CN114477193B - Anisotropic silica aerogel with double refraction effect and preparation method thereof - Google Patents
Anisotropic silica aerogel with double refraction effect and preparation method thereof Download PDFInfo
- Publication number
- CN114477193B CN114477193B CN202210046410.4A CN202210046410A CN114477193B CN 114477193 B CN114477193 B CN 114477193B CN 202210046410 A CN202210046410 A CN 202210046410A CN 114477193 B CN114477193 B CN 114477193B
- Authority
- CN
- China
- Prior art keywords
- supercritical drying
- drying kettle
- stainless steel
- methanol
- steel container
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
- C01B33/157—After-treatment of gels
- C01B33/158—Purification; Drying; Dehydrating
- C01B33/1585—Dehydration into aerogels
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids
Landscapes
- Chemical & Material Sciences (AREA)
- Dispersion Chemistry (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Silicon Compounds (AREA)
Abstract
The invention discloses a preparation method of anisotropic silica aerogel with double refraction effect, which comprises the following steps: step 1, uniformly mixing methyl orthosilicate and methanol to obtain a mixed solution A; step 2, dropwise adding dilute ammonia water into the mixed solution A, and uniformly mixing to obtain precursor sol B; step 3, transferring the precursor sol B into a stainless steel container, pouring and molding in a quartz tube, and obtaining methanol gel after gel curing; step 4, heating and pressurizing the stainless steel container and the methanol gel in a supercritical drying kettle so as to convert the methanol medium in the gel into a supercritical state; and 5, opening an air outlet valve of the supercritical drying kettle to release air, and simultaneously increasing the temperature of the kettle body, stopping heating when the air is released, and naturally cooling the supercritical drying kettle to the room temperature. Also disclosed is an anisotropic silica aerogel having a birefringent effect, exhibiting pronounced birefringent properties in the path of polarized light transmitted therethrough.
Description
Technical Field
The invention belongs to the technical field of material preparation and structure regulation, and particularly relates to anisotropic silica aerogel with a double refraction effect and a preparation method of the anisotropic silica aerogel with the double refraction effect.
Background
Since the advent of silica aerogel, there has been increasing interest in this new class of porous materials. The aerogel has a unique nano porous structure and has wide application in the fields of high-energy physics, astronomy, material science, condensed state physics, chemistry and the like. The aerogel has extremely high porosity and specific surface area, and the unique porous structure of the aerogel leads to extremely low heat conductivity, so that the aerogel is an extremely good heat preservation and insulation material. Silica aerogel having a porosity of 98% or more generally has important applications in research of supercritical phenomenon of quantum fluid and phase transition process of liquid crystal, and in particular silica aerogel having macroscopic anisotropy plays an important role in related research.
Researchers at university of kaneer and university of northwest in the united statesImmersing silica aerogel blocks into 3 In He superfluid, silica aerogel was found to promote 3 The phase transition temperature of He superfluid decreases sharply. Subsequent researchers observed in anisotropic silica aerogels 3 He superfluid has a new superfluid phase, and anisotropic silica aerogel can keep the new superfluid phase stable, the new findings raise a great deal of attention and continuously explore the new superfluid phase, and the research has important significance for revealing the physical laws of quantum fluid, superconducting and ultralow-temperature refrigeration, so the related researches are continuously tracked and reported by International journal Nature Physics and Physical Review Letters. The anisotropic silica aerogel referred to in the above studies has a regular cylindrical or cubic shape with a volume of about 1cm 3 About, the density is only about 50mg/cm 3 The porosity is about 98%, and experiments strictly require that the aerogel have a regular shape, a uniform texture and a controllable anisotropy. However, since the process of preparing the aerogel involves complicated processes such as hydrolytic polycondensation of precursor, gel aging and supercritical drying, the extremely delicate and fragile gel skeleton is easy to collapse during the preparation process, and the aerogel is contracted and cracked to destroy the uniformity of morphology and structure, so that the aerogel cannot be used for the above experiment. That is, an aerogel having a uniform texture is inherently difficult to obtain, and it is more difficult to further achieve anisotropic control while ensuring good uniformity of the aerogel. It is therefore still a great challenge to construct an anisotropic silica aerogel with uniform texture and to achieve regulation of the anisotropy.
In the gel forming process, the growth mechanism of the silica aerogel accords with the rule of diffusion limiting gel, the formed particles are distributed in a multi-level fractal structure, researches show that the basic particle size of the silica aerogel is about 3-5nm, on a macroscopic scale, usually a scale of a plurality of mm, the aerogel is isotropic, that is, the aerogel shows the same property in all directions in a three-dimensional space, and the structure and the physical and chemical properties of all parts inside the aerogel are completely the same. Experiments show that by a certain means, the aerogel can be enabled to exhibit anisotropy on a macroscopic scale. In 2008, two mechanisms of formation of anisotropic silica aerogel were studied by Pollanen et al, university of North SiC, U.S., and the uniformity of the anisotropy of the aerogel was studied by observing the birefringence phenomenon exhibited by the aerogel. In 2012, lee et al used nuclear magnetic resonance, a special container containing methanol liquid was installed inside the superconducting magnet, and aerogel was placed at one end of the container, and the device was able to control and accurately measure the pressure of methanol gas. When methanol gas diffuses in the aerogel, the proton resonance signal of the aerogel sample is captured by an induction coil wound on the periphery of the special container, and the average free path of the diffusion of methanol gas molecules in the aerogel can be obtained through calculation. When the direction of diffusion is changed, the mean free path measured will change, which is consistent with the degree of anisotropy of the aerogel. In 2013, zimmerman et al studied the anisotropy of aerogels due to slight strain and the difference in PH of the sol.
Sodium alginate and silver nanowires are uniformly mixed from Huai Ping et al (national patent publication No. CN 112876731A), a long-range ordered silver nanowire-sodium alginate aerogel substrate with a layered structure is formed by a bidirectional freezing method, and then a monomer and a cross-linking agent are added into the aerogel to construct hydrogel with the layered structure, so that the anisotropic property is shown.
Liu Pengbo et al (national patent publication No. CN 110818945A) firstly prepare aqueous dispersion of polyamic acid ammonium salt/graphene, then directionally freeze and thermally imidize the aqueous dispersion, and the prepared polyimide/graphene composite aerogel has the characteristics of anisotropy in conductivity, electromagnetic shielding performance, heat transfer performance and mechanical property.
Zhang Dong et al (national patent publication No. CN 111072318A) mixed graphene oxide solution with expanded graphite to form a uniform dispersion, and frozen the dispersion in a liquid nitrogen atmosphere to obtain an ice-containing GO/EG anisotropic mixed hydrogel; freeze-drying the ice-containing GO/EG anisotropic mixed hydrogel in a freeze dryer to obtain GO/EG anisotropic aerogel; and heating the GO/EG anisotropic aerogel in an oven to obtain the rGO/EG anisotropic mixed aerogel.
Xu Min et al (national patent publication No. CN 111312431A) uses wood-derived cellulose aerogel as a matrix, and carbon nanotubes are self-assembled in ordered pore channels in the aerogel to form a uniform continuous stable conductive layer, and test shows that the conductive film prepared by cold pressing has anisotropy in the radial and axial conductivity.
Wu Hui et al (national patent publication No. CN 110184683A) mix a polymer solution, an inorganic precursor and a chloride to obtain a spinning precursor mixed solution; performing jet spinning on the spinning precursor mixed solution to obtain composite fiber aerogel; and sequentially performing pre-oxidation treatment and carbonization treatment on the composite fiber aerogel to obtain the anisotropic layered carbon fiber-based aerogel material.
Fan Wei et al (national patent publication No. CN 110157035A) to prepare polyamic acid spinning solution, and preparing polyamic acid nanofiber by electrostatic spinning; uniformly mixing the obtained polyamide acid nanofiber, water-soluble polyamide acid and organic amine in water, and dispersing to obtain a uniform dispersion liquid of the polyamide acid nanofiber and the water-soluble polyamide acid; the obtained dispersion liquid is placed in a mould, is subjected to bidirectional freezing in a constant-temperature reaction bath, and is placed in a freeze dryer for drying; and carrying out thermal imidization on the obtained sample in a tube furnace to obtain the polyimide nanofiber aerogel with heat insulation anisotropy.
Zhang Jianming et al (national patent publication No. CN 109096526A) prepare graphene oxide-dual-electrical chitin nanofiber hybrid particles suspension, cast to form a film, and dry to obtain a layer-by-layer stacked graphene oxide-dual-electrical chitin nanofiber hybrid film; and soaking the graphene oxide-dual-electrical chitin nanofiber hybrid membrane in an expanding agent, and drying to obtain the graphene oxide aerogel.
In summary, the aerogel can have a certain anisotropy through external compression, directional freezing and changing the pH value of the reaction, however, the report of obtaining the anisotropy of the silica aerogel through regulating and controlling the supercritical drying process is relatively less.
Disclosure of Invention
The invention aims to provide the anisotropic silica aerogel with the double refraction effect, and the shrinkage rate of the silica aerogel is regulated and controlled by controlling the parameters such as the temperature rising rate, the temperature, the pressure, the air release and decompression rate of a supercritical drying kettle, so as to obtain the anisotropic silica aerogel with the double refraction effect.
The second object of the present invention is to provide a method for preparing anisotropic silica aerogel having a birefringence effect.
The first technical scheme adopted by the invention is that the preparation method of the anisotropic silica aerogel with the double refraction effect comprises the following steps:
step 1, uniformly mixing methyl orthosilicate and methanol to obtain a mixed solution A;
step 2, dropwise adding dilute ammonia water into the mixed solution A obtained in the step 1, magnetically stirring for 0.5-1h, and uniformly mixing to obtain precursor sol B;
step 3, transferring the precursor sol B obtained in the step 2 into a stainless steel container, standing for 3-4d, transferring the stainless steel container into a supercritical drying kettle, adding methanol to the stainless steel container, and enabling the liquid level in the supercritical drying kettle to be not higher than two thirds of the volume;
step 4, the supercritical drying kettle in the step 3 is sealed and heated until the temperature of the kettle is higher than the supercritical temperature of methanol, the internal pressure of the kettle is higher than the supercritical pressure of the methanol, and the temperature is kept constant for a period of time to ensure that the internal temperature and the external temperature of the supercritical drying kettle are uniform, and the methanol medium in gel is converted into a supercritical state;
and 5, opening an air outlet valve of the supercritical drying kettle in the step 4 to deflate, simultaneously increasing the temperature, stopping heating when the air is exhausted, naturally cooling the supercritical drying kettle to the room temperature, taking out the stainless steel container from the supercritical drying kettle, carefully opening a cover, and carefully taking out the aerogel from the quartz tube to obtain the anisotropic silica aerogel with the double refraction effect.
The present invention is also characterized in that,
in the step 1, the volume ratio of the methyl orthosilicate to the methanol is 10:80-100.
In the step 2, the concentration of the dilute ammonia water is 0.003-0.005M, and the volume ratio of the dilute ammonia water to the methyl orthosilicate used in the step 1 is 2.4:10.
In the step 4, the supercritical drying kettle is heated to 260-280 ℃ at a heating rate of 5-10 ℃/h, the air pressure in the supercritical drying kettle reaches 10-11MPa, and the temperature of 260-280 ℃ is kept for 1-2h.
In the step 5, the air is exhausted at a decompression rate of 3-10MPa/h, and meanwhile, the supercritical drying kettle is heated to 280-300 ℃ at a heating rate of 5-10 ℃/h, and the temperature of 280-300 ℃ is kept until the air pressure drop in the supercritical drying kettle is 0MPa.
The second technical scheme adopted by the invention is that the anisotropic silica aerogel with the double refraction effect is prepared by adopting the preparation method.
The beneficial effects of the invention are as follows:
(1) The process is simple and easy to operate, and the prepared anisotropic silica aerogel with the double refraction effect has important significance for revealing the physical laws of quantum fluid, super-conduction and ultralow-temperature refrigeration and has wide application in the ultralow-temperature physical field.
(2) According to the invention, a quartz tube and a cylindrical stainless steel container are adopted to assist in a supercritical drying process, and the shrinkage rate of the silica aerogel is regulated and controlled by controlling parameters such as the temperature rising rate, the temperature, the pressure, the air release and pressure reduction rate of the supercritical drying kettle, so that the silica aerogel has a double refraction effect and has anisotropic characteristics.
Drawings
FIG. 1 is a flow chart of a method of making the present invention;
FIG. 2 is a photograph (scale bar 1 cm) of a stainless steel container used in the preparation of example 1 of the present invention;
FIG. 3 is a photograph (scale: 1 cm) of an anisotropic silica aerogel having a birefringent effect prepared in example 1 of the present invention;
FIG. 4 is an SEM image (scale bar 500 nm) of an anisotropic silica aerogel having a birefringent effect prepared in example 1 of the present invention;
FIG. 5 is an SEM image (scale bar 200 nm) of an anisotropic silica aerogel having a birefringent effect prepared in example 1 of the present invention;
fig. 6 is a graph showing the experimental effect of birefringence exhibited by the anisotropic silica aerogel with birefringence prepared in example 1 of the present invention in the transmission path of polarized light.
FIG. 7 is a graph showing the experimental effect of birefringence exhibited by the isotropic silica aerogel prepared by the method in the transmission path of polarized light.
Detailed Description
The invention will be described in detail below with reference to the drawings and the detailed description.
The invention provides a preparation method of anisotropic silica aerogel with a double refraction effect, which is shown in figure 1 and specifically comprises the following steps:
step 1, uniformly mixing methyl orthosilicate and methanol to obtain a mixed solution A;
in the step 1, the volume ratio of the methyl orthosilicate to the methanol is 10:80-100.
Step 2, dropwise adding dilute ammonia water into the mixed solution A obtained in the step 1, magnetically stirring for 0.5-1h, and uniformly mixing to obtain precursor sol B;
in the step 2, the concentration of the dilute ammonia water is 0.003-0.005M, and the volume ratio of the dilute ammonia water to the methyl orthosilicate used in the step 1 is 2.4:10.
Step 3, transferring the precursor sol B obtained in the step 2 into a stainless steel container, wherein the axis of a quartz tube is parallel to the axis of the stainless steel container, covering a stainless steel cover in a cylindrical stainless steel container, standing for 3-4d, transferring the stainless steel container into a supercritical drying kettle, adding methanol to the stainless steel container, and enabling the liquid level in the supercritical drying kettle to be not higher than two thirds of the volume;
in the step 3, the inner diameter of the stainless steel container is 80mm, the inner height is 50mm, the wall thickness is 5mm, the inner diameter of the quartz tube is 5-10mm, the length is 50mm equal to the inner height of the stainless steel container, and the wall thickness is 2-3mm.
Step 4, the supercritical drying kettle in the step 3 is sealed and heated until the temperature of the kettle is higher than the supercritical temperature of methanol, the internal pressure of the kettle is higher than the supercritical pressure of the methanol, and the temperature is kept constant for a period of time to ensure that the internal temperature and the external temperature of the supercritical drying kettle are uniform, and the methanol medium in gel is converted into a supercritical state;
in the step 4, the supercritical drying kettle is heated to 260-280 ℃ at a heating rate of 5-10 ℃/h, the air pressure in the supercritical drying kettle reaches 10-11MPa, and the temperature of 260-280 ℃ is kept for 1-2h.
And 5, opening an air outlet valve of the supercritical drying kettle in the step 4 to deflate, simultaneously increasing the temperature, stopping heating when the air is exhausted, naturally cooling the supercritical drying kettle to the room temperature, taking out the stainless steel container from the supercritical drying kettle, carefully opening a cover, and carefully taking out the aerogel from the quartz tube to obtain the anisotropic silica aerogel with the double refraction effect.
In the step 5, the air is exhausted at a decompression rate of 3-10MPa/h, and meanwhile, the supercritical drying kettle is heated to 280-300 ℃ at a heating rate of 5-10 ℃/h, and the temperature of 280-300 ℃ is kept until the air pressure drop in the supercritical drying kettle is 0MPa.
The invention also provides the anisotropic silica aerogel with the double refraction effect, which is prepared by adopting the preparation method.
Example 1
The method comprises the steps of exhausting gas at a reduced pressure rate of 5MPa/h according to a volume ratio of 10:80 by methyl orthosilicate to methanol with a concentration of 0.004M of dilute ammonia water, and heating a supercritical drying kettle to 280 ℃ at a heating rate of 10 ℃/h at the same time, and drying to obtain the silica aerogel.
Firstly, uniformly mixing methyl orthosilicate and methanol according to the volume ratio of 10:80 to obtain a mixed solution A;
secondly, dropwise adding dilute ammonia water with the concentration of 0.004M into the mixed solution A according to the volume ratio of the dilute ammonia water to the methyl orthosilicate of 2.4:10, magnetically stirring for 0.5h, and uniformly mixing to obtain precursor sol B;
thirdly, transferring the precursor sol B into a stainless steel container which is pre-placed with a quartz tube, wherein the inner diameter of the stainless steel container is 80mm, the inner height is 50mm, the wall thickness is 5mm, the inner diameter of the quartz tube is 8mm, the length is 50mm equal to the inner height of the stainless steel container, the wall thickness is 2mm, the axis of the quartz tube is parallel to the axis of the stainless steel container, the stainless steel container is cylindrical, a stainless steel cover is covered, standing is carried out for 3 days, the sol in the stainless steel container is subjected to gel curing, the stainless steel container is transferred into a supercritical drying kettle, methanol is added to the stainless steel container, and the liquid level in the supercritical drying kettle is not higher than two thirds of the volume, as shown in fig. 2;
fourthly, sealing the supercritical drying kettle, heating the supercritical drying kettle to 260 ℃ at a heating rate of 10 ℃/h, wherein the air pressure in the supercritical drying kettle reaches 11MPa, and is higher than the supercritical pressure of methanol, and the temperature of 260 ℃ is kept for 1h to ensure that the internal and external temperatures of the supercritical drying kettle are uniform, and the methanol medium in the gel is converted into a supercritical state;
finally, the air outlet valve of the supercritical drying kettle is opened to discharge air at a decompression rate of 5MPa/h, meanwhile, the supercritical drying kettle is heated to 280 ℃ at a heating rate of 10 ℃/h, the temperature of 280 ℃ is kept until the air pressure drop in the supercritical drying kettle is 0MPa, the heating is stopped when the air is discharged, the supercritical drying kettle is naturally cooled to the room temperature, the stainless steel container is taken out from the supercritical drying kettle, the cover is carefully opened, the aerogel is carefully taken out from the quartz tube, and the anisotropic silica aerogel with the birefringent effect can be obtained, as shown in figure 3. FIG. 2 is a photograph of a stainless steel vessel used in the preparation of the present invention; FIG. 3 is a photograph of an anisotropic silica aerogel having a birefringent effect prepared according to the present invention; from fig. 4 to 5, the morphology of the anisotropic silica aerogel with birefringence effect prepared according to the present invention can be seen; FIG. 6 is a graph showing the experimental effect of birefringence exhibited by the anisotropic silica aerogel with birefringence produced by the present invention in the path of polarized light transmission, from which it can be seen that the aerogel produced by this example was irradiated with polarized light, and the transmitted light produced by the polarization analyzer has interference bright fringes, which are due to the enhanced interference of the transmitted light caused by the anisotropy of the aerogel, thereby demonstrating that the aerogel has birefringence characteristics; the shrinkage of the aerogel can be effectively inhibited by adopting a slow decompression rate (less than or equal to 1 MPa/h), the isotropic silica aerogel (shown in figure 7) can be obtained by drying, under the same test conditions, the isotropic silica aerogel can not generate interference bright fringes after being irradiated by polarized light and passing through an analyzer, namely, almost one dark piece in a field of view is generated, and the isotropic silica aerogel has no birefringence property. In conclusion, the anisotropic silica aerogel with the birefringence effect prepared by the invention has obvious birefringence characteristics.
Example 2
The method comprises the steps of exhausting gas at a reduced pressure rate of 5MPa/h according to a volume ratio of 10:100 by methyl orthosilicate to methanol with a concentration of 0.004M, heating a supercritical drying kettle to 280 ℃ at a heating rate of 10 ℃/h, and drying to obtain the silica aerogel.
Firstly, uniformly mixing methyl orthosilicate and methanol according to the volume ratio of 10:100 to obtain a mixed solution A;
secondly, dropwise adding dilute ammonia water with the concentration of 0.004M into the mixed solution A according to the volume ratio of the dilute ammonia water to the methyl orthosilicate of 2.4:10, magnetically stirring for 0.5h, and uniformly mixing to obtain precursor sol B;
thirdly, transferring the precursor sol B into a stainless steel container which is pre-placed with a quartz tube, wherein the inner diameter of the stainless steel container is 80mm, the inner height is 50mm, the wall thickness is 5mm, the inner diameter of the quartz tube is 8mm, the length is 50mm equal to the inner height of the stainless steel container, the wall thickness is 2mm, the axis of the quartz tube is parallel to the axis of the stainless steel container, the stainless steel container is cylindrical, a stainless steel cover is covered, standing is carried out for 3 days, the sol in the stainless steel container is subjected to gel curing, the stainless steel container is transferred into a supercritical drying kettle, methanol is added to the stainless steel container, and the liquid level in the supercritical drying kettle is not higher than two thirds of the volume;
fourthly, sealing the supercritical drying kettle, heating the supercritical drying kettle to 260 ℃ at a heating rate of 10 ℃/h, wherein the air pressure in the supercritical drying kettle reaches 11MPa, and is higher than the supercritical pressure of methanol, and the temperature of 260 ℃ is kept for 1h to ensure that the internal and external temperatures of the supercritical drying kettle are uniform, and the methanol medium in the gel is converted into a supercritical state;
and finally, opening an air outlet valve of the supercritical drying kettle to discharge air at a decompression rate of 5MPa/h, heating the supercritical drying kettle to 280 ℃ at a heating rate of 10 ℃/h, keeping the temperature of 280 ℃ until the air pressure drop in the supercritical drying kettle is 0MPa, stopping heating when the air is discharged, naturally cooling the supercritical drying kettle to room temperature, taking out the stainless steel container from the supercritical drying kettle, carefully opening a cover, and carefully taking out the aerogel from the quartz tube to obtain the anisotropic silica aerogel with the birefringent effect.
Example 3
The method comprises the steps of exhausting gas at a reduced pressure rate of 5MPa/h according to a volume ratio of 10:80 by methyl orthosilicate to methanol with a concentration of 0.004M of dilute ammonia water, and heating a supercritical drying kettle to 300 ℃ at a heating rate of 10 ℃/h to obtain the silica aerogel after drying.
Firstly, uniformly mixing methyl orthosilicate and methanol according to the volume ratio of 10:80 to obtain a mixed solution A;
secondly, dropwise adding dilute ammonia water with the concentration of 0.004M into the mixed solution A according to the volume ratio of the dilute ammonia water to the methyl orthosilicate of 2.4:10, magnetically stirring for 0.5h, and uniformly mixing to obtain precursor sol B;
thirdly, transferring the precursor sol B into a stainless steel container which is pre-placed with a quartz tube, wherein the inner diameter of the stainless steel container is 80mm, the inner height is 50mm, the wall thickness is 5mm, the inner diameter of the quartz tube is 8mm, the length is 50mm equal to the inner height of the stainless steel container, the wall thickness is 2mm, the axis of the quartz tube is parallel to the axis of the stainless steel container, the stainless steel container is cylindrical, a stainless steel cover is covered, standing is carried out for 3 days, the sol in the stainless steel container is subjected to gel curing, the stainless steel container is transferred into a supercritical drying kettle, methanol is added to the stainless steel container, and the liquid level in the supercritical drying kettle is not higher than two thirds of the volume;
fourthly, sealing the supercritical drying kettle, heating the supercritical drying kettle to 280 ℃ at a heating rate of 10 ℃/h, wherein the air pressure in the supercritical drying kettle reaches 11MPa, and is higher than the supercritical pressure of methanol, and the temperature of 280 ℃ is kept for 1h to ensure that the internal and external temperatures of the supercritical drying kettle are uniform, and the methanol medium in the gel is converted into a supercritical state;
and finally, opening an air outlet valve of the supercritical drying kettle to discharge air at a decompression rate of 5MPa/h, heating the supercritical drying kettle to 300 ℃ at a heating rate of 10 ℃/h, keeping the temperature of 300 ℃ until the air pressure drop in the supercritical drying kettle is 0MPa, stopping heating when the air is discharged, naturally cooling the supercritical drying kettle to room temperature, taking out the stainless steel container from the supercritical drying kettle, carefully opening a cover, and carefully taking out the aerogel from the quartz tube to obtain the anisotropic silica aerogel with the birefringent effect.
Example 4
The method comprises the steps of exhausting gas at a reduced pressure rate of 10MPa/h according to a volume ratio of 10:80 by using methyl orthosilicate to methanol, heating a supercritical drying kettle to 280 ℃ at a heating rate of 10 ℃/h, and drying to obtain the silica aerogel.
Firstly, uniformly mixing methyl orthosilicate and methanol according to the volume ratio of 10:80 to obtain a mixed solution A;
secondly, dropwise adding dilute ammonia water with the concentration of 0.004M into the mixed solution A according to the volume ratio of the dilute ammonia water to the methyl orthosilicate of 2.4:10, magnetically stirring for 0.5h, and uniformly mixing to obtain precursor sol B;
thirdly, transferring the precursor sol B into a stainless steel container which is pre-placed with a quartz tube, wherein the inner diameter of the stainless steel container is 80mm, the inner height is 50mm, the wall thickness is 5mm, the inner diameter of the quartz tube is 8mm, the length is 50mm equal to the inner height of the stainless steel container, the wall thickness is 2mm, the axis of the quartz tube is parallel to the axis of the stainless steel container, the stainless steel container is cylindrical, a stainless steel cover is covered, standing is carried out for 3 days, the sol in the stainless steel container is subjected to gel curing, the stainless steel container is transferred into a supercritical drying kettle, methanol is added to the stainless steel container, and the liquid level in the supercritical drying kettle is not higher than two thirds of the volume;
fourthly, sealing the supercritical drying kettle, heating the supercritical drying kettle to 260 ℃ at a heating rate of 10 ℃/h, wherein the air pressure in the supercritical drying kettle reaches 11MPa, and is higher than the supercritical pressure of methanol, and the temperature of 260 ℃ is kept for 1h to ensure that the internal and external temperatures of the supercritical drying kettle are uniform, and the methanol medium in the gel is converted into a supercritical state;
and finally, opening an air outlet valve of the supercritical drying kettle to discharge air at a decompression rate of 10MPa/h, heating the supercritical drying kettle to 280 ℃ at a heating rate of 10 ℃/h, keeping the temperature of 280 ℃ until the air pressure drop in the supercritical drying kettle is 0MPa, stopping heating when the air is discharged, naturally cooling the supercritical drying kettle to room temperature, taking out the stainless steel container from the supercritical drying kettle, carefully opening a cover, and carefully taking out the aerogel from the quartz tube to obtain the anisotropic silica aerogel with the birefringent effect.
Example 5
The method comprises the steps of exhausting gas at a reduced pressure rate of 6MPa/h according to a volume ratio of 10:80 by using methyl orthosilicate to methanol, heating a supercritical drying kettle to 280 ℃ at a heating rate of 10 ℃/h, and drying to obtain the silica aerogel.
Firstly, uniformly mixing methyl orthosilicate and methanol according to the volume ratio of 10:80 to obtain a mixed solution A;
secondly, dropwise adding dilute ammonia water with the concentration of 0.004M into the mixed solution A according to the volume ratio of the dilute ammonia water to the methyl orthosilicate of 2.4:10, magnetically stirring for 0.5h, and uniformly mixing to obtain precursor sol B;
thirdly, transferring the precursor sol B into a stainless steel container which is pre-placed with a quartz tube, wherein the inner diameter of the stainless steel container is 80mm, the inner height is 50mm, the wall thickness is 5mm, the inner diameter of the quartz tube is 8mm, the length is 50mm equal to the inner height of the stainless steel container, the wall thickness is 2mm, the axis of the quartz tube is parallel to the axis of the stainless steel container, the stainless steel container is cylindrical, a stainless steel cover is covered, standing is carried out for 3 days, the sol in the stainless steel container is subjected to gel curing, the stainless steel container is transferred into a supercritical drying kettle, methanol is added to the stainless steel container, and the liquid level in the supercritical drying kettle is not higher than two thirds of the volume;
fourthly, sealing the supercritical drying kettle, heating the supercritical drying kettle to 260 ℃ at a heating rate of 10 ℃/h, wherein the air pressure in the supercritical drying kettle reaches 11MPa, and is higher than the supercritical pressure of methanol, and the temperature of 260 ℃ is kept for 1h to ensure that the internal and external temperatures of the supercritical drying kettle are uniform, and the methanol medium in the gel is converted into a supercritical state;
and finally, opening an air outlet valve of the supercritical drying kettle to discharge air at a decompression rate of 6MPa/h, heating the supercritical drying kettle to 280 ℃ at a heating rate of 10 ℃/h, keeping the temperature of 280 ℃ until the air pressure drop in the supercritical drying kettle is 0MPa, stopping heating when the air is discharged, naturally cooling the supercritical drying kettle to room temperature, taking out the stainless steel container from the supercritical drying kettle, carefully opening a cover, and carefully taking out the aerogel from the quartz tube to obtain the anisotropic silica aerogel with the birefringent effect.
Example 6
The method comprises the steps of exhausting gas at a reduced pressure rate of 4MPa/h according to a volume ratio of 10:80 by using methyl orthosilicate to methanol, heating a supercritical drying kettle to 280 ℃ at a heating rate of 10 ℃/h, and drying to obtain the silica aerogel.
Firstly, uniformly mixing methyl orthosilicate and methanol according to the volume ratio of 10:80 to obtain a mixed solution A;
secondly, dropwise adding dilute ammonia water with the concentration of 0.004M into the mixed solution A according to the volume ratio of the dilute ammonia water to the methyl orthosilicate of 2.4:10, magnetically stirring for 0.5h, and uniformly mixing to obtain precursor sol B;
thirdly, transferring the precursor sol B into a stainless steel container which is pre-placed with a quartz tube, wherein the inner diameter of the stainless steel container is 80mm, the inner height is 50mm, the wall thickness is 5mm, the inner diameter of the quartz tube is 8mm, the length is 50mm equal to the inner height of the stainless steel container, the wall thickness is 2mm, the axis of the quartz tube is parallel to the axis of the stainless steel container, the stainless steel container is cylindrical, a stainless steel cover is covered, standing is carried out for 3 days, the sol in the stainless steel container is subjected to gel curing, the stainless steel container is transferred into a supercritical drying kettle, methanol is added to the stainless steel container, and the liquid level in the supercritical drying kettle is not higher than two thirds of the volume;
fourthly, sealing the supercritical drying kettle, heating the supercritical drying kettle to 260 ℃ at a heating rate of 10 ℃/h, wherein the air pressure in the supercritical drying kettle reaches 11MPa, and is higher than the supercritical pressure of methanol, and the temperature of 260 ℃ is kept for 1h to ensure that the internal and external temperatures of the supercritical drying kettle are uniform, and the methanol medium in the gel is converted into a supercritical state;
and finally, opening an air outlet valve of the supercritical drying kettle to discharge air at a decompression rate of 4MPa/h, heating the supercritical drying kettle to 280 ℃ at a heating rate of 10 ℃/h, keeping the temperature of 280 ℃ until the air pressure drop in the supercritical drying kettle is 0MPa, stopping heating when the air is discharged, naturally cooling the supercritical drying kettle to room temperature, taking out the stainless steel container from the supercritical drying kettle, carefully opening a cover, and carefully taking out the aerogel from the quartz tube to obtain the anisotropic silica aerogel with the birefringent effect.
Example 7
The method comprises the steps of exhausting gas at a reduced pressure rate of 3MPa/h according to a volume ratio of 10:80 by methyl orthosilicate to methanol with a concentration of 0.004M of dilute ammonia water, heating a supercritical drying kettle to 280 ℃ at a heating rate of 10 ℃/h, and drying to obtain the silica aerogel.
Firstly, uniformly mixing methyl orthosilicate and methanol according to the volume ratio of 10:80 to obtain a mixed solution A;
secondly, dropwise adding dilute ammonia water with the concentration of 0.004M into the mixed solution A according to the volume ratio of the dilute ammonia water to the methyl orthosilicate of 2.4:10, magnetically stirring for 0.5h, and uniformly mixing to obtain precursor sol B;
thirdly, transferring the precursor sol B into a stainless steel container which is pre-placed with a quartz tube, wherein the inner diameter of the stainless steel container is 80mm, the inner height is 50mm, the wall thickness is 5mm, the inner diameter of the quartz tube is 8mm, the length is 50mm equal to the inner height of the stainless steel container, the wall thickness is 2mm, the axis of the quartz tube is parallel to the axis of the stainless steel container, the stainless steel container is cylindrical, a stainless steel cover is covered, standing is carried out for 3 days, the sol in the stainless steel container is subjected to gel curing, the stainless steel container is transferred into a supercritical drying kettle, methanol is added to the stainless steel container, and the liquid level in the supercritical drying kettle is not higher than two thirds of the volume;
fourthly, sealing the supercritical drying kettle, heating the supercritical drying kettle to 260 ℃ at a heating rate of 10 ℃/h, wherein the air pressure in the supercritical drying kettle reaches 11MPa, and is higher than the supercritical pressure of methanol, and the temperature of 260 ℃ is kept for 1h to ensure that the internal and external temperatures of the supercritical drying kettle are uniform, and the methanol medium in the gel is converted into a supercritical state;
and finally, opening an air outlet valve of the supercritical drying kettle to discharge air at a decompression rate of 3MPa/h, heating the supercritical drying kettle to 280 ℃ at a heating rate of 10 ℃/h, keeping the temperature of 280 ℃ until the air pressure drop in the supercritical drying kettle is 0MPa, stopping heating when the air is discharged, naturally cooling the supercritical drying kettle to room temperature, taking out the stainless steel container from the supercritical drying kettle, carefully opening a cover, and carefully taking out the aerogel from the quartz tube to obtain the anisotropic silica aerogel with the birefringent effect.
Claims (2)
1. The preparation method of the anisotropic silica aerogel with the double refraction effect is characterized by comprising the following steps of:
step 1, uniformly mixing methyl orthosilicate and methanol to obtain a mixed solution A;
step 2, dropwise adding dilute ammonia water into the mixed solution A obtained in the step 1, magnetically stirring for 0.5-1h, and uniformly mixing to obtain precursor sol B;
step 3, transferring the precursor sol B obtained in the step 2 into a stainless steel container, standing for 3-4d, transferring the stainless steel container into a supercritical drying kettle, adding methanol to the stainless steel container, and enabling the liquid level in the supercritical drying kettle to be not higher than two thirds of the volume;
step 4, the supercritical drying kettle in the step 3 is sealed and heated until the temperature of the kettle is higher than the supercritical temperature of methanol, the internal pressure of the kettle is higher than the supercritical pressure of the methanol, and the temperature is kept constant for a period of time to ensure that the internal temperature and the external temperature of the supercritical drying kettle are uniform, and the methanol medium in gel is converted into a supercritical state;
step 5, opening an air outlet valve of the supercritical drying kettle in the step 4 to deflate, simultaneously increasing the temperature, stopping heating when the air is exhausted, naturally cooling the supercritical drying kettle to room temperature, taking out the stainless steel container from the supercritical drying kettle, opening a cover, and taking out the aerogel from the quartz tube to obtain the anisotropic silica aerogel with the double refraction effect;
in the step 1, the volume ratio of the methyl orthosilicate to the methanol is 10:80-100;
in the step 2, the concentration of the dilute ammonia water is 0.003-0.005M, and the volume ratio of the dilute ammonia water to the methyl orthosilicate used in the step 1 is 2.4:10;
in the step 4, heating the supercritical drying kettle to 260-280 ℃ at a heating rate of 5-10 ℃/h, wherein the air pressure in the supercritical drying kettle reaches 10-11MPa, and maintaining the temperature of 260-280 ℃ for 1-2h;
in the step 5, the air is exhausted at a decompression rate of 3-10MPa/h, and meanwhile, the supercritical drying kettle is heated to 280-300 ℃ at a heating rate of 5-10 ℃/h, and the temperature of 280-300 ℃ is kept until the air pressure drop in the supercritical drying kettle is 0MPa.
2. An anisotropic silica aerogel having a birefringent effect, which is prepared by the method of claim 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210046410.4A CN114477193B (en) | 2022-01-12 | 2022-01-12 | Anisotropic silica aerogel with double refraction effect and preparation method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210046410.4A CN114477193B (en) | 2022-01-12 | 2022-01-12 | Anisotropic silica aerogel with double refraction effect and preparation method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114477193A CN114477193A (en) | 2022-05-13 |
| CN114477193B true CN114477193B (en) | 2023-06-30 |
Family
ID=81512539
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210046410.4A Active CN114477193B (en) | 2022-01-12 | 2022-01-12 | Anisotropic silica aerogel with double refraction effect and preparation method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114477193B (en) |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102964055B (en) * | 2012-10-17 | 2015-04-01 | 厦门纳美特新材料科技有限公司 | Ultra-fast preparation method for highly transparent aerogel glass |
| CN103435320B (en) * | 2013-08-19 | 2016-05-04 | 航天特种材料及工艺技术研究所 | A kind of high-performance aerogel composite and preparation method thereof and equipment |
| CN105536655B (en) * | 2015-12-11 | 2018-02-27 | 中国科学院兰州化学物理研究所 | A kind of fast preparation method of aerogel material |
| CN106495169A (en) * | 2016-10-28 | 2017-03-15 | 浙江省普瑞科技有限公司 | A kind of hydrophobic type aerosil and preparation method thereof |
| CN106866106A (en) * | 2017-03-18 | 2017-06-20 | 江苏国科新材料科技有限公司 | A kind of preparation method of silicon dioxide silica aerogel composite material |
-
2022
- 2022-01-12 CN CN202210046410.4A patent/CN114477193B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN114477193A (en) | 2022-05-13 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN107417961B (en) | Anisotropic polyimide aerogel material and preparation method thereof | |
| Yu et al. | Preparation and characterization of hydrophobic silica aerogel sphere products by co-precursor method | |
| Li et al. | Fabrication and morphological characterization of microencapsulated phase change materials (MicroPCMs) and macrocapsules containing MicroPCMs for thermal energy storage | |
| CN106495109B (en) | A kind of foam-like boron nitride block materials preparation method | |
| Jiang et al. | Synthesis and characterization of ambient-dried microglass fibers/silica aerogel nanocomposites with low thermal conductivity | |
| CN107849348A (en) | Aerogel material and its production method | |
| CN109133040A (en) | A kind of preparation method of the adjustable graphene aerogel of pore-size | |
| CN109810282A (en) | A kind of anisotropy polyimide aerogels material and preparation method thereof | |
| Zhang et al. | Controlling the microstructure of resorcinol–furfural aerogels and derived carbon aerogels via the salt templating approach | |
| Guo et al. | Preparation and properties of AlN ceramic suspension for non-aqueous gel casting | |
| CN111848140B (en) | Alumina nanowire aerogel thermal insulation material and preparation method thereof | |
| Yuan et al. | Preparation of calcium hexaluminate porous ceramics by novel pectin based gelcasting freeze-drying method | |
| Hou et al. | SiC whiskers‐reinforced polyimide aerogel composites with robust compressive properties and efficient thermal insulation performance | |
| Wu et al. | Anisotropic polyimide aerogels fabricated by directional freezing | |
| Zhang et al. | Hydrophobic silica aerogels prepared by microwave irradiation | |
| CN114832741B (en) | Preparation method of heat-conducting wave-absorbing composite aerogel and heat-conducting wave-absorbing composite aerogel | |
| Liu et al. | Effect of the thermal treatment on microstructure and physical properties of low-density and high transparency silica aerogels via acetonitrile supercritical drying | |
| CN114477193B (en) | Anisotropic silica aerogel with double refraction effect and preparation method thereof | |
| CN109180992A (en) | A kind of polyimide aerogels material and preparation method thereof of bore diameter gradient variation | |
| Zhang et al. | Innovative application of PVA hydrogel for the forming of porous Si3N4 ceramics via freeze-thaw technique | |
| CN114369446A (en) | Preparation method of novel graphene micro-nano cavity phase change superconducting material | |
| CN114836645A (en) | Preparation method of carbon nanotube-graphene hybrid porous preform with designable configuration | |
| Li et al. | Near net shape fabrication of porous cordierite by combination of foam gel‐casting and freeze‐drying | |
| Li et al. | Erythritol confined in multiwalled carbon nanotubes reinforced silica aerogel as novel form-stable phase change materials | |
| Yang et al. | Robust ambient pressure dried polyimide aerogels and their graphene oxide directed growth of 1D–2D nanohybrid aerogels using water as the only solvent |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |