Porous Apatite Coating on Various Titanium Metallic Materials via Low Temperature Processing - Biomaterials Science and Engineering - page 77

hours. Ti disk treated with the hydrothermal NaOH solution is referred to as “HYDRO”
surface. After the above-mentioned treatments with NaOH solution, the Ti disks were
washed by deionized water, and then dried in air. The surface conditions of Ti disks are
summarized in Table 2.
In order to characterize the Ti surfaces, the surfaces were observed using scanning electron
microscopy (SEM: HITACHI FE-SEM S-4300, Japan) and were examined using FT-Raman
spectroscopy. The microprobe instrument used for the FT-Raman spectroscopy consisted of
a spectrometer (JOBIN YVON-HORIBA SPEX) fitted with a microscope (OLYMPUS-BX30,
Japan) which had spatial resolution on the sample close to 1m. The 632.8nm line of an He-
Ne laser was used as excitation, focused in a spot of approximately 1m diameter, with an
incident power of 2mW.

NaOH Treatment

873K
Heat

Type

Temp.(K) Time(h)

NORMAL - - -

IMMER 333 24 -

HEAT 333 24 1h

HYDRO 423 2 -

Table 2. Conditions of the surface modifications of the Ti disks.

In order to characterize the reaction products formed on the Ti surface products,
observation by SEM of the Ti surfaces treated with the NaOH solution were conducted for
the “NORMAL”, “IMMER”, “HEAT” and “HYDRO” specimens, respectively. Furthermore,
analytical results of Raman spectroscopy analysis were obtained of the “NORMAL”,
“IMMER”, “HEAT” and “HYDRO” specimens, respectively.
The surface morphology of the “NORMAL” specimen exhibits finishing lines in the nearly
horizontal direction, which were formed at the stage of surface polishing with the emery
paper. Raman spectra for the “NORMAL” specimen shows no distinct peak. The surface
morphology of the “IMMER” specimen has a very fine network structure (0.1m scale) with
finishing lines in the perpendicular direction. In the Raman spectra of the “IMMER”
specimen, the peaks of TiO 2 (both of anatase and rutile phase) and sodium titanate
(Na 2 Ti 5 O 11 ) could be detected. The surface morphology of the “HEAT” specimen has a
sponge-like structure and no finishing lines are visible on it. In the Raman spectra of the
“HEAT” specimen, the peaks of TiO 2 (only rutile phase) and sodium titanate (Na 2 Ti 5 O 11 )
could be detected. Indeed, it has been reported in the literature [Kim et al., 1997] that in a Ti
specimen treated with NaOH solution dehydration of the reaction layer took place by the