| AVS 60th International Symposium and Exhibition | |
| Advanced Surface Engineering | Thursday Sessions |
| Session SE+NS+TF-ThA |
| Session: | Nanostructured Thin Films and Coatings |
| Presenter: | C. Kunze, University of Paderborn, Germany |
| Authors: | C. Kunze, University of Paderborn, Germany S. Waschke, University of Paderborn, Germany M. Baben, RWTH Aachen University, Germany D. Music, RWTH Aachen University, Germany J.M. Schneider, RWTH Aachen University, Germany G. Grundmeier, University of Paderborn, Germany |
| Correspondent: | Click to Email |
Plasma deposited coatings of TiAlN and TiAlNO are a promising approach to decrease wear and friction of tools within polymer processing such as extrusion and injection molding. Up to now the mechanisms defining the interaction between the protective coating and the polymer melt are not well understood.
An experimental approach is presented that analyzes the surface chemistry of TiAlN and TiAlNO films as a function of film composition and deposition parameters by means of X-ray photoelectron spectroscopy (XPS). The investigated coatings were synthesized via high power pulsed magnetron sputtering (HPPMS) under varying plasma compositions.
It could be shown that the surface composition of TiAlNO films significantly differs from the integral film composition due to a passivation of the surface near region upon contact with ambient atmosphere or residual gas immediately after deposition[1]. These effects have to be taken into account considering adhesion phenomena and interaction with the polymer melt.
The formation of the passive layer on TiAlN was monitored in-situ by time resolved XPS spectroscopy with a time resolution of several seconds. It could be shown that the kinetics of the oxidation reaction is quite fast and occurs within a few minutes even at low oxygen partial pressures of less than 1·10-8 mbar. The experimentally observed preferential oxidation reaction of a single element (Ti vs. Al) is compared to DFT based simulations.
The interaction of the TiAlNO passive layer with polymers (polypropylene and polycarbonate) was studied towards a technical application within plastics processing. Besides the passive layer a native contamination film consisting of low-weight (hydro-)carbon species adsorbed from the environmental atmosphere has to be discussed when considering the adhesion to the polymer phase.
To investigate the role of the surface contaminations, an approach using a model adsorbate which carries a marker element (such as P or F) was chosen. TiAlNO coatings with model adsorbate surface layers were brought into contact with the polymer melt. The interface between the coating and the polymer was cleaved under high vacuum conditions to avoid re-contamination from the atmosphere. It could be shown that the adsorbate layer remains on the TiAlNO coating even during contact with the polymer melt. Thus the native contamination layer also has to be carefully considered for the interaction and adhesion to the polymer.
[1] C. Gnoth, C. Kunze, M. Hans, M. to Baben, J. Emmerlich, J. M. Schneider, G. Grundmeier, Surface chemistry of TiAlN and TiAlNO coatings deposited by means of high power pulsed magnetron sputtering. J. Phys. D., 46, 2013.