Hydrotalcite-like nano super-hydrophilic coating growing on surface of stainless steel mesh in situ, method and application

Abstract

The invention provides a hydrotalcite-like nano super-hydrophilic coating grown on the surface of a stainless steel mesh in situ, a method and application. The method comprises the following steps: (1) carrying out pretreatment and roughening treatment on a stainless steel mesh to obtain a roughened mesh; and (2) dipping the coarsened net obtained in the step (1) in an in-situ growth solution for hydrothermal reaction, and after drying treatment, performing in-situ growth on the surface of the stainless steel net to obtain the hydrotalcite-like nano super-hydrophilic coating. The hydrotalcite-like nano super-hydrophilic coating disclosed by the invention has excellent super-hydrophilicity and capillary reflux capability, and has good salt spray corrosion resistance; the stainless steel mesh containing the coating can be applied to a capillary structure component of a VC (Vapor Chambber) vapor chamber system, the liquid guide speed, the water adsorptivity and the overall heat conduction efficiency can be remarkably improved by constructing the nano-structure coating with efficient capillary force and durable super-hydrophilicity, and the stainless steel mesh is suitable for heat dissipation modules of high-performance electronic devices, servers and wearable devices.

Description

Technical Field

[0001] This invention belongs to the field of surface treatment technology, and relates to a hydrotalcite-like nano-superhydrophilic coating, method and application grown in situ on the surface of stainless steel mesh. Specifically, it relates to a method for surface modification of stainless steel mesh suitable for the capillary structure of VC (Vapor Chamber) and its application in heat dissipation devices. Background Technology

[0002] As electronic devices develop towards higher integration and higher power density, heat dissipation performance has become a core bottleneck restricting the improvement of device performance and long-term reliability. VC (Vapor Chamber) heat sinks, as efficient phase change heat dissipation elements, drive the working fluid (such as pure water, ethanol, etc.) to complete the evaporation-condensation cycle through internal capillary structures, achieving rapid heat conduction and uniform diffusion. Their heat dissipation efficiency directly depends on the wettability, capillary lifting capacity, and long-term stability of the capillary structure.

[0003] Stainless steel mesh has become one of the most commonly used capillary structure elements in VC heat exchange plates due to its excellent mechanical strength, controllable porosity, and cost advantages. To meet the requirements of rapid spreading and circulation of working fluid, the wettability of stainless steel mesh needs to be optimized through surface treatment. The existing mainstream treatment technologies mainly include the following categories: (1) Mechanical roughening treatment: physical methods such as sandblasting and electric brushing are used to increase the surface roughness of stainless steel mesh, improve the contact area between capillary structure and working fluid, and thus enhance wettability; (2) High temperature film treatment: the typical process is to carry out oxidation treatment in an atmospheric atmosphere at 300~400°C, and impart a certain hydrophilicity to the metal mesh by forming a surface oxide film. This method is widely used in the industry but has inherent limitations; (3) Surface microstructure design: laser etching, chemical etching and other technologies are used to construct micro-nano texture structures on the surface of stainless steel mesh to achieve super-hydrophilic properties, and the short-term wettability improvement effect is significant; (4) Coating modification technology: some research and patents (such as US20150226493A1) disclose the enhancement of wettability by coating with hydrophilic oxide films (such as TiO2, SiO2) or by using atomic layer deposition (ALD). The relevant technical results have been published in MDPI Energies It has been reported in publications such as 2020 and Sci. Direct 2022.

[0004] However, the existing processing technologies still have many unresolved technical defects, which seriously restrict the performance improvement and industrial application of VC heat exchangers. Regarding high-temperature film formation: this process requires maintaining a high-temperature environment of 300~400°C for a long time, which is not only energy-intensive and has a long production cycle, but also results in limited improvement in the hydrophilicity of the formed oxide film; more importantly, the film structure is prone to aging during storage or use, leading to a gradual decline in wettability and affecting the long-term heat dissipation stability of the VC heat exchanger. Regarding coating modification technology: the interfacial bonding force between TiO2, SiO2, and other coating layers and the stainless steel mesh substrate is insufficient, easily leading to uneven film thickness and peeling; at the same time, the hydrophilicity and corrosion resistance of the coating are difficult to maintain in the long term, and it is prone to failure under working fluid cyclic scouring or complex service environments, resulting in the loss of capillary structure function. Regarding surface microstructure design: although the superhydrophilic texture structure formed by laser etching can achieve high wettability in the short term, it lacks long-term chemical stability, and the surface microstructure is easily contaminated by impurities in the working fluid or destroyed by corrosive media, failing to meet the long-term service requirements of VC heat exchangers.

[0005] In summary, existing capillary processing technologies for stainless steel mesh cannot simultaneously meet the core requirements of "in-situ growth on the substrate surface, superhydrophilicity, high stability, and controllable nanostructure." The industry urgently needs a new surface treatment technology that can overcome the above-mentioned defects in order to further improve the heat dissipation efficiency, long-term reliability, and industrial competitiveness of VC heat exchangers. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method, application, and in-situ growth of a hydrotalcite-like nano-superhydrophilic coating on the surface of stainless steel mesh. The hydrotalcite-like nano-superhydrophilic coating of this invention is used in VC heat exchanger systems, particularly in their capillary structural components. By constructing a nano-structured hydrotalcite-like coating with high capillary force and durable superhydrophilicity on the stainless steel surface, it significantly improves liquid conduction speed, water adsorption, and overall thermal conductivity, making it suitable for heat dissipation modules in high-performance electronic devices, servers, or wearable devices.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a hydrotalcite-like nano-superhydrophilic coating, the method comprising the following steps:

[0009] (1) Pre-treatment and roughening treatment of stainless steel mesh to obtain roughened mesh;

[0010] (2) The roughened mesh obtained in step (1) is immersed in the in-situ growth solution for hydrothermal reaction. After drying, the hydrotalcite-like nano-superhydrophilic coating is grown in situ on the surface of the stainless steel mesh.

[0011] This invention achieves the deposition of a hydrotalcite-like nano-superhydrophilic coating on the surface of a stainless steel mesh through sequential roughening and hydrothermal treatment (co-precipitation in-situ growth), which significantly improves the liquid conduction speed, water adsorption and overall thermal conductivity.

[0012] In addition, the hydrotalcite-like nano-superhydrophilic coating has a villous nanostructure, and its measured water droplet angle is <5°. It can quickly adsorb water droplets within 2 seconds, exhibiting high capillary efficiency and corrosion resistance.

[0013] As a preferred technical solution of the present invention, the wire diameter of the stainless steel mesh in step (1) is 10~40μm, for example, it can be 10μm, 20μm, 30μm or 40μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0014] Preferably, the pretreatment in step (1) includes sequential ultrasonic treatment with acetone, ultrasonic treatment with ethanol, and ultrasonic treatment with water.

[0015] Preferably, the roughening treatment in step (1) includes any one of sandblasting, chemical etching, electrochemical etching, chemical etching or laser etching, with chemical etching being the preferred method.

[0016] The etching solution used in the chemical etching process includes a mixture of nitric acid and hydrochloric acid, or a mixture of ferric chloride, copper chloride, sulfuric acid and hydrofluoric acid.

[0017] It is worth noting that the present invention does not limit the method of roughening treatment, or the composition or process parameters of the etching solution used in the chemical / electrochemical etching treatment, as long as the roughening of the stainless steel mesh can be achieved.

[0018] As a preferred technical solution of the present invention, the roughness SQ of the roughened mesh in step (1) is 2~3μm, for example, it can be 2μm, 2.2μm, 2.4μm, 2.6μm, 2.8μm or 3μm, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] In this invention, the roughness of the roughening mesh affects the bonding force between the in-situ deposited hydrotalcite-like coating and the substrate, as well as the performance of the hydrotalcite-like coating. If the roughness SQ of the roughening mesh is too high, the surface grooves will be too deep and sharp, which will easily lead to excessive local corrosion and stress concentration during the hydrothermal reaction, resulting in reduced film adhesion or even local peeling. If the roughness SQ is too low, the surface specific surface area will be insufficient and the number of nucleation sites will be reduced, resulting in discontinuous and incomplete coverage of the obtained hydrotalcite-like coating, which will significantly reduce hydrophilicity and capillary recovery rate.

[0020] As a preferred technical solution of the present invention, the in-situ growth solution in step (2) includes an alkaline solution, an oxidant, an aluminum salt and a metal ion donor.

[0021] Preferably, the total metal ion concentration in the in-situ growth solution is 0.05~1 mol / L, for example, it can be 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L or 1 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, the pH value of the in-situ growth solution is 10 to 14, for example, it can be 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5 or 14, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 12 to 14.

[0023] As a preferred embodiment of the present invention, the oxidant includes sodium hypochlorite and / or sodium persulfate.

[0024] Preferably, the alkaline solution comprises a sodium hydroxide solution.

[0025] Preferably, the metal ion donor comprises a nickel salt or a magnesium salt; the nickel salt is Ni(NO3)2·6H2O; and the magnesium salt is Mg(NO3)2·6H2O.

[0026] Preferably, the concentration of the alkaline solution in the in-situ growth solution is 1.5~2.5 mol / L, for example, it can be 1.5 mol / L, 1.7 mol / L, 1.9 mol / L, 2.1 mol / L, 2.3 mol / L or 2.5 mol / L, but is not limited to the listed values. Other values ​​within the range that are not listed are also applicable.

[0027] Preferably, the concentration of the oxidant in the in-situ growth solution is 0.015~0.03 mol / L, for example, it can be 0.015 mol / L, 0.018 mol / L, 0.021 mol / L, 0.024 mol / L, 0.027 mol / L or 0.03 mol / L, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] Preferably, the concentration of aluminum salt in the in-situ growth solution is 0.02~0.03 mol / L, for example, it can be 0.02 mol / L, 0.022 mol / L, 0.024 mol / L, 0.026 mol / L, 0.028 mol / L or 0.03 mol / L, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, the aluminum salt is Al(NO3)3·9H2O.

[0030] Preferably, the concentration of the metal ion donor in the in-situ growth solution is 0.04~0.06 mol / L, for example, it can be 0.04 mol / L, 0.044 mol / L, 0.048 mol / L, 0.052 mol / L, 0.056 mol / L or 0.06 mol / L, but is not limited to the listed values. Other values ​​within the range that are not listed are also applicable.

[0031] It is worth mentioning that the hydrotalcite-like nano-superhydrophilic coating on the surface of the stainless steel mesh of the present invention has a hydrotalcite-like nano-thin sheet precipitate in situ on the surface of the metal substrate, with divalent metal hydroxide as the main body and some divalent metal ions being replaced by trivalent metal ions.

[0032] As a preferred technical solution of the present invention, the temperature of the hydrothermal reaction in step (2) is 50~110℃, for example, it can be 50℃, 60℃, 70℃, 80℃, 90℃, 100℃ or 110℃, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] Preferably, the hydrothermal reaction time in step (2) is 20 to 60 minutes, for example, it can be 20 minutes, 30 minutes, 40 minutes, 50 minutes or 60 minutes, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] It is worth noting that the temperature and time of the hydrothermal reaction described in this invention have a significant impact on the nucleation, growth, and film density of the hydrotalcite-like nanosheets: by optimizing the appropriate hydrothermal reaction temperature and time, it is possible to ensure sufficient film formation and good adhesion while avoiding excessive corrosion of the stainless steel substrate; if the hydrothermal reaction temperature is too high, it will lead to excessive growth of the hydrotalcite-like grains, agglomeration of the sheets, blockage of local pores, and exacerbation of substrate corrosion, resulting in decreased capillary channel connectivity; if the temperature is too low, it will lead to insufficient nucleation rate, excessively thin and discontinuous film, and a significant decrease in superhydrophilicity and capillary recovery rate.

[0035] Preferably, the drying temperature in step (2) is 60~150℃, for example, it can be 60℃, 80℃, 100℃, 120℃, 140℃ or 150℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the drying process further includes a water washing process to remove unreacted substances and attached salts.

[0037] As a preferred embodiment of the present invention, the method for in-situ growth of a hydrotalcite-like nano-superhydrophilic coating on the surface of a stainless steel mesh, provided by the first aspect of the present invention, includes the following steps:

[0038] (1) Pre-treatment and roughening treatment of stainless steel mesh with wire diameter of 10~40μm are carried out to obtain roughened mesh with roughness SQ of 2~3μm;

[0039] The pretreatment includes sequential ultrasonic treatment with acetone, ultrasonic treatment with ethanol, and ultrasonic treatment with water.

[0040] The roughening treatment includes any one of sandblasting, chemical etching, electrochemical etching, or laser etching.

[0041] (2) The roughened mesh obtained in step (1) is immersed in the in-situ growth solution for hydrothermal reaction, and after drying, a hydrotalcite-like nano-superhydrophilic coating is grown in situ on the surface of the stainless steel mesh.

[0042] The hydrothermal reaction is carried out at a temperature of 50-110℃ for 20-60 minutes; the drying process is carried out at a temperature of 60-150℃.

[0043] The in-situ growth solution comprises sodium hydroxide solution, oxidant (sodium hypochlorite and / or sodium persulfate), aluminum salt, and metal ion donor (nickel salt or magnesium salt); the concentration of sodium hydroxide solution in the in-situ growth solution is 1.5~2.5 mol / L, the concentration of oxidant is 0.015~0.03 mol / L, the concentration of aluminum salt is 0.02~0.03 mol / L, and the concentration of metal ion donor is 0.04~0.06 mol / L.

[0044] The total metal ion concentration in the in-situ growth solution is 0.05~1 mol / L, and the pH value is 10~14.

[0045] In a second aspect, the present invention provides a stainless steel mesh having a hydrotalcite-like nano-superhydrophilic coating grown in situ on the surface of the stainless steel mesh, wherein the hydrotalcite-like nano-superhydrophilic coating is grown in situ on the surface of the stainless steel mesh using the method provided in the first aspect.

[0046] Preferably, the thickness of the hydrotalcite-like nano-superhydrophilic coating on the surface of the stainless steel mesh is 20~800nm, for example, it can be 20nm, 100nm, 200nm, 400nm, 600nm or 800nm, etc., but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] Thirdly, the present invention provides a heat spreader, the heat spreader comprising a stainless steel mesh having a hydrotalcite-like nano-superhydrophilic coating grown in situ on the surface of the stainless steel mesh as described in the second aspect.

[0048] The stainless steel mesh serves as a capillary structure component inside the heat spreader, enhancing the capillary reflux capacity and heat dissipation performance of the working fluid.

[0049] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] (1) The hydrotalcite-like nano-superhydrophilic coating on the surface of the stainless steel mesh provided by the present invention has a rough structure at the micron + nano level, which can promote capillary liquid absorption and liquid diffusion, and the capillary recovery rate can be increased by 50%;

[0052] (2) The hydrotalcite-like nano-superhydrophilic coating on the surface of the stainless steel mesh provided by the present invention has an ultra-low water droplet angle, which can quickly adsorb and shrink liquid water;

[0053] (3) The hydrotalcite-like nano-superhydrophilic coating on the surface of the stainless steel mesh provided by the present invention has good chemical stability and salt spray corrosion resistance. When used in VC heat exchange plates, it can improve the performance and life of VC heat exchange plates and effectively reduce costs. Attached Figure Description

[0054] Figure 1 This is an SEM image of the surface morphology of the roughened mesh provided in Embodiment 1 of the present invention, with a magnification of 500.

[0055] Figure 2 This is an SEM image of the surface morphology of the roughened mesh provided in Embodiment 1 of the present invention, with a magnification of 5000.

[0056] Figure 3 The SEM surface morphology image provided in Embodiment 1 of the present invention has a magnification of 100k.

[0057] Figure 4 This is a SEM side view of the superhydrophilic coating provided in Embodiment 1 of the present invention, with a magnification of 100k.

[0058] Figure 5 The image shows the SEM surface morphology of the superhydrophilic coating provided in Example 2 of this invention, with a scale bar of 10 μm. Detailed Implementation

[0059] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0060] Example 1

[0061] This embodiment provides a hydrotalcite-like nano-superhydrophilic coating on a stainless steel surface. The method for in-situ growing the hydrotalcite-like nano-superhydrophilic coating on the stainless steel surface includes the following steps:

[0062] (1) A SUS316L stainless steel mesh with a wire diameter of 20μm and a size of 10mm×80mm was pretreated and roughened to obtain a surface roughness SQ of 2.5μm. Figure 1 and Figure 2 The roughened mesh shown;

[0063] The pretreatment includes sequential 10-minute ultrasonic treatment with acetone, 10-minute ultrasonic treatment with ethanol, and 10-minute ultrasonic treatment with water to remove grease and impurities.

[0064] The roughening treatment includes: immersing the stainless steel mesh in a mixed acid solution of 3wt% HNO3 and 20wt% HCl for 30 minutes for etching to enhance surface roughness and hydrophilic sites.

[0065] (2) The roughened mesh obtained in step (1) is immersed in the in-situ growth solution and subjected to hydrothermal reaction in a stainless steel high-pressure reactor with a polytetrafluoroethylene inner liner. After washing with water, it is dried to obtain the desired result. Figure 3 and Figure 4 The stainless steel surface shown has a hydrotalcite-like nano-superhydrophilic coating.

[0066] The hydrothermal reaction was carried out at a temperature of 100°C for 60 minutes; the drying process was carried out at a temperature of 60°C for 2 hours.

[0067] The in-situ growth solution comprises sodium hydroxide solution, oxidant (sodium persulfate), aluminum salt (Al(NO3)3·9H2O), and metal ion donor (Ni(NO3)2·6H2O); the concentration of sodium hydroxide solution in the in-situ growth solution is 2 mol / L, the concentration of oxidant is 0.02 mol / L, the concentration of aluminum salt is 0.025 mol / L, and the concentration of metal ion donor is 0.05 mol / L.

[0068] according to Figure 3 and Figure 4 It can be seen that the hydrotalcite-like nano-superhydrophilic coating on the stainless steel surface provided in this embodiment has a uniform sheet-like nanostructure with an average size of about 20~300nm, and is stacked in a "petal" shape.

[0069] Example 2

[0070] This embodiment provides a hydrotalcite-like nano-superhydrophilic coating on a stainless steel surface. The method for in-situ growing the hydrotalcite-like nano-superhydrophilic coating on the stainless steel surface includes the following steps:

[0071] (1) A SUS316 stainless steel mesh with a wire diameter of 10μm and a size of 10mm×80mm was pretreated and roughened to obtain a roughened mesh with a roughness SQ of 2μm.

[0072] The pretreatment includes sequential 10 min of acetone ultrasonic treatment, 10 min of ethanol ultrasonic treatment, and 10 min of water ultrasonic treatment.

[0073] The roughening process is a laser etching process;

[0074] (2) The roughened mesh obtained in step (1) is immersed in the in-situ growth solution and subjected to hydrothermal reaction in a stainless steel high-pressure reactor with a polytetrafluoroethylene inner liner. After washing with water, it is dried to obtain the desired result. Figure 5 The stainless steel surface shown has a hydrotalcite-like nano-superhydrophilic coating.

[0075] The hydrothermal reaction was carried out at a temperature of 110°C for 40 minutes; the drying process was carried out at a temperature of 80°C for 1.5 hours.

[0076] The in-situ growth solution comprises sodium hydroxide solution, oxidant (sodium hypochlorite), aluminum salt (Al(NO3)3·9H2O), and metal ion donor (Mg(NO3)2·6H2O); the concentration of sodium hydroxide solution in the in-situ growth solution is 2.5 mol / L, the concentration of oxidant is 0.03 mol / L, the concentration of aluminum salt is 0.02 mol / L, and the concentration of metal ion donor is 0.05 mol / L.

[0077] As shown in Figure 5, the surface of the superhydrophilic stainless steel mesh provided in this embodiment has a uniform and continuous sheet-like hydrotalcite nanostructure. The layers are stacked in an interlaced manner to form a three-dimensional porous "fluffy" morphology, which is conducive to the rapid spread and reflux of liquid in the capillary structure.

[0078] Example 3

[0079] This embodiment provides a hydrotalcite-like nano-superhydrophilic coating on a stainless steel surface. The preparation method of the hydrotalcite-like nano-superhydrophilic coating grown in situ on the stainless steel surface includes the following steps:

[0080] (1) A SUS304 stainless steel mesh with a wire diameter of 40μm and a size of 10mm×80mm was pretreated and roughened to obtain a roughened mesh with a roughness SQ of 3μm.

[0081] The pretreatment includes sequential 10 min of acetone ultrasonic treatment, 10 min of ethanol ultrasonic treatment, and 10 min of water ultrasonic treatment.

[0082] The roughening treatment is sandblasting.

[0083] (2) The roughened mesh obtained in step (1) is immersed in the in-situ growth solution for hydrothermal reaction, washed with water and dried to obtain the hydrotalcite-like nano-superhydrophilic coating on the surface of the stainless steel.

[0084] The hydrothermal reaction was carried out at a temperature of 50°C for 60 minutes; the drying process was carried out at a temperature of 60°C for 2 hours.

[0085] The in-situ growth solution comprises sodium hydroxide solution, oxidant (sodium hypochlorite), aluminum salt (Al(NO3)3·9H2O), and metal ion donor (Ni(NO3)2·6H2O); the concentration of sodium hydroxide solution in the in-situ growth solution is 1.5 mol / L, the concentration of oxidant is 0.03 mol / L, the concentration of aluminum salt is 0.03 mol / L, and the concentration of metal ion donor is 0.06 mol / L.

[0086] Example 4

[0087] This embodiment provides a hydrotalcite-like nano-superhydrophilic coating on a stainless steel surface. The method for in-situ growing the hydrotalcite-like nano-superhydrophilic coating on the stainless steel surface includes the following steps:

[0088] (1) A SUS316L stainless steel mesh with a wire diameter of 30μm and a size of 10mm×80mm was pretreated and roughened to obtain a roughened mesh with a roughness SQ of 2.6μm.

[0089] The pretreatment includes sequential 10 min of acetone ultrasonic treatment, 10 min of ethanol ultrasonic treatment, and 10 min of water ultrasonic treatment.

[0090] The roughening treatment includes: immersing the stainless steel mesh in a mixed acid solution of 3wt% HNO3 and 20wt% HCl for 30 minutes for etching to enhance surface roughness and hydrophilic sites.

[0091] (2) The roughened mesh obtained in step (1) is immersed in the in-situ growth solution for hydrothermal reaction, and after drying, a hydrotalcite-like nano-superhydrophilic coating is obtained on the surface of the stainless steel.

[0092] The hydrothermal reaction was carried out at a temperature of 80°C for 50 minutes; the drying process was carried out at a temperature of 100°C for 1.5 hours.

[0093] The in-situ growth solution includes sodium hydroxide solution, oxidant (sodium persulfate), aluminum salt (Al(NO3)3·9H2O), and metal ion donor (Ni(NO3)2·6H2O); the concentration of the alkali solution in the in-situ growth solution is 1.8 mol / L, the concentration of the oxidant is 0.025 mol / L, the concentration of the aluminum salt is 0.025 mol / L, and the concentration of the metal ion donor is 0.06 mol / L.

[0094] Example 5

[0095] This embodiment provides a hydrotalcite-like nano-superhydrophilic coating on a stainless steel surface. The method for in-situ growing the hydrotalcite-like nano-superhydrophilic coating on the stainless steel surface differs from that in Embodiment 1 only in that:

[0096] In this embodiment, the roughness SQ of the roughened mesh described in step (1) is adjusted to 1.5 μm.

[0097] Example 6

[0098] This embodiment provides a hydrotalcite-like nano-superhydrophilic coating on a stainless steel surface. The method for in-situ growing the hydrotalcite-like nano-superhydrophilic coating on the stainless steel surface differs from that in Embodiment 1 only in that:

[0099] In this embodiment, the roughness SQ of the roughened mesh described in step (1) is adjusted to 3.5 μm.

[0100] Example 7

[0101] This embodiment provides a hydrotalcite-like nano-superhydrophilic coating on a stainless steel surface. The method for in-situ growing the hydrotalcite-like nano-superhydrophilic coating on the stainless steel surface differs from that in Embodiment 1 only in that:

[0102] In this embodiment, the temperature of the hydrothermal reaction in step (2) is adjusted to 40°C.

[0103] Example 8

[0104] This embodiment provides a hydrotalcite-like nano-superhydrophilic coating on a stainless steel surface. The method for in-situ growing the hydrotalcite-like nano-superhydrophilic coating on the stainless steel surface differs from that in Embodiment 1 only in that:

[0105] In this embodiment, the temperature of the hydrothermal reaction in step (2) is adjusted to 120°C.

[0106] Example 9

[0107] This embodiment provides a hydrotalcite-like nano-superhydrophilic coating on a stainless steel surface. The method for in-situ growing the hydrotalcite-like nano-superhydrophilic coating on the stainless steel surface differs from that in Embodiment 1 only in that:

[0108] In this embodiment, the concentration of aluminum salt in the in-situ growth solution described in step (2) is adjusted to 0.02 mol / L, the concentration of metal ion donor is adjusted to 0.04 mol / L, and the total metal ion concentration is 0.06 mol / L.

[0109] Example 10

[0110] This embodiment provides a hydrotalcite-like nano-superhydrophilic coating on a stainless steel surface. The method for in-situ growing the hydrotalcite-like nano-superhydrophilic coating on the stainless steel surface differs from that in Embodiment 1 only in that:

[0111] In this embodiment, the concentration of aluminum salt in the in-situ growth solution described in step (2) is adjusted to 0.035 mol / L, the concentration of metal ion donor is adjusted to 0.065 mol / L, and the total metal ion concentration is 0.1 mol / L.

[0112] Comparative Example 1

[0113] This comparative example provides a stainless steel mesh that has not undergone roughening or hydrothermal treatment.

[0114] Comparative Example 2

[0115] This comparative example provides a hydrotalcite-like nano-superhydrophilic coating on a stainless steel surface. The method for preparing the hydrotalcite-like nano-superhydrophilic coating on the stainless steel surface includes:

[0116] Stainless steel mesh is placed in an atmospheric environment and heated at 360°C for 6 hours to form an oxide film.

[0117] Comparative Example 3

[0118] This comparative example provides a hydrotalcite-like nano-superhydrophilic coating on a stainless steel surface. The method for growing the hydrotalcite-like nano-superhydrophilic coating in situ on the stainless steel surface differs from that in Example 1 only in that:

[0119] This comparative example omits the coarsening process described in step (1).

[0120] Comparative Example 4

[0121] This comparative example provides a hydrotalcite-like nano-superhydrophilic coating on a stainless steel surface. The method for growing the hydrotalcite-like nano-superhydrophilic coating in situ on the stainless steel surface differs from that in Example 1 only in that:

[0122] This comparative example first undergoes the hydrothermal treatment described in Example 1, and then undergoes roughening treatment.

[0123] Performance testing:

[0124] Contact angle, salt spray and capillary recovery rate tests were performed on the stainless steel surfaces provided in the above embodiments and comparative examples. The results are shown in Table 1.

[0125] The salt spray test includes: placing the sample in a neutral salt spray chamber, using a 5 wt% NaCl solution as the spray medium, and continuously spraying at 35±2℃ for 48 h, during which the corrosion of the sample surface is observed periodically; no obvious corrosion spots are found after 48 h of neutral salt spray, indicating good corrosion resistance;

[0126] The capillary recovery rate test includes the following steps: (a) the stainless steel mesh is firmly welded to the surface of the stainless steel cavity cover plate (the cover plate material is the same as the stainless steel mesh material) by laser spot welding to form a capillary liquid absorption assembly with an internal structure similar to that of a VC heat exchanger plate; (b) the capillary liquid absorption assembly described in step (a) is vertically suspended on the test fixture, and a metal scale is attached to one side of it to record the liquid absorption height; a 250mL beaker filled with deionized water is placed below the capillary liquid absorption assembly so that the bottom of the assembly is initially just in contact with the liquid surface; (c) timing is started and video is recorded simultaneously: after the liquid contacts the bottom of the sample, the height and speed of the liquid migrating upward in the capillary structure are observed and recorded; (d) based on the liquid surface climbing time and climbing height (20mm) in the video, the capillary rate (mm / s) can be calculated to evaluate the effect of the stainless steel mesh surface modification on the liquid adsorption and recovery capacity.

[0127] The capillary rate is equal to the climbing height divided by the climbing time; the climbing height is 20 mm.

[0128] Table 1

[0129]

[0130] According to Table 1, the following points can be observed:

[0131] (1) Comprehensive analysis of Examples 1-4 shows that the stainless steel mesh obtained by the preparation method provided by the present invention has an ultra-low water droplet contact angle (<5°) in the initial state. After 48h of neutral salt spray test, the equivalent thermal resistance change ΔRth is controlled within about 5%, indicating that the hydrotalcite-like nano-superhydrophilic coating provided by the present invention has good chemical stability and salt spray corrosion resistance. At the same time, the capillary recovery rates of Examples 1-3 are 1.93 mm / s, 3.26 mm / s and 6.60 mm / s, respectively, indicating that the stainless steel mesh of the present invention has excellent capillary recovery ability during the capillary recovery rate test, which can effectively promote capillary liquid absorption and liquid diffusion.

[0132] (2) Comprehensive analysis of Examples 1 and 5-6 shows that the roughness of the roughened mesh is one of the important factors affecting the morphology and capillary properties of the hydrotalcite-like film: excessive roughness will lead to excessively deep and sharp surface grooves, and the hydrotalcite-like film is prone to stress concentration and local peeling during hydrothermal reaction and subsequent use, thereby reducing the connectivity of capillary channels and the capillary recovery rate; excessive roughness will lead to insufficient surface specific area, reduced nucleation sites, incomplete coverage of the obtained hydrotalcite-like film, or even exposed areas, decreased hydrophilicity, and significantly reduced capillary recovery rate;

[0133] (3) A comprehensive analysis of Examples 1 and 7-10 shows that the hydrothermal reaction is one of the key factors affecting the performance of the membrane:

[0134] If the hydrothermal reaction temperature is too low, the nucleation and growth rate of hydrotalcite-like particles will be insufficient, resulting in a thin and discontinuous film that is difficult to form a complete villous nanostructure. This will increase the water droplet contact angle and reduce the capillary recovery rate. If the temperature is too high, the hydrotalcite-like particles will grow excessively, the lamellar aggregates will agglomerate, and the local capillary channels will be blocked. At the same time, the corrosion of the stainless steel substrate will be aggravated, and the film adhesion and capillary transport performance will be adversely affected. If the total metal ion concentration in the in-situ growth solution used in the hydrothermal reaction is too low, the number of nuclei will be insufficient, the deposition rate will be too slow, the film will not be dense and will have many defects, and both superhydrophilicity and capillary recovery rate will be insufficient. If the total metal ion concentration is too high, the nucleation will be too fast, the particles will agglomerate severely, forming blocky or dense deposits, and some capillary channels will be blocked, thereby increasing the liquid transport resistance and actually reducing the capillary recovery rate.

[0135] (4) Comprehensive analysis of Example 1 and Comparative Example 1 shows that the untreated stainless steel mesh shows that the liquid can hardly rise along the capillary structure during the capillary recovery rate test, the adsorption rate is extremely low, and there is no obvious liquid level rise within the specified capillary climbing time, which shows extremely poor capillary adsorption capacity. The corresponding capillary recovery rate is about 0 mm / s, and the water droplet contact angle is about 84.7°, which is difficult to meet the requirements of VC heat exchange plate for capillary reflux.

[0136] A comprehensive analysis of Example 1 and Comparative Example 2 shows that the initial water droplet contact angle of the sample after high-temperature film oxidation treatment commonly used in the prior art can also be controlled to be less than 5°, and the capillary recovery rate is about 4.35 mm / s, which is significantly better than the untreated sample. However, after 48 hours of neutral salt spray test, the change in equivalent thermal resistance ΔRth is about 10%, which is greater than the range of less than 5% controlled by the embodiment of the present invention. Moreover, the oxide film is prone to aging, deactivation and local corrosion in air storage and salt spray environment. Its long-term stability and thermal performance retention are not as good as the hydrotalcite-like coating described in the present invention.

[0137] A comprehensive analysis of Example 1 and Comparative Example 3 shows that omitting the roughening treatment will result in insufficient surface roughness of the stainless steel mesh, fewer nucleation sites for hydrotalcite-like materials, uneven film coverage or even local exposure, significantly reduced hydrophilicity and capillary recovery rate, and difficulty in obtaining a stable superhydrophilic capillary structure.

[0138] A comprehensive analysis of Example 1 and Comparative Example 4 shows that if the order of roughening and hydrothermal treatment is reversed, i.e., hydrothermal deposition of hydrotalcite-like material is performed first and then roughening etching is performed, the generated hydrotalcite-like film layer will be severely etched and damaged during the roughening process, resulting in a large number of gaps and detachment areas, which will cause discontinuity of capillary channels and significant deterioration of capillary recovery performance.

[0139] In summary, the stainless steel mesh described in this invention is used in VC heat exchanger systems, particularly as an internal capillary structure component. By constructing a nanostructured hydrotalcite-like coating with high-efficiency capillary force and durable superhydrophilicity on the stainless steel surface, the liquid conduction speed, water adsorption, and overall heat conduction efficiency can be significantly improved. It is suitable for heat dissipation modules of high-performance electronic devices, servers, or wearable devices.

[0140] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for in-situ growing a hydrotalcite-like nano-superhydrophilic coating on the surface of a stainless steel mesh, characterized in that, The method includes the following steps: (1) Pre-treatment and roughening treatment of stainless steel mesh to obtain roughened mesh; (2) The roughened mesh obtained in step (1) is immersed in the in-situ growth solution for hydrothermal reaction. After drying, a hydrotalcite-like nano-superhydrophilic coating is grown in situ on the surface of the stainless steel mesh.

2. The method according to claim 1, characterized in that, The wire diameter of the stainless steel mesh in step (1) is 10~40μm; Preferably, the pretreatment includes sequential ultrasonic treatment with acetone, ultrasonic treatment with ethanol, and ultrasonic treatment with water; Preferably, the roughening treatment includes one or more of sandblasting, chemical etching, electrochemical etching, or laser etching, with chemical or electrochemical etching being the most preferred.

3. The method according to claim 1 or 2, characterized in that, The roughness Sq value of the roughened mesh in step (1) is 2~3μm.

4. The method according to any one of claims 1-3, characterized in that, The in-situ growth solution in step (2) includes an alkaline solution, an oxidant, an aluminum salt, and a metal ion donor; Preferably, the total metal ion concentration in the in-situ growth solution is 0.05~1 mol / L; Preferably, the pH value of the in-situ growth solution is 10-14.

5. The method according to claim 4, characterized in that, The oxidant includes sodium hypochlorite and / or persulfate; Preferably, the alkaline solution comprises a sodium hydroxide or potassium hydroxide solution; Preferably, the metal ion donor comprises a nickel salt or a magnesium salt and may further comprise a copper salt, a zinc salt, or a cobalt salt; Preferably, the concentration of the alkaline solution in the in-situ growth solution is 1.5~2.5 mol / L; Preferably, the concentration of the oxidant in the in-situ growth solution is 0.015~0.03 mol / L; Preferably, the concentration of aluminum salt in the in-situ growth solution is 0.02~0.03 mol / L; Preferably, the concentration of metal ion donor in the in-situ growth solution is 0.07~0.09 mol / L.

6. The method according to any one of claims 1-5, characterized in that, The temperature of the hydrothermal reaction in step (2) is 50~110℃; Preferably, the temperature of the hydrothermal reaction in step (2) is 60~100℃ and the time is 20~60min.

7. The method according to any one of claims 1-6, characterized in that, The drying temperature in step (2) is 60~150℃.

8. A stainless steel mesh with an in-situ grown hydrotalcite-like nano-superhydrophilic coating on its surface, characterized in that, The hydrotalcite-like nano-superhydrophilic coating is obtained by in-situ growth on the surface of a stainless steel mesh using the method described in any one of claims 1-7.

9. The stainless steel mesh according to claim 8, characterized in that, The thickness of the hydrotalcite-like nano-superhydrophilic coating is 20~800nm.

10. A heat spreader, characterized in that, The heat spreader includes a stainless steel mesh as described in claim 8 or 9, which has a hydrotalcite-like nano-superhydrophilic coating grown in situ on the surface of the stainless steel mesh. The stainless steel mesh serves as a capillary structure component inside the heat spreader, enhancing the capillary reflux capacity and heat dissipation performance of the working fluid.

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