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Volume 46, Issue 3
Displaying 1-19 of 19 articles from this issue
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Koji Amezawa1999 Volume 46 Issue 3 Pages 207-211
Published: March 15, 1999
Released on J-STAGE: July 12, 2010
JOURNAL OPEN ACCESSSignificant protonic conduction has been found at high temperature in LaPO4-based ceramics, in which protons are considered to dissolve as defects in the presence of hydrogen-containing gases. This report describes electrolyte properties of 5mol% Sr-substituted LaPO4. In air, this material can be regarded as a pure protonic conductor at 600°C when PH2O>1kPa, and at 700°C when PH2O> 3kPa. At high temperature, low PH2O, and high PO2, the material shows mixed conduction by protons and electron holes. The contribution of electron hole conduction to the total conductivity becomes significant as temperature increases, PO2 increases, and PH2O decreases, although protonic conduction is still dominant even at 900°C in wet air.View full abstractDownload PDF (334K) -
Takehisa Ohno1999 Volume 46 Issue 3 Pages 212-218
Published: March 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSX-Y composite nanoparticles, in which X are Al, Cu, Ge and Si, and Y are In, Zn and Mg, were prepared by the condensation of Y vapor onto flying X nanoparticles which were produced in advance by a gas-evaporation technique. The structural and morphological observation of these nanoparticles was carried out by means of a transmission electron microscope.
It has been found that each Al-In particle is composed of an Al sphere which is replaced in part by an In crystallite, where the Si-In particles are composed of Si spheres with In crystallites attached to the neck of neckelace-like Si particles. A Cu-Zn particle or a Ge-Mg particle grown under the appropriate preparation connditions was also found to be composed of two phases of Cu-Zn alloy and Zn or Ge and MgzGe, respectively, where the latter surrounds the former in both systems. Their morphological features are discussed in relation to the growth process with reference to their phase diagrams.View full abstractDownload PDF (9199K) -
Shigeru Katsuyama1999 Volume 46 Issue 3 Pages 219-226
Published: March 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSWe have examined the thermoelectric properties of Co1-xFexSb3 ternary system and CoSb3-FeSb2 composite system. The Seebeck coefficient and the electrical resistivity are generallyreduced by the substitution for Co by Fe. The thermal conductivity is also reduced by the substitution especially at high iron content region. These behaviors of the thermoelectric properties in the samples with low iron content are ascribed to the substituted Fe, while those in the samples with high iron content are ascribed to the precipitated FeSb2 (Fe0.73Co0.27Sb2) compound. Co0.75 Fe0.25Sb3 has a maximum value of figure of merit of 4.8×10-4 K-1 at 773K. For the purpose of more reducing of the thermal conductivity, we have prepared the CoSb3-FeSb2 composite where the FeSb2 particles are dispersed in the CoSb3 matrix by MG (mechanical grinding) technique. The thermal conductivity of the composite is smaller than that of Co1-xFexSb3. The electrical resistivity of the composite increases with increasing MG time, but it is smaller than that of CoSb3 at high temperature. The decrease of the thermal conductivity and the less increase of the electrical resistivity are ascribed to the enhancement of the phonon scattering caused by the dispersed FeSb2 in the matrix and the low electrical resistivity of FeSb2, respectively. As a result, the composite whose molar ratio of CoSb3 to FeSb2 is 0.7 to 0.3 and MG time is 25h has a maximum value of figure of merit of 6.1×10-4 K-1 at 756K. This value is larger than the maximum value of 4.8×10-4 K-1 for Co1-xFexSb3 system.View full abstractDownload PDF (4431K) -
Hidetoshi Kotera, Susumu Shima1999 Volume 46 Issue 3 Pages 227-231
Published: March 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSNumerical method based on the Cosserat continuum theory is proposed for simulation of a magnetic powder in an applied magnetic field. The Maxwell stress is induced in the magnetic powder. During powder forming process in the magnetic field, the magnetic particles are thus rotated and transferred by both mechanical and magnetic interaction. To simulate this powder behavior, new finite element method considering Maxwell is formulated on the basis of the Cosserat continuum theory of compressible plasticity. The powder behavior with magnetic alignment during compaction in magnetic field is simulated by the proposed method to discus the effect of couple-stress on the powder behaviour. The relationship between the direction of magnetic field and the compaction process can be also analyzed: difference of magnetization in cross compaction, transverse compaction and isostatic compaction. In the calculation, the directions of the easy axes are given by a set of random numbers. The rotation of the axes is thus calculated at various conditions of applied magnetic field. The results are discussed comparing with those by particle dynamics simulation.View full abstractDownload PDF (375K) -
Kazuharu Iwasaki, Takuya Itoh, Tsutomu Yamamura1999 Volume 46 Issue 3 Pages 235-240
Published: March 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe formation process of acicular α-FeOOH particles, which was prepared from the colloidal solution of amorphous ferric oxyhydroxide, was investigated with using IR, XRD and TEM measurements. The formation mechanism of crystal particles was considered to be by the dissolution-recrystallization process. The rate constant and activation energy of the process showed strong pH dependence of the mother liquid. The crystallite size of particles also showed pH dependence. The rate constants increased and reached maximum values, after that decreased with increasing pH. The maximum values showed a tendency to shift on the lower pH side with increasing aging temperature. The activation energy decreased and reached minimum values near pH12.5, and increased at higher pH region exceeding 12.5. On the other hand, the crystallite size of (110) of particles decreased with increasing pH. Their pH dependencies might be due to promotion of crystal growth depend on increasing the supersaturation of solute and inhibitory action of its crystal growth depend on singular adsorption of OH- on the side face parallel to c axis of particles.View full abstractDownload PDF (4227K) -
Kazuharu Iwasaki, Takuya Itoh, Tsutomu Yamamura1999 Volume 46 Issue 3 Pages 241-246
Published: March 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe relationship between rate constant, activation energy and growth rate of crystallite for formation of acicular α-FeOOH particles, and FeCl3 concentration of colloidal mother liquid was discussed. Both rate constant and growth rate of crystallite decreased with increasing FeCl3 concentration at aging above 80°C. At below 55°C it did not almost show the concentration dependence. The activation energy monotonically decreased, and decreased rapidly for the case in which FeCl3 concentration is less than 0.1kmol/m3. The observed dependenCles on FeCl3 concentration can be explained in the following manner: crystal growth of side face parallel to c axis of acicular particles is restrained by singular adsorption of Cl-on the side face. It is considered that activation energy decreases with increasing FeCl3 concentration, because recrystallization process of Fe(OH)4- changes from the surface reaction controlled process to the diffusion controlled process. The crystallite size of acicular α-FeOOH. particles increased steeply with increasing FeCl3 concentration at aging above 80°C. At below 55°C it increased slightly. The particle size grew larger maintainning acicular shape with increasing FeCl3 concentration. The length of major axis and aspect ratio of acicular particles increased especially. It is considered that increasing their size is due to growth of crystallite by coalescence of each nuclei.View full abstractDownload PDF (4935K) -
Kazuharu Iwasaki, Tsutomu Yamamura1999 Volume 46 Issue 3 Pages 247-251
Published: March 15, 1999
Released on J-STAGE: July 12, 2010
JOURNAL OPEN ACCESSThe relationship between rate constant, activation energy for formation of acicular α-FeOOH particles and addition quantity of CO32- to colloidal mother liquid was discussed under the conditions: the pH and FeCl3 concentration of mother liquid are constant 12.0-12.1 and 0.040-0.044 kmol/m3 respectively. The rate constant decreased with increasing addition quantity of CO32-upto 0.25kmol/m3, and was constant over 0.25 kmol/m3 for the aging at 80°C. At the temperature lower than 55°C, it did not show the dependence on CO32- concentration. Similarly, the activation energy decreased with increasing addition quantity of Co32-upto 0.25 kmol/m3, and further addition did not affect the activation energy. The observed dependence of the rate constant on the addition quantity of CO32-can be attributed to the following reason: the crystal growth of α-FeOOH is restrained by the adsorption of CO32- on the specified crystal plane. The fact that activation energy decreases with increasing addition quantity of CO32- indicates that recrystallization process of Fe(OH)4- changes from the surface reaction controlled process to the diffusion controlled process. Both crystallite size and median diameter of acicular, α-FeOOH particles decreased with increasing addition quantity of CO32-. Both lengths of major axis and minor axis of acicular particles similarly decreased with increasing addition quantity of CO32-. These dependencies indicate that the CO32- ions adsorb on the crystal planes homogeneously without any preference of the crystal planes among a, b, and c planes. This resulted in the decrease of dimension of the acicular α-FeOOH formed with similar aspect ratio.View full abstractDownload PDF (2233K) -
Kazuharu Iwasaki, Tsutomu Yamamura1999 Volume 46 Issue 3 Pages 252-256
Published: March 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe relationship between rate constant, activation energy and growth rate of crystallite for formation of acicular α-FeOOH particles, and pH of colloidal mother liquid containing carbonate ion was discussed for the case, in which addition quantity of CO32- and FeCl3 concentration were constant. Both rate constant and growth rate of crystallite increased with increasing pH, and increased steeply above pH11.6 and pH11.0, respectively. The activation energy decreased and reached minimum values at pH of about 11.6, and increased at higher pH region exceeding 11.6. The supersaturation of solute, Fe(OH)4- increases with increasing pH. At the same time, the singular adsorption of OH- on the side face of acicular particles is restrained by the coating of coexisting CO32- on their surfaces. These may be the reasons for the pH dependencies of rate constant and growth rate of crystallite observed. Both crystallite size and median diameter of the formed α-FeOOH particles increased with increasing pH, then α-FeOOH particles grew larger with keeping needle shape similar according to TEM observation. Moreover, raft-shaped particles which single crystal coalesced with each other, were formed at higher pH region exceeding 11.6. The increase of activation energy may be caused by the formation of raft-shaped particles. The granular hematite particles were also formed with acicular α-FeOOH particles at lower pH region below 11.0.View full abstractDownload PDF (2676K) -
Hisakazu Tomino, Akira Tsukuda, Yoshihito Kondo, Kozo Ishizaki1999 Volume 46 Issue 3 Pages 257-261
Published: March 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe porous cast-iron bonded (PCIB) diamond grinding wheel, which has recently been developed, had an excellent grinding performance for structural ceramics. Although this grinding performance of PCIB wheel depends on the porosity, the effect of the porosity on the grinding performance has not yet been studied.
In this paper, the PCIB diamond grinding wheels, which have several porosities under a constant grain volume percentage, were produced by the pulse electric current sintering method. And the grinding tests using these PCIB wheels built as a trial were undergone for silicon nitride. From experimental results, the influence of the porosity on the grinding performance was discussed. The results were as follows: (1) The wear rate of wheel increased with decreasing mechanical strength due to porosity. (2) The PCIB wheels with porosity over 25% were a low specific grinding energy with no relation to the grinding pressure.
(3) There was the optimum porosity that gave the maximum grinding ratio.View full abstractDownload PDF (336K) -
Masae Nakahara, Yoshihito Kondo, Kenya Hamano1999 Volume 46 Issue 3 Pages 262-268
Published: March 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSWe studied the effect of a corundum and gibbsite on the reaction process andphysical properties of cordierite ceramics. The results were as follows:
(1) In the fired bodies obtained from the kaolin-talc-gibbsite mixture, gibbsite attributed to the cordierite formation without rearrangement into corundum in the firing process.
(2) In the case of small particle size of ground mixture, apparent porosity of bodies fired at 1200°C were 0% in both case of kaolin-talc-corundum mixture and kaolin-talc-gibbsite mixture.
(3) The bending strength and thermal expansion coefficient of bodies fired at1300°C obtained from both mixtures increased with decrease in particle size ofground mixtures. The optimum particle size of kaolin-talc-gibbsite mixture wasabout 0.4μm, because over grinding mixture caused a decrease in cordieritecontent of body fired at 1300°C.View full abstractDownload PDF (1782K) -
Masao Tokita, Masakazu Kawahara, Masayuki Sonoda, Mamoru Omori, Akira ...1999 Volume 46 Issue 3 Pages 269-276
Published: March 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSComposite Functionally Graded Materials of ZrO2(3Y)+20wt%Al2O3/SUS410L Stainless steel were prepared using Spark Plasma Sintering method. Mixed powders for inter layers were made of SUS410L and ZrO2(3Y)of 90, 80, 70, 60, 50 and 30 vol%. Three kinds of ceramic 100% layer were provided. Each of the ceramic 100% top coat layers were A=ZrO2(3Y), B=ZrO2(2Y)+20vol%aAl2O3 and C=ZrO2(3Y)+20wt%Al2O3. These were stacked and laminated and sintered for 10 min. The sintering temperature of the ZrO2 layer was ca. 1473K-1643K and that of the SUS410L layar was ca. 1273K-1373K. The FGM containing SUS410L was fabricated dense and free from pores or cracks. The stress due to the thermal expansion mismatch was delocalized by the graded structures and no crack appeared. However, the compressive residual stress acted to decrease the fracture toughness of the ZrO2(3Y) layer. The ZrO2+20wt%Al2O3 composite layer achieved higher fracture toughness and higher wear resistance than the ZrO2(3Y) layer. Triborogical characterization is also investigated.View full abstractDownload PDF (4126K) -
Kenji Nakahara, Shigeya Sakaguchi, Yasunori Hayashi1999 Volume 46 Issue 3 Pages 277-282
Published: March 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe structures of passivation films of sintered Ti-(0, 10, 20, 30, 40, 100)mass%Mo alloys formed in 35%HCl, 3%NaCl and 103mol/m3(3.8%)NaOH solution were studied by X-ray photoelectron spectroscopy (XPS). X-ray photoelectron spectra of Mo3d, Ti2p and Ols of Ti-Mo alloys immersed in a 35%HCI solution showed that Mo4+/Mo6+ ratio of the passivation film increased with increasing Mo content in the alloy and that Mo in the passivation film was enriched by the preferential dissolution of Ti. This showed that Mo4+ in this film was important for improving its corrosion resistance. From X-ray photoelectron spectra of Ti-Mo alloys immersed in a 3%NaCI solution, it was indicated that the Mo content in the passivation film was equal to that in the alloy and that the passivation film were composed of Mo6+ and Ti4+. On the other hand, X-ray photoelectron spectra of Ti-Mo alloys immersed in a 3.8%NaOH solution showed that Ti in the passivation film was enriched by the active preferential dissolution of Mo. It was thought that the passivation film composed of a stable Ti oxide improved the corrosion resistance in NaOH solution.View full abstractDownload PDF (2118K) -
[in Japanese]1999 Volume 46 Issue 3 Pages 284
Published: March 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSDownload PDF (123K) -
Yasuo Takeda1999 Volume 46 Issue 3 Pages 285-292
Published: March 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSThe perovskite type manganite systems, Ln1-xAxMO3 (Ln=rare earth, A=Sr, Ca) were studied as the electrode materials for solid oxide fuel cells (SOFC). The highest cathodic activity was obtained for the La1-xSrxCoO3 electrode. The reactivity tests of La1-xAxMO3 with yttria-stabilized zirconia (YSZ) showed that the formation of the pyrochlore Ln2Zr2O7 decreases the electrode activity. However, this was suppressed for the perovskites having smaller lanthanoids than La, for example, for the Gd1-xAxMnO3 and GdCoO3 systems. No reaction product appeared between the Gd1-xAxMnO3 perovskite and YSZ even at a high annealing temperature of 1400°C. GdCoO3 did not react with YSZ even at 1000°C. The adjustment of the thermal expansion rate to YSZ needed the formation of solid solution such as Ln1-xSrxMn1-yO3, some of which showed the high cathodic activity and good compatibility.View full abstractDownload PDF (552K) -
Yoshinori Sakaki, Yasuo Takeda, Ai Kato, Nobuyuki Imanishi, Osamu Yama ...1999 Volume 46 Issue 3 Pages 293-299
Published: March 15, 1999
Released on J-STAGE: December 04, 2009
JOURNAL OPEN ACCESSThe perovskite type manganite systems, Ln1-xSrxMnO3 (Ln=La, Pr, Nd, Sm and Gd; 0.0≤x≤0.5) were studied as the electrode materials for solid oxide fuel cells (SOFC) from the view point of applications to the co-firing process of the electrolyte and electrode at higher temperature. The reactivity tests with yttria-stabilized zirconia (YSZ), no reaction product appeared between the Ln1-xSrxMnO3 perovskite and YSZ even at a high annealing temperature of 1400°C when the lanthanoid elements were Pr, Nd and Sm and the Sr content was around 30% (x=0.3). The adjustment of the thermal expansion rate of Ln1-xSrxMnO3 to YSZ, around x=0.1-0.2 in La1-xSrxMnO3, 0.3 in Pr1-xSrxMnO3 and Nd1-xSrxMnO3 and more than 0.4 in Sm1-xSrxMnO3 and Gd1-xSrxMnO3. The electrical conductivity reached to 200 S/cm at 1000°C for all Ln0.7Sr0.3MnO3 systems. The polarization measurements as an air electrode showed no significant dependence on the kind of lanthanoid elements. In the point of the electrode activity, high electrical conductivity, and low reactivity and good compatibility with YSZ, Pr0.7Sr0.3MnO3 and Nd0.7Sr0.3MnO3 are considered to be the most suitable electrode materials for the co-firing process.View full abstractDownload PDF (2413K) -
Shinichi Kikkawa, Yoshinori Kohno, Yonghong Teng1999 Volume 46 Issue 3 Pages 300-304
Published: March 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSHydrotalcite-like compound was obtained in compositional range of 0.2<Mg/(Mg+Al)<0.35 by aging the coprecipitated gel from MgCl2 and AICl3 with NaOH in mixed aqueous solution. Its thermal behavior was investigated on the representative composition of Mg/(Mg+Al)=0.25. The decomposed product in a temperature range of 500-800°C was a MgO-Al2O3 solid solution and both MgO and spinel crystallized above this temperature range. Hydrotalcite structure was recovered when the former decomposed product was immersed in sodium carbonate aqueous solution. The hydrotalcite gel could be supported in micro pore with its pore diameter>1μm of porous alumina tube. The hydrotalcite supported porous tube showed a reversible absorption of CO2 from atmosphere. The CO2 absorption behavior was affected with humidity.View full abstractDownload PDF (407K) -
Mika Eguchi, Kiyoshi Ozawa, Yoshio Sakka, Tomiya Kishi1999 Volume 46 Issue 3 Pages 305-311
Published: March 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSElectrochemical behaviour of (NH3(CH2)3NH3)y[V4O10] (1) was investigated as lithium insertion host. By thermal treatment above 250°C it was possible to remove the organic constituent in the interlayer from the compound (1) at 250°C, and the original layer structure was maintained up to about y>0.75 in (NH3(CH2)3NH3)y[V4O10]. Lithium ions were inserted electrochemically in the compound (1), and amount of lithium inserted in the interlayer increased as y decreased. This increase was caused by increase in the available sites for lithium ions and largely by enhancement of diffusion rate in the interlayer.View full abstractDownload PDF (476K) -
Akihisa Kajiyama, Tatsuya Nakamura1999 Volume 46 Issue 3 Pages 312-316
Published: March 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSLiCoO2 with uniform size distribution was synthesized using Co3O4 fine particles. The effects of Li/Co molar ratio and sintering temperature on the microstructural and electric properties were investigated. The grain size increased with the sintering temperature and the Li/Co molar ratio. The grain size distribution was also influenced by them. Small amount of impurity phases were detected with AC impedance analysis, and it gave the optimum Li/ Co molar ratio. The electrochemical charge/discharge capacity took a maximum value (approximately 130mAh/g) at the optimum preparation conditions (Li/Co=1.03).View full abstractDownload PDF (3948K) -
Kazuhiro Hasezaki, Masatomo Kamada1999 Volume 46 Issue 3 Pages 317-320
Published: March 15, 1999
Released on J-STAGE: May 22, 2009
JOURNAL OPEN ACCESSLithium manganese spinel (LiMn2O4) for Li-secondary battery was prepared by mechanical milling of raw materials in a argon atmosphere for 200 h. After milling and heating at 823 K for 3 h, the powder was observed X-ray diffraction pattern of lithium manganese spinel structure. The average milling powder diameter was approximately .0.1μm.
The compounds of the MA-Li1.02Mn2O4 powder heated at 973 K for 3 h was evaluated as a 4 V cathode in a lithium non aqueous cell. The MA-Li1.02Mn2O4 have 136 Ah/kg of second discharge capacity.View full abstractDownload PDF (1637K)
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