CN116102333B - High-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material and preparation method thereof - Google Patents

High-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material and preparation method thereof Download PDF

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CN116102333B
CN116102333B CN202210954448.1A CN202210954448A CN116102333B CN 116102333 B CN116102333 B CN 116102333B CN 202210954448 A CN202210954448 A CN 202210954448A CN 116102333 B CN116102333 B CN 116102333B
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sic
nanofiber
oxide ceramic
sio
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CN116102333A (en
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张晚林
刘圆圆
李文静
黄红岩
张恩爽
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Aerospace Research Institute of Materials and Processing Technology
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Abstract

The invention relates to a high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material and a preparation method thereof, wherein the method comprises the following steps: carrying out chemical vapor deposition reaction on a carbon source and a silicon source to obtain SiC nanofibers; oxidizing the SiC nanofiber to obtain a SiC@SiO 2 single-core-shell structure nanofiber; carrying out atomic layer deposition treatment on the SiC@SiO 2 single-core-shell structure nanofiber to obtain the SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber; dispersing the obtained nano fiber with the double-core-shell structure, and then sequentially performing pre-freezing, freeze drying and thermal annealing treatment to obtain the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nano fiber aerogel material. The invention can obviously improve the temperature resistance of the silicon carbide nanowire aerogel under the aerobic environment of less than 1000 ℃, and the prepared material has the remarkable advantages of high temperature resistance, high elasticity, ultra-light weight, high heat insulation and the like.

Description

High-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material and preparation method thereof
Technical Field
The invention belongs to the technical field of silicon carbide nanofiber aerogel, and particularly relates to a high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material and a preparation method thereof.
Background
The silicon carbide aerogel is a nano porous material formed by connecting or lapping silicon carbide nano particles or silicon carbide nano wires in a three-dimensional space, and the intrinsic property of the silicon carbide material endows the aerogel with a plurality of excellent performances such as high temperature resistance, low thermal expansion, thermal shock resistance, oxidation resistance, corrosion resistance and the like, so that the silicon carbide aerogel has wide application prospects in the fields of high-temperature heat insulation, electromagnetic wave absorption, filtration, adsorption and the like in extreme thermal environments and high corrosive environments.
The conventional silicon carbide aerogel is formed by nano particles, shows a typical pearl necklace structure, adopts SiO 2 aerogel as a supporting framework by an organic/SiO 2 composite aerogel carbothermal reduction method, and the prepared SiC aerogel inherits the microstructure of SiO 2 aerogel, such as Chinese patent application CN102910926A, CN114315365A, CN103864076A and the like; in addition, the SiC aerogel can be formed by hydrosilylation reaction and high-temperature cracking of precursors such as polycarbosilane, divinylbenzene and the like, such as China patent application CN105600785A, CN107324339A, CN112537964A and the like. However, the silicon carbide aerogel formed due to insufficient connection between the nanoparticles exhibits brittle mechanical characteristics, which greatly limits its application in the elastic field.
The SiC nanowire not only has the excellent properties of SiC ceramic, but also has excellent flexibility, elasticity, high bending strength and Young modulus, so that the preparation of the three-dimensional SiC nanowire aerogel is an important thought for improving the brittleness of the SiC aerogel. In the prior art, a carbon source for providing carbon monoxide gas and a silicon source for providing silicon monoxide gas are subjected to chemical vapor deposition reaction under an inert atmosphere to generate silicon carbide nanofibers, and then the silicon carbide nanofibers are interwoven into three-dimensional silicon carbide nanofiber aerogel, such as chinese patent application CN113968582a and the like. Such silicon carbide aerogels composed of one-dimensional silicon carbide nanowires have attracted attention in recent years.
However, although the currently prepared silicon carbide nanofiber aerogel has excellent flame retardant property (flame ablative property) and can often resist butane flame assessment at about 1200 ℃, the currently prepared silicon carbide nanofiber aerogel can be oxidized at a high temperature of which the aerobic environment exceeds 900 ℃ and is easily subjected to structural degradation under high-temperature air or rapid thermal shock, so that the practical application of the currently prepared silicon carbide nanofiber aerogel in the high-temperature aerobic environment is greatly limited. The size of the SiC nanowire composing the silicon carbide nanofiber aerogel is between 20 and 100nm, compared with the SiC microfiber, the SiC nanowire has larger specific surface energy and larger influence caused by a small number of lattice defects on the surface, so that the SiC nanowire is easier to oxidize at high temperature, and the temperature resistance of the SiC microfiber cannot be achieved. Therefore, how to improve the oxidation resistance of the SiC nanofiber without affecting the excellent elastic mechanical property of the SiC nanofiber is a key technology for preparing the high-temperature-resistant high-elasticity silicon carbide nanofiber aerogel.
Disclosure of Invention
In order to solve one or more technical problems in the prior art, the invention provides a high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material and a preparation method thereof. The high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material prepared by the method has a unique core-shell nanostructure, and has the remarkable advantages of high temperature resistance, high elasticity, ultra-light weight, high heat insulation and the like compared with the silicon carbide nanofiber aerogel material prepared by the prior art.
The invention provides a preparation method of a high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material, which comprises the following steps:
(1) Carrying out chemical vapor deposition reaction on a carbon source and a silicon source to obtain SiC nanofibers;
(2) Oxidizing the SiC nanofiber to obtain a SiC@SiO 2 single core-shell structure nanofiber;
(3) Carrying out atomic layer deposition treatment on the SiC@SiO 2 single-core-shell structure nanofiber to obtain a SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber;
(4) Uniformly dispersing the SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber by using water to obtain a core-shell structure nanofiber dispersion, and then sequentially performing the steps of pre-freezing and freeze-drying on the core-shell structure nanofiber dispersion to obtain SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber aerogel;
(5) And carrying out thermal annealing treatment on the SiC@SiO 2 @oxide ceramic nano fiber aerogel with the dual-core-shell structure to obtain the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nano fiber aerogel material.
Preferably, the average diameter of the SiC nanofibers obtained in the step (1) is 20-100 nm; the average thickness of SiO 2 shell layers contained in the SiC@SiO 2 single core-shell structure nanofiber obtained in the step (2) is 2-20 nm, preferably 7nm; and/or the average thickness of the oxide ceramic shell layer contained in the SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber obtained in the step (3) is 2-20 nm, preferably 6nm.
Preferably, step (2) comprises the following sub-steps:
(a) Placing the SiC nanofiber in an atmosphere furnace, and heating to an oxidation treatment temperature in an argon atmosphere environment;
(b) Controlling the oxygen content by adjusting the oxygen flow and the argon flow, and oxidizing the SiC nanofiber in an aerobic environment;
(c) And cooling to room temperature along with a furnace in an argon atmosphere to obtain the SiC@SiO 2 single core-shell structure nanofiber.
Preferably, in the step (b), the air inlet rate of the oxygen is 0.01-2 mL/min, preferably 0.5mL/min, and the air inlet rate of the argon is 3-50 mL/min, preferably 25mL/min; the oxidation treatment temperature is 700-1200 ℃, preferably 900 ℃; and/or the time of the oxidation treatment is 5 to 240min, preferably 30min.
Preferably, the oxide ceramic is one or more of aluminum oxide, zirconium oxide and hafnium oxide.
Preferably, step (3) comprises the following sub-steps:
S1, placing nano fibers with a SiC@SiO 2 single-core-shell structure in a cavity of an atomic layer deposition device, enabling oxide ceramic precursors to enter the cavity of the atomic layer deposition device in a pulse mode and chemically adsorbing the oxide ceramic precursors on the surface of the nano fibers with the SiC@SiO 2 single-core-shell structure, and blowing out the redundant oxide ceramic precursors from the cavity of the atomic layer deposition device by using nitrogen;
S2, enabling ultrapure water to enter the cavity of the atomic layer deposition equipment in a pulse mode and carrying out deposition reaction with the oxide ceramic precursor chemically adsorbed on the surface of the SiC@SiO 2 single-core-shell structure nanofiber in the step S1, and blowing out the redundant ultrapure water and byproducts generated after the deposition reaction out of the cavity of the atomic layer deposition equipment by using nitrogen;
And S3, sequentially repeating the step S1 and the step S2 for a plurality of times until the thickness of the oxide ceramic shell layer formed on the surface of the SiC@SiO 2 single-core-shell structure nanofiber reaches a preset thickness, thereby obtaining the SiC@SiO 2 @oxide ceramic double-core-shell structure nanofiber.
Preferably, the oxide ceramic precursor is trimethylaluminum; the pulse time of the oxide ceramic precursor is 0.08-0.25 s, preferably 0.15s; the pulse time of the ultrapure water is 0.1 to 0.35s, preferably 0.25s; in step S1 and step S2, the purging with nitrogen is carried out for 10 to 120S, preferably 60S; the temperature for carrying out the deposition reaction is 40-100 ℃, preferably 65 ℃; and/or repeating step S1 and step S2 in sequence 22 to 222 times, preferably 67 times.
Preferably, the mass concentration of the SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber contained in the core-shell structure nanofiber dispersion liquid is 0.06-8%, preferably 2%; and/or stirring the SiC@SiO 2 @oxide ceramic nano fiber with the double-core-shell structure with water for 1-3 hours at 1500-3000 rpm to uniformly disperse, thereby obtaining a nano fiber dispersion liquid with the core-shell structure.
Preferably, the pre-freezing is freezing for 10-60 min under liquid nitrogen; the freeze drying is carried out in a freeze dryer, in the freeze drying process, the temperature of a chamber of the freeze dryer is controlled to be 10-35 ℃, the temperature of a cold trap of the freeze dryer is controlled to be minus 80-minus 50 ℃, the pressure of the freeze drying is 1-30 Pa, and the time of the freeze drying is 24-96 h; and/or the temperature of the thermal annealing treatment is 1100-1400 ℃, preferably 1300 ℃, and the time of the thermal annealing treatment is 1-30 min, preferably 5min.
The present invention provides in a second aspect a high temperature resistant, high elasticity silicon carbide @ oxide ceramic core-shell nanofiber aerogel material made by the method of the present invention described in the first aspect; preferably, the high temperature resistant high elasticity silicon carbide @ oxide ceramic core-shell nanofiber aerogel material has one or more of the following properties: the temperature resistance limit of the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material in an aerobic environment is 1200-1300 ℃; the maximum compression deformation of the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material is more than 95%, and the rebound rate is 98-100%; the density of the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material is 0.7-80 mg/cm 3; the room temperature thermal conductivity of the high temperature resistant high elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material is 0.021-0.028W/(m.K).
Compared with the prior art, the invention has at least the following beneficial effects:
(1) According to the invention, the silicon oxide and oxide ceramic shell layers are sequentially generated on the surface of the silicon carbide nanofiber, so that the temperature resistance of the silicon carbide nanofiber aerogel in air can be greatly improved from less than 1000 ℃, for example, the temperature can be improved to more than 1150 ℃, and more preferably, the temperature can be improved to more than 1200-1300 ℃; the silicon oxide shell layer with controllable thickness formed by active oxidation on the surface of the SiC nanofiber not only can prevent oxygen from diffusing to the surface of the SiC, but also can provide a better attachment point for the formation of an oxide ceramic shell layer deposited by an atomic layer, and a strong bonding effect is formed between silicon dioxide and oxide after high-temperature thermal annealing, for example, a Si-O-Al strong bonding effect is formed between silicon dioxide and aluminum oxide after high-temperature thermal annealing, so that the temperature resistance of the silicon carbide nanofiber can be greatly improved; the invention discovers that the oxidation resistance strategy is also suitable for improving the temperature resistance of other metal carbide nano materials in an air environment, and is a relatively universal strategy.
(2) After the silicon oxide and oxide ceramic shell layers are introduced into the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material, the high-elasticity mechanical property of the material is not affected, which is attributed to the fact that the thickness of a silicon dioxide shell layer formed by active oxidation and the thickness of an oxide ceramic shell layer formed by atomic layer deposition are highly controllable on the nanoscale, and shell inorganic oxides are continuous on the length direction and do not negatively affect the mechanical property of the silicon carbide nanofiber.
(3) Compared with the silicon carbide nanofiber aerogel in the prior art, the high-temperature-resistant and high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material prepared by the invention has stronger heat insulation capability, probably because interfaces among silicon carbide, silicon oxide and oxide ceramic shell layers in the silicon carbide@oxide ceramic core-shell nanofiber can effectively reflect and scatter infrared radiation for many times, and can effectively reduce radiation heat transmission.
Drawings
FIG. 1 is a scanning electron microscope, a high resolution transmission electron microscope and a selected area electron diffraction pattern of the SiC nanofiber prepared in example 1 of the present invention; in fig. 1, (a) is a scanning electron microscope, (b) is a high resolution transmission electron microscope, and (c) is a selected area electron diffraction pattern.
FIG. 2 is a high resolution transmission electron microscope image of the SiC@SiO 2 single core-shell structured nanofiber prepared in example 1 of the present invention.
FIG. 3 is a transmission electron microscope image of the SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber prepared in example 1 of the invention.
FIG. 4 is a profile view and a scanning electron microscope view of the high temperature resistant elastic silicon carbide@oxide ceramic core-shell nanofiber aerogel material prepared in example 1 of the invention; in fig. 4, (a) is an outline view, and (b) is a scanning electron microscope view.
FIG. 5 is a high resolution transmission electron microscope image and a selected area electron diffraction image of an alumina ceramic shell layer of the high temperature resistant high elasticity silicon carbide @ oxide ceramic core-shell nanofiber aerogel material prepared in example 1 of the present invention; in fig. 5, (a) is a high resolution transmission electron micrograph, and (b) is a selected area electron diffraction micrograph.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below in connection with the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides a preparation method of a high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material, which comprises the following steps:
(1) Carrying out chemical vapor deposition reaction on a carbon source and a silicon source to obtain SiC nanofibers; in the present invention, the carbon source is, for example, coke powder (coke powder), and the silicon source is, for example, silicon powder; in the invention, when chemical vapor deposition reaction is carried out, for example, the silicon powder is placed in a graphite crucible, the invention has no special requirement on the dosage of the coke powder, so that the coke powder can fully bury the graphite crucible filled with the silicon powder; in the invention, the chemical vapor deposition reaction is carried out under inert atmosphere (such as argon), and the temperature of the chemical vapor deposition reaction is 1400-1600 ℃ for 4-8 hours; in the invention, after a silicon carbide nanowire ball polymer is obtained through a chemical vapor deposition reaction, the silicon carbide nanowire ball polymer is calcined in an air atmosphere muffle furnace at 500-800 ℃ for 1-3 hours so as to completely remove residual carbon and obtain SiC nanofiber;
(2) Oxidizing the SiC nanofiber to obtain a SiC@SiO 2 single core-shell structure nanofiber; in the invention, the nanofiber contained in the SiC@SiO 2 single core-shell structure nanofiber comprises a SiC core layer and a SiO 2 shell layer (silicon dioxide shell layer) wrapped on the outer side of the SiC core layer; in the invention, the oxidation treatment is an active controllable oxidation treatment; the oxidation treatment is carried out in an atmosphere furnace, and the oxygen content is controlled by adjusting the oxygen flow and the argon flow under the condition of the oxidation treatment temperature, so that the SiC nanofiber is subjected to active controllable oxidation treatment under a high-temperature aerobic environment, and the average thickness of SiO 2 shell layers contained in the obtained SiC@SiO 2 single-core-shell structure nanofiber is preferably 2-20 nm, and is preferably 7nm;
(3) Carrying out atomic layer deposition treatment on the SiC@SiO 2 single-core-shell structure nanofiber to obtain a SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber; in the present invention, the nanofiber contained in the nanofiber with the sic@sio 2 @oxide ceramic dual-core-shell structure comprises a SiC core layer, a SiO 2 shell layer wrapped on the outer side of the SiC core layer, and an oxide ceramic shell layer wrapped on the outer side of the SiO 2 shell layer, for example, as shown in fig. 3, the sic@sio 2 @oxide ceramic dual-core-shell structure has a dual-core-shell structure; in the present invention, it is preferable that the average thickness of the oxide ceramic shell layer contained in the nano fiber with the sic@sio 2 @oxide ceramic dual core-shell structure is 2 to 20nm, preferably 6nm;
(4) Uniformly dispersing the SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber by using water to obtain a core-shell structure nanofiber dispersion, and then sequentially performing the steps of pre-freezing and freeze-drying on the core-shell structure nanofiber dispersion to obtain SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber aerogel;
(5) Carrying out thermal annealing treatment on the SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber aerogel to obtain a high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material; according to the invention, the oxide ceramic shell layer subjected to atomic layer deposition treatment can be subjected to crystal form transformation through the thermal annealing treatment, for example, the alumina shell layer is changed into more stable alpha-alumina, in addition, reaction can occur between the silica and the alumina coating, and Si-O-Al strong bonding effect is formed between the silica and the alumina after the thermal annealing to generate more stable mullite crystal phase, so that the temperature resistance and the like of the silicon carbide@oxide ceramic core-shell nanofiber aerogel material can be greatly improved; in the invention, the thermal annealing treatment is carried out in an air atmosphere, for example, and the nano fiber contained in the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nano fiber aerogel material obtained after the thermal annealing treatment still comprises a SiC core layer, a SiO 2 shell layer and an oxide ceramic shell layer.
The invention provides a preparation method of a high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material, which comprises the steps of forming SiC@SiO 2 single-core-shell nanofiber by controllable oxidization of SiC nanofiber generated by chemical vapor deposition reaction, then forming a compact ceramic shell layer such as alumina on the surface of the SiC@SiO 2 core-shell nanofiber by utilizing an atomic layer deposition strategy to obtain SiC@SiO 2 @oxide ceramic dual-core-shell nanofiber, and pre-freezing, freeze-drying and high-temperature-annealing the SiC@SiO 2 @oxide ceramic dual-core-shell nanofiber to form the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material; the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material prepared by the method has a unique core-shell nanostructure, and has the remarkable advantages of high temperature resistance, high elasticity, ultra-light weight, high heat insulation and the like compared with the silicon carbide nanofiber aerogel material prepared by the prior art.
The silicon oxide shell layer with controllable thickness formed by active oxidation on the surface of the SiC nanofiber not only can prevent oxygen from diffusing to the surface of the SiC, but also can provide a better attachment point for the formation of an oxide ceramic shell layer deposited by an atomic layer, and a strong bonding effect is formed between silicon dioxide and oxide after high-temperature thermal annealing, for example, a Si-O-Al strong bonding effect is formed between silicon dioxide and aluminum oxide after high-temperature thermal annealing, so that the temperature resistance of the silicon carbide nanofiber can be greatly improved; after the silicon oxide and oxide ceramic shell layers are introduced into the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material, the high-elasticity mechanical property of the material is not affected, which is attributed to the fact that the thickness of a silicon dioxide shell layer formed by active oxidation and the thickness of an oxide ceramic shell layer formed by atomic layer deposition are highly controllable on the nanoscale, and shell inorganic oxides are continuous on the length direction and do not negatively affect the mechanical property of the silicon carbide nanofiber; compared with the silicon carbide nanofiber aerogel in the prior art, the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material has stronger heat insulation capability, because interfaces among silicon carbide, silicon oxide and oxide ceramic shell layers in the silicon carbide@oxide ceramic core-shell nanofiber can effectively reflect and scatter infrared radiation for a plurality of times, and can effectively reduce radiation heat transmission, and the heat insulation capability of the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material is improved.
According to some preferred embodiments, the SiC nanofibers obtained in step (1) have an average diameter of 20 to 100nm; the average thickness of SiO 2 shell layer contained in the SiC@SiO 2 single core-shell structure nanofiber obtained in the step (2) is 2-20 nm (for example, 2,3, 4,5, 6,7, 8,9, 10,11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 nm) preferably 7nm; and/or the average thickness of the oxide ceramic shell layer contained in the sic@sio 2 @oxide ceramic dual core-shell structure nanofiber obtained in the step (3) is 2-20 nm (for example, 2,3, 4,5, 6,7, 8,9, 10,11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 nm), preferably 6nm; in the present invention, the average thickness of the SiO 2 shell layer is preferably 2-20 nm, in the present invention, the SiO 2 shell layer can block oxygen from diffusing to the SiC surface at high temperature on the one hand, and can provide a better attachment point for the formation of an oxide ceramic shell layer deposited by an atomic layer on the other hand, the present invention finds that if the SiO 2 shell layer is too thin, the functions of the above two aspects are more effectively performed, if the SiO 2 shell layer is too thick, the total diameter of the subsequent nanofibers is affected, and if the total diameter of the nanofibers contained in the final aerogel material is too thick, the elasticity and the heat insulation performance of the finally produced aerogel material are adversely affected; in the present invention, it is preferable that the average thickness of the oxide ceramic shell layer is 2 to 20nm, and it has been found that if the thickness of the oxide ceramic shell layer is too thin, it cannot be more effectively resistant to high temperature, and if the thickness of the oxide ceramic shell layer is too thick, it is also disadvantageous to some extent in terms of elasticity, heat insulation property, etc. of the finally produced aerogel material.
According to some preferred embodiments, step (2) comprises the following sub-steps:
(a) Placing the SiC nanofiber in an atmosphere furnace, and heating to an oxidation treatment temperature in an argon atmosphere environment;
(b) Controlling the oxygen content by adjusting the oxygen flow and the argon flow, and oxidizing the SiC nanofiber in an aerobic environment;
(c) And cooling to room temperature (for example, 15-30 ℃ at room temperature) along with a furnace under the argon atmosphere to obtain the SiC@SiO 2 single core-shell structure nanofiber.
According to some preferred embodiments, in step (b), the oxygen intake rate is 0.01-2 mL/min (e.g. 0.01, 0.05, 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.5, 1.8 or 2 mL/min), preferably 0.1-2 mL/min, more preferably 0.5mL/min, and the argon intake rate is 3-50 mL/min (e.g. 3, 5, 8, 10, 15, 20, 25, 30, 35, 40, 45 or 50 mL/min), preferably 10-40 mL/min, more preferably 25mL/min; in the invention, the air inlet rate of the oxygen is preferably 0.01-2 mL/min, and the invention discovers that if the air inlet rate of the oxygen is too high, the oxidation rate is too high, the thickness controllability and uniformity of the SiO 2 shell layer are relatively poor, so that the performance and the like of the material can be influenced to a certain extent, and if the air inlet rate of the oxygen is too low, the oxidation rate is too low, and the experimental efficiency is influenced; the oxidation treatment temperature is 700-1200deg.C (e.g., 700 deg.C, 750 deg.C, 800 deg.C, 850 deg.C, 900 deg.C, 950 deg.C, 1000 deg.C, 1050 deg.C, 1100 deg.C, 1150 deg.C or 1200 deg.C), preferably 900 deg.C; and/or the time of the oxidation treatment is 5 to 240min (e.g., 5, 10, 20, 30, 40, 50, 60, 80, 100, 120, 150, 180, 200, 220, or 240 min), preferably 20 to 60min, more preferably 30min.
According to some preferred embodiments, the oxide ceramic is one or more of alumina, zirconia, hafnia, etc., preferably alumina.
According to some preferred embodiments, step (3) comprises the following sub-steps:
S1, placing nano fibers with a SiC@SiO 2 single-core-shell structure in a cavity of Atomic Layer Deposition (ALD) equipment, enabling oxide ceramic precursors to enter the cavity of the atomic layer deposition equipment in a pulse mode and to be chemically adsorbed on the surfaces of the nano fibers with the SiC@SiO 2 single-core-shell structure, and purging the redundant oxide ceramic precursors out of the cavity of the atomic layer deposition equipment by using nitrogen, namely purging the redundant oxide ceramic precursors by using nitrogen;
S2, enabling ultrapure water to enter the cavity of the atomic layer deposition equipment in a pulse mode and carrying out deposition reaction with the oxide ceramic precursor chemically adsorbed on the surface of the SiC@SiO 2 single-core-shell structure nanofiber in the step S1, and blowing out the redundant ultrapure water and byproducts generated after the deposition reaction out of the cavity of the atomic layer deposition equipment by using nitrogen;
And S3, sequentially repeating the step S1 and the step S2 for a plurality of times until the thickness of an oxide ceramic shell layer (oxide ceramic layer) formed on the surface of the SiC@SiO 2 single-core-shell structure nanofiber reaches a preset thickness (for example, the preset thickness is 2-20 nm), so as to obtain the SiC@SiO 2 @oxide ceramic double-core-shell structure nanofiber.
According to some preferred embodiments, the oxide ceramic precursor is trimethylaluminum; the pulse time of the oxide ceramic precursor is 0.08 to 0.25s (e.g., 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22, 0.23, 0.24, or 0.25 s), preferably 0.15s; the pulse time of the ultrapure water is 0.1 to 0.35s (for example 0.1、0.11、0.12、0.13、0.14、0.15、0.16、0.17、0.18、0.19、0.2、0.21、0.22、0.23、0.24、0.25、0.26、0.27、0.28、0.29、0.3、0.31、0.32、0.33、0.34 or 0.35 s), preferably 0.25s; in step S1 and step S2, the purging with nitrogen is performed for 10 to 120 seconds (e.g., 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110 or 120 seconds), preferably 60 seconds; the deposition reaction is carried out at a temperature of 40 to 100 ℃ (e.g., 40 ℃, 45 ℃,50 ℃, 55 ℃, 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃) preferably 65 ℃; and/or repeating steps S1 and S2 in sequence 22 to 222 times (e.g., 22, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, or 222 times), preferably 67 times.
According to some preferred embodiments, the mass concentration of sic@sio 2 @oxide ceramic dual core-shell structured nanofibers contained in the core-shell structured nanofiber dispersion is 0.06-8% (e.g. 0.06%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7% or 8%), preferably 1-4%, more preferably 2%; and/or uniformly dispersing the SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber with water at 1500-3000 rpm (such as 1500, 1600, 1700, 1800, 1900, 2000, 2100, 2200, 2300, 2400, 2500, 2600, 2700, 2800, 2900 or 3000 rpm) for 1-3 h (such as 1, 1.5, 2, 2.5 or 3 h) to obtain the core-shell structure nanofiber dispersion.
According to some preferred embodiments, the pre-freezing is freezing under liquid nitrogen for 10-60 min; the freeze drying is carried out in a freeze dryer, in the freeze drying process, the temperature of a chamber of the freeze dryer is controlled to be 10-35 ℃, the temperature of a cold trap of the freeze dryer is controlled to be minus 80-minus 50 ℃, the pressure of the freeze drying is 1-30 Pa, and the time of the freeze drying is 24-96 h; and/or the temperature of the thermal annealing treatment is 1100-1400 ℃ (e.g. 1100 ℃, 1150 ℃, 1200 ℃, 1250 ℃, 1300 ℃, 1350 ℃ or 1400 ℃) preferably 1300 ℃, and the time of the thermal annealing treatment is 1-30 min (e.g. 1, 5, 10, 15, 20, 25 or 30 min) preferably 5min.
The present invention provides in a second aspect a high temperature resistant, high elasticity silicon carbide @ oxide ceramic core-shell nanofiber aerogel material made by the method of the present invention described in the first aspect; preferably, the high temperature resistant high elasticity silicon carbide @ oxide ceramic core-shell nanofiber aerogel material has one or more of the following properties: the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material has the temperature resistance limit of 1150 ℃ or higher, more preferably 1200-1300 ℃ or higher under an aerobic environment (muffle furnace examination under an air atmosphere), and exhibits the ultrahigh temperature resistance characteristic; the maximum compression deformation of the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material is more than 95%, the rebound rate is more than 85%, more preferably the rebound rate is 98-100%, and the super-elasticity mechanical behavior is shown; the density of the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material is 0.7-80 mg/cm 3, and the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material shows ultra-light characteristics; the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material has the room temperature thermal conductivity of 0.021-0.028W/(m.K) and has super heat insulation capacity.
The invention will be further illustrated by way of example, but the scope of the invention is not limited to these examples.
Example 1
① Placing 6g of silicon powder in a graphite crucible with the diameter of 4cm and the height of 5cm, covering a graphite cover (graphite crucible cover), placing the graphite crucible with the silicon powder in a corundum crucible with larger size (with the diameter of 8cm and the height of 10 cm), and pouring coke powder into the corundum crucible until the graphite crucible is completely buried; placing the corundum crucible into a high-temperature atmosphere furnace (argon atmosphere), heating to 1450 ℃ at a speed of 3 ℃/min, keeping the temperature for 5 hours, naturally cooling to room temperature, scraping out silicon carbide nanowire cluster polymer deposited on a graphite cover, and calcining in an air atmosphere muffle furnace at 600 ℃ for 2 hours to completely remove residual carbon, thereby obtaining SiC nanofiber with an average diameter of 60 nm; in this example, 10 sets of batch experiments were performed in the same manner as in step ①, and the SiC nanofibers from the 10 sets of experiments were collected together.
② Placing the SiC nanofiber into an atmosphere furnace, and repeatedly pumping and discharging three times to enable the atmosphere furnace to be in an argon environment, and heating to 900 ℃ at a speed of 5 ℃/min (oxidation treatment temperature); adjusting the oxygen inlet rate to be 0.5mL/min and the argon inlet rate to be 25mL/min to control the oxygen content in the atmosphere furnace, and oxidizing the SiC nanofiber at 900 ℃ for 30min; and closing the oxygen flow, regulating the argon inlet rate to be 50mL/min to enable the atmosphere in the atmosphere furnace to quickly change into an argon environment, and taking out the furnace until the temperature in the furnace is reduced to room temperature to obtain the SiC@SiO 2 single core-shell structure nanofiber, wherein the average thickness of the SiO 2 shell layer contained in the nanofiber is 7nm.
③ Placing the SiC@SiO 2 single-core-shell structure nanofiber into an ALD equipment cavity, enabling trimethylaluminum (oxide ceramic precursor) to enter the ALD equipment cavity in a 0.15s pulse mode by using nitrogen as carrier gas, and chemically adsorbing the trimethylaluminum on the surface of the SiC@SiO 2 single-core-shell structure nanofiber, and purging the redundant trimethylaluminum out of the ALD equipment cavity by using nitrogen for 60s; then, the ultrapure water enters the cavity of the ALD equipment in a 0.25s pulse mode, and is subjected to deposition reaction with trimethylaluminum chemically adsorbed on the surface of the SiC@SiO 2 single core-shell structure nanofiber at 65 ℃, and after the reaction is completed, the extra ultrapure water and deposition reaction byproducts are blown out of the cavity of the ALD equipment by nitrogen for 60s, so that one ALD cycle is completed. Repeating the ALD cycle 67 times to obtain the SiC@SiO 2@Al2O3 ceramic dual-core-shell structure nanofiber, wherein the average thickness of the alumina ceramic shell layer is 6nm.
④ Adding 100g of water and 2g of SiC@SiO 2@Al2O3 ceramic nano-fiber with a double-core-shell structure into a beaker, and stirring for 2 hours at a stirring speed of 2000rpm to form uniformly and stably dispersed nano-fiber dispersion liquid with a core-shell structure; and (3) rapidly freezing the beaker filled with the core-shell structure nanofiber dispersion liquid in liquid nitrogen for 20min, then putting the beaker into a freeze dryer for freeze drying, controlling the pressure in the freeze dryer below 20Pa, controlling the temperature of a chamber of the freeze dryer at 25 ℃, controlling the temperature of a freeze drying cold trap at-70 ℃, and freeze drying for 48h to obtain the SiC@SiO 2@Al2O3 ceramic dual-core-shell structure nanofiber aerogel.
⑤ And (3) loading the SiC@SiO 2@Al2O3 ceramic nano fiber aerogel with the double-core-shell structure into a corundum crucible, putting the corundum crucible into an air atmosphere muffle furnace with the temperature of 1300 ℃ for heat annealing treatment for 5min, taking out and cooling to room temperature, and obtaining the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nano fiber aerogel material.
Example 2
① The same as in step ① of example 1.
② Placing the SiC nanofiber into an atmosphere furnace, and repeatedly pumping and discharging three times to enable the atmosphere furnace to be in an argon environment, and heating to 900 ℃ at a speed of 5 ℃/min (oxidation treatment temperature); adjusting the oxygen inlet rate to be 0.5mL/min and the argon inlet rate to be 25mL/min to control the oxygen content in the atmosphere furnace, and oxidizing the SiC nanofiber at 900 ℃ for 8min; and closing the oxygen flow, regulating the argon inlet rate to be 50mL/min to enable the atmosphere in the atmosphere furnace to quickly change into an argon environment, and taking out the furnace until the temperature in the furnace is reduced to room temperature to obtain the SiC@SiO 2 single core-shell structure nanofiber, wherein the average thickness of the SiO 2 shell layer contained in the nanofiber is 2nm.
③ Placing the SiC@SiO 2 single-core-shell structure nanofiber into an ALD equipment cavity, enabling trimethylaluminum (oxide ceramic precursor) to enter the ALD equipment cavity in a 0.15s pulse mode by using nitrogen as carrier gas, and chemically adsorbing the trimethylaluminum on the surface of the SiC@SiO 2 single-core-shell structure nanofiber, and purging the redundant trimethylaluminum out of the ALD equipment cavity by using nitrogen for 60s; then, the ultrapure water enters the cavity of the ALD equipment in a 0.25s pulse mode, and is subjected to deposition reaction with trimethylaluminum chemically adsorbed on the surface of the SiC@SiO 2 single core-shell structure nanofiber at 65 ℃, and after the reaction is completed, the extra ultrapure water and deposition reaction byproducts are blown out of the cavity of the ALD equipment by nitrogen for 60s, so that one ALD cycle is completed. Repeating the ALD cycle for 22 times to obtain the SiC@SiO 2@Al2O3 ceramic dual-core-shell structure nanofiber, wherein the average thickness of the alumina ceramic shell layer is 2nm.
④ The same as in step ④ of example 1.
⑤ The same as in step ⑤ of example 1.
Example 3
① The same as in step ① of example 1.
② Placing the SiC nanofiber into an atmosphere furnace, and repeatedly pumping and discharging three times to enable the atmosphere furnace to be in an argon environment, and heating to 900 ℃ at a speed of 5 ℃/min (oxidation treatment temperature); adjusting the oxygen inlet rate to be 0.5mL/min and the argon inlet rate to be 25mL/min to control the oxygen content in the atmosphere furnace, and oxidizing the SiC nanofiber at 900 ℃ for 86min; and closing the oxygen flow, regulating the argon inlet rate to be 50mL/min to enable the atmosphere in the atmosphere furnace to quickly change into an argon environment, and taking out the furnace until the temperature in the furnace is reduced to room temperature to obtain the SiC@SiO 2 single core-shell structure nanofiber, wherein the average thickness of the SiO 2 shell layer contained in the nanofiber is 20nm.
③ Placing the SiC@SiO 2 single-core-shell structure nanofiber into an ALD equipment cavity, enabling trimethylaluminum (oxide ceramic precursor) to enter the ALD equipment cavity in a 0.15s pulse mode by using nitrogen as carrier gas, and chemically adsorbing the trimethylaluminum on the surface of the SiC@SiO 2 single-core-shell structure nanofiber, and purging the redundant trimethylaluminum out of the ALD equipment cavity by using nitrogen for 60s; then, the ultrapure water enters the cavity of the ALD equipment in a 0.25s pulse mode, and is subjected to deposition reaction with trimethylaluminum chemically adsorbed on the surface of the SiC@SiO 2 single core-shell structure nanofiber at 65 ℃, and after the reaction is completed, the extra ultrapure water and deposition reaction byproducts are blown out of the cavity of the ALD equipment by nitrogen for 60s, so that one ALD cycle is completed. Repeating the ALD cycle for 222 times to obtain the SiC@SiO 2@Al2O3 ceramic dual-core-shell structure nanofiber, wherein the average thickness of the alumina ceramic shell layer is 20nm.
④ The same as in step ④ of example 1.
⑤ The same as in step ⑤ of example 1.
Example 4
① The same as in step ① of example 1.
② Placing the SiC nanofiber into an atmosphere furnace, and repeatedly pumping and discharging three times to enable the atmosphere furnace to be in an argon environment, and heating to 900 ℃ at a speed of 5 ℃/min (oxidation treatment temperature); adjusting the oxygen inlet rate to be 0.5mL/min and the argon inlet rate to be 25mL/min to control the oxygen content in the atmosphere furnace, and oxidizing the SiC nanofiber for 4min at 900 ℃; and closing the oxygen flow, regulating the argon inlet rate to be 50mL/min to enable the atmosphere in the atmosphere furnace to quickly change into an argon environment, and taking out the furnace until the temperature in the furnace is reduced to room temperature to obtain the SiC@SiO 2 single core-shell structure nanofiber, wherein the average thickness of the SiO 2 shell layer contained in the nanofiber is 1nm.
③ Placing the SiC@SiO 2 single-core-shell structure nanofiber into an ALD equipment cavity, enabling trimethylaluminum (oxide ceramic precursor) to enter the ALD equipment cavity in a 0.15s pulse mode by using nitrogen as carrier gas, and chemically adsorbing the trimethylaluminum on the surface of the SiC@SiO 2 single-core-shell structure nanofiber, and purging the redundant trimethylaluminum out of the ALD equipment cavity by using nitrogen for 60s; then, the ultrapure water enters the cavity of the ALD equipment in a 0.25s pulse mode, and is subjected to deposition reaction with trimethylaluminum chemically adsorbed on the surface of the SiC@SiO 2 single core-shell structure nanofiber at 65 ℃, and after the reaction is completed, the extra ultrapure water and deposition reaction byproducts are blown out of the cavity of the ALD equipment by nitrogen for 60s, so that one ALD cycle is completed. Repeating the ALD cycle for 11 times to obtain the SiC@SiO 2@Al2O3 ceramic dual-core-shell structure nanofiber, wherein the average thickness of the alumina ceramic shell layer is 1nm.
④ The same as in step ④ of example 1.
⑤ The same as in step ⑤ of example 1.
Example 5
① The same as in step ① of example 1.
② Placing the SiC nanofiber into an atmosphere furnace, and repeatedly pumping and discharging three times to enable the atmosphere furnace to be in an argon environment, and heating to 900 ℃ at a speed of 5 ℃/min (oxidation treatment temperature); adjusting the oxygen inlet rate to be 0.5mL/min and the argon inlet rate to be 25mL/min to control the oxygen content in the atmosphere furnace, and oxidizing the SiC nanofiber at 900 ℃ for 130min; and closing the oxygen flow, regulating the argon inlet rate to be 50mL/min to enable the atmosphere in the atmosphere furnace to quickly change into an argon environment, and taking out the furnace until the temperature in the furnace is reduced to room temperature to obtain the SiC@SiO 2 single core-shell structure nanofiber, wherein the average thickness of the SiO 2 shell layer is 30nm.
③ Placing the SiC@SiO 2 single-core-shell structure nanofiber into an ALD equipment cavity, enabling trimethylaluminum (oxide ceramic precursor) to enter the ALD equipment cavity in a 0.15s pulse mode by using nitrogen as carrier gas, and chemically adsorbing the trimethylaluminum on the surface of the SiC@SiO 2 single-core-shell structure nanofiber, and purging the redundant trimethylaluminum out of the ALD equipment cavity by using nitrogen for 60s; then, the ultrapure water enters the cavity of the ALD equipment in a 0.25s pulse mode, and is subjected to deposition reaction with trimethylaluminum chemically adsorbed on the surface of the SiC@SiO 2 single core-shell structure nanofiber at 65 ℃, and after the reaction is completed, the extra ultrapure water and deposition reaction byproducts are blown out of the cavity of the ALD equipment by nitrogen for 60s, so that one ALD cycle is completed. The ALD cycle is repeated 333 times to obtain the SiC@SiO 2@Al2O3 ceramic dual-core-shell structure nanofiber, wherein the average thickness of the alumina ceramic shell layer is 30nm.
④ The same as in step ④ of example 1.
⑤ The same as in step ⑤ of example 1.
Example 6
① The same as in step ① of example 1.
② Placing the SiC nanofiber into an atmosphere furnace, and repeatedly pumping and discharging three times to enable the atmosphere furnace to be in an argon environment, and heating to 900 ℃ at a speed of 5 ℃/min (oxidation treatment temperature); adjusting the oxygen inlet rate to be 2.5mL/min and the argon inlet rate to be 125mL/min to control the oxygen content in the atmosphere furnace, and oxidizing the SiC nanofiber at 900 ℃ for 8min; and (3) closing the oxygen flow to quickly change the atmosphere into an argon environment in the atmosphere furnace, and taking out the furnace after the temperature in the furnace is reduced to the room temperature to obtain the SiC@SiO 2 single core-shell structure nanofiber, wherein the average thickness of the SiO 2 shell layer is 7nm.
③ The same as in step ③ of example 1.
④ The same as in step ④ of example 1.
⑤ The same as in step ⑤ of example 1.
Comparative example 1
Comparative example 1 is substantially the same as example 1 except that:
Step ⑤ is not included, and the SiC@SiO 2@Al2O3 ceramic nanofiber aerogel with the double-core-shell structure is obtained.
Comparative example 2
Comparative example 2 is substantially the same as example 1 except that:
① The same as in step ① of example 1.
② Placing the SiC nanofiber into an atmosphere furnace, and repeatedly pumping and discharging three times to enable the atmosphere furnace to be in an argon environment, and heating to 900 ℃ at a speed of 5 ℃/min (oxidation treatment temperature); adjusting the oxygen inlet rate to be 0.5mL/min and the argon inlet rate to be 25mL/min to control the oxygen content in the atmosphere furnace, and oxidizing the SiC nanofiber at 900 ℃ for 30min; and closing the oxygen flow, regulating the argon inlet rate to be 50mL/min to enable the atmosphere in the atmosphere furnace to quickly change into an argon environment, and taking out the furnace until the temperature in the furnace is reduced to room temperature to obtain the SiC@SiO 2 single core-shell structure nanofiber, wherein the average thickness of the SiO 2 shell layer contained in the nanofiber is 7nm.
③ Adding 100g of water and 2g of SiC@SiO 2 single core-shell structure nanofiber into a beaker, and stirring for 2 hours at a stirring speed of 2000rpm to form a uniformly and stably dispersed core-shell structure nanofiber dispersion; and (3) rapidly freezing the beaker filled with the core-shell structure nanofiber dispersion liquid in liquid nitrogen for 20min, then putting the beaker into a freeze dryer for freeze drying, controlling the pressure in the freeze dryer below 20Pa, controlling the temperature of a chamber of the freeze dryer at 25 ℃, controlling the temperature of a freeze drying cold trap at-70 ℃, and freeze drying for 48h to obtain the SiC@SiO 2 single core-shell structure nanofiber aerogel.
④ And (3) loading the SiC@SiO 2 single-core-shell structure nanofiber aerogel into a corundum crucible, putting the corundum crucible into an air atmosphere muffle furnace with the temperature of 1300 ℃ for heat annealing treatment for 5min, taking out and cooling to room temperature, and obtaining the silicon carbide@silicon oxide core-shell nanofiber aerogel material.
Comparative example 3
① The same as in step ① of example 1.
② Placing the SiC nanofiber into an ALD equipment cavity, enabling trimethylaluminum (oxide ceramic precursor) to enter the ALD equipment cavity in a 0.15s pulse mode by using nitrogen as carrier gas and to be chemically adsorbed on the surface of the SiC nanofiber, and blowing the redundant trimethylaluminum out of the ALD equipment cavity by using the nitrogen for 60s; then, the ultrapure water enters the cavity of the ALD equipment in a 0.25s pulse mode, and is subjected to deposition reaction with trimethylaluminum chemically adsorbed on the surface of the SiC nanofiber at 65 ℃ at last time, and after the reaction is completed, the superfluous ultrapure water and deposition reaction byproducts are blown out of the cavity of the ALD equipment by nitrogen for 60s, so that one ALD cycle is completed. Repeating the ALD cycle 67 times to obtain the SiC@Al 2O3 ceramic single core-shell structure nanofiber, wherein the average thickness of the alumina ceramic shell layer is 6nm.
③ Adding 100g of water and 2g of SiC@Al 2O3 ceramic single-core-shell structure nanofiber into a beaker, and stirring for 2 hours at a stirring speed of 2000rpm to form a uniformly and stably dispersed core-shell structure nanofiber dispersion; and (3) rapidly freezing the beaker filled with the core-shell structure nanofiber dispersion liquid in liquid nitrogen for 20min, then putting the beaker into a freeze dryer for freeze drying, controlling the pressure in the freeze dryer below 20Pa, controlling the temperature of a chamber of the freeze dryer at 25 ℃, controlling the temperature of a freeze drying cold trap at-70 ℃, and freeze drying for 48h to obtain the SiC@Al 2O3 ceramic single core-shell structure nanofiber aerogel.
④ And (3) loading the SiC@Al 2O3 ceramic single-core-shell structure nanofiber aerogel into a corundum crucible, putting the corundum crucible into an air atmosphere muffle furnace with the temperature of 1300 ℃ for heat annealing treatment for 5min, taking out and cooling to room temperature, and obtaining the silicon carbide@alumina ceramic core-shell nanofiber aerogel material.
Comparative example 4
① The same as in step ① of example 1.
② Adding 100g of water and 2g of SiC nanofiber into a beaker, and stirring for 2 hours at a stirring speed of 2000rpm to form a uniformly and stably dispersed nanofiber solution; and (3) rapidly freezing the beaker filled with the nanofiber solution in liquid nitrogen for 20min, then putting the beaker into a freeze dryer for freeze drying, controlling the internal pressure of the freeze dryer to be below 20Pa, controlling the temperature of a chamber of the freeze dryer to be 25 ℃, controlling the temperature of a freeze drying cold trap to be-70 ℃, and freeze drying for 48h to obtain the SiC nanofiber aerogel.
③ And (3) loading the SiC nanofiber aerogel into a corundum crucible, putting the corundum crucible into an air atmosphere muffle furnace with the temperature of 1300 ℃ for heat annealing treatment for 5min, taking out and cooling to room temperature, and thus obtaining the silicon carbide nanofiber aerogel material.
Comparative example 5
① The preparation method comprises the steps of preparing silica sol by taking ethyl orthosilicate (67 wt%) as a sol raw material, taking water as a cross-linking agent (22 wt%) and absolute ethyl alcohol as a solvent (11 wt%) and fully soaking 60g of chopped carbon fibers with the length of about 20mm in the silica sol, and then draining and drying to obtain 112g of carbon fiber aggregate with the surface coated with SiO 2.
② The carbon fiber aggregate with SiO 2 coated on the surface is occluded and dispersed by a cotton fluffer to obtain 105g of carbon fiber felt with SiO 2 coated on the surface.
③ In the preparation of silica sol according to the scheme of step ①, a certain amount of expandable graphite (the mass is 10% of that of ethyl orthosilicate) is added, stirring is continued until the gel is naturally gelled, and the gel is dried and crushed to obtain SiO 2/C gel powder.
④ 200G of SiO 2/C gel powder is flatly paved at the bottom of a graphite crucible, then 24g of carbon fiber felt with SiO 2 coated on the surface is uniformly dispersed above the SiO 2/C gel powder in a square preset shape, a crucible cover is covered, and the crucible is placed in an argon atmosphere high-temperature atmosphere furnace.
⑤ And (3) controlling the temperature by a high-temperature atmosphere furnace program, heating to 1600 ℃, and preserving the heat for 5 hours to obtain the silicon carbide nanofiber aerogel material.
Comparative example 6
① Placing 100g of calcium carbonate and 30g of activated carbon into a stainless steel ball grinding tank, placing 300g of zirconia grinding balls, and ball-milling for 5 hours at the speed of 100r/min to obtain a carbon source with the particle size of 340 nm;
② Putting 28g of silicon powder and 60g of silicon dioxide into a stainless steel ball grinding tank, placing 200g of zirconia grinding balls, and ball-milling for 4 hours at the speed of 200r/min to obtain a silicon source with the particle size of 200 nm;
③ And (3) placing 50g of carbon source and 100g of silicon source into a graphite crucible, uniformly mixing, carrying out chemical vapor deposition reaction for 5 hours at 1500 ℃ under the argon atmosphere, and collecting the product on the surface of the graphite crucible cover to obtain the silicon carbide fiber aerogel material.
The performance indexes of the materials finally prepared in examples 1 to 6 and comparative examples 1 to 6 are tested, and the test results are shown in Table 1; in the present invention, 95% compression set is the amount of compression of a material in the thickness direction that is 95% of the initial thickness of the material; in the invention, the temperature resistance limit test is as follows: the materials finally prepared in each example and the comparative example are checked in a muffle furnace at a certain high temperature in an air atmosphere for 12 hours, the average value of the linear shrinkage of the materials in the x, y and z directions is less than 2%, the materials are considered to be capable of tolerating the high temperature, taking example 1 as an example, the average value of the linear shrinkage of the materials prepared in example 1in the x, y and z directions is 0.3% after the materials are checked in the muffle furnace at the high temperature of 1300 ℃ in the air atmosphere for 12 hours, namely the temperature resistance limit is 1300 ℃; the symbol "-" in table 1 indicates that the performance index was not tested.
Table 1: performance indicators of the materials prepared in examples 1 to 6 and comparative examples 1 to 6.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims (23)

1. The preparation method of the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material is characterized by comprising the following steps of:
(1) Carrying out chemical vapor deposition reaction on a carbon source and a silicon source to obtain SiC nanofibers;
(2) Oxidizing the SiC nanofiber to obtain a SiC@SiO 2 single core-shell structure nanofiber;
(3) Carrying out atomic layer deposition treatment on the SiC@SiO 2 single-core-shell structure nanofiber to obtain a SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber; the step (3) comprises the following sub-steps: s1, placing nano fibers with a SiC@SiO 2 single-core-shell structure in a cavity of an atomic layer deposition device, enabling oxide ceramic precursors to enter the cavity of the atomic layer deposition device in a pulse mode and chemically adsorbing the oxide ceramic precursors on the surface of the nano fibers with the SiC@SiO 2 single-core-shell structure, and blowing out the redundant oxide ceramic precursors from the cavity of the atomic layer deposition device by using nitrogen; s2, enabling ultrapure water to enter the cavity of the atomic layer deposition equipment in a pulse mode and carrying out deposition reaction with the oxide ceramic precursor chemically adsorbed on the surface of the SiC@SiO 2 single-core-shell structure nanofiber in the step S1, and blowing out the redundant ultrapure water and byproducts generated after the deposition reaction out of the cavity of the atomic layer deposition equipment by using nitrogen; s3, sequentially repeating the step S1 and the step S2 for a plurality of times until the thickness of an oxide ceramic shell layer formed on the surface of the SiC@SiO 2 single-core-shell structure nanofiber reaches a preset thickness, so as to obtain the SiC@SiO 2 @oxide ceramic double-core-shell structure nanofiber;
(4) Uniformly dispersing the SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber by using water to obtain a core-shell structure nanofiber dispersion, and then sequentially performing the steps of pre-freezing and freeze-drying on the core-shell structure nanofiber dispersion to obtain SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber aerogel;
(5) And carrying out thermal annealing treatment on the SiC@SiO 2 @oxide ceramic nano fiber aerogel with the dual-core-shell structure to obtain the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nano fiber aerogel material.
2. The method of manufacturing according to claim 1, characterized in that:
the average diameter of the SiC nanofibers obtained in the step (1) is 20-100 nm;
The average thickness of SiO 2 shell layers contained in the SiC@SiO 2 single core-shell structure nanofiber obtained in the step (2) is 2-20 nm; and/or
And (3) obtaining the SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber, wherein the average thickness of an oxide ceramic shell layer contained in the SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber is 2-20 nm.
3. The preparation method according to claim 2, characterized in that:
The average thickness of SiO 2 shell layer contained in the SiC@SiO 2 single core-shell structure nanofiber obtained in the step (2) is 7nm.
4. The preparation method according to claim 2, characterized in that:
And (3) obtaining the SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber, wherein the average thickness of an oxide ceramic shell layer contained in the SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber obtained in the step (3) is 6nm.
5. The method of claim 1, wherein step (2) comprises the sub-steps of:
(a) Placing the SiC nanofiber in an atmosphere furnace, and heating to an oxidation treatment temperature in an argon atmosphere environment;
(b) Controlling the oxygen content by adjusting the oxygen flow and the argon flow, and oxidizing the SiC nanofiber in an aerobic environment;
(c) And cooling to room temperature along with a furnace in an argon atmosphere to obtain the SiC@SiO 2 single core-shell structure nanofiber.
6. The method of manufacturing according to claim 5, wherein:
In the step (b), the air inlet rate of the oxygen is 0.01-2 mL/min, and the air inlet rate of the argon is 3-50 mL/min;
The oxidation treatment temperature is 700-1200 ℃; and/or
The time of the oxidation treatment is 5-240 min.
7. The method of manufacturing according to claim 6, wherein:
in step (b), the intake rate of oxygen is 0.5mL/min.
8. The method of manufacturing according to claim 6, wherein:
in step (b), the argon gas is introduced at a rate of 25mL/min.
9. The method of manufacturing according to claim 6, wherein:
the oxidation treatment temperature is 900 ℃.
10. The method of manufacturing according to claim 6, wherein:
the time of the oxidation treatment is 30min.
11. The method of manufacturing according to claim 1, characterized in that:
The oxide ceramic is one or more of aluminum oxide, zirconium oxide and hafnium oxide.
12. The method of manufacturing according to claim 1, characterized in that:
The oxide ceramic precursor is trimethylaluminum;
the pulse time of the oxide ceramic precursor is 0.08-0.25 s;
The pulse time of the ultrapure water is 0.1-0.35 s;
in the step S1 and the step S2, the purging is carried out with nitrogen for 10-120S;
in the step S2, the temperature for carrying out the deposition reaction is 40-100 ℃; and/or
The steps S1 and S2 are repeated 22-222 times in sequence.
13. The method of manufacturing according to claim 12, wherein:
the pulse time of the oxide ceramic precursor was 0.15s.
14. The method of manufacturing according to claim 12, wherein:
The pulse time of the ultrapure water was 0.25s.
15. The method of manufacturing according to claim 12, wherein:
in step S1 and step S2, the purge with nitrogen was performed for 60S.
16. The method of manufacturing according to claim 12, wherein:
In step S2, the deposition reaction is carried out at a temperature of 65 ℃.
17. The method of manufacturing according to claim 12, wherein:
the number of times of sequentially repeating step S1 and step S2 was 67 times.
18. The method of manufacturing according to claim 1, characterized in that:
The mass concentration of the SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber contained in the core-shell structure nanofiber dispersion liquid is 0.06-8%; and/or
And stirring the SiC@SiO 2 @oxide ceramic nanofiber with the double-core-shell structure with water for 1-3 hours at 1500-3000 rpm to uniformly disperse, so as to obtain a nanofiber dispersion liquid with the core-shell structure.
19. The method of manufacturing according to claim 18, wherein:
The mass concentration of the SiC@SiO 2 @oxide ceramic dual-core-shell structure nanofiber contained in the core-shell structure nanofiber dispersion liquid is 2%.
20. The method of manufacturing according to claim 1, characterized in that:
the pre-freezing is freezing under liquid nitrogen for 10-60 min;
The freeze drying is carried out in a freeze dryer, in the freeze drying process, the temperature of a chamber of the freeze dryer is controlled to be 10-35 ℃, the temperature of a cold trap of the freeze dryer is controlled to be-80 ℃ to-50 ℃, the pressure of the freeze drying is 1-30 Pa, and the time of the freeze drying is 24-96 h; and/or
The temperature of the thermal annealing treatment is 1100-1400 ℃, and the time of the thermal annealing treatment is 1-30 min.
21. The method of manufacturing according to claim 20, wherein:
The temperature of the thermal annealing treatment is 1300 ℃, and the time of the thermal annealing treatment is 5min.
22. A high temperature resistant high elasticity silicon carbide @ oxide ceramic core-shell nanofiber aerogel material made by the method of any one of claims 1 to 21.
23. The high temperature resistant, resilient silicon carbide @ oxide ceramic core-shell nanofiber aerogel material of claim 22, wherein the high temperature resistant, resilient silicon carbide @ oxide ceramic core-shell nanofiber aerogel material has one or more of the following properties:
the temperature resistance limit of the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material in an aerobic environment is 1200-1300 ℃;
the maximum compression deformation of the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material is more than 95%, and the rebound rate is 98-100%;
the density of the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material is 0.7-80 mg/cm 3;
the room temperature thermal conductivity of the high-temperature-resistant high-elasticity silicon carbide@oxide ceramic core-shell nanofiber aerogel material is 0.021-0.028W/(m.K).
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