Method for modifying silicon dioxide aerogel by using electron beam irradiation technology

Abstract

The invention belongs to the technical field of silicon dioxide aerogel modification, and particularly relates to a method for modifying silicon dioxide aerogel by using an electron beam irradiation technology, which comprises the following steps: (1) preparing a precursor: uniformly mixing an organic silicon source, water and an organic solvent according to a ratio at normal temperature and pressure in an air atmosphere, and then stirring and hydrolyzing to obtain the precursor; (2) preparing gel: adding ammonia water into the precursor to adjust the pH value, uniformly mixing, and standing to obtain wet gel; and (3) modifying the gel, namely adding a hydrophobic modifier solution into the wet gel, soaking, irradiating the soaked gel under an electron beam, washing, and drying to obtain the silicon dioxide aerogel. The preparation method has the advantages that the aerogel and the hydrophobic modifier are activated through electron beam irradiation, the reaction rate of the hydrophobic modifier and the aerogel is increased, the grafting rate of hydrophobic groups on the aerogel is increased, and therefore the hydrophobicity of the prepared silicon dioxide aerogel is high.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon dioxide aerogel modification, and in particular relates to a method for modifying silicon dioxide aerogel by utilizing electron beam irradiation technology. Background Art

[0002] Silica aerogel is a nanoporous material composed of nanoparticles with an ultra-low bulk density (0.03-0.35 g·cm -3 ), high porosity (80-99%) and high surface area (500-1500m 2 ·g -1 ) and other unique properties. Due to its excellent performance, silica aerogel has received extensive attention in the fields of thermal insulation, adsorption, catalysis and sensing. Since there are a large number of hydroxyl groups distributed on the surface of silica aerogel, the performance of the aerogel will be reduced or even the structure will be destroyed due to the absorption of water. Therefore, hydrophobic modification plays an important role in improving the performance of silica aerogel.

[0003] At present, a variety of methods have been developed for the hydrophobic modification of silica aerogels, such as the in-situ method of changing and modifying the internal skeleton through a co-precursor, the post-modification method of modifying the surface of the gel skeleton after synthesis through an organic silane solution, and the chemical vapor deposition method of modifying the aerogel surface. However, these methods all have problems such as high cost, long time, complex process, and poor effect of hydrophobic modification, which are not conducive to commercialization and are not convenient for large-scale industrial production. Summary of the invention

[0004] In view of the above problems, the present invention provides a method for modifying silica aerogel using electron beam irradiation technology.

[0005] The present invention relates to a method for modifying silica aerogel by using electron beam irradiation technology, comprising the following steps: (1) Precursor configuration: At room temperature and pressure, in an air atmosphere, an organosilicon source, water and an organic solvent are mixed evenly in proportion, and then stirred and hydrolyzed to obtain a precursor; (2) Preparation of gel: Adding ammonia water to the precursor prepared in step (1) to adjust the pH value, mixing evenly, and allowing to stand to obtain a wet gel; (3) Gel modification: The hydrophobic modifier solution is added to the wet gel prepared in step (2) and soaked, and then the soaked gel is irradiated under electron beam, washed and dried to obtain silica aerogel.

[0006] Preferably, in step (1), the volume ratio of the organosilicon source, water and organic solvent is 1:0.3-0.5:1-1.5; the organosilicon source is one of trimethoxymethylsilane and triethoxymethylsilane; and the organic solvent is one of methanol and ethanol.

[0007] Preferably, in step (1), the hydrolysis is carried out at 20°C to 30°C for 12h to 24h.

[0008] Preferably, in step (2), ammonia water is added to adjust the pH value to 8-9; and the mixture is allowed to stand for 2-4 hours to form a gel.

[0009] Preferably, in step (3), the hydrophobic modifier solution is a mixed solution of trimethylchlorosilane and ethanol; the volume ratio of trimethylchlorosilane to ethanol is 2:8; the volume ratio of the organosilicon source to trimethylchlorosilane is 1:1; and the wet gel is immersed in the hydrophobic modifier solution for 1 h to 2 h.

[0010] Preferably, in step (3), the dose of electron beam irradiation is 15 kGy to 60 kGy.

[0011] Preferably, in step (3), the temperature of electron beam irradiation is 20°C to 35°C.

[0012] Preferably, in step (3), the humidity of the electron beam irradiation is 40% to 90%.

[0013] Preferably, in step (3), the electron beam irradiation time is 0.8s to 3.4s.

[0014] Preferably, in step (3), the drying method is atmospheric pressure drying or freeze drying.

[0015] Compared with the prior art, the advantages and positive effects of the present invention are: (1) The method of modifying silica aerogel using electron beam irradiation technology activates aerogel and hydrophobic modifier by electron beam irradiation, thereby increasing the reaction rate of hydrophobic modifier and aerogel and improving the grafting rate of hydrophobic groups on aerogel, thereby obtaining silica aerogel with high hydrophobicity; (2) The method of modifying silica aerogel using electron beam irradiation technology combines hydrophobic modifier immersion and electron beam irradiation. Compared with the traditional immersion modification method, the immersion time is shortened and the electron beam irradiation time is short, thereby saving time cost; (3) The method of modifying silica aerogel using electron beam irradiation technology has a simple process, readily available raw materials, and no need to introduce any external material system, thus avoiding secondary pollution. It is suitable for large-scale industrial modification of silica aerogel. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the following briefly introduces the drawings required for describing the embodiment. Figure 1 is a flow chart of the preparation of silica aerogel in the present invention; Figure 2 Physical pictures of silica aerogels 1#, 2#, and 3# provided in Example 1; Figure 3 Fourier transform infrared spectra of silica aerogels 1#, 2#, and 3# provided in Example 1; Figure 4 The water contact angles of silica aerogels 1#, 2#, and 3# provided in Example 1; Figure 5 This is a relationship diagram between the dosage and contact angle of silica aerogels 1#, 2#, and 3# provided in Example 1; Figure 6 The water contact angles of silica aerogels 4#, 5#, and 6# provided in Example 2; Figure 7 This is a relationship diagram between the dosage and contact angle of silica aerogels 4#, 5#, and 6# provided in Example 2. DETAILED DESCRIPTION

[0017] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described below in conjunction with embodiments.

[0018] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments of the following disclosure.

[0019] Example 1 A method for modifying silica aerogel using electron beam irradiation technology comprises the following steps: (1) Precursor configuration: At room temperature and pressure, in an air atmosphere, 3 ml of triethoxymethylsilane, 1.65 ml of methanol, 1.35 ml of water and 30 mg of hexadecyltrimethylammonium bromide were mixed evenly, then stirred and hydrolyzed for 20 hours to obtain a precursor.

[0020] (2) Preparation of gel: Add 210 μL of aqueous ammonia to the precursor prepared in step (1), mix well, and let stand for 2 h to obtain a wet gel.

[0021] (3) Gel modification: To the wet gel obtained in step (2), add 3 ml of ethanol solution of trimethylchlorosilane with a volume fraction of 20%, soak for 2 hours, and then divide the soaked gel into three parts, and irradiate them under electron beam for 2 seconds respectively; the parameters of electron beam irradiation are: dose 0 kGy, 15 kGy, 30 kGy, temperature 25 ° C, humidity 70%; wash with 2 ml of methanol for 4 times respectively, freeze-dry at -70 ° C for 20 hours, and obtain silica aerogels 1#, 2#, and 3#. The actual picture is as follows Figure 2 As shown (from left to right are silica aerogels 1#, 2#, and 3#).

[0022] Example 2 A method for modifying silica aerogel using electron beam irradiation technology comprises the following steps: (1) Precursor configuration: At room temperature and pressure, in an air atmosphere, 3 ml of trimethoxymethylsilane, 1.65 ml of ethanol, and 1.35 ml of water were measured and mixed evenly, and then stirred and hydrolyzed for 15 hours to obtain a precursor.

[0023] (2) Preparation of gel: Add 60 μL of aqueous ammonia to the precursor prepared in step (1), mix well, and let stand for 4 h to obtain a wet gel.

[0024] (3) Gel modification: To the wet gel obtained in step (2), add 3 ml of ethanol solution of trimethylchlorosilane with a volume fraction of 20%, soak for 2 hours, and then divide the soaked gel into three parts, and irradiate them under electron beam for 3 seconds respectively; the parameters of electron beam irradiation are: dose 0 kGy, 21 kGy, 42 kGy, temperature 25°C, humidity 70%; wash with 2 ml of methanol 4 times respectively, and dry at 60°C under normal pressure for 24 hours to obtain silica aerogels 4#, 5#, and 6#.

[0025] Test Example 1, The silica aerogels prepared in Example 1 and Example 2 were tested for water contact angle according to the following test method. The test results are shown in Tables 1-2 and Figure 4-7 .

[0026] Test method: Grind the silica aerogel in a mortar, and then use a tablet press to press at a pressure of 30 MPa for 20 minutes to obtain a sample sheet. The sample sheet is tested for hydrophobicity by a contact angle meter to obtain the water contact angle data of the silica aerogel.

[0027] Table 1. Water contact angle test results of Example 1 name Radiation dose (kGy) Contact angle (°) Silica Aerogel 1# 0 135 Silica Aerogel 2# 15 138.5 Silica Aerogel 3# 30 148.75 Table 2. Water contact angle test results of Example 2 name Radiation dose (kGy) Contact angle (°) Silica Aerogel 4# 0 138 Silica Aerogel 5# 21 141.5 Silica Aerogel 6# 42 147 From Table 1-2 and Figure 4-7 It was concluded that the silica aerogel of Example 1 had different hydrophobicities under different irradiation doses, and as the irradiation dose increased, the contact angle increased, indicating that the hydrophobicity of the aerogel was improved; at the same time, the silica aerogel of Example 2 also had different hydrophobicities under different irradiation doses, and as the irradiation dose increased, the contact angle increased, indicating that the hydrophobicity of the aerogel was improved.

[0028] Test Example 2, The silica aerogels 1#, 2#, and 3# obtained in Example 1 were analyzed for functional groups by Fourier transform infrared spectroscopy (FT-IR). The results are as follows: Figure 3 shown.

[0029] exist Figure 3 Medium, 2972cm -1 , 1277cm -1 , 772cm -1 The peaks appearing near represent Si-CH3; at 3442cm -1 and 1635cm -1 It is the characteristic peak of H-OH; 1039cm -1 、849cm -1 The characteristic absorption peaks near are attributed to the bending vibration, symmetric stretching vibration and antisymmetric stretching vibration of Si-O-Si; Figure 3 The results showed that the Si-O-Si absorption peak of silica aerogel 3# (30 kGy) was the strongest and the number of grafted hydrophobic groups was the largest, indicating that the hydrophobic modification effect of silica aerogel was enhanced with the increase of irradiation dose.

[0030] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes for application in other fields. However, any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for modifying silica aerogel using electron beam irradiation technology, characterized in that: The following steps are involved: (1) Precursor configuration: At room temperature and pressure, in an air atmosphere, an organosilicon source, water and an organic solvent are mixed evenly in proportion, and then stirred and hydrolyzed to obtain a precursor; (2) Preparation of gel: Adding ammonia water to the precursor prepared in step (1) to adjust the pH value, mixing evenly, and allowing to stand to obtain a wet gel; (3) Gel modification: The hydrophobic modifier solution is added to the wet gel prepared in step (2) and soaked, and then the soaked gel is irradiated under electron beam, washed and dried to obtain silica aerogel.

2. The method for modifying silica aerogel using electron beam irradiation technology according to claim 1, characterized in that: In the step (1), the volume ratio of the organosilicon source, water and organic solvent is 1:0.3-0.5:1-1.5; the organosilicon source is one of trimethoxymethylsilane and triethoxymethylsilane; and the organic solvent is one of methanol and ethanol.

3. The method for modifying silica aerogel using electron beam irradiation technology according to claim 1, characterized in that: In the step (1), the hydrolysis is carried out at 20°C to 30°C for 12h to 24h.

4. The method for modifying silica aerogel using electron beam irradiation technology according to claim 1, characterized in that: In the step (2), ammonia water is added to adjust the pH value to 8-9; and the mixture is allowed to stand for 2-4 hours to form a gel.

5. The method for modifying silica aerogel using electron beam irradiation technology according to claim 1, characterized in that: In the step (3), the hydrophobic modifier solution is a mixed solution of trimethylchlorosilane and ethanol; the volume ratio of trimethylchlorosilane to ethanol is 2:8; the volume ratio of the organic silicon source to trimethylchlorosilane is 1:1; and the wet gel is immersed in the hydrophobic modifier solution for 1 hour to 2 hours.

6. The method for modifying silica aerogel using electron beam irradiation technology according to claim 1, characterized in that: In the step (3), the dose of electron beam irradiation is 15 kGy to 60 kGy.

7. The method for modifying silica aerogel using electron beam irradiation technology according to claim 1, characterized in that: In the step (3), the temperature of the electron beam irradiation is 20°C to 35°C.

8. The method for modifying silica aerogel using electron beam irradiation technology according to claim 1, characterized in that: In the step (3), the humidity of the electron beam irradiation is 40% to 90%.

9. The method for modifying silica aerogel using electron beam irradiation technology according to claim 1, characterized in that: In the step (3), the electron beam irradiation time is 0.8s to 3.4s.

10. The method for modifying silica aerogel using electron beam irradiation technology according to claim 1, characterized in that: In the step (3), the drying method is atmospheric pressure drying or freeze drying.

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