Biomedical Engineering Reference
In-Depth Information
(d-1)
(d-2)
20 kV ×1000 10 µm 16 44 7Pa
20 kV ×1000 10 µm 16 45 7Pa
(e-1)
(e-2)
20 kV ×1000 10 µm 16 45 7Pa
20 kV ×1000 10 µm 16 45 7Pa
FIGURE 4.21 (Continued)
the thermal-sprayed coatings have significant effect on their mechanical properties (e.g.,
Young's modulus) (Sevostianov et al. 2000), fracture toughness (Callus et al. 1999), and so
forth. The random existence of the pores within a coating was believed to be one of the
main factors responsible for the anisotropy in mechanical performances of the coating
(Sevostianov et al. 2000). To date, increasing studies on formation mechanism of splats
have been conducted (Pasandideh-Fard et al. 2002; Sampath et al. 2001; Gougeon et al. 2001).
Additionally, numerous constructive experimental investigations on the splat formation,
mainly on clarification of relationships between splat morphology and spray parameters
including substrate state (roughness, temperature, etc.) (Sampath et al. 2001; Montavon et
al. 1995), have shed insight into this topic. Meanwhile, useful attempts have been made in
recent years toward theoretical understanding of the impact behavior of the individual
splats during thermal spray (Pasandideh-Fard et al. 2002; Gougeon et al. 2001; Bertagnolli
et al. 1997) even though the assumptions for the simulations more or less restricted their
valid applications.
Due to the phase transformation of HA during coating formation to tricalcium phos-
phate (TCP), tetracalcium phosphate (TTCP), CaO, or even amorphous calcium phosphate
(ACP) (Gross et al. 1998c; McPherson et al. 1995; Li et al. 2000), full dissolution of the subse-
quent splat is possible through controlling the dissolution/precipitation procedures dur-
ing the test (Li et al. 2004c).
Small pores are observed from the surface of the splats prepared by both HVOF and
plasma-spray techniques. Typical views under SEM suggest the size of the pores to be 1 to
Search WWH ::
Custom Search