Cobalt nano-rods were fabricated using a template-free electrochemical-deposition process. The structure of cobalt electro-deposits strongly depends on the electrolyte composition and on the density of the applied current. In particular, as the content of boric acid increased in the electrolyte, deposits of semi-spherical nuclei formed, and then grew into one-dimensional nano-rods. From analysis of the electro-deposits created under the conditions of continuous and pulsed current, it is suggested that the distribution of the active species around the electrode/electrolyte interface, and their transport, might be an important factor affecting the shape of the deposits. When transport of the active species was suppressed by lowering the deposition temperature, more of the well-defined nano-rod structures were obtained. The optimal conditions for the preparation of well-defined nano-rods were determined by observing the morphologies resulting from different deposition conditions. The maximum height of the cobalt nano-rods created in this work was 1μm and it had a diameter of 200 nm. Structural analysis proved that the nano-rods have preferred orientations of (111).

In this study, a cobalt sulfate ceramic coating was sintered on various clays at 1250˚C. The specimen characteristics were investigated by X-ray diffraction(XRD), scanning electron microscopy(SEM), TG-DTA, UV-vis spectrophotometer, and HRDPM. The ceramic coating had a constant thickness of thousands μm, and the surface was confirmed to be densely fused. Other new compounds were produced by the cobalt sulfate sintering process and reactions. These compounds were a CoAl2O4 phase, Co2SiO4 phase, anorthite(CaAl2Si2O8) phase, and FeAl2O4 phase, respectively. UV properties of the coated specimen were investigated, celadon clay specimen in 530-550 nm band is showing a dark gray color. The white clay and white mix clay specimen in 460-500 nm band is showing a blue color. The cobalt-aluminate(CoAl2O4) spinel and the cobalt-silicate olivine(Co2SiO4) were the strongest of the ceramic pigments, producing a very pure, navy blue color.

Nano-sized cobalt powder was fabricated by wet chemical reduction method at room temperature. The effects of various experimental variables on the overall properties of fabricated nano-sized cobalt powders have been investigated in detail, and amount of NaOH and reducing agent and dropping speed of reducing agent have been prop- erly selected as experimental variables in the present research. Minitab program which could find optimized conditions was adopted as a statistic analysis. 3D Scatter-Plot and DOE (Design of Experiments) conditions for synthesis of nano- sized cobalt powder were well developed using Box-Behnken DOE method. Based on the results of the DOE process, reproducibility test were performed for nano-sized cobalt powder. Spherical nano-sized cobalt powders with an average size of 70-100 nm were successfully developed and crystalline peaks for the HCP and FCC structure were observed without second phase such as Co(OH).

코발트는 자연적으로 암석, 토양 물 등에서 발견되는 요소일 뿐만 아니라 산업화에 의해 생성되는 유해물질 중의 하나이다. 환경에서는 코발트 (II)와 코발트 (III)의 두 가지 산화물로 존재하며, 연안 해역으로 유입 시 먹이연쇄를 통해 해양생태계 전반에 영향을 미칠 수 있다. 따라서 본 연구는 유용 수산생물로써 조간대 암반 지역에 서식하는 말똥성게(Hemicentrotus pulcherrimus)를 이용하여 cobalt (Co (II); 10,

Nanostructured cobalt materials have recently attracted considerable attention due to their potential applications in high-density data storage, magnetic separation and heterogeneous catalysts. The size as well as the morphology at the nano scale strongly influences the physical and chemical properties of cobalt nano materials. In this study, cobalt nano particles synthesized by a a polyol process, which is a liquid-phase reduction method, were investigated. Cobalt hydroxide (Co(OH)2), as an intermediate reaction product, was synthesized by the reaction between cobalt sulphate heptahydrate (CoSO4·7H2O) used as a precursor and sodium hydroxide (NaOH) dissolved in DI water. As-synthesized Co(OH)2 was washed and filtered several times with DI water, because intermediate reaction products had not only Co(OH)2 but also sodium sulphate (Na2SO4), as an impurity. Then the cobalt powder was synthesized by diethylene glycol (DEG), as a reduction agent, with various temperatures and times. Polyvinylpyrrolidone (PVP), as a capping agent, was also added to control agglomeration and dispersion of the cobalt nano particles. The optimized synthesis condition was achieved at 220˚C for 4 hours with 0.6 of the PVP/Co(OH)2 molar ratio. Consequently, it was confirmed that the synthesized nano sized cobalt particles had a face centered cubic (fcc) structure and with a size range of 100-200 nm.

[ ] a cathode material for lithium rechargeable batteries, was prepared using recycled . First, the cobalt hydroxide powders were separated from waste WC-Co hard metal with acid-base chemical treatment, and then the impurities were eliminated by centrifuge method. Subsequently, powders were prepared by thermal treatment of resulting . By adding a certain amount of and , the was obtained by sintering for 10 h in air at . The synthesized particles were characterized by X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) analysis.

Spherical nanosized cobalt powder with an average size of 150-400 nm was successfully prepared at room temperature from cobalt sulfate heptahydrate (). Wet chemical reduction method was adopted to synthesize nano cobalt powder and hypophosphorous acid () was used as reduction agent. Both the HCP and the FCC Co phase were developed while concentration ranged from 0.7 M to 1.1 M. Secondary phase such as and were also observed. Peaks for the crystalline Co phase having HCP and FCC structure crystallized as increasing the concentration of , indicating that the amount of reduction agent was enough to reduce . Consequently, a homogeneous Co phase could be developed without second phase when the ratio exceeded 7.

A cobalt oxide - tin oxide nanocomposite based gas sensor on an SiO2 substrate was fabricated. Granular thin film of tin oxide was formed by a rheotaxial growth and thermal oxidation method using dc magnetron sputtering of Sn. Nano particles of cobalt oxide were spin-coated on the tin oxide. The cobalt oxide nanoparticles were synthesized by polymer-assisted deposition method, which is a simple cost-effective versatile synthesis method for various metal oxides. The thickness of the film can be controlled over a wide range of thicknesses. The composite structures thus formed were characterized in terms of morphology and gas sensing properties for reduction gas of H2. The composites showed a highest response of 240% at 250˚C upon exposure to 4% H2. This response is higher than those observed in pure SnO2 (90%) and Co3O4 (70%) thin films. The improved response with the composite structure may be related to the additional formation of electrically active defects at the interfaces. The composite sensor shows a very fast response and good reproducibility.

For this paper, we investigated the area specific resistance (ASR) of commercially available ferritic stainless steels with different chemical compositions for use as solid oxide fuel cells (SOFC) interconnect. After 430h of oxidation, the STS446M alloy demonstrated excellent oxidation resistance and low ASR, of approximately 40 mΩcm2, of the thermally grown oxide scale, compared to those of other stainless steels. The reason for the low ASR is that the contact resistance between the Pt paste and the oxide scale is reduced due to the plate-like shape of the Cr2O3(s). However, the acceptable ASR level is considered to be below 100 mΩcm2 after 40,000 h of use. To further improve the electrical conductivity of the thermally grown oxide on stainless steels, the Co layer was deposited on the stainless steel by means of an electroless deposition method; it was then thermally oxidized to obtain the Co3O4 layer, which is a highly conductive layer. With the increase of the Co coating thickness, the ASR value decreased. For Co deposited STS444 with 2 μmhickness, the measured ASR at 800˚ after 300 h oxidation is around 10 mΩcm2, which is lower than that of the STS446M, which alloy has a lower ASR value than that of the non-coated STS. The reason for this improved high temperature conductivity seems to be that the Mn is efficiently diffused into the coating layer, which diffusion formed the highly conductive (Mn,Co)3O4 spinel phases and the thickness of the Cr2O3(S), which is the rate controlling layer of the electrical conductivity in the SOFC environment and is very thin

We investigated the effects of Co doping on the NO gas sensing characteristics of ZnO-carbon nanotube (ZnO-CNT) layered composites fabricated by coaxial coating of single-walled CNTs with ZnO using pulsed laser deposition. Structural examinations clearly confirmed a distinct nanostructure of the CNTs coated with ZnO nanoparticles of an average diameter as small as 10 nm and showed little influence of doping 1 at.% Co into ZnO on the morphology of the ZnO-CNT composites. It was found from the gas sensing measurements that 1 at.% Co doping into ZnO gave rise to a significant improvement in the response of the ZnO-CNT composite sensor to NO gas exposure. In particular, the Co-doped ZnO-CNT composite sensor shows a highly sensitive and fast response to NO gas at relatively low temperatures and even at low NO concentrations. The observed significant improvement of the NO gas sensing properties is attributed to an increase in the specific surface area and the role as a catalyst of the doped Co elements. These results suggest that Co-doped ZnOCNT composites are suitable for use as practical high-performance NO gas sensors.

Fisher-Tropsch synthesis for the production of hydrocarbon from syngas was investigated on 20% cobalt-based catalysts (20% Co/HSA, 20% Co/Si-MMS), which were prepared by home-made supports with high surface areas such as high surface alumina (HSA) and silica mesopores molecular sieve (Si-MMS). In the gas phase reaction by syngas only, 20% Co/Si-MMS catalyst was shown in higher CO conversion and lower carbon dioxide formation than 20% Co/HSA, whereas the olefin selectivity was higher in 20% Co/HSA than in 20% Co/Si-MMS. In the effect of n-hexane added in syngas, the selectivities of C5+ and olefin were increased by comparing the supercritical phase reaction with the gas phase reaction in addition to reduce unexpected methane and carbon dioxide.

The deposition behavior and structural and magnetic properties of electroless Co-B and Co-Fe-B deposits, as well as the amorphous ribbon substrates, were investigated. These Co-based alloy deposits exhibited characteristic polycrystalline structures and surface morphology and magnetic properties that were dependent on the type of amorphous substrates. The catalytic activity sequence of the amorphous ribbon electrodes for anodic oxidation of DMAB was estimated from the current density-potential curve in the anodic partial electrolytic bath that did not contain the metal ions. Both the deposition rate and potential in the initial region were obtained in order of the catalytic activity, depending on the alloy compositions of the substrates. The deposition rate linearly varied against the deposition time. The initial deposition potential may have also determined the structural and magnetic properties of the deposit based on the thickness of μm order. Furthermore, a basic study of the electroless deposition processes on an amorphous ribbon substrate has been carried out in connection with the structural and magnetic properties of the deposits.