title: Structure of low-density nanoporous dielectrics revealed by low-vacuum electron microscopy and small-angle X-ray scattering.
abstract: 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.
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
authors.forename: Sergei O
authors.initials: SO
authors.lastname: Kucheyev
authors.forename: Milos
authors.initials: M
authors.lastname: Toth
authors.forename: Theodore F
authors.initials: TF
authors.lastname: Baumann
authors.forename: Alex V
authors.initials: AV
authors.lastname: Hamza
authors.forename: Jan
authors.initials: J
authors.lastname: Ilavsky
authors.forename: W Ralph
authors.initials: WR
authors.lastname: Knowles
authors.forename: Cheng K
authors.initials: CK
authors.lastname: Saw
authors.forename: Bradley L
authors.initials: BL
authors.lastname: Thiel
authors.forename: Vasiliki
authors.initials: V
authors.lastname: Tileli
authors.forename: Tony van
authors.initials: Tv
authors.lastname: Buuren
authors.forename: Y Morris
authors.initials: YM
authors.lastname: Wang
authors.forename: Trevor M
authors.initials: TM
authors.lastname: Willey