• Korean Journal of Materials Research
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• v.22 no.12
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• pp.706-710
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• 2012

The growing conditions of barium nitrate $Ba(NO_3)_2$ single crystals using the aqueous solution method have been studied. Supersaturation can be calculated by measuring the temperature of the solution and its equilibrium temperature. Supersaturation of $Ba(NO_3)_2$ was 0.7% at $32.0^{\circ}C$ and about 3% at $34.0^{\circ}C$. The obtained single crystals have three kind of morphology: tetrahedral, cubic, and, rarely, dodecahedral. The normal growth rate is proportional to the supersaturation; it is necessary to make the solution below 5% supersaturation in order to obtain transparent $Ba(NO_3)_2$ single crystals. The normal growth rate for {1$\bar{1}$1} faces was $2.51{\times}10^{-6}$ mm/s for the 0.7% supersaturation condition ($32.0^{\circ}C$), $6.43{\times}10^{-6}$ mm/s for the the condition of 3.0% supersaturation, and $7.01{\times}10^{-6}$ mm/s for the condition of 5.0% supersaturation. The quality of the grown crystals depends on the nature of the seed, the cooling rate employed, and the agitation of the solution. The faces of the obtained crystals have been identified uising an X-ray diffractometer. The surface diffusion is responsible for the low growth rates of the {1$\bar{1}$1} faces.

• Journal of the Korean Ceramic Society
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• v.56 no.6
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• pp.589-595
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• 2019

The top-seeded solution growth (TSSG) method is an effective approach for the growth of high-quality SiC single crystals. In this method, the temperature gradient in the melt is the key factor determining the crystal growth rate and crystal quality. In this study, the effects of the aperture at the top of the hot-zone on the growth of the SiC single crystal obtained using the TSSG method were evaluated using multiphysics simulations. The temperature distribution and C concentration profile in the Si melt were taken into consideration. The simulation results showed that the adjustment of the aperture at the top of the hot-zone and the temperature gradient in the melt could be finely controlled. The surface morphology, crystal quality, and polytype stability of the grown SiC crystals were investigated using optical microscopy, high-resolution X-ray diffraction, and micro-Raman spectroscopy, respectively. The simulation and experimental results suggested that a small temperature gradient at the crystal-melt interface is suitable for growing high-quality SiC single crystals via the TSSG method.

• Journal of Bio-Environment Control
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• v.12 no.2
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• pp.89-94
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• 2003

This study was conducted to identify the effect of recycling method of drained solution on the concentration of drained solution, and growth and yield of tomato in the recycling system. The recycling methods of drained solution were composed of control, MEC (measurement of EC) and ANS (analysis of nutrient solution). The plant height in the early growth stage was not different among the treatments, but plant fresh weight and dry weight were higher in the MEC or the ANS than in the control. The growth including fruit number, fruit weight, and yield of tomato in the ANS as compared with the control was favorable. The EC of drained solution tended to decrease in the early growth stage, but that of drained solution increased in the late growth stage. It was low in the MEC and the ANS as compared with the control. The pH of drained solution was maintained by 6.2 to 6.5 throughout the growth period in the MEC and the ANS, but the pH of the control increased up to 7.2 at the late growth stage. The N and K concentrations of drained solution tended to decrease in the early growth stage, while those of P, Ca and Mg increased. In the late growth stage, concentrations of N, P, Ca and Mg tended to decrease, but that of K in the ANS was very low. Concentrations of N, P, K, Ca and Mg were lower in the MEC and the ANS than in the control.

• Korean Journal of Mathematics
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• v.23 no.3
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• pp.379-391
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• 2015

We investigate the existence of solutions of the nonlinear biharmonic equation with variable coefficient polynomial growth nonlinear term and Dirichlet boundary condition. We get a theorem which shows that there exists a bounded solution and a large norm solution depending on the variable coefficient. We obtain this result by variational method, generalized mountain pass geometry and critical point theory.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.09a
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• pp.55-63
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• 1998

The growing conditions of barium nitrate Ba(NO3)2 single crystals by aqueous solution method have been studied. Supersaturation of Ba(NO3)2 was 0.7% at 32.0$^{\circ}C$ and about 3% 34.0$^{\circ}C$. The obtained single crystals have three kind of morphology; the tertrahedron, the cube and rarely dodecahedron face. The faces of obtained crystals have been identified by X-ray diffractometer.

• Journal of the Korean Ceramic Society
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• v.22 no.4
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• pp.26-32
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• 1985

The subcritical crack growth of sintered SiC is investigated under various corrosive atmospheres such as distilled water Murakami solution and saturated KOH solution. The KI-V diagrams are obtained by the load relaxation method and incremental displacement rate method using the double torsion technique. The obtained fracture mechanics parameters (n) of sintered SiC are 79 in Murakami solution and 39 in saturated KOH solution. These data indicate that the subcritical crack growth of sintered SiC is taking place in these two conditions and the stress-corrosion cracking is suggested to be the mechanism. With these KI-V diagrams the life of sintered SiC in these conditions is predicted.

• The Korean Journal of Ceramics
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• v.3 no.1
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• pp.57-61
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• 1997

The effects of pH of solution on structural, electrical, and optical properties of CdS thin films prepared by solution growth method were investigated. With increasing pH of the solution, both crystallinity and transmittance of CdS thin film were deteriorated due to impurities and CdS particles, which were produced by homogeneous nucleation and adsorbed on the surface of CdS thin films. The films were strongly adherent to substrates and has low resistivity of 10~$10^2{\omega}cm$ regrardless of deposition conditions. After annealing at 30$0^{\circ}C$ in Ar atmosphere, the resistivity decreased due to desorption of impurity ions as well as the formation of S vacancies, but after annealing above 35$0^{\circ}C$ it increased by an agglomeration of S vacancies. After annealing in air atmosphere, the film resistivity increased because of the formation of oxide particle in grain boundaries.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.4
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• pp.153-156
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• 2003

Pure and Ethylenediaminetetraacetic acid (EDTA) doped L-arginine phosphate (LAP) single crystals were grown from the aqueous solution by temperature lowering method. The effect of EDTA additive on the solubility and metastable zone width of LAP solution has been investigated. Addition of EDTA has enhanced the metastable zone width of LAP and hence bulk crystals could be grown. The growth rate along the [100] direction increases with EDTA additive. Powder X-ray diffraction and FTIR studies reveal the absence of EDTA in the lattice of LAP, This reveals that the addition of EDTA to LAP doesn't influence the crystallinity. However, the transmittance and NLO properties significantly increase with EDTA additive and hence bulk LAP crystals are useful for laser fusion experiments.

• Korean Journal of Mathematics
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• v.13 no.2
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• pp.161-176
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• 2005

We consider a model of population dynamics whose mortality function is unbounded. We note that the regularity of the solution depends on the growth rate of the mortality near the maximum age. We propose Gauss-Legendre methods along the characteristics to approximate the solution when the solution is smooth enough. It is proven that the scheme is convergent at fourth-order rate in the maximum norm. We also propose discontinuous Galerkin finite element methods to approximate the solution which is not smooth enough. The stability of the method is discussed. Several numerical examples are presented.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.1
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• pp.60-65
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• 1991

The hydrothermal growth of $GaPO_{4}$ Single Crystals was carried out by the horizontal temperature gradient method. The most promising solvents for the crystal growth of $GaPO_{4}$ are $H_{3}PO_{4}$ and HCl solutions. Single crystals have been hydothermally grown at temperatures over the range $210-290^{\circ}C$ in these solutions with seed crystals. The glowth rates in HCl solution were higher than that for comparable conditions in $H_{3}PO_{4}$ solution. Morphologies of crystals grown at temperatures below $200^{\circ}C$ tended to be bounded by small major rhombohedral(10$\bar{1}$1) faces. In the temperature range from 200 to $430^{\circ}C$, the single crystals have morphologies bounded by prism (10$\bar{1}$0), small major rhombohedral(10$\bar{1}$1) and minor rhombohedral(01$\bar{1}$1) faces at the early stage, and grew with well developed basal(0001) faces by increasing the growth temperature.