Thermal Sprayed Bioceramic Coatings: Nanostructured Hydroxyapatite (HA) and HA-Based Composites - Biological and Biomedical Coatings: Processing and Characterization - page 183

Steam
generator

Jig for coating/splats
deposition

Steam
nozzle

Hot
plate

FIGURE 4.35
Facility setup for the HA coating/splat deposition with water steam treatment. (From Li et al., J. Therm. Spray
Technol. , 15, 610-616, 2006. With permission.)

Another attempt to avoid/reverse the decomposition of HA is to use steam treatment
during the spraying process (Li et al. JTST 2006). A steam generator was employed for the
steam generation using distilled water. A stable steam with 2 bar (~120°C) was provided
through two separate pipes into the jig (Figure 4.35) for the treatment during the spraying.
It is interesting to note that the improvement on the crystallinity by the steam treatment
is significant for these coatings (Figure 4.36) (Li et al. 2006). Water steam was provided

HA
β-TCP
TTCP
CaO
α-TCP

(c) Plasma-sprayed HA coating with
steam treatment and sub. heating

(b) Plasma-sprayed HA coating without
steam treatment but with sub. heating

(a) Plasma-sprayed HA coating
without steam treatment and sub. heating

27 28 29 30 31 32 33 34 35
2 θ (deg)

FIGURE 4.36
XRD patterns of the coatings made with the powders with a particle size of less than 25 μm showing a signifi-
cant effect of the steam treatment. (From Li et al., J. Therm. Spray Technol. , 15, 610-616, 2006. With permission.)