Introduction: One of the most remarkable findings from of the study of comet samples returned by the Stardust mission is the apparent scarcity of pre-solar grains. Unlike common expectations, the abundance of pre-solar grains in comet Wild 2 appears to be less than in primitive meteorites, micrometeorites and IDPs. The best measurements of the abundances of isotopically anomalous pre-solar grai...

This chapter focuses on one of the most studied aerogel materials, silica aerogels. It aims at presenting a brief overview of the elaboration steps (sol–gel synthesis, aging, and drying), the textural and chemical characteristics (aggregation features, porosity, and surface chemistry), the main physical properties (from thermal, mechanical, acoustical, and optical, to biological, medical, etc.)...

Optical transmission measurements were made on 98% porosity silica aerogel samples under various degrees of uniaxial strain. Uniaxially compressed aerogels exhibit large birefringence, proportional to the amount of compression, up to the 15% strain studied. The birefringence is mostly reversible and reproducible through multiple compression-decompression cycles. Our study demonstrates that unia...

Ethylene polymerization was carried out using Phillips chromium catalyst based on silica supports such as silica aerogel, SiO2 (Grace 643), and titanium modified SiO2 (G 643), and the results were compared with other catalysts based on SiO2 (Aldrich), SBA-15(Hex), SBA-15(Sp) and MCM-41. A combination of TGA, DSC, XRD, nitrogen adsorption, SEM, ICP, FTIR and other analyses were used to character...

Silica aerogels are highly porous 3D nanostructures and have exhibited excellent physio-chemical properties. Although silica aerogels have broad potential in many fields, the poor mechanical properties greatly limit further applications. In this study, we have applied the finite volume method (FVM) method to calculate the mechanical properties of silica aerogels with different geometric propert...

Introduction: Dust from comet Wild 2 was collected at a velocity of 6.1 km/s by the Stardust spacecraft using low-density silica aerogel [1]. During deceleration, dust particles fragmented, mixed with aerogel, and were thermally modified, often melted. In order to disentangle the properties of impacting cometary particles from those caused by the capture process, Wild 2 material from various lo...