• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 13th KACG Technical Meeting `97 Industrial Crystallization Symposium(ICS)-Doosan Resort, Chunchon, October 30-31, 1997
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• pp.123-127
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• 1997

Various recrystallization techniques has been applied to control morphology and size of NTO(3-nitro-1, 2, 4-triazole-5-one) crystals. With cooling method, it was found that the size of NTO at aqueous solution was controlled in the range of 5 to 500 $\mu\textrm{m}$. The spherical or cubic shapes of particles were obtained by adjusting operating conditions. Hexagonal and cubic shaped crystals of NTO were also obtained by sonication and evaporative method using aqueous solution of NTO. Their particle sizes were ranged 20 to 30 $\mu\textrm{m}$. In gas anti-solvent method with NTO/DMF and NTO/DMSO solutions, cubic type of NTO was obtained and the range of their sizes was 0.5-2$\mu\textrm{m}$.

• 한국세라믹학회지
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• 제33권10호
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• pp.1089-1094
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• 1996

In this study the formation mechanism of AlN synthesized by SHS(Self-propagating high-temperature Syn-thesis) was studied in order to obtain uniform AlN powder size and morphology. Based on the morphology of AlN synthesized and the calculation of the temperature of Al powder as a function AlN layer thickness the formation mechanism of AlN was proposed.

• Bulletin of the Korean Chemical Society
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• 제33권5호
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• pp.1699-1702
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• 2012

$TiO_2$ nanostructures with various morphologies like cubes, spheres, hexahedral pillars and spherical tubes were synthesized by microwave-assisted hydrothermal process. Each structure was obtained by changing the relative concentrations of titanium tetraisoproxide (TTIP), tetrabutylammonium hydroxide (TBAH) and ethanol. Scanning electron microscopy (SEM), transmission electoron microscopy (TEM), X-ray diffraction and Brunauer-Emmett-Teller (BET) surface area analysis were used to characterize the synthesized $TiO_2$ nanostructures. From these results, it has been proved that $TiO_2$ structure could be controlled to have specific morphology, size, surface area, pore volume and pore size distribution.

• KSBB Journal
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• 제27권4호
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• pp.237-242
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• 2012

In this study, zein microparticles and drug-loaded zein microparticles were prepared using supercritical ASES technique. The effects of operating parameters on particle size and morphology were investigated. ASES-processed zein microparticles consisted of agglomerates of very fine unit particles. As temperature increased, the size of unit particles increased and their morphology became more spherical. The addition of water to the solvents for zein resulted in the formation of more spherical microparticles. The release characteristics of drug-loaded zein microparticles were also studied.

• Bulletin of the Korean Chemical Society
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• 제32권3호
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• pp.943-946
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• 2011

The electronic absorption and surface morphology evolution of two types of molecular double layer thin films, copper phthalocyanine (CuPc) layer deposited on chloro[subphthalocyaninato]boron(III) (SubPc) layer, denoted as SubPc/CuPc, and vice versa, with various thicknesses were investigated using ultraviolet (UV)-visible spectroscopy and atomic force microscopy (AFM). Both types of double layer structures showed similar broadened absorption patterns in the UV-visible region that were consistent with the fitted spectra following simple linear combination of the single layer absorption spectra of the two materials. In contrast, the surface morphology of double layer structures was dependent on the order of deposition. For the CuPc/SubPc structures, surface morphology was characterized by elongated grains, which are characteristic of SubPc thin films, indicating that the morphological influence of the underlying CuPc layer on the subsequent SubPc layer was not large. For the SubPc/CuPc structures, however, the underlying SubPc layer acted as a morphological template for the subsequently deposited CuPc layer. It was also observed that the grain size of the CuPc layer varied according to the thickness of the underlying SubPc layer.

• 한국광물학회지
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• 제11권2호
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• pp.126-134
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• 1998

Surface site and areas of particles are geometrically calculated for the cubic structures to investigate how the surface sites vary with the variation of morphology and particle size. The numbers of surface site and area become smaller when the particles become equi-dimensional shape. The ratios of surface site to surface area are almost constant except the case of anion of fluorite structure. The ratios of the number of surface site to area are almost constant regardless of particle size except the size of up to 5 to 10 times of the unit cell dimension. This quantification method can be used to obtain data related to the surface reaction.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 춘계학술발표회논문집(2)
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• pp.123-128
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• 1997

The effects of heat treatment on fatigue crack growth rates (FCGRs) of Inconel 690 have been investigated in terms of carbide morphology and grain size. Cycling tests in air at room temperature have shown that FCGR in low stress intensity factor range (ΔK) region can be effectively reduced by increasing the grain boundary carbide precipitate size and grain size. Decrease in FCGR is attributed to the crack tip blunting at the precipitates of grain boundary chromium carbides.

• Macromolecular Research
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• 제17권6호
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• pp.397-402
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• 2009

In emulsifier-free, emulsion polymerization with ionizable comonomer, the ionization of the comonomer is critical in determining the size of the final polymerie particles at sub-micrometer scale. In this study, polystyrene latex beads with carboxylates on the surface were synthesized using acrylic acid as a comonomer. Specifically, ammonium hydroxide was added to the emulsifier-free polymerization system to promote the ionization of acrylic acid by increasing pH. Smaller polystyrene latex particles were produced by increasing the ammonium hydroxide concentration in the reaction system, due to the enhanced stability promoted by the ionization of acrylic acid during the nucleation step. In addition, the surface morphology of the polystyrene latex particles was controlled by the concentration of acrylic acid, the dissociation of which was influenced by the ammonium hydroxide concentration.

• 한국분말재료학회지
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• 제11권6호
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• pp.477-485
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• 2004

Monodispersed flaky silver powder was obtained by controlling the ratios of $H_{2}O_{2}/NH_{3}$ and Agin in a mixed solution of ethylene glycol and ammonia with an addition of PVP. The effects of $NH_{3}/Ag,\; H_{2}O_{2}/Ag\;and\;H_{2}PtCl_{6}/Ag$ on its morphology and size were investigated. In $H_{2}O_{2}-NH_{3}-AgNO_{3}\;system,\;NH_{3}/Ag$ molar ratio was found to be an important reaction factor for the nucleation and crystal growth of Ag powder. The synthesis of flaky powder was optimized at over 6 of $NH_{3}/Ag \;and\;5\;of\;H_{2}O_{2}/Ag\;under\;1.0{\times}10^{-3}\;of\;Pt/Ag.\;Moreover,\;as\;the\; NH_{3}/Ag$ molar ratio increased, the size of precipitates was increased regardless of the amount of Pt. In the absence of $H_{2}PtCI$, the morphology and size of reduced Ag powder were found to be irregular in shape $2-4{\mu}m$ in diameter. However, homogenized fine Ag powder was obtained due to heterogeneous nucleation when $H_{2}PtCI$ used as a cat-alyst, and flaky one was synthesized with the addition of Pt over $1.0{\times}10^{-3}$ of Pt/Ag.

• 한국재료학회지
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• 제22권2호
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• pp.78-81
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• 2012

$Y_2O_3$ nanomaterials have been widely used in transparent ceramics and luminescent devices. Recently, many studies have focused on controlling the size and morphology of $Y_2O_3$ in order to obtain better material performance. $Y_2O_3$ powders were prepared under a modified solvothermal condition involving precipitation from metal nitrates with aqueous ammonium hydroxide. The powders were obtained at temperatures at $250^{\circ}C$ after a 6h process. The properties of the $Y_2O_3$ powders were studied as a function of the solvent ratio. The synthesis of $Y_2O_3$ crystalline particles is possible under a modified solvothermal condition in a water/ethylene glycol solution. Solvothermal processing condition parameters including the pH, reaction temperature and solvent ratio, have significant effects on the formation, phase component, morphology and particle size of yttria powders. Ethylene glycol is a versatile, widely used, inexpensive, and safe capping organic molecule for uniform nanoparticles besides as a solvent. The characterization of the synthesized Y2O3 powders were studied by XRD, SEM (FE-SEM) and TG/DSC. An X-ray diffraction analysis of the synthesized powders indicated the formation of the $Y_2O_3$ cubic structure upon calcination. The average crystalline sizes and distribution of the synthesized $Y_2O_3$ powders was less than 2 um and broad, respectively. The synthesized particles were spherical and hexagonal in shape. The morphology of the synthesized powders changed with the water and ethylene glycol ratio. The average size and shape of the synthesized particles could be controlled by adjusting the solvent ratio.