CN113831581B - High-elasticity anti-radiation nanofiber aerogel material and preparation method thereof - Google Patents

Abstract

The invention relates to a high-elasticity anti-radiation nanofiber aerogel material and a preparation method thereof, wherein the method comprises the following steps: uniformly mixing tetraethoxysilane, phosphoric acid and water, stirring for 1-24 h, adding titanium dioxide nano powder, continuously stirring for 1-12h, and performing ultrasonic treatment to obtain composite hydrolysate; uniformly mixing the polyvinyl alcohol aqueous solution and the composite hydrolysate with water, stirring for 1-12h, and then carrying out electrostatic spinning on the precursor solution to obtain a hybrid nanofiber membrane; carrying out heat treatment on the hybrid nanofiber membrane; adding the hybrid nanofiber membrane subjected to heat treatment, ethyl orthosilicate, boric acid and aluminum chloride into water, and adding a graphene oxide solution into the water to perform high-speed stirring to obtain a homogeneous dispersion liquid; and then sequentially freezing, freeze-drying and post-treating the homogeneous dispersion to prepare the high-elasticity anti-radiation nanofiber aerogel material. The material prepared by the invention has high elasticity, and has excellent radiation resistance, temperature resistance and high-temperature heat insulation performance.

Description

A kind of highly elastic anti-radiation nanofiber airgel material and preparation method thereof

technical field

The invention relates to the technical field of airgel preparation, in particular to a highly elastic anti-radiation nanofiber airgel material and a preparation method thereof.

Background technique

Nanoporous airgel (airgel for short) material is a kind of gel material whose dispersion medium is gas. It is a nanoporous solid material with a network structure composed of colloidal particles or polymer molecules. The size of the pores in the material is on the order of nanometers. Its porosity is as high as 80-99.8%, the typical size of the pores is 1-100nm, the specific surface area is 200-1000m ² /g, the density can be as low as 3kg/m ³ , and the thermal conductivity at room temperature can be as low as 0.012W/m·K . It is precisely because of these characteristics that airgel materials have broad application potential in thermal, acoustic, optical, microelectronics, and particle detection. At present, the most widely used field of aerogel is still the field of heat insulation, because the unique nanostructure of aerogel can effectively reduce convective conduction, solid phase conduction and thermal radiation. Existing studies have proved that airgel is an effective thermal insulation material, but most of the airgel materials reported so far are rigid airgel materials with nano-skeleton as nano-pearl necklace structure. Airgel materials with high elasticity are often considered to be the properties of organic aerogels, and the preparation of elastic inorganic aerogels is relatively difficult. In recent years, the preparation of inorganic nanofiber airgel materials has become the focus of researchers. The elastic characteristics of inorganic nanofibers with high aspect ratio can be used to endow inorganic nanofiber airgel with high elasticity. However, although nanofiber airgel solves the problem of elasticity, its thermal insulation performance is far behind that of traditional airgel materials. Chinese patent application CN201910202661.5 discloses a method for preparing a modified silica powder/silica nanofiber composite airgel material, which consists of electrospun silica nanofibers and silica airgel powder The modified silica powder/silica nanofiber composite airgel material was prepared by combining the bulk phase, the compression rebound rate can reach 85%, and the uniform and stable dispersion of the nano-scale airgel powder improves the simple The heat insulation performance of nanofiber airgel, but the nanofibers in this patent application are pure silica phase, the radiation resistance performance is not good at high temperature, the thermal conductivity coefficient is large at high temperature, and the heat insulation performance is insufficient at high temperature .

In addition, nanofibrous airgel has larger pores and a more continuous skeleton, which determines that it has greater solid-phase heat conduction and gas-phase heat conduction, while the single-component structure makes its radiation resistance poor. A small amount of research work involves the preparation of silicon carbide nanofiber airgel materials with anti-radiation effect, however, pure silicon carbide nanofibers are prone to oxidation reactions in air, and their temperature resistance is poor.

With the development of science and technology, various fields have put forward higher requirements for the temperature resistance, compression resilience and high temperature insulation performance of airgel materials. Therefore, it is very necessary to develop an effective method to prepare a high Elastic radiation-resistant nanofibrous airgel materials.

Contents of the invention

In order to solve one or more technical problems in the prior art, the present invention provides a highly elastic anti-radiation nanofiber airgel material and a preparation method thereof. The highly elastic radiation-resistant nanofiber airgel material prepared by the invention has high elasticity and excellent radiation resistance performance, temperature resistance performance and high temperature heat insulation performance.

The present invention provides a kind of preparation method of highly elastic anti-radiation nanofiber airgel material in the first aspect, described method comprises the following steps:

(1) Mix ethyl orthosilicate, phosphoric acid and water evenly to obtain a mixed solution, then stir the mixed solution for 1 to 24 hours to obtain a hydrolyzate, then add titanium dioxide nanopowder to the hydrolyzate and continue stirring for 1 ～12h, and finally undergo ultrasonic treatment for 0.5～2h to obtain a composite hydrolyzate;

(2) mixing the polyvinyl alcohol aqueous solution and the composite hydrolyzate obtained in step (1) with water and stirring for 1 to 12 hours to obtain a precursor solution, and then performing electrospinning with the precursor solution as an electrospinning solution, A hybrid nanofibrous membrane is obtained;

(3) heat-treating the hybrid nanofiber membrane obtained in step (2) in an inert atmosphere; the heat treatment is: first heat-treating at 300-600°C for 1-10h, then heat-treating at 600-900°C for 1-5h, Then naturally cool to room temperature;

(4) Add the hybrid nanofiber membrane, tetraethyl orthosilicate, boric acid, and aluminum chloride into water after heat treatment in step (3) to obtain the dispersion to be dispersed, and then add graphene oxide solution to the dispersion to be dispersed And carry out high-speed stirring to obtain a homogeneous dispersion;

(5) performing the steps of freezing and freeze-drying the homogeneous dispersion liquid obtained in step (4) successively to obtain the nanofiber airgel material;

(6) Post-treating the nanofiber airgel material obtained in step (5) in an inert atmosphere to prepare a highly elastic and radiation-resistant nanofiber airgel material.

Preferably, in step (1): the molar ratio of the ethyl orthosilicate, the phosphoric acid and the water is (0.5-1): (0.005-0.05): (1-20), preferably 1 : (0.015～0.025): (8～15), more preferably 1:0.02:10; and/or the consumption of the titanium dioxide nanopowder is 0.4～10% of the quality of the hydrolyzate, preferably 0.5～5% %, more preferably 0.8 to 2.5%.

Preferably, in step (2): the mass fraction of polyvinyl alcohol contained in the polyvinyl alcohol aqueous solution is 1 to 20%; the mass ratio of the composite hydrolyzate, the polyvinyl alcohol aqueous solution and the water (1-5): (1-5): (0.5-5), preferably (2.5-3.5): (2.5-3.5): 2, more preferably 3:3:2; and/or the stirring The time is 3 ~ 6h.

Preferably, the parameters for electrospinning are as follows: voltage 10-30kV, perfusion speed 0.5-2mL/h, receiving distance 10-25cm, and/or temperature in the spinning chamber 15-35°C.

Preferably, in step (2), the obtained hybrid nanofiber membrane is also vacuum-dried; preferably, the obtained hybrid nanofiber membrane is vacuum-dried in a vacuum drying oven at 60-120°C for 1- 3h.

Preferably, in step (4): the graphene oxide solution is a graphene oxide aqueous solution with a concentration of 15 to 25 g/L; the amount of the graphene oxide solution is 0.5 to 2% of the quality of the liquid to be dispersed. %; and/or the mass fraction of the hybrid nanofiber film contained in the liquid to be dispersed is 0.4 to 0.6%, and the mass fraction of ethyl orthosilicate contained in the liquid to be dispersed is 0.4 to 0.6%, so The mass fraction of boric acid contained in the liquid to be dispersed is 0.05-0.2%, and the mass fraction of aluminum chloride contained in the liquid to be dispersed is 0.1-0.3%.

Preferably, in step (4): the rotational speed of the high-speed stirring is 5000-20000 r/min, and the time of the high-speed stirring is 5-30 min.

Preferably, in step (5): the freezing is freezing under liquid nitrogen for 10 to 60 minutes; the freezing is carried out in a mold, and the top and sides of the mold are made of materials with low thermal conductivity, The bottom of the mold is made of a material with high thermal conductivity, preferably, the top and sides of the mold are made of polytetrafluoroethylene, and the bottom of the mold is made of copper; and/or the The above-mentioned freeze-drying is vacuum freeze-drying, preferably, vacuum freeze-drying under the conditions of a vacuum degree of 0.5-10 Pa and a temperature of -50-70°C for 2-5 days.

Preferably, in step (6): the temperature of the post-treatment is 800-1000° C., and the time of the post-treatment is 0.1-12 h.

The second aspect of the present invention provides the highly elastic anti-radiation nanofiber airgel material prepared by the preparation method described in the first aspect of the present invention.

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

(1) In the method of the present invention, the anti-radiation agent is doped in the composite hydrolyzate, and after the heat treatment process, the in-situ doping of the anti-radiation agent is realized, so that the anti-radiation agent can be embedded in the nanofiber in situ; Compared with single-component nanofiber airgel (silicon dioxide, zirconia, mullite), the present invention has excellent anti-radiation properties, and the anti-radiation agent (titania nanopowder) is embedded in the nanofiber in situ It can be uniformly dispersed, avoiding the agglomeration between particles, can achieve better anti-radiation effect, and has good high-temperature heat insulation performance. The coefficient is low.

(2) The present invention prepares a hybrid nanofiber membrane (composite nanofiber) by doping titanium dioxide nanopowder in the composite hydrolyzate, and the present invention adopts composite nanofiber as the airgel basic unit to realize composite nanofiber The self-assembly of nanofibers with good elasticity is achieved by utilizing the bendable properties of nanofibers with high aspect ratio.

(3) The present invention adopts the silicon-aluminum composite component as the basic composition of the airgel, and obtains the airgel material of the composite component. During high-temperature use, the composite component can form a more temperature-resistant phase, which can effectively improve the durability of the material. temperature resistance.

(4) In the nanofiber airgel material of the present invention, anti-radiation nanoparticles are embedded in nanofibers, realizing the preparation of the core-shell structure porous network airgel, which can effectively make titanium dioxide nanopowder evenly distributed in the nanofiber airgel The interior of the material improves the radiation resistance of the airgel material.

(5) The present invention adopts a freeze-drying process instead of a supercritical drying process, which reduces the cost and period in the material preparation process, and improves the environmental protection of the preparation method at the same time.

(6) The highly elastic radiation-resistant nanofiber airgel material prepared by the method of the present invention also has excellent elasticity under the premise of maintaining a low thermal conductivity of not more than 0.032W/m K, and can achieve short-term temperatures above 1100°C. High temperature resistance, and low thermal conductivity at a high temperature of 800 ° C, excellent high temperature heat insulation performance, and excellent radiation resistance.

(7) The porosity of the highly elastic anti-radiation nanofiber airgel material prepared by the method of the present invention is more than 90%, the pore size is 5-500nm, the diameter of the nanofiber is 100-500nm, and the compression rebound rate is not less than 80%, The heat resistance temperature is above 1100°C.

Description of drawings

Fig. 1 is the preparation flowchart of the present invention.

Fig. 2 is a schematic diagram of the structure change of the material in the process of preparing the highly elastic radiation-resistant nanofiber airgel material in the present invention.

Fig. 3 is a SEM image of the heat-treated PVA/SiO ₂ /TiO ₂ hybrid nanofiber membrane prepared in Example 1 of the present invention. It can be seen from Figure 3 that there is no titanium dioxide nanopowder distributed on the surface of the PVA/SiO ₂ /TiO ₂ hybrid nanofiber membrane.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The present invention provides a kind of preparation method of highly elastic anti-radiation nanofiber airgel material in the first aspect, described method comprises the following steps:

(1) Mix tetraethyl orthosilicate (TEOS), phosphoric acid (H ₃ PO ₄ ) and water (such as deionized water) uniformly to obtain a mixed solution, and then stir the mixed solution for 1 to 24 hours (such as 1, 6 , 12 or 24h), to obtain a hydrolyzate, then add titanium dioxide nanopowder to the hydrolyzate and continue to stir for 1 to 12h (for example, 1, 3, 6, 8, 10 or 12h), and finally undergo ultrasonic treatment for 0.5 to 2h ( Such as 0.5, 1, 1.5 or 2h), to obtain a composite hydrolyzate (also referred to as TEOS composite hydrolyzate); specifically, step (1) is: at room temperature, take a certain mass of TEOS, H ₃ PO ₄ and deionized Water according to n(TEOS):n(H ₃ PO ₄ ):n(H ₂ O)=(0.5～1):(0.005～0.05):(1～20), preferably 1:(0.015～0.025): (8～15) are more preferably mixed in a molar ratio of 1:0.02:10, placed on a magnetic stirrer and stirred for 1 to 12 hours, preferably 12 hours, to obtain a hydrolyzate; subsequently add titanium dioxide nanopowder to the hydrolyzate to ensure that The dosage of the titanium dioxide nano powder (anti-radiation agent) is 0.4-10% of the mass of the hydrolyzed solution, preferably 0.8-2.5%, stirring for 1-12 hours, ultrasonication for 0.5-2 hours, so that the titanium dioxide nano-powder is evenly dispersed in the hydrolyzed solution , to obtain a composite hydrolyzate; in the present invention, the particle size of the titanium dioxide nanopowder is not particularly limited, and nanometer-sized titanium dioxide nanopowder can be used. In some specific embodiments, the titanium dioxide nanopowder is preferably Adopt the titanium dioxide nano-powder that particle size scope is 40～100nm; The present invention does not have special limitation to the operating frequency of described ultrasonic treatment, adopt conventional frequency to carry out, for example can be 25～40kHz; In the present invention, need first The mixed solution formed by mixing tetraethyl orthosilicate (TEOS), phosphoric acid (H ₃ PO ₄ ) and water is hydrolyzed first, and then titanium dioxide nanopowder is added to the hydrolyzed solution, which is stirred and ultrasonically treated, so that Only in this way can the titanium dioxide nano powder be evenly dispersed in the hydrolyzate, which is beneficial to the uniform doping of the titanium dioxide nano powder in the subsequent electrospinning process and the uniform in-situ doping of the titanium dioxide nano powder after the heat treatment process, so that the titanium dioxide nano powder can be Evenly embedded in the inside of the nanofiber, it can be evenly dispersed and avoid the agglomeration between particles, so as to effectively ensure that the titanium dioxide nanopowder can achieve excellent anti-radiation effect, improve the thermal stability of the airgel material, and reduce the airgel The high-temperature thermal conductivity of the material; the present invention finds that before hydrolysis, ethyl orthosilicate and water are phase-separated states, and the addition of titanium dioxide nano-powders will lead to adsorption, which will affect the hydrolysis effect and the dispersion effect of titanium dioxide nano-powders; Adding titanium dioxide nanopowder after complete hydrolysis of ethyl ester can disperse more uniformly and form a homogeneous composite hydrolyzed solution; the present invention finds that if ethyl orthosilicate (TEOS), phosphoric acid (H ₃ PO ₄ ), titanium dioxide nano-powder and water are mixed and hydrolyzed or directly in subsequent step (2), polyvinyl alcohol aqueous solution, titanium dioxide nano-powder and the hydrolyzate that do not contain titanium dioxide nano-powder are mixed and stirred with water to obtain the precursor solution, these two None of these methods can realize the uniform dispersion of titanium dioxide nanopowder, and finally the titanium dioxide nanopowder can only be partially embedded in the inside of the nanofiber, and the titanium dioxide nanopowder has obvious uneven distribution; in addition, the present invention finds that the present invention The dispersion method of the titanium dioxide nanopowder is compared to directly mixing tetraethyl orthosilicate (TEOS), phosphoric acid (H ₃ PO ₄ ), titanium dioxide nanopowder and water and hydrolyzing or directly in the subsequent step (2), dissolving with water The dispersion method of mixing and stirring the polyvinyl alcohol aqueous solution, the titanium dioxide nanopowder and the hydrolyzed solution without the titanium dioxide nanopowder can also significantly improve the compression resilience of the highly elastic anti-radiation nanofiber airgel material.

(2) Mix the polyvinyl alcohol aqueous solution and the composite hydrolyzate obtained in step (1) with water and stir for 1 to 12 hours (such as 1, 2, 4, 5, 6, 8, 10 or 12 hours) to obtain a precursor solution , and then use the precursor solution as the electrospinning solution to carry out electrospinning to obtain a hybrid nanofiber membrane (also referred to as PVA/SiO ₂ /TiO ₂ hybrid nanofiber membrane); in the present invention, the poly The preparation of vinyl alcohol aqueous solution (PVA aqueous solution) can be, for example, as follows: weigh a certain mass of polyvinyl alcohol powder and add it to deionized water, stir for 1-12 hours, and dissolve it by heating at 60-120°C; take it out after stirring, and put it in Stir and dissipate heat at room temperature on a magnetic stirrer until it drops to room temperature; the mass fraction of the prepared PVA aqueous solution is 1 to 20wt%; specifically, step (2) is: mix TEOS composite hydrolyzate, PVA aqueous solution, and deionized water according to (1～5):(1～5):(0.5～5) mass ratio mixed, placed on a magnetic stirrer at room temperature and stirred for 1～12h to obtain a uniform and clear precursor solution; then use a syringe to extract the precursor solution, Use an electrospinning machine to prepare PVA/SiO ₂ /TiO ₂ hybrid nanofiber membranes; the present invention finds that in the present invention, using water to prepare the TEOS composite hydrolyzate and polyvinyl alcohol aqueous solution into a precursor solution, compared with directly The method of directly mixing tetraethyl orthosilicate and polymers and then hydrolyzing can significantly improve the high-temperature heat insulation performance of nanofiber airgel materials; the present invention finds that if TEOS, titanium dioxide nanopowder, and polyvinyl alcohol are directly mixed and then hydrolyzed, On the one hand, polyvinyl alcohol needs to be dissolved more uniformly under heating conditions, and heating conditions will lead to accelerated hydrolysis and partial condensation reactions, resulting in the growth of a single particle of silica sol, which is not conducive to the formation of a homogeneous dispersion system of small particles. It will obviously affect the effect of TEOS after hydrolysis, and will eventually significantly affect the high temperature heat insulation performance of the airgel material. The hydrolysis effect and the dispersion effect of titanium dioxide nanopowder will eventually obviously affect the high-temperature heat insulation performance and compression resilience of the prepared airgel material.

(3) heat-treat the hybrid nanofiber membrane obtained in step (2) in an inert atmosphere (such as nitrogen, argon, or a mixed atmosphere of nitrogen and argon); °C (eg 300°C, 350°C, 400°C, 450°C, 500°C, 550°C or 600°C) heat treatment for 1 to 10 hours such as (eg 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 hours ), then heat treatment at 600-900°C (eg 600°C, 650°C, 700°C, 750°C, 800°C, 850°C or 900°C) for 1-5h (eg 1, 2, 3, 4 or 5h), and then naturally Cool to room temperature; in some specific embodiments, step (3) is: place the hybrid nanofiber membrane obtained in step (2) in an inert atmosphere furnace, and set the heating rate to 1-6° C./min, preferably 3 ～6 ℃/min is more preferably 5 ℃/min, first rises to 500 ℃ heat treatment 2h, then heats up to 800 ℃, heat treatment 3h, then naturally cools to room temperature; Compression rebound rate) high elastic anti-radiation nanofiber airgel material, the heat treatment process in step (3) is very important, if the heat treatment process is not carried out or only calcined at 300 ~ 600 ° C, the material will be significantly reduced High temperature resistance and high temperature rebound characteristics.

(4) Add the hybrid nanofiber membrane, tetraethyl orthosilicate, boric acid, and aluminum chloride into water after heat treatment in step (3) to obtain the dispersion to be dispersed, and then add graphene oxide solution to the dispersion to be dispersed And carry out high-speed stirring to obtain a homogeneous dispersion; in some specific embodiments, the hybrid nanofiber membrane, tetraethyl orthosilicate, boric acid and aluminum chloride after the heat treatment in step (3) are added to water to obtain Dispersion liquid, then add graphene oxide solution to the liquid to be dispersed and use a high-speed shearing machine to stir at a high speed of 5000 to 20000r/min, preferably 10000r/min, for 5 to 30min, preferably 20min, to obtain a homogeneous dispersion; the present invention It was found that the addition of tetraethyl orthosilicate and aluminum chloride can make the formation of silicon-aluminum composites at the nodes of nanofibers, and the addition of boric acid can make the fibers generate boric oxide at high temperature to form continuous boric oxide. to ensure that the nodes between the nanofibers are firm; the present invention finds that only the addition of tetraethyl orthosilicate, boric acid and aluminum chloride can ensure the high elasticity radiation resistance with high elasticity, room temperature thermal conductivity and high temperature thermal conductivity lower Nanofiber airgel material; the present invention finds that the addition of the graphene oxide solution will improve the flexibility of nanofibers, and the graphene sheet improves the flexibility of nanofibers as a toughening agent, and improves the nanofiber airgel material to a certain extent. Compression resilience, while improving the radiation resistance of nanofiber airgel materials, and improving the thermal insulation performance of nanofiber airgel materials at high temperatures.

(5) The steps of freezing and freeze-drying the homogeneous dispersion liquid obtained in step (4) are carried out successively to obtain the nanofiber airgel material; the present invention finds that only by carrying out freezing and freeze-drying sequentially can a composite material with excellent comprehensive properties be obtained. For the highly elastic radiation-resistant nanofiber airgel material, if the obtained homogeneous dispersion liquid is subjected to the steps of freezing and drying under normal pressure in sequence, it will not only increase the density, room temperature thermal conductivity and high temperature thermal conductivity of the material, but also increase the thermal conductivity of the material. The material does not have compression resilience.

(6) post-treatment (cracking) the nanofiber airgel material obtained in step (5) in an inert atmosphere to obtain a highly elastic radiation-resistant nanofiber airgel material; the present invention finds that step (5) After the obtained nanofiber airgel material is post-treated in an inert atmosphere, it can effectively ensure the compression resilience and high-temperature heat insulation performance of the final high-elastic radiation-resistant nanofiber airgel material, and significantly reduce the high temperature of the material. Thermal Conductivity.

In the method of the present invention, the anti-radiation agent is doped in the composite hydrolyzate, and after the heat treatment process, the in-situ doping of the anti-radiation agent is realized, so that the anti-radiation agent can be embedded in the nanofiber in situ, and the anti-radiation agent can be ensured. Uniform dispersion of the radiation agent to avoid agglomeration between particles; the components and structure of the composite nanofiber involved in the present invention are specially designed for high elastic anti-radiation heat insulation performance, and the high elastic anti-radiation nanofiber airgel prepared by the present invention While the material has high elasticity, it has excellent radiation resistance, temperature resistance and high temperature heat insulation performance.

The invention adopts the electrospinning method to prepare the nano-skeleton as the pearl string nano-fiber material, and prepares the three-dimensional nano-fiber airgel material with anti-radiation effect through the assembly process. Due to the coating effect of nanofibers, the inner nano-titanium dioxide can be evenly distributed inside the nanofiber airgel material, which can achieve effective anti-radiation effect. Finally, the preparation of nanofiber airgel material with high temperature resistance, high temperature heat insulation performance, radiation resistance and high elasticity has been realized.

According to some preferred embodiments, in step (1): the molar ratio of the tetraethylorthosilicate, the phosphoric acid and the water is (0.5-1): (0.005-0.05): (1-20) , preferably 1:(0.015～0.025):(8～15), more preferably 1:0.02:10; and/or the amount of titanium dioxide nanopowder is 0.4～10% of the mass of the hydrolyzate (for example 0.4%, 0.8%, 1%, 1.5%, 2%, 5%, 8% or 10%), preferably 0.5-5% (such as 0.5%, 0.8%, 1%, 1.5%, 2%, 3% , 4% or 5%), more preferably 0.8 to 2.5% (such as 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2% or 2.5%); in the present invention, more preferably The dosage of the titanium dioxide nanopowder is 0.8% to 2.5% of the mass of the hydrolyzed solution. The present invention finds that if the dosage of the titanium dioxide nanopowder is too small, the anti-radiation effect of the material will be insufficient, and if the said If the amount of titanium dioxide nano powder is too much, it will make the titanium dioxide nano powder difficult to disperse, and the titanium dioxide nano powder will agglomerate seriously, and too much titanium dioxide nano powder will cause the fiber formed in the electrospinning process to be insufficiently continuous, and finally significantly reduce the obtained high elasticity. Compression resilience and bulk strength of radiation-resistant nanofibrous airgel materials.

According to some preferred embodiments, in step (2): the mass fraction of polyvinyl alcohol contained in the polyvinyl alcohol aqueous solution is 1-20% (such as 1, 5, 8, 10, 12, 15, 18 or 20%) is preferably 8～12% (such as 8%, 9%, 10%, 11% or 12%); The mass ratio of described composite hydrolyzate, described polyvinyl alcohol aqueous solution and described water is (1～ 5): (1～5): (0.5～5), preferably (2.5～3.5): (2.5～3.5): 2, more preferably 3:3:2; in the present invention, polyvinyl alcohol can be Adjusting the viscosity of the spinning solution has a great influence on the fiber diameter in the spinning process, and the fiber diameter determines the thermal conductivity of the nanofiber airgel material; secondly, the polyvinyl alcohol will be decomposed in the subsequent heat treatment process, and the polyethylene The higher the alcohol content, the smaller the fiber diameter, and the too high content of polyvinyl alcohol will cause the discontinuity of the fiber with too little inorganic component in the heat treatment process, so the suitable composite hydrolyzate, the polyvinyl alcohol aqueous solution The mass ratio of the nanofiber airgel material to the water can make the fiber diameter of the nanofibrous airgel material as small as possible while maintaining continuity, which is beneficial to ensure the heat insulation performance of the final airgel material.

According to some preferred embodiments, in step (2): the stirring time is 3-6 hours (for example, 3, 4, 5 or 6 hours).

According to some preferred embodiments, the parameters for electrospinning are as follows: voltage 10-30kV, perfusion speed 0.5-2mL/h, receiving distance 10-25cm, and/or temperature in the spinning chamber (i.e. ambient temperature) 15-35 °C; in the present invention, the perfusion speed refers to the flow rate of the electrospinning solution.

According to some preferred embodiments, in step (2), the obtained hybrid nanofiber membrane is also subjected to vacuum drying; preferably, the obtained hybrid nanofiber membrane is dried in a vacuum oven at 60-120°C. Vacuum drying for 1-3 hours to remove moisture and residual solvent in the hybrid nanofiber membrane.

According to some preferred embodiments, in step (4): the graphene oxide solution is a graphene oxide aqueous solution with a concentration of 15 to 25 g/L (such as 15, 20 or 25 g/L); and/or the graphene oxide solution The consumption of graphene solution is 0.5～2% (such as 0.5%, 1%, 1.5% or 2%) of the quality of described pending dispersion liquid; The present invention finds, the adding of described graphene oxide solution of suitable content can further Improve the compression resilience of the highly elastic radiation-resistant nanofiber airgel material, if the mass fraction of graphene oxide contained in the homogeneous dispersion is too small, then improve the compression resilience of the highly elastic radiation-resistant nanofiber airgel material The effect of elasticity is not obvious, and if the mass fraction of graphene oxide contained in the homogeneous dispersion is too high, it will have an adverse effect on the temperature resistance of the material.

According to some preferred embodiments, the mass fraction of the hybrid nanofiber membrane contained in the liquid to be dispersed is 0.4-0.6%, and the mass fraction of ethyl orthosilicate contained in the liquid to be dispersed is 0.4-0.6% , the mass fraction of boric acid contained in the liquid to be dispersed is 0.05 to 0.2%, and the mass fraction of aluminum chloride contained in the liquid to be dispersed is 0.1 to 0.3%; in some preferred embodiments, the The mass fraction of the hybrid nanofiber membrane contained in the dispersion liquid is 0.53%, the mass fraction of the tetraethyl orthosilicate contained in the described liquid to be dispersed is 0.5%, and the mass fraction of the boric acid contained in the described liquid to be dispersed is 0.1%, the mass fraction of aluminum chloride contained in the described liquid to be dispersed is 0.15%.

According to some preferred embodiments, in step (4): the speed of the high-speed stirring is 5000-20000r/min (for example, 5000, 10000, 15000 or 20000r/min), and the time of the high-speed stirring is 5-30min ( For example, 5, 10, 15, 20, 25 or 30 minutes); in some preferred embodiments, the speed of the high-speed stirring is 10000 r/min, and the time of the high-speed stirring is 20 minutes.

According to some preferred embodiments, in step (5): the freezing is freezing under liquid nitrogen for 10 to 60 minutes (such as 10, 20, 30, 40, 50 or 60 minutes), preferably 10 to 30 minutes; Carried out in a mould, the top and sides of which are made of a material with low thermal conductivity and the bottom of the mould, which is made of a material with high thermal conductivity, preferably the top and sides of the mold It is made of polytetrafluoroethylene, and the bottom of the mold is made of copper material; and/or the freeze-drying is vacuum freeze-drying, preferably at a vacuum degree of 0.5 to 10 Pa and a temperature of -50 to -70 Vacuum freeze-drying under the condition of ℃ for 2-5 days (for example, 2, 3, 4 or 5 days).

According to some preferred embodiments, in step (6): the temperature of the post-treatment is 800-1000°C (for example, 800, 850, 900, 950 or 1000°C), and the time of the post-treatment is 0.1-12h, preferably 3-8h (eg 3, 4, 5, 6, 7 or 8h).

According to some specific embodiments, the preparation of the highly elastic radiation-resistant nanofiber airgel material includes the following steps:

① Preparation of hybrid nanofiber membrane

Preparation of TEOS composite hydrolyzate: at room temperature, take a certain mass of TEOS, H ₃ PO ₄ and deionized water according to n(TEOS):n(H ₃ PO ₄ ):n(H ₂ O)=(0.5～1 ):(0.005～0.05):(1～20) molar ratio mixed, placed on a magnetic stirrer and stirred for 1～24 hours to obtain a hydrolyzate; then add titanium dioxide nanopowder to the hydrolyzate to ensure that the titanium dioxide nanopowder accounts for the hydrolysis 0.4-10% of the mass of the liquid, stirred for 1-12 hours, and ultrasonicated for 0.5-2 hours to uniformly disperse the titanium dioxide nanometer powder in the hydrolyzate to obtain a TEOS composite hydrolyzate.

Preparation of PVA aqueous solution: weigh a certain mass of polyvinyl alcohol powder and add it to deionized water, dissolve it by heating at 60-120°C, and stir for 1-12 hours; take it out after stirring, put it on a magnetic stirrer and stir at room temperature heat dissipation until it drops to room temperature; the mass fraction of the prepared PVA aqueous solution is 1-20 wt%.

Preparation of precursor solution for electrospinning: mix TEOS composite hydrolyzate, PVA aqueous solution, and deionized water according to the mass ratio of (1~5):(1~5):(0.5~5), and place at room temperature Stirring on a magnetic stirrer for 1-12 hours to obtain a uniform and clear precursor solution.

The precursor solution was extracted with a syringe as the electrospinning solution, and the PVA/SiO ₂ /TiO ₂ hybrid nanofiber membrane was prepared using an electrospinning machine. The process parameters of electrospinning are: voltage 5-40kV, perfusion speed 0.5-2mL/h, receiving distance 10-25cm, temperature in spinning chamber 25±10°C. After the test, the hybrid nanofiber membrane (PVA/SiO ₂ /TiO ₂ hybrid nanofiber membrane) was collected and dried in a vacuum oven at 60-120°C for 2 hours to remove moisture and moisture in the hybrid nanofiber membrane. remaining solvent.

②Heat treatment process

Put the PVA/SiO ₂ /TiO ₂ hybrid nanofiber membrane prepared by electrospinning into the atmosphere furnace, the protective gas can be nitrogen, argon or argon-hydrogen mixed gas, and the heating rate is preferably set at 1-6°C/min 3-6°C/min, first raised to 300-600°C, kept for 1-10h, then raised to 600-900°C, kept for 1-5h, then naturally cooled to room temperature; the room temperature in the present invention is to carry out the present invention The ambient temperature may be, for example, a room temperature of 15-35°C.

③ Homogeneous dispersion process

Adding the hybrid nanofiber membrane, tetraethyl orthosilicate, boric acid, and aluminum chloride after heat treatment in step ② into water to obtain a liquid to be dispersed, then adding graphene oxide solution to the liquid to be dispersed and using high-speed shearing The machine is stirred for 5-30 minutes under the condition of rotating speed of 5000-20000r/min to obtain a homogeneous dispersion.

④ Freezing process: Add the above-mentioned homogeneous dispersion into a mold with a fixed shape. The top and sides of the mold are made of materials with low thermal conductivity (polytetrafluoroethylene), and the bottom is made of copper with good thermal conductivity (higher thermal conductivity). Place the sealed mold in liquid nitrogen for 10-60 minutes of freezing.

⑤ Freeze-drying process: After the homogeneous dispersion liquid is completely frozen and formed, it is transferred to a freeze dryer for vacuum freeze-drying. 0.5～10Pa.

⑥Post-treatment process: Post-treat (crack) the nanofiber airgel material prepared in step ⑤ under a protective atmosphere (nitrogen, argon or argon-hydrogen mixed gas), and post-treat at 900°C for 0.1-12h to stabilize The overlapping connection between the nanofibers makes a highly elastic and anti-radiation nanofiber airgel material.

The second aspect of the present invention provides the highly elastic anti-radiation nanofiber airgel material prepared by the preparation method described in the first aspect of the present invention.

The present invention will be further described below by means of examples, but the protection scope of the present invention is not limited to these examples.

Example 1

① Preparation of hybrid nanofiber membrane

Preparation of TEOS composite hydrolyzate: at room temperature, take TEOS (tetraethyl orthosilicate), H ₃ PO ₄ (phosphoric acid) and deionized water according to n(TEOS):n(H ₃ PO ₄ ):n(H ₂ (2)=1:0.02:10 molar ratio mixes, is placed on magnetic stirrer and stirs 12 hours, obtains hydrolyzate; Then adds titanium dioxide nanopowder in hydrolyzate, guarantees that titanium dioxide nanopowder accounts for 2% of the quality of hydrolyzate, Stir for 5 hours and ultrasonically treat for 1 hour to disperse the titanium dioxide nanopowder in the hydrolyzate evenly to obtain a TEOS composite hydrolyzate.

Preparation of PVA aqueous solution: Weigh polyvinyl alcohol powder and add it to deionized water, dissolve it by heating at 80°C, and stir for 5 hours; take it out after stirring, put it on a magnetic stirrer at room temperature and stir to dissipate heat until it drops to room temperature; The mass fraction of the prepared PVA aqueous solution is 10wt%.

Preparation of precursor solution for electrospinning: Mix TEOS composite hydrolyzate, PVA aqueous solution, and deionized water in a mass ratio of 3:3:2, and stir on a magnetic stirrer at room temperature for 4 hours to obtain a uniform and clear precursor body solution.

The precursor solution was extracted with a syringe as the electrospinning solution, and the PVA/SiO ₂ /TiO ₂ hybrid nanofiber membrane was prepared using an electrospinning machine. The process parameters of electrospinning are: voltage 20kV, perfusion speed 1.5mL/h, receiving distance 15cm, temperature in spinning chamber 25°C. After the test, the hybrid nanofiber membrane (PVA/SiO ₂ /TiO ₂ hybrid nanofiber membrane) was collected and dried in a vacuum oven at 80°C for 2 hours to remove moisture and residual solvent in the hybrid nanofiber membrane .

②Heat treatment process

Put the PVA/SiO ₂ /TiO ₂ hybrid nanofiber membrane prepared by electrospinning into an atmosphere furnace, the inert protective gas is nitrogen, and the heating rate is set at 5°C/min. First heat treatment at 500°C for 2h, then Heat up to 800°C for 3 hours, then cool down to room temperature naturally.

③ Homogeneous dispersion process

Add the hybrid nanofiber membrane, tetraethyl orthosilicate, boric acid, and aluminum chloride into water (deionized water) after heat treatment in step ② to obtain a liquid to be dispersed, and then add graphene oxide to the liquid to be dispersed solution and using a high-speed shearing machine to stir at a high speed for 20min at a speed of 10000r/min to obtain a homogeneous dispersion; the graphene oxide solution is a graphene oxide aqueous solution with a concentration of 20g/L; the graphene oxide solution The addition amount of is 1% of the mass of described liquid to be dispersed; The mass fraction of the hybrid nanofiber film contained in described liquid to be dispersed is 0.53%, the mass fraction of the tetraethyl orthosilicate contained in described liquid to be dispersed Fraction is 0.5%, the mass fraction of the boric acid contained in the described liquid to be dispersed is 0.1%, the mass fraction of the aluminum chloride contained in the described liquid to be dispersed is 0.15%, the mass fraction of the water contained in the described liquid to be dispersed The score is 98.72%.

④ Freezing process: Add the above-mentioned homogeneous dispersion into a mold with a fixed shape. The top and sides of the mold are made of materials with low thermal conductivity (polytetrafluoroethylene), and the bottom is made of copper with good thermal conductivity (higher thermal conductivity). slices, the sealed mold was placed in liquid nitrogen, and the freezing process was carried out for 20 minutes.

⑤ Freeze-drying process: After the homogeneous dispersion is completely freeze-formed, it is transferred to a freeze-dryer for vacuum freeze-drying. The freeze-drying temperature is -70°C, the freeze-drying time is 3 days, and the vacuum degree of freeze-drying is 5Pa.

⑥Post-treatment process: the nanofiber airgel material prepared in step ⑤ is post-treated (cracked) for 5 hours at a temperature of 900°C under an inert protective atmosphere (nitrogen) to stabilize the overlap between the nanofibers and produce High elasticity and anti-radiation nanofiber airgel material.

The performance test of the highly elastic radiation-resistant nanofiber airgel material in Example 1 is shown in Table 1.

The highly elastic anti-radiation nanofiber airgel material prepared in Example 1 has a density of 0.06g/cm ³ , a porosity of 95%, an average nanofiber diameter of 200nm, a compression rebound rate of 90%, and a linear shrinkage rate of 1100°C. The thermal conductivity at room temperature is 0.030W/m·K, and the thermal conductivity at 800°C is 0.050W/m·K.

After the highly elastic and anti-radiation nanofiber airgel material prepared in this example is used at 1100°C for 1200s, the linear shrinkage is only 0.5%, which means that it can withstand temperatures above 1100°C. In particular, the 1100°C linear shrinkage in Table 1 of the present invention refers to the linear shrinkage of the materials prepared in each example and comparative example after being used at 1100°C for 1200s; The larger the shrinkage rate, the worse the material's resistance to 1100°C.

Example 2

Embodiment 2 is basically the same as Embodiment 1, the difference is:

In step ①, the preparation of the TEOS composite hydrolyzate is as follows: at room temperature, take TEOS, H ₃ PO ₄ and deionized water according to n(TEOS):n(H ₃ PO ₄ ):n(H ₂ O) =1:0.02:10 molar ratio mixed, placed on a magnetic stirrer and stirred for 12 hours to obtain a hydrolyzed solution; subsequently, adding titanium dioxide nanopowder to the hydrolyzed solution to ensure that the titanium dioxide nanopowder accounted for 1% of the quality of the hydrolyzed solution, and stirred for 6h , sonicated for 1 h, so that the titanium dioxide nano-powder was evenly dispersed in the hydrolyzate, and the TEOS composite hydrolyzate was obtained.

The performance test of the highly elastic radiation-resistant nanofiber airgel material in Example 2 is shown in Table 1.

Example 3

Embodiment 3 is basically the same as Embodiment 1, the difference is:

③The process of homogeneous dispersion is: adding the hybrid nanofiber membrane, tetraethyl orthosilicate, boric acid, and aluminum chloride after heat treatment in step ② into water to obtain the liquid to be dispersed, and then the liquid to be dispersed is subjected to high-speed shearing The machine was stirred at a high speed for 20min under the condition that the rotating speed was 10000r/min to obtain a homogeneous dispersion; the mass fraction of the hybrid nanofiber membrane contained in the dispersion to be dispersed was 0.53%, and the orthosilicon contained in the dispersion to be dispersed was The mass fraction of ethyl acetate is 0.5%, the mass fraction of boric acid contained in the described liquid to be dispersed is 0.1%, the mass fraction of aluminum chloride contained in the described liquid to be dispersed is 0.15%, and the mass fraction of boric acid contained in the described liquid to be dispersed is 0.15%. The mass fraction of water contained is 98.72%.

The performance test was carried out on the material prepared in Example 3, and the results are shown in Table 1.

Example 4

Embodiment 4 is basically the same as Embodiment 1, the difference is:

The PVA/SiO ₂ /TiO ₂ hybrid nanofiber membrane prepared by electrospinning was not subjected to heat treatment, but was directly subjected to the same homogeneous dispersion process, freezing process, freeze-drying process and post-treatment process as in Example 1.

Performance tests were performed on the materials prepared in this example, and the results are shown in Table 1.

Example 5

Embodiment 5 is basically the same as Embodiment 1, the difference is:

In step ③, the liquid to be dispersed was stirred for 20 min with a high-speed shearing machine at a speed of 1000 r/min to obtain a homogeneous dispersion.

Performance tests were performed on the materials prepared in this example, and the results are shown in Table 1.

Example 6

Embodiment 6 is basically the same as Embodiment 1, the difference is:

In step ③, the homogeneous dispersion process is: adding the hybrid nanofiber membrane heat-treated in step ② into water to obtain a liquid to be dispersed; then adding graphene oxide solution to the liquid to be dispersed and using a high-speed shear Stir for 20min under the condition of 10000r/min at the rotating speed to obtain a homogeneous dispersion; the graphene oxide solution is a graphene oxide aqueous solution with a concentration of 20g/L; the amount of the graphene oxide solution is the amount of the liquid to be dispersed The mass fraction of the hybrid nanofiber membrane contained in the liquid to be dispersed is 0.53%, and the mass fraction of water contained in the liquid to be dispersed is 99.47%.

Performance tests were performed on the materials prepared in this example, and the results are shown in Table 1.

Example 7

Embodiment 7 is basically the same as Embodiment 1, the difference is:

Step ⑤ is the normal pressure drying process: after the homogeneous dispersion liquid is completely frozen and formed, it is transferred and dried at normal temperature and pressure for 144 hours.

The performance test of the material prepared in this example is shown in Table 1; the material prepared in this example has basically no resilience, and it can be considered that the compression rebound rate is 0.

Example 8

Embodiment 8 is basically the same as Embodiment 1, the difference is:

This embodiment does not include the post-processing of step ⑥.

Performance tests were performed on the materials prepared in this example, and the results are shown in Table 1.

Example 9

Embodiment 9 is basically the same as Embodiment 1, the difference is:

In step ①, the preparation of the TEOS composite hydrolyzate: at room temperature, take TEOS, H ₃ PO ₄ and deionized water according to n(TEOS):n(H ₃ PO ₄ ):n(H ₂ O)= Mix at a molar ratio of 1:0.02:10 to obtain a mixed solution; then add 2% titanium dioxide nanopowder of the mass of the mixed solution to the mixed solution and place it on a magnetic stirrer for continuous stirring for 18 hours to obtain a TEOS composite hydrolyzate .

Performance tests were performed on the materials prepared in this example, and the results are shown in Table 1.

Example 10

Embodiment 10 is basically the same as Embodiment 1, the difference is:

In step ①, the preparation of TEOS hydrolyzate: at room temperature, take TEOS, H ₃ PO ₄ and deionized water according to n(TEOS):n(H ₃ PO ₄ ):n(H ₂ O)=1:0.02 : 10 molar ratio mixed, placed on a magnetic stirrer and continued to stir for 12 hours to obtain a TEOS hydrolyzate; in the present embodiment, the TEOS hydrolyzate was used to replace the TEOS composite hydrolyzate in Example 1 for follow-up experiments.

Preparation of PVA aqueous solution: Weigh polyvinyl alcohol powder and add it to deionized water, dissolve it by heating at 80°C, and stir for 5 hours; take it out after stirring, put it on a magnetic stirrer at room temperature and stir to dissipate heat until it drops to room temperature; The mass fraction of the prepared PVA aqueous solution is 10wt%.

The preparation of the precursor solution for electrospinning is as follows: TEOS hydrolyzate, PVA aqueous solution, and deionized water are mixed according to the mass ratio of 3:3:2 to obtain a mixed solution; 5% titanium dioxide nanopowder by the mass of the solution was mixed and stirred on a magnetic stirrer at room temperature for 4 hours to obtain a uniform and clear precursor solution.

The precursor solution was extracted with a syringe as the electrospinning solution, and the PVA/SiO ₂ /TiO ₂ hybrid nanofiber membrane was prepared using an electrospinning machine. The process parameters of electrospinning are: voltage 20kV, perfusion speed 1.5mL/h, receiving distance 15cm, temperature in spinning chamber 25°C. After the test, the hybrid nanofiber membrane (PVA/SiO ₂ /TiO ₂ hybrid nanofiber membrane) was collected and dried in a vacuum oven at 80°C for 2 hours to remove moisture and residual solvent in the hybrid nanofiber membrane .

Performance tests were performed on the materials prepared in this example, and the results are shown in Table 1.

Example 11

Embodiment 11 is basically the same as Embodiment 1, the difference is:

In step ①, the preparation of the TEOS composite hydrolyzate is as follows: at room temperature, take TEOS, H ₃ PO ₄ and deionized water according to n(TEOS):n(H ₃ PO ₄ ):n(H ₂ O) =1:0.02:10 molar ratio mixed, placed on a magnetic stirrer and stirred for 12 hours to obtain a hydrolyzate; subsequently, adding titanium dioxide nanopowder to the hydrolyzate to ensure that the titanium dioxide nanopowder accounted for 4% of the quality of the hydrolyzate, and stirred for 6h , sonicated for 1 h, so that the titanium dioxide nano-powder was evenly dispersed in the hydrolyzate, and the TEOS composite hydrolyzate was obtained.

Performance tests were performed on the materials prepared in this example, and the results are shown in Table 1.

Example 12

Embodiment 12 is basically the same as Embodiment 1, the difference is:

The heat treatment process of step ② is: put the PVA/SiO ₂ /TiO ₂ hybrid nanofiber membrane prepared by electrospinning into an atmosphere furnace, the inert protective gas is nitrogen, and the heating rate is set at 5°C/min, rising to Heat treatment at 500°C for 5h, then naturally cool to room temperature.

Performance tests were performed on the materials prepared in this example, and the results are shown in Table 1.

Example 13

Embodiment 13 is basically the same as Embodiment 1, the difference is:

In step ①, the preparation of TEOS hydrolyzate is: at room temperature, take TEOS, H ₃ PO ₄ and deionized water according to n(TEOS):n(H ₃ PO ₄ ):n(H ₂ O)=1: Mixed at a molar ratio of 0.02:10, placed on a magnetic stirrer and continuously stirred for 12 hours to obtain a TEOS hydrolyzate; in subsequent steps, the TEOS hydrolyzate was used to replace the TEOS composite hydrolyzate in Example 1 for experiments.

Performance tests were performed on the materials prepared in this example, and the results are shown in Table 1.

Example 14

Embodiment 14 is basically the same as Embodiment 1, the difference is:

③ The homogeneous dispersion process is: adding the hybrid nanofiber membrane, tetraethyl orthosilicate, boric acid, and aluminum chloride after heat treatment in step ② into water to obtain a liquid to be dispersed, and then adding graphite oxide to the liquid to be dispersed ene solution and adopt high-speed shearing machine to stir at high speed under the condition of 10000r/min for 20min at a high speed to obtain a homogeneous dispersion; the graphene oxide solution is a graphene oxide aqueous solution with a concentration of 20g/L; the graphene oxide The amount of solution added is 4% of the mass of the liquid to be dispersed; the mass fraction of the hybrid nanofiber membrane contained in the liquid to be dispersed is 0.53%, and the amount of tetraethyl orthosilicate contained in the liquid to be dispersed is The mass fraction is 0.5%, the mass fraction of the boric acid contained in the described liquid to be dispersed is 0.1%, the mass fraction of the aluminum chloride contained in the described liquid to be dispersed is 0.15%, and the mass fraction of the water contained in the described liquid to be dispersed is The quality score is 98.72%.

Performance tests were performed on the materials prepared in this example, and the results are shown in Table 1.

Comparative example 1

①Preparation of nanofiber membrane: Dissolve polyvinyl alcohol and ethyl orthosilicate in deionized water with stirring at 80°C to obtain a precursor solution; the molar ratio of ethyl orthosilicate to water is 1:20 ; The mass fraction of polyvinyl alcohol contained in the precursor solution is 10%. The precursor solution was extracted with a syringe as the electrospinning solution, and the nanofiber membrane was prepared using an electrospinning machine. The process parameters of electrospinning are: voltage 20kV, perfusion speed 1.5mL/h, receiving distance 15cm, temperature in spinning chamber 25°C. After the test, the nanofiber membrane was collected and dried in a vacuum oven at 80° C. for 2 hours to remove moisture and residual solvent in the nanofiber membrane.

②Heat treatment process

The nanofibrous membrane prepared by electrospinning was placed in a muffle furnace, the heating rate was set at 5 °C/min, and the temperature was raised to 500 °C for 5 h, and then naturally cooled to room temperature.

③ Homogeneous dispersion process

Collect the nanofiber membrane heat-treated in step ③, add it to deionized water, and obtain the liquid to be dispersed, and then stir the liquid to be dispersed with a high-speed shearing machine at a speed of 10000r/min for 20 minutes to obtain a homogeneous dispersion liquid; the mass fraction of the nanofibrous membrane contained in the liquid to be dispersed is 0.53%.

④ Freezing process: Add the above-mentioned homogeneous dispersion into a mold with a fixed shape. The top and sides of the mold are made of materials with low thermal conductivity (polytetrafluoroethylene), and the bottom is made of copper with good thermal conductivity (higher thermal conductivity). slices, the sealed mold was placed in liquid nitrogen, and the freezing process was carried out for 20 minutes.

⑤ Freeze-drying process: After the homogeneous dispersion is completely freeze-formed, it is transferred to a freeze-dryer for vacuum freeze-drying. The freeze-drying temperature is -70°C, the freeze-drying time is 3 days, and the vacuum degree of freeze-drying is 5Pa.

⑥Post-treatment process: The material obtained in step ⑥ was post-treated (cracked) for 5 hours under an inert protective atmosphere (nitrogen) at a temperature of 900°C.

Performance tests were performed on the materials prepared in this comparative example, and the results are shown in Table 1.

Comparative example 2

Comparative Example 2 is basically the same as Comparative Example 1, the difference is:

In step ①, polyvinyl alcohol, tetraethyl orthosilicate, and titanium dioxide nanopowder are heated and stirred at 80° C. and uniformly dispersed in deionized water to obtain a precursor solution in which polyvinyl alcohol is dissolved and titanium dioxide nanopowder is dispersed; The molar ratio of ethyl tetrasilicate and water is 1:20; The mass fraction of the polyvinyl alcohol contained in the precursor solution is 10%; The mass fraction of the titanium dioxide nanopowder contained in the precursor solution is 2% . The precursor solution was extracted with a syringe as the electrospinning solution, and the nanofiber membrane was prepared using an electrospinning machine. The process parameters of electrospinning are: voltage 20kV, perfusion speed 1.5mL/h, receiving distance 15cm, temperature in spinning chamber 25°C. After the test, the nanofiber membrane was collected and dried in a vacuum oven at 80°C for 2 hours to remove moisture and residual solvent in the nanofiber membrane.

Performance tests were performed on the materials prepared in this comparative example, and the results are shown in Table 1.

In particular, the symbol "-" in Table 1 indicates that the performance index has not been tested.

Parts not described in detail in the present invention are well-known technologies for those skilled in the art.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims (19)

1. A preparation method of a high-elasticity radiation-resistant nanofiber aerogel material is characterized by comprising the following steps:

(1) Uniformly mixing ethyl orthosilicate, phosphoric acid and water to obtain a mixed solution, stirring the mixed solution for 1 to 24h to obtain a hydrolysate, adding titanium dioxide nanopowder into the hydrolysate, continuously stirring for 1 to 12h, and finally performing ultrasonic treatment for 0.5 to 2h to obtain a composite hydrolysate;

(2) Uniformly mixing a polyvinyl alcohol aqueous solution and the composite hydrolysate obtained in the step (1) with water, stirring for 1-12h to obtain a precursor solution, and then performing electrostatic spinning by taking the precursor solution as an electrostatic spinning solution to obtain a hybrid nanofiber membrane;

(3) Carrying out heat treatment on the hybrid nanofiber membrane obtained in the step (2) in an inert atmosphere; the heat treatment comprises the following steps: firstly, carrying out heat treatment at 300 to 600 ℃ for 1 to 10h, then carrying out heat treatment at 600 to 900 ℃ for 1 to 5h, and then naturally cooling to room temperature;

(4) Adding the hybrid nanofiber membrane subjected to heat treatment in the step (3), ethyl orthosilicate, boric acid and aluminum chloride into water to obtain a to-be-dispersed solution, and then adding a graphene oxide solution into the to-be-dispersed solution and stirring at a high speed to obtain a homogeneous phase dispersed solution;

(5) Sequentially freezing and freeze-drying the homogeneous dispersion liquid obtained in the step (4) to obtain a nanofiber aerogel material;

(6) And (5) carrying out post-treatment on the nanofiber aerogel material obtained in the step (5) in an inert atmosphere to obtain the high-elasticity anti-radiation nanofiber aerogel material.

2. The production method according to claim 1, wherein in step (1):

the molar ratio of the ethyl orthosilicate to the phosphoric acid to the water is (0.5 to 1): (0.005 to 0.05): (1 to 20); and/or

The dosage of the titanium dioxide nano powder is 0.4 to 10 percent of the mass of the hydrolysate.

3. The method of claim 2, wherein:

in the step (1), the molar ratio of the ethyl orthosilicate, the phosphoric acid and the water is 1: (0.015 to 0.025): (8 to 15).

4. The production method according to claim 3, characterized in that:

in step (1), the molar ratio of the ethyl orthosilicate, the phosphoric acid and the water is 1.

5. The method of claim 2, wherein:

in the step (1), the using amount of the titanium dioxide nano powder is 0.5-5% of the mass of the hydrolysate.

6. The method of claim 5, wherein:

in the step (1), the using amount of the titanium dioxide nano powder is 0.8-2.5% of the mass of the hydrolysate.

7. The production method according to claim 1, wherein in step (2):

the mass fraction of polyvinyl alcohol contained in the polyvinyl alcohol aqueous solution is 1-20%;

the mass ratio of the composite hydrolysate to the polyvinyl alcohol aqueous solution to the water is (1 to 5): (1 to 5): (0.5 to 5); and/or

The stirring time is 3 to 6 hours.

8. The method for producing according to claim 7, characterized in that:

in the step (2), the mass ratio of the composite hydrolysate to the polyvinyl alcohol aqueous solution to the water is (2.5 to 3.5): (2.5 to 3.5): 2.

9. the method for producing according to claim 8, characterized in that:

in the step (2), the mass ratio of the composite hydrolysate to the polyvinyl alcohol aqueous solution to the water is 3.

10. The method of claim 1, wherein the electrospinning is carried out with the following parameters:

the voltage is 10 to 30kV, the filling speed is 0.5 to 2mL/h, the receiving distance is 10 to 25cm, and/or the temperature in a spinning room is 15 to 35 ℃.

11. The production method according to claim 1, characterized in that:

in step (2), the obtained hybrid nanofiber membrane is also subjected to vacuum drying.

12. The method of claim 11, wherein:

and (3) carrying out vacuum drying on the obtained hybrid nanofiber membrane for 1 to 3 hours in a vacuum drying box at the temperature of 60 to 120 ℃.

13. The production method according to claim 1, wherein in step (4):

the graphene oxide solution is a graphene oxide aqueous solution with the concentration of 15 to 25g/L; the using amount of the graphene oxide solution is 0.5 to 2 percent of the mass of the liquid to be dispersed; and/or

The mass fraction of the hybrid nanofiber membrane contained in the to-be-dispersed liquid is 0.4 to 0.6%, the mass fraction of ethyl orthosilicate contained in the to-be-dispersed liquid is 0.4 to 0.6%, the mass fraction of boric acid contained in the to-be-dispersed liquid is 0.05 to 0.2%, and the mass fraction of aluminum chloride contained in the to-be-dispersed liquid is 0.1 to 0.3%.

14. The production method according to claim 1, wherein in step (4):

the high-speed stirring speed is 5000 to 20000r/min, and the high-speed stirring time is 5 to 30min.

15. The production method according to claim 1, wherein in step (5):

the freezing is performed under liquid nitrogen for 10 to 60min;

the freezing is carried out in a mould, the top and the side of the mould are made of materials with lower thermal conductivity, and the bottom of the mould is made of materials with higher thermal conductivity; and/or

The freeze drying is vacuum freeze drying.

16. The method of claim 15, wherein:

the top and the side of the mould are made of polytetrafluoroethylene, and the bottom of the mould is made of a copper material.

17. The method of manufacturing according to claim 15, characterized in that:

vacuum freeze drying at-50 deg.C to-70 deg.C under vacuum degree of 0.5-10Pa for 2-5d.

18. The production method according to claim 1, wherein in step (6):

the temperature of the post-treatment is 800 to 1000 ℃, and the time of the post-treatment is 0.1 to 12h.

19. The high-elasticity radiation-resistant nanofiber aerogel material prepared by the preparation method of any one of claims 1 to 18.

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