A method for preparing permanently hydrophobic
aerogel and permanently hydrophobic
aerogel prepared by the method. The method comprises adding
sodium silicate to HCl at 30 to 90° C. until an acidity reaches pH 3-5, to form silica hydrogel under acidic conditions of pH 3-5, washing the silica hydrogel with
distilled water using a mixer, followed by filtering, adding the silica hydrogel to a silylating solution of silylating agent in n-
butanol at pH 1-5 using an acid selected from
hydrochloric acid,
sulfuric acid,
phosphoric acid and
nitric acid, to simultaneously conduct
silylation and
solvent replacement, and
drying the silica hydrogel; The method has the following advantages; i)
silylation and
solvent replacement can be simultaneously conducted, ii) n-
butanol is used as a reaction
solvent instead of
methanol upon
silylation, thus obtaining a
thermal conductivity comparable to conventional
aerogel powders, iii) silylation is conducted under improved conditions, i.e., strong acidic conditions of pH 1-5, and as a result, all of the aerogel powders can be reacted with a silylating agent, thereby obtaining permanently hydrophobic aerogel, iv) the washing with a mixer makes the amount of removed
sodium ions uniform, thus it is suitable for
mass-production, and v) the method provides a relatively simplified procedure and the use of the silylating agent in a small amount enables low costs and
mass-production.