Acoustic resonance assisted nano-SiO2 coated flaky carbonyl iron powder as well as preparation method and application thereof

Abstract

The invention discloses an acoustic resonance assisted nano-SiO2 coated flaky carbonyl iron powder as well as a preparation method and application thereof, the flaky carbonyl iron powder is taken as a main raw material, an acoustic resonance assisted modification technology is adopted, a compact and uniform SiO2 coating layer is constructed on the surface of the flaky carbonyl iron powder, and an FCIP coated SiO2 composite material with a core-shell structure is prepared. According to the coating treatment, the oxidation resistance and corrosion resistance of the carbonyl iron powder are remarkably improved, electromagnetic parameters of the carbonyl iron powder are regulated and controlled, and particularly the wave absorbing performance of the material in a low-frequency wave band is enhanced. An electromagnetic parameter test and reflection loss calculation show that the obtained composite material has better impedance matching characteristics and lower reflection loss value. In practical application, a coated sample shows higher thermal stability and lower surface corrosion rate, and the service life of the material in a complex service environment is effectively prolonged. The method is simple and convenient in process, low in cost and suitable for being applied to functional material systems such as electric conduction, wave absorption and electromagnetic interference prevention on a large scale.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbonyl iron powder, and in particular relates to an acoustic resonance-assisted nano-SiO2-coated flaky carbonyl iron powder and a preparation method and application thereof. Background Art

[0002] In the field of microwave absorbing materials, carbonyl iron (CIP) has been widely studied for its high saturation magnetization and broadband magnetic loss properties. Flake carbonyl iron (FCIP), due to its unique flat geometry, exhibits superior magnetic anisotropy and multiple scattering compared to spherical carbonyl iron, significantly enhancing hysteresis and eddy current losses. However, the high aspect ratio of the flake structure leads to uneven surface charge distribution, significantly increasing the dielectric constant and causing severe impedance mismatch. This results in a large amount of electromagnetic waves being reflected from the material surface rather than absorbed, greatly limiting its practical applications.

[0003] Furthermore, due to its large surface area and sharp edges, flake carbonyl iron is more susceptible to exposing active sites in humid or salty environments, exacerbating electrochemical corrosion and leading to a decrease in magnetic permeability and rapid degradation of its microwave absorption performance. Although spherical carbonyl iron exhibits better corrosion resistance due to its uniform surface curvature and fewer defects, its magnetic loss capacity is significantly lower than that of flake structures, and it is difficult to achieve broadband microwave absorption through morphology control.

[0004] Current research on FCIP modification (such as sol-gel coating of SiO2 and in-situ polymerization of conductive polymers) focuses on reducing the dielectric constant. However, traditional processes suffer from drawbacks such as a loose coating layer and weak interfacial bonding, making them ineffective in blocking the penetration of corrosive media. Furthermore, over-coating can lead to degraded magnetic properties. Therefore, how to simultaneously address the impedance mismatch and corrosion resistance challenges of flaky carbonyl iron while retaining its high magnetic loss advantage has become a pressing technical bottleneck in the field of microwave absorbing materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention provides a flaky carbonyl iron powder coated with nano-SiO2 using acoustic resonance, as well as its preparation method and application. This invention utilizes acoustic resonance-assisted modification technology to successfully coat the surface of flaky carbonyl iron with nano-SiO2, significantly optimizing impedance matching, improving wave absorption, and enhancing oxidation and corrosion resistance.

[0006] The present invention is achieved through the following technical solutions.

[0007] A method for preparing flaky carbonyl iron powder coated with nano-SiO2 assisted by acoustic resonance comprises the following steps:

[0008] Using flaky carbonyl iron powder and nano-silicon dioxide as raw materials, acoustic resonance-assisted modification technology was used to construct a dense and uniform SiO2 coating on the surface of the flaky carbonyl iron powder to prepare a core-shell structured FCIP@SiO2 composite material.

[0009] The mass ratio of the flaky carbonyl iron powder to the nano-silicon dioxide is 99:1-95:5.

[0010] Preferably, the mass ratio of the flaky carbonyl iron powder to nano-silicon dioxide is 99:1-97:3.

[0011] Preferably, the acoustic resonance-assisted modification technology is to use an acoustic resonance instrument to pre-mix the flaky carbonyl iron powder and nano-silicon dioxide under the protection of an inert atmosphere, and then perform the main mixing, maintaining temperature control throughout the process, and finally obtain the FCIP@SiO2 composite material.

[0012] Preferably, the main mixing acceleration is 80g-100g, and the main mixing time is 50min-90min.

[0013] Preferably, the premixing acceleration is 20g-30g, the premixing time is 5min-10min, the main mixing acceleration is 80g-100g, the main mixing time is 50min-90min, the temperature is controlled throughout the process, the cooling water circulation temperature is 20℃-25℃, and the material temperature is 50℃-60℃.

[0014] Preferably, the inert atmosphere is argon, and the inert gas pressure is set to 0.1-0.3 MPa.

[0015] Preferably, the flaky carbonyl iron powder is pretreated before use, and the pretreatment comprises the following steps:

[0016] The flaky carbonyl iron powder is added to a dispersing solvent and then dried after ultrasonic treatment.

[0017] Preferably, the dispersing and dissolving agent is isopropyl alcohol, and the added amount is 100wt%-200wt% of the flaky carbonyl iron powder, and more preferably 100wt%.

[0018] Preferably, the ultrasound time is 30 min-60 min

[0019] Preferably, the drying temperature is 100° C.-120° C., and the drying time is 60 min-120 min.

[0020] Preferably, the reaction vessel of the acoustic resonance instrument is made of high borosilicate glass with a thickness of 5mm-7mm.

[0021] A core-shell structured FCIP@SiO2 composite material prepared by any of the preparation methods described above.

[0022] The application of the core-shell structured FCIP@SiO2 composite material described above in absorbing materials.

[0023] Preferably, the above application comprises the following steps:

[0024] The FCIP@SiO2 composite material is mixed with epoxy resin, diluent, and dispersant in a mass ratio of 60-70%:15-20%:10-15%:1-2%. After stirring, dispersion, and vacuum degassing, the mixture is sprayed in layers on a pretreated substrate using a high-pressure airless spraying process. After curing, a multifunctional absorbing coating with broadband absorption, strong adhesion, and corrosion resistance is obtained.

[0025] More preferably, the stirring and dispersing condition is 300 rpm / 2h.

[0026] Further preferably, the layered spraying is to control the spraying pressure to 10-15 MPa and the distance to 20-30 cm to form a coating of 0.6-1 mm (the bottom layer is an aluminum alloy metal back plate).

[0027] More preferably, the curing is performed by step curing, 80°C / 2h→120°C / 1h.

[0028] The present invention provides a flaky carbonyl iron@silicon dioxide (FCIP@SiO2) composite absorbing material and its acoustic resonance-assisted preparation method. Through the "hummingbird acoustic resonance-assisted modification technology (HAM)", high-frequency vibration induces nano-SiO2 to self-assemble into a continuous and dense coating layer (thickness 10-50nm) on the FCIP surface, which can effectively solve the impedance mismatch problem caused by the high dielectric constant of flaky carbonyl iron and its easy electrochemical corrosion in humid or salt spray environments, and achieve the synergistic improvement of broadband impedance matching optimization and long-term corrosion protection. The prepared material exhibits high magnetic loss characteristics and excellent environmental durability in the 1-18GHz frequency band, providing a new solution for the engineering application of flaky carbonyl iron in harsh environments.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] (1) Higher coating uniformity and interface bonding strength. The traditional sol-gel method is prone to problems such as agglomeration and local concentration during the coating process, resulting in discontinuous or uneven coating layer. The acoustic resonance-assisted modification technology of the present invention uses high-frequency mechanical waves and acoustic energy fields to induce rapid nucleation and uniform deposition of liquid species on the powder surface, significantly improving the uniformity and density of the coating layer. At the same time, high-frequency acoustic energy promotes the activation reaction between the interfaces, enhances the physical-chemical bonding strength between the SiO2 coating layer and the FCIP matrix, and improves the long-term stability and service reliability of the material.

[0031] (2) Reduce temperature and energy consumption, and achieve mild process conditions. The ball mill coating method usually relies on long-term mechanical force, which can easily introduce lattice defects or even structural damage, and there is a risk of powder contamination; while the sol-gel method has strict requirements on drying and heat treatment conditions and a complex process flow. In contrast, the acoustic resonance-assisted technology can achieve coating reactions under normal pressure and low temperature (around 50°C), with lower energy consumption, avoiding the damage to magnetic or structural properties caused by high-temperature processes, and is more suitable for large-scale green preparation.

[0032] (3) Highly sealed equipment, suitable for active material processing. The present invention uses a closed reactor and operates under argon protection, effectively preventing oxidation and moisture absorption of carbonyl iron powder during the coating process. Compared with open ball milling or sol dispersion reactions, the closed, inert atmosphere is more suitable for processing easily oxidized, high-specific-surface-area active powder materials, improving material reproducibility and process stability.

[0033] (4) Significantly improve electromagnetic performance, especially low-frequency absorption performance. Traditional coating methods have certain limitations in regulating electromagnetic parameters. For example, uneven SiO2 distribution may lead to impedance mismatch or incomplete loss mechanism. The acoustic resonance-assisted method can not only regulate the thickness and distribution of the SiO2 layer, but also induce the formation of interface polarization centers, so that the material exhibits better magneto-electric coupling effect and loss characteristics in the low-frequency band, which helps to achieve a wider frequency band and more efficient absorption capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention and the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art.

[0035] Figure 1 These are the SEM and EDS images of the FCIP@SiO2 composite material prepared using acoustic resonance-assisted modification technology in Example 1.

[0036] Figure 2 These are the SEM and EDS images of the FCIP@SiO2 composite material prepared using acoustic resonance-assisted modification technology in Example 2.

[0037] Figure 3 These are the SEM and EDS images of the FCIP@SiO2 composite material prepared using acoustic resonance-assisted modification technology in Example 3.

[0038] Figure 4 This is the SEM image of the FCIP@SiO2 composite material prepared using acoustic resonance assisted modification technology in Example 4.

[0039] Figure 5 These are the SEM and EDS images of the FCIP@SiO2 composite material prepared using acoustic resonance-assisted modification technology in Example 5.

[0040] Figure 6 These are the SEM and EDS images of the FCIP@SiO2 composite material prepared using acoustic resonance-assisted modification technology in Example 6.

[0041] Figure 7 SEM and EDS images of the original FCIP sample of Comparative Example 1.

[0042] Figure 8 This is the SEM image of the original FCIP sample of Comparative Example 2. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below with reference to specific examples and drawings. The described examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0044] The test method for the electromagnetic parameters εˊ, μˊ, thickness, and absorption peak in the present invention is as follows: the desired test sample (FCIP@SiO2 powder) and solid paraffin are mixed in a certain mass ratio, and then placed in a mold to form a hollow cylindrical coaxial sample with an outer diameter of 7 mm, an inner diameter of 3 mm, and a thickness of 2-4 mm. The coaxial sample is then loaded into a vector network analyzer for testing.

[0045] Tafel corrosion current test method: Corrosion resistance measurement was performed using a GAMRY Reference 600 electrochemical workstation with a three-electrode detection system. The reference electrode used was a saturated KCl electrode, while graphite was used as the counter electrode. The effective surface area of ​​the sample was kept at 1 cm 2 To ensure the electrochemical stability, Tafel test was performed in 3.5% NaCl solution.

[0046] Test standard: National electronics industry military standard SJ 20512-1995.

[0047] Example 1

[0048] Use an electronic balance to weigh 50g of flaky carbonyl iron powder, then add it to 50g of isopropanol and ultrasonicate it for 30 minutes. Then place it in a vacuum oven at 110℃ and dry it for two hours. Then cool it to room temperature and take it out. Then take 1wt% of nano-SiO2 and put the material into the reactor. Vacuum it to 10pa, pass argon to 0.1Mpa, set the premixing acceleration to 20g, premix it for 5 minutes, then set the main mixing acceleration to 80g, mix it for 50 minutes, control the temperature throughout the process, keep the cooling water circulation temperature at 20℃, and keep the material temperature at around 50℃. The SEM and EDS images of the composite powder after this process are as follows: Figure 1 shown.

[0049] Example 2

[0050] The steps of this embodiment are basically the same as those of embodiment 1, except that the main mixing acceleration in step (1) is set to 90g. The SEM and EDS images of the composite powder after this process are as follows: Figure 2 shown.

[0051] Example 3

[0052] The steps of this embodiment are basically the same as those of embodiment 1, except that the main mixing acceleration in step (1) is set to 100g. The SEM and EDS images of the composite powder after this process are as follows: Figure 3 shown.

[0053] Example 4

[0054] The steps of this embodiment are basically the same as those of embodiment 2, except that the content of nano-SiO2 in step (2) is increased to 3%. The high magnification SEM image of the composite powder after this process is as follows: Figure 4 shown.

[0055] It can be seen that there are fine white contrast nano-SiO2 powders on the surface of the flake carbonyl iron.

[0056] Example 5

[0057] The steps of this embodiment are basically the same as those of embodiment 4, except that the main mixing time of step (2) is 70 min. The SEM and EDS images of the composite powder after this process are as follows: Figure 5 shown.

[0058] Example 6

[0059] The steps of this embodiment are basically the same as those of embodiment 4, except that the main mixing time of step (2) is 90 minutes. Figure 6 shown.

[0060] Comparative Example 1

[0061] The steps of this comparative example are basically the same as those of Example 1, except that nano-SiO2 is not added to the raw materials, that is, the raw materials during the acoustic resonance process are only flake carbonyl iron powder. The SEM and EDS images of the iron powder after this process are as follows: Figure 7 As shown. Figure 1 In comparison, this comparative example ( Figure 7 ) in the EDS image, no obvious Si element signal was detected on the sheet-like carbonyl iron. Figure 1 The EDS image clearly shows the coating contour of Si element, and the coating effect is more obvious and uniform, without any local enrichment phenomenon.

[0062] Comparative Example 2

[0063] The steps of this comparative example are basically the same as those of Example 4, except that only the pretreatment step was performed and no acoustic resonance-assisted modification treatment was performed. Figure 8 As shown. Figure 4 In comparison, the surface morphology of the comparative sample is relatively smooth and uniform, with no obvious nanoparticle attachment or agglomeration structure, indicating that no effective nano-SiO2 coating behavior occurs on its surface.

[0064] Table 1 Particle size distribution data of glass powder after treatment in different embodiments

[0065]

[0066]

[0067] It can be seen from the data in Table 1 that the SiO2-coated carbonyl iron powder (FCIP@SiO2) prepared by the acoustic resonance-assisted coating process of the present invention exhibits excellent comprehensive wave absorption characteristics in terms of electromagnetic performance. By controlling the acoustic resonance parameters and temperature conditions under the protection of an inert atmosphere, the dense and uniform coating of nano-SiO2 on the surface of the carbonyl iron powder is achieved, and the frequency response characteristics of the magnetic permeability and dielectric parameters are effectively regulated. Compared with traditional uncoated samples, the prepared material exhibits better impedance matching capability and reflection loss performance in the low-frequency to medium-frequency band, and the wave absorption efficiency is significantly improved. The present invention provides a surface coating treatment method for flaky carbonyl iron powder based on acoustic resonance assistance, which has a controllable process flow and strong environmental adaptability. It is suitable for the large-scale preparation of high-performance electromagnetic wave absorbing materials and has broad engineering application prospects.

[0068] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing flaky carbonyl iron powder coated with nano-SiO2 assisted by acoustic resonance, characterized in that: The following steps are involved: Using flaky carbonyl iron powder and nano-silicon dioxide as raw materials, acoustic resonance-assisted modification technology was used to construct a dense and uniform SiO2 coating on the surface of the flaky carbonyl iron powder to prepare a core-shell structured FCIP@SiO2 composite material. The mass ratio of the flaky carbonyl iron powder to the nano-silicon dioxide is 99:1-95:

5.

2. The method for preparing an acoustic resonance-assisted nano-SiO2-coated flaky carbonyl iron powder according to claim 1, characterized in that: The mass ratio of the flaky carbonyl iron powder to the nano-silicon dioxide is 99:1-97:

3.

3. The method for preparing an acoustic resonance-assisted nano-SiO2-coated flaky carbonyl iron powder according to claim 1 or 2, characterized in that: The acoustic resonance-assisted modification technology uses an acoustic resonance instrument to pre-mix flaky carbonyl iron powder and nano-silicon dioxide under inert atmosphere protection, and then performs main mixing, maintaining temperature control throughout the process, and finally obtaining the FCIP@SiO2 composite material.

4. The method for preparing an acoustic resonance-assisted nano-SiO2-coated flaky carbonyl iron powder according to claim 3, characterized in that: The premixing acceleration is 20g-30g, the premixing time is 5min-10min, the main mixing acceleration is 80g-100g, the main mixing time is 50min-90min, the temperature is controlled throughout the process, the cooling water circulation temperature is 20℃-25℃, and the material temperature is 50℃-60℃.

5. The method for preparing an acoustic resonance-assisted nano-SiO2-coated flaky carbonyl iron powder according to claim 3, characterized in that: The inert atmosphere is argon, and the inert gas pressure is set to 0.1-0.3 MPa.

6. The method for preparing an acoustic resonance-assisted nano-SiO2-coated flaky carbonyl iron powder according to claim 1, characterized in that: The flaky carbonyl iron powder is pretreated before use, and the pretreatment includes the following steps: The flaky carbonyl iron powder is added to a dispersing solvent and dried after ultrasonic treatment.

7. The method for preparing an acoustic resonance-assisted nano-SiO2-coated flaky carbonyl iron powder according to claim 6, characterized in that: The dispersing and dissolving agent is isopropyl alcohol, and the added amount is 100-200wt% of the flaky carbonyl iron powder; the ultrasonic time is 30min-60min; the drying temperature is 100℃-120℃, and the drying time is 60min-120min.

8. A core-shell structured FCIP@SiO2 composite material prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the core-shell structured FCIP@SiO2 composite material according to claim 8 in a microwave absorbing material.

10. The use of the core-shell structured FCIP@SiO2 composite material in a microwave absorbing material according to claim 9, characterized in that: The following steps are involved: The FCIP@SiO2 composite material is mixed with epoxy resin, diluent, and dispersant in a mass ratio of 60-70%:15-20%:10-15%:1-2%. After stirring, dispersion, and vacuum degassing, the composite material is sprayed layer by layer on a pretreated substrate using a high-pressure airless spraying process. After curing, an absorbing coating is obtained.

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