CN113912406A - Polymer-converted SiC/CfMethod for producing aerogels - Google Patents

Polymer-converted SiC/CfMethod for producing aerogels Download PDF

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CN113912406A
CN113912406A CN202111259104.0A CN202111259104A CN113912406A CN 113912406 A CN113912406 A CN 113912406A CN 202111259104 A CN202111259104 A CN 202111259104A CN 113912406 A CN113912406 A CN 113912406A
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freezing
precursor slurry
aerogel
carbon fibers
carbon fiber
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李福平
赵琳娜
赵康
党薇
许卓利
汤玉斐
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Xian University of Technology
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Abstract

The invention discloses a polymer converted SiC/CfThe preparation method of the aerogel comprises the following steps: pretreating carbon fibers, preparing precursor slurry, carrying out hydrothermal treatment on the precursor slurry, stirring and stirring at a high speed to mix the precursor slurry, sequentially carrying out ultrasonic treatment and freezing treatment on the mixed precursor slurry to obtain a cylindrical composite frozen body FnThe cylindrical composite frozen body F is frozennFreeze drying to obtain porous blank, curing, and pyrolyzing in vacuum tubular furnace to obtain polymer converted SiC/CfAn aerogel. The polymer of the invention is converted into SiC/CfPreparation of aerogelsThe method utilizes the polymer converted SiC ceramic as a fiber node, solves the problem of agglomeration of the prior aerogel in high-temperature service, and has better heat insulation performance and simple preparation process.

Description

Polymer-converted SiC/CfMethod for producing aerogels
Technical Field
The invention belongs to the technical field of preparation methods of ceramic fiber aerogel, and relates to a polymer-converted SiC/CfA preparation method of aerogel.
Background
With the rapid development of aerospace technology in China, the flight speed and service life of aerospace craft have become the key issues of scientific research workers. The further improvement of the performance of the thermal protection system of the new-generation aerospace craft which is long in time, high in temperature and safe is vital to develop. The method breaks through the prior art, develops a new generation of more reliable and more effective thermal protection material, and can provide more powerful guarantee in the high-speed, long-time and high-temperature operation process of the aircraft. The current thermal protection requirements of high-speed aerospace craft are generally above 1600 ℃, therefore, high-temperature thermal insulation materials are often adopted to provide design protection for the front end of the aircraft engine.
The heat insulating material applied to the engine of the aerospace craft firstly meets the requirement of light weight so as to ensure the requirement of flight quality of the craft. Several types of heat insulating materials are common at present: fibrous porous heat insulating material, foamed heat insulating material, and granular heat insulating material. The fiber porous heat-insulating material has the advantages of light weight, low heat conductivity, good mechanical property and the like, and basically meets the application requirement of the heat-insulating material of the aircraft engine. The fiber porous heat-insulating materials reported in the prior research are divided into the following parts: organic fiber thermal insulation materials, inorganic fiber thermal insulation materials, and fiber composite aerogel thermal insulation materials.
The aerogel material can be almost used in all heat insulation fields, overcomes various defects of the traditional heat insulation material, and has obvious energy saving and consumption reduction. The aerogel is a gel material taking a dispersion medium as gas, is a solid nano material with a three-dimensional network framework and mainly formed by mutual polymerization of colloidal particles or polymer monomers, and has excellent performances of ultralow density, low thermal conductivity, high specific surface area, high porosity and the like. The porosity of the aerogel material is more than 90%, and the aerogel has excellent heat insulation performance due to the mesoporous structure in the aerogel material. But the prior aerogel is easy to agglomerate in high-temperature service and has complex preparation method. Therefore, the preparation method of the novel aerogel is provided, and has profound significance in the aspect of aerospace engine heat insulation materials.
Disclosure of Invention
The invention aims to provide a polymer converted SiC/CfThe preparation method of the aerogel utilizes the SiC ceramic converted from the polymer as a fiber node, solves the problem of agglomeration of the prior aerogel in high-temperature service, and has better heat-insulating property and simple preparation process.
The invention adopts the technical scheme that a polymer is converted into SiC/CfThe preparation method of the aerogel is specifically implemented according to the following steps:
step 1, carbon fiber pretreatment
Ball-milling carbon fibers, placing the carbon fibers in an acetone solution for hydrothermal reaction for a certain time, carrying out vacuum filtration on the obtained solution, carrying out suction filtration on the carbon fibers obtained by suction filtration sequentially by using a nitric acid solution and deionized water, and then drying the carbon fibers after the suction filtration after centrifugal cleaning;
step 2, preparing precursor slurry
Placing camphene crystallized at room temperature into a beaker, placing the beaker into a water bath stirring pot, keeping the temperature at 60-80 ℃ to convert camphene into liquid as a solvent, then adding polycarbosilane powder and the carbon fiber treated in the step 1, mixing to obtain precursor slurry, preparing n groups of precursor slurry with the number T being more than or equal to 2, and marking the precursor slurry as T1，T2，T3，…，Tn-1，TnWherein the total addition amount of the polycarbosilane powder and the treated carbon fiber in the nth group is more than that of the (n-1) th group;
step 3, hydrothermal treatment
Respectively transferring the precursor slurry prepared in the step 2 to a hydrothermal reaction kettle for hydrothermal treatment;
step 4, heating and stirring
Continuously stirring the precursor slurry hydrothermally finished in the step 3 at the temperature of 60-80 ℃ for 3-6h to obtain mixed precursor slurry;
step 5, high-speed stirring
Stirring the precursor slurry stirred in the step 4 at 5000rpm for 15min, then continuously stirring at 7000rpm for 5min to obtain completely uniform mixed precursor slurry, and keeping the temperature of the precursor slurry at 60-80 ℃ during stirring;
step 6, freezing
Sequentially carrying out ultrasonic treatment and freezing treatment on the mixed precursor slurry obtained in the step 5, wherein the freezing treatment adopts directional freezing and freezing mold freezing, the side wall of the freezing mold is a tubular heat-insulating material, the bottom surface of the freezing mold is a heat-conducting metal, the freezing direction is vertical to the ground and is upward, n groups of the freezing molds are more than or equal to 2 groups, and the groups are respectively marked as M1，M2，M3，…，Mn-1，MnThe cylindrical composite frozen bodies obtained after each freezing are respectively marked as F1，F2，F3，…，Fn-1，Fn；
Step 7, vacuum freeze drying
Subjecting the cylindrical composite frozen body F obtained in step 6 tonAfter demolding, freeze-drying in a vacuum environment to obtain a porous blank;
step 8, thermal oxidation curing
Curing the porous blank obtained in the step 7 in air at 180-200 ℃ for 1.5-2 h;
step 9, pyrolysis
Placing the cured porous blank prepared in the step 8 into a vacuum tube furnace, and pyrolyzing for 1-2h at the temperature of 1500 ℃ under the protection of Ar gas at 1000 ℃ to obtain polymer converted SiC/CfAn aerogel.
The present invention is also characterized in that,
the carbon fiber in the step 1 is commercial carbon fiber, and the ball milling time is 12-24 h.
In the step 1, placing the ball-milled carbon fibers in an acetone solution for hydrothermal reaction for a certain time, and then carrying out vacuum filtration on the obtained solution, wherein the vacuum filtration specifically comprises the following steps:
and (3) placing the ball-milled carbon fibers in an acetone solution, treating for 36-48h at 70-75 ℃ of a hydrothermal reaction kettle, and then carrying out vacuum filtration on the solution for 1-1.5 h.
The suction filtration of the carbon fiber obtained by suction filtration in the step 1 sequentially adopts nitric acid solution and deionized water to carry out suction filtration, and specifically comprises the following steps:
and (3) placing the carbon fiber subjected to vacuum filtration in a 65% nitric acid solution for treatment for 3 hours, then carrying out vacuum filtration to obtain the carbon fiber, and carrying out vacuum filtration with deionized water for 1-1.5 hours.
In the step 1, the carbon fiber after suction filtration is centrifugally cleaned and then dried, and the method specifically comprises the following steps: and (3) centrifugally cleaning the filtered carbon fiber at 8000-8500rpm for 5-10min, and finally treating the carbon fiber in a vacuum drying oven at 80 ℃ for 3 h.
The hydrothermal treatment in step 3 is carried out at 180 ℃ for 3 h.
The total adding amount of the polycarbosilane powder and the treated carbon fiber in the step 2 is 1-3 wt% of the adding amount of the camphene.
The mass ratio of the polycarbosilane powder to the treated carbon fiber is 1: 1.
In the step 6, the directional freezing temperature is-40 to-20 ℃, and the freezing time t is more than or equal to 1 h.
The invention has the beneficial effects that the polymer-converted SiC ceramic is used as a fiber node, the problems of agglomeration and the like of the existing aerogel in high-temperature service are solved, the heat-insulating property is better, and the preparation process is simple.
Drawings
FIG. 1 shows a polymer-converted SiC/C of the present inventionfPolymer conversion SiC/C prepared in example 2 in method for preparing aerogelfOptical photographs of the aerogels;
FIG. 2 shows a polymer-converted SiC/C of the present inventionfPolymer conversion SiC/C prepared in example 2 in method for preparing aerogelfThe microstructure of the aerogel pore structure;
FIG. 3 is a polymer converted SiC/C prepared in example 2 of the present inventionfAerogel and Al2O3Infrared thermal imaging contrast of fibrous aerogels.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
The invention relates to a polymer converted SiC/CfThe preparation method of the aerogel is specifically implemented according to the following steps:
step 1, carbon fiber pretreatment
Ball-milling commercial carbon fibers for 12-24h, then placing the ball-milled commercial carbon fibers in an acetone solution, treating the ball-milled commercial carbon fibers in a hydrothermal reaction kettle at 70-75 ℃ for 36-48h, then carrying out vacuum filtration on the solution for 1-1.5h, carrying out vacuum filtration on the obtained carbon fibers in a 65% nitric acid solution for 3h, then carrying out vacuum filtration on the carbon fibers, carrying out vacuum filtration on the carbon fibers for 1-1.5h, then carrying out centrifugal cleaning treatment on the filtered carbon fibers at 8000-8500rpm for 5-10min, and finally treating the carbon fibers in a vacuum drying oven at 80 ℃ for 3 h;
step 2, preparing precursor slurry
Placing camphene crystallized at room temperature into a beaker, placing the beaker into a water bath stirring pot, keeping the temperature at 60-80 ℃ to convert camphene into liquid as a solvent, then adding polycarbosilane powder and the carbon fiber treated in the step 1, mixing to obtain precursor slurry, preparing n groups of precursor slurry with the number T being more than or equal to 2, and marking the precursor slurry as T1，T2，T3，…，Tn-1，TnWherein the total addition amount of the polycarbosilane powder and the treated carbon fiber in the nth group is larger than that of the nth-1 group, wherein the total addition amount of the polycarbosilane powder and the treated carbon fiber is 1-3 wt% of the addition amount of camphene, and the mass ratio of the polycarbosilane powder to the treated carbon fiber is 1: 1;
step 3, hydrothermal treatment
Transferring the precursor slurry prepared in the step 2 to a hydrothermal reaction kettle respectively for hydrothermal treatment for 3 hours at 180 ℃;
step 4, heating and stirring
Continuously stirring the precursor slurry hydrothermally finished in the step 3 at the temperature of 60-80 ℃ for 3-6h to obtain mixed precursor slurry;
step 5, high-speed stirring
Stirring the precursor slurry stirred in the step 4 at 5000rpm for 15min, then continuously stirring at 7000rpm for 5min to obtain completely uniform mixed precursor slurry, and keeping the temperature of the precursor slurry at 60-80 ℃ during stirring;
step 6, freezing
Sequentially carrying out ultrasonic treatment and freezing treatment on the mixed precursor slurry obtained in the step 5, wherein directional freezing is adopted for freezing, the directional freezing temperature is-40 to-20 ℃, the freezing time t is more than or equal to 1h, a freezing mold is adopted for freezing, the side wall of the freezing mold is made of a tubular heat-insulating material, the bottom surface of the freezing mold is made of a heat-conducting metal, the freezing direction is vertical to the ground upwards, n groups of the freezing molds are more than or equal to 2, and the groups are respectively marked as M1，M2，M3，…，Mn-1，MnThe cylindrical composite frozen bodies obtained after each freezing are respectively marked as F1，F2，F3，…，Fn-1，Fn；
Step 7, vacuum freeze drying
Subjecting the cylindrical composite frozen body F obtained in step 6 tonAfter demolding, freeze-drying in a vacuum environment to obtain a porous blank;
step 8, thermal oxidation curing
Curing the porous blank obtained in the step 7 in air at 180-200 ℃ for 1.5-2 h;
step 9, pyrolysis
Placing the cured porous blank prepared in the step 8 into a vacuum tube furnace, and pyrolyzing for 1-2h at the temperature of 1500 ℃ under the protection of Ar gas at 1000 ℃ to obtain polymer converted SiC/CfAn aerogel.
Example 1
Polymer-converted SiC/CfThe preparation method of the aerogel specifically comprises the following steps:
step 1, carbon fiber pretreatment
The method comprises the steps of ball-milling commercial carbon fibers for 24 hours, then placing the commercial carbon fibers into an acetone solution, treating the commercial carbon fibers at 70 ℃ for 48 hours in a hydrothermal reaction kettle, then carrying out vacuum filtration on the solution for 1 hour, placing the cleaned carbon fibers into a 65% nitric acid solution for treating for 3 hours, carrying out vacuum filtration on the treated nitric acid waste liquid to obtain carbon fibers, carrying out vacuum filtration on the carbon fibers for 1 hour by using deionized water, carrying out centrifugal cleaning treatment on the filtered carbon fibers at 8000rpm for 5min, and finally treating the carbon fibers in a vacuum drying oven at 80 ℃ for 3 hours.
Step 2, preparing precursor slurry
10g of camphene crystallized at room temperature is taken and placed in a beaker, the beaker is placed in a water bath stirring pot, the temperature is kept at 60 ℃, so that the camphene is converted into liquid as a solvent. Then adding polycarbosilane powder and the treated carbon fiber, wherein the total addition amount of the polycarbosilane powder and the treated carbon fiber is 1 wt% of the addition amount of camphene, the mass ratio of the polycarbosilane powder to the treated carbon fiber is 1:1, mixing to obtain precursor slurry, preparing n groups of precursor slurry with the number being more than or equal to 2, and marking the precursor slurry as T1，T2，T3，…，Tn-1，TnWherein the total addition amount of the polycarbosilane powder and the prefabricated carbon fiber in the nth group is more than that of the (n-1) th group;
step 3, hydrothermal treatment
Transferring the precursor slurry prepared in the step 2 into a hydrothermal reaction kettle, and treating for 3h at 180 ℃;
step 4, heating and stirring:
continuously stirring the precursor slurry hydrothermally finished in the step 3 at 60 ℃ for 3h to obtain uniform mixed precursor slurry;
step 5, high-speed stirring
Stirring the precursor slurry stirred in the step 4 at 5000rpm for 15min, and then continuously stirring at 7000rpm for 5min to obtain completely uniform mixed precursor slurry;
step 6, freezing:
and (3) carrying out ultrasonic treatment on the precursor slurry obtained in the step (5) to remove air bubbles in the precursor slurry, and then carrying out freezing treatment, wherein directional freezing is adopted for freezing, a freezing mold is adopted for freezing, the side wall of the freezing mold is made of a tubular heat-insulating material, the bottom surface of the freezing mold is made of a heat-conducting metal, and the freezing direction is vertical to the ground upwards. The total n of the freezing molds is more than or equal to 2 groups and respectively marked as M1，M2，M3，…，Mn-1，MnThe cylindrical composite frozen bodies obtained after each freezing are respectively marked as F1，F2，F3，…，Fn-1，Fn；
Step 7, vacuum freeze drying:
subjecting the cylindrical composite frozen body F obtained in step 6 tonFreeze-drying the mixture in a vacuum environment,making the cylindrical composite frozen body FnSublimating the solvent crystal to obtain a porous blank;
step 8, thermal oxidation curing:
carrying out curing treatment on the porous blank obtained in the step 7 for 1.5h at 180 ℃ in air to form a cross-linked three-dimensional network structure in the porous blank so as to prevent the porous blank prepared in the step 7 from melting;
step 9, pyrolysis:
putting the cured porous blank prepared in the step 8 into a vacuum tube furnace, and pyrolyzing for 1h at 1000 ℃ under the protection of Ar gas to obtain polymer converted SiC/CfAn aerogel;
example 2
Polymer-converted SiC/CfThe preparation method of the aerogel specifically comprises the following steps:
step 1, carbon fiber pretreatment
The method comprises the steps of ball-milling commercial carbon fibers for 24 hours, then placing the commercial carbon fibers into an acetone solution, treating the commercial carbon fibers at 70 ℃ for 48 hours in a hydrothermal reaction kettle, then carrying out vacuum filtration on the solution for 1 hour, placing the cleaned carbon fibers into a 65% nitric acid solution for treating for 3 hours, carrying out vacuum filtration on the treated nitric acid waste liquid to obtain carbon fibers, carrying out vacuum filtration on the carbon fibers for 1 hour by using deionized water, carrying out centrifugal cleaning treatment on the filtered carbon fibers at 8000rpm for 5min, and finally treating the carbon fibers in a vacuum drying oven at 80 ℃ for 3 hours.
Step 2, preparing precursor slurry
10g of camphene crystallized at room temperature is taken and placed in a beaker, the beaker is placed in a water bath stirring pot, the temperature is kept at 80 ℃, so that camphene is converted into liquid as a solvent. Then adding polycarbosilane powder and the treated carbon fiber, wherein the total addition amount of the polycarbosilane powder and the treated carbon fiber is 3 wt% of the addition amount of camphene, the mass ratio of the polycarbosilane powder to the treated carbon fiber is 1:1, mixing to obtain precursor slurry, preparing n groups of precursor slurry with the number being more than or equal to 2, and marking the precursor slurry as T1，T2，T3，…，Tn-1，TnWherein the total addition amount of the polycarbosilane powder and the prefabricated carbon fiber in the nth group is more than that of the (n-1) th group;
step 3, hydrothermal treatment
Transferring the precursor slurry prepared in the step 2 into a hydrothermal reaction kettle, and treating for 3h at 180 ℃;
step 4, heating and stirring:
continuously stirring the precursor slurry hydrothermally finished in the step 3 at 80 ℃ for 6 hours to obtain uniform mixed precursor slurry;
step 5, high-speed stirring
Stirring the precursor slurry stirred in the step 4 at 5000rpm for 15min, and then continuously stirring at 7000rpm for 5min to obtain completely uniform mixed precursor slurry;
step 6, freezing:
and (3) carrying out ultrasonic treatment on the precursor slurry obtained in the step (5) to remove air bubbles in the precursor slurry, and then carrying out freezing treatment, wherein directional freezing is adopted for freezing, a freezing mold is adopted for freezing, the side wall of the freezing mold is made of a tubular heat-insulating material, the bottom surface of the freezing mold is made of a heat-conducting metal, and the freezing direction is vertical to the ground upwards. The total n of the freezing molds is more than or equal to 2 groups and respectively marked as M1，M2，M3，…，Mn-1，MnThe cylindrical composite frozen bodies obtained after each freezing are respectively marked as F1，F2，F3，…，Fn-1，Fn；
Step 7, vacuum freeze drying:
subjecting the cylindrical composite frozen body F obtained in step 6 tonFreeze-drying under vacuum to obtain cylindrical composite frozen body FnSublimating the solvent crystal to obtain a porous blank;
step 8, thermal oxidation curing:
carrying out curing treatment on the porous blank obtained in the step 7 for 2 hours at 200 ℃ in the air, so that a cross-linked three-dimensional network structure is formed in the porous blank to prevent the porous blank prepared in the step 7 from melting;
step 9, pyrolysis:
putting the cured porous blank prepared in the step 8 into a vacuum tube furnace, and pyrolyzing for 2h at 1500 ℃ under the protection of Ar gas to obtain polymer converted SiC/CfAn aerogel;
example 3
Polymer-converted SiC/CfThe preparation method of the aerogel specifically comprises the following steps:
step 1, carbon fiber pretreatment
The method comprises the steps of ball-milling commercial carbon fibers for 24 hours, then placing the commercial carbon fibers into an acetone solution, treating the commercial carbon fibers at 70 ℃ for 48 hours in a hydrothermal reaction kettle, then carrying out vacuum filtration on the solution for 1 hour, placing the cleaned carbon fibers into a 65% nitric acid solution for treating for 3 hours, carrying out vacuum filtration on the treated nitric acid waste liquid to obtain carbon fibers, carrying out vacuum filtration on the carbon fibers for 1 hour by using deionized water, carrying out centrifugal cleaning treatment on the filtered carbon fibers at 8000rpm for 5min, and finally treating the carbon fibers in a vacuum drying oven at 80 ℃ for 3 hours.
Step 2, preparing precursor slurry
10g of camphene crystallized at room temperature is taken and placed in a beaker, the beaker is placed in a water bath stirring pot, the temperature is kept at 60 ℃, so that the camphene is converted into liquid as a solvent. Then adding polycarbosilane powder and the treated carbon fiber, wherein the total addition amount of the polycarbosilane powder and the treated carbon fiber is 2 wt% of the addition amount of camphene, the mass ratio of the polycarbosilane powder to the treated carbon fiber is 1:1, mixing to obtain precursor slurry, preparing n groups of precursor slurry with the number being more than or equal to 2, and marking the precursor slurry as T1，T2，T3，…，Tn-1，TnWherein the total addition amount of the polycarbosilane powder and the prefabricated carbon fiber in the nth group is more than that of the (n-1) th group;
step 3, hydrothermal treatment
Transferring the precursor slurry prepared in the step 2 into a hydrothermal reaction kettle, and treating for 3h at 180 ℃;
step 4, heating and stirring:
continuously stirring the precursor slurry hydrothermally finished in the step 3 at 60 ℃ for 6 hours to obtain uniform mixed precursor slurry;
step 5, high-speed stirring
Stirring the precursor slurry stirred in the step 4 at 5000rpm for 15min, and then continuously stirring at 7000rpm for 5min to obtain completely uniform mixed precursor slurry;
step 6, freezing:
and (3) carrying out ultrasonic treatment on the precursor slurry obtained in the step (5) to remove air bubbles in the precursor slurry, and then carrying out freezing treatment, wherein directional freezing is adopted for freezing, a freezing mold is adopted for freezing, the side wall of the freezing mold is made of a tubular heat-insulating material, the bottom surface of the freezing mold is made of a heat-conducting metal, and the freezing direction is vertical to the ground upwards. The total n of the freezing molds is more than or equal to 2 groups and respectively marked as M1，M2，M3，…，Mn-1，MnThe cylindrical composite frozen bodies obtained after each freezing are respectively marked as F1，F2，F3，…，Fn-1，Fn；
Step 7, vacuum freeze drying:
subjecting the cylindrical composite frozen body F obtained in step 6 tonFreeze-drying under vacuum to obtain cylindrical composite frozen body FnSublimating the solvent crystal to obtain a porous blank;
step 8, thermal oxidation curing:
carrying out curing treatment on the porous blank obtained in the step 7 for 2h at 180 ℃ in air to form a cross-linked three-dimensional network structure in the porous blank so as to prevent the porous blank prepared in the step 7 from melting;
step 9, pyrolysis:
placing the cured porous blank prepared in the step 8 in a vacuum tube furnace, and pyrolyzing for 2h at 1200 ℃ under the protection of Ar gas to obtain polymer converted SiC/CfAn aerogel.
FIGS. 1 and 2 are both polymer-converted SiC/C prepared in example 1fThe aerogel can be observed to have a stable three-dimensional structure, and the pore structure is formed by lapping fibers.
FIG. 3 shows conventional Al2O3Fiber aerogels and Polymer conversion SiC/C of the inventionfComparative infrared thermography of aerogels, from which Al can be observed2O3The heat transfer temperature of the fiber aerogel and the polymer converted SiC/Cf aerogel is higher than that of the fiber aerogel and the polymer converted SiC/Cf aerogel at the same heating table temperature, no matter at the bottom, the middle or the top, and the polymer converted SiC/C can be seenfThe aerogel has better heat-insulating property than Al2O3A fibrous aerogel.
Example 4
The invention relates to a polymer converted SiC/CfThe preparation method of the aerogel is specifically implemented according to the following steps:
step 1, carbon fiber pretreatment
Ball-milling commercial carbon fibers for 12 hours, then placing the commercial carbon fibers in an acetone solution, treating the commercial carbon fibers at 70 ℃ for 36 hours in a hydrothermal reaction kettle, then carrying out vacuum filtration on the solution for 1 hour, carrying out vacuum filtration on the obtained carbon fibers in a 65% nitric acid solution for 3 hours, then carrying out vacuum filtration on the obtained carbon fibers, carrying out vacuum filtration on the obtained carbon fibers for 1 hour, carrying out centrifugal cleaning treatment on the obtained carbon fibers at 8000rpm for 5 minutes, and finally treating the obtained carbon fibers in a vacuum drying oven at 80 ℃ for 3 hours;
step 2, preparing precursor slurry
Placing camphene crystallized at room temperature into a beaker, placing the beaker into a water bath stirring pot, keeping the temperature at 60 ℃ to convert camphene into liquid to be used as a solvent, then adding polycarbosilane powder and the carbon fiber treated in the step 1, mixing to obtain precursor slurry, preparing n groups of precursor slurry with the number T being more than or equal to 2, and marking the group as the group T1，T2，T3，…，Tn-1，TnWherein the total addition amount of the polycarbosilane powder and the treated carbon fiber in the nth group is larger than that of the (n-1) th group, wherein the total addition amount of the polycarbosilane powder and the treated carbon fiber is 1 wt% of the addition amount of camphene, and the mass ratio of the polycarbosilane powder to the treated carbon fiber is 1: 1;
step 3, hydrothermal treatment
Transferring the precursor slurry prepared in the step 2 to a hydrothermal reaction kettle respectively for hydrothermal treatment for 3 hours at 180 ℃;
step 4, heating and stirring
Continuously stirring the precursor slurry hydrothermally finished in the step 3 at 60 ℃ for 3 hours to obtain mixed precursor slurry;
step 5, high-speed stirring
Stirring the precursor slurry stirred in the step 4 at 5000rpm for 15min, then continuously stirring at 7000rpm for 5min to obtain completely uniform mixed precursor slurry, and keeping the temperature of the precursor slurry at 60 ℃ during stirring;
step 6, freezing
Sequentially carrying out ultrasonic treatment and freezing treatment on the mixed precursor slurry obtained in the step 5, wherein directional freezing is adopted for freezing, the directional freezing temperature is-40 ℃, the freezing time t is more than or equal to 1h, freezing is adopted by a freezing mould, the side wall of the freezing mould is a tubular heat-insulating material, the bottom surface of the freezing mould is a heat-conducting metal, the freezing direction is vertical to the ground, n groups of the freezing moulds are more than or equal to 2, and the groups are respectively marked as M1，M2，M3，…，Mn-1，MnThe cylindrical composite frozen bodies obtained after each freezing are respectively marked as F1，F2，F3，…，Fn-1，Fn；
Step 7, vacuum freeze drying
Subjecting the cylindrical composite frozen body F obtained in step 6 tonAfter demolding, freeze-drying in a vacuum environment to obtain a porous blank;
step 8, thermal oxidation curing
Curing the porous blank obtained in the step 7 in air at 180 ℃ for 1.5 h;
step 9, pyrolysis
Placing the cured porous blank prepared in the step 8 in a vacuum tube furnace, and pyrolyzing for 1h at 1000 ℃ under the protection of Ar gas to obtain polymer converted SiC/CfAn aerogel.
Example 5
The invention relates to a polymer converted SiC/CfThe preparation method of the aerogel is specifically implemented according to the following steps:
step 1, carbon fiber pretreatment
Ball-milling commercial carbon fibers for 24 hours, then placing the commercial carbon fibers in an acetone solution, treating the commercial carbon fibers at 75 ℃ for 48 hours in a hydrothermal reaction kettle, then carrying out vacuum filtration on the solution for 1.5 hours to obtain carbon fibers, placing the carbon fibers in a 65% nitric acid solution for treatment for 3 hours, then carrying out vacuum filtration to obtain the carbon fibers, carrying out vacuum filtration on the carbon fibers for 1.5 hours by using deionized water, then carrying out centrifugal cleaning treatment on the carbon fibers after the vacuum filtration for 10 minutes at 8500rpm, and finally treating the carbon fibers for 3 hours in a vacuum drying oven at 80 ℃;
step 2, preparing precursor slurry
Placing camphene crystallized at room temperature into a beaker, placing the beaker into a water bath stirring pot, keeping the temperature at 60-80 ℃ to convert camphene into liquid as a solvent, then adding polycarbosilane powder and the carbon fiber treated in the step 1, mixing to obtain precursor slurry, preparing n groups of precursor slurry with the number T being more than or equal to 2, and marking the precursor slurry as T1，T2，T3，…，Tn-1，TnWherein the total addition amount of the polycarbosilane powder and the treated carbon fiber in the nth group is greater than that of the (n-1) th group, wherein the total addition amount of the polycarbosilane powder and the treated carbon fiber is 3 wt% of the addition amount of camphene, and the mass ratio of the polycarbosilane powder to the treated carbon fiber is 1: 1;
step 3, hydrothermal treatment
Transferring the precursor slurry prepared in the step 2 to a hydrothermal reaction kettle respectively for hydrothermal treatment for 3 hours at 180 ℃;
step 4, heating and stirring
Continuously stirring the precursor slurry hydrothermally finished in the step 3 at 80 ℃ for 6 hours to obtain mixed precursor slurry;
step 5, high-speed stirring
Stirring the precursor slurry stirred in the step 4 at 5000rpm for 15min, then continuously stirring at 7000rpm for 5min to obtain completely uniform mixed precursor slurry, and keeping the temperature of the precursor slurry at 80 ℃ during stirring;
step 6, freezing
Sequentially carrying out ultrasonic treatment and freezing treatment on the mixed precursor slurry obtained in the step 5, wherein directional freezing is adopted for freezing, the directional freezing temperature is-20 ℃, the freezing time t is more than or equal to 1h, freezing is adopted by a freezing mould, the side wall of the freezing mould is a tubular heat-insulating material, the bottom surface of the freezing mould is a heat-conducting metal, the freezing direction is vertical to the ground, n groups of the freezing moulds are more than or equal to 2, and the groups are respectively marked as M1，M2，M3，…，Mn-1，MnThe cylindrical composite frozen bodies obtained after each freezing are respectively marked as F1，F2，F3，…，Fn-1，Fn；
Step 7, vacuum freeze drying
Subjecting the cylindrical composite frozen body F obtained in step 6 tonAfter demolding, freeze-drying in a vacuum environment to obtain a porous blank;
step 8, thermal oxidation curing
Curing the porous blank obtained in the step 7 in air at 200 ℃ for 2 h;
step 9, pyrolysis
Placing the cured porous blank prepared in the step 8 in a vacuum tube furnace, and pyrolyzing for 2h at 1500 ℃ under the protection of Ar gas to obtain polymer converted SiC/CfAn aerogel.
Example 6
The invention relates to a polymer converted SiC/CfThe preparation method of the aerogel is specifically implemented according to the following steps:
step 1, carbon fiber pretreatment
Ball-milling commercial carbon fibers for 18 hours, then placing the commercial carbon fibers in an acetone solution, treating the commercial carbon fibers at 73 ℃ for 42 hours in a hydrothermal reaction kettle, then carrying out vacuum filtration on the solution for 1.2 hours to obtain carbon fibers, placing the carbon fibers in a 65% nitric acid solution for treatment for 3 hours, then carrying out vacuum filtration to obtain carbon fibers, carrying out vacuum filtration on the carbon fibers for 1.3 hours by using deionized water, then carrying out centrifugal cleaning treatment on the carbon fibers subjected to vacuum filtration for 8 minutes at 8300rpm, and finally treating the carbon fibers in a vacuum drying oven at 80 ℃ for 3 hours;
step 2, preparing precursor slurry
Placing camphene crystallized at room temperature into a beaker, placing the beaker into a water bath stirring pot, keeping the temperature at 70 ℃ to convert camphene into liquid to be used as a solvent, then adding polycarbosilane powder and the carbon fiber treated in the step 1, mixing to obtain precursor slurry, preparing n groups of precursor slurry with the number T being more than or equal to 2, and marking the group as the group T1，T2，T3，…，Tn-1，TnWherein the total addition amount of the polycarbosilane powder and the treated carbon fiber in the nth group is greater than that of the (n-1) th group, wherein the total addition amount of the polycarbosilane powder and the treated carbon fiber is 2 wt% of the addition amount of camphene, and the mass ratio of the polycarbosilane powder to the treated carbon fiber is 1: 1;
step 3, hydrothermal treatment
Transferring the precursor slurry prepared in the step 2 to a hydrothermal reaction kettle respectively for hydrothermal treatment for 3 hours at 180 ℃;
step 4, heating and stirring
Continuously stirring the precursor slurry hydrothermally finished in the step 3 at 70 ℃ for 4.5 hours to obtain mixed precursor slurry;
step 5, high-speed stirring
Stirring the precursor slurry stirred in the step 4 at 5000rpm for 15min, then continuously stirring at 7000rpm for 5min to obtain completely uniform mixed precursor slurry, and keeping the temperature of the precursor slurry at 70 ℃ during stirring;
step 6, freezing
Sequentially carrying out ultrasonic treatment and freezing treatment on the mixed precursor slurry obtained in the step 5, wherein directional freezing is adopted for freezing, the directional freezing temperature is-30 ℃, the freezing time t is more than or equal to 1h, freezing is adopted by a freezing mould, the side wall of the freezing mould is a tubular heat-insulating material, the bottom surface of the freezing mould is a heat-conducting metal, the freezing direction is vertical to the ground, n groups of the freezing moulds are more than or equal to 2, and the groups are respectively marked as M1，M2，M3，…，Mn-1，MnThe cylindrical composite frozen bodies obtained after each freezing are respectively marked as F1，F2，F3，…，Fn-1，Fn；
Step 7, vacuum freeze drying
Subjecting the cylindrical composite frozen body F obtained in step 6 tonAfter demolding, freeze-drying in a vacuum environment to obtain a porous blank;
step 8, thermal oxidation curing
Curing the porous blank obtained in the step 7 in air at 190 ℃ for 1.7 h;
step 9, pyrolysis
Placing the cured porous blank prepared in the step 8 in a vacuum tube furnace, and pyrolyzing for 1.5h at 1300 ℃ under the protection of Ar gas to obtain polymer converted SiC/CfAn aerogel.

Claims (9)

1. Polymer conversionSiC/CfThe preparation method of the aerogel is characterized by comprising the following steps:
step 1, carbon fiber pretreatment
Ball-milling carbon fibers, placing the carbon fibers in an acetone solution for hydrothermal reaction for a certain time, carrying out vacuum filtration on the obtained solution, carrying out suction filtration on the carbon fibers obtained by suction filtration sequentially by using a nitric acid solution and deionized water, and then drying the carbon fibers after the suction filtration after centrifugal cleaning;
step 2, preparing precursor slurry
Placing camphene crystallized at room temperature into a beaker, placing the beaker into a water bath stirring pot, keeping the temperature at 60-80 ℃ to convert camphene into liquid as a solvent, then adding polycarbosilane powder and the carbon fiber treated in the step 1, mixing to obtain precursor slurry, preparing n groups of precursor slurry with the number T being more than or equal to 2, and marking the precursor slurry as T1，T2，T3，…，Tn-1，TnWherein the total addition amount of the polycarbosilane powder and the treated carbon fiber in the nth group is more than that of the (n-1) th group;
step 3, hydrothermal treatment
Respectively transferring the precursor slurry prepared in the step 2 to a hydrothermal reaction kettle for hydrothermal treatment;
step 4, heating and stirring
Continuously stirring the precursor slurry hydrothermally finished in the step 3 at the temperature of 60-80 ℃ for 3-6h to obtain mixed precursor slurry;
step 5, high-speed stirring
Stirring the precursor slurry stirred in the step 4 at 5000rpm for 15min, then continuously stirring at 7000rpm for 5min to obtain completely uniform mixed precursor slurry, and keeping the temperature of the precursor slurry at 60-80 ℃ during stirring;
step 6, freezing
Sequentially carrying out ultrasonic treatment and freezing treatment on the mixed precursor slurry obtained in the step 5, wherein the freezing treatment adopts directional freezing and freezing mold freezing, the side wall of the freezing mold is a tubular heat-insulating material, the bottom surface of the freezing mold is a heat-conducting metal, the freezing direction is vertical to the ground and is upward, n groups of the freezing molds are more than or equal to 2 groups, and the groups are respectively marked as M1，M2，M3，…，Mn-1，MnThe cylindrical composite frozen bodies obtained after each freezing are respectively marked as F1，F2，F3，…，Fn-1，Fn；
Step 7, vacuum freeze drying
Subjecting the cylindrical composite frozen body F obtained in step 6 tonAfter demolding, freeze-drying in a vacuum environment to obtain a porous blank;
step 8, thermal oxidation curing
Curing the porous blank obtained in the step 7 in air at 180-200 ℃ for 1.5-2 h;
step 9, pyrolysis
Placing the cured porous blank prepared in the step 8 into a vacuum tube furnace, and pyrolyzing for 1-2h at the temperature of 1500 ℃ under the protection of Ar gas at 1000 ℃ to obtain polymer converted SiC/CfAn aerogel.
2. A polymer converted SiC/C according to claim 1fThe preparation method of the aerogel is characterized in that the carbon fibers in the step 1 are commercial carbon fibers, and the ball milling time is 12-24 h.
3. A polymer converted SiC/C according to claim 2fThe preparation method of the aerogel is characterized in that in the step 1, the ball-milled carbon fibers are placed in an acetone solution for hydrothermal reaction for a certain time, and then the obtained solution is subjected to vacuum filtration, specifically:
and (3) placing the ball-milled carbon fibers in an acetone solution, treating for 36-48h at 70-75 ℃ of a hydrothermal reaction kettle, and then carrying out vacuum filtration on the solution for 1-1.5 h.
4. A polymer converted SiC/C according to claim 3fThe preparation method of the aerogel is characterized in that the carbon fiber obtained by suction filtration in the step 1 is subjected to suction filtration by sequentially adopting nitric acid solution and deionized water, and specifically comprises the following steps:
and (3) placing the carbon fiber subjected to vacuum filtration in a 65% nitric acid solution for treatment for 3 hours, then carrying out vacuum filtration to obtain the carbon fiber, and carrying out vacuum filtration with deionized water for 1-1.5 hours.
5. A polymer converted SiC/C according to claim 4fThe preparation method of the aerogel is characterized in that the step 1 of centrifugally cleaning the carbon fibers subjected to suction filtration and then drying specifically comprises the following steps: and (3) centrifugally cleaning the filtered carbon fiber at 8000-8500rpm for 5-10min, and finally treating the carbon fiber in a vacuum drying oven at 80 ℃ for 3 h.
6. A polymer converted SiC/C according to claim 5fThe preparation method of the aerogel is characterized in that the hydrothermal treatment in the step 3 is treatment at 180 ℃ for 3 hours.
7. A polymer converted SiC/C according to claim 6fThe preparation method of the aerogel is characterized in that the total adding amount of the polycarbosilane powder and the treated carbon fiber in the step 2 is 1-3 wt% of the adding amount of camphene.
8. A polymer converted SiC/C according to claim 7fThe preparation method of the aerogel is characterized in that the mass ratio of the polycarbosilane powder to the treated carbon fiber is 1: 1.
9. A polymer converted SiC/C according to claim 8fThe preparation method of the aerogel is characterized in that the directional freezing temperature in the step 6 is-40 to-20 ℃, and the freezing time t is more than or equal to 1 h.
CN202111259104.0A 2021-10-27 2021-10-27 Polymer-converted SiC/CfMethod for producing aerogels Withdrawn CN113912406A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115318210A (en) * 2022-08-11 2022-11-11 宿辉 Preparation method and application of cobalt disulfide/porous carbon/silicon carbide aerogel composite material for electromagnetic shielding

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115318210A (en) * 2022-08-11 2022-11-11 宿辉 Preparation method and application of cobalt disulfide/porous carbon/silicon carbide aerogel composite material for electromagnetic shielding
CN115318210B (en) * 2022-08-11 2024-04-02 宿辉 Preparation method and application of cobalt disulfide/porous carbon/silicon carbide aerogel composite material for electromagnetic shielding

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