CN112745099A - Interpenetrating network type cotton fiber/flexible SiO2Preparation method of aerogel composite material - Google Patents
Interpenetrating network type cotton fiber/flexible SiO2Preparation method of aerogel composite material Download PDFInfo
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- 239000004964 aerogel Substances 0.000 title claims abstract description 50
- 229920000742 Cotton Polymers 0.000 title claims abstract description 33
- 239000002131 composite material Substances 0.000 title claims abstract description 21
- 238000000034 method Methods 0.000 title claims abstract description 19
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 19
- 229910052681 coesite Inorganic materials 0.000 claims abstract description 15
- 229910052906 cristobalite Inorganic materials 0.000 claims abstract description 15
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 15
- 239000002904 solvent Substances 0.000 claims abstract description 15
- 229910052682 stishovite Inorganic materials 0.000 claims abstract description 15
- 229910052905 tridymite Inorganic materials 0.000 claims abstract description 15
- DKGAVHZHDRPRBM-UHFFFAOYSA-N Tert-Butanol Chemical compound CC(C)(C)O DKGAVHZHDRPRBM-UHFFFAOYSA-N 0.000 claims description 32
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 30
- 239000002243 precursor Substances 0.000 claims description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 17
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 16
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 16
- 229910052710 silicon Inorganic materials 0.000 claims description 16
- 239000010703 silicon Substances 0.000 claims description 16
- LZZYPRNAOMGNLH-UHFFFAOYSA-M Cetrimonium bromide Chemical compound [Br-].CCCCCCCCCCCCCCCC[N+](C)(C)C LZZYPRNAOMGNLH-UHFFFAOYSA-M 0.000 claims description 13
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 12
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 12
- 238000002156 mixing Methods 0.000 claims description 12
- CPUDPFPXCZDNGI-UHFFFAOYSA-N triethoxy(methyl)silane Chemical compound CCO[Si](C)(OCC)OCC CPUDPFPXCZDNGI-UHFFFAOYSA-N 0.000 claims description 10
- YYLGKUPAFFKGRQ-UHFFFAOYSA-N dimethyldiethoxysilane Chemical compound CCO[Si](C)(C)OCC YYLGKUPAFFKGRQ-UHFFFAOYSA-N 0.000 claims description 7
- 238000009777 vacuum freeze-drying Methods 0.000 claims description 7
- 230000002378 acidificating effect Effects 0.000 claims description 5
- 230000032683 aging Effects 0.000 claims description 5
- 238000006243 chemical reaction Methods 0.000 claims description 5
- 230000003301 hydrolyzing effect Effects 0.000 claims description 5
- 238000003760 magnetic stirring Methods 0.000 claims description 5
- 238000002454 metastable transfer emission spectrometry Methods 0.000 claims description 5
- 238000003756 stirring Methods 0.000 claims description 5
- 230000003197 catalytic effect Effects 0.000 claims description 2
- 238000013329 compounding Methods 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims description 2
- 238000003980 solgel method Methods 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 26
- 238000010521 absorption reaction Methods 0.000 abstract description 11
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 abstract description 9
- 238000009413 insulation Methods 0.000 abstract description 7
- 238000002360 preparation method Methods 0.000 abstract description 7
- 238000001035 drying Methods 0.000 abstract description 6
- 238000001179 sorption measurement Methods 0.000 abstract description 6
- 230000007547 defect Effects 0.000 abstract description 3
- 238000000352 supercritical drying Methods 0.000 abstract description 3
- 239000000843 powder Substances 0.000 abstract description 2
- 231100000419 toxicity Toxicity 0.000 abstract description 2
- 230000001988 toxicity Effects 0.000 abstract description 2
- 238000005470 impregnation Methods 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 12
- 239000003921 oil Substances 0.000 description 11
- 235000019198 oils Nutrition 0.000 description 11
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 6
- 239000011148 porous material Substances 0.000 description 6
- 230000000052 comparative effect Effects 0.000 description 5
- 239000004965 Silica aerogel Substances 0.000 description 4
- 238000012512 characterization method Methods 0.000 description 4
- 239000003153 chemical reaction reagent Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 238000005452 bending Methods 0.000 description 3
- 238000005485 electric heating Methods 0.000 description 3
- 235000019441 ethanol Nutrition 0.000 description 3
- 230000002209 hydrophobic effect Effects 0.000 description 3
- 239000011259 mixed solution Substances 0.000 description 3
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
- 239000003549 soybean oil Substances 0.000 description 3
- 235000012424 soybean oil Nutrition 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000010779 crude oil Substances 0.000 description 2
- 238000003912 environmental pollution Methods 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
- 239000000413 hydrolysate Substances 0.000 description 2
- 239000010687 lubricating oil Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000002657 fibrous material Substances 0.000 description 1
- 238000004108 freeze drying Methods 0.000 description 1
- 239000004519 grease Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B30/00—Compositions for artificial stone, not containing binders
- C04B30/02—Compositions for artificial stone, not containing binders containing fibrous materials
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/30—Mortars, concrete or artificial stone characterised by specific physical values for heat transfer properties such as thermal insulation values, e.g. R-values
- C04B2201/32—Mortars, concrete or artificial stone characterised by specific physical values for heat transfer properties such as thermal insulation values, e.g. R-values for the thermal conductivity, e.g. K-factors
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
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- Silicon Compounds (AREA)
Abstract
The invention discloses an interpenetrating network type cotton fiber/flexible SiO2The preparation method of the aerogel material is mainly applied to the field of heat insulation or adsorption. The invention aims to solve the problem of flexible pure SiO2The defects of poor toughness and easy powder falling when the material is deformed of the aerogel, and the technical problems that the preparation of large-size materials is difficult by a supercritical drying method and the preparation period is long by a normal pressure drying method, and the conventionally used methanol solvent has toxicity and the like are solved. According to the invention, the cotton fibers and the flexible aerogel are compounded, an interpenetrating network structure is obtained by impregnation, the material obtains better toughness under the condition of keeping the flexibility of the material by adding the cotton fibers, and the comprehensive mechanical property is improved. The density of the obtained composite material is 0.14-0.24 g/cm3The porosity is 85-93%, and the product has hydrophobicity, oil absorption and heat insulation. At the same time, the obtained tubular special-shaped piece can meet special requirementsInsulation is provided, for example, by thermal insulation of the pipe.
Description
Technical Field
The invention relates to interpenetrating network type cotton fiber/flexible SiO2A preparation method of aerogel material, belonging to the technical field of functional material preparation.
Background
Due to the changing environment and the requirement of sustainable development, the energy-saving, environment-friendly and pollution-treatment type material with multiple functions becomes a hot point of research. The aerogel has been paid much attention by researchers at home and abroad since the advent, and is mainly due to the fact that the three-dimensional network nano-porous structure of the aerogel has excellent performances such as extremely low density, extremely low thermal conductivity, ultrahigh specific surface area of porosity and the like, and is widely applied to the fields of energy chemical industry, catalyst carriers, hydrogen storage, building heat preservation and the like. The porosity of the aerogel can reach more than 80%, so the volume ratio of the internal skeleton structure of the aerogel is very small, and the aerogel directly shows high brittleness in macroscopical view, which greatly limits the practical application of the aerogel as a structural support material. With the continuous and intensive research on the problem in recent years, relevant scholars develop a flexible silica aerogel, and the problem of great brittleness of the aerogel is overcome to a great extent. Although this kind of flexible aerogel has fine resistance to compression and resilience performance, nevertheless there is obviously not enough in the aspect of tensile strength, through carrying out the doping of cotton fiber to flexible aerogel, can show its internal skeleton texture of reinforcing, makes its tensile strength performance obtain obviously promoting.
In recent years, aerogels begin to be applied to the field of adsorption, and due to the fact that aerogels contain excellent porous structures and abundant surface functional groups, the aerogels can effectively adsorb some common grease and organic reagents. With the large-scale use of fossil energy, the problem of environmental pollution such as crude oil leakage exists in the marine transportation process, and the traditional aerogel has excellent oil absorption property but has hydrophilicityLimit crude oil adsorption on the sea surface, and the novel precursor is flexible SiO2Due to the existence of methyl functional groups, the hydrophobicity of the aerogel is greatly improved, excellent hydrophobic oleophylic performance is shown, and the application space in the aspect of oil-water separation is huge. Studies have shown that a single flexible SiO is used2The aerogel collapses in internal framework structure after absorbing oil, and is difficult to recover and reuse, for which purpose the flexible SiO is impregnated with cotton fibers2The aerogel is doped, and the internal three-dimensional frame-shaped network structure of the aerogel is effectively enhanced. Due to the existence of the cotton fiber structure, the complete skeleton structure can be still maintained after full oil absorption, and the recovery and the reutilization after oil absorption are facilitated. The use value of the utility model is greatly improved. Therefore, the novel precursor is adopted to prepare the flexible silica aerogel material, so that the flexible silica aerogel material has excellent hydrophobic property, meanwhile, the cotton fiber and the inorganic silica aerogel are compounded to obtain an interpenetrating network structure, and the mechanical property and flexibility of the material are improved while the microporous structure is regulated.
Disclosure of Invention
The invention aims to solve the problem of flexible SiO2Poor toughness of aerogel and easy powder falling during material deformation, and solves the technical problems that the preparation period of a normal pressure drying method is long and the conventionally used methanol solvent has toxicity and the like because a supercritical drying method is difficult to prepare a large-size material, so that the interpenetrating network type cotton fiber/flexible SiO is provided2A method for preparing aerogel composite material.
In order to realize the purpose, the invention utilizes an acid-base two-step catalytic sol-gel method to prepare DMDES-MTES type flexible SiO2Compounding the aerogel precursor sol with cotton fiber, and preparing the cotton fiber/flexible SiO through vacuum freeze drying2An aerogel composite, the method comprising the steps of:
step 1: mixing dimethyldiethoxysilane, methyltriethoxysilane and absolute ethyl alcohol, and hydrolyzing for 24-48 h under magnetic stirring to obtain a silicon source precursor solution;
step 2: uniformly mixing the silicon source precursor solution obtained in the step 1 with water, hydrochloric acid and hexadecyl trimethyl ammonium bromide, and fully stirring to enable the silicon source precursor to be fully hydrolyzed under an acidic condition to obtain a silicon source precursor sol;
and step 3: uniformly mixing the silicon source precursor sol obtained in the step 2 with ammonia water for 10-30 min, pouring the mixture into a mold containing cotton fibers, and carrying out sol-gel reaction and aging of gel at a constant temperature of 50-60 ℃ for 48-72 h to obtain a gel complex;
and 4, step 4: demolding the gel complex obtained in the step 3, and then adding tert-butyl alcohol for solvent replacement;
and 5: precooling the product obtained in the step 4 for 12-24 h at-18-12 ℃, and then carrying out vacuum freeze drying for 24-48 h at-30-50 ℃ under the vacuum degree of 15-30 Pa to obtain the cotton fiber/flexible SiO2An aerogel composite.
Further, the molar ratio of the dimethyl diethoxy silane, the methyl triethoxy silane, the absolute ethyl alcohol, the water, the hexadecyl trimethyl ammonium bromide, the hydrochloric acid and the ammonia water is as follows: 1: 1-2: 5-7: 12-14: 0.1-0.5: 2.5X 10-3：0.5～1。
Furthermore, the molar concentration of the hydrochloric acid is 0.05-0.2 mol/L, and the molar concentration of the ammonia water is 2-5 mol/L.
Further, the volume fraction of the cotton fiber in the step 3 is 1-30 wt.%.
Further, tertiary butanol is added in the step 4 for solvent replacement, and the tertiary butanol is replaced every 24-48 hours for 3-5 times.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention uses cotton fiber material and flexible SiO2Aerogel composite, the cotton fiber has low price, wide source and good flexibility, and is combined with flexible SiO2The aerogel forms an interpenetrating network structure, improves the toughness of the aerogel and overcomes the defect that the aerogel is easy to fall off after being bent.
2. The invention uses the freeze drying process, avoids the defects that a supercritical drying method is difficult to prepare large-size materials, the equipment cost is high, and the equipment is dangerous, avoids the problems of long preparation period and environmental pollution caused by waste liquid due to multi-step solvent exchange in a normal pressure drying method, saves the cost, and is beneficial to large-scale production.
3. The composite material prepared by the invention can obtain block materials, tubular special-shaped pieces and the like by controlling the proportion of raw materials and adopting moulds with different shapes, and is favorable for further widening the application of the material.
4. The porosity of the composite material prepared by the invention is 85-93%, the pore structure comprises nano and micron pores, the lowest value of the thermal conductivity coefficient at normal temperature can reach 0.038W/(m.K), and the composite material has good heat insulation performance, hydrophobic property and oil absorption and can be applied to the fields of heat insulation and adsorption.
5. The invention adopts ethanol as solvent to prepare the flexible SiO2Compared with the toxic methanol solvent adopted in the prior art, the aerogel and the composite material thereof are safer and more environment-friendly.
Drawings
FIG. 1 shows the flexible SiO film of comparative example 12SEM images of aerogel materials;
FIG. 2 shows the cotton fiber/flexible SiO solid of example 12SEM images of aerogel composites;
FIG. 3 is a comparative graph of flexural testing characterization of materials made according to the present invention, wherein: (a) is the flexible SiO of comparative example 12A bendability test characterization graph of the aerogel; (b) is the cotton fiber/Flexible SiO of example 12A bendability test characterization plot of an aerogel composite; (c) is the cotton fiber/Flexible SiO of example 22Characterization of the aerogels composites by flexural testing.
Detailed Description
The following describes embodiments of the present invention in detail. The following described embodiments are exemplary only, and are not to be construed as limiting the invention.
Example 1
Step 1: mixing dimethyldiethoxysilane, methyltriethoxysilane and absolute ethyl alcohol, and hydrolyzing for 24h under magnetic stirring to obtain a precursor solution, wherein the molar ratio of the used reagents is as follows: n (dmdes): n (MTES): n (etoh) ═ 1: 1.22: 6.67;
step 2: adding water, hydrochloric acid and hexadecyl trimethyl ammonium bromide into the precursor solution obtained in the step 1, and fully stirring to ensure that the precursor is fully hydrolyzed under an acidic condition to obtain sol, wherein the molar concentration of the used hydrochloric acid is 0.1mol/L, and the molar ratio of a silicon source to the water to the hydrochloric acid to the hexadecyl trimethyl ammonium bromide is as follows: n (dmdes): n (H)2O)：n(HCI)：n(CTAB)＝1：13.3：2.5×10-3：0.16；
And step 3: adding an ammonia water solution with the molar concentration of 5mol/L into the mixed solution in the step 2, wherein the molar ratio of the silicon source to the ammonia water is n (DMDES): n (NH)3H2O) ═ 1: 0.67, mixing for 20min, pouring the solution into a cylindrical mold containing 10 wt.% cotton fiber, placing in an electric heating constant temperature blast drying oven, keeping at a constant temperature of 50 ℃ for 48h, and performing sol-gel reaction and aging of gel;
and 4, step 4: demolding the gel complex obtained in the step 3, adding a proper amount of tert-butyl alcohol for solvent replacement to replace the solvent and water in the gel, and replacing the tert-butyl alcohol once every 24 times for 3 times;
and 5: precooling the product obtained in the step 4 for 18h at-18 ℃, and then carrying out vacuum freeze-drying for 24h at-50 ℃ under the vacuum degree of 20Pa to obtain the cotton fiber/flexible SiO2An aerogel material.
Cotton fiber/Flexible SiO obtained in example 12The aerogel composite material has the porosity of 91 percent, the pore size of the aerogel composite material coexists with nano-sized and micron-sized pores, and has the advantages of hydrophobicity, oil absorption and heat insulation, the contact angle with water is 136 degrees, the adsorption rate to normal hexane, acetone or ethanol is 4-5 times of the self mass, the oil absorption rate to soybean oil and lubricating oil is 5-6 times of the self mass, and the heat conductivity coefficient value at room temperature is 0.038W/(m.K). The material has good toughness, no obvious crack appears in the process of bending 180 degrees, and more than 80 percent of the original shape can be gradually recovered after external force is released.
Example 2
Step 1: mixing dimethyl diethoxy silane, methyl triethoxy silane and absolute ethyl alcohol, and hydrolyzing for 24 hours under magnetic stirring to obtain a precursor solution. Wherein the molar ratio of the used reagents is as follows: n (dmdes): n (MTES): n (etoh) ═ 1: 1.22: 6.67.
step 2: adding water, hydrochloric acid and hexadecyl trimethyl ammonium bromide into the hydrolysate obtained in the step 1, and fully stirring to fully hydrolyze the precursor under an acidic condition to obtain sol, wherein the molar concentration of the used hydrochloric acid is 0.1mol/L, and the molar ratio of the silicon source to the water to the hydrochloric acid to the hexadecyl trimethyl ammonium bromide is as follows: n (dmdes): n (H)2O)：n(HCI)：n(CTAB)＝1：13.3：2.5×10-3：0.16；
And step 3: adding an ammonia water solution with the molar concentration of 5mol/L into the mixed solution in the step 2, wherein the molar ratio of the silicon source to the ammonia water is n (DMDES): n (NH)3H2O) ═ 1: 0.67, mixing for 20min, pouring the solution into a tubular mold containing 20 wt.% cotton fiber, placing in an electric heating constant temperature blast drying oven, keeping at a constant temperature of 50 ℃ for 48h, and performing sol-gel reaction and aging of gel;
and 4, step 4: demolding the gel obtained in the step 3, adding a proper amount of tert-butyl alcohol for solvent replacement to replace the solvent and water in the gel, and replacing the tert-butyl alcohol every 24 times for 3 times;
and 5: precooling the sample obtained in the step 4 for 18h at-18 ℃, and then carrying out vacuum freeze-drying for 24h at-50 ℃ under the vacuum degree of 20Pa to obtain the cotton fiber/flexible SiO2An aerogel material.
Tubular Cotton fiber/Flexible SiO obtained in example 22The aerogel composite material has the porosity of 89%, a nano-scale and micro-scale pore structure, good hydrophobicity, oil absorption and heat insulation performance, a contact angle with water of 131 degrees, an adsorption rate on n-hexane, acetone or ethanol of 4-5 times of the self-mass, an oil absorption rate on soybean oil and lubricating oil of 4-5 times of the self-mass, and a heat conductivity value at room temperature of 0.043W/(m.K). The material has good toughness, no obvious crack appears in the process of bending 180 degrees, and more than 80 percent of the original shape can be gradually recovered after external force is released.
Comparative example 1
Step 1: mixing dimethyl diethoxy silane, methyl triethoxy silane and absolute ethyl alcohol, and hydrolyzing for 24 hours under magnetic stirring to obtain a precursor solution. Wherein the molar ratio of the used reagents is as follows: n (dmdes): n (MTES): n (etoh) ═ 1: 1.22: 6.67.
step 2: adding water, hydrochloric acid and hexadecyl trimethyl ammonium bromide into the hydrolysate obtained in the step 1, and fully stirring to fully hydrolyze the precursor under an acidic condition to obtain sol, wherein the molar concentration of the used hydrochloric acid is 0.1mol/L, and the molar ratio of the silicon source to the water to the hydrochloric acid to the hexadecyl trimethyl ammonium bromide is as follows: n (dmdes): n (H)2O)：n(HCI)：n(CTAB)＝1：13.3：2.5×10-3：0.16；
And step 3: adding an ammonia water solution with the molar concentration of 5mol/L into the mixed solution in the step 2, wherein the molar ratio of the silicon source to the ammonia water is n (DMDES): n (NH)3H2O) ═ 1: 0.67, after mixing for 20min, pouring the solution into a mould, placing the mould in an electric heating constant temperature air blast drying oven, keeping the constant temperature of 50 ℃ for 48h, and carrying out sol-gel reaction and aging of gel;
and 4, step 4: demolding the gel obtained in the step 3, adding a proper amount of tert-butyl alcohol for solvent replacement to replace the solvent and water in the gel, and replacing the tert-butyl alcohol every 24 times for 3 times;
and 5: precooling the sample obtained in the step 4 for 18h at-18 ℃, and then carrying out vacuum freeze-drying for 24h at-50 ℃ under the vacuum degree of 20Pa to obtain flexible SiO2An aerogel material.
Flexible SiO obtained in comparative example 12The aerogel material has a porosity of 93.4%, a nano-pore structure, a lowest value of thermal conductivity coefficient of 0.031W/(m.K) at normal temperature, hydrophobicity and oil absorption, a contact angle with water is 145 degrees, and the oil absorption rate of soybean oil is 6-7 times of the self-mass. The toughness of the material is poor, and the fracture phenomenon occurs in the process of bending 180 degrees.
Claims (5)
1. Interpenetrating network type cotton fiber/flexible SiO2Method for preparing aerogel composite material, and aerogel composite materialIs characterized in that: method for preparing DMDES-MTES type flexible SiO by acid-base two-step catalytic sol-gel method2Compounding the aerogel precursor sol with cotton fiber, and preparing the cotton fiber/flexible SiO through vacuum freeze drying2An aerogel composite;
the method comprises the following steps:
step 1: mixing dimethyldiethoxysilane, methyltriethoxysilane and absolute ethyl alcohol, and hydrolyzing for 24-48 h under magnetic stirring to obtain a silicon source precursor solution;
step 2: uniformly mixing the silicon source precursor solution obtained in the step 1 with water, hydrochloric acid and hexadecyl trimethyl ammonium bromide, and fully stirring to enable the silicon source precursor to be fully hydrolyzed under an acidic condition to obtain a silicon source precursor sol;
and step 3: uniformly mixing the silicon source precursor sol obtained in the step 2 with ammonia water for 10-30 min, pouring the mixture into a mold containing cotton fibers, and carrying out sol-gel reaction and aging of gel at a constant temperature of 50-60 ℃ for 48-72 h to obtain a gel complex;
and 4, step 4: demolding the gel complex obtained in the step 3, and then adding tert-butyl alcohol for solvent replacement;
and 5: precooling the product obtained in the step 4 for 12-24 h at-18-12 ℃, and then carrying out vacuum freeze drying for 24-48 h at-30-50 ℃ under the vacuum degree of 15-30 Pa to obtain the cotton fiber/flexible SiO2An aerogel composite.
2. The method of claim 1, wherein: the molar ratio of the dimethyl diethoxysilane, the methyl triethoxysilane, the absolute ethyl alcohol, the water, the hexadecyl trimethyl ammonium bromide, the hydrochloric acid and the ammonia water is as follows: 1: 1-2: 5-7: 12-14: 0.1-0.5: 2.5X 10-3：0.5～1。
3. The method of claim 1, wherein: the molar concentration of the hydrochloric acid is 0.05-0.2 mol/L, and the molar concentration of the ammonia water is 2-5 mol/L.
4. The method of claim 1, wherein: the volume fraction of the cotton fiber in the step 3 is 1-30 wt.%.
5. The method of claim 1, wherein: and (4) adding tert-butyl alcohol to perform solvent replacement, and replacing the tert-butyl alcohol once every 24-48 hours for 3-5 times.
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| CN114409424A (en) * | 2021-12-09 | 2022-04-29 | 中国科学院金属研究所 | Method for preparing low-density, high-strength and large-size carbon aerogel composite material by water-phase normal-pressure drying |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
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