• 한국전기전자재료학회논문지
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• 제18권10호
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• pp.896-901
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• 2005

The microstructure and electrical properties of praseodymium-based zinc oxide varistors were investigated at various cobalt oxide contents in the range of $0.5{\~}5.0 mol\%$. The ceramic density increased in the range of $5.25{\~}5.55 g/cm^3$ with increasing cobalt oxide content. The varistor doped with cobalt oxide of $1.0 mol\%$ exhibited the highest nonlinearity, with 66.6 in nonlinear exponent and 1.2 $\mu$A in leakage current. The donor concentration, density of interface states, and tamer height were in the range of $(1.06{\~}1.69){\times}10^{18}/cm^3$, $(3.11 {\~}3.56){\times}10^{12}/cm^2$, and 0.80${\~}$1.07 eV, respectively.

• 접착 및 계면
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• 제15권2호
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• pp.49-56
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• 2014

본 연구에서는 아연 코팅 스틸코드와 접착증진제가 적용된 배합고무와의 접착 특성을 연구하였다. 접착증진제로는 cobalt boroacylate (코발트 염), resorcinol-formaldehyde resin (RF resin) 그리고 hexamethoxymethylmelamine (HMMM)을 사용하였다. 코발트 염이 첨가된 배합고무에서는 코발트 염이 아연 코팅 스틸코드 표면에서 아연 황화물 성장을 촉진시켜 코발트 염이 포함되지 않은 배합고에 비하여 pullout force가 증가하는 것을 확인하였다. 또한 코발트 염, RF resin과 HMMM을 모두 적용한 배합고무의 경우, 코발트 염은 아연 황화물 성장을 촉진시키고, RF resin과 HMMM은 배합고무의 modulus를 높여 고무 matrix로 성장한 아연 황화물을 더 강하게 interlocking하기 때문에 pullout force와 스틸코드의 고무 부착율이 가장 높게 나타난다는 것을 확인하였다.

• 한국세라믹학회지
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• 제48권2호
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• pp.173-177
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• 2011

Decomposition promoting factors and decomposition mechanism in the zinc decomposition process of waste hard metals which are composed mostly of tungsten carbide and cobalt were evaluated. Zinc volatility amount was suppressed and zinc valatilization pressure was produced in the reaction graphite crucible inside an electric furnace for ZDP. Reaction was done for 2 h at $650^{\circ}C$, which 100 % decomposed the waste hard metals that were over 30 mm thick. As for the separation-decomposition of waste hard metals, zinc melted alloy formed a liquid composed of a mixture of ${\gamma}-{\beta}1$ phase from the cobalt binder layer (reaction interface). The volume of reacted zone was expanded and the waste hard metal layer was decomposed-separated horizontally from the hard metal. Zinc used in the ZDP process was almost completely removed-collected by decantation and volatilization-collection process at $1000^{\circ}C$.

• Asian-Australasian Journal of Animal Sciences
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• 제14권4호
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• pp.564-566
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• 2001

A study was undertaken to record the utilization of some micro-elements during inflammation of the mammary gland. Two groups of twenty five animals each suffering from subclinical and clinical mastitis were selected for the study. All the animals were maintained on identical diets. Blood zinc level in cows with subclinical mastitis ($5.66{\pm}0.52$) was significantly (p<0.05) lower than that of healthy cows ($8.46{\pm}1.10ppm$). No significant difference was, however, recorded in blood copper and cobalt levels between healthy and mastitic cows.

• 한국표면공학회지
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• 제40권1호
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• pp.23-31
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• 2007

The objective of this study is to investigate the effect of Al addition on the reaction behavior of cobalt with molten zinc. Pure cobalt specimen was immersion tested in the three kinds of molten zinc (pure, 0.12%Al added and 0.24%Al added) baths at $460^{\circ}C,\;490^{\circ}C\;and\;520^{\circ}C$. For the understanding of degradation processes, specimens were analyzed with scanning electron microscope (SEM) and energy dispersive spectrum (EDS), and electrochemical stripping method. When 0.12% and 0.24% Al was added in molten zinc baths, three intermetallic compounds layers of ${\gamma},\;{\gamma}_1,\;and\;{\gamma}_2$ were formed on the Co matrix and ${\beta}_1$ layer was not formed between the Co matrix and the ${\gamma}$ layer. Particles of CoAl intermetallic compound were formed at the interface between the ${\gamma}_2$ layer and zinc melt and they did not adhere to the Co-Zn intermetallic layer. Weight loss of the Co specimen increased as Al content in the molten zinc increased and the relationship of weight loss vs. immersion time followed parabolic rate law. Rate controlling process for the reaction rate of Co with Al added molten zinc was analyzed as the diffusion process of Al atom through a boundary layer between the ${\gamma}_2$ layer and the Al added zinc melt.

• The Korean Journal of Ecology
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• 제23권1호
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• pp.59-64
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• 2000

진해만의 중금속 오염도를 평가하기 위해 해저퇴적물, 해수 및 참굴의 중금속 농도를 측정하였다. 해저퇴적물내 카드뮴, 코발트, 구리, 니켈, 납, 아연의 농도범위는 0.1∼2.4, 12.6∼14.4, 25.3∼92.3, 32. 4∼93.5, 24.1∼81.2, 124∼477 ㎍/g 으로 나타났다. 인간의 산업활동과 관련된 카드뮴, 구리, 납, 아연의 농도는 마산 내만에서 높게 나타났다. 해수내의 용존성 카드뮴, 코발트, 구리, 니켈, 납, 아연의 농도범위는 ＜0.010∼0.043, 0.008∼0.120,0.31∼0.90,0.25∼3.10, 0.010∼0.142,0.27∼9.04 ㎍/L로 나타났다. 해수의 카드뮴, 구리, 납, 아연의 농도도 퇴적물에서처럼 마산 내만에서 높게 나타났으므로 마산만이 진해만의 주오염원임을 알 수 있었다. 참굴의 아연, 구리, 카드뮴, 납, 코발트, 니켈 둥의 생물농축계수(BCF)는 647373, 280861, 145069, 44559, 13524, 2745 순으로 나타났으며, 다른 이매패류에 비해 강한 중금속 축적종으로 나타났다.

• Asian-Australasian Journal of Animal Sciences
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• 제20권9호
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• pp.1433-1437
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• 2007

Two field trials were carried out to evaluate the performance of a soluble glass copper, cobalt and selenium bolus for maintaining adequate levels of the three trace elements in yaks. Forty yaks were used in trial 1 and 60 yaks were used in trial 2. In each trial two commercial soluble glass boluses were administered to half of the yaks. Blood samples were taken from the jugular vein at day 0, 30, 60, 90 in trial 1 and at day 0, 45, 75 and 105 in trial 2. The samples were analysed for copper status (serum caeruloplasmin activity and copper concentration), cobalt status (serum vitamin $B_{12}$ concentration and cobalt concentration), selenium status (erythrocyte glutathione peroxidase activity and selenium concentration) and serum zinc concentration. The erythrocyte glutathione peroxidase activities, serum caeruloplasmin activities and serum vitamin $B_{12}$ concentrations for trial 1 and 2 were all significantly increased for the bolused yaks (p<0.001 or p<0.01) on all sampling days. The bolused yaks had a significantly higher selenium and copper status in serum than the control yaks on all sampling days in trial 1 and 2 (p<0.05 or p<0.01). There were no significant differences in zinc and cobalt concentrations between the bolused yaks and the controls.

• 한국재료학회지
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• 제15권11호
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• pp.722-729
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• 2005

The electrical and dielectric stability of zinc oxide-based varistors were investigated with the cobalt oxide contents in the range of $0.5\~5.0 mo\l%$. As cobalt oxide contents increased, the ceramic density increased in the range of $5.25\~5.55g/cm^3$ and the varistor voltage decreased in the range of $235.3\~86.0V$. The varistor with on addition of cobalt oxide $1.0 mol\%$ exhibited good nonlinearity. in which the nonlinear exponent is 66.6 and the leakage current is $1.2{\mu}A$. Furthermore, the varistors exhibited the highest electrical and dielectric stability, with $\%{\Delta}V_{1mA}=-1.9\%,\;\%{\Delta}{\alpha}=-10.5\%,\;\%{\Delta}I_L=+275.0\%,\;and\;\%{\Delta}tna{\delta}=+55.6\%$, under DC accelerated aging $0.95V_{1mA}/150^{\circ}C/24h$.

• 생명과학회지
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• 제12권6호
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• pp.682-687
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• 2002

다양한 금속이온의 첨가에 따른 CPase Taq의 효소활성의 개선에 관한 연구를 행하였다. 1 mA의 코발트이온의 첨가에 의해 효소활성이 4배 이상 증가했고, 1 mA의 칼슘이온의 첨가에 의해서는 효소활성이 거의 3배 정도로 증가했다. 하지만 활성중심에 존재하는 아연이온은 효소활성에 영향을 주지 않았다. 활성중심의 금속 이온이 효소활성에 영향을 주는지를 알아보기 위해 활성중심을 차지하고 있는 아연이온을 본 효소를 효과적으로 활성화시키는 코발트이온으로 치환하였다. 그 결과, 코발트이온으로의 치환이 CPase Taq의 효소활성에 영향을 주지 않으므로, 코발트이온은 본 효소의 활성중심의 금속이온인 아연이온을 대신하여 CPase Taq가 효소활성을 가지는데 있어서 동일한 역할을 할 수 있는 금속이온이라 사료된다.

• 한국세라믹학회지
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• 제43권11호
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• pp.703-709
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• 2006

We report on the synthesis of highly uniform, single phase zinc and cobalt thin films prepared by the Liquid Phase Deposition (LPD) method. X-Ray diffraction, TGA and EDX measurements support the assumption that the as deposited films are constituted by a mixture of crystallized FeOOH and amorphous M(OH)$_2$ (M=Co, Zn) which is converted upon heat treatment in air at 600?C into the corresponding zinc ferrites. The films with adjustable chemical compositions are identified with a crystal structure as spinel-type and present a spherical or rod-like microstructure, depending on the both the nature and concentration of the divalent transition metal ions. Zinc ferrite thin films present a superparamagnetic behavior above blocking temperatures which decrease with increasing the Zn content and are ferromagnetic at 5 K with coercivities ranging between 797.8 and 948.5 Oe, whereas the cobalt ferrite films are ferromagnetic at room temperature with magnetic characteristics strongly dependent on the chemical composition.