Preparation method of modified nanocellulose / graphene wave-absorbing aerogel
By employing a dual oxidation method and amino hyperbranched polymers, the problem of weak bonding between nanocellulose and graphene composite materials was solved, resulting in the preparation of modified nanocellulose/graphene microwave absorbing aerogels with high microwave absorption properties. This simplified the preparation process and reduced costs.
Patent Information
- Application Number
- CN202511224709.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-29
- Publication Date
- 2025-12-12
AI Technical Summary
In existing technologies, the preparation of nanocellulose and graphene composite materials suffers from graphene agglomeration and impedance mismatch, resulting in weak bonding, affecting microwave absorption performance and durability. Furthermore, the preparation process is complex and costly.
Modified nanocellulose powder was prepared by a dual oxidation method, and then mixed with graphene oxide by end-amino hyperbranched polymers to form modified nanocellulose/graphene microwave absorbing aerogel. Graphene was firmly loaded onto cellulose by hydrogen bonding and electrostatic adsorption, forming a three-dimensional porous network structure.
It achieves a strong bond between graphene and cellulose, improving the microwave absorption performance, the compatibility and durability of the microwave absorption material, and is simple to operate, low in cost, and has excellent microwave absorption performance.
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Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the technical field of functional materials, in particular to a preparation method of modified nanocellulose / graphene wave-absorbing aerogel. BACKGROUND
[0002] With the rapid development of modern science and technology and information technology, electronic equipment and communication facilities are widely used in military and civilian fields, so that the human living environment is filled with a large amount of electromagnetic waves. Electromagnetic radiation pollution has become the “fourth pollution” threatening human health after air pollution, water pollution and noise pollution. In terms of human health, electromagnetic waves can interfere with natural physiological laws, cause symptoms such as headache and insomnia, and may damage immune function and affect the reproductive system, and even induce disease. In the industrial and scientific research fields, electromagnetic radiation of different frequencies and intensities can interfere with the normal operation of electronic instruments and hinder the precise transmission of information by communication facilities. In the field of national defense and military, electromagnetic waves are the core carriers of radar detection, electromagnetic pulse attack and electronic communication. How to avoid radar reconnaissance, resist electromagnetic pulses and ensure communication security is directly related to national military security. Therefore, the development of high-performance wave-absorbing materials has become a key issue in the field of material science.
[0003] As a derivative of natural polymer materials, nanocellulose retains the advantages of good biocompatibility, wide source and environmental friendliness. At the same time, due to the nanoscale effect, it has high specific surface area, high crystallinity and good mechanical properties. In the field of wave absorption, nanocellulose itself has no wave absorption ability, but its unique one-dimensional structure can be used as a composite substrate to build a porous network and provide a dispersion carrier for other wave-absorbing components. Researchers have tried to load magnetic nanoparticles on the surface of nanocellulose, and then mix with graphene oxide, reduce and freeze-thaw to prepare composite aerogel. However, this technology has obvious shortcomings. On the one hand, additional reducing agents need to be added during the preparation process, which increases the reaction steps and cost, and may introduce impurities affecting the wave absorption performance. On the other hand, the surface of graphene lacks active groups, and only physical mixing between nanocellulose and graphene can not form a firm combination, resulting in poor stability of graphene loading, easy to fall off during long-term use, affecting the structural integrity and wave absorption durability of the material. In addition, there are problems of dispersion and easy aggregation of graphene. Therefore, it is of great theoretical significance and practical value to develop a composite wave-absorbing material preparation technology with simple process, low cost, which can effectively solve the problems of graphene aggregation and impedance mismatch, and realize the firm combination of graphene and nanocellulose. SUMMARY
[0004] In view of the problems in the prior art, the application designs a preparation method of modified nanocellulose / graphene wave-absorbing aerogel, uses cotton fibers as raw materials, adopts a double oxidation method to prepare modified nanocellulose powder and oxidized graphene composite, and uses an end amino hyperbranched polymer (HBP-NH2) to reduce and prepare aerogel materials, so that the graphene agglomeration condition can be effectively avoided, the combination degree of graphene and cellulose can be improved, and excellent wave-absorbing performance can be obtained.
[0005] To achieve the above technical purposes, the application provides a preparation method of modified nanocellulose / graphene wave-absorbing aerogel, which comprises the following steps:
[0006] Step 1: cut and stir cellulose materials and disperse them in water, add sodium bromide, 2,2,6,6-tetramethylpiperidine oxide (TEMPO) solution and sodium hypochlorite solution in the dispersion liquid to perform an oxidation reaction, and obtain carboxyl-modified nanocellulose powder;
[0007] Step 2: the carboxyl-modified nanocellulose powder is further reacted with a high iodate aqueous solution to obtain modified nanocellulose powder;
[0008] Step 3: the modified nanocellulose water dispersion liquid is mixed with the oxidized graphene water dispersion liquid and a polyamino compound to prepare a modified nanocellulose / graphene dispersion liquid;
[0009] Step 4: the dispersion liquid is injected into a mold, and the modified nanocellulose / graphene wave-absorbing aerogel is obtained after freeze-drying.
[0010] In some technical solutions of the application, the cellulose materials include at least one of cotton fibers, wood pulp fibers, viscose fibers and Tencel fibers.
[0011] In some technical solutions of the application, the oxidation reaction preparation process in step 1 mainly includes: (1) the pH value of the reaction solution system is controlled to be 10-11 by adding appropriate sodium hydroxide, the reaction is continuously performed for 24 h, and the reaction is terminated by dropwise adding anhydrous ethanol after the pH value of the system remains unchanged; (2) the reaction liquid is treated by ultrasonic cell crushing for 10 min and then centrifuged, the lower sediment is washed by centrifugation with water and then filtered and washed with anhydrous ethanol, and the oxidation-modified nanocellulose powder is obtained after drying.
[0012] In some technical solutions of the application, the mass ratio of the cellulose materials to water in step 1 is 1: (70-90).
[0013] In some technical solutions of the application, the mass ratio of the cellulose materials to sodium bromide in step 1 is (9-11): 1.
[0014] In some technical solutions of the present application, the mass concentration of the TEMPO solution in step 1 is 0.07-0.09 g / mL, and the active chlorine content of the sodium hypochlorite aqueous solution is 6-14%.
[0015] In some technical solutions of the present application, the volume ratio of water, TEMPO solution and sodium hypochlorite in step 1 is (140-180):4:15.
[0016] In some technical solutions of the present application, the mass concentration of the high iodate aqueous solution in step 2 is 2-8 g / L, and the high iodate can further oxidize the carboxyl-modified nanocellulose to introduce more carbonyl and aldehyde structures.
[0017] In some technical solutions of the present application, the multi-amino compound in step 3 includes multi-amino hyperbranched polymers, polyamides and other nonlinear macromolecular polymers with a large number of amino groups on the surface.
[0018] In some technical solutions of the present application, the mass ratio of the multi-amino compound to nanocellulose in step 3 is 1:(20-30).
[0019] In some technical solutions of the present application, the mass ratio of graphene oxide to nanocellulose in step 3 is 1:(1-4).
[0020] In some technical solutions of the present application, the freeze-drying temperature in step 4 is -50--80℃, and the freeze-drying time is 24-48 h.
[0021] Compared with the prior art, the present application has the following beneficial effects:
[0022] 1. The present application solves the problem of poor combination of graphene and cellulose by double oxidation, and the modified cellulose filaments after double oxidation are entangled and crosslinked with each other to form thicker cellulose fiber bundles and sheet-like layers, and the cationic amino groups and aldehyde groups can reduce and oxidize graphene, and play a role in coating and dispersing graphene, at the same time, the synthesized graphene is coated with amino groups to be positively charged, and the cellulose surface contains a large number of hydroxyl groups to be negatively charged, which can firmly load graphene on cellulose through hydrogen bonding and electrostatic adsorption, inhibit the self-stacking of graphene layers, and form a three-dimensional porous network structure with graphene layers and cellulose, which is more conducive to the entry of electromagnetic waves into the material interior to produce multiple reflection and refraction and thus improve the absorption effect of electromagnetic waves.
[0023] 2. The modified nanocellulose / graphene wave-absorbing aerogel prepared by the present application has an RLmin of-43.6 dB and an effective absorption bandwidth of 2.02 GHz when the matching thickness is 2 mm.
[0024] 3. The application has simple experimental operation, mild reaction, safe and stable preparation process, easy implementation and low raw material cost. BRIEF DESCRIPTION OF DRAWINGS
[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.
[0026] Figure 1 : Aerogel morphology diagram of the embodiment and the comparative example of the present application;
[0027] Figure 2 : Three-dimensional reflection loss diagrams of Example 1-2 and Comparative Example 1-2 at different thicknesses and frequencies: (a) Comparative Example 2, (b) Comparative Example 1, (c) Example 1, (d) Example 2;
[0028] Figure 3 : Dielectric loss performance diagrams of the embodiment and the comparative example (a) Real part of complex dielectric constant, (b) Imaginary part of complex dielectric constant, (c) Dielectric loss factor, (d) Attenuation coefficient vs. frequency diagram DETAILED DESCRIPTION
[0029] The technical solutions in the present application will be described clearly and completely in combination with the embodiments in the present application. The described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.
[0030] Example 1
[0031] Step 1: 3.2 g TEMPO was weighed, heated and stirred and added to an appropriate amount of water to prepare a 40 mL solution, and a 0.5 mol / L NaOH solution was prepared. The experiment was carried out by weighing 4 g of cotton fiber pieces, stirring and dispersing in 300 mL of water, adding 0.4 g of NaBr and 8 mL of TEMPO solution, then adding 30 mL of NaClO solution, placing it on a magnetic stirrer for continuous stirring, and using a pH meter to detect the pH of the reaction system. As the reaction proceeds, the pH of the system gradually decreases, and an appropriate amount of NaOH solution is added to control the pH of the system at about 10.5. After continuous reaction for 24 h, the pH of the system remains basically unchanged, and the oxidation reaction can be considered to have been completed, and anhydrous ethanol is added to terminate the reaction. The above reaction liquid is treated with an ultrasonic cell disruptor for 10 min, then centrifuged at 9000 r / min for 7 min, the supernatant is removed, and the nanocellulose powder is obtained.
[0032] Step 2: A solution of potassium periodate was prepared, with a potassium periodate concentration of 4 g / L, and 2 g of cellulose powder was placed in 100 mL of the solution, and the reaction was carried out at 40°C for 30 min. After filtration and drying, the modified nanocellulose powder was obtained.
[0033] Step 3: An appropriate amount of modified nanocellulose powder was weighed, added to an appropriate amount of water, and dispersed with the aid of ultrasonic waves to obtain a 1 wt% dispersion. An appropriate amount of cellulose dispersion and graphene oxide dispersion, and amino hyperbranched polymer solution (concentration 10 g / L) were taken. The mass ratio of cellulose to graphene oxide was 4:1, and a constant temperature water bath magnetic stirrer was used for continuous stirring and heating for 2 h, with the temperature set to 100°C.
[0034] Step 4: Then the mixed liquid was injected into a 12-hole mold, placed in a refrigerator at -80°C for 24 h, and then placed in a freeze dryer for 48 h to obtain composite aerogels of different mass ratios.
[0035] Example 2
[0036] A method for preparing a modified nanocellulose / graphene wave-absorbing aerogel, comprising the following steps:
[0037] Step 1: 3.2 g TEMPO was weighed, heated and stirred and added to an appropriate amount of water to prepare a 40 mL solution, and a 0.5 mol / L NaOH solution was prepared. The experiment was carried out by weighing 4 g of cotton fiber pieces, stirring and dispersing them in 300 mL of water, adding 0.4 g of NaBr and 8 mL of TEMPO solution, and then adding 30 mL of NaClO solution. The reaction system was placed on a magnetic stirrer for continuous stirring, and a pH meter was used to detect the pH of the reaction system. As the reaction proceeded, the pH of the system gradually decreased, and an appropriate amount of NaOH solution was added to control the pH of the system at about 10.5. After continuous reaction for 24 h, the pH of the system remained basically unchanged, and the oxidation reaction could be considered to have been completed. Anhydrous ethanol was added to terminate the reaction. The above reaction liquid was treated with an ultrasonic cell disruptor for 10 min, and then centrifuged at 9000 r / min for 7 min. The supernatant was removed to obtain a nanocellulose powder.
[0038] Step 2: A solution of potassium periodate was prepared, with a potassium periodate concentration of 4 g / L. 2 g of cellulose powder was placed in 100 mL of the solution, and the reaction was carried out at 40°C for 30 min. After filtration and drying, a modified nanocellulose powder was obtained.
[0039] Step 3: An appropriate amount of modified nanocellulose powder was weighed, added to an appropriate amount of water, and dispersed with the aid of ultrasonic waves to obtain a 1 wt% dispersion. An appropriate amount of cellulose dispersion and graphene oxide dispersion, and an amino hyperbranched polymer solution (concentration of 10 g / L) were taken. The mass ratio of cellulose to graphene oxide was 7:3, and a constant temperature water bath magnetic stirrer was used for continuous stirring and heating for 2 h, with the temperature set to 100°C.
[0040] Step 4: The mixed solution was then injected into a 12-hole mold, placed in a refrigerator at -80°C for 24 h, and then placed in a freeze dryer for 48 h to obtain composite aerogels with different mass ratios.
[0041] Comparative Example 1: Compared with Example 1, the sample was not treated with potassium periodate.
[0042] Comparative Example 2: Compared with Example 1, the sample was not treated with an amino hyperbranched polymer.
[0043] Test experiments and results:
[0044] 1. Density and morphology test: The densities of the examples and comparative examples were tested, and it was found that the densities of Examples 1 and 2 were significantly lower than those of Comparative Examples 1 and 2.
[0045]
[0046] The morphology of the samples of the examples and comparative examples is shown in Figure 1As shown, the nanocellulose fibers of embodiments 1 and 2 can be seen to be interpenetrated between the graphene layers, forming a three-dimensional network structure that inhibits the self-stacking of the graphene layers to some extent.
[0047] 2. Absorption performance test analysis: Take appropriate aerogel samples to make powders, mix with paraffin at a mass ratio of 1:3, heat, and prepare into a certain specification of a circular ring sample. Use a network vector analyzer to test the absorption performance using a coaxial transmission line method, and the test frequency band is 2-18 GHz. The absorption performance is shown in the following table:
[0048]
[0049] It can be seen that the electromagnetic wave absorption capacity of the embodiments is enhanced, and the matching degree is similar, with minimum absorption peak values of 30.1 dB and -40.3 dB, respectively. The sample has a small reflection loss, indicating good electromagnetic wave absorption capacity. The two comparative examples have an absorption of less than 90% for incident electromagnetic waves, which is significantly weaker than the embodiments.
[0050] Figure 3 The dielectric loss performance of the embodiments and comparative examples is shown in the following table. It can be seen that the dielectric loss performance of the embodiments is better than that of the comparative examples.
[0051] Finally, it should be noted that: although the above has been described in detail with general description and specific embodiments, on the basis of the present application, the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.
Claims
1. A method for preparing a modified nanocellulose / graphene microwave absorbing aerogel, characterized in that, The method includes at least the following steps: Step 1: Chop the cellulose material into small pieces, stir and disperse it in water. Add sodium bromide, 2,2,6,6-tetramethylpiperidine oxide (TEMPO) solution and sodium hypochlorite solution to the dispersion to carry out an oxidation reaction, and obtain carboxyl-modified nanocellulose powder. Step 2: The carboxyl-modified nanocellulose powder is further reacted with periodate aqueous solution to obtain modified nanocellulose powder; Step 3: Mix the modified nanocellulose aqueous dispersion with the graphene oxide aqueous dispersion and the polyamine compound to prepare the modified nanocellulose / graphene dispersion. Step 4: The dispersion is injected into the mold and freeze-dried to obtain the modified nanocellulose / graphene microwave absorbing aerogel.
2. The preparation method according to claim 1, characterized in that, The cellulose material mentioned in step 1 includes at least one of cotton fiber, wood pulp fiber, viscose fiber, and Tencel fiber.
3. The preparation method according to claim 1, characterized in that, The oxidation reaction preparation process described in step 1 mainly includes: (1) controlling the pH value of the reaction solution system at 10-11 by adding an appropriate amount of sodium hydroxide, continuing the reaction for 24 hours, and then adding anhydrous ethanol to terminate the reaction after the pH value of the system remains unchanged; (2) centrifuging the reaction solution after ultrasonic cell disruption treatment for 10 minutes, taking the lower layer sediment, washing it with water by centrifugation, then filtering and washing it with anhydrous ethanol, and drying it to obtain the oxidized modified nanocellulose powder.
4. The preparation method according to claim 1, characterized in that, In step 1, the mass ratio of cellulose material to water is 1:(70-90); the mass ratio of cellulose material to sodium bromide is (9-11):
1.
5. The preparation method according to claim 1, characterized in that, The mass concentration of the TEMPO solution in step 1 is 0.07-0.09 g / mL, and the active chlorine content of the sodium hypochlorite aqueous solution is 6-14%; the volume ratio of water, TEMPO solution and sodium hypochlorite is (140-180):4:
15.
6. The preparation method according to claim 1, characterized in that, The periodate aqueous solution in step 2 has a mass concentration of 2-8 g / L.
7. The preparation method according to claim 1, characterized in that, The polyamine compound mentioned in step 3 includes at least one of polyamine hyperbranched polymers and polyamides.
8. The preparation method according to claim 1, characterized in that, The mass ratio of the polyamino compound to nanocellulose in step 3 is 1:(20-30).
9. The preparation method according to claim 1, characterized in that, The mass ratio of graphene oxide to cellulose nanoparticles in step 3 is 1:(1-4).
10. The preparation method according to claim 1, characterized in that, The freeze-drying temperature in step 4 is -50 to 80°C, and the freeze-drying time is 24 to 48 hours.