WO2025091542A1 - Flexible conductive wood, preparation method therefor and use thereof - Google Patents

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

The 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

Natural wood has the advantages of high strength, low density, green environmental protection and renewable, and is a traditional building material. However, wood is generally not conductive, and the number of free electrons inside it is very small, which cannot form an effective electron channel. Under normal conditions, the conductivity is almost zero. In order to expand the application of wood in electronic devices, energy storage and other fields, it is necessary to develop new types of conductive wood.

The development of traditional conductive wood is mainly achieved by filling the pores of wood with conductive additives, such as graphene, carbon nanotubes, polyaniline and other conductive materials. The introduction of conductive agents can effectively improve the conductivity of wood, so that conductive wood can play a role in electronic devices. In addition, the conductivity of wood can be improved by carbonization, but the carbonized wood will become brittle and is generally made into powder for use in energy storage devices and other fields.

Technical issues

In addition to poor conductivity, the rigid structure of wood itself also limits its application in flexible batteries, wearable devices and other fields. The rigidity of wood mainly comes from the internal lignin and hemicellulose skeleton. Chemical reagents can be used to remove some of the lignin and hemicellulose components and soften the wood.

Technical Solutions

The present invention provides a flexible conductive wood, a preparation method and an application thereof, so as to overcome the disadvantages of wood itself being non-conductive and having strong rigidity, and expand the application of wood in the fields of flexible electronic devices, wearable devices, etc.

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

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

(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 and immersing the wood chips impregnated with graphene oxide in the reducing agent solution to reduce the graphene oxide, thereby improving the electrical conductivity of the composite material and obtaining flexible conductive wood.

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.

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. The sulfite is one or more of sodium sulfite, potassium sulfite, and ammonium sulfite.

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.

Furthermore, in step (1), the wood chips are immersed in a chemical washing liquid 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.

Furthermore, 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.

Furthermore, 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 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.

Furthermore, in step (3), the reducing agent is selected from hydrazine hydrate, hydroiodic acid, vitamin C, NaHB ₄ or NaHSO ₃ , 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

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

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 loading amount of graphene and achieve uniform preparation of composite materials. The composite materials have broad application prospects in the fields of flexible electronics, wearable devices, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 SEM comparison before and after delignification.

Fig. 2 Flexibility properties of wood chips after delignification.

Figure 3 Photograph of composite graphene conductive wood.

Figure 4 SEM image of composite graphene conductive wood.

Embodiments of the present invention

Example 1

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

The balsa wood was cut into 1 mm thick wood chips, which were immersed in the eluent (2.5 mol/L NaOH+0.5 mol/L K ₂ SO ₃ aqueous solution), heated to reflux at 90 ℃ for 10 h, and then repeatedly washed with distilled water and dried at 80 ℃ for 12 h. A 1 mg/ml ethanol solution of small-diameter graphene oxide was prepared with an average sheet diameter of 1μm, and the wood chips were vacuum immersed in it for 2h, and then dried at 70 ℃ for 5h. A 0.5 mg/ml ethanol solution of large-diameter graphene oxide was prepared with an average sheet diameter of 40μm, and the wood chips were vacuum immersed in it for 2h, and then dried at 70 ℃ for 5h. The wood chips were then immersed in hydrazine hydrate, heated to reflux at 80 ℃ for 5h, then washed with clean water, and dried at 80 ℃ for 12h to obtain flexible conductive composite wood.

Example 2

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

The beech wood was cut into 2 mm thick wood chips, and the wood chips were immersed in the eluent (2 mol/L NaOH+1 mol/L Na ₂ SO ₃ aqueous solution), heated and refluxed at 90 ℃ for 8 h, and then washed with distilled water and dried at 80 ℃ for 12 h. A 2 mg/ml small-diameter graphene oxide ethanol solution with an average sheet diameter of 1μm was prepared, and the wood chips were vacuum immersed in it for 2h, and then dried at 70 ℃ for 5h. A 1 mg/ml large-diameter graphene oxide ethanol solution with an average sheet diameter of 20μm was prepared, and the wood chips were vacuum immersed in it for 2h, and then dried at 70 ℃ for 8h. The wood chips were then immersed in 2 mol/L vitamin C, heated and refluxed at 90 ℃ for 10h, then washed with clean water, and dried at 80 ℃ for 12h to obtain flexible conductive composite wood.

Example 3

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

Cut the fir into 1 mm thick chips, immerse the chips in the eluent (2 mol/L KOH+1.2 mol/L (NH ₄ ) ₂ SO ₃ aqueous solution), heat and reflux at 90 ℃ for 12 h, then wash the chips with distilled water and dry them at 80 ℃ for 12 h. Prepare a 2 mg/ml ethanol solution of small-diameter graphene oxide with an average chip diameter of 0.6 μm, vacuum immerse the chips in it for 1 h, and then dry them at 70 ℃ for 5 h. Prepare a 1.5 mg/ml ethanol solution of large-diameter graphene oxide with an average chip diameter of 40 μm, vacuum immerse the chips in it for 3 h, and then dry them at 80 ℃ for 10 h. Then immerse the chips in 1 mol/L NaHB ₄ , heat and reflux at 90 ℃ for 8 h, then wash with clean water and dry them at 80 ℃ for 12 h to obtain flexible conductive composite wood.

Taking the balsa wood of Example 1 as an example, part of the lignin and hemicellulose can be removed by soaking in NaOH+Na ₂ SO ₃ solution for 2 hours, softening the wood, and then rinsing repeatedly and drying naturally to obtain wood chips with certain flexibility. 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 flexibility (Figure 2). The uniform loading of graphene is achieved by the stepwise 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, and its conductivity is measured to be 5.9*10 ^-2 S/m.

Claims (10)

A method for preparing flexible conductive wood, characterized in that it comprises the following steps: (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. The method for preparing flexible conductive wood according to claim 1 is characterized in that 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. The method for preparing flexible conductive wood according to claim 1 is characterized in that the chemical eluent in step (1) consists of an alkali solution and a sulfite, which can dissolve and remove part of the lignin and hemicellulose and soften the wood, and 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. The method for preparing flexible conductive wood according to claim 3 is 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. The method for preparing flexible conductive wood according to claim 1 is characterized in that in step (1), the wood chips are immersed in a chemical eluent 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. The method for preparing flexible conductive wood according to claim 1 is characterized in that the small-diameter graphene oxide solution prepared in step (2) uses a single-layer graphene oxide, ethanol is used as a solvent, the concentration is 0.2-5 mg/mL, the graphene oxide flake size is 0.1-5 μm, and the vacuum impregnation process can make the small-diameter graphene oxide fully fill the pores of the wood, followed by vacuum drying, the drying temperature is 50-80°C, and the time is 6-24 h. The method for preparing flexible conductive wood according to claim 1 is characterized in that a secondary impregnation is performed in step (2), a single-layer graphene oxide is used to prepare a large-diameter graphene oxide solution, 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. The method for preparing flexible conductive wood according to claim 1 is characterized in that in step (3), the reducing agent is selected from hydrazine hydrate, hydroiodic acid, vitamin C, NaHB ₄ or NaHSO ₃ , 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 the flexible conductive wood, and the total graphene loading in the flexible conductive wood is 0.1-10%. A flexible conductive wood prepared according to the method according to any one of claims 1 to 8. An application of the flexible conductive wood according to claim 9, characterized in that it is applied in the fields of flexible electronic devices, flexible batteries, and wearable devices.