Composite cellulose aerogel, preparation method and application thereof in electromagnetic interference shielding

Abstract

The application discloses a kind of composite cellulose aerogel, preparation method and its application in electromagnetic interference shielding, belong to the field of biological functional materials, the aerogel includes the methyl trimethoxysilane and two-dimensional transition metal carbide and / or nitride nanosheet attached on the surface of cellulose of different scales, and composite cellulose aerogel is prepared using chemical crosslinking method.The aerogel can be applied to electromagnetic wave shielding under pressure environment, it has very high electromagnetic interference shielding efficiency, and has good mechanical properties, and has good application prospect in the field of compression resistance and electromagnetic interference shielding.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of biological functional materials, and relates to a composite cellulose aerogel, a preparation method and application thereof in electromagnetic interference shielding. BACKGROUND

[0002] Lightweight compressible aerogels have been widely studied and applied in different fields such as filtration, electromagnetic interference shielding, adsorption, etc. due to their significant advantages such as good elasticity, low density and unique three-dimensional porous structure, and have the potential to be modified by various ways to prepare functional materials. MXene has attracted much attention in the field of material science due to its excellent conductivity similar to metal, outstanding mechanical properties, large aspect ratio and specific surface area, and the unique property of being easy to process in water dispersion derived from hydrophilic functional groups. Therefore, it is necessary to construct MXene macrostructure with mechanical strength in a reasonable way, including fibers, films or aerogels, etc. to fully utilize the unique properties of MXene.

[0003] In recent years, polymers have been widely introduced as adhesives or matrices to improve the mechanical properties and use stability of MXene aerogels. Among them, bacterial cellulose (BC) can form strong hydrogen bond interactions with MXene due to its rich hydrophilic functional groups, thereby effectively avoiding the serious aggregation of MXene nanosheets. The interface formed between BC and MXene not only improves the mechanical properties of MXene through effective stress transfer, but also plays a crucial role in optimizing the function of MXene-based aerogels. Compared with pure MXene or pure polymer aerogels, BC / MXene aerogels exhibit higher compressive strength. In addition, the existence of serious conductivity mismatch at the interface can cause high polarization of the interface under the action of incident electromagnetic wave electric field, thereby increasing the energy loss of the incident electromagnetic wave, and finally effectively improving the electromagnetic interference shielding performance of the composite material. SUMMARY

[0004] The purpose of the present application is to provide a composite cellulose aerogel, a preparation method and application thereof in electromagnetic interference shielding.

[0005] The purpose of the present application is achieved by the following technical solutions:

[0006] In a first aspect, the present application provides a preparation method of a composite cellulose aerogel, comprising the following steps:

[0007] Step one: BC / CF mixed dispersion liquid is prepared by mixing BC with a diameter of 20-100 nm and cotton fibers (CF) with a diameter of 20-50 μm at a mass ratio of 2:1;

[0008] Step two: adding the MXene aqueous dispersion liquid containing monolayer nanosheets into the mixed dispersion liquid obtained in step one, stirring for a period of time, then adding the MTMS solution to perform cross-linking reaction and freeze-drying to obtain the composite cellulose aerogel.

[0009] Further, the solid content of the BC / CF mixed dispersion liquid is 0.1-5wt%, preferably 2wt%; the concentration of the MTMS solution is 1-5mmol / L, preferably 1.5mmol / L; and the solid content of the MXene aqueous dispersion liquid is 1-10wt%, preferably 3.5wt%.

[0010] Further, the precursor of the MXene aqueous dispersion liquid containing monolayer nanosheets is Ti3AlC2.

[0011] Further, the mass ratio of BC, Ti3AlC2 and MTMS is 1:2:1.5, calculated based on the precursor Ti3AlC2 of MXene.

[0012] Further, the stirring for a period of time refers to stirring for more than 60min.

[0013] Further, the cross-linking reaction time is more than 2h.

[0014] In a second aspect, the present application provides a composite cellulose aerogel prepared by the method of the first aspect.

[0015] In a third aspect, the present application provides an application of the composite cellulose aerogel prepared by the method of the first aspect in electromagnetic interference shielding.

[0016] Compared with the prior art, the present application prepares the composite cellulose aerogel by the chemical cross-linking method, constructs the multi-scale micro-nano aerogel network structure, and greatly improves the mechanical properties and electromagnetic interference shielding efficiency of the composite aerogel. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is the SEM image of BC / CF / Mxene / MTMS prepared in Example 3 of the present application, with the scale of (a) being 50μm and the scale of (b) being 1μm.

[0018] Figure 2 is the FTIR graph of BC / CF / MTMS prepared in Example 1, BC / CF / Mxene prepared in Example 2 and BC / CF / Mxene / MTMS prepared in Example 3 of the present application.

[0019] Figure 3is the XRD graph of BC / CF / MTMS prepared in Example 1 of the present application, BC / CF / Mxene prepared in Example 2 and BC / CF / Mxene / MTMS prepared in Example 3.

[0020] Figure 4 is the TG graph of BC / CF / MTMS prepared in Example 1 of the present application, BC / CF / Mxene prepared in Example 2 and BC / CF / Mxene / MTMS prepared in Example 3.

[0021] Figure 5 is the XPS fine spectrum of BC / CF / Mxene / MTMS prepared in Example 3 of the present application.

[0022] Figure 6 is the comparison graph of mechanical property test in vertical direction (a) and parallel direction (b) of BC / CF / Mxene / MTMS prepared in Example 3 of the present application and BC / Mxene / MTMS prepared in Example 4.

[0023] Figure 7 is the comparison graph of electromagnetic interference shielding effectiveness of BC / CF / Mxene / MTMS prepared in Example 3 of the present application and BC / Mxene / MTMS prepared in Example 4. DETAILED DESCRIPTION

[0024] In order to make the technical problems to be solved by the present application, technical solutions and beneficial effects more clear and explicit, the present application is further described in detail in combination with embodiments and drawings. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application. The technical solutions of the present application are described in detail below in combination with embodiments and drawings, but the protection scope is not limited thereto.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0026] Unless otherwise specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. Unless otherwise specified, the reagents or instruments used are conventional products that can be commercially purchased.

[0027] As used herein, the term "about" is used to provide flexibility to a given term, measurement, or value associated with a given term, measurement, or value. One of ordinary skill in the art can readily determine the degree of flexibility afforded by the term "about" based on the context of the specific variable.

[0028] The application realizes the preparation of super-light and strong BC / CF / Mxene / MTMS aerogel by efficiently utilizing BC, CF and MTMS as efficient cross-linking agents of MXene nanosheets. The nanoscale BC and micrometer-scale CF construct a multi-scale network structure through hydrogen bond cross-linking, which significantly improves the mechanical properties of the cell wall and the whole aerogel. The compression strength of the composite aerogel in the vertical and parallel directions is 96.3kPa and 15.5kPa respectively. In addition, its electromagnetic interference shielding effectiveness can reach 63.9-72.1dB in the frequency range of 8.2-12.4GHz (X-band).

[0029] The single-layer nanosheet MXene used in the application can be prepared according to existing literature or purchased as a commercial product. The application is self-made by the following steps:

[0030] (1) 2g of LiF and 2g of Ti3AlC2 are added to 35mL of concentrated hydrochloric acid, and magnetic stirring is carried out at 400r / min for 40h at 35℃ to etch and remove the Al layer.

[0031] (2) The solution prepared in step (1) is washed with deionized water and centrifuged to a neutral pH, the centrifuge speed is 3500r / min, the time is 1min, and the operation is repeated ten times.

[0032] (3) The Mxene obtained in step (2) is added to 50mL of deionized water, and intercalation is carried out under ice bath for 30min, and 10000r / min centrifugation is carried out for 15min to obtain a MXene aqueous dispersion containing single-layer nanosheets.

[0033] Example 1

[0034] (1) 5g of BC (20-100nm) and 0.8g of CF (20-50μm) are added to 40mL of deionized water, and 500r / min magnetic stirring is carried out for 6h to obtain a uniformly dispersed BC / CF water dispersion.

[0035] (2) 0.5mL of MTMS and 10μL of acetic acid are added to 2mL of deionized water, 500r / min stirring is carried out for 1min, and the operation is repeated five times.

[0036] (3) The polysiloxane obtained in step (2) is added to the dispersion prepared in step (1), and 500r / min magnetic stirring is carried out for 120min to obtain a uniform BC / CF / MTMS dispersion.

[0037] (4) The dispersion solution configured in step (3) was added to a resin mold of 20x20x20 mm, frozen in liquid nitrogen for 20 min, and then placed in a freeze dryer at -50°C for drying for 48 h; the obtained product was BC / CF / MTMS aerogel.

[0038] Figure 2 FTIR test and Figure 3 XRD test of the BC / CF / MTMS determined the successful loading of MTMS, Figure 4 TG test of the BC / CF / MTMS determined the thermodynamic properties of the BC / CF / MTMS.

[0039] Example 2

[0040] (1) 5 g of BC (20-100 nm) and 0.8 g of CF (20-50 μm) were taken and added to 40 mL of deionized water, and magnetically stirred at 500 r / min for 6 h to obtain a uniformly dispersed BC / CF aqueous dispersion.

[0041] (2) The MXene aqueous dispersion was added to the dispersion solution configured in step (1), and magnetically stirred at 500 r / min for 30 min to obtain a uniformly dispersed BC / CF / MXene dispersion.

[0042] (3) The dispersion solution configured in step (2) was added to a resin mold of 20x20x20 mm, frozen in liquid nitrogen for 20 min, and then placed in a freeze dryer at -50°C for drying for 48 h; the obtained product was BC / CF / Mxene aerogel.

[0043] Figure 2 FTIR test and Figure 3 XRD test of the BC / CF / MXene determined the successful loading of MXene, Figure 4 TG test of the BC / CF / MXene determined the thermodynamic properties of the BC / CF / MXene.

[0044] Example 3

[0045] (1) 5 g of BC (20-100 nm) and 0.8 g of CF (20-50 μm) were taken and added to 40 mL of deionized water, and magnetically stirred at 500 r / min for 6 h to obtain a uniformly dispersed BC / CF aqueous dispersion.

[0046] (2) The MXene aqueous dispersion was added to the dispersion solution configured in step (1), and magnetically stirred at 500 r / min for 30 min to obtain a uniformly dispersed BC / CF / MXene dispersion.

[0047] (3) 0.5 mL of MTMS and 10 μL of acetic acid were taken and added to 2 mL of deionized water, and magnetically stirred at 500 r / min for 1 min, repeated five times.

[0048] (4) The polysiloxane obtained in step (3) is added to the dispersion liquid prepared in step (2), and 500 r / min magnetic stirring is performed for 120 min to obtain a uniform BC / CF / Mxene / MTMS dispersion liquid.

[0049] (5) The dispersion liquid prepared in step (4) is added to a 20x20x20mm resin mold, frozen in liquid nitrogen for 20min, and then placed in a-50℃ freeze dryer for drying for 48h; the obtained product is a BC / CF / Mxene / MTMS aerogel.

[0050] Figure 1 SEM tests determine the multi-scale microstructure of BC / CF / Mxene / MTMS, Figure 2 FTIR tests and Figure 3 XRD tests determine the successful loading of Mxene and MTMS, Figure 4 TG tests determine the thermodynamic properties thereof, Figure 5 XPS tests determine the chemical state of the Ti element on the surface of BC / CF / Mxene / MTMS.

[0051] Figure 6 Compression tests test the mechanical properties of the BC / CF / Mxene / MTMS aerogel in the form of a cube with a length, width, and height of 20mm by using a tensile compression testing machine. The compression speed is 2mm·min -1 The compression test is performed in the vertical direction with a compression strain of 80%, and the compression-rebound test is performed in the parallel direction with a compression strain of 50%. The compression strength of the composite aerogel in the vertical and parallel directions is 96.3kPa and 15.5kPa, respectively, which is much higher than that of the BC / Mxene / MTMS aerogel. The multi-scale micro-nano internal structure effectively improves the overall mechanical properties.

[0052] Figure 7 The electromagnetic interference shielding effectiveness is characterized by using a waveguide method in the X-band frequency range by using a vector network analyzer. The electromagnetic interference shielding effectiveness of the BC / CF / Mxene / MTMS aerogel can reach 63.9-72.1dB.

[0053] Example 4

[0054] (1) 5g of BC (20-100nm) is added to 40mL of deionized water, and 500r / min magnetic stirring is performed for 6h to obtain a uniformly dispersed BC water dispersion liquid.

[0055] (2) The MXene aqueous dispersion liquid is added to the dispersion liquid prepared in step (1), and 500 r / min magnetic stirring is performed for 30 min to obtain a uniform BC / MXene dispersion liquid.

[0056] (3) Take 0.5 mL of MTMS and 10 μL of acetic acid and add them to 2 mL of deionized water. Stir at 500 r / min for 1 min and repeat five times.

[0057] (4) Add the polysiloxane obtained in step (3) to the dispersion prepared in step (2) and stir magnetically at 500 r / min for 120 min to obtain a uniform BC / Mxene / MTMS dispersion.

[0058] (5) Add the dispersion prepared in step (4) into a 20×20×20mm resin mold, freeze it with liquid nitrogen for 20 min, and then place it in a freeze dryer at -50℃ for 48 h; the product obtained is BC / Mxene / MTMS aerogel.

[0059] Figure 6 Compression test and Figure 7 Vector network analysis determined the mechanical properties and electromagnetic interference (EMI) shielding effectiveness of BC / Mxene / MTMS aerogel. The compressive strength of BC / Mxene / MTMS aerogel in the vertical and horizontal directions were 33.5 kPa and 4.6 kPa, respectively, and its EMI shielding effectiveness in the X-band was 43.3–50.2 dB.

[0060] The above description is a further detailed explanation of the present invention in conjunction with specific preferred embodiments. It should not be considered that the specific embodiments of the present invention are limited to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the present invention, and all of these should be considered to fall within the scope of patent protection determined by the submitted claims.

Claims

1. A method for preparing a composite cellulose aerogel, characterized by, The method comprises the following steps: Step 1: BC with a diameter of 20-100 nm and CF with a diameter of 20-50 μm are mixed to prepare a BC / CF mixed dispersion liquid at a mass ratio of 6.25:1; Step 2: a MXene aqueous dispersion liquid containing monolayer nanosheets is added to the mixed dispersion liquid obtained in step 1, stirred for a period of time, then MTMS solution is added to perform cross-linking reaction, and freeze-drying is performed to obtain a composite cellulose aerogel; In step 2, the precursor of the MXene aqueous dispersion liquid containing monolayer nanosheets is Ti3AlC2; the mass ratio of BC, Ti3AlC2 and MTMS is 10:4:0.

95.

2. The method of claim 1, wherein, In step 1, the BC / CF mixed dispersion liquid is obtained by adding 5 g of BC with a diameter of 20-100 nm and 0.8 g of CF with a diameter of 20-50 μm to 40 mL of deionized water.

3. The method of claim 1, wherein, The concentration of the MTMS solution is 1-5 mmol / L.

4. The method of claim 1, wherein, The concentration of the MTMS solution is 1.5 mmol / L.

5. The method of claim 1, wherein, The solid content of the MXene aqueous dispersion liquid is 1-10 wt%.

6. The method of claim 1, wherein, The solid content of the MXene aqueous dispersion liquid is 3.5 wt%.

7. The method of claim 1, wherein, In step 2, the stirring is performed for more than 60 min; the cross-linking reaction is performed for more than 2 h.

8. A composite cellulose aerogel prepared by the method of any one of claims 1-7.

9. Use of a composite cellulose aerogel prepared by the method of any one of claims 1-7 in electromagnetic interference shielding.

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