Layered composite film with vertical and in-plane bidirectional high conductivity and preparation method thereof
The cold casting and gelation process aligns fillers to enhance vertical and in-plane conductivity in composite films, addressing the inefficiencies of existing materials by creating a structured composite with interlayer bridges for improved thermal and electrical performance.
Patent Information
- Application Number
- CN202510606875.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-12
- Publication Date
- 2025-07-15
AI Technical Summary
It is difficult to improve the conductivity efficiency of existing layered composite materials at the same time in both vertical and in-plane, especially the thermal conductivity and electrical conductivity in the vertical direction are low, which affects the heat dissipation and current conductivity efficiency.
The frozen casting-thaw-geling process is adopted, and the filler is arranged in the growth direction of ice crystals, combined with the molding densification process, a three-dimensional conductive framework and interlayer phonon bridge network are constructed to achieve efficient vertical and in-plane conduction.
The vertical and in-plane thermal conductivity and electrical conductivity of the layered composite film is significantly improved, forming a continuous heat and current transmission path, meeting the heat dissipation and circuit requirements of high-power density electronic devices.
Smart Images
Figure CN120310018A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of preparation of layered composites, and particularly relates to a layered composite film with high vertical and in-plane bidirectional conductivity and a preparation method thereof. Background Art
[0002] With the rapid development of miniaturized, integrated, and high-power density electronic devices, higher requirements are put forward for their heat dissipation ability and electrical conductivity. Layered composites can be used to manufacture heat dissipation components of electronic devices to prevent thermal failure of devices caused by local overheating, and play a key role in solving heat dissipation problems. At the same time, in some high-precision electronic circuits, layered composites can be used as conductive circuit or electrode materials, and their good electrical conductivity and designability can meet the complex wiring and high-performance requirements of circuits. In recent years, research on high-performance layered composites has mainly focused on improving in-plane conductivity. In terms of heat conduction, the layered structure helps to form continuous heat conduction paths, enabling heat to be quickly transferred inside the material to achieve efficient heat dissipation. In contrast, the thermal and electrical conductivity perpendicular to the in-plane direction is largely ignored. For vertical heat conduction, it plays a crucial role in absorbing and diffusing heat along the cross-sectional direction, which directly affects the in-plane heat diffusion efficiency. In terms of electrical conductivity, layered composites can provide directional conductive channels, enabling current to quickly conduct in a specific direction and improving the conductivity efficiency. Therefore, to meet the urgent thermal / electrical conductivity requirements in various fields, how to construct effective transmission paths between the layers of layered composites, break through the bottleneck of low vertical conduction, and achieve bidirectional high conduction simultaneously is the primary challenge in the development of layered composites. Summary of the Invention
[0003] In order to solve the current situation that it is difficult to simultaneously improve the vertical and in-plane conduction efficiencies of existing layered composites, the purpose of the present invention is to provide a layered composite film with high vertical and in-plane bidirectional conductivity and a preparation method thereof.
[0004] To achieve the above purpose, the technical solutions adopted by the present invention are as follows: A preparation method of a layered composite film with high vertical and in-plane bidirectional conductivity, the steps are as follows: (1). Select a good solvent according to the polymer matrix, and add the polymer matrix and functional fillers into the good solvent to prepare a uniformly dispersed polymer / filler suspension; (2). Use the freeze-casting process for the polymer / filler suspension prepared in step (1) to prepare a polymer / filler frozen block; (3). Immerse the polymer / filler frozen block prepared in step (2) into a pre-cooled gelation solution for a thawing-gelation process to obtain a polymer / filler gel block; (4) Pressurize and densify the polymer / filler gel block prepared in step (3) perpendicular to the ice crystal growth direction to obtain a polymer / filler wet film. (5) Dry the polymer / filler wet film prepared in step (4) to obtain a laminated composite film with high in-plane and out-of-plane conductivity.
[0005] Preferably, in step (1), the concentration of the polymer matrix in the polymer / filler suspension is 1-10 wt%, and the mass ratio of the polymer matrix to the functional filler is (1-9):(1-9).
[0006] Preferably, in step (1), the polymer matrix is one or more of aramid nanofibers, poly(p-phenylene benzobisoxazole) nanofibers, cellulose nanofibers, and polyvinyl alcohol, and the functional filler is one or more combinations of a thermal conductive filler, an electrically conductive filler, or a filler with both thermal and electrical conductivity. A good solvent refers to a solvent that has good solubility or swelling ability for the polymer. For example, when the polymer is aramid nanofibers, its good solvent is preferably DMSO or a DMSO / H2O mixed solvent, and more preferably a strong base is added to the good solvent. The strong base is KOH or NaOH, and the strong base can provide sufficient OH - ions to weaken the hydrogen bond interaction between molecular chains in aramid nanofibers.
[0007] Further, in step (1), the functional filler is one or more combinations of hexagonal boron nitride, graphene, MXene, carbon nanotubes, SiC, Al2O3, and SiO2.
[0008] Preferably, in step (2), the freeze-casting process is an ice-templated directional freezing method or a refrigerator low-temperature freezing method. The ice-templated directional freezing method means pouring the polymer / filler suspension into a mold with a copper base and performing directional freezing under the low temperature provided by liquid nitrogen or the like. The refrigerator low-temperature freezing method means casting or scraping the polymer / filler suspension on a substrate and then placing it in the freezer layer of a refrigerator for freezing.
[0009] Preferably, in step (3), the pre-cooling temperature is -20 to 0 °C.
[0010] Preferably, in step (3), the gelling solution is a mixed solution prepared by mixing one of methanol, absolute ethanol, concentrated hydrochloric acid, and glacial acetic acid with water, and the volume fraction of methanol, absolute ethanol, concentrated hydrochloric acid, or glacial acetic acid in the gelling solution is 0-70%.
[0011] Preferably, in step (4), the pressure for the press densification is 1-10 MPa, the temperature is 25-80 °C, and the time is 0.5-5 h.
[0012] Preferably, in step (5), the drying temperature is 25~50°C and the time is 12~48 h.
[0013] A layered composite film with vertically and in-plane bidirectional high conductivity prepared by using the said preparation method.
[0014] The preparation principle of the present invention: Through the freeze-casting process, the fillers are arranged along the growth direction of ice crystals (crystals formed by the good solvent), and the polymer matrix will also be affected by the extrusion of ice crystals and act as a "binder" to assist the orientation arrangement of the thermal conductive fillers, constructing a three-dimensional interconnected filler conduction framework inside; through the thawing-gelation process, the frozen block undergoes in-situ gelation during the thawing process in the pre-cooled gelation solution, maintaining the original three-dimensional conduction framework structure inside and obtaining a gel block; subsequently, it is subjected to molding densification perpendicular to the ice crystal growth direction to extrude the excess solvent inside, constructing a unique structure with in-plane layered stacking and phonon bridging between layers, and simultaneously achieving a significant improvement in the vertical and in-plane bidirectional conduction performance.
[0015] Beneficial effects: (1) The present invention adopts the freeze-casting - thawing - gelation process. On the one hand, by using the repulsive force during the ice crystal growth process, the fillers are oriented along the growth direction to obtain a three-dimensional conduction framework formed by the mutual overlap of fillers; on the other hand, the obtained frozen block is immersed in the pre-cooled gelation solution, and by utilizing the gel transformation ability of the polymer, the frozen block undergoes in-situ gelation during the thawing process to obtain a gel block and maintain the original constructed three-dimensional conduction framework; subsequently, it is subjected to molding densification perpendicular to the ice crystal growth direction to construct phonon bridges connecting layers in the in-plane stacked layered network, obtaining a layered composite film with vertically and in-plane bidirectional high conductivity, solving the problems existing in the current layered composite film such as difficult construction of interlayer conduction paths, large interfacial thermal / electrical resistance, and low thermal / electrical conductivity in the vertical direction. (2) Through the molding densification process of the present invention, the three-dimensional conduction framework structure inside the gel block is gradually compressed, which is beneficial to the formation of a dense in-plane layered stacking structure with a phonon bridging network between layers, and simultaneously constructs effective transmission paths in the vertical and in-plane directions. (3) The layered composite film obtained by the present invention simultaneously realizes a significant improvement in the vertical and in-plane bidirectional conduction coefficients, showing great application prospects in the field of heat dissipation management. Description of the Drawings
[0016] Figure 1 : Cross-sectional SEM image of the aramid nanofiber / hBN layered composite film prepared in Example 1 of the present invention.
[0017] Figure 2 : Cross-sectional SEM image of the aramid nanofiber / hBN layered composite film prepared in Comparative Example 1 of the present invention.
[0018] Figure 3 : Thermal conductivity diagram of the aramid nanofiber / hBN layered composite film prepared in Example 1 of the present invention.
[0019] Figure 4 : Thermal conductivity diagram of the aramid nanofiber / hBN layered composite film prepared in Comparative Example 1 of the present invention. Detailed implementation manners
[0020] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all embodiments. Based on the described embodiments, all other embodiments obtained by those skilled in the art without creative efforts fall within the protection scope of the present invention.
[0021] Example 1 A preparation method of an aramid nanofiber / hBN layered composite film, comprising the following steps: (1), Para-aramid nanofibers, hBN nanosheets (density 2.27 g / cm 3 ), and KOH are added to a mixed solvent composed of DMSO and H2O, and a uniformly dispersed aramid nanofiber / hBN suspension is obtained through a wet ball milling process, wherein the concentration of aramid nanofibers is 1 wt%, and the mass ratio of aramid nanofibers∶hBN nanosheets∶KOH is 1∶4∶1.5, and the mass ratio of DMSO and H2O is 5∶0.2; (2), The aramid nanofiber / hBN suspension prepared in step (1) is subjected to a freeze-casting process, that is, an ice template directional freezing method (pour liquid nitrogen into a square plastic mold with a copper base, the liquid nitrogen does not cover the top of the copper base, pre-cool the copper base, and after the pre-cooling is completed, place the container containing the aramid nanofiber / hBN suspension on the copper base to promote the vertical growth of ice crystals from bottom to top in the suspension), to obtain an aramid nanofiber / hBN frozen block; (3), The aramid nanofiber / hBN frozen block prepared in step (2) is immersed in a gelation solution pre-cooled to -15 °C for a thawing-gelation process. After gelation, KOH remains in the gelated solution. Just fish out the formed gel block from the gelated solution to obtain an aramid nanofiber / hBN gel block; the gelation solution is a solution prepared by mixing absolute ethanol and deionized water in a volume ratio of 3∶7; (4) Vertically press and densify the aramid nanofiber / h-BN gel block prepared in step (3) perpendicular to the ice crystal growth direction to obtain an aramid nanofiber / h-BN wet film while extruding the internal solvent; the pressing pressure is 5 MPa, the temperature is 60 °C, and the time is 0.5 h; (5) Dry the aramid nanofiber / h-BN wet film prepared in step (4) at 40 °C for 24 h to obtain an aramid nanofiber / h-BN layered composite film.
[0022] Comparative Example 1 The difference from Example 1 is that the freeze-casting process of step (2) is not used. The specific steps are as follows: (1) Add para-aramid nanofibers, h-BN nanosheets (density 2.27 g / cm 3 ), and KOH to a mixed solvent composed of DMSO and H2O, and obtain a uniformly dispersed aramid nanofiber / h-BN suspension through a wet ball-milling process. The concentration of aramid nanofibers is 1 wt%, and the mass ratio of aramid nanofibers:h-BN nanosheets:KOH is 1:4:1.5, and the mass ratio of DMSO and H2O is 5:0.2; (2) Pour the aramid nanofiber / h-BN suspension prepared in step (1) into a container such as a square plastic box, and then immerse the container such as the square plastic box into the gelling solution. After gelling, KOH remains in the gelling solution. Just fish out the formed gel block from the gelling solution to obtain an aramid nanofiber / h-BN gel block; the gelling solution is a solution prepared by mixing anhydrous ethanol and deionized water at a volume ratio of 3:7; (3) Press and densify the aramid nanofiber / h-BN gel block prepared in step (2) along the thickness direction of the gel block to obtain an aramid nanofiber / h-BN wet film while extruding the internal solvent; the pressing pressure is 5 MPa, the temperature is 60 °C, and the time is 0.5 h; (4) Dry the aramid nanofiber / h-BN wet film prepared in step (3) at 40 °C for 24 h to obtain an aramid nanofiber / h-BN layered composite film.
[0023] Structural Characterization Figure 1 This is the cross-sectional SEM image of the aramid nanofiber / h-BN layered composite film prepared in Example 1 of the present invention. The SEM image shows that the aramid nanofiber / h-BN layered composite film prepared in Example 1 has a highly oriented layered dense stacking structure in the horizontal direction, and a phonon / electron bridging network structure in which each layer is interconnected in the vertical direction, providing effective conduction paths in both the vertical and in-plane directions.
[0024] Figure 2 Cross-sectional SEM image of the aramid nanofiber / hBN layered composite film prepared in Comparative Example 1 of the present invention. The SEM image shows that the aramid nanofiber / hBN suspension prepared in Comparative Example 1 was not subjected to the freeze-casting step, and the hBN nanosheets were randomly wrapped in the aramid nanofiber gel network. Compression resulted in a relatively poor filler stacking structure in the composite film, with no directionality in the vertical direction and no interlayer bridging effect.
[0025] Performance characterization Figure 3 Thermal conductivity diagram of the aramid nanofiber / hBN layered composite film prepared in Example 1 of the present invention. Figure 4 Thermal conductivity diagram of the aramid nanofiber / hBN layered composite film prepared in Comparative Example 1 of the present invention. It can be seen from Figure 3 that: the in-plane thermal conductivity of the aramid nanofiber / hBN layered composite film prepared in Example 1 is 26.2 W / mK, and the through-plane thermal conductivity is 5.4 W / mK. This is because the dense layered stacking structure and the interlayer phonon / electron bridging network have established an efficient heat flow transmission channel, achieving a significant increase in the bi-directional thermal conductivity. It can be seen from Figure 4 that: even though the same filler content was used in Comparative Example 1 and Example 1, its in-plane thermal conductivity is 17.6 W / mK, and the through-plane thermal conductivity is only 0.9 W / mK. This is because the aramid nanofiber / hBN layered composite film prepared in Comparative Example 1 has a relatively poor filler stacking structure and no interlayer bridging network in the vertical direction.
Claims
1. A preparation method of a layered composite film with vertical and in-plane bidirectional high conductivity, characterized in that The steps are as follows: (1) Select a good solvent according to the polymer matrix, add the polymer matrix and functional fillers into the good solvent, and prepare a uniformly dispersed polymer / filler suspension; (2) Use the freeze-casting process on the polymer / filler suspension prepared in step (1) to obtain a polymer / filler frozen block; (3) Immerse the polymer / filler frozen block prepared in step (2) in a pre-cooled gelation solution to carry out a thawing-gelation process to obtain a polymer / filler gel block; (4) Perform molding densification on the polymer / filler gel block prepared in step (3) along the direction perpendicular to the ice crystal growth direction to obtain a polymer / filler wet film; (5) Dry the polymer / filler wet film prepared in step (4) to obtain a layered composite film with high vertical and in-plane bidirectional conductivity.
2. The preparation method of the layered composite film with vertical and in-plane bi-directional high conductivity according to claim 1, characterized in that: In step (1), the concentration of the polymer matrix in the polymer / filler suspension is 1-10 wt%, and the mass ratio of the polymer matrix to the functional fillers is (1-9):(1-9).
3. The preparation method of the layered composite film with vertical and in-plane bi-directional high conductivity as described in claim 1, characterized in that: In step (1), the polymer matrix is one or more of aramid nanofibers, poly(p-phenylene benzobisoxazole) nanofibers, cellulose nanofibers, and polyvinyl alcohol, and the functional fillers are one or more combinations of thermal conductive fillers, conductive fillers, or fillers with both thermal conductivity and conductivity.
4. The preparation method of the laminated composite film with vertical and in-plane bi-directional high conductivity according to claim 3, characterized in that: In step (1), the functional fillers are one or more combinations of hexagonal boron nitride, graphene, MXene, carbon nanotubes, SiC, Al2O3, and SiO2.
5. The preparation method of the laminated composite film with vertical and in-plane bi-directional high conductivity according to claim 1, characterized in that: In step (2), the freeze-casting process is the ice template directional freezing method or the refrigerator low-temperature freezing method.
6. The preparation method of the layered composite film with vertical and in-plane bidirectional high conductivity according to claim 1, characterized in that: In step (3), the pre-cooling temperature is -20 to 0 °C.
7. The preparation method of the layered composite film with vertical and in-plane bi-directional high conductivity according to claim 1, characterized in that: In step (3), the gelation solution is a mixed solution prepared by mixing one of methanol, absolute ethanol, concentrated hydrochloric acid, and glacial acetic acid with water, and the volume fraction of methanol, absolute ethanol, concentrated hydrochloric acid, or glacial acetic acid in the gelation solution is 0-70%.
8. The preparation method of the layered composite film with vertical and in-plane bi-directional high conductivity as described in claim 1, characterized in that: In step (4), the pressure of the molding densification is 1-10 MPa, the temperature is 25-80 °C, and the time is 0.5-5 h.
9. The preparation method of the layered composite film with vertical and in-plane bi-directional high conductivity as described in claim 1, characterized in that: In step (5), the drying temperature is 25-50 °C and the time is 12-48 h.
10. A layered composite film with high vertical and in-plane bidirectional conductivity prepared by the preparation method according to any one of claims 1-9.