Intelligent light-heat composite material for improving cold resistance of cement material and preparation method and application thereof

Abstract

The application discloses an intelligent light-heat composite material for improving cold resistance of cement materials and a preparation method and application thereof. The intelligent light-heat composite material comprises a core formed by composite graphene with carbon quantum dots on the surface, a polymer coating layer with amino groups and carboxyl groups grafted on the surface of the core, and a temperature-sensitive polymer shell coated on the surface of the polymer coating layer. The light-heat composite material can not only form chemical bonding with cement hydration products, but also widen the light absorption range to the visible light and near-infrared region, thereby improving the light-heat conversion efficiency. In addition, the intelligent light-heat composite material has the characteristics of automatically adjusting the light-heat conversion degree according to the environmental temperature, and realizes precise temperature control.

Description

Technical Field

[0001] This invention relates to the field of cement-based materials, specifically to a smart photothermal composite material for improving the cold resistance of cement materials, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] In cold conditions, the internal moisture of cement freezes and expands, which not only inhibits the hydration reaction, resulting in slow hardening and insufficient early strength, but also easily leads to matrix cracking, spalling, and reduced durability and freeze-thaw resistance. Traditional antifreeze methods mainly rely on adding chemical antifreeze agents or external heating. However, chemical antifreeze agents have limited effectiveness in extremely cold weather and cannot guarantee the temperature required for cement hydration. For example, in environments below -20°C, chemical antifreeze agents alone may not be sufficient to achieve the desired strength development in cement. External heating, on the other hand, suffers from high energy consumption, high cost, and inconvenience in field construction.

[0004] By adding intelligent photothermal composite materials to cement-based materials, solar energy can be converted into heat energy to raise the local temperature of the cement, which helps to alleviate the above-mentioned problems. However, this invention found that existing photothermal materials (such as Ti2O3 nanoparticles, Prussian blue, graphite, etc.) are prone to agglomeration and uneven dispersion when added to cement, and their interaction with the cement matrix is ​​weak, making it difficult to exert a reinforcing effect. In addition, traditional photothermal materials also have a narrow light absorption range, mainly concentrated in the ultraviolet region, and low photothermal conversion efficiency. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a smart photothermal composite material for improving the cold resistance of cement materials, its preparation method, and its application. This photothermal composite material not only forms chemical bonds with cement hydration products but also broadens the light absorption range to the visible and near-infrared regions, thereby improving photothermal conversion efficiency. Specifically, this invention discloses the technical solution shown below.

[0006] First, the present invention provides an intelligent photothermal composite material for improving the cold resistance of cement materials, comprising: a core formed by composite graphene with carbon quantum dots on its surface, a polymer coating layer containing amino and carboxyl groups grafted onto the surface of the core, and a temperature-sensitive polymer shell coating the surface of the polymer coating layer.

[0007] Furthermore, the polymer is formed by polymerizing acrylamide and acrylic acid monomers.

[0008] Furthermore, the temperature-sensitive polymer layer is polymerized from temperature-sensitive polymer monomers. Optionally, the temperature-sensitive polymer monomers include at least one selected from N-isopropylacrylamide, acrylamide, methacrylamide, acrylic acid, methacrylic acid, etc.

[0009] Secondly, this invention discloses a method for preparing a smart photothermal composite material, comprising the following steps:

[0010] (1) Add carbon quantum dot precursor to graphene oxide dispersion, then heat to react, and after completion, separate the solid product, wash and obtain composite graphene with carbon quantum dots on the surface.

[0011] (2) The composite graphene is dispersed in a monomer solution containing amino and carboxyl groups, then an initiator is added and a polymerization reaction is carried out under heating conditions. After completion, the solid product is separated to obtain a composite graphene core-shell structure with a polymer coating layer containing amino and carboxyl groups grafted on the surface.

[0012] (3) After mixing the core-shell structure with a thermosensitive polymer monomer solution, an initiator is added, and polymerization is carried out under heating and a protective atmosphere to uniformly coat the surface of the core-shell structure with the formed thermosensitive polymer. After the reaction is completed, the solid product is separated, washed, and the intelligent photothermal composite material is obtained.

[0013] Further, in step (1), the mass ratio of the carbon quantum dot precursor to graphene oxide is 1:2~10. Optionally, the carbon quantum dot precursor includes at least one of citric acid, ascorbic acid, glucose, etc.

[0014] Furthermore, in step (1), the heating temperature is 60~100℃ and the reaction time is 8~16 hours.

[0015] Further, in step (2), the mass ratio of the composite graphene to the monomer is 1:10~50. Optionally, the monomer includes at least one of acrylamide and acrylic acid monomer, methacrylamide and methacrylic acid monomer, etc. Optionally, the mass ratio of acrylamide to acrylic acid monomer is 1~5:1, and the mass ratio of methacrylamide to methacrylic acid monomer is 1~5:1.

[0016] Further, in step (2), the mass ratio of the initiator to the monomer containing amino and carboxyl groups is 0.1~5:100. Optionally, the initiator includes at least one of potassium persulfate, ammonium persulfate, sodium persulfate, etc.

[0017] Further, in step (2), the heating temperature is 50~80℃, and the polymerization reaction time is 4~8 hours. During this process, the epoxy or carbonyl groups on the surface of the composite graphene form a strong chemical bond with the amino or carboxyl groups on the monomer, resulting in a composite graphene core-shell structure with a polymer coating layer containing amino and carboxyl groups grafted onto the surface.

[0018] Further, in step (3), the mass ratio of the core-shell structure to the thermosensitive polymer monomer is 1:10~50.

[0019] Further, in step (3), the mass ratio of the initiator to the thermosensitive polymer monomer is 0.1~5:100. Optionally, the initiator includes at least one of potassium persulfate, ammonium persulfate, sodium persulfate, etc.

[0020] Further, in step (3), the heating temperature is 50~80℃, and the polymerization reaction time is 4~8 hours. Optionally, the protective atmosphere includes at least one of nitrogen, argon, etc.

[0021] Finally, this invention discloses the application of the intelligent photothermal composite material in cement-based structures. Optionally, the intelligent photothermal composite material can be applied to the surface of the cement-based structure to be cured.

[0022] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:

[0023] The intelligent photothermal composite material of the present invention first uses graphene with carbon quantum dots grown in situ on its surface as the core, which can broaden the light absorption range of graphene to the visible light and near-infrared regions, thereby significantly improving the light energy capture efficiency. This enables the intelligent photothermal composite material to generate heat rapidly under sunlight, reduce internal moisture freezing, and provide temperature protection for cement hydration reaction.

[0024] Furthermore, the present invention grafts a polymer layer containing amino (-NH2) and carboxyl (-COOH) functional groups onto the surface of the core, thereby enabling the intelligent photothermal composite material of the present invention to form chemical bonds with cement hydration products (the hydration products are rich in magnesium ions (Mg²⁺) and phosphate ions (PO₄³⁻), the carboxyl groups form stable coordination bonds with Mg²⁺, and the amino groups form hydrogen bonds with PO₄³⁻), enhancing the bonding degree between the intelligent photothermal composite material and the cement-based structure. This allows the intelligent photothermal composite material to not only serve as a functional phase for photothermal conversion but also improve the heat transfer efficiency to the cement-based structure, effectively preventing the coating formed on the surface of the composite material on the cement-based structure from easily peeling off at low temperatures, thus reducing the heat transfer efficiency.

[0025] Finally, the surface of the intelligent photothermal composite material of the present invention also features an intelligent response release system formed by a temperature-sensitive polymer shell to achieve precise temperature control. When the ambient temperature is below a certain temperature, the shell layer contracts, allowing the core to be more fully exposed and enhancing the photothermal conversion efficiency of the core. Conversely, when the temperature rises to a certain temperature, the shell layer expands, reducing the exposure of the core layer and decreasing the photothermal conversion efficiency. This prevents excessively high internal temperatures in the cement-based material from causing rapid moisture evaporation, which would affect subsequent hydration and lead to insufficient strength development. Simultaneously, it also helps prevent cracks caused by excessively high internal temperatures in the cement-based material, thus preventing a decrease in strength. Attached Figure Description

[0026] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0027] Figure 1 The image shows a physical sample of the smart photothermal composite material prepared in Example 1 below.

[0028] Figure 2 The following is a diagram showing the compressive strength test results for Example 1. Detailed Implementation

[0029] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer.

[0030] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as those skilled in the art. All reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions.

[0031] Furthermore, any methods and materials similar to or equivalent to those described herein can be applied to the method of this invention. The technical solution of this invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0032] Example 1

[0033] A method for preparing a smart photothermal composite material to improve the cold resistance of cement materials includes the following steps:

[0034] (1) Graphene oxide was ultrasonically dispersed in water for 30 min to obtain a dispersion. Then, carbon quantum dot precursor (citric acid) was dissolved in ethanol and slowly added to the dispersion. The mass ratio of carbon quantum dot precursor to graphene oxide was 1:5. The resulting mixture was heated to 80°C and kept at that temperature under reflux for 12 hours. After the reaction was completed, the mixture was centrifuged, and the resulting solid product was washed with anhydrous ethanol to obtain composite graphene with carbon quantum dots on its surface, which was then set aside.

[0035] (2) The composite graphene was added to a solution containing acrylamide and acrylic acid monomer (mass ratio of 4:1) in DMF solvent, wherein the mass ratio of the composite graphene to the monomer was 1:30. Then an initiator (ammonium persulfate) was added, and the mixture was heated to 70°C for 6 hours to polymerize, wherein the mass ratio of the initiator to the monomer was 1:50. After the reaction was completed, the mixture was centrifuged, and the resulting solid product was washed with anhydrous ethanol to obtain a composite graphene core-shell structure with a polymer coating layer containing amino and carboxyl groups grafted onto its surface.

[0036] (3) The core-shell structure was mixed with an N-isopropylacrylamide solution (solvent: DMF) and stirred until homogeneous, with a mass ratio of the core-shell structure to the thermosensitive polymer monomer of 1:25. Then, an initiator (ammonium persulfate) was added, with a mass ratio of the initiator to the thermosensitive polymer monomer of 3:100. The mixture was then heated to 65°C and polymerized under a nitrogen atmosphere for 8 hours. After the reaction was complete, the mixture was centrifuged, and the resulting solid product was washed with anhydrous ethanol to obtain the intelligent photothermal composite material, as shown below. Figure 1 As shown.

[0037] Performance Testing: Cement mortar test blocks with dimensions of 40mm × 40mm × 40mm were prepared according to GB / T 17671-2021. A 1mm thick layer of the intelligent photothermal composite material prepared in this embodiment was then uniformly coated onto the surface of the test blocks. The test blocks were then cured in constant temperature and humidity curing chambers at test temperatures of -10℃ and 0℃ (humidity set to 99%), respectively, while being irradiated with light at an intensity of 1000W / m² for 18 hours per day. The compressive strength of the test blocks was then tested at 3d, 7d, and 28d, and the results are shown in the table below:

[0038] .

[0039] Example 2

[0040] A method for preparing a smart photothermal composite material to improve the cold resistance of cement materials includes the following steps:

[0041] (1) Graphene oxide was ultrasonically dispersed in water for 25 min to obtain a dispersion. Then, a carbon quantum dot precursor (glucose) was dissolved in water and slowly added to the dispersion. The mass ratio of the carbon quantum dot precursor to graphene oxide was 1:2. The resulting mixture was heated to 60°C and kept at that temperature under reflux for 16 hours. After the reaction was completed, the mixture was centrifuged, and the resulting solid product was washed with anhydrous ethanol to obtain composite graphene with carbon quantum dots on its surface, which was then set aside.

[0042] (2) The composite graphene was added to a solution containing acrylamide and acrylic acid monomer (mass ratio of 1:1) in DMF solvent, wherein the mass ratio of the composite graphene to the monomer was 1:50. Then an initiator (potassium persulfate) was added, and the mixture was heated to 80°C for 4 hours to polymerize, wherein the mass ratio of the initiator to the monomer was 1:20. After the reaction was completed, the mixture was centrifuged, and the resulting solid product was washed with anhydrous ethanol to obtain a composite graphene core-shell structure with a polymer coating layer containing amino and carboxyl groups grafted onto its surface.

[0043] (3) The core-shell structure is mixed with a methacrylic acid solution (DMF solvent) and stirred until homogeneous, with a mass ratio of the core-shell structure to the thermosensitive polymer monomer of 1:50. Then, an initiator (potassium persulfate) is added, with a mass ratio of the initiator to the thermosensitive polymer monomer of 1:20. The mixture is then heated to 80°C and polymerized under a nitrogen atmosphere for 4 hours. After the reaction is complete, the mixture is centrifuged, and the resulting solid product is washed with anhydrous ethanol to obtain the intelligent photothermal composite material.

[0044] The compressive strength of cement mortar specimens coated with the intelligent photothermal composite material prepared in this embodiment was tested using the same method as in Example 1 above. The results are shown in the table below:

[0045] .

[0046] Example 3

[0047] A method for preparing a smart photothermal composite material to improve the cold resistance of cement materials includes the following steps:

[0048] (1) Graphene oxide was ultrasonically dispersed in water for 30 min to obtain a dispersion. Then, a carbon quantum dot precursor (citric acid) was dissolved in ethanol and slowly added to the dispersion. The mass ratio of the carbon quantum dot precursor to graphene oxide was 1:10. The resulting mixture was heated to 100°C and kept at that temperature under reflux for 8 hours. After the reaction was completed, the mixture was centrifuged, and the resulting solid product was washed with anhydrous ethanol to obtain composite graphene with carbon quantum dots on its surface, which was then set aside.

[0049] (2) The composite graphene was added to a solution containing acrylamide and acrylic acid monomers (mass ratio of 5:1) in DMF solvent, wherein the mass ratio of the composite graphene to the monomers was 0.1:100. Then an initiator (ammonium persulfate) was added, and the mixture was heated to 50°C for 8 hours to polymerize, wherein the mass ratio of the initiator to the monomers was 1:50. After the reaction was completed, the mixture was centrifuged, and the resulting solid product was washed with anhydrous ethanol to obtain a composite graphene core-shell structure with a polymer coating layer containing amino and carboxyl groups grafted onto its surface.

[0050] (3) The core-shell structure is mixed with an acrylamide solution (DMF solvent) and stirred until homogeneous, with a mass ratio of the core-shell structure to the thermosensitive polymer monomer of 1:10. Then, an initiator (ammonium persulfate) is added, with a mass ratio of the initiator to the thermosensitive polymer monomer of 0.1:100. The mixture is then heated to 50°C and polymerized under a nitrogen atmosphere for 6 hours. After the reaction is complete, the mixture is centrifuged, and the resulting solid product is washed with anhydrous ethanol to obtain the intelligent photothermal composite material.

[0051] The compressive strength of cement mortar specimens coated with the intelligent photothermal composite material prepared in this embodiment was tested using the same method as in Example 1 above. The results are shown in the table below:

[0052] .

[0053] Example 4

[0054] A method for preparing a smart photothermal composite material to improve the cold resistance of cement materials includes the following steps:

[0055] (1) Graphene oxide was ultrasonically dispersed in water for 30 min to obtain a dispersion. Then, carbon quantum dot precursor (citric acid) was dissolved in ethanol and slowly added to the dispersion. The mass ratio of carbon quantum dot precursor to graphene oxide was 1:5. The resulting mixture was heated to 80°C and kept at that temperature under reflux for 12 hours. After the reaction was completed, the mixture was centrifuged, and the resulting solid product was washed with anhydrous ethanol to obtain composite graphene with carbon quantum dots on its surface, which was then set aside.

[0056] (2) The composite graphene was mixed with an N-isopropylacrylamide solution (DMF solvent) and stirred until homogeneous, with the mass ratio of the core-shell structure to the thermosensitive polymer monomer being 1:25. Then, an initiator (ammonium persulfate) was added, with the mass ratio of the initiator to the thermosensitive polymer monomer being 3:100. The mixture was then heated to 65°C and polymerized under a nitrogen atmosphere for 8 hours. After the reaction was completed, the mixture was centrifuged, and the resulting solid product was washed with anhydrous ethanol to obtain the intelligent photothermal composite material.

[0057] The compressive strength of cement mortar specimens coated with the intelligent photothermal composite material prepared in this embodiment was tested using the same method as in Example 1 above. The results are shown in the table below:

[0058] .

[0059] Example 5

[0060] A method for preparing a smart photothermal composite material to improve the cold resistance of cement materials includes the following steps:

[0061] (1) Graphene oxide was ultrasonically dispersed in water for 25 min to obtain a dispersion. Then, a carbon quantum dot precursor (glucose) was dissolved in water and slowly added to the dispersion. The mass ratio of the carbon quantum dot precursor to graphene oxide was 1:2. The resulting mixture was heated to 60°C and kept at that temperature under reflux for 16 hours. After the reaction was completed, the mixture was centrifuged, and the resulting solid product was washed with anhydrous ethanol to obtain composite graphene with carbon quantum dots on its surface, which was then set aside.

[0062] (2) The composite graphene was added to a solution containing acrylamide and acrylic acid monomers (mass ratio of 1:1) in DMF solvent, wherein the mass ratio of the composite graphene to the monomers was 1:50. Then an initiator (potassium persulfate) was added, and the mixture was heated to 80°C for 4 hours to polymerize, wherein the mass ratio of the initiator to the monomers was 1:20. After the reaction was completed, the mixture was centrifuged, and the resulting solid product was washed with anhydrous ethanol to obtain a composite graphene core-shell structure with a polymer coating containing amino and carboxyl groups grafted onto its surface, which is the intelligent photothermal composite material.

[0063] The compressive strength of cement mortar specimens coated with the intelligent photothermal composite material prepared in this embodiment was tested using the same method as in Example 1 above. The results are shown in the table below:

[0064] .

[0065] Example 6

[0066] A method for preparing a smart photothermal composite material to improve the cold resistance of cement materials includes the following steps:

[0067] (1) Graphene oxide was added to a solution containing acrylamide and acrylic acid monomers (mass ratio of 5:1) in DMF solvent, wherein the mass ratio of the composite graphene to the monomers was 0.1:100. Then an initiator (ammonium persulfate) was added, and the mixture was heated to 50°C for 8 hours to polymerize, wherein the mass ratio of the initiator to the monomers was 1:50. After the reaction was completed, the mixture was centrifuged, and the resulting solid product was washed with anhydrous ethanol to obtain a composite graphene core-shell structure with a polymer coating layer containing amino and carboxyl groups grafted onto its surface.

[0068] (2) The core-shell structure is mixed with an acrylamide solution (DMF solvent) and stirred until homogeneous, with a mass ratio of the core-shell structure to the thermosensitive polymer monomer of 1:10. Then, an initiator (ammonium persulfate) is added, with a mass ratio of the initiator to the thermosensitive polymer monomer of 0.1:100. The mixture is then heated to 50°C and polymerized under a nitrogen atmosphere for 6 hours. After the reaction is complete, the mixture is centrifuged, and the resulting solid product is washed with anhydrous ethanol to obtain the intelligent photothermal composite material.

[0069] The compressive strength of cement mortar specimens coated with the intelligent photothermal composite material prepared in this embodiment was tested using the same method as in Example 1 above. The results are shown in the table below:

[0070] .

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A smart photothermal composite material for improving the cold resistance of cement materials, characterized in that, include: A core formed by composite graphene with carbon quantum dots on its surface, a polymer coating layer containing amino and carboxyl groups grafted onto the surface of the core, and a temperature-sensitive polymer shell coating the surface of the polymer coating layer. The composite graphene with carbon quantum dots on its surface is obtained by the following method: adding a carbon quantum dot precursor to a graphene oxide dispersion, then heating and reacting, separating the solid product after completion, and washing to obtain the composite graphene with carbon quantum dots on its surface. The carbon quantum dot precursor includes at least one of citric acid, ascorbic acid, and glucose.

2. The intelligent photothermal composite material for improving the cold resistance of cement materials according to claim 1, characterized in that, The polymer in the polymer coating layer is polymerized from acrylamide and acrylic acid monomers.

3. The intelligent photothermal composite material for improving the cold resistance of cement materials according to claim 1 or 2, characterized in that, The temperature-sensitive polymer shell is polymerized from temperature-sensitive polymer monomers.

4. The intelligent photothermal composite material for improving the cold resistance of cement materials according to claim 3, characterized in that, The thermosensitive polymer monomer includes N-isopropylacrylamide.

5. A method for preparing a smart photothermal composite material to improve the cold resistance of cement materials, characterized in that, Includes the following steps: (1) Add carbon quantum dot precursor to graphene oxide dispersion, then heat to react, separate the solid product after completion, wash and obtain composite graphene with carbon quantum dots on the surface. The carbon quantum dot precursor includes at least one of citric acid, ascorbic acid, and glucose. (2) The composite graphene is dispersed in a monomer solution containing amino and carboxyl groups, then an initiator is added and a polymerization reaction is carried out under heating conditions. After completion, the solid product is separated to obtain a composite graphene core-shell structure with a polymer coating layer containing amino and carboxyl groups grafted on the surface. (3) After mixing the core-shell structure with the thermosensitive polymer monomer solution, an initiator is added and a polymerization reaction is carried out under heating and protective atmosphere conditions so that the thermosensitive polymer formed is uniformly coated on the surface of the core-shell structure; after the reaction is completed, the solid product is separated and washed to obtain the intelligent photothermal composite material.

6. The method for preparing the intelligent photothermal composite material according to claim 5, characterized in that, In step (1), the mass ratio of the carbon quantum dot precursor to graphene oxide is 1:2~10.

7. The method for preparing the intelligent photothermal composite material according to claim 5, characterized in that, In step (1), the heating temperature is 60~100℃ and the reaction time is 8~16 hours.

8. The method for preparing the intelligent photothermal composite material according to claim 5, characterized in that, In step (2), the mass ratio of the composite graphene to the monomer is 1:10~50.

9. The method for preparing the intelligent photothermal composite material according to claim 5, characterized in that, In step (2), the monomers include at least one of acrylamide and acrylic acid monomers, methacrylamide and methacrylic acid monomers; the mass ratio of acrylamide and acrylic acid monomers is 1~5:1; the mass ratio of methacrylamide and methacrylic acid monomers is 1~5:

1.

10. The method for preparing the intelligent photothermal composite material according to claim 5, characterized in that, In step (2), the mass ratio of the initiator to the monomer containing amino and carboxyl groups is 0.1~5:

100.

11. The method for preparing the intelligent photothermal composite material according to claim 5, characterized in that, In step (2), the initiator includes at least one of potassium persulfate, ammonium persulfate, and sodium persulfate.

12. The method for preparing the intelligent photothermal composite material according to claim 5, characterized in that, In step (2), the heating temperature is 50~80℃ and the polymerization reaction time is 4~8 hours.

13. The method for preparing the intelligent photothermal composite material according to claim 5, characterized in that, In step (3), the mass ratio of the core-shell structure to the thermosensitive polymer monomer is 1:10~50.

14. The method for preparing the intelligent photothermal composite material according to claim 5, characterized in that, In step (3), the mass ratio of the initiator to the thermosensitive polymer monomer is 0.1~5:

100.

15. The method for preparing the intelligent photothermal composite material according to claim 5, characterized in that, In step (3), the initiator includes at least one of potassium persulfate, ammonium persulfate, and sodium persulfate.

16. The method for preparing the intelligent photothermal composite material according to any one of claims 5-15, characterized in that, In step (3), the heating temperature is 50~80℃ and the polymerization reaction time is 4~8 hours.

17. The method for preparing the intelligent photothermal composite material according to claim 5, characterized in that, In step (3), the protective atmosphere includes at least one of nitrogen and argon.

18. The application of the intelligent photothermal composite material for improving the cold resistance of cement materials according to any one of claims 1-4, or the intelligent photothermal composite material obtained by the preparation method according to any one of claims 5-17, in cement-based structures.

19. The application according to claim 18, characterized in that, The intelligent photothermal composite material can be applied to the surface of the cement-based structure to be cured.

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