• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1659-1661
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• 2004

Measurement of supersaturation is important in crystallization processes, because it is one of key factors to control crystal size distribution and shape determining product quality. A monitoring system of the supersaturation using a quartz crystal sensor is applied to the supersaturation measurement. From the variation of resonant frequency, the beginning of the formation of salt crystal on the sensor surface is detected while the sensor is directly cooled down. The degree of supersaturation is computed from the solubility difference at the temperatures of the salt solution and the sensor. The performance of the propsed system of the supersaturation measurement is examined by applying the system to the crystallization of three different salt solutions. The experimental outcome compared with eye observation result and photographic analysis indicates that the proposed system is effective and useful to determine the supersaturation in the crystallization process. In addition, the microscopic monitoring of the initial stage crystallization is available with the sensor system.

• 한국재료학회지
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• 제22권12호
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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.

• 한국세라믹학회지
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• 제24권5호
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• pp.461-469
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• 1987

Single crystals of Mn-Zn Ferrite were grown by slow cooling method using Na2B4O7 as flux agent. The effects of flux content and cooling rate on the types of crystals, and the relation between supersaturation and growth mechanism were studied. As a result, the types of grown crystals occurred as plate, hopper and octahedral crystals. The occurrence of these crystal types was dependent on flux content. The habit was found to correlate with the growth rate and supersaturation. The lateral growth of a dendritic crystal is related to the twin layer. The growth of crystals from borax melts mainly occurred by the layer-spreading growth following corner and edge nucleation caused by high supersaturation in the melt. Especially, the plate crystals were produced on top of the melts. The hopper and octahedral crystals occurred at lower supersaturation than the plate crystals.

• 한국물환경학회지
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• 제28권2호
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• pp.213-218
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• 2012

Abnormal dissolved oxygen concentration in aquatic habitat, both depletion and supersaturation, can be stress factor to aquatic animals. In this study the nationwide distribution of oxygen supersaturation was analyzed for three categories of streams (43 urban streams, 15 rural streams, and 14 forest streams) by using monitoring network data of the Korean Ministry of Environment. From the distribution analysis 30% of urban streams showed hyperoxic condition of eutrophic level, while no forest stream showed hyperoxic condition. The physiological effect of hyperoxia on fish was examined using two species of fish Zacco koreanus, which resulted in higher concentration of a stress hormone (cortisol) in fish exposed to hyperoxic concentration (196%) of oxygen. This study shows that hyperoxic condition is ubiquitous in urban and rural Korean streams, and it can be a stress factor to aquatic animals.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1885-1890
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• 2008

3-D heterogeneous nucleation was simulated by classical molecular dynamics (MD), where the Lennard-Jones (LJ) gas and solid cluster-seed molecules have argon and aluminum properties, respectively. There are three shapes of cluster-seeds, cube, rod, and sphere, and three classes of masses and the simulation took place under nine supersaturation ratios, making a total of 81 calculations. Results show that the dimension of the cluster-seed highly affects the rates of cluster development. In order to analyze heterogeneous nucleation above and below the critical supersaturation ratio, growth rate and liquefaction rate were separately defined to supplement the investigation. Design of experiments (DOE) was used for analysis which displayed that the shape and mass of the cluster-seed are prominent for the growth rate, while the supersaturation ratio is most significant followed by the mass for liquefaction rate. The significance of the supersaturation ratio for overall liquefaction suggests that thermal diffusion is more dominant than mass interactions for this system.

• Membrane and Water Treatment
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• 제5권3호
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• pp.221-233
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• 2014

Simulations were conducted to predict supersaturation along Reverse Osmosis (RO) modules for seawater desalination. The modeling approach is based on the use of conservation principles and chemical equilibria equations along RO modules. Full Pitzer ion interactive forces model for concentrated solutions was implement to calculate activity coefficients. An average rejection rate for all ionic species was considered. Supersaturation has been used to assess scaling. Supersaturations with respect to all calcium carbonate forms and calcium sulfate were calculated up to 50% recovery rate in seawater RO desalination. The results for four different seawater qualities are shown. The predictions were in a good agreement with the experimental results.

• 산업기술연구
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• 제6권
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• pp.13-17
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• 1986

The effect of supersaturation on morphology of silicon carbide by chemical vapor deposition using $CH_3SiCl_3-H_2$ gas mixture system was investigated. The experimental results show that the final structure of silicon carbide deposits is coarser as total pressure increases or ${\alpha}$-ratio decreases. It is believed because supersataration of Si-source decreases as total pressure increases or ${\alpha}$-ratio decreases.

• 한국응용과학기술학회지
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• 제24권3호
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• pp.219-232
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• 2007

In T-mixer crystallization, supersaturation is generated by mixing of another solvent or non-solvent in order to reduce the solubility of the compound. Also, T-mixer is a type of continuous crystallization. In order to induce micro-mixing, two solutions were mixed rapidly by T-mixer, which formed high supersaturation. As the results, mean size of HMX crystals decreased with increasing de-supersaturation rate $(R_s)$. Eventually, HMX particles ranging from 0.5 to $5{\mu}m$ can be obtained by T-mixer crystallization. Mixing efficiency in T-mixer increased with increasing $R_s$ values. In T-mixer crystallization without surfactants, homogeneous nucleation was formed when S and $R_s$ was over 54 and $1.6{\times}10^3/sec$. In T-mixer crystallization with surfactants, homogeneous nucleation was formed when S and $R_s$ was over 26 and 7.4/sec.

• 대한기계학회논문집
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• 제12권3호
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• pp.582-589
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• 1988

본 연구에서는 작동유체로서 습공기를 사용하였을때 수반되는 응축에 의한 전 압손실을 실험과 수치해석을 통하여 정체점에 있어서의 습공기의 온도, 과포화도 및 노즐 팽창율의 효과와 액적 질량비 (g)과의 관계로서 구명하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1196-1200
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• 2003

The degree of supersaturation is an important measure for the operation of crystallization processes, because it is directly related to the control of crystal size distribution and shape. A conventional technique utilizing solution composition and temperature has a variety of problems caused from the measurement error and the handling of analyzing samples. A monitoring system of the supersaturation using a quartz crystal sensor is proposed here, and its performance is examined applying different manipulations of coolant temperature. The experimental outcome and photographic examination indicate that the measurements of resonant frequency and resistance of the sensor can be used for the prediction of the formation and growth of solid crystal from the crystallization process. The monitoring system eliminates the intrinsic error source of the conventional system to give the improved measurement and on-line application availability.