Optical properties of monolithic and granular SiO2-aerogels

A. Beck; J. Linsmeier; W. Koerner; H. Scheller; Jochen Fricke

doi:10.1117/12.185404

9 September 1994 Optical properties of monolithic and granular SiO₂ aerogels

A. Beck, J. Linsmeier, W. Koerner, H. Scheller, Jochen Fricke

Proceedings Volume 2255, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XIII; (1994) https://doi.org/10.1117/12.185404
Event: Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XIII, 1994, Freiburg, Germany

Abstract

The optical and thermal properties of aerogels play an important role for their application in transparent insulation (TI) or daylighting systems. In this paper the directional-directional transmission t_dd as well as the directional-hemispherical transmission t_dh are presented for 20 mm thick aerogel specimens. For optimized monolithic aerogels we obtained solar averaged values of ^-t_dh,sol equals (91 +/- 1/4)% and ^-t_dh,vis equals (84 +/- 2)% in the solar and visible spectral region, respectively. The investigated granular aerogels show a visual transmission of ^-t_dh,vis equals (58 +/- 4)% for waterglass as a precursor and of ^-t_dh,vis equals (78 +/- 4)% for tetramethoxysilane. In order to correlate the structural build-up of the SiO₂-network of the aerogels with their light scattering properties angular-dependent light and X-ray scattering measurements are performed. To characterize the visual image transmission the modulation transfer function (MTF) was measured for 20 mm thick monolithic layers. In order to explain the measured data a Monte Carlo based simulation model was developed. The analysis yields that the MTF is mainly effected by surface scattering.

Citation Download Citation

A. Beck, J. Linsmeier, W. Koerner, H. Scheller, and Jochen Fricke "Optical properties of monolithic and granular SiO₂ aerogels", Proc. SPIE 2255, Optical Materials Technology for Energy Efficiency and Solar Energy Conversion XIII, (9 September 1994); https://doi.org/10.1117/12.185404

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