The plasma technology for industrial processes
essentially uses two different types of plasma: the
first one, named ‘‘thermal plasma’’, is produced at
high pressure (>10 kpa) by means of direct or
alternating current (dc–ac) or radio frequency (rf)
or microwave sources. These devices, known as
torches, produce plasmas with electron and ion
temperatures of the order of 1–2 eV and with a
very low gas ionisation. Dc and ac torches can be
divided into transferred and non-transferred arc
and can be realised with power higher than some
MW. The produced plasma is mainly utilised to
destroy toxic-harmful substances or, as in the case
of the plasma spray, to produce coatings of thick
films. The second type of plasma, named cold or
non-equilibrium plasma, is characterised by the
electron temperature higher than the ion temperature; it is produced under vacuum conditions using
low power rf or microwave or dc sources. The
interactions of the plasma particles on the
materials produce the modification of the surfaces
in order to add different functional properties with
respect to the bulk material.
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