CN115057705B - Preparation method of blocky carbon/silicon-oxygen-carbon composite aerogel - Google Patents
Preparation method of blocky carbon/silicon-oxygen-carbon composite aerogel Download PDFInfo
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Abstract
The invention discloses a preparation method of blocky carbon/silicon-oxygen-carbon composite aerogel, relates to the technical field of aerogel material preparation, and particularly relates to a preparation method of blocky carbon/silicon-oxygen-carbon composite aerogel. The invention aims to solve the technical problems of complex preparation process, higher cost and difficulty in large-scale production in the existing preparation of carbon/silicon-oxygen-carbon composite aerogel. The preparation process of the invention comprises the following steps: 1. preparing sol; 2. gelling and curing; 3. solvent replacement; 4. drying under normal pressure; 5. and (4) high-temperature heat treatment. The preparation method adopts one-step normal pressure drying for preparation, has the advantages of simple operation, low cost, short period, safety, reliability and the like, and is expected to realize large-scale production. The method is suitable for preparing the blocky carbon/silicon-oxygen-carbon composite aerogel material.
Description
Technical Field
The invention relates to the technical field of aerogel material preparation, in particular to a preparation method of a blocky carbon/silicon-oxygen-carbon composite aerogel.
Background
The carbon aerogel is a nano material with a three-dimensional network structure formed by mutually connecting carbon nano particles, has lower density and thermal conductivity and excellent high-temperature stability, can bear high temperature of over 2000 ℃ in an oxygen-free environment, and has wide application prospect in the fields of aerospace, national defense and the like. However, in an aerobic environment, carbon aerogel is easily oxidized above 400 ℃, which greatly limits its application range. In addition, the weak mechanical properties of the carbon aerogel are also an important reason for limiting the application of the carbon aerogel. Therefore, how to improve the oxidation resistance and mechanical properties of the carbon aerogel becomes a key factor for determining whether the carbon aerogel can be widely applied.
In recent years, researchers have proposed the preparation of composite aerogels to improve the oxidation resistance and mechanical properties of carbon aerogels, such as carbon/silica, carbon/silicon carbide, carbon/titania, carbon/zirconium carbide, carbon/zirconium oxycarbon, carbon/alumina, and ternary carbon/silica/silicon carbide composite aerogels. The composite aerogel improves the oxidation resistance of the carbon aerogel on one hand by introducing the ceramic phase, and effectively improves the mechanical property of the carbon aerogel on the other hand by forming a double or multiple interpenetrating nano-network structure. The silica-carbon aerogel has the excellent performances of low density, high strength, good oxidation resistance and the like. The silica carbon aerogel and the carbon aerogel are effectively compounded, and the mechanical property and the oxidation resistance of the carbon aerogel are expected to be improved. However, there is currently less research on carbon/silicon-oxygen-carbon composite aerogels. The preparation process disclosed at present is complex and high in cost, and needs to be subjected to high-pressure kettle supercritical drying, so that the process is extremely dangerous and is difficult to realize large-scale production. In addition, a toxic formaldehyde raw material is required in the preparation process, which may cause harm to a human body. Therefore, the method for preparing the carbon/silicon-oxygen-carbon composite aerogel is simple to operate, low in cost, safe and reliable, and has important significance for application of the carbon/silicon-oxygen-carbon composite aerogel.
Disclosure of Invention
The invention provides a preparation method of a massive carbon/silicon-oxygen-carbon composite aerogel, aiming at solving the technical problems of complex preparation process, higher cost and difficulty in large-scale production in the existing preparation method of the carbon/silicon-oxygen-carbon composite aerogel.
A preparation method of a blocky carbon/silicon-oxygen-carbon composite aerogel specifically comprises the following steps:
1. preparing sol: mixing phenolic resin and alcohol solvent, and stirring for 10-30 min to obtain sol A;
then mixing dimethyl dimethoxysilane, methyl trimethoxysilane, absolute ethyl alcohol and deionized water, and stirring for 30-60 min to obtain sol B;
mixing the sol A and the sol B, adding a catalyst, and stirring for 10-30 min to obtain mixed sol C;
2. gelling and curing: transferring the mixed sol C obtained in the step one to a closed container, preserving heat for 1-3 h at the temperature of 80-100 ℃, preserving heat for 1-3 h at the temperature of 110-130 ℃, and preserving heat for 1-5 h at the temperature of 150-180 ℃ to obtain phenolic/organosilicon wet gel;
3. solvent replacement: soaking the phenolic aldehyde/organic silicon wet gel obtained in the step two in an organic solvent for solvent replacement, wherein the replacement time is 24-72 hours, and the organic solvent is replaced every 3-12 hours;
4. drying under normal pressure: drying the phenolic aldehyde/organic silicon wet gel treated in the step three under normal pressure for 24-72 hours to obtain blocky phenolic aldehyde/organic silicon composite aerogel;
5. high-temperature heat treatment: and (3) heating the blocky phenolic aldehyde/organic silicon composite aerogel obtained in the fourth step to 800-1300 ℃ at the heating rate of 3-5 ℃/min in the protective atmosphere, preserving the heat for 1-3 h, and then cooling the blocky phenolic aldehyde/organic silicon composite aerogel to the room temperature along with the furnace to obtain the blocky carbon/silicon-oxygen-carbon composite aerogel.
The invention has the beneficial effects that:
the invention provides a preparation method of a blocky carbon/silicon-oxygen-carbon composite aerogel. The carbon/silicon-oxygen-carbon composite aerogel prepared by the invention can form a complete block, and the density is 0.1-0.5 g/cm 3 The compression strength reaches 2-6 MPa, the initial oxidation temperature reaches 500-650 ℃, and the mass retention rate at 1000 ℃ reaches 15-85%.
The invention has the advantages that:
(1) By adopting a one-pot synthesis process, the gelling process of the carbon precursor and the silicon-oxygen-carbon precursor is carried out simultaneously, so that the composition of the material is more uniform;
(2) The preparation is carried out by adopting a one-step method, the operation is simple, the efficiency is high, and the preparation period is short;
(3) The normal pressure drying technology is adopted for drying, so that the preparation cost is greatly reduced, and compared with supercritical drying, the method is safer and more reliable and has better industrial prospect;
(4) The resin with low price is used as the carbon source, so that the preparation cost is reduced, the use of toxic aldehyde raw materials is avoided, and the preparation method is safer and more environment-friendly;
(5) According to the invention, the silica-carbon aerogel and the carbon aerogel are effectively compounded, and the mechanical property and the oxidation resistance of the carbon aerogel are obviously improved due to the introduction of the silica-carbon ceramic phase and the construction of a double nano-structure network.
The method is used for preparing the blocky carbon/silicon-oxygen-carbon composite aerogel.
Drawings
FIG. 1 is a photomicrograph of a bulk carbon/silica-carbon composite aerogel prepared in example 3;
FIG. 2 is an XRD spectrum of the bulk carbon/silica-carbon composite aerogel prepared in example 3;
FIG. 3 is an infrared spectrum of the carbon/silica-carbon composite aerogel prepared in example 3;
FIG. 4 is an SEM photograph of the bulk carbon/silica-carbon composite aerogel prepared in example 3;
FIG. 5 is a diagram showing the distribution of elements in the bulk carbon/silica-carbon composite aerogel obtained in example 3;
FIG. 6 is a graph of compressive stress-strain curves for the bulk carbon/silica-carbon composite aerogel prepared in example 3;
FIG. 7 is a TG curve of the bulk carbon/silica-carbon composite aerogel prepared in example 3 in air from room temperature to 1000 ℃.
Detailed Description
The technical solution of the present invention is not limited to the specific embodiments listed below, and includes any combination of the specific embodiments.
The first embodiment is as follows: the embodiment provides a preparation method of a blocky carbon/silicon-oxygen-carbon composite aerogel, which specifically comprises the following steps of:
1. preparing sol: mixing phenolic resin and alcohol solvent, and stirring for 10-30 min to obtain sol A;
then mixing dimethyl dimethoxysilane, methyl trimethoxysilane, absolute ethyl alcohol and deionized water, and stirring for 30-60 min to obtain sol B;
mixing the sol A and the sol B, adding a catalyst, and stirring for 10-30 min to obtain mixed sol C;
2. gelling and curing: transferring the mixed sol C obtained in the step one to a closed container, preserving heat for 1-3 h at the temperature of 80-100 ℃, preserving heat for 1-3 h at the temperature of 110-130 ℃, and preserving heat for 1-5 h at the temperature of 150-180 ℃ to obtain phenolic/organosilicon wet gel;
3. solvent replacement: soaking the phenolic aldehyde/organic silicon wet gel obtained in the step two in an organic solvent for solvent replacement, wherein the replacement time is 24-72 hours, and the organic solvent is replaced every 3-12 hours;
4. drying under normal pressure: drying the phenolic aldehyde/organic silicon wet gel treated in the step three under normal pressure for 24-72 hours to obtain blocky phenolic aldehyde/organic silicon composite aerogel;
5. high-temperature heat treatment: and (3) heating the blocky phenolic aldehyde/organic silicon composite aerogel obtained in the fourth step to 800-1300 ℃ at the heating rate of 3-5 ℃/min under the protective atmosphere, preserving the heat for 1-3 h, and then cooling to room temperature along with the furnace to obtain the blocky carbon/silicon-oxygen-carbon composite aerogel.
The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: the phenolic resin in the first step is linear thermosetting phenolic resin;
the alcohol solvent is ethanol, glycol, isopropanol or glycerol;
the catalyst is p-toluenesulfonic acid, ammonium hydroxide or hexamethylenetetramine. The rest is the same as the first embodiment.
The third concrete implementation mode: the present embodiment differs from the first or second embodiment in that: step one, mixing phenolic resin and alcohol solvent according to the mass ratio of 1 (2-10). The other is the same as in the first or second embodiment.
The fourth concrete implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is: mixing dimethyl dimethoxysilane, methyl trimethoxy silane, absolute ethyl alcohol and deionized water according to the mass ratio of 1 (4-8) to (2-10) to (2-5). The others are the same as in one of the first to third embodiments.
The fifth concrete implementation mode: the difference between this embodiment and one of the first to fourth embodiments is: in the first step, the mixing mass of the sol A and the sol B is 5 (1-25). The other is the same as one of the first to fourth embodiments.
The sixth specific implementation mode: the difference between this embodiment and one of the first to fifth embodiments is: in the first step, the addition amount of the catalyst is 1-5% of the mass of the mixed sol C. The other is the same as one of the first to fifth embodiments.
The seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is: the organic solvent in the third step is one or more than two of methanol, absolute ethyl alcohol, isopropanol, acetone, ether and n-hexane which are mixed in any proportion. The other is the same as one of the first to sixth embodiments.
The specific implementation mode is eight: the present embodiment differs from one of the first to seventh embodiments in that: and step three, controlling the soaking temperature to be 20-70 ℃. The other is the same as one of the first to seventh embodiments.
The specific implementation method nine: the present embodiment differs from the first to eighth embodiments in that: and the drying temperature under normal pressure in the fourth step is 20-100 ℃. The rest is the same as the first to eighth embodiments.
The detailed implementation mode is ten: the present embodiment differs from one of the first to ninth embodiments in that: and fifthly, the protective atmosphere is argon, nitrogen or helium. The other is the same as one of the first to ninth embodiments.
The following examples were used to demonstrate the beneficial effects of the present invention:
the first embodiment is as follows:
the preparation method of the blocky carbon/silicon-oxygen-carbon composite aerogel is specifically carried out according to the following steps:
1. preparing sol: mixing phenolic resin and isopropanol according to a mass ratio of 1; the phenolic resin is linear thermosetting phenolic resin which is an oligomer of phenol and formaldehyde, the molecular weight is 500-1500, and the mass fraction is 66.7%;
then mixing dimethyl dimethoxysilane, methyl trimethoxysilane, absolute ethyl alcohol and deionized water according to a mass ratio of 1;
mixing the sol A and the sol B according to a mass ratio of 5; the adding amount of the catalyst is 5 percent of the mass of the mixed sol C;
2. gelling and curing: transferring the mixed sol C obtained in the step one to a closed container, preserving heat for 3 hours at the temperature of 80 ℃, preserving heat for 3 hours at the temperature of 120 ℃, and then preserving heat for 1 hour at the temperature of 180 ℃ to obtain phenolic aldehyde/organosilicon wet gel;
3. solvent replacement: soaking the phenolic aldehyde/organic silicon wet gel obtained in the step two in organic solvent ether at the temperature of 40 ℃ for solvent replacement, wherein the replacement time is 48h, and the organic solvent is replaced every 8 h;
4. drying under normal pressure: placing the phenolic aldehyde/organic silicon wet gel treated in the step three into a forced air drying oven, and drying at normal pressure, wherein the drying temperature is controlled to be 80 ℃, and the drying time is controlled to be 36 hours, so as to obtain the blocky phenolic aldehyde/organic silicon composite aerogel;
5. high-temperature heat treatment: and D, heating the blocky phenolic aldehyde/organic silicon composite aerogel obtained in the fourth step to 800 ℃ at a heating rate of 5 ℃/min in an argon atmosphere, preserving the heat for 3 hours, and then cooling the blocky phenolic aldehyde/organic silicon composite aerogel to room temperature along with a furnace to obtain the blocky carbon/silicon-oxygen-carbon composite aerogel.
Example two:
the preparation method of the blocky carbon/silicon-oxygen-carbon composite aerogel is specifically carried out according to the following steps:
1. preparing sol: mixing phenolic resin and ethylene glycol according to a mass ratio of 1; the phenolic resin is linear thermosetting phenolic resin which is an oligomer of phenol and formaldehyde, the molecular weight is 500-1500, and the mass fraction is 66.7%;
then mixing dimethyl dimethoxysilane, methyl trimethoxysilane, absolute ethyl alcohol and deionized water according to a mass ratio of 1;
mixing the sol A and the sol B according to a mass ratio of 2; the adding amount of the catalyst is 1 percent of the mass of the mixed sol C;
2. gelling and curing: transferring the mixed sol C obtained in the step one to a closed container, preserving heat for 2 hours at the temperature of 90 ℃, preserving heat for 3 hours at the temperature of 120 ℃, and preserving heat for 3 hours at the temperature of 160 ℃ to obtain phenolic aldehyde/organosilicon wet gel;
3. solvent replacement: soaking the phenolic aldehyde/organic silicon wet gel obtained in the step two in organic solvent absolute ethyl alcohol at the temperature of 70 ℃ for solvent replacement, wherein the replacement time is 24 hours, and the organic solvent is replaced every 3 hours;
4. drying under normal pressure: placing the phenolic aldehyde/organic silicon wet gel treated in the step three into a forced air drying oven, and drying at normal pressure, wherein the drying temperature is controlled at 100 ℃, and the drying time is 24 hours, so as to obtain the blocky phenolic aldehyde/organic silicon composite aerogel;
5. high-temperature heat treatment: and (3) heating the blocky phenolic aldehyde/organic silicon composite aerogel obtained in the fourth step to 900 ℃ at the heating rate of 3 ℃/min in the argon atmosphere, preserving the heat for 3 hours, and then cooling the blocky phenolic aldehyde/organic silicon composite aerogel to the room temperature along with the furnace to obtain the blocky carbon/silicon-oxygen-carbon composite aerogel.
Example three:
the preparation method of the blocky carbon/silicon-oxygen-carbon composite aerogel is specifically carried out according to the following steps:
1. preparing sol: mixing phenolic resin and ethylene glycol according to a mass ratio of 1; the phenolic resin is linear thermosetting phenolic resin which is an oligomer of phenol and formaldehyde, the molecular weight is 500-1500, and the mass fraction is 66.7%;
then mixing dimethyl dimethoxysilane, methyl trimethoxysilane, absolute ethyl alcohol and deionized water according to a mass ratio of 1;
mixing the sol A and the sol B according to a mass ratio of 2; the addition amount of the catalyst is 2 percent of the mass of the mixed sol C;
2. gelling and curing: transferring the mixed sol C obtained in the step one to a closed container, preserving heat for 3h at 90 ℃, preserving heat for 3h at 120 ℃, and preserving heat for 3h at 170 ℃ to obtain phenolic aldehyde/organosilicon wet gel;
3. solvent replacement: soaking the phenolic aldehyde/organic silicon wet gel obtained in the step two in absolute ethyl alcohol serving as an organic solvent at the temperature of 50 ℃ for solvent replacement, wherein the replacement time is 48 hours, and the organic solvent is replaced every 6 hours;
4. drying under normal pressure: placing the phenolic aldehyde/organic silicon wet gel processed in the step three into a forced air drying oven, and drying at normal pressure, wherein the drying temperature is controlled at 50 ℃ and the drying time is 48h, so as to obtain the blocky phenolic aldehyde/organic silicon composite aerogel;
5. high-temperature heat treatment: and D, heating the blocky phenolic aldehyde/organic silicon composite aerogel obtained in the step four to 1000 ℃ at the heating rate of 3 ℃/min in the argon atmosphere, preserving the heat for 1h, and then cooling to room temperature along with the furnace to obtain the blocky carbon/silicon-oxygen-carbon composite aerogel.
Fig. 1 is a macro-photograph of the block carbon/silica carbon composite aerogel prepared in example 3, which shows that the block carbon/silica carbon composite aerogel prepared in the present invention has a perfect structure and no obvious defects such as cracks and holes;
FIG. 2 is an XRD pattern of the bulk carbon/silica-carbon composite aerogel prepared in example 3, in which no peak appears in the XRD pattern of the carbon/silica-carbon composite aerogel, indicating its amorphous structural characteristics;
FIG. 3 is an infrared spectrum of the carbon/silica-carbon composite aerogel prepared in example 3, in which infrared vibration absorption peaks of Si-C, si-O-Si, C-O bond and C = C double bond were detected;
FIG. 4 is an SEM picture of the bulk carbon/silica-carbon composite aerogel prepared in example 3, from which it can be seen that the carbon/silica-carbon composite aerogel has a typical aerogel three-dimensional interconnected nano-network structure, and the average particle size is about 50 nm;
fig. 5 is an element distribution diagram of the bulk carbon/silicon-oxygen-carbon composite aerogel prepared in example 3, and it can be seen that the composite aerogel mainly comprises three elements, i.e., si, C and O, and the three elements are distributed uniformly.
Fig. 6 is a compressive stress-strain curve of the bulk carbon/silicon-oxygen-carbon composite aerogel prepared in example 3, and it can be seen that the compressive strength of the carbon/silicon-oxygen-carbon composite aerogel reaches 2.9MPa, and the mechanical properties of the carbon aerogel and the silicon-oxygen-carbon aerogel are significantly improved due to the double interpenetrating nano-network structure thereof;
fig. 7 is a TG curve of the bulk carbon/silica-carbon composite aerogel prepared in example 3 from room temperature to 1000 ℃ in air, and due to the introduction of the silica-carbon aerogel, the initial oxidation temperature of the carbon/silica-carbon composite aerogel reaches about 550 ℃, the mass retention rate at 1000 ℃ can be kept at about 35%, and the oxidation resistance is significantly improved compared with the carbon aerogel.
Example four:
the preparation method of the blocky carbon/silicon-oxygen-carbon composite aerogel is specifically carried out according to the following steps:
1. preparing sol: mixing phenolic resin and glycerol according to the mass ratio of 1; the phenolic resin is linear thermosetting phenolic resin which is an oligomer of phenol and formaldehyde, the molecular weight is 500-1500, and the mass fraction is 66.7%;
then mixing dimethyl dimethoxysilane, methyl trimethoxysilane, absolute ethyl alcohol and deionized water according to a mass ratio of 1;
mixing the sol A and the sol B according to a mass ratio of 1; the adding amount of the catalyst is 3 percent of the mass of the mixed sol C;
2. gelling and curing: transferring the mixed sol C obtained in the step one to a closed container, preserving heat for 1h at 100 ℃, preserving heat for 1h at 130 ℃, and then preserving heat for 3h at 165 ℃ to obtain phenolic aldehyde/organosilicon wet gel;
3. solvent replacement: soaking the phenolic aldehyde/organic silicon wet gel obtained in the step two in an organic solvent acetone at the temperature of 20 ℃ for solvent replacement, wherein the replacement time is 72 hours, and the organic solvent is replaced every 9 hours;
4. drying under normal pressure: placing the phenolic aldehyde/organic silicon wet gel treated in the step three into a forced air drying oven, and drying at normal pressure, wherein the drying temperature is controlled to be 20 ℃, and the drying time is controlled to be 72 hours, so as to obtain the blocky phenolic aldehyde/organic silicon composite aerogel;
5. high-temperature heat treatment: and C, heating the blocky phenolic aldehyde/organic silicon composite aerogel obtained in the step four to 1000 ℃ at the heating rate of 5 ℃/min in the argon atmosphere, preserving the heat for 2 hours, and then cooling to room temperature along with the furnace to obtain the blocky carbon/silicon-oxygen-carbon composite aerogel.
Example five:
the preparation method of the blocky carbon/silicon-oxygen-carbon composite aerogel is specifically carried out according to the following steps:
1. preparing sol: mixing phenolic resin and ethylene glycol according to a mass ratio of 1; the phenolic resin is linear thermosetting phenolic resin, is an oligomer of phenol and formaldehyde, has the molecular weight of 500-1500, and has the mass fraction of 66.7%;
then mixing dimethyl dimethoxysilane, methyl trimethoxysilane, absolute ethyl alcohol and deionized water according to a mass ratio of 1;
mixing the sol A and the sol B according to a mass ratio of 3; the adding amount of the catalyst is 3 percent of the mass of the mixed sol C;
2. gelling and curing: transferring the mixed sol C obtained in the step one to a closed container, preserving heat for 2 hours at 95 ℃, preserving heat for 3 hours at 120 ℃, and preserving heat for 2 hours at 170 ℃ to obtain phenolic aldehyde/organosilicon wet gel;
3. solvent replacement: soaking the phenolic aldehyde/organic silicon wet gel obtained in the step two in an organic solvent isopropanol at the temperature of 60 ℃ for solvent replacement, wherein the replacement time is 48h, and the organic solvent is replaced every 12 h;
4. drying under normal pressure: placing the phenolic aldehyde/organic silicon wet gel treated in the step three into a forced air drying oven, and drying at normal pressure, wherein the drying temperature is controlled to be 60 ℃, and the drying time is 60 hours, so as to obtain the blocky phenolic aldehyde/organic silicon composite aerogel;
5. high-temperature heat treatment: and D, heating the blocky phenolic aldehyde/organic silicon composite aerogel obtained in the fourth step to 1100 ℃ at the heating rate of 3 ℃/min in the argon atmosphere, preserving the heat for 1h, and then cooling to room temperature along with the furnace to obtain the blocky carbon/silicon-oxygen-carbon composite aerogel.
Example six:
the preparation method of the blocky carbon/silicon-oxygen-carbon composite aerogel is specifically carried out according to the following steps:
1. preparing sol: mixing phenolic resin and absolute ethyl alcohol according to a mass ratio of 1; the phenolic resin is linear thermosetting phenolic resin, is an oligomer of phenol and formaldehyde, has the molecular weight of 500-1500, and has the mass fraction of 66.7%;
then mixing dimethyl dimethoxysilane, methyl trimethoxysilane, absolute ethyl alcohol and deionized water according to a mass ratio of 1;
mixing the sol A and the sol B according to a mass ratio of 5; the addition amount of the catalyst is 2 percent of the mass of the mixed sol C;
2. gelling and curing: transferring the mixed sol C obtained in the step one to a closed container, preserving heat for 3 hours at the temperature of 80 ℃, preserving heat for 3 hours at the temperature of 110 ℃, and preserving heat for 5 hours at the temperature of 150 ℃ to obtain phenolic aldehyde/organosilicon wet gel;
3. solvent replacement: soaking the phenolic aldehyde/organic silicon wet gel obtained in the step two in organic solvent n-hexane at the temperature of 35 ℃ for solvent replacement, wherein the replacement time is 48h, and the organic solvent is replaced every 8 h;
4. drying under normal pressure: placing the phenolic aldehyde/organic silicon wet gel treated in the step three into a forced air drying oven, and drying at normal pressure, wherein the drying temperature is controlled to be 70 ℃, and the drying time is 60 hours, so as to obtain the blocky phenolic aldehyde/organic silicon composite aerogel;
5. high-temperature heat treatment: and D, heating the blocky phenolic aldehyde/organic silicon composite aerogel obtained in the fourth step to 1050 ℃ at the heating rate of 5 ℃/min in the argon atmosphere, preserving the heat for 1h, and then cooling to room temperature along with the furnace to obtain the blocky carbon/silicon-oxygen-carbon composite aerogel.
Example seven:
the embodiment provides a preparation method of a blocky carbon/silicon-oxygen-carbon composite aerogel, which specifically comprises the following steps of:
1. preparing sol: mixing phenolic resin and ethylene glycol according to a mass ratio of 1; the phenolic resin is linear thermosetting phenolic resin which is an oligomer of phenol and formaldehyde, the molecular weight is 500-1500, and the mass fraction is 66.7%;
then mixing dimethyl dimethoxysilane, methyl trimethoxysilane, absolute ethyl alcohol and deionized water according to a mass ratio of 1;
mixing the sol A and the sol B according to a mass ratio of 1; the addition amount of the catalyst is 2 percent of the mass of the mixed sol C;
2. gelling and curing: transferring the mixed sol C obtained in the step one to a closed container, preserving heat for 2 hours at the temperature of 90 ℃, then preserving heat for 3 hours at the temperature of 120 ℃, and then preserving heat for 4 hours at the temperature of 160 ℃ to obtain phenolic aldehyde/organic silicon wet gel;
3. solvent replacement: soaking the phenolic aldehyde/organic silicon wet gel obtained in the step two in an organic solvent at the temperature of 45 ℃ for solvent replacement, wherein the replacement time is 72 hours, and the organic solvent is replaced every 12 hours; the organic solvent is methanol and absolute ethyl alcohol according to the volume ratio of 1:1, mixing;
4. drying under normal pressure: placing the phenolic aldehyde/organic silicon wet gel processed in the step three into a forced air drying oven, and drying at normal pressure, wherein the drying temperature is controlled to be 90 ℃, and the drying time is 30 hours, so as to obtain the blocky phenolic aldehyde/organic silicon composite aerogel;
5. high-temperature heat treatment: and D, heating the blocky phenolic aldehyde/organic silicon composite aerogel obtained in the fourth step to 1300 ℃ at the heating rate of 3 ℃/min in the argon atmosphere, preserving the heat for 1h, and then cooling to room temperature along with the furnace to obtain the blocky carbon/silicon-oxygen-carbon composite aerogel.
Claims (7)
1. The preparation method of the blocky carbon/silicon-oxygen-carbon composite aerogel is characterized by comprising the following steps of:
1. preparing sol: mixing phenolic resin and alcohol solvent, and stirring for 10-30 min to obtain sol A;
then mixing dimethyl dimethoxysilane, methyl trimethoxysilane, absolute ethyl alcohol and deionized water, and stirring for 30-60 min to obtain sol B;
mixing the sol A and the sol B, adding a catalyst, and stirring for 10-30 min to obtain mixed sol C;
2. gelling and curing: transferring the mixed sol C obtained in the step one to a closed container, preserving heat for 1-3 h at the temperature of 80-100 ℃, preserving heat for 1-3 h at the temperature of 110-130 ℃, and preserving heat for 1-5 h at the temperature of 150-180 ℃ to obtain phenolic/organosilicon wet gel;
3. solvent replacement: soaking the phenolic aldehyde/organic silicon wet gel obtained in the step two in an organic solvent for solvent replacement, wherein the replacement time is 24-72 hours, and the organic solvent is replaced every 3-12 hours;
4. drying under normal pressure: drying the phenolic aldehyde/organic silicon wet gel treated in the step three under normal pressure for 24-72 hours to obtain blocky phenolic aldehyde/organic silicon composite aerogel;
5. high-temperature heat treatment: heating the blocky phenolic aldehyde/organic silicon composite aerogel obtained in the fourth step to 800-1300 ℃ at a heating rate of 3-5 ℃/min in a protective atmosphere, preserving the heat for 1-3 h, and then cooling the blocky phenolic aldehyde/organic silicon composite aerogel to room temperature along with a furnace to obtain blocky carbon/silicon-oxygen-carbon composite aerogel;
the phenolic resin in the step one is linear thermosetting phenolic resin;
the alcohol solvent is ethanol, glycol, isopropanol or glycerol;
the catalyst is p-toluenesulfonic acid, ammonium hydroxide or hexamethylenetetramine;
mixing dimethyl dimethoxysilane, methyl trimethoxy silane, absolute ethyl alcohol and deionized water according to the mass ratio of 1 (4-8) to (2-10) to (2-5);
the drying temperature under normal pressure in the fourth step is 20-100 ℃.
2. The preparation method of the massive carbon/silicon-oxygen-carbon composite aerogel according to claim 1, wherein the phenolic resin and the alcohol solvent are mixed according to a mass ratio of 1 (2-10).
3. The preparation method of the massive carbon/silicon-oxygen-carbon composite aerogel according to claim 1, wherein the mixing mass of the sol A and the sol B in the step one is 5 (1-25).
4. The method for preparing the massive carbon/silicon-oxygen-carbon composite aerogel according to claim 1, wherein the addition amount of the catalyst in the first step is 1-5% of the mass of the mixed sol C.
5. The method for preparing the blocky carbon/silicon-oxygen-carbon composite aerogel according to claim 1, wherein the organic solvent in the third step is one or more of methanol, absolute ethyl alcohol, isopropanol, acetone, diethyl ether and n-hexane which are mixed in any proportion.
6. The method for preparing the block-shaped carbon/silicon-oxygen-carbon composite aerogel according to claim 1, wherein the soaking temperature in the third step is controlled to be 20-70 ℃.
7. The method for preparing the bulk carbon/silicon-oxygen-carbon composite aerogel according to claim 1, wherein the protective atmosphere in the fifth step is argon, nitrogen or helium.
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| CN112940445A (en) * | 2021-01-27 | 2021-06-11 | 哈尔滨工业大学 | Ceramic microsphere modified carbon fiber preform reinforced silicon-oxygen-carbon-phenolic aldehyde composite material and preparation method thereof |
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