A graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material and its preparation method

Abstract

A graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material and its preparation method are disclosed. The raw materials of the composite material include graphene oxide, carbonyl iron powder, and nano-titanium dioxide, wherein the mass ratio of graphene oxide to carbonyl iron powder is 1:0.5-1.5, and the molar ratio of carbonyl iron powder to nano-titanium dioxide is 1:(1-3). The graphene oxide, carbonyl iron powder, and nano-titanium dioxide are combined with each other by spray drying. The present application has the advantages of improving the impedance matching performance of graphene-based materials, having a high reflection loss rate and a wide effective absorption bandwidth with a low filler content, which is beneficial to the processing of composite materials and reduces costs.

Description

Technical Field

[0001] This application relates to the technical field of composite materials, and in particular to a graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material and its preparation method. Background Technology

[0002] Traditional microwave absorbing materials, such as ferrites, magnetic metals, and conductive polymers, are greatly limited in practical applications due to their high density, poor environmental stability, and difficulty in processing.

[0003] Graphene, as the thinnest material in the carbon family, has a considerable dielectric loss due to its low density, easy availability, large aspect ratio, abundant functional groups, and tunable electrical properties. However, its impedance matching capability is poor, and it cannot effectively dissipate electromagnetic waves by converting them into heat or other forms of energy.

[0004] Spherical carbonyl iron particles (CIPs) are widely used in composite materials due to their excellent magnetic properties, such as high saturation magnetization and low coercivity. CIPs have strong microwave absorption capabilities and exhibit dielectric loss, resistive loss, and magnetic loss mechanisms, and have been used as microwave absorbing materials in the gigahertz range. However, CIPs typically have disadvantages such as high density, poor temperature stability, and narrow absorption bandwidth.

[0005] Furthermore, due to the high conductivity of CIP itself, its impedance matching with free space is poor, which cannot meet the requirements of "thin, light, wide, and strong" for absorbing materials, thus limiting the improvement of its absorbing performance. Summary of the Invention

[0006] This application addresses the aforementioned shortcomings of the prior art by providing a graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material that improves the impedance matching performance of graphene-based materials, exhibits a high reflection loss rate and a wide effective absorption bandwidth even with a low filler content, and facilitates the processing of composite materials while reducing costs.

[0007] To solve the above-mentioned technical problems, the technical solution adopted in this application is as follows: a graphene-based carbonyl iron powder doped nano-titanium dioxide composite material, the raw materials of which include: graphene oxide, carbonyl iron powder and nano-titanium dioxide, wherein the mass ratio of graphene oxide to carbonyl iron powder is 1:0.5-1.5, and the molar ratio of carbonyl iron powder to nano-titanium dioxide is 1:(1-3); the graphene oxide, carbonyl iron powder and nano-titanium dioxide are combined with each other by spray drying method.

[0008] Furthermore, the particle size of the nano-titanium dioxide is below 100 nm.

[0009] Furthermore, the particle size of the carbonyl iron powder is between 1 and 5 μm.

[0010] Furthermore, the mass ratio of graphene oxide to carbonyl iron powder is 1:0.8-1.2.

[0011] Furthermore, the molar ratio of the carbonyl iron powder to the nano titanium dioxide is 1:(1-2).

[0012] This application also provides a method for preparing a graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material, the specific steps of which include: (1) Preparation of aqueous dispersion of graphene oxide: Weigh graphene oxide powder and add it to deionized water, then mix it with ultrasound to obtain a brownish-yellow aqueous dispersion of graphene oxide. (2) Preparation of the mixture: Add carbonyl iron powder and nano titanium dioxide to the graphene aqueous dispersion obtained in step (1) above, stir at room temperature to obtain the mixture; (3) Preparation of graphene-based carbonyl iron powder doped nano-titanium dioxide composite material: The mixture obtained in step (2) is atomized through a nozzle under a pressure of 0.1-0.5 MPa, and carried by preheated air through a cyclone separator to make the GO sheet fold and shrink, thereby wrapping the carbonyl iron powder doped nano-titanium dioxide; after cooling, the prepared graphene-based carbonyl iron powder doped nano-titanium dioxide composite material is obtained.

[0013] Furthermore, the ratio of graphene oxide powder to deionized water in step (1) is 0.5-2 g / 100 mL.

[0014] Furthermore, the ultrasonic mixing temperature in step (1) is 20-30℃, and the ultrasonic time is 1-3h.

[0015] Furthermore, the stirring at room temperature for 0.5-2 hours is described in step (2).

[0016] Furthermore, the pressure described in step (3) is 0.15-0.2 MPa.

[0017] Furthermore, the temperature of the preheated air in step (3) is 140-160°C.

[0018] The advantages and beneficial effects of this application are as follows: 1. The titanium dioxide (TiO2) used in this application has low density and dielectric constant, thus exhibiting excellent electrical properties and improving the impedance matching performance of microwave absorbing materials, enabling the preparation of lightweight composite microwave absorbing materials. Furthermore, the high polarity of the Ti-O bonds in TiO2 makes it highly adsorbable. This adsorption property of nano-titanium dioxide is beneficial for the successful construction of composite materials and is also key to improving the impedance matching performance of graphene materials, directly affecting the material's electromagnetic wave loss performance. Therefore, this graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material improves impedance matching performance through the three-phase material composition, and the interfacial polarization loss between the three phases further enhances the microwave absorption performance of the composite material.

[0019] 2. The composite material of this application can improve the impedance matching performance and wave absorption performance of the dielectric material graphene. Carbonyl iron powder, as a magnetic material, can enhance the magnetic loss capability and improve the defect of graphene-based materials lacking magnetic loss performance. In the solution, nano-titanium dioxide is adsorbed on the graphene oxide sheets, and then the carbonyl iron powder can be well wrapped by spray drying. The carbonyl iron powder and nano-titanium dioxide are mainly used to regulate the impedance matching performance of graphene materials, form a heterogeneous interface with the graphene sheets, and enhance polarization loss.

[0020] 3. This application forms a specific structure through specific process parameters, optimizing the synergistic effect among graphene sheets, carbonyl iron powder, and nano-titanium dioxide. The synergistic effect between nano-titanium dioxide and graphene oxide sheets regulates the impedance matching performance of graphene-based materials, allowing electromagnetic waves incident on the material surface to penetrate into the material interior to a greater extent. The synergistic effect between carbonyl iron powder and graphene oxide sheets is due to the interfacial polarization loss at the heterogeneous interface between the two, and the fact that carbonyl iron powder, as a ferromagnetic material, can also provide the magnetic loss capability of the composite material itself.

[0021] 4. In the process of preparing the composite material, this application uses spray drying to combine nano-titanium dioxide and spherical carbonyl iron particles with graphene oxide to solve the problem of poor impedance matching performance of graphene-based microwave absorbing materials, so that the microwave absorbing material meets the requirements of "thin, light, wide and strong".

[0022] 5. This application uses spray drying to obtain graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material with good rigidity and anti-aggregation properties, which can effectively avoid the accumulation of graphene oxide sheets and achieve excellent microwave absorption performance. The spray drying technology used in this application is a highly scalable manufacturing technology that can avoid complex reactions, solvent removal and the use of templates, showing high cost-effectiveness and advantages for large-scale production.

[0023] 6. The graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in this application can effectively improve the impedance matching performance of graphene-based materials. It has a high reflection loss rate and a wide effective absorption bandwidth even with a low filler ratio, which is beneficial for the processing of composite materials and reduces costs.

[0024] 7. The graphene-based carbonyl iron powder doped nano-titanium dioxide composite material prepared in this application combines the advantages of lightweight and high dielectric properties of carbon-based material graphene oxide with the advantages of strong microwave loss capability of magnetic shielding filler carbonyl iron powder and nano-titanium dioxide, and can optimize the synergistic effect among the three to achieve high microwave loss capability. Attached Figure Description

[0025] Figure 1 The images show SEM images of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in Example 1, the wrinkled graphene oxide, nano-titanium dioxide, and carbonyl iron powder prepared in Comparative Example 1.

[0026] Figure 2 The image shows the FTIR spectrum of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material (CIP@TiO2 / GO) prepared in Example 1.

[0027] Figure 3 The images show the XRD patterns of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material (CIP@TiO2 / GO) prepared in Example 1, the wrinkled graphene oxide, nano-titanium dioxide, and carbonyl iron powder prepared in Comparative Example 1.

[0028] Figure 4 The graph shows the reflection loss curves of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in Example 1 at different thicknesses in the X-band (8.2–12.4 GHz) frequency range.

[0029] Figure 5 The reflection loss curves of the wrinkled graphene oxide prepared in Comparative Example 1 at different thicknesses in the X-band (8.2–12.4 GHz) frequency range are shown.

[0030] Figure 6 The graph shows the reflection loss curves of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in Example 2 at different thicknesses in the X-band (8.2–12.4 GHz) frequency range.

[0031] Figure 7 The graph shows the reflection loss curves of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in Example 3 at different thicknesses in the X-band (8.2–12.4 GHz) frequency range.

[0032] Figure 8 The images show SEM images of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite materials prepared in Examples 1-3.

[0033] Figure 9 The image shows a SEM image of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared by hydrothermal reaction in Comparative Example 2.

[0034] Figure 10 The graph shows the reflection loss curves of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared by hydrothermal reaction in the X-band (8.2–12.4 GHz) at different thicknesses. Detailed Implementation

[0035] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are merely preferred embodiments, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application. Example 1

[0036] A graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material and its preparation method are disclosed, with the specific implementation steps as follows: (1) Preparation of graphene oxide aqueous dispersion: Weigh 1g of graphene oxide powder and add it to 100mL of deionized water, and then sonicate at 25℃ for 2h to obtain a brownish-yellow graphene oxide aqueous dispersion (mass fraction of 1%).

[0037] (2) Preparation of the mixture: Add 1g of carbonyl iron powder and 0.4g of nano titanium dioxide to the above-mentioned graphene aqueous dispersion, stir at room temperature for 1h to obtain the mixture.

[0038] (3) Preparation of graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material: The mixture obtained in step (2) is atomized through a nozzle at a pressure of 0.2 MPa (considering the actual granulation capacity of the spray dryer, the spray flow rate is not controlled). The mixture is then carried by preheated air (150°C) through a cyclone separator (the cyclone separator is a component of the spray drying device; the material reaches the nozzle through the feed pipe and is then sprayed out from the nozzle, carried by the air into the drying chamber to obtain the product; the air and the product enter the cyclone separator from the outlet of the drying chamber, and the product enters the dry chamber). The air is discharged from the top of the cyclone separator (the air is discharged into the collection bottle below), causing the GO sheet to fold and shrink, thereby encapsulating the carbonyl iron powder-doped nano-titanium dioxide; after cooling, the prepared graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material is obtained; during the high-temperature drying process, some oxygen-containing functional groups on the surface of graphene oxide will decompose, producing defects and pores, so that the "carbonyl iron powder and nano-titanium dioxide" encapsulated in the wrinkled graphene oxide can also exert their properties, thus making the final composite material locally achieve the synergistic effect of the three materials.

[0039] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that nano-titanium dioxide and carbonyl iron powder are not added in step (2), that is, only the aqueous dispersion of graphene oxide is spray-dried, and the rest of the process is exactly the same.

[0040] Figure 1 The images show SEM images of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in Example 1, the wrinkled graphene oxide, nano-titanium dioxide, and carbonyl iron powder prepared in Comparative Example 1. Figure 1 a represents the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material (CIP@TiO2 / GO) prepared in Example 1; Figure 1 b is a SEM image of the wrinkled graphene oxide (GO) prepared in Comparative Example 1. Figure 1 c represents nano-titanium dioxide (TiO2). Figure 1 Image d shows the SEM image of carbonyl iron powder (CIP). As can be seen from the image, the strong adsorption of TiO2 allows it to adsorb onto the graphene oxide nanosheets. Through the high-temperature and high-pressure spray drying process of this application, the graphene oxide sheets adsorbed with nano-titanium dioxide particles can coat the surface of the carbonyl iron powder particles, forming a core-shell structure. Figure 1 As shown in a), this fully demonstrates the successful synthesis of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material of the present application.

[0041] Figure 2The image shows the FTIR spectrum of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material (CIP@TiO2 / GO) prepared in Example 1. The image shows that the infrared absorption peak at 1043 cm⁻¹ corresponds to the bending vibration of the CO bond in the epoxy group, confirming that TiO2 is adsorbed on the oxygen-containing functional groups of graphene oxide and forms epoxy groups. This is because TiO2 has a highly polar Ti-O bond, resulting in strong adsorption. The infrared absorption peak at 1218 cm⁻¹ corresponds to the in-plane deformation of =CH, confirming the presence of sp² bonded carbon atoms in the system. The infrared absorption peak at 1732 cm⁻¹ corresponds to the stretching vibration of the C=O bond, the infrared absorption peak at 1406 cm⁻¹ corresponds to the stretching vibration of C-OH, and the infrared absorption peak at 800 cm⁻¹ corresponds to the out-of-plane bending vibration of CH, confirming the presence of GO in the composite material. The infrared absorption peaks at 1146 and 1629 cm⁻¹ correspond to the characteristic peaks of CIP, while the peak at 2361 cm⁻¹ is a characteristic peak of CO₂, indicating the presence of CIP in the composite material. These results demonstrate the successful preparation of graphene-based carbonyl iron powder-doped nano-titanium dioxide composite materials.

[0042] Figure 3The XRD patterns are of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material (CIP@TiO2 / GO) prepared in Example 1, the wrinkled graphene oxide, nano-titanium dioxide, and carbonyl iron powder prepared in Comparative Example 1. For GO, the (001) crystal plane of GO is shown at 2θ = 11.0°. The intensity of this peak varies after the composite of titanium dioxide (TiO2) and carbonyl iron powder (CIP), indicating a change in the graphene oxide structure. Furthermore, a broad peak exists at 2θ = 18.5°, representing disordered components generated during the spray drying process of GO. The peak at 2θ = 42.5° corresponds to the (101) crystal plane of graphite. These results demonstrate that spray drying of GO can achieve a suitable degree of crystallization, which is beneficial for ensuring good impedance matching between the absorber and free space, thereby improving its microwave loss capability. For CIP, the peaks at 2θ = 44.9° and 82.5° correspond to the (110) and (211) crystal planes of body-centered cubic (bcc) α-Fe. These two peaks can also be observed in CIP@TiO2 / GO, indicating that the structure of CIP does not change after GO encapsulates it. For TiO2, the peaks at 2θ = 27.3°, 36.1°, 39.0°, 54.3°, 56.6°, and 62.8° correspond to the (101), (004), (112), (105), (211), and (213) crystal planes of tetragonal anatase. For CIP@TiO2 / GO, the XRD pattern shows the (001) and (101) crystal planes belonging to GO, the (110) and (211) crystal planes belonging to CIP corresponding to body-centered cubic (bcc) α-Fe, and the (101), (004), (112), and (105) crystal planes belonging to TiO2 corresponding to tetragonal anatase. These results demonstrate the successful preparation of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material (CIP@TiO2 / GO).

[0043] The graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in Example 1 was added to molten paraffin (the filling rate of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material in molten paraffin was 1 wt%), and molded into cylinders and cylindrical rings, which were used for conductivity testing and microwave absorption (MA) measurement, respectively. The test results are as follows.

[0044] Figure 4The graph shows the reflection loss curves of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in Example 1 at different thicknesses within the X-band (8.2–12.4 GHz) frequency range. When the matched thickness of the sample is only 1.6 mm, the reflection loss (RLmin) is -34.8402 dB across the entire frequency range, and the absorption value of electromagnetic wave energy can reach over 99.9%. When the matched thickness of the sample is 1.9 mm, the reflection loss (RLmin) is -22.3187 dB, and the effective absorption bandwidth (EAB) can reach as high as 3.17 GHz. Furthermore, the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in Example 1 has a density of only 0.26 g / cm³, and the reflection loss can still reach -31.2559 dB at a frequency of 12.4 GHz, which shows promise for achieving excellent absorption performance in higher frequency ranges.

[0045] The wrinkled graphene oxide material prepared in Comparative Example 1 was added to molten paraffin (the filling rate of the wrinkled graphene oxide material in the molten paraffin was 1 wt%), and molded into cylinders and cylindrical rings, which were used for conductivity testing and microwave absorption (MA) measurement, respectively. The test results are as follows.

[0046] Figure 5 The graph shows the reflection loss curves of the wrinkled graphene oxide prepared in Comparative Example 1 at different thicknesses within the X-band (8.2–12.4 GHz) frequency range. When the matched thickness of the sample is 6.0 mm, the reflection loss (RLmin) across the entire frequency range is -3.7798 dB, and the absorption of electromagnetic wave energy is only 50%, indicating poor absorption performance. Compared to the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in Example 1, after combining graphene oxide with carbonyl iron powder and nano-titanium dioxide via spray drying, the overall synergistic effect of the composite material increases, the impedance matching characteristics improve, and the ability to dissipate electromagnetic waves is significantly enhanced.

[0047] To investigate the effect of the ratio of carbonyl iron powder to nano-titanium dioxide on the microwave absorption performance of graphene-based microwave absorbing materials, this scheme is illustrated through Examples 2 and 3. Example 2

[0048] A graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material and its preparation method are disclosed, with the specific implementation steps as follows: (1) Preparation of graphene oxide aqueous dispersion: Weigh 1g of graphene oxide powder and add it to 100mL of deionized water, and then sonicate at 25℃ for 2h to obtain a brownish-yellow graphene oxide aqueous dispersion (mass fraction of 1%).

[0049] (2) Preparation of the mixture: Add 1g of carbonyl iron powder and 0.8g of nano titanium dioxide to the above-mentioned aqueous graphene dispersion, stir at room temperature for 1h to obtain the mixture; The mass ratio of graphene oxide to carbonyl iron powder is 1:1, and the molar ratio of carbonyl iron powder to nano titanium dioxide is 1:2.

[0050] (3) Preparation of graphene-based carbonyl iron powder doped nano-titanium dioxide composite material: The mixture obtained in step (2) is atomized through a nozzle under a pressure of 0.2 MPa, and carried by preheated air (150°C) through a cyclone separator to make the GO sheet fold and shrink, thereby encapsulating the carbonyl iron powder doped nano-titanium dioxide; after cooling, the prepared graphene-based carbonyl iron powder doped nano-titanium dioxide composite material is obtained.

[0051] The graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in Example 2 was added to molten paraffin (the filling rate of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material in molten paraffin was 1 wt%), and molded into cylinders and cylindrical rings, which were used for conductivity testing and microwave absorption (MA) measurement, respectively. The test results are as follows.

[0052] Figure 6 The graph shows the reflection loss curves of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in Example 2 at different thicknesses within the X-band (8.2–12.4 GHz) frequency range. When the matched thickness of the sample is 9.7 mm, the reflection loss (RLmin) is -23.2065 dB across the entire frequency range, and the absorption value of electromagnetic wave energy can reach over 99.9%, which contradicts the "lightweight" and "thin" high-performance microwave absorbing material designed in this project. Example 3

[0053] A graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material and its preparation method are disclosed, with the specific implementation steps as follows: (1) Preparation of graphene oxide aqueous dispersion: Weigh 1g of graphene oxide powder and add it to 100mL of deionized water, and then sonicate at 25℃ for 2h to obtain a brownish-yellow graphene oxide aqueous dispersion (mass fraction of 1%).

[0054] (2) Preparation of the mixture: Add 1g of carbonyl iron powder and 1.2g of nano titanium dioxide to the above-mentioned aqueous graphene dispersion, stir at room temperature for 1h to obtain the mixture; The mass ratio of graphene oxide to carbonyl iron powder is 1:1, and the molar ratio of carbonyl iron powder to nano titanium dioxide is 1:3.

[0055] (3) Preparation of graphene-based carbonyl iron powder doped nano-titanium dioxide composite material: The mixture obtained in step (2) is atomized through a nozzle under a pressure of 0.2 MPa, and carried by preheated air (150°C) through a cyclone separator to make the GO sheet fold and shrink, thereby encapsulating the carbonyl iron powder doped nano-titanium dioxide; after cooling, the prepared graphene-based carbonyl iron powder doped nano-titanium dioxide composite material is obtained.

[0056] The graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in Example 3 was added to molten paraffin (the filling rate of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material in molten paraffin was 1 wt%), and molded into cylinders and cylindrical rings, which were used for conductivity testing and microwave absorption (MA) measurement, respectively. The test results are as follows.

[0057] Figure 7 The graph shows the reflection loss curves of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in Example 3 at different thicknesses within the X-band (8.2–12.4 GHz) frequency range. As can be seen from the graph, the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in Example 3 only achieves a reflection loss (RLmin) of -13.9356 dB across the entire frequency range when the matching thickness is 10 mm. This contradicts the "lightweight" and "thin" high-performance absorbing material designed in this project.

[0058] Figure 8 SEM images of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite materials prepared in Examples 1-3 are shown. In Examples 1-3, the mass ratio of graphene oxide to carbonyl iron powder was 1:1, and the molar ratio of carbonyl iron powder to nano-titanium dioxide was 1:1. Figure 8 -a), 1:2( Figure 8 -b, c) and 1:3 ( Figure 8 -d). With the increase of nano-titanium dioxide content, a large amount of nano-titanium dioxide is adsorbed on the surface of graphene oxide, resulting in severe agglomeration and inability to completely encapsulate carbonyl iron powder particles, such as... Figure 8 As shown in d. Generally, close-packed structures are unfavorable for electromagnetic wave incidence, which contradicts the original intention of this invention to design a material with high wave absorption performance. When the molar ratio of carbonyl iron powder to nano-titanium dioxide is 1:2, the nano-titanium dioxide adsorbs on the surface of graphene oxide, completely encapsulating the carbonyl iron powder particles, as shown in d. Figure 8 As shown in b and c.

[0059] To illustrate the advantages of this method for preparing graphene-based carbonyl iron powder-doped nano-titanium dioxide composite materials via spray drying, comparative example 2 was used to prepare graphene-based carbonyl iron powder-doped nano-titanium dioxide composite materials via hydrothermal reaction.

[0060] Comparative Example 2 (without spray drying) The graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material was prepared by hydrothermal reaction. The specific implementation steps are as follows: (1) Preparation of graphene oxide aqueous dispersion: Weigh 1g of graphene oxide powder and add it to 100mL of deionized water, and then sonicate at 25℃ for 2h to obtain a brownish-yellow graphene oxide aqueous dispersion (mass fraction of 1%).

[0061] (2) Preparation of the mixture: Add 1g of carbonyl iron powder and 0.4g of nano titanium dioxide to the above-mentioned aqueous graphene dispersion, stir at room temperature for 1h to obtain the mixture; (3) Preparation of graphene-based carbonyl iron powder doped nano titanium dioxide composite material: The above mixture was placed in a polytetrafluoroethylene liner and kept at 150°C for 3 hours. After cooling to room temperature, it was washed three times by centrifugation with deionized water and dried at 60°C for 12 hours.

[0062] Figure 9 This is a SEM image of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared by hydrothermal reaction in Comparative Example 2. From... Figure 9 As can be seen, in the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared by hydrothermal reaction, the nano-titanium dioxide is adsorbed on the graphene oxide nanosheets, forming an aerogel-like structure, and it is difficult to see carbonyl iron particles (the adsorption between nano-titanium dioxide and graphene oxide sheets makes it difficult for graphene to properly encapsulate carbonyl iron powder particles, reducing the adsorption between carbonyl iron powder and graphene oxide sheets, thus making carbonyl iron particles invisible). Figure 9 As shown in -a. Carbonyl iron particles were found in other locations, such as... Figure 9 As shown in Figure -b, in the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared by hydrothermal reaction, the carbonyl iron is independently distributed within the graphene aerogel. This confirms that the spray drying method of this invention can obtain a graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material with good synergistic effects between graphene oxide, carbonyl iron powder, and nano-titanium dioxide, exhibiting certain structural advantages and contributing to the improvement of the composite material's microwave absorption performance.

[0063] The graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared by hydrothermal reaction in Comparative Example 2 was added to molten paraffin (the filling rate of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material in molten paraffin was 1 wt%), and molded into cylinders and cylindrical rings, which were used for conductivity testing and microwave absorption (MA) measurement, respectively. The test results are as follows.

[0064] Figure 10The graph shows the reflection loss curves of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared by hydrothermal reaction in Comparative Example 2 at different thicknesses within the X-band (8.2–12.4 GHz) frequency range. As can be seen from the graph, the composite material achieves RL < -10 dB absorption performance at high frequencies only with a high matching thickness, which contradicts the "lightweight," "thin," and high-performance absorbing material designed in this application.

Claims

1. A graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material, characterized in that: The raw materials of this composite material include: graphene oxide, carbonyl iron powder and nano titanium dioxide, wherein the mass ratio of graphene oxide to carbonyl iron powder is 1:0.5-1.5, and the molar ratio of carbonyl iron powder to nano titanium dioxide is 1:(1-3); the graphene oxide, carbonyl iron powder and nano titanium dioxide are combined with each other by spray drying method. The specific preparation steps of this composite material include: (1) Preparation of aqueous dispersion of graphene oxide: Weigh graphene oxide powder and add it to deionized water, then mix it with ultrasound to obtain a brownish-yellow aqueous dispersion of graphene oxide. (2) Preparation of the mixture: Add carbonyl iron powder and nano titanium dioxide to the graphene aqueous dispersion obtained in step (1) above, stir at room temperature to obtain the mixture; (3) Preparation of graphene-based carbonyl iron powder doped nano-titanium dioxide composite material: The mixture obtained in step (2) is atomized through a nozzle under a pressure of 0.1-0.5 MPa, and carried by preheated air through a cyclone separator to fold and shrink the graphene oxide sheets, thereby encapsulating the carbonyl iron powder doped nano-titanium dioxide; after cooling, the prepared graphene-based carbonyl iron powder doped nano-titanium dioxide composite material is obtained.

2. The graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material according to claim 1, characterized in that: The particle size of the nano-titanium dioxide is below 100 nm.

3. The graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material according to claim 1, characterized in that: The particle size of the carbonyl iron powder is 1–5 μm.

4. The graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material according to claim 1, characterized in that: The mass ratio of graphene oxide to carbonyl iron powder is 1:0.8-1.

2.

5. The graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material according to claim 1, characterized in that: The molar ratio of the carbonyl iron powder to the nano titanium dioxide is 1:(1-2).

6. The graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material according to claim 1, characterized in that: The ratio of graphene oxide powder to deionized water in step (1) is 0.5-2 g / 100 mL; the ultrasonic mixing temperature in step (1) is 20-30 °C, and the ultrasonic time is 1-3 h.

7. The graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material according to claim 1, characterized in that: Stir at room temperature for 0.5-2 hours as described in step (2).

8. The graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material according to claim 1, characterized in that: The pressure mentioned in step (3) is 0.15-0.2 MPa.

9. The method for preparing the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material according to claim 1, characterized in that: The temperature of the preheated air in step (3) is 140-160℃.

Images