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A. Eder, G. Schmid, L. Stöttinger, H. Mahr, C. Eisenmenger-Sittner:
"PVD coatings on arbitrary shaped granular materials, prediction and measurement of film properties";
Vortrag: 16th Joint Vacuum Conference (JVC-16), Slovenien, Portoroz; 06.06.2016 - 10.06.2016.

Granular materials attract increased attention in the field of material science and catalysis especially if coated with functional surface layers. With Physical Vapor Deposition (PVD) in general and DC magnetron sputtering in special, various layers ranging from metals via oxides and nitrides to multilayer structures can be deposited. To achieve homogeneous layers each particle surface has to be exposed equally to the vapor beam therefore continuous intermixing is necessary and in addition the agglomeration taking place while coating has to be suppressed effectively.
In this work different coating geometries and agglomeration suppression systems will be presented, based on a coating mechanism developed on the Vienna University of Technology [1,2]. It is capable to coat up to one liter of granular material with particle diameters ranging from 10 µm to 500 µm. Since the total surface area depends on the particle diameter the coating process duration with the given sputter device can take up to several hours. Therefore one can easily understand the need of estimating the film thickness on the particles in advance to keep the time effort as low as possible. A theoretical film thickness prediction model will be presented and verified on granulates of different size and shape. Special focus will be laid on assessing the film thickness and uniformity with different methods such as gravimetric measurements, optical and electron microscopy to verify the model. In addition a method to measure electrical conductivity on granular materials and coated granulates will be shown, and different influences e.g. of film thickness and particle diameter will be discussed.

[1] G. H. S. Schmid, C. Eisenmenger-Sittner, J. Hell, M. Horkel, M. Keding, H. Mahr, Surface & Coatings Technology 205(7) (2010) 1929.
[2] G. H. S. Schmid, C. Eisenmenger-Sittner, Surface & Coatings Technology 236 (2013) 353.