Bionic radiation heat dissipation and friction reduction double-layer coating and preparation method thereof
By forming a graded micro-nano structure of metal oxide ceramic layer and h-BN/CNTs layer on the metal surface of the matrix, the existing coatings have insufficient heat dissipation and friction reduction performance in high-temperature environments, and efficient radiation heat dissipation and friction reduction effects are achieved. It is suitable for aerospace, electronic packaging and other fields.
Patent Information
- Application Number
- CN202510512771.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-23
- Publication Date
- 2025-07-25
AI Technical Summary
The existing coating technology has limited heat dissipation effect in high temperature environments, and it is difficult to have excellent friction reduction performance at the same time. The process is complex and the cost is high, and the applicability is poor, making it difficult to meet the needs of aerospace, electronic packaging and other fields.
A metal oxide ceramic layer is formed on the metal surface of the matrix by microarc plasma oxidation process, and the h-BN/CNTs layer is covered thereon. Combined with the graded micro-nano structure, the heat dissipation performance is improved and the friction coefficient is reduced by imitating the graded micro-nano protrusions of the legs of tropical ants.
It achieves excellent radiation heat dissipation and friction reduction performance in high temperature environments. It is suitable for light metal surfaces, significantly reduces heat accumulation and wear caused by friction, improves equipment heat dissipation efficiency, extends service life, is simple, environmentally friendly, and has low cost.
Smart Images
Figure CN120366865A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of functional coatings, and particularly to a bionic radiative cooling and friction-reducing double-layer coating and a preparation method thereof. Background Art
[0002] In modern industry, with the wide application of mechanical equipment under high-temperature and high-speed operating conditions, the problems of heat dissipation and friction reduction have become key factors in improving equipment performance and extending service life. Although traditional heat dissipation methods such as natural convection, forced convection, and conduction are applied in some fields, their heat dissipation effects are limited in high-temperature environments. Moreover, in fields such as aerospace and electronic packaging, due to strict space and weight restrictions, traditional heat dissipation methods often cannot meet specific requirements. Friction and wear are common problems faced by mechanical systems. Especially in the case of high load and high-speed operation, the energy loss and component damage caused by friction pose a threat to the long-term stability of equipment. Traditional friction-reducing methods mainly rely on lubricants. However, in high-temperature environments, the volatilization or decomposition of lubricants will cause a significant decline in their lubrication effects, thereby affecting the operating efficiency of equipment.
[0003] In order to solve the problems of heat dissipation and friction reduction simultaneously, developing coatings with both heat dissipation and friction-reducing properties has become an effective solution. However, most of the existing coating technologies have problems such as complex processes, high manufacturing costs, and poor applicability. Many coating preparation processes require multiple steps, such as high-temperature sintering, chemical vapor deposition (CVD), physical vapor deposition (PVD), etc. These processes are complex and require high-precision equipment, resulting in high production costs. At the same time, the coatings in the existing technology are usually optimized for specific materials or environments, with limited applicability, and it is difficult to balance the heat dissipation and friction-reducing properties, making it difficult to be widely applied. Therefore, developing a new coating technology that simplifies the process, reduces costs, and can simultaneously possess excellent heat dissipation and friction-reducing properties has important research significance and broad application prospects. Summary of the Invention
[0004] The purpose of the present invention is to provide a bionic radiative cooling and friction-reducing double-layer coating and a preparation method thereof to solve the problems existing in the above-mentioned prior art.
[0005] To achieve the above purpose, the present invention provides the following solutions:
[0006] One of the technical solutions of the present invention: A bionic radiative cooling and friction-reducing double-layer coating includes a metal oxide ceramic layer formed by a base metal and an h-BN (hexagonal boron nitride) / CNTs (carbon nanotubes) layer covering the surface of the metal oxide ceramic layer; the surface of the bionic radiative cooling and friction-reducing double-layer coating is spherical-crown-shaped micro-protrusions; the h-BN in the h-BN / CNTs layer is horizontally arranged.
[0007] Tropical ants' legs have hierarchical micro-nano protrusions, which help them dissipate heat in high-temperature environments. At the same time, the surface structure of the hierarchical micro-nano protrusions can effectively disperse the contact pressure and reduce the direct frictional contact between surfaces by increasing the complexity and irregularity of surface micro-contact. Drawing on the hierarchical micro-nano protrusions of tropical ants, the bionic coating of the present invention is proposed. In the coating of the present invention, the metal oxide ceramic layer serves as the main body of the coating (the surface of the metal oxide ceramic layer itself is spherical-crowned micro-protrusions), and the h-BN / CNTs layer covering its surface plays a role in optimizing the microstructure of the coating. The metal oxide ceramic layer with spherical-crowned micro-protrusions on its surface and the h-BN / CNTs layer covering the spherical-crowned micro-protrusions on its surface form a hierarchical micro-nano structure. The hierarchical micro-nano structure can endow the coating surface with an optical trapping effect, effectively improve the heat dissipation performance of the coating, and significantly enhance the emissivity of the coating in the mid-infrared band. The surface hierarchical micro-nano structure of the coating can also optimize the heat dissipation ability of the coating by increasing the surface contact complexity and irregularity, and at the same time reduce the friction coefficient by reducing surface direct contact. Moreover, both CNTs and h-BN in the coating have extremely high thermal conductivities, and their addition can effectively improve the thermal conductivity of the coating. In addition, CNTs can provide additional lubrication, and the layered crystal structure of h-BN can also effectively reduce the friction coefficient. The h-BN / CNTs layer formed by the two acts as a lubricating layer during friction, making the coating have excellent antifriction and durability.
[0008] Furthermore, the bionic radiation heat dissipation and antifriction double-layer coating has a hierarchical micro-nano structure.
[0009] Furthermore, the radius of the spherical-crowned micro-protrusions is 1-20 μm (the surface of the metal oxide ceramic layer itself is spherical-crowned micro-protrusions, and the h-BN / CNTs layer closely covers the surface of the metal oxide ceramic layer along the shape of the spherical-crowned micro-protrusions on the surface of the metal oxide ceramic layer. The spherical-crowned micro-protrusions existing on the surfaces of the h-BN / CNTs layer and the metal oxide ceramic layer together form the spherical-crowned micro-protrusion structure of the final double-layer coating. The radius defined here is the radius of the spherical-crowned micro-protrusions on the surface of the final double-layer coating after covering the h-BN / CNTs layer).
[0010] Furthermore, the thickness of the bionic radiation heat dissipation and antifriction double-layer coating is 10-130 μm, and the thickness of the h-BN / CNTs layer is 1-30 μm.
[0011] When the radius of the spherical-crowned micro-protrusions on the coating surface is in the range of 1-20 μm and the overall thickness of the coating is in the range of 10-130 μm, a better radiation emissivity in the mid-infrared band (3-14 μm) can be obtained.
[0012] The second technical solution of the present invention: The preparation method of the above-mentioned bionic radiation heat dissipation and friction reduction double-layer coating includes the following steps:
[0013] Perform micro-arc plasma oxidation on the substrate metal in the electrolyte after plasma pretreatment to obtain the bionic radiation heat dissipation and friction reduction double-layer coating;
[0014] The components of the electrolyte include: 25-35 g / L of h-BN and 1-2 g / L of CNTs;
[0015] The operation parameters of the micro-arc plasma oxidation include: duty cycle of 10-20%, voltage of 500-600 V, frequency of 500-600 Hz, temperature of -10-10 °C (that is, maintaining the temperature of the electrolyte at -10-10 °C during the micro-arc plasma oxidation process), and treatment time of 20-40 minutes.
[0016] Before micro-arc plasma oxidation, plasma pretreatment is carried out on the electrolyte. The main purpose is to functionalize CNTs and h-BN in the electrolyte by plasma pretreatment. The high-energy particles and ultraviolet rays generated during the plasma discharge will interact with the surfaces of CNTs and h-BN in the electrolyte, thereby introducing oxygen-containing functional groups such as carboxyl (-COOH) and hydroxyl (-OH) on the surfaces of CNTs and h-BN, increasing the hydrophilicity and polarity of CNTs and h-BN, thus improving the dispersion of CNTs and h-BN in the electrolyte. At the same time, the electrolyte is activated, and the interaction between CNTs and h-BN and the metal oxide ceramic layer is enhanced, improving the deposition efficiency of h-BN and CNTs during the subsequent micro-arc plasma oxidation process, ensuring uniform surface distribution and stable bonding, so that a large amount of h-BN and CNTs are deposited into layers on the surface of the metal oxide ceramic layer during the micro-arc plasma oxidation process. Moreover, during the micro-arc plasma oxidation process, h-BN is oriented and distributed on the surface of the metal oxide ceramic layer, and forms an anisotropic horizontal arrangement during the electric field-induced deposition process. The horizontally distributed h-BN and CNTs on the coating surface act synergistically to significantly improve the friction reduction effect of the coating.
[0017] The preparation method of the present invention forms spherical crown-shaped micro-protrusions on the surface of the substrate metal through the micro-arc plasma oxidation process. The formation of the spherical crown-shaped micro-protrusion structure is affected by the high energy during the micro-arc plasma oxidation process. The high energy conditions are achieved by increasing the micro-arc plasma oxidation voltage (500 - 600V) and frequency (500 - 600Hz). The higher voltage and frequency enhance the local discharge intensity, causing a melt to form on the surface of the substrate metal. When the melt encounters the cold electrolyte, it cools rapidly. The high thermal conductivity of CNTs and h-BN accelerates the cooling of the melt, preventing long-term flow or spread, and thus maintaining a locally aggregated state to form a spherical crown-shaped micro-protrusion structure. By adjusting the concentrations of h-BN and CNTs, as well as the process parameters of micro-arc plasma oxidation, the size and uniformity of the micro-protrusions on the coating surface can be controlled. Specifically, during the micro-arc plasma oxidation process, h-BN and CNTs promote the uniform distribution of heat on the surface of the metal oxide ceramic layer through their high thermal conductivity, thereby stabilizing the arc and promoting the formation of a uniform spherical crown-shaped micro-protrusion structure; in addition, CNTs can also promote the homogenization of the microstructure by enhancing the stability of the arc and providing surface sites. Moreover, during the micro-arc plasma oxidation process, electrophoresis migration and deposition of h-BN and CNTs occur, and h-BN and CNTs are deposited on the surface of the metal oxide ceramic layer along the shape of the spherical crown-shaped micro-protrusions on the surface of the metal oxide ceramic layer, forming an h-BN / CNTs layer. The h-BN / CNTs layer and the metal oxide ceramic layer together form a coating with a hierarchical micro-nano structure (i.e., hierarchical micro-nano protrusions).
[0018] In addition, the acquisition of the outer layer of h-BN / CNTs is also related to the composition of the electrolyte and the process parameters of micro-arc plasma oxidation. By optimizing the electrolyte composition and micro-arc plasma oxidation process parameters, the directional arrangement of h-BN and its efficient combination with CNTs are achieved. During the micro-arc discharge process, h-BN is negatively charged under the action of the plasma electric field and migrates along the electric field direction to the surface of the metal substrate, where it is oriented and distributed on the surface of the micro-protrusions and forms an anisotropic arrangement through electric field-induced deposition. The micro-arc plasma oxidation voltage (500 - 600V), frequency (500 - 600Hz), duty cycle (10 - 20%), and electrolyte temperature (-10 - 10°C) all affect the orientation distribution of h-BN. Among them, higher voltage and duty cycle can enhance the local discharge intensity and improve the ordered arrangement of h-BN along the micro-protrusion structure. The pretreated CNTs are sintered under the action of electrophoresis force and local high temperature, and jointly construct a stable composite layer structure with h-BN.
[0019] The above method can obtain a coating through one-step micro-arc plasma oxidation, which has the advantages of simple process, environmental protection, and low cost.
[0020] Furthermore, the substrate metal includes one of titanium alloy, aluminum alloy, and magnesium alloy.
[0021] Furthermore, the composition of the electrolyte also includes: 5 - 15 g / L of Na2SiO3, 5 - 15 g / L of (NaPO3)6, and 1 - 5 g / L of KOH.
[0022] Furthermore, the pH value of the electrolyte is 9 - 10.
[0023] Furthermore, the operating parameters of the plasma pretreatment include: voltage of 450 - 500 V, frequency of 550 - 600 Hz, and treatment time of 5 - 10 minutes.
[0024] After plasma pretreatment of the electrolyte containing CNTs and h - BN nanoparticles, carboxyl and hydroxyl oxygen - containing groups are formed on the surfaces of CNTs and h - BN; and after plasma pretreatment in the horizontal direction, h - BN is negatively charged and has orientation, enabling it to migrate towards the anode in the electrolyte.
[0025] Furthermore, the micro - arc plasma oxidation of the substrate metal in the electrolyte after plasma pretreatment includes: performing plasma pretreatment on the electrolyte, and then using the substrate metal as the anode and a stainless - steel tube as the cathode to carry out micro - arc plasma oxidation in the electrolyte after plasma pretreatment.
[0026] Furthermore, the micro - arc plasma oxidation uses a pulsed bipolar plasma power supply as the power source.
[0027] Based on the particle - modified micro - arc plasma oxidation technology, the present invention uses h - BN and CNTs as auxiliary materials, and successfully prepares a composite coating with a hierarchical micro - nano structure on the surface of substrate metals such as magnesium, aluminum, and titanium alloys. This coating successfully combines the advantages of photonics and bionic non - smooth textures, and through the optimized surface structure, achieves excellent radiative heat dissipation performance and friction - reducing performance. The average infrared emissivity of the bionic radiative heat dissipation and friction - reducing double - layer coating is > 0.8 in the wavelength range of 3 - 14 μm, and the average friction coefficient is 0.1 - 0.6 when sliding 6000 circles repeatedly within a sliding distance of 94.2 m.
[0028] The hierarchical micro - nano structure of this coating achieves excellent radiative heat dissipation and friction - reducing performance through synergistic effects, where both h - BN and CNTs provide high radiative emissivity and self - lubricating effects.
[0029] The present invention discloses the following technical effects:
[0030] The bionic radiative heat dissipation and friction - reducing double - layer coating of the present invention has both excellent radiative heat dissipation performance and friction - reducing performance, is applicable to the surfaces of light metals such as magnesium alloys, aluminum alloys, and titanium alloys, and has broad industrial application prospects, especially in high - performance thermal management fields such as aerospace, electronic packaging, and the automotive industry that require efficient heat dissipation and low friction, and can meet strict working conditions requirements.
[0031] The bionic radiation heat dissipation and friction reduction double-layer coating of the present invention can significantly reduce the heat accumulation and wear caused by friction, and is particularly suitable for working conditions with high friction and high load, such as mechanical equipment and moving parts. It can effectively improve the heat dissipation efficiency of the equipment, reduce the operating temperature, and extend the service life of the equipment.
[0032] By adopting the process of combining plasma pretreatment and micro-arc plasma oxidation, a coating with excellent heat dissipation and friction reduction performance can be formed in one-step operation. Compared with the complex multi-step processes in the prior art, it has the advantages of simple process, environmental protection, low cost, and can achieve batch production, which is suitable for popularization in large-scale industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.
[0034] Figure 1 It is a schematic structural diagram of the bionic radiation heat dissipation and friction reduction double-layer coating of the present invention;
[0035] Figure 2 It is the surface scanning electron microscope (SEM) images of the bionic radiation heat dissipation and friction reduction double-layer coating on the titanium alloy surface prepared in Example 1 at different magnification ratios;
[0036] Figure 3 It is the transmission electron microscope photo of the bionic radiation heat dissipation and friction reduction double-layer coating on the titanium alloy surface prepared in Example 1;
[0037] Figure 4 It is the cross-sectional SEM image and Raman imaging map of the bionic radiation heat dissipation and friction reduction double-layer coating on the titanium alloy surface prepared in Example 1, where (a) is the cross-sectional SEM image, and (b)-(d) are the Raman imaging maps of the distribution of different components in the coating;
[0038] Figure 5 It is the surface SEM images of the bionic radiation heat dissipation and friction reduction double-layer coating on the aluminum alloy surface prepared in Example 2 at different magnification ratios;
[0039] Figure 6 It is the surface SEM image of the bionic radiation heat dissipation and friction reduction double-layer coating on the magnesium alloy surface prepared in Example 3;
[0040] Figure 7 It is the surface SEM images of the TiO2 coating on the titanium alloy surface prepared in Comparative Example 1 at different magnification ratios;
[0041] Figure 8 SEM images of the Al2O3 coating on the surface of the aluminum alloy prepared in Comparative Example 2 at different magnifications;
[0042] Figure 9 SEM image of the surface of the coating prepared in Comparative Example 4;
[0043] Figure 10 SEM image of the surface of the coating prepared in Comparative Example 5;
[0044] Figure 11 SEM image of the surface of the coating prepared in Comparative Example 6;
[0045] Figure 12 Infrared emissivity spectrum of the bionic radiation heat dissipation and friction reduction double-layer coating on the surface of the titanium alloy prepared in Example 1;
[0046] Figure 13 Radiation heat dissipation cooling curves of the titanium alloy substrate before and after preparing the bionic radiation heat dissipation and friction reduction double-layer coating on the surface of the titanium alloy in Example 1;
[0047] Figure 14 Friction coefficient curve of the bionic radiation heat dissipation and friction reduction double-layer coating on the surface of the titanium alloy prepared in Example 1. Detailed Description of the Invention
[0048] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation on the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.
[0049] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.
[0050] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.
[0051] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific embodiments of the description of the present invention, which will be obvious to those skilled in the art. Other embodiments obtained from the description of the present invention will be obvious to those skilled in the art. The description and examples of the present invention are merely exemplary.
[0052] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.
[0053] It should be noted that the parts not described in detail in the present invention are all conventional operating means in the art and are not the focus of the present invention.
[0054] As a first aspect of the present invention, the present invention provides a bionic radiation heat dissipation and friction reduction double-layer coating, including a metal oxide ceramic layer formed by a base metal and an h-BN / CNTs layer covering the surface of the metal oxide ceramic layer; the surface of the bionic radiation heat dissipation and friction reduction coating is spherical crown-shaped micro-protrusions (spherical crown-shaped means having a partial arc shape of a sphere); the h-BN in the h-BN / CNTs layer is horizontally arranged.
[0055] The structural schematic diagram of the bionic radiation heat dissipation and friction reduction double-layer coating of the present invention is as Figure 1 shown. The main body of the coating is a metal oxide ceramic layer with spherical crown-shaped micro-protrusions on the surface, and the spherical crown-shaped micro-protrusions on the surface of the metal oxide ceramic layer are covered with an h-BN / CNTs layer.
[0056] As an embodiment of the present invention, the radius of the spherical crown-shaped micro-protrusions is 1-20 μm.
[0057] As an embodiment of the present invention, the thickness of the bionic radiation heat dissipation and friction reduction double-layer coating (including the spherical crown-shaped micro-protrusion part) is 10-130 μm, and the thickness of the h-BN / CNTs layer is 1-30 μm.
[0058] As a second aspect of the present invention, the present invention provides a preparation method of the above-mentioned bionic radiation heat dissipation and friction reduction double-layer coating, including the following steps:
[0059] Subject the base metal to micro-arc plasma oxidation in an electrolyte after plasma pretreatment to obtain the bionic radiation heat dissipation and friction reduction double-layer coating;
[0060] The components of the electrolyte include: 25-35 g / L of h-BN and 1-2 g / L of CNTs;
[0061] The operating parameters of the micro-arc plasma oxidation include: duty cycle of 10-20%, voltage of 500-600V, frequency of 500-600Hz, temperature of -10-10°C, and treatment time of 20-40 minutes.
[0062] As an embodiment of the present invention, the base metal includes one of titanium alloy, aluminum alloy, and magnesium alloy.
[0063] As an embodiment of the present invention, the composition of the electrolyte further includes: 5-15g / L of Na2SiO3, 5-15g / L of (NaPO3)6, and 1-5g / L of KOH.
[0064] As an embodiment of the present invention, the pH value of the electrolyte is 9-10.
[0065] As a preferred embodiment of the present invention, the operating parameters of the plasma pretreatment include: voltage of 450-500V, frequency of 550-600Hz, and treatment time of 5-10 minutes.
[0066] As an embodiment of the present invention, the micro-arc plasma oxidation of the base metal in the electrolyte after plasma pretreatment includes: performing plasma pretreatment on the electrolyte, and then using the base metal as the anode and a stainless steel tube as the cathode to perform micro-arc plasma oxidation in the electrolyte after plasma pretreatment.
[0067] As an embodiment of the present invention, the micro-arc plasma oxidation uses a pulsed bipolar plasma power supply as the power source.
[0068] As a preferred embodiment of the present invention, before the micro-arc plasma oxidation, a pretreatment operation on the base metal is further included, and the pretreatment operation includes: mechanical treatment and pickling treatment, aiming to remove the oxides on the surface of the base metal. The specific operations of the mechanical treatment and pickling treatment are not defined in the present invention, and common mechanical treatment methods and pickling treatment methods in the art can be selected as long as the effect of removing the oxides on the surface of the base metal can be achieved.
[0069] As a preferred embodiment of the present invention, after the micro-arc plasma oxidation, operations of cooling, rinsing, and drying are further included.
[0070] The technical solutions of the present invention are further described below in conjunction with specific embodiments.
[0071] All raw materials used in the specific embodiments of the present invention are ordinary commercially available products. Among them, the size of h-BN is 30 - 50 nm (the h-BN used in the specific embodiments of the present invention is flaky h-BN, and 30 - 50 nm is its diameter range); the length of CNTs is 3 μm to 1 mm, and the radius is 0.5 - 50 nm.
[0072] The room temperature involved in the specific embodiments of the present invention specifically refers to 20 - 30 °C.
[0073] Example 1
[0074] A bionic radiation heat dissipation and friction reduction double-layer coating on the surface of a titanium alloy is prepared according to the following steps:
[0075] (1) Preparation of the electrolyte and plasma pretreatment
[0076] Prepare the electrolyte with deionized water as the solvent according to the electrolyte composition of 8 g / L Na2SiO3, 8 g / L (NaPO3)6, 3 g / L KOH, 25 g / L h-BN, and 1 g / L CNTs. Measure the pH value of the electrolyte to be 9.5, and then functionalize the CNTs in the electrolyte through plasma pretreatment. Set the voltage of the plasma pretreatment to 500 V, the frequency to 550 Hz, and the treatment time to 5 minutes;
[0077] (2) Pretreatment of the substrate metal
[0078] Mechanically polish and acid-wash the surface of the substrate metal (TC4 titanium alloy). After removing the surface oxides, wash it clean with deionized water.
[0079] (3) Preparation of the coating
[0080] Use the pretreated substrate metal as the anode and a stainless steel tube as the cathode, and perform micro-arc plasma oxidation in the electrolyte after plasma pretreatment. The micro-arc plasma oxidation uses a pulsed bipolar plasma power supply. Set the voltage to 550 V, the duty cycle to 15%, and the frequency to 500 Hz. During the micro-arc plasma oxidation process, control the temperature of the electrolyte to -5 °C and the treatment time to 20 minutes. After the micro-arc plasma oxidation is completed, immediately take out the substrate metal with the bionic radiation heat dissipation and friction reduction double-layer coating formed on its surface and let it cool naturally to room temperature. Then, rinse it with deionized water to remove the residual electrolyte and dry it in clean air.
[0081] The bionic radiation heat dissipation and friction reduction double-layer coating on the surface of the titanium alloy prepared in this example is simply referred to as the TiO2-BN / CNTs coating.
[0082] Figure 2 For the surface SEM images of the bionic radiation heat dissipation and friction reduction double-layer coating on the surface of the titanium alloy prepared in this example at different magnification ratios, fromFigure 2 It can be seen that the coating surface is covered with nanoparticles to form a nanoparticle layer (h-BN / CNTs layer), and the overall coating surface presents a spherical crown-shaped micro-protrusion structure with a protrusion radius between 5 - 7 μm.
[0083] Figure 3 This is a transmission electron microscope photograph of the bionic radiation heat dissipation and friction reduction double-layer coating on the surface of the titanium alloy prepared in this example. It can be observed that h-BN are arranged horizontally and parallel to each other.
[0084] Figure 4 This is a cross-sectional SEM image and a Raman imaging map of the bionic radiation heat dissipation and friction reduction double-layer coating on the surface of the titanium alloy prepared in this example. Among them, (a) is the cross-sectional SEM image, and (b)-(d) are Raman imaging maps of the distribution of different components in the coating. It can be seen from the cross-sectional SEM image that the coating and the matrix metal are metallurgically bonded, and the overall thickness (average thickness) of the coating is 40 μm. Among them, the thickness (average thickness) of the h-BN / CNTs layer is 10 μm. The Raman imaging map shows the phase composition and the distribution of each phase of the double-layer structure coating. It can be seen that titanium oxide is mainly distributed in the inner layer of the coating, and h-BN and CNTs are mainly distributed in the outer layer of the coating, thus forming a TiO2 / BN-CNTs double-layer coating.
[0085] Example 2
[0086] A bionic radiation heat dissipation and friction reduction double-layer coating on the surface of an aluminum alloy is prepared according to the following steps:
[0087] (1) Preparation and pretreatment of the electrolyte
[0088] Prepare an electrolyte according to the electrolyte composition of 15 g / L Na2SiO3, 12 g / L (NaPO3)6, 3 g / L KOH, 30 g / L h-BN, and 2 g / L CNTs with deionized water as the solvent. Measure the pH value of the electrolyte to be 9.8, and then functionalize the CNTs in the electrolyte by plasma pretreatment. Set the voltage of the plasma pretreatment to 500 V, the frequency to 600 Hz, and the treatment time to 10 minutes;
[0089] (2) Pretreatment of the matrix metal
[0090] Mechanically polish and acid-wash the surface of the matrix metal (6061 aluminum alloy). After removing the surface oxides, wash it clean with deionized water.
[0091] (3) Preparation of the coating
[0092] Using the pretreated substrate metal as the anode and a stainless steel tube as the cathode, micro-arc plasma oxidation is carried out in the electrolyte after plasma pretreatment. A pulsed bipolar plasma power supply is used for micro-arc plasma oxidation, with the set voltage of 600 V, duty cycle of 18%, and frequency of 600 Hz. During the micro-arc plasma oxidation process, the temperature of the electrolyte is controlled at -5 °C, and the treatment time is 20 minutes. After the micro-arc plasma oxidation is completed, the substrate metal with a bionic radiation heat dissipation and friction reduction double-layer coating formed on its surface is immediately taken out and naturally cooled to room temperature. Subsequently, it is rinsed with deionized water to remove the residual electrolyte and dried in clean air.
[0093] In this example, the bionic radiation heat dissipation and friction reduction double-layer coating on the surface of the aluminum alloy is simply referred to as the Al2O3-BN / CNTs coating.
[0094] Figure 5 This is the surface SEM image of the bionic radiation heat dissipation and friction reduction double-layer coating on the surface of the aluminum alloy obtained in this example at different magnification ratios. It can be seen from Figure 5 that the surface of the coating is covered with nanoparticles to form a nanoparticle layer (h-BN / CNTs layer), and the overall coating surface presents a spherical crown micro-protrusion structure with the protrusion radius between 3 - 9 μm.
[0095] It is detected that the overall thickness (average thickness) of the coating is 60 μm, among which the thickness (average thickness) of the h-BN / CNTs layer is 12 μm.
[0096] Example 3
[0097] A bionic radiation heat dissipation and friction reduction double-layer coating on the surface of a magnesium alloy is prepared as follows:
[0098] (1) Preparation and pretreatment of the electrolyte
[0099] Prepare the electrolyte with a solvent of deionized water according to the electrolyte composition of 15 g / L Na2SiO3, 5 g / L (NaPO3)6, 5 g / L KOH, 30 g / L h-BN, and 2 g / L CNTs. The pH value of the electrolyte measured at room temperature is 9.5. Then, functionalize the CNTs in the electrolyte through plasma pretreatment, with the set plasma pretreatment voltage of 450 V, frequency of 550 Hz, and treatment time of 8 minutes;
[0100] (2) Pretreatment of the substrate metal
[0101] The surface of the substrate metal (AZ31 magnesium alloy) is mechanically polished and pickled to remove the surface oxides, and then washed clean with deionized water.
[0102] (3) Preparation of the coating
[0103] Using the pretreated substrate metal as the anode and a stainless steel tube as the cathode, micro-arc plasma oxidation is carried out in the electrolyte pretreated by plasma. The micro-arc plasma oxidation uses a pulsed bipolar plasma power supply, with the set voltage being 500 V, the duty cycle being 10%, and the frequency being 500 Hz. During the micro-arc plasma oxidation process, the temperature of the electrolyte is controlled at 0 °C, and the treatment time is 40 minutes. After the micro-arc plasma oxidation is completed, the substrate metal with a bionic radiation heat dissipation and friction reduction double-layer coating formed on its surface is immediately taken out and naturally cooled to room temperature. Subsequently, it is rinsed with deionized water to remove the residual electrolyte and dried in clean air.
[0104] The bionic radiation heat dissipation and friction reduction double-layer coating on the magnesium alloy prepared in this example is simply referred to as the MgO-BN / CNTs coating.
[0105] Figure 6 This is the surface SEM image of the bionic radiation heat dissipation and friction reduction double-layer coating on the surface of the magnesium alloy prepared in this example. As can be seen from Figure 6 it, the surface of the coating is covered with nanoparticles to form a nanoparticle layer (h-BN / CNTs layer), and the overall coating surface presents a spherical crown-shaped micro-protrusion structure with the protrusion radius between 5 - 20 μm.
[0106] It can be detected that the overall thickness (average thickness) of the coating is 20 μm, among which the thickness (average thickness) of the h-BN / CNTs layer is 3 μm.
[0107] Comparative Example 1
[0108] Same as Example 1, the only difference is that the use of h-BN and CNTs is omitted in the electrolyte, and the obtained coating is a TiO2 coating.
[0109] The surface SEM images of the TiO2 coating on the surface of the titanium alloy prepared in this comparative example at different magnification ratios are as shown in Figure 7 and as can be seen from Figure 7 it, the surface of the TiO2 coating presents a porous morphology and does not have a spherical crown-shaped micro-protrusion structure.
[0110] Comparative Example 2
[0111] Same as Example 2, the only difference is that the use of h-BN and CNTs is omitted in the electrolyte, and the obtained coating is an Al2O3 coating.
[0112] The surface SEM images of the Al2O3 coating on the surface of the aluminum alloy prepared in this comparative example at different magnification ratios are as shown in Figure 8 and as can be seen from Figure 8 it, the surface of the Al2O3 coating presents a porous morphology and does not have a spherical crown-shaped micro-protrusion structure.
[0113] Comparative Example 3
[0114] Same as Example 3, except that the use of h-BN and CNTs is omitted in the electrolyte, and the obtained coating is a MgO coating.
[0115] The MgO coating on the surface of the magnesium alloy prepared in this comparative example also presents a porous morphology and does not have a spherical crown micro-protrusion structure (the SEM image of its surface is similar to that of Comparative Examples 1-2 and is not provided again).
[0116] Comparative Example 4
[0117] Same as Example 1, except that the composition of the electrolyte is: 8 g / L Na2SiO3, 8 g / L (NaPO3)6, 3 g / L KOH, and 25 g / L h-BN.
[0118] The SEM image of the surface of the coating prepared in this comparative example is as Figure 9 shown. It can be seen from Figure 9 that the surface of the coating presents a micro-protrusion structure, but still presents a single layer (there are very few nanoparticles on the surface of the coating and no layering is formed), and the deposition amount of h-BN is very small. Moreover, because CNTs are omitted, the bilayer structure is not formed, which affects the size of the micro-protrusions (the radius of the micro-protrusions is 3-5 μm), and the uniformity of the micro-protrusions is reduced.
[0119] It is detected that the overall thickness (average thickness) of the coating is 32 μm.
[0120] Comparative Example 5
[0121] Same as Example 1, except that the composition of the electrolyte is: 8 g / L Na2SiO3, 8 g / L (NaPO3)6, 3 g / L KOH, and 1 g / L CNTs.
[0122] The SEM image of the surface of the coating prepared in this comparative example is as Figure 10 shown. It can be seen from Figure 10 that the surface of the coating presents a porous morphology and does not have a spherical crown micro-protrusion structure.
[0123] It is detected that the overall thickness (average thickness) of the coating is 21 μm.
[0124] Comparative Example 6
[0125] Same as Example 1, except that the process parameters of micro-arc plasma oxidation are: duty cycle is 30%, voltage is 400 V, frequency is 400 Hz, temperature is 30 °C (the temperature of the electrolyte is controlled at 30 °C during the micro-arc plasma oxidation process), and the treatment time is 10 minutes.
[0126] The SEM image of the surface of the coating prepared in this comparative example is as Figure 11 shown. It can be seen from Figure 11It can be seen that the surface of the coating presents a porous morphology and does not have a spherical crown micro-protrusion structure.
[0127] It can be detected that the overall thickness (average thickness) of the coating is 11 μm.
[0128] Test Example 1
[0129] Performance Test of the Coating
[0130] (1) Radiation Heat Dissipation Performance Test
[0131] Figure 12 It is the infrared emissivity spectrogram of the bionic radiation heat dissipation and friction reduction double-layer coating on the titanium alloy surface prepared in Example 1. It can be seen from Figure 12 that the average infrared emissivity of the TiO2-BN / CNTs coating prepared in Example 1 in the wavelength range of 3 - 14 μm is 0.9.
[0132] The average emissivity in the wavelength range refers to the average value of the radiation emission ability of an object within a given wavelength range. It can be calculated by the following formula:
[0133]
[0134] In the formula: λ1 —— starting wavelength;
[0135] λ2 —— ending wavelength;
[0136] e λb —— blackbody radiation power;
[0137] ε λ (λ, T) —— spectral emissivity at the measured wavelength.
[0138] Measured by the same test method, the average infrared emissivity of the Al2O3-BN / CNTs coating prepared in Example 2 in the wavelength range of 3 - 14 μm is 0.92; the average infrared emissivity of the MgO-BN / CNTs coating prepared in Example 3 in the wavelength range of 3 - 14 μm is 0.82; the average infrared emissivity of the TiO2 coating prepared in Comparative Example 1 in the wavelength range of 3 - 14 μm is 0.80; the average infrared emissivity of the Al2O3 coating prepared in Comparative Example 2 in the wavelength range of 3 - 14 μm is 0.77; the average infrared emissivity of the MgO coating prepared in Comparative Example 3 in the wavelength range of 3 - 14 μm is 0.75; the average infrared emissivity of the coating prepared in Comparative Example 4 in the wavelength range of 3 - 14 μm is 0.89; the average infrared emissivity of the coating prepared in Comparative Example 5 in the wavelength range of 3 - 14 μm is 0.78; the average infrared emissivity of the coating prepared in Comparative Example 6 in the wavelength range of 3 - 14 μm is 0.77.
[0139] Figure 13Before and after the preparation of the bionic radiation heat dissipation and friction reduction double-layer coating on the titanium alloy matrix in Example 1, the radiation heat dissipation and cooling curves of the titanium alloy matrix were obtained. It can be seen from Figure 13 that compared with the titanium alloy matrix without coating, the equilibrium temperature of the titanium alloy at the 5W LED solder joint decreased by 21.5 °C after the coating was prepared (the equilibrium temperature of the titanium alloy matrix without coating was 194.1 °C, and the equilibrium temperature after the coating was prepared was 172.6 °C, and the equilibrium temperature decreased by 11.1% after the coating was prepared), showing excellent radiation heat dissipation performance. This test used an independently developed constant power heat source radiation heat dissipation performance test system to study the radiation heat dissipation performance of different coatings. The LED chip used in the experiment had a diameter of 8 mm and a power of 5 W. In a closed environment, it was bonded to the coating sample with E1 IC ESSENTIAL thermal conductive adhesive (thermal conductivity greater than 4.5 W / m·K). Since the temperature of the LED chip could not be directly measured, and the change in the chip temperature was consistent with the change in the solder joint temperature, the change in the chip temperature was reflected by measuring the solder joint temperature. Then, a TP9008 multi-channel temperature data recorder was used to monitor the temperature change of the LED solder joint and compare it with the temperature change of the alloy.
[0140] By the same test method, it was measured that compared with the aluminum alloy matrix without coating, the Al2O3-BN / CNTs coating prepared in Example 2 reduced the equilibrium temperature at the 5W LED solder joint by 15 °C (the equilibrium temperature of the aluminum alloy matrix without coating was 160.6 °C, and the equilibrium temperature after the coating was prepared was 145.6 °C, and the equilibrium temperature decreased by 9.3% after the coating was prepared), showing excellent radiation heat dissipation performance; compared with the magnesium alloy matrix without coating, the MgO-BN / CNTs coating prepared in Example 3 reduced the equilibrium temperature at the 5W LED solder joint by 10 °C (the equilibrium temperature of the aluminum alloy matrix without coating was 158.1 °C, and the equilibrium temperature after the coating was prepared was 148.1 °C, and the equilibrium temperature decreased by 6.3% after the coating was prepared), showing excellent radiation heat dissipation performance; compared with the titanium alloy matrix without coating, the coatings prepared in Comparative Examples 1, 4, 5, and 6 reduced the equilibrium temperature at the 5W LED solder joint by 8.4 °C, 9.5 °C, 7.8 °C, and 7.2 °C respectively; compared with the aluminum alloy matrix without coating, the coating prepared in Comparative Example 2 reduced the equilibrium temperature at the 5W LED solder joint by 8 °C; compared with the magnesium alloy matrix without coating, the coating prepared in Comparative Example 3 reduced the equilibrium temperature at the 5W LED solder joint by 7.2 °C.
[0141] (2) Friction reduction performance test
[0142] Figure 14 The friction coefficient curve of the bionic radiation heat dissipation and friction reduction double-layer coating on the titanium alloy surface prepared in Example 1 is shown in Figure 14It can be seen that the coating exhibits excellent anti-friction performance within a sliding distance of 94.2 m. The anti-friction performance remains good after repeated sliding for 6000 cycles, and the average friction coefficient is as low as 0.15, which is mainly due to the lubricating effect of h-BN and CNTs.
[0143] The tribological performance test conditions are as follows: The tribological properties of the coating were evaluated by a ball-on-disk test on a friction and wear tester (HT-1000) under dry sliding conditions. The counter ball used in the experiment was a GCr15 steel ball with a diameter of 5.6 mm and a hardness of 700 HV. The specific parameter settings for the friction test were: rotation diameter 5 mm, sliding distance 94.2 m, sliding cycle 6000 cycles, applied load 2 N, and speed 5 r / s.
[0144] Measured by the same test method, the average friction coefficient of the TiO2 coating in Comparative Example 1 was 0.91 after sliding 6000 cycles within a sliding distance of 94.2 m. Example 1 was 84% lower than Comparative Example 1, showing excellent anti-friction performance; the average friction coefficient of the Al2O3-BN / CNTs coating prepared in Example 2 was 0.32 after sliding 6000 cycles within a sliding distance of 94.2 m, which was 20% lower than that of the Al2O3 coating in Comparative Example 2 (0.4 in Comparative Example 2), showing excellent anti-friction performance; the average friction coefficient of the MgO-BN / CNTs coating prepared in Example 3 was 0.57 after sliding 6000 cycles within a sliding distance of 94.2 m, which was 21% lower than that of the MgO coating in Comparative Example 3 (0.72 in Comparative Example 3), showing excellent anti-friction performance; the average friction coefficients of the coatings in Comparative Example 4, Comparative Example 5, and Comparative Example 6 were 0.82, 0.84, and 0.85 respectively after sliding 6000 cycles within a sliding distance of 94.2 m.
[0145] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.
Claims
1. A bionic radiation heat dissipation and friction reduction double-layer coating, characterized in that, It includes a metal oxide ceramic layer formed of a base metal and an h-BN / CNTs layer covering the surface of the metal oxide ceramic layer; the surface of the bionic radiation heat dissipation and friction reduction double-layer coating is spherical crown-shaped micro-protrusions; the h-BN in the h-BN / CNTs layer is horizontally arranged.
2. The bionic radiation heat dissipation and friction reduction double-layer coating according to claim 1, wherein The radius of the spherical crown-shaped micro-protrusions is 1-20 μm.
3. The bionic radiation heat dissipation and friction reduction double-layer coating according to claim 1, characterized in that The total thickness of the bionic radiation heat dissipation and friction reduction double-layer coating is 10-130 μm, and the thickness of the h-BN / CNTs layer is 1-30 μm.
4. The preparation method of the bionic radiation heat dissipation and friction reduction double-layer coating according to any one of claims 1 to 3, characterized in that, It includes the following steps: The base metal is subjected to micro-arc plasma oxidation in the electrolyte after plasma pretreatment to obtain the bionic radiation heat dissipation and friction reduction double-layer coating; The components of the electrolyte include: 25-35 g / L of h-BN and 1-2 g / L of CNTs; The operating parameters of the micro-arc plasma oxidation include: duty cycle of 10-20%, voltage of 500-600 V, frequency of 500-600 Hz, temperature of -10-10 °C, and treatment time of 20-40 minutes.
5. The preparation method of the bionic radiation heat dissipation and friction reduction double-layer coating according to claim 4, characterized in that, The base metal includes one of titanium alloy, aluminum alloy, and magnesium alloy.
6. The preparation method of the bionic radiation heat dissipation and friction reduction double-layer coating according to claim 4, characterized in that The components of the electrolyte also include: 5-15 g / L of Na2SiO3, 5-15 g / L of (NaPO3)6, and 1-5 g / L of KOH.
7. The preparation method of the bionic radiation heat dissipation and friction reduction double-layer coating according to claim 4, characterized in that The pH value of the electrolyte is 9-10.
8. The preparation method of the bionic radiation heat dissipation and friction reduction double-layer coating according to claim 4, characterized in that, The operating parameters of the plasma pretreatment include: voltage of 450-500 V, frequency of 550-600 Hz, and treatment time of 5-10 minutes.