• Title, Summary, Keyword: Cobalt

Search Result 1,482, Processing Time 0.035 seconds

Reaction of Cobalt Doubledecker Sandwich Complexes with Oximes for Synthesizing Cobalt Oxime Sandwich Complex (Cobalt Oxime Sandwich형 화합물을 합성하기 위하여 Oxime류와 (${\eta}^5$-Cyclopentadienyl)cobalt를 포함하는 착물과의 반응)

  • Won-Sik Lee;Hyuk Lee;Sang-In Byun;Young-Bae Park;Kwang Lee;Jae-Kook Uhm;Young-Woo Kwak;Tae-Jeong Kim
    • Journal of the Korean Chemical Society
    • /
    • v.36 no.2
    • /
    • pp.305-310
    • /
    • 1992
  • (${\eta}^5$-Cyclopentadienyl)bis(ethylene)cobalt (Jonas reagent), (${\eta}^5$-cyclopentadienyl)di(carbonyl)cobalt, and bis(${\eta}^5$-cyclopentadienyl)cobalt (cobaltocene) were reacted with oximes, respectively, under various conditions for synthesizing cobalt oxime sandwich complex. Jonas reagent and a dienemonooxime, 2,4-hexadienealdoxime underwent the reaction. This produced unexpected compound, (${\eta}^5$-cyclopentadienyl)(2,4-hexadienenitrile)cobalt [VII]. The compound [VII] was identified by NMR, mass spectrometer, IR and elemental analyzer etc.

  • PDF

Coating of Cobalt Over Tungsten Carbide Powder by Wet Chemical Reduction Method

  • Hong, Hyun-Seon;Yoon, Jin-Ho
    • Journal of Korean Powder Metallurgy Institute
    • /
    • v.21 no.2
    • /
    • pp.93-96
    • /
    • 2014
  • Cobalt coated tungsten carbide-cobalt composite powder has been prepared through wet chemical reduction method. The cobalt sulfate solution was converted to the cobalt chloride then the cobalt hydroxide. The tungsten carbide powders were added in to the cobalt hydroxide, the cobalt hydroxide was reduced and coated over tungsten carbide powder using hypo-phosphorous acid. Both the cobalt and the tungsten carbide phase peaks were evident in the tungsten carbide-cobalt composite powder by X-ray diffraction. The average particle size measured via scanning electron microscope, particle size analysis was around 380 nm and the thickness of coated cobalt was determined to be 30~40 nm by transmission electron microscopy.

Preparation of Porous Cobalt Thin Films by Using an Electrochemical Method (전기화학적 방법을 통한 다공성 코발트 박막 합성)

  • Ha, Seong-Hyeok;Shin, Heon-Cheol
    • Journal of the Korean institute of surface engineering
    • /
    • v.53 no.6
    • /
    • pp.312-321
    • /
    • 2020
  • Morphology of porous cobalt electro-deposits was systematically investigated as functions of cobalt precursors in the plating bath and applied cathodic current density with a special focus on cobalt nano-rod formation. It was proved that the concentration of cobalt precursor plays little effect on the morphology of cobalt electro-deposits at relatively low plating current density while it significantly affects the morphology with increasing plating current density. Such a dependence was discussed in terms of the kinetics of two competitive reactions of cobalt reduction and hydrogen evolution. Cobalt nano-rod structure was created at specific ranges of cobalt precursor content and applied cathodic current density, and its diameter and length varied with plating time without notable formation of side branches which is usually found during dendrite formation. Specifically, the nano-rod length was preferentially increased in relative short plating time (<15 s), resulting in higher aspect ratio of nano-rod with plating time. Whereas, both the nano-rod length and diameter were increased nearly at the same level in a prolonged plating time, making the aspect ratio unchanged. From the analysis of crystal structure, it was confirmed that the cobalt nano-rod preferentially grew in the form of single crystal on a dense poly-crystalline cobalt thin film initially formed on the substrate.

X-ray Photoelectron Spectroscopy Study of Cobalt Supported Multi-walled Carbon Nanotubes Prepared by Different Precursors

  • Lee, Jeong-Min;Kim, Ju-Wan;Lim, Ji-Sun;Kim, Tae-Jin;Kim, Shin-Dong;Park, Soo-Jin;Lee, Young-Seak
    • Carbon letters
    • /
    • v.8 no.2
    • /
    • pp.120-126
    • /
    • 2007
  • The effect of cobalt precursor on the structure of Co supported multi-walled carbon nanotubes (MWCNTs) were studied by using X-ray photoelectron spectroscopy (XPS). MWCNTs were treated with a mixture of nitric and sulfuric acids and decorated with cobalt and/or cobalt oxides via aqueous impregnation solutions of cobalt nitrate or cobalt acetate followed by reduction in hydrogen. XPS was mainly used to investigate the phase of cobalt on MWCNTs after reduction with $H_2$ flow at $400^{\circ}C$ for 2 h. Higher cobalt-nanoparticle dispersion was found in the MWCNTS prepared via cobalt nitrate decomposition. A typical XPS spectrum of Co 2p showed the peaks at binding energy (BE) values equal to 781 and 797 eV, respectively. It is found that cobalt nitrate supported MWCNTs is more dispersive and have catalytic activity than that of cobalt acetate supported MWCNTs at same preparation condition such as concentration of precursor solution and reduction environment.

The Fabrication of Cobalt Nanopowder by Sonochemical Polyol Synthesis of Cobalt Hydroxide and Magnetic Separation Method (수산화코발트의 초음파 폴리올 합성과 자성 선별법을 이용한 코발트 나노 분말의 제조)

  • Byun, Jong Min;Choi, Myoung Hwan;Shim, Chang Min;Kim, Ji Young;Kim, Young Do
    • Journal of Korean Powder Metallurgy Institute
    • /
    • v.22 no.1
    • /
    • pp.39-45
    • /
    • 2015
  • In this study, cobalt nanopowder is fabricated by sonochemical polyol synthesis and magnetic separation method. First, sonochemical polyol synthesis is carried out at $220^{\circ}C$ for up to 120 minutes in diethylene glycol ($C_4H_{10}O_3$). As a result, when sonochemical polyol synthesis is performed for 50 minutes, most of the cobalt precursor ($Co(OH)_2$) is reduced to spherical cobalt nanopowder of approximately 100 nm. In particular, aggregation and growth of cobalt particles are effectively suppressed as compared to common polyol synthesis. Furthermore, in order to obtain finer cobalt nanopowder, magnetic separation method using magnetic property of cobalt is introduced at an early reduction stage of sonochemical polyol synthesis when cobalt and cobalt precursor coexist. Finally, spherical cobalt nanopowder having an average particle size of 22 nm is successfully separated.

Exposure Assessment of Airborne Cobalt in Manufacturing Industries (코발트 취급사업장의 공기 중 코발트 노출평가)

  • Kim, Jae Hong;Jung, Jong-Hyon;Phee, Young Gyu
    • Journal of Korean Society of Occupational and Environmental Hygiene
    • /
    • v.25 no.2
    • /
    • pp.166-173
    • /
    • 2015
  • Objectives: The purpose of this study was to evaluate cobalt concentrations in airborne inhalable, total and respirable dust from manufacturing industries using cobalt. Methods: To compare cobalt concentrations, three types of dust samplers(a 37mm closed cassette sampler, Institute of Occupational Medicine(IOM) sampler, and Aluminum cyclone sampler) were used. The analysis of cobalt concentrations was conducted using AAs based on the NIOSH 7300 method. Results: The geometric mean of cobalt concentration in total dust was $1.47{\mu}g/m^3$, and the rate of excess of the Korean Occupational Exposure Limit(KOEL) was 10.0%. The geometric mean concentrations of cobalt in super alloy manufacturing industries were higher than those in plating industries, and molding operations showed higher exposure levels to cobalt than did other operations. Conclusions: The rate of cobalt concentration in inhalable dust from super alloy manufacturing industries exceeding the Workplace Exposure Limit(WEL) as recommended by the Health & Safety Executive(HSE) was 7.1%, which means proper work environmental management is required through wet work environments. Given that molding operations had higher cobalt concentrations, it is necessary to apply measures such as local exhaust for reducing airborne dust in cobalt manufacture industries.

Synthesis of Cobalt Oxide Film by Thermal Decomposition for Potential Various Applications

  • Han, Seong Ho;Park, Bo Keun;Son, Seong Uk;Kim, Chang Gyoun;Chung, Taek-Mo
    • Proceedings of the Korean Vacuum Society Conference
    • /
    • /
    • pp.365.1-365.1
    • /
    • 2014
  • Cobalt oxide has excellent various properties such as high catalytic activity, antiferromagnetism, and electrochromism. So cobalt oxides offer a great potential for their applications in the various areas such as optical gas sensor, catalysts for oxidation reaction, electrochromic devices, high temperature solar selective absorbers, magnetic materials, pigment for glasses and ceramics, and negative electrodes for lithium-ion batteries. We have synthesized novel cobalt complexes by simple reaction of cobalt bistrimethylsilylamide as a starting material with a lot of conventional ligands as potential cobalt oxide precursors. The studies include the facile preparation, structural characterization, and spectroscopic analysis of the new precursors. We are making efforts to grow cobalt oxide thin films using cobalt complexes newly synthesized in this study using deposition techniques.

  • PDF

The Effects of Cobalt on Wear and Friction Characteristics of High Speed Steel by Powder Metallurgy (분말고속도공구강의 마찰마모특성에 미치는 Co의 영향)

  • 이한영;배종수;김용진
    • Tribology and Lubricants
    • /
    • v.15 no.2
    • /
    • pp.156-163
    • /
    • 1999
  • The mechanical characteristics of the high speed steel by Powder metallurgy Process (PM-HSS) has been reported to improve with several alloying constituents, such as high carbon, vanadium and cobalt. In this paper, sliding wear test has been conducted using a pin-on-disc machine for three PM-HSS which contains 0%, 5% and 12% cobalt respectively, in order to evaluate the effect of cobalt on wear properties of PM-HSS. The results of this study showed that the wear resistance of PM-HSS has been increased by the addition of cobalt on the range of experimental friction velocities. When compared with the effect of addition of cobalt, the wear resistance of PM-HSS with 5% cobalt has been found to be superior to that of PM-HSS with 12% cobalt.

Cobalt Chloride-induced Apoptosis and Extracellular Signal-regulated Protein Kinase Activation in Human Cervical Cancer HeLa Cells

  • Kim, Hyun-Jeong;Yang, Seung-Ju;Kim, Yoon-Suk;Kim, Tae-Ue
    • BMB Reports
    • /
    • v.36 no.5
    • /
    • pp.468-474
    • /
    • 2003
  • The molecular mechanism of hypoxia-induced apoptosis has not been clearly elucidated. In this study, we investigated the involvement of extracellular signal-regulated protein kinase (ERK 1/2) in hypoxia-induced apoptosis using cobalt chloride in HeLa human cervical cancer cells. The cobalt chloride was used for the induction of hypoxia, and its $IC_{50}$ was $471.4\;{\mu}M$. We demonstrated the DNA fragmentation after incubation with concentrations more than $50\;{\mu}M$ cobalt chloride for 24 h, and also evidenced the morphological changes of the cells undergoing apoptosis with electron microscopy. Next, we examined the signaling pathway of cobalt chloride-induced apoptosis in HeLa cells. ERK1/2 activation occurred 6 and 9 h after treatment with $600\;{\mu}M$ cobalt chloride. Meanwhile, the pretreatment of the MEK 1 inhibitor (PD98059) completely blocked the cobalt chloride-induced ERK 1/2 activation. At the same time, the activated ERK 1/2 translocated into the nucleus and phosphorylated its transcriptional factor, c-Jun. In addition, the pretreatment of PD98059 inhibited the cobalt chloride-induced DNA fragmentation and apoptotic cell death. These results suggest that cobalt chloride is able to induce apoptotic activity in HeLa cells, and its apoptotic mechanism may be associated with signal transduction via ERK 1/2.

Structural change of cobalt dodecanesulfate (Cobalt dodecanesulfate의 구조변화)

  • 허영덕;권석순;김지현
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.14 no.2
    • /
    • pp.63-67
    • /
    • 2004
  • The layered structure of cobalt dodecanesulfate was synthesized. A phase transition takes place at various temperature ranges and results in a drastic change of the layer distance. A monolayer structure of cobalt dodecanesulfate at room temperature transformed to a bilayer structure as a dehydrated form at high temperature.