CN110241374B - Nano-zinc oxide doped coating and preparation method and application thereof - Google Patents
Nano-zinc oxide doped coating and preparation method and application thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
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- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
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Abstract
The invention discloses a doped nano zinc oxide coating, a preparation method and application thereofThe coating comprises a nano ZnO framework and nano Zn coated on the outer surface layer of the nano ZnO framework1‑xMxAn O layer; the nano ZnO framework has a loose porous structure; the nano Zn1‑xMxThe O layer is in a fine velvet shape and is made of superfine nano Zn1‑xMxO particles are assembled to form the superfine nano Zn1‑xMxThe particle size of the O particles is 10-50 nm; m is at least one element selected from Cu, Fe, Mn, Al and Sn, and x is 0.005-0.1.
Description
Technical Field
The invention relates to the technical field of zinc oxide coatings, in particular to a doped nano zinc oxide coating and a preparation method and application thereof.
Background
With the rapid development of urbanization and industrialization, human activities generate a great deal of pollution, which causes serious atmospheric environmental pollution. On one hand, with the continuous expansion of industrial production scale, the number of motor vehicles is increased, the urban development and infrastructure construction are continuously promoted, and a large amount of primary pollutants such as nitrogen oxides, sulfur compounds, organic pollutants, particulate matters and the like are discharged into the atmosphere; on the other hand, a large amount of secondary pollutants are generated after various gas pollutants are subjected to a complex physical and chemical process in an atmospheric environment, so that regional atmospheric pollution is caused.
In the indoor environment, air pollutants mainly comprise Volatile Organic Compounds (VOCs), particles (PM2.5) capable of entering the lung, bacteria and viruses and the like, have the characteristics of wide influence range, long contact time, high pollutant concentration, long pollutant release period and the like, have greater influence on the human body, possibly cause chronic respiratory diseases, lung diseases and cardiopulmonary diseases, and directly harm the health of the human body. The commonly used indoor air purification method mainly comprises a physical adsorption method and a photocatalysis technology, wherein the physical adsorption method adopts porous materials such as activated carbon and the like to adsorb suspended particles and organic matters in the air, and has the problems of slow effect and secondary pollution. The volatile organic compounds can be separated under the condition of illumination by utilizing the photocatalysis technologyDecomposed into CO2And water, and has certain effect of eliminating peculiar smell sources such as oxynitride, sulfur-containing compounds and the like in indoor air.
Generally, ZnO and TiO are used2Wide bandgap semiconductors are typically studied more in the field of photocatalysis. TiO 22The photocatalytic material has the characteristics of high catalytic efficiency under ultraviolet, good chemical stability and relatively lower preparation cost, so the photocatalytic material is most widely applied to the current photocatalytic technology. And ZnO has greater development potential in the field of photocatalysis due to the characteristics of higher quantum efficiency, wider light absorption range and wider raw material source. However, the effect of the existing photocatalyst is limited by various factors such as small light absorption range, insufficient self-catalytic activity, effective load of the photocatalyst and the like; in addition, compared with the purification of water, the purification of indoor polluted air has the characteristics of high pollutant concentration, multiple pollution types, slow pollutant adsorption-desorption and the like, so that the purification has greater difficulty.
Chinese patent publication No. CN 108970601a discloses a photocatalytic coating with a zinc oxide/titanium dioxide heterostructure, and a preparation method and applications thereof. The photocatalytic coating comprises a ZnO cluster formed by stacking nanometer ZnO grains with the diameter of 10-50nm and nanometer TiO embedded in the ZnO cluster2Particles; the ZnO cluster is in a cluster structure, has a loose porous structure and has a diameter of 3-30 mu m. The photocatalytic coating disclosed by the technical scheme utilizes the coupling and synergistic effect of two wide-bandgap semiconductor materials of zinc oxide and titanium dioxide, has a larger spectral absorption range and a lower approximate bandgap width, but the lowest value of the approximate bandgap width can only reach 2.80 eV.
Disclosure of Invention
Aiming at the problems in the prior art, the invention discloses a doped nano zinc oxide coating, which has better photocatalytic performance and is further applied to the field of air purification by forming a special morphology structure in the coating and combining the doping of metal elements such as copper and the like, thereby obviously reducing the approximate band gap width of the coating and obviously enhancing the generation and separation of photo-generated electron-hole pairs.
The specific technical scheme is as follows:
a nano-zinc oxide doped coating comprises a substrate and a coating deposited on the substrate, wherein the coating comprises a nano ZnO framework and nano Zn coated on the outer surface layer of the nano ZnO framework1-xMxAn O layer;
the nano ZnO framework has a loose porous structure;
the nano Zn1-xMxThe O layer is in a fine velvet shape and is made of superfine nano Zn1-xMxO particles are assembled to form the superfine nano Zn1-xMxThe particle size of the O particles is 10-50 nm;
m is at least one of elements Cu, Fe, Mn, Al and Sn, and x is 0.005-0.1.
The "fine fluff" in the invention refers to a layer of fine particle clusters which are uniformly spread.
The invention discloses a novel doped nano zinc oxide coating, which has a novel microstructure, takes a nano ZnO assembly structure formed by the modification of a surfactant and a binder as a protruded porous framework, uniformly coats spherical nano particles on the surface layer, and has rich pores among particles.
Preferably, the pore diameter of the nanometer ZnO framework is 1-20 μm.
Preferably, M is selected from the element Cu, and x is 0.01-0.1; the superfine nano Zn1-xMxThe particle size of the O particles is 10-20 nm.
Preferably, the thickness of the coating is 5-20 μm.
Through Tauc model fitting calculation, the doped nano zinc oxide coating with the composition and the special morphology has the approximate band gap width of 2.32-3.03 eV.
The invention also discloses a preparation method of the doped nano zinc oxide coating, which comprises the following steps:
(1) mixing zinc salt, doped metal M salt and a solvent to obtain a mixed solution, adjusting the pH value of the mixed solution to be weakly acidic, and adding a surfactant, a binder and nano zinc oxide powder particles to obtain a spraying raw material;
(2) and spraying the spraying raw material to the surface of a base material by a plasma spraying process to prepare the doped nano zinc oxide coating.
In the suspension spraying process, as the melting point of ZnO is far higher than the temperature of Zn salt for pyrolytic reaction, the metal salt (zinc salt and doped metal salt) solution added in the liquid material is atomized and then crushed into small-sized liquid drops, and the processes of solvent evaporation, solute precipitation, pyrolysis, nucleation, crystallization and the like are carried out, so that the Zn with superfine nanometer size is finally obtained1- xMxAnd O. And for the nano ZnO particles dispersed in the liquid material, the nano ZnO particles are sent to the center of a plasma arc in the form of clusters with different sizes, the solvent evaporation-solid phase particle heating process happens immediately, and the surfactant and the binder added in the liquid material further enter the interior of the cluster structure. And as the surface of the cluster is gradually melted due to high temperature, ZnO nano powder particles are continuously transferred from the center to the surface, and a hard sintered shell is gradually formed. Meanwhile, the added ZnO nanoparticles are gradually assembled into a hollow spherical shell structure due to the blowing effect caused by thermal decomposition of the surfactant and the binder under the high-temperature condition. Zn produced by in-situ pyrolysis of metal salt solutions1- xMxThe O superfine particles are attached to the surface of the spherical shell with the surface in a semi-molten state in the subsequent process, and are taken as nucleation sites, the processes of spherical shell collision, crushing and particle accumulation forming are carried out, and finally the surface of the obtained coating is covered with Zn1-xMxAnd O ultrafine nanoparticles.
In the step (1):
the zinc salt is selected from soluble salts of zinc, such as common salts of zinc nitrate, zinc acetate, zinc chloride and the like.
The doped metal M salt is selected from soluble salts of the doped metal M, such as acetate, chloride, nitrate and other common salts.
Preferably, the zinc salt and the doping metal M salt are chosen to be the same anion to avoid introducing too much impurities.
Preferably:
the molar ratio of the zinc salt to the doped metal M salt is 5-1000: 1; further preferably: the molar ratio of the zinc salt to the doped metal M salt is 9-99: 1.
the total concentration of the metal salt in the mixed solution is 0.1-1 mol/L. The metal salt comprises zinc salt and doped metal M salt.
In the step (1):
the solvent is selected from a mixed solvent consisting of ethanol and water; preferably, the volume ratio of the ethanol to the water is 1-4: 1; further preferably mixed in equal volumes.
Preferably, adjusting the pH value of the mixed solution to 4-6; in particular, it can be adjusted by adding an acidic substance, preferably the same anion of the acid as the zinc salt and the doping metal M salt, to avoid introducing excessive impurities.
If the zinc salt and the doped metal M salt are both acetates, glacial acetic acid can be added to adjust the pH value of the mixed solution.
In the step (1):
the surfactant is selected from at least one of polyethylene glycol, polyacrylic acid and ammonium citrate;
the binder is selected from at least one of polyvinylpyrrolidone, polyvinyl alcohol and polyacrylamide;
the particle size of the nano zinc oxide powder particles is 10-100 nm;
the mass ratio of the surfactant to the binder to the nano zinc oxide powder particles is 5-50: 5-50: 100, respectively;
the molar ratio of the zinc salt to the nano zinc oxide powder particles is 100: 5 to 50.
Still more preferably:
the molar ratio of the zinc salt to the doped metal M salt is 9-19: 1;
the total concentration of the metal salt in the mixed solution is 0.1 mol/L;
the mass ratio of the surfactant to the binder to the nano zinc oxide powder particles is 10: 20: 100, respectively;
the molar ratio of the zinc salt to the nano zinc oxide powder particles is 100: 20.
the addition content of the nano zinc oxide powder particles and the use amounts of the surfactant and the binder in the suspension system liquid material are strictly controlled, so that the uniformity of a rough protruding structure and a hollow spherical shell forming process in a microstructure of a finally prepared coating can be guaranteed.
More preferably: the molar ratio of the zinc salt to the doped metal M salt is 9: 1;
the total concentration of the metal salt in the mixed solution is 0.1 mol/L;
the mass ratio of the surfactant to the binder to the nano zinc oxide powder particles is 10: 20: 100, respectively;
the molar ratio of the zinc salt to the nano zinc oxide powder particles is 100: 20.
the coating prepared under more preferable process parameters has the advantages of optimal uniformity of the rough protrusion structure in the microstructure and the forming process of the hollow spherical shell, and the band gap width can be as low as 2.323 eV.
In the step (2), the plasma spraying process comprises the following steps:
the spraying current is 400-600A, the spraying voltage is 450-600, the flow of the spraying raw materials is 30-120 ml/min, the spraying distance is 6-10 mm, the transverse speed of a plasma gun is 100-1000 mm/min, and the spraying frequency is 3-10 times.
In general, the nano powder is difficult to accelerate by carrier gas in the spraying process due to small size and light weight, and is easy to agglomerate to block powder feeding and difficult to directly deposit. In addition, the nano powder has large specific surface area and high powder activity, and the nano crystal grains are easy to coarsen and lose the original nano characteristic under the thermal action in the spraying process. In order to overcome the difficulties, the invention adopts a liquid material feeding mode, nano powder particles are prepared into suspension or are generated in a precursor solution in-situ pyrolysis reaction process to be indirectly sent into a plasma arc flame, under the load and protection action of a solvent, the nano particles generate a series of physical-chemical processes similar to powder spraying, and finally are deposited to form the nano-structure coating.
Specifically, the zinc salt doped with metal is used as a raw material for coating preparation, and the links of nano powder preparation and coating forming are integrated, so that the complicated link of nano powder synthesis is avoided, and the processes of nano powder grain coarsening and loss in the powder spraying process can be avoided. In addition, the addition of the nano particles is beneficial to the formation of a micro-nano porous structure coating, and the coating has a larger specific surface area and an integral structure and is beneficial to the adsorption of polluted gas.
The doped nano zinc oxide coating prepared by the process has a special micro-morphology, is doped with metal elements such as copper and the like, obviously reduces the approximate band gap width of the coating, and obviously enhances the generation and separation of photo-generated electron-hole pairs, so that the doped nano zinc oxide coating can be applied to the field of air purification.
Compared with the prior art, the invention has the beneficial effects that:
the invention discloses a doped nano zinc oxide coating prepared by a plasma spraying process, which constructs a porous ZnO framework with a convex structure and superfine nano Zn through the preparation and component control of a suspension precursor liquid material and the plasma spraying process of liquid material feeding1-xMxAnd O, coating structure of the fine velvet layer. The coating is loose, the framework and the surface layer have rich pores, and the interface of the nanometer powder particles with a larger proportion and the in-situ synthesized superfine nanometer particles is provided, which is beneficial to the adsorption process of air pollutants. The superfine nano Zn on the surface of the coating1-xMxThe O layer has a lower band gap width, expanding the wavelength range in which light can be absorbed. On the basis of the special morphology, a proper amount of metal ions are doped, and the separation of photoproduction electrons and holes in the photocatalytic reaction process is further facilitated under the dual functions of morphology regulation and component regulation, so that the reaction efficiency of the photocatalyst on gas pollutants is improved.
Drawings
FIG. 1 is a schematic view of the preparation process of the doped nano-zinc oxide coating of the present invention;
FIG. 2 is an XRD spectrum of the ZnO doped Cu coating in examples 1-3 and comparative example 1;
FIG. 3 is SEM images of the surfaces (a-c) and sections (d) of the ZnO-doped Cu coating in example 1;
FIG. 4 shows the UV-visible diffuse reflection absorption spectrum (a) and Tauc curves of the ZnO doped coatings and the corresponding band gap widths (b) in examples 1-3 and comparative example 1;
FIG. 5 shows the room temperature photoluminescence spectra (325nm) of the ZnO-doped Cu coatings in examples 1 to 3 and comparative example 1.
Detailed Description
The present invention will be described in further detail with reference to examples, but the embodiments of the present invention are not limited thereto.
Example 1
In this example, the substrate material was a 316L stainless steel sheet with a thickness of 1.5mm, the thickness of the ZnO coating on the substrate was about 15 μm, and the coating was loose ZnO cluster particles and fine nano Zn in the form of fine velvet on the surface thereof0.99Cu0.01The O particles are arranged in a stacking way. In the embodiment, zinc acetate-copper acetate solution doped with 5% of molar ratio and zinc oxide nano powder particles suspended in mixed metal salt solution are used as liquid materials, and after a plasma spraying process, the nano zinc oxide particles are in a loose and porous cluster structure in a coating layer, and the surface of the nano zinc oxide particles is coated with a fine velvet layer consisting of Cu-doped nano ZnO particles with the diameter of 10-20 nm. The preparation flow of the ZnO coating of the structural coating is shown in figure 1, and the specific preparation method is as follows:
1. firstly, commercial Zn (CH)3COO)2·2H2O and Cu (CH)3COO)2Adding the mixed solution into a solvent with the volume ratio of absolute ethyl alcohol to deionized water of 99:1, uniformly stirring to prepare 0.5mol/L mixed metal salt solution, adjusting the pH value of the zinc acetate solution to about 6 by glacial acetic acid, adding surfactant polyethylene glycol (PEG400) and binder polyvinylpyrrolidone (PVP) which respectively account for 10 wt% and 20% of the mass of the nano ZnO powder into the mixed metal salt solution after the solution is clarified (adding PEG and PVP firstly), then adding nano zinc oxide powder accounting for 20% of the molar ratio of the zinc acetate, and dispersing and uniformly stirring under an ultrasonic condition to obtain a suspension, namely a spraying raw material;
2. carrying out sand blasting treatment on a stainless steel substrate by using 60-mesh brown corundum sand, roughening the surface, sequentially washing and removing oil by using acetone, absolute ethyl alcohol and deionized water under the compressed air pressure of about 0.5MPa, and finally blowing off the surface of the substrate by using compressed air;
3. adopts a plasma spray gun radial feeding mode, and a certain amount of liquid material passes through the peristaltic pump
And the nozzle is vertically fed into the root of the flame flow. The liquid material is atomized, broken, evaporated, concentrated, precipitated, sintered, melted and solidified under the action of plasma flame flow at high temperature and high speed, and a coating with the thickness of about 20 mu m is formed on the surface of a substrate. Wherein, the plasma spraying gun has the following spraying parameters: the current is 500A, the voltage is 50V, the flow rate of the spraying liquid material is 100mL/min, the spraying distance is 80mm, the transverse speed of the plasma gun is 400mm/s, and the spraying times of the coating are 3 times.
Comparative example 1
In this comparative example, a substrate material was selected as 316L stainless steel sheet having a thickness of 1.5mm, the ZnO coating thickness on the substrate was about 20 μm, and the coating was obtained by stacking loose ZnO cluster particles and fine-velvet nanoparticles on the surface thereof. In the embodiment, zinc acetate solution and zinc oxide nano powder particles in uniformly dispersed solution are used as liquid materials, and after a plasma spraying process, the zinc oxide nano particles are in a loose and porous cluster structure in a coating layer, and the surface of the coating layer is coated with a fine velvet layer consisting of nano ZnO particles with the diameter of 10-20 nm. The preparation method comprises the following steps:
1. firstly, commercial Zn (CH)3COO)2·2H2Adding O into a solvent with the volume ratio of absolute ethyl alcohol to deionized water, uniformly stirring to prepare a 0.5mol/L zinc acetate solution, adjusting the pH value of the zinc acetate solution to about 6 by using glacial acetic acid, adding a surfactant polyethylene glycol (PEG400) and a binder polyvinylpyrrolidone (PVP) which respectively account for 10 wt% and 20% of the mass of the nano ZnO powder into the zinc acetate solution (adding PEG and PVP firstly) after the solution is clarified, then adding the nano zinc oxide powder accounting for 20% of the molar ratio of the zinc acetate, and dispersing and uniformly stirring under an ultrasonic condition to obtain a suspension, namely a spraying raw material;
2. carrying out sand blasting treatment on a stainless steel substrate by using 60-mesh brown corundum sand, roughening the surface, sequentially washing and removing oil by using acetone, absolute ethyl alcohol and deionized water under the compressed air pressure of about 0.5MPa, and finally blowing off the surface of the substrate by using compressed air;
3. adopts a plasma spray gun radial feeding mode, and a certain amount of liquid material passes through the peristaltic pump
And the nozzle is vertically fed into the root of the flame flow. The liquid material is atomized, broken, evaporated, concentrated, precipitated, sintered, melted and solidified under the action of plasma flame flow at high temperature and high speed, and a coating with the thickness of about 20 mu m is formed on the surface of a substrate. Wherein, the plasma spraying gun has the following spraying parameters: the current is 500A, the voltage is 50V, the flow rate of the spraying liquid material is 100mL/min, the spraying distance is 80mm, the transverse speed of the plasma gun is 400mm/s, and the spraying times of the coating are 3 times.
Example 2
In this example, the substrate material was a 316L stainless steel sheet with a thickness of 1.5mm, the thickness of the ZnO coating on the substrate was about 15 μm, and the coating was loose ZnO cluster particles and fine nano Zn in the form of fine velvet on the surface thereof0.95Cu0.05The O particles are arranged in a stacking way. In the embodiment, zinc acetate-copper acetate solution doped with 5 mol% and zinc oxide nano powder particles suspended in the solution are used as liquid materials, and after a plasma spraying process, the zinc oxide particles are in a loose and porous cluster structure in a coating layer, and the surface of the zinc oxide particles is coated with a fine pile layer consisting of Cu-doped nano ZnO particles with the diameter of 10-20 nm. The preparation flow of the ZnO coating of the structural coating is shown in figure 1, and the specific preparation method is as follows:
1. firstly, commercial Zn (CH)3COO)2·2H2O and Cu (CH)3COO)2Adding the mixed solution into a solvent with the volume ratio of absolute ethyl alcohol to deionized water of 19:1, uniformly stirring to prepare a mixed metal salt solution with the volume ratio of 0.5mol/L, adjusting the pH value of the zinc acetate solution to about 6 by glacial acetic acid, adding a surfactant polyethylene glycol (PEG400) and a binder polyvinylpyrrolidone (PVP) which respectively account for 10 wt% and 20% of the mass of the nano ZnO powder into the mixed metal salt solution after the solution is clarified (adding PEG and PVP firstly), then adding the nano zinc oxide powder accounting for 20% of the molar ratio of the zinc acetate, and carrying out ultrasonic treatment on the mixed metal salt solutionDispersing and uniformly stirring to obtain a suspension, namely the spraying raw material;
2. carrying out sand blasting treatment on a stainless steel substrate by using 60-mesh brown corundum sand, roughening the surface, sequentially washing and removing oil by using acetone, absolute ethyl alcohol and deionized water under the compressed air pressure of about 0.5MPa, and finally blowing off the surface of the substrate by using compressed air;
3. adopts a plasma spray gun radial feeding mode, and a certain amount of liquid material passes through the peristaltic pump
And the nozzle is vertically fed into the root of the flame flow. The liquid material is atomized, broken, evaporated, concentrated, precipitated, sintered, melted and solidified under the action of plasma flame flow at high temperature and high speed, and a coating with the thickness of about 20 mu m is formed on the surface of a substrate. Wherein, the plasma spraying gun has the following spraying parameters: the current is 500A, the voltage is 50V, the flow rate of the spraying liquid material is 100mL/min, the spraying distance is 80mm, the transverse speed of the plasma gun is 400mm/s, and the spraying times of the coating are 3 times.
Example 3
In this example, the substrate material was a 316L stainless steel sheet with a thickness of 1.5mm, the thickness of the ZnO coating on the substrate was about 15 μm, and the coating was loose ZnO cluster particles and fine nano Zn in the form of fine velvet on the surface thereof0.9Cu0.1The O particles are arranged in a stacking way. In the embodiment, zinc acetate-copper acetate solution doped with 5 mol% and zinc oxide nano powder particles suspended in the solution are used as liquid materials, and after a plasma spraying process, the zinc oxide nano particles are in a loose and porous cluster structure in a coating layer, and the surface of the coating layer is coated with a fine pile layer consisting of Cu-doped nano ZnO particles with the diameter of 10-20 nm. The preparation flow of the ZnO coating of the structural coating is shown in figure 1, and the specific preparation method is as follows:
1. firstly, commercial Zn (CH)3COO)2·2H2O and Cu (CH)3COO)2Adding the mixture into a solvent with the volume ratio of absolute ethyl alcohol to deionized water being equal to that of absolute ethyl alcohol to be equal to that of deionized water in a molar ratio of 9:1, uniformly stirring the mixture to prepare a mixed metal salt solution with the concentration of 0.5mol/L, adjusting the pH value of the zinc acetate solution to about 6 by using glacial acetic acid, and respectively accounting for the zinc acetate solution after the solution is clarifiedAdding surfactant polyethylene glycol (PEG400) and binder polyvinylpyrrolidone (PVP) which account for 10 wt% and 20% of the mass of the nano ZnO powder into mixed metal salt solution (adding PEG and PVP firstly), then adding nano zinc oxide powder accounting for 20% of the molar ratio of zinc acetate, and dispersing and uniformly stirring under an ultrasonic condition to obtain a suspension, namely a spraying raw material;
2. carrying out sand blasting treatment on a stainless steel substrate by using 60-mesh brown corundum sand, roughening the surface, sequentially washing and removing oil by using acetone, absolute ethyl alcohol and deionized water under the compressed air pressure of about 0.5MPa, and finally blowing off the surface of the substrate by using compressed air;
3. adopts a plasma spray gun radial feeding mode, and a certain amount of liquid material passes through the peristaltic pump
And the nozzle is vertically fed into the root of the flame flow. The liquid material is atomized, broken, evaporated, concentrated, precipitated, sintered, melted and solidified under the action of plasma flame flow at high temperature and high speed, and a coating with the thickness of about 20 mu m is formed on the surface of a substrate. Wherein, the plasma spraying gun has the following spraying parameters: the current is 500A, the voltage is 50V, the flow rate of the spraying liquid material is 100mL/min, the spraying distance is 80mm, the transverse speed of the plasma gun is 400mm/s, and the spraying times of the coating are 3 times.
The products prepared in the above embodiments are subjected to phase analysis, microscopic morphology observation and coating surface element distribution test, and the test method and results are as follows:
1. phase analysis: and (4) flatly placing the coating sample to be flush with the sample stage, and detecting the crystal structure of the coating sample by using an X-ray diffractometer.
Compared with the comparative examples in examples 1-3, the sprayed product is single-phase wurtzite phase ZnO, and because the coating is thin, an austenite peak belonging to a stainless steel matrix appears in an X-ray diffraction pattern. With the increase of the Cu doping content in the sample, the peak shape of ZnO does not generate obvious shift, and no second phase is generated, which indicates that Cu ions are successfully doped into ZnO crystal lattices.
2. And (3) microstructure analysis: and (3) taking a coating sample, fixing the coating sample on a sample table by using conductive adhesive, spraying Au, and observing the microstructure of the coating surface or section by using a field emission scanning electron microscope.
From SEM microscopic morphology, it can be found that the 1% Cu-doped ZnO coating still presents a convex and loose dual-mode structure, and fine nano-particles are uniformly distributed on a porous network structure. The observation on the cross section shows that the coating deposition is more uniform, and the local area close to the matrix has a certain degree of sintering densification phenomenon.
3. Coating spectral absorption curve: taking a coating sample, fixing the coating sample on a sample rack, and coating with BaSO4And (3) as a background, testing the absorbance of the coating with the wavelength within the range of 200-800 nm, and performing fitting calculation according to a Tauc model to obtain the approximate band gap width of the coating.
As the Cu doping content increases, the absorbance of the coating in the visible range increases significantly with a concomitant red-shift of the absorption edge. Further according to the results of the Tacu curve fitting, it can be known that the band gap width of the Cu-doped coating is gradually reduced from 3.03eV in comparative example 1 to 2.32eV in example 3, and the corresponding absorption wavelength is increased accordingly.
4. Coating room temperature photoluminescence spectrum: and collecting a photoluminescence spectrum of the surface of the coating of the measured sample by using a 325nm He-Cd laser as a laser source.
The fluorescence curve in comparative example 1 has a high intensity and fluorescence peaks occur in both the ultraviolet region and the visible region, indicating that the ratio of fluorescence signals generated by photo-generated electron-hole recombination in the coating is large. And with the increase of the Cu doping content, the fluorescence curve intensity of the coating is sharply weakened, which shows that the electron-hole recombination proportion is reduced, the separation efficiency is improved due to the function of impurity energy level introduced by doping, and the photocatalytic reaction is favorably carried out.
Claims (10)
1. The nano-zinc oxide doped coating comprises a substrate and is characterized by also comprising a coating deposited on the substrate, wherein the coating comprises a nano ZnO framework and nano Zn coated on the outer surface layer of the nano ZnO framework1-xMxAn O layer;
the nano ZnO framework has a loose porous structure;
the nanometer isZn1-xMxThe O layer is in a fine velvet shape and is made of superfine nano Zn1-xMxO particles are assembled to form the superfine nano Zn1- xMxThe particle size of the O particles is 10-50 nm;
m is at least one element selected from Cu, Fe, Mn, Al and Sn, and x is 0.005-0.1.
2. The doped nano zinc oxide coating of claim 1, wherein the pore diameter of the nano ZnO framework is 1-20 μm.
3. The doped nano zinc oxide coating according to claim 1, wherein M is selected from the group consisting of Cu, x is 0.01 to 0.1;
the superfine nano Zn1-xMxThe particle size of the O particles is 10-20 nm.
4. The doped nano zinc oxide coating according to claim 1, wherein the thickness of the coating is 5-20 μm.
5. The preparation method of the doped nano zinc oxide coating according to any one of claims 1 to 4, characterized by comprising the following steps:
(1) mixing zinc salt, doped metal M salt and a solvent to obtain a mixed solution, adjusting the pH value of the mixed solution to be weakly acidic, and adding a surfactant, a binder and nano zinc oxide powder particles to obtain a spraying raw material;
(2) and spraying the spraying raw material to the surface of a base material by a plasma spraying process to prepare the doped nano zinc oxide coating.
6. The method for preparing doped nano zinc oxide coating according to claim 5, wherein in the step (1):
the zinc salt is selected from soluble salts of zinc;
the doped metal M salt is soluble salt of a doped metal M;
the molar ratio of the zinc salt to the doped metal M salt is 5-1000: 1;
the total concentration of the metal salt in the mixed solution is 0.1-1 mol/L.
7. The method for preparing doped nano zinc oxide coating according to claim 5, wherein in the step (1):
the solvent is selected from a mixed solvent consisting of ethanol and water;
the volume ratio of the ethanol to the water is 1-4: 1;
and adjusting the pH value of the mixed solution to 4-6.
8. The method for preparing doped nano zinc oxide coating according to claim 5, wherein in the step (1):
the surfactant is selected from at least one of polyethylene glycol, polyacrylic acid and ammonium citrate;
the binder is selected from at least one of polyvinylpyrrolidone, polyvinyl alcohol and polyacrylamide;
the mass ratio of the surfactant to the binder to the nano zinc oxide powder particles is 5-50: 5-50: 100, respectively;
the molar ratio of the zinc salt to the nano zinc oxide powder particles is 100: 5 to 50.
9. The preparation method of the doped nano zinc oxide coating according to claim 5, wherein in the step (2), the plasma spraying process comprises the following steps:
the spraying current is 400-600A, the spraying voltage is 500-600V, the flow of the spraying raw material is 30-120 mL/min, the spraying distance is 6-10 mm, the transverse speed of the plasma gun is 100-1000 mm/s, and the spraying frequency is 3-10 times.
10. The application of the doped nano zinc oxide coating as claimed in any one of claims 1 to 4 in the field of air purification.
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