| Summary: | 碩士 === 中山醫學大學 === 口腔材料科學研究所 === 95 === Hydroxyapatite coating have been used as load-bearing implant
applications. The aim of this work is to deposit functionally graded HA/Ti
layers using plasma spray to improve the coating-substrate interface
properties. In addition to the Ti bondcoat and the top HA biolayer, the
alternating layers were created by means of changing the feeding rate and
input powder of Ti and HA. The stability of the graded coatings such as
corrosion resistance and fatigue, and bonding strength of the potential
graded coatings without and with post-deposition heat treatment were
examined. Results showed that surface chemistry and morphology of the
graded coatings were similar to those of monolithic HA coatings. The
bonding strength values of the as-sprayed graded coating were much
superior to those of monolithic HA coatings. The cyclic fatigue did have a
statistically significant effect on bond strength of monolithic HA coatings,
with a decrease of 23%. However, the graded coatings were able to survive 1
million cycles of loading in air without significantly reduced bond strength.
The in vitro electrochemical measurement results also indicated that the
graded coatings had a more beneficial and desired behavior than monolithic
HA coatings after fatigue. An appropriate heat treatment resulted in
recrystallization of amorphous calcium phosphate of as-sprayed coatings.
The enhancement of the resistance to corrosion took place after heat
treatment. Consequently, we concluded that the heat treatment at 600℃,
endowing with increased crystallinity and the reduced defects as well as
enhanced bond strength, may be a suitable post-deposition treatment method
to promote the characteristics of graded HA/Ti coatings.
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