SiC loaded LDH nanocomposite, preparation method thereof and application of the nanocomposite as wave-absorbing anticorrosion material

Abstract

This invention discloses a SiC-supported LDH nanocomposite material, its preparation method, and its application as a microwave absorbing and corrosion-resistant material. The SiC-supported LDH nanocomposite material has a core-shell structure, wherein the core is silicon carbide nanowires and the shell is a layered bimetallic hydroxide doped with a third metal. nw The loading of the third metal-doped layered bimetallic hydroxide is 43.1%–168%. This invention improves the microwave absorption performance of the composite material by adjusting the LDH shell content and doping the LDH with cobalt to form a ternary LDH. Furthermore, the core-shell structure of the SiC-loaded LDH nanocomposite not only provides multiple scattering conditions for microwaves but also acts as a physical barrier, extending the corrosion path and acting as a labyrinth effect to hinder the intrusion of corrosive media. Moreover, the LDH memory effect and anion exchange effect further resist chloride ion intrusion, achieving a lightweight, integrated application of microwave absorption and corrosion protection.

Description

Technical Field

[0001] This invention belongs to the field of microwave absorbing materials technology, and relates to a SiC-supported LDH nanocomposite material, its preparation method, and its application as a microwave absorbing and anti-corrosion material. Background Technology

[0002] With the rapid development of information technology, electronic devices that rely on electromagnetic waves as information carriers are widely used in various fields. In particular, the achievements of modern science and technology have promoted the improvement of ship automation. More and more electronic devices are being used in wireless electronic communication, navigation, radar, etc., bringing great convenience, but also generating a lot of microwave pollution. This not only harms the environment and human health, but also has a serious adverse impact on the normal operation of equipment and information technology security. Therefore, the current problem can be solved from the perspective of materials. Microwave absorbing materials (referred to as microwave absorbing materials) can effectively absorb incident electromagnetic waves and convert them into heat energy or other forms of energy through the magnetic / dielectric loss mechanism of the material, thereby achieving protection against electromagnetic radiation pollution. Microwave absorbing materials occupy an increasingly larger space in marine vessels, including for ensuring the normal operation of instruments and personal protection, as well as for military applications such as stealth technology development and information technology security. They are used in various advanced weapons and electronic products. However, due to the long-term exposure of ships and warships to the marine environment, such as humidity, high seawater salinity, rain, waves, salt spray, and other environmental factors, the performance of shipboard electronic equipment deteriorates and fails due to corrosion of metal materials, leading to a gradual increase in the cost of equipment maintenance. Therefore, traditional microwave absorbing materials (thin, light, wide, and strong) can no longer meet the demands of complex marine environmental changes. The manufacture of corrosion-resistant microwave absorbing materials with dual functionalities has become a focus of attention. Consequently, the research on corrosion-resistant microwave absorbing materials has become a popular and important research subject, and is also an inevitable result of the rapid development of information technology in my country.

[0003] Currently, the synergistic effect of magnetic and dielectric loss materials to improve impedance matching is considered an effective way to enhance electromagnetic wave absorbing materials. However, studies have shown that magnetic loss absorbing materials suffer from defects such as poor corrosion resistance, easy oxidation, high density, and significant eddy current loss and skin effect on their surface, leading to electromagnetic wave reflection. Furthermore, magnetic absorbing materials can mask the performance of dielectric loss absorbing materials, greatly limiting the practical application of traditional electromagnetic wave absorbing materials in the environment. Therefore, novel electromagnetic wave absorbers are emerging, exhibiting good environmental adaptability.

[0004] Silicon carbide (SiC) has attracted widespread attention as a special dielectric material due to its excellent properties, including higher mechanical strength, high-temperature chemical stability, low density, and a commendable wide absorption band. In particular, silicon carbide nanowires (SiC...)nw Due to its high aspect ratio and anisotropy, SiC exhibits better microwave absorption performance. However, single SiC... nw The inability to meet the requirements for novel microwave absorbing materials is due to limitations imposed by the single-polarization mechanism and low conductivity losses. To date, researchers have employed numerous strategies to enhance SiC. nw Microwave absorption properties. For example, in SiC nw Doping with N, C, B, and other nonmetallic elements causes lattice distortion, induces defects, and optimizes electromagnetic wave absorption performance; increasing magnetic loss enhances impedance matching and optimizes absorption performance, as seen in Fe / SiC and Ni@SiC. However, while these additives and modification methods can enhance SiC to some extent... nw The microwave absorption properties of SiC are good, but this often makes SiC... nw It is denser and more susceptible to corrosion. However, if we simply increase the density of SiC... nw The corrosion resistance of SiC may lead to further corrosion problems. nw The inherent microwave absorption properties of SiC decrease, therefore, improving SiC's absorption performance is crucial. nw There is a dilemma regarding the balance between microwave absorption properties and corrosion resistance of SiC. Therefore, how to maintain the desired microwave absorption and corrosion resistance is a key challenge. nw It is desirable to preserve the inherent microwave absorption properties of a substance while protecting it from corrosion by chloride ions in seawater.

[0005] In addition, for a single SiC nw Materials often have many limitations, such as simple structure, limited functionality, and difficulty in parameter adjustment, which prevent them from meeting environmental adaptability requirements. Therefore, it is desirable to prepare a high-performance composite material that allows for easy adjustment of the dielectric constant and control of the loading to achieve a significant improvement in material performance.

[0006] The present invention aims to solve the above-mentioned problems. Summary of the Invention

[0007] This invention aims to overcome the shortcomings of existing technologies and to improve the performance of SiC. nw The present invention presents a dilemma regarding the balance between microwave absorption performance and corrosion resistance. nw As a carrier, LDH is coated onto SiC nwOn the surface, a core-shell structure of SiC-loaded LDH nanocomposite material with a silicon carbide nanowire core and a third metal-doped layered bimetallic hydroxide shell is prepared. This invention achieves superior microwave absorption performance by adjusting the LDH shell content in the composite material and doping the LDH with cobalt to form a ternary LDH, thereby enhancing the dielectric loss mechanism and optimizing impedance matching of the composite material. Furthermore, the complex and dense 3D spatial structure of the SiC-loaded LDH nanocomposite material not only provides multiple scattering conditions for microwaves but also acts as a physical barrier, extending the corrosion path and acting as a labyrinth effect to hinder the intrusion of corrosive media. Moreover, the LDH memory effect and anion exchange effect further resist chloride ion intrusion, realizing a lightweight, microwave-absorbing, and corrosion-resistant dual-function integrated application.

[0008] The technical solution adopted in this invention is as follows:

[0009] The first aspect of this invention provides a SiC-supported LDH nanocomposite material with a core-shell structure, wherein the core is silicon carbide nanowires (SiC). nw The shell is a layered bimetallic hydroxide doped with a third metal, based on SiC. nw The quality of the third metal-doped layered bimetallic hydroxide is such that the loading of the third metal-doped layered bimetallic hydroxide is 43.1%-168%. This invention is based on SiC. nw In-situ growth of LDH, therefore relative to SiC nw The mass of SiC and the LDH loading are calculated as follows: Subtract the mass of SiC before reaction from the mass of the SiC-loaded LDH nanocomposite after the reaction. nw The mass, then divided by SiC nw The quality.

[0010] Preferably, the silicon carbide nanowires have a diameter of 0.1-0.6 μm, a length of 50-100 μm, and an aspect ratio of 100-200.

[0011] Preferably, the third metal-doped layered bimetallic hydroxide is a Co-doped NiFe layered bimetallic hydroxide, and the mass percentage of Co is 25% based on the total mass of the metal cations in the Co-doped NiFe layered bimetallic hydroxide. The molar ratio of nickel nitrate, cobalt nitrate, and iron nitrate is 2:1:1.

[0012] A second aspect of the present invention provides a method for preparing the SiC-supported LDH nanocomposite material described in the first aspect of the present invention, characterized by comprising the following steps:

[0013] (1) Disperse silicon carbide nanowires in a polytetrafluoroethylene liner containing deionized water and stir to obtain a silicon carbide suspension.

[0014] (2) Add nickel nitrate, cobalt nitrate, ferric nitrate, 0.173g urea and trisodium citrate to the silicon carbide suspension obtained in step (1), stir, and obtain a mixed solution;

[0015] (3) The mixed solution obtained in step (2) is reacted in a rotary oven. After the reaction is completed, it is cooled to room temperature, centrifuged and washed, and then the mixture is dried to obtain the SiC-supported LDH nanocomposite material.

[0016] Preferably, in step (1), the ratio of silicon carbide nanowires to deionized water is 1.23-1.53 ​​mg / ml water; and the mixture is stirred ultrasonically for 20-30 minutes.

[0017] Preferably, in step (2), the molar ratio of nickel nitrate, cobalt nitrate, ferric nitrate, urea and trisodium citrate is 2:1:1.

[0018] Preferably, in step (2), the total amount of metal cations fed is 0-1.6 mmol and not 0, the amount of urea added is 2.9 mmol, and the amount of trisodium citrate added is 0.16 mmol; the stirring time is 15 min-30 min.

[0019] Preferably, in step (3), the temperature of the rotary oven is 160-180℃; the reaction time is 18-24h; the centrifugal washing method is: centrifugation and washing with deionized water and ethanol three to four times, with ethanol used for the last wash; the drying temperature is 60-70℃; and the drying time is 8-12h.

[0020] The third aspect of the present invention provides an application of the SiC-supported LDH nanocomposite material described in the first aspect of the present invention as a microwave absorbing and anti-corrosion material. Specifically, it can be used as an integrated microwave absorbing and anti-corrosion coating.

[0021] The fourth aspect of the present invention provides a method for improving the corrosion resistance of silicon carbide nanowire microwave absorbing materials, characterized in that a third metal-doped layered bimetallic hydroxide is loaded onto silicon carbide nanowires using the preparation method described in the second aspect of the present invention, forming a core-shell composite material with silicon carbide nanowires as the core and a third metal-doped layered bimetallic hydroxide as the shell.

[0022] The performance tests of the SiC-supported LDH nanocomposite materials prepared by this invention include microwave absorption capacity testing and corrosion resistance testing:

[0023] Microwave absorption capacity test method:

[0024] This experiment measures electromagnetic parameters by immersing the prepared sample in dilute polydimethylsiloxane (PDMS, Sylgard 184, Dow Corning). The test sample and PDMS are cured to form a coaxial ring, and then the absorption parameters are measured. Table 1 shows that SiC… nw @LDH and PDMS are mixed and pressed into a coaxial ring, ensuring that each coaxial ring contains the same mass of SiC. nw SiC can be obtained nw The LDH under load, with a weight of 65 mg SiC nw @LDH3, 46.375mg SiC nw @LDH2, 35.775mg SiC nw @LDH1, 25mg SiC nw (SiC composite material with a filler ratio of 3%) nw @LDH and 97% PDMS; coaxial ring: outer diameter, 7.0 mm, inner diameter, 3.0 mm). The complex permeability (μ) of the composite material was measured in the frequency range of 2-18 GHz using a vector network analyzer (Agilent VNA, HP8722D). r =μ'-jμ”) and complex permittivity (ε r =ε'-jε”). According to classical transmission line theory, the formula for calculating reflection loss (RL) is as follows:

[0025]

[0026]

[0027] Z in Z0 is the input impedance of the material, f is the impedance of the air, d is the frequency of the electron wave, and c is the thickness of the absorbing sample.

[0028] Preparation and anti-corrosion performance testing of anti-corrosion coatings:

[0029] (1) Coating preparation: Q235 steel plate (100mm×100mm×2mm) was polished on 400, 600, 1000, and 1200 grit sandpaper, respectively, and then ultrasonically cleaned in aqueous alcohol for 20 minutes to obtain a clean and smooth surface. 1.5g of epoxy resin and 1.5g of curing agent were dissolved in 10ml of ethyl acetate solution, and then 0%, 0.3%, 0.5%, and 0.7% SiC by mass ratio were added. nw@LDH2 filler was heated and stirred to obtain a homogeneous solution. The solution was sprayed onto a polished substrate using a spray gun, and then cured in stages at 120°C for 5 hours and 180°C for 1 hour to obtain a cured coating with an average thickness of 100±8 μm. The coating was specified as pure epoxy resin (0%), with 0.3 wt.% SiC. nw @LDH2, 0.5 wt.% SiC nw @LDH2, 0.7wt.% SiC nw @LDH2.

[0030] (2) Corrosion Resistance Testing: In marine environments, absorbers must possess not only excellent electron flow dissipation performance but also excellent corrosion resistance. Electrochemical impedance spectroscopy (EIS) data were measured using a three-electrode system and an electrochemical workstation (Chenhua, CHI 660E) in the frequency range of 100 kHz to 0.01 Hz for SiC… nw The corrosion resistance of @LDH2 was evaluated. A saturated calomel electrode was used as the reference electrode, and a platinum sheet as the counter electrode. The working electrode was placed in a homogeneous solution of 3.5 wt.% NaCl to simulate a seawater environment (exposed area of ​​4π cm²). 2 Soaking times are 10, 20, and 30 days.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. This invention uses SiC nw As a carrier, LDH is coated onto SiC nw On the surface, a core-shell structure of SiC-supported LDH nanocomposite material with a silicon carbide nanowire core and a third metal-doped layered bimetallic hydroxide shell was prepared.

[0033] For a single SiC nw To address the problem of poor corrosion resistance in materials, this invention first considered combining LDH and silicon carbide. Layered double hydroxides (LDH), also known as hydrotalcite compounds, have attracted widespread attention as a typical two-dimensional layered negative ion clay material. They consist of a positively charged host layer and interlayer anions. Their general formula is [M... 2+ 1-x M 3+ x(OH)2] x+ [A n- ] x / n ·mH2O, where M 2+ M 3+ A n-These represent divalent metal cations, trivalent metal cations, and interlayer anions, respectively. LDH has advantages such as low cost, tunable morphology, controllable composition and structure, exchangeability of interlayer anions, abundant interfaces, and structural stability. Combining LDH with silicon carbide can improve the corrosion resistance of silicon carbide to a certain extent.

[0034] However, LDH, as a discontinuous two-dimensional powder material, suffers from poor conductivity, poor microwave absorption performance, and a tendency to agglomerate, resulting in poor dispersibility in epoxy coatings. To address these issues, this invention further incorporates cobalt metal with a similar ionic radius to form a ternary metal LDH. Through the synergistic effect between the dopant metal and the host metal, the electronic structure of the original binary LDH is effectively adjusted, stimulating more active sites and enhancing the material's conductivity. More importantly, NiCoFe LDH itself is a magnetic material, exhibiting both dielectric and magnetic losses, which contributes to microwave attenuation. Furthermore, while the corrosion resistance of ternary LDH is similar to that of binary LDH, NiCoFe LDH demonstrates stronger microwave attenuation capabilities. Additionally, NiCoFe LDH possesses a unique 3D layered spatial structure, providing a large specific surface area and abundant interfaces. This not only offers multiple scattering and strong polarization relaxation energy to further attenuate microwave loss but also acts as a physical barrier, extending the corrosion path and acting as a maze effect to hinder the intrusion of corrosive media. Unlike traditional nano-trap LDH, it incorporates CO3... 2- LDH is difficult to exchange with chloride ions, but conversely, it is more resistant to chloride ion intrusion, achieving highly efficient corrosion-resistant applications. This invention employs a one-step hydrothermal method on SiC... nw In-situ growth of low-conductivity LDH on SiC can serve as an excellent microwave absorbing carrier, dispersing LDH on SiC and encapsulating it to form a well-dispersed and uniform morphology, which can solve the problem of LDH being prone to agglomeration.

[0035] In summary, this invention employs a one-step hydrothermal method for SiC nw A core-shell structured SiC was synthesized by in-situ growth of low-conductivity LDH. nw @LDH composite material. By adjusting the LDH shell content in the composite material and doping LDH with cobalt metal to form ternary LDH, the dielectric loss mechanism of the composite material is enhanced and impedance matching is optimized to achieve superior microwave absorption performance. Furthermore, the core-shell structure of the SiC-supported LDH nanocomposite material with a complex and dense 3D spatial structure not only provides multiple scattering conditions for microwaves and extends the erosion path of corrosive media, but also allows LDH to... nwA passivation film forms on the material surface, protecting the metal from corrosion. Most importantly, the LDH film, acting as a protective barrier, exposes fewer active sites that readily adsorb chlorides. Therefore, the electrode potential must shift towards a more positive state to adsorb chlorides from the negative electrode, driving these chlorides to move towards the surface of the metal material. This ultimately leads to a higher pitting potential, causing pitting corrosion, thereby reducing the risk of galvanic corrosion, enhancing the corrosion resistance of the composite material, and meeting the requirements of the service environment.

[0036] 2. When the filler ratio is only 3%, SiCnw@LDH2 exhibits significant electro-microwave absorption performance, with a minimum reflection loss of -22.27 dB and an effective bandwidth of up to 6.19 GHz at 2.47 mm. Furthermore, EIS data analysis shows that when only 0.5% filler is added to the epoxy coating, SiC... nw @LDH2 exhibits the best corrosion resistance, its |Z| 0.01Hz Maintained at 7.8×10 for 30 days 9 Ω·cm 2 It is two orders of magnitude better than pure epoxy coating. Attached Figure Description

[0037] Figure 1 For novel SiC nw X-ray diffraction pattern (a) and infrared spectrum (b) of @LDH nanocomposite material.

[0038] Figure 2 For novel SiC nw X-ray photoelectron spectroscopy of @LDH nanocomposites.

[0039] Figure 3 For novel SiC nw Scanning electron microscope (SEM) images of LDH nanocomposites, (a) pure SiC nw (b)SiC nw @LDH3;(c)SiC nw @LDH2;(d)SiC nw @LDH1.

[0040] Figure 4 For novel SiC nw Vibrational sample magnetometer (VSM) of @LDH nanocomposite material.

[0041] Figure 5 For novel SiC nw @LDH nanocomposite material reflection loss and EAB performance diagram, (a, e) pure SiC nw ;(b,f)SiC nw @LDH3;(c,g)SiC nw @LDH2;(d,h)SiC nw@LDH1; (i, j) pure ternary NiCoFe LDH; (k, l) SiC nw @binary NiFe LDH2.

[0042] Figure 6 represents the dielectric constant and magnetic permeability of the composite material.

[0043] Figure 7 For novel SiC nw Attenuation constant and impedance diagram of @LDH nanocomposite material.

[0044] Figure 8 For novel SiC nw @LDH nanocomposite Bode plot (ad) and Nyquist plot (df).

[0045] Figure 9 For salt spray testing, the scratched composite coating sample was immersed in salt water for 10 days. Detailed Implementation

[0046] The present invention will be further described below through embodiments, but is not limited to these embodiments. Experimental methods not specifically described in the embodiments generally use conventional conditions and conditions described in manuals, or conditions recommended by the manufacturer. The general equipment, materials, reagents, etc., used are all commercially available unless otherwise specified.

[0047] The specific steps of the method described in this invention are as follows:

[0048] (1) Disperse 80 mg of silicon carbide nanowires in a polytetrafluoroethylene (PTFE) liner containing 65 mL of deionized water, with a volume of 100 mL, and stir with ultrasonic magnetic force for 10 minutes to obtain a silicon carbide suspension.

[0049] (2) Nickel nitrate (Ni(NO3)2·6H2O), cobalt nitrate (Co(NO3)2·6H2O), ferric nitrate (Fe(NO3)3·9H2O), 0.173g urea (urea, Co(NH2)2) and 0.047g trisodium citrate (TSC, C6H5Na3O7) were subsequently added to the silicon carbide suspension in step (1). The sample was deposited in a 100ml PTFE container and magnetically stirred for 15min to obtain a homogeneous solution.

[0050] (3) The homogeneous solution was reacted in a rotary oven at 180°C for 24 hours. After the reaction was cooled to room temperature, it was washed three to four times by centrifugation with deionized water and alcohol. The resulting mixture was dried at 60°C for 12 hours to obtain the silicon carbide-supported magnetic nickel-cobalt-iron layered bimetallic hydroxide ultrafine magnetic powder. Under the condition of Ni:Co:Fe=2:1:1, the total feed amounts of metal cations were 1.6 mmol, 0.8 mmol, 0.4 mmol, and 0 mmol, respectively. It was named SiC. nw @LDH3,SiC nw @LDH2,SiC nw @LDH1,SiC nw The collected samples were weighed and the weights calculated, as shown in Table 1.

[0051] Table 1: Weight gain rate of SiC nw @LDH

[0052]

[0053]

[0054] For this novel nanocomposite material, the present invention uses analytical methods such as scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy to characterize the chemical composition and morphology of the nanocomposite material. Its absorption performance is tested by using a vector network analyzer through the coaxial method. Electrochemical impedance spectroscopy (EIS) data are measured using a three-electrode system and an electrochemical workstation (Chenhua, CHI 660E).

[0055] Novel SiC nw Characterization of LDH nanocomposites:

[0056] Figure 1 For novel SiC nw The X-ray diffraction pattern (a) and infrared spectrum (b) of the @LDH nanocomposite reflect the crystal structure, chemical composition, and functional groups of the composite material.

[0057] Figure 1 X-ray diffraction (XRD) analysis was performed on the crystal structures of SiC and SiC@LDH. The XRD patterns showed characteristic diffraction peaks of LDH, including (003), (006), (012), (015), and (018). The positions of the crystal planes were consistent with those on the standard card JCPDS-40-0215, indicating that Co ions were successfully doped into the LDH crystal without altering the crystal structure. The resulting LDH belongs to the hexagonal crystal system. The positions of the characteristic peaks in the XRD spectra of the (003) and (110) crystal surfaces correspond to the interlayer spacing and arrangement of the layered elements, respectively. The intensity of the diffraction peaks reflects the crystallinity and integrity of the crystal.nw The peak intensity of the LDH peak is stronger, while the peak intensity of the LDH peak is weaker. However, with the increase of LDH content, the intensity of the (003), (110) and (113) diffraction peaks gradually increases, indicating that the integrity of the prepared LDH crystal is enhanced.

[0058] Figure 1 The infrared spectrum (FT-IR) shown in b is for SiC. nw Evidence was provided for the efficient formation of LDH. Comparable absorption peaks were observed in all samples across different wavenumber regions, particularly at 803.5 cm⁻¹. -1 and 925.58cm -1 There are two prominent absorption peaks at this point, which are attributed to the transverse optical (TO) photonic and longitudinal optical (LO) phonon vibrational modes of the Si-C single bond. Specifically, SiC nw @LDH2 sample at 3440.22cm -1 and 1629.33cm -1 The strong absorption peaks at 1383.01 cm⁻¹ are attributed to the stretching vibrations of interlayer water molecules and the bending vibrations of crystal water molecules in LDH, respectively. Furthermore, the peak at 1383.01 cm⁻¹ is also significant. -1 The peak value is attributed to interlayer CO3 in the LDH. 2- The stretching vibration of anions. Furthermore, in the range of 654–455 cm⁻¹ -1 The bending vibration modes observed within the range are attributed to the presence of metal-hydroxide complexes, including Ni, Co, and Fe, which include MO, MOM, and M-OH modes.

[0059] Figure 2 For novel SiC nw X-ray photoelectron spectroscopy of @LDH nanocomposites reflects their surface chemical properties and elemental composition.

[0060] XPS spectroscopy revealed the presence of Ni, Co, Fe, C, O, and Si elements in the material. Figure 2 a) where Ni2p:Co2p:Fe2p = 2.5:1:1.4, and Co accounts for approximately 20%. Since XPS is semi-quantitative, this basically matches the proportion of total metal cations in the added LDH (25%). The C1s spectrum was deconvolved into four characteristic peaks: CC (284.8 eV), CO (286.2 eV), C=O (289.1 eV), and Si-C (282.3 eV). Figure 2 As shown in b. Si 2p spectrum ( Figure 2 c) Two peaks are shown at 99.7 eV and 101.9 eV, which are related to Si-C and Si-O-Si, respectively. Figure 2 The Ni 2p spectrum in d exhibits two distinct peaks, Ni 2p 1 / 2(873.2eV) and Ni 2p 3 / 2 (855.1 eV), this is generated by spin-orbit coupling, indicating that Ni 2+ The main components, with satellite peak values ​​at 861.9 eV and 878.7 eV. Figure 2 XPS spectra in e show Co 2p 1 / 2 (795.8 eV) and Co 2p 3 / 2 The binding energy peak of the (780.2 eV) orbital indicates the presence of Co. 2+ The presence of two satellite peaks at 785.9 eV and 802.7 eV indicates that the valence state of Co in LDH is primarily divalent. (Fe 2p orbital spectrum) Figure 2 f) revealed two main peaks: Fe 2p 3 / 2 (712.1eV) and Fe 2p 1 / 2 (723.7 eV), accompanied by binding energies of 717.5 eV and 733.6 eV for their respective satellite peaks, confirming that Fe... 3+ The presence of [something] was confirmed by X-ray photoelectron spectroscopy (XPS) analysis in SiC. nw Co-doped NiFe layered double hydroxide (LDH) was successfully prepared, consistent with the scanning electron microscope (SEM) image shown below. The presence of the core-shell structured SiCnw@LDH composite material has the potential to enhance the performance of pure SiC. nw Impedance matching leads to an increase in the incidence of electromagnetic waves inside the material.

[0061] Figure 3 For novel SiC nw Scanning electron microscope (SEM) images of LDH nanocomposites, (a) pure SiC nw (b)SiC nw @LDH3;(c)SiC nw @LDH2;(d)SiC nw @LDH1 reflects the morphology and structure of the composite material.

[0062] The microstructure of all samples at different magnifications is as follows: Figure 3 As shown in the diagram. Initially, pure silicon carbide has a smooth surface (…). Figure 3 a). LDH is grown using a one-step hydrothermal method, forming a three-dimensional porous core-shell structure. Due to strong electrostatic effects, LDH with a positive surface charge tends to grow parallel to SiC with a negative surface charge. Figure 3 d and d-1), but with the increase of metal cation count and the number of LDH nanosheets, more LDH tends to grow vertically due to electrostatic repulsion, thus producing a special 3D void structure (d and d-1). Figure 3bc). However, when the metal cation feed is 1.6 mM, LDH nanosheets begin to aggregate, leading to a reduction in porosity (in Figure 3 (marked in circle b). Excessive LDH leads to aggregation, while a small amount of LDH does not form this special void space, resulting in a smaller specific surface area and void space, both of which are detrimental to electronic warfare scattering and absorption.

[0063] Figure 4 For novel SiC nw Vibrational sample magnetometer (VSM) plots of the @LDH nanocomposite material reveal that the composite exhibits superparamagnetism with increasing LDH loading, corresponding to very low coercivity and remanence (approximately 0), but high saturation magnetization. (SiC) nw @LDH3 (2.3 emu / g); SiC nw @LDH2 (2.05 emu / g); SiC nw @LDH1 (1.07 emu / g); SiC nw (0.05 emu / g).

[0064] From the XRD, XPS, SEM, VSM, and FT-IR characterization results above, it can be seen that SiC nw Successful preparation of @NiCoFe LDH nanocomposite materials.

[0065] Novel SiC nw Performance testing of LDH nanocomposites:

[0066] Microwave absorption capacity testing method: This experiment measures electromagnetic parameters by immersing the prepared sample in dilute polydimethylsiloxane (PDMS, Sylgard 184, Dow Corning). Table 1 shows that SiC... nw @LDH and PDMS are mixed and pressed into a coaxial line. As shown in Table 1, SiC nw @LDH and PDMS are mixed and pressed into a coaxial ring, ensuring that each coaxial ring contains the same mass of SiC. nw SiC can be obtained nw The LDH under load, with a weight of 65 mg SiC nw @LDH3, 46.375mg SiC nw @LDH2, 35.775mg SiC nw @LDH1, 25mg SiC nw (3% composite SiC) nw@LDH and 97% PDMS; coaxial ring: outer diameter, 7.0 mm, inner diameter, 3.0 mm). The complex permeability (μ) of the composite material was measured in the frequency range of 2-18 GHz using a vector network analyzer (Agilent VNA, HP8722D). r =μ'-jμ”) and complex permittivity (ε r =ε'-jε”). According to classical transmission line theory, the formula for calculating reflection loss (RL) is as follows:

[0067]

[0068]

[0069] Z in Z0 is the input impedance of the material, f is the impedance of the air, d is the frequency of the electron wave, and c is the thickness of the absorbing sample.

[0070] According to calculations, the lower the reflection loss (RL), the stronger the absorber's ability to absorb microwaves. When the reflection loss is below -10dB, it means that it can absorb 90% of the microwaves in that band. The corresponding bandwidth is the effective absorption bandwidth (EAB).

[0071] Figure 5 For novel SiC nw @LDH nanocomposite material reflection loss and EAB performance diagram, (a, e) pure SiC nw ;(b,f)SiC nw @LDH3;(c,g)SiC nw @LDH2;(d,h)SiC nw @LDH1; (i, j) pure ternary NiCoFe LDH; (k, l) SiC nw @binary NiFe LDH2; reflects the microwave absorption performance of this composite material.

[0072] By calculating the reflection loss values ​​of all composite materials, 3D loss maps and 2D planar maps are plotted. Figure 5 A comparative analysis shows that SiC nw @LDH2 exhibits lower reflection loss and a wider effective absorption bandwidth, indicating that the composite material SiC has better performance compared to a single material. nw @LDH2 can improve microwave absorption performance, compared to Figure 5 As can be seen from k and l, the ternary-loaded LDH exhibits superior performance compared to the binary LDH. In conclusion, the SiC composite material… nw@LDH2 has the lowest reflection loss (-22.27dB) and the best microwave absorption performance at a maximum effective absorption bandwidth (6.19GHz) at a thickness of 2.47mm.

[0073] Figure 6 The dielectric constant and permeability of the composite material are given. To further explain the microwave absorption performance of the absorber, the complex dielectric constant (ε) of the material was analyzed. r =ε'-jε”) and complex permeability (μ r =μ'-jμ”). Through Figure 6 The dielectric properties of the absorbing material are analyzed using the complex permittivity in ε', where the real part (ε', μ') and the imaginary part (ε', μ") represent the electromagnetic wave storage capacity and dissipation capacity of the absorbing material, respectively.

[0074] like Figure 6 As shown in ac, on the one hand, compared with pure SiC nw In comparison, SiC nw The high values ​​of ε' and ε” in the @LDH composite material indicate strong dielectric loss and storage capacity, which is due to the high dielectric loss and storage capacity of SiC. nw @LDH possesses a high aspect ratio and a three-dimensional layered structure, synergistically forming a core-shell heterostructure. This structure facilitates an increase in the number of interfaces and stacked dislocations, enabling the accumulation of a large number of charge carriers (holes and electrons). Therefore, this composite structure provides excellent interfacial polarization and dipole polarization capabilities, making the SiC composite material... nw @LDH has a high dielectric constant, demonstrating superior microwave attenuation performance.

[0075] also, Figure 6 c, through tanδ ε (Assessing the inherent dielectric loss capability of a material) indicates that SiC nw @LDH2 exhibits the highest dielectric loss, which may further suggest that too much or too little micromagnetic LDH can lead to agglomeration or uneven distribution in the composite material. This results in fewer interface and spatial voids, leading to a decrease in dielectric loss capability. Therefore, SiC nw @LDH2 composite material has excellent dielectric loss properties.

[0076] from Figure 6 As shown in df, there is a weak magnetism, but the proportion of magnetic loss is small and can be ignored.

[0077] Figure 7 For novel SiC nw Attenuation constant and impedance diagram of @LDH nanocomposite materials. The superior performance of absorbing materials can be judged by the calculated attenuation constant. A larger attenuation constant α indicates that more electromagnetic waves can be dissipated as heat energy. Additionally, impedance matching (Z...in : Represents material impedance, Z o (Represents free space impedance) is what allows electromagnetic waves to penetrate as much of the material as possible, so when Z... in / Z o The closer the impedance is to 1, the better the impedance matching. Figure 7 further demonstrates this for SiC. nw @LDH2 composite material has excellent dielectric loss properties.

[0078] Figure 8 For novel SiC nw @LDH nanocomposite Bode plot (ad) and Nyquist plot (df). EIS is considered a convenient, direct, and important method for assessing the corrosion resistance of coatings. The material at 0.01 Hz (|Z| 0.01Hz The larger the impedance modulus at time t=0, the larger the radius of the Nyquist plot, and the better the corrosion resistance of the material. EIS data were fitted using ZSimDemo software, where points represent the original data and lines represent the fitted data. Bode plots and Nyquist plots are shown below. Figure 8 As shown, for all coatings, |Z| increases with immersion time. 0.01Hz The radius and Nyquist plot gradually decrease, indicating a decline in corrosion resistance. Initial time, such as... Figure 8 As shown in the diagram, pure epoxy resin, 0.3 wt.% SiC nw @LDH2, 0.5wt.%SiC nw @LDH2, 0.7wt.%SiC nw @LDH2's |Z| 0.01Hz All values ​​reached the 9th power, reflecting that the coating provides excellent corrosion protection for Q235 steel plates. With increasing penetration time, the corrosion resistance of the pure epoxy coating significantly decreased, with the impedance dropping to 1.11 × 10⁻⁶ on day 30. 8 Ω·cm 2 Furthermore, the integrity of the coating under the influence of corrosive electrolyte can be assessed by the phase angle (θ). On days 20 and 30, the phase angle exhibits oscillations, and the Nyquist plot shows two radii, indicating that the corrosive medium penetrates the coating, causing delamination and rendering the coating's corrosion protection ineffective. However, by comparing the |Z| values ​​of all coatings... 0.01Hz Based on the Nyquist plot radius, 0.5 wt% SiC was found. nw @LDH2 has the largest radius and impedance modulus, without significant decrease, indicating that SiC nw @LDH2 composite materials provide corrosion protection. Furthermore, when the phase angle is -45°, the corresponding frequency is the breakpoint frequency, which is an important parameter for analyzing coating damage and delamination. Figure 8As shown in a, b, and c, the breakpoint frequency gradually increases with increasing immersion time, verifying a decrease in the coating's protective properties. However, with 0.5wt% SiCnw@LDH2, the breakpoint frequency shows only a slight increase and remains essentially unchanged. In summary, both excessive and insufficient filler content worsen the coating's corrosion resistance. Too little filler, due to its low content, may not provide adequate corrosion protection. Excessive filler content can lead to agglomeration and uneven distribution of the coating within the dispersed phase, resulting in localized electrocoupling corrosion and decreased corrosion resistance. The 0.5wt% SiCnw@LDH2... nw @LDH2 maintains excellent corrosion resistance for up to 30 days.

[0079] Figure 9 For the salt spray test, specifically, the scratched composite coating sample was immersed in salt water for 10 days. This was done to visually verify the corrosion resistance of the composite material. Figure 9 Macroscopic photographs of all coatings after 10 days of exposure to salt spray are shown. The pure epoxy coating shows pitting and peeling, which can be attributed to the epoxy coating's susceptibility to damage, resulting in numerous cracks and pores. Corrosive media propagate through these pores. 0.3wt% SiC nw @LDH2 exhibits increased corrosion at scratched areas because the amount added is insufficient to block the corrosive medium. 0.7wt% SiC nw @LDH2, if added in excess, can cause the nanocomposite material to agglomerate, affecting coating adhesion. Corrosive media can easily penetrate from scratches, causing blistering and resulting in a large accumulation of corrosion products at defects. Adding 0.5wt% SiC... nw @LDH2 not only blocks corrosive media but also has little effect on adhesion. Therefore, the results show that 0.5wt% SiC nw @LDH2's corrosion-resistant coating is the best.

[0080] In summary, this study demonstrates the synergistic effect of modifying the composition and structure of the composite material and optimizing its dielectric constant. Experimental results prove that this composite material exhibits excellent performance in the field of marine corrosion protection and microwave absorption. The ability to control both the structure and composition (dielectric constant) of this composite material provides new insights into the design of high-performance integrated corrosion protection and microwave absorption composite materials with good impedance matching, and shows promising application prospects.

[0081] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A SiC supported LDH nanocomposite, characterized in that, It is a core-shell structure, wherein the core is a silicon carbide nanowire SiC nw , and the shell is a third metal-doped layered double hydroxide, the loading of the third metal-doped layered double hydroxide being 43.1%-168% based on the mass of SiC nw . The third metal-doped layered double hydroxide is a Co-doped NiFe layered double hydroxide.

2. The SiC-supported LDH nanocomposite of claim 1, wherein The silicon carbide nanowire has a diameter of 0.1-0.6 μm, a length of 50-100 μm, and an aspect ratio of 100-200.

3. The SiC-supported LDH nanocomposite of claim 1, wherein The mass percentage of Co in the total mass of metal cations in the Co-doped NiFe layered double hydroxide is 25%.

4. A process for the preparation of the SiC supported LDH nanocomposite of any one of claims 1 to 3, characterized in that, The method comprises the following steps: (1) dispersing the silicon carbide nanowire in a polytetrafluoroethylene liner containing deionized water and stirring to obtain a silicon carbide suspension; (2) adding nickel nitrate, cobalt nitrate, iron nitrate, urea, and trisodium citrate to the silicon carbide suspension obtained in step (1) and stirring to obtain a mixed solution; (3) reacting the mixed solution obtained in step (2) in a rotary oven, cooling to room temperature after the reaction is completed, centrifugal washing, and then drying the obtained mixture to obtain the SiC-loaded LDH nanocomposite.

5. The production method according to claim 4, characterized by, In step (1), the ratio of the silicon carbide nanowire to deionized water is 1.23-1.53 mg / ml; and the stirring time is 20-30 min.

6. The preparation method according to claim 4, characterized in that, In step (2), the molar ratio of nickel nitrate, cobalt nitrate, and iron nitrate is 2:1:

1.

7. The preparation method according to claim 4, characterized in that, In step (2), the total feeding amount of metal cations is 0-1.6 mmol and is not 0, the amount of urea added is 2.9 mmol, and the amount of trisodium citrate added is 0.16 mmol; and the stirring time is 15-30 min.

8. The preparation method according to claim 4, characterized in that, In step (3), the temperature of the rotary oven is 160-180℃; the reaction time is 18-24 h; the centrifugal washing mode is to use deionized water and ethanol for centrifugal washing three to four times; the drying temperature is 60-70℃; and the drying time is 8-12 h.

9. Use of the SiC-loaded LDH nanocomposite of any one of claims 1-3 as a wave-absorbing anticorrosion material.

10. A method of improving the corrosion resistance of a silicon carbide nanowire microwave absorbing material, the method comprising: The method of any one of claims 4-8 is used to load a third metal-doped layered double hydroxide on the silicon carbide nanowire to form a core-shell structure composite material with the silicon carbide nanowire as the core and the third metal-doped layered double hydroxide as the shell.

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