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Express Letter
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Saeki YAMAMURO and Toshiro TANAKA
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This report presents a new route to fabricating a ferrite-based magnetic nanocomposite consisting of a ferromagnetic metal (α-Fe) and a ferrimagnetic spinel ferrite (Fe3O4). The process is based on the eutectoid decomposition of FeO, leading to the formation of a lamellar nanostructure of α-Fe and Fe3O4. A sandwiched nanostructure of this type is preferable for exchange coupling between adjacent lamellae, because each lamella is subjected to exchange coupling via either side of the interface. It was found that decomposition of FeO takes place preferentially in the temperature range of 723–773 K, in which the decomposition is almost fully completed within 10 h. The room-temperature magnetization measurements gave rise to a high saturation magnetization above 100 emu/g, which is larger than that of single-phase Fe3O4. Since a smooth magnetization curve with single-phase-like behavior was observed despite the coexistence of two magnetic phases, the two phases could be magnetically exchange-coupled. Due to the ease of tuning the magnetic properties of the spinel ferrites with the substitution of constituent metal ions, the fabrication process described here could represent a potential route to making a variety of iron-based metal/ferrite magnetic nanocomposites.
Full Paper
published : vol. 126, no.2, February 2018
Keishi KIMINAMI, Kohei NAGATA, Toshiisa KONISHI, Minori MIZUMOTO, Michiyo HONDA, Kazuaki NAKANO, Masaki NAGAYA, Hidetoshi ARIMURA, Hiroshi NAGASHIMA and Mamoru AIZAWA
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Calcium-phosphate cements (CPCs) are widely used to reconstruct and augment bones. To enhance the clinical usefulness of these cements, researchers have put great effort into improving their material properties and bioresorbability. To create a novel bioresorbable CPC, we successfully incorporated gelatin particles into a chelate-setting CPC, whose powder component consisted of hydroxyapatite surface-modified with inositol hexaphosphate and α-tricalcium phosphate. We expected that interconnected macropores could be formed inside the cement specimen through the degradation of the gelatin particles, resulting in cellular infiltration, specimen bioresorption, and subsequent new bone formation. To verify this hypothesis, we evaluated the bioresorbability and bone-forming ability of a gelatin-hybridized CPC implanted for eight weeks into porcine tibial defects. We also assessed the effects on the bioresorbability of polysaccharides (chitosan and chondroitin 6-sulfate) included in the liquid component of the CPC. Micro-CT observations and histological evaluations revealed that the use of chondroitin 6-sulfate could lead to enhancement of the bioresorbability and bone-forming ability. Of special note, the resorption rate reached nearly 85%, and new bone was observed at the resorbed sites inside the specimen. We conclude that gelatin-hybridized chelate-setting CPC containing chondroitin 6-sulfate is a promising bone substitute for non-load-bearing applications.
Full Paper
published : vol. 126, no.2, February 2018
Jilin HU, Qizhong HUANG, Xin YANG, Xiuying TIAN, Hongxia PENG and Yangxi PENG
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Al2O3–AlN composite powders were synthesised in N2 by the carbothermal reduction–nitridation method with Al(OH)3 and different carbon sources (i.e. carbon black, graphite and starch) as starting materials. The effects of the carbon source type, carbon source dosage and reaction temperature on the synthesis performance of the Al2O3–AlN composite powders were investigated. The dried precursors and their synthesised products were characterised by X-ray diffractometer, comprehensive thermal analysis instrument and scanning electron microscope. The results showed that when the denoted mass ratio of Al2O3/AlN is 7:3, the optimum conditions for the synthesis of Al2O3–AlN composite powders with carbon black and starch as carbon sources are 1500°C for 2 h and 1600°C for 2 h, respectively. In addition to generating elemental carbon and gaseous H2O, the single-phase starch raw material produces gaseous CxHy during heating. The actual mass loss rate generated in the system is consequently significantly higher than the theoretical mass loss rate. The Al2O3–AlN composite powder samples synthesised at 1500°C with carbon black as the carbon source are mainly composed of approximately hedgehog-shaped aggregates, which consist of a mixture of flakes and nearly spherical particles (100–300 nm). The powder samples synthesised at 1500°C with graphite as the carbon source form diverse microstructures composed of spherical, flaky and rod-like particles. When starch is used as the carbon source, the encapsulated structure particles formed at 1500°C tend to increase gradually with decreases in the Al2O3/AlN mass ratio.
Full Paper
published : vol. 126, no.2, February 2018
Phattranit DUMRONGROJTHANATH, Anukorn PHURUANGRAT, Somchai THONGTEM and Titipun THONGTEM
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In this research, Bi2WO6 nanoplates doped with 0, 1, 3 and 4% by weight of Mo were successfully synthesized by hydrothermal method. X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and ultraviolet–visible spectroscopy certified that the as-synthesized products were uniform orthorhombic Bi2WO6 nanoplates with absorbance of the pure product in ultraviolet region and of the doped ones in both ultraviolet and visible regions. Photocatalysis of the products was also evaluated through the degradation of rhodamine B under visible light irradiation. The Bi2WO6 nanoplates doped with 3% by weight of Mo have the highest rate constant of 0.023 min−1.
Full Paper
published : vol. 126, no.2, February 2018
Kiyoshi KOBAYASHI, Yukihito IGARASHI, Noriko SAITO, Tohru HIGUCHI, Yoshio SAKKA and Tohru S. SUZUKI
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The high-temperature phase of lanthanum germanate is useful due to its high oxide ion conductivity. While the transition from the high- to low-temperature phase could be suppressed by yttrium substitution in lanthanum sites, full stabilization of the high-temperature phase was difficult to achieve by yttrium substitution under conditions of different lanthanum-deficient compositions, as some X-ray diffraction (XRD) peaks were broadened after annealing at 873 K. With lattice constant analysis using the XRD peaks, the degree of lattice asymmetry for the low-temperature phase with triclinic lattice was found to decrease with increases in the deficiency of the lanthanum site and yttrium concentration. Formation of the low-temperature phase was difficult to detect even from Raman shift spectra. On the other hand, Raman shift spectra showed high sensitivity to detection of the La2GeO5 impurity phase. The influence of the total conductivity on the phase transition showed different trends with increases in the lanthanum deficiency and yttrium concentration. With tuning of the composition, the highest conductivity was observed in La8.51Y0.96(GeO4)6O2.205. This conductivity (6.12 × 10−1 S/m−1 at 873 K) is higher than that of yttria-stabilized zirconia at the same temperature.
Full Paper
published : vol. 126, no.2, February 2018
Tomohiro YOKOTA, Takuya MIKI, Michiyo HONDA, Tomoko IKEDA-FUKAZAWA, Ken ISHII, Morio MATSUMOTO and Mamoru AIZAWA
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Biological apatite present in the bones and teeth of mammals contains various minerals, which create numerous nanoscale defects in their crystal structures. Substitution of the ions of these minerals into hydroxyapatite [Ca10(PO4)6(OH)2; HAp] induces considerable strain and various defects in the crystal structure of HAp. Although autogenous bone and synthetic HAp ceramics have been used clinically as bone grafts, autografting generally has better clinical results than artificial-bone grafting. In the present study, we fabricated HAp ceramics including bone minerals (bone HAp ceramics) as model materials to clarify the relationship between the nanoscale defect structure and bioactivity of the biological apatite. We also implanted bone HAp ceramics in the tibiae of rabbits, along with standard HAp ceramics without bone minerals (pure HAp ceramics) as a control, and examined the biological response of the living hard tissue to the implants histologically. The single-phase HAp and carbonate ion content of the bone HAp ceramics could be maintained by sintering at 1000°C for 5 h under a flow of carbon dioxide gas. The inclusion of trace elements and changes in the lattice constants were confirmed, and Raman spectroscopy indicated the presence of defects. Biological evaluation showed significantly more newly formed bone around the bone HAp ceramics at 4 weeks than around the pure HAp ceramics. These results demonstrated that bone HAp ceramics that include trace minerals and nanoscale defect structures may promote early-stage bone formation.
Full Paper
published : vol. 126, no.2, February 2018
Yutaka AIKAWA, Kan SHINOBE, Yukiko UEDA, Nobukazu NITO and Etsuo SAKAI
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This paper presents a theoretical analysis of the hydration and hydrated layers of blast furnace slag grains in high-volume blast furnace slag cement. Hydrated high-volume blast furnace slag cement paste contains a large number of unreacted slag grains, and hydrated layers are observed surrounding the unreacted slag grains. To analyze the hydration reaction of the blast furnace slag components, an extended effective coefficient is adopted instead of the conventionally used Tomosawa’s equation. This makes it possible to explain the rate of heat liberation of blast furnace slag in comparison to that of ordinary Portland cement. The simulation results for the thickness of the hydrated layer around the slag particles in terms of its conversion radius dependence are in good agreement with the measured values.
Full Paper
published : vol. 126, no.2, February 2018
Makoto KASAI, Yosei KOBAYASHI, Kaname YOSHIDA, Yukichi SASAKI, Masakazu TOGO and Atsushi NAKAHIRA
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Perlite is a volcanic glass composed mainly of amorphous aluminum silicate that has SiO2 and Al2O3 with fewer impurities such as heavy metals as its main components. Amorphous (glassy) perlite with physical properties such as lightweight and excellent heat resistance, fire resistance, chemical resistance and heat-insulating properties is used in lightweight aggregates and insulation. It has also been used as a filter aid after grinding foamed perlite. It has not been used as an environmental cleanup materials, however, because the ion-exchange capacity of perlite is very low. In this study, we tried to synthesize a hybrid filter aid with a chemical adsorption capability by synthesizing zeolite on the surface of the perlite to enhance its filtering abilities. Observation of scanning electron microscope images was conducted to confirm the generation of Linde Type A (LTA-type) zeolites on the surface of the perlite. LTA-type zeolites were found to be precipitated on the surface of perlite from the transmission electron microscope observation results.
Full Paper
published : vol. 126, no.2, February 2018
Daichi TANAKA, Toshihiro ISOBE, Sachiko MATSUSHITA and Akira NAKAJIMA
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Titanium dioxide (TiO2) surface was modified with MnOx, SnOx or (Mn0.8, Sn0.2)Ox by chemisorption calcination cycle (CCC) processing. Samples modified with SnOx or (Mn0.8, Sn0.2)Ox were also modified with MnOx by subsequent CCC processing. Then the decomposition activity on 2-naphthol in water was evaluated at 50°C in the dark or under visible light illumination. The modification with MnOx engendered a decrease in the sample bandgap. Although the samples modified with SnOx or (Mn0.8, Sn0.2)Ox only did not show decomposition activity in the dark, they decomposed 2-naphthol in water by subsequent modification with MnOx on their surface. The results suggest that the interaction between the base material and modified MnOx plays an important role on the activity order. Samples modified with SnOx or (Mn0.8, Sn0.2)Ox and MnOx exhibited decomposition activity both in the dark and under visible light. Although the activity in the dark decreased gradually through repeated use, it recovered by ultraviolet light illumination at room temperature or heating at 300°C in ambient air.
Full Paper
published : vol. 126, no.2, February 2018
Wen-Ling JI, Heng-Yong WEI, Hui LI, Yi CUI, Shi-Lei HU, Pan LIU, Jing-Long BU, Jin-Meng YANG and Ran WANG
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Mesoporous magnesium aluminate (MgAl2O4) spinel fibers were prepared using a coaxial electrospinning technique. The phase composition, porous structure and adsorption performance of the mesoporous MgAl2O4 spinel fibers were investigated. Differential thermal/thermo-gravimetric and X-ray-diffraction analysis revealed that gel fibers began to crystallize into the MgAl2O4 spinel phase at 700°C and became fully crystallized at 900°C. The morphology changes in the fibers were tracked by use of a scanning electron microscope and transmission electron microscope, which showed fibers with a mesoporous structure formed at 900°C. The Brunner-Emmet-Teller specific surface area of MgAl2O4 spinel fibers is 36.95 m2/g. In addition, the dye adsorption capacity of the fibers shows an adsorption percentage of over 80.0% in 20 mg/l methylene blue after 2 min of adsorption. The kinetic study demonstrated that the adsorption data fit the pseudo-second-order kinetic model more naturally.
Note
published : vol. 126, no.2, February 2018
Mariko KOBAYASHI, Yoshikazu SUZUKI, Tomoyo GOTO, Sung Hun CHO, Tohru SEKINO, Yusuke ASAKURA and Shu YIN
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SrTiO3 is an excellent photocatalyst due to its high photocorrosion resistance and thermal stability. In this study, we synthesized SrTiO3 nanoparticles with high specific surface areas by the hydrothermal method at reduced temperature. Titanium(IV) bis(ammonium lactato)dihydroxide (TALH) solution and strontium hydroxide octahydrate [Sr(OH)2·8H2O] were used as starting materials. SrTiO3 nanoparticles were directly synthesized by hydrothermal heating at 150°C for 72–120 h. The synthesized nanoparticles had diameters of 20–40 nm, and the SrTiO3 powder heated for 72 h exhibited the highest specific surface area of 33.1 m2/g. This sample also showed the highest degradation rate for NO gas.

Special Call for Papers

Specially Scheduled Issue “the 56th Symposium on Basic Science of Ceramics”PDF
Posted Deadline:March 31, 2018
Posted schedule No.:2018. October issue