Thermal Plasma Processes and Nanomaterial Preparation
77
Plasma forming gas
Arc
Plasma plume
(a)
(b)
Fig. 1 Schematic of a (a) typical non-transferred plasma arc torch (b) with powder injection into
the plasma plume
plume end) resulting in evaporation, and as it moves down axially, with decreasing
temperature, forms clusters of nanostructures.
In the transferred arc plasma (as shown in Fig. 2) type, the job (material of interest)
is placed in a crucible, and positive potential of the electric power supply is connected
to it. A refractory material (typically tungsten or graphite) is used as a cathode. To
strike an arc and create plasma between the electrodes, two options are available: (i)
the electrodes are brought closer and made to touch each other, thereby “shorting”
the circuit, and once the current starts flowing, the electrodes are moved apart slowly
Fig. 2 Schematic of
transferred arc plasma
77
Plasma forming gas
Arc
Plasma plume
(a)
(b)
Fig. 1 Schematic of a (a) typical non-transferred plasma arc torch (b) with powder injection into
the plasma plume
plume end) resulting in evaporation, and as it moves down axially, with decreasing
temperature, forms clusters of nanostructures.
In the transferred arc plasma (as shown in Fig. 2) type, the job (material of interest)
is placed in a crucible, and positive potential of the electric power supply is connected
to it. A refractory material (typically tungsten or graphite) is used as a cathode. To
strike an arc and create plasma between the electrodes, two options are available: (i)
the electrodes are brought closer and made to touch each other, thereby “shorting”
the circuit, and once the current starts flowing, the electrodes are moved apart slowly
Fig. 2 Schematic of
transferred arc plasma