阅读说明：本技术 一种优异电磁波吸收性能的四氧化三铁/碳纳米片复合材料及其制备方法和应用 (Ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance and preparation method and application thereof ) 是由 龙东辉 苏哲 张亚运 牛波 张琬钰 曹宇 于 2021-09-09 设计创作，主要内容包括：本发明涉及一种优异电磁波吸收性能的四氧化三铁/碳纳米片复合材料及其制备方法和应用,该材料合成线路采用葡萄糖酸铁复合物为原料,基于葡萄糖酸铁复合物碳化初期自发泡特性,通过一步碳化,成功批量制备了千克级产量的四氧化三铁/碳纳米片复合材料。该复合材料具有高分散、高负载量的四氧化三铁和大二维片层尺寸。二维的碳纳米片与高度分散的四氧化三铁纳米粒子之间的协同作用诱导形成了强烈的界面极化,优异的电导损失和多重散射吸收。与现有技术相比,本发明的四氧化三铁/碳纳米片复合材料对电磁波具有极高的吸收性能。此外,对电磁波吸收有效带宽高达6.24GHz。本发明为高性能电磁波吸收材料的实际规模化制备提供了可行的技术途径。(The invention relates to a ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance, and a preparation method and application thereof. The composite material has high-dispersion and high-load ferroferric oxide and large two-dimensional lamella size. The strong interface polarization, excellent conductivity loss and multiple scattering absorption are induced by the synergistic effect between the two-dimensional carbon nano-sheets and the highly dispersed ferroferric oxide nano-particles. Compared with the prior art, the ferroferric oxide/carbon nano sheet composite material has extremely high absorption performance on electromagnetic waves. In addition, the effective bandwidth for absorbing the electromagnetic waves is up to 6.24 GHz. The invention provides a feasible technical approach for the practical large-scale preparation of the high-performance electromagnetic wave absorption material.)

1. The ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance is characterized by comprising the following components in percentage by mass: 54-58% of carbon and Fe₃O₄ 42-46％。

2. The ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance according to claim 1, wherein the composite material has a specific saturation magnetization of 33-38emu/g and a coercive force of 63-110 Oe.

3. The ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance as claimed in claim 1, wherein the BET specific surface area of the composite material is 170-340m²A pore surface area of 110-280m²(ii)/g; the total pore volume is 0.15-0.30cm³Per g, wherein the pore volume of the micropores is 0.06-0.11cm³/g。

4. The preparation method of the ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance according to claim 1, wherein the preparation method comprises the following steps:

(1) weighing ferric trichloride hexahydrate and water, and preparing a ferric trichloride solution after uniformly stirring;

(2) adjusting the pH value of the ferric trichloride solution to prepare ferric hydroxide precipitate, performing suction filtration separation on the prepared ferric hydroxide precipitate, and washing and performing suction filtration to obtain the ferric hydroxide precipitate;

(3) adding the washed ferric hydroxide precipitate into a gluconic acid aqueous solution, heating and stirring to completely dissolve the ferric hydroxide precipitate to obtain a gluconic acid ferric solution;

(4) adding the ferric gluconate solution into absolute ethyl alcohol, separating ferric gluconate, and drying the separated ferric gluconate precipitate to obtain a ferric gluconate compound;

(5) and carbonizing the ferric gluconate composite to obtain the ferroferric oxide/carbon nano sheet composite material with excellent electromagnetic wave absorption performance.

5. The preparation method of the ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance according to claim 4, wherein the molar ratio of ferric trichloride hexahydrate to gluconic acid is (2.5-3.5): 1.

6. The preparation method of the ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance according to claim 4, wherein the gluconic acid aqueous solution contains 49-53% of gluconic acid by mass.

7. The preparation method of the ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance according to claim 4, wherein the heating and stirring temperature in the step (3) is 80-90 ℃.

8. The preparation method of the ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance according to claim 4, wherein the carbonization treatment conditions are as follows: heating to 600-800 deg.C at a rate of 2.5-3.5 deg.C/min, maintaining for 0.5-2h, and naturally cooling.

9. The method for preparing a ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance as defined in claim 8, wherein a flow rate of protective gas of 200mL/min is 100-.

10. The application of the ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance according to claim 1, wherein the composite material is applied to electromagnetic wave absorption, and is particularly applied to military equipment such as: the invisible of fighters, missiles, surface ships, missiles and surface ships, the discharge magnetic radiation of civil buildings and the application in the field of wearable electromagnetic radiation prevention clothes.

Technical Field

The invention relates to the technical field of electromagnetic wave absorption materials, in particular to a ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance and a preparation method and application thereof.

Background

With the rapid development of electronic communication and radar detection technologies, negative problems such as electromagnetic pollution, electromagnetic wave radiation, electromagnetic interference and the like are increasingly highlighted. The electromagnetic wave absorbing material converts electromagnetic waves into heat energy through various energy dissipation mechanisms, thereby effectively absorbing the electromagnetic waves. The electromagnetic wave absorbing material has great application potential in civil and military fields, and the electromagnetic wave absorbing performance is closely related to the composite dielectric constant, the composite magnetic conductivity and the morphology thereof. The construction of nanostructured composite materials having excellent dielectric and magnetic losses has proven to be an effective electromagnetic wave absorbing material and has been a hot spot of research on electromagnetic wave absorbing materials. Meanwhile, the electromagnetic wave absorbing material with advanced morphology and structure can enhance interface and defect induced polarization and meet impedance matching.

Nanostructured composites are a class of materials that are composed of at least two components, with at least one component having dimensions on the nanometer scale. Among various nanostructure composite materials, two-dimensional nanostructure materials with thin thickness and large transverse dimension have been the research hot spot of the materials science community. When it is used for electromagnetic wave absorption, the two-dimensional hybrid material promotes attenuation of electromagnetic waves by enhancing polarization on large-sized interfaces and multiple scattering between layers. Specially for treating diabetesOther than by dielectric or magnetic metal oxides (Fe)₃O₄，TiO₂，MnO₂，Co₃O₄Etc.) nanocrystals and carbon nanoplates are promising electromagnetic wave absorbing materials. In one aspect, the synergy between the dielectric or magnetic metal oxide and the conductive carbon skeleton may enhance dielectric and magnetic losses. On the other hand, the two-dimensional lamellar structure can promote reflection dissipation between layers, and the rich interface generated can enhance interface polarization. In metal oxides Fe₃O₄Has appreciable conductivity, which benefits from delocalized electrons in octahedral structures. In addition, the appropriate saturation magnetization and high Curie temperature (850K) are such that Fe₃O₄Becoming one of the most commonly used magnetic materials. However, the most Fe is currently reported₃O₄The preparation strategy of the/carbon nano sheet composite material has the problems of complex synthetic route, complex additive and the like.

Therefore, the development of an efficient, large-scale-producible and sustainable strategy for constructing the ferroferric oxide/carbon nano sheet composite material with excellent electromagnetic wave absorption performance is an urgent need for human health, environmental protection and national defense safety.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a simple and effective ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance, which can be used for large-scale production, and a preparation method and application thereof.

The purpose of the invention can be realized by the following technical scheme:

one of the technical schemes of the invention provides a ferroferric oxide/carbon nano sheet composite material with high electromagnetic wave absorption performance, ultra-wide frequency absorption capacity and excellent electromagnetic wave absorption performance, and the composite material has large (diameter)>20 μm) two-dimensional lamellar structure, and ferroferric oxide nanocrystals are distributed on the carbon sheet. Wherein, the content of ferroferric oxide can reach 46 percent, namely the composite material comprises the following components in percentage by mass: 54-58% of carbon and Fe₃O₄ 42-46％。

Furthermore, the specific saturation magnetization of the composite material is 33-38emu/g, and the coercive force is 63-110 Oe.

Further, the BET specific surface area of the composite material is 170-340m²A pore surface area of 110-280m²(ii)/g; the total pore volume is 0.15-0.30cm³Per g, wherein the pore volume of the micropores is 0.06-0.11cm³/g。

A preparation method of the ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance comprises the following steps:

(1) weighing a proper amount of ferric trichloride hexahydrate and water, and preparing a ferric trichloride solution after uniformly stirring;

(2) adding a proper amount of ammonia water into the ferric trichloride solution, adjusting the pH value of the ferric trichloride solution to be about 7 to prepare ferric hydroxide precipitate, performing suction filtration separation on the prepared ferric hydroxide precipitate, and washing the ferric hydroxide precipitate obtained by suction filtration with water for three times;

(3) adding the ferric hydroxide precipitate washed by water into a proper amount of gluconic acid aqueous solution according to the molar ratio of the ferric chloride precipitate to ferric trichloride, and heating and stirring the mixture to be completely dissolved to obtain a gluconic acid ferric solution;

(4) adding the ferric gluconate solution into absolute ethyl alcohol, separating ferric gluconate, and drying the separated ferric gluconate precipitate in a 50 ℃ oven for 24 hours to obtain a ferric gluconate complex;

(5) and carbonizing the ferric gluconate composite to obtain the ferroferric oxide/carbon nano sheet composite material with excellent electromagnetic wave absorption performance.

Further, the composite material is uniformly mixed with paraffin and is pressed and molded to obtain the electromagnetic wave absorbing material.

In the invention, the preparation principle of the ferroferric oxide/carbon nanosheet composite material is as follows: as shown in fig. 1, a ferric gluconate carbonized precursor is obtained by reacting freshly prepared ferric hydroxide with gluconic acid, and then the ferric oxide/carbon nanosheet composite material can be obtained by directly carbonizing the ferric gluconate precursor. The two-dimensional plane structure of the composite material is derived from a foam-like structure generated by the self-foaming behavior of ferric gluconate in the initial stage of carbonization.

The self-foaming principle of the ferric gluconate in the initial carbonization stage is as follows: as shown in FIG. 2, the amorphous ferric gluconate releases a large amount of H at a temperature of 140 ℃ and 250 DEG C₂O and CO₂Experiencing rapid thermal weight loss. And an endothermic peak appears in the range of 130-190 ℃, which indicates that the melting phase transition occurs. Therefore, before 300 ℃, the spontaneously generated pyrolysis gas can foam molten ferric gluconate and form a large amount of cavity morphology. After subsequent high-temperature calcination at 600-800 ℃, the cavity structure can be retained and evolves into a two-dimensional sheet structure. Meanwhile, organic glucose chains and ferric ions are structurally rearranged and respectively converted into carbon nano sheets and ferroferric oxide nano crystals.

Further, as shown in fig. 3, 0.787kg of ferric gluconate raw material was successfully prepared, and 0.413kg of ferric gluconate was carbonized to successfully obtain 0.141kg of ferroferric oxide/carbon nanosheet composite material with a yield as high as 34.1%.

Further, the molar ratio of ferric trichloride hexahydrate to gluconic acid is (2.5-3.5): 1.

Furthermore, the mass fraction of ammonia in the ammonia water is 25-28%, and the mass fraction of gluconic acid in the gluconic acid aqueous solution is 49-53%.

Further, the temperature of the heating and stirring in the step (3) is 80-90 ℃.

Further, the carbonization conditions are as follows: heating to 600-800 deg.C at a heating rate of 2.5-3.5 deg.C/min, preferably 700 deg.C, maintaining for 0.5-2h, and naturally cooling.

Further, a flow rate of 200mL/min of protective gas, such as nitrogen, is used during the carbonization treatment.

The application of the ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance is applied to electromagnetic wave absorption, and is particularly applied to military equipment such as: the invisible of fighters, missiles, surface ships, missiles and surface ships, the discharge magnetic radiation of civil buildings and the application in the field of wearable electromagnetic radiation prevention clothes.

The synthetic line of the invention adopts the gluconic acid iron compound as the raw material, and based on the self-foaming characteristic of the gluconic acid iron compound in the initial stage of carbonization, the ferroferric oxide/carbon nanosheet composite material with kilogram-level yield is successfully prepared in batches through one-step carbonization. The composite material has high-dispersion and high-load capacity (the load capacity can reach 42-46%) ferroferric oxide and large two-dimensional lamella size (the diameter is more than 20 mu m). The strong interface polarization, excellent conductivity loss and multiple scattering absorption are induced by the synergistic effect between the two-dimensional carbon nano-sheets and the highly dispersed ferroferric oxide nano-particles.

Compared with the prior art, the invention has the following advantages:

(1) the preparation of the ferroferric oxide/carbon nano sheet composite material is a simple process, a complex synthetic route and an exogenous chemical foaming agent are not needed, and the raw material is cheap, wherein the gluconic acid is a non-corrosive, non-toxic and mild organic acid and can be massively generated by the oxidation of cheap glucose. The composite material is expected to realize large-scale preparation and large-scale application;

(2) in the ferroferric oxide/carbon nano sheet composite material, a large number of heterogeneous interfaces can be generated by the ferroferric oxide nanocrystals, the carbon nano sheets and the unique yolk shell nano structure formed under the calcination treatment at the temperature of 700 ℃, and charge aggregation is generated, so that the obvious interface polarization loss is caused;

(3) the highly graphitized carbon nanosheet produced after the ferroferric oxide/carbon nanosheet composite material is calcined at high temperature can form a three-dimensional conductive network, so that strong conductive loss is realized; meanwhile, the two-dimensional plane structure enhances the multiple scattering and absorption of electromagnetic waves in the paraffin-ferroferric oxide/carbon nanosheet compound; in addition, the synergetic effect between the dielectric loss and the magnetic loss enables the ferroferric oxide/carbon nano sheet composite material to have good impedance matching and excellent loss capability;

(4) the nano material provided by the invention is applied to the field of electromagnetic wave absorption and has the advantages of high reflection loss and high absorption bandwidth. The maximum reflection loss of the ferroferric oxide/carbon nano sheet composite material obtained by calcination treatment at 700 ℃ is-65.4 dB, which is equivalent to 99.99997% of electromagnetic wave absorption rate, and the maximum effective absorption bandwidth can reach 6.24GHz, namely 11.68 to 17.92 GHz;

(5) the invention provides inspiration and paradigm for developing an efficient spontaneous foaming strategy to synthesize other metal oxide/carbon nanosheet composite materials, and promotes the design of excellent electromagnetic wave absorbing materials.

Drawings

FIG. 1 is a schematic diagram of the preparation principle of the present invention;

FIG. 2 is a thermogravimetric graph of thermogravimetry and differential scanning of ferric gluconate of the present invention and an in-situ Fourier infrared spectrum of carbonized pyrolysis gas;

FIG. 3 is a photograph of a preparation process of a ferroferric oxide/carbon nanosheet composite of the present invention;

FIG. 4 is a scanning electron microscope, a projection electron microscope and a high-resolution projection electron microscope of the ferroferric oxide/carbon nanosheet composite prepared in example 1;

FIG. 5 is an XRD spectrum of the ferroferric oxide/carbon nanosheet composite prepared in example 1;

fig. 6 shows the reflection loss values of the ferroferric oxide/carbon nanosheet composite prepared in example 1 at different thicknesses.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

A preparation method of a ferroferric oxide/carbon nanosheet composite material with excellent electromagnetic wave absorption performance is characterized by comprising the following steps:

(1) weighing a proper amount of ferric trichloride hexahydrate and water, and preparing a ferric trichloride solution after uniformly stirring;

(2) adding a proper amount of ammonia water into the ferric trichloride solution, adjusting the pH value of the ferric trichloride solution to be about 7 to prepare ferric hydroxide precipitate, performing suction filtration separation on the prepared ferric hydroxide precipitate, and washing the ferric hydroxide precipitate obtained by suction filtration with water for three times; the mass fraction of ammonia in the ammonia water is 25-28%,

(3) adding the ferric hydroxide precipitate washed by water into a proper amount of gluconic acid aqueous solution according to the molar ratio of the ferric chloride precipitate to ferric trichloride, and heating and stirring the mixture at the temperature of 80-90 ℃ to completely dissolve the ferric hydroxide precipitate to obtain a gluconic acid iron solution; wherein the molar ratio of ferric trichloride hexahydrate to gluconic acid is (2.5-3.5) to 1, and the mass fraction of the gluconic acid in the gluconic acid aqueous solution is 49-53%;

(4) adding the ferric gluconate solution into absolute ethyl alcohol, separating ferric gluconate, and drying the separated ferric gluconate precipitate in a 50 ℃ oven for 24 hours to obtain a ferric gluconate complex;

(5) carbonizing the ferric gluconate compound under the following conditions: heating to 800 ℃ at the heating rate of 2.5-3.5 ℃/min, keeping the temperature for 0.5-2h, then naturally cooling, and finally obtaining the ferroferric oxide/carbon nano sheet composite material with excellent electromagnetic wave absorption performance by using protective gas, such as nitrogen, with the flow rate of 100 plus 200mL/min in the treatment process, wherein the composite material has a large (the diameter is more than 20 mu m) two-dimensional lamellar structure, and the ferroferric oxide nano crystals are distributed on the carbon sheet. Wherein, the content of ferroferric oxide can reach 46 percent.

Example 1

Referring to the flow shown in fig. 1, the preparation of the ferroferric oxide/carbon nanosheet composite material FeOC-700 specifically comprises the following steps:

(1) preparation of ferric gluconate precursor

Weighing 5.41g of ferric chloride hexahydrate, adding the weighed ferric chloride hexahydrate into 200mL of water, and stirring until the ferric chloride hexahydrate is completely dissolved to prepare a ferric chloride solution; adding a proper amount of ammonia water into the ferric trichloride solution, adjusting the pH value to be about 7 to prepare ferric hydroxide precipitate, performing suction filtration separation on the prepared brick red ferric hydroxide precipitate, and washing the ferric hydroxide precipitate obtained by suction filtration with water for three times; adding the ferric hydroxide precipitate washed by water into 24g of gluconic acid aqueous solution (the mass content of gluconic acid is 50%), then adding 20mL of water, heating the mixture to 85 ℃, and then violently stirring until the ferric hydroxide precipitate is completely dissolved to obtain a reddish brown ferric gluconate solution; adding the ferric gluconate solution into absolute ethyl alcohol, separating ferric gluconate, washing the separated ferric gluconate precipitate with ethanol for 3 times, and drying the obtained solid in an oven at 50 ℃ for 24h to obtain the ferric gluconate precursor.

(2) Preparation of ferroferric oxide/carbon nanosheet composite FeOC-700

And (2) carrying out temperature programming on the ferric gluconate precursor in a tubular furnace, taking nitrogen with the flow rate of 100 plus one year (200 mL/min) as protective gas, heating to 700 ℃ at the heating rate of 3 ℃/min, keeping for 1h, and then naturally cooling to room temperature to obtain the ferroferric oxide/carbon nanosheet composite material, which is recorded as FeOC-700, wherein 700 refers to the retention temperature in the carbonization process and has the unit of ℃.

Fig. 4a is a scanning electron microscope image of the ferroferric oxide/carbon nanosheet composite FeOC-700 prepared in the present embodiment, fig. 4b is a projection electron microscope image, and fig. 4c is a high-resolution projection electron microscope image. It can be seen that FeOC-700 has a larger size (diameter)>20 μm), ferroferric oxide nanocrystals with a diameter of about 100nm are uniformly dispersed in the framework of FeOC-700, and a secondary nanostructure of the yolk shell appears in the framework of FeOC-700. The XRD pattern (figure 5) shows a group of peaks which are consistent with a ferroferric oxide standard spectrum (JCPDS card No.89-2355) and prove that the peaks are in a highly crystalline ferroferric oxide cubic crystal structure. The content of ferroferric oxide in FeOC-700 is 44.5 percent, the specific saturation magnetization is 36.1emu/g, and the coercive force is 109.0 Oe. The BET specific surface area of FeOC-700 is 331m²Per g, wherein the micropore surface area is 124m²(ii)/g; the total pore volume is 0.30cm³Per g, wherein the pore volume of the micropores is 0.06cm³/g。

Mixing the obtained FeOC-700 and paraffin according to the mass ratio of 4:6, pressing and molding, and carrying out the test of the reflectivity of the electromagnetic wave frequency band of 2-18GHz by a coaxial method. As shown in FIG. 6, FeOC-700 has the advantages of high reflection loss and high absorption bandwidth. Wherein, the maximum reflection loss is-65.4 dB (the thickness is 1.81mm), which is equivalent to 99.99997 percent of the electromagnetic wave absorption rate; the effective absorption bandwidth can reach 6.24GHz (the thickness is 1.81mm), and the coverage frequency band is as follows: 11.68-17.92 GHz.

Example 2

The preparation method of the ferroferric oxide/carbon nanosheet composite material FeOC-600 comprises the following specific preparation steps:

the difference from the embodiment 1 is that: the retention temperature of the carbonization process in the step (2) is changed to 600 ℃.

The content of ferroferric oxide in the prepared FeOC-600 is 42.6 percent, the specific saturation magnetization is 33.6emu/g, and the coercive force is 63.3 Oe. The BET specific surface area of FeOC-600 is 296m²Per g, wherein the micropore surface area is 272m²(ii)/g; the total pore volume is 0.15cm³Per g, wherein the pore volume of the micropores is 0.11cm³/g。

Example 3

The preparation method of the ferroferric oxide/carbon nanosheet composite material FeOC-650 comprises the following specific preparation steps:

the difference from the embodiment 1 is that: the residence temperature of the carbonization process in the step (2) is changed to 650 ℃.

Example 4

The preparation method of the ferroferric oxide/carbon nanosheet composite material FeOC-750 comprises the following specific preparation steps:

the difference from the embodiment 1 is that: the retention temperature of the carbonization process in the step (2) is changed to 750 ℃.

Example 5

The preparation method of the ferroferric oxide/carbon nanosheet composite material FeOC-800 comprises the following specific preparation steps:

the difference from the embodiment 1 is that: the retention temperature of the carbonization process in the step (2) is changed to 800 ℃.

The content of ferroferric oxide in the prepared FeOC-800 is 45.1 percent, the specific saturation magnetization is 37.2emu/g, and the coercive force is 104.4 Oe. The BET specific surface area of FeOC-600 is 179m²Per g, wherein the micropore surface area is 113m²(ii)/g; the total pore volume is 0.19cm³Per g, wherein the pore volume of the micropores is 0.06cm³(ii) in terms of/g. Mixing the obtained FeOC-800 and paraffin according to the mass ratio of 4:6, pressing and molding, and carrying out the test of the reflectivity of the electromagnetic wave frequency band of 2-18GHz by a coaxial method. The maximum reflection loss of FeOC-800 is-60.6 dB (thickness: 2.14 mm); the effective absorption bandwidth can reach 3.90GHz, and the coverage frequency band is as follows: 13.97-17.87 GHz.

The foregoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.