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Key engineering materials
Trans Tech Publications Ltd.
Key engineering materials

Trans Tech Publications Ltd.

半月刊

1013-9826

Key engineering materials/Journal Key engineering materials
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    Preparation of Barium Titanate and Strontium Titanate Nanocube Particles and Their Accumulation using Smart Glue

    Ai NozawaTetuo KuwabaraHiroshi UchidaChikako Moriyoshi...
    514-517页
    查看更多>>摘要：Barium titanate (BaTiO_3, BT) and strontium titanate (SrTiO_3, ST) nanocube particles were successfully prepared by a solvothermal method. The prepared particles were collected by a centrifugal separator. The X-ray diffraction (XRD) measurement confirmed the formation of perovskite BT and ST nanoparticles with sizes of around 17 run while a transmittance electron microscope (TEM) observation revealed formation of cubic-shaped nanoparticles with sharp edge and corner. These nanocube particles were monodistributed in hexane with tri-n-octylphosphine oxide (TOPO) as dispersant, separately, and then, the 2-dimentional checkerboard-structured accumulations composed of the BT and ST nanocubes were built up using DNA base pair such as adenine and thymine as smart glue. TEM observation confirmed that a part of accumulations had a checkerboard-structure.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Relaxation Phenomena of MgCuZn Ferrites

    Taku MuraseHidenobu Umeda
    521-524页
    查看更多>>摘要：The decrease of initial relative permeability at 10~3-10~6Hz is observed in MgCuZn or MnMgCuZn ferrites. By measuring the temperature dependence of loss factor, the gradual deterioration of initial relative permeability is attributed to a relaxation phenomenon. The relaxation phenomena of MnMgCuZn ferrites occur in the condition of the stoichiometoric composition and the higher sintering temperatures. The activation energies of the relaxation phenomena are calculated to be 0.3-1.0eV. The relaxation times at infinite temperature are calculated to be 10~(-12)-10~(-16) second. The initial relative permeability of MgCuZn or MnMgCuZn ferrites with the relaxation phenomena is higher than the value calculated from the resonance frequency and Snoek's limit law.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Effect of Thermal Annealing on Electrical Degradation Characteristics of Sb_2O_3-Bi-Mn-Co-doped ZnO Varistors

    Masayuki TakadaYuuki SatoShinzo Yoshikado
    525-528页
    查看更多>>摘要：The effects of thermal annealing on the electrical degradation of Sb_2O_3-Bi-Mn-Co-doped ZnO varistors were investigated. For samples with 0.04 mol% Sb_2O_3 or more, the nonlinearity index α of the voltage-current (V-I) characteristics after electrical degradation increased upon annealing. Moreover, the value of α after electrical degradation was proportional to the full width at half maximum (FWHM) of the X-ray diffraction peak for Zn_(2.33)Sb_(0.67)O_4-type spinel particles under various annealing conditions. The added Sb_2O_3 did not dissolve in the ZnO grains but became segregated at grain boundaries. Therefore, it is speculated that the increase in the FWHM of the spinel particles is due to an increase in the numbers of fine spinel particles at grain boundaries and triple points during annealing. Furthermore, it is suggested that the improvement in the electrical degradation upon annealing is due to a decrease in the mobility of oxide ions or Zn~(2+) ions owing to their being blocked by uniformly distributed fine spinel particles at grain boundaries.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    The Effect of Reoxidation on Thermal Shock Resistance of SrTiO_3-based Varistors

    Atsushi HitomiNaoki ChidaMinoru OgasawaraDai Matsuoka...
    529-532页
    查看更多>>摘要：The fabrication processes of SrTiO_3-based varistors were investigated to obtain highly thermal-shock-resistant devices. It has been found that the reoxidation conditions are strongly related to the thermal cracking ratio (%) of the varistors. A large compressive stress was generated on the varistor surface by reoxidation, consequent upon the lattice parameter difference between its surface portion and its internal portion. This residual stress on the surface is thought to be the key factor of the achieved thermal-shock-resistance.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Millimeter wave sintering of AlN ceramics for heat sink application

    Akira KishimotoTetsuya MorimotoHidetaka Hayashi
    533-536页
    查看更多>>摘要：By using 24 GHz millimeter-wave irradiation, full densification of AlN added with Y_2O_3 was attained at 1700 ℃, which is comparable to 28GHz-wave irradiation. Thermal conductivity of a resultant sample exceeded 200 W/mK, which is the highest value in AlN fabricated in non-reducing atmosphere.
      原文链接:
    • NETL
    • NSTL

    Thermophysical Behaviour of Crystalline Halides with Temperature

    M. Anis-ur-Rehman
    537-540页
    查看更多>>摘要：The thermal conductivity, thermal diffusivity and volumetric heat capacity of monocrystalline AgCl and AgBr were measured simultaneously, by Advantageous Transient Plane Source method in the temperature range 77-350 K. Both thermal conductivity and thermal diffusivity follow Eucken's law in the temperature region studied. The heat capacity at constant pressure (C_p) determined from the volumetric heat capacity agrees with the calculated one at room temperature. The values of C_p obtained from this experiment along with the reported data as a function of temperature are also reported. The ratio of the thermal conductivity (λ) of AgBr and AgCl calculated from the Leibfried-Schlomann (LS) formula are in excellent agreement with the ratio λ_(AgBr)/λ_(AgCl) measured experimentally.The dielectric constant and loss factor, of these crystalline hallides, are also reported as a function of frequency in the range 100 Hz to 1 MHz at room temperature.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    High frequency characteristic of elements substituted hexagonal ferrites

    Nobuyuki HiratsukaKoichi KakizakiKenji Kamishima
    541-545页
    查看更多>>摘要：The initial permeability μ' (at 0.1 GHz) of Ba_3Co_2R_(0.1)Fe_(23.9)O_(41) (x=0.1, R= Gd, Dy, Ho, Yb) samples is higher than that of the Co_2Z ferrite without substitution. In particular, μ' of Gd~(3+) substituted Z-type ferrite sample (x=0.1) is the highest of all samples. The substituted sample of Ba_3Co_2Ti_xZn_xFe_(24-2x)O_(41) with x= 0.85 has a maximum μ' of 24, which is twice as large as that of the non-substituted sample with x=0. Ba_3Co_(2-2x) Li_xFe_(24+x)O_(41)(x=0-1.0) are also prepared. The sample with x=0 shows μ'of 8 at 50MHz. The maximum μ' is 24.5 at x=0.3. An apparent magnetic anisotropy constant K~*, calculated by using H_a~* and Ms, decreases. Therefore, the decrease of the magnetic anisotropy contributes to the increase of μ'.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    New Titanium Oxide Compound for Photocatalytic Water Splitting, Hydrous Na_(16)Ti_(10)O_(28)

    Sae NakajimaSoichiro WatanabeKazuyoshi UematsuTadashi Ishigaki...
    546-549页
    查看更多>>摘要：Photochemical splitting of water into H_2 and O_2 using solar energy is process of great economic and environmental interest. In this study, we investigated novel photocatalytic compound, Na_(16)Ti_(10)O_(28), for water splitting. Na_(16)Ti_(10)O_(28) was prepared by solid-state reaction at 900 ℃ for 1 h. Prepared sample was characterized using powder X-ray diffraction, diffuse reflectance spectrum, and scanning electron microscopy. As-prepared Na_(16)Ti_(10)O_(28) sample is easily hydrated in water. Hydrous Na_(16)Ti_(10)O_(28) showed H_2 evolution without co-catalyst.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Effect of Vibro- Milling Time on Phase Formation and Particle Size of ZnNbO_6 Nano-powders

    Athipong NgamjarurojanaRattikorn YimnirunSupon Ananta
    550-553页
    查看更多>>摘要：Zinc niobate, ZnNb_2O_6, nanopowders was synthesized by a solid-state reaction via a rapid vibro-milling technique. The effect of milling time on the phase formation and particle size of ZnNb_2O_5 powder was investigated. The formation of the ZnNb_2O_ 6 phase investigated as a function of calcination conditions by DTA and XRD. The particle size distribution of the calcined powders was determined by laser diffraction technique, while morphology, crystal structure and phase composition were determined via a SEM techniques. In addition, by employing an appropriate choice of milling time, a narrow particle size distribution curve was also observed.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Photocatalytic Activity of Bismuth Layered Perovskite Treated with Acid

    Soihiro WatanabeYousuke NarumiKenji TodaTadashi Ihigaki...
    554-557页
    查看更多>>摘要：We synthesized Sr_(0.7)La_(0.2)[ ]_(0.1)Bi_2Ta_2O_9 (SBTL, [ ] vacancy), and measured their photocatalytic activity for water decomposition under UV light irradiation after acid treatment. They showed the high photocatalytic activity under UV light irradiation (H_2 evolution (213μm.mol / h) , O_2 evolution (82μmol / h)).
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd