Thermal Plasma Processes and Nanomaterial Preparation
79
In the first type, the material of interest is directly placed on an anode crucible
(could be made of graphite or any electrically conducting material). The heat content
of the plasma plume would melt and evaporate it. The vapourised material, as it moves
away from the plasma zone, would nucleate and form clusters of atoms/molecules.
In the second type, micron-sized powder of the material of interest is fed into
plasma plume either at the gap between the two electrodes or where the plume exits
the anode region. The introduced powder, due to the high heat content, will evaporate
or melt and as it moves down will form small clusters of atoms/molecules.
3.2 Transferred Arc Plasma Process for Synthesis
of Nanostructures
In transferred arc plasma process (as shown in Fig. 2), an electric arc is struck between
the cathode and anode wherein the anode itself will melt and evaporate due to the
plasma created between the two electrodes. The element of the material of interest is
placed in a crucible (graphite or any conducting material), and positive potential of
the electric power supply is connected to it. A refractory material (typically tungsten
or graphite) is used as a cathode.
Once the arc is struck and plasma created, the high enthalpy from the plasma
would evaporate the anode material turning it into charged particles within the plasma
column which, as it moves away from the plasma zone, becomes neutral atoms
followed by reaction with the surrounding gas ambient and then onto nucleation and
growth of clusters, finally to condensation. A schematic of the arc plasma synthesis
of nanoparticles is shown in Fig. 3.
Fig. 3 Schematic of the nanomaterial generation using a transferred arc plasma process
79
In the first type, the material of interest is directly placed on an anode crucible
(could be made of graphite or any electrically conducting material). The heat content
of the plasma plume would melt and evaporate it. The vapourised material, as it moves
away from the plasma zone, would nucleate and form clusters of atoms/molecules.
In the second type, micron-sized powder of the material of interest is fed into
plasma plume either at the gap between the two electrodes or where the plume exits
the anode region. The introduced powder, due to the high heat content, will evaporate
or melt and as it moves down will form small clusters of atoms/molecules.
3.2 Transferred Arc Plasma Process for Synthesis
of Nanostructures
In transferred arc plasma process (as shown in Fig. 2), an electric arc is struck between
the cathode and anode wherein the anode itself will melt and evaporate due to the
plasma created between the two electrodes. The element of the material of interest is
placed in a crucible (graphite or any conducting material), and positive potential of
the electric power supply is connected to it. A refractory material (typically tungsten
or graphite) is used as a cathode.
Once the arc is struck and plasma created, the high enthalpy from the plasma
would evaporate the anode material turning it into charged particles within the plasma
column which, as it moves away from the plasma zone, becomes neutral atoms
followed by reaction with the surrounding gas ambient and then onto nucleation and
growth of clusters, finally to condensation. A schematic of the arc plasma synthesis
of nanoparticles is shown in Fig. 3.
Fig. 3 Schematic of the nanomaterial generation using a transferred arc plasma process