CN111117564A - Yolk-eggshell type magnetic carbon composite material, preparation method and application - Google Patents
Yolk-eggshell type magnetic carbon composite material, preparation method and application Download PDFInfo
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Abstract
The invention discloses a yolk-eggshell type magnetic carbon composite material, a preparation method and application thereof, wherein the preparation method comprises the following steps: s1: cubic shape of Fe2O3And (3) synthesis of particles: adding FeCl into NaOH solution3·6H2O, magnetically stirring for 20-40min, placing the mixed solution in a polytetrafluoroethylene-lined stainless steel autoclave, keeping the temperature at 130-150 ℃ for 12-18h, and then centrifuging the reaction product to obtain Fe2O3Particles; s2: core-shell type Fe2O3Synthesis of @ PDA composite material; s3: yolk-eggshell type Fe3O4Synthesis of @ C composite material: at H2Annealing for 4-6h in the Ar atmosphere, controlling the temperature at 500 ℃ to obtain the yolk-eggshell type Fe3O4@ C composite material; s4: synthesizing the yolk-eggshell type Fe @ void @ C composite material: at H2Annealing for 4-6h in the Ar atmosphere, controlling the temperature at 700 ℃ to prepare the yolk-containing materialThe eggshell type Fe @ void @ C composite material. The magnetic carbon composite material prepared by the invention has excellent electromagnetic property and high-efficiency energy conversion performance, and meets the requirements of modern microwave absorption materials on wide attenuation frequency, thin thickness and strong absorption capacity.
Description
Technical Field
The invention relates to the technical field of electromagnetic wave absorbing materials, in particular to a yolk-eggshell type magnetic carbon composite material, a preparation method and application.
Background
With the rapid development of the wireless communication industry, the frequency problem of electromagnetic waves in gigahertz band absorption materials has attracted people's attention. At present, the broadband efficient electromagnetic wave absorption material is widely applied to the fields of industry, commerce, military and the like, and has important application value. In recent years, magnetic metals and magnetic metal alloys, which have high magnetic loss ability and magnetocrystalline anisotropy, have been attracting attention. However, it is very difficult to prepare an electromagnetic wave responsive material matched with strong loss and broadband absorption, especially in the case of a thin thickness.
Disclosure of Invention
Based on the technical problems in the background art, the invention provides the yolk-eggshell type magnetic carbon composite material, the preparation method and the application, and the prepared magnetic carbon composite material has excellent electromagnetic performance and high-efficiency energy conversion performance and meets the requirements of modern microwave absorbing materials on wide attenuation frequency, thin thickness and strong absorbing capacity.
The yolk-eggshell type magnetic carbon composite material provided by the invention uses Fe2O3The @ PDA composite material is used as a precursor and is prepared by a phase transition method.
The method for preparing the yolk-eggshell type magnetic carbon composite material provided by the invention comprises the following steps:
s1: cubic shape of Fe2O3Synthesizing particles;
s2: core-shell type Fe2O3Synthesis of @ PDA composite material;
s3: yolk-eggshell type Fe3O4Synthesis of @ C composite material
Subjecting the S2 medium core-shell type Fe2O3@ PDA composite material in H2Heating to 480-520 ℃ from room temperature in the Ar atmosphere, and annealing for 4-6h at the temperature to obtain the yolk-eggshell type Fe3O4@ C composite material;
s4: synthesis of yolk-eggshell type Fe @ void @ C composite material
Subjecting the S2 medium core-shell type Fe2O3@ PDA composite material in H2Raising the temperature from room temperature to 680-720 ℃ in an Ar atmosphere, and annealing for 4-6h at the temperature to prepare the yolk-eggshell type Fe @ void @ C composite material.
Preferably, the S1 contains cubic Fe2O3The particles are synthesized by a hydrothermal method, and the method comprises the following steps:
adding FeCl into NaOH solution3·6H2O, magnetically stirring for 20-40min, placing the mixed solution in a polytetrafluoroethylene-lined stainless steel autoclave, keeping the temperature at 130-150 ℃ for 12-18h, centrifuging the reaction product, and sequentially washing the solid components obtained by centrifugation with ethanol and deionized water for 2-4 times to obtain Fe2O3Particles;
preferably, the NaOH and FeCl3·6H2The molar ratio of O is 1.8-2.2: 1.
Preferably, the S2 core-shell type Fe2O3The method for synthesizing the @ PDA composite material comprises the following steps:
fe prepared by the S12O3Adding the particles and dopamine hydrochloride into a Tris buffer solution with the pH value of 8-9, magnetically stirring at the rotation speed of 450-2O3@ PDA composite material.
Preferably, the Fe2O3The mass ratio of the granules to the dopamine hydrochloride is 0.7-0.8: 1.
Preferably, the heating rate in S3 is 1-3 ℃/min.
Preferably, the heating rate in S4 is 1-3 ℃/min.
The yolk-eggshell type Fe prepared by the method provided by the invention3O4@ C composite material.
The yolk-eggshell type Fe @ void @ C composite material prepared by the method is provided by the invention.
The invention provides a yolk-eggShell type Fe3O4The application of the @ C composite material in electromagnetic wave absorption.
The invention provides an application of a yolk-eggshell type Fe @ void @ C composite material in electromagnetic wave absorption.
The action mechanism is as follows:
for the magnetic yolk-eggshell structure Fe prepared in this application3O4@ C, two phase transformation processes are generated during the calcination process, one is the transformation of the PDA shell layer into a hollow cubic carbon layer, and the other is the internal hexagon α -Fe2O3Conversion of the core into a face-centered cubic structure Fe3O4Particles due to α -Fe2O3And Fe3O4The magnetic yolk-eggshell structure Fe @ void @ C composite material prepared by the method can also generate two phase transformation processes in the calcining process, wherein one phase transformation process is that a PDA shell layer is transformed into a hollow cubic carbon layer, and the other phase transformation process is that hexagon α -Fe is arranged inside the hollow cubic carbon layer2O3The core is converted into a face-centered cubic structure Fe particle due to α -Fe2O3The difference between the lattice constant of the Fe particle and the lattice constant of the Fe particle is large, so that phase transformation occurs on the basis of the original core-shell structure, and the Fe particle breaks a carbon layer. The composite material prepared by the invention has excellent electromagnetic property and high-efficiency energy conversion property due to the phase transition generated in the calcining process.
Compared with the prior art, the invention has the beneficial technical effects that:
the method of the invention uses Fe through phase transformation2O3Successfully preparing magnetic yolk-eggshell type structure Fe by using @ PDA as precursor3O4The @ C and Fe @ void @ C composite material has good electromagnetic parameters and strong microwave absorption loss capacity. Core-shell Fe when the thickness of the absorption layer is only 1.5mm3O4Minimum Reflection Loss (RL) of @ C productmin) The value is as high as-41.8 dB, and the effective absorption bandwidth is 5.4GHz (from 10.7GHz to 16.1GHz) when the thickness is 2.0 mm. With the enhancement of magnetic property and polarization behavior, the minimum reflection loss value of Fe @ void @ C under the thickness of 1.7mm is-64.5 dB, and strong wave-absorbing energy is shownForce. Fe3O4The @ C and Fe @ void @ C composite materials exhibit high-performance microwave absorption in the microwave band. Magnetic Fe3O4The @ C and Fe @ void @ C composite material has magnetic loss, dielectric loss and synergistic effect, and is expected to become a candidate material of modern wave-absorbing materials.
Drawings
FIG. 1 shows (a) Fe according to the present invention2O3，Fe2O3@PDA，Fe3O4XRD patterns of @ C and Fe @ void @ C composite materials, (b) Raman shift pattern, (C, d) Fe3O4A hysteresis loop of @ C and Fe @ void @ C composite;
FIG. 2 shows (a, b) Fe according to the present invention2O3，(c，d)Fe2O3@PDA，(e，f)Fe3O4SEM images of @ C and (g-i) Fe @ void @ C materials;
FIG. 3 shows (a-c) Fe proposed by the present invention2O3@PDA，(d-f)Fe3O4TEM images of @ C and (g-i) Fe @ void @ C materials;
FIG. 4 shows (a, d) Fe according to the present invention2O3@PDA，(b，e)Fe3O4Reflected loss curves and three-dimensional plots projected for @ C and (C, f) Fe @ void @ C composites; (g) fe of different thickness2O3@PDA，Fe3O4The columnar distribution of the reflection loss values of the @ C and Fe @ void @ C composite materials; (h) fe3O4The effective absorption bandwidth of @ C and Fe @ void @ C composites, and (i) the reflection loss value and the effective absorption bandwidth at the same thickness;
FIG. 5 shows (a) Fe according to the present invention2O3@PDA，(b)Fe3O4@ C, and (C) an electromagnetic parameter of Fe @ void @ C, (d) a real part of the dielectric constant, (e) an imaginary part of the dielectric constant, (f) an electromagnetic parameter of the dielectric loss tangent value;
FIG. 6 shows the impedance matching characteristics of the yolk-shell type Fe @ void @ C composite materials with different thicknesses at 2-18 GHz.
Detailed Description
The present invention will be further illustrated with reference to the following specific examples.
Example 1
The method for preparing the yolk-eggshell type magnetic carbon composite material provided by the invention comprises the following steps:
s1: cubic shape of Fe2O3Synthesizing particles;
s2: core-shell type Fe2O3Synthesis of @ PDA composite material;
s3: yolk-eggshell type Fe3O4Synthesis of @ C composite material
Subjecting the S2 medium core-shell type Fe2O3@ PDA composite material in H2Heating to 500 deg.C from room temperature in Ar atmosphere, and annealing at the temperature for 5 hr to obtain yolk-eggshell type Fe3O4@ C composite material;
s4: synthesis of yolk-eggshell type Fe @ void @ C composite material
Subjecting the S2 medium core-shell type Fe2O3@ PDA composite material in H2Raising the temperature from room temperature to 700 ℃ in an/Ar atmosphere, and annealing for 5 hours at the temperature to prepare the yolk-egg shell type Fe @ void @ C composite material.
Square Fe in S12O3The particles are synthesized by a hydrothermal method, and the method comprises the following steps: adding FeCl into NaOH solution3·6H2O, magnetically stirring for 30min, placing the mixed solution in a polytetrafluoroethylene-lined stainless steel autoclave, keeping the temperature at 140 ℃ for 15h, centrifuging a reaction product, and sequentially washing solid components obtained by centrifugation for 3 times by using ethanol and deionized water to obtain Fe2O3Particles; NaOH and FeCl3·6H2The molar ratio of O is 2: 1.
Core-shell Fe in S22O3The method for synthesizing the @ PDA composite material comprises the following steps: fe prepared by the S12O3Adding the particles and dopamine hydrochloride into a Tris buffer solution with the pH value of 8.5, magnetically stirring at the room temperature at the rotating speed of 500r/min for 12 hours, centrifuging a reaction product, washing a solid component obtained by centrifugation by deionized water, and drying at the temperature of 60 ℃ for 8 hours to obtain core-shell type Fe2O3@ PDA composite; fe2O3Granules and dopa hydrochlorideThe mass ratio of amine was 3: 4.
The heating rate in S3 was 2 deg.C/min.
The heating rate in S4 was 2 deg.C/min.
Figure 1(a) is the XRD pattern of the product at each stage of this example from which it can be seen that the high intensity diffraction peaks appear at 24.3 °, 33.3 °, 35.7 °, 41.0 °, 49.5 °, 54.1 °, 57.6 °, 62.5 °, 64.0 ° and 71.9 ° to the standard α -Fe2O3(012) The (104), (110), (113), (024), (116), (122), (214), (300) and (119) planes are identical (JCPDS: 86-0550). In the form of cubes of Fe2O3Surface coating the PDA did not cause significant compositional changes. The broad peak in the range of 24-26 degrees 2 theta can be classified as polydopamine. In Fe3O4Observed in the XRD pattern of the @ C composite material, α -Fe2O3With Fe3O4With a pronounced phase transition, α -Fe2O3The diffraction of (2) disappears. After annealing at 500 ℃ for 5h, the new peaks for 2 θ data at 18.5 °, 30.3 °, 35.6 °, 37.3 °, 43.3 °, 5.36 °, 57.1 ° and 62.7 ° can be well indexed to Fe3O4(111) Wavelet peaks of (220), (311), (222), (400), (511), and (440) planes (JCPDS: 19-0629) at 24-26 ° 2 θ belong to the transformed carbon shell, α -Fe synthesized after annealing at 700 ℃ for 5h2O3The oxygen is completely converted into α crystal Fe (JCPDS: 06-0696) in a reducing atmosphere, and the detailed structural characteristics of the conversion process from the PDA material to the carbon shell are shown in FIG. 1(b), and two display peaks are located at 1330cm-1And 1596.6cm-1And (3) respectively belong to a D wave band and a G wave band. In general, ID/IGThe strength ratio of (a) is related to the carbon alignment, including defects and graphitic structure. Fe3O4I of @ C and Fe @ void @ CD/IGThe values were 0.98 and 0.94, respectively, indicating that disordered carbon or defects still exist in the carbon shell.
After conversion from semiconductor to magnetic substance, Fe3O4The saturation magnetization of @ C and Fe @ void @ C increases (FIG. 1(C, d)). Core-shell Fe3O4The saturation magnetization value of the @ C cube is about 32.5emu/g, due to Fe3O4The core is finally converted into Fe particles, the yolk-eggshell type Fe @ void @ C has higher magnetism, and the saturation magnetization is improved to 67.5 emu/g. The high saturation magnetization and the low coercive force are beneficial to improving the magnetic conductivity and the magnetic loss capability.
The morphology and microstructure of the composite material were observed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). As shown in FIGS. 2 and 3, cubic α -Fe was first synthesized2O3Particles having a particle diameter of about 1.2um (fig. 2(a, b)). The surface of the iron oxide was coated with a polymer layer, and the rough surface was smoothed (fig. 2 (c)). In FIGS. 3(a) and (b), Fe2O3@ PDA with Fe2O3The particles are cores and the PDA is shells, and an obvious core-shell structure is shown. By controlling the polymerization process (fig. 3(c)), a coating PDA layer of uniform thickness (110nm) was obtained. In the subsequent annealing treatment, core-shell Fe3O4The @ C composite maintained the original morphology without collapse or aggregation (FIG. 2 (d-f)). The results show that Fe is lost due to oxygen3O4The polymer is transformed into a carbon cage, thinner than the PDA layer (fig. 3 (d-f)). when the reaction temperature reaches 700 ℃, the semiconductor is completely transformed into a strong magnetic α -Fe core with huge volume contraction (fig. 3 (g-i)). from the scanning electron microscope image, the originally intact carbon shell is destroyed by the growth of iron (fig. 2 (g-i)).
And calculating the electromagnetic wave absorption performance of the prepared composite material in the microwave band according to the transmission line theory. The reflective loss etching is the most important research content and contains most important information such as reflective loss value, effective absorption bandwidth and thickness data. By utilizing the relative complex dielectric constant and the magnetic conductivity, the RL value can be obtained by the following theoretical formula under 2-18 GHz:
RL＝20log|(Zin-Z0)/(Zin+Z0)| (2)
wherein Z isinIs a normalized input impedance of the absorber, Z0Is free space impedance,. epsilonrAnd murComplex permittivity and complex permeability, f is the test frequency, c represents the speed of light, and d represents the simulated thickness.
FIG. 4 shows Fe prepared2O3@PDA、Fe3O4The absorbing performance of the absorbing agent @ C and Fe @ void @ C. Thus, core-shell Fe2O3@ PDA has neither strong absorption characteristics nor broad band characteristics (fig. 4(a, d)).
Due to Fe2O3The @ PDA composite material has poor electronic conductivity and few magnetic response components, and cannot be used as a candidate material for preparing an excellent wave-absorbing material. After the phase change and the reduction atmosphere treatment, the microwave absorption capacity is greatly improved. At 16.5GHz, Fe3O4The minimum reflection loss value of the @ C cubic magnet is-41.8 dB, and the thickness is only 1.5 mm. Generally, there is a standard reflection loss value of-10 dB, indicating that 90% of the microwave energy can be dissipated. The reflection loss performance is strongly related to the thickness and the frequency band. core-Shell Fe, as shown in FIG. 4(b)3O4@ C has different absorption behavior at different thicknesses. The thickness is from 1.0mm to 5.0mm, and the data of the minimum reflection loss are respectively-4.6 dB, -41.8dB, -31.4dB, -26.3dB, -27.7dB, -29.4dB, -26.9dB, -38.7dB and-23.5 dB. Synthesized Fe when the simulated thickness is 1.5mm3O4The effective absorption bandwidth of the @ C composite is 4.0GHz, from 14.0GHz to 18GHz (FIG. 4 (e)). The effective absorption bandwidth after optimization is 5.4GHz at a thickness of 2.0mm, from 10.7GHz to 16.1 GHz. By adjusting the film thickness, the effective absorption bandwidth can be effectively adjusted from the Ku band to the S band. For the yolk-shell type Fe @ void @ C composite, the minimum reflection loss reached-64.5 dB at 1.7mm thickness, showing high absorbing capacity at thin absorbing layer thickness (fig. 4 (C)). The thickness was adjusted from 1mm to 5mm, the effective absorption bandwidth was 14.2GHz, from 3.8GHz to 18GHz, to meet the requirements of the optional absorption band (fig. 4 (f)). With Fe2O3@ PDA comparison, core-Shell Fe3O4The @ C and yolk-shell Fe @ void @ C composites all had significant enhanced Microwave Absorption (MA) behavior in terms of reflection loss values, lamella thickness and effective absorption bandwidth (fig. 4(g, h)).
Magnetic core-shell Fe3O4The @ C and yolk-eggshell type Fe @ void @ C wave-absorbing material has excellent wave-absorbing performance, and is beneficial to improving dielectric loss, magnetic loss, good impedance matching performance and magnetic medium synergistic effect. Fe3O4The intrinsic dielectric properties and energy conversion capabilities of @ C and Fe @ void @ C are influenced by phase transitions, in particular the magnetic loss behavior. The specific electromagnetic parameters of the three composites are shown in fig. 5. It is well known that the final reflection loss value depends on the electromagnetic properties, i.e. these parameters relate to the storage and attenuation capabilities. The real part of the permittivity (. epsilon. ') and permeability (. mu.') represent the ability to store electromagnetic wave energy. The imaginary part of the permittivity (. epsilon. ") and the imaginary part of the permeability (. mu.") are related to the dissipation or loss behavior of the electrical and magnetic energy. The frequency dependence of the parametric notch indicates the potential of the synthetic composite in microwave absorbing applications in the gigahertz band (fig. 5 (a-c)).
Fig. 5(c) shows the change law of epsilon 'of the complex dielectric constant, and it is clear that all the epsilon' values show similar changes, showing a downward trend from the low frequency region to the high frequency region (fig. 5 (d)). With increasing frequency, Fe2O3The ε' value of the @ PDA sample decreased from 4.8 to 2.8. Fe3O4The ε' value for the @ C sample was higher, decreasing from 10.5 at 2GHz to 6.9 at 18 GHz. The electromagnetic wave energy storage capacity of the Fe @ void @ C composite material is strongest and higher than that of other materials. The corresponding ε' value of the Fe @ void @ C absorber decreased from 13.5 to 7.7 at the same experimental frequency. As can be seen from FIG. 5(e), the decrease in ε "is similar between 2 and 18 ghz. As the frequency increased, the ε "value of the Fe @ void @ C product changed from 5.0 to 3.1. It can be seen that Fe @ void @ C exhibits the highest value of e "in these absorbers, which means that it has the strongest attenuation capability for dielectric losses. It is noted that there are distinct resonance peaks in the high frequency region, probably caused by the resonant behavior (fig. 5 (e)). Magnetic core Fe3O4The electronegativity difference between Fe and the carbon cage causes a large amount of charge electrons to gather near the interface, and the polarization of the interface under a high-frequency microwave field is promoted. In addition, with Fe2O3@ PDA Material comparison, Fe3O4@ C and Fe @ void @ C complexThe materials all had higher dielectric loss tangent (tan δ e), from which it can be inferred that the wave-absorbing capacity was increased (fig. 5 (f)).
Polarization behavior and conduction losses are the dominant dielectric losses, expressed as follows:
it can be seen that ε 'and ε' have a high correlation with both angular frequency (ω) and polarization relaxation time (τ). The polarization loss mainly comes from the interfacial polarization and electric dipole motion of the magnetic carbon composite material. As shown in FIG. 2, Fe3O4A large number of interfaces exist in the @ C or Fe @ void @ C composite material, and interface polarization behaviors are promoted. In a high frequency electromagnetic environment, positive and negative charges accumulated on the interface will produce strong polarization and promote attenuation of microwave energy. Equally important, defects in the carbon cage will also cause more electric dipole motion, consuming incoming energy. The dielectric loss capacity (. epsilon. ") is proportional to the conductivity (. sigma.), indicating its significance for microwave absorption. I of magnetic carbon material with increasing degree of graphitizationD/IGThe intensity ratio tended to decrease (fig. 1 (b)). Under the action of an external electric field, a large number of electrons in the carbon cage matrix can be transmitted along a certain direction, so that micro-current is generated. At the same time, these effects contribute to conductivity loss and energy conversion.
After phase change treatment, magnetic Fe3O4The @ C and Fe @ void @ C composite material can provide more magnetic loss mechanisms, and the magnetic loss mechanisms are in pure Fe2O3The @ PDA system is not possible. During magnetization and demagnetization of a magnetic material, a part of energy is converted into heat energy, and energy is lost in an irreversible process. Magnetic losses can be caused by eddy current losses, natural resonances, hysteresis losses, etc. Following this equation, the relationship between magnetic properties and electromagnetic energy attenuation can be found:
μ′＝1+(M/H)cosσ (5)
μ″＝(M/H)sinσ (6)
as can be seen from the above formula, the larger the magnetization M, the larger the μ' and μ ″, and the stronger the magnetic storage and loss capacities. In this system, the magnetic loss behavior comes from Fe3O4And a Fe core. The saturation magnetization of Fe @ void @ C (ms:67.5emu/g) is higher than that of Fe3O4The saturation magnetization of @ C composite (ms:32.5emu/g) (FIG. 1 (C)). Thus, the yolk-shell type Fe @ void @ C exhibited the minimum RL value and broadband absorption frequency (fig. 4 (i)). As a ferromagnetic absorber, magnetic losses are mainly manifested as eddy current losses, natural resonances and domain wall resonances. The domain wall resonance has good response characteristics in the low frequency band (mhz) and has less influence on the high frequency band. Thus, the eddy current loss and natural resonance of ferromagnetic materials play an important role in the magnetic loss mechanism. Due to Fe3O4the/Fe magnetic core generates induction current, generates eddy current loss inside the magnetic material and dissipates microwave energy. According to Aharoni's theory, natural resonance typically occurs at low frequencies (6 GHz).
As an excellent wave-absorbing material, the material not only has stronger loss capacity, but also has good impedance matching. Good impedance matching allows the microwaves to easily penetrate the absorber interior rather than being reflected back into free space. As shown in FIG. 6, the RL peak of the yolk-shell Fe @ void @ C composite shifts as the thickness of the absorbent body increases. Meanwhile, the minimum RL map has a high correlation with the impedance matching value. The impedance matching plot for the Fe @ void @ C absorber is shown in fig. 6. With increasing frequency, the impedance matching value (Z)in/Z0) Showing a tendency of ascending first and then descending. When Z isin/Z0At values close to 1, the Fe @ void @ C product shows the lowest reflection loss values at different thicknesses. The matching properties further indicate good Zin/Z0The value is the first requirement for designing high-performance wave-absorbing materials. Magnetic core-shell Fe, in contrast to the magnetic literature (Table 1) representative in recent years3O4The @ C and yolk-eggshell type Fe @ void @ C composite material has strong reflection loss capability and broadband absorption response characteristic.
Table 1 comparison of properties of magnetic microwave absorbing materials reported in the literature
Example 2
The method for preparing the yolk-eggshell type magnetic carbon composite material provided by the invention comprises the following steps:
s1: cubic shape of Fe2O3Synthesizing particles;
s2: core-shell type Fe2O3Synthesis of @ PDA composite material;
s3: yolk-eggshell type Fe3O4Synthesis of @ C composite material
Subjecting the S2 medium core-shell type Fe2O3@ PDA composite material in H2Heating to 480 deg.C from room temperature in Ar atmosphere, and annealing at the temperature for 4 hr to obtain yolk-eggshell type Fe3O4@ C composite material;
s4: synthesis of yolk-eggshell type Fe @ void @ C composite material
Subjecting the S2 medium core-shell type Fe2O3@ PDA composite material in H2Raising the temperature from room temperature to 680 ℃ in an/Ar atmosphere, and annealing for 5 hours at the temperature to prepare the yolk-eggshell type Fe @ void @ C composite material.
Square Fe in S12O3The particles are synthesized by a hydrothermal method, and the method comprises the following steps: adding FeCl into NaOH solution3·6H2O, magnetically stirring for 20min, placing the mixed solution in a polytetrafluoroethylene-lined stainless steel autoclave, keeping the temperature at 130 ℃ for 12h, centrifuging a reaction product, and sequentially washing solid components obtained by centrifugation for 2 times by using ethanol and deionized water to obtain Fe2O3Particles; NaOH and FeCl3·6H2The molar ratio of O was 1.8: 1.
Core-shell Fe in S22O3The method for synthesizing the @ PDA composite material comprises the following steps: fe prepared by the S12O3Adding the particles and dopamine hydrochloride into a Tris buffer solution with the pH value of 8, magnetically stirring at the rotation speed of 450r/min for 10 hours at room temperature, centrifuging a reaction product, washing a solid component obtained by centrifugation with deionized water, and drying at 50 ℃ for 5 hours to obtain core-shell Fe2O3@ PDA composite; fe2O3The mass ratio of the granules to dopamine hydrochloride is 0.7: 1.
The heating rate in S3 was 1 deg.C/min.
The heating rate in S4 was 1 deg.C/min.
Example 3
The method for preparing the yolk-eggshell type magnetic carbon composite material provided by the invention comprises the following steps:
s1: cubic shape of Fe2O3Synthesizing particles;
s2: core-shell type Fe2O3Synthesis of @ PDA composite material;
s3: yolk-eggshell type Fe3O4Synthesis of @ C composite material
Subjecting the S2 medium core-shell type Fe2O3@ PDA composite material in H2Heating to 520 deg.C from room temperature in Ar atmosphere, and annealing at the temperature for 6 hr to obtain yolk-eggshell type Fe3O4@ C composite material;
s4: synthesis of yolk-eggshell type Fe @ void @ C composite material
Subjecting the S2 medium core-shell type Fe2O3@ PDA composite material in H2Raising the temperature from room temperature to 720 ℃ in an/Ar atmosphere, and annealing for 6 hours at the temperature to prepare the yolk-egg shell type Fe @ void @ C composite material.
Square Fe in S12O3The particles are synthesized by a hydrothermal method, and the method comprises the following steps: adding FeCl into NaOH solution3·6H2O, magnetically stirring for 40min, placing the mixed solution in a polytetrafluoroethylene-lined stainless steel autoclave, keeping the temperature at 150 ℃ for 18h, centrifuging a reaction product, and sequentially washing solid components obtained by centrifugation for 4 times by using ethanol and deionized water to obtain Fe2O3Particles; NaOH and FeCl3·6H2The molar ratio of O is 2.2: 1.
Core-shell Fe in S22O3The method for synthesizing the @ PDA composite material comprises the following steps: fe prepared by the S12O3Adding the particles and dopamine hydrochloride into a Tris buffer solution with the pH value of 9, magnetically stirring for 14 hours at the room temperature at the rotating speed of 550r/min, centrifuging a reaction product, washing a solid component obtained by centrifugation by using deionized water, and drying for 10 hours at 70 ℃ to obtain core-shell Fe2O3@ PDA composite; fe2O3The mass ratio of the granules to dopamine hydrochloride is 0.8: 1.
The heating rate in S3 was 3 ℃/min.
The heating rate in S4 was 3 ℃/min.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (10)
1. The yolk-eggshell type magnetic carbon composite material is characterized in that Fe is used2O3The @ PDA composite material is used as a precursor and is prepared by a phase transition method.
2. A method for preparing a yolk-shell type magnetic carbon composite material according to claim 1, which comprises the following steps:
s1: cubic shape of Fe2O3Synthesizing particles;
s2: core-shell type Fe2O3Synthesis of @ PDA composite material;
s3: yolk-eggshell type Fe3O4Synthesis of @ C composite material
Subjecting the S2 medium core-shell type Fe2O3@ PDA composite material in H2Heating to 480-520 ℃ from room temperature in the Ar atmosphere, and annealing for 4-6h at the temperature to obtain the yolk-eggshell type Fe3O4@ C composite material;
s4: synthesis of yolk-eggshell type Fe @ void @ C composite material
Subjecting the S2 medium core-shell type Fe2O3@ PDA composite material in H2Raising the temperature from room temperature to 680-720 ℃ in an Ar atmosphere, and annealing for 4-6h at the temperature to prepare the yolk-eggshell type Fe @ void @ C composite material.
3. The method of claim 2, wherein the S1 is Fe-neutral2O3The particles are synthesized by a hydrothermal method, and the method comprises the following steps:
adding FeCl into NaOH solution3·6H2O, magnetically stirring for 20-40min, placing the mixed solution in a polytetrafluoroethylene-lined stainless steel autoclave, keeping the temperature at 130-150 ℃ for 12-18h, centrifuging the reaction product, and sequentially washing the solid components obtained by centrifugation with ethanol and deionized water for 2-4 times to obtain Fe2O3Particles;
preferably, the NaOH and FeCl3·6H2The molar ratio of O is 1.8-2.2: 1.
4. The method of claim 2, wherein the core-shell Fe is S22O3The method for synthesizing the @ PDA composite material comprises the following steps:
fe prepared by the S12O3Adding the particles and dopamine hydrochloride into a Tris buffer solution with the pH value of 8-9, magnetically stirring at the rotation speed of 450-2O3@ PDA composite material.
Preferably, the Fe2O3The mass ratio of the granules to the dopamine hydrochloride is 0.7-0.8: 1.
5. The method of claim 2, wherein the heating rate in S3 is 1-3 ℃/min.
6. The method of claim 2, wherein the heating rate in S4 is 1-3 ℃/min.
7. Yolk-eggshell type Fe prepared by the method of any one of claims 2 to 63O4@ C composite material.
8. A yolk-shell Fe @ void @ C composite prepared according to the method of any one of claims 2-6.
9. A yolk-shell type Fe according to claim 73O4The application of the @ C composite material in electromagnetic wave absorption.
10. Use of the yolk-shell type Fe @ void @ C composite material according to claim 8 for electromagnetic wave absorption.
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