| Summary: | 碩士 === 國立成功大學 === 材料科學(工程)研究所 === 81 === HA-coated Ti6Al4V has recently been used as a bone subs-
titute in orthopedic and dental application, because of its
favorable bioactivity and mechanical properties. Plasma spray-
ing technique appears to be the most favorable one in term of
mechanical properties, biocorrosion resistance, coating-subs-
trate bonding strength, and process feasibility. Studies in the
literature have shown that the bioactivity of calcium
phosphate bioactive glass (BG) is higher than that of HA. In
an attempt to increase the bioactivity of HA-coated Ti6Al4V
and enhance the bonding strength between coating and
substrate, in the present study, HA/BG composite (including 75
HA/25BG, 50HA/50BG and 25HA/75BG in weight) are applied onto
Ti6Al4V using a plasma spraying technique. Microstructure and
phase changes of the composite coatings after plasma spraying
are studied. The coating-substrate bond- ing strength is
evaluated using an Instron following ASTM C633 method. Since
accidentally observing a degradationin the mea- sured
bonding strength of plasma-sprayed HA on Ti6Al4V when the
coated specimens were exposed in humid air for a few days, we
have carried out a systematic study of environmental effect
(particularly humidity and storage time) on bonding strength.
In vitro behavior of these coatings were also studied by im-
mersion in Hank''s physiological solution. The results indicate
that surface roughness of HA/BG com- posite coatings are much
larger than HA coating. The HA/BG composite coating offers
sufficient bonding strength and are less affected by air
humidity. When immersed in Hank''s solu- tion, HA/BG coatings
are more active than pure HA or BG coat- ing. After immersed
about 10 days, a Ca, P-rich apatite layer forms on all
coatings (BG, HA, or HA/BG). All of them, 75HA/25 BG coating
performs the best. Since, implants bonded with bone directly is
by means of the apatite structure. We except that HA/BG
composite coating will behave well in vivo.
|
|---|
