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Volume 69, Issue 1
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[in Japanese]2005 Volume 69 Issue 1 Pages 1
Published: 2005
Released on J-STAGE: September 06, 2005
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Norio Yamaguchi, Kunihiko Wada, Hideaki Matsubara2005 Volume 69 Issue 1 Pages 2-5
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSYttria-stabilized zirconia (YSZ) layers were prepared by electron beam physical vapor deposition (EB-PVD) in order to investigate the formation mechanism of columnar and feather-like structure. Substrate rotation caused a drastic change in morphology and porosity of the YSZ layers. The layer deposited on a stationary substrate comprised relatively dense-packed columnar grains. The layers deposited on rotated substrates consisted of columnar grains separated by submicron gaps. These columnar grains contained well-developed feather-like structures with nano-scale gaps and pores. The flux shadowing effect, which was understood as an interruption of vapor flux incident obliquely to crystal growth orientation during substrate rotation, was the origin of the columnar and feather-like structure formation by EB-PVD. Mechanism of porous structure in the EB-PVD layers can be classified into three types, in relation to competitive growth of columnar grains, substrate rotation and rotation speed.
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Kunihiko Wada, Norio Yamaguchi, Hideaki Matsubara2005 Volume 69 Issue 1 Pages 6-11
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSCrystallographic orientation of columnar structure in yttria-stabilized zirconia (YSZ) layers produced by electron beam physical vapor deposition (EB-PVD) is an important aspect to develop nanostructure-controlled thermal barrier coatings (TBCs). Several specimens were produced by EB-PVD on a rotating sample holder whose horizontal axis is normal to the vapor plume axis. The developments of the out-of-plane and in-plane crystallographic orientations in the YSZ layers were investigated by using XRD pole figure analysis. <100>-oriented columns were developed perpendicular to the YSZ layer/bond layer interface. This out-of-plane orientation rapidly grew and was completed in the early stage of the deposition. On the other hand, a twisted zone in which in-plane <100> direction differed at about 10° from the direction of the substrate rotation axis during deposition was formed up to 60 μm from the interface. Well-aligned in-plane <100> orientation along the substrate rotation axis was observed directly above the twisted zone. Processing parameters, such as substrate rotation speeds or deposition temperatures, affected the growth of the in-plane twisted zone. Raising the substrate rotation speed promoted the growth of the twisted zone and delayed the development of the in-plane orientation. In contrast, high deposition temperature accelerated the development of the in-plane orientation. Strain energy in the coating layer during deposition probably dominates the formation of the twisted zone.
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Teiichi Kimura, Rong Tu, Takashi Goto2005 Volume 69 Issue 1 Pages 12-16
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSNano-structure of YSZ films prepared by laser CVD (LCVD) was studied using TEM and SEM. LCVD-YSZ films had columnar structure which varied depending on deposition rates. The columnar grains had a significant (200) orientation. Each column with a diameter of 2~5 μm was constructed from sub-columns with 300-500 nm. At low deposition rates around 50 μm/h (14 nm/s), the sub-columns were almost single crystalline and pores of 20 nm in diameter were formed at column boundaries. At high deposition rates around 450 μm/h (125 nm/s), the sub-columns were polycrystalline, and many nano-pores of 1-5 nm were formed in the grain. The thermal conductivity decreased with increasing deposition rates; and the lowest value of 0.7 W/mK was obtained at 450 μm/h.
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Keisuke Eguchi, Heji Huang, Makoto Kambara, Toyonobu Yoshida2005 Volume 69 Issue 1 Pages 17-22
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSWe have developed a 300 kW level high power hybrid plasma spray system for developing next generation thermal barrier coatings. The system made it possible to melt large size YSZ powders up to 100 μm, and evaporate completely small YSZ powders less than 5 μm. The system enabled to realize both plasma powder spraying and thermal plasma physical vapor deposition (i.e. TP-PVD) of YSZ. In addition, an attempt was made to deposit composite coatings consisted of the flattened splats embedded in the PVD columnar structure by cyclic deposition with the two torches assigned for powder spraying and TP-PVD. It was found that such composite coatings could be deposited at the maximum rate of a few μm/s, and also that the structure largely depends upon the feeding rates and the size of YSZ powders, suggesting controllability of the spacing between splats as well as PVD structure by the system.
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Masato Suzuki, Satoshi Sodeoka, Takahiro Inoue2005 Volume 69 Issue 1 Pages 23-30
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSNano-dispersed α-Al2O3/YAG composite coatings were successfully obtained by atmospheric plasma spraying (APS) of the granulated Al2O3/Y2O3 powder and the post heat treatment. The as-sprayed coating was composed of an amorphous phase, metastable Y-Al-O solid solution. After the heat treatment about 1473 K, two crystalline phases, α-Al2O3 and YAG, precipitated. So that the fine dispersed α-Al2O3/YAG composite coatings were obtained. The sizes of the precipitates could be widely controlled by time and temperature of the post heat treatment. The diameter of both particles was varied from about 10 to 150 nm, depending on the heat treatment time.
It was found that crystallization of α-Al2O3 and YAG occurred during the heat treatment about 1218 K with huge volume shrinkage. Many cracks were formed in the coatings because of this volume shrinkage during the heat treatment. This affected the wear mechanism in Ball on Disk Test, and caused a fracture in the coatings heat-treated for 1-10 hr.
Plasma pre-heating of the substrate before and during the plasma spray process was carried out, in order to keep the substrate temperature about 1423 K for in-situ crystallization. The as-sprayed coating with plasma pre-heating was composed of crystallized α-Al2O3 and YAG particles without any cracks. Open porosity of this coating was maintained about 2-3% even after the heat treatment at 1473 K, while the open porosity of the APS coatings increased up to 8%. Anti wear property of the coatings with plasma pre-heating were highly superior to that of the APS coatings even after the heat treatments.
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Tadashi Serikawa, Momoko Henmi, Takashi Yamaguchi, Hideki Oginuma, Kat ...2005 Volume 69 Issue 1 Pages 31-35
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSMagnesium-silicon thin films are deposited on glass substrates by ion beam sputtering in employing the target composed of Mg and Si plates. Thin films consist of magnesium silicide (Mg2Si) intermetallics in the case of the target where the area ratio of Mg to Si is 50%:50%. Structural, mechanical, and electrical properties of the thin films are evaluated. The films show two-layers structures; the upper one consists of the crystalline Mg2Si with columnar structures and the lower shows amorphous structures. The elastic modulus and hardness of the amorphous layer are higher than those of the crystalline. The film indicates semiconducting properties where the resistivity decreases with increasing temperature. In this paper, the behavior in forming Mg2Si thin films, in particular Mg migration to surface and its evaporation from the film surface, is discussed in terms.
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Kazuhide Matsumoto, Yutaka Ishiwata, Yoshiyasu Itoh2005 Volume 69 Issue 1 Pages 36-42
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSIn general, 8 mass%Y2O3-ZrO2(8YSZ) coating materials are used as the top layer of thermal barrier coatings(TBCs). The development of hafnium oxide TBC was started in order to realize the high reliability and durability in comparison with 8YSZ, and the 7.5 mass%Y2O3-HfO2(7.5YSH) was selected for top coating layer. By the investigation of Electron Beam-Physical Vapor Deposition (EB-PVD) process, 7.5YSH top coating with about 200 μm thickness was formed. The 7.5YSH coating layer formed at substrate temperature of 956°C was composed of large solid columns aligned in the <200> and <311> direction of tetragonal crystallite. The thermal conductivity of 7.5YSH coating was lower than that of 8YSZ coating at temperature range of 1000°C~1300°C. From the result of sintering behavior obtained by heating test for 7.5YSH coating, it was recognized that the thermal durability for sintering behavior of 7.5YSH coating was improved up to about 100°C in comparison with 8YSZ coating.
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Mineaki Matsumoto, Norio Yamaguchi, Hideaki Matsubara2005 Volume 69 Issue 1 Pages 43-47
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSEffect of La2O3 addition on phase stability and thermal cycle life of Y2O3 stabilized ZrO2 (YSZ) coatings produced by EB-PVD was investigated. The developed coating showed low thermal conductivity even after high temperature exposure due to its high resistance to sintering. However, phase stability and thermal cycle life of the coating decreased as the amount of La2O3 was increased. Further experiments were necessary to optimize the amount of stabilizers (Y2O3, La2O3) in order to develop advanced thermal barrier coatings.
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Masakazu Okazaki, Hideaki Matsubara, Toyonobu Yoshida2005 Volume 69 Issue 1 Pages 48-55
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSElastic moduli of YSZ top coats for thermal barrier coatings(TBCs) were measured, where the top coats were fabricated by the following different types of methods: a traditional atmospheric plasma spraying(APS) method; a hybrid plasma spraying(HYPS) method that has been originally developed by Yoshida group; and an electron-beam physical vapor deposition(EB-PVD) process. The top coat material was ZrO2 stabilized by 8 mass%Y2O3. Through the work special attention was paid to investigate the effects of the processing methods, the process variables in APS and the long term thermal aging at high temperature. It was found that the advanced methods; HYPS and EB-PVD methods, could provide the top coat film with lower elastic moduli, that may have a beneficial effect to prevent the failures of TBCs induced by thermal stress. Some discussions were made for their low elastic moduli, based on the analysis of the microstructure of the top coats and the Eshelby's approach.
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Byung-Koog Jang, Masato Yoshiya, Hideaki Matsubara2005 Volume 69 Issue 1 Pages 56-60
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSThis work describes the experimental results of thermal conductivity and thermal diffusivity of the multi-layered ZrO2-4 mol%Y2O3 (YSZ) film to develop the low thermal conductive thermal barrier coating. YSZ films with 2~5 layers were deposited on zirconia substrates by Electron Beam-Physical Vapor Deposition (EB-PVD). The YSZ layers consist of porous-columnar grains containing nano-pores. It is noted that multi layers contain residual pores at interface between layers. Density and thermal diffusivity of the multi-layered YSZ film decreased with increasing the number of layers. Consequently, the thermal conductivity of films decreased with increasing the number of layers. The decrease of thermal conductivity in multi layers is caused by increase of total porosity due to increase of the layer-interface pores, resulting the increase of the phonon scattering.
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Masato Yoshiya, Hideaki Matsubara2005 Volume 69 Issue 1 Pages 61-66
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSThermal conductivitys of ZrO2 in various crystallographic directions were calculated using the perturbed molecular dynamics method. Anisotropic thermal conductivity is found at low temperature regardless of Y2O3 concentration. It is also found that pure ZrO2 and Y2O3 exhibit less anisotropic thermal conductivity at high temperature. Thermal conductivity increased in order of <100>, <110>, and <111>, while <112> is found to be smaller than <111>. The change in thermal conductivity is analyzed in terms of the density of O2- ions in an O-plane and its interplanar distance.
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Akio Shinmi, Makoto Hasegawa, Yutaka Kagawa, Masashi Kawamura, Takeshi ...2005 Volume 69 Issue 1 Pages 67-72
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSThe change of microstructure in an atmospheric plasma sprayed thermal barrier coating (APS-TBC) by isothermal heat exposure has been studied. Used 8 mass%Y2O3-ZrO2 TBC layer, a Ni-Co-Cr-Al-Y bond coat (BC) layer, and an IN738 superalloy substrate. The TBC system is subjected to heat exposure at 1423 K in ambient air for 10, 50, 100, 200, 300, and 400 h. Polished transverse sections of heat-exposed TBCs are examined and the changes of constitutes are discussed. Both sintering and cracking of the TBC layer are observed and these behaviors are strongly correlated with the morphology of as-sprayed intersplat boundaries and heat exposure time, respectively. A thermally grown oxide (TGO) layer is formed after heat exposure, and the thickness increases with the increase in heat exposure time. The chemical composition and morphology of the TGO layer depend on the heat exposure time. Micro-cracking in the TGO layer and TBC layer is observed after formation of a spinel, which is attributed to a lack of Al in the BC layer. The composition and phases in the BC layer are strongly correlated with the growth behavior of the TGO layer.
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Koichiro Kamiya, Hideyuki Murakami2005 Volume 69 Issue 1 Pages 73-79
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSHigh temperature oxidation resistance and the topcoat spallation lives of Ir-Hf coated and aluminized Ni-base superalloys are investigated in comparison to Pt coated and aluminized ones. An Ir-Hf binary alloy, proposed as a novel metallic bond coat material, was coated on a Ni-base single crystal superalloy TMS-82+ using electron beam physical vapor deposition followed by a conventional Al pack cementation process. Although cyclic oxidation tests revealed that these Ir-Hf coated and aluminized specimens did not exhibit as good oxidation resistance as the Pt coated and aluminized specimens, formation of TCP phases in the substrate is suppressed by the presence of the Ir-Hf enriched layer. On the other hand, thermal cyclic tests for YSZ coated specimens revealed that Ir-Hf coated and aluminized specimens showed better adhesion to the ceramic top coat layer and demonstrated a longer spallation life than Pt-coated and aluminized specimens, which can be explained by the formation of Al2O3 and HfO2 two-phase structure in the TGO layer. These results indicated that the Ir-Hf alloy system is promising as a new metallic bond coat material for high temperature structural materials.
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Yasuo Matsunaga, Kenichi Mashino, Yasuhiro Shigegaki, Takahito Araki, ...2005 Volume 69 Issue 1 Pages 80-85
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSThe thermally grown oxide (TGO) growth between bond coating and ceramic top coating during high temperature operation causes the spallation of thermal barrier coating (TBC). To improve the oxidation resistance of bond coating, a thin alumina layer was forwed by electron beam physical vapor deposition (EB-PVD) method. The microstructure and the high temperature oxidation behavior were investigated. The EB-PVD alumina layer on CoNiCrAlY bond coating showed an amorphous structure, and the alumina layer was transformed to an alpha alumina after heat treatment at 1323 K for 7.2 ks. During the high temperature oxidation test in air at 1373 K, the TGO growth on the CoNiCrAlY bond coating was suppressed by the application of alpha alumina layer. The existence of yttria stabilized zirconia (YSZ) top coating did not affect on the oxidation rate of the bond coating. The oxidation rate suppression by alumina layer deposition was also performed on the TBC specimen.
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Takeo Sasaki, Teruyasu Mizoguchi, Katsuyuki Matsunaga, Shingo Tanaka, ...2005 Volume 69 Issue 1 Pages 86-89
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSHigh-resolution transmission electron microscopy (HRTEM) observation was performed for a Cu/Al2O3(0001) interface fabricated by a pulsed laser deposition method to investigate the orientation relationship and atomic structure. The interface electronic structure was studied by nano-probe electron energy loss spectroscopy (EELS), and the obtained electron energy loss near edge structure (ELNES) was analyzed by the first-principles calculations. It was found that Cu was epitaxially oriented to the Al2O3(0001) surface, and the following orientation relationship was observed: (111)Cu//(0001)Al2O3, [110]Cu//[1100]Al2O3. The experimental O-K ELNES exhibited a shoulder before the main peak, which was consistent with the theoretical spectrum for the interface. The shoulder is thought to originate from the Cu-O interaction across the interface.
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Yoshihiko Hangai, Nobuhiro Yoshikawa, S. V. Dmitriev, Masanori Kohyama ...2005 Volume 69 Issue 1 Pages 90-95
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSWe propose a multiscale model for what consists of ab initio calculation, molecular dynamics simulation and a quasicontinuum model. First, we develop the interatomic interaction of the Cu/Al2O3 interface which is reproduced on the basis of the results of rigid tensile tests of ab initio calculations. Next, we analyze the Cu/Al2O3 interface via a quasicontinuum model, using the interlayer potential identified above. The quasicontinuum model 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, so that the computational time is significantly decreased. The atomistic-scale Cu/Al2O3 interface is investigated to determine the versatility of the quasicontinuum model. Relaxation simulations of the Cu/Al2O3 interface are carried out for both “large-scale analysis” and “small-scale analysis” via a quasicontinuum model. The influence of misfit in small-scale analysis is found to be much larger than the large-scale analysis upon comparing the displacement of atoms. We conclude that the results of the atomistic simulations with different sizes of the analytical region are strongly affected by the mechanical boundary conditions, and to obtain the accurate mechanical properties of interface, it is necessary to calculate with real size we subject of. The quasicontinuum method has great potential to realize an atomistic-continuum multiscale simulation.
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Toshikazu Akahori, Mitsuo Niinomi, Masaaki Harada, Junji Takeda, Hiroy ...2005 Volume 69 Issue 1 Pages 96-102
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSTi-29Nb-13Zr-2Cr, Ti-29Nb-15Zr-1.5Fe, Ti-29Nb-10Zr-0.5Si, Ti-29Nb-10Zr-0.5Cr-0.5Fe and Ti-29Nb-18Zr-2Cr-0.5Si were newly designed for dental applications. These alloys were designed based on Ti-29Nb-13Ta-4.6Zr (TNTZ), replacing relatively high melting point element, Ta, with beta stabilizing elements such as Cr, Fe and Si, which would lower the melting point of the alloy. Their melting points, mechanical properties, and cytotoxicity were investigated in this study. The following results were obtained.
Melting points of designed alloys decrease about 50 to 370 K as compared with that of TNTZ, and Ti-29Nb-13Zr-2Cr has the lowest melting point around 2050 K.
Vickers hardness of the surface of each designed alloy cast into modified magnesia based investment material is in the range of 400HV to 500HV, which is lower than that of TNTZ (around 560HV).
Balances of the strength and the ductility of Ti-29Nb-13Zr-2Cr, Ti-29Nb-15Zr-1.5Fe and Ti-29Nb-10Zr-0.5Cr-0.5Fe are nearly equal to those of TNTZ.
Cell viability of each designed alloy is excellent.
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Tomiei Hori, Yoshinori Tsuchiya, Yoshinobu Ishii, Kiichi Hojou2005 Volume 69 Issue 1 Pages 103-107
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSWe conducted X-ray and neutron diffraction experiments and magnetic susceptibility measurements for γ-MnFe alloys with a small amount of Cu or Pt, and for γ-MnCu and γ-MnZn alloys. γ-(Mn1-xFex)0.95Cu0.05 alloy with x=0.26 around 10 K shows a face-centered orthorhombic structure with a=0.3681, b=0.3655 and c=0.3622 nm, and a non-collinear antiferromagnetic structure with μa=0 and μb/μc=0.62. With increasing temperature, orthorhombic-tetragonal with c/a>1 structural transition occurs at To(=125 K) and the tetragonal structure finally transforms to a cubic structure at Tt(=352 K), which is lower than the Néel temperature TN(=440 K). The γ-(Mn1-xFex)0.95Pt0.05 alloy with x=0.13 at 10 K also shows a similar structure with a=0.3745, b=0.3714 and c=0.3649 nm, which has a non-collinear antiferromagnetic structure with μa=0, μb=1.03 and μc=1.65 μB/(Mn or Fe) atom. However, the γ-Mn1-xCux alloy with x≤0.26 and γ-Mn1-xZnx alloy with x≤0.28 show a tetragonal structure with c/a<1 at low temperature.
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Hirokazu Ohno, Tetsumori Shinoda, Yoshihiro Oya-Seimiya2005 Volume 69 Issue 1 Pages 108-112
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSAt the interface between A15-phase layer and Nb solid-solution (NbS.S) region in a bulky Nb/Al composite, a layer of two-phase structure of Nb3Al plus NbS.S is formed when the composite is heated at 2073 K, whereas it is not formed when heated at 2023 K or less. The morphology and width of the two-phase structure layers are significantly influenced by the cooling rate from 2073 K and by the heating time at that temperature. These facts, as well as the theoretical consideration, suggests that the two-phase structure is formed during the cooling process from 2073 K. When cooled more slowly from 2073 K than a certain cooling rate, there observed anomalous growth of A15-phase, which is strongly correlated with formation of the two-phase structure. Most favorite performance of the bulky Nb/Al composite as the super-conducting material is obtained by cooling it at the slowest cooling rate after 1 h heating at 2073 K as far as the present study is concerned.
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Eishi Tanabe, Yasuyuki Kitano, Kazushi Yamada, Minehiro Miyamoto, Yosh ...2005 Volume 69 Issue 1 Pages 113-120
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSMicrostructures of graphite mechanically milled under a hydrogen gas or an argon gas atmosphere using zirconia balls as well as chromium steel balls were investigated. Using transmission electron microscopes, high-resolution transmission electron microscopy (HREM), selected area electron diffraction (SAD), electron energy loss spectroscopy (EELS) and energy dispersive X-ray analysis (EDS) were carried out to compare the microstructures. Hydrogen concentration reaches up to 7.4 mass% after 80 h milling under a hydrogen gas atmosphere using chromium steel balls and homogeneous distribution of iron nano crystals was observed. No significant difference was observed in microstructures of 80 h milled graphite under the different gas atmosphere using the balls of different materials. This suggests that the significant absorption of hydrogen into the mechanically milled graphite strongly relates to the iron nano crystals included there.
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Masaharu Michihashi, Takashi Araki, Yuichi Aoyagi, Akio Fuwa2005 Volume 69 Issue 1 Pages 121-126
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSIn this study, we have clarified the structural and electronic properties of Cl6Benzene onto Cu5(100) cluster using ab initio molecular orbital method. The results obtained in this study are as follows: (1) the result of Mulliken Charge analysis shows that a large number of electrons are transfered from the Cu cluster to the adsorbent, (2) with single-point calculation, transition state exists 4×10-2 nm away from the adsorption state and this potential energy curve is valid untile 5×10-2 nm away from the adsorption state, and. (3) Homo-1 and Homo-2 at adsorption state are resulted from orbital interaction between Cu5 cluster and Cl6Benzene due to this smallest cluster model.
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Shin-ichi Hasegawa, Hitoshi Yamaguchi, Katsura Yamada, Takeshi Kobayas ...2005 Volume 69 Issue 1 Pages 127-131
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSWe attempted a simple pretreating method consisting of solid-phase extraction using bonded silica gel with benzenesulfonic acid (SCX) as the solid-phase sorbent to determine trace elements in pure molybdenum samples by means of inductively coupled plasma mass spectrometry (ICP-MS). Molybdenum was anionized by adding hydrogen peroxide solution to a sample decomposed with acid, and separated from cation trace impurities that had been kept in the chemically bonded silica gel of the ion-exchange type. The target elements retained in the solid phase were eluent with a small amount of dilute nitric acid. In this method, some trace elements, such as Be, Al, Mg, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Cd, In, Tl, Pb and Bi were determined by ICP-MS using the eluate. The detection limit (3σ), as follows: Be:0.028, Al:2.64, Mg:1.99, Cr:0.20, Mn:0.13, Fe:3.85, Co:0.019, Ni:0.48, Cu:0.084, Zn:0.25, Ga:0.092, Cd:0.014, In:0.059, Tl:0.027, Pb:0.044 and Bi:0.012 ng/g(ppb).
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Atsushi Yamaguchi, Akio Furusawa, Kazuto Nishida, Hiroaki Iwanishi, Ta ...2005 Volume 69 Issue 1 Pages 132-138
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSIn order to investigate the use of Sn-8Zn-3Bi solder as a potential substitute for Sn-Pb solder, which has lower melting point than Sn-Ag family solder, we studied interfacial microstructure and mechanical properties of CSP joints with various thickness of Au and Ni plated on Cu pad compared with Cu pad. Joint strength and other mechanical properties were evaluated in relation to reflow peak temperature. The combination of Au plating thickness of 0.05 μm and reflow peak temperature of 498 K resulted in the best joint reliability both as soldered and after aging treatment. The joint had thin Ni3Sn4 type interfacial reaction layer that included Cu and Zn between the solder and the Ni plating. This interfacial microstructure caused to improve the joint strength.
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Atsushi Yamaguchi, Yuhei Yamashita, Akio Furusawa, Kazuto Nishida, Tak ...2005 Volume 69 Issue 1 Pages 139-146
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSThe lead-free soldering technology has been developed all over the world while IEEE RoHS prohibits the use of lead contained solder in 2006. Sn-Ag-Cu solder of which melting point is 219°C has the highest solder joints reliability of leadfree solder materials. This melting point is much higher than that of the conventional solder of 183°C. So reflow process for low heat-resistant components on Print Circuit Board needs lower melting point solder. Sn-Zn-Bi solder with low melting point of 197°C has a high barrier to apply to electric products due to lower reliability at high temperature, in high humidity and after reheating a joint comparing to conventional solder. Adding both bismuth and indium into Sn-Ag solder alloy is effective especially for decrease of melting point of Sn-Ag solder and Sn-Ag-Bi-In solder which had a melting point of 206°C was developed. In this paper, we mentioned design of the solder alloy and soldering properties of Sn-Ag-Bi-In to the point of appearance and microstructure of solder joints concerning about the influences of temperature, humidity and heat story on joints reliability. As the results a corrugated pattern appeared on the joint surface after 1000 cycles at -40°C/125°C and after 1000-hour at 85°C/85%RH. But the solder jont strength of Sn-Ag-Bi-In is comparable to that of Sn-Pb eutectic solder in each test. And no significant deterioration of Sn-Ag-Bi-In solder joint with heat story was also observed. Therefore we clarified the Sn-Ag-Bi-In solder had the same reliability as conventional solder and could be useful to expand the practical use of lead-free solder for a lot kinds of products.
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Koichiro Inoue, Nobuto Sasaki, Takashi Sasahira, Tohru Watanabe, Takes ...2005 Volume 69 Issue 1 Pages 147-151
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSAn Au-Co alloy with an extensive composition range was electrodeposited from a gold sulfite and cobalt sulfate mixture. The Au-Co alloy electrodeposits were analyzed by XRD and TEM and the relationship between the phase and thermal equilibrium diagrams was investigated. The Au-Co alloy electrodeposits formed a solid solution over an extensive composition range. It was also revealed that the composition of the electrodeposited Au-Co alloy was equal to that of the quenched phase at a high temperature, about 950°C.
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Noritaka Saito, Daiji Nakata, Ayumu Umemoto, Kunihiko Nakashima2005 Volume 69 Issue 1 Pages 152-158
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSThe effect of adding RE2O3 (RE=Y, Gd, Nd and La) on the liquidus temperature of 45.2MgO-54.8SiO2 (mol%) system has been measured by the hot-thermocouple method. Moreover, The effect of adding RE2O3 (RE=Y, Gd, Nd and La) on the viscosity of 45.2MgO-54.8SiO2 (mol%) melt has been measured with a rotating crucible viscometer. In addition, structural characterization of the quench vitreous samples was investigated by using IR spectra.
Liquidus temperature and viscosity decreased with increasing of RE2O3 content, depending on the ionic radius of adding rare-earth elements. A marked change was observed in the order of ionic radius from La to Y. These results indicate that RE2O3 behaves as a network modifier in RE2O3- (45.2MgO-54.8SiO2) melts. It is very likely that the RE2O3 with the larger ionic radius will modify the silicate networks more strongly.
The IR spectra indicated that the degree of polymerization of silicate anions in RE2O3-(45.2MgO-54.8SiO2) melts decreased with increasing RE2O3 content.
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Takuya Sakaguchi, Tomohisa Ueura, Yasuo Kogo, Shin Takeuchi, Naohiro I ...2005 Volume 69 Issue 1 Pages 159-163
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSTi-Ni shape memory alloy is one of the most promising materials among high damping alloys. Ti-Ni alloys show a transient damping peak due to martensitic transformation and an almost temperature independent damping in the martensitic phase. Since the transient damping peak is useless due to many limitations, we can utilize only the damping capacity of martensitic phase. In the present work, we doped hydrogen into a ternary Ti-Ni-Cu alloy, which is known to exhibit higher damping capacity than binary Ti-Ni alloy, to improve further the damping capacity. Ti50Ni25Cu25 alloy was produced by a lamination process from a high workability point of view. As a result of hydrogen doping, a new damping peak occurred at around 260 K. The temperature of damping peak was shifted with change in oscillation frequency. The activation energy (H) and relaxation time constant (τ0) of the damping peak were calculated according to the Arrhenius plot as H=57.5 kJ/mol. τ0=2.2×10-13 s. The damping capacity due to hydrogen doping increased with increasing hydrogen concentration up to 0.45 at% hydrogen showing tan φ=0.05, but thereafter decreased. On the other hand, the peak temperature increased monotonously with increasing hydrogen concentration, and the peak shape was broader than single Debye relaxation peak.
From these results, we conclude that this damping peak is not the Snoek peak but the Snoek-Koster peak possibly caused by hydrogen and dislocation interaction effect; G. Schoecks theory for Snoek-Koester peak may be applicable.
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Hiroyuki Kitagawa, Yoshinori Morisaki, Hiroyuki Ishibashi, Masaki Orih ...2005 Volume 69 Issue 1 Pages 164-169
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSPlastic deformation study of Bi2Te3-related materials was performed. The ingots were grown by the Bridgman method using the following source materials with the nominal compositions of Bi0.5Sb1.5Te3, Bi2Te2.85Se0.15 and Bi1.8Sb0.2Te2.85Se0.15. Disks were cut from the ingots, and then they were deformed by cold and hot-pressing under pulse-current heating. The crystal structures of the deformed samples were identified by X-ray diffraction. All diffraction peaks were assigned to Bi2Te3 structure and the diffraction patterns indicate that the surface and bottom of the samples were highly oriented in the hexagonal (00•l) plane. The Hall effect measurements show that carrier concentration of the samples is in the order of magnitude of 1025 m-3 at room temperature. The power factor for the samples after the hot-press deformation exceeded those for the original ingots. The results indicate that the hot press deformation can be expected to enhance thermoelectric properties of Bi2Te3-related materials.
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Hiroshi Hayakawa, Etsuo Akiba, Midori Gotho, Tatsuoki Kohno2005 Volume 69 Issue 1 Pages 170-178
Published: 2005
Released on J-STAGE: September 06, 2005
JOURNAL FREE ACCESSNew alloys of La-Mg-Ni (Ni/(La+Mg)=3~4) system absorb and desorb hydrogen at room temperature, and the hydrogen capacity is higher than conventional AB5-type alloys. The crystal structures of La0.7Mg0.3Ni2.5Co0.5 (alloy T1) and La0.75Mg0.25Ni3.0Co0.5 (alloy T2) were investigated using ICP, SEM-EDX and XRD. We found that the alloy T1 consisted of Ce2Ni7-type La3Mg(Ni, Co)14 and PuNi3-type La2Mg(Ni, Co)9 phases and that the alloy T2 consisted of Ce2Ni7-type La3Mg(Ni, Co)14 and Pr5Co19-type La4Mg(Ni, Co)19 phases. These alloys system has layered structure and shows polytypism that is originated from difference in stacking of some [CaCu5]-type layers and one [MgZn2]-type layer along c-axis. Crystal structure of La3Mg(Ni, Co)14 is hexagonal 2H-Ce2Ni7-type, a=0.5052(1) nm, c=2.4245(3) nm. La2Mg(Ni, Co)9 is trigonal 3R-PuNi3-type, a=0.5062(1) nm, c=2.4500(2) nm. La4Mg(Ni, Co)19 is 2H-Pr5Co19-type, a=0.5042(2) nm, c=3.2232(5) nm. In these all structure, La-La distance in the [CaCu5] layer was 0.38~0.40 nm but that in the [MgZn2] layer was 0.32 nm. It was also found that Mg occupied the La site in the [MgZn2] layer. Selective occupation of Mg at the La site in the [MgZn2] layer makes the alloy stable in repeated reaction cycles with hydrogen. This alloy system has formed an agent group is described by the general formula Lan+1MgNi5n+4 where n=0, 1, 2, 3, 4…….
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