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Full Paper
published : vol. 127, no.3, March 2019
Akira SAITOH, Yukihide ISHIBASHI, Ryo KIHARA, Tatsuaki SAKAMOTO, Ryusei HAYASHI, Tsuyoshi ASAHI and Hiromichi TAKEBE
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Calcium phosphates are essential compounds for the sustenance of life, since, for example, many grains that enable to convert food are necessary for use of the fertilizers made of chemically synthesized crystals. We have demonstrated two alternative dry processes for the conversion of hydroxyapatite to tricalcium phosphate by means of thermodynamically controlled heat and electronically generated heat with pulsed laser light. In addition, the conversion efficiency has been quantitatively determined from the Rietveld analysis for powder X-ray diffractionpatterns of the fired and laser-ablated samples. Both conversion processes recycled animals’ bones as the source of calcium phosphate, and in the future, this could compensate for the niche area in the absence of wet process for a phosphorus containing sludge through a sewage treatment.
Full Paper
published : vol. 127, no.3, March 2019
Shin-Il GO, Jae-Woong KO, Ha-Neul KIM, Se-Hun KWON, Hai-Doo KIM and Young-Jo PARK
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The effects of the size of Si powder on the thermal conductivity and strength of sintered reaction-bonded silicon nitride (SRBSN) were investigated. Si powders with various sizes were prepared by controlling the high-energy milling duration of the starting Si powder, where the median Si size varied from 3.97 to 0.62 µm, corresponding to an oxygen content of 0.54 to 2.57 wt %. The thermal conductivity increased gradually up to the 4 h milling (D50 = 1.10 µm or 1.60 wt % oxygen) owing to a gain in the relative density, but decreased by 25% for the 12 h milling (D50 = 0.62 µm or 2.57 wt % oxygen). On the other hand, the flexural strength showed almost no change until the 4 h milling, but increased by 20% for 12 h milling. This opposite tendency was elucidated by the difference in grain size distribution and thickness of intergranular grain boundary phase (IGP); Clear bimodal size distribution of grains contributed to high strength, and the nearly doubled thickness of IGP was observed for SRBSN from the finest Si powder (D50 = 0.62 µm or 2.57 wt % oxygen). In order to meet the required thermal properties for the substrate usages by sintering at 1900°C, the size of silicon powder of D50 = 1.10 µm (1.60 wt % oxygen) is allowed for 6 h sintering, but that of D50 = 0.62 µm (2.57 wt % oxygen) needs prolonged sintering time over 6 h (12 h in the current experiment) to reach required grain growth.
Full Paper
published : vol. 127, no.3, March 2019
Koichiro FUKUDA, Yuki TSUNODA, Daisuke URUSHIHARA, Toru ASAKA and Hideto YOSHIDA
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We have for the first time succeeded in the preparation of thin tabular crystals of K2O- and F-doped lanthanum silicate oxyapatite, which were grown by the high-temperature solution technique using KF as solvent. The crystals were characterized using microscopy, energy dispersive X-ray spectroscopy, electron probe microanalysis (EPMA), and X-ray diffractometry (XRD). The atomic compositions determined by EPMA showed the significant correlations among the numbers of atoms (N) for La, Si, and F. They were well expressed by the two linear equations of NLa = 17.52 − 1.426NSi and NF = −1.20 + 0.243NSi, which enabled us to derive the general formula of [La8.964+1.426xK0.850−0.035x]Σ9.814+1.391x[Si6−xx]Σ6[O25.742+0.243xF0.258−0.243x]Σ26 (0 ≤ x ≤ 0.134), where x represents the amount of silicon deficiency denoted by □. Based on the single crystal XRD data, the crystal structure was refined for one of the grains, the chemical formula of which was eventually determined to be [La9.11K0.85]Σ9.96[Si5.900.10]Σ6[O25.77F0.23]Σ26 (x = 0.10). The K and F ions preferentially occupied, respectively, the La and O (channel oxide-ion) sites, with the silicon site being deficient by ca. 1.7%. Since the tabular crystals showed the well-developed {001} faces with relatively high aspect ratios, they could act as satisfactory templates for the preparation of the c-axis-oriented polycrystals.
Full Paper
published : vol. 127, no.3, March 2019
Koichiro FUKUDA, Shin HASEGAWA, Eisei HASEGAWA, Daisuke URUSHIHARA and Toru ASAKA
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We successfully prepared the c-axis-oriented polycrystalline sodium titanoaluminate (NTAO) by the reactive diffusion between solid Al2TiO5 and liquid [25 mol % Na2O and 75 mol % TiO2]. When the Na2Ti3O7/Al2TiO5 diffusion couple was isothermally heated at 1673 K for 3 h, the Na0.78Ti2.22Al4.78O12 polycrystal was readily formed in the presence of a liquid phase. The resulting polycrystalline material was characterized by X-ray diffractometry, electron microscopy, and impedance spectroscopy. We mechanically processed the annealed diffusion couple, and obtained the thin-plate electrolyte consisting mostly of the grain-aligned NTAO polycrystal. The ionic conductivity of the electrolyte along the common c-axis direction steadily increased from 1.29 × 10−2 to 1.31 × 10−2 S cm−1 as the temperature increases from 923 to 1073 K, with the activation energy being 0.095 eV. The crystal structure of NTAO (space group Pbam) was isomorphous with that of NaTi2Al5O12. The Na+ ions occupied ∼78% of the Wyckoff position 2d site, the deficiency of which would contribute to the relatively high ionic conductivity along the c-axis. The present solid–liquid reactive diffusion technique could be widely applicable to the preparation of the other grain-aligned ceramics of multi-component systems.
Full Paper
published : vol. 127, no.3, March 2019
Yue LI, Sibo SHEN, Lingjun ZHU, Shu CAI, Yangyang JIANG, Rui LING, Song JIANG, Yishu LIN, Shaoshuai HUA and Guohua XU
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Magnesium (Mg) and its alloy as promising biodegradable orthopaedic implants have gained immense attention by virtue of their superior biocompatibility and mechanical compatibility. In order to increase the long-term corrosion resistance of Mg and its alloys in clinical application, in this work, a series of strontium-substituted hydroxyapatite (SrHA) coatings were constructed on Mg alloy via hydrothermal route. These SrHA coatings possessed bilayer structure with flower-like clusters as the surface layer and flat surface as the bottom layer. Coating III with Sr/Ca molar ratio of 0.07 exhibited crack-free bottom layer and good interfacial adhesion, and its electrochemical corrosion resistance was higher than the counterparts. Moreover, this coating with high dissolution and rough surface rapidly induced SrHA mineralized layer formation, which gradually grew dense and thick, providing favorable long-term protection for Mg alloy. After immersion in simulated body fluid for 29 days, the average degradation rate of Mg alloy decreased to 0.17 mg/day·cm2. The present work demonstrated that this SrHA coating was a potential protective coating for Mg and Mg alloy implants.
Full Paper
published : vol. 127, no.3, March 2019
Xiao CHEN, Mingkai ZHOU, Xuexiang GE, Zidong NIU and Yuguang GUO
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In order to explore the microscopic mechanism of the remarkable improvement of the organic polymer on the mechanical properties of the geopolymer, fourier transform infrared spectroscopy, 29Si nuclear magnetic resonance, scanning electron microscope and molecular imprinted polymer were used to investigate the effects of polyacrylate (PAAS) on the microstructure of the metakaolin-based geopolymer (MKG). The load-deflection curves were also tested to confirm the toughing effect. The results show that the organic polymer can modify the structure of the geopolymer at the molecular scale and submicroscopic scale. At the molecular scale, Si–O–C bonds formed in MKG after the incorporation of PAAS and the polymerization degree of [SiO4] tetrahedra reduced resulting in the mean chain length of [SiO4]/[AlO4] tetrahedra change. At the submicroscopic scale, the MKG became denser after adding PAAS because PAAS could fill the cracks and capillary pores of MKG. Also, PAAS formed a film with an interconnected network structure, which interpenetrated to geopolymer. The load-deflection curves confirmed increase by 50% in the flexural toughness coefficient of the MKG with the incorporation of 0.8 wt % PAAS.
Technical Report
published : vol. 127, no.3, March 2019
Tatsuro HORIUCHI and Tsutomu SONODA
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Aluminum-doped ZnO (AZO) thin films was deposited by sputtering on glass substrates. Normally, the radio frequency method is applied for sputtering of insulators. However, in this study, the AZO target was made conductive, and then, the thin AZO films were deposited on it by direct current sputtering. We found that there is a significant problem involving the creation of oxygen anions at the target surface, which are then driven into the AZO films, thus resulting in a loss of conductivity due to the formation of oxygen vacancies. At first, the AZO films were deposited on silicon wafers to search for the off-axis positions. After deposition, we observed a white circle on the wafers. We investigated the distribution of surface sheet resistances on the wafer, and found that these were high within the circle (diameter: 87 mm), whereas outside of it, the sheet resistances were quite low and the incidence of oxygen anions was negligible. A small aluminum fitting was made to hold the substrates in the off-axis position, and although the sputtering was carried out at room temperature, crystalline AZO films were obtained. Sputtering at 400 W for 5 min resulted in the best reflectance, with the AZO film reflected in the near-infrared region above 1250 nm. The maximum specular reflectance was 60% at 2500 nm and the film thickness was about 300 nm (although it was somewhat inhomogeneous, probably because of differences in the sputter-particle density). Hall measurements were performed to determine the quality of the resulting AZO films. The carrier concentration was excellent, whereas the resistivity and Hall mobility were average.
Technical Report
published : vol. 127, no.3, March 2019
Guizhou ZHAO, Lingling ZHANG and Daqiang CANG
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Steel slag is a by-product in steel production process with considerable volume and low utilization rate in China. This paper investigated the fundamental and industrial feasibility of preparation and properties of high acidity coefficient slag wool using steel slag and fly ash (FA) as raw materials. Slag samples with 30–50 wt % steel slag were modified by FA and viscosity of the modified melts were tested by rotating cylinder method. The slag samples were melted in cupola furnace and then produced into slag wool through melt spinning fiberization method. Modification of steel slag, viscosity of the modified melts and industrial parameters were systematically investigated. Produced slag wool were characterized by X-Ray diffraction, scanning electron microscope and differential thermal analysis. Properties (acidity coefficient, average diameter, shot content, thermal conductivity, etc.), leaching tests and radionuclides were tested according to Chinese national standards. High acidity coefficient slag wool produced by steel slag and FA exhibited properties superior to industrial rock wool. Steel slag and FA can be massively utilized and huge amount of natural resources can be correspondingly saved by substituting rock wool with the slag wool.
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.