阅读说明：本技术 高强高韧碳纳米管复合相变纤维、其制备方法及应用 (High-strength high-toughness carbon nanotube composite phase change fiber, and preparation method and application thereof ) 是由 赵静娜 王娇娇 李清文 于 2021-07-12 设计创作，主要内容包括：本发明公开了一种高强高韧碳纳米管复合相变纤维、其制备方法及应用。所述复合相变纤维包括碳纳米管纤维和相变材料,所述相变材料均匀分布于碳纳米管纤维内或其形成的网络结构中。所述制备方法包括：使碳纳米管纤维在电解所产生的气体的作用下产生均匀膨胀；将得到的具有膨胀网络结构的碳纳米管纤维浸渍于相变材料溶液中,使其中的相变材料充分渗透入所述碳纳米管纤维的膨胀网络结构内部,再进行致密化处理,制得高强高韧碳纳米管复合相变纤维。本发明制备的高强高韧碳纳米管复合相变纤维具有更高的耐温特性,强度高,相变温度可调范围宽,相变潜热高,可溶于有机溶剂的各种石蜡材料,有望在未来可穿戴环境能源收集器件上有非常广阔的应用前景。(The invention discloses a high-strength high-toughness carbon nanotube composite phase change fiber, and a preparation method and application thereof. The composite phase-change fiber comprises carbon nanotube fiber and phase-change material, and the phase-change material is uniformly distributed in the carbon nanotube fiber or in a network structure formed by the carbon nanotube fiber. The preparation method comprises the following steps: so that the carbon nano tube fiber can be uniformly expanded under the action of gas generated by electrolysis; and (3) soaking the obtained carbon nanotube fiber with the expansion network structure in a phase-change material solution to enable the phase-change material in the carbon nanotube fiber to fully penetrate into the expansion network structure of the carbon nanotube fiber, and then performing densification treatment to obtain the high-strength high-toughness carbon nanotube composite phase-change fiber. The high-strength high-toughness carbon nanotube composite phase change fiber prepared by the invention has the advantages of higher temperature resistance, high strength, wide adjustable range of phase change temperature and high phase change latent heat, and various paraffin materials which can be dissolved in organic solvents are expected to have very wide application prospects on wearable environmental energy collecting devices in the future.)

1. The high-strength high-toughness carbon nanotube composite phase change fiber is characterized by comprising carbon nanotube fibers and phase change materials, wherein the phase change materials are uniformly distributed in the carbon nanotube fibers and/or in a network structure formed by the carbon nanotube fibers, the content of the phase change materials in the high-strength high-toughness carbon nanotube composite phase change fiber is 35-70 wt%, the phase change temperature of the high-strength high-toughness carbon nanotube composite phase change fiber is 50-65 ℃, the latent heat of phase change is more than 105.9J/g, the tensile strength is more than 2GPa, the fiber can convert and store electric energy into heat energy in any shape, and the density is 0.5-1.5 g/cm³。

2. The high-strength high-toughness carbon nanotube composite phase change fiber according to claim 1, wherein: the phase-change material comprises one or the combination of more than two of stearic acid, palmitic acid, myristic acid, lauric acid, n-octadecane, paraffin and polyethylene glycol.

3. A preparation method of a high-strength high-toughness carbon nanotube composite phase-change fiber is characterized by comprising the following steps:

carbon nanotube fibers are used as a cathode, and an electrochemical reaction system is constructed together with an anode and electrolyte, wherein the electrolyte is an aqueous phase system containing electrolyte; electrifying the electrochemical reaction system, and enabling the carbon nano tube fiber to generate uniform expansion in the radial direction and/or the length direction under the action of gas generated by electrolysis;

and (3) soaking the obtained carbon nanotube fiber with the expansion network structure in a phase-change material solution to enable the phase-change material in the carbon nanotube fiber to fully penetrate into the expansion network structure of the carbon nanotube fiber, and then performing densification treatment to obtain the high-strength high-toughness carbon nanotube composite phase-change fiber.

4. The production method according to claim 3, characterized in that: the electrolyte comprises any one or the combination of more than two of sulfuric acid, sodium chloride, sodium hydroxide, zinc sulfate, potassium hydroxide and potassium chloride.

5. The production method according to claim 3, characterized in that: the gas produced by the electrolysis comprises hydrogen and/or chlorine, preferably hydrogen.

6. The production method according to claim 3, characterized by comprising: applying a voltage between two selected stations on the carbon nanotube fiber or passing a current through the carbon nanotube fiber to generate a gas, and then uniformly expanding the carbon nanotube fiber in the radial direction and/or the length direction to 400-2000 times of the original carbon nanotube fiber, wherein the two selected stations are distributed at different positions on the carbon nanotube fiber along the length direction; preferably, the current is 30-90 mA.

7. The production method according to claim 3, characterized in that: the phase-change material solution comprises a phase-change material and a solvent, wherein the phase-change material comprises any one or a combination of more than two of stearic acid, palmitic acid, myristic acid, lauric acid, n-octadecane, paraffin and polyethylene glycol, and the solvent comprises any one or a combination of more than two of water, diethyl ether, xylene and acetone; preferably, the concentration of the phase-change material in the phase-change material solution is 10-30 wt%.

8. The production method according to claim 3, characterized by comprising: and performing densification treatment on the carbon nanotube fiber permeated with the phase change material at least in a twisting mode.

9. The high-strength high-toughness carbon nanotube composite phase change fiber prepared by the method of any one of claims 3 to 8.

10. Use of the high-strength high-toughness carbon nanotube composite phase change fiber of any one of claims 1-2 and 9 in preparation of wearable environmental energy collection devices.

Technical Field

The invention relates to a carbon nano tube composite material, in particular to a high-strength high-toughness carbon nano tube composite phase change fiber, a preparation method and application thereof, belonging to the technical field of nano science.

Background

With the rapid development of Carbon Nanotube (CNT) fibers, multifunctional CNT composite fibers have been developed. When the carbon nanotube fiber and the composite fiber formed by compounding different materials have different functionalities, the composite fiber can be applied to a plurality of fields such as artificial muscle, intelligent wearing, super capacitors, light-weight wires, composite materials and the like. If the carbon nanotube fiber is used as a substrate, copper plating is carried out on the carbon nanotube fiber to prepare a lightweight cable, the problem of interface bonding between the carbon nanotube and copper is solved, and the conductivity of the cable can be improved by nearly two orders of magnitude compared with that of fibril (Nanoscale,2011,3(10): 4215-; coating a titanium dioxide Nano layer on the surface of the carbon nanotube fiber, adsorbing dye by using titanium dioxide to generate photocharge, and rapidly transferring the photocharge to the carbon nanotube fiber to prepare a linear dye-sensitized solar cell of the carbon nanotube fiber (Nano letters,2012,12(5):2568 and 2572); a group of carbon nanotube yarns with a layered structure are twisted to prepare the ultra-large electrochemical yarn with rapid contraction driving, and the carbon nanotube yarns have high muscle circulation stability and large driving quantity (Materials Horizons,2020,7(11): 3043-.

As is well known, polyethylene glycol (PEG) as a phase change energy storage material has the advantages of high phase change enthalpy, stable performance, no corrosiveness and the like. The carbon nano tube is used as a medium supporting material, and the polyethylene glycol and the carbon nano tube fiber are compounded to obtain the composite phase change fiber material with excellent mechanical property and structural strength. The phase change heat storage belongs to latent heat type heat storage and has the advantages of high energy density, simple device, energy conservation, high efficiency and the like. At present, the phase change energy storage material has important application value and wide development prospect in a plurality of fields such as aerospace, solar energy utilization, textile industry, heat storage building and the like. However, the pure polyethylene glycol as a phase change material realizes heat storage and energy storage in a solid-liquid conversion mode, which results in difficulty in realizing practical engineering due to large difference of polyethylene glycol forms in the energy storage process.

In summary, the prior art mainly has the following disadvantages: 1) pure polyethylene glycol is used as a phase change material, and solid-liquid state mutual transformation can occur in the phase change process, so that a certain form is difficult to maintain; 2) at present, the preparation method of the composite phase change heat storage material using polyethylene glycol as a working substance mainly comprises a chemical method and a blending method, and the preparation process is relatively complex; 3) in addition, the mechanical properties of the composite phase change material using polyethylene glycol as a working substance are relatively weak; 4) the polyethylene glycol and the organic polymer are compounded to have the problems of weak thermal response and poor inflammability, and are compounded with inorganic matters to have poor toughness and be fragile.

Disclosure of Invention

The invention mainly aims to provide a high-strength high-toughness carbon nanotube composite phase change fiber and a preparation method thereof, so as to overcome the defects in the prior art.

The invention also aims to provide application of the high-strength high-toughness carbon nanotube composite phase change fiber.

In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:

the embodiment of the invention provides a high-strength high-toughness carbon nanotube composite phase change fiber, which comprises carbon nanotube fibers and phase change materials, wherein the phase change materials are uniformly distributed in the carbon nanotube fibers and/or in a network structure formed by the carbon nanotube fibers, the content of the phase change materials in the high-strength high-toughness carbon nanotube composite phase change fiber is 35-70 wt%, the phase change temperature of the high-strength high-toughness carbon nanotube composite phase change fiber is 50-65 ℃, the latent heat of phase change is more than 105.9J/g, the tensile strength is more than 2GPa, the high-strength high-toughness carbon nanotube composite phase change fiber can convert and store electric energy into heat energy in any shape, and the density is 0.5-1.5 g/cm³。

The embodiment of the invention also provides a preparation method of the high-strength high-toughness carbon nanotube composite phase-change fiber, which comprises the following steps:

carbon nanotube fibers are used as a cathode, and an electrochemical reaction system is constructed together with an anode and electrolyte, wherein the electrolyte is an aqueous phase system containing electrolyte; electrifying the electrochemical reaction system, and enabling the carbon nano tube fiber to generate uniform expansion in the radial direction and/or the length direction under the action of gas generated by electrolysis;

and (3) soaking the obtained carbon nanotube fiber with the expansion network structure in a phase-change material solution to enable the phase-change material in the carbon nanotube fiber to fully penetrate into the expansion network structure of the carbon nanotube fiber, and then performing densification treatment to obtain the high-strength high-toughness carbon nanotube composite phase-change fiber.

In some embodiments, the phase change material solution includes a phase change material and a solvent, wherein the phase change material includes any one or a combination of two or more of stearic acid, palmitic acid, myristic acid, lauric acid, n-octadecane, paraffin, polyethylene glycol, and the like.

The embodiment of the invention also provides the high-strength high-toughness carbon nanotube composite phase-change fiber prepared by the method.

Correspondingly, the embodiment of the invention also provides application of the high-strength high-toughness carbon nanotube composite phase change fiber in preparation of wearable environmental energy collecting devices.

Compared with the prior art, the invention has the advantages that:

1) the carbon nanotube-phase change material composite phase change fiber prepared by using electrolytic water for hydrogen evolution and utilizing interface foaming has good uniformity, the phase change material can further enhance the densified carbon nanotube fiber, and the twisted composite fiber has higher tensile strength and various paraffin materials which have low density, wide adjustable range of phase change temperature, high phase change enthalpy or latent heat and are soluble in organic solvents;

2) the high-strength and high-toughness carbon nanotube-phase change material composite phase change fiber prepared by the method has good structural uniformity, still maintains a solid state in the phase change process, and is well bound in a carbon nanotube network structure by an in-situ impregnation method, so that the phase change material is effectively prevented from leaking out in the phase change process;

3) the high-strength high-toughness carbon nanotube composite phase change fiber prepared by the method does not relate to toxic dangerous articles, and electrolytes such as sulfuric acid and the like can be recycled, so that the method accords with the concept of environmental protection;

4) the preparation method of the high-strength high-toughness carbon nanotube composite phase change fiber provided by the invention is simple and efficient, can expand continuous production and realize industrialization, and the super-strong carbon nanotube-phase change material composite phase change fiber is expected to have very wide application prospect in wearable environment energy collecting devices in the future.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic illustration of the mechanism by which hydrogen gas is generated by electrolysis of water to expand a carbon nanotube fiber network in an exemplary embodiment of the invention;

FIGS. 2A-2D are topographical representations of CNT-PEG composite phase-change fibers in accordance with an exemplary embodiment of the present invention;

FIG. 3 is a thermogravimetric plot of pure CNT fibers and CNT-PEG composite phase change fibers at different PEG loadings in an exemplary embodiment of the invention;

FIG. 4 is a stress-strain graph of pure CNT fibers and CNT-PEG composite phase change fibers with different PEG loadings in accordance with an exemplary embodiment of the present invention;

FIG. 5 is a DSC plot of pure PEG and CNT-PEG composite phase change fibers with different PEG loadings in an exemplary embodiment of the invention;

FIG. 6 is a graph of electrical energy to thermal energy conversion and storage curves for pure CNT fibers and PEG-loaded (67%) CNT-PEG composite phase change fibers in an exemplary embodiment of the invention;

FIGS. 7A and 7B are graphs showing flexibility characteristics of CNT-PEG composite phase-change fibers according to an exemplary embodiment of the present invention;

fig. 8A and 8B are infrared thermal imaging diagrams of CNT-PEG composite phase-change fibers during power-on and power-off processes according to an exemplary embodiment of the present invention.

Detailed Description

In view of the defects in the prior art, the inventors of the present invention have long studied and practiced a lot of times to prepare a carbon nanotube (hereinafter, may be abbreviated as CNT) -phase change material (such as polyethylene glycol) (preferably CNT-PEG) composite phase change fiber based on the excellent mechanical and thermal conductivity of the carbon nanotube fiber and a stable one-dimensional structure, so that not only the solid structure can be maintained during the phase change process, but also the thermal conductivity of the phase change material (such as polyethylene glycol) is greatly improved by the carbon nanotube with high thermal conductivity.

The technical idea of the invention mainly lies in that: the carbon nano tube composite phase change fiber is prepared by adopting a method of electrolyzing water to generate hydrogen and utilizing interface foaming. The composite phase change fiber realizes faster electrothermal response under low voltage, and the method further develops the phase change material with low power consumption. And is expected to be applied to future intelligent energy storage equipment. The super-strong carbon nanotube-phase change material (such as polyethylene glycol) (preferably CNT-PEG) composite phase change fiber is expected to have very wide application prospect in wearable environmental energy collection devices in the future. Therefore, the carbon nano tube fiber expanded by electrolyzing water to separate out hydrogen is not only beneficial to the reassembly of the CNT, but also beneficial to the preparation of the high-performance and multifunctional CNT composite fiber, and widens the way for preparing the multifunctional CNT composite fiber in the future.

The technical solution, its implementation and principles, etc. will be further explained as follows.

One aspect of the embodiment of the invention provides a high-strength high-toughness carbon nanotube composite phase change fiber, which comprises carbon nanotube fibers and phase change materials, wherein the phase change materials are uniformly distributed in the carbon nanotube fibers and/or in a network structure formed by the carbon nanotube fibers, the content of the phase change materials in the high-strength high-toughness carbon nanotube composite phase change fiber is 35-70 wt%, the phase change temperature of the high-strength high-toughness carbon nanotube composite phase change fiber is 50-65 ℃, the latent heat of phase change is more than 105.9J/g, the tensile strength is more than 2GPa, and the high-strength high-toughness carbon nanotube composite phase change fiber can be used in any placeThe shape is used for converting and storing electric energy into heat energy, and the density is 0.5-1.5 g/cm³。

In some embodiments, the phase change material includes any one or a combination of two or more of stearic acid, palmitic acid, myristic acid, lauric acid, n-octadecane, paraffin, polyethylene glycol, and the like, but is not limited thereto.

Further, the paraffin may be paraffin C16 to C18, paraffin C20 to C33, paraffin C22 to C45, paraffin C21 to C50, and the like, but is not limited thereto.

Further, the polyethylene glycol may be PEG3500, or may be replaced by other PEG types, such as PEG600, PEG1000, PEG6000, and the like.

Another aspect of the embodiments of the present invention provides a method for preparing a high-strength high-toughness carbon nanotube composite phase-change fiber, including:

carbon nanotube fibers are used as a cathode, and an electrochemical reaction system is constructed together with an anode and electrolyte, wherein the electrolyte is an aqueous phase system containing electrolyte; electrifying the electrochemical reaction system, and enabling the carbon nano tube fiber to generate uniform expansion in the radial direction and/or the length direction under the action of gas generated by electrolysis;

and (3) soaking the obtained carbon nanotube fiber with the expansion network structure in a phase-change material solution to enable the phase-change material in the carbon nanotube fiber to fully penetrate into the expansion network structure of the carbon nanotube fiber, and then performing densification treatment to obtain the high-strength high-toughness carbon nanotube composite phase-change fiber.

In some embodiments, the invention mainly uses electrolyzed water to separate out hydrogen so as to foam the carbon nanotube fiber interface to prepare the carbon nanotube composite phase-change fiber. Meanwhile, as the electrolyzed water in the whole process only plays a role in transferring charges, the electrolyte can be replaced by any soluble ionic compound such as sodium chloride, sodium hydroxide, zinc sulfate, potassium hydroxide, potassium chloride and the like. Note that when the electrolyte is sodium chloride or potassium chloride, hydrogen is evolved at the cathode and chlorine gas is generated at the anode.

Furthermore, the high-strength and high-toughness carbon nanotube composite phase change fiber prepared by the method does not relate to toxic dangerous articles, and electrolytes such as sulfuric acid and the like can be recycled, so that the method is in line with the concept of environmental protection.

In some exemplary embodiments, the preparation method specifically includes: applying a voltage between two selected stations on the carbon nanotube fiber or passing a current through the carbon nanotube fiber to generate a gas, and then uniformly expanding the carbon nanotube fiber in the radial direction and/or the length direction to 400-2000 times of the original carbon nanotube fiber, wherein the two selected stations are distributed at different positions on the carbon nanotube fiber along the length direction; preferably, the current is 30-90 mA.

In some exemplary embodiments, the phase-change material solution includes a phase-change material and a solvent, wherein the phase-change material includes any one or a combination of two or more of stearic acid, palmitic acid, myristic acid, lauric acid, n-octadecane, paraffin, polyethylene glycol, and the like, and the solvent includes any one or a combination of two or more of water, diethyl ether, xylene, acetone, and the like.

Further, the concentration of the phase-change material in the phase-change material solution is 10-30 wt%.

In some exemplary embodiments, the preparation method specifically includes: and performing densification treatment on the carbon nanotube fiber permeated with the phase change material at least in a twisting mode.

In some exemplary embodiments, the preparation method specifically includes:

the invention takes the mixed solution of sulfuric acid and polyethylene glycol polymer as the electrolyte solvent, can realize the expansion of the carbon nano tube fiber with ultrahigh volume ratio, and the polyethylene glycol can fully enter the carbon nano tube fiber, the polyethylene glycol with polyhydroxy structure can further strengthen the densified carbon nano tube fiber, and the strength of the twisted composite fiber can exceed 2 GPa.

In conclusion, the invention utilizes the electrolyzed water to separate out hydrogen to enable the carbon nano tube fiber to expand from inside to outside without damage, the carbon nano tube fiber can realize instant expansion after being electrified, the expansion is uniform and has high efficiency, the simplicity and the efficiency are higher, the safety is higher, the continuous production can be expanded, and the industrialization is realized.

The preparation method of the high-strength high-toughness carbon nanotube composite phase change fiber provided by the invention is simple and efficient, can enlarge continuous production, and realizes industrialization.

Another aspect of the embodiments of the present invention provides a high-strength and high-toughness carbon nanotube composite phase-change fiber prepared by the foregoing method.

In conclusion, the carbon nanotube-phase change material composite phase change fiber prepared by utilizing interfacial foaming has good uniformity, the phase change material can further enhance the densification of the carbon nanotube fiber, and the twisted composite fiber has high tensile strength and various paraffin materials which have low density, wide adjustable range of phase change temperature, high enthalpy or latent heat of phase change and are soluble in organic solvents.

The high-strength and high-toughness carbon nanotube-phase change material composite phase change fiber prepared by the method has good structural uniformity, still maintains a solid state in the phase change process, and is well bound in a carbon nanotube network structure by an in-situ impregnation method, so that the phase change material is effectively prevented from leaking out in the phase change process.

Further, the invention also provides an application of the high-strength high-toughness carbon nanotube composite phase change fiber in preparation of wearable environmental energy collecting devices.

Furthermore, the ultra-strong CNT/phase-change material composite phase-change fiber is expected to have a very wide application prospect in a wearable environment energy collecting device in the future.

The technical solutions of the present invention will be described in further detail below with reference to several preferred embodiments and accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out under conventional conditions or conditions recommended by the manufacturers.

Example 1

The specific technical steps of this embodiment are as follows:

1) carbon nanotube fibers: carbon nanotube fibers prepared by a floating catalyst chemical deposition (CVD) method were used. (from Suzhou Jiedi nanotechnology Co., Ltd.)

2) Carbon nano tube/phase change material composite phase change fiber (mixed solution of sulfuric acid and polyethylene glycol polymer is used as electrolyte solvent)

Preparing a solution of 0.2mol/L sulfuric acid as an electrolyte: 450ml of deionized water is prepared and measured in a 500ml beaker, 10g of 98% concentrated sulfuric acid is accurately weighed, and the concentrated sulfuric acid is slowly added into the deionized water along a glass rod in a cold water bath while stirring. Finally, deionized water is added to 500ml, and the mixture is stirred until the mixture is uniform.

3) And (3) electrolyzing water to expand the fibers: 700mL of electrolyte is added into an electrolytic cell, the anode is an inert electrode, and the cathode is carbon nanotube fiber. Respectively adopting a voltage and current method (the current is 30-90 mA, and the voltage is changed along with the current) to control, electrolyzing water to separate hydrogen so as to realize the expansion of the carbon nano tube fiber with ultrahigh volume ratio, and obtaining the carbon nano tube fiber with an expansion network structure;

4) and (3) dipping: the carbon nanotube fiber with the expanded network structure is immersed in a polyethylene glycol (PEG) aqueous solution with the concentration of 10-30 wt%, the PEG in the carbon nanotube fiber is made to fully permeate into the expanded network structure of the carbon nanotube fiber, the polyethylene glycol with the polyhydroxy structure can further enhance the densification of the carbon nanotube fiber, and then densification treatment is carried out, so that a series of CNT-PEG composite phase-change fibers with different PEG loading amounts (35 wt% and 67 wt%) are prepared.

5) Electric heat conversion and energy storage: twisting and combining 5-10 CNT fibers and 5-10 CNT-PEG (67%) composite phase-change fibers respectively to obtain the CNT yarn and the CNT-PEG composite yarn. The conversion and storage of electrical energy to thermal energy under the effect of a current of 0.275A for 67% CNT/PEG phase-change composite fibers and protocnt fibers, respectively, were compared.

In this embodiment, the carbon nanotube fiber with the expanded network structure obtained after expansion is immersed in a PEG solution with a low temperature region phase transition, and by adjusting the concentration of PEG, PEG can be loaded by more than 64.3% in the composite CNT fiber, and the CNT/PEG composite phase transition fiber has higher temperature resistance compared to PEG. The composite phase change fiber has obvious phase change at 50-65 ℃, and the latent heat of the phase change can reach 105.9J/g. In addition, the PEG with the polyhydroxy structure can further enhance the densified CNT fiber, and the strength of the twisted composite fiber can exceed 2 GPa. The ultra-strong CNT/PEG phase-change fiber is expected to have very wide application prospect in a wearable environment energy collecting device in the future.

Further, the solvent water in the aqueous solution of polyethylene glycol (PEG) in the present embodiment may also be replaced by ethyl ether, xylene, acetone, or the like, but is not limited thereto.

Furthermore, the CNT-PEG composite phase-change fiber still keeps a solid state in the phase-change process, and polyethylene glycol is well bound in a carbon nano tube network structure through an in-situ impregnation method, so that the polyethylene glycol is effectively prevented from leaking out in the phase-change process. Moreover, the carbon nano tube and the polyethylene glycol are compounded to change the solid-liquid form in the traditional polyethylene glycol phase transition process, namely the CNT-PEG composite phase transition fiber can still keep the solid form even in a molten state.

In the invention, hydrogen is generated by mainly utilizing electrolyzed water to expand the CNT network, and the expansion mechanism is shown as the following figure 1:

FIG. 1 is H₂Evolution of the bubble and a force balance model of the bubble under the constraint of the carbon nano tube. First, the present inventors considered H₂Related to the way current is conducted through the CNT assembly. Due to the skin effect, the current inside the carbon nanotube assembly is mainly conducted along the surface of the large-sized carbon nanotube bundle, while the conduction along the small-sized bundle or a single carbon nanotube results in much larger resistance. Thus, H₂Mainly at the surface evolution of large size beams, especially at the junctions between them, because geometric irregularities are an effective way of gas molecule accumulation. Thus, H₂The bubbles can grow gradually between the large-size CNT bundles.

Secondly, it is necessary to divideThe force acting on the bubble reveals the mechanism of bubble expansion. When the external pressure P of the circular bubble₀(ambient pressure around the bubble) and internal pressure P_iThe bubble may exist stably when equilibrium (i.e., the surface tension of the bubble) is reached. I.e. P_i-P₀2T/r, where r is the radius of the bubble. When the bubbles are formed early in the carbon nanotube assembly, they are generally not spherical, but rather more elliptical. As the bubbles grow, the equilibrium is disrupted, i.e. P_i-P₀>2T/r, where the bubble is constrained by the CNT network, the bubble becomes longer and narrower from a circular shape. At the long bulb end, the constraint is weakest, the radius of curvature is smallest, r_min≈2T/(P_i-P₀) (ii) a While in the middle part the radius of curvature is maximized by the constraint, r_max≈2T/(P_i–P₀–P_c) In which P is_cThe pressure is constrained for the CNT network.

The characterization results of the high-strength and high-toughness carbon nanotube composite phase-change fiber obtained in the embodiment are as follows:

FIGS. 2A-2D are the morphology characterization of the CNT-PEG composite phase-change fiber, from which it can be seen that a large amount of polyethylene glycol is enriched in the carbon nanotube network structure. Through an in-situ impregnation method, the polyethylene glycol is well bound in the carbon nano tube network structure, and the uniformity is good, so that the leakage of the polyethylene glycol caused by the CNT-PEG composite phase-change fiber in the phase-change process is effectively prevented.

Fig. 3 is a thermogravimetric plot of pure CNT fibers and CNT-PEG composite phase-change fibers with different PEG loadings. By an in-situ impregnation method, two kinds of phase-change material solutions with PEG content of 10% (v/w) and 30% are respectively adopted to prepare the CNT-PEG composite phase-change fiber, and two kinds of CNT-PEG composite phase-change fibers with PEG content of 32 wt% and 64 wt% are respectively obtained, and a thermogravimetric curve is shown in figure 3.

Fig. 4 is a stress-strain curve for pure CNT fibers and CNT-PEG composite phase change fibers with different PEG loadings. The tensile stress of the CNT/PEG composite phase-change fiber with the PEG content of 35 wt% is 2.19GPa, and the tensile stress of the CNT/PEG composite phase-change fiber with the PEG content of 67 wt% is 1.61 GPa. Compared with the mechanical property of pure CNT fiber (1.46GPa), the CNT/PEG composite phase-change fiber is improved to a different extent, because the PEG with a polyhydroxy structure can further strengthen the densified CNT fiber.

FIG. 5 is a DSC curve of pure PEG and CNT-PEG composite phase-change fibers with different PEG loadings. The composite phase-change fiber is subjected to energy storage at 56-64 ℃ and energy release at 35-43 ℃, which is consistent with the phase-change temperature region of pure PEG. Wherein, the phase-change latent heat of the CNT/PEG composite phase-change fiber with the content of 35 wt% is only 33.7J/g, while the phase-change latent heat of the CNT/PEG composite phase-change fiber with the content of 67 wt% can reach 136.2J/g, and the phase-change enthalpy can reach 59% of pure PEG. Under the condition of keeping a certain mechanical strength, the CNT-PEG composite phase-change fiber with the content of 67 wt% has good phase-change latent heat. The problems of weak thermal response and poor inflammability of PEG and organic polymer composite and the problems of poor toughness, frangibility and the like of PEG and inorganic matter composite are solved.

FIG. 6 is a graph of electrical energy to thermal energy conversion and storage for pure CNT fibers and CNT-PEG (67 wt%) composite phase change fibers. Compare 67 wt% of CNT/PEG composite phase-change fibers and protocnt fibers, respectively, for conversion and storage of electrical energy to thermal energy under a current of 0.275A. Although 67 wt% of PEG is compounded in the CNT fiber, the response rate of the electric heating is still faster, and the temperature reaches 65 ℃ after 50s of electrification. The power was turned off and the composite phase change fiber developed a plateau at 40 ℃ and sustained the exotherm for 60s compared to the fibril. This is due to the solid-liquid phase transition of PEG from crystalline to amorphous state. The CNT-PEG composite phase-change fiber realizes faster electrothermal response under low voltage, and the method further develops the phase-change material with low power consumption.

FIGS. 7A and 7B are representations of flexibility of CNT-PEG composite phase-change fibers in an exemplary embodiment. The compounded CNT-PEG composite phase-change fiber has good flexibility, and can convert and store electric energy into heat energy under any shape.

Fig. 8A and 8B are infrared thermal imaging diagrams of CNT-PEG composite phase-change fibers during power-on and power-off processes according to an exemplary embodiment. As can be seen from the figure, after the power is turned on, the CNT-PEG composite phase-change fiber can realize rapid temperature rise. After power failure, the composite fiber can realize the heat preservation process for 1 min.

Example 2

The specific technical steps of this embodiment are as follows:

1) carbon nanotube fibers: carbon nanotube fibers prepared by a floating catalyst chemical deposition (CVD) method were used. (from Suzhou Jiedi nanotechnology Co., Ltd.)

2) Preparing electrolyte: 0.1mol/L zinc sulfate is used as electrolyte.

3) Preparing a phase-change solution: 10% and 30% paraffin solutions were prepared using xylene and diethyl ether as solvents, respectively.

3) And (3) electrolyzing water to expand the fibers: 700mL of electrolyte is added into an electrolytic cell, the anode is an inert electrode, and the cathode is carbon nanotube fiber. Adjusting the current to 50mA, electrolyzing water to separate out hydrogen to enable the carbon nano tube fiber to realize expansion with ultrahigh volume ratio, and obtaining the carbon nano tube fiber with an expansion network structure;

4) and (3) dipping: and (2) soaking the carbon nanotube fiber with the expansion network structure in a paraffin solution to ensure that the paraffin in the carbon nanotube fiber fully permeates into the expansion network structure of the carbon nanotube fiber, and then performing densification treatment to prepare a series of CNT composite phase-change fibers with different paraffin loading amounts.

Through tests, the performance parameters of the CNT composite phase-change fiber loaded with paraffin wax obtained in the present example are substantially the same as those of example 1.

Example 3

The specific technical steps of this embodiment are as follows:

1) carbon nanotube fibers: carbon nanotube fibers prepared by a floating catalyst chemical deposition (CVD) method were used. (from Suzhou Jiedi nanotechnology Co., Ltd.)

2) Preparing electrolyte: 0.1mol/L sulfuric acid was used as an electrolyte.

3) Preparing a phase-change solution: 15% and 20% stearic acid solutions were prepared using toluene and benzene as solvents, respectively.

3) And (3) electrolyzing water to expand the fibers: 700mL of electrolyte is added into an electrolytic cell, the anode is an inert electrode, and the cathode is carbon nanotube fiber. Adjusting the current to 50mA, electrolyzing water to separate out hydrogen to enable the carbon nano tube fiber to realize expansion with ultrahigh volume ratio, and obtaining the carbon nano tube fiber with an expansion network structure;

4) and (3) dipping: and (2) soaking the carbon nanotube fiber with the expanded network structure in stearic acid solution to enable paraffin in the carbon nanotube fiber to fully permeate into the expanded network structure of the carbon nanotube fiber, and then performing densification treatment to prepare a series of CNT composite phase-change fibers with different stearic acid loading amounts.

Through tests, the performance parameters of the stearic acid-loaded CNT composite phase-change fiber obtained in the embodiment are basically consistent with those of the embodiment 1.

In addition, the inventors of the present invention have also made experiments with reference to the above examples and other raw materials, process operations and process conditions described in the present specification, and for example, preferable results were obtained by replacing polyethylene glycol, stearic acid and paraffin wax in examples 1 to 3 with palmitic acid, myristic acid, lauric acid, n-octadecane, etc., respectively, and replacing sulfuric acid and zinc sulfate in examples 1 to 2 with sodium chloride, sodium hydroxide, potassium chloride, etc.

In summary, the method for preparing the CNT-PEG composite phase-change fiber by using the electrolytic water for hydrogen evolution and the interfacial foaming of the carbon nanotube fiber is novel, unique, green and efficient, the obtained CNT-PEG composite phase-change fiber has good structural uniformity, PEG with a polyhydroxy structure is well bound in a carbon nanotube network structure, meanwhile, the polyhydroxy structure of the polyethylene glycol is beneficial to further enhancing the densified CNT fiber of the carbon nanotube fiber, and the twisted composite fiber has high tensile strength.

While the invention has been described with reference to illustrative embodiments, 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 its scope. 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.