CN112657805B - A kind of nanowire-fluorocarbon composite coating and preparation method thereof - Google Patents

Abstract

The invention provides a nanowire-fluorocarbon composite coating and a preparation method thereof. According to the method, the directionally-arranged high-thermal-conductivity nanowire network is introduced into the traditional fluorocarbon coating so as to prepare the nanowire-fluorocarbon composite coating. The composite coating prepared by the invention can obviously improve the effective heat-conducting property of the fluorocarbon coating, and the maximum effective heat-conducting property can reach more than 150 times, meanwhile, the bonding strength of the coating and the substrate can reach 0 grade, the surface contact angle is increased to 152 degrees, the problems of poor heat-conducting property, short service life, easy dust deposition and the like of the coating of the traditional heat exchanger can be effectively solved, and the composite coating can be used in industrial processes of power generation, petrochemical industry, seawater desalination and the like.

Description

A kind of nanowire-fluorocarbon composite coating and preparation method thereof

technical field

The invention relates to the technical field of functional material surface and heat transfer enhancement, in particular, to a nanowire-fluorocarbon composite coating and a preparation method thereof. In particular: the use of high thermal conductivity materials to modify fluorocarbon coatings to prepare composite coatings can improve the effective thermal conductivity and hydrophobic properties of the coating and the bonding force with the substrate, thereby improving the heat transfer performance and anti-pilling of the heat exchanger. Ash performance.

Background technique

At present, heat exchangers are essential equipment in many fields such as petrochemical industry, power generation, refrigeration and so on. However, in the application process, the condensation mode of most equipment is film condensation, and the formed thick liquid film greatly affects the heat transfer performance. In addition, due to the long-term operation of the heat exchanger, dirt, dust and other pollutants will adhere to the surface, which further affects the performance of the heat exchanger. In order to effectively improve the safety and economy of the equipment, modifying the heat exchange surface and reducing its surface energy to achieve long-term stable droplet condensation is the key to improving the heat transfer performance of the heat exchanger and preventing fouling.

At present, the most commonly used coatings on the surface of heat exchangers are epoxy resin coatings and fluorocarbon coatings. Among them, Teflon PFA fluorocarbon coatings (PFA for short) have excellent chemical inertness, thermal stability, good Anti-fouling properties, has been widely used in anti-corrosion, anti-stick lubrication treatment and so on. Due to the low surface energy of the PFA coating, the intrinsic contact angle can reach more than 110°, and stable droplet condensation can be achieved. However, since PFA is an organic polymer material, its thermal conductivity is lower than that of metals with good thermal conductivity, only 0.2 to 0.3 W/m·K; and in order to achieve long-term and stable droplet condensation, the coating used Generally thicker, resulting in greater additional thermal resistance.

Usually, the current research mostly adopts the blending method to add high thermal conductivity fillers in fluorocarbon coatings to improve the thermal conductivity of the coatings, such as metal particles, graphene, etc. Patent CN 200510047351.9 discloses a method for improving the thermal conductivity of fluorocarbon coating by utilizing iron, copper and other nanoparticles, and the effective thermal conductivity of the coating can be increased to 0.3-1.5W/m·K. When the blending method is used, the nanoparticles are randomly dispersed in the coating and cannot be arranged along the heat flow direction to form an effective heat transfer channel. Moreover, when the filler content increases to a certain value, it will greatly affect the curing film-forming properties of the coating, resulting in a reduction in the bonding force from grade 0 to grade 1 to 2; and the added high surface energy particles will reduce the hydrophobicity of the fluorocarbon coating. It is not conducive to the occurrence of dropwise condensation. Therefore, in order to more effectively improve the thermal conductivity of the coating, it is necessary to develop a method of directionally arranging the thermally conductive network and closely combining the thermally conductive network with the substrate.

SUMMARY OF THE INVENTION

According to the above-mentioned existing technologies for enhancing the thermal conductivity of coatings, most of them use the blending method, but the filler particles are randomly dispersed in the coating, and cannot be arranged along the direction of heat flow to form an effective heat transfer channel, and there is no Combined with the substrate, it greatly affects the bonding force between the composite coating and the substrate; when the filler content increases to a certain value, it will greatly affect the cured film-forming properties of the coating, resulting in a reduction of the bonding force from 0 to 1 to 2; and the added The high surface energy particles can reduce the hydrophobicity of the fluorocarbon coating, which is not conducive to the technical problem of droplet condensation, and provides a nanowire-fluorocarbon composite coating and a preparation method thereof. The present invention mainly constructs nanowire-fluorocarbon composite coating by prefabricating the directionally-arranged nanowires as a thermally conductive network on a substrate, and through the film-forming process of the fluorocarbon coating, and the nanocomposite coating can significantly improve the Improve the heat exchange performance of the heat exchanger and slow down the fouling of the heat exchanger, which can be used in industrial systems such as flue gas waste heat recovery, power generation, seawater desalination and thermal management of electronic devices.

The technical means adopted in the present invention are as follows:

A nanowire-fluorocarbon composite coating, the nanowire-fluorocarbon composite coating is a composite structure composed of a nanowire array and a fluorocarbon coating, and the fluorocarbon coating is directly sprayed on the surface of the nanowire array;

The nanowire array is a directionally arranged high thermal conductivity nanowire network, and the height of the nanowire array is 5-30 μm;

The thickness of the fluorocarbon coating is 5-50 μm.

Further, the nanowires are copper nanowires, silver nanowires, iron nanowires or nickel nanowires.

Further, the fluorocarbon coating is formed by spraying a fluorocarbon coating, and the fluorocarbon coating is Teflon-PFA, PTFE coating or FEVE coating.

The invention also provides a method for preparing a nanowire-fluorocarbon composite coating. By controlling the structure and morphology of the nanowire and the forming process of the fluorocarbon coating, a connected nanowire network is formed in the fluorocarbon coating; the height of the nanowire is The thickness of the sprayed fluorocarbon coating is 5-50 μm;

The method includes the following steps:

Step 1: ultrasonically clean the polished copper substrate with acetone, ethanol and deionized water, respectively, and fix the copper substrate, porous anodized aluminum template, filter paper soaked with electroplating solution, and copper sheet connected to the counter electrode with clips in turn. A constant potential is applied between the copper substrate and the copper sheet for electroplating, so that the porous anodized aluminum template is closely connected with the copper substrate, and at the same time, a layer of short copper nanowire arrays is attached to the copper substrate;

Step 2: After that, remove the filter paper, copper sheets and clips, and immerse the connected porous anodized aluminum template and copper substrate in the electroplating solution for electroplating for 0.5-5 hours; Dissolve the template to obtain an independent copper nanowire array;

Step 3: Add N,N-dimethylacetamide solvent to the fluorocarbon coating to adjust the viscosity to 50-500mPa·s, and spray the surface of the nanowire array prepared in step 2 with air, and control the spraying pressure to be 0.1-0.6MPa , the spraying time is 5 to 50s;

Step 4: The nanowire array after spraying the fluorocarbon coating is heated with a programmed temperature under nitrogen protection. The average heating rate is 3-10°C/min. At a constant temperature of 10-50 min, and then naturally cooled under the protection of nitrogen to obtain a nanowire-fluorocarbon composite coating.

Further, the pore diameter of the porous alumina template is between 50 and 300 nm, and the pore spacing is between 100 and 500 nm.

Further, the nanowires are copper nanowires, silver nanowires, iron nanowires or nickel nanowires.

Further, the components of the electroplating solution are copper pyrophosphate, copper sulfate aqueous solution, silver nitrate solution, iron sulfate solution, nickel chloride or nickel sulfate aqueous solution, and the mass fraction is 3% to 20%.

Further, the fluorocarbon coating is Teflon-PFA, PTFE coating or FEVE coating.

Further, the solvent for adjusting the viscosity is N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone or dimethylsulfoxide.

Further, the porous alumina template dissolving agent is NaOH solution, KOH solution, HCl solution or H ₂ SO ₄ solution.

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

1. The nanowire-fluorocarbon composite coating provided by the present invention and the preparation method thereof, the nanowires grow on the substrate, are closely combined with the substrate, and are arranged in a direction, which greatly improves the effective thermal conductivity of the fluorocarbon coating. Compared with the prior art, the bonding force between the composite coating and the substrate prepared by the present invention can reach grade 0. Compared with the pure PFA surface, the nanowire agglomerates form a large number of convex structures, and the contact angle is increased from 118° of pure PFA to 152° of the composite coating, reaching a super-hydrophobic state, which can effectively prevent dust and dirt during the application process. The accumulation of heat exchangers can effectively solve the problems of poor thermal conductivity and short service life of traditional heat exchanger coatings. Due to the high thermal conductivity of copper, the thermal conductivity of the composite coating can reach 39W/m·K, which is 150 times that of the pure PFA coating.

2. The nanowire-fluorocarbon composite coating and the preparation method thereof provided by the present invention can effectively control the wettability of the composite coating by controlling the height of the nanowires and regulating the deposition morphology of the fluorocarbon coating. When the fluorocarbon coating is completely covered on the connected nanowires, the wetting angle of the composite coating is 118°, and the composite surface is generally hydrophobic; however, by adjusting the deposition morphology of the fluorocarbon coating, it is only filled on the nanowires In the groove, a large number of protruding structures of nanowire agglomerates are exposed, and the contact angle of the composite coating can reach 152° at this time, making the surface superhydrophobic.

To sum up, most of the existing technologies for enhancing the thermal conductivity of coatings by applying the technical solutions of the present invention use the blending method, but the filler particles are randomly dispersed in the coating and cannot be arranged along the direction of heat flow to form an effective thermal conductivity. The heat transfer channel of the coating is not combined with the substrate, which greatly affects the bonding force between the composite coating and the substrate; when the filler content increases to a certain value, it will greatly affect the curing and film-forming properties of the coating, resulting in a decrease in the bonding force from grade 0 to grade 1. ~ Grade 2; and the added high surface energy particles will reduce the hydrophobicity of the fluorocarbon coating, which is not conducive to the problem of droplet condensation.

Based on the above reasons, the present invention can be widely promoted in industrial process fields such as power generation, petrochemical industry, seawater desalination and the like.

Description of drawings

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can also be obtained from these drawings without any creative effort.

FIG. 1 is a process flow diagram of the present invention for preparing the metal nanowire-PFA composite coating.

2 is a schematic diagram of a 3# nanowire-PFA composite coating prepared by utilizing the surface of 1# nanowire in Example 2 of the present invention, wherein (a) is a schematic diagram of the surface of 1# nanowire, and (b) is a 1# nanowire Schematic diagram of the 3# nanowire-PFA composite coating prepared by spraying PFA on the surface, (c) is the enlarged view of A in (b).

3 is a schematic diagram of a 4# nanowire-PFA composite coating prepared by utilizing the surface of 2# nanowires in Example 4 of the present invention, wherein (a) is a schematic diagram of the surface of 2# nanowires, and (b) is the surface of 2# nanowires Schematic diagram of the 4# nanowire-PFA composite coating prepared by spraying PFA, (c) is the enlarged view of B in (b), (d) is the enlarged view of (c), (e) is the middle of (d) Enlarged image at C.

Figure 4 is a schematic diagram of the contact angle of different surfaces of the present invention, wherein (a) is a schematic diagram of the contact angle of the pure PFA surface, (b) is a schematic diagram of the contact angle of the 4# composite coating, (c) is the contact angle of the 3# composite coating Corner diagram.

Fig. 5 is the electron microscope picture after the coating adhesion test of the present invention, wherein (a) is the result of the 2# nanowire surface adhesion test, (b) is the enlarged view of D in (a), (c) is 4# nanowire-PFA composite coating adhesion test results, (d) is the enlarged view of E in (c).

Detailed ways

It should be noted that the embodiments of the present invention and the features of the embodiments may be combined with each other under the condition of no conflict. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments It is only a part of the embodiments of the present invention, but not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components and/or combinations thereof.

The relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the invention unless specifically stated otherwise. Meanwhile, it should be understood that, for convenience of description, the dimensions of various parts shown in the accompanying drawings are not drawn in an actual proportional relationship. Techniques, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the authorized specification. In all examples shown and discussed herein, any specific values should be construed as illustrative only and not limiting. Accordingly, other examples of exemplary embodiments may have different values. It should be noted that like numerals and letters refer to like items in the following figures, so once an item is defined in one figure, it does not require further discussion in subsequent figures.

As shown in the figure, the present invention provides a nanowire-fluorocarbon composite coating, the nanowire-fluorocarbon composite coating is a composite structure composed of a nanowire array and a fluorocarbon coating, and the fluorocarbon coating directly sprayed on the surface of the nanowire array.

The nanowire array is a directionally arranged high thermal conductivity nanowire network, and the height of the nanowire array is 5-30 μm.

The thickness of the fluorocarbon coating is 5-50 μm.

Preferably, the nanowires are copper nanowires, silver nanowires, iron nanowires or nickel nanowires.

Preferably, the fluorocarbon coating is formed by spraying a fluorocarbon coating, and the fluorocarbon coating is Teflon-PFA, PTFE coating or FEVE coating.

The invention also provides a method for preparing a nanowire-fluorocarbon composite coating. By controlling the structure and morphology of the nanowire and the forming process of the fluorocarbon coating, a connected nanowire network is formed in the fluorocarbon coating; the height of the nanowire is The thickness of the sprayed fluorocarbon coating is 5-50 μm;

The method includes the following steps:

Step 1: ultrasonically clean the polished copper substrate with acetone, ethanol and deionized water, respectively, and fix the copper substrate, porous anodized aluminum template, filter paper soaked with electroplating solution, and copper sheet connected to the counter electrode with clips in turn. A constant potential is applied between the copper substrate and the copper sheet for electroplating, so that the porous anodized aluminum template is closely connected with the copper substrate, and at the same time, a layer of short copper nanowire arrays is attached to the copper substrate;

Step 2: After that, remove the filter paper, copper sheets and clips, and immerse the connected porous anodized aluminum template and copper substrate in the electroplating solution for electroplating for 0.5-5 hours; Dissolve the template to obtain an independent copper nanowire array;

Step 3: Add N,N-dimethylacetamide solvent to the fluorocarbon coating to adjust the viscosity to 50-500mPa·s, and spray the surface of the nanowire array prepared in step 2 with air, and control the spraying pressure to be 0.1-0.6MPa , the spraying time is 5 to 50s;

Step 4: The nanowire array after spraying the fluorocarbon coating is heated with a programmed temperature under nitrogen protection. The average heating rate is 3-10°C/min. At a constant temperature of 10-50 min, and then naturally cooled under the protection of nitrogen to obtain a nanowire-fluorocarbon composite coating.

Preferably, the pore size of the used porous alumina template is between 50 and 300 nm, and the pore spacing is between 100 and 500 nm.

Preferably, the nanowires used include but are not limited to copper nanowires, silver nanowires, iron nanowires or nickel nanowires.

Preferably, the components of the electroplating solution used include but are not limited to copper pyrophosphate, copper sulfate aqueous solution, silver nitrate solution, ferric sulfate solution, nickel chloride or nickel sulfate aqueous solution, etc., and the mass fraction is 3% to 20%.

Preferably, the fluorocarbon coating used includes, but is not limited to, Teflon-PFA, PTFE coating or FEVE coating.

Preferably, the viscosity-adjusting solvent includes, but is not limited to, N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, dimethylsulfoxide, and the like.

Preferably, the used porous alumina template dissolving agent includes but is not limited to NaOH solution, KOH solution, HCl solution or H ₂ SO ₄ solution and the like.

Figure 1 shows the process flow diagram of preparing the metal nanowire-PFA composite coating. It is predicted that the thickness of PFA coating will gradually increase with the increase of spraying time. When the spraying thickness is thick, the PFA completely covers the nanowire structure, and the contact angle of the composite coating can be regarded as the contact angle of the PFA surface.

Example 1

The technical scheme of the present invention is as follows: first, use electrochemical deposition to grow copper nanowires with a certain height on the surface of the metal substrate, then adjust the viscosity of the paint, and use an appropriate spraying process to form a film in the nanowire voids, so as to achieve stable long-term dripping. It solves the problem of poor heat transfer performance while condensing in the form of a condensate. The specific process flow is as follows:

1. Substrate pretreatment: Use 800# and 3000# sandpaper to polish the copper substrate (copper substrate) in turn, and polish the surface of the copper substrate. The polished substrate (copper substrate) was ultrasonically cleaned with acetone and ethanol, respectively, and then rinsed with deionized water.

2. Electroplating of nanowires: The copper substrate, porous alumina (PAA) template, filter paper and copper sheet connected to the counter electrode are placed in order and fixed with clips, and the edge of the filter paper is immersed in the electroplating solution to ensure that the solution can pass through capillary action completely Absorbed by filter paper and evenly distributed in the PAA template. A constant potential was applied between the copper substrate and the copper sheet to electroplate the nanowires. After a certain period of time, a layer of short copper nanowire arrays was attached to the copper substrate, and the porous alumina template was tightly connected with the copper substrate. After that, the filter paper, copper sheets and clips were removed, and then the connected porous alumina template and copper substrate were immersed in copper pyrophosphate electroplating solution for electroplating. Nanowires of different lengths were obtained using a three-electrode system because it allows for more precise control of the potential. A copper substrate with a template was used as the working electrode, a copper sheet without a template was used for the counter electrode, and an Ag/AgCl electrode was selected as the reference electrode. The plating time and the voltage applied between the working and auxiliary electrodes were adjusted to the corresponding values to achieve the desired nanowire length.

3. Removing the template: After depositing the copper nanowire array, the PAA template was removed by wet etching in a 2 mol/L NaOH solution to obtain an independent copper nanowire array. The copper blocks were then rinsed in deionized water and dried in a vacuum chamber.

4. Spraying fluorocarbon paint: before spraying, add N,N-dimethylacetamide solvent to the fluorocarbon paint to adjust the viscosity of the fluorocarbon paint to 100mPa·s and stir for 24h for standby, and then carry out the coating under the air pressure of 0.1～0.6MPa For spraying, control the distance between the nozzle of the spray gun and the surface of the substrate to be 20cm; Teflon PFA is selected for the fluorocarbon coating.

5. Obtain the nanowire-fluorocarbon composite coating: in a nitrogen atmosphere, control the average heating rate at 3-10°C/min in the sintering and curing stage, keep the temperature constant for 20-70min when the temperature is raised to 120°C, and finally keep the constant temperature at 250-450°C 10-50min, then slowly cooled to room temperature under nitrogen protection; at 120 ℃, filled with an appropriate amount of nitrogen to ensure stable airflow; after the coating was cured, filled with nitrogen, and allowed the coating to cool naturally under the protection of nitrogen.

In the existing technology for enhancing the thermal conductivity of the coating, such as the blending method, the filler particles are randomly dispersed and distributed in the coating, and are not combined with the substrate, which greatly affects the bonding force between the composite coating and the substrate. In the present invention, the nanowires It grows on the substrate, is closely combined with the substrate, and is directionally arranged, which greatly improves the effective thermal conductivity of the fluorocarbon coating. Compared with the prior art, the bonding force between the composite coating and the substrate prepared by the present invention can reach grade 0. Compared with the pure PFA surface, the nanowire agglomerates form a large number of convex structures, and the contact angle is increased from 118° of pure PFA to 152° of the composite coating, reaching a super-hydrophobic state, which can effectively prevent dust and dirt during the application process. accumulation. Due to the high thermal conductivity of copper, the thermal conductivity of the composite coating can reach 39W/m K, which is 150 times that of the pure PFA coating.

By controlling the height of the nanowires and regulating the deposition morphology of the fluorocarbon coating, the wettability of the composite coating can be effectively regulated. When the fluorocarbon coating is completely covered on the connected nanowires, the wetting angle of the composite coating is 118°, and the composite surface is generally hydrophobic; however, by adjusting the deposition morphology of the fluorocarbon coating, it is only filled on the nanowires In the groove, a large number of protruding structures of nanowire agglomerates are exposed, and the contact angle of the composite coating can reach 152° at this time, making the surface superhydrophobic.

Example 2

The 1# nanowire surface was constructed, and PFA was sprayed to prepare the 3# nanowire-PFA composite coating. The preparation steps were as follows: the copper substrate was polished with 800# and 3000# sandpapers in turn, and the surface of the substrate was well polished. The ground substrates were ultrasonically cleaned with acetone and ethanol, respectively, and then rinsed with deionized water. The porous alumina (PAA) template (model 450-200), the counter electrode of the filter paper and copper sheet are placed in order and fixed with clips, and the edge of the filter paper is immersed in the plating solution to ensure that the solution can be completely absorbed by the filter paper by capillary action , and evenly distributed in the PAA template. A constant potential was applied between the copper substrate and the counter electrode to electroplate the nanowires. After electroplating for 1100 s, a layer of short copper nanowire arrays was attached to the copper substrate. After that, the filter paper, copper sheets, and clips were removed, and the rest were immersed in a copper pyrophosphate plating solution for electroplating. The electroplating time is 0.5-5h. After depositing the copper nanowire arrays, the template was removed by wet etching in 2 mol/L NaOH solution to obtain freestanding copper nanowire arrays. The copper blocks were then rinsed in deionized water and dried in a vacuum chamber. Before spraying, add N,N-dimethylacetamide solvent to PFA to adjust the viscosity of PFA to 100mPa·s and stir overnight for standby, then spray at 0.4-0.6MPa, control the distance between the nozzle of the spray gun and the surface of the substrate to 20cm, spray The time is 5-10s; in the sintering and solidification stage, the average heating rate is controlled at 3 °C/min, and the temperature is kept constant for 20 minutes at 120 °C, and finally at 370 °C for 30 minutes, and then slowly cooled to room temperature under nitrogen protection; Fill nitrogen, adjust the speed of filling nitrogen, so that the speed is appropriate and the airflow is stable; when the coating is cured, stop filling with nitrogen, and let the coating cool naturally under the protection of nitrogen.

Example 3

Construct the 2# nanowire surface, and spray PFA to prepare the nanowire-PFA composite surface. The difference between this example and Example 1 is that the model of the template used, that is, the spacing of the nanowires, is changed. The preparation steps are as follows: use 800# and 3000# sandpaper was used to polish the copper substrate in turn, and the surface of the substrate was well polished. The ground substrates were ultrasonically cleaned with acetone and ethanol, respectively, and then rinsed with deionized water. The porous alumina (PAA) template (model 450-110), filter paper and the counter electrode of the copper sheet are placed in order and fixed with clips, and the edge of the filter paper is immersed in the plating solution to ensure that the solution can be completely absorbed by the filter paper by capillary action , and evenly distributed in the PAA template. A constant potential was applied between the copper substrate and the counter electrode to electroplate the nanowires. After electroplating for 1100 s, a layer of short copper nanowire arrays was attached to the copper substrate. After that, the filter paper, copper sheets, and clips were removed, and the rest were immersed in a copper pyrophosphate plating solution for electroplating. The electroplating time is 0.5-5h. After depositing the copper nanowire arrays, the template was removed by wet etching in 2 mol/L NaOH solution to obtain freestanding copper nanowire arrays. The copper blocks were then rinsed in deionized water and dried in a vacuum chamber. Before spraying, add N,N-dimethylacetamide solvent to PFA to adjust the viscosity of PFA to 100mPa·s and stir overnight for standby, then spray at 0.4-0.6MPa, control the distance between the nozzle of the spray gun and the surface of the substrate to 20cm, and the spraying time In the sintering and solidification stage, the average heating rate is controlled at 3 °C/min, when the temperature is raised to 120 °C, the temperature is kept constant for 20 minutes, and finally at 370 °C for 30 minutes, and then slowly cooled to room temperature under nitrogen protection; Fill nitrogen, adjust the speed of nitrogen filling, so that the speed is appropriate and the airflow is stable; when the coating is cured, stop filling with nitrogen, and let the coating cool naturally under the protection of nitrogen.

Example 4

Construct 2# nanowire surface, and spray PFA to prepare 4# nanowire-PFA composite surface. The difference between this example and Example 2 is that the spraying time of the coating is changed. The preparation steps are as follows: use 800# and 3000# sandpaper in turn Grind the copper substrate to give a good finish to the substrate surface. The ground substrates were ultrasonically cleaned with acetone and ethanol, respectively, and then rinsed with deionized water. The porous alumina (PAA) template (model 450-110), filter paper and the counter electrode of the copper sheet are placed in order and fixed with clips, and the edge of the filter paper is immersed in the plating solution to ensure that the solution can be completely absorbed by the filter paper by capillary action , and evenly distributed in the PAA template. A constant potential was applied between the copper substrate and the counter electrode to electroplate the nanowires. After electroplating for 1100 s, a layer of short copper nanowire arrays was attached to the copper substrate. After that, the filter paper, copper sheets, and clips were removed, and the rest were immersed in a copper pyrophosphate plating solution for electroplating. The electroplating time is 0.5-5h. After depositing the copper nanowire arrays, the template was removed by wet etching in 2 mol/L NaOH solution to obtain freestanding copper nanowire arrays. The copper blocks were then rinsed in deionized water and dried in a vacuum chamber. Before spraying, add N,N-dimethylacetamide solvent to PFA to adjust the viscosity of PFA to 100mPa·s and stir overnight for standby, then spray at 0.4-0.6MPa, control the distance between the nozzle of the spray gun and the surface of the substrate to 20cm, and the spraying time In the sintering and solidification stage, the average heating rate is controlled at 3°C/min, the temperature is kept at 120°C for 20min, and finally at 370°C for 30min, and then slowly cooled to room temperature under nitrogen protection; charged at 120°C Fill nitrogen, adjust the speed of nitrogen filling, so that the speed is appropriate and the airflow is stable; when the coating is cured, stop filling with nitrogen, and let the coating cool naturally under the protection of nitrogen.

Figure 5 shows the electron microscope image after the coating adhesion test. Figure 5 (a) and (b) are the results of the surface adhesion test of 2# nanowires, and Figure 5 (c) and (d) are the test results of the adhesion force of the 4# nanowire-PFA composite coating. The adhesion test method is based on the national standard GB/T 9286-1998 "Cross-cut test of paint and varnish film". After the test, the nanowire layer on the surface of the 2# nanowire was almost completely peeled off, and the bonding force was 4 to 5, while the 4# composite coating basically did not fall off, and the bonding force reached the 0 level.

Finally, it should be noted that the above embodiments are only used to help understand the method and the core idea of the present invention. It should be pointed out that for those skilled in the art and scientific researchers, without departing from the principle of the present invention, the present invention can also be improved in several ways, such as changing the material, diameter, spacing of metal nanowires, or changing the type of coating and corresponding Types of plating solutions, solvents, such improvements and modifications will be apparent to those skilled in the art. Therefore, the protection scope of the present invention will not be limited to the embodiments shown herein, but should conform to the broadest scope consistent with the principles and core ideas of the present invention.

Claims (4)

1. The preparation method of the nanowire-fluorocarbon composite coating is characterized in that the nanowire-fluorocarbon composite coating is a composite structure consisting of a nanowire array and a fluorocarbon coating, and the fluorocarbon coating is directly sprayed on the surface of the nanowire array;

the nanowire array is a high-thermal-conductivity nanowire network which is arranged in an oriented mode, and the height of the nanowire array is 5-30 mu m;

the thickness of the fluorocarbon coating is 5-50 mu m;

the preparation method of the nanowire-fluorocarbon composite coating forms a communicated nanowire network in the fluorocarbon coating by controlling the structural morphology of the nanowire and the forming process of the fluorocarbon coating; the height of the nano wire is 5-30 mu m, and the thickness of the sprayed fluorocarbon coating is 5-50 mu m;

the method comprises the following steps:

step 1: ultrasonically cleaning the polished copper substrate with acetone, ethanol and deionized water respectively, fixing the copper substrate, a porous anodic aluminum oxide template, filter paper soaked with electroplating solution and a copper sheet connected with a counter electrode in sequence by using a clamp, applying constant potential between the copper substrate and the copper sheet for electroplating to tightly connect the porous anodic aluminum oxide template and the copper substrate, and simultaneously attaching a layer of short copper nanowire array on the copper substrate;

and 2, step: then, taking down the filter paper, the copper sheet and the clamp, and immersing the connected porous anodic alumina template and the copper substrate into electroplating solution for electroplating for 0.5-5 h; after depositing the copper nanowire array, dissolving a template in NaOH solution to obtain an independent copper nanowire array;

and step 3: adding an N, N-dimethylacetamide solvent into the fluorocarbon coating to adjust the viscosity to 50-500 mPa ∙ s, and performing air spraying on the surface of the nanowire array prepared in the step 2, wherein the spraying pressure is controlled to be 0.1-0.6 MPa, and the spraying time is 5-50 s;

and 4, step 4: and (3) carrying out temperature programming heating on the nanowire array sprayed with the fluorocarbon coating under the nitrogen protection condition, wherein the average heating rate is 3-10 ℃/min, keeping the temperature constant for 20-70 min when the temperature is raised to 120 ℃, keeping the temperature constant for 10-50 min at 250-450 ℃, and then naturally cooling under the protection of nitrogen to obtain the nanowire-fluorocarbon composite coating.

2. The method of claim 1, wherein the fluorocarbon coating is formed by spraying a fluorocarbon coating, and the fluorocarbon coating is Teflon-PFA, PTFE coating, or FEVE coating.

3. The method according to claim 1, wherein the porous alumina template has a pore size of 50 to 300nm and a pore spacing of 100 to 500 nm.

4. The method as claimed in claim 1, wherein the plating solution comprises 3-20 wt% of copper pyrophosphate or copper sulfate aqueous solution.

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