Intelligent photo-thermal composite material for improving cold resistance of cement material as well as preparation method and application of intelligent photo-thermal composite material

Abstract

The invention discloses an intelligent photo-thermal composite material capable of improving the cold resistance of a cement material and a preparation method and application of the intelligent photo-thermal composite material. The intelligent photo-thermal composite material comprises a core formed by composite graphene with carbon quantum dots on the surface, a polymer coating layer grafted on the surface of the core and containing amino and carboxyl, and a thermo-sensitive polymer shell coated on the surface of the polymer coating layer. The photo-thermal composite material provided by the invention not only can form chemical bonding with cement hydration products, but also widens the light absorption range to visible light and near-infrared regions, and improves the photo-thermal conversion efficiency. In addition, the intelligent photo-thermal composite material also has the characteristic that the photo-thermal conversion degree can be automatically adjusted according to the environment temperature, and accurate temperature control is realized.

Description

Technical Field

[0001] The present invention relates to the field of cement-based materials, and particularly to an intelligent photothermal composite material for improving the cold resistance of cement materials, its preparation method and application. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the overall understanding of the present invention, and it is not necessarily regarded as an admission or an indication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] Under cold conditions, the water inside the cement freezes and expands, which not only inhibits the hydration reaction of the cement, resulting in a slow hardening speed and insufficient early strength, but also easily causes the matrix to crack and peel, reducing the durability and freeze-thaw resistance. Traditional anti-freezing mainly relies on adding chemical anti-freezing agents or external heating methods. Among them, chemical anti-freezing agents have limited effects in extremely cold weather and are difficult to ensure the temperature required for the cement hydration reaction. For example, in an environment below -20°C, relying solely on chemical anti-freezing agents may not enable the cement to achieve ideal strength development. External heating has problems such as high energy consumption, high cost, and inconvenience in field construction.

[0004] By adding an intelligent photothermal composite material to the cement-based material and converting solar energy into heat energy to raise the local temperature of the cement, it helps to alleviate the above problems. However, the present invention finds that when existing photothermal materials (such as Ti2O3 nanoparticles, Prussian blue, graphite, etc.) are added to cement, problems such as easy agglomeration and uneven dispersion occur, and the interaction with the cement matrix is weak, making it difficult to exert an enhancement 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] In view of the above problems, the present invention provides an intelligent photothermal composite material for improving the cold resistance of cement materials, its preparation method and application. This photothermal composite material can not only form chemical bonding with the cement hydration products, but also broaden the light absorption range to the visible light and near-infrared regions, improving the photothermal conversion efficiency. Specifically, the present invention discloses the following technical solutions.

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

[0007] Further, the polymer is polymerized from acrylamide and acrylic acid monomers.

[0008] Further, the thermosensitive polymer layer is formed by polymerizing thermosensitive polymer monomers. Optionally, the thermosensitive polymer monomers include at least one of N-isopropylacrylamide, acrylamide, methacrylamide, acrylic acid, methacrylic acid, etc.

[0009] Secondly, the present invention discloses a preparation method of an intelligent photothermal composite material, comprising the following steps: (1) Add a carbon quantum dot precursor to a graphene oxide dispersion, then heat and react. After completion, separate the solid product, and obtain composite graphene with carbon quantum dots on the surface after washing.

[0010] (2) Disperse the composite graphene into a monomer solution containing amino groups and carboxyl groups, then add an initiator and carry out a polymerization reaction under heating conditions. After completion, separate the solid product to obtain a composite graphene core-shell structure with a polymer coating layer containing amino groups and carboxyl groups grafted on the surface.

[0011] (3) Mix the core-shell structure with a thermosensitive polymer monomer solution, then add an initiator and carry out a polymerization reaction under heating and protective atmosphere conditions to uniformly coat the formed thermosensitive polymer on the surface of the core-shell structure. After the reaction is completed, separate the solid product, and the intelligent photothermal composite material is obtained after washing.

[0012] Further, in step (1), the mass ratio of the carbon quantum dot precursor to graphene oxide is 1:2 to 10. Optionally, the carbon quantum dot precursor includes at least one of citric acid, ascorbic acid, glucose, etc.

[0013] Further, in step (1), the heating temperature is 60 to 100 °C, and the reaction time is 8 to 16 hours.

[0014] Further, in step (2), the mass ratio of the composite graphene to the monomer is 1:10 to 50. Optionally, the monomer includes at least one of acrylamide and acrylic acid monomers, methacrylamide and methacrylic acid monomers, etc. Optionally, the mass ratio of acrylamide to acrylic acid monomers is 1 to 5:1, and the mass ratio of methacrylamide to methacrylic acid monomers is 1 to 5:1.

[0015] Further, in step (2), the mass ratio of the initiator to the monomer containing amino groups and carboxyl groups is 0.1 to 5:100. Optionally, the initiator includes at least one of potassium persulfate, ammonium persulfate, sodium persulfate, etc.

[0016] Further, in step (2), the heating temperature is 50-80 °C, and the polymerization reaction time is 4-8 hours. During this process, strong chemical bonds are formed between the epoxy groups or carbonyl groups on the surface of the composite graphene and the amino groups or carboxyl groups on the monomers, resulting in a composite graphene core-shell structure with a polymer coating layer containing amino and carboxyl groups grafted on the surface.

[0017] Further, in step (3), the mass ratio of the core-shell structure to the thermosensitive polymer monomer is 1:10-50.

[0018] 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.

[0019] Further, in step (3), the heating temperature is 50-80 °C, and the polymerization reaction time is 4-8 hours. Optionally, the protective atmosphere includes at least one of nitrogen, argon, etc.

[0020] Finally, the present invention discloses the application of the intelligent photothermal composite material in a cement-based structure. Optionally, the intelligent photothermal composite material can be applied to the surface of the cement-based structure to be cured.

[0021] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: The intelligent photothermal composite material of the present invention first uses graphene with carbon quantum dots grown in situ on the 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, enabling the intelligent photothermal composite material to quickly generate heat under sunlight irradiation, reducing internal water freezing, and providing a temperature guarantee for the cement hydration reaction.

[0022] Further, the present invention grafts a functional group polymer layer containing amino (-NH2) and carboxyl (-COOH) groups on the surface of the core, so that the intelligent photothermal composite material of the present invention can form chemical bonding with the cement hydration products (the hydration products are rich in magnesium ions (Mg²⁺) and phosphate ions (PO4³⁻), the carboxyl group forms a stable coordination bond with Mg²⁺, and the amino group forms a hydrogen bond with PO4³⁻), enhancing the bonding degree between the intelligent photothermal composite material and the cement-based structure, making the intelligent photothermal composite material not only serve as a functional phase for photothermal conversion, but also improving the heat transfer efficiency to the cement-based structure, effectively preventing the problem that the coating formed by the composite material on the surface of the cement-based structure is prone to peeling in a low-temperature environment, resulting in a decrease in heat transfer efficiency.

[0023] Finally, the surface of the intelligent photothermal composite material of the present invention also has an intelligent response release system formed by a temperature-sensitive polymer shell to achieve precise temperature control. When the ambient temperature is lower than a certain temperature, the shell layer shrinks, making the core more fully exposed and enhancing the photothermal conversion efficiency of the core. When the temperature rises to a certain temperature, the shell layer expands, reducing the exposure of the core layer and lowering the photothermal conversion efficiency, thereby avoiding excessive internal temperature of the cement-based material leading to too rapid evaporation of water, affecting later hydration and resulting in insufficient development of later strength. At the same time, it also helps to prevent cracks caused by excessive internal temperature of the cement-based material, resulting in a decrease in strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings forming a part of this specification are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0025] Figure 1 The physical sample diagram of the intelligent photothermal composite material prepared for Example 1 below.

[0026] Figure 2 The compressive strength test diagram for Example 1 below. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The experimental methods without specific conditions noted in the following embodiments are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0028] Unless otherwise defined, all professional and scientific terms used in the present invention have the same meaning as those familiar to persons skilled in the art. The reagents or raw materials used in the present invention can be obtained through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in the conventional manner in the art or according to the product instructions.

[0029] In addition, any methods and materials similar or equivalent to the described content can be applied to the method of the present invention. The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0030] Example 1 A preparation method of an intelligent photothermal composite material for improving the cold resistance of cement materials includes the following steps: (1) Add graphene oxide to water and disperse it by ultrasonic wave for 30 min to obtain a dispersion. Then dissolve the carbon quantum dot precursor (citric acid) in ethanol and slowly add it to the dispersion. The mass ratio of the carbon quantum dot precursor to graphene oxide is 1:5. Heat the obtained mixture to 80 °C, keep it warm, and stir and reflux at this temperature for 12 hours. After the reaction is completed, centrifuge, and wash the obtained solid product with absolute ethanol to obtain composite graphene with carbon quantum dots on the surface for standby.

[0031] (2) Add the composite graphene to a solution containing acrylamide and acrylic acid monomers (the mass ratio of the two is 4:1) (the solvent is DMF). The mass ratio of the composite graphene to the monomers is 1:30. Then add an initiator (ammonium persulfate), and heat to 70 °C for polymerization reaction for 6 hours. The mass ratio of the initiator to the monomers is 1:50. After the reaction is completed, centrifuge, and wash the obtained solid product with absolute ethanol to obtain a composite graphene core-shell structure with a polymer coating layer containing amino and carboxyl groups grafted on the surface.

[0032] (3) Mix the core-shell structure with an N-isopropylacrylamide solution (the solvent is DMF) and stir evenly. The mass ratio of the core-shell structure to the thermosensitive polymer monomer is 1:25. Then add an initiator (ammonium persulfate), and the mass ratio of the initiator to the thermosensitive polymer monomer is 3:100. Then heat to 65 °C and carry out a polymerization reaction for 8 hours in a nitrogen protection atmosphere. After the reaction is completed, centrifuge, and wash the obtained solid product with absolute ethanol to obtain the intelligent photothermal composite material, as Figure 1 shown.

[0033] Performance test: Prepare a cement mortar test block with a size of 40 mm × 40 mm × 40 mm according to GB / T 17671-2021. Then evenly coat a layer of the intelligent photothermal composite material prepared in this example with a thickness of 1 mm on the surface of the test block. Then cure the test blocks in a constant temperature and humidity curing box with a test temperature of -10 °C and 0 °C (the humidity is set to 99%), and at the same time irradiate the test pieces with a light intensity of 1000 W / m², and the daily light irradiation time is 18 hours. Then, at the ages of 3 d, 7 d, and 28 d, test the compressive strength of the test pieces, and the results are shown in the following table: .

[0034] Example 2 A preparation method of an intelligent photothermal composite material for improving the cold resistance of cement materials, comprising the following steps: (1) Add graphene oxide to water and ultrasonically disperse for 25 min to obtain a dispersion. Then dissolve the carbon quantum dot precursor (glucose) in water and slowly add it to the dispersion. The mass ratio of the carbon quantum dot precursor to graphene oxide is 1:2. Heat the obtained mixture to 60 °C, keep it warm, and stir and reflux at this temperature for 16 hours. After the reaction is completed, centrifuge, and wash the obtained solid product with absolute ethanol to obtain composite graphene with carbon quantum dots on the surface for standby.

[0035] (2) Add the composite graphene to a solution containing acrylamide and acrylic acid monomers (the mass ratio of the two is 1:1) (the solvent is DMF). The mass ratio of the composite graphene to the monomers is 1:50. Then add an initiator (potassium persulfate), and heat to 80 °C for polymerization reaction for 4 hours. The mass ratio of the initiator to the monomers is 1:20. After the reaction is completed, centrifuge, and wash the obtained solid product with absolute ethanol to obtain a composite graphene core-shell structure with a polymer coating layer containing amino and carboxyl groups grafted on the surface.

[0036] (3) Mix the core-shell structure with methacrylic acid solution (the solvent is DMF) and stir evenly. The mass ratio of the core-shell structure to the thermosensitive polymer monomer is 1:50. Then add an initiator (potassium persulfate), and the mass ratio of the initiator to the thermosensitive polymer monomer is 1:20. Then heat to 80 °C and carry out polymerization reaction for 4 hours in a nitrogen protection atmosphere. After the reaction is completed, centrifuge, and wash the obtained solid product with absolute ethanol to obtain the intelligent photothermal composite material.

[0037] Use the same method as in Example 1 above to test the compressive strength of the cement mortar specimens coated with the intelligent photothermal composite material prepared in this example. The results are shown in the following table: 。

[0038] Example 3 A preparation method of an intelligent photothermal composite material for improving the cold resistance of cement materials, comprising the following steps: (1) Add graphene oxide to water and ultrasonically disperse for 30 min to obtain a dispersion. Then dissolve the carbon quantum dot precursor (citric acid) in ethanol and slowly add it to the dispersion. The mass ratio of the carbon quantum dot precursor to graphene oxide is 1:10. Heat the obtained mixture to 100 °C, keep it warm, and stir and reflux at this temperature for 8 hours. After the reaction is completed, centrifuge, and wash the obtained solid product with absolute ethanol to obtain composite graphene with carbon quantum dots on the surface for standby.

[0039] (2) Add the composite graphene into a solution containing acrylamide and acrylic acid monomers (the mass ratio of the two is 5:1) (the solvent is DMF), and the mass ratio of the composite graphene to the monomers is 0.1:100. Then add an initiator (ammonium persulfate), and heat to 50 °C for polymerization reaction for 8 hours, and the mass ratio of the initiator to the monomers is 1:50. After the reaction is completed, centrifuge, and wash the obtained solid product with absolute ethanol to obtain a composite graphene core-shell structure with a polymer coating layer containing amino and carboxyl groups grafted on the surface.

[0040] (3) Mix the core-shell structure with an acrylamide solution (the solvent is DMF) and stir evenly, and the mass ratio of the core-shell structure to the thermosensitive polymer monomer is 1:10. Then add an initiator (ammonium persulfate), and the mass ratio of the initiator to the thermosensitive polymer monomer is 0.1:100. Then heat to 50 °C, and carry out the polymerization reaction for 6 hours in a nitrogen protection atmosphere. After the reaction is completed, centrifuge, and wash the obtained solid product with absolute ethanol to obtain the intelligent photothermal composite material.

[0041] Use the same method as in Example 1 above to test the compressive strength of the cement mortar specimens coated with the intelligent photothermal composite material prepared in this example. The results are shown in the following table: 。

[0042] Example 4 A preparation method of an intelligent photothermal composite material for improving the cold resistance of cement materials, comprising the following steps: (1) Add graphene oxide into water and ultrasonically disperse for 30 min to obtain a dispersion. Then dissolve the carbon quantum dot precursor (citric acid) in ethanol and slowly add it to the dispersion, and the mass ratio of the carbon quantum dot precursor to graphene oxide is 1:5. Heat the obtained mixed solution to 80 °C and keep it warm, and stir and reflux at this temperature for 12 hours. After the reaction is completed, centrifuge, and wash the obtained solid product with absolute ethanol to obtain composite graphene with carbon quantum dots on the surface for standby.

[0043] (2) Mix the composite graphene with an N-isopropylacrylamide solution (the solvent is DMF) and stir evenly, and the mass ratio of the core-shell structure to the thermosensitive polymer monomer is 1:25. Then add an initiator (ammonium persulfate), and the mass ratio of the initiator to the thermosensitive polymer monomer is 3:100. Then heat to 65 °C, and carry out the polymerization reaction for 8 hours in a nitrogen protection atmosphere. After the reaction is completed, centrifuge, and wash the obtained solid product with absolute ethanol to obtain the intelligent photothermal composite material.

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

[0045] Example 5 A preparation method of an intelligent photothermal composite material for improving the cold resistance of cement materials, comprising the following steps: (1) Graphene oxide was added to water and ultrasonically dispersed for 25 min to obtain a dispersion. Then, a carbon quantum dot precursor (glucose) was dissolved in water and slowly added to the dispersion, and the mass ratio of the carbon quantum dot precursor to graphene oxide was 1:2. The obtained mixture was heated to 60 °C and kept warm, and stirred and refluxed at this temperature for 16 hours. After the reaction was completed, centrifugation was carried out, and the obtained solid product was washed with absolute ethanol to obtain composite graphene with carbon quantum dots on the surface, and it was reserved for use.

[0046] (2) The composite graphene was added to a solution containing acrylamide and acrylic acid monomers (the mass ratio of the two is 1:1) (the solvent is DMF), and 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 a polymerization reaction for 4 hours, and the mass ratio of the initiator to the monomers was 1:20. After the reaction was completed, centrifugation was carried out, and the obtained solid product was washed with absolute ethanol to obtain a composite graphene core-shell structure with a polymer coating layer containing amino and carboxyl groups grafted on the surface, that is, the intelligent photothermal composite material.

[0047] The compressive strength of the cement mortar specimens coated with the intelligent photothermal composite material prepared in this example was tested using the same method as in Example 1 above, and the results are shown in the following table: 。

[0048] Example 6 A preparation method of an intelligent photothermal composite material for improving the cold resistance of cement materials, comprising the following steps: (1) Graphene oxide was added to a solution containing acrylamide and acrylic acid monomers (the mass ratio of the two is 5:1) (the solvent is DMF), and 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 a polymerization reaction for 8 hours, and the mass ratio of the initiator to the monomers was 1:50. After the reaction was completed, centrifugation was carried out, and the obtained solid product was washed with absolute ethanol to obtain a composite graphene core-shell structure with a polymer coating layer containing amino and carboxyl groups grafted on the surface.

[0049] (2) Mix the core-shell structure with an acrylamide solution (the solvent is DMF) and stir evenly. The mass ratio of the core-shell structure to the thermosensitive polymer monomer is 1:10. Then add an initiator (ammonium persulfate), and the mass ratio of the initiator to the thermosensitive polymer monomer is 0.1:100. Then heat to 50 °C and carry out a polymerization reaction for 6 hours in a nitrogen-protected atmosphere. After the reaction is completed, centrifuge, and wash the obtained solid product with absolute ethanol to obtain the intelligent photothermal composite material.

[0050] Use the same method as in Example 1 above to test the compressive strength of the cement mortar specimens coated with the intelligent photothermal composite material prepared in this example. The results are shown in the following table: .

[0051] The foregoing are only the preferred embodiments of the present invention and are 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 perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An intelligent photothermal composite material for improving the cold resistance of cement materials, characterized in that, Comprising: A core formed by composite graphene with carbon quantum dots on its surface, a polymer coating layer containing amino and carboxyl groups grafted on the surface of the core, and a thermosensitive polymer shell coated on the surface of the polymer coating layer.

2. The intelligent photothermal composite material for improving the cold resistance of cement materials according to claim 1, wherein The polymer is formed by polymerizing 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 thermosensitive polymer layer is formed by polymerizing thermosensitive polymer monomers; optionally, the thermosensitive polymer monomers include at least one of N-isopropylacrylamide, acrylamide, methacrylamide, acrylic acid, and methacrylic acid.

4. A preparation method of an intelligent photothermal composite material for improving the cold resistance of cement materials, characterized in that, Including the following steps: (1) Adding a carbon quantum dot precursor to a graphene oxide dispersion, then heating and reacting. After completion, separating the solid product and washing to obtain composite graphene with carbon quantum dots on its surface; (2) Dispersing the composite graphene into a monomer solution containing amino and carboxyl groups, then adding an initiator and carrying out a polymerization reaction under heating conditions. After completion, separating the solid product to obtain a composite graphene core-shell structure with a polymer coating layer containing amino and carboxyl groups grafted on its surface; (3) Mixing the core-shell structure with a thermosensitive polymer monomer solution, adding an initiator, and carrying out a polymerization reaction under heating and protective atmosphere conditions to uniformly coat the formed thermosensitive polymer on the surface of the core-shell structure; after the reaction is completed, separating the solid product and washing to obtain the intelligent photothermal composite material.

5. The preparation method of the intelligent photothermal composite material according to claim 4, wherein, In step (1), the mass ratio of the carbon quantum dot precursor to graphene oxide is 1:2 to 10; Optionally, in step (1), the carbon quantum dot precursor includes at least one of citric acid, ascorbic acid, and glucose; Optionally, in step (1), the heating temperature is 60 to 100 °C and the reaction time is 8 to 16 hours.

6. The preparation method of the intelligent photothermal composite material according to claim 4, wherein In step (2), the mass ratio of the composite graphene to the monomer is 1:10 to 50; Optionally, the monomer includes at least one of acrylamide and acrylic acid monomers, and methacrylamide and methacrylic acid; Optionally, the mass ratio of acrylamide to acrylic acid monomers is 1 to 5:1; Optionally, the mass ratio of methacrylamide to methacrylic acid monomers is 1 to 5:

1.

7. The preparation method of the intelligent photothermal composite material according to claim 4, characterized in that, In step (2), the mass ratio of the initiator to the monomer containing amino and carboxyl groups is 0.1 to 5:100; Optionally, in step (2), the initiator includes at least one of potassium persulfate, ammonium persulfate, and sodium persulfate; Optionally, in step (2), the heating temperature is 50 to 80 °C and the polymerization reaction time is 4 to 8 hours.

8. The preparation method of the intelligent photothermal composite material according to claim 4, characterized in that In step (3), the mass ratio of the core-shell structure to the thermosensitive polymer monomer is 1:10 to 50; Optionally, in step (3), the mass ratio of the initiator to the thermosensitive polymer monomer is 0.1 to 5:100; Optionally, in step (3), the initiator includes at least one of potassium persulfate, ammonium persulfate, and sodium persulfate.

9. The preparation method of the intelligent photothermal composite material according to any one of claims 4-8, characterized in that, In step (3), in step (3), the heating temperature is 50 to 80 °C and the polymerization reaction time is 4 to 8 hours; optionally, the protective atmosphere includes at least one of nitrogen and argon.

10. The application of the intelligent photothermal composite material for improving the cold resistance of cement materials according to any one of claims 1 to 3, or the intelligent photothermal composite material obtained by the preparation method according to any one of claims 4 to 9 in a cement-based structure; optionally, the intelligent photothermal composite material can be applied to the surface of the cement-based structure to be cured.

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