Three-dimensional high-thermal-conductivity attapulgite / graphene oxide aerogel composite phase change material and preparation method thereof

Abstract

The application discloses a three-dimensional high-thermal-conductivity attapulgite / graphene oxide aerogel composite phase change material and a preparation method thereof. The preparation method comprises the following steps: (1) treating attapulgite by acid activation; (2) mixing and stirring attapulgite nanofibers, a silane coupling agent and ethanol to obtain aminoized attapulgite nanofibers; (3) mixing graphene oxide nanosheets, microfibrillated cellulose and deionized water to form a uniform graphene oxide suspension; (4) adding the aminoized attapulgite nanofibers into the graphene oxide suspension and mixing and stirring to obtain a uniform dispersion liquid, and the dispersion liquid is subjected to a hydrothermal reaction to prepare attapulgite / graphene oxide hydrogel with a three-dimensional structure; (5) freezing to obtain attapulgite / graphene oxide aerogel; and (6) vacuum impregnating the attapulgite / graphene oxide aerogel with a phase change material to obtain the composite phase change material. The composite phase change material can realize extremely high energy storage density, excellent leakage prevention performance and good thermal conductivity.

Description

Technical Field

[0001] This invention relates to the field of phase change materials technology, and in particular to a three-dimensional high thermal conductivity attapulgite / graphene oxide aerogel composite phase change material and its preparation method. Background Technology

[0002] With the escalating energy crisis and environmental problems, solar energy, as the most abundant renewable energy source on Earth, has received widespread global attention. However, the instability and discontinuity of solar energy utilization and conversion limit its efficient use, necessitating the exploration of efficient solar energy storage technologies. Phase change thermal energy storage (latent heat storage) technology is an energy storage technology that utilizes phase change materials (PCMs) to absorb or release large amounts of heat while maintaining a relatively constant temperature. Organic PCMs (lauric acid, paraffin, etc.) have advantages such as high latent heat of phase change, low supercooling, and no phase separation, leading to their widespread application. However, the application of organic PCMs in solar energy conversion and storage still suffers from two fatal flaws: easy leakage during the solid-liquid phase change process and extremely low thermal conductivity.

[0003] To address the leakage problem of phase change materials (PCMs) during solid-liquid phase transitions, porous framework carrier materials are typically introduced to construct composite PCMs. Attapulgite, a natural porous clay mineral, possesses advantages such as high specific surface area and low cost, making it a suitable carrier material for encapsulating PCMs. Furthermore, the abundant -OH sites on the surface of attapulgite facilitate chemical modification and composite with PCMs, further enhancing the leakage-proof performance of the CPCMs. However, the low thermal conductivity and high density of attapulgite itself lead to a significant reduction in the energy storage density of the prepared CPCMs.

[0004] Aerogels, as a novel porous material, possess ultra-low density, high porosity, hierarchical pore structure, and good compatibility with PCMs, and have been widely used in recent years for encapsulating large quantities of PCMs. Furthermore, the addition of high thermal conductivity fillers can effectively address the low thermal conductivity of PCMs. Among these, carbon-based fillers such as graphene and carbon nanotubes have been the most extensively studied; however, the addition of large amounts of fillers can significantly impair the thermal storage performance of PCMs. Graphene oxide, as a two-dimensional carbon nanomaterial, is more likely to self-assemble into aerogel materials compared to other carbon-based materials. The resulting graphene oxide aerogel (GO) possesses a rich hierarchical pore structure and surface activity, attracting widespread attention as a porous carrier for PCMs. However, because graphene oxide sheets are assembled through van der Waals forces or hydrogen bonds, the weak interactions between the sheets cause strong phonon scattering at the interface sites. Furthermore, due to the lack of a supporting framework between graphene oxide sheets, the internal framework can partially collapse, which severely weakens the leak-proof and thermal conductivity properties of graphene oxide aerogel composite phase change materials, resulting in low solar energy utilization efficiency and significant heat loss during the application of CPCMs.

[0005] To address the issue that a single carrier material cannot simultaneously improve the thermal storage performance, leak prevention performance, and thermal conductivity of CPCMs, developing a novel multi-component composite carrier material that can guarantee the thermal storage performance of CPCMs while also improving their leak prevention and thermal conductivity is the preferred approach. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned shortcomings of existing technologies by proposing a three-dimensional high thermal conductivity attapulgite / graphene oxide aerogel composite phase change material and its preparation method. This material can achieve extremely high energy storage density, excellent leak-proof performance, and good thermal conductivity, which is of great significance in the application field of solar energy conversion and storage.

[0007] The present invention discloses a method for preparing a three-dimensional high thermal conductivity attapulgite / graphene oxide aerogel composite phase change material, comprising the following steps:

[0008] (1) Attapulgite clusters were dissociated into attapulgite nanofibers by acid activation treatment;

[0009] (2) The attapulgite nanofibers obtained in step (1) are mixed and stirred with silane coupling agent and ethanol to obtain aminated attapulgite nanofibers.

[0010] (3) Mix graphene oxide nanosheets, microfibrillated cellulose and deionized water to form a uniform graphene oxide suspension.

[0011] (4) The aminoated attapulgite nanofibers obtained in step (2) are added to the graphene oxide suspension formed in step (3), and the mixture is stirred to obtain a uniform dispersion. The dispersion is then subjected to a hydrothermal reaction to prepare an attapulgite / graphene oxide hydrogel with a three-dimensional structure.

[0012] (5) Attapulgite / graphene oxide hydrogel was frozen in a freeze dryer to obtain attapulgite / graphene oxide aerogel.

[0013] (6) Vacuum impregnation of attapulgite / graphene oxide aerogel with phase change material yields three-dimensional attapulgite / graphene oxide aerogel composite phase change material.

[0014] There is no specific order between steps (2) and (3).

[0015] Furthermore, in step (1), the acid activation process mainly includes: acid soaking, solid-liquid separation, washing, and drying; wherein the acid solution is a hydrochloric acid aqueous solution with a mass fraction of 1 to 12 wt.%, the soaking is carried out by stirring, the stirring speed is 600 to 1200 r / min, the soaking temperature is 60 to 90℃, and the soaking time is 30 to 120 min;

[0016] In step (1), the grade of the attapulgite is greater than 80% and the particle size is less than 200 mesh;

[0017] Furthermore, step (1) also includes a ball milling process, in which the acidified attapulgite is ball milled. The ball-to-material mass ratio in the ball milling process is 2 to 10, the grinding time is 10 to 120 min, the grinding temperature is 20 to 120 °C, and the rotation speed is 200 to 500 r / min.

[0018] Furthermore, in step (2), the mass concentration fraction of ethanol is 70-100 wt.%.

[0019] The attapulgite nanofibers and silane coupling agent (C8H) 22 N2O3Si) and ethanol are in the following parts by weight:

[0020] Attapulgite nanofibers: 1-7 parts

[0021] Silane coupling agent: 1-7 parts

[0022] Ethanol: 20–140 parts;

[0023] In step (2), the amination modification process mainly includes: mixing of the mixture, sonication, solid-liquid separation, washing, and drying; wherein the stirring speed is 600-1200 r / min, the stirring time is 2-6 h, the stirring temperature is 20-50 ℃, the sonication time is 10-40 min, and the sonication temperature is 20-50 ℃.

[0024] Furthermore, in step (3), the graphene oxide nanosheets, microfibrillated cellulose, and deionized water are in the following weight proportions:

[0025] Graphene oxide nanosheets: 4-8 parts

[0026] Microfibrillated cellulose: 1-3 parts

[0027] Deionized water: 20-120 parts.

[0028] Furthermore, in step (3), graphene oxide nanosheets, microfibrillated cellulose and deionized water are mixed and then dispersed by ultrasonication to obtain a graphene oxide suspension. The ultrasonication time is 30-120 min and the ultrasonication temperature is 20-40 min. In step (4), the dispersion is uniformly dispersed by stirring, wherein the stirring speed is 600-1200 r / min and the stirring time is 10-30 min.

[0029] Furthermore, in step (4), the ratio of the amount of aminated attapulgite nanofibers to graphene oxide suspension is: 10-40 wt.% : 60 wt.%-90 wt.%.

[0030] Furthermore, in step (4), the dispersion is placed in a high-temperature reactor and kept in a forced-air drying oven at 150-200°C for 8-15 hours.

[0031] Furthermore, in step (5), the attapulgite / graphene oxide hydrogel is freeze-dried at a temperature of -70 to 0°C for 48 to 72 hours in a freeze dryer.

[0032] Furthermore, in step (6), the ratio of attapulgite-graphene oxide aerogel to lauric acid is: 5-25 wt.% : 75-95 wt.%.

[0033] In step (6), the vacuum impregnation is first performed by evacuating at room temperature for 20 to 40 minutes, and then by evacuating at 60 to 90°C for 20 to 60 minutes. This process is repeated 2 to 4 times.

[0034] In step (6), the attapulgite / graphene oxide aerogel composite phase change material is placed in a forced-air drying oven at 40-70°C and heat-filtered at 12-48°C to remove excess phase change material adsorbed on the aerogel surface.

[0035] A three-dimensional high thermal conductivity attapulgite / graphene oxide aerogel composite phase change material prepared by the above-described preparation method.

[0036] This invention dissociates attapulgite fiber clusters into attapulgite nanofibers through acid activation, and replaces the -OH groups on the nanofiber surface with -NH3 groups using a silane coupling agent. During a hydrothermal reaction, the aminated attapulgite nanofibers can react and graft with graphene oxide nanosheets rich in hydrophilic groups such as -OH / -COOH to form an attapulgite-graphene oxide hydrogel. The substitution of hydrophilic groups reduces surface defects and lowers surface thermal resistance in both the attapulgite nanofibers and graphene oxide nanosheets, facilitating heat conduction along the nanofiber and nanosheet directions. After freeze-drying, an attapulgite / graphene oxide aerogel with a three-dimensional thermal conductivity network framework and a dense porous structure is formed. Encapsulating the phase change material within the rigid structure of the attapulgite / graphene oxide aerogel effectively prevents leakage and further improves the thermal conductivity of the composite phase change material. This novel aerogel composite phase change material improves the leakage prevention and thermal conductivity of existing graphene oxide aerogel-based composite phase change materials, thus addressing the problems of low solar energy utilization efficiency and significant heat loss during heat transfer.

[0037] This invention integrates the advantages of graphene oxide nanosheets forming three-dimensional aerogels through self-assembly and the easily modifiable surface of attapulgite. It fully utilizes the synergistic effect of the two different materials, and optimizes the three-dimensional framework and pore structure of graphene oxide aerogels through aminated attapulgite nanofibers. The three-dimensional high thermal conductivity attapulgite / graphene oxide aerogel composite phase change material improves the leakage prevention and thermal conductivity of existing graphene oxide aerogel-based composite phase change materials, thus addressing the problems of low solar energy utilization efficiency and large heat loss during heat transfer. It can achieve extremely high energy storage density, excellent leakage prevention performance and good thermal conductivity, which is of great significance in the field of solar energy conversion and storage applications.

[0038] The attapulgite / graphene oxide aerogel composite phase change material prepared using the invented method possesses a 3D network structure, which effectively improves its thermal properties. The attapulgite / graphene oxide aerogel composite phase change material exhibits excellent thermal conductivity (1.164 W / (m·K)), which is 257% higher than that of pure lauric acid and 255% higher than that of graphene oxide aerogel composite phase change material.

[0039] The attapulgite / graphene oxide aerogel composite phase change material prepared using the method of this invention effectively improves the pore structure of the graphene oxide aerogel by incorporating attapulgite nanofibers. The microstructure of the attapulgite / graphene oxide aerogel shows excellent pore size (1016.43 nm) and specific surface area (131.31 m²). 2 / g), compared to the pore size (3717.96 nm) and specific surface area (36.66 m²) of graphene oxide aerogel. 2 / g), which can effectively encapsulate lauric acid and prevent its leakage. The latent heat of the attapulgite / graphene oxide aerogel composite phase change material increases with the increase of attapulgite nanofibers. The lauric acid content is about 90.7-93.8%, and after 2000 heating / cooling cycles, the lauric acid content can still be guaranteed to be 88.4-92.4%. Attached Figure Description

[0040] Figure 1 The materials used to prepare aerogels in Examples 1-4 and Comparative Examples 1 and 2 are GNA0, GNA1, GNA2, GNA3, and GNA4. r2 GNA q2 Digital photos;

[0041] Figure 2 Scanning electron microscope images of the materials prepared for the technical solutions of Examples 1 and 2 and Comparative Example 1;

[0042] Figure 3a Materials GNA0, GNA1, GNA2, and GNA used to prepare aerogels for Examples 1-3 and Comparative Examples 1 and 2 r2 GNA q2 Aperture distribution diagram;

[0043] Figure 3b Materials GNA0, GNA1, GNA2, and GNA used to prepare aerogels for Examples 1-3 and Comparative Examples 1 and 2 r2 GNA q2 Adsorption-desorption curves;

[0044] Figure 4 The materials LA / GNA0, LA / GNA1, LA / GNA2, and LA / GNA are used to prepare aerogels according to the technical schemes of Examples 1-3 and Comparative Examples 1 and 2. r2 LA / GNA q2 The thermal conductivity of LA;

[0045] Figure 5 Materials LA / GNA0 and LA / GNA were prepared using the technical solutions of Comparative Example 2 and Example 3. q2 DSC curve of LA;

[0046] Figure 6 Materials LA / GNA0, LA / GNA1, LA / GNA2, and LA / GNA used to prepare aerogels for the techniques described in Examples 1-3 and Comparative Examples 1 and 2 r2 LA / GNA q2 The thermal leakage performance test results of LA are shown in the figure.

[0047] Figure 7LA / GNA is the material used to prepare the aerogel in Example 2. q2 The results of the cyclic stability test are shown in the figure. Detailed Implementation

[0048] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0049] Example 1:

[0050] This embodiment prepares LA / GNA2.

[0051] (1) Weigh 40g of raw attapulgite ore (ATP) and place it in a beaker containing 400mL of 4 wt% hydrochloric acid solution. Place the beaker in an 80℃ constant temperature water bath, stir, sonicate, and acid wash in a water bath for 60min. Then, clean it to neutral by filtration, dry it, and grind it to obtain acid-activated attapulgite.

[0052] (2) Weigh out 7g of acid-activated attapulgite and 7g of silane coupling agent (C8H). 22 N2O3Si) and 140 mL of 90 wt.% ethanol were placed in a three-necked flask and sonicated at 50 °C for 40 min. Then, the mixture was placed in a 50 °C constant temperature water bath and stirred for 6 h. After washing to neutrality by vacuum filtration, drying and grinding were performed to obtain amino-modified attapulgite (NATP).

[0053] (3) Weigh 0.15g of graphene oxide nanosheets, 0.06g of microfibrillated cellulose and 36mL of deionized water and mix them in a centrifuge tube and sonicate for 2h to obtain a graphene oxide dispersion.

[0054] (4) Weigh 0.09g of amino-modified attapulgite (NATP) and place it in a centrifuge tube containing the graphene oxide dispersion prepared in step (3). Mix and stir for 15 min, then place the dispersion in the liner of a 100mL reactor and perform a hydrothermal reaction at 180℃ for 12 h. After cooling, a three-dimensional attapulgite / graphene oxide hydrogel is obtained.

[0055] (5) After washing the three-dimensional attapulgite / graphene oxide hydrogel twice with deionized water, it was pre-frozen in liquid nitrogen for 10 min and then placed in a freeze dryer to freeze dry at -50℃ for 48 h to obtain the three-dimensional attapulgite / graphene oxide hydrogel (named GNA2).

[0056] (6) The prepared GNA2 and 3g of lauric acid (LA) were transferred to a vacuum flask and vacuumed at room temperature for 20min. Then, vacuumed at 60℃ for 20min and restored to normal pressure. The above operation was repeated 3 times. The sample was then taken out and heat filtered in a 60℃ oven for 24h to obtain a three-dimensional attapulgite / graphene oxide aerogel composite phase change material (LA / GNA2).

[0057] Example 2:

[0058] This embodiment prepares LA / GNA q2 .

[0059] (1) Weigh 40g of raw attapulgite ore (ATP) and place it in a beaker containing 400mL of 4wt% hydrochloric acid solution. Place the beaker in an 80℃ constant temperature water bath and stir, sonicate, and acid wash in a water bath for 60min. Clean the attapulgite to neutrality by filtration, dry, and grind to obtain acid-activated attapulgite. Take 10g of acid-activated attapulgite and place it in a ball mill jar. Grind it thoroughly (ball-to-material mass ratio of 10) for 120min to obtain ball-milled attapulgite nanofibers (ATP). q );

[0060] (2) Weigh out 7g of ball-milled attapulgite nanofibers and 7g of silane coupling agent (C8H). 22 N2O3Si) and 140 mL of 90 wt.% ethanol were placed in a three-necked flask and sonicated at 50 °C for 40 min. Then, the mixture was placed in a 50 °C constant temperature water bath and stirred for 6 h. After washing until neutral by vacuum filtration, drying, and grinding, ball-milled aminated attapulgite nanofibers (NATP) were obtained. q );

[0061] (3) Weigh 0.15g of graphene oxide nanosheets, 0.06g of microfibrillated cellulose and 36mL of deionized water and mix them in a centrifuge tube and sonicate for 2h to obtain a graphene oxide dispersion.

[0062] (4) Weigh 0.09g of ball-milled aminated attapulgite nanofibers (NATP) q Place the mixture in a centrifuge tube containing the graphene oxide dispersion prepared in step (3), mix and stir for 15 min, then place the dispersion in a 100 mL reaction vessel liner and perform a hydrothermal reaction at 180 °C for 12 h. After cooling, a three-dimensional attapulgite / graphene oxide hydrogel is obtained.

[0063] (5) After washing the three-dimensional attapulgite / graphene oxide hydrogel twice with deionized water, it was pre-frozen in liquid nitrogen for 10 min and then freeze-dried in a freeze dryer at -50℃ for 48 h to obtain the three-dimensional attapulgite / graphene oxide hydrogel (named GNA). q2 );

[0064] (6) Prepare GNA q2 3g of lauric acid (LA) was transferred to a vacuum filtration flask, and the mixture was evacuated at room temperature for 20 min. Then, it was evacuated again at 60℃ for 20 min and restored to normal pressure. This process was repeated three times. The sample was then removed and heat-filtered in a 60℃ oven for 24 h to obtain a three-dimensional attapulgite / graphene oxide aerogel composite phase change material (LA / GNA). q2 ).

[0065] Example 3:

[0066] This embodiment prepares LA / GNA1.

[0067] (1) Weigh 40g of raw attapulgite ore (ATP) and place it in a beaker containing 400mL of 4 wt% hydrochloric acid solution. Place the beaker in an 80℃ constant temperature water bath, stir, sonicate, and acid wash in a water bath for 60min. Then, clean it to neutral by filtration, dry it, and grind it to obtain acid-activated attapulgite.

[0068] (2) Weigh out 7g of acid-activated attapulgite and 7g of silane coupling agent (C8H). 22 N2O3Si) and 140 mL of 90 wt.% ethanol were placed in a three-necked flask and sonicated at 50 °C for 40 min. Then, the mixture was placed in a 50 °C constant temperature water bath and stirred for 6 h. After washing to neutrality by vacuum filtration, drying and grinding were performed to obtain amino-modified attapulgite (NATP).

[0069] (3) Weigh 0.195g of graphene oxide nanosheets, 0.06g of microfibrillated cellulose and 36mL of deionized water and mix them in a centrifuge tube and sonicate for 2h to obtain a graphene oxide dispersion.

[0070] (4) Weigh 0.045g of amino-modified attapulgite (NATP) and place it in a centrifuge tube containing the graphene oxide dispersion prepared in step (3). Mix and stir for 15 minutes, then place the dispersion in the liner of a 100mL reactor and perform a hydrothermal reaction at 180℃ for 12 hours. After cooling, a three-dimensional attapulgite / graphene oxide hydrogel is obtained.

[0071] (5) The three-dimensional attapulgite / graphene oxide hydrogel was washed twice with deionized water, pre-frozen in liquid nitrogen for 10 min, and then placed in a freeze dryer and freeze-dried at -50℃ for 48 h to obtain the three-dimensional attapulgite / graphene oxide hydrogel (named GNA1).

[0072] (6) The prepared GNA1 and 3g of lauric acid (LA) were transferred to a vacuum flask and vacuumed at room temperature for 20min. Then, vacuumed at 60℃ for 20min and restored to normal pressure. The above operation was repeated 3 times. The sample was then taken out and heat filtered in a 60℃ oven for 24h to obtain the three-dimensional attapulgite / graphene oxide aerogel composite phase change material (LA / GNA1).

[0073] Example 4:

[0074] This embodiment prepares LA / GNA3.

[0075] (1) Weigh 40g of raw attapulgite ore (ATP) and place it in a beaker containing 400mL of 4 wt% hydrochloric acid solution. Place the beaker in an 80℃ constant temperature water bath, stir, sonicate, and acid wash in a water bath for 60min. Then, clean it to neutral by filtration, dry it, and grind it to obtain acid-activated attapulgite.

[0076] (2) Weigh out 7g of acid-activated attapulgite and 7g of silane coupling agent (C8H). 22 N2O3Si) and 140 mL of 90 wt.% ethanol were placed in a three-necked flask and sonicated at 50 °C for 40 min. Then, the mixture was placed in a 50 °C constant temperature water bath and stirred for 6 h. After washing to neutrality by vacuum filtration, drying and grinding were performed to obtain amino-modified attapulgite (NATP).

[0077] (3) Weigh 0.12g of graphene oxide nanosheets, 0.06g of microfibrillated cellulose and 36mL of deionized water into a centrifuge tube, mix and sonicate for 2h to obtain graphene oxide dispersion;

[0078] (4) Weigh 0.12g of amino-modified attapulgite (NATP) and place it in a centrifuge tube containing the graphene oxide dispersion prepared in step (3). Mix and stir for 15 minutes, then place the dispersion in the liner of a 100mL reactor and perform a hydrothermal reaction at 180℃ for 12 hours. After cooling, a three-dimensional attapulgite / graphene oxide hydrogel is obtained.

[0079] (5) The three-dimensional attapulgite / graphene oxide hydrogel was washed twice with deionized water, pre-frozen in liquid nitrogen for 10 min, and then placed in a freeze dryer and freeze-dried at -50℃ for 48 h to obtain the three-dimensional attapulgite / graphene oxide hydrogel (named GNA3).

[0080] (6) The prepared GNA3 and 3g of lauric acid (LA) were transferred to a vacuum flask and vacuumed at room temperature for 20min. Then, vacuumed at 60℃ for 20min and restored to normal pressure. The above operation was repeated 3 times. The sample was then taken out and heat filtered in a 60℃ oven for 24h to obtain a three-dimensional attapulgite / graphene oxide aerogel composite phase change material (LA / GNA3).

[0081] Comparative Example 1:

[0082] This embodiment prepares LA / GNA r2 .

[0083] (1) Weigh 40g of raw attapulgite ore (ATP) and place it in a beaker containing 400mL of 4wt% hydrochloric acid solution. Place the beaker in an 80℃ constant temperature water bath, stir, sonicate, and acid wash in a water bath for 60min. Clean the attapulgite to neutrality by filtration, dry, and grind to obtain acid-activated attapulgite. Take 10g of acid-activated attapulgite and 1000mL of deionized water and place them in a high-speed emulsifying shear machine. Emulsify the attapulgite at an emulsification rate of 6000r / min for 30min. Clean the attapulgite to neutrality by filtration, dry, and grind to obtain emulsified attapulgite nanofibers (ATP). r );

[0084] (2) Weigh 7g of emulsified attapulgite nanofibers (ATP) r ), 7g silane coupling agent (C8H) 22 N2O3Si) and 140 mL of 90 wt.% ethanol were added to a three-necked flask and sonicated at 50 °C for 40 min. The mixture was then placed in a 50 °C water bath and stirred for 6 h. Afterward, the mixture was washed until neutral by filtration, dried, and ground to obtain emulsified aminated attapulgite nanofibers (NATP). r );

[0085] (3) Weigh 0.15g of graphene oxide nanosheets, 0.06g of microfibrillated cellulose and 36mL of deionized water and mix them in a centrifuge tube and sonicate for 2h to obtain a graphene oxide dispersion.

[0086] (4) Weigh 0.09g of emulsified amino-modified attapulgite nanofibers (NATP). r Place the mixture in a centrifuge tube containing the graphene oxide dispersion prepared in step (3), mix and stir for 15 min, then place the dispersion in a 100 mL reaction vessel liner and perform a hydrothermal reaction at 180 °C for 12 h. After cooling, a three-dimensional attapulgite / graphene oxide hydrogel is obtained.

[0087] (5) After washing the three-dimensional attapulgite / graphene oxide hydrogel twice with deionized water, it was pre-frozen in liquid nitrogen for 10 min and then freeze-dried in a freeze dryer at -50℃ for 48 h to obtain the three-dimensional attapulgite / graphene oxide hydrogel (named GNA). r2 );

[0088] (6) Prepare GNA r23g of lauric acid (LA) was transferred to a vacuum filtration flask, and the mixture was evacuated at room temperature for 20 min. Then, it was evacuated again at 60℃ for 20 min and restored to normal pressure. This process was repeated three times. The sample was then removed and heat-filtered in a 60℃ oven for 24 h to obtain a three-dimensional attapulgite / graphene oxide aerogel composite phase change material (LA / GNA). r2 ).

[0089] Comparative Example 2:

[0090] This embodiment prepares a graphene oxide aerogel composite phase change material (LA / GNA0).

[0091] (1) Weigh 0.24g of graphene oxide nanosheets, 0.06g of microfibrillated cellulose and 36mL of deionized water and mix them in a centrifuge tube and sonicate for 2h to obtain a graphene oxide dispersion.

[0092] (4) Place the graphene oxide dispersion prepared in step (3) into the liner of a 100 mL reactor and perform a hydrothermal reaction at 180 °C for 12 h. After cooling, a three-dimensional graphene oxide hydrogel is obtained.

[0093] (5) After washing the three-dimensional graphene oxide hydrogel twice with deionized water, it was pre-frozen in liquid nitrogen for 10 min and then placed in a freeze dryer to freeze dry at -50℃ for 48 h to obtain the three-dimensional graphene oxide hydrogel (named GNA0).

[0094] (6) The prepared GNA0 and 3g of lauric acid (LA) were transferred to a vacuum flask, and vacuumed at room temperature for 20min. Then, vacuumed at 60℃ for 20min and restored to normal pressure. The above operation was repeated 3 times. The sample was then taken out and heat filtered in a 60℃ oven for 24h to obtain graphene oxide aerogel composite phase change material (LA / GNA0).

[0095] See appendix Figure 1 It is the material GNA0, GNA1, GNA2, GNA3, GNA4 used in the preparation of aerogels according to the technical solutions of Examples 1-4 and Comparative Examples 1 and 2. r2 GNA q2 Digital photographs show that the aerogel morphology shrinks with increasing content of aminated attapulgite nanofibers. This is due to the enhanced interaction between the nanofibers and graphene oxide sheets; however, excessive nanofibers can affect the aerogel's formation. The prepared aerogel material has extremely low density, with an apparent density of approximately 0.043-0.046 kg / cm³. 3 This indicates that the aerogel has a large number of pores, which is beneficial for loading LA and preparing composite phase change materials with extremely high heat storage capacity.

[0096] See appendix Figure 2It is a material prepared using the technical solutions of Example 1, Comparative Example 1, and Example 2: (a) Aminated attapulgite fiber clusters (NATP); (b) Emulsified aminated attapulgite nanofibers (NATP). r (c) Ball-milled amination-modified attapulgite nanofibers (NATP) q (d) Attapulgite / graphene oxide aerogel (GNA2); (e) Emulsified attapulgite / graphene oxide aerogel (GNA2) r2 (f) Ball-milled attapulgite / graphene oxide aerogel (GNA) q2 Scanning electron microscope images of GNA. From (a), (b), and (c), it can be seen that the emulsified amino-modified attapulgite fiber clusters have a higher degree of dissociation compared to the untreated amino-modified attapulgite. The ball-milled amino-modified attapulgite is essentially dissociated into short rod-shaped nanofibers, which is beneficial for grafting with graphene oxide nanosheets to form a denser porous structure and three-dimensional mesh framework. From (d), (e), and (f), it can be seen that the ball-milled attapulgite / graphene oxide aerogel (GNA)... q2 The pores are denser, and the good pore structure can effectively encapsulate the phase change material and prevent leakage.

[0097] Referring to Figure 3 and Table 1, these are the materials GNA0, GNA1, GNA2, and GNA3 used in the preparation of aerogels according to the technical schemes of Examples 1-3 and Comparative Examples 1 and 2. r2 GNA q2 The pore size distribution (a), adsorption-desorption curves (b), and specific surface area and average pore size distribution are shown in Appendix Table 1. From the pore size distribution and adsorption-desorption curves, it can be seen that ball-milled attapulgite can effectively increase the specific surface area of ​​graphene oxide aerogel while reducing the average pore size. A larger specific surface area is beneficial for loading more LA (attapulgite-to-plastic composite), thus improving the thermal storage capacity of the attapulgite / graphene oxide aerogel composite phase change material. Smaller pore sizes can effectively encapsulate LA and prevent LA leakage.

[0098] See appendix Figure 4 It is the material LA / GNA0, LA / GNA1, LA / GNA2, and LA / GNA used in the preparation of aerogels according to the technical schemes of Examples 1-3 and Comparative Examples 1 and 2. r2 LA / GNA q2The thermal conductivity of LA and GA is compared. It can be seen that the thermal conductivity of the graphene oxide aerogel composite phase change material (LA / GNA0) shows a very slight improvement compared to LA. Due to amino reduction and grafting, aminated attapulgite can effectively improve the thermal conductivity of the composite phase change material, and the thermal conductivity gradually increases with the increase of aminated attapulgite content. The thermal conductivity of LA / GNA2 is 213% higher than that of LA. After ball milling, the heat transfer effect of the grafted aerogel network framework structure is improved due to the formation of short nanofibers from attapulgite fiber clusters, resulting in a higher thermal conductivity of the composite phase change material (LA / GNA0) after loading with LA. q2 The thermal conductivity is 257% higher than that of LA.

[0099] See appendix Figure 5 Appendix 2 shows the materials LA, LA / GNA0, and LA / GNA prepared using the technical solutions of Comparative Example 2 and Example 2. q2 The DSC curves and thermophysical property parameter tables show the prepared LA / GNA. q2 Compared to LA / GNA0, it has a higher latent heat value and a heat storage efficiency close to that of pure LA, reaching 93.1%, indicating that the attapulgite / graphene oxide aerogel composite phase change material has superior heat storage capacity.

[0100] See appendix Figure 6 It is the material LA / GNA0, LA / GNA1, LA / GNA2, and LA / GNA used in the preparation of aerogels according to the technical schemes of Examples 1-3 and Comparative Examples 1 and 2. r2 LA / GNA q2 Thermal leakage performance tests were conducted on LA / GNA. It can be seen that, due to the limitation of pore size, LA / GNA... q2 The attapulgite exhibits the best leak-proof performance. After 15 minutes of continuous heating at 60°C, only a very small amount of LA leaked. Compared to LA and LA / GNA0, the addition of aminated attapulgite can effectively improve the leak-proof performance of the composite phase change material, indicating that the attapulgite / graphene oxide aerogel composite phase change material has good leak-proof capability.

[0101] See appendix Figure 7 It is the LA / GNA material used in the preparation of aerogels according to the technical solution of Example 2. q2 Cyclic stability testing. Take a small piece of LA / GNA. q2 The attapulgite / graphene oxide aerogel composite phase change material was tested after 600, 1000, and 2000 heating / cooling cycles in an adjustable dry thermostat to assess its heat storage capacity after multiple phase change cycles. It can be seen that after 2000 heating / cooling cycles, the LA / GNA... q2The thermal storage efficiency decreased from 93.1% to 92.0%, a loss of only 1.1%, indicating that the attapulgite / graphene oxide aerogel composite phase change material possesses excellent cycle stability and can guarantee extremely high thermal storage efficiency. This is beneficial for practical applications in the field of solar energy storage and conversion. Table 1 GNA0, GNA1, GNA2, GNA r2 GNA q2 Table of specific surface area and average pore size distribution

[0102]

[0103] Table 2 LA / GNA0 and LA / GNA q2 DSC curves and thermophysical property parameter tables

[0104]

[0105] Any aspects not covered above are applicable to existing technologies. Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and not for limiting the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a three-dimensional high thermal conductivity attapulgite / graphene oxide aerogel composite phase change material, characterized in that: Includes the following steps: (1) Attapulgite clusters were dissociated into attapulgite nanofibers by acid activation treatment; (2) The attapulgite nanofibers obtained in step (1) are mixed and stirred with silane coupling agent and ethanol to obtain aminated attapulgite nanofibers. (3) Mix graphene oxide nanosheets, microfibrillated cellulose and deionized water to form a uniform graphene oxide suspension; (4) The aminoated attapulgite nanofibers obtained in step (2) are added to the graphene oxide suspension formed in step (3), and the mixture is stirred to obtain a uniform dispersion. The dispersion is then subjected to a hydrothermal reaction to prepare an attapulgite / graphene oxide hydrogel with a three-dimensional structure. (5) Attapulgite / graphene oxide hydrogel was frozen in a freeze dryer to obtain attapulgite / graphene oxide aerogel. (6) Vacuum impregnation of attapulgite / graphene oxide aerogel with a phase change material yields a three-dimensional attapulgite / graphene oxide aerogel composite phase change material; the phase change material is lauric acid. Steps (2) and (3) have no specific order. In step (2), the mass concentration fraction of ethanol is 70-100 wt.%; The attapulgite nanofibers and silane coupling agent C8H 22 N2O3Si and ethanol are weighed in the following proportions: Attapulgite nanofibers: 1-7 parts Silane coupling agent: 1-7 parts Ethanol: 20-140 parts; In step (2), the amination modification process mainly includes: mixing of the mixture, sonication, solid-liquid separation, washing, and drying; wherein the stirring speed is 600~1200 r / min, the stirring time is 2~6 h, the stirring temperature is 20~50 ℃, the sonication time is 10~40 min, and the sonication temperature is 20~50 ℃. In step (6), the ratio of attapulgite-graphene oxide aerogel to lauric acid is: 5~25 wt.% : 75~95 wt.%; In step (6), vacuum impregnation is first performed at room temperature for 20-40 min, and then at 60-90 °C for 20-60 min. The above steps are repeated 2-4 times. In step (6), the attapulgite / graphene oxide aerogel composite phase change material is placed in a forced-air drying oven at 40~70 ℃ and hot-filtered for 12~48 hours to remove excess phase change material adsorbed on the aerogel surface.

2. The preparation method of a three-dimensional high thermal conductivity attapulgite / graphene oxide aerogel composite phase change material as described in claim 1, characterized in that: In step (1), the acid activation process mainly includes: acid soaking, solid-liquid separation, washing, and drying; wherein the acid solution is a hydrochloric acid aqueous solution with a mass fraction of 1~12 wt.%, the soaking is carried out by stirring, the stirring speed is 600~1200 r / min, the soaking temperature is 60~90 ℃, and the soaking time is 30~120 min; In step (1), the grade of the attapulgite is greater than 80% and the particle size is less than 200 mesh.

3. The preparation method of a three-dimensional high thermal conductivity attapulgite / graphene oxide aerogel composite phase change material as described in claim 1, characterized in that: Step (1) also includes a ball milling process, in which the acid-treated attapulgite is ball-milled. The ball-to-material mass ratio in the ball milling process is 2 to 10, the grinding time is 10 to 120 min, the grinding temperature is 20 to 120 ℃, and the rotation speed is 200 to 500 r / min.

4. The preparation method of a three-dimensional high thermal conductivity attapulgite / graphene oxide aerogel composite phase change material as described in claim 1, characterized in that: In step (3), the graphene oxide nanosheets, microfibrillated cellulose, and deionized water are in the following weight proportions: Graphene oxide nanosheets: 4-8 parts Microfibrillated cellulose: 1-3 parts Deionized water: 20-120 parts.

5. The preparation method of a three-dimensional high thermal conductivity attapulgite / graphene oxide aerogel composite phase change material as described in claim 1, characterized in that: In step (3), graphene oxide nanosheets, microfibrillated cellulose and deionized water are mixed and then dispersed by ultrasonication to obtain graphene oxide suspension. The ultrasonication time is 30~120 min and the ultrasonication temperature is 20~40 min. In step (4), the dispersion is uniformly dispersed by stirring. The stirring speed is 600~1200 r / min and the stirring time is 10~30 min.

6. The preparation method of a three-dimensional high thermal conductivity attapulgite / graphene oxide aerogel composite phase change material as described in claim 1, characterized in that: In step (4), the ratio of the amounts of aminated attapulgite nanofibers to graphene oxide suspension is: 10~40 wt.% : 60 wt.% ~90 wt.%; In step (4), the dispersion is placed in a high-temperature reactor and kept in a forced-air drying oven at 150~200 ℃ for 8~15 h.

7. The preparation method of a three-dimensional high thermal conductivity attapulgite / graphene oxide aerogel composite phase change material as described in claim 1, characterized in that: In step (5), the attapulgite / graphene oxide hydrogel is freeze-dried at a temperature of -70 to 0 ℃ for 48 to 72 h in a freeze dryer.

8. A three-dimensional high thermal conductivity attapulgite / graphene oxide aerogel composite phase change material prepared by the preparation method according to any one of claims 1-7.

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