CN107338024B - Co-Fe alloy/carbon sphere composite microwave absorbent and preparation method thereof - Google Patents
Co-Fe alloy/carbon sphere composite microwave absorbent and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a Co-Fe alloy/carbon sphere composite microwave absorbent and a preparation method thereof, the carbon sphere is taken as a core, the outer side of the carbon sphere is coated by Co-Fe alloy particles, the outer side of the Co-Fe alloy particles is coated with a layer of graphite, a multi-stage core-shell structure is integrally formed, the preparation method of the composite microwave absorbent comprises the steps of firstly preparing incompletely carbonized polysaccharide microspheres by using glucose and a dispersing agent, then impregnating the polysaccharide microspheres with a mixed solution of cobalt ions and iron ions, finally placing the obtained mixture in an inert atmosphere at high temperature for heat treatment, the graphitization of the carbon spheres and the reduction of the metal ions are simultaneously carried out, and the obtained composite microwave absorbent combines the advantages of carbon materials and magnetic metal powder, has the characteristics of good microwave absorption performance and light weight, and can be widely applied to various environments and fields.
Description
Technical Field
The invention relates to a microwave absorbent and a preparation method thereof, in particular to a composite microwave absorbent with a multistage core-shell structure and a preparation method thereof.
Background
With the rapid development of the electronic industry, various electronic devices are becoming more and more popular. The electromagnetic wave generated by the electronic equipment can cause pollution to the environment while promoting the industrial production revolution and improving the living conditions of people. It may not only interfere with the normal operation of other electronic devices, but also endanger human health. Electromagnetic waves have become a further source of pollution to the human living environment following exhaust gases, waste residues, waste water and noise. Although the electromagnetic wave is invisible, invisible and inaudible, the electromagnetic wave is everywhere, and when the frequency exceeds 105Hz, the electromagnetic wave is harmful to human bodies. On the other hand, in military affairs, the stealth technology is an important technical means in the future informatization war. The radar wave absorbing stealth material can consume part of energy of radar waves through the absorption effect of the radar wave absorbing stealth material on electromagnetic waves, so that reflected echoes are incomplete, and a target is not easy to detect.
At present, the radar wave-absorbing material mainly comprises an absorbent and a high polymer matrix material, wherein the key for determining the wave-absorbing performance is the type and the content of the absorbent. Generally, the absorption principle of the absorbent is different, and the absorbent can be classified into an electrical loss type and a magnetic loss type. Common wave absorbing agents of the electric loss type wave absorbing material comprise conductive carbon black, graphite, carbon fiber, silicon carbide, barium titanate ferroelectric ceramics, conductive polymers and the like, and the electromagnetic waves are absorbed by means of electronic polarization, ion polarization and interface polarization attenuation of media. The electric loss type wave-absorbing material has the advantages of low density, narrow absorption frequency band and relatively weak absorption capacity. Common wave absorbing agents for magnetic loss type wave absorbing materials include ferrite, superfine metal powder, carbonyl iron powder and the like. They attenuate and absorb electromagnetic waves mainly by mechanisms such as hysteresis loss, natural resonance, domain wall resonance, and the like. The magnetic loss type wave-absorbing material has strong absorption capacity and wide absorption frequency band, but has the defect of high density. Due to their respective disadvantages, a single magnetically or electrically lossy absorber does not fully satisfy the requirements of the application. The development of a novel light and efficient composite absorbent by combining the advantages of the two is an important research direction in recent years.
In order to achieve the objective of obtaining a novel composite absorbent with light weight and high efficiency, modification treatment of a carbon material loaded with a magnetic metal or alloy based on graphite or carbon nanotubes has become an important issue in the research of microwave absorbing materials. A general method is to prepare a carbon material and then load metal particles on the surface of the carbon material by a mechanical mixing method, a sputtering method, a pyrolysis method, a chemical plating method, a coprecipitation reduction method, or the like. However, the surface of carbon materials such as carbon nanotubes, graphite powder, etc. is generally lacking in defects and dangling bonds, and the C — C single bond is also a stable chemical bond, so that it is difficult to be infiltrated by metals or compounds, and the metal particles filled thereon by physical adsorption, sputtering or pyrolysis are generally easily distributed unevenly and have an excessively large size. Chinese patent CN105820796A discloses a method for preparing a composite wave-absorbing material using porous carbon spheres to load magnetic alloy, which utilizes the high specific surface area and strong adsorption of porous carbon spheres to introduce a precursor solution of magnetic metal into the pore canal of the carbon spheres through capillary action and then combine with hydrophilic oxygen-containing functional groups, but as mentioned above, the surface of the porous carbon spheres is defect-free and dangling bond-free, because the porous carbon spheres are completely carbonized, the hydrophilic functional groups on the surface are very few and are difficult to form chemical action or bonding with magnetic metal ions, therefore, the magnetic alloy particles on the surface of the wave-absorbing material obtained by the method are not uniformly distributed, the combination quantity of the magnetic alloy particles is limited and the size is too large, so the wave-absorbing performance is greatly influenced, in addition, the surface of the metal particles on the surface of the carbon spheres is lack of protection and is easy to be oxidized, and the wave-absorbing material is often used in some harsh environments, this greatly limits the range of applications for the material.
Disclosure of Invention
Aiming at the defects of the existing composite wave-absorbing material and the preparation method thereof, the invention provides a Co-Fe alloy/carbon sphere composite microwave absorbent and a preparation method thereof.
The technical scheme for solving the technical problems is as follows:
a Co-Fe alloy/carbon sphere composite microwave absorbent takes a carbon sphere as a core, the outer side of the carbon sphere is coated with Co-Fe alloy particles, the outer side of the Co-Fe alloy particles is coated with a layer of graphite, and a multi-stage core-shell structure is integrally formed.
Further, the diameter of the carbon sphere is 1-10 μm, and the particle size of the Co-Fe alloy particles is 20-80 nm.
Further, the mass fraction of the Co-Fe alloy particles is 10-20%.
The composite microwave absorbent provided by the invention has the beneficial effects that:
1) on one hand, the graphite layer on the surface can protect the cobalt-iron alloy particles from being oxidized in the using process; on the other hand, the agglomeration and growth of the cobalt-iron alloy particles can be prevented, and the activity is greatly increased and the microwave absorption performance is improved due to the refinement of the metal particles;
2) the cobalt-iron alloy particles are uniformly distributed on the surface of the carbon sphere, the carbon sphere which just completes carbonization in the heating treatment process has high activity, a villous carbon nano tube is easily formed on the surface of the carbon sphere under the catalysis of the cobalt-iron alloy, and the wave absorbing performance is further improved;
3) the composite wave absorbing agent provided by the invention combines the advantages of carbon materials and magnetic metal powder, has the characteristics of good microwave absorption performance and light weight, and can be widely applied to various environments and fields.
The invention also claims a preparation method of the Co-Fe alloy/carbon ball composite microwave absorbent, which comprises the following steps:
1) preparing polysaccharide microspheres: weighing glucose and a dispersing agent, dissolving the glucose and the dispersing agent in deionized water, fully stirring, pouring the solution into a reaction kettle after the glucose and the dispersing agent are completely dissolved, placing the reaction kettle at 180-200 ℃ for reaction, wherein the glucose and the dispersing agent are dissolved in no sequence, the concentration of the glucose in the solution is controlled to be 6-10 wt%, the concentration of the dispersing agent is 2-2.5 g/L, cooling the mixture in the reaction kettle after the reaction is finished to room temperature, performing suction filtration and washing to obtain a precipitate, and drying to obtain polysaccharide microspheres;
2) alkali treatment: placing the polysaccharide microspheres obtained in the step 1) in 0.1-1.0 mol/L inorganic alkali solution, stirring at constant temperature of 40-80 ℃, performing suction filtration, washing and drying to obtain alkali-treated polysaccharide microspheres;
3) weighing soluble cobalt salt and soluble iron salt, dissolving the soluble cobalt salt and the soluble iron salt in water to prepare a mixed solution of cobalt and iron, wherein the concentration of cobalt ions is controlled to be 0.2-0.3 mol/L, and the amount of iron ions is 1.4-3.0 × 10 per gram of carbon spheres-3Ultrasonically dispersing the polysaccharide microspheres subjected to alkali treatment in the step 2) in the obtained mixed solution of cobalt and iron, controlling the molar ratio of cobalt ions to iron ions on final adsorption to be 1:2, stirring and dipping, then performing suction filtration, washing and drying;
4) and (3) heat treatment: and (3) placing the product obtained in the step 3) in an inert atmosphere for heat treatment at 900-1200 ℃, and then naturally cooling to obtain the Co-Fe alloy/carbon sphere composite microwave absorbent.
On the basis of the technical scheme, the invention can be further improved as follows.
Further, the dispersant is any one of cetyl trimethyl ammonium bromide, sodium dodecyl sulfate and sodium dodecyl benzene sulfonate.
Further, in the step 2), the inorganic base is any one or a compound of more of potassium hydroxide, sodium hydroxide, ammonium hydroxide and barium hydroxide.
Further, the soluble ferric salt in the step 3) is any one of ferric chloride hexahydrate, ferric sulfate, ferric nitrate, ferric oxalate, ferrous chloride, ferrous sulfate and ferrous oxalate, and the soluble cobalt salt is any one of cobalt chloride, cobalt sulfate and cobalt nitrate.
Further, the reaction time in the step 1) is 4-8 h.
Further, the constant-temperature stirring time in the step 2) is 12-18 h.
Further, the stirring and dipping time in the step 3) is 12-24 hours, and the heat treatment time in the step 4) is 1-4 hours.
The preparation method provided by the invention has the advantages that:
1) the method adopts the carbon-containing polysaccharide microsphere which is not completely carbonized as a template, the surface of the polysaccharide microsphere is provided with rich hydroxyl groups, and the number of the hydroxyl groups on the surface of the polysaccharide microsphere is further increased after alkaline leaching treatment, so that magnetic metal ions can be combined through chemical adsorption, and electron clouds on the surface of oxygen atoms in the hydroxyl groups and positive charges of the magnetic metal ions are mutually attracted to form chemical bonding;
2) according to the method, the carbonization process of the carbon spheres and the reduction process of the metal ions are combined together, in the heat treatment process, the graphitization of the polysaccharide microspheres and the reduction of the metal ions are carried out simultaneously, the graphitized carbon spheres are coated on the surfaces of the cobalt-iron alloy particles, and on one hand, the graphite layer coated on the surfaces of the cobalt-iron alloy particles can protect the cobalt-iron alloy particles from being oxidized in the use process; on the other hand, the method can also prevent the cobalt-iron alloy particles from agglomerating and growing, the activity is greatly increased due to the refinement of the metal particles, atoms and electrons move more rapidly under the microwave radiation, the magnetization can be promoted, the ferromagnetic ultrafine metal micro powder has larger magnetic conductivity and strong interaction with high-frequency electromagnetic waves, and the microwave absorption performance can be improved.
3) In the heat treatment process under the inert atmosphere, the carbon spheres which just finish carbonization have high activity, and villous carbon nano tubes are easily formed on the surfaces of the carbon spheres under the catalysis of the cobalt-iron alloy, so that the wave absorbing performance is improved.
In the following, we combine the TG-DSC curve (see fig. 4) of the product obtained after cobalt and iron impregnation before heat treatment and TEM and SEM pictures (fig. 3) of the product before and after heat treatment to describe in detail the chemical changes that occur during heat treatment, below 200 ℃, free water and structural water in the sample gradually lose, weight loss 8.9%, and show endotherm at this stage; in the temperature range of 200-700 ℃, the cobalt and iron coated outside the carbon spheres are gradually reduced to release CO2The weight is reduced sharply, heat is released continuously in the reduction process, a heat release peak which is not obvious is also formed in the temperature range of 500-600 ℃, and cobalt and iron form an alloy in the process; after the temperature exceeds 700 ℃, the carbon spheres are graphitized and have obvious exothermic peaks. By combining with SEM and TEM picture representation, in the whole process, because metal ions are adsorbed by chemical action, the carbon material is tightly combined with the carbon material, the carbon material which just completes carbonization has high activity and is easy to infiltrate with metal, carbon spheres can be coated on the surface of cobalt-iron alloy particles after graphitization, and carbon nano tubes are easy to form on the surface of the carbon spheres under the catalysis of the cobalt-iron alloy, so that the wave absorbing performance is improved, a C @ CoFe capsule structure with a graphite layer coated on the surface of the alloy particles is formed, and the small capsules are coated on the surface of the carbon spheres, so that a C/(C @ CoFe) multistage core-shell structure is formed.
The preparation method of the invention has the beneficial effects that:
1) the characteristic that the surface of the polysaccharide microsphere is rich in hydroxyl is fully utilized, so that the polysaccharide microsphere and magnetic metal ions form chemical adsorption and bonding, the amount of the metal ions combined on the surface of the polysaccharide microsphere is large, the combination is firm, the distribution is uniform, and the absorption performance of microwaves can be improved;
2) the method of the invention simultaneously conducts graphitization of the polysaccharide microsphere and reduction of metal ions, on one hand, graphite on the surface of the carbon sphere plays a role in protecting the metal ions from oxidation, on the other hand, the agglomeration and growth of the ferrocobalt alloy particles can be prevented, and the refinement of the metal ions greatly improves the microwave absorption performance;
3) the carbon spheres which are just carbonized in the heat treatment process have high activity, and villous carbon nano tubes are easily formed on the surfaces of the carbon spheres under the catalysis of the cobalt-iron alloy, so that the wave absorbing performance is further improved.
4) The composite wave absorbing agent prepared by the method has the characteristics of good microwave absorption performance and light weight, and can be widely applied to various environments and fields.
Drawings
FIG. 1 is an XRD spectrum of the composite wave absorber obtained in example 1 of the present invention;
FIG. 2 is a TG-DSC curve of the product obtained in step 3) of example 1;
FIG. 3 is TEM and SEM pictures of the product of example 1 before and after heat treatment;
FIG. 4 is a reflection loss chart of the composite wave absorber obtained in example 1 and the carbon spheres obtained in step 1) of the present invention.
Fig. 3, (a) an overall SEM image of the microwave absorber after heat treatment; (b) TEM image of the front clad layer heat-treated in argon atmosphere; (c) TEM images of the heat treated clad layer; (d) finally obtaining a TEM image of the CoFe particles coated by the graphite layer; (e) finally obtaining a CoFe particle high-resolution TEM image coated by the graphite layer; (f) and (4) carbon tubes separated from the surface of the finally obtained product.
Detailed Description
The principles and features of this invention are described below in conjunction with examples, which are set forth to illustrate, but are not to be construed to limit the scope of the invention.
Example 1:
a preparation method of a Co-Fe alloy/carbon sphere composite microwave absorbent comprises the following steps:
1) 36g of glucose and 0.9g of cetyltrimethylammonium bromide (CTAB) are weighed and added into 380ml of deionized water, fully stirred, placed into a 500ml reaction kettle after being completely dissolved, and placed into an oven for heat preservation at 180 ℃ for 5 hours. After cooling, carrying out suction filtration washing, firstly carrying out ultrasonic washing twice by using deionized water, then carrying out ultrasonic washing twice by using alcohol, and finally putting into a drying oven at 60 ℃ for 12h until the polysaccharide microspheres are dried;
2) weighing 1g of the polysaccharide microspheres obtained in the step 1), adding 22.44g of KOH into 400ml of water to prepare an alkali solution, immersing the polysaccharide microspheres in the alkali solution, stirring at the constant temperature of 80 ℃ for 12 hours, performing suction filtration and washing, and drying in an oven at the temperature of 80 ℃;
3) 11.90g of CoCl was taken2·6H2O，0.45g FeCl3·6H2Dissolving O in 200ml of deionized water, ultrasonically dispersing the alkali-treated polysaccharide microspheres obtained in the step 2) into the obtained mixed solution of ferric chloride and cobalt chloride, stirring and soaking for 24 hours, finally, performing suction filtration, washing and drying, wherein the molar ratio of cobalt ions to iron ions adsorbed on the microspheres is 1: 2;
4) loading the sample obtained in the step 3) after dipping and coating into a porcelain boat, and carrying out heat treatment under the argon atmosphere, wherein the temperature rise procedure of the heat treatment is as follows: raising the temperature to 900 ℃ after 180min at 50 ℃, preserving the heat for 240min, then reducing the temperature to 500 ℃ after 100min, and then naturally cooling along with the furnace to obtain the Co-Fe alloy/carbon sphere composite microwave absorbent with the mass fraction of Co-Fe alloy particles being 12%.
In order to reveal the crystal structure, the micro-morphology and the changes during the heat treatment of the composite microwave absorbent obtained in the present invention, XRD, TG-DSC, TEM and SEM tests were performed on the composite microwave absorbent obtained in example 1, and the results are shown in fig. 1, 2 and 3, respectively.
As can be seen from FIG. 1, the wave absorbing agent obtained in example 1 has characteristic diffraction peaks of both graphite and cobalt-iron alloy, which indicates that cobalt and iron ions coated after calcination are reduced to form cobalt-iron alloy; the carbon-containing polysaccharide microsphere is graphitized to a certain degree and is transformed from an amorphous state to crystallization to a certain degree. The main parameters in the XRD test process are set as follows: the scanning angle is 10-90 degrees, and the scanning speed is 0.1 degree per second.
As can be seen from figure 2, when the temperature is 200 ℃, the weight loss of the sample reaches 8.9%, mainly free water and structural water in the sample are gradually lost, at the moment, heat absorption is shown, and in the range of 200-700 ℃, cobalt and iron coated outside the carbon spheres are gradually reduced to release CO2The weight is reduced sharply, heat is released continuously in the reduction process, a heat release peak which is not obvious is also formed in the temperature range of 500-600 ℃, the cobalt and the iron form an alloy in the process, and the weight loss of a sample in the stage reaches 36.7 percent; after the temperature exceeds 700 ℃, the carbon spheres are graphitized, and have obvious exothermic peaks, and the weight loss of the sample is 3.9% after the temperature exceeds 700 ℃.
As can be seen from FIG. 3, after heat treatment, Co-Fe alloy particles are formed on the surfaces of the carbon spheres, the size of the alloy particles is 20-80 nm, the Co-Fe alloy particles are uniformly distributed on the surfaces of the carbon spheres, a protective layer of a graphite layer is formed on the surfaces of the Co-Fe alloy particles, and carbon nanotubes are formed on the outer sides of the Co-Fe alloy particles, so that the wave absorbing performance of the wave absorbing agent is improved.
In order to verify the wave absorbing performance of the composite wave absorbing agent obtained by the invention, 40 wt% of the wave absorbing agent prepared in the embodiment 1 is mixed with paraffin, then the mixture is pressed into a circular sample with the outer diameter of 7mm and the inner diameter of 3mm, and then the circular sample is tested by using a vector network analyzer. The test range of the vector network analyzer is 1-18 GHz, and as can be seen from FIG. 4, the lowest decibel reflectivity of the composite wave absorber in the embodiment 1 reaches-16 dB, and the bandwidth of RL < -10dB is 2GHz (7.6-9.6 GHz).
Example 2:
a preparation method of a Co-Fe alloy/carbon sphere composite microwave absorbent comprises the following steps:
1) 30g of glucose and 0.94g of sodium dodecyl sulfate are weighed and added into 470ml of deionized water, the mixture is fully stirred, the mixture is placed into a 600ml reaction kettle after being completely dissolved, and the reaction kettle is placed into an oven to be kept at 200 ℃ for 1 h. After cooling, carrying out suction filtration washing, firstly carrying out ultrasonic washing twice by using deionized water, then carrying out ultrasonic washing twice by using alcohol, and finally putting into a drying oven at 60 ℃ for 12h until the polysaccharide microspheres are dried;
2) weighing 1g of the polysaccharide microspheres obtained in step 1), 8.57g of Ba (OH)2Adding 500ml of water to prepare an alkali solution, immersing the polysaccharide microspheres in the alkali solution, stirring at the constant temperature of 40 ℃ for 18 hours, performing suction filtration and washing, and drying in an oven at the temperature of 80 ℃;
3) 11.25g of CoSO was taken4˙7H2O，0.25g Fe(NO3)3Dissolving in 200ml deionized water, and mixing
2) Ultrasonically dispersing the obtained polysaccharide microspheres subjected to alkali treatment into the obtained mixed solution of cobalt sulfate and ferric nitrate, stirring and soaking for 24 hours until the molar ratio of cobalt ions to iron ions adsorbed is 1:2, and then performing suction filtration, washing and drying;
4) loading the sample obtained in the step 3) after dipping and coating into a porcelain boat, and carrying out heat treatment under the argon atmosphere, wherein the temperature rise procedure of the heat treatment is as follows: heating to 1100 ℃ after 250min at 50 ℃, preserving heat for 120min, then cooling to 500 ℃ after 100min, and then naturally cooling along with the furnace to obtain the Co-Fe alloy/carbon sphere composite microwave absorbent with 10 mass percent of Co-Fe alloy particles.
Example 3:
a preparation method of a Co-Fe alloy/carbon sphere composite microwave absorbent comprises the following steps:
1) 33g of glucose and 0.6g of cetyltrimethylammonium bromide (CTAB) are weighed and added into 300ml of deionized water, fully stirred, placed into a 500ml reaction kettle after being completely dissolved, and placed into an oven for heat preservation at 180 ℃ for 3 hours. After cooling, carrying out suction filtration washing, firstly carrying out ultrasonic washing twice by using deionized water, then carrying out ultrasonic washing twice by using alcohol, and finally putting into a drying oven at 60 ℃ for 12h until the polysaccharide microspheres are dried;
2) weighing 1g of the polysaccharide microspheres obtained in step 1), 14g of NH4OH is added into 400ml water to prepare alkali solution, and carbon spheres are immersed in the alkali solutionStirring in an alkali solution at a constant temperature of 60 ℃ for 14 hours, then performing suction filtration and washing, and drying in an oven at a temperature of 80 ℃;
3) 17.46g of Co (NO) was taken3)2·6H2O，0.69g FeSO4·7H2Dissolving O in 200ml of deionized water, ultrasonically dispersing the alkali-treated polysaccharide microspheres obtained in the step 2) into the obtained mixed solution of cobalt nitrate and ferrous sulfate, stirring and soaking for 24 hours until the molar ratio of cobalt ions to iron ions on the microspheres is 1:2, and then carrying out suction filtration, washing and drying;
4) loading the sample obtained in the step 3) after dipping and coating into a porcelain boat, and carrying out heat treatment under the argon atmosphere, wherein the temperature rise procedure of the heat treatment is as follows: heating to 1200 ℃ after 250min at 50 ℃, preserving heat for 60min, then cooling to 500 ℃ after 100min, and then naturally cooling along with the furnace to obtain the Co-Fe alloy/carbon sphere composite microwave absorbent with the mass fraction of Co-Fe alloy particles being 17.5%.
Example 4:
a preparation method of a Co-Fe alloy/carbon sphere composite microwave absorbent comprises the following steps:
1) weighing 36g of glucose and 0.95g of sodium dodecyl benzene sulfonate, adding the glucose and the sodium dodecyl benzene sulfonate into 380ml of deionized water, fully stirring, putting the mixture into a 500ml reaction kettle after the mixture is completely dissolved, and putting the reaction kettle into an oven for heat preservation at 180 ℃ for 5 hours. After cooling, carrying out suction filtration washing, firstly carrying out ultrasonic washing twice by using deionized water, then carrying out ultrasonic washing twice by using alcohol, and finally putting into a drying oven at 60 ℃ for 12h until the polysaccharide microspheres are dried;
2) weighing 1g of the polysaccharide microspheres obtained in the step 1), adding 10g of NaOH into 500ml of water to prepare an alkali solution, immersing the polysaccharide microspheres in the alkali solution, stirring at the constant temperature of 80 ℃ for 12 hours, performing suction filtration and washing, and drying in an oven at the temperature of 80 ℃;
3) 11.90g of CoCl was taken2·6H2O，0.38g FeCl2·4H2Dissolving O in 200ml of deionized water, ultrasonically dispersing the alkali-treated polysaccharide microspheres obtained in the step 2) into the obtained mixed solution of ferrous chloride and cobalt chloride, stirring and soaking for 24 hours, and then carrying out suction filtration, washing and drying;
4) loading the sample obtained in the step 3) after dipping and coating into a porcelain boat, and carrying out heat treatment under the argon atmosphere, wherein the temperature rise procedure of the heat treatment is as follows: heating to 1100 ℃ after 220min at 50 ℃, preserving heat for 120min, then cooling to 500 ℃ after 100min, and then naturally cooling along with the furnace to obtain the Co-Fe alloy/carbon sphere composite microwave absorbent with the mass fraction of Co-Fe alloy particles being 20%.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (8)
1. The Co-Fe alloy/carbon ball composite microwave absorbent is characterized in that carbon balls are used as cores, the outer sides of the carbon balls are coated with Co-Fe alloy particles, the outer sides of the Co-Fe alloy particles are coated with a layer of graphite, a multi-stage core-shell structure is integrally formed, the diameter of each carbon ball is 1-10 mu m, the particle size of the Co-Fe alloy particles is 20-80 nm, and the mass fraction of the Co-Fe alloy particles is 10-20%;
the preparation method of the Co-Fe alloy/carbon sphere composite microwave absorbent comprises the following steps:
1) preparing polysaccharide microspheres: weighing glucose and a dispersing agent, dissolving the glucose and the dispersing agent in deionized water, fully stirring, pouring the solution into a reaction kettle after the glucose and the dispersing agent are completely dissolved, placing the reaction kettle at 180-200 ℃ for reaction, wherein the glucose and the dispersing agent are dissolved in no sequence, the concentration of the glucose in the solution is controlled to be 6-10 wt%, the addition of the dispersing agent is 2-2.5 g/L, cooling the mixture in the reaction kettle after the reaction is finished to room temperature, performing suction filtration and washing to obtain a precipitate, and drying to obtain polysaccharide microspheres;
2) alkali treatment: placing the polysaccharide microspheres obtained in the step 1) in 0.1-1.0 mol/L inorganic alkali solution, stirring at constant temperature of 40-80 ℃, performing suction filtration, washing and drying to obtain alkali-treated polysaccharide microspheres;
3) weighing soluble cobalt salt and soluble iron salt, dissolving the soluble cobalt salt and the soluble iron salt in water to prepare a mixed solution of cobalt and iron, wherein the concentration of cobalt ions is controlled to be 0.2-0.3 mol/L, and the amount of iron ions is controlled to be1.4-3.0 × 10 per gram of carbon spheres-3And (2) ultrasonically dispersing the alkali-treated polysaccharide microspheres obtained in the step 2) into the obtained mixed solution of cobalt and iron, and controlling the molar ratio of cobalt ions to iron ions on final adsorption to be 1:2, stirring, dipping, then carrying out suction filtration, washing and drying;
4) and (3) heat treatment: and (3) placing the product obtained in the step 3) in an inert atmosphere for heat treatment at 900-1200 ℃, and then naturally cooling to obtain the Co-Fe alloy/carbon sphere composite microwave absorbent.
2. A method for preparing the composite microwave absorbent according to claim 1, comprising the steps of:
1) preparing polysaccharide microspheres: weighing glucose and a dispersing agent, dissolving the glucose and the dispersing agent in deionized water, fully stirring, pouring the solution into a reaction kettle after the glucose and the dispersing agent are completely dissolved, placing the reaction kettle at 180-200 ℃ for reaction, wherein the glucose and the dispersing agent are dissolved in no sequence, the concentration of the glucose in the solution is controlled to be 6-10 wt%, the addition of the dispersing agent is 2-2.5 g/L, cooling the mixture in the reaction kettle after the reaction is finished to room temperature, performing suction filtration and washing to obtain a precipitate, and drying to obtain polysaccharide microspheres;
2) alkali treatment: placing the polysaccharide microspheres obtained in the step 1) in 0.1-1.0 mol/L inorganic alkali solution, stirring at constant temperature of 40-80 ℃, performing suction filtration, washing and drying to obtain alkali-treated polysaccharide microspheres;
3) weighing soluble cobalt salt and soluble iron salt, dissolving the soluble cobalt salt and the soluble iron salt in water to prepare a mixed solution of cobalt and iron, wherein the concentration of cobalt ions is controlled to be 0.2-0.3 mol/L, and the amount of iron ions is 1.4-3.0 × 10 per gram of carbon spheres-3And (2) ultrasonically dispersing the alkali-treated polysaccharide microspheres obtained in the step 2) into the obtained mixed solution of cobalt and iron, and controlling the molar ratio of cobalt ions to iron ions on final adsorption to be 1:2, stirring, dipping, then carrying out suction filtration, washing and drying;
and (3) heat treatment: and (3) placing the product obtained in the step 3) in an inert atmosphere for heat treatment at 900-1200 ℃, and then naturally cooling to obtain the Co-Fe alloy/carbon sphere composite microwave absorbent.
3. The method according to claim 2, wherein the dispersant is any one of cetyltrimethylammonium bromide, sodium dodecyl sulfate, and sodium dodecyl benzene sulfonate.
4. The preparation method according to claim 2 or 3, wherein the inorganic base in step 2) is any one or more of potassium hydroxide, sodium hydroxide, ammonium hydroxide and barium hydroxide.
5. The method according to claim 4, wherein the soluble ferric salt in step 3) is any one of ferric chloride hexahydrate, ferric sulfate, ferric nitrate, ferric oxalate, ferrous chloride, ferrous sulfate and ferrous oxalate, and the soluble cobalt salt is any one of cobalt chloride, cobalt sulfate and cobalt nitrate.
6. The preparation method of claim 4, wherein the reaction time in the step 1) is 4-8 h.
7. The preparation method of claim 4, wherein the constant-temperature stirring time in the step 2) is 12-18 h.
8. The preparation method according to claim 4, wherein the stirring and dipping time in the step 3) is 12-24 hours, and the heat treatment time in the step 4) is 1-4 hours.
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| CN113423255B (en) * | 2021-06-09 | 2022-09-27 | 西北工业大学 | Core-shell structure Ti 4 O 7 Magnetic metal composite absorbent and preparation method thereof |
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