CN116265559A - Hollow carbon material coated ferrite wave absorber powder and preparation method and application thereof - Google Patents
Hollow carbon material coated ferrite wave absorber powder and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a hollow carbon material coated ferrite wave absorber powder, and a preparation method and application thereof. The method comprises the following steps: step S1, at Fe 3 O 4 Coating SiO on microsphere surface 2 Layer of Fe 3 O 4 /SiO 2 Core-shell microspheres; step S2, fe 3 O 4 /SiO 2 Dispersing the core-shell microspheres into a first solvent, and adding PVP to form PVP modified Fe 3 O 4 /SiO 2 Core-shell microspheres; step S3, PVP modified Fe 3 O 4 /SiO 2 Dispersing the core-shell microspheres into a second solvent, adding an oxidant and pyrrole for polymerization reaction to obtain Fe 3 O 4 /SiO 2 PPy core-shell microspheres; step S4, calcining Fe 3 O 4 /SiO 2 The PPy core-shell microsphere is carbonized; and S5, placing the carbonized microspheres in an alkali solution to form wave absorber powder. The wave absorber powder disclosed by the invention has the advantages of high absorption performance, low density and stable chemical performance.
Description
Technical Field
The invention relates to the field of wave-absorbing materials, in particular to a hollow carbon material coated ferrite wave-absorbing agent powder, and a preparation method and application thereof.
Background
With the rapid development of electronic information and the like, electromagnetic radiation is more and more serious, electromagnetic pollution is more common than chemical pollution, and the electromagnetic radiation is a serious social public hazard, so that the wave-absorbing stealth material is attracting more and more attention at home and abroad.
Ferrite is a traditional wave-absorbing material with the greatest research, lowest cost and the widest application, has the characteristics of wide raw material range, low price, simple and convenient manufacturing process, strong absorption, wider frequency band, strong corrosion resistance and low cost, and ferroferric oxide is a typical representative thereof, has double wave-absorbing capability of magnetic loss and dielectric loss, and is a common wave-absorbing material. However, the ferrite density is large, and the principle that the relative permittivity and the relative permeability are as close as possible is difficult to meet, so that the impedance is not easy to match, and the single ferrite is difficult to meet the requirements of high-performance wave absorbing materials such as strong absorption, wide frequency band, light weight, thin thickness and the like. The carbon material has excellent dielectric property, good composite property, special microstructure, lower density and stronger chemical stability, has high resonant frequency and high magnetic permeability, enhances the wave absorbing effect, has wide application in the radar wave absorbing field, and becomes a hot point for study at home and abroad.
In many existing preparation process patents for loading ferroferric oxide, porous carbon and ferroferric oxide precursor solution are mostly used as raw materials, and a mixture obtained after the raw materials are mixed is heated in a water bath, aged and dried to obtain the ferroferric oxide/porous carbon composite wave-absorbing material. The method for preparing the composite wave-absorbing material has simple process and low cost of raw materials, is suitable for industrial production, but has single absorption loss mechanism, further improves absorption efficiency and bandwidth, has poorer stable chemical performance and can not realize low-density characteristic.
Therefore, it is necessary to provide a novel wave absorber powder having good absorption properties, low density, stable chemical properties and good comprehensive properties.
Disclosure of Invention
The invention mainly aims to provide a hollow carbon material coated ferrite wave absorber powder, and a preparation method and application thereof, so as to solve the problems that the ferrite wave absorber powder in the prior art is difficult to consider high absorption performance, low density, stable chemical performance and the like.
In order to achieve the above object, according to one aspect of the present invention, there is provided a method for preparing a hollow carbon material coated ferrite wave absorber powder, comprising the steps of: step S1, at Fe 3 O 4 Coating SiO on the surface of microsphere 2 Layer of Fe 3 O 4 /SiO 2 Core-shell microspheres; step S2, fe 3 O 4 /SiO 2 Dispersing the core-shell microspheres into a first solvent, and then adding PVP to the Fe 3 O 4 /SiO 2 Surface modification is carried out on the core-shell microsphere to form PVP modified Fe 3 O 4 /SiO 2 Core-shell microspheres; step S3, PVP modified Fe 3 O 4 /SiO 2 Dispersing the core-shell microsphere into a second solvent, adding an oxidant and pyrrole, and performing polymerization reaction to obtain PVP modified Fe 3 O 4 /SiO 2 Further forming a PPy coating layer on the surface of the core-shell microsphere to obtain Fe 3 O 4 /SiO 2 PPy core-shell microspheres; step S4, calcining Fe in inert gas 3 O 4 /SiO 2 The PPy core-shell microsphere is carbonized to obtain carbonized microsphere; step S5, placing the carbonized microspheres in an alkali solution, and etching to remove SiO 2 The layer is further formed to be hollow carbon material coated ferrite wave absorber powder.
Further, step S1 includes: fe is added to 3 O 4 Dispersing the microspheres in a third solvent to form a dispersion; adjusting the pH value of the dispersion liquid to 8-9, then adding tetraethoxysilane into the dispersion liquid, and reacting in a stirring state to obtain reaction slurry; separating the solid in the reaction slurry, and drying to obtain Fe 3 O 4 /SiO 2 Core-shell microspheres; preferably Fe 3 O 4 The particle size of the microsphere is 200-800 nm; preferably Fe 3 O 4 The weight ratio of the microsphere to the tetraethoxysilane is that(2-10), 1-6); preferably, the third solvent is a mixed solvent of ethanol and water, and the weight ratio of the third solvent to the water is (8-12): 2-5; preferably, the agent for adjusting the pH value of the dispersion liquid adopts ammonia water; preferably, after the ethyl orthosilicate is added, the reaction is carried out for 3 to 6 hours under the conditions of stirring speed of 400 to 1000r/min and temperature of 40 to 80 ℃.
Further, fe 3 O 4 The microsphere is prepared by the following method: dispersing ferrous salt and ferric salt in a fourth solvent, adding alkali for reaction, carrying out solid-liquid separation, and drying to obtain Fe 3 O 4 A microsphere; preferably, the ferrous salt is ferrous chloride and/or ferrous sulfate, and the ferric salt is ferric chloride and/or ferric sulfate; preferably, the base is anhydrous sodium acetate; preferably, the total weight of ferrous salt and ferric salt is recorded as m1, the weight of alkali is recorded as m2, and the ratio of m1/m2 is (1-6): 4-30; preferably, the fourth solvent is glycol aqueous solution with the mass concentration of 96-99%; preferably, after adding the alkali, the reaction is carried out for 5 to 10 hours under the conditions of stirring speed of 1500 to 2500r/min and temperature of 150 to 250 ℃.
Further, in step S2, fe 3 O 4 /SiO 2 The weight ratio of the core-shell microsphere to PVP is (1-6) (3-8); preferably, the first solvent is an aqueous ethanol solution, more preferably an aqueous ethanol solution having a mass concentration of 50 to 80%.
Further, step S3 includes: fe modified by PVP 3 O 4 /SiO 2 Dispersing the core-shell microspheres into a second solvent, adding an oxidant, stirring for 30-80 min, and adding pyrrole for polymerization reaction to obtain Fe 3 O 4 /SiO 2 PPy core-shell microspheres; preferably, PVP modified Fe 3 O 4 /SiO 2 The weight ratio of the core-shell microsphere to the oxidant is (1-6) (5-10); preferably, PVP modified Fe 3 O 4 /SiO 2 The weight ratio of the core-shell microsphere to the pyrrole is (1-6) 1-5; preferably, the temperature in the polymerization reaction process is 30-50 ℃, the stirring speed is 400-800 r/min, and the reaction time is 6-12 h; preferably, the oxidizing agent is ferric chloride; preferably, the second solvent is water.
Further, the steps ofS4, calcining Fe 3 O 4 /SiO 2 In the process of the PPy core-shell microsphere, the calcination temperature is 500-800 ℃ and the calcination time is 2-6 h.
Further, in step S5, the alkali solution is 10-30wt% sodium hydroxide aqueous solution.
Further, in step S5, after the carbonized microspheres are placed in an alkali solution, the carbonized microspheres are reacted for 10 to 20 hours under the conditions of stirring speed of 800 to 1500r/min and temperature of 40 to 80 ℃ so as to remove SiO by etching 2 A layer; preferably, in step S5, after the reaction is completed, the precipitate is separated and dried to obtain the hollow carbon material coated ferrite wave absorber powder.
According to another aspect of the invention, there is also provided a hollow carbon material coated ferrite wave absorber powder prepared by the above preparation method.
According to still another aspect of the present invention, there is also provided a wave-absorbing material including a wave-absorbing powder, which is the above-mentioned carbon material-coated ferrite wave-absorbing agent powder.
The preparation method of the invention is a hollow carbon material coated ferrite wave absorber powder which is prepared by the method of the invention, wherein the ferrite wave absorber powder is prepared by the method of the invention by mixing Fe with the carbon material 3 O 4 Coating SiO on the surface of the microsphere 2 The layer is further coated with a polypyrrole layer formed by PVP surface modification and pyrrole in-situ polymerization to form Fe 3 O 4 /SiO 2 PPy core-shell microspheres. Next, the invention is calcined in inert gas to carbonize the polypyrrole layer to form Fe 3 O 4 /SiO 2 core-shell/C microsphere (carbonized microsphere) is etched in alkali solution to remove SiO in the middle 2 And a layer, thus, a ferrite wave absorber powder coated with a carbon material having a hollow structure is finally formed. The wave absorber powder has a hollow core-shell structure (the core layer is Fe) 3 O 4 The microsphere, the shell layer is a carbon layer, and a hollow structure is arranged between the microsphere and the shell layer), besides the absorption, reflection and other loss electromagnetic waves, multiple reflection and multiple absorption can be generated in the cavity, the propagation path of the electromagnetic waves is increased, an effective conductive network structure can be formed, and the dielectric loss of the material is increased, so that the prepared wave absorbing material can have a wide frequency rangeThe high-performance wave-absorbing material has better wave-absorbing performance and meets the high-performance requirement of the wave-absorbing material. Meanwhile, the hollow structure and the carbon layer coating also reduce the ferrite density, improve the aggregation of ferroferric oxide particles, have the performances of corrosion resistance, oxidation resistance and the like, and have stable chemical properties.
In a word, the hollow carbon material coated ferrite wave absorber powder prepared by the invention has high absorption performance, low density and stable chemical performance, and has excellent comprehensive performance.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
fig. 1 shows a schematic flow chart of a method for preparing a hollow carbon material coated ferrite wave absorber powder according to an embodiment of the invention.
Detailed Description
It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The invention will be described in detail below with reference to the drawings in connection with embodiments.
As described in the background section, it is difficult to achieve high absorption performance, low density, stable chemical properties, and the like of the ferrite wave-absorbing powder in the prior art. In order to solve the above problems, the present invention provides a method for preparing a hollow carbon material coated ferrite wave absorber powder, as shown in fig. 1, comprising the steps of: step S1, at Fe 3 O 4 Coating SiO on the surface of microsphere a 2 Layer of Fe 3 O 4 /SiO 2 Core-shell microspheres b; step S2, fe 3 O 4 /SiO 2 Dispersing the core-shell microsphere b into a first solvent, and then adding PVP to the Fe 3 O 4 /SiO 2 Surface modification is carried out on the core-shell microsphere to form PVP modified Fe 3 O 4 /SiO 2 Core-shell microsphere c; step S3, PVP modified Fe 3 O 4 /SiO 2 Core-shell microsphere c dispersed into a secondIn the solvent, oxidant and pyrrole are added and polymerization reaction is carried out to obtain PVP modified Fe 3 O 4 /SiO 2 Further forming a PPy coating layer (polypyrrole coating layer) on the surface of the core-shell microsphere to obtain Fe 3 O 4 /SiO 2 PPy core-shell microsphere d; step S4, calcining Fe in inert gas 3 O 4 /SiO 2 The PPy core-shell microsphere d is carbonized to obtain carbonized microspheres; step S5, placing the carbonized microspheres in an alkali solution, and etching to remove SiO 2 The layer is further formed to be hollow carbon material coated ferrite wave absorber powder e.
The preparation method of the invention is a hollow carbon material coated ferrite wave absorber powder which is prepared by the method of the invention, wherein the ferrite wave absorber powder is prepared by the method of the invention by mixing Fe with the carbon material 3 O 4 Coating SiO on the surface of the microsphere 2 The layer is further coated with a polypyrrole layer formed by PVP surface modification and pyrrole in-situ polymerization to form Fe 3 O 4 /SiO 2 PPy core-shell microspheres. Next, the invention is calcined in inert gas to carbonize the polypyrrole layer to form Fe 3 O 4 /SiO 2 core-shell/C microsphere (carbonized microsphere) is etched in alkali solution to remove SiO in the middle 2 And a layer, thus, a ferrite wave absorber powder coated with a carbon material having a hollow structure is finally formed. It should be noted that the illustration in FIG. 1 is only schematic, and SiO is finally removed 2 After the layer, the carbon layer of the outer layer and the core layer Fe 3 O 4 The microspheres are not completely separated, but are attached and fixed at some positions, but gaps exist between the two layers, and the microspheres are not compact enough, so that a hollow structure exists.
The hollow carbon material coated ferrite wave absorber powder prepared by the method has excellent dielectric property, good matrix combination, low density, good corrosion resistance and oxidation resistance and good chemical stability; meanwhile, the carbon coating layer improves the agglomeration phenomenon of ferroferric oxide particles, and the dual wave absorbing capacity of ferrite with magnetic loss and dielectric loss is reserved; more importantly, besides absorbing, reflecting and other loss electromagnetic waves, the hollow structural powder can generate multiple reflection and multiple absorption in the cavity, the propagation path of the electromagnetic waves is increased, an effective conductive network structure can be formed, and the dielectric loss of the material is increased, so that the prepared wave-absorbing material has good wave-absorbing performance in a wider frequency range, the powder has good matching performance, strong absorption and high frequency band, and the high-performance requirement on the wave-absorbing material is met.
In a word, the hollow carbon material coated ferrite wave absorber powder prepared by the invention well combines high absorption performance, low density and stable chemical performance, has excellent comprehensive performance, and can meet different comprehensive performance requirements of wave absorber materials in the military fields of electronic information products, aerospace and the like.
In a preferred embodiment, step S1 comprises: fe is added to 3 O 4 Dispersing the microspheres in a third solvent to form a dispersion; adjusting the pH value of the dispersion liquid to 8-9, then adding tetraethoxysilane into the dispersion liquid, and reacting in a stirring state to obtain reaction slurry; separating the solid in the reaction slurry, and drying to obtain Fe 3 O 4 /SiO 2 Core-shell microspheres. Under the process conditions, can be used in Fe 3 O 4 More complete SiO is coated on the microsphere surface 2 The layer is further beneficial to the formation of a subsequent hollow structure, and has better effects on absorbing the wave absorbing performance of the powder, low density, preventing agglomeration and the like.
Preferably Fe 3 O 4 The particle diameter of the microspheres is 200-800 nm, more preferably Fe 3 O 4 The particle size of the microsphere is 400-600 nm; to make SiO 2 The layer is more complete and the thickness is more suitable, preferably Fe 3 O 4 The weight ratio of the microsphere to the tetraethoxysilane is (2-10) and (1-6). Controlling the weight ratio of the two to be within the range 2 The coating is more complete and the thickness is more suitable, on one hand, the coating can play a better supporting role on the outer shell layer in the carbonization process of the PPy coating agent, the final hollow structure of the powder is promoted to be more complete, on the other hand, the carbonized carbon layer can be better fixed, the overall structural stability of the powder is higher, and the stability of the powder in all aspects is more beneficial.
In a preferred embodiment of the present invention,the third solvent is a mixed solvent of ethanol and water, and the weight ratio of the third solvent to the water is (8-12) (2-5). In the solvent, fe 3 O 4 The microspheres can be better dispersed, and the stability of the coating process and SiO are improved 2 The coating effect of the layer is more advantageous. Preferably, the agent for adjusting the pH of the dispersion is aqueous ammonia. Preferably, after the ethyl orthosilicate is added, the reaction is carried out for 3 to 6 hours under the conditions of stirring speed of 400 to 1000r/min and temperature of 40 to 80 ℃. The reaction is carried out under the above conditions, which is favorable for further improving SiO 2 The coating effect of the layer plays a better promoting role in the formation of the hollow structure and the structural stability.
Illustratively, siO can be performed using the following steps 2 Coating of the layer: 2 to 10 parts of Fe by weight 3 O 4 Adding the microspheres into a mixed solvent of 800-1200 parts of absolute ethyl alcohol and 200-500 parts of deionized water, and carrying out ultrasonic treatment for 30-50 min to ensure that Fe 3 O 4 The microspheres are more uniformly dispersed in the solvent; ammonia water is used as pH regulating solution, the pH of the reaction solution is regulated to 8-9, then 1-6 parts of tetraethoxysilane is dripped into the reaction solution, and the reaction solution is continuously stirred for 3-6 hours in a water bath kettle with the rotating speed of 400-1000 r/min and the temperature of 40-80 ℃. After the reaction is finished, collecting the precipitate by using a magnet, pouring out the supernatant, washing the supernatant with ethanol for 3 to 6 times, putting the precipitate into a blast oven with the temperature of 60 to 120 ℃ for drying treatment for 8 to 15 hours, and completing Fe 3 O 4 /SiO 2 And (3) preparing the core-shell microsphere.
In a preferred embodiment, fe 3 O 4 The microsphere is prepared by the following method: dispersing ferrous salt and ferric salt in a fourth solvent, adding alkali for reaction, carrying out solid-liquid separation, and drying to obtain Fe 3 O 4 And (3) microspheres. Fe prepared by using the method 3 O 4 The microsphere shape is better and the granularity is more uniform. Preferably, the ferrous salt is ferrous chloride and/or ferrous sulfate and the ferric salt is ferric chloride and/or ferric sulfate. The ferrous salt and the ferric salt with the types and the amounts can react more stably under the action of alkali to form Fe 3 O 4 The microspheres are more uniform. Preferably, the base is anhydrous sodium acetate; preferably, a ferrous salt andthe total weight of the ferric salt is denoted as m1, the weight of the alkali is denoted as m2, and the ratio of m1/m2 is (1-6) (4-30). The use of the alkali of the type is beneficial to the reaction to be carried out more fully and efficiently by controlling the dosage within the range, and the excessive waste of raw materials is avoided.
To provide a more stable reaction environment, the prepared Fe 3 O 4 The microsphere morphology has more uniform particle size, and preferably, the fourth solvent is an aqueous ethylene glycol solution with a mass concentration of 96-99%. Preferably, after adding the alkali, the reaction is carried out for 5 to 10 hours under the conditions of stirring speed of 1500 to 2500r/min and temperature of 150 to 250 ℃. The reaction is more sufficient under the above conditions, and the prepared Fe 3 O 4 The microsphere has better magnetic property and better promotion effect on the wave absorbing performance of the final wave absorbing powder.
For example, fe can be prepared by the following steps 3 O 4 Microspheres: dispersing 5-30 parts of ferric salt (ferrous iron and ferric iron) into 400-800 parts of glycol solution, uniformly stirring, adding 20-150 parts of anhydrous sodium acetate, continuously uniformly stirring, and then placing the mixed solution into an oil bath pot at 150-250 ℃ and continuously stirring for 5-10 hours at a rotating speed of 1500-2500 r/min; after the reaction is completed, collecting the precipitate by using a magnet, respectively washing the precipitate by using water and ethanol for 3 to 6 times, and then drying the obtained sample in a blast oven at 60 to 120 ℃ for 8 to 15 hours to obtain Fe 3 O 4 The particle size of the microsphere is 200-800 nm.
Use of PVP (polyvinylpyrrolidone) for Fe 3 O 4 /SiO 2 The core-shell microsphere is subjected to surface modification, so that on one hand, good dispersion can be promoted in a subsequent second solvent, on the other hand, polypyrrole formed by polymerization can form more complete coating on the surface of the core-shell microsphere in the in-situ polymerization process, and the polypyrrole coating is tightly adhered to the surface of the core-shell microsphere, so that the core-shell microsphere has a better promoting effect on the stability of a hollow structure after subsequent carbonization and etching. To exert this effect further, in a preferred embodiment, in step S2, fe 3 O 4 /SiO 2 The weight ratio of the core-shell microsphere to PVP is (1-6) to (3-8). Preferably, the first solvent is an aqueous ethanol solution, more preferablyIs ethanol water solution with the mass concentration of 50-80 percent. In the solvent, fe 3 O 4 /SiO 2 The dispersion and surface modification effects of the core-shell microspheres are better.
Illustratively, the PVP modification can be performed using the following steps: 1 to 6 parts of Fe by weight 3 O 4 /SiO 2 Dispersing the core-shell microspheres into 50-400 parts of ethanol solution for ultrasonic treatment for 20-40 min, adding 3-8 parts of PVP, continuously carrying out ultrasonic treatment for 40-60 min, washing with distilled water for 3-6 times for standby, and then placing the washed precipitate into a blast oven at 60-120 ℃ for drying treatment for 8-15 h to finish Fe 3 O 4 /SiO 2 PVP modification of core-shell microspheres.
In a preferred embodiment, the step S3 includes: fe modified by PVP 3 O 4 /SiO 2 Dispersing the core-shell microspheres into a second solvent, adding an oxidant, stirring for 30-80 min, and adding pyrrole for polymerization reaction to obtain Fe 3 O 4 /SiO 2 PPy core-shell microspheres. Through the steps, under the action of an oxidant, pyrrole can be subjected to PVP modified Fe 3 O 4 /SiO 2 The surface of the core-shell microsphere is subjected to in-situ polymerization more stably, the coating effect is better, and the method has better promotion effect on the structural stability of the powder of the ferrite wave absorber coated by the carbon material with a final hollow structure, thereby being beneficial to improving the comprehensive properties of the powder, such as wave absorbing property, low density, anti-agglomeration property and the like. Preferably, PVP modified Fe 3 O 4 /SiO 2 The weight ratio of the core-shell microsphere to the oxidant is (1-6) and (5-10). In this way, the polymerization process of pyrrole is more stable. Preferably, PVP modified Fe 3 O 4 /SiO 2 The weight ratio of the core-shell microsphere to the pyrrole is (1-6) 1-5. The use amount of pyrrole is controlled in the range, the thickness of the pyrrole is more suitable, the thickness of the finally formed carbon coating layer is also more suitable, the density of powder can be further reduced, the dielectric constant and the dielectric loss are increased so as to further improve the absorption efficiency, the problem that the magnetic permeability is reduced too much after the carbon coating layer is used is avoided, and the overall performances of the powder such as the matching property, the wave absorbing property and the like are better.
In order to stabilize the polymerization, in a preferred embodiment, the temperature during the polymerization is 30 to 50 ℃, the stirring speed is 400 to 800r/min, and the reaction time is 6 to 12 hours. Preferably, the oxidizing agent is ferric chloride; preferably, the second solvent is water.
For example, fe may be performed by the following steps 3 O 4 /SiO 2 Preparation of PPy core-shell microspheres: 1 to 6 parts by weight of PVP modified Fe 3 O 4 /SiO 2 Dispersing the core-shell microspheres into 100-400 parts of deionized water, adding 5-10 parts of ferric chloride after ultrasonic treatment for 15-30 min, stirring for 30-80 min, adding 1-5 parts of pyrrole, and reacting for 6-12 h at a rotating speed of 400-800 r/min under water bath stirring at 30-50 ℃; collecting precipitate with magnet after reaction, pouring out supernatant, washing with distilled water and ethanol for 3-6 times, respectively, drying the precipitate in a blast oven at 40-80deg.C for 8-15 h to obtain Fe 3 O 4 /SiO 2 The particle size of the PPy core-shell microsphere is 200-800 nm.
In order to carbonize the polypyrrole layer more sufficiently and to stabilize the carbon layer formed after calcination, in a preferred embodiment, in step S4, fe is calcined 3 O 4 /SiO 2 In the process of the PPy core-shell microsphere, the calcination temperature is 500-800 ℃ and the calcination time is 2-6 h. Inert gases employed during this period include, but are not limited to, nitrogen or argon. The equipment for specific calcination can be a tube furnace.
After calcination, the polypyrrole layer is carbonized to form micropores on the carbon layer, and the alkali solution can penetrate through the carbon layer to enter the inside and complete SiO 2 Etching of the layer. In a preferred embodiment, in step S5, the alkali solution is an aqueous solution of sodium hydroxide having a concentration of 10 to 30wt%, which has a better etching effect. Preferably, in step S5, after the carbonized microspheres are placed in an alkali solution, the carbonized microspheres are reacted for 10 to 20 hours under the conditions of stirring speed of 800 to 1500r/min and temperature of 40 to 80 ℃ so as to etch and remove SiO 2 A layer; preferably, in step S5, after the reaction is completed, the precipitate is separated and dried to obtain the hollow carbon material coated ferrite wave absorber powder. Under the above conditions, the composition of the present invention,can more fully etch SiO 2 And the layers are finally formed into a hollow structure with a more complete and stable structure.
Illustratively, the following steps may be employed to etch SiO 2 Layer (c): fe in parts by weight 3 O 4 /SiO 2 Dispersing the/C microspheres (carbonized microspheres) into 100-400 parts of 10-30% sodium hydroxide aqueous solution for etching, stirring at the temperature of 40-80 ℃ and the rotating speed of 800-1500 r/min for 10-20 hours, collecting the precipitate by using a magnet, pouring out the supernatant, washing the supernatant with distilled water for 3-6 times, putting the precipitate into a blast oven at the temperature of 40-80 ℃ for drying for 8-15 hours, and obtaining the hollow carbon material coated ferrite wave absorber powder.
More preferably, in the above step S1, in Fe 3 O 4 Microsphere and Fe 3 O 4 /SiO 2 In the preparation process of the core-shell microsphere, the related drying treatment time and the related drying treatment temperature are preferably 80 ℃ for 12 hours; the number of times of washing the powder particles is preferably 3. More preferably, in the above steps S2 to S5, the temperature during the drying treatment is preferably 60 ℃, the time is preferably 15 hours, and the number of times of washing the powder particles is 5.
According to another aspect of the present invention, there is also provided a hollow carbon material coated ferrite wave absorber powder prepared by the above preparation method.
According to still another aspect of the present invention, there is also provided a wave-absorbing material including the wave-absorbing powder, which is the above hollow carbon material coated ferrite wave-absorbing powder.
The present application is described in further detail below in conjunction with specific embodiments, which should not be construed as limiting the scope of the claims.
Comparative example 1
Fe (Fe) 3 O 4 The preparation method of the wave absorber powder comprises the following steps:
Fe 3 O 4 preparation of microspheres
15 parts of ferric salt (mass ratio FeCl) 3 /Fe(SO 4 ) =6:5) into 600 parts of 99% glycol aqueous solution, stirring uniformly, adding 100Continuously stirring the mixed solution with anhydrous sodium acetate uniformly, putting the mixed solution into an oil bath pot at 200 ℃ and continuously stirring the mixed solution for 8 hours at a rotating speed of 2000r/min, collecting the precipitate by using a magnet after the reaction is completed, respectively cleaning the precipitate by using water and ethanol for 5 times, and drying the obtained sample in a blast oven at 80 ℃ for 12 hours to obtain Fe with the particle size of 400-600 nm 3 O 4 And (3) microspheres.
Example 1
Carbon-coated Fe of hollow core-shell structure 3 O 4 The preparation method of the wave absorber powder comprises the following steps:
1、Fe 3 O 4 preparation of microspheres
15 parts of ferric salt (mass ratio FeCl) 3 /Fe(SO 4 ) =6:5) dispersing into 600 parts of 99% glycol aqueous solution, stirring uniformly, adding 100 parts of anhydrous sodium acetate, continuously stirring uniformly, placing the mixed solution into an oil bath pot at 200 ℃ and continuously stirring at a speed of 2000r/min for 8 hours, collecting precipitate after the reaction is completed, washing with water and ethanol for 5 times respectively, drying the obtained sample in a blast oven at 80 ℃ for 12 hours to obtain Fe with a particle size of 400-600 nm 3 O 4 And (3) microspheres.
2、Fe 3 O 4 /SiO 2 Preparation of core-shell microspheres
2 parts of prepared Fe 3 O 4 Adding the microspheres into 1200 parts of absolute ethyl alcohol and 500 parts of deionized water, and performing ultrasonic treatment for 30min to ensure that Fe 3 O 4 The microspheres can be uniformly dispersed in the reaction liquid, dilute ammonia water is used as pH regulating liquid, the pH of the reaction liquid is controlled to be about 8, then 1 part of tetraethoxysilane is dripped into the solution, and the solution is continuously stirred for 3 hours in a water bath kettle at 60 ℃ at the rotating speed of 500 r/min. After the reaction is finished, collecting the precipitate by using a magnet, pouring out the supernatant, washing the supernatant with ethanol for 5 times, putting the precipitate into a blast oven at 60 ℃ for drying treatment for 15 hours, and completing Fe 3 O 4 /SiO 2 And (3) preparing the core-shell microsphere.
3、Fe 3 O 4 /SiO 2 Modification of core-shell microspheres
1 part of Fe 3 O 4 /SiO 2 Dispersing the core-shell microspheres into 400 parts of ethanol solution, performing ultrasonic treatment for 20min, adding 3 parts of PVP (polyvinylpyrrolidone), continuously performing ultrasonic treatment for 40min, washing with distilled water for 5 times for standby, and then placing the washed precipitate into a 60 ℃ blast oven for drying treatment for 15h to finish Fe 3 O 4 /SiO 2 PVP modification of core-shell microspheres.
4、Fe 3 O 4 /SiO 2 Preparation of PPy core-shell microsphere
1 part of PVP modified Fe 3 O 4 /SiO 2 Dispersing core-shell microspheres into 400 parts of deionized water, ultrasonically treating for 15min, adding 5 parts of ferric chloride, stirring for 30min, adding 1 part of pyrrole, reacting for 8h at a rotating speed of 400r/min under water bath stirring at 40 ℃, collecting precipitate with a magnet after the reaction is finished, pouring out supernatant, respectively washing with distilled water and ethanol for 5 times, putting the precipitate into a blast oven at 60 ℃ for drying for 15h, and obtaining Fe 3 0 4 /SiO 2 PPy core-shell microspheres.
5. Calcination
Fe is added to 3 0 4 /SiO 2 Calcining the PPy core-shell microspheres for 3 hours at 500 ℃ in a tube furnace under the nitrogen condition to form carbonized microspheres.
6、SiO 2 Layer etching
Dispersing carbonized microspheres into 100 parts of 10% sodium hydroxide aqueous solution for etching, stirring at 40 ℃ for 100 hours at a rotating speed of 800r/min, collecting the precipitate by using a magnet, pouring out the supernatant, washing for 5 times by using distilled water, putting the precipitate into a blast oven at 60 ℃ for drying treatment for 8 hours, thus obtaining the Fe with a hollow core-shell structure 3 O 4 and/C powder.
Example 2
Carbon-coated Fe of hollow core-shell structure 3 O 4 The preparation method of the wave absorber powder comprises the following steps:
1、Fe 3 O 4 preparation of microspheres
15 parts of ferric salt (mass ratio FeCl) 3 /Fe(SO 4 ) =6:5) was dispersed into 600 parts of 99% glycol aqueous solution, stirredAdding 100 parts of anhydrous sodium acetate after uniformly stirring, continuously stirring uniformly, putting the mixed solution into an oil bath pot at 200 ℃ and continuously stirring for 8 hours at a rotating speed of 2000r/min, collecting precipitates by using a magnet after the reaction is completed, respectively cleaning the precipitates by using water and ethanol for 5 times, and drying the obtained samples in a blast oven at 80 ℃ for 12 hours to obtain Fe with the particle size of 400-600 nm 3 O 4 And (3) microspheres.
2、Fe 3 O 4 /SiO 2 Preparation of core-shell microspheres
5 parts of prepared Fe 3 O 4 Adding the microspheres into 1000 parts of absolute ethyl alcohol and 400 parts of deionized water, and performing ultrasonic treatment for 40min to ensure that Fe 3 O 4 The microspheres can be uniformly dispersed in the reaction liquid, dilute ammonia water is used as pH regulating liquid, the pH of the reaction liquid is controlled to be about 8, 3 parts of tetraethoxysilane is dripped into the solution, and the solution is continuously stirred in a water bath kettle at 60 ℃ for 4 hours at the rotating speed of 800 r/min. After the reaction is finished, collecting the precipitate by using a magnet, pouring out the supernatant, washing the supernatant with ethanol for 5 times, putting the precipitate into a blast oven at 80 ℃ for drying treatment for 12 hours, and completing Fe 3 O 4 /SiO 2 And (3) preparing the core-shell microsphere.
3、Fe 3 O 4 /SiO 2 Modification of core-shell microspheres
4 parts of Fe 3 O 4 /SiO 2 Dispersing core-shell microspheres into 200 parts of ethanol solution, performing ultrasonic treatment for 30min, adding 6 parts of PVP (polyvinylpyrrolidone), continuously performing ultrasonic treatment for 50min, cleaning with distilled water for 5 times for standby, and then placing the cleaned precipitate into a 80 ℃ blast oven for drying treatment for 12h to finish Fe 3 O 4 /SiO 2 PVP modification of core-shell microspheres.
4、Fe 3 O 4 /SiO 2 Preparation of PPy core-shell microsphere
4 parts of PVP-modified Fe 3 O 4 /SiO 2 Dispersing core-shell microspheres into 200 parts of deionized water, performing ultrasonic treatment for 20min, adding 8 parts of ferric chloride, stirring for 60min, adding 3 parts of pyrrole, reacting for 10h at 600r/min under water bath stirring at 50 ℃, collecting precipitate with magnet after the reaction, pouring out supernatant, and respectivelyWashing with distilled water and ethanol for 5 times, and oven drying the precipitate at 60deg.C in a blast oven for 15 hr to obtain Fe 3 0 4 /SiO 2 PPy core-shell microspheres.
5. Calcination
Fe is added to 3 0 4 /SiO 2 Calcining the PPy core-shell microspheres for 4 hours at 600 ℃ in a tube furnace under the nitrogen condition to form carbonized microspheres.
6、SiO 2 Layer etching
Dispersing carbonized microspheres into 200 parts of sodium hydroxide aqueous solution with the mass concentration of 20% for etching, stirring at the temperature of 60 ℃ for 15 hours at the rotating speed of 1000r/min, collecting the precipitate by using a magnet, pouring out the supernatant, washing for 5 times by using distilled water, putting the precipitate into a blast oven at the temperature of 60 ℃ for drying treatment for 15 hours, thus obtaining the Fe with a hollow core-shell structure 3 O 4 and/C powder.
Example 3
Carbon-coated Fe of hollow core-shell structure 3 O 4 The preparation method of the wave absorber powder comprises the following two steps:
1、Fe 3 O 4 preparation of microspheres
15 parts of ferric salt (mass ratio FeCl) 3 /Fe(SO 4 ) =6:5) dispersing into 600 parts of 99% glycol aqueous solution, stirring uniformly, adding 100 parts of anhydrous sodium acetate, continuously stirring uniformly, placing the mixed solution into an oil bath pot at 200 ℃ and continuously stirring at a speed of 2000r/min for 8 hours, collecting precipitate after the reaction is completed, washing with water and ethanol for 5 times respectively, drying the obtained sample in a blast oven at 80 ℃ for 12 hours to obtain Fe with a particle size of 400-600 nm 3 O 4 And (3) microspheres.
2、Fe 3 O 4 /SiO 2 Preparation of core-shell microspheres
10 parts of prepared Fe 3 O 4 Adding the microspheres into 800 parts of absolute ethyl alcohol and 200 parts of deionized water, and performing ultrasonic treatment for 50min to ensure that Fe 3 O 4 The microspheres can be uniformly dispersed in the reaction liquid, the pH of the reaction liquid is controlled to be about 9 by using dilute ammonia water as pH regulating liquid, and then6 parts of ethyl orthosilicate is dripped into the solution, and the mixture is stirred for 6 hours in a water bath kettle at 80 ℃ at the rotating speed of 1000 r/min. After the reaction is finished, collecting the precipitate by using a magnet, pouring out the supernatant, washing the supernatant with ethanol for 5 times, putting the precipitate into a blast oven at 80 ℃ for drying treatment for 12 hours, and completing Fe 3 O 4 /SiO 2 And (3) preparing the core-shell microsphere.
3、Fe 3 O 4 /SiO 2 Modification of core-shell microspheres
6 parts of Fe 3 O 4 /SiO 2 Dispersing core-shell microspheres into 50 parts of ethanol solution, performing ultrasonic treatment for 40min, adding 8 parts of PVP (polyvinylpyrrolidone), continuously performing ultrasonic treatment for 60min, cleaning with distilled water for 5 times for standby, and then placing the cleaned precipitate into a 80 ℃ blast oven for drying treatment for 12h to finish Fe 3 O 4 /SiO 2 PVP modification of core-shell microspheres.
4、Fe 3 O 4 /SiO 2 Preparation of PPy core-shell microsphere
6 parts of PVP-modified Fe 3 O 4 /SiO 2 Dispersing core-shell microspheres into 100 parts of deionized water, performing ultrasonic treatment for 30min, adding 10 parts of ferric chloride, stirring for 80min, adding 5 parts of pyrrole, reacting for 12h at a rotation speed of 800r/min under water bath stirring at 50 ℃, collecting precipitate with a magnet after the reaction is finished, pouring out supernatant, respectively washing with distilled water and ethanol for 5 times, placing the precipitate into a blast oven at 60 ℃ for drying treatment for 15h, and obtaining Fe 3 0 4 /SiO 2 PPy core-shell microspheres.
5. Calcination
Fe is added to 3 0 4 /SiO 2 Calcining the PPy core-shell microspheres at 800 ℃ for 6 hours in a tube furnace under the nitrogen condition to form carbonized microspheres.
6、SiO 2 Layer etching
Dispersing carbonized microsphere into 100 parts of 30% sodium hydroxide aqueous solution, etching, stirring at 60deg.C for 20 hr at 1500r/min, collecting precipitate with magnet, pouring out supernatant, washing with distilled water for 5 times, and oven drying at 60deg.C for 15 hrFe to hollow core-shell architecture 3 O 4 and/C powder.
Example 4
Carbon-coated Fe of hollow core-shell structure 3 O 4 The preparation method of the wave absorber powder comprises the following two steps:
1、Fe 3 O 4 preparation of microspheres
5 parts of ferric salt (mass ratio FeCl) 3 /Fe(SO 4 ) =6:5) dispersing into 800 parts of 99% glycol solution, stirring uniformly, adding 150 parts of anhydrous sodium acetate, continuously stirring uniformly, placing the mixed solution into an oil bath pot at 250 ℃ and continuously stirring at a rotating speed of 1500r/min for 5 hours, collecting precipitate after the reaction is completed, washing with water and ethanol for 5 times respectively, drying the obtained sample in a blast oven at 80 ℃ for 12 hours to obtain Fe with a particle size of 200-300 nm 3 O 4 And (3) microspheres.
2、Fe 3 O 4 /SiO 2 Preparation of core-shell microspheres
5 parts of prepared Fe 3 O 4 Adding the microspheres into 1000 parts of absolute ethyl alcohol and 400 parts of deionized water, and performing ultrasonic treatment for 40min to ensure that Fe 3 O 4 The microspheres can be uniformly dispersed in the reaction liquid, dilute ammonia water is used as pH regulating liquid, the pH of the reaction liquid is controlled to be about 8, 3 parts of tetraethoxysilane is dripped into the solution, and the solution is continuously stirred in a water bath kettle at 60 ℃ for 4 hours at the rotating speed of 800 r/min. After the reaction is finished, collecting the precipitate by using a magnet, pouring out the supernatant, washing the supernatant with ethanol for 5 times, putting the precipitate into a blast oven at 80 ℃ for drying treatment for 12 hours, and completing Fe 3 O 4 /SiO 2 And (3) preparing the core-shell microsphere.
3、Fe 3 O 4 /SiO 2 Modification of core-shell microspheres
4 parts of Fe 3 O 4 /SiO 2 Dispersing core-shell microspheres into 200 parts of ethanol solution, performing ultrasonic treatment for 30min, adding 6 parts of PVP (polyvinylpyrrolidone), continuously performing ultrasonic treatment for 50min, cleaning with distilled water for 5 times for standby, and then placing the cleaned precipitate into a 80 ℃ blast oven for drying treatment for 12h to finish Fe 3 O 4 /SiO 2 PVP modification of core-shell microspheres.
4、Fe 3 O 4 /SiO 2 Preparation of PPy core-shell microsphere
4 parts of PVP-modified Fe 3 O 4 /SiO 2 Dispersing core-shell microspheres into 200 parts of deionized water, ultrasonically treating for 20min, adding 8 parts of ferric chloride, stirring for 60min, adding 3 parts of pyrrole, reacting for 10h at a rotating speed of 600r/min under water bath stirring at 50 ℃, collecting precipitate with a magnet after the reaction is finished, pouring out supernatant, respectively washing with distilled water and ethanol for 5 times, putting the precipitate into a blast oven at 60 ℃ for drying for 15h, and obtaining Fe 3 0 4 /SiO 2 PPy core-shell microspheres.
5. Calcination
Fe is added to 3 0 4 /SiO 2 Calcining the PPy core-shell microspheres for 4 hours at 600 ℃ in a tube furnace under the nitrogen condition to form carbonized microspheres.
6、SiO 2 Layer etching
Dispersing carbonized microspheres into 200 parts of sodium hydroxide aqueous solution with the mass concentration of 20% for etching, stirring at the temperature of 60 ℃ for 15 hours at the rotating speed of 1000r/min, collecting the precipitate by using a magnet, pouring out the supernatant, washing for 5 times by using distilled water, putting the precipitate into a blast oven at the temperature of 60 ℃ for drying treatment for 15 hours, thus obtaining the Fe with a hollow core-shell structure 3 O 4 and/C powder.
Example 5
Carbon-coated Fe of hollow core-shell structure 3 O 4 The preparation method of the wave absorber powder comprises the following two steps:
1、Fe 3 O 4 preparation of microspheres
30 parts of ferric salt (mass ratio (Fel) 3 )/Fe(SO 4 ) =6:5) into 400 parts of 99% glycol solution, adding 20 parts of anhydrous sodium acetate after stirring uniformly, continuously stirring uniformly, placing the mixed solution into an oil bath pot at 150 ℃ and continuously stirring at a rotating speed of 2000r/min for 10 hours, collecting precipitate by a magnet after the reaction is complete, washing with water and ethanol for 5 times respectively, and then blowing the obtained sample into a blast oven at 80 DEG CThe Fe with the grain diameter of 600 to 800nm can be obtained after the medium drying treatment for 12 hours 3 O 4 And (3) microspheres.
2、Fe 3 O 4 /SiO 2 Preparation of core-shell microspheres
5 parts of prepared Fe 3 O 4 Adding the microspheres into 1000 parts of absolute ethyl alcohol and 400 parts of deionized water, and performing ultrasonic treatment for 40min to ensure that Fe 3 O 4 The microspheres can be uniformly dispersed in the reaction liquid, dilute ammonia water is used as pH regulating liquid, the pH of the reaction liquid is controlled to be about 8, 3 parts of tetraethoxysilane is dripped into the solution, and the solution is continuously stirred in a water bath kettle at 60 ℃ for 4 hours at the rotating speed of 800 r/min. After the reaction is finished, collecting the precipitate by using a magnet, pouring out the supernatant, washing the supernatant with ethanol for 5 times, putting the precipitate into a blast oven at 80 ℃ for drying treatment for 12 hours, and completing Fe 3 O 4 /SiO 2 And (3) preparing the core-shell microsphere.
3、Fe 3 O 4 /SiO 2 Modification of core-shell microspheres
4 parts of Fe 3 O 4 /SiO 2 Dispersing core-shell microspheres into 200 parts of ethanol solution, performing ultrasonic treatment for 30min, adding 6 parts of PVP (polyvinylpyrrolidone), continuously performing ultrasonic treatment for 50min, cleaning with distilled water for 5 times for standby, and then placing the cleaned precipitate into a 80 ℃ blast oven for drying treatment for 12h to finish Fe 3 O 4 /SiO 2 PVP modification of core-shell microspheres.
4、Fe 3 O 4 /SiO 2 Preparation of PPy core-shell microsphere
4 parts of PVP-modified Fe 3 O 4 /SiO 2 Dispersing core-shell microspheres into 200 parts of deionized water, ultrasonically treating for 20min, adding 8 parts of ferric chloride, stirring for 60min, adding 3 parts of pyrrole, reacting for 10h at a rotating speed of 600r/min under water bath stirring at 50 ℃, collecting precipitate with a magnet after the reaction is finished, pouring out supernatant, respectively washing with distilled water and ethanol for 5 times, putting the precipitate into a blast oven at 60 ℃ for drying for 15h, and obtaining Fe 3 0 4 /SiO 2 PPy core-shell microspheres.
5. Calcination
Fe is added to 3 0 4 /SiO 2 Calcining the PPy core-shell microspheres for 4 hours at 600 ℃ in a tube furnace under the nitrogen condition to form carbonized microspheres.
6、SiO 2 Layer etching
Dispersing carbonized microspheres into 200 parts of sodium hydroxide aqueous solution with the mass concentration of 20% for etching, stirring at the temperature of 60 ℃ for 15 hours at the rotating speed of 1000r/min, collecting the precipitate by using a magnet, pouring out the supernatant, washing for 5 times by using distilled water, putting the precipitate into a blast oven at the temperature of 60 ℃ for drying treatment for 15 hours, thus obtaining the Fe with a hollow core-shell structure 3 O 4 and/C powder.
Characterization of the properties:
8 parts of Fe prepared in comparative example 1, example 1 to example 5, respectively 3 O 4 Particulate and hollow Fe 3 O 4 The preparation of 80% coaxial sample and testing of powder/C, the main steps are: firstly, respectively mixing powder with paraffin according to the weight ratio of 8:2, putting the mixture into a high-temperature oven at 65 ℃ for heating for 10min, then quickly taking out and uniformly mixing the mixture, preparing a viscous solid, filling the viscous solid into a coaxial circular mold (the outer diameter of the mold is 7mm, the inner diameter of the mold is 3.04 mm), respectively preparing a sample with the thickness of 1-2 mm, respectively measuring complex dielectric constant (epsilon ') and complex magnetic conductivity (mu') by adopting a network vector analyzer, and then calculating a reflection loss curve of the test sample with the frequency change curve when the thickness of the test sample is 2.5mm through matlab simulation according to an electromagnetic field transmission line theory. And measuring the tap density of the powder by using a tap density meter. The powder was added to 25% diluted hydrochloric acid, and the time for the solution to generate bubbles or for the solution to change in color was observed. Characterization results are shown in table 1:
TABLE 1
| Comparative example 1 | Example 1 | Example 2 | Example 3 | Example 4 | Example 5 | |
| Average particle diameter | 402nm | 405nm | 410nm | 420nm | 220nm | 760nm |
| ε′(6GHz) | 10.64 | 8.23 | 9.77 | 10.88 | 9.15 | 11.32 |
| μ′(6GHz) | 1.39 | 1.61 | 1.56 | 1.44 | 1.42 | 1.66 |
| Frequency point (GHz) | 6.93 | 6.71 | 6.56 | 6.43 | 6.31 | 6.48 |
| Absorption peak (dB) | -26 | -32 | -35 | -28 | -29 | -31 |
| Bandwidth (less than or equal to 10 dB) | 2.6 | 3.8 | 3.9 | 3.5 | 3.3 | 3.4 |
| Tap density | 2.67 | 1.63 | 1.23 | 1.18 | 1.33 | 1.42 |
| Acid corrosion resistance (color) | 12min | 106min | 255min | 294min | 238min | 267min |
Generally, low dielectric constant and high permeability form a relatively good impedance match. The lower the absorption peak intensity, the better the absorption effect.
The following test shows that: compared with Fe prepared in comparative example 1 3 O 4 Microspheres, hollow Fe prepared in examples 1 to 5 of the present invention 3 O 4 The density of the powder is lower, the absorption efficiency and the bandwidth are better, the hollow structure generates multiple reflection and multiple absorption, the propagation path of electromagnetic waves is increased, and the powder has acid and alkali corrosion resistance compared with Fe 3 O 4 The microsphere is greatly improved; hollow Fe in examples 1 to 3 3 O 4 According to the powder/C, as the carbon coating content is increased, the density and the magnetic conductivity of the powder are correspondingly reduced, the dielectric constant is increased, the dielectric loss in the material is increased, an effective conductive network structure is easier to form, the absorption efficiency is improved, and the reduction of the magnetic conductivity can cause some influence on the absorption efficiency; in the powder properties of examples 4, 2 and 5, fe was produced in accordance with the production of Fe 3 O 4 Particle size is increased, and hollow Fe is prepared 3 O 4 The particle size of the/C is too large, the dielectric effect is obviously increased, impedance matching is not facilitated, and the density is correspondingly improved; but prepared hollow Fe 3 O 4 The particle size of the catalyst is too small, so that the magnetic loss effect is reduced, and the absorption efficiency strength is not improved; thus finding a more suitable particle size range is advantageous for obtaining better absorption properties. In the embodiment 2, the powder density is obviously reduced, the acid-base corrosion resistance is obviously improved, better magnetic conductivity and dielectric constant can be achieved, the particle size is more suitable, and better absorption efficiency and absorption bandwidth are achieved.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The preparation method of the hollow carbon material coated ferrite wave absorber powder is characterized by comprising the following steps of:
step S1, at Fe 3 O 4 Coating SiO on the surface of microsphere 2 Layer of Fe 3 O 4 /SiO 2 Core-shell microspheres;
step S2, the Fe is processed 3 O 4 /SiO 2 Dispersing core-shell microspheres into a first solvent, and then adding PVP to the Fe 3 O 4 /SiO 2 Surface modification is carried out on the core-shell microsphere to form PVP modified Fe 3 O 4 /SiO 2 Core-shell microspheres;
step S3, the PVP modified Fe 3 O 4 /SiO 2 Dispersing core-shell microsphere in a second solvent, adding oxidant and pyrrole, and performing polymerization reaction to obtain PVP modified Fe 3 O 4 /SiO 2 Further forming a PPy coating layer on the surface of the core-shell microsphere to obtain Fe 3 O 4 /SiO 2 PPy core-shell microspheres;
step S4, calcining the Fe in inert gas 3 O 4 /SiO 2 The PPy core-shell microsphere is carbonized to obtain carbonized microsphere;
step S5, placing the carbonized microspheres in an alkali solution, and etching to remove the SiO 2 And a layer, so that the hollow carbon material coated ferrite wave absorber powder is formed.
2. The method according to claim 1, wherein the step S1 comprises:
the Fe is 3 O 4 Dispersing the microspheres in a third solvent to form a dispersion;
regulating the pH value of the dispersion liquid to 8-9, then adding tetraethoxysilane into the dispersion liquid, and reacting in a stirring state to obtain reaction slurry;
separating the solid in the reaction slurry, and drying to obtain the Fe 3 O 4 /SiO 2 Core-shell microspheres;
preferably, the Fe 3 O 4 The particle size of the microsphere is 200-800 nm;
preferably, the Fe 3 O 4 The weight ratio of the microsphere to the tetraethoxysilane is (2-10): 1-6;
preferably, the third solvent is a mixed solvent of ethanol and water, and the weight ratio of the third solvent to the water is (8-12): 2-5;
preferably, the agent for adjusting the pH value of the dispersion liquid adopts ammonia water;
preferably, after the tetraethoxysilane is added, the reaction is carried out for 3 to 6 hours under the conditions of stirring speed of 400 to 1000r/min and temperature of 40 to 80 ℃.
3. The method according to claim 2, wherein the Fe 3 O 4 The microsphere is prepared by the following method: dispersing ferrous salt and ferric salt in a fourth solvent, adding alkali for reaction, carrying out solid-liquid separation, and drying to obtain Fe 3 O 4 A microsphere;
preferably, the ferrous salt is ferrous chloride and/or ferrous sulfate, and the ferric salt is ferric chloride and/or ferric sulfate;
preferably, the base is anhydrous sodium acetate;
preferably, the total weight of the ferrous salt and the ferric salt is denoted as m1, the weight of the alkali is denoted as m2, and then m1/m2 is (1-6): 4-30;
preferably, the fourth solvent is an aqueous solution of ethylene glycol with the mass concentration of 96-99%;
preferably, after adding the alkali, the reaction is carried out for 5 to 10 hours under the conditions of stirring speed of 1500 to 2500r/min and temperature of 150 to 250 ℃.
4. A production method according to any one of claims 1 to 3, wherein in the step S2, the Fe 3 O 4 /SiO 2 The weight ratio of the core-shell microsphere to the PVP is (1-6) to (3-8);
preferably, the first solvent is an aqueous ethanol solution, more preferably an aqueous ethanol solution with a mass concentration of 50-80%.
5. The method according to any one of claims 1 to 4, wherein the step S3 comprises:
fe modified by PVP 3 O 4 /SiO 2 Dispersing core-shell microspheres into a second solvent, adding the oxidant, stirring for 30-80 min, and adding the pyrrole to perform the polymerization reaction to obtain the Fe 3 O 4 /SiO 2 PPy core-shell microspheres;
preferably, the PVP modified Fe 3 O 4 /SiO 2 The weight ratio of the core-shell microspheres to the oxidant is (1-6) (5-10);
preferably, the PVP modified Fe 3 O 4 /SiO 2 The weight ratio of the core-shell microsphere to the pyrrole is (1-6): 1-5;
preferably, the temperature in the polymerization reaction process is 30-50 ℃, the stirring speed is 400-800 r/min, and the reaction time is 6-12 h;
preferably, the oxidizing agent is ferric chloride;
preferably, the second solvent is water.
6. The production method according to any one of claims 1 to 5, characterized in that in the step S4, the Fe is calcined 3 O 4 /SiO 2 In the process of the PPy core-shell microsphere, the calcination temperature is 500-800 ℃ and the calcination time is 2-6 h.
7. The method according to any one of claims 1 to 6, wherein in step S5, the alkali solution is an aqueous sodium hydroxide solution having a concentration of 10 to 30 wt%.
8. The method according to claim 7, wherein in the step S5, the carbonized microsphere is reacted at a stirring speed of 800 to 1500r/min and a temperature of 40 to 80 ℃ after being placed in an alkali solution for 1:0 to 20 hours to etch and remove the SiO 2 A layer; preferably, in the step S5, after the reaction is completed, the precipitate is separated and dried, so as to obtain the hollow carbon material coated ferrite wave absorber powder.
9. A hollow carbon material coated ferrite wave absorber powder prepared by the preparation method of any one of claims 1 to 8.
10. A wave-absorbing material comprising a wave-absorbing powder, wherein the wave-absorbing powder is the hollow carbon material-coated ferrite wave-absorbing powder of claim 9.
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