Structure of low-density nanoporous dielectrics revealed by low-vacuum electron microscopy and small-angle X-ray scattering.
Aerogels (AGs) are ultralow-density nanoporous solids that have numerous potential applications. However, as most AGs are strong insulators with poor mechanical properties, direct studies of the complex nanoporous structure of AGs by methods such as atomic force and conventional scanning electron microscopy (SEM) have not proven feasible. Here, we use low-vacuum SEM to image directly the ligament and pore size and shape distributions of representative AGs over a wide range of length scales (approximately 100-105 nm). The structural information obtained is used for unambiguous, real-space interpretation of small-angle X-ray scattering curves for these complex nanoporous systems. Low-vacuum SEM permits imaging of both cross-sections and skin layers of AG monoliths. Images of skin layers reveal the presence of microcracks, which alter the properties of cast monolithic AGs.
Kucheyev
Sergei O
SO
Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
Toth
Milos
M
Baumann
Theodore F
TF
Hamza
Alex V
AV
Ilavsky
Jan
J
Knowles
W Ralph
WR
Saw
Cheng K
CK
Thiel
Bradley L
BL
Tileli
Vasiliki
V
Buuren
Tony van
Tv
Wang
Y Morris
YM
Willey
Trevor M
TM