Graphene-based carbonyl iron powder doped nano titanium dioxide composite material and preparation method thereof

Abstract

The invention relates to a graphene-based carbonyl iron powder doped nano titanium dioxide composite material and a preparation method thereof, the composite material comprises the following raw materials: graphene oxide, carbonyl iron powder and nano titanium dioxide, 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, the carbonyl iron powder and the nano titanium dioxide are mutually combined through a spray drying method; the scheme provided by the invention has the advantages that the impedance matching performance of the graphene-based material is improved, the graphene-based material has a relatively high reflection loss rate and a relatively wide effective absorption bandwidth when the graphene-based material has a relatively low filling rate, the processing of the composite material is facilitated, and the cost is reduced.

Description

Technical Field

[0001] The present 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 a preparation method thereof. Background Art

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

[0003] Graphene, the thinnest material in the carbon family, has considerable dielectric loss due to its low density, easy availability, large aspect ratio, rich functional groups, and adjustable 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, including high saturation magnetization and low coercivity. CIPs exhibit strong microwave absorption in the microwave range, exhibiting dielectric, resistive, and magnetic loss mechanisms. They have been used as microwave absorbers in the gigahertz range. However, CIPs typically suffer from high density, poor temperature stability, and a narrow absorption bandwidth.

[0005] In addition, due to the high conductivity of CIP itself, the 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] In response to the above-mentioned deficiencies in the prior art, the present application provides a graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material that improves the impedance matching performance of graphene-based materials, has a higher reflection loss rate and a wider effective absorption bandwidth at a lower filling rate, is beneficial to the processing of the composite material and reduces costs.

[0007] In order to solve the above technical problems, the technical solution adopted in this application is: a graphene-based carbonyl iron powder doped nano-titanium dioxide composite material, 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 a 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 1 to 5 μm.

[0010] Furthermore, the mass ratio of the graphene oxide to the 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] The present 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:

[0013] (1) preparing a graphene oxide aqueous dispersion: weighing graphene oxide powder and adding it to deionized water, and then ultrasonically mixing it to obtain a brown-yellow graphene oxide aqueous dispersion;

[0014] (2) preparing a mixed solution: adding carbonyl iron powder and nano-titanium dioxide to the aqueous graphene dispersion obtained in the above step (1), stirring at room temperature to obtain a mixed solution;

[0015] (3) Preparation of graphene-based carbonyl iron powder-doped nano-titanium dioxide composite materials: The mixed solution obtained in step (2) is atomized through a nozzle at a pressure of 0.1-0.5 MPa, and is carried by preheated air through a cyclone separator to fold and shrink the GO sheets, 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.

[0016] Furthermore, the ratio of the graphene oxide powder to deionized water in step (1) is 0.5-2 g / 100 ml.

[0017] Furthermore, the temperature of the ultrasonic mixing in step (1) is 20-30° C., and the ultrasonic time is 1-3 h.

[0018] Furthermore, the stirring in step (2) is carried out at room temperature for 0.5-2 h.

[0019] Furthermore, the pressure in step (3) is 0.15-0.2 MPa.

[0020] Furthermore, the temperature of the preheated air in step (3) is 140-160°C.

[0021] Advantages and beneficial effects of this application:

[0022] 1. The titanium dioxide (TiO2) used in this application has a low density and dielectric constant, thus having excellent electrical properties, and can improve the impedance matching performance of the absorbing material and prepare a lightweight composite absorbing material; in addition, the large polarity of the Ti-O bond in TiO2 also makes it extremely easy to adsorb. This easy adsorption property of nano-titanium dioxide is conducive to the successful construction of the composite material on the one hand, and on the other hand, it is also the key to improving the impedance matching performance of the graphene material, which directly affects the material's loss performance for electromagnetic waves; therefore, the graphene-based carbonyl iron powder doped nano-titanium dioxide composite material of the present application, on the one hand, improves the impedance matching performance through the three-phase material combination, and on the other hand, the interface polarization loss between the three-phase materials can also further improve the composite material's absorbing performance.

[0023] 2. The composite material of the present 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 capacity and improve the defect of magnetic loss performance of graphene-based materials. Nano-titanium dioxide is adsorbed on the graphene oxide sheet in the solution, and then the graphene nanosheets adsorbed with nano-titanium dioxide can be well wrapped with carbonyl iron powder by spray drying; 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.

[0024] 3. The present application forms a specific structure through specific process parameters to optimize the synergistic effect between 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, so that electromagnetic waves incident on the surface of the material enter the interior of the material to a greater extent; the synergistic effect between carbonyl iron powder and graphene oxide sheets, on the one hand, is that there is interface polarization loss at the heterogeneous interface between the two, and on the other hand, carbonyl iron powder as a ferromagnetic material can also provide the magnetic loss capacity of the composite material itself.

[0025] 4. In the process of preparing the composite material, the present application uses a spray-drying method to compound nano-titanium dioxide and spherical carbonyl iron particles with graphene oxide to solve the problem of poor impedance matching performance of graphene-based absorbing materials, so that the absorbing materials meet the requirements of "thin, light, wide and strong".

[0026] 5. The present application adopts a spray drying method, and the obtained graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material has good rigid structure and anti-aggregation properties, which can effectively avoid the accumulation of graphene oxide sheets and achieve excellent wave absorbing performance; the spray drying technology used in the present application is a highly scalable manufacturing technology that can avoid complex reactions, solvent removal and the use of templates, showing high cost-effectiveness and the advantages of large-scale production.

[0027] 6. The graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in this application can greatly improve the impedance matching performance of the graphene-based material. When the filling rate is low, it has a higher reflection loss rate and a wider effective absorption bandwidth, which is beneficial to the processing of the composite material and reduces costs.

[0028] 7. The graphene-based carbonyl iron powder doped nano-titanium dioxide composite material prepared in this application combines the advantages of carbon-based materials - graphene oxide, which is lightweight and has high dielectric properties, and the advantages of magnetic shielding fillers - carbonyl iron powder and nano-titanium dioxide, which have strong microwave loss capabilities, and can optimize the synergistic effect between the three to achieve higher microwave loss capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 These are SEM images of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in Example 1, and the wrinkled graphene oxide, nano-titanium dioxide and carbonyl iron powder prepared in Comparative Example 1.

[0030] Figure 2 This is the FTIR graph of the graphene-based carbonyl iron powder doped nano-titanium dioxide composite material (CIP@TiO2 / GO) prepared in Example 1.

[0031] Figure 3 XRD patterns of the graphene-based carbonyl iron powder doped nano-titania composite material (CIP@TiO2 / GO) prepared in Example 1 and the wrinkled graphene oxide, nano-titania and carbonyl iron powder prepared in Comparative Example 1.

[0032] Figure 4 This is a reflection loss curve 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.

[0033] Figure 5 This is a reflection loss curve of the wrinkled graphene oxide prepared in Comparative Example 1 at different thicknesses within the X-band (8.2-12.4 GHz) frequency range.

[0034] Figure 6 This is a reflection loss curve 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.

[0035] Figure 7 This is a reflection loss curve 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.

[0036] Figure 8 These are SEM images of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite materials prepared in Examples 1 to 3.

[0037] Figure 9 This is an SEM image of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared by hydrothermal reaction in Comparative Example 2.

[0038] Figure 10 This is a reflection loss curve 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. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of this application in conjunction with the embodiments and drawings. Obviously, the embodiments described are only preferred embodiments, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0040] Example 1:

[0041] A graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material and a preparation method thereof, the specific implementation steps are as follows:

[0042] (1) Preparation of graphene oxide aqueous dispersion: 1 g of graphene oxide powder was weighed and added to 100 mL of deionized water, followed by ultrasonic treatment at 25° C. for 2 h to obtain a brown-yellow graphene oxide aqueous dispersion (mass fraction: 1%).

[0043] (2) Preparation of a mixed solution: Add 1 g of carbonyl iron powder and 0.4 g of nano-titanium dioxide to the above-mentioned graphene aqueous dispersion, and stir at room temperature for 1 h to obtain a mixed solution.

[0044] (3) Preparation of graphene-based carbonyl iron powder-doped nano-titanium dioxide composite materials: The mixed liquid obtained in step (2) was atomized through a nozzle at a pressure of 0.2 MPa (considering the actual granulation capacity of the spray dryer, the spray flow rate was not controlled), and the mixed liquid was carried by preheated air (150°C) through a cyclone separator (the cyclone separator is a structure of the spray drying device. The material reaches the nozzle through the feed pipe and is then sprayed from the nozzle and 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 cyclone separator. into the collection bottle below, and the air is discharged from the upper end of the cyclone separator), causing the GO sheets to 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; during the high-temperature drying process, some oxygen-containing functional groups on the surface of the graphene oxide will decompose, generating defects and pores, so that the "carbonyl iron powder and nano-titanium dioxide" wrapped in the wrinkled graphene oxide can also exert their properties, so that the final composite material partially realizes the synergistic effect of the three materials.

[0045] Comparative Example 1

[0046] 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 graphene oxide aqueous dispersion is spray-dried, and the rest of the processes are exactly the same.

[0047] Figure 1 These are SEM images of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material prepared in Example 1, and the wrinkled graphene oxide, nano-titanium dioxide and carbonyl iron powder prepared in Comparative Example 1. Figure 1 a is the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material (CIP@TiO2 / GO) prepared in Example 1; Figure 1 b is the SEM image of the wrinkled graphene oxide (GO) prepared in Comparative Example 1, Figure 1 c is nano titanium dioxide (TiO2), Figure 1 d is the SEM image of carbonyl iron powder (CIP). As can be seen from the figure, the strong adsorption of TiO2 can make it adsorbed on the nanosheets of graphene oxide. Through the spray drying process under high temperature and high pressure of the present application, the graphene oxide sheets adsorbed with nano-titanium dioxide particles can be wrapped on the surface of the carbonyl iron powder particles to form a core-shell structure ( Figure 1 a), thereby fully confirming the successful synthesis of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material of the technical solution of the present application.

[0048] Figure 2This is the FTIR spectrum of the graphene-based carbonyl iron powder doped nano-titanium dioxide composite material (CIP@TiO2 / GO) prepared in Example 1. As can be seen from the figure, at 1043 cm -1 The infrared absorption peak corresponds to the bending vibration of the CO bond in the epoxy group, which confirms that TiO2 is adsorbed on the oxygen-containing functional group of graphene oxide and forms an epoxy group. This is because TiO2 has a larger polar Ti-O bond, which makes TiO2 have a stronger adsorption effect. -1 The infrared absorption peak corresponds to the in-plane deformation of =CH, proving the existence of sp 2 Bonded carbon atoms. At 1732 cm -1 The infrared absorption peak at 1406 cm corresponds to the stretching vibration of the C=O bond. -1 The infrared absorption peak at 800 cm corresponds to the stretching vibration of C-OH. -1 The infrared absorption peaks at 1146 and 1629 cm-1 correspond to the out-of-plane bending vibration of CH, confirming the presence of GO in the composite. -1 The infrared absorption peak at 2361 cm corresponds to the characteristic peak of CIP. -1 The peak at the bottom is the characteristic peak of CO2, indicating the presence of CIP in the composite material. The above results illustrate the successful preparation of graphene-based carbonyl iron powder doped nano-titanium dioxide composite materials.

[0049] Figure 3XRD patterns of the graphene-based carbonyl iron powder doped nano-titania composite material (CIP@TiO2 / GO) prepared in Example 1, and the wrinkled graphene oxide, nano-titania and carbonyl iron powder prepared in Comparative Example 1. For GO, the (001) crystal plane of GO is displayed at 2θ=11.0°. After the titanium dioxide (TiO2) and carbonyl iron powder (CIP) are compounded, the intensity of this peak changes, and the structure of graphene oxide changes. In addition, there is a broad peak at 2θ=18.5°, which is the disordered component produced by GO during the spray drying process. The peak at 2θ=42.5° corresponds to the (101) crystal plane of graphite. The above results show that spray drying of GO can make it have a suitable degree of crystallization, which is beneficial to ensure good impedance matching between the absorber and free space, thereby improving its microwave loss capacity. 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 CIP. 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 reveals the (001) and (101) crystal planes of GO, the (110) and (211) crystal planes of CIP corresponding to body-centered cubic (bcc) α-Fe, and the (101), (004), (112), and (105) crystal planes of TiO2 corresponding to tetragonal anatase. These results demonstrate the successful preparation of the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite (CIP@TiO2 / GO).

[0050] The graphene-based carbonyl iron powder-doped nano-titania composite material prepared in Example 1 was added to molten paraffin (the filling rate of the graphene-based carbonyl iron powder-doped nano-titania composite material in the molten paraffin was 1 wt%) and molded into a cylinder and a cylindrical ring, which were used for conductivity testing and microwave absorption (MA) measurement, respectively. The test results are described as follows.

[0051] Figure 4 This is a reflection loss curve 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 matching thickness of the sample is only 1.6 mm, the reflection loss (RL min) is -34.8402dB, and the absorption value of electromagnetic wave energy can reach more than 99.9%. When the matching thickness of the sample is 1.9mm, the reflection loss (RL min ) is -22.3187dB, and the effective absorption bandwidth (EAB) can be as high as 3.17GHz. In addition, the density of the graphene-based carbonyl iron powder doped nano-titanium dioxide composite material prepared in Example 1 is only 0.26g / cm 3 , the reflection loss can still reach -31.2559dB at a frequency of 12.4GHz, and it is expected to achieve excellent absorption performance in a higher frequency range.

[0052] 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 a cylinder and a cylindrical ring, which were used for conductivity testing and microwave absorption (MA) measurement, respectively. The test results are described as follows.

[0053] Figure 5 The reflection loss curve of the wrinkled graphene oxide prepared in comparative example 1 at different thicknesses in the X-band (8.2-12.4 GHz) frequency range is shown in Figure 1. When the matching thickness of the sample is 6.0 mm, the reflection loss (RL min ) was -3.7798 dB, indicating a mere 50% absorption of electromagnetic wave energy, indicating poor absorption performance. The graphene-based carbonyl iron powder-doped nano-titanium dioxide composite prepared in Example 1 was spray-dried to combine graphene oxide with carbonyl iron powder and nano-titanium dioxide. The composite exhibited enhanced synergistic effects, improved impedance matching characteristics, and significantly enhanced electromagnetic wave loss resistance.

[0054] In order to explore the effect of the ratio of carbonyl iron powder to nano-titanium dioxide on the absorbing performance of graphene-based absorbing materials, this scheme is illustrated through Examples 2 to 3.

[0055] Example 2:

[0056] A graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material and a preparation method thereof, the specific implementation steps are as follows:

[0057] (1) Preparation of graphene oxide aqueous dispersion: 1 g of graphene oxide powder was weighed and added to 100 mL of deionized water, followed by ultrasonic treatment at 25° C. for 2 h to obtain a brown-yellow graphene oxide aqueous dispersion (mass fraction: 1%).

[0058] (2) preparing a mixed solution: adding 1 g of carbonyl iron powder and 0.8 g of nano-titanium dioxide to the above-mentioned graphene aqueous dispersion, stirring at room temperature for 1 h to obtain a mixed solution;

[0059] The mass ratio of the graphene oxide to the carbonyl iron powder is 1:1, and the molar ratio of the carbonyl iron powder to the nano-titanium dioxide is 1:2.

[0060] (3) Preparation of graphene-based carbonyl iron powder-doped nano-titanium dioxide composite materials: The mixed solution obtained in step (2) is atomized through a nozzle at a pressure of 0.2 MPa, and is carried through a cyclone separator by preheated air (150°C) to fold and shrink the GO sheets, 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.

[0061] The graphene-based carbonyl iron powder-doped nano-titania composite material prepared in Example 2 was added to molten paraffin (the filling rate of the graphene-based carbonyl iron powder-doped nano-titania composite material in the molten paraffin was 1 wt%) and molded into a cylinder and a cylindrical ring, which were used for conductivity testing and microwave absorption (MA) measurement, respectively. The test results are described as follows.

[0062] Figure 6 This is a reflection loss curve 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 matching thickness of the sample is 9.7 mm, the reflection loss (RL min ) is -23.2065dB, and the absorption value of electromagnetic wave energy can reach more than 99.9%, which is contrary to the "light" and "thin" high-performance absorbing materials designed for this project.

[0063] Example 3:

[0064] A graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material and a preparation method thereof, the specific implementation steps are as follows:

[0065] (1) Preparation of graphene oxide aqueous dispersion: 1 g of graphene oxide powder was weighed and added to 100 mL of deionized water, followed by ultrasonic treatment at 25° C. for 2 h to obtain a brown-yellow graphene oxide aqueous dispersion (mass fraction: 1%).

[0066] (2) preparing a mixed solution: adding 1 g of carbonyl iron powder and 1.2 g of nano-titanium dioxide to the above-mentioned graphene aqueous dispersion, stirring at room temperature for 1 h to obtain a mixed solution;

[0067] The mass ratio of the graphene oxide to the carbonyl iron powder is 1:1, and the molar ratio of the carbonyl iron powder to the nano-titanium dioxide is 1:3.

[0068] (3) Preparation of graphene-based carbonyl iron powder-doped nano-titanium dioxide composite materials: The mixed solution obtained in step (2) is atomized through a nozzle at a pressure of 0.2 MPa, and is carried through a cyclone separator by preheated air (150°C) to fold and shrink the GO sheets, 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.

[0069] The graphene-based carbonyl iron powder-doped nano-titania composite material prepared in Example 3 was added to molten paraffin (the filling rate of the graphene-based carbonyl iron powder-doped nano-titania composite material in the molten paraffin was 1 wt%) and molded into a cylinder and a cylindrical ring, which were used for conductivity testing and microwave absorption (MA) measurement, respectively. The test results are described as follows.

[0070] Figure 7 The graph of the reflection loss curve 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 is shown in the figure. As can be seen from the figure, the reflection loss (RL) of the graphene-based carbonyl iron powder doped nano-titanium dioxide composite material prepared in Example 3 can be reduced to 100% in the entire frequency range when the thickness is 10 mm. min ) reaches -13.9356dB, which is contrary to the "light" and "thin" high-performance absorbing materials designed for this project.

[0071] Figure 8 The SEM images of the graphene-based carbonyl iron powder doped nano-titanium dioxide composite materials prepared in Examples 1 to 3. In Examples 1 to 3, 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 1:1 ( Figure 8 -a)、1:2( Figure 8 -b, c) and 1:3( Figure 8 -d). As the content of nano-titanium dioxide increases, a large amount of nano-titanium dioxide is adsorbed on the surface of graphene oxide, and the agglomeration is serious, and the carbonyl iron powder particles cannot be completely wrapped. Figure 8 d. Generally, a tightly packed structure is not conducive to the incidence of electromagnetic waves, which does not conform to the original intention of the present 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, nano-titanium dioxide is adsorbed on the surface of graphene oxide and can completely wrap the carbonyl iron powder particles, such as Figure 8 As shown in b and c.

[0072] In order to illustrate the advantages of the present scheme in preparing graphene-based carbonyl iron powder-doped nano-titanium dioxide composite materials by spray drying, a graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material was prepared by hydrothermal reaction in Comparative Example 2.

[0073] Comparative Example 2 (without spray drying)

[0074] The graphene-based carbonyl iron powder doped nano-titanium dioxide composite material is prepared by hydrothermal reaction, and the specific implementation steps are as follows:

[0075] (1) Preparation of graphene oxide aqueous dispersion: 1 g of graphene oxide powder was weighed and added to 100 mL of deionized water, followed by ultrasonic treatment at 25° C. for 2 h to obtain a brown-yellow graphene oxide aqueous dispersion (mass fraction: 1%).

[0076] (2) preparing a mixed solution: adding 1 g of carbonyl iron powder and 0.4 g of nano-titanium dioxide to the above-mentioned graphene aqueous dispersion, stirring at room temperature for 1 h to obtain a mixed solution;

[0077] (3) Preparation of graphene-based carbonyl iron powder-doped nano-titanium dioxide composite materials: The above-mentioned mixed solution was placed in a polytetrafluoroethylene liner and kept at 150°C for 3 hours. After cooling to room temperature, it was centrifuged and washed three times with deionized water and dried at 60°C for 12 hours.

[0078] Figure 9 The SEM image of the graphene-based carbonyl iron powder doped nano-titanium dioxide composite material prepared by hydrothermal reaction in comparative example 2. Figure 9 It can be seen that in the graphene-based carbonyl iron powder doped nano-titania composite material prepared by hydrothermal reaction, nano-titania is adsorbed on the graphene oxide nanosheets to form an aerogel-like structure, and it is difficult to see carbonyl iron particles (the adsorption between nano-titania and graphene oxide sheets makes it difficult for graphene to normally wrap the carbonyl iron powder particles, and the adsorption between carbonyl iron powder and graphene oxide sheets is reduced, so carbonyl iron particles cannot be seen). Figure 9 -a. Carbonyl iron particles are found in other locations, such as Figure 9 As shown in Figures 1 and 2, carbonyl iron powder-doped nano-titania composites prepared via a hydrothermal reaction show that carbonyl iron is independently distributed within the graphene aerogel. This also confirms that the present invention's spray-drying preparation method can produce a graphene-based carbonyl iron powder-doped nano-titania composite material with excellent synergistic effects between graphene oxide, carbonyl iron powder, and nano-titania. This composite material exhibits certain structural advantages and is beneficial for improving the composite's microwave absorption properties.

[0079] The graphene-based carbonyl iron powder-doped nano-titania composite material prepared by hydrothermal reaction in Example 2 was added to molten paraffin (the filling rate of the graphene-based carbonyl iron powder-doped nano-titania composite material in the molten paraffin was 1 wt%) and molded into a cylinder and a cylindrical ring, which were used for conductivity testing and microwave absorption (MA) measurement, respectively. The test results are described as follows.

[0080] Figure 10 This figure 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 figure, the composite material achieves RL < -10 dB absorption performance at high frequencies only when the thickness is highly matched, which contradicts the "light," "thin," and high-performance absorber designed in this application.

Claims

1. A graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material, characterized by: 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 through a spray drying method.

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 to 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 the graphene oxide to the 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. A method for preparing the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material according to any one of claims 1 to 5, characterized in that: The specific steps include: (1) preparing a graphene oxide aqueous dispersion: weighing graphene oxide powder and adding it to deionized water, and then ultrasonically mixing it to obtain a brown-yellow graphene oxide aqueous dispersion; (2) preparing a mixed solution: adding carbonyl iron powder and nano-titanium dioxide to the aqueous graphene dispersion obtained in the above step (1), stirring at room temperature to obtain a mixed solution; (3) Preparation of graphene-based carbonyl iron powder-doped nano-titanium dioxide composite materials: The mixed liquid obtained in step (2) is atomized through a nozzle at a pressure of 0.1-0.5 MPa, and is carried by preheated air through a cyclone separator to fold and shrink the graphene oxide sheets, 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.

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

8. The method for preparing the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material according to claim 6, characterized in that: Stir at room temperature for 0.5-2h as described in step (2).

9. The method for preparing the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material according to claim 6, characterized in that: The pressure in step (3) is 0.15-0.2 MPa.

10. The method for preparing the graphene-based carbonyl iron powder-doped nano-titanium dioxide composite material according to claim 6, characterized in that: The temperature of the preheated air in step (3) is 140-160°C.

Images