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Full Paper
published : vol. 129, no. 12, December 2021
Niansheng GUO, Zhaoqiang CHEN, Guangchun XIAO, Qi LI, Shuai ZHANG, Mingdong YI, Jingjie ZHANG and Chonghai XU
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For the sake of enhance the cutting performance of self-lubricating ceramic tools, in this paper, we prepared self-lubricating tool materials by adding CaF2@Al2O3 coated powder with core–shell structured as solid lubricant, the cutting performance of ceramic tool materials were investigated through dry machining of hardened steel, and the wear mechanism was explored. The results showed that CaF2@Al2O3 core–shell structured solid lubricant in the ceramic tool material was more effective than CaF2 in improving the wear resistance. The addition of CaF2@Al2O3 core–shell structured solid lubricant in the ceramic tool materials can reduce the cutting force and cutting temperature. Under the same cutting conditions, compared with Al2O3/TiC/CaF2 ceramic cutting tool, the Al2O3/TiC/CaF2@Al2O3 tool had lower surface roughness of workpieces, while the main cutting force and cutting temperature are reduced by 27.7 and 52.6 % respectively in the cutting process. The wear of the rake face included micro-chipping, crater wear and adhesive wear, while the wear of flank face included micro-chipping, adhesive wear and abrasive wear. The ceramic tool with CaF2@Al2O3 core–shell structured solid lubricant obtained outstanding cutting performance.
Full Paper
published : vol. 129, no. 12, December 2021
Yuuki KAGAMI, Syuuichi YAMAMOTO, Yuta YOKOBAYASHI, Ryunosuke UCHIDA, Koki SUZUKI, Seiichi TARUTA and Toshinori TAISHI
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Polycrystalline SiC coating on large-sized SiC ceramics was investigated for its application to SiC susceptors for use in severe environments in LSI processes. The proposed coating process is simple and special gases are not used. SiC coating on the SiC substrate is achieved by positioning the ceramics above Si melt maintained in a carbon crucible in a furnace constructed using carbon materials. First, we evaluated the effect on the SiC grain size and the thickness of the SiC coating of varying the temperature and the distance maintained between a 1-inch diameter SiC substrate and the melt surface. We found that 6H-SiC grains several micrometers in size were densely deposited on the substrate, and the grain size and thickness of the SiC coating increased with increasing temperature. Next, based on these results, we achieved crystalline SiC coating on both sides of a 6-inch diameter SiC substrate. The number of carbon or SiC particles released from the SiC ceramic surface was evaluated with a submerged particle counter, and this number was found to be reduced by 99 % or more with a sample coated at 1800 °C as compared to the uncoated product. A discussion of possible chemical reactions for crystalline SiC formation is presented here based on the analysis of chemical species in the furnace using quadrupole mass spectrometers.
Full Paper
published : vol. 129, no. 12, December 2021
Du-Cheng TSAI, Feng-Kuan CHEN, Zue-Chin CHANG, Bing-Hau KUO, Erh-Chiang CHEN, Yen-Lin HUANG and Fuh-Sheng SHIEU
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ZnMgO:Al coatings were prepared by radio frequency (RF) magnetron sputtering on glass substrates, and the effects of the substrate temperature on the structural, electrical, and optical properties of ZnMgO:Al coatings were studied. The ZnMgO:Al coatings had a hexagonal wurtzite crystal structure oriented along the c-axis, regardless of the substrate temperature. Increasing the substrate temperature increased the grain sizes of the coatings and thus their Hall mobilities. The high substrate temperature also promoted the doping concentration efficiency of Al3+ ions, leading to enhanced carrier concentration. The optimal deposition was obtained at 400 °C, which led to the lowest resistivity (2.82 × 10−3 Ω cm) and 91 % transmission in the visible range. The optical bandgap increased to 3.632 eV as the substrate temperature increased to 400 °C. Wide bandgap, highly transparent, and conductive ZnMgO:Al coatings can be used as electrodes for ultraviolet photovoltaic applications.
Full Paper
published : vol. 129, no. 12, December 2021
Kohei KASUYA, Md. SHAHIDUZZAMAN, Makoto KOBAYASHI, Shu YIN, Masato KAKIHANA and Koji TOMITA
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We present a method for synthesizing brookite-type titanium dioxide (TiO2) using an emulsion-assisted hydrothermal approach and a water-soluble titanium complex with glycolic acid as a complexing agent. In this study, stirred hydrothermal synthesis was used to synthesize water-in-oil emulsions with titanium glycolate complex in the aqueous phase. The resulting brookite-type TiO2 was investigated using Raman spectroscopy for crystal polymorph identification, X-ray Diffraction to identify crystal polymorphs and crystallite size, Transmission Electron Microscope for primary particle size, and crystal shape, and Dynamic Light Scattering for TiO2 secondary particle size in aqueous dispersion. The synthesized brookite-type TiO2 was a needle-like crystal with a width between 20 and 30 nm and a length of more than 70 nm, growing in the b-axis direction at an angle of about 70° from the (120) plane. Furthermore, compared to the conventional synthesis method, the secondary particle size was smaller, and the dispersibility in water was improved. The results show that the brookite-type TiO2 dispersion obtained using the emulsion-assisted hydrothermal method can facilitate the formation of uniform films and can be applied to the electron transport layer of organic perovskite solar cells.
Full Paper
published : vol. 129, no. 12, December 2021
Dandan WEI and Wenxuan LI
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36Pb(In1/2Nb1/2)O3–30Pb(Mg1/3Nb2/3)O3–34PbTiO3 (36PIN–30PMN–34PT) ternary ceramics with morphotropic phase boundary (MPB) composition were fabricated by two-columbite precursor method. The effects of sintering temperature on phase formation, densification and electrical performance of PIN–PMN–PT ceramics were investigated in detail. It was found that the optimized sintering condition was 1240 °C for 5 h. The electric properties of the 36PIN–30PMN–34PT ceramics were dependent on sintering temperature. More importantly, the dielectric and piezoelectric constant increased as the sintering temperature increased. However, the increasing trends between electric properties and the sintering temperature were interrupted when the ceramics were sintered above 1260 °C as a result of PbO vaporization.
Full Paper
published : vol. 129, no. 12, December 2021
Ruirui LIU, Qi ZHAO and Zhijiang JI
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Ternary Au/Bi2WO6/BiOBr composites were skillfully prepared via a two-step synthetic route. The two-component Bi2WO6/BiOBr heterojunction was firstly fabricated by hydrothermal method, and Au nanoparticles (NPs) were further introduced and uniformly anchored on the surface of Bi2WO6/BiOBr, where the loaded Au NPs could be beneficial for improving visible-light absorption and adjusting photoinduced charge carriers in the heterostructure through surface plasmon resonance (SPR). In comparison with pristine Bi2WO6 and two-component Bi2WO6/BiOBr, the ternary Au/Bi2WO6/BiOBr composite exhibits a better photocatalytic activity for removal of rhodamine B (RhB) under visible light irradiation. The degradation efficiency of GTB-3 composite 1.9 times higher than that of the pure Bi2WO6 and 1.24 times than that of Bi2WO6/BiOBr. Trapping tests with different scavengers revealed that not hydroxyl radicals but superoxide radicals and photogenerated holes were highly responsible for the degradation process. The enhanced photocatalytic activity was ascribed to the synergetic effect of heterojunction effect (efficient separation of charge carriers), porous structure of Bi2WO6 (strong adsorption), SPR of Au.
Full Paper
published : vol. 129, no. 12, December 2021
Yutaka AIKAWA, Mamiko UMETSU, Toshinari MUKAI and Etsuo SAKAI
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An equation was derived to analyze carbonation phenomena in cement based on the Tomosawa theory, and it was applied to examine the difference between the cement content and degree of charcoal oxidation. Two types of fly ash cement based on ordinary Portland cement (OPC), high-alite cement (HAC), low-heat Portland cement (LHC), and moderate-heat Portland cement (MPC) were prepared, and the degree of carbonation was measured by acceleration examination. With these measurements, long-term carbonation was simulated using the new equation. Under the accelerated condition (CO2 5 %), when 18 % fly ash was added to Portland cement (OPC+FA18) and 18 % fly ash to HAC (HAC+FA18), the degree of carbonation in one month was examined relative to unmodified cement, and the carbonation rate increased by approximately 1.8 and 1.6 times, respectively. The degree of carbonation of MPC was approximately the same as that of OPC, but the carbonation of LHC was about three times greater. Therefore, fly ash cement (OPC+FA18, HAC+FA18) and LHC are more useful in the environment because these cements have a superior ability to prevent carbon dioxide release compared with that of OPC.
Full Paper
published : vol. 129, no. 12, December 2021
Shigeomi TAKAI, Yoshinobu TAWA, Masashi TAKEMOTO, Jian KANG, Takeshi YABUTSUKA and Takeshi YAO
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LiMn2O4 has been prepared by means of high-energy ball-milling of Li2CO3 and MnCO3 followed by one-pot sintering. Milling at 800 rpm for 4 h with sintering at 700 °C for 12 h leads the enhanced cathode performance as 123.5 mAh g−1 of initial discharge capacity under 1 C charge–discharge rate, retaining 95.1 and 91.6 % of capacity after 100 and 200 cycles, respectively. Mechanochemical reaction facilitates the sintering reaction to form the favorable microstructure homogeneously without second phase. Relaxation analysis showed that, at the charging around x = 0.2 for LixMn2O4, the sample prepared by optimal milling time varies mainly lithium concentration in Li-rich phase, while excessively milled sample alter the molar ratio of Li-rich and Li-lean phases. This indicates that optimal milling time allows the sample to undergo the less structural change at the charging, which enables the improved cycle performance.
Full Paper
published : vol. 129, no. 12, December 2021
Dasong PENG, Xiaodong WANG, Yanchao REN, Xiaoqiang DU and Zhihua DAI
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In this work, based on the sol–gel and titration technology, an innovative method to prepare the yttria stabilized ZrO2–Al2O3 composite beads which can greatly improve the bead properties is proposed. Using this method, the yttria stabilized ZrO2–Al2O3 composite beads samples with different proportion of alumina component were prepared and tested. The density results show that the density of the ceramic beads is very close to the theoretical value, which implies that the new method can prepare the beads with high compactness and without containing pores. Vickers hardness results show that the hardness of the composite beads is higher than the zirconia beads without containing alumina. The SEM analyses show that the average grain size of the composite beads is about 180 nm, much smaller than that of the beads prepared by the conventional rolling process. X-ray diffraction results show that there is no monoclinic phase in the composite beads after sintering at 1250 °C. The EDS analyses show that the aluminum element exists in composite beads and the alumina grains are evenly distributed. Furthermore, the beads sintering temperature using this new process can achieve low-temperature which is about 1250 °C, much lower than that of the beads prepared by the conventional rolling process.
Note
published : vol. 129, no. 12, December 2021
Yuki NAKASHIMA, Hideki HYUGA, Kiyoshi HIRAO, You ZHOU, Manabu FUKUSHIMA and Norimitsu MURAYAMA
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Silicon nitride ceramics have attracted increasing attention as insulated heat-dissipating substrates for power modules due to their high thermal conductivity and mechanical strength. However, there are very few reports on their dielectric breakdown strength, which was only evaluated for the substrates with thicknesses between 250 and 640 µm, though thinner substrates are preferable for attaining better performance of the module. In this work, dielectric breakdown of sintered silicon nitride substrates with thicknesses ranging from 285 to 15 µm was evaluated for the first time. Average breakdown strength increased from 36.38 to 103.80 kV/mm with decreasing thickness from 285 to 15 µm. It should be noted that the silicon nitride specimen had very high dielectric breakdown voltage of 1.5 kV even with a thickness as small as 15 µm.
Note
published : vol. 129, no. 12, December 2021
Yuki OBUKURO and Shigenori MATSUSHIMA
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The electronic structure of Pr-doped ZrSiO4 is calculated using modified Becke–Johnson potential plus on-site Coulomb interaction (MBJ + U). The minimum energy gap of ZrSiO4 calculated using the MBJ method is 5.8 eV, which is close to the experimental value. When a Pr atom replaced one of Zr atoms, strongly localized Pr 4f states appear in the forbidden gap of ZrSiO4. By considering the on-site Coulomb interaction in addition to the MBJ potential, the empty Pr 4f states appear about 2 eV above the valence band maximum of ZrSiO4. Compared with generalized gradient approximation (GGA), MBJ, and GGA + U approaches, MBJ + U better describes the position of empty Pr 4f states for Pr-yellow pigment.
Full Paper
published : vol. 129, no. 11, November 2021
Manabu KOIDE, Khaled JABRI and Tomohiro SATO
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The effect of TiB2 and TiN contents on the phase formations and their mechanical properties in the binary systems of Ti–TiB2 and Ti–TiN, and in the ternary system of Ti–TiB2–TiN was investigated. In the binary systems, TiB2 and TiN addition improved the hardness of Ti but reduced its bending strength. In the ternary system of Ti–TiB2–TiN, the addition of TiB2–TiN mixture to Ti further improved the hardness to around Hv = 10.0 GPa compared to 7.0 GPa in the binary systems, but it did not improve the bending strength. The increase of hardness in the binary system of Ti–TiB2 was mainly attributed to the formation of TiB (or non-stoichiometric solid solution of TiB1−x) and to remaining TiB2 in samples with high TiB2 contents. The reduction of bending strength, however, was attributed to the disappearance of metallic Ti, to the formation of TiB1−x, and to porous structure in samples with high TiB2 contents. The increase of hardness in the binary system of Ti–TiN was attributed mainly to the formation of non-stoichiometric solid solution of TiN1−x. The reduction of bending strength was attributed to the large crystal growth of flake like structure of TiN1−x. The further improvement of hardness in the ternary system of 80Ti–20(TiB2–TiN) was attributed to the formation of fine crystals of TiB (or TiB1−x) within the flake like structure of N-diffused α(Ti) crystal phase. The reduction of bending strength is mainly attributed to the large growth of flake like structure of N-diffused α(Ti) crystal phase.
The 75th CerSJ Awards for Academic Achievements in Ceramic Science and Technology: Review
Special Article
published : vol. 129, no. 11, November 2021
Shinji TAMURA
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Various kinds of conducting ion species in solids have been discovered by selecting the NASICON-type three-dimensional network structure. By introducing high-valence Nb5+ into NASICON-type solids, both the thermal stability and crystallinity of NASICON-type trivalent cation conductors were simultaneously improved, leading to 13 kinds of trivalent cations that were newly reported to migrate in solids. In addition, highly selective low-temperature operative gas sensors were successfully fabricated using the (Al0.2Zr0.8)20/19Nb(PO4)3 solid, which possesses a high trivalent cation conductivity of over 10−4 S·cm−1 at 600 °C, as well as high thermal and chemical stabilities.
The 66th CerSJ Awards for Advancements in Ceramic Science and Technology: Review
Special Article
published : vol. 129, no. 11, November 2021
Akihiko ITO
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High-intensity laser irradiation promotes a chemical reaction between the vapor phase and the film surface in the chemical vapor deposition (CVD) process, resulting in a high-speed deposition and a significant oriented growth of various kinds of oxides, nitrides, carbides, and their compounds and composites. TEM observation revealed unique microstructures, such as columnar, feather-like, and single-crystalline growth, in the produced CVD coatings. This CVD process enables the combination of high-speed epitaxial growth and excellent properties for structural and functional ceramic coatings. Traditional ceramics, such as Al2O3, TiO2, Al2TiO5, BaAl12O19, BaTiO3, YBa2Cu3O7−δ, and CeO2, can be still highly valued as practical materials by functionalization of ceramic coatings with the control of orientation and nanostructure.
Full Paper
published : vol. 129, no. 11, November 2021
Jingren LI, Wenzhong LU and Hai JIANG
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Dense silicon carbide (SiC) ceramics were fabricated through hot-pressing with a novel combination of rare earth oxides and fluorides (CeO2–CeF3, Nd2O3–NdF3, Gd2O3–GdF3 and Y2O3–YF3) as additive. Effects of these additive combinations on microstructure, phase composition, flexural strength and thermal conductivity of SiC ceramics were evaluated. The samples with 1 wt %Nd2O3–2 wt %NdF3 (1Nd2Nd sample) and 1 wt %Gd2O3–2 wt %GdF3 (1Gd2Gd sample) additive exhibited the highest thermal conductivity of 187.8 W/m·K and highest flexural strength of 607.6 MPa respectively. Impedance spectroscopy analysis was employed to further investigate the variations of defects and impurities in SiC ceramics. 1Nd2Nd sample exhibited a higher fitting grain and grain boundary resistance that suggested a lower concentration of V””Si vacancies than other samples, which resulted in a higher thermal conductivity. On the other hand, the highest flexural strength of 1Gd2Gd sample was attributed to a combined effect of its small grain size, contiguous microstructure and low content of grain boundary phases. All in all, Re2O3–ReF3 additive combinations are suitable for tailoring and improving the thermal conductivity and flexural strength of SiC ceramics.
Full Paper
published : vol. 129, no. 11, November 2021
Sung Il YUN, Sahn NAHM and Sang Whan PARK
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Liquid phase bonded (LPB) porous SiC with neck bonding phases consisting of yttrium aluminate (Y4Al2O9, Y3Al5O12), yttrium silicate (Y2Si2O7), and Al2O3 were fabricated using varying amounts of an Al2O3–Y2O3–SiO2 bonding additive in Ar at 1500 °C for 1 h. LPB porous SiC ceramics exhibited unimodal pore-size distributions, porosities of 36.6–44.8 %, and pore sizes of 7.7–8.5 µm. The particle-size distribution of SiC powders was an important factor in determining the pore characteristics, including pore-size distribution, pore shape, porosity, and pore size, and the flexural strength as well as the gas permeability of LPB porous SiC ceramics. The porosity and pore size increased, and the pore-size distribution narrowed by using SiC powders with a narrow size distribution. The flexural strength of porous SiC varied in the range of 39.7–66.7 MPa and was mainly dependent on the porosity, pore shape, pore size, and solid boning area varied by the SiC particle-size distribution. A relatively high permeability (1.28–1.84 × 10−12 m2) of LPB porous SiC was attained mainly due to the unimodal pore size distribution of pores with sizes of 7.7–8.5 µm.
Full Paper
published : vol. 129, no. 11, November 2021
Zhongfeng XIA, Zhoufu WANG, Yan MA, Hao LIU and Xitang WANG
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Drying process is necessary in the preparation and application of refractory castables. In this work, the effects of conventional drying, microwave drying and freeze drying on the composition and properties of cured calcium aluminate cement (CAC) pastes were comparatively investigated. The differences in the microstructures evolution process under various drying mechanisms were discussed. The results show that metastable CAH10 and C2AH8 are completely transformed into stable phases in the conventional dried pastes, while a small amount of flaky C2AH8 remained in pastes dried via microwave. Nevertheless, the major hydrates in the freeze-dried pastes are CAH10 and C2AH8. In addition, the pores in pastes dried by microwave are mainly distributed in the range of 20–2000 nm, while the freeze-dried pastes contain more gel pores and show higher elastic modulus. A new approach to effectively regulate the pore structure of CAC bonded materials via non-conventional drying methods is proposed in the present work.
Full Paper
published : vol. 129, no. 11, November 2021
Takeo HYODO, Azusa IWANAGA, Keijiro ISHIDA, Kai KAMADA, Taro UEDA and Yasuhiro SHIMIZU
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Fundamental gas-sensing properties of porous (pr-)In2O3 powders loaded with and without 0.5 mass % noble metal (pr-0.5N/In2O3 and pr-In2O3, respectively, N: noble metal (Au or Pd)) to NO2, H2, and ethanol balanced with dry air were investigated at 30 °C under UV-light irradiation (main wavelength: 365 nm). The spherical pr-0.5N/In2O3 and pr-In2O3 powders were prepared by ultrasonic-spray pyrolysis employing polymethylmethacrylate microspheres with a diameter of ca. 70 nm, which were synthesized by ultrasonic-assisted emulsion polymerization. The Au loading largely improved the NO2 response of the pr-In2O3 sensor, a ratio of the resistance in NO2 to that in air, especially under weak UV-light irradiation, because of the relatively large resistance in air. On the other hand, the Pd loading efficiently increased the difference in the conductance of the pr-In2O3 sensor between in NO2 and in air under the whole UV-light irradiation range. The UV-light irradiation is effective in improving the NO2-sensing properties of these sensors at room temperature, but the sensing performance was a little inferior to that operated at elevated temperatures under no UV-light irradiation. These sensors also responded to reducing gases, H2 and ethanol, under UV-light irradiation, and the responses to ethanol were much larger than those to H2. However, the responses to both the gases were much smaller than that to NO2.
Full Paper
published : vol. 129, no. 11, November 2021
Kazuya UJIIE, Takashi KOJIMA, Kosuke OTA, Shuhei HOSOYA and Naofumi UEKAWA
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Strontium titanate (SrTiO3) particles are expected to be applied to various catalysts, and many kinds of synthesis procedures of SrTiO3 particles with a high specific surface area have been proposed. This study investigates a synthesis procedure of preparing SrTiO3 particles with a high specific surface area by minimizing the crystallization temperature to the least possible value. The SrTiO3 particles are prepared by maintaining spherical hydrous titania particles with smooth or porous surfaces in highly concentrated strontium hydroxide solutions at ≤120 °C. When porous hydrous titania particles are used as the raw material and the Sr/Ti ratio in the reaction solution is set at 10, spherical protrusions of SrTiO3 develop on the surface of the original hydrous titania, even at a low temperature (25 °C). Single-phase SrTiO3 particles with spherical protrusions composed of very fine crystallites are obtained by treatment at 40 °C for 24 h. These particles have a high BET specific surface area of 237 m2 g−1. The process developed herein is eco-friendly and effective for fabricating various perovskite-type compounds with a high specific surface area.
Note
published : vol. 129, no. 11, November 2021
Kunihiko KATO, Takafumi SUDO, Yunzi XIN and Takashi SHIRAI
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To create a highly photocatalytic performance in addressing the global environmental issues, we develop a highly efficient photocatalyst engineered by a combination of control of exposed facet in TiO2 and composite with the non-noble metal nanoparticle. The formation of a fluorinated surface during crystal growth assists the morphology control of TiO2 with coexposed {001}/{101} facets. In addition, the deposition of nano-sized Sn particles (>10 nm) is achieved via photochemical reduction on the faceted TiO2 from anhydrous chelated tin(II) complexes by amino acid. Here, the bidentate ligands (i.e., carboxyl and amino group) in proline molecular play a vital role in associating the strong interaction between TiO2 surface and chelated Sn complexes. The optimal balance in the ratio of exposed {001}/{101} facets and loading amount of Sn nanoparticles are essential factors for an enhancement of photocatalytic activity for efficiently consume photo-exited electrons in the degradation of azo-dye water pollutants.
Full Paper
published : vol. 129, no. 10, October 2021
Chihiro KATO, Nobutomo OTSUKA, Kayano SUNADA, Toshihiro ISOBE, Sachiko MATSUSHITA, Takeshi NAGAI, Hitoshi ISHIGURO and Akira NAKAJIMA
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Using hydrothermal processing, we prepared a cerium bismuth solid solution oxide ((Ce0.8,Bi0.2)O2−δ, CBO) and a cerium lanthanum solid solution oxide ((Ce0.8,La0.2)O2−δ, CLO). The resultant powders possessed fluorite-type crystal structure. They also decomposed 2-naphthol in water in the dark. From their valence change and temperature dependence, we infer that the Mars–van Krevelen (MvK) mechanism of Ce contributes to this decomposition activity. These materials showed higher decomposition activity under visible light. Modification of CoOx onto these materials enabled an apparent bandgap decrease and the MvK mechanism of Ce and Co, which led to higher decomposition activity in the dark and under visible light. The CBO activity was higher than that of CLO on the decomposition of 2-naphthol in water, but the CLO antiviral activity was higher than that of CBO. Results suggest that the CLO antiviral activity results from virus deactivation by direct contact with the powder surface.
Express Letter
published : vol. 129, no. 10, October 2021
Yusuke DAIKO, Junki KATO, Sawao HONDA and Yuji IWAMOTO
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A few GPa-order high-pressure impedance measurement was performed by utilizing an indentation method, which is often used to evaluate mechanical characteristics, and the alternating current (AC) impedance method simultaneously. We succeeded in estimating the activation volume (Δ V = 3.2 cm3/mol) for O2− ion conduction of YSZ with a single sweep of load at 0.25 N/s up to 25 N. Such a quick and easy method for determining Δ V is completely new that has not been proposed so far.
Full Paper
published : vol. 129, no. 10, October 2021
Jaegyeom KIM, Hiroaki KATSUKI, Oratai JONGPRATEEP, Sansanee BOONSALEE and Jae-Hwan PEE
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Alumina, mullite, and cordierite powder were added to a whiteware porcelain slurry and sintered at 1280 °C to investigate the correlation between porcelain composition and strength. The X-ray diffraction patterns of the sintered bodies show that no new phase was formed, and that the added material remained intact. Except for the sample group to which cordierite was added, the strength increased as the additive content increased. A Rietveld quantitative analysis indicated that the amorphous phase decreased with increasing additional alumina and mullite content, while the amorphous content remained constant regardless of the additional cordierite content. The decrease in the amorphous content increased the strength of the porcelain, which, in the case of the sample with 15 wt.% alumina, increased by 57 %. The dramatic increase in strength is attributed to the increase in residual stress due to the difference in the thermal expansion coefficient between the alumina and the amorphous phase, as well as the increased formation of mullite by the addition of alumina.
Full Paper
published : vol. 129, no. 10, October 2021
Hiromichi ICHINOSE, Mitsunori YADA and Kohjiro HARA
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Titanium oxide films were prepared from peroxotitanium complex aqueous solution containing a peroxo complex of vanadium, molybdenum or tungsten of 2, 5, 10 mol % by heating at 200 °C for the purpose of suppressing the photocatalytic activities that may be developed by crystallization during long-term use as a prevention film against potential-induced degradation (PID) of crystalline silicon (c-Si) photovoltaic (PV) module. The films containing those dopants crystallized to anatase by hydrothermal treatment at 100 °C for 15 h as an acceleration test, but hardly showed any photocatalytic activity. According to the lattice constants, X-ray photoelectron spectroscopy analyses and UV–visible light reflection spectra, it was estimated that vanadium (V), molybdenum (VI) and tungsten (VI) were substituted with titanium (IV) in titanium oxide heated at low temperature of 200 °C. The titanium oxide films containing the dopants of 2 mol % were coated at 200 °C onto the rear side of front cover glass with 200 nm thickness. No significant PID was observed in the c-Si PV modules based on the film-coated glass by a PID test by applying −1000 V at 85 °C for 2 h.