Method of preparing silica aerogel granules
A method of preparing transparent or nontransparent silica aerogel granules. The method includes forming a granular wet gel by spraying a silica sol into alcohol, the silica sol being prepared by mixing a water glass solution or an opacifier-containing water glass solution with an inorganic acid solution, forming a granular alcohol gel through gelation aging and solvent substitution of the granular wet gel in alcohol, hydrophobically modifying the surface of the granular alcohol gel using an organic silane compound, and drying the surface modified gel at ambient pressure or in a vacuum. The method may prepare silica aerogel granules in a short period of time through heat treatment at a relatively low temperature and at ambient pressure or in a vacuum, thereby ensuring excellent economic feasibility, continuity and reliability, suited for mass production.
1. A method of preparing silica aerogel granules, comprising:
forming a granular wet gel by spraying a silica sol into alcohol, the silica sol being prepared by mixing a water glass solution or an opacifier-containing water glass solution with an inorganic acid solution;
forming a granular alcohol gel through gelation aging and solvent substitution of the granular wet gel in alcohol;
hydrophobically modifying a surface of the granular alcohol gel using an organic silane compound; and
drying the surface modified gel at ambient pressure or in a vacuum.
2. The method of claim 1 , wherein the inorganic acid solution has a molar concentration of 1.0˜2.0M and is mixed in a volume ratio of 0.4˜1.0 with respect to the water glass solution, and the alcohol is used in a volume ratio of 0.6˜1.2 with respect to the silica sol.
3. The method of claim 1 , wherein the inorganic acid is at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid.
4. The method of claim 1 , wherein the opacifier is at least one selected from the group consisting of carbon black, titania, alumina, iron oxide, and ilmenite.
5. The method of claim 1 , wherein the alcohol is at least one selected from the group consisting of ethanol, methanol, and isopropyl alcohol.
6. The method of claim 1 , wherein the organic silane compound is at least one selected from the group consisting of trimethylchlorosilane, hexamethyldisilazane, methyltrimethoxysilane, trimethylethoxysilane, ethyltriethoxysilane, and phenyltriethoxysilane.
7. The method of claim 1 , wherein the organic silane compound is mixed in a volume ratio of 2˜5 with respect to the granular alcohol gel when hydrophobically modifying the surface of the granular alcohol gel.
8. The method of claim 1 , wherein the drying of the surface modified gel is performed at a temperature of 50˜90° C. for 1˜2 hours and then at a temperature from a solvent boiling point to 190° C. for 2˜3 hours at ambient pressure or in a vacuum.