Thermal Plasma Processes and Nanomaterial Preparation
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Fig. 11 XRD spectra of AlN nanostructure prepared under three different arc currents of a 50 A,
b 100 A and c 150 A. The filled circles denote cubic phase AlN and the open circles denote hexagonal
phase of AlN
50 A arc current (indicated by (a) in the spectra below) had five diffraction peaks—all
matching with cubic phase of AlN. No other phases were detected. It is to be noted
that cubic phase of AlN is a metastable crystalline phase in the bulk form. In the
second sample (prepared under 100 A arc current—(b) in the spectra below) apart
from the five peaks of 50 A sample, small, additional peaks were detected and they
were found to be that of hexagonal crystal structure of AlN. The intensity of these
hexagonal structure increased with increase in arc current to 150 A.
Morphological analyses of these samples brought out the significant changes in
the nanostructure formation. The 50 A arc current samples consisted of nanowires
and nanocoils, whereas the 150 A arc current samples consisted of nanoparticles.