Flexible conductive wood, preparation method therefor and use thereof

Abstract

A method for preparing flexible conductive wood, comprising the following steps: (1) cutting wood in the vertical growth direction to form wood chips having a certain thickness, impregnating the wood chips with a chemical eluent, then repeatedly cleaning the wood chips several times by using clear water, and then subjecting the wood chips to vacuum drying treatment; (2) preparing a small-size graphene oxide solution, impregnating the delignified wood chips with the small-size graphene oxide solution in vacuum, then drying the delignified wood chips in vacuum, then preparing a large-size graphene oxide solution, impregnating the wood chips with the large-size graphene oxide solution, and then drying the wood chips in vacuum; and (3) preparing a reducing agent solution and subjecting the wood chips impregnated with the graphene oxide to impregnation with the reducing agent solution to obtain the flexible conductive wood. By removing lignin by means of the chemical method to soften wood, wood having good flexibility is obtained, and by loading graphene flakes having different particle sizes onto the surface of the wood and into pore channels of the wood by means of gradient impregnation, the conductivity of the wood is improved. The prepared composite wood has wide application prospects in the fields of flexible electronic devices, flexible batteries, wearable devices, etc.

Description

Flexible conductive wood, preparation method and application thereof Technical Field

[0001] The present invention belongs to the technical field of conductive wood preparation, and in particular relates to flexible conductive wood, a preparation method and application thereof. Background Art

[0002] Natural wood, with its high strength, low density, environmental friendliness, and renewable nature, is a traditional building material. However, wood is generally non-conductive. Its minimal number of free electrons prevents effective electron pathways, resulting in near-zero conductivity under normal conditions. To expand wood's applications in electronics, energy storage, and other fields, the development of new conductive wood materials is necessary.

[0003] Traditionally, conductive wood has been developed by filling the wood's pores with conductive additives, such as graphene, carbon nanotubes, and polyaniline. The introduction of these additives effectively enhances the wood's conductivity, enabling its use in electronic devices. Carbonization can also improve wood's conductivity, but this process makes the wood brittle and is typically converted into a powder for applications in energy storage devices and other fields. Technical issues

[0004] In addition to its poor electrical conductivity, wood's inherent rigid structure also limits its application in flexible batteries, wearable devices, and other fields. Wood's rigidity primarily comes from its internal lignin and hemicellulose skeleton. Chemical elution can remove some of these components, softening the wood. Technical Solutions

[0005] The present invention provides a flexible conductive wood, a preparation method and its application, so as to overcome the shortcomings of wood itself, such as non-conductivity and strong rigidity, and expand the application of wood in the fields of flexible electronic devices, wearable devices and the like.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing flexible conductive wood comprises the following steps:

[0008] (1) Cut the wood into wood chips of a certain thickness along the vertical growth direction, immerse them in a chemical elution solution to remove some lignin and hemicellulose, then wash them repeatedly with clean water several times, and then vacuum dry them;

[0009] (2) preparing a small-diameter graphene oxide solution, vacuum-impregnating the delignified wood chips therein, and then vacuum-drying the solution; then preparing a large-diameter graphene oxide solution, impregnating the wood chips therein, and then vacuum-drying the solution;

[0010] (3) Prepare a reducing agent solution and immerse the wood chips impregnated with graphene oxide in it to reduce the graphene oxide, thereby improving the electrical conductivity of the composite material and obtaining flexible conductive wood.

[0011] Furthermore, the wood in step (1) is selected from one of balsa, basswood, teak, fir, maple, beech, willow, elm, pine, poplar, walnut, birch, and oak, and the thickness of the slices along the vertical growth direction ranges from 1 to 50 mm.

[0012] Furthermore, the chemical eluent in step (1) is composed of an alkali solution and a sulfite, which can dissolve and remove part of the lignin and hemicellulose and soften the wood. The alkali solution is one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, and ammonium carbonate, and the sulfite is one or more of sodium sulfite, potassium sulfite, and ammonium sulfite.

[0013] Furthermore, the concentration of the chemical eluent is in the range of 0.5-10 mol / L, wherein the alkali solution accounts for 50-90% of the total molar ratio.

[0014] Furthermore, in step (1), the wood chips are immersed in a chemical elution solution for 5-48 h at a temperature of 60-100°C, and then washed with clean water and vacuum dried at a temperature of 50-100°C for 6-24 h.

[0015] Furthermore, the small-diameter graphene oxide solution prepared in step (2) uses single-layer graphene oxide, ethanol as a solvent, a concentration of 0.2-5 mg / mL, and a graphene oxide flake size of 0.1-5 μm. The vacuum impregnation process can allow the small-diameter graphene oxide flakes to fully fill the pores of the wood, followed by vacuum drying at a temperature of 50-80°C for 6-24 h.

[0016] Furthermore, a secondary impregnation is performed in step (2), and a large-diameter graphene oxide solution is prepared using a single-layer graphene oxide, ethanol is used as a solvent, the concentration is 0.2-2 mg / mL, and the graphene oxide flake size is 10-100 μm. The vacuum impregnation process can allow a portion of the large-diameter graphene oxide to enter the pores of the wood, and the other portion is coated on the surface of the wood chip. The secondary impregnation further improves the overall uniformity and graphene loading of the composite material, and then vacuum drying is performed.

[0017] Furthermore, in step (3), the reducing agent is selected from hydrazine hydrate, hydroiodic acid, vitamin C, NaHB4 or NaHSO3, and the wood chips loaded with graphene oxide are immersed in the reducing agent solution, heated under reflux to reduce the graphene oxide, the heating temperature is 50-100°C, the reaction time is 1-24 h, and then washed with clean water and dried to obtain flexible conductive wood, and the total graphene loading in the flexible conductive wood is 0.1-10%. Beneficial effects

[0018] Compared with the prior art, the present invention has the following technical advantages:

[0019] The present invention prepares a series of flexible, wearable composite woods with high electrical conductivity through the strategy of lignin removal and composite graphene. Graphene sheets of different particle sizes are loaded on the surface and pores of the wood through a step-by-step impregnation method to increase the graphene loading amount and achieve uniform preparation of the composite material. It has broad application prospects in the fields of flexible electronics, wearable devices, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 SEM comparison of before and after delignification.

[0021] Figure 2. Flexibility of wood chips after delignification.

[0022] Figure 3 Photograph of composite graphene conductive wood.

[0023] Figure 4 SEM image of composite graphene conductive wood. Modes for Carrying Out the Invention

[0024] Example 1

[0025] A method for preparing flexible conductive wood comprises the following steps:

[0026] Balsa wood was cut into 1 mm thick chips and immersed in an eluent (2.5 mol / L NaOH + 0.5 mol / L K₂SO₃ aqueous solution), heated under reflux at 90°C for 10 hours, then repeatedly rinsed with distilled water and dried at 80°C for 12 hours. A 1 mg / ml ethanolic solution of small-diameter graphene oxide (with an average flake size of 1 μm) was prepared. The chips were vacuum-impregnated for 2 hours and then dried at 70°C for 5 hours. A 0.5 mg / ml ethanolic solution of large-diameter graphene oxide (with an average flake size of 40 μm) was prepared. The chips were vacuum-impregnated for 2 hours and then dried at 70°C for 5 hours. The chips were then immersed in hydrazine hydrate, heated under reflux at 80°C for 5 hours, rinsed with water, and dried at 80°C for 12 hours to produce a flexible conductive composite wood.

[0027] Example 2

[0028] A method for preparing flexible conductive wood comprises the following steps:

[0029] Beech wood was cut into 2 mm thick chips and immersed in an eluent (2 mol / L NaOH + 1 mol / L Na₂SO₃ aqueous solution), heated under reflux at 90°C for 8 hours, then rinsed with distilled water and dried at 80°C for 12 hours. A 2 mg / ml ethanolic solution of small-diameter graphene oxide (with an average flake size of 1 μm) was prepared. The chips were vacuum-impregnated for 2 hours and then dried at 70°C for 5 hours. A 1 mg / ml ethanolic solution of large-diameter graphene oxide (with an average flake size of 20 μm) was prepared. The chips were vacuum-impregnated for 2 hours and then dried at 70°C for 8 hours. The chips were then immersed in 2 mol / L vitamin C, heated under reflux at 90°C for 10 hours, rinsed with water, and dried at 80°C for 12 hours to produce a flexible conductive composite wood.

[0030] Example 3

[0031] A method for preparing flexible conductive wood comprises the following steps:

[0032] Chinese fir wood was cut into 1 mm thick chips and immersed in an eluent (2 mol / L KOH + 1.2 mol / L (NH₄)₂SO₃ aqueous solution), heated under reflux at 90°C for 12 hours, then rinsed with distilled water and dried at 80°C for 12 hours. A 2 mg / mL ethanolic solution of small-diameter graphene oxide (with an average flake size of 0.6 μm) was prepared. The chips were vacuum-impregnated for 1 hour and then dried at 70°C for 5 hours. A 1.5 mg / mL ethanolic solution of large-diameter graphene oxide (with an average flake size of 40 μm) was prepared. The chips were vacuum-impregnated for 3 hours and then dried at 80°C for 10 hours. The chips were then immersed in 1 mol / L NaHB₄, heated under reflux at 90°C for 8 hours, rinsed with water, and dried at 80°C for 12 hours to produce a flexible conductive composite wood.

[0033] Taking the balsa wood in Example 1 as an example, soaking it in NaOH+Na2SO3 solution for 2 hours can remove part of the lignin and hemicellulose, soften the wood, and then after repeated rinsing and natural drying, wood chips with a certain degree of flexibility can be obtained. As shown in SEM (Figure 1), the interior of the wood is mainly a hexagonal pore structure with a size of about 50 microns. After being treated with a chemical eluent and dried, the pores are twisted to produce more wrinkles, thereby achieving the bending of the wood and improving its flexibility (Figure 2). Uniform loading of graphene is achieved by a step-by-step impregnation method and chemical reduction. As shown in Figures 3 and 4, the graphene sheets are evenly coated on the surface of the wood, thereby improving the conductivity of the substrate. Its conductivity is measured to be 5.9*10 -2 S / m.

Claims

1. A method for preparing flexible conductive wood, characterized in that: The following steps are involved: (1) Cut the wood into wood chips of a certain thickness along the vertical growth direction, immerse them in a chemical washing liquid to remove part of the lignin and hemicellulose, then wash them repeatedly with clean water several times, and then vacuum dry them; (2) preparing a small-diameter graphene oxide solution, vacuum impregnating the delignified wood chips therein, and then vacuum drying, and then preparing a large-diameter graphene oxide solution, impregnating the wood chips therein, and then vacuum drying; (3) preparing a reducing agent solution, impregnating the wood chips impregnated with graphene oxide into the reducing agent solution to reduce the graphene oxide, and then vacuum drying to improve the electrical conductivity of the composite material to obtain flexible conductive wood.

2. The method for preparing the flexible conductive wood according to claim 1, characterized in that: The wood in step (1) is selected from balsa, basswood, teak, fir, maple, beech, willow, elm, pine, poplar, walnut, birch, and oak, and the thickness of the slices along the vertical growth direction ranges from 1 to 50 mm.

3. The method for preparing the flexible conductive wood according to claim 1, characterized in that: The chemical eluent in step (1) is composed of an alkali solution and a sulfite, which can dissolve and remove part of the lignin and hemicellulose and soften the wood. The alkali solution is one or more of sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, and ammonium carbonate. The sulfite is one or more of sodium sulfite, potassium sulfite, and ammonium sulfite.

4. The method for preparing the flexible conductive wood according to claim 3, characterized in that: The concentration of the chemical eluent is in the range of 0.5-10 mol / L, wherein the alkali solution accounts for 50-90% of the total molar ratio.

5. The method for preparing the flexible conductive wood according to claim 1, characterized in that: In step (1), the wood chips are immersed in a chemical washing liquid for 5-48 hours at a temperature of 60-100°C, and then washed with clean water and vacuum dried at a temperature of 50-100°C for 6-24 hours.

6. The method for preparing the flexible conductive wood according to claim 1, characterized in that: The small-diameter graphene oxide solution prepared in step (2) uses a single-layer graphene oxide, ethanol as a solvent, a concentration of 0.2-5 mg / mL, and a graphene oxide flake size of 0.1-5 μm. The vacuum impregnation process can allow the small-diameter graphene oxide flakes to fully fill the pores of the wood, followed by vacuum drying at a temperature of 50-80°C for 6-24 h.

7. The method for preparing the flexible conductive wood according to claim 1, characterized in that: In step (2), a secondary impregnation is performed, and a large-diameter graphene oxide solution is prepared using a single-layer graphene oxide, ethanol is used as a solvent, the concentration is 0.2-2 mg / mL, and the graphene oxide flake size is 10-100 μm. The vacuum impregnation process allows a portion of the large-diameter graphene oxide to enter the pores of the wood, and the other portion is coated on the surface of the wood chip. The secondary impregnation further improves the overall uniformity and graphene loading of the composite material, and then vacuum drying is performed.

8. The method for preparing the flexible conductive wood according to claim 1, characterized in that: In step (3), the reducing agent is selected from hydrazine hydrate, hydroiodic acid, vitamin C, NaHB4 or NaHSO3, and the wood chips loaded with graphene oxide are immersed in the reducing agent solution, heated under reflux to reduce the graphene oxide, the heating temperature is 50-100°C, the reaction time is 1-24 h, and then washed with clean water and dried to obtain flexible conductive wood, the total graphene loading in the flexible conductive wood is 0.1-10%.

9. A flexible conductive wood prepared according to the method according to any one of claims 1 to 8.

10. An application of the flexible conductive wood according to claim 9, characterized in that: Applications include flexible electronic devices, flexible batteries, and wearable devices.

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