• Progress in Superconductivity
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• v.5 no.1
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• pp.65-69
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• 2003

Many researches on fabrication process for BSCCO precursor powders have been developed for high J$_{c}$ BSCCO-2223 tape. Spray pyrolysis method for fabrication of precursor powder has many advantages, such as high purity, fine particle size and low carbon content of BSCCO precursor powder. Fine, spherical powders were prepared by ultrasonic spray pyrolysis from the aqueous solution of metal nitrates. BSCCO precursor powders were synthesized with various solutes concentration and heat treatment conditions. Average particle size for spray pyrolysis powders was $1.5∼3\mu\textrm{m}$. Bi-2223/Ag tape was prepared by PIT method and followed by various sintering conditions. BSCCO precursor powders were characterized by XRD, SEM, EDS, Carbon content and particle size analysis.s.

• Journal of the Korean Ceramic Society
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• v.27 no.8
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• pp.1064-1070
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• 1990

ZrO2 fine powders were prepared by hydrolysis, adding 0.1, 0.2, 0.3, 0.4, 0.5, 0.6mol/1H2O/ethanol to 0.1 mol/l Zr(OC3H7)4/ethanol. When hydrolized by adding 0.1mol/l Zr(OC3H7)4/ethanol to 0.1, 0.2mol/l H2O/ethanol., spherical monodispersed ZrO2 fine powders were obtained. And in this condition average sizes were about 0.5, 0.3${\mu}{\textrm}{m}$, respectively. The more H2O/ethanol concentration increased, the more the particle size decreased and the particles were agglomerated strongly. Prepared powders were amorphous and hydrates. The calcined powders with 43$0^{\circ}C$ and 100$0^{\circ}C$ were showed tetragonal and monoclinic phase, respectively.

• Journal of the Korean Ceramic Society
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• v.28 no.3
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• pp.205-214
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• 1991

Calcium carbonate fine powders were synthesized by blowing CO2 gas in CaO or Ca(OH)2 suspension, and the shapes of powders obtained were examined for each synthetic condition. When water was used as a solvent, ultrafine calcite powders with the average size of∼0.03$\mu\textrm{m}$ were obtained. When synthesized using methanol as a solvent, amorphous phase and spherical vaterite phase were obtained by suction filtering and non-filtering, respectively. Reaction did not occured in ethanol medium, but spherical vaterite phase was obtained by adding ethylene glycol in ethanol.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.4
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• pp.47-53
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• 2002

In this study, two different (NiCuZn)-ferrite which were fabricated by using ultra-fine powders synthesized by the wet processing and conventionally commercialized powder, were investigated and compared each other in terms of the low temperature sintering and electromagnetic properties. Composition of x and w in $(Ni_{0.4-x}Cu_xZn_{0.6})_{1+w}(Fe_2O_4)_{1-w}$ were controlled as 0.2 and 0.03, respectively. The sintering temperature were $900^{\circ}C$ for ultra-fine powders by way of initial heat treatment and $1150^{\circ}C$ for commercialized powders. The (NiCuZn)-ferrite by ultra-fine powders showed love. sintering temperature than that of commercialized powders by over $200^{\circ}C$, and excellent electromagnetic properties such as the quality factor which is a important factor in the multi-layered chip inductor. In addition, characteristics of B-H hysteresis, crystallinity, microstructure and powder morphology were analyzed by a vibrating sample method(VSM), x-ray diffractometer(XRD), transmission electron microscope (TEM) and scanning electron microscope(SEM).

• Korean Journal of Materials Research
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• v.18 no.3
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• pp.137-142
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• 2008

Blue-emitting BAM:Eu phosphor powders were formed by post-treatment of precursor powders with hollow or dense morphologies. The morphologies of the precursor powders obtained by spray pyrolysis were controlled by changing the preparation conditions and by changing the type of spray solution. The effects of the morphologies of the precursor powders on the characteristics of the BAM : Eu phosphor powders reacted with $AlF_3$ flux were investigated. Precursor powders with a spherical shape and a hollow morphology produced BAM : Eu phosphor powders with a plate-like morphology, a fine size and a narrow size distribution. On the other hand, precursor powders with a spherical shape and dense morphology produced BAM : Eu phosphor powders with a plate-like morphology and a large size. $AlF_3$ flux improved the photoluminescence intensities of the BAM : Eu phosphor powders. The photoluminescence intensity of the fine-sized BAM : Eu phosphor powders with a plate-like morphology was 90% of the commercial product under vacuum ultraviolet conditions.

• Journal of the Korean Ceramic Society
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• v.26 no.4
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• pp.532-538
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• 1989

The properties and sinterabilities of the ZrO2-3m/oY2O3 powders prepared by coprecipitation were investigated. The specific surface area and the total proe volume were decreased with the increasing pH of the sediments. The partially stabilized zirconia powders were fine powders with high specific surface area. The powders prepared by freeze drying method showed low tendency for agglomeration, and the powders obtained from spray drying method showed fine powders and narrow pore size distribution. At 140$0^{\circ}C$, their relative densities were up to 96%.

• Korean Journal of Materials Research
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• v.15 no.3
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• pp.166-171
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• 2005

Fe-6Al-9Si(N) alloy powders were synthesized by hybrid process of chemical nitrification and mechanical milling. The nitriding treatment on Fe-6Al-9Si alloy powders formed $\gamma'-Fe_4N$ phase on the powders surface. The nitriding-treated powders were pulverized by horizontal high-energy ball milling machine. The longer ball milling time tended to reduce the size of alloy powders. In ball milling for 36h, extremely fine powders with about $7\~9wt\%$ nitrogen were obtained. Through X-ray diffraction analysis on the powders, it was found out that the longer milling time caused a disappearance of the crystallinity of $\alpha-Fe$ in the powders. TEM study confirmed that the powders is comprised of a few tens nano-meter sized crystals, including $\alpha-Fe$ phase with partially $\gamma'-Fe_4N$ phase. Hysteresis curves of the synthesized powders measured by VSM revealed lower saturation magnetization and higher coercivity, which seemed to be attributed to nitrogen-impregnation and severe residual stress developed during the high energy milling. Microstructure observation on the powder annealed at 873 K for 1 h showed 10 to 20 nm sized $\alpha-Fe$ crystal. Such a enhanced crystallinity significantly increased the magnetization and decreased the coercivity, which was attributed to not only the crystallinity but also residual stress relaxation.

• Journal of the Korean Ceramic Society
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• v.28 no.7
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• pp.503-508
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• 1991

High pure and fine mullite powders were synthesized from Al-secbutoxide[Al(OC4H9)3] and TEOS[Si(OC2H5)4] (SiO2/Al2O3=2/3 mole). Sol-Gel process by partial hydrolysis technique, as it were, first, TEOS was partially hydrolysized and then mixed with Al-secbutoxide for complete hydrolysis was used. The mullite precursor was synthesized within 30 hrs, which was reduced about a half of synthetic time in comparison with the other's study. Al-Si spinel was formed at 980℃ and mullite crystal was formed at 1200℃. Mullite powders synthesized in this study was spherical type like those of the other studies and particle sizes were very fine. Also mullite powders calcined at 1,600℃ had a stoichiometric composition (3Al2O3·2SiO2) and lattice constants were coincided with known theoretical values.

• Journal of Powder Materials
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• v.22 no.4
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• pp.260-265
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• 2015

Spherical fine cobalt powders were fabricated by new liquid reduction method. Commercial cobalt sufate heptahydrate was used as raw material. Also ethylene glycol was used as solvent and hydrazine-sodium hypophosphite mixture was used as reduction agent for the new liquid reduction method. A plate shaped cobalt powders with an approximately 300 nm were prepared by a traditional wet ruduction method using distilled water as solvent and hydrazine. Spherical fine cobalt powders with an average size of $1-3{\mu}m$ were synthesized by a new liquid reduction method in 0.3M cobalt sulfate and 1.5M hydrazine-0.6M sodium hypophosphite mixture at 333K.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.10a
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• pp.99-102
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• 2003

Many researches on synthesis process for BSCCO precursor powders have been developed for high J$_{c}$ BSCCO-2223/Ag tape. Spray pyrolysis method for fabrication of precursor powder has many advantages, such as high purity, fine particle size of BSCCO precursor powder. Fine, spherical powders were prepared by ultrasonic spray pyrolysis from the aqueous solution of metal nitrates. BSCCO precursor powders were synthesized with 0.1 M concentration and heat treatment conditions. Average particle size for spray pyrolysis powders was 1.5 ~ 3 ${\mu}{\textrm}{m}$. BSCCO -2223/Ag tape was prepared by PIT method and followed by various sintering conditions. The critical current density of BSCCO-2223/Ag tape sintered in low oxygen partial pressure was ~ 23 kAcm$^{-2}$.