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Tadasi TAKENAKA
2002 Volume 110 Issue 1280 Pages
215-224
Published: April 01, 2002
Released on J-STAGE: August 06, 2010
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The grain orientation technique, which is one of several ceramic preparation methods with a controlled grain structure during the ceramic sintering process, gives an anisotropic single-crystal-like behavior to the ceramics with lower symmetric crystal structure such as the bismuth layer-structured and the tungsten bronze types than the perovskite structure. Bismuth layer-structured ferroelectrics (BLSF) are characterized by low dielectric constant, high Curie temperature and large anisotropy in electromechanical coupling factors than those of PZT family. Further more, the characteristics can be easily enhanced by the grain orientation. This paper describes the effects of grain orientation on electrical properties such as dielectric, ferroelectric, piezoelectric and pyroelectric properties of some grain-oriented BLSF ceramics by the hotforged (HF) method, comparing them with ordinarily fired (OF) non-oriented ones.
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Minoru OSADA, Masato KAKIHANA, Ryuji ADACHI, Takashi ICHIHARA, Naoto K ...
2002 Volume 110 Issue 1280 Pages
225-227
Published: April 01, 2002
Released on J-STAGE: August 06, 2010
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Near-infrared (NIR) Raman spectroscopy has shown its unique advantages for characterization of ZnS:Cu, Al materials, emitting a strong luminescence in the visible region. We demonstrate that, because of a rapid decrease of luminescence in the NIR region, Raman spectra with 752.5-nm excitation are free from the visible luminescence, which usually masks Raman signals with visible excitations. By comparing the spectra of ZnS:Cu, Al samples with different luminescence efficiencies, we also find that crystal imperfections, including coexistence of hexagonal domains, can lead to a reduction of luminescence properties.
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Taras PELEKH, Jun-ichi MATSUSHITA
2002 Volume 110 Issue 1280 Pages
228-231
Published: April 01, 2002
Released on J-STAGE: August 06, 2010
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The influence of high temperature oxidation on the Vickers hardness of a cemented carbide, tungsten carbide (WC) added with cobalt (Co), was investigated in order to determine its suitability for improvement hardness. The Vickers hardness of WC-Co was improved by high temperature oxidation treatment. The oxidation thickness of the sample from 973 to 1273K depended on oxidation temperature and time. The oxidation thickness increased with increasing oxidation temperature and time, especially, significant oxidation of samples occurred at 1073K.
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Tsuguto TAKEUCHI, Toshihiko TANI
2002 Volume 110 Issue 1280 Pages
232-236
Published: April 01, 2002
Released on J-STAGE: August 06, 2010
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In-situ reaction and texture development were investigated during heat treatment in reactive templated grain growth (RTGG) processing for textured SrTiO
3 (ST) ceramics. Platelike Sr
3Ti
2O
7 (S3T2) particles were used as a template and aligned S3T2 particles were heat-treated with stoichiometrically required amounts of TiO
2 for textured ST ceramics. The sintered ceramics exhibited uniaxial ‹100› orientation and the degree of orientation reached was 0.43 (Lotgering's factor). X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses revealed that an S3T2 single-crystal template was converted into an ST polycrystal with its outer shape maintained. The following grain growth mechanism of converted ST caused a marked increase in the degree of orientation.
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Yutaka SAITO, Junichi NYUMURA, Kiyoteru FUKAI, Yao ZHANG, Nozomu UCHID ...
2002 Volume 110 Issue 1280 Pages
237-242
Published: April 01, 2002
Released on J-STAGE: August 06, 2010
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Moisture content is one of the most important factors governing both structure and properties of green powder compacts of ceramics made through a compaction process. To control the moisture content in powder granules, it is necessary to understand kinetic changes of moisture content in granules, and pressed compacts. The apparent diffusion coefficient of moisture was directly measured for powder compacts containing polyvinyl alcohol (PVA) by following the weight change of the specimen. The parameters examined in this paper were size of specimen, forming pressure, average relative humidity and binder content. The observed rate of change was clearly affected by the PVA content in the compact. Examination of the distribution of PVA in the granules and compacts using optical microscopy (using immersion liquid method) was found to be nonuniform. The diffusion path consisted of an alternate sequence of thin layers of PVA-rich regions and thick layers of PVA-poor regions. The PVA-rich layers had a non-homogeneous structure which contained open pores.
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Tohru KANNO, Keisuke KAWAMURA, Kiyoshi TADA, Jun-ichi HORIUCH, Masayos ...
2002 Volume 110 Issue 1280 Pages
243-247
Published: April 01, 2002
Released on J-STAGE: August 06, 2010
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Deodorizing ability of a diatomaceous material mined from Wakkanai district in Hokkaido Pref. was examined in detail. This material is widely distributed in the market as a material of environmentally-friendly inner-wallboard. Alternative introductions of a model odor {NH
3, CH
3CHO, or (CH
3)
2S} mixed-N
2 gas flow and a pure N
2 gas flow into the diatomaceous material showed reversible adsorption and desorption of the odor components at 25°C, reconfirming regeneration of deodorizing ability for the diatomaceous-wallboard by ventilation of rooms with these wallboards. The adsorbed quantities of the odors onto the diatomaceous material during one hour readily cleared the odor level 3:2.3ppm for NH
3, 0.14ppm for CH
3CHO, and 0.044ppm for (CH
3)
2S, respectively.
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Ayako OYANE, Masakazu KAWASHITA, Tadashi KOKUBO, Masahiko MINODA, Take ...
2002 Volume 110 Issue 1280 Pages
248-254
Published: April 01, 2002
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The surface of an ethylene-vinyl alcohol copolymer (EVOH) was modified with Ti-OH groups by a silane coupling treatment followed by treatment with a titania solution. The arrangement of the Ti-OH groups formed on EVOH was changed from amorphous into anatase structure by a subsequent HCl solution treatment. Bonelike nanoapatite was successfully formed on the surface-modified EVOH even in a form of fibers as well as plates within 2d at 36.5°C in a simulated body fluid (SBF) with ion concentrations approximately equal to those of human blood plasma. The resultant nanoapatite-polymer fiber composite was similar to that of natural bone in its structure where apatite nanocrystals are deposited on fine organic fibers constituting a composite. Therefore, if the present surface modification can be applied to a three-dimensional fabric with a structure similar to the collagen fibers of natural bone, a composite with an analogous structure to that of natural bone would be obtained. The resultant composite is expected to exhibit mechanical properties analogous to those of natural bone, as well as bone-bonding ability, and hence be truly useful as a new bone substitute.
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Kazuya KOMAGATA, Hiroaki TAKEDA, Tadashi SHIOSAKI
2002 Volume 110 Issue 1280 Pages
255-258
Published: April 01, 2002
Released on J-STAGE: August 06, 2010
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Bismuth layer-structured ferroelectrics (BLSFs), M
0.5Bi
2.5Ta
2O
9 (M=Na, K) were synthesized using a solidstate reaction. Na
0.5Bi
2.5Ta
2O
9 (NBT) single phase polycrystals were obtained by heating raw material powders at 1100°C. On the other hand, K
0.5Bi
2.5Ta
2O
9 (KBT) powder contained KTaO
3 as a main impurity phase. Dense ceramics of NBT were prepared by considering Bi
2O
3 vaporization and using a binder. Result of dielectric and ferroelectric characterizations of the NBT ceramic were as follows: Curie temperature,
TC=780°C, dielectric constant, ε
s=158, dielectric loss factor, tan δ=0.011 as measured at room temperature and 1MHz and the remanent polarization,
Pr=15-18μC·cm
-2. The
Pr value is the largest among reported BLSFs that are composed of two perovskite layers.
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Tsutomu SAKAKIBARA, Yasuo TAKIGAWA, Akihiro KAMEYAMA, Kou KUROSAWA
2002 Volume 110 Issue 1280 Pages
259-263
Published: April 01, 2002
Released on J-STAGE: August 06, 2010
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We prepare composite materials that Ag
2Te grains were dispersed in AgBiTe
2 matrices with the compositions of (AgBiTe
2)
1-x(Ag
2Te)
x. The textures depend on the composition. We measured electrical conductivity, thermal conductivity, Seebeck coefficients and Hall coefficients as a function of the composition. Eased on these data, we estimate Hall mobility and lattice thermal conductivity, and finally thermoelectric figure of merit. We show that the figure of merit is enhanced in the composite system by means of enhancement of phonon scattering at the grain boundaries.
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Anze SHUI, Atsushi MAKIYA, Satoshi TANAKA, Nozomu UCHIDA, Keizo UEMATS ...
2002 Volume 110 Issue 1280 Pages
264-269
Published: April 01, 2002
Released on J-STAGE: August 06, 2010
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The effect of cold isostatic pressing (CIP) on microstructure and shrinkage anisotropy during sintering is systematically and quantitatively examined for uniaxially pressed alumina compacts made from spray-dried granules. This study helps to clarify the abnormal effect of CIP on their sintering behavior. Uniaxial pressing caused anisotropic deformation of granules in the compacts, making spherical granules into an elliptical shape and developing the arrangement structure of particles. A subsequent CIP slightly reduced the apparent deformation of granules, but increased the degree of particle arrangement evaluated by optical microscopy. It also increased the shrinkage anisotropy of the compacts during sintering. The experimental results indicated that there was a linear relationship between the degree of particle arrangement and the shrinkage anisotropy during sintering when employing the pressed alumina compacts.
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Temperature Dependence of Internal Friction and Shear Modulus of ALON-Based Composite Ceramics
Akihiro SHIMPO, Masanori UEKI, Kenichi OTA, Masaaki NAKA
2002 Volume 110 Issue 1280 Pages
270-275
Published: April 01, 2002
Released on J-STAGE: August 06, 2010
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Correlation between mechanical properties such as internal friction and shear modulus and the microstructure of ALON-based composite ceramics incorporated with BN was investigated at elevated temperatures in air. Internal friction (
Q-1) of the ALON-based composite ceramics exhibited peaks, independent of the amount of BN added, at around 250-350°C, 700-750°C and 1000-1100°C, then increased monotonically at 1250°C which is the maximum temperature measured, On the other hand, by high temperature X-ray diffractometry (XRD), ALON (Al
(64+x)/3_??_(8-x)/3O
32-xN
x) and BN phase, and aluminum borates oxidized both, were identified as the microstructures (formed crystalline phases) formation temperatures of the phases corresponded to the three peaks of internal friction (
Q-1). However, shear modulus measured at the same time with internal friction, decreased monotonically with temperature and did not reflect any microstructural change at high temperature. Therefore, it was clarified that the microstructural evolution of ALON-based composite ceramics at high temperature, can be detected by internal friction measurement.
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Takashi OKAWA, Masahiro IMAEDA, Hitoshi OHSATO
2002 Volume 110 Issue 1280 Pages
276-282
Published: April 01, 2002
Released on J-STAGE: August 06, 2010
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The solid solution's formation and microwave dielectric properties of Bi-doped Ba
6-3xR8+2xTi
18O
54 (R: rare earth,
x=2/3) series were investigated based on the crystal structure. The crystal structure is the tungstenbronze-type like with perovskite blocks including
R ions and pentagonal sites with Ba ions. Bi ions have been substituted for Ba ions in pentagonal sites at early stage in La and Nd-series. Subsequent substitutions of Bi ions occur for
R ions in rhombic sites same as other Sm, Eu and Gd series. The Bi ion's substitution affects the microwave dielectric constants (ε
r) as having inflection point for La and Nd-series. In the case of other Sm, Eu and Gd, dielectric constant (ε
r) increased and the quality factor (
Q⋅
f) value decreased, according to the increase of
y in the Ba
4(
R1-yBi
y)
9+1/3Ti
18O
54 compositions. The temperature coefficients of the resonant frequency (τ
f) has an inflection point at
y=0.1-0.15 composition.
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Kenji TODA, Yu-ichiro IMANARI, Takashi NONOGAWA, Junichi MIYOSI, Kazuy ...
2002 Volume 110 Issue 1280 Pages
283-288
Published: April 01, 2002
Released on J-STAGE: August 06, 2010
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Rare earth-doped alkaline earth silicates, Sr
2MgSi
2O
7:Eu
2+, Dy
3+ and Ca
2MgSi
2O
7:Eu
2+, Dy
3+, with an akermanite-type structure show bright and long-lasting phosphorescence. After irradiation by a white-color fluorescent lamp (780lm) for 5min, the light blue emission of Sr
2MgSi
2O
7:Eu
2+, Dy
3+ was observable by naked eye in the dark for over 100min after removal of the excitation light source.
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Hisanori YAMANE, Takashi ARAKI, Takashi SEKIGUCI, Shunichi KUDOTA, Mas ...
2002 Volume 110 Issue 1280 Pages
289-292
Published: April 01, 2002
Released on J-STAGE: August 06, 2010
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Granular and platelet-shaped gallium nitride (GaN) crystals were prepared at 600-700°C and 4-7MPa of N
2 for 24-96h by using a K-Ga melt. The granular crystals with a size of 50-80μm were a mixture of cubic zincblende-type GaN (c-GaN) and hexagonal wurztite-type GaN (h-GaN). The ratio of c-GaN in the mixture increased with decreasing temperature and with decreasing N
2 pressure. The platelet crystals obtained were h-GaN and have a size of about 1mm. A colorless transparent grain of GaN with a size of 80μm was characterized by cathodoluminescence (CL) spectroscopy at room temperature. A CL peak with a full width at half maximum of 76meV was observed at 3.209eV which agreed with the near band emission peak position reported for c-GaN thin films.
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Ken MURAOKA, Hideyuki YOSHIMATSU, Satoru UENO, Hideaki SATO, Yoshinari ...
2002 Volume 110 Issue 1280 Pages
293-298
Published: April 01, 2002
Released on J-STAGE: August 06, 2010
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Calcium hydroxide powder was coated with a silicon alkoxide and a chelate compound of aluminum, and heated at 500-800°C to prepare silica- and alumina-coated lime powders. Specific surface area and SO
2 absorbability of silica- and alumina-coated lime powders were higher than those of the uncoated powder. Calcium silicate and calcium aluminate formed on the surface of these powders. It was considered that the improvement of SO
2 absorbability for the silica-coated powder was attributed to an increase of specific surface area, while that for the alumina-coated powder arose from on increased acidity.
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Koji TAMAI, Shin'ichi ARATANI, Hidenori OJIMA, Kazuyoshi TAKAYAMA
2002 Volume 110 Issue 1280 Pages
299-303
Published: April 01, 2002
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A method for the production of 2.0mm thick tempered glass plates by using the impingement of air jets and its subsequent heat transfer was studied experimentally. Tempering degree of glass plate specimen was estimated by measuring the fragment density. It was found that 2.0mm thick tempered glass plates produced by lack-expansion flow had favorable tempering degree and also good surface condition for practical use. Heat transfer coefficient was approximately calculated by Reynolds number and nozzle stand-off distance in the condition of the lack-expansion flow instead of subsonic flow.
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Yuko SHIRATORI, Hiroyuki SAITO, Masashi HIGUCHI, Keiichi KATAYAMA, Yas ...
2002 Volume 110 Issue 1280 Pages
304-309
Published: April 01, 2002
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Spherical mesoporous silica particles were successfully prepared upon hydrolysis of tetraethylortosilicate (TEOS) in presence of dodecylamine (DDA) as on organic template. Comparison of the products obtained by a other method and synthesis conditions were also studied. The product obtained by HMS method using DDA was more homogeneous and truly spherical as compared to that obtained by other method using dodecyltrimethylamonium bromide (DTAB) and cetyltrimethylammonium bromide (CTAB). The particle size could be modified by adjusting the molar ratio of DDA/TEOS and EtOH/TEOS of the solution, particle sizes ranging from 0.2 to 1.2μm. The surface area of spherical mesoporous silica particles 1.23μm in size was about 423m
2/g, their density was 1.4g/cm
3 and their pore mean diameter was 3.6nm.
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Toshitaka OTA, Naoto YAMAUCHI, Keiji DAIMON, Yasuo HIKICHI, Hidetoshi ...
2002 Volume 110 Issue 1280 Pages
310-313
Published: April 01, 2002
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Electroconductive composites were prepared from graphite as a filler material, piezoelectric ceramics as a matrix, and epoxy resin as a binder. When the filler volume fraction was near
Vc on a percolation curve, the composite exhibited a nonlinear
I-V characteristics, in analogy with varistors. It was assumed that this phenomenon was due to the distortion of the piezoelectric matrix upon applying a potential through the sample.
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Hailei ZHAO, Keisuke HIRAGUSHI, Yasuo MIZOTA
2002 Volume 110 Issue 1280 Pages
314-319
Published: April 01, 2002
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The reactivity of B
4C with mullite was investigated under Ar and reductive atmospheres, respectively. The results indicated that B
4C could coexist stably with mullite under Ar atmosphere below 1350°C, above which some reaction would occur to form Al
2O
3 and Al
3SiB
48 phases. Under a reductive atmosphere, whereas, they exhibited a relatively higher co-existing temperature of 1500°C, which is deemed to be dependent on the partial pressure of CO
2 gas in heating atmosphere. Coating technique was employed in this study to suppress the reaction between B
4C and mullite by producing a TiO
2 thin coating layer on the surface of B
4C particles. TiO
2 will react with B
4C at high temperature to produce TiB
2 and B
2O
3. The latter phase, existing on the grain boundary of B
4C particles by a liquid state at high temperature, will, together with TiB
2, serve as a barrier to inhibit the reaction between B
4C and mullite. A2mass% TiO
2 on B
4C powders can effectively suppress the occurrence of this reaction.
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Shuji KARIYA, Mamoru MIZUTANI, Toshitaka OTA, Keiji DAIMON, Yasuo HIKI ...
2002 Volume 110 Issue 1280 Pages
320-324
Published: April 01, 2002
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A new type of composite PTC thermistor was fabricated from ZnO-varistor particles and silicone rubber. The non-ohmic varistor characteristics were held in the composites. The ZnO-varistor particles were found to behave as a conducting filler at voltage higher than the varistor voltage, The PTC effect appeared in the composites containing varistor particles with volume fraction over the percolation threshold (≥250vol%). The electrical resistivity at room temperature and the temperature region showing PTC effect varied according to the applied voltage.
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Takeshi TAMAOKA, Setsuhisa TANABE, Teiichi HANADA
2002 Volume 110 Issue 1280 Pages
325-328
Published: April 01, 2002
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Concentration dependence of emission properties and lifetimes of Tm
3+ doped tellurite glasses in telecommunication wavelength region were investigated. According to Judd-Ofelt analysis, it was clarified that the quantum efficiency of 1.46μm in Tm
3+-doped tellurite glasses was almost equal to that in fluoride glasses, which were used as host materials for Tm
3+-doped fiber amplifiers (TDFA). The emission intensity ratio of the 1.80μm band to the 1.46μm band increased with increasing Tm
3+ content. Moreover, the lifetimes of the
3H
4 level decreased rapidly with increasing Tm
3+ content. These results show that tellurite glass is useful as host materials of TDFA and in order to achieve a high quantum efficiency of 1.46μm emission in tellurite glasses, the concentration of Tm
3+ should be low so that cross relaxation can be suppressed.
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Ryosuke UEYAMA, Tamotsu UEYAMA, Kunihito KOUMOTO
2002 Volume 110 Issue 1280 Pages
329-332
Published: April 01, 2002
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The addition of sintering suppressor to Ni paste was studied in order to enable further thinning of the MLC Ni electrode. The contraction rate of the Ni paste without the sintering suppressor increased as the paste grain diameter decreased. A considerable difference was observed between the sintering contraction rate of a dielectric green sheet and that of Ni paste. This finding led us to consider that the sintering contraction behavior of Ni paste should be close to that of the dielectric green sheet in the manufacturing process of current ceramic capacitors. Therefore, we studied an organometallic acid salt with the same composition as the ceramic. According to the results of our study, sintering of electrode paste film was inhibited when using Ni paste with an organometallic acid salt in contrast to the case of using Ni paste without an organometallic acid salt. Furthermore, the study of resistivity to determine the electrical characteristics revealed that the Ni paste film with the sintering suppressor exhibited low resistivity compared to the Ni paste film without the sintering suppressor. It was clarified that Ni paste with a sintering suppressor has excellent electrical characteristics.
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2002 Volume 110 Issue 1280 Pages
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Published: 2002
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