CN116288759A - Air flow blowing device of SiOC precursor fiber and preparation method of SiC nanofiber - Google Patents

Air flow blowing device of SiOC precursor fiber and preparation method of SiC nanofiber Download PDF

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CN116288759A
CN116288759A CN202211089639.2A CN202211089639A CN116288759A CN 116288759 A CN116288759 A CN 116288759A CN 202211089639 A CN202211089639 A CN 202211089639A CN 116288759 A CN116288759 A CN 116288759A
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air flow
fiber
temperature
needle
air
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陈建军
陶吉雨
刘佳乐
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Zhejiang Sci Tech University ZSTU
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Zhejiang Sci Tech University ZSTU
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    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
    • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
    • D01F9/10—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material by decomposition of organic substances
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/90—Carbides
    • C01B32/914—Carbides of single elements
    • C01B32/956—Silicon carbide
    • C01B32/963—Preparation from compounds containing silicon
    • C01B32/977—Preparation from organic compounds containing silicon
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D10/00—Physical treatment of artificial filaments or the like during manufacture, i.e. during a continuous production process before the filaments have been collected
    • D01D10/06—Washing or drying
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/04—Dry spinning methods
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/12—Stretch-spinning methods
    • D01D5/14—Stretch-spinning methods with flowing liquid or gaseous stretching media, e.g. solution-blowing
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D5/00—Formation of filaments, threads, or the like
    • D01D5/28—Formation of filaments, threads, or the like while mixing different spinning solutions or melts during the spinning operation; Spinnerette packs therefor
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/10—Particle morphology extending in one dimension, e.g. needle-like
    • C01P2004/16—Nanowires or nanorods, i.e. solid nanofibres with two nearly equal dimensions between 1-100 nanometer
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention discloses an air flow blowing device of SiOC precursor fiber and a preparation method of SiC nanofiber. The device comprises: (1) The air flow spraying device comprises an air inlet, an air nozzle and a needle through hole; (2) Liquid inlet device and liquid collecting deviceThe groove is provided with compressed gas and an injection needle, and is inserted into the airflow spraying device; (3) a fiber collecting device based on hot air flow heating. The preparation method comprises the following steps: firstly, preparing spinning solution with certain viscosity, then flowing out from a needle point by pushing of compressed gas, drawing fine liquid drops under the action of high-speed air flow of the needle point, spraying the fine liquid drops into fibrous fine flow, spraying the fibrous fine flow into a fiber collecting device, volatilizing and solidifying solvent under the action of upward hot air flow, and gathering upward to obtain polymer/SiO 2 And (3) the composite fiber is subjected to high-temperature pyrolysis to obtain SiOC precursor fiber, and finally the SiC nanofiber is obtained through in-situ growth by a high-temperature carbothermal reduction method.

Description

Air flow blowing device of SiOC precursor fiber and preparation method of SiC nanofiber
Technical Field
The invention belongs to the technical field of SiC nanofiber preparation, and particularly relates to an air flow blowing device of SiOC precursor fibers and a preparation method of SiC nanofibers.
Background
The SiC nanofiber has the excellent physical and chemical properties of light weight, high temperature resistance, high strength, high modulus, oxidation resistance, low thermal conductivity, mechanical shock resistance and the like, is an important high-performance reinforced ceramic fiber for metal-based and ceramic-based composite materials, and has wide application prospects in industries of machinery, metallurgy, chemical industry, petroleum, ceramics, glass, electronics and the like. Therefore, the continuous preparation of a large amount of SiC nanofibers is of great significance for the application of ceramic fibers and the development of various industries.
At present, the preparation methods of SiC nanofibers are various and mainly comprise a chemical vapor deposition method, an electrostatic spinning method, a sol-gel method, a precursor conversion method and the like.
Among the preparation methods, the CVD method is the earliest method for preparing SiC nanowires, and is a method for vaporizing a silicon source and a carbon source at a specific pressure and temperature, then transporting them to the surface of a substrate to nucleate and grow SiC nanomaterial by a certain flow of carrier gas. The prepared SiC fiber has high purity, strong tensile resistance, high bending strength and higher strength and stability at high temperature. Literature' fluidized bed-chemical vapor deposition method for continuously preparing SiC nanowire [ J ]]The ceramic school report 2017,38 (03): 305-308' uses methyl trichlorosilane as a precursor, ferrocene as a catalyst, and a fluidized bed chemical vapor deposition method is adopted to successfully prepare the SiC nano fiber with the diameter of 50-100 nm and the length of more than 100 mu m. The patent 'a SiC nanowire and a preparation method and application thereof' (patent number: CN 201910903443.4) provides a method for preparing the SiC nanowire by adopting carbon-containing source gas and silicon-containing source gas through a hot wire chemical vapor deposition method. The precursor conversion method is also a currently adopted methodThe preparation method of the SiC nanofiber is characterized in that polysiloxane is used as a silicon-containing polymer precursor, wood powder is used as a carbon source, and the SiC nanofiber is synthesized by in-situ reaction. In addition, carbothermic processes are currently the dominant method of preparing SiC nanowires. The patent 'a synthesis method of beta-SiC nanowire' (patent number: CN 200810150116.8) discloses a method for preparing the beta-SiC nanowire on the surface of a biological active carbon sheet through carbothermic reduction reaction in a temperature range of 1200-1400 ℃ by taking SiO generated by the reaction of diatomite and silicon powder at high temperature as a silicon source and taking the biological active carbon sheet as a carbon source. The patent 'a synthesis method of beta-SiC nanowire' (patent number: CN 201210516420.6) uses Si powder and SiO 2 The powder and the carbon nano tube are used as raw materials, sintered at 1200-1500 ℃, and then treated by carbon removal and hydrofluoric acid to obtain the beta-SiC nano fiber.
However, the preparation of the nanofiber still has certain problems, such as more impurities in the preparation of SiC fibers by a fluidized bed CVD method, hydrogen chloride corrosive gas generated by cracking of a methyl trichlorosilane precursor raw material, easily-exploded hydrogen byproducts and the like; the conversion method of the silicon-containing precursor is complex in process, long in precursor preparation time, high in equipment cost and low in production level; the traditional carbothermic reduction method adopts carbon powder as a carbon source, and the product contains more silicon carbide particles, has low purity, difficult atmosphere control and poor reproducibility. In order to solve the problems, the applicant provides a method for preparing SiC nanofibers and air-jet forming SiOC precursor fibers by improving the preparation method.
Disclosure of Invention
The invention provides an air flow blowing device of SiOC precursor fiber and a preparation method of SiC nanofiber, which aims to solve the problems in the background art, and the invention adopts a porous spinneret plate, so that spinning solution at a needle opening is drawn into a Taylor cone under the action of high-speed air flow of a needle point, and is led out into fibrous trickles to be sprayed into a fiber collecting device, and under the action of upward hot air flow, a solvent volatilizes, solidifies and is gathered upwards to obtain polymer/SiO 2 Composite fiber is then passed through high temperatureAnd (3) cracking to obtain SiOC precursor fiber, and finally obtaining the SiC nanofiber by a high-temperature carbothermal reduction method.
The technical scheme disclosed by the invention is as follows:
1. air flow blowing device for SiOC precursor fiber
The air flow blowing device comprises an air injection device, a liquid inlet device and a heating and collecting device.
The air injection device comprises an air compressor, a porous spinneret plate and an air flow pipe, and the air compressor is connected with the porous spinneret plate through the air flow pipe I; the porous spinneret plate comprises an upper nozzle and a lower nozzle which are in up-down butt joint, the upper nozzle and the lower nozzle are respectively provided with an upper bulge and a lower bulge end cover, a plurality of evenly distributed airflow through holes are formed in the upper end cover and the lower end cover, and the lower nozzle is provided with an air nozzle connected with an airflow pipe I.
The liquid inlet device comprises an injection needle, a silica gel hose, a liquid collecting tank, an airflow pipe II and a compressed gas cylinder, wherein the top of the liquid collecting tank is connected to the compressed gas cylinder through the airflow pipe II, a plurality of connecting holes are formed in the bottom of the liquid collecting tank, and each connecting hole is connected with the injection needle through the silica gel hose.
The heating and collecting device comprises a cylindrical pipeline, infrared heating lamps and an iron wire net cover, wherein the cylindrical pipeline is communicated up and down, the inner peripheral surface of the cylindrical pipeline is uniformly provided with the infrared heating lamps, and the iron wire net cover is arranged at the top of the cylindrical pipeline.
All the injection needles are respectively inserted into all the airflow through holes of the lower spray head from bottom to top and then extend out of the airflow through holes of the upper spray head.
The porous spinneret plate is located under the cylindrical pipeline, and a wind shielding baffle plate is arranged around the porous spinneret plate.
The diameter of an end cover of the porous spinneret plate is 100mm, the number of airflow through holes is 10-40, and the aperture is 2mm; the distance between the upper nozzle end cover and the lower nozzle end cover is 20-50 mm;
the length of the injection needle is 160mm, the outer diameter of the needle is 0.9mm, and the inner diameter of the needle is 0.6mm; the length of the injection needle extending out of the air nozzle is 30-40 mm;
the inner diameter of a connecting hole at the bottom of the liquid collecting tank is 2mm;
the diameter of the cylindrical pipeline is 20-40 cm, and the height is 50-70 cm.
2. Method for preparing SiC nanofiber by adopting device
The method comprises the following steps:
step 1) hydrolysis of precursor solution: polyethylene glycol (PEO), tetraethoxysilane (TEOS), deionized water and phosphoric acid are mixed according to a certain proportion, and the mixed solution is fully hydrolyzed by stirring to obtain a homogeneous precursor spinning solution with wiredrawing performance;
step 2) compressed gas assisted liquid feeding: connecting an injection needle and a liquid collecting tank by using a silica gel hose, filling the precursor spinning solution in the step 1) into the liquid collecting tank, opening a compressed gas cylinder, and conveying the liquid in the liquid collecting tank to the injection needle through an airflow pipe II after flowing out of a bottom connecting hole under the action of compressed gas;
step 3) high-speed airflow jet: inserting all injection needles into a spinneret plate, connecting the spinneret plate with an air compressor, opening the air compressor, spraying high-speed air flow from a through hole from bottom to top after passing through an air jet, and stretching spinning solution flowing out of the needle tips of the injection needles under the action of the high-speed air flow to form liquid yarn to spray upwards;
step 4) high-temperature drying: the liquid yarn sprayed in the step 3 enters a cylindrical pipeline, is dried at high temperature in the cylindrical pipeline, moves upwards under the action of high-speed air flow and gathers on the iron wire mesh cover at the top upwards, thus obtaining the dried polymer/SiO 2 A fiber;
the solvent in the liquid yarn volatilizes under the action of hot air flow in the cylindrical pipeline;
Polymer/SiO 2 The fiber is polyethylene glycol and SiO 2 Is a composite fiber of (a);
step 5) cracking: polymer/SiO obtained in step 4 2 The SiOC precursor fiber is obtained by high-temperature pyrolysis of the fiber;
step 6) carbothermic reduction method of SiC fiber: and (3) placing the SiOC precursor fiber obtained in the step (5) in an atmosphere furnace, and performing vapor phase in-situ growth at high temperature by a carbothermic method to obtain the SiC nanofiber.
In the step 1):
the mass ratio of polyethylene glycol, deionized water and tetraethoxysilane is 1: 3-10: 10 to 15 percent; the adding amount of phosphoric acid is 1-10 drops;
stirring at room temperature for 2-6 h;
the viscosity of the precursor spinning solution is in the range of 70-100 mPa.s.
In the step 2), the flow rate of the precursor spinning solution is controlled to be 0.5-1.5 ml/min by adjusting the flow rate of the compressed gas.
In the step 3), high-speed air flow is conveyed to the spinneret plate under the pressure of 5-7 kPa, and then is sprayed out through an air flow hole of the spinneret plate.
In the step 4), the temperature in the cylindrical pipe is 400-500 ℃.
In the step 5), the high-temperature pyrolysis temperature is 800-1000 ℃ and the time is 1-2 h.
In the step 6), the temperature rising rate of the atmosphere furnace is 5 ℃/min, the reaction temperature is 1400-1650 ℃, the pressure in the furnace is 0.02-0.04 MPa, and the reaction time is 1-5 h.
The invention provides an SiOC precursor obtained by air flow blowing and high-temperature pyrolysis and a SiC nanofiber obtained by combining a high-temperature carbothermal reduction method. The porous spinneret plate adopted by the invention can greatly increase the preparation efficiency of the fiber, can easily realize the preparation of a large number of SiC nanofibers by combining a high-temperature carbothermic reduction method, and the obtained SiC fibers have the characteristics of high modulus and high strength. According to the invention, siOC precursor fiber is adopted, a silicon-oxygen-carbon component is directly introduced into the system, and a carbothermal reduction method is directly carried out at high temperature, so that SiC nanofiber is obtained by gas-phase in-situ growth. Compared with the traditional preparation method of ceramic fibers, the preparation method has the following technical advantages:
the preparation process is simple, the porous spinneret plate can greatly increase the preparation efficiency of the fiber, and the preparation of a large number of precursor fibers is easy to realize. Meanwhile, the method for preparing the fluffy SiOC precursor fiber and obtaining the SiC ceramic fiber through high-temperature carbothermal reduction is adopted, the fluffy SiOC precursor fiber provides sufficient growth space for the SiC nanofiber, the advantages of high yield and low cost are achieved, and the prepared SiC nanofiber has high strength and flexibility and has wide application prospects in the fields of composite materials, fire resistance, heat insulation and the like.
Drawings
FIG. 1 is a schematic diagram of an air flow blowing device
FIG. 2 is a schematic view of a jet device
FIG. 3 is a schematic view of a liquid inlet device
FIG. 4 is a schematic view of a heating and collecting device
FIG. 5 is a schematic view of a multi-hole spinneret employed in the present invention
FIG. 6 is a flow chart of a process for preparing SiOC precursor and SiC nanofibers
FIG. 7 is a digital photograph of blown fibers
FIG. 8 is an SEM image of SiOC precursor fiber obtained after pyrolysis of blown fiber
FIG. 9 is an SEM image of SiC nanofibers obtained by providing examples of the present invention
In the figure: an air compressor 1.1, a porous spinneret plate 1.2 and an air flow pipe I1.3; 2.1 of injection needle, 2.2 of silica gel hose, 2.3 of liquid collecting tank, 2.4 of air flow pipe II and 2.5 of compressed air bottle; cylindrical pipeline 3.1, infrared heating lamp 3.2, collection iron wire screen 3.3, fiber 3.4 obtained by blowing.
Detailed Description
The invention will be further described with reference to the drawings and examples. These examples are only for illustrating the present invention and are not intended to limit the scope of the present invention.
As shown in fig. 1 to 5, the device for blowing fibers by using the air flow according to the invention comprises the following components:
the air injection device comprises an air compressor 1.1, a porous spinneret plate 1.2 and an air flow pipeline 1.3;
the liquid inlet device comprises an injection needle 2.1, a silica gel hose 2.2, a liquid collecting tank 2.3, an airflow pipe 2.4 and a compressed gas cylinder 2.5;
heating and collecting device, cylindrical pipeline 3.1, infrared heating lamp 3.2, wire net cover 3.3, and fiber 3.4 obtained by blowing.
As shown in fig. 6, an embodiment of the present invention is as follows:
example 1
a. 1g of polyethylene glycol (PEO) was dissolved in 10g of deionized water, then 10g of tetraethyl orthosilicate (TEOS, 99%) and 1 drop of phosphoric acid were added to the PEO solution, and the mixed solution was magnetically stirred at room temperature for 4 hours to obtain a homogeneous precursor spinning solution.
b. Sucking the precursor spinning solution into an injection needle tube, connecting an injection needle with a silica gel hose, inserting the needle into a spinneret plate, selecting the type of the needle to be 20G, and setting the injection speed of the injector to be 0.5ml/min.
c. The infrared heating lamp in the collecting device is turned on, so that the temperature in the collecting device is maintained at about 500 ℃, and an iron wire net cover is erected at the top of the collecting device for collecting fibers.
d. Connecting a spinneret plate with an air compressor, opening an air compressor switch and an air flow switch, maintaining the air pressure at 5kPa, allowing high-speed air flow to draft the liquid at the needle opening to form liquid filaments upwards, and obtaining a dried polymer/SiO at the top of a collecting device 2 A composite fiber.
e. polymer/SiO 2 And placing the composite fiber in a muffle furnace, and carrying out high-temperature pyrolysis at 700 ℃ for 2 hours at a heating rate of 5 ℃/min to obtain the SiOC precursor fiber.
f. And (3) placing the SiOC precursor fiber in an atmosphere furnace, and performing carbothermic reduction reaction for 5 hours at 1450 ℃ at a heating rate of 5 ℃/min to obtain the SiC nanofiber.
The polymer/SiO obtained by blowing in this example 2 As shown in FIG. 7, the digital photographs of the fibers are shown in FIG. 7, the blown fibers of this example are fluffy, large in amount, and bulky, and the blown precursor fibers are shown in FIG. 7 at about 0.8dm, c and d 3 The volume of the catalyst is only 4.00g, and the fluffy volume provides sufficient growth space for the growth of SiC nanowires in the subsequent carbothermic reaction.
Example 2
a. 1.5g of polyethylene glycol (PEO) was dissolved in 15g of deionized water, then 15g of tetraethyl orthosilicate (TEOS, 99%) and 2 drops of phosphoric acid were added to the PEO solution, and the mixed solution was magnetically stirred at room temperature for 6 hours to obtain a homogeneous precursor spinning solution.
b. Sucking the precursor spinning solution into an injection needle tube, connecting an injection needle with a silica gel hose, inserting the needle into a spinneret plate, selecting the type of the needle to be 20G, and setting the injection speed of the injector to be 0.7ml/min.
c. The infrared heating lamp in the collecting device is turned on, so that the temperature in the collecting device is maintained at about 500 ℃, and an iron wire net cover is erected at the top of the collecting device for collecting fibers.
d. Connecting a spinneret plate with an air compressor, opening an air compressor switch and an air flow switch, maintaining the air pressure at 6kPa, allowing high-speed air flow to draft the liquid at the needle opening to form liquid filaments upwards, and obtaining a dried polymer/SiO at the top of a collecting device 2 A composite fiber.
e. polymer/SiO 2 And (3) placing the composite fiber in a muffle furnace, and performing high-temperature pyrolysis at 600 ℃ for 2 hours at a heating rate of 5 ℃/min to obtain the SiOC precursor fiber.
f. And (3) placing the SiOC precursor fiber in an atmosphere furnace, and performing carbothermic reduction reaction for 4 hours at 1500 ℃ at a heating rate of 5 ℃/min to obtain the SiC nanofiber.
Example 3
a. 2g of polyethylene glycol (PEO) was dissolved in 30g of deionized water, then 30g of tetraethyl orthosilicate (TEOS, 99%) and 5 drops of phosphoric acid were added to the PEO solution, and the mixed solution was magnetically stirred at room temperature for 6 hours to obtain a homogeneous precursor spinning solution.
b. Sucking the precursor spinning solution into an injection needle tube, connecting an injection needle with a silica gel hose, inserting the needle into a spinneret plate, selecting the type of the needle to be 20G, and setting the injection speed of the injector to be 1ml/min.
c. The infrared heating lamp in the collecting device is turned on, so that the temperature in the collecting device is maintained at about 500 ℃, and an iron wire net cover is erected at the top of the collecting device for collecting fibers.
d. Connecting a spinneret plate with an air compressor, opening an air compressor switch and an air flow switch, maintaining the air pressure at 7kPa, allowing high-speed air flow to draft the liquid at the needle opening to form liquid filaments upwards, and obtaining a dried polymer/SiO at the top of a collecting device 2 A composite fiber.
e. polymer/SiO 2 And placing the composite fiber in a muffle furnace, and carrying out high-temperature pyrolysis at 800 ℃ for 1.5h at a heating rate of 5 ℃/min to obtain the SiOC precursor fiber.
f. And (3) placing the SiOC precursor fiber in an atmosphere furnace, and performing carbothermic reduction reaction for 6 hours at 1550 ℃ at a heating rate of 5 ℃/min to obtain the SiC nanofiber.
In this example, SEM images of SiOC precursor fibers obtained by high-temperature pyrolysis of the blown fibers are shown in fig. 8, and it is clear from fig. 8 that the blown fibers are still fibrous without breaking the original structure after pyrolysis.
Example 4
a. 1g of polyethylene glycol (PEO) was dissolved in 15g of deionized water, then 3g of tetraethyl orthosilicate (TEOS, 99%) and 1 drop of phosphoric acid were added to the PEO solution, and the mixed solution was magnetically stirred at room temperature for 3 hours to obtain a homogeneous precursor spinning solution.
b. Sucking the precursor spinning solution into an injection needle tube, connecting an injection needle with a silica gel hose, inserting the needle into a spinneret plate, selecting the type of the needle to be 20G, and setting the injection speed of the injector to be 0.6ml/min.
c. The infrared heating lamp in the collecting device is turned on, so that the temperature in the collecting device is maintained at about 500 ℃, and an iron wire net cover is erected at the top of the collecting device for collecting fibers.
d. Connecting a spinneret plate with an air compressor, opening an air compressor switch and an air flow switch, maintaining the air pressure at 5kPa, allowing high-speed air flow to draft the liquid at the needle opening to form liquid filaments upwards, and obtaining a dried polymer/SiO at the top of a collecting device 2 A composite fiber.
e. polymer/SiO 2 And placing the composite fiber in a muffle furnace, and carrying out high-temperature pyrolysis at 500 ℃ for 1.5h at a heating rate of 5 ℃/min to obtain the SiOC precursor fiber.
f. And (3) placing the SiOC precursor fiber in an atmosphere furnace, and performing carbothermic reduction reaction for 4 hours at 1600 ℃ at a heating rate of 5 ℃/min to obtain the SiC nanofiber.
An SEM image of the SiC nanowire prepared in this example is shown in fig. 9, and it can be seen from fig. 9 that the diameter of the prepared SiC fiber is in the nanometer scale, the fiber is slender, and the aspect ratio is high.

Claims (10)

1. The air flow blowing device for the SiOC precursor fiber is characterized by comprising an air blowing device, a liquid inlet device and a heating and collecting device;
the air injection device comprises an air compressor (1.1), a porous spinneret plate (1.2) and an air flow pipe (1.3), wherein the air compressor (1.1) is connected with the porous spinneret plate (1.2) through the air flow pipe I (1.3); the multi-hole spinneret plate (1.2) comprises an upper spray head (1.21) and a lower spray head (1.22) which are in up-down butt joint, wherein the upper spray head (1.21) and the lower spray head (1.22) are respectively provided with an upper bulge end cover and a lower bulge end cover, a plurality of evenly-distributed airflow through holes (1.23) are formed in the upper end cover and the lower end cover, and the lower spray head (1.22) is provided with an air nozzle connected with an airflow pipe I (1.3);
the liquid inlet device comprises an injection needle (2.1), a silica gel hose (2.2), a liquid collecting groove (2.3), an air flow pipe II (2.4) and a compressed gas cylinder (2.5), wherein the top of the liquid collecting groove (2.3) is connected to the compressed gas cylinder (2.5) through the air flow pipe II (2.4), a plurality of connecting holes are formed in the bottom of the liquid collecting groove (2.3), and each connecting hole is connected with the injection needle (2.1) through the silica gel hose (2.2);
the heating and collecting device comprises a cylindrical pipeline (3.1), infrared heating lamps (3.2) and an iron wire mesh cover (3.3), wherein the cylindrical pipeline (3.1) is communicated up and down, the plurality of infrared heating lamps (3.2) are uniformly distributed on the inner peripheral surface of the cylindrical pipeline (3.1), and the iron wire mesh cover (3.3) is arranged at the top.
2. A gas-flow blowing device for SiOC precursor fiber according to claim 1, wherein all injection needles (2.1) are inserted into the respective gas-flow through holes (1.23) of the lower nozzle (1.22) of the porous spinneret (1.2) from bottom to top, respectively, and then protrude from the gas-flow through holes (1.23) of the upper nozzle (1.21);
the porous spinneret plate (1.2) is positioned right below the cylindrical pipeline (3.1).
3. The gas flow blowing device of SiOC precursor fiber according to claim 1, wherein the end cap diameter of the porous spinneret plate (1.2) is 100mm, the number of gas flow holes (1.23) is 10-40, and the aperture is 2mm; the distance between the end cover of the upper nozzle (1.21) and the end cover of the lower nozzle (1.22) is 20-50 mm;
the length of the injection needle (2.1) is 160mm, the outer diameter of the needle is 0.9mm, and the inner diameter of the needle is 0.6mm; the length of the injection needle (2.1) extending out of the air nozzle is 30-40 mm;
the inner diameter of a connecting hole at the bottom of the liquid collecting groove (2.3) is 2mm;
the diameter of the cylindrical pipeline (3.1) is 20-40 cm, and the height is 50-70 cm.
4. A method for preparing SiC nanofibers on the basis of the device of any one of claims 1 to 3, characterized by comprising the steps of:
step 1) hydrolysis of precursor solution: mixing polyethylene glycol, tetraethoxysilane, deionized water and phosphoric acid according to a certain proportion, and stirring to fully hydrolyze the mixed solution to obtain a homogeneous precursor spinning solution with wiredrawing performance;
step 2) compressed gas assisted liquid feeding: connecting an injection needle (2.1) and a liquid collecting tank (2.3) by using a silica gel hose, filling the precursor spinning solution in the step 1) into the liquid collecting tank (2.3), opening a compressed gas cylinder, and conveying the liquid in the liquid collecting tank (2.3) to the injection needle (2.1) through a gas flow pipe II after flowing out from a bottom connecting hole under the action of compressed gas;
step 3) high-speed airflow jet: all injection needles (2.1) are inserted into a spinneret plate, the spinneret plate is connected with an air compressor, the air compressor is turned on, high-speed air flow is sprayed out from an air flow through hole (1.23) from bottom to top after passing through an air jet, and spinning solution flowing out from the needle tips of the injection needles (2.1) is drawn under the action of the high-speed air flow to form liquid yarn to be sprayed upwards;
step 4) high-temperature drying: the liquid yarn sprayed from the step 3 enters a cylindrical pipeline (3.1), is dried at high temperature in the cylindrical pipeline (3.1), moves upwards under the action of high-speed air flow and gathers on the iron wire mesh cover (3.3) at the top upwards, thus obtaining the dried polymer/SiO 2 A fiber;
step 5) cracking: polymer/SiO obtained in step 4 2 The SiOC precursor fiber is obtained by high-temperature pyrolysis of the fiber;
step 6) carbothermic reduction method of SiC fiber: and (3) placing the SiOC precursor fiber obtained in the step (5) in an atmosphere furnace, and performing vapor phase in-situ growth at high temperature by a carbothermic method to obtain the SiC nanofiber.
5. The method for preparing SiC nanofibers according to claim 4, wherein in said step 1):
the mass ratio of polyethylene glycol, deionized water and tetraethoxysilane is 1: 3-10: 10 to 15 percent; the adding amount of phosphoric acid is 1-10 drops;
stirring at room temperature for 2-6 h;
the viscosity of the precursor spinning solution is in the range of 70-100 mPa.s.
6. The method for preparing SiC nanofibers according to claim 4, wherein in said step 2), the flow rate of the precursor spinning solution is controlled to be 0.5 to 1.5ml/min by adjusting the size of the compressed gas flow.
7. The method of producing SiC nanofibers according to claim 4, wherein in said step 3), the high-speed gas stream is delivered to the spinneret at a pressure of 5 to 7kPa and then ejected through the gas flow holes of the spinneret.
8. The method for producing SiC nanofibers according to claim 4, wherein in said step 4), the temperature inside the cylindrical tube (3.1) is 400-500 ℃.
9. The method for preparing SiC nanofibers according to claim 4, wherein in said step 5), the pyrolysis temperature is 800-1000 ℃ for 1-2 hours.
10. The method for preparing SiC nanofibers according to claim 4, wherein in said step 6), the temperature rising rate of the atmosphere furnace is 5 ℃/min, the reaction temperature is 1400-1650 ℃, the pressure in the furnace is 0.02-0.04 MPa, and the reaction time is 1-5 h.
CN202211089639.2A 2022-09-07 2022-09-07 Air flow blowing device of SiOC precursor fiber and preparation method of SiC nanofiber Pending CN116288759A (en)

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