Optical properties of monolithic and granular SiO{sub 2}-aerogels

Book · Sat Dec 31 04:00:00 EST 1994

OSTI ID:194859

Beck, A; Linsmeier, J; Koerner, W; Scheller, H; Fricke, J ^[1]

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1. Univ. Wuerzburg (Germany). Physikalisches Inst.

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{sub dd} as well as the directional-hemispherical transmission t{sub dh} are presented for 20 mm thick aerogel specimens. For optimized monolithic aerogels the authors obtained solar averaged values of {bar t}{sub dh,sol} = 91(+1,{minus}4)% and {bar t}{sub dd,vis} = (84{+-}2)% in the solar and visible spectral region, respectively. The investigated granular aerogels show a visual transmission of {bar t}{sub dh,vis} = (58{+-}4)% for water glass as a precursor and of {bar t}{sub dh,vis} = (78{+-}4)% for tetramethoxysilane. In order to correlate the structural build-up of the SiO{sub 2}-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.

• OSTI ID: 194859
• Report Number(s): CONF-9404167--; ISBN 0-8194-1564-2
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
36 MATERIALS SCIENCE
DAYLIGHTING
EXPERIMENTAL DATA
FOAMS
GRANULAR MATERIALS
OPTICAL PROPERTIES
SILICON OXIDES
SOLAR COLLECTORS
THERMAL INSULATION
USES
WINDOWS