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Shigeru Katsuyama, Kouji Akai, Hiroaki Anno, Kazuhiro Hasezaki, Kaoru ...
2012 Volume 53 Issue 7 Pages
1207
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
JOURNAL
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Yun Lu, Katsuhiro Sagara, Liang Hao, Ziwu Ji, Hiroyuki Yoshida
2012 Volume 53 Issue 7 Pages
1208-1211
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
JOURNAL
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To obtain non-stoichiometric titanium dioxide, TiO
2 powder was sintered in a graphite die by spark plasma sintering (SPS). The microstructure and the crystal type of the compacts were examined. Thermoelectric properties of the compacts were measured and discussed. The results revealed that TiO
2 could be easy to be reduced in the graphite die by SPS to obtain non-stoichiometric titanium dioxide, TiO
2−x with uniform composition distribution. Electrical resistivity of the compacts decreased with increase of SPS temperature. Seebeck coefficient also decreased with increase of SPS temperature, but kept large absolute values over 300 µV·K
−1. Therefore, the compacts fabricated by SPS showed relatively high thermoelectric performance. The power factor reached 5 × 10
−5 W m
−1 K
−2 at 523 K.
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Theerayuth Plirdpring, Ken Kurosaki, Atsuko Kosuga, Manabu Ishimaru, A ...
2012 Volume 53 Issue 7 Pages
1212-1215
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: April 18, 2012
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The Cu–Ga–Te ternary compounds: Cu
3Ga
5Te
9, Cu
2Ga
4Te
7, CuGa
3Te
5, CuGa
5Te
8, and CuGaTe
2 have zinc-blende or chalcopyrite structure. The compounds except for CuGaTe
2 contain vacancies in the cation site due to the valence mismatch between cation and anion, and the vacancy concentration is different between these compounds. Here we investigated the effect of the amount of vacancies on the thermoelectric (TE) properties of the Cu–Ga–Te ternary compounds. At room temperature, the presence of vacancies reduced the Hall mobility (μ
H) and the lattice thermal conductivity (κ
lat), showing that the vacancies scattered both carriers and phonons. It was found that the decreasing rate of the μ
H was larger than that of the κ
lat. Therefore, the presence of vacancies degraded the TE performance of the Cu–Ga–Te ternary compounds. In other words, CuGaTe
2 without vacancies would show the best TE figure of merit. The room temperature
ZT values for Cu
3Ga
5Te
9, Cu
2Ga
4Te
7, CuGa
3Te
5, CuGa
5Te
8, and CuGaTe
2 were 2.0 × 10
−2, 2.4 × 10
−2, 8.9 × 10
−3, 1.3 × 10
−2, and 5.6 × 10
−3, respectively.
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Do-young Jung, Ken Kurosaki, Yuji Ohishi, Hiroaki Muta, Shinsuke Yaman ...
2012 Volume 53 Issue 7 Pages
1216-1219
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: June 20, 2012
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Ag
2Te is well-known as a silver ion conductor. In this compound, a phase transition occurs at around 420 K and silver ions jump to interstitial sites repeatedly at the point of starting the phase transition. We consider that the active movement of silver ions would have influence on the scatterings of both charge carriers and heat carrying phonons in Ag
2Te. In order to evaluate the effect of the silver ion conduction on the thermoelectric properties of Ag
2Te, the Seebeck coefficient, electrical resistivity, thermal conductivity and Hall coefficient of polycrystalline bulk samples of Ag
2Te were examined in the temperature range from room temperature to 650 K. The electrical resistivity and the Seebeck coefficient dramatically changed at around 420 K due to the change of the carrier concentration before and after the phase transition. However, the carrier mobility and the lattice thermal conductivity showed no remarkable change at around the phase transition temperature. These results imply that the thermoelectric transport properties of Ag
2Te were affected by the change of the crystal structure rather than the presence or absence of the movement of silver ions.
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H. Anno, K. Okita, K. Koga, S. Harima, T. Nakabayashi, M. Hokazono, K. ...
2012 Volume 53 Issue 7 Pages
1220-1225
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: June 20, 2012
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The effect of the substitution of a rare-earth element for a guest element on the electronic and thermoelectric properties is investigated for clathrates with the nominal composition Ba
8−xEu
xCu
ySi
46−y (
x = 0, 1, 2;
y = 4, 5, 6). The Seebeck coefficient and the electrical conductivity of the rare-earth-substituted Ba
8−xEu
xCu
ySi
46−y samples are consistent with
n-type conduction and metal-like behavior. The Hall carrier mobility of Ba
8−xEu
xCu
6Si
40 at room temperature decreases with increasing Eu substitution. The conduction band effective mass of rare-earth-substituted Ba
8−xEu
xCu
6Si
40 (
x = 1, 2) is experimentally estimated to be larger than that of Ba
8Cu
6Si
40. On the basis of
ab initio electronic structure calculations for Ba
6Eu
2Cu
6Si
40 and Ba
8Cu
6Si
40, it is deduced that the conduction band edges of Ba
8Cu
6Si
40 are modified by the substitution of Eu for the guest atom Ba, resulting in an increase in the density-of-states effective mass, which is consistent with the experimental result.
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Akihiro Ishida, Yutaro Sugiyama, Hirokazu Tatsuoka, Tomoki Ariga, Miki ...
2012 Volume 53 Issue 7 Pages
1226-1233
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: May 09, 2012
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Seebeck effect, Peltier effect, Thomson effect, electronic thermal conductivity, Hall effect, and Nernst effect are described on the basis of electronic conduction theory, taking account of effective mass anisotropy, nonparabolicity in
E–
k relation, and temperature dependent band gap. It is shown that the temperature dependence of the band gap does not modify the basic equations for the Seebeck coefficient, thermal conductivity, and Nernst coefficient. In narrow gap semiconductors, existence of minority carriers significantly enhances the electronic thermal conductivity, owing to the multiple carrier transport known as bipolar diffusion. Calibration coefficient γ for the Hall effect (
RH = - γ /
en) is increased by nonparabolicity in the
E–
k relation. Nernst coefficient gives useful information on scattering properties of the materials.
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Gonzalo Gonzalez, Chedly Braham, Jean L. Lebrun, Yvan Chastel, Wilfrid ...
2012 Volume 53 Issue 7 Pages
1234-1239
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
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The influence of Sn on the microstructure, microstrain and grain morphology in Al–2Si–
xSn samples processed by ECAP is reported and discussed. The pseudo-binary Al–
xSn alloys (where
x = 0, 4, 8 mass%) were produced by conventional ingot casting. Samples were characterised by X-ray diffractometry (XRD), transmission electron microscopy (TEM), dynamical mechanical analysis (DMA) and microhardness. Results showed that the initial texture was modified after several ECAP passes and the formation of subgrains were observed. The presence of Sn enhanced the tribological properties of the alloy but, the ECAP capacity for grain refining was reduced. Besides, it was also confirmed that the damping capacity and microhardness behaviour were dependent of the Sn contents.
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Masahiro Hida, Masanori Kajihara
2012 Volume 53 Issue 7 Pages
1240-1246
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: June 06, 2012
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The kinetics of the reactive diffusion between solid Fe and liquid Sn was experimentally examined using Fe/Sn diffusion couples. The diffusion couples were prepared by an isothermal bonding technique and then immediately annealed in the temperature range of
T = 703–773 K for various times up to
t = 90 ks (25 h). During annealing, a compound layer of FeSn
2 is formed at the initial Fe/Sn interface in the diffusion couple and grows mainly into the liquid Sn specimen. At
T = 703 K, the compound layer indicates a needle-like microstructure in the early stages but a columnar microstructure in the late stages. On the other hand, at
T = 723–773 K, only the columnar microstructure is realized in the compound layer within the experimental annealing times. The mean thickness of the compound layer is proportional to a power function of the annealing time. The exponent
n of the power function is mostly close to 0.6. In the early stages at
T = 703 K, however,
n is equal to unity within experimental uncertainty. If growth of a compound layer with a uniform thickness is controlled by volume diffusion,
n is equivalent to 0.5. In contrast,
n is equal to unity for longitudinal growth of a needle-like grain, even though volume diffusion is the rate-controlling process. This is the case for the layer growth in the early stages at
T = 703 K. Since independent longitudinal growth of each columnar grain contributes to the layer growth governed by volume diffusion,
n is slightly greater than 0.5 for the compound layer with the columnar microstructure. Consequently, the discontinuous variation of
n corresponds to the transition from the needle-like microstructure to the columnar microstructure.
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Hongcun Zhai, Xiaofeng Li, Junyi Du
2012 Volume 53 Issue 7 Pages
1247-1251
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
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First-principles calculations of the crystal structure and the elastic properties of tetragonal WN
2 have been performed with the plane-wave pseudopotential density functional theory method. The calculated structural parameters and elastic constants at zero pressure and temperature are in excellent agreement with the available theoretical results. The dependence of the elastic constants
Cij, the aggregate elastic moduli
B,
G and the anisotropies on pressure have been investigated. WN
2 is a brittle system below about 66 GPa, whereas it becomes ductile under high pressure. By the elastic stability criteria, it is predicted that tetragonal WN
2 are not stable above 232.1 GPa.
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Byeong Deok Lee, Eun Jeong Kim, Eui Hyuk Kwon, Hyeon Taek Son, Jeong W ...
2012 Volume 53 Issue 7 Pages
1252-1257
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: June 13, 2012
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Mg and Mg alloys are unsuitable for use at temperatures greater than 393 K owing to their poor creep resistance and strength at elevated temperatures. Therefore, it is essential to develop high-strength magnesium alloys for use in elevated-temperature automotive applications. Therefore phase diagrams for Mg–3Zn–2Sn–0.4Ag–
xNd alloys were calculated in order to present clear guidelines for Mg alloy development. The results will help in determining solid solutions and aging treatment conditions. The effect of extruded Mg–3Zn–2Sn–0.4Ag–
xNd alloys on the microstructure, texture and mechanical properties at room temperature and a high temperature of 423 K were examined.
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Sudsakorn Inthidech, Attasit Chooprajong, Prasonk Sricharoenchai, Yasu ...
2012 Volume 53 Issue 7 Pages
1258-1266
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: June 06, 2012
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Hypoeutectic 26 mass% Cr cast irons with 0–3 mass% Mo were prepared in order to investigate their abrasive wear behavior. The annealed test pieces were hardened from 1323 K and then tempered at three levels of temperatures between 673 and 823 K for 7.2 ks, the temperature giving the maximum hardness (
HTmax), lower temperature than that at
HTmax (
L-
HTmax) and higher temperature than that at
HTmax (
H-
HTmax). The abrasive wear resistance was evaluated using Suga wear test (two-body-type) and Rubber wheel wear test (three-body-type). It was found that hardness and
Vγ in the heat-treated specimens varied depending on the Cr and Mo contents. A linear relation was obtained between wear loss and wear distance. The lowest wear rate (
RW) was obtained in both the as-hardened and
HTmax specimens. The highest
RW was mostly obtained in the
H-
HTmax specimens. Under the same heat treatment condition, the
RW in Suga wear test was much greater than that in Rubber wheel wear test. The
RW decreased with increasing hardness. The lowest
RW obtained in the specimen with a certain amount of retained austenite, 10–15%
Vγ. The
RW decreased with increasing Mo content in Suga abrasive test and it decreased little by Mo addition in Rubber wheel wear test.
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Keiko Sasaki, Shoichi Tsuruyama, Sayo Moriyama, Stephanie Handley-Sidh ...
2012 Volume 53 Issue 7 Pages
1267-1272
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: May 23, 2012
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With the recent Fukushima incident, there is an urgent need to find cost effective and workable permeable reactive barrier (PRBs) for the remediation/retardation of problematic radionuclides. Catfish bones were calcined at various temperatures (400–1100°C) to remove the organic matter (87.1 mg·g
−1) and to change the structural properties of the hydroxyapatite (HAP). Increasing temperatures increased the HAP crystallinity as indicated by a decrease in lattice strain (0.0098 to 0.00135) and an increase in crystallite sizes (5.0 × 10
−8 to 7.7 × 10
−8 m). There was also an observed decrease in specific surface areas (98.9 to 0.99 m
2·g
−1) and increase in particle sizes (50 to 1000 nm). The sorption densities of Sr
2+ decreased with increasing calcination temperatures, from 0.34 to 0.05 mmol·g
−1. However, once normalized for surface area, the sorption densities increased from 1.8 to 5.9 mmol·m
−2. Overall, this research has important implications for the design of hydroxyapatite PRBs with higher calcination temperatures producing a more reactive material with larger particle sizes for increased permeability. Lower calcination temperatures produced amorphous HAP material, which released more aqueous PO
43− and resulted in the precipitation of strontium phosphates, ultimately reducing the permeability of PRBs.
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Nobumitsu Shohoji
2012 Volume 53 Issue 7 Pages
1273-1277
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: May 23, 2012
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Hydrogen (H) absorption performance in a four monolayers (4 ML) thick body centered cubic (
bcc) vanadium (110) interface layer being in contact with non-H absorbing molybdenum layer (Mo/V (110) superlattice) reported by Öhrmalm
et al. was analyzed in terms of statistical thermodynamics. Number θ of the available interstitial sites for occupation by H atoms per V atom was determined to be 0.45 in the 4ML
bcc V (110) superlattice while θ was evaluated to be 0.55 for poly-crystalline bulk
bcc V lattice. With this choice of θ value, nearest neighbor H–H interaction energy
E(H–H) in the 4ML
bcc V (110) superlattice was evaluated to be zero and the extent
Q of stabilization of H atom in the
bcc V (110) superlattice was evaluated to be comparable to that in the bulk
bcc V lattice. The evaluated reduction of θ for the 4ML
bcc Mo/V (110) superlattice to 0.45 from 0.55 for the bulk
bcc V lattice was concluded to be the consequence of modulation of electronic structure in the
bcc V lattice in the vicinity of non-H absorbing Mo layer.
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Zhengcao Li, Ye Yang, Xian Zhang, Zhengjun Zhang
2012 Volume 53 Issue 7 Pages
1278-1281
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: June 20, 2012
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Silicon wafers were corroded by NaOH aqueous with a high concentration as a substrate preprocessing. These corroded Si wafers with rougher surfaces could provide some initial small discontinuous ‘islands’ for the deposition of silver via glancing angle deposition technique. It turned out that this pretreatment could help to improve the separation of Ag nanorods and result in an enhancement on the Raman intensity, with an increase of 223% at most compared with the one without alkali corrosion. This preprocessing is considered to be a simple, practical and effective way to prepare better SERS-active substrates and improve the sensitivity of trace amount detection using SERS in the future.
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Yoshitake Nishi, Hiroaki Takei, Hideki Kawazu, Yuu Nakahara
2012 Volume 53 Issue 7 Pages
1282-1287
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: May 30, 2012
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Homogeneous low voltage electron beam irradiation (HLEBI) with small dose of 0.30 to 1.17 MGy enhanced the elasticity indicated by the initial and maximum slope values of stress–strain curves ((dσ/dε)
i and (dσ/dε)
max) of 250 µm diameter optical fiber (OF), which was constructed with both core (10 µm diameter) and clad (125 µm diameter) silica glasses covered with acryl-urethane sheath (62.5 µm thickness). The highest (dσ/dε)
i and (dσ/dε)
max values of 5.3 and 5.9 GPa, which were about 10 and 20% higher than those (4.8 and 4.9 GPa) before irradiation, were found at 0.104 MGy, respectively. Moreover, remarkable effects of HLEBI of 0.65 MGy on both tensile strength (σ
f) and fracture strain (ε
f) of OF were obtained at each fracture probability (
Pf) value. Since HLEBI also enhanced the density of dangling bonds of each material of OF, effects of compressive stress on pull-out resistance and elasticity enhancements of fiber and sheath probably occurred. Thus, 0.64 MGy-HLEBI enhanced the (dσ/dε)
i and (dσ/dε)
max as well as ε
f, resulting in enhancement of σ
f of OF.
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Yoshitake Nishi, Naoya Tsuchikura, Shinichiro Nanba, Tatsuya Yamamoto, ...
2012 Volume 53 Issue 7 Pages
1288-1294
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: May 30, 2012
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The purpose of this study is to investigate a lighter, cheaper and possibly stronger alternative to CFRP, by obtaining the Charpy impact values (
auc) of a sandwich structural composite (CFRP/PC/CFRP) constructed of a polycarbonate (PC) core between two thin plies of carbon cross textile fiber/epoxy (CFRP) within the temperature range of aircraft operation, from 200 to 403 K below the glass transition temperature of PC (
Tg = 422 K). The
auc of CFRP/PC/CFRP were compared with a 2.0 mm thick 12-ply CFRP laminate. Results showed overall, the CFRP/PC/CFRP had higher
auc than the CFRP at each fracture probability (
Pf) from 300 to 373 K except at 200 K with low
Pf and 403 K with high
Pf. Specifically, although the volume fraction of carbon fiber (12%) of CFRP/PC/CFRP was much smaller than that (60%) of the CFRP, the
auc at room temperature (300 K) of CFRP/PC/CFRP was approximately 64% higher than that of CFRP at mid-fracture probability (
Pf) of 0.50. Fracture modes of CFRP/PC/CFRP were explained by delamination between PC core and the CFRP thin sheet surfaces, bending plastic deformation, and CFRP fracture. The highest Weibull coefficient (
n) was obtained at 323 K. Based on the 3-parameter Weibull equation, the limiting impact value (
as) also exhibited the highest value at 323 K. In addition, the cost of CFRP/PC/CFRP was 40% lower than that of CFRP at the time of this study. Since the use of PC resin as the core enhanced the safety design at low cost, practical use of sandwich structural composites of CFRP/PC/CFRP is possible.
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Masayoshi Adachi, Masashi Sugiyama, Akikazu Tanaka, Hiroyuki Fukuyama
2012 Volume 53 Issue 7 Pages
1295-1300
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: May 23, 2012
JOURNAL
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We have been investigating crystal growth of AlN on nitrided sapphire substrates, and have grown
c-axis oriented AlN layers using liquid phase epitaxy (LPE) with Ga–Al fluxes. However, rotational domains having 1-deg difference around the
c-axis exist in the AlN layers. One of the purposes of this study is to eliminate the rotational domains. To do so, an annealing process at elevated temperatures was attempted before the LPE process. Then, its effectiveness was discussed. The origin of the rotational domain was explained using distortion of O
2− ions arrangement in (0002) sapphire surface. The mechanism of the eliminating the domains was discussed using the lattice vibration of the sapphire at elevated temperatures. Secondly, effects of growth temperature on the AlN layers were investigated in terms of the growth rate, surface morphology and crystal quality. The growth rate of the LPE AlN layer increased concomitantly with increasing growth temperature at 1373–1673 K. The growth rate attained at 1673 K was 0.52 µm·h
−1. Crystal quality is almost independent of the growth temperature in that temperature range.
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Kazuhito Shida, Ryoji Sahara, Hiroshi Mizuseki, Yoshiyuki Kawazoe
2012 Volume 53 Issue 7 Pages
1301-1304
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: May 30, 2012
JOURNAL
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When one attempts to modulate and control the characteristics of composite materials, the mathematical threshold of the percolation transition dictates the modulation limit. Using a series of computer simulations, we have been investigating the dependence of the percolation threshold on particle size distributions. However, one of the other factors that can deeply affect percolation behavior, the design of lattice, is always fixed to simple square or cubic lattices. This report presents the first calculation of a percolation threshold in a 2D triangular lattice with binary size distributions of conductor particles. Although a small quantitative difference was found, the results qualitatively matched to the results already reported for 2D square lattices, thus confirming our previous finding: the introduction of large conductor particles increases the percolation threshold in 2D.
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Hidetaka Uno, Zhi-hong Wang, Noriko Takada, Toru Ishizuka, Hiromu Yawo ...
2012 Volume 53 Issue 7 Pages
1305-1309
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: May 30, 2012
JOURNAL
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The light-gated ion-channel protein is expected to be able to improve the performance of ionchannel devices for the multi-point screening and neural network devices based on the planar patch clamp. However, no studies with light-gated ion channels on a planar patch clamp have been reported. We constructed an incubation type of planar patch clamp biosensor using silicon-on-insulator substrates with a 1–2 µm micropore in them. Channelrhodopsin 2-expressing C2C12 cells and channelrhodopsin/wide receiver-expressing HEK293 cells were seeded on the surface of the sensor chip and incubated to almost complete confluence. A laser beam (473 nm wavelength) was radiated on the cells adsorbing to the sensor chip’s micropore and the light-gated channel currents of the voltage clamp and action potentials of the current clamp modes were observed. Good signal to noise ratios were obtained, although the seal resistance was not so large, 10–30 MΩ. The observed pulse shape of the ion-channel currents also qualitatively resembled reported results measured with a pipette patch clamp. These results strongly suggest that the light-gated ion channel proteins are useful biomaterials for ionchannel devices.
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Narguess Nemati, Massoud Emamy, Ali Reza Emami, Mashhood Mashhoodi
2012 Volume 53 Issue 7 Pages
1310-1317
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
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Al–Mg alloys close to β-Al
3Mg
2 intermetallic phase were processed by neutral gas coverage melting process of pure elemental Al and Mg with the composition of Al–40 mass% Mg. Mechanical milling was applied in order to convert the pre-alloyed ingots to nanocrystalline or amorphous alloy. X-ray diffraction and transmission electron microscopy (TEM) tests were carried out to investigate the formation of Al
3Mg
2 single phase nanoparticle. Having prepared the single phase intermetallic, it was added to the pre-alloyed matrix powder of Al–4.5 mass% Cu, in different contents. The effect of the reinforcing agent on the microhardness and wear behavior of the nanocopmosites were studied thoroughly with the aid of press-sinter methodology and quantitative data recorders via pin-on-disk wear test. The results of microhardness tests revealed that the hardness of nanocomposites is significantly improved with increasing reinforcement content with in the matrix. The coexisted wear mechanisms, mainly delamination and abrasive, of the consolidated nanocopmosites were investigated through scanning electron microscopy (SEM) and TEM observations.
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Woei-Shyan Lee, Tien-Yin Chan
2012 Volume 53 Issue 7 Pages
1318-1323
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
JOURNAL
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A two-stage sintering practice was applied to W–3.99Ni–1.71Fe (mass%) to control its microstructural evolution and, accordingly, mechanical properties under high strain rates. Unlike the traditional one-stage liquid phase sintering, the alloy was first solid-state-sintered to close to full densification, and then liquid-phase-sintered by induction heating where the cooling rate was fast. With the two-stage sintering, the growth of tungsten grains and the contiguity of tungsten grains could be closely tailored, and a high dissolved tungsten concentration in the matrix phase could be maintained. All of these microstructural characteristics led to enhanced mechanical properties of this alloy tested under high strain rates.
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Hyangsig Ahn, Ho Young Jo, Geon-Young Kim, Yong-Kwon Koh
2012 Volume 53 Issue 7 Pages
1324-1329
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
JOURNAL
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This study examined the effect of NaCl on the removal of Cr(VI) by ZVI in aqueous solutions and proposes a potential mechanism of Cr(VI) removal by ZVI in aqueous solutions with NaCl. A series of batch tests was conducted on ZVI using 100 mg/L Cr(VI) solutions at an initial pH of 3 at various NaCl concentrations. The NaCl in aqueous solutions improved the removal efficiency for Cr(VI) by ZVI. Fe(III)–Cr(III) (oxy)hydroxides were precipitated both on the ZVI surface and in the solution via the reduction reactions of Cr(VI) to Cr(III) in the presence of NaCl. The increase in the Cr(VI) removal efficiency in the solutions with NaCl was attributed to the Cl
− ions, which accumulate at the anodic sites of ZVI, thereby enhancing ZVI oxidation and colloidal particle formation. In the NaCl solutions, small grains were initially precipitated on the ZVI surface, via relatively fast reactions. The subsequent slowing of these reactions resulted in the precipitation of large grains on the ZVI surface and colloidal particles in the solutions.
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Yoshikatsu Inada, Zentaro Akase, Daisuke Shindo, Akira Taniyama
2012 Volume 53 Issue 7 Pages
1330-1333
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: June 06, 2012
JOURNAL
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To investigate the interaction between magnetic domain walls and defects in an electrical steel sheet by transmission electron microscopy, size-controlled holes were artificially introduced into specimens by a focused ion beam. By applying an external magnetic field in a transmission electron microscope, the magnetic domain structures around the holes were dynamically observed by Lorentz microscopy. Similar magnetic domain structures were observed around the holes, but the domain-wall pinning strength was found to depend on the hole size. Micromagnetic analysis was performed to ascertain the magnetic domain structures around the holes and to investigate the change in the magnetic energy during domain-wall pinning.
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Hwa-Teng Lee, Wen-Hsin Hou
2012 Volume 53 Issue 7 Pages
1334-1342
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: June 20, 2012
JOURNAL
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Post heat treatment fails to refine the grain structure of superalloy 718. Thus, for components with demanding grain size requirements, the forging process should be performed within an extremely limited temperature region just below the δ solvus temperature, yet higher than that required to induce dynamic recrystallization. The grain size of superalloy 718 is generally controlled during manufacturing by inducing full dynamic recrystallization through means of a carefully-controlled hot forming process performed in a powerful and precise forging machine. This work presents an alternative method for obtaining a fine and uniform grain structure through means of static recrystallization and a proper control of the δ phase formation. In the proposed method, the component is cooled in water immediately after forging to suppress δ phase precipitation and preserve the internal strain energy produced by the hot deformation process. The component is then heated to a temperature 30°C lower than the δ solvus temperature 1030°C; resulting in a continuous recrystallization of the microstructure. Experimental results indicate that γ′′ phase precipitation and δ phase precipitation dominate the dynamic and static recrystallization behaviors observed in the conventional and proposed grain refinement methods, respectively. Our results further demonstrate that the proposed static recrystallization method yields a fine microstructure with an average grain size of ASTM No. 7 (31.8 µm). Thus, the proposed method provides an inexpensive and technically straightforward alternative to the conventional hot forming grain refinement method.
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Naru Shiraishi, Rong Tu, Risa Uzuka, Takahisa Anada, Takayuki Narushim ...
2012 Volume 53 Issue 7 Pages
1343-1348
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: June 20, 2012
JOURNAL
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Ti–29Nb–13Ta–4.6Zr alloy (TNTZ), a new β-type Ti alloy, has excellent advantages as a biomaterial, such as low Young’s modulus and cytotoxicity, and the absence of allergens. However, it is unclear whether TNTZ can achieve sufficient osseointegration for it to be used as a dental implant. The effectiveness of surface modification of TNTZ implants by radiofrequency (RF) magnetron sputtering is also unclear. We investigated the biomechanical behaviors of TNTZ implants
in vivo, using cylindrical implants of four types: pure Ti, TNTZ, and pure Ti and TNTZ coated with amorphous calcium phosphate (ACP). The implants were inserted in rat femurs, and the femurs were subjected to biomechanical analyses after various time intervals. The results suggest that TNTZ implants can achieve osseointegration similar to that of pure Ti, and that surface modification with ACP by RF magnetron sputtering improves osseointegration, especially in the later stages of healing.
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Kyoung Won Ryu, Young Nam Jang, Myung Gyu Lee
2012 Volume 53 Issue 7 Pages
1349-1352
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: May 30, 2012
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The carbonation of chrysotile [Mg
3Si
2O
5(OH)
4] was studied at various temperatures in order to examine the carbonation rate and Mg leaching properties in an alkali solution and distilled water using the direct method. For the efficient carbonation reaction, the chrysotile was converted to metachrysotile by heating at 630°C for 2 h. The carbonation rate was found to increase with the reaction temperature: 5 and 31% at 100°C and 45 and 53% at 260°C in distilled water and alkali solution, respectively. The carbonation in the alkali solution was faster producing well-faceted rhombohedral magnesite (MgCO
3) in comparision to the case in the distilled water. Highly crystalline magnesite could be obtained after the carbonation for 1 h at 260°C under a CO
2 pressure of 3 MPa in the alkali solution.
The additional object of this study was to convert the fibrous chrysotile to a non-hazardous material. During carbonation, the magnesite exhibited the typical rhombohedral morphology while the unreacted chrysotile changed primarily to aggregations of chrysotile crystals. This result has an important implication for the elimination of toxicity through the transformation of chrysotile asbestos into a non-hazardous material.
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Min-Sung Kim, Geun-Hyoung Lee
2012 Volume 53 Issue 7 Pages
1353-1355
Published: July 01, 2012
Released on J-STAGE: June 25, 2012
Advance online publication: June 20, 2012
JOURNAL
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Chestnut bur-like zinc oxide crystals were synthesized by the thermal evaporation of zinc sulfide powder without the use of any catalyst. A magnifying lens was used to heat up the zinc sulfide powder. Thermal solar energy was concentrated on the zinc sulfide powder by the magnifying lens. Then the zinc sulfide powder was heated and evaporated within a relatively short time. The zinc sulfide vapor was oxidized in air and the chestnut bur-like zinc oxide crystals were formed. EDX spectrum revealed that the zinc oxide crystals had wurtzite hexagonal structure. A strong green emission was observed in cathodoluminescence spectrum. The thermal evaporation technique using solar energy is one of the techniques to reduce the energy consumption and costs.
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