A method for producing gradient density aerogel |
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Authors: | Steven M Jones |
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Institution: | (1) Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA |
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Abstract: | The Stardust Mission used gradient density aerogel as the hypervelocity particle capture medium in both the cometary and interstellar
collection grids. The development and production of these materials was performed exclusively for this mission as a means
of improving the efficiency of the collection process. The density of an aerogel can be dictated by controlling the ratio
of the condensable silica to that of the solvent used in the aerogel precursor solution. A density gradient was established
by gradually mixing the precursor solution for low density aerogel into the precursor solution for high density aerogel and
continuously pumping the resultant mixture into a mold. The aerogel designed for the capture of cometary particles had a density
gradient ranging from 10 mg/cm3 to 50 mg/cm3 across the 3 cm profile of each block. Whereas those designed for the capture of interstellar grains had a gradient ranging
from 10 mg/cm3 to 20 mg/cm3 across a 1 cm profile. Since various physical properties, e.g., refractive index, thermal conductivity, acoustic impedance,
dielectric constant, are correlated to the density, they also vary with the density. This method of establishing a density
gradient in aerogel can be used to produce other material gradients, e.g., gradient oxide, gradient dopant, in any sol–gel
based material. |
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Keywords: | Aerogel Gradient density Sol– gel |
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