MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Volume 50 , Issue 3
Showing 1-43 articles out of 43 articles from the selected issue
  • Masataka Hakamada, Mamoru Mabuchi
    2009 Volume 50 Issue 3 Pages 431-435
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: December 25, 2008
    JOURNALS FREE ACCESS
    Anodic polarization behaviors of Pd-M (M=Fe, Co, Ni) alloys in H2SO4 solution are investigated for the preparation of nanoporous palladium by dealloying. For Pd0.2Co0.8 alloy, the current monotonically increased with the increase in potential. However, anodic polarization curves for Pd0.2Fe0.8 and Pd0.2Ni0.8 alloys showed passive regions at high potentials, although the standard electrode potentials for Fe, Co, Ni are similar. As a result, nanoporous Pd was successfully fabricated via electrolysis under a constant potential (=+0.5 V vs standard calomel electrode) only when the starting alloy was Pd-Co. Passivation, as well as standard electrode potentials, must be considered for the efficient production of nanoporous Pd. The preparation of nanoporous structure on the surface of bulk Pd was also demonstrated using alloying/dealloying process involving Co electrodeposition, thermal alloying and subsequent dealloying.
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  • Tomo Takeda, Yasuhide Shindo, Fumio Narita, Yuya Mito
    2009 Volume 50 Issue 3 Pages 436-445
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: January 21, 2009
    JOURNALS FREE ACCESS
    The purpose of this research is to experimentally and numerically evaluate the mechanical performance of carbon nanotube (CNT)-reinforced polymer composites subjected to tension in a cryogenic environment. Cryogenic tensile tests were conducted on CNT/polycarbonate composites to identify the effects of CNTs on their tensile properties. Finite element computations were also conducted using a model for the representative volume element (RVE) of CNT-reinforced composites in order to determine the effective composite elastic modulus and the stress state within the composites. The possible existence of the imperfect interface bonding between the CNT and the matrix was considered in the finite element model. The CNT properties used in the analysis were obtained by employing an analytical molecular structural mechanics model. The numerical findings were then correlated with the experimental results.
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  • Tatsuya Okada, Hiroshi Kinoshita, Minoru Tagami, Fukuji Inoko
    2009 Volume 50 Issue 3 Pages 446-452
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: January 21, 2009
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    In order to study the kind band (KB) formation and its effect on recrystallization in copper, single crystals and an asymmetric bicrystal in which the primary slip system had a Schmid factor of 0.5, were deformed in tension and subsequently annealed. Several indents were made on the surface of one of the single crystals to promote KB formation. In kink bands (KBs), slip systems on the critical slip plane were activated, which induced the rotation of KBs in the direction opposite to that of the deformation matrix (DM). The orientation difference between the DM and KB reached 20° to 25° at a nominal tensile strain of 0.4. The KBs in the bicrystal were about ten times broader than those in the single crystals. After annealing, recrystallized grains having twin-relationships one another formed in the bicrystal and the single crystal with indents. A comparison was made with aluminum single crystals and bicrystals of the same orientation.
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  • Kenichi Nakajima, Osamu Takeda, Takahiro Miki, Tetsuya Nagasaka
    2009 Volume 50 Issue 3 Pages 453-460
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: January 28, 2009
    JOURNALS FREE ACCESS
    Currently, several metals are commercially recycled from by-products and wastes by metallurgical processing. However, the metallurgical process has each characteristic, which causes limitation for resource recovery. The combinations of elements in secondary resources, such as by-products and wastes, are often different from those in natural resources. There are even combinations that are not present in natural resources. Conventional metallurgical processes have been optimized for economical and efficient extraction of desired elements only from large amount of ores under constant grade. Therefore, in order to extract metals from secondary resources by the conventional metallurgical process, it is necessary to estimate the recoverability of the constituent elements by taking into account their chemical properties well in advance. In particular, analysis for combination of elements is significantly important.
    In this study, we developed the evaluation method of metal resources recyclability based on thermodynamic analysis, and made clear the element distribution among gas, slag and metal phases during metal recovery based on thermodynamic analysis. In an application of the method shows that Cu, and precious metals (Ag, Au, Pt, Pd) present in mobile phones can be recovered as metals in the pyrometallurgy process of Cu in a converter, while Pb and Zn can be recovered as vapor. Other elements distributed in the slag phase are difficult to recover. The result of our analysis reflects the trends observed in the distribution of metals in copper metallurgy, thereby indicating the validity of our proposed evaluation method.
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  • Teiko Okazaki, Masamune Tanaka, Naoki Ogasawara, Yasubumi Furuya, Chih ...
    2009 Volume 50 Issue 3 Pages 461-466
    Published: March 01, 2009
    Released: February 25, 2009
    JOURNALS FREE ACCESS
    Giant magnetostrictive Fe-Pd and Fe-Ga alloys are promising as actuator/sensor materials with high respective velocity and stress created by magnetostriction. To apply them to a micro-gas valve, we developed magnetostrictive actuators, that is, Fe80Ga20/Ni and Fe70.4Pd29.6/Ni bimorph layers. These cantilever-type actuators can be bent by applying magnetic field parallel to length. An actuator point displaced about 300 μm under a low magnetic field of 37 kAm−1. Small and large actuators were applied to a micro-gas valve. The opening and closing action of a gas valve consisting of magnetostrictive bimorph layers can be controlled remotely by magnetic fields. Gas flow rate can be driven from 50 to 0 mL·min−1 by increasing the magnetic field to 40 kAm−1. The response time to the applied magnetic field is below 0.15 s.
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  • Ryuichi Suenaga, Alain Vautrin, Yoshitake Nishi
    2009 Volume 50 Issue 3 Pages 467-472
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: February 12, 2009
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    The influence of dipping in hot salt solution on water absorption in nylon6 composites with dispersed aluminum powders was investigated. Dipping in hot salt solution (3 mass%NaCl in distilled water) for 105 s at 373 K increased the overweight of composite samples, whereas the addition of aluminum with dispersed powders (A1-addition) from zero to 40 vol%Al decreased the overweigh of the sample. Based on the experiment results and kinetic analysis, aluminum powder dispersion in nylon6 decreased the saturated overweigh of composites at infinite time. Both hot salt dipping and Al addition increased the reaction index (n). The Al addition apparently increased the n value of composites with less than 20 vol%Al in salt solution, as well as with less than 30 vol%Al in distilled water. The A1 addition apparently increased the kinetic constant (k) at less than 20 vol%Al in hot salt solution. However, the Al addition decreased the k value of composites at more than 30 vol%Al in hot salt dipping, as same as that of the composites dipped in hot distilled water. Compared with dipping in distilled water, dipping in hot salt solution apparently decreased the saturated overweigh and remarkably increased both n and k values of nylon6 composites with 10 and 20 vol%Al. Since Electron Probe Micro Analyzer (EPMA) analysis could not clearly detect sodium (Na) in the nylon6 matrix, the reaction rate of nylon6 composites dipped in hot salt solution was probably dominated by an interface control process.
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  • Jae-hwa Lee, Takashi Fukuda, Tomoyuki Kakeshita
    2009 Volume 50 Issue 3 Pages 473-478
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: February 04, 2009
    JOURNALS FREE ACCESS
    We have investigated martensitic transformation behavior in a sensitized SUS304 austenitic stainless steel to know the stability of the austenitic phase at cryogenic temperatures. We found that the sensitized specimen exhibits an isothermal martensitic transformation when the specimen is held in the temperature range between 60 and 260 K. The time-temperature-transformation (TTT) diagram corresponding to the formation of 0.5 vol% of α′-martensite shows a double-C curve with two noses located at about 100 and 200 K. An in-situ optical microscope observation has revealed that the double C-curve is due to two different transformation sequences. That is, the upper part of the C-curve is attributed to the direct γ (fcc) → α′ (bcc) martensitic transformation and the lower part of the C-curve is due to the successive γ (fcc) → ε′ (hcp) → α′ (bcc) martensitic transformation. The direct γ→α′ transformation occurs in the vicinity of grain boundaries, while the successive γ→ε′→α′ transformation occurs near the center of each grain. The reason for appearing two types of isothermal transformation sequence in the sensitized SUS304 stainless steel will be due to the difference in concentration by sensitization heat-treatment.
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  • Takashi Hattori, Nana Fukamachi, Ryota Goto, Nobuki Tezuka, Satoshi Su ...
    2009 Volume 50 Issue 3 Pages 479-482
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: February 04, 2009
    JOURNALS FREE ACCESS
    In this investigation, we evaluated the microstructure of SC alloys using SEM, TEM and XRD. The composition of SC alloys was Nd14.4Fe79.6B6.0 and Nd10.4Dy3.5Fe80B6.1, and the SC alloys show petal-shape or dendritic structure at the wheel surface or the free surface, respectively. Grain size distribution is broad at the wheel surface and the microstructure is changed at the distance of around 50 μm from the wheel surface. XRD analyses are consistent with the results. Average interval of R-rich (R: rare earth) lamella structure in Nd10.4Dy3.5Fe80B6.1 and Nd14.4Fe79.6B6.0 SC alloys are 3.9 μm and 3.7 μm, respectively.
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  • Shun Fujieda, Asaya Fujita, Kazuaki Fukamichi
    2009 Volume 50 Issue 3 Pages 483-486
    Published: March 01, 2009
    Released: February 25, 2009
    JOURNALS FREE ACCESS
    The initial pressure shift of the Curie temperature Tc for the first-order transition, dTcdP, for La(Fe0.88Si0.12)13 becomes small after hydrogen absorption. In addition, the hydrogen absorption reduces the ratio of the volume change at Tc to the magnetization squared at Tc, Δω(Tc)⁄M(Tc)F2, suggesting the decrease of the magnetoelastic coupling constant κCmv. On the other hand, dTcdP is enhanced by the partial substitution of Ce for La in connection with the change of the band structure. Consequently, dTcdP of La0.7Ce0.3(Fe0.88Si0.12)13Hy is larger than that of La(Fe0.88Si0.12)13Hy in a wide change of Tc.
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  • Zhankui Zhao, Chuntao Chang, Akihiro Makino, Akira Okubo, Akihisa Inou ...
    2009 Volume 50 Issue 3 Pages 487-489
    Published: March 01, 2009
    Released: February 25, 2009
    JOURNALS FREE ACCESS
    Preparation of a soft magnetic Fe76Si9B10P5 glassy bulk material has been carried out by the spark plasma sintering (SPS) technique below the glass transition temperature. The glassy powders were consolidated into bulk forms with relative densities above 98.7% through sintering them at 740 K under a pressure of 600 MPa while the samples still keep a glassy state. These as-sintered samples with a diameter of 15 mm exhibited excellent soft magnetic characteristics, which is as good as that of the cast samples with a size of 2.5 mm.
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  • Sangmin Lee, Hidemi Kato, Akihiro Makino, Akihisa Inoue
    2009 Volume 50 Issue 3 Pages 490-493
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: February 12, 2009
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    (Fe0.72B0.24Nb0.04)95.5Y4.5 metallic glassy powders were fabricated with a gas-atomizing method and then densely consolidated by the spark plasma sintering (SPS) technique. Densification behavior during the SPS procedure enables us to understand the thermal behavior and viscous deformation profiles of glassy particles. The glassy powders were consolidated under various temperatures to determine the effect of applied stress on the viscous densification behavior. Consequently, viscous densification commenced under a preset stress of 600 MPa at a flow temperature of Tf=663 K, which is approximately 248 K lower than that under a stress of 32 kPa, as shown by thermo-mechanical analysis (TMA). Furthermore, even below Tg, SEM images demonstrated fine imprintability on the glassy powders during this stress-enhanced viscous densification.
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  • Yugo Takeda, Takahiro Kuriiwa, Atsunori Kamegawa, Masuo Okada
    2009 Volume 50 Issue 3 Pages 494-498
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: February 04, 2009
    JOURNALS FREE ACCESS
    In the present paper, the possibility of occurrence of HDDR (hydrogenation disproportionation desorption recombination) phenomena were studied in an Au-2 mass%Mg alloy. Cathodic hydrogen-charging at R.T. in the alloy resulted in causing disproportionation reaction which formed MgH2 embedded in an Au matrix. After the heat-treatment in vacuum for 4 h at 500°C, MgH2 decomposed into Mg and hydrogen. Mg resolved into Au matrix phase again. The original Au-Mg solid-solution alloys with size of 20–100 nm fine grains were obtained. This is the first observation of occurrence of HDDR phenomena in the Au-Mg alloys. The HDDR treated sample shows the slightly higher hardness in comparing with those of as-quenched samples.
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  • Toru Iwaki, Takahiro Kuriiwa, Atsunori Kamegawa, Hitoshi Takamura, Mas ...
    2009 Volume 50 Issue 3 Pages 499-505
    Published: March 01, 2009
    Released: February 25, 2009
    JOURNALS FREE ACCESS
    The present paper describes the grain size refinements of Cu-3 mass%Ti alloys by hydrogen heat-treatment of so-called Hydrogenation-Disproportionation-Desorption-Recombination (HDDR) process. During hydrogenation process, the disproportionation reaction occurred with forming of Ti hydrides in the alloy. With decomposition of Ti hydrides by the subsequent desorption process, Ti resolved into Cu matrix. In consequence, the original solid solution phase of the alloys formed. This means that the HDDR phenomena could take place in the Cu-3 mass%Ti alloy. The grain size of the alloy is found to be about 20–50 nm after HDDR treatments such as hydrogenation treatment at 350°C under hydrogen pressure of 7.5 MPa for 48 h, followed by the hydrogen desorption treatment at 530°C for 4 h in vacuum. On the other hand, it is found that remarkable simultaneous improvements of mechanical strength of 1100 MPa and electrical properties of 21%IACS are obtained in the hydrogenated alloy.
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  • Hiroo Takahashi, Hitoshi Takamura
    2009 Volume 50 Issue 3 Pages 506-508
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: February 12, 2009
    JOURNALS FREE ACCESS
    An oxygen permeable membrane based on mixed oxide-ion and electronic conduction is a promising material for hydrogen production from methane at high temperatures. To increase an oxygen permeation flux, decreasing in thickness is required. In this study, integrated oxygen permeable membranes supported on a porous layer was prepared by partial reduction of dense composite materials. The dense samples of (ZrO2-3 mol%Y2O3)-x vol%NiFe2O4 (x=33,40,50) were prepared by sintering at 1400°C under air for 5 h. The one side of the sample was reduced at a temperature range of 800 to 1000°C under Ar-5%H2. The microstructure and oxygen flux density were analyzed by using a scanning electron microscopy and a quadrupole mass spectroscopy, respectively. An integrated oxygen permeable membrane of (ZrO2-3 mol%Y2O3)-50 vol%NiFe2O4 having a dense layer of 200 μm and a porous layer of 300 μm was successfully prepared. The oxygen flux density of the membrane was found to be 4.3–7.4×10−7 mol·cm−2·s−1.
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  • Yuichiro Koike, Wang-Jae Chun, Kaoru Ijima, Shushi Suzuki, Kiyotaka As ...
    2009 Volume 50 Issue 3 Pages 509-515
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: February 12, 2009
    JOURNALS FREE ACCESS
    Metal–oxide surface interaction is important in catalysis. We have studied Ni on TiO2 (110) and Al2O3 (0001) by means of polarization-dependent total-reflection fluorescence extended X-ray absorption fine structure (PTRF-EXAFS) observations to elucidate the origin of metal–oxide interactions. Ni atoms interact with the dangling bond of the oxygen atoms. The Ni atoms are positively charged and bonded with more than two oxygen atoms.
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  • Kenji Sumiyama, Atsushi Monden, Ryoji Katoh, Naokage Tanaka, Dong-Lian ...
    2009 Volume 50 Issue 3 Pages 516-522
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: February 18, 2009
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    Fe and Ni clusters have been simultaneously deposited on substrates using an improved plasma-gas-condensation cluster deposition apparatus, and investigated by transmission electron microscopy, X-ray photoelectron spectroscopy and magnetometry. In these Fe/Ni cluster hybrids Fe and Ni clusters are randomly mixed, where bcc Fe and fcc Ni diffraction rings are detected, and their lattice constants are almost same as those of pure Fe and Ni metals. The peak positions of core-levels, Fe-2p3⁄2 and Ni-2p3⁄2 lines, of Fe/Ni cluster hybrids are similar to those of pure Fe and Ni clusters. Since Fe and Ni are miscible with each other in bulk, equilibrium and film specimens, no nano-scale heterogeneity can be attained by other methods. Therefore, present results demonstrate formation of novel Fe/Ni nano-hybrid materials.
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  • Naokage Tanaka, Subhajit Sarkar, Kenji Sumiyama, Dong-Liang Peng, Take ...
    2009 Volume 50 Issue 3 Pages 523-527
    Published: March 01, 2009
    Released: February 25, 2009
    JOURNALS FREE ACCESS
    Ti clusters have been prepared by a plasma-gas-condensation cluster deposition system (PGCCD) with controlling an Ar gas flow rate, RAr and a He gas flow rate, RHe, and observed by transmission electron microscopy (TEM) at their as-prepared and annealed states. In Ti clusters whose sizes are about 18 nm, an hcp phase is predominant in the as-prepared state, while TiOX crystallites are formed on the hcp phase cores after annealed at 623 K, revealing a core-shell morphology. In small Ti clusters whose sizes are about 10 nm, an fcc phase coexists with the TiOX phase in the as-prepared state, while the TiOX phase is predominant after annealed at 623 K, revealing no core-shell morphology. The electrical resistivity, ρ, of these cluster assemblies increases with decreasing temperature. After annealed at 623 K, the absolute ρ value of hcp Ti cluster assemblies increases remarkably while that of fcc cluster assemblies does not change so much. These results demonstrate the difference in the oxidation behaviors and morphologies between large and small Ti clusters.
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  • K. Kashihara, H. Inagaki
    2009 Volume 50 Issue 3 Pages 528-536
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: February 12, 2009
    JOURNALS FREE ACCESS
    Three types of specimens, namely solution treated, peak aged and overaged specimens, were prepared from hot-rolled sheets of a commercial 6061 aluminum alloy, so that they contain precipitates different in size and distribution. These specimens were cold rolled to 95% reduction in thickness and then annealed at 300°C. The rolling texture and work hardening rate during cold rolling differed, depending on the state of the precipitate. In particular, no increase in hardness during rolling was observed in the peak aged specimen. The recrystallizations in the overaged and solution treated specimens were completed more rapidly than that in the peak aged specimen. This is interpreted to be due to pinning effect caused by precipitation and difference in driving force of recrystallization. In the overaged specimen, the recrystallization texture revealed a strong {100} ⟨001⟩ orientation, which has the favored orientation relationship with deformed matrix. In the peak aged specimen, the recrystallization texture revealed a {110} ⟨111⟩ orientation. The {100} ⟨001⟩ orientation was also formed, however, the intensity relative to random orientation was much weaker than that observed in the peak aged specimen.
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  • Su-Hyeon Kim, Seung Zeon Han, Chang Joo Kim, In-Youb Hwang, Fuxing Yin
    2009 Volume 50 Issue 3 Pages 537-543
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: January 21, 2009
    JOURNALS FREE ACCESS
    The texture evolution of cold rolled tough pitch copper foils could be changed by altering the initial texture and microstructure before cold rolling. The development of β-fiber texture was substantially suppressed even after 92% reduction for the case of abnormally coarse initial grain structure and extremely strong initial cube texture. Instead, the intensity of cube and RD (rolling direction)-rotated cube texture components was increased continuously by increasing the intensity of the initial cube texture.
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  • Wei-Chih Chung, Leu-Wen Tsay, Chun Chen
    2009 Volume 50 Issue 3 Pages 544-550
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: January 21, 2009
    JOURNALS FREE ACCESS
    The microstructure and transformation behavior of Ti-4.5Al-3V-2Mo-2Fe alloy and its laser welds after various heat treatments were investigated. Notch properties, such as impact toughness and notched tensile strength, were also measured on the welds to choose an appropriate post-weld heat treatment (PWHT) of the alloy. The temperature regimes in which β transformed into α′, α″ or retained as β after quenching were identified and discussed. The results indicated that α″ could be obtained primarily by rapid quenching from 880∼840°C solution temperatures and was identified as a base-centered orthorhombic (centered on the C face) with the lattice parameters of a=0.305 nm, b=0.489 nm, and c=0.457 nm. The as-welded specimen exhibited fine acicular α in the β matrix with hardness considerably higher than the mill-annealed base metal. For a PWHT temperature lower than 800°C, the change in microstructure and hardness of the welds depended mainly on the temperature, not on the cooling rate. If the PWHT temperature was higher than 800°C, both the temperature and the cooling rate were important in altering microstructure and hardness of the welds. The welds after a 704°C/4 h treatment could prevent notch brittleness, reduce hardness variation in different regions of the weld, and obtain notch properties similar to the mill-annealed base metal.
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  • Kouji Tanaka, Yasuhiro Yogo, Koukichi Nakanishi, Carlos Capdevila
    2009 Volume 50 Issue 3 Pages 551-555
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: January 21, 2009
    JOURNALS FREE ACCESS
    The successive ferrite (α) + pearlite (P) transformations from austenite (γ) were modeled to predict the presence of bainite in as-forged medium-carbon manganese steels. The kinetics of diffusional transformations were calculated based on classical nucleation and growth theory coupled with CALPHAD multi-component thermodynamics. The description of the growth rate of proeutectoid-α includes a time dependence due to the carbon enrichment in the remaining γ. The γ/α interface was assumed to be in negligible-partitioned local equilibrium (NPLE). The kinetics calculation of P nucleating on the α surface was integrated into the α model. Given the transformation temperature range in continuous cooling, the growth rate of P was also expressed in the NPLE constraint for γ/cementite. The concentration of untransformed γ (γU) can be monitored and should be dependent on the extent of the preceding transformations. Thus, the energies available for the nucleation and diffusionless growth of bainitic-α were evaluated from the thermodynamics of the γU single-phase system, which is proposed as a method to predict the inclusion of bainite in the final α+P microstructure.
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  • Kouji Tanaka, Masashi Hara, Koukichi Nakanishi, Carlos Capdevila
    2009 Volume 50 Issue 3 Pages 556-561
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: January 28, 2009
    JOURNALS FREE ACCESS
    A theoretical model for the presence of bainite (B) in ferrite (α) + pearlite (P) microstructures was validated experimentally for commercial-grade medium-carbon manganese steels. The energies concerning the nucleation and growth of bainitic-α were used as the criteria for the B formation during the α+P transformations, which has been first applied to the changing composition of untransformed austenite (γU). Three steels were chosen to study the effect of Mn content on the B fraction at various cooling rates. To account for local variation of austenite grain size (d0), a log-normal distribution was employed. In this model, C enrichment in γU proceeds faster in smaller grains, and the shift to P or B transformation occurs in a specific temperature range. Calculations predicted the onset of B at around 603 K, with a fraction that increases with increasing cooling rate. In general, the agreement was good for all steels in terms of both calculated/observed kinetics and final α⁄PB fractions. Thus, the model provides a practical prediction of the critical cooling rate in order to avoid B in as-forged product.
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  • Jun Du, Kazuhiko Iwai
    2009 Volume 50 Issue 3 Pages 562-569
    Published: March 01, 2009
    Released: February 25, 2009
    JOURNALS FREE ACCESS
    The effect of application alternating current on the modification of primary Mg2Si crystals in the hypereutectic Mg-4.8 mass%Si alloy has been investigated in the present study. The liquidus and eutectic temperatures of the Mg-4.8 mass%Si alloy are 761°C and 638°C, respectively. An alternating current of 60 A with frequency of 1 kHz was applied into the hypereutectic Mg-Si melt from different starting temperatures (770, 740, 700 and 670°C) till 630°C. The results show that primary Mg2Si crystals could be refined effectively by application alternating current. The average sizes of primary Mg2Si crystals were decreased to almost a half after being subjected to the alternating current. The starting temperature of the application alternating current is a very significant factor to determine the size uniformity of the primary Mg2Si crystals, while it has no obvious effect on the average size of the primary Mg2Si crystals. The refined primary Mg2Si crystals have the lowest average size and the highest uniformity in sizes when the hypereutectic Mg-Si melt was treated by application alternating current from the starting temperature of 700°C.
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  • Motohiro Yuasa, Hiromi Nakano, Yoshiaki Nakamoto, Mamoru Mabuchi
    2009 Volume 50 Issue 3 Pages 570-578
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: January 28, 2009
    JOURNALS FREE ACCESS
    An electrodeposited Co-Cu alloy with a nanoscale lamellar structure was annealed at 673–973 K. The effects of annealing on the mechanical properties and the microstructures of the alloy such as the lamellar area ratio and the lamellar spacing were investigated. The Young’s modulus of the Co-Cu alloy increased by annealing. This is mainly due to a decrease in the lamellar area ratio. The as-deposited specimens exhibited a low value of the activation volume for plastic deformation; however, the activation volume was increased by annealing. This appears to be related to an increase in lamellar spacing caused by annealing. The origins of the lamellar spacing dependence of the activation volume are discussed from the viewpoint of the emission of dislocations from the lamellar boundary.
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  • Yosuke Tamura, Yusaku Kida, Ayumi Suzuki, Hiroshi Soda, Alexander McLe ...
    2009 Volume 50 Issue 3 Pages 579-587
    Published: March 01, 2009
    Released: February 25, 2009
    JOURNALS FREE ACCESS
    In the present study, the continuous and discontinuous precipitation behavior of the commercial AZ91 alloy containing manganese and the AZ91 alloy produced from high-purity elemental components with no manganese addition has been investigated. It was found that for the commercial alloy, the solute manganese segregated within the primary α-Mg dendrites during solidification and played a major role in the initiation of non-uniform distribution of β-precipitates within the matrix grains. In addition, the solute manganese significantly suppressed the growth of discontinuous (lamellar) precipitates. The high-purity alloy also exhibited non-uniform precipitation. However, the precipitation patterns differed from those observed in the commercial alloy due to the inhomogeneous distribution of aluminum, the origin of which was rooted in the solute segregation within the interdendritic regions of the solidification structure. These differences in the precipitation mode caused by the presence or absence of manganese influenced the age hardening of the alloys. The high-purity specimens aged at lower temperatures attained higher peak-hardness owing to greater area fractions of discontinuous precipitation cells.
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  • François O. Méar, Guoqiang Xie, Dmitri V. Louzguine-Luzg ...
    2009 Volume 50 Issue 3 Pages 588-591
    Published: March 01, 2009
    Released: February 25, 2009
    JOURNALS FREE ACCESS
    In the present study, we report the formation of the Mg-based bulk metallic glass (BMG) samples by spark plasma sintering of the amorphous powders prepared by ball-milling. The sintering was performed in the supercooled liquid region (TgTx) and fully glassy Mg-based samples were successfully sintered at 398 K. The deformation on the surface associated with Vickers indentation hardness tests of the compacts reveals the presence of the semi-circular shear-bands around the indents and also reveals inhomogeneous nature of plastic deformation.
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  • Yi-Yun Li, Wen-Hsiung Wang, Yung-Fu Hsu, You-Luen Chang, Shan Trong
    2009 Volume 50 Issue 3 Pages 592-598
    Published: March 01, 2009
    Released: February 25, 2009
    JOURNALS FREE ACCESS
    This study examines the influence of overaging on the superplastic behavior of an Al-8.55Zn-2.65Mg-2.48Cu-0.1Zr-0.06Sc alloy (in mass%). Results show that the M-phase particles formed during overaging play the most crucial role during the high-temperature tensile deformation of the Al-Zn-Mg-Cu-Zr-Sc alloy. Even though specimens without overaging maintain their small grain structure due to the existence of fine coherent Al3(ScxZr1−x) particles, overaged specimens exhibit better superplasticity. The presence of liquid-like viscous flow may be the main factor contributing to the superior superplasticity of overaged specimens.
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  • Masaru Yokota, Misako Tochihara, Masao Tanaka, Naoto Iijima, Yasuhiro ...
    2009 Volume 50 Issue 3 Pages 599-604
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: February 18, 2009
    JOURNALS FREE ACCESS
    We obtained ancient bronze mirrors and carried out: scanning electron microscopy (SEM) of fractured altered layers; biologic microscopic observation of Gram-stained samples; and DNA analyses of samples removed from altered sites.
    Fine particles about 2 μm in length were confirmed in the altered layer by SEM. Microorganisms of identical size were observed in the Gram-stained sample removed from the altered layer through a biologic microscope. Fine particles observed under SEM were considered to be microorganisms. Many fine particles were confirmed, particularly in the altered sites, by SEM. Certain types of microorganisms may have played a part in the alteration (deterioration) of the ancient bronze mirrors while the latter were buried in soil.
    From the base sequences obtained by DGGE analysis, two types of microorganisms were present in the altered layer of the mirror. One was 94.7% homologous to the 16S rDNA of the uncultured bacterium (accession number: AY 053488). It was also highly homologous to the sequence derived from the 16S rDNA of the Xanthomonadaceae family (e.g., Stenotrophomonas, Xanthomona). That is, the sequence was derived from a strain belonging to the Xanthomonadaceae family. The other base sequence was 97.4% homologous to the 16S rDNA of the Bacteroidales order such as uncultured Bacteroidales bacterium (accession number: AY 859647). That is, the sequence was derived from a strain belonging to the Bacteroidales order.
    Genes of microorganisms, presumed to belong to the Acetobacter and Gluconacetobacter genera and the Fe(III)-reducing bacterium, Shewanella algae, were detected from base sequence analysis by cloning.
    Microbial activity around the mirrors was assumed to be high. The alteration containing corrosion mechanism of bronze mirrors appears complex, but several types of microbes that possibly altered the bronze mirrors were verified.
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  • F. X. Qin, X. M. Wang, T. Wada, G. Q. Xie, K. Asami, A. Inoue
    2009 Volume 50 Issue 3 Pages 605-609
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: February 18, 2009
    JOURNALS FREE ACCESS
    In this research, Ti coating was conducted on Ti40Zr10Cu36Pd14 bulk metallic glass (BMG) in order to increase the formation rate of hydroxyapatite layer. The formation behavior of bone-like hydroxyapatite on Ti-coated and uncoated Ti40Zr10Cu36Pd14 bulk metallic glasses (BMGs) was studied. The surface morphology of Ti-coated and uncoated Ti40Zr10Cu36Pd14 BMG was investigated by scanning electron microscopy and energy dispersive X-ray spectroscopy. The results revealed that the alkali pretreatment in 5 M NaOH solution at 60°C for 24 h had a beneficial effect on the formation of porous sodium titanate on Ti-coated Ti40Zr10Cu36Pd14 BMG. A bone-like hydroxyapatite layer was able to form on the alkali-treated Ti-coated Ti40Zr10Cu36Pd14 BMG after a short-time immersion in simulated body fluid (SBF). On the contrary, hydroxyapatite formation was not observed on the uncoated Ti40Zr10Cu36Pd14 BMG after the same chemical treatments.
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  • Sergey Mironov, Yoshinobu Motohashi, Rustam Kaibyshev, Hidetoshi Somek ...
    2009 Volume 50 Issue 3 Pages 610-617
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: January 28, 2009
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    A fine-grained microstructure average grain size of which is around 2 μm was developed in ZK60A magnesium alloy subjected to a FSW process. Material flow arose mainly from basal slips and was governed by simple shear deformations caused by the tool rotation.
    The development of the fine-grained structure was a complex process driven by severe plastic deformations, formation of deformation bands, grain splitting, twinning and dynamic and/or static recrystallizations. It appears also that the microstructural evolution depended on morphology of fine dispersoids.
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  • G. M. Lalev, J.-W. Lim, N. R. Munirathnam, G.-S. Choi, M. Uchikoshi, K ...
    2009 Volume 50 Issue 3 Pages 618-621
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: February 12, 2009
    JOURNALS FREE ACCESS
    Removal of non-metallic impurities like O, N, C and S in 4N Cu rods by argon plasma-arc zone melting and hydrogen plasma-arc zone melting was investigated. The experimental results were discussed on the basis of thermodynamic estimation. Substantial removal of these impurities along the length of the Cu rods by argon plasma-arc zone melting was observed and relatively better removal by hydrogen plasma-arc zone melting was found to be due to activated hydrogen atoms. The removal of O, N, C and S was ascribed to the segregation effect as well as evaporation in the form of CH4, H2O and H2S. As a result, it was found that hydrogen plasma-arc zone melting is a better technique to eliminate non-metallic impurities like O, N, C and S in Cu.
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  • Jun Du, Kazuhiko Iwai
    2009 Volume 50 Issue 3 Pages 622-630
    Published: March 01, 2009
    Released: February 25, 2009
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    An alternating current (AC) of 60 A with a frequency of 1 kHz was imposed on the hypereutectic Mg-4.8 mass% Si melt during solidification in order to modify the primary Mg2Si crystals. The liquidus and eutectic temperatures of the Mg-4.8 mass% Si alloy are 761°C and 638°C, respectively. In order to investigate the effect of temperature ranges with application of AC on the modification of the primary Mg2Si crystals, six temperature ranges from 770°C to 740, 700 and 630°C, and from 700°C to 680, 650 and 630°C were adopted. The temperature ranges examined had an obvious influence on the modification of the primary Mg2Si crystals. For a starting temperature of 770°C, the average size of the primary Mg2Si crystals could be significantly reduced with further decrease in the ending temperature to 700 and 630°C, with agglomeration of the refined primary Mg2Si crystals in these two samples was observed. For a starting temperature of 700°C, the average sizes of the primary Mg2Si crystals could also be reduced, although no obvious agglomeration of the refined primary Mg2Si crystals was observed. The sample treated in the temperature range between 700 and 630°C had primary Mg2Si crystals with the lowest average size and the highest uniformity of size.
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  • Takeshi Eto, Kengo Kishimoto, Kenji Koga, Koji Akai, Tsuyoshi Koyanagi ...
    2009 Volume 50 Issue 3 Pages 631-639
    Published: March 01, 2009
    Released: February 25, 2009
    JOURNALS FREE ACCESS
    The thermoelectric properties of the clathrate compounds Ba8ZnxGe46−x were studied theoretically and experimentally. First, a first-principles electronic structure calculation was performed. The calculated result showed that Ba8Zn8Ge38 is an intrinsic semiconductor with an indirect band gap, while Ba8Zn6Ge40 is an n-type degenerate semiconductor and Ba8Zn10Ge36 is a p-type degenerate semiconductor. A large x dependence for the band gap was found between x=6 and 8, i.e., the widths of band gap Eg at x=6, 8 and 10 were 0.83 eV, 0.40 eV, 0.35 eV, respectively. Thus, for a thermoelectric material with high performance at high temperatures, the band gap of the intrinsic semiconductor Ba8Zn8Ge38 is relatively small. On the other hand, it was found that the double substituted clathrate Ba8Zn6Ga4Ge36 is an intrinsic semiconductor with a relatively large band gap: Eg=0.69 eV. Second, we synthesized Zn substituted clathrate compounds by using the mechanical alloying and spark plasma sintering method, and measured the thermoelectric properties of the synthesized samples to show the concrete advantage of the Ba-Zn-Ga-Ge system. The experimental results showed that all of the Ba8ZnxGe46−x (x=6,8,10,12) samples were n-type semiconductors, and that some of the Zn clathrates (x=6∼10) had a reasonably good n-type thermoelectric ability. Moreover, it was confirmed that the band gap of Ba8Zn6Ga4Ge36 (Eg=0.9 eV) is wider than that of Ba8Zn8Ge38 (Eg=0.4 eV), and that Ba8Zn6Ga4Ge36 has better thermoelectric characteristics than Ba8Zn8Ge38 at high temperatures. Finally, the experimental thermoelectric properties were theoretically analyzed by using the results of the electronic structure calculation and good agreement was obtained.
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  • H. J. Choi, S. W. Lee, J. S. Park, D. H. Bae
    2009 Volume 50 Issue 3 Pages 640-643
    Published: March 01, 2009
    Released: February 25, 2009
    JOURNALS FREE ACCESS
    The grain size dependence of yield stress has been investigated for nanocrystalline (nc) bulk aluminum produced by hot extrusion of ball-milled powders. The Hall-Petch slope is positively deviated as the grain size is reduced below 60 nm. For the specific grain size range from 60 nm down to 48 nm, structural analyses and estimation of deformation mechanism exhibit that perfect dislocation emission critically governs deformation of nc aluminum, since the inherent aluminum properties of high stacking fault energy and low twinability can not afford any other deformation modes.
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  • Chul-Hyun Park, Ho-Seok Jeon
    2009 Volume 50 Issue 3 Pages 644-649
    Published: March 01, 2009
    Released: February 25, 2009
    JOURNALS FREE ACCESS
    In this research, on the basis of the control of electrostatic charge, a laboratory-scale triboelectrostatic separation for separating polypropylene (PP) and acrylonitrile-butadiene-styrene (ABS) in seaweed-drying net frame plastic wastes has been carried out. High density polyethylene (HDPE) in a charger material selection tests using a vertical-reciprocation system was found to be the most effective materials for a tribo-charger in the separation of PP, and ABS. In lab-scale triboelectrostatic separation tests using the HDPE pipeline charger, the charge-to-mass ratio (nC/g) of the mixed PP and ABS increased when the air velocity was adjusted to over 10 m/s. The optimum splitter position estimated by Newton’s separation efficiency (ηn) was a position +4 cm from the central. Furthermore, under the conditions of over 385 kV/m electric field and less than 30% relative humidity, a PP grade of 99.70% and a recovery of 92.30% could be obtained.
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  • Hiroki Hatayama, Ichiro Daigo, Yasunari Matsuno, Yoshihiro Adachi
    2009 Volume 50 Issue 3 Pages 650-656
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: January 28, 2009
    JOURNALS FREE ACCESS
    Global aluminum consumption has exhibited significant growth in recent years, because of aluminum’s useful properties. As this will result in a large amount of aluminum accumulation in “urban mines”, the exploitation of these urban stocks will be an important issue in the future.
    To examine the recycling potential of urban stocks, a dynamic material flow analysis of aluminum was conducted focusing on Japan, the United States, Europe and China. The concentrations of the alloying elements were also investigated, because carryover of alloying elements during recycling can result in off-specification secondary metals and alloys. The recycling of aluminum scrap was optimized from the results of dynamic material flow analysis using multimaterial pinch analysis.
    It was estimated that Japan, the United States, Europe and China have the potential to reduce their primary aluminum consumption to 60%, 65%, 30% and 85% of their present levels, respectively. In 2050, it is estimated that 11400 kt of primary aluminum will be required among the four countries, while 12400 kt of obsolete scrap will not be able to be recycled because of high concentrations of alloying elements.
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  • M. C. Young, J. Y. Huang, R. C. Kuo
    2009 Volume 50 Issue 3 Pages 657-663
    Published: March 01, 2009
    Released: February 25, 2009
    JOURNALS FREE ACCESS
    Fatigue crack growth tests were performed to evaluate the effect of cold work on the fatigue behavior of 304L stainless steel in the ambient air at room temperature and 300°C and in a simulated BWR coolant environment, respectively. The fatigue crack growth rates (FCGRs) for the as-received (AR) and cold-rolled specimens at room temperature were in the same range and the FCGRs obtained at 300°C in air were higher than those at room temperature. In addition, the FCGRs for the AR specimens were higher at 300°C in air compared with those for the cold-rolled. The specimens tested in the water environment at 300°C showed higher corrosion fatigue crack growth rates (CFCGRs) relative to those measured in air at room temperature and 300°C. Local quasi-cleavages could account for the observation that the FCGRs in air at 300°C were faster than at room temperature. The dominant fracture features of quasi-cleavages, along with corrosion products, were observed with all the 304L specimens tested in the simulated BWR water environment, which could be related to the higher crack growth rates in the corrosive environment.
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  • Kengo Kumagai, Takeshi Yamabuchi, Dong-Liang Peng, Kenji Sumiyama, Ryo ...
    2009 Volume 50 Issue 3 Pages 664-670
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: January 28, 2009
    JOURNALS FREE ACCESS
    Using a plasma-gas-condensation cluster deposition apparatus, Fe22Ni78 clusters are deposited on substrates. When a bias voltage, VA, is applied to a substrate, neutral and charged clusters are formed in a plasma region and hard-landed on the substrate, forming dense Fe22Ni78 cluster assembled films. For specimens prepared without introduction of O2 gas into a sputtering chamber (the oxygen flow rate, RO2=0 mol/s), the magnetic coercivity, HC, decreases, while the saturation magnetization, MS, increases as VA is increased up to 20 kV. The real part of magnetic permeability, μ′ is very small for VA=0 kV and it becomes a few hundreds for VA=5∼20 kV. For the dense Fe22Ni78 cluster-assembled films prepared at VA=20 kV with RO2≠0 mol/s, MS decreases, while the magnetic anisotropy field, HK, and the electrical resistivity, ρ, increase, and the ferromagnetic resonance frequency, fFMR, increases up to a frequency (f) range of GHz. There are two magnetically optimized states: (1) μ′=760 at f=10 MHz for the specimen prepared at VA=20 kV with the oxygen flow rate, RO2=0 mol/s and the Ar flow rate, RAr=4.5×10−4 mol/s, and (2) μ′=370 at 10 MHz and fFMR=1.10 GHz for the one prepared at VA=20 kV with RO2=3.7×10−8 mol/s and RAr=4.5×10−4 mol/s.
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  • Duck Y. Hwang, Yong M. Kim, Dong H. Shin
    2009 Volume 50 Issue 3 Pages 671-678
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: January 28, 2009
    JOURNALS FREE ACCESS
    Plasma Electrolyte Oxidation (PEO) behavior of AZ91 Mg alloy was investigated in the electrolytes with/without potassium fluoride. Growth rate of coating thickness in the electrolyte containing potassium fluoride (Bath B) was much higher than that in the electrolyte without potassium fluoride (Bath A). The oxide layer formed on AZ91 Mg alloy in electrolyte with potassium fluoride and sodium silicate consisted of MgO, MgF2 and Mg2SiO4. Corrosion current density of oxide layer coated from the electrolyte with potassium fluoride was much lower than that of oxide layer coated from the electrolyte without potassium fluoride. From the result of EIS analysis, it was known that inner barrier layer in the oxide layer coated from the electrolyte with potassium fluoride had a good influence of the corrosion resistance of Mg alloy. The corrosion resistance curves of Bath B were similar to the thickness curves, indicating that the thickness of the oxide layer played an important role in corrosion resistance of AZ91 Mg alloy. The oxide layer in the Bath B containing potassium fluoride was found to be a compact barrier-type passive film in presence of fluoride ions. The existence of the dense MgO and MgF2 in the barrier layer had a favorable effect on the corrosion resistance of the AZ91 Mg alloy formed from Bath B by PEO process.
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  • Wei Zhang, Qingsheng Zhang, Akihisa Inoue
    2009 Volume 50 Issue 3 Pages 679-682
    Published: March 01, 2009
    Released: February 25, 2009
    JOURNALS FREE ACCESS
    We have discovered new Cu-rich Cu-Zr-Al-Ag bulk glassy alloys with high glass-forming ability and excellent mechanical properties. As the composition shifted to Cu-rich range in the Cu46+xZr46−xAg4Al4 alloy series, the supercooled liquid region, reduced glass transition temperature and γ value increased, leading to the improvement of the GFA. The full glassy samples with a diameter of 10 mm could be fabricated by copper mold casting for the Cu46+xZr46−xAg4Al4 (x=1–3) alloys. In addition to high GFA, the BGAs exhibit good mechanical properties under a compressive deformation mode, i.e., large Young’s modulus of 104–109 GPa, high fracture strength of 1905–1932 MPa and distinct plastic strain of 0.2–0.4%.
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  • Teruo Anraku, Iwao Sakaihara, Takeshi Hoshikawa, Masafumi Taniwaki
    2009 Volume 50 Issue 3 Pages 683-688
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: February 12, 2009
    JOURNALS FREE ACCESS
    Thermal expansion behavior in a stoichiometric AuCu alloy was investigated from the viewpoint of a phase transition. Thermal expansion measurements were conducted from room temperature to 873 K at various heating and cooling rates. The crystal structures and phase transitions were analyzed by X-ray diffractometry and differential scanning calorimetry, respectively. The cast sample showed a disordered face-centered cubic (fcc) structure, which changed into a face-centered tetragonal structure AuCu I or mixed structure of fcc and AuCu I after thermal expansion measurement. In the thermal expansion curves, the break points corresponded to order-disorder transition. During the heating process, three break points corresponding to three different ordering stages were observed. The activation energy for each stage was obtained using the Kissinger method. It is believed that the first and second stages are ascribable to the migration of excess vacancies induced by quenching, and that the third is predominantly due to self-diffusion.
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  • Jie H. Chen, Pei N. Chen, Pei H. Hua, Ming C. Chen, Yin Y. Chang, Weit ...
    2009 Volume 50 Issue 3 Pages 689-694
    Published: March 01, 2009
    Released: February 25, 2009
    JOURNALS FREE ACCESS
    In this study, multicomponent alloy fillers were deposited on low-carbon steel substrates using gas tungsten arc welding (GTAW) process. The microstructure and wear properties of Al-Co-Cr-Ni-Mo-Fe-Si multicomponent alloys were studied. The GTAW cladding layers were analyzed by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), X-ray energy dispersive spectroscopy (EDS), and transmission electron microscope (TEM). The results show that the microstructure mainly consisted of dendritic FeMoSi and interdendritic BCC phases and that the addition of Si coarsened the primary FeMoSi phase. In addition, different precipitate morphologies were found in the interdendrites. As the Si content increased from 5.92 to 14.53 at%, the microhardness also increased from 826 to 885 Hv and the wear resistance improved significantly. The FeMoSi dendrites possessed covalent-dominant strong atomic bonds that enhanced the hardness and wear resistance of claddings.
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  • Young-Cheol Yang, Soo-Bok Jeong, Shi-Young Yang, Young-Bae Chae, Hyung ...
    2009 Volume 50 Issue 3 Pages 695-701
    Published: March 01, 2009
    Released: February 25, 2009
    [Advance publication] Released: February 18, 2009
    JOURNALS FREE ACCESS
    The chemisorption isotherm of stearic acid on a calcite powder was established by calculating the amounts adsorbed using a UV-Visible spectrophotometer. The changes in surface properties of the calcite powder with the surface treatment were examined using contact angle measurements and inverse gas chromatography (IGC) at an infinite dilution. The adsorption of stearic acid was available only at their dilute concentration. The contact angle with water and formamide increased with increasing amount of stearic acid adsorbed on the calcite powder. The adsorption of stearic acid onto the calcite powder surface resulted in a significant decrease in the dispersive component of the surface free energy, γSD of calcite powder. The γSD value of calcite powder with 90% surface coverage was 27.2 mJ·m−2 at 120°C, whereas that of untreated calcite powder was 103.3 mJ·m−2. The standard adsorption enthalpy, −ΔHA0 values of the non-polar probes (n-alkanes) for stearic acid-treated calcite powder had decreased to almost the heat of liquefaction of the corresponding probes. The specific component of the surface free energy, −ΔGASP values of the polar probes for stearic acid-treated calcite powder were lower than those of untreated calcite powder.
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