixed powder.

[0036] Step 3: Weigh the MB mixed powder and liquid polysiloxane (PSO) according to the mass ratio of (1~3):(1~3). Add the MB mixed powder into PSO and stir magnetically for 12 h, then disperse ultrasonically for 6 h to obtain a uniform blend slurry. Place the blend slurry in an alumina crucible, and in a flowing Ar atmosphere, heat it to 100~300 °C at a rate of 5 °C / min, hold for 0.5~2 h, then turn off the power and let it cool naturally to room temperature to complete the cross-linking reaction and obtain the cross-linked material.

[0037] Step 4: Grind the cross-linked material in a planetary ball mill and then sieve it through a 200-mesh sieve to obtain ceramic composite powder with uniform particle size. Press the ceramic composite powder. The pressing is carried out using a hydraulic press to press the powder into two types of specimens, including: Ring specimen: inner diameter 3 mm, outer diameter 12 mm, height 3 mm; Flat specimen: 240 mm×240 mm×5 mm.

[0038] Step 5: Put the pressed ceramic composite material into a heat treatment furnace with a resistance wire as the heating element. In a flowing Ar atmosphere, heat it from room temperature to 800~1000 °C at a heating rate of 5 °C / min, hold for 1~4 h, then turn off the power and let it cool naturally to room temperature to obtain the S-MB ceramic composite material.

[0039] In some embodiments, process the S-MB ceramic composite material into specimens with corresponding sizes as required for dielectric constant and reflectivity tests. The required specimens include: (1) Coaxial method ring test specimen: outer diameter 7 mm, inner diameter 3 mm; (2) High-temperature reflectivity test method specimen: 180 mm×180 mm×3 mm.

[0040] The second object of the present invention is to provide a multi-component boride-reinforced adjustable dielectric polymer-derived ceramic-based high-temperature microwave absorbing material. The ceramic-based high-temperature microwave absorbing material includes polymer-derived SiOC ceramic and multi-component ultra-high-temperature boride ceramic. The ceramic-based high-temperature microwave absorbing material uses polymer-derived SiOC ceramic as the matrix, and multi-component ultra-high-temperature boride ceramic is uniformly dispersed in the polymer-derived SiOC ceramic to form an S-MB ceramic composite material containing amorphous carbon, amorphous SiO x C y phase and multi-component ultra-high-temperature boride ceramic. The complex dielectric constant of the S-MB ceramic composite material prepared by the preparation method provided by the present invention shows obvious dispersion characteristics, that is, the dielectric value rapidly decreases with the increase of frequency. The dielectric dispersion characteristics of the S-MB ceramic composite material are regulated by the inter-component ratio of the multi-component ultra-high-temperature boride ceramic and can still be effectively maintained at high temperatures.

[0041] The third object of the present invention is to provide an application of a multi-component boride-reinforced adjustable dielectric polymer-derived ceramic-based high-temperature microwave absorbing material on an aircraft.

[0042] In the following examples, unless otherwise specified, all materials used can be obtained through ordinary channels; the testing methods adopted are conventional methods in the art.

[0043] Example 1: Step 1: Place five kinds of nanoscale ultra-high temperature boride ceramic powders of ZrB2, TiB2, NbB2, HfB2, and TaB2 in alumina crucibles respectively, and then transfer them into a resistance wire heating type heat treatment furnace. In a flowing Ar atmosphere, heat from room temperature to 600 °C at a heating rate of 5 °C / min, keep the temperature for 3 h, then turn off the power supply, and then naturally cool to room temperature to obtain heat-treated ceramic powders.

[0044] Step 2: Weigh the ZrB2, TiB2, NbB2, HfB2, and TaB2 after heat treatment in Step 1 according to the mass ratio. The mass ratio of the ZrB2, TiB2, NbB2, HfB2, and TaB2 powders is 10:10:1:1:1. Then place them all in a ball mill for ball milling for 2 h to make the five boride ceramic powders evenly mixed, and obtain the MB mixed powder.

[0045] Step 3: Weigh the MB mixed powder and liquid polysiloxane (PSO) according to the mass ratio of 2:3. Add the MB mixed powder to PSO and stir magnetically for 12 h and then ultrasonically disperse for 6 h to obtain a uniform blend slurry; place the blend slurry in an alumina crucible, and in a flowing Ar atmosphere, heat to 150 °C at a heating rate of 5 °C / min, keep the temperature for 2 h, and then naturally cool to room temperature to complete the crosslinking reaction and obtain the crosslinked material.

[0046] Step 4: Grind the crosslinked material in a planetary ball mill and then pass through a 200-mesh sieve to obtain ceramic composite powders with uniform particle sizes; press the ceramic composite powders. The pressing uses a hydraulic press to press the powders into two specifications of specimens, including: annular specimen: inner diameter 3 mm, outer diameter 12 mm, height 3 mm; flat specimen: 240 mm×240 mm×5 mm.

[0047] Step 5: Put the pressed ceramic composite material into a heat treatment furnace with a resistance wire as the heating element. In a flowing Ar atmosphere, heat from room temperature to 1000 °C at a heating rate of 5 °C / min, keep the temperature for 2 h, then turn off the power supply, and then naturally cool to room temperature to obtain the S-MB ceramic composite material.

[0048] Step 6: Process the S-MB ceramic composite material prepared in this example into specimens with corresponding sizes according to requirements for dielectric constant and reflectivity tests. The required specimens include: (1) coaxial method annular test specimen: outer diameter 7 mm, inner diameter 3 mm; (2) high-temperature reflectivity test method specimen: 180 mm×180 mm×3 mm.

[0049] Example 2 Step 1: Place five kinds of nano-scale ultra-high temperature boride ceramic powders of ZrB2, TiB2, NbB2, HfB2, and TaB2 in alumina crucibles respectively, and then transfer them into a resistance wire heating type heat treatment furnace. In a flowing Ar atmosphere, heat from room temperature to 600 °C at a heating rate of 5 °C / min, keep the temperature for 3 h, then turn off the power supply, and then naturally cool to room temperature to obtain the heat-treated ceramic powders.

[0050] Step 2: Weigh the ZrB2, TiB2, NbB2, HfB2, and TaB2 after heat treatment in Step 1 according to the mass ratio. The mass ratio of ZrB2, TiB2, NbB2, HfB2, and TaB2 powders is 1:1:10:1:10. Then place them all in a ball mill for ball milling for 2 h to make the five boride ceramic powders evenly mixed and obtain the MB mixed powder.

[0051] Step 3: Weigh the MB mixed powder and liquid polysiloxane (PSO) according to the mass ratio of 1:1. Add the MB mixed powder to the PSO and stir magnetically for 12 h and then ultrasonically disperse for 6 h to obtain a uniform blend slurry. Place the blend slurry in an alumina crucible. In a flowing Ar atmosphere, heat to 160 °C at a heating rate of 5 °C / min, keep the temperature for 1 h, and then naturally cool to room temperature to complete the cross-linking reaction and obtain the cross-linked material.

[0052] Step 4: Grind the cross-linked material in a planetary ball mill and then pass it through a 200-mesh sieve to obtain ceramic composite powder with uniform particle size. Press the ceramic composite powder. The pressing uses a hydraulic press to press the powder into two specifications of specimens, including: annular specimen: inner diameter 3 mm, outer diameter 12 mm, height 3 mm; flat specimen: 240 mm×240 mm×5 mm.

[0053] Step 5: Place the pressed ceramic composite material into a heat treatment furnace with a resistance wire as the heating element. In a flowing Ar atmosphere, heat from room temperature to 1000 °C at a heating rate of 5 °C / min, keep the temperature for 2 h, then turn off the power supply, and then naturally cool to room temperature to obtain the S-MB ceramic composite material.

[0054] Step 6: Process the S~MB ceramic composite material prepared in this example into specimens with corresponding sizes according to requirements for dielectric constant and reflectivity tests. The required specimens include: (1) coaxial method annular test specimen: outer diameter 7 mm, inner diameter 3 mm; (2) high-temperature reflectivity test method specimen: 180 mm×180 mm×3 mm.

[0055] Example 3 Step 1: Place the five kinds of nanoscale ultra-high temperature boride ceramic powders of ZrB2, TiB2, NbB2, HfB2, and TaB2 in alumina crucibles respectively, and then transfer them into a resistance wire heating type heat treatment furnace. In a flowing Ar atmosphere, heat from room temperature to 650 °C at a heating rate of 5 °C / min, keep warm for 2 h, then turn off the power supply, and then naturally cool to room temperature to obtain the heat-treated ceramic powders.

[0056] Step 2: Weigh the ZrB2, TiB2, NbB2, HfB2, and TaB2 after heat treatment in Step 1 according to the mass ratio. The mass ratio of the ZrB2, TiB2, NbB2, HfB2, and TaB2 powders is 1:2:10:1:10. Then place them all in a ball mill for ball milling for 2 h to make the five boride ceramic powders evenly mixed, and obtain the MB mixed powder.

[0057] Step 3: Weigh the MB mixed powder and liquid polysiloxane (PSO) according to the mass ratio of 3:2. Add the MB mixed powder to PSO, stir magnetically for 12 h, and then ultrasonically disperse for 6 h to obtain a uniform blend slurry; place the blend slurry in an alumina crucible, in a flowing Ar atmosphere, heat to 150 °C at a rate of 5 °C / min, keep warm for 1 h, and then naturally cool to room temperature to complete the cross-linking reaction and obtain the cross-linked material.

[0058] Step 4: Grind the cross-linked material in a planetary ball mill and then pass through a 200-mesh sieve to obtain ceramic composite powder with uniform particle size; press the ceramic composite powder. The pressing uses a hydraulic press to press the powder into two types of specimens, including: annular specimen: inner diameter 3 mm, outer diameter 12 mm, height 3 mm; flat specimen: 240 mm×240 mm×5 mm.

[0059] Step 5: Put the pressed ceramic composite material into a heat treatment furnace with a resistance wire as the heating element. In a flowing Ar atmosphere, heat from room temperature to 900 °C at a heating rate of 5 °C / min, keep warm for 3 h, then turn off the power supply, and then naturally cool to room temperature to obtain the S-MB ceramic composite material.

[0060] Step 6: Process the S-MB ceramic composite material prepared in this example into specimens with corresponding sizes according to requirements for dielectric constant and reflectivity tests. The required specimens include: (1) coaxial method annular test specimen: outer diameter 7 mm, inner diameter 3 mm; (2) high-temperature reflectivity test method specimen: 180 mm×180 mm×3 mm.

[0061] Example 4 Step 1: Place the five kinds of nanoscale ultra-high temperature boride ceramic powders of ZrB2, TiB2, NbB2, HfB2, and TaB2 in alumina crucibles respectively, and then transfer them into a resistance wire heating type heat treatment furnace. In a flowing Ar atmosphere, heat from room temperature to 600 °C at a heating rate of 5 °C / min, keep the temperature for 3 h, then turn off the power supply, and then naturally cool to room temperature to obtain the heat-treated ceramic powders.

[0062] Step 2: Weigh the ZrB2, TiB2, NbB2, HfB2, and TaB2 after heat treatment in Step 1 according to the mass ratio. The mass ratio of the ZrB2, TiB2, NbB2, HfB2, and TaB2 powders is 1:1:2:1:7. Then place them all in a ball mill and conduct ball milling for 3 h to make the five kinds of boride ceramic powders evenly mixed, and obtain the MB mixed powder.

[0063] Step 3: Weigh the MB mixed powder and liquid polysiloxane (PSO) according to the mass ratio of 1:1. Add the MB mixed powder into the PSO and stir magnetically for 12 h and then disperse ultrasonically for 6 h to obtain a uniform blend slurry; place the blend slurry in an alumina crucible, in a flowing Ar atmosphere, heat to 140 °C at a heating rate of 5 °C / min, keep the temperature for 2 h, and then naturally cool to room temperature to complete the cross-linking reaction and obtain the cross-linked material.

[0064] Step 4: Grind the cross-linked material in a planetary ball mill and then pass it through a 200-mesh sieve to obtain ceramic composite powder with uniform particle size; press the ceramic composite powder. The pressing uses a hydraulic press to press the powder into two specifications of specimens, including: annular specimen: inner diameter 3 mm, outer diameter 12 mm, height 3 mm; flat specimen: 240 mm×240 mm×5 mm.

[0065] Step 5: Put the pressed ceramic composite material into a heat treatment furnace with a resistance wire as the heating element. In a flowing Ar atmosphere, heat from room temperature to 1000 °C at a heating rate of 5 °C / min, keep the temperature for 2.5 h, then turn off the power supply, and then naturally cool to room temperature to obtain the S-MB ceramic composite material.

[0066] Step 6: Process the S~MB ceramic composite material prepared in this example into specimens with corresponding sizes according to requirements for dielectric constant and reflectivity tests. The required specimens include: (1) coaxial method annular test specimen: outer diameter 7 mm, inner diameter 3 mm; (2) high-temperature reflectivity test method specimen: 180 mm×180 mm×3 mm.

[0067] Example 5 Step 1: Place the five kinds of nanoscale ultra-high temperature boride ceramic powders of ZrB2, TiB2, NbB2, HfB2, and TaB2 in alumina crucibles respectively, and then transfer them into a resistance wire heating type heat treatment furnace. In a flowing Ar atmosphere, heat from room temperature to 550 °C at a heating rate of 5 °C / min, keep warm for 3 h, then turn off the power supply, and then naturally cool to room temperature to obtain the heat-treated ceramic powders.

[0068] Step 2: Weigh the ZrB2, TiB2, NbB2, HfB2, and TaB2 after heat treatment in Step 1 according to the mass ratio. The mass ratio of the ZrB2, TiB2, NbB2, HfB2, and TaB2 powders is 1:1:5:2:10. Then place them all in a ball mill for ball milling for 3 h to make the five kinds of boride ceramic powders evenly mixed and obtain the MB mixed powder.

[0069] Step 3: Weigh the MB mixed powder and liquid polysiloxane (PSO) according to the mass ratio of 3:2. Add the MB mixed powder to the PSO and stir magnetically for 12 h and then disperse ultrasonically for 6 h to obtain a uniform blend slurry; place the blend slurry in an alumina crucible. In a flowing Ar atmosphere, heat to 130 °C at a heating rate of 5 °C / min, keep warm for 2 h, and then naturally cool to room temperature to complete the cross-linking reaction and obtain the cross-linked material.

[0070] Step 4: Grind the cross-linked material in a planetary ball mill and then pass it through a 200-mesh sieve to obtain ceramic composite powder with uniform particle size; press the ceramic composite powder. The pressing uses a hydraulic press to press the powder into two specifications of specimens, including: ring specimen: inner diameter 3 mm, outer diameter 12 mm, height 3 mm; flat specimen: 240 mm×240 mm×5 mm.

[0071] Step 5: Put the pressed ceramic composite material into a heat treatment furnace with a resistance wire as the heating element. In a flowing Ar atmosphere, heat from room temperature to 1000 °C at a heating rate of 5 °C / min, keep warm for 2 h, then turn off the power supply, and then naturally cool to room temperature to obtain the S-MB ceramic composite material.

[0072] Example 6 Step 1: Place the five kinds of nanoscale ultra-high temperature boride ceramic powders of ZrB2, TiB2, NbB2, HfB2, and TaB2 in alumina crucibles respectively, and then transfer them into a resistance wire heating type heat treatment furnace. In a flowing Ar atmosphere, heat from room temperature to 800 °C at a heating rate of 5 °C / min, keep warm for 1 h, then turn off the power supply, and then naturally cool to room temperature to obtain the heat-treated ceramic powders.

[0073] Step 2: Weigh ZrB2, TiB2, NbB2, HfB2, and TaB2 after heat treatment in Step 1 according to the mass ratio. The mass ratio of ZrB2, TiB2, NbB2, HfB2, and TaB2 powders is 1:1:2:1:7. Then place them all in a ball mill and conduct ball milling for 2 h to make the five boride ceramic powders evenly mixed, thus obtaining the MB mixed powder.

[0074] Step 3: Weigh the MB mixed powder and liquid polysiloxane (PSO) according to the mass ratio of 1:3. Add the MB mixed powder to PSO and stir magnetically for 12 h, then disperse ultrasonically for 6 h to obtain a uniform blend slurry. Place the blend slurry in an alumina crucible, and in a flowing Ar atmosphere, heat it to 300 °C at a heating rate of 5 °C / min, keep it warm for 1 h, and then cool it naturally to room temperature to complete the cross-linking reaction and obtain the cross-linked material.

[0075] Step 4: Grind the cross-linked material in a planetary ball mill and then pass it through a 200-mesh sieve to obtain ceramic composite powder with uniform particle size. Press the ceramic composite powder. The pressing is to press the powder into two types of specimens using a hydraulic press, including: annular specimen: inner diameter 3 mm, outer diameter 12 mm, height 3 mm; flat specimen: 240 mm × 240 mm × 5 mm.

[0076] Step 5: Put the pressed ceramic composite material into a heat treatment furnace with a resistance wire as the heating element. In a flowing Ar atmosphere, heat it from room temperature to 800 °C at a heating rate of 5 °C / min, keep it warm for 4 h, then turn off the power supply, and then cool it naturally to room temperature to obtain the S-MB ceramic composite material.

[0077] Example 7 Step 1: Place the five kinds of nano-scale ultra-high temperature boride ceramic powders of ZrB2, TiB2, NbB2, HfB2, and TaB2 in alumina crucibles respectively, and then transfer them into a resistance wire heating type heat treatment furnace. In a flowing Ar atmosphere, heat it from room temperature to 600 °C at a heating rate of 5 °C / min, keep it warm for 4 h, then turn off the power supply, and then cool it naturally to room temperature to obtain the heat-treated ceramic powders.

[0078] Step 2: Weigh ZrB2, TiB2, NbB2, HfB2, and TaB2 after heat treatment in Step 1 according to the mass ratio. The mass ratio of ZrB2, TiB2, NbB2, HfB2, and TaB2 powders is 1:1:2:1:7. Then place them all in a ball mill and conduct ball milling for 2 h to make the five boride ceramic powders evenly mixed, thus obtaining the MB mixed powder.

[0079] Step 3: Weigh the MB mixed powder and liquid polysiloxane (PSO) according to a mass ratio of 3:1. Add the MB mixed powder to PSO and stir magnetically for 12 h, then disperse ultrasonically for 6 h to obtain a uniform blend slurry. Place the blend slurry in an alumina crucible, and in a flowing Ar atmosphere, heat it to 100 °C at a rate of 5 °C / min, hold for 2 h, and then cool naturally to room temperature to complete the cross-linking reaction and obtain the cross-linked material.

[0080] Step 4: Grind the cross-linked material in a planetary ball mill and then pass it through a 200-mesh sieve to obtain ceramic composite powder with uniform particle size. Press the ceramic composite powder. The pressing uses a hydraulic press to press the powder into two types of specimens with specific specifications, including: annular specimen: inner diameter 3 mm, outer diameter 12 mm, height 3 mm; flat specimen: 240 mm×240 mm×5 mm.

[0081] Step 5: Place the pressed ceramic composite material in a heat treatment furnace with a resistance wire as the heating element. In a flowing Ar atmosphere, heat it from room temperature to 1000 °C at a heating rate of 5 °C / min, hold for 2.5 h, then turn off the power, and subsequently cool naturally to room temperature to obtain the S-MB ceramic composite material.

[0082] Comparative example: Preparation method of SiOC-unit boride ceramic composite material: Step 1: Mix 5 different boride ceramics (ZrB2, TiB2, NbB2, HfB2, TaB2) with liquid polysiloxane (PSO) according to a mass ratio of 2:3 respectively. Add the five ceramic powders to PSO respectively and stir magnetically for 12 h, then disperse ultrasonically for 6 h to obtain five uniform blend slurries. Place the five blend slurries in alumina crucibles respectively, and in a flowing Ar atmosphere, heat them to 160 °C at a rate of 5 °C / min, hold for 2 h, and then cool naturally to room temperature to complete the cross-linking reaction and obtain five cross-linked materials.

[0083] Step 2: Grind the five cross-linked materials in a planetary ball mill respectively and then pass them through a 200-mesh sieve to obtain five ceramic composite powders with uniform particle size. Press the five ceramic composite powders respectively. The pressing uses a hydraulic press to press the powder into a specific specification annular specimen: inner diameter 3 mm, outer diameter 12 mm, height 3 mm.

[0084] Step 3: Place the five pressed ceramic composite materials in a heat treatment furnace with a resistance wire as the heating element. In a flowing Ar atmosphere, heat them from room temperature to 1000 °C at a heating rate of 5 °C / min, hold for 2 h, then turn off the power, and subsequently cool naturally to room temperature to obtain S-ZrB2 ceramic composite material, S-TiB2 ceramic composite material, S-NbB2 ceramic composite material, S-HfB2 ceramic composite material, and S-TaB2 ceramic composite material respectively.

[0085] Step 4: Process the five prepared SiOC-unit boride ceramic composites into specific specifications for coaxial method dielectric testing. Specifications: outer diameter 7 mm, inner diameter 3 mm.

[0086] Figure 1 XRD patterns corresponding to Examples (1)-(4). It can be seen from the figure that the PDC-SiOC ceramics pyrolyzed at low temperature are amorphous and have no obvious characteristic diffraction peaks. In addition, the XRD refined patterns show the diffraction peaks of the pentaboride ceramics (ZrB2, TiB2, NbB2, HfB2, TaB2), proving the successful synthesis of the S-MB ceramic composites.

[0087] Figure 2 (a) is the micrograph of the S-MB ceramic composite of Example 4. It can be seen that there are a large number of pores in the PDC-SiOC matrix. During the transformation of SiOC from polymer to ceramic, the rapid release of gaseous by-products causes local pressure imbalance, resulting in stress concentration, and pores and cracks are formed during the material shrinkage process. Figure 2 (b)-(e) are the backscattered electron scanning photographs, energy dispersive spectroscopy (EDS) photographs, and corresponding area scanning element analysis and point scanning element analysis of the S-MB ceramic composite corresponding to Example 4, respectively. It can be proved from the figure that the multi-boride absorbent has been successfully introduced.

[0088] Figure 3 (a)-(c) are the test result comparisons of the real part, imaginary part, and tangent of loss angle of the five SiOC-unit boride ceramic composites prepared in the comparative example. It can be seen from the figure that the dielectric dispersion characteristics are not obvious. Figure 3 (d)-(e) are the test result comparisons of the real part and imaginary part values of the S-MB ceramic composites containing different proportions of multi-borides prepared in Examples (1)-(4); according to the test results, the introduction of multi-borides effectively regulates the dispersion characteristics of the ceramic composites, and the value of the real part of the dielectric decreases rapidly with the increase of frequency.

[0089] Figure 4 (a)-(e) are the electromagnetic wave absorption performances of the S-MB ceramic composites containing different proportions of multi-borides in Examples (1)-(4) tested by the coaxial method. Taking -10 dB as the standard for the material to achieve effective electromagnetic wave absorption, it can be seen that different S-MB ceramic composites exhibit excellent electromagnetic wave absorption performances. Among them, the best EAB of the S-MB ceramic composite in Example 4 can reach 10.08 GHz, and the lowest reflection loss is as low as -57.02 dB, which means that 99.999% of the electromagnetic waves are loss-absorbed. Compared with the electromagnetic wave absorption ability of the five SiOC-unit boride ceramic composites in the comparative example, such asFigure 4 (f)-(k), the electromagnetic wave absorption properties of the S-MB ceramic composites prepared in Examples (1)-(4) have been significantly improved.

[0090] Figure 5 (a) shows the room-temperature absorption properties of the S-MB ceramic composite of Example 4 tested by the high-temperature reflection method in the range of 2-40 GHz. The EAB can reach 26.98 GHz, and the thickness is only 2.8 mm. Figure 5 (b) shows the high-temperature absorption properties of the S-MB ceramic composite of Example 4 from room temperature to high temperature of 1473 K. The EAB is stable at 11.95 GHz - 12.03 GHz in the temperature range of 298 K - 873 K, and can still maintain a broadband absorption ability of 7.54 GHz - 7.70 GHz in the high-temperature range of 1073 K - 1473 K, exceeding other reported high-temperature wave-absorbing materials at present, and achieving a breakthrough in temperature.

[0091] In summary, introducing multi-component ultra-high-temperature boride ceramics into PDC-SiOC ceramics to construct multiple heterogeneous interfaces in the present invention can not only enhance the interfacial polarization effect of the composite material to improve the dielectric dispersion characteristics, but also provide additional variables for comprehensively optimizing and designing dielectric properties.

[0092] The endpoints and any values within the ranges disclosed in the present invention are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and a single point value, and between single point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein. In the following text, in principle, the various technical solutions can be combined with each other to obtain new technical solutions, which should also be regarded as specifically disclosed herein.

[0093] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art can still modify the specific implementation manners of the present invention or make equivalent replacements. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the scope of the claims of the present invention pending approval.

Claims

1. A multi-boride enhanced tunable dielectric polymer converted ceramic-based high-temperature microwave absorbing material, characterized in that, The ceramic-based high-temperature wave-absorbing material includes polymer-derived SiOC ceramics and multi-component ultra-high-temperature boride ceramics. The ceramic-based high-temperature wave-absorbing material uses polymer-derived SiOC ceramics as the matrix, and the multi-component ultra-high-temperature boride ceramics are uniformly dispersed in the polymer-derived SiOC ceramics.

2. The adjustable dielectric polymer converted ceramic-based high-temperature wave-absorbing material reinforced by a multi-boride according to claim 1, characterized in that The multi-component ultra-high-temperature boride ceramics include ZrB2, TiB2, NbB2, HfB2, and TaB2.

3. A preparation method of a multi-boride enhanced adjustable dielectric polymer converted ceramic-based high-temperature wave-absorbing material according to any one of claims 1 or 2, characterized in that, It includes: Placing the powders of ZrB2, TiB2, NbB2, HfB2, and TaB2 in an inert atmosphere for the first heat treatment respectively; Mixing the ZrB2, TiB2, NbB2, HfB2, and TaB2 after the first heat treatment according to a preset mass ratio, and performing ball milling to obtain an MB mixed powder; Mixing the MB mixed powder and liquid polysiloxane evenly according to a preset mass ratio to obtain a blended slurry, and performing the second heat treatment on the blended slurry in an inert atmosphere to obtain a cross-linked material; Performing ball milling and sieving on the cross-linked material to obtain a ceramic composite material; Performing sample pressing on the ceramic composite material, and performing the third heat treatment on the ceramic composite material after sample pressing in an inert atmosphere to prepare an S-MB ceramic composite material.

4. The preparation method of the multi-boride enhanced tunable dielectric polymer converted ceramic-based high-temperature wave-absorbing material according to claim 3, wherein, The mass ratio of the ZrB2, TiB2, NbB2, HfB2, and TaB2 powders is (1~10):(1~10):(1~10):(1~10):(1~10).

5. The preparation method of the multi-boride enhanced tunable dielectric polymer converted ceramic-based high-temperature wave-absorbing material according to claim 3, characterized in that, The mass ratio of the MB mixed powder and liquid polysiloxane is (1~3):(1~3).

6. The preparation method of the multi-boride enhanced tunable dielectric polymer converted ceramic-based high-temperature wave-absorbing material according to claim 3, characterized in that, The specific process of the first heat treatment is: Heating at a heating rate of 5 °C / min to 400~800 °C, holding for 1~4 h, and then naturally cooling to room temperature.

7. The preparation method of the multi-boride enhanced tunable dielectric polymer converted ceramic-based high-temperature wave-absorbing material according to claim 3, characterized in that, The specific process of the second heat treatment is: Heating at a heating rate of 5 °C / min to 100~300 °C, holding for 0.5~2 h, and then naturally cooling to room temperature.

8. The preparation method of the multi-boride enhanced tunable dielectric polymer converted ceramic-based high-temperature wave-absorbing material according to claim 3, characterized in that, The specific process of the third heat treatment is: Heating at a heating rate of 5 °C / min to 800~1000 °C, holding for 1~4 h, and then naturally cooling to room temperature.

9. The preparation method of the multi-boride enhanced tunable dielectric polymer converted ceramic-based high-temperature wave-absorbing material according to claim 3, characterized in that, The particle size of the ceramic composite material is less than 200 mesh.

10. Application of the multi-boride-reinforced tunable dielectric polymer-derived ceramic-based high-temperature wave-absorbing material according to any one of claims 1 or 2 on an aircraft.

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