CN112961650B - Three-metal organic framework derived iron-nickel alloy/porous carbon ultrathin wave absorber and preparation method thereof - Google Patents

Abstract

The invention discloses a three-Metal Organic Frameworks (MOFs) derived iron-nickel alloy/porous carbon ultrathin wave absorber and a preparation method thereof. Iron salt, zinc salt and nickel salt of different kinds are used as precursors, trimesic acid is used as an organic ligand, N, N-dimethylformamide, deionized water and absolute ethyl alcohol are used as mixed solvents, polyvinylpyrrolidone is used as a stabilizer, and the iron-zinc-nickel trimetallic MOFs derivative iron-nickel alloy/porous carbon composite wave-absorbing material is prepared through a solvothermal and pyrolysis two-step method. The preparation method is green and environment-friendly, does not generate any toxic byproducts, and has simple preparation process. The prepared composite material enables the shape of the carbon framework to gradually evolve from a porous shape to a pomegranate shape, a hollow structure and a core-shell structure by simply changing the salt type in the precursor, and meanwhile, the calcination temperature and the matching thickness are changed to realize strong absorption and wide bandwidth, so that the Ku wave band is almost completely covered by effective absorption, and the composite material has important application value in the fields of electromagnetic wave absorption and electromagnetic shielding.

Description

A tri-metal organic framework derived iron-nickel alloy/porous carbon ultra-thin absorber and its Preparation

technical field

The invention belongs to the field of electromagnetic wave absorbing materials, and in particular relates to a preparation method of a tri-metal organic framework derived iron-nickel alloy/porous carbon composite wave absorbing material.

technical background

With the development of radio technology and information industry, electronic products have been widely used, which has brought a series of electromagnetic radiation problems, which have brought many impacts on people's production and life. In addition, with the changes in the international strategic environment, stealth technology has become an important manifestation of the military power competition of various countries. Therefore, seeking effective technology to reduce or eliminate electromagnetic radiation is of great significance in the fields of life and military affairs. An important way to reduce electromagnetic radiation is electromagnetic wave absorption. Previous studies have shown that wave-absorbing materials can promote the conversion of electromagnetic energy into heat energy or eliminate electromagnetic waves fundamentally through interference and cancellation, so as to achieve the purpose of eliminating electromagnetic radiation. In practical applications, new electromagnetic wave absorbing materials that meet the requirements of "thin thickness, light weight, wide absorption frequency band, and high absorption strength" have important application prospects.

As a new wave-absorbing material, porous carbon reduces the difficulty of coating, enhances the wave-absorbing effect, and easily meets the urgent needs of "thin, light, wide, and strong" stealth materials for aircraft. Compared with non-porous materials, porous carbon materials are light in weight, and with the deepening of people's understanding, it is found that its large specific surface area and pore structure are conducive to absorbing incident electromagnetic waves, converting electromagnetic waves into heat energy consumption, so as to achieve the attenuation of electromagnetic waves .

Metal-Organic Frameworks (MOFs) is a new type of porous crystal material, which is a three-dimensional space structure formed by the complexation of adjustable metal ions and organic ligands. Compared with traditional porous materials (molecular sieves, activated carbon, etc.), the biggest advantage of MOFs materials lies in their variable and adjustable metal ion and ligand components. MOFs have the advantages of three-dimensional pore structure, high porosity, low density, large specific surface area, regular pore size, adjustable pore size, diversity of topology and tailorability, etc. Bulk components, MOFs materials can be used as precursors or templates to obtain porous carbon materials through high-temperature heat treatment.

Magnetic metals have a wide range of applications in the field of electromagnetic wave absorption due to their large saturation magnetization, high Snoek limit, and compatible dielectric-magnetic loss. Alloys have two-component characteristics. Compared with single-component magnetic metals, magnetic metal alloys have stronger electron transfer and spin polarization coupling characteristics, and have certain advantages in the field of electromagnetic wave absorption. In addition, the combination of magnetic alloy and carbon can also slow down the oxidation of the alloy and reduce the density. Magnetic alloy/carbon composite materials have dual loss characteristics of magnetic loss and dielectric loss, and are widely used in the field of electromagnetic wave absorption.

The invention first adopts solvothermal reaction to synthesize FeZnNi three-metal MOFs, and then prepares iron-nickel alloy/porous carbon composite wave-absorbing material by high-temperature pyrolysis in argon atmosphere. By simply changing the type of salt in the precursor, the morphology of the carbon framework gradually evolves from porous to pomegranate, hollow, and core-shell structures; adjusting the type of salt in the precursor, the calcination temperature and the matching thickness can realize the composite material’s electromagnetic waves in different bands. Absorbs effectively.

Contents of the invention

The purpose of the present invention is to provide a three-metal organic framework derived iron-nickel alloy/porous carbon composite absorbing material and its preparation method. The composite material not only has the characteristics of thin thickness, high absorption strength, wide absorption frequency band, and easy adjustment of absorption band. , and its preparation process is simple and environmentally friendly.

The present invention is realized through the following technical solutions:

A three-metal organic framework derived iron-nickel alloy/porous carbon composite wave-absorbing material, the wave-absorbing material is composed of iron-nickel alloy and porous carbon.

A three-metal organic framework derived iron-nickel alloy/porous carbon composite wave-absorbing material, the preparation steps of which are as follows:

(1) Take a 150mL beaker, add 60mL N,N-dimethylformamide (DMF), 3.6mL deionized water (H ₂ O) and 3.6mL absolute ethanol (C ₂ H ₅ OH), mix well , take by weighing 1.0mmol iron salt, 1.0mmol zinc salt and 1.0mmol nickel salt, add vigorous stirring successively until completely dissolving, obtain mixed solution (iron salt, zinc salt and nickel salt are respectively: ferric chloride hexahydrate (FeCl ₃ . 6H ₂ O), zinc chloride (ZnCl ₂ ) and nickel chloride hexahydrate (NiCl ₂ 6H ₂ O); iron nitrate nonahydrate (Fe(NO ₃ ) ₃ 9H ₂ O), zinc nitrate hexahydrate (Zn (NO ₃ ) ₂ 6H ₂ O) and nickel nitrate hexahydrate (Ni(NO ₃ ) ₂ 6H ₂ O); FeCl ₃ 6H ₂ O, ZnCl ₂ and Ni(NO ₃ ) ₂ 6H ₂ O; four Ferrous chloride hydrate (FeCl ₂ 4H ₂ O), Zn(NO ₃ ) ₂ 6H ₂ O and Ni(NO ₃ ) ₂ 6H ₂ O);

(2) Add 1.5mmol trimesic acid (H ₃ BTC) to the above solution and stir vigorously until completely dissolved, then add 1.0g polyvinylpyrrolidone (PVP, K-30) vigorously stir until completely dissolved, and finally stir vigorously for 2h , to obtain a homogeneous solution;

(3) Transfer the obtained solution to a polytetrafluoroethylene-lined autoclave with a volume of 100 mL, and conduct a solvothermal reaction at 150° C. for 24 h;

(4) After the reaction is finished, cool to room temperature, repeatedly use DMF and absolute ethanol to centrifuge and wash several times, and collect the precipitate;

(5) Transfer the collected precipitate to a vacuum freeze dryer, dry for 24 hours to constant weight, and grind evenly to obtain the precursor;

(6) Perform high-temperature thermal annealing treatment on the precursor in a tube furnace with an argon atmosphere. The temperatures are 700, 800, 900 and 950 °C respectively, the heating rate is 5 °C/min, the holding time is 2 h, and cooling The final product was obtained after reaching room temperature.

Compared with the prior art, the beneficial technical effects of the present invention are reflected in the following aspects:

1. The present invention adopts two steps of solvothermal and high-temperature pyrolysis to prepare trimetallic MOFs derived iron-nickel alloy/porous carbon composite wave-absorbing material, which is easy to operate, green and safe, and does not produce any toxic and harmful substances.

2. The present invention uses the combination of different salt types of three metal salts, and finds that simply changing the salt type in the precursor makes the carbon framework morphology gradually evolve from porous to pomegranate, hollow, and core-shell structures.

3. The present invention finds that the type of salt has a great influence on the microwave-absorbing performance of the composite material. Studies have shown that when the three metal salts are FeCl ₃ ·6H ₂ O, ZnCl ₂ , and NiCl ₂ ·6H ₂ O, the composite material simultaneously achieves the characteristics of thin thickness, strong absorption, and wide frequency band.

4. The present invention finds that the calcination temperature has a great influence on the morphology and absorbing performance of the composite material. When the calcination temperature is 900°C, the carbon frame is porous and the absorbing performance is optimal.

5. The iron-nickel alloy/porous carbon composite wave-absorbing material prepared by the present invention has excellent wave-absorbing properties. At a thickness of 1.35mm, the maximum absorption strength can reach -66.4dB; at a thickness of 1.4mm, microwaves within the range of 12.3-18.0GHz The absorption intensity is below -10dB, the effective absorption bandwidth reaches 5.7GHz, and almost completely covers the Ku band (12.0-18.0GHz); by adjusting the type of salt in the precursor, the calcination temperature and the matching thickness, the composite material can be effective for electromagnetic waves of different bands absorb.

6. The iron-nickel alloy/porous carbon composite wave-absorbing material prepared by the present invention realizes effective attenuation of electromagnetic waves through the synergy of physical mechanisms such as optimized impedance matching, interface polarization, dipole polarization, and magnetic loss.

Description of drawings

Fig. 1 is the XRD spectrogram of product in embodiment 1,2,3,4;

Fig. 2 is the XRD spectrogram of product in embodiment 5,6,7;

Fig. 3 is the TG curve of product precursor in embodiment 1,2,3,4;

Fig. 4 is the Raman spectrogram of product in embodiment 1,2,3,4;

Fig. 5 is the Raman spectrogram of product in embodiment 5,6,7;

Fig. 6 is the XPS spectrogram of product S3 in embodiment 3;

Fig. 7 is the SEM photo of product in embodiment 1,2,3,4;

Fig. 8 is the SEM photograph of product in embodiment 5,6,7;

Fig. 9 is the variation curve of the reflection loss of product S1 with frequency in embodiment 1;

Fig. 10 is the variation curve of the reflection loss of product S2 with frequency in embodiment 2;

Fig. 11 is the variation curve of the reflection loss of product S3 with frequency in embodiment 3;

Fig. 12 is the variation curve of the reflection loss of product S4 with frequency in embodiment 4;

Fig. 13 is the variation curve of the reflection loss of product S5 with frequency in embodiment 5;

Fig. 14 is the variation curve of the reflection loss of product S6 with frequency in embodiment 6;

FIG. 15 is a curve of the reflection loss of the product S7 in Example 7 as a function of frequency.

Specific implementation method

Now in conjunction with embodiment and accompanying drawing, the present invention will be further described:

Example 1

1. Take a 150mL beaker, add 60mL DMF, 3.6mL H ₂ O and 3.6mL C ₂ H ₅ OH, mix well, weigh 1.0mmol FeCl ₃ 6H ₂ O, 1.0mmol ZnCl ₂ and 1.0mmol NiCl ₂ Add 6H ₂ O in sequence and stir vigorously until completely dissolved to obtain a uniform solution;

2. First add 1.5mmol H ₃ BTC to the homogeneous solution obtained above and stir vigorously until completely dissolved, then add 1.0g PVP vigorously stir until completely dissolved, and finally stir vigorously for 2 hours;

3. Transfer the obtained solution to a polytetrafluoroethylene-lined autoclave with a volume of 100mL, and conduct a solvothermal reaction at 150°C for 24h;

4. After the reaction, cool to room temperature, repeatedly wash with DMF and absolute ethanol for several times, and collect the precipitate;

(5) Transfer the collected precipitate to a vacuum freeze dryer, dry for 24 hours to constant weight, and grind evenly to obtain the precursor;

(6) Perform high-temperature thermal annealing treatment on the precursor in a tube furnace with an argon atmosphere, the temperature is 700 °C, the heating rate is 5 °C/min, the holding time is 2 h, and the final product is obtained after cooling to room temperature. Denote it as S1.

The XRD spectrogram of embodiment 1 product sees Fig. 1, 2θ=31.7 °, 34.4 °, 36.2 °, 47.6 °, 56.6 °, and 62.8 ° and zinc oxide (ZnO) standard card (JCPDS Card No.89-0510) The positions corresponding to (100), (002), (101), (102), (110) and (103) crystal planes are consistent. 2θ=43.7°, 50.8° and 74.7° are consistent with the positions corresponding to the (111), (200) and (220) crystal planes of the iron-nickel (FeNi) alloy standard card (JCPDS Card No. 47-1417). 2θ=42.7, 49.7° and 73.2° are consistent with the positions corresponding to the (111), (200) and (220) crystal planes of the iron (Fe) standard card (JCPDS Card No. 52-0513). The TG curve of the precursor of the product of Example 1 is shown in Figure 3; under nitrogen atmosphere, 30°C to 900°C, the heating rate is 10°C/min. The weight loss of pyrolysis of FeZnNi-MOFs was 17.5wt.% and 54.3wt.% at 30°C-245°C and 245°C-532°C, respectively. The first stage is mainly the evaporation of adsorbed water, and the second stage is mainly the decomposition of organic ligands. The Raman spectrum of the product of Example 1 is shown in Figure 4; S1 has two obvious diffraction peaks around 1602cm ^-1 (G band) and 1336cm ^-1 (D band), and the _ID / _IG is 0.92. The SEM photo of the product of Example 1 is shown in Figure 7(a); at 700°C, it appears as microspheres with uneven surfaces. The powder product and paraffin in Example 1 are pressed into a coaxial sample with an outer diameter of 7.00mm, an inner diameter of 3.04mm, and a thickness of about 2mm in a special mold according to the mass ratio of 5:5, and the model is AV3629D vector network analyzer test Its electromagnetic parameters are calculated to obtain the absorbing performance, and the test frequency range is 2.0-18.0GHz. The variation curve of reflection loss with frequency of sample S1 is shown in Fig. 9. When the matching thickness is 3.5mm, the maximum absorption intensity reaches -12.8dB at 7.6GHz.

Example 2

1. Take a 150mL beaker, add 60mL DMF, 3.6mL H ₂ O and 3.6mL C ₂ H ₅ OH, mix well, weigh 1.0mmol FeCl ₃ 6H ₂ O, 1.0mmol ZnCl ₂ and 1.0mmol NiCl ₂ Add 6H ₂ O in sequence and stir vigorously until completely dissolved to obtain a uniform solution;

2. First add 1.5mmol H ₃ BTC to the homogeneous solution obtained above and stir vigorously until completely dissolved, then add 1.0g PVP vigorously stir until completely dissolved, and finally stir vigorously for 2 hours;

3. Transfer the obtained solution to a polytetrafluoroethylene-lined autoclave with a volume of 100mL, and conduct a solvothermal reaction at 150°C for 24h;

4. After the reaction, cool to room temperature, repeatedly wash with DMF and absolute ethanol for several times, and collect the precipitate;

(5) Transfer the collected precipitate to a vacuum freeze dryer, dry for 24 hours to constant weight, and grind evenly to obtain the precursor;

(6) Perform high-temperature thermal annealing treatment on the precursor in a tube furnace with an argon atmosphere. The temperature is 800 °C, the heating rate is 5 °C/min, and the holding time is 2 h. After cooling to room temperature, the final product is obtained. Denote it as S2.

The XRD spectrum of the product of Example 2 is shown in Fig. 1, 2θ=43.7 °, 50.8 ° and 74.7 ° and (111), (200) and (220) crystal planes of the FeNi alloy standard card (JCPDS Card No.47-1417) The corresponding positions are the same. The TG curve of the precursor of the product of Example 2 is shown in Figure 3; under nitrogen atmosphere, 30°C to 900°C, the heating rate is 10°C/min. The weight loss of pyrolysis of FeZnNi-MOFs was 17.5wt.% and 54.3wt.% at 30°C-245°C and 245°C-532°C, respectively. The first stage is mainly the evaporation of adsorbed water, and the second stage is mainly the decomposition of organic ligands. The Raman spectrum of the product of Example 2 is shown in Figure 4; S2 has two obvious diffraction peaks around 1602cm ^-1 (G band) and 1336cm ^-1 (D band), and the _ID / _IG is 0.87. The SEM photo of the product of Example 2 is shown in Figure 7(b); at 800°C, it appears as smooth microspheres. The powder product and paraffin in Example 2 are pressed into a coaxial sample with an outer diameter of 7.00mm, an inner diameter of 3.04mm and a thickness of about 2mm in a special mold according to the mass ratio of 5:5, and the model is AV3629D vector network analyzer test Its electromagnetic parameters are calculated to obtain the absorbing performance, and the test frequency range is 2.0-18.0GHz. The curve of reflection loss versus frequency of sample S2 is shown in Figure 10. When the matching thickness is 1.53mm, the maximum absorption intensity reaches -62.4dB at 17.4GHz. When the matching thickness is 1.78mm, the microwave absorption intensity is below -10dB in the range of 12.6-18.0GHz, and the effective absorption bandwidth reaches 5.4GHz.

Example 3

1. Take a 150mL beaker, add 60mL DMF, 3.6mL H ₂ O and 3.6mL C ₂ H ₅ OH, mix well, weigh 1.0mmol FeCl ₃ 6H ₂ O, 1.0mmol ZnCl ₂ and 1.0mmol NiCl ₂ Add 6H ₂ O in sequence and stir vigorously until completely dissolved to obtain a uniform solution;

2. First add 1.5mmol H ₃ BTC to the homogeneous solution obtained above and stir vigorously until completely dissolved, then add 1.0g PVP vigorously stir until completely dissolved, and finally stir vigorously for 2 hours;

3. Transfer the obtained solution to a polytetrafluoroethylene-lined autoclave with a volume of 100mL, and conduct a solvothermal reaction at 150°C for 24h;

4. After the reaction, cool to room temperature, repeatedly wash with DMF and absolute ethanol for several times, and collect the precipitate;

(5) Transfer the collected precipitate to a vacuum freeze dryer, dry for 24 hours to constant weight, and grind evenly to obtain the precursor;

(6) Perform high-temperature thermal annealing treatment on the precursor in a tube furnace with an argon atmosphere. The temperature is 900 °C, the heating rate is 5 °C/min, and the holding time is 2 h. After cooling to room temperature, the final product is obtained. Denote it as S3.

The XRD spectrum of the product of Example 3 is shown in Fig. 1, 2θ=43.7 °, 50.8 ° and 74.7 ° and (111), (200) and (220) crystal planes of the FeNi alloy standard card (JCPDS Card No.47-1417) The corresponding positions are the same. The TG curve of the precursor of the product of Example 3 is shown in Figure 3; under nitrogen atmosphere, 30°C to 900°C, the heating rate is 10°C/min. The weight loss of pyrolysis of FeZnNi-MOFs was 17.5wt.% and 54.3wt.% at 30°C-245°C and 245°C-532°C, respectively. The first stage is mainly the evaporation of adsorbed water, and the second stage is mainly the decomposition of organic ligands. The Raman spectrum of the product of Example 3 is shown in Fig. 4; S3 has two obvious diffraction peaks near 1602cm ^-1 (G band) and 1336cm ^-1 (D band), _ID / _IG is 0.83, indicating that the calcination temperature Increased, the degree of graphitization increased. The XPS spectrum of the product of Example 3 is shown in Figure 6. It can be seen that the sample contains Fe, Zn, Ni, C and O elements, which are consistent with the types of elements in the prepared composite material. The appearance of Zn element shows that zinc species still exists at 900 °C, but no diffraction peak of zinc species is observed in XRD characterization, indicating that zinc may be evaporated or exist in the sample in an amorphous form. The SEM photo of the product of Example 3 is shown in Figure 7(c); at 900°C, it appears as microspheres with holes on the surface. The powder product and paraffin in Example 3 are pressed into a coaxial sample with an outer diameter of 7.00mm, an inner diameter of 3.04mm, and a thickness of about 2mm in a special mold according to the mass ratio of 5:5, and the model is AV3629D vector network analyzer test Its electromagnetic parameters are calculated to obtain the absorbing performance, and the test frequency range is 2.0-18.0GHz. The curve of reflection loss versus frequency of sample S3 is shown in Figure 11. When the matching thickness is 1.35mm, the maximum absorption intensity reaches -66.4dB at 15.76GHz. When the matching thickness is 1.4mm, the microwave absorption intensity is below -10dB in the range of 12.3-18.0GHz, and the effective absorption bandwidth reaches 5.7GHz.

Example 4

1. Take a 150mL beaker, add 60mL DMF, 3.6mL H ₂ O and 3.6mL C ₂ H ₅ OH, mix well, weigh 1.0mmol FeCl ₃ 6H ₂ O, 1.0mmol ZnCl ₂ and 1.0mmol NiCl ₂ Add 6H ₂ O in sequence and stir vigorously until completely dissolved to obtain a uniform solution;

2. First add 1.5mmol H ₃ BTC to the homogeneous solution obtained above and stir vigorously until completely dissolved, then add 1.0g PVP vigorously stir until completely dissolved, and finally stir vigorously for 2 hours;

3. Transfer the obtained solution to a polytetrafluoroethylene-lined autoclave with a volume of 100mL, and conduct a solvothermal reaction at 150°C for 24h;

4. After the reaction, cool to room temperature, repeatedly wash with DMF and absolute ethanol for several times, and collect the precipitate;

(5) Transfer the collected precipitate to a vacuum freeze dryer, dry for 24 hours to constant weight, and grind evenly to obtain the precursor;

(6) Perform high-temperature thermal annealing treatment on the precursor in a tube furnace with an argon atmosphere. The temperature is 950 ° C, the heating rate is 5 ° C / min, and the holding time is 2 h. After cooling to room temperature, the final product is obtained. Denote it as S4.

The XRD spectrum of the product of Example 4 is shown in Fig. 1, 2θ=43.7 °, 50.8 ° and 74.7 ° and (111), (200) and (220) crystal planes of the FeNi alloy standard card (JCPDS Card No.47-1417) The corresponding positions are the same. The TG curve of the precursor of the product of Example 4 is shown in Figure 3; under nitrogen atmosphere, 30°C to 900°C, the heating rate is 10°C/min. The weight loss of pyrolysis of FeZnNi-MOFs was 17.5wt.% and 54.3wt.% at 30°C-245°C and 245°C-532°C, respectively. The first stage is mainly the evaporation of adsorbed water, and the second stage is mainly the decomposition of organic ligands. The Raman spectrum of the product of Example 4 is shown in Fig. 4; S4 has two obvious diffraction peaks near 1602cm ^-1 (G band) and 1336cm ^-1 (D band), _ID / _IG is 0.81, indicating that the calcination temperature As the temperature rises, the degree of graphitization increases. The SEM photo of the product of Example 4 is shown in Figure 7(d); at 950°C, it appears as microspheres with porous surfaces and a little collapse, indicating that as the calcination temperature increases, the morphology of the sample will also change. The powder product and paraffin in Example 4 are pressed into a coaxial sample with an outer diameter of 7.00mm, an inner diameter of 3.04mm, and a thickness of about 2mm in a special mold according to a mass ratio of 5:5, and the model is AV3629D vector network analyzer test Its electromagnetic parameters are calculated to obtain the absorbing performance, and the test frequency range is 2.0-18.0GHz. The variation curve of reflection loss with frequency of sample S4 is shown in Figure 12. When the matching thickness is 2.5mm, the maximum absorption intensity reaches -11.27dB at 5.68GHz.

Example 5

1. Take a 150mL beaker, add 60mL DMF, 3.6mL H ₂ O and 3.6mL C ₂ H ₅ OH, mix well, weigh 1.0mmol Fe(NO ₃ ) ₃ 9H ₂ O, 1.0mmol Zn(NO ₃ ) ₂ ·6H ₂ O and 1.0mmol Ni(NO ₃ ) ₂ ·6H ₂ O were added in sequence and vigorously stirred until completely dissolved to obtain a uniform solution;

2. First add 1.5mmol H ₃ BTC to the homogeneous solution obtained above and stir vigorously until completely dissolved, then add 1.0g PVP vigorously stir until completely dissolved, and finally stir vigorously for 2 hours;

3. Transfer the obtained solution to a polytetrafluoroethylene-lined autoclave with a volume of 100mL, and conduct a solvothermal reaction at 150°C for 24h;

4. After the reaction, cool to room temperature, repeatedly wash with DMF and absolute ethanol for several times, and collect the precipitate;

(5) Transfer the collected precipitate to a vacuum freeze dryer, dry for 24 hours to constant weight, and grind evenly to obtain the precursor;

(6) Perform high-temperature thermal annealing treatment on the precursor in a tube furnace with an argon atmosphere. The temperature is 900 °C, the heating rate is 5 °C/min, and the holding time is 2 h. After cooling to room temperature, the final product is obtained. Denote it as S5.

The XRD spectrum of the product of Example 5 is shown in Fig. 2, 2θ=43.7 °, 50.8 ° and 74.7 ° and (111), (200) and (220) crystal planes of the FeNi alloy standard card (JCPDS Card No.47-1417) The corresponding positions are the same. 2θ=44.2°, 51.5° and 76.1° are consistent with the positions corresponding to the (111), (200) and (220) crystal planes of the FeNi ₃ alloy standard card (JCPDS Card No.38-0419). The Raman spectrum of the product of Example 5 is shown in Figure 5; S5 has two obvious diffraction peaks around 1594cm ^-1 (G band) and 1326cm ^-1 (D band), and the _ID / _IG is 0.88. The SEM photo of the product of Example 5 is shown in Figure 8(a); S5 is a microsphere with a diameter of about 1 μm, indicating that different salt types have a great influence on the shape of the sample. The powder product and paraffin in Example 5 are pressed into a coaxial sample with an outer diameter of 7.00mm, an inner diameter of 3.04mm, and a thickness of about 2mm in a special mold according to a mass ratio of 5:5, and the model is AV3629D vector network analyzer test Its electromagnetic parameters are calculated to obtain the absorbing performance, and the test frequency range is 2.0-18.0GHz. The variation curve of reflection loss with frequency of sample S5 is shown in Figure 13. When the matching thickness is 3.5mm, the maximum absorption intensity reaches -9.0dB at 5.12GHz.

Example 6

1. Take a 150mL beaker, add 60mL DMF, 3.6mL H ₂ O and 3.6mL C ₂ H ₅ OH, mix well, weigh 1mmol FeCl ₃ 6H ₂ O, 1mmol ZnCl ₂ and 1mmol Ni(NO ₃ ) ₂ 6H ₂ O was added in sequence and vigorously stirred until completely dissolved to obtain a uniform solution;

2. First add 1.5mmol H ₃ BTC to the homogeneous solution obtained above and stir vigorously until completely dissolved, then add 1.0g PVP vigorously stir until completely dissolved, and finally stir vigorously for 2 hours;

3. Transfer the obtained solution to a polytetrafluoroethylene-lined autoclave with a volume of 100mL, and conduct a solvothermal reaction at 150°C for 24h;

4. After the reaction, cool to room temperature, repeatedly wash with DMF and absolute ethanol for several times, and collect the precipitate;

(5) Transfer the collected precipitate to a vacuum freeze dryer, dry for 24 hours to constant weight, and grind evenly to obtain the precursor;

(6) Perform high-temperature thermal annealing treatment on the precursor in a tube furnace with an argon atmosphere. The temperature is 900 °C, the heating rate is 5 °C/min, and the holding time is 2 h. After cooling to room temperature, the final product is obtained. Denote it as S6.

The XRD spectrum of the product of Example 6 is shown in Fig. 2, 2θ=43.7 °, 50.8 ° and 74.7 ° and the (111), (200) and (220) crystal planes of the FeNi alloy standard card (JCPDS Card No.47-1417) The corresponding positions are the same. The Raman spectrum of the product of Example 6 is shown in Figure 5; S6 has two obvious diffraction peaks around 1582cm ^-1 (G band) and 1349cm ^-1 (D band), and the _ID / _IG is 0.83. The SEM photo of the product of Example 6 is shown in Figure 8(b); S6 is a microsphere with a diameter of about 10 microns, indicating that different salt types have a great influence on the shape and size of the sample. The powder product and paraffin in Example 6 are pressed into a coaxial sample with an outer diameter of 7.00mm, an inner diameter of 3.04mm and a thickness of about 2mm in a special mold according to the mass ratio of 5:5, and the model is AV3629D vector network analyzer test Its electromagnetic parameters are calculated to obtain the absorbing performance, and the test frequency range is 2.0-18.0GHz. The curve of reflection loss versus frequency of sample S6 is shown in Figure 14. When the matching thickness is 3.0mm, the maximum absorption intensity reaches -17.68dB at 7.84GHz.

Example 7

1. Take a 150mL beaker, add 60mL DMF, 3.6mL H ₂ O and 3.6mL C ₂ H ₅ OH, mix well, weigh 1mmol FeCl ₂ 4H ₂ O, 1mmol Zn(NO ₃ ) ₂ 6H ₂ O , 1mmol Ni(NO ₃ ) ₂ ·6H ₂ O was added in turn and vigorously stirred until completely dissolved to obtain a uniform solution;

2. First add 1.5mmol H ₃ BTC to the homogeneous solution obtained above and stir vigorously until completely dissolved, then add 1.0g PVP vigorously stir until completely dissolved, and finally stir vigorously for 2 hours;

3. Transfer the obtained solution to a polytetrafluoroethylene-lined autoclave with a volume of 100mL, and conduct a solvothermal reaction at 150°C for 24h;

4. After the reaction, cool to room temperature, repeatedly wash with DMF and absolute ethanol for several times, and collect the precipitate;

(5) Transfer the collected precipitate to a vacuum freeze dryer, dry it for 24 hours to constant weight, and grind it evenly to obtain the precursor;

(6) Perform high-temperature thermal annealing treatment on the precursor in a tube furnace with an argon atmosphere. The temperature is 900 °C, the heating rate is 5 °C/min, and the holding time is 2 h. After cooling to room temperature, the final product is obtained. Denote it as S7.

The XRD spectrum pattern of the product of Example 7 is shown in Figure 2. 2θ=43.7°, 50.8° and 74.7° with the (111), (200) and (220) crystal planes of the FeNi alloy standard card (JCPDS Card No.47-1417) The corresponding positions are the same. 2θ=44.2°, 51.5° and 76.1° are consistent with the positions corresponding to the (111), (200) and (220) crystal planes of the FeNi ₃ alloy standard card (JCPDS Card No.38-0419). The Raman spectrum of the product of Example 7 is shown in Figure 5; S7 has two obvious diffraction peaks around 1588cm ^-1 (G band) and 1346cm ^-1 (D band), and the _ID / _IG is 0.89. The SEM photo of the product of Example 7 is shown in Figure 8(c); S7 is a hollow microsphere with a diameter of about 10 μm, with broken holes on the surface, indicating that different salt types have a great influence on the shape and size of the sample. The powder product and paraffin in Example 7 are pressed into a coaxial sample with an outer diameter of 7.00mm, an inner diameter of 3.04mm, and a thickness of about 2mm in a special mold according to the mass ratio of 5:5, and the model is AV3629D vector network analyzer test Its electromagnetic parameters are calculated to obtain the absorbing performance, and the test frequency range is 2.0-18.0GHz. The curve of reflection loss versus frequency of sample S7 is shown in Figure 15. When the matching thickness is 4.5mm, the maximum absorption intensity reaches -20.0dB at 4.64GHz.

From the test results of the above examples, it can be seen that the present invention uses a two-step method of solvothermal and high-temperature pyrolysis to obtain a three-metal MOFs derived iron-nickel alloy/porous carbon composite absorbing material. The method is simple to operate, safe and green, and has no toxic substances. The comprehensive absorbing performance of the composite material is excellent. When the matching thickness is 1.35mm, the maximum absorption intensity of sample S3 reaches -66.4dB; when the matching thickness is 1.35mm, the maximum effective absorption bandwidth reaches 5.7GHz, almost completely covering the Ku band. By adjusting the type of salt in the precursor, the calcination temperature and the matching thickness, the composite material can effectively absorb electromagnetic waves in different bands. Therefore, Fe-Ni alloy/porous carbon material is an ideal ultrathin and high-efficiency electromagnetic wave absorber.

Claims (7)

1. A preparation method of a trimetallic organic framework derived iron-nickel alloy/porous carbon composite wave-absorbing material is characterized by comprising the following steps: the wave absorbing material consists of iron-nickel alloy and porous carbon;

the composite wave-absorbing material is prepared by the following method:

(1) Taking 1 beaker of 150mL, adding 60mL of N, N-dimethylformamide, 3.6mL of deionized water and 3.6mL of absolute ethyl alcohol, uniformly mixing, weighing 1.0mmol of ferric chloride hexahydrate, 1.0mmol of zinc chloride and 1.0mmol of nickel chloride hexahydrate, and sequentially adding intense stirring until the materials are completely dissolved to obtain a mixed solution;

(2) Adding 1.5mmol of trimesic acid into the solution, stirring vigorously to dissolve completely, adding 1.0g of polyvinylpyrrolidone, stirring vigorously to dissolve completely, and stirring vigorously for 2h to obtain uniform solution;

(3) Transferring the obtained solution into an autoclave with a polytetrafluoroethylene liner and a volume of 100mL, and performing solvothermal reaction for 24 hours at 150 ℃;

(4) After the reaction is finished, cooling to room temperature, repeatedly centrifuging and washing with N, N-dimethylformamide and absolute ethyl alcohol for a plurality of times, and collecting a precipitate;

(5) Transferring the collected precipitate to a vacuum freeze dryer, drying for 24 hours to constant weight, and grinding uniformly to obtain a precursor;

(6) And (3) carrying out high-temperature heat treatment on the precursor in a tubular furnace filled with argon, wherein the calcination temperature is 900 ℃, the heating rate is 5 ℃/min, the heat preservation time is 2h, and the final product is obtained after cooling to room temperature.

2. The method for preparing the trimetallic organic framework-derived iron-nickel alloy/porous carbon composite material according to claim 1, wherein the method comprises the following steps: the step (1) is to add 1.0mmol of ferric chloride hexahydrate and stir vigorously to dissolve completely, then add 1.0mmol of zinc chloride and stir vigorously to dissolve completely, and finally add 1.0mmol of nickel chloride hexahydrate and stir vigorously to dissolve completely.

3. The method for preparing the trimetallic organic framework-derived iron-nickel alloy/porous carbon composite material according to claim 1, wherein the method comprises the following steps: in the step (2), 1.5mmol of trimesic acid is added and stirred vigorously until the trimesic acid is completely dissolved, 1.0g of polyvinylpyrrolidone is added and stirred vigorously until the trimesic acid and the polyvinylpyrrolidone are completely dissolved, and the mixture is stirred for 2 hours after the trimesic acid and the polyvinylpyrrolidone are completely dissolved.

4. The method for preparing the trimetallic organic framework-derived iron-nickel alloy/porous carbon composite material according to claim 1, wherein the method comprises the following steps: the solvothermal reaction conditions in step (3) must be at a temperature of 150 ℃ for 24 hours.

5. The method for preparing the trimetallic organic framework-derived iron-nickel alloy/porous carbon composite material according to claim 1, wherein the method comprises the following steps: after the solvothermal reaction in the step (4) is finished, repeatedly centrifuging and washing with N, N-dimethylformamide, and repeatedly centrifuging and washing with absolute ethyl alcohol to obtain a precipitate.

6. The method for preparing the trimetallic organic framework-derived iron-nickel alloy/porous carbon composite material according to claim 1, wherein the method comprises the following steps: the specific operation of the step (5) is that the freeze drying time is required to be 24 hours.

7. A trimetallic organic framework-derived iron nickel alloy/porous carbon composite wave absorbing material, characterized in that it is prepared by the method according to any one of claims 1-6.

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