• Resources Recycling
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• v.20 no.3
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• pp.55-61
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• 2011

In order to develop economical production process from metallurgical grade silicon(MG-Si) to solar grade(SOG-Si), removal of boron by slag treatment was investigated at 1823 K using CaO-$SiO_2$ based slags. In the present study boron removal ratio in CaO-$SiO_2$ stags and $CaCO_3-SiO_2$ slags were increased to 63% and 73% respectively with slag basicity (%CaO/$%SiO_2$). However, bubbling time with Ar gas of slag and metal was not affected on removal ratio of boron. The addition of $Na_2CO_3$ to CaO-$SiO_2$ slags did not improve the removal ratio of boron from molten silicon. Boron contend was decreased from 20.6 ppm to 1.03 ppm by three times treatment using $CaCO_3-SiO_2$ slag (basicity=1.2).

• Journal of Powder Materials
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• v.21 no.5
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• pp.377-381
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• 2014

This work describes the coloration, chemical stability of $SiO_2$ and $SnO_2$-coated blue $CoAl_2O_4$ pigment. The $CoAl_2O_4$, raw materials, were synthesized by a co-precipitation method and coated with silica ($SiO_2$) and tin oxide ($SnO_2$) using sol-gel method, respectively. To study phase and coloration of $CoAl_2O_4$, we prepared nano sized $CoAl_2O_4$ pigments which were coated $SiO_2$ and $SnO_2$ using tetraethylorthosilicate, $Na_2SiO_3$ and $Na_2SiO_3$ as a coating material. To determine the stability of the coated samples and their colloidal solutions under acidic and basic conditions, colloidal nanoparticle solutions with various pH values were prepared and monitored over time. Blue $CoAl_2O_4$ solutions were tuned yellow color under all acidic/basic conditions. On the other hand, the chemical stability of $SiO_2$ and $SnO_2$-coated $CoAl_2O_4$ solution were improved when all samples pH values, respectively. Phase stability under acidic/basic condition of the core-shell type $CoAl_2O_4$ powders were characterized by transmission electron microscope, X-ray diffraction, CIE $L^*a^*b^*$ color parameter measurements.

• Korean Journal of Materials Research
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• v.7 no.7
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• pp.587-591
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• 1997

RBS와 XRD를 이용하여 C o-Nb이중층 실리사이드와 구리 배선층간의 열적안정성에 관하여 조사하였다. Cu$_{3}$Si등의 구리 실리사이드는 열처리시 40$0^{\circ}C$정도에서 처음 형성되기 시작하였는데, 이 때 형성되는 구리 실리사이드는 기판의 상부에 존재하던 준안정한 CoSi의 분해시에 발생한 Si원자와의 반응에 의한 것이다. 한편, $600^{\circ}C$에서의 열처리 후에는 CoSi$_{2}$층을 확산.통과한 Cu원자와 기판 Si와의 반응에 의하여 CoSi$_{2}$/Si계면에도 구리 실리사이드가 성장하였는데, 이렇게 구리 실리사이드가 CoSi$_{2}$/Si 계면에 형성되는 것은 Cu원자의 확산속도가 여러 중간층에서 Si 원자의 확산속도 보다 더 빠르기 때문이다. 열처리 결과 최종적으로 얻어진 층구조는 CuNbO$_{3}$/Cu$_{3}$Si/Co-Nb합금층/Nb$_{2}$O$_{5}$CoSi$_{2}$/Cu$_{3}$Si/Si이었다. 여기서 상부에 형성된 CuNbO$_{3}$는 Cu원자가 Nb$_{2}$O$_{5}$및 Co-Nb합금층과 반응하여 기지조직의 입계에 석출되어 형성된 것이다.

• Korean Journal of Materials Research
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• v.13 no.9
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• pp.572-580
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• 2003

Synthesizing behavior and microstructural evolution of $CaZrO_3$and $m-ZrO_2$in a thermal reaction process of $ZrSiO_4$-$xCaCO_3$mixtures, where x is 7 and 19, were investigated to determine the addition amount of CaO in CaO:$ZrO_2$:$SiO_2$ternary composition. CaZrO$_3$-Ca$_2$SiO$_4$precursor prepared by the mixture of $ZrSiO_4$and CaCO$_3$in aqueous suspending media was controlled to the acidic (pH=4.0) condition with HCI solution to enhance the thermal reaction. The addition amount of dispersant into the $ZrSiO_4$-$xCaCO_3$slip increased with increasing mole ratio of $CaCO_3$, which was associated with the viscosity of slip. Decarbonation reaction was activated with an increase of the addition amount of $CaCO_3$, showing different final temperatures in $ZrSiO_4$-$7CaCO_3$and $ZrSiO_4$-$19CaCO_3$mixtures as about 980 and 116$0^{\circ}C$, respectively, for finishing decarbonation reaction. The grain morphology was changed to spherical shape for all samples with an increase of sintering temperature. The grain size and phase composition of the synthesized composites depended on the mixture ratio of Zrsi04 and CacO3 powders, indicating that the main crystals were m-ZrO2 ($\leq$3 $\mu\textrm{m}$) and $CaZrO_3$ ($\leq$ 7 $\mu\textrm{m}$) in $ZrSiO_4$$>-7CaCO_3$and $ZrSiO_4$-$19CaCO_3$mixtures, respectively.

• Journal of the Korean Society of Safety
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• v.21 no.2 s.74
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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.

• Korean Journal of Materials Research
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• v.6 no.12
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• pp.1192-1198
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• 1996

배선 재료나 salicide 트랜지스터에 적용될 것으로 기대되는 Cu 배선과 Co 단일층 및 Co/Ti 이중층을 사용하여 형성된 코발트 실리사이드간의 열적 안정성에 대하여 조사하였다. 40$0^{\circ}C$열처리후 Cu3Si 막이 CoSi2층과 Si 기판 사이에 형성되었는데, 이것은 Cu 원자의 확산에 기인한 것이다. $600^{\circ}C$에서의 열처리 후에 형성된 최종막의 구조는 각각 Cu/CoSi2/Cu3Si/Si과 TiO2/Co-Ti-Si 합금/CoSi2/Cu3Si/Si였으며, 상부에 형성된 TiO2층은 산소 오염에 의한 것으로 밝혀졌다.

• 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.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1338-1342
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• 2005

We have synthesized an $Eu^{2+}$-activated $Sr_3MgSi_2O_8$ blue phosphor and $Ba_2SiO_4$ green phosphor and $Ba^{2+}$ co-doped $Sr_3SiO_5$ red phosphor investigated an attempt to develop white LEDs by combining it with a GaN blue LED $chip(\lambda_{em}=405 nm)$. Three distinct emission bands from the GaN-based LED and the $(Sr_3MgSi_2O_8:Eu\; +\; Ba_2SiO_4:Eu\; +\; Ba^{2+}\; co-doped\; Sr_3SiO_5:Eu)$ phosphor are clearly observed at 460nm, 520 nm and at around 600 nm, respectively. These three emission bands combine to give a spectrum that appears white to the naked eye. Our results show that GaN (405 nm chip)-based $(Sr_3MgSi_2O_8:Eu\; +\; Ba_2SiO_4:Eu\; +\; Ba^{2+}\; co-doped\; Sr_3SiO_5:Eu) exhibits a better luminous efficiency than that of the industrially available product InGaN (460 nm chip)-based YAG:Ce.

• Journal of Korean Ophthalmic Optics Society
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• v.5 no.1
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• pp.49-53
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• 2000

Sodium borate silicate glass of composition $10Na_2O-39B_2O_3-50SiO_2-CoO$ and $20Na_2O-14B_2O_3-65SiO_2-CoO$ were prepared by melting oxide mixtures in alumina crucible at $1210^{\circ}C$ in an electric furance in air for 2h, and then quenching in air. The dielectric behavior of the quenched glasses are the subject of the present work. Properties such as dielectric constant and resistivity as a function frequency and temperature are reported. From the dielectric spectra, the glass phase transition temperature has been found to decrease at a rate $Na_2O$ 20 mol% and the dielectric constants increase with increasing $Na_2O$ content. The frequency dependent resistivity response of glass exhibits a non-Debye type relaxation.

• Journal of Electrochemical Science and Technology
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• v.8 no.2
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• pp.101-106
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• 2017

$Li_2SiO_3$ was used as a coating material to improve the electrochemical performance of $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$. $Li_2SiO_3$ is not only a stable oxide but also an ionic conductor and can, therefore, facilitate the movement of lithium ions at the cathode/electrolyte interface. The surface of the $Li_2SiO_3$-coated $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$ was covered with island-type $Li_2SiO_3$ particles, and the coating process did not affect the structural integrity of the $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$ powder. The $Li_2SiO_3$ coating improved the discharge capacity and rate capability; moreover, the $Li_2SiO_3$-coated electrodes showed reduced impedance values. The surface of the lithium-ion battery cathode is typically attacked by the HF-containing electrolyte, which forms an undesired surface layer that hinders the movement of lithium ions and electrons. However, the $Li_2SiO_3$ coating layer can prevent the undesired side reactions between the cathode surface and the electrolyte, thus enhancing the rate capability and discharge capacity. The thermal stability of $Li[Ni_{0.8}Co_{0.15}Al_{0.05}]O_2$ was also improved by the $Li_2SiO_3$ coating.