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C. Balasubramanian
also a good photocatalytic agent under UV light—helping in stain removal as well as
antibacterial. There are three crystallographic forms of titania, viz. rutile (tetragonal),
anatase (tetragonal; however, anatase has a steeper pyramid with a larger angle over
the polar edge as compared to rutile phase) and brookite (orthorhombic).
Thermal plasma has proven to be an ideal process for production of these nanomaterials. Titanium metal block/pellets kept in graphite crucible are used as anode
and tungsten or titanium was used as cathode. A current of 80–110 A was applied
(depending on the anode dimensions) between the electrodes in an air ambient. The
titanium metal vapours close to the plasma zone reacted with oxygen in the air to
form titanium dioxide followed by nucleation and growth of clusters. The chamber wall temperature was maintained at 25 °C by way of water circulation between
the two layers of the chamber wall. The process was run for duration of 5–10 min
and then the plasma extinguished. After allowing a few hours time duration for the
fine particles to settle down, the chamber was opened and the product removed for
analysis.
High-resolution transmission electron microscopy was used to analyse the morphological features and X-ray diffraction technique to study the crystalline features.
Figure 5 shows the TEM images.
The image on the left clearly shows the particles to be spherical in shape with
fairly uniform size of ~40 nm. The image on the right is a magnified image of a single
particle of size ~25 nm. One can clearly observe the highly crystalline structure from
the well-defined atomic planes.
The formation of TiO 2 and its crystalline phase was confirmed by X-ray diffraction technique, as shown in Fig. 6. Both anatase and rutile phases are seen to be
present in the sample. Multiphase formation is quite common in plasma processes.
Fig. 5 Titanium dioxide nanoparticles, (a) larger area indicating a typical size range of 30–40 nm
(scale bar: 20 nm) and (b) highly crystalline small particle of size ~25 nm (scale bar: 2 nm)
C. Balasubramanian
also a good photocatalytic agent under UV light—helping in stain removal as well as
antibacterial. There are three crystallographic forms of titania, viz. rutile (tetragonal),
anatase (tetragonal; however, anatase has a steeper pyramid with a larger angle over
the polar edge as compared to rutile phase) and brookite (orthorhombic).
Thermal plasma has proven to be an ideal process for production of these nanomaterials. Titanium metal block/pellets kept in graphite crucible are used as anode
and tungsten or titanium was used as cathode. A current of 80–110 A was applied
(depending on the anode dimensions) between the electrodes in an air ambient. The
titanium metal vapours close to the plasma zone reacted with oxygen in the air to
form titanium dioxide followed by nucleation and growth of clusters. The chamber wall temperature was maintained at 25 °C by way of water circulation between
the two layers of the chamber wall. The process was run for duration of 5–10 min
and then the plasma extinguished. After allowing a few hours time duration for the
fine particles to settle down, the chamber was opened and the product removed for
analysis.
High-resolution transmission electron microscopy was used to analyse the morphological features and X-ray diffraction technique to study the crystalline features.
Figure 5 shows the TEM images.
The image on the left clearly shows the particles to be spherical in shape with
fairly uniform size of ~40 nm. The image on the right is a magnified image of a single
particle of size ~25 nm. One can clearly observe the highly crystalline structure from
the well-defined atomic planes.
The formation of TiO 2 and its crystalline phase was confirmed by X-ray diffraction technique, as shown in Fig. 6. Both anatase and rutile phases are seen to be
present in the sample. Multiphase formation is quite common in plasma processes.
Fig. 5 Titanium dioxide nanoparticles, (a) larger area indicating a typical size range of 30–40 nm
(scale bar: 20 nm) and (b) highly crystalline small particle of size ~25 nm (scale bar: 2 nm)