LIGHT-HEAT ENERGY CONVERSION AND HEAT ENERGY STORAGE SHAPE-STABILIZED PHASE-CHANGE COMPOSITE MATERIAL AND PRODUCTION METHOD THEREFOR

Abstract

A composite material is applicable for photothermal energy conversion and thermal energy storage form-stable phase change. The composite material includes a supporting material and an organic phase-change material. The mass ratio of the supporting material to the organic phase change material is 3:7 to 1:9. The supporting material is lamellar, and the organic phase change material is evenly filled between supporting material layers to form a layered stacked structure. The supporting material is a nanosheet of Ti.sub.2C, Ti.sub.3C.sub.2, Ti.sub.3CN, V.sub.2C, Nb.sub.2C, TiNBC, Nb.sub.4C.sub.3, TA.sub.4C.sub.3, (Ti.sub.0.5Nb.sub.0.5).sub.2C, or (V.sub.0.5Cr.sub.0.5).sub.3C.sub.2. The organic phase-change material is paraffin, fatty acid, fatty acid ester or alcohol compound.

Claims

1. A photothermal energy conversion and thermal energy storage form-stable phase change composite material, comprising a supporting material and an organic phase change material, wherein a mass ratio of the supporting material and the organic phase change material is 3:7 to 1:9; the supporting material is lamellar, and the organic phase change material is evenly filled between the layers of the supporting material to form a layered stacked structure; the supporting material is a nanosheet of Ti.sub.2C, Ti.sub.3C.sub.2, Ti.sub.3CN, V.sub.2C, Nb.sub.2C, TiNbC, Nb4C.sub.3, Ta.sub.4C.sub.3, (Ti.sub.0.5Nb.sub.0.5).sub.2C, or (V.sub.0.5Cr.sub.0.5).sub.3C.sub.2; wherein the nanosheet is single layer or multilayer having a size of 1.5 to 2.2 μm; and the organic phase change material is paraffin, fatty acid, ester of fatty acid, or alcohol compound.

2. The material according to claim 1, wherein the paraffin has a melting point of 20 to 60° C.

3. The material according to claim 1, wherein the fatty acid is dodecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, or stearic acid.

4. The material according to claim 1, wherein the alcohol compound is lauryl alcohol, tetradecyl alcohol, hexadecanol, octadecanol, or polyethylene glycol having a molecular weight of 2000 to 20000.

5. A method for preparing the photothermal energy conversion and thermal energy storage form-stable phase change composite material in claim 1, comprising the following steps: S1. mixing a precursor with 40 vol. % hydrofluoric acid at a ratio of 1 g:8 mL to 1 g:10 mL and placing for 1 to 3 days, to obtain stacked Mxenes, wherein the precursor is Ti.sub.2AlC, Ti.sub.3AlC.sub.2, Ti.sub.3AlCN, V.sub.2AlC, Nb.sub.2AlC, TiNbAlC, Nb.sub.4AlC.sub.3, Ta.sub.4AlC.sub.3, (Ti.sub.0.5Nb.sub.0.5).sub.2AlC, or (V.sub.0.5Cr.sub.0.5).sub.3AlC.sub.2; S2. centrifugally washing the obtained stacked MXenes with deionized water to pH 7 and drying, mixing MXenes with dimethyl sulfoxide at a ratio of 1 g:10 mL to 1 g:14 mL, magnetic stirring the solution at room temperature for 18 hours, and obtaining a precipitate by centrifugal separation. S3. mixing the precipitate obtained in step S2 with deionized water at a ratio of 1 g:200 mL to 1 g:300 mL, ultrasonic stripping the solution for 5 hours, obtaining the MXenes nanosheets after solid-liquid separation and ultrasonic cleaning, and dissolving the MXenes nanosheets in a solvent to obtain a MXenes nanosheet dispersion liquid with a mass fraction of 1% to 5%; S4. adding an organic phase change material to the MXenes nanosheet dispersion liquid, wherein the mass ratio of the organic phase change material to the MXenes nanosheet is 9:1 to 7:3, obtaining the photothermal energy conversion and thermal energy storage form-stable phase change composite after ultrasonic mixing and drying; wherein the organic phase change material is paraffin, fatty acid, ester of fatty acid or alcohol compound.

6. The method according to claim 5, wherein the operations of step S3 are as follows: after ultrasonic stripping, obtaining precipitates of MXenes nanosheets by solid-liquid separation; ultrasonically cleaning the precipitates with deionized water for 3 times, removing supernatant by solid-liquid separation, and then evenly dispersing the precipitates of MXenes nanosheets in water or ethanol to obtain MXenes nanosheet dispersion liquid; wherein the solid-liquid separation is centrifugal separation.

7. The method according to claim 5, wherein in step S4, after ultrasonic mixing, adjusting pH of the solution to 8, and drying in vacuum at 50° C.

8. The method according to claim 5, wherein the paraffin has a melting point of 20 to 60° C.; the fatty acid is dodecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, or stearic acid; and the alcohol compound is lauryl alcohol, tetradecyl alcohol, hexadecanol, octadecanol, or polyethylene glycol having a molecular weight of 2000 to 20000.

Description

DETAILED DESCRIPTION OF DRAWINGS

[0031] FIGS. 1A and 1B are the scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the MXenes in Embodiment 1.

[0032] FIGS. 2A and 2B are the SEM images of the PCM in Embodiment 1.

[0033] FIG. 3 is an X-ray diffraction (XRD) image of the PEG and the composite form-stable phase change energy storage material in Embodiment 1.

[0034] FIG. 4 is a dynamic stability control (DSC) curve of the PEG and the composite form-stable phase change energy storage material in Embodiment 1.

[0035] FIG. 5 is a photothermal conversion curve of the composite phase change energy storage composite in Embodiment 1 (the optical power density is 128.6 mW/cm.sup.2).

[0036] FIG. 6 is digital photographs of the PEG and the composite phase change energy storage material in Embodiment 1 heated at 30° C., 65° C. and 95° C. for 20 min.

[0037] FIG. 7 is a thermogravimetry (TG) curve of the PEG and the composite form-stable phase change energy storage material in Embodiment 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0038] The following unrestricted embodiments may give a more complete understanding of the present disclosure to the ordinary skilled in the art, but do not in any way limit the disclosure.

[0039] The test methods in the following embodiments are all conventional methods unless specified; and the reagents and materials are commercially available unless specified.

Embodiment 1

[0040] A photothermal energy conversion and thermal energy storage form-stable phase change composite material was prepared by the following steps:

[0041] S1. 1 g of Ti.sub.3AlC.sub.2 was dissolved in 8 mL of water to obtain the precursor solution, and 1 g of hydrofluoric acid was dissolved in 10 mL of water to obtain the hydrofluoric acid solution. The precursor solution was mixed with the hydrofluoric acid solution and placed for 3 days to obtain the stacked Ti.sub.3C.sub.2.

[0042] S2. The stacked Ti.sub.3C.sub.2 after treatment was centrifugally washed with deionized water until pH 7, dried and mixed with dimethyl sulfoxide (DMSO) at a ratio of 1 g:12 mL, the mixture was stirred by magnetic force at room temperature for 18 hours, and then the supernatant was poured out by centrifugation to obtain the multilayer Ti.sub.3C.sub.2 precipitate with DMSO intercalation.

[0043] S3. The multilayer Ti.sub.3C.sub.2 precipitate with DMSO intercalation was mixed with deionized water at a ratio of 1 g:300 mL, and was ultrasonic stripped for 5 hours; the supernatant was poured out by centrifugation, and the precipitate was ultrasonically cleaned with deionized water for 3 times to obtain the Ti.sub.3C.sub.2 nanosheets. Taking deionized water as the solvent, the Ti.sub.3C.sub.2 nanosheets were evenly dispersed in deionized water to obtain the Ti.sub.3C.sub.2 nanosheet dispersion liquid, and the mass fraction of the Ti.sub.3C.sub.2 nanosheet in the Ti.sub.3C.sub.2 nanosheet dispersion liquid was 1.4%.

[0044] S4. The PEG 6000 was added to the Ti.sub.3C.sub.2 nanosheet dispersion liquid, and the mass ratio of PEG to the Ti.sub.3C.sub.2 nanosheet was 4:1. The mix solution was treated by ultrasonic for 30 min and adjusted pH to 8, and was dried in vacuum at 50° C. to obtain the Ti.sub.3C.sub.2 nanosheet phase change composite material.

[0045] It can be seen from the SEM and TEM images (as shown in FIGS. 1A and 1B) of the material, the diameter of the Ti.sub.3C.sub.2 nanosheet is about 0.5 to 2.2 μm, the layer thickness is single layer or several layers. After compositing with PEG, the composite is a layered stacked structure (as shown in FIGS. 2A and 2B). It can be seen from the XRD image (as shown in FIG. 3) of the material, the obtained nanosheet composite phase change energy storage material has similar crystallization characteristic with PEG, but the diffraction peak height of the phase change composite material is lower than that of PEG, that because the crystallization of PEG is restricted and disturbed by the supporting material. It can be seen from the DSC curve (as shown in FIG. 4) that the phase change enthalpy and phase change temperature of the Ti.sub.3C.sub.2/PEG shape-stabilized form-stable phase change energy storage composite material are obviously lower than those of PEG. The main reason is that the crystallization of PEG in Ti.sub.3C.sub.2/PEG is restricted and interfered by the Ti.sub.3C.sub.2 nanosheets which act as skeleton support. In the DSC, the phase change enthalpy of the Ti.sub.3C.sub.2/PEG phase change composite material reaches about 167 J/g, indicating that the obtained composite phase change energy storage material has good performance of phase change heat storage. Under the light, the temperature of the Ti.sub.3C.sub.2/PEG composite form-stable phase change energy storage material rises rapidly, the temperature evolution curve shows a temperature change inflection point at a range of 59° C. to 63° C., indicating that the material occurs phase change here, light energy is converted into thermal energy and stored in the form of latent heat. After stopping the light, the temperature of the nanosheet composite phase change energy storage material goes down rapidly; when the temperature falls to about 49° C. and no longer falls, and slightly rises, and maintains at about 49° C. for a period of time, the latent heat is released, which indicates that the material has the characteristics of photothermal conversion and phase change thermal storage. It can be seen from the form-stable effect diagram of the material at different temperatures (as shown in FIG. 6), the material remains solid at 95° C., while PEG has partially melted at 65° C., indicating that the obtained Ti.sub.3C.sub.2 nanosheet composite phase change energy storage material has excellent form-stable phase change characteristic. It can be seen from the TG curve of the material (as shown in FIG. 7) that the decomposition of the material occurs at 350° C., which is much higher than the phase change temperature, indicating that the obtained material has high thermal stability.

Embodiment 2

[0046] The mass ratio of PEG 6000 to the Ti.sub.3C.sub.2 nanosheet was changed to 7:3, the Ti.sub.3C.sub.2 nanosheet form-stable phase change composite material was obtained by compositing, and the other conditions were the same as those of Embodiment 1. The phase change enthalpy of the obtained form-stable phase change composite material can still reach about 154 J/g, having the same high thermal stability as Embodiment 1.

Embodiment 3

[0047] The mass ratio of PEG 6000 to the Ti.sub.3C.sub.2 nanosheet was changed to 9:1, the Ti.sub.3C.sub.2 nanosheet form-stable phase change composite material was obtained by compositing, and the other conditions were the same as those of Embodiment 1. The phase change enthalpy value of the obtained form-stable phase change composite material can still reach about 177 J/g, having the same high thermal stability as Embodiment 1.

Embodiments 4 to 12

[0048] The precursor in Embodiment 1 was substituted with Ti.sub.2AlC, Ti.sub.3AlCN, V.sub.2AlC, Nb.sub.2AlC, TiNbAlC, Nb.sub.4AlC.sub.3, Ta.sub.4AlC.sub.3, (Ti.sub.0.5Nb.sub.0.5).sub.2AlC, or (V.sub.0.5Cr.sub.0.5).sub.3AlC.sub.2, and the other conditions were the same as those of Embodiment 1. The obtained materials can realize photothermal conversion and thermal energy storage, and still have excellent shape stability, energy storage density and thermal stability.

Embodiments 13 to 21

[0049] The precursor in Embodiment 2 was substituted with Ti.sub.2AlC, Ti.sub.3AlCN, V.sub.2AlC, Nb.sub.2AlC, TiNbAlC, Nb.sub.4AlC.sub.3, Ta.sub.4AlC.sub.3, (Ti.sub.0.5Nb.sub.0.5).sub.2AlC, or (V.sub.0.5Cr.sub.0.5).sub.3AlC.sub.2, and the other conditions were the same as those of Embodiment 2. The obtained materials can realize photothermal conversion and thermal energy storage, and still have excellent shape stability, energy storage density and thermal stability.

Embodiments 22 to 30

[0050] The precursor in Embodiment 3 was substituted with Ti.sub.2AlC, Ti.sub.3AlCN, V.sub.2AlC, Nb.sub.2AlC, TiNbAlC, Nb.sub.4AlC.sub.3, Ta.sub.4AlC.sub.3, (Ti.sub.0.5Nb.sub.0.5).sub.2AlC, or (V.sub.0.5Cr.sub.0.5).sub.3AlC.sub.2, and the other conditions were the same as those of Embodiment 3. The obtained materials can realize photothermal conversion and thermal energy storage, and still have excellent shape stability, energy storage density and thermal stability.

Embodiments 31 to 45

[0051] The organic solid-liquid phase change materials in Embodiments 1 to 3 were substituted with dodecanoic acid, myristic acid, pentadecanoic acid, palmitic acid and stearic acid, the solvent of deionized water in step S3 was substituted with ethanol in which the Ti.sub.3C.sub.2 nanosheets were dispersed, and the other conditions were the same as those of Embodiments 1 to 3 to prepare the Ti.sub.3C.sub.2 nanosheet form-stable phase change composite material. The obtained materials can realize photothermal conversion and thermal energy storage, and still have excellent shape stability, energy storage density and thermal stability.

Embodiments 46 to 57

[0052] The organic solid-liquid phase change materials in Embodiments 1 to 3 were substituted with lauryl alcohol, tetradecyl alcohol, hexadecanol, and octadecanol, the solvent of deionized water in step S3 was substituted with ethanol in which the Ti.sub.3C.sub.2 nanosheets were dispersed, and the other conditions were the same as those of Embodiments 1 to 3 to prepare the Ti.sub.3C.sub.2 nanosheet form-stable phase change composite material. The obtained materials can realize photothermal conversion and thermal energy storage, and still have excellent shape stability, energy storage density and thermal stability.