CN107638851B - Bell-shaped Fe3O4@void@SiO2Nano-chain and preparation method - Google Patents

Bell-shaped Fe3O4@void@SiO2Nano-chain and preparation method Download PDF

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CN107638851B
CN107638851B CN201710774684.4A CN201710774684A CN107638851B CN 107638851 B CN107638851 B CN 107638851B CN 201710774684 A CN201710774684 A CN 201710774684A CN 107638851 B CN107638851 B CN 107638851B
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张秋禹
乔明涛
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Northwestern Polytechnical University
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Abstract

The invention relates to bell-shaped Fe3O4@void@SiO2Firstly, under the induction action of external magnetic field, magnetic Fe3O4Assembling and arranging the nano particles to promote a polymer shell layer P (DVB-MAA) to wrap Fe3O4Nanoparticles to form core-shell type Fe3O4@ P (DVB-MAA) nanochain; by sol-gel method, for Fe3O4@ P (DVB-MAA) nanochain for SiO2Coating of the shell layer to realize double-shell layer Fe3O4@P(DVB‑MAA)@SiO2Preparing a nano chain; finally, effective protection of Fe by recrystallization of salts3O4@P(DVB‑MAA)@SiO2The structure of the nano chain is pyrolyzed in the argon atmosphere, and the final product is the bell-shaped Fe3O4@void@SiO2And (4) nano-chains. The material has good microwave absorption performance due to the special micro-nano structure, the minimum reflection loss value is-45.03 dB (13.57GHz), and the effective absorption frequency band can reach more than 5.5 GHz. The invention of the technology effectively solves the problem that the existing wave-absorbing material has a narrow absorption band.

Description

Bell-shaped Fe3O4@void@SiO2Nano-chain and preparation method
Technical Field
The invention belongs to the field of microwave absorption, and particularly relates to bell-shaped Fe3O4@void@SiO2A nano-chain and a preparation method.
Background
With the rapid development of microwave and communication technologies, electronic devices such as mobile communication, computers, household appliances and the like are increasingly popularized, and great convenience is brought to the work and life of people. Meanwhile, the electronic equipment can release electromagnetic waves with different frequencies in the working process, so that the normal operation of other electronic equipment is interfered, certain harm is caused to the health of human beings, and the problem of electromagnetic pollution of different degrees is caused to the surrounding environment. There is a great need to solve the problem of electromagnetic pollution currently faced. The microwave absorbing material can convert electromagnetic wave energy into heat energy or other forms of energy through a magnetic loss and dielectric loss mechanism, greatly reduces electromagnetic wave radiation energy, can effectively alleviate or even eliminate the electromagnetic pollution problem, and is considered to be a candidate with great potential.
According to a microwave absorption mechanism, the composition of the magnetic material and the dielectric material is beneficial to improving the impedance matching degree of the microwave absorption material and air, so that incident waves are completely immersed into the material as much as possible, and the dissipation of electromagnetic wave energy is increased; meanwhile, the combination of magnetic loss and dielectric loss can further enhance the microwave absorption effect. Therefore, in recent years, a great deal of research is mainly performed around the material composition and structural design of the magnetic-dielectric composite material, and the development of a novel efficient microwave absorbing material is focused. Common magnetic materials include ferrite, simple substance iron-cobalt-nickel, barium titanate and the like, common dielectric materials include silicon dioxide, metal oxide semiconductors (zinc oxide, tin oxide, titanium dioxide, copper sulfide), carbon materials (graphene, carbon nano tubes, amorphous carbon), conductive polymers (polypyrrole, polythiophene, polyaniline) and the like, and a series of novel nano microwave absorbing materials are obtained by performing multi-component compounding by adopting different preparation methods. It is well known that ideal microwave absorbing materials need to have strong absorption, broad band, light weight, low density, etc. at the same time. Although many highly absorbing microwave absorbing materials have emerged, there are limitations to the width of the material that absorbs (≦ 5.0 GHz).
Disclosure of Invention
Technical problem to be solved
In order to avoid the defects of the prior art, the invention provides bell-shaped Fe3O4@void@SiO2The nano chain and the preparation method provide a novel wide-frequency-domain nano wave-absorbing material.
Technical scheme
Bell-shaped Fe3O4@void@SiO2A nanochain, characterized by: the core is Fe3O4The outer shell is SiO2A cavity is arranged between the two; wherein: the length of the nano chain is 10-30 um, the pore diameter is 5-23 nm, and the BET specific surface area is 90-120 m2The volume of BJH pore is 0.20-0.22 cm3。
Preparing the bell-shaped Fe3O4@void@SiO2The method of the nano chain is characterized by comprising the following steps:
step 1, core-shell type Fe3O4Preparation of @ P (DVB-MAA) nanochain: mixing Fe3O4Adding particles, monomer MAA (methacrylic acid) and a cross-linking agent divinylbenzene DVB (DVB) into 80-100 mL of acetonitrile, dispersing the acetonitrile by ultrasound, adding an initiator, carrying out external magnetic field induced distillation precipitation polymerization at the water bath temperature of 80-85 ℃, and reacting for 1-1.5 hours to obtain core-shell Fe3O4@ P (DVB-MAA) nanochain; said Fe3O4The concentration of the particles is 0.25 g/L-0.40 g/L, the concentration of the monomer is 3.0 g/L-3.75 g/L, and the concentration of the cross-linking agent is 0.875 g/L-1.0 g/L; the dosage of the initiator is 1.5 to 2.0 weight percent of the total dosage of the monomer and the cross-linking agent;
step 2, double-shell Fe3O4@P(DVB-MAA)@SiO2Preparing a nano chain: mixing core and shell type Fe3O4Dispersing a @ P (DVB-MAA) nano chain in 80mL of ethanol-water mixed solvent, then adding 1.5-2.0 mL of ammonia water, and mechanically stirring for 1-1.5 hours to uniformly mix the solution; slowly dripping 0.09-0.11 g of silicon source, and reacting for 5-6 hours at room temperature; magnetic separation, freeze drying to obtain solid powder of Fe3O4@P(DVB-MAA)@SiO2A nanochain; the ratio of ethanol to water in the ethanol-water mixed solvent is 9-11;
step 3, shaking bell-shaped Fe3O4@void@SiO2Preparing a nano chain: mixing double shell Fe3O4@P(DVB-MAA)@SiO2Dispersing the nano-chain in 50-80 mL of saturated salt solution, and raising the temperature to 80-85 ℃ to evaporate water; adding saturated salt water at the temperature of 60-70 ℃ into the solution for multiple times, and evaporating the water to obtain a mixture; placing the mixture in a tube furnace, calcining at 550-650 ℃ under the protection of argon atmosphere, cooling to room temperature, washing sodium chloride crystals and byproducts with deionized water at 80-90 ℃, and collecting products by magnetic separation to obtain bell-shaped Fe3O4@void@SiO2And (4) nano-chains.
The initiator is Azobisisobutyronitrile (AIBN) or Benzoyl Peroxide (BPO).
The silicon source is one or more of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate and butyl orthosilicate.
The concentration of the ammonia water is 25-28%.
The temperature rise rate of the calcination in the step 3 is 1-2 ℃/min, and the calcination time is 6-8 h.
Advantageous effects
The invention provides bell-shaped Fe3O4@void@SiO2Firstly, under the induction action of external magnetic field, magnetic Fe3O4The nanoparticles are assembled and arranged, and meanwhile, the distillation precipitation polymerization is carried out, so that the polymer shell layer P (DVB-MAA) is promoted to firmly wrap Fe3O4Nanoparticles to form core-shell type Fe3O4@ P (DVB-MAA) nanochain; by simple sol-gel method, for Fe3O4@ P (DVB-MAA) nanochain for SiO2Coating of the shell layer to realize double-shell layer Fe3O4@P(DVB-MAA)@SiO2Preparing a nano chain; finally, effective protection of Fe by recrystallization of salts3O4@P(DVB-MAA)@SiO2The structure of the nano chain is pyrolyzed in the argon atmosphere, and the final product is the bell-shaped Fe3O4@void@SiO2And (4) nano-chains. The material has good microwave absorption performance due to the special micro-nano structure, the minimum reflection loss value is-45.03 dB (13.57GHz), and the effective absorption frequency band can reach more than 5.5 GHz. The invention of the technology effectively solves the problem that the existing wave-absorbing material has a narrow absorption band.
Compared with the existing wave-absorbing material, the novel broadband domain nano wave-absorbing material has the following advantages:
1) the one-dimensional tropism and the high length-diameter ratio of the electromagnetic composite nano chain are similar to those of an infinite number of microwave antennas, a directional channel is provided for transmission of electromagnetic waves, transmission time is prolonged, and dissipation of electromagnetic energy is facilitated;
2) the nano-chain self-assembly is easy to form a three-dimensional network structure, so that electromagnetic waves are scattered and absorbed for multiple times in the material, and the loss of the electromagnetic waves is increased;
3) a large number of nano cavities are introduced through the design of the bell-shaped structure, so that the quality of the material is reduced, and the multiple reflection and multiple absorption of electromagnetic waves in the cavities can be enhanced;
4) the special structure endows the material with excellent microwave absorption performance, and when the coating thickness is 3.1mm, the strongest reflection loss value is-45.03 dB (13.57GHz), and when the coating thickness is between 2.9 mm and 3.3mm, the absorption width is larger than 5.5 GHz.
Drawings
FIG. 1 shows core-shell type Fe3O4SEM and TEM images of @ P (DVB-MAA) nanochains;
FIG. 2 shows double-shell Fe3O4@P(DVB-MAA)@SiO2SEM and TEM images of nanochains;
FIG. 3 shows bell-shaped Fe3O4@void@SiO2SEM and TEM images of nanochains;
FIG. 4 is a reflection loss curve of a broadband domain nano wave-absorbing material;
FIG. 5 shows the absorption frequency bandwidth of the broadband nano wave-absorbing material;
Detailed Description
The invention will now be further described with reference to the following examples and drawings:
example 1
Step 1, core-shell type Fe3O4Preparation of @ P (DVB-MAA) nanochain: mixing 0.028g of Fe3O4Adding particles, 0.26g of monomer MAA (methacrylic acid) and 0.08g of cross-linking agent divinylbenzene DVB into 80mL of acetonitrile, uniformly dispersing the particles by ultrasonic treatment, adding an initiator Azobisisobutyronitrile (AIBN) accounting for 1.6 wt% of the total amount of the monomers and the cross-linking agent, carrying out external magnetic field induced distillation precipitation polymerization at the water bath temperature of 80 ℃, and reacting for 1 hour to obtain the core-shell type Fe3O4@ P (DVB-MAA) nanochain;
step 2, double-shell Fe3O4@P(DVB-MAA)@SiO2Preparing a nano chain: mixing core and shell type Fe3O4@ P (DVB-MAA) nanochainDispersing in a mixed solvent of 73mL of ethanol and 7mL of water; then adding 1.8mL of 25% ammonia water, and mechanically stirring for 1 hour to uniformly mix the solution; slowly dropwise adding 0.09g of tetraethoxysilane, and reacting for 5 hours at room temperature; magnetic separation, freeze drying to obtain solid powder of Fe3O4@P(DVB-MAA)@SiO2A nanochain;
step 3, shaking bell-shaped Fe3O4@void@SiO2Preparing a nano chain: mixing double shell Fe3O4@P(DVB-MAA)@SiO2Dispersing the nano-chain in 60mL of saturated salt water, and raising the temperature to 80-85 ℃ to slowly evaporate the water; adding saturated salt water at the temperature of 60-70 ℃ into the solution for multiple times, and evaporating the water to obtain a mixture; placing the mixture in a tube furnace, heating the mixture from room temperature to 650 ℃ at the heating rate of 2 ℃/min under the protection of argon atmosphere, calcining for 7.5h, cooling to room temperature, washing out sodium chloride crystals and byproducts by using deionized water at the temperature of 80-90 ℃, and collecting products by using magnetic separation to obtain bell-shaped Fe3O4@void@SiO2And (4) nano-chains.
FIG. 1 shows core-shell Fe prepared in example 1 of the present invention3O4In SEM and TEM images of @ P (DVB-MAA) nanochains, as can be seen from FIG. 1, the nanochains in example 1 have a length of 10 to 30um, and the thickness of the P (DVB-MAA) shell is about 15 to 20 nm.
FIG. 2 shows a double-shell Fe prepared in example 1 of the present invention3O4@P(DVB-MAA)@SiO2As can be seen from the SEM image and the TEM image of the nanochain in FIG. 2, the shell thickness of the nanochain is increased to 70-80 nm.
FIG. 3 shows Bell-shaped Fe prepared in example 1 of the present invention3O4@void@SiO2SEM image and TEM image of nano-chain, and as can be seen from FIG. 3, the inner core is porous magnetic Fe3O4Microspheres with a shell layer of SiO2And a large number of nano cavities are left in the middle.
FIGS. 4 and 5 show Bell-shaped Fe prepared in example 1 of the present invention3O4@void@SiO2The reflection loss curve and the effective absorption frequency bandwidth of the nano-chain.
Example 2
Step 1, core-shell type Fe3O4Preparation of @ P (DVB-MAA) nanochain: 0.3g of Fe3O4Adding particles, 0.3g of monomer MAA (methacrylic acid) and 0.09g of cross-linking agent divinylbenzene DVB into 100mL of acetonitrile, uniformly dispersing the particles by ultrasonic treatment, adding an initiator Azobisisobutyronitrile (AIBN) accounting for 1.9 wt% of the total amount of the monomers and the cross-linking agent, carrying out external magnetic field induced distillation precipitation polymerization at the water bath temperature of 85 ℃, and reacting for 1.5 hours to obtain the core-shell type Fe3O4@ P (DVB-MAA) nanochain;
step 2, double-shell Fe3O4@P(DVB-MAA)@SiO2Preparing a nano chain: mixing core and shell type Fe3O4@ P (DVB-MAA) nanochains are dispersed in a mixed solvent of 72mL of ethanol and 8mL of water; then adding 1.6mL of 28% ammonia water, and mechanically stirring for 1.5 hours to uniformly mix the solution; slowly dropwise adding 0.1g of methyl orthosilicate, and reacting for 6 hours at room temperature; magnetic separation, freeze drying to obtain solid powder of Fe3O4@P(DVB-MAA)@SiO2A nanochain;
step 3, shaking bell-shaped Fe3O4@void@SiO2Preparing a nano chain: mixing double shell Fe3O4@P(DVB-MAA)@SiO2Dispersing the nano-chain in 70mL of saturated salt water, and raising the temperature to 80-85 ℃ to slowly evaporate the water; adding saturated salt water at the temperature of 60-70 ℃ into the solution for multiple times, and evaporating the water to obtain a mixture; placing the mixture in a tube furnace, heating the mixture from room temperature to 600 ℃ at a heating rate of 1 ℃/min under the protection of argon atmosphere, calcining for 6 hours, cooling to room temperature, washing sodium chloride crystals and byproducts with deionized water at 80-90 ℃, and collecting products by magnetic separation to obtain bell-shaped Fe3O4@void@SiO2And (4) nano-chains.
Example 3
Step 1, core-shell type Fe3O4Preparation of @ P (DVB-MAA) nanochain: 0.026g of Fe3O4Pellets, 0.3g of monomeric MAA methacrylic acid, 0.08g ofAdding divinyl benzene DVB serving as a coupling agent into 90mL of acetonitrile, uniformly dispersing the mixture by ultrasonic treatment, adding Benzoyl Peroxide (BPO) serving as an initiator accounting for 1.6 wt% of the total amount of the monomers and the crosslinking agent, carrying out external magnetic field induced distillation precipitation polymerization at the water bath temperature of 80 ℃, and reacting for 1 hour to obtain core-shell Fe3O4@ P (DVB-MAA) nanochain;
step 2, double-shell Fe3O4@P(DVB-MAA)@SiO2Preparing a nano chain: mixing core and shell type Fe3O4@ P (DVB-MAA) nanochains are dispersed in a mixed solvent of 72mL of ethanol and 8mL of water; then adding 2.0mL of 28% ammonia water, and mechanically stirring for 1.5 hours to uniformly mix the solution; slowly dropwise adding 0.11g of tetraethoxysilane, and reacting for 6 hours at room temperature; magnetic separation, freeze drying to obtain solid powder of Fe3O4@P(DVB-MAA)@SiO2A nanochain;
step 3, shaking bell-shaped Fe3O4@void@SiO2Preparing a nano chain: mixing double shell Fe3O4@P(DVB-MAA)@SiO2Dispersing the nano-chain in 80mL of saturated salt water, and raising the temperature to 80-85 ℃ to slowly evaporate the water; adding saturated salt water at the temperature of 60-70 ℃ into the solution for multiple times, and evaporating the water to obtain a mixture; placing the mixture in a tube furnace, heating the mixture from room temperature to 550 ℃ at the heating rate of 2 ℃/min under the protection of argon atmosphere, calcining for 8 hours, cooling to room temperature, washing sodium chloride crystals and byproducts with deionized water at the temperature of 80-90 ℃, and collecting products by magnetic separation to obtain bell-shaped Fe3O4@void@SiO2And (4) nano-chains.
Example 4
Step 1, core-shell type Fe3O4Preparation of @ P (DVB-MAA) nanochain: 0.3g of Fe3O4Adding particles, 0.28g of monomer MAA (methacrylic acid) and 0.07g of cross-linking agent divinylbenzene DVB into 80mL of acetonitrile, uniformly dispersing by ultrasonic, adding initiator Azobisisobutyronitrile (AIBN) accounting for 1.6 wt% of the total amount of the monomers and the cross-linking agent, carrying out external magnetic field induced distillation precipitation polymerization at the water bath temperature of 85 ℃, and reacting for 1.5 hoursThen obtaining the core-shell type Fe3O4@ P (DVB-MAA) nanochain;
step 2, double-shell Fe3O4@P(DVB-MAA)@SiO2Preparing a nano chain: mixing core and shell type Fe3O4@ P (DVB-MAA) nanochains are dispersed in a mixed solvent of 73mL of ethanol and 7mL of water; then 2.0mL of 25% ammonia water is added, and the mixture is mechanically stirred for 1.5 hours to ensure that the solution is uniformly mixed; slowly dropwise adding 0.09g of methyl orthosilicate, and reacting for 6 hours at room temperature; magnetic separation, freeze drying to obtain solid powder of Fe3O4@P(DVB-MAA)@SiO2A nanochain;
step 3, shaking bell-shaped Fe3O4@void@SiO2Preparing a nano chain: mixing double shell Fe3O4@P(DVB-MAA)@SiO2Dispersing the nano-chain in 60mL of saturated salt water, and raising the temperature to 80-85 ℃ to slowly evaporate the water; adding saturated salt water at the temperature of 60-70 ℃ into the solution for multiple times, and evaporating the water to obtain a mixture; placing the mixture in a tube furnace, heating the mixture from room temperature to 600 ℃ at the heating rate of 2 ℃/min under the protection of argon atmosphere, calcining for 6 hours, cooling to room temperature, washing sodium chloride crystals and byproducts with deionized water at the temperature of 80-90 ℃, and collecting products by magnetic separation to obtain bell-shaped Fe3O4@void@SiO2And (4) nano-chains.
Example 5
Step 1, core-shell type Fe3O4Preparation of @ P (DVB-MAA) nanochain: mixing 0.028g of Fe3O4Adding particles, 0.3g of monomer MAA (methacrylic acid) and 0.09g of cross-linking agent divinylbenzene DVB into 100mL of acetonitrile, uniformly dispersing the particles by ultrasonic treatment, adding an initiator Azobisisobutyronitrile (AIBN) accounting for 1.7 wt% of the total amount of the monomers and the cross-linking agent, carrying out external magnetic field induced distillation precipitation polymerization at the water bath temperature of 85 ℃, and reacting for 1 hour to obtain the core-shell type Fe3O4@ P (DVB-MAA) nanochain;
step 2, double-shell Fe3O4@P(DVB-MAA)@SiO2Preparing a nano chain: mixing core and shell type Fe3O4@P(DVB-MAA) nano-chain is dispersed in a mixed solvent of 72mL of ethanol and 8mL of water; then adding 1.8mL of 25% ammonia water, and mechanically stirring for 1 hour to uniformly mix the solution; slowly dropwise adding 0.11g of butyl orthosilicate, and reacting for 6 hours at room temperature; magnetic separation, freeze drying to obtain solid powder of Fe3O4@P(DVB-MAA)@SiO2A nanochain;
step 3, shaking bell-shaped Fe3O4@void@SiO2Preparing a nano chain: mixing double shell Fe3O4@P(DVB-MAA)@SiO2Dispersing the nano-chain in 80mL of saturated salt water, and raising the temperature to 80-85 ℃ to slowly evaporate the water; adding saturated salt water at the temperature of 60-70 ℃ into the solution for multiple times, and evaporating the water to obtain a mixture; placing the mixture in a tube furnace, heating the mixture from room temperature to 600 ℃ at a heating rate of 1 ℃/min under the protection of argon atmosphere, calcining for 7 hours, cooling to room temperature, washing sodium chloride crystals and byproducts with deionized water at 80-90 ℃, and collecting products by magnetic separation to obtain bell-shaped Fe3O4@void@SiO2And (4) nano-chains.
Example 6
Step 1, core-shell type Fe3O4Preparation of @ P (DVB-MAA) nanochain: 0.3g of Fe3O4Adding particles, 0.32g of monomer MAA (methacrylic acid) and 0.08g of cross-linking agent divinylbenzene DVB into 100mL of acetonitrile, uniformly dispersing the particles by ultrasonic treatment, adding an initiator Azobisisobutyronitrile (AIBN) accounting for 1.8 wt% of the total amount of the monomers and the cross-linking agent, carrying out external magnetic field induced distillation precipitation polymerization at the water bath temperature of 85 ℃, and reacting for 1.5 hours to obtain the core-shell type Fe3O4@ P (DVB-MAA) nanochain;
step 2, double-shell Fe3O4@P(DVB-MAA)@SiO2Preparing a nano chain: mixing core and shell type Fe3O4@ P (DVB-MAA) nanochains are dispersed in a mixed solvent of 72.5mL of ethanol and 7.5mL of water; then adding 1.5mL of 28% ammonia water, and mechanically stirring for 1 hour to uniformly mix the solution; slowly dropwise adding 0.09g of tetraethoxysilane, and reacting for 5 hours at room temperature; magnetic separation and freeze dryingThe dried solid powder is Fe3O4@P(DVB-MAA)@SiO2A nanochain;
step 3, shaking bell-shaped Fe3O4@void@SiO2Preparing a nano chain: mixing double shell Fe3O4@P(DVB-MAA)@SiO2Dispersing the nano-chain in 80mL of saturated salt water, and raising the temperature to 80-85 ℃ to slowly evaporate the water; adding saturated salt water at the temperature of 60-70 ℃ into the solution for multiple times, and evaporating the water to obtain a mixture; placing the mixture in a tube furnace, heating the mixture from room temperature to 600 ℃ at a heating rate of 1 ℃/min under the protection of argon atmosphere, calcining for 8 hours, cooling to room temperature, washing sodium chloride crystals and byproducts with deionized water at 80-90 ℃, and collecting products by magnetic separation to obtain bell-shaped Fe3O4@void@SiO2And (4) nano-chains.

Claims (5)

1. Bell-shaped Fe3O4@void@SiO2The preparation method of the nano-chain is characterized by comprising the following steps: the bell-shaped Fe3O4@void@SiO2The core of the nano chain is Fe3O4The outer shell is SiO2A cavity is arranged between the two; wherein: the length of the nano chain is 10-30 mu m, the pore diameter is 5-23 nm, and the BET specific surface area is 90-120 m2The volume of BJH pore is 0.20-0.22 cm3；
The preparation method comprises the following specific steps:
step 1, core-shell type Fe3O4Preparation of @ P (DVB-MAA) nanochain: mixing Fe3O4Adding particles, monomer MAA (methacrylic acid) and a cross-linking agent divinylbenzene DVB (DVB) into 80-100 mL of acetonitrile, dispersing the acetonitrile by ultrasound, adding an initiator, carrying out external magnetic field induced distillation precipitation polymerization at the water bath temperature of 80-85 ℃, and reacting for 1-1.5 hours to obtain core-shell Fe3O4@ P (DVB-MAA) nanochain; said Fe3O4The concentration of the particles is 0.25 g/L-0.40 g/L, the concentration of the monomer is 3.0 g/L-3.75 g/L, and the concentration of the cross-linking agent is 0.875 g/L-1.0 g/L; the initiator is used in the total amount of the monomer and the cross-linking agent1.5wt％～2.0wt％；
Step 2, double-shell Fe3O4@P(DVB-MAA)@SiO2Preparing a nano chain: mixing core and shell type Fe3O4Dispersing a @ P (DVB-MAA) nano chain in 80mL of ethanol-water mixed solvent, then adding 1.5-2.0 mL of ammonia water, and mechanically stirring for 1-1.5 hours to uniformly mix the solution; slowly dripping 0.09-0.11 g of silicon source, and reacting for 5-6 hours at room temperature; magnetic separation, freeze drying to obtain solid powder of Fe3O4@P(DVB-MAA)@SiO2A nanochain; the volume ratio of ethanol to water in the ethanol-water mixed solvent is 9-11;
step 3, shaking bell-shaped Fe3O4@void@SiO2Preparing a nano chain: mixing double shell Fe3O4@P(DVB-MAA)@SiO2Dispersing the nano-chain in 50-80 mL of saturated salt solution, and raising the temperature to 80-85 ℃ to evaporate water; adding saturated salt water at the temperature of 60-70 ℃ for multiple times, and evaporating the water to obtain a mixture; placing the mixture in a tube furnace, calcining at 550-650 ℃ under the protection of argon atmosphere, cooling to room temperature, washing sodium chloride crystals and byproducts with deionized water at 80-90 ℃, and collecting products by magnetic separation to obtain bell-shaped Fe3O4@void@SiO2And (4) nano-chains.
2. The method of claim 1, wherein: the initiator is Azobisisobutyronitrile (AIBN) or Benzoyl Peroxide (BPO).
3. The method of claim 1, wherein: the silicon source is one or more of methyl orthosilicate, ethyl orthosilicate, propyl orthosilicate and butyl orthosilicate.
4. The method of claim 1, wherein: the concentration of the ammonia water is 25-28%.
5. The method of claim 1, wherein: the temperature rise rate of the calcination in the step 3 is 1-2 ℃/min, and the calcination time is 6-8 h.
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