CN114162828B - Preparation method of graphene/silicon dioxide composite aerogel - Google Patents
Preparation method of graphene/silicon dioxide composite aerogel Download PDFInfo
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- CN114162828B CN114162828B CN202111660996.5A CN202111660996A CN114162828B CN 114162828 B CN114162828 B CN 114162828B CN 202111660996 A CN202111660996 A CN 202111660996A CN 114162828 B CN114162828 B CN 114162828B
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 139
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 113
- 229910021389 graphene Inorganic materials 0.000 title claims abstract description 113
- 239000004964 aerogel Substances 0.000 title claims abstract description 103
- 239000002131 composite material Substances 0.000 title claims abstract description 64
- 239000000377 silicon dioxide Substances 0.000 title claims abstract description 53
- 235000012239 silicon dioxide Nutrition 0.000 title claims abstract description 46
- 238000002360 preparation method Methods 0.000 title abstract description 9
- 230000033444 hydroxylation Effects 0.000 claims abstract description 4
- 238000005805 hydroxylation reaction Methods 0.000 claims abstract description 4
- 239000011259 mixed solution Substances 0.000 claims description 64
- 239000000843 powder Substances 0.000 claims description 38
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 34
- 239000007864 aqueous solution Substances 0.000 claims description 34
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 33
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 claims description 32
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 30
- 239000004593 Epoxy Substances 0.000 claims description 26
- KPUWHANPEXNPJT-UHFFFAOYSA-N disiloxane Chemical class [SiH3]O[SiH3] KPUWHANPEXNPJT-UHFFFAOYSA-N 0.000 claims description 26
- 238000001035 drying Methods 0.000 claims description 21
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 18
- 229960005070 ascorbic acid Drugs 0.000 claims description 16
- 235000010323 ascorbic acid Nutrition 0.000 claims description 16
- 239000011668 ascorbic acid Substances 0.000 claims description 16
- 238000003756 stirring Methods 0.000 claims description 16
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 15
- 238000000889 atomisation Methods 0.000 claims description 15
- 238000001914 filtration Methods 0.000 claims description 14
- 238000005406 washing Methods 0.000 claims description 14
- 230000001105 regulatory effect Effects 0.000 claims description 13
- 239000002356 single layer Substances 0.000 claims description 11
- 238000010438 heat treatment Methods 0.000 claims description 9
- 239000000243 solution Substances 0.000 claims description 9
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 6
- 235000006408 oxalic acid Nutrition 0.000 claims description 5
- 239000002253 acid Substances 0.000 claims description 4
- 239000010410 layer Substances 0.000 claims description 4
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 claims description 2
- 229960001484 edetic acid Drugs 0.000 claims description 2
- 239000004965 Silica aerogel Substances 0.000 abstract description 31
- 229910052710 silicon Inorganic materials 0.000 abstract description 20
- 239000010703 silicon Substances 0.000 abstract description 20
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 abstract description 18
- 238000000034 method Methods 0.000 abstract description 8
- 230000008569 process Effects 0.000 abstract description 4
- 239000011159 matrix material Substances 0.000 abstract description 3
- 238000002156 mixing Methods 0.000 abstract description 2
- 230000008878 coupling Effects 0.000 abstract 1
- 238000010168 coupling process Methods 0.000 abstract 1
- 238000005859 coupling reaction Methods 0.000 abstract 1
- 238000001694 spray drying Methods 0.000 abstract 1
- 238000010907 mechanical stirring Methods 0.000 description 20
- 239000011148 porous material Substances 0.000 description 14
- 239000002245 particle Substances 0.000 description 13
- 229910004298 SiO 2 Inorganic materials 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 9
- 230000002378 acidificating effect Effects 0.000 description 7
- 230000002209 hydrophobic effect Effects 0.000 description 7
- 239000000203 mixture Substances 0.000 description 7
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 6
- 125000003700 epoxy group Chemical group 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 238000006722 reduction reaction Methods 0.000 description 5
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 4
- 230000009467 reduction Effects 0.000 description 4
- 238000011160 research Methods 0.000 description 4
- 239000003638 chemical reducing agent Substances 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 238000007796 conventional method Methods 0.000 description 3
- 125000000524 functional group Chemical group 0.000 description 3
- 238000009413 insulation Methods 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 230000032683 aging Effects 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000000499 gel Substances 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000004005 microsphere Substances 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000000352 supercritical drying Methods 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- 239000011240 wet gel Substances 0.000 description 2
- WYTZZXDRDKSJID-UHFFFAOYSA-N (3-aminopropyl)triethoxysilane Chemical compound CCO[Si](OCC)(OCC)CCCN WYTZZXDRDKSJID-UHFFFAOYSA-N 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- 239000006087 Silane Coupling Agent Substances 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 239000003929 acidic solution Substances 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 239000002612 dispersion medium Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000001125 extrusion Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000001879 gelation Methods 0.000 description 1
- -1 graphene modified SiO Chemical class 0.000 description 1
- FFUAGWLWBBFQJT-UHFFFAOYSA-N hexamethyldisilazane Chemical compound C[Si](C)(C)N[Si](C)(C)C FFUAGWLWBBFQJT-UHFFFAOYSA-N 0.000 description 1
- 239000000017 hydrogel Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 230000000640 hydroxylating effect Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000002985 plastic film Substances 0.000 description 1
- 229920006255 plastic film Polymers 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 125000002924 primary amino group Chemical group [H]N([H])* 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 239000012779 reinforcing material Substances 0.000 description 1
- 238000007142 ring opening reaction Methods 0.000 description 1
- 150000003376 silicon Chemical class 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000009210 therapy by ultrasound Methods 0.000 description 1
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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
- B01J13/0091—Preparation of aerogels, e.g. xerogels
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/182—Graphene
- C01B32/184—Preparation
-
- 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
- C01B33/159—Coating or hydrophobisation
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/32—Thermal properties
Abstract
The invention discloses a preparation method of graphene/silicon dioxide composite aerogel, which is formed by combining graphene sheets and silicon dioxide aerogel. The composite aerogel is prepared by firstly carrying out hydroxylation and coupling treatment on silica aerogel, then mixing the silica aerogel with graphene oxide, wrapping the silica aerogel and the graphene together through bonding, and finally carrying out spray drying. The graphene/silicon dioxide composite aerogel prepared by the method has low heat conductivity coefficient, high hydrophobicity and high porosity under the condition that only a small amount of graphene is added, and the addition of the graphene can effectively absorb impact, reduce the damage of external force to a silicon aerogel matrix structure, greatly improve the problem of high brittleness of the silicon dioxide aerogel, and is difficult to abrade and stable in structure. The method has the advantages of simple process, low cost, strong operability, environment-friendly and pollution-free preparation process and remarkable practical value.
Description
Technical Field
The invention belongs to the technical field of material preparation, and particularly relates to graphene/silicon dioxide composite aerogel and a preparation method thereof.
Background
Silicon dioxide (SiO) 2 ) The aerogel is a low-density porous solid material formed by nano-scale particle phase polymerization, is filled with a gaseous dispersion medium, has the characteristics of high porosity, high specific surface area, low thermal conductivity, low light refractive index, lighter material and the like, and has unique properties in various fields such as heat insulation, optics, electricity and the like. But due to SiO 2 The aerogel has large brittleness, poor mechanical property and easy abrasion and breaking, so that the structure of the aerogel is damaged, and the original performance of the aerogel is lost, thereby severely limiting the large-scale application of the aerogel; furthermore SiO 2 The hydrophobic property of aerogel is one of the important factors influencing the heat insulation property, because a large amount of silicon hydroxyl exists on the inner surface of the aerogel holes, when the aerogel contacts with water in the air, the surface of the aerogel is cracked, the structure collapses and pulverized due to the adsorption of the water, the performance of the aerogel is seriously reduced, and the heat conductivity coefficient of the water is larger than that of the air, so that the heat insulation property of the aerogel is greatly reduced. Thus, it is necessary to make SiO 2 The aerogel is enhanced and improved. Currently aimed at SiO 2 The research of aerogel composite materials mainly focuses on two aspects, on one hand, the research of multi-component aerogel is that in a sol stage, the multi-component aerogel and other sol are compounded in a certain mode to obtain composite sol, and then the composite aerogel material is obtained through operations such as drying: on the other hand is SiO 2 The research on improvement of the mechanical properties of the aerogel is mostly carried out by combining SiO 2 The aerogel is compounded with fibrous porous ceramic or other reinforcing material mechanically or chemically, or by adding nanofillers to SiO 2 Reinforcing the aerogel nanostructure to produce a reinforced aerogel composite.
Graphene is a new material with a two-dimensional structure formed by single-layer or oligolayer sp2 hybridized carbon atoms, and has excellent electrical property, mechanical property, thermal property, high specific surface area and the like. Incorporating many of the good properties of graphene into SiO 2 Aerogel field, development of high performance, special functionality SiO 2 Air coagulationGlue is a current research hotspot. According to the normal pressure preparation method of the high specific surface area strong hydrophobic graphene oxide/silicon dioxide composite aerogel disclosed by the Chinese patent No. 201910556360.2, tetraethoxysilane is used as a precursor, silane coupling agent aminopropyl triethoxysilane is used for replacing a traditional alkaline catalyst, graphene oxide suspension is added under an acidic condition, and the alkaline group amino contained in the system is more easily combined with the acidic group carboxyl in the graphene oxide to carry out chemical bond, so that the bonding force is enhanced, the gel forming time is greatly reduced, and the graphene oxide/silicon dioxide aerogel with high specific surface area, strong hydrophobicity and low heat conductivity is obtained through normal pressure drying. The patent CN201710255537.6 (graphene/silicon dioxide composite aerogel material and preparation method thereof) prepares the composite aerogel with good high-temperature hydrophobic property and the like through the processes of graphene oxide/silicon dioxide system hydrogel, alcogel, supercritical drying, high-temperature treatment and the like, and can possibly resist the temperature of more than 400 ℃. However, in the two schemes, graphene oxide is added in a silicon source stage, and aggregation and reduction of graphene oxide can be easily caused under the conditions of containing amino groups, alkalinity and poor solvents, so that the dispersibility of graphene oxide in a system is poor, and in addition, after the mixing and bonding processes are carried out, the lamellar structure of graphene oxide can influence the formation of the original silica aerogel structure, and the graphene can show different distribution of each position in the structure of the aerogel, so that the hydrophobic property and the thermal conductivity are not greatly improved. In addition, in the scheme of the patent CN201710255537.6, supercritical drying and high-temperature reduction under inert gas are also required, and the problems of high temperature and high pressure, inflammability of organic reagents, higher equipment cost, higher energy consumption, more complicated steps and the like exist.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides graphene/silicon dioxide composite aerogel. The composite aerogel has low heat conductivity, high hydrophobicity and high porosity, and the addition of the graphene greatly improves the problem of high brittleness of the silica aerogel, is not easy to wear and has a stable structure.
The invention aims at realizing the following technical scheme:
(1) Dispersing 100 parts by weight of silicon dioxide aerogel powder in a mixed solution of concentrated sulfuric acid and hydrogen peroxide for hydroxylation treatment;
(2) Filtering, washing, dispersing into water solution containing 100-500 parts by weight of epoxy siloxane, and stirring;
(3) Adding 0.1-20 parts by weight of graphene oxide, adjusting the pH value to be less than 3, and mechanically stirring at 50 ℃;
(4) Adding an ascorbic acid aqueous solution, heating to 80 ℃, and maintaining for 10-30 min; heating to 150 ℃ and maintaining for 1-3 h;
(5) Regulating the viscosity to 200-600 cp, and obtaining the graphene/silicon dioxide composite aerogel powder by an atomization drying method.
Further, the silicon dioxide aerogel powder is nano aerogel powder, the grain diameter is 5-50 mu m, and the aperture is 10-30 nm.
Further, the graphene oxide is one or more of single-layer graphene oxide, double-layer graphene oxide and multi-layer graphene oxide. The transverse size of the graphene oxide sheet diameter is 2-50 μm.
Further, the acid solution is one or more of 10wt% of acetic acid, 10wt% of oxalic acid, 20wt% of citric acid and 5wt% of ethylene diamine tetraacetic acid.
The invention has the beneficial effects that:
the invention can make the combination of the graphene and the silicon aerogel more compact, does not destroy the original structure of the silicon aerogel, and the addition of the graphene can not only improve the problem of large brittleness of the silicon aerogel, but also has good mechanical property and strong stability, and can effectively absorb impact by taking the graphene as a support, thereby reducing the damage of external force to the silicon aerogel matrix structure. The graphene/silicon dioxide composite aerogel has excellent performances of low heat conductivity coefficient, high hydrophobicity, high porosity and the like under the condition that only a small amount of graphene is added.
Drawings
FIG. 1 is a sample graph of a raw silica aerogel powder, graphene/silica composite aerogel of examples 2, 5, 8;
fig. 2 is a graph of the hydrophobic properties of the raw silica aerogel powder, the graphene/silica composite aerogels of examples 2, 5, and 8.
Detailed Description
Firstly, hydroxylating the silica aerogel by using a mixed solution of concentrated sulfuric acid and hydrogen peroxide, and then slowly adding the mixed solution into an epoxy siloxane aqueous solution to uniformly combine hydroxyl groups on the surface of the silica aerogel with the epoxy siloxane, so that the epoxy groups are exposed outside, and the combination of the aerogel with other substances is facilitated; the pH value is regulated to be less than 3 by acid, ring opening of epoxy groups is facilitated at 50 ℃, the epoxy groups are tightly combined with graphene oxide, the graphene oxide sheets are tightly wrapped on the surfaces of aerogel microspheres by the bonding action force of the surfaces of modified silicon aerogel, the graphene has good mechanical properties, the problem of large brittleness of silicon aerogel and the like can be solved, the ascorbic acid is used as a weak reducing agent, the graphene oxide sheets wrap the aerogel microspheres to be attached between the ascorbic acid and the weak reducing agent in a molecular form along with the surfaces of the graphene oxide sheets, the graphene oxide can be slightly reduced, the volume expansion is reduced, the temperature is increased, the oxygen-containing functional groups between part of the reducing agent and the surfaces of the graphene oxide react, the product is separated along with volatilization of a solvent, the reduction reaction can be slowly carried out at the temperature of 80 ℃ in a first section, the slight reduction is carried out, the problem that the graphene sheets are separated from the silicon aerogel due to the volume expansion caused by the reduction is reduced, the hydroxyl groups on the surfaces of the composite aerogel can be reduced better at the high temperature of 150 ℃ in a second section, and the hydrophobicity is increased; under a certain viscosity, the composite aerogel mixed solution can be controlled, and the phenomenon of composite aerogel accumulation caused by too high viscosity can be avoided by an atomization drying method, so that uniform composite aerogel particles can be prepared.
The present invention is described in detail below by way of examples, which are only for further illustration of the present invention and are not to be construed as limiting the scope of the present invention, as many insubstantial changes and modifications will be apparent to those skilled in the art from the foregoing disclosure.
Example 1
(1) 100 parts of silica aerogel powder (particle diameter 5 μm, pore diameter 10 nm) was dispersed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide by mechanical stirring to subject silica to hydroxylation treatment. In the mixed solution of concentrated sulfuric acid and hydrogen peroxide, the sulfuric acid concentration was 18mol/L and the hydrogen peroxide concentration was 10mol/L (the same as in the following examples).
(2) Filtering and washing the mixed solution obtained in the step (1). Then dispersed into 100 parts of an aqueous solution of epoxysiloxane with stirring, the mass ratio of epoxysiloxane to water was 0.5:100.
(3) Subsequently, 0.5 parts of monolayer graphene oxide (average lateral dimension: 5 μm) was added in step (2), followed by adding 1 part of 10wt% aqueous acetic acid, and adjusting the pH to 1.9. Mechanical stirring at 50 ℃, adding 2 parts of ascorbic acid aqueous solution slowly, heating to 80 ℃, maintaining for 30min, heating to 150 ℃ and maintaining for 2h.
(4) And (3) adding pure water into the mixed solution obtained in the step (3) to dilute the mixed solution to a viscosity of about 300cp, and obtaining the graphene/silicon dioxide composite aerogel powder by an atomization drying method.
Through the steps, the graphene/silicon dioxide composite aerogel is obtained, and the performances are shown in table 1.
Example 2
(1) 100 parts of silica aerogel powder (particle diameter 5 μm, pore diameter 10 nm) was dispersed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide by mechanical stirring.
(2) Filtering and washing the mixed solution obtained in the step (1). Then, the mixture was dispersed in 300 parts of an aqueous solution of epoxysiloxane with stirring, and the mass ratio of epoxysiloxane to water was 5:100.
(3) Then, 0.5 part of single-layer graphene oxide (with an average transverse dimension of 5 μm) is added in the step (2), 1 part of 10wt% acetic acid aqueous solution is added, the pH value is regulated to 2.3, the mechanical stirring is carried out at 50 ℃, 2 parts of ascorbic acid aqueous solution is slowly added and heated to 80 ℃ for 30min, and then the temperature is raised to 150 ℃ for 2h.
(4) And (3) adding pure water into the mixed solution obtained in the step (3) to dilute the mixed solution to a viscosity of about 300cp, and obtaining the graphene/silicon dioxide composite aerogel powder by an atomization drying method.
Through the steps, the graphene/silicon dioxide composite aerogel is obtained, and the performances are shown in table 1.
Example 3
(1) 100 parts of silica aerogel powder (particle diameter 5 μm, pore diameter 10 nm) was dispersed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide by mechanical stirring.
(2) Filtering and washing the mixed solution obtained in the step (1). Then dispersing into 500 parts of aqueous solution of epoxy siloxane, and stirring the epoxy siloxane and water in a mass ratio of 8:100.
(3) Then, 0.5 part of single-layer graphene oxide (with an average transverse dimension of 5 μm) is added in the step (2), 1 part of 10wt% acetic acid aqueous solution is added, the pH value is regulated to 2.6, the mechanical stirring is carried out at 50 ℃, 2 parts of ascorbic acid aqueous solution is slowly added and heated to 80 ℃ for 30min, and then the temperature is raised to 150 ℃ for 2h.
(4) And (3) adding pure water into the mixed solution obtained in the step (3) to dilute the mixed solution to a viscosity of about 300cp, and obtaining the graphene/silicon dioxide composite aerogel powder by an atomization drying method.
Through the steps, the graphene/silicon dioxide composite aerogel is obtained, and the performances are shown in table 1.
Example 4
(1) 100 parts of silica aerogel powder (particle diameter 25 μm, pore diameter 20 nm) was dispersed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide by mechanical stirring.
(2) Filtering and washing the mixed solution obtained in the step (1). Then dispersing into 250 parts of aqueous solution of epoxy siloxane, and stirring, wherein the mass ratio of the epoxy siloxane to water is 5:100.
(3) Subsequently, 0.8 part of single-layer graphene oxide (with an average transverse dimension of 10 μm) is added in the step (2), then 0.1 part of 10wt% oxalic acid aqueous solution is added, the pH value is regulated to 2.8, the mechanical stirring is carried out at 50 ℃, then 3 parts of ascorbic acid aqueous solution is slowly added and the temperature is raised to 80 ℃, the temperature is maintained for 30min, and then the temperature is raised to 150 ℃ and the temperature is maintained for 3h.
(4) And (3) adding pure water into the mixed solution obtained in the step (3) to dilute the mixed solution to a viscosity of about 400cp, and obtaining the graphene/silicon dioxide composite aerogel powder by an atomization drying method.
Through the steps, the graphene/silicon dioxide composite aerogel is obtained, and the performances are shown in table 1.
Example 5
(1) 100 parts of silica aerogel powder (particle diameter 25 μm, pore diameter 20 nm) was dispersed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide by mechanical stirring.
(2) Filtering and washing the mixed solution obtained in the step (1). Then dispersing into 250 parts of aqueous solution of epoxy siloxane, and stirring, wherein the mass ratio of the epoxy siloxane to water is 5:100.
(3) Then, 0.8 part of single-layer graphene oxide (with the average transverse dimension of 10 mu m) is added in the step (2), 1 part of 10wt% oxalic acid aqueous solution is added, the pH value is regulated to 2.2, the mechanical stirring is carried out at 50 ℃, 3 parts of ascorbic acid aqueous solution is slowly added and heated to 80 ℃, the temperature is maintained for 30min, and then the temperature is further raised to 150 ℃ and maintained for 3h.
(4) And (3) adding pure water into the mixed solution obtained in the step (3) to dilute the mixed solution to a viscosity of about 400cp, and obtaining the graphene/silicon dioxide composite aerogel powder by an atomization drying method.
Through the steps, the graphene/silicon dioxide composite aerogel is obtained, and the performances are shown in table 1.
Example 6
(1) 100 parts of silica aerogel powder (particle diameter 25 μm, pore diameter 20 nm) was dispersed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide by mechanical stirring.
(2) Filtering and washing the mixed solution obtained in the step (1). Then dispersing into 250 parts of aqueous solution of epoxy siloxane, and stirring, wherein the mass ratio of the epoxy siloxane to water is 5:100.
(3) Then, 0.8 part of single-layer graphene oxide (with the average transverse dimension of 10 mu m) is added in the step (2), then 5 parts of 10wt% oxalic acid aqueous solution is added, the pH value is regulated to 1.3, the mechanical stirring is carried out at 50 ℃, 3 parts of ascorbic acid aqueous solution is slowly added and the temperature is raised to 80 ℃ for 30min, and then the temperature is raised to 150 ℃ for 3h.
(4) And (3) adding pure water into the mixed solution obtained in the step (3) to dilute the mixed solution to a viscosity of about 400cp, and obtaining the graphene/silicon dioxide composite aerogel powder by an atomization drying method.
Through the steps, the graphene/silicon dioxide composite aerogel is obtained, and the performances are shown in table 1.
Example 7
(1) 100 parts of silica aerogel powder (particle diameter: 10 μm, pore diameter: 10 nm) was dispersed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide by mechanical stirring.
(2) Filtering and washing the mixed solution obtained in the step (1), and then dispersing the mixed solution into 300 parts of aqueous solution of epoxy siloxane, and stirring the mixed solution, wherein the mass ratio of the epoxy siloxane to water is 5:100.
(3) Then, 0.2 part of graphene oxide (average transverse dimension: 30 μm) was added in the step (2), then 4 parts of 10wt% aqueous acetic acid was added, the pH was adjusted to 1.7, and the mixture was stirred mechanically at 50℃and then 4 parts of aqueous ascorbic acid was slowly added and heated to 80℃for 30 minutes, and then heated to 150℃and maintained for 3 hours.
(4) And (3) adding pure water into the mixed solution obtained in the step (3) to dilute the mixed solution to a viscosity of about 400cp, and obtaining the graphene/silicon dioxide composite aerogel powder by an atomization drying method.
Through the steps, the graphene/silicon dioxide composite aerogel is obtained, and the performances are shown in table 1.
Example 8
(1) 100 parts of silica aerogel powder (particle diameter: 10 μm, pore diameter: 10 nm) was dispersed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide by mechanical stirring.
(2) Filtering and washing the mixed solution obtained in the step (1), and then dispersing the mixed solution into 300 parts of aqueous solution of epoxy siloxane, and stirring the mixed solution, wherein the mass ratio of the epoxy siloxane to water is 5:100.
(3) Then 2 parts of graphene oxide (average transverse dimension: 30 μm) was added in the step (2), then 4 parts of 10wt% aqueous acetic acid was added, the pH was adjusted to 1.5, and the mixture was mechanically stirred at 50 ℃, then 4 parts of aqueous ascorbic acid was slowly added and heated to 80 ℃, and after maintaining for 30 minutes, the temperature was further raised to 150 ℃ and maintained for 3 hours.
(4) And (3) adding pure water into the mixed solution obtained in the step (3) to dilute the mixed solution to a viscosity of about 400cp, and obtaining the graphene/silicon dioxide composite aerogel powder by an atomization drying method.
Through the steps, the graphene/silicon dioxide composite aerogel is obtained, and the performances are shown in table 1.
Example 9
(1) 100 parts of silica aerogel powder (particle diameter: 10 μm, pore diameter: 10 nm) was dispersed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide by mechanical stirring.
(2) Filtering and washing the mixed solution obtained in the step (1), and then dispersing the mixed solution into 300 parts of aqueous solution of epoxy siloxane, and stirring the mixed solution, wherein the mass ratio of the epoxy siloxane to water is 5:100.
(3) Subsequently, 15 parts of graphene oxide (average transverse dimension: 30 μm) was added in the step (2), then 4 parts of 10wt% aqueous acetic acid was added, the pH was adjusted to 1.1, and the mixture was mechanically stirred at 50 ℃, then 4 parts of aqueous ascorbic acid was slowly added and heated to 80 ℃, and after maintaining for 30 minutes, the temperature was further raised to 150 ℃ and maintained for 3 hours.
(4) And (3) adding pure water into the mixed solution obtained in the step (3) to dilute the mixed solution to a viscosity of about 400cp, and obtaining the graphene/silicon dioxide composite aerogel powder by an atomization drying method.
Through the steps, the graphene/silicon dioxide composite aerogel is obtained, and the performances are shown in table 1.
Comparative example 10
(1) 100 parts of silica aerogel powder (particle diameter 5 μm, pore diameter 10 nm) was dispersed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide by mechanical stirring.
(2) Filtering, washing and dispersing the mixed solution obtained in the step (1) with water.
(3) Then, 0.5 part of single-layer graphene oxide (with an average transverse dimension of 5 μm) is added in the step (2), 1 part of 10wt% acetic acid aqueous solution is added, the pH value is regulated to 2.2, the mechanical stirring is carried out at 50 ℃, 2 parts of ascorbic acid aqueous solution is slowly added and heated to 80 ℃ for 30min, and then the temperature is raised to 150 ℃ for 2h.
(4) And (3) adding pure water into the mixed solution obtained in the step (3) to dilute the mixed solution to a viscosity of about 300cp, and obtaining the graphene/silicon dioxide composite aerogel powder by an atomization drying method.
Through the steps, the graphene/silicon dioxide composite aerogel is obtained, and the performances are shown in table 1.
Comparative example 11
(1) 100 parts of silica aerogel powder (particle diameter 25 μm, pore diameter 20 nm) was dispersed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide by mechanical stirring.
(2) Filtering and washing the mixed solution obtained in the step (1), and then dispersing the mixed solution into 300 parts of aqueous solution of epoxy siloxane, and stirring the mixed solution, wherein the mass ratio of the epoxy siloxane to water is 5:100.
(3) Subsequently, 0.8 parts of monolayer graphene oxide (average transverse dimension 10 μm) was added to step (2), followed by mechanical stirring at 50 ℃, followed by slow addition of 3 parts of an aqueous solution of ascorbic acid and heating to 80 ℃, maintaining for 30min, and then heating to 150 ℃ and maintaining for 3h.
(4) And (3) adding pure water into the mixed solution obtained in the step (3) to dilute the mixed solution to a viscosity of about 400cp, and obtaining the graphene/silicon dioxide composite aerogel powder by an atomization drying method.
Through the steps, the graphene/silicon dioxide composite aerogel is obtained, and the performances are shown in table 1.
Comparative example 12
(1) 100 parts of silica aerogel powder (particle diameter: 10 μm, pore diameter: 10 nm) was dispersed in a mixed solution of concentrated sulfuric acid and hydrogen peroxide by mechanical stirring.
(2) Filtering and washing the mixed solution obtained in the step (1), and then dispersing the mixed solution into 300 parts of aqueous solution of epoxy siloxane, and stirring the mixed solution, wherein the mass ratio of the epoxy siloxane to water is 5:100.
(3) Subsequently, 4 parts of 10wt% aqueous acetic acid was added to the step (2), the pH was adjusted to 1.8, and the mixture was mechanically stirred at 50℃and 4 parts of aqueous ascorbic acid was slowly added thereto and heated to 80℃for 30 minutes, and then heated to 150℃for 3 hours.
(4) And (3) adding pure water into the mixed solution obtained in the step (3) to dilute the mixed solution to a viscosity of about 400cp, and obtaining the graphene/silicon dioxide composite aerogel powder by an atomization drying method.
Through the steps, the graphene/silicon dioxide composite aerogel is obtained, and the performances are shown in table 1.
Comparative example 13
TEOS、EtOH、H 2 O is added into the precursor solution according to the mol ratio of 1:8:3.75, the pH value is regulated to 3-4, the mixture is stirred for 60min under a magnetic stirrer, and the mixture is hydrolyzed for 16h at constant temperature in a water bath kettle; adding 0.5mol/L ammonia water solution, adjusting the pH value to 7-8, adding graphene oxide suspension, placing in an ultrasonic cleaner for ultrasonic treatment for about 30min, stirring, standing, adding ethanol solution after gel is formed, and aging for 12h; solvent exchange is carried out for 1-2 d, ethanol is carried out for 1 time and n-hexane is carried out for 2 times according to the sequence, then HMDZ is adopted to modify wet gel, n-hexane is adopted to wash off residual modified liquid, finally the wet gel is put into a drying oven, and each drying is carried out for 3h at 80 ℃, and the hydrophobic graphene modified SiO can be obtained after the drying is finished 2 Composite aerogel.
The specific properties are shown in Table 1.
Table 1 composite aerogel performance tables of examples
Remarks: contact angle measurement refers to GB/T30693-2014, measurement of contact angle of plastic film and water, porosity measurement refers to skeleton density back-extrusion method, and heat conductivity measurement refers to ISO 22007-2-2008, measurement of thermal conductivity and thermal diffusivity, part 2 instantaneous plane Heat Source (heating disk) method.
According to the contact angle of the above cases, the contact angle of the product (examples 1-9) is higher than that of the raw material silica aerogel, and fig. 1 and 2 are respectively a sample graph and a hydrophobic performance graph of the raw material silica aerogel powder and the graphene/silica composite aerogel of examples 2, 5 and 8, and it can be seen from fig. 1 that the graphene/silica composite aerogel samples of examples 2, 5 and 8 have color uniformity, are consistent with the state of the raw material silica aerogel powder, fig. 2 can find that water drops drop on the raw material silica aerogel powder and obvious recessions appear, while water drops drop on the graphene/silica composite aerogel samples of examples 2, 5 and 8 can be stabilized on the samples without generating recessions, and the method of the invention realizes the coating of graphene on silica, which is probably because the silicon hydroxyl generated after the hydrolysis of the epoxy siloxane and the modified silica aerogel are adsorbed on the surface of the silicon aerogel under the action of hydrogen bond in the aqueous solution, so that the epoxy group is exposed to the outside, and the epoxy group is favorable to open loop under the acidic solution and a certain temperature condition, and the graphene group can be well covered by graphene oxide functional groups such as graphene oxide groups, graphene oxide functional groups can be effectively coated on the surface of graphene oxide. In the conventional preparation method, graphene oxide is added into a silicon source, graphene oxide sheets exist in a silicon source solution, and an integral composite material is formed through the processes of gelation, aging, drying and the like, but under the alkaline condition, the graphene oxide can generate an agglomeration phenomenon, so that the graphene oxide is unevenly distributed, and therefore, the graphene oxide cannot form cladding.
Further, by comparing the composite product of the coating product of the present invention with the conventional method, the products of the present invention (examples 1 to 9) are greatly improved in compressive strength and the like as compared with the raw material silica aerogel, comparative examples 11 to 13. The reduced graphene has good mechanical properties and strong stability, and the graphene is supported on the surface of the silicon aerogel, so that the impact can be effectively absorbed, the damage of external force to the silicon aerogel matrix structure is reduced, the problem of high brittleness of the silicon aerogel can be solved, and the compressive strength of the silicon aerogel is improved.
Further comparing the composite product of the coating product of the present invention with the conventional method, the product of the present invention (examples 1 to 9) maintains the porosity of the silica aerogel powder itself, whereas the conventional method has low porosity because the collapse of the pore structure or the formation of pores is suppressed due to the change of the structure of the original silica aerogel after doping the graphene sheets.
Further, as can be seen from examples 1 to 9 and comparative examples 10 to 12, when the addition amount of the epoxysiloxane, the acidic aqueous solution and the graphene oxide is regulated, the improvement of the related performance of the composite aerogel is facilitated, and examples 1 to 3 and comparative example 10 regulate the amount of the epoxysiloxane, improve the related performance and have obvious influence on the compressive strength of the composite silica aerogel along with the increase of the amount; examples 4 to 6 and comparative example 11, the amount of the acidic aqueous solution is regulated, the correlation performance is improved, and the contact angle and the compressive strength of the composite silicon aerogel are obviously influenced along with the increase of the amount; examples 7-9 and comparative example 12 control the amount of epoxysiloxane to improve the relevant properties, and as the amount increases, the contact angle, compressive strength, porosity and thermal conductivity of the composite silica aerogel are significantly affected, and the possible reasons for the above effects are that the addition of epoxysiloxane and acidic aqueous solution both contribute to the combination of graphene oxide and GO, so that more graphene sheets are tightly wrapped on the surface of the silica aerogel to form a stable structure, which contributes to improving the relevant properties of the composite silica aerogel. However, when the addition amount of the epoxy siloxane and the acidic aqueous solution reaches a certain amount, the related performance of the composite aerogel is not obviously improved, because the quantity of the epoxy siloxane connected to the surface of the silicon aerogel is limited, saturation is achieved, the performance cannot be well affected by changing the addition amount of the epoxy siloxane and the acidic aqueous solution, and in addition, when the addition amount of the graphene is too high, a plurality of pieces cannot be fully wrapped on the surface of the silicon aerogel, free graphene pieces exist, and stacking can be formed, so that the overall performance of the composite aerogel is affected.
Claims (1)
1. The graphene/silicon dioxide composite aerogel is characterized by being prepared by the following steps:
(1) Dispersing 100 parts by weight of silicon dioxide aerogel powder in a mixed solution of concentrated sulfuric acid and hydrogen peroxide for hydroxylation treatment; the silicon dioxide aerogel powder is nano aerogel powder, the grain diameter is 5-50 mu m, and the aperture is 10-30 nm;
(2) Filtering, washing, dispersing into water solution containing 100-500 parts by weight of epoxy siloxane, and stirring;
(3) Adding 0.1-20 parts by weight of graphene oxide, regulating the pH value to be less than 3 by using an acid solution, and mechanically stirring at 50 ℃; the graphene oxide consists of one or more of single-layer graphene oxide, double-layer graphene oxide and multi-layer graphene oxide; the transverse size of the graphene oxide sheet diameter is 2-50 mu m; the acid solution is one or more of 10wt% of acetic acid, 10wt% of oxalic acid, 20wt% of citric acid and 5wt% of ethylene diamine tetraacetic acid;
(4) Adding an ascorbic acid aqueous solution, heating to 80 ℃, and maintaining for 10-30 min; heating to 150 ℃ and maintaining for 1-3 h;
(5) Regulating the viscosity to 200-600 cp, and obtaining the graphene/silicon dioxide composite aerogel powder by an atomization drying method.
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