CN113860284A - Method for simply and ultra-quickly preparing carbon aerogel - Google Patents
Method for simply and ultra-quickly preparing carbon aerogel Download PDFInfo
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Abstract
The invention discloses a simple and ultrafast method for preparing carbon aerogel, which comprises mixing graphite-like microcrystalline carbon nano-material, phenol, formaldehyde, catalyst and deionized water into uniform suspension, sealing and standing to realize gelation; and then aging the gel in an oven, drying in a tubular furnace, and carbonizing to obtain the carbon aerogel. According to the method, the graphite-like microcrystalline carbon nano material is added, so that the phenolic solution can be quickly gelatinized at normal temperature, the phenolic gel can be quickly heated and dried under normal pressure, and finally, the time required by the whole preparation process of the carbon aerogel is rapidly reduced to within 1 day from 1-2 weeks in the past. Meanwhile, the carbon aerogel block prepared by the technology has no crack, high specific surface area, developed pore structure, excellent mechanical property and conductivity, and is a quick and simple carbon aerogel preparation method.
Description
Technical Field
The invention relates to the technical field of carbon materials, in particular to a simple and ultra-fast method for preparing carbon aerogel.
Background
The carbon aerogel is a novel porous carbon material with a three-dimensional network structure and is obtained by carbonizing organic aerogel. Since the carbon gel was invented in the early 90 s of the 20 th century, with the continuous and deep research, people gradually realize that the carbon gel has excellent performances of adsorption, catalysis, electric conduction, heat insulation and the like, and has wide application potential in many fields of chemical industry, energy, electronics and the like. However, although carbon aerogel has been studied for decades, the preparation process is tedious, long-lasting and high-cost, so that the industrial production of carbon aerogel is not really realized at present. The relatively mature carbon aerogel is prepared by adopting resorcinol and formaldehyde as raw materials, and sequentially forming phenolic sol and hydrogel in aqueous solution through condensation and polymerization reaction between the resorcinol and the formaldehyde under the condition of a small amount of alkali catalysts such as sodium carbonate and the like; then the hydrogel is aged, dried and carbonized to prepare the carbon gel. The main challenges of the industrial production of carbon gel at present are derived from the following 2 aspects: (1) the sol, gel and sol aging process of resorcinol and formaldehyde solution needs to be continuously carried out for 3-4 days at the temperature of 60-90 ℃; (2) drying methods and times are cumbersome and costly. The reason is that the organic hydrogel contains a large amount of polar solvent water, and before carbonization, if the water cannot be removed, the water is quickly evaporated in the temperature rise process to form an interface with large surface tension between the surface of the organic gel and air, so that very large contraction pressure is generated, the carbon aerogel is cracked or even collapsed, the carbon aerogel in a block shape or a certain forming shape cannot be prepared, and meanwhile, the carbon aerogel with a developed pore structure cannot be obtained due to the large collapse or contraction of pores. In general, it is necessary to remove a large amount of water contained in the organic hydrogel by means of supercritical carbon dioxide extraction. The specific operation process is as follows: in order to reduce the huge surface tension generated in the organic gel in the supercritical carbon dioxide extraction process, firstly, organic solvents with large dissolving capacity in water such as acetone and the like are adopted to extract moisture in the organic gel for multiple times in a grading manner, and then the gel containing a large amount of organic volatile solvents such as acetone and the like is extracted under supercritical carbon dioxide fluid, so that the purposes of removing moisture and obtaining the massive organic aerogel with strong mechanical strength, good formed body maintenance and no crack are achieved. In the process of extracting a large amount of water from sol by using an organic solvent, the mixed solution of acetone and water is required to be adopted, the concentration of acetone is gradually increased, and the step-by-step extraction is carried out, so that the good appearance and the mechanical strength of the gel can be guaranteed, and therefore, the process not only needs to use a large amount of organic volatile solvents, but also is very tedious and needs to spend 3-4 days. The supercritical extraction process is carried out under the pressure of dozens of MPa, has high requirements on equipment conditions and is difficult to prepare on a large scale. Therefore, in general, not only the preparation process of carbon aerogel is very complicated, but also a preparation period takes as long as 10 days or more, which results in high price and difficulty in industrialization.
In view of the above problems, a great deal of research work has been conducted on (1) how to shorten the preparation time of the carbon aerogel, (2) how to use a more simple and efficient drying method, and the like. In methods that reduce the preparation time, mainly the sol-gel preparation process, the shortest gel time can be reduced to about 1 day using relatively high concentrations of alkaline (e.g., sodium carbonate) catalysts. In the research of the drying method, the freeze drying method is directly adopted, but the freeze drying is a process with high energy consumption and long time (several days are needed) because the hydrogel contains a large amount of water. The simplest drying method adopted at present is slow drying at normal temperature and normal pressure, and the slow drying of the hydrogel at normal temperature and normal pressure is realized by controlling the internal connection structure of the hydrogel in the prior research; this drying process is convenient but takes several days and places more specific requirements on the internal structure of the hydrogel, otherwise gel breakage can easily occur. Although many researches are carried out on rapid preparation and simple and cheap drying methods, the researches do not simultaneously solve the problems of the two aspects, namely the rapid preparation of sol and gel is realized, but the simple normal-temperature normal-pressure drying method is difficult to adopt; or simple normal temperature and normal pressure drying is realized, but a rapid sol-gel preparation process is not realized. The reason is that the hydrogel prepared by the rapid gelling method researched at present is difficult to be consistent with the hydrogel structure required by the normal-temperature normal-pressure drying method. These methods and techniques also have difficulty solving the technical difficulties of the carbon aerogel preparation process.
Disclosure of Invention
Aiming at the defects in the prior art, the method for preparing the carbon aerogel simply and ultra-quickly is provided.
In order to solve the technical problem, the technical scheme adopted by the application is as follows:
a simple and ultra-fast method for preparing carbon aerogel comprises the following steps:
1) uniformly dispersing graphite-like microcrystalline carbon nano-material, phenol, formaldehyde solution and catalyst in water to prepare mixed solution; wherein the mass ratio of the graphite-like microcrystalline carbon nano material to phenol is 1: 1-7, the molar ratio of phenol to formaldehyde is 1: 1.5-3, and the molar ratio of phenol to sodium carbonate is 50-1500: 1;
2) sealing and standing the mixed solution prepared in the step 1) for 5-120 min at 20-40 ℃ for sol-gelation to obtain hydrogel;
3) heating the hydrogel prepared in the step 2) to 40-120 ℃ at a heating rate of 0.5-5 ℃/min, and aging for 3-12 h;
4) heating the aged hydrogel obtained in the step 3) to 80-100 ℃ at a heating rate of 0.5-2 ℃/min, and drying the hydrogel for 1-2 hours at normal pressure;
5) directly heating the gel dried in the step 4) to 800-1000 ℃ at a heating rate of 1-5 ℃/min, carbonizing for 1-3 h, and cooling to obtain the carbon aerogel.
The graphite-like microcrystalline carbon nano material is prepared from charcoal, bamboo charcoal, coconut shell carbon, wood activated carbon, coconut shell activated carbon and coal activated carbon serving as raw materials.
The phenol is selected from phenol, resorcinol and cresol.
The catalyst is selected from one of sodium carbonate, potassium hydroxide, sodium hydroxide and ammonia water.
In the step 1), mixing by adopting a mechanical stirring or ultrasonic method; when ultrasonic mixing is adopted, the ultrasonic time is less than 5 min.
In the step 1), the mixing mode is as follows: firstly, preparing a graphite-like microcrystalline carbon nano material into a uniformly dispersed suspension, and then adding phenol, a catalyst and a formaldehyde solution.
In the step 2), the standing temperature of the mixed solution is preferably 25-35 ℃, and the standing time is preferably 10-30 min.
In the step 3), the temperature rise rate for aging is preferably 2-3 ℃/min, and the aging temperature is preferably 90-110 ℃; in the temperature rising process, the temperature is firstly raised to 90 ℃, the aging is carried out for 2-7 h, then the temperature is raised to 100-110 ℃, and the aging is carried out for 1-2 h.
In the step 4), in the drying process, the heating rate is preferably 0.5-1 ℃/min, the hydrogel is preferably directly heated to 80-100 ℃, and the hydrogel is dried for 1-2 hours under normal pressure.
In the step 5), in the carbonization process, the carbonization atmosphere is preferably inert atmosphere, and the heating rate is preferably 2-3 ℃/min.
The graphite-like microcrystalline carbon nano material is a novel carbon nano material invented by the applicant in recent years (a graphite-like microcrystalline carbon nano material and a preparation method and application thereof, CN201780002578.2, Japanese Tejing No. 6762417, US16/307,508). The catalyst is prepared by Selective oxidation from raw materials such as charcoal, bamboo charcoal, biomass charcoal and the like with abundant sources, and the yield can exceed 80% (Selective oxidation reaction porous biomass-based activated carbon antibodies in organic crystalline substances, carbon, 2018, 140: 504-507). The prepared graphite-like microcrystalline carbon nano material has high-concentration oxygen-containing polar groups, can be uniformly dispersed in water at high concentration, and the dispersed concentration can reach 50mg/mL (water). The applicant of the invention researches and discovers that the graphite-like microcrystalline carbon nano material can be highly dispersed in a phenolic aldehyde aqueous solution, can remarkably catalyze the phenolic aldehyde gelation process, enables resorcinol and formaldehyde solutions to realize gelation at normal temperature, enables hydrogel prepared by rapid gelation at normal temperature to be directly heated at normal pressure to realize rapid drying, and finally enables the whole preparation process of carbon aerogel to be rapidly reduced from about one week in the past to within 1 day, thereby achieving the purpose of simply and ultra-rapidly preparing the carbon aerogel.
Has the advantages that: compared with the prior art, the method can realize the rapid and simple preparation of the carbon aerogel. The graphite-like microcrystalline carbon nano material is added, so that not only can the rapid gelation of the phenolic solution be realized at normal temperature, but also the direct heating and rapid drying of the phenolic gel under normal pressure can be realized, and finally the phenolic carbon can be obtainedThe time required by the whole preparation process of the aerogel is sharply reduced to within 1 day from 1-2 weeks in the past. Moreover, the technology can prepare carbon aerogel block without any crack, and has high specific surface area, excellent mechanical property and conductivity. The compressive strength of the material can reach more than 80MPa, and the conductivity of the material can reach 27S.cm-1The specific surface area reaches 600m2The specific pore volume reaches 1.0cm3In which the pore structure is highly developed. In contrast, if the graphite-like microcrystalline carbon nanomaterial is not added, gelation of the phenolic solution cannot be realized at normal temperature.
Drawings
FIG. 1 is a physical representation of carbon aerogels prepared in examples 1-4 (a, b) and a physical representation of dried organogels prepared without the addition of graphite-like microcrystalline carbon nanomaterials (c);
FIG. 2 is a graph of the surface topography (SEM pictures) of a carbon aerogel prepared with (a) and without (b) the addition of graphite-like microcrystalline carbon nanomaterial (comparative example 2);
FIG. 3 is a plot of the nitrogen adsorption isotherms of the carbon aerogels prepared in examples 1-4;
FIG. 4 is a graph of pore size distribution of the carbon aerogels prepared in examples 1-4.
Detailed Description
The simple and ultra-fast preparation method of the carbon aerogel comprises the following steps:
(1) uniformly dispersing graphite-like microcrystalline carbon nano materials, phenol, formaldehyde and a catalyst in water at a mass ratio of 1: 1-7, a molar ratio of the phenol to the formaldehyde of 1: 1.5-3 and a molar ratio of the phenol to the catalyst of 50-1500: 1, and preparing a mixed solution at room temperature. The phenol is phenol, resorcinol, cresol, etc.; the graphite-like microcrystalline carbon nano material is prepared from one of charcoal, bamboo charcoal, coconut shell carbon, wood activated carbon, coconut shell activated carbon, coal activated carbon and the like; the catalyst is one of sodium carbonate, potassium hydroxide, sodium hydroxide and ammonia water.
(2) And (2) sealing and standing the mixed solution of the graphite-like microcrystalline carbon nano material prepared in the step (1), phenol, formaldehyde and sodium carbonate at the temperature of 20-40 ℃ for 5 min-2 h, and carrying out sol-gelation.
(3) Heating the hydrogel prepared in the step (2) to 40-120 ℃ at a heating rate of 0.5-5 ℃/min, and aging for 3-12 h;
(4) heating the hydrogel prepared in the step (3) to 90-100 ℃ at a heating rate of 0.5-2 ℃/min, and drying for 1-3 h;
(5) and finally, directly heating the dried gel to 800-1000 ℃ at the heating rate of 1-5 ℃/min, carbonizing for 1-3 h, and cooling to obtain the carbon aerogel.
In the invention, the graphite-like microcrystalline carbon nano material, the phenol, the formaldehyde and the catalyst are mixed in water, and mechanical stirring or an ultrasonic method is adopted, and the ultrasonic method is preferred. If ultrasonic mixing is used, the sonication time is recommended to be less than 5 min. The mixing mode can be that firstly the graphite-like microcrystalline carbon nano material is prepared into evenly dispersed suspension, and then phenol, catalyst and formaldehyde solution are added; mixing the four together may also be employed; the first mode is preferred. Deionized water is preferably selected as water for mixing, and the total water consumption is 10-30 times, preferably 15-25 times of the total mass of the carbon nano material and the phenol. (adjusted the data by student's accounting)
In the present invention, the sol-gelation temperature of the mixed solution in step (2) is preferably 25 to 30 ℃, and the gelation time is preferably 10 to 30 min. During the gelation process, ultraviolet light irradiation may be assisted to promote the gelation process.
In the step (3), the temperature rise rate for aging is preferably 2-3 ℃/min, and the aging temperature is preferably 90-110 ℃. In the temperature rising process, a temperature programming aging mode can be selected, namely, the temperature is firstly raised to 80-90 ℃ and aged for 2-7 h, then the temperature is raised to 100-110 ℃ and aged for 1-2 h; or directly heating to 80-120 ℃, preferably 90-110 ℃, and preferably aging for 6-10 h. The first mode is preferred. The aging process can be assisted by ultraviolet light illumination to promote the aging process.
In the step (4), the temperature rise rate is preferably 0.5-1 ℃/min.
In the step (5), the carbonization atmosphere can be inert atmosphere such as nitrogen or argon, and can also be spontaneous atmosphere; an inert atmosphere is preferred. In the heating process, different heating rates can be set in different temperature areas, a lower heating rate is suitable for a lower temperature area, and a faster heating rate can be adopted in a higher temperature area. A temperature rise rate may also be employed, in which case the temperature rise rate is preferably 2 to 3 ℃/min. The carbonized carbon aerogel formed body has no crack and excellent mechanical property and electric conductivity. The carbon aerogel molded body to be produced may have a cylindrical shape, a discoidal shape, a square shape or the like, depending on the shape of the vessel used in the gelling process.
In order to fully understand the present invention, the following examples are given to illustrate the specific embodiments of the present invention and the properties of the prepared carbon aerogel in more detail. The present invention may be embodied in other specific forms than those herein described and it will be recognized by those skilled in the art that similar language is used herein without departing from the spirit and scope of the invention as defined by the appended claims and therefore, it is not intended that the invention be limited to the specific embodiments disclosed below.
Example 1
According to the molar ratio of resorcinol to sodium carbonate of 500: 1 and the mass ratio of the graphite-like microcrystalline carbon nano material to resorcinol of 1: 2, the graphite-like microcrystalline carbon nano material, resorcinol and sodium carbonate are mixed with deionized water of which the mass is 20 times that of the mixture, and the mixture is stirred to form uniform suspension. Then, 37% of formaldehyde was slowly dropped into the suspension in a molar ratio of resorcinol to formaldehyde of 1: 2, sonicated for 2 minutes, and then they were sealed in a beaker and left to stand at 25 ℃ for 25 minutes to effect gelation. Then the gel in the sealed state is transferred to an oven, heated to 90 ℃ for 6h at the heating rate of 2 ℃/min, and then aged for 1h at the heating rate of 105 ℃. Taking out the gel from the sealed container, directly heating the gel in a tubular furnace at a heating rate of 1 ℃/min to 90 ℃, and drying the gel for 2 hours to obtain dry organogel; and then continuously heating to 900 ℃ in a tubular furnace at the heating rate of 2 ℃/min in the nitrogen atmosphere, and carbonizing for 2h to obtain the carbon aerogel. This sample was designated as GCN-RF-R2G.
Example 2
A carbon aerogel was prepared as in example 1, except that the mass ratio of the graphite-like microcrystalline carbon nanomaterial to resorcinol was 1: 3. The prepared carbon aerogel has a sample number of GCN-RF-R3G.
Example 3
A carbon aerogel was prepared as in example 1, except that the mass ratio of the graphite-like microcrystalline carbon nanomaterial to resorcinol was 1: 4. The prepared carbon aerogel has a sample number of GCN-RF-R4G.
Example 4
A carbon aerogel was prepared as in example 1, except that the mass ratio of the graphite-like microcrystalline carbon nanomaterial to resorcinol was 1: 5. The prepared carbon aerogel has a sample number of GCN-RF-R5G.
Comparative example 1
In the same manner as in example 1, but without the addition of graphite-like microcrystalline carbon nanomaterial.
The method comprises the following specific steps: mixing resorcinol, formaldehyde and sodium carbonate according to the molar ratio of the resorcinol to the sodium carbonate of 1: 50-500 and the molar ratio of the resorcinol to the formaldehyde of 1: 2, and dissolving the mixture in deionized water of 5-8 times. Sealing the mixture in a beaker, standing the mixture at 25-30 ℃, and observing the gelation condition.
Comparative example 2
The same drying method as in example 1 was used, but no graphite-like microcrystalline carbon nanomaterial was added; in order to ensure that gelation is achieved without adding graphite-like microcrystalline carbon nanomaterials, the conventionally generally used conditions for gelation of resorcinol and formaldehyde are employed.
The method comprises the following specific steps: resorcinol, formaldehyde and sodium carbonate were mixed uniformly with a molar ratio of resorcinol to formaldehyde of 1: 2 and a molar ratio of resorcinol to sodium carbonate catalyst of 100: 1 (if 500: 1 of example 1 is used, it is difficult to obtain gel in a conventional time), then sealed in a beaker and heated in a water bath to 80 ℃ (instead of normal temperature), allowed to stand at this temperature for 48h to achieve gelation, then heated to 90 ℃ again and aged for 72h or more, and after taking out the gel, heat-dried according to the conditions of example 1. And then heating to 900 ℃ in a tubular furnace at the heating rate of 2 ℃/min in the nitrogen atmosphere, and carbonizing for 2 hours to obtain the carbon aerogel.
To observe the integrity of the samples, FIGS. 1a and b show photographs of carbon aerogels prepared from examples 1-4, otherwise similar. As can be seen from fig. 1, the prepared carbon aerogel maintained a complete and regular cylindrical shape, had a smooth surface, and was free from any cracks. In the case of comparative example 1, it was found that gelation could not be achieved even after being left for one week, which is in agreement with the previous research results, that gelation of resorcinol and formaldehyde could not be achieved at normal temperature. Under the conditions of comparative example 2, i.e., the sol gelation temperature was 80 ℃, gelation could be achieved within 48 hours, but when direct heat drying was employed, a regular gel could not be obtained, all of which were broken, and the photograph thereof is shown in FIG. 1 c. These comparisons fully demonstrate that the key to the process is the use of graphite-like microcrystalline carbon nanomaterials. Through theoretical analysis and further research, the fact that the graphite-like microcrystalline carbon nano material can remarkably catalyze resorcinol and formaldehyde polymerization reaction in the preparation process of the carbon aerogel, provides strong supporting effect to resist huge surface tension brought by a rapid drying process, and can construct a rapid channel for water transportation on the surface of the gel (figure 2a), while the carbon aerogel prepared without adding the graphite-like microcrystalline carbon nano material (comparative example 2) is a more compact structure (figure 2 b). Therefore, under the condition of adding the graphite-like microcrystalline carbon nano material, rapid gelation can be realized at normal temperature, and the organic gel is directly heated and dried under normal pressure, so that the process is simple and convenient, the preparation time is greatly shortened, and the drying and carbonization processes are integrated into a heating continuous operation process; solves the technical problem of preparing carbon aerogel in the past.
In order to further understand the structure and performance of the carbon aerogel prepared by the application, the structure of the carbon aerogel is observed by using a Scanning Electron Microscope (SEM), the adsorption isotherm and the pore size distribution of the carbon aerogel are analyzed by using a nitrogen adsorption method, and the specific surface area, the total specific pore volume and the mesopore volume are calculated; the compressive strength of the carbon aerogel is tested by adopting a universal testing machine, and the conductivity of the carbon aerogel is tested by adopting a multifunctional digital four-probe tester. The pore structure, density, compressive strength and electrical conductivity data of the carbon aerogels prepared in examples 1-4 are shown in table 1. The nitrogen adsorption isotherms and pore size profiles of the carbon aerogels prepared in examples 1-4 are shown in fig. 3 and 4, respectively. As can be seen from the table 1, the figures 3 and the figure 4, the carbon aerogel prepared by the method has a high specific surface area and a developed mesoporous structure, the specific surface area of the carbon aerogel is similar to that of the carbon aerogel prepared by long-time gelling, aging, freeze drying and supercritical drying which are adopted in the prior art, and the addition amount of the graphite-like microcrystalline carbon nano material can regulate and control the mesoporous structure of the carbon aerogel in a large range of pore sizes of 4-20 nm; the carbon aerogel prepared by the method also has very high compressive strength and conductivity, which shows that the technology of the invention can obtain a high-strength carbon aerogel product even if a quick and simple drying method is adopted, breaks through the key problem of the carbon aerogel preparation technology and produces obvious effects.
TABLE 1 pore structure, compressive strength, and conductivity data for the carbon aerogels prepared
| Sample (I) | Example 1 | Example 2 | Example 3 | Example 4 |
| Specific surface area (S)BET，m2/g) | 507 | 539 | 595 | 658 |
| Total pore volume (cm)3/g) | 0.600 | 0.786 | 1.018 | 1.162 |
| Pore volume (cm) of micropores3/g) | 0.195 | 0.208 | 0.231 | 0.252 |
| Pore volume of mesopores (cm)3/g) | 0.405 | 0.578 | 0.787 | 0.910 |
| Average pore width (nm) | 7.1 | 8.9 | 13.3 | 20.9 |
| Density (g/cm)3) | 0.79 | 0.61 | 0.44 | 0.41 |
| Compressive strength (MPa) | 82 | 72 | 32 | 24 |
| Conductivity (S/cm) | 27 | 18 | 12 | 9 |
Example 5
According to the molar ratio of resorcinol to sodium carbonate of 250: 1 and the mass ratio of the graphite-like microcrystalline carbon nano material to resorcinol of 1: 3, the graphite-like microcrystalline carbon nano material, resorcinol and sodium carbonate are mixed with deionized water of which the mass is 20 times that of the mixture, and the mixture is stirred to form uniform suspension. Then, 37% of formaldehyde was slowly dropped into the suspension in a molar ratio of resorcinol to formaldehyde of 1: 2, sonicated for 2 minutes, and then they were sealed in a beaker and left to stand at 25 ℃ for 30 minutes to effect gelation. Then the gel in the sealed state is transferred to an oven, heated to 90 ℃ for 6h at a heating rate of 1 ℃/min, and then aged for 1h at a heating rate of 105 ℃. Taking out the gel from the sealed container, directly heating the gel in a tubular furnace at a heating rate of 1 ℃/min to 90 ℃, and drying the gel for 2 hours to obtain dry organogel; and then continuously heating to 900 ℃ in a tubular furnace at the heating rate of 2 ℃/min in the nitrogen atmosphere, and carbonizing for 2h to obtain the carbon aerogel. This sample was designated as GCN-C1/250.
Example 6
A carbon aerogel was prepared as in example 5, except that the molar ratio of resorcinol to sodium carbonate catalyst was 500: 1. The prepared carbon aerogel has a sample number of GCN-C1/500.
Example 7
A carbon aerogel was prepared as in example 5, except that the molar ratio of resorcinol to sodium carbonate catalyst was 1000: 1. The prepared carbon aerogel sample number is marked as GCN-C1/ 1000.
The carbon aerogels prepared in examples 5 to 7 are formed carbon aerogels without any cracks, and the data of density, compressive strength, electric conductivity, specific surface area, specific pore volume and the like are shown in table 2. The data in Table 2 show that even with very low catalyst usage, carbon aerogel molded bodies with high strength, good electrical conductivity and highly developed mesoporous structure can be produced.
Table 2 density, strength, conductivity and pore structure of carbon aerogels prepared in examples 5-7
| Sample (I) | GCA-C1/250 | GCA-C1/500 | GCAC1/1000 |
| Specific surface area (S)BET，m2/g) | 607 | 550 | 533 |
| Total pore volume (cm)3/g) | 1.09 | 0.794 | 0.666 |
| Pore volume (cm) of micropores3/g) | 0.228 | 0.211 | 0.200 |
| Pore volume of mesopores (cm)3/g) | 0.862 | 0.583 | 0.466 |
| Density (g/cm)3) | 0.67 | 0.60 | 0.50 |
| Compressive strength (MPa) | 59 | 73 | 47 |
| Conductivity (S/cm) | 19 | 17 | 15 |
Example 8
Carbon aerogels were prepared in the manner of example 7, except that irradiation with ultraviolet light was assisted in the aging stage. The carbon aerogel prepared under the condition has a regular shape, and no crack is generated in the preparation process. The specific surface area, the total pore volume and the mesopore volume of the prepared carbon aerogel formed body are 612m respectively through detection and analysis2/g、0.845cm3/g-1And 0.526cm3/g-1(ii) a The compressive strength and the electric conductivity of the alloy are respectively 70MPa and 16S/cm.
Example 9
A carbon aerogel was prepared as in example 2, except that it was aged for 10 hours in the aging stage by directly raising the temperature from room temperature to 95 ℃. The carbon aerogel prepared under the condition has regular shape and no crack.The specific surface area, the total pore volume and the mesopore volume of the prepared carbon aerogel molded body were 630m, respectively, by detection analysis2/g、0.967cm3/g-1And 0.832cm3/g-1(ii) a The compressive strength and the electric conductivity of the alloy are respectively 20MPa and 12S/cm.
The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A method for simply and ultra-quickly preparing carbon aerogel is characterized by comprising the following steps:
1) uniformly dispersing graphite-like microcrystalline carbon nano-material, phenol, formaldehyde solution and catalyst in water to prepare mixed solution; wherein the mass ratio of the graphite-like microcrystalline carbon nano material to phenol is 1: 1-7, the molar ratio of phenol to formaldehyde is 1: 1.5-3, and the molar ratio of phenol to sodium carbonate is 50-1500: 1;
2) sealing and standing the mixed solution prepared in the step 1) for 5-120 min at 20-40 ℃ for sol-gelation to obtain hydrogel;
3) heating the hydrogel prepared in the step 2) to 40-120 ℃ at a heating rate of 0.5-5 ℃/min, and aging for 3-12 h;
4) heating the aged hydrogel obtained in the step 3) to 80-100 ℃ at a heating rate of 0.5-2 ℃/min, and drying the hydrogel for 1-2 hours at normal pressure;
5) directly heating the gel dried in the step 4) to 800-1000 ℃ at a heating rate of 1-5 ℃/min, carbonizing for 1-3 h, and cooling to obtain the carbon aerogel.
2. The process for the simple and ultra-fast preparation of carbon aerogel according to claim 1, characterized in that: the graphite-like microcrystalline carbon nano material is prepared from charcoal, bamboo charcoal, coconut shell carbon, wood activated carbon, coconut shell activated carbon and coal activated carbon serving as raw materials.
3. The process for the simple and ultra-fast preparation of carbon aerogel according to claim 1, characterized in that: the phenol is selected from phenol, resorcinol and cresol.
4. The process for the simple and ultra-fast preparation of carbon aerogel according to claim 1, characterized in that: the catalyst is selected from one of sodium carbonate, potassium hydroxide, sodium hydroxide and ammonia water.
5. The process for the simple and ultra-fast preparation of carbon aerogel according to claim 1, characterized in that: in the step 1), mixing by adopting a mechanical stirring or ultrasonic method; when ultrasonic mixing is adopted, the ultrasonic time is less than 5 min.
6. The process for the simple and ultra-fast preparation of carbon aerogel according to claim 1, characterized in that: in the step 1), the mixing mode is as follows: firstly, preparing a graphite-like microcrystalline carbon nano material into a uniformly dispersed suspension, and then adding phenol, a catalyst and a formaldehyde solution.
7. The process for the simple and ultra-fast preparation of carbon aerogel according to claim 1, characterized in that: in the step 2), the mixed solution is kept still at the temperature of 25-35 ℃ for 10-30 min.
8. The process for the simple and ultra-fast preparation of carbon aerogel according to claim 1, characterized in that: in the step 3), the temperature rise rate for aging is 2-3 ℃/min, and the aging temperature is 90-110 ℃; in the temperature rising process, the temperature is firstly raised to 90 ℃, the aging is carried out for 2-7 h, then the temperature is raised to 100-110 ℃, and the aging is carried out for 1-2 h.
9. The process for the simple and ultra-fast preparation of carbon aerogel according to claim 1, characterized in that: in the step 4), in the drying process, the heating rate is 0.5-1 ℃/min, the hydrogel is directly heated to 80-100 ℃, and the hydrogel is dried for 1-2 hours under normal pressure.
10. The process for the simple and ultra-fast preparation of carbon aerogel according to claim 1, characterized in that: in the step 5), in the carbonization process, the carbonization atmosphere is inert atmosphere, and the temperature rise rate is 2-3 ℃/min.
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