Journal of the Ceramic Society of Japan
Online ISSN : 1348-6535
Print ISSN : 1882-0743
117 巻 , 1365 号
(May)
選択された号の論文の41件中1~41を表示しています
Special Article: Review
  • Soo-Jin CHOI, Jae-Min OH, Jin-Ho CHOY
    2009 年 117 巻 1365 号 p. 543-549
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Layered double hydroxides, a class of anionic nanoclays, have emerged as drug delivery carriers characterized by an effective uptake mechanism via clathrin-mediated endocytosis and high reservoir capacity. In the present review, the efficacy of an anticancer drug with ceramic nanocarriers, i.e. layered double hydroxides, is discussed in context of the cellular uptake mechanism in cell culture lines and pharmacokinetic and tissue distribution studies in whole animals. In addition, research results on the biodistribution patterns of only fluorescently labeled layered double hydroxides and the subsequent histopathological analysis are described in detail to assess the biocompatibility of layered double hydroxides in vivo. The determination of relationships between delivery efficiency and toxicity can be useful for the rational development of layered double hydroxides as drug delivery systems.
Review
Papers
  • Hyo June KIM, Seung Yong CHA, Doo Jin CHOI
    2009 年 117 巻 1365 号 p. 555-557
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    The electrical properties (including memory windows and leakage current densities) of Al2O3/La2O3/Al2O3 (ALA) films equipped with 5 nm, 7.5 nm, and 10 nm tunnel oxide layer were investigated. The dielectric constants of all of the tunnel oxide films using Al2O3 were the same and the equivalent oxide thickness was dependent on film thickness. The optimized conditions were exhibited in the ALA films with a 5 nm tunnel oxide. The memory window of the ALA films using the 5 nm tunnel oxide was about 1.31 V in the program condition (11 V for 10 ms) and in the erase condition (-13 V for 100 ms). Measurement of the leakage current density showed that all of the films are sufficient for use with flash memory device.
  • Sung Hyuk CHO, Doo Jin CHOI
    2009 年 117 巻 1365 号 p. 558-560
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Amorphous SiC:H films were deposited on (100) silicon wafer by remote-Plasma Enhanced Chemical Vapor Deposition system in the temperature range of 400°C-450°C. Hexamethyldisilane (HMDS) and C2H2 gas were used as a precursor and a dilution gas, respectively. The lower deposition temperature and lower sp3/sp2 carbon bonding ratio made lower dielectric constant.
  • Yongjoon CHO, Chanseok HONG, Hohyeong KIM, Chongmu LEE
    2009 年 117 巻 1365 号 p. 561-565
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Recently it has been reported that porous silicon (PSi) can be used as a therapeutic agent for cancer thermotherapy based on near-infrared (NIR) light irradiation. It is more important than anything else to develop a nanomaterial thermal coupling agent with a high photothermal effect in order to secure irreversible destruction of cancer cells and high selectivity between tumor tissues and healthy tissues in thermotherapy. In this paper we report the influence of anodization process parameters or the microstructure of PSi on the photothermal effect of PSi during NIR light irradiation. As the HF concentration, current density and etching time in the anodization process for PSi synthesis increases, the photothermal effect is enhanced since the pore size or the nanocrystallite size of the PSi decreases and the porosity of the PSi increases. The influence of quantum size effect on the photothermal effect in PSi is also discussed.
  • Chanseok HONG, Hohyeong KIM, Hyoun Woo KIM, Namhee CHO, Ilhang LEE, Ik ...
    2009 年 117 巻 1365 号 p. 566-569
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    InAlZnO films were deposited on glass substrates by sputtering InZnO (In2O3-10 wt% ZnO) and AlZnO (3 wt% Al2O3-97 wt% ZnO) targets simultaneously at room temperature using a DC and AC magnetron cosputtering system. The concentration of Al in the film was varied by using different DC powers for sputtering the InZnO target with the AC power for sputtering the AlZnO target fixed. It has been found that the total concentration of Al and In in the InAlZnO films tends to be maintained constant below a certain Al doping concentration. It has been found that the electrical resistivity of the InZnO film can be decreased by doping Al the concentration of which is higher than a certain lower limit. The cause of the decrease in the resistivity of InZnO by doping 5.2 mol% Al are discussed. The optical transmittance has been found to be also enhanced in all the wavelength range except the range from 410-490 nm by doping 5.2 mol% Al.
  • Jung-Sik KIM, Chang-Woo HAM
    2009 年 117 巻 1365 号 p. 570-573
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    This study investigated the photocatalytic behavior of titanium dioxide (TiO2)-coated phosphorescent materials. Nanocrystalline TiO2 was directly deposited on the alkaline earth aluminate phosphor of CaAl2O4:Eu2+,Nd3+ by chemical vapor deposition (CVD) and its photocatalytic behavior was examined with the degradation of methylene blue (MB) aqueous solution under visible light irradiation. With increasing deposition temperature, the CVD TiO2 thin film exhibited a columnar structure and preferred crystal growth in the (112) orientation. The mechanism of the photocatalytic reactivity for the coupling of TiO2-phosphorescent materials was discussed in terms of the energy band structure and phosphorescence. The coupling of TiO2 with phosphor may result in energy band bending in the junction region, which rendered the TiO2 crystal at the interface photo-reactive under visible light irradiation. The CVD TiO2-coated phosphors showed active photocatalytic reaction under visible irradiation. In addition, the TiO2-coated phosphorescent materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM).
  • Jun Gyu KIM, Yoo Youl CHOI, Doo Jin CHOI, Jung Il KIM, Bae Seok KIM, S ...
    2009 年 117 巻 1365 号 p. 574-577
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Chemical vapor deposited (CVD) silicon carbide (SiC) provides many advantages over other materials due to its high thermal, chemical and mechanical stability at high temperature. For these reasons, CVD SiC has replaced Si in components for semiconductor process. For application of CVD SiC to semiconductor fabrication equipment, thermoelectric properties controls are important. Therefore, we have studied the effects of different diluent gases, deposition temperatures and microstructures of deposited SiC on change of thermoelectric properties. The electrical conductivity of SiC which used N2 diluent gas was larger than SiC deposited with H2 diluent gas. Electrical resistivity varied by an order of 102 for different diluent gases at the same deposition temperature, and Seebeck coefficient also depended on the gas used. Additionally, SiC deposited with H2 showed n-type semiconductor behavior while that deposited with N2 showed p-type characteristics.
  • Ik Whan KIM, Sung Hyuk CHO, Jun Gyu KIM, Doo-Jin CHOI
    2009 年 117 巻 1365 号 p. 578-581
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    β-silicon carbide whiskers have been synthesized on a carbon fabric by a vapor-solid (VS) mechanism using the Chemical Vapor Infiltration (CVI) process. Optimum processing conditions for SiC whisker growth were determined by mapping of SiC deposition behavior. SiC was deposited on a carbon fabric substrate as a film or whiskers, depending on processing conditions. The mean diameter and line density of the whiskers was the highest at an input gas ratio of 50. As temperature increases, the mean diameter of the whiskers increased and the line density of whiskers decreased. In the optimum processing conditions, whiskers grew uniformly with high growth density and formed a networking structure between each of the carbon filaments resulting in a structure suitable for filter applications.
  • Kyung Soon JANG, Eugene LEE, Tae Woo KIM, In Sub HAN, Sang Kuk WOO, Ke ...
    2009 年 117 巻 1365 号 p. 582-587
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    The present research attempts to analyze and evaluate the mechanical behavior of SiCf in SiCf/SiC composites with and without soft coatings. The effects of soft fiber coating in the alleviation of indentation or flexural stress in the layered structure are investigated. Boron nitride and/or pyrocarbon as soft coating layer on SiC fiber are selected for the structure. Modeling is performed by changing the type of fiber, the type of soft layer, and layered stacking sequence of the soft layer. Finite element method (FEM) analyses are conducted to evaluate stress distributions under indentation or flexure loadings by displacement loading. Experimentally, the fiber coatings are conducted in the SiC fiber reinforced SiC composites. It was found that BN and/or pyrocarbon coating on the fiber alleviate the stress under the contact or flexure loading, which indicates that the appropriate design by soft layer on the fiber can reduce the maximum stress.
  • Jun-Hyun BAE, Byung-Geun KIM, Dae-Seop BYEON, Hong-Lim LEE
    2009 年 117 巻 1365 号 p. 588-591
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    In this study, the phase change behavior of PRAM recording layer during 1 cycle operation was investigated by finite element method (FEM) simulation. The JMAK equation was used for simulation of phase change behavior of the Ge2Sb2Te5 (GST) recording layer of PRAM. The RESET simulation of the PRAM unit cell of 100 nm thick recording layer model shows that the amorphous region of the recording layer was partially crystallized after RESET current was removed. This crystallization may cause the sensing error for data reading operation of PRAM. To avoid this sensing error, a 25 nm thick recording layer model of PRAM was subjected to simulation. The thin (25 nm) recording layer model shows higher cooling rate than the thick (100 nm) layer model. Therefore, the crystallization fraction of the thin layer model during RESET operation was decreased and the difference of electrical resistance between RESET and SET state of thin recording layer model was greater than the thick recording layer model.
  • Min Soo KIM, Soon Jong JEONG, In Sung KIM, Jae Sung SONG
    2009 年 117 巻 1365 号 p. 592-595
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Lead-free piezoelectric ceramics, (Na0.4875K0.4625Li0.05)(Nb0.95Ta0.05)O3 systems, were developed using the conventional sintering process. The grain growth behavior and piezoelectric properties of the ceramics were investigated. Their sintering temperature was lowered by adding 1 mol% of Li2O as a sintering aid. When the sample was sintered at 1050°C for 4 h with a composition of 1 mol% of excess Li2O (Na0.4875K0.4625Li0.05)(Nb0.95Ta0.05)O3, the electro-mechanical coupling factor (kP) and the piezoelectric coefficient (d33) were found to reach the highest values of 0.42 and 244 pC/N, respectively.
  • Hun PARK, Dae-Jin YANG, Jin-Seong YOO, Kyu-Shik MUN, Woong-Rae KIM, Ho ...
    2009 年 117 巻 1365 号 p. 596-599
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Highly ordered TiO2 nanotube arrays have attracted much attention in an application to dye-sensitized solar cells (DSCs) due to their superior charge percolation. However, the efficiency of TiO2-nanotube-based DSCs is 6.89%, which is still lower than that of TiO2-nanoparticle-based DSCs. In this study, the surface passivation of highly ordered TiO2 nanotube arrays has been applied to increase the performance of TiO2-nanotube-based DSCs using the concept of isoelectric point. Both acidic oxide such as WO3 and basic oxides such as MgO, ZnO have been used as materials for surface passivation. The overall conversion efficiency of DSCs based on surface-passivated TiO2 nanotube arrays has been improved by these passivating layers.
  • Dong-Won LEE, Jung-Yeul YUN, Farkhod R. TURAEV, Jin-Chun KIM, Sung-Jin ...
    2009 年 117 巻 1365 号 p. 600-603
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    The ultrafine titanium carbonitride particles (TiC0.7N0.3) below 100 nm in mean size were successfully synthesized by Mg-thermal reduction process. The nanostructured sub-stoichimetric titanium carbide (TiC0.7) particles were produced by the magnesium reduction at 1163 K of gaseous TiCl4 + xC2Cl4 and the vacuum heat treatments were performed for five hours to remove residual magnesium and magnesium chloride mixed with TiC0.7. And final TiC0.7N0.3 phase was obtained by nitrification under normal nitrogen gas at 1373 K for 2 h. The high quality of crystal form of TiC0.7N0.3 with the purity above 99.5% and the level near 0.1 mass% oxygen, were produced. We discovered in particular that the temperature lower than 1123 K in vacuum treatment helped to produce the finer and uniform TiCN particles.
  • Hyeong-Ho PARK, Hong-Sub LEE, Hyung-Ho PARK, Ross H. HILL, Yun Taek HW ...
    2009 年 117 巻 1365 号 p. 604-607
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    The surface microstructure and ferroelectric properties of direct-patternable Bi4-xLaxTi3O12 (BLT) films prepared by photochemical metal-organic deposition as a function of La contents were characterized. The surface microstructure showed that La substitution (x = 0.75 and 1.00) to Bi4Ti3O12 films was effective to induce an improved microstructure of the BLT films without the formation of surface holes. The measured remnant polarization values of BLT films with x = 0, 0.25, 0.50, 0.75, and 1.00 were 3.7, 7.1, 11.3, 16.0, and 8.1 μC/cm2, respectively. After 109 cycles, the remaining remnant polarizations of Bi4-xLaxTi3O12 films with x = 0, 0.25, 0.50, 0.75, and 1.00 were 64.9, 69.5, 75.9, 94.8, and 95.0%, respectively. Considering the surface microstructure and ferroelectric properties of the BLT films, the BLT film with x = 0.75 showed the best microstructure and ferroelectric properties among all the BLT films. These results suggest the possible application of ferroelectric BLT film, relatively easily and without high cost process such as dry etching.
  • Hyeong-Ho PARK, Xin ZHANG, Hyuncheol KIM, Jongchul PARK, Hyung-Ho PARK ...
    2009 年 117 巻 1365 号 p. 608-611
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    In this study, we characterized the optical and electric properties of direct-patternable SnO2 films with embedded Ag nanorods/nanowires prepared by photochemical metal-organic deposition using photosensitive precursors. SnO2 films showed a random orientation of growth independent on the presence of Ag nanorods/nanowires and annealing temperature. The values for sheet resistance and average transmittance of the SnO2 films with and without Ag nanorods/nanowires after annealing at 600°C were 6 kΩ/square and 82.2%, and 418 kΩ/square and 87.2%, respectively. Due to the incorporation of Ag nanorods/nanowires into the SnO2 films, the sheet resistance was remarkably improved, but the optical transmittance was slightly decreased. These results and the direct-patternability of photochemical deposition suggest that SnO2 films with embedded Ag nanorods/nanowires could easily be used in transparent electrodes, eliminating the need for high cost processes such as dry etching.
  • Young Joo KIM, Shalendra KUMAR, Chan Gyu LEE, Bon Heun KOO
    2009 年 117 巻 1365 号 p. 612-615
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    During the last few years the studies on the divalent ion substituted rare earth manganites R1-xAxMnO3 (R = rare earth, A = alkaline earth ions), gained impetus after the compound were found to show colossal magnetoresistance. The physical properties of the substituted manganites depend on their structure, composition and oxidation states of Mn ions. Doping of the divalent metal ions in LaMnO3 induces ferromagnetism due to the change in the oxidation state of Mn ions. This indicates that the valence state of Mn ions play a key role in the tuning of the physical properties of manganites. In the present work, we study the effect of Co ions substitution at Mn side in La0.7Ca0.3Mn1-xCoxO3 (x = 0.01-0.05) thin films. Thin films of La0.7Ca0.3Mn1-xCoxO3 were grown epitaxially at 700°C under the oxygen pressure of 300 mTorr using pulsed laser deposition technique on LaAlO3 (001) substrate. X-ray diffraction study infers that all films grow epitaxially along the c-axis. The field cooled magnetization measured as a function of temperature indicates that all film exhibits ferromagnetic (FM) to paramagnetic (PM) transition with increase in the temperature. Moreover, the doping of Co affects the colossal magnetoresistance (CMR) effect in the present materials.
  • Shalendra KUMAR, Sanjeev GAUTAM, Young Joo KIM, Bon Heun KOO, Keun Hwa ...
    2009 年 117 巻 1365 号 p. 616-618
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    The samples of Zn1-xFexO (0.0 ≤ x ≤ 0.05) were prepared using co-precipitation method. The effect of Fe ions substitution on structural, magnetic and electronic structure studies have been carried out using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), DC magnetization and near edge X-ray absorption fine structure spectroscopy (NEXAFS) measurements. XRD and FTIR measurements demonstrate that all the samples are polycrystalline single phase nature and belong to the wurtzite lattice, and rule out the presence of any secondary phase formation. From the analysis of XRD data, it is observed that the peaks position shifted toward lower 2θ with increase in Fe content. DC magnetization measurements performed at 5 K and 300 K represent that all samples exhibit room temperature ferromagnetism. NEXAFS measurements performed at Fe K-edge reflects that Fe is in Fe3+ state. PACS: 75.50.Pp; 18.70.Dm; 61.46. +w; 82.80.Ej
  • Fumiaki MIYAJI, Takashi MURAKAMI, Yoko SUYAMA
    2009 年 117 巻 1365 号 p. 619-622
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Zeolitic products formed by hydrothermal treatment of coal fly ash (FA) with KOH aqueous solution under various reaction conditions were examined. Only linde F-type zeolite (K2Al2Si2O8·3H2O) was newly formed at atmospheric pressure, except formation of a small amount of kalsilite (KAlSiO4) at longer reaction time. The yield of the linde F zeolite was highest when reaction time, temperature, KOH concentration and (KOH solution / FA) ratio were 48 h, 95°C, 8 mol dm-3 and 25 ml g-1, respectively. In this case, the original FA spheres were almost completely dissolved out, and regular prisms of the linde F zeolite crystal with 0.5 to 1 μm in width and 1 to a few μm in length were formed. The specific surface area and cation exchange capacity of the FA-derived linde F zeolite were 20.2 m2 g-1 and 2.3 meq g-1, respectively.
  • Hideo AWAJI, Yoshitaka NISHIMURA, Seong-Min CHOI, Yoshikazu TAKAHASHI, ...
    2009 年 117 巻 1365 号 p. 623-629
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    In order to improve the fracture toughness of intrinsically brittle ceramics, it is essential to expand the frontal process zone (FPZ) ahead of a crack tip. Nanocomposites proposed by Niihara utilize dislocations generated around the dispersed nano-sized particles in matrix and expand the FPZ. In this paper, we discussed the toughening mechanism of ceramics using our experimental data on alumina-based nanocomposites, focusing on fundamental theories of fracture mechanics, such as Griffith-Irwin energy equilibrium and the local fracture criterion. We estimated the FPZ size using an indirect technique proposed recently, and clarified that the FPZ expansion toughening mechanism is achieved in nanocomposites by means of dislocation activities. The results revealed that ceramics with a larger FPZ size had higher fracture toughness and properly annealed nanocomposites had the largest FPZ size. The FPZ expansion mechanism in nanocomposites was considered that sessile dislocations generated around a crack tip in matrix, served as nano-crack nuclei, and hence expanded the FPZ size. It is clarified that the critical local stress is the strength of an infinite plate with no crack, and must be the true strength with no size effect. The fracture toughness, the critical local stress, and the FPZ size are the mutually dependent material properties, and the relation among them is clarified.
  • Soichiro SAMESHIMA, Yoshihiro HIRATA, Kosuke HAMASAKI, Hironori OHSHIG ...
    2009 年 117 巻 1365 号 p. 630-634
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Thermal decomposition of methane (CH4 → C + 2H2) needed a high temperature above 900°C and only 15% of methane decomposed at 1000°C. On the other hand, 90% of methane decomposed to form H2 and C at 700-900°C by passing through the 70 vol% Al2O3-30 vol% Ni porous compact. When 50% CH4-50% CO2 mixed gases were passed through the porous compact with Ni, 55% H2-45% CO fuel was produced at 700-900°C (CH4 + CO2 → 2H2 + 2CO). In a high temperature range from 700 to 900°C, the reforming rate of CH4 with CO2 became higher than the pyrolysis rate of CH4. The above results were well explained by the thermodynamic calculation along the distance from the surface of Ni-Al2O3 compact against the inlet gas.
  • Daisuke MORIYAMA, Yoshihiro HIRATA, Soichiro SAMESHIMA, Naoki MATSUNAG ...
    2009 年 117 巻 1365 号 p. 635-638
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    La0.6Sr0.4Ru0.9Mg0.1O3-δ (LSRM) powder was prepared by co-precipitation method using ammonium carbonate solution and nitrate solutions. The freeze-dried suspension was decomposed at 1000°C in air. The obtained LSRM powder was sintered in air at 1200°C for 4 h to measure the electrical conductivity. The LSRM solid solution, which was stable in the temperature range from 1000 to 1500°C in air, was referred to an orthorhombic structure. The measured true density of LSRM powder was close to the density calculated using X-ray diffraction data. No chemical reaction occurred between LSRM and Gd-doped ceria electrolyte at 1000°C in air. The electronic conductivity of LSRM measured by a four-terminal DC method was 423 and 361 S·cm-1 at 300 and 800°C, respectively.
  • Takeshi YOKOTA, Shotaro MURATA, Shinya KITO, Manabu GOMI
    2009 年 117 巻 1365 号 p. 639-642
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    We have investigated the relationships between electric field-induced resistance change and the magnetic properties of the Cr2O3/ultra-thin La0.7Sr0.3MnO3 (LSMO) magnetic hetero structure. The LSMO with a thickness of 40 nm has two transition temperatures, the ferromagnetic Curie temperature of 312 K and the spin-glass temperature of 180 K. Resulting from the magnetic properties, the exchange interaction in the Cr2O3/LSMO behavior below 180 K differed from that below 312 K. With the application an electric field on the Cr2O3 gate, the resistance of LSMO film was changed. This resistance change is most likely due to the magnetic state of LSMO and the interface interaction between the Cr2O3 and LSMO film
  • Jong Won PARK, Dong Ha KWAK, Sun Ho YOON, Seung Chul CHOI
    2009 年 117 巻 1365 号 p. 643-646
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Highly oriented, Bi-substituted Ca3Co4O9(Ca2.7Bi0.3Co4O9) was processed by the rolling method and its thermoelectric properties were investigated. The electrical conductivity (σ), Seebeck coefficient (α), thermal conductivity (k) and ZT value at 870 K were 123.4 S/cm, 172.7 μV/K, 2.1 W/mK, and 0.152, respectively. The electrical conductivity was about 1.5 times higher than that of a conventionally sintered sample. This rolling process is a very powerful method to produce a plate-like particle orientation in a ceramic microstructure and will be useful in the mass production of thermoelectric elements in powder injection molding (PIM).
  • Hyun Goo KANG, Joung Kyu PARK, Chang Hae KIM, Seung Chul CHOI
    2009 年 117 巻 1365 号 p. 647-649
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    The luminescence properties of Mn4+-activated MAl12O19 (M = Ca, Sr, Ba) were studied. The Mn4+-activated MAl12O19 compounds were synthesized in an air atmosphere for oxidation from Mn2+ to Mn4+. Mn4+-activated CaAl12O19 and SrAl12O19 materials could be excited under the UV region but Mn4+-activated BaAl12O19 materials could not be efficiently emitted under the UV region. The luminescence properties of the Ba-containing compounds deviated from the other compounds, which was attributed to different co-ordinations of the activator ions. Mn4+-activated CaAl12O19 and SrAl12O19 compounds exhibited a main emission peak at 658 nm because of the 2E→4A2 transition of the Mn4+ ion. The CaAl12O19 and SrAl12O19 phosphors had a hexagonal structure. The highest crystallinity and luminescent intensity of these phosphors were obtained at 1873 K for 3 h.
  • Min-Goon JUNG, Jong-Hoon KIM, Seung-Koo LEE, Yoon-Suk OH, Dae-Soon LIM
    2009 年 117 巻 1365 号 p. 650-653
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Conventional structural ceramic substrates were coated with 1 μm thick polycrystalline CVD diamond layer by using the hot filament CVD system and subsequently tested. The substrates chosen were silicate, alumina, silicon nitride, and silicon carbide ceramics. To achieve a high nucleation density and to improve the adhesion between the diamond and the ceramic substrate, the newly developed Electrostatic Self-Assembly of Nano Diamond (ESAND) seeding method was used. This seeding method initiates the growth of crystalline diamond. For this seeding procedure, each negatively charged substrate surface was covered with a cationic polymer monolayer. Next, anionic polymer coated cationic nanodiamond particles were attached to the substrate by the electrostatic self-assembly process. The degree of adhesion between the diamond film and each substrate was investigated by micro-scratch testing. These tests involved the use of a Rockwell C indenter (r = 0.2 mm), which scratched the samples at a speed of 10 mm/min under a progressive normal load (from 0 to 21N). The morphology of the poly-crystalline diamond films on the various substrates was analyzed using Raman spectroscopy.
  • Masataka BABA, Hideaki SANO, Guo-Bin ZHENG, Yasuo UCHIYAMA
    2009 年 117 巻 1365 号 p. 654-658
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Carbon nanotubes (CNTs) were synthesized at 650-770°C using Co/MgO and Co-Mo/MgO as catalysts and ethylene as carbon source. The dependence of the carbon yield on Mo amount in catalyst, synthesis temperature and time were investigated, and the structures of CNTs were characterized using FESEM, TEM, and Raman spectroscopy. It was found that CNTs with "bamboo-like" structure were synthesized using Co-Mo/MgO catalysts, in contrast to typical multi-walled carbon nanotubes with hollow inner tube obtained from Co/MgO catalyst. Addition of 5-10% Mo in catalysts resulted in the highest carbon yield, e.g. 5500% for 60 min synthesis, which is about 20 times higher than that of Co/MgO. The addition of Mo also extended the lifespan of catalyst for the growth of CNTs. TEM observation showed that the growth of CNTs was in a root-growth mode. The structure of CNTs obtained from Co-Mo/MgO catalysts was explained based on the growth mechanism of CNTs.
  • Woosuck SHIN, Maiko NISHIBORI, Masayoshi OHASHI, Noriya IZU, Toshio IT ...
    2009 年 117 巻 1365 号 p. 659-665
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Ceramic catalysts for the integration of the combustor patterns onto microdevices have been prepared. The catalyst powder of 40 wt% Pt-loaded on alumina was mixed with the organic vehicle of terpineol and ethyl cellulose, to make various paste compositions of different particle concentration and ethyl cellulous. The pastes with 5 wt% and 10 wt% ethyl cellulous have enhanced the linear Newtonian regions of the viscosity down to the shear rate about 5 s-1 and 0.1 s-1, respectively. For the dispensing the paste of 5 wt% ethyl cellulous and 13.7 vol% particle, the shear rate within the nozzle of 0.1 mm was calculated from the dispensed volume and speed to be 357 1/s and the viscosity data and yield stress data have been analyzed to be reasonable 0.3 Pa·s, and 100 Pa, approximately. The performance of the catalyst combustors dispensed on the microdevices have been carried out by the hydrogen mixed air gas flow, changing the catalyst temperature from 10 to 120°C.
  • Kenji MATSUMOTO, Yutaka ADACHI, Takeshi OHGAKI, Isao SAKAGUCHI, Naoki ...
    2009 年 117 巻 1365 号 p. 666-670
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Oxygen isotopic heterostructural zinc-oxide thin films, i.e., Zn16O/Zn18O/Zn16O, were synthesized. Pulsed-laser deposition was used to deposit the films. First, only 18O2 gas was leaked into the deposition chamber, then 16O-enriched ZnO thin film was deposited, and after this 18O-enriched layer was obtained using 18O radicals as a source of isotopes. Finally, the 16O-enriched layer was deposited by turning off the radical source. The resulting thin films were annealed at various diffusion-annealing temperatures. The change in 18O-diffusion profiles due to annealing was evaluated with secondary ion mass spectrometry (SIMS). The diffusion coefficients were slightly higher near the interface between the thin film and the substrate (inner region) than those near the surface (outer region). The dependencies of oxide ion diffusion on temperature for the outer and inner regions areexpressed as $D_{outer} = 3.2 \times 10^1 \left({_{5.5 \times 10^{-1}}^{1.9 \times 10^3}} \right)\exp \left({-\frac{{397 \pm 42(kJ/mol)}}{{RT}}} \right)cm^2/s$ and $D_{inner} = 6.7 \times 10^1 \left({_{4.2 \times 10^{-5}}^{1.0 \times 10^4}} \right)\exp \left({-\frac{{346 \pm 96(kJ/mol)}}{{RT}}} \right)cm^2/s$. The activation energy is concluded to consist of the enthalpy of the oxygen migration and the oxygen vacancy formation, comparing the present data with the reported theoretical results.
Papers
  • Hirokazu MASAI, Yoshiyuki SUZUKI, Yoshihiro TAKAHASHI, Hiroshi MORI, T ...
    2009 年 117 巻 1365 号 p. 671-674
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    We have examined the dependence of the optical nonlinearity of the 30BaO·15TiO2·55GeO2 (BTG55) crystallized glass on the temperature at which the BTG55 glass melts are held in a molten state (called the "melt temperature" in the present paper). The absorption coefficient and the refractive index of the BTG55 precursor glass, and the second harmonic efficiency of its crystallized glass increased with increasing melt temperature of the precursor glass. We have defined the local structure similar to that of a crystal, "embryos of crystallites", and the embryos are envisioned as the origin of precipitated Ba2TiGe2O8 crystallites. The second harmonic generation efficiency of the BTG55 crystallized glass increased with increasing melt temperature. This is explained as due to an increase of the number of embryos of Ba2TiGe2O8 crystallites with increasing melt temperature.
  • Dae Soo JUNG, You Na KO, Jang Heui YI, Seung Kwon HONG, Yun Chan KANG
    2009 年 117 巻 1365 号 p. 675-679
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    In this study, it was found that BaO-B2O3-SiO2 glass powders with fine particle sizes and spherical shapes improved the sintering characteristics of nanosized BaTiO3 powders. The mean sizes of the prepared glass powders and BaTiO3 powders were 940 nm and 110 nm, respectively. The densities of BaTiO3 pellets containing 0, 1, 3, and 5 mass% of a glass additive were 4.2, 5.2, 5.5 and 5.7 gcm-3, respectively, at a sintering temperature of 900°C. The densities of BaTiO3 pellets sintered at 900°C and containing 5 mass% of the glass additive were similar to that of the pellet sintered at 1280°C and containing no glass additive. Dielectric constants of pellets containing 5 mass% of the glass additive and of pellets containing no glass additive were 1599 and 469, respectively, at a sintering temperature of 900°C. Dielectric constants of pellets containing 1 mass% of the glass additive increased from 602 to 4109 when the sintering temperature was increased from 800 to 1200°C.
  • Chun-Huy WANG
    2009 年 117 巻 1365 号 p. 680-684
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Extending the investigations on (Na0.5K0.5)NbO3-based solid solution for lead-free piezoelectric ceramics, this paper consider the complex solid-solution system (Na0.5K0.5)NbO3-Ba(Zr0.04Ti0.96)O3 [NKN-BZT]. (Na0.5K0.5)NbO3 with 0-10 mol% Ba(Zr0.04Ti0.96)O3 has been prepared following the conventional mixed oxide process. X-ray diffraction analysis revealed that, during sintering, all of the Ba(Zr0.04Ti0.96)O3 diffuses into the lattice of (Na0.5K0.5)NbO3 to form a solid solution. Only a orthorhombic phase with a perovskite structure was found in this system. It was found that the samples with a low content of Ba(Zr0.04Ti0.96)O3 exhibit relatively good physical and electric properties. For 0.98 (Na0.5K0.5)NbO3-0.02Ba(Zr0.04Ti0.96)O3 ceramics, the electromechanical coupling coefficients of the planar mode kp and the thickness mode kt reach 0.26 and 0.52, respectively, at the sintering of 1100°C for 2 h. The ratio of thickness coupling coefficient to planar coupling coefficient is 2. For 0.98(Na0.5K0.5)NbO3-0.02Ba(Ti0.96Zr0.04)O3 ceramics, the electromechanical coupling coefficients of the planar mode kp and the thickness mode kt reach 0.3 and 0.55, respectively, at the sintering of 1100°C for 5 h. With suitable Ba(Zr0.04Ti0.96)O3 concentration and sintering condition, good physical and electric properties were obtained. Our results show that 0.98(Na0.5K0.5)NbO3-0.02Ba(Zr0.04Ti0.96)O3 solid solution ceramics are one of the promising lead-free ceramics for high frequency electromechanical transducer applications.
  • Shalendra KUMAR, S. K. SHARMA, R. J. CHOUDHARY, Chan Gyu LEE, B. H. KO ...
    2009 年 117 巻 1365 号 p. 685-688
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Pulsed laser deposited thin films of Mg0.95Mn0.05Fe2O4 ferrite were irradiated by 200 MeV Au14+ with a maximum dose up to 1 × 1012 ions/cm2. The as-deposited and irradiated thin films are investigated using X-ray diffraction (XRD), Raman Spectroscopy, Field emission electron microscopy (FESEM) and dc magnetization measurements. XRD and Raman spectroscopy measurements reflect the cubic spinel structure of films before and after irradiation. FESEM measurements demonstrate that films are composed of nano rods and nanocrystalline grains. Magnetic hysteresis loop measurements reveal that all the films have ferrimagnetic ordering at room temperature with enhancement in the coercive field and remnant magnetization due to irradiation.
  • Shalendra KUMAR, Ravi KUMAR, B. H. KOO, H. CHOI, Dong Uk KIM, Chan Gyu ...
    2009 年 117 巻 1365 号 p. 689-692
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    We have studied the structural and electrical properties of Mg2TiO4 inverse spinel using X-ray diffraction, Raman spectroscopy, ac conductivity and dielectric spectroscopy. Polycrystalline sample of Mg2TiO4 was prepared by the conventional solid state reaction technique. Powder X-ray diffraction analysis indicates single phase nature of inverse spinel Mg2TiO4. Raman study also infers that Mg2TiO4 exhibits inverse spinel structure. The dielectric constant measured as a function of frequency exhibits a resonance peak at 9 MHz. The dielectric constant measured as function of temperature (100-300 K) at 500 kHz is found to increase with temperature. The value of the loss tangent (tanδ) was found to be small ∼ 0.01 through out the whole temperature range. The value of the exponent (s), evaluated using the power law σAC = ωS, is found to be ∼1, which indicates the good correlation of the hoping of carriers in the system.
  • Chun-Huy WANG
    2009 年 117 巻 1365 号 p. 693-697
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Although PbZrO3-PbTiO3 (PZT)-based ceramics are playing a dominant role in piezoelectric materials, their evaporation of harmful lead oxide during the sintering process causes a crucial environment problem. It is necessary to search for lead-free piezoelectric materials that have such excellent properties as those found in the PZT-based ceramics. Therefore (Na0.5Bi0.5)TiO3-based solid solutions were studied to improve piezoelectric properties. In the present study, various quantities of Bi2O3 were added into 0.99(Na0.5Bi0.5)TiO3-0.01Ba(Zr0.04Ti0.96)O3 (0.99NBT-0.01BZT) ceramics. High-density samples were obtained through the addition of Bi2O3 into 0.99NBT-0.01BZT ceramic. It was found that 0.99NBT-0.01BZT with the addition of 0-4.0 wt% Bi2O3 exhibit relatively good piezoelectric properties. For 0.99NBT-0.01BZT ceramic with the addition of 0.5 wt% Bi2O3, the electromechanical coupling coefficients of the planar mode kp and the thickness mode kt reach 0.15 and 0.55, respectively, at the sintering of 1100°C for 2 h. The ratio of thickness coupling coefficient to planar coupling coefficient is 3.6. It is obvious that 0.99NBT-0.01BZT solid solution ceramic by adding low quantities of Bi2O3 is one of the promising lead-free ceramics for high frequency electromechanical transducer applications.
  • Gang HE, Takashi IIJIMA, Hiroshi FUNAKUBO
    2009 年 117 巻 1365 号 p. 698-702
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Based on the image of the combinatorial synthesis, a new preparation process to fabricate Pb(Zr1-xTix)O3 (PZT) thin films with a series change in composition from only two kinds elemental solutions was developed. It is different from the conventional gol-gel method that the PZT thin films with any composition can be obtained easily from two precursor solutions, Lead-Titanium (PT) and Lead-Zirconium (PZ) metal organic chemical solutions, by mixing the two precursor solutions in the certain ratio. Pb(Zr1-xTix)O3 thin films with composition of series changed from x = 0.1 to 0.9 were fabricated from the two precursor solutions by the chemical solution deposition (CSD) method. Comparing with the conventional process, it was so fast and convenient to fabricate the PZT thin films with the any compositions by mixing the two precursor solutions of PT and PZ. The composition dependences of orientation, structure and ferroelectric property for the PZT thin films were investigated. The results showed good agreement with those of bulk and film PZT prepared by conventional method. It is concluded that this mixed solution method is applicable in the combinatorial study and results in reliable and brief process to discover new thin film materials by the CSD method.
  • Anze SHUI, Shumei WANG, Hui WANG, Xiaosu CHENG
    2009 年 117 巻 1365 号 p. 703-705
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    Zinc oxide powders of different Al doping contents (AZO) were prepared with the coprecipitation method from zinc nitrate solution and aluminum nitrate solution in this study. The effects of process parameters such as the Al doping content, calcination temperature and calcination time etc. on electric conductivity were examined quantificationally. The AZO powders had good electric conductivity than that of zinc oxide powders. The resistivity of the AZO powders significantly depended on the Al doping content, calcination temperature and calcination time. The minimum resistivity 179.2 Ω·cm was obtained from the 2 mol% Al doped powders in this work, which were prepared at the calcination temperature 1300°C for 2 h. The AZO powders were also characterized with the X-ray diffraction (XRD) and scanning electron microscopy (SEM). The experimental results show that when the Al doping content is less than 2 mol%, the Al3+ enters into the ZnO lattice to form the solid solution, and causes the current carrier increase and the resistivity drop, but the excessive Al3+ doping brings the ZnAl2O4 spinel phase generate, resulting in the resistivity increase.
  • Guanshi QIN, Meisong LIAO, Chitrarekha CHAUDHARI, Yusuke ARAI, Takenob ...
    2009 年 117 巻 1365 号 p. 706-708
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    We report what we believe to be the first demonstration of flattened supercontinuum (SC) generation from a microstructure tellurite fiber pumped by a tunable ultrafast laser source with a pulse width of 180 fs. When the pump light is launched into 0.574 m long air-cladding tellurite fiber with small size air holes, which are comparable with the core diameter, we obtain flattened SC spectra expanding from 1000 to 2100 nm by tuning the pumping wavelength to the range of 1400-1600 nm.
Technical report
  • Hee Chan JANG, Seo Hee JU, Yun Chan KANG
    2009 年 117 巻 1365 号 p. 709-712
    発行日: 2009年
    公開日: 2009/05/01
    ジャーナル フリー
    LiCoO2 cathode powders were prepared by the two different spray pyrolysis processes. The mean size of the post-treated LiCoO2 powders prepared by the FEAG process was 1.6 μm when the excess amount of lithium component was 10 mol% of the stoichiometric value. The post-treated LiCoO2 powders obtained by ultrasonic spray pyrolysis were finer than those prepared by the FEAG process. The initial discharge capacities of the LiCoO2 powders prepared by the FEAG process changed from 119 to 156 mAh/g when the excess amounts of lithium component were changed from 3 to 20 mol% of the stoichiometric value. The maximum initial discharge capacity of the LiCoO2 powders prepared by the ultrasonic spray pyroysis was 151 mAh/g obtained from the excess amount of lithium component of 3 mol% of the stoichiometric value.
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