Biomedical Engineering Reference
In-Depth Information
in pelleted drugs. In addition, ACPs are used in glass and pottery
production and as a raw material for production of some organic
phosphates. To get further details on ACPs, the readers are referred
to both special reviews [269, 290, 300, 301] and Chapter 2 of this
book.
Figure 1.7
A model of ACP structure. reprinted from ref. [289] with
permission.
1.3.9  CDHA (or Ca-def HA)
Calcium-deficient hydroxyapatite (Ca
(HPO
)
(PO
)
(OH)
(0
10−
x
4
x
4
6−
x
2−
x
<
< 1)) can be easily prepared by simultaneous addition of calcium-
and orthophosphate-containing solutions into boiling water followed
by boiling the suspension for several hours (an ageing stage). That is
why in literature it might be called as “precipitated HA (PHA)” [302,
303]. Besides, it might be prepared by hydrolysis of α-TCP [258-260].
Other preparation techniques of CDHA are known as well [304-
306]. During ageing, initially precipitated ACPs are restructured and
transformed into CDHA [307]. Therefore, there are many similarities
in the structure, properties and application between the precipitated
in alkaline solutions (pH > 8) ACPs and CDHA. recent data indicated
on presence of intermediate phases during further hydrolysis
of CDHA to a more stable HA-like phase [311]. CDHA crystals are
x
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