We present herein a characterization of a standard method used at the High Energy Accelerator Research Organization (KEK) to produce hydrophobic silica aerogels and expand this method to obtain a wide range of refractive index (n = 1.006−1.14). We describe in detail the entire production process and explain the methods used to measure the characteristic parameters of aerogels, namely the refractive index, transmittance, and density. We use a small-angle X-ray scattering (SAXS) technique to relate the transparency to the fine structure of aerogels.
An innovative way of enhancing the coupling‐out efficiency in light‐emitting diodes (LEDs) is revealed. A very low‐refractive‐index silica aerogel is placed between the substrate and the emissive layer to obtain a perfect decoupling of the propagation modes within the emissive layer from the glass substrate. The Figure shows an ultrathin emissive layer on a glass substrate with (left) and without (right) an aerogel spacer layer under UV irradiation (see also cover).
We have succeeded in developing hydrophobic silica aerogels over a wide range
of densities (i.e. refractive indices). A pinhole drying method was invented to
make possible producing highly transparent aerogels with entirely new region of
refractive indices of 1.06-1.26. Obtained aerogels are more transparent than
conventional ones, and the refractive index is well controlled in the pinhole
drying process. A test beam experiment was carried out in order to evaluate the
performance of the pinhole-dried aerogels as a Cherenkov radiator. A clear
Cherenkov ring was successfully observed by a ring imaging Cherenkov counter.
We also developed monolithic and hydrophobic aerogels with a density of 0.01
g/cm^3 (a low refractive index of 1.0026) as a cosmic dust capturer for the
first time. Consequently, aerogels with any refractive indices between 1.0026
and 1.26 can be produced freely.Comment: Proceedings of 1st International Conference on Technology and
Instrumentation in Particle Physics (TIPP 2009) in Nucl. Instr. and Meth. A,
3 pages, 6 figure
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