CN110028070B - Single crystal silicon carbide/graphene core-shell structure nanofiber and preparation method and application thereof - Google Patents
Single crystal silicon carbide/graphene core-shell structure nanofiber and preparation method and application thereof Download PDFInfo
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Abstract
The invention provides a single crystal silicon carbide/graphene core-shell structure nanofiber as well as a preparation method and application thereof, wherein the preparation method comprises the following steps: (1) uniformly mixing a carbon source and white carbon black by a wet method, wherein C in the carbon source and SiO in the white carbon black2The molar ratio of (3-4) to 1, and drying after reaction to obtain a precursor; (2) performing a carbothermic reduction reaction on the precursor obtained in the step (1) in an atmosphere heating furnace at 1400-1600 ℃ for 1-4h to obtain a crude product; (3) and (3) removing impurities from the crude product obtained in the step (2) by adopting an acid pickling soaking and liquid-solid separation method, and drying to obtain the single crystal silicon carbide/graphene core-shell structure nanofiber. The invention belongs to the field of nano materials, has short process flow and simple required equipment and operation, can realize the large-scale preparation of high-performance nano fiber reinforced phase materials, and has good industrial prospect. The single crystal silicon carbide/graphene core-shell structure nanofiber prepared by the method can be used as a reinforcing and toughening phase of a ceramic material, a high polymer material or a metal material.
Description
Technical Field
The invention belongs to the field of novel nano materials, and relates to a preparation method and application of single crystal silicon carbide/graphene core-shell structure nano fibers.
Background
The SiC fiber is a common high-temperature resistant material and a common reinforcing material, has very beneficial mechanical properties at normal temperature and high temperature, and is widely applied to various composite materials. Researchers have developed a series of processes for preparing fibrous SiC, such as carbothermic, Chemical Vapor Deposition (CVD), arc discharge, silane organic decomposition, laser ablation, solvothermal, magnesiothermic reduction, and the like. However, the widespread use of these methods also faces some limitations: the chemical vapor deposition method has the advantages of complex equipment, long flow path and high requirement on the purity of raw materials; the arc discharge method and the laser ablation method are expensive; the raw materials for the silane organic matter decomposition method have high toxicity; the solvent thermal reaction method and the magnesiothermic reduction method have low product purity and poor process repeatability. In contrast, the carbothermic process is considered to be the most economically feasible due to its high yield, low cost and ease of operation. Briefly, the carbothermic reduction reaction isReduction of SiO with a carbon source at elevated temperatures2And preparing SiC. Despite the significant progress made in recent years in the research on the preparation of SiC by carbothermic reduction, there is still a great room for further perfecting the preparation process of SiC fibers and improving the product properties from an industrial point of view.
The SiC single crystal fiber has few internal defects in crystal lattices, and has quite good high-temperature resistance, strength and toughness. Graphene is the most interesting two-dimensional material in recent years, not only is one of the materials with the highest known strength, but also has good toughness and can be bent, the theoretical young modulus of graphene reaches 1.0 TPa, and the inherent tensile strength is 130 GPa. In addition, the graphene has very good compatibility and matching property with ceramic materials, high polymer materials and metal materials, has the interlayer sliding property like graphite, and can improve the contact interface property between SiC fibers and various matrixes.
At present, research indicates that in a high-temperature environment, Si atoms on the surface of SiC powder can be volatilized out first due to high activity, and residual C atoms can form a graphene film with a good structure and uniform coating through a self-assembly process under a high-temperature condition. If the single crystal silicon carbide/graphene core-shell structure nanofiber can be prepared, the single crystal silicon carbide/graphene core-shell structure nanofiber can have very excellent reinforcing and toughening effects when applied to various composite materials (ceramic base, polymer base, metal base and the like).
Disclosure of Invention
The invention aims to provide a preparation method of single crystal silicon carbide/graphene core-shell structure nanofibers, which is short in process flow, simple in required equipment and operation, capable of realizing large-scale preparation of high-performance nanofiber reinforced phase materials and good in industrial prospect.
The invention also provides the single crystal silicon carbide/graphene core-shell structure nanofiber.
The invention also provides application of the single crystal silicon carbide/graphene core-shell structure nanofiber, mainly in the aspect of reinforcing and toughening phases in composite materials.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a preparation method of single crystal silicon carbide/graphene core-shell structure nano fibers comprises the following steps:
(1) uniformly mixing a carbon source and white carbon black by a wet method, wherein the molar ratio of C in the carbon source to SiO2 in the white carbon black is (3-4) to 1, and drying after reaction to obtain a precursor;
(2) performing a carbothermic reduction reaction on the precursor obtained in the step (1) in an atmosphere heating furnace at 1400-1600 ℃ for 1-4h to obtain a crude product;
(3) and (3) removing impurities from the crude product obtained in the step (2) by adopting an acid pickling soaking and liquid-solid separation method, and drying to obtain the single crystal silicon carbide/graphene core-shell structure nanofiber.
Preferably, the carbon source in step (1) is selected from activated carbon, carbon black or any mixture of the activated carbon and the carbon black.
Preferably, the white carbon black in the step (1) is nano powder with the content of SiO2 being more than 99%; the average particle size of the white carbon black is less than 100 nm; the specific surface area of the white carbon black is more than 200 m 2/g.
Preferably, the wet ball milling is adopted for the wet uniform mixing in the step (1), the liquid phase of the wet ball milling is water, and the liquid-solid volume-mass ratio is 10-50 mL/g; and simultaneously adding 0.2-0.5 mg/mL of dispersant, wherein the dispersant is selected from sodium hexametaphosphate or carboxymethyl cellulose.
Preferably, the ball milling medium of the wet ball milling is silicon carbide balls, and the mass ratio of the balls to the materials is 5-50; the rotation speed of the wet ball milling is 200-600 rpm, and the ball milling time is 10-60 min.
Preferably, the slurry after wet ball milling is dried (drying, freeze drying or vacuum drying is adopted), and the water content of the dried precursor is less than 1 wt%.
Preferably, the carbothermic reduction reaction of step (2) is carried out in an inert gas atmosphere at a pressure of 10 < -4 > to 10 < -3 > Pa; and the inert gas is argon.
Preferably, the step (3) adopts acid pickling soaking and liquid-solid separation to remove impurities as follows;
soaking the crude product in 5-40% hydrofluoric acid solution at 10-40 deg.C for 30-120 min, wherein the liquid-solid volume/mass ratio of the acid solution to the crude product is 3-10 mL/g;
removing unreacted SiO2 by acid washing, removing unreacted impurity C by flotation, performing liquid-solid separation, repeatedly washing the separated solid by using water or alcohol after separation, and drying at 50-100 ℃ until the water content is less than 1wt% to obtain the single crystal silicon carbide/graphene core-shell structure nanofiber.
The single crystal silicon carbide/graphene core-shell structure nanofiber prepared by the preparation method.
The single crystal silicon carbide/graphene core-shell structure nanofiber is applied to reinforcing and toughening phases of ceramic materials, high polymer materials or metal materials.
The preparation principle of the invention is as follows:
firstly, in-situ nucleation growth of the silicon carbide whisker occurs, the white carbon black is reduced into silicon carbide crystal nucleus by a carbon source through carbothermic reduction reaction, and the silicon carbide crystal nucleus is grown into silicon carbide single crystal fiber according to a V-L-S mechanism; in the heat preservation process, Si atoms on the surface of the silicon carbide single crystal fibers are volatilized out due to higher activity in a high-temperature environment in the furnace, and residual C atoms can form a graphene film with a good structure and uniform coating through a self-assembly process under a high-temperature condition.
According to the invention, a plurality of material synthesis steps of carbon thermal reduction reaction, surface Si vacancy generation and diffusion, surface C atom self-assembly and the like are coupled in the same reactor, and the finished product has a compact silicon carbide/graphene heterogeneous interface generated in situ, so that the finished product nanofiber has good compatibility with a ceramic matrix, a polymer matrix or a metal matrix, and the reinforcing and toughening performance of the finished product is ensured.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention adopts an in-situ nucleation growth method, and a compact silicon carbide/graphene heterogeneous interface is generated in situ, so that the prepared single crystal silicon carbide/graphene core-shell structure nanofiber has good reinforcing and toughening properties.
2. The diameter of the prepared single crystal silicon carbide/graphene core-shell structure nanofiber is less than 100nm, and the length of the prepared single crystal silicon carbide/graphene core-shell structure nanofiber can reach tens of microns. The fiber core part is silicon carbide single crystal, and the mechanical property of the fiber is better than that of common polycrystal or amorphous fiber; the outer shell layer of the fiber is graphene, so that the fiber can be protected from oxidation and corrosion erosion, and meanwhile, the toughness of the fiber and the compatibility with a blank are improved. The product of the invention is suitable for being used as a novel reinforcing and toughening material of ceramic materials, high polymer materials or metal materials.
3. The preparation method is simple and easy to implement, low in sintering energy consumption and low in equipment requirement, and is suitable for industrial production.
4. The invention has the advantages of low cost of raw materials and process, high added value of products and good economic benefit.
Drawings
FIG. 1 is a process flow diagram (also shown in the abstract) for preparing single crystal silicon carbide/graphene core-shell structured nanofibers according to the present invention;
FIG. 2 is an SEM image of single-crystal silicon carbide/graphene core-shell structure nanofibers prepared in example 1 of the present invention;
FIG. 3 is an HR-TEM image of the single crystal silicon carbide/graphene core-shell structure nanofiber prepared in example 1 of the present invention;
FIG. 4 is a SAED diagram of a single-crystal silicon carbide/graphene core-shell structured nanofiber prepared in example 1 of the present invention;
fig. 5 is a raman spectrum of the single crystal silicon carbide/graphene core-shell structured nanofiber prepared in example 1 of the present invention.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
The following examples were selected from the following raw materials:
the carbon Black is selected from Hi Black 5L, LG Chemical Co. Ltd., Reublic of Korea;
the activated carbon is coconut shell activated carbon, Aldrich of a production company, and is ball-milled into powder with the particle size of less than 100 meshes of a Chinese standard sieve;
white carbon black is a product with the particle size of less than 100nm produced by Aldrich company;
example 1
The preparation method of the single crystal silicon carbide/graphene core-shell structure nanofiber according to the embodiment of fig. 1 comprises the following preparation steps:
(1) preparing carbon black and white carbon black according to C in the carbon black and SiO in the white carbon black2The mixture is added into a ball mill according to the molar ratio of 3:1, the ball milling medium is silicon carbide, the mass ratio of ball materials is 5, water is added according to the volume-to-solid mass ratio of 10mL/g of the raw material to prepare wet materials, and 0.5mg/mL of sodium hexametaphosphate is added into the wet materials to serve as a dispersing agent; the rotation speed of the wet ball milling is 600rpm, the ball milling time is 10min, the obtained precursor is dried in an oven at the temperature of 80 ℃, and the drying is carried out until the water content of the precursor is less than 1 wt%.
(2) The precursor obtained in the step (1) is added to 10-3And (3) carrying out a carbothermic reduction reaction for 4 hours at 1600 ℃ under Pa argon atmosphere to obtain a crude product.
(3) Soaking the crude product obtained in the step (2) in an HF acid solution with the mass fraction of 5% at 40 ℃ for 30 min according to the liquid-solid volume-mass ratio of 10mL/mg, scraping a turbid layer on the surface to remove impurities C, and then carrying out liquid-solid separation, wherein SiO residues2Dissolving in acid solution, and removing liquid-solid separation; and washing the solid after liquid-solid separation for multiple times by using water, drying the obtained solid product in an oven at the temperature of 80 ℃ until the water content is less than 1wt%, and obtaining the solid product, namely the single crystal silicon carbide/graphene core-shell structure nanofiber.
An SEM image of the single crystal silicon carbide/graphene core-shell structured nanofiber obtained in the present embodiment is shown in fig. 2, and it can be seen from the SEM image that the nanofiber prepared by the present invention is linear, has a large length-diameter, and has a smooth surface;
HR-TEM images and SAED images of the single crystal silicon carbide/graphene core-shell structure nanofibers obtained in this example are shown in fig. 3 and fig. 4, respectively, and regular lattice fringes (d =0.25 nm) and diffraction spots of the silicon carbide single crystal indicate that the interior of the fiber is a silicon carbide single crystal structure;
a raman spectrum of the single crystal silicon carbide/graphene core-shell structure nanofiber obtained in the embodiment is shown in fig. 5, in which a graphene film coated on the surface of the fiber can be clearly seen, which shows that the material prepared by the invention is a single crystal silicon carbide/graphene core-shell structure nanofiber material.
Example 2
The preparation method of the single crystal silicon carbide/graphene core-shell structure nanofiber comprises the following specific preparation processes:
(1) raw materials of active carbon and white carbon black are mixed according to C in the active carbon and SiO in the white carbon black2Adding the mixture into a ball mill according to the molar ratio of 4:1, wherein the ball milling medium is silicon carbide, the mass ratio of ball materials is 50, adding water according to the volume-to-solid mass ratio of 50mL/g of the mixture to the raw material to prepare a wet material, and adding sodium hexametaphosphate as a dispersing agent into the wet material according to the amount of 0.2 mg/mL; the rotation speed of the wet ball milling is 200 rpm, the ball milling time is 60 min, and the obtained precursor is dried in a vacuum drying oven at the temperature of 80 ℃ under the pressure of 100Pa until the water content is less than 1 wt%.
(2) The precursor obtained in the step (1) is added to 10-4And (3) carrying out carbon thermal reduction reaction for 4 hours at 1400 ℃ in a Pa argon atmosphere to obtain a crude product.
(3) Soaking the crude product obtained in the step (2) in an HF acid solution with the mass fraction of 5% at 10 ℃ for 120 min according to the liquid-solid volume-mass ratio of 3 mL/mg, scraping a turbid layer on the surface, and then carrying out liquid-solid separation, wherein SiO remains2Dissolving in acid solution, and removing liquid-solid separation; and washing the solid product obtained after the liquid-solid separation for many times by using absolute ethyl alcohol, and drying the obtained solid product in an oven at the temperature of 80 ℃ until the water content is less than 1wt%, thus obtaining the single crystal silicon carbide/graphene core-shell structure nanofiber.
Example 3
The preparation method of the single crystal silicon carbide/graphene core-shell structure nanofiber comprises the following specific preparation processes:
(1) raw materials of active carbon and white carbon black are mixed according to C in the active carbon and SiO in the white carbon black2The molar ratio of the silicon carbide to the raw material is 3.5:1, the silicon carbide is used as a ball milling medium, the mass ratio of ball materials is 25, and water is added into the raw material according to the volume-to-solid mass ratio of 25 mL/g to prepare a wet materialAdding carboxymethyl cellulose as a dispersing agent into the wet material according to the proportion of 0.2 mg/mL; the rotation speed of the wet ball milling is 500 rpm, the ball milling time is 30 min, and the obtained precursor is dried in a freeze drying oven at the temperature of 10Pa and 50 ℃ below zero until the water content is less than 1 wt%.
(2) The precursor obtained in the step (1) is added to 10-4And (3) carrying out carbothermic reduction reaction for 1h at 1600 ℃ under Pa argon atmosphere to obtain a crude product.
(3) Soaking the crude product obtained in the step (2) in an HF acid solution with the mass fraction of 10% at 25 ℃ for 60 min according to the liquid-solid volume-mass ratio of 5 mL/mg, scraping a turbid layer on the surface, and then carrying out liquid-solid separation, wherein SiO remains2Dissolving in acid solution, and removing liquid-solid separation; and washing the solid product obtained after the liquid-solid separation for many times by using water, and drying the obtained solid product in an oven at the temperature of 70 ℃ until the water content is less than 1wt%, thus obtaining the single crystal silicon carbide/graphene core-shell structure nanofiber.
Example 4
The preparation method of the single crystal silicon carbide/graphene core-shell structure nanofiber comprises the following specific preparation processes:
(1) mixing activated carbon and white carbon black according to C in the activated carbon and SiO in the white carbon black2Adding the mixture into a ball mill according to the molar ratio of (3.2: 1), wherein the ball milling medium is silicon carbide, the ball material mass ratio is selected to be 30, adding water according to the liquid-solid volume-mass ratio of 20mL/g, and finally adding carboxymethyl cellulose serving as a dispersing agent in an amount of 0.5 mg/mL; the rotation speed of the wet ball milling is 300 rpm, the ball milling time is 15 min, the obtained precursor is dried in an oven at the temperature of 80 ℃, and the drying is carried out until the water content is less than 1 wt%.
(2) The precursor obtained in the step (1) is added to 10-3And (3) carrying out carbon thermal reduction reaction for 1h at 1400 ℃ in a Pa argon atmosphere to obtain a crude product.
(3) Soaking the crude product obtained in the step (2) in an HF acid solution with the mass fraction of 15% at the temperature of 30 ℃ for 45 min according to the liquid-solid volume-mass ratio of 8mL/mg, scraping a turbid layer on the surface, and then carrying out liquid-solid separation, wherein SiO remains2Dissolving in acid solution, and removing liquid-solid separation; washing the solid product after liquid-solid separation with water to obtain solid productAnd drying in an oven at 60 ℃ until the water content is less than 1wt%, thus obtaining the single crystal silicon carbide/graphene core-shell structure nanofiber.
Example 5
The preparation method of the single crystal silicon carbide/graphene core-shell structure nanofiber comprises the following specific preparation processes:
(1) raw materials of active carbon and white carbon black are mixed according to C in the active carbon and SiO in the white carbon black2Adding the mixture into a ball mill according to the molar ratio of 3.1:1, wherein the ball milling medium is silicon carbide, the mass ratio of ball materials is 35, adding water according to the volume-to-solid mass ratio of 40 mL/g of the mixture to the raw material to prepare a wet material, and adding sodium hexametaphosphate as a dispersing agent into the wet material according to the amount of 0.3 mg/mL; the rotation speed of the wet ball milling is 400 rpm, the ball milling time is 50 min, and the obtained precursor is dried in an oven at the temperature of 80 ℃ until the water content is less than 1 wt%.
(2) The precursor obtained in the step (1) is added to 10-4And (3) carrying out carbon thermal reduction reaction for 3 h at 1500 ℃ in the atmosphere of Pa argon to obtain a crude product.
(3) Soaking the crude product obtained in the step (2) in an HF acid solution with the mass fraction of 30% at 35 ℃ for 35 min according to the liquid-solid volume-mass ratio of 9 mL/mg, scraping a turbid layer on the surface, and then carrying out liquid-solid separation, wherein SiO remains2Dissolving in acid solution, and removing liquid-solid separation; and washing the solid product obtained after the liquid-solid separation for many times by using water, and drying the obtained solid product in an oven at the temperature of 80 ℃ until the water content is less than 1wt%, thus obtaining the single crystal silicon carbide/graphene core-shell structure nanofiber.
Example 6
The preparation method of the single crystal silicon carbide/graphene core-shell structure nanofiber comprises the following specific preparation processes:
(1) raw materials of active carbon and white carbon black are mixed according to C in the active carbon and SiO in the white carbon black2Adding the mixture into a ball mill according to the molar ratio of 3.3:1, wherein a ball milling medium is silicon carbide, the mass ratio of a ball material is 45, adding water according to the volume-to-solid mass ratio of 35 mL/g of the raw material to prepare a wet material, and adding carboxymethyl cellulose as a dispersing agent into the wet material according to the amount of 0.3 mg/mL; the rotation speed of the wet ball milling is 450 rpm, and the ball milling time is 25 min to obtain the ball milling productDrying the precursor in an oven at 80 ℃ until the water content is less than 1 wt%.
(2) The precursor obtained in the step (1) is added to 10-3And (3) carrying out carbothermic reduction reaction for 2 h at 1550 ℃ in the atmosphere of Pa argon to obtain a crude product.
(3) Soaking the crude product obtained in the step (2) in an HF acid solution with the mass fraction of 10% at 35 ℃ for 90 min according to the liquid-solid volume-mass ratio of 10mL/mg, scraping a turbid layer on the surface, and then carrying out liquid-solid separation, wherein SiO remains2Dissolving in acid solution, and removing liquid-solid separation; and (3) washing the solid after liquid-solid separation for multiple times by using alcohol, and drying the solid product in an oven at the temperature of 80 ℃ until the water content is less than 1wt%, thus obtaining the single crystal silicon carbide/graphene core-shell structure nanofiber.
Example 7
The preparation method of the single crystal silicon carbide/graphene core-shell structure nanofiber comprises the following specific preparation processes:
(1) taking raw materials of active carbon, carbon ink and white carbon black, and mixing the active carbon, the carbon ink and the white carbon black according to the total C in the active carbon and the carbon black and SiO in the white carbon black2Is added into a ball mill at a molar ratio of 3.5:1, wherein the molar ratio of the activated carbon to the carbon black C is 1: 1. the ball milling medium is silicon carbide, the mass ratio of the ball material is 35, water is added according to the volume-to-solid mass ratio of 35 mL/g of the ball material to the raw material to prepare a wet material, and carboxymethyl cellulose is added into the wet material according to the amount of 0.3mg/mL to serve as a dispersing agent; the rotation speed of the wet ball milling is 500 rpm, the ball milling time is 40 min, and the obtained precursor is dried in an oven at the temperature of 80 ℃ until the water content is less than 1 wt%.
(2) The precursor obtained in the step (1) is added to 10-3And (3) carrying out carbothermic reduction reaction for 3 hours at 1550 ℃ in the atmosphere of Pa argon to obtain a crude product.
(3) Soaking the crude product obtained in the step (2) in an HF acid solution with the mass fraction of 10% at 35 ℃ for 100 min according to the liquid-solid volume-mass ratio of 10mL/mg, scraping a turbid layer on the surface, and then carrying out liquid-solid separation, wherein SiO remains2Dissolving in acid solution, and removing liquid-solid separation; washing the solid after liquid-solid separation with absolute alcohol for many times, drying the solid product in an oven at 80 ℃ until the water content is less than 1wt%, thus obtaining the single crystal silicon carbide/stoneNano fiber with graphene core-shell structure.
Example 8
The embodiment provides a preparation method of a single crystal silicon carbide/graphene core-shell structure nanofiber, wherein a carbon source is a mixture of activated carbon and carbon black, and the molar ratio of C in the activated carbon to the carbon black is 2:1, the rest of the same procedure as in example 7.
Comparative example 1
This example provides a method for preparing a fiber material, which comprises the following steps:
this comparative example differs from example 1 in that the reaction temperature in step (2) was 1390 ℃.
The preparation process comprises the following steps:
(1) adding raw materials of carbon black and white carbon black into a ball mill according to the molar ratio of 3:1, wherein the ball milling medium is silicon carbide, the mass ratio of ball materials is 5, adding water according to the volume-to-solid ratio of 10mL/g of the raw materials to obtain a wet material, and adding 0.5mg/mL of sodium hexametaphosphate as a dispersing agent into the wet material; the rotation speed of the wet ball milling is 600rpm, and the ball milling time is 10min to obtain the precursor. And drying the obtained precursor in an oven at 80 ℃ until the water content of the precursor is less than 1 wt%.
(2) The precursor obtained in the step (1) is added to 10-3Pa argon atmosphere, and carrying out carbothermic reduction reaction for 4h at 1390 ℃ to obtain a crude product.
(3) And (3) adding an HF acid solution with the mass concentration of 5% into the crude product obtained in the step (2) according to the liquid-solid volume-mass ratio of 10mL/mg, soaking for 30 min at 40 ℃, scraping a turbid layer on the surface, performing liquid-solid separation, washing the solid product for multiple times with water, and drying the solid product in an oven at 80 ℃ until the water content is less than 1wt%, thus obtaining the product.
The product obtained in comparative example 1 does not show characteristic peaks of D, G and 2D of graphene through Raman spectrum test, which indicates that a graphene coating layer structure cannot be formed when the reaction temperature is lower than 1400 ℃.
Comparative example 2
This example provides a method for preparing a fiber material, which comprises the following steps:
this comparative example differs from example 1 in that the reaction time of step (2) was 50 min.
The product obtained in comparative example 2 does not show characteristic peaks of D, G and 2D of graphene through Raman spectrum test, which indicates that a graphene coating layer cannot be formed when the reaction time is less than 1 h.
Comparative example 3
This example provides a method for preparing a fiber material, which comprises the following steps:
the only difference from example 1 is that the gas pressure introduced in step (2) is 10-3A mixed gas of air and argon gas at Pa (volume flow ratio: 1: 10) was used in the same manner as in example 1.
The product obtained in comparative example 3 has no characteristic peak of silicon carbide and graphene in XRD and Raman spectrum tests, which indicates that the reaction must be carried out under the protection of high-purity inert atmosphere.
Application example 1
Comparing the performances of pure ZrC ceramic and ZrC composite ceramic added with 10 wt% of single crystal silicon carbide/graphene core-shell structure nanofiber prepared in the embodiment 1 of the invention under the same preparation process, tests show that the bending strength of the ceramic material added with the nanofiber prepared by the invention is improved from 205.8 MPa to 389 MPa, and the fracture toughness is improved from 3.8 MPa/m1/2Is increased to 6.0 MPa/m1/2The microhardness is improved from 21.3 GPa to 26.5 GPa, the material performance is obviously improved, and the fiber material can play a role in strengthening and toughening when being applied to ceramic materials.
Application example 2
Comparing the performances of pure nylon 6 and nylon 6 added with 10 wt% of the single crystal silicon carbide/graphene core-shell structure nanofiber prepared in the embodiment 1 of the invention under the same preparation process, tests show that the tensile strength of the nylon material added with the nanofiber prepared in the invention is improved from 62.8 MPa to 7.5 MPa, the bending strength is improved from 65.3 MPa to 128.4 MPa, the bending modulus is improved from 2.0 GPa to 3.5 GPa, and the impact strength is improved from 8.5 kJ/m2Is lifted to 10.2 kJ/m2The elongation at break is improved from 66.3 percent to 67.7 percent, and the ball indentation hardness is improved from 54.4N/m2Is increased to 95.8N/m2The material performance is obviously improved, thus the hair is seenThe bright fiber material can play a role in strengthening and toughening when being applied to a nylon material.
Application example 3
Comparing various properties of the pure metal aluminum and the aluminum composite material added with 10 wt% of the single crystal silicon carbide/graphene core-shell structure nanofiber prepared in the embodiment 1 of the invention under the same preparation process, the aluminum composite material added with the nanofiber prepared in the invention is found to have the material breaking load improved to 2213N from 1311N, the bending strength improved to 460.4 MPa from 284.4 MPa, the bending modulus improved to 275.4 GPa from 181.2 GPa, and obviously improved material properties, so that the fiber material can play a role in strengthening and toughening when being applied to the aluminum composite material.
Application examples 1-3 illustrate that the product of the invention can show the performance of the matrix material after being applied to the compounding of ceramic materials, high polymer materials or metal materials.
From examples 1 to 6, it can be known that the preparation method of the single crystal silicon carbide/graphene core-shell structure nanofiber provided by the invention is simple and easy to implement, the diameter of the prepared single crystal silicon carbide/graphene core-shell structure nanofiber is below 100nm, and the length of the prepared single crystal silicon carbide/graphene core-shell structure nanofiber can reach tens of micrometers. The fiber core part is silicon carbide single crystal, and the mechanical property of the fiber is better than that of common polycrystal or amorphous fiber; the outer shell layer is made of graphene, so that the fiber can be protected from oxidation and corrosion erosion, and meanwhile, the toughness of the fiber and the compatibility with a blank are improved. The product of the invention is a novel reinforcing and toughening material of a ceramic material, a high polymer material or a metal material.
The applicant states that the present invention is illustrated by the above examples to describe the method for preparing the beta-silicon carbide whisker of the present invention, but the present invention is not limited to the above examples, i.e., it does not mean that the present invention must be implemented by the above examples. It will be apparent to those skilled in the art that any modification of the present invention, equivalent substitutions of selected materials and additions of auxiliary components, selection of specific modes and the like, which are within the scope and disclosure of the present invention, are contemplated by the present invention.
Claims (9)
1. A preparation method of single crystal silicon carbide/graphene core-shell structure nano fibers is characterized by comprising the following steps:
(1) uniformly mixing a carbon source and white carbon black by a wet method, wherein C in the carbon source and SiO in the white carbon black2The molar ratio of (3-4) to 1, and drying after reaction to obtain a precursor;
(2) performing a carbothermic reduction reaction on the precursor obtained in the step (1) in an atmosphere heating furnace at 1400-1600 ℃ for 1-4h to obtain a crude product; the carbothermic reduction reaction is at 10-4-10-3The reaction is carried out in an inert gas atmosphere under the pressure of Pa; argon is selected as the inert gas;
(3) and (3) removing impurities from the crude product obtained in the step (2) by adopting an acid pickling soaking and liquid-solid separation method, and drying to obtain the single crystal silicon carbide/graphene core-shell structure nanofiber.
2. The preparation method of the single crystal silicon carbide/graphene core-shell structure nanofiber according to claim 1, wherein the carbon source in the step (1) is selected from activated carbon, carbon black or any mixture of the activated carbon and the carbon black.
3. The method for preparing single crystal silicon carbide/graphene core-shell structure nanofibers according to claim 2, wherein in step (1), the white carbon black is SiO2Nanopowder in an amount greater than 99%; the average particle size of the white carbon black is less than 100 nm; the specific surface area of the white carbon black is more than 200 m2/g。
4. The preparation method of the single crystal silicon carbide/graphene core-shell structure nanofiber according to any one of claims 1 to 3, wherein the wet uniform mixing in the step (1) is performed by wet ball milling, the liquid phase of the wet ball milling is water, and the liquid-solid volume-mass ratio is 10 to 50 mL/g; and simultaneously adding 0.2-0.5 mg/mL of dispersant, wherein the dispersant is selected from sodium hexametaphosphate or carboxymethyl cellulose.
5. The preparation method of the single crystal silicon carbide/graphene core-shell structure nanofiber according to claim 4, wherein the ball milling medium of the wet ball milling is silicon carbide balls, and the mass ratio of the ball materials is 5-50; the rotation speed of the wet ball milling is 200-600 rpm, and the ball milling time is 10-60 min.
6. The method for preparing single crystal silicon carbide/graphene core-shell structure nanofibers according to claim 5, wherein the slurry obtained after wet ball milling is dried, and the water content of the dried precursor is less than 1 wt%.
7. The preparation method of the single crystal silicon carbide/graphene core-shell structure nanofiber according to claim 6, wherein the impurity removal process by acid pickling and soaking and liquid-solid separation in the step (3) is as follows;
soaking the crude product in 5-40% hydrofluoric acid solution at 10-40 deg.C for 30-120 min, wherein the liquid-solid volume/mass ratio of the acid solution to the crude product is 3-10 mL/g;
acid washing to remove unreacted SiO2And simultaneously removing unreacted impurity C by flotation, then carrying out liquid-solid separation, repeatedly washing the separated solid by using water or alcohol after separation, and then drying at 50-100 ℃ until the water content is less than 1wt% to obtain the single crystal silicon carbide/graphene core-shell structure nanofiber.
8. The single crystal silicon carbide/graphene core-shell structure nanofiber prepared by the preparation method of claim 1.
9. The application of the single crystal silicon carbide/graphene core-shell structure nanofiber as claimed in claim 8 as a reinforcing and toughening phase of a ceramic material, a polymer material or a metal material.
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