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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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    Effects of CO_2O_3 on the Piezoelectric Properties of Na_(0.5)Bi_(0.5)TiO_3 Lead-free Piezoelectric Ceramics

    Jiang XiangpingFeng ZiyiLin meiChen Chao...
    340-342页
    查看更多>>摘要：Lead-free piezoelectric ceramics Na_(0.5)Bi_(0.5)TiO_3+xmol%Co~(3+) (NBT-xC) were synthesized by conventional solid-state process. Effects of Co~(3+) addition on the phase structure, dielectric and piezoelectric properties of NBT-xC were investigated. The X-ray diffraction suggested that all specimens were rhombohedral perovskite structure. After a small addition of CO_2O_3, a dense microstructure with increased grains was developed. The doping with Co~(3+) enhanced mechanical quality factor Q_m significantly, whereas piezoelectric constant d_(33) and electromechanical coupling factor k_p decreased slightly with increasing amount of Co~(3+). For the ceramics with x=3, the electric properties become optimum, which are as follows: d_(33)=～70pC/N, k_p=～13%, Q_m=～934, tanδ=～0.02 (1kHz), respectively. These results indicate that the Co~(3+) ion was considered to replace Ti~(4+) ion and present "hard doping" effect.
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    • NSTL
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    The Left-handed Properties of the Composite Medium Composed of Ferrite Cubes' Array and Copper Net

    Lihui ZhangYang BaiJinxu LiLijie Qiao...
    343-345页
    查看更多>>摘要：Left-handed material (LHM), whose permittivity and permeability are both negative, has attracted much attention due to its exotic electromagnetic properties, such as negative refraction, backward wave propagation and evanescent wave amplification. The microwave left-handed property of a composite medium composed of ferrite cubes' array and copper net was studied using the method of finite difference time domain in this paper. An obvious left-handed pass band emerged when ferrite cubes were combined with longitudinal copper wires, because the ferrite produced negative permeability by the ferromagnetic resonance and the copper wires produced negative permittivity by the plasma. With the addition of horizontal copper wires, the transmission intensity of the pass band was gradually weakened. It can be concluded that the horizontal wires played a negative role in realizing the composite LHM with ferrite cubes and copper net. This work gives an instructive direction to the fabrication of 3D LHMs.
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    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Effect of Specific Surface Area on Growth and Porosity of Oxide Superconducting Ceramic YBCO Single Domain

    C P ZhangX ChaudH T CaoE Beaugnon...
    346-349页
    查看更多>>摘要：The effect of specific surface area on the growth and the porosity of oxide ceramic superconductor YBCO single domain are investigated. The enhancement of growth depth depends on the large specific surface area σ. When the specific surface area a is more than the critical value 200mm~2/g, the YBCO single domain is full-growth in the sample of size Φ20mm×18mm. It reveals that a large specific surface area providing an effective tunnel of oxygen diffusion for the crystal growth. On the other hand, this tunnel makes oxygen gas emitting out resulting in porosity diameter decreased. The mean porosity diameter is observed as 5μm in hole sample smaller than 80μm in plain sample. The porosity distribution is calculated as 1/(100μm)~2 in plain sample and 8/(10μm)~2 in hole sample.
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    Comparative Study on Ni-Zn Ferrites by One-step Synthesis and Conventional Two-step Synthesis

    Zhijian PengHuilin GeDan LiZhiqiang Fu...
    350-353页
    查看更多>>摘要：The magnetic hysteresis parameters like coercivity (H_c) and saturation magnetization (M_s), and dielectric parameters like dielectric constant (ε') and dielectric loss (ε" /ε') of Ni_(0.5)Zn_(0.5)Fe_2O_4 prepared by "one-step synthesis" and conventional two-step synthesis methods, respectively, were comparatively investigated. It was observed that the saturation magnetization, dielectric constant and dielectric loss for samples prepared by "one-step synthesis" method are lower than those of ferrite samples prepared by conventional synthesis method. However, the coercivity of the former is higher due to its smaller grain size. The low dielectric loss makes these samples especially attractive for use at high frequencies.
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    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Synthesis of Magnetic Nano-Composite by Partial Reduction of Barium Hexaferrite via High-Energy Ball Milling

    M. J. MolaeiA. AtaieSh. Raygan
    354-356页
    查看更多>>摘要：In this work, nano-composite of barium hexaferrite/magnetite was produced by partial reduction of barium hexaferrite with graphite via ball milling. Phase composition, morphology and magnetic properties of the samples were evaluated by XRD, SEM and VSM, respectively. XRD results revealed that after 15 hours milling, a nano-composite of BaFe_(12)O_(19)/Fe_3O_4 formed which mean crystallite size of BaFe_(12)O_(19) was 17 nm. After milling for 20 and 40 hours, the peaks of BaFe_(12)O_(19) were weakened and Fe_3O_4 was detected as a dominant phase. The coercivity decreased from 703 to 153 Oe when the milling time increased from 15 to 20 hours.
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    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Low Temperature Sintering of Ferro-materials with Both Capacitance and Inductance Properties

    Xiwei QiWeiqi HanPeihua Wang-yangHaifeng Wang...
    357-360页
    查看更多>>摘要：Ferro-materials which possess both capacitance and inductance were sintered at low temperature using Bi_2O_3 as sintering additives. The composition of ferro-materials is 0.4PMZNT-0.6NiCuZn. PMZNT relaxor ferroelectric is a solid solution that consists of Pb(Mg_(1/3)Nb_(2/3))O-3, Pb(Zn_(1/3)Nb_(2/3))O_3 and PbTiO_3. NiCuZn ferrite with general formula is Ni_(0.2)Cu_(0.2)Zn_(0.6)Fe_2O_4. Effects of the content of Bi_2O_3 and sintering temperature on the relative density of prepared ferro-materials have been studied. Dense ferro-materials were obtained at as low as 890℃ with 2.0 wt% of Bi_2O_3. The X-ray diffractometer (XRD) identifications showed that ferro-materials consisted of distinct ferroelectric and ferromagnetic phases. Scanning electron microscopy (SEM) observations revealed that low temperature sintered ferro-materials possess high density and fine-grained microstructures. Prepared ferro-materials exhibit electromagnetic properties.
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    • NETL
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    CO_2Z, CO_2Y and CoM-Type Hexagonal Ferrites for Multilayer Inductors

    S. KracunovskaJ. Toepfer
    361-365页
    查看更多>>摘要：Hexagonal Co-containing Z-; Y- and M-type ferrites are used as soft magnetic materials for multilayer inductors for operating frequencies up to 3 GHz. CO_2Z-type Ba_3CO_2Fe_(24)O_(41), iron excess Ba_3CO_(2-y)Fe_(24+y)O_(41) (0≤ y ≤ 0.8) and Ba_3CO_(2-)Cu_xFe_(24)O_(41) (0 ≤ x ≤ 1.0) ferrites have their stability intervals between 1260-1350℃. The permeability of a ferrite with y = 0.6 sintered at 1300℃ is u = 30 throughout the MHz. Addition of Bi_2O_3 shifts the maximum shrinkage down to 950℃. Their permeability is μ = 5 because of partial decomposition of the CO_2Z phase. Y-type ferrite Ba_2Co_(1.2-x)Zn_xCu_(0.8)Fe_(12)O_(22) (x = 1.2) sintered at 1100℃ shows a permeability of μ = 20. Sintering at 900℃ reduces the permeability to μ = 10. M-type BaCo_(1.2)Ti_(1.2)Fe_(9.6)O_(19) ferrites sintered at 970℃ display a permeability of μ = 35.
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    • NETL
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    • Trans Tech Publications Ltd

    Glass Binder in Thick Film Metallization Paste for AIN

    Wang LiliWang YuYang De-An
    366-368页
    查看更多>>摘要：In this paper, the sol-gel process was used to synthesize a glass binder in thick-film paste for aluminum nitride (AlN) metallization. Some major factors that influenced the sol-gel process including PH value, quantity of water were discussed in detail. The xerogel was analyzed by means of TG-DSC in order to determine its optimum heat treatment process. Meanwhile, the sintering behavior of silver/glass composite thick film had been studied by varying the glass content. The results show that a glass powder of a low melting point and chemically compatible with AlN substrate can be obtained by sol-gel method when the composition (wt %) is CaO (40), B_2O_3(15), SiO_2 (35), BaO (10). During sintering, the glass becomes liquid and largely affects the microstructure development and square resistance of the thick film. When the glass content is optimum (10wt %), the film adhesion strength achieves maximum and the square resistance has a relatively low value.
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    • NETL
    • NSTL
    • Trans Tech Publications Ltd

    Microwave Assisted Deposit Oxide Ceramic Coating onto Metal

    Zhenqian ChengJiachen LiuCaifen WangHai Xu...
    369-370页
    查看更多>>摘要：A new way to deposit oxide ceramic coating on the metal was prepared by Gel-casting and microwave assisted heating. The oxide ceramic coating was obtained by dipping the metal substrate whose surface carried positive charge through acid treatment to the gel slurry which was composited by oxide powder with negative charge, and then gelating, drying and heating by microwave. It was showed that it was feasible to realize coating of ceramics on metal surface through microwave heating.
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    • NETL
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    Dielectric and Sintering Properties of the Doping CaO-B_2O_3-SiO_2 System Low Temperature Co-fired Ceramics

    He MingZhang ShurenZhou XiaohuaHu Jiangeng...
    371-375页
    查看更多>>摘要：A doping CaO-B_2O_3-SiO_2 system low temperature co-fired ceramics (LTCC) was prepared with a mixture of high temperature melting glass and sol-gel glass for different ratio. The effects of sol-gel glass content on the microstructure, crystalline phases, sintering properties and dielectric properties of CaO-B_2O_3-SiO_2 system were investigated at 850℃. The results show that the samples with sol-gel glass doping had little change in phase composition, but contained more calcium silicates, and less calcium borate. As the amount of sol-gel glass increased, the shrinkage improved, the sintered density slightly decreased, the dielectric constant (ε_r) reduced, and the dielectric loss (tgδ) decreased. When the amount of sol-gel glass was 14.5wt%, ε_r and tgδ of the doping sample were 5.80, 4.6× 10~(-5) (at 1 MHz), respectively. Moreover, the doping system had a good matching ability with gold slurry and Au-Pt-Pd slurry.
      原文链接:
    • NETL
    • NSTL
    • Trans Tech Publications Ltd