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CN117025175A - Composite phase change material with hydrophobic and high-efficiency photo-thermal conversion performance, and preparation method and application thereof - Google Patents

Composite phase change material with hydrophobic and high-efficiency photo-thermal conversion performance, and preparation method and application thereof Download PDF

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Publication number
CN117025175A
CN117025175A CN202310910728.7A CN202310910728A CN117025175A CN 117025175 A CN117025175 A CN 117025175A CN 202310910728 A CN202310910728 A CN 202310910728A CN 117025175 A CN117025175 A CN 117025175A
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tme
change material
composite phase
mcg
prepared
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谢兰
吴昌梅
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Kangmingyuan Guizhou Technology Development Co ltd
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Kangmingyuan Guizhou Technology Development Co ltd
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
    • B01J13/0091—Preparation of aerogels, e.g. xerogels
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K5/00—Heat-transfer, heat-exchange or heat-storage materials, e.g. refrigerants; Materials for the production of heat or cold by chemical reactions other than by combustion
    • C09K5/02—Materials undergoing a change of physical state when used
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N15/00—Thermoelectric devices without a junction of dissimilar materials; Thermomagnetic devices, e.g. using the Nernst-Ettingshausen effect

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Abstract

The invention discloses a composite phase-change material with hydrophobic and high-efficiency photo-thermal conversion performance, a preparation method and application thereof, and relates to the technical field of hydrophobic and electromagnetic shielding composite materials. The invention provides a method for preparing a T-TME@MCG composite phase change material by simple vacuum auxiliary packaging and subsequent surface photo-thermal etching and PDMS coating strategies. And dipping the CNF/GNP mixed solution into an MF skeleton and performing freeze drying to prepare the MCG composite aerogel. And then immersing the material into a saturated methanol solution of TME, and carrying out vacuum drying to obtain the TME@MCG composite phase change material. Further, carrying out surface treatment on TME@MCG by adopting photo-thermal etching and PDMS coating technology to obtain the final T-TME@MCG composite phase-change material. The preparation method has the advantages of simple preparation process, controllable technology and easy mass production.

Description

Composite phase change material with hydrophobic and high-efficiency photo-thermal conversion performance, and preparation method and application thereof
Technical Field
The invention relates to the technical field of hydrophobic and photo-thermal conversion composite phase-change materials, in particular to a composite phase-change material with hydrophobic and high-efficiency photo-thermal conversion performance, and a preparation method and application thereof.
Background
According to domestic and foreign researches, the photo-thermal conversion performance of the surface of a large amount of Composite Phase Change Materials (CPCMs) is poor, because the surface of the CPCMs is only exposed with a small amount of photo-thermal nano-filler. Thus, it is urgent to prepare CPCMs with high surface light-heat absorption and conversion efficiency. The tris (hydroxymethyl) ethane (TME) as a solid-solid phase change material has the advantages of high latent enthalpy, no toxicity, environmental friendliness and the like of most organic phase change materials, and the characteristic of volatilizing at 130 ℃ is beneficial to carrying out surface photo-thermal etching on TME-based CPCMs so as to expose a photo-thermal matrix skeleton on the surface, thereby preparing the CPCMs with high-efficiency surface photo-thermal conversion. However, the porous photo-thermal network exposed on the surface of TME-based CPCMs is inevitably damaged by external force, and the superhydrophilic TME is easily eroded or even dissolved by humid air or rainwater, so that TME-based CPCMs cannot exert their functional characteristics. In addition, solar heat absorbed by TME-based CPCMs is easy to generate thermal convection and radiation with the surrounding environment, and efficient photo-thermal conversion is difficult to achieve. Therefore, structural design is required to make TME-based CPCMs possess both hydrophobic and efficient photothermal conversion properties.
Therefore, the invention discloses a composite phase change material with hydrophobic and high-efficiency photo-thermal conversion performance, and a preparation strategy and application thereof. The Melamine Foam (MF)/Cellulose Nanofiber (CNF)/Graphene Nanosheet (GNP) (MCG) composite aerogel with anisotropic heat conduction is prepared by simple physical blending and subsequent freeze drying technology, and is further subjected to TME encapsulation, surface thermal etching and Polydimethylsiloxane (PDMS) coating to obtain the final TME@MCG (T-TME@MCG) composite phase change material subjected to surface thermal etching and PDMS coating treatment. The composite phase change material provided by the invention has excellent heat-off conversion efficiency (93.07%), and meanwhile, the static Water Contact Angle (WCA) is as high as 140 degrees, and the composite phase change material can be used as a photo-thermal conversion material of a photo-thermal-electric generator in a dry or even wet environment. The preparation method has the advantages of simple preparation process, controllable technology and easy mass production.
Disclosure of Invention
The invention provides a preparation method and application of a composite phase-change material with hydrophobic and high-efficiency photo-thermal conversion performance, and aims to make up for the defects of the prior art.
The invention adopts the following technical scheme to realize the aim of the invention:
a composite phase change material with hydrophobic and high-efficiency photo-thermal conversion performance is disclosed, wherein the composite phase change material is T-TME@MCG.
The preparation method of the composite phase change material with the hydrophobic and high-efficiency photo-thermal conversion performance comprises the following steps:
step S1: preparing a cellulose nanofiber/graphene nanoplatelet (CNF/GNP) mixed solution, then vacuum-assisted dipping in Melamine Foam (MF), and further freeze-drying to prepare MCG aerogel;
step S2: immersing the MCG aerogel prepared in the step S1 into a saturated methanol solution containing tris (hydroxymethyl) ethane (TME), carrying out vacuum treatment for 3 times, taking out a sample, and carrying out vacuum drying, and circulating in such a way to obtain a TME@MCG composite phase change material;
step S3: and (3) carrying out surface photo-thermal etching and PDMS coating on the TME@MCG composite phase-change material prepared in the step (S2) to prepare the T-TME@MCG composite phase-change material.
The preparation method of the MCG aerogel in the step S1 comprises the following steps:
Step S11: weighing GNPs powder with certain mass, adding the GNPs powder into CNFs water solution, and alternately carrying out magnetic stirring and ultrasonic treatment to uniformly disperse the GNPs powder to obtain CNF/GNP mixed solution;
step S12: immersing the cut MF into the CNF/GNP mixed solution prepared in the step S11, and placing the immersed solution into a vacuum oven for vacuum auxiliary immersion, so that the CNF/GNP mixed solution is embedded into an MF skeleton, thereby obtaining an MF/CNF/GNP composite sol;
step S13: and (3) placing the MF/CNF/GNP composite sol prepared in the step (S12) in a low-temperature refrigerator to gel, and then performing liquid nitrogen directional freezing and low-temperature vacuum drying to prepare the MF/CNF/GNP aerogel, namely the MCG aerogel.
The concentration of CNFs in the step S11 is 7 mg/ml, the concentration of GNPs is 5-25 mg/ml, the magnetic stirring speed and time are 1300 rpm and 6 h respectively, the ultrasonic treatment power and time are 240W and 2 h respectively, and the times of alternating magnetic stirring and ultrasonic treatment are 3; the vacuum assisted impregnation pressures and times in step S12 were about 82 Pa and 24 h, respectively; the temperature of the refrigerator for gelation in the aforementioned step S13 was 6℃for 8 h, the pressure of the low-temperature vacuum drying was 6 Pa, the temperature was-72℃and the time was 48 h.
The preparation method of the TME@MCG composite phase change material in the step S2 comprises the following steps:
Step S21: weighing TME, adding the TME into a methanol solution, and magnetically stirring at room temperature to obtain a methanol saturated solution of TME;
step S22: immersing the MCG aerogel skeleton prepared in the step S1 into the saturated methanol solution of TME prepared in the step S21, carrying out vacuum treatment for 3 times, taking out a sample, and drying in a vacuum drying oven to obtain a TME@MCG semi-finished product 1;
step S23: immersing the TME@MCG semi-finished product 1 prepared in the step S22 into the saturated methanol solution of the TME prepared in the step S21 for 3 times, taking out a sample, and drying in a vacuum drying oven to obtain a TME@MCG semi-finished product 2;
step S24: immersing the TME@MCG semi-finished product 2 prepared in the step S23 into the saturated methanol solution of the TME prepared in the step S21 again, carrying out vacuum treatment for 3 times, taking out a sample, and drying in a vacuum drying oven to obtain the TME@MCG composite phase change material;
the TME in the step S21 has a mass of 8 g, a volume of 20 mL, and a magnetic stirring speed and time of 800 rpm and 6 h, respectively; the vacuum treatment in the steps S22, S23 and S24 was performed at a pressure of 80 Pa for a time of 0.5 h, and the vacuum drying oven was performed at a pressure of 80 Pa for a time of 1 h.
The preparation method of the T-TME@MCG composite phase change material in the step S3 comprises the following steps:
step S31: wrapping the surface of the TME@MCG composite phase-change material prepared in the step S2 except the upper surface by using a heat-insulating adhesive tape, placing the heat-insulating adhesive tape under simulated sunlight, adjusting the illumination intensity until the surface temperature reaches 130-135 ℃, sublimating TME on the surface layer, and keeping 1-1.5 h to obtain a T-TME@MCG semi-finished product with a specific etching depth;
step S32: adding a PDMS prepolymer (poly (dimethyl-methyl vinyl siloxane)) and a cross-linking agent (poly (dimethyl-methyl-hydrogen siloxane)) matched with the PDMS prepolymer into an n-heptane solution, magnetically stirring the mixture to obtain a PDMS uniform n-heptane composite solution containing the cross-linking agent, placing the T-TME@MCG semi-finished product prepared in the step S31 into the PDMS uniform n-heptane composite solution containing the cross-linking agent, transferring the PDMS uniform n-heptane composite solution into a blast oven for curing and cross-linking, coating a PDMS transparent thin layer on the surface of a sample, and repeating the step for 2 times to obtain the final T-TME@MCG composite phase-change material.
The etching depth of the T-TME@MCG semi-finished product in the step S31 is 0.55 mm; the mass of PDMS prepolymer in the step S32 was 1 g, the mass of the crosslinking agent was 0.1 g, the mass of n-heptane was 10g, the magnetic stirring speed was 600 rpm, the stirring time was 6 h, the temperature of the air oven was 60℃and the curing crosslinking time was 4 h.
The application of the composite phase-change material with the hydrophobic and high-efficiency photo-thermal conversion performance adopts the composite phase-change material as the photo-thermal conversion material of the photo-thermal-electric generator in dry and even wet environments.
Advantageous effects
Compared with the prior art, the invention has the following beneficial effects:
1. the invention provides a method for preparing a T-TME@MCG composite phase change material by simple vacuum auxiliary packaging and subsequent surface photo-thermal etching and PDMS coating strategies. And dipping the CNF/GNP mixed solution into an MF skeleton and performing freeze drying to prepare the MCG composite aerogel. And then immersing the material into a saturated methanol solution of TME, and carrying out vacuum drying to obtain the TME@MCG composite phase change material. Further, carrying out surface treatment on TME@MCG by adopting photo-thermal etching and PDMS coating technology to obtain the final T-TME@MCG composite phase-change material. The preparation method has the advantages of simple preparation process, controllable technology and easy mass production.
2. The MCG composite aerogel provided by the invention has an anisotropic porous structure, provides adsorption sites for TME, and simultaneously provides an effective heat conduction network for phonon conduction for the final T-TME@MCG composite phase change material. The photo-thermal etching and PDMS coating treatment of the surface not only increases the photo-thermal absorption and conversion efficiency of the T-TME@MCG composite phase-change material, but also endows the material with outstanding hydrophobic property.
3. When the filling content of GNPs is 2.8 wt%, the T-TME@MCG composite phase-change material provided by the invention shows excellent photo-thermal conversion efficiency (93.07%), and the photo-thermal-electric generator combined with the material can output open-circuit voltage as high as 158.8 mV and short-circuit current of 26.6 mA; in addition, static water contact angles can be up to approximately 140 °. Can be used as a photo-thermal conversion material of a photo-thermal-electric generator in a dry or even wet environment, and is beneficial to relieving energy crisis caused by consumption of a large amount of fossil fuel.
4. The preparation method has the advantages of simple preparation process, controllable technology and easy mass production.
Drawings
FIG. 1 is a SEM of a cross-section (perpendicular to the freezing direction) and a longitudinal cross-section (along the freezing direction) of an MCG25 aerogel prepared according to the present invention (FIG. 1 a) and (FIG. 1 b), FIG. 1b' being a further enlarged view of FIG. 1 b;
FIG. 2 is a SEM (FIG. 2 a) of a cross-section (perpendicular to the freezing direction) of a TME@MCG25 composite phase change material prepared according to the invention, FIG. 2a' being a further enlarged view of FIG. 2 a;
FIG. 3 is a FTIR (FIG. 3 a) and XRD (FIG. 3 b) chart of the raw material TME and the prepared TME@MF, TME@MF/CNF and TME@MCG25 composite phase change material;
FIG. 4 shows the phase transition temperature (FIG. 4 a) and latent enthalpy (FIG. 4 b) of the composite phase change material of the present invention, TME@MF/CNF and TME@MCG5, 10, 15, 20, 25 prepared from TME@MF/CNF;
FIG. 5 is a surface SEM image before photo-thermal etching (FIG. 5 a) and a surface SEM image after photo-thermal etching (FIG. 5 b) of the TME@MCG25 composite phase change material prepared by the method; a surface SEM image of the T-tme@mcg25 composite phase change material (fig. 5C 1), a SEM image for scanning element distribution (fig. 5C 2), a total surface EDS image containing C, O, si and N elements (fig. 5C 3), a surface EDS image containing C elements (fig. 5C 4), a surface EDS image containing O elements (fig. 5C 5), a surface EDS image containing Si elements (fig. 5C 6), and a surface EDS image containing N elements (fig. 5C 7);
FIG. 6 is a photograph of various solution droplets on the surface of a TME@MF/CNF and T-TME@MCG5, 10, 15, 20, 25 composite phase change material prepared by the method (FIG. 6 a), and a self-cleaning schematic diagram of the TME@MCG25 and T-TME@MCG25 composite phase change material (FIG. 6 c);
FIG. 7 shows the thermal conductivity of TME and TME@MF/CNF and TME@MCG5, 10, 15, 20, 25 composite phase change materials prepared by the method;
FIG. 8 is a UV-vis-NIR of the raw TME of the invention and the prepared TME@MCG25 surface, TME@MCG25 etched surface and T-TME@MCG25 surface (FIG. 8 a); TME@MCG25, and TME@MCG25 and T-TME@MCG25 composite phase change material with photo-thermal etching surface at ratio of 400 mW/cm 2 A time-temperature response plot under simulated solar illumination (fig. 8 b); T-TME@MCG5, 10, 15, 20, 25 composite phase change material with the density of 400 mW/cm 2 A time-temperature response plot under simulated solar illumination (fig. 8 c);
FIG. 9 shows STEG at 400 mW/cm combined with T-TME@MCG5, 10, 15, 20, 25 composite phase change material prepared according to the invention 2 Outputting an open circuit voltage diagram (figure 9 a) and a short circuit current diagram (figure 9 b) at different times under simulated sunlight; a cycle time-voltage plot (fig. 9 c) and a time-voltage plot (fig. 9 d) of the T-tme@mcg25 composite phase change material-bound STEG.
Description of the embodiments
In order that the manner in which the invention may be better understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
Example 1. A T-TME@MCG5 composite phase change material.
The preparation method of the T-TME@MCG5 composite phase change material comprises the following steps:
step S1: preparing a CNF/GNP5 mixed solution, then vacuum-assisted dipping in MF, and further freeze-drying to prepare MCG5 aerogel;
Specifically, step S11: weighing 0.3 g of GNPs powder, adding the powder into an aqueous solution (7 mg/mL, 60 mL) with the concentration of CNFs, and carrying out 3 times of alternating magnetic stirring (1300 rpm,6 h) and ultrasonic treatment (240W, 2 h) to uniformly disperse the powder, wherein the concentration of the GNPs in the step is 5 mg/mL, so as to obtain a CNF/GNP5 mixed solution;
step S12: immersing the cut MF into the CNF/GNP5 mixed solution prepared in the step S11, and placing the cut MF into a vacuum oven with the pressure of about 82 Pa for vacuum auxiliary impregnation for 24 h, so that the CNF/GNP5 mixed solution is embedded into an MF skeleton to obtain an MF/CNF/GNP5 composite sol;
step S13: and (3) placing the MF/CNF/GNP5 composite sol prepared in the step (S12) in a low-temperature refrigerator with the temperature of 6 ℃ to gel 8 h, and further performing liquid nitrogen directional freezing and low-temperature vacuum drying with the pressure, temperature and time of 6 Pa, -72 ℃ and 48 h respectively to prepare the MF/CNF/GNP5 (simplified as MCG 5) aerogel.
Step S2: immersing the MCG5 aerogel prepared in the step S1 into a saturated methanol solution containing TME, carrying out vacuum treatment for 3 times, taking out a sample, and carrying out vacuum drying, and thus, circulating to obtain a TME@MCG5 composite phase change material;
specifically, step S21: 8g of TME is weighed and added into 20 mL methanol solution, magnetic stirring is carried out at room temperature, and the stirring speed and the stirring time are respectively 800 rpm and 6 h, so as to obtain a methanol saturated solution of TME;
Step S22: immersing the MCG5 aerogel skeleton prepared in the step S1 into the saturated methanol solution of TME prepared in the step S21, performing vacuum treatment (the pressure and the time are about 80 Pa and 0.5 h respectively) for 3 times, taking out a sample, and placing the sample in a vacuum drying oven of 80 Pa for drying 1 h to obtain a TME@MCG5 semi-finished product 1;
step S23: immersing the TME@MCG5 semi-finished product 1 prepared in the step S22 into the saturated methanol solution of the TME prepared in the step S21 for 3 times, taking out a sample, and drying the sample in a vacuum drying oven of 80 Pa for 1 h to obtain a TME@MCG5 semi-finished product 2;
step S24: immersing the TME@MCG5 semi-finished product 2 prepared in the step S23 into the saturated methanol solution of the TME prepared in the step S21 again, performing vacuum treatment (the pressure and the time are about 80 Pa and 0.5 h respectively) for 3 times, taking out a sample, and placing the sample in a vacuum drying oven of 80 Pa for drying 1 h to obtain the TME@MCG5 composite phase change material;
step S3: and (3) carrying out surface photo-thermal etching and subsequent PDMS coating on the TME@MCG5 composite phase-change material prepared in the step (S2) to prepare the T-TME@MCG5 composite phase-change material.
Specifically, step S31: wrapping the surface (except the upper surface) of the TME@MCG5 composite phase-change material prepared in the step S2 by using a heat-insulating adhesive tape, placing the heat-insulating adhesive tape under simulated sunlight, adjusting the illumination intensity until the surface temperature reaches 130-135 ℃, sublimating TME on the surface layer, and keeping 1-1.5 h to obtain a T-TME@MCG5 semi-finished product with a specific etching depth of 0.55 mm;
Step S32: adding 1 g of PDMS prepolymer poly (dimethyl-methyl vinyl siloxane) and 0.1 g cross-linking agent matched with the PDMS prepolymer poly (dimethyl-methyl-hydrogen siloxane) into 10 g n-heptane solution, magnetically stirring the mixture at 600 rpm for 6 h to obtain PDMS uniform n-heptane composite solution containing the cross-linking agent, placing the semi-finished product of T-TME@MCG5 prepared in the step S31 into the PDMS uniform n-heptane composite solution containing the cross-linking agent, transferring the semi-finished product into a blast oven at 60 ℃ for curing and cross-linking for 4 h, coating a PDMS transparent thin layer on the surface of a sample, and repeating the steps for 2 times to obtain the final T-TME@MCG5 composite phase change material.
Example 2. A T-TME@MCG10 composite phase change material.
The preparation method of the T-TME@MCG10 composite phase change material comprises the following steps:
step S1: preparing a CNF/GNP10 mixed solution, then vacuum-assisted dipping in MF, and further freeze-drying to prepare MCG10 aerogel;
specifically, step S11: weighing 0.6 g of GNPs powder, adding the powder into CNFs water solution (7 mg/mL, 60 mL), and carrying out 3 times of alternate magnetic stirring (1300 rpm,6 h) and ultrasonic treatment (240W, 2 h) to uniformly disperse the powder, wherein the concentration of the GNPs in the step is 10 mg/mL, so as to obtain CNF/GNP10 mixed solution;
Step S12: immersing the cut MF into the CNF/GNP10 mixed solution prepared in the step S11, and placing the cut MF into a vacuum oven with the pressure of about 82 Pa for vacuum auxiliary impregnation for 24 h, so that the CNF/GNP10 mixed solution is embedded into an MF skeleton to obtain an MF/CNF/GNP10 composite sol;
step S13: and (3) placing the MF/CNF/GNP10 composite sol prepared in the step (S12) in a low-temperature refrigerator with the temperature of 6 ℃ to gel 8 h, and further performing liquid nitrogen directional freezing and low-temperature vacuum drying with the pressure, temperature and time of 6 Pa, -72 ℃ and 48 h respectively to prepare the MF/CNF/GNP10 (simplified as MCG 10) aerogel.
Step S2: immersing the MCG10 aerogel prepared in the step S1 into a saturated methanol solution containing TME, carrying out vacuum treatment for 3 times, taking out a sample, and carrying out vacuum drying, and thus, circulating to obtain a TME@MCG10 composite phase change material;
specifically, step S21: 8g of TME is weighed and added into 20 mL methanol solution, magnetic stirring is carried out at room temperature, and the stirring speed and the stirring time are respectively 800 rpm and 6 h, so as to obtain a methanol saturated solution of TME;
step S22: immersing the MCG10 aerogel skeleton prepared in the step S1 into the saturated methanol solution of TME prepared in the step S21, performing vacuum treatment (the pressure and the time are about 80 Pa and 0.5 h respectively) for 3 times, taking out a sample, and drying in a vacuum drying oven of 80 Pa for 1h to obtain a TME@MCG10 semi-finished product 1;
Step S23: immersing the TME@MCG10 semi-finished product 1 prepared in the step S22 into the saturated methanol solution of the TME prepared in the step S21 for 3 times, taking out a sample, and drying the sample in a vacuum drying oven of 80 Pa for 1 h to obtain a TME@MCG10 semi-finished product 2;
step S24: immersing the TME@MCG10 semi-finished product 2 prepared in the step S23 into the saturated methanol solution of the TME prepared in the step S21 again, performing vacuum treatment (the pressure and the time are about 80 Pa and 0.5 h respectively) for 3 times, taking out a sample, and placing the sample in a vacuum drying oven of 80 Pa for drying 1 h to obtain the TME@MCG10 composite phase change material;
step S3: and (3) carrying out surface photo-thermal etching and subsequent PDMS coating on the TME@MCG10 composite phase-change material prepared in the step (S2) to prepare the T-TME@MCG10 composite phase-change material.
Specifically, step S31: wrapping the surface (except the upper surface) of the TME@MCG10 composite phase-change material prepared in the step S2 by using a heat-insulating adhesive tape, placing the heat-insulating adhesive tape under simulated sunlight, adjusting the illumination intensity until the surface temperature reaches 130-135 ℃, sublimating TME on the surface layer, and keeping 1-1.5 h to obtain a T-TME@MCG10 semi-finished product with a specific etching depth of 0.55 mm;
Step S32: adding 1 g of PDMS prepolymer poly (dimethyl-methyl vinyl siloxane) and 0.1 g cross-linking agent matched with the PDMS prepolymer poly (dimethyl-methyl-hydrogen siloxane) into 10 g n-heptane solution, magnetically stirring the mixture at 600 rpm for 6 h to obtain PDMS uniform n-heptane composite solution containing the cross-linking agent, placing the semi-finished product of T-TME@MCG10 prepared in the step S31 into the PDMS uniform n-heptane composite solution containing the cross-linking agent, transferring the semi-finished product into a blast oven at 60 ℃ for curing and cross-linking for 4 h, coating a PDMS transparent thin layer on the surface of a sample, and repeating the steps for 2 times to obtain the final T-TME@MCG10 composite phase change material.
Example 3. A T-TME@MCG15 composite phase change material.
The preparation method of the T-TME@MCG15 composite phase change material comprises the following steps:
step S1: preparing a CNF/GNP15 mixed solution, then vacuum-assisted dipping in MF, and further freeze-drying to prepare MCG15 aerogel;
specifically, step S11: weighing 0.9 g of GNPs powder, adding the powder into CNFs water solution (7 mg/mL, 60 mL), and carrying out 3 times of alternate magnetic stirring (1300 rpm,6 h) and ultrasonic treatment (240W, 2 h) to uniformly disperse the powder, wherein the concentration of the GNPs in the step is 15 mg/mL, so as to obtain CNF/GNP15 mixed solution;
Step S12: immersing the cut MF into the CNF/GNP15 mixed solution prepared in the step S11, and placing the cut MF into a vacuum oven with the pressure of about 82 Pa for vacuum auxiliary impregnation for 24 h, so that the CNF/GNP15 mixed solution is embedded into an MF skeleton to obtain an MF/CNF/GNP15 composite sol;
step S13: and (3) placing the MF/CNF/GNP15 composite sol prepared in the step (S12) in a low-temperature refrigerator with the temperature of 6 ℃ to gel 8 h, and further performing liquid nitrogen directional freezing and low-temperature vacuum drying with the pressure, temperature and time of 6 Pa, -72 ℃ and 48 h respectively to prepare the MF/CNF/GNP15 (simplified as MCG 15) aerogel.
Step S2: immersing the MCG15 aerogel prepared in the step S1 into a saturated methanol solution containing TME, carrying out vacuum treatment for 3 times, taking out a sample, and carrying out vacuum drying, and thus, circulating to obtain a TME@MCG15 composite phase change material;
specifically, step S21: 8 g of TME is weighed and added into 20 mL methanol solution, magnetic stirring is carried out at room temperature, and the stirring speed and the stirring time are respectively 800 rpm and 6 h, so as to obtain a methanol saturated solution of TME;
step S22: immersing the MCG15 aerogel skeleton prepared in the step S1 into the saturated methanol solution of TME prepared in the step S21, performing vacuum treatment (the pressure and the time are about 80 Pa and 0.5 h respectively) for 3 times, taking out a sample, and placing the sample in a vacuum drying oven of 80 Pa for drying 1 h to obtain a TME@MCG15 semi-finished product 1;
Step S23: immersing the TME@MCG15 semi-finished product 1 prepared in the step S22 into the saturated methanol solution of the TME prepared in the step S21 for 3 times, taking out a sample, and drying the sample in a vacuum drying oven of 80 Pa for 1 h to obtain a TME@MCG15 semi-finished product 2;
step S24: immersing the TME@MCG15 semi-finished product 2 prepared in the step S23 into the saturated methanol solution of the TME prepared in the step S21 again, performing vacuum treatment (the pressure and the time are about 80 Pa and 0.5 h respectively) for 3 times, taking out a sample, and placing the sample in a vacuum drying oven of 80 Pa for drying 1 h to obtain the TME@MCG15 composite phase change material;
step S3: and (3) carrying out surface photo-thermal etching and subsequent PDMS coating on the TME@MCG15 composite phase-change material prepared in the step (S2) to prepare the T-TME@MCG15 composite phase-change material.
Specifically, step S31: wrapping the surface (except the upper surface) of the TME@MCG15 composite phase-change material prepared in the step S2 by using a heat-insulating adhesive tape, placing the heat-insulating adhesive tape under simulated sunlight, adjusting the illumination intensity until the surface temperature reaches 130-135 ℃, sublimating TME on the surface layer, and keeping 1-1.5 h to obtain a T-TME@MCG15 semi-finished product with a specific etching depth of 0.55 mm;
Step S32: adding 1 g of PDMS prepolymer poly (dimethyl-methyl vinyl siloxane) and 0.1 g cross-linking agent matched with the PDMS prepolymer poly (dimethyl-methyl-hydrogen siloxane) into 10 g n-heptane solution, magnetically stirring the mixture at 600 rpm for 6 h to obtain PDMS uniform n-heptane composite solution containing the cross-linking agent, placing the semi-finished product of T-TME@MCG15 prepared in the step S31 into the PDMS uniform n-heptane composite solution containing the cross-linking agent, transferring the semi-finished product into a blast oven at 60 ℃ for curing and cross-linking for 4 h, coating a PDMS transparent thin layer on the surface of a sample, and repeating the steps for 2 times to obtain the final T-TME@MCG15 composite phase change material.
Example 4. A T-TME@MCG20 composite phase change material.
The preparation method of the T-TME@MCG20 composite phase-change material comprises the following steps:
step S1: preparing a CNF/GNP20 mixed solution, then vacuum-assisted dipping in MF, and further freeze-drying to prepare MCG20 aerogel;
specifically, step S11: 1.2 g of GNPs powder is weighed and added into CNFs water solution (7 mg/mL, 60 mL), and is subjected to 3 times of alternate magnetic stirring (1300 rpm,6 h) and ultrasonic treatment (240W, 2 h) to uniformly disperse the GNPs powder, wherein the concentration of the GNPs is 20 mg/mL in the step, so as to obtain CNF/GNP20 mixed solution;
Step S12: immersing the cut MF into the CNF/GNP20 mixed solution prepared in the step S11, and placing the cut MF into a vacuum oven with the pressure of about 82 Pa for vacuum auxiliary impregnation for 24 h, so that the CNF/GNP20 mixed solution is embedded into an MF skeleton to obtain an MF/CNF/GNP20 composite sol;
step S13: and (3) placing the MF/CNF/GNP20 composite sol prepared in the step (S12) in a low-temperature refrigerator with the temperature of 6 ℃ to gel 8 h, and further performing liquid nitrogen directional freezing and low-temperature vacuum drying with the pressure, temperature and time of 6 Pa, -72 ℃ and 48 h respectively to prepare the MF/CNF/GNP20 (simplified as MCG 20) aerogel.
Step S2: immersing the MCG20 aerogel prepared in the step S1 into a saturated methanol solution containing TME, carrying out vacuum treatment for 3 times, taking out a sample, and carrying out vacuum drying, and thus, circulating to obtain a TME@MCG20 composite phase change material;
specifically, step S21: 8 g of TME is weighed and added into 20 mL methanol solution, magnetic stirring is carried out at room temperature, and the stirring speed and the stirring time are respectively 800 rpm and 6 h, so as to obtain a methanol saturated solution of TME;
step S22: immersing the MCG20 aerogel skeleton prepared in the step S1 into the saturated methanol solution of TME prepared in the step S21, performing vacuum treatment (the pressure and the time are about 80 Pa and 0.5 h respectively) for 3 times, taking out a sample, and placing the sample in a vacuum drying oven of 80 Pa for drying 1 h to obtain a TME@MCG20 semi-finished product 1;
Step S23: immersing the TME@MCG20 semi-finished product 1 prepared in the step S22 into the saturated methanol solution of the TME prepared in the step S21 for 3 times, taking out a sample, and drying the sample in a vacuum drying oven of 80 Pa for 1 h to obtain a TME@MCG20 semi-finished product 2;
step S24: immersing the TME@MCG20 semi-finished product 2 prepared in the step S23 into the saturated methanol solution of the TME prepared in the step S21 again, performing vacuum treatment (the pressure and the time are about 80 Pa and 0.5 h respectively) for 3 times, taking out a sample, and placing the sample in a vacuum drying oven of 80 Pa for drying 1 h to obtain the TME@MCG20 composite phase change material;
step S3: and (3) carrying out surface photo-thermal etching and subsequent PDMS coating on the TME@MCG20 composite phase-change material prepared in the step (S2) to prepare the T-TME@MCG20 composite phase-change material.
Specifically, step S31: wrapping the surface (except the upper surface) of the TME@MCG20 composite phase-change material prepared in the step S2 by using a heat-insulating adhesive tape, placing the heat-insulating adhesive tape under simulated sunlight, adjusting the illumination intensity until the surface temperature reaches 130-135 ℃, sublimating TME on the surface layer, and keeping 1-1.5 h to obtain a T-TME@MCG20 semi-finished product with a specific etching depth of 0.55 mm;
Step S32: adding 1 g of PDMS prepolymer poly (dimethyl-methyl vinyl siloxane) and 0.1 g cross-linking agent matched with the PDMS prepolymer poly (dimethyl-methyl-hydrogen siloxane) into 10 g n-heptane solution, magnetically stirring the mixture at 600 rpm for 6 h to obtain PDMS uniform n-heptane composite solution containing the cross-linking agent, placing the semi-finished product of T-TME@MCG20 prepared in the step S31 into the PDMS uniform n-heptane composite solution containing the cross-linking agent, transferring the semi-finished product into a blast oven at 60 ℃ for curing and cross-linking for 4 h, coating a PDMS transparent thin layer on the surface of a sample, and repeating the steps for 2 times to obtain the final T-TME@MCG20 composite phase change material.
Example 5. A T-TME@MCG25 composite phase change material.
The preparation method of the T-TME@MCG25 composite phase-change material comprises the following steps:
step S1: preparing a CNF/GNP25 mixed solution, then vacuum-assisted dipping in MF, and further freeze-drying to prepare MCG25 aerogel;
specifically, step S11: weighing 1.5 g of GNPs powder, adding the powder into CNFs water solution (7 mg/mL, 60 mL), and carrying out 3 times of alternate magnetic stirring (1300 rpm,6 h) and ultrasonic treatment (240W, 2 h) to uniformly disperse the powder, wherein the concentration of the GNPs in the step is 25 mg/mL, so as to obtain CNF/GNP25 mixed solution;
Step S12: immersing the cut MF into the CNF/GNP25 mixed solution prepared in the step S11, and placing the cut MF into a vacuum oven with the pressure of about 82 Pa for vacuum auxiliary impregnation for 24 h, so that the CNF/GNP25 mixed solution is embedded into an MF skeleton to obtain an MF/CNF/GNP25 composite sol;
step S13: and (3) placing the MF/CNF/GNP25 composite sol prepared in the step (S12) in a low-temperature refrigerator with the temperature of 6 ℃ to gel 8 h, and further performing liquid nitrogen directional freezing and low-temperature vacuum drying with the pressure, temperature and time of 6 Pa, -72 ℃ and 48 h respectively to prepare the MF/CNF/GNP25 (simplified as MCG 25) aerogel.
Step S2: immersing the MCG25 aerogel prepared in the step S1 into a saturated methanol solution containing TME, carrying out vacuum treatment for 3 times, taking out a sample, and carrying out vacuum drying, and thus, circulating to obtain a TME@MCG25 composite phase change material;
specifically, step S21: 8 g of TME is weighed and added into 20 mL methanol solution, magnetic stirring is carried out at room temperature, and the stirring speed and the stirring time are respectively 800 rpm and 6 h, so as to obtain a methanol saturated solution of TME;
step S22: immersing the MCG25 aerogel skeleton prepared in the step S1 into the saturated methanol solution of TME prepared in the step S21, performing vacuum treatment (the pressure and the time are about 80 Pa and 0.5 h respectively) for 3 times, taking out a sample, and placing the sample in a vacuum drying oven of 80 Pa for drying 1 h to obtain a TME@MCG25 semi-finished product 1;
Step S23: immersing the TME@MCG25 semi-finished product 1 prepared in the step S22 into the saturated methanol solution of the TME prepared in the step S21 for 3 times, taking out a sample, and drying the sample in a vacuum drying oven of 80 Pa for 1 h to obtain a TME@MCG25 semi-finished product 2;
step S24: immersing the TME@MCG25 semi-finished product 2 prepared in the step S23 into the saturated methanol solution of the TME prepared in the step S21 again, performing vacuum treatment (the pressure and the time are about 80 Pa and 0.5 h respectively) for 3 times, taking out a sample, and placing the sample in a vacuum drying oven of 80 Pa for drying 1 h to obtain the TME@MCG25 composite phase change material;
step S3: and (3) carrying out surface photo-thermal etching and subsequent PDMS coating on the TME@MCG25 composite phase-change material prepared in the step (S2) to prepare the T-TME@MCG25 composite phase-change material.
Specifically, step S31: wrapping the surface (except the upper surface) of the TME@MCG25 composite phase-change material prepared in the step S2 by using a heat-insulating adhesive tape, placing the heat-insulating adhesive tape under simulated sunlight, adjusting the illumination intensity until the surface temperature reaches 130-135 ℃, sublimating TME on the surface layer, and keeping 1-1.5 h to obtain a T-TME@MCG25 semi-finished product with a specific etching depth of 0.55 mm;
Step S32: adding 1 g of PDMS prepolymer poly (dimethyl-methyl vinyl siloxane) and 0.1 g cross-linking agent matched with the PDMS prepolymer poly (dimethyl-methyl-hydrogen siloxane) into 10 g n-heptane solution, magnetically stirring the mixture at 600 rpm for 6 h to obtain PDMS uniform n-heptane composite solution containing the cross-linking agent, placing the semi-finished product of T-TME@MCG25 prepared in the step S31 into the PDMS uniform n-heptane composite solution containing the cross-linking agent, transferring the semi-finished product into a blast oven at 60 ℃ for curing and cross-linking for 4 h, coating a PDMS transparent thin layer on the surface of a sample, and repeating the steps for 2 times to obtain the final T-TME@MCG25 composite phase change material.
Control example. T-TME@MF/CNF composite phase change material.
The preparation method of the T-TME@MF/CNF composite phase change material comprises the following steps:
step S1: dipping the CNFs water solution into the cut MF with the aid of vacuum, and further performing freeze drying to prepare MF/CNF aerogel;
specifically, step S11: immersing the cut MF into an aqueous solution of CNFs (7 mg/mL,60 mL), and placing the cut MF into a vacuum oven with the pressure of about 82 Pa for vacuum auxiliary impregnation 24 h, so that the CNFs solution is embedded into an MF skeleton, thereby obtaining an MF/CNF composite sol;
step S12: and (3) placing the MF/CNF composite sol prepared in the step (S11) in a low-temperature refrigerator with the temperature of 6 ℃ to gel 8 h, and further performing liquid nitrogen directional freezing and low-temperature vacuum drying, wherein the pressure, temperature and time of the low-temperature vacuum drying are 6 Pa, -72 ℃ and 48 h respectively, so as to prepare the MF/CNF aerogel.
Step S2: immersing the MF/CNF aerogel prepared in the step S1 into a saturated methanol solution containing TME, carrying out vacuum treatment for 3 times, taking out a sample, and carrying out vacuum drying, and thus, circulating to obtain a TME@MF/CNF composite phase change material;
specifically, step S21: 8 g of TME is weighed and added into 20 mL methanol solution, magnetic stirring is carried out at room temperature, and the stirring speed and the stirring time are respectively 800 rpm and 6 h, so as to obtain a methanol saturated solution of TME;
step S22: immersing the MF/CNF aerogel skeleton prepared in the step S1 into the saturated methanol solution of TME prepared in the step S21, performing vacuum treatment (the pressure and the time are about 80 Pa and 0.5 h respectively) for 3 times, taking out a sample, and placing the sample in a vacuum drying oven of 80 Pa for drying 1 h to obtain a TME@MF/CNF semi-finished product 1;
step S23: immersing the TME@MF/CNF semi-finished product 1 prepared in the step S22 into the saturated methanol solution of the TME prepared in the step S21 for 3 times, taking out a sample, and drying the sample in a vacuum drying oven of 80 Pa for 1 h to obtain a TME@MF/CNF semi-finished product 2;
step S24: immersing the TME@MF/CNF semi-finished product 2 prepared in the step S23 into the saturated methanol solution of the TME prepared in the step S21 again, performing vacuum treatment (the pressure and the time are about 80 Pa and 0.5 h respectively) for 3 times, taking out a sample, and placing the sample in a vacuum drying oven of 80 Pa for drying 1 h to obtain the TME@MF/CNF composite phase-change material;
Step S3: and (3) carrying out surface photo-thermal etching and subsequent PDMS coating on the TME@MF/CNF composite phase-change material prepared in the step (S2) to prepare the T-TME@MF/CNF composite phase-change material.
Specifically, step S31: wrapping the surface (except the upper surface) of the TME@MF/CNF composite phase-change material prepared in the step S2 by using a heat-insulating adhesive tape, placing the heat-insulating adhesive tape under simulated solar illumination, adjusting the illumination intensity until the surface temperature reaches 130-135 ℃, sublimating TME on the surface layer, and keeping for 1-1.5 h time to obtain a T-TME@MF/CNF semi-finished product with a specific etching depth of 0.55 mm;
step S32: adding 1 g of PDMS prepolymer poly (dimethyl-methyl vinyl siloxane) and 0.1 g cross-linking agent matched with the PDMS prepolymer poly (dimethyl-methyl-hydrogen siloxane) into 10 g n-heptane solution, magnetically stirring the mixture at 600 rpm for 6 h to obtain PDMS uniform n-heptane composite solution containing the cross-linking agent, placing the T-TME@MF/CNF semi-finished product prepared in the step S31 into the PDMS uniform n-heptane composite solution containing the cross-linking agent, transferring the PDMS uniform n-heptane composite solution into a blast oven at 60 ℃ for curing and cross-linking for 4 h, coating a PDMS transparent thin layer on the surface of a sample, and repeating the steps for 2 times to obtain the final T-TME@MF/CNF composite phase-change material.
In the research process of the invention, a great deal of experimental study is carried out, and partial experimental results are shown in figures 1-9.
As can be seen from fig. 1, the MCG25 aerogel shows similar tubular (fig. 1 a) and honeycomb (fig. 1 b) structures in the longitudinal (in the freezing direction) and transverse (perpendicular to the freezing direction) directions, respectively, and the CNF/GNP composite is tightly packed on the MF skeleton (fig. 1 a'), which indicates that the three-dimensional MCG25 porous skeleton with anisotropy is constructed by directional freeze-drying technology, which is beneficial to construct a high-efficiency GNP heat conducting network in the MCG25 aerogel, and further to obtain the tme@mcg25 composite phase change material with high heat conducting capability.
As can be seen from fig. 2, TEM fills well in the pores of MCG25, and the representative tme@mcg25 composite phase change material does not show very large pores or cracks (fig. 2a and a'), indicating good interfacial compatibility between TME and the prepared MCG25 scaffold.
As can be seen from fig. 3, the prepared tme@mcg25 composite phase change material has no absorption peak except for the raw material component in FTIR (fig. 3 a) and XRD (fig. 3 b) curves, and shows all typical characteristic peaks of TME, indicating that TME is bonded to MCG25 skeleton through physical interactions of hydrogen bond, capillary force, van der waals force, surface tension, etc., and the crystal structure of TME is maintained during encapsulation, which is favorable for TME to maintain its inherent phase change characteristics.
As can be seen from fig. 4, the endothermic solid-solid phase transition temperatures (T en ) Slightly reduced, heat-set-solid phase transition temperature (T ex ) Obviously improves the supercooling degree (T) en And T is ex Difference) is reduced (fig. 4 a) because the MCG5, 10, 15, 20, 25 aerogel network enhances heat transfer corresponding to the composite phase change material, and the physical interactions (e.g., hydrogen bonding, capillary forces, van der waals forces) between the MCG5, 10, 15, 20, 25 framework and TME promote crystallization of TME. The reduced subcooling facilitates the release of a higher latent heat enthalpy. In addition, the endothermic solid-solid phase transition latent enthalpy (fating H) en ) And exothermic solid-solid phase transition latent enthalpy fathalin H ex ) Decrease with the addition of MF/CNF framework and increase in GNP loading (fig. 4 b), since MF/CNF framework and GNPs did not exhibit phase change ability. However, tme@mcg5, 10, 15, 20, 25 composite phase change materials have higher latent enthalpy and enthalpy efficiency. For example, TME@MCG25 composite phase change material is en 159.6J/g, fating H ex The heat absorption and heat release enthalpy efficiencies of 154.9J/g are up to 91.51 and 91.38 percent respectively and are close to TME load fraction (94.70 percent), which shows that the prepared TME@MCG25 composite phase change material has excellent heat storage capacity and great solar heat storage potential.
As can be seen from fig. 5, the tme@mcg25 composite phase change material has a flat, non-porous surface (fig. 5 a). After surface photo-thermal etching, the TME is sublimated and the 3D porous MCG25 network is exposed at the tme@mcg25 composite phase change material surface (fig. 5 b), which helps to better capture sunlight. After further PDMS coating, the surface of the obtained T-TME@MCG25 composite phase change material has a surface pore structure similar to that of the photo-thermal etched TME@MCG25 composite phase change material (fig. 5c 1), and C, O, si and N elements are uniformly distributed on an exposed MCG25 skeleton (fig. 5c 2-7), which shows that the PDMS is uniformly coated on the surface of the MCG25 skeleton, and the surface pore structure is not destroyed. This will contribute to the hydrophobicity of the T-tme@mcg25 composite phase change material surface.
As can be seen from fig. 6, the static Water Contact Angle (WCA) of the tme@mf/CNF composite phase change material is close to 0 ° (fig. 6 a), indicating its excellent hydrophilicity, which is mainly attributed to the strong hydrophilicity of the hydroxyl groups, amino groups and hydroxyl and carboxyl groups of TME, MF and carboxylated CNFs. The T-TME@MF/CNF composite phase change material has a WCA of up to 136.57 DEG, due to the exposed microscale porous scaffold surface and the PDMS coating further lowering its surface energy. As the GNPs content increased, the WCA of the T-tme@mcg5, 10, 15, 20, 25 composite phase change material increased slightly from 138.16 ° to 140.7 °, due to the gradual decrease in the microporous surface deposited by PDMS. In addition, the various solutions (e.g., HCl, naOH, naCl, milk, tea, cola, coffee) maintained nearly spherical droplet-like shapes (FIG. 6 b) on the surface of the T-TME@MCG25 composite phase change material block, with WCA similar to pure water (about 140). At the same time, the T-TME@MCG25 composite phase change material block is not destroyed after the droplets are removed from their surfaces. These phenomena confirm that the T-TME@MCG25 composite phase change material has good hydrophobicity and solvent resistance, and ensures that the energy storage property of the material is not damaged by corrosion of water or rainwater. Notably, the spherical water drop can take away SiO which is flatly placed on the surface of the T-TME@MCG25 composite phase change material 2 The powder (fig. 6 c), which shows a remarkable self-cleaning property on its surface, helps to remove surface impurities and maintains its original Gao Guangre absorption capacity.
As can be seen from FIG. 7, TME showed only 0.27W m -1 K -1 At the same time, the TC of TME@MF/CNF composite phase change material is only 0.28W m -1 K -1 The MF/CNF aerogel network is shown to have no contribution to heat transfer enhancement of TME@MF/CNF composite phase change materials. However, as the content of GNPs increases, the TC of the tme@mcg5, 10, 15, 20, 25 composite phase change material gradually goes from 0.41 wm -1 K -1 Increased to 0.73W m -1 K -1 The GNPs are shown to construct an effective heat conduction network in TME@MCG5, 10, 15, 20 and 25Co-phonon conduction, which facilitates faster heat transfer in energy storage applications.
As can be seen from fig. 8, pure TME shows weak absorbance in the UV-vis-NIR full spectrum (fig. 8 a), with poor solar light absorption. The absorbance of the surface of TME@MCG25 composite phase change material is higher than that of TME, because GNPs exposed on the surface have light absorption characteristics. The absorption performance of the TME@MCG25 composite phase change material surface after photo-thermal etching is remarkably improved compared with that of the original TME@MCG25 composite phase change material surface, and the exposed MCG25 network layer provides more light absorption area. After further PDMS coating, the absorbance of the resulting T-tme@mcg25 composite phase change material surface was only slightly reduced, since the highly transparent PDMS had only a weak blocking effect on sunlight. When the simulated solar radiation intensity is 400 mW/cm 2 At this time, the temperature of the tme@mcg25 composite phase change material increases with the increase of irradiation time (fig. 8 b), since GNPs exposed on its surface can achieve photon capturing and molecular heating, and a satisfactory MCG25 thermally conductive network transfers the obtained thermal energy to its interior for storage. Meanwhile, the temperature of the photo-thermal etched TME@MCG25 composite phase change material rises much faster than that of the original TME@MCG25 composite phase change material. This is due to the increased solar absorption of the 3d mcg25 network layer created by the photo-thermal etching process. After further coating of PDMS, the temperature rise rate of the resulting T-tme@mcg25 composite phase change material is further accelerated, which is in contrast to the UV-vis-NIR absorption spectroscopy results discussed above, probably due to the thin layer of PDMS preventing the absorbed solar heat energy from radiating and convecting to the environment. In addition, the rate of temperature rise of the T-tme@mcg5, 10, 15, 20, 25 composite phase change material increases significantly with increasing GNPs content (fig. 8 c). This phenomenon is due to more photon capture, molecular heating and construction of a thermally conductive network of GNPs, facilitating more solar thermal energy capture and transfer. Notably, the T-tme@mcg5, 10, 15, 20, 25 composite phase change materials present a significant "plateau" of temperature during light and natural cooling, which is created by the latent heat storage and release of solar energy. It was calculated that the photothermal conversion efficiency of T-tme@mcg5, 10, 15, 20, 25 was gradually increased from 57.43% to 93.07%, which was beneficial in solar energy conversion Has great potential in application.
As can be seen from FIG. 9, the photo-thermo-electric generator (STEG) combined with the control group T-TME@MF/CNF composite phase change material was at 400 mW/cm 2 Is output under the simulated sun illumination of open circuit voltage (V) OC ) And short-circuit current (I) SC ) Only 81.8 mV and 14.5 mA (fig. 9a and b), respectively, due to their very poor photo-thermal capabilities. STEG V combined with T-TME@MCG5, 10, 15, 20, 25 composite phase change material OC And I SC The trend of evolution along time is similar to that of a control group, and the trend of evolution along time is continuously enhanced along with the increase of the content of the GNPs, because the higher the content of the GNPs is, the stronger the corresponding photo-thermal absorption capability is, and the temperature difference and V are caused OC And I SC The higher the value. In particular, V of T-TME@MCG5 composite phase change material OC And I SC Up to 158.8 mV and 26.6 mA, respectively, and exhibit significant stability after 10 cycles (fig. 9c and d). Therefore, the prepared T-TME@MCG5 composite phase change material can be embedded into a STEG device and is used for collecting solar heat energy and converting the solar heat energy into electric energy for human use, so that the electric energy consumption is saved, and the energy crisis is relieved.
The invention relates to equipment and raw materials in the prior art, and can be directly purchased and used by a person skilled in the art. The foregoing is merely a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and variations may be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (9)

1. A composite phase change material with hydrophobic and high-efficiency photo-thermal conversion performance is characterized in that: the composite phase change material is T-TME@MCG.
2. The method for preparing the composite phase-change material with hydrophobic and high-efficiency photo-thermal conversion performance according to claim 1, wherein the method is characterized in that: the preparation method comprises the following steps:
step S1: preparing graphene nano sheet/cellulose nano fiber (CNF/GNP) mixed solution, then vacuum-assisted dipping in Melamine Foam (MF), and further freeze-drying to prepare MCG aerogel;
step S2: immersing the MCG aerogel prepared in the step S1 into a saturated methanol solution containing tris (hydroxymethyl) ethane (TME), carrying out vacuum treatment for 3 times, taking out a sample, and carrying out vacuum drying, and circulating in such a way to obtain a TME@MCG composite phase change material;
step S3: and (3) carrying out surface photo-thermal etching and Polydimethylsiloxane (PDMS) coating on the TME@MCG composite phase-change material prepared in the step (S2) to prepare the T-TME@MCG composite phase-change material.
3. The method for preparing the composite phase-change material with hydrophobic and high-efficiency photo-thermal conversion performance as claimed in claim 2, wherein the method comprises the following steps: the preparation method of the MCG aerogel in the step S1 comprises the following steps:
Step S11: weighing GNPs powder with certain mass, adding the GNPs powder into CNFs water solution, and alternately carrying out magnetic stirring and ultrasonic treatment to uniformly disperse the GNPs powder to obtain CNF/GNP mixed solution;
step S12: immersing the cut MF into the CNF/GNP mixed solution prepared in the step S11, and placing the immersed solution into a vacuum oven for vacuum auxiliary immersion, so that the CNF/GNP mixed solution is embedded into an MF skeleton, thereby obtaining an MF/CNF/GNP composite sol;
step S13: and (3) placing the MF/CNF/GNP composite sol prepared in the step (S12) in a low-temperature refrigerator to gel, and then performing liquid nitrogen directional freezing and low-temperature vacuum drying to prepare the MF/CNF/GNP aerogel, namely the MCG aerogel.
4. The method for preparing the composite phase-change material with hydrophobic and high-efficiency photo-thermal conversion performance as claimed in claim 3, wherein: the concentration of CNFs in the step S11 is 7mg/ml, the concentration of GNPs is 5-25 mg/ml, the magnetic stirring speed and time are 1300 rpm and 6 h respectively, the ultrasonic treatment power and time are 240W and 2 h respectively, and the alternating magnetic stirring and ultrasonic treatment times are 3; the vacuum assisted impregnation pressures and times in step S12 are about 82 Pa and 24 h, respectively; the temperature of the refrigerator for gelation in the step S13 is 6 ℃, the time is 8 h, the pressure of low-temperature vacuum drying is 6 Pa, the temperature is-72 ℃, and the time is 48 h.
5. The method for preparing the composite phase-change material with hydrophobic and high-efficiency photo-thermal conversion performance as claimed in claim 2, wherein the method comprises the following steps: the preparation method of the TME@MCG composite phase change material in the step S2 comprises the following steps:
step S21: weighing TME, adding the TME into a methanol solution, and magnetically stirring at room temperature to obtain a methanol saturated solution of TME;
step S22: immersing the MCG aerogel skeleton prepared in the step S1 into the saturated methanol solution of TME prepared in the step S21, carrying out vacuum treatment for 3 times, taking out a sample, and drying in a vacuum drying oven to obtain a TME@MCG semi-finished product 1;
step S23: immersing the TME@MCG semi-finished product 1 prepared in the step S22 into the saturated methanol solution of the TME prepared in the step S21 for 3 times, taking out a sample, and drying in a vacuum drying oven to obtain a TME@MCG semi-finished product 2;
step S24: and (3) immersing the TME@MCG semi-finished product 2 prepared in the step (S23) into the saturated methanol solution of the TME prepared in the step (S21) again, carrying out vacuum treatment for 3 times, taking out a sample, and drying in a vacuum drying oven to obtain the TME@MCG composite phase change material.
6. The method for preparing the composite phase-change material with the hydrophobic and high-efficiency photo-thermal conversion performance as claimed in claim 5, wherein the method comprises the following steps: the TME in the step S21 has a mass of 8 g, a volume of methanol solution of 20 mL, and a magnetic stirring speed and time of 800 rpm and 6 h, respectively; the vacuum treatment in the steps S22, S23 and S24 has a pressure of 80 Pa and a time of 0.5 h, and the vacuum drying oven has a pressure of 80 Pa and a time of 1 h.
7. The method for preparing the composite phase-change material with hydrophobic and high-efficiency photo-thermal conversion performance as claimed in claim 2, wherein the method comprises the following steps: the preparation method of the T-TME@MCG composite phase change material in the step S3 comprises the following steps:
step S31: wrapping the surface of the TME@MCG composite phase-change material prepared in the step S2 except the upper surface by using a heat-insulating adhesive tape, placing the heat-insulating adhesive tape under simulated sunlight, adjusting the illumination intensity until the surface temperature reaches 130-135 ℃, sublimating TME on the surface layer, and keeping 1-1.5 h to obtain a T-TME@MCG semi-finished product with a specific etching depth;
step S32: adding a PDMS prepolymer (poly (dimethyl-methyl vinyl siloxane)) and a cross-linking agent (poly (dimethyl-methyl-hydrogen siloxane)) matched with the PDMS prepolymer into an n-heptane solution, magnetically stirring the mixture to obtain a PDMS uniform n-heptane composite solution containing the cross-linking agent, placing the T-TME@MCG semi-finished product prepared in the step S31 into the PDMS uniform n-heptane composite solution containing the cross-linking agent, transferring the PDMS uniform n-heptane composite solution into a blast oven for curing and cross-linking, coating a PDMS transparent thin layer on the surface of a sample, and repeating the step for 2 times to obtain the final T-TME@MCG composite phase-change material.
8. The method for preparing the composite phase-change material with hydrophobic and high-efficiency photo-thermal conversion performance according to claim 7, wherein the method comprises the following steps: the etching depth of the T-TME@MCG semi-finished product in the step S31 is 0.55 mm, the mass of the PDMS prepolymer in the step S32 is 1 g, the mass of the cross-linking agent is 0.1 g, the mass of n-heptane is 10 g, the magnetic stirring speed is 600 rpm, the stirring time is 6 h, the temperature of the blast oven is 60 ℃, and the curing and cross-linking time is 4 h.
9. Use of a composite phase change material with hydrophobic and efficient photothermal conversion properties according to any of claims 1-8, characterized in that: the composite phase change material is used as a photo-thermal conversion material of a photo-thermal-electric generator in a dry or even wet environment.
CN202310910728.7A 2023-07-24 2023-07-24 Composite phase change material with hydrophobic and high-efficiency photo-thermal conversion performance, and preparation method and application thereof Pending CN117025175A (en)

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