NANOMECHANICAL PROPERTY ANALYSIS OF SILICA AEROGEL

Aerogels (AGs) are open-cell nanofoams. AGs are lightweight and possess high thermal and acoustic insulation properties. Due to their ~ 90% porosity, AGs are very brittle and fragile, which inhibits its use for load-bearing applications. For this reason an area of open research is the study and improvement of the mechanical properties of aerogels without altering their unique properties. Due to the extreme brittleness and low applied stress that AGs can support, direct mechanical measurements of AGs are challenging. To date very few experiments have been carried out to characterize the mechanical properties of aerogels; in particular at small contact dimensions and ultralow loads (nN-?N). In this paper, silica aerogel has been studied by nanoindentation using a diamond Berkovich indenter. We characterize the elasticity, stiffness, and hardness of the material as a function of contact depth (<= 500 nm) at ultralow loads. The modulus and hardness are shown to change with depth with moduli and hardness ranging from 15-23 MPa and 3.5-6.8 MPa, respectively.