Globally Anisotropic High Porosity Silica Aerogels

Abstract

We discuss two methods by which high porosity silica aerogels can be engineered to exhibit global anisotropy. First, anisotropy can be introduced with axial strain. In addition, intrinsic anisotropy can result during growth and drying stages and, suitably controlled, it can be correlated with preferential radial shrinkage in cylindrical samples. We have performed small angle X-ray scattering (SAXS) to characterize these two types of anisotropy. We show that global anisotropy originating from either strain or shrinkage leads to optical birefringence and that optical cross-polarization studies are a useful characterization of the uniformity of the imposed global anisotropy.

arXiv comment18 pages, 14 figures, submitted to Journal of Non-Crystalline Solids

References in corpus (5)

• Pairing States of Superfluid 3He in Uniaxially Anisotropic Aerogel
• Small Angle Scattering by Fractal Aggregates: A Numerical Investigation of the Crossover Between the Fractal Regime and the Porod Regime
• Two new topologically ordered glass phases of smectics confined in anisotropic random media
• Helium-Three in Aerogel
• Acoustic Spectroscopy of Superfluid 3He in Aerogel

Cited by in corpus (21)

• New Chiral Phases of Superfluid 3He Stabilized by Anisotropic Silica Aerogel
• Phase diagram of superfluid 3He in "nematically ordered" aerogel
• The Superfluid Glass Phase of 3He-A
• Chiral Phases of Superfluid 3He in an Anisotropic Medium
• Identification of Superfluid Phases of 3He in Uniformly Isotropic 98.2% Aerogel
• Superfluid 3He in Aerogel
• Stability of superfluid 3He-B in compressed aerogel
• Anisotropic phases of superfluid 3He in compressed aerogel
• Orientation of the Angular Momentum in Superfluid 3He-A in a Stretched Aerogel
• Modification of the 3He Phase Diagram by Anisotropic Disorder
• Aerogel Waveplates
• Superfluid ${}^3$He in Planar Aerogel
• Planar and Nematic Aerogels: DLCA and Superfluid 3He
• Magnetic Susceptibility of Andreev Bound States in Superfluid ${}^3$He-B
• Ultrasound attenuation and a P-B-T phase diagram of superfluid 3He in 98% aerogel
• Anomalous Thermal Hall Effect in Chiral Phases of ${}^3$He-Aerogel
• Dissipation signatures of the normal and superfluid phases in torsion pendulum experiments with 3He in aerogel
• Orbital-Flop Transition of Angular Momentum in a Topological Superfluid
• Disorder Induced Anomalous Thermal Hall Effect in Chiral Phases of Superfluid ${}^3$He
• Linear theory of random textures of 3He-A in aerogel
• Superfluid Phase Stability of ${}^3$He in Axially Anisotropic Aerogel