CN114988417A - Super-white silica aerogel, preparation method and application thereof - Google Patents
Super-white silica aerogel, preparation method and application thereof Download PDFInfo
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- CN114988417A CN114988417A CN202210839360.5A CN202210839360A CN114988417A CN 114988417 A CN114988417 A CN 114988417A CN 202210839360 A CN202210839360 A CN 202210839360A CN 114988417 A CN114988417 A CN 114988417A
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- silica aerogel
- white silica
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- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 165
- 239000004965 Silica aerogel Substances 0.000 title claims abstract description 112
- 238000002360 preparation method Methods 0.000 title abstract description 21
- 239000002245 particle Substances 0.000 claims abstract description 40
- 238000002310 reflectometry Methods 0.000 claims abstract description 23
- 230000003287 optical effect Effects 0.000 claims abstract description 17
- 238000000034 method Methods 0.000 claims abstract description 11
- 230000005855 radiation Effects 0.000 claims abstract description 11
- 238000005057 refrigeration Methods 0.000 claims abstract description 11
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 8
- 229920003217 poly(methylsilsesquioxane) Polymers 0.000 claims abstract description 4
- -1 polymethylsiloxane Polymers 0.000 claims abstract description 4
- 229910052814 silicon oxide Inorganic materials 0.000 claims abstract description 4
- 239000002243 precursor Substances 0.000 claims description 45
- 239000000741 silica gel Substances 0.000 claims description 26
- 229910002027 silica gel Inorganic materials 0.000 claims description 26
- 238000003756 stirring Methods 0.000 claims description 25
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 23
- 238000002156 mixing Methods 0.000 claims description 23
- 238000006068 polycondensation reaction Methods 0.000 claims description 23
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 22
- 239000002904 solvent Substances 0.000 claims description 22
- BFXIKLCIZHOAAZ-UHFFFAOYSA-N methyltrimethoxysilane Chemical compound CO[Si](C)(OC)OC BFXIKLCIZHOAAZ-UHFFFAOYSA-N 0.000 claims description 21
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 20
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 claims description 19
- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 claims description 18
- 238000001035 drying Methods 0.000 claims description 18
- 238000006460 hydrolysis reaction Methods 0.000 claims description 15
- 230000002209 hydrophobic effect Effects 0.000 claims description 13
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 12
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 12
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 12
- 125000005375 organosiloxane group Chemical group 0.000 claims description 12
- WGTYBPLFGIVFAS-UHFFFAOYSA-M tetramethylammonium hydroxide Chemical compound [OH-].C[N+](C)(C)C WGTYBPLFGIVFAS-UHFFFAOYSA-M 0.000 claims description 12
- GVGUFUZHNYFZLC-UHFFFAOYSA-N dodecyl benzenesulfonate;sodium Chemical compound [Na].CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 GVGUFUZHNYFZLC-UHFFFAOYSA-N 0.000 claims description 11
- 229940080264 sodium dodecylbenzenesulfonate Drugs 0.000 claims description 11
- 239000004094 surface-active agent Substances 0.000 claims description 11
- CPUDPFPXCZDNGI-UHFFFAOYSA-N triethoxy(methyl)silane Chemical compound CCO[Si](C)(OCC)OCC CPUDPFPXCZDNGI-UHFFFAOYSA-N 0.000 claims description 11
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 10
- 229910017604 nitric acid Inorganic materials 0.000 claims description 10
- WOWHHFRSBJGXCM-UHFFFAOYSA-M cetyltrimethylammonium chloride Chemical compound [Cl-].CCCCCCCCCCCCCCCC[N+](C)(C)C WOWHHFRSBJGXCM-UHFFFAOYSA-M 0.000 claims description 9
- DKGAVHZHDRPRBM-UHFFFAOYSA-N Tert-Butanol Chemical compound CC(C)(C)O DKGAVHZHDRPRBM-UHFFFAOYSA-N 0.000 claims description 8
- 239000003054 catalyst Substances 0.000 claims description 8
- 239000011148 porous material Substances 0.000 claims description 8
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 7
- LZZYPRNAOMGNLH-UHFFFAOYSA-M Cetrimonium bromide Chemical compound [Br-].CCCCCCCCCCCCCCCC[N+](C)(C)C LZZYPRNAOMGNLH-UHFFFAOYSA-M 0.000 claims description 7
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 7
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 7
- 239000003377 acid catalyst Substances 0.000 claims description 7
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 7
- JJQZDUKDJDQPMQ-UHFFFAOYSA-N dimethoxy(dimethyl)silane Chemical compound CO[Si](C)(C)OC JJQZDUKDJDQPMQ-UHFFFAOYSA-N 0.000 claims description 7
- KPUWHANPEXNPJT-UHFFFAOYSA-N disiloxane Chemical class [SiH3]O[SiH3] KPUWHANPEXNPJT-UHFFFAOYSA-N 0.000 claims description 7
- 239000004202 carbamide Substances 0.000 claims description 6
- YYLGKUPAFFKGRQ-UHFFFAOYSA-N dimethyldiethoxysilane Chemical compound CCO[Si](C)(C)OCC YYLGKUPAFFKGRQ-UHFFFAOYSA-N 0.000 claims description 6
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 6
- 239000003513 alkali Substances 0.000 claims description 4
- WVDDGKGOMKODPV-ZQBYOMGUSA-N phenyl(114C)methanol Chemical compound O[14CH2]C1=CC=CC=C1 WVDDGKGOMKODPV-ZQBYOMGUSA-N 0.000 claims description 4
- 239000002585 base Substances 0.000 claims description 3
- 230000007774 longterm Effects 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 230000001788 irregular Effects 0.000 claims 1
- 230000035484 reaction time Effects 0.000 claims 1
- 230000006835 compression Effects 0.000 abstract description 6
- 238000007906 compression Methods 0.000 abstract description 6
- 238000006243 chemical reaction Methods 0.000 abstract description 3
- 235000012239 silicon dioxide Nutrition 0.000 abstract description 3
- 230000003075 superhydrophobic effect Effects 0.000 abstract 1
- 239000000243 solution Substances 0.000 description 29
- 239000000463 material Substances 0.000 description 12
- 239000007864 aqueous solution Substances 0.000 description 8
- 230000007062 hydrolysis Effects 0.000 description 8
- WVDDGKGOMKODPV-UHFFFAOYSA-N Benzyl alcohol Chemical compound OCC1=CC=CC=C1 WVDDGKGOMKODPV-UHFFFAOYSA-N 0.000 description 6
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 6
- 238000009826 distribution Methods 0.000 description 6
- 239000000499 gel Substances 0.000 description 6
- 239000011347 resin Substances 0.000 description 6
- 229920005989 resin Polymers 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 230000001105 regulatory effect Effects 0.000 description 5
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 230000003301 hydrolyzing effect Effects 0.000 description 4
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 4
- 239000002105 nanoparticle Substances 0.000 description 4
- 238000005191 phase separation Methods 0.000 description 4
- 239000004964 aerogel Substances 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- JEGUKCSWCFPDGT-UHFFFAOYSA-N h2o hydrate Chemical compound O.O JEGUKCSWCFPDGT-UHFFFAOYSA-N 0.000 description 3
- 230000031700 light absorption Effects 0.000 description 3
- 239000004408 titanium dioxide Substances 0.000 description 3
- 238000002834 transmittance Methods 0.000 description 3
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 2
- 229910010413 TiO 2 Inorganic materials 0.000 description 2
- 239000012237 artificial material Substances 0.000 description 2
- 235000019445 benzyl alcohol Nutrition 0.000 description 2
- JYYOBHFYCIDXHH-UHFFFAOYSA-N carbonic acid;hydrate Chemical compound O.OC(O)=O JYYOBHFYCIDXHH-UHFFFAOYSA-N 0.000 description 2
- 239000011246 composite particle Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000007888 film coating Substances 0.000 description 2
- 238000009501 film coating Methods 0.000 description 2
- 235000019253 formic acid Nutrition 0.000 description 2
- 239000011521 glass Substances 0.000 description 2
- 239000000017 hydrogel Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000011022 opal Substances 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 229910052709 silver Inorganic materials 0.000 description 2
- 239000004332 silver Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 238000003917 TEM image Methods 0.000 description 1
- JUGOREOARAHOCO-UHFFFAOYSA-M acetylcholine chloride Chemical compound [Cl-].CC(=O)OCC[N+](C)(C)C JUGOREOARAHOCO-UHFFFAOYSA-M 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 238000000149 argon plasma sintering Methods 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 238000001723 curing Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000003795 desorption Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910052809 inorganic oxide Inorganic materials 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 239000005445 natural material Substances 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 230000005693 optoelectronics Effects 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 150000001282 organosilanes Chemical class 0.000 description 1
- 230000000737 periodic effect Effects 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 230000000379 polymerizing effect Effects 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000007790 scraping Methods 0.000 description 1
- 238000007789 sealing Methods 0.000 description 1
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000002336 sorption--desorption measurement Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000002210 supercritical carbon dioxide drying Methods 0.000 description 1
- 238000002411 thermogravimetry Methods 0.000 description 1
- QQQSFSZALRVCSZ-UHFFFAOYSA-N triethoxysilane Chemical compound CCO[SiH](OCC)OCC QQQSFSZALRVCSZ-UHFFFAOYSA-N 0.000 description 1
- 239000007762 w/o emulsion Substances 0.000 description 1
Images
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- 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
-
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
- C01P2002/84—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by UV- or VIS- data
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- C01P2002/00—Crystal-structural characteristics
- C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
- C01P2002/88—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by thermal analysis data, e.g. TGA, DTA, DSC
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- 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
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- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
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- C01P2004/01—Particle morphology depicted by an image
- C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
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- C01P2004/50—Agglomerated particles
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- C01P2006/10—Solid density
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- C01P2006/14—Pore volume
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- C01P2006/16—Pore diameter
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- 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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention discloses an ultra-white silica aerogel, a preparation method and application thereof. The ultra-white silica aerogel is in a three-dimensional porous network structure formed by interconnecting silica particles, the particle size of the silica particles is 100-3000 nm, the power weighted average reflectivity of the ultra-white silica aerogel to sunlight with the wavelength of 250-2500 nm is 98-99.5%, and the average reflectivity of the ultra-white silica aerogel to visible light with the wavelength of 380-780 nm is 98.5-99.9%. The silicon oxide particles comprise silicon dioxide, polymethylsilsesquioxane, polymethylsiloxane and the like. The super-white silica aerogel disclosed by the invention has excellent mechanical properties, can be elastically recovered after compression or shear deformation, and has super-hydrophobic properties; meanwhile, the preparation process is simple, the reaction conditions are mild, and the method has great application prospects in the fields of radiation refrigeration, laser display, solar cell reflecting plates, optical instruments and the like.
Description
Technical Field
The invention relates to a preparation method of silica aerogel, in particular to ultra-white silica aerogel and a preparation method and application thereof, belonging to the technical field of nano optical materials.
Background
The metamaterial means an artificial material having extraordinary physical properties that can be realized by using an artificial structure as a basic functional unit, which are not possessed by a natural material. In the past decade, a series of novel artificial material systems with singular characteristics are developed, and high attention is paid to countries in the world, so that subversive technologies can be generated in various fields. They possess special properties such as allowing sound, light, electricity to change their general properties, which cannot be achieved with conventional materials. The peculiar properties of metamaterials derive from their precise geometry and size. Photonic metamaterials are man-made materials containing nanostructures that impart particular optical properties (patent: methods of creating metamaterials and metamaterials created thereby, 2012800281983). Their structure is obtained with at least two different materials. The structure of the material is typically periodic and the period is comparable to or less than the wavelength of light.
The super-white material has great application prospect in the fields of radiation refrigeration, Light Emitting Diode (LED) display, solar cell back reflecting plates, optical instruments and the like. The highest reflectivity device at present is a distributed bragg reflector (patent CNCN1732604A, distributed bragg reflector for optoelectronic device), which is formed by alternately and periodically stacking films with different refractive indexes, and when light passes through the films with different refractive indexes, the light reflected by each layer interferes due to the change of phase angle and then combines with each other to obtain strong reflection light. However, a distributed bragg reflector can only strongly reflect light over a range of wavelengths, and the reflectivity and reflection bandwidth are limited by the refractive index contrast between the stacked materials, which are typically selected as titanium dioxide (n ≈ 2.6) and silicon dioxide (n ≈ 1.5), with bandwidth limited to within 200 nm.
The patent CN211180278U discloses a high reflection film structure, which uses PET as a substrate, a resin layer is cured on the top end face, a plurality of reflection recesses arranged in a stacked structure are pressed on the resin layer, a metal film layer is evaporated or sputtered on the space where the top end of the resin layer matches the space between two adjacent reflection recesses and the inner side wall of each reflection recess, and the reflection of the recess microstructure and the metal is utilized to achieve the high reflection rate of the wide band. Patent CN111628716A discloses an environment-friendly high-reflection film for photovoltaic glass back plate, which uses a mirror aluminum foil layer as a main reflection layer to reflect sunlight onto the photovoltaic glass back plate to improve lightThe generating efficiency of the photovoltaic panel assembly. Although metals such as aluminum and silver can reflect light in a broad band, the light absorption of the metal reflective layer does not exceed 95% due to the intrinsic light absorption of the metal (aluminum: 15%, silver: 5%). Some inorganic oxides with wide band gap have low light absorption rate and are widely used in reflective layers, for example, patent CN110256888A discloses a high-reflectivity diffuse reflection coating, a preparation method thereof, and a light reflecting device, in which titanium dioxide, silica, and barium sulfate particles are dispersed in an aqueous resin, and the large difference in refractive index between silica and titanium dioxide can make the composite particles diffuse reflection incident light, and the composite particles can also fill the gaps of barium sulfate, so as to further improve the reflection effect of the diffuse reflection coating. Patent CN112745712A discloses a scrape coatable light high-efficiency radiation refrigeration coating, a preparation method and application thereof, the preparation method comprises the steps of mixing, scraping and curing a reflective pigment, a resin binder, an organic solvent and an auxiliary agent, and the reflectivity of the coating in a 300-2500 nm waveband is not less than 94%. However, the monodisperse reflective particles cannot be used alone, and must be bonded using a resin. TiO 2 2 The low electronic band gap (3.2eV) absorbs ultraviolet rays in sunlight, resulting in TiO 2 The solar reflectivity of the material as the reflecting medium is lower than 95 percent. Porous structures have also been explored to increase solar reflectance by using the difference in refractive index between the solid skeleton and the air in the pores to cause scattering to reflect sunlight. Patent CN112375418A discloses a preparation method of a multi-stage porous radiation refrigeration film coating, which comprises dissolving organosilane and high-molecular prepolymer or monomer in oil phase by using high internal phase water-in-oil emulsion as template, heating and polymerizing to form organic-inorganic composite framework, and drying to obtain the multi-stage porous radiation refrigeration film coating. However, such emulsion templates are not easily controlled, scattering of the skeletal particles is insufficient, and their reflectance is below 98%.
Silicon oxide is an excellent optical material, has a forbidden band width as high as 9eV, does not absorb light rays in a solar wave band, and is widely applied to various optical instruments. In 1995, the Vasil and Astratov team proposed opals (ordered aggregated SiO) 2 Spherical composition) is an optical metamaterial in the visible region. When light passes through the micro-structure of the opal, thisThe ordered silica spheres cause interference and diffraction of light to produce color change, and the diffraction condition for a particular color is satisfied when the distance between 2 successive layers is approximately equal to the wavelength of the color divided by the refractive index of the sphere. The diffraction wavelength is proportional to the size of the spheres, and the distance between the regularly stacked planes of spheres is about half the wavelength of visible light. For example, red is produced by spheres about 250nm in diameter, and other colors are diffracted by smaller spheres, which may be down to 140nm in diameter. However, the particle size of the opal particles is uniform, and only light with specific wavelength can be reflected, and broadband high reflection cannot be achieved. The aerogel serving as a typical porous material has high porosity (80-99.8%), and light can be scattered due to the difference between the refractive indexes of the solid skeleton and air in pores. And the density, the particle size and the pore size of the aerogel skeleton can be regulated and controlled in the aerogel preparation process of sol-gel to enhance the scattering of light, so that the silica aerogel is an ideal sunlight scattering material. However, silica aerogels are generally small (< 30nm) in particle size, have limited ability to scatter sunlight, exhibit a faint blue color, and have low reflectivity. And the silica aerogel has fragile skeleton, low strength, easy pulverization and difficult compression rebound (for example, the silica aerogel prepared by the patent CN109592689A is powder and has no compression and shear elasticity). Therefore, the preparation of the super-white silica aerogel with wide band, high reflectivity and high elasticity has important significance.
Disclosure of Invention
The invention mainly aims to provide an ultra-white silica aerogel, a preparation method and application thereof, and solves the technical problem of low silica aerogel reflectivity in the prior art.
In order to achieve the purpose, the technical scheme adopted by the invention comprises the following steps:
the embodiment of the invention provides ultra-white silica aerogel, which is formed by mutually connecting silica particles to form a three-dimensional porous network structure, wherein the particle size of the silica particles is 100-3000 nm, the power weighted average reflectivity of the ultra-white silica aerogel to sunlight with the wavelength of 250-2500 nm is 98-99.5%, and the average reflectivity of the ultra-white silica aerogel to visible light with the wavelength of 380-780 nm is 98.5-99.9%; the super-white silica aerogel can be elastically recovered after being deformed or bent for 3mm after being compressed for 50%, the hydrophobic angle of the super-white silica aerogel is 150-160 degrees, and the silica particles comprise any one or a combination of more than two of silica, polymethylsilsesquioxane and polymethylsiloxane.
The embodiment of the invention also provides a preparation method of the super-white silica aerogel, which comprises the following steps:
1) dissolving a methyl-containing organosiloxane precursor in a solvent, selectively adding or not adding a surfactant, and uniformly stirring to form a precursor solution;
2) adding an acid catalyst into the precursor solution obtained in the step 1) to perform hydrolysis reaction, and then adding an alkali catalyst to perform polycondensation reaction to obtain ultra-white silica gel;
3) and (3) carrying out solvent replacement and normal-pressure drying treatment on the ultra-white silica gel obtained in the step 2) to obtain the ultra-white silica aerogel.
The embodiment of the invention also provides the ultra-white silica aerogel prepared by the preparation method.
The embodiment of the invention also provides application of the ultra-white silica aerogel in the fields of radiation refrigeration, laser display, laser protection, solar cell reflecting plates or optical instruments and the like.
Compared with the prior art, the invention has the beneficial effects that:
the super-white silica aerogel provided by the invention takes methyl-containing organic siloxane as a precursor, and the silica aerogel blocks with large-particle-size nanoparticles and wide particle size distribution are obtained by regulating the proportion of the methyl-containing organic siloxane and the content of a solvent and a surfactant and accurately controlling the gel phase separation degree, so that the controllable preparation of the particle diameter is realized, the preparation process is simple, and the reaction conditions are mild; the prepared ultra-white silica aerogel has high reflectivity in a sunlight wave band (250-2500 nm); the material has good mechanical property, good flexibility and excellent super-hydrophobicity, can be bent and folded, can be compressed by 50 percent and rebound, and can bear loads such as impact and the like; the method has great application prospect in the fields of radiation refrigeration, laser display, solar cell reflecting plates, optical instruments and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a nitrogen adsorption/desorption graph of the ultra-white silica aerogel obtained in example 1 of the present invention;
FIG. 2 is a scanning electron microscope photograph of a super-white silica aerogel obtained in example 1 of the present invention;
FIG. 3 is a transmission electron microscope photograph of the ultra-white silica aerogel obtained in example 1 of the present invention;
FIG. 4 is a graph showing a distribution of particle sizes of ultra-white silica aerogel obtained in example 1 of the present invention;
FIG. 5 is an optical photograph of a super white silica aerogel obtained in example 1 of the present invention;
FIG. 6 is a compression rebound optical photograph of the ultra white silica aerogel obtained in example 1 of the present invention;
FIG. 7 is a stress-strain curve of the ultra-white silica aerogel obtained in example 1 of the present invention;
FIG. 8 is a scanning electron micrograph of a super white silica aerogel obtained in example 2 of the present invention;
FIG. 9 is a TEM photograph of the super-white silica aerogel obtained in example 2 of the present invention;
FIG. 10 is a TG curve of a super-white silica aerogel obtained in example 2 of the present invention;
FIG. 11 is a reflection spectrum of a super-white silica aerogel obtained in example 2 of the present invention.
Detailed Description
In view of the defects in the prior art, the inventors of the present invention have made extensive studies and practice to provide a technical solution of the present invention, which is to obtain a high-reflectance low-transmittance ultra-white silica aerogel mainly by controlling the methyl-containing organosiloxane precursor. Specifically, the silica aerogel particles are generally small in size (less than 30nm), limited in light scattering capacity and low in reflectivity, the gel phase separation degree is accurately controlled by regulating the proportion of methyl-containing organic silicon and the contents of a solvent and a surfactant to obtain silica aerogel blocks with large-particle-size nanoparticles and wide particle size distribution, the silica aerogel with the large-particle-size nanoparticles and wide particle size distribution can efficiently scatter light rays in a wide range of wave bands, and the technical scheme, the implementation process and the principle of the silica aerogel are further explained as follows.
According to one aspect of the embodiment of the invention, the ultra-white silica aerogel is formed by interconnecting silica particles to form a three-dimensional porous network structure, the particle size of the silica particles is 100-3000 nm, the power weighted average reflectivity of the ultra-white silica aerogel to sunlight (wavelength of 250-2500 nm) is 98-99.5%, and the average reflectivity to visible light (wavelength of 380-780 nm) is 98.5-99.9%. The super-white silica aerogel can be elastically recovered after being deformed or bent by 50% after being compressed for 3mm, has excellent super-hydrophobicity, has a hydrophobic angle of 150-160 degrees, and comprises any one or combination of more than two of silicon dioxide, polymethylsilsesquioxane and polymethylsiloxane.
In some embodiments, the silica aerogel has a particle size of 100 to 3000 nm. The large-size particle size obtained by the invention can reflect 250-2500 nm light more efficiently.
In some embodiments, the three-dimensional porous network structure comprises mesopores with a pore size of 2-50 nm and macropores with a pore size of 50 nm-50 μm.
In some embodiments, the morphology of the silica particles of the ultra-white silica aerogel includes any one or a combination of two or more of spheres, ellipsoids, irregularities, and the like, but is not limited thereto.
In some embodiments, the ultra-white silica aerogel has a density of 50 to 500mg/cm 3 Preferably 80 to 200mg/cm 3 。
Further, the specific surface area of the ultra-white silica aerogel is 0.1-400 m 2 A preferred ratio is 2 to 100m 2 /g。
Further, the pore volume of the ultra-white silica aerogel is 1-10 cm 3 A/g, preferably 3 to 6cm 3 /g。
Further, the porosity of the ultra-white silica aerogel is 50-99%, and preferably 75-95%.
In some embodiments, the ultrawhite silica aerogel has a long-term use temperature above 300 ℃.
In conclusion, the ultra-white silica aerogel has high reflectivity, controllable density, excellent thermal stability and super-hydrophobicity within a wave band of 250-2500 nm. Meanwhile, the material has good mechanical properties, can be compressed and sheared and rebounded, and can bear loads such as impact and the like. The ultra-white silica aerogel also has good flexibility and can be bent and folded.
One aspect of the embodiment of the present invention provides a preparation method of the above ultra-white silica aerogel, which mainly includes: the preparation method comprises the following steps of (1) taking methyl-containing organic siloxane as a precursor, and accurately controlling the gel phase separation degree by regulating the proportion of the methyl-containing organic siloxane and the content of a solvent and a surfactant to obtain silica aerogel blocks with large-particle-size nanoparticles and wide particle size distribution, so as to realize controllable preparation of particle diameters; and hydrolyzing and polycondensing the organic siloxane precursor under the condition of a catalyst to form gel, and performing solvent replacement and drying to obtain the ultra-white silica aerogel.
In some embodiments, the method of making consists essentially of:
1) dissolving a methyl-containing organic siloxane precursor in a solvent according to a certain proportion, selectively adding or not adding a surfactant, and uniformly stirring to form a precursor solution;
2) adding an acid catalyst into the precursor solution obtained in the step 1) to perform hydrolysis reaction, then adding an alkali catalyst to perform polycondensation reaction, and separating to obtain ultra-white silica gel;
3) and (3) carrying out solvent replacement and normal-pressure drying treatment on the ultra-white silica gel obtained in the step 2) to obtain the ultra-white silica aerogel.
In some embodiments, the methyl-containing organosiloxane precursor in step 1) includes any one or a combination of two or more of methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, and the like, and is not limited thereto.
Further, the solvent includes any one or a combination of two or more of water, ethanol, benzyl alcohol, N-Dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and the like, without being limited thereto.
Further, the molar ratio of the solvent to the methyl group-containing organosiloxane precursor is 10 -1 About 50: 1, preferably about 1-5: 1.
Further, the surfactant includes any one or a combination of two or more of cetyltrimethylammonium bromide (CTAB), cetyltrimethylammonium chloride (CTAC), Sodium Dodecylbenzenesulfonate (SDBS), and the like, without being limited thereto.
Further, the molar ratio of the surfactant to the methyl-containing organosiloxane precursor is 0-0.1: 1, preferably 0-0.01: 1.
In some embodiments, the acid catalyst in step 2) includes any one or a combination of two or more of hydrochloric acid, nitric acid, sulfuric acid, and the like, and is not limited thereto.
Further, the molar ratio of the acid catalyst to the methyl group-containing organosiloxane precursor is 10 -2 ～10 -5 1, preferably 10 -3 ～10 -4 ∶1。
Further, the base catalyst includes any one or a combination of two or more of ammonia, urea, triethylamine, tetramethylammonium hydroxide, sodium carbonate, and the like, and is not limited thereto.
Further, the molar ratio of the base catalyst to the methyl group-containing organosiloxane precursor is 10 -1 ～10 -4 1, preferably 10 -2 ～10 -3 ∶1。
In some embodiments, in the step 2), the time of the hydrolysis reaction is 0.1 to 24 hours, preferably 0.5 to 2 hours, and the temperature of the hydrolysis reaction is 10 to 60 ℃, preferably 20 to 40 ℃.
Further, the time of the polycondensation reaction is 48-96 hours, preferably 48-72 hours, and the temperature of the polycondensation reaction is 60-120 ℃, preferably 80-100 ℃.
In some embodiments, the substitution solvent in step 3) includes any one or a combination of two or more of water, ethanol, DMSO, tert-butanol, methanol, and the like, and is not limited thereto.
Further, the temperature of the solvent replacement is 20-60 ℃, and preferably 30-60 ℃.
Further, the number of times of solvent replacement is 0-6.
In some embodiments, in the step 3), the temperature of the drying treatment under normal pressure is 30-120 ℃, and the drying is performed until the solvent is completely removed without any requirement for time.
In conclusion, the preparation process of the ultra-white silica aerogel provided by the invention is simple, mild in reaction conditions, easy to operate, low in energy consumption, low in cost, green and pollution-free, and can realize large-scale continuous production.
In another aspect, the embodiment of the invention also provides a huge application prospect of the ultra-white silica aerogel in the fields of radiation refrigeration, laser display, laser protection, solar cell reflecting plates, optical instruments and the like.
As one of the preferable schemes, the application of the ultra-white silica aerogel specifically comprises
1) The ultra-white silica aerogel has high sunlight reflectivity and low transmittance, and can be applied to radiation refrigeration in normal temperature and high temperature environments.
2) The high reflectivity of the ultra-white silica aerogel can be applied to one or more application fields of laser protection, solar sails, optical instruments and the like, but is not limited to the application fields.
By the technical scheme, the ultra-white silica aerogel provided by the invention has high reflectivity, low light transmittance and low density, and has great application prospects in the fields of radiation refrigeration, laser protection, solar sails, optical instruments and the like.
The technical solutions of the present invention will be described in further detail below with reference to several preferred embodiments and accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. It is to be noted that the following examples are intended to facilitate the understanding of the present invention, and do not set forth any limitation thereto. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out under conventional conditions or conditions recommended by the manufacturers.
Example 1
(1) Mixing and stirring methyltrimethoxysilane (MTMS), dimethyldimethoxysilane (DMDMS), hexadecyltrimethylammonium chloride and water to form a precursor solution;
(2) and (2) adding hydrochloric acid into the precursor solution in the step (1), mixing and stirring at 60 ℃ for 0.1 hour for hydrolysis, adding ammonia water for polycondensation reaction at 60 ℃ for 72 hours, and obtaining the ultra-white silica gel. Wherein the mol ratio of MTMS, DMDMS, hexadecyl trimethyl ammonium chloride, hydrochloric acid, water and ammonia water is 1: 0.1: 0.01: 10: 0.1.
(3) And (3) replacing the ultra-white silica gel in the step (2) with ethanol for 3 times at 20 ℃, and drying at 30 ℃ under normal pressure to obtain the ultra-white silica aerogel.
The nitrogen adsorption and desorption curves of the ultra-white silica aerogel obtained in the example are shown in fig. 1, the SEM structure is shown in fig. 2, the TEM is shown in fig. 3, the particle size distribution is shown in fig. 4, the optical photograph is shown in fig. 5, the compression elastic recovery optical photograph is shown in fig. 6, and the stress-strain curve is shown in fig. 7. The physical parameters of the ultra-white silica aerogel obtained in this example, such as average particle size, specific surface area, reflectance, and hydrophobic angle, are shown in table 1.
Example 2
(1) Mixing and stirring methyltrimethoxysilane, hexadecyl trimethyl ammonium chloride and water to form a precursor solution;
(2) and (2) adding hydrochloric acid into the precursor solution in the step (1), mixing and stirring at 10 ℃ for 24 hours, hydrolyzing, adding ammonia water, and performing polycondensation reaction at 90 ℃ for 48 hours to obtain the ultra-white silica gel. Wherein the mol ratio of MTMS, hexadecyl trimethyl ammonium chloride, hydrochloric acid, water and ammonia water is 1: 0.001: 10 -5 ∶4∶10 -4 。
(3) And (3) replacing the super white silica gel obtained in the step (2) with tert-butyl alcohol at 20 ℃ for 6 times, and drying at 30 ℃ under normal pressure to obtain the super white silica aerogel.
The SEM structure of the ultra-white silica aerogel obtained in this example is shown in FIG. 8, the TEM image is shown in FIG. 9, the thermogravimetric analysis image is shown in FIG. 10, and the reflectance is shown in FIG. 11. The physical parameters of the ultra-white silica aerogel obtained in this example, such as average particle size, specific surface area, reflectance, and hydrophobic angle, are shown in table 1.
Example 3
(1) Mixing and stirring methyl triethoxysilane, hexadecyl trimethyl ammonium bromide and ethanol to form a precursor solution;
(2) and (2) adding a sulfuric acid aqueous solution into the precursor solution in the step (1), mixing and stirring at 10 ℃ for 3 hours for hydrolysis, adding urea for polycondensation reaction at the polycondensation temperature of 60 ℃ for 72 hours, and obtaining the ultra-white silica gel. Wherein the mol ratio of the methyl triethoxysilane, the hexadecyl trimethyl ammonium bromide, the sulfuric acid, the ethanol, the water and the urea is 1: 10 -5 ∶10 -2 ∶0.1∶3∶10 -4 。
(3) And (3) replacing the super white silica gel in the step (2) with tertiary butanol at 20 ℃ for 3 times, and drying at 40 ℃ under normal pressure to obtain the super white silica aerogel.
The physical parameters of the ultra-white silica aerogel obtained in this example, such as average particle size, specific surface area, reflectance, and hydrophobic angle, are shown in table 1.
Example 4
(1) Mixing and stirring methyl triethoxysilane, hexadecyl trimethyl ammonium bromide and ethanol to form a precursor solution;
(2) adding a sulfuric acid aqueous solution into the precursor solution in the step (1) at 10 DEG CMixing and stirring for 3 hours, hydrolyzing, adding urea, and performing polycondensation reaction at 60 ℃ for 72 hours to obtain the ultra-white silica gel. Wherein the mol ratio of the methyl triethoxysilane, the hexadecyl trimethyl ammonium bromide, the sulfuric acid, the ethanol, the water and the urea is 1: 0.01: 10 -4 ∶4∶4∶10 -3 。
(3) And (3) replacing the ultra-white silica gel in the step (2) with ethanol for 6 times at 20 ℃, and drying at 30 ℃ under normal pressure to obtain the ultra-white silica aerogel.
The physical parameters of the ultra-white silica aerogel obtained in this example, such as average particle size, specific surface area, reflectance, and hydrophobic angle, are shown in table 1.
Example 5
(1) Mixing and stirring methyl trimethoxy silane, methyl triethoxy silane, sodium dodecyl benzene sulfonate and benzyl alcohol to form a precursor solution;
(2) and (2) adding a nitric acid aqueous solution into the precursor solution in the step (1), mixing and stirring at 60 ℃ for 1 hour for hydrolysis, adding triethylamine for polycondensation reaction at 60 ℃ for 72 hours, and obtaining the ultra-white silica gel. Wherein the mol ratio of methyltrimethoxysilane, methyltriethoxysilane, sodium dodecyl benzene sulfonate, benzyl alcohol, nitric acid, water and triethylamine is 1: 10 -3 ∶5∶10 -2 ∶6∶10 -1 。
(3) And (3) replacing the ultra-white silica gel in the step (2) with DMSO for 6 times at 30 ℃, and drying at 120 ℃ under normal pressure to obtain the ultra-white silica aerogel.
The physical parameters of the ultra-white silica aerogel obtained in this example, such as average particle size, specific surface area, reflectance, and hydrophobic angle, are shown in table 1.
Example 6
(1) Mixing and stirring methyl trimethoxy silane, methyl triethoxy silane, sodium dodecyl benzene sulfonate and benzyl alcohol to form a precursor solution;
(2) adding a nitric acid aqueous solution into the precursor solution obtained in the step (1), mixing and stirring at 40 ℃ for 1 hour for hydrolysis, adding triethylamine for polycondensation reaction at 40 ℃ for 48 hours to obtain the catalystUltra white silica gel. Wherein the mol ratio of the methyltrimethoxysilane, the methyltriethoxysilane, the sodium dodecyl benzene sulfonate, the benzyl alcohol, the nitric acid, the water and the triethylamine is 1: 0.01: 4: 10 -5 ∶6∶10 -4 。
(3) And (3) replacing the ultra-white silica gel in the step (2) with DMSO for 2 times at 60 ℃, and drying at 120 ℃ under normal pressure to obtain the ultra-white silica aerogel.
The physical parameters of the ultra-white silica aerogel obtained in this example, such as average particle size, specific surface area, reflectance, and hydrophobic angle, are shown in table 1.
Example 7
(1) Mixing and stirring methyltrimethoxysilane, dimethyl dimethoxysilane, sodium dodecyl benzene sulfonate and DMF to form a precursor solution;
(2) and (2) adding a nitric acid aqueous solution into the precursor solution in the step (1), mixing and stirring at 40 ℃ for 1 hour for hydrolysis, adding tetramethylammonium hydroxide for polycondensation reaction at the polycondensation temperature of 100 ℃ for 48 hours, and obtaining the ultra-white silica gel. Wherein the mol ratio of the methyltrimethoxysilane, the methyltriethoxysilane, the sodium dodecyl benzene sulfonate, the DMF, the nitric acid, the water and the tetramethylammonium hydroxide is 1: 0.005: 4: 10 -5 ∶6∶10 -4 。
(3) And (3) replacing the ultra-white silica gel in the step (2) with methanol for 2 times at 30 ℃, and drying at 40 ℃ under normal pressure to obtain the ultra-white silica aerogel.
The physical parameters of the ultra-white silica aerogel obtained in this example, such as average particle size, specific surface area, reflectance, and hydrophobic angle, are shown in table 1.
Example 8
(1) Mixing and stirring methyltrimethoxysilane, dimethyl dimethoxysilane, sodium dodecyl benzene sulfonate and DMF to form a precursor solution;
(2) and (2) adding a nitric acid aqueous solution into the precursor solution in the step (1), mixing and stirring at 40 ℃ for 1 hour for hydrolysis, adding tetramethylammonium hydroxide for polycondensation reaction at the polycondensation temperature of 120 ℃ for 48 hours, and obtaining the ultra-white silica gel. Wherein, methyl trimethoxy silane and methylThe mol ratio of the triethoxy silane, the sodium dodecyl benzene sulfonate, the DMF, the nitric acid, the water and the tetramethyl ammonium hydroxide is 1: 0.004: 4: 10 -5 ∶6∶10 -4 。
(3) And (3) replacing the ultra-white silica gel obtained in the step (2) with methanol at 30 ℃ for 2 times, and drying at 40 ℃ under normal pressure to obtain the ultra-white silica aerogel.
The physical parameters of the ultra-white silica aerogel obtained in this example, such as average particle size, specific surface area, reflectance, and hydrophobic angle, are shown in table 1.
Example 9
(1) Mixing and stirring methyltrimethoxysilane, dimethyl diethoxysilane and DMSO to form a precursor solution;
(2) and (2) adding a hydrochloric acid aqueous solution into the precursor solution in the step (1), mixing and stirring at 30 ℃ for 1 hour for hydrolysis, adding sodium carbonate for polycondensation reaction at the polycondensation temperature of 80 ℃ for 96 hours, and obtaining the ultra-white silica gel. Wherein the mol ratio of methyltrimethoxysilane, dimethyldiethoxysilane, DMSO, hydrochloric acid, water and sodium carbonate is 1: 5: 10 -3 ∶3∶10 -2 。
(3) And (3) replacing the ultra-white silica gel in the step (2) with water at 30 ℃ for 6 times, and drying at 60 ℃ under normal pressure to obtain the ultra-white silica aerogel.
The physical parameters of the ultra-white silica aerogel obtained in this example, such as average particle size, specific surface area, reflectance, and hydrophobic angle, are shown in table 1.
Example 10
(1) Mixing and stirring methyltrimethoxysilane, dimethyl diethoxysilane and DMSO to form a precursor solution;
(2) and (2) adding a hydrochloric acid aqueous solution into the precursor solution in the step (1), mixing and stirring at 30 ℃ for 1 hour for hydrolysis, adding sodium carbonate for polycondensation reaction at the polycondensation temperature of 80 ℃ for 96 hours, and obtaining the ultra-white silica gel. Wherein the mol ratio of methyltrimethoxysilane, dimethyldiethoxysilane, DMSO, hydrochloric acid, water and sodium carbonate is 1: 5: 10 -5 ∶3∶10 -4 。
(3) And (3) replacing the ultra-white silica gel in the step (2) with water at 30 ℃ for 6 times, and drying at 60 ℃ under normal pressure to obtain the ultra-white silica aerogel.
The physical parameters of the ultra-white silica aerogel obtained in this example, such as average particle size, specific surface area, reflectance, and hydrophobic angle, are shown in table 1.
TABLE 1 structural and performance parameters of the ultra-white silica aerogels obtained in examples 1-12
Comparative example 1
(1) Mixing and stirring MTMS, hexadecyl trimethyl ammonium chloride and water to form a precursor solution, adding formic acid, mixing and stirring at 60 ℃ for 24 hours, hydrolyzing, and adding ammonia water for polycondensation. Wherein the mol ratio of MTMS, hexadecyl trimethyl ammonium chloride, formic acid, water and ammonia water is 1: 0.1: 10 -1 ∶100∶10 -1 。
(2) And (2) sealing and storing the precursor solution in the step (1) in an oven at 60 ℃ for 72 hours to obtain the hydrogel.
(3) And (3) replacing the scatterer hydrogel obtained in the step (2) with ethanol for 6 times at 30 ℃, and obtaining the silica aerogel by adopting a supercritical carbon dioxide drying process, wherein the particle size is only 2-50 nm.
By comparison, in the embodiment 1 of the invention, the gel phase separation degree is accurately controlled by regulating the proportion of methyl-containing organic silicon and the content of the solvent and the surfactant, and the particle size of the obtained ultra-white silica aerogel is 200nm and is far larger than that (2-50 nm) of the silica aerogel in the comparative example 1, so that the ultra-white silica aerogel can have a strong reflection effect on the whole sunlight spectrum and visible light, and the reflectivity is higher than 98%. While the silica aerogel in comparative example 1 has a small particle size and is only transparent to light. In addition, the large size particles had strong neck-ties and good compression and shear recovery properties, whereas the silica aerogel of comparative example 1 was very brittle.
In addition, the inventor also prepares a series of ultra-white silica aerogels by using other raw materials and process conditions listed in the specification and referring to the modes of examples 1-10. These ultra-white silica aerogels have also been found to have the excellent properties described herein.
It should be understood that the above describes only some embodiments of the present invention and that various other changes and modifications may be affected therein by one of ordinary skill in the related art without departing from the scope or spirit of the invention.
Claims (10)
1. The ultra-white silica aerogel is characterized in that silica particles are connected with one another to form a three-dimensional porous network structure, the particle size of the silica particles is 100-3000 nm, the power weighted average reflectivity of the ultra-white silica aerogel to sunlight with the wavelength of 250-2500 nm is 98-99.5%, and the average reflectivity of the ultra-white silica aerogel to visible light with the wavelength of 380-780 nm is 98.5-99.9%; the super-white silica aerogel can be elastically recovered after being compressed by 50% and deformed or bent by 3mm, the hydrophobic angle of the super-white silica aerogel is 150-160 degrees, and the silica particles comprise any one or a combination of more than two of silica, polymethylsilsesquioxane and polymethylsiloxane.
2. The ultra-white silica aerogel according to claim 1, wherein: the three-dimensional porous network structure comprises mesopores with the aperture of 2-50 nm and macropores with the aperture of 50 nm-50 mu m;
and/or the particle size of the silicon oxide particles is 100-500 nm;
and/or the form of the silicon oxide particles comprises any one or the combination of more than two of spheres, ellipsoids and irregular bodies;
and/or the density of the ultra-white silica aerogel is 50-500 mg/cm 3 Preferably 80 to 200mg/cm 3 ；
And/or the specific surface area of the ultra-white silica aerogel is 0.1-400 m 2 Preferably 2 to 100 m/g 2 /g；
And/or the pore volume of the ultra-white silica aerogel is 1-10 cm 3 Preferably 3 to 6 cm/g 3 /g；
And/or the porosity of the ultra-white silica aerogel is 50-99%, preferably 75-95%.
3. The ultra-white silica aerogel according to claim 1, wherein: the long-term use temperature of the ultra-white silica aerogel is above 300 ℃.
4. The method of preparing the ultra-white silica aerogel according to any of claims 1 to 3, comprising
1) Dissolving a methyl-containing organosiloxane precursor in a solvent, selectively adding or not adding a surfactant, and uniformly stirring to form a precursor solution;
2) adding an acid catalyst into the precursor solution obtained in the step 1) to perform hydrolysis reaction, and then adding an alkali catalyst to perform polycondensation reaction to obtain ultra-white silica gel;
3) and (3) carrying out solvent replacement and normal-pressure drying treatment on the ultra-white silica gel obtained in the step 2) to obtain the ultra-white silica aerogel.
5. The method of manufacturing according to claim 4, characterized in that: in the step 1), the organic siloxane precursor containing methyl comprises any one or the combination of more than two of methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane and dimethyldiethoxysilane; and/or the solvent comprises any one or the combination of more than two of water, ethanol, benzyl alcohol, N-dimethylformamide and dimethyl sulfoxide; and/or the molar ratio of the solvent to the methyl-containing organosiloxane precursor is 0.1-10: 1, preferably 1-5: 1; and/or the surfactant comprises any one or the combination of more than two of cetyl trimethyl ammonium bromide, cetyl trimethyl ammonium chloride and sodium dodecyl benzene sulfonate; and/or the molar ratio of the surfactant to the methyl-containing organosiloxane precursor is 0-0.01: 1, preferably 0-0.05: 1.
6. The method of claim 4, wherein: in the step 2), the acid catalyst comprises any one or the combination of more than two of hydrochloric acid, nitric acid and sulfuric acid; and/or the molar ratio of the acid catalyst to the methyl-containing organosiloxane precursor is 10 -2 ～10 -5 1, preferably 10 -3 ～10 -4 1: mixing; and/or the alkali catalyst comprises one or the combination of more than two of ammonia water, urea, triethylamine, tetramethylammonium hydroxide and sodium carbonate; and/or the molar ratio of the base catalyst to the organosiloxane precursor is 10 -1 ～10 -4 1, preferably 10 -2 ～10 -3 ∶1。
7. The method of claim 4, wherein: in the step 2), the hydrolysis reaction time is 0.1-24 hours, preferably 0.5-2 hours, the hydrolysis reaction temperature is 10-60 ℃, and preferably 20-40 ℃; and/or the time of the polycondensation reaction is 48-96 hours, preferably 48-72 hours, and the temperature of the polycondensation reaction is 60-120 ℃, preferably 80-100 ℃.
8. The method of claim 4, wherein: in the step 3), the replacement solvent comprises any one or a combination of more than two of water, ethanol, DMSO, tert-butanol and methanol; and/or the temperature of the solvent replacement is 20-60 ℃, preferably 30-60 ℃; and/or the number of times of solvent replacement is 0-6.
9. The method of claim 4, wherein: in the step 3), the temperature of the normal-pressure drying treatment is 30-120 ℃.
10. Use of the ultra-white silica aerogel according to any of claims 1 to 3 in the field of radiation refrigeration, laser display, laser protection, solar cell reflector panels or optical instruments.
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