23.5.2 Structure of Novel Hydroxyapatites
The powder morphology was observed by using transmission electron microscope
(TEM, Hitachi, 7500) at an accelerating voltage of 80–100 kV with a resolution of
0.2 nm. The powder samples were subjected to ultrasonication in ethanol and a drop
of this suspension was dropped on a 300 mesh carbon-coated copper grid.
As-synthesized stoichiometric and ionic substituted HA powder particles were
nanodimensional (<40 nm). These powders exhibited either flakelike or rodlike
morphology as shown in TEM micrographs (Fig. 23.2). The length parameter of the
powder particles decreased on ionic substitution of HA, though the extent of
decrease varied depending on the type of substitution and crystal size of substituting
element (Table 23.3).
TEM micrographs of novel HA nanopowders after heat treatment showed two
modifications. One modification is the increase in particle size as compared with the
corresponding as-synthesized HA nanopowders, and the other is its morphology
(Fig. 23.3). The particle morphology changed from flakelike or rodlike to a regular
hexagonal shape on heat treatment from 800 C to 1200 C, and also there was a
notable increase in the size of particles.
XRD analysis of as-synthesized and heat-treated nanodimensional powders was
carried out to determine their structure using Philips X’Pert 1710 X-ray diffractom-
eter using CuKα radiation, λ = 1.54 Å, step size 0.017, time per step 20.03 s,
between the range of 20–80 degree, and speed of scan 0.005/s. The phases,
crystallinity, lattice parameters, and mean crystallite size were determined from
XRD spectra. The relative proportions of various phases were determined on the
basis of peak intensity variation by means of external standard method. The XRD
spectra
were
compared
with
JCPDS
files:
JCPDS
Card
No.
9-432
for
(Flake-like)
(Rod-like)
Fig. 23.2 TEM micrographs of two morphologies of as-synthesized novel hydroxyapatites
23
Unleashing Potential of Bone Mimicking Nanodimensional Hydroxyapatites and. . .
431