Biomedical Engineering Reference
In-Depth Information
25
Amorphous
α-TCP
β-TCP
TP
CaO
20
15
10
5
0
20
400
500
600
700
800
Temperature (
º
C)
FIGURE 6.8
Phase content (in wt.%) of amorphous and calcium phosphate phases changed with vacuum heating
temperatures.
the atmospheric heat-treated HACs (AH series), the partial water vapor pressure of atmo-
spheric moisture can recover and promote the reconstitution of TCP, TP, and ACP into
crystalline HA. The residual compound with a phase content of about 5 wt.% for 600°C to
800°C atmospheric heat-treated HACs is thought of as CaO [119]. Referring to the previous
presentation in Section 6.2.2, the Rietveld analysis method with QPA is another effective
way to determine the phase content of the plasma-sprayed and heat-treated HACs. Since
the heat during plasma spraying and crystallization processes is difficult to ascertain,
the quantity of ACP is not easy to determine in relation to the heat liberated. Therefore, the
Rietveld analysis method with QPA provides a powerful way to completely quantify the
associated amorphous component and crystalline phases within a multiphase system for
any thermally treated material [60,108,109]. Figure 6.9 illustrates the variation in phase
composition of plasma-sprayed powders with changing a series of plate power, which is
determined by the QPA technique via Rietveld method [60]. It can be seen that the phase
content of crystalline HA, ACP, and other impurity phases, including α-TCP, β-TCP, TP,
Composition vs. plate power
Composition vs. plate power
Amorp.
HA
Alpha-TCP
Beta-TCP
TTCP
CaO
Amorp.
HA
Alpha-TCP
Beta-TCP
TTCP
CaO
70
70
(a)
(b)
60
60
50
50
40
40
30
30
20
20
10
10
0
10
0
12
14
16
18
20
22
10
12
14
16
18
20
22
Plate power (kW)
Plate power (kW)
FIGURE 6.9
Phase composition of plasma-sprayed powders determined by quantitative phase analysis (QPA) technique via
Rietveld method of (a) 7 wt.% and (b) 14 wt.% HA suspension feedstock for changing a series of plate power.
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