Biomedical Engineering Reference
In-Depth Information
materials (Lin, Zhou, et al. 2011). Wang et al. (2011) reported a template-free
microwave-assisted hydrothermal method for the preparation of HAp hol-
low microspheres constructed by the self-assembly of nanosheets using
Ca(CH
3
COO)
2
, Na
2
HPO4, NaH
2
PO
4
, and sodium citrate in aqueous solution.
During the microwave-hydrothermal process, HAp nanosheets were formed
first, and then these HAp nanosheets were bound together toward microag-
gregates through the interaction between -COO groups of Na
3
Cit molecules
and Ca
2+
ions of the HAp nanosheets, thus an assembling process occurred.
The hard templates were also used to fabricate HAp hollow nanostructures.
Recently, we developed a facile strategy to delicately control the morphologies
of HAp materials from simple 0D morphologies to complicated 3D architec-
tures using hard precursors with similar structures, which provided a new
platform for HAp materials to be efficiently synthesized and manipulated
(Lin, Chang, and Zhu 2011). The HAp nanoparticles, nanowires, and hol-
low nanostructured microspheres (Figure 6.7) were facilely synthesized via
hydrothermal treatment of the similar structured precursors of calcium car-
bonate (CaCO
3
) nanoparticles, xonotlite [Ca
6
(Si
6
O
17
)(OH)
2
] nanowires, and hol-
low CaCO
3
microspheres in Na
3
PO
4
solutions, respectively. In addition, their
sizes could be easily regulated by changing the template conditions. Li and
Hashida (2006) further fabricated HAp-whisker ceramics with a hydrother-
mal hot-pressing (HHP) method using α-TCP as the precursors and in water
or ammonia water condition. When the additive was water, the obtained
HAp grains showed whisker-like and platelike features. When the addi-
tive was ammonia water, the resultants consisted of Hap whiskers only. The
results show that treating α-TCP with addition of ammonia water by the HHP
method is a useful method for
in situ
fabrication of HAp whisker ceramics.
The alloys have been widely used as the load-bearing implants in clini-
cal application fields. However, the bioinert of the alloys limits their wider
applications. The Ca-P-based bioceramic coating on alloys is one of the most
popular methods to improve the bioactivity of the alloys. Several methods
have been explored to deposit Ca-P coatings in order to enhance implant
(a)
(b)
(c)
200 nm
0.2 µm
1 µm
FIGURE 6.7
Morphologies of the HA nanoparticles, nanowires, and nanostructured hollow HAp micro-
spheres transformed from CaCO
3
nanoparticles, Ca
6
(Si
6
O
17
)(OH)
2
nanowires, and hollow
CaCO
3
microsphere precursor, respectively.
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