CN111394771B - Method for preparing coating on surface of copper and copper alloy and copper product - Google Patents
Method for preparing coating on surface of copper and copper alloy and copper product Download PDFInfo
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- CN111394771B CN111394771B CN202010320807.9A CN202010320807A CN111394771B CN 111394771 B CN111394771 B CN 111394771B CN 202010320807 A CN202010320807 A CN 202010320807A CN 111394771 B CN111394771 B CN 111394771B
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
- C25D11/024—Anodisation under pulsed or modulated current or potential
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
- C25D11/34—Anodisation of metals or alloys not provided for in groups C25D11/04 - C25D11/32
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24S—SOLAR HEAT COLLECTORS; SOLAR HEAT SYSTEMS
- F24S70/00—Details of absorbing elements
- F24S70/20—Details of absorbing elements characterised by absorbing coatings; characterised by surface treatment for increasing absorption
- F24S70/225—Details of absorbing elements characterised by absorbing coatings; characterised by surface treatment for increasing absorption for spectrally selective absorption
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/40—Solar thermal energy, e.g. solar towers
Abstract
The invention provides a method for preparing a coating on the surface of copper and copper alloy and a copper product. The method for preparing the coating on the surface of the copper and the copper alloy comprises the following steps: taking a stainless steel plate or a stainless steel pool as a cathode, taking copper and copper alloy as an anode, controlling the temperature of the composite electrolyte to be 20-40 ℃, applying pulse voltage of more than 600V between the cathode and the anode, and carrying out pulse discharge reaction on the surface of the copper and the copper alloy so as to form a ceramic coating with a micro-bulge structure on the surface of the copper and the copper alloy; the composite electrolyte contains alcohols, the alcohols are ionized in a discharge environment to form bubbles, high-frequency strong discharge is promoted again, and the bubbles are sprayed to enable the coating to slightly expand under stress to form a convex structure. The ceramic coating prepared by the invention has high compactness and a micro-convex structure, and increases the shape complexity of the surface of the coating and the area of the coating. The copper with the ceramic coating is used in the field of solar heat collection, and has strong sunlight absorption and photo-thermal conversion.
Description
Technical Field
The invention relates to the technical field of surface treatment of copper and copper alloy, in particular to a method for preparing a coating on the surface of copper and copper alloy and a copper product.
Background
Copper and its composite material are widely used in the fields of machinery, electricity, light industry, building, national defense, aerospace and the like, and the consumption and application of domestic non-ferrous metal materials are second to aluminum, and the copper and its composite material are used as green metal materials, have low melting point, are easy to recycle, and greatly reduce the application cost. In addition, copper and its composite material are relatively soft metals, have good ductility, high thermal conductivity (the thermal conductivity coefficient of copper is about 381/W (m.K) -1) and high electrical conductivity, and are widely applied in the industries of electric cables, electronic components, solar energy utilization, LEDs and the like.
The copper and the alloy surface oxidation coating mainly use copper oxide as a main material, and the copper oxide and the cuprous oxide are p-type semiconductor materials, have narrow band gaps (2.2eV), are black materials, have strong sunlight absorption capacity, and have application prospects in the fields of solar heat collection, photocatalysis and the like. As a solar energy absorption type coating, the quality and optical characteristics of the coating determine the photo-thermal conversion efficiency of a heat collector, and the heat radiation loss of materials to the environment needs to be reduced, the solar energy absorption rate needs to be improved, and the solar energy is fully utilized. In the prior art, the coating is prepared on the surface of copper and copper alloy by methods such as CVD, PVD, spraying, magnetron sputtering, vacuum coating and the like, but the coating with large area or complex special-shaped components is difficult to prepare.
Disclosure of Invention
The invention solves the problem that the existing CVD, PVD, spraying, magnetron sputtering, vacuum coating and other methods can not prepare large-area or coating with complex special-shaped components on the surface of copper and copper alloy.
In order to solve the problems, the invention provides a method for preparing a coating on the surface of copper and copper alloy, which comprises the following steps: taking a stainless steel plate or a stainless steel pool as a cathode, taking copper and copper alloy as an anode, controlling the temperature of the composite electrolyte to be 20-40 ℃, applying pulse voltage of more than 600V between the cathode and the anode, and carrying out pulse discharge reaction on the surface of the copper and the copper alloy so as to form a ceramic coating with a micro-bulge structure on the surface of the copper and the copper alloy; wherein the composite electrolyte contains alcohols.
Preferably, the preparation process of the composite electrolyte comprises the following steps: adding ethanol with the volume concentration of 10-100ml/L into a base electrolyte, wherein the base electrolyte comprises sodium hexametaphosphate and sodium borate.
Preferably, the mass concentration of the sodium hexametaphosphate is 1-20g/L, and the mass concentration of the sodium borate is 1-20 g/L.
Preferably, the mass concentration ratio of the sodium hexametaphosphate to the sodium borate is 1:1-9: 1.
Preferably, the process of preparing the composite electrolyte further comprises: and adding glycerol with the volume concentration of 20-100ml/L into the base electrolyte.
Preferably, the pulse voltage is 600V-1000V.
Preferably, the time of the pulse discharge reaction is 3-40 min.
Preferably, before the pulse discharge reaction, the method further comprises: polishing the surface of copper and copper alloy with sand paper, ultrasonically cleaning with absolute ethyl alcohol, cleaning with distilled water, and drying.
Compared with the prior art, the preparation method provided by the invention has the following beneficial effects:
the invention adopts the composite electrolyte containing alcohols, prepares the black ceramic coating on the surface of the copper and the copper alloy by one step at a certain temperature and high pulse voltage, has high compactness and a micro-convex structure, and increases the shape complexity and the coating area of the coating surface. The copper and the copper alloy material with the ceramic coating are used in the field of solar heat collection, and have strong sunlight absorption capacity and photothermal conversion efficiency.
The invention also provides a copper product, which comprises copper and an alloy thereof, and also comprises a ceramic coating formed on the surface of the copper and the alloy thereof, wherein the ceramic coating is prepared by the method for preparing the coating on the surface of the copper and the alloy thereof.
Preferably, the thickness of the ceramic coating is 10-60 μm.
Compared with the prior art, the copper product prepared by the invention has the same beneficial effect as the method for preparing the coating on the surface of the copper and the copper alloy, and the description is omitted.
Drawings
FIG. 1 is an XRD pattern of a coating formed on a pure copper surface in example 1 of the present invention;
FIG. 2 is a surface micro-topography photograph of a coating made on a pure copper surface in example 1 of the present invention;
FIG. 3 is a cross-sectional micro-topography photograph of a coating made on a pure copper surface in example 1 of the present invention;
FIG. 4 is a graph showing the reflectance of a coating formed on a pure copper surface according to example 1 of the present invention;
FIG. 5 is a physical diagram of the contact angle and a schematic diagram of the static contact angle of the coating on the surface of pure copper in example 1 of the present invention;
FIG. 6 is a polarization curve of a coating formed on a pure copper surface according to example 1 of the present invention;
FIG. 7 is a surface micro-topography photograph of a coating made on a pure copper surface according to comparative example 1 of the present invention;
FIG. 8 is a cross-sectional micro-topography photograph of a coating made on a pure copper surface in comparative example 1 of the present invention.
Detailed Description
The copper-based composite material has high heat conduction and electric conduction performance, the copper oxide and the cuprous oxide are black materials and have strong sunlight absorption capacity, and the black coating capable of being selectively absorbed is prepared on the surface of the copper and the copper alloy, so that a foundation is provided for the application of the copper and the copper composite material in the field of solar photo-thermal conversion.
Micro-arc oxidation, also known as plasma electrolytic oxidation, is a plasma-assisted electrochemical conversion technique that grows a ceramic film layer based on matrix metal oxide on the surface of valve metal or its alloy by means of arc discharge. The specific process of micro-arc oxidation is as follows: the discharge induces ion migration, a discharge channel is formed, under the action of high temperature and high pressure in the channel, gas formed in the micro-area escapes from the membrane/liquid interface through the channel, and reaction products or remelted coating materials in the channel are sprayed and deposited near the channel port under the action of pressure, so that the shape of the volcano port is formed. After the spark is extinguished, the molten mass is cooled and solidified to form a dense inner layer and a loose outer layer.
Because copper and copper alloy are not valve metal, spark is not generated in the process, so spark discharge can not be carried out under certain voltage and current like valve metal such as Al, Mg, Ti and the like, and a discharge channel penetrating through the coating is further formed, so that the breakdown-channel-fusion effect is caused, and the growth of the coating is realized.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
The invention provides a preparation method of a coating on the surface of copper and copper alloy, aiming at solving the problem that a black coating cannot be prepared on the surface of copper and copper alloy by using a micro-arc oxidation technology, comprising the following steps:
the method comprises the steps of taking a stainless steel plate or a stainless steel pool as a cathode, taking copper and copper alloy as an anode, controlling the temperature of the composite electrolyte to be 20-40 ℃, applying pulse voltage of more than 600V between a cathode and an anode, and carrying out pulse discharge reaction on the surface of the copper and the copper alloy so as to form a ceramic coating on the surface of the copper and the copper alloy, wherein the ceramic coating has a micro-convex structure. Wherein the composite electrolyte contains alcohols, and the pulse discharge reaction time is 3-40 min.
According to the embodiment of the invention, alcohols such as ethanol are added into the composite electrolyte, the self electric conduction and heat conduction properties of copper and copper alloy are utilized, and high pulse voltage is applied, so that the electrochemical behavior of the surface of the copper and copper alloy is changed, the microstructure and composition of the coating formed on the surface of the copper and copper alloy are further changed, and the thickness, compactness and corrosion resistance of the ceramic coating prepared by the embodiment are greatly improved.
According to the high-speed photography and shooting coating forming process, the forming mechanism of the copper and the copper alloy surface coating in the embodiment may be: micro-arc discharge induction, in-situ growth, dissolution and regrowth of the coating, namely, in the growth process of the coating, under the action of high pulse voltage and large current (related to alcohol addition in the composite electrolyte), the growth rate of the coating is greater than the dissolution rate, so that a relatively compact oxide film which is well combined with copper and an alloy matrix thereof can be formed in the regrowth process of the coating, the oxide film grows layer by layer until an oxide layer with a certain thickness is formed, and the ceramic coating is further generated on the surface of the copper and the alloy thereof. The method comprises the following specific steps:
adding alcohols (ethanol is preferred in the embodiment, and other alcohols except ethanol can be adopted, on one hand), so that the pH of the composite electrolyte is adjusted, and a pH regulator is not required to be additionally added into the composite electrolyte; on the other hand, under the constant voltage mode, the conductivity of the composite electrolyte (especially the conductivity in the pulse discharge process) is greatly improved, so for the coating which is subjected to discharge breakdown and dissolution regeneration, ions can rapidly move and jump in the coating preparation process, the growth rate of the coating is effectively improved, the growth rate of the coating is greater than the dissolution rate, the growth of the coating is accelerated, and the thickness and the compactness of the coating are improved.
When the pulse voltage of the composite electrolyte added with the ethanol is less than 150V, the current density is linearly increased, and the increase rate of the current density is greater than that of the basic electrolyte (without the ethanol), so that the surfaces of the copper and the copper alloy are more easily broken down to form a passivation film, and a foundation is provided for the growth of a subsequent coating. It is noted that when a resistive oxide film (passivation film) is formed earlier, stronger discharge occurs, and the film thickness and density increase at a constant rate according to the discharge intensity. The discharge intensity is higher in the composite electrolyte containing ethanol, namely, the coating under the composite electrolyte provided by the embodiment grows thicker and denser.
When the pulse voltage is more than 150V, the current density of the composite electrolyte added with the ethanol begins to generate oscillation (up-down jumping) along with the increase of the oxidation time, the discharge is uniform and strong, and the ethanol can generate a large amount of bubbles under the action of pulse discharge, high temperature and high pressure, the bubbles are accumulated on the surface of the coating, so that the electric field intensity of the edge of the bubble converged on a potential line is increased, and the coating is further promoted to grow by the strong electric field effect.
Meanwhile, under the conditions of high voltage and large current, ethanol is decomposed to generate a large amount of bubbles, and on one hand, the generation of the bubbles is beneficial to improving the growth rate of the coating so that the coating grows in situ. On the other hand, the temperature of the composite electrolyte can be quickly raised, so that the coating is easier to grow and a micro-convex structure is easy to form. Meanwhile, the temperature of the composite electrolyte rises to form a heat affected zone, so that the electrical insulation of the coating is reduced, the surface of the coating is further subjected to breakdown, electrochemical erosion and discharge growth, dissolution and expansion, the continuous volume expansion and development of a surface oxide layer are caused, and the oxide layer with a micro-convex appearance is formed.
When the applied pulse voltage is more than 600V, the micro-arc discharge induction effect is enhanced under the high pulse voltage, so that a compact oxide film is rapidly formed on the coating at the initial stage, the growth rate of the coating is obviously higher than the dissolution rate of the coating, and the coating with a micro-convex structure is formed on the surface of copper and the alloy thereof in the growth process. The specific forming process of the micro-bulge structure coating comprises the following steps: under the action of micro-arc induction, loose micropores and micro-cracks are formed on the surfaces of copper and copper alloy, the discharge energy is continuously increased along with the continuous increase of pulse voltage and current, the positions of weak points begin to be broken down, the coating grows in situ, and meanwhile, the oxide layer with loose surfaces begins to dissolve and peel off. In the growth process, large current promotes alcohols in the composite electrolyte to form a large amount of oxygen bubbles, so that the continuous volume expansion of the oxide layer finally forms a micro-convex structure.
In this embodiment, the growth of the coating is promoted by the pulse voltage of more than 600V and the current density increase of the composite electrolyte caused by the addition of the alcohol, so that the volume of the surface of the coating expands, and thus the surface of the copper and the alloy thereof forms a micro-convex structure.
In addition, copper and its alloy have high electrical conductivity and high thermal conductivity, and thus, it is helpful to form ceramic coating on the surface of copper and its alloy during the growth of the coating. The method specifically comprises the following steps:
under the pulse discharge condition, because copper and its alloy conductivity is high, easily receive the influence of high frequency electric field, copper and its alloy surface form high temperature, high electric field environment, and under this environment, ion and the composition in the compound electrolyte are easily migrated for the ethanol ionization forms the oxygen bubble, further forms high frequency strong discharge, promotes the coating growth, and a large amount of bubbles erupt, leads to the coating inflation arch, forms the little protruding structure.
Because copper has low activity, a passivation film is not easy to form in electrolyte, and a film layer can be formed under the stimulation of current and voltage under the action of a high electric field, but the compactness of the film layer is poor. In the embodiment, after alcohols such as ethanol are added into the composite electrolyte, the current density of the composite electrolyte is greatly improved in a constant voltage mode, and copper is easy to form a coating on the surface of the copper under the action of the electric field under the action of deposition and adsorption.
Copper also has higher thermal conductivity, so that a thermal micro-area can be formed at the interface of the copper and the composite electrolyte, ions in the composite electrolyte are easier to activate and migrate under the high-temperature and high-frequency discharge environment, ethanol is evaporated to form bubbles under the high-temperature environment and form ions, and the ions of the composite electrolyte react with a copper matrix under the strong discharge action of plasma and the bubbles to form copper oxide, cuprous oxide and a small amount of amorphous substances in situ, so that a compact oxide film is formed. Meanwhile, current flows through the composite electrolyte, negatively charged ions migrate to the anode due to the directional migration of the ions, oxygen and hydrogen are released from the electrolyte, gas eruption is caused by evaporation and condensation at an interface, the coating is easier to expand by the gas, and a layer of metallurgically bonded compact micro-convex copper oxide or cuprous oxide ceramic film layer is formed on the surface of the copper matrix.
The ceramic coating prepared by the embodiment mainly comprises copper oxide, cuprous oxide and a small amount of amorphous phase, the thickness of the coating is 10-60 mu m, and the coating also has strong corrosion resistance and hydrophobicity.
The ceramic coating prepared by the embodiment has a micro-convex structure, increases the shape complexity of the surface of the coating and the coating area, and has stronger sunlight absorption capacity and photothermal conversion efficiency when the copper and the alloy material with the ceramic coating are used in the field of solar heat collection.
In addition, the black ceramic coating is prepared on the surface of the copper and the alloy thereof in one step by adopting micro-arc discharge in the embodiment, compared with the prior art, a valve metal intermediate film layer suitable for the micro-arc oxidation technology is not required to be prepared on the surface of the copper and the alloy thereof by methods of spraying, magnetron sputtering and the like, the preparation process is simple, and the cost is saved.
The preparation process of the composite electrolyte comprises the following steps:
mixing sodium hexametaphosphate with the concentration of 1-20g/L and sodium borate with the concentration of 1-20g/L, adding ethanol with the concentration of 10-100ml/L, and ultrasonically mixing for 10-25min to prepare the composite electrolyte. Wherein the concentration (g/L) ratio of the sodium hexametaphosphate to the sodium borate is 1:1-9: 1.
Preferably, the composite electrolyte is also added with glycerol with the concentration of 20-100 ml/L.
In the embodiment, the addition of the sodium hexametaphosphate can greatly improve the conductivity of the composite electrolyte, promote the growth of the surface coating of the matrix (copper and alloy thereof), improve the surface roughness of the coating, increase the nonuniformity of the coating thickness under continuous micro-arc induction, change the morphology of the film layer, easily induce a micro-protrusion structure, and increase the number of micro-protrusions.
The addition of sodium tetraborate can cause strong passivation of the metal. Granular sediments possibly appear on the surface of the coating in the early growth stage of the coating, a reticular communicated microprotrusion structure is formed by expansion, and later-stage growths can be separated out from the early-stage sediments.
In the embodiment, the glycerol is added into the composite electrolyte, so that the electrolyte has the effect of stabilizing the electrolyte, and although the thickness of the coating is reduced, the coating can be densified and grown, and holes and defects generated in the growth of the coating are reduced.
In order to facilitate the generation of a coating on the surface of copper and copper alloy, the surface of copper and copper alloy is pretreated, and the pretreatment steps are as follows:
the surface of the copper and the alloy thereof is polished by abrasive paper to remove impurities, oxide layers and the like on the surface of the copper and the alloy thereof, and specifically, the surface of the copper and the alloy thereof is polished by using 800# and 1200# abrasive paper in sequence.
Then, absolute ethyl alcohol is used for ultrasonic cleaning for 10-20min, and then deionized water is used for cleaning, so that the cleanliness of the surfaces of the copper and the copper alloy is improved.
And finally, drying, preferably in a drying mode.
The present invention will be described in detail with reference to specific embodiments.
Example 1
The embodiment provides a method for preparing a coating on a copper surface, which comprises the following steps:
1.1, selecting pure copper as a substrate, polishing by using 800 and 1200# abrasive paper in sequence, then ultrasonically cleaning for 20min by using absolute ethyl alcohol, cleaning by using distilled water, and drying;
1.2, mechanically and uniformly stirring 18g/L sodium hexametaphosphate and 2g/L sodium borate to prepare a basic electrolyte;
1.3, adding 12% of absolute ethyl alcohol by volume fraction and 20% of glycerol by volume fraction into the basic electrolyte, and carrying out ultrasonic treatment for 10min to prepare the stable micro-arc induced composite electrolyte;
and 1.4, taking a stainless steel plate or a stainless steel pool as a cathode, taking pure copper as an anode, applying 650V pulse voltage (constant voltage mode) to two ends of an electrolytic tank, controlling the solution temperature of the composite electrolyte to be 30 ℃, and carrying out micro-arc discharge reaction for 30min under the stirring condition to obtain the black coating with the micro-protrusion structure.
The black coating prepared on the surface of the pure copper in the embodiment is tested, and the method specifically comprises the following steps:
fig. 1 shows the XRD pattern of the black coating on the surface of pure copper, wherein the abscissa 2Theta represents 2Theta and the ordinate Intensity represents Intensity in arbitrary units representing relative Intensity. As can be seen from fig. 1, the main phase components of the oxide film formed on the copper metal surface are a copper oxide phase and a cuprous oxide phase, which indicates that a black oxide film mainly composed of the copper oxide phase and the cuprous oxide phase is formed on the copper surface under the micro-arc induction.
Fig. 2 shows a surface micro-topography photograph of a black coating on a pure copper surface, and it can be seen from fig. 2 that the surface topography of the coating is a surface micro-convex topography, which is mainly because the rapid growth of the coating can be promoted under the composite electrolyte and the application of a pulse voltage of more than 600V, and under the action of micro-arc induction, loose micropores and micro-cracks are formed on the pure copper surface first, and as the pulse voltage and current are increased continuously, the discharge energy is increased continuously, the weak point position starts to be punctured, the coating grows in situ, and simultaneously, the oxide layer with loose surface starts to be dissolved and peeled off. In the growth process, a large amount of oxygen bubbles are formed in the composite electrolyte under the action of large current and high temperature, so that the oxide layer continuously expands in volume to form a micro-convex structure.
FIG. 3 is a photograph showing the micro-morphology of the black coating on the surface of pure copper, and it can be seen from FIG. 3 that the black coating is prepared on the surface of copper metal in one step, and the thickness of the coating reaches 50 μm.
Fig. 4 shows the reflectance value of the black coating on the surface of pure copper, and as can be seen from fig. 4, the reflectance of the black coating is as low as 3.88%, and the solar light absorption rate is as high as 95% or more, which indicates that the coating has strong solar light absorption capacity and light-heat conversion efficiency.
Fig. 5 is a physical graph of the contact angle of the black coating on the surface of pure copper and a schematic diagram of the static contact angle. As can be seen from fig. 5, the contact angle of the coating surface is greater than 100 °, and the coating has excellent hydrophobicity.
Fig. 6 is a polarization curve of a black coating on a pure copper surface. Wherein the abscissa is corrosion current, and the unit is A--2The ordinate is the corrosion potential in volts V. From the comprehensive view of corrosion potential, corrosion current and polarization resistance, the corrosion resistance of the black coating is higher than that of a copper matrix, and the large-scale high-efficiency application of copper in the field of solar photo-thermal conversion is effectively expanded.
Comparative example 1
The embodiment provides a method for preparing a coating on a copper surface, which comprises the following steps:
1.1' selecting pure copper as a substrate, polishing by using 800 and 1200# abrasive paper in sequence, then carrying out ultrasonic treatment for 20min by using absolute ethyl alcohol, cleaning by using distilled water, and drying;
1.2', mechanically and uniformly stirring 18g/L sodium hexametaphosphate and 2g/L sodium borate to prepare a basic electrolyte;
1.3' taking a stainless steel plate or a stainless steel pool as a cathode, taking pure copper as an anode, applying 400V pulse voltage to two ends of an electrolytic tank, controlling the solution temperature of the composite electrolyte to be 30 ℃, and carrying out micro-arc discharge reaction for 30min under the condition of stirring to obtain a black coating;
the black coating prepared on the surface of the pure copper in the embodiment is tested, and the method specifically comprises the following steps:
fig. 7 is a surface micro-topography photograph of a black coating on the surface of pure copper, and it can be seen from fig. 7 that loose pores and large cracks are formed on the surface of the coating, and the length of the cracks is long. The results show that under the conditions of basic electrolyte without adding alcohol such as ethanol and the like and low pulse voltage (400V), the coating is continuously dissolved and peeled off in the growth process, and the regrowth process is not carried out, so that the coating is loose and has more defects.
FIG. 8 is a photograph showing the micro-topography of the black coating on the surface of pure copper, and it can be seen from FIG. 8 that the thickness of the coating is less than 20 μm. Indicating that the growth rate of the coating is low and the growth is unstable. Meanwhile, the coating is loose and not compact, which indicates that the low voltage and the basic electrolyte can lead the growth of the coating to be not compact, especially the low voltage leads the growth rate of the coating to be lower, and leads the coating not to grow compactly.
The black coating prepared on the surface of pure copper in the embodiment has the reflectivity of 4.07 percent and the sunlight absorption capacity is lower than that of the black coating prepared in the embodiment 1.
Example 2
The embodiment provides a method for preparing a coating on the surface of a copper alloy, which comprises the following steps:
2.1 selecting copper alloy as a substrate, polishing with 800# and 1200# abrasive paper in sequence, then ultrasonically cleaning with absolute ethyl alcohol for 10min, cleaning with distilled water, and drying;
2.2 mechanically and uniformly stirring 12g/L sodium hexametaphosphate and 12g/L sodium borate to prepare a basic electrolyte;
2.3, adding anhydrous ethanol with the volume fraction of 20% and glycerol with the volume fraction of 40% into the basic electrolyte, and carrying out ultrasonic treatment for 15min to prepare the stable micro-arc induced composite electrolyte;
and 2.4, taking a stainless steel plate or a stainless steel pool as a cathode, taking pure copper as an anode, applying 650V pulse voltage (constant voltage mode) to two ends of the electrolytic bath, controlling the solution temperature of the composite electrolyte to be 30 ℃, and carrying out micro-arc discharge reaction for 20min under the stirring condition to obtain the black coating with the micro-protrusion structure.
The surface appearance of the black coating prepared on the surface of the copper alloy is formed by a micro-convex structure, the thickness of the coating can reach 45 mu m, the reflectivity is 4.35%, the black coating has strong sunlight absorption capacity and photo-thermal conversion efficiency, the contact angle is larger than 100 degrees, the black coating has excellent hydrophobicity, the corrosion resistance of the black coating is higher than that of a copper alloy matrix, and the large-scale high-efficiency application of the copper alloy material in the field of solar photo-thermal conversion is effectively expanded.
Example 3
The embodiment provides a method for preparing a coating on a copper surface, which comprises the following steps:
3.1, selecting pure copper as a substrate, polishing by using 800 and 1200# abrasive paper in sequence, then ultrasonically cleaning for 10-20min by using absolute ethyl alcohol, cleaning by using distilled water, and drying;
3.2, mechanically and uniformly stirring 10g/L sodium hexametaphosphate and 10g/L sodium borate to prepare a basic electrolyte;
3.3, adding absolute ethyl alcohol with the volume fraction of 12% and glycerol with the volume fraction of 20% into the basic electrolyte, and carrying out ultrasonic treatment for 10min to prepare the stable micro-arc induced composite electrolyte;
and 3.4, taking a stainless steel plate or a stainless steel pool as a cathode, taking pure copper as an anode, applying 650V pulse voltage (constant voltage mode) to two ends of the electrolytic bath, controlling the solution temperature of the composite electrolyte to be 30 ℃, and carrying out micro-arc discharge reaction for 30min under the stirring condition to obtain the black coating with the micro-protrusion structure.
Example 4
The embodiment provides a method for preparing a coating on a copper surface, which comprises the following steps:
4.1 selecting pure copper as a substrate, polishing by using 800 and 1200# abrasive paper in sequence, then ultrasonically cleaning for 15min by using absolute ethyl alcohol, cleaning by using distilled water, and drying;
4.2, mechanically and uniformly stirring 15g/L sodium hexametaphosphate and 6g/L sodium borate to prepare a basic electrolyte;
4.3, adding absolute ethyl alcohol with the volume fraction of 70% and glycerol with the volume fraction of 30% into the basic electrolyte, and carrying out ultrasonic treatment for 20min to prepare the stable micro-arc induced composite electrolyte;
and 4.4, taking a stainless steel plate or a stainless steel pool as a cathode, taking pure copper as an anode, applying 800V pulse voltage (constant voltage mode) to two ends of the electrolytic bath, controlling the solution temperature of the composite electrolyte to be 40 ℃, and carrying out micro-arc discharge reaction for 40min under the stirring condition to obtain the black coating with the micro-protrusion structure.
Example 5
The embodiment provides a method for preparing a coating on a copper surface, which comprises the following steps:
5.1 selecting copper alloy as a substrate, polishing with 800# and 1200# abrasive paper in sequence, then ultrasonically cleaning with absolute ethyl alcohol for 10min, cleaning with distilled water, and drying;
5.2, mechanically and uniformly stirring 18g/L sodium hexametaphosphate and 4g/L sodium borate to prepare a basic electrolyte;
5.3, adding absolute ethyl alcohol with the volume fraction of 85% and glycerol with the volume fraction of 85% into the basic electrolyte, and carrying out ultrasonic treatment for 25min to prepare the stable micro-arc induced composite electrolyte;
and 5.4, taking a stainless steel plate or a stainless steel pool as a cathode, taking pure copper as an anode, applying 850V pulse voltage (constant voltage mode) to two ends of the electrolytic bath, controlling the solution temperature of the composite electrolyte to be 40 ℃, and carrying out micro-arc discharge reaction for 40min under the stirring condition to obtain the black coating with the micro-protrusion structure.
Example 6
The embodiment provides a method for preparing a coating on a copper surface, which comprises the following steps:
6.1 selecting pure copper as a substrate, polishing by using 800 and 1200# abrasive paper in sequence, then ultrasonically cleaning for 20min by using absolute ethyl alcohol, cleaning by using distilled water, and drying;
6.2 mechanically and uniformly stirring 10g/L sodium hexametaphosphate and 10g/L sodium borate to prepare a basic electrolyte;
6.3, adding absolute ethyl alcohol with the volume fraction of 40% and glycerol with the volume fraction of 60% into the basic electrolyte, and carrying out ultrasonic treatment for 15min to prepare the stable micro-arc induced composite electrolyte;
and 6.4, taking a stainless steel plate or a stainless steel pool as a cathode, taking pure copper as an anode, applying a pulse voltage of 600V (constant voltage mode) at two ends of the electrolytic bath, controlling the solution temperature of the composite electrolyte to be 20 ℃, and carrying out micro-arc discharge reaction for 10min under the stirring condition to obtain the black coating with the micro-protrusion structure.
Although the present disclosure has been described above, the scope of the present disclosure is not limited thereto. Various changes and modifications may be effected therein by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present disclosure, and these changes and modifications are intended to be within the scope of the present disclosure.
Claims (9)
1. A method for preparing a coating on the surface of copper and copper alloy is characterized by comprising the following steps:
taking a stainless steel plate or a stainless steel pool as a cathode, taking copper and copper alloy as an anode, controlling the temperature of the composite electrolyte to be 20-40 ℃, applying pulse voltage of more than 600V between the cathode and the anode, and carrying out pulse discharge reaction on the surface of the copper and the copper alloy so as to form a ceramic coating with a micro-convex structure on the surface of the copper and the copper alloy; wherein the composite electrolyte contains alcohols; the preparation process of the composite electrolyte comprises the following steps: adding ethanol with the volume concentration of 10-100ml/L into a base electrolyte, wherein the base electrolyte comprises sodium hexametaphosphate and sodium borate.
2. The method for preparing the coating on the surface of the copper and the copper alloy as claimed in claim 1, wherein the mass concentration of the sodium hexametaphosphate is 1-20g/L, and the mass concentration of the sodium borate is 1-20 g/L.
3. The method for preparing the coating on the surface of the copper and the copper alloy as claimed in claim 2, wherein the mass concentration ratio of the sodium hexametaphosphate to the sodium borate is 1:1-9: 1.
4. The method for preparing the coating on the surface of the copper and the copper alloy according to claim 1, wherein the preparation process of the composite electrolyte further comprises the following steps: and adding glycerol with the volume concentration of 20-100ml/L into the base electrolyte.
5. The method for preparing the coating on the surface of the copper and the copper alloy according to claim 1, wherein the pulse voltage is 600V-1000V.
6. The method for preparing the coating on the surface of the copper and the copper alloy according to claim 1, wherein the time of the pulse discharge reaction is 3-40 min.
7. The method for preparing the coating on the surface of the copper and the copper alloy according to claim 1, which further comprises the following steps before the pulse discharge reaction is carried out: and polishing the surfaces of the copper and the copper alloy by using sand paper, ultrasonically cleaning by using absolute ethyl alcohol, cleaning by using distilled water, and drying.
8. A copper product, comprising copper and its alloy, and a ceramic coating formed on the surface of the copper and its alloy, wherein the ceramic coating is prepared by the method for preparing a coating on the surface of copper and its alloy as claimed in any one of claims 1 to 7.
9. The copper article according to claim 8, characterised in that the ceramic coating has a thickness of 10-60 μm.
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