Preparation method and application of cellulose nanocrystal-based electromagnetic wave absorbing material

Abstract

The application discloses a preparation method of an electromagnetic wave absorbing material based on cellulose nanocrystals, and steps are as follows: cellulose nanocrystal aerogel is prepared; aniline monomer, ammonium persulfate and hydrochloric acid are added into an ethanol solvent to obtain a mixed solution; the cellulose nanocrystal aerogel is added into the mixed solution for in-situ polymerization; and the polymerized aerogel is washed with ethanol and vacuum dried. The application prepares the cellulose nanocrystal aerogel with a chiral structure, and in-situ polyaniline is polymerized on the aerogel, so that the conductivity of the material is improved, the electromagnetic wave absorbing material based on the cellulose nanocrystals 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 in particular 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 (CNC) is a promising new product isolated from cellulose. Its well-defined crystal structure and chirality, high specific surface area, low density, active surface, liquid crystalization, and self-assembly have made it a research hotspot in the cellulose field. Its high processability and unique nano-effect allow it to be combined with other polymer materials to achieve even better performance, making it a potential candidate for electromagnetic wave absorption. However, due to the inherent lack of electrical conductivity of cellulose nanocrystals, their application in electromagnetic wave absorption faces significant challenges. Chemically modifying cellulose nanocrystal aerogels to improve their electrical conductivity through the introduction of conductive polymers is an effective method for enhancing the electromagnetic wave absorption performance of cellulose nanocrystal materials.

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

[0004] To overcome the shortcomings of the prior art, the present invention provides a method for preparing and applying a cellulose nanocrystal-based electromagnetic wave absorbing material. This material is prepared by preparing a chiral cellulose nanocrystal aerogel and in situ polymerizing polyaniline onto the aerogel to enhance its conductivity. The preparation method is simple, and the product exhibits excellent electromagnetic wave absorption properties, including lightweight, broadband, and strong absorption.

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

[0006] A method for preparing an electromagnetic wave absorbing material based on cellulose nanocrystals comprises the following steps:

[0007] Step 1, preparing cellulose nanocrystal aerogel;

[0008] Step 2, adding aniline monomer, ammonium persulfate and hydrochloric acid to an ethanol solvent to obtain a mixed solution;

[0009] Step 3, adding the cellulose nanocrystal aerogel to the mixed solution to perform in-situ polymerization;

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

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

[0012] Step 11, preparing an aqueous dispersion of cellulose nanocrystals and performing sonication, followed by refrigeration and standing for stratification;

[0013] Step 12, packaging the upper and lower layers of the separated dispersion, and heating the lower layer of the dispersion to gel the product;

[0014] Step 13: Freeze and vacuum freeze-dry the gelled product of step 12 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 condition is: heating at 90-95° C. for 60-72 hours.

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

[0018] In one embodiment, in step 3, the in-situ polymerization is carried out for 6-24 hours at a temperature of 0-4°C.

[0019] In one embodiment, in step 3, the amount of the cellulose nanocrystal aerogel and the mixed solution satisfies the following relationship: 5 mL of aerogel prepared from 5% cellulose nanocrystals 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 increasing concentration. By polymerizing for different lengths of time, such as 6 hours, 12 hours, and 24 hours, the polymerization amount increases, and the conductivity increases with increasing polymerization time.

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

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

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The method of in situ polymerization of polyaniline on chiral nematic cellulose nanocrystal aerogel is simple, has significant effects on enhancing conductivity and optimizing impedance matching. At the same time, the chiral nematic structure of the composite aerogel material can significantly improve the electromagnetic wave absorption performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

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

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

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

[0033] Figure 9 The maximum absorption bandwidth and minimum reflection loss diagram of the composite material of 5% concentration cellulose nanocrystal aerogel and polyaniline with different polymerization times. DETAILED DESCRIPTION

[0034] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0035] This invention discloses a method for preparing and applying electromagnetic wave absorbing materials based on cellulose nanocrystals. Cellulose nanocrystal aerogels with a chiral nematic structure are first prepared. Polyaniline is then in situ polymerized onto the aerogels to enhance the material's conductivity. This results in a series of chiral nematic cellulose nanocrystal and polyaniline composite aerogels with varying electrical conductivity and electromagnetic wave absorption properties. This method boasts a simple preparation method, a chiral nematic structure, lightweight materials, a wide bandwidth, and strong absorption, demonstrating excellent electromagnetic wave absorption properties. It has potential applications in the field of polymer composite absorbing materials.

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

[0037] Step 1: preparing cellulose nanocrystal aerogel. A specific method may be as follows:

[0038] Step 11: Prepare a CNC aqueous dispersion by dispersing CNC powder in deionized water, stirring evenly, and then ultrasonically dispersing it to obtain a uniform CNC suspension. Then, refrigerate and let it stand for a period of time to allow the suspension to separate into an upper isotropic phase and a lower anisotropic phase.

[0039] The CNC aqueous dispersion can be prepared by dispersing commercial cellulose nanocrystal powder in deionized water, preferably at a concentration of 4-5%. For example, 3 g of commercial cellulose nanocrystals and 57 g of deionized water can be added to prepare a CNC aqueous dispersion with a concentration of 5%.

[0040] Specifically, stirring and sonication in this step can be performed using a magnetic stirrer for three days, followed by sonication in a cell disrupter at 50% power for five minutes to evenly disperse the cellulose nanocrystal powder. The mixture is then refrigerated and allowed to stand for separation. Typically, after about two weeks, the dispersion separates into layers, with the lower layer being an anisotropic suspension with a chiral nematic structure.

[0041] Step 12: Separate the upper and lower layers of the stratified CNC dispersion and heat the lower dispersion to achieve gelation of cellulose nanocrystals while maintaining the chiral nematic structure of the anisotropic phase suspension. The heating condition can be selected to be 90-95° C. for 60-72 hours.

[0042] This step ensures that the volume and shape of each dispersion are consistent by quantitative packaging, avoiding uneven heat transfer due to thickness or volume differences in the subsequent gelation process, which affects the structural uniformity. High temperature (95°C) promotes the formation of some sulfonic acid groups (-OSO3 - ) from the CNC surface, weakening the electrostatic repulsion of the CNC surface charge. This also promotes the formation of hydrogen bonds between hydroxyl groups and the physical entanglement of rod-shaped CNCs, forming a three-dimensional network structure. This limits the growth space of ice crystals during subsequent freezing and prevents large ice crystals from disrupting the chiral arrangement. After heating, the mixture is cooled to room temperature.

[0043] Step 13: Freeze and vacuum freeze-dry the gelled product of step 12 to obtain the cellulose nanocrystal aerogel.

[0044] Freezing the gel, such as by placing it in a refrigerator, causes the water in the gel to form tiny ice crystals, which then occupy the space. Freeze-drying under vacuum allows the ice to sublime directly, forming through-holes that facilitate subsequent functionalization (such as loading the conductive component polyaniline), resulting in a low-density CNC aerogel. For example, this step can be performed in a vacuum dryer for at least 24 hours to obtain a cellulose nanocrystal aerogel with a chiral structure.

[0045] Step 2: adding aniline monomer, ammonium persulfate and hydrochloric acid solution into ethanol solvent and mixing them 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. + ), the acidic environment causes the aniline monomer to be protonated into aniline cation (C6H5NH3 + ), providing active monomers for oxidative polymerization. Ammonium persulfate APS ((NH4)2S2O8) acts as a strong oxidant, releasing free radicals under acidic conditions, initiating the chain polymerization reaction of aniline.

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

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

[0049] In this step, the porous structure of the aerogel absorbs the aniline monomer solution through capillary action, allowing the monomer to penetrate into the pores. APS-induced free radical polymerization occurs within the aerogel pores, and polyaniline (PANI) grows directly on the CNC surface or pore walls, forming a conductive network (CNC@PANI). Hydrogen bonding or π-π interactions between PANI and CNC enhance the compressive strength of the composite.

[0050] For example, the in-situ polymerization time is 6-24 hours, and the temperature is 0-4° C. The amount of cellulose nanocrystal aerogel and the mixed solution is such that 5 mL of aerogel prepared from 5% cellulose nanocrystals corresponds to 0.8-1 mL of aniline monomer.

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

[0052] In this step, ethanol is used to dissolve unreacted aniline monomers, oligomers, and APS decomposition products (such as sulfate). Vacuum drying (at room temperature) is then performed to completely remove residual solvent and moisture to prevent pore collapse caused by drying shrinkage.

[0053] The method described in the present invention can be applied to improving the conductive properties of cellulose nanocrystal aerogels using polyaniline of the same type but different concentrations or polymerization times. It can also be applied to improving the conductive properties of cellulose nanocrystal aerogels using 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] A preparation method of an electromagnetic wave absorbing material based on cellulose nanocrystals comprises the following steps:

[0057] Step 1: 60 g of a 5 wt% aqueous dispersion of CNCs was prepared using commercial cellulose nanocrystals. The dispersion was ultrasonically treated with a cell crusher at 50% energy for 5 minutes, and then refrigerated and allowed to stand for stratification.

[0058] Step 2: The lower suspension of the stratified CNC dispersion was divided into 20 mL sample bottles in 5 mL portions and heated in an oven at 95 °C for 72 h.

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

[0060] Step 4: 1 mL of aniline monomer, 0.8 g of ammonium persulfate, and 3 mL of concentrated hydrochloric acid solution are sequentially added to 40 mL of ethanol solution and mixed. The ethanol solution is composed of ethanol solvent and deionized water. The deionized water content in the mixed solution must be able to meet the dissolution requirements of ammonium persulfate.

[0061] Step 5: adding the aerogel to the mixed solution obtained in step 4, polymerizing at 0° C. for 6 h.

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

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

[0064] Example 2

[0065] A preparation method of an electromagnetic wave absorbing material based on cellulose nanocrystals comprises the following steps:

[0066] Step 1: 60 g of a 5 wt% aqueous dispersion of CNCs was prepared using commercial cellulose nanocrystals. The dispersion was ultrasonically treated with a cell crusher at 50% energy for 5 minutes, and then refrigerated and allowed to stand for stratification.

[0067] Step 2: The lower suspension of the stratified CNC dispersion was divided into 20 mL sample bottles in 5 mL portions and heated in an oven at 95 °C for 72 h.

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

[0069] Step 4: 1 mL of aniline monomer, 0.8 g of ammonium persulfate, and 2.5 mL of concentrated hydrochloric acid solution are sequentially added to 40 mL of ethanol solution and mixed. The ethanol solution is composed of ethanol solvent and deionized water. The deionized water content in the mixed solution must be able to meet the dissolution requirements of ammonium persulfate.

[0070] Step 5: adding the aerogel to the mixed solution obtained in step 4, polymerizing at 0° C. for 12 h.

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

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

[0073] Example 3

[0074] A preparation method of an electromagnetic wave absorbing material based on cellulose nanocrystals comprises the following steps:

[0075] Step 1: 60 g of a 5 wt% aqueous dispersion of CNCs was prepared using commercial cellulose nanocrystals. The dispersion was ultrasonically treated with a cell crusher at 50% energy for 5 minutes, and then refrigerated and allowed to stand for stratification.

[0076] Step 2: The lower suspension of the stratified CNC dispersion was divided into 20 mL sample bottles in 5 mL portions and heated in an oven at 95 °C for 72 h.

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

[0078] Step 4: 1 mL of aniline monomer, 0.7 g of ammonium persulfate, and 3 mL of concentrated hydrochloric acid solution are sequentially added to 40 mL of ethanol solution and mixed. The ethanol solution is composed of ethanol solvent and deionized water. The deionized water content in the mixed solution must be able to meet the dissolution requirements of ammonium persulfate.

[0079] Step 5: adding the aerogel to the mixed solution obtained in step 4, polymerizing at 2° C. for 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 and polyaniline with a concentration of 5% and a chiral nematic structure and a polymerization time of 24 hours in this embodiment is as follows: Figure 5 As shown, the relationship between impedance matching value and electromagnetic frequency is as follows Figure 6 As shown, the maximum absorption bandwidth and minimum reflection loss are as follows Figure 9 As shown, it can be seen that polyaniline successfully enhances the conductivity of cellulose nanocrystal aerogel, and the impedance matching is significantly optimized, and the absorption performance of electromagnetic waves is significantly enhanced.

[0082] Example 4

[0083] A preparation method of an electromagnetic wave absorbing material based on cellulose nanocrystals comprises the following steps:

[0084] Step 1: 60 g of a 5 wt% aqueous dispersion of CNCs was prepared using commercial cellulose nanocrystals. The dispersion was ultrasonically treated with a cell crusher at 50% energy for 5 minutes, and then refrigerated and allowed to stand for stratification.

[0085] Step 2: The upper suspension of the stratified CNC dispersion was divided into 20 mL sample bottles in 5 mL portions and heated in an oven at 95 °C for 72 h.

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

[0087] Step 4: 1 mL of aniline monomer, 0.7 g of ammonium persulfate, and 3 mL of concentrated hydrochloric acid solution are sequentially added to 40 mL of ethanol solution and mixed. The ethanol solution is composed of ethanol solvent and deionized water. The deionized water content in the mixed solution must be able to meet the dissolution requirements of ammonium persulfate.

[0088] Step 5: adding the aerogel to the mixed solution obtained in step 4, polymerizing at 2° C. for 24 h.

[0089] Step 6: Rinse the polymerized aerogel with ethanol and vacuum dry it.

[0090] The relationship between the reflection loss and electromagnetic frequency of the composite material of cellulose nanocrystal aerogel and polyaniline without chiral nematic structure at a concentration of 5% with a polymerization time of 24 hours in this embodiment is as follows: Figure 7 As shown, the relationship between impedance matching value and electromagnetic frequency is as follows Figure 8 As shown, the maximum absorption bandwidth and minimum reflection loss are as follows Figure 9 As shown, it can be seen that although the conductivity, impedance matching optimization effect and electromagnetic wave absorption performance of the cellulose nanocrystal aerogel are improved, they are not as good as those in Example 3.

[0091] At the same time, reference Figures 1 to 9 It can be seen that with the increase of polymerization time, 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 by the lower layer suspension with a chiral nematic structure is significantly better than that of the upper layer aerogel without a chiral nematic structure.

[0092] As can be seen from the above examples, the described implementation steps confirm that polyaniline successfully enhances the conductivity of cellulose nanocrystal aerogels, thereby optimizing impedance matching and enhancing their electromagnetic wave absorption performance. This demonstrates the effectiveness of the method proposed in the present invention for in situ polymerization of polyaniline on chiral nematic cellulose nanocrystal aerogels.

Claims

1. A method for preparing an electromagnetic wave absorbing material based on cellulose nanocrystals, characterized in that: The steps include: Step 1: Prepare cellulose nanocrystal aerogel by the following method: Step 11, preparing an aqueous dispersion of cellulose nanocrystals and performing sonication, followed by refrigeration and standing for stratification, wherein the lower layer is an anisotropic suspension having a chiral nematic structure; Step 12, packaging the upper and lower layers of the separated dispersion, and heating the lower layer of the dispersion to gel the product; Step 13, freezing and vacuum-freezing the gelled product of step 12 to obtain the cellulose nanocrystal aerogel; Step 2, adding aniline monomer, ammonium persulfate and hydrochloric acid to an ethanol solvent to obtain a mixed solution; Step 3, adding the cellulose nanocrystal aerogel to the mixed solution to perform in-situ polymerization; Step 4: Rinse the polymerized aerogel with ethanol and vacuum dry it.

2. The method for preparing an electromagnetic wave absorbing material based on cellulose nanocrystals according to claim 1, characterized in that: The aqueous dispersion of cellulose nanocrystals is prepared by dispersing commercial cellulose nanocrystal powder in deionized water, with a mass concentration of 4-5%.

3. The method for preparing an electromagnetic wave absorbing material based on cellulose nanocrystals according to claim 1, characterized in that: In step 12, the heating conditions are: heating at 90-95° C. for 60-72 hours.

4. The method for preparing an electromagnetic wave absorbing material based on cellulose nanocrystals according to claim 1, characterized in that: In the mixed solution, the amount of aniline monomer is 0.8-1 mL, the amount of ammonium persulfate is 0.5-0.8 g, and deionized water for dissolving the ammonium persulfate is added. The amount of ethanol solvent is 40 mL, and the mass concentration of hydrochloric acid is 36-38%, and the amount is 1.5-3 mL.

5. The method for preparing an electromagnetic wave absorbing material based on cellulose nanocrystals according to claim 1, characterized in that: In step 3, the in-situ polymerization is carried out for 6-24 hours at a temperature of 0-4°C.

6. The method for preparing an electromagnetic wave absorbing material based on cellulose nanocrystals according to claim 1, characterized in that: In step 3, the amount of the cellulose nanocrystal aerogel and the mixed solution is such that 5 mL of aerogel prepared from 5% cellulose nanocrystals corresponds to 0.8-1 mL of aniline monomer.

7. The method for preparing an electromagnetic wave absorbing material based on cellulose nanocrystals according to claim 1, characterized in that: Using different amounts of aniline monomer, the polymerization amount increases with increasing concentration, and the conductivity enhances with increasing polymerization time.

8. The method for preparing an electromagnetic wave absorbing material based on cellulose nanocrystals according to claim 1, characterized in that: The obtained electromagnetic wave absorbing material has a maximum absorption bandwidth of 7.9 GHz and a minimum reflection loss of -47.9 dB.

9. Use 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 equipment of stealth coating.

Images