Preparation method of three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles

Abstract

The application relates to a preparation method of a three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles, and belongs to the technical field of electromagnetic wave absorbing materials, and particularly relates to a method for preparing a three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles. The application aims at solving the problems of the existing three-dimensional porous carbon / Mo2C composite material, such as large Mo2C particle size, complicated preparation method, high cost, long time consumption and the like. The method is as follows: PVP, Zn(NO3)2.6H2O and H 24 Mo7N6O 24 2O are used as raw materials, high-temperature carbonization and etching are carried out to obtain the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles. The method is simple and low in cost, the prepared product has a uniform three-dimensional porous structure, the Mo2C particle size is about 10 nm, the ultra-small Mo2C encapsulated in the carbon skeleton brings abundant heterogeneous interfaces, impedance matching is improved, and the composite material exhibits excellent wave-absorbing performance. The prepared composite material is applied to the field of electromagnetic wave absorption.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a foam wave-absorbing material, in particular to a preparation method of a three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles, and belongs to the technical field of electromagnetic wave absorption. BACKGROUND

[0002] The popularity of various wireless communications and electronic devices brings convenience and speed to human life, but the resulting electromagnetic pollution has become one of the common environmental problems in people's daily production and life. In addition, electromagnetic waves play an important role in the field of military reconnaissance. In order to improve military security protection, strengthen the combat effectiveness of weapons and equipment, and develop radar stealth technology, the development of electromagnetic protection technology is also of great significance to the maintenance of national security. Therefore, in the field of electronic information security and military radar stealth, developing microwave absorbing materials that can effectively and sustainably dissipate excess electromagnetic waves in electronic and military equipment is the goal that scientists strive for. In the past two decades, carbon-based materials have been widely studied as potential high-performance wave-absorbing materials, and researchers have made great efforts in exploring the relationship between structure and performance. Literature reviews show that carbon materials with a foam structure have broad application prospects in the field of microwave absorption because their unique three-dimensional porous structure can promote multiple reflections of incident electromagnetic waves, reduce the effective dielectric constant, and facilitate the construction of a strong conductive network at low filling. In recent years, Mo2C has been widely studied in the field of wave absorption because of its good chemical stability under extreme conditions such as acidity and alkalinity, and its inherent polarization relaxation characteristics make it a common secondary component for combining with carbon materials to obtain high-efficiency wave-absorbing materials, laying a foundation for efficiently absorbing electromagnetic energy. However, the Mo2C particles in some existing three-dimensional porous carbon / Mo2C composites are large (>100 nm), which cannot produce enough heterojunction interfaces to dissipate electromagnetic waves. On the other hand, the complex synthesis process is usually time-consuming and costly, hindering their practical application. SUMMARY

[0003] The application is to solve the problem of Mo2C particles with large particle size in some existing three-dimensional porous carbon / Mo2C composites, and the preparation method is complicated, and the cost is high and time-consuming. Therefore, a preparation method of a three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles is proposed.

[0004] The technical scheme adopted by the application to solve the above problems is:

[0005] The application comprises the following steps:

[0006] Step one, dissolve PVP (polyvinylpyrrolidone) in deionized water, stir uniformly to obtain a transparent solution, then add Zn(NO3)2.6H2O and H 24 Mo7N6O24 ·4H2O, fully stirring until the mixed solution is uniformly mixed;

[0007] Step two, the mixed solution obtained in step one is placed in an oven until it is dried, and the obtained solid is ground into powder;

[0008] Step three, the powder obtained in step two is placed in a porcelain boat and high-temperature calcination is carried out in a tube furnace under an argon atmosphere to obtain a black foam-shaped product;

[0009] Step four, the product obtained in step three is placed in a hydrochloric acid solution, stirred, then washed with deionized water and anhydrous ethanol, and dried to obtain a three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles.

[0010] The washing is carried out with deionized water and anhydrous ethanol in sequence.

[0011] Further, in step one, the mass of PVP is 0.5-1 gram, the deionized water is 20-40 mL, the Zn(NO3)2·6H2O is 0.3-0.6 gram, the H 24 Mo7N6O 24 ·4H2O is 0.1-0.3 gram.

[0012] Further, in step one, the stirring time is 20-40 minutes.

[0013] Further, in step two, the oven temperature is 60℃, and the drying time is 24 hours.

[0014] Further, in step three, the high-temperature calcination process is as follows: the temperature rising rate is controlled to be 5℃ / min, the calcination temperature is 700℃, and the calcination time is 1 hour.

[0015] Further, in step four, the concentration of the hydrochloric acid solution is 3-5 mol / L, the volume of the hydrochloric acid solution is 20-50 mL, and the etching time in the hydrochloric acid solution is controlled to be 12 hours.

[0016] The beneficial effects of the present application are as follows:

[0017] 1. The three-dimensional porous carbon / Mo2C material prepared by the present application encapsulates Mo2C particles uniformly in the carbon skeleton, and the Mo2C particle size is ultra-small, about 10 nm.

[0018] 2. The raw materials used in the preparation of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles are economically available, the preparation process is simple, the cost is low, and the obtained product has a complete three-dimensional structure.

[0019] 3. The three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles prepared by the method has a good three-dimensional porous structure, and the multiple reflection loss of electromagnetic waves in the wave-absorbing agent is strengthened.

[0020] 4. The material prepared by the method is used for manufacturing a light and efficient wave-absorbing coating. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The scanning electron microscope picture and the transmission electron microscope picture of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles prepared in the embodiment one of the application are shown in the figure, wherein a is the scanning electron microscope picture of the carbon skeleton of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles, and b is the transmission electron microscope picture;

[0022] Figure 2 The high-resolution transmission electron microscope picture of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles prepared in the embodiment one of the application is shown in the figure;

[0023] Figure 3 The XRD graph of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles prepared in the embodiment one of the application and the comparative sample is shown in the figure;

[0024] Figure 4 The mercury immersion curve of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles prepared in the embodiment one of the application is shown in the figure, wherein a is the mercury immersion / mercury withdrawal curve, and b is the pore size distribution graph;

[0025] Figure 5 The real part of the dielectric constant of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles prepared in the embodiment one of the application and the comparative sample is shown in the figure;

[0026] Figure 6 The imaginary part of the dielectric constant of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles prepared in the embodiment one of the application and the comparative sample is shown in the figure;

[0027] Figure 7 The Cole-Cole ring graph of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles prepared in the embodiment one of the application and the comparative sample is shown in the figure, wherein a is the Cole-Cole ring graph of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles, and b is the Cole-Cole ring graph of the comparative sample;

[0028] Figure 8 The wave impedance curve graph of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles prepared in the embodiment one of the application and the comparative sample is shown in the figure;

[0029] Figure 9 The electromagnetic wave absorption performance diagram of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles prepared in Embodiment One of the present application, a diagram is a three-dimensional reflection loss diagram, and b diagram is a two-dimensional reflection loss diagram. DETAILED DESCRIPTION

[0030] Specific embodiment one: the preparation method of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles in the present embodiment, the preparation method comprises the following steps:

[0031] Step one, dissolve PVP in deionized water, stir uniformly to obtain a transparent solution, then add Zn(NO3)2·6H2O and H 24 Mo7N6O 24 ·4H2O, fully stir until the mixture is uniform, and obtain the mixed solution;

[0032] Step two, place the mixed solution obtained in step one in an oven until it is dried, and grind the obtained solid into a powder;

[0033] Step three, place the powder obtained in step two in a porcelain boat, and perform high-temperature calcination under an argon atmosphere in a tube furnace to obtain a black foam-shaped product;

[0034] Step four, place the product obtained in step three in a hydrochloric acid solution, stir, then wash with deionized water and anhydrous ethanol, and dry to obtain the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles.

[0035] The hydrochloric acid solution used in step four can etch away the metal zinc.

[0036] The three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles formed by the method provided in the present embodiment has a uniform pore structure, and encapsulates ultra-small Mo2C particles in the carbon skeleton. In addition, the material as a whole presents an amorphous crystal structure, has low electrical conductivity, and can effectively adjust the degree of impedance matching.

[0037] The three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles prepared in the present embodiment, when preparing the wave-absorbing agent, uses paraffin and the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles. The mass percentage of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles in the absorber can be adjusted according to actual needs. When the mass percentage of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles in the absorber is 35%, under this filler ratio, the frequency range of the reflection loss intensity less than -10 dB is 4.4-18.0 GHz.

[0038] Specific implementation two: the difference between this embodiment and specific implementation one is: the mass of PVP in step one of this embodiment is 1 gram, the deionized water is 30 mL, the Zn(NO3)2·6H2O is 0.5 gram, and the H 24 Mo7N6O 24 ·4H2O is 0.2 gram. The others are the same as specific implementation one.

[0039] Specific implementation three: the difference between this embodiment and specific implementation one or two is: the stirring time in step one of this embodiment is 30 minutes. The others are the same as specific implementation one or two.

[0040] Specific implementation four: the difference between this embodiment and one of specific implementation one to three is: the oven temperature in step two of this embodiment is 60℃, and the drying time is 24 hours. The others are the same as one of specific implementation one to three.

[0041] Specific implementation five: the difference between this embodiment and one of specific implementation one to four is: the high-temperature calcination process in step three of this embodiment: the control of the heating rate is 5℃ / min, the calcination temperature is 700℃, and the calcination time is 1 hour. The others are the same as one of specific implementation one to four.

[0042] Specific implementation six: the difference between this embodiment and one of specific implementation one to five is: the concentration of the hydrochloric acid solution in step four of this embodiment is 4 mol / L, the volume of the hydrochloric acid solution is 30 mL, and the etching time in the hydrochloric acid solution is controlled to be 12 hours. The others are the same as one of specific implementation one to five.

[0043] Specific implementation seven: the difference between this embodiment and one of specific implementation one to six is: the mass of the powder in step three of this embodiment is 0.5 gram. The others are the same as one of specific implementation one to six.

[0044] The following examples are used to verify the beneficial effects of the present application:

[0045] Example one:

[0046] I. Dissolve PVP in deionized water, stir thoroughly until mixed evenly, then add Zn(NO3)2·6H2O and H 24 Mo7N6O 24 ·4H2O, and stir evenly;

[0047] The mass of PVP in step one is 1 gram, the deionized water is 30 mL, the mass of Zn(NO3)2·6H2O is 0.5 gram, and the mass of H 24 Mo7N6O 24 ·4H2O is 0.2 gram;

[0048] II. The mixed solution obtained in step I is dried in an oven, and the obtained solid is ground into powder;

[0049] The oven temperature is 60℃, and the drying time is 24 hours;

[0050] III. The powder obtained in step II is placed in a porcelain boat and calcined at high temperature in a tube furnace to obtain a black foam product;

[0051] The heating rate is 5℃ / min, the calcination temperature is 700℃, the calcination time is 1 hour, and the protective gas is argon;

[0052] IV. The black foam product obtained in step III is etched in a hydrochloric acid solution, washed and dried to obtain the final product, i.e., the encapsulated ultra-small Mo2C particle three-dimensional porous carbon foam wave-absorbing material.

[0053] The concentration of the hydrochloric acid solution is 4 mol / L, the volume is 30 mL, and the stirring time in the hydrochloric acid solution is controlled to be 12 hours to ensure that the metal zinc is etched off.

[0054] The comparative sample is prepared by replacing H 24 Mo7N6O 24 with (NH4)2SO4 in step I, and the other conditions are the same as in Example I.

[0055] Figure 1 The scanning electron microscope picture and the transmission electron microscope picture of the encapsulated ultra-small Mo2C particle three-dimensional porous carbon foam wave-absorbing material prepared in Example I are shown in a and b. As can be seen from the a picture, the encapsulated ultra-small Mo2C particle three-dimensional porous carbon foam wave-absorbing material has a uniform three-dimensional porous structure. As can be seen from the b picture, the pore wall of the encapsulated ultra-small Mo2C particle three-dimensional porous carbon foam wave-absorbing material is very thin, and a large number of nanoparticles are uniformly dispersed thereon.

[0056] Figure 2 The high-resolution transmission picture of the encapsulated ultra-small Mo2C particle three-dimensional porous carbon foam wave-absorbing material prepared in Example I is shown in the figure. As can be seen from the figure, the nanoparticle lattice fringe in the encapsulated ultra-small Mo2C particle three-dimensional porous carbon foam wave-absorbing material is 0.24 nm, corresponding to the face-centered cubic phase Mo2C, and the particle size of the particle is ultra-small, about 10 nm.

[0057] Figure 3The XRD diagram of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles prepared in the embodiment one of the present application and the comparative sample, wherein curve a is the XRD of the comparative sample; curve b is the XRD of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles. As can be seen from the comparison with the X-ray standard card, the three-dimensional porous carbon foam material prepared in the embodiment one is mainly amorphous carbon and contains Mo2C particles, while the comparative sample is pure carbon material mainly containing amorphous carbon.

[0058] Figure 4 The mercury intrusion curve of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles prepared in the embodiment one of the present application, wherein a is the mercury intrusion / mercury extrusion curve; b is the pore size distribution diagram. The saturation pressure point of the mercury intrusion / mercury extrusion isotherm of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles prepared in the embodiment one is increased to above 1000 psia, and the saturation intrusion volume and the corresponding porosity are 5.3 mL / g and 89.0%, respectively. As can be inferred from the pore size distribution curve, the most possible distribution of the macropores in the three-dimensional porous carbon foam material prepared in the embodiment one is concentrated around 2.0 and 5.0 μm.

[0059] Figure 5 The real part of the dielectric constant of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles prepared in the embodiment one of the present application, wherein curve a is the real part of the dielectric constant of the comparative sample; curve b is the real part of the dielectric constant of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles. As can be seen from the diagram, both curves show typical dispersion effect and gradually decrease with the increase of frequency. The real part of the dielectric constant of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles is lower than that of the comparative sample, because the introduction of ultra-small Mo2C particles reduces the order degree of carbon atoms in the composite material.

[0060] Figure 6 The imaginary part of the dielectric constant of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles prepared in the embodiment one of the present application, wherein curve a is the imaginary part of the dielectric constant of the comparative sample; curve b is the imaginary part of the dielectric constant of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles. As can be seen from the diagram, the imaginary part of the dielectric constant of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles is lower than that of the comparative sample, because the introduction of ultra-small Mo2C particles reduces the electrical conductivity of the composite material.

[0061] Figure 7Cole-Cole circle diagrams of the packaged ultra-small Mo2C particle three-dimensional porous carbon foam wave-absorbing material prepared in Embodiment I and the comparative sample, a diagram is the Cole-Cole circle diagram of the packaged ultra-small Mo2C particle three-dimensional porous carbon foam wave-absorbing material, b diagram is the Cole-Cole circle diagram of the comparative sample. As can be seen from the diagram, there are four polarization relaxation processes in the Cole-Cole circle diagram of the packaged ultra-small Mo2C particle three-dimensional porous carbon foam wave-absorbing material and the comparative sample, while there are only two polarization relaxation processes in the comparative sample, which shows that the ultra-small Mo2C particles introduce more heterogeneous interfaces, enrich the loss mechanism, and are more conducive to the loss of electromagnetic waves.

[0062] Figure 8 Wave impedance curve diagrams of the packaged ultra-small Mo2C particle three-dimensional porous carbon foam wave-absorbing material prepared in Embodiment I and the comparative sample, a is the wave impedance curve of the packaged ultra-small Mo2C particle three-dimensional porous carbon foam wave-absorbing material; b is the wave impedance curve of the comparative sample. As can be seen from the diagram, the wave impedance value of the packaged ultra-small Mo2C particle three-dimensional porous carbon foam wave-absorbing material is higher than that of the comparative sample, which further shows that the introduction of ultra-small Mo2C particles can significantly improve the impedance matching.

[0063] Figure 9 Electromagnetic wave absorption performance diagrams of the packaged ultra-small Mo2C particle three-dimensional porous carbon foam wave-absorbing material prepared in Embodiment I, a diagram is a three-dimensional reflection loss diagram, b diagram is a two-dimensional reflection loss diagram; the minimum reflection loss value of the packaged ultra-small Mo2C particle three-dimensional porous carbon foam wave-absorbing material prepared in Embodiment I reaches-72.2 dB at 16.3 GHz, and its effective wave-absorbing bandwidth reaches 6.7 GHz (11.3-18.0 GHz), and the thickness is 2.3 mm; the range of its reflection loss less than-10 dB is 4.4-18.0 GHz, which shows excellent wave-absorbing performance.

[0064] The above is only a preferred embodiment of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed as above with a preferred embodiment, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the technical solution range of the present application, and make equivalent embodiments with equivalent changes. Any simple modification, equivalent replacement and improvement of the above embodiments within the technical solution content of the present application, in accordance with the technical essence of the present application, within the spirit and principles of the present application, are all within the protection scope of the present application technical solution.

Claims

1. A method for preparing a three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles, characterized in that: The preparation method of the three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles is realized through the following steps: Step one, PVP was dissolved in deionized water, stirred uniformly, to get a transparent solution, then Zn(NO3)2-6H2O and H 24 Mo7N6O 24 4H2O, fully stirred to mix evenly, the mixed solution obtained; Step two, the mixed solution obtained in step one is placed in an oven until it is dried, and the obtained solid is ground into powder; Step three, the powder obtained in step two is placed in a porcelain boat and high-temperature calcination is carried out in a tube furnace under argon atmosphere to obtain a black foam product; Step four, the product obtained in step three is placed in a hydrochloric acid solution and stirred, then washed with deionized water and anhydrous ethanol, and dried to obtain a three-dimensional porous carbon foam wave-absorbing material encapsulating ultra-small Mo2C particles.

2. The method for preparing a three-dimensional porous carbon foam microwave absorbing material encapsulating ultra-small Mo2C particles according to claim 1, characterized in that: The mass of PVP in step one is 0.5-1 gram, deionized water is 20-40 mL, Zn(NO3)2·6H2O is 0.3-0.6 gram, H 24 Mo7N6O 24 ·4H2O is 01-0.3 gram.

3. The method for preparing a three-dimensional porous carbon foam microwave absorbing material encapsulating ultra-small Mo2C particles according to claim 1, characterized in that: The stirring time in step one is 20-40 minutes.

4. The method for preparing a three-dimensional porous carbon foam microwave absorbing material encapsulating ultra-small Mo2C particles according to claim 1, characterized in that: The oven temperature in step two is 60℃, and the drying time is 24 hours.

5. The method for preparing a three-dimensional porous carbon foam microwave absorbing material encapsulating ultra-small Mo2C particles according to claim 1, characterized in that: The high-temperature calcination process in step three: control the heating rate to be 5℃ / min, the calcination temperature is 700℃, and the calcination time is 1 hour.

6. The method for preparing a three-dimensional porous carbon foam microwave absorbing material encapsulating ultra-small Mo2C particles according to claim 1, characterized in that: In step four, the concentration of the hydrochloric acid solution is 3-5mol / L, the volume of the hydrochloric acid solution is 20-50mL, and the etching time in the hydrochloric acid solution is controlled to be 12 hours.

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