CN112839500B - Yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material and preparation method thereof - Google Patents
Yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material and preparation method thereof Download PDFInfo
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Abstract
The invention relates to the technical field of electromagnetic wave absorption, in particular to a yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material and a preparation method thereof, wherein the preparation method comprises the following steps: (1) SiO is coated on the surface of the hollow ferroferric oxide nano particle2(ii) a (2) Performing carboxylation modification on the surface; (3) growing MIL-100 (Fe) on the surface in situ; (4) calcining at high temperature in nitrogen atmosphere; (5) heating and stirring in alkali liquor to remove SiO2And washing and drying the layer to obtain the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material. The preparation method has the advantages of low cost, environmental protection, safety, no generation of any toxic and harmful substance, no secondary pollution, easy mass synthesis and industrial prospect; the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material prepared by the preparation method has the characteristics of thin thickness, light weight, low filling ratio, strong absorption, wide frequency band and easiness in regulation and control of wave-absorbing performance, and has wide application prospect.
Description
Technical Field
The invention relates to the technical field of electromagnetic wave absorption, in particular to a yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material derived from a metal organic framework and a preparation method thereof.
Background
In recent years, with the wide development and application of communication equipment and electronic equipment, the electromagnetic pollution-free immune system provides great convenience for human beings, causes secret electromagnetic signal leakage and electromagnetic wave interference, harms human health, and influences the normal work of the immune system to increase the risk of diseases after being in an environment with high electromagnetic radiation pollution for a long time. In addition, the radar is also important in the military field as a technical device for detecting and positioning an object by using an electromagnetic wave, and the principle of the radar is that the emitted electromagnetic wave is reflected when encountering the surface of the object, and information such as the distance, the size, the speed, the height and the like of the object is acquired through a received reflected signal. Radar stealth technology is one of the key factors that determine weapon system viability in modern war.
In both civil and military application fields, the effect and the status of the wave-absorbing material for absorbing electromagnetic waves or converting the electromagnetic waves into heat are very outstanding, the efficient electromagnetic wave-absorbing material meets the requirements of wide absorption bandwidth, strong absorption capacity, light weight and thin thickness, and the research and development of the high-performance microwave-absorbing material has very important research significance and practical value.
Disclosure of Invention
In order to overcome the problems in the prior art, the invention provides the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material which is light in weight, low in filling ratio, strong in absorption, wide in frequency band and easy to regulate and control wave-absorbing performance.
The invention also provides a preparation method of the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material, which has the advantages of low cost, greenness, safety, no generation of any toxic and harmful substance, no secondary pollution, easiness in mass synthesis and industrial prospect.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of a yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material comprises the following steps:
(1) SiO is coated on the surface of the hollow ferroferric oxide nano particle2Obtaining Fe3O4@SiO2Nanoparticles;
(2) mixing hollow Fe3O4@SiO2The surface of the nano particle is subjected to carboxylation modification to obtain carboxylated Fe3O4@SiO2Nanoparticles; the step of passingCarboxylation treatment, Fe3O4@SiO2The carboxyl on the surface of the nano particle can react with Fe3+Adsorption binding, providing binding sites for the growth of MOF materials in the reaction system of the step (3);
(3) in carboxylation of Fe3O4@SiO2MIL-100 (Fe) grows on the surface of the nano particle in situ to obtain Fe3O4@SiO2Nanoparticle @ MIL-100 (Fe) composites; the step further coats a metal organic framework MIL-100 (Fe) taking iron ions as metal clusters, the MOF material has the characteristics of porosity, high specific surface area and uniform distribution of metal ions, and magnetic metal iron elements and porous carbon generated after the MOF material is used as a precursor and calcined at high temperature can generate good electromagnetic wave absorption capacity;
(4) by carboxylation of Fe3O4@SiO2Calcining the nano particle @ MIL-100 (Fe) composite material at high temperature in a nitrogen atmosphere to obtain Fe3O4@SiO2@ C composite material; in the step, the calcining atmosphere is critical, and the carbon layer can be successfully obtained by calcining in the nitrogen atmosphere and used as a conductive material;
(5) mixing Fe3O4@SiO2Heating and stirring @ C composite material in alkali liquor to remove SiO2And washing and drying the layer to obtain the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material. In this step, SiO2The layer is dissolved in alkali liquor, so that a hollow cavity is formed between the ferric oxide layer and the carbon layer.
The preparation method of the invention has the advantages of low cost, environmental protection, safety, no generation of any toxic and harmful substance, no secondary pollution, easy mass synthesis and industrial prospect.
Preferably, in the step (1), the preparation method of the hollow ferroferric oxide nanoparticles comprises the following steps: dissolving ferric chloride hexahydrate, sodium citrate and urea in deionized water in sequence, adding polyacrylamide, carrying out high-pressure hydrothermal reaction at the temperature of 180-200 ℃ for 10-12 h h, removing precipitates, washing, and drying to obtain the hollow ferroferric oxide nanoparticles.
Preferably, step (1)) In, the surface is coated with SiO2The method comprises the following steps: dispersing hollow ferroferric oxide nano particles in ethanol/deionized water mixed solution, adding concentrated ammonia water, adding tetraethyl orthosilicate, stirring for reaction, washing and drying the obtained product to obtain Fe3O4@SiO2Nanoparticles.
Preferably, the volume ratio of the ethanol to the water in the ethanol/deionized water mixed solution is (3-5): 1; the total mass of the hollow ferroferric oxide nano particles is taken as a reference, and the adding amount of tetraethyl orthosilicate is 0.01 mL/mg.
Preferably, in the step (2), the carboxylation modification method comprises the following steps: mixing Fe3O4@SiO2Dispersing nano particles in ethanol, adding strong ammonia water, adding a carboxylation reagent, violently stirring at room temperature for reaction, washing and drying an obtained product to obtain carboxylated Fe3O4@SiO2Nanoparticles. The carboxylation reagent may be any reagent capable of achieving carboxylation in the prior art.
Preferably, the preparation method of the carboxylation reagent comprises the following steps: 0.5g succinic anhydride is dissolved in 5 mL anhydrous DMF by ultrasonic, 300 mu L aminopropyl trimethoxy silane (APTMS) is added, and the mixture is slowly stirred for 16 hours at room temperature, thus obtaining the carboxylation reagent.
The concentration of the strong ammonia water is 25-28 wt%;
with Fe3O4@SiO2The total mass of the nano particles is taken as a reference, and the adding amount of the carboxylation reagent is 0.03 mL/mg.
Preferably, in the step (3), the method for growing MIL-100 (Fe) in situ is as follows: by carboxylation of Fe3O4@SiO2Uniformly dispersing the nano particles in deionized water, adding ferric chloride hexahydrate, uniformly dispersing by ultrasonic, adding trimesic acid, dissolving by ultrasonic, keeping at the high temperature and the high pressure of 120-150 ℃ for 1-5 days, washing and drying the obtained product to obtain Fe3O4@SiO2Nanoparticle @ MIL-100 (Fe) composites.
Preferably, Fe is carboxylated3O4@SiO2Nanoparticle aggregateThe addition amount of the ferric chloride hexahydrate is 17mg/mg by taking the amount as a reference; the addition amount of the trimesic acid is 2.94 mg/mg.
Preferably, in the step (4), the heating rate of the high-temperature calcination is 1-5 ℃/min, the calcination temperature is 600-900 ℃, and the calcination time is 1-3 h; a series of materials with different wave absorption properties can be obtained by adjusting the calcining temperature, and the wave absorption properties are excellent, which shows that the preparation method can realize controllable properties.
In the step (5), the alkali liquor is 0.5-1 mol/L sodium hydroxide solution; the heating temperature is 30-50 ℃. The concentration of the sodium hydroxide solution is critical, and the silicon dioxide layer cannot be completely removed due to the low concentration; too high may cause corrosion of the ferroferric oxide core by the sodium hydroxide solution. The heating is favorable for accelerating the reaction between the sodium hydroxide solution and the silicon dioxide, and meanwhile, the heating temperature is not too high, which can cause the ferroferric oxide core to be corroded by the sodium hydroxide solution.
The yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material prepared by the preparation method is provided. The material has the characteristics of thin thickness, light weight, low filling ratio, strong absorption, wide frequency band and easy regulation of wave absorption performance, and has wide application prospect. By adjusting the calcining temperature, a series of materials with different wave absorbing properties can be obtained, and the wave absorbing properties are excellent. Calcining the obtained product at 700 ℃, filling the product in a paraffin matrix in a proportion of 30 wt%, wherein when the thickness of the coating is 3mm, the maximum absorption strength of the composite material can reach-27.7 dB; when the thickness of the coating is 2 mm, the effective absorption bandwidth is up to 8GHz, and the X-band (8-12 GHz) and the Ku-band (12-18 GHz) are almost covered. The effective absorption of electromagnetic waves of different wave bands can be realized by adjusting the thickness of each coating in the precursor.
Therefore, the invention has the following beneficial effects:
(1) the preparation method has the advantages of low cost, environmental protection, safety, no generation of any toxic and harmful substance, no secondary pollution, easy mass synthesis and industrial prospect;
(2) the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material prepared by the preparation method has the characteristics of thin thickness, light weight, low filling ratio, strong absorption, wide frequency band and easiness in regulation and control of wave-absorbing performance, and has wide application prospect.
Drawings
FIG. 1 is an SEM image of the yolk shell hollow ferroferric oxide @ air @ carbon nanocomposite wave-absorbing material prepared in example 1.
FIG. 2 is a TEM image of the yolk shell hollow ferroferric oxide @ air @ carbon nanocomposite wave-absorbing material prepared in example 1.
FIG. 3 is an X-ray diffraction pattern of the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material, MIL-100 (Fe) and hollow ferroferric oxide nano particles prepared in example 1.
FIG. 4 is a wave absorption loss diagram of the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material (700 ℃) prepared in example 2.
Detailed Description
The technical solution of the present invention is further specifically described below by using specific embodiments and with reference to the accompanying drawings.
In the present invention, all the equipment and materials are commercially available or commonly used in the art, and the methods in the following examples are conventional in the art unless otherwise specified.
Example 1
(1) Weighing 3.2436 g of ferric chloride hexahydrate, 7.0584 g of sodium citrate dihydrate and 2.1624 g of urea, sequentially dissolving in 210 mL of deionized water, adding 1.8 g of polyacrylamide, stirring the solution at room temperature for 5 hours until the solution is uniformly clear, keeping the solution in a polytetrafluoroethylene-lined high-pressure reaction kettle at 200 ℃ for 10 hours, washing the obtained black mud-shaped product with deionized water for 5 times, washing with absolute ethyl alcohol for 3 times, and drying at 60 ℃ to obtain the hollow ferroferric oxide nanoparticles;
(2) 300 mg of hollow ferroferric oxide nano particles are weighed and dispersed in 150 mL of ethanol and 50mL of deionized water mixed solution, ultrasonic dispersion is carried out for 30 min, 4 mL of strong ammonia water (the concentration is 25 wt/%) is added, mechanical stirring is carried out for 5 min, 1mL of TEOS (tetraethyl orthosilicate) is added, and the mixture is added once every 30 min and is added for 3 times in totalMechanically stirring for 6 h, washing the obtained product with ethanol for 5 times, and drying at 60 ℃ to obtain Fe3O4@SiO2Nanoparticles;
(3) 100 mg of Fe was weighed3O4@SiO2Ultrasonically dispersing the nano particles in 200 mL of ethanol, adding 5 mL of concentrated ammonia water, mechanically stirring for 5 min, adding 1mL of carboxylation reagent, and violently stirring at room temperature for reaction. Adding carboxylation reagent for 1 time every 2 hours, adding carboxylation reagent for 3 times in total in the whole process, reacting for 6 hours, washing the obtained product for 5 times by using ethanol, and drying at 60 ℃ to obtain carboxylated Fe3O4@SiO2Nanoparticles;
the preparation method of the carboxylation reagent comprises the following steps: dissolving 0.5g succinic anhydride in 5 mL anhydrous DMF by ultrasonic, adding 300 μ L aminopropyl trimethoxy silane (APTMS), and slowly stirring at room temperature for 16 hr to obtain carboxylation reagent;
(4) 50 mg of carboxylated Fe are weighed3O4@SiO2Uniformly dispersing the nanoparticles in 13 mL of deionized water, adding 0.7 g of ferric chloride hexahydrate, ultrasonically dispersing for 30 min, and then adding 0.15 g H3Ultrasonic dissolving BTC (trimesic acid), transferring to a polytetrafluoroethylene-lined high-pressure reaction kettle at 130 ℃ for 3 days, washing the obtained yellow mud-like product with deionized water for 5 times, washing with absolute ethanol for 3 times, drying at 60 ℃, and performing Fe extraction3O4@SiO2Nanoparticle @ MIL-100 (Fe) composites;
(5) sample Fe3O4@SiO2The @ MIL-100 composite material is placed in a tubular furnace for high-temperature calcination, the calcination atmosphere is nitrogen, the heating rate is 2 ℃/min, the calcination temperature is 600 ℃, the calcination is carried out for 2 hours, and Fe is obtained3O4@SiO2@ C composite material;
(6) weighing 100 mg of calcined black powder Fe3O4@SiO2The @ C composite material is prepared by mechanically stirring 50mL of 1mol/L sodium hydroxide solution with the concentration of 50 ℃ to remove a silicon dioxide layer, washing the obtained product to be neutral by using deionized water, and drying at 60 ℃ to obtain the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material. The black product is named as P-600 and its SEM picture is as followsAs shown in fig. 1, as can be seen from fig. 1, the wave-absorbing material prepared in the embodiment has a complete spherical structure and uniform particle size, and the particle size is about 250-400 nm; the TEM image is shown in FIG. 2, and it can be seen from FIG. 2 that the wave-absorbing material prepared by the embodiment has a hollow layered structure.
The yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material (P-600) prepared in the embodiment is mixed with paraffin, the paraffin accounts for 70wt%, a coaxial sample with the outer diameter of 7.00 mm, the inner diameter of 3.04 mm and the thickness of about 2 mm is prepared in a special die in a pressing mode, the mass fraction of the product is 30%, an N5224A type vector network analyzer is used for testing the electromagnetic parameters of the sample, the wave-absorbing performance is obtained through calculation, and the testing frequency range is 2-18 GHz.
Through detection, when the thickness of the coating is 3.5 mm, the maximum absorption strength of the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material prepared by the embodiment is-7.5 dB.
Example 2
Example 2 differs from example 1 in that in step (5), the calcination temperature is 700 ℃, the remaining process conditions are exactly the same, and the black product obtained in this example is designated as P-700.
The yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material (P-700) prepared in the embodiment is mixed with paraffin, the paraffin accounts for 70wt%, a coaxial sample with the outer diameter of 7.00 mm, the inner diameter of 3.04 mm and the thickness of about 2 mm is prepared in a special die in a pressing mode, the mass fraction of the product is 30%, an N5224A type vector network analyzer is used for testing the electromagnetic parameters of the sample, the wave-absorbing performance is obtained through calculation, and the testing frequency range is 2-18 GHz.
The change curve of the reflection loss of the sample P-700 along with the frequency is shown in FIG. 4, and when the coating thickness is 3mm, the maximum absorption intensity of the composite material can reach-27.7 dB; when the thickness of the coating is 2 mm, the effective absorption bandwidth reaches 8GHz, and the X waveband (8-12 GHz) and the Ku waveband (12-18 GHz) are almost covered. The thickness of each coating in the precursor can be adjusted to realize the effective absorption of electromagnetic waves of different wave bands.
Example 3
Example 3 differs from example 1 in that in step (5), the calcination temperature is 800 ℃, the remaining process conditions are exactly the same, and the black product obtained in this example is designated as P-800.
The yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material (P-800) prepared in the embodiment is mixed with paraffin, the ratio of the paraffin is 70wt%, a coaxial sample with the outer diameter of 7.00 mm, the inner diameter of 3.04 mm and the thickness of about 2 mm is prepared in a special die, the mass fraction of the product is 30%, an N5224A type vector network analyzer is used for testing the electromagnetic parameters of the sample, the wave-absorbing performance is obtained through calculation, and the testing frequency range is 2-18 GHz.
When the thickness of the coating is 5.5 mm, the maximum absorption strength of the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material prepared by the embodiment can reach-25 dB, and the effective absorption bandwidth is 2 GHz.
Example 4
(1) Weighing 3.2436 g of ferric chloride hexahydrate, 7.0584 g of sodium citrate dihydrate and 2.1624 g of urea, sequentially dissolving in 210 mL of deionized water, adding 1.8 g of polyacrylamide, stirring the solution at room temperature for 5 hours until the solution is uniformly clear, keeping the solution in a polytetrafluoroethylene-lined high-pressure reaction kettle at 180 ℃ for 12 hours, washing the obtained black mud-shaped product with deionized water for 5 times, washing with absolute ethyl alcohol for 3 times, and drying at 60 ℃ to obtain the hollow ferroferric oxide nanoparticles;
(2) weighing 300 mg of hollow ferroferric oxide nano particles, dispersing the hollow ferroferric oxide nano particles in 250 mL of ethanol and 50mL of deionized water mixed solution, ultrasonically dispersing the hollow ferroferric oxide nano particles for 30 min, adding 4 mL of concentrated ammonia water (the concentration is 26 wt/%), mechanically stirring the mixture for 5 min, adding 1mL of TEOS (tetraethyl orthosilicate), adding the mixture once every 30 min, adding the mixture 3 times in total, mechanically stirring the mixture for 6 h, washing the obtained product for 5 times by using ethanol, and drying the product at 60 ℃ to obtain Fe3O4@SiO2Nanoparticles;
(3) 100 mg of Fe was weighed3O4@SiO2Ultrasonically dispersing the nano particles in 200 mL of ethanol, adding 5 mL of concentrated ammonia water, mechanically stirring for 5 min, adding 1mL of carboxylation reagent, and violently stirring at room temperature for reaction. Adding carboxylation agent 1 time every 2 hours, adding carboxylation agent 3 times in total in the whole process, reacting for 6 hours, and using ethanol to obtain the productWashing for 5 times, and drying at 60 ℃ to obtain carboxylated Fe3O4@SiO2Nanoparticles;
the preparation method of the carboxylation reagent comprises the following steps: dissolving 0.5g succinic anhydride in 5 mL anhydrous DMF by ultrasonic, adding 300 μ L aminopropyl trimethoxy silane (APTMS), and slowly stirring at room temperature for 16 hr to obtain carboxylation reagent;
(4) 50 mg of carboxylated Fe are weighed3O4@SiO2Uniformly dispersing the nanoparticles in 13 mL of deionized water, adding 0.7 g of ferric chloride hexahydrate, ultrasonically dispersing for 30 min, and then adding 0.15 g H3Ultrasonic dissolving BTC (trimesic acid), transferring to a polytetrafluoroethylene-lined high-pressure reaction kettle at 120 ℃ for 5 days, washing the obtained yellow mud-like product with deionized water for 5 times, washing with absolute ethanol for 3 times, drying at 60 ℃, and performing Fe extraction3O4@SiO2Nanoparticle @ MIL-100 (Fe) composites;
(5) sample Fe3O4@SiO2The @ MIL-100 composite material is placed in a tubular furnace for high-temperature calcination, the calcination atmosphere is nitrogen, the heating rate is 1 ℃/min, the calcination temperature is 650 ℃, the calcination time is 2 hours, and Fe is obtained3O4@SiO2@ C composite material;
(6) weighing 100 mg of calcined black powder Fe3O4@SiO2The @ C composite material is prepared by mechanically stirring 50mL of 1mol/L sodium hydroxide solution with the concentration of 50 ℃ to remove a silicon dioxide layer, washing the obtained product to be neutral by using deionized water, and drying at 60 ℃ to obtain the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material. The black product was named P-650.
The yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material (P-700) prepared in the embodiment is mixed with paraffin, the paraffin accounts for 70wt%, a coaxial sample with the outer diameter of 7.00 mm, the inner diameter of 3.04 mm and the thickness of about 2 mm is prepared in a special die in a pressing mode, the mass fraction of the product is 30%, an N5224A type vector network analyzer is used for testing the electromagnetic parameters of the sample, the wave-absorbing performance is obtained through calculation, and the testing frequency range is 2-18 GHz.
Through detection, when the thickness of the coating is 2.5 mm, the maximum absorption strength of the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material prepared by the embodiment is-10.5 dB.
Example 5
(1) Weighing 3.2436 g of ferric chloride hexahydrate, 7.0584 g of sodium citrate dihydrate and 2.1624 g of urea, sequentially dissolving in 210 mL of deionized water, adding 1.8 g of polyacrylamide, stirring the solution at room temperature for 5 hours until the solution is uniformly clear, keeping the solution in a polytetrafluoroethylene-lined high-pressure reaction kettle at 190 ℃ for 11 hours, washing the obtained black mud-shaped product with deionized water for 5 times, washing with absolute ethyl alcohol for 3 times, and drying at 60 ℃ to obtain the hollow ferroferric oxide nanoparticles;
(2) weighing 300 mg of hollow ferroferric oxide nano particles, dispersing the hollow ferroferric oxide nano particles in 200 mL of ethanol and 50mL of deionized water mixed solution, ultrasonically dispersing the hollow ferroferric oxide nano particles for 30 min, adding 4 mL of concentrated ammonia water (the concentration is 28 wt/%), mechanically stirring the mixture for 5 min, adding 1mL of TEOS (tetraethyl orthosilicate), adding the mixture once every 30 min, adding the mixture 3 times in total, mechanically stirring the mixture for 6 h, washing the obtained product for 5 times by using ethanol, and drying the product at 60 ℃ to obtain Fe3O4@SiO2Nanoparticles;
(3) 100 mg of Fe was weighed3O4@SiO2Ultrasonically dispersing the nano particles in 200 mL of ethanol, adding 5 mL of concentrated ammonia water, mechanically stirring for 5 min, adding 1mL of carboxylation reagent, and violently stirring at room temperature for reaction. Adding carboxylation reagent for 1 time every 2 hours, adding carboxylation reagent for 3 times in total in the whole process, reacting for 6 hours, washing the obtained product for 5 times by using ethanol, and drying at 60 ℃ to obtain carboxylated Fe3O4@SiO2Nanoparticles;
the preparation method of the carboxylation reagent comprises the following steps: dissolving 0.5g succinic anhydride in 5 mL anhydrous DMF by ultrasonic, adding 300 μ L aminopropyl trimethoxy silane (APTMS), and slowly stirring at room temperature for 16 hr to obtain carboxylation reagent;
(4) 50 mg of carboxylated Fe are weighed3O4@SiO2Uniformly dispersing the nanoparticles in 13 mL of deionized water, adding 0.7 g of ferric chloride hexahydrate, ultrasonically dispersing for 30 min, and then adding 0.15 g H3Ultrasonic dissolving BTC (trimesic acid), transferring to a polytetrafluoroethylene-lined high-pressure reaction kettle at 150 deg.CKeeping for 1 day, washing the obtained yellow mud product with deionized water for 5 times, washing with anhydrous ethanol for 3 times, oven drying at 60 deg.C, and removing Fe3O4@SiO2Nanoparticle @ MIL-100 (Fe) composites;
(5) sample Fe3O4@SiO2The @ MIL-100 composite material is placed in a tubular furnace for high-temperature calcination, the calcination atmosphere is nitrogen, the heating rate is 5 ℃/min, the calcination temperature is 900 ℃, the calcination time is 1 hour, and Fe is obtained3O4@SiO2@ C composite material;
(6) weighing 100 mg of calcined black powder Fe3O4@SiO2The @ C composite material is prepared by mechanically stirring 50mL of 1mol/L sodium hydroxide solution with the concentration of 50 ℃ to remove a silicon dioxide layer, washing the obtained product to be neutral by using deionized water, and drying at 60 ℃ to obtain the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material. The black product was named P-900;
the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material (P-900) prepared in the embodiment is mixed with paraffin, the paraffin accounts for 70wt%, a coaxial sample with the outer diameter of 7.00 mm, the inner diameter of 3.04 mm and the thickness of about 2 mm is prepared in a special die in a pressing mode, the mass fraction of the product is 30%, an N5224A type vector network analyzer is used for testing the electromagnetic parameters of the sample, the wave-absorbing performance is obtained through calculation, and the testing frequency range is 2-18 GHz.
According to detection, when the thickness of the coating is 3mm, the maximum absorption strength of the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material prepared by the embodiment is-20.8 dB.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention in any way, and other variations and modifications may be made without departing from the spirit of the invention as set forth in the claims.
Claims (10)
1. A preparation method of a yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material is characterized by comprising the following steps:
(1) SiO is coated on the surface of the hollow ferroferric oxide nano particle2Obtaining Fe3O4@SiO2Nanoparticles;
(2) mixing hollow Fe3O4@SiO2The surface of the nano particle is subjected to carboxylation modification to obtain carboxylated Fe3O4@SiO2Nanoparticles;
(3) in carboxylation of Fe3O4@SiO2MIL-100 (Fe) grows on the surface of the nano particle in situ to obtain Fe3O4@SiO2Nanoparticle @ MIL-100 (Fe) composites;
(4) by carboxylation of Fe3O4@SiO2Calcining the nano particle @ MIL-100 (Fe) composite material at high temperature in a nitrogen atmosphere to obtain Fe3O4@SiO2@ C composite material;
(5) mixing Fe3O4@SiO2Heating and stirring @ C composite material in alkali liquor to remove SiO2And washing and drying the layer to obtain the yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material.
2. The preparation method according to claim 1, wherein in the step (1), the preparation method of the hollow ferroferric oxide nanoparticles comprises the following steps: dissolving ferric chloride hexahydrate, sodium citrate and urea in deionized water in sequence, adding polyacrylamide, carrying out high-pressure hydrothermal reaction at the temperature of 180-200 ℃ for 10-12 h, removing precipitate, washing, and drying to obtain the hollow ferroferric oxide nanoparticles.
3. The method according to claim 1, wherein in the step (1), the surface is coated with SiO2The method comprises the following steps: dispersing hollow ferroferric oxide nano particles in ethanol/deionized water mixed solution, adding concentrated ammonia water, adding tetraethyl orthosilicate, stirring for reaction, washing and drying the obtained product to obtain Fe3O4@SiO2Nanoparticles.
4. The preparation method according to claim 3, wherein the volume ratio of ethanol to water in the ethanol/deionized water mixed solution is (3-5): 1; the total mass of the hollow ferroferric oxide nano particles is taken as a reference, and the adding amount of tetraethyl orthosilicate is 0.01 mL/mg.
5. The method according to claim 1, wherein in the step (2), the carboxylation modification is carried out by: mixing Fe3O4@SiO2Dispersing nano particles in ethanol, adding strong ammonia water, adding a carboxylation reagent, violently stirring at room temperature for reaction, washing and drying an obtained product to obtain carboxylated Fe3O4@SiO2Nanoparticles.
6. The production method according to claim 5,
the concentration of the strong ammonia water is 25-28 wt%;
with Fe3O4@SiO2The total mass of the nano particles is taken as a reference, and the adding amount of the carboxylation reagent is 0.03 mL/mg.
7. The method of claim 1, wherein in step (3), the method for growing MIL-100 (Fe) in situ comprises: by carboxylation of Fe3O4@SiO2Uniformly dispersing the nano particles in deionized water, adding ferric chloride hexahydrate, uniformly dispersing by ultrasonic, adding trimesic acid, dissolving by ultrasonic, keeping at the high temperature and the high pressure of 120-150 ℃ for 1-5 days, washing and drying the obtained product to obtain Fe3O4@SiO2Nanoparticle @ MIL-100 (Fe) composites.
8. The method according to claim 7, wherein Fe is carboxylated3O4@SiO2The total mass of the nano particles is taken as a reference, and the adding amount of the ferric chloride hexahydrate is 17 mg/mg; the addition amount of the trimesic acid is 2.94 mg/mg.
9. The production method according to claim 1,
in the step (4), the temperature rise rate of high-temperature calcination is 1-5 ℃/min, the calcination temperature is 600-900 ℃, and the calcination time is 1-3 h;
in the step (5), the alkali liquor is 0.5-1 mol/L sodium hydroxide solution; the heating temperature is 30-50 ℃.
10. An egg yolk shell hollow ferroferric oxide @ air @ carbon nano composite wave-absorbing material prepared by the preparation method of any one of claims 1-9.
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