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Volume 69, Issue 2
Displaying 1-23 of 23 articles from this issue
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Hidemi Nawafune, Kensuke Akamatsu2005 Volume 69 Issue 2 Pages 179-189
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSNanoscale metal particles have been of great interest in the development of next generation micro- and nano-electronics devices. In this review, we describe the characteristics and applications of monolayer-protected metal nanoparticles as well as importance of controlling their surface and interfacial structures for electronics applications, on the basis on our recent experimental results. Recently, much effort has been devoted to directing monolayer-protected metal nanoparticles into organized structures onto solid supports by a variety of fabrication techniques. One of the emerging techniques for immobilization is to use organic monolayers attached on the nanoparticles and substrate of interest to guide the assembly of the nanoparticles through predesigned chemical and physical interactions. We demonstrate a novel technique for the fabrication of two-dimensional microscopic assembly of monolayer-protected gold nanoparticles onto substrates. Selective integration of the nanoparticles onto either hydrophobic or hydrophilic region on the substrates could be achieved by controlling dispersion-aggregation process of gold nanoparticles, thereby providing effective methodology for fabrication of various patterns of integrated mesoscopic nanoparticle assemblies that can be further used for development of metallic circuits.
Our next interest is to develop simple strategy for fabrication of metallic circuits on polymeric substrate, with high adhesive strength achieved via novel concept of nanoscale interlocking mediated by metal nanoparticles. We proposed novel process for forming metallic circuit patterns on polyimide substrate, which has excellent electrical, thermal, chemical and dielectric properties. The process involved a surface modification of polyimide, incorporation of metallic ions followed by reduction to form thin films consisting of metal nanoparticles. We have succeeded to fabricate metallic silver and copper circuit patterns that are highly adhesive due to the interlocking mediated by metal nanoparticles at metal/polymer interface. The interfacial structures presented here are promising for future miniatulization of metallic circuit patterns in microelectronic devices.
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Masaaki Imade, Seiji Fukuyama, Lin Zhang, Mao Wen, Kiyoshi Yokogawa2005 Volume 69 Issue 2 Pages 190-193
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSHydrogen environment embrittlement (HEE) of the heat-treated SCM440 steels was investigated at room temperature with the strain rate range from 4.2×10-5 to 4.2×10-2 s-1 by using specially designed testing equipment for materials under high-pressure hydrogen of 70 MPa. Hydrogen showed marked effect on the tensile properties of SCM440 steel. The HEE of SCM440 steel increased with increasing hydrogen pressure and increased with decreasing strain rate. HEE increased from the annealed to the normalized and then to the quenched steel. HEE of the quenched-tempered SCM440 steel decreased with increasing the tempering temperture. It was observed that hydrogen causes quasi-cleavage fracture for annealed and normalized steel, and the mixture of the quasi-cleavage fracture and intergranular fracture for the quenched steel.
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Yoshihiko Hangai, Nobuhiro Yoshikawa, Sergey V. Dmitriev, Masanori Koh ...2005 Volume 69 Issue 2 Pages 194-197
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSThe atomistic scale tensile test of mixed O-terminated and Al-terminated α-Al2O3(0001)/Cu(111) interface has been examined by quasicontinuum method. The quasicontinuum method has been developed for large-scale atomistic simulations. In this approach, the number of degrees of freedom is much reduced in comparison to molecular dynamics simulation, so that the computational time is significantly decreased. In the Al2O3/Cu interface, the O-terminated interface has quite large adhesive energy, and the Cu-O bond is much stronger than the Cu-Cu bond. The Al-terminated interface has quite a small adhesive energy, and the Cu-Al bond is much smaller than the Cu-Cu bond. In the tensile test, adhesive energy of mixed interface of O-terminated and Al-terminated is the mean value of that of O-terminated interface and Al-terminated interface.
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Atsushi Nakano, Kazuya Higashiiriki, Nurul Taufiqu Rochman, Kosaku Yam ...2005 Volume 69 Issue 2 Pages 198-201
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSTo date, Pb has been added to brass to increase its machinability. Due to the extreme toxicity of Pb, however, the public demand for the use of Pb-free brass has increased and regulations to limit the amount of Pb permitted in drinking water supplies have been enforced. Therefore, recycling brass cannot be utilized and a large amount of scrap brass will become industrial waste. In the present study, the use of the compound-separation method is attempted for the removal of Pb from brass containing 2.15 mass%Pb. The result shows that Pb removal was effective up to 83% when using a Ca-Si compound as an addition agent for Pb-compound formation and NaF as an aggregation agent.
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Yusuke Tsuboi, Koji Kakehi2005 Volume 69 Issue 2 Pages 202-205
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSThe inner and outer regions of a turbine disks are exposed to service temperatures and the required properties are different. Although the anisotropy of properties in single crystal Ni-base superalloys has been reported, the anisotropy in polycrystalline superalloys has not been reported yet. The purpose of this study is to investigate the effect of heat treatment on the microstructure, the proof strength and the plastic anisotropy in polycrystalline superalloy U720Li. The solution heat treatment was performed at 1100, 1150 and 1170°C. In the as-received billet, it was found that the crystal grains were equiaxial in the inner region and elongated in the outer region. For the specimens heat treated at 1150°C, different crystal grain structures were observed in the inner and outer regions, as the grain growth was only observed in the inner region. The difference in proof stresses between the inner and outer region increased as the solution-heat-treatment temperature was increased. For every heat treatment condition, the proof stress in tension was approximately the same as that in compression.
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Mitsuhiro Wada, Yasunori Tabira2005 Volume 69 Issue 2 Pages 206-209
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSThese days many functional materials exert high functions under various service conditions through undergoing a variety of structural changes such as phase transformation. In line with such circumstances, the in-situ XRD system, which is able to conduct structural analyses of a material while evaluating the vapor-solid phase reaction quantitatively, is utilized extensively in materials evaluation. Many reports have been presented on materials such as hydrogen storage alloys that undergo phase transformation in the process of the vapor-solid phrase reaction. It is generally known that as the temperature of a material varies, so does its crystal structure, and efforts have been made to evaluate the structural change continuously in parallel with the passage of time. Recently, to perform these evaluations, devices equipped with sophisticated detectors, such as various types of time-resolved assessment systems, have been developed. However, there have been few reports of evaluation systems that enable quantitative measurement of the kinetic reaction between the atmospheric gas and the material and time-resolved evaluation of the structural change in the material at the same time.
We developed an original time-resolved in-situ XRD system that enables both sequential in-situ assessment of structural change in the material, including phase transformation, and quantitative measurement of the reaction with the atmospheric gas in parallel. As a practical application, we used the system to evaluate the process of hydrogen absorption by LaNi5, a known hydrogen storage alloy. Over a period of several minutes, we observed the phase transformation of the master alloy, LaNi5, into a hydride of LaNi5H6 during the hydrogen absorption process and evaluated the process sequentially at intervals of a few seconds. We succeeded in clearly evaluating the phase transformation during the vapor-solid phase reaction of the master alloy with hydrogen, which diffused very quickly. We expect that in future this system will be applied to various types of functional materials to evaluate their structures kinetically.
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Mitsuhiro Wada, Yasunori Tabira2005 Volume 69 Issue 2 Pages 210-212
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSAlthough recently there have been many reports on the in-situ structural characterization of hydrogen storage alloys, these studies were all conducted under equilibrium states. In practice, however, hydrogen storage alloys alternate hydrogen absorption and desorption processes ceaselessly. Therefore, in functional situations where hydrogen storage alloys are utilized, their hydrogen absorption properties cannot be evaluated precisely by applying the results of observations made under equilibrium states.
We assessed the hydrogen absorption behavior and phase transformation of LaNi5 during the hydrogen absorption process using our newly developed time-resolved in-situ XRD system for vapor-solid phase reaction. This system, which comprises a chamber for performing in-situ XRD measurements, a Sieverts' component for measuring hydrogenation speed, and a PSPC (position-sensitive proportional counter) X-ray detector, enables sequential XRD measurement in an in-situ atmosphere. Over a period of several minutes, we observed the phase transformation of the master alloy of LaNi5 into a hydride of LaNi5H6 during the hydrogen absorption process and evaluated the process sequentially at intervals of a few seconds.
Our results showed that the actual phase transformation during the process of hydrogen storage differs from what had been characterized previously under an equilibrium state. It was also made clear that the lattice volume of the hydride produced remains unchanged between the onset of hydride formation and attainment of the equilibrium state.
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Hideo Mano, Satoru Kondo, Toru Imura, Akihito Matsumuro2005 Volume 69 Issue 2 Pages 213-216
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSThe shot peening process produces a nanocrystalline layer on the surface of carbon steel. This nanocrystalline surface layer is harder than the matrix phase. Therefore, there are expectations that this nanocrystalline layer could become a new solution for surface hardening. However, little information exists on the effect this nanocrystalline surface layer has on fatigue properties. In this study, coil springs prepared with this nanocrystalline surface layer were investigated and were compared with springs of the same physical properties without this nanocrystalline surface layer.
Coil springs were made from oil-tempered steel wire with chemical composition of 0.6C, 1.4Si, 0.7Mn and 0.7Cr(mass%) and were formed into compressive coil springs. Two types of springs were manufactured using different shot peening conditions. These springs had the same surface hardness and residual stress destruction, one with a nanocrystalline surface layer, and the other without.
Fatigue testing was carried out on a spring fatigue test machine operated over 5×107 cycles. This test method has the merit of reproducing almost exactly the actual working condition of the valve springs. The results of the fatigue test showed that the spring with a nanocrystalline layer had a fatigue limit of τm±τa=600±531 MPa at 107 cycles, whereas the other spring had a limit of τm±τa=600±489 MPa. Thus, it was evident that this nanocrystalline surface layer could increase the fatigue life by 8%.
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Emiko Gotoh, Yoshimitsu Okazaki2005 Volume 69 Issue 2 Pages 217-220
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSThe effects of V and Ni concentration on the activation of mouse macrophage-like J774.1 cells was investigated. High-purity V and Ni powder were immersed in the RPMI culture medium containing 10% fetal bovine serum. After completely removing the metal powder, the RPMI culture medium was diluted with a fresh medium to change the metal concentration. Macrophage-like J774.1 cells (initial number: 1.0×106 cells) were cultured in the RPMI medium containing various V and Ni concentrations at 24, 48, 72 and 96 h in an incubator. The morphology of macrophage-like J774.1 cells and their relative growth ratio was examined. After removing the cells, the concentration of nitric oxide (NO) in the RPMI medium, which was produced following the activation of macrophages, was also measured. Lipopolysaccharide (LPS), a macrophage activator, was used as the positive control. The effect of V ions on the relative growth ratio of macrophage-like J774.1 cells was slightly milder than that on mouse fibroblast L929 and mouse osteoblastic MC3T3-E1 cells, while Ni ions had a more pronounced effect. The rate of increase for the NO concentration per cell in the medium containing V ions increased at a low concentration of metal compared with that in the medium containing Ni ions. The V and Ni ions possessed a certain macrophage activation ability, although lower than that of LPS.
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Kenichi Nakajima, Tetsuya Nagasaka, Kohmei Halada, Kiyoshi Ijima2005 Volume 69 Issue 2 Pages 221-224
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSLCA (life cycle assessment) is an environmental evaluation tool for a product system based on life cycle thinking. After ISO14040 established in 1997, seven years have passed, and LCA has begun to be use in business. However, it is difficult to evaluate an open-loop recycling system or a system which produces several kinds of products. It seems to be a cause that a conventional LCA is an evaluation tool for a product system with single function unit. In this study, a new LCA method for a system with multi-function units was developed, which was based on matrix LCA method.
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Naoki Okamoto, Tohru Watanabe2005 Volume 69 Issue 2 Pages 225-228
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSAdhesive properties and microstructures of various substitution-deposited films to Cu substrates were investigated in detail. The adhesive strength of Au, Ag and Pd thin films which were substitution-deposited on the copper foils were evaluated by adhesive tape test, while their structures and surface morphologies were analyzed by using SEM, GD-OES and TEM. Results show that the different combinations of the electrodeposited films and substrates reveal the different interface adhesive feature. Typically showing a strong adhesion in Au film/Cu substrate and Pd film/Cu substrate, but a weak adhesion presents in Ag film/Cu substrate. The morphology of initial deposited Au film was strongly related to crystallographic structure of Cu substrate. However, the morphology of initial deposited Ag film was not related to crystallographic structure of Cu substrate.
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Hitoshi Izuno, Tadaharu Yokokawa, Hiroshi Harada2005 Volume 69 Issue 2 Pages 229-232
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSA new creep constitutive equation for Ni-base superalloys under high temperature-low stress condition was proposed previously. This creep curve had good reproducibility of the creep behavior under the condition of 1100°C/137 MPa. In this paper, an improvement of this creep constitutive equation is reported; in particular, to achieve better regression at the early secondary creep stage with a logarithmic function. The refined creep constitutive equation was fitted to the same creep curves that had been with the previous equation and an improved regression was obtained. The new creep curve gives very good estimations especially for creep ratios of all creep stages. The result of multi regression with composition for an additional parameter, due to the improvement, is also reported.
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Atsushi Kadowaki, You Tsukayama, Yoshihito Matsumura, Yoshitake Nishi2005 Volume 69 Issue 2 Pages 233-236
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSSmFe2.2 alloy thin films were prepared by DC magnetron sputtering process at different substrate temperatures from 323 to 623 K. High values of magnetostrictive suseptibility were obtained for Sm-Fe2.2 amorphous alloy thin films, when substrates were heated at the temperature from 473 to 523 K. The magnetostrictive susceptibility was strongly affected by morphology changes of film. On the other hand, heating above 623 K formed crystalline phases with low magnetostriction in amorphous structure phase. Based on the results, we concluded that the decrease in volume fraction of amorphous phase decreased the magnetostriction.
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Yuya Yamada, Yusuke Ariyama, Hiromitsu Ino, Kohmei Halada2005 Volume 69 Issue 2 Pages 237-240
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSAutomobile industry aims breakaway from oil system fuel vehicle, and develops hybrid, electric, and fuel cell vehicles for reduction of green house gas emissions. This report assessed the energy consumption and CO2 emission for a fuel cell vehicle (FCV) in comparison with compressed natural gas vehicle (CNGV) and gasoline vehicle (GV) by LCA. In FCV, the stage of fuel manufacture accounts for a large part of life cycle, together with that of membrane production. In GV and CNGV, the stage of running accounts for a large part of life cycle. The total CO2 emission of life cycle for FCV is 36 percent smaller than those of GV and CNGV, whereas the total energy consumption of FCV is 35 percent larger than those of the others.
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Toshiharu Kobayashi, Yutaka Koizumi, Hiroshi Harada, Tadaharu Yokokawa ...2005 Volume 69 Issue 2 Pages 241-244
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSThe relationships between the microstructure and the amount of alloying elements, Ru, Ta and Nb, in the 5th generation Ni-base single crystal superalloy TMS-173 (TMS-138++), which was developed by the authors, were investigated. TMS-173 was employed as the master alloy and three types of alloys were produced; one with 1 mass%Ru, another with a reduction of 0.6 mass%Ta and an addition of 0.5 mass%Nb, and another with a reduction of 0.4 mass%Ta. Using these alloys, the effects of the alloying elements on microstructure and the creep strength were investigated.
Under 900°C-392 MPa creep test condition, all three alloys had longer rupture lives than the master alloy TMS-173. In particular, the alloy with 0.4 mass% reduction in Ta content exhibited an increase of approximately 35%, and under 1100°C-137 MPa condition, the alloy with a reduction of 0.6 mass%Ta and an addition of 0.5 mass%Nb exhibited approximately 50% increase in the creep rupture life. From the microstructural analysis, it is suggested that the increased creep strength at 900°C was achieved because the precipitation of TCP phases was inhibited through the increased microstructural stability, and the creep strength at 1100°C was governed mainly by the spacing of γ/γ′ interfacial dislocation network.
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Toshiharu Kobayashi, Yutaka Koizumi, Hiroshi Harada, Atsushi Sato, Mak ...2005 Volume 69 Issue 2 Pages 245-248
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSThe expansion of the creep database for commercial Ni-base single crystal superalloys has been started at National Institute for Materials Science (NIMS). Presented in this report are, PWA1480 and PWA1484, a 1st generation and a 2nd generation single crystal superalloy respectively, which were developed by Pratt & Whitney, one of the largest aircraft engine manufacturers in the world. In this investigation, samples were heat treated in accordance with the literature on the alloy development, and creep tests were carried out at 800°C-735 MPa, 900°C-392 MPa, 1000°C-245 MPa, 1100°C-137 MPa, and 1150°C-137 MPa. Microstructural observations were carried out prior to and after the creep tests. PWA1484 was confirmed to have longer creep rupture lives than PWA1480 under all creep test conditions. However, at low temperature-high stress conditions, e.g. 800°C-735 MPa, large elongations were observed in PWA1484 during the primary creep stage, thus PWA1480 was found to be superior with respect to the time to 1% creep deformation. Furthermore, after the creep test at 1100°C-137 MPa, TCP phase precipitates of a plate-like morphology were observed in the microstructure of PWA1484. For the application of this alloy in components with a long expected service life, careful examinations will be required because of the TCP phase precipitation that leads to a decrease in strength.
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Kyoko Kawagishi, Atsushi Sato, Toshiharu Kobayashi, Hiroshi Harada2005 Volume 69 Issue 2 Pages 249-252
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSThe 4th generation Ni-base single crystal superalloys, which contain large amounts of refractory metals for strengthening and platinum group metals, e.g., Ru, for TCP-phase prevention, show excellent high-temperature strengths. However, these alloying elements seem to decrease high-temperature oxidation resistance, and the improvement of high-temperature oxidation resistance is one of the important issues for practical use of these superalloys.
In this study, Ni-base superalloys with various amounts of Hf, Ta, Re and Ru were examined in isothermal and cyclic exposures at 1100°C to investigate the effect on the oxide growth rate and resistance to scale spallation. Structures of the oxide for the alloys were analyzed by XRD and SEM, and it is clarified that the existence of Hf and Ta contributes to the improvement of adhesiveness between the oxide and the matrix.
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Atsushi Sato, Takao Murakumo, Yutaka Koizumi, Toshiharu Kobayashi, Tad ...2005 Volume 69 Issue 2 Pages 253-256
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSThe addition of ruthenium can control Topologically Close Packed (TCP) phases precipitation in nickel-base superalloys. Thus it becomes possible to add more solid solution strengthening elements such as molybdenum or rhenium. 4th generation nickel-base single crystal (SC) superalloys, with platinum group metals (PGMs) elements such as ruthenium, show superior creep strengths, although the change in the TCP phases crystallography or compositions have not yet been reported.
This study was carried out based on a 3rd generation nickel-base SC superalloy, TMS-121, which contains 5 mass pct rhenium and is known to precipitate TCP phases; a series of alloys with different amounts of ruthenium addition to TMS-121, TMS-138 and TMS-138+, were cast and heat treated in a variety of time and temperature conditions. TEM microstructural observations at different aging time and temperatures showed that, R phase, which is the most harmful phase in TCP phases with large amounts of γ′envelope, disappeared by the addition of ruthenium. It was also found that 2 mass% ruthenium addition increased the solubility limit of multi-phase nickel-base superalloys by about 7-8%.
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Takashi Yamada, Shigeo Asai2005 Volume 69 Issue 2 Pages 257-262
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSA new fabrication method of composite films by use of an electrodeposition under a high magnetic field is proposed here. This method enables dispersed particles in a matrix film to distribute in a honeycomb pattern or align along the grooves scratched on a cathode, which is not available in conventional composite plating methods. That is, this tailor-made film provides a new function in composite materials. The formations of various distribution patterns attribute to the micro-eddy generated in the vicinity of a particle or the scratched portion on a cathode by Lorentz force caused by a distorted electrolytic current and an applied magnetic field. The flow of the micro-eddy aligns the particles to be embedded in electrodeposits in a particular pattern. It is noticed that the imposition of a high magnetic field enhances Lorentz force to induce the appreciable micro-eddy in the electrolytic solution even under a small distorted electrolytic current.
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Shumpei Ozawa, Tetsuichi Motegi, Kazuhiko Kuribayashi2005 Volume 69 Issue 2 Pages 263-266
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSAl-In alloys with monotectic and hyper-monotectic compositions were produced by vertical Ohno Continuous Casting (OCC) technique. The resultant alloys had a diameter of 8 mm and a length of 400 mm. A very beautiful surface and a unidirectional macrostructure were obtained by controlling the mold temperature and solidification velocity regardless of the alloy compositions. Even in the hyper-monotectic composition samples the Al-In alloys exhibited a good distribution of β-In particles throughout all sections without any segregation of β-In phase. The morphology of the microstructure depended on the growth velocity and temperature gradient of the melt.
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Hisao Kikugawa, Takashi Asaka2005 Volume 69 Issue 2 Pages 267-271
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSTo precisely determine the mechanical properties of a bone, the effects of the preservation method on its mechanical properties need to be minimized. It seems likely that prolonged exposure to formalin (formaldehyde solution) will have some affect the mechanical properties of bone. This study investigated the effect of the formalin fixation method on the bending properties and fracture toughness of bovine cortical bone after short-term and relatively long-term preservation. To determine the elements and the quantities eluted from bone into formalin solution (the preservation medium), qualitative and quantitative analyses were performed by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Formalin fixation augments the bending stiffness of the cortical bone while diminishing its fracture toughness. As the bending strength diminishes concurrently with removal of Ca2+, this implies that inorganic components of bone contribute to its bending strength.
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Toshiharu Kobayashi, Yutaka Koizumi, Tadaharu Yokokawa, Makoto Osawa, ...2005 Volume 69 Issue 2 Pages 272-275
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSAdvanced high-temperature strengths in Ni-base single crystal (SC) superalloys have been achieved through the addition of Re in small amounts. However, Re has a strong tendency to form topologically close-packed (TCP) phases that decrease the creep strength, thus, increasing the Re content has undesirable consequences. This effect of Re addition is controlled in 4th generation superalloys where the formation of TCP phases is avoided by the addition of platinum-group metals (PGMs) such as Ru and Ir, and increased creep strengths have been achieved. Furthermore, PGM elements and solution strengthening elements including Re have been added in 5th generation superalloys to achieve superior high temperature strength. However, because Re is an expensive element and longer homogenization time is required for high-Re alloys, the use of this alloying element results in higher material and production cost, and lower productivity.
In this paper, a new type of Ni-base single crystal superalloy is proposed. This alloy does not contain Re but still reaches the high temperature capabilities of 4th and 5th generation superalloys, and has the advantages of low material cost and easy heat treatment. 1st generation single crystal superalloys do not contain Re, therefore, these are suitable material to be used as the master alloy for this alloy development. TMS-26, which was developed through High Temperature Materials 21 Project, NIMS, was used as the master alloy and, by the addition of Mo and Ru, a new single crystal superalloy TMS-174 was developed. Mo has the effect of controlling the lattice misfit and solid solution strengthening. Mo also promotes TCP formation, however this is avoided by the addition of Ru. The creep rupture life of TMS-174 at 900°C and 392 MPa was slightly shorter than that of TMS-138, which is a conventional 4th generation single-crystal superalloy with 5 mass%Ru. However, at 1100°C and 137 MPa, creep rupture life of TMS-174 was found to be 18% longer compared to TMS-138. This new alloy development strategy of adding solid solution strengthening elements and PGM elements to form non-Re containing superalloys was demonstrated to be successful. This strategy has the potential for superior alloy developments in the future because of the benefits of cost reduction and attainable material properties that are comparable to 4th and 5th generation superalloys.
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Sumiko Sanuki, Nobuaki Kita2005 Volume 69 Issue 2 Pages 276-282
Published: 2005
Released on J-STAGE: October 12, 2005
JOURNAL FREE ACCESSIn order to elucidate the role of formic acid (HCOOH) during the photocatalytic reduction of Se(IV) and Se(VI) ions, the amount of HCOOH consumed and the resultant CO2 gas generated were quantitatively determined in the presence and absence of oxygen. Also the various factors affecting the oxidation of formic acid were investigated. The principal findings are as follows: Photocatalytic reduction of Se ions under N2 gas bubbling conditions requires the sacrificial oxidation of HCOOH. Photocatalytic reduction of Se ions was suppressed by air bubbling; conversely, oxidation of HCOOH was slightly enhanced. The product of the oxidation of HCOOH was identified as CO2. The amount of HCOOH is stoichiometrically equal to the amount of Se ions reduced to H2Se. UV irradiation was more efficient in reducing Se(VI) to Se° than in reducing Se° to H2Se.
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