title: Quantitative image analysis for evaluating the abrasion resistance of nanoporous silica films on glass.
abstract: The abrasion resistance of coated glass surfaces is an important parameter for judging lifetime performance, but practical testing procedures remain overly simplistic and do often not allow for direct conclusions on real-world degradation. Here, we combine quantitative two-dimensional image analysis and mechanical abrasion into a facile tool for probing the abrasion resistance of anti-reflective (AR) coatings. We determine variations in the average coated area, during and after controlled abrasion. Through comparison with other experimental techniques, we show that this method provides a practical, rapid and versatile tool for the evaluation of the abrasion resistance of sol-gel-derived thin films on glass. The method yields informative data, which correlates with measurements of diffuse reflectance and is further supported by qualitative investigations through scanning electron microscopy. In particular, the method directly addresses degradation of coating performance, i.e., the gradual areal loss of antireflective functionality. As an exemplary subject, we studied the abrasion resistance of state-of-the-art nanoporous SiO2 thin films which were derived from 5-6 wt% aqueous solutions of potassium silicates, or from colloidal suspensions of SiO2 nanoparticles. It is shown how abrasion resistance is governed by coating density and film adhesion, defining the trade-off between optimal AR performance and acceptable mechanical performance.
authors.affiliation: Otto Schott Institute of Materials Research, University of Jena, Fraunhoferstrasse 6, D-07743 Jena, Germany.
authors.forename: Karsten H
authors.initials: KH
authors.lastname: Nielsen
authors.affiliation: Otto Schott Institute of Materials Research, University of Jena, Fraunhoferstrasse 6, D-07743 Jena, Germany.|Glafo-the Glass Research Institute, PG Vejdes väg 15, SE-351 96 Växjö, Sweden.
authors.forename: Stefan
authors.initials: S
authors.lastname: Karlsson
authors.affiliation: Otto Schott Institute of Materials Research, University of Jena, Fraunhoferstrasse 6, D-07743 Jena, Germany.
authors.forename: Rene
authors.initials: R
authors.lastname: Limbach
authors.affiliation: Otto Schott Institute of Materials Research, University of Jena, Fraunhoferstrasse 6, D-07743 Jena, Germany.|Center of Energy and Environmental Chemistry (CEEC), University of Jena, Max-Wien-Platz 1, D-07743 Jena, Germany.
authors.forename: Lothar
authors.initials: L
authors.lastname: Wondraczek