A high-strength and high-thermal-conductivity composite phase-change fiber, preparation method and application

Abstract

The present invention relates to the technical field of phase change composite materials, and specifically to a high-strength and high-thermal-conductivity composite phase change fiber, a preparation method, and an application thereof. Using carbon nanotube fibers as a substrate, hydrothermal method and freeze casting technology are adopted to rapidly solidify water molecules distributed in the pores of the carbon nanotube fibers or between the carbon nanotubes to form an ordered ice crystal structure, thereby forming a multi-layer ordered pore structure in the carbon nanotube fibers. The carbon nanotube fibers with a porous ordered structure are then immersed in a phase change material solution. Under evaporation concentration and capillary action, the phase change material fully penetrates into the multi-layer ordered pore structure of the carbon nanotube fibers, and is washed in a hot water bath to obtain a composite phase change fiber having high tensile strength, high thermal conductivity, low density, a wide adjustable range of phase change temperature, and high phase change enthalpy or latent heat. It has very broad application prospects in the fields of thermal interface materials, energy storage materials, and high-temperature protective materials.

Description

Technical Field

[0001] The present invention relates to the technical field of phase change composite materials, and in particular to a high-strength and high-thermal-conductivity composite phase change fiber, a preparation method and applications thereof. Background Art

[0002] With the rapid development of carbon nanotube fibers, multifunctional carbon nanotube composite fibers have also developed. When carbon nanotube fibers are combined with different functional materials, the composite fibers have specific functionalities and can be applied in many fields such as artificial muscles, electronic devices, smart wearables, and composite materials.

[0003] Phase change materials (PCMs) can undergo a phase transition at a specific temperature, storing energy lost to the external environment as latent heat, releasing it autonomously on demand while maintaining a near-constant temperature. Polyethylene glycol (PEG) is a commonly used PCM due to its high phase change enthalpy, stable performance, chemical stability, and biocompatibility, offering significant advantages in numerous applications. It is worth noting that CNT fibers are one-dimensional continuous fibers composed of oriented carbon nanotubes. The strong sp2 bonds between adjacent carbon atoms within the CNTs give CNT fibers excellent mechanical strength, high electrical conductivity, and high thermal conductivity. Furthermore, the abundant surface area of ​​CNTs provides a rich interface within the CNT composite fiber material. Therefore, using CNT fibers as the primary material and loading them with PCMs can significantly enhance the mechanical strength and thermal conductivity of the fibers during the phase change process.

[0004] In summary, the existing technologies mainly have the following disadvantages: 1) It is difficult to maintain the morphological structure during the phase change process when polyethylene glycol is used as the phase change material; 2) At present, the assembly with polyethylene glycol adsorbed as the phase change material is difficult to weave; 3) The thermal conductivity of the assembly with polyethylene glycol adsorbed as the phase change material is relatively low; 4) The mechanical properties of the assembly with polyethylene glycol adsorbed as the phase change material are relatively low. Summary of the Invention

[0005] In response to the defects of phase change composite materials in the existing technology, such as low thermal conductivity, poor heat storage capacity, difficulty in maintaining morphological structure and poor mechanical properties during the phase change process, the present invention provides a high-strength and high-thermal conductivity composite phase change fiber, preparation method and application. By uniformly distributing the phase change material in the pores of carbon nanotube fibers or in the gaps between carbon nanotubes, the composite phase change fiber has excellent electrical conductivity, thermal properties and mechanical properties while maintaining excellent shape stability under high load, thereby overcoming the shortcomings of the existing technology.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] In one aspect, the present invention provides a method for preparing a high-strength and high-thermal-conductivity composite phase change fiber, comprising the following steps:

[0008] S1. The carbon nanotube fibers are impregnated with a porogen and heated to allow the porogen to penetrate into the pores of the carbon nanotube fibers and / or the gaps between the tubes;

[0009] S2. The mixture of S1 is solidified and cured, so that the pore-forming agent infiltrated into the pores of the carbon nanotube fibers and / or the gaps between the tubes is rapidly solidified to form a crystalline structure;

[0010] S3 removes the crystal structure in the carbon nanotube fiber pores and / or inter-tube gaps in S2 to form a carbon nanotube fiber having an interlayer multi-level pore structure;

[0011] S4. The carbon nanotube fibers obtained in S3 are immersed in a phase change material solution and heated to allow the phase change material to penetrate into the multi-level pore structure between the carbon nanotube fibers to obtain a crude composite phase change fiber;

[0012] S5. The crude composite phase change fiber is washed with a solvent and dried to obtain a composite phase change fiber.

[0013] In some specific embodiments, carbon nanotube fibers are used as a substrate, and a hydrothermal method is first used to quickly intercalate water molecules into the gaps between carbon nanotubes; then the carbon nanotube fiber solution is frozen, so that the water molecules distributed in the pores of the carbon nanotube fibers or between the carbon nanotubes quickly solidify to form an ordered ice crystal structure, thereby forming a multi-layer ordered pore structure in the carbon nanotube fibers.

[0014] In some specific embodiments, carbon nanotube fibers with a porous ordered structure are immersed in a phase change material solution. Under evaporation concentration and capillary action, the phase change material is fully penetrated into the multi-layer ordered pore structure of the carbon nanotube fibers. The fibers are washed in a hot water bath to obtain high-strength and high-thermal-conductivity carbon nanotube composite phase change fibers.

[0015] Furthermore, the pore-forming agent is selected from one or more of water, ethanol, methanol and acetone; or the pore-forming agent is selected from one of water, ethanol, methanol and acetone; preferably, the pore-forming agent is selected from water.

[0016] It should be noted that when the pore-forming agent changes from a liquid state to a solidified state, its volume increases, so that an ordered crystal structure is formed in the gaps between the carbon nanotubes.

[0017] Furthermore, in S2, the solidification treatment is a combination of one or more of aging treatment, freezing treatment, and solubilization treatment; or the solidification treatment is one of aging treatment, freezing treatment, and solubilization treatment; preferably, the solidification treatment is freezing treatment.

[0018] Furthermore, in S3, the removal of the crystal structure in S2 adopts a combination of one or more of supercritical drying, freeze drying, vacuum drying, spray drying, microwave drying and infrared drying; or the removal of the crystal structure in S2 adopts one of supercritical drying, freeze drying, vacuum drying, spray drying, microwave drying and infrared drying; preferably, the removal of the crystal structure in S2 adopts vacuum drying.

[0019] It should be noted that the crystal structure in the pores of the carbon nanotube fibers and / or in the gaps between the tubes is removed by sublimation, directly changing from liquid to gas, which can greatly preserve the integrity of the porous structure on the carbon nanotube fibers.

[0020] Furthermore, the phase change material solution includes the following components in parts by mass: 5-50 parts of phase change material and 50-95 parts of solvent; the phase change material is selected from one or a combination of two or more of polyethylene glycol, paraffin, n-hexane, n-octadecane, n-decanoic acid, lauric acid, myristic acid, stearic acid, neopentyl glycol, and pentaerythritol; and the solvent is selected from one or a combination of two or more of water, ethanol, ethylene glycol, isopropyl alcohol, ether, and acetone.

[0021] Furthermore, the phase change material solution includes the following components in parts by mass: 10-40 parts of phase change material, 60-90 parts of solvent; or 10-30 parts of phase change material, 70-90 parts of solvent.

[0022] Furthermore, the phase change material is selected from one of polyethylene glycol, paraffin, n-hexane, n-octadecane, n-decanoic acid, lauric acid, myristic acid, stearic acid, neopentyl glycol, and pentaerythritol; preferably, the phase change material is selected from polyethylene glycol; the solvent is selected from one of water, ethanol, ethylene glycol, isopropanol, ether, and acetone; preferably, the solvent is selected from ethanol.

[0023] Furthermore, in said S5, the process conditions of solvent washing are: immersing the composite phase change fiber in the solvent, and the washing time is 5 to 60 seconds.

[0024] In a second aspect, the present invention provides a high-strength and high-thermal-conductivity composite phase-change fiber, comprising carbon nanotube fibers and a phase-change material, wherein the phase-change material is uniformly distributed in the pores of the carbon nanotube fibers or in the gaps between the tubes, and the amount of the phase-change material is 15-35% by weight of the composite material, and the thermal conductivity of the composite material is 100-300 m -1 K -1 , tensile strength ≥500MPa, phase change temperature is 50-65℃, and phase change latent heat ≥20J / g.

[0025] In a third aspect, the present invention provides an application of a high-strength and high-thermal-conductivity composite phase change fiber in thermal interface materials, energy storage materials, and high-temperature protective materials.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The preparation process of the present invention is simple. It adopts hydrothermal method and freeze casting technology, and utilizes ice crystal pore formation to prepare carbon nanotube-phase change material composite phase change fiber with good uniformity. It can still maintain solid form during the phase change process. Through impregnation evaporation concentration and capillary action, the phase change material is well bound in the multi-level pore structure between carbon nanotube layers, effectively preventing the penetration of the phase change material caused by the phase change process;

[0028] (2) The composite phase change fiber prepared by the present invention is soluble in organic solvents, has high tensile strength, high thermal conductivity, low density, a wide adjustable range of phase change temperature, and high phase change enthalpy or latent heat; it has very broad application prospects in the fields of thermal interface materials, energy storage materials, and high-temperature protective materials;

[0029] (3) The present invention solves the bottleneck problem that the assembly using polyethylene glycol as the phase change material cannot achieve both shape stability and high mechanical properties and thermal conductivity, and does not involve toxic and dangerous substances and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the preparation process principle of the present invention;

[0031] Figure 2 This is a morphological representation of a carbon nanotube fiber with an interlayer multi-level pore structure according to an embodiment of the present invention;

[0032] Figure 3 This is a morphological representation of a carbon nanotube composite phase change fiber with an interlayer multi-level pore structure according to an embodiment of the present invention;

[0033] Figure 4 is a stress-strain curve diagram of the carbon nanotube composite phase change fiber of the present invention;

[0034] Figure 5 is a DSC curve diagram of the carbon nanotube composite phase change fiber of the present invention;

[0035] Figure 6 This is a comparison chart of the thermal conductivity of the carbon nanotube composite phase change fiber of the present invention. DETAILED DESCRIPTION

[0036] In order to make those skilled in the art better understand the technical scheme of the present invention, the present invention is described in detail below in conjunction with specific embodiments. The experimental methods for which specific conditions are not specified in the following examples are usually based on conventional conditions or the conditions recommended by the manufacturer. The test materials used in the following examples, unless otherwise specified, are purchased from conventional biochemical reagent stores. Unless otherwise specified, percentages and parts are calculated by weight. Unless otherwise defined, all professional and scientific terms used in the text have the same meaning as those familiar to those skilled in the art. In addition, any method and material similar to or equivalent to the described content can be applied to the present invention. The preferred implementation methods and materials described in the text are only for demonstration purposes.

[0037] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0038] Based on the present invention, the CNT / PEG composite phase change fiber is prepared based on the excellent mechanical and thermal conductivity properties and stable one-dimensional structure of carbon nanotube (CNT) fibers. During the phase change process, it can not only maintain a solid structure, but also polyethylene glycol (PEG) is well bound in the multi-level pore structure between the carbon nanotube layers, effectively preventing the leakage of PEG during the phase change process, and changing the solid-liquid phase transition of the traditional polyethylene glycol phase change process. That is, the CNT / PEG composite phase change fiber can still maintain a solid form even in a molten state, and the carbon nanotube skeleton with high thermal conductivity improves the thermal conductivity of the phase change material.

[0039] According to the present invention, the phase change material is evenly distributed in the pores of the carbon nanotube fibers or in the gaps between the tubes. The amount of the phase change material is 15-35% of the weight of the composite material. The thermal conductivity of the composite material is 100-300 Wm -1 K -1 , tensile strength ≥500MPa, phase change temperature is 50-65℃, and phase change latent heat ≥20J / g.

[0040] Based on the present invention, high-strength and high-thermal-conductivity composite phase-change fibers are prepared by the following steps: impregnating carbon nanotube fibers in a pore-forming agent, heating, and allowing the pore-forming agent to penetrate into the pores of the carbon nanotube fibers and / or the gaps between the tubes; subjecting the mixture prepared in S1 to a solidification treatment, so that the pore-forming agent that has penetrated into the pores of the carbon nanotube fibers and / or the gaps between the tubes is rapidly solidified to form a crystal structure; removing the crystal structure in the pores of the carbon nanotube fibers and / or the gaps between the tubes to form carbon nanotube fibers with an interlayer multilevel pore structure; immersing the obtained carbon nanotube fibers with an interlayer multilevel pore structure in a phase change material solution, heating, and allowing the phase change material to penetrate into the interlayer multilevel pore structure of the carbon nanotube fibers to obtain a crude composite phase-change fiber; and washing and drying the crude composite phase-change fiber with a solvent to obtain the obtained fiber.

[0041] Based on the present invention, the carbon nanotube fibers include carbon nanotube fibers wet-spun by a protonic acid system and / or directly spun by floating catalysis. In specific experiments, reasonable selection can be made according to the situation, and will not be described in detail here.

[0042] In some preferred embodiments, the carbon nanotube fibers have a diameter of 10 to 25 μm, a tensile strength of 1 to 2 GPa, a tensile modulus of 50 to 120 GPa, and a thermal conductivity of 330 to 340 Wm -1 K -1 .

[0043] Based on the present invention, the impregnation process can be carried out under normal pressure or vacuum conditions.

[0044] Based on the present invention, the pore-forming agent is selected from one or more of water, ethanol, methanol and acetone; when the pore-forming agent changes from a liquid state to a solidified state, its volume will increase, so that an ordered crystal structure is formed in the gaps between the carbon nanotubes. In specific experiments, a reasonable selection can be made according to the situation, and will not be repeated here.

[0045] In some preferred embodiments, the pore former is selected from water.

[0046] Based on the present invention, the solidification treatment is a combination of one or more of aging treatment, freezing treatment, and sol treatment; the solidification treatment causes the phase change material uniformly distributed in the pores of the carbon nanotube fibers or in the gaps between the tubes to undergo a phase change, from liquid to solid, to form an ordered crystal structure. In specific experiments, reasonable selection can be made according to the circumstances, and will not be repeated here.

[0047] In some preferred embodiments, the solidification process is a freezing process.

[0048] Based on the present invention, a combination of one or more of supercritical drying, freeze drying, vacuum drying, spray drying, microwave drying and infrared drying is used to remove the crystal structure in the gaps between carbon nanotubes; the crystal structure in the pores of the carbon nanotube fibers and / or in the gaps between tubes is removed by sublimation, directly changing from liquid to gas, which can greatly preserve the integrity of the porous structure on the carbon nanotube fibers. In specific experiments, reasonable selection can be made according to the situation, and will not be repeated here.

[0049] In some preferred embodiments, the removal of the crystal structure in the gaps between the carbon nanotubes is performed by vacuum drying.

[0050] According to the present invention, the phase change material solution includes the following components by weight: 5-50 parts of phase change material, 50-95 parts of solvent;

[0051] According to the present invention, the phase change material solution includes the following components by weight: 10-40 parts of phase change material, 60-90 parts of solvent;

[0052] In some preferred embodiments, the phase change material solution includes the following components in parts by weight: 10-30 parts of phase change material and 70-90 parts of solvent.

[0053] Based on the present invention, the phase change material is selected from one or a combination of two or more of polyethylene glycol, paraffin, n-hexane, n-octadecane, n-decanoic acid, lauric acid, myristic acid, stearic acid, neopentyl glycol, and pentaerythritol; in specific experiments, a reasonable selection can be made according to the situation, and will not be repeated here.

[0054] In some preferred embodiments, the phase change material is selected from polyethylene glycol; based on the present invention, the polyethylene glycol is selected from one of PEG3000, PEG600, PEG1000, PEG6000 or other PEG types.

[0055] Based on the present invention, the solvent is selected from one or a combination of two or more of water, ethanol, ethylene glycol, isopropyl alcohol, ether, and acetone; in specific experiments, a reasonable selection can be made according to the situation, and will not be repeated here.

[0056] In some preferred embodiments, the solvent is selected from ethanol.

[0057] According to the present invention, the process conditions for solvent washing are: immersing the composite phase change fiber in the solvent, and the washing time is 5 to 60 seconds.

[0058] The technical solution of the present invention is further described in detail below in conjunction with several preferred embodiments and the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0059] Example 1

[0060] 1) Prepare carbon nanotube fibers by wet spinning.

[0061] 2) Phase change material solution: Prepare a 10 wt% polyethylene glycol solution by measuring 30 ml of ethanol in a 50 ml beaker, accurately weighing 3 g of polyethylene glycol, and stirring in a warm water bath until uniform.

[0062] 3) The carbon nanotube fibers were placed in a 200ml beaker containing 100ml of deionized water and kept constant at 90°C in a water bath for 1 hour. The sample solution was then freeze-cast. The ice crystal structure made the carbon nanotube fibers porous, resulting in carbon nanotube fibers (CNTF@V) with an interlayer multi-level pore structure.

[0063] 4) The pure carbon nanotube fiber is immersed in a polyethylene glycol solution with a concentration of 10 wt %, and at 80°C and normal pressure, the polyethylene glycol therein is evaporated and concentrated, and the capillary action causes the phase change material to penetrate into the interlayer multilevel pore structure of the carbon nanotube fiber, thereby preparing an unwashed carbon nanotube-PEG composite phase change fiber.

[0064] 5) Immersing the unwashed carbon nanotube-PEG composite phase change fiber in an ethanol bath for 5 to 60 seconds and drying it to obtain a high-strength and high-thermal-conductivity carbon nanotube composite phase change fiber (CNTF@V-PEG).

[0065] The SEM image of the carbon nanotube fiber (CNTF@V) of this example ( Figure 2 ).like Figure 2 As shown, it shows that using carbon nanotube fiber (CNTF) as a substrate, the hydrothermal method is used to promote the rapid intercalation of water molecules into the gaps between carbon nanotubes; the carbon nanotube fiber solution is freeze-casted to quickly solidify between the tubes to form an ordered ice crystal structure, and the multi-layer ordered pore structure of the carbon nanotube fiber is formed.

[0066] The performance of the carbon nanotube composite phase change fiber (CNTF@V-PEG) of this embodiment is characterized, as shown in the stress-strain curve ( Figure 4 )、DSC curve diagram( Figure 5 ) and thermal conductivity diagram ( Figure 6), the results showed that the tensile strength of the high-strength and high-thermal-conductivity carbon nanotube composite phase change fiber was 1.06 GPa, and the thermal conductivity of the fiber was 281.21 Wm -1 K -1 , the latent heat of phase change can reach 24.64J / g.

[0067] Example 2

[0068] 1) Prepare carbon nanotube fibers by wet spinning.

[0069] 2) Phase change material solution: Prepare a 20 wt% polyethylene glycol solution by measuring 30 ml of ethanol in a 50 ml beaker, accurately weighing 6 g of polyethylene glycol, and stirring in a warm water bath until uniform.

[0070] 3) The carbon nanotube fibers were placed in a 200ml beaker containing 100ml of deionized water and kept constant at 90°C in a water bath for 1 hour. The sample solution was then freeze-cast. The ice crystal structure made the carbon nanotube fibers porous, resulting in carbon nanotube fibers (CNTF@V) with an interlayer multi-level pore structure.

[0071] 4) The pure carbon nanotube fiber is immersed in a polyethylene glycol solution with a concentration of 20 wt%, and at 80°C and normal pressure, the polyethylene glycol therein is evaporated and concentrated, and the capillary action causes the phase change material to penetrate into the interlayer multi-level pore structure of the carbon nanotube fiber, thereby preparing an unwashed carbon nanotube-PEG composite phase change fiber.

[0072] 5) Immersing the unwashed carbon nanotube-PEG composite phase change fiber in an ethanol bath for 5 to 60 seconds and drying it to obtain a high-strength and high-thermal-conductivity carbon nanotube composite phase change fiber (CNTF@V-PEG).

[0073] The performance of the carbon nanotube composite phase change fiber (CNTF@V-PEG) of this embodiment is characterized, as shown in the stress-strain curve ( Figure 4 )、DSC curve diagram( Figure 5 ) and thermal conductivity diagram ( Figure 6 ), the results show that the tensile strength of the high-strength and high-thermal-conductivity carbon nanotube composite phase change fiber is 0.84GPa, and the thermal conductivity of the fiber is 250.80Wm -1 K -1 , the latent heat of phase change can reach 39.65 J g -1 .

[0074] Example 3

[0075] 1) Prepare carbon nanotube fibers by wet spinning.

[0076] 2) Phase change material solution: Prepare a 30 wt% polyethylene glycol solution by measuring 30 ml of ethanol in a 50 ml beaker, accurately weighing 9 g of polyethylene glycol, and stirring in a warm water bath until uniform.

[0077] 3) The carbon nanotube fibers were placed in a 200ml beaker containing 100ml of deionized water and kept constant at 90°C in a water bath for 1 hour. The sample solution was then freeze-cast. The ice crystal structure made the carbon nanotube fibers porous, resulting in carbon nanotube fibers (CNTF@V) with an interlayer multi-level pore structure.

[0078] 4) The pure carbon nanotube fiber is immersed in a polyethylene glycol solution with a concentration of 30 wt %, and at 80°C and normal pressure, the polyethylene glycol therein is evaporated and concentrated, and the capillary action causes the phase change material to penetrate into the interlayer multi-level pore structure of the carbon nanotube fiber, thereby preparing an unwashed carbon nanotube-PEG composite phase change fiber.

[0079] 5) Immersing the unwashed carbon nanotube-PEG composite phase change fiber in an ethanol bath for 5 to 60 seconds and drying it to obtain a high-strength and high-thermal-conductivity carbon nanotube composite phase change fiber (CNTF@V-PEG).

[0080] The SEM image of the composite phase change fiber (CNTF@V-PEG) of this example ( Figure 3 ).like Figure 3 As shown, it is shown that the phase change material fully penetrates into the multi-layer ordered pore structure of the carbon nanotube fiber under evaporation concentration and capillary action.

[0081] The performance of the carbon nanotube composite phase change fiber (CNTF@V-PEG) of this embodiment is characterized, as shown in the stress-strain curve ( Figure 4 )、DSC curve diagram( Figure 5 ) and thermal conductivity diagram ( Figure 6 ), the results show that the tensile strength of the high-strength and high-thermal-conductivity carbon nanotube composite phase change fiber is 0.72GPa, and the thermal conductivity of the fiber is 122Wm -1 K -1 , the latent heat of phase change can reach 60J g -1 .

[0082] Example 4

[0083] 1) Prepare carbon nanotube fibers by wet spinning.

[0084] 2) Phase change material solution: Prepare a 30 wt% lauric acid solution by measuring 30 ml of ethanol in a 50 ml beaker, accurately weighing 9 g of lauric acid, and stirring in a warm water bath until uniform.

[0085] 3) The carbon nanotube fibers were placed in a 200ml beaker containing 100ml of deionized water and kept constant at 90°C in a water bath for 1 hour. The sample solution was then freeze-cast. The ice crystal structure made the carbon nanotube fibers porous, resulting in carbon nanotube fibers (CNTF@V) with an interlayer multi-level pore structure.

[0086] 4) The pure carbon nanotube fiber is immersed in a 30wt% lauric acid solution at 80°C and atmospheric pressure, so that the lauric acid therein evaporates and concentrates, and the capillary action causes the phase change material to penetrate into the interlayer multi-level pore structure of the carbon nanotube fiber, thereby preparing an unwashed carbon nanotube-lauric acid composite phase change fiber.

[0087] 5) Immersing the unwashed carbon nanotube-lauric acid composite phase change fiber in an ethanol bath for 5 to 60 seconds and drying it to obtain a high-strength and high-thermal-conductivity carbon nanotube composite phase change fiber (CNTF@V-lauric acid).

[0088] The performance of the carbon nanotube composite phase change fiber (CNTF@V-lauric acid) of this embodiment is characterized, as shown in the stress-strain curve ( Figure 4 )、DSC curve diagram( Figure 5 ) and thermal conductivity diagram ( Figure 6 ), the results show that the tensile strength of the high-strength and high-thermal-conductivity carbon nanotube composite phase change fiber is 0.59GPa, and the thermal conductivity of the fiber is 151.21Wm -1 K -1 , the latent heat of phase change can reach 57.53 J g -1 .

[0089] Example 5

[0090] 1) Prepare carbon nanotube fibers by wet spinning.

[0091] 2) Phase change material solution: Prepare a 30 wt% n-hexane solution by measuring 30 ml of ethanol in a 50 ml beaker, accurately weighing 9 g of n-hexane, and stirring in a warm water bath until uniform.

[0092] 3) The carbon nanotube fibers were placed in a 200ml beaker containing 100ml of deionized water and kept constant at 90°C in a water bath for 1 hour. The sample solution was then freeze-cast. The ice crystal structure made the carbon nanotube fibers porous, resulting in carbon nanotube fibers (CNTF@V) with an interlayer multi-level pore structure.

[0093] 4) The pure carbon nanotube fiber is immersed in a 30wt% n-hexane solution at 80°C and normal pressure, so that the n-hexane therein evaporates and concentrates, and the capillary action causes the phase change material to penetrate into the interlayer multi-level pore structure of the carbon nanotube fiber, thereby preparing an unwashed carbon nanotube-n-hexane composite phase change fiber.

[0094] 5) Immersing the unwashed carbon nanotube-n-hexane composite phase change fiber in an ethanol bath for 5 to 60 seconds and drying the resulting carbon nanotube composite phase change fiber (CNTF@V-n-hexane) with high strength and high thermal conductivity.

[0095] The performance of the carbon nanotube composite phase change fiber (CNTF@V-n-hexane) of this embodiment is characterized, as shown in the stress-strain curve ( Figure 4 )、DSC curve diagram( Figure 5 ) and thermal conductivity diagram ( Figure 6 ), the results showed that the tensile strength of the high-strength and high-thermal-conductivity carbon nanotube composite phase change fiber was 0.69GPa, and the thermal conductivity of the fiber was 131.13Wm -1 K -1 , the latent heat of phase change can reach 45.51 J g -1 .

[0096] Example 6

[0097] The preparation method is the same as that of Example 1, except that the phase change material solution is prepared as follows: prepare a 10 wt% polyethylene glycol mixed solution, measure 30 ml of water in a 50 ml beaker, accurately weigh 3 g of polyethylene glycol, and stir in a warm water bath until uniform.

[0098] Performance characterization: The tensile strength of the high thermal conductivity carbon nanotube composite phase change fiber is 1.21GPa, and the thermal conductivity of the fiber is 151.1Wm measured by the electric heating steady-state method. -1 K -1 , the latent heat of phase change can reach 4.11 J g -1 .

[0099] Example 7

[0100] The preparation method is the same as that of Example 1, except that the phase change material solution is prepared as follows: prepare a 10 wt% octadecane solution, measure 30 ml of ethanol in a 50 ml beaker, accurately weigh 3 g of octadecane, and stir in a warm water bath until uniform.

[0101] Performance characterization: The tensile strength of the high-strength and high-thermal-conductivity carbon nanotube composite phase change fiber is 0.15GPa, and the thermal conductivity of the fiber is 61.2Wm-2 measured by the electric heating steady-state method. -1 K -1 , the latent heat of phase change is 121.1 J g -1 .

[0102] Finally, it should be noted that the above description is only a preferred embodiment of the present invention. Under the guidance of the present invention, those skilled in the art can make a variety of similar expressions without violating the purpose and claims of the present invention. Such changes fall within the scope of protection of the present invention.

Claims

1. A method for preparing high-strength and high-thermal-conductivity composite phase-change fiber, characterized in that: The following steps are involved: S1. The carbon nanotube fibers are impregnated with a porogen and heated to allow the porogen to penetrate into the pores of the carbon nanotube fibers and / or the gaps between the tubes; S2 S1 mixture is solidified and cured, so that the pore-forming agent infiltrating the carbon nanotube fiber pores and / or the gaps between the tubes is rapidly solidified to form a crystal structure; S3 removes the crystal structure in the carbon nanotube fiber pores and / or the gaps between tubes in S2 to form a carbon nanotube fiber having a multi-level interlayer pore structure; S4. The carbon nanotube fibers obtained in S3 are immersed in a phase change material solution and heated to allow the phase change material to penetrate into the multi-level pore structure between the carbon nanotube fibers to obtain a crude composite phase change fiber; S5. The crude composite phase change fiber is washed with a solvent and dried to obtain a composite phase change fiber.

2. The method for preparing a high-strength and high-thermal-conductivity composite phase change fiber according to claim 1, characterized in that: The pore-forming agent is selected from a combination of multiple ones of water, ethanol, methanol and acetone.

3. The method for preparing a high-strength and high-thermal-conductivity composite phase-change fiber according to claim 1, characterized in that: The pore-forming agent is selected from one of water, ethanol, methanol and acetone.

4. The method for preparing a high-strength and high-thermal-conductivity composite phase-change fiber according to claim 1, characterized in that: The pore former is selected from water.

5. The method for preparing a high-strength and high-thermal-conductivity composite phase-change fiber according to claim 1, characterized in that: In the above-mentioned S2, the solidification treatment is a combination of aging treatment, freezing treatment, and solubilization treatment.

6. The method for preparing a high-strength and high-thermal-conductivity composite phase-change fiber according to claim 1, characterized in that: In the step S2, the solidification treatment is one of aging treatment, freezing treatment, and solubilization treatment.

7. The method for preparing a high-strength and high-thermal-conductivity composite phase-change fiber according to claim 1, characterized in that: In the above-mentioned S2, the solidification process is a freezing process.

8. The method for preparing a high-strength and high-thermal-conductivity composite phase-change fiber according to claim 1, characterized in that: In said S3, the crystal structure in said S2 is removed by a combination of supercritical drying, freeze drying, vacuum drying, spray drying, microwave drying and infrared drying.

9. The method for preparing a high-strength and high-thermal-conductivity composite phase-change fiber according to claim 1, characterized in that: In said S3, the crystal structure in said S2 is removed by one of supercritical drying, freeze drying, vacuum drying, spray drying, microwave drying and infrared drying.

10. The method for preparing a high-strength and high-thermal-conductivity composite phase-change fiber according to claim 1, characterized in that: In said S3, the crystal structure in said S2 is removed by vacuum drying.

11. The method for preparing a high-strength and high-thermal-conductivity composite phase-change fiber according to claim 1, characterized in that: The phase change material solution includes the following components by weight: 5-50 parts of phase change material and 50-95 parts of solvent; the phase change material is selected from one or a combination of two or more of polyethylene glycol, paraffin, n-hexane, n-octadecane, n-decanoic acid, lauric acid, myristic acid, stearic acid, neopentyl glycol, and pentaerythritol; and the solvent is selected from one or a combination of two or more of water, ethanol, ethylene glycol, isopropyl alcohol, ether, and acetone.

12. The method for preparing a high-strength and high-thermal-conductivity composite phase-change fiber according to claim 1, characterized in that: The phase change material solution includes the following components in parts by mass: 10-40 parts of phase change material and 60-90 parts of solvent; or 10-30 parts of phase change material and 70-90 parts of solvent.

13. The method for preparing a high-strength and high-thermal-conductivity composite phase-change fiber according to claim 12, characterized in that: The phase change material is selected from polyethylene glycol; and the solvent is selected from ethanol.

14. The method for preparing a high-strength and high-thermal-conductivity composite phase-change fiber according to claim 11, characterized in that: In said S5, the process conditions of solvent washing are: immersing the composite phase change fiber in the solvent, and the washing time is 5 to 60 seconds.

15. A high-strength and high-thermal-conductivity composite phase-change fiber produced by the method according to any one of claims 1 to 14, characterized in that: The amount of the phase change material is 15-35% of the weight of the composite phase change fiber, and the thermal conductivity of the composite phase change fiber is 100-300 Wm -1 K -1 , tensile strength ≥500 MPa, phase change temperature 50-65℃, phase change latent heat ≥20J / g.

16. Use of the high-strength and high-thermal-conductivity composite phase-change fiber according to claim 15 or the composite fiber prepared by the method according to any one of claims 1 to 14 in thermal interface materials, energy storage materials, and high-temperature protective materials.

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