Design of Nanocluster Based Material with Catalytic Properties

Tadachika Nakayama,Kim Chang-Yeoul,Tohru Sekino,Choa Yong-Ho,Takafumi Kusunose,Yamato Hayashi,Koichi Niibara 한국분말야금학회 2001 한국분말야금학회지 Vol.8 No.3

Modified inert gas condensation method was used to produce the nanocluster composites of . High-resolution TEM, SEM and catalytic measurements have been used to characterize the samples and study the synergistic effect between the CuO phase and (ceria) support. By varying the He pressure, the heating temperature and configuration of the heating boats inside the modified gas condensation chamber, nanoclusters of varying sizes, shapes and composition can be produced. The composition and nanostructured morphology were shown to influence the catalytic properties of the system. A copper content around 10 at% with a morphology that favors high-energy surfaces of ceria is shown to be beneficial for a high catalytic activity.

The nobel solution process using the extreme energy state for anisotropic structured nanomaterials

Tadachika Nakayama,Takashi Minagawa,Shuntaro Suzuki,Hisayuki Suematsu,Koichi Nihara 한국물리학회 2009 Current Applied Physics Vol.9 No.3

A wide variety of materials have been synthesized using procedures that rely on extremely high-energy densities produced by high temperatures and pressures. Anisotropic silver nanomaterials were synthesized by a process that uses high temperatures and pressures in the liquid phase, replacing conventional vacuum production. Powder forms of light-sensitive silver oxide and silver carbonate were dispersed in water and exposed to 355-nm laser illumination, producing nanosheets with a thickness of 10 nm and areas of tens of ㎛2. These large nanosheets of interest since they can be used as structural components of devices having anisotropic electrical and thermal conductivities. A wide variety of materials have been synthesized using procedures that rely on extremely high-energy densities produced by high temperatures and pressures. Anisotropic silver nanomaterials were synthesized by a process that uses high temperatures and pressures in the liquid phase, replacing conventional vacuum production. Powder forms of light-sensitive silver oxide and silver carbonate were dispersed in water and exposed to 355-nm laser illumination, producing nanosheets with a thickness of 10 nm and areas of tens of ㎛2. These large nanosheets of interest since they can be used as structural components of devices having anisotropic electrical and thermal conductivities.

Multifunction Integrasted Ceramic Based Nanocomposites

Niihara Koichi,Nakayama Tadachika,Suematsu Hisayuki,Sekino Tohru,Kusunose Takafumi 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1

Special Issue Paper : Polyvilylidenefluoride-based Nanocomposite Films Induced-by Exfoliated Boron Nitride Nanosheets with Controlled Orientation

( Hongbaek Cho ),( Tadachika Nakayama ),( Daeyong Jeong ),( Satoshi Tanaka ),( Hisayuki Suematsu ),( Koichi Niihara ),( Yongho Choa ) 한국복합재료학회 2015 Composites research Vol.28 No.5

Polyvinylidene fluoride (PVDF)-based nanocomposites are fabricated by incorporation of boron nitride (BN) nanosheets with anisotropic orientation for a potential high thermal conducting ferroelectric materials. The PVDF is dissolved in dimethylformamide (DMF) and homogeneously mixed with exfoliated BN nanosheets, which is then cast into a polyimide film under application of high magnetic fields (0.45~10 T), where the direction of the filler alignment was controlled. The BN nanosheets are exfoliated by a mixed way of solvothermal method and ultrasonication prior to incorporation into the PVDF-based polymer suspension. X-ray diffraction, scanning electron microscope and thermal diffusivity are measured for the characterization of the polymer nanocomposites. Analysis shows that BN nanosheets are exfoliated into the fewer layers, whose basal planes are oriented either perpendicular or parallel to the composite surfaces without necessitating the surface modification induced by high magnetic fields. Moreover, the nanocomposites show a dramatic thermal diffusivity enhancement of 1056% by BN nanosheets with perpendicular orientation in comparison with the pristine PVDF at 10 vol % of BN, which relies on the degree of filler orientation. The mechanism for the magnetic field-induced orientation of BN and enhancement of thermal property of PVDF-based composites by the BN assembly are elucidated.

Glucose Sensors Using Lipoic Acid Self-Assembled Monolayers

( Ji Yeong Kim ),( Tadachika Nakayama ),( Jae Hun Kim ),( Sang Sub Kim ) 한국센서학회 2014 센서학회지 Vol.23 No.5

A novel approach to fabricating high-performance glucose sensors is reported, which is based on the process of self assembled monolayers (SAMs). In this study, we have particularly used α-lipoic acid (LA) SAMs for the glucose sensors. To our best knowledge, this study is the first one to use LA as SAMs for this purpose. N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) were deliberately attached at the same time on the LA SAM. Then, glucose oxidase (GOX) and horseradish peroxidase (HRP) were sequentially immobilized. Thus, the HRP/GOX/NHS-EDC/LA-SAM/Au/Cr/glass working electrode was developed. The glucose-sensing capability of the fabricated sensor was systematically measured by the use of cyclic voltammetry in the range of 1 30 mM glucose in phosphate-buffered saline. The result showed a good sensitivity, that is, as high as 27.5 μA/(mM·cm2). This result conspicuously demonstrates that LA can be one of promising substances for use as SAMs for accurately monitoring trace levels of glucose concentration in human blood.

하소이트리아 소결체의 특성과 플라즈마저항성 평가

최진삼,배원태,Choi, Jinsam,Nakayama, Tadachika,Bae, Won Tae 한국세라믹학회 2013 한국세라믹학회지 Vol.50 No.5

The evaluation of plasma resistance and the characteristics of yttria ceramics fabricated by calcination yttria as a starting material without dopants under an oxidation atmosphere was investigated. Regardless of the starting materials, as-received, and calcined yttria powder, XRD patterns showed that all samples have $Y_2O_3$ phase. The three cycling process inhibited a large grain, which occurs frequently during the yttria sintering, and a high density ceramic with a homogeneous grain size was obtained. The grain size of the sintered ceramic was affected by the starting powders. The smaller the grain size, the larger were the Young's modulus and KIC. Compared to $Al_2O_3$ and $ZrO_2$ ceramics, yttria ceramics showed a 3 times larger plasma resistance and a 1.4~2.2 times lower weight loss during the plasma etching test, respectively.

Effect of energy deposition on TiO2 nanosized powder synthesized by pulsed wire discharge

Yoshinori Tokoi,Tsuneo Suzuki,Tadachika Nakayama,Hisayuki Suematsu,Futao Kaneko,Koichi Niihara 한국물리학회 2009 Current Applied Physics Vol.9 No.3

Titanium dioxide (TiO2) nanosized powder was synthesized by pulsed wire discharge (PWD) using Ti wire in O2 gas. The pressure of O2 gas (P) and relative energy (K), which is defined as the ratio of the charged energy of the capacitor to the vaporization energy in the wire, were varied from 10 to 100 kPa and 4.3– 51.9, respectively. The density of the plasma/vapor (Dexp), determined by the maximum volume, was decreased with decreasing P and increasing K as observed by high-speed photography during PWD. Xray diffraction analysis confirmed that the rutile content (CR) was increased from 7 to 84 vol% with decreasing Dexp. The median diameter (D50), determined from scanning electron microscopy, was decreased from 36.5 to 10 nm with decreasing Dexp. Therefore, an increase in CR and decrease in D50 both accompany the decrease in Dexp. Titanium dioxide (TiO2) nanosized powder was synthesized by pulsed wire discharge (PWD) using Ti wire in O2 gas. The pressure of O2 gas (P) and relative energy (K), which is defined as the ratio of the charged energy of the capacitor to the vaporization energy in the wire, were varied from 10 to 100 kPa and 4.3– 51.9, respectively. The density of the plasma/vapor (Dexp), determined by the maximum volume, was decreased with decreasing P and increasing K as observed by high-speed photography during PWD. Xray diffraction analysis confirmed that the rutile content (CR) was increased from 7 to 84 vol% with decreasing Dexp. The median diameter (D50), determined from scanning electron microscopy, was decreased from 36.5 to 10 nm with decreasing Dexp. Therefore, an increase in CR and decrease in D50 both accompany the decrease in Dexp.

Texture-controlled hybrid materials fabricated using nanosecond technology

CHO, Hong-Baek,NAKAYAMA, Tadachika,HUYNH, Minh Triet Tan,NGUYEN, Son Thanh,JIANG, Weihua,SUZUKI, Tsuneo,SUEMATSU, Hisayuki,NIIHARA, Koichi,SHIN, Jung Ho,CHOA, Yong-Ho CERAMIC SOC OF JAPAN 2016 JOURNAL- CERAMIC SOCIETY JAPAN Vol.124 No.3

<P>The controlled assembly of micro- and nano-ceramic fillers in polymer nanocomposites provides robust properties such as wetting, adhesion, thermal conductivity, electrical insulation and optical activity, and enable the extended application of these hybrid materials as thermal interfacing materials in microelectronics and for energy conversion. However, the required properties can only be obtained either by homogeneous mixing or by anisotropic orientation of a large amount (> 50 vol.%) of expensive fillers, which is economically inefficient. Here we propose a strategy for tuning the orientation and assembly of ceramic boron nitride nanofillers in a polymer nanocomposite using a small amount (< 5 vol.%) of filler to enhance thermal conduction. The texture of the BN fillers is tuned by application of a nanosecond pulse electric field and a superconductor magnetic field (10 T); the three-dimensional structure of the products was analyzed using 3-D X-ray CT scanning. The enhanced anisotropic orientation and thermal properties of the products were assessed as a function of the structural variation of the boron nitride fillers in the polymer. (C) 2016 The Ceramic Society of Japan. All rights reserved.</P>

Synthesis of Ferromagnetic Nickel Ferrite Nanofibers via Electrospinning with Iron Acetate as an Iron Precursor

Jin Zhang,Ryo Kurosawa,Hisayuki Suematsu,Tadachika Nakayama,김상섭 대한금속·재료학회 2012 METALS AND MATERIALS International Vol.18 No.3

We report the synthesis of nickel ferrite nanofibers via an elecrospinning technique particularly using iron (II) acetate as an iron precursor. Nanofibers of a single-phase nickel ferrite with a uniform diameter of ~90nm were successfully synthesized by adopting a properly prepared solution and calcination condition. Indi-vidual nickel ferrite nanofibers synthesized by electrospinning were made up of nanograins of ~20 nm in diameter. In addition, the hysteresis observed in a magnetization measurement confirmed their ferromagnetism,supporting their potential use in magnetic devices. These results demonstrate that the use of iron (II)acetate as an iron precursor is another way to synthesize ferromagnetic nickel ferrite nanofibers.

금속 필러가 첨가된 Pb-B-O계 유리와 Ni-Cr 합금 와이어 간의 전기 화학적 반응과 단락 거동

최진삼,다타치카 나까야마,Choi, Jin Sam,Nakayama, Tadachika 한국재료학회 2021 한국재료학회지 Vol.31 No.8

The electrochemical reaction between lead borate glass frit doped with Sn metal filler and Ni-Cr wire of a J-type resistor during a term of Joule heating is investigated. The fusing behavior in which the Ni-Cr wire is melted is not observed for the control group but measured for the Sn-doped specimen under 30 V and 500 mA. The Sn-doped lead borate glass frit shows a fusing property compared with other metal-doped specimens. Meanwhile, the redox reaction significantly contributes to the fusing behavior due to the release of free electrons of the metal toward the glass. The electrons derived from the glass, which used Joule heat to reach the melting point of Ni-Cr wire, increase with increasing corrosion rate at interface of metal/glass. Finally, the confidence interval is 95 ± 1.95₉ %, and the adjusted regression coefficient, R in the optimal linear graph, is 0.93, reflecting 93% of the data and providing great potential for fusible resistor applications.