Aerogel materials AND (Aerogel Capture Medium)

Silica Aerogels:
With the primary mission of Stardust being to capture dust particles from Wild 2, the Aerogel capture material is one of the most important parts of the craft. Travelling at up to 12.8km/s, the particles possess huge kinetic energy. The aerogel material must strip this energy from the particles without allowing them to alter their composition by being heated or pulverized.

Aerogel is a silicon-based porous, sponge-like structure, with 99.8% of its volume being air space. Although made from silica, aerogel is less than 1/1000th the density of glass, making it one of the world's lightest solids. The large amounts of air in the aerogel are used to provide a cushioning effect, so when a particle hits the surface it buries itself in the aerogel, creating a long track up to 200 times the length of the particle. This allows the particle to slow down and prevents it from altering in physical or chemical composition. Back on Earth, scientists will remove the dust particles from the aerogel for extensive analysis.
Properties
Value                                                                               

Density                                                                             0.1 (0.3 - 0.05) g/cm3
Dielectric Constant                                                         1.14 (18 - 40 Ghz)
Surface Area, BET                                                          800 m2/g
Percent Solids                                                                 0.13 - 15%
Mean Pore Diameter                                                      ~20 nm
Primary Particle Diameter                                               2 - 5 nm
Index of Refraction                                                          1.0 - 1.05
Thermal Tolerance                                                          to 500°C
Poisson's Ratio                                                                0.2
Young's Modulus                                                             106 - 107 Nm2
Tensile Strength                                                              16 kPa
Fracture Toughness                                                       ~0.8 kPa*m1/2
Compressive Modulus                                                    0.3 MPa
Coefficient of Thermal Expansion (CTE)                    2 ppm/C° @20 - 80°C
Electrical Resistivity                                                       1015 ohm-cm
Thermal Conductivity in Air                                            0.016 W/m/°K
Thermal Conductivity in cuum                                       0.004 W/m/°K
Sound Velocity Through the Medium                          100 m/sec
Color                                                                                  translucent

HOW TO MAKE AEROGEL
SINGLE-STEP BASE: CATALYZED SILICA AEROGEL
This will produce an aerogel with a density of approx. 0.08 g/cm3. The gel time should be 60-
120 minutes, depending on temperature.
Mix two solutions:

Silica solution containing 50 mL of TEOS, 40 mL of ethanol

Catalyst solution containing 35 mL of ethanol, 70 mL of water, 0.275 mL of 30% aqueous ammonia, and 1.21 mL of 0.5 M ammonium fluoride.

Slowly add the catalyst solution to the silica solution with stirring.

Pour the mixture into an appropriate mold until gelation

TWO-STEP ACID-BASE: CATALYZED SILICA AEROGEL
This will produce an aerogel with a density of approx. 0.08 g/cm3. The gel time should be 30-
90 minutes, depending on temperature.

Mix two solutions:

Silica solution containing 50 mL of precondensed silica (Silbond H-5, or equivalent), 50mL of ethanol

Catalyst solution containing 35 mL of ethanol, 75 mL of water, and 0.35 mL of 30% aqueous ammonia.

Slowly add the catalyst solution to the silica solution with stirring.

Pour the mixture into an appropriate mold until gelation.