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

Abstract

The invention discloses composite cellulose aerogel, a preparation method and application of the composite cellulose aerogel to electromagnetic interference shielding, and belongs to the field of biological functional materials.The aerogel comprises methyltrimethoxysilane and two-dimensional transition metal carbide and / or nitride nanosheets which are attached to the surfaces of cellulose of different scales, the composite cellulose aerogel is prepared by adopting a chemical cross-linking method. The aerogel can be applied to electromagnetic wave shielding in a pressed environment, has extremely high electromagnetic interference shielding effectiveness, has very good mechanical properties, and has very good application prospects in the fields of compression resistance and electromagnetic interference shielding.

Description

Technical Field

[0001] The invention 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 Art

[0002] Lightweight, compressible aerogels have the potential to be modified in various ways to prepare functional materials due to their good elasticity, low density, and unique three-dimensional porous structure. Therefore, they have been widely studied and applied in various fields such as filtration, electromagnetic interference shielding, and adsorption. MXene has attracted much attention in the field of materials science due to its excellent electrical conductivity similar to that of metals, outstanding mechanical properties, large aspect ratio and specific surface area, and the unique property of being easy to process in aqueous dispersions derived from hydrophilic functional groups. Therefore, it is necessary to construct a mechanically robust MXene macrostructure in a reasonable way, including various forms such as fibers, films, or aerogels, so as 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 stability of MXene aerogels. Among them, bacterial cellulose (BC), with its rich hydrophilic functional groups, can form strong hydrogen bond interactions with MXene, thereby effectively avoiding the serious aggregation of MXene nanosheets. The interface formed between BC and MXene can not only improve the mechanical properties of MXene through effective stress transfer, but also play an extremely critical role in optimizing the functions of MXene-based aerogels. Among them, BC / MXene aerogels show higher compressive strength than pure MXene or pure polymer aerogels. In addition, the severe mismatch of conductivity at the interface will cause a high degree of polarization of the interface under the action of the electric field of the incident electromagnetic wave, thereby increasing the energy loss of the incident electromagnetic wave, and ultimately achieving an effective improvement in the electromagnetic interference shielding performance of the composite material. Summary of the invention

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

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing a composite cellulose aerogel, comprising the following steps:

[0007] Step 1: Prepare a BC / CF mixed dispersion by mixing BC with a diameter of 20 to 100 nm and cotton fiber (CF) with a diameter of 20 to 50 μm in a mass ratio of 2:1;

[0008] Step 2: Add the MXene aqueous dispersion containing the single-layer nanosheets to the mixed dispersion obtained in step 1, stir for a period of time, add the MTMS solution for cross-linking reaction, and then freeze-dry to obtain a composite cellulose aerogel.

[0009] Furthermore, the solid content of the BC / CF mixed dispersion 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 is 1-10wt%, preferably 3.5wt%.

[0010] Furthermore, the precursor of the MXene aqueous dispersion containing the single-layer nanosheet is Ti 3 AlC 2 .

[0011] Furthermore, the MXene precursor Ti 3 AlC 2 BC, Ti 3 AlC 2 The mass ratio of the three is 1:2:1.5.

[0012] Furthermore, stirring for a period of time refers to stirring for more than 60 minutes.

[0013] Furthermore, the cross-linking reaction time is more than 2 hours.

[0014] In a second aspect, the present invention provides a composite cellulose aerogel prepared by the method described in the first aspect.

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

[0016] Compared with the prior art, the present invention prepares the composite cellulose aerogel by chemical crosslinking method, constructs a multi-level micro-nano aerogel network structure, and greatly improves the mechanical properties and electromagnetic interference shielding effectiveness of the composite aerogel. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 These are SEM images of BC / CF / Mxene / MTMS prepared in Example 3 of the present invention with (a) a scale of 50 μm and (b) a scale of 1 μm.

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

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

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

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

[0022] Figure 6 It is a comparison chart of the mechanical properties tests of BC / CF / Mxene / MTMS prepared in Example 3 of the present invention and BC / Mxene / MTMS prepared in Example 4 in the vertical direction (a) and the parallel direction (b).

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

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

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

[0026] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0027] As used herein, the term "about" is used to provide flexibility and imprecision associated with a given term, measurement or value. The degree of flexibility for a particular variable can be easily determined by one skilled in the art.

[0028] The present invention realizes the preparation of ultra-light and strong BC / CF / Mxene / MTMS aerogel by efficiently utilizing BC, CF and MTMS as efficient cross-linking agents for MXene nanosheets. Nanoscale BC and micron-scale CF construct a multi-scale mesh structure through hydrogen bond cross-linking, which significantly improves the mechanical properties of the cell wall and the aerogel as a whole. The compressive 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 present invention can be prepared according to existing literature or purchased from the market. The present invention adopts the following steps to make it by itself:

[0030] (1) Take 2g of LiF and 2g of Ti 3 AlC 2 35 mL of concentrated hydrochloric acid was added, and magnetic stirring was performed at 35° C. and 400 r / min for 40 h to etch away the Al layer.

[0031] (2) The solution prepared in step (1) was washed with deionized water and centrifuged until the pH value reached neutral. The centrifuge speed was 3500 r / min for 1 min, and the process was repeated ten times.

[0032] (3) The MXene obtained in step (2) was added to 50 mL of deionized water, and intercalated by ultrasonication for 30 min in an ice bath, and centrifuged at 10,000 r / min for 15 min to obtain an aqueous dispersion of MXene containing a single-layer nanosheet.

[0033] Example 1

[0034] (1) Take 5 g of BC (20-100 nm) and 0.8 g of CF (20-50 μm) and add them into 40 mL of deionized water. Stir magnetically at 500 rpm for 6 h to obtain a uniformly dispersed BC / CF aqueous dispersion.

[0035] (2) Take 0.5 mL of MTMS and 10 μL of acetic acid and add them to 2 mL of deionized water. Rotate at 500 rpm for 1 min. Repeat five times.

[0036] (3) Add the polysiloxane obtained in step (2) to the dispersion prepared in step (1), and stir magnetically at 500 r / min for 120 min to obtain a uniform BC / CF / MTMS dispersion.

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

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

[0039] Example 2

[0040] (1) Take 5 g of BC (20-100 nm) and 0.8 g of CF (20-50 μm) and add them into 40 mL of deionized water. Stir magnetically at 500 rpm for 6 h to obtain a uniformly dispersed BC / CF aqueous dispersion.

[0041] (2) Add the MXene aqueous dispersion to the dispersion prepared in step (1), and stir magnetically at 500 r / min for 30 min to obtain a uniform BC / CF / MXene dispersion.

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

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

[0044] Example 3

[0045] (1) Take 5 g of BC (20-100 nm) and 0.8 g of CF (20-50 μm) and add them into 40 mL of deionized water. Stir magnetically at 500 rpm for 6 h to obtain a uniformly dispersed BC / CF aqueous dispersion.

[0046] (2) Add the MXene aqueous dispersion to the dispersion prepared in step (1), and stir magnetically at 500 r / min for 30 min to obtain a uniform BC / CF / MXene dispersion.

[0047] (3) Take 0.5 mL of MTMS and 10 μL of acetic acid and add them to 2 mL of deionized water. Rotate at 500 rpm for 1 min. Repeat five times.

[0048] (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 / CF / Mxene / MTMS dispersion.

[0049] (5) The dispersion prepared in step (4) was added into a 20×20×20 mm resin mold, frozen with liquid nitrogen for 20 min, and then placed in a -50°C freeze dryer for 48 h; the obtained product was BC / CF / Mxene / MTMS aerogel.

[0050] Figure 1 The SEM test determined the multi-scale microstructure of BC / CF / Mxene / MTMS. Figure 2 FTIR test and Figure 3 The XRD test confirmed the successful loading of MXene and MTMS. Figure 4 The TG test determined its thermodynamic properties. Figure 5 XPS test determined the chemical state of Ti element on the surface of BC / CF / Mxene / MTMS.

[0051] Figure 6 The mechanical properties of the BC / CF / Mxene / MTMS aerogel in the shape of a cube with a length, width and height of 20 mm were tested by a tensile compression tester. The compression speed was 2 mm min -1 , compression test was carried out in the vertical direction, with a compression strain of 80%, and compression-rebound test was carried out in the parallel direction, with a compression strain of 50%. The compressive strength of the composite aerogel in the vertical and parallel directions was 96.3kPa and 15.5kPa respectively, which were much higher than BC / Mxene / MTMS aerogel. The multi-scale micro-nano internal structure effectively improved the overall mechanical properties.

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

[0053] Example 4

[0054] (1) Take 5 g of BC (20-100 nm) and add it into 40 mL of deionized water. Stir magnetically at 500 rpm for 6 h to obtain a uniformly dispersed BC aqueous dispersion.

[0055] (2) Add the MXene aqueous dispersion to the dispersion prepared in step (1), and stir magnetically at 500 r / min for 30 min to obtain a uniform BC / MXene dispersion.

[0056] (3) Take 0.5 mL of MTMS and 10 μL of acetic acid and add them to 2 mL of deionized water. Rotate at 500 rpm for 1 min. 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) The dispersion prepared in step (4) was added into a 20×20×20 mm resin mold, frozen with liquid nitrogen for 20 min, and then placed in a -50°C freeze dryer for 48 h; the obtained product was BC / Mxene / MTMS aerogel.

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

[0060] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the present invention, which should be regarded as belonging to the present invention and the scope of patent protection determined by the submitted claims.

Claims

1. A method for preparing a composite cellulose aerogel, characterized in that: The steps include: Step 1: Prepare a BC / CF mixed dispersion by mixing BC with a diameter of 20 to 100 nm and CF with a diameter of 20 to 50 μm at a mass ratio of 2:1; Step 2: Add the MXene aqueous dispersion containing the single-layer nanosheets to the mixed dispersion obtained in step 1, stir for a period of time, add the MTMS solution for cross-linking reaction, and then freeze-dry to obtain the composite cellulose aerogel.

2. The method according to claim 1, characterized in that In step 1, the solid content of the BC / CF mixed dispersion is 0.1-5wt%, preferably 2wt%; the concentration of the MTMS solution is 1-5mmol / L, preferably 1.5mmol / L; the solid content of the MXene aqueous dispersion is 1-10wt%, preferably 3.5wt%.

3. The method according to claim 1, characterized in that In step 2, the precursor of the MXene aqueous dispersion containing single-layer nanosheets is Ti3AlC2; the mass ratio of BC, Ti3AlC2 and MTMS is 1:2:1.

5.

4. The method according to claim 1, characterized in that In step 2, stirring is performed for more than 60 minutes; and the cross-linking reaction is performed for more than 2 hours.

5. A composite cellulose aerogel prepared by the method according to any one of claims 1 to 4.

6. Use of the composite cellulose aerogel prepared by the method according to any one of claims 1 to 4 in electromagnetic interference shielding.

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