Biomedical Engineering Reference
In-Depth Information
Nanocrystalline HA powder was synthesized at a low calcination
temperature of 750°C by the citric acid sol-gel combustion method
[404]. The attractive features of this method were to synthesize
materials with a high purity, a better homogeneity, and a high surface
area in a single step [404, 408]. An array of highly ordered HA nano-
sized tubes of uniform length and diameter was synthesized by sol-gel
auto-combustion method with porous anodic aluminum oxide template
[322]. Varma et al
synthesized nano-sized HA by polymeric combustion
method and self-propagating combustion synthesis by using novel
body fluid solutions [409]. Furthermore, nano-sized particles of both
FA and β-TCP might be synthesized by a simultaneous combustion of
calcium carboxylate and tributylphosphate based precursors in a flame
spray reactor [410]. Both a flame-based technique [411] and a spray
drying approach [106, 412] might be applied as well. Furthermore,
crystalline and phase pure nano-sized HA and CDHA were synthesized
in a continuous hydrothermal flow system using supercritical water at
t < 400°C and 24 MPa pressure [298].
Nanopowders of the stoichiometric HA of ~20 nm particle size
were synthesized by hydrolysis of a mixture of DCPD and CaCO
.
3
performed with 2.5 M aqueous solution of NaOH at 75°C for 1
h. The only product synthesized was nanocrystalline HA and its
crystallinity was improved with increasing annealing temperature
[356]. Similar results were obtained in other studies [357, 358].
Furthermore, Xu et al
used radio frequency plasma spray process
to synthesize nanodimensional HA powders with particle size
in the range of 10-100 nm [340]. Kuriakose et al
.
synthesized
nanocrystalline HA of size ~1.3 nm that was thermally stable until
1200°C [323]. Nanocrystalline plate-shaped particles of HA were
directly precipitated at ambient temperature and pH ~7.4 from dilute
aqueous solutions of calcium chloride and sodium orthophosphate.
The direct precipitation of nano-sized HA was achieved by submitting
the aqueous suspension to microwave irradiation immediately after
mixing [402]. A simple and easy approach for synthesizing thermally
stable nanostructured stoichiometric HA powder under invariant
pH conditions of 7.5, known as the NanoCaP process, was developed.
Under these conditions, the synthesized HA not only remained in
the nanostructured state but also did not exhibit any compositional
fluctuations that were observed in conventional approaches for
synthesizing HA [12]. Other preparation techniques of nano-sized
.
Search WWH ::
Custom Search