• 문화기술의 융합
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• 제9권3호
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• pp.587-592
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• 2023

CoCl₂·6H₂O 수용액을 결정성셀룰로오스에 함침시켜 건조한 후, 하소, 소성을 통하여 산화코발트(Co₃O₄·CoO) 초미세입자를 합성하였다. 합성된 코발트 산화물 입자의 결정구조 및 표면구조를 주사전자현미경(SEM)과 X-선회절분석(XRD)으로 조사하였다. CoCl₂·6H₂O 수용액을 함침시키는 매개체로 사용한 결정성셀룰로오스(crystalline cellulose)는 470℃ 정도에서 열분해 되었고, Co₃O₄ 결정상은 350℃에서 생성되기 시작하였다. Co₃O₄ 결정상은 500℃까지 유지되었으며, 500℃ 이상의 온도에서는 CoO 결정상으로 변화하는 것을 알 수 있었다. 열처리 온도가 증가함에 따라 산화코발트 입자의 크기가 커지는 현상이 나타났으며, 900℃ 이상의 온도에서는 입자간 용융이 일어나는 것이 관찰되었다. 하소온도 700℃ 이하의 온도에서 입자크기 2-10㎛의 Co₃O₄와 CoO의 초미세입자가 생성되는 것을 확인하였다.

• 한국안전학회지
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• 제19권4호
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• pp.74-79
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• 2004

[ $CO_3O_4/{\gamma}-Al_2O_3$ ] catalysts were reported high activity on the low temperature CO oxidation. The effects of the calcination temperature, the loaded amount of cobalt and the oxygen concentration on the characteristics of CO oxidation have been investigated for a emergency escape mask cartridge. $Co(NO_3)_2\cdot6H_2O$ was used as cobalt precursor and the catalysts were prepared by incipient wetness impregnation. TGA shows that enough calcination is accomplished at $450^{\circ}C$ and cobalt phase is $Co_3O_4$ after calcination in the temperature range of $300\ ~500^{\circ}C$. The specific surface area and pore volume of catalysts are decreased with increasing of loaded amount of cobalt. And with the increase of loaded amount of cobalt and the oxygen concentration, the catalytic activity is increased.

• 한국분말재료학회지
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• 제5권4호
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• pp.279-285
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• 1998

The microstructures and mechanical properties of submicron WC-Co cemented carbides were investigated in relation to cobalt content. To inhibit the WC grain growth during sintering, VC was added as a inhibitor in each alloy with 3 mass% to the cobalt content. The WC-(5, 8, 10, 15, 20) mass% Co compacts were sintered at $1400^{\circ}C$ for 30 min in vacuum. Some of WC-(5, 8, 10) mass% Co sintered compacts were HIPed with 120 atm at 130$0^{\circ}C$ for 1 hr. The shrinkages of all HIPed alloys were increased without depending on the cobalt contents and the sintered densities of them. The relative densities of the alloys were increased with the cobalt content and HIPing. The less the cobalt content, the larger the WC grain. Many contiguities of WC grains were found in WC-5 mass% Co alloy. The sizes and numbers of pores in the alloys were decreased by HIPing. And also the strength and the hardness of each alloy were increased. The maximum hardness was about 18.95 GPa in the WC-5 mass% Co alloy HIPed and the maximum transverse-rupture strength (T.R.S.) 3.2 GPa in the WC-20 mass% Co alloy sintered.

• 한국안전학회지
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• 제21권2호
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• pp.35-45
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• 2006

Cobalt catalysts for gas mask loaded on various supports such as $Al_{2}O_{3},\;TiO_{2}$, AC(activated carbon) and $SiO_{2}$ were used to examine influences of calcination temperatures and reaction temperatures for CO oxidation. $Co(NO_{3})_2{\cdot}6H_{2}O$ was used as cobalt precursor and the catalysts were prepared by incipient wetness impregnation. The catalysts were characterized using XRD, TGA/DTA, TEM, $N_{2}$ sorption, and XPS. For the catalytic activity, support was in the order of ${\gamma}-Al_{2}O_{3}>TiO_{2}>SiO_{2}>AC\;and\;Al_{2}O_{3}$. The catalytic activity at lower temperature than $80^{\circ}C$ showed that with the increase of reaction temperature, cobalt catalysts on ${\gamma}-Al_{2}O_{3},\;TiO_{2},\;AC\$ has the negative activation energy but that of $SiO_{2}$ was positive.

• 분석과학
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• 제8권1호
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• pp.55-62
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• 1995

네 자리 Schiff base cobalt(II) 착물로서 $Co(II)_2-N$, N-bis(salicylidene)-m-phenylendiimine : [$Co(II)_2(SMPD)_2(H_2O)_4$] 및 $Co(II)_2-N$, N-bis(salicylidene)-p-phenylendiimine : [$Co(II)_2(SPPD)_2(H_2O)_4$]들을 합성하였다. Pyridine 용액에서 이와 같은 착물들에 산소를 가하여 산소 첨가된 생성착물로서 [$Co(III)_2O_2(SMPD)_2(Py)_2$] 및 [$Co(III)_2O_2(SPPD)_2(Py)_2$]들을 합성하였다. 원소분석과 금속정량, IR spectia 및 TGA를 측정한 결과로부터 pyridine과 산소가 중심금속에 6배위로 결합함을 밝혔다. 0.1M TEAP-pyridine 용액에서 순환 전압-전류법에 의한 산소 첨가 생성 착물들의 산화-환원 과정은 다음과 같이 5단계의 일전자 반응으로 진행됨을 알았다. $$[Co(III)_2-O_2-CO(III)]\rightarrow^{e^-}[Co(III)-O_2-Co(II)]\rightarrow^{e^-}[Co(II)-O_2-Co(II)]\rightleftarrows^{e^-}[Co(II)+Co(II)+O_2{\cdot}^-]\rightleftarrows^{e^-}[Co(II)+Co(I)+O_2{\cdot}^-]\rightleftarrows^{e^-}[Co(I)+Co(I)+O_2{\cdot}^-]$$.

• 자원리싸이클링
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• 제20권6호
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• pp.78-82
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• 2011

초임계 ₂추출은 기존의 금속추출/용매추출 공정을 대체할 수 있는 새로운 공정으로써의 큰 가능성을 가지고 있는 기술이다. 초임계 ₂를 이용하여 황산코발트용액으로부터 코발트의 추출에 대한 연구를 수행하였다. 코발트의 추출을 위해 bis (2,4,4-trimethylpentyl) phosphinic acid 및 diethylamine을 초임계 ₂와 함께 추출제로 사용하였으며 ₂의 추출거동을 관찰하였다. 초임계 ₂추출은 $60^{\circ}C$, 200 bar의 조건에서 실시하였고 실험은 초임계 ₂추출제 착염화과정과 금속추출과정으로 구성된 공정을 이용하여 진행하였다. 실험결과 코발트의 추출률은 추출제 투입량에 따라 16-99%까지 증가하였다.

• Journal of Magnetics
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• 제20권3호
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• pp.207-210
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• 2015

Modifications in the structural and magnetic properties of co-precipitated cobalt ferrite nanoparticles can be accomplished by varying the annealing time periods during the synthetic process. Experimental results show that high-purity cobalt ferrite nanoparticles are obtained using a co-precipitation process. The dependence of the crystallite sizes on the annealing time was successfully demonstrated using XRD and SEM. Finally, vibrating sample magnetometer analyses show that the magnetic properties of the cobalt ferrite nanoparticles depend on their relative particle sizes.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.41-41
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• 2010

반도체 소자의 선폭이 감소함에 따른 금속배선의 저항이 증가하면서 반도체 배선물질을 copper로 대체하려는 연구가 진행되고 있다. 그러나 copper를 금속배선에 사용하게 되면 대기 상에서 노출 시 쉽게 산화가 일어나며 형성된 산화물의 미세조직이 치밀하지 못하여 계속적인 산화가 진행되고, 후속 열처리 공정 시 copper가 유전체로 확산되어 소자의 정상적인 작동을 방해하게 되는 문제점을 가지고 있다. 이러한 문제점을 해결하기 위해서 copper의 확산 및 산화를 방지하는 물질로 cobalt가 각광받고 있다. Cobalt는 낮은 저항과 열적 안정성이 우수하여 copper와의 연동에 문제가 없으며, 소자의 작동에도 영향을 미치지 않는다. Cobalt 박막의 적용을 위해 patterning 단계를 줄일 수 있는 선택적 증착공정의 개발도 요구되고 있다. 본 연구에서는 우수한 층덮힘(step coverage)과 양질의 박막을 증착할 수 있는 MOCVD 공정을 이용하였고, cobalt 전구체로서 $Co(hfac)_2$ (hfac: hexafluoroacethylacetonate) 전구체와 $Co_2$ (CO)8 (CO: carbonyl) 전구체를 사용하였다. 각각의 전구체에 따라 선택적 증착이 가능한 공정조건을 찾기 위한 연구를 진행하였다.

• Bulletin of the Korean Chemical Society
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• 제21권1호
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• pp.39-43
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• 2000

New coordination polymers of general form, $$[CoL_2X_2]_n$$ (L = 3,3'-oxybis(pyridine) (obp), 1,4-bis(3-pyri-doxy) benzene (bpob); X = Cl, NCS), have been prepared via a slow diffusion method. The reaction of the present linkers with cobalt(II) ion affords infinite 2-dimensional sheet products. For $[Co(obp) $_2Cl_2]_n$$, the local geometry of the cobalt center is an octahedral arrangement with four nitrogen donors and two chlorine ions in trans positions. $$[Co(bpob)_2(NCS)_2]_n$$ has provided a similar structure: the local geometry of the cobalt atom is an octahedral arrangement with four pyridine units and two NCS groups in transpositions. The obp and bpob linkers connect two cobalt(II) ions defining the edges of 40- and 60-membered $[Co(II)]_4$ ring, respectively. Thermal analyses of the coordination polymers show significant thermal behavior associated with the characteristic structures.

• 한국분말재료학회지
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• 제28권6호
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• pp.497-501
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• 2021

Cobalt (Co) is mainly used to prepare cathode materials for lithium-ion batteries (LIBs) and binder metals for WC-Co hard metals. Developing an effective method for recovering Co from WC-Co waste sludge is of immense significance. In this study, Co is extracted from waste cemented carbide soft scrap via mechanochemical milling. The leaching ratio of Co reaches approximately 93%, and the leached solution, from which impurities except nickel are removed by pH titration, exhibits a purity of approximately 97%. The titrated aqueous Co salts are precipitated using oxalic acid and hydroxide precipitation, and the effects of the precipitating agent (oxalic acid and hydroxide) on the cobalt microstructure are investigated. It is confirmed that the type of Co compound and the crystal growth direction change according to the precipitation method, both of which affect the microstructure of the cobalt powders. This novel mechanochemical process is of significant importance for the recovery of Co from waste WC-Co hard metal. The recycled Co can be applied as a cemented carbide binder or a cathode material for lithium secondary batteries.