CN113563842B - Preparation method of tremella-shaped iron-based complex converted electromagnetic wave absorbent - Google Patents
Preparation method of tremella-shaped iron-based complex converted electromagnetic wave absorbent Download PDFInfo
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Abstract
The invention discloses a preparation method of a tremella-shaped iron-based complex converted electromagnetic wave absorbent, which comprises the following steps: step S1, preparing tremella iron-based complex FeTCNQ powder: respectively weighing ferrous chloride tetrahydrate and 7, 8-tetracyanoquinodimethane TCNQ, sequentially dissolving in N, N-dimethylformamide DMF, and stirring ultrasonically; reacting the mixed solution at 145-150 ℃, standing the reacted mixed solution for 12-24 hours, filtering to obtain a precipitate, and vacuum drying at 65-70 ℃ to obtain blue-black tremella-like iron-based complex FeTCNQ powder; s2, preparing an electromagnetic wave absorber Fe/C/N nano composite: taking and grinding the iron-based complex FeTCNQ powder in the step S1; and pyrolyzing the powder in an argon atmosphere to obtain the nanocomposite electromagnetic wave absorbent Fe/C/N. Carbon metal composite materials with different graphite degrees are formed by adjusting different pyrolysis temperatures, the tremella-shaped iron-based complex converted electromagnetic wave absorbent is prepared, and Fe/C/N can realize low-frequency microwave absorption at a lower thickness.
Description
Technical Field
The invention belongs to the technical field of functional electromagnetic materials, and particularly relates to a low-frequency and high-frequency electromagnetic wave absorbent and a preparation method thereof.
Background
The rapid development of wireless communication devices and electronic devices has led to a great deal of microwave radiation, signal pollution and interference to living environment and unpredictable potential hazard to human living health, and development of advanced electromagnetic wave absorbing materials is needed to solve and match the technical problems faced. At the same time, the rapid replacement of new generation mobile communication technology has accelerated the urgent need for advanced electromagnetic wave absorbing materials, and development of microwave absorbing materials satisfying "thin, light, wide, and strong" is required. Carbon-based materials are widely favored in achieving high-performance electromagnetic wave attenuation due to their advantages of light weight, strong dielectric loss, high conductivity, and the like. In the current research, combining carbon materials (reduced graphene oxide, carbon nanotubes, carbon fibers, colloidal carbon, etc.) with magnetic materials (magnetic metals, ferrites, magnetic oxides) is considered as an effective way to widen the effective bandwidth of electromagnetic wave absorbers. For example: a series of optimized composite microwave absorbers such as graphene oxide and iron oxide, carbon nanotubes and iron oxide, graphene oxide and cobalt nickel alloy, etc. are reported. In addition, the microstructure of the electromagnetic wave absorber has obvious influence on the impedance change and the wave absorbing performance of electromagnetic wave absorption. In the prior report, the regulation and control of the micro-morphology is limited to the influence of the micro-morphology change of the metal and the metal oxide on the electromagnetic wave absorption performance, and the development and research of the microwave absorber aiming at the metal/carbon micro-morphology are very little. This puts new demands on the broadband expansion of the composite microwave absorber using carbon and metal. The currently reported metal/carbon-based composite microwave absorbent products are low in cost and poor in environmental friendliness, and are difficult to widely develop and apply. The development of the novel (high yield, low cost and environmental protection) metal/carbon microwave material with the microstructure can effectively expand the wide use of the microwave absorbing material in national defense, weapons and civil electronic products.
Disclosure of Invention
The invention aims to provide a preparation method of a tremella-shaped iron-based complex converted electromagnetic wave absorber, which can realize low-frequency microwave absorption at a lower thickness, and carbon metal composite materials with different graphite degrees are formed by adjusting different pyrolysis temperatures, so that the tremella-shaped iron-based complex converted electromagnetic wave absorber is prepared.
The invention adopts the following technical scheme: a preparation method of tremella iron-based complex converted electromagnetic wave absorbent comprises the following steps:
step S1, preparing tremella iron-based complex FeTCNQ powder:
respectively weighing ferrous chloride tetrahydrate and 7, 8-tetracyanoquinodimethane TCNQ, sequentially dissolving in N, N-dimethylformamide DMF, and ultrasonically stirring to form a uniformly dispersed deep black mixed solution; in the mixed solution, the molar ratio of ferrous chloride tetrahydrate to 7, 8-tetracyano-terephthalquinone dimethane TCNQ is 1:1.0-1.1;
when the color of the mixed solution is changed from dark black to blue black, standing the reacted mixed solution for 12-24 hours, filtering to obtain a precipitate, cleaning the precipitate, and vacuum drying the precipitate at 65-70 ℃ to obtain blue black tremella-like iron-based complex FeTCNQ powder;
s2, preparing an electromagnetic wave absorber Fe/C/N nano composite:
taking and grinding the iron-based complex FeTCNQ powder in the step S1 to finally obtain powder with the particle size of 500-700 nm;
the powder is pyrolyzed under argon atmosphere, specifically: heating to 40 ℃, then programming to 800 ℃, and preserving heat for 2h for pyrolysis; and then the temperature is reduced to 400 ℃ by the program, and then the temperature is naturally cooled to the room temperature, so that the nano-composite electromagnetic wave absorbent Fe/C/N is obtained.
Further, in step S2, the temperature programming rate is 2 ℃/min, and the temperature programming rate is 5 ℃/min.
Further, in step S2, the tremella iron-based complex FeTCNQ powder is placed into a vacuum tube furnace for pyrolysis.
Further, in the step S1, the mixed solution reacts for 9.5 to 12 hours at 145 to 150 ℃; vacuum drying at 65-70 deg.c for 12-24 hr.
The beneficial effects of the invention are as follows: 1. the tremella-shaped nano sheet stacking particles FeTCNQ with microwave absorption performance are directly prepared, nano sheets are stacked around the nano particles, and the iron-based nano particles with rich anisotropic interface structures are formed to cause more electromagnetic waves to generate scattering loss. The electromagnetic wave absorber with the Fe/C/N concentric rings has remarkable wave absorbing performance, the matching thickness is only 2.9mm, the reflection loss is-52.3 dB, and-10 dB represents that 90% of electromagnetic waves are absorbed, and the effective absorption bandwidth can reach 3.1GHz from 14.0 to 17.1GHz.3. The problems of strong absorption and broadband absorption at 4-5mm under low frequency are solved, and the effective absorption frequency width is 3.0GHz.4. The raw materials are cheap, the yield of the synthesized FeTCNQ complex is high and can reach 40%, and the method has great potential application value.
Drawings
FIG. 1 is a representation of a tremella-like iron-based complex FeTCNQ powder;
1a is a scanning electron microscope SEM image of the tremella-like iron-based complex FeTCNQ powder prepared in example 1;
1b is a transmission electron microscope TEM image of the tremella-like iron-based complex FeTCNQ powder prepared in example 1;
1c is a powder TG-MS plot of the tremella iron-based complex FeTCNQ powder prepared in example 1;
1d is a powder X-ray diffraction PXRD pattern of the tremella iron-based complex FeTCNQ powder prepared in example 1;
FIG. 2 is a PXRD pattern of the electromagnetic wave absorbers Fe/C/N prepared at different pyrolysis temperatures in example 1 and comparative example 1;
FIG. 3 is a graph showing the wave absorbing properties of FeTCNQ powders prepared in example 1 and comparative example 1, and electromagnetic wave absorbers Fe/C/N coaxial paraffin-based composite materials prepared at different pyrolysis temperatures;
FIG. 4 is a graph showing the wave-absorbing properties of Ni/C/N prepared in comparative example 2;
FIG. 5 is a graph showing Mn/C/N wave-absorbing properties under the condition of replacing transition metals, which is prepared in comparative example 3;
FIG. 6 shows electromagnetic parameters of the electromagnetic wave absorber Fe/C/N at different pyrolysis temperatures.
Detailed Description
The invention will be described in detail below with reference to the drawings and the detailed description.
The FeTCNQ powder used in the invention is a complex of ferrous chloride tetrahydrate and 7, 8-tetracyanoquinodimethane, and is synthesized by adopting the method of the invention. The ferrous chloride tetrahydrate and the 7, 8-tetracyanoquinodimethane are both reagent grade. Both room temperature and normal temperature are referred to herein as 25 ℃.
The invention discloses a preparation method of a tremella-shaped iron-based complex converted electromagnetic wave absorbent, which comprises the following steps:
step S1, preparing tremella iron-based complex FeTCNQ powder:
respectively weighing ferrous chloride tetrahydrate and 7, 8-tetracyanoquinodimethane TCNQ, sequentially dissolving in N, N-dimethylformamide DMF, and ultrasonically stirring to form a uniformly dispersed deep black mixed solution; in the mixed solution, the molar ratio of ferrous chloride tetrahydrate to 7, 8-tetracyano-terephthalquinone dimethane TCNQ is 1:1.0-1.1;
when the color of the mixed solution is changed from dark black to blue black, standing the reacted mixed solution for 12-24 hours, filtering to obtain a precipitate, cleaning the precipitate, and vacuum drying the precipitate at 65-70 ℃ to obtain blue black tremella-like iron-based complex FeTCNQ powder;
s2, preparing an electromagnetic wave absorber Fe/C/N nano composite:
taking and grinding the iron-based complex FeTCNQ powder in the step S1 to finally obtain powder with the particle size of 500-700 nm;
the powder is pyrolyzed under argon atmosphere, specifically: placing the tremella iron-based complex FeTCNQ powder into a vacuum tube furnace, heating to 40 ℃, then heating to 800 ℃ by programming, and preserving heat for 2h for pyrolysis; and then the temperature is reduced to 400 ℃ by the program, and then the temperature is naturally cooled to the room temperature, so that the nano-composite electromagnetic wave absorbent Fe/C/N is obtained. The temperature programming rate is 2 ℃/min, and the temperature programming rate is 5 ℃/min.
To verify the process of the present invention, the following specific examples and comparative examples are given:
example 1
The embodiment provides a preparation method of a tremella iron-based complex converted electromagnetic wave absorbent, which comprises the following steps:
step S1, preparing tremella iron-based complex FeTCNQ powder: respectively weighing ferrous chloride tetrahydrate and 7, 8-tetracyanoquinodimethane TCNQ, sequentially dissolving in N, N-dimethylformamide DMF, and ultrasonically stirring to form a uniformly dispersed deep black mixed solution; in the mixed solution, the molar ratio of ferrous chloride tetrahydrate to 7, 8-tetracyano-terephthalquinone dimethane TCNQ is 1:1.0-1.1; the amount of 7, 8-tetracyanoquinodimethane TCNQ in the mixed solution is more than or equal to the amount of ferrous chloride tetrahydrate, so as to ensure the more complete reaction of the ferrous chloride tetrahydrate. However, the amount is not too large, and the waste is caused by too much amount. Through multiple experiments, it is determined that ferrous chloride tetrahydrate can completely react at the molar ratio.
And (3) reacting the mixed solution at 145-150 ℃, standing the reacted mixed solution for 12-24 hours when the color of the mixed solution is changed from dark black to blue black, filtering to obtain a precipitate, cleaning the precipitate, and vacuum drying at 65-70 ℃ after cleaning to obtain blue black tremella-like iron-based complex FeTCNQ powder.
S2, taking 1.0g of the iron-based complex FeTCNQ powder in the step S1, and grinding to obtain powder with the particle size of 500-700 nm;
placing the tremella iron-based complex FeTCNQ powder into a vacuum tube furnace, pyrolyzing under argon atmosphere, and pyrolyzing by adopting a programmed heating and programmed cooling mode. The method comprises the following steps: heating to 40 ℃, then programming to 800 ℃, and preserving heat for 2h for pyrolysis; and then the temperature is reduced to 400 ℃ by the program, and then the temperature is naturally cooled to the room temperature, so that the nano-composite electromagnetic wave absorbent Fe/C/N is obtained. Wherein, the temperature programming rate is 2 ℃/min, and the temperature programming rate is 5 ℃/min.
Comparative example 1
In order to verify the performance of the prepared nanocomposite electromagnetic wave absorber Fe/C/N at different pyrolysis temperatures, the iron-based complex FeTCNQ powder in the step S1 is pyrolyzed at different pyrolysis temperatures, specifically: placing tremella iron-based complex FeTCNQ powder into a vacuum tube furnace, heating to 40 ℃, then programming to 600 ℃ or 700 ℃, preserving heat for 2 hours for pyrolysis, programming to heat at a speed of 2 ℃/min, programming to cool to 400 ℃, programming to cool at a speed of 5 ℃/min, and naturally cooling to room temperature to obtain the nanocomposite electromagnetic wave absorbent Fe/C/N.
The FeTCNQ prepared in step S1 of example 1 was tested, and as shown in fig. 1a, it was shown in fig. 1 that the microstructure of FeTCNQ was tremella-like in SEM image of FeTCNQ. As shown in fig. 1b, the TEM image of FeTCNQ is a transmission electron microscope TEM image, and as shown in fig. 1b, feTCNQ is a nano-sheet stacking particle structure, and nano-sheets are stacked around the nano-particles, so that iron-based nano-particles with rich anisotropic interface structures can induce more electromagnetic waves to generate scattering loss. As shown in fig. 1c, the powder TG-MS diagram of the FeTCNQ powder shows that the pyrolysis degree of FeTCNQ gradually deepens with increasing temperature, and the pyrolysis degree is highest and remains constant at 800 ℃ at the pyrolysis temperature, so the pyrolysis temperature is selected to be 800 ℃. In addition, the weight loss yield is high in the pyrolysis process, and the weight of the weight loss residue is about 45% at 800 ℃. During pyrolysis, nitrogen is evolved in the form of nitrogen. As shown in fig. 1d, the PXRD powder diffraction pattern of FeTCNQ produced bulges between 20 and 40 ° in 2θ, indicating that FeTCNQ has a crystal structure.
Comparative example 2
The embodiment prepares the NiTCNQ and the derivative electromagnetic wave absorber thereof, and specifically comprises the following components: 20mmol of nickel nitrate hexahydrate and 20mmol of TCNQ are respectively added into 30mL of DMF solution, and stirred for 1h at the ultrasonic normal temperature to obtain a pale green complex. The pale green complex solution is reacted for 9 hours at 150 ℃ to obtain off-white powder, the off-white powder is washed by DMF and ethanol for 3 to 5 times in sequence, and the NiTCNQ powder is obtained by vacuum drying.
Placing 1.0g of NiTCNQ powder into a ceramic boat, transferring the ceramic boat filled with the NiTCNQ powder into a tube furnace, setting the heating rate of the tube furnace to be 2 ℃/min, setting the atmosphere to be argon atmosphere, heating to 800 ℃ and preserving heat for 2 hours, setting the cooling rate to be 5 ℃/min, and naturally cooling to room temperature when cooling to 400 ℃ to obtain the powder wave absorber Ni/C/N.
Comparative example 3
The electromagnetic wave absorber of MnTCNQ and the derivative thereof is prepared in the embodiment, and specifically comprises the following components: 20mmol of manganese chloride tetrahydrate and 20mmol of TCNQ are respectively added into 30mL of DMF solution, and stirred for 1h at the ultrasonic normal temperature to obtain a blue-black mixture. Reacting the blue-black mixture solution for 9 hours at 150 ℃ to obtain black powder, washing the black powder with DMF and ethanol for 3 to 5 times in sequence, and drying the black powder in vacuum to obtain MnTCNQ powder.
And (3) placing 1.0g of MnTCNQ powder in a ceramic boat, transferring the ceramic boat filled with the MnTCNQ powder into a tube furnace, setting the heating rate of the tube furnace to be 2 ℃/min, setting the atmosphere to be argon atmosphere, heating to 800 ℃ and preserving heat for 2 hours, setting the cooling rate to be 5 ℃/min, and naturally cooling to room temperature when cooling to 400 ℃ to obtain the powder wave absorber Mn/C/N.
Placing Fe/C/N powder and paraffin-based composite phase samples thereof prepared at different pyrolysis temperatures into a coaxial ring mold respectively, wherein the mass ratio of the Fe/C/N powder to the paraffin in the paraffin-based composite phase is 1:1, in a coaxial ring mould, the compression strength is 5-10 MPa, and the dwell time is 0.1-0.5 h, so as to obtain the prefabricated coaxial ring. The same collar sizes were 7.0mm by 3.04mm. Samples were prepared to different thicknesses, selected thicknesses of 1.5mm,2.0mm,2.5mm,3.0mm,3.5mm,4.0mm and 4.5mm, samples with a thickness of 2.9mm were also prepared for Fe/C/N prepared at a pyrolysis temperature of 800 ℃, and coaxial rings of two samples in the same group were tested by a coaxial line method under a vector network analyzer, respectively.
The test results of the coaxial line method for the above samples are as follows: as shown in fig. 3, the broken line in the figure represents that 90% of the electromagnetic wave is absorbed, and the closer to the lower the broken line, the better the electromagnetic wave absorption performance of the sample is. As can be seen from the graph, the electromagnetic wave absorption performance of Fe/C/N prepared at the pyrolysis temperature of 800℃is the best.
In FIG. 3d, the effective absorption bandwidth EAB of Fe/C/N is 3.1GHz, i.e. in the interval 14.0-17.1GHz, at a sample thickness of 2.0 mm. When the thickness of the sample is 2.9mm, the reflection loss intensity RL value of Fe/C/N is-52.3 dB, and the sample shows that the absorber can absorb 99.99% of electromagnetic waves at the position of the thickness of the sample being 2.9mm, and the wave band of the electromagnetic waves is Ku wave band, so that the sample has good absorption performance.
In the invention, the same method is adopted for testing Fe/C/N, ni/C/N and Mn/C/N prepared in comparative examples 2 and 3 are respectively prepared into concentric rings, and are respectively tested under a vector network analyzer by adopting a coaxial line method, as shown in fig. 4 and 5, and as shown in fig. 4, a Ni/C/N sample has better electromagnetic wave absorbability, and when the thickness of the Ni/C/N sample is 2.0mm, the effective absorption bandwidth EAB is more than 6GHz, namely, the interval is 11.2-18.0 GHz. As shown in FIG. 5, the Mn/C/N sample has an electromagnetic wave absorption intensity close to-50 dB at a thickness of 2.500mm, and has a good electromagnetic wave absorbability. The effective absorption bandwidth EAB is smaller than the effective absorption bandwidth of Fe/C/N.
In the invention, the electromagnetic wave absorption performance of Fe/C/N, ni/C/N and Mn/C/N is calculated according to the following formula:
taking the Fe/C/N prepared in example 1 and comparative example 1 as an example, electromagnetic parameters of the Fe/C/N prepared at different pyrolysis temperatures were measured, and as can be seen from FIG. 6, the Fe/C/N obtained at the pyrolysis temperature of 800 ℃ has a remarkable relaxation phenomenon in the X-band, the dielectric real part epsilon 'thereof gradually decreases between the band frequencies of 6 to 12GHz, the remarkable fluctuation of the X-band is indistinguishable from the anisotropy of the microstructure thereof, and the value of the dielectric imaginary part epsilon' thereof gradually increases from 2.5 to 14 between the band frequencies of 6 to 13GHz, and then decreases to about 3. The electromagnetic parameters of Fe/C/N prepared by pyrolysis at 600 ℃ and 700 ℃ are compared, the electromagnetic parameters show obvious dispersion characteristics, the dielectric real part epsilon ' of the electromagnetic parameters is distributed from the band frequency of about 8.5 to 8 at 600 ℃, the dielectric real part epsilon ' is changed from about 1 to 1.5, and the loss capacity is weak from the dielectric imaginary part epsilon '. The dielectric real part epsilon ' of the Fe/C/N nano-composite prepared by pyrolysis at 700 ℃ also changes at the band frequency of 10-19.5, so that the Fe/C/N nano-composite shows strong electric storage capacity, the value of the dielectric imaginary part epsilon ' changes at 19.0-7.5, and the Fe/C/N nano-composite is in a shielding state at high frequency due to the fact that the value of the dielectric imaginary part epsilon ' is too high, and the reflection is generated on electromagnetic waves, so that the electromagnetic absorption capacity is reduced. The real and imaginary dielectric constants of the electromagnetic absorber are measured, as shown in a and b of fig. 6, and as shown in a, the real dielectric constant epsilon' decreases rapidly in the X-band due to interfacial polarization within the electromagnetic absorber caused by relaxation. The value of the dielectric imaginary part epsilon "changes rapidly in 6b to the electron polarization. As shown in fig. 6 c and d, the real part μ' and the imaginary part μ″ of the magnetic permeability exhibit a distinct band phenomenon, which is affected by hysteresis resonance generated at the internal hetero interface of the electromagnetic absorber, indicating that the frequency of the electromagnetic wave changes faster than the magnetic domain resonance.
Claims (4)
1. The preparation method of the tremella iron-based complex converted electromagnetic wave absorbent is characterized by comprising the following steps of:
step S1, preparing tremella iron-based complex FeTCNQ powder:
respectively weighing ferrous chloride tetrahydrate and 7, 8-tetracyanoquinodimethane TCNQ, sequentially dissolving in N, N-dimethylformamide DMF, and ultrasonically stirring to form a uniformly dispersed deep black mixed solution; in the mixed solution, the molar ratio of ferrous chloride tetrahydrate to 7, 8-tetracyano-terephthalquinone dimethane TCNQ is 1:1.0-1.1;
when the color of the mixed solution is changed from dark black to blue black, standing the reacted mixed solution for 12-24 hours, filtering to obtain a precipitate, cleaning the precipitate, and vacuum drying the precipitate at 65-70 ℃ to obtain blue black tremella-like iron-based complex FeTCNQ powder; the FeTCNQ powder is of a nano sheet stacking particle structure, and nano sheets are stacked around the nano particles;
s2, preparing an electromagnetic wave absorber Fe/C/N nano composite:
taking and grinding the iron-based complex FeTCNQ powder in the step S1 to finally obtain powder with the particle size of 500-700 nm;
the powder is pyrolyzed under argon atmosphere, specifically: heating to 40 ℃, then programming to 800 ℃, and preserving heat for 2h for pyrolysis; and then the temperature is reduced to 400 ℃ by the program, and then the temperature is naturally cooled to the room temperature, so that the nano-composite electromagnetic wave absorbent Fe/C/N is obtained.
2. The method for preparing the tremella iron-based complex converted electromagnetic wave absorber according to claim 1, wherein in the step S2, the temperature programming rate is 2 ℃/min, and the temperature programming rate is 5 ℃/min.
3. The method for preparing the tremella iron-based complex converted electromagnetic wave absorber according to claim 2, wherein in the step S2, the tremella iron-based complex FeTCNQ powder is placed into a vacuum tube furnace for pyrolysis.
4. The method for preparing the tremella iron-based complex converted electromagnetic wave absorbent according to claim 1, wherein in the step S1, the mixed solution is reacted for 9.5-12 hours at 145-150 ℃; vacuum drying at 65-70 deg.c for 12-24 hr.
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| CN112300402A (en) * | 2020-10-30 | 2021-02-02 | 西北工业大学 | Preparation method of two-dimensional conductive metal organic framework electromagnetic wave absorbent |
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| WO2010117110A1 (en) * | 2009-04-07 | 2010-10-14 | 한양대학교 산학협력단 | Flaky powder for an electromagnetic wave absorber, and method for producing same |
| CN112300402A (en) * | 2020-10-30 | 2021-02-02 | 西北工业大学 | Preparation method of two-dimensional conductive metal organic framework electromagnetic wave absorbent |
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