CN111099596B - Simple method for coating high-hydrophobicity boron nitride nanosheet thin layer on surface of silicon dioxide aerogel particle - Google Patents
Simple method for coating high-hydrophobicity boron nitride nanosheet thin layer on surface of silicon dioxide aerogel particle Download PDFInfo
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Abstract
A simple method for coating a high-hydrophobicity boron nitride nanosheet thin layer on the surface of a silicon dioxide aerogel particle relates to the field of surface modification, in particular to a silicon dioxide aerogel particle surface modification method. The invention aims to solve the problem that the hydrophobic performance of the hydrophobic silica aerogel particles prepared by the existing modification method is reduced or lost in a high-temperature environment. The method comprises the following steps: firstly, preparing a ceramic boat loaded with a mixture of urea or melamine, boric acid and silica aerogel particles; secondly, chemical vapor deposition; and thirdly, naturally cooling to obtain the silicon dioxide aerogel particles with the surfaces coated with the high-hydrophobicity boron nitride nanosheet thin layers. According to the invention, the silicon dioxide aerogel particles with the surface coated with the high-hydrophobicity boron nitride nanosheet thin layer can be obtained.
Description
Technical Field
The invention relates to the field of surface modification, in particular to a method for modifying the surface of silicon dioxide aerogel particles.
Background
The silica aerogel is a nano porous network structure formed by mutually gathering nano-scale colloidal particles, and the nano-scale particles and pores of the silica aerogel have very low thermal conductivity due to the distribution of the nano-scale particles and pores, so that the silica aerogel has the most potential application as a super heat insulation material.
The preparation of silica aerogel usually comprises a sol-gel process and a drying process, and the sol-gel reaction mechanism shows that a large amount of hydrophilic hydroxyl groups and unhydrolyzed ethoxy functional groups exist on the surface of the silica aerogel, so that the silica aerogel is sensitive to moisture, the thermal conductivity of the silica aerogel is reduced, and the durability, the corrosion resistance and other properties of the silica aerogel are influenced. There have been many studies and reports on the hydrophobic modification of silica aerogels. There are two ways to prepare hydrophobic silica aerogels: 1 surface post-treatment method: the surface of the silica gel prepared by the sol-gel process has a large amount of hydroxyl; and adding a compound which can chemically react with silicon hydroxyl on the surface of the gel by utilizing the reactivity of the surface hydroxyl, eliminating the surface hydroxyl, connecting with a hydrophobic group to prepare hydrophobic silica gel, and drying to obtain the hydrophobic silica aerogel. 2, an in-situ method: adding silicon alkoxide containing hydrophobic groups into a sol-gel system of the silicon alkoxide, directly forming hydrophobic silicon dioxide gel through a sol-gel process, and drying to obtain the silicon dioxide aerogel. For example, Rao, Kulkarni and the like use tetraethoxysilane, methyl orthosilicate and water glass as silicon sources, respectively adopt hydrophobic surface modifiers such as trimethylol methylamine, trimethyl chlorosilane, hexamethyldisiloxane, hexamethyldisilazane and the like to carry out hydrophobic modification on hydrophilic gel, and prepare the hydrophobic silica aerogel by combining supercritical drying. Fritz et al, when methyltriethoxysilane mixture is used as a precursor of sol-gel, hydrophobic gel is obtained through a sol-gel process under an alkaline condition, and hydrophobic silica aerogel is obtained through supercritical drying. However, the existing hydrophobic modification methods have the problems that the hydrophobic functional groups are broken after being heated, and the hydrophobic performance is reduced.
Since 1995, Chotra et al synthesized boron nitride nanotubes for the first time by arc discharge, and they have attracted much attention because of their similar structure to carbon nanotubes, their mechanical properties comparable to those of carbon nanotubes, their more excellent chemical properties, their better heat resistance and oxidation resistance. Due to the special properties of the micro-nano structure of the boron nitride nanotube, the boron nitride nanotube is applied to the field of super-hydrophobic coatings. The invention discloses a preparation method of a hydrophobic film of a boron nitride nanotube, which is disclosed by China patent application with application number 201210391481.4, namely Liuxianhao et al, Haerbin Industrial university, in 2013, 1 and 30, wherein the boron nitride nanotube is deposited on a stainless steel substrate through vapor deposition, the composite material has excellent super-hydrophobicity, and the invention proves that the boron nitride nanotube can be coated on the surface layer of other materials to carry out hydrophobic modification on the materials. But have not been found in SiO 2 The invention discloses research on a super-hydrophobic boron nitride nanosheet thin layer grown on aerogel particles.
Thus, by reasonable means, in SiO 2 The super-hydrophobic boron nitride nanosheet thin layer grows on the surface of the aerogel, so that SiO can be formed at high temperature 2 The surface of the aerogel still has hydrophobicity, and has important significance for ensuring the performance of the material and widening the application field of the material.
Disclosure of Invention
The invention aims to solve the problem that the hydrophobic performance of the hydrophobic silica aerogel particles prepared by the existing modification method is reduced or lost in a high-temperature environment, and provides a simple method for coating a high-hydrophobic boron nitride nanosheet thin layer on the surface of the silica aerogel particles.
A simple method for coating a high-hydrophobicity boron nitride nanosheet thin layer on the surface of silicon dioxide aerogel particles is completed according to the following steps:
firstly, preparing a ceramic boat carrying the mixture by adopting the method 1 or the method 2;
the method 1 comprises the following steps: spreading urea or melamine at the bottom of the ceramic boat, spreading boric acid above the urea or melamine, and finally spreading silica aerogel particles above the boric acid to obtain the ceramic boat loaded with the mixture;
the method 2 comprises the following steps: uniformly mixing urea or melamine, boric acid and silica aerogel particles to obtain a mixture; spreading the mixture at the bottom of the ceramic boat to obtain the ceramic boat carrying the mixture;
secondly, placing the ceramic boat carrying the mixture in a reaction zone of a tube furnace, connecting vent pipes at two ends of the tube furnace respectively, sealing, and placing the tube furnace in a state of 1000 mL/min -1 ～2000mL·min -1 Introducing protective gas at the gas flow rate for 10-20 min, exhausting air in the tubular furnace at normal pressure, and adjusting the flow rate of the protective gas to 80-200 mL/min -1 Starting the tubular furnace, raising the temperature of a reaction zone of the tubular furnace to 1100-1150 ℃, and preserving the temperature for 30-180 min at 1100-1150 ℃;
thirdly, closing the tube furnace and maintaining the protective gas in the tube furnaceThe flow rate is 80 mL/min -1 ～200mL·min -1 And then the flow rate of the protective gas is 80 mL/min -1 ～200mL·min -1 And naturally cooling the tube furnace to room temperature, and taking out the ceramic boat to obtain the silicon dioxide aerogel particles with the surfaces coated with the high-hydrophobic boron nitride nanosheet thin layers, namely completing the simple method for coating the high-hydrophobic boron nitride nanosheet thin layers on the surfaces of the silicon dioxide aerogel particles.
Compared with the prior art, the invention has the advantages that:
according to the invention, silicon dioxide aerogel particles are directly used as a substrate for growth of boron nitride nanosheets, a chemical vapor deposition method is adopted, and the optimal reaction condition for coating the boron nitride nanosheets on the surface layers of the silicon dioxide aerogel particles is realized by reasonably controlling the flow of nitrogen and the proportion and mixing mode of urea or melamine, boric acid and a silicon dioxide aerogel mixture, so that the boron nitride nanosheets with optimal hydrophobicity are obtained;
secondly, preparing the silicon dioxide aerogel particles with the surfaces coated with the high-hydrophobicity boron nitride nanosheet thin layers under normal pressure by using the method;
the ammonia source adopts urea or melamine, the boron source adopts boric acid, and the raw materials are nontoxic, low in price and easy to purchase; the harm of the raw materials to human bodies is substantially reduced, and the cost is greatly saved;
the invention adopts inert gas nitrogen as the protective gas, and improves the safety of the process and the possibility of large-scale industrialization compared with the common method of using hydrogen or ammonia as the protective gas;
the silicon dioxide aerogel particles coated with the high-hydrophobicity boron nitride nanosheet thin layers on the surfaces still keep the original state at the high temperature of 350-700 ℃, do not deform and keep high hydrophobicity, and the hydrophobic performance of the hydrophobic silicon dioxide aerogel particles prepared by the existing method is reduced to disappear along with the increase of the temperature when the temperature is higher than 250 ℃, because the hydrophobic silicon dioxide aerogel particles prepared by the existing method are hydrophobic by virtue of organic functional groups, and the quantity of the organic functional groups is reduced along with the increase of the temperature, so that the hydrophobic performance is reduced. The silica aerogel coated with the highly hydrophobic boron nitride nanosheet thin layer on the surface is hydrophobic by virtue of the special micro-nano structure of the surface boron nitride nanotube, and theoretically, the hydrophobicity of the boron nitride nanosheet microstructure can possibly disappear only when the reaction temperature in the air is higher than 900 ℃.
According to the invention, the silicon dioxide aerogel particles with the surface coated with the highly hydrophobic boron nitride nanosheet thin layer can be obtained.
Drawings
FIG. 1 is an SEM image of silica aerogel particles coated with a thin layer of highly hydrophobic boron nitride nanosheets prepared in the third step of the example;
FIG. 2 is an infrared spectrum of silica aerogel particles coated with a thin layer of highly hydrophobic boron nitride nanosheets prepared in the third step of the example;
FIG. 3 is a thermogravimetric plot of silica aerogel particles surface-coated with a thin layer of highly hydrophobic boron nitride nanosheets prepared in the third step of the example;
FIG. 4 is a photograph of the contact angle of silica aerogel particles coated with a thin layer of highly hydrophobic boron nitride nanosheets prepared in the third step of the example;
fig. 5 is a contact angle photograph of silica aerogel particles coated with a thin layer of highly hydrophobic boron nitride nanosheet prepared in the third step of the example after being heated to 700 ℃ in air and kept for 60 min.
Detailed Description
The first specific implementation way is as follows: the embodiment is a simple method for coating a high-hydrophobicity boron nitride nanosheet thin layer on the surface of silica aerogel particles, and the method is completed according to the following steps:
firstly, preparing a ceramic boat carrying the mixture by adopting the method 1 or the method 2;
the method 1 comprises the following steps: spreading urea or melamine at the bottom of the ceramic boat, spreading boric acid above the urea or melamine, and finally spreading silica aerogel particles above the boric acid to obtain the ceramic boat loaded with the mixture;
the method 2 comprises the following steps: uniformly mixing urea or melamine, boric acid and silica aerogel particles to obtain a mixture; spreading the mixture at the bottom of the ceramic boat to obtain the ceramic boat carrying the mixture;
secondly, placing the ceramic boat carrying the mixture in a reaction zone of a tube furnace, connecting vent pipes at two ends of the tube furnace respectively, sealing, and placing the tube furnace in a state of 1000 mL/min -1 ～2000mL·min -1 Introducing protective gas at the gas flow rate for 10-20 min, exhausting air in the tubular furnace at normal pressure, and adjusting the flow rate of the protective gas to 80-200 mL/min -1 Starting the tubular furnace, raising the temperature of a reaction zone of the tubular furnace to 1100-1150 ℃, and preserving the temperature for 30-180 min at 1100-1150 ℃;
thirdly, closing the tube furnace, and keeping the flow of the protective gas in the tube furnace at 80 mL/min -1 ～200mL·min -1 And then the flow rate of the protective gas is 80 mL/min -1 ～200mL·min -1 And naturally cooling the tube furnace to room temperature, and taking out the ceramic boat to obtain the silicon dioxide aerogel particles coated with the highly hydrophobic boron nitride nanosheet thin layer on the surface, namely completing the simple method for coating the highly hydrophobic boron nitride nanosheet thin layer on the surface of the silicon dioxide aerogel particles.
Compared with the prior art, the embodiment has the advantages that:
firstly, the silicon dioxide aerogel particles are directly used as a substrate for the growth of the boron nitride nanosheets, a chemical vapor deposition method is adopted, and the optimal reaction condition for coating the boron nitride nanosheets on the surface layers of the silicon dioxide aerogel particles is realized by reasonably controlling the flow rate of nitrogen and the proportion and the mixing mode of urea or melamine, boric acid and a silicon dioxide aerogel mixture, so that the boron nitride nanosheets with optimal hydrophobicity are obtained;
secondly, the method of the embodiment can prepare the silicon dioxide aerogel particles with the surface coated with the high-hydrophobicity boron nitride nanosheet thin layer under normal pressure;
in the embodiment, the ammonia source adopts urea or melamine, the boron source adopts boric acid, and the raw materials are nontoxic, low in price and easy to purchase; the harm of the raw materials to human bodies is substantially reduced, and the cost is greatly saved;
the embodiment adopts the inert gas nitrogen as the protective gas, and improves the safety of the process and the possibility of large-scale industrialization compared with the common use of hydrogen or ammonia as the protective gas;
fifth, the silica aerogel particles coated with the highly hydrophobic boron nitride nanosheet thin layer on the surface of the embodiment still keep the original state at a high temperature of 350 ℃ to 700 ℃, do not deform, and keep high hydrophobicity, while the hydrophobic silica aerogel particles prepared by the existing method have the problem that the hydrophobic property is reduced to disappear along with the increase of the temperature at a temperature of more than 250 ℃, because the hydrophobic silica aerogel particles prepared by the existing method are hydrophobic by virtue of organic functional groups, and the number of the organic functional groups is reduced along with the increase of the temperature, so that the hydrophobic property is reduced. The silica aerogel coated with the highly hydrophobic boron nitride nanosheet thin layer on the surface, which is prepared by the embodiment, is hydrophobic by virtue of the special micro-nano structure of the surface boron nitride nanotube, and theoretically, the hydrophobicity of the boron nitride nanosheet microstructure can disappear only when the reaction temperature in the air is higher than 900 ℃.
According to the embodiment, the silicon dioxide aerogel particles with the surfaces coated with the highly hydrophobic boron nitride nanosheet thin layers can be obtained.
The second embodiment is as follows: the present embodiment differs from the present embodiment in that: the silica aerogel particles described in step one are prepared by the following steps:
uniformly mixing tetraethoxysilane, absolute ethyl alcohol and deionized water according to a molar ratio of 1:8:3.75 to obtain a precursor solution;
adjusting the pH value of the precursor solution to 3-4 by using an oxalic acid solution with the concentration of 0.1mol/L, and stirring for 60min under a magnetic stirrer to obtain a mixed solution; placing the mixed solution in a water bath kettle, and hydrolyzing at the constant temperature of 60 ℃ for 16h to obtain a hydrolyzed mixed solution;
thirdly, adjusting the pH value of the hydrolyzed mixed solution to 7-8 by using an ammonia water solution with the concentration of 0.5mol/L, uniformly stirring, and standing for 30min to obtain gel;
adding absolute ethyl alcohol into the gel, aging for 12h, adding normal hexane into the gel, aging for 12h, and finally adding normal hexane into the gel again, and aging for 12 h;
the volume ratio of the absolute ethyl alcohol to the gel in the step (iv) is 1: 5;
the volume ratio of the normal hexane to the gel in the step (iv) is 1: 5;
fifthly, circulating the step (iv) for 1 to 2 times, finally putting the obtained product into a drying oven, firstly drying the product at 50 ℃ for 4 hours, then drying the product at 80 ℃ for 3 hours, finally drying the product at 120 ℃ for 2 hours, and grinding the product after drying to obtain silicon dioxide aerogel particles;
the particle size of the silicon dioxide aerogel particles in the fifth step is 50-150 μm. Other steps are the same as in the first embodiment.
The third concrete implementation mode: the present embodiment differs from the first or second embodiment in that: the particle size of the urea in the step one is 50-150 μm, the particle size of the melamine is 50-150 μm, and the particle size of the boric acid is 50-150 μm. The other steps are the same as those in the first or second embodiment.
The fourth concrete implementation mode is as follows: the difference between this embodiment and one of the first to third embodiments is as follows: in the method 1, the molar ratio of the silicon dioxide aerogel particles to the boric acid is 1 (1-10), the molar ratio of the boric acid to the urea is 1 (2-4), and the molar ratio of the boric acid to the melamine is 1 (1-3). The other steps are the same as those in the first to third embodiments.
The fifth concrete implementation mode is as follows: the difference between this embodiment and one of the first to fourth embodiments is: in the method 2, the molar ratio of the silicon dioxide aerogel particles to the boric acid is 1 (1-10), the molar ratio of the boric acid to the urea is 1 (2-4), and the molar ratio of the boric acid to the melamine is 1 (1-3). The other steps are the same as those in the first to fourth embodiments.
The sixth specific implementation mode is as follows: the difference between this embodiment and one of the first to fifth embodiments is as follows: and the protective gas in the second step is nitrogen. The other steps are the same as those in the first to fifth embodiments.
The seventh embodiment: the difference between this embodiment and one of the first to sixth embodiments is: the protective gas in the third step is nitrogen. The other steps are the same as those in the first to sixth embodiments.
The specific implementation mode is eight: the difference between this embodiment and one of the first to seventh embodiments is: placing the ceramic boat carrying the mixture in a reaction zone of a tube furnace, connecting an air pipe at two ends of the tube furnace respectively, sealing, and placing the tube furnace at 1100 mL/min -1 Introducing protective gas at the gas flow rate for 10min, exhausting air in the tubular furnace at normal pressure, and regulating the flow rate of the protective gas to 80 mL/min -1 Starting the tube furnace, raising the temperature of the reaction zone of the tube furnace to 1100 ℃, and preserving the heat at 1100 ℃ for 30-60 min. The other steps are the same as those in the first to seventh embodiments.
The specific implementation method nine: the difference between this embodiment and the first to eighth embodiments is: step two, placing the ceramic boat carrying the mixture in a reaction zone of a tube furnace, connecting vent pipes at two ends of the tube furnace respectively, sealing, and placing the tube furnace in a state of 1000 mL/min -1 ～1500mL·min -1 Introducing protective gas at the gas flow rate for 10-15 min, exhausting air in the tubular furnace at normal pressure, and adjusting the flow rate of the protective gas to 100-150 mL/min -1 Starting the tube furnace, raising the temperature of the reaction zone of the tube furnace to 1100 ℃, and preserving the temperature at 1100 ℃ for 60-120 min. The other steps are the same as those in the first to eighth embodiments.
The detailed implementation mode is ten: the difference between this embodiment and one of the first to ninth embodiments is as follows: and thirdly, applying the silicon dioxide aerogel particles with the surfaces coated with the high-hydrophobicity boron nitride nanosheet thin layers obtained in the third step to chemical engineering, oil fields, electric power or pipeline heat supply. The other steps are the same as those in the first to ninth embodiments.
The invention is further illustrated with reference to the following figures and examples:
the first embodiment is as follows: a simple method for coating a high-hydrophobicity boron nitride nanosheet thin layer on the surface of silicon dioxide aerogel particles is completed according to the following steps:
firstly, spreading 0.93g of urea at the bottom of a ceramic boat, spreading 0.31g of boric acid above the urea, and finally spreading 0.31g of silicon dioxide aerogel particles above the boric acid to obtain the ceramic boat carrying the mixture;
the particle size of the urea in the step one is 50-150 μm, and the particle size of the boric acid is 50-150 μm;
the ceramic boat in the step one is 8cm long and 4cm wide;
secondly, placing the ceramic boat carrying the mixture in a reaction zone of a tube furnace, connecting vent pipes at two ends of the tube furnace respectively, sealing, and placing the tube furnace in a state of 1000 mL/min -1 Introducing protective gas at the gas flow rate for 10min, exhausting air in the tubular furnace at normal pressure, and regulating the flow rate of the protective gas to 80 mL/min -1 Starting the tubular furnace, raising the temperature of a reaction zone of the tubular furnace to 1100 ℃, and preserving the heat at 1100 ℃ for 60 min;
the protective gas in the second step is nitrogen;
thirdly, closing the tube furnace, and keeping the flow of the protective gas in the tube furnace at 80 mL/min -1 And then the flow rate of the protective gas is 80 mL/min -1 Naturally cooling the tube furnace to room temperature, taking out the ceramic boat to obtain the silicon dioxide aerogel particles with the surfaces coated with the high-hydrophobic boron nitride nanosheet thin layers, namely completing the simple method for coating the high-hydrophobic boron nitride nanosheet thin layers on the surfaces of the silicon dioxide aerogel particles;
the protective gas in the third step is nitrogen.
FIG. 1 is an SEM image of silica aerogel particles coated with a thin layer of highly hydrophobic boron nitride nanosheets prepared in the third step of the example;
as can be seen from fig. 1, a layer of boron nitride nanosheet thin layer is coated on the surface of the silica aerogel particle, and due to the template effect of the silica aerogel particle, the boron nitride nanosheet thin layer has a micro-nano structure, so that the boron nitride nanosheet thin layer has good hydrophobic performance.
FIG. 2 is an infrared spectrum of silica aerogel particles coated with a thin layer of highly hydrophobic boron nitride nanosheets prepared in the third step of the example;
as can be seen in FIG. 2, 1383.70cm -1 The vibration peak at (A) is generated by the in-plane B-N bond transverse optical vibration mode, and 798.85cm -1 The vibration peak can be attributed to the out-of-plane bending vibration mode of B-N-B, and each spectrum peak is very strong, which indicates that the material contains h-BN. 1108.2cm -1 The peak of vibration at (A) was attributed to the vibration mode of Si-O-Si, 471.51cm -1 The vibration peak at (a) is due to the bending vibration mode of the O-Si-O bond. In summary, the material should be a boron nitride-silica aerogel composite.
FIG. 3 is a thermogravimetric plot of silica aerogel particles coated with a thin layer of highly hydrophobic boron nitride nanosheets prepared in the third step of the example;
as can be seen from fig. 3, the quality of the silica aerogel particles with the surface coated with the thin layer of highly hydrophobic boron nitride nanosheet prepared in the third step of the example is slightly reduced in the initial stage due to the trace amount of nitrogen adsorbed in the pores when the porous substance is prepared, and the product is heated and sucked out. The subsequent slight rise in the curve may be related to impurities contained in the material, and continuing with the rise in temperature, the curve falls again, which is related to the removal of impurities such as C contained in the sample. The mass of the alloy is obviously increased at about 800 ℃, because boron nitride is oxidized and converted into boron oxide. That is, the oxidation resistance temperature of the sample was 800 ℃, consistent with its high hydrophobicity remaining after calcination at 700 ℃.
Dropping 5 microliter of water drops on the silica aerogel particles coated with the high-hydrophobicity boron nitride nanosheet thin layer prepared in the third step of the example, and testing the contact angle of the silicon dioxide aerogel particles, as shown in fig. 4;
FIG. 4 is a photograph of the contact angle of silica aerogel particles coated with a thin layer of highly hydrophobic boron nitride nanosheets prepared in the third step of the example;
as can be seen from fig. 4, the hydrophobic angle of the silica aerogel with the surface coated with the thin layer of highly hydrophobic boron nitride nanosheet prepared in the third step of the example is 136.53 °, and it can be seen that the silica aerogel with the surface coated with the thin layer of highly hydrophobic boron nitride nanosheet is a highly hydrophobic material.
Heating the silica aerogel particles coated with the high-hydrophobic boron nitride nanosheet thin layer in the third step of the embodiment in the air to 700 ℃, and preserving the heat at 700 ℃ for 60min to obtain the heated silica aerogel particles coated with the high-hydrophobic boron nitride nanosheet thin layer; dropping 5 microliter of water drops on the silica aerogel particles coated with the high-hydrophobicity boron nitride nanosheet thin layer on the surface subjected to the heating treatment, and testing the contact angle of the water drops, wherein the contact angle is shown in fig. 5;
fig. 5 is a contact angle photograph of silica aerogel particles coated with a thin layer of highly hydrophobic boron nitride nanosheet prepared in the third step of the example after being heated to 700 ℃ in air and kept for 60 min.
As can be seen from fig. 5, the silica aerogel particles with the surface coated with the thin highly hydrophobic boron nitride nanosheet layer prepared in the third step of the example are heated to 700 ℃ in the air, and the hydrophobic angle after the temperature is maintained for 60min is 135.98 °, which shows that the hydrophobicity of the silica aerogel particles is not affected at high temperature.
The second embodiment: a simple method for coating a high-hydrophobicity boron nitride nanosheet thin layer on the surface of silicon dioxide aerogel particles is completed according to the following steps:
firstly, uniformly mixing 1.86g of urea, 0.62g of boric acid and 0.31g of silicon dioxide aerogel particles to obtain a mixture; spreading the mixture at the bottom of the ceramic boat to obtain the ceramic boat carrying the mixture;
the particle size of the urea in the step one is 50-150 μm, and the particle size of the boric acid is 50-150 μm;
the ceramic boat in the step one is 8cm long and 4cm wide;
secondly, placing the ceramic boat carrying the mixture in a reaction zone of a tube furnace, connecting vent pipes at two ends of the tube furnace respectively, sealing, and placing the tube furnace in a state of 1000 mL/min -1 Introducing protective gas at the gas flow rate for 10min, exhausting air in the tubular furnace at normal pressure, and regulating the flow rate of the protective gas to 80 mL/min -1 Starting the tubular furnace, raising the temperature of a reaction zone of the tubular furnace to 1100 ℃, and preserving the heat at 1100 ℃ for 60 min;
the protective gas in the second step is nitrogen;
thirdly, closing the tube furnace, and keeping the flow of the protective gas in the tube furnace at 80 mL/min -1 And then the flow rate of the protective gas is 80 mL/min -1 Naturally cooling the tube furnace to room temperature, taking out the ceramic boat to obtain the silicon dioxide aerogel particles with the surfaces coated with the high-hydrophobic boron nitride nanosheet thin layers, namely completing the simple method for coating the high-hydrophobic boron nitride nanosheet thin layers on the surfaces of the silicon dioxide aerogel particles;
the protective gas in the third step is nitrogen.
The hydrophobic angle of the silica aerogel particle with the surface coated with the thin layer of the highly hydrophobic boron nitride nanosheet prepared in example two was 132.96 °.
The silica aerogel particles coated with the highly hydrophobic boron nitride nanosheet thin layer on the surface, prepared in example two, have a hydrophobic angle of 131.87 degrees after being heated to 700 ℃ in air and subjected to heat preservation for 60 min.
Example three: a simple method for coating a high-hydrophobicity boron nitride nanosheet thin layer on the surface of silicon dioxide aerogel particles is completed according to the following steps:
firstly, spreading 1.86g of urea at the bottom of a ceramic boat, spreading 0.62g of boric acid above the urea, and finally spreading 0.31g of silicon dioxide aerogel particles above the boric acid to obtain the ceramic boat carrying the mixture;
the particle size of the urea in the step one is 50-150 μm, and the particle size of the boric acid is 50-150 μm;
the ceramic boat in the step one is 8cm long and 4cm wide;
secondly, placing the ceramic boat carrying the mixture in a reaction zone of a tube furnace, connecting vent pipes at two ends of the tube furnace respectively, sealing, and placing the tube furnace in a state of 1000 mL/min -1 Introducing protective gas at the gas flow rate for 10min, exhausting air in the tubular furnace at normal pressure, and regulating the flow rate of the protective gas to 80 mL/min -1 Starting the tubular furnace, raising the temperature of a reaction zone of the tubular furnace to 1100 ℃, and preserving the heat at 1100 ℃ for 60 min;
the protective gas in the second step is nitrogen;
thirdly, closing the tube furnace and keeping the tubeThe flow rate of the shielding gas in the furnace was 80 mL/min -1 And then the flow rate of the protective gas is 80 mL/min -1 Naturally cooling the tube furnace to room temperature, taking out the ceramic boat to obtain the silicon dioxide aerogel particles with the surfaces coated with the high-hydrophobic boron nitride nanosheet thin layers, namely completing the simple method for coating the high-hydrophobic boron nitride nanosheet thin layers on the surfaces of the silicon dioxide aerogel particles;
the protective gas in the third step is nitrogen.
The hydrophobic angle of the silica aerogel particle with the surface coated with the thin layer of the highly hydrophobic boron nitride nanosheet prepared in example three was 137.55 °.
The silica aerogel particles coated with the highly hydrophobic boron nitride nanosheet thin layer on the surface, prepared in the third example, are heated to 700 ℃ in the air, and the hydrophobic angle is 136.47 degrees after the temperature is kept for 60 min.
Example four: a simple method for coating a high-hydrophobicity boron nitride nanosheet thin layer on the surface of silicon dioxide aerogel particles is completed according to the following steps:
firstly, spreading 2.5g of melamine at the bottom of a ceramic boat, spreading 0.62g of boric acid above urea, and finally spreading 0.31g of silicon dioxide aerogel particles above the boric acid to obtain the ceramic boat carrying the mixture;
the particle size of the melamine in the step one is 50-150 μm, and the particle size of the boric acid is 50-150 μm;
the length of the ceramic boat in the step one is 8cm, and the width of the ceramic boat is 4 cm;
secondly, placing the ceramic boat carrying the mixture in a reaction zone of a tube furnace, connecting vent pipes at two ends of the tube furnace respectively, sealing, and placing the tube furnace in a state of 1000 mL/min -1 Introducing protective gas at the gas flow rate for 10min, exhausting air in the tubular furnace at normal pressure, and regulating the flow rate of the protective gas to 80 mL/min -1 Starting the tubular furnace, raising the temperature of a reaction zone of the tubular furnace to 1100 ℃, and preserving the heat at 1100 ℃ for 60 min;
the protective gas in the second step is nitrogen;
thirdly, closing the tube furnace and maintaining the flow of the protective gas in the tube furnaceThe amount is 80 mL/min -1 And then the flow rate of the protective gas is 80 mL/min -1 Naturally cooling the tube furnace to room temperature, taking out the ceramic boat to obtain the silicon dioxide aerogel particles with the surfaces coated with the high-hydrophobic boron nitride nanosheet thin layers, namely completing the simple method for coating the high-hydrophobic boron nitride nanosheet thin layers on the surfaces of the silicon dioxide aerogel particles;
the protective gas in the third step is nitrogen.
The hydrophobic angle of the silica aerogel particles with the surface coated with the thin layer of highly hydrophobic boron nitride nanosheets prepared in example four was 134.13 °.
The silica aerogel particles coated with the highly hydrophobic boron nitride nanosheet thin layer on the surface, prepared in example four, have a hydrophobic angle of 133.14 degrees after being heated to 700 ℃ in air and kept warm for 60 min.
The silica aerogel particles described in the first, second, third and fourth examples are the same, and the specific preparation method is prepared by the following steps:
uniformly mixing tetraethoxysilane, absolute ethyl alcohol and deionized water according to a molar ratio of 1:8:3.75 to obtain a precursor solution;
adjusting the pH value of the precursor solution to 3-4 by using an oxalic acid solution with the concentration of 0.1mol/L, and stirring for 60min under a magnetic stirrer to obtain a mixed solution; placing the mixed solution in a water bath kettle, and hydrolyzing at the constant temperature of 60 ℃ for 16h to obtain a hydrolyzed mixed solution;
thirdly, adjusting the pH value of the hydrolyzed mixed solution to 7-8 by using an ammonia water solution with the concentration of 0.5mol/L, uniformly stirring, and standing for 30min to obtain gel;
adding absolute ethyl alcohol into the gel for aging for 12 hours, wherein the volume ratio of the absolute ethyl alcohol to the gel is 1:5, then adding n-hexane into the gel for aging for 12 hours, wherein the volume ratio of the n-hexane to the gel is 1:5, and finally adding the n-hexane into the gel again for aging for 12 hours, wherein the volume ratio of the n-hexane to the gel is 1: 5;
fifthly, circulating the step IV for 1 time, finally putting the mixture into a drying oven, drying the mixture for 4 hours at 50 ℃, then drying the mixture for 3 hours at 80 ℃, finally drying the mixture for 2 hours at 120 ℃, and grinding the mixture after the drying is finished to obtain silicon dioxide aerogel particles;
the particle size of the silicon dioxide aerogel particles in the fifth step is 50-150 μm.
The above contents are only for explaining the technical idea of the present invention, and the protection scope of the present invention should not be limited thereby, and any modification made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.
Claims (10)
1. A simple method for coating a high-hydrophobicity boron nitride nanosheet thin layer on the surface of a silicon dioxide aerogel particle is characterized by comprising the following steps of:
firstly, preparing a ceramic boat carrying the mixture by adopting the method 1 or the method 2;
the method 1 comprises the following steps: spreading urea or melamine at the bottom of the ceramic boat, spreading boric acid above the urea or melamine, and finally spreading silica aerogel particles above the boric acid to obtain the ceramic boat loaded with the mixture;
the method 2 comprises the following steps: uniformly mixing urea or melamine, boric acid and silica aerogel particles to obtain a mixture; spreading the mixture at the bottom of the ceramic boat to obtain the ceramic boat carrying the mixture;
secondly, placing the ceramic boat carrying the mixture in a reaction zone of a tube furnace, connecting an air pipe at two ends of the tube furnace respectively, sealing, and placing the tube furnace at a temperature of 1000 mL/min -1 ～2000mL·min -1 Introducing protective gas at the gas flow rate for 10-20 min, exhausting air in the tubular furnace at normal pressure, and adjusting the flow rate of the protective gas to 80-200 mL/min -1 Starting the tubular furnace, raising the temperature of a reaction zone of the tubular furnace to 1100-1150 ℃, and preserving the temperature for 30-180 min at 1100-1150 ℃;
thirdly, closing the tube furnace, and keeping the flow of the protective gas in the tube furnace at 80 mL/min -1 ～200mL·min -1 Then the flow rate of the protective gas is 80 mL/min -1 ～200mL·min -1 Lower connecting pipeAnd naturally cooling the furnace to room temperature, and taking out the ceramic boat to obtain the silica aerogel particles with the surfaces coated with the high-hydrophobic boron nitride nanosheet thin layers, namely completing the simple method for coating the high-hydrophobic boron nitride nanosheet thin layers on the surfaces of the silica aerogel particles.
2. The simple method for coating the high-hydrophobicity boron nitride nanosheet thin layer on the surface of the silica aerogel particle according to claim 1, wherein the silica aerogel particle in the first step is prepared by the following steps:
uniformly mixing tetraethoxysilane, absolute ethyl alcohol and deionized water according to a molar ratio of 1:8:3.75 to obtain a precursor solution;
adjusting the pH value of the precursor solution to 3-4 by using an oxalic acid solution with the concentration of 0.1mol/L, and stirring for 60min under a magnetic stirrer to obtain a mixed solution; placing the mixed solution in a water bath kettle, and hydrolyzing at the constant temperature of 60 ℃ for 16h to obtain a hydrolyzed mixed solution;
thirdly, adjusting the pH value of the hydrolyzed mixed solution to 7-8 by using an ammonia water solution with the concentration of 0.5mol/L, uniformly stirring, and standing for 30min to obtain gel;
adding absolute ethyl alcohol into the gel, aging for 12h, adding normal hexane into the gel, aging for 12h, and finally adding normal hexane into the gel again, and aging for 12 h;
the volume ratio of the absolute ethyl alcohol to the gel in the step (iv) is 1: 5;
the volume ratio of the n-hexane to the gel in the step (iv) is 1: 5;
fifthly, circulating the step (iv) for 1 to 2 times, finally putting the obtained product into a drying oven, firstly drying the product at 50 ℃ for 4 hours, then drying the product at 80 ℃ for 3 hours, finally drying the product at 120 ℃ for 2 hours, and grinding the product after drying to obtain silicon dioxide aerogel particles;
the particle size of the silicon dioxide aerogel particles in the fifth step is 50-150 μm.
3. The simple method for coating the highly hydrophobic boron nitride nanosheet thin layer on the surface of the silica aerogel particle according to claim 1, wherein the urea in the first step has a particle size of 50 μm to 150 μm, the melamine has a particle size of 50 μm to 150 μm, and the boric acid has a particle size of 50 μm to 150 μm.
4. The simple method for coating the highly hydrophobic boron nitride nanosheet thin layer on the surface of the silica aerogel particle according to claim 1, wherein in the method 1, the molar ratio of the silica aerogel particle to the boric acid is 1 (1-10), the molar ratio of the boric acid to the urea is 1 (2-4), and the molar ratio of the boric acid to the melamine is 1 (1-3).
5. The simple method for coating the highly hydrophobic boron nitride nanosheet thin layer on the surface of the silica aerogel particle according to claim 1, wherein in the method 2, the molar ratio of the silica aerogel particle to the boric acid is 1 (1-10), the molar ratio of the boric acid to the urea is 1 (2-4), and the molar ratio of the boric acid to the melamine is 1 (1-3).
6. The simple method for coating the highly hydrophobic boron nitride nanosheet thin layer on the surface of the silica aerogel particle according to claim 1, wherein the protective gas in the second step is nitrogen.
7. The simple method for coating the high-hydrophobicity boron nitride nanosheet thin layer on the surface of the silica aerogel particle according to claim 1, wherein the protective gas in the third step is nitrogen.
8. The simple method for coating the highly hydrophobic boron nitride nanosheet thin layer on the surface of the silica aerogel particles as defined in claim 1, wherein in step two, the ceramic boat carrying the mixture is placed in a reaction zone of a tube furnace, and then the tube furnace is sealed by connecting vent pipes to both ends of the tube furnace respectively, and is placed in the tube furnace at a flow rate of 1100 mL-min -1 Introducing protective gas for 10min at the gas flow rate, exhausting air in the tubular furnace at normal pressure, and flowing the protective gasThe amount is adjusted to 80 mL/min -1 Starting the tube furnace, raising the temperature of the reaction zone of the tube furnace to 1100 ℃, and preserving the heat at 1100 ℃ for 30-60 min.
9. The simple method for coating the highly hydrophobic boron nitride nanosheet thin layer on the surface of the silica aerogel particles as claimed in claim 1, wherein in step two, the ceramic boat carrying the mixture is placed in the reaction zone of the tube furnace, then the two ends of the tube furnace are respectively connected with the vent pipes and sealed, and the mixture is fed into the tube furnace at a flow rate of 1000 mL-min -1 ～1500mL·min -1 Introducing protective gas at the gas flow rate for 10-15 min, exhausting air in the tubular furnace at normal pressure, and adjusting the flow rate of the protective gas to 100-150 mL/min -1 Starting the tube furnace, raising the temperature of the reaction zone of the tube furnace to 1100 ℃, and preserving the heat at 1100 ℃ for 60-120 min.
10. The simple method for coating the high-hydrophobicity boron nitride nanosheet thin layer on the surface of the silica aerogel particle according to claim 1, wherein the silica aerogel particle coated with the high-hydrophobicity boron nitride nanosheet thin layer obtained in the third step is applied to chemical industry, oil fields, electric power or pipeline heat supply.
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