• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.434-438
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• 2013

Monodispersed 3Y-$ZrO_2$ spherical agglomerates were synthesized by thermal hydrolysis process followed by crystallization processes (hydrothermal treatment and calcination). The crystallization process affected the properties of the final particles, such as the primary particle size, the agglomeration state, and the fraction of $ZrO_2$ monoclinic phase. The hydrothermal treated spherical particles were porous microstructures (weak agglomerates) composed of small primary particles with a size of 14 nm, but the calcined spherical particles had a dense microstructure due to the hard aggregation between primary particles. While the calcined particles had a low green density due to the hard aggregation, hydrothermal treated ones were soft agglomerates and had a deflection point at 50 MPa due to the rearrangement of secondary spherical particles and the filling of the interstices with the primary particles. Finally, the green density of hydrothermally treated $ZrO_2$ particles was 58% at 200 MPa.

• Journal of Information Display
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• v.2 no.4
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• pp.57-62
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• 2001

Green-emitting $Zn_2SiO_4$:Mn phosphor particles having a spherical shape and high luminescence intensities under VUV were prepared by spray pyrolysis process under severe preparation conditions. The type of precursor solutions affected the morphology and luminescence characteristics of the prepared particles. The particles prepared from the clear solution by laboratory-scale process had spherical shape and dense morphology, while the particles prepared from the severe preparation conditions had rough surface and collapsed structure. However, the particles prepared from the colloidal solution utilizing fumed silica were spherical in shape and filled morphology at the severe preparation conditions of high flow rate of carrier gas, high concentration of solution, and large reactor size. The prepared $Zn_2SiO_4$:Mn phosphor particles with complete spherical shape had higher photoluminescence intensity than that of the commercial product prepared by solid state reaction.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.426-427
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• 2006

Mono-sized silicon particles were effectively fabricated by a novel way named pulsated orifice ejection method (POEM). The particles are with very narrow particles size distribution and very small standard deviation of mean particle size. There are two different types spherical silicon particles were found. One consists of many grains mainly in random boundaries. The other consists of two or three grains with only twin orientation relationships, even single crystal in cross-section was also found within this type of spherical silicon particles.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.1060-1062
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• 2002

Spherical and dense BAM phosphor particles were prepared by spray pyrolysis. The key idea of dense BAM particles is to lead gelation in droplets, which was successfully achieved by using the aluminum polycation as the precursor solution for the spray pyrolysis. The BAM phosphor particles prepared by spraying the aluminum polycation solution have completely spherical shape and dense structure. When directly applied to make phosphor film on the glass by the screen-printing method, the prepared spherical BAM phosphor particles showed better packing density and surface morphology than that of commercial one, which has irregular shape and large particle size. It was also found that the thermal degradation in the photoluminescence intensity for dense and spherical BAM particles was less than that of commercial one.

• Journal of Institute of Convergence Technology
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• v.3 no.1
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• pp.45-49
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• 2013

Spherical active carbon materials have been used for the removal of pollutants in the area of food processing, water treatment, air purification, oral administration. Moreover, they are now expected to make an epoch in the areas of electronics, life science, environmental technology, and so on due to their superior physical properties. Carbon particles should be requested for the edgeless spherical shapes in order to minimize the loss due to the abrasion during the process and/or practical use, but the carbon particles manufactured from petroleum-based pitch do not meet these needs. Nowadays, thus, the spherical active carbon particles carbonized from various spherical polymer beads are studied with thermoplastic and/or thermosetting polymers. In this paper, the synthesis of spherical phenolic beads and furan beads, which are thermosetting polymers, and their carbonization techniques are examined.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.631-635
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• 2011

Spherical and non-spherical silica particles prepared by the direct oxidation were studied for the effect of the particle size and shape of these particles on oxide CMP removal rate. Spherical silica particles, which have 10~100 nm in size, were prepared by the direct oxidation process from silicon in the presence of alkali catalyst. The 10 nm silica particles were aggregated by addition of an acid, an alcohol, or a silane as an aggregation inducer between the particles. Two or more aggregated silica particles were used as a seed to grow non spherical silica particles in the direct oxidation process of silicon in the presence of alkali catalyst. The oxide removal rate of spherical silica particles increased with increasing an average particle size for spherical silica abrasives in the oxide CMP. It further increased non-spherical particles, compared with the spherical particles in the similar average particle size.

• Korean Journal of Materials Research
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• v.16 no.2
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• pp.123-128
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• 2006

[ $BaMgAl_{10}O_{19}:Mn^{2+}$ ](BAM:Mn) phosphor particles with spherical shape were prepared by spray pyrolysis from colloidal solution with silica. The phosphor particles prepared by spray pyrolysis from aqueous solution had irregular morphology after high temperature post-treatment. On the other hand, the phosphor particles prepared from spray solution with colloidal silica had spherical shape after post-treatment. Colloidal silica used as additive improved the spherical shape and filled morphology of the precursor particles prepared by spray pyrolysis. The precursor particles with filled structure produced the BAM:Mn phosphor particles with spherical shape and non-aggregation characteristics after post-treatment at $1400^{\circ}C$ under reducing atmosphere. The phosphor particles prepared from colloidal solutions formed the crystal structure of BAM:Mn phosphor irrespective of the silica contents. The BAM:Mn phosphor particles prepared from aqueous and colloidal solutions had similar photoluminescence intensities under vacuum ultraviolet.

• Korean Journal of Materials Research
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• v.15 no.8
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• pp.496-502
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• 2005

Green-light emitting $BaMgAl_{10}O_{19}:Mn^{2+}$ (BAM:Mn) phosphor particles were prepared by spray Pyrolysis. The effect of reactor temperature and flow rate of carrier gas in the spray Pyrolysis on the morphology, crystallinity and photoluminescence characteristics under vacuum ultraviolet were investigated. The morphology of the as-Prepared Particles obtained by spray Pyrolysis had spherical shape and non-aggregation characteristics regardless of the reactor temperature. The spherical shape of the as-prepared Particles obtained by spray pyrolysis at low temperature disappeared after Post-treatment. On the other hand the as-Prepared Particles obtained by spray Pyrolysis at $1600^{\circ}C$ maintained spherical shape and non-aggregation characteristics after post-treatment at $1400^{\circ}C$ for 3 h under reducing atmosphere. The BAM:Mn Phosphor Particles Prepared by spray Pyrolysis at different reactor temperatures had pure crystal structure and high photoluminescence intensities under vacuum ultraviolet after post-treatment. BAM:Mn phosphor particles prepared by spray Pyrolysis at low How rate of carrier gas had complete spherical shape and filed morphology and high photoluminescence intensity after post-treatment under reducing atmosphere.

• Tribology and Lubricants
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• v.11 no.5
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• pp.1-9
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• 1995

The mechanism of various spherical particles formation from wide range of tribo-systerns is suggested and deduced by the action of micro-explosion on the basis of the thermally-activated wear theory, in which the flash temperature at contact could be reached clearly upto the material molten temperature due to the secondary activation energy from the exothermic reactions involving lubricant thermo-decomposition, metals oxidation, hydrogen reactions and other possible complex thermo-reactions at the contacts. Various shapes of spherical particles generated from the tribosystem can be explained by the toroidal action of micro-explosion accompanied with the complex thermo-chemical reactions at the contact surfaces or sub-surfaces.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.1
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• pp.11-17
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• 2007

The spherical NiZn ferrite particles were prepared by ultrasonic spray pyrolysis with mixed solution of aqueous metal nitrates. The NiZn ferrite particle was observed with nano-sized primary particles of about 10 nm or less before annealing which represented as paramagnetic behavior measured at 77 K and room temperature. The typical abnormal growth of primary particles like polyhedral primary particles was observed by annealing at 1273 K with Zn-concentration dependency. The XRD patterns showed good crystallinity of NiZn ferrite powder after annealing. In annealing process, the intra-particle sintering phenomenon was observed and the spherical particle morphology was collapsed at 1673 K. The saturation magnetization of NiZn ferrite powder for each annealing temperature was decreased with measuring temperature of $77{\sim}$300K.