• Transactions of the Korean hydrogen and new energy society
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• v.14 no.3
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• pp.217-228
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• 2003

Li 이차 전지 음극용 활물질인 $Co_3O_4$의 초기 충방전 효율을 향상시키기 위해 chemical reduction method나 mechanical milling법을 이용하여 $Co_3O_4$에 Ni을 첨가하여 $Ni-Co_3O_4$, 복합물을 제조하였다. 그 결과 초기 충방전 효율이 약 69%에 불과한 $Co_3O_4$에 비해 mechanical milling법을 이용하여 제조된 $Ni-Co_3O_4$ 복합물은 약 79%이상의 대폭 향상된 초기 충방전 효율 특성을 나타내었다. 하지만 chemical reduction method를 이용하여 제조된 $Ni-Co_3O_4$ 복합물은 약 71%의 초기 충방전 효율 특성만을 나타내었다. SEM 분석을 통해 각 물질의 표면 형상을 관찰한 결과 mechanical milling법과 chemical reduction method를 통해 제조된 $Ni-Co_3O_4$ 복합물에서는 $Co_3O_4$ 표면에 분포된 Ni의 균일성의 차이가 존재하였다. $Co_3O_4$가 $Li_2O$의 분해, 형성에 의해 충방전되고 Ni이 $Li_2O$의 분해를 촉진시키는 효과를 가지고 있음을 고려할 때 이러한 균일성의 차이는 결국 Ni 과 $Co_3O_4$ 사이의 접촉면적의 차이로 이어져 $Ni-Co_3O_4$ 복합물의 초기 충방전 효율 특성이 그 제조 방법에 따라 달라지는 것으로 보인다.

• Clean Technology
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• v.24 no.1
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• pp.35-40
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• 2018

$Co_3O_4$ catalysts for $N_2O$ decomposition were prepared by co-precipitation method. Ce and Zr were added during the preparation of the catalyst as promoter with the molar ratio (Ce or Zr) / Co = 0.05. Also, 1 wt% $K_2CO_3$ was doped to the prepared catalyst with impregnation method to investigate the effect of K on the catalyst performance. The prepared catalysts were characterized with SEM, BET, XRD, XPS and $H_2-TPR$. The $Co_3O_4$ catalyst exhibited a spinel crystal phase, and the addition of the promoter increased the specific surface area and reduced the particle and crystal size. It was confirmed that the doping of K improves the catalytic activity by increasing the concentration of $Co^{2+}$ in the catalyst which is an active site for catalytic reaction. The catalytic activity tests were carried out at a GHSV of $45,000h^{-1}$ and a temperature range of $250{\sim}375^{\circ}C$. The K-impregnated $Co_3O_4$ catalyst showed much higher activity than $Co_3O_4$ catalysts with promoter only. It is found that the K-impregnation increased the concentration of $Co^{2+}$ more than the added of promoter did, and lowered the reduction temperature to a great extent.

• Korean Journal of Materials Research
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• v.22 no.3
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• pp.118-122
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• 2012

We synthesized porous $Co_3O_4/RuO_2$ composite using the soft template method. Cetyl trimethyl ammonium bromide (CTAB) was used to make micell as a cation surfactant. The precipitation of cobalt ion and ruthenium ion for making porosity in particles was induced by $OH^-$ ion. The porous $Co_3O_4/RuO_2$ composite was completely synthesiszed after anealing until $250^{\circ}C$ at $3^{\circ}C$/min. From the XRD ananysis, we were able to determine that the porous $Co_3O_4$/RuO2 composite was comprised of nanoparticles with low crystallinity. The shape or structure of the porous $Co_3O_4/RuO_2$ composite was studied by FE-SEM and FE-TEM. The size of the porous $Co_3O_4/RuO_2$ composite was 20~40 nm. From the FE-TEM, we were able to determine that porous cavities were formed in the composite particles. The electrochemical performance of the porous $Co_3O_4/RuO_2$ composite was measured by CV and charge-discharge methods. The specific capacitances, determined through cyclic voltammetry (CV) measurement, were ~51, ~47, ~42, and ~33 F/g at 5, 10, 20, and 50 mV/sec scan rates, respectively. The specific capacitance through charge-discharge measurement was ~63 F/g in the range of 0.0~1.0 V cutoff voltage and 50 mAh/g current density.

• Journal of the Korean Ceramic Society
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• v.24 no.5
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• pp.484-490
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• 1987

Diffusion coupling experiment was done to study expansion of body and soild reaction in BaCO3-TiO2 system. Specimen of BaCO3 and TiO2 was formed with Pt-mark's method. Each specimen was fired at interval of 25℃ from 900℃ to 1000℃ for 2hrs. After that, specimen was fixed with resin and polished. Product layers of specimen were observed with SEM and EDS. The result were following; 1. Diffusion component is Ba2+, which diffuse toward TiO2. 2. Large crack between layer of BaCO3 and Ba2TiO4 was generated because of difference of thermal expansion coefficient. 3. Ba2TiO4 is formed to TiO2 body by the reaction of BaTiO3 and BaO and its structure is very porous. 4. BaTiO3 changes immediately to Ba2TiO4 by the reaction of BaO. But BaTiO3 which formed by the reaction of TiO2 and Ba2TiO4 exsists as layer because the diffusion distance of Ba2+ is far.

• The Journal of the Convergence on Culture Technology
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• v.9 no.3
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• pp.587-592
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• 2023

Cobalt oxide (Co₃O₄·CoO) ultra fine particles were synthesized by liquid phase precursor method. cobalt(II) chloride hexahydrate (CoCl₂·6H₂O) was as a starting material. A plant-derived crystalline cellulose was used as impregnating materials. A impregnated precursor was calcined at a temperature of 350 to 900℃ to obtain cobalt oxide particles having a particle size of 1 to 10㎛. The crystallization process and morphology according to the calcination temperature were examined, and the properties of the synthesized powder were evaluated using SEM and XRD. It was confirmed that a crystal phase of Co₃O₄ began to form around 350℃ and crystal growth occurred up to 900℃. At a temperature above 500℃, the Co₃O₄ crystal was changed to another crystal phase CoO.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.464-467
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• 2002

$TiO_{2}-Co_{3}O_{4}$ humidity sensors were fabricated by conventional ceramic process and their humid sensing characteristics were investigated. The sample which was added 10wt% $Co_{3}O_{4}$ and heat-treated $1200^{\circ}C$ showed the highest sensitivity to humidity changes and improved a linearity. As $Co_{3}O_{4}$ content was increasing, the sensor consists a uniform pore distribution and grain in the surface. This was analyzed by SEM photographs.

• Journal of Environmental Science International
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• v.16 no.12
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• pp.1431-1437
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• 2007

Cobalt titanates($CoTiO_x$), such as $CoTiO_3$ and $Co_2TiO_4$, have been synthesized via a solid-state reaction and characterized using X-ray diffraction(XRD) and X-ray photoelectron spectroscopic(XPS) measurement techniques, prior to being used for continuous wet trichloroethylene(TCE) oxidation at $36^{\circ}C$, to support our earlier chemical structure model for Co species in 5 wt% $CoO_x/TiO_2$(fresh) and(spent) catalysts. Each XRD pattern for the synthesized $CoTiO_3$ and $Co_2TiO_4$ was very close to those obtained from the respective standard XRD data files. The two $CoTiO_x$ samples gave Co 2p XPS spectra consisting of very strong main peaks for Co $2p_{3/2}$ and $2p_{1/2}$ with corresponding satellite structures at higher binding energies. The Co $2p_{3/2}$ main structure appeared at 781.3 eV for the $CoTiO_3$, and it was indicated at 781.1 eV with the $Co_2TiO_4$. Not only could these binding energy values be very similar to that exhibited for the 5 wt% $CoO_x/TiO_2$(fresh), but the spin-orbit splitting(${\Delta}E$) had also no noticeable difference between the cobalt titanates and a sample of the fresh catalyst. Neither of all the $CoTiO_x$ samples were active for the wet TCE oxidation, as expected, but a sample of pure $Co_3O_4$ had a good activity for this reaction. The earlier proposed model for the surface $CoO_x$ species existing with the fresh and spent catalysts is very consistent with the XPS characterization and activity measurements for the cobalt titanates.

• Journal of the Korean Ceramic Society
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• v.41 no.10 s.269
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• pp.735-741
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• 2004

$LiMn_{1.92}Co_{0.08}O_4$ and $LiNi_{0.7}Co_{0.3}O_2$ synthesized by a simplified combustion method had good electrochemical properties. Mixtures $LiMn_{1.92}Co_{0.08}O_4$-x wt$\%$ $LiNi_{0.7}Co_{0.3}O_2$ (x=9, 23, 33, 41, and 47) were prepared by milling for 30 min and their electrochemical properties were investigated. The electrode with x=9 had a relatively large first discharge capacity (109.9 mAh/g at 0.1 C) and good cycling performance. The decrease in the discharge capacity of the mixture electrodes with cycling is considered to result mainly from the degradation of $LiNi_{0.7}Co_{0.3}O_2$, caused by coating of $LiNi_{0.7}Co_{0.3}O_2$ with Mn dissolved from $LiMn_{1.92}Co_{0.08}O_4$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.2
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• pp.78-83
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• 2021

In this study, we prepared NiCo2O4 nanoparticles with large surface area by hydrothermal synthesis. In order to optimize the processing conditions for spinel NiCo2O4 nanoparticles with large surface area, experimental variables including concentration of Ni and Co precursor, reaction time, and temperature for post-heat treatment were evaluated. Optimized conditions for spinel NiCo2O4 with large surface area were [Ni]/[Co] 1:2 ratio, reaction time for 12 h, and post-heat treatment at 400℃. To investigate the feasibility as potential application for glucose sensor, electrochemical tests of the prepared NiCo2O4 nanoparticles in response to glucose was performed, which suggests that the NiCo2O4 can be suitable for a non-enzymatic-based electrochemical glucose sensor based on its high sensitivity and selectivity for glucose detection.

• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.454-457
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• 2011

We report the preparation of nanocrystalline cobalt ferrite, $CoFe_2O_4$, particles using recycled $Co_3O_4$ and their surface coating with silica using micro emulsion method. Firstly, the $Co_3O_4$ powders were separated from waste cemented carbide with acid-base chemical treatment. The cobalt ferrite nanoparticles with the size 10 nm are prepared by thermal decomposition method using recycled $Co_3O_4$. $SiO_2$ was coated onto the $CoFe_2O_4$ particles by the micro-emulsion method. The $SiO_2$-coated $CoFe_2O_4$ particles were studied their physical properties and characterized by X-ray diffraction (XRD), high resolution-transmission electron microscopy (TEM) analysis and CIE Lab value.