Public Thesis defense - IMMC

Kinetic, compositional and morphological aspects of etching and frosting of glass substrates by Nicolas PIRET

Pour l’obtention du grade de Docteur en sciences de l’ingénieur et technologie

Mat glass is a widely present material in our everyday life, especially for its particular aesthetics or for its anti-glare feature highly wanted for screens. This mat or anti-glare aspect is caused by the formation of microstructures on the glass surface that can therefore scatter the light. Industrially, such kind of modified glass surfaces are produced by wet acid-etching technique, also called glass frosting. The glass surface is exposed to a frosting solution that generally contains hydrofluoric acid and texturing salts. Depending on several key parameters, the morphology of microstructures can vary a lot, and so does the resulting glass aspect. The glass frosting process is a delicate combination/competition of two phenomena: the dissolution of glass by the hydrofluoric acid, and the gradual appearance of a texturing crust on the glass surface caused by the precipitation of glass dissolution products. Even if the dissolution of glass is rather largely described in the scientific literature, the whole frosting process is less documented.

In order to understand more fundamentally the glass frosting process with a prospect of a more rational mastering of this technique, this thesis approaches three main themes related to the glass frosting : the kinetics of glass etching and frosting, the composition of crusts appearing on glass surface during the glass frosting (investigated by ICP-OES and XRD analyses), and the direct microscopic observation of the time evolution of crystals composing the frosting crust. These different themes are investigated for different glass compositions and different etching or frosting solutions in order to observe the influence of these factors.

For the glass etching and frosting kinetics study, a kinetic dissolution/precipitation model from the literature used to fit our experimental data is extensively commented and some new kinetics parameters and crust parameters are proposed.

Image series of the direct microscopic observation of the time evolution of crystals composing the frosting crust are analyzed by both a more conventional particle analysis technique and by a more original image analysis technique based on the study of Fourier transform of these images.

Jury members :

• Prof. Joris Proost (UCLouvain), supervisor
• Prof. Renaud Ronsse (UCLouvain), chairperson
• Prof. Pascal Jacques (UCLouvain), secretary
• Prof. Juray De Wilde (UCLouvain)
• Prof. Olivier Deparis (UNamur, Belgium)
• Dr. Eugénie Peyroux (AGC Glass, Europe, Belgium)
• Dr. Nadia Pellerin (Univ. Orléans, France)

Pay attention :

The public defense of Nicolas Piret scheduled for Friday 03 July at 04:15 p.m will indeed take place in the form of a video conference Teams.

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