• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.4
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• pp.395-400
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• 2011

Scanning Probe Lithography is a method to localized oxidation on single crystal silicon wafer surface. This study demonstrates nanometer scale non contact lithography process on (100) silicon (p-type) wafer surface using AFM(Atomic force microscope) apparatuses and pulse controlling methods. AFM-based experimental apparatuses are connected the DC pulse generator that supplies ultra short pulses between conductive tip and single crystal silicon wafer surface maintaining constant humidity during processes. Then ultra short pulse durations are controlled according to various experimental conditions. Non contact lithography of using ultra short pulse induces electrochemical reaction between micro-scale tip and silicon wafer surface. Various growths of oxides can be created by ultra short pulse non contact lithography modification according to various pulse durations and applied constant humidity environment.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.5
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• pp.350-355
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• 2000

The fabrication of sapphire wafer in C plane has been developed by horizontal Bridgeman method and GaN based semiconductor epitaxial growth has been carried out in metal organic chemical vapour deposition. The single crystalline ingot of sapphire has been utilized for 2 inch sapphire wafers and wafer slicing and lapping machines were designed. These several steps of lapping processes provided the mirror-like surface of sapphire wafer. The measurements of the surface flatness and the roughness were carried out by the atomic force microscope. The GaN thin film growth on the developed wafer was confirmed the wafer quality and applicability to blue light emitting devices.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.18 no.5
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• pp.184-190
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• 2008

$CaMoO_4$ crystals with ellipsoid, peanut, dumbbell, and notched sphere shapes were synthesized using a simple precipitation reaction. The morphology of $CaMoO_4$ crystals evolved from ellipsoids, through peanut-like structures and dumbbells, to notched spheres with increasing the concentration of $Ca^{2+}$ and $MoO_4^{2-}$ ions. This morphology evolution of $CaMoO_4$ crystals is attributed to a fractal mechanism. Branched crystal growth started at both ends of the ellipsoids. The peanut-like and dumbbell morphologies were formed by the first and second fractal growths, respectively. Finally, the notched spheres were formed by further fractal growth of dumbbells.

• Journal of Industrial Technology
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• v.40 no.1
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• pp.25-32
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• 2020

In this study, the effects of thermodynamic hydrate inhibitors on hydrate formation and dissociation behaviors were identified. The nucleation and growth of CP hydrate in the presence of methanol were monitored by optical microscope. Cyclopentane was used to demonstrate the oil phase in the pipeline in this study. Hydrate morphology, required time for hydrate formation, hydrate dissociation temperature were also identified by experiments. With the addition of methanol in water solution, the hydrate nucleation as well as hydrate growth were delayed. Moreover, hydrate morphology was also varied with the addition of methanol. Hydrate formation and dissociation temperature also decrease as the concentration of methanol increases.

• Applied Chemistry for Engineering
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• v.2 no.2
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• pp.97-107
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• 1991

Highly-siliceous dealuminated zeolite, silicalite(end member of ZSM-5) was synthesized from a batch composition of 2.55 $Na_2O-5.0$ TPABr-$100SiO_2-2800H_2O $ at $180^{\circ}C$ and at times ranging from one to seven days of reaction time. Autoclaves containing the synthesis mixture were centrifuged within the specially-equipped convection oven to provide an elevated gravitational force field like 30 and 50 G. Tests were also conducted at normal gravity. For synthesis performed under elevated gravities, average and maximum crystal sizes were substantially greater than those synthesized under normal gravity and product yields were also found to be affected by elevated gravity ; that is, product yields were substantially enhanced under elevated gravity from 4 % to 55 % with respect to normal gravity. The average crystal sizes of silicalite synthesized at normal gravity were 50 to $70{\mu}m$ over an entire range of reaction time, one to seven days while the average crystal sizes synthsized under elevated gravities, 30 and 50 G, were 160 to $190{\mu}m$ respectively. For the elevated gravity, in particular, two separate nucleations and growths were observed. For examples, at 50G, large crystals of $200{\mu}m$ were produced through the second growing stage after 5 days of reaction following the rapid first growing stage where fairly large crystals of $135{\mu}m$ were produced only in 2 days of reaction. The maximum crystal sizes obtained through the above two growing stages were 190 and $300{\mu}m$, respectively. A discussion of how elevated gravity affects nucleation, growth, yield and crystal size of silicalite is presented.