CN106379904A - Preparation method for high-temperature-resistant silica aerogel - Google Patents

Abstract

The invention relates to a preparation method of high-temperature-resistant silicon oxide airgel. Using cheap industrial water glass as the precursor, water as the reaction solvent, and ammonia water as the basic catalyst, a high-temperature-resistant bulk silica aerogel with excellent performance was prepared through an atmospheric drying process. The obtained airgel sample has low density, high specific surface area, good temperature resistance, and the hydrophobic temperature resistance in air can reach 586.6°C. The method has the advantages of simple preparation process and low cost, and the excellent high-temperature stability of the prepared aerogel expands the scope of application of the aerogel, so that it can be widely used in the field of heat insulation.

Description

A kind of preparation method of high temperature resistant silica airgel

technical field

The invention belongs to the technical field of preparation of inorganic nanoporous materials, and in particular relates to a preparation method of high-temperature-resistant silica airgel.

Background technique

Airgel is a nano-porous network structure composed of colloidal particles or polymer molecules, and a highly dispersed solid-state material filled with gaseous dispersion media in the pores. This material with a sponge-like open-pore structure has a very large specific surface area, and the structure of the material can be controlled at the microscopic scale of nanometer scale, so that it has many unique properties. The unique structural characteristics of aerogels make aerogels have singular properties in thermal, electrical, acoustic, optical and other aspects.

The preparation of SiO ₂ airgel is usually carried out by supercritical drying, the molding effect is better, and the nanoporous network structure can be well maintained. However, the equipment required for supercritical drying is expensive, and there is a relatively high risk of high temperature and high pressure. Therefore, the preparation of _SiO2 airgel by atmospheric pressure drying is an inevitable requirement for large-scale production and application. At present, the silicon sources used in the synthesis of silica airgel include orthosilicates, polysiloxanes, silica sol, water glass, and rice husk or fly ash. The use of orthosilicates and polysiloxanes as silicon sources has problems such as high price, high cost, and strong toxicity. Although rice husk or fly ash is cheap, the preparation process is complicated, and the performance of the prepared airgel is relatively low. Difference.

Chinese patents CN201210121968.0 and CN201210114691.9 use sodium silicate as a raw material and are prepared by a two-step sol-gel method. After ion exchange, they are aged with an ethanol solution of tetraethyl orthosilicate, and finally undergo solvent exchange and modification. The airgel is obtained by drying, and the tetraethyl orthosilicate used greatly increases the preparation cost, and the density of the obtained airgel is also relatively high. Liu Guangwu of Tongji University used water glass as the silicon source, and directly modified the surface groups of the wet gel with a mixture of hexamethyldisiloxane and hydrochloric acid after replacement with ethanol solvent, and dried at normal pressure to obtain hydrophobic SiO ₂ Airgel, the specific surface area of which is 568m ² /g, the modifier is expensive and used in a large amount. Ni Xingyuan et al. (Chinese Patent, Application No. 200810042222.4) disclosed a method for preparing hydrophobic silica aerogels under normal pressure by using straw ash as a raw material, through solvent replacement and surface modification, but the process is relatively complicated. At present, there are many research reports on the preparation of silica airgel by atmospheric drying, but there are certain defects, such as high cost, complicated process, and the prepared airgel has a small specific surface area and poor temperature resistance, which restricts the Industrial applications of airgel. Therefore, there is an urgent need to study silica aerogels with simple preparation process, low cost and high temperature resistance.

Contents of the invention

The present invention aims at the above-mentioned problems of the prior art, and provides a method for preparing high-temperature-resistant silicon oxide airgel with simple process and low cost.

In order to achieve the above-mentioned purpose of the invention, the technical solution adopted in the present invention is: a kind of preparation method of high-temperature-resistant silicon oxide aerogel, obtains according to the following steps:

Step 1: Dilute industrial water glass with deionized water to obtain a water glass solution, filter and ultrasonicate for a certain period of time, and then obtain an active silicic acid solution with a pH of 1 to 4 through ion exchange;

Step 2: Take a certain volume of active silicic acid solution, add a certain amount of dry chemical control agent to it, stir for 2-10 minutes, add a certain concentration of ammonia water until it gels;

Step 3: Aging the wet gel in an organic reagent at a certain temperature for a period of time;

Step 4: After aging, replace the wet gel in a non-polar solvent;

Step 5: placing the replaced wet gel in a mixture of siloxane solvent and non-polar solvent for surface modification;

Step 6: The wet gel modified in Step 5 is washed with a non-polar solvent and then dried under normal pressure to obtain a transparent massive silica airgel.

The volume ratio of the silicon source and deionized water described in step 1 is preferably 1:2~1:10, the modulus of the silicon source is industrial water glass of 3~3.5, and the ultrasonic treatment time is 0~10min.

The volume of silicic acid described in step 2 is 10 ~ 50ml, and the dry chemical control agent is one of formamide, N,N-dimethylformamide, polyethylene glycol, glycerol, oxalic acid, and it is mixed with Si The molar ratio is 0~1:1, and the concentration of ammonia water is 0~4mol/L.

The organic solvent described in step 3 is one of methanol, ethanol, isopropanol and butanol, the aging temperature is 30-70° C., and the aging time is 0-5 days.

The non-polar solvent described in step 4 is preferably one of n-hexane, cyclohexane and n-heptane.

The siloxane solvent described in step 5 is preferably one of trimethylchlorosilane, hexamethyldisilazane, hexamethyldisiloxane, 3-aminopropyltriethoxysilane, silane The volume ratio of the coupling agent to the wet gel is 0.05-0.5, and the non-polar solvent is preferably one of n-hexane, cyclohexane, and n-heptane.

The non-polar solvent described in step 6 is preferably one of n-hexane, cyclohexane, and n-heptane, the drying temperature under normal pressure is 30-200° C., and the drying time is 5-15 hours.

The invention discloses a method for preparing high-temperature-resistant silicon oxide aerogels. The low-density silicon oxide airgel is prepared by drying under normal pressure with cheap industrial water glass as a silicon source. In the high-temperature-resistant silica airgel, the silica airgel is prepared by ultrasonic treatment and drying under normal pressure with the addition of a drying chemical control agent. The sample has the characteristics of low density, uniform pore structure, etc., and the hydrophobic temperature resistance reaches 586.6°C.

Description of drawings:

Accompanying drawing 1 is the macrophotograph of the silica airgel prepared by the present invention.

Accompanying drawing 2 is the scanning electron micrograph of the silica airgel prepared in Example 3.

detailed description

Example 1

Take 20ml of industrial water glass with a modulus of 3.2 according to the volume ratio of industrial water glass and water 1:4, mix 80ml of deionized water in a beaker, stir for 10 minutes, then filter and ultrasonicate for 5 minutes, and then obtain pH by ion exchange =2.5 active silicic acid solution, take the above 30ml active silicic acid, add 0.47ml glycerin to it, stir for 3min, add 2 drops of 0.01mol/L ammonia solution, stir for 1min, wait for it to completely gel, add ethanol, and then It was aged in a water bath at 40°C for three days, and the wet gel was modified by placing it in a mixture of trimethylchlorosilane and n-hexane for 10 hours in a water bath at 40°C. The fully modified gel floats on the modified liquid product as a whole, and after being washed with n-hexane, it is dried at 40°C, 60°C, 80°C, and 100°C for two hours each to obtain an airgel sample.

The obtained airgel sample had a density of 0.214 g/cm ³ , a specific surface area of 704 m ² /g, a pore volume of 2.80 cm ³ /g, and an average pore diameter of 15.9 nm.

Example 2

Take 20ml of industrial water glass with a modulus of 3.2 according to the volume ratio of industrial water glass and water 1:4, mix 80ml of deionized water in a beaker, stir for 10 minutes, then filter and ultrasonicate for 5 minutes, and then obtain pH by ion exchange =2.5 active silicic acid solution, take the above 30ml silicic acid, add 0.93ml glycerin to it, stir for 3min, add 2 drops of 0.1mol/L ammonia solution, stir for 1min, wait until it is completely gelled, add ethanol, and then Place in a water bath at 40°C for three days for aging, and place the wet gel in a mixture of trimethylchlorosilane and n-hexane for modification, and carry out the modification in a water bath at 40°C for 10 hours. The fully modified gel floats on the modified liquid product as a whole, and after being washed with n-hexane, it is dried at 40°C, 60°C, 80°C, and 100°C for two hours each to obtain an airgel sample.

The obtained airgel sample had a density of 0.1890 g/cm ³ , a specific surface area of 703 m ² /g, a pore volume of 3.21 cm ³ /g and an average pore diameter of 18.2 nm.

Example 3

Take 20ml of industrial water glass with a modulus of 3.2 according to the volume ratio of industrial water glass and water 1:4, mix 80ml of deionized water in a beaker, stir for 10 minutes, then filter and ultrasonicate for 3 minutes, and then obtain pH by ion exchange =2.5 active silicic acid solution, take the above 30ml silicic acid, add 0.93ml glycerin to it, stir for 3min, add 2 drops of 0.5mol/L ammonia solution, stir for 1min, wait for it to completely gel, add ethanol, and then Place in a water bath at 40°C for three days for aging, and place the wet gel in a mixture of trimethylchlorosilane and n-hexane for modification, and carry out the modification in a water bath at 40°C for 10 hours. The fully modified gel floats on the modified liquid product as a whole, and after being washed with n-hexane, it is dried at 40°C, 60°C, 80°C, and 100°C for two hours each to obtain an airgel sample.

The obtained airgel sample had a density of 0.1119 g/cm ³ , a specific surface area of 726 m ² /g, a pore volume of 3.50 cm ³ /g and an average pore diameter of 19.3 nm.

Example 4

Take 20ml of industrial water glass with a modulus of 3.2 according to the volume ratio of industrial water glass and water 1:4, mix 80ml of deionized water in a beaker, stir for 10 minutes, then filter and ultrasonicate for 4 minutes, and then obtain pH by ion exchange =2.5 active silicic acid solution, take the above 30ml silicic acid, add 0.47ml glycerin to it, stir for 3min, add 2 drops of 1mol/L ammonia solution, stir for 1min, wait for it to completely gel, add ethanol, and then place it After aging in a water bath at 40°C for three days, the wet gel was modified in a mixture of trimethylchlorosilane and n-hexane for 10 hours in a water bath at 40°C. The fully modified gel floats on the modified liquid product as a whole, and after being washed with n-hexane, it is dried at 40°C, 60°C, 80°C, and 100°C for two hours each to obtain an airgel sample.

The obtained airgel sample had a density of 0.0869 g/cm ³ , a specific surface area of 737 m ² /g, a pore volume of 3.50 cm ³ /g and an average pore diameter of 19.0 nm.

Example 5

Take 20ml of industrial water glass with a modulus of 3.2 according to the volume ratio of industrial water glass and water 1:4, mix 80ml of deionized water in a beaker, stir for 10 minutes, then filter and ultrasonicate for 5 minutes, and then obtain pH by ion exchange =2.5 active silicic acid solution, take the above 30ml silicic acid, add 0.47ml glycerin to it, stir for 3min, add 2 drops of 1.5mol/L ammonia solution, stir for 1min, wait for it to completely gel, add ethanol, and then Place in a water bath at 40°C for three days for aging, and place the wet gel in a mixture of trimethylchlorosilane and n-hexane for modification, and carry out the modification in a water bath at 40°C for 10 hours. The fully modified gel floats on the modified liquid product as a whole, and after being washed with n-hexane, it is dried at 40°C, 60°C, 80°C, and 100°C for two hours each to obtain an airgel sample.

The obtained airgel sample had a density of 0.1109 g/cm ³ , a specific surface area of 710 m ² /g, a pore volume of 3.51 cm ³ /g, and an average pore diameter of 19.8 nm.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments, and those skilled in the art can also make various equivalent modifications or replacements without departing from the spirit of the present invention. , these equivalent modifications or replacements are all included within the scope defined by the claims of the present application.

Claims (7)

1. a kind of preparation method of high temperature oxidation resisting silica aerogel is it is characterised in that be prepared in the steps below：

Step one：Industrial waterglass is added deionized water dilution to obtain water glass solution, ultrasonically treated certain time after filtration, then the active silicic acid solution that pH is 1 ~ 4 is obtained by ion exchange；

Step 2：Take the active silicic acid solution of certain volume, be added thereto to a certain amount of dry chemistry controlling agent, after stirring 2 ~ 10min, add finite concentration ammoniacal liquor and treat its gel；

Step 3：Wet gel is placed at a certain temperature in organic reagent aging a period of time；

Step 4：After aging, wet gel is placed in displacement in non-polar solven；

Step 5：Wet gel after displacement is placed in the mixed liquor that siloxane solvent is with non-polar solven and carries out surface modification；

Step 6：By the wet gel after step 5 modification, after non-polar solven washing, constant pressure and dry can get transparent cake silica aerogel.

2. high temperature oxidation resisting silica aerogel according to claim 1 preparation method it is characterised in that in described step one silicon source and the ratio of the volume of deionized water be preferably 1:2~1:10, the modulus of described silicon source is 3 ~ 3.5 industrial waterglass, and sonication treatment time is 0 ~ 10min.

3. the preparation method of high temperature oxidation resisting silica aerogel according to claim 1, it is characterized in that, in described step 2, silicic acid volume is 5 ~ 30ml, dry chemistry controlling agent is formamide, N, one of dinethylformamide, polyethylene glycol, glycerine, oxalic acid, it is 0 ~ 1 with the mol ratio of Si:1, the concentration of ammoniacal liquor is 0 ~ 4mol/L.

4. high temperature oxidation resisting silica aerogel according to claim 1 preparation method it is characterised in that in described step 3 organic solvent be one of methyl alcohol, ethanol, isopropanol, butanol, aging temperature be 30 ~ 70 DEG C, the time be 0 ~ 5d.

5. the preparation method of high temperature oxidation resisting silica aerogel according to claim 1 is it is characterised in that non-polar solven described in described step 4 is preferably one of n-hexane, hexamethylene, normal heptane.

6. the preparation method of high temperature oxidation resisting silica aerogel according to claim 1, it is characterized in that, siloxane solvent described in described step 5 is preferably one of trim,ethylchlorosilane, HMDS, hexamethyldisiloxane, APTES, silane coupler is 0.05 ~ 0.5 with the ratio of the volume of wet gel, and described non-polar solven is preferably one of n-hexane, hexamethylene, normal heptane.

7. high temperature oxidation resisting silica aerogel according to claim 1 preparation method it is characterised in that in described step 6 non-polar solven be preferably one of n-hexane, hexamethylene, normal heptane, constant pressure and dry temperature be 30 ~ 200 DEG C, drying time be 5 ~ 15h.