▎ 摘　　要

NOVELTY - Preparing very low density nano-grade insulating aerogel comprises e.g. (i) preparing silicon source, then adding silicon source into absolute ethanol, and ultrasonic stirring uniformly to obtain alcohol sol, (ii) continuously stirring the alcohol sol, adding graphene into the alcohol gel, ad continuously stirring for 35 minutes to obtain modified alcohol sol, (iii) adding the modified alcohol sol into container filled with absolute ethanol, replacing to remove redundant water, (iv) adding the replaced alcohol sol solution into aging device and aging to obtain modified alcohol gel, and (v) placing the reinforcing fiber in a mold, subsequently introducing into obtained modified alcohol gel, supercritical drying under pressure of 20 MPa at 50 degrees C for 3 hours, then reliving pressure at 50 degrees C at a constant speed for 3 hours until the pressure reaches to 6 MPa, supercritical drying until the pressure returns to normal atmospheric pressure, and removing mold to obtain final product. USE - The method is useful for preparing very low density nano-grade insulating aerogel. ADVANTAGE - The aerogel: has very high porosity, very low density, excellent heat preservation performance; and uses reinforcing fiber which improves insulating intensity and flexibility of aerogel. DETAILED DESCRIPTION - Preparing very low density nano-grade insulating aerogel comprises (i) preparing silicon source, then adding silicon source into absolute ethanol, and ultrasonic stirring uniformly at 40-42 degrees C to obtain alcohol sol, where the molar ratio of silicon source to absolute ethanol is 0.04-0.07:1, (ii) continuously stirring the alcohol sol, adding graphene into the alcohol gel, ad continuously stirring for 35 minutes to obtain modified alcohol sol, (iii) adding the modified alcohol sol into container filled with absolute ethanol, replacing to remove redundant water for 8-9 hours, and repeating for 2-3 times until complete replacement, (iv) adding the replaced alcohol sol solution into aging device and aging to obtain modified alcohol gel, and (v) placing the reinforcing fiber in a mold, subsequently introducing into obtained modified alcohol gel, supercritical drying under pressure of 20 MPa at 50 degrees C for 3 hours, then reliving pressure at 50 degrees C at a constant speed for 3 hours until the pressure reaches to 6 MPa, supercritical drying until the pressure returns to normal atmospheric pressure, and removing mold to obtain final product.