Preparation method and application of electromagnetic wave absorbing material based on cellulose nanocrystals

Abstract

The invention discloses a preparation method of an electromagnetic wave absorbing material based on cellulose nanocrystals. The preparation method comprises the following steps: preparing cellulose nanocrystal aerogel; adding an aniline monomer, ammonium persulfate and hydrochloric acid into an ethanol solvent to obtain a mixed solution; adding the cellulose nanocrystal aerogel into the mixed solution, and carrying out in-situ polymerization; and washing the polymerized aerogel with ethanol, and carrying out vacuum drying. The cellulose nanocrystal aerogel with a chiral structure is prepared, polyaniline is polymerized on the aerogel in situ, the conductivity of the material is improved, the electromagnetic wave absorbing material based on the cellulose nanocrystal is prepared, the preparation method is simple, and the product has excellent electromagnetic wave absorbing performance such as light weight, wide frequency band and strong absorption.

Description

Technical Field

[0001] The present invention belongs to the field of electromagnetic wave absorbing materials, and particularly relates to a preparation method and application of an electromagnetic wave absorbing material based on cellulose nanocrystals. Background Art

[0002] Chiral nematic cellulose nanocrystal aerogel (Cellulose nanocrystal, CNC) is a new and promising product separated from cellulose. It has become one of the research hotspots in the field of cellulose due to its good crystal structure, chirality, high specific surface area, low density, active surface, liquid crystal formation and self-assembly. Its high processability and unique nano-effects enable it to combine with other polymer materials to exhibit more excellent properties, making it a potential candidate material for electromagnetic wave absorbing materials. However, due to the non-conductivity of cellulose nanocrystals themselves, their application in the field of electromagnetic wave absorption faces great challenges. Introducing conductive polymers and chemically modifying cellulose nanocrystal aerogels to improve their conductivity is an effective method to enhance the electromagnetic wave absorption performance of cellulose nanocrystal materials.

[0003] Ji et al. developed a cellulose-chitosan / polyaniline composite aerogel, a three-dimensional cellulose framework coated with polyaniline conductive polymer on the surface. This aerogel can not only effectively absorb electromagnetic waves, but also has great potential in thermal insulation applications. However, the absorption bandwidth of the material needs to be improved. Tian, Meng et al. designed a double-chiral hierarchical structure to achieve a synergistic enhancement effect of microwave absorption through the hybridization of nanomaterials. Chiral-tunable polyaniline nanorods were grown on helical carbon nanotubes by in-situ polymerization. Experimental results show that compared with pure polyaniline or helical carbon nanotubes, the hybrid material exhibits significant enhancement of electromagnetic loss. However, the characteristics of the material powder limit its further application. Summary of the Invention

[0004] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a preparation method and application of an electromagnetic wave absorbing material based on cellulose nanocrystals. By preparing cellulose nanocrystal aerogels with chiral structures and in-situ polymerizing polyaniline on the aerogels, the conductivity of the material is improved, and an electromagnetic wave absorbing material based on cellulose nanocrystals is prepared. The preparation method of the present invention is simple, and the product has excellent electromagnetic wave absorption properties such as light weight, wide frequency band and strong absorption.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0006] A preparation method of an electromagnetic wave absorbing material based on cellulose nanocrystals, comprising the following steps:

[0007] Step 1, preparing cellulose nanocrystal aerogel;

[0008] Step 2: Add aniline monomer, ammonium persulfate, and hydrochloric acid into an ethanol solvent to obtain a mixed solution.

[0009] Step 3: Add the cellulose nanocrystal aerogel into the mixed solution for in-situ polymerization.

[0010] Step 4: Rinse the polymerized aerogel with ethanol and dry it under vacuum.

[0011] In one embodiment, the cellulose nanocrystal aerogel is prepared as follows:

[0012] Step 11: Prepare an aqueous dispersion of cellulose nanocrystals, perform ultrasonic treatment, and then refrigerate and let it stand for stratification.

[0013] Step 12: Separate and package the upper and lower layers of the stratified dispersion, and heat the lower-layer dispersion to gel the product.

[0014] Step 13: Freeze the gelled product obtained in Step 12 and lyophilize it under vacuum to obtain the cellulose nanocrystal aerogel.

[0015] In one embodiment, the aqueous dispersion of cellulose nanocrystals is prepared by dispersing commercial cellulose nanocrystal powder in deionized water, with a mass concentration of 4 - 5%.

[0016] In one embodiment, in Step 12, the heating conditions are: heating at 90 - 95 °C for 60 - 72 h.

[0017] In one embodiment, in the mixed solution, the dosage of aniline monomer is 0.8 - 1 mL, the dosage of ammonium persulfate is 0.5 - 0.8 g, deionized water for dissolving ammonium persulfate is added, the dosage of ethanol solvent is 40 mL, the mass concentration of hydrochloric acid is 36 - 38%, and the dosage is 1.5 - 3 mL.

[0018] In one embodiment, in Step 3, the duration of in-situ polymerization is 6 - 24 h, and the temperature is 0 - 4 °C.

[0019] In one embodiment, in Step 3, the dosage relationship between the cellulose nanocrystal aerogel and the mixed solution satisfies that the aerogel prepared from 5 mL of cellulose nanocrystals with a mass concentration of 5% corresponds to 0.8 - 1 mL of aniline monomer.

[0020] In one embodiment, when different amounts of aniline monomer are used, the polymerization amount increases with the increase in concentration. By polymerizing for different durations, such as 6 hours, 12 hours, and 24 hours, the polymerization amount increases, and the conductivity increases with the increase in polymerization duration.

[0021] In one embodiment, the maximum absorption bandwidth of the obtained electromagnetic wave absorbing material is 7.9 GHz, and the minimum reflection loss is -47.9 dB.

[0022] The electromagnetic wave absorbing material obtained by the preparation method of the present invention, as a polymer composite wave absorbing material, can be used for stealth coatings of flexible electronic devices and equipment such as aerospace.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] The method of in-situ polymerization of polyaniline on the chiral nematic cellulose nanocrystal aerogel is simple, the enhancement effect of electrical conductivity is significant, the optimization effect of impedance matching is obvious, and the chiral nematic structure of the composite aerogel material can significantly improve the electromagnetic wave absorption performance of the material. Description of the Drawings

[0025] Figure 1 It is a graph showing the relationship between the reflection loss and the electromagnetic frequency of a composite material of 5% concentration chiral nematic cellulose nanocrystal aerogel and polyaniline with a polymerization time of 6 hours.

[0026] Figure 2 It is a graph showing the relationship between the impedance matching value and the electromagnetic frequency of a composite material of 5% concentration chiral nematic cellulose nanocrystal aerogel and polyaniline with a polymerization time of 6 hours.

[0027] Figure 3 It is a graph showing the relationship between the reflection loss and the electromagnetic frequency of a composite material of 5% concentration chiral nematic cellulose nanocrystal aerogel and polyaniline with a polymerization time of 12 hours.

[0028] Figure 4 It is a graph showing the relationship between the impedance matching value and the electromagnetic frequency of a composite material of 5% concentration chiral nematic cellulose nanocrystal aerogel and polyaniline with a polymerization time of 12 hours.

[0029] Figure 5 It is a graph showing the relationship between the reflection loss and the electromagnetic frequency of a composite material of 5% concentration chiral nematic cellulose nanocrystal aerogel and polyaniline with a polymerization time of 24 hours.

[0030] Figure 6 It is a graph showing the relationship between the impedance matching value and the electromagnetic frequency of a composite material of 5% concentration chiral nematic cellulose nanocrystal aerogel and polyaniline with a polymerization time of 24 hours.

[0031] Figure 7 It is a graph showing the relationship between the reflection loss and the electromagnetic frequency of a composite material of 5% concentration cellulose nanocrystal aerogel and polyaniline without chiral nematic structure with a polymerization time of 24 hours.

[0032] Figure 8It is a graph showing the relationship between the impedance matching value and the electromagnetic frequency of a composite material of cellulose nanocrystal aerogel without a chiral nematic structure and polyaniline with a concentration of 5% and a polymerization time of 24 hours.

[0033] Figure 9 It is a graph of the maximum absorption bandwidth and the minimum reflection loss of a composite material of cellulose nanocrystal aerogel and polyaniline with a concentration of 5% at different polymerization times. Detailed implementation mode

[0034] The implementation mode of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0035] The present invention discloses a preparation method and application of an electromagnetic wave absorbing material based on cellulose nanocrystals. First, a cellulose nanocrystal aerogel with a chiral nematic structure is prepared, and polyaniline is in-situ polymerized on the aerogel to improve the conductivity of the material, obtaining a series of composite aerogels of cellulose nanocrystals with a chiral nematic structure and polyaniline with different conductivities and electromagnetic wave absorption properties. The present invention has the excellent electromagnetic wave absorption performance characteristics of simple preparation method, chiral nematic structure, light weight, wide frequency band and strong absorption, and has potential applications in the field of polymer composite wave absorbing materials.

[0036] The specific preparation method of the present invention can be described as including the following steps:

[0037] Step 1, prepare cellulose nanocrystal aerogel. A specific method can be as follows:

[0038] Step 11, prepare an aqueous dispersion of CNC. Disperse the CNC powder in deionized water, stir evenly, and then ultrasonically disperse it to obtain a uniform CNC suspension. Subsequently, refrigerate and let it stand for a period of time to make the suspension layer into an upper isotropic phase and a lower anisotropic phase.

[0039] Among them, the aqueous dispersion of CNC can be prepared by dispersing commercial cellulose nanocrystal powder in deionized water, and the mass concentration is preferably 4-5%. For example, using 3 g of commercial cellulose nanocrystals and adding 57 g of deionized water, the concentration of the prepared aqueous dispersion of CNC is 5%.

[0040] For the stirring and ultrasonic treatment in this step, specifically, it can be stirred with a magnetic stirrer for three days, and then ultrasonically treated with a cell crusher at 50% energy for 5 minutes to make the cellulose nanocrystal powder evenly dispersed. Subsequently, put it in the refrigerator for low-temperature refrigeration and let it stand, waiting for stratification. Generally, after standing for about two weeks, the dispersion liquid stratifies, and the lower layer is anisotropic and has a suspension with a chiral nematic structure.

[0041] Step 12: Separate and package the upper and lower layers of the stratified CNC dispersion liquid. Heat the lower-layer dispersion liquid. While maintaining the cholesteric structure of the anisotropic phase suspension, the gelation of cellulose nanocrystals is achieved. The heating conditions can be selected as heating at 90 - 95 °C for 60 - 72 h.

[0042] In this step, through quantitative packaging, it is ensured that the volume and shape of each portion of the dispersion liquid are consistent, avoiding uneven heat transfer caused by differences in thickness or volume during the subsequent gelation process and affecting the structural uniformity. High temperature (95 °C) promotes the detachment of some sulfonic acid groups (-OSO3 - ) from the surface of CNC, weakening the electrostatic repulsion of the surface charge of CNC. At the same time, it promotes the formation of hydrogen bonds between hydroxyl groups and the physical entanglement of rod-shaped CNC, forming a three-dimensional network structure, restricting the growth space of ice crystals during the subsequent freezing process, and preventing large-sized ice crystals from destroying the chiral arrangement structure. After heating is completed, cool it to room temperature.

[0043] Step 13: Freeze and vacuum freeze-dry the gelation product obtained in Step 12 to obtain the cellulose nanocrystal aerogel.

[0044] By freezing through methods such as putting it in the refrigerator, the water in the gel can form tiny ice crystals, and the ice crystal template occupies space. Under vacuum conditions, the ice directly sublimes to form through pores, which is beneficial for subsequent functionalization (such as loading conductive component polyaniline), and a low-density CNC aerogel is obtained. For example, in this step, a vacuum dryer can be used, and vacuum freeze-dry for more than 24 h to obtain a cellulose nanocrystal aerogel with a chiral structure.

[0045] Step 2: Add aniline monomer, ammonium persulfate, and hydrochloric acid solution to an ethanol solvent for mixing to obtain a mixed solution.

[0046] In this step, ethanol is used as a co-solvent because aniline has low solubility in water, and ethanol can improve its dispersibility. Hydrochloric acid HCl provides protons (H + ), and the acidic environment protonates aniline monomer to aniline cation (C6H5NH3 + ), providing an active monomer for oxidative polymerization. Ammonium persulfate APS ((NH4)2S2O8) is used as a strong oxidant, which releases free radicals under acidic conditions and initiates the chain polymerization reaction of aniline.

[0047] For example, a feasible ratio is that in the mixed solution, the dosage of aniline monomer is 0.8 - 1 mL, the dosage of ammonium persulfate is 0.5 - 0.8 g, the dosage of deionized water is at least sufficient to dissolve ammonium persulfate, for example, it can be 1.54 mL, the dosage of ethanol solvent is 40 mL, hydrochloric acid is of analytical pure AR, with a mass concentration of 36 - 38%, and the dosage is 1.5 - 3 mL.

[0048] Step 3: Add the cellulose nanocrystal aerogel to the mixed solution for in-situ polymerization.

[0049] In this step, the porous structure of the aerogel adsorbs the aniline monomer solution through capillary action, enabling the monomer to penetrate into the pores. The free radical polymerization initiated by APS occurs within the pores of the aerogel, and polyaniline (PANI) grows directly on the surface of CNC or the pore walls to form a conductive network (CNC@PANI). The hydrogen bonds or π-π interactions between PANI and CNC enhance the compressive strength of the composite material.

[0050] Exemplarily, the duration of in-situ polymerization is 6 - 24 h, and the temperature is 0 - 4 °C. The dosage relationship between the cellulose nanocrystal aerogel and the mixed solution satisfies that the aerogel prepared from 5 mL of cellulose nanocrystals with a mass concentration of 5% corresponds to 0.8 - 1 mL of aniline monomer.

[0051] Step 4: Rinse the polymerized aerogel with ethanol and dry it under vacuum.

[0052] In this step, ethanol rinsing is used to dissolve unreacted aniline monomer, oligomers, and APS decomposition products (such as sulfates). Vacuum drying (at room temperature) thoroughly removes residual solvents and moisture, avoiding pore collapse caused by drying shrinkage.

[0053] The method of the present invention can, on the one hand, be applied to the improvement of the electrical conductivity of cellulose nanocrystal aerogel by different concentrations or different polymerization durations of the same type of polyaniline; on the other hand, it is also applicable to the improvement of the electrical conductivity of cellulose nanocrystal aerogel by different types of conductive polymers (such as polypyrrole (PPy) and polythiophene (PTh)).

[0054] The following are several specific embodiments of the present invention.

[0055] Example 1

[0056] Preparation of an electromagnetic wave absorption material based on cellulose nanocrystals, including the following steps:

[0057] Step 1: Prepare 60 g of an aqueous dispersion of 5 wt% CNC using commercial cellulose nanocrystals, ultrasonically treat the dispersion with a cell disruptor at 50% energy for 5 minutes, and refrigerate and let it stand for layering.

[0058] Step 2: Dispense the lower suspension of the well-layered CNC dispersion into 20 mL sample bottles at 5 mL per portion and heat in an oven at 95 °C for 72 h.

[0059] Step 3: Freeze the heated CNC dispersion and vacuum freeze-dry it for more than 24 h to obtain cellulose nanocrystal aerogel.

[0060] Step 4: Sequentially add 1 mL of aniline monomer, 0.8 g of ammonium persulfate, and 3 mL of concentrated hydrochloric acid solution to 40 mL of ethanol solution for mixing. The ethanol solution consists of ethanol solvent and deionized water, and the content of deionized water in the mixed solution should be able to meet the dissolution requirement of ammonium persulfate.

[0061] Step 5: Add the aerogel to the mixed solution obtained in Step 4 and polymerize at 0 °C for 6 h.

[0062] Step 6: Rinse the polymerized aerogel with ethanol and dry it under vacuum.

[0063] In this example, the relationship between the reflection loss and electromagnetic frequency of the composite material of cellulose nanocrystal aerogel and polyaniline with a chiral nematic structure at a concentration of 5% and a polymerization time of 6 hours is as Figure 1 shown, the relationship between the impedance matching value and electromagnetic frequency is as Figure 2 shown, and the maximum absorption bandwidth and minimum reflection loss are as Figure 9 shown. It can be seen that polyaniline successfully enhances the conductivity of cellulose nanocrystal aerogel, and the impedance matching is significantly optimized, and the electromagnetic wave absorption performance is significantly enhanced.

[0064] Example 2

[0065] Preparation of an electromagnetic wave absorbing material based on cellulose nanocrystals, comprising the following steps:

[0066] Step 1: Prepare a 60 g aqueous dispersion of 5 wt% CNC using commercial cellulose nanocrystals, ultrasonically treat the dispersion with a cell crusher at 50% energy for 5 minutes, and refrigerate and let it stand for layering.

[0067] Step 2: Dispense the lower suspension of the well-layered CNC dispersion into 20 mL sample bottles at 5 mL per portion and heat in an oven at 95 °C for 72 h.

[0068] Step 3: Freeze the heated CNC dispersion and vacuum freeze-dry it for more than 24 h to obtain cellulose nanocrystal aerogel.

[0069] Step 4: Sequentially add 1 mL of aniline monomer, 0.8 g of ammonium persulfate, and 2.5 mL of concentrated hydrochloric acid solution to 40 mL of ethanol solution for mixing. The ethanol solution consists of ethanol solvent and deionized water, and the content of deionized water in the mixed solution should be able to meet the dissolution requirement of ammonium persulfate.

[0070] Step 5: Add the aerogel to the mixed solution obtained in Step 4 and polymerize at 0 °C for 12 h.

[0071] Step 6: Rinse the polymerized aerogel with ethanol and dry it under vacuum.

[0072] The relationship between the reflection loss and electromagnetic frequency of the composite material of cellulose nanocrystal aerogel with a chiral nematic structure and polyaniline at a concentration of 5% and a polymerization time of 12 hours in this example is as follows Figure 3 shown, and the relationship between the impedance matching value and electromagnetic frequency is as follows Figure 4 shown, and the maximum absorption bandwidth and minimum reflection loss are as follows Figure 9 shown. It can be seen that polyaniline successfully enhances the conductivity of cellulose nanocrystal aerogel, and the impedance matching is significantly optimized, and the electromagnetic wave absorption performance is significantly enhanced.

[0073] Example 3

[0074] Preparation of an electromagnetic wave absorbing material based on cellulose nanocrystals, comprising the following steps:

[0075] Step 1: Prepare a 60 g aqueous dispersion of 5 wt% CNC using commercial cellulose nanocrystals. Ultrasonically treat the dispersion with a cell disruptor at 50% energy for 5 minutes, and refrigerate and let it stand for layering.

[0076] Step 2: Aliquot the lower suspension of the layered CNC dispersion into 20 mL sample bottles at 5 mL per portion, and heat in an oven at 95 °C for 72 h.

[0077] Step 3: Freeze the heated CNC dispersion and vacuum freeze-dry it for more than 24 h to obtain cellulose nanocrystal aerogel.

[0078] Step 4: Add 1 mL of aniline monomer, 0.7 g of ammonium persulfate, and 3 mL of concentrated hydrochloric acid solution to 40 mL of ethanol solution in sequence for mixing. The ethanol solution consists of ethanol solvent and deionized water, and the content of deionized water in the mixed solution should be able to meet the dissolution requirement of ammonium persulfate.

[0079] Step 5: Add the aerogel to the mixed solution obtained in Step 4, and polymerize at 2 °C for a polymerization duration of 24 h.

[0080] Step 6: Rinse the polymerized aerogel with ethanol and vacuum dry it.

[0081] The relationship between the reflection loss and electromagnetic frequency of the composite material of cellulose nanocrystal aerogel with a chiral nematic structure and polyaniline at a concentration of 5% and a polymerization time of 24 hours in this example is as follows Figure 5 shown, and the relationship between the impedance matching value and electromagnetic frequency is as follows Figure 6 shown, and the maximum absorption bandwidth and minimum reflection loss are as follows Figure 9 shown. It can be seen that polyaniline successfully enhances the conductivity of cellulose nanocrystal aerogel, and the impedance matching is significantly optimized, and the electromagnetic wave absorption performance is significantly enhanced.

[0082] Example 4

[0083] Preparation of an electromagnetic wave absorbing material based on cellulose nanocrystals, comprising the following steps:

[0084] Step 1, prepare 60 g of an aqueous dispersion of 5 wt% CNC using commercial cellulose nanocrystals, ultrasonically treat the dispersion with a cell crusher at 50% energy for 5 minutes, and refrigerate and let it stand for layering.

[0085] Step 2, dispense the upper suspension of the layered CNC dispersion into 20 mL sample bottles at 5 mL per portion and heat in an oven at 95 °C for 72 h.

[0086] Step 3, freeze the heated CNC dispersion and vacuum freeze-dry it for more than 24 h to obtain cellulose nanocrystal aerogel.

[0087] Step 4, sequentially add 1 mL of aniline monomer, 0.7 g of ammonium persulfate, and 3 mL of concentrated hydrochloric acid solution to 40 mL of an ethanol solution for mixing. The ethanol solution consists of an ethanol solvent and deionized water, and the content of deionized water in the mixed solution needs to be able to meet the dissolution requirement of ammonium persulfate.

[0088] Step 5, add the aerogel to the mixed solution obtained in Step 4 and polymerize at 2 °C for 24 h.

[0089] Step 6, rinse the polymerized aerogel with ethanol and vacuum dry it.

[0090] In this example, the relationship between the reflection loss and electromagnetic frequency of the composite material of cellulose nanocrystal aerogel and polyaniline with a 5% concentration and no chiral nematic structure polymerized for 24 hours is as Figure 7 shown, the relationship between the impedance matching value and electromagnetic frequency is as Figure 8 shown, and the maximum absorption bandwidth and minimum reflection loss are as Figure 9 shown. It can be seen that although the conductivity of the cellulose nanocrystal aerogel, the optimization effect of impedance matching, and the electromagnetic wave absorption performance have been improved, they are not as good as those in Example 3.

[0091] Meanwhile, referring to Figures 1 to 9 , it can be seen that as the polymerization time increases, the value of the maximum absorption bandwidth becomes larger, and the absolute value of the minimum reflection loss becomes larger. Among them, the performance of the aerogel prepared from the lower suspension with a chiral nematic structure is significantly better than that of the upper aerogel without a chiral nematic structure.

[0092] From the above examples, it can be seen that through the described implementation steps, it is confirmed that polyaniline has successfully enhanced the conductivity of cellulose nanocrystal aerogel, thereby optimizing impedance matching and enhancing its electromagnetic wave absorption performance. It proves the effectiveness of the method of in-situ polymerization of polyaniline on chiral nematic cellulose nanocrystal aerogel proposed in the present invention.

Claims

1. A preparation method of an electromagnetic wave absorbing material based on cellulose nanocrystals, characterized in that, It includes the following steps: Step 1, prepare cellulose nanocrystal aerogel; Step 2, add aniline monomer, ammonium persulfate and hydrochloric acid into an ethanol solvent to obtain a mixed solution; Step 3, add the cellulose nanocrystal aerogel to the mixed solution for in-situ polymerization; Step 4, rinse the polymerized aerogel with ethanol and dry it under vacuum.

2. The preparation method of the cellulose nanocrystal-based electromagnetic wave absorption material according to claim 1, wherein The cellulose nanocrystal aerogel is prepared by the following method: Step 11, prepare an aqueous dispersion of cellulose nanocrystals and perform ultrasonic treatment, and then refrigerate and let it stand for stratification; Step 12, separately package the upper layer and the lower layer of the stratified dispersion liquid, and heat the lower layer dispersion liquid to gel the product; Step 13, freeze the gelled product in Step 12 and freeze-dry it under vacuum to obtain the cellulose nanocrystal aerogel.

3. The preparation method of the cellulose nanocrystal-based electromagnetic wave absorption material according to claim 2, characterized in that The aqueous dispersion of cellulose nanocrystals is prepared by dispersing commercial cellulose nanocrystal powder in deionized water, and the mass concentration is 4-5%.

4. The preparation method of the cellulose nanocrystal-based electromagnetic wave absorption material according to claim 2, wherein In Step 12, the heating conditions are: heating at 90-95°C for 60-72 h.

5. The preparation method of the cellulose nanocrystal-based electromagnetic wave absorption material according to claim 1, wherein In the mixed solution, the dosage of aniline monomer is 0.8-1 mL, the dosage of ammonium persulfate is 0.5-0.8 g, deionized water for dissolving ammonium persulfate is added, the dosage of ethanol solvent is 40 mL, the mass concentration of hydrochloric acid is 36-38%, and the dosage is 1.5-3 mL.

6. The preparation method of the cellulose nanocrystal-based electromagnetic wave absorption material according to claim 1, wherein, In Step 3, the duration of in-situ polymerization is 6-24 h, and the temperature is 0-4°C.

7. The preparation method of the cellulose nanocrystal-based electromagnetic wave absorption material according to claim 1, characterized in that, In Step 3, the dosage relationship between the cellulose nanocrystal aerogel and the mixed solution satisfies that the aerogel prepared from 5 mL of cellulose nanocrystals with a mass concentration of 5% corresponds to 0.8-1 mL of aniline monomer.

8. The preparation method of the cellulose nanocrystal-based electromagnetic wave absorption material according to claim 1, wherein Using different amounts of aniline monomer, the polymerization amount increases with the increase of concentration, and the conductivity increases with the increase of polymerization duration.

9. The preparation method of the cellulose nanocrystal-based electromagnetic wave absorption material according to claim 1, characterized in that, The maximum absorption bandwidth of the obtained electromagnetic wave absorbing material is 7.9 GHz, and the minimum reflection loss is -47.9 dB.

10. Application of the electromagnetic wave absorbing material obtained by the preparation method of the electromagnetic wave absorbing material based on cellulose nanocrystals according to Claim 1 in an equipment stealth coating.

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