A method for uniformly coating powdery substrates by magnetron sputtering

DC magnetron sputtering was used to coat fine-grained powders, i.e. hollow glass microspheres (particle diameter approx. 2–70μm). To accomplish the exposure of the whole surface of each powder particle the powder was put into a rotating vessel which makes the particles tumble so that they are coated...

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Bibliographic Details
Published in:Surface & coatings technology 2013-12, Vol.236, p.353-360
Main Authors: Schmid, G.H.S., Eisenmenger-Sittner, C.
Format: Article
Language:English
Subjects:
Applied sciences
Clusters
Coating
Cross-disciplinary physics: materials science
rheology
Exact sciences and technology
Glass
Gravitation
Magnetron sputtering
Materials science
Metals. Metallurgy
Methods of deposition of films and coatings
film growth and epitaxy
Microspheres
Oxide coatings
Particle coating
Particle size distribution
Physics
Powder behaviour under vacuum conditions
Powder substrate
Production techniques
Surface treatment
Surface treatments
Thin films
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Summary:DC magnetron sputtering was used to coat fine-grained powders, i.e. hollow glass microspheres (particle diameter approx. 2–70μm). To accomplish the exposure of the whole surface of each powder particle the powder was put into a rotating vessel which makes the particles tumble so that they are coated uniformly. However, there are problems of sticking and cluster formation of the powder during the sputtering process, which prevent the complete coating of the particles. To resolve this issue a concussion mechanism had been used which now was completely redesigned for better upscalability. This newly designed mechanism is based on gravity and will be described in this work as well as its ability to deposit metal and oxide films on powder particles. For the better understanding of the trickling behaviour of the used particles (glass microspheres), experiments addressing this behaviour with regard to different particle size distributions have been carried out in vacuum with the concussion mechanism and without it. Furthermore the influence of the sputter beam is taken into account. It will be shown that it is possible to coat powders, which strongly tend to agglutinate in vacuum and even more under sputter conditions, by using the new concussion mechanism. •A mechanism to uniformly coat powdery substrates which tend to form clusters during the process was developed.•The trickling behaviour of small particles in vacuum regarding cluster formation depends on the particle size distribution.•The trickling behaviour of small particles in vacuum strongly depends on the pressure in the vacuum chamber.•The trickling behaviour depends on type of coating, i.e. pure metal film or oxide film.
ISSN:0257-8972
1879-3347
DOI:10.1016/j.surfcoat.2013.10.012