CN114716236A

CN114716236A - Carbon-coated silicon dioxide micro-nanofiber material and preparation method and application thereof

Info

Publication number: CN114716236A
Application number: CN202210641487.6A
Authority: CN
Inventors: 李臻; 李柏霄; 刘行勇
Original assignee: Foshan Zhongrou Material Technology Co ltd
Current assignee: Foshan Zhongrou Material Technology Co ltd
Priority date: 2022-06-08
Filing date: 2022-06-08
Publication date: 2022-07-08
Anticipated expiration: 2042-06-08
Also published as: CN114716236B

Abstract

The application discloses a carbon-coated silicon dioxide micro-nanofiber material as well as a preparation method and application thereof, belonging to the field of ceramic materials, wherein the preparation method comprises the following steps: (1) preparing a spinnable raw material mixed solution: (2) preparing a precursor: (3) sintering a precursor: after the sealed ventilation sintering, taking out a primary sintering product, and reserving carbide deposited on the inner wall of the sintering furnace; (4) and (3) circulating n times of sintering: repeating the steps (1), (2) and (3); the above circulation is carried out for n times, and after each sintering, the carbide deposited on the inner wall of the sintering furnace is reserved; the obtained n + 1-time sintered product is a carbon-coated silicon dioxide micro-nanofiber material; wherein n is more than or equal to 5 and more than or equal to 0; when n =0, the volume ratio of the precursor to the sintering furnace inner cavity is more than or equal to 0.8: 1. The invention has simple preparation flow, low production cost, good thermal stability, chemical stability, electrochemical inertia and fire resistance, and can be used as a sensor, an electro-catalytic material and a battery cathode.

Description

Carbon-coated silicon dioxide micro-nanofiber material and preparation method and application thereof

Technical Field

The application relates to a ceramic material, in particular to a carbon-coated silicon dioxide micro-nanofiber material and a preparation method and application thereof.

Background

As a material with stable chemical properties, acid resistance, oxidation resistance and high temperature resistance, the ceramic has wide engineering application prospect. However, the existing ceramic materials in the market are insulators or semiconductors, and do not have the characteristic of normal-temperature conductivity, so that the application of the ceramic materials in wider fields is greatly limited. Meanwhile, ceramic materials generally have the characteristics of hardness, brittleness, high density and low porosity, so that the excellent chemical stability of the ceramic materials cannot be applied to some special fields, such as the field of catalysis under severe conditions.

The flexible memory ceramic conductive material is soft, not fragile, compressible, resilient, low in density, high in porosity, high in precision, high in sensitivity and large in working range, and has a huge application prospect.

Disclosure of Invention

The carbon-coated silicon dioxide micro-nanofiber material with high precision, high sensitivity and large working range is prepared by a method with simple process flow.

According to one aspect of the application, the carbon-coated silicon dioxide micro-nano fiber material with the flexible memory is obtained by sintering treatment under the normal pressure condition without introducing special atmosphere additionally.

According to another aspect of the application, a preparation method of a carbon-coated silica micro-nanofiber material is provided, which comprises the following steps:

(1) preparing a spinnable raw material mixed solution:

dissolving a polymer in a solvent, and stirring at a first stirring speed for a first stirring time until the solution is uniform to form a polymer solution; adding the catalyst, the polymer solution and the silicon source in the charging sequence or the silicon source, the polymer solution and the catalyst in the charging sequence into a stirrer, stirring at a second stirring speed for a second stirring time, and standing to obtain a spinnable raw material mixed solution;

(2) preparing a precursor: spinning the spinnable mixed solution into solid micro-nano fibers through a spinning device, and accumulating the micro-nano fibers to obtain a carbon-coated silicon dioxide micro-nano fiber material precursor;

(3) sintering a precursor: forming a through hole on the wall of the sealed sintering furnace to enable the interior of the sealed sintering furnace to be communicated with the atmosphere, and putting the precursor into the sealed sintering furnace to be sintered at high temperature to obtain a white or gray micro-nano fiber substance which is a primary sintered product; taking out the primary sintering product, and reserving carbide deposited on the inner wall of the sintering furnace;

(4) and (3) circulating n times of sintering: repeating the step (1) and the step (2), putting the precursor obtained in the step (2) into a closed sintering furnace deposited with carbide for high-temperature sintering again to obtain a secondary sintered product, and taking out the secondary sintered product; the above circulation is carried out for n times, and after each sintering, the carbide deposited on the inner wall of the sintering furnace is reserved; finally, the obtained n + 1-time sintered product is a black micro-nanofiber substance, namely a carbon-coated silicon dioxide micro-nanofiber material;

wherein n is more than or equal to 5 and more than or equal to 0; when n =0, the volume ratio of the precursor to the sintering furnace inner cavity is more than or equal to 0.8: 1.

Optionally, the polymer is selected from at least one of polyvinylpyrrolidone PVP, polyethylene oxide PEO, polyethylene glycol PEG, polyacrylamide PAM, polyurethane PU and polyvinyl alcohol PVA; the mass ratio of the polymer to the solvent in the polymer solution is 2: 98-20: 80.

Optionally, the solvent is selected from at least one of deionized water, absolute ethanol, acetonitrile, acetone, and dimethylformamide.

Optionally, the silicon source is selected from at least one of tetraethyl silicate, ethyl silicate 32, ethyl silicate 40, and sodium silicate.

Optionally, the catalyst is selected from at least one of phosphoric acid, hydrochloric acid, citric acid, acetic acid, urea, and cetyltrimethylammonium bromide.

Optionally, the mass ratio of the polymer solution, the silicon source, and the catalyst is 1:0.15-0.8: 0.0015-0.008.

Optionally, the first stirring speed is 500-; the second stirring speed is 700-1300rpm, the second stirring time is 1-2.5 hours, and the standing time is 0-3 hours.

Optionally, the spinning device is a centrifugal spinning device or an air flow spinning device, the temperature of the spinning environment is 0-35 ℃, the relative humidity of the environment is 20-65% RH, and the preferred relative humidity of the environment is 35-45% RH.

Optionally, the sintering process is as follows: raising the temperature from room temperature to 800-1000 ℃ at the temperature raising rate of 2-5 ℃/min, keeping sintering for 1-2 hours in the environment of 800-1000 ℃, and then lowering the temperature from 800-1000 ℃ to room temperature at the temperature lowering rate of 5-10 ℃.

The carbon-coated silicon dioxide micro-nanofiber material provided by the invention is prepared according to the preparation method.

The invention provides an application of the carbon-coated silicon dioxide micro-nanofiber material in the fields of sensors, electrocatalysis materials or battery cathodes and the like.

The invention has the following advantages:

1. the sintering process is carried out under normal pressure, and compared with a sintering furnace under vacuum or high pressure, the sintering furnace used in the invention has lower equipment requirement, lower equipment investment cost and safer production.

2. The sintering process of the invention does not need to introduce special atmosphere (such as argon, nitrogen and the like), thereby greatly saving the cost generated by using the atmosphere.

3. The material obtained by the invention is a ceramic material which can conduct electricity at normal temperature, while the traditional ceramic material can conduct electricity at high temperature.

4. The ceramic material obtained by the invention has the properties of low density, high porosity, high specific surface area, compressibility, bendability, resilience and the like, and breaks through the current situation that the traditional ceramic material is compact and fragile.

5. The ceramic material obtained by the invention has good thermal stability, chemical stability, electrochemical inertia and fire resistance, is suitable for various severe environments, and can resist acid and alkali, resist high temperature up to 1000 ℃ and resist low temperature up to-196 ℃.

6. The carbon-coated silicon dioxide micro-nanofiber material disclosed by the invention has the following effects: a. as a sensor material, the sensor can normally work in a severe environment, and the microstructure of the material is a micro-nano fiber structure which can detect nano-scale vibration, so that the sensitivity is extremely high. b. The micro-nano fiber material is a silicon-carbon material, can be used as a battery cathode material, and improves the battery capacity ratio. c. The micro-nano fiber material has large specific surface area and high porosity, and the surface layer is carbon and can be used as an electro-catalytic material.

7. According to the invention, inorganic silicon is used as a raw material to replace organic silicon completely or partially, so that the cost of the raw material is reduced, and the risk resistance capability of market quotation of the raw material is improved.

The above and other objects, advantages and features of the present application will become more apparent to those skilled in the art from the following detailed description of specific embodiments thereof, taken in conjunction with the accompanying drawings.

Drawings

FIG. 1 shows a white or gray micro-nanofiber material obtained by the present invention;

FIG. 2 is a multilayer stacked carbon-coated silica micro-nanofiber material obtained after the n-th cycle of the present invention;

FIG. 3 is a single-layer carbon-coated silica micro-nanofiber material obtained after the n-th cycle of the present invention;

FIG. 4 is a scanning electron microscope image of a carbon-coated silica micro-nanofiber material provided by the invention;

FIG. 5 is a scanning electron microscope image of the cross section of a single carbon-coated silica micro-nanofiber material and energy spectrograms of Si element, O element and C element.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The invention provides a preparation method of a carbon-coated silicon dioxide micro-nanofiber material, which comprises the following steps:

(1) preparing a spinnable raw material mixed solution:

firstly, dissolving a polymer in a solvent, and stirring for 2-8 hours at a first stirring speed of 500-1000rpm until the solution is uniform to form a polymer solution; adding the catalyst, the polymer solution and the silicon source or the silicon source, the polymer solution and the catalyst into a stirrer according to the charging sequence, stirring at a second stirring speed of 700-1300rpm for 1-2.5 hours, and standing for 0-3 hours to obtain a spinnable raw material mixed solution;

preferably, the mass ratio of the polymer solution, the silicon source and the catalyst is 1:0.15-0.8: 0.0015-0.008.

Wherein the polymer is selected from at least one of polyvinylpyrrolidone (PVP), polyethylene oxide (PEO), polyethylene glycol (PEG), Polyacrylamide (PAM), Polyurethane (PU) and polyvinyl alcohol (PVA); the mass ratio of the polymer to the solvent in the polymer solution is 2: 98-20: 80.

The solvent is at least one selected from deionized water, absolute ethyl alcohol, acetonitrile, acetone and dimethyl amide.

The silicon source is at least one selected from tetraethyl silicate, ethyl silicate 32, ethyl silicate 40 and sodium silicate.

The catalyst is at least one selected from phosphoric acid, hydrochloric acid, citric acid, acetic acid, urea and cetyl trimethyl ammonium bromide.

The invention uses ethyl silicate 40 to have the following advantages compared with tetraethyl silicate: the content of silicon dioxide in the ethyl silicate 40 is 40%, the content of silicon dioxide in the tetraethyl silicate is only 28%, and the chemical component of the material to be finally obtained is silicon dioxide, so that when two types of organic silicon with the same mass are used, more silicon dioxide is finally generated by the ethyl silicate 40, and the production efficiency is higher. In addition, tetraethyl silicate is a monomer, ethyl silicate 40 is a polymer, and the molecular structure of ethyl silicate 40 is more stable.

The solvent, the polymer, the silicon source and the catalyst are prepared into the spinnable raw material mixed solution of the non-Newtonian fluid according to a certain formula proportion. In the process of preparing the mixed solution, strict control of the raw material placing sequence, the stirring speed of the stirrer and the stirring time of the solution is required to be followed, so that the silicon source can be fully and uniformly hydrolyzed to obtain the ideal non-Newtonian fluid mixed solution with spinnability. By adopting the feeding sequence of the invention, the problem that the spinnability of the solution is influenced because the partial rheological property of the spinnable non-Newtonian fluid mixed solution is abnormal due to the fact that the hydrolysis degree of a part of silicon source is greater than that of the other part of silicon source because a small amount of silicon source is excessively contacted with the catalyst before the solution is not uniformly mixed and stirred is avoided.

(2) Preparing a precursor: spinning the spinnable mixed solution into solid micro-nano fibers by using a spinning device, and accumulating the micro-nano fibers to obtain a carbon-coated silicon dioxide micro-nano fiber material precursor;

the process of spinning the micro-nano fiber can use one of a centrifugal spinning method and an air flow spinning method. The ambient temperature of the spinning is 0-35 deg.C, the ambient relative humidity is 20-65% RH, and the preferred ambient relative humidity is 35-45% RH.

The ambient temperature and humidity have a severe impact on the solvent evaporation rate during spinning. If the humidity is too high, the solvent can not be volatilized rapidly, the sprayed solution can not form fibers, but the solution state is kept to fall into a collecting device, and the spinning effect is influenced. The spinning temperature and the spinning humidity of the invention can ensure good spinning effect.

(3) Sintering a precursor: and (3) putting the carbon-coated silicon dioxide micro-nanofiber material precursor into a sintering furnace with only one small hole for high-temperature sintering. The sintering furnace cavity is not communicated with any gas and is in a natural sealing state, only a small hole with the aperture of 1-5mm is reserved, the connection of the inner cavity of the sintering furnace and the external atmospheric pressure is ensured, the internal pressure of the sintering furnace is ensured to be consistent with the atmospheric pressure environment, meanwhile, most of carbide generated in the sintering process can be deposited in the inner cavity of the sintering furnace, and the carbide generated when a polymer is carbonized in a high-temperature environment is deposited on the inner wall of the sintering furnace to form a deposit. The control of the sintering furnace temperature gradient during the sintering process is set according to the following temperature gradient. The initial temperature in the sintering process is room temperature, the temperature is raised from the room temperature to 800-1000 ℃ at the temperature rise rate of 2-5 ℃/min, the sintering is kept for 1-2 hours in the environment of 800-1000 ℃, and then the temperature is lowered from 800-1000 ℃ to the room temperature at the temperature reduction rate of 5-10 ℃. The obtained white or gray micro-nano fiber material is non-conductive as shown in figure 1, and can be used as materials for heat preservation, heat insulation and sound insulation, battery diaphragms, super capacitor diaphragms and the like. And taking out the white or gray micro-nano fiber material, and reserving the carbide deposited on the inner wall of the sintering furnace.

(4) Repeating the step (1), the step (2) and the step (3) for n times, wherein the sintering materials are in the same sintering furnace, taking out the sinter after completing one-time sintering, reserving the carbide deposited on the inner wall of the sintering furnace, adding the precursor into the sintering furnace for sintering again, and obtaining a black substance after sintering for n +1 times, namely the carbon-coated silica micro-nano fiber material, wherein the material stacked in multiple layers is black as shown in fig. 2; as shown in fig. 3, the single layer material is also black, but has a large porosity. The black carbon-coated silicon dioxide micro-nano fiber material is formed under the combined action of a high-temperature environment and deposits after a certain amount of deposits are deposited on the inner wall of a sintering furnace.

Wherein n is more than or equal to 5 and more than or equal to 0. When n =0, the volume ratio of the precursor to the sintering furnace cavity is more than or equal to 0.8:1, the precursor is completely filled in the sintering furnace cavity, the step (4) of cyclic sintering is not needed, the black micro-nano fiber material which is the carbon-coated silica micro-nano fiber material can be prepared at one time, and the carbon-coated silica micro-nano fiber material can be directly obtained in the step (3). In order to ensure the successful obtainment of the carbon-coated silica micro-nanofiber material, the cyclic sintering in the step (4) is required to be carried out if necessary, and before each sintering, carbide deposited on the inner wall of the sintering furnace cannot be removed.

The product shown in fig. 1 is obtained by sintering the carbon-coated silica micro-nanofiber material for several times, and is a white or gray micro-nanofiber material. For example, sintering for 4 times to obtain a carbon-coated silica micro-nanofiber material, sintering for 1 st time and 2 nd time to obtain a white micro-nanofiber material, sintering for 3 rd time to obtain a gray micro-nanofiber material, and sintering for 4 th time to obtain a black micro-nanofiber material, namely the carbon-coated silica micro-nanofiber material.

The three steps are repeated for n times, and after sintering in the same sintering furnace is completed each time, the inner cavity of the sintering furnace is not cleaned, so that the generated carbonized sediments are attached to the wall of the inner cavity of the sintering furnace. And when the precursor is sintered for the (n + 1) th time, under the action of high temperature, the carbide is attached to the surface of the silica micro-nanofiber to form a layer of carbon, and finally the carbon-coated silica micro-nanofiber material is obtained. Fig. 4 shows a Scanning Electron Microscope (SEM) of the carbon-coated silica micro-nanofiber material. As shown in fig. 5, (a) is a cross-sectional Scanning Electron Microscope (SEM) of a single carbon-coated silica micro-nanofiber material, and (b) is an energy spectrum under a Si element SEM; (c) is an energy spectrum of the O element under a scanning electron microscope; (d) is an energy spectrum of a C element under a scanning electron microscope, and the carbon content of the fiber surface layer is clearly shown to be obviously higher than that of silicon.

The present application is further illustrated by the following specific examples:

example 1

(1) Firstly, preparing a spinnable raw material mixed solution, mixing PVP and deionized water according to the mass ratio of 15:85, and stirring at 600rpm for 5 hours until the solution is uniform to obtain a polymer solution. Mixing phosphoric acid, urea and hexadecyl trimethyl ammonium bromide according to the mass ratio of 8:1:1 to obtain the catalyst. Putting the polymer solution, the silicon source and the catalyst in a mass ratio of 1:0.4:0.004 into a stirrer according to the charging sequence of the catalyst, the polymer solution, the tetraethyl silicate and the sodium silicate, stirring at the speed of 800rpm for 2 hours, and standing for 0.2 hour to obtain a spinnable raw material mixed solution; the tetraethyl silicate and the sodium silicate can be in any proportion, and the sum of the tetraethyl silicate and the sodium silicate after mixing meets the proportion of the tetraethyl silicate and the sodium silicate to the polymer solution.

(2) And (3) injecting the spinnable raw material mixed solution into a liquid storage device of centrifugal spinning equipment for spinning to obtain the micro-nano fiber. The device parameter modulation is as follows:

(3) putting the collected micro-nano fibers into a sintering furnace cavity with only one small hole (the aperture is 2 mm) connected with the atmosphere, wherein the volume ratio of the micro-nano fibers to the sintering furnace cavity is 0.2:1, heating the micro-nano fibers from room temperature to 1000 ℃ at the heating rate of 5 ℃/min, keeping the micro-nano fibers at the temperature of 1000 ℃ for 1 hour, and then cooling the micro-nano fibers to the room temperature at the cooling rate of 8 ℃/min. Obtaining a white or gray micro-nano fiber material; taking out the white or gray micro-nano fiber material, and reserving carbide deposited on the inner wall of the sintering furnace;

(4) repeating the step (1) and the step (2), putting the precursor obtained in the step (2) into a closed sintering furnace deposited with carbide, sintering at high temperature again according to the heating rate and the heating temperature in the step (3), then cooling to room temperature at the cooling rate of 8 ℃/min to obtain a secondary sintering product, and taking out the secondary sintering product; the mixture is recycled for 2 times, namely sintered for 4 times, and carbide deposited on the inner wall of the sintering furnace is reserved after each time of sintering; finally, the obtained 4-time sintered product is a black micro-nanofiber substance, namely a carbon-coated silicon dioxide micro-nanofiber material;

the relevant properties of the carbon-coated silica micro-nanofiber material obtained in the example are shown in the following table:

example 2:

(1) firstly, preparing a spinnable raw material mixed solution, mixing PVP and deionized water according to the mass ratio of 15:85, and stirring at 700rpm for 5 hours until the solution is uniform to obtain a polymer solution. According to the mass ratio of 1:0.38:0.0036 of the polymer solution, the silicon source and the catalyst, the mixture is placed into a stirrer according to the charging sequence of hydrochloric acid, the polymer solution and tetraethyl silicate, stirred for 1 hour at 1300rpm, and then kept stand for 0.2 hour to obtain a spinnable raw material mixed solution.

(3) putting the collected micro-nano fibers into a sintering furnace cavity with only one small hole (the aperture is 3 mm) connected with the atmosphere, wherein the volume ratio of the micro-nano fibers to the sintering furnace cavity is 0.3:1, heating the micro-nano fibers from room temperature to 1000 ℃ at the heating rate of 5 ℃/min, keeping the micro-nano fibers at the temperature of 1000 ℃ for 1 hour, and then cooling the micro-nano fibers to the room temperature at the cooling rate of 10 ℃/min. Obtaining a white or gray micro-nano fiber material; taking out the white or gray micro-nano fiber material, and reserving carbide deposited on the inner wall of the sintering furnace;

(4) repeating the step (1), the step (2) and the step (3) for 2 times, wherein each time of sintering is carried out in a sintering furnace for the last time of sintering, and after each time of sintering is finished, taking out a corresponding sinter and reserving carbide deposited on the inner wall of the sintering furnace; and (3) sintering the obtained micro-nanofiber material for the 3 rd time to obtain the black micro-nanofiber material, namely the carbon-coated silicon dioxide micro-nanofiber material.

example 3:

(1) firstly, preparing a spinnable raw material mixed solution, mixing PEO and acetonitrile according to the mass ratio of 7:93, and stirring at the speed of 800rpm for 8 hours until the solution is uniform to obtain a polymer solution. According to the mass ratio of 1:0.7:0.008 of the polymer solution, the silicon source and the catalyst, the polymer solution and the tetraethyl silicate are put into a stirrer in the sequence of adding the phosphoric acid, the polymer solution and the tetraethyl silicate, stirred for 2 hours at the speed of 780rpm and then kept stand for 0.2 hour to obtain a spinnable raw material mixed solution.

(3) putting the collected micro-nano fibers into a sintering furnace cavity with only one small hole (the aperture is 3 mm) connected with the atmosphere, wherein the volume ratio of the micro-nano fibers to the sintering furnace cavity is 1:1, heating the micro-nano fibers from room temperature to 1000 ℃ at the heating rate of 4 ℃/min, keeping the micro-nano fibers at the temperature of 1000 ℃ for 1 hour, and then cooling the micro-nano fibers to the room temperature at the cooling rate of 9 ℃/min. Obtaining the black carbon-coated silicon dioxide micro-nanofiber material.

example 4:

(1) firstly, preparing a spinnable raw material mixed solution, mixing PVP and absolute ethyl alcohol according to the mass ratio of 5:95, and stirring at the speed of 750rpm for 4 hours until the solution is uniform to obtain a polymer solution. Putting the polymer solution, the silicon source and the catalyst in a mass ratio of 1:0.38:0.0036 into a stirrer according to the charging sequence of acetic acid, the polymer solution and tetraethyl silicate, stirring at the speed of 1000rpm for 2.5 hours, and standing for 0.2 hours to obtain a spinnable raw material mixed solution.

(2) And (3) injecting the spinnable raw material mixed solution into a liquid storage device of airflow spinning equipment for spinning to obtain the micro-nano fiber. The device parameter modulation is as follows:

(3) putting the collected micro-nano fibers into a sintering furnace cavity with only one small hole (the aperture is 4 mm) connected with the atmosphere, wherein the volume ratio of the micro-nano fibers to the sintering furnace cavity is 0.1:1, heating the micro-nano fibers from room temperature to 900 ℃ at the heating rate of 5 ℃/min, keeping the micro-nano fibers at the temperature of 900 ℃ for 1.5 hours, and then cooling the micro-nano fibers to the room temperature at the cooling rate of 7 ℃/min. Obtaining a white or gray micro-nano fiber material, taking out the white or gray micro-nano fiber material, and reserving carbide deposited on the inner wall of the sintering furnace;

(4) repeating the step (1), the step (2) and the step (3) for 4 times, wherein each time of sintering is carried out in a sintering furnace for the last time of sintering, and after each time of sintering is finished, taking out a corresponding sinter and reserving carbide deposited on the inner wall of the sintering furnace; and (4) obtaining a black micro-nanofiber material after the 5 th sintering, namely the carbon-coated silicon dioxide micro-nanofiber material.

example 5:

(1) firstly, preparing a spinnable raw material mixed solution, mixing PEO, PEG and deionized water according to the mass ratio of 6:2:92, and stirring at the speed of 720rpm for 4.5 hours until the solution is uniform to obtain a polymer solution. According to the mass ratio of the polymer solution, the silicon source and the catalyst of 1:0.8:0.008, the citric acid, the polymer solution and the tetraethyl silicate are put into a stirrer in the sequence of adding, stirred at the speed of 1100rpm for 2.2 hours and then kept stand for 0.25 hour to obtain a spinnable raw material mixed solution.

(3) putting the collected micro-nano fibers into a sintering furnace cavity with only one small hole (the aperture is 4 mm) connected with the atmosphere, wherein the volume ratio of the micro-nano fibers to the sintering furnace cavity is 0.5:1, heating the micro-nano fibers from room temperature to 800 ℃ at the heating rate of 2 ℃/min, keeping the micro-nano fibers at the temperature of 800 ℃ for 2 hours, and then cooling the micro-nano fibers to the room temperature at the cooling rate of 9 ℃/min. Obtaining a white or gray micro-nano fiber material, taking out the white or gray micro-nano fiber material, and reserving carbide deposited on the inner wall of the sintering furnace;

(4) repeating the step (1), the step (2) and the step (3), wherein the two times of sintering are carried out in the same sintering furnace; and (3) the micro-nanofiber material obtained after the 2 nd sintering is black, namely the carbon-coated silicon dioxide micro-nanofiber material.

example 6:

(1) preparing a spinnable raw material mixed solution, mixing PVA and deionized water according to the mass ratio of 20:80, and stirring at 700rpm for 4.5 hours until the solution is uniform to obtain a polymer solution. According to the mass ratio of the polymer solution, the silicon source and the catalyst of 1:0.15:0.0015, the polymer solution and the tetraethyl silicate are put into a stirrer in the sequence of adding the phosphoric acid, the polymer solution and the tetraethyl silicate, stirred for 1.8 hours at the speed of 880rpm and then kept stand for 0.15 hour to obtain a spinnable raw material mixed solution.

(3) putting the collected micro-nano fibers into a sintering furnace cavity with only one small hole (the aperture is 4 mm) connected with the atmosphere, wherein the volume ratio of the micro-nano fibers to the sintering furnace cavity is 0.2:1, heating the micro-nano fibers from room temperature to 800 ℃ at the heating rate of 5 ℃/min, keeping the micro-nano fibers at the temperature of 800 ℃ for 2 hours, and then cooling the micro-nano fibers to the room temperature at the cooling rate of 9 ℃/min. Obtaining a white or gray micro-nano fiber material, taking out the white or gray micro-nano fiber material, and reserving carbide deposited on the inner wall of the sintering furnace;

(4) repeating the step (1), the step (2) and the step (3) for 3 times, wherein each time of sintering is carried out in a sintering furnace for the last time of sintering, and after each time of sintering is finished, taking out a corresponding sinter and reserving carbide deposited on the inner wall of the sintering furnace; and (4) sintering the carbon-coated silica micro-nanofiber material for the 4 th time to obtain the black carbon-coated silica micro-nanofiber material.

example 7:

(1) firstly, preparing a spinnable raw material mixed solution, mixing PEO and acetonitrile according to the mass ratio of 7:93, and stirring at the speed of 800rpm for 8 hours until the solution is uniform to obtain a polymer solution. According to the mass ratio of 1:0.4:0.008 of the polymer solution, the silicon source and the catalyst, the polymer solution and the tetraethyl silicate are put into a stirrer in the sequence of adding the phosphoric acid, the polymer solution and the tetraethyl silicate, stirred for 2 hours at the speed of 780rpm and then kept stand for 0.2 hour to obtain a spinnable raw material mixed solution.

(3) putting the collected micro-nano fibers into a sintering furnace cavity with only one small hole (the aperture is 3 mm) connected with the atmosphere, wherein the volume ratio of the micro-nano fibers to the sintering furnace cavity is 0.9:1, heating the micro-nano fibers from room temperature to 1000 ℃ at the heating rate of 5 ℃/min, keeping the micro-nano fibers at the temperature of 1000 ℃ for 1 hour, and then cooling the micro-nano fibers to the room temperature at the cooling rate of 9 ℃/min. Obtaining the black carbon-coated silicon dioxide micro-nanofiber material.

example 8:

(3) putting the collected micro-nano fibers into a sintering furnace cavity with only one small hole (the aperture is 3 mm) connected with the atmosphere, wherein the volume ratio of the micro-nano fibers to the sintering furnace cavity is 0.8:1, heating the micro-nano fibers from room temperature to 1000 ℃ at the heating rate of 4 ℃/min, keeping the micro-nano fibers at the temperature of 1000 ℃ for 1 hour, and then cooling the micro-nano fibers to the room temperature at the cooling rate of 9 ℃/min. Obtaining the black carbon-coated silicon dioxide micro-nano fiber material.

it can be seen from the resistivity data of all the above embodiments that when the compression deformation amount of the material is weak, the resistivity in the 5% compression state is compared with the resistivity in the 0% compression state, and the change range of the resistivity is huge, so that the resistivity of the material obtained by the invention is extremely sensitive under the condition of micro-deformation. Therefore, the material can be used for a sensor for detecting nano-scale vibration.

It is to be noted that, unless otherwise specified, technical or scientific terms used herein shall have the ordinary meaning as understood by those skilled in the art to which this application belongs.

The above description is only for the preferred embodiment of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present application should be covered within the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A preparation method of a carbon-coated silicon dioxide micro-nanofiber material comprises the following steps:

(1) preparing a spinnable raw material mixed solution:

(2) preparing a precursor: spinning the spinnable mixed solution into solid micro-nano fibers by using a spinning device, and accumulating the micro-nano fibers to obtain a precursor of the carbon-coated silicon dioxide micro-nano fiber material;

(3) sintering a precursor: forming a through hole on the wall of the sealed sintering furnace, communicating the inside of the sealed sintering furnace with the atmosphere, putting the precursor into the sealed sintering furnace for high-temperature sintering to obtain a white or gray micro-nano fiber substance which is a primary sintering product; taking out the primary sintering product, and reserving carbide deposited on the inner wall of the sintering furnace;

(4) and (3) circulating n times of sintering: repeating the step (1) and the step (2), putting the precursor obtained in the step (2) into a closed sintering furnace deposited with carbide for high-temperature sintering again to obtain a secondary sintering product, and taking out the secondary sintering product; the above circulation is carried out for n times, and after each sintering, the carbide deposited on the inner wall of the sintering furnace is reserved; finally, the obtained n + 1-time sintered product is a black micro-nanofiber substance, namely a carbon-coated silicon dioxide micro-nanofiber material;

2. The production method according to claim 1,

the aperture of the through hole is 1-5 mm.

3. The method according to claim 1,

the polymer is selected from at least one of polyvinylpyrrolidone PVP, polyethylene oxide PEO, polyethylene glycol PEG, polyacrylamide PAM, polyurethane PU and polyvinyl alcohol PVA; the mass ratio of the polymer to the solvent in the polymer solution is 2: 98-20: 80;

and/or the solvent is at least one selected from deionized water, absolute ethyl alcohol, acetonitrile, acetone and dimethyl amide.

4. The method of claim 1, wherein the silicon source is at least one selected from the group consisting of tetraethyl silicate, ethyl silicate 32, ethyl silicate 40, and sodium silicate;

and/or the catalyst is selected from at least one of phosphoric acid, hydrochloric acid, citric acid, acetic acid, urea and hexadecyl trimethyl ammonium bromide.

5. The preparation method according to claim 1, wherein the mass ratio of the polymer solution, the silicon source and the catalyst is 1:0.15-0.8: 0.0015-0.008.

6. The production method according to any one of claims 1 to 5, wherein the first stirring speed is 500-1000 rpm; the first stirring time is 4-8 hours; the second stirring speed is 700-1300 rpm; the second stirring time is 1-2.5 hours, and the standing time is 0-3 hours.

7. The method of claim 6, wherein the spinning device is a centrifugal spinning device or a gas flow spinning device, the ambient temperature of the spinning is 0-35 ℃, and the ambient relative humidity is 20-65% RH.

8. The method according to claim 6, wherein the sintering process is: raising the temperature from room temperature to 800-1000 ℃ at the temperature raising rate of 2-5 ℃/min, keeping sintering for 1-2 hours in the environment of 800-1000 ℃, and then lowering the temperature from 800-1000 ℃ to room temperature at the temperature lowering rate of 5-10 ℃.

9. A carbon-coated silica micro-nanofiber material, which is characterized by being prepared according to the preparation method of any one of claims 1 to 8.

10. An application of the carbon-coated silica micro-nanofiber material as claimed in claim 9 as a sensor, an electrocatalytic material or a battery cathode.