阅读说明：本技术 一种链珠状碳化硅纳米材料、制备方法及其应用 (Chain bead-shaped silicon carbide nano material, preparation method and application thereof ) 是由 李杨 庞亮 肖鹏 于 2021-01-13 设计创作，主要内容包括：本发明属于碳化硅纳米材料领域,具体提供一种链珠状碳化硅纳米材料、制备方法及其应用。本专利采用液相法制备前驱体溶液,再通过静电纺丝对溶液在静电力的作用下进行拉拔抽丝获得一维SiC预制体纤维膜,最后通过热处理去除杂质并结晶获得大规模连续一维SiC纳米材料。本发明制备具有链珠状分级结构的一维SiC纳米材料,是作为结构单元或复合组元的优质原料。它所具备的电学性能,在能量存储和转化、传感、光电子以及场辐射等方面具有巨大的应用价值。链珠状的分级结构,有望用于作为基体增强相来提高材料的机械性能。(The invention belongs to the field of silicon carbide nano materials, and particularly provides a chain bead-shaped silicon carbide nano material, a preparation method and application thereof. The preparation method comprises the steps of preparing a precursor solution by a liquid phase method, drawing and spinning the solution under the action of electrostatic force through electrostatic spinning to obtain a one-dimensional SiC prefabricated fiber membrane, and finally removing impurities through heat treatment and crystallizing to obtain the large-scale continuous one-dimensional SiC nano material. The one-dimensional SiC nanometer material with the chain bead-shaped hierarchical structure is a high-quality raw material used as a structural unit or a composite component. The prepared material has the advantages of good electrical properties, and great application value in the aspects of energy storage and conversion, sensing, photoelectron, field radiation and the like. The chain bead-shaped hierarchical structure is expected to be used as a matrix reinforcing phase to improve the mechanical property of the material.)

1. The preparation method of the chain bead-shaped silicon carbide nano material is characterized by comprising the following steps of:

s1, preparation of a pre-spinning solution: the silicon source, the carbon source and the solvent are mixed according to the mass percentage of 3-10: 5-20: 75-92, and uniformly mixing to obtain a pre-spinning solution;

wherein: the solvent comprises a first solvent and a second solvent, the first solvent comprises a carbon source solvent and a silicon source solvent, and the mass percentages of the carbon source solvent and the silicon source solvent are 5-10: 90-95; the solvent II is one of Tween 80 or polyvinyl alcohol mixed with high-purity ethanol, and the mass percentage of the Tween 80 or the polyvinyl alcohol to the high-purity ethanol is 1: 1-5; the solvent I and the solvent II are mixed according to the proportion of 1: 2-4, mixing;

s2, electrostatic spinning: carrying out an electrostatic spinning process on the pre-spinning solution obtained in the step S1 to obtain a one-dimensional SiC nano material prefabricated body fiber membrane;

s3, heat treatment: and (4) drying the one-dimensional SiC nanometer material prefabricated body fiber membrane obtained in the step (S2) and then carrying out heat treatment to obtain the one-dimensional SiC nanometer material with the chain bead-shaped hierarchical structure.

2. The method for preparing the chain bead-shaped silicon carbide nanomaterial as claimed in claim 1, wherein the heat treatment process specifically comprises: heating the dried one-dimensional SiC nano material prefabricated body fiber film from room temperature to 170-250 ℃, wherein the heating rate is 1-3 ℃/min, and the heat preservation time is more than 1 hour; vacuumizing, filling inert gas, maintaining the pressure in the furnace to be greater than atmospheric pressure, continuously heating to 600-850 ℃, heating at the rate of 1-3 ℃/min, and keeping the temperature for 1-5 hours; and continuously heating to 1200-1450 ℃, keeping the temperature at the heating rate of 1-5 ℃/min, keeping the temperature for 1-5 h, and finally cooling to room temperature along with the furnace.

3. The method as claimed in claim 1, wherein in step S1, the silicon source is at least one of Polymethylsilane (PMS) and Polycarbosilane (PCS).

4. The method of claim 1, wherein in step S1, the carbon source is at least one of Polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP).

5. The method for preparing the chain bead-shaped silicon carbide nanomaterial according to claim 1, wherein in the step S1, the first solvent and the second solvent are stirred at a constant temperature of 10-80 ℃ for 0.5-6 h to obtain a mixed solvent.

6. The method for preparing the chain bead-shaped silicon carbide nanomaterial according to claim 1, wherein in step S1, the silicon source, the carbon source and the solvent are mixed and stirred at room temperature for 2-24 hours to obtain a pre-spinning solution.

7. The method for preparing the chain bead-shaped silicon carbide nanomaterial according to claim 1, wherein in the step S2, the electrostatic spinning process specifically comprises the following steps: the pre-spinning solution is placed in an injector, the spinning space is a closed space, an electrostatic voltage anode is connected between the injector needles, an aluminum plate rotating drum is connected with a cathode, the voltage of two ends is 8-21 KV, the central linear distance between the anode and the cathode is 12-24 cm, the propelling speed of the injector is 0.8-1.5 ml/h, and the relative humidity of the environment is 20-60%.

8. The method for preparing the chain bead-shaped silicon carbide nanomaterial according to claim 1, wherein in the step S3, the internal pressure is 5-15 KPa greater than the atmospheric pressure.

9. The silicon carbide nanomaterial prepared by the method for preparing the chain bead-shaped silicon carbide nanomaterial of any one of claims 1 to 8.

10. The application of the silicon carbide nanomaterial prepared by the preparation method of the chain bead-shaped silicon carbide nanomaterial disclosed by any one of claims 1-8 in catalyst carriers, electromagnetic wave absorption, hydrogen storage, functional composite materials, heat insulation materials, high-temperature sensors and supercapacitors.

Technical Field

The invention belongs to the field of silicon carbide nano materials, and particularly relates to a chain bead-shaped silicon carbide nano material, a preparation method and application thereof.

Background

In the prior art, the main trend of obtaining high-performance functional materials is to make materials into nanometer, in particular to functional elements of devices applied in the fields of energy, medicine, environmental protection and the like. As an emerging semiconductor material, SiC exhibits different electromagnetic properties in various nanostructures, and has been primarily used. The one-dimensional SiC nano material has various excellent performances, and particularly has more advantages than a micron material and other nano structures in the aspects of mechanical and electrical properties. The gas phase method and the liquid phase method are effective means for preparing the one-dimensional SiC nanometer material, and the one-dimensional nanometer structures with different structures can be obtained by regulating and controlling different process parameters. Meanwhile, the electrostatic spinning technology is an effective means for continuously preparing long-range one-dimensional nano materials on a large scale. In addition, the one-dimensional SiC nanometer material can be compounded with other materials, so that the mechanical property and the electrical property of the whole material are improved, and the requirement of practical application is met.

One-dimensional nanomaterials, such as nanowires/nanorods, nanoneedles, nanotubes, nanorods, etc., exhibit great potential application values in the fields of mechanics, thermal, optics, electromagnetism, etc., due to their unique aspect ratios and physicochemical properties, and have received much attention in the last decade. At present, one-dimensional nano materials are commonly used as functional or structural elements of nano devices such as energy storage and conversion, sensing, photoelectron, field radiation and the like.

As a new member of the semiconductor family, one-dimensional SiC nanomaterials exhibit broadband semiconductor characteristics, and are therefore expected to be semiconductor materials with greater prospects than Si. In addition, the one-dimensional SiC nanometer material has the characteristics of better mechanical property, lower conductivity threshold, easier compounding with other materials and the like compared with micron materials. Various advantages show that the one-dimensional SiC nanometer material is an ideal material for electronic and optoelectronic nanometer devices, and has great potential application value in the aspects of storage, conversion and absorption of electromagnetic energy.

At present, the preparation methods of one-dimensional SiC nano materials at home and abroad are mainly divided into a gas phase method and a liquid phase method. The vapor phase method is to crack a pre-set precursor compound under high temperature conditions, nucleate and grow on the substrate and form a nanostructure during the cooling process. Many factors are considered, including the preparation of raw materials, the type of catalyst, the cracking temperature of the precursor, the time for the precursor to turn into steam, the used carrier gas, the pressure of the surrounding environment, the cooling rate in the nucleation process, the combination of the nanostructure and the substrate and the like, and all are effective means for preparing the superfine nanostructure and the high-precision nanomaterial. Obviously, the synthesis of the one-dimensional SiC nano material by the vapor phase method needs to be carried out at high temperature, has higher requirements on the high temperature resistance (generally over 1200 ℃) and the pressure resistance of equipment, and has more rigorous process conditions, thereby greatly increasing the preparation cost. Compared with a gas phase method, the liquid phase method does not need the harsh conditions, and is an effective means for preparing the one-dimensional SiC nanometer material closer to practical application. At present, a plurality of researchers have successfully prepared one-dimensional SiC nanometer materials with various shapes by a water bath method and electrochemical etching. However, the nanostructures synthesized by the above methods are mainly distributed on the surface of the substrate, and have certain limitations for large-scale preparation and application.

Disclosure of Invention

The technical problem to be solved by the invention is to overcome the defects and shortcomings in the background technology and provide a preparation method of the chain bead-shaped silicon carbide nano material with short process period, low requirement on preparation conditions and large finished product quantity. The method successfully obtains the one-dimensional SiC nano material with the chain bead hierarchical structure by controlling the process parameters.

Another purpose of the invention is to provide a chain bead-shaped silicon carbide nanometer material with great application value in the aspects of energy storage and conversion, sensing, photoelectron, field radiation and the like.

The invention also aims to provide application of the chain bead-shaped silicon carbide nano material in catalyst carriers, electromagnetic wave absorption, hydrogen storage, functional composite materials, heat insulation materials, high-temperature sensors and supercapacitors.

In order to achieve the purpose, the technical scheme of the invention is as follows:

the invention discloses a preparation method of a chain bead-shaped silicon carbide nano material, which comprises the following steps:

s1, preparation of a pre-spinning solution: the silicon source, the carbon source and the solvent are mixed according to the mass percentage of 3-10: 5-20: 75-92, and uniformly stirring to obtain a pre-spinning solution;

wherein: the solvent comprises a first solvent and a second solvent, the first solvent comprises a carbon source solvent and a silicon source solvent, and the mass percentages of the carbon source solvent and the silicon source solvent are 5-10: 90-95; the solvent II is one of Tween 80 or polyvinyl alcohol mixed with high-purity ethanol, and the mass percentage of the Tween 80 or the polyvinyl alcohol to the high-purity ethanol is 1: 1-5; the solvent I and the solvent II are mixed according to the proportion of 1: 2-4, mixing;

s2, electrostatic spinning: carrying out an electrostatic spinning process on the pre-spinning solution obtained in the step S1 to obtain a one-dimensional SiC nano material prefabricated body fiber membrane;

s3, heat treatment: and (4) drying the one-dimensional SiC nano material preform fiber membrane obtained in the step (S2), and then carrying out stage heat treatment to obtain the one-dimensional SiC nano material with a chain bead hierarchical structure.

Further, the heat treatment process specifically comprises the following steps: heating the dried one-dimensional SiC nano material prefabricated body fiber film from room temperature to 170-250 ℃, wherein the heating rate is 1-3 ℃/min, and the heat preservation time is more than 1 hour; vacuumizing, filling inert gas (nitrogen or Ar gas), maintaining the pressure in the furnace to be greater than atmospheric pressure, continuously heating to 600-850 ℃, heating at the speed of 1-3 ℃/min, and keeping the temperature for 1-5 hours; and continuously heating to 1200-1450 ℃, keeping the temperature at the heating rate of 1-5 ℃/min, keeping the temperature for 1-5 h, and finally cooling to room temperature along with the furnace to obtain the one-dimensional SiC nano material with the chain bead-shaped hierarchical structure.

Preferably, in step S1, the silicon source is at least one of Polymethylsilane (PMS) and Polycarbosilane (PCS).

Preferably, in step S1, the carbon source is at least one of Polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP).

Preferably, in the step S1, the solvent I and the solvent II are stirred for 0.5 to 6 hours at a constant temperature of 10 to 80 ℃ to obtain a mixed solvent.

Preferably, in step S1, the silicon source, the carbon source, and the solvent are mixed and stirred at room temperature for 2 to 24 hours to obtain a pre-spinning solution.

As a preferable scheme of the scheme, in step S1, the mass percentages of the carbon source solvent and the silicon source solvent in the solvent are 1: 9; the mass percentage of the tween 80 (or polyvinyl alcohol) and the high-purity ethanol is 1: 4; the solvent I and the solvent II are mixed according to the proportion of 1: 3, mixing; mixing the pre-spinning solvent with PAN and PCS according to the mass ratio of 86.1 wt%, 4.1 wt% and 9.8 wt%, and magnetically stirring and mixing for 12 hours at room temperature to obtain a pre-spinning solution.

Preferably, in step S2, the electrospinning process specifically includes: the pre-spinning solution is placed in an injector, the spinning space is a closed space, an electrostatic voltage anode is connected between the injector needles, a cylindrical aluminum plate rotating drum is connected with a cathode, the voltage of two ends is 8-21 KV, the central linear distance between the anode and the cathode is 12-24 cm, the propelling speed of the injector is 0.8-1.5 ml/h, and the relative humidity of the environment is 20-60%.

Preferably, in step S3, the internal pressure is 5 to 15 KPa greater than the atmospheric pressure.

The invention also discloses a silicon carbide nano material prepared by the preparation method of the chain bead-shaped silicon carbide nano material.

The invention also discloses application of the silicon carbide nano material prepared by the preparation method of the chain bead-shaped silicon carbide nano material in catalyst carriers, electromagnetic wave absorption, hydrogen storage, functional composite materials, heat insulation materials, high-temperature sensors and supercapacitors.

Compared with the prior art, the invention has the following beneficial effects:

the invention adopts electrostatic spinning to prepare the one-dimensional SiC nano material, has the advantages of short process period, low requirement on preparation conditions, large finished product quantity and the like, and solves the problem of high preparation price of the one-dimensional nano material in the aspect of preparation process.

The invention can well regulate and control the size and the appearance of the one-dimensional nano material by controllable solution concentration, electrostatic spinning process and matching with heat treatment conditions, and obtains the chain bead-shaped hierarchical structure from the size and the appearance:

(1) in the solution proportioning process, Polycarbosilane (PCS) is preferably adopted as an organic precursor Si source, so that the PCS has rich carbon sources, and the sufficient guarantee of required elements is provided for synthesizing SiC by pyrolysis. And secondly, polycarbosilane is not dissolved in N, N-Dimethylformamide (DMF) and can be well dissolved in Chloroform (CF), and the mixing of the polycarbosilane and a solution with the proportion of polyacrylonitrile and DMF is realized by preparing a mixed solubilizer of Tween 80 or polyvinyl alcohol and high-purity ethanol, and the viscosity control of a pre-spinning solution can be well realized. Finally, the solution is preferably mixed and stirred at 50 ℃ which is different from normal temperature, so that the organic precursor can be fully and uniformly mixed below the glass transition temperature;

(2) in the electrostatic spinning process, the spinning voltage is 8-21 KV, the center linear distance between a positive electrode and a negative electrode is 12-24 cm, the propelling speed of an injector is 0.8-1.5 ml/h, and the relative humidity of the environment is 20-60%, so that a set of spinning process formed under the precondition of the solution proportioning process in the step (1) is a necessary process for forming a chain bead-shaped structure;

(3) the invention provides a final synthesis means of a one-dimensional SiC nano material based on the electrostatic spinning process in the steps (1) and (2), and the fiber membrane with the corresponding morphology is subjected to heat treatment.

The three processes are all indispensable in the process of preparing the one-dimensional SiC nano material, have synergistic effect, and are necessary conditions for realizing controllable preparation conditions, uniform product structure and excellent performance.

The one-dimensional SiC nanometer material with the chain bead-shaped hierarchical structure is a high-quality raw material used as a structural unit or a composite component. The prepared material has the advantages of good electrical properties, and great application value in the aspects of energy storage and conversion, sensing, photoelectron, field radiation and the like. The chain bead-shaped hierarchical structure is expected to be used as a matrix reinforcing phase to improve the mechanical property of the material.

Drawings

FIG. 1a is an optical morphology diagram of a one-dimensional SiC nanomaterial preform fiber membrane prepared by electrostatic spinning treatment of the preparation method of the chain bead-shaped silicon carbide nanomaterial of the present invention.

FIG. 1b is an optical morphology of a fiber membrane after pre-oxidation according to the preparation method of the chain bead-shaped silicon carbide nanomaterial.

FIG. 1c is an optical morphology of the material after high temperature treatment of the pre-oxidized preform fiber of the preparation method of the chain bead-shaped silicon carbide nanomaterial of the present invention.

FIG. 2a is a microscopic micrograph of the pre-oxidized preform fiber film of FIG. 1 b.

FIG. 2b is a microscopic topographic map of the pre-oxidized preform fiber of FIG. 1c after high temperature treatment.

Figure 2c is an EDS energy spectrum from the area enlarged in figure 2 b.

Figure 3 is an XRD pattern from the enlarged area of figure 2 b.

FIG. 4 is a micrograph of a product of chain bead-like silicon carbide nanomaterial described in example 2.

FIG. 5 is a micrograph of a product of chain bead-like silicon carbide nanomaterial described in example 3.

FIG. 6 is a micrograph of a product of chain bead-like silicon carbide nanomaterial described in example 4.

Fig. 7 is a picture of the configuration of the pre-spinning solution in comparative example 1.

FIG. 8 is a topographical map of the final product of comparative example 2.

FIG. 9 is a topographical map of the final product of comparative example 3.

FIG. 10 is a topographical map of the final product of comparative example 4.

Detailed Description

In order to facilitate an understanding of the invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the specific embodiments below.

Unless otherwise defined, all terms of art used hereinafter have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention.

Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.

Example 1

The embodiment provides a preparation method of a one-dimensional SiC nano material with a chain bead-shaped hierarchical structure, which comprises the following steps:

s1, preparation of pre-spinning solution

S1-1. solute allocation

(1) Carbon source: polyacrylonitrile (PAN): 4.1 wt% (mass percent);

(2) silicon source: polycarbosilane (PCS): 9.8 wt% (mass percent).

S1-2. solvent preparation:

content of Pre-spinning solvent (remainder of total solution, solvent in this place is mixed solvent of solvent one and solvent two, percentage is percentage of each solvent formulation, percentage of non-total solution)

The solvent content is divided into two parts:

(1) a first solvent: n, N-Dimethylformamide (DMF) is taken as a carbon source solvent: 10 wt% (mass percent); xylene is a silicon source solvent: 90 wt% (mass percent);

(2) and a second solvent: the solvent is a solubilizer which is a mixed solvent of tween 80 and high-purity ethanol, and the ratio of the tween 80 to the high-purity ethanol is 1: 4;

mixing a first solvent and a second solvent according to a ratio of 1: 3 stirring for 2h in a magnetic stirrer at constant temperature of 50 ℃ to obtain a precursor solvent,

and mixing the obtained precursor solvent with PAN and PCS according to the mass ratio of 86.1 wt%, 4.1 wt% and 9.8 wt%, and magnetically stirring and mixing at room temperature for 12 hours to obtain a pre-spinning solution.

S2, electrostatic spinning:

and (3) placing the pre-spinning solution obtained in the step (S1) into a 21G injector, connecting an electrostatic voltage anode between injector needles in a closed space with a spinning space of 60cm x 50cm, connecting a cylindrical aluminum plate rotating drum with a cathode connected at two ends of 8-21 KV, keeping the center linear distance between the anode and the cathode at 12-24 cm, and controlling the propelling speed of the injector to be 0.8-1.5 ml/h and the relative humidity of the environment to be 20-60%. The optical appearance of the fiber film of the one-dimensional SiC nano material preform spun by the spinning method is shown in FIG. 1a, and the fiber film can be known as a white fiber film, and the surface of the white fiber film is uniform and dense.

S3, heat treatment:

and (4) placing the one-dimensional SiC nano material preform fiber membrane obtained in the step S2 in a forced air drying oven at 80 ℃ for 12h to remove the solvent, and then placing the fiber membrane in a vacuum sintering furnace for heat treatment.

The specific heat treatment process comprises the following steps: the temperature is raised to 150 ℃ at the rate of 2 ℃/min; 150 ℃ to 250 ℃, a heating rate of 1 ℃/min, and then holding for two hours. The fiber film after the partial pre-oxidation process is taken out, the optical appearance of the fiber film is shown as figure 1b, the fiber film is yellow or brown, and the fiber film can show extremely excellent flexibility under the action of stress. The microscopic morphology is shown in FIG. 2a, and the fibers are in a chain bead-like structure.

Vacuumizing, filling argon (Ar) as protective gas, maintaining the pressure in the furnace to be higher than the atmospheric pressure by 8 KPa, continuously heating to 850 ℃, heating at the rate of 1 ℃/min, and keeping the temperature for 2 hours; and continuously heating to 1350 ℃, keeping the temperature at the heating rate of 2 ℃/min for 5h, and finally cooling to room temperature along with the furnace to finally obtain the one-dimensional SiC nano material with the chain bead-shaped hierarchical structure. The optical appearance and the microscopic appearance of the chain bead are respectively shown in fig. 1c and fig. 2b, the chain bead is a tan or black fiber membrane under the optical appearance, certain flexibility is shown, the diameter of the chain bead fiber after high-temperature heat treatment is smaller than that of pre-oxidized chain bead, and the surface of the chain bead is uniform, smooth and compact.

As can be seen from the enlarged region of FIG. 2b, the SiC fibers have a distinct bead-like hierarchical structure (such as bead-like necklace shown in the figure), and the beads of the material obtained by the present invention have a diameter of about 1-2 um and are uniformly distributed. The EDS spectrum of this region (fig. 2C) shows that the main elements of the bead SiC are carbon (C), silicon (Si), and oxygen (O), the mass percentages of which are 30.06%, 64.17%, and 5.76%, and the atomic percentages of which are 48.62%, 44.38%, and 7.00%, respectively, and that a portion of the oxygen element is present because the bead SiC is slightly oxidized, but does not affect the overall performance. From the XRD pattern (fig. 3), it can be seen that the phase of the beads SiC is β -silicon carbide and is free of any other impurities, in comparison to the standard PDF Card (ICCD Card 65-0360).

Example 2

Example 2 is basically the same as example 1, except that: the polyacrylonitrile content is adjusted to be 3 percent, the polycarbosilane content is adjusted to be 12 percent, namely, the ratio of the silicon source to the carbon source is increased.

Wherein, S1-2. solvent preparation:

content of Pre-spinning solvent (remainder of total solution, solvent in this place is mixed solvent of solvent one and solvent two, percentage is percentage of each solvent formulation, percentage of non-total solution)

The solvent content is divided into two parts:

(1) a first solvent: n, N-Dimethylformamide (DMF) is taken as a carbon source solvent: 10 wt% (mass percent); xylene is a silicon source solvent: 90 wt% (mass percent);

(2) and a second solvent: the solvent is a solubilizer which is a mixed solvent of tween 80 and high-purity ethanol, and the ratio of the tween 80 to the high-purity ethanol is 1: 5;

mixing a first solvent and a second solvent according to a ratio of 1: 2 stirring for 2h in a magnetic stirrer at constant temperature of 50 ℃ to obtain a precursor solvent,

and mixing the obtained precursor solvent with PAN and PCS according to the mass ratio of 85wt%, 3wt% and 12 wt%, and magnetically stirring and mixing for 12 hours at room temperature to obtain a pre-spinning solution.

The final microscopic morphology of the product is shown in FIG. 4, and it can be seen that the product is also chain bead-like, but compared with example 1, the chain beads have irregular shapes and cracks on the surface.

Example 3

Example 3 is basically the same as example 1, except that: the polyacrylonitrile content is adjusted to 5.2%, the polycarbosilane content is adjusted to 8.3%, namely the ratio of the silicon source to the carbon source is reduced. The final microscopic morphology of the product is shown in fig. 5, and it can be seen that the product is also chain bead-shaped structure, but compared with example 1, the joints between the chain beads are wider and thicker, and the phenomenon of chain bead agglomeration and agglomeration exists.

Example 4

Example 4 is basically the same as example 1, except that: the polyacrylonitrile content is adjusted to 10 percent, the polycarbosilane content is adjusted to 20 percent, namely, the integral proportion of the silicon source and the carbon source is greatly increased.

In the solvent configuration:

(1) a first solvent: n, N-Dimethylformamide (DMF) is taken as a carbon source solvent: 5wt% (mass percent); xylene is a silicon source solvent: 95 wt% (mass percent);

(2) and a second solvent: the solvent is a solubilizer which is a mixed solvent of polyvinyl alcohol and high-purity ethanol, and the ratio of the polyvinyl alcohol to the high-purity ethanol is 1: 1;

mixing a first solvent and a second solvent according to a ratio of 1:4 stirring for 2 hours in a magnetic stirrer at constant temperature of 50 ℃ to obtain a precursor solvent,

and mixing the obtained precursor solvent with PAN and PCS according to the mass ratio of 70 wt%, 10 wt% and 20 wt%, and magnetically stirring and mixing for 12 hours at room temperature to obtain a pre-spinning solution.

The final microscopic morphology of the product is shown in fig. 6, but compared with example 1, due to the excessively high concentrations of the carbon source and the silicon source, the secondary chain bead structures between the fibers are coagulated and gradually disappear, and the overall diameter of the fibers is increased due to the reduction of the solvent.

Comparative example 1

This comparative example is substantially identical to example 1, except that, in step S1, solvent two or high purity ethanol was absent. As shown in fig. 7, the carbon source and the silicon source are not sufficiently dissolved in the solvent.

Comparative example 2

The comparative example is substantially the same as example 1, except that in step S1, the silicon source, the carbon source, and the solvent are, in mass percent, 0: 10: 90, and the mass percentages of the carbon source solvent and the silicon source solvent are 100: 0, no solvent II is added, and the rest steps are the same as the steps in the example 1, namely the product is pure carbon fiber. The morphology of the final product is shown in fig. 8, and the product can be found to be carbon fiber with uniform diameter and no continuous chain bead-shaped secondary structure is generated.

Comparative example 3

The comparative example is substantially the same as example 1, except that in step S1, the silicon source, the carbon source, and the solvent are, in mass percent, 15: 0: 85, and the rest steps are the same as those in the embodiment 1, namely the product is pure silicon carbide fiber, and the mass percentages of the carbon source solvent and the silicon source solvent are 0: 100, no addition of solvent two, the rest of the procedure was the same as in example 1. The morphology of the final product is shown in fig. 9, the product is silicon carbide fiber with uniform diameter, and no continuous chain bead-shaped secondary structure is generated.

Comparative example 4

The comparative example is basically the same as the example 1, and is different from the example 1 in that the specific heat treatment process of the heat treatment of S3 is as follows: heating the dried one-dimensional SiC nano material prefabricated body fiber membrane from room temperature to 250 ℃, wherein the heating rate is 1 ℃/min, and the heat preservation is carried out for 3 hours; vacuumizing, filling inert gas, maintaining the pressure in the furnace to be higher than atmospheric pressure, continuously heating to 1450 ℃, heating at a rate of 3 ℃/min, keeping the temperature for 2h, and finally cooling to room temperature along with the furnace. Namely, the heat treatment process is not carried out at 850 ℃, the appearance of the final product is shown in figure 10, the sample which is not subjected to the heat treatment at 850 ℃ has an overburning phenomenon, and the chain bead-shaped secondary structure is melted and disappears at high temperature.

The invention also provides a silicon carbide nano material prepared by the preparation method of the chain bead-shaped silicon carbide nano material, and the chain bead-shaped silicon carbide nano material is prepared by the method of the embodiment 1-4. The SiC fiber has obvious chain bead-shaped hierarchical structure, the diameter of chain beads is about 1-2 um, and the chain beads are uniformly distributed.

The one-dimensional SiC nanometer material with the chain bead-shaped hierarchical structure is a high-quality raw material used as a structural unit or a composite component. The prepared material has the advantages of good electrical properties, and great application value in the aspects of energy storage and conversion, sensing, photoelectron, field radiation and the like. The chain bead-shaped hierarchical structure is expected to be used as a matrix reinforcing phase to improve the mechanical property of the material.

The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.