Janus structure silicon carbide / carbon nanofiber and preparation method thereof, and phase change composite material and preparation method thereof

Abstract

The invention relates to the technical field of phase-change composite materials, in particular to a Janus structure silicon carbide / carbon nanofiber and a preparation method thereof, and a phase-change composite material and a preparation method thereof. The preparation method comprises the following steps: dissolving a silicon carbide precursor and a spinning aid in a first solvent, and mixing to obtain a first spinning solution; dissolving a carbon precursor and an organic salt in a second solvent, and mixing to obtain a second spinning solution; performing side-by-side electrostatic spinning on the first spinning solution and the second spinning solution to obtain Janus structure silicon carbide / carbon precursor nanofibers; and sequentially carrying out drying, curing cross-linking and high-temperature pyrolysis on the Janus structure silicon carbide / carbon precursor nanofiber to obtain the Janus structure silicon carbide / carbon nanofiber. The Janus-structure silicon carbide / carbon nanofiber provided by the invention can be used as an electrothermal conversion material, can be compounded with a phase change material to obtain a phase change composite material which is used as an electrothermal conversion type phase change material, has excellent thermal conductivity, electrothermal conversion capability and high temperature resistance, and has relatively high practical application value.

Description

Technical Field

[0001] This invention relates to the field of phase change composite materials technology, and in particular to a Janus structure silicon carbide / carbon nanofiber and its preparation method, and a phase change composite material and its preparation method. Background Technology

[0002] With the increasing urgency of global demand for efficient energy utilization, phase change materials (PCMs) have become a focus of attention due to their unique advantages in energy storage and temperature regulation. Currently, solid-solid and solid-liquid PCMs are the most widely used. Among them, solid-liquid PCMs have the advantages of high latent heat of phase change and relatively low cost. However, they pose a risk of liquid phase leakage during the phase change process, which requires technologies such as microencapsulation to solve, and these shortcomings limit their application to some extent. In contrast, solid-solid PCMs have become an important direction for replacing solid-liquid PCMs due to their core advantages such as no liquid phase leakage during the phase change process, no need for complex encapsulation, and excellent cycle stability. However, they still have shortcomings such as low phase change enthalpy, insufficient thermal / electrical conductivity, and insufficient high-temperature stability.

[0003] Furthermore, both photothermal and electrothermal phase change materials (PCTs) have attracted widespread attention in thermal energy storage and conversion technologies. Photothermal PCTs show promise in solar energy utilization, but the significant intermittency of solar energy limits their widespread application due to their strong environmental dependence, large efficiency fluctuations, and poor stability. In contrast, electrothermal PCTs not only possess highly efficient energy conversion capabilities but also achieve precise temperature control, rapid response, and long-term stable operation, enabling all-weather energy supply.

[0004] Therefore, there is an urgent need to provide an electrothermal conversion phase change material with high thermal conductivity, high electrothermal conversion capability, and high temperature resistance. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a Janus-structured silicon carbide / carbon nanofiber and its preparation method, as well as a phase change composite material and its preparation method. The Janus-structured silicon carbide / carbon nanofiber provided by this invention serves as an electrothermal conversion material, and the nylon elastomer phase change material serves as a phase change material. The phase change composite material obtained by combining the two is an electrothermal conversion type phase change material, exhibiting excellent thermal conductivity, electrothermal conversion capability, and high temperature resistance, and has high practical application value.

[0006] This invention provides a method for preparing Janus-structured silicon carbide / carbon nanofibers, comprising the following steps:

[0007] (1) A silicon carbide precursor and a spinning aid are dissolved in a first solvent and mixed to obtain a first spinning solution; a carbon precursor and an organic salt are dissolved in a second solvent and mixed to obtain a second spinning solution.

[0008] (2) The first spinning solution and the second spinning solution are electrospun side by side to obtain Janus structure silicon carbide / carbon precursor nanofibers.

[0009] (3) The Janus structure silicon carbide / carbon precursor nanofibers are dried, cured, crosslinked and pyrolyzed at high temperature in sequence to obtain Janus structure silicon carbide / carbon nanofibers.

[0010] Preferably, the silicon carbide precursor includes at least one of polycarbosilane, polysilazane, polysilane, polysiloxane, and phenyl-modified polycarbosilane;

[0011] The spinning aid includes at least one of polyacrylonitrile, thermoplastic polyurethane, polyvinylpyrrolidone, polycaprolactone, polylactic acid, polyglycolic acid, polysulfone, and polystyrene.

[0012] The first solvent is at least one of N,N-dimethylformamide, tetrahydrofuran, xylene, chloroform, and dichloromethane;

[0013] In the first spinning solution, the content of the silicon carbide precursor is 5-15 wt%, and the content of the spinning aid is 1-12 wt%.

[0014] Preferably, the carbon precursor includes at least one of polyacrylonitrile, pitch polymers, and cellulose;

[0015] The organic salt is a conductive carbide precursor salt, which includes at least one of zirconium tetrachloride, zirconium acetylacetonate, zirconium isopropoxide, trimethylzirconium, tetramethoxyzirconium, tetraacetylacetonate, tetraisopropoxyzirconium, and titanium isopropoxide.

[0016] The second solvent is at least one of N,N-dimethylformamide, tetrahydrofuran, xylene, chloroform, and dichloromethane;

[0017] In the second spinning solution, the content of the carbon precursor is 10-22 wt%, and the content of the organic salt is 1-15 wt% of the carbon precursor content.

[0018] Preferably, the parameters of the parallel electrospinning are as follows: the spinning voltage is 12-24kV, the distance from the spinneret to the receiving plate is 10-20cm, the propulsion speed of the first spinning solution and the second spinning solution is the same and is 0.01-0.03mL / min, and the diameter of the two spinnerets of the parallel electrospinning needles is 0.7-0.9mm.

[0019] Preferably, the curing and crosslinking are carried out in an air atmosphere, at a temperature of 180-200°C, for a time of 5-7 hours.

[0020] The high-temperature pyrolysis is carried out in an inert gas atmosphere, and the temperature of the high-temperature pyrolysis is 1400-1600℃, and the time is 6-8h.

[0021] On the other hand, the present invention also provides a Janus-structured silicon carbide / carbon nanofiber, which is prepared by any of the preparation methods described in the foregoing technical solutions.

[0022] On the other hand, the present invention also provides a phase change composite material, comprising a thin film composed of Janus structure silicon carbide / carbon nanofibers as described in the above-mentioned technical solution as the core layer and a phase change material as the surface layer, wherein the phase change material is a nylon elastomer with polytetrahydrofuran ether as the soft segment.

[0023] Preferably, the nylon elastomer includes at least one selected from PA1010-based nylon elastomer, PA1012-based nylon elastomer, PA510-based nylon elastomer, PA512-based nylon elastomer, and PA612-based nylon elastomer.

[0024] The core layer has a thickness of 0.3-0.5 mm; the two surface layers each have a thickness of 0.8-1.2 mm.

[0025] On the other hand, the present invention also provides a method for preparing the phase change composite material described in the above technical solution, comprising the following steps:

[0026] The surface layer, core layer, and surface layer are stacked in sequence and then hot-pressed to obtain a phase change composite material.

[0027] Preferably, the hot pressing temperature is 180-210℃ and the pressure is 5-20 kg / cm². 2 The time is 3-10 minutes.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The Janus-structured silicon carbide / carbon nanofibers prepared by the parallel electrospinning method can be used as electrothermal conversion materials. When combined with nylon elastomer phase change materials, electrothermal conversion type phase change composite materials can be obtained. These phase change composite materials have high thermal conductivity, high electrothermal conversion performance, high temperature resistance, and excellent phase change performance. They effectively eliminate dependence on light energy, realize all-weather management functions, and are conducive to the industrial production of high-performance all-weather phase change composite materials. Attached Figure Description

[0030] The above and other objects, features, and advantages of the invention will be apparent from the following description of preferred embodiments illustrating the gist of the invention and its use, and the accompanying drawings, in which:

[0031] Figure 1 This is a schematic diagram of a side-by-side electrospinning apparatus.

[0032] Figure 2 This is a transmission electron microscope image of the Janus structure silicon carbide / carbon nanofibers obtained in Example 1 of the present invention.

[0033] Figure 3 This is a schematic diagram of the electrospinning apparatus in Comparative Example 1 of the present invention.

[0034] Figure 4 The image shows the differential scanning calorimetry (DSC) curve of the phase change composite material obtained in Example 1 of this invention. Detailed Implementation

[0035] The present invention will be described below through specific embodiments. Those skilled in the art will understand that the specific embodiments described below are for illustrative purposes only and do not limit the scope of the invention in any way. Furthermore, in the following embodiments, unless otherwise specified, the reagents and equipment used are commercially available. If specific processing conditions and methods are not explicitly described in the following embodiments, conditions and methods known in the art can be used for processing.

[0036] On one hand, the present invention provides a method for preparing Janus-structured silicon carbide / carbon nanofibers, comprising the following steps:

[0037] (1) A silicon carbide precursor, a spinning aid, and a first solvent are mixed to obtain a first spinning solution; a carbon precursor, an organic salt, and a second solvent are mixed to obtain a second spinning solution.

[0038] (2) The first spinning solution and the second spinning solution are electrospun side by side to obtain Janus structure silicon carbide / carbon precursor nanofibers.

[0039] (3) The Janus structure silicon carbide / carbon precursor nanofibers are dried, cured, crosslinked and pyrolyzed at high temperature in sequence to obtain Janus structure silicon carbide / carbon nanofibers.

[0040] This invention employs a side-by-side electrospinning method to obtain Janus-structured silicon carbide / carbon precursor nanofibers. Further drying, curing, crosslinking, and high-temperature pyrolysis yield Janus-structured silicon carbide / carbon nanofibers. These Janus-structured silicon carbide / carbon nanofibers can be used as electrothermal conversion materials and combined with phase change materials to prepare phase change composite materials with excellent thermal conductivity, electrothermal conversion capability, and high-temperature resistance.

[0041] The present invention first mixes a silicon carbide precursor, a spinning aid and a first solvent to obtain a first spinning solution; then mixes a carbon precursor, an organic salt and a second solvent to obtain a second spinning solution.

[0042] In some embodiments of the present invention, the silicon carbide precursor includes at least one of polycarbosilane, polysilazane, polysilane, polysiloxane, and phenyl-modified polycarbosilane, preferably polycarbosilane.

[0043] In some embodiments of the present invention, the spinning aid includes at least one selected from polyacrylonitrile, thermoplastic polyurethane, polyvinylpyrrolidone, polycaprolactone, polylactic acid, polyhydroxyacetic acid, polysulfone, and polystyrene. In the present invention, the spinning aid facilitates the spinning of the silicon carbide precursor into fibers, thus smoothly obtaining the spinning solution of the silicon carbide precursor, i.e., the first spinning solution.

[0044] In some embodiments of the present invention, the first solvent is at least one of N,N-dimethylformamide, tetrahydrofuran, xylene, chloroform, and dichloromethane. Specifically, it can be a mixed solvent of N,N-dimethylformamide and tetrahydrofuran, wherein the volume ratio of the two is 2:8, or a mixed solvent of N,N-dimethylformamide and dichloromethane, wherein the volume ratio of the two is 3:7.

[0045] In some embodiments of the present invention, the content of the silicon carbide precursor in the first spinning solution is 5-15 wt%, specifically 5 wt%, 8 wt%, 10 wt%, 12 wt%, and 15 wt%, etc.; the content of the spinning aid is 1-12 wt%, specifically 1 wt%, 5 wt%, 8 wt%, 9 wt%, 10 wt%, and 12 wt%, etc. In the present invention, the above contents can further ensure complete dissolution of the solute.

[0046] In some embodiments of the present invention, the carbon precursor includes at least one of polyacrylonitrile, pitch polymers, and cellulose.

[0047] In some embodiments of the present invention, the organic salt is a conductive carbide precursor salt, which includes at least one selected from zirconium tetrachloride, zirconium acetylacetonate, zirconium isopropoxide, trimethylzirconium, tetramethoxyzirconium, tetraacetylacetonate, tetraisopropoxyzirconium, and titanium isopropoxide. In the present invention, the organic salt is converted into a metal carbide during high-temperature pyrolysis, thereby significantly improving the conductivity of Janus-structured silicon carbide / carbon nanofibers.

[0048] In some embodiments of the present invention, the second solvent is at least one of N,N-dimethylformamide, tetrahydrofuran, xylene, chloroform, and dichloromethane, preferably N,N-dimethylformamide.

[0049] In some embodiments of the present invention, the carbon precursor content in the second spinning solution is 10-22 wt%, and the organic salt content is 1-15 wt% of the carbon precursor content. In the present invention, the above contents can further ensure complete dissolution of the solute.

[0050] After obtaining the first spinning solution and the second spinning solution, the present invention performs parallel electrospinning of the first spinning solution and the second spinning solution to obtain Janus structure silicon carbide / carbon precursor nanofibers.

[0051] This invention does not specifically limit the particular operation method of the side-by-side electrospinning; conventional side-by-side electrospinning methods can be used. In the embodiments of this invention, the specific method used is as follows: Figure 1 The parallel electrospinning apparatus shown performs parallel electrospinning by adding the first and second spinning solutions into two push syringes connected to the parallel electrospinning needles, respectively, to perform parallel electrospinning.

[0052] In some embodiments of the present invention, the parameters of the side-by-side electrospinning are as follows: the spinning voltage is 12-24kV, specifically 17kV, 18kV, 20kV, 21kV, and 22kV, etc.; the distance from the spinneret to the receiving plate is 10-20cm, specifically 16cm, 18cm, and 20cm, etc.; the propulsion speed of the first spinning solution and the second spinning solution is the same and is 0.01-0.03mL / min, specifically 0.015mL / min, 0.017mL / min, 0.018mL / min, and 0.020mL / min, etc.; the diameter of the two spinnerets of the side-by-side electrospinning needle is 0.7-0.9mm, preferably 0.8mm, and in the embodiments, the side-by-side electrospinning needle consists of two 21G flat-mouth stainless steel spinnerets. In this invention, the above parameters further ensure the successful acquisition of Janus-structured silicon carbide / carbon precursor nanofibers, and the obtained Janus-structured silicon carbide / carbon precursor nanofibers are deposited on the receiving plate to form a thin film (also referred to as Janus-structured silicon carbide / carbon precursor nanofibers in thin film form, or Janus-structured silicon carbide / carbon precursor nanofiber membrane). This invention does not specifically limit the side-by-side electrospinning time; those skilled in the art can select the side-by-side electrospinning time according to the desired thickness of the precursor nanofiber membrane. In the embodiments of the invention, the side-by-side electrospinning time is 6 hours.

[0053] After obtaining Janus-structured silicon carbide / carbon precursor nanofibers, the present invention sequentially dries, cures, crosslinks, and pyrolyzes the Janus-structured silicon carbide / carbon precursor nanofibers to obtain Janus-structured silicon carbide / carbon nanofibers.

[0054] In some embodiments of the present invention, the drying is vacuum drying, and the temperature of the vacuum drying is 55-65°C, preferably 60°C; the time is based on drying to constant weight. In the embodiments of the present invention, the vacuum drying time is 1.5-2.5 hours, preferably 2 hours.

[0055] In some embodiments of the present invention, the curing and crosslinking are carried out in an air atmosphere at a temperature of 180-200°C for 5-7 hours. In the present invention, the above temperature and time further ensure complete curing of the precursor nanofibers.

[0056] In some embodiments of the present invention, the high-temperature pyrolysis is carried out in an inert gas atmosphere, and the temperature of the high-temperature pyrolysis is 1400-1600℃, specifically 1400℃, 1500℃, 1600℃, etc.; the time of the high-temperature pyrolysis is 6-8 hours, specifically 6 hours, 7 hours, 8 hours, etc. In the present invention, during the high-temperature pyrolysis process, the silicon carbide precursor and the carbon precursor decompose at high temperature, generating silicon carbide and carbon respectively, thereby obtaining Janus-structured silicon carbide / carbon nanofibers. In the present invention, the above temperature and time can ensure that the silicon carbide precursor, the carbon precursor, and the organic salt are fully pyrolyzed to form highly conductive Janus-structured silicon carbide / carbon nanofibers. Furthermore, since the Janus-structured silicon carbide / carbon precursor nanofibers form a thin film on the receiving plate, the obtained Janus-structured silicon carbide / carbon nanofibers are also in thin film form.

[0057] On the one hand, the present invention also provides Janus-structured silicon carbide / carbon nanofibers, prepared by any of the preparation methods described in the foregoing technical solutions. In some embodiments of the present invention, the diameter of the Janus-structured silicon carbide / carbon nanofibers is 200-400 nm, that is, the diameter distribution of the obtained Janus-structured silicon carbide / carbon nanofibers is in the range of 200-400 nm.

[0058] On the other hand, the present invention also provides a phase change composite material, comprising a thin film composed of Janus-structured silicon carbide / carbon nanofibers as described in the aforementioned technical solution as the core layer and a phase change material as the surface layer, wherein the phase change material is a nylon elastomer with polytetrahydrofuran ether as the soft segment. In the present invention, the phase change composite material is a sandwich structure of a phase change material layer - a Janus-structured silicon carbide / carbon nanofiber layer - a phase change material layer, wherein the Janus-structured silicon carbide / carbon nanofiber layer has excellent electrical conductivity and electrothermal conversion performance, and the phase change composite material of this sandwich structure also has high thermal conductivity, high electrothermal conversion performance, and high temperature resistance.

[0059] In some embodiments of the present invention, the nylon elastomer includes at least one selected from PA1010-based nylon elastomer, PA1012-based nylon elastomer, PA510-based nylon elastomer, PA512-based nylon elastomer, and PA612-based nylon elastomer. The thickness of the core layer is 0.3-0.5 mm, specifically 0.3 mm, 0.4 mm, and 0.5 mm. The thicknesses of the two surface layers are independently 0.8-1.2 mm, specifically 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, and 1.2 mm, etc. In embodiments of the present invention, the thicknesses of the two surface layers are the same. In the present invention, the phase change composite material with the above-mentioned thickness range has superior thermal conductivity, electrothermal conversion performance, and heat resistance.

[0060] The present invention also provides a method for preparing the phase change composite material described in the above technical solution, comprising the following steps:

[0061] The surface layer, core layer, and surface layer are stacked in sequence and then hot-pressed to obtain a phase change composite material.

[0062] In some embodiments of the present invention, the hot pressing temperature is 180-210°C, specifically 190°C, 195°C, 200°C, 205°C, or 210°C; the hot pressing pressure is 5-15 kg / cm². 2 Specifically, it can be 10 or 15 kg / cm². 2 The hot pressing time is 3-10 minutes, specifically 3 minutes, 5 minutes, 7 minutes, 8 minutes, 10 minutes, etc.

[0063] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. The embodiments of this application are only examples, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0064] Example 1

[0065] (1) Polycarbosilane and thermoplastic polyurethane are dissolved in a mixed solvent of N,N-dimethylformamide and tetrahydrofuran (volume ratio of 2:8) to obtain a first spinning solution, wherein the content of polycarbosilane is 10wt% and the content of thermoplastic polyurethane is 5wt%.

[0066] Polyacrylonitrile and zirconium isopropoxide are dissolved in N,N-dimethylformamide to obtain a second spinning solution, wherein the content of polyacrylonitrile is 14 wt% and the content of zirconium isopropoxide is 0.7 wt% (i.e., 5 wt% of the content of polyacrylonitrile).

[0067] (2) The first spinning solution and the second spinning solution are respectively added to two push syringes connected to parallel electrospinning needles to perform parallel electrospinning. The spinning voltage is 20kV, the push speed of the first spinning solution and the second spinning solution is 0.018mL / min, the distance from the spinneret to the receiving plate is 20cm, the spinning time is 6h, and the parallel electrospinning needles are composed of two 21G flat stainless steel needles to obtain Janus structure silicon carbide / carbon precursor nanofibers. The Janus structure silicon carbide / carbon precursor nanofibers are deposited on the receiving plate to form a thin film.

[0068] (3) The Janus structure silicon carbide / carbon precursor nanofibers were vacuum dried at 60°C for 2 hours, then cured and crosslinked at 190°C in an air atmosphere for 6 hours, and then carbothermally reduced at 1500°C in a nitrogen atmosphere for 7 hours to obtain Janus structure silicon carbide / carbon nanofibers in thin film form, wherein the diameter of the Janus structure silicon carbide / carbon nanofibers is 200-400 nm.

[0069] (4) After stacking the PA1012-based nylon elastomer layer, the Janus-structured silicon carbide / carbon nanofiber in thin film form, and the PA1012-based nylon elastomer layer, the mixture was subjected to a temperature of 190℃ and a pressure of 10 kg / cm². 2 Under the condition of hot pressing for 5 minutes, a phase change composite material was obtained. The thickness of the two PA1012-based nylon elastomer layers of the obtained phase change composite material is 1 mm, and the thickness of the Janus structure silicon carbide / carbon nanofiber is 0.4 mm.

[0070] Example 2

[0071] (1) Polycarbosilane and polycaprolactone are dissolved in a mixed solvent of N,N-dimethylformamide and tetrahydrofuran (volume ratio of 2:8) to obtain a first spinning solution, wherein the content of polycarbosilane is 10wt% and the content of polycaprolactone is 8wt%.

[0072] Polyacrylonitrile and zirconium isopropoxide were dissolved in N,N-dimethylformamide to obtain a second spinning solution, wherein the content of polyacrylonitrile was 16 wt% and the content of zirconium isopropoxide was 1.12 wt% (i.e., 7 wt% of the content of polyacrylonitrile).

[0073] (2) The first spinning solution and the second spinning solution are respectively added to two push syringes connected to parallel electrospinning needles to perform parallel electrospinning. The spinning voltage is 22kV, the push speed of the first spinning solution and the second spinning solution is 0.020mL / min, the distance from the spinneret to the receiving plate is 16cm, the spinning time is 6h, and the parallel electrospinning needles are composed of two 21G flat stainless steel needles to obtain Janus structure silicon carbide / carbon precursor nanofibers. The Janus structure silicon carbide / carbon precursor nanofibers are deposited on the receiving plate to form a thin film.

[0074] (3) The Janus structure silicon carbide / carbon precursor nanofibers were vacuum dried at 60°C for 2 hours, then cured and crosslinked at 190°C in an air atmosphere for 6 hours, and then carbothermally reduced at 1500°C in a nitrogen atmosphere for 7 hours to obtain Janus structure silicon carbide / carbon nanofibers in thin film form, wherein the diameter of the Janus structure silicon carbide / carbon nanofibers is 200-400 nm.

[0075] (4) After stacking the PA510-based nylon elastomer layer, the Janus structured silicon carbide / carbon nanofiber in thin film form, and the PA510-based nylon elastomer layer, the mixture was subjected to a temperature of 210℃ and a pressure of 15 kg / cm². 2 Under the condition of hot pressing for 3 minutes, a phase change composite material was obtained. The thickness of the two PA510-based nylon elastomer layers of the obtained phase change composite material is 1 mm, and the thickness of the Janus structure silicon carbide / carbon nanofiber is 0.4 mm.

[0076] Example 3

[0077] (1) Polycarbosilane and polyvinylpyrrolidone are dissolved in a mixed solvent of N,N-dimethylformamide and tetrahydrofuran (volume ratio of 2:8) to obtain a first spinning solution, wherein the content of polycarbosilane is 10wt% and the content of polyvinylpyrrolidone is 10wt%.

[0078] Polyacrylonitrile and zirconium tetraacetylacetonate were dissolved in N,N-dimethylformamide to obtain a second spinning solution, wherein the content of polyacrylonitrile was 15 wt% and the content of zirconium tetraacetylacetonate was 1.2 wt% (i.e., 8 wt% of the content of polyacrylonitrile).

[0079] (2) The first spinning solution and the second spinning solution were respectively added to two push injectors connected to parallel electrospinning needles to perform parallel electrospinning. The spinning voltage was 17kV, the push speed of the first spinning solution and the second spinning solution was 0.015mL / min, the distance from the spinneret to the receiving plate was 18cm, the spinning time was 6h, and the parallel electrospinning needles were composed of two 21G flat stainless steel needles to obtain Janus structure silicon carbide / carbon precursor nanofibers. The Janus structure silicon carbide / carbon precursor nanofibers were deposited on the receiving plate to form a thin film.

[0080] (3) The Janus structure silicon carbide / carbon precursor nanofibers were vacuum dried at 60°C for 2 hours, then cured and crosslinked at 190°C in an air atmosphere for 6 hours, and then carbothermally reduced at 1500°C in a nitrogen atmosphere for 7 hours to obtain Janus structure silicon carbide / carbon nanofibers in thin film form, wherein the diameter of the Janus structure silicon carbide / carbon nanofibers is 200-400 nm.

[0081] (4) After stacking the PA1010-based nylon elastomer layer, the Janus structured silicon carbide / carbon nanofiber in thin film form, and the PA1010-based nylon elastomer layer, the mixture was subjected to a temperature of 195℃ and a pressure of 10 kg / cm². 2 Under the condition of hot pressing for 7 minutes, a phase change composite material was obtained. The thickness of the two PA1010-based nylon elastomer layers of the obtained phase change composite material is 1 mm, and the thickness of the Janus structure silicon carbide / carbon nanofiber is 0.4 mm.

[0082] Example 4

[0083] (1) Polycarbosilane and polylactic acid are dissolved in a mixed solvent of N,N-dimethylformamide and dichloromethane (volume ratio of 3:7) to obtain a first spinning solution, wherein the content of polycarbosilane is 10wt% and the content of polylactic acid is 9wt%.

[0084] Polyacrylonitrile and tetramethoxyzirconium were dissolved in N,N-dimethylformamide to obtain a second spinning solution, wherein the content of polyacrylonitrile was 15 wt% and the content of tetramethoxyzirconium was 1.2 wt% (i.e., 8 wt% of the content of polyacrylonitrile).

[0085] (2) The first spinning solution and the second spinning solution were respectively added to two push syringes connected to parallel electrospinning needles to perform parallel electrospinning. The spinning voltage was 21kV, the push speed of the first spinning solution and the second spinning solution was 0.017mL / min, the distance from the spinneret to the receiving plate was 18cm, the spinning time was 6h, and the parallel electrospinning needles were composed of two 21G flat stainless steel needles to obtain Janus structure silicon carbide / carbon precursor nanofibers. The Janus structure silicon carbide / carbon precursor nanofibers were deposited on the receiving plate to form a thin film.

[0086] (3) The Janus structure silicon carbide / carbon precursor nanofibers were vacuum dried at 60°C for 2 hours, then cured and crosslinked at 190°C in an air atmosphere for 6 hours, and then carbothermally reduced at 1500°C in a nitrogen atmosphere for 7 hours to obtain Janus structure silicon carbide / carbon nanofibers in thin film form, wherein the diameter of the Janus structure silicon carbide / carbon nanofibers is 200-400 nm.

[0087] (4) After stacking the PA512-based nylon elastomer layer, the Janus-structured silicon carbide / carbon nanofiber in thin film form, and the PA512-based nylon elastomer layer, the mixture was subjected to a temperature of 205℃ and a pressure of 15 kg / cm². 2 Under the condition of hot pressing for 8 minutes, a phase change composite material was obtained. The thickness of the two PA512-based nylon elastomer layers of the obtained phase change composite material is 1 mm, and the thickness of the Janus structure silicon carbide / carbon nanofiber is 0.4 mm.

[0088] Example 5

[0089] (1) Polycarbosilane, polyvinylpyrrolidone and polystyrene are dissolved in a mixed solvent of N,N-dimethylformamide and tetrahydrofuran (volume ratio of 2:8) to obtain a first spinning solution, wherein the content of polycarbosilane is 10wt%, the content of polyvinylpyrrolidone is 3wt% and the content of polystyrene is 6wt%.

[0090] Polyacrylonitrile and titanium isopropoxide were dissolved in N,N-dimethylformamide to obtain a second spinning solution, wherein the content of polyacrylonitrile was 15 wt% and the content of titanium isopropoxide was 0.9 wt% (i.e., 6 wt% of the content of polyacrylonitrile).

[0091] (2) The first spinning solution and the second spinning solution are respectively added to two push injectors connected to parallel electrospinning needles to perform parallel electrospinning. The spinning voltage is 18kV, the push speed of the first spinning solution and the second spinning solution is 0.020mL / min, the distance from the spinneret to the receiving plate is 20cm, the spinning time is 6h, and the parallel electrospinning needles are composed of two 21G flat stainless steel needles to obtain Janus structure silicon carbide / carbon precursor nanofibers. The Janus structure silicon carbide / carbon precursor nanofibers are deposited on the receiving plate to form a thin film.

[0092] (3) The Janus structure silicon carbide / carbon precursor nanofibers were vacuum dried at 60°C for 2 hours, then cured and crosslinked at 190°C in an air atmosphere for 6 hours, and then carbothermally reduced at 1500°C in a nitrogen atmosphere for 7 hours to obtain Janus structure silicon carbide / carbon nanofibers in thin film form, wherein the diameter of the Janus structure silicon carbide / carbon nanofibers is 200-400 nm.

[0093] (4) After stacking the PA612-based nylon elastomer layer, the Janus-structured silicon carbide / carbon nanofiber in thin film form, and the PA612-based nylon elastomer layer, the mixture was subjected to a temperature of 200℃ and a pressure of 15 kg / cm². 2 Under the condition of hot pressing for 10 min, a phase change composite material was obtained. The thickness of the two PA612-based nylon elastomer layers of the obtained phase change composite material is 1 mm, and the thickness of the Janus structure silicon carbide / carbon nanofiber is 0.4 mm.

[0094] Comparative Example 1

[0095] (1) The first spinning solution and the second spinning solution were prepared according to the method of Example 1.

[0096] (2) Use Figure 3 The apparatus shown involves adding the first and second spinning solutions into two separate uniaxial electrospinning needles via a propulsion injector for electrospinning. The spinning voltage is 18 kV, the propulsion speed of both the first and second spinning solutions is 0.020 mL / min, the distance from the spinneret to the receiving plate is 20 cm, the spinning time is 6 h, and the electrospinning needles are two 21G flat-tipped stainless steel needles. The result is a mixed silicon carbide / carbon precursor nanofiber.

[0097] (3)-(4): The mixed silicon carbide / carbon precursor nanofibers were dried, cured, crosslinked and carbotherm reduced in sequence according to the methods of steps (3) and (4) in Example 1 to obtain mixed silicon carbide / carbon nanofibers, and then a phase change composite material was prepared.

[0098] Comparative Example 2

[0099] Phase change composite materials were prepared according to the method of Example 1, except that zirconium isopropoxide was not added to the second spinning solution.

[0100] The structure of the Janus-structured silicon carbide / carbon nanofibers in Example 1 was characterized using transmission electron microscopy, and the results are as follows: Figure 2 As shown, by Figure 2 It can be seen that the two sides of the same nanofiber have a large difference in depth under TEM, indicating that the nanofiber has a Janus structure.

[0101] The electrical conductivity, thermal conductivity, and surface temperature (i.e., the stable temperature) of the phase change composite materials obtained in Examples 1-5 and Comparative Examples 1-2 were tested, and the results are shown in Table 1.

[0102] Table 1. Electrical conductivity and electrothermal conversion properties of the phase change composite materials obtained in Examples 1-5 and Comparative Examples 1-2.

[0103] Example Electrical conductivity (s / cm) Thermal conductivity (W / m·K) Surface temperature (°C) Example 1 7.136 0.4162 186 Example 2 7.021 0.4109 179 Example 3 7.251 0.4218 190 Example 4 7.368 0.4306 194 Example 5 7.232 0.4214 189 Comparative Example 1 4.258 0.3722 125 Comparative Example 2 1.4 0.3233 64

[0104] As shown in Table 1, the electrical conductivity and surface temperature of the phase change composite material obtained by the technical method provided by this invention are much higher than those of Comparative Examples 1-2, indicating that the phase change composite material provided by this invention has excellent electrothermal conversion performance. Furthermore, the testing process revealed that the electrical conductivity distribution of the phase change composite material obtained in Comparative Example 1 was uneven. This is mainly attributed to the random distribution of silicon carbide nanofibers and carbon nanofibers during electrospinning, which prevents them from exerting a synergistic effect.

[0105] The melting temperature, enthalpy of melting, crystallization temperature, and enthalpy of crystallization of the soft segment of the phase change composite material obtained in Example 1 were tested using differential scanning calorimetry. The results were 26.4℃, 64.8 J / g, 10.5℃, and 60.4 J / g, respectively, indicating that the phase change composite material provided by this invention has excellent phase change properties. This invention... Figure 4 The differential scanning calorimetry curve of the phase change composite material obtained in Example 1 is shown in the figure.

[0106] In summary, this invention provides a Janus-structured silicon carbide / carbon nanofiber-based phase change composite material that not only possesses high thermal conductivity, efficient electrothermal conversion capability, high temperature resistance, and excellent phase change performance, but also effectively eliminates dependence on light energy, achieving all-weather thermal management functionality. This facilitates the large-scale preparation of high-performance all-weather phase change composite materials and has strong practical application value.

[0107] Although preferred embodiments of the invention have been shown and described, it is conceivable that those skilled in the art can devise various modifications to the invention within the spirit and scope of the appended claims.

Claims

1. A method for preparing Janus-structured silicon carbide / carbon nanofibers, comprising the following steps: (1) A silicon carbide precursor and a spinning aid are dissolved in a first solvent and mixed to obtain a first spinning solution; a carbon precursor and an organic salt are dissolved in a second solvent and mixed to obtain a second spinning solution. (2) The first spinning solution and the second spinning solution are electrospun side by side to obtain Janus structure silicon carbide / carbon precursor nanofibers. (3) The Janus structure silicon carbide / carbon precursor nanofibers are dried, cured, crosslinked and pyrolyzed at high temperature in sequence to obtain Janus structure silicon carbide / carbon nanofibers.

2. The preparation method according to claim 1, characterized in that, The silicon carbide precursor includes at least one of polycarbosilane, polysilazane, polysilane, polysiloxane, and phenyl-modified polycarbosilane; The spinning aid includes at least one of polyacrylonitrile, thermoplastic polyurethane, polyvinylpyrrolidone, polycaprolactone, polylactic acid, polyglycolic acid, polysulfone, and polystyrene. The first solvent is at least one of N,N-dimethylformamide, tetrahydrofuran, xylene, chloroform, and dichloromethane; In the first spinning solution, the content of the silicon carbide precursor is 5-15 wt%, and the content of the spinning aid is 1-12 wt%.

3. The preparation method according to claim 1, characterized in that, The carbon precursor includes at least one of polyacrylonitrile, pitch polymers and cellulose; The organic salt is a conductive carbide precursor salt, which includes at least one of zirconium tetrachloride, zirconium acetylacetonate, zirconium isopropoxide, trimethylzirconium, tetramethoxyzirconium, tetraacetylacetonate, tetraisopropoxyzirconium, and titanium isopropoxide. The second solvent is at least one of N,N-dimethylformamide, tetrahydrofuran, xylene, chloroform, and dichloromethane; In the second spinning solution, the content of the carbon precursor is 10-22 wt%, and the content of the organic salt is 1-15 wt% of the carbon precursor content.

4. The preparation method according to any one of claims 1-3, characterized in that, The parameters for the parallel electrospinning are as follows: the spinning voltage is 12-24kV, the distance from the spinneret to the receiving plate is 10-20cm, the propulsion speed of the first and second spinning solutions is the same and is 0.01-0.03mL / min, and the diameter of the two spinnerets of the parallel electrospinning needles is 0.7-0.9mm.

5. The preparation method according to any one of claims 1-3, characterized in that, The curing and crosslinking are carried out in an air atmosphere at a temperature of 180-200℃ for 5-7 hours. The high-temperature pyrolysis is carried out in an inert gas atmosphere, and the temperature of the high-temperature pyrolysis is 1400-1600℃, and the time is 6-8h.

6. A Janus-structured silicon carbide / carbon nanofiber, prepared by the preparation method according to any one of claims 1-5.

7. A phase change composite material comprising a thin film of Janus structured silicon carbide / carbon nanofibers as the core layer as described in claim 6 and a phase change material as the surface layer, wherein the phase change material is a nylon elastomer with polytetrahydrofuran ether as the soft segment.

8. The phase change composite material according to claim 7, characterized in that, The nylon elastomer includes at least one of PA1010-based nylon elastomer, PA1012-based nylon elastomer, PA510-based nylon elastomer, PA512-based nylon elastomer, and PA612-based nylon elastomer. The core layer has a thickness of 0.3-0.5 mm; the two surface layers each have a thickness of 0.8-1.2 mm.

9. A method for preparing the phase change composite material according to claim 7 or 8, comprising the following steps: The surface layer, core layer, and surface layer are stacked in sequence and then hot-pressed to obtain a phase change composite material.

10. The preparation method according to claim 9, characterized in that, The hot pressing temperature is 180-210℃, and the pressure is 5-20 kg / cm². 2 The time is 3-10 minutes.

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