An ITO-CNTs co-doped antistatic thermal management bilayer coating and its preparation method

Abstract

This invention proposes an ITO-CNTs co-doped antistatic thermal management bilayer coating and its preparation method, belonging to the field of multifunctional coating preparation technology. The ITO-CNTs co-doped antistatic thermal management bilayer coating of this invention comprises a porous oxide underlayer and a conductive outer layer, wherein the conductive outer layer is an ITO-CNTs composite material, and the thickness of the bilayer coating is 80-105 μm. This invention employs micro-arc plasma oxidation technology and plasma pretreatment of an electrolyte containing CNTs and ITO nanoparticles, allowing the CNTs to act as conductive channels connecting the ITO particles, forming a complete conductive network. The underlayer coating has a microporous structure, thereby obtaining the ITO-CNTs co-doped antistatic thermal management bilayer coating. This invention achieves the preparation of a thermal control and antistatic functional coating. The coating and substrate are bonded through chemical anchoring and physical embedding mechanisms, exhibiting good impact resistance and mechanical stability.

Description

Technical Field

[0001] This invention belongs to the field of multifunctional coating preparation technology, and particularly relates to an ITO-CNTs co-doped antistatic thermal management bilayer coating and its preparation method. Background Technology

[0002] With the development of high-performance, high-power electronic devices, electronic components generate a large amount of heat during operation, causing their operating temperature to rise sharply, thereby reducing their efficiency and lifespan. At the same time, electronic components are susceptible to the effects of static electricity buildup, and electrostatic discharge (ESD) can lead to device malfunction or damage. Therefore, the surface of electronic devices needs to be coated with a coating that can effectively dissipate heat and prevent static electricity.

[0003] While existing coating technologies have made some progress in combining heat dissipation and antistatic functions, they still face several limitations in practical applications. For example, silicone coatings filled with carbon black possess excellent electrical conductivity and thermal management capabilities, along with high infrared emissivity and solar energy absorption. However, these organic coatings are susceptible to temperature and radiation effects during long-term use, leading to coating aging, decreased adhesion, and ultimately affecting the coating's antistatic effect and thermal conductivity. Furthermore, these coatings typically employ multi-step preparation processes, making production complex and difficult to adapt to the demands of large-scale industrial production. They also struggle to simultaneously achieve both horizontal conductivity and vertical insulation, making it difficult to optimize thermal control and antistatic performance within a single coating. Therefore, there is an urgent need to develop a coating technology that can be rapidly and cost-effectively prepared while simultaneously possessing excellent antistatic and thermal management properties to meet the demands of high-performance electronic devices. Summary of the Invention

[0004] To address the problems in existing technologies where complex processes or organic coatings are used to achieve conductivity and heat dissipation but suffer from poor adhesion, easy aging, and inability to withstand temperature fluctuations in extreme environments over long periods, making it difficult to simultaneously optimize thermal control and antistatic performance in the same coating, this invention proposes an ITO-CNTs co-doped antistatic thermal management bilayer coating and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] One of the technical solutions of the present invention:

[0007] An ITO-CNTs co-doped antistatic thermal management bilayer coating comprises a porous oxide underlayer and a conductive outer layer, wherein the conductive outer layer is an ITO-CNTs composite material; in the ITO-CNTs composite material, CNTs serve as conductive channels connecting ITO particles to form a complete conductive network, and the porous oxide underlayer has a microporous structure.

[0008] Furthermore, the thickness of the ITO-CNTs co-doped antistatic thermal management bilayer coating is 80-105 μm.

[0009] Furthermore, the pore size of the microporous structure in the porous oxide substrate is 1-5 μm.

[0010] The second technical solution of the present invention:

[0011] A method for preparing an ITO-CNTs co-doped antistatic thermal management bilayer coating involves first pretreating an electrolyte containing CNTs (carbon nanotubes) and ITO (indium tin oxide) nanoparticles using plasma. Under plasma irradiation, the CNTs surface is functionalized through high-energy electrons, ultraviolet radiation, and reactive oxygen species (such as O*, O2*, OH*, etc.), introducing oxygen-containing groups such as carboxyl groups (-COOH) and hydroxyl groups (-OH), thereby improving the surface polarity and hydrophilicity of CNTs and significantly improving their dispersibility in the electrolyte. The dispersed CNTs, due to the polar groups introduced on their surface, form weak chemical bonds or electrostatic forces (such as hydrogen bonds and van der Waals forces) with the ITO nanoparticles, improving the dispersion stability of the ITO nanoparticles in the electrolyte, avoiding particle aggregation, and promoting uniform deposition on the substrate surface. Then, using the plasma-pretreated electrolyte combined with micro-arc oxidation technology, the ITO-CNTs co-doped antistatic thermal management bilayer coating is prepared on the substrate surface. During micro-arc oxidation, ITO and CNT nanoparticles in the electrolyte migrate to the substrate surface via electrophoresis. Under the high temperature and pressure generated by plasma discharge, ITO nanoparticles and CNTs sinter with molten oxide to form an ITO-CNTs composite top layer. Simultaneously, the micro-arc oxidation process also generates a porous oxide bottom layer on the substrate surface. This is mainly due to the structural inhomogeneity caused by the high-temperature melting and rapid cooling during micro-arc discharge, resulting in a large number of pores and a porous oxide bottom layer with a microporous structure.

[0012] Furthermore, the concentration of ITO nanoparticles in the electrolyte is 30-50 g / L, and the concentration of CNTs is 1.5-2.5 g / L.

[0013] Furthermore, the electrolyte is obtained by adding ITO nanoparticles and CNTs to an initial electrolyte and then ultrasonically treating it, wherein the initial electrolyte contains 30-50 g / L sodium hexametaphosphate, 3-8 g / L sodium silicate, and 1-3 g / L sodium hydroxide.

[0014] Furthermore, the plasma pretreatment voltage is 500-600V, the frequency is 400-700Hz, and the treatment time is 30-90min.

[0015] Furthermore, the plasma pretreatment voltage is 550V, the frequency is 600Hz, and the treatment time is 60min.

[0016] Plasma pretreatment can improve the dispersion of CNTs in electrolytes, forming a stable suspension containing functionalized CNTs. The voltage, frequency, and treatment time of plasma pretreatment have a significant impact on the performance of the bilayer coating: too low a voltage leads to insufficient CNT functionalization, affecting their dispersibility and the formation of the conductive network, thus reducing the antistatic effect of the coating; too high a voltage may damage the CNT structure, weakening the mechanical stability of the coating. Too low a frequency results in poor treatment effect, while too high a frequency may damage the material surface structure. Too short a treatment time leads to insufficient functionalization, while too long a time may cause overtreatment, resulting in surface defects. These parameters also affect the quality of the porous oxide underlayer and the uniformity of the conductive outer layer, thereby affecting the thermal management and antistatic properties of the coating.

[0017] Furthermore, the voltage of the micro-arc oxidation technology is 450-600V, the frequency is 400-700Hz, the processing time is 15-30min, and the temperature is 50-90℃.

[0018] Furthermore, the micro-arc oxidation technology has a voltage of 550V, a frequency of 600Hz, a processing time of 20min, and a temperature of 70℃.

[0019] In this invention, the voltage, frequency, and processing time of the micro-arc oxidation technology have a significant impact on the performance of the bilayer coating: higher voltage facilitates the sintering of ITO and CNTs, forming a dense composite outer layer and increasing the porosity of the porous underlayer, thereby improving radiative heat dissipation performance. Increased frequency enhances discharge stability, optimizes coating uniformity and antistatic properties, while extended processing time helps improve coating quality, enhances conductivity and thermal management capabilities. Appropriate adjustment of these parameters can achieve optimal coating performance.

[0020] Furthermore, the anode of the micro-arc oxidation technology is a substrate, and the cathode is a stainless steel plate; the substrate is an aluminum alloy substrate.

[0021] Furthermore, the substrate needs to undergo surface polishing pretreatment before use.

[0022] The principle of this invention:

[0023] This invention, based on micro-arc oxidation technology, achieves the preparation of a highly efficient antistatic thermal management double-layer coating by constructing a micro-nano-scale bilayer structure on the surface of an aluminum alloy substrate. Firstly, this invention functionalizes CNTs through plasma pretreatment, solving the problem of poor dispersibility of nanomaterials caused by traditional mechanical stirring, ensuring uniform distribution and effective deposition of CNTs in the coating. Plasma pretreatment of an electrolyte containing CNTs (carbon nanotubes) and ITO (indium tin oxide) nanoparticles functionalizes the CNT surface under plasma conditions through high-energy electrons, ultraviolet radiation, and reactive oxygen species (such as O*, O2*, OH*, etc.), introducing oxygen-containing groups such as carboxyl groups (-COOH) and hydroxyl groups (-OH), thereby improving the surface polarity and hydrophilicity of CNTs and significantly enhancing their dispersibility in the electrolyte. Functionalized CNTs, through the polar groups introduced on their surface, form weak chemical bonds or electrostatic interactions (such as hydrogen bonds and van der Waals forces) with ITO nanoparticles, achieving effective loading of ITO nanoparticles. The functionalized CNTs and nanoparticles migrate towards the substrate surface driven by a plasma electric field, and are sintered and deposited under the high temperature and pressure of micro-discharge, thus constructing a stable nanocomposite structure. The microporous structure of the bottom coating melts oxides through partial discharge, forming a glassy phase that prevents vertical current conduction, ensuring insulation. In the top coating, interwoven CNTs synergize with ITO particles under plasma induction, using CNTs as conductive channels to connect the ITO particles, forming a continuous and stable conductive network channel, thereby achieving stable antistatic properties in the horizontal direction. The microporous structure also optimizes the optical properties of the coating, improving infrared emissivity and solar absorptivity through multiple reflections of light by the surface unevenness and pores.

[0024] Compared with the prior art, the present invention has the following advantages and technical effects:

[0025] This invention achieves the simultaneous preparation of thermal control and antistatic functional coatings through a one-step micro-arc oxidation technology. A double-layer coating can be rapidly formed on the aluminum alloy surface in a single deposition, eliminating the complex multi-step preparation process of traditional methods, significantly reducing production costs and time consumption, and facilitating large-scale production and application. The coating obtained by this invention is free of organic matter, avoiding the aging problems common in organic coatings, and possesses the ability to be used for extended periods in extreme environments. The coating and substrate are bonded through chemical anchoring and physical embedding mechanisms, achieving adhesion level 0 according to ISO 2409 standards. Attached Figure Description

[0026] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0027] Figure 1A schematic diagram of the structure of an antistatic thermal management bilayer coating co-doped with ITO-CNTs;

[0028] Figure 2 The sedimentation of the electrolyte containing CNTs and ITO nanoparticles prepared in step (2) of Example 1 and Comparative Example 1 is shown.

[0029] Figure 3 The images show the microstructure and surface morphology of the ITO-CNTs co-doped bilayer coating prepared in Example 1 at different magnifications, where (a) is a scale bar of 20 μm, (b) is a scale bar of 200 nm, and (c) is a surface morphology diagram.

[0030] Figure 4 The image shows a cross-sectional morphology of the ITO-CNTs co-doped bilayer coating prepared in Example 1.

[0031] Figure 5 The infrared emissivity curve of the ITO-CNTs co-doped bilayer coating prepared in Example 1;

[0032] Figure 6 The solar absorptivity curve of the ITO-CNTs co-doped bilayer coating prepared in Example 1 is shown.

[0033] Figure 7 The radiation heat dissipation and cooling curves of the 6061 aluminum alloy substrate and the prepared double-layer coating used in Example 1 are shown.

[0034] Figure 8 The morphology of the ITO-CNTs co-doped bilayer coating prepared in Example 1 after cross-cut test is shown. Detailed Implementation

[0035] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0036] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0037] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0038] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0039] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0040] This invention proposes an ITO-CNTs co-doped antistatic thermal management bilayer coating, the structural schematic of which is shown in the figure. Figure 1 It consists of two layers, including a porous oxide bottom layer and a conductive outer layer. The conductive outer layer is an ITO-CNTs composite material. In the ITO-CNTs composite material, CNTs act as conductive channels to connect ITO particles and form a complete conductive network. The porous oxide bottom layer has a microporous structure.

[0041] In a preferred embodiment of the present invention, the thickness of the ITO-CNTs co-doped antistatic thermal management bilayer coating is 80-105 μm.

[0042] In a preferred embodiment of the present invention, the pore size of the microporous structure of the porous oxide substrate is 1-5 μm.

[0043] This invention also proposes a method for preparing the ITO-CNTs co-doped antistatic thermal management bilayer coating. The method involves pretreating an electrolyte containing CNTs (carbon nanotubes) and ITO (indium tin oxide) nanoparticles with plasma to functionalize the CNTs and improve their dispersibility. Then, the pretreated electrolyte is combined with micro-arc oxidation technology to prepare the ITO-CNTs co-doped antistatic thermal management bilayer coating on the substrate surface.

[0044] In a preferred embodiment of the present invention, the concentration of ITO nanoparticles in the electrolyte is 30-50 g / L, and the concentration of CNTs is 1.5-2.5 g / L; preferably, the electrolyte is obtained by adding ITO nanoparticles and CNTs to an initial electrolyte and then ultrasonically treating it, wherein the initial electrolyte contains 30-50 g / L of sodium hexametaphosphate, 3-8 g / L of sodium silicate, and 1-3 g / L of sodium hydroxide.

[0045] In a preferred embodiment of the present invention, the plasma pretreatment voltage is 500-600V, the frequency is 400-700Hz, and the treatment time is 30-90min; preferably, the plasma pretreatment voltage is 550V, the frequency is 600Hz, and the treatment time is 60min.

[0046] In a preferred embodiment of the present invention, the voltage of the micro-arc oxidation technology is 450-600V, the frequency is 400-700Hz, the processing time is 15-30min, and the temperature is 50-90℃; preferably, the voltage of the micro-arc oxidation technology is 550V, the frequency is 600Hz, the processing time is 20min, and the temperature is 70℃.

[0047] In a preferred embodiment of the present invention, the anode of the micro-arc oxidation technology is a substrate, and the cathode is a stainless steel plate; the substrate is an aluminum alloy substrate.

[0048] In a preferred embodiment of the present invention, the substrate needs to undergo surface polishing pretreatment before use.

[0049] In a preferred embodiment of the present invention, the surface polishing pretreatment of the substrate specifically includes:

[0050] Aluminum alloy is selected as the base material. First, its surface is polished step by step with 600#-1200# SiC sandpaper to ensure that the surface is smooth and burr-free.

[0051] Use acetone to ultrasonically clean the aluminum alloy surface for 15 minutes to remove surface oil and impurities, then rinse thoroughly with deionized water to ensure the surface is clean.

[0052] Finally, the aluminum alloy substrate is placed in a constant temperature drying oven and dried for 1 hour to remove residual moisture from the surface.

[0053] The "plasma pretreatment" method used in this invention is a surface modification technology. By interacting with the material surface through plasma, the physical and chemical properties of the material are changed to improve the adhesion, wettability, and chemical activity of the material surface. This invention improves the dispersion performance of CNTs in the electrolyte by controlling the parameters of the plasma pretreatment process, forming a stable suspension containing functionalized CNTs. The functionalized CNTs form a stable suspension with significantly improved dispersibility, which is beneficial for subsequent deposition.

[0054] The "micro-arc oxidation technology" used in this invention is a technique for in-situ growing a ceramic film mainly composed of a substrate metal oxide on the surface of metals such as aluminum, magnesium, and titanium and their alloys by combining an electrolyte with corresponding electrical parameters and relying on the instantaneous high temperature and high pressure generated by arc discharge. Under the action of an external electric field, micro-arc discharge is generated on the material surface under the action of a micro-arc region voltage higher than that outside the Faraday discharge region. This discharge generates instantaneous high temperature and high pressure, and through the combined action of thermochemical, plasma chemical, and electrochemical factors, a ceramic film is formed on the metal surface. This invention does not limit the specific operation method of micro-arc oxidation technology; it only controls the parameters of micro-arc oxidation technology to achieve the preparation of an ITO-CNTs co-doped antistatic thermal management double-layer coating.

[0055] The CNTs used in the embodiments of this invention were purchased from Jiaxing Naco New Materials Co., Ltd., and the ITO nanoparticles were purchased from Andy Metal Materials Co., Ltd.

[0056] In this invention, the type of aluminum alloy substrate is not limited. Any aluminum alloy substrate can be used to prepare an antistatic thermal management double-layer coating using the method of this invention. In some embodiments of this invention, 6061 aluminum alloy substrate, 5052 aluminum alloy substrate, 7075 aluminum alloy substrate, and aluminum-magnesium alloy substrate are used as examples. The 6061, 5052, 7075, and aluminum-magnesium alloy substrates used were purchased from Langfang Yuchen Metal Materials Co., Ltd.

[0057] The technical solution of the present invention will be further illustrated by the following embodiments.

[0058] Example 1

[0059] A method for preparing an ITO-CNTs co-doped antistatic thermal management bilayer coating on the surface of a 6061 aluminum alloy substrate specifically includes the following steps:

[0060] (1) Select 6061 aluminum alloy as the substrate, and polish it with 600 mesh, 1000 mesh and 1200 mesh SiC sandpaper in sequence to ensure that the surface is smooth and the roughness is less than 0.5μm. Then, immerse the substrate in acetone solution for ultrasonic cleaning for 5min to remove oil stains. After cleaning, use anhydrous ethanol and deionized water for ultrasonic cleaning for 30min respectively, and dry in a constant temperature drying oven for 1h.

[0061] (2) ITO nanoparticles and CNTs were added to an initial electrolyte containing 35 g / L sodium hexametaphosphate, 6 g / L sodium silicate and 1.2 g / L sodium hydroxide, so that the concentration of ITO nanoparticles in the electrolyte was 40 g / L and the concentration of CNTs in the electrolyte was 2 g / L. After ultrasonic treatment for 30 min, the electrolyte was subjected to plasma pretreatment. The plasma pretreatment voltage was 550 V, the frequency was 600 Hz and the treatment time was 60 min, in order to functionalize CNTs and improve the dispersibility of CNTs, so as to obtain an electrolyte containing functionalized CNTs and ITO nanoparticles.

[0062] (3) Pour the electrolyte obtained in step (2) into an electrolytic cell, use a stainless steel plate as the cathode and the 6061 aluminum alloy substrate obtained in step (1) as the anode, and use micro-arc oxidation to prepare the coating. Set the voltage of micro-arc oxidation to 550V, the frequency to 600Hz, the processing time to 20min, and the temperature to 70℃ to obtain a double-layer coating with a thickness of about 104μm. The thickness of the conductive outer layer (ITO-CNTs composite material) is 22μm, the thickness of the porous oxide bottom layer is 82μm, and the pore size of the microporous structure of the porous oxide bottom layer is 1-5μm.

[0063] Example 2

[0064] A method for preparing an ITO-CNTs co-doped antistatic thermal management bilayer coating on the surface of a 5052 aluminum alloy substrate, specifically including the following steps:

[0065] (1) 5052 aluminum alloy was selected as the substrate. It was polished with 800-mesh and 1000-mesh SiC sandpaper in sequence to ensure that the surface was smooth and the roughness was less than 0.4μm. Then the substrate was immersed in acetone solution and ultrasonically cleaned for 5 minutes to remove oil stains. After cleaning, it was ultrasonically cleaned with anhydrous ethanol and deionized water for 30 minutes respectively, and then dried in a constant temperature drying oven for 1 hour.

[0066] (2) ITO nanoparticles and CNTs were added to an initial electrolyte containing 30 g / L sodium hexametaphosphate, 3 g / L sodium silicate and 1 g / L sodium hydroxide, so that the concentration of ITO nanoparticles in the electrolyte was 30 g / L and the concentration of CNTs in the electrolyte was 1.8 g / L. After ultrasonic treatment for 30 min, the electrolyte was subjected to plasma pretreatment, wherein the voltage of plasma pretreatment was 500 V, the frequency was 600 Hz and the treatment time was 45 min, in order to functionalize CNTs and improve the dispersibility of CNTs, and an electrolyte containing functionalized CNTs and ITO nanoparticles was obtained.

[0067] (3) Pour the electrolyte obtained in step (2) into the electrolytic cell, use a stainless steel plate as the cathode and the 5052 aluminum alloy substrate obtained in step (1) as the anode, and use micro-arc oxidation technology to prepare the coating. Set the voltage of the micro-arc oxidation technology to 480V, the frequency to 600Hz, the processing time to 25min, and the temperature to 60℃ to obtain a double-layer coating with a thickness of about 105μm. The thickness of the conductive outer layer (ITO-CNTs composite material) is 24μm, the thickness of the porous oxide bottom layer is 81μm, and the pore size of the microporous structure of the porous oxide bottom layer is 2-5μm.

[0068] Example 3

[0069] A method for preparing an ITO-CNTs co-doped antistatic thermal management bilayer coating on the surface of a 7075 aluminum alloy substrate specifically includes the following steps:

[0070] (1) 7075 aluminum alloy was selected as the substrate. It was polished with 600-mesh and 1000-mesh SiC sandpaper in sequence to ensure that the surface was smooth and the roughness was less than 0.5μm. Then the substrate was immersed in acetone solution and ultrasonically cleaned for 5 minutes to remove oil stains. After cleaning, it was ultrasonically cleaned with anhydrous ethanol and deionized water for 30 minutes respectively, and then dried in a constant temperature drying oven for 1 hour.

[0071] (2) ITO nanoparticles and CNTs were added to an initial electrolyte containing 50 g / L sodium hexametaphosphate, 8 g / L sodium silicate and 3 g / L sodium hydroxide, so that the concentration of ITO nanoparticles in the electrolyte was 35 g / L and the concentration of CNTs in the electrolyte was 2.5 g / L. After ultrasonic treatment for 30 min, the electrolyte was subjected to plasma pretreatment, wherein the voltage of plasma pretreatment was 600 V, the frequency was 600 Hz and the treatment time was 60 min, in order to functionalize CNTs and improve the dispersibility of CNTs, and an electrolyte containing functionalized CNTs and ITO nanoparticles was obtained.

[0072] (3) Pour the electrolyte obtained in step (2) into the electrolytic cell, use a stainless steel plate as the cathode and the 7075 aluminum alloy substrate obtained in step (1) as the anode, and use micro-arc oxidation technology to prepare the coating. Set the voltage of micro-arc oxidation technology to 600V, the frequency to 600Hz, the processing time to 15min, and the temperature to 80℃ to obtain a double-layer coating with a thickness of about 88μm. The thickness of the conductive outer layer (ITO-CNTs composite material) is 15μm, the thickness of the porous oxide bottom layer is 73μm, and the pore size of the microporous structure of the porous oxide bottom layer is 1-4μm.

[0073] Example 4

[0074] A method for preparing an ITO-CNTs co-doped antistatic thermal management bilayer coating on the surface of an aluminum-magnesium alloy substrate, specifically including the following steps:

[0075] (1) Select aluminum-magnesium alloy as the substrate, polish it with 1000-mesh SiC sandpaper to ensure a smooth surface with a roughness of less than 0.5μm, use acetone for ultrasonic cleaning to remove oil stains, rinse it in deionized water and then put it in a constant temperature drying oven to dry for 1 hour.

[0076] (2) ITO nanoparticles and CNTs were added to an initial electrolyte containing 35 g / L sodium hexametaphosphate, 6 g / L sodium silicate and 2 g / L sodium hydroxide, so that the concentration of ITO nanoparticles in the electrolyte was 35 g / L and the concentration of CNTs in the electrolyte was 2 g / L. After ultrasonic treatment for 30 min, the electrolyte was subjected to plasma pretreatment. The plasma pretreatment voltage was 500 V, the frequency was 400 Hz and the treatment time was 45 min, in order to functionalize CNTs and improve the dispersibility of CNTs, so as to obtain an electrolyte containing functionalized CNTs and ITO nanoparticles.

[0077] (3) Pour the electrolyte obtained in step (2) into an electrolytic cell, use a stainless steel plate as the cathode and the aluminum-magnesium alloy substrate obtained in step (1) as the anode, and use micro-arc oxidation technology to prepare the coating. Set the voltage of the micro-arc oxidation technology to 500V, the frequency to 400Hz, the processing time to 30min, and the temperature to 50℃ to obtain a double-layer coating with a thickness of about 80μm. The thickness of the conductive outer layer (ITO-CNTs composite material) is 12μm, the thickness of the porous oxide bottom layer is 68μm, and the pore size of the microporous structure of the porous oxide bottom layer is 2-5μm.

[0078] Comparative Example 1

[0079] Same as Example 1, except that step (2) is different, omitting the plasma pretreatment step, specifically:

[0080] ITO nanoparticles and CNTs were added to an initial electrolyte containing 35 g / L sodium hexametaphosphate, 6 g / L sodium silicate, and 1.2 g / L sodium hydroxide, so that the content of ITO nanoparticles in the electrolyte was 40 g / L and the content of CNTs in the electrolyte was 2 g / L. The electrolyte was ultrasonically treated for 30 min to obtain an electrolyte containing CNTs and ITO nanoparticles.

[0081] Performance testing

[0082] The infrared emissivity spectrum of the coating in the 3-20 μm wavelength range was acquired using a Fourier transform infrared spectrometer (FT / IR-6100, JASCO) equipped with an integrating sphere. Surface resistivity was measured using a Napson RT-70V surface resistivity meter. Volume resistivity was measured using an insulation resistance meter (CHT3530) to characterize vertical electrical insulation. Each test was performed in five parallel measurements, and the average value was taken as the final results for surface resistivity and volume resistivity.

[0083] Measurements showed that the coating prepared in Example 1 of this invention had an infrared emissivity of 0.94 and a surface resistivity of 3.46 × 10⁻⁶. 2 Ω, volume resistivity is 4.20×10 7 Ω; The coating prepared in Example 2 of this invention has an infrared emissivity of 0.93 and a surface resistivity of 5.13 × 10⁻⁶. 2 Ω, volume resistivity is 6.40×10 7 Ω; The coating prepared in Example 3 of this invention has an infrared emissivity of 0.93 and a surface resistivity of 1.23 × 10⁻⁶. 3 Ω, volume resistivity is 1.30×10 7 Ω; The coating prepared in Example 4 of this invention has an infrared emissivity of 0.92 and a surface resistivity of 6.90 × 10⁻⁶. 2 Ω, volume resistivity is 7.10×10 7 Ω.

[0084] The electrolytes containing CNTs and ITO nanoparticles prepared in step (2) of Example 1 and Comparative Example 1 showed sedimentation after 3 hours of standing. Figure 2 As can be seen, the electrolyte without plasma pretreatment (Comparative Example 1) showed particle aggregation at the bottom of the test tube, while the electrolyte after plasma pretreatment (Example 1) did not show aggregation.

[0085] The microstructure and surface morphology diagrams of the ITO-CNTs co-doped bilayer coating prepared in Example 1 at different magnifications are shown below. Figure 3 (a) Scale bar is 20 μm, (b) Scale bar is 200 nm, (c) Schematic diagram of surface morphology. It can be seen that the coating of Example 1 has micropores with a size of 1 to 2 μm. The surface and pores are covered and filled by nanoparticles. Spherical ITO nanoparticles and CNTs are clearly visible. This is because dispersed CNTs are more likely to migrate to the sample surface than aggregated CNTs and participate in the coating growth during plasma discharge.

[0086] The cross-sectional morphology of the ITO-CNTs co-doped bilayer coating prepared in Example 1 of this invention is shown in the figure. Figure 4(The resin in the figure is used to fix the ITO-CNTs co-doped double layer coating, and is not a component of the double layer coating.) It can be seen that the total thickness of the coating is 104 μm, of which the inner layer is 82 μm thick and the outer layer is 22 μm thick.

[0087] The infrared emissivity curve of the ITO-CNTs co-doped bilayer coating prepared in Example 1 of this invention is shown in the figure. Figure 5 It can be seen that the coating exhibits excellent emissivity in the wavelength range of 3–14 μm, with an average emissivity as high as 0.94.

[0088] The solar absorptivity in the 200-2500 nm wavelength range was measured using a UV-Vis spectrometer (Lambda 950, PerkinElmer) equipped with an integrating sphere. The solar absorptivity curves of the ITO-CNTs co-doped bilayer coating prepared in Example 1 of this invention are shown below. Figure 6 As can be seen, the average absorptivity in the 200–2500 nm band is 0.92. This is because the incorporated CNTs have good absorption characteristics and almost zero light reflectivity. Secondly, the micron and nano-scale protrusions and pores formed on the coating surface play a key role in improving light absorption. These surface protrusions and micropores constitute optical traps, causing the incident light to be reflected multiple times on the coating surface, thereby increasing absorption.

[0089] The heat dissipation performance of the 6061 aluminum alloy substrate and the prepared double-layer coating used in Example 1 was tested. A constant power heat source radiation heat dissipation performance testing system was used to test the radiation heat dissipation performance of the 6061 aluminum alloy substrate and the double-layer coating. The LED chip used had a diameter of 8 mm and a power of 5 W. In a closed environment, it was bonded to the sample with E1 ICESSENTIAL type thermally conductive adhesive (thermal conductivity greater than 4.5 W / m·K). Since the temperature of the LED chip cannot be directly measured, and the temperature change of the chip is consistent with the temperature change of the solder joint, the temperature change of the solder joint was measured to reflect the temperature change of the chip. Then, a TP9008 multi-channel temperature data logger was used to monitor the temperature change of the LED solder joint and compared it with the temperature change of the alloy. The radiation heat dissipation cooling curve is shown in [Figure number missing]. Figure 7 As can be seen, compared with 6061 aluminum alloy, the equilibrium temperature at the LED solder joint is reduced by 22.3℃ with the double coating, which shows excellent heat dissipation performance.

[0090] The adhesion strength of the coating was evaluated according to ISO 2409 standard. A grid pattern was created on the sample surface using a hard tool, with a grid spacing of 1 mm. Loose particles or debris were then gently brushed away. Next, a piece of 3M 898 tape was firmly adhered to the surface of the etched area, left to stand for 10 seconds, and then quickly peeled off perpendicular to the grid lines. Finally, the macroscopic morphology of the etched area was photographed and recorded. The macroscopic morphology of the ITO-CNTs co-doped bilayer coating prepared in Example 1 of this invention after the cross-cut adhesion test is shown below. Figure 8 As shown, the surface shows no peeling, meeting ISO 2409 standard level 0.

[0091] Example 5

[0092] A method for preparing an ITO-CNTs co-doped antistatic thermal management bilayer coating on the surface of a 6061 aluminum alloy substrate specifically includes the following steps:

[0093] (1) Select 6061 aluminum alloy as the substrate, and polish it with 600 mesh, 1000 mesh and 1200 mesh SiC sandpaper in sequence to ensure that the surface is smooth and the roughness is less than 0.5μm. Then, immerse the substrate in acetone solution for ultrasonic cleaning for 5min to remove oil stains. After cleaning, use anhydrous ethanol and deionized water for ultrasonic cleaning for 30min respectively, and dry in a constant temperature drying oven for 1h.

[0094] (2) ITO nanoparticles and CNTs were added to an initial electrolyte containing 35 g / L sodium hexametaphosphate, 6 g / L sodium silicate and 1.2 g / L sodium hydroxide, so that the concentration of ITO nanoparticles in the electrolyte was 50 g / L and the concentration of CNTs in the electrolyte was 1.5 g / L. After ultrasonic treatment for 30 min, the electrolyte was subjected to plasma pretreatment, wherein the voltage of plasma pretreatment was 600 V, the frequency was 500 Hz and the treatment time was 90 min, in order to functionalize CNTs and improve the dispersibility of CNTs, and an electrolyte containing functionalized CNTs and ITO nanoparticles was obtained.

[0095] (3) Pour the electrolyte obtained in step (2) into the electrolytic cell, use a stainless steel plate as the cathode and the 6061 aluminum alloy substrate obtained in step (1) as the anode, and use micro-arc oxidation technology to prepare the coating. Set the voltage of micro-arc oxidation technology to 450V, the frequency to 700Hz, the processing time to 30min, and the temperature to 90℃ to obtain a coating with a thickness of about 105μm.

[0096] Example 6

[0097] A method for preparing an ITO-CNTs co-doped antistatic thermal management bilayer coating on the surface of a 6061 aluminum alloy substrate specifically includes the following steps:

[0098] (1) Select 6061 aluminum alloy as the substrate, and polish it with 600 mesh, 1000 mesh and 1200 mesh SiC sandpaper in sequence to ensure that the surface is smooth and the roughness is less than 0.5μm. Then, immerse the substrate in acetone solution for ultrasonic cleaning for 5min to remove oil stains. After cleaning, use anhydrous ethanol and deionized water for ultrasonic cleaning for 30min respectively, and dry in a constant temperature drying oven for 1h.

[0099] (2) ITO nanoparticles and CNTs were added to an initial electrolyte containing 35 g / L sodium hexametaphosphate, 6 g / L sodium silicate and 1.2 g / L sodium hydroxide, so that the concentration of ITO nanoparticles in the electrolyte was 30 g / L and the concentration of CNTs in the electrolyte was 2.5 g / L. After ultrasonic treatment for 30 min, the electrolyte was subjected to plasma pretreatment. The plasma pretreatment voltage was 500 V, the frequency was 700 Hz and the treatment time was 30 min, in order to functionalize CNTs and improve the dispersibility of CNTs, so as to obtain an electrolyte containing functionalized CNTs and ITO nanoparticles.

[0100] (3) Pour the electrolyte obtained in step (2) into the electrolytic cell, use a stainless steel plate as the cathode and the 6061 aluminum alloy substrate obtained in step (1) as the anode, and use micro-arc oxidation technology to prepare the coating. Set the voltage of the micro-arc oxidation technology to 600V, the frequency to 400Hz, the processing time to 15min, and the temperature to 50℃ to obtain a coating with a thickness of about 98μm.

[0101] Comparative Example 2

[0102] Same as Example 1, except that step (2) is as follows: CNTs are added to the initial electrolyte containing 35 g / L sodium hexametaphosphate, 6 g / L sodium silicate and 1.2 g / L sodium hydroxide, so that the concentration of CNTs in the electrolyte is 2.5 g / L. After ultrasonic treatment for 30 min, the electrolyte is subjected to plasma pretreatment, wherein the voltage of plasma pretreatment is 500 V, the frequency is 700 Hz and the treatment time is 30 min, in order to functionalize CNTs and improve the dispersibility of CNTs, so as to obtain an electrolyte containing functionalized CNTs.

[0103] Comparative Example 3

[0104] Same as Example 1, except that the voltage of the micro-arc plasma oxidation is 800V, the frequency is 600Hz, the processing time is 20min, and the temperature is 70℃.

[0105] Comparative Example 4

[0106] Same as Example 1, except that the voltage of the micro-arc plasma oxidation is 550V, the frequency is 1000Hz, the processing time is 20min, and the temperature is 70℃.

[0107] Comparative Example 5

[0108] Same as Example 1, except that the voltage of the micro-arc plasma oxidation is 550V, the frequency is 600Hz, the processing time is 20min, and the temperature is 90℃.

[0109] Comparative Example 6

[0110] Same as Example 1, except that the plasma pretreatment voltage is 800V, the frequency is 600Hz, and the treatment time is 60min.

[0111] Comparative Example 7

[0112] Same as Example 1, except that the plasma pretreatment voltage is 550V, the frequency is 300Hz, and the treatment time is 60min.

[0113] Comparative Example 8

[0114] Same as Example 1, except that the plasma pretreatment voltage is 550V, the frequency is 600Hz, and the treatment time is 150min.

[0115] Performance testing

[0116] Measurements showed that the coating prepared in Example 5 of this invention had an infrared emissivity of 0.90 and a surface resistivity of 3.17 × 10⁻⁶. 2 Ω, volume resistivity is 3.20×10 7 Ω;

[0117] The coating prepared in Example 6 of this invention has an infrared emissivity of 0.91 and a surface resistivity of 4.28 × 10⁻⁶. 2 Ω, volume resistivity is 3.71×10 7 Ω;

[0118] The coating prepared in Comparative Example 2 of this invention has an infrared emissivity of 0.85 and a surface resistivity of 3.25 × 10⁻⁶. 7 Ω, volume resistivity is 4.78×10 8 Ω;

[0119] The coating prepared in Comparative Example 3 of this invention has an infrared emissivity of 0.92 and a surface resistivity of 6.13 × 10⁻⁶. 3 Ω, volume resistivity is 9.15×10 7 Ω;

[0120] The coating prepared in Comparative Example 4 of this invention has an infrared emissivity of 0.90 and a surface resistivity of 7.58 × 10⁻⁶. 3 Ω, volume resistivity is 8.24×10 7 Ω;

[0121] The coating prepared in Comparative Example 5 of this invention has an infrared emissivity of 0.94 and a surface resistivity of 3.56 × 10⁻⁶. 3 Ω, volume resistivity is 6.52×10 7 Ω;

[0122] The coating prepared in Comparative Example 6 of this invention has an infrared emissivity of 0.73 and a surface resistivity of 8.74 × 10⁻⁶. 6 Ω, volume resistivity is 2.56×10 6 Ω;

[0123] The coating prepared in Comparative Example 7 of this invention has an infrared emissivity of 0.74 and a surface resistivity of 4.21 × 10⁻⁶. 6 Ω, volume resistivity is 1.37×10 7 Ω;

[0124] The coating prepared in Comparative Example 8 of this invention has an infrared emissivity of 0.76 and a surface resistivity of 4.53 × 10⁻⁶. 7 Ω, volume resistivity is 6.56×10 8 Ω;

[0125] Compared to Example 1, Comparative Example 2 showed a decrease in infrared emissivity to 0.85, and a significant increase in surface resistivity and volume resistivity (3.25 × 10⁻⁶, respectively). 7 Ω and 4.78×10 8 (Ω), which may be because Comparative Example 2 did not incorporate ITO nanoparticles. The conductivity and infrared absorption properties of ITO nanoparticles can significantly improve the conductivity and infrared emissivity of the coating. The absence of ITO particles leads to an increase in resistivity and a decrease in infrared emissivity, which in turn affects the emissivity and conductivity.

[0126] Compared to Example 1, Comparative Example 3 showed a decrease in infrared emissivity to 0.92, and a significant increase in surface resistivity and volume resistivity (6.13 × 10⁻⁶, respectively). 3 Ω and 9.15×10 7 The decrease in voltage (Ω) in Comparative Example 3, where the micro-arc oxidation voltage was increased to 800V, resulted in a porous and loose oxide coating structure, which easily leads to a decline in electrical performance and an increase in surface and volume resistivity. The infrared emissivity also decreased slightly due to the increased surface defects in the coating.

[0127] Compared to Example 1, Comparative Example 4 showed a decrease in infrared emissivity to 0.90, and an increase in surface resistivity and volume resistivity (7.58 × 10⁻⁶, respectively). 3 Ω and 8.24×10 7The difference (Ω) may be because Comparative Example 4 increased the micro-arc oxidation frequency to 1000Hz. Excessively high frequencies can lead to uneven partial discharge, affecting the coating's microstructure and causing increased porosity. This structural degradation reduces the coating's conductivity and radiation performance, resulting in lower infrared emissivity and conductivity compared to Example 1.

[0128] Compared to Example 1, Comparative Example 5 maintained an infrared emissivity of 0.94, but its surface resistivity and volume resistivity were 3.56 × 10⁻⁶. 3 Ω and 6.52×10 7 The resistance (Ω) increased slightly, possibly because Comparative Example 5 increased the micro-arc oxidation temperature to 150℃. The high temperature caused the coating grains to grow, reducing density and conductivity, thus leading to a slight increase in resistance. However, the infrared emissivity remained stable, indicating that temperature changes had little effect on emissivity.

[0129] Compared to Example 1, Comparative Example 6 has an infrared emissivity of 0.73, a surface resistivity of 8.74 × 10⁻⁶, and a volume resistivity of 8.74 × 10⁻⁶. 6 Ω and 2.56×10 6 The Ω value is likely due to the excessively high plasma pretreatment voltage in Comparative Example 6, which damaged the CNT structure, preventing it from promoting the deposition and sintering of ITO nanoparticles. Therefore, the reduction in the content of the conductive phase ITO and CNTs in the coating leads to a decrease in surface resistivity, while the reduced CNT doping concentration results in a decrease in emissivity.

[0130] Compared to Example 1, Comparative Example 7 has an infrared emissivity of 0.74, a surface resistivity of 4.21 × 10⁻⁶, and a volume resistivity of 4.21 × 10⁻⁶. 6 Ω and 1.37×10 7 Ω, which may be because the plasma pretreatment frequency of Comparative Example 7 is too low, the insufficiently functionalized CNTs have poor dispersibility in the electrolyte, are prone to agglomeration, resulting in uneven distribution of particles on the substrate surface.

[0131] Compared to Example 1, Comparative Example 8 has an infrared emissivity of 0.76, a surface resistivity of 4.53 × 10⁻⁶, and a volume resistivity of 4.53 × 10⁻⁶. 7 Ω and 6.56×10 8Excessive plasma pretreatment time can lead to decreased conductivity of the coating (manifested as increased surface resistivity and volume resistivity) and decreased thermal management performance (manifested as decreased emissivity). This may be because excessive functionalization of CNTs reduces their conductivity, potentially affecting the uniformity and density of the pore structure during coating formation. The above is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An ITO-CNTs co-doped antistatic and thermal management dual-layer coating, characterized in that, The porous oxide bottom layer and the conductive outer layer, the conductive outer layer is ITO-CNTs composite material; The CNTs in the ITO-CNTs composite material connect the ITO particles as conductive channels to form a complete conductive network, and the porous oxide bottom layer has a microporous structure; The ITO-CNTs co-doped antistatic and thermal management double-layer coating is prepared by using electrolyte containing CNTs and ITO nanoparticles for plasma pretreatment, then using the plasma pretreated electrolyte, and combining micro-arc plasma oxidation technology on the surface of the substrate.

2. The ITO-CNTs co-doped antistatic and thermal management dual-layer coating according to claim 1, wherein, The thickness of the ITO-CNTs co-doped antistatic and thermal management double-layer coating is 80-105 μm.

3. The ITO-CNTs co-doped antistatic and thermal management dual-layer coating according to claim 1, wherein, The pore size of the microporous structure in the porous oxide bottom layer is 1-5 μm.

4. A method for preparing the ITO-CNTs co-doped antistatic and thermal management dual-layer coating according to any one of claims 1-3, characterized in that, The ITO-CNTs co-doped antistatic and thermal management double-layer coating is prepared by using electrolyte containing CNTs and ITO nanoparticles for plasma pretreatment, then using the plasma pretreated electrolyte, and combining micro-arc plasma oxidation technology on the surface of the substrate.

5. The method for preparing the ITO-CNTs co-doped antistatic and thermal management bilayer coating according to claim 4, characterized in that, After the electrolyte containing CNTs and ITO nanoparticles is pretreated by plasma, carboxyl, hydroxyl and oxygen-containing groups are introduced on the surface of CNTs.

6. The method of claim 4, wherein the ITO-CNTs co-doped antistatic and thermal management dual-layer coating is prepared by the steps of: The concentration of ITO nanoparticles in the electrolyte is 30-50 g / L, and the concentration of CNTs is 1.5-2.5 g / L.

7. The method for preparing the ITO-CNTs co-doped antistatic and thermal management bilayer coating according to claim 4, characterized in that, The voltage of the plasma pretreatment is 500-600 V, the frequency is 400-700 Hz, and the treatment time is 30-90 min.

8. The method for preparing the ITO-CNTs co-doped antistatic and thermal management bilayer coating according to claim 7, characterized in that, The voltage of the plasma pretreatment is 550 V, the frequency is 600 Hz, and the treatment time is 60 min.

9. The method of claim 4, wherein the ITO-CNTs co-doped antistatic and thermal management dual layer coating is prepared by, The voltage of the micro-arc plasma oxidation technology is 450-600 V, the frequency is 400-700 Hz, the treatment time is 15-30 min, and the temperature is 50-90 ℃.

10. The method for preparing the ITO-CNTs co-doped antistatic and thermal management bilayer coating according to claim 9, characterized in that, The voltage of the micro-arc plasma oxidation technology is 550 V, the frequency is 600 Hz, the treatment time is 20 min, and the temperature is 70 ℃.

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