Biomedical Engineering Reference
In-Depth Information
Amongst the different methods to process functionally-graded materials
(FGM), electrophoretic deposition (EPD) is explored here to process complex-
shaped FGM hip prosthesis components. During EPD, particles having acquired
an electric charge in the liquid in which they are suspended are forced to move
toward one of the electrodes by applying an electric fi eld and forming a coherent
deposit on it. The deposit takes the shape imposed by this electrode. Hence, after
drying and removal from the electrode, a shaped green ceramic body is obtained.
Firing this green body results in the ceramic component.
10.4 ELECTROPHORETIC DEPOSITION AS A SHAPING TECHNIQUE
FOR FGM BIOMATERIALS
In order to produce a FGM by conventional powder processing, a green body of
powders containing the desired phase gradient is fi rst fabricated. After formation,
this green body is densifi ed by sintering. A wide range of powder processes can be
used to obtain a gradient, including common powder metallurgy and colloidal
(wet) processes [Anné et al., 2006a]. Whereas only discrete layers can be made by
dry powder processing, continuous gradients can be made by colloidal processes.
Among the different colloidal processing techniques, electrophoretic deposition
is very promising because it is a fairly rapid, low-cost process for the fabrication
of ceramic coatings, monoliths, composites, laminates, and functionally graded
materials varying in thickness from a few nanometers to centimeters [Cordingley
et al., 2003].
Electrophoretic deposition (EPD) is a two-step process (Figure 10.3). In a
fi rst step, particles having acquired an electric charge in the liquid in which they
are suspended, are forced to move towards one of the electrodes by applying an
electric fi eld to the suspension (electrophoresis). In a second step (deposition),
the particles collect at one of the electrodes and form a coherent deposit on it.
+
-
V
-
-
+
-
+
-
-
-
-
-
+
Charged particle
Positive ion
Negative ion
+
-
+
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Electrode
Suspension
Electrode
Figure 10.3.
Schematic of the EPD process. [Anné, 2005a].
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