Characterization of double layer coatings on flat glass by neutron reflectivity and spectrophotometry

A. Menelle, M. Montecchi, E. Nichelatti, P. Polato

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Abstract

Coatings are currently deposited on flat glass to improve the luminous, solar and thermal properties of fenestration. An appropriate choice of coated glasses for use in building is mainly based on the knowledge of their light transmittance and solar factor as functions of the solar radiation incidence angle. The determination of these two parameters by the direct measurement of coated glass angular transmittance and reflectance is not straightforward. Alternatively, with the use of a suitable model one can extrapolate the light transmittance and solar factor from spectrophotometric transmittance and reflectance measurements at a (near) normal incidence of radiation on the glass and coating. An application of this alternative method requires a knowledge of the complex refractive index and thickness value of each layer. The complex refractive index and the thickness of a single layer coating can be estimated by means of a totally optical method. When one considers double layer coatings, further information, using at least one complementary technique (e.g. SIMS, RBS, etc) is needed to confirm the number of the layers and their composition. The thickness value(s) of the layer(s) can also be measured by means of neutron reflectivity which gives the density of the layer(s) and the roughness of the coating surface and of each interface too. In this investigation we consider single and double layer coatings on glass and compare the estimates of their homogeneity and thickness obtained by means of spectrophotometry and neutron reflectivity, respectively. Reasons for some discrepancies due to the different approaches and models adopted within the two techniques are also discussed.
Original languageEnglish
Pages (from-to)160 - 166
Number of pages7
JournalGlass Technology
Volume40
Issue number5
Publication statusPublished - Oct 1999

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All Science Journal Classification (ASJC) codes

  • Ceramics and Composites

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