Heteroatom-oxide co-doped carbon layer coated flaky carbonyl iron as well as preparation method and application method thereof

Abstract

The invention relates to heteroatom-oxide co-doped carbon layer coated flaky carbonyl iron as well as a preparation method and an application method thereof, and the preparation method comprises the following steps: carrying out wet mechanical ball milling on spherical carbonyl iron to obtain flaky carbonyl iron powder; secondly, plant polyphenol, ethidene diamine and ferric iron salt are mixed and then added into the flaky carbonyl iron, the plant polyphenol is oxidized into benzoquinone molecules, the benzoquinone molecules and ethidene diamine are subjected to Michael addition and rearrangement to form a cross-linked polymer, and the cross-linked polymer is coated on the surface of the flaky carbonyl iron powder; and finally, the modified flaky carbonyl iron is placed in a tubular furnace to be subjected to high-temperature treatment, and the heteroatom-oxide co-doped carbon layer coated flaky carbonyl iron with the electromagnetic synergistic loss is obtained. The preparation method is simple, and the material has excellent electromagnetic wave absorption capacity and has wide application prospects in the fields of daily protection, flight equipment stealth and the like.

Description

Technical Field

[0001] This invention relates to the field of microwave absorbing materials technology, specifically to heteroatom-oxide co-doped carbon layer coated sheet-like carbonyl iron and its preparation and application methods. Background Technology

[0002] The rapid development of wireless communication devices has brought tremendous benefits to human society, but the electromagnetic radiation they generate poses a safety hazard to human health. Furthermore, in the military field, with the continuous upgrading of radar detection equipment, there is an urgent need to develop a radar-absorbing material with a wide absorption band and low reflection loss to avoid detection on the modern battlefield. To address these issues, many researchers have conducted research on electromagnetic wave absorption and achieved excellent results.

[0003] Electromagnetic wave absorbing materials dissipate incident electromagnetic waves by converting them into heat or other forms of energy through electrical or magnetic losses. Iron carbonyl is a widely used magnetic loss radar absorber, characterized by its low cost and high saturation magnetization. However, the traditional loss mechanism of iron carbonyl is magnetic loss, which limits its application due to its singular loss mechanism and high density. Therefore, modifying iron carbonyl is crucial. Electromagnetic wave absorption is mainly related to impedance matching and loss mechanisms. The synergistic effect of multiple loss mechanisms and good impedance matching can improve electromagnetic wave absorption. Chinese patent CN117750751B provides a method for preparing a sheet-like iron carbonyl / molybdenum disulfide composite absorbing material. This patent first obtains molybdenum disulfide nanomaterials through hydrothermal reaction and centrifugal cleaning. Then, iron carbonyl and molybdenum disulfide are mixed and ground in a certain ratio to obtain a mixed powder. The mixed powder is then bonded to obtain the sheet-like iron carbonyl / molybdenum disulfide composite absorbing material, which has a reflection loss of -55.53 dB and an effective absorption bandwidth of 3.3 GHz. Summary of the Invention

[0004] The purpose of this invention is to provide a heteroatom-oxide co-doped carbon layer coated sheet-like carbonyl iron and its preparation and application methods, which can simply and efficiently prepare a broadband strong absorption microwave absorber.

[0005] To achieve the above objectives, the present invention provides a method for preparing sheet-like carbonyl iron coated with a heteroatom-oxide co-doped carbon layer, comprising: Step 1, wet mechanical ball milling of spherical carbonyl iron to obtain sheet-like carbonyl iron powder; Step 2, dispersing 1g of sheet-like carbonyl iron powder into 100mL of a 0.2mol / L~0.8mol / L trivalent iron salt solution, then weighing plant polyphenols and ethylenediamine and adding them to the above solution, stirring at room temperature to obtain plant polyphenol-modified carbonyl iron powder microwave absorber; Step 3, placing the modified sheet-like carbonyl iron in a tube furnace, heating it to 600℃~800℃ at a certain rate, and holding it at that temperature for 2h~4h to obtain sheet-like carbonyl iron coated with a heteroatom-oxide co-doped carbon layer.

[0006] In the above-mentioned method for preparing sheet-like carbonyl iron coated with a heteroatom-oxide co-doped carbon layer, in step 1, the ball-to-material ratio is 10:1 to 25:1; the ball mill speed is 300 rpm / min to 600 rpm / min; the ball milling time is 8h to 14h; and the ball milling medium is at least one of anhydrous ethanol and deionized water.

[0007] In the above-mentioned method for preparing sheet-like carbonyl iron coated with a heteroatom-oxide co-doped carbon layer, in step 2, the plant polyphenol is one of tannic acid, gallic acid, caffeic acid, catechin, and chlorogenic acid; the molar ratio of the phenolic hydroxyl group in the plant polyphenol to the amino group in ethylenediamine is 2:1 to 1:4; the trivalent iron salt is one of ferric chloride and ferric nitrate, with a concentration of 0.1 mol / L to 0.8 mol / L; and the stirring time is 3 h to 6 h.

[0008] The above-mentioned method for preparing sheet-like carbonyl iron coated with heteroatom-oxide co-doped carbon layer includes a step of extracting sheet-like carbonyl iron coated with plant polyphenols after step 2 and before step 3. The sheet-like carbonyl iron coated with plant polyphenols is extracted by magnetic separation, washed with anhydrous ethanol, and then dried in a vacuum oven.

[0009] In the above method for preparing sheet-like carbonyl iron coated with a heteroatom-oxide co-doped carbon layer, in step 3, the heating rate is 5℃ / min and the gas atmosphere is nitrogen or argon.

[0010] The present invention also provides a heteroatom-oxide co-doped carbon layer coated sheet-like carbonyl iron, which is prepared by the above-mentioned heteroatom-oxide co-doped carbon layer coated sheet-like carbonyl iron preparation method.

[0011] The present invention also provides a method for applying the above-mentioned heteroatom-oxide co-doped carbon layer coated sheet-like carbonyl iron as an electromagnetic wave absorbing material.

[0012] Compared with the prior art, the beneficial technical effects of the present invention are:

[0013] 1) Trivalent iron salts have a dual function: they can catalyze the aggregation of plant polyphenols and also be uniformly doped in situ to form metal oxides during high-temperature carbonization, thereby enhancing the microwave absorption performance.

[0014] 2) Using ethylenediamine as a crosslinking agent, nitrogen-doped carbon layer coated sheet-like carbonyl iron was obtained, achieving a wide absorption band and low loss value;

[0015] 3) This invention constructs a carbon layer coated with sheet-like carbonyl iron co-doped with nitrogen atoms and iron oxide, which solves the problem of narrow bandwidth and low absorption of carbonyl iron powder. It has the potential for large-scale application in the field of wave absorption and has broad application prospects in the fields of daily protection and stealth of flight equipment. Attached Figure Description

[0016] The heteroatom-doped carbon layer-coated sheet-like carbonyl iron of the present invention, its preparation method, and its application method are given in the following examples and figures.

[0017] Figure 1 This is a morphology diagram of the flake carbonyl iron powder obtained after ball milling in Example 4 of the present invention.

[0018] Figure 2 This is a morphology diagram of the nitrogen-iron oxide co-doped carbon layer coated sheet-like carbonyl iron obtained in Example 8 of the present invention. Detailed Implementation

[0019] The following will combine Figures 1-2 The present invention provides a further detailed description of the heteroatom-doped carbon layer-coated sheet-like carbonyl iron, its preparation method, and its application method.

[0020] This invention provides a method for preparing a heteroatom-doped carbon layer coated sheet-like carbonyl iron, comprising:

[0021] Step 1: Wet mechanical ball milling of spherical carbonyl iron to obtain flake carbonyl iron powder;

[0022] The ball-to-material ratio (i.e., the ratio of grinding balls to spherical carbonyl iron) is 10:1 to 25:1;

[0023] The ball mill speed is 300 rpm / min to 600 rpm / min; the ball milling time is 8 h to 14 h; the ball milling media is at least one of anhydrous ethanol and deionized water.

[0024] Step 2: Disperse 1g of flake carbonyl iron powder into a 0.2mol / L~0.8mol / L trivalent iron salt solution (100 mL), then weigh plant polyphenols and ethylenediamine and add them to the above solution. Stir at room temperature to obtain plant polyphenol modified carbonyl iron powder microwave absorber.

[0025] Plant polyphenols are one of tannic acid, gallic acid, caffeic acid, catechin, and chlorogenic acid; the molar ratio of phenolic hydroxyl groups to amino groups in ethylenediamine in plant polyphenols is 2:1 to 1:4;

[0026] Ferric salts are one of ferric chloride and ferric nitrate, with a concentration of 0.1 mol / L to 0.8 mol / L;

[0027] In this step, plant polyphenols are oxidized into benzoquinone molecules, which undergo Michael addition with ethylenediamine, and after rearrangement, form a cross-linked polymer that is coated on the surface of sheet-like carbonyl iron powder.

[0028] Step 3: The modified sheet carbonyl iron is placed in a tube furnace and heated to 600℃~800℃ at a rate of 5℃ / min, and held for 2h~4h to obtain sheet carbonyl iron with a heteroatom-oxide co-doped carbon layer having electromagnetic synergistic loss.

[0029] The gas atmosphere in the tubular furnace is nitrogen or argon.

[0030] This invention is simple to prepare and, while possessing multiple loss mechanisms, can achieve a wide absorption band and a strong absorption peak. As an electromagnetic wave absorbing material, it has the potential for large-scale application and broad application prospects in fields such as daily protection and stealth of flight equipment.

[0031] Example 1

[0032] 3 g of spherical carbonyl iron and 30 g of agate grinding balls (6 mm in diameter) were added to an agate jar. 15 ml of anhydrous ethanol was used as the grinding medium. The mixture was ball-milled for 480 min at 350 rpm / min using a planetary ball mill. The carbonyl iron powder after ball milling was removed by magnetic separation. The powder was washed three times with anhydrous ethanol and dried in a vacuum oven at 60 °C to obtain flake-like carbonyl iron powder with a thickness of 700 nm.

[0033] Example 2:

[0034] 3 g of spherical carbonyl iron and 45 g of agate grinding balls (6 mm in diameter) were added to an agate jar. 15 ml of anhydrous ethanol was used as the grinding medium. The mixture was ball-milled for 480 min at 450 rpm / min using a planetary ball mill. The carbonyl iron powder after ball milling was removed by magnetic separation. The powder was washed three times with anhydrous ethanol and dried in a vacuum oven at 60 °C to obtain flake-like carbonyl iron powder with a thickness of 300 nm.

[0035] Example 3:

[0036] 3 g of spherical carbonyl iron and 60 g of agate grinding balls (6 mm in diameter) were added to an agate jar. 15 ml of anhydrous ethanol was used as the grinding medium. The mixture was ball-milled for 480 min at 450 rpm / min using a planetary ball mill. The carbonyl iron powder after ball milling was removed by magnetic separation. The powder was washed three times with anhydrous ethanol and dried in a vacuum oven at 60 °C to obtain flake-like carbonyl iron powder with a thickness of 200 nm.

[0037] Example 4:

[0038] 3 g of spherical iron carbonyl and 75 g of agate grinding balls (6 mm in diameter) were added to an agate jar. 15 ml of anhydrous ethanol was used as the milling medium. The mixture was milled using a planetary ball mill at 550 rpm for 480 min. The milled iron carbonyl powder was removed using magnetic separation, washed three times with anhydrous ethanol, and dried in a vacuum oven at 60 °C to obtain flake-like iron carbonyl powder with a thickness of 30 nm. Figure 1 .

[0039] Example 5:

[0040] 3 g of spherical carbonyl iron and 75 g of agate grinding balls (6 mm in diameter) were added to an agate jar. 15 ml of anhydrous ethanol was used as the grinding medium. The mixture was ball-milled for 480 min at 600 rpm using a planetary ball mill. The carbonyl iron powder after ball milling was removed by magnetic separation. The powder was washed three times with anhydrous ethanol and dried in a vacuum oven at 60 °C to obtain flake-like carbonyl iron powder with a thickness of 60 nm.

[0041] Example 6:

[0042] 1 g of flake-shaped iron carbonyl powder from Example 4 was dispersed in a 0.8 mol / L ferric chloride solution. Then, 0.4 g of gallic acid and 200 μL of ethylenediamine were added to the solution and stirred for 3 h. The plant polyphenol-coated iron carbonyl powder was removed by magnetic separation, washed three times with anhydrous ethanol, and dried in a vacuum oven at 60 °C. The thickness of the plant polyphenol was 120 nm. The plant polyphenol-coated iron carbonyl powder was placed in a tube furnace and heated to 700 °C at a heating rate of 5 °C / min and held for 4 h to obtain flake-shaped iron carbonyl powder coated with a carbon layer co-doped with N atoms and iron oxide. This was then doped with paraffin in a 7:3 ratio to prepare a coaxial ring with an effective absorption bandwidth of 7.1 GHz and a minimum reflection loss of -42 dB.

[0043] Example 7:

[0044] 1 g of flake-shaped iron carbonyl powder from Example 4 was dispersed in a 0.5 mol / L ferric chloride solution. Then, 0.2 g of gallic acid and 120 μL of ethylenediamine were added to the solution and stirred for 3 h. The plant polyphenol-coated iron carbonyl powder was removed by magnetic separation, washed three times with anhydrous ethanol, and dried in a vacuum oven at 60 °C. The plant polyphenol thickness was 50 nm. The plant polyphenol-coated iron carbonyl powder was placed in a tube furnace and heated to 700 °C at a heating rate of 5 °C / min and held for 4 h to obtain flake-shaped iron carbonyl powder coated with a carbon layer co-doped with N atoms and iron oxide. This was then doped with paraffin in a 7:3 ratio to prepare a coaxial ring with an effective absorption bandwidth of 6.2 GHz and a reflection loss of -37 dB.

[0045] Example 8:

[0046] 1 g of flake-shaped iron carbonyl powder from Example 4 was dispersed in a 0.3 mol / L ferric chloride solution. Then, 0.3 g of gallic acid and 150 μL of ethylenediamine were added to the solution and stirred for 3 h. The plant polyphenol-coated iron carbonyl powder was removed by magnetic separation, washed three times with anhydrous ethanol, and dried in a vacuum oven at 60 °C. The thickness of the plant polyphenol was 80 nm. The plant polyphenol-coated iron carbonyl powder was placed in a tube furnace and heated to 700 °C at a heating rate of 5 °C / min and held for 4 h to obtain flake-shaped iron carbonyl powder coated with a carbon layer co-doped with N atoms and iron oxide. This was then doped with paraffin in a 7:3 ratio to prepare a coaxial ring with an absorption bandwidth of 5.5 GHz and a reflection loss of -28 dB.

[0047] Comparative Example 1:

[0048] 3g of spherical carbonyl iron and 75g of agate grinding balls (6 mm in diameter) were added to an agate jar. 15 ml of anhydrous ethanol was used as the grinding medium. The mixture was ball-milled for 480 min at 550 rpm / min using a planetary ball mill. The carbonyl iron powder after ball milling was removed by magnetic separation. It was washed three times with anhydrous ethanol and dried. After drying, it was mixed with paraffin at a ratio of 7:3 to prepare a coaxial ring with an absorption bandwidth of 3.7 GHz and a reflection loss of -18 dB.

[0049] Comparative Example 2:

[0050] 1 g of flake-shaped iron carbonyl powder from Example 4 was dispersed in a Tris buffer solution (pH=8.5), and then 0.4 g of gallic acid and 200 μL of ethylenediamine were added to the above solution sequentially and stirred for 3 h. The plant polyphenol-coated iron carbonyl powder was removed by magnetic separation, washed three times with anhydrous ethanol, and dried in a vacuum oven at 60 °C. The thickness of the plant polyphenol was 70 nm. The plant polyphenol-coated iron carbonyl powder was placed in a tube furnace and heated to 700 °C at a heating rate of 5 °C / min and held for 4 h to obtain N-atom-doped carbon layer-coated flake-shaped iron carbonyl powder. This was then doped with paraffin in a 7:3 ratio to prepare a coaxial ring with an effective absorption bandwidth of 4.6 GHz and a minimum reflection loss of -24 dB.

Claims

1. A method for preparing sheet-like carbonyl iron coated with a heteroatom-oxide co-doped carbon layer, characterized in that, include: Step 1: Wet mechanical ball milling of spherical carbonyl iron to obtain flake carbonyl iron powder; Step 2: Disperse 1g of flake carbonyl iron powder into 100mL of ferric salt solution with a concentration of 0.2mol / L~0.8mol / L, then weigh plant polyphenols and ethylenediamine and add them to the above solution. Stir at room temperature to obtain plant polyphenol modified carbonyl iron powder microwave absorber. Step 3: Place the modified sheet carbonyl iron in a tube furnace and heat it to 600℃~800℃ at a certain rate, and hold it for 2h~4h to obtain sheet carbonyl iron coated with heteroatom-oxide co-doped carbon layer.

2. The method for preparing sheet-like carbonyl iron coated with a heteroatom-oxide co-doped carbon layer as described in claim 1, characterized in that, In step 1, the ball-to-material ratio is 10:1 to 25:

1.

3. The method for preparing sheet-like carbonyl iron coated with a heteroatom-oxide co-doped carbon layer as described in claim 1, characterized in that, In step 1, the ball mill speed is 300 rpm / min to 600 rpm / min; the ball milling time is 8h to 14h; and the ball milling medium is at least one of anhydrous ethanol and deionized water.

4. The method for preparing sheet-like carbonyl iron coated with a heteroatom-oxide co-doped carbon layer as described in claim 1, characterized in that, In step 2, the plant polyphenol is one of tannic acid, gallic acid, caffeic acid, catechin, and chlorogenic acid; the molar ratio of the phenolic hydroxyl group in the plant polyphenol to the amino group in ethylenediamine is 2:1 to 1:

4.

5. The method for preparing sheet-like carbonyl iron coated with a heteroatom-doped carbon layer as described in claim 1, characterized in that, In step 2, the ferric salt is either ferric chloride or ferric nitrate, with a concentration of 0.1 mol / L to 0.8 mol / L.

6. The method for preparing sheet-like carbonyl iron coated with a heteroatom-oxide co-doped carbon layer as described in claim 1, characterized in that, In step 2, the stirring time is 3 to 6 hours.

7. The method for preparing sheet-like carbonyl iron coated with a heteroatom-doped carbon layer as described in claim 1, characterized in that, After step 2 and before step 3, there is also a step of extracting plant polyphenol-coated flake carbonyl iron. The plant polyphenol-coated flake carbonyl iron is extracted by magnetic separation, washed with anhydrous ethanol, and then dried in a vacuum oven.

8. The method for preparing sheet-like carbonyl iron coated with a heteroatom-oxide co-doped carbon layer as described in claim 1, characterized in that, In step 3, the heating rate is 5℃ / min, and the gas atmosphere is nitrogen or argon.

9. A heteroatom-oxide co-doped carbon layer coated with plate-like carbonyl iron, characterized in that, It is prepared by the method for preparing sheet-like carbonyl iron coated with a heteroatom-oxide co-doped carbon layer as described in any one of claims 1 to 8.

10. The method of applying the heteroatom-oxide co-doped carbon layer coated sheet-like carbonyl iron according to claim 9, characterized in that, Used as an electromagnetic wave absorbing material.

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