Authors: Yasuo Yamada, Yun Cang Li, Jian Yu Xiong, Takumi Banno, Peter Hodgson, Cui E Wen
Abstract: Porous Ti-Mo alloy samples with different porosities from 52% to 72% were successfully fabricated by the space-holder sintering method. The pore size of the porous Ti-Mo alloy samples were ranged from 200 to 500 μm. The plateau stress and elastic modulus of the porous Ti-Mo alloy samples increases with the decreasing of the porosity. Moreover, an apatite coating on the Ti-Mo alloy after an alkali and heat treatment was obtained through soaking into a simulated body fluid (SBF). The porous Ti-Mo alloy provides promising potential for new implant materials with new bone tissue ingrowth ability, bioactivity and mechanical properties mimicking those of natural bone.
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Authors: Yasuo Yamada, Takumi Banno, Yun Cang Li, Cui E Wen
Abstract: In the present study, porous nickel foam samples with pore sizes of 20 μm and 150 μm and
porosities of 60 % and 70 % were fabricated by the space-holding sintering method via powder
metallurgy. Electron scanning microscopy (SEM) and Image-Pro Plus were used to characterise the
morphological features of the porous nickel foam samples. The anisotropic mechanical properties of
porous nickel foams were investigated by compressive testing loading in different directions, i.e. the
major pore axis and minor pore axis. Results indicated that the nominal stress of the nickel foam
samples increases with the decreasing of the porosity. Moreover, the foam sample exhibited
significantly higher nominal stress for loading in the direction of the major pore axis than loading in
direction of the minor pore axis. It is also noticeable that the nominal stress of the nickel foams
increases with the decreasing of the pore size. It seems that the deformation behaviour of the foams
with a pore size in the micron-order differs from those with a macro-porous structure.
277
Authors: Takumi Banno, Yun Cang Li, Cui E Wen, Yasuo Yamada
Abstract: Micro-porous nickel foams with an open cell structure were fabricated by the
space-holding sintering. The average pore size of the micro-porous nickel specimens ranged from 30
μm to 150 μm, and the porosity ranged from 60 % to 80 %. The porous characteristics of the nickel
specimens were observed using scanning electron microscopy (SEM). The mechanical properties
were studied using compressive tests. For comparison, macro-porous nickel foams prepared by the
chemical vapour deposition method with pore sizes of 800 μm and 1300 μm and porosity of 95 %
were also presented. Results indicated that the ratio value of 6 and higher for the specimen length to
cell size (L/d) is satisfying for obtaining stable compressive properties. The micro-porous nickel
specimens exhibited different deformation behaviour and dramatically increased mechanical
properties, compared to those of the macro-porous nickel specimens.
75
Authors: Jian Yu Xiong, Yun Cang Li, Yasuo Yamada, Peter Hodgson, Cui E Wen
Abstract: Ti-26 at.%Nb (hereafter Ti-26Nb) alloy foams were fabricated by space-holder sintering
process. The porous structures of the foams were characterized by scanning electron microscopy
(SEM). The mechanical properties of the Ti-26Nb foam samples were investigated using
compressive test. Results indicate that mechanical properties of Ti-26Nb foam samples are
influenced by foam porosity. The plateau stresses and elastic moduli of the foams under
compression decrease with the increase of their porosities. The plateau stresses and elastic moduli
are measured to be from 10~200 MPa and 0.4~5.0 GPa for the Ti-26Nb foam samples with
porosities ranged from 80~50 %, respectively.
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Authors: Masataka Hakamada, Yuuki Asao, Tetsumune Kuromura, Yasuo Yamada, Y. Chen, Hiromu Kusuda, Mamoru Mabuchi
Abstract: Spacer method is excellent technique of processing porous metals with well-controlled
pore characteristics such as porosity (up to 90%) and pore size (as small as several hundred
micrometers). Compressive properties of porous aluminum fabricated by the spacer method are
investigated. They were subjected to monotonic compression tests at room temperature, and showed
less fluctuated flow stress during their compressive deformation than conventional porous aluminum
alloy, reflecting their homogeneous pore characteristics. Also, shortening behavior of the porous
aluminum fabricated by the spacer method during cyclic compression was significantly differed from
that of conventional porous aluminum alloy. Therefore, it can be concluded that the homogeneity of
pore characteristics is responsible for compressive properties of porous metals. Monotonic
compression tests on porous copper specimens with various porosities, which were made by the
spacer method, were also conducted. The yield stress of the porous copper with high porosity (or low
relative density) depended on the relative density more strongly than that of the porous copper with
low porosity (or high relative density). It is presumed that porous metals with high porosity and ones
with low porosities have different deformation mechanisms.
415
Authors: Zhen Kai Xie, Yasuo Yamada, Takumi Banno
Abstract: Highly porous materials with a cellular structure are known to have many interesting
combinations of physical and mechanical properties, such as very low specific weight combined
with high thermal conductivity. However, when the pore size of the foam metal grows, the strength
maintenance is scarce because the array of the pore is not uniform. In the present work, micro
porous aluminum with porosities between 5% and 50% and pore sizes of 20~50 μm was produced
by applying the powder metallurgical technique, i.e. by sintering the aluminum metal powders and
PMMA powder mixture at 913 K. The effect of sintering temperature on the compressive properties
of porous aluminum was investigated. The effects of particle size and fraction of space holding
particle and metal powder on the porosity pore size and mechanical properties of porous sintered
specimens were mainly investigated. The pore size of porous aluminum can be controlled by
changing the PMMA powder diameter. The results show the fabrication of the micro porous
aluminum with middle porosity and high strength is possible.
2778
Authors: Yasuo Yamada, Takumi Banno, Zhen Kai Xie, Yun Cang Li, Cui E Wen
Abstract: In the present study, nickel foams with an open cell microporous structure were fabricated
by the so-called space-holding particle sintering method, which included the adding of a particulate
polymeric material (PMMA). The average pore size of the nickel foams approximated 10.5 μm; and
the porosity ranged from 70 % to 80 %. The porous characteristics of the nickel foams were observed
using scanning electron microscopy and the mechanical properties were evaluated using compressive
tests. For comparison, nickel foams with an open-cell macroporous structure (pore size
approximately 1.3 mm) were also presented. Results indicated that the nickel foams with a
microporous structure possess enhanced mechanical properties than those with a macroporous
structure.
1833
Authors: Cui E Wen, Yasuo Yamada, A. Nouri, Peter Hodgson
Abstract: Highly porous titanium and titanium alloys with an open cell structure are promising
implant materials due to their low elastic modulus, excellent bioactivity, biocompatibility and the
ability for bone regeneration. However, the mechanical strength of the porous titanium decreases
dramatically with increasing porosity, which is a prerequisite for the ingrowth of new bone tissues
and vascularization. In the present study, porous titanium with porosity gradients, i.e. solid core with
highly porous outer shell was successfully fabricated using a powder metallurgy approach.
Satisfactory mechanical properties derived from the solid core and osseointegration capacity derived
from the outer shell can be achieved simultaneously through the design of the porosity gradients of
the porous titanium. The outer shell of porous titanium exhibited a porous architecture very close to
that of natural bone, i.e. a porosity of 70% and pore size distribution in the range of 200 - 500 μm. The
peak stress and the elastic modulus of the porous titanium with a porosity gradient (an overall
porosity 63%) under compression were approximately 152 MPa and 4 GPa, respectively. These
properties are very close to those of natural bone. For comparison, porous titanium with a uniform
porosity of 63% was also prepared and characterised in the present study. The peak stress and the
elastic modulus were 109 MPa and 4 GPa, respectively. The topography of the porous titanium
affected the mechanical properties significantly.
720
Authors: Emilien Durif, Wen Yi Yan, Yasuo Yamada, Cui E Wen
629
Authors: Yasuo Yamada, Yun Cang Li, Takumi Banno, Zhen Kai Xie, Cui E Wen
Abstract: Micro-porous nickel (Ni) with an open cell structure was fabricated by a special powder
metallurgical process, which includes the adding of a space-holding material. The average pore size
of the micro-porous Ni samples approximated 30 μm and 150 μm, and the porosity ranged from 60 %
to 80 %. The porous characteristics of the Ni samples were observed using scanning electron
microscopy (SEM) and the mechanical properties were evaluated using compressive tests. For
comparison, porous Ni samples with a macro-porous structure prepared by both powder metallurgy
(pore size 800 μm) and the traditional chemical vapour deposition (CVD) method (pore size 1300
μm) were also presented. Results indicated that the porous Ni samples with a micro-porous structure
exhibited different deformation behaviour and dramatically increased mechanical properties,
compared to those of the macro-porous Ni samples.
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