• 한국재료학회지
• /
• 제24권2호
• /
• pp.93-97
• /
• 2014

In this study, a cobalt sulfate ceramic coating was sintered on various clays at $1250^{\circ}C$. The specimen characteristics were investigated by X-ray diffraction(XRD), scanning electron microscopy(SEM), TG-DTA, UV-vis spectrophotometer, and HRDPM. The ceramic coating had a constant thickness of thousands ${\mu}m$, and the surface was confirmed to be densely fused. Other new compounds were produced by the cobalt sulfate sintering process and reactions. These compounds were a $CoAl_2O_4$ phase, $Co_2SiO_4$ phase, anorthite($CaAl_2Si_2O_8$) phase, and $FeAl_2O_4$ phase, respectively. UV properties of the coated specimen were investigated, celadon clay specimen in 530-550 nm band is showing a dark gray color. The white clay and white mix clay specimen in 460-500 nm band is showing a blue color. The cobalt-aluminate($CoAl_2O_4$) spinel and the cobalt-silicate olivine($Co_2SiO_4$) were the strongest of the ceramic pigments, producing a very pure, navy blue color.

• 한국재료학회:학술대회논문집
• /
• 한국재료학회 2001년도 추계 학술발표강연 및 논문개요집
• /
• pp.105-105
• /
• 2001

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2013년도 춘계학술대회 논문집
• /
• pp.180-180
• /
• 2013

Ceramic glaze has been developed by numerous experiences and knowhow of potters for a long time. It has offered curiosity and beauty to many people with a variety of colors. This study first verifies the color difference according to clays and glazing used for the coloration experiment based on generation process and chemical reaction of cobalt sulfate, and determines the effect of a dilution ratio with water on changes in coloration concentration. The cobalt-aluminate spinel and the cobalt-silicate olivine are the strongest of the ceramic pigment, producing a very pure, navy blue color.

• 한국재료학회지
• /
• 제32권8호
• /
• pp.354-360
• /
• 2022

In this study, an Co/Fe coated porcelain using a cobalt and ferrous sulfate was sintered at 1,250 ℃. The specimens were investigated by HR-XRD, FE-SEM (EDS), Dilatometer, and UV-vis spectrophotometer. The surface of the porcelain was uniformly fused with the pigment, and white ware and celadon body specimens were densely fused to a certain thickness from the surface. Other new compounds were produced by the chemical reaction of cobalt/ferrous sulfate with the porcelain body during the sintering process. These compounds were identified as cobalt ferrite spinel phases for white ware and white mixed ware, and an andradite phase for the celadon body, and the amorphous phase, respectively. As for the color of the specimens coated with cobalt and ferrous mixed pigments, it was found that the L^* value was greatly affected by the white ware, and the a^* and b^* values were significantly changed in the celadon body. The L^* values of the specimens fired with pure white ware, celadon body, and white mix ware were 72.1, 60.92, 82.34, respectively. The C7F3 pigment coated porcelain fired at 1,250 ℃ had L^* values of 39.91, 50.17, and 40.53 for the white ware, celadon body, and white mixed ware, respectively; with a^* values of -1.07, -2.04, and -0.19, and at b^* values of 0.46 and 6.01, it was found to be 4.03. As a new cobalt ferrite spinel phase was formed, it seemed to have had a great influence on the color change of the ceramic surface.

• 한국분말재료학회지
• /
• 제18권3호
• /
• pp.244-249
• /
• 2011

Spherical nanosized cobalt powder with an average size of 150-400 nm was successfully prepared at room temperature from cobalt sulfate heptahydrate ($CoSO_4{\cdot}7H_2O$). Wet chemical reduction method was adopted to synthesize nano cobalt powder and hypophosphorous acid ($H_3PO_2$) was used as reduction agent. Both the HCP and the FCC Co phase were developed while $CoSO_4{\cdot}7H_2O$ concentration ranged from 0.7 M to 1.1 M. Secondary phase such as $Co(OH)_2$ and $CO_3O_4$ were also observed. Peaks for the crystalline Co phase having HCP and FCC structure crystallized as increasing the concentration of $H_3PO_2$, indicating that the amount of reduction agent was enough to reduce $Co(OH)_2$. Consequently, a homogeneous Co phase could be developed without second phase when the $H_3PO_2/CoSO_4{\cdot}7H_2O$ ratio exceeded 7.

• 한국분말재료학회지
• /
• 제21권2호
• /
• 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.

• 자원리싸이클링
• /
• 제7권3호
• /
• pp.11-16
• /
• 1998

모의폐액으로 제조한 50ppm의 코발트이온을 sodium lauryl sulfate 계면활성제를 사용하여 침전 포말부선법으로 제거하였다. 부선법으로 코발트이온을 제거하기 전에 35% $H_2O_2$를 모의폐액에 첨가하여 폐액의 전처리 과정을 도입하였다. 그 겨로가 최적 pH 및 처리후 잔존용액의 pH가 낮아졌고, 넓은 범위의 pH에서 높은 제거율을 나타내었다. 초기 코발트 이온농도, pH, 계면활성제 농도, 부선시간, 공급기체 유속, 외부이온 농도 등을 변수라하여 실험한 결과, 초기 코발트 이온농도 50ppm, pH 9.5, 공급기체 유속 $70m\ell$/min, 부선시간 30분 등의 조건에서 99.8%의 제거율을 나타내었다. 침전물과 계면활성제의 흡착은 zeta potential 뿐만 아니라 침전물의 용해도 및 pH에 따라 변화하는 화학종과의 친화력과도 관계가 되는 것으로 추측되었다. 외부이온으로서 ${NO}_{3}^{-}$, ${SO}_{4}^{2-}$, ${Na}^{+}$, ${Ca}^{2+}$를 첨가하여 그 영향을 관찰하였으며, $SO_4^{2-}$가 0.1M 함유된 cobalt 용액을 침전 포말부선법으로 처리한 결과 zeta potential의 감소 및 침전방해 등의 이유로 제거효율은 90%를 나타내었다.

• 자원리싸이클링
• /
• 제7권3호
• /
• pp.3-10
• /
• 1998

모의폐액으로 제조한 50ppm의 코발트이온을 Fe(III) 및 Al(III)의 응집제와 sodium lauryl sulfate의 계면활성제를 사용하여 흡착 교질 포말부선법으로 제거하였다. 용액의 pH, 계면활성제 농도, Fe(III) 및 Al(III) 농도, 공급기체의 유속 등을 변수로 하여 실험한 결과, Fe(III)를 응집제로 사용한 경우 초기 코발트이온농도 50ppm, pH 8.5, 공급기체유속 $70mell$/min, 제거시간 15분 등의 조건에서 99.8%의 제거율을 나타내었다. 코발트 이온 제거에 앞서 모의폐액에 35% $H_2O_2$를 첨가하여 폐액을 전처리하였다. 그 결과, 최적 pH 및 처리 후 잔존용액의 pH가 낮아졌고, 넓은 범위의 pH에서 높은 제거율을 나타내었다. Fe(III) 50 ppm을 사용하여 코발트이온과 공침시킨 후 20ppm의 Al(III)를 첨가한 결과, Fe(III) 또는 Al(III)를 각각 단독으로 사용하였던 경우에 비하여 제거 가능한 pH 범위가 더욱 더 확대되었다. 이 현상은 zeta potential 의 증가 및 공침효과의 상승요인으로 추측되었다. $NO_3^-$, $SO_4^{2-}$, $Na^+$, $Ca^{2+}$를 첨가하여 외부이온의 영향을 관찰하였으며, $SO_4^{2-}$가 0.1M 함유된 코발트용액을 Fe(III) 및 Al(III)를 사용하여 처리한 결과 제거효율은 99%를 나타내었다.

• 한국결정성장학회지
• /
• 제24권6호
• /
• pp.256-260
• /
• 2014

본 연구는 코발트 코팅 두께에 따른 점토 표면과의 반응성을 연구하였다. 시편에서 표면으로 부터 일정한 두께로 코발트가 확산된 것을 볼 수가 있으며, 황화코발트의 도포양과 함께 청자토보다 백자토에서 확산층의 두께가 증가하였다. 백자토에 코팅된 시편은 grayish blue가 blue 색으로 변화되는 것을 알 수 있으며 $L^*$값이 51.78에서 37.61로 감소하고, 청자토에 코팅된 시편인 경우 dark olive gray에서 dark gray색으로 $L^*$값이 53.91에서 38.93로 적어지는 것을 알 수가 있다. 시편의 물성 평가는 XRD, SEM, 열팽창기, TG-DTA, UV-vis spectrophotometer와 HRDPM을 이용하였다.

• 한국표면공학회지
• /
• 제53권6호
• /
• 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.