Photo-thermal material with antireflection functional coating and preparation method of photo-thermal material

Abstract

The invention belongs to the technical field of material preparation, and particularly relates to a photo-thermal material with an antireflection functional coating and a preparation method of the photo-thermal material. Micron-scale or nano-scale magnetic particles are used as inner cores, and inorganic materials with an antireflection function are used as functional coatings to be coated on the surfaces of the magnetic particles; wherein the functional coating is a metal oxide or a non-metal oxide with a function of inhibiting light reflection. The method is easy and convenient to operate and mild in reaction condition, the coating of the prepared material has an antireflection effect, energy loss of a diffuse reflection form on the surface of the material in the photo-thermal conversion process can be reduced, and high energy conversion efficiency is shown. Besides, the chemical property of the coating material is relatively stable, so that the prepared composite particles have certain oxidation resistance, and can be widely applied to the fields of coatings, water treatment chemical industry and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation, and particularly relates to a photothermal material with an antireflection functional coating and a preparation method thereof. Background Art

[0002] Photothermal materials are a class of materials that convert absorbed light energy into heat energy. With the continuous in-depth research on the photothermal effect, photothermal materials are increasingly widely used in the fields of chemical engineering, energy, sensing, and life health, and have become a new type of material that cannot be ignored in the field of materials science research. Among them, black magnetic micro-nano materials, including permanent magnet alloys and iron oxides, have excellent photothermal effects due to their relatively narrow band gaps.

[0003] At present, magnetic micro-nano materials have been applied to the research of solar interfacial evaporation technology for seawater desalination to solve the problem of freshwater shortage. This technology can efficiently convert solar energy into heat energy through photothermal materials and confine the generated heat on the surface of water to rapidly heat the water to generate water vapor. However, during the process of solar interfacial evaporation, part of the light is reflected on the surface of the material and cannot be effectively utilized. According to the Fresnel formula, adding an intermediate layer with a refractive index between air and the material can reduce the overall reflection loss of the material. However, at present, some antireflection coatings do not have good thermal stability and antioxidant properties, and are prone to problems such as failure or deformation in application scenarios with higher temperature and humidity. In addition, some antireflection coatings have problems such as cumbersome preparation methods, harsh requirements, and high costs, and cannot be mass-produced and applied. Summary of the Invention

[0004] The purpose of the present invention is to provide a magnetic photothermal material with an antireflection functional coating and a preparation method thereof.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A preparation method of a photothermal material with an antireflection functional coating uses micron- or nano-scale magnetic particles as the core, and an inorganic material with an antireflection function as the functional coating to coat the surface of the magnetic particles; wherein, the functional coating is a metal oxide or non-metal oxide with the function of suppressing light reflection.

[0007] The functional coating is formed by one or several of magnesium oxide, zinc oxide, and silicon dioxide; wherein, the ratio of the micron- or nano-scale magnetic particles to the substances used to form the functional coating is 1.9 mmol - 3.8 mmol: 0.9 mmol - 1.8 mmol.

[0008] The magnetic micro-nano materials mainly include black permanent magnet alloys and iron oxides, specifically including iron-chromium-cobalt alloys, magnetite, strontium ferrite, and perovskite-type lanthanum-strontium-cobalt-iron oxides.

[0009] Furthermore, by using the sol-gel method, micron- or nano-scale magnetic particles are dispersed in a solution. After dispersion, a precursor substance of the functional coating is added to the system, and under stirring conditions, the precursor substance undergoes hydrolysis and polymerization reactions in the magnetic particle suspension to form metal or non-metal oxides, and the formed substances uniformly coat the surfaces of the micron- or nano-scale magnetic particles.

[0010] Specifically:

[0011] (1) Dispersed micron- or nano-scale magnetic particles into dilute hydrochloric acid, and then washed with water until the pH value of the washing solution is between 5 and 7;

[0012] (2) Dispersed the washed magnetic microparticles in deionized water and / or ethanol solution, and stirred to make the particles uniformly dispersed;

[0013] (3) While maintaining stirring, a catalyst and a precursor substance for forming the functional coating are successively added to the mixed system in which the magnetic nanoparticles are dispersed. Under stirring conditions, the precursor substance undergoes hydrolysis and polymerization reactions in the magnetic particle suspension to form metal or non-metal oxides, and the formed substances uniformly coat the surfaces of the micron- or nano-scale magnetic particles. After post-treatment of the reaction, a magnetic photothermal material with an antireflection functional coating is obtained.

[0014] In step (1), the micron- or nano-scale magnetic particles are ultrasonically dispersed into dilute hydrochloric acid at room temperature for 10 min - 20 min; among them, the concentration of the dilute hydrochloric acid is 0.1 - 0.2 mol / L.

[0015] The washed magnetic microparticles in step (2) are ultrasonically dispersed in deionized water and / or ethanol solution at room temperature for 20 min - 30 min; among them, 0.3 g - 0.6 g of the washed magnetic microparticles are washed with every 50 mL - 100 mL of deionized water and / or ethanol solution.

[0016] When the solution is a mixed solution of deionized water and ethanol, the volume ratio of deionized water to ethanol is 1:4 - 1:2.

[0017] In step (3), a catalyst for promoting the formation of the functional coating substance is added to the mixed system in which the magnetic nanoparticles are dispersed, and high-speed mechanical stirring is continued at room temperature; under stirring conditions, a precursor substance for forming the functional coating is added, and high-speed mechanical stirring of the mixed solution is continued at room temperature to carry out the reaction to form metal or non-metal oxides and uniformly coat the surfaces of the micron- or nano-scale magnetic particles. After post-treatment of the reaction, a magnetic photothermal material with an antireflection functional coating is obtained; among them, the final dosage of the catalyst in the system is 0.01 mol - 0.02 mmol.

[0018] When adding the catalyst, the stirring speed is 500 - 600 r / min and the stirring time is 30 min; when adding the precursor substance, the stirring speed is 500 - 600 r / min and the stirring time is 12 - 24 h.

[0019] In the above description, when forming magnesium oxide, the catalyst can be ammonia water; the corresponding precursor substance is magnesium nitrate hexahydrate;

[0020] When forming zinc oxide, the catalyst can be sodium hydroxide; the corresponding precursor substance is zinc acetate;

[0021] When forming silicon dioxide, the catalyst can be ammonia water; the corresponding precursor substance is tetraethyl orthosilicate.

[0022] After the reaction in step (3) ends, the product is separated from the solution by attracting the product with a magnet, and washed with anhydrous ethanol and deionized water respectively. After washing, it is dried in a vacuum drying oven at 60 - 70 °C for 12 - 24 h to obtain a photothermal material with an antireflection functional coating.

[0023] A magnetic photothermal material with an antireflection functional coating prepared by the described method: The material prepared by the described method appears black under natural light. The powdery solid is a magnetic photothermal material with an antireflection functional coating. When a magnet approaches, it can move quickly and has good magnetic response ability.

[0024] The present invention uses the antireflection and stability of magnesium oxide, zinc oxide, and silicon dioxide to prepare magnetic micro-nanoparticles with an antireflection coating, which can improve the light absorption and antioxidant properties of the material. In addition, solid-liquid separation of the material can be carried out through an external magnetic field, which is beneficial to the recycling and reuse of the material.

[0025] The present invention has the following advantages and positive effects:

[0026] The present invention coats a magnetic micro-nanomaterial with an antireflection functional coating, which reduces light reflection loss while protecting the stability of the core magnetic material; specifically:

[0027] 1. The present invention uses magnesium oxide, zinc oxide, and silicon dioxide as the antireflection functional coating, which has good antireflection and chemical stability. After coating the corresponding materials on the magnetic micro-nanoparticles, the particles can have good antireflection and improve the light absorption ability.

[0028] 2. The material coated with the coating of the present invention has better chemical stability and is not easily oxidized in an application environment with high humidity and high temperature. In addition, the material has good magnetism, and the material can be recycled and reused through an external magnetic field, reducing costs.

[0029] 3. The magnesium oxide, zinc oxide, and silicon dioxide used in the present invention have good biocompatibility, which enables the composite particles to be easily further bio-functionalized and broadens their application scope in water treatment. At the same time, silicon dioxide is an acidic oxide and does not react with common acids. After coating on the magnetic micro-nano particles, the acid resistance of the composite particles will be improved.

[0030] 4. The preparation process is simple to operate, easy to master, has mild reaction conditions, and is easy to scale up production. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the preparation process of the magnetic photothermal material with an antireflection functional coating provided by the embodiment of the present invention.

[0032] Figure 2 The SEM images of Fe3O4@SiO2 and the original Fe3O4 provided by the embodiment of the present invention are shown; among them, a is commercially available Fe3O4, and b is Fe3O4@SiO2 with SiO2 coated on the outside of Fe3O4.

[0033] Figure 3 It is the XRD pattern of Fe3O4@SiO2 provided by the embodiment of the present invention.

[0034] Figure 4 It is the FTIR-infrared spectra of Fe3O4@SiO2 and the original Fe3O4 provided by the embodiment of the present invention.

[0035] Figure 5 It is the contact angle test diagram of Fe3O4@SiO2 and the original Fe3O4 provided by the embodiment of the present invention; among them, a is commercially available Fe3O4, and b is Fe3O4@SiO2 with SiO2 coated on the outside of Fe3O4.

[0036] Figure 6 It is the diffuse reflection diagram of Fe3O4@SiO2 and the original Fe3O4 provided by the embodiment of the invention in the range of 250 - 2800 nm.

[0037] Figure 7 It is the light absorption diagram of Fe3O4@SiO2 and the original Fe3O4 provided by the embodiment of the invention in the range of 250 - 2800 nm.

[0038] Figure 8 It is the VSM diagram of Fe3O4@SiO2 and the original Fe3O4 provided by the embodiment of the invention at room temperature.

[0039] Figure 9 It is the XRD pattern of the original Fe3O4 before and after heat treatment at 100 °C for 12 h; among them, a is the heat-treated Fe3O4, and b is the non-heat-treated Fe3O4.

[0040] Figure 10 XRD patterns of Fe3O4@SiO2 provided for the invention examples before and after heat treatment at 100 °C for 12 h; wherein, a is Fe3O4@SiO2 after heat treatment, and b is Fe3O4@SiO2 without heat treatment.

[0041] Figure 11 Diffuse reflectance diagrams of the original Fe3O4 before and after heat treatment at 100 °C for 12 h in the range of 250 - 2800 nm; wherein, a is Fe3O4 after heat treatment, and b is Fe3O4 without heat treatment.

[0042] Figure 12 Diffuse reflectance diagrams of Fe3O4@SiO2 provided for the invention examples before and after heat treatment at 100 °C for 12 h in the range of 250 - 2800 nm; wherein, a is Fe3O4@SiO2 after heat treatment, and b is Fe3O4@SiO2 without heat treatment. Detailed implementation mode

[0043] The present invention will be described in detail below with reference to the accompanying drawings and examples.

[0044] In the specific embodiments of the present invention, magnetite nanoparticles are selected as the core material and silica as the coating material. For example, to verify the relevant effects of the present application, any substances with corresponding effects described in the present invention can achieve the purpose. In addition, no surfactants are used during the preparation process of the materials to change the physical and chemical properties and dispersion effects of the particles. Although the present invention only describes the preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains.

[0045] Furthermore, by coating silica on the surface of magnetite nanoparticles, the schematic diagram of the realization of Fe3O4@SiO2 is as Figure 1 shown. First, an improved sol-gel method is adopted. The Fe3O4 nanoparticles are ultrasonically dispersed in a mixed system of ethanol and water at room temperature. Then, ammonia water is added to the mixed system to cause the hydrolysis and polymerization of tetraethyl orthosilicate under the catalysis of ammonia water, forming amorphous SiO2 coated on the surface of Fe3O4 nanoparticles. After separation, washing, and drying, Fe3O4@SiO2 particles are obtained.

[0046] Example 1

[0047] (1) Weigh 0.3 g of Fe3O4 nanoparticles and ultrasonically disperse them in 0.1 mol / L dilute hydrochloric acid at room temperature for 15 min to remove impurities. Then, wash the micro-nanoparticles with deionized water until the pH value of the washing solution is between 5 and 7.

[0048] (2) The pickled Fe3O4 nanoparticles were ultrasonically dispersed in an alcohol / water system composed of 20 ml of deionized water and 80 ml of ethanol at room temperature for 15 min.

[0049] (3) After the ultrasonic treatment, 2 ml of ammonia water was added to the mixed solution, and mechanical stirring was carried out at room temperature. The stirring speed was 500 r / min, and the stirring time was 30 min.

[0050] (4) Under continuous stirring, 0.2 ml of tetraethyl orthosilicate was added dropwise to the mixed solution, and mechanical stirring of the mixed solution was continued at room temperature for 12 h.

[0051] (5) After the reaction, the product was separated from the solution by the attraction of a magnet. The product was washed three times with anhydrous ethanol and deionized water successively. During the washing process, the product was ultrasonically dispersed.

[0052] (6) After washing, the product was placed in a vacuum drying oven at 70 °C for 12 h to obtain the magnetic photothermal material Fe3O4@SiO2 with SiO2-coated Fe3O4 nanoparticles (see Figures 2 - 4 ).

[0053] From Figure 2 the SEM images of Fe3O4@SiO2 and the original Fe3O4, it can be seen that due to the mutual attraction between magnetic particles, there is a certain degree of aggregation of Fe3O4 and Fe3O4@SiO2 particles. The edges and corners of the original Fe3O4 particles are more obvious, while they become blurred after being coated with SiO2, and the morphology becomes smoother, indicating that SiO2 has been successfully coated on the surface of Fe3O4 particles.

[0054] From Figure 3 the XRD pattern of Fe3O4@SiO2, the six obvious diffraction peaks correspond to the (311), (220), (400), (422), (511), and (440) crystal planes of Fe3O4, indicating that Fe3O4 inside is not damaged during the SiO2 coating process, ensuring the chemical stability of Fe3O4. In addition, the diffraction peak near 22° is the broad amorphous diffraction peak of amorphous SiO2, indicating the existence of amorphous SiO2 coated on the outer layer.

[0055] From Figure 4 the FTIR-infrared spectra of Fe3O4@SiO2 and the original Fe3O4, the characteristic absorption peak of Fe3O4 is at 586.4 cm -1 , and at 3436.7 cm -1 and 1634.8 cm -1The absorption bands at [specific location] correspond to the O-H stretching vibration and bending vibration of adsorbed water on the particles respectively. 1091.1 cm -1 The absorption at [specific location] is the antisymmetric stretching vibration of Si-O-Si, 806.7 cm -1 and 469.1 cm -1 are the symmetric stretching vibration and bending vibration absorption peaks of Si-O-Si. Therefore, the SiO2 layer effectively coats the Fe3O4 nanoparticles.

[0056] Perform performance measurements on the Fe3O4@SiO2 obtained in step (6) of the above examples:

[0057] 1) Contact angle test

[0058] Perform contact angle tests on the Fe3O4@SiO2 obtained in Example 1 above and the original Fe3O4 material. From Figure 5 It can be seen that compared with the original Fe3O4, the hydrophilicity of Fe3O4@SiO2 with an outer SiO2 coating slightly decreases, but it still maintains good water spreading performance.

[0059] 2) Absorbance

[0060] Perform UV-vis-NIR tests on the Fe3O4@SiO2 obtained in Example 1 above and the original Fe3O4 material in the wavelength range of 250 nm - 2500 nm. From Figure 6 It can be seen that compared with Fe3O4, the overall diffuse reflection of Fe3O4@SiO2 decreases, indicating that the outer SiO2 layer has an antireflection function and shows better spectral absorption performance. From Figure 7 It can be seen that the light absorption of the original Fe3O4 in the wavelength range of 250 nm - 2500 nm reaches 88.9%, while that of Fe3O4@SiO2 reaches 91.1%.

[0061] 3) Magnetic property test

[0062] Perform VSM tests on the Fe3O4@SiO2 obtained in Example 1 above and the original Fe3O4 material at room temperature. From Figure 8 It can be seen that the specific saturation magnetization of the original Fe3O4 is 82.7 emu / g, and that of Fe3O4@SiO2 after coating with silica is 48.2 emu / g. After coating with SiO2, the relative content of Fe3O4 decreases, resulting in a decrease in the saturation magnetization of the composite particles, but the coercivity remains basically unchanged, and it still has good superparamagnetism, which is beneficial for the recycling and reuse of the material.

[0063] 3) Thermal stability test

[0064] Perform heat treatment at 100 °C on the Fe3O4@SiO2 obtained in Example 1 above and the original Fe3O4 material. FromFigure 9 It can be seen that after heat-treating Fe3O4 at 100 °C, characteristic peaks of spinel-structured Fe2O3 appeared in its spectrum a. From this, it can be inferred that Fe3O4 will oxidize after heat treatment at 100 °C for a sufficient time, and part of it will be converted into Fe2O3. From Figure 10 It can be seen that the spectra before and after heat-treating Fe3O4@SiO2 at 100 °C did not change, and characteristic peaks of Fe3O4 and a broad amorphous diffraction peak of amorphous SiO2 near 22° both existed. From this, it can be inferred that Fe3O4@SiO2 has higher thermal stability than Fe3O4. From Figure 11 It can be seen that after heat-treating Fe3O4 at 100 °C, its diffuse reflection slightly increased, indicating that part of Fe3O4 was oxidized into Fe2O3 with lower light absorption. From Figure 12 It can be seen that after heat-treating Fe3O4@SiO2 at 100 °C, its diffuse reflection remained basically unchanged, indicating that the outer SiO2 played a protective role on the inner-core Fe3O4 and inhibited the oxidation of Fe3O4 during the heat treatment process.

[0065] Example 2

[0066] The difference from Example 1 is that: according to the preparation method of Example 1, the dosage of Fe3O4 in step 1) was adjusted to 0.6 g, and the ultrasonic time was adjusted to 30 min.

[0067] Example 3

[0068] The difference from Example 1 is that: according to the preparation method of Example 1, the dosage of deionized water in step 2) was adjusted to 10 ml, the dosage of ethanol was adjusted to 40 ml, and the ultrasonic time was adjusted to 30 min.

[0069] Example 4

[0070] The difference from Example 1 is that: according to the preparation method of Example 1, the dosage of ammonia water in step 3) was adjusted to 1 ml, and the speed of mechanical stirring was adjusted to 600 r / min.

[0071] Example 5

[0072] The difference from Example 1 is that: according to the preparation method of Example 1, the dosage of tetraethyl orthosilicate in step 4) was 0.1 ml, and the stirring time was adjusted to 6 h.

[0073] Example 6

[0074] The difference from Example 1 is that: according to the preparation method of Example 1, the washing sequence of the product with ethanol and deionized water in step 5) was adjusted to first wash three times with deionized water and then wash three times with ethanol.

[0075] Example 7

[0076] The difference from Example 1 is that: according to the preparation method of Example 1, the temperature of vacuum drying in step 6) is adjusted to 60 °C, and the drying time is adjusted to 24 h.

[0077] The Fe3O4@SiO2 obtained in the above Examples 2-7 can all achieve the corresponding properties of the material obtained in Example 1.

[0078] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a photothermal material with an antireflection functional coating, characterized in that: Using magnetic particles at the micron or nanometer scale as the core, and an inorganic material with an antireflection function as the functional coating, which is coated on the surface of the magnetic particles; wherein, the functional coating is a metal oxide or a non-metal oxide with the function of suppressing light reflection.

2. The preparation method of the photothermal material with an antireflection functional coating according to claim 1, characterized in that: The functional coating is formed by one or several substances among magnesium oxide, zinc oxide, and silicon dioxide; wherein, the ratio of the micron or nanometer scale magnetic particles to the substances used to form the functional coating is 1.9 mmol - 3.8 mmol: 0.9 mmol - 1.8 mmol.

3. The preparation method of the magnetic photothermal material with an antireflection functional coating according to claim 1 or 2, characterized in that: Using the sol-gel method, the micron or nanometer scale magnetic particles are dispersed in a solution. After dispersion, a precursor substance of the functional coating is added to the system, and under stirring conditions, the precursor substance undergoes hydrolysis and polymerization reactions in the magnetic particle suspension to form a metal or non-metal oxide, and the formed substance is uniformly coated on the surface of the micron or nanometer scale magnetic particles.

4. The preparation method of the magnetic photothermal material with an antireflection functional coating according to claim 3, characterized in that: (1) Dispersing the micron or nanometer scale magnetic particles into dilute hydrochloric acid, and then washing with water until the pH value of the washing liquid is between 5 and 7; (2) Dispersing the washed magnetic microparticles in deionized water and / or an ethanol solution, and stirring to make the particles uniformly dispersed; (3) Keeping stirring, successively adding a catalyst and a precursor substance for forming the functional coating to the mixed system in which magnetic nanoparticles are dispersed. Under stirring conditions, the precursor substance undergoes hydrolysis and polymerization reactions in the magnetic particle suspension to form a metal or non-metal oxide, and the formed substance is uniformly coated on the surface of the micron or nanometer scale magnetic particles. After reaction treatment, a magnetic photothermal material with an antireflection functional coating is obtained.

5. The preparation method of the magnetic photothermal material with an antireflection functional coating according to claim 4, characterized in that: In the step (1), the micron or nanometer scale magnetic particles are ultrasonically dispersed into dilute hydrochloric acid at room temperature for 10 min - 20 min; wherein, the concentration of the dilute hydrochloric acid is 0.1 mol / L - 0.2 mol / L.

6. The preparation method of the magnetic photothermal material with an antireflection functional coating according to claim 4, characterized in that: The washed magnetic microparticles are ultrasonically dispersed in deionized water and / or an ethanol solution at room temperature for 20 min - 30 min.

7. The preparation method of the magnetic photothermal material with an antireflection functional coating according to claim 6, characterized in that: When the solution is a mixed solution of deionized water and ethanol, the volume ratio of deionized water to ethanol is 1:4 - 1:

2.

8. The preparation method of the magnetic photothermal material with an antireflection functional coating according to claim 4, characterized in that: In the step (3), a catalyst for promoting the formation of the functional coating substance is added to the mixed system in which magnetic nanoparticles are dispersed, and high-speed mechanical stirring is continued at room temperature; under stirring conditions, a precursor substance for forming the functional coating is added, and high-speed mechanical stirring of the mixed solution is continued at room temperature. A reaction occurs to form a metal or non-metal oxide and uniformly coat it on the surface of the micron or nanometer scale magnetic particles. After reaction treatment, a magnetic photothermal material with an antireflection functional coating is obtained; wherein, the final dosage of the catalyst in the system is 0.01 mol - 0.02 mmol.

9. The preparation method of the magnetic photothermal material with an antireflection functional coating according to claim 4 or 8, characterized in that: After the reaction in the step (3) ends, the product is separated from the solution by the attraction of a magnet, and washed with anhydrous ethanol and deionized water respectively. After washing, it is dried in a vacuum drying oven at 60 - 70 °C for 12 - 24 h to obtain a photothermal material with an antireflection functional coating.

10. The magnetic photothermal material with an antireflection functional coating prepared by the method according to claim 1, characterized in that: The material prepared by the method according to claim 1 presents as black under natural light, and the powdery solid is a magnetic photothermal material with an antireflection functional coating.

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