Gradient conductive material and preparation method thereof

Abstract

The invention discloses a gradient conductive material and a preparation method thereof. The material is composed of graphene and graphene with silicon dioxide loaded on the surface, and is characterized in that the concentration of the graphene is in gradient distribution in a certain direction to form a film-shaped structure with resistance changing in a gradient mode, and then directional regulation and control of heating power are achieved. The material is prepared by adopting an electrostatic spraying technology, depositing different proportions of graphene oxide and graphene oxide dispersion liquid loaded with silicon dioxide on the surface into a film according to a gradient sequence, and reducing by a reducing agent. When the material is applied to ice prevention and removal, customized design can be carried out according to the icing severity of different areas, and the energy consumption is reduced while the deicing effect is ensured. The method has the advantages of high efficiency, energy conservation and customization, and has wide application prospects in the fields of wind power, aviation and the like.

Description

Technical Field

[0001] This invention belongs to the field of conductive materials technology, specifically relating to a gradient conductive material, its preparation method, and its applications. Background Technology

[0002] As a clean, renewable, and green energy source, wind power is receiving increasing attention and vigorous development from countries around the world, driven by global energy structure transformation and carbon neutrality goals. Statistics show that global wind power installed capacity has continued to grow rapidly in recent years, becoming an important component of many countries' energy strategies. Especially in cold regions, due to higher air density, wind energy resources can increase the additional power generation potential by about 10% compared to warmer regions, making high-latitude, high-altitude cold areas preferred locations for wind farm construction.

[0003] However, the harsh climatic conditions in these regions, especially the low temperatures and high humidity in winter, pose a significant challenge to the stable operation of wind turbines. Among these challenges, blade icing is particularly prominent. Icing on the blade surface alters its precisely designed aerodynamic shape, leading to a significant decrease in aerodynamic performance and severely impacting wind energy capture efficiency. This can typically cause a 20% to 30% reduction in turbine output power, or even complete shutdown. Furthermore, icing increases the load on the blades, alters their mass distribution, and intensifies vibration and load imbalance. Over long-term operation, this can easily lead to structural fatigue damage, bearing wear, and even blade breakage, resulting in serious mechanical failures. This not only affects power generation efficiency but also significantly increases operation and maintenance costs and safety risks.

[0004] Therefore, developing efficient and reliable wind turbine blade de-icing technology is of vital engineering significance and economic value for ensuring the safe and stable operation of wind turbines in cold regions, increasing annual power generation, and reducing operation and maintenance costs. Among numerous de-icing methods, electrothermal de-icing technology is considered one of the most promising active anti-icing and de-icing solutions due to its rapid response, precise control, ease of integration, and strong adaptability. The principle of this technology is to lay conductive materials on or inside the blade to form an electrothermal layer. When current passes through, the conductive network generates a Joule heating effect, maintaining the blade surface temperature above the freezing point, thereby preventing icing; or it melts the interface between the existing ice layer and the blade surface, allowing it to detach under the action of external wind force and centrifugal force, achieving efficient de-icing.

[0005] Research has found that existing electrothermal layers used for electrothermal de-icing on wind turbine blades are generally uniformly distributed, meaning the heating power and surface temperature are the same in the horizontal direction. However, due to varying degrees of icing severity across different parts of the wind turbine blade, this results in an unreasonable distribution of the electrothermal layer's power density. Typically, the severity of icing gradually decreases from the leading edge to the trailing edge; areas with severe icing at the leading edge require higher power densities, while areas with less icing at the trailing edge can achieve good anti-icing / de-icing effects with lower power densities. Against this backdrop, this patent proposes a novel gradient conductive material to address these issues, significantly improving de-icing efficiency and reducing energy consumption, providing a practical technical solution for the efficient and stable operation of wind power in cold regions. Summary of the Invention

[0006] This invention provides a gradient conductive material, its preparation method, and its applications. The concentration of the conductive component in the gradient conductive material varies gradient along a certain direction, forming an electrothermal material with a resistance gradient along that direction. When the electrothermal layer prepared from this material is applied to the blade surface, it can meet the different power density requirements of different areas of the blade. The gradient conductive material has the advantage of a power density gradient along a certain direction. When applied to wind turbine blade anti-icing / de-icing, it can achieve better anti-icing / de-icing effects and also realize energy saving and consumption reduction.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A gradient conductive material, comprising conductive and non-conductive materials, wherein the concentration of the conductive material is distributed in a gradient along a certain direction.

[0009] In this invention, "gradient distribution" means that the concentration of the conductive material (e.g., mass percentage, volume percentage, or molar percentage) changes in a stepwise manner along a certain direction, such as increasing or decreasing in a stepwise manner along a certain direction. Here, "a certain direction" refers to a direction parallel to a horizontal plane, for example, along the length direction, width direction, or a direction forming a certain angle with the length direction of the conductive material (film).

[0010] According to an embodiment of the present invention, in the gradient conductive material, the concentration of non-conductive material (such as mass percentage, volume percentage or molar percentage) is distributed in a gradient and is opposite to the concentration distribution direction of conductive material.

[0011] According to an embodiment of the present invention, in the gradient conductive material, the concentration difference n between adjacent gradient conductive materials is ≥1%. For example, the concentration difference n between adjacent gradient conductive materials is 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 15%, 18%, 20%, 30%, 40%, or 50%.

[0012] According to an embodiment of the present invention, the conductive material is distributed in a gradient from a to b along a certain direction according to its concentration (e.g., mass percentage, volume percentage, or molar percentage), wherein 100% ≥ a ≥ 20%, 90% ≥ b ≥ 10%, and a > b. Exemplarily, a is 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%, and b is 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%.

[0013] According to an embodiment of the present invention, the gradient conductive material is in the form of a film, specifically in the form of paper.

[0014] According to an embodiment of the present invention, the thickness of the gradient conductive material is 2 to 50 μm, for example, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, or 20 μm.

[0015] According to an embodiment of the present invention, the resistance of the gradient conductive material varies in a gradient along a certain direction.

[0016] According to an embodiment of the present invention, the conductive material is graphene, and the non-conductive material is graphene with silicon dioxide loaded on its surface.

[0017] According to an embodiment of the present invention, the graphene in the graphene and the graphene with silicon dioxide loaded on the surface has a graphene size of 100 nm to 100 μm.

[0018] According to an embodiment of the present invention, the mass percentage of silicon dioxide in the graphene with silicon dioxide loaded on its surface is 1% to 50%.

[0019] According to an embodiment of the present invention, the average particle size of the silicon dioxide in the graphene with silicon dioxide loaded on its surface is 5-200 nm.

[0020] This invention also provides a method for preparing the above-mentioned graphene gradient conductive material, the method comprising the following steps:

[0021] a) Add alkyl orthosilicate and silane coupling agent to the ethanol / water dispersion of graphene oxide, react, wash repeatedly with ethanol, disperse in water, and freeze dry to obtain a graphene oxide dispersion loaded with silica.

[0022] b) Prepare a series of aqueous dispersions containing different concentrations of graphene oxide and graphene oxide with silica loaded on its surface.

[0023] c) The gradient conductive material precursor is prepared by electrostatic spraying according to the gradient distribution.

[0024] d) Further, the gradient conductive material is prepared by a reduction step.

[0025] According to an embodiment of the present invention, in step (a), the alkyl orthosilicate is selected from at least one of methyl orthosilicate, ethyl orthosilicate, n-propyl orthosilicate, isopropyl orthosilicate, n-butyl orthosilicate, and isobutyl orthosilicate. Preferably, the alkyl orthosilicate is selected from at least one of ethyl orthosilicate, n-propyl orthosilicate, and isopropyl orthosilicate.

[0026] According to an embodiment of the present invention, in step (a), the silane coupling agent is selected from γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 3-aminopropyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, 1,2-bis(triethoxysilyl)ethane, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane.

[0027] According to an embodiment of the present invention, in step (a), the mass ratio of the alkyl orthosilicate ester to the silane coupling agent is 1:0.1 to 0.5.

[0028] According to an embodiment of the present invention, in step (a), the mass ratio of graphene oxide to alkyl orthosilicate is 1 to 5:1, for example, 1:1, 1:2, 1:3, 1:4, or 1:5.

[0029] According to an embodiment of the present invention, in step (a), the volume ratio of ethanol to water in the ethanol-water mixture is 45-49:5-1.

[0030] According to an embodiment of the present invention, in step (a), the concentration of graphene oxide in the graphene oxide dispersion is 1 g / L to 5 g / L, for example, 1 g / L, 2 g / L, 3 g / L, 4 g / L or 5 g / L.

[0031] According to an embodiment of the present invention, in step (a), the reaction needs to be stirred, the reaction temperature is room temperature, and the reaction time is 4 to 8 hours.

[0032] According to an embodiment of the present invention, in step b), the mass ratio of the graphene oxide to the graphene oxide with silica loaded on its surface is 10:0 to 1:9, for example, 10:0, 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8 and 1:9.

[0033] According to an embodiment of the present invention, in step b), the total concentration of graphene oxide and graphene oxide with silica loaded on its surface in the dispersion is 0.5 to 2 g / L, for example, 0.5 g / L, 0.8 g / L, 1 g / L, 1.2 g / L, 1.5 g / L, 1.8 g / L or 2 g / L.

[0034] According to an embodiment of the present invention, in step c), the electrostatic spraying is performed by atomizing the dispersion liquid using an electrostatic generator and then spraying it onto the heated substrate surface, with the substrate surface temperature being 50°C to 100°C.

[0035] According to an embodiment of the present invention, in step c), during the electrostatic spraying process, the voltage is 5-50KV, the needle spacing of the syringe is 5-30mm, the distance from the syringe needle to the collecting plate is 5-50cm, and the spraying rate is 1-10ml / h.

[0036] According to an embodiment of the present invention, in step c), the thickness of the gradient conductive material is 2 to 50 μm.

[0037] According to an embodiment of the present invention, in step d), the gradient conductive film is added to an aqueous solution of a reducing agent and heated to carry out a reduction reaction to prepare the gradient conductive material.

[0038] The reducing agent is selected from at least one of hydroiodic acid and vitamin C.

[0039] The mass ratio of the gradient distribution material to the reducing agent is 1:1 to 1:100.

[0040] The reaction temperature is 50–100°C, and the reaction time is 8–24 hours.

[0041] According to an embodiment of the present invention, the gradient conductive material has the advantage of power density varying along a certain direction. When applied to wind turbine blades for anti-icing / de-icing, it can achieve better anti-icing / de-icing effect and also realize energy saving and consumption reduction.

[0042] The beneficial effects of this invention are:

[0043] This invention provides a gradient conductive material, its preparation method, and its applications. The concentration of conductive components (such as graphene) in the gradient conductive material varies gradient along a certain direction, forming an electrothermal material with a resistance gradient along that direction. When a voltage is applied across the electrothermal material, its heating power density and surface temperature can exhibit gradient changes, enabling customized design. When applied as an electrothermal de-icing material to wind turbine blades for anti-icing / de-icing, it can achieve energy saving and consumption reduction while meeting the requirements of different areas. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of a cross-section of an electrothermal layer with gradient conductivity. The dark circles in the diagram represent graphene, and the light circles represent graphene with silicon dioxide loaded on its surface. Detailed Implementation

[0045] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0046] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0047] Example 1

[0048] (1) Graphene oxide (GrO) powder was added to a mixed solution of ethanol / water with a volume ratio of 49:1 and stirred at high speed for 0.5 h to obtain a stable GrO dispersion with a concentration of 2.0 g / L. Then, tetraethyl orthosilicate (TEOS) and aminopropyltriethoxysilane (APTES) were added. The mass ratio of GrO, TEOS and APTES was 1:1:0.2. After stirring at room temperature for 6 h, the mixture was washed and filtered three times with ethanol, dispersed in water, and then freeze-dried to obtain a graphene oxide (SiO2@GrO) dispersion with silica loaded on the surface.

[0049] (2) Different masses of GrO powder and SiO2@GrO powder were added to water and stirred at high speed for 1.0 h to obtain a dispersion with a total concentration of GrO and SiO2@GrO of 1.0 g / L. The mass ratios of the two were 10:0, 10:1, 10:2, 10:5 and 10:10, respectively.

[0050] (3) The above dispersions with different mass ratios were loaded into a syringe, and the needles were arranged in parallel in sequence with a 5cm interval. Electrostatic spraying was used (30kV voltage, 20cm distance from the needle to the collection plate, spraying rate 3ml / h, substrate temperature 90℃) to obtain a graphene oxide gradient film with a thickness of 10μm.

[0051] (4) The graphene oxide gradient film with a size of 10cm×30cm prepared above was immersed in HI aqueous solution (20%) and reacted at 100℃ for 12h to obtain a graphene gradient conductive film.

[0052] Example 2

[0053] (1) Graphene oxide (GrO) powder was added to a mixed solution of ethanol / water with a volume ratio of 45:5. After stirring at high speed for 0.5 h, a stable GrO dispersion with a concentration of 1.0 g / L was obtained. Then, tetraethyl orthosilicate (TEOS) and aminopropyltriethoxysilane (APTES) were added. The mass ratio of GrO, TEOS and APTES was 1:2:0.2. After stirring at room temperature for 6 h, the mixture was washed and filtered three times with ethanol, dispersed in water, and then freeze-dried to obtain a graphene oxide (SiO2@GrO) dispersion with silica loaded on the surface.

[0054] (2) Different masses of GrO powder and SiO2@GrO powder were added to water and stirred at high speed for 1.0 h to obtain a dispersion with a total concentration of GrO and SiO2@GrO of 2.0 g / L. The mass ratios of the two were 10:0, 10:1, 10:2, 10:5 and 10:10, respectively.

[0055] (3) The above dispersions with different mass ratios were loaded into a syringe, and the needles were arranged in parallel in sequence with a 5cm interval. Electrostatic spraying was used (30kV voltage, 20cm distance from the needle to the collection plate, spraying rate 3ml / h, substrate temperature 80℃) to obtain a graphene oxide gradient film with a thickness of 20μm.

[0056] (4) The graphene oxide gradient film with a size of 10cm×30cm prepared above was immersed in vitamin C aqueous solution (20%) and reacted at 100℃ for 12h to obtain a graphene gradient conductive film.

[0057] Example 3

[0058] Compared with Example 1, all other conditions remained the same, except that the reducing agent was changed to hydrazine hydrate.

[0059] Example 4

[0060] Compared with Example 1, other conditions remained unchanged, and the graphene oxide gradient film was not reduced.

[0061] Example 5

[0062] Compared to Example 1, no SiO2@GrO was added to the system.

[0063] Performance Comparison Analysis

[0064] At room temperature, the gradient conductive materials obtained in Examples 1-5 of this invention were energized, and the current was adjusted to 5A. After the temperature stabilized, the temperature of each region was measured using thermocouples. Each region was measured 5 times, and the average value was recorded as the average temperature of that region. The results are shown in the table below:

[0065]

[0066] As shown in Examples 1 and 2 above, the gradient conductive material obtained by this invention has the function of zoned heating. In regions 1 to 5, due to the gradually increasing resistance, the heating effect becomes more pronounced under the same current, leading to a gradually increasing temperature rise. Compared to Example 1, the temperature in Example 2 is lower, which may be mainly due to the larger film thickness and lower overall resistance in Example 2. In Example 3, due to the intense reducing properties of hydrazine hydrate, a large amount of heat and bubbles are rapidly released inside the film material during the reduction process, causing it to disintegrate, and a gradient conductive film material was not obtained. In Example 4, the graphene oxide was not reduced and is insulating, so it cannot be heated by electricity. Example 5 is a graphene film material, and the temperature of the entire film is relatively uniform.

[0067] In summary, this invention proposes a gradient conductive material and its preparation method, which can realize customized design of heating effect in different regions. It provides an effective and innovative heating material for the electrothermal anti-icing technology of wind turbines, and can reduce energy consumption while ensuring anti-icing effect.

[0068] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A graphene gradient conductive material, characterized in that, The gradient conductive material is in the form of a film, composed of graphene and graphene with silicon dioxide loaded on its surface, and the graphene content is distributed in a gradient along a certain direction.

2. The graphene gradient conductive material according to claim 1, characterized in that, The graphene is distributed in a gradient from a to b along a certain direction according to the concentration (such as mass percentage, volume percentage or molar percentage), wherein 100% ≥ a ≥ 20%, 90% ≥ b ≥ 10%, and a > b, and the concentration difference of the graphene conductive material in the gradient between adjacent regions is n ≥ 1%.

3. The graphene gradient conductive material according to claim 1, characterized in that, The thickness of the gradient conductive material is 2–50 μm.

4. The graphene gradient conductive material according to claim 1, characterized in that, The graphene and the graphene with silica loaded on the surface have a graphene size of 100 nm to 100 μm.

5. The graphene gradient conductive material according to claim 1, characterized in that, The graphene with silica loaded on its surface has a silica mass percentage of 1% to 50% and a silica particle size of 5-200 nm.

6. The method for preparing the graphene gradient conductive material according to claims 1 to 5, characterized in that, The preparation method includes the following steps: a) Add alkyl orthosilicate and silane coupling agent to the ethanol / water dispersion of graphene oxide, react, wash repeatedly with ethanol, disperse in water, and freeze dry to obtain a graphene oxide dispersion loaded with silica. b) Prepare a series of aqueous dispersions containing different concentrations of graphene oxide and graphene oxide with silica loaded on its surface. c) The gradient conductive material precursor is prepared by electrostatic spraying according to the gradient distribution. d) Further, the gradient conductive material is prepared by a reduction step.

7. The preparation method according to claim 6, characterized in that, In step (a), the alkyl orthosilicate is selected from at least one of methyl orthosilicate, ethyl orthosilicate, n-propyl orthosilicate, isopropyl orthosilicate, n-butyl orthosilicate, and isobutyl orthosilicate. And / or, in step (a), the silane coupling agent is selected from γ-(2,3-epoxypropoxy)propyltrimethoxysilane, 3-aminopropyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, 1,2-bis(triethoxysilyl)ethane, and N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane. And / or, in step (a), the mass ratio of graphene oxide to alkyl orthosilicate is 1 to 5:1, and the mass ratio of alkyl orthosilicate to silane coupling agent is 1:0.1 to 0.

5. And / or, in step (a), the volume ratio of ethanol to water in the ethanol-water mixture is 45-49:5-1. And / or, in step (a), the concentration of graphene oxide in the graphene oxide dispersion is 1 g / L to 5 g / L. And / or, in step (a), the reaction requires stirring, the reaction temperature is room temperature, and the reaction time is 4 to 8 hours.

8. The preparation method according to claim 6, characterized in that, In step b), the mass ratio of the graphene oxide to the graphene oxide with silica loaded on its surface is 10:0 to 1:

9. And / or, in step b), the total concentration of graphene oxide and graphene oxide with silica loaded on its surface in the dispersion is 0.5 to 2 g / L.

9. The preparation method according to claim 6, characterized in that, In step c), the electrostatic spraying is performed by atomizing the dispersion liquid using an electrostatic generator and then spraying it onto the heated substrate surface, where the substrate surface temperature is 50℃~100℃. And / or, in step c), during the electrostatic spraying process, the voltage is 5-50KV, the needle spacing of the syringe is 5-30mm, the distance from the syringe needle to the collecting plate is 5-50cm, and the spraying rate is 1-10ml / h. And / or, in step c), the thickness of the gradient conductive material is 2 to 50 μm.

10. The preparation method according to claim 6, characterized in that, In step d), the gradient conductive film is added to an aqueous solution of a reducing agent and heated to carry out a reduction reaction, thereby preparing the gradient conductive material. And / or, in step d), the reducing agent is selected from at least one of hydroiodic acid and vitamin C. And / or, in step d), the mass ratio of the gradient distribution material to the reducing agent is 1:1 to 1:

100. And / or, in step d), the reaction temperature is 50–100°C, and the reaction time is 8–24 h.

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