CN113528084B - Co 9 S 8 Composite electromagnetic wave absorbing material coated with humins carbon, preparation method and application - Google Patents
Co 9 S 8 Composite electromagnetic wave absorbing material coated with humins carbon, preparation method and application Download PDFInfo
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Abstract
Co 9 S 8 A composite electromagnetic wave absorbing material coated with biomass conversion byproduct humins carbon, a preparation method and application thereof belong to the technical field of electromagnetic wave absorbing functional materials. Taking humus (humins) as a carbon source, coating sulfides, and calcining at different temperatures to obtain Co 9 S 8 A composite electromagnetic wave absorbing material with a/humins carbon core-shell structure. The composite material prepared by the method has a large amount of interface polarization, and the semiconductor Co 9 S 8 The internal rich defects and the gaps between the internal rich defects and the carbon spheres optimize impedance matching, and meanwhile, the internal carbon spheres can enhance the conductive loss. Therefore, the Co obtained through reasonable composition, interface regulation and control, multilayer structure design and defect regulation and control 9 S 8 The core-shell structure composite electromagnetic wave absorbing material coated with the biomass conversion byproduct humins carbon has excellent wave absorbing capacity. The method is environment-friendly, simple to operate, mild in condition, easy for large-scale production and suitable for practical industrial application.
Description
Technical Field
The invention belongs to the technical field of electromagnetic wave absorption functional materials, and particularly relates to a method for obtaining Co by using byproduct humus (humins) generated by condensation polymerization of furfural or xylose in biomass catalytic reaction as a carbon source 9 S 8 A humins carbon-coated core-shell structure composite electromagnetic wave absorption material, a preparation method and application thereof in the aspect of electromagnetic wave absorption.
Background
With the rapid development of information technology, electromagnetic pollution is increasingly serious. The redundant electromagnetic waves generated by various electronic equipment not only seriously threaten the health and interfere the normal operation of the equipment, but also have important influence on national defense safety. Therefore, the search for high-performance electromagnetic wave absorbing materials is of great significance in both civilian and military fields. The ideal electromagnetic wave absorbing material should have the characteristics of light weight, strong absorption, wide bandwidth, thin matching thickness and the like so as to meet different application requirements. At present, related researches have widely explored various electromagnetic wave absorbing materials, and show that the excellent absorption performance of the materials mainly comes from the attenuation capability and the impedance matching. Among a plurality of material systems, the carbon material has the great advantages of light weight, good conductivity, good mechanical stability, strong dielectric loss capability and the like, and is widely concerned in the field of electromagnetic wave absorption. However, two issues restrict its practical application. 1. The production process of common carbon materials such as carbon nano tubes, graphene and the like needs strong oxidant and strong acid, which causes environmental pollution, and the preparation process is complex and has high cost. Therefore, it is imperative to develop a new class of available carbon materials with simple process and low cost. 2. The higher conductivity causes impedance mismatch between the carbon material and air, so that incident electromagnetic waves are reflected on the surface of the wave-absorbing material, and meanwhile, the single component also causes a limited loss mechanism, thereby limiting the microwave absorption performance of the wave-absorbing material. The composite electromagnetic wave absorbing material formed by multiple chemical bonds among different chemical components can improve the electronic structure of the material due to the interaction among the components, weaken the skin effect, enable electromagnetic waves to easily enter the material, and solve the problem of poor impedance matching of the carbon material.
Based on the method, humus which is a byproduct waste material formed by catalytic polymerization of compounds such as pentose and the like is used as a carbon source in the process of converting catalytic biomass into compounds with high added values, functional groups such as-COOH, -OH and the like exist in the structure of the humus, a transition metal sulfide semiconductor material with adjustable electronic state and structure is further constructed on the surface of the humus, the potential performance of the biomass-derived carbon and sulfide composite electromagnetic wave absorbing material is explored through reasonable structural design and an efficient synthesis strategy, and the novel efficient carbon-based electromagnetic wave absorbing material is prepared by combining the characteristics of good dielectric loss capacity, unique structural characteristics, adjustable defect sites and the like.
Disclosure of Invention
The invention aims to obtain Co by taking humus (humins) as a carbon source, coating sulfides and calcining at different temperatures 9 S 8 A composite electromagnetic wave absorption material with a hubs carbon core-shell structure. The composite electromagnetic wave absorbing material prepared by the method has a large amount of interface polarization, and the semiconductor Co 9 S 8 The internal rich defects and the gaps between the internal rich defects and the carbon spheres optimize impedance matching, and meanwhile, the internal carbon spheres can enhance the conductive loss. Therefore, the Co obtained through reasonable composition, interface regulation and control, multilayer structure design and defect regulation and control 9 S 8 The core-shell structure composite electromagnetic wave absorbing material coated with the biomass conversion byproduct humins carbon has excellent wave absorbing capacity. The method is environment-friendly, simple to operate, mild in condition, easy for large-scale production and suitable for practical industrial application.
Co 9 S 8 The preparation method of the composite electromagnetic wave absorbing material coated with the biomass conversion byproduct humins carbon comprises the following steps:
(1) dispersing 5-15 mmol of xylose into 20-80 mL of 0.01-0.12M phosphoric acid aqueous solution, transferring the dissolved xylose into a high-pressure reaction kettle, reacting for 2-10 h at 160-200 ℃, cooling, performing suction filtration on a product, washing with water and absolute ethyl alcohol for 3-5 times respectively, and drying for 10-15 h at 60-100 ℃ to obtain humins;
(2) dispersing 1-8 mmol of cobalt acetate tetrahydrate into 20-70 mL of water, adding 0.05-0.15 g of the humins prepared in the step (1), stirring for 5-36 h, adding 0.5-1.5 mL of ethylenediamine, stirring for 1-10 h, adding 5-10 mmol of thiourea, magnetically stirring for 1-5 h, and transferring to a high-pressure reaction kettle for reaction at 160-240 ℃ for 5-15 h; naturally cooling to room temperature, performing suction filtration, washing with water and absolute ethyl alcohol for 3-5 times respectively, and drying to obtain Co 9 S 8 Coating the precursors of the humins carbon;
(3) co obtained in the step (2) 9 S 8 Precursors coated with humins carbonCalcining the body for 1-4 h at 500-900 ℃ in an argon atmosphere to obtain Co 9 S 8 The core-shell structure composite electromagnetic wave absorbing material which coats biomass conversion byproduct humins carbon is marked as CS @ C.
Co 9 S 8 The composite electromagnetic wave absorption material coated with the biomass conversion byproduct humins carbon is prepared by the method, and the inner core of the composite electromagnetic wave absorption material is spherical humins carbon and the shell layer is Co 9 S 8 The composite material is of a two-dimensional sheet or granular structure, and the composite material is in a core-shell shape with the diameter of 300-1000 nm.
The prepared material is applied to electromagnetic wave absorption in a frequency range of 2-18 GHz, and the performance test conditions are as follows:
the paraffin is used as a matrix, the paraffin and the prepared composite electromagnetic wave absorbing material are mixed and placed on a constant temperature heater, after the paraffin is melted, the paraffin and the material are uniformly mixed by stirring (the mass sum of the paraffin and the composite electromagnetic wave absorbing material is 20-50 percent of the mass sum of the paraffin and the composite electromagnetic wave absorbing material), the mixture is placed into a mold and pressed into concentric rings with the outer diameter of 7.00mm and the inner diameter of 3.04mm, and the thickness of the concentric rings is 1.5-5.0 mm. Using Agilent N5222A to test the electromagnetic parameters of the concentric rings within 2-18 GHz, and finally calculating the reflection loss value (RL) of the composite electromagnetic wave absorption material by using a transmission line theory, wherein the formula is as follows:
ε r ＝ε′-jε″
μ r ＝μ′-jμ″
wherein epsilon 0 And mu 0 Are respectively vacuumDielectric constant and vacuum permeability; z is a linear or branched member in And Z 0 Respectively the input impedance and the free space impedance of the wave-absorbing material; epsilon r And mu r Complex permittivity and complex permeability, respectively; f is the frequency of the electromagnetic wave, d is the thickness of the electromagnetic wave absorbing material, c is the propagation rate of the electromagnetic wave in free space, and j is the imaginary unit of the complex permittivity and complex permeability. Electromagnetic parameters (epsilon ', epsilon ', mu ') of different electromagnetic wave frequencies are tested by using Agilent N5222A, and reflection loss values are obtained.
Drawings
FIG. 1 is an XRD pattern of CS @ C-600, CS @ C-700 and CS @ C-800 prepared in example 1, example 2 and example 3.
FIG. 2 is an SEM image of the prepared humins.
FIG. 3 is an SEM image of a sample prepared in example 1.
FIG. 4 is a TEM image of a sample prepared in example 1.
FIG. 5 is an SEM image of a sample prepared in example 2.
FIG. 6 is a TEM image of a sample prepared in example 2.
FIG. 7 is an SEM image of a sample prepared in example 3.
FIG. 8 is a TEM image of a sample prepared in example 3.
FIG. 9 is a graph of reflection loss as a function of frequency for different thicknesses of samples prepared in example 1.
FIG. 10 is a graph of reflection loss as a function of frequency for different thicknesses of samples prepared in example 2.
FIG. 11 is a graph of reflection loss as a function of frequency for different thicknesses of samples prepared in example 3.
Detailed Description
To further illustrate the features of the present invention, specific embodiments are described in detail below with reference to the accompanying drawings and preferred embodiments.
Example 1
(1) Dispersing 10mmol xylose in 0.08M phosphoric acid solution (40mL), dissolving, transferring to a high-pressure reaction kettle, reacting at 180 ℃ for 6h, cooling, suction-filtering the product, washing with water and absolute ethyl alcohol for 3 times respectively, and drying at 80 ℃ for 12h to obtain humins. The SEM is shown in FIG. 2 and exhibits a spherical morphology with a diameter of about 700 nm.
(2) Dispersing 3mmol of cobalt acetate tetrahydrate in 35mL of water, adding 0.1g of humins, stirring for 12 hours, adding 1.2mL of ethylenediamine, stirring for 2 hours, finally adding 6mmol of thiourea, magnetically stirring for 2 hours, and then transferring to a high-pressure reaction kettle to react for 9 hours at 200 ℃. Naturally cooling to room temperature, performing suction filtration, washing with water and absolute ethyl alcohol for 3 times respectively, and drying in an oven to obtain Co 9 S 8 Coating the precursors of the humins carbon.
(3) Putting the product of the step (2) into a tube furnace, calcining for 2h at 600 ℃ in an argon atmosphere to obtain Co 9 S 8 The composite electromagnetic wave absorption material of the core-shell structure coated with the humins carbon is marked as CS @ C-600. XRD is shown in figure 1, which shows that Co is successfully prepared 9 S 8 . SEM and TEM are respectively shown in figures 3 and 4, the composite electromagnetic wave absorption material is in a core-shell structure, the outer shell is in a two-dimensional sheet structure, and the inner shells are in a spherical shape.
(4) The prepared sample and paraffin are uniformly mixed according to the mass percentage of 30 percent of the sample, the electromagnetic parameters of the sample are tested by using a vector network analyzer, and the reflection loss value of the composite electromagnetic wave absorbing material is calculated by using a transmission line theory. As shown in fig. 9. The minimum reflection loss value is-13.8 dB at a frequency of 16.56 GHz.
Example 2
(1) Dispersing 10mmol of xylose into 0.08M phosphoric acid solution (40mL), transferring to a high-pressure reaction kettle after dissolution, reacting for 6h at 180 ℃, filtering a product after cooling, washing for 3 times by water and absolute ethyl alcohol respectively, and drying for 12h at 80 ℃ to obtain humins. The SEM is shown in FIG. 2 and exhibits a spherical morphology with a diameter of about 700 nm.
(2) Dispersing 3mmol of cobalt acetate tetrahydrate in 35mL of water, adding 0.1g of humins, stirring for 12 hours, adding 1.2mL of ethylenediamine, stirring for 2 hours, finally adding 6mmol of thiourea, magnetically stirring for 2 hours, and then transferring to a high-pressure reaction kettle to react for 9 hours at 200 ℃. Naturally cooling to room temperature, performing suction filtration, washing with water and absolute ethyl alcohol for 3 times respectively, and drying in an oven to obtain Co 9 S 8 Coating the precursors of the humins carbon.
(3) Putting the product of the step (2) into a tube furnace, calcining for 2h at 700 ℃ in an argon atmosphere to obtain Co 9 S 8 The composite electromagnetic wave absorption material of the core-shell structure coated with the humins carbon is marked as CS @ C-700. XRD is shown in figure 1, which shows that Co is successfully prepared 9 S 8 . SEM and TEM as shown in fig. 5 and 6, respectively, a part of the outer sheet layer was converted into a granular form as compared with example 1.
(4) The prepared sample and paraffin are uniformly mixed according to the mass percentage of 30 percent of the sample, the electromagnetic parameters of the sample are tested by using a vector network analyzer, and the reflection loss value of the composite electromagnetic wave absorbing material is calculated by using a transmission line theory. As shown in fig. 10. The reflection loss value is-51.4 dB at a thickness of 1.84mm, and the effective absorption bandwidth is up to 5.92GHz at an ultra-thin coating thickness of 1.8 mm.
Example 3
(1) Dispersing 10mmol xylose in 0.08M phosphoric acid solution (40mL), dissolving, transferring to a high-pressure reaction kettle, reacting at 180 ℃ for 6h, cooling, suction-filtering the product, washing with water and absolute ethyl alcohol for 3 times respectively, and drying at 80 ℃ for 12h to obtain humins. The SEM is shown in FIG. 2 and exhibits a spherical morphology with a diameter of about 700 nm.
(2) Dispersing 3mmol of cobalt acetate tetrahydrate in 35mL of water, adding 0.1g of humins, stirring for 12 hours, adding 1.2mL of ethylenediamine, stirring for 2 hours, finally adding 6mmol of thiourea, magnetically stirring for 2 hours, and then transferring to a high-pressure reaction kettle to react for 9 hours at 200 ℃. Naturally cooling to room temperature, performing suction filtration, washing with water and absolute ethyl alcohol for 3 times respectively, and drying in an oven to obtain Co 9 S 8 Coating the precursors of the humins carbon.
(3) Putting the product of the step (2) into a tube furnace, calcining for 2h at 800 ℃ in an argon atmosphere to obtain Co 9 S 8 The composite electromagnetic wave absorbing material of the core-shell structure coated with the humins carbon is marked as CS @ C-800. XRD is shown in figure 1, which shows that Co is successfully prepared 9 S 8 . SEM and TEM as shown in fig. 7 and 8, respectively, the outer lamella was completely transformed into the granular form, compared to example 1 and example 2.
(4) The prepared sample and paraffin are uniformly mixed according to the mass percentage of 30 percent of the sample, the electromagnetic parameters of the sample are tested by using a vector network analyzer, and the reflection loss value of the composite electromagnetic wave absorbing material is calculated by using a transmission line theory. As shown in fig. 11. The minimum reflection loss value is-48.1 dB at a frequency of 12.88 GHz.
Claims (5)
1. Co 9 S 8 The preparation method of the composite electromagnetic wave absorbing material coated with the biomass conversion byproduct humins carbon comprises the following steps:
(1) dispersing 5-15 mmol of xylose into 20-80 mL of 0.01-0.12M phosphoric acid aqueous solution, transferring the dissolved xylose into a high-pressure reaction kettle, reacting for 2-10 h at 160-200 ℃, cooling, performing suction filtration on a product, washing 3-5 times with water and absolute ethyl alcohol respectively, and drying for 10-15 h at 60-100 ℃ to obtain humins;
(2) dispersing 1-8 mmol of cobalt acetate tetrahydrate into 20-70 mL of water, adding 0.05-0.15 g of the humins prepared in the step (1), stirring for 5-36 h, adding 0.5-1.5 mL of ethylenediamine, stirring for 1-10 h, adding 5-10 mmol of thiourea, magnetically stirring for 1-5 h, and transferring to a high-pressure reaction kettle for reaction at 160-240 ℃ for 5-15 h; naturally cooling to room temperature, performing suction filtration, washing with water and absolute ethyl alcohol for 3-5 times respectively, and drying to obtain Co 9 S 8 Coating the precursors of the humins carbon;
(3) co obtained in the step (2) 9 S 8 Calcining the precursor coated with humins carbon in an argon atmosphere at 500-900 ℃ for 1-4 h to obtain Co 9 S 8 A composite electromagnetic wave absorbing material for coating biomass conversion byproduct humins carbon.
2. Co 9 S 8 The composite electromagnetic wave absorbing material coated with the biomass conversion byproduct humins carbon is characterized in that: is prepared by the method of claim 1.
3. A Co as claimed in claim 2 9 S 8 The composite electromagnetic wave absorbing material coated with the biomass conversion byproduct humins carbon is characterized in that: the inner core of the composite electromagnetic wave absorbing material is spherical humins carbon, shell Co 9 S 8 The composite material is of a two-dimensional sheet or granular structure, and the composite material is in a core-shell shape with the diameter of 300-1000 nm.
4. A Co as claimed in claim 2 or 3 9 S 8 The composite electromagnetic wave absorption material coated with biomass conversion byproduct humins carbon is used for absorbing electromagnetic waves in a frequency range of 2-18 GHz.
5. A Co as claimed in claim 4 9 S 8 The composite electromagnetic wave absorption material coated with biomass conversion byproduct humins carbon is used for absorbing electromagnetic waves in a frequency band of 2-18 GHz, and is characterized in that: taking paraffin as a matrix, mixing the paraffin with the prepared composite electromagnetic wave absorbing material, placing the mixture on a constant temperature heater, stirring the mixture to uniformly mix the paraffin and the material after the paraffin is melted, putting the composite electromagnetic wave absorbing material accounting for 20-50% of the sum of the mass of the paraffin and the composite electromagnetic wave absorbing material into a mold, and pressing the mixture into concentric rings with the outer diameter of 7.00mm and the inner diameter of 3.04mm and the thickness of 1.5-5.0 mm; the electromagnetic parameters of the concentric rings within 2-18 GHz are tested by using Agilent N5222A.
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