Biomedical Engineering Reference
In-Depth Information
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FIGURE 7.12
Deposition of calcium phosphate coating by precipitation. SEM images: (Aa, Ab) before deposition; (Ba, Bb) mon-
etite (CaHPO
4
) coating formed by precipitation; (Ca, Cb) apatite coating obtained by treatment of B with NaOH
causing transformation of monetite to nanocrystals of apatite that followed the outline of the original monetite
crystals. Scale: 10
μ
m for Aa, Ab, Ba, Bb, Ca, Cb; 50
μ
m for Ba, Ca. X-ray diffraction profiles: (Ac) untreated Ti
alloy surface; (Bc) monetite coating; (Cc) apatite coating after transformation of monetite. The monetite coating
was thicker than the apatite coating as deduced from the comparative intensities of the Ti diffraction peaks
between Bc and Cc. (From Rohanizadeh et al.,
J. Biomed. Mater. Res
., 72A, 428-438, 2005. With permission.)
An experimental precipitation method is by treatment of the Ti alloy with acidic cal-
cium phosphate solution resulting in the form of an acidic calcium phosphate, monetite,
CaHPO
4
, which can be transformed to apatite, if desired, by reacting with NaOH (Fig-
ure 7.12) (Rohanizadeh et al., 2005; Rohanizadeh and LeGeros, 2006). If a more reactive
coating is desired, the transformation to apatite step can be eliminated. Formation of car-
bonate apatite after immersion in simulated body fluid (SBF) of the Ti alloy surface pre-
treated with NaOH (with and without subsequent heating) is another biomimetic method
of depositing calcium phosphate (Lakstein et al., 2009; Nishiguchi et al., 2001).
Calcium phosphate coating using modulated electrochemical deposition method
. An alternative
to plasma-spray method is the electrochemical method of depositing apatite and other cal-
cium phosphates, such as brushite or dicalcium phosphate dihydrate (DCPD), octacalcium
