CN115142154A - Silicon dioxide fiber aerogel, preparation method and modification method thereof - Google Patents
Silicon dioxide fiber aerogel, preparation method and modification method thereof Download PDFInfo
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- D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
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Abstract
The invention discloses a silicon dioxide fiber aerogel, a preparation method and a modification method thereof, wherein the preparation method comprises the following steps: mixing tetraethyl silicate, ethanol, water and a catalyst, then carrying out hydrolysis reaction to obtain a silicon dioxide spinning solution, and carrying out electrostatic spinning on the silicon dioxide spinning solution to obtain flexible silicon dioxide nano fibers; uniformly dispersing the flexible silicon dioxide nano fibers in a solvent containing an adhesive to obtain silicon dioxide fiber dispersion liquid; and directionally freezing and drying the silicon dioxide fiber dispersion liquid to obtain a silicon dioxide fiber aerogel precursor, and drying the silicon dioxide fiber aerogel precursor in the air atmosphere to obtain the silicon dioxide fiber aerogel. The preparation process has simple flow, improves the utilization efficiency of raw materials and reduces the production cost.
Description
Technical Field
The invention belongs to the technical field of nanofiber aerogel, and particularly relates to silicon dioxide fiber aerogel, a preparation method and a modification method thereof.
Background
Ceramic aerogels, as an emerging material, have the unique advantages of low density, low thermal conductivity, high porosity, and excellent thermal and chemical stability, and are considered ideal candidates for thermal insulation, energy storage, and catalyst support applications. Ceramic aerogels are generally brittle because they are essentially a brittle network of randomly connected nanoparticles, which are generally susceptible to structural collapse when subjected to external stress. Meanwhile, the ultra-light and interconnected porous structure is beneficial to loading of various oil/organic solvents, which is particularly important for constructing an effective separation surface. Therefore, the design of ceramic aerogels with excellent thermal insulation properties, strong mechanical properties and adjustable wettability is the key to solve the above-mentioned bottleneck problems.
The silicon dioxide nanofiber aerogel material prepared by the existing method has the problems of poor flexibility, low raw material utilization rate and the like, and the preparation process is complex, the production cost is high, and the large-scale production is not facilitated. For example, chinese patent application No. CN 113461364A discloses a silica nanofiber polyimide composite aerogel, and a preparation method and an application thereof, in the patent, a silicon source and a polymer are first dissolved in a solvent, a polymer/silica nanofiber membrane is prepared through electrostatic spinning, then high-temperature calcination is performed to remove a high-molecular polymer, so as to obtain silica nanofibers with a diameter of 100 to 400nm, and the silica nanofibers/polyimide composite aerogel is obtained by re-dispersing in a polyamic acid aqueous solution, and performing freeze drying and high-temperature heat treatment. Chinese patent with application number CN 110424067A discloses a flexible silica fiber aerogel material and a preparation method thereof, the patent mixes high molecular materials to obtain a first mixed solution, then adds a silica precursor and a catalyst into the first mixed solution to obtain a second mixed solution, the second mixed solution is sprayed out from a spinneret orifice by a solution jet spinning method,and finally, carrying out high-temperature calcination treatment on the composite aerogel to obtain the flexible silica fiber aerogel material. Chinese patent with application number CN 113244913A discloses a method for purifying industrial wastewater by using manganese oxide loaded on silica fiber aerogel as an ozone oxidation catalyst, in the method, tetraethoxysilane precursor solution and PVA aqueous solution are uniformly mixed and subjected to electrostatic spinning to obtain a PVA/silica composite fiber membrane, then the PVA/silica composite fiber membrane is calcined at high temperature in the air atmosphere to obtain a silica composite fiber membrane, the silica composite fiber membrane is dispersed in PAM aqueous solution, and MnCl is added 2 And carrying out freeze drying and high-temperature calcination on the aluminoborosilicate sol to obtain the manganese oxide-loaded silicon dioxide fiber aerogel.
The preparation of the silica fiber aerogel by the template method requires high-temperature calcination to remove polymer components, firstly, an organic-inorganic composite precursor nanofiber is prepared, then, organic matters are removed by high-temperature calcination treatment to obtain inorganic silica nanofibers, and after the aerogel material is further prepared, high-temperature calcination treatment is still required. The method needs to add organic matters, so that the production cost is increased, the structure of the catalyst is influenced in the high-temperature calcination process, the process is complex, and the energy consumption is increased.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides the silicon dioxide fiber aerogel, the preparation method and the modification method thereof, the preparation process flow is simple, the utilization efficiency of raw materials is improved, and the production cost is reduced.
In order to solve the technical problems, the invention is realized by the following technical scheme:
a method for preparing a silica fiber aerogel, comprising:
mixing tetraethyl silicate, ethanol, water and a catalyst, then carrying out hydrolysis reaction to obtain a silicon dioxide spinning solution, and carrying out electrostatic spinning on the silicon dioxide spinning solution to obtain flexible silicon dioxide nano fibers;
uniformly dispersing the flexible silicon dioxide nano fibers in a solvent containing an adhesive to obtain silicon dioxide fiber dispersion liquid;
and directionally freezing and drying the silicon dioxide fiber dispersion liquid to obtain a silicon dioxide fiber aerogel precursor, and drying the silicon dioxide fiber aerogel precursor in the air atmosphere to obtain the silicon dioxide fiber aerogel.
Further, the mole ratio of the tetraethyl silicate to the ethanol to the water to the catalyst is 1:2:2.5:0.01 to 0.1, the temperature of the hydrolysis reaction is 75 to 85 ℃, and the silica spinning solution is obtained by adopting a sol-gel method.
Further, the catalyst is at least one of hydrochloric acid, acetic acid and phosphoric acid.
Further, the concentration of the adhesive is 0.1% -0.01%, and the adhesive is at least one of silica sol solution, nano-silica, polyethylene oxide, polyacrylamide, polyvinylpyrrolidone, tetraethyl silicate and methyl orthosilicate.
Further, the solvent includes at least one of deionized water, t-butanol, ethanol, isopropanol, and n-butanol.
Further, the directional freeze-drying of the silica nanofiber solution is specifically as follows:
liquid nitrogen is adopted for directional freezing, the temperature of freeze drying is-35 ℃ to-60 ℃, the vacuum degree is 1Pa to 3Pa, and the time of freeze drying is 20h to 60h.
Further, when the drying is carried out in the air atmosphere, the drying temperature is 80-800 ℃, the heating speed is 1-5 ℃/min, and the heat preservation time is 0.5-2 h.
The silica fiber aerogel is prepared by the preparation method of the silica fiber aerogel.
A modification method of silica fiber aerogel comprises the steps of immersing a silica fiber aerogel precursor into a methyl silane solution and carrying out drying treatment to obtain hydrophobic silica fiber aerogel.
Further, the methylsilane is at least one of methyltrimethoxysilane, dimethyldimethoxysilane and octadecyltrimethoxysilane;
when the silicon dioxide fiber aerogel precursor is immersed into a methyl silane solution and dried, the immersion time is 6-12 h, the drying temperature is 50-600 ℃, the heating rate is 1-5 ℃/min, and the heat preservation time is 0.5-2 h.
Compared with the prior art, the invention has at least the following beneficial effects:
according to the invention, the silicon dioxide spinning solution is subjected to electrostatic spinning to obtain the flexible silicon dioxide nanofiber, so that the addition of an organic polymer is omitted, the high-temperature heat treatment process is omitted, the ethanol is recovered, the raw material cost is saved, and the energy consumption is reduced; then uniformly dispersing the flexible silicon dioxide nano fibers in a solvent containing an adhesive to obtain silicon dioxide fiber dispersion liquid, wherein the adhesive improves the in-situ construction of an elastic bonding structure in the bionic nano fiber frame; and finally, directionally freezing and drying the silicon dioxide fiber solution, and then drying to obtain the silicon dioxide fiber aerogel, wherein in the directional freezing and forming process, silicon dioxide nano fibers penetrate and are staggered with each other to form a three-dimensional network structure, effective bonding is formed among the fibers by Si-O-Si bonds, and the mechanical property of the aerogel is improved by improving the structural continuity among the nano fibers. The preparation method has the advantages of high preparation efficiency, low process cost and simple operation, and the silica fiber aerogel which is convenient for large-scale production and preparation can be regarded as a preferential candidate material in the fields of next-generation heat insulation and fire prevention in extreme environments or can be used as an oil-water separation sponge in pollution of seawater household and the like.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the description below are some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a physical diagram of a flexible silica nanofiber material prepared in example 1 of the present invention;
FIG. 2 is a scanning electron microscope image of a flexible silica nanofiber (left) and a silica fiber aerogel material (right) prepared in example 1 of the present invention;
FIG. 3 is an FTIR plot of silica fiber aerogel (left) and flexible silica nanofiber (right) materials prepared in example 1 of the present invention;
FIG. 4 is an XRD pattern of a silica fiber aerogel material prepared in example 5 of the present invention;
FIG. 5 is a graph showing the compressibility test of the silica fiber aerogel material prepared in example 6 of the present invention;
FIG. 6 shows a high temperature resistance test chart of the silica fiber aerogel material prepared in example 6 of the present invention;
FIG. 7 shows a graph of wettability testing of hydrophobic silica fiber aerogel materials prepared in example 7 of the present invention;
FIG. 8 shows a physical representation of the hydrophobic silica fiber aerogel material prepared in example 7 of the present invention.
Detailed Description
To make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention discloses a preparation method of silicon dioxide fiber aerogel, which specifically comprises the following steps:
Preferably, the molar ratio of the ethyl orthosilicate, the ethanol, the water and the catalyst is 1:2:2.5: 0.01-0.1, carrying out hydrolysis reaction at 75-85 ℃, obtaining the silica spinning solution with proper viscosity by adopting a sol-gel method, being beneficial to preparing flexible silica nano fibers by an electrostatic spinning method in the subsequent steps, and the prepared composite fibers have smaller diameter and better flexibility, and the finally prepared silica fiber aerogel material has better flexibility.
Preferably, the catalyst for the hydrolysis reaction is at least one of hydrochloric acid, acetic acid and phosphoric acid.
And 2, performing electrostatic spinning on the silicon dioxide spinning solution to obtain the flexible silicon dioxide nanofiber.
Preferably, the electrospinning conditions are as follows: the stirring speed of electrostatic spinning is 300 r/min-500 r/min, the voltage of electrostatic spinning is 18-20 KV, the receiving distance is 18cm, the diameter of a needle tube is less than 2mm, the relative humidity is 30% -50%, and the temperature of the spinning process is 24 +/-2 ℃.
And 3, shearing the flexible silicon dioxide nano fibers, and uniformly dispersing the flexible silicon dioxide nano fibers in a solvent containing an adhesive to obtain a silicon dioxide fiber dispersion liquid.
Preferably, the flexible silica nanofibers are cut into 1cm × 1cm squares, stirred for 5min to 15min at the rotation speed of 12000rpm of a high-speed homogenizer, and uniformly dispersed in a solvent containing a binder to obtain a silica fiber dispersion liquid.
Preferably, the concentration of the adhesive is 0.1-0.01%, and the adhesive is at least one of silica sol solution, nano-silica, polyethylene oxide, polyacrylamide, polyvinylpyrrolidone, tetraethyl silicate, methyl orthosilicate, methyltrimethoxysilane and dimethyldimethoxysilane. Therefore, the fiber connection is enhanced, the nanofiber framework is consolidated, and the service performance of the prepared silica fiber aerogel material is further improved.
Preferably, the adhesive silica sol solution is prepared by mixing ethyl orthosilicate, ethanol, water and a catalyst in a molar ratio of 1:40:40:0.01, and stirring and hydrolyzing for 5min at the rotating speed of 500 r/min. The catalyst comprises at least one of hydrochloric acid, acetic acid and phosphoric acid.
Preferably, the solvent includes at least one of deionized water, t-butanol, ethanol, isopropanol, and n-butanol. Therefore, the service performance of the prepared silica fiber aerogel material is further improved.
And 4, directionally freezing and drying the silicon dioxide fiber dispersion liquid to obtain a silicon dioxide fiber aerogel precursor, and then drying the silicon dioxide fiber aerogel precursor in the air atmosphere to obtain the silicon dioxide fiber aerogel.
Preferably, the silicon dioxide nanofiber solution is poured into a mold, liquid nitrogen is adopted for directional freezing, the temperature of freeze drying is-35 ℃ to-60 ℃, the vacuum degree is 1Pa, and the time of freeze drying is 20h to 60h. Drying treatment temperature is 80-800 ℃ in air atmosphere, heating rate is 1-5 ℃/min, and heat preservation is carried out for 0.5-2 h.
According to the invention, the flexible silica nanofiber is prepared by using a sol-gel method and an electrostatic spinning technology, and the silica fiber aerogel material is prepared by dispersing and directionally freeze-drying the flexible silica nanofiber, so that the addition of an organic polymer is omitted, the high-temperature heat treatment process is omitted, the raw material cost is saved, the energy consumption is reduced, the preparation efficiency is improved, the operation is simple and convenient, and the large-scale production is facilitated.
The invention also discloses a method for modifying the silicon dioxide fiber aerogel prepared by the preparation method, which comprises the following steps:
immersing the silicon dioxide fiber aerogel precursor into a methyl silane solution, forming a more stable three-dimensional network structure while performing hydrophobic modification on the methyl silane, and then performing drying treatment to obtain the hydrophobic silicon dioxide fiber aerogel. The immersion time is 6 h-12 h, the drying temperature is 50-600 ℃, the heating speed is 1 ℃/min-5 ℃/min, and the drying time is 0.5 h-2 h.
Preferably, the methylsilane includes at least one of methyltrimethoxysilane, dimethyldimethoxysilane, and octadecyltrimethoxysilane. The methylsilane is dissolved in at least one of toluene, n-hexane, ethanol or dimethyl sulfoxide. Therefore, the service performance of the prepared flexible silica fiber aerogel material is further improved.
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The following examples are intended to illustrate the invention and should not be construed as limiting the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by manufacturers, and are all conventional products available on the market.
Example 1
A preparation method of silica fiber aerogel comprises the following steps:
a. at normal temperature, ethyl orthosilicate, ethanol, water and hydrochloric acid are weighed according to a molar ratio of 1:2:2.5:0.05, heating to 85 ℃ for hydrolysis, stirring at the rotating speed of 500r/min, and recovering 12.1g of ethanol through condensation to prepare the silicon dioxide spinning solution with the viscosity of 210mpa.s.
b. And (b) performing electrostatic spinning on the silicon dioxide spinning solution obtained in the step a to obtain the flexible silicon dioxide nano fiber. Parameters during electrostatic spinning: the relative humidity is 40%, the voltage is 18kV, and the temperature in the spinning process is 18cm away from the receiving device and the spinning nozzle at 24 ℃.
c. Weighing ethyl orthosilicate, ethanol, water and hydrochloric acid in a molar ratio of 1:40:40:0.01, stirring and hydrolyzing for 5min at the rotating speed of 500r/min to obtain the adhesive silicon dioxide sol solution.
d. Shearing a flexible silicon dioxide fiber membrane accounting for 1% of the mass fraction of deionized water, adding the cut flexible silicon dioxide fiber membrane, stirring for 10 minutes at the rotating speed of 12000rpm of a high-speed homogenizer, then adding a silicon dioxide sol solution accounting for 0.005% of the mass fraction of the deionized water, and stirring for 3 minutes to obtain a homogeneous and stable silicon dioxide fiber dispersion solution.
e. And d, directionally freezing the silicon dioxide fiber dispersion liquid in the step d under liquid nitrogen, wherein the temperature of freeze drying is-60 ℃, the vacuum degree is 1Pa, and the time of freeze drying is 24 hours, so as to obtain the silicon dioxide fiber aerogel precursor.
f. And e, heating the precursor of the silica fiber aerogel prepared in the step e to 80 ℃ in the air atmosphere at the heating speed of 5 ℃/min, and preserving the heat for 1h to obtain the silica fiber aerogel. And (b) preparing the flexible silica nanofiber (shown in figure 1) by an electrostatic spinning method, wherein the prepared composite fiber has a small diameter and good flexibility, and the finally prepared silica fiber aerogel material has good flexibility.
Analyzing the microstructures and the surface morphologies of the flexible silica nanofiber material and the silica fiber aerogel material by using a Scanning Electron Microscope (SEM), wherein the graph of FIG. 2-a is a sample graph of the flexible silica nanofiber, the diameter of the fiber is uniform and continuous, and the diameter of the fiber is about 300-600nm; FIG. 2-b is a diagram of a silica fiber aerogel sample, wherein the fibers are cross-linked with each other to form a three-dimensional fiber network structure of nanometer order, so that the aerogel has better elasticity.
A comparison of the properties of the flexible silica nanofiber material and silica fiber aerogel material samples was analyzed, and it was confirmed from the FTIR spectrum (FIG. 3-a) that the strongest absorption peaks at 1000cm-1 and 801cm-1 confirmed that the main component was Si-O-Si bonds, and a small absorption peak at 670cm-1 indicated that a small amount of Si-C bonds were present. Except that the flexible silica nanofiber sample in fig. 3-b shows an O-H stretching vibration peak at 3750-3000 cm-1.
Example 2
A preparation method of silica fiber aerogel comprises the following steps:
a. at normal temperature, weighing tetraethoxysilane, ethanol, water and hydrochloric acid according to a molar ratio of 1:2:2.5:0.01, heating to 83 ℃ for hydrolysis, stirring at the rotating speed of 400r/min, and recovering 11.7g of ethanol through condensation to prepare the silicon dioxide spinning solution with the viscosity of 211mpa.s.
b. And (b) performing electrostatic spinning on the silicon dioxide spinning solution obtained in the step a to obtain the flexible silicon dioxide nano fiber. Parameters during electrostatic spinning: the relative humidity is 45%, the voltage is 20kV, and the temperature in the spinning process is 18cm away from the receiving device and the spinning nozzle at 25 ℃.
c. Shearing a flexible silicon dioxide fiber membrane accounting for 1% of the mass fraction of deionized water, adding the cut flexible silicon dioxide fiber membrane into 0.01% of polyacrylamide aqueous solution by mass fraction, and stirring the flexible silicon dioxide fiber membrane for 10 minutes at the rotating speed of 12000rpm of a high-speed homogenizer to obtain a homogeneous and stable silicon dioxide fiber dispersion liquid.
d. And d, directionally freezing the silicon dioxide fiber dispersion liquid in the step c under liquid nitrogen, wherein the temperature of freeze drying is-50 ℃, the vacuum degree is 2Pa, and the time of freeze drying is 60h, so as to obtain the silicon dioxide fiber aerogel precursor.
e. And d, heating the hydrophobic silica fiber aerogel precursor obtained in the step d to 800 ℃ in the air atmosphere at the heating speed of 5 ℃/min, and preserving the heat for 2h to obtain the silica fiber aerogel.
In this embodiment, the silica fiber aerogel is immersed in octadecyltrimethoxysilane with a mass fraction of 1% of the toluene solution for 6 hours to obtain a hydrophobic silica fiber aerogel precursor, and then the obtained hydrophobic silica fiber aerogel precursor is heated up to 200 ℃ in the air atmosphere at a heating rate of 5 ℃/min and is kept warm for 2 hours to obtain the hydrophobic silica fiber aerogel.
Example 3
A preparation method of silica fiber aerogel comprises the following steps:
a. at normal temperature, ethyl orthosilicate, ethanol, water and acetic acid are weighed according to a molar ratio of 1:2:2.5:0.1, heating to 75 ℃ for hydrolysis, stirring at the rotating speed of 300r/min, and recovering 12.2g of ethanol through condensation to prepare the silica spinning solution with the viscosity of 215mpa.s.
b. And (b) performing electrostatic spinning on the silicon dioxide spinning solution obtained in the step a to obtain the flexible silicon dioxide nano fiber. Parameters during electrostatic spinning: the relative humidity is 35 percent, the voltage is 20kV, and the temperature in the spinning process is 18cm away from the receiving device and the spinning nozzle at 22 ℃.
c. Deionized water and tert-butyl alcohol are mixed in a molar ratio of 5:1, shearing a flexible silicon dioxide fiber membrane accounting for 1 percent of the mass of the mixed solution, adding the flexible silicon dioxide fiber membrane into a polyethylene oxide mixed solution accounting for 0.01 percent of the mass of the mixed solution, and stirring the mixture for 10 minutes at the rotating speed of 12000rpm of a high-speed homogenizer to obtain a homogeneous and stable silicon dioxide fiber dispersion liquid.
d. And d, directionally freezing the silicon dioxide fiber dispersion liquid in the step c under liquid nitrogen, wherein the temperature of freeze drying is-50 ℃, the vacuum degree is 2Pa, and the time of freeze drying is 50h, so as to obtain the silicon dioxide fiber aerogel precursor.
e. And e, heating the precursor of the silica fiber aerogel obtained in the step d to 800 ℃ in the air atmosphere at the heating speed of 1 ℃/min, and preserving the heat for 0.5h to obtain the silica fiber aerogel.
In this embodiment, the silica fiber aerogel is immersed in methyltrimethoxysilane with the mass fraction of 1% of the n-hexane solution for 8 hours to obtain a hydrophobic silica fiber aerogel precursor, and then the obtained hydrophobic silica fiber aerogel precursor is heated up to 75 ℃ in the air atmosphere at the heating rate of 1 ℃/min and is kept warm for 1 hour to obtain the hydrophobic silica fiber aerogel.
Example 4
A preparation method of silica fiber aerogel comprises the following steps:
a. at normal temperature, ethyl orthosilicate, ethanol, water and phosphoric acid are weighed according to a molar ratio of 1:2:2.5:0.06 of the mixture is mixed, the temperature is increased to 78 ℃ for hydrolysis, the mixture is stirred at the rotating speed of 350r/min, 11.6g of ethanol is recovered through condensation, and the silicon dioxide spinning solution with the viscosity of 210mpa.s is prepared.
b. And (b) performing electrostatic spinning on the silicon dioxide spinning solution obtained in the step a to obtain the flexible silicon dioxide nano fiber. Parameters during electrostatic spinning: the relative humidity is 30 percent, the voltage is 18kV, and the temperature in the spinning process is 18cm away from the receiving device and the spinning nozzle at 26 ℃.
c. Deionized water and ethanol were mixed in a molar ratio of 6:1, shearing a flexible silicon dioxide fiber membrane accounting for 1 percent of the mass fraction of the mixed solution, adding the cut flexible silicon dioxide fiber membrane into a polyvinylpyrrolidone mixed solution accounting for 0.01 percent of the mass fraction, and stirring the mixture for 10 minutes at the rotating speed of 12000rpm of a high-speed homogenizer to obtain a homogeneous and stable silicon dioxide fiber dispersion liquid.
d. And d, directionally freezing the silicon dioxide fiber dispersion liquid in the step c under liquid nitrogen, wherein the temperature of freeze drying is-35 ℃, the vacuum degree is 3Pa, and the time of freeze drying is 36h, so as to obtain the silicon dioxide fiber aerogel precursor.
e. And d, heating the precursor of the silica fiber aerogel obtained in the step d to 500 ℃ in the air atmosphere at the heating speed of 3 ℃/min, and preserving the heat for 1h to obtain the silica fiber aerogel.
In this embodiment, the silica fiber aerogel is immersed in dimethyldimethoxysilane with the mass fraction of 1% of the ethanol solution for 10 hours to obtain a hydrophobic silica fiber aerogel precursor, and then the obtained hydrophobic silica fiber aerogel precursor is heated to 100 ℃ in the air atmosphere at the heating speed of 2 ℃/min and is kept warm for 2 hours to obtain the hydrophobic silica fiber aerogel.
Example 5
A preparation method of silica fiber aerogel comprises the following steps:
a. at normal temperature, weighing tetraethoxysilane, ethanol, water and hydrochloric acid according to a molar ratio of 1:2:2.5:0.04, heating to 78 ℃ for hydrolysis, stirring at the rotating speed of 450r/min, and recovering 12.2g of ethanol by condensation to prepare the silicon dioxide spinning solution with viscosity of 212mpa.s.
b. And (b) performing electrostatic spinning on the silicon dioxide spinning solution obtained in the step a to obtain the flexible silicon dioxide nano fiber. Parameters during electrostatic spinning: the relative humidity is 40%, the voltage is 18kV, and the temperature in the spinning process is 18cm away from the receiving device and the spinning nozzle at 24 ℃.
c. Deionized water and n-butanol are added according to a molar ratio of 6:1, shearing the flexible silicon dioxide fiber film with the mass fraction of 1 percent of the mixed solution, adding the cut flexible silicon dioxide fiber film into the nano silicon dioxide mixed solution with the mass fraction of 0.1 percent, and stirring the mixed solution for 15 minutes at the rotating speed of 12000rpm of a high-speed homogenizer to obtain a homogeneous and stable silicon dioxide fiber dispersion liquid.
d. And d, directionally freezing the silicon dioxide fiber dispersion liquid in the step c under liquid nitrogen, wherein the temperature of freeze drying is-60 ℃, the vacuum degree is 1Pa, and the time of freeze drying is 20h, so as to obtain the silicon dioxide fiber aerogel precursor.
e. And e, heating the precursor of the silica fiber aerogel obtained in the step d to 800 ℃ in the air atmosphere at the heating speed of 5 ℃/min, and preserving the heat for 2 hours to obtain the silica fiber aerogel.
The XRD result of FIG. 4 can analyze that the silica fiber aerogel sample has an amorphous structure, 1 distinct characteristic peak and SiO 2 The standard spectrum (JCPDS # 76-0931) was well-registered, confirming the successful synthesis of the silica fiber aerogel sample. The silica fiber aerogel sample has the strongest diffraction peak near the 2 theta angle of 21.5 degrees, and the strongest diffraction peak corresponds to the (111) crystal face of SiO 2.
Example 6
A preparation method of silica fiber aerogel comprises the following steps:
a. at normal temperature, weighing tetraethoxysilane, ethanol, water and hydrochloric acid according to a molar ratio of 1:2:2.5:0.01, heating to 81 ℃ for hydrolysis, stirring at the rotating speed of 400r/min, and recovering 11.9g of ethanol by condensation to prepare the silicon dioxide spinning solution with viscosity of 208mpa.s.
b. And (b) performing electrostatic spinning on the silicon dioxide spinning solution obtained in the step a to obtain the flexible silicon dioxide nano fiber. Parameters during electrostatic spinning: the relative humidity is 50%, the voltage is 19kV, and the temperature in the spinning process is 18cm away from the spinning nozzle and the receiving device at 24 ℃.
c. Deionized water and isopropanol were mixed in a molar ratio of 5:1, shearing a flexible silicon dioxide fiber membrane with the mass fraction of 1 percent of the mixed solution, then adding the flexible silicon dioxide fiber membrane into a tetraethyl silicate mixed solution with the mass fraction of 0.1 percent, and stirring for 5 minutes at the rotating speed of 12000rpm of a high-speed homogenizer to obtain a homogeneous and stable silicon dioxide fiber dispersion liquid.
d. And d, directionally freezing the silicon dioxide fiber dispersion liquid in the step c under liquid nitrogen, wherein the temperature of freeze drying is-50 ℃, the vacuum degree is 1Pa, and the time of freeze drying is 45h, so as to obtain the silicon dioxide fiber aerogel precursor.
e. And e, heating the precursor of the silica fiber aerogel obtained in the step d to 800 ℃ in the air atmosphere at the heating speed of 5 ℃/min, and preserving the heat for 2 hours to obtain the silica fiber aerogel.
In this embodiment, the silica fiber aerogel is immersed in methyltrimethoxysilane with the mass fraction of 1% of the dimethyl sulfoxide solution for 12 hours to obtain a hydrophobic silica fiber aerogel precursor, and then the obtained hydrophobic silica fiber aerogel precursor is heated up to 600 ℃ in the air atmosphere at the heating rate of 2 ℃/min and is kept warm for 2 hours to obtain the hydrophobic silica fiber aerogel.
Fig. 5 is a simple elasticity test of the hydrophobic silica fiber aerogel sample, which comprises compressing 60% of the aerogel sample, releasing the sample, and recovering the fiber, so that the construction of the three-dimensional network structure can be seen, and the elasticity of the fiber can be greatly improved.
Fig. 6 shows that the silica fiber aerogel sample has no any combustion sign under open fire in the high temperature test, and the fibers have no appearance change, and the silica fiber aerogel sample can be used under extreme conditions or in the aerospace field.
Example 7
A preparation method of silica fiber aerogel comprises the following steps:
a. at normal temperature, ethyl orthosilicate, ethanol, water and hydrochloric acid are weighed according to a molar ratio of 1:2:2.5:0.05, heating to 85 ℃ for hydrolysis, stirring at the rotating speed of 500r/min, and recovering 12.1g of ethanol through condensation to prepare the silicon dioxide spinning solution with the viscosity of 210mpa.s.
b. And (b) performing electrostatic spinning on the silicon dioxide spinning solution obtained in the step a to obtain the flexible silicon dioxide nano fiber. Parameters during electrostatic spinning: the relative humidity is 40%, the voltage is 18kV, and the temperature in the spinning process is 18cm away from the receiving device and the spinning nozzle at 24 ℃.
c. Weighing ethyl orthosilicate, ethanol, water and hydrochloric acid in a molar ratio of 1:40:40:0.01, stirring and hydrolyzing for 5min at the rotating speed of 500r/min to obtain the silica sol solution.
d. Shearing a flexible silicon dioxide fiber membrane accounting for 1% of the mass fraction of the deionized water, adding the flexible silicon dioxide fiber membrane into the flexible silicon dioxide fiber membrane, stirring the flexible silicon dioxide fiber membrane for 10 minutes at the rotating speed of 12000rpm of a high-speed homogenizer, then adding a silicon dioxide sol solution accounting for 0.005% of the mass fraction of the deionized water into the flexible silicon dioxide fiber membrane, and stirring the mixture for 3 minutes to obtain a homogeneous and stable silicon dioxide fiber dispersion solution.
e. And d, directionally freezing the silicon dioxide fiber dispersion liquid in the step d under liquid nitrogen, wherein the temperature of freeze drying is-50 ℃, the vacuum degree is 1Pa, and the time of freeze drying is 26h to obtain the silicon dioxide fiber aerogel precursor.
f. And e, heating the precursor of the silica fiber aerogel obtained in the step e to 200 ℃ in the air atmosphere at the heating speed of 5 ℃/min, and preserving the heat for 1h to obtain the silica fiber aerogel.
In this embodiment, the silica fiber aerogel is immersed in octadecyltrimethoxysilane with a mass fraction of 1% of the toluene solution for 6 hours to obtain a hydrophobic silica fiber aerogel precursor, and then the obtained hydrophobic silica fiber aerogel precursor is heated to 50 ℃ in the air atmosphere at a heating rate of 5 ℃/min, and is kept warm for 1 hour to obtain the hydrophobic silica fiber aerogel.
Fig. 7 shows that the product shows strong hydrophobicity after being reformed by methyl through hydrophobic detection of a hydrophobic silica fiber aerogel sample, and is expected to develop in the field of oil-water separation in the future. Meanwhile, the hydrophobic silica fiber aerogel sample can be modified, and the density of the sample is very low, as shown in fig. 8.
Finally, it should be noted that: the above-mentioned embodiments are only specific embodiments of the present invention, which are used for illustrating the technical solutions of the present invention and not for limiting the same, and the protection scope of the present invention is not limited thereto, although the present invention is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or equivalent substitutes for some technical features within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the embodiments of the present invention, and they should be construed as being included therein. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A preparation method of silica fiber aerogel is characterized by comprising the following steps:
mixing tetraethyl silicate, ethanol, water and a catalyst, then carrying out hydrolysis reaction to obtain a silicon dioxide spinning solution, and carrying out electrostatic spinning on the silicon dioxide spinning solution to obtain flexible silicon dioxide nano fibers;
uniformly dispersing the flexible silicon dioxide nano fibers in a solvent containing an adhesive to obtain silicon dioxide fiber dispersion liquid;
and directionally freezing and drying the silicon dioxide fiber dispersion liquid to obtain a silicon dioxide fiber aerogel precursor, and drying the silicon dioxide fiber aerogel precursor in the air atmosphere to obtain the silicon dioxide fiber aerogel.
2. The method for preparing the silica fiber aerogel according to claim 1, wherein the mole ratio of the tetraethyl silicate, the ethanol, the water and the catalyst is 1:2:2.5: 0.01-0.1, the temperature of the hydrolysis reaction is 75-85 ℃, and the silica spinning solution is obtained by adopting a sol-gel method.
3. The method for preparing silica fiber aerogel according to claim 1, wherein the catalyst is at least one of hydrochloric acid, acetic acid and phosphoric acid.
4. The method for preparing silica fiber aerogel according to claim 1, wherein the concentration of the binder is 0.1% -0.01%, and the binder is at least one of silica sol solution, nano silica, polyethylene oxide, polyacrylamide, polyvinylpyrrolidone, tetraethyl silicate and methyl orthosilicate.
5. The method of claim 1, wherein the solvent comprises at least one of deionized water, t-butanol, ethanol, isopropanol, and n-butanol.
6. The method for preparing the silica fiber aerogel according to claim 1, wherein the silica nanofiber solution is directionally freeze-dried, and specifically comprises the following steps:
liquid nitrogen is adopted for directional freezing, the temperature of freeze drying is-35 ℃ to-60 ℃, the vacuum degree is 1Pa to 3Pa, and the time of freeze drying is 20h to 60h.
7. The method for preparing silica fiber aerogel according to claim 1, wherein the drying temperature is 80 ℃ to 800 ℃, the heating rate is 1 ℃/min to 5 ℃/min, and the temperature is maintained for 0.5h to 2h.
8. Silica fiber aerogel produced by the method for producing a silica fiber aerogel according to any one of claims 1 to 7.
9. The method for modifying silica fiber aerogel according to claim 8, wherein the silica fiber aerogel precursor is immersed in a methyl silane solution and dried to obtain hydrophobic silica fiber aerogel.
10. The method for modifying silica fiber aerogel according to claim 8, wherein said methylsilane is at least one of methyltrimethoxysilane, dimethyldimethoxysilane and octadecyltrimethoxysilane;
when the silicon dioxide fiber aerogel precursor is immersed into a methyl silane solution and dried, the immersion time is 6-12 h, the drying temperature is 50-600 ℃, the heating rate is 1-5 ℃/min, and the heat preservation time is 0.5-2 h.
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