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Micropowder processing using low-pressure plasma technology

New, plasma based technologies have been developed for sub-micron sized powder engineering. The size and the structure of highly monodisperse particles are engineered by using an appropriate control and modification of the plasma chemistry during or after the particles growth process.

Particles in silane plasmas:
Complete understanding of the particle nucleation and growth process in silane plasmas has been obtained and shows that the smallest particles can be crystalline. Amorphous, hydrogenated silicon films can be deposited at higher rates and with better film quality if plasma conditions are chosen in a regime close to where dust formation takes place.

Nanomaterial synthesis:
The small crystallites which are present in silane discharges have been deposited on a surface. Subsequently, amorphous silicon was deposited on top of it. After annealing, micro-crystalline silicon films are resulting, of which the grain size can be influenced by the surface density of the nanocrystallites. If the nanocrystals are embedded in a transparent, conducting, matrix material, then photoluminescent films and electroluminescent devices can be produced. Solar cells produced with nanostructured silicon films show a stable efficiency of 10%; the traditional decrease of the efficiency by 50% in the first few days of light soaking does not occur.

Submicron scale new catalysts:
In a first step the possible use of silicon carbide and silicon nitride as support for metal catalysts has been tested, together with their performances for the methane total oxydation. Then stable, mono-disperse submicron ceramic powders have been grown. The powders can be coated with palladium by adding palladium vapour to the discharge. The palladium coating has the form of small, nm sized speckles on the surface of the carrier particle. For catalysis, this is about the ideal geometry.

Reported by

Eindhoven University of Technology
5600 MB Eindhoven
Netherlands
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