Biomedical Engineering Reference
In-Depth Information
because calcium phosphate coatings with high and low crystallinity are expected to have
high bonding strength and biocompatibility, respectively. Preparation of double-layered
HAp/OAp and OAp/ACP coatings was carried out. In the preparation of double-layered
HAp/OAp coating, an HAp film was first prepared on a substrate by heat treating an as-
sputtered OAp film in air at 873 K for 7.2 ks; this HAp film was considered to be the inner
layer, which was then covered with an as-sputtered OAp film. In the case of double-layered
OAp/ACP coating, inner-layer OAp and outer-layer ACP films were coated on the CP Ti
substrate under different sputtering conditions. The thickness of each layer was controlled
to be 0.5 μm, and the total thickness of the double-layered coatings was around 1 μm. The
XRD patterns and FTIR spectra of the HAp (inner) layer and HAp/OAp double layer are
demonstrated in Figure 7.37a and b, respectively. Figure 7.38 shows a cross section of the
double-layered HAp/OAp coating prepared on the mirror-polished CP Ti substrate. Both
layers of the coating were dense, uniform, and firmly in contact with each other.
TABLE 7.5
Phase, Structure, and Properties of Coatings Prepared by RF Magnetron Sputtering and Thermal
and Laser CVD
Phaseand
Structure
Processes
Parameters
Remarks
RF magnetron
sputtering
Heat treatment (>773 K)
In air
(water-vapor
containing
atmosphere)
HAp (crystalline)
Bioactive
In vacuum
OAp (crystalline)
Bioactive
RF power (as-sputtered)
High (>150 W)
OAp (low
crystalline)
Bioresorbable
Bioactive
Possible (002) orientation
Low (<150 W)
ACP (amorphous)
Highly bioresorbable
Bioactive
Thermal CVD
Temperature
Over 900 K
(Ca/P molar
ratio < 1)
HAp
Bioactive
Highly (002) orientation
α-TCP
Bioresorbable
Highly (510) orientation:
grainlike
Laser CVD
Temperature (laser
power: 30 W)
750-950 K
(Ca/P molar
ratio > 0.5)
HAp + TTCP
Bioactive
Non-orientation
800-900 K
(Ca/P molar
ratio = 0.5)
HAp
Bioactive
Non-orientation
850-950 K
(Ca/P molar
ratio < 0.4)
β-TCP + HAp
Bioresorbable
Non-orientation
Temperature (laser
power: 50 W)
800-900 K
(Ca/P molar
ratio > 0.4)
HAp
Bioactive
(300) orientation
950 K
(Ca/P molar
ratio < 0.4)
Bioresorbable
(220) orientation
β-TCP
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