• Korean Chemical Engineering Research
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• 제55권6호
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• pp.861-867
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• 2017

니켈 함량이 높은 리튬이차전지용 NCA 양극소재의 용량 및 수명특성을 향상시키기 위하여 붕소와 코발트를 상업용 $Li_{1.06}Ni_{0.91}Co_{0.08}Al_{0.01}O_2$ (NCA)에 도핑하여 리튬이차전지의 양극소재로 사용하였다. 상업용 NCA 양극소재는 약 $5{\mu}m$와 $12{\mu}m$ 크기의 2차 입자들이 혼합되어 있고 붕소와 코발트 도핑후 입자크기는 조금 감소되었다. 붕소와 코발트를 도핑한 NCA-B와 NCA-Co의 초기 방전용량은 각각 214 mAh/g과 200 mAh/g으로 도핑하지 않은 NCA에 비해 높게 나타났으며, 특히 NCA-Co는 20번째의 방전용량이 157 mAh/g으로 가장 우수한 방전용량특성을 나타내었다. 이는 코발트를 도핑함으로써 c축 방향으로의 결정이 성장되어 리튬이온의 확산이 용이하기 때문이다.

• 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.

• 한국재료학회지
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• 제11권11호
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• pp.953-959
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• 2001

Homogeneous spherical W-Co salt powders were made by spray drying of aqueous solution of ammonium $metatungstate(NH_4)_6(H_2W_{12}O_{40}){\cdot}4H_2O,\; AMT)$ and cobalt nitrate $hexahydrate(Co(NO_3)_2{\cdot}6H_2O)$. The thermal decomposition process of spray dried W-Co salt powders was studied by TG, XRD, SEM, TEM and FT-IR. Spray dried W-Co salt powders were calcined for 1 hour in the temperature from$ 350^{\circ}C$ to $800^{\circ}C$ in atmosphere of air. At the temperatures over $600^{\circ}C$, spherical $CoWO_4/WO_3$ composite oxide powders were obtained. The primary particle size of W/Co composite oxide powders increased with increasing thermal decomposition temperature due to the particle growth. The observed crystallite size by TEM was in the range of 60nm and that of $CoWO_4$ calculated by Scherrer's formula at $800^{\circ}C$ was smaller than 55nm. The crystallite site was identified by XRD and TEM.

• 한국분말재료학회지
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• 제9권3호
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• pp.167-173
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• 2002

A new approach to produce nanostructured WC/Co composite powders by a mechanochemical process was made to improve the mechanical properties of advanced hardmetals. Homogeneous spherical W-Co salt powders were made by spray drying of aqueous solution from ammonium metatungstate($(NH_4)_6(H_2W_{12}O_{40})\cdo4H_2O$,AMT) and cobalt nitrate hexahydrate (Co(NO$_3$)$_2$.6$H_2O$). spray dried W-Co salt powders were calcined for 1 hr at $700^{\circ}C$ in atmosphere of air. The oxide powder was mixed with carbon black by ball milling and this mixture was heated with various temperatures and times in $H_2$. The $WO_3/CoWO_4$ composite oxide powders were obtained by calcinations at $700^{\circ}C$. The primary particle size of W/Co composite oxide powders by SEM was 100 nm. The reduction/carburization time decreased with increasing temperatures and carbon additions. The average size of WC particle carburized at $800^{\circ}C$ by TEM was smaller than 50 nm.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.240-244
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• 2001

Recycling process involving mechanical, thermal, hydrometallurgical, and sol-gel step has been applied to recover cobalt and lithium from spent lithium ion batteries and to synthesize LiCoO$_2$from leach liquor as cathodic active materials. Electrode materials containing lithium and cobalt could be concentrated with 2-step thermal and mechanical treatment. Leaching behaviors of the lithium and cobalt in nitric acid media was investigated in terms of reaction variables. Hydrogen peroxide in 1 M HNO$_3$solution turned out to be an effective reducing agent by enhancing the leaching efficiency. O f many possible processes to produce LiCoO$_2$, the amorphous citrate precursor process (ACP) has been applied to synthesize powders with a large specific surface area and an exact stoichiometry. After leaching used LiCoO$_2$with nitric acid, the molar ratio of Li/Co in the leach liquor was adjusted at 1.1 by adding a fresh LiNO$_3$solution. Then, 1 M citric acid solution at a 100% stoichiometry was also added to prepare a gelatinous precursor. When the precursor was calcined at 95$0^{\circ}C$ for 24 hr, purely crystalline LiCoO$_2$was successfully obtained. The particle size and specific surface area of the resulting crystalline powders were 20 пm and 30 $\textrm{cm}^2$/g, respectively The LiCoO$_2$powder was proved to have good characteristics as cathode active materials in charge/discharge capacity and cyclic performance.

• 한국광물학회지
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• 제23권3호
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• pp.227-234
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• 2010

본 연구에서는 라테라이트광의 건식 분쇄가 니켈 및 코발트의 침출에 미치는 영향을 조사하였다. 시료로 사용한 라테라이트광은 주로 $SiO_2$, $Fe_2O_3$, MgO로 이루어져 있으며, 니켈과 코발트의 함량은 0.81% Ni, 0.02% Co이었다. 주 구성 광물은 리자다이트와 석영이며, 미량의 포스터라이트와 엔스터타이트를 함유하고 있었다. 분쇄가 진행됨에 따라 시료의 평균입도, 비표면적, 밀도는 감소하는 경향을 보였으며, X-선 회절분석을 통해 리자다이트의 비정질화가 진행됨을 확인하였다. 분쇄에 의한 석영의 물성변화는 나타나지 않았으나, 리자다이트의 Mg-OH 결합이 파괴됨으로써 니켈 및 코발트의 침출율이 향상됨을 알 수 있었다. 분쇄가 진행됨에 따라 니켈과 코발트의 침출율은 증가하였으며, 60분 분쇄한 시료의 경우, 사용한 무기산의 종류에 관계없이 니켈과 코발트의 침출율은 약 80%로 나타났다.

• Journal of Magnetics
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• 제21권3호
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• pp.308-314
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• 2016

Cobalt-, zinc-, and nickel-zinc-substituted nano-size manganese ferrite powders, $MnFe_2O_4$, $Mn_{0.8}Co_{0.2}Fe_2O_4$, $Mn_{0.8}Zn_{0.2}Fe_2O_4$ and $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$, were fabricated using a sol-gel method, and their crystallographic and magnetic properties were subsequently studied. The $MnFe_2O_4$ ferrite powder annealed at temperatures above 523 K exhibited a spinel structure, and the particle size increased as the annealing temperature increased. All ferrites annealed at 773 K showed a single spinel structure, and the lattice constants and particle size decreased with the substitution of Co, Zn, and Ni-Zn. The $M{\ddot{o}}ssbauer$ spectrum of the $MnFe_2O_4$ ferrite powder annealed at 523 K only showed a doublet due to its superparamagnetic phase, and the $M{\ddot{o}}ssbauer$ spectra of the $MnFe_2O_4$, $Mn_{0.8}Co_{0.2}Fe_2O_4$, and $Mn_{0.8}Zn_{0.2}Fe_2O_4$ ferrite powders annealed at 773 K could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. However, the $M{\ddot{o}}ssbauer$ spectrum of the $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$ ferrite powder annealed at 773 K consisted of two Zeeman sextets and one quadrupole doublet due to its ferrimagnetic and paramagnetic behavior. The area ratio of the $M{\ddot{o}}ssbauer$ spectra could be used to determine the cation distribution equation, and we also explained the variation in the $M{\ddot{o}}ssbauer$ parameters by using this cation distribution equation, the superexchange interaction and the particle size. Relative to pure $MnFe_2O_4$, the saturation magnetizations and coercivities were larger in $Mn_{0.8}Co_{0.2}Fe_2O_4$ and smaller in $Mn_{0.8}Zn_{0.2}Fe_2O_4$, and $Mn_{0.8}Ni_{0.1}Zn_{0.1}Fe_2O_4$. These variations could be explained using the site distribution equations, particle sizes and magnetic moments of the substituted ions.

• 한국세라믹학회지
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• 제53권3호
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• pp.367-375
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• 2016

A novel strategy for the synthesis of $CoSb_2$ nanoparticles is demonstrated via preparation of novel organometallic complexes. Hydrated cobalt oleate (CoOl) and non-hydrated antimony oleate (SbOl) complexes are synthesized as precursors. The $CoSb_2$ nanoparticles are prepared by hot injection, which involves thermolysis of CoOl and SbOl in a non-coordinating solvent at $320^{\circ}C$. The coordination modes and distinct thermal behaviors of the intermediate non-hydrated SbOl complexes are comparatively investigated by thermo-analytical techniques. When the reaction temperature is increased, the particle size is found to increase linearly. The crystallinity of the $CoSb_2$ nanoparticles prepared at $250^{\circ}C$ is amorphous phase without any peaks. $CoSb_2$ structural peaks start to appear at $300^{\circ}C$ and dominant peaks with high crystallinity are synthesized at $320^{\circ}C$. The potential chemical structures of non-hydrated SbOl and their reaction mechanisms by thermolysis are elucidated. The elemental composition and crystallographic structure of $CoSb_2$ nanoparticles suggest a bimodal interaction of the organic shell and the nanoparticle surface, with a chemical absorbed inner layer and physically absorbed outer layer of carboxylic acid.

• Journal of Magnetics
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• 제20권1호
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• pp.26-30
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• 2015

The crystallographic and magnetic properties of gallium-substituted cobalt ferrite ($CoGa_xFe_{2-x}O_4$) were investigated. The new material was synthesized using conventional ceramic methods, with gallium substituted for ferrite in the range of x = 0.0 to 1.0, in steps of 0.2. X-ray diffraction and M$\ddot{o}$ssbauer spectroscopy were used to confirm the presence of crystallized particles in the $CoGa_xFe_{2-x}O_4$ ferrite powders. All of the samples exhibited a single phase with a spinel structure, and the lattice parameters decreased as the gallium content increased. The particle size of the samples also decreased as gallium increased. For $x{\leq}0.4$, the M$\ddot{o}$ssbauer spectra of $CoGa_xFe_{2-x}O_4$ could be fitted with two Zeeman sextets, which are the typical spinel ferrite spectra of $Fe^{3+}$ with A- and B-sites. However, for $x{\geq}0.6$, the M$\ddot{o}$ssbauer spectra could be fitted with two Zeeman sextets and one doublet. The variation in the M$\ddot{o}$ssbauer parameters and the absorption area ratio indicated a cation distribution of $(Co_{0.2-0.2x}Ga_xFe_{0.8-0.6x})[Co_{0.8+0.2x}Fe_{1.2-0.4x}]O_4$, and the magnetic behavior of the samples suggested that the increase in gallium content led to a decrease in the saturation magnetization and in the coercivity.

• 한국재료학회지
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• 제16권1호
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• pp.11-18
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• 2006

[ $Co_3O_4$ ] particles with non-aggregation characteristics were prepared by various conditions such as preparation temperature, flow rate of carrier gas, and concentration of spray solution using spray pyrolysis. The morphology and crystallinity of the preformed particles obtained by spray pyrolysis at various conditions affected the mean size and morphology of the post-treated $Co_3O_4$ particles. The preformed particles with hollow and porous morphology obtained from spray solution with citric acid and ethylene glycol turned to $Co_3O_4$ particles with nano size, regular morphology and non-aggregation characteristics after post-treatment at $800^{\circ}C$. On the other hand, the preformed particles obtained by the preparation conditions of short residence time of particles inside hot wall reactor and high reactor temperature turned to $Co_3O_4$ particles with aggregated morphology after post-treatment. The mean crystallite size and particle size of the $Co_3O_4$ particles prepared from optimum preparation conditions were 47 nm and 210 nm at post-treatment temperature of $800^{\circ}C$.