Porous Apatite Coating on Various Titanium Metallic Materials via Low Temperature Processing - Biomaterials Science and Engineering - page 95

successful attempt to form direct bonding between the Ti-based bulk metallic glass:
Ti 40 Zr 10 Cu 36 Pd 14 and HA bulk ceramics. The bonding could be obtained in only cases of the
BMG with the GIL. It was demonstrated that a series of hydrothermal techniques could be
very useful for bonding bulk ceramics and bulk metallic materials. The surface of the Ti-
based BMG can be made bioactive by coating bioactive ceramics like as hydroxyapatite
(HA) through the low temperature techniques in the range of RT and 150°C. In order to
form a growing integrated layer (GIL) on the BMG surface for improving adhesive
properties to HA ceramics, the BMG substrates needs to be treated in 5mol/L NaOH
solution at 90°C for 120 minutes by hydrothermal-electrochemical techniques.
Hydrothermal hot-pressing (HHP) treatment (150°C, 40MPa, 2hours) of the BMG and
powder mixture of CaHPO 4 ･ 2H 2 O and Ca(OH) 2 is appropriate way for bonding the BMG
and HA ceramics because of low operating temperature.
Additionally, it was demonstrated that HA ceramics could be coated to Ti rods at the
temperature as low as 135˚C by using the newly developed double capsule HHP method
(DC-HHP method). Thickness of the HA coating prepared was approximately 50m. No
chemical decomposition and no impurity was observed in the XRD analyses of the HA
coating prepared by DC-HHP method. The HA coating layer was shown to have a porous
microstructure with the density of 1.9 Mgm -3 and the relative density of approximately 60 %,
which is relatively close to those of human bone. In order to evaluate the adhesion
properties of the HA coatings on the Ti rods, pull-out tests were conducted. It was revealed
that the crack propagated not along the HA/Ti interface but within the HA ceramic layer in
the pull-out tests. The fracture property of the HA/Ti interface was suggested to be close to
or higher than that of the HA ceramics. The shear strength obtained from the pull-out tests
was in the range of 4.0-5.5 MPa. Finally, it was demonstrated that various hydrothermal
techniques were very useful and effective to hydroxyapatite ceramics coating on various Ti
metallic materials.
7. Acknowledgment
These works were partly supported by “Grant-in-Aid for Cooperative Research Project of
Nationwide Joint-Use Research Institutes on Development Base of Joining Technology for
New Metallic Glasses and Inorganic Materials” and “Grant-in-Aid for Young Scientists (B),
18760516” from the Ministry of Education, Science, Sports, and Culture of Japan.
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