CN116903919B - Cellulose-based radiation refrigeration aerogel material and preparation method thereof - Google Patents
Cellulose-based radiation refrigeration aerogel material and preparation method thereof Download PDFInfo
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- 239000000463 material Substances 0.000 title claims abstract description 75
- 229920002678 cellulose Polymers 0.000 title claims abstract description 67
- 239000001913 cellulose Substances 0.000 title claims abstract description 67
- 230000005855 radiation Effects 0.000 title claims abstract description 45
- 238000005057 refrigeration Methods 0.000 title claims abstract description 38
- 239000004964 aerogel Substances 0.000 title claims abstract description 31
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- 229920003043 Cellulose fiber Polymers 0.000 claims abstract description 60
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 27
- 238000004061 bleaching Methods 0.000 claims abstract description 24
- 235000017166 Bambusa arundinacea Nutrition 0.000 claims abstract description 17
- 235000017491 Bambusa tulda Nutrition 0.000 claims abstract description 17
- 241001330002 Bambuseae Species 0.000 claims abstract description 17
- 235000015334 Phyllostachys viridis Nutrition 0.000 claims abstract description 17
- 239000011425 bamboo Substances 0.000 claims abstract description 17
- 239000002994 raw material Substances 0.000 claims abstract description 16
- 239000003054 catalyst Substances 0.000 claims abstract description 15
- 230000001105 regulatory effect Effects 0.000 claims abstract description 14
- 229920005610 lignin Polymers 0.000 claims abstract description 13
- 238000004108 freeze drying Methods 0.000 claims abstract description 10
- 239000003431 cross linking reagent Substances 0.000 claims abstract description 8
- 238000006243 chemical reaction Methods 0.000 claims abstract description 7
- 240000008564 Boehmeria nivea Species 0.000 claims abstract description 5
- 239000000428 dust Substances 0.000 claims abstract description 3
- 239000002023 wood Substances 0.000 claims abstract description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 108
- GEHJYWRUCIMESM-UHFFFAOYSA-L sodium sulfite Chemical compound [Na+].[Na+].[O-]S([O-])=O GEHJYWRUCIMESM-UHFFFAOYSA-L 0.000 claims description 70
- 235000010265 sodium sulphite Nutrition 0.000 claims description 35
- 239000000243 solution Substances 0.000 claims description 28
- 239000007864 aqueous solution Substances 0.000 claims description 27
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 22
- 238000003756 stirring Methods 0.000 claims description 16
- 239000006185 dispersion Substances 0.000 claims description 15
- 239000007788 liquid Substances 0.000 claims description 15
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical group [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 9
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 9
- BFXIKLCIZHOAAZ-UHFFFAOYSA-N methyltrimethoxysilane Chemical compound CO[Si](C)(OC)OC BFXIKLCIZHOAAZ-UHFFFAOYSA-N 0.000 claims description 9
- 238000010438 heat treatment Methods 0.000 claims description 8
- 238000000034 method Methods 0.000 claims description 6
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 4
- 239000005708 Sodium hypochlorite Substances 0.000 claims description 4
- AMXOYNBUYSYVKV-UHFFFAOYSA-M lithium bromide Chemical compound [Li+].[Br-] AMXOYNBUYSYVKV-UHFFFAOYSA-M 0.000 claims description 4
- SUKJFIGYRHOWBL-UHFFFAOYSA-N sodium hypochlorite Chemical compound [Na+].Cl[O-] SUKJFIGYRHOWBL-UHFFFAOYSA-N 0.000 claims description 4
- RYHBNJHYFVUHQT-UHFFFAOYSA-N 1,4-Dioxane Chemical compound C1COCCO1 RYHBNJHYFVUHQT-UHFFFAOYSA-N 0.000 claims description 2
- BRLQWZUYTZBJKN-UHFFFAOYSA-N Epichlorohydrin Chemical compound ClCC1CO1 BRLQWZUYTZBJKN-UHFFFAOYSA-N 0.000 claims description 2
- 239000004952 Polyamide Substances 0.000 claims description 2
- 239000012295 chemical reaction liquid Substances 0.000 claims description 2
- 229940089951 perfluorooctyl triethoxysilane Drugs 0.000 claims description 2
- 229920002647 polyamide Polymers 0.000 claims description 2
- AVYKQOAMZCAHRG-UHFFFAOYSA-N triethoxy(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane Chemical compound CCO[Si](OCC)(OCC)CCC(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)F AVYKQOAMZCAHRG-UHFFFAOYSA-N 0.000 claims description 2
- 230000003075 superhydrophobic effect Effects 0.000 description 19
- 238000009413 insulation Methods 0.000 description 16
- 239000008367 deionised water Substances 0.000 description 14
- 229910021641 deionized water Inorganic materials 0.000 description 14
- 239000000843 powder Substances 0.000 description 12
- 230000000694 effects Effects 0.000 description 8
- 239000003507 refrigerant Substances 0.000 description 8
- 239000012153 distilled water Substances 0.000 description 7
- 238000007710 freezing Methods 0.000 description 7
- 230000008014 freezing Effects 0.000 description 7
- 239000000203 mixture Substances 0.000 description 7
- 238000005406 washing Methods 0.000 description 7
- 238000002310 reflectometry Methods 0.000 description 5
- 239000004480 active ingredient Substances 0.000 description 3
- 230000002776 aggregation Effects 0.000 description 3
- 238000004220 aggregation Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 239000000835 fiber Substances 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 230000003595 spectral effect Effects 0.000 description 3
- 229920002488 Hemicellulose Polymers 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 239000012782 phase change material Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 238000000985 reflectance spectrum Methods 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000002657 fibrous material Substances 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 238000004476 mid-IR spectroscopy Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229920005615 natural polymer Polymers 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000002269 spontaneous effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000004083 survival effect Effects 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
Classifications
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J9/00—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof
- C08J9/28—Working-up of macromolecular substances to porous or cellular articles or materials; After-treatment thereof by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2301/00—Characterised by the use of cellulose, modified cellulose or cellulose derivatives
- C08J2301/02—Cellulose; Modified cellulose
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
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- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Chemical Or Physical Treatment Of Fibers (AREA)
Abstract
The invention discloses a cellulose-based radiation refrigeration aerogel material and a preparation method thereof, comprising the following steps: (1) Removing lignin in the natural cellulose raw material to obtain cellulose fibers; (2) Treating cellulose fiber by adopting a bleaching solution, and regulating the size of the cellulose fiber to be 1.8-12 mu m; (3) Dispersing the cellulose fiber treated in the step (2) into water, adding a cross-linking agent and a catalyst for reaction, and freeze-drying after the reaction is finished to obtain a radiation refrigeration aerogel material; the natural cellulose raw material is at least one of wood dust, ramie and bamboo. The cellulose-based radiation refrigeration aerogel material is pure cellulose-based material, is green and degradable, and has the advantages of simple preparation method and low cost.
Description
Technical Field
The invention relates to the technical field of natural polymer heat management functions, in particular to a cellulose-based radiation refrigeration aerogel material and a preparation method thereof.
Background
With the increase of global warming, summer hot weather becomes normal, and human survival health is seriously threatened. Meanwhile, the high-temperature weather forces people to continuously increase the demands of refrigeration equipment such as electric power and the like, and further aggravates the emission of greenhouse gases, thereby forming vicious circle. Therefore, a new refrigeration system that does not require energy input is needed to alleviate the current situation.
The daytime passive radiation refrigeration is a novel refrigeration mode without energy input, and mainly utilizes the high solar reflectivity of the material at 0.3-2.5 mu m and the high mid-infrared emissivity at 8-13 mu m, so that the solar heat input is reduced, and meanwhile, the heat is emitted to the cold outer space to the greatest extent, and further, the spontaneous cooling of the surface of the material is realized, so that the material has attracted the wide attention of researchers. However, the existing single radiation refrigeration material has limited refrigeration effect, and the surface of the material is directly exposed in the outdoor environment, at the moment, the surface temperature of the material is lower than the ambient temperature, and heat is easily absorbed from the surrounding environment in a convection heat exchange mode, so that the surface temperature of the material is increased, and the refrigeration effect is reduced.
The Chinese patent document with the application number of CN202110639646.4 discloses the preparation of a cellulose-based radiation temperature regulating material, and a temperature regulating material with the dual-function characteristics of phase change energy storage and radiation refrigeration is developed by doping a phase change material into the cellulose material, but the phase change material has higher cost, the temperature regulating range is narrower, and an organic solvent is used in the preparation process.
The chinese patent document CN202211721315.6 discloses a functional material having radiation refrigeration added to a cellulose material. The radiation refrigeration aerogel film with high rebound resilience is prepared by comprehensively utilizing the radiation refrigeration characteristic of the functional material and the high flexibility of cellulose. However, the concentration, size and distribution of the functional material in the cellulosic material have a great influence on the spectral properties of the prepared material.
The chinese patent document with application number CN202210733590.3 discloses a cellulose nanocrystalline aerogel for radiation refrigeration, and uses the surface in-situ growth of cellulose nanocrystalline to form nano silica particles to enhance the scattering of solar light, so as to achieve the purpose of high reflection.
In summary, in order to meet the requirement of high solar reflectance, the existing cellulose-based radiation refrigeration material still adopts a method of doping with radiation refrigeration functional particles or organic/inorganic compounding, on one hand, the preparation process is complex, the cost is high, and the problem that inorganic and petroleum-based polymer materials are difficult to degrade still exists. It is therefore necessary to construct a pure cellulose-based high-efficiency radiation refrigerating material.
Disclosure of Invention
The invention provides a super-hydrophobic and high-heat-insulation cellulose-based radiation refrigeration aerogel material and a preparation method thereof.
The technical scheme of the invention is as follows:
A method for preparing a cellulose-based radiation refrigeration aerogel material, comprising the following steps:
(1) Removing lignin in the natural cellulose raw material to obtain cellulose fibers;
(2) Treating cellulose fiber by adopting a bleaching solution, and regulating the size of the cellulose fiber to be 1.8-12 mu m;
(3) Dispersing the cellulose fiber treated in the step (2) into water, adding a cross-linking agent and a catalyst for reaction, and freeze-drying after the reaction is finished to obtain a radiation refrigeration aerogel material;
the natural cellulose raw material is at least one of wood dust, ramie and bamboo.
The preparation method of the invention fully utilizes the multi-level aggregation state structure of the natural cellulose and the regulation and control of the cellulose fiber size, and realizes the improvement of the solar reflectance of the pure cellulose-based material. Meanwhile, due to the treatment of lignin removal and bleaching, a large number of air hole structures exist in the obtained cellulose fiber, so that the scattering of sunlight is improved, meanwhile, the ultralow heat conductivity of the cellulose material is endowed, the convective heat exchange between the cellulose material and the surrounding environment is blocked, and the refrigerating effect of the cellulose-based material is further improved; the super-hydrophobic finishing is carried out on the surface of the material to avoid environmental pollution, so that the actual service durability of the material is improved, and the service life of the prepared cellulose-based radiation refrigeration aerogel material is greatly prolonged.
Preferably, the natural cellulose raw material is at least one of ramie and bamboo.
After lignin removal and bleaching treatment, the ramie or bamboo fiber material has more hollow pores, more uniform distribution, lower heat conductivity and better heat insulation performance.
Preferably, in the step (1), the natural cellulose raw material is added into the delignification solution, and the lignin is removed by heating and stirring; the delignification solution is at least one of sodium sulfite/sodium hydroxide aqueous solution, lithium bromide solution, dioxane and acetone.
Further preferably, in the delignification solution, the concentration of the active ingredient is 10-30wt%; in the step (1), the heating temperature is 80-120 ℃ and the heating time is 1-10 h.
When the concentration of the active ingredients in the delignification solution is smaller and the treatment time is shorter, the residual lignin content in the natural cellulose raw material is higher, the reflectivity of the natural cellulose raw material to sunlight and the emissivity of the natural cellulose raw material in a middle infrared atmospheric window can be reduced, and the natural cellulose raw material is unfavorable for passive radiation refrigeration in daytime; with the increase of the concentration of the active ingredients in the lignin solution and the extension of the treatment time, the solar reflectance and the mid-infrared emissivity of the natural cellulose raw material are increased along with the decrease of the residual lignin content in the natural cellulose raw material, but the spectral performance of the natural cellulose raw material is basically unchanged after the lignin is completely removed.
Further preferably, the delignification solution is sodium sulfite/sodium hydroxide aqueous solution; the sodium sulfite/sodium hydroxide aqueous solution has sodium sulfite concentration of 5-10wt% and sodium hydroxide concentration of 10-20wt%; in the step (1), the heating temperature is 80-100 ℃ and the heating time is 3-8 h.
Preferably, the bleaching solution is at least one of hydrogen peroxide and sodium hypochlorite.
Further preferably, in the bleaching solution, the mass fraction of the hydrogen peroxide and/or the sodium hypochlorite is 1-8wt%; in the step (2), the bleaching treatment temperature is 60-120 ℃; the bleaching treatment time is 2-24 h.
When the concentration of the bleaching solution is low and the treatment time is short, the size of the prepared cellulose fiber is large, and the cellulose fiber is not matched with sunlight wave bands, so that passive radiation refrigeration in the daytime is not facilitated; along with the increase of the concentration of the bleaching solution and the extension of the bleaching time, the size of the cellulose fiber is continuously reduced until the cellulose fiber is matched with a solar light wave band, and the air hole structure in the obtained cellulose fiber is increased due to the removal of residual lignin and hemicellulose, so that the scattering effect of the cellulose fiber on sunlight is further enhanced, and finally the aim of high sunlight reflection is achieved.
Preferably, in step (2), the size of the cellulose fibers is controlled to 1.8 to 8 μm by a bleaching treatment.
Preferably, the concentration of the cellulose fiber in the reaction liquid in the step (3) is 1.5-21 mg.ml -1; the mass fraction of the cross-linking agent is 1.0-8.0 wt%; the mass fraction of the catalyst is 0.5-2.0 wt%.
When the concentration of cellulose fibers is too dilute, the resulting aerogel is prone to collapse. When the cellulose concentration is too high, the porosity of the aerogel may decrease, thereby affecting the solar reflectance and thermal insulation properties of the material.
More preferably, the concentration of the cellulose fiber in the reaction solution in the step (3) is 1.5 to 10 mg.ml -1; the mass fraction of the cross-linking agent is 1.0-5.0 wt%; the mass fraction of the catalyst is 0.5-1.0 wt%.
Further preferably, the cross-linking agent is at least one of methyltrimethoxysilane, perfluorooctyltriethoxysilane and polyamide epichlorohydrin; the catalyst is ammonia water.
The invention also provides the cellulose-based radiation refrigeration aerogel material prepared by the preparation method.
Preferably, the solar reflectance of the cellulose-based radiation refrigeration aerogel material is more than 90%; the average emissivity of the atmospheric window is more than 90%; the thermal conductivity is below 0.03 W.m -1·K-1.
Compared with the prior art, the invention has the beneficial effects that:
The preparation method comprehensively utilizes the synergistic scattering effect of the multilayer aggregation state structure of the natural cellulose material and the porous cellulose fiber structures with different sizes to prepare the pure cellulose-based radiation refrigeration aerogel material with multilayer structure, high heat insulation and superhydrophobicity, and the material has excellent visible-near infrared high reflectivity and spectral selectivity characteristic of infrared strong radiation in an atmospheric window (8-13 mu m), simultaneously has ultralow heat conductivity coefficient, can greatly improve the actual refrigeration effect of the material, and can cool the aerogel material to more than 6.8 ℃ at most when the aerogel material is directly irradiated by sunlight.
Drawings
FIG. 1 is a graph showing the particle size of cellulose fibers of examples 1 to 4 at different bleaching times;
FIG. 2 is a graph showing the visible-near infrared reflectance spectrum of the cellulose-based radiant refrigerant materials prepared in examples 1-4;
FIG. 3 is a graph of the mid-IR spectrum of 8 to 13 μm for the cellulose-based radiant refrigerant materials prepared in examples 1 to 4;
FIG. 4 is an SEM image of cellulose fibers prepared according to example 4;
FIG. 5 is a graph showing the temperature drop profile of the cellulose-based radiant refrigerant material prepared in example 4 through a temperature measuring device;
Fig. 6 is a graph of water contact angle of the cellulose-based radiant refrigerant material prepared in example 4.
Detailed Description
Example 1
Firstly, 100g of sodium sulfite/sodium hydroxide aqueous solution (namely, sodium sulfite/sodium hydroxide aqueous solution with the sodium sulfite concentration of 8.0wt percent and sodium hydroxide concentration of 16wt percent) with the mass ratio of (8/16/76 wt percent) is prepared, then 2.0g of bamboo powder is weighed and added into the sodium sulfite/sodium hydroxide aqueous solution, stirred for 5.0h at the temperature of 100 ℃, then the mixture is stood, and repeatedly washed by distilled water to obtain colorless transparent solution. Then preparing a hydrogen peroxide solution with the mass fraction of 6.0wt%, immersing the bamboo powder into the hydrogen peroxide solution, and stirring for 6.0h at 120 ℃ until the sample completely presents white. Then taking out, washing with deionized water for many times, redispersing in deionized water, regulating the concentration of cellulose fiber to 2.1 mg/ml -1, adding methyltrimethoxysilane (0.6 ml), stirring for 1h, adding 0.004g ammonia water as a catalyst, then putting the cellulose fiber dispersion liquid into a refrigerator (-20 ℃) for freezing for 24h, putting the cellulose fiber dispersion liquid into a freeze dryer (-50 ℃) for freeze drying for 72h, and finally preparing the high-heat-insulation super-hydrophobic cellulose-based radiation refrigerating material with a multi-layer structure.
Example 2
Firstly, 100g of sodium sulfite/sodium hydroxide aqueous solution (namely, sodium sulfite/sodium hydroxide aqueous solution with the sodium sulfite concentration of 8.0wt percent and sodium hydroxide concentration of 16wt percent) with the mass ratio of (8/16/76 wt percent) is prepared, then 2.0g of bamboo powder is weighed and added into the sodium sulfite/sodium hydroxide aqueous solution, stirred for 5.0h at the temperature of 100 ℃, then the mixture is stood, and repeatedly washed by distilled water to obtain colorless transparent solution. Then preparing a hydrogen peroxide solution with the mass fraction of 6.0wt%, immersing the bamboo powder into the hydrogen peroxide solution, and stirring for 8 hours at 120 ℃ until the sample completely presents white. Then taking out, washing with deionized water for many times, dispersing in deionized water again, regulating the concentration of cellulose fiber to 2.1 mg/ml -1, respectively adding methyltrimethoxysilane (0.6 ml), stirring for 1h, adding 0.004g ammonia water as a catalyst, then putting the cellulose fiber dispersion liquid into a refrigerator (-20 ℃) for freezing for 24h, putting the cellulose fiber dispersion liquid into a freeze dryer (-50 ℃) for freeze drying for 72h, and finally preparing the high-heat-insulation super-hydrophobic cellulose-based radiation refrigerating material with a multi-layer structure.
Example 3
Firstly, 100g of sodium sulfite/sodium hydroxide aqueous solution (namely, sodium sulfite/sodium hydroxide aqueous solution with the sodium sulfite concentration of 8.0wt percent and sodium hydroxide concentration of 16wt percent) with the mass ratio of (8/16/76 wt percent) is prepared, then 2.0g of bamboo powder is weighed and added into the sodium sulfite/sodium hydroxide aqueous solution, stirred for 5.0h at the temperature of 100 ℃, then the mixture is stood, and repeatedly washed by distilled water to obtain colorless transparent solution. Then preparing a hydrogen peroxide solution with the mass fraction of 6.0wt%, immersing the bamboo powder into the hydrogen peroxide solution, and stirring for 10 hours at 120 ℃ until the sample completely presents white. Then taking out, washing with deionized water for many times, redispersing in deionized water, regulating the concentration of cellulose fiber to 2.1 mg/ml -1, adding methyltrimethoxysilane (0.6 ml), stirring for 1h, adding 0.004g ammonia water as a catalyst, then putting the cellulose fiber dispersion liquid into a refrigerator (-20 ℃) for freezing for 24h, putting the cellulose fiber dispersion liquid into a freeze dryer (-50 ℃) for freeze drying for 72h, and finally preparing the high-heat-insulation super-hydrophobic cellulose-based radiation refrigerating material with a multi-layer structure.
Example 4
Firstly, 100g of sodium sulfite/sodium hydroxide aqueous solution (namely, sodium sulfite/sodium hydroxide aqueous solution with the sodium sulfite concentration of 8.0wt percent and sodium hydroxide concentration of 16wt percent) with the mass ratio of (8/16/76 wt percent) is prepared, then 2.0g of bamboo powder is weighed and added into the sodium sulfite/sodium hydroxide aqueous solution, stirred for 5.0h at the temperature of 100 ℃, then the mixture is stood, and repeatedly washed by distilled water to obtain colorless transparent solution. And preparing a hydrogen peroxide solution with the mass fraction of 6.0wt%, immersing the cellulose sample into the hydrogen peroxide solution, and stirring at 120 ℃ for 12 hours until the sample completely appears white. Then taking out, washing with deionized water for many times, dispersing in deionized water again, regulating the concentration of cellulose fiber to 2.1 mg/ml -1, respectively adding methyltrimethoxysilane (0.6 ml), stirring for 1h, adding 0.004g ammonia water as a catalyst, then putting the cellulose fiber dispersion liquid into a refrigerator (-20 ℃) for freezing for 24h, putting the cellulose fiber dispersion liquid into a freeze dryer (-50 ℃) for freeze drying for 72h, and finally preparing the high-heat-insulation super-hydrophobic cellulose-based radiation refrigerating material with a multi-layer structure.
Examples 1-4 above are essentially the same, except that the bleaching treatment times are different. This is mainly because different bleaching times have a large influence on the size of the cellulose fibers. When the treatment time is shorter, the size of the prepared cellulose fiber is larger, and the cellulose fiber is not matched with sunlight wave bands, so that the cellulose fiber is unfavorable for passive radiation refrigeration in the daytime. Along with the extension of the bleaching time, the size of the cellulose fiber is continuously reduced, and the pore structure in the obtained fiber is increased due to the removal of residual lignin and hemicellulose, so that the scattering effect of the fiber on sunlight is further enhanced, and finally the aim of high sunlight reflection is fulfilled.
FIG. 1 is a graph showing the particle size distribution of cellulose fibers obtained by different bleaching treatment times in examples 1 to 4. From the figure it can be seen that the size of the cellulose fibres produced gradually decreases with increasing bleaching time.
Fig. 2 is a graph of the visible-near infrared reflectance spectrum of the highly thermally insulating, superhydrophobic cellulose-based radiant refrigerant materials with multi-layered structure prepared in examples 1-4. From the graph, as the fiber size is reduced, the reflectivity of the corresponding cellulose material is increased, and when the treatment time is 12 hours, the reflectivity of the prepared material to sunlight can reach more than 90 percent.
Fig. 3 is an emissivity spectrum of the highly insulating, super hydrophobic cellulose-based radiant refrigerant material with a multi-layered structure prepared in examples 1 to 4. As can be seen from the graph, the emissivity of the material in the wave band of the atmospheric window (8-13 μm) is more than 90%.
Fig. 4 is an SEM image of the cellulose fiber in example 4. From the figure, it can be seen that the prepared cellulose fiber has a natural multi-level aggregation state and a porous structure.
Fig. 5 is a temperature-time graph of the highly insulating, superhydrophobic cellulose-based radiant refrigerant material having a multi-layered structure prepared in example 4. Compared with the environment temperature, the high heat insulation and super-hydrophobic cellulose-based radiation refrigerating material with a multi-layer structure obtained in the embodiment 4 can achieve the cooling of 6.8 ℃ at the highest, which shows that the material has a good daytime passive radiation refrigerating effect.
Fig. 6 is a graph of water contact angle of the highly insulating, superhydrophobic cellulose-based radiation refrigerant material having a multi-layered structure prepared in example 4. The water contact angle of the high heat insulation and super-hydrophobic cellulose-based radiation refrigeration material with the multilayer structure can reach 153.6 degrees, and the super-hydrophobic effect is achieved.
The heat conductivity coefficient of the high heat insulation and super-hydrophobic cellulose-based radiation refrigerating material with a multilayer structure prepared in the example 4 is 0.03 W.m -1·K-1.
Example 5
Firstly, 100g of sodium sulfite/sodium hydroxide aqueous solution (namely, sodium sulfite/sodium hydroxide aqueous solution with the sodium sulfite concentration of 5.0wt percent and sodium hydroxide concentration of 10wt percent) with the mass ratio of (5/10/85 wt percent) is prepared, then 2.0g of bamboo powder is weighed and added into the sodium sulfite/sodium hydroxide aqueous solution, stirred for 5.0h at the temperature of 100 ℃, then the mixture is stood, and repeatedly washed by distilled water to obtain colorless transparent solution. Then preparing a hydrogen peroxide solution with the mass fraction of 6.0wt%, immersing the bamboo powder into the hydrogen peroxide solution, and stirring for 12 hours at 120 ℃ until the sample completely presents white. And then taking out, washing with deionized water for multiple times, then dispersing in deionized water again, regulating the concentration of cellulose fibers to 2.1 mg/ml -1, respectively adding methyltrimethoxysilane (0.6 ml), stirring for 1h, adding 0.004g of ammonia water as a catalyst, then putting the cellulose fiber dispersion liquid into a refrigerator (-20 ℃) for freezing for 24h, putting the cellulose fiber dispersion liquid into a freeze dryer (-50 ℃) for freeze drying for 72h, and finally preparing the super-hydrophobic high-heat-insulation aerogel material with radiation refrigeration.
Example 6
Firstly, 100g of sodium sulfite/sodium hydroxide aqueous solution (namely, sodium sulfite/sodium hydroxide aqueous solution with the sodium sulfite concentration of 6wt percent and sodium hydroxide concentration of 12wt percent) with the mass ratio of (6/12/82 wt percent) is prepared, then 2.0g of bamboo powder is weighed and added into the sodium sulfite/sodium hydroxide aqueous solution, stirred for 5.0h at the temperature of 100 ℃, then the mixture is stood and repeatedly washed by distilled water, so as to obtain colorless transparent solution. Then preparing a hydrogen peroxide solution with the mass fraction of 6.0wt%, immersing the cellulose sample into the hydrogen peroxide solution, and stirring for 12 hours at 120 ℃ until the cellulose completely presents white. And then taking out, washing with deionized water for multiple times, then dispersing in deionized water again, regulating the concentration of cellulose fibers to 2.1 mg/ml -1, respectively adding methyltrimethoxysilane (0.6 ml), stirring for 1h, adding 0.004g of ammonia water as a catalyst, then putting the cellulose fiber dispersion liquid into a refrigerator (-20 ℃) for freezing for 24h, putting the cellulose fiber dispersion liquid into a freeze dryer (-50 ℃) for freeze drying for 72h, and finally preparing the super-hydrophobic high-heat-insulation aerogel material with radiation refrigeration.
Example 7
Firstly, 100g of sodium sulfite/sodium hydroxide aqueous solution (namely, sodium sulfite/sodium hydroxide aqueous solution with the sodium sulfite concentration of 7.0wt percent and sodium hydroxide concentration of 14wt percent) with the mass ratio of (7/14/79 wt percent) is prepared, then 2.0g of bamboo powder is weighed and added into the sodium sulfite/sodium hydroxide aqueous solution, stirred for 5.0h at the temperature of 100 ℃, then the mixture is stood, and repeatedly washed by distilled water to obtain colorless transparent solution. Then preparing a hydrogen peroxide solution with the mass fraction of 6.0wt%, immersing the bamboo powder into the hydrogen peroxide solution, and stirring for 12 hours at 120 ℃ until the sample completely presents white. And then taking out, washing with deionized water for multiple times, then dispersing in deionized water again, regulating the concentration of cellulose fibers to 2.1 mg/ml -1, respectively adding methyltrimethoxysilane (0.6 ml), stirring for 1h, adding 0.004g of ammonia water as a catalyst, then putting the cellulose fiber dispersion liquid into a refrigerator (-20 ℃) for freezing for 24h, putting the cellulose fiber dispersion liquid into a freeze dryer (-50 ℃) for freeze drying for 72h, and finally preparing the super-hydrophobic high-heat-insulation aerogel material with radiation refrigeration.
The performance of the superhydrophobic high thermal insulation aerogel materials prepared in examples 5-7 was similar to the performance of the superhydrophobic high thermal insulation aerogel materials prepared in examples 1-4.
The foregoing embodiments have described the technical solutions and advantages of the present invention in detail, and it should be understood that the foregoing embodiments are merely illustrative of the present invention and are not intended to limit the invention, and any modifications, additions, substitutions and the like that fall within the principles of the present invention should be included in the scope of the invention.
Claims (5)
1. A method for preparing a cellulose-based radiation refrigeration aerogel material, which is characterized by comprising the following steps:
(1) Removing lignin in the natural cellulose raw material to obtain cellulose fibers;
(2) Treating cellulose fibers by adopting a bleaching solution, and regulating the size of the cellulose fibers to be 1.8-12 mu m;
the bleaching solution is at least one of hydrogen peroxide and sodium hypochlorite; in the bleaching solution, the mass fraction of hydrogen peroxide and/or sodium hypochlorite is 1-8wt%; the bleaching treatment temperature is 60-120 ℃; the bleaching treatment time is 12-24 hours;
(3) Dispersing the cellulose fibers treated in the step (2) into water, adding a cross-linking agent and a catalyst for reaction, and freeze-drying the reaction liquid after the reaction is finished to obtain a radiation refrigeration aerogel material; the solar reflectance of the radiation refrigeration aerogel material is more than 90%; the average emissivity of the atmospheric window is more than 90%; the heat conductivity coefficient is below 0.03W m -1·K-1;
the cross-linking agent is at least one of methyltrimethoxysilane, perfluorooctyl triethoxysilane and polyamide epichlorohydrin; the catalyst is ammonia water;
The concentration of cellulose fiber in the cellulose fiber dispersion liquid is 1.5-21 mg.ml -1; the mass fraction of the cross-linking agent is 1.0-8.0wt%; the mass fraction of the catalyst is 0.5-2.0 wt%;
the natural cellulose raw material is at least one of wood dust, ramie and bamboo.
2. The method for preparing a cellulose-based radiation-cooled aerogel material according to claim 1, wherein in step (1), a natural cellulose raw material is added into a delignification solution, and lignin is removed by heating and stirring; the delignification solution is at least one of sodium sulfite/sodium hydroxide aqueous solution, lithium bromide solution, dioxane and acetone.
3. The method for preparing a cellulose-based radiation-cooled aerogel material according to claim 2, wherein the delignification solution is sodium sulfite/sodium hydroxide aqueous solution; the sodium sulfite/sodium hydroxide aqueous solution has the concentration of 5-10wt% and the concentration of 10-20wt% of sodium hydroxide; in the step (1), the heating temperature is 80-100 ℃, and the heating time is 3-8 hours.
4. The method for preparing a cellulose-based radiation refrigerating aerogel material according to claim 1, wherein in the step (2), the size of the cellulose fiber is regulated and controlled to be 1.8-8 μm through bleaching treatment.
5. A cellulose-based radiation-based aerogel material, which is prepared by the preparation method according to any one of claims 1 to 4.
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