Biomedical Engineering Reference
In-Depth Information
(a)
(b)
10 µm
10 µm
FIGURE 7.26
Surface morphology of (290)- and (400)-oriented β-TCP (290). Orientation of (a) is more prominent than that of
(b).
coatings by laser CVD is about 1000 µm/h at most; that is, 10 to 100 times faster than that
of thermal CVD and more than 1000 times of sputtering.
PerformanceofBioceramicCoatingPreparedbyVaporDeposition
In this section, the properties of bioceramic coatings prepared by vapor deposition are
discussed with a focus on bonding strength to substrates, apatite formation in simulated
body fluid (SBF), and biological response.
Bonding Strength
High bonding strength of bioceramic coatings to substrates is essential for implant appli-
cations because of the possible delayed failures associated with inflammatory diseases.
Figure 7.27 shows the values of bonding strength of ACP and OAp coatings with a thick-
ness of 0.5 μm, which were prepared using RF magnetron sputtering, to mirror-polished
CP Ti and blasted Ti-6Al-4V alloy substrates. The values were calculated from the maxi-
mum load in a pulling test using aluminum studs. It appears that the bonding strength of
the coatings were 60 to 70 MPa independent of the crystallinity of the coatings and the sur-
face roughness of the substrates. Table 7.3 summarizes the bonding strengths between Ti
substrates and calcium phosphate coatings prepared by PVD (12,18,33,35-38) as compared with
those by plasma spraying. (60-64) The bonding strengths listed in Table 7.3 were obtained by
pulling tests using aluminum studs attached to the surface of the coating on Ti substrates
using epoxy glue. The bonding strength exceeded 60 MPa for the calcium phosphate coat-
ings prepared by RF magnetron sputtering and IBD, which is much higher than that pre-
pared by plasma spraying. The higher bonding strength in coatings prepared by PVD is
perhaps caused by (1) the thin thickness of the coatings as compared with that prepared
 
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