Biomedical Engineering Reference
In-Depth Information
6.0
5.0
: Amorphous
: Amorphous + crystalline
: Crystalline
4.0
3.0
ACP
OAp
2.0
1.0
0
40
60
80
100
RF power,
P
(W)
200
400
600
800
1000
FIGURE 7.10
Effects of total gas pressure and RF power on phase of calcium phosphate coating prepared at room tempera-
gas pressure and RF power on phase of calcium phosphate coating prepared at room tempera-
pressure and RF power on phase of calcium phosphate coating prepared at room tempera-
of calcium phosphate coating prepared at room tempera-
calcium phosphate coating prepared at room tempera-
coating prepared at room tempera-
at room tempera-
ture without addition of oxygen gas.
oxygen gas. Figure 7.11 shows the effects of oxygen gas concentration in the sputtering gas
and RF power on the phase of coatings.
(15)
The crystallinity of calcium phosphate coating
depends on the degrees of RF power, oxygen gas concentration in the sputtering gas, and
total pressure. Sputtering is advantageous for low-temperature coating; however, calcium
phosphate coatings may be crystallized by an increase in substrate temperature
(31-33)
or by
heat treatment of ACP coatings.
(14,34,38)
Figure 7.12 shows the FTIR spectra of the oxyapatite
(Ca
10
(PO
4
)
6
O, OAp) coatings prepared by RF magnetron sputtering on mirror-polished CP
Ti substrates before and after heat treatment at 873 K for 7.2 ks in air. A hydroxyl stretching
band was observed at 3570 cm
−1
in the coating after the heat treatment. Hydroxyl group is
not usually introduced into the calcium phosphates by sputtering methods because sput-
tering is conducted under low total gas pressure conditions. The heat treatment in air or
60
60
(a)
(b)
50
50
OAp
OAp
40
40
ACP
+
OAp
ACP+OAp
30
30
20
20
10
10
ACP
ACP
0
0
50
75
100
125
150
50
75
100
125
150
RF power,
P
(W)
RF power,
P
(W)
FIGURE 7.11
Effects of oxygen gas concentration in sputtering gas (
C
O2
) and RF power on phase in coatings at total pressures
of (a) 0.5 Pa and (b) 5 Pa. (Deposition time = 18 ks.)
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