最新コンテンツ

Full Paper
published : vol. 126, no.8, August 2018
Hiroyuki INANO, Keiichi TOMITA, Tatsumi TADA and Naoki HIROYOSHI
MORE
Reduction-melting is a method to separate lead from waste cathode ray tube (CRT) lead glass. To study the mechanism of lead separation, melting tests using model lead silicate glass rather than actual CRT glass were carried out. Crushed model lead glass mixed with activated carbon (reducing agent) and Na2CO3 (flux) was heated and quenched at target temperatures to stop the reaction. Tomographic images of the quenched samples were observed by X-ray computed tomography. Further, the samples were evaluated by X-ray diffractometer, X-ray fluorescence spectrometer, and mass change determinations. From these results, it was found that reduction of lead glass and separation of lead occur with the following mechanisms. Elemental Pb (lead) was generated from below 973 K before the sample had melted completely. At 1273 K and above, whole of the sample had become a melt, and the Pb separated and settled out of the glass. Gas released during the melting process agitate the melt and promote the Pb settling.
The 72th CerSJ Awards for Advancements in Ceramic Science and Technology: Review
Special Article
published : vol. 126, no.8, August 2018
Masaki KAKIAGE
MORE
The carbothermal reduction of boron oxide (B2O3) is an important process for the synthesis of boride powders. As a low-temperature synthesis method for boron carbide (B4C) powder by carbothermal reduction, we focused on an approach using a condensed product prepared from boric acid (H3BO3) and an organic compound with a number of hydroxyl groups (a polyol) such as glycerin, mannitol, or poly(vinyl alcohol). A borate ester bond was formed by the dehydration condensation of H3BO3 and a polyol, leading to the homogeneous dispersion of the boron and carbon sources at the molecular level. The thermal decomposition of a condensed H3BO3-polyol product in air was performed to control the amount of carbon to the stoichiometric C/B2O3 ratio required for carbothermal reduction. Within the thermally decomposed product consisting of B2O3 and carbon components (B4C precursor), a B2O3/carbon structure at the nanometer scale was formed. The improved dispersibility and homogeneity of the B2O3/carbon microstructure accelerated the B4C formation at a lower temperature. Consequently, crystalline B4C powder with little free carbon was synthesized by heat treatment at a low temperature of 1200°C in an Ar flow. This low-temperature synthesis approach was applied to the low-temperature synthesis of other boride powders, i.e., boron nitride and calcium hexaboride powders.
The 70th CerSJ Awards for Advancements in Ceramic Science and Technology: Review
Special Article
published : vol. 126, no.8, August 2018
Yoshihiro TSUJIMOTO
MORE
Considerable attention has been paid to reduced transition metal nanomaterials because they exhibit attractive properties for practical applications in fuel cells, memory or thermoelectric devices, and photocatalysts. In particular, a series of oxygen-nonstoichiometric titanium oxides has advantages such as abundance of the elements, non-toxicity, corrosion resistance, and high electrical conductivity. However, the control of nanostructures is not straightforward because a high-temperature reductive condition is required for the synthesis of highly reduced metal oxides. Recently, it has been demonstrated that the novel low-temperature reduction technique can afford highly reduced titania nanoparticles with different particle sizes ranging from 20 to 300 nm diameter. This review article is focused on the synthesis of corundum-type Ti2O3 nanoparticles, the reaction mechanism, and the correlation between structure and physical properties.
The 67th CerSJ Awards for Advancements in Ceramic Science and Technology: Review
Special Article
published : vol. 126, no.8, August 2018
Masayuki NISHI
MORE
Gold nanoparticles grow area-selectively on focused-ion-beam-irradiated areas of a silicon substrate in response to exposure to a pure chloroauric acid solution. Thus, this area-selective metal deposition does not use resist films, silane-coupling agents, and electrolysis. Hydrofluoric acid, almost always used in electroless deposition of gold on silicon, is also unnecessary as long as micro/nanoscopic areas are targeted. This review highlights how we developed the method for the growth of gold on a desired local region of silicon products, including commercially available atomic force microscopy probes as well as silicon wafers, and discusses the mechanism.
The 72th CerSJ Awards for Advancements in Ceramic Science and Technology: Paper
Special Article
published : vol. 126, no.8, August 2018
Sayaka YANAGIDA
MORE
TiO2 photocatalyst is one of the most important photocatalysts for practical use owing to its low toxicity, high chemical stability, natural abundance, and strong oxidation power. However, its low quantum efficiency which is derived from fast electron-charge recombination and its low decomposition rate against organic compounds in low concentration and/or low affinity for TiO2 surface is problematic for environmental purification. To overcome these problems, functionalized photocatalysts that have a nano/microsized structure were prepared by combining TiO2 and other materials in our study. A Z-scheme photocatalyst thin film, a TiO2-coated porous glass composite with high adsorption capacity, and a TiO2-coated stainless mesh for electric field-assisted photocatalysis were prepared using liquid and colloidal processes. This study reports the photocatalytic properties of these composites in air and water environments and their decomposition mechanisms.
Full Paper
published : vol. 126, no.8, August 2018
Xi TAN, Wei LIU, Lamei CAO and Shenglong DAI
MORE
A novel lanthanum monazite (LaPO4) coating was applied to silicon carbide fiber using a simple hydrothermal method to afford a SiCf/LaPO4/SiBCN composite that could be fabricated using resin transfer molding & polymer impregnation and pyrolysis processing technologies. Microstructural analysis showed that silicon carbide fibers were coated uniformly with a ∼700 nm layer of LaPO4, with X-ray diffraction results confirming that the coating formed in the deposition process were compatible with the fiber and matrix materials produced during the pyrolysis process. The mechanical properties of the resultant SiCf/SiBCN, SiCf/BN/SiBCN, SiCf/LaPO4/SiBCN composites were compared using bending, tensile strength, fracture toughness and oxidation tests. These tests indicate that the SiCf/LaPO4/SiBCN composite exhibits excellent mechanical properties, with tests at evaluated temperatures (1350°C for 50 h) revealing that the LaPO4 coating does not undergo oxidation. These results indicate that the SiCf/LaPO4/SiBCN composite has good thermal properties for high temperature applications.
Full Paper
published : vol. 126, no.8, August 2018
Jianan LIU, Chaofeng ZHU, Meimei ZHANG and Xuena YANG
MORE
Ferrimagnetic bulk glass-ceramics and glass fibers containing magnetite crystals in the system SiO2–Al2O3–Fe2O3–B2O3–CaO–MgO–ZnO were prepared via different fabrication methods. The X-ray diffraction, scanning and transmission electron microscopy, vibrating sample magnetometer, electromagnetic parameters, Mössbauer spectra and calorimetric measurements were employed to characterize structure and detect performance of the samples. The estimated size of the spontaneous crystallized magnetite is about 30 nm. The influence of intermediate oxide alumina substituting for network former oxide silica on the spontaneous crystallization of magnetite in glass was investigated. Our results indicated that the ability of magnetite spontaneous crystallization without performing nucleation and crystallization heat treatments was dependent on the chemical composition and fabrication methods.
Full Paper
published : vol. 126, no.8, August 2018
Tengfei DENG, Junjie HONG, Bing LIU, Huachen LIU and Yikun CHEN
MORE
Porous ceramic of high heat conductivity was prepared by using SiC and Al(OH)3 as main raw materials and was applied as oil carrier of smoke atomizer. Graphite and starch were added as pore-forming agents. Results exhibited that the mixture of two pore-forming agents has significant effect on apparent porosity and bending strength of the samples. The mixture of pore formers starch and graphite kept the porosity and remained the sample strength. The best comprehensive physical property was obtained by the additional pore-forming agent that was composed by starch of 40 wt % and graphite of 25 wt %. The oil absorption rate and bending strength met the requirements of porous ceramic as oil absorber. The phase compositions are SiC, SiO2 and needle-like mullite after fired at 1325°C. The distribution of pores was uniform. Smoke atomizer was designed through the combination of porous ceramic and metal ceramic heater (MCH) disk. A simulation of heat conductivity involved in the smoke atomizer was carried out. Both computational simulation and experiment were taken to figure out the efficiency of gas generation by different porous ceramics.
Full Paper
published : vol. 126, no.8, August 2018
Satoshi TANAKA, Keisuke SANO, Tomohiro HARADA, Hiroyuki SHIMIZU and Yutaka DOSHIDA
MORE
Crystal-oriented (Bi0.5, Na0.5)1−xBaxTiO3 (BNBT), (x = 0.1–0.25) ceramics with a perovskite crystal structure were prepared by colloidal processing in a strong rotating magnetic field with the aim of improving their piezoelectric properties. The advantages of increasing the amount of Ba in these ceramics are twofold; specifically, this will lead to anisotropic crystal lattices and it will also increases the tetragonality. The crystal-oriented BNBT (x = 0.1–0.25) ceramics were prepared by using a rotating magnetic field to orient the a– and c-axes of the crystal in the powder compact. The degree of orientation also increased with the tetragonality. The phase transformation that occurred above Curie temperature during sintering redistributed the c-axis-oriented structure along both the a– and c-axes. Again, the c-axis orientation was enhanced by electrical field polarization. The piezoelectric d33 constant, which depended on the Ba content, achieved a maximum value of 122 pC N−1 at a Ba content of 15 mol %.
Full Paper
published : vol. 126, no.8, August 2018
Yuki MAKINOSE, Daisuke ASAKURA, Hirofumi MATSUDA and Eiji HOSONO
MORE
Nanostructured SnO2 is a candidate anode material for lithium ion batteries because of its relaxation of the large volume change accompanying lithium insertion/extraction. Additionally, SnO2 is a relatively low-cost and high-capacity material. Carbon composite materials with high electroconductivity are suitable for high power performances. In this study, core-sheath structured fiber materials constructed of a vapor grown carbon fiber-core and a composite sheath of poly-crystalline SnO2/amorphous carbon are fabricated by electrospinning. This electrospinning method is a useful technique for obtaining nanostructured composite fiber materials.

Special Call for Papers