MATERIALS TRANSACTIONS
New Arrival Alert : OFF

You can use this feature after you logged into the site.
Please click the button below.

Log in / Sign up
ONLINE ISSN: 1347-5320
PRINT ISSN: 1345-9678

MATERIALS TRANSACTIONS Vol. 61 (2020), No. 8

  • PREFACE

    pp. 1421-1421

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MPR2020903

  • Nanomaterials for Organic Optoelectronic Devices: Organic Light-Emitting Diodes, Organics Solar Cells and Organic Gas Sensors

    pp. 1422-1429

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019042

    This paper presents a unified view on applied nanomaterials that have been developed for a group of organic optoelectronic devices such as Organic Light-Emitting Diodes (OLEDs), Solar Cells (OSCs) and Gas Sensors (OGSs). From recent references, included our unpublished one, it has been demonstrated that nanostructured particles of metals, semiconductors, and oxides in conducting polymers embedded in conducting polymers have significantly contributed to improving both the performance parameters and working time of devices. The presence of inorganic nanoparticles in polymeric matrices has strongly influenced all physical properties of the polymers. However, herein the most interesting properties of OLEDs, OSCs, and OGSs are of electro-luminescence, photo-electrical conversion, and gas sensing, respectively. A publication has been seen regarding the nanostructured materials used for the fabrication of nanocomposite devices which aim at different practical purposes.
  • Automated Identification of Facet Pair Orientations

    pp. 1430-1433

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019004

    Screening of surfaces that spontaneously reconstruct is important when investigating realistic surfaces. Evaluating the surface energy after macroscopic reconstruction to form pairs of facets is a very fast procedure to identify surfaces that spontaneously reconstruct. This paper discusses a method to identify orientations of pairs of facets that can form on an arbitrary crystal orientation, which can then be used to derive the surface energy after facet reconstruction. Another use of the algorithm is to find possible orientations of terrace surfaces when the vicinal surface orientation is known for a surface with step edges. The algorithm is expected to further accelerate high-throughput calculations of surface properties.
  • Ab-Initio Study on Structural and Magnetic Properties of Fe-Doped MnCoGe

    pp. 1434-1437

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019013

    First-principles calculations were performed to investigate the effect of Fe substitution on the structural transformation of (Mn,Fe)CoGe and Mn(Co,Fe)Ge. The activation energy (barrier) between orthorhombic and hexagonal structures was estimated from the total energy of each of several virtual structures between them.Fe substitution reduces the activation energy, and movements of both of Co and Mn are closely related to the reduction. Moreover, the calculation result for the Fe substitution at the sites of both Mn and Co indicates that Fe atoms randomly occupy Mn and Co sites.
  • Structural, Electronic and Mechanical Properties of Few-Layer GaN Nanosheet: A First-Principle Study

    pp. 1438-1444

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019030

    The low-dimensional III-V semiconductors are interesting candidate materials for the tailoring of two dimensional (2D) layered structures. We have performed the first-principles calculations on the structural, electronic, and mechanical properties of few-layer gallium nitride (GaN) nanosheet, formed from various bulk phases and stacking patterns, to investigate the effects of structural modification and sheet thickness on their structural, electronic, and mechanical properties. We observed that with the thickness increases, few-layer GaN nanosheets have suffered from the size-induced transition from indirect semiconductor to metallic as well as from the graphitic – planar honeycomb to the wurtzite buckled 2D form. Optimized geometries, binding energy, phonon spectra, electronic band structure, and elastic tensor calculation has ensured the dynamical and mechanical stability of the sheet. Our study indicates that there are two competing mechanisms that govern the polarity compensation with the sheet’s net dipole served as an important parameter for determining the sheet’s stable formation.
  • Electronic Properties of Sr4V2O6Fe2As2 Superconductor by Mean of DFT Investigations

    pp. 1445-1448

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019008

    Based on the Full potential linearized augmented plane wave (FLAPW) method, the electronic properties of incommensurate anti-ferromagnetic Sr4V2O6Fe2As2 with wave vector q = (0, 0, 0.306) have been investigated. Comparing total energy between those of non-magnetic and incommensurate anti-ferromagnetic states (i-AF) we suggest that the i-AF is the stable configuration in this superconductor. The density of states data exhibit strong spin-polarized effect on the V site and possible hybridization between V-3d and Fe-3d orbitals. We found as many as six bands crossing the Fermi level, indicating strong inter-band scattering. The analysis of Fermi surfaces reveals a multi-sheet character, which is compiled of several hole-type cylinders around the center and electron-type sheets at the corners of the Brillouin zone.
  • Adsorption of Acetone and Toluene on Single-Vacancy Silicene by Density Functional Theory Calculations

    pp. 1449-1454

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019022

    In this work, we investigated the adsorption mechanism of acetone and toluene on the surface of single-vacancy silicene by Density Functional Theory method with taking into account the van der Waals interaction via the optPBE-vdW functional. The potential energy surface and adsorption energy profile are obtained by using the Computational DFT–based Nanoscope tool. It is found that acetone prefers an inclined configuration while toluene favors the parallel one towards the substrate. The single-vacancy silicene maintains its metallic electronic structure after adsorption. The adsorption energies for acetone and toluene adsorptions are −0.36 eV and −0.57 eV, respectively. The Bader charge analysis shows a charge transfer of 0.17e and 0.30e for adsorption of acetone and toluene on silicene, respectively.
  • Numerical Solution for the Counterions Distribution in a Hexagonal DNA Lattice within Mean Field Theory Using Finite Element Method

    pp. 1455-1461

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019020

    DNA has proven to be a promising material in fabrication and construction of complex structures with precise controlled nanoscale features. Most of the systems involving DNA are functioned in an aqueous solution where DNA molecules are strongly negatively charged. Therefore, understanding electrostatics of DNA system is essential for better understanding and design of DNA as a biomaterial and as a biological structure. In this work, the mean-field Poisson-Boltzmann equation for the distribution of mobile ions in a two-dimensional hexagonal lattice of DNA cylinders is solved numerically using finite element method. The weak formulation of the Poisson-Boltzmann equation is derived. The equation is then solved numerically using FreeFem++ scripting language. Our results show that the excess counterions of DNA dominate over the bulk ion concentration for the physiological salt concentration considered, and they condense on the DNA surface leading to very high charge density. The results also demonstrate the strong influence of the entropic confinement of the ions when the distance between neighboring DNA is smaller than 10 nm. This effect cannot be ignored in this case, and should be taken into account in any electrostatic investigation of DNA system.
  • Reduced-Shifted Conjugate-Gradient Method with Seed Switching for Calculating X-ray Absorption Spectra

    pp. 1462-1467

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019044

    We propose a new algorithm for numerical evaluation of x-ray absorption spectra based on the Green's function formalism in this paper. The method stands on the reduced-shifted conjugate-gradient (RSCG) method, which enables us to obtain the Green's functions with different energy-shifts simultaneously. The seed switching technique is combined into the RSCG method to improve the numerical accuracy and robustness of the algorithm, which we refer to the RSCG-SS method. The RSCG-SS method is applied for calculations of x-ray absorption spectra at the L2,3-edges of transition metals in simple oxides as a benchmark. The theoretical spectra obtained by the new algorithms are identical to those obtained by the full-diagonalization method following the Fermi's golden rule. The RSCG-SS method can also be applied for the calculation of spectra with a sizable Hamiltonian matrix (∼300,000) with reasonable computational costs.
  • Theoretical Study of the Influence of Confined Phonons and a Strong Electromagnetic Wave on the Hall Effect in an One–Dimensional Cylindrical Quantum Wire GaAs/GaAsAl

    pp. 1468-1472

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019017

    The Hall effect in an one-dimensional cylindrical quantum wire (CQW) with an infinite potential is studied by using the quantum kinetic equation under the influence a strong electromagnetic wave within the mechanising of scattering on confined acoustic phonons. We consider a case where an one-dimensional CQW is placed in a magnetic field [ This part of text is omitted ], a constant–electric field [ This part of text is omitted ] and a strong electromagnetic wave [ This part of text is omitted ] (where E0 and Ω are the amplitude and the frequency of the strong electromagnetic wave, respectively). Analytical expressions for the Hall conductivity tensors and the Hall coefficient (HC) are obtained. It is found that the Hall conductivity tensors and the Hall coefficient depend on the frequency Ω and the amplitude E0 of the strong electromagnetic wave, the magnetic field B, the temperature T the system, the radius of CQW, and the quantum indies m1 and m2 characterizing the phonon confinement. These are different from the case of normal bulk semiconductor and from the case of cylindrical quantum wire with electron–unconfined acoustic phonons scattering mechanism. Numerical calculations are performed using parameters of a GaAs/GaAsAl one-dimensional cylindrical quantum wire. The phonon confinement increase of Hall coefficient by 2.3 times in comparition with the case of unconfined acoustic phonons. When the quantum numbers m1 and m2 go to zero, the result is the same as in the case of unconfined phonons. The Hall conductivity tensors (The Shubnikov–de Haas magnetoresistance oscillations) in the case of confined acoustic phonon scattering mechanism and in the presence of a strong electromagnetic wave have more resonance peaks.
  • Magnetic Properties of Weak Itinerant Electron Ferromagnet Au4V

    pp. 1473-1475

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019011

    The magnetization measurements were carried out for polycrystalline Au4V in magnetic fields up to 130 kOe. The spontaneous magnetic moment ps was determined to be 0.255 μB/V at 4 K by high field magnetization. The magnetization process was analyzed on the basis of Takahashi’s spin fluctuation theory for weak itinerant electron ferromagnets. The characteristic parameters of the spin fluctuation were estimated to be TA = 1.3 × 103 K and T0 = 2.3 × 103 K using the data for 110–130 kOe.
  • Magnetic Measurements of Narrow-Gap Semiconductor FeSb2 under High Pressure

    pp. 1476-1479

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019015

    Pressure effects on magnetic susceptibility χ and energy gap Eg0 of narrow-gap semiconductor FeSb2 were investigated for the temperature range of 50–300 K and pressures up to 13 kbar. The estimated Eg0 for ambient pressure, Eg0(0), was 29 meV. By application of pressure, χ was suppressed, and Eg0(P) was estimated to be 52 meV for 13 kbar. The fourth-order expansion coefficient γ of the free energy in magnetization was positive and enhanced by applying pressures.
  • Effect of Temperature on Structure of La1−yCeyFe11.44Si1.56 (y = 0.1 and 0.3)

    pp. 1480-1482

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019036

    This study presents results on crystal structure and phase transition in La1−yCeyFe11.44Si1.56 (y = 0.1 and 0.3) compounds. All the samples were prepared by using arc-melting method in argon atmosphere. The effect of temperature was studied by X-ray diffraction method. As shown, the compounds possess clear NaZn13-type cubic phase with ferromagnetic spin arrangement of Fe atoms. There reveals a sudden change of lattice constants at 195 K (y = 0.1) and 175 K (y = 0.3) which corresponds to type 1 phase transition.
  • Pressure Effects on Magnetic and Transport Properties in CoFe-Based Spin Valve

    pp. 1483-1486

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019040

    We have studied the magnetoresistance of an enhanced-biased spin valve device under high pressure. The magnetoresistance decreases by 0.0014 up to 2 GPa with increasing pressure, which is inferred to be due to slight deviation from an antiparallel-spin configuration of the free and pinned layers. In the pressure range between 2 and 2.75 GPa, the exchange bias field generated in the pinned layer decreases and the coercivity of the free layers clearly increases by ∼5 Oe, which is likely to be related to less hydrostatic pressure.
  • Magnetic Field Effect on Nitrogenation of Sm2Fe17

    pp. 1487-1491

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019012

    Nitrogenation of Sm2Fe17 powder was performed under a zero field and a magnetic field of 5 T at 623, 673 and 743 K to clarify the magnetic field effect on nitrogenation. Applying a magnetic field of 5 T induced nitrogenation compared with zero-field nitrogenation, and almost fully nitride Sm2Fe17N2.9 was obtained at 743 K. Mössbauer spectroscopy results suggested that a 5-T magnetic field promoted the phase transformation to the fully-nitride Sm2Fe17N3 phase. The magnetic field effect was discussed based on the magnetic energy gain and magnetic properties of host Sm2Fe17 and fully nitride Sm2Fe17N3.
  • Effects of Substituted Elements on Spin Reorientation in Mn2−xFexSb1−ySny

    pp. 1492-1495

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019016

    The spin reorientation and Curie temperature of Mn2−xFexSb1−ySny (0 ≤ x, y ≤ 0.15) compound were investigated by magnetization measurements. Spin reorientation temperature increased from 255 K at x = 0 to 383 K at x = 0.15, whereas it almost unchanged by Sn substitution. Curie temperature decreased down to 518 K with both Fe and Sn substitution. Substitution of Fe stabilized the ferrimagnetic state with magnetic moment lying in c-plane. Substitution of Sn induced the antiferromagnetic phase at low temperature. It was found that the magnetic hysteresis derived from quasi first-order magnetic phase transition exhibited at x ≥ 0.10 or T ≥ 300 K.
  • Magnetocaloric Effects of La0.8R0.2(Fe0.88Si0.12)13 (R = Y, Ho and Yb) Compounds in Low Applied Magnetic Field

    pp. 1496-1499

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019035

    Low field magneto-caloric response is important for application. We present here the results of a study on crystal structure and magnetic properties of rare-earth doped compounds La0.8R0.2(Fe0.88Si0.12)13 (R = Y, Ho and Yb). All samples were prepared by using arc-melting method in argon atmosphere. The lattices revealed by X-ray diffraction method show a well-defined NaZn13-type structure with small amounts of α-Fe phase. The dependence of magnetization on temperature M(T) and on field M(H) curves were recorded. The magnetic entropy change −ΔSm and cooling powers (RCP) of compounds were estimated. The results show considerable better magneto-caloric responses of doped compounds in comparison with that of the undoped compound.
  • Crystal Structure Refinement of the A-Site-Ordered Double-Perovskite Oxide PrBaCo2O6−δ

    pp. 1500-1502

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019031

    Crystal structures of double perovskite cobalt oxide PrBaCo2O6−δ with a wide range of oxygen deficiency content δ (0 ≤ δ ≤ 0.85) have been analyzed by using Rietveld refinement of synchrotron X-ray powder diffraction data. The bond valence sum calculation indicates a monotonic reduction in Co valence with increasing δ. The atomic position of Co ion shifts toward the apical oxygen with whole occupation with increasing δ, together with the gradual decrease in the occupancy for the opposite apical oxygen with partial deficiency. This finding indicates that the local structure around Co ions as catalytically active sites is significantly varied by oxygen deficiency.
  • Magnetotransport Property for the Magnetoplumbite-Derived Oxide BaCo6O11

    pp. 1503-1506

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019033

    We studied magnetotransport property for the layered cobalt oxide BaCo6O11, which was recently reported as a novel compound with isostructure of magnetoplumbite-derived oxide of SrCo6O11. A polycrystalline sample of BaCo6O11 exhibits metallic behavior in the electrical resistivity below the ferromagnetic transition temperature of 11.5 K. A tunneling-type magnetoresistance up to −20% was observed at 11.5 K and 90 kOe. These observations propose a half-metallic electronic state for BaCo6O11.
  • Electrocatalytic Activity of Tetravalent Fe–Co Mixed Oxide for Oxygen and Hydrogen Evolution Reactions

    pp. 1507-1509

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019032

    Electrochemical water splitting is a useful way for sustainable hydrogen production, whereas sluggish kinetics of oxygen/hydrogen evolution reactions (OER/HER) limits the efficiency; thus, active electrocatalysts to reduce overpotentials are desired. Mixing of multiple transition-metal elements is a promising way to enhance electrochemical catalysis. In the present study, we investigated the OER and HER catalytic activities of tetravalent Fe–Co mixed perovskite oxide CaFe0.5Co0.5O3. CaFe0.5Co0.5O3 demonstrated a higher OER activity than those of the parent compounds CaFeO3 and CaCoO3. In contrast, the HER activity of CaFe0.5Co0.5O3 was not significantly enhanced. These observations suggest that the mixing of Fe4+ and Co4+ ions is an efficient way to activate OER.
  • Development of Yttrium Titanate/Nickel Nanocomposites with Self Crack-Healing Ability and Potential Application as Thermal Barrier Coating Material

    pp. 1510-1516

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019006

    Thermal barrier coatings (TBCs) are necessary to protect nickel-based alloy blades of gas turbine against oxidation and thermal fatigue in high-temperature operating conditions. Ceramic materials, which are very good natural thermal insulator, attract the most interests from engineers and scientists. However, the brittleness of ceramics is a major obstacle for utilizing them as the TBCs, which are also required very good damage tolerance against physical impacts. The cracks appear on the blade surfaces during its operation can lead to the severe failure. In this research, a composite of Y2Ti2O7 and Ni was developed as a self-crack healing material to overcome this problem. The crack-healing behavior is investigated by using Vickers indenter to create cracks on the composite surface intentionally, followed by annealing in an oxidizing environment. It is found that the main crack-healing mechanism is the filling of NiO, which was formed from the oxidation of the Ni fillers, into the cracks. Complete heal of cracks is achieved with 10 vol% Ni filler, which is confirmed by X-ray diffraction and scanning electron microscopy. Thermal conductivity and Weibull distribution for the strength of the composite were also investigated to find the appropriate volume fraction of Ni nanoparticles in this self-healing material.
  • Metal-Insulator Transition in (La0.7Sr0.3Mn0.98Co0.02O3)1−x(BaTiO3)x Multiferroic

    pp. 1517-1522

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019025

    (La0.7Sr0.3Mn0.98Co0.02O3)1−x(BaTiO3)x (x = 0.1; 0.2; 0.3) mixed perovskite were prepared by the solid state reaction method. It is shown that this compound exposes the multiferroic (magnetic and ferroelectric) behavior comparing with magnetic pristine La0.7Sr0.3Mn0.98Co0.02O3. The increase of BaTiO3 fraction from x = 0.1 to 0.3 leads to weakening (enhancing) of the ferromagnetic (ferroelectric) order. The metal-insulator transition (MIT) in the ferromagnetic La0.7Sr0.3Mn0.98Co0.02O3 (x = 0) and the multiferroic x = 0.1, 0.2 samples were registered with reduction of the MIT temperature TMI from 380 K of the x = 0 to 117 K of the x = 0.2 samples. Temperature dependence of resistivity and MIT of these samples are well described by the mixed conducting carrier model, which has crossover between the low temperature spin-scattering electron and the hopping small polarons conductions at TMI.
  • Oxygen Evolution Catalysis for Iron Oxides with Various Structures

    pp. 1523-1526

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019043

    The catalytic activity on the oxygen evolution reaction (OER) was investigated for Fe3+-containing oxides with various crystal structures: spinel ZnFe2O4, post-spinel CaFe2O4, and stuffed-tridymite BaFe2O4. The latter two oxides exhibited higher catalytic activity than ZnFe2O4, indicating that the differences in the coordination polyhedra and their connections are important factors to affect OER activity.
  • Effect of Maleic Anhydride Grafted Ethylene Vinyl Acetate Compatibilizer on the Mechanical, Thermal Properties and Weathering Resistance of Polyamide 11/Bamboo Fiber Composite

    pp. 1527-1534

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019001

    In this research, short bamboo fiber (BF) has been used as filler in the fabrication of the composite based on polyamide 11 (PA11) by melt-mixing method. In order to improve the compatibility between BF and PA11, maleic anhydride grafted ethylene vinyl acetate copolymer (EVAgMA) was introduced into the composite preparation process. The effect of EVAgMA contents on mechanical, thermal or weathering resistant properties of the composites was investigated. In the presence of the EVAgMA, the tensile strength, impact strength and flexural modulus of composites showed the improvement in comparison to without compatibilizer. Differential scanning calorimetry (DSC) analysis indicated that the melting temperature of composites did not depend on the EVAgMA contents, while its fusion heat (ΔHm) decreased with increasing EVAgMA contents. Dynamic mechanical thermal analysis (DMTA) evaluated the role of EVAgMA on the enhancement of composites’s storage modulus (G′) in the glassy plateau and the interaction between BF and PA11 matrix. After 840 hours of accelerated weathering test, the composites using EVAgMA were decomposed faster than that of neat PA11 and PA11/BF composite. This result was also agreed with the observation of scanning electronic microscopy (SEM) images and the change of carbonyl index (CI). However, the retention of tensile properties of PA11/EVAgMA/BF composites is higher than that of PA11/BF composite.
  • Plasma-Assisted Preparation of MoS2/Graphene/MOF Hybrid Materials and Their Electrochemical Behaviours

    pp. 1535-1539

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019003

    In our work, MoS2/graphene/MOF hybrid materials were synthesized via a two-step process consisting of the plasma-assisted electrochemical preparation of MoS2/graphene and the wet formation of Cu-based metal-organic framework (MOF). The hybrid materials were characterized with Field Emission Scanning Electron Microscopy, High-Resolution Transmission Electron Microscopy, X-ray Diffraction and Raman Spectroscopy. Furthermore, some initial results on their electrochemical properties for hydrogen evolution and oxygen evolution reactions were also presented, showing the potential to be a bi-functional catalyst.
  • Development of NH3 Gas Sensors at Room Temperature Based on Modified Carbon Nanotubes

    pp. 1540-1543

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019005

    Multiwalled carbon nanotubes (CNTs) were modified with the Hummers method and coated onto Pt electrodes patterned on SiO2/Si(001) surface to fabricate chemical sensors. The modified CNTs showed a different structure and increased number of defects compared with pristine CNTs, these properties facilitated the adsorption of NH3 gas molecules on the CNT surfaces. NH3 gas sensing results indicate that the sensor exhibited an enhanced response to gas at room temperature. The response of the modified CNT-based sensor was 10 times higher than that of pristine CNT-based sensors.
  • Preparation of Electromagnetic Shielding Coating Based on Natural Rubber

    pp. 1544-1549

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019010

    In this study, natural rubber-based electromagnetic shielding materials for coating application were made. Expanded graphite was prepared using our method and dispersed in the polyaniline/natural rubber matrix. The effect of PAni and expanded graphite on the properties of resulting materials was evaluated. The characterization of properties that are important for an electromagnetic shielding coating (i.e., mechanical properties, electromagnetic shielding, wettability resistance, thermal properties, and the morphology of the material) was investigated. The result shows that the properties of natural rubber/polyaniline blends are enhanced owing to the presence of expanded graphite. The superior properties are achieved when the amount of added expanded graphite in natural rubber/polyaniline is 5 parts per 100 g of natural rubber. The enhancement of properties is attributed to the good dispersion of expanded graphite in the natural rubber/polyaniline matrix, which improves the compatibility of the natural rubber and polyaniline phase.
  • Advanced Fabrication and Applications of Cellulose Acetate Aerogels from Cigarette Butts

    pp. 1550-1554

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019009

    Every year, trillions of cigarette butts (CB) are discarded all over the world without being recycled, thus causing negative impacts on the ecological environment as well as the health of living species. Cellulose acetate (CA), the main component of cigarette butts, is a valuable polymer for numerous applications. For the first time, by using a cost-effective freeze-drying method in the presence of polyvinyl alcohol (PVA) as a cross-linker, high-value engineering cellulose acetate aerogels were successfully fabricated from CB. The effects of component concentrations on the morphology of the CA aerogels were investigated by changing concentration of CA fibers (1–3.0 wt.%) and PVA (0.1–1.0 wt.%). The CA aerogels exhibited an extremely low density (25.4–45.6 mg/cm3), a high porosity (96.46–98.01%), and a low thermal conductivity (0.034–0.039 W/(m*K)). The modified CA aerogels also expressed a great capacity of oil absorption (11.82–25.22 g/g). Hence, the CA aerogel is a promising material for future uses in thermal insulation and oil spill treatment.
  • Field Emission Properties of Vertically-Aligned Carbon Nanotubes Grown on Stainless Steel by Hot-Filament Chemical Vapor Deposition

    pp. 1555-1559

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019046

    Carbon nanotubes (CNTs) for field emission applications were grown directly on 304 stainless steel (SS304) by using hot-filament chemical vapour deposition (hot-filament CVD). Vertically-aligned CNTs (VACNTs) with 1.5-millimetre-diameter in shape were successfully grown on the SS304 substrate. We obtained efficient electron emission with turn-on fields as low as 0.66 V/µm, emitting currents of 1.5 mA at an applied field of about 1.5 V/µm. The VACNTs-SS304 emitter also demonstrated high stability in emission current of 860 µA (± 12.5 µA) which even better than that of the VACNTs grown on conventional silicon. This VACNTs-stainless steel is a promising candidate for X-ray tubes that require small, bright, and cold emitters.
  • Facile Catalyst-Free One-Pot Synthesis and Optical Properties of MgO Nanocrystals with Different Morphologies in Atmospheric Air

    pp. 1560-1563

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019026

    MgO nanocrystals with cube, wire and flower shapes were fabricated by thermal evaporation technique in air at atmospheric pressure. Mg powder mixed with graphite powder was used as the source material and no catalyst was used in the synthesis process. The morphology of the MgO nanocrystals was significantly changed from cube shape to wire and then flower-like shape with increasing the mass ratio of graphite to Mg in the source material. This indicates that the mass ratio of Mg/graphite in the source material played a crucial role in the morphological change of MgO nanocrystals. All the MgO crystals had a cubic crystal structure. The cube-shaped MgO crystals exhibited a blue emission centered at 420 nm, whereas the wire and flower-shaped MgO crystals showed an ultraviolet emission at 380 nm.
  • Preparation and Optical Properties of La3PO7:Eu3+ Nanophosphors Synthesized by Combustion Method

    pp. 1564-1568

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019027

    Eu3+ doped La3PO7 nanoparticles were successfully synthesized under facial combustion method. The nano-phosphors then were characterized by some techniques including X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), photoluminescence spectrum (PL), and lifetime decay. SEM and TEM micrographs reveal exhibit of the La3PO7: Eu3+ nanopowders in spherical morphology with an average size of about 20 nm, matching with Scherrer’s formula calculation. Otherwise, the influence of annealing temperature and concentration of Eu3+ ions on optical characteristics of Eu3+ was doped La3PO7, and optical properties were investigated too. The photoluminescence shows the strong red emission originating from the 5D07FJ (J = 1, 2, 3, and 4) transitions of Eu3+ and the 614 nm emission from the 5D07F2 electronic dipole transition is dominant.
  • Upconversion Luminescence Properties of Gd2O3: Er3+ Nanospheres and Gd2O3: Er3+@Silica Nanocomposites

    pp. 1569-1574

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019021

    The upconversion luminescence (UCL) of Gd2O3: Er3+ monodisperse nanospheres, synthesized by multistep chemical method, and nanoparticles, produced by combustion synthesis, are presented for comparison. The UCL of nanospheres Gd2O3: Er3+ and Gd2O3: Er3+@Silica have shown strong red or green emission under excitation at 976 nm or 980 nm by a diode laser with a remarkable increase of the bright red color in the nanospheres. In the core/shell structured nanospheres Gd2O3: Er3+@Silica, we find a higher intensity of upcoversion emission, increased stability and better dispersion capability in solvents and water. The UCL intensities of green and red color while 976 nm or 980 nm excitation were dependent on the diode laser power. The slope values of Er3+ ion’s transitions 2H11/24I15/2, 4S3/24I15/2 and 4F9/24I15/2 in the silica-coated nanospheres are 1.99, 1.62 and 1.66 respectively, which properly indicate the two-photon mechanism of upconversion emission. The synthesized Gd2O3 nanospheres codoped with Yb and Er show strong UCL intensity than those of Gd2O3: Er3+. The obtained Gd2O3: Er3+ nanospheres and nanoparticles, as well as Gd2O3: Yb3+, Er3+ and its silica-coated versions, are promising materials to develop with potential application in high technology and biomedicine.
  • Characterization of Gd2O3:Eu3+ Nanocomplexes Conjugate with IgG for the Identification of CEA Tumor Cells

    pp. 1575-1579

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-MN2019037

    In this paper, the Gd2O3:Eu3+ nanospheres with the ratio Eu3+/Gd3+ of 6% mol were successfully synthesized by a multi-step chemical method with the mean nanoparticles size of about 200 to 220 nm and a low standard deviation. The morphology, structure and optical behavior of as-synthesized and annealed Gd2O3:6%Eu3+ samples were investigated by field-emission scanning electron microscopy (FESEM), X-ray diffractions (XRD), and photoluminescence spectroscope (PL) The luminescence lifetime of samples was also investigated and discussed. The biomedical nanocomplexes of Gd2O3:6%Eu3+ with IgG were fabricated by glutaraldehyde linking after covering nanospheres with amino Silica. The luminescent nanocomplexes Gd2O3:6%Eu3+@Silica-NH2-IgG with different concentrations have been incubated with CEA tumor cells to investigate and evaluate the detection capacity by using a fluorescence optical microscopy for the early detection and treatment of cancer.
  • Effects of Carbonization on Electrophysical Properties of Cellulose-Based Nanocomposites with Triglycine Sulfate

    pp. 1580-1583

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-M2020093

    In this study, a ferroelectric nanocomposite was prepared from triglycine sulfate (TGS) with cellulose nanoparticles (CNP) pretreated at different carbonization temperatures. The results showed that along with the increase in electrical conductivity, the phase transition temperature of TGS decreased significantly with increasing carbonization temperatures due to the partial destruction of interaction between CNP and TGS during cellulose carbonization. The dielectric measurements were performed under a weak electric field (2 V/cm) in the frequency range of 10−3–106 Hz. The work provides deeper insights on the influence of dielectric components on the properties of ferroelectrics.
  • Interpretability of Deep Learning Classification for Low-Carbon Steel Microstructures

    pp. 1584-1592

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-M2020131

    In this paper, a model is developed to identify the microstructure of low-carbon steel by deep learning. In classifying steel microstructures using a machine learning model, predictions are interpreted using local interpretable model-agnostic explanations (LIME) for the first time. The constructed model can accurately distinguish between eight microstructure types, including upper bainite, lower bainite, martensite, and their mixed structures. The model accuracy is 94.1% when individually predicted and 97.9% when predicted by majority vote. In addition, as a result of interpreting the predictions of the model by LIME, it is evident that the recognition criterion of the constructed model is partially consistent with the classic recognition criterion.
  • Effectiveness of Ultrasonic Shot Peening on Stainless Cast Steel SCS6 Containing a Fatigue Crack

    pp. 1593-1599

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.Z-M2020829

    In order to investigate the effectiveness of ultrasonic shot peening treatment (USP) as repairing method for SCS6 material with surficial fatigue crack for hydraulic turbine runner, plane bending fatigue tests were carried out for USP treated SCS6 containing a surface fatigue crack with 1 mm in length and the fatigue crack propagation after USP was observed by a plastic replica method. As a result, the fatigue crack propagation life of SCS6 containing a surface fatigue crack was dramatically improved by USP treatment. Furthermore, the initial effective stress intensity factor ranges were calculated in the USP treated and untreated SCS6 containing a surface fatigue crack, respectively. According to the calculation, it was clear that the surficial fatigue crack could be harmless under the condition that the calculated initial effective stress intensity factor range considering the stress opening a fatigue crack, which was acquired by the unloading elastic compliance method, was less than the threshold of effective stress intensity factor range. Therefore, USP treatment is effective for repairing method of SCS6 containing surficial fatigue crack for hydraulic turbine runner. This Paper was Originally Published in Japanese in J. Soc. Mater. Sci., Japan 68 (2019) 897–903.
  • Intergranular Fracture of Al–5%Mg Alloys Containing a High Amount of Sodium and Its Suppression by Bismuth or Indium Additions

    pp. 1600-1606

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-M2020080

    The effect of high amounts of sodium on intergranular fracture of Al–5% Mg alloys without and with additional bismuth or indium was studied under different heat treatment conditions. A set of experiments made it evident that the intergranular fracture occurred even at room temperature when the amount of sodium in the Al–5%Mg alloy exceeded 23 ppm under homogenization treatment. On the contrary, Al–5%Mg alloy with large amounts of sodium (23 and 200 ppm) did not show intergranular fracture at 300°C under homogenization treatment. In addition, the Al–5%Mg alloy containing 4 ppm of sodium showed obvious intergranular fracture when the alloy was pre-deformed and subjected to the solution heat treatment. This suggests that the effect of sodium on the intergranular fracture of the Al–Mg alloys varies according to the sodium concentration, heat treatment, and testing temperature. We have also clarified that the room-temperature intergranular fracture caused by 200 ppm of sodium in the Al–5%Mg alloys was suppressed by 0.1%-ordered additional elements such as bismuth or indium. It is presumed that the suppression of the intergranular fracture by the addition of bismuth or indium was caused by the formation of sodium-bearing compounds in the Al–5%Mg alloys, leading to scavenging of sodium from GBs at room temperature.
  • Mechanical Property and Fracture Characteristic of Ti–Cu–Ni–Alx Bulk Metallic Glasses under Different Strain Rates

    pp. 1607-1612

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-M2020085

    In this study, a Ti-based bulk metallic glass (BMG) was used to investigate the influence of the addition of Al on mechanical properties and glass forming ability (GFA). The experimental results show that the plastic flow stress value of the alloy will change with the change of strain and strain rate. As the strain rate increases, the plastic flow stress value increases. The fracture surface of the specimens can be observed through a scanning electron microscope. It can be seen that the fracture surface has the characteristics of a dimple-like structure. The appearance, distribution density, and grain density of the vein-like structure depend on the strain rate and the addition of the Al element.
  • Surface Microstructure Modifications of Low Carbon Steel Welds Produced by Low-Heat-Input Friction Stir Processing

    pp. 1613-1619

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-M2020117

    Friction stir processing (FSP) is a solid state method for surface modifications through severe plastic deformation and frictional heat using a rotational tool. Reducing the heat input of FSP should improve the mechanical properties of the stir zone. This study investigated a low-heat-input FSP on beads of low carbon steel plates using tungsten inert gas welding. The FSP was controlled by decreasing the rotational speed and increasing the travel speed of the tool. Low-heat-input FSP produced significant grain refinement in the weld microstructure and the associated hardness increased at the stir zone surface. The estimated improvement ratio of fatigue strength was twice as large as that produced by the conventional FSP. The fatigue strength in the stir zone at the retreating and advancing sides produced by low-heat-input FSP were independent of the residual stress because the hard stir zone helped prevent fatigue crack initiating at the surface. To improve fatigue strength, increasing the hardness in the stir zone is preferable to decreasing the tensile residual stress associated with the incomplete recovery and recrystallization. Consequently, further grain refinement upon decreasing the FSP heat input can be an effective way to significantly improve the mechanical properties of steel welds.
  • Prediction Mechanical Strength of Sand Mold Samples Fabricated by Three-Dimensional Printing

    pp. 1620-1628

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-M2020102

    Three-dimensional printing (3DP) was widely applied in sand mold fabrication. One of the major concerns about sand mold is the mechanical strength which determines such defects as sand cut, sand blister, sand explosion, and expansion of the castings. In this study, the linear regression and the BP neural network were applied to predict the bending strength of 3DP samples. Orthogonal experiments were designed to obtain data for training the prediction models. Three-point bending test was used to characterize the actual bending strength. The results showed that the sample weight, resolution X and layer thickness are significant factors while the activator content, recoater speed and sample location are not significant. The maximum error of linear regression is 11.2%, which is very big. A three-layer BP neural network with 6 input nods, 14 hidden nods and 1 output nod was proposed to predict the bending strength of 3DP samples, and the maximum error is 4.3%, which is lower than that of linear regression. So it is more valuable in practical applications.
  • Effect of Aqueous Antimony Species on Corrosion of Pb–Sn–Ca Alloy in Copper Electrowinning

    pp. 1629-1637

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.M-M2020831

    Copper electrowinning is important not only for the solvent extraction – electrowinning process (SX-EW), which produces primary copper metal from copper oxide minerals, but also for the copper recycling process, which comprises smelting, leaching, and electrowinning. The electrolyte used in the copper recycling process contains various impurities that are usually negligible in the electrolyte used in the SX-EW process. In this study, the effect of aqueous antimony species on the corrosion of a Pb–Sn–Ca alloy in copper electrowinning was investigated using galvanostatic electrolysis, followed by X-ray diffractometry, scanning electron microscopy – energy dispersive X-ray spectroscopy, and inductively coupled plasma – optical emission spectrometry analyses. The electrolysis was conducted at various current densities in a synthetic copper electrolyte containing H2SO4, Cu(II), Ni(II), Co(II), and 0–4.1 mmol·dm−3 of Sb(III) at 65°C. When the electrolyte did not contain any antimony species, the anode surface was covered with scale comprised of αPbO2 and βPbO2. The PbO2 scale grew along the grain boundaries, and its growth rate was considerably slow. In contrast, when the electrolysis was conducted in an electrolyte containing Sb(III), scale consisting of Sb2O5 and αPbO2 formed on the anode surface. A laminated Sb2O5–αPbO2 mixture scale was observed on the anode surface, and its growth rate was significantly faster than that of the PbO2 scale. The flakes of the Sb2O5–αPbO2 mixture scale periodically fell from the anode surface, and consequently, the corrosion of the Pb–Sn–Ca alloy anode was accelerated. The oxidation of Sb(III) to Sb2O5 was likely caused by an anode reaction rather than by direct reaction with the oxygen formed on the anode surface. The formation of Sb2O5 on the Pb–Sn–Ca alloy resulted in a considerable decrease in aqueous antimony in the copper electrolyte, indicating its effectiveness in enhancing the electrowinning process targeting pure copper cathode production, copper liberation, and antimony removal from the tailing electrolyte in copper electrorefining.
  • A Method for Core Reorientation Based on Rock Remanent Magnetization: Application to Hemipelagic Sedimentary Soft Rock

    pp. 1638-1644

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.Z-M2020832

    The in-situ orientation of drilled core samples provides valuable information for a broad range of geological and geophysical studies, such as the determination of in-situ principal stress directions or analyses of geological structure. However, the in-situ orientation of core samples is not available in many cases. In this paper, we present a method for restoring the in-situ orientation of drilled whole-round core samples and its application to hemipelagic sedimentary rocks. The method is based on the natural remanent magnetization (NRM) of rocks. As a case study, we apply this method to 15 oceanic sedimentary soft rock samples recovered from the toe of the Nankai Trough off Cape Muroto, SW Japan, during International Ocean Discovery Program Expedition 370.We developed a new sample-preparation procedure that enables more data acquisition and evaluated the NRM measurement results. Some samples could not be reoriented owing to magnetic overprints associated with the drilling operations. To evaluate the magnetic overprints caused by drilling and assess the data quality of the core reorientation by this method, we propose an evaluation system with three ranks defined for different levels by which NRM results are affected by drilling. This evaluation system is also useful for assessing the data quality of core reorientation by the NRM method in other similar applications. This Paper was Originally Published in Japanese in J. Soc. Mater. Sci., Japan 69 (2020) 256–262.
  • Enhanced Pyrophyllite Flotation Performance Using Sodium Oleate as an Anionic Collector in the Presence of Ammonium Ion

    pp. 1645-1650

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-M2019284

    Flotation of pyrophyllite using the anionic collector (sodium oleate, SO) was examined in this study. The floatability of pyrophyllite was improved by increasing SO concentration (1.0 × 10−7–1.0 × 10−2 M). The adsorption of SO on the pyrophyllite surface was confirmed by the zeta potential changes and FT-IR spectrometry. However, due to the high concertation of SO to achieve the higher floatability of pyrophyllite, it was tried to enhance the floatability of pyrophyllite at a low SO concentration. Ammonium ion (ammonium chloride, AC) was introduced to induce the additional interactions in between the pyrophyllite surface and SO. The floatability of pyrophyllite was improved in the presence of AC (0.2–1.0 M) at a low SO concentration (1.0 × 10−7 M). In the same flotation conditions employing AC and SO, the amounts of the floated quartz which is main gangue mineral in the pyrophyllite ore were smaller than those of pyrophyllite. The adsorption of AC and SO on the pyrophyllite surface was also confirmed by the zeta potential changes and FT-IR spectrometry.
  • Low Temperature Electrodeposition of Titanium in Fluoride-Added LiCl–KCl–CsCl Molten Salt

    pp. 1651-1656

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-M2020083

    We investigated electroreduction of Ti2+ to metallic titanium in the LiCl–KCl–CsCl system, which has a eutectic point at 263 °C. Cyclic voltammetry was carried out in the TiCl2-saturated LiCl–KCl–CsCl at 300 °C, and the effect of F addition on the reduction behavior of Ti2+ was investigated. It was revealed that addition of F increases the limiting current density of electrodeposition of titanium at 300–500 °C. This might be mainly attributed to the increase in total concentration of soluble titanium ions in the molten salt. Then, we demonstrated the electrodeposition of metallic titanium in the LiCl–KCl–CsCl with and without F at 350 °C. After the electrolysis in F-added molten salt and acid leaching, LiF remained on the deposited titanium. This is because the solubility of LiF in aqueous solution is quite low. An efficient method to remove LiF is required when F-added LiCl–KCl–CsCl is used as electrolyte.
  • Structures and Hardness of Materials Formed by Melting and Liquid Diffusion of Mg Alloy Substrate with Pure Al Surface

    pp. 1657-1662

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.F-M2020830

    In this study, pure Al powder was compression molded on the surface of flame-retardant Mg alloy plate, and integration of pure Al and Mg alloy was attempted by melting and solidification in air. In order to integrate different materials by liquid diffusion of metal elements, the structure, composition phase and hardness of the formed integrated materials were investigated.It was found that heating the specimens for 180 s results in melting and liquid diffusion between Al and Mg. When heated and melted with pure Al down and Mg alloy up (Type B), shrinkage cavity was formed on the former Mg alloy side of the former Al/former Mg alloy interface. When heated at 450 s, the specimen was composed of Al–Mg system stable phases of Al3Mg2 and Al12Mg17, and Al–Mg system metastable phases of Al0.37Mg0.63 and Al0.1Mg0.9. In Type A with pure Al up and Mg alloy down and Type B, stable phases of Al3Mg2 and Al12Mg17 were formed on the former Al side. The constituent phase of the former Mg alloy side was composed of metastable phases of Al0.37Mg0.63 and Al0.1Mg0.9, but the structure morphologies of Type A and B differed near the surface of the former Mg alloy side, and the primary phase was Al0.37Mg0.63 and Al0.1Mg0.9 respectively. The final solidification phase consisted of eutectic phases of Al0.37Mg0.63 and Al0.1Mg0.9. The hardness on the former Al side was about 250 HV, and the hardness on the former Mg alloy side had decreased. Type B was evaluated to be lower than Type A. This Paper was Originally Published in Japanese in J. JFS 92 (2020) 69–74.
  • Numerical Simulation of Grain Growth of Directionally Solidified DZ4125 Alloy under Varied Blade Orientations

    pp. 1663-1670

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-M2019383

    The ProCAST simulation software is used to simulate the temperature field and the mushy zone of the blade under different blade orientations, and then grain growth was investigated based on them. It is found that the temperature field and the mushy zone of the blade samples in the parallel orientation are stably horizontally distributed at the same height, while the perpendicular orientation has a degree of inclination. In the heat preservation zone, the sample temperature close to the furnace wall is higher than that of the sample temperature near the center (referred to here as the Center-Side), and the temperature field is inclined upwards. However, in the cooling zone, the temperature field is inclined downwards because the temperature near the furnace wall (referred to here as the Wall-Side) is lower than that of the Center-Side. The grain growth of the blades with parallel orientation is superior as single crystal blade castings are formed. The blade samples in a perpendicular orientation have a certain heterocrystal tendency. The grain growth of the mutated cross-section of the blade samples is summarized using variable cross-section samples. Heterocrystals are used to be formed at the edge plate of complex structure, the mutation section and the end of spiral crystal separator.
  • Microstructure and Oxidation Behavior of Pt and Pt–Ir Diffusion Coatings on Ni-Based Single Crystal Superalloy

    pp. 1671-1678

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-M2020125

    The effects of Ir addition and coating method on the microstructure and oxidation behavior of Pt–xIr (x = 0–30 at%) diffusion coatings were investigated. A nickel-based single crystal superalloy UCSX-8 was used as a substrate material, while the coatings were developed by either an electroplating or a paste coating method followed by an annealing heat treatment. The phase identification and microstructure analyses by XRD and SEM/EDS revealed that the alloying of Ir in Pt diffusion coating resulted in the formation of L10 ordered α-NiPt2Al structure. Cyclic oxidation tests were carried out at 1423 K in still air in order to investigate the thermal stability and oxidation behavior of the coatings. It was found that Ir can significantly retard the formation of voids in both the coating and substrate. In addition, by replacing electroplating method to the paste coating method, the crack problem due to the brittle feature of electroplated Pt–Ir coatings could be solved. Therefore, the Pt–20Ir diffusion coating prepared by the paste-coating method is promising as the bond-coating material due to formation of less voids, no crack and stable Al2O3 on the surface.
  • Immobilization of Fluorine in Reduced Slag by Addition of Crystalline Hydroxyapatite and Glassy Calcium Phosphate Using a Calcining Process

    pp. 1679-1683

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-M2020098

    The ability of a variety of hydroxyapatite (HAp) sources, including animal bone and calcium phosphate glasses, is demonstrated to immobilize fluorine in slag through calcining processes. The slowly cooled slags were calcined in a furnace along with hydroxyapatite, animal bone, and calcium meta-phosphate glasses. As a result, fluoro-hydroxyapatite was formed, confining the fluorine ions in the formed crystal, leading to the suppression of the dissolution of fluorine ion. Each of the samples demonstrated a low elution of fluorine ions (less than 0.8 ppm), measured by leaching method. The quantity evaluation of formed apatite-like crystal and other subsidiaries were conducted for the treatments by adding recycled animals’ bones as the source of calcium phosphate, as well as reagent HAp and meta calcium phosphate glasses.
  • Development of Lead-Free High-Strength Copper Alloy

    pp. 1684-1688

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-M2020045

    C6932 is a lead-free 75.5Cu–3Si–Zn alloy (hereinafter, “C6932”) which is excellent in machinability, strength, corrosion resistance, hot workability, and castability. C6932 is widely used for water-related products and in automobile and electricity fields, and over 40,000 tons of this alloy is distributed world-wide under the brand name of ECOBRASS®.In the United States, a law to restrict lead in drinking water was put into force across the nation in 2014. Lead is going to be restricted in Europe also in the automobile field as well as electronic and electrical field. Considering this trend, more free-cutting copper alloys are likely to be free of lead. Concurrently, in the automobile field, for instance, there is a higher demand for improved fuel efficiency by reducing component weight and improved reliability by using components of higher strength.Based on these backgrounds, we have developed a lead-free, high-strength free-cutting copper alloy by optimizing the composition of a Cu–Si–Zn alloy and controlling its metallographic structure. The developed alloy shows significantly higher strength compared to C6932 without sacrificing its machinability and ductility. The alloy we have developed is a lead-free, high strength free-cutting copper alloy with tensile strength of 650 MPa and an elongation of 43%, which can be realized by annealing a 76.3Cu–3.2Si–0.2Sn–Zn alloy and controlling the grain size to 8 µm. This Paper was Originally Published in Japanese in J. Japan Inst. Copper 58 (2019) 40–44. Captions of Figures and Tables were slightly modified.
  • Microstructure Evolution during Isothermal Aging for Wrought Nickel-Based Superalloy Udimet 520

    pp. 1689-1697

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-M2020115

    This paper investigates the evolution of microstructure during isothermal aging at 1173 K in the wrought nickel-based superalloy Udimet 520, after being solution-treated at 1393 K for 4 h, followed by various cooling rates. Age-hardening behavior was observed during isothermal aging for water-quenched (WQ) and air-cooled (AC) specimens after the solution treatment, whereas it could not be detected for a furnace-cooled (FC) specimen. No primary γ′ particles were observed in any continuously cooled samples. For the WQ and AC specimens, the size of the secondary γ′ precipitates increased during the isothermal aging along the Ostwald ripening and their morphology evolved from spherical to an intermediate shape between spherical and cuboidal. Conversely, the secondary γ′ particles exhibited an octodendritic shape for the FC specimen, and the octodendritic character of the secondary γ′ particles was emphasized during isothermal aging, resulting in the splitting of the secondary γ′ particles. It was found that the splitting of γ′ particles occurred during the isothermal aging for Alloy 80A with a lower volume fraction of γ′ phase around 20%. This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 84 (2020) 11–18.
  • Effects of Size and Crystallinity of CaCu3Fe4O12 on Catalytic Activity for Oxygen Evolution Reaction

    pp. 1698-1702

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-M2020147

    Effects of size and crystallinity of a quadruple perovskite oxide, CaCu3Fe4O12, were investigated for its catalytic activity for the oxygen evolution reaction (OER). Pristine CaCu3Fe4O12 powder sample was synthesized under high-pressure and high-temperature conditions of 8 GPa and 1000°C, and a portion was treated by ball milling for 120 min to obtain a powder sample with smaller particle size. The specific surface area significantly increased from 0.38 to 10.30 m2g−1 by ball-milling, leading to increased OER activity. However, it was found that the milling did not improve the OER activity efficiency in proportion to that expected from the increase in specific surface area as determined by Brunauer-Emmett-Teller analysis of adsorption/desorption isotherms measured with nitrogen gas because the crystallinity was lowered by ball milling, which suppressed the catalytic activity. This study provides important information on how to achieve the best OER catalytic performance in terms of both size and crystallinity.
  • Continuous Foaming of Multiple Aluminum Foam Precursors by Combining Conveyor and Optical Heating

    pp. 1703-1706

    Bookmark

    You can use this feature after you logged into the site.
    Please click the button below.

    Log in / Sign Up

    DOI:10.2320/matertrans.MT-M2020137

    Precursor foaming is one of the production processes for manufacturing aluminum foam. In this study, the continuous foaming of multiple precursors by combining a conveyor and optical heating with halogen lamps was conducted. First, in a preliminary test, the current of the halogen lamps was adjusted to enable the foaming of a precursor as it moves on the conveyor. Then, multiple precursors were continuously foamed at the adjusted current of the halogen lamps. It was shown that the multiple precursors exhibited similar temperature histories and were sufficiently foamed using the conveyor.

Article Access Ranking

12 Aug. (Last 30 Days)

  1. An Evaluation Method for Hydrogen Embrittlement of High Strength Steel Sheets Using U-bend Specimens ISIJ International Advance Publication
  2. Perspective toward Long-term Global Goal for Carbon Dioxide Mitigation in Steel Industry Tetsu-to-Hagané Vol.105(2019), No.6
  3. Influence of Atmosphere and Basicity on Softening and Melting Behaviors of the CaO–FeO–SiO2–Al2O3–MgO System ISIJ International Vol.60(2020), No.7
  4. Preface to the Special Issue on “Recent Approaches to Control of Cohesive Zone Phenomena and Improvement of Permeability in Blast Furnace” ISIJ International Vol.60(2020), No.7
  5. Method for Evaluating Hydrogen Embrittlement of High-Strength Steel Sheets Considering Press Formation and Hydrogen Existence State in Steel ISIJ International Advance Publication
  6. Effect of Pre-reduction Degree on Softening Behavior of Simulant Sinter Iron Ore ISIJ International Vol.60(2020), No.7
  7. Prediction of Softening Behavior of Simulant Sinter Ore by ADEM-SPH Model ISIJ International Vol.60(2020), No.7
  8. Numerical Simulation of Coexisting Solid-liquid Slag Trickle Flow in a Coke Bed by the SPH Method with a Non-Newtonian Fluid Model ISIJ International Vol.60(2020), No.7
  9. Numerical Simulation on Phenomena of Fine Particles Passing through an Orifice under Gas Flow Condition ISIJ International Vol.60(2020), No.7
  10. Influence of Gasification Reaction of Coke on Sliding and Dynamic Contact Angles of Droplets in a Blast Furnace ISIJ International Vol.60(2020), No.7

Search Phrase Ranking

12 Aug. (Last 30 Days)

  1. blast furnace
  2. blast furnace productivity
  3. blast furnace permeability
  4. blockage orifice
  5. skew rolling plate
  6. trip steel
  7. 780mpa
  8. hole expansion ratio
  9. intensive cooling in continuous casting
  10. suehiro masayoshi