Biomedical Engineering Reference
In-Depth Information
Vacuum evaporation
Ion plating
Sputtering
Pulsed laser deposition
(Laser ablation)
Physical vapor
deposition (PVD)
Vapor
deposition
ermal CVD
Plasma CVD
Laser CVD
Chemical vapor
deposition (CVD)
FIGURE 7.3
Typical methods of PVD and CVD.
thin films does not change significantly from that of the source materials. PVD methods
such as vacuum deposition, sputtering, ion plating, pulsed laser deposition (PLD), and
ion beam deposition (IBD) have been applied to bioceramic coating of metallic biomateri-
als. Figure 7.5 shows schematics of vacuum deposition, sputtering, ion plating, and PLD
methods. In CVD, on the other hand, thin films or powders via chemical reactions such as
thermal decomposition or hydrogen reduction of source gases are synthesized, and there-
fore the composition of films are often significantly different from that of the source gases.
A schematic of the CVD method is depicted in Figure 7.6. Since CVD has generally more
process parameters (deposition temperature, total pressure, partial pressure of each source
gas, etc.) than PVD, the morphology and crystallographic orientation of coatings are more
widely controllable. Therefore, pure, dense, and highly oriented films can be synthesized
by CVD. In order to activate the chemical reactions, various energy sources such as heat,
plasma, and laser are utilized in CVD.
Tables 7.1 and 7.2 summarize studies
(12-23)
of bioceramic coatings on Ti by PVD and
CVD, respectively. Some characteristics and advantages of each PVD and CVD methods
are included in these tables. As the target or source materials for PVD, hydroxyapatite
(Ca
10
(PO
4
)
6
(OH)
2
, HAp)
(12-14,18,19)
, β-type tricalcium phosphate (Ca
3
P
2
O
8
, β-TCP),
(15)
HAp +
β-TCP
(17)
, and CaO-P
2
O
5
glasses
(24)
have been fabricated by sintering or spraying. The thick-
ness of bioceramic coatings prepared by PVD is usually less than several micrometers.
Regarding CVD, on the other hand, few studies on bioceramic coating have been reported.
Thermal
(22,25-27)
and laser
(23,28)
CVD methods have been applied to the bioceramic coatings
Ion
Ion
To substrate
Substrate
Target
Substrate
Deposition
(Precipitation)
0.1-1
Sputtering
Ion implantation
1-100
10
3
-10
5
Low
High
Kinetic energy of particles,
E
(eV)
FIGURE 7.4
Interaction between particles and the solid surface.
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