Biomedical Engineering Reference
In-Depth Information
Figure 9.17
Fracture surfaces of
two specimens after tensile
adhesion test: (a) HA-coated disk
made of LT1CA30; (b) Ti-coated
disk made of Motis
(a)
(b)
. Substrate
disks (25.4 mm diameter, 6 mm
height) are on the left. The yellow
ring around the disk is the
excess of adhesive, which has
been used to join the coated
disks to the metal supports.
Table 9.4
Chemical Characterization of Plasma-Sprayed HA Coating for PEEK Optima
LT1 and
LT1CA30 Substrates
Phase Composition and Crystallinity
Metallic Elements Analysis
Mass fraction of crystalline HA
¼
55%e60%
Cd
0.10 mg/kg
<
Mass fraction of
b
-TCP
5%
Pb
0.40 mg/kg
<
<
CaO: not detected
Ca/P ratio
As
0.10 mg/kg
<
¼
1.67
Hg
0.10 mg/kg
<
Cu
<
0.55 mg/kg
W
<
0.10 mg/kg
The amount of copper (Cu) and tungsten (W) was determined since these elements are used as cathode and anode in the plasma torch.
Figure 9.18
Example of XRD spectrum
of an HA coating sprayed on PEEK
Optima
LT1. Compared to the spectra
of
Fig. 9.6
, the sprayed HA
demonstrates a lower crystallinity value
(intensity
peaks
are
smaller)
but
contains only minor amounts of
b
-TCP
and no traces of CaO.
larger for PEEK, because PEEK is much more
elastic than CFR-PEEK (
became uncoated in short time and had similar
fatigue limit than uncoated ones. For Ti-coated
PEEK specimens, titanium layers began to crack
but no detachments of coating from substrate were
observed. Fractured sections at failure still show Ti
coating surrounding PEEK. It is likely that cracks
E
z
4 GPa for PEEK
versus
E
z
20 GPa for CF-PEEK) and two
different phenomena were observed. Because of its
brittle nature, HA coatings cracked and detached
from substrates during fatigue cycling. Specimens
