CN109250738B - Preparation method of high-temperature resistant block alumina aerogel - Google Patents
Preparation method of high-temperature resistant block alumina aerogel Download PDFInfo
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Abstract
The invention discloses a preparation method of high-temperature resistant block alumina aerogel, which comprises the following steps: dissolving an aluminum source in a mixed solvent of distilled water and ethanol, stirring in a water bath at the temperature of 60-80 ℃ for 20-50 min, and cooling to room temperature to obtain a mixture solution; adding concentrated nitric acid into the mixture solution under the stirring action, adjusting the pH value to 1.6-1.8, mixing methanol, acetone and a catalyst, and adding the mixture into the mixture solution; and then stirring the mixture solution for 10-60 s, pouring the mixture solution into a mold, forming gel after 10-30 min generally, aging, exchanging the solvent for three days by using ethanol, and placing the wet gel into an ethanol autoclave for supercritical drying to obtain the alumina aerogel. The invention adopts a sol-gel method to prepare Al2O3Preparation of Al by wet gel and supercritical fluid drying method2O3The aerogel has simple process, easy control of reaction process and easy realization of industrialized production, and the prepared alumina aerogel has complete surface, no crack, good high temperature resistance and wide application prospect.
Description
Technical Field
The invention belongs to the technical field of aerogel material preparation, and relates to a preparation method of a high-temperature resistant block alumina aerogel material.
Background
The aerogel prepared by using the metal oxide as the matrix material has extremely poor formability, and a large number of cracks can be generated before drying, so that the application and the development of the aerogel are seriously influenced. The melting point of alumina is 2054 ℃. Therefore, alumina aerogel prepared by using alumina as a matrix can be theoretically used at high temperature and high pressure. However, the current research still does not solve the problems that the phase transformation is easy to occur at high temperature, the mechanical property is poor and the like fundamentally. This is also a direct reason why few in recent years have studied alumina aerogels exclusively against the background of heat insulation and high temperature resistance. Therefore, if scientists make a breakthrough in enhancing the mechanical properties of alumina aerogel and simultaneously making alumina aerogel have excellent heat insulation and high temperature resistance, the research on alumina aerogel with heat insulation and high temperature resistance as a research background is a hot topic in the scientific community.
Alumina aerogels are generally prepared by a sol-gel method using an organic aluminum alkoxide or an inorganic aluminum salt as a precursor. The preparation of the complete crack-free block alumina aerogel by taking inorganic aluminum salt as a precursor is very difficult because the inorganic aluminum salt has low activity, is difficult to control and is very easy to crack in the drying process. To date, there have been few reports of alumina aerogels that remain intact and crack-free at high temperatures of 1000 ℃. The super-heat-resistant strong alumina aerogel reported by the Shen topic group in 2013 is prepared into alumina aerogel capable of being used at 1000 ℃ by combining an aniline-acetone in-situ water forming method, a supercritical fluid modification method and a hexamethyldisilazane gas-phase modification method, and the use temperature of the alumina aerogel is effectively increased. However, the shrinkage is huge, and Al-Yassir N topic group prepares Al by using aluminum sec-butoxide and yttrium nitrate hexahydrate as precursors2O3-Y2O3The composite aerogel, but the aerogel is mainly used as a catalyst carrier, and the high temperature resistance of the composite aerogel is not obviously improved compared with that of the conventional alumina aerogel. So far, no reports have been made that the shrinkage of alumina aerogel is almost zero at temperatures above 1050 ℃. How to obtain complete crack-free high-temperature-resistant alumina aerogel becomes a problem which needs to be solved and considered now.
Disclosure of Invention
An object of the present invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.
To achieve these objects and other advantages in accordance with the present invention, there is provided a method for preparing a high temperature resistant bulk alumina aerogel comprising the steps of:
dissolving an aluminum source in a mixed solvent of distilled water and ethanol, stirring in a water bath at the temperature of 60-80 ℃ for 20-50 min, and cooling to room temperature to obtain a mixture solution;
step two, adding concentrated nitric acid into the mixture solution under the stirring action, adjusting the pH value to 1.6-1.8, mixing methanol, acetone and a catalyst, and adding the mixture solutionIn liquid; then stirring the mixture solution for 10-60 s, pouring the mixture solution into a mold, generally forming gel after 10-30 min, aging, exchanging the solvent with ethanol for three days, placing the wet gel into an ethanol autoclave for supercritical drying to obtain Al2O3An aerogel.
Preferably, the aluminum source is any one of aluminum sec-butoxide, aluminum acetate and aluminum oxalate.
Preferably, the ratio of ethanol: methanol: acetone: distilled water: the molar ratio of the catalyst is 10-25: 0.5-2: 0.1-0.5: 0.05-0.25; the aluminum source is as follows: the molar ratio of distilled water is 1: 0.5 to 2.5.
Preferably, the pressure of the supercritical drying is 6-8 MPa, and the temperature is 250-260 ℃; the catalyst is any one of aniline, phenylenediamine, thiourea and urea.
Preferably, in the first step, the modified attapulgite accounting for 1-20% of the mass of the silicon source and the ionic liquid accounting for 0.5-1.5% of the mass of the silicon source are added into the mixture solution.
Preferably, the preparation method of the modified attapulgite comprises the following steps: mixing attapulgite with oxalic acid with the concentration of 1.5mol/L, activating with acid at 60 ℃ for 1-3 hours, washing with water until the pH value is 4-5 to obtain acid modified attapulgite, wherein the liquid-solid ratio of the oxalic acid to the attapulgite is 1-3: 1, preparing acid-modified attapulgite into acid-modified attapulgite suspension with the concentration of 25-30 wt%; according to parts by weight, adding 30-50 parts of acid modified attapulgite suspension, 10-20 parts of a rare earth aqueous solution with the mass fraction of 30-35% and 5-10 parts of a multi-walled carbon nanotube solution with the mass fraction of 1-2% into a sealed container with a stirrer, introducing nitrogen into the sealed container to saturate the nitrogen, placing the sealed container into an electron accelerator with the mass fraction of 1.5MeV and 30mA for irradiation stirring treatment, and then performing centrifugal separation, drying and crushing to obtain the modified attapulgite.
Preferably, the irradiation dose rate adopted by irradiation is 200-500 kGy/h, the irradiation dose is 500-1000 kGy, and the stirring speed is 200-300 r/min; the rare earth aqueous solution is any one of aqueous solutions of lanthanum nitrate, neodymium nitrate, yttrium nitrate, cerium nitrate, samarium nitrate and rhenium nitrate.
Preferably, the ionic liquid is any one of 1, 3-dimethylimidazole methyl sulfate, 1, 3-dimethylimidazole nitrate, 1-ethyl-3-methylimidazole acetate and 1-ethyl-3-methylimidazole lactic acid.
Preferably, in the second step, Al is obtained2O3The aerogel is reprocessed, and the process comprises the following steps: mixing Al2O3Feeding the aerogel into an atmospheric pressure low-temperature plasma device to enable Al to be contained2O3The method comprises the steps that aerogel is located at an injection outlet of an atmospheric pressure low-temperature plasma body by 20-60 mm, a gas medium is introduced into an atmospheric pressure low-temperature plasma body device according to the gas flow of 8-12L/h, working voltage is applied to form plasma jet flow, the moving speed of the injection outlet of the atmospheric pressure low-temperature plasma body device is controlled to be 5-10 mm/s, and the plasma jet flow is injected to Al2O3On aerogel, on Al2O3Treating the aerogel for 30-60 min, and then carrying out Al treatment2O3Placing the aerogel into a closed container containing hexamethyldisilazane, and standing at room temperature for 0.5-1.5 days; wherein Al is2O3The solid-liquid ratio of aerogel to hexamethyldisilazane is 1: 10 to 12.
Preferably, the working voltage is provided by a high-voltage alternating current power supply, the working voltage is an alternating current voltage of 50-100 kV, and the frequency is 100-300 kHz; the gas medium is rare gas/oxygen, nitrogen, ammonia gas, CF4、CCl4、SF6A mixture of one or more of them.
The invention at least comprises the following beneficial effects: the invention adopts a sol-gel method to prepare Al2O3Preparation of Al by wet gel and supercritical fluid drying method2O3The aerogel has simple process, easy control of reaction process and easy realization of industrialized production, and the prepared alumina aerogel has complete surface, no crack, good high temperature resistance and wide application prospect.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Description of the drawings:
FIG. 1 is a scanning electron micrograph of an alumina aerogel prepared according to example 1 of the present invention before heat treatment;
FIG. 2 is a scanning electron micrograph of an alumina aerogel prepared according to example 1 of the present invention after heat treatment at 900 ℃;
FIG. 3 is a pictorial representation of an alumina aerogel prepared in accordance with example 1 of the present invention prior to heat treatment;
FIG. 4 is a pictorial representation of an alumina aerogel prepared in accordance with example 1 of the present invention after heat treatment at 900 ℃;
FIG. 5 is a pictorial representation of an alumina aerogel prepared in accordance with example 1 of the present invention after heat treatment at 1100 ℃;
FIG. 6 is a scanning electron micrograph of an alumina aerogel prepared according to example 2 of the present invention before heat treatment;
FIG. 7 is a scanning electron micrograph of an alumina aerogel prepared according to example 2 of the present invention after heat treatment at 900 ℃;
FIG. 8 is a pictorial representation of an alumina aerogel prepared in accordance with example 2 of the present invention prior to heat treatment;
FIG. 9 is a pictorial representation of an alumina aerogel prepared in accordance with example 2 of the present invention after heat treatment at 900 ℃;
FIG. 10 is a pictorial representation of an alumina aerogel prepared in accordance with example 2 of the present invention after heat treatment at 1100 ℃;
FIG. 11 is a scanning electron micrograph of an alumina aerogel prepared in example 3 of the present invention before heat treatment;
FIG. 12 is a scanning electron micrograph of an alumina aerogel prepared according to example 3 of the present invention after heat treatment at 900 ℃;
FIG. 13 is a pictorial representation of an alumina aerogel prepared in accordance with example 3 of the present invention prior to heat treatment;
FIG. 14 is a pictorial representation of an alumina aerogel prepared in accordance with example 3 of the present invention after heat treatment at 900 ℃;
FIG. 15 is a pictorial representation of an alumina aerogel prepared in accordance with example 3 of the present invention after heat treatment at 1100 ℃;
FIG. 16 is a scanning electron micrograph of an alumina aerogel prepared according to example 4 of the present invention before heat treatment;
FIG. 17 is a scanning electron micrograph of an alumina aerogel prepared according to example 4 of the present invention after heat treatment at 900 ℃;
FIG. 18 is a pictorial representation of an alumina aerogel prepared in accordance with example 4 of the present invention prior to heat treatment;
FIG. 19 is a pictorial representation of an alumina aerogel prepared in accordance with example 4 of the present invention after heat treatment at 900 ℃;
FIG. 20 is a pictorial representation of an alumina aerogel prepared in accordance with example 4 of the present invention after heat treatment at 1100 ℃;
FIG. 21 is a scanning electron micrograph of an alumina aerogel prepared according to comparative example 1 of the present invention before heat treatment;
FIG. 22 is a scanning electron micrograph of an alumina aerogel prepared according to comparative example 1 of the present invention after heat treatment at 900 ℃;
FIG. 23 is a pictorial representation of an alumina aerogel prepared in accordance with comparative example 1 of the present invention prior to heat treatment;
FIG. 24 is a pictorial representation of an alumina aerogel prepared in accordance with comparative example 1 of the present invention after heat treatment at 900 ℃;
FIG. 25 is a pictorial representation of an alumina aerogel prepared in accordance with comparative example 1 of the present invention after heat treatment at 1100 ℃.
FIG. 26 is an XRD pattern of alumina aerogels prepared in examples 1 to 4 of the present invention and comparative example 1 before heat treatment;
FIG. 27 is an XRD pattern of alumina aerogels prepared in examples 1 to 4 of the present invention and comparative example 1 after heat treatment at 900 ℃;
FIG. 28 is an XRD pattern of alumina aerogels prepared in examples 1 to 4 of the present invention and comparative example 1 after heat treatment at 1100 ℃.
The specific implementation mode is as follows:
the present invention is further described in detail below with reference to the attached drawings so that those skilled in the art can implement the invention by referring to the description text.
It will be understood that terms such as "having," "including," and "comprising," as used herein, do not preclude the presence or addition of one or more other elements or groups thereof.
Example 1:
a preparation method of high-temperature resistant block alumina aerogel comprises the following steps:
step one, dissolving aluminum sec-butoxide in a mixed solvent of distilled water and ethanol, stirring in a water bath at 70 ℃ for 30min, and cooling to room temperature to obtain a mixture solution;
adding concentrated nitric acid into the mixture solution under the stirring action, adjusting the pH value to 1.8, mixing methanol, acetone and aniline, and then adding the mixture solution; the mixture solution is then stirred for 30s and poured into moulds, a gel is formed, generally after 20min, after ageing and exchange of the solvent with ethanol for three days, the wet gel is placed in an ethanol autoclave for supercritical drying to give Al2O3An aerogel;
the pressure of the supercritical drying is 7MPa, and the temperature is 255 ℃; the ethanol: methanol: acetone: distilled water: the molar ratio of aniline is 21:1:1:0.18: 0.1; the aluminum sec-butoxide: the molar ratio of distilled water is 1: 1.
the alumina aerogel prepared by the embodiment has a complete surface without cracks and good high-temperature resistance, and is treated in an air atmosphere at 900 ℃ for 2 hours, the shrinkage of the alumina aerogel is about 2 percent, and treated in an air atmosphere at 1100 ℃ for 2 hours, and the volume shrinkage of the alumina aerogel is about 30 percent.
Example 2:
a preparation method of high-temperature resistant block alumina aerogel comprises the following steps:
step one, dissolving aluminum sec-butoxide in a mixed solvent of distilled water and ethanol, stirring in a water bath at 70 ℃ for 30min, and cooling to room temperature to obtain a mixture solution;
adding concentrated nitric acid into the mixture solution under the stirring action, adjusting the pH value to 1.8, mixing methanol, acetone and phenylenediamine, and adding the mixture solution; the mixture solution is then stirred for 30s and poured into moulds, a gel is formed, generally after 20min, after ageing and exchange of the solvent with ethanol for three days, the wet gel is placed in an ethanol autoclave for supercritical drying to give Al2O3An aerogel;
the pressure of the supercritical drying is 7MPa, and the temperature is 255 ℃; the ethanol: methanol: acetone: distilled water: the molar ratio of phenylenediamine is 21:1:1:0.18: 0.1; the aluminum sec-butoxide: the molar ratio of distilled water is 1: 1.
the alumina aerogel prepared by the embodiment has the advantages of complete surface, no crack and good high-temperature resistance, and the volume shrinkage of the alumina aerogel is about 4% after being treated in an air atmosphere at 900 ℃ for 2h and about 25% after being treated in an air atmosphere at 1100 ℃.
Example 3:
a preparation method of high-temperature resistant block alumina aerogel comprises the following steps:
step one, dissolving aluminum sec-butoxide in a mixed solvent of distilled water and ethanol, stirring in a water bath at 70 ℃ for 30min, and cooling to room temperature to obtain a mixture solution;
adding concentrated nitric acid into the mixture solution under the stirring action, adjusting the pH value to 1.8, mixing methanol, acetone and thiourea, and adding the mixture into the mixture solution; the mixture solution is then stirred for 30s and poured into moulds, a gel is formed, generally after 20min, after ageing and exchange of the solvent with ethanol for three days, the wet gel is placed in an ethanol autoclave for supercritical drying to give Al2O3An aerogel;
the pressure of the supercritical drying is 7MPa, and the temperature is 255 ℃; the ethanol: methanol: acetone: distilled water: the molar ratio of thiourea is 21:1:1:0.18: 0.1; the aluminum sec-butoxide: the molar ratio of distilled water is 1: 1.
the alumina aerogel prepared by the embodiment has a complete surface without cracks and good high-temperature resistance, and the volume shrinkage of the alumina aerogel is about 1 percent after being treated in an air atmosphere at 900 ℃ for 2 hours and about 20 percent after being treated in an air atmosphere at 1100 ℃.
Example 4:
a preparation method of high-temperature resistant block alumina aerogel comprises the following steps:
step one, dissolving aluminum sec-butoxide in a mixed solvent of distilled water and ethanol, stirring in a water bath at 70 ℃ for 30min, and cooling to room temperature to obtain a mixture solution;
adding concentrated nitric acid into the mixture solution under the stirring action, adjusting the pH value to 1.8, mixing methanol, acetone and urea, and adding the mixture into the mixture solution; the mixture solution is then stirred for 30s and poured into moulds, a gel is formed, generally after 20min, after ageing and exchange of the solvent with ethanol for three days, the wet gel is placed in an ethanol autoclave for supercritical drying to give Al2O3An aerogel;
the pressure of the supercritical drying is 7MPa, and the temperature is 255 ℃; the ethanol: methanol: acetone: distilled water: the molar ratio of urea is 21:1:1:0.18: 0.1; the aluminum sec-butoxide: the molar ratio of distilled water is 1: 1.
the alumina aerogel prepared by the embodiment has a complete surface without cracks and good high-temperature resistance, and the volume shrinkage of the alumina aerogel is about 2 percent after being treated in an air atmosphere at 900 ℃ for 2 hours and about 30 percent after being treated in an air atmosphere at 1100 ℃.
Comparative example 1:
a preparation method of high-temperature resistant block alumina aerogel comprises the following steps:
step one, dissolving aluminum sec-butoxide in a mixed solvent of distilled water and ethanol, stirring in a water bath at 70 ℃ for 30min, and cooling to room temperature to obtain a mixture solution;
adding concentrated nitric acid into the mixture solution under the stirring action, adjusting the pH value to 1.8, mixing methanol and acetone, and adding the mixture solution; the mixture solution is then stirred for 30s and poured into moulds, a gel is formed, generally after 20min, after ageing and exchange of the solvent with ethanol for three days, the wet gel is placed in an ethanol autoclave for supercritical drying to give Al2O3An aerogel;
the pressure of the supercritical drying is 7MPa, and the temperature is 255 ℃; the ethanol: methanol: acetone: the molar ratio of distilled water is 21:1:1: 0.18; the aluminum sec-butoxide: the molar ratio of distilled water is 1: 1.
the alumina aerogel prepared by the embodiment has the advantages of complete surface, no crack and good high-temperature resistance, and the volume shrinkage of the alumina aerogel is about 5 percent after being treated in an air atmosphere at 900 ℃ for 2 hours and about 50 percent after being treated in an air atmosphere at 1100 ℃.
Example 5:
in the first step, modified attapulgite accounting for 5% of the mass of the silicon source and ionic liquid accounting for 0.5% of the mass of the silicon source are added into the mixture solution;
the preparation method of the modified attapulgite comprises the following steps: mixing attapulgite with oxalic acid with the concentration of 1.5mol/L, activating with acid at 60 ℃ for 1 hour, washing with water until the pH value reaches 5 to obtain acid-modified attapulgite, wherein the liquid-solid ratio of the oxalic acid to the attapulgite is 3: 1, preparing acid-modified attapulgite into acid-modified attapulgite suspension with the concentration of 30 wt%; according to parts by weight, adding 30 parts of acid modified attapulgite suspension, 10 parts of rare earth aqueous solution with the mass fraction of 30% and 10 parts of multi-walled carbon nanotube solution with the mass fraction of 2% into a sealed container with a stirrer, introducing nitrogen into the sealed container to saturate the nitrogen, placing the sealed container into an electron accelerator with the mass fraction of 1.5MeV and 30mA to perform irradiation stirring treatment, then performing centrifugal separation, drying and crushing to obtain modified attapulgite; the irradiation dose rate adopted by the irradiation is 500kGy/h, the irradiation dose is 1000kGy, and the stirring speed is 300 r/min; the rare earth aqueous solution is lanthanum nitrate; the ionic liquid is 1, 3-dimethyl imidazole methyl sulfate; the modified attapulgite is added in the process of preparing the alumina aerogel, and the framework structures of the attapulgite and the multi-walled carbon nano tube are utilized, so that the framework structure of the prepared alumina aerogel is more regular, the heat resistance of the alumina aerogel is further improved, and meanwhile, the heat resistance of the alumina aerogel can be further improved by the added rare earth material.
The remaining process parameters and procedures were exactly the same as in example 1. The alumina aerogel prepared by the embodiment has the advantages of complete surface, no crack and good high-temperature resistance, and the shrinkage of the alumina aerogel is about 1% after being treated in an air atmosphere at 900 ℃ for 2 hours, and the volume shrinkage of the alumina aerogel is about 10% after being treated in an air atmosphere at 1100 ℃.
Example 6:
in the first step, modified attapulgite accounting for 10% of the mass of the silicon source and ionic liquid accounting for 1.5% of the mass of the silicon source are added into the mixture solution;
the preparation method of the modified attapulgite comprises the following steps: mixing attapulgite with oxalic acid with the concentration of 1.5mol/L, activating with acid at 60 ℃ for 2 hours, washing with water until the pH value is 4 to obtain acid modified attapulgite, wherein the liquid-solid ratio of the oxalic acid to the attapulgite is 2: 1, preparing acid-modified attapulgite into acid-modified attapulgite suspension with the concentration of 30 wt%; adding 50 parts by weight of acid modified attapulgite suspension, 10 parts by weight of 35% rare earth aqueous solution and 10 parts by weight of 2% multi-walled carbon nanotube solution into a sealed container with a stirrer, introducing nitrogen into the sealed container to saturate the nitrogen, placing the sealed container into an electron accelerator of 1.5MeV and 30mA for irradiation stirring treatment, then carrying out centrifugal separation, drying and crushing to obtain modified attapulgite; the irradiation dose rate adopted by the irradiation is 500kGy/h, the irradiation dose is 1000kGy, and the stirring speed is 300 r/min; the rare earth aqueous solution is samarium nitrate; the ionic liquid is 1-ethyl-3-methylimidazolium lactic acid.
The remaining process parameters and procedures were exactly the same as in example 1. The alumina aerogel prepared by the embodiment has the advantages of complete surface, no crack and good high-temperature resistance, and the shrinkage of the alumina aerogel is about 1% after being treated in an air atmosphere at 900 ℃ for 2 hours, and the volume shrinkage of the alumina aerogel is about 10% after being treated in an air atmosphere at 1100 ℃.
Example 7:
in the second step, the obtained Al2O3The aerogel is reprocessed, and the process comprises the following steps: mixing Al2O3Feeding the aerogel into an atmospheric pressure low-temperature plasma device to enable Al to be contained2O3The aerogel is 20mm at the jet outlet of the atmospheric pressure low-temperature plasma, a gas medium is introduced into the atmospheric pressure low-temperature plasma device according to the gas flow of 12L/h, working voltage is applied to form plasma jet, the moving speed of the jet outlet of the atmospheric pressure low-temperature plasma device is controlled to be 10mm/s, and the plasma jet is jetted on Al2O3On aerogel, on Al2O3Treating the aerogel for 60min, and thenAl2O3Placing the aerogel in a closed container containing hexamethyldisilazane, standing at room temperature for 1.5 days; wherein Al is2O3The solid-liquid ratio of aerogel to hexamethyldisilazane is 1: 12; the working voltage is provided by a high-voltage alternating current power supply, the working voltage is 100kV alternating current voltage, and the frequency is 300 kHz; the gas medium is nitrogen. By the atmospheric pressure low-temperature plasma treatment technology, the surface structure of the alumina aerogel can be changed on the premise of not influencing the performance of a material matrix, so that silica formed by hexamethyldisilazane is easier to coat the surface of the alumina aerogel, and the heat resistance of the alumina aerogel can be further improved.
The remaining process parameters and procedures were exactly the same as in example 1. The alumina aerogel prepared by the embodiment has the advantages of complete surface, no crack and good high-temperature resistance, and the shrinkage of the alumina aerogel is about 0.5 percent when the alumina aerogel is treated in an air atmosphere at 900 ℃ for 2 hours and the volume shrinkage of the alumina aerogel is about 7 percent when the alumina aerogel is treated in an air atmosphere at 1100 ℃.
Example 8:
in the second step, the obtained Al2O3The aerogel is reprocessed, and the process comprises the following steps: mixing Al2O3Feeding the aerogel into an atmospheric pressure low-temperature plasma device to enable Al to be contained2O3The aerogel is 50mm at the jet outlet of the atmospheric pressure low-temperature plasma, a gas medium is introduced into the atmospheric pressure low-temperature plasma device according to the gas flow of 10L/h, working voltage is applied to form plasma jet, the moving speed of the jet outlet of the atmospheric pressure low-temperature plasma device is controlled to be 10mm/s, and the plasma jet is jetted on Al2O3On aerogel, on Al2O3Aerogel treatment for 50min, then Al2O3Placing the aerogel in a closed container containing hexamethyldisilazane, and standing at room temperature for 1 day; wherein Al is2O3The solid-liquid ratio of aerogel to hexamethyldisilazane is 1: 10; the working voltage is provided by a high-voltage alternating current power supply, the working voltage is 100kV alternating current voltage, and the frequency is 300 kHz; the gas medium is CF4。
The remaining process parameters and procedures were exactly the same as in example 1. The alumina aerogel prepared by the embodiment has the advantages of complete surface, no crack and good high-temperature resistance, and the shrinkage of the alumina aerogel is about 0.5 percent when the alumina aerogel is treated in an air atmosphere at 900 ℃ for 2 hours and the volume shrinkage of the alumina aerogel is about 7 percent when the alumina aerogel is treated in an air atmosphere at 1100 ℃.
Example 9:
in the first step, modified attapulgite accounting for 5% of the mass of the silicon source and ionic liquid accounting for 0.5% of the mass of the silicon source are added into the mixture solution;
the preparation method of the modified attapulgite comprises the following steps: mixing attapulgite with oxalic acid with the concentration of 1.5mol/L, activating with acid at 60 ℃ for 1 hour, washing with water until the pH value reaches 5 to obtain acid-modified attapulgite, wherein the liquid-solid ratio of the oxalic acid to the attapulgite is 3: 1, preparing acid-modified attapulgite into acid-modified attapulgite suspension with the concentration of 30 wt%; according to parts by weight, adding 30 parts of acid modified attapulgite suspension, 10 parts of rare earth aqueous solution with the mass fraction of 30% and 10 parts of multi-walled carbon nanotube solution with the mass fraction of 2% into a sealed container with a stirrer, introducing nitrogen into the sealed container to saturate the nitrogen, placing the sealed container into an electron accelerator with the mass fraction of 1.5MeV and 30mA to perform irradiation stirring treatment, then performing centrifugal separation, drying and crushing to obtain modified attapulgite; the irradiation dose rate adopted by the irradiation is 500kGy/h, the irradiation dose is 1000kGy, and the stirring speed is 300 r/min; the rare earth aqueous solution is lanthanum nitrate; the ionic liquid is 1, 3-dimethyl imidazole methyl sulfate.
The remaining process parameters and procedures were exactly the same as in example 7. The alumina aerogel prepared by the embodiment has the advantages of complete surface, no crack and good high-temperature resistance, basically has no shrinkage after being treated for 2 hours in an air atmosphere at 900 ℃, and has the volume shrinkage of about 3 percent after being treated for 2 hours in an air atmosphere at 1100 ℃.
Example 10:
a preparation method of high-temperature resistant block alumina aerogel comprises the following steps:
step one, dissolving aluminum oxalate in a mixed solvent of distilled water and ethanol, stirring for 30min in a water bath at 70 ℃, and cooling to room temperature to obtain a mixture solution;
adding concentrated nitric acid into the mixture solution under the stirring action, adjusting the pH value to 1.8, mixing methanol, acetone and aniline, and then adding the mixture solution; the mixture solution is then stirred for 30s and poured into moulds, a gel is formed, generally after 20min, after ageing and exchange of the solvent with ethanol for three days, the wet gel is placed in an ethanol autoclave for supercritical drying to give Al2O3An aerogel;
the pressure of the supercritical drying is 7MPa, and the temperature is 255 ℃; the ethanol: methanol: acetone: distilled water: the molar ratio of aniline is 21:1:1:0.18: 0.1; the ratio of the aluminum oxalate: the molar ratio of distilled water is 1: 1.
the alumina aerogel prepared by the embodiment has a complete surface without cracks and good high-temperature resistance, and is treated in an air atmosphere at 900 ℃ for 2 hours, the shrinkage of the alumina aerogel is about 3 percent, and treated in an air atmosphere at 1100 ℃ for 2 hours, and the volume shrinkage of the alumina aerogel is about 15 percent.
Example 11:
in the first step, modified attapulgite accounting for 5% of the mass of the silicon source and ionic liquid accounting for 0.5% of the mass of the silicon source are added into the mixture solution;
the preparation method of the modified attapulgite comprises the following steps: mixing attapulgite with oxalic acid with the concentration of 1.5mol/L, activating with acid at 60 ℃ for 2 hours, washing with water until the pH value is 4 to obtain acid modified attapulgite, wherein the liquid-solid ratio of the oxalic acid to the attapulgite is 3: 1, preparing acid-modified attapulgite into acid-modified attapulgite suspension with the concentration of 30 wt%; adding 50 parts by weight of acid modified attapulgite suspension, 20 parts by weight of a rare earth aqueous solution with the mass fraction of 30% and 10 parts by weight of a multi-walled carbon nanotube solution with the mass fraction of 2% into a sealed container with a stirrer, introducing nitrogen into the sealed container to saturate the nitrogen, placing the sealed container into an electron accelerator with the mass fraction of 1.5MeV and 30mA for irradiation stirring treatment, then carrying out centrifugal separation, drying and crushing to obtain modified attapulgite; the irradiation dose rate adopted by the irradiation is 500kGy/h, the irradiation dose is 1000kGy, and the stirring speed is 300 r/min; the rare earth aqueous solution is lanthanum nitrate; the ionic liquid is 1, 3-dimethyl imidazole methyl sulfate.
The remaining process parameters and procedures were exactly the same as in example 10. The alumina aerogel prepared by the embodiment has the advantages of complete surface, no crack and good high-temperature resistance, and the shrinkage of the alumina aerogel is about 1% after being treated in an air atmosphere at 900 ℃ for 2 hours, and the volume shrinkage of the alumina aerogel is about 10% after being treated in an air atmosphere at 1100 ℃.
Example 12:
in the second step, the obtained Al2O3The aerogel is reprocessed, and the process comprises the following steps: mixing Al2O3Feeding the aerogel into an atmospheric pressure low-temperature plasma device to enable Al to be contained2O3The aerogel is 50mm at the jet outlet of the atmospheric pressure low-temperature plasma, a gas medium is introduced into the atmospheric pressure low-temperature plasma device according to the gas flow of 10L/h, working voltage is applied to form plasma jet, the moving speed of the jet outlet of the atmospheric pressure low-temperature plasma device is controlled to be 10mm/s, and the plasma jet is jetted on Al2O3On aerogel, on Al2O3Aerogel treatment for 50min, then Al2O3Placing the aerogel in a closed container containing hexamethyldisilazane, and standing at room temperature for 1 day; wherein Al is2O3The solid-liquid ratio of aerogel to hexamethyldisilazane is 1: 10; the working voltage is provided by a high-voltage alternating current power supply, the working voltage is 100kV alternating current voltage, and the frequency is 300 kHz; the gas medium is CF4。
The remaining process parameters and procedures were exactly the same as in example 10. The alumina aerogel prepared by the embodiment has the advantages of complete surface, no crack and good high-temperature resistance, and the shrinkage of the alumina aerogel is about 0.5 percent when the alumina aerogel is treated in an air atmosphere at 900 ℃ for 2 hours, and the volume shrinkage of the alumina aerogel is about 6 percent when the alumina aerogel is treated in an air atmosphere at 1100 ℃.
It can be seen from fig. 26 to 28 of the present invention that the alumina aerogels prepared in examples 1 to 4 and comparative example 1 mainly exist in the form of γ -aluminum oxide hydroxide at normal temperature, and after calcination at 900 ℃ for 2 hours, the alumina aerogels mainly exist in the form of γ -aluminum oxide; after calcining for 2 hours at 1100 ℃, the sample mainly exists in a form of theta-alumina, so that the aerogel material prepared by the invention is proved to have high heat resistance.
While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable in various fields of endeavor to which the invention pertains, and further modifications may readily be made by those skilled in the art, it being understood that the invention is not limited to the details shown and described herein without departing from the general concept defined by the appended claims and their equivalents.
Claims (3)
1. A preparation method of high-temperature resistant block alumina aerogel is characterized by comprising the following steps:
dissolving an aluminum source in a mixed solvent of distilled water and ethanol, stirring in a water bath at the temperature of 60-80 ℃ for 20-50 min, and cooling to room temperature to obtain a mixture solution;
adding concentrated nitric acid into the mixture solution under the stirring action, adjusting the pH value to 1.6-1.8, mixing methanol, acetone and a catalyst, and adding the mixture into the mixture solution; then stirring the mixture solution for 10-60 s, pouring the mixture solution into a mold, forming gel after 10-30 min, aging, exchanging the solvent with ethanol for three days, placing the wet gel into an ethanol autoclave for supercritical drying to obtain Al2O3An aerogel;
the aluminum source is any one of aluminum sec-butoxide, aluminum acetate and aluminum oxalate;
the ethanol: methanol: acetone: distilled water: the molar ratio of the catalyst is 10-25: 0.5-2: 0.1-0.5: 0.05-0.25; the aluminum source is as follows: the molar ratio of distilled water is 1: 0.5 to 2.5;
the pressure of the supercritical drying is 6-8 MPa, and the temperature is 250-260 ℃; the catalyst is any one of aniline, phenylenediamine, thiourea and urea;
in the first step, adding modified attapulgite accounting for 1-20% of the mass of an aluminum source and ionic liquid accounting for 0.5-1.5% of the mass of the aluminum source into a mixture solution;
the preparation method of the modified attapulgite comprises the following steps: mixing attapulgite with oxalic acid with the concentration of 1.5mol/L, activating with acid at 60 ℃ for 1-3 hours, washing with water until the pH value is 4-5 to obtain acid modified attapulgite, wherein the liquid-solid ratio of the oxalic acid to the attapulgite is 1-3: 1, preparing acid-modified attapulgite into acid-modified attapulgite suspension with the concentration of 25-30 wt%; according to parts by weight, adding 30-50 parts of acid modified attapulgite suspension, 10-20 parts of a rare earth aqueous solution with the mass fraction of 30-35% and 5-10 parts of a multi-walled carbon nanotube solution with the mass fraction of 1-2% into a sealed container with a stirrer, introducing nitrogen into the sealed container to saturate the nitrogen, placing the sealed container into an electron accelerator with the mass fraction of 1.5MeV and 30mA for irradiation stirring treatment, then performing centrifugal separation, drying and crushing to obtain modified attapulgite;
the irradiation dose rate adopted by irradiation is 200-500 kGy/h, the irradiation dose is 500-1000 kGy, and the stirring speed is 200-300 r/min; the rare earth aqueous solution is any one of lanthanum nitrate, neodymium nitrate, yttrium nitrate, cerium nitrate, samarium nitrate and rhenium nitrate aqueous solution;
the ionic liquid is any one of 1, 3-dimethyl imidazole methyl sulfate, 1, 3-dimethyl imidazole nitrate, 1-ethyl-3-methyl imidazole acetate and 1-ethyl-3-methyl imidazole lactic acid.
2. The method of claim 1, wherein in step two, the obtained Al is added to the slurry2O3The aerogel is reprocessed, and the process comprises the following steps: mixing Al2O3Feeding the aerogel into an atmospheric pressure low-temperature plasma device to enable Al to be contained2O3The method comprises the steps that aerogel is located at an injection outlet of an atmospheric pressure low-temperature plasma body by 20-60 mm, a gas medium is introduced into an atmospheric pressure low-temperature plasma body device according to the gas flow of 8-12L/h, working voltage is applied to form plasma jet flow, the moving speed of the injection outlet of the atmospheric pressure low-temperature plasma body device is controlled to be 5-10 mm/s, and the plasma jet flow is injected to Al2O3On aerogel, on Al2O3Treating the aerogel for 30-60 min, and then carrying out Al treatment2O3Placing the aerogel in a container containing hexamethyldisilazaneStanding in a closed container at room temperature for 0.5-1.5 days; wherein Al is2O3The solid-liquid ratio of aerogel to hexamethyldisilazane is 1: 10 to 12.
3. The method for preparing the high temperature resistant bulk alumina aerogel according to claim 2, wherein the working voltage is provided by a high voltage alternating current power supply, the working voltage is an alternating current voltage of 50-100 kV, and the frequency is 100-300 kHz; the gas medium is oxygen, nitrogen, ammonia gas, CF4、CCl4、SF6A mixture of one or more of them.
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