A photothermal material with an anti-reflection functional coating and a preparation method thereof
By coating the surface of magnetic micro- and nanomaterials with materials such as magnesium oxide, zinc oxide, or silicon dioxide, the problems of high light reflection loss and poor stability of magnetic micro- and nanomaterials during solar energy interface evaporation are solved, achieving efficient light absorption and improved stability, making them suitable for large-scale production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN UNIV OF TECH
- Filing Date
- 2023-12-27
- Publication Date
- 2026-06-26
AI Technical Summary
Existing magnetic micro/nano materials suffer from high light reflection loss during solar interface evaporation, poor thermal stability and oxidation resistance of anti-reflective coatings, and complicated and costly preparation processes, making large-scale application difficult.
Photothermal materials with anti-reflective properties are prepared by using micron or nano-sized magnetic particles as the core and coating them with materials such as magnesium oxide, zinc oxide or silicon dioxide as anti-reflective coatings. A uniform coating is formed on the surface of the magnetic particles by means of a sol-gel method.
It improves the light absorption capacity and antioxidant properties of the material, enhances material stability, facilitates recycling, reduces costs, broadens the application range, and the preparation process is simple and easy to mass-produce.
Smart Images
Figure CN120208340B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of materials preparation technology, specifically relating to a photothermal material with an anti-reflection coating and its preparation method. Background Technology
[0002] Photothermal materials are a class of materials that convert absorbed light energy into heat energy. With the continuous deepening of research on the photothermal effect, photothermal materials are increasingly widely used in chemical engineering, energy, sensing, and life sciences, becoming a new type of material that cannot be ignored in the field of materials science research. Among them, black magnetic micro / nanomaterials, including permanent magnet alloys and iron oxides, possess excellent photothermal effects due to their narrow band gaps.
[0003] Currently, magnetic micro / nanomaterials have been applied to the research of solar interfacial evaporation technology for seawater desalination to address the freshwater shortage problem. This technology efficiently converts solar energy into heat energy through photothermal materials, confining the generated heat to the water surface, thus rapidly heating the water to generate water vapor. However, during the solar interfacial evaporation process, some light is reflected from the material surface and cannot be effectively utilized. According to the Fresnel equation, adding an intermediate layer with a refractive index between air and the material can reduce the overall reflection loss of the material. However, some anti-reflective coatings currently lack good thermal stability and oxidation resistance, and are prone to failure or deformation in high-temperature and high-humidity application scenarios. In addition, the preparation methods of some anti-reflective coatings are cumbersome, demanding, and costly, preventing large-scale practical production and application. Summary of the Invention
[0004] The purpose of this invention is to provide a magnetic photothermal material with an anti-reflection coating and its preparation method.
[0005] To achieve the above objectives, the present invention adopts the following technical solution:
[0006] A method for preparing a photothermal material with an anti-reflection coating involves using micron- or nano-sized magnetic particles as a core and coating the surface of the magnetic particles with an inorganic material having anti-reflection properties as a functional coating; wherein the functional coating is a metal oxide or non-metal oxide with light reflection suppression function.
[0007] The functional coating is formed from one or more of magnesium oxide, zinc oxide, and silicon dioxide; wherein the ratio of micron or nano-sized magnetic particles to the material 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 iron-chromium-cobalt alloys, iron(II,III) oxide, strontium ferrite, and perovskite-type lanthanum-strontium-cobalt-iron oxides.
[0009] Furthermore, the sol-gel method is used to disperse micron or nano-sized magnetic particles in a solution. After dispersion, a functional coating precursor is added to the system. Under stirring conditions, the precursor undergoes hydrolysis and polymerization reactions in the magnetic particle suspension to form metal or non-metal oxides, and the formed substances are uniformly coated on the surface of the micron or nano-sized magnetic particles.
[0010] Specifically:
[0011] (1) Disperse micron or nano-sized magnetic particles in dilute hydrochloric acid, and then wash with water until the pH of the washing solution is between 5 and 7.
[0012] (2) Disperse the washed magnetic microparticles in deionized water and / or ethanol solution and stir to make the particles evenly dispersed.
[0013] (3) While stirring, add the catalyst and the precursor material for forming the functional coating to the mixed system containing the magnetic nanoparticles. Under stirring conditions, the precursor material undergoes hydrolysis and polymerization in the magnetic particle suspension to form metal or non-metal oxides and uniformly coats the surface of the micron or nano-sized magnetic particles. After post-reaction treatment, the magnetic photothermal material with anti-reflection functional coating is obtained.
[0014] In step (1), micron or nano-sized magnetic particles are ultrasonically dispersed in dilute hydrochloric acid at room temperature for 10-20 minutes; wherein the concentration of dilute hydrochloric acid is 0.1-0.2 mol / L.
[0015] The magnetic microparticles washed in step (2) are ultrasonically dispersed in deionized water and / or ethanol solution at room temperature for 20-30 minutes; wherein, 0.3g-0.6g of the washed magnetic microparticles are washed with 50mL-100mL of deionized water and / or ethanol solution.
[0016] When the solution is a mixture of deionized water and ethanol, the volume ratio of deionized water to ethanol is 1:4 to 1:2.
[0017] In step (3), a catalyst that promotes the formation of a functional coating is added to the mixed system containing dispersed magnetic nanoparticles, and high-speed mechanical stirring is continued at room temperature. Under stirring conditions, a precursor material for forming a functional coating is added, and the mixed solution is further mechanically stirred at room temperature to form a metal or non-metal oxide that is uniformly coated on the surface of micron or nano-sized magnetic particles. After post-reaction treatment, a magnetic photothermal material with an anti-reflection functional coating is obtained. The final amount of catalyst used in the system is 0.01 mol to 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, the stirring speed is 500-600 r / min and the stirring time is 12-24 h.
[0019] If magnesium oxide is formed as described above, the catalyst can be ammonia; the corresponding precursor is magnesium nitrate hexahydrate.
[0020] When zinc oxide is formed, sodium hydroxide can be used as the catalyst; the corresponding precursor is zinc acetate.
[0021] When silicon dioxide is formed, the catalyst can be ammonia; the corresponding precursor is tetraethyl orthosilicate.
[0022] After the reaction in step (3) is completed, the product is separated from the solution by using a magnet to attract the product, and then washed with anhydrous ethanol and deionized water. After washing, the product is dried in a vacuum drying oven at 60-70℃ for 12-24 hours to obtain a photothermal material with an anti-reflection coating.
[0023] A magnetic photothermal material with an anti-reflective coating prepared by the method described above: The material prepared by the method appears black under natural light and is a powdery solid magnetic photothermal material with an anti-reflective coating. It can move rapidly when a magnet approaches, exhibiting good magnetic response capability.
[0024] This invention utilizes the antireflective properties and stability of magnesium oxide, zinc oxide, and silicon dioxide to prepare magnetic micro / nanoparticles with an antireflective coating, which can enhance the light absorption and oxidation resistance of the material. Furthermore, the material can be separated into solid and liquid phases using an external magnetic field, facilitating its recycling and reuse.
[0025] This invention has the following advantages and positive effects:
[0026] This invention involves coating magnetic micro / nanomaterials with an anti-reflection coating, thereby reducing light reflection loss while protecting the stability of the core magnetic material; specifically:
[0027] 1. This invention uses magnesium oxide, zinc oxide, and silicon dioxide as anti-reflective coatings, which have good anti-reflective properties and chemical stability. After the magnetic micro- and nano-particles are coated with the corresponding materials, the particles can have good anti-reflective properties and improve light absorption capacity.
[0028] 2. The material coated with the present invention exhibits better chemical stability and is less prone to oxidation in high-humidity and high-temperature application environments. Furthermore, the material possesses good magnetic properties, allowing for recycling and reuse via an external magnetic field, thus reducing costs.
[0029] 3. The magnesium oxide, zinc oxide and silicon dioxide used in this invention have good biocompatibility, which makes it easy to further biofunctionalize the composite particles and broaden their application range in water treatment. At the same time, silicon dioxide is an acidic oxide and does not react with common acids. After being coated with magnetic micro and 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 for production. Attached Figure Description
[0031] Figure 1 This is a schematic diagram illustrating the preparation process of the magnetic photothermal material with an anti-reflection coating provided in an embodiment of the present invention.
[0032] Figure 2 This invention provides SEM images of Fe3O4@SiO2 and raw Fe3O4; wherein, a is commercially available Fe3O4, and b is Fe3O4@SiO2 with SiO2 coating.
[0033] Figure 3 The XRD pattern of Fe3O4@SiO2 provided in the embodiments of the present invention.
[0034] Figure 4 FTIR-infrared spectra of Fe3O4@SiO2 and original Fe3O4 provided for embodiments of the present invention.
[0035] Figure 5 The contact angle test diagrams of Fe3O4@SiO2 and original Fe3O4 provided in the embodiments of the present invention are shown; wherein, a is commercially available Fe3O4, and b is Fe3O4@SiO2 with SiO2 coated on Fe3O4.
[0036] Figure 6 The diffuse reflectance of Fe3O4@SiO2 and pristine Fe3O4 in the 250-2800 nm range is provided for embodiments of the invention.
[0037] Figure 7 The light absorption patterns of Fe3O4@SiO2 and pristine Fe3O4 in the 250-2800 nm range are provided for embodiments of the invention.
[0038] Figure 8 VSM diagrams of Fe3O4@SiO2 and pristine Fe3O4 at room temperature, provided for embodiments of the invention.
[0039] Figure 9 The images show the XRD patterns of raw Fe3O4 before and after heat treatment at 100℃ for 12 hours; where a represents Fe3O4 after heat treatment and b represents Fe3O4 without heat treatment.
[0040] Figure 10 The XRD patterns of Fe3O4@SiO2 before and after heat treatment at 100℃ for 12h are provided for the embodiments of the invention; wherein, a is Fe3O4@SiO2 after heat treatment, and b is Fe3O4@SiO2 without heat treatment.
[0041] Figure 11 The images show the diffuse reflectance of raw Fe3O4 in the 250-2800 nm range before and after heat treatment at 100℃ for 12 h; where a represents Fe3O4 after heat treatment and b represents Fe3O4 without heat treatment.
[0042] Figure 12 The diffuse reflectance images of Fe3O4@SiO2 before and after heat treatment at 100℃ for 12h, provided for the embodiments of the invention, are in the range of 250-2800nm; wherein, a is Fe3O4@SiO2 after heat treatment, and b is Fe3O4@SiO2 without heat treatment. Detailed Implementation
[0043] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.
[0044] In a specific embodiment of this invention, iron(II,III) oxide nanoparticles are selected as the core material and silicon dioxide as the coating material. This serves as an example to verify the effects described in this application. All substances with corresponding effects described in this invention can achieve the desired results. Furthermore, no surfactants are used in the material preparation process to alter the physicochemical properties and dispersion effect of the particles. Although this invention only describes preferred methods and materials, any methods and materials similar to or equivalent to those described herein can be used in the implementation or testing of this invention. Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.
[0045] Furthermore, a schematic diagram of Fe3O4@SiO2 achieved by coating silicon dioxide onto iron(III) oxide nanoparticles is shown below. Figure 1 As shown, Fe3O4 nanoparticles were first ultrasonically dispersed in a mixture of ethanol and water using a modified sol-gel method. Then, ammonia was added to the mixture to cause tetraethyl orthosilicate to hydrolyze and polymerize under the catalysis of ammonia, forming amorphous SiO2 coatings on the Fe3O4 nanoparticle surface. After separation, washing, and drying, Fe3O4@SiO2 particles were obtained.
[0046] Example 1
[0047] (1) Weigh 0.3g of Fe3O4 nanoparticles and ultrasonically disperse them in 0.1mol / L dilute hydrochloric acid at room temperature for 15min to remove impurities. Then, wash the micro-nanoparticles with deionized water until the pH of the washing solution is between 5 and 7.
[0048] (2) The acid-washed Fe3O4 nanoparticles were ultrasonically dispersed in an alcohol / water system consisting of 20 ml of deionized water and 80 ml of ethanol at room temperature for 15 min.
[0049] (3) After sonication, add 2 ml of ammonia to the mixture and mechanically stir at room temperature. The stirring speed is 500 r / min and the stirring time is 30 min.
[0050] (4) Add 0.2 ml of tetraethyl orthosilicate to the mixed solution while stirring continuously, and continue to mechanically stir the mixed solution at room temperature for 12 h.
[0051] (5) After the reaction was complete, the product was separated from the solution by using a magnet to attract it. The product was washed three times with anhydrous ethanol and deionized water. 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 hours to obtain Fe3O4@SiO2 magnetic photothermal material with SiO2 coated on the surface of nano-Fe3O4 (see...). Figure 2-4 ).
[0053] Depend on Figure 2 SEM images of Fe3O4@SiO2 and original Fe3O4 show that, due to the mutual attraction between magnetic particles, both Fe3O4 and Fe3O4@SiO2 particles exhibit some aggregation. The original Fe3O4 particles have relatively sharp edges, while those coated with SiO2 become blurred and more rounded, indicating that SiO2 has been successfully coated onto the surface of the Fe3O4 particles.
[0054] Depend on Figure 3 The XRD pattern of Fe3O4@SiO2 shows six distinct diffraction peaks corresponding to the (311), (220), (400), (422), (511), and (440) crystal planes of Fe3O4, indicating that the SiO2 coating process did not damage the inner Fe3O4, thus ensuring its chemical stability. Furthermore, the diffraction peak appearing near 22° is a broadened amorphous diffraction peak of amorphous SiO2, indicating the presence of the outer layer of amorphous SiO2.
[0055] Depend on Figure 4 The FTIR-IR spectra of Fe3O4@SiO2 and virgin Fe3O4 show that the wavelength is 586.4 cm⁻¹. -1 The characteristic absorption peak of Fe3O4 is at 3436.7 cm⁻¹. -1 and 1634.8cm -1The absorption bands at these points correspond to the stretching and bending vibrations of adsorbed water OH groups, respectively. 1091.1 cm⁻¹ -1 The absorption occurs at 806.7 cm⁻¹ due to the antisymmetric stretching vibration of Si-O-Si. -1 and 469.1cm -1 These are absorption peaks from the symmetrical stretching and bending vibrations of Si-O-Si. Therefore, the SiO2 layer effectively coats the Fe3O4 nanoparticles.
[0056] The performance of Fe3O4@SiO2 obtained in step (6) of the above embodiments was measured:
[0057] 1) Contact angle test
[0058] Contact angle tests were performed on the Fe3O4@SiO2 material obtained in Example 1 and the original Fe3O4 material. Figure 5 It can be seen that the hydrophilicity of Fe3O4@SiO2 coated with SiO2 is slightly reduced compared with the original Fe3O4, but it still maintains good water spreading performance.
[0059] 2) Absorbance
[0060] The Fe3O4@SiO2 and pristine Fe3O4 materials obtained in Example 1 were subjected to UV-vis-NIR tests in the wavelength range of 250 nm to 2500 nm. Figure 6 It can be seen that, compared to Fe3O4, the overall diffuse reflectance of Fe3O4@SiO2 decreases, indicating that the outer SiO2 layer possesses anti-reflection properties and exhibits better spectral absorption performance. Figure 7 It can be seen that the original Fe3O4 has a light absorption of 88.9% in the wavelength range of 250nm-2500nm, while Fe3O4@SiO2 has a light absorption of 91.1%.
[0061] 3) Magnetic test
[0062] The Fe3O4@SiO2 and pristine Fe3O4 materials obtained in Example 1 were subjected to VSM tests at room temperature. Figure 8 It can be seen that the specific saturation magnetization of the original Fe3O4 is 82.7 emu / g, while that of Fe3O4@SiO2 after coating with silicon dioxide is 48.2 emu / g. The relative content of Fe3O4 decreases after coating with SiO2, leading to a decrease in the saturation magnetization of the composite particles, but the coercivity remains essentially unchanged, and it still exhibits good superparamagnetism, which is beneficial for the recycling and reuse of the material.
[0063] 3) Thermal stability test
[0064] The Fe3O4@SiO2 and original Fe3O4 materials obtained in Example 1 above were subjected to heat treatment at 100°C. Figure 9 It can be seen that after heat treatment of Fe3O4 at 100℃, the characteristic peaks of spinel-structured Fe2O3 appeared in its spectrum a. Therefore, it can be inferred that Fe3O4 undergoes oxidation after sufficient heat treatment at 100℃, with a portion transforming into Fe2O3. Figure 10 It can be seen that the spectral lines of Fe3O4@SiO2 did not change before and after heat treatment at 100℃, and both exhibited the characteristic peaks of Fe3O4 and the broadened amorphous diffraction peaks of amorphous SiO2 around 22°. Therefore, it can be inferred that Fe3O4@SiO2 has higher thermal stability than Fe3O4. Figure 11 It can be seen that after heat treatment at 100℃, the diffuse reflectance of Fe3O4 increases slightly, indicating that Fe3O4 is partially oxidized into Fe2O3, which has lower light absorption. Figure 12 It can be seen that after Fe3O4@SiO2 is heat-treated at 100℃, its diffuse reflection remains basically unchanged, indicating that the outer SiO2 layer protects the Fe3O4 core and inhibits 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 amount of Fe3O4 in step 1) is adjusted to 0.6g and the ultrasonic time is adjusted to 30min.
[0067] Example 3
[0068] The difference from Example 1 is that, according to the preparation method of Example 1, the amount of deionized water in step 2) is adjusted to 10 ml, the amount of ethanol is adjusted to 40 ml, and the ultrasonic time is adjusted to 30 min.
[0069] Example 4
[0070] The difference from Example 1 is that, according to the preparation method of Example 1, the amount of ammonia water used in step 3) is adjusted to 1 ml, and the mechanical stirring speed is 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 amount of tetraethyl orthosilicate used in step 4) is 0.1 ml, and the stirring time is adjusted to 6 h.
[0073] Example 6
[0074] The difference from Example 1 is that, according to the preparation method of Example 1, the order of washing the product with ethanol and deionized water in step 5) is adjusted to first washing with deionized water three times, and then washing with ethanol three times.
[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 24h.
[0077] The Fe3O4@SiO2 obtained in Examples 2-7 above can all achieve the corresponding properties of the material obtained in Example 1.
[0078] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a photothermal material with an anti-reflection coating, characterized in that: The magnetic particles are made of micron or nanometer size as the core, and an inorganic material with anti-reflection function is used as a 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. The functional coating is formed from one or more of magnesium oxide, zinc oxide, and silicon dioxide; wherein the ratio of micron or nano-sized magnetic particles to the material used to form the functional coating is 1.9 mmol-3.8 mmol: 0.9 mmol-1.8 mmol. The sol-gel method is used to disperse micron or nano-sized magnetic particles in a solution. After dispersion, a functional coating precursor is added to the system. Under stirring conditions, the precursor undergoes hydrolysis and polymerization reactions in the magnetic particle suspension to form metal or non-metal oxides, and the formed substances are uniformly coated on the surface of micron or nano-sized magnetic particles. The specific preparation method includes the following steps: (1) Disperse micron or nano-sized magnetic particles in dilute hydrochloric acid and then wash with water until the pH of the washing solution is between 5 and 7. (2) Disperse the washed magnetic microparticles in deionized water and / or ethanol solution, and stir to ensure uniform dispersion of the particles; (3) Keep stirring and add the catalyst and the precursor material for forming the functional coating to the mixed system containing the magnetic nanoparticles. Under stirring conditions, the precursor material undergoes hydrolysis and polymerization in the magnetic particle suspension to form metal or non-metal oxides and uniformly coats the surface of the micron or nano-sized magnetic particles. After the reaction is processed, the magnetic photothermal material with anti-reflection functional coating is obtained. In step (3), a catalyst that promotes the formation of a functional coating is added to the mixed system containing dispersed magnetic nanoparticles, and high-speed mechanical stirring is continued at room temperature. Under stirring conditions, a precursor material for forming a functional coating is added, and the mixed solution is further mechanically stirred at room temperature to form a metal or non-metal oxide that is uniformly coated on the surface of micron or nano-sized magnetic particles. After post-reaction treatment, a magnetic photothermal material with an anti-reflection functional coating is obtained. The final amount of catalyst used in the system is 0.01 mol-0.02 mmol.
2. A method for preparing a photothermal material with an anti-reflection coating as described in claim 1, characterized in that: In step (1), micron or nano-sized magnetic particles are ultrasonically dispersed in dilute hydrochloric acid at room temperature for 10 min-20 min; wherein the concentration of dilute hydrochloric acid is 0.1 mol / L - 0.2 mol / L.
3. A method for preparing a photothermal material with an anti-reflection coating as described in claim 1, characterized in that: The washed magnetic microparticles were ultrasonically dispersed in deionized water and / or ethanol solution at room temperature for 20-30 minutes.
4. A method for preparing a photothermal material with an anti-reflection coating as described in claim 3, characterized in that: When the solution is a mixture of deionized water and ethanol, the volume ratio of deionized water to ethanol is 1:4 to 1:
2.
5. A method for preparing a photothermal material with an anti-reflection coating as described in claim 1, characterized in that: After the reaction in step (3) is completed, the product is separated from the solution by the attraction of a magnet, and washed with anhydrous ethanol and deionized water respectively. After washing, the product is dried in a vacuum drying oven at 60-70 ℃ for 12-24 h to obtain a photothermal material with an anti-reflection coating.
6. A magnetic photothermal material with an anti-reflection coating prepared by the method for preparing the photothermal material with an anti-reflection coating as described in claim 1, characterized in that: The material prepared by the method of claim 1 for preparing a photothermal material with an anti-reflection coating appears black under natural light. It is a magnetic photothermal material with an anti-reflection coating in powder form.