Abstract: In many biomedical devices such as catheters and diagnostic sensors, blood compatibility
is required. The best way to control this property is to prevent or drastically reduce the adsorption of
proteins. Poly(ethylene glycol) terminated amine at both terminals, NH2-PEG-NH2, is immobilized
on a commercially pure titanium, a 316L austenitic stainless steel, and a
cobalt-chromium-molybdenum alloy with immersion or electrodeposition. Chemical bonding states
at the interface and orientation of PEG molecules were characterized using X-ray photoelectron
spectroscopy, glow discharge optical emission spectroscopy, and Fourie-transformed infrared
spectrometer with a reflection absorption spectrometer. As a result, NH2-PEG-NH2 was immobilized
onto metal surface as a U-shape mainly with stable NHO bonding in electrodeposition. In the case of
electrodepostion, the concentration of active surface hydroxyl groups on surface oxide film played an
important role in the immobilization.
Abstract: The microstructure and mechanical properties of compacts produced from hot-pressing the
Co-29Cr-6Mo alloy powder, fabricated by gas atomization, were investigated in this study. The
average diameter of the alloy powder is 41 μm. Electron probe micro analysis revealed that the
concentration scattering of chromium and molybdenum is relatively small between the powders. The
compact hot-pressed at 1273 K in Ar with an applied pressure of 80 MPa possesses the relative
density of 97% and the fine grain (2.7 μm). The ultimate tensile strength of the compact is 1240 MPa,
which is comparable to that of the forged Co-29Cr-6Mo alloy.
Abstract: Phase stability of cation co-doped zirconia ceramics is examined. As the result, in
contrast to the result in small amount of single cation doped zirconia, phase stability of co-doped
zirconia ceramics can not be simply explained from ionic radius and valency of dopant or from the
change in axis ratio. We focus on oxygen vacancy concentration and binding energy between
oxygen vacancy and doped cation. By estimating phase stability from these factors, it is found that
concentration of oxygen vacancy and the binding energy between the dopant and the oxygen
vacancy are important factors for understanding the phase stability of zirconia ceramics.
Abstract: Effect of the sigma (σ) phase in Co-29Cr-6Mo alloy on corrosion and mechanical behavior has
been investigated. The area fraction of the σ phase varies depending on the aging time at 1023 K. The area
fraction of the sigma phase increases with increasing aging time and reaches 0.6 % after aging at 1023 K for
21.6 ks. Inductively coupled plasma atomic emission spectrometer (ICP-AES) analysis revealed the quantity
of released Co ion shows almost the same values regardless of different area fraction of the σ phase. In
addition, plastic elongation and 0.2% proof strength exhibit almost the same values, although the alloys have
different area fraction of the σ phase. These results suggest that a small amount of the σ phase (<0.6%) hardly
affect the corrosion and mechanical properties in the Co-29Cr-6Mo alloy.
Abstract: The effect of second phase particles on tetragonal to monoclinic (t-m) phase
transformation of zirconia is examined, which causes the degradation of zirconia in vivo. Silica is
selected as the second phase particles and dispersed 0.1 to 10mol% into 3mol% yttria stabilized
tetragonal zirconia polycrystal (3Y-TZP). As the result, phase transformation is promoted in all the
samples examined in comparison with 3Y-TZP. Non-dispersed specimen exhibits better phase
stability than that in silica doped one. Since the thermal expansion coefficient is smaller in order of
silica and zirconia, the residual stresses induced during cooling from the sintering temperature must
be the dominant factor to determine the phase stability in these materials.
Abstract: We started investigation of new Ti-based bulk metallic glass (BMG) alloys with higher
glass forming ability (GFA) for dental implants for medical market. These Ti-based BMG alloys do
not contain Ni, Al and Be elements which are well known to be harmful for human body. In
particular, cylindrical rod specimens of newly designed Ti-based BMG alloys with produced by
copper mold casting exhibit compressive strength of above 1800 MPa. Ti-based BMG alloys also
have high corrosion resistance that is passivated at the lower passive current densities of
approximately 10-2Am-2 in 1 mass% lactic acid, 10-2~10-3Am-2 in PBS (-) at 310K which are lower
than those of pure Titanium and Ti-6Al-4V alloy. These BMG alloys have high potentials to be
applied as biomaterials in various forms, such as melt spun ribbons and cylindrical rods.
Abstract: Microstructure and texture of Ti-Nb-Si based alloys, prepared by water quenching from
β-phase field, cold rolling and recrystallization heat treatment followed by water quenching, were
investigated in terms of optical microstructure and analysis of X-ray pole figure result. Optical
microstructure observation and X-ray diffraction analysis revealed that the microstructure of
as-quenched sample appeared to mixture appearance consisting of mostly bcc-structured β phase and
small amount of orthorhombic-structured α″ phase. After cold rolling elongated structure parallel to
the rolling direction was observed, and equiaxed structure with the average grain size of about
20~30μm was developed for the sample after recrystallization heat treatment. In as-cold rolled sample
we have found well-developed α-fiber texture components which are frequently observed in
bcc-structured metals and alloys. In recrystallized sample, rotated cube texture component was
weakly detected. The variation of elastic modulus values was interpreted in terms of changes in
texture components depending on thermomechanical processing.
Abstract: Most structural optimization methods are based on mathematical algorithms that require
substantial gradient information. The selection of the starting values is also important to ensure that
the algorithm converges to the global optimum. This paper describes a new structural configuration
optimization method based on the harmony search (HS) meta-heuristic algorithm. The HS algorithm
does not require initial values and uses a random search instead of a gradient search, so derivative
information is unnecessary. A benchmark truss example is presented to demonstrate the effectiveness
and robustness of the proposed approach compared to other optimization methods. Results reveal that
the proposed approach is capable of solving configuration optimization problems, and may yield
better solutions than those obtained using earlier methods.
Abstract: In this work, triethyl phosphate (TEP) was used to bioactivating titanium. Titanium plates
grafted with TEP were immersed in a two times concentrated simulated body fluid (2SBF) to
investigate deposition of hydoxyapatite (HA) on the surface. A phosphate buffer solution (PBS) with
bovine serum albumin (BSA) was used to evaluate adsorption of protein on the grafted titanium
surface. The morphology, component and structure of samples were examined by scanning electronic
microscopy, attenuated total reflection Fourier transform infrared spectroscopy and X-ray diffraction
respectively. The concentration change of BSA in adsorption test was examined with the
ultraviolet-visible absorption spectra (UV). The analyses showed that TEP grafted onto the titanium
surface. In 2SBF, calcium and phosphate ions deposited spontaneously onto the grafted titanium
surface and formed a HA coating with a network-like microporous structure after being immersed for
3 days. The coating consisted of HA particles with 180-265nm in thickness and 72-85nm in width.
The diameter of the micropores was about 200nm. The HA coating appeared better uniformity than
that on the modified titanium using phosphoric acid. BSA rapidly adsorbed onto the grafted titanium
surface at first half an hour and then the adsorption quantity almost kept constant. These results
indicate that TEP grafting is an effective approach to modify bioactivity of titanium.
Abstract: A silicon-containing apatite layer was prepared on a metallic titanium substrate coated
with a silica layer. The silica layer on a titanium substrate was derived from water glass through
heat-treatment at 300 °C for 2 hr and subsequent acid-treatment using 0.1 N-HCl at 50 °C for 2 hr.
The silica layer was homogeneously coated with nano-sized vaterite powders (~ 0.5 μm in diameter).
The vaterite coating was achieved by utilizing the interaction of surface potentials between the
positively charged vaterite and the negatively charged silica layer. After soaking the sample in
simulated body fluid at 37 °C for 3 days, hydroxyapatite (HA) formed on the surface of the
silica-coated titanium. The HA layer was found to include a trace amount of releasable silicon, which
may enhance the osteoblast proliferation.