CN110809395A - Magnetic carbon nanofiber aerogel wave-absorbing material and preparation method thereof - Google Patents
Magnetic carbon nanofiber aerogel wave-absorbing material and preparation method thereof Download PDFInfo
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- CN110809395A CN110809395A CN201911148529.7A CN201911148529A CN110809395A CN 110809395 A CN110809395 A CN 110809395A CN 201911148529 A CN201911148529 A CN 201911148529A CN 110809395 A CN110809395 A CN 110809395A
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Abstract
The invention discloses a magnetic carbon nanofiber aerogel wave-absorbing material, which comprises carbon nanofibers and magnetic nanoparticles, wherein the magnetic nanoparticles are dispersed on the carbon nanofibers, the carbon nanofibers are carbon nanofibers formed by pyrolysis of a biomass material, the fiber diameter of the carbon nanofibers is 30-50 nm, and the length-diameter ratio of the carbon nanofibers is 1000-3000, the magnetic carbon nanofiber aerogel wave-absorbing material provided by the invention has a high length-diameter ratio, a porous network structure constructed by staggered fibers is formed in the magnetic carbon nanofiber aerogel wave-absorbing material, the construction of a conductive network under low fillers is facilitated, the optimal wave-absorbing performance is obtained under the low fillers, meanwhile, the characteristics of light weight and flexibility are given to the magnetic carbon nanofiber wave-absorbing material by the porous aerogel structure constructed by the low fillers and the staggered fibers, the application value of the wave-absorbing material is improved, and strong interface polarization and magnetic loss are achieved at the same time, thereby facilitating the loss of the incident electromagnetic wave.
Description
Technical Field
The invention relates to the field of wave-absorbing materials, in particular to a magnetic carbon nanofiber aerogel wave-absorbing material and a preparation method thereof.
Background
With the development of science and technology and the electronic industry, the application of various electronic devices is gradually increased, and electromagnetic wave radiation has become a new social public nuisance. On one hand, radiated electromagnetic waves can affect the normal operation of surrounding electrical equipment and systems, and on the other hand, the physical and psychological health of people is seriously affected when the people are exposed to the electromagnetic wave radiation for a long time. The wave-absorbing material is increasingly prominent in the field of modern science and technology as an effective electromagnetic wave absorber. The basic requirement of the absorbing material is that the absorbing material has stronger absorbing capacity in a required absorbing wave band, and in addition, the light weight, the lower filling content and the special performance such as flexibility have very important practical values, especially in the aerospace industry, the military industry and the portable electronic industry.
Compared with the traditional microwave absorbing materials such as magnetic metal/oxide, conductive polymer and the like, the carbon material has the physical and chemical advantages of high conductivity, low density, excellent electrochemical stability and the like. In addition, many allotropes of carbon materials, including graphene, carbon nanotubes, porous carbon, and the like, have great potential in the design of high-efficiency electromagnetic absorbers. Currently, porous carbon prepared by pyrolysis of biomass is considered to be an ideal absorber. Porous carbon is a material with a naturally graded porous structure. Due to the presence of a large amount of air, the porous carbon has extremely low density, high specific surface area and low thermal conductivity. As a microwave absorbing material, the addition of high volume fraction of air can greatly increase the impedance match between the incident electromagnetic wave and the absorber, reducing the reflection of the electromagnetic wave on the carbon surface. Meanwhile, the air/carbon skeleton interface rich in the porous carbon improves the loss capacity of electromagnetic energy through strong interface polarization and medium relaxation.
However, in the existing composite wave-absorbing material using biomass material as raw material, during the preparation process, in the process of grinding the biomass material into powder, the natural three-dimensional network structure is destroyed to form short fibers or particles which are randomly and disorderly distributed, and although the surface adsorbs magnetic nanoparticles, the practical application of the composite wave-absorbing material is limited by the higher conductive threshold required for realizing excellent wave-absorbing performance. Meanwhile, for a common biomass material, porous carbon formed after carbonization is used for a wave-absorbing material, on one hand, a hierarchical porous structure is damaged due to physical grinding, interface polarization and related loss are not facilitated, and on the other hand, the porous carbon can obtain the best absorption performance only under the condition of high filling amount due to the lack of a microstructure with a high length-diameter ratio, so that the low-efficiency utilization of the filler is caused.
Disclosure of Invention
The invention aims to provide a magnetic carbon nanofiber aerogel wave-absorbing material and a preparation method thereof, which can provide a microstructure with a higher length-diameter ratio, are beneficial to the construction of a conductive network under low filler, obtain the best wave-absorbing performance under low filler, and simultaneously have strong interface polarization and magnetic loss, thereby being beneficial to the loss of incident electromagnetic waves.
In order to solve the problems, the technical scheme of the invention is as follows:
a magnetic carbon nanofiber aerogel wave-absorbing material comprises:
a carbon nanofiber; and
the magnetic nano particles are dispersed on the carbon nano fibers and are any one or more of iron, cobalt and nickel;
the carbon nanofiber is prepared by pyrolyzing a biomass material, the biomass material is bacterial cellulose, the fiber diameter of the carbon nanofiber is 30-50 nm, the length-diameter ratio of the carbon nanofiber is 1000-3000, and the density of the magnetic carbon nanofiber aerogel wave-absorbing material is 6-7 mg/cm3。
Preferably, the thickness of the bacterial cellulose is 5-20 mm, and the fiber diameter of the bacterial cellulose is 50-80 nm.
Preferably, the carbon nanofibers are composed of graphitized carbon, which has I in Raman spectrumD/IG0.6 to 0.9.
Preferably, the diameter of the magnetic nanoparticles is 4-20 nm.
Based on the same inventive concept, the invention also provides a preparation method of the magnetic carbon nanofiber aerogel wave-absorbing material, which comprises the following steps:
a1, obtaining a purified biomass material for preparing the magnetic carbon nanofiber aerogel wave-absorbing material in a solution treatment mode;
a2, adding the purified biomass material into a transition metal salt solution, and soaking for 24-72 hours to obtain a first precursor product, wherein the transition metal salt solution is any one salt solution or two or more salt solutions of nitrates and sulfates of iron, cobalt and nickel;
a3, carrying out freeze drying treatment on the first precursor product to obtain a second precursor product, wherein the freezing pressure is 0.5-2 Pa, the freezing temperature is-50 to-20 ℃, and the drying time is 48-96 hours;
a4, performing high-temperature carbonization treatment on the second precursor product to prepare the magnetic carbon nanofiber aerogel wave-absorbing material;
magnetic carbon nanofiber aerogel wave-absorbing material comprises carbon nanofibers and magnetic nanoparticles, wherein the magnetic nanoparticles are dispersed on the carbon nanofibers, the fiber diameter of the carbon nanofibers is 30-50 nm, the length-diameter ratio of the carbon nanofibers is 1000-3000, and the density of the magnetic carbon nanofiber aerogel wave-absorbing material is 6-7 mg/cm3。
Preferably, the step a1 further comprises:
a101, obtaining a first biological material, wherein the first biological material is bacterial cellulose;
a102, adding the first biomass material into a NaOH solution with the mass fraction of 1-2 wt%, carrying out first water bath heat preservation treatment, wherein the temperature of the first water bath is 80-100 ℃, the time of the first water bath is 1-3 h, carrying out first ultrasonic cleaning treatment after the water bath heat preservation treatment, and the time of the first ultrasonic cleaning treatment is 0.5-2 h, and repeating the steps twice to obtain a second biomass material;
a103, putting the second biomass material into an acetic acid solution with the mass fraction of 1-2 wt%, performing second water bath heat preservation treatment, wherein the temperature of the second water bath is 80-100 ℃, the time of the second water bath is 1-3 hours, performing second ultrasonic cleaning treatment after the water bath heat preservation treatment, and the time of the second ultrasonic cleaning treatment is 0.5-2 hours, and repeating the steps twice to obtain the purified biomass material.
Preferably, the thickness of the bacterial cellulose is 5-20 mm, and the fiber diameter of the bacterial cellulose is 50-80 nm.
Preferably, the concentration of the transition metal salt solution in the step A2 is 0.01-0.05 mol/L.
Preferably, the step a4 further comprises:
a401, putting the second precursor product into a vacuum furnace;
a402, filling inert gas into the vacuum furnace;
a403, heating the vacuum furnace for the first time at a first heating rate of 1-3 ℃/min, at a first heating temperature of 300-500 ℃ and for a first heat preservation time of 1-3 h;
a404, heating the vacuum furnace for the second time at a heating rate of 4-6 ℃/min, at a heating temperature of 600-900 ℃ for the second time, and at a heat preservation time of 1-3 h, so as to prepare the magnetic carbon nanofiber aerogel wave-absorbing material.
Preferably, the first temperature rising rate in the step 403 is 2 ℃/min, the first temperature rising temperature is 400 ℃, the first heat preservation time is 2h, the second temperature rising rate in the step 404 is 5 ℃/min, the second temperature rising temperature is 900 ℃, and the second heat preservation time is 2 h.
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages and positive effects:
1) the invention provides a magnetic carbon nanofiber aerogel wave-absorbing material, which comprises carbon nanofibers and magnetic nanoparticles, wherein the magnetic nanoparticles are dispersed on the carbon nanofibers, the carbon nanofibers are carbon nanofibers formed by pyrolysis of a biomass material, the fiber diameter of the carbon nanofibers is 30-50 nm, and the length-diameter ratio of the carbon nanofibers is 1000-3000, the magnetic carbon nanofiber aerogel wave-absorbing material provided by the invention has a high length-diameter ratio, a porous network structure constructed by staggered fibers is formed in the magnetic carbon nanofiber aerogel wave-absorbing material, the construction of a conductive network under low fillers is facilitated, the optimal wave-absorbing performance is obtained under the low fillers, meanwhile, the characteristics of light weight and flexibility are given to the magnetic carbon nanofiber wave-absorbing material by the porous network structure constructed by the low fillers and the staggered fibers, the application value of the wave-absorbing material is improved, and strong interface polarization and magnetic loss are achieved at the same time, thereby facilitating the loss of the incident electromagnetic wave.
2) The invention also provides a preparation method of the magnetic carbon nanofiber aerogel wave-absorbing material, by combining wet chemistry and high-temperature carbonization processes, the biomass material does not need to be ground into powder, then the nanofibers are naturally connected with each other in the graphitization process of the biomass material, the appearance of the ultra-long nanofibers can be well maintained, the magnetic carbon nanofiber aerogel wave-absorbing material with high length-diameter ratio is obtained, a porous network structure constructed by staggered fibers is formed in the magnetic carbon nanofiber aerogel wave-absorbing material, the construction of a conductive network constructed by the staggered fibers is facilitated, the optimal wave-absorbing performance is obtained under the low filler, the characteristics of light weight and flexibility are endowed to the magnetic carbon nanofiber aerogel wave-absorbing material by the porous network structure constructed by the low filler filling and the staggered fibers, the application value of the wave-absorbing material is improved, and meanwhile, the magnetic nanoparticles can play a role of catalyzing graphitization in the high-temperature reduction process, brings strong interface polarization and magnetic loss, and is beneficial to the loss of incident electromagnetic waves.
Drawings
Fig. 1 is a schematic view of a scanning electron microscope of a magnetic carbon nanofiber aerogel wave-absorbing material provided in an embodiment of the present invention;
fig. 2 is a schematic diagram of light weight characteristics of a magnetic carbon nanofiber aerogel wave-absorbing material provided in an embodiment of the present invention;
fig. 3 is a schematic raman spectrum of a magnetic carbon nanofiber aerogel wave-absorbing material provided in an embodiment of the present invention;
fig. 4 is a flowchart of a method for preparing a magnetic carbon nanofiber aerogel wave-absorbing material according to an embodiment of the present invention;
FIG. 5 is a detailed flowchart of step A1 in FIG. 4;
FIG. 6 is a detailed flowchart of step A4 in FIG. 4;
fig. 7 is a schematic diagram of a stress-strain curve of a magnetic carbon nanofiber aerogel wave-absorbing material according to an embodiment of the present invention;
fig. 8 is a schematic view of a reflection loss curve of the magnetic carbon nanofiber aerogel wave-absorbing material provided in the embodiment of the present invention.
Description of reference numerals:
1: a carbon nanofiber; 2: magnetic nanoparticles.
Detailed Description
The magnetic carbon nanofiber aerogel wave-absorbing material and the preparation method provided by the invention are further described in detail with reference to the accompanying drawings and specific embodiments. Advantages and features of the present invention will become apparent from the following description and from the claims.
Example one
Referring to fig. 1, fig. 1 is a schematic scanning electron microscope diagram of a magnetic carbon nanofiber aerogel wave-absorbing material provided by an embodiment of the present invention, and the present invention discloses a magnetic carbon nanofiber aerogel wave-absorbing material, which includes a carbon nanofiber 1 and magnetic nanoparticles 2, wherein the magnetic nanoparticles 2 are dispersed on the carbon nanofiber 1, the carbon nanofiber 1 is obtained by pyrolysis of a biomass material, the fiber diameter of the carbon nanofiber 1 is 30-50 nm, and the length-diameter ratio of the carbon nanofiber 1 is 1000-3000 Referring to the characteristic of flexibility, as shown in fig. 2, fig. 2 is a schematic diagram of light weight characteristics of a magnetic carbon nanofiber aerogel wave-absorbing material provided by an embodiment of the present invention, as can be seen from fig. 2, the aerogel wave-absorbing material provided by the present invention can stand on erigeron grass, which indicates that the mass of the aerogel wave-absorbing material is very light, the application value of the wave-absorbing material is improved, and the aerogel wave-absorbing material has strong interface polarization and magnetic loss, thereby facilitating the loss of incident electromagnetic waves.
Preferably, the density of the magnetic carbon nanofiber aerogel wave-absorbing material is 6-7 mg/cm3。
Preferably, the biomass material is bacterial cellulose with high length-diameter ratio nanofiber, so that the construction of a conductive network under low filler can be further facilitated, better wave-absorbing performance can be obtained under low filler, meanwhile, the quality of the wave-absorbing material can be reduced, the flexibility of the wave-absorbing material is improved, and the application value of the wave-absorbing material is further improved. In the embodiment, the thickness of the bacterial cellulose is 5-20 mm, and the fiber diameter of the bacterial cellulose is 50-80 nm.
Preferably, the carbon nanofiber 1 is made of highly graphitized carbon, as shown in fig. 3, fig. 3 is a schematic raman spectrum diagram of a magnetic carbon nanofiber aerogel wave-absorbing material provided in an embodiment of the present invention, where ID/IG0.6 to 0.9, and the presence of a 2D peak, demonstrating the high graphitization of the carbon nanofiber 1.
Preferably, the magnetic nanoparticles 2 are any one or more of iron, cobalt and nickel, and the introduced magnetic nanoparticles 2 can play a role in catalyzing graphitization in a high-temperature reduction process, bring strong interface polarization and magnetic loss, and contribute to loss of incident electromagnetic waves. The diameter of the magnetic nanoparticles 2 is 4 to 20 nm.
Example two
Based on the same inventive concept, referring to fig. 4, fig. 4 is a flowchart of a method for preparing a magnetic carbon nanofiber aerogel wave-absorbing material according to an embodiment of the present invention, and the present invention further provides a method for preparing a magnetic carbon nanofiber aerogel wave-absorbing material, including the following steps:
a1, obtaining a purified biomass material for preparing the magnetic carbon nanofiber aerogel wave-absorbing material in a solution treatment mode;
a2, adding the purified biomass material into a transition metal salt solution for soaking to obtain a first precursor product, wherein the soaking time is 24-72 hours, and preferably 48 hours. In the embodiment, the transition metal salt solution is any one salt solution or two or more salt solutions of nitrates and sulfates of iron, cobalt and nickel, the concentration of the transition metal salt solution is 0.01-0.05 mol/L, preferably 0.02mol/L, and the introduced magnetic nanoparticles can play a role in catalyzing graphitization in a high-temperature reduction process, bring strong interface polarization and magnetic loss, and are beneficial to loss of incident electromagnetic waves.
A3, performing freeze drying treatment on the first precursor product to obtain a second precursor product, wherein the freezing pressure is 0.5-2 Pa, preferably 1Pa, the freezing temperature is-50 to-20 ℃, preferably-35 ℃, and the drying time is 48-96 h, preferably 72 h.
A4, performing high-temperature carbonization treatment on the second precursor product to prepare the magnetic carbon nanofiber aerogel wave-absorbing material;
the prepared magnetic carbon nanofiber aerogel wave-absorbing material comprises carbon nanofibers and magnetic nanoparticles, wherein the magnetic nanoparticles are dispersed on the carbon nanofibers, the fiber diameter of the carbon nanofibers is 30-50 nm, and the length-diameter ratio of the carbon nanofibers is 1000-3000.
Preferably, referring to fig. 5, fig. 5 is a detailed flowchart of step a1 in fig. 4, and step a1 further includes:
a101, obtaining a first biomass material, preferably, the first biomass material is bacterial cellulose, the biomass material is selected from the bacterial cellulose with nanofiber with high length-diameter ratio, the construction of a conductive network under low filler can be further facilitated, better wave-absorbing performance can be obtained under low filler, meanwhile, the quality of the wave-absorbing material can be reduced, the flexibility of the wave-absorbing material is improved, and the application value of the wave-absorbing material is further improved. The thickness of the selected bacterial cellulose is 5-20 mm, and the fiber diameter of the bacterial cellulose is 50-80 nm;
a102, adding a first biomass material into a NaOH solution with the mass fraction of 1-2 wt%, carrying out first water bath heat preservation treatment, wherein the temperature of the first water bath is 80-100 ℃, the time of the first water bath is 1-3 h, carrying out first ultrasonic cleaning treatment after the water bath heat preservation treatment, and the time of the first ultrasonic cleaning treatment is 0.5-2 h, and repeating the steps twice to obtain a second biomass material. In the embodiment, the mass fraction of the NaOH solution is preferably 1.94 wt%, the first water bath temperature is preferably 100 ℃, the first water bath time is preferably 2 hours, and the first ultrasonic cleaning treatment time is preferably 1 hour;
a103, putting a second biomass material into an acetic acid solution with the mass fraction of 1-2 wt%, carrying out second water bath heat preservation treatment, wherein the temperature of the second water bath is 80-100 ℃, the time of the second water bath is 1-3 h, carrying out second ultrasonic cleaning treatment after the water bath heat preservation treatment, and the time of the second ultrasonic cleaning treatment is 0.5-2 h, and repeating the steps twice to obtain the purified biomass material. In the embodiment, the mass fraction of the acetic acid solution is preferably 1.5 wt%, the second water bath temperature is preferably 100 ℃, the second water bath time is preferably 2h, and the second ultrasonic cleaning treatment time is preferably 1 h. .
Preferably, referring to fig. 6, fig. 6 is a detailed flowchart of step a4 in fig. 4, and step a4 further includes:
a401, putting a second precursor product into a vacuum furnace;
a402, filling inert gas into the vacuum furnace, wherein in the embodiment, the inert gas is preferably nitrogen or argon;
a403, heating the vacuum furnace for the first time at a first heating rate of 1-3 ℃/min, at a first heating temperature of 300-500 ℃ and for a first heat preservation time of 1-3 h. In the embodiment, the first temperature rise rate is 2 ℃/min, the first temperature rise temperature is 400 ℃, and the first heat preservation time is 2 h;
a404, heating the vacuum furnace for the second time at a heating rate of 4-6 ℃/min, at a heating temperature of 600-900 ℃ for the second time, and keeping the temperature for 1-3 hours, thereby preparing the magnetic carbon nanofiber aerogel wave-absorbing material. In this example, the second temperature rise rate was 5 ℃/min, the second temperature rise temperature was 900 ℃, and the second heat retention time was 2 hours.
Preferably, the density of the magnetic carbon nanofiber aerogel wave-absorbing material is 6-7 mg/cm3。
Preferably, referring to fig. 3, the carbon nanofibers are composed of graphitized carbon, which has I in the raman spectrumD/IG0.6 to 0.9, and the presence of a 2D peak, demonstrating the high graphitization of the carbon nanofiber 1.
Preferably, the diameter of the magnetic nanoparticles is 4-20 nm.
EXAMPLE III
Based on the same inventive concept, the embodiment provides a specific preparation method of a magnetic carbon nanofiber aerogel wave-absorbing material, which comprises the following steps:
the method comprises the following steps: cutting bacterial cellulose with the thickness of 15mm into small pieces of 5cm x 3cm, putting the small pieces into NaOH solution with the mass fraction of 1.94 wt%, preserving the heat in a water bath kettle at the temperature of 100 ℃ for 2 hours, putting the small pieces into an ultrasonic cleaning machine for ultrasonic treatment for 1 hour, and repeatedly treating the small pieces twice by the method;
step two: putting the product obtained in the first step into an acetic acid solution with the mass fraction of 1.5 wt%, preserving the heat for 2 hours in a water bath kettle at the temperature of 100 ℃, putting the product into an ultrasonic cleaning machine for ultrasonic treatment for 1 hour, and repeating the treatment twice by the method;
step three: putting the purified bacterial cellulose obtained in the step two into 500mL of Ni (NO) with the volume fraction of 30 vol%3)2In solution, Ni (NO)3)2The concentration of the solution is 0.02mol/L, and the solution is soaked for 48 hours;
step four: putting the precursor obtained in the third step into a freeze dryer, and drying for 72 hours under the condition that the air pressure is 1 Pa;
step five: transferring the freeze-dried precursor aerogel in the fourth step to a vacuum tube furnace, heating to 400 ℃ at a speed of 2 ℃/min under the nitrogen atmosphere, preserving heat for 2 hours, then heating to 900 ℃ at a speed of 5 ℃/min, preserving heat for 2 hours, and cooling to room temperature to obtain the final product, namely the magnetic carbon nanofiber aerogel wave-absorbing material.
Example four
Based on the same inventive concept, the embodiment provides a specific preparation method of a magnetic carbon nanofiber aerogel wave-absorbing material, which comprises the following steps:
the method comprises the following steps: cutting bacterial cellulose with the thickness of 15mm into small pieces of 5cm x 3cm, putting the small pieces into NaOH solution with the mass fraction of 1.94 wt%, preserving the heat in a water bath kettle at the temperature of 100 ℃ for 2 hours, putting the small pieces into an ultrasonic cleaning machine for ultrasonic treatment for 1 hour, and repeatedly treating the small pieces twice by the method;
step two: putting the product obtained in the first step into an acetic acid solution with the mass fraction of 1.5 wt%, preserving the heat for 2 hours in a water bath kettle at the temperature of 100 ℃, putting the product into an ultrasonic cleaning machine for ultrasonic treatment for 1 hour, and repeating the treatment twice by the method;
step three: placing the purified bacterial cellulose obtained in the step two into 500mL of Co (NO) with the volume fraction of 30 vol%3)2In solution, Co (NO)3)2The concentration of the solution is 0.02mol/L, and the solution is soaked for 48 hours;
step four: putting the precursor obtained in the third step into a freeze dryer, and drying for 72 hours under the condition that the air pressure is 1 Pa;
step five: transferring the freeze-dried precursor aerogel in the fourth step to a vacuum tube furnace, heating to 400 ℃ at a speed of 2 ℃/min under the nitrogen atmosphere, preserving heat for 2 hours, then heating to 900 ℃ at a speed of 5 ℃/min, preserving heat for 2 hours, and cooling to room temperature to obtain the final product, namely the magnetic carbon nanofiber aerogel wave-absorbing material.
EXAMPLE five
Based on the same inventive concept, the embodiment provides a specific preparation method of a magnetic carbon nanofiber aerogel wave-absorbing material, which comprises the following steps:
the method comprises the following steps: cutting bacterial cellulose with the thickness of 15mm into small pieces of 5cm x 3cm, putting the small pieces into NaOH solution with the mass fraction of 1.94 wt%, preserving the heat in a water bath kettle at the temperature of 100 ℃ for 2 hours, putting the small pieces into an ultrasonic cleaning machine for ultrasonic treatment for 1 hour, and repeatedly treating the small pieces twice by the method;
step two: putting the product obtained in the first step into an acetic acid solution with the mass fraction of 1.5 wt%, preserving the heat for 2 hours in a water bath kettle at the temperature of 100 ℃, putting the product into an ultrasonic cleaning machine for ultrasonic treatment for 1 hour, and repeating the treatment twice by the method;
step three: putting the purified bacterial cellulose obtained in the step two into 500mL of Fe (NO) with the volume fraction of 30 vol%3)3In solution, Fe (NO)3)3The concentration of the solution is 0.02mol/L, and the solution is soaked for 48 hours;
step four: putting the precursor obtained in the third step into a freeze dryer, and drying for 72 hours under the condition that the air pressure is 1 Pa;
step five: transferring the freeze-dried precursor aerogel in the fourth step to a vacuum tube furnace, heating to 400 ℃ at a speed of 2 ℃/min under the nitrogen atmosphere, preserving heat for 2 hours, then heating to 900 ℃ at a speed of 5 ℃/min, preserving heat for 2 hours, and cooling to room temperature to obtain the final product, namely the magnetic carbon nanofiber aerogel wave-absorbing material.
Various performance tests are carried out on the magnetic carbon nanofiber aerogel wave-absorbing material obtained by the preparation method according to the embodiment, and as shown in figure 2, the magnetic carbon nanofiber aerogel wave-absorbing material can stand on erigeron sieboldii, so that the aim of light weight is fulfilled; referring to fig. 3, the prepared magnetic carbon nanofiber aerogel wave-absorbing material is subjected to raman spectrum test, and as can be seen from the graph, ID/IG0.62, and the presence of a 2D peak, demonstrating highly graphitized carbon nanofibers; referring to fig. 7, fig. 7 is a schematic diagram of a stress-strain curve of a magnetic carbon nanofiber aerogel wave-absorbing material provided in an embodiment of the present invention, and it can be seen from fig. 7 that the wave-absorbing material still maintains excellent mechanical properties after 200 cycles of compression deformation, so as to achieve the purpose of flexibility; referring to fig. 1, it can be seen from fig. 1 that the carbon nanofibers 1 have a fine nano-network structure while the magnetic nanoparticles 2 are uniformly distributed on the carbon nanofibers; referring to fig. 8, fig. 8 is a schematic view of a reflection loss curve of a magnetic carbon nanofiber aerogel wave-absorbing material according to an embodiment of the present invention, and in order to verify the wave-absorbing performance of the magnetic carbon nanofiber aerogel wave-absorbing material obtained in the present invention, a piece of 0.1g of the magnetic carbon nanofiber aerogel wave-absorbing material is placed in the wave-absorbing materialPutting into molten paraffin, taking out after paraffin is saturated, naturally solidifying at room temperature, cutting a partially solidified composite sample, and preparing a wave-absorbing test ring (inner diameter: 3mm, outer diameter: 7mm, height: 2mm) by using a mould. Through testing, when the carbonization temperature is fixed at 900 ℃, as can be seen from fig. 8, the magnetic carbon nanofiber aerogel wave-absorbing material shows excellent electromagnetic wave absorption capability, i.e. the effective absorption band is 3.95GHz (reflection loss < -10dB) with the minimum reflection loss of-52 dB at a thickness of 3.5mm and a wave-absorbing agent filling content of only 0.8 wt%.
The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, it is still within the scope of the present invention if they fall within the scope of the claims of the present invention and their equivalents.
Claims (10)
1. A magnetic carbon nanofiber aerogel wave-absorbing material is characterized by comprising:
a carbon nanofiber; and
the magnetic nano particles are dispersed on the carbon nano fibers and are any one or more of iron, cobalt and nickel;
the carbon nanofiber is prepared by pyrolyzing a biomass material, the biomass material is bacterial cellulose, the fiber diameter of the carbon nanofiber is 30-50 nm, the length-diameter ratio of the carbon nanofiber is 1000-3000, and the density of the magnetic carbon nanofiber aerogel wave-absorbing material is 6-7 mg/cm3。
2. The magnetic carbon nanofiber aerogel wave-absorbing material as claimed in claim 1, wherein the thickness of the bacterial cellulose is 5-20 mm, and the fiber diameter of the bacterial cellulose is 50-80 nm.
3. The magnetic carbon nanofiber aerogel wave-absorbing material as claimed in claim 1, wherein the magnetic carbon nanofiber aerogel wave-absorbing material is characterized in thatThen, the carbon nanofibers are composed of graphitized carbon, which has I in Raman spectrumD/IG0.6 to 0.9.
4. The magnetic carbon nanofiber aerogel wave-absorbing material as claimed in claim 1, wherein the diameter of the magnetic nanoparticles is 4-20 nm.
5. A preparation method of a magnetic carbon nanofiber aerogel wave-absorbing material is characterized by comprising the following steps:
a1, obtaining a purified biomass material for preparing the magnetic carbon nanofiber aerogel wave-absorbing material in a solution treatment mode;
a2, adding the purified biomass material into a transition metal salt solution, and soaking for 24-72 hours to obtain a first precursor product, wherein the transition metal salt solution is any one salt solution or two or more salt solutions of nitrates and sulfates of iron, cobalt and nickel;
a3, carrying out freeze drying treatment on the first precursor product to obtain a second precursor product, wherein the freezing pressure is 0.5-2 Pa, the freezing temperature is-50 to-20 ℃, and the drying time is 48-96 hours;
a4, performing high-temperature carbonization treatment on the second precursor product to prepare the magnetic carbon nanofiber aerogel wave-absorbing material;
magnetic carbon nanofiber aerogel wave-absorbing material comprises carbon nanofibers and magnetic nanoparticles, wherein the magnetic nanoparticles are dispersed on the carbon nanofibers, the fiber diameter of the carbon nanofibers is 30-50 nm, the length-diameter ratio of the carbon nanofibers is 1000-3000, and the density of the magnetic carbon nanofiber aerogel wave-absorbing material is 6-7 mg/cm3。
6. The preparation method of the magnetic carbon nanofiber aerogel wave-absorbing material according to claim 5, wherein the step A1 further comprises:
a101, obtaining a first biological material, wherein the first biological material is bacterial cellulose;
a102, adding the first biomass material into a NaOH solution with the mass fraction of 1-2 wt%, carrying out first water bath heat preservation treatment, wherein the temperature of the first water bath is 80-100 ℃, the time of the first water bath is 1-3 h, carrying out first ultrasonic cleaning treatment after the water bath heat preservation treatment, and the time of the first ultrasonic cleaning treatment is 0.5-2 h, and repeating the steps twice to obtain a second biomass material;
a103, putting the second biomass material into an acetic acid solution with the mass fraction of 1-2 wt%, performing second water bath heat preservation treatment, wherein the temperature of the second water bath is 80-100 ℃, the time of the second water bath is 1-3 hours, performing second ultrasonic cleaning treatment after the water bath heat preservation treatment, and the time of the second ultrasonic cleaning treatment is 0.5-2 hours, and repeating the steps twice to obtain the purified biomass material.
7. The preparation method of the magnetic carbon nanofiber aerogel wave-absorbing material according to claim 6, wherein the thickness of the bacterial cellulose is 5-20 mm, and the fiber diameter of the bacterial cellulose is 50-80 nm.
8. The preparation method of the magnetic carbon nanofiber aerogel wave-absorbing material according to claim 5, wherein the concentration of the transition metal salt solution in the step A2 is 0.01-0.05 mol/L.
9. The preparation method of the magnetic carbon nanofiber aerogel wave-absorbing material according to claim 5, wherein the step A4 further comprises:
a401, putting the second precursor product into a vacuum furnace;
a402, filling inert gas into the vacuum furnace;
a403, heating the vacuum furnace for the first time at a first heating rate of 1-3 ℃/min, at a first heating temperature of 300-500 ℃ and for a first heat preservation time of 1-3 h;
a404, heating the vacuum furnace for the second time at a heating rate of 4-6 ℃/min, at a heating temperature of 600-900 ℃ for the second time, and at a heat preservation time of 1-3 h, so as to prepare the magnetic carbon nanofiber aerogel wave-absorbing material.
10. The method for preparing the magnetic carbon nanofiber aerogel wave-absorbing material according to claim 9, wherein the first temperature rise rate in the step 403 is 2 ℃/min, the first temperature rise temperature is 400 ℃, the first heat preservation time is 2 hours, the second temperature rise rate in the step 404 is 5 ℃/min, the second temperature rise temperature is 900 ℃, and the second heat preservation time is 2 hours.
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