CN112851292B - Wave-transparent and efficient heat-insulating aerogel composite material and preparation method thereof - Google Patents
Wave-transparent and efficient heat-insulating aerogel composite material and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a wave-transparent and efficient heat-insulating aerogel composite material and a preparation method thereof, and the preparation method specifically comprises the following steps: firstly preparing silica sol, uniformly mixing the silica sol and an acid catalyst according to a certain proportion to form a precursor, then adding an alkaline catalyst to prepare a silica-based sol solution, performing programmed vacuum impregnation on a fiber prefabricated member and liquid sealing of the solvent, then heating and aging the fiber prefabricated member and simultaneously performing solvent replacement until an initial gel is formed, then placing the initial gel in a carbon dioxide supercritical fluid drying kettle for drying, after the drying process is finished, treating the composite material by adopting a high-temperature process, and cooling to room temperature after drying treatment to obtain the wave-transmitting and efficient heat-insulating aerogel composite material. The method for preparing the wave-transmitting and efficient heat-insulating aerogel composite material by utilizing supercritical drying and programmed vacuum impregnation does not need to introduce any surfactant or dispersant, and is easy to operate.
Description
Technical Field
The invention belongs to the technical field of aerogel composite materials, and particularly relates to a wave-transparent and efficient heat-insulation aerogel composite material and a preparation method thereof.
Background
In recent years, with the development of countries, the national defense strength is required to be higher and higher, one of the high requirement signs of the national defense level is the high requirement of aerospace technology, and thus the quality requirement of equipment and instrument materials is also higher and higher.
When the hypersonic aircraft flies at a high speed, the temperature of the outer surface of the hypersonic aircraft can reach 1200 ℃, and if the hypersonic aircraft flies at a higher speed, higher heat is generated, so that a material with better heat insulation performance is needed. In addition, light weight is also one of the indispensable requirements in view of the problem of energy loss of the aircraft. Finally, in order to enable signals of communication equipment of aircrafts in the aerospace field to be transmitted normally, the requirement on wave transmission performance of the communication equipment is further advanced.
In the face of increasingly stringent material quality requirements, conventional materials have been unable to effectively address the diverse needs. Therefore, the field of materials is now facing a serious challenge in the transition from single functionalization to multiple functionalization.
The aerogel is a porous material which has a porous nano structure and a three-dimensional network structure, and the pores of the aerogel are filled with gas as a dispersion medium, so that the heat insulation performance of the aerogel is superior to that of the traditional heat insulation material. However, the common light aerogel is difficult to overcome the defects of large brittleness, high shrinkage rate and the like, and in addition,the wave-transparent performance of the partially translucent aerogel is also obviously reduced due to the influence of the temperature, the air pressure and the ultra-high speed flight speed in the high space. The prior conventional solution generally adopts a fiber material and aerogel to prepare an aerogel fiber composite material, so that the physical strength of the aerogel fiber composite material is improved, and the wave-transmitting performance is improved. There have been studies on aerogel composite materials, such as a high temperature resistant, high strength, low thermal conductivity SiO in Chinese patent application CN2018109396122Aerogel composite material comprising a hollow carbon foam skeleton, a SiC coating and SiO2The aerogel protective shell is formed by hollow carbon foam frameworks which are three-dimensional net-shaped interconnected and comprise three-dimensional nodes and fibrous hollow tubes, the SiC coating is uniformly coated on the outer wall of the hollow carbon foam frameworks, the SiC coating is compact and uniform, and SiO is coated on the outer wall of the hollow carbon foam frameworks2The aerogel protective shell is made of SiO uniformly filled in the pores of the hollow carbon foam skeleton2The aerogel is obtained after heat treatment, volume shrinkage and agglomeration. For another example, the preparation method of the CN201911053850 high-temperature resistant SiC aerogel comprises the following steps: preparing solution A and solution B, and mixing the solution A and the solution B to obtain hydrolysate; preparing wet gel; preparing aerogel; fourthly, after the aerogel reacts with the magnesium powder, the mixture is washed and dried to obtain the SiC aerogel.
At present, the most mature and commonly used material for fiber composite is silicon-based aerogel, however, the existing silicon-based fiber composite aerogel has improved physical strength, but leads to increased thermal conductivity and reduced wave-transmitting performance.
If the heat insulation and wave transmission performance of the aerogel fiber composite material can be improved by researching the improvement on the process or the use of the material, the positive and profound influence on the aerospace field and other fields in China is certainly generated.
Disclosure of Invention
The invention aims to provide a wave-transmitting and efficient heat-insulating aerogel composite material and a preparation method thereof, aiming at the defects that the physical strength of the existing aerogel composite material is improved, but the heat conductivity is increased and the wave-transmitting performance is weakened, and the obtained wave-transmitting and efficient heat-insulating aerogel composite material has good heat-insulating performance and strong wave-transmitting performance.
The preparation method of the wave-transparent and efficient heat-insulating aerogel composite material comprises the following steps of:
1) dissolving an acid catalyst in silica sol, and uniformly stirring to form a precursor;
2) adding an alkali catalyst into the precursor obtained in the step 1), and uniformly mixing to prepare a silicon-based sol solution;
3) taking the silicon-based sol solution obtained in the step 2), adding polyvinylpyrrolidone with the mass of 0.02-0.03% of that of the silicon-based sol solution, uniformly mixing, soaking the mixture in a selected fiber prefabricated member, and performing programmed vacuum soaking treatment to prepare initial gel;
4) carrying out liquid sealing treatment on the initial gel obtained in the step 3) by using a selected solvent, and then carrying out aging and solvent replacement treatment to obtain a final gel;
5) drying and drying the final-state gel obtained in the step 4) to obtain a wave-transparent efficient heat-insulating aerogel composite material;
the acid catalyst in the step 1) is selected from one of phosphoric acid, nitric acid, hydrochloric acid, acetic acid, oxalic acid, carboxylic acid, sulfonic acid or sulfinic acid;
the silica sol in the step 1) is selected from mixed liquid of more than two-element alkoxy silane and silicate ester, the mixed liquid is in any proportion, the more than two-element alkoxy silane is selected from tetraethoxy silane and vinyl triethoxy silane, and the silicate ester is selected from methyl orthosilicate and tetraethyl orthosilicate;
the alkali catalyst in the step 2) is selected from one of calcium hydroxide, sodium hydroxide, ammonia water or triethylamine, diethylamine and pyridine;
silica sol described in step 1), step 2): acid catalyst: basic catalyst according to (80-120): (3-6): (3-6) ratio of amounts of substances; the concentration of the acid catalyst and the alkali catalyst is 2-6mol/L, the dissolving time of the acid catalyst in the silica sol is 1-3h, the dissolving time of the alkali catalyst in the precursor is 0.5-3h, the dissolving temperature of the acid catalyst is 0-5 ℃, the dissolving temperature of the alkali catalyst is 20-45 ℃, and the stirring speed is 200-400 rpm;
the fiber prefabricated part in the step 3) is selected from one or a mixture of more of silicon high-purity quartz fiber, aluminum sulfate fiber, graphite fiber, stone carbon fiber, zirconia fiber, glass fiber, polycrystalline mullite fiber, basalt fiber or polycrystalline alumina fiber, and the mixture is in any proportion;
the solvent in the step 4) is one selected from normal hexane, cyclohexane, normal butanol, isobutanol, ethanol, tertiary butanol, methanol and diethyl ether;
and 3) performing programmed vacuum impregnation treatment, wherein the specific process comprises the steps of regulating the vacuum degree to be-0.1 MPa, maintaining the pressure for 4 hours, regulating the vacuum degree to be-0.05 MPa, maintaining the pressure for 4 hours, regulating the vacuum degree to be-0.1 MPa, maintaining the pressure for 3 hours, regulating the vacuum degree to be-0.03 MPa, maintaining the pressure for 2 hours, regulating the vacuum degree to be-0.1 MPa, maintaining the pressure for 2 hours, regulating the vacuum degree to be-0.01 MPa, maintaining the pressure for 1 hour, boosting the pressure to normal pressure, and finishing the programmed vacuum impregnation treatment.
In the invention:
programmed vacuum impregnation treatment in the step 3), wherein the vacuum degree of programmed vacuum impregnation is controlled to be-0.1-0.01 MPa, and gradient shortening is performed when the vacuum degree is changed once, for example: hold at-0.1 MPa for 4h, then-0.0.5 MPa for 2h, then-0.1 MPa for 2h, and finally-0.04 MPa for 1 h.
And 4) carrying out liquid sealing treatment, aging treatment and solvent replacement treatment on the material by using the selected solvent, and considering that the physical strength of the material is changed due to the influence of surface tension on the skeleton, so that the solvent used in the solvent replacement is an organic solvent with lower surface tension.
The ratio of the volume of the solvent added for liquid sealing or solvent replacement to the volume of the initial gel in the step 4) is as follows: initial gel volume: volume of liquid-sealed solvent or solvent replacement solvent is 1: (2-4), aging and solvent replacement are carried out simultaneously, namely, solvent replacement is carried out while water bath heating is carried out in a water bath kettle, the temperature provided by the water bath kettle is 40-60 ℃, the replacement solvent is replaced once every 12-36h for 4-8 times, in order to ensure that the solvent replacement is more sufficient, a synchronous stirring replacement process is adopted, and the stirring speed is 200-400 rpm.
Further, the solvent replacement treatment in the step 4), wherein the solvent replacement time is changed every 14-24h for 4-6 times.
The drying in the step 5) is carried out by adopting CO2Drying in a supercritical drying kettle at the pressure of 10-18MPa, the temperature of 40-65 ℃, the flow of 20-35kg/h and the time of 8-24 h.
Further, the drying in the step 5) is carried out by using CO2Drying in a supercritical drying kettle at the pressure of 14-17MPa, the temperature of 45-65 ℃, the flow rate of 27-33kg/h and the time of 8-24 h.
And 5) drying by adopting an oven or a vacuum drying oven, wherein the temperature is increased in a stepwise manner from room temperature, the gradient is 5-30 ℃, the time gradient is 1-4h, and the total drying time is 48-96 h.
The invention also relates to a wave-transmitting high-efficiency heat-insulating aerogel composite material obtained by the preparation method, wherein the thermal conductivity at 1000 ℃ is 0.120-0.29W/(m.K), the thermal conductivity at 1200 ℃ is 0.260-0.268W/(m.K), the thermal conductivity at room temperature is 0.018-0.020W/(m.K), and the dielectric constant is 7-14GHz and is 1.19-1.27.
Compared with the prior art, the invention has the following advantages:
1. the wave-transmitting and efficient heat-insulating aerogel composite material prepared by the invention has lower heat conductivity and good wave-transmitting property; besides good heat insulation performance and wave transmission performance, the composite material also has the advantages of high physical strength, good shock absorption performance, light weight and the like.
2. The invention provides a preparation method of a wave-transparent and efficient heat-insulating aerogel composite material, which is characterized in that a silicon-based sol solution is synthesized by an acid-base two-step method under the condition of normal temperature, and then the aerogel composite material with better heat-insulating property is prepared by adopting an original programmed vacuum impregnation method; although the crosslinking speed is inhibited under the normal temperature condition, the physical strength of the aerogel skeleton obtained by normal-temperature crosslinking is higher and the thermal conductivity is lower through observation, then the preparation time is greatly shortened through the adopted synchronous replacement aging process, the defect of low normal-temperature crosslinking speed of the aerogel skeleton is overcome, and finally the aerogel composite material obtained by adopting the programmed vacuum impregnation method and the aerogel composite material prepared by the conventional impregnation method have better wave transmission performance and heat insulation performance.
Drawings
FIG. 1 is a schematic process flow diagram of the preparation method of the present invention.
Detailed Description
The present invention is described in further detail below by way of examples, which should not be construed as limiting the invention thereto.
Example 1:
a preparation method of a wave-transparent and efficient heat-insulating aerogel composite material comprises the following steps:
1) dissolving an acid catalyst (phosphoric acid) in silica sol, and uniformly stirring to form a precursor;
2) adding an alkali catalyst (calcium hydroxide) into the precursor obtained in the step 1), and uniformly mixing to prepare a silicon-based sol solution;
3) taking the silicon-based sol solution obtained in the step 2), adding polyvinylpyrrolidone with the mass equivalent to 0.02% of that of the silicon-based sol solution, uniformly mixing, soaking the silicon-based sol solution in a selected fiber prefabricated member, and performing programmed vacuum impregnation treatment, wherein the specific process comprises the steps of regulating the vacuum degree to-0.1 MPa, maintaining the pressure for 4 hours, regulating the vacuum degree to-0.05 MPa, maintaining the pressure for 4 hours, regulating the vacuum degree to-0.1 MPa, maintaining the pressure for 3 hours, regulating the vacuum degree to-0.03 MPa, maintaining the pressure for 2 hours, regulating the vacuum degree to-0.01 MPa, maintaining the pressure for 2 hours, regulating the vacuum degree to-0.1 MPa, maintaining the pressure for 1 hour, and finally boosting the pressure to normal pressure, finishing the programmed vacuum impregnation treatment, and preparing initial gel;
4) carrying out liquid sealing treatment on the initial gel obtained in the step 3) by using a selected solvent, and then carrying out aging and solvent replacement treatment to obtain a final gel;
5) adopting CO for the final state gel obtained in the step 4)2Drying in a supercritical drying kettle at the pressure of 10MPa, the temperature of 40 ℃, the flow of 20kg/h and the time of 8h, then drying in an oven at the temperature of 5 ℃ and the time gradient of 1h, wherein the temperature is raised in a stepwise manner from room temperature, and the total drying time is 48h to obtain the wave-transmitting and efficient heat-insulating aerogel composite material;
the silica sol in the step 1) is selected from mixed liquid of tetraethoxysilane and methyl orthosilicate in equal volume;
silica sol described in step 1), step 2): acid catalyst: basic catalyst, according to 80: 6: 3 the ratio of the amounts of the substances; the concentration of the acid catalyst and the concentration of the alkali catalyst are both 2mol/L, the dissolving time of the acid catalyst in silica sol is 3h, the dissolving time of the alkali catalyst in precursor is 0.5h, the dissolving temperature of the acid catalyst is 0 ℃, the dissolving temperature of the alkali catalyst is 20 ℃, and the stirring speed is 200 rpm;
the fiber prefabricated member in the step 3) is selected from silicon high-purity quartz fiber;
the solvent in the step 4) is selected from n-hexane;
the ratio of the volume of the solvent added for liquid sealing or solvent replacement to the volume of the initial gel in the step 4) is as follows: initial gel volume: volume of liquid-sealed solvent or solvent replacement solvent is 1:2, aging and solvent replacement are carried out simultaneously, namely, solvent replacement is carried out while water bath heating is carried out in a water bath kettle, the temperature provided by the water bath kettle is 40 ℃, the replacement solvent is replaced once every 12 hours for 4 times, in order to ensure that the solvent replacement is more sufficient, a synchronous stirring replacement process is adopted, and the stirring speed is 200 rpm.
Example 2:
a preparation method of a wave-transparent and efficient heat-insulating aerogel composite material comprises the following steps:
1) dissolving an acid catalyst (nitric acid) in silica sol, and uniformly stirring to form a precursor;
2) adding an alkali catalyst (sodium hydroxide) into the precursor obtained in the step 1), and uniformly mixing to prepare a silicon-based sol solution;
3) taking the silicon-based sol solution obtained in the step 2), adding polyvinylpyrrolidone with the mass equivalent to 0.03 percent of that of the silicon-based sol solution, uniformly mixing, soaking the silicon-based sol solution in a selected fiber prefabricated member, and performing programmed vacuum impregnation treatment, wherein the specific process comprises the steps of regulating the vacuum degree to be-0.1 MPa, maintaining the pressure for 4 hours, regulating the vacuum degree to be-0.05 MPa, maintaining the pressure for 4 hours, regulating the vacuum degree to be-0.1 MPa, maintaining the pressure for 3 hours, regulating the vacuum degree to be-0.03 MPa, maintaining the pressure for 2 hours, regulating the vacuum degree to be-0.01 MPa, maintaining the pressure for 2 hours, regulating the vacuum degree to be-0.1 MPa, maintaining the pressure for 1 hour, and finally boosting the pressure to be normal pressure, finishing the programmed vacuum impregnation treatment, and preparing initial gel;
4) carrying out liquid sealing treatment on the initial gel obtained in the step 3) by using a selected solvent, and then carrying out aging and solvent replacement treatment to obtain a final gel;
5) adopting CO for the final state gel obtained in the step 4)2Drying in a supercritical drying kettle at the pressure of 18MPa, the temperature of 50 ℃, the flow of 30kg/h and the time of 24h, then drying in a vacuum drying oven at the temperature of 10 ℃ and 2h from room temperature in a stepped manner, wherein the total drying time is 96h, so as to obtain the wave-transmitting and efficient heat-insulating aerogel composite material;
the silica sol in the step 1) is selected from mixed solution of vinyl triethoxysilane and tetraethyl orthosilicate according to the volume ratio of 1: 2;
silica sol described in step 1), step 2): acid catalyst: basic catalyst, according to 120: 5: 4 ratio of the amounts of substances; the concentration of the acid catalyst and the concentration of the alkali catalyst are both 3mol/L, the dissolving time of the acid catalyst in silica sol is 2h, the dissolving time of the alkali catalyst in precursor is 1h, the dissolving temperature of the acid catalyst is both 5 ℃, the dissolving temperature of the alkali catalyst is both 45 ℃, and the stirring speed is 400 rpm;
the fiber preform of step 3) selected from the group consisting of aluminum fibers;
the solvent in the step 4) is selected from cyclohexane;
the ratio of the volume of the solvent added for liquid sealing or solvent replacement to the volume of the initial gel in the step 4) is as follows: initial gel volume: volume of liquid-sealed solvent or solvent replacement solvent is 1: and 3, aging and solvent replacement are carried out simultaneously, namely, the solvent replacement is carried out while the water bath heating is carried out in a water bath kettle, the temperature provided by the water bath kettle is 60 ℃, the replacement solvent is replaced once every 24 hours for 6 times, and in order to ensure that the solvent replacement is more sufficient, a synchronous stirring replacement process is adopted, and the stirring speed is 400 rpm.
Example 3:
a preparation method of a wave-transparent and efficient heat-insulating aerogel composite material comprises the following steps:
1) dissolving an acid catalyst (hydrochloric acid) in silica sol, and uniformly stirring to form a precursor;
2) adding an alkali catalyst (ammonia water) into the precursor obtained in the step 1), and uniformly mixing to prepare a silicon-based sol solution;
3) taking the silicon-based sol solution obtained in the step 2), adding polyvinylpyrrolidone with the mass equivalent to 0.025 percent of the silicon-based sol solution, uniformly mixing, soaking the silicon-based sol solution in a selected fiber prefabricated member, and performing programmed vacuum impregnation treatment, wherein the specific process comprises the steps of regulating the vacuum degree to be-0.1 MPa, maintaining the pressure for 4 hours, regulating the vacuum degree to be-0.05 MPa, maintaining the pressure for 4 hours, regulating the vacuum degree to be-0.1 MPa, maintaining the pressure for 3 hours, regulating the vacuum degree to be-0.03 MPa, maintaining the pressure for 2 hours, regulating the vacuum degree to be-0.01 MPa, maintaining the pressure for 2 hours, regulating the vacuum degree to be-0.1 MPa, maintaining the pressure for 1 hour, and finally boosting the pressure to be normal, finishing the programmed vacuum impregnation treatment, and preparing initial gel;
4) carrying out liquid sealing treatment on the initial gel obtained in the step 3) by using a selected solvent, and then carrying out aging and solvent replacement treatment to obtain a final gel;
5) adopting CO for the final state gel obtained in the step 4)2Drying in a supercritical drying kettle at the pressure of 15MPa, the temperature of 65 ℃, the flow rate of 35kg/h and the time of 16h, then drying in an oven at the temperature of 15MPa, the temperature of 15 ℃ and the time gradient of 3h, wherein the total drying time is 72h, so as to obtain the wave-transmitting and efficient heat-insulating aerogel composite material;
the silica sol in the step 1) is selected from mixed liquid of vinyl triethoxysilane and methyl orthosilicate in equal volume;
silica sol described in step 1), step 2): acid catalyst: basic catalyst, according to 100: 4: 5 ratio of the amounts of substances; the concentration of the acid catalyst and the concentration of the alkali catalyst are both 4mol/L, the dissolving time of the acid catalyst in silica sol is 1h, the dissolving time of the alkali catalyst in precursor is 1.5h, the dissolving temperature of the acid catalyst is 3 ℃, the dissolving temperature of the alkali catalyst is 30 ℃, and the stirring speed is 300 rpm;
the fiber prefabricated member in the step 3) is selected from equal weight mixing of graphite fiber, stone carbon fiber and zirconia fiber;
the solvent in the step 4) is selected from diethyl ether;
the ratio of the volume of the solvent added for liquid sealing or solvent replacement to the volume of the initial gel in the step 4) is as follows: initial gel volume: volume of liquid-sealed solvent or solvent replacement solvent is 1: and 4, aging and solvent replacement are carried out simultaneously, namely, solvent replacement is carried out while water bath heating is carried out in a water bath kettle, the temperature provided by the water bath kettle is 50 ℃, the replacement solvent is replaced once every 36h for 8 times, in order to ensure that the solvent replacement is more sufficient, a synchronous stirring replacement process is adopted, and the stirring speed is 300 rpm.
Example 4:
a preparation method of a wave-transparent and efficient heat-insulating aerogel composite material comprises the following steps:
1) dissolving an acid catalyst (acetic acid) in silica sol, and uniformly stirring to form a precursor;
2) adding an alkali catalyst (triethylamine) into the precursor obtained in the step 1), and uniformly mixing to prepare a silicon-based sol solution;
3) taking the silicon-based sol solution obtained in the step 2), adding polyvinylpyrrolidone with the mass equivalent to 0.02% of that of the silicon-based sol solution, uniformly mixing, soaking the silicon-based sol solution in a selected fiber prefabricated member, and performing programmed vacuum impregnation treatment, wherein the specific process comprises the steps of regulating the vacuum degree to-0.1 MPa, maintaining the pressure for 4 hours, regulating the vacuum degree to-0.05 MPa, maintaining the pressure for 4 hours, regulating the vacuum degree to-0.1 MPa, maintaining the pressure for 3 hours, regulating the vacuum degree to-0.03 MPa, maintaining the pressure for 2 hours, regulating the vacuum degree to-0.01 MPa, maintaining the pressure for 2 hours, regulating the vacuum degree to-0.1 MPa, maintaining the pressure for 1 hour, and finally boosting the pressure to normal pressure, finishing the programmed vacuum impregnation treatment, and preparing initial gel;
4) carrying out liquid sealing treatment on the initial gel obtained in the step 3) by using a selected solvent, and then carrying out aging and solvent replacement treatment to obtain a final gel;
5) adopting CO for the final state gel obtained in the step 4)2Drying in a supercritical drying kettle at the pressure of 14MPa, the temperature of 45 ℃, the flow rate of 27kg/h and the time of 20h, then drying in a vacuum drying oven at the temperature of 20 ℃ and 4h from room temperature by adopting step-type heating, and obtaining the wave-transmitting and efficient heat-insulating aerogel composite material, wherein the total drying time is 48 h;
the silica sol in the step 1) is selected from mixed liquor of tetraethoxysilane, vinyl triethoxysilane and methyl orthosilicate in equal volume ratio;
silica sol described in step 1), step 2): acid catalyst: basic catalyst, according to a ratio of 90: 3: 5 ratio of the amounts of substances; the concentration of the acid catalyst and the concentration of the alkali catalyst are both 5mol/L, the dissolving time of the acid catalyst in silica sol is 2h, the dissolving time of the alkali catalyst in precursor is 2h, the dissolving temperature of the acid catalyst is 2 ℃, the dissolving temperature of the alkali catalyst is 25 ℃, and the stirring speed is 250 rpm;
the fiber prefabricated member in the step 3) is selected from equal-volume mixing of glass fiber and polycrystalline mullite fiber;
the solvent in the step 4) is selected from n-butanol;
the ratio of the volume of the solvent added for liquid sealing or solvent replacement to the volume of the initial gel in the step 4) is as follows: initial gel volume: volume of liquid-sealed solvent or solvent replacement solvent is 1: and 3, aging and solvent replacement are carried out simultaneously, namely, the solvent replacement is carried out while the water bath heating is carried out in a water bath kettle, the temperature provided by the water bath kettle is 45 ℃, the replacement solvent is replaced once every 14 hours for 4 times, in order to ensure that the solvent replacement is more sufficient, a synchronous stirring replacement process is adopted, and the stirring speed is 250 rpm.
Example 5:
a preparation method of a wave-transparent and efficient heat-insulating aerogel composite material comprises the following steps:
1) dissolving an acid catalyst (sulfinic acid) in silica sol, and uniformly stirring to form a precursor;
2) adding an alkali catalyst (diethylamine) into the precursor obtained in the step 1), and uniformly mixing to prepare a silicon-based sol solution;
3) taking the silicon-based sol solution obtained in the step 2), adding polyvinylpyrrolidone with the mass equivalent to 0.03 percent of that of the silicon-based sol solution, uniformly mixing, soaking the silicon-based sol solution in a selected fiber prefabricated member, and performing programmed vacuum impregnation treatment, wherein the specific process comprises the steps of regulating the vacuum degree to be-0.1 MPa, maintaining the pressure for 4 hours, regulating the vacuum degree to be-0.05 MPa, maintaining the pressure for 4 hours, regulating the vacuum degree to be-0.1 MPa, maintaining the pressure for 3 hours, regulating the vacuum degree to be-0.03 MPa, maintaining the pressure for 2 hours, regulating the vacuum degree to be-0.01 MPa, maintaining the pressure for 2 hours, regulating the vacuum degree to be-0.1 MPa, maintaining the pressure for 1 hour, and finally boosting the pressure to be normal pressure, finishing the programmed vacuum impregnation treatment, and preparing initial gel;
4) carrying out liquid sealing treatment on the initial gel obtained in the step 3) by using a selected solvent, and then carrying out aging and solvent replacement treatment to obtain a final gel;
5) adopting CO for the final state gel obtained in the step 4)2Drying in a supercritical drying kettle at the pressure of 17MPa, the temperature of 65 ℃, the flow rate of 33kg/h and the time of 24h, then drying in an oven at the temperature of 30 ℃ for 4h, wherein the temperature is raised in a stepped manner from room temperature, and the total drying time is 96h, so as to obtain the wave-transparent and efficient heat-insulating aerogel composite material;
the silica sol in the step 1) is selected from tetraethoxysilane, methyl orthosilicate and tetraethyl orthosilicate, and is mixed liquid according to the volume ratio of 2:1: 1;
silica sol described in step 1), step 2): acid catalyst: basic catalyst, as per 110: 5: 6 amount of substance; the concentration of the acid catalyst and the concentration of the alkali catalyst are both 6mol/L, the dissolving time of the acid catalyst in silica sol is 3h, the dissolving time of the alkali catalyst in precursor is 3h, the dissolving temperature of the acid catalyst is 1 ℃, the dissolving temperature of the alkali catalyst is 40 ℃, and the stirring speed is 350 rpm;
the fiber prefabricated part in the step 3) is selected from graphite fiber, basalt fiber and polycrystalline alumina fiber, and the weight ratio is 2:1:1, mixing in equal volume;
the solvent in the step 4) is selected from isobutanol;
the ratio of the volume of the solvent added for liquid sealing or solvent replacement to the volume of the initial gel in the step 4) is as follows: initial gel volume: volume of liquid-sealed solvent or solvent replacement solvent is 1:2, aging and solvent replacement are carried out simultaneously, namely, solvent replacement is carried out while water bath heating is carried out in a water bath kettle, the temperature provided by the water bath kettle is 55 ℃, the replacement solvent is replaced once every 24 hours for 6 times, in order to ensure that the solvent replacement is more sufficient, a synchronous stirring replacement process is adopted, and the stirring speed is 350 rpm.
Comparative example 1:
compared with the embodiment 1, the step 3) lacks programmed vacuum impregnation treatment, adopts common vacuum impregnation treatment, impregnates the fiber preform into a selected fiber preform, and carries out vacuum impregnation treatment, and the specific flow is that the vacuum degree is adjusted to be-0.05-0.08 MPa, and the pressure is maintained for 8 hours.
Comparative example 2:
in comparison with example 1, step 3) lacks the addition of polyvinylpyrrolidone, otherwise the same as example 1.
Experimental example:
the products obtained in the above examples and comparative examples were tested for technical indicators as follows:
and (4) analyzing results:
compared with the comparative example, the heat conductivity of the wave-transmitting and efficient heat-insulating aerogel composite material obtained in the example is reduced by more than 11.0% at 1000 ℃, reduced by more than 6.9% at 1200 ℃, and improved by more than 8.0%, which shows that the silicon-based sol solution is synthesized by an acid-base two-step method under the normal temperature condition, and then the aerogel composite material with better heat-insulating property is prepared by adopting an original programmed vacuum impregnation method; although the crosslinking speed is inhibited under the normal temperature condition, the physical strength of the aerogel skeleton obtained by normal-temperature crosslinking is higher and the thermal conductivity is lower through observation, then the preparation time is greatly shortened through the adopted synchronous replacement aging process, the defect of low normal-temperature crosslinking speed of the aerogel skeleton is overcome, and finally the aerogel composite material obtained by adopting the programmed vacuum impregnation method and the aerogel composite material prepared by the conventional impregnation method have better wave transmission performance and heat insulation performance.
The comparison of the basic properties of the examples and comparative examples shows that the preparation process of the examples is significantly superior to the comparative examples.
Claims (6)
1. A preparation method of a wave-transparent and efficient heat-insulating aerogel composite material is characterized by comprising the following steps of: the method comprises the following steps:
1) dissolving an acid catalyst in silica sol, and uniformly stirring to form a precursor;
2) adding an alkali catalyst into the precursor obtained in the step 1), and uniformly mixing to prepare a silicon-based sol solution;
3) taking the silicon-based sol solution obtained in the step 2), adding polyvinylpyrrolidone with the mass of 0.02-0.03% of that of the silicon-based sol solution, uniformly mixing, soaking the mixture in a selected fiber prefabricated member, and performing programmed vacuum soaking treatment to prepare initial gel;
4) carrying out liquid sealing treatment on the initial gel obtained in the step 3) by using a selected solvent, and then carrying out aging and solvent replacement treatment to obtain a final gel;
5) drying and drying the final-state gel obtained in the step 4) to obtain a wave-transparent efficient heat-insulating aerogel composite material;
the acid catalyst in the step 1) is selected from one of phosphoric acid, nitric acid, hydrochloric acid, acetic acid, oxalic acid, carboxylic acid, sulfonic acid or sulfinic acid;
the silica sol in the step 1) is selected from mixed liquid of more than two-element alkoxy silane and silicate ester, the mixed liquid is in any proportion, the more than two-element alkoxy silane is selected from tetraethoxy silane and vinyl triethoxy silane, and the silicate ester is selected from methyl orthosilicate and tetraethyl orthosilicate;
the alkali catalyst in the step 2) is selected from one of calcium hydroxide, sodium hydroxide, ammonia water, triethylamine, diethylamine or pyridine;
silica sol described in step 1), step 2): acid catalyst: basic catalyst according to (80-120): (3-6): (3-6) ratio of amounts of substances; the concentration of the acid catalyst and the alkali catalyst is 2-6mol/L, the dissolving time of the acid catalyst in the silica sol is 1-3h, the dissolving time of the alkali catalyst in the precursor is 0.5-3h, the dissolving temperature of the acid catalyst is 0-5 ℃, the dissolving temperature of the alkali catalyst is 20-45 ℃, and the stirring speed is 200-400 rpm;
the fiber prefabricated part in the step 3) is selected from one or a mixture of more of silicon high-purity quartz fiber, aluminum acid fiber, graphite fiber, stone carbon fiber, zirconia fiber, glass fiber, polycrystalline mullite fiber, basalt fiber or polycrystalline alumina fiber, and the mixture is in any proportion;
the solvent in the step 4) is selected from one of normal hexane, cyclohexane, normal butanol, isobutanol, ethanol, tertiary butanol, methanol or diethyl ether; the volume ratio of the solvent added for liquid sealing or solvent replacement to the volume of the initial gel in the step 4) is the volume of the initial gel: volume of liquid-sealed solvent or solvent replacement solvent is 1: (2-4), aging and solvent replacement are carried out simultaneously, namely, the solvent replacement is carried out while water bath heating is carried out in a water bath kettle, the temperature provided by the water bath kettle is 40-60 ℃, the replacement solvent is replaced every 12-36h for 4-8 times, a synchronous stirring replacement process is adopted, and the stirring speed is 200-400 rpm;
and 3) performing programmed vacuum impregnation treatment, wherein the specific process comprises the steps of regulating the vacuum degree to be-0.1 MPa, maintaining the pressure for 4 hours, regulating the vacuum degree to be-0.05 MPa, maintaining the pressure for 4 hours, regulating the vacuum degree to be-0.1 MPa, maintaining the pressure for 3 hours, regulating the vacuum degree to be-0.03 MPa, maintaining the pressure for 2 hours, regulating the vacuum degree to be-0.1 MPa, maintaining the pressure for 2 hours, regulating the vacuum degree to be-0.01 MPa, maintaining the pressure for 1 hour, boosting the pressure to normal pressure, and finishing the programmed vacuum impregnation treatment.
2. The preparation method of the wave-transparent and efficient heat-insulating aerogel composite material according to claim 1, wherein the preparation method comprises the following steps: and 4) carrying out solvent replacement treatment, wherein the solvent replacement time is that the solvent is replaced once every 14-24h and is 4-6 times.
3. The preparation method of the wave-transparent and efficient heat-insulating aerogel composite material according to claim 1, wherein the preparation method comprises the following steps: the drying in the step 5) is carried out by adopting CO2Drying in a supercritical drying kettle at the pressure of 10-18MPa, the temperature of 40-65 ℃, the flow of 20-35kg/h and the time of 8-24 h.
4. The preparation method of the wave-transparent and efficient heat-insulating aerogel composite material according to claim 3, wherein the preparation method comprises the following steps: the drying in the step 5) is carried out by adopting CO2Drying in a supercritical drying kettle at the pressure of 14-17MPa, the temperature of 45-65 ℃, the flow rate of 27-33kg/h and the time of 8-24 h.
5. The preparation method of the wave-transparent and efficient heat-insulating aerogel composite material according to claim 1, wherein the preparation method comprises the following steps: and 5) drying by adopting an oven or a vacuum drying oven, wherein the temperature is increased in a stepwise manner from room temperature, the gradient is 5-30 ℃, the time gradient is 1-4h, and the total drying time is 48-96 h.
6. The wave-transparent and efficient heat-insulating aerogel composite material is characterized in that: the wave-transparent high-efficiency heat-insulating aerogel composite material is prepared by the method for preparing the wave-transparent high-efficiency heat-insulating aerogel composite material according to any one of claims 1 to 5, the thermal conductivity at 1000 ℃ is 0.120-0.129W/(m.K), the thermal conductivity at 1200 ℃ is 0.260-0.268W/(m.K), the thermal conductivity at room temperature is 0.018-0.020W/(m.K), and the dielectric constant is 7-14GHz and is 1.19-1.27.
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