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Express Letter
published : vol. 127, no.1, January 2019
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. 127, no.1, January 2019
Dingyin ZHANG, Lingyu LI, Xiaoping CHEN, Lina YANG, Xiaoxia HU, Anran GUO, Dieni XIE, Wenjie WANG and Haiyan DU
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In this study, mullite fibrous porous ceramics (MFPCs) were fabricated by freeze-drying wetted bodies formed using vacuum filtration. The effects of freezing temperatures on the microstructure and mechanical properties were investigated. The investigations revealed that freeze-drying could effectively stop silica sol migration and obtain a uniform porous ceramic microstructure in which the binder covered the fiber surfaces and bonded the fibers at nodes. Owing to the homogeneous microstructure, the compressive strength of the obtained MFPCs with open porosity of 85.4% was more than 2.0 MPa, and there were two elastic regimes and one plastic regime in the stress–strain curve of the MFPCs, moreover, which revealed that the MFPCs fractured step by step under compression. In addition, the freezing temperatures affected the properties of the MFPCs because of the formation of plates derived from the binder.
Full Paper
published : vol. 127, no.1, January 2019
Soontaree (Grace) INTASA-ARD, Sareeya BUREEKAEW and Makoto OGAWA
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A large quantity of MgAl-layered double hydroxide (LDH) nanoparticle was successfully obtained from a single batch from high concentration (as high as 1 M) of metal salts solution. LDH were obtained by the precipitation at room temperature under ambient pressure and subsequent aging. The phase purity, crystallinity, anion composition, and morphology (shape and size of the LDH crystals) were investigated to characterize the products. Chloride type MgAl LDH with well-defined platy shapes of the lateral size of 50 nm was obtained with the very high efficiency (approximately 10 g from the 160 mL of the starting solution).
Full Paper
published : vol. 127, no.1, January 2019
Akira NISHIO, Atsushi INOISHI, Ayuko KITAJOU and Shigeto OKADA
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All-solid-state Li-ion battery is expected as the post Li-ion battery because of its high reliability and safety. However, the biggest issue for the all-solid-state Li-ion battery is the interfacial resistance between electrode and electrolyte rather than the bulk ionic conductivity of the solid electrolyte. In order to reduce the interfacial resistance, we recently adopted a new concept, “single-phase all-solid-state battery”, which is made of a single material. In principle, single-phase all-solid-state battery has low interfacial resistance between the solid electrolyte and electrodes, because the solid electrolyte and electrodes are same material. Here, the electrochemical properties of single-phase all-solid-state battery based on Li1.5Cr0.5Ti1.5(PO4)3 and the effect of Li3BO3 additive as flux to Li1.5Cr0.5Ti1.5(PO4)3 are shown. The pellet of Li1.5Cr0.5Ti1.5(PO4)3 with Li3BO3 additive showed higher density by filling the voids of Li1.5Cr0.5Ti1.5(PO4)3. As the result of the low electronic conductivity of Li3BO3, the overpotential was increased. However, the electron leakage was suppressed. On the other hand, the operation voltage and the reversible capacity were improved due to the high lithium-ionic conductivity of Li3BO3. It was found that Li3BO3 additive is useful for the improvement of the single-phase battery.
Full Paper
published : vol. 127, no.1, January 2019
Jinze ZHAI, Hongchao WANG, Wenbin SU, Teng WANG, Xue WANG, Tingting CHEN and Chunlei WANG
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The CuFeO2 powders have been synthesized by the microwave hydrothermal reaction at different reaction temperatures. The pure rhombohedral phase for CuFeO2 has been formed and confirmed by the X-ray diffraction (XRD). The microstructure and morphology for all CuFeO2 samples have been scanned by the Transmission Electronic Microscope (TEM). Various scales of grains for powders have been found spanning from several nanometers to hundreds of nanometers, and even few scales are over 1 µm for some grains. The average grain sizes for all powders have been calculated basing on the XRD patterns to show the changing of grain sizes with the temperature. The distributions of the grain size have also been studied by counting grain numbers from the TEM images. Based on the above results, the mechanism of grain growth has been analyzed and found to be the classical Ostwald ripening.
Full Paper
published : vol. 127, no.1, January 2019
Sae ARAI, Takio NOGUCHI, Tsutomu AIDA, Akira YOKO, Takaaki TOMAI, Tadafumi ADSCHIRI, Masanori KOSHIMIZU, Yutaka FUJIMOTO and Keisuke ASAI
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To determine whether neutrinoless double-beta decay occurs is an enormous challenge in particle physics. For this purpose, developing a highly transparent liquid scintillator that contains a candidate isotope at high concentration is required. In this work, 100Mo was selected as the isotope and surface-modified nanoparticles were applied. AMoO4 alkaline earth molybdates (A = Ca, Sr, and Ba) were synthesized with a subcritical hydrothermal method so that they were well dispersed in organic solvents. The crystalline phase of the nanoparticles was confirmed with X-ray diffraction measurements. The particle size of SrMoO4 nanoparticles was found to be the smallest from a transmission electron microscope examination. The SrMoO4 nanoparticles were incorporated in liquid scintillators, resulting in high transparency and efficient scintillation. In conclusion, liquid scintillators loaded with organic modified SrMoO4 nanoparticles were successfully developed.
Full Paper
published : vol. 127, no.1, January 2019
Jongman LEE, Jang-Hoon HA, In-Hyuck SONG and Jin-Woo PARK
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Inorganic surface modification was performed using a SiO2 sol–gel technique to mitigate the fouling of alumina microfiltration membranes. A positively charged alumina membrane was coated with SiO2 to generate a negative charge, and as a result, electrostatic repulsion prevented the serious adsorption (or deposition) of model foulants on the membrane. Upon the formation of the SiO2 layer, small changes in the surface morphology, pore size, and surface roughness were detected. In particular, as the pore size decreased, the pure water permeability gradually decreased. When the membrane fouling was accelerated with model foulants, the highest normalized flux level and the lowest flux decline ratio (%) were observed in the smallest SiO2-coated microfiltration membrane (0.1 M SiO2). In summary, the SiO2 coating contributed to the optimization of the antifouling properties of the ceramic membranes, although the pore size was reduced.
Full Paper
published : vol. 127, no.1, January 2019
Qinwen TAN, Na LI, Zhonghui XU, Xiaoyue CHEN, Xi PENG, Qin SHUAI and Zhengzhen YAO
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This paper presents the comparative performance of ordinary Portland cement and metakaolin-based geopolymer blocks for strontium immobilization. The geopolymer solidified blocks had better leaching resistance in deionized water, sulfuric acid, magnesium sulfuric and acetic acid buffer solutions than the cemented blocks. Meanwhile, the geopolymer solidified blocks exhibited lower compressive strength loss after freeze-thaw cycles and high-temperature tests. The more dense and compact structure of the geopolymer specimens is more beneficial for the retention of the strontium radionuclide. Most of the strontium radionuclide within the geopolymer and cement solidified blocks may be incorporated into the amorphous gels. It could be concluded that the metakaolin based-geopolymer matrix exhibited much better solidification performance and appeared to be more suitable for radioactive waste immobilization.
Note
published : vol. 127, no.1, January 2019
Tomoya GAKE, Shigenori MATSUSHIMA, Masao ARAI and Kenji OBATA
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Electronic structures and optical properties of CuMgVO4 and AgMgVO4 with optimized structures were investigated using the generalized gradient approximation proposed by Perdew-Burke-Ernzerhof and the Heyd-Scuseria-Ernzerhof hybrid functional. From the energy band calculation, we found that CuMgVO4 and AgMgVO4 have indirect band gaps. The upper valence band is mainly composed of fully occupied Cu 3d (Ag 4d) states, and the lower is mainly comprises O 2p states. The conduction band can be divided into two regions because of the crystal-field splitting by the interaction between the V 3d and the O 2p states. The optical properties of CuMgVO4 and AgMgVO4 were predicted from the complex dielectric function, ε(ω) = ε1(ω) + iε2(ω). The static dielectric constants were estimated from the real part of the dielectric functions, ε1(ω). The imaginary part of the dielectric functions, ε2(ω), demonstrated optical anisotropy, with the component along the z (y) direction being larger than the others for CuMgVO4 (AgMgVO4) in the wavelength range of visible light. The absorption coefficient I(ω) was also calculated from the dielectric function.
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.