Research Centre Germany
Low temperature plasmas have become a useful tool for surface treatment in many applications. For particle processing it
offers a unique possibility of confinement, control and tailoring of their properties. The aim is to tailor particle properties
for specific purposes like deposition, etching, cleaning or surface activation. The treatment of nanoparticles and nanofibres
is a high challenge because of their agglomeration. For a homogeneous treatment of powder special fluidization methods
are necessary. The selection of methods depends on the pressure range, the particle size and the specific material. In
addition, the fluidization behavior is influenced by interactions between the walls in the plasma zone of the apparatus
and the particles.
Carbon nanofibres (vapour grown carbon fibres, VGCF) can be used as filler in polymers to adjust certain thermal,
electrical and mechanical properties. Fibres can be incorporated in polymeric or metallic materials. To ensure these
properties a good bonding between fibres and polymer is necessary. Therefore, the surface of the graphitic carbon fibres
has to be activated or coated.
For the reinforcement of polymeric materials the carbon nano fibres has to be activated by plasma treatment. At this
treatment functional groups like hydroxyl, carbonyl and carboxy groups are covalent bonded on the surface and the
surface energy is enhanced. To achieve a homogeneous treatment of VGCF in large enough quantities to prepare polymerfibre
test samples appropriate techniques have to be developed. The plasma treatment was carried out in three reactors
in which the fibres were agitated by different means: mechanical vibration (vibrating bed reactor), a gas stream (fluidised
bed reactor) and a rotating drum, respectively. The surface energy and surface composition of the fibres were
characterised before and after the treatment by contact angle measurement, XPS (X-ray photoelectron spectroscopy) and
water contact angle measurement.
Carbon fibres have been used as reinforcement in various metallic matrices. Many applications have been identified for
example: heat sink materials, electric contact materials or lightweight materials. To improve the interface between carbon
surface and metal matrix fibres have to be coated. The coating process was carried out by magnetron sputter deposition.
The fibres were investigated by TEM (transmission electron microscopy) and SEM (scanning electron microscopy).
