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Volume 54, Issue 5
May
Displaying 1-14 of 14 articles from this issue
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Paper
Paper
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Tadahiro Wada2007 Volume 54 Issue 5 Pages 311-316
Published: 2007
Released on J-STAGE: January 23, 2008
JOURNAL OPEN ACCESSIn a cutting cemented carbide using a polycrystalline diamond compact (PCD) cutting tool, cutting forces, surface roughness and tool wear were experimentally investigated to understand tool machining characteristics. WC-16mass%Co was turned with the various kinds of PCD cutting tools that had different diamond particle sizes and different diamond contents. The following results were obtained: (1) The wear of PCD cutting tool with rake angle 0° was slower than that with −6°. (2) The tool wear decreased with increase of the diamond particle size. (3) In case of short cutting distance, the surface roughness decreased with decrease of the diamond particle size. However, when the tool wear was larger, the surface roughness increased with decrease of the diamond particle size.
As mention above, it was considered that a PCD with both the rake angle 0° and the diamond particle size 30μm was the most effective tool material in cutting of WC-16mass%Co from the standpoint of the surface roughness and the tool wear.View full abstractDownload PDF (795K) -
Kaduichi Kitagawa, Shizuo Nakamura, Masaki Miyamoto, Kentaro Ohhashi, ...2007 Volume 54 Issue 5 Pages 317-321
Published: 2007
Released on J-STAGE: January 23, 2008
JOURNAL OPEN ACCESSNoto-diatomaceous earth is porous material that is composed of diatom shell and clay mineral. The pore of diatom shell is macro pore, and the pore of clay mineral is nano meter size pore. Pellet type catalyst carrier was prepared from Noto-diatomaceous earth. Deodorant catalyst was synthesized using this carrier. The catalyst performance was evaluated with fixed-bed continuous-flow reactor using 0.2%CO-2%O2-N2 mixed gas. The CO oxidation was occurred at room temperature by powder type Pd-catalyst. In case of pellet type Pd-catalyst, CO oxidation occurred at 170°C.View full abstractDownload PDF (532K) -
Satoshi Sunada, Masaru Kawagishi, Kazuhiko Majima2007 Volume 54 Issue 5 Pages 322-329
Published: 2007
Released on J-STAGE: January 23, 2008
JOURNAL OPEN ACCESSThere exist difficulties in preparing pure titanium or titanium alloys by the ingot metallurgy (I/M) because of their poor machinability. Recently, powder metallurgy (P/M) has been applied to produce the titanium products since it has the advantage of better formability. There are, however, still some significant issues concerned in fabricating three dimensional complex shape products by the above mentioned conventional P/M process. Metal injection molding (MIM) process has the advantage of better formability of three dimensional complex shape products with high density and high performance properties. Two kinds of pure titanium specimens, i.e., the first one is prepared by the I/M process and the second one is prepared by MIM process are used in this experiment, and their corrosion behavior under stress has been investigated in several aqueous solutions by Slow Strain Rate Tensile (SSRT) test. Both I/M and MIM specimens showed good corrosion resistance in the aqueous solution composed of 2.5 kmol/m3 H2SO4 and 0.2 kmol/m3 NaCl as well as saline solution. This aqueous solution is noted one in which Type 304 stainless steel showed SCC. In the aqueous solution composed of CH3OH and 0.1 kmol/m3 HCl containing 8.6kg/m3 H2O, the elongation of MIM specimen was slightly higher than that of I/M specimen though both specimens indicated the remarkable decrease in elongation.View full abstractDownload PDF (1081K) -
Satoshi Sunada, Takahisa Yamamoto, Shigeo Tanaka, Norio Kada, Kazuhiko ...2007 Volume 54 Issue 5 Pages 330-335
Published: 2007
Released on J-STAGE: January 23, 2008
JOURNAL OPEN ACCESSThe SCC (Stress Corrosion Cracking) behavior of the MIM (Metal Injection Molding) 304 stainless steel specimen in aqueous solutions containing 2.5 kmol·m−3 H2SO4 and NaCl of varying concentrations was studied in comparison with that of I/M (Ingot Metallurgy) 304 stainless steel specimen. Both MIM and I/M specimens showed the SCC in the aqueous solutions containing 2.5 kmol·m−3 H2SO4 and NaCl of particular concentration ranges, and the general corrosion in the solutions of the other NaCl concentration ranges.
The V-shape plots were obtained in the relationship between the corrosion mass loss against NaCl concentration for both I/M and MIM specimens, in which the NaCl concentration of the MIM specimen showing the minimum corrosion mass shifted to the higher concentration side than that of the I/M specimen. The similar V-shape plots were obtained in the relationship between the crack length against NaCl for both MIM and I/M specimens, in which the NaCl concentration of the MIM specimen showing the maximum crack length shifted to the higher concentration side than that of the I/M specimen. The concentration ranges of NaCl for the minimum peak of corrosion mass loss and for the maximum peak of crack length are approximately the same.View full abstractDownload PDF (973K) -
Satoshi Sunada, Takahisa Yamamoto, Shigeo Tanaka, Norio Kada, Kazuhiko ...2007 Volume 54 Issue 5 Pages 336-344
Published: 2007
Released on J-STAGE: January 23, 2008
JOURNAL OPEN ACCESSIn this study, the corrosion behavior of MIM (Metal Injection Molding) specimen has been investigated by SSRT (Slow Strain Rate Tensile) test and EIS (Electrochemical Impedance Spectroscopy) method in comparison with I/M (Ingot Metallurgy) specimen. In the SSRT test, the aqueous solution composed of 2.5 kmol·m−3 H2SO4 and 0.20 kmol·m−3 NaCl (hereafter shortened as SCC solution) in which SCC occurs was used. In addition to this solution, the aqueous solution of 2.5 kmol·m−3 H2SO4 and 3.0 kmol·m−3 NaCl (hereafter shortened as general corrosion solution) in which general corrosion occurs was used in the EIS test.
Cdl (Electric Double Layer Capacitance) of I/M specimen has increased abruptly at 7.2 ks during holding in the SCC solution under applied stress, while it has increased gradually without applied stress. On the other hand, the Cdl of MIM specimen has increased gradually increased irrespective of with or without applied stress for MIM specimen. The remarkable Rct difference was observed in two cases with or without applied stress in the SCC solution for both I/M and MIM specimen while the slight Rct difference was observed in the general corrosion solution. The fracture surface appearance by SEM showed that the typical transgranular SCC occurred on I/M specimen while the intergranular SCC along grain boundaries occurred on MIM specimen. It was also confirmed that the more significant HE-SCC (Hydrogen Embrittlement) and the weaker APC-SCC (Active Path Corrosion) were observed on the MIM specimen compared with the I/M specimen.View full abstractDownload PDF (1320K)
Special Issue:Thermoelectric Materials
Summarization
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Shigeru Katsuyama2007 Volume 54 Issue 5 Pages 346
Published: 2007
Released on J-STAGE: January 23, 2008
JOURNAL OPEN ACCESSDownload PDF (143K)
Review
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Shinsuke Yamanaka, Ken Kurosaki, Hiroaki Muta2007 Volume 54 Issue 5 Pages 347-350
Published: 2007
Released on J-STAGE: January 23, 2008
JOURNAL OPEN ACCESSWe have prepared polycrystalline bulk samples of various thallium compounds and measured their thermoelectric properties. Almost all the thallium compounds exhibit extremely low values of the thermal conductivity (∼0.5 Wm−1K−1). This extremely low thermal conductivity leads a great advantage for an enhancement of the thermoelectric performance. In this paper, we review the thermoelectric properties of various thallium compounds selected for study as novel thermoelectric materials. One of them seems to have a high thermoelectric figure of merit comparable to those of state-of-the-art materials.View full abstractDownload PDF (441K)
Paper
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Ken-ichi Horiguchi, Yasuo Teduka, Sunao Sugihara2007 Volume 54 Issue 5 Pages 351-355
Published: 2007
Released on J-STAGE: January 23, 2008
JOURNAL OPEN ACCESSA perovskite structure contains local carriers, which conduct electricity by hopping. CaMnO3 displayed as a perovskite structure has superior thermal and oxidation resistance. An attempt was made to elevate thermoelectric performance by introducing impurities into the Mn site of CaMnO3.
The Seebeck coefficient α of the substituted CaMnO3 didn't exceed that of the standard for all temperature ranges. In all cases Seebeck coefficient showed roughly similar values. And in all cases, the Seebeck coefficient of the sample with a substituent of x=0.01 showed a high value, while that of the sample with a substituent of x=0.1 showed the greatest decrease.
Electrical resistivity ρ showed a constant value, as did Seebeck coefficient α. As the substitution percentage is increased, the electrical resistivity should decrease.
The thermal conductivity κ was measured on the samples only with a substituent of x=0.01. The standard sample showed about 1 (Wm−1K−1) over any temperature field.
As for the figure of merit Z, Ta and Nb substituted samples showed higher values than standard around 400(K). Above 400(K), standard showed higher value. The value of standard reached 5.2×10−5(K−1) at 800(K).View full abstractDownload PDF (770K) -
Kotaro Sotojima, Ryosuke O. Suzuki, Koji Amezawa, Yoichi Tomii2007 Volume 54 Issue 5 Pages 356-361
Published: 2007
Released on J-STAGE: January 23, 2008
JOURNAL OPEN ACCESSPhase stability and thermoelectric properties of a layered structure of (ZnxCu2-x)V2O7 solid solution were studied at x ≥ 0.2. X-ray diffraction measurements, compositional studies and thermal analysis clarified that the low temperature form of (ZnxCu2-x)V2O7 solid solution (monoclinic structure, C2/c) was stable at 0.2 ≤ x ≤ 2 when annealed at 823 K in air. On heating, the phase transformation occurred at 0.2 ≤ x ≤ 2 at a nearly constant temperature around 873 K, above which a high temperature form of (ZnxCu2-x)V2O7 solid solution was formed.
Seebeck coefficients of the low temperature form of (ZnxCu2-x)V2O7 solid solution showed the large negative value of about −520 to −700μV/K, and the electrical resistivity increased with Zn addition. Power factor was the maximum of 1.99 × 10−7 W/m K2 at 873K for the low temperature form of the (Zn0.2Cu1.8)V2O7 solid solution.View full abstractDownload PDF (698K) -
Sunao Sugihara, Kohjiro Nishiyama2007 Volume 54 Issue 5 Pages 362-365
Published: 2007
Released on J-STAGE: January 23, 2008
JOURNAL OPEN ACCESSWe have investigated α-Fe2O3 system as the oxide thermoelectric (TE) materials to convert energy from temperature differences to electricity. Generally, an oxide TE material has a large thermoelectric power (Seebeck coefficient) and lower thermal conductivity. However, this system has a large electrical resistivity (more than 10−5 Ωm) and thermal conductivity (35 Wm−1K−1 at room temperature) which are not good properties for TE material. The aim of this research is to reduce thermal conductivity mainly, and to reduce electrical resistivity as well. For our approach we calculate the electronic structures to know around Fermi energy level and bonding characteristics using ab-inito calculation with discrete variational Xα method (DV-Xα). DV-Xα is one of molecular orbital methods. Actual material of (Fe1-x, Tix)2O3 system was also formed by powder metallurgical method by adding TiO2 to α-Fe2O3. As the one of calculation results, the impurity level existed in an energy gap (about 3.5 eV) which lessen the energy gap. Electron behaviors are covalent according to the calculation results and combination of Fe and Ti seems to be better in terms of reduction-oxidation potential of them. Thermal conductivity reduced down to 3 Wm−1K−1 for 5 mol% specimen at 600 K and higher temperature. Furthermore, dimensionless figure of merit (ZT) was 0.04.View full abstractDownload PDF (374K) -
Masaya Tsurizawa, Keiko Ando, Sunao Sugihara2007 Volume 54 Issue 5 Pages 366-369
Published: 2007
Released on J-STAGE: January 23, 2008
JOURNAL OPEN ACCESSn-type semiconductor is formed by addition of Al2O3 to ZnO. As an oxide thermoelectric material, the electrical resistivity of (Zn, Al)O is higher than 10−5 (Ωm) and the Seebeck coefficient is not so high. The thermal conductivity at room temperature is high value of 40 (W/mK), therefore dimensionless figure of merit is not high enough. The aim of our research is to reduce the thermal conductivity by addition of an oxide to Zn0.98Al0.02O. The added oxide in this research is Co3O4. The thermal conductivity in 0.5 mol% added-sample was reduced by around 20% at room temperature and became to be 7 (W/mK) at 873K, while the standard sample showed 10 (W/mK) at the same temperature. Furthermore, Seebeck coefficient of the 0.5mol% added-sample increased by 20% in absolute value as compared with that of the standard at room temperature. The value of the Seebeck coefficient increased with increasing temperature. On the other hand, electrical resistivity increased with increasing added amount of Co3O4. However, the 0.1mol% added-sample showed almost the same electrical resistivity as the standard, and moreover it did not much change with temperature. The highest Z and ZT in the 0.1mol% added-sample were 0.06 × 10−3 (1/K) and 0.05 at 873K, normatively.View full abstractDownload PDF (682K)
Review
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Ken Kurosaki, Takeyuki Sekimoto, Kenta Kawano, Hiroaki Muta, Shinsuke ...2007 Volume 54 Issue 5 Pages 370-374
Published: 2007
Released on J-STAGE: January 23, 2008
JOURNAL OPEN ACCESSWe studied the thermoelectric properties of LnPdX (Ln: La, Gd, Er, X: Bi or Sb). The values of the thermoelectric power were positive and relatively large (60-220μVK−1). The values of the electrical resistivity were on the order of 10−4 Ωcm, which is relatively low in view of the large values of the Seebeck coefficient. From the Hall effect measurements, the low electrical resistivity was confirmed to be caused by the large carrier mobility. LaPdSb indicated the largest power factor of 50μWcm−1K−2 at 327 K and the highest dimensionless figure of merit of 0.26 at around room temperature. LnPdX, especially LaPdSb should attract great interest in the search for new high performance p-type thermoelectric materials.View full abstractDownload PDF (710K)
Paper
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Shigeru Katsuyama, Hiroshi Okada2007 Volume 54 Issue 5 Pages 375-380
Published: 2007
Released on J-STAGE: January 23, 2008
JOURNAL OPEN ACCESSWe have tried to improve the performance of the thermoelectric properties of the skutterudite CoSb3 by controlling the microscopic structure. The thermal conductivity of CoSb3 is much reduced by the insertion of Ce into voids and the substitution for Co by Fe. We have also investigated the effect of mechanical milling on the thermoelectric properties of CeFe3CoSb12, The Seebeck coefficient of the milled CeFe3CoSb12 decreases, while the thermal conductivity of them increases, which is perhaps due to the precipitated impurity phases during mechanical milling. As a result, the dimensionless figure of merit, ZT, was reduced by mechanical milling. Next, we have prepared CeFe3CoSb12-MoO2 or -WO2 composites where MoO2 or WO2 particles are dispersed in the CeFe3CoSb12 matrix by mechanical milling. The electrical resistivity and thermal conductivity of the CeFe3CoSb12-MoO2 composite whose mechanical milling time is 5h become smaller than those of CeFe3CoSb12. The composite whose molar ratio of CeFe3CoSb12 to MoO2 is 0.95:0.05 shows a maximum ZT of 1.22 at 773K, which is larger than ZT of CeFe3CoSb12.View full abstractDownload PDF (1190K) -
Kentarou Morikawa, Hiroyuki Chikauchi, Hiroyuki Mizoguchi, Sunao Sugih ...2007 Volume 54 Issue 5 Pages 381-385
Published: 2007
Released on J-STAGE: January 23, 2008
JOURNAL OPEN ACCESSIn resent years, there are various energy problems and environmental problems, such as the lack of fossil fuels and global warming, due to the burning of fossil fuels that lead to the generation of CO2 and NOx. Therefore, successive studies have been carried out using thermoelectric power, which can convert thermal energy into electric energy directly using temperature differences. Our goal is the improvement of thermoelectric properties for FeSi2. FeSi2 is a cheap and eco-friendly resource. We investigated the decrease in thermal conductivity of FeSi2 by the addition of oxide.
Fe, Si and Co powders were mixed to form the composition n-type FeSi2. Oxide was added to the sample and they were mixed. The resulting powder was molded at 153MPa in a 10mmφ die. The molded sample was calcined at 670K for five hours in air atmosphere, calcined at 1463K for two hours in a vacuum, and then heat-treated at 1033K for twelve hours keeping in a vacuum. And thermoelectric properties were measured by DC method, four-probe method and laser flash method.
As for figure of merit, n-type FeSi2 added with 1wt% of Dy2O3 and 3wt% of Ta2O5 showed higher value than the unadditive n-type FeSi2. The highest performance was 0.3×10−3K−1 at 614K on the n-type FeSi2 added with 1wt% of Dy2O3. As for dimensionless figure of merit, the highest performance was 0.24 at 864 K on the n-type FeSi2 added with 3wt% of Ta2O5.View full abstractDownload PDF (858K)
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