最新コンテンツ

Express Letter
published : Advanve Publication
Ken WATANABE, Shingo IDE, Takashi KUMAGAI, Takaaki FUJINO, Koichi SUEMATSU and Kengo SHIMANOE
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A new electrochemical oxygen separation pump was developed by using c-axis-oriented La9.66Si5.3B0.7O26.14 (c-LSBO), which has high oxide-ionic conductivity (>10−3 S cm−1) up to 300°C. Interfacial resistance between the electrode and c-LSBO was investigated to realize the full potential of LSBO as an oxygen separation material. The formation of a Sm-doped CeO2 (SDC) thin film (thickness: 300 nm) between the electrode and c-LSBO was effective for suppressing the interfacial resistance. Furthermore, a mixed conductive La0.6Sr0.4Co0.78Ni0.02Fe0.2O3−δ (LSCFN) was applied to the electrode for enhancing the oxygen reduction/evolution activity on the electrode. The LSCFN/SDC/c-LSBO symmetric cell showed an oxygen permeation flux of 3.5 mL cm−2 min−1 (1.0 A cm−2) at 600°C under an applied DC voltage of 1.5 V; this value was 67 times that of Pt/c-LSBO. This oxygen pump based on the LSCFN/SDC/c-LSBO symmetric cell would find promising application in oxygen separation at intermediate temperatures. Further reduction of the interfacial resistance and polarization resistance of the electrode may decrease the operating temperatures to below 400°C.
Full Paper
published : vol. 126, no.11, November 2018
Shengfang SHI, Tomoyo GOTO, Sung Hun CHO and Tohru SEKINO
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In this work, a potentially novel ceramic-based composite was developed for photocatalytic activity. Hot-press sintered Al2O3/Ti composites containing 20 vol.% of metallic Ti were treated with NaOH and heated to generate a nanometer-scale structure to induce an active surface layer for photocatalytic activity. Because NaOH treatment does not affect Al2O3 ceramics, to form a nano-structured titania layer over the entire surface of a composite whose surface contains both Al2O3 and Ti, strict control was exerted over the NaOH concentration, treatment temperature, and time. The results showed that Al2O3/Ti composites were fully covered by nano-structured sodium containing titanate layers after being treated with 5-M NaOH at room temperature for 3 h and at 60°C for 1 h. After HCl treatment at 25°C or water treatment at 80°C for 24 h, Na+ ions were sufficiently removed and a nano-porous structure of titanate remained despite a widened network. HCl treatment and heat treatment at temperatures of 400–600°C changed the surface structure from a nano-porous network to nano-plates or nanorods of titania. The photocatalytic activity of Al2O3/Ti composites treated with NaOH, HCl, and heat was also investigated. Samples heated at 600°C exhibited the highest Rhodamine B degradation efficiency of 35% after exposure to ultraviolet light for 12 h, implying the multifunctionality of the surface-modified ceramic/metal composites.
Express Letter
published : vol. 126, no.11, November 2018
Shigeru HORII, Itsuki ARIMOTO and Toshiya DOI
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Equipment that can generate a linear drive type of modulated rotating magnetic field (MRF) was developed for three-dimensional magnetic alignment applicable to a continuous production process. This equipment consists of an arrayed magnet unit assembled using permanent magnets and a linear drive system, and it can generate a static magnetic field region with 0.9 T and a rotating magnetic field region with 0.5–0.9 T and 520 rpm. The equipment has been used to successfully biaxially align powders of an orthorhombic cuprate superconductor DyBa2Cu3Oy (y∼7) with twin microstructures in epoxy resin at room temperature without rotating the sample.
The 72th CerSJ Awards for Academic Achievements in Ceramic Science and Technology: Review
Special Article
published : vol. 126, no.11, November 2018
Tetsuo TSUCHIYA
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New technological demand has been opened rapidly to develop a fabrication of coating thin film on various substrates via relatively sustainable methods with consuming least resources and conserving energy. To satisfy the new demand, we propose an original process to fabricate functional ceramic films at ambient temperature by an ultraviolet light reaction after coating of metal–organic compound and nanoparticles on substrates. Based on our research, oxide thin films containing of epitaxially grown grains as well as polycrystals can be individually fabricated by changing the process parameter. In this review, I introduce about highly functional thin films developed with my collaborators. The novel thin films include a flexible transparent conductive film, a high-brightness phosphor film, and bolometer film with a high temperature coefficient of resistivity. I introduce an effectiveness of our laser irradiation process to control a texture such as polycrystals and epitaxially grown grains in novel and/or flexible ceramic thin films. In addition, I explain the mechanism and influencing factors of the generation of these thin films and discuss the applications of the films to electronic and optical components and devices.
Full Paper
published : vol. 126, no.11, November 2018
Shuai LU, Xiaoqiang LI, Youfu ZHOU, Wentao XU, Junrong LING and Wei PAN
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TiB2/Ti2AlN composites with different proportions were successfully fabricated through solid state reaction of Ti/Al/AlN/BN powders and subsequent hot pressing sintering. The reaction mechanism, microstructures and mechanical properties of the composites were investigated. The Vickers hardness of the samples ascended with increases in the TiB2 content and reached the highest value of 11.32 ± 0.12 GPa at a TiB2/Ti2AlN mole ratio of 1:2 (M2T1). TiB2/Ti2AlN composites with a mole ratio of 1:3 (M3T1) and 1:4 (M4T1) exhibited the maximum flexural strength of 497 ± 15 MPa and the highest fracture toughness of 9.52 ± 0.14 MPa·m1/2, respectively, which are 1.3 times and 1.8 times that of pure Ti2AlN (MT0) ceramic.
Full Paper
published : vol. 126, no.11, November 2018
Mahmudi MAHMUDI, Widiyastuti WIDIYASTUTI, Puspita NURLILASARI, Samsudin AFFANDI and Heru SETYAWAN
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Manganese dioxide having nanorod and nanoflake morphologies have been successfully prepared by electrolysis of KMnO4 at a temperature of 60°C. The acidity of the solution substantially influenced the particle morphology. The particles had nanorod morphology at a very acid solution (pH 0.2) whereas they had nanoflake shape at the base condition (pH 9). X-ray diffraction analysis revealed that the particles generated at very acid condition were α-MnO2. On the other hand, the particles synthesized at base condition were amorphous MnO2. The electrocatalytic activity towards oxygen reduction reaction (ORR) of the materials was studied in oxygen-saturated 0.6 M KOH solution. The electrons transferred per oxygen molecules of ORR for nanorod and nanoflake MnO2 particles were 2.23 and 1.75, respectively. The results suggest that nanorod MnO2 particles exhibit better ORR activity corresponding to 2-electron transferred ORR mechanism.
Full Paper
published : vol. 126, no.11, November 2018
Jae Min KIM and Eung Soo KIM
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Microwave dielectric properties of MgTi1−x(Zn1/3B2/3)xO3 (B = Nb5+, Ta5+, 0.025 ≤ x ≤ 0.125) were investigated based on their structural characteristics and the electronegativity difference of the constituent ions. For the specimens of MgTi1−x(Zn1/3Nb2/3)xO3, a single phase of the rhombohedral ilmenite structure appeared for the entire range of compositions (0.025 ≤ x ≤ 0.125), while MgTi1−x(Zn1/3Ta2/3)xO3 showed a single phase of ilmenite structure up to x = 0.075, and then MgTi2O5 was detected as a secondary phase on further substitution of (Zn1/3Ta2/3)4+ at Ti4+-site of MgTiO3. Quality factor value increased with the electronegativity difference up to an electronegativity difference of 2.015 and was dependent on the degree of covalent character of the bond. Temperature coefficient of resonant frequency decreased with an increase in oxygen octahedral distortion. Dielectric constant of the specimens did not exhibit any remarkable change with the substitution of (Zn1/3B2/3)4+ at Ti4+-site of MgTiO3.
Full Paper
published : vol. 126, no.11, November 2018
Masaki INABAYASHI, Yoshihiro DOI, Makoto WAKESHIMA and Yukio HINATSU
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Ternary rare earth rhenium oxides Ln3ReO7 (Ln = Y, Er–Lu) have been prepared. Their X-ray diffraction measurements and the Rietveld analysis show that these compounds have an orthorhombic superstructure of fluorite-type with space group C2221 (for Ln = Y, Er, Tm) or a defect-fluorite structure Fm−3m (for Ln = Yb, Lu). The zero-field-cooling and field-cooling magnetic susceptibility for Y3ReO7 diverse when the temperature is decreased through 10 K. At the same temperature, specific heat anomaly is also observed. The results of the specific heat measurements for Tm3ReO7 and Yb3ReO7 indicate the existence of magnetic anomaly below 7 and 2.2 K, respectively. On the other hand, Er3ReO7 and Lu3ReO7 are paramagnetic down to 1.8 K.
Full Paper
published : vol. 126, no.11, November 2018
Yuji NAKABAYASHI, Satoru YAMADA, Satoshi ITOH and Takeshi KAWAE
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Single-crystal thin films of gallium oxide (Ga2O3), an ultra-wide bandgap semiconductor, were fabricated on c-plane sapphire by mist chemical vapor deposition (mist CVD). The grown α-Ga2O3 thin films had low surface roughness, and we characterized their initial crystal growth phase by using atomic force microscopy and X-ray diffraction. By varying the precursor concentration, we changed the surface roughness and crystallinity of the thin films. The lattice constants of the α-Ga2O3 thin films almost matched those of the single crystal in the initial growth phase. We also found that these thin films grew hetero-epitaxially. Finally, mist CVD might have a very short incubation time in this system.
Full Paper
published : vol. 126, no.11, November 2018
Kazumi KANEDA, Yoshiki IWAZAKI and Yukihiro KONISHI
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One of the methods to improve the lifetime of a multilayer ceramic capacitor with Ni electrode (Ni-MLCC) is vanadium addition. With the addition of vanadium, insulation resistance deteriorates and reliability improves. The resistance elements of the three resistor-capacitor electrical equivalent circuit: dielectric-electrode interface, grain boundary, and grain, all deteriorated. In particular, the interface resistance significantly deteriorated with the increase in vanadium. The experimental results suggest that the high interface resistance is not always necessary to improve reliability of Ni-MLCCs. It is deduced that oxygen vacancy formation is suppressed with vanadium addition from the first principles calculation and the thermally stimulated depolarization current analysis. Therefore, the decrease in oxygen concentration is the main factor for improving reliability with vanadium addition.
Full Paper
published : vol. 126, no.11, November 2018
Masamichi NISHIDE, Takashi KATODA, Hiroshi FUNAKUBO and Ken NISHIDA
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We proposed a novel method to evaluate strain components in PbTiO3 thin films using Raman spectroscopy. In this method, the strain components are calculated from peak shifts of three E(TO)-modes. The coefficients to calculate the strain components were decided via least square technique using experimental values for two-dimensional stress and hydrostatic pressure. The strain components that were estimated using the obtained coefficients were in good agreement with those measured by X-ray diffraction measurement (XRD). The average error between the strain components evaluated by XRD and Raman spectroscopy was about 0.05%.
Full Paper
published : vol. 126, no.11, November 2018
Ju-Young CHA, Chun-Ho KIM and Young-Jin KIM
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In this study, the surface of zirconia (ZrO2) substrates was modified by the combination of plasma treatment and coating with silicon-substituted hydroxyapatite (Si-HA) sols, comprising an expected theoretical Si content of 0 (Si-HA0), 1.70 (Si-HA1), 3.44 (Si-HA2), and 7.01 wt % (Si-HA4) for improving the biological performance of substrate. The Si-HA-coating layers were successfully deposited on the ZrO2 substrate surface. These coating layers exhibited a three-dimensional interconnected microporous structure and a single-phase crystal owing to HA, implying that the Si content hardly affects the phase composition and microstructure of the coating layers. The dissolution rate of the Si-HA coating layers in deionized water increased with the Si content, which affected the proliferation of mouse calvaria pre-osteoblasts (MC3T3-E1). Cytocompatibility test results revealed that Zr-Si-HA2 substrate, which was coated with Si-HA2, promoted the proliferation and differentiation of MC3T3-E1 more rapidly than the other substrates. These results revealed that Zr-Si-HA substrates are ideal biomaterials for bone tissue engineering.
Technical Report
published : vol. 126, no.11, November 2018
Naoto KITAMURA, Akira NOMURA, Akira SAITOH, Hidekazu KOBAYASHI, Ippei AMAMOTO and Hiromichi TAKEBE
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We have studied the water durability of ZrO2 containing FeO–Fe2O3–P2O5 glasses for the immobilization of nuclear waste including Zr isotope. ZrP2O7 crystals with 1–2 micrometer in diameter were precipitated in the glass matrix incorporated with ≥1 mol % ZrO2. The molecular structure of phosphate network including ZrP2O7 precipitates was analyzed by micro-Raman spectroscopy. Formations of Q1 and Q0 phosphate units contributing to better water durability are ascribed to preferential precipitation of ZrP2O7 crystals with Q1 units and the compensation of phosphate component in residual glass matrix.
Note
published : vol. 126, no.11, November 2018
Saeki YAMAMURO, Keigo SUZUKI and Toshiro TANAKA
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Microwave heating is known to provide extremely rapid synthesis of silicon carbide (SiC) from mixtures of silicon and carbon powders. The formation mechanism has long been considered to be a solid-state reaction among the powders in the mixture. Here, we present a new reaction mechanism via a gas-phase route. We have confirmed successful synthesis of β-SiC powder by microwave-heating of a small amount of Si powder that was entered into a quartz tube and then embedded in graphite powder, although no direct contact between the Si and graphite powders was allowed. Scanning electron microscopy observations revealed that the β-SiC powder was formed by direct carbonization of the Si powder. Since the atmosphere during the reaction comprises a vast majority of carbon monoxide (CO) gas according to the Boudouard equilibrium, the carbonization appears to have taken place via the CO gas. The contribution of such a gas-phase reaction could account in part for the rapidity of the microwave-heating reactions reported so far, which can hardly be explained solely by solid-state reactions among the mixed powders.
Note
published : vol. 126, no.11, November 2018
Kazutoshi IIJIMA, Ayako IIZUKA, Ryo SUZUKI, Hitomi UENO-YOKOHATA, Nobutaka KIYOKAWA and Mineo HASHIZUME
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We have developed methods to functionalize polystyrene (PS) substrates with hydroxyapatite (HAp) via protein adsorption layers in simulated body fluid (SBF), a solution with similar inorganic ion concentrations to those of human plasma. In this study, three-dimensional (3D) porous HAp cell scaffolds were prepared by using PS substrates as a template. Human serum albumin was adsorbed on the 3D porous PS. Then substrates were pretreated with alternate soaking process using solutions containing calcium ions and phosphate ions followed by incubation with SBF. By optimizing the treatment conditions, 3D porous substrates were completely coated with bone-like HAp maintaining porous structures. Human mesenchymal stem cells proliferated and migrated into inside of the HAp-coated scaffolds and secreted abundant fibrous extracellular matrix. This method can provide porous HAp substrates with the specific functions such as biodegradability or excellent strength to weight ratio by changing polymers used as templates.
Note
published : vol. 126, no.11, November 2018
Masayoshi OHASHI, Keiji KUSUMOTO and Katsuya KATO
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A tantalum(V) nitride (Ta3N5)-containing powder for non-toxic red pigments was prepared by heat-treatment for the mixed powders of tantalum(V) oxide (Ta2O5), aluminum nitride and potassium fluoride in nitrogen atmosphere without flowing ammonia. The foreign ions of K+ and Al3+ were incorporated into Ta3N5 in the synthetic process. The incorporation of the ions had an influence on the hue of Ta3N5. It can coordinate a reddish color of Ta3N5 pigments.
The 72th CerSJ Awards for Advancements in Ceramic Science and Technology: Review
Special Article
published : vol. 126, no.10, October 2018
Kotaro FUJII and Masatomo YASHIMA
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This article provides the first critical review on the discovery and development of BaNdInO4. Exploring a new structure family of ionic conductors is an important task to develop ceramic ionic conductors. Since some A2BO4 compositions exhibit high oxide-ion conductivities, we investigated ABCO4 compositions to explore new oxide-ion conductors with A/B/C cation-ordered structures. Here A, B and C are cations [ionic radii: r(A) ≥ r(B) ≥ r(C)]. In 2014, we discovered a new material BaNdInO4 which belongs to a new structure family of perovskite-related structures. This BaNdInO4-type structure (monoclinic, P21/c) consists of alternative stacking of the A rare earth oxide unit and perovskite unit with a b c tilt system. We also discovered new materials BaRInO4 (R = Sm, Y, Ho, Er, Yb) having the BaNdInO4-type structure, and report their lattice parameters and anisotropic chemical expansion. Electrical conductivity of BaNdInO4 was higher than those of BaRInO4 (R = Sm, Y, Er). Oxide-ion conduction was dominant for BaNdInO4 in the P(O2) region from 3.8 × 10−22 to 5.5 × 10−9 atm at 858°C. Oxide-ion conductivities of Ba1.1Nd0.9InO3.95, BaSr0.1Nd0.9InO3.95 and BaCa0.2Nd0.8InO3.9 were higher than that of BaNdInO4. Structure analyses of Ba1.1Nd0.9InO3.95 and BaSr0.1Nd0.9InO3.95 indicated that the excess Ba and doped Sr cations were partially substituted for Nd cation and that there existed oxygen vacancies, leading to the increase of the carrier concentration and higher oxide-ion conductivity. Following the discovery of BaNdInO4, BaRScO4 (R = Nd, Eu, Y, Yb) and SrYbInO4 were reported as new ABCO4 materials. BaYScO4 and BaYbScO4 have the BaNdInO4-type structure. BaNdScO4 and BaEuScO4 crystallize into the space group Cmcm, which has a higher symmetry than P21/c for BaNdInO4. SrYbInO4 is the first example of pure oxide-ion conductors with CaFe2O4-type structure. Further investigations of ABCO4 compositions and BaNdInO4 related materials will lead to development of materials science and solid state ionics.
Full Paper
published : vol. 126, no.10, October 2018
Jang-Hoon HA, Sujin LEE, Syed Zaighum Abbas BUKHARI, Jongman LEE, In-Hyuck SONG, Seung Jun LEE and Jaeho CHOI
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Porous ceramic membranes have received increasing attention for decades. Due to their excellent thermal and chemical properties. Because their pore sizes of as-sintered silicon carbide supports are within the microfiltration range, silicon carbide membranes have been actively investigated by many researchers and industries. For example, silicon carbide supports by themselves (average pore size of 1–10 µm) and microfiltration layer-coated silicon carbide supports (average pore size of 0.1–1 µm) can be easily prepared. However, there is insufficient data concerning the combination of ultrafiltration layer-coated silicon carbide supports (average pore size of below 0.1 µm). Therefore, the authors first prepared typical microfiltration layer-coated silicon carbide supports, and then deposited ultrafiltration layers on them. Furthermore, the authors characterized the membrane properties of the ultrafiltration layer-coated silicon carbide supports. In addition, the possibility of reducing the average pore size of microfiltration layer-coated silicon carbide supports below 0.1 µm was investigated, and improving the water permeability of ultrafiltration layer-coated silicon carbide supports by controlling processing conditions such as the heat-treatment temperature, dip-coating conditions, and composition of the alumina coating slurry was explored.
Full Paper
published : vol. 126, no.10, October 2018
Yoshiteru ITAGAKI, Jian CUI, Naoto ITO, Hiromichi AONO and Hidenori YAHIRO
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Samaria-doped ceria, (SmO1.5)0.2(CeO2)0.8 (SDC), containing nickel (Ni) was prepared as the anode of solid oxide fuel cell fueled with 6% ammonia (NH3). The Ni-free SDC powders prepared by the reverse co-precipitation method exhibited poor catalytic activities for NH3 decomposition in 6% NH3/Ar. Impregnation of Ni onto the SDC powders significantly enhanced its catalytic activity. The catalytic activity was highest at 10 wt % Ni–SDC, but it decreased with an increase in the Ni content. Contrary to expectation, the anodic performances were similar between 10 and 40 wt % of Ni loading and the highest maximum power densities were 98.8 and 96.5 mW·cm−2 at 900°C, respectively. Impedance analysis of the anodes revealed that the anodic performance was rate-controlled by the similar process in 4%H2 fuel and that was electrochemical oxidation and diffusion processes.