CN109607509A - A kind of preparation method of the full biomass-based carbon aerogels of high electromagnet shield effect - Google Patents
A kind of preparation method of the full biomass-based carbon aerogels of high electromagnet shield effect Download PDFInfo
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Abstract
The invention discloses a kind of preparation method of high full biomass-based carbon aerogels of electromagnet shield effect, required raw material is as follows: cellulose；Through following step: (1) raw material drying；(2) preparation of cellulose solution.(3) preparation of cellulose aerogels；(4) preparation of carbon aerogels.The present invention is using cellulose as presoma, regulate and control the continuous apertured topsheet multi-layered network structure of three-dimensional of cellulose aerogels by dissolution regeneration, cosolvent processing, freeze-drying, high temperature cabonization constructs stable and excellent conductive network (592.3S/m), realizes the efficient electromagnetic shielding performance of carbon aerogels (106.3dB).And presoma of the present invention is from a wealth of sources, environmentally protective, dicyandiamide solution is nontoxic, inexpensive, and material preparation process is simple, and technique is easy to grasp, and production cost is low, there is the great potential of large-scale production.
Description
Technical field
The present invention relates to full biomass-based carbon aerogels preparation technical fields, in particular to a kind of to have high electromagnetic shielding effect
The preparation method of energy cellulose base carbon aerogels.
Background technique
With the fast development of electronic science and technology, electronic equipment makes rapid progress, and is widely used in military, industrial and civilian
Equal fields, the following electromagnetic pollution, electromagnetic interference, the problems such as divulging a secret, not only interfere the normal operation of sophisticated electronics,
Also different degrees of harm (D.Chung et al.Carbon, 2001,39,279.) is generated to human organ, tissue and system.
Therefore, a kind of efficient electromagnetic shielding material is researched and developed, inhibits interference of the electromagnetic radiation to electronic equipment, protects the mankind not by electromagnetism
Wave radiation harm is of great significance.
The advantages that composite conducting polymer material (CPCs) is light with its, at low cost, easy processing, before being a kind of great application
Scape, Combined Electromagnetic Shielding Materials (J.M.Thomassin, et the al.Materials Science for being expected to substitution metal material
and Engineering:R:Reports,2013,74,211.).But conventional entity CPCs electromagnetic shielding material and air borne
There are apparent impedance mismatchs between medium, are electromagnetically shielded mechanism based on reflection of electromagnetic wave, it is anti-to generate a large amount of electromagnetic wave
It penetrates, causes secondary electromagnetic pollution.In view of the above problems, numerous studies pass through chemical blowing, supercritical CO2Foam, be freeze-dried,
The means such as particle leaching, 3D printing construct porous structure in CPCs to weaken impedance mismatch, while it is close that material is greatly reduced
Degree and cost.Such as Gupta (Gupta M, et al.Advanced Materials, 2005,17 (16), 1999) is using chemistry
Foaming is prepared for the carbon nano-tube/poly styrene porous C PCs that electromagnet shield effect reaches 20dB.Although the certain journey of porous structure
Degree alleviates the reflection of electromagnetic wave, but due to hole-closing structure and biggish density (0.56g cm-3), the electromagnetic shielding machine of this material
Reason is still based on reflection.Yan etc. (D.-X.Yan, et al.Journal of Materials Chemistry, 2012,22,
18772.) continuous through-hole and lower (the 0.45g cm of density are prepared for by particle leaching-3) graphene/polystyrene porous it is multiple
Condensation material, electromagnet shield effect reaches 29dB and shielding mechanism is mainly based on electro-magnetic wave absorption.The above porous C PCs material
Conductive path be strongly depend on high-content carbon system nanofiller addition, there are reunion, deteriorate mechanical property risk.And
The density of material is still larger, seriously limits it in the application of aerospace and field of microelectronic devices.
In recent years, by high temperature cabonization organic aerogel or by carbon nanomaterial (such as carbon nanotube, graphene) from group
The carbon aerogels of preparation are filled with its unique three-dimensional porous structure, extremely low density, high conductivity and good chemical stabilization
Property, it is considered to be a kind of high-efficiency electromagnetic shielding material of great potential.As Li et al. (Q.Li, et al.Carbon, 2016,104,
90.) organic aerogel of phenolic resin is prepared using sol-gel method, in the process the carbon nanometer in situ for introducing 2.0wt%
Pipe and 7.0wt% ferroso-ferric oxide, through carbonization treatment, acquisition density is 0.126g cm-3, electromagnet shield effect is~62dB
Compound carbon aerogels.Song etc. (Q.Song, et al.Advanced Materials, 2017,29,1701583.) successively passes through
Chemical vapor deposition and plasma reinforced chemical vapour deposition method generate carbon in nanometer silica line foam formwork surface in situ
Nanotube and multi-layer graphene, preparation density is only 0.009g cm-3The composite carbon airsetting for being 47.5dB with electromagnet shield effect
Glue.Gao etc. (C.Gao, et al.Carbon, 2018,135,44.) utilizes solution-cast, electronation, high-temperature heat expansion processing
Being prepared for density is 0.41g cm-3, electromagnet shield effect is the graphene carbon aeroge of 70~105dB.Although above-mentioned carbon airsetting
Glue shows excellent electromagnet shield effect, but still remains following problems: (1) organic aerogel material source height relies on
Petroleum resources；(2) chemical vapour deposition technique be prepared in situ carbon aerogels presoma is expensive, toxic and technical process is multiple
It is miscellaneous；(3) the carbon aerogels mechanical stability that carbon based nano-material is directly constructed is poor, and molding processing difficulty is big；(4) above method
Seldom it is related to the Effective Regulation of carbon aerogels pore structure.Therefore, develop it is a kind of come source green and environment-friendly, structure-controllable, technique it is easy
It is particularly important in the high electromagnet shield effect carbon aerogels of grasp in electromagnetic shielding field.
Summary of the invention
The present invention is using from a wealth of sources, environmentally protective cellulose as presoma, and by simply dissolving regeneration, cosolvent soaks
Bubble processing, the method being freeze-dried are prepared for structure-controllable, performance stabilization and the cellulose aerogels with three-dimensional porous structure,
It recycles high temperature cabonization processing to construct carbon aerogels three-dimensional net structure, prepares low-density, high conductivity, excellent electromagnetic shielding
The carbon aerogels of the multi-level three-dimensional sheet network structure of energy.Material preparation process is environmentally protective, and technique is easy to grasp.From current
From the point of view of the patent of application and the document delivered, using holocellulos material as presoma, high-efficiency electromagnetic shielding properties three is prepared
Porous carbon aerogels are tieed up to have not been reported.
The present invention is realized by following means:
A kind of preparation method of the full biomass-based carbon aerogels of high electromagnet shield effect, used raw material, reagent are as follows:
Raw material: cellulose；
Reagent: lithium hydroxide, urea, the tert-butyl alcohol, water；
The preparation method uses following step:
(1) cellulose is dry: cellulose is sufficiently dry；
(2) preparation of cellulose solution: at room temperature, will be dry in step (1) after cellulose be added to lithium hydroxide,
The in the mixed solvent of urea, water, stirring is until obtain the cellulose solution of stable transparent；
(3) preparation of cellulose aerogels: at room temperature, cellulose solution gelation in step (2) is formed into cellulose
Hydrogel；Then the cellulose aquagel is dipped in water, is washed to neutrality, to remove lithium hydroxide and urea, to be formed
Neutral fibre hydrogel；The neutral fibre hydrogel is dipped in the aqueous solution of the tert-butyl alcohol and is impregnated, freezing obtains gel state
Sample cryogenic freezing solid phase, then abundant lyophilization restore to obtain cellulose aerogels to room temperature；
(4) preparation of carbon aerogels: by step (3) resulting cellulose aerogels under protective gas or vacuum
High temperature cabonization then cools to room temperature acquisition carbon aerogels.
In the step (2), lithium hydroxide, urea, water mass ratio be (5~10): (10~20): (70~85).
In the step (2), lithium hydroxide, urea, water mixed solvent temperature be -20.0~0 DEG C.
In the step (2), the mass fraction of cellulose is 0.1~10wt% in the cellulose solution.
In the step (3), cellulose solution gelation is formed to gelling temperature≤80 DEG C of cellulose aquagel.
In the step (3), in the step (3), gelling temperature is 20~80 DEG C.
In the step (3), freeze slowly to freeze or being rapidly frozen.
In the step (3), the mass fraction of the tert-butyl alcohol is 0~100wt% in the aqueous solution of the tert-butyl alcohol.
In the step (4), the protective gas is one or more among helium, neon, argon gas or nitrogen.
In the step (4), carburizing temperature is 500~2500 DEG C.
The method of the present invention is to pass through dissolution regeneration, cosolvent processing, freeze-drying, pyrocarbon using cellulose as presoma
The method of change prepares the carbon aerogels with three-dimensional sheet network structure.Prepared carbon aerogels have low-density (0.158g
cm-3), high porosity (97.0%), excellent electrical conductivity (592.3S/m) the advantages of, electromagnet shield effect is up to 106.3dB.Separately
Outside, advantages of the present invention is also embodied in the following aspects:
(1) present invention prepares cellulose airsetting using the method that dissolution regeneration-cosolvent processing-freeze-drying combines
Glue can handle refinement hydrone crystal grain, stabilizing network structure by cosolvent；Utilize freezing rate regulation cellulose aerogels
Three dimensional skeletal structure is changed from threadiness to sheet, is laid the foundation for the preparation of function carbon aerogels.
(2) present invention is obtained by high temperature cabonization has sheet framework structure carbon aerogels, is obtaining the same of high conductivity
When, the network structure on chip of multistage multilayer time can increase incident electromagnetic wave in the transmission path of material internal, absorption loss is improved,
Obtain the electromagnetic shielding performance based on absorbing.
(3) present invention is from a wealth of sources, environmentally protective using cellulose as presoma；Alkalinuria dicyandiamide solution is nontoxic, it is environmentally friendly,
It is inexpensive；Material preparation process is simple, and technique is easy to grasp, and production cost is low, there is the great potential of large-scale production.
Detailed description of the invention
Fig. 1 is the microstructure scanning electron microscope diagram of (a) and (b) after carbonization before embodiment carbonization.
Fig. 2 is the microstructure scanning electron microscope diagram after comparative example 1 is carbonized.
Fig. 3 is the microstructure scanning electron microscope diagram after comparative example 2 is carbonized.
Fig. 4 is embodiment (2.0~4.0wt% of mass fraction of cellulose in cellulose solution) electrical property figure.
Fig. 5 is embodiment (the mass fraction 4.0wt% of cellulose in cellulose solution) electromagnetic shielding performance figure.
Specific embodiment
Example given below is to specific descriptions of the invention, it is necessary to which indicated herein is that following embodiment is only used
In the present invention is further illustrated, it should not be understood as limiting the scope of the invention, field person skilled in the art
Protection scope of the present invention is still fallen within according to the nonessential modifications and adaptations that aforementioned present invention content makes the present invention.This hair
Bright preparation process mainly includes three raw material drying, the preparation of cellulose aerogels and the preparation of carbon aerogels parts, hereinafter
The present invention will be described so that the degree of polymerization is 500 cellulose as an example.
Examples 1 to 36 (is shown in Table 1)
A kind of preparation method of high full biomass-based carbon aerogels of electromagnet shield effect of the invention, used raw material, examination
Agent is as follows:
Raw material: cellulose；
Reagent: lithium hydroxide, urea, the tert-butyl alcohol, water；
The preparation method uses following step:
(1) raw material drying: cellulose is sufficiently dry.
(2) preparation of cellulose solution: at room temperature, will be dry in step (1) after cellulose be added to lithium hydroxide,
The in the mixed solvent of urea, water, stirring is until obtain the cellulose solution of stable transparent；Step
(2) in, for example, lithium hydroxide: urea: the optional 8:15:77 of water quality ratio；The temperature of mixed solvent be low temperature compared with
It is good, for example temperature can choose -20.0 DEG C, -10.0 DEG C or 0 DEG C etc., be shown in Table 1；Stirring such as can be acute with the revolving speed of 3000r/min
Strong stirring.
(3) preparation of cellulose aerogels: at room temperature, cellulose solution gelation in step (2) is formed into cellulose
Hydrogel；Then the cellulose aquagel is dipped in water, is washed repeatedly, washing to neutrality, to remove lithium hydroxide and urea,
To form neutral fibre hydrogel；The neutral fibre hydrogel is dipped in the aqueous solution of the tert-butyl alcohol and is impregnated, is freezed
To gel-state specimen cryogenic freezing solid phase, then abundant lyophilization restores to obtain cellulose aerogels to room temperature.Step (3)
Middle gelling temperature≤80 DEG C that cellulose solution gelation is formed to cellulose aquagel, specifically for example, temperature can choose 0
DEG C, 10 DEG C, 20 DEG C, 50 DEG C or 80 DEG C etc., be shown in Table 1, such as can be in 50 DEG C or less gelation 1h or more；The aqueous solution of the tert-butyl alcohol
Mass fraction is shown in Table 1；Lyophilization can in temperature lower than -20 DEG C, air pressure lower than distilling under 100Pa, dry 30h or more compared with
It is good.
(4) preparation of carbon aerogels: step (3) resulting cellulose aerogels are high under protective gas or vacuum
Temperature carbonization, then cools to room temperature acquisition carbon aerogels.High temperature cabonization processing, cellulose aerogels are converted into carbon aerogels, obtain
Obtain stable, excellent conductive network and efficient electromagnet shield effect.In step (4), high temperature cabonization temperature is shown in Table 1, pyrocarbon
Change within 2h preferably.
Aqueous solution processing and freezing mode through the tert-butyl alcohol in step (3) regulate and control the ice of water phase in cellulose aquagel jointly
Brilliant size obtains the continuous aperture three-dimensional sheet of height or fibrous-network structure.
Comparative example 1 (is shown in Table 1)
Processing step uses:
(1) raw material drying: cellulose is sufficiently dry；
(2) preparation of cellulose solution: at room temperature, the cellulose obtained after drying in step (1) is added to temperature
Lithium hydroxide for -12.0 DEG C: urea: the in the mixed solvent of water (such as the optional 8:15:77 of mass ratio), stirring (such as can
To be vigorously stirred with the revolving speed of 3000r/min) until obtaining the cellulose solution of stable transparent；
(3) preparation of cellulose aerogels: at room temperature, by the transparent mixed liquor of cellulose in step (2) in temperature≤80
Gelation (such as can be in 50 DEG C or less gelation 1h or more) forms cellulose aquagel at DEG C, then by the cellulose water-setting
Glue is dipped in water, is washed repeatedly, washing to neutrality, to remove lithium hydroxide and urea, so that neutral fibre hydrogel is formed,
The neutral fibre hydrogel is freezed to obtain gel-state specimen cryogenic freezing solid phase, then abundant lyophilization is (such as in temperature
Degree is lower than -20 DEG C, air pressure lower than lyophilization 30h or more under 100Pa), restore to obtain cellulose aerogels to room temperature；
(4) preparation of carbon aerogels: by step (3) resulting cellulose aerogels under protective gas and vacuum
1200 DEG C of high temperature cabonizations, then cool to room temperature acquisition carbon aerogels.
Comparative example 2 (is shown in Table 1)
Processing step uses:
(1) raw material drying: cellulose is sufficiently dry.
(2) preparation of cellulose solution: at room temperature, the cellulose obtained after drying in step (1) is added to temperature
Lithium hydroxide for -12.0 DEG C: urea: the in the mixed solvent of water (such as the optional 8:15:77 of mass ratio), stirring (such as can
To be vigorously stirred with the revolving speed of 3000r/min) until obtaining the cellulose solution of stable transparent；
(3) preparation of cellulose aerogels: at room temperature, cellulose solution in step (2) is coagulated at temperature≤80 DEG C
Gelatinization (such as can be in 50 DEG C or less gelation 1h or more) forms cellulose aquagel, is then dipped in the cellulose aquagel
It in water, washs, is washed to neutrality, to remove lithium hydroxide and urea, to form neutral fibre hydrogel repeatedly；It will be in this
Property cellulose aquagel be dipped in the aqueous solution (mass fraction is shown in Table 1) of the tert-butyl alcohol and impregnate, freezing obtains gel-state specimen low temperature
Freeze solid phase, then abundant lyophilization (such as temperature lower than -20 DEG C, air pressure lower than lyophilization 30h under 100Pa with
On), restore to obtain cellulose aerogels to room temperature；
(4) preparation of carbon aerogels: under nitrogen atmosphere by cellulose aerogels obtained by step (3), in 1200 DEG C of high temperature
Carbonization, cooled to room temperature obtain carbon aerogels.
1 Examples 1 to 36 of table and comparative example 1~2 are formulated
Density, conductivity and the electromagnet shield effect of table 2 Examples 1 to 36 and comparative example 1~2
Above-mentioned cellulose can be, but not limited to as cellulose cotton short flannel.In step (2), the quality of lithium hydroxide, urea, water
Ratio is (5~10): (10~20): (70~85).In step (2), lithium hydroxide, urea, water low-temperature mixed solvent temperature
Preferably for -20.0~0 DEG C, cellulose can be carried out effective dissolution to degree in this temperature range.In step (3), it is slowly cold for freezing
Freeze or be rapidly frozen, for example can also be rapidly frozen using liquid nitrogen etc. using the slowly freezing such as refrigerator.In step (3), coagulate
Gelatinization temperature is 20~80 DEG C preferable, and cellulose solution is in the available abundant gelation of this temperature range.In step (3), uncle
The mass fraction of the aqueous solution of butanol can select within the scope of 0~100wt%.
In above-mentioned steps (4), carburizing temperature is 500~2500 DEG C preferable, can guarantee that sample is abundant in this temperature range
Graphitization, and keep the stability of its appearance structure.Above-mentioned protective gas can be among helium, neon, argon gas or nitrogen one
Kind is a variety of.
Morphology observation: for the feasibility and material three-dimensional for evaluating high electromagnet shield effect holocellulos base carbon aerogels preparation
The development law of porous microstructure, field emission scanning electron microscope (model Inspect-F, FEI Co.) be used to observe
Sample brittle failure face microscopic appearance.As shown in Figure 1a, slowly freezing-is dry using dissolution regeneration-cosolvent processing-for the embodiment
The cellulose carbon aerogels of dry method preparation, have stable structure, and integrality is high, the continuous three-dimensional sheet aperture network of height
Structure.After 1200 DEG C of high temperature cabonizations, aperture is substantially reduced, and hole wall is thinning, but the continuous sheet high porosity of sample
Obtain intact holding (Fig. 1 b).It can be seen that dissolution regeneration-cosolvent processing-freeze-drying-high temperature cabonization is that a kind of exploitation is low
Density (0.068g cm-3, be shown in Table 2), the continuous apertured topsheet multi-layered network structure holocellulos base carbon aerogels of height it is simple, high
Efficacious prescriptions method.Wherein, cosolvent processing and freezing method have effectively regulated and controled the microscopic appearance of material.As shown in Fig. 2, without tertiary fourth
The cellulose carbon aerogels of the water cosolvent processing of alcohol show large aperture, the non-uniform porous chips stratiform network structure of size,
And this poor structural integrity, machine-shaping difficulty are big.This is mainly due in slow refrigerating process, in cellulose aquagel
Water phase Ice crystal size it is big, cellulose is mutually ostracised, is enriched with and forms the structure of the big network in piece thickness, aperture (density is
0.097g cm-3, it is shown in Table 2).And cosolvent processing can induce water phase and form acicular crystal in refrigerating process, thus Effective Regulation
The size of ice crystal farthest keeps aeroge so that Ice crystal size and cellulose phase three-dimensional net structure match
The integrality of structure.In addition, the method for control rate of temperature fall also can effectively regulate and control the microscopic appearance of carbon aerogels sample.Such as figure
Shown in 3, comparative example 2 shows that aperture is small, continuous aperture fibrous-network structure (density 0.082g of size distribution uniform
cm-3, it is shown in Table 2).This is because water phase nucleation site is more in cellulose aquagel, crystal using the rapid freezing method of liquid nitrogen cooling
Growth rate is limited, to obtain the lesser crystalline size of size, cellulose mutually can only be gathered into fiber tufted in finite time
Structure.The above result shows that the method for its " dissolution regeneration-cosolvent processing-freeze-drying-high temperature cabonization " of the present invention
The microscopic appearance of cellulose base carbon aerogels can effectively be regulated and controled, be research pore structure (diameter, skeleton etc.) to carbon aerogels material
The influence of material electromagnet shield effect is laid a good foundation.
Electrical property and electromagnetic shielding performance: electrical property and electricity in order to investigate cellulose base carbon aerogels electromagnetic shielding material
Four probe of RTS-8 type (four probe Science and Technology Ltd. of Guangzhou, China) and N5274A type is respectively adopted in magnetic shield performance
Agilent vector network analyzer (Agilent, the U.S.) has carried out electrical property and electromagnetic shielding performance to embodiment and comparative example
Test, as a result as shown in Fig. 4,5 and table 2.When the mass fraction of cellulose in cellulose solution is only 2.0wt%, embodiment
The electrical property of sample has reached 47.3S/m, this, which has benefited from high temperature cabonization process, can remove the oxygen-containing official on cellulosic molecule surface
It can roll into a ball, its carbon chain backbone of exposure improves the regularity of strand；And under high temperature, cellulose molecular chain can be from six carbon glucose
Based structures are excessive to four carbon intermediate states, ultimately form the carbonization structure of class aromatic ring.This structure is beneficial to free electron and exists
Migration inside strand, to assign material excellent conductivity.With the mass fraction of cellulose in cellulose solution
Increase, more cellulose molecular chains can flock together under the squeezing action of ice-crystal growth, so that sample interior porous web
Network is more closely knit, forms more perfect conductive network, shows superior electrical property.When the matter of cellulose in cellulose solution
When amount score is 4.0wt%, the conductivity of embodiment sample is improved to 276.3S/m.And comparative example 1 is due at without cosolvent
Reason leads to the undue growth of ice crystal, shows more closely knit sheet packed structures, conductive network is even closer, and conductivity is higher
(310.9S/m).Closely knit, the continuous fibrous-network structure because fast freezing is formed of comparative example 2, also shows excellent conductance
Rate (416.6S/m).
As shown in table 2, when solution concentration is 2.0wt%, the electromagnet shield effect of carbon aerogels is 32.5dB, has been expired
The requirement (20.0dB) of sufficient business electromagnetic shielding material.With the increase of the mass fraction of cellulose in cellulose solution, implement
The electromagnetic shielding performance of example carbon aerogels sample shows changing rule identical with electrical property, the electromagnetic shielding performance of sample from
32.5dB increasing to 106.3dB.On the one hand the excellent electromagnet shield effect of cellulose base carbon aerogels is attributed to material because of high temperature
Be carbonized the excellent electrical properties assigned, is on the other hand since electricity can be significantly increased in the closely knit sheet porous network (Fig. 1 b) of sample
Motion path of the magnetic wave after incident sample and increase absorption loss, improve electromagnet shield effect.But 1 sample of comparative example is loose
Macroporous structure is unfavorable for the multiple reflections loss of electromagnetic wave, and electromagnet shield effect is only 15.3dB.Comparative example 2 is also because it is internal fine
The skeleton structure of dimension shape can not form effective absorption loss to the electromagnetic wave inside incident material, can only also obtain 40.6dB's
Electromagnet shield effect.By the shielding mechanism (Fig. 5) of analysis of material, discovery is slowly freezed obtained embodiment cellulose base carbon
Aeroge shows the electromagnetic shielding mechanism based on absorbing.This is mainly due to the low-density of material, high porosity and uniqueness
The continuous apertured topsheet multi-layered network structure of height.When the high porosity of carbon aerogels can significantly reduce electromagnetic wave incident material surface
Impedance mismatch phenomenon, reduce reflection loss；Electromagnetism inside continuous apertured topsheet multi-layered network structure multipath reflection material
Wave dramatically increases absorption loss.In conclusion of the present invention prepares high electromagnet shield effect cellulose base carbon aerogels tool
The characteristics such as standby low-density, high porosity, excellent electrical conductivity, material preparation process is simple, and technique is easy to grasp, and production cost is low,
There is the great potential of large-scale production.
Claims (10)
1. a kind of preparation method of the full biomass-based carbon aerogels of high electromagnet shield effect, used raw material, reagent are as follows:
Raw material: cellulose；
Reagent: lithium hydroxide, urea, the tert-butyl alcohol, water；
The preparation method uses following step:
(1) raw material drying: cellulose is sufficiently dry；
(2) preparation of cellulose solution: at room temperature, the cellulose in step (1) after drying is added to lithium hydroxide, urine
The in the mixed solvent of element, water, stirring is until obtain the cellulose solution of stable transparent；
(3) preparation of cellulose aerogels: at room temperature, cellulose solution gelation in step (2) is formed into cellulose water-setting
Glue；Then the cellulose aquagel is dipped in water, is washed to neutrality, to remove lithium hydroxide and urea, to form neutrality
Cellulose aquagel；The neutral fibre hydrogel is dipped in the aqueous solution of the tert-butyl alcohol and is impregnated, freezing obtains gel-state specimen
Cryogenic freezing solid phase, then abundant lyophilization restore to obtain cellulose aerogels to room temperature；
(4) preparation of carbon aerogels: by step (3) resulting cellulose aerogels high temperature under protective gas or vacuum
Carbonization, then cools to room temperature acquisition carbon aerogels.
2. preparation method according to claim 1, which is characterized in that in the step (2), the matter of lithium hydroxide, urea, water
Amount ratio is (5~10): (10~20): (70~85).
3. preparation method according to claim 1, which is characterized in that in the step (2), lithium hydroxide, urea, water it is mixed
The temperature of bonding solvent is -20.0~0 DEG C.
4. preparation method according to claim 1, which is characterized in that in the step (2), cellulose in cellulose solution
Mass fraction is 0.1~10wt%.
5. preparation method according to claim 1, which is characterized in that in the step (3), by cellulose solution gelation shape
At gelling temperature≤80 DEG C of cellulose aquagel.
6. preparation method according to claim 4, which is characterized in that the gelling temperature is 20~80 DEG C.
7. preparation method according to claim 1, which is characterized in that in the step (3), freeze slowly to freeze or quickly
Freezing.
8. preparation method according to claim 1, which is characterized in that in the step (3), in the aqueous solution of the tert-butyl alcohol
The mass fraction of the tert-butyl alcohol is 0~100wt%.
9. preparation method according to claim 1, which is characterized in that in the step (4), the protective gas be helium,
It is one or more among neon, argon gas or nitrogen.
10. preparation method according to claim 1, which is characterized in that in the step (4), carburizing temperature is 500~2500
℃。
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