CN112657805A - Nanowire-fluorocarbon composite coating and preparation method thereof - Google Patents
Nanowire-fluorocarbon composite coating and preparation method thereof Download PDFInfo
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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
Technical Field
The invention relates to the technical field of functional material surfaces and enhanced heat transfer, in particular to a nanowire-fluorocarbon composite coating and a preparation method thereof. In particular to: the fluorocarbon coating is modified by the high-heat-conduction material to prepare the composite coating, so that the effective heat-conduction performance and the hydrophobic performance of the coating and the binding force between the coating and the substrate can be improved, and the heat-transfer performance and the dust deposition prevention performance of the heat exchanger are improved.
Background
At present, heat exchangers are indispensable equipment in various fields of petrochemical industry, power generation, refrigeration and the like. However, in the application process, the condensation mode of most devices is film-shaped condensation, and the formed thick liquid film greatly influences the heat transfer performance. In addition, after the heat exchanger is operated for a long time, pollutants such as dirt and dust can be attached to the surface of the heat exchanger, and the performance of the heat exchanger is further influenced. In order to effectively improve the safety and the economical efficiency of equipment, the heat exchange surface is modified and the surface energy of the heat exchange surface is reduced, and long-term stable drop-shaped condensation is realized, so that the key points of improving the heat transfer performance of the heat exchanger and preventing dust deposition are realized.
At present, the coatings used on the surface of the heat exchanger are mainly epoxy resin coatings and fluorocarbon coatings, wherein the Teflon PFA fluorocarbon coatings (PFA for short) are widely applied to the aspects of corrosion prevention, anti-sticking lubrication treatment and the like due to excellent chemical inertia, thermal stability and good anti-contamination property. Because the surface energy of the PFA coating is lower, the intrinsic contact angle can reach more than 110 degrees, and stable drop-shaped condensation can be realized. However, PFA belongs to an organic polymer material, and compared with metal with good heat conductivity, the PFA has a low heat conductivity coefficient of only 0.2-0.3W/m.K; and in order to realize long-term stable drop-shaped condensation, the adopted coating is generally thicker, and the brought additional thermal resistance is larger.
In general, most of the current researches adopt a blending method to add a filler with high thermal conductivity into a fluorocarbon coating to improve the thermal conductivity of the coating, such as metal particles, graphene and the like. Patent CN 200510047351.9 discloses a method for improving the heat conductivity of fluorocarbon coating by using nanoparticles of iron, copper and the like, and the effective heat conductivity of the coating can be improved to 0.3-1.5W/m.K. When the blending method is adopted, the nano particles are randomly dispersed and distributed in the coating and cannot be arranged along the heat flow direction to form an effective heat transfer channel. Moreover, when the content of the filler is increased to a certain value, the curing film-forming property of the coating is greatly influenced, so that the binding force is reduced from 0 grade to 1-2 grade; and the added high surface energy particles can reduce the hydrophobicity of the fluorocarbon coating, so that the generation of dropwise condensation is not facilitated. Therefore, in order to more effectively improve the thermal conductivity of the coating, it is necessary to develop a method for orienting the thermal conductive network and tightly bonding the thermal conductive network to the substrate.
Disclosure of Invention
According to the existing technology for enhancing the heat conduction of the coating, a blending method is mostly adopted, but filler particles are randomly dispersed and distributed in the coating, cannot be distributed along the heat flow direction to form an effective heat transfer channel, and are not combined with the substrate, so that the combination force of the composite coating and the substrate is greatly influenced; when the content of the filler is increased to a certain value, the curing film-forming property of the coating is greatly influenced, so that the binding force is reduced from 0 grade to 1-2 grade; and the added high surface energy particles can reduce the hydrophobicity of the fluorocarbon coating and are not beneficial to the technical problem of generation of drop-shaped condensation, thereby providing the nanowire-fluorocarbon composite coating and the preparation method thereof. The nano-wire-fluorocarbon composite coating is constructed by prefabricating the directionally arranged nano-wires as a heat conduction network on a substrate and adopting a film forming process of the fluorocarbon coating, can remarkably improve the heat exchange performance of the heat exchanger and slow down the dust deposition of the heat exchanger, and can be applied to industrial systems of flue gas waste heat recovery, power generation, seawater desalination, electronic device heat management and the like.
The technical means adopted by the invention are as follows:
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.
Further, the nanowire is a copper nanowire, a silver nanowire, an iron nanowire or a nickel nanowire.
Further, the fluorocarbon coating is formed by spraying fluorocarbon coating, and the fluorocarbon coating is Teflon-PFA, PTFE coating or FEVE coating.
The invention also provides a preparation method of the nanowire-fluorocarbon composite coating, wherein a communicated nanowire network is formed 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;
step 2: 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 controlled to be 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.
Furthermore, the aperture of the porous alumina template is 50-300 nm, and the pore spacing is 100-500 nm.
Further, the nanowire is a copper nanowire, a silver nanowire, an iron nanowire or a nickel nanowire.
Furthermore, the electroplating solution comprises copper pyrophosphate and copper sulfate aqueous solution, silver nitrate solution, ferric sulfate solution, nickel chloride or nickel sulfate aqueous solution, and the mass fraction of the electroplating solution is 3-20%.
Further, the fluorocarbon coating is Teflon-PFA, PTFE coating or FEVE coating.
Further, the solvent for adjusting the viscosity is N, N-dimethylacetamide, N-dimethylformamide, N-methylpyrrolidone or dimethylsulfoxide.
Further, the porous alumina template dissolving agent is NaOH solution, KOH solution, HCl solution or H2SO4And (3) solution.
Compared with the prior art, the invention has the following advantages:
1. according to the nanowire-fluorocarbon composite coating and the preparation method thereof, the nanowires grow on the substrate, are tightly combined with the substrate and are directionally arranged, so that the effective heat conductivity coefficient of the fluorocarbon coating is greatly improved. Compared with the prior art, the composite coating prepared by the invention has the binding force with the substrate reaching 0 level. Compared with the surface of pure PFA, the nanowire aggregate forms a large number of convex structures, the contact angle is increased from 118 degrees of pure PFA to 152 degrees of the composite coating, a super-hydrophobic state is achieved, accumulation of dust and dirt in the application process can be effectively prevented, and the problems of poor thermal conductivity, short service life and the like of the traditional heat exchanger coating can be effectively solved. Due to the high heat conductivity coefficient of copper materials, the heat conductivity of the composite coating can reach 39W/m.K, which is 150 times of that of a pure PFA coating.
2. According to the nanowire-fluorocarbon composite coating and the preparation method thereof, the wettability of the composite coating can be effectively regulated and controlled by controlling the height of the nanowire and regulating and controlling the deposition morphology of the fluorocarbon coating. When the fluorocarbon coating completely covers the communicated nanowires, the wetting angle of the composite coating is 118 degrees, and the composite surface has general hydrophobicity; but the fluorocarbon coating is only filled in the groove of the nanowire by regulating and controlling the deposition morphology of the fluorocarbon coating, a large number of convex structures of the nanowire aggregate are exposed, and the contact angle of the composite coating can reach 152 degrees at the moment, so that the surface has super-hydrophobicity.
In conclusion, the technical scheme of the invention can solve the problems that in the prior art of enhancing the heat conduction of the coating, a blending method is mostly adopted, but filler particles are randomly dispersed and distributed in the coating, cannot be arranged along the heat flow direction to form an effective heat transfer channel, and are not combined with the substrate, so that the combination force of the composite coating and the substrate is greatly influenced; when the content of the filler is increased to a certain value, the curing film-forming property of the coating is greatly influenced, so that the binding force is reduced from 0 grade to 1-2 grade; and the added high surface energy particles can reduce the hydrophobicity of the fluorocarbon coating, so that the problem of generation of dropwise condensation is not facilitated.
Based on the reasons, the invention can be widely popularized in the fields of industrial processes such as power generation, petrochemical industry, seawater desalination and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a process flow diagram for preparing a metal nanowire-PFA composite coating according to the present invention.
Fig. 2 is a schematic view of a # 3 nanowire-PFA composite coating prepared by using a # 1 nanowire surface in example 2 of the present invention, wherein (a) is a schematic view of a # 1 nanowire surface, (b) is a schematic view of a # 3 nanowire-PFA composite coating prepared by spraying PFA on a # 1 nanowire surface, and (c) is an enlarged view of a point a in (b).
Fig. 3 is a schematic view of a # 4 nanowire-PFA composite coating layer prepared using a # 2 nanowire surface in example 4 of the present invention, wherein (a) is a schematic view of a # 2 nanowire surface, (B) is a schematic view of a # 4 nanowire-PFA composite coating layer prepared by spraying PFA on a # 2 nanowire surface, (C) is an enlarged view at B in (B), (d) is an enlarged view at (C), and (e) is an enlarged view at C in (d).
Fig. 4 is a schematic diagram of contact angles of different surfaces of the present invention, wherein (a) is a schematic diagram of contact angle of pure PFA surface, (b) is a schematic diagram of contact angle of 4# composite coating, and (c) is a schematic diagram of contact angle of 3# composite coating.
FIG. 5 is an electron microscope image after the coating adhesion force test of the present invention, wherein (a) is a result image after the 2# nanowire surface adhesion force test, (b) is an enlarged image of D in (a), (c) is a result image of the 4# nanowire-PFA composite coating adhesion force test, and (D) is an enlarged image of E in (c).
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
In order to make the objects, 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 drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and 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. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
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 present invention unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. Any specific values in all examples shown and discussed herein are to be construed as exemplary only and not as limiting. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.
As shown in the figure, the invention provides a nanowire-fluorocarbon composite coating, 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.
Preferably, the nanowire is a copper nanowire, a silver nanowire, an iron nanowire or a nickel nanowire.
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 preparation method of the nanowire-fluorocarbon composite coating, wherein a communicated nanowire network is formed 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;
step 2: 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 controlled to be 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.
Preferably, the aperture of the used porous alumina template is between 50 and 300nm, 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, etc.
Preferably, the components of the electroplating solution 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. with the mass fraction of 3-20%.
Preferably, the fluorocarbon coating used includes, but is not limited to, Teflon-PFA, PTFE coating or FEVE coating, etc.
Preferably, the viscosity-adjusting solvent includes, but is not limited to, N-dimethylacetamide, N-dimethylformamide, N-methylpyrrolidone, dimethylsulfoxide, or the like.
Preferably, the porous alumina template dissolvent used includes, but is not limited to, NaOH solution, KOH solution, HCl solution or H2SO4Solutions, and the like.
Fig. 1 shows a process flow chart of preparing a metal nanowire-PFA composite coating. It is predicted that the PFA coating thickness gradually increases with increasing spray time. When the spray coating is thicker, the PFA completely covers the nanowire structure, and the composite coating contact angle can be considered as the contact angle of the PFA surface.
Example 1
The technical scheme of the invention is as follows: firstly, growing copper nanowires with a certain height on the surface of a metal substrate by an electrochemical deposition method, then adjusting the viscosity of the coating, and adopting a proper spraying process to form a film in the gaps of the nanowires, thereby realizing stable long-term dropwise condensation and simultaneously solving the problem of poor heat transfer performance. The specific process flow is as follows:
1. pretreatment of a base material: the copper substrate (copper substrate) was polished with 800# and 3000# sandpaper in this order, and the surface of the copper substrate was polished. The polished substrate (copper substrate) was ultrasonically cleaned with acetone and ethanol, respectively, and then rinsed with deionized water.
2. Electroplating the nanowires: a copper substrate, a porous alumina (PAA) template, filter paper and a copper sheet attached to a counter electrode were placed in order and fixed with a clip, and the edge of the filter paper was immersed in the plating solution to ensure that the solution could be completely absorbed by the filter paper by capillary action and uniformly distributed in the PAA template. A constant potential is applied between the copper substrate and the copper sheet to electroplate the nanowires. After a certain time, a layer of short copper nanowire array is attached to the copper substrate, and the porous alumina template is tightly connected with the copper substrate. Then, the filter paper, the copper sheet and the clip were removed, and the connected porous alumina template and copper substrate were immersed in a copper pyrophosphate plating solution for plating. Nanowires of different lengths are obtained with a three-electrode system because it allows more precise control of the potential. A copper substrate with a template was used as the working electrode, a copper sheet without template was used as the counter electrode, and an Ag/AgCl electrode was selected as the reference electrode. The plating time and the voltage applied between the working electrode and the auxiliary electrode are adjusted to respective 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 2mol/L NaOH solution to obtain an independent copper nanowire array. The copper block was then rinsed in deionized water and dried in a vacuum chamber.
4. Spraying fluorocarbon paint: adding an N, N-dimethylacetamide solvent into the fluorocarbon coating before spraying to adjust the viscosity of the fluorocarbon coating to 100mPa & s, stirring for 24 hours for later use, then spraying the coating under the air pressure of 0.1-0.6 MPa, and controlling the distance between a spray gun opening and the surface of the base material to be 20 cm; the fluorocarbon coating is made of Teflon PFA.
5. Obtaining the nanowire-fluorocarbon composite coating: in a nitrogen atmosphere, controlling the average heating rate at 3-10 ℃/min in a sintering and curing stage, 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 slowly cooling to room temperature under the protection of nitrogen; a proper amount of nitrogen is filled at 120 ℃ to ensure stable airflow; and stopping filling nitrogen gas after the coating is solidified, and naturally cooling the coating under the protection of the nitrogen gas.
In the prior art of enhancing the heat conduction of the coating, such as a blending method, filler particles are dispersed and distributed in the coating at random and are not combined with the substrate, so that the combination force of the composite coating and the substrate is greatly influenced. Compared with the prior art, the composite coating prepared by the invention has the binding force with the substrate reaching 0 level. Compared with the surface of pure PFA, the nanowire aggregate forms a large number of convex structures, the contact angle is increased from 118 degrees of pure PFA to 152 degrees of the composite coating, a super-hydrophobic state is achieved, and accumulation of dust and dirt in the application process can be effectively prevented. Due to the high thermal conductivity coefficient of the copper material, the thermal conductivity of the composite coating can reach 39W/m K, which is 150 times of that of a pure PFA coating.
The wettability of the composite coating can be effectively regulated and controlled by controlling the height of the nanowire and regulating and controlling the deposition morphology of the fluorocarbon coating. When the fluorocarbon coating completely covers the communicated nanowires, the wetting angle of the composite coating is 118 degrees, and the composite surface has general hydrophobicity; but the fluorocarbon coating is only filled in the groove of the nanowire by regulating and controlling the deposition morphology of the fluorocarbon coating, a large number of convex structures of the nanowire aggregate are exposed, and the contact angle of the composite coating can reach 152 degrees at the moment, so that the surface has super-hydrophobicity.
Example 2
Constructing the surface of the 1# nanowire, and spraying PFA to prepare the 3# nanowire-PFA composite coating, wherein the preparation steps are as follows: the copper substrate was sanded with 800# and 3000# sandpaper in that order to provide good polishing of the substrate surface. And ultrasonically cleaning the polished substrate with acetone and ethanol respectively, and then washing with deionized water. A porous alumina (PAA) template (model number 450-. A constant potential is applied between the copper substrate and the counter electrode to plate the nanowires. After 1100s of electroplating, a layer of short copper nanowire array was attached to the copper substrate. Thereafter, the filter paper, the copper sheet and the clip were removed, and the rest was immersed in a copper pyrophosphate plating solution to perform plating. The electroplating time is 0.5-5 h. After depositing the copper nanowire array, the template was removed by wet etching in a 2mol/L NaOH solution to obtain an independent copper nanowire array. The copper block was then rinsed in deionized water and dried in a vacuum chamber. Adding an N, N-dimethylacetamide solvent into PFA to adjust the viscosity of the PFA to 100mPa & s before spraying, stirring for standby at night, then spraying under 0.4-0.6 MPa, controlling the distance between a spray gun opening and the surface of a base material to be 20cm, and controlling the spraying time to be 5-10 s; controlling the average heating rate at 3 ℃/min in the sintering and curing stage, keeping the temperature constant for 20min when the temperature is raised to 120 ℃, keeping the temperature constant for 30min at 370 ℃, and then slowly cooling to room temperature under the protection of nitrogen; filling nitrogen at 120 ℃, and adjusting the speed of filling nitrogen to ensure proper speed and stable airflow; and stopping filling nitrogen gas after the coating is solidified, and naturally cooling the coating under the protection of the nitrogen gas.
Example 3
The method comprises the following steps of constructing the surface of a 2# nanowire, spraying PFA to prepare a nanowire-PFA composite surface, wherein the difference between the embodiment and the embodiment 1 is that the model of a template, namely the distance between the nanowires is changed, and the preparation steps are as follows: the copper substrate was sanded with 800# and 3000# sandpaper in that order to provide good polishing of the substrate surface. And ultrasonically cleaning the polished substrate with acetone and ethanol respectively, and then washing with deionized water. A porous alumina (PAA) template (model number 450-. A constant potential is applied between the copper substrate and the counter electrode to plate the nanowires. After 1100s of electroplating, a layer of short copper nanowire array was attached to the copper substrate. Thereafter, the filter paper, the copper sheet and the clip were removed, and the rest was immersed in a copper pyrophosphate plating solution to perform plating. The electroplating time is 0.5-5 h. After depositing the copper nanowire array, the template was removed by wet etching in a 2mol/L NaOH solution to obtain an independent copper nanowire array. The copper block was then rinsed in deionized water and dried in a vacuum chamber. Adding an N, N-dimethylacetamide solvent into PFA to adjust the viscosity of the PFA to 100mPa & s before spraying, stirring overnight for later use, then spraying under 0.4-0.6 MPa, controlling the distance between a spray gun opening and the surface of a base material to be 20cm, and controlling the spraying time to be 5-10 s; (ii) a Controlling the average heating rate at 3 ℃/min in the sintering and curing stage, keeping the temperature constant for 20min when the temperature is raised to 120 ℃, keeping the temperature constant for 30min at 370 ℃, and then slowly cooling to room temperature under the protection of nitrogen; filling nitrogen at 120 ℃, and adjusting the speed of filling nitrogen to ensure proper speed and stable airflow; and stopping filling nitrogen gas after the coating is solidified, and naturally cooling the coating under the protection of the nitrogen gas.
Example 4
The method comprises the following steps of constructing a 2# nanowire surface, and spraying PFA to prepare a 4# nanowire-PFA composite surface, wherein the difference between the embodiment and the embodiment 2 is that the spraying time of the coating is changed, and the preparation steps are as follows: the copper substrate was sanded with 800# and 3000# sandpaper in that order to provide good polishing of the substrate surface. And ultrasonically cleaning the polished substrate with acetone and ethanol respectively, and then washing with deionized water. A porous alumina (PAA) template (model number 450-. A constant potential is applied between the copper substrate and the counter electrode to plate the nanowires. After 1100s of electroplating, a layer of short copper nanowire array was attached to the copper substrate. Thereafter, the filter paper, the copper sheet and the clip were removed, and the rest was immersed in a copper pyrophosphate plating solution to perform plating. The electroplating time is 0.5-5 h. After depositing the copper nanowire array, the template was removed by wet etching in a 2mol/L NaOH solution to obtain an independent copper nanowire array. The copper block was then rinsed in deionized water and dried in a vacuum chamber. Adding an N, N-dimethylacetamide solvent into PFA to adjust the viscosity of the PFA to 100mPa & s before spraying, stirring overnight for later use, then spraying under 0.4-0.6 MPa, controlling the distance between a spray gun opening and the surface of a base material to be 20cm, and controlling the spraying time to be 20-30 s; (ii) a Controlling the average heating rate at 3 ℃/min in the sintering and curing stage, keeping the temperature constant for 20min when the temperature is raised to 120 ℃, keeping the temperature constant for 30min at 370 ℃, and then slowly cooling to room temperature under the protection of nitrogen; filling nitrogen at 120 ℃, and adjusting the speed of filling nitrogen to ensure proper speed and stable airflow; and stopping filling nitrogen gas after the coating is solidified, and naturally cooling the coating under the protection of the nitrogen gas.
FIG. 5 is an electron micrograph of the coating after adhesion testing. Fig. 5 (a) and (b) show results after 2# nanowire surface bonding force test, and fig. 5(c) and (d) show results of 4# nanowire-PFA composite coating bonding force test. The binding force test method is based on the national standard GB/T9286 1998 the test of dividing grids of paint films of colored paint and varnish. After testing, the nanowire layer on the surface of the 2# nanowire almost completely falls off, the binding force is 4-5 grade, the 4# composite coating basically does not fall off, and the binding force reaches 0 grade.
Finally, it should be noted that: the above embodiments are merely provided to aid understanding of the method of the present invention and its core ideas. It should be noted that it will be apparent to those skilled in the art and scientific research that the present invention can be modified in several ways, such as changing the material, diameter, and spacing of the metal nanowires, or changing the type of coating and the type of plating solution and solvent, without departing from the principle of the present invention. Thus, the scope of the present invention should not be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and core concepts of the present invention.
Claims (10)
1. 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.
2. The nanowire-fluorocarbon composite coating of claim 1, wherein the nanowire is a copper, silver, iron or nickel nanowire.
3. The nanowire-fluorocarbon composite coating of claim 1, wherein the fluorocarbon coating is formed by spraying a fluorocarbon coating, the fluorocarbon coating being Teflon-PFA, PTFE coating or FEVE coating.
4. A method for preparing the nanowire-fluorocarbon composite coating according to any one of claims 1 to 3, characterized in that a connected nanowire network is formed in the fluorocarbon coating by controlling the structural morphology of the nanowires 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;
step 2: 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 controlled to be 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.
5. The preparation method according to claim 1, wherein the pore diameter of the porous alumina template is 50-300 nm, and the pore distance is 100-500 nm.
6. The method of claim 1, wherein the nanowires are copper nanowires, silver nanowires, iron nanowires, or nickel nanowires.
7. The method as claimed in claim 1, wherein the plating solution is composed of an aqueous solution of copper pyrophosphate, copper sulfate, silver nitrate, iron sulfate, nickel chloride or nickel sulfate in an amount of 3 to 20% by mass.
8. The method of claim 1, wherein the fluorocarbon coating is Teflon-PFA, PTFE coating, or FEVE coating.
9. The method according to claim 1, wherein the viscosity-adjusting solvent is N, N-dimethylacetamide, N-dimethylformamide, N-methylpyrrolidone, or dimethylsulfoxide.
10. The method according to claim 1, wherein the porous alumina template dissolving agent is NaOH solution, KOH solution, HCl solution or H solution2SO4And (3) solution.
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