CN114688905B - Flexible thermal diode, preparation method and application thereof - Google Patents
Flexible thermal diode, preparation method and application thereof Download PDFInfo
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- CN114688905B CN114688905B CN202011621418.6A CN202011621418A CN114688905B CN 114688905 B CN114688905 B CN 114688905B CN 202011621418 A CN202011621418 A CN 202011621418A CN 114688905 B CN114688905 B CN 114688905B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D15/00—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies
- F28D15/02—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes
- F28D15/04—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes with tubes having a capillary structure
- F28D15/046—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes with tubes having a capillary structure characterised by the material or the construction of the capillary structure
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Abstract
The invention discloses a flexible thermal diode, a preparation method and application thereof. The flexible thermal diode comprises a first phase-change composite film and a second phase-change composite film with different thermal conductivity temperature coefficients, the first phase-change composite film and the second phase-change composite film are in thermal contact with each other, the first phase-change composite film and the second phase-change composite film are stable in form and flexible before and after phase change, the thermal conductivities of the first phase-change composite film and the second phase-change composite film are in opposite trend along with temperature change, and the phase change temperature difference value of the first phase-change composite film and the second phase-change composite film is smaller than 10 ℃; the first phase change composite film and the second phase change composite film have opposite surface wettability and incompatible interfaces. Compared with the traditional thermal diode, the flexible thermal diode provided by the invention can be conformally attached to the curved surface or the irregular surface which needs to be subjected to thermal management, so that the application field of the phase-change film is expanded, and meanwhile, the practicability of the thermal diode is improved.
Description
Technical Field
The invention belongs to the technical field of thermal management materials, and particularly relates to a flexible thermal diode, a preparation method and application thereof.
Background
Thermal diodes, like electronic diodes, also contain two poles, a temperature input and a temperature output, respectively. When one electrode is connected with the hot end and the other electrode is connected with the cold end, the heat flow is J f After the cold and hot end positions are exchanged, the heat flow is J r If J f And J r Unequal values break the fourier law, a phenomenon known as thermal rectification, and this component is known as a thermal diode (see patent CN111895827 a). Although the thermal management material can simultaneously have the heat conduction and energy storage functions (CN 111439001A), the thermal diode has better thermal rectification functionThe control of heat transfer has wide application prospect in a plurality of fields.
The thermal diode can realize thermal rectification, and the thermal conductivity temperature coefficients of the two-pole materials are required to be different, preferably the thermal conductivity has opposite trend along with the change of temperature, and the one-pole material has good heat transfer in a high-temperature state and poor heat transfer in a low-temperature state; the other pole has good heat transfer at low temperature and poor heat transfer at high temperature. So that heat transfer in the forward and reverse directions is asymmetric, and thermal rectification is generated. Bipolar materials meeting the above requirements are critical for constructing thermal diodes. The thermal conductivity of alloy materials and metal oxides is generally changed along with the change of temperature (Sci.Technol.Adv.Mater.2014, 15,064801;Appl.Phys.Lett.2009,95,171905), so that the alloy materials and the metal oxides can be used for preparing thermal diodes, however, the thermal conductivity of the materials is changed in a large temperature range, the working temperature range is also extreme temperature, and the alloy materials and the metal oxides cannot be widely applied to actual production and life.
The characteristics of the phase change material that a large amount of latent heat is absorbed or released during phase transition can be utilized to carry out thermal management (CN 109449131A) on electronic components, meanwhile, the thermal conductivity of the phase change material is suddenly changed (adv. Mater.2019,31,1806518) in the process of phase transition, and the temperature interval of the transition is relatively narrow, so that two phase change materials with close phase change temperature and opposite thermal conductivity along with temperature change are selected to be assembled into a thermal diode, the working temperature difference is small, and the thermal rectification ratio is large. However, all the currently reported phase change thermal diodes are formed by packaging phase change materials in plastic pipes, and the assembled thermal diodes are rigid (Mater. Horiz.,2015,2,125-129;Adv.Energy Mater.2018,8,1702692), so that flexibility cannot be obtained, and the wide application of the thermal diodes is limited.
Disclosure of Invention
The invention mainly aims to provide a flexible thermal diode, a preparation method and application thereof, so as to overcome the defects of the prior art.
In order to achieve the purpose of the invention, the technical scheme adopted by the invention comprises the following steps:
the embodiment of the invention provides a flexible thermal diode, which comprises a first phase-change composite film and a second phase-change composite film with different thermal conductivity temperature coefficients, wherein the first phase-change composite film and the second phase-change composite film are in thermal contact with each other, the first phase-change composite film and the second phase-change composite film are stable in form and have flexibility before and after phase change, the thermal conductivities of the first phase-change composite film and the second phase-change composite film are in opposite trend along with the change of temperature, and the phase change temperature difference of the first phase-change composite film and the second phase-change composite film is smaller than 10 ℃; the first phase change composite film and the second phase change composite film have opposite surface wettability and incompatible interfaces.
The embodiment of the invention also provides a preparation method of the flexible thermal diode, which comprises the following steps:
respectively loading the negative temperature coefficient phase change material and the positive temperature coefficient phase change material into the aerogel film so as to respectively prepare a first phase change composite film and a second phase change composite film;
and assembling the first phase-change composite film and the second phase-change composite film to form the flexible thermal diode.
The embodiment of the invention also provides the application of the flexible thermal diode in the field of thermal management.
Compared with the prior art, the invention has the beneficial effects that:
(1) The flexible thermal diode provided by the invention has good flexibility, the tradition that the traditional thermal diode is rigid is overturned, and meanwhile, the working temperature difference of the flexible thermal diode is small and the thermal rectification ratio is large;
(2) The preparation method and the assembly process of the flexible thermal diode are simple, and the flexible thermal diode is easy to realize large-scale production;
(3) The flexible thermal diode provided by the invention has wide application prospect, and can be conformally attached to a curved surface or an irregular surface which needs to be subjected to thermal management.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings may be obtained according to the drawings without inventive effort to those skilled in the art.
FIG. 1 is an optical photograph of a flexible thermal diode according to an exemplary embodiment of the present invention;
FIG. 2 is a schematic structural view of a flexible thermal diode according to example 1 of the present invention;
FIG. 3 is a stress-strain graph of the flexible thermal diode obtained in example 2 of the present invention in a tensile mode;
FIGS. 4a to 4b are graphs showing thermal conductivities of the C20/PI phase change composite film and PNIPAM/PI phase change composite film obtained in example 4 of the present invention, respectively, according to temperature;
FIGS. 5a to 5b are photographs showing the hydrophobic angles of the C20/cell phase change composite film and PNIPAM/cell phase change composite film obtained in example 5 of the present invention, respectively;
FIG. 6 is a graph showing the variation of heat flux in the forward and reverse directions with temperature difference of the flexible thermal diode obtained in example 9 of the present invention;
FIG. 7 is a schematic diagram showing the thermal rectification ratio of the flexible thermal diode obtained in example 10 of the present invention;
fig. 8 is a schematic diagram showing the application of the flexible thermal diode in embodiment 11 of the present invention.
Detailed Description
In view of the defects of the prior art, the inventor of the present invention has provided a technical scheme through long-term research and a great deal of practice, the phase change material has larger change in thermal conductivity in a narrower temperature range near the phase change temperature, when two phase change materials are screened out, the phase change temperature is close, the thermal conductivity temperature coefficients are opposite, and the two phase change materials are respectively packaged in two high-strength flexible aerogel films with opposite surface wettability. And then the two phase-change composite films are assembled into the thermal diode, and the thermal diode has good flexibility, smaller working temperature difference and better thermal rectification performance. Therefore, the invention can be conformally attached to the curved surface or irregular surface which needs to be subjected to thermal management, expands the application field of the phase-change film, and improves the practicability of the thermal diode.
The following description of the present invention will be made clearly and fully, and it is apparent that the embodiments described are some, but not all, of the embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
An aspect of an embodiment of the present invention provides a flexible thermal diode, including a first phase-change composite film and a second phase-change composite film having different thermal conductivity temperature coefficients, the first phase-change composite film and the second phase-change composite film being in thermal contact with each other, the first phase-change composite film and the second phase-change composite film being stable in morphology and having flexibility both before and after phase change, the thermal conductivities of the first phase-change composite film and the second phase-change composite film being in opposite trend with temperature change, a phase-change temperature difference value of the first phase-change composite film and the second phase-change composite film being less than 10 ℃; the first phase change composite film and the second phase change composite film have opposite surface wettability and incompatible interfaces.
Further, the working temperature difference of the flexible thermal diode is small.
Further, the phase transition temperatures of the first phase transition composite film and the second phase transition composite film are close.
In some more specific embodiments, the flexible thermal diode has a thermal rectification ratio of 1.5 to 3.0.
In some more specific embodiments, the first phase change composite film and the second phase change composite film in the flexible thermal diode are interfacial incompatible.
Further, the first phase-change composite film is obtained by loading a negative temperature coefficient phase-change material on an aerogel film.
Further, the load capacity of the negative temperature coefficient phase change material in the first phase change composite film is 30-98wt%.
Further, the second phase change composite film is obtained by loading positive temperature coefficient phase change materials with aerogel films.
Further, the loading amount of the positive temperature coefficient phase change material in the second phase change composite film is 30-98wt%.
Further, the contact angle between the surface of the first phase-change composite film and water is 100-180 degrees.
Further, the contact angle between the surface of the second phase-change composite film and water is 0-80 degrees. Further, the thickness ratio of the first phase-change composite film to the second phase-change composite film is 1:10-10:1.
In some more specific embodiments, the thermal conductivity of the negative temperature coefficient phase change material and the positive temperature coefficient phase change material at the phase change point have opposite trends with temperature.
Further, the thermal conductivity of the negative temperature coefficient phase change material decreases with increasing temperature.
Further, the negative temperature coefficient phase change material includes any one or a combination of more than two of paraffin (Paraffin), hexadecane (C16), octadecane (C18), eicosane (C20) and Polyethylene (PE), and is not limited thereto.
Further, the thermal conductivity of the positive temperature coefficient phase change material increases with the increase of temperature.
Further, the positive temperature coefficient phase change material comprises poly (N-isopropyl acrylamide) (PNIPAM) aqueous solution and/or vanadium dioxide (VO 2 )。
Further, the concentration of the poly (N-isopropyl acrylamide) (PNIPAM) aqueous solution is 10-50 wt%.
In some more specific embodiments, the aerogel film is a flexible self-supporting aerogel film.
Further, the aerogel film has a tensile strength of 1MPa or more.
Further, the aerogel film has a porosity of 60% or more.
Further, the aerogel film has a thermal conductivity of 0.1W/mK or less.
Further, the aerogel film includes any one or a combination of two or more of Kevlar (Kevlar) aerogel film, polyimide (PI) aerogel film, cellulose (Cellulose) aerogel film, poly-p-Phenylene Benzobisoxazole (PBO) aerogel film, and is not limited thereto.
In some more specific embodiments, referring to FIG. 1, the flexible thermal diode includes a first phase change composite film and a second phase change composite film having different thermal conductivity temperature coefficients; the two phase-change composite films are respectively obtained by loading a negative temperature coefficient phase-change material and a positive temperature coefficient phase-change material on a high-strength flexible aerogel film.
Another aspect of the embodiment of the present invention further provides a method for preparing the aforementioned flexible thermal diode, which includes:
respectively loading the negative temperature coefficient phase change material and the positive temperature coefficient phase change material into holes of the aerogel film, so as to respectively prepare a first phase change composite film and a second phase change composite film;
and assembling the first phase-change composite film and the second phase-change composite film to form the flexible thermal diode.
Further, the aerogel film is a high strength, flexible self-supporting aerogel film.
In some more specific embodiments, the preparation method specifically comprises: and loading the molten or solution-state negative temperature coefficient phase change material into the aerogel film by utilizing capillary action to prepare the first phase change composite film.
In some more specific embodiments, the preparation method specifically comprises: and loading the positive temperature coefficient phase change material in a molten state or a solution state into the aerogel film by utilizing capillary action, or compositing the positive temperature coefficient phase change material and the aerogel film by adopting an in-situ growth mode, so as to obtain the second phase change composite film.
In some more specific embodiments, the method of making comprises: and attaching the first phase change composite film and the second phase change composite film to form the flexible thermal diode.
Further, the preparation method specifically comprises the following steps: the first phase change composite film and the second phase change composite film are in thermal contact with each other, and then assembled to form the flexible thermal diode.
In some more specific embodiments, the method of making further comprises: and performing densification treatment on the aerogel film.
Further, the densification treatment method includes any one of a hot pressing method and a cold pressing method, and is not limited thereto.
Further, the densification process may increase the strength and flexibility of the aerogel film.
Another aspect of embodiments of the present invention also provides the use of the aforementioned flexible thermal diode in the field of thermal management.
The flexible thermal diode provided by the invention has simple preparation and assembly processes and is easy to realize large-scale production.
Further, the use of the flexible thermal diode in the thermal management of curved or irregularly shaped surfaces.
By the technical scheme, the flexible thermal diode provided by the invention is formed by two flexible phase-change composite films with different thermal conductivity temperature coefficients in thermal contact with each other. The two phase-change composite films are respectively obtained by loading phase-change materials with aerogel films with excellent mechanical properties, are stable in form and have flexibility before and after phase change; the phase transition temperature is close; the thermal conductivity has opposite trend along with the temperature; the surface wetting properties are opposite. Compared with the traditional thermal diode, the flexible thermal diode provided by the invention can be conformally attached to the curved surface or the irregular surface which needs to be subjected to thermal management, so that the application field of the phase-change film is expanded, and meanwhile, the practicability of the thermal diode is improved.
The technical scheme of the present invention is further described in detail below with reference to several preferred embodiments and the accompanying drawings, and the embodiments are implemented on the premise of the technical scheme of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.
The experimental materials used in the examples described below, unless otherwise specified, were all commercially available from conventional biochemicals.
Example 1
Paraffin (Paraffin) and PNIPAM aqueous solution are respectively used as a negative temperature coefficient phase-change material and a positive temperature coefficient phase-change material with opposite heat conductivity temperature coefficients, then are respectively loaded into Kevlar aerogel films with different thicknesses to respectively obtain Paraffin/Kevlar phase-change composite films and PNIPAM/Kevlar phase-change composite films, the thickness ratio of the Paraffin/Kevlar phase-change composite films to the PNIPAM/Kevlar phase-change composite films is 1:10, the Paraffin/Kevlar phase-change composite films and the PNIPAM phase-change composite films are cut into the same size, and are attached together to form the flexible thermal diode. Fig. 2 shows a schematic structure of the flexible thermal diode according to the embodiment, and other parameters are shown in table 1.
Example 2
Paraffin (Paraffin) and PNIPAM aqueous solution are respectively used as a negative temperature coefficient phase-change material and a positive temperature coefficient phase-change material with opposite thermal conductivity temperature coefficients, then are respectively loaded into Kevlar aerogel films after densification treatment to respectively obtain a Paraffin/D-Kevlar phase-change composite film and a PNIPAM/D-Kevlar phase-change composite film, the thickness ratio of the Paraffin/D-Kevlar phase-change composite film to the PNIPAM aqueous solution is 1:5, and the Paraffin/D-Kevlar phase-change composite film and the PNIPAM aqueous solution are cut into the same size and are bonded together to form the flexible thermal diode. The detailed parameters are shown in Table 1.
Example 3
And respectively taking the C20 and PNIPAM aqueous solutions as a negative temperature coefficient phase-change material and a positive temperature coefficient phase-change material with opposite thermal conductivity temperature coefficients, respectively loading the materials into the densified Kevlar aerogel film and the undensified Kevlar aerogel film to respectively obtain a C20/D-Kevlar phase-change composite film and a PNIPAM/Kevlar phase-change composite film, wherein the thickness ratio of the two is 1:6. Cutting the two materials into the same size, attaching the two materials together, and assembling the flexible thermal diode. Fig. 3 shows the tensile strength curves of the flexible thermal diode obtained in this example, and other parameters are shown in table 1.
Example 4
And respectively taking the C20 and PNIPAM aqueous solutions as a negative temperature coefficient phase-change material and a positive temperature coefficient phase-change material with opposite heat conductivity temperature coefficients, respectively loading the materials into PI aerogel films with different thicknesses to respectively obtain a C20/PI phase-change composite film and a PNIPAM/PI phase-change composite film, wherein the thickness ratio of the C20/PI phase-change composite film to the PNIPAM/PI phase-change composite film is 1:6. Cutting the two materials into the same size, and attaching the two materials together to assemble the flexible thermal diode. Fig. 4 shows the thermal conductivity curves of the C20/PI phase change composite film and the PNIPAM/PI phase change composite film of the flexible thermal diode obtained in this example with temperature, and other parameters are shown in table 1.
Example 5
And respectively taking the C20 and PNIPAM aqueous solutions as a negative temperature coefficient phase-change material and a positive temperature coefficient phase-change material with opposite heat conductivity temperature coefficients, respectively loading the materials into Cellulose aerogel films with different thicknesses to respectively obtain a C20/Cellulose phase-change composite film and a PNIPAM/Cellulose phase-change composite film, cutting the materials into the same size according to the thickness ratio of 1:6, and bonding the materials together to assemble the flexible thermal diode. Fig. 5 shows the surface wettability of the two-polar material C20/cell phase-change composite film and PNIPAM/cell phase-change composite film of the flexible thermal diode obtained in this example, and other parameters are shown in table 1.
Example 6
And respectively taking the C18 and PNIPAM aqueous solutions as a negative temperature coefficient phase-change material and a positive temperature coefficient phase-change material with opposite thermal conductivity temperature coefficients, respectively loading the materials into a Kevlar aerogel film after densification treatment and a Kevlar aerogel film without densification treatment to respectively obtain a C18/D-Kevlar phase-change composite film and a PNIPAM/Kevlar phase-change composite film, wherein the thickness ratio of the C18/D-Kevlar phase-change composite film to the PNIPAM/Kevlar phase-change composite film is 1:6, cutting the C18/Kevlar phase-change composite film to the PNIPAM/Kevlar phase-change composite film into the same size, and bonding the C18/PNIPAM phase-change composite film to the PNIPAM/Kevlar phase-change composite film to form the flexible thermal diode. Other parameters are shown in Table 1.
Example 7
Selection of PE and VO 2 Respectively used as a negative temperature coefficient phase-change material and a positive temperature coefficient phase-change material with opposite heat conductivity temperature coefficients, PE is loaded into a PBO aerogel film by a solution filling method, and VO is carried out 2 The PE/PBO phase-change composite film and the VO are respectively obtained by loading the PE/PBO phase-change composite film into the PBO aerogel film through an in-situ growth method 2 And (3) cutting the PBO phase-change composite film into the same size by the thickness ratio of 10:1, and bonding the two to form the flexible thermal diode. Parameters are shown in Table 1.
Example 8
Selection of PE and VO 2 Respectively used as a negative temperature coefficient phase-change material and a positive temperature coefficient phase-change material with opposite heat conductivity temperature coefficients, PE is loaded into a PBO aerogel film by a solution filling method, and VO is carried out 2 The PE/PBO phase-change composite film and the VO are respectively obtained by loading the PE/PBO phase-change composite film into the PBO aerogel film through an in-situ growth method 2 And (3) cutting the PBO phase-change composite film into the same size by the thickness ratio of 2.5:1, and bonding the two films together to assemble the flexible thermal diode. Parameters are shown in Table 1.
Example 9
And respectively taking the C18 and PNIPAM aqueous solutions as a negative temperature coefficient phase-change material and a positive temperature coefficient phase-change material with opposite thermal conductivity temperature coefficients, respectively loading the materials into a Kevlar aerogel film and a Cellulose aerogel film after densification treatment to respectively obtain a C18/D-Kevlar phase-change composite film and a PNIPAM/Cellulose phase-change composite film, cutting the materials into the same size according to the thickness ratio of 1:6, and bonding the materials together to assemble the flexible thermal diode. Fig. 6 shows the variation curves of the heat flows of the flexible thermal diode obtained in this embodiment in the forward and reverse directions along with the temperature difference of the two poles, and other parameters are shown in table 1.
Example 10
And respectively taking the C16 and PNIPAM aqueous solutions as a negative temperature coefficient phase-change material and a positive temperature coefficient phase-change material with opposite heat conductivity temperature coefficients, and respectively loading the materials into PI aerogel films and Cellulose aerogel films with different thicknesses to respectively obtain a C20/PI phase-change composite film and a PNIPAM/Cellulose phase-change composite film, wherein the thickness ratio of the two is 1:6. Cutting the two materials into the same size, and bonding the two materials together to assemble the thermal diode. Fig. 7 shows the thermal rectification ratio of the flexible thermal diode obtained in this example, and other parameters are shown in table 1.
TABLE 1 Structure and Performance parameters of the Flexible thermal diodes obtained in examples 1-10
Example 11
C20/D-Kevlar is used as a first phase-change composite film, PNIPAM/Kevlar is used as a second phase-change composite film, the thickness ratio of the two is 1:6, and the two is cut into the same size, and the two are attached together to assemble the flexible thermal diode. The second phase change composite film is outside, and the first phase change composite film is inside, attached to the surface of the water pipe, can heat water when the external temperature is higher than the temperature of water in the water pipe, can keep the temperature of water when the external temperature is lower than the temperature of water in the water pipe, and realizes the function of thermal management. Fig. 8 shows a schematic application diagram of the flexible thermal diode in the present embodiment.
Through examples 1-11, it can be found that the thermal diode obtained by the above technical scheme of the present invention has good flexibility, small working temperature difference and excellent thermal rectification performance, and the preparation and assembly processes are simple, and the thermal diode is easy to carry out mass production and can be conformally attached to a curved surface or an irregular surface which needs thermal management.
In addition, the inventors have conducted experiments with other materials, process operations, and process conditions as described in this specification with reference to the foregoing examples, and have all obtained desirable results.
The various aspects, embodiments, features and examples of the invention are to be considered in all respects as illustrative and not intended to limit the invention, the scope of which is defined solely by the claims. Other embodiments, modifications, and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.
The use of headings and chapters in this disclosure is not meant to limit the disclosure; each section may apply to any aspect, embodiment, or feature of the present invention.
Throughout this disclosure, where a composition is described as having, comprising, or including a particular component, or where a process is described as having, comprising, or including a particular process step, it is contemplated that the composition of the teachings of the present invention also consist essentially of, or consist of, the recited component, and that the process of the teachings of the present invention also consist essentially of, or consist of, the recited process step.
It should be understood that the order of steps or order in which a particular action is performed is not critical, as long as the present teachings remain operable. Furthermore, two or more steps or actions may be performed simultaneously.
While the invention has been described with reference to an illustrative embodiment, it will be understood by those skilled in the art that various other changes, omissions and/or additions may be made and substantial equivalents may be substituted for elements thereof without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated any use of the terms first, second, etc. do not denote any order or importance, but rather the terms first, second, etc. are used to distinguish one element from another.
Claims (21)
1. The flexible thermal diode is characterized by comprising a first phase-change composite film and a second phase-change composite film with different thermal conductivity temperature coefficients, wherein the first phase-change composite film and the second phase-change composite film are in thermal contact with each other, the first phase-change composite film and the second phase-change composite film are stable in form and have flexibility before and after phase change, the thermal conductivities of the first phase-change composite film and the second phase-change composite film are in opposite trend along with the change of temperature, and the phase change temperature difference of the first phase-change composite film and the second phase-change composite film is smaller than 10 ℃; the first phase change composite film and the second phase change composite film have opposite surface wettability and incompatible interfaces; the first phase-change composite film is obtained by loading a negative temperature coefficient phase-change material by an aerogel film, and the second phase-change composite film is obtained by loading a positive temperature coefficient phase-change material by an aerogel film.
2. A flexible thermal diode as defined in claim 1, wherein: the thermal rectification ratio of the flexible thermal diode is 1.5-3.0.
3. A flexible thermal diode as defined in claim 1, wherein: the load capacity of the negative temperature coefficient phase change material in the first phase change composite film is 30-98wt%.
4. A flexible thermal diode as defined in claim 1, wherein: the loading amount of the positive temperature coefficient phase change material in the second phase change composite film is 30-98wt%.
5. A flexible thermal diode as defined in claim 1, wherein: the contact angle between the surface of the first phase-change composite film and water is 100-180 degrees.
6. A flexible thermal diode as defined in claim 1, wherein: the contact angle between the surface of the second phase-change composite film and water is 0-80 degrees.
7. A flexible thermal diode as defined in claim 1, wherein: the thickness ratio of the first phase-change composite film to the second phase-change composite film is 1:10-10:1.
8. A flexible thermal diode as defined in claim 1, wherein: the thermal conductivities of the negative temperature coefficient phase change material and the positive temperature coefficient phase change material at the phase change point are in opposite trend along with the temperature change.
9. A flexible thermal diode as defined in claim 1, wherein: the negative temperature coefficient phase change material is selected from any one or more than two of paraffin, hexadecane, octadecane, eicosane and polyethylene.
10. A flexible thermal diode as defined in claim 1, wherein: the positive temperature coefficient phase change material is selected from poly (N-isopropyl acrylamide) aqueous solution and/or vanadium dioxide; wherein the concentration of the poly (N-isopropyl acrylamide) aqueous solution is 10-50 wt%.
11. A flexible thermal diode as defined in claim 1, wherein: the aerogel film is a flexible self-supporting aerogel film.
12. A flexible thermal diode as defined in claim 1, wherein: the tensile strength of the aerogel film is above 1MPa, the porosity is above 60%, and the thermal conductivity is below 0.1W/m ‧ K.
13. A flexible thermal diode as defined in claim 1, wherein: the aerogel film is selected from one or a combination of more than two of Kevlar aerogel film, polyimide aerogel film, cellulose aerogel film and poly-p-phenylene benzobisoxazole aerogel film.
14. A method of manufacturing a flexible thermal diode as claimed in any one of claims 1 to 13, comprising:
respectively loading the negative temperature coefficient phase change material and the positive temperature coefficient phase change material into holes of the aerogel film, so as to respectively prepare a first phase change composite film and a second phase change composite film;
and assembling the first phase-change composite film and the second phase-change composite film to form the flexible thermal diode.
15. The preparation method according to claim 14, characterized by comprising the following steps:
and loading the molten or solution-state negative temperature coefficient phase change material into the aerogel film by utilizing capillary action to prepare the first phase change composite film.
16. The preparation method according to claim 14, characterized by comprising the following steps: and loading the positive temperature coefficient phase change material in a molten state or a solution state into the aerogel film by utilizing capillary action, or compositing the positive temperature coefficient phase change material and the aerogel film by adopting an in-situ growth mode, so as to obtain the second phase change composite film.
17. A method of preparation according to claim 14, characterized by comprising: and attaching the first phase change composite film and the second phase change composite film to form the flexible thermal diode.
18. The preparation method according to claim 14, characterized by comprising the following steps: the first phase change composite film and the second phase change composite film are in thermal contact with each other, and then assembled to form the flexible thermal diode.
19. The method of manufacturing according to claim 14, further comprising: the aerogel film is firstly densified, and the densification method is selected from a hot pressing method and/or a cold pressing method.
20. Use of the flexible thermal diode of any one of claims 1-13 in the field of thermal management.
21. Use according to claim 20, characterized in that: the use is the use of the flexible thermal diode in the thermal management of curved or irregularly shaped surfaces.
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