CN114656281B - Preparation method of carbonized cotton cellulose aerogel electromagnetic wave-absorbing material - Google Patents
Preparation method of carbonized cotton cellulose aerogel electromagnetic wave-absorbing material Download PDFInfo
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Abstract
The invention discloses a preparation method of carbonized cotton cellulose aerogel electromagnetic wave-absorbing material, which uses cotton cellulose as a carbon source, firstly mixes cotton cellulose with a foaming agent to obtain a foaming solution, and then uses a freeze-drying method to obtain a three-dimensional network carbon skeleton; finally, a three-dimensional network carbon skeleton with micropores and mesopores is prepared by utilizing a high-temperature pyrolysis reaction. The method adopts renewable cotton cellulose and a foaming agent to form foaming solution, and uses freeze drying to form a three-dimensional network framework; obtaining porous carbon with rich surfaces of the three-dimensional network skeleton by utilizing a high-temperature pyrolysis reaction; with the increase of the heat treatment temperature, the pore canal structure is increased, the porosity is increased, the density is reduced, and the filling degree is reduced, the carbonized aerogel electromagnetic wave-absorbing material prepared by the preparation method still has a wide effective absorption frequency band below the thickness of 2mm, thereby realizing the preparation of the lightweight high-efficiency electromagnetic wave-absorbing material; the raw materials used in the preparation method can be regenerated, are easy to degrade, have low cost and are suitable for large-scale industrial production.
Description
Technical Field
The invention relates to a preparation method of carbonized cotton cellulose aerogel electromagnetic wave-absorbing material.
Background
With the rapid development of electronic technology, harmful electromagnetic waves, particularly electromagnetic waves in the GHz band, cause serious radiation and interference to human health and normal operation of electronic equipment. Carbon materials are considered as promising electromagnetic wave-absorbing candidate materials because of the advantages of low density, higher complex dielectric constant, good environmental stability and the like. Unfortunately, the higher complex dielectric constant tends to cause impedance mismatch of the carbon material, thus limiting its use as a microwave absorbing material. Therefore, the introduction of porous structures to lower their high complex dielectric constants is highly desirable in order to balance the impedance matching of carbon materials.
In recent years, the carbonized aerogel material has excellent electromagnetic properties and can be applied to electromagnetic wave-absorbing materials. For example, liu Panbo teaching subject group of university of northwest industry chemical industry, namely chemical industry, uses rigid organic polymer aerogel as raw material, synthesizes N-doped porous carbon aerogel by a gelatin method, and can reach the maximum reflectivity of-61.7 dB at the thickness of 2.6 mm. (P.B.Liu, S.Gao, C.Chen, F.T.Zhou, Z.Y.Meng, Y.Huang, Y.Wang, organic polymer aerogel derived N-doped carbon aerogel with vacancies for ultrahigh microwave absorption. Carbon,2020,169,276-287). The Yan Dingxiang teaching subject group of the university of Sichuan high molecular science and engineering college develops the high-efficiency carbon nano tube aerogel, the maximum reflectivity can reach-43.6 dB under the thickness of 3.0mm, and the frequency bandwidth can reach 7.42GHz. (Y.Y.Wang, Z.H.Zhou, J.L.Zhu, W.J.Sun, D.X.Yan, K.Dai, Z.M.Li, low-temperature carbonized carbon nanotube/cellulose aerogel for efficient microwave absorption. Composition. Part B Eng.,2021,220,108985). However, the method cannot produce carbonized aerogel electromagnetic wave-absorbing materials with good electromagnetic wave-absorbing performance under the conditions of low filling degree (20-30 w%) and low thickness (below 2 mm).
Disclosure of Invention
The invention aims to: the invention aims to provide a preparation method of carbonized cotton cellulose aerogel electromagnetic wave-absorbing material, which can meet good electromagnetic wave-absorbing performance under the conditions of low filling degree (20-30wt%) and low thickness (less than 2 mm).
The technical scheme is as follows: the invention relates to a preparation method of carbonized cotton cellulose aerogel electromagnetic wave-absorbing material, which comprises the steps of taking cotton cellulose as a carbon source, mixing the cotton cellulose with a foaming agent to obtain a foaming solution, and obtaining a three-dimensional network carbon skeleton by a freeze drying method; finally, a three-dimensional network carbon skeleton with micropores and mesopores is prepared by utilizing a high-temperature pyrolysis reaction.
The preparation method of the carbonized cotton cellulose aerogel electromagnetic wave-absorbing material specifically comprises the following steps:
(1) Adding cotton cellulose and sodium dodecyl sulfate (foaming agent) into deionized water, and stirring to form a foam solution;
(2) Placing the foam solution obtained in the step (1) into a mold, and freeze-drying;
(3) Calcining the product after vacuum freeze drying under nitrogen atmosphere to obtain the required product.
Wherein in the step (1), the adding mass ratio of the sodium dodecyl sulfate to the cotton cellulose is 1:2.
in the step (1), the rotating speed in the stirring process is 3500r/min, and the stirring time is 10min.
In the step (2), the foam solution is pre-frozen to freeze the solution, and freeze drying is carried out after the solution is frozen, wherein the freezing temperature is-50 to-60 ℃.
Wherein, the pre-freezing time is 6 hours, and the freeze drying time is 48 hours.
Wherein in the step (3), the calcining temperature is 500-900 ℃ and the heat preservation time is 1h; the calcination temperature rise rate is 2 ℃/min.
The beneficial effects are that: the method adopts renewable cotton cellulose and a foaming agent to form foaming solution, and uses freeze drying to form a three-dimensional network framework; obtaining porous carbon with rich surfaces of the three-dimensional network skeleton by utilizing a high-temperature pyrolysis reaction; with the increase of the heat treatment temperature, the pore canal structure is increased, the porosity is increased, the density is reduced, and the filling degree is reduced, the carbonized aerogel electromagnetic wave-absorbing material prepared by the preparation method still has a wide effective absorption band and stronger reflection loss under the filling degree of 30 weight percent and the thickness of less than 2mm, thereby realizing the preparation of the lightweight high-efficiency electromagnetic wave-absorbing material; the raw materials used in the preparation method can be regenerated, are easy to degrade, have low cost and are suitable for large-scale industrial production.
Drawings
FIG. 1 is an X-ray diffraction pattern of the carbonized cotton cellulose aerogel prepared in examples 1,2, and 3;
FIG. 2 is a Raman spectrum diagram of the carbonized cotton cellulose aerogel prepared in examples 1,2, and 3;
FIG. 3 is a graph showing isothermal adsorption and desorption of nitrogen gas from the carbonized cotton cellulose aerogel prepared in example 1;
FIG. 4 is a graph showing isothermal adsorption and desorption of nitrogen gas from the carbonized cotton cellulose aerogel prepared in example 2;
FIG. 5 is a graph showing isothermal adsorption and desorption of nitrogen gas from the carbonized cotton cellulose aerogel prepared in example 3;
FIG. 6 is an SEM image of a carbonized cotton cellulose aerogel produced in example 1;
FIG. 7 is an SEM image of a carbonized cotton cellulose aerogel produced in example 2;
FIG. 8 is an SEM image of a carbonized cotton cellulose aerogel produced in example 3;
FIG. 9 is a graph showing the reflection loss of the carbonized cotton cellulose aerogel produced in example 1;
FIG. 10 is a graph showing the reflection loss of the carbonized cotton cellulose aerogel produced in example 2;
FIG. 11 is a graph showing the reflection loss of the carbonized cotton cellulose aerogel produced in example 3.
Detailed Description
The technical scheme of the invention is further described below with reference to the attached drawings and specific embodiments.
Example 1
The invention relates to a preparation method of carbonized cotton cellulose aerogel electromagnetic wave-absorbing material, which specifically comprises the following steps:
(1) Adding 0.8g of cotton cellulose and 0.4g of sodium dodecyl sulfate into 200mL of deionized water, setting the mechanical stirring rotation speed to 3500r/min, and stirring for 10min to form a uniform foam solution; the stirring speed is too high, and the solution is easy to splash in the stirring process;
(2) Placing the foam solution obtained in the step (1) into a mould, pre-freezing for 6 hours at the temperature of minus 60 ℃ in a freeze dryer, and then re-freeze drying for 48 hours;
(3) And (3) placing the compound obtained in the step (2) into a tube furnace, calcining for 1h at 500 ℃ under nitrogen, and obtaining a product, wherein the heating rate is 2 ℃/min, and the marked product is S1. The porosity of the product S1 was 98.7%.
Example 2
The invention relates to a preparation method of carbonized cotton cellulose aerogel electromagnetic wave-absorbing material, which specifically comprises the following steps:
(1) Adding 0.8g of cotton cellulose and 0.4g of sodium dodecyl sulfate into 200mL of deionized water, setting the mechanical stirring rotation speed to 3500r/min, and stirring for 10min to form a uniform foam solution; the stirring speed is too high, and the solution is easy to splash in the stirring process;
(2) Placing the foam solution obtained in the step (1) into a mould, pre-freezing for 6 hours at the temperature of minus 60 ℃ in a freeze dryer, and then re-freeze drying for 48 hours;
(3) And (3) placing the compound obtained in the step (2) into a tube furnace, calcining for 1h at 700 ℃ under nitrogen, and obtaining a product, wherein the heating rate is 2 ℃/min, and the marked product is S2. The product S2 porosity was 99.1%.
Example 3
The invention relates to a preparation method of carbonized cotton cellulose aerogel electromagnetic wave-absorbing material, which specifically comprises the following steps:
(1) Adding 0.8g of cotton cellulose and 0.4g of sodium dodecyl sulfate into 200mL of deionized water, setting the mechanical stirring rotation speed to 3500r/min, and stirring for 10min to form a uniform foam solution; the stirring speed is too high, and the solution is easy to splash in the stirring process;
(2) Placing the foam solution obtained in the step (1) into a mould, pre-freezing for 6 hours at the temperature of minus 60 ℃ in a freeze dryer, and then re-freeze drying for 48 hours;
(3) And (3) placing the compound obtained in the step (2) into a tube furnace, calcining for 1h at 900 ℃ under nitrogen, and obtaining a product, wherein the heating rate is 2 ℃/min, and the marked product is S3. The product S3 porosity was 99.5%.
FIG. 1 is an X-ray diffraction pattern of the carbonized cotton cellulose aerogel prepared in examples 1,2, and 3, and it is apparent from FIG. 1 that examples 1,2, and 3 have similar diffraction peaks, and that the diffraction peak of 21℃carbon is apparent.
FIG. 2 is a Raman spectrum of the carbonized cotton cellulose aerogel prepared in examples 1,2 and 3, and it can be seen from FIG. 2 that the products prepared in examples 1,2 and 3 all have a certain graphitization tendency, and the graphitization degree of the product prepared in example 3 is highest with the increase of the calcination temperature.
Fig. 3, 4 and 5 are graphs of isothermal adsorption and desorption of nitrogen gas of the carbonized cotton cellulose aerogel prepared in examples 1,2 and 3, respectively, and it can be seen from fig. 3 to 5 that as the calcination temperature increases, the specific surface area of the carbonized cotton cellulose aerogel is larger and larger, and the porosity is larger and larger, so that the density of the material is lower and lower.
Fig. 6, 7 and 8 are SEM images of the carbonized cotton cellulose aerogel prepared in examples 1,2 and 3, and as can be seen from fig. 6 to 8, the products prepared in examples 1,2 and 3 all show a three-dimensional porous network structure which is mutually entangled and connected, the curling degree of the carbonized cotton cellulose aerogel is gradually increased along with the increase of the calcination temperature, and the surface of the carbonized cotton cellulose aerogel is obviously roughened by the mesoporous structure, so that the electromagnetic wave absorption effect of the carbonized cotton cellulose aerogel is improved, and the lightweight and efficient electromagnetic wave absorbing material is prepared by using the carbonized cotton cellulose aerogel.
FIGS. 9, 10 and 11 are reflection loss diagrams of the carbonized cotton cellulose aerogels prepared in examples 1,2 and 3, and it can be seen from FIGS. 9 to 11 that S2 shows excellent electromagnetic absorption performance, the carbonized cotton cellulose aerogels prepared in examples 1,2 and 3 are mixed with paraffin wax, the filling degree of the carbonized cotton cellulose aerogel is 30wt%, the maximum effective absorption frequency bandwidth is 4.64GHz (11.48-16.12 GHz) when the matching thickness is 1.6mm, and the maximum reflection loss can reach-19.48 dB when the frequency is 10.36GHz when the matching thickness is 2.0 mm. Therefore, the carbonized cotton cellulose aerogel S2 has wider absorption band and stronger reflection loss under the conditions of low thickness and low filling degree. Whereas the electromagnetic absorption properties of S1 and S3 are inferior to those of S2. As can be seen from the examples 1,2 and 3, the density of the material is greatly reduced due to the increase of the mesoporous structure in the heat treatment process along with the increase of the calcination temperature, the lower the mesoporous number is, the lower the material density is, and the lower the filling degree is, but the too large the hole number is, the absorption of electromagnetic waves is not facilitated, and instead, the electromagnetic waves directly penetrate the material, rather than repeatedly refracting and dissipating in the material.
The method of the invention utilizes a foaming method to prepare foam solution of cotton cellulose and foaming agent, obtains a macroscopic three-dimensional porous structure through a subsequent freeze drying method, and obtains a microscopic mesoporous structure with more abundant pores through further high-temperature treatment, and the three-dimensional porous carbon structure with micropores and mesopores has strong dielectric loss capacity, is beneficial to realizing the absorption and loss of electromagnetic waves, and can lead the electromagnetic waves to be further reflected and refracted in the material to be lost.
Claims (1)
1. The preparation method of the carbonized cotton cellulose aerogel electromagnetic wave-absorbing material is characterized by comprising the following steps of:
(1) Adding 0.8g of cotton cellulose and 0.4g of sodium dodecyl sulfate into 200mL of deionized water, setting the mechanical stirring rotation speed to 3500r/min, and stirring for 10min to form a uniform foam solution; the stirring speed is too high, and the solution is easy to splash in the stirring process;
(2) Placing the foam solution obtained in the step (1) into a mould, pre-freezing for 6 hours at the temperature of minus 60 ℃ in a freeze dryer, and then re-freeze drying for 48 hours;
(3) Placing the compound obtained in the step (2) into a tube furnace, calcining for 1h at 700 ℃ under nitrogen, wherein the heating rate is 2 ℃/min, and obtaining a product, and the marked product is S2; the porosity of the product S2 is 99.1%;
the maximum effective absorption bandwidth is 4.64GHz when the matching thickness is 1.6mm, and the maximum reflection loss can reach-19.48 dB when the frequency is 10.36GHz when the matching thickness is 2.0 mm.
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| CN106513027B (en) * | 2016-09-30 | 2019-01-29 | 浙江理工大学 | A kind of three-dimensional porous g-C based on cellulose3N4/ C aeroge and preparation method thereof |
| CN110642590B (en) * | 2019-11-01 | 2022-02-01 | 江苏集萃先进高分子材料研究所有限公司 | Preparation method of super-hydrophobic and high-absorption electromagnetic shielding cellulose-based composite carbon aerogel |
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