• Title, Summary, Keyword: crystallization

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Crystallization Mechanisms of Joule-Heating-Induced Crystallization

  • Park, Doo-Jung;Ro, Jae-Sang
    • Journal of Information Display
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    • v.10 no.2
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    • pp.76-79
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    • 2009
  • In Joule-heating-induced crystallization, solid-to-solid or liquid-to-solid phase transformation could occur. It was found that novel physical phenomena that randomly nucleated liquid seeds, followed by rapid solidification in an amorphous matrix, during the Joule-heating-up period play an important role especially in liquid-to-solid transformation. Under some processing conditions, super-grains sized 6-8 ${\um}m$ were produced by the lateral growth from the initial seeds, without any artificially control.

Drowning-out Crystallization of Calcium Lactate for Crystal Size Control (결정입자 제어를 위한 젖산칼슘 용석결정화 기술)

  • Kim, Jong-Min;Chang, Sang Mok;Kim, In-Ho;Koo, Yoon-Mo;Hong, Haehyun;Kim, Woo-Sik
    • Korean Chemical Engineering Research
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    • v.47 no.6
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    • pp.740-746
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    • 2009
  • In the present study, the drowning-out crystallization of L(+)-calcium lactate was investigated in order to develop the crystallization separation process. The crystallization of the calcium lactate was induced by injecting the alcoholic anti-solvent into the aqueous solution of calcium lactate and the control of the calcium lactate crystal size during the crystallization was primarily investigated under the consideration of the anti-solvent species, anti-solvent composition and agitation speed as the key operating factors. Alcohols of methanol, ethanol, n-propanol and i-propanol were used as the anti-solvent for the drowning-out crystallization. Prior to the crystallization experiment, the solubility of calcium lactate in the water-alcohol mixture was measured along with the variation of the alcohol species and composition, which was necessary to estimate the supersaturation level of the crystallization. By the drowning-out crystallization, the calcium lactate crystals of the fabric shape were obtained. Using the ethanol as the antisolvent, the fabric crystals close to the needle shape were produced. However, the hairy crystals were obtained by using the propanol as the anti-solvent. Due to such morphological features, the crystals was highly apt to form the aggregates. The aggregation of the crystals was intensified as increasing the alcohol fraction in the water-alcohol mixture. Meanwhile, the agitation caused the breakage of crystals, resulting in the decrease of the crystal size. Therefore, the crystal size in the crystallization was predominantly determined by the competition between the crystal aggregation and breakage.

The crystallization behavior of glass made from coal bottom ash (석탄 바닥재로 제조된 유리의 결정화 거동 분석)

  • Jang, Seok-Joo;Kang, Seung-Gu
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.20 no.1
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    • pp.58-63
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    • 2010
  • The glass-ceramics made from the mixture of coal bottom ash, produced from a thermal power plant mixed with $Na_2O$ and $Li_2O$ was fabricated and their crystallization behavior was studied using a non-isothermal analyzing method. The temperature for 50% crystallization was higher than the exothermic peak temperature $T_p$ at DTA curve and the quickest crystallization temperature was much the same as $T_p$ as identified from the relationships of crystallized fraction and crystallization rate with temperature. By using Kissinger equation describing a crystallization behavior, the activation energy (262 kJ/mol), the Avrami constant (1.7) and the frequency ($5.7{\times}10^{16}/s$) for crystallization were calculated from which the nepheline crystal could be expected as showing an 1~2-dimensional surface crystallization behavior mainly with some bulk crystallization tendency at the same time. The actual observation of microstructure using SEM showed the considerable amount of surface crystals of dendrite and the bulk crystals with low fraction, so the prediction by the Kissinger equation was in accord with the crystallization behavior of glass-ceramics fabricated in this study.

The crystallization behaviours of cordierite gel derived from sil-gel method and glass prepared by the conventional melting method. (용융법과 졸겔법으로 제조된 Cordierite 계 유리와 겔의 결정화 거동)

  • Park, Won-Gyu
    • The Journal of Engineering Research
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    • v.1 no.1
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    • pp.15-22
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    • 1997
  • The crystallization behaviours of cordierite gel derived from sol-gel method and glass prepared from conventional melting method with or without $TiO_2$ as nucleants are compared. The densification temperature of gel is $810^{\circ}C$ and its chemical structure identified by IR analysis is same as that of glass melted by conventional method. The beginning crystallization temperature of gel is $965^{\circ}C$ lower than that of melted glass with 10wt% $TiO_2$, which is $978^{\circ}C$. The crystalline phases developed from gel during heat treatment are identified as spinel, $\beta$-quartz solid solution and $\alpha$-cordierite crystal and crystalline phases in case of glass are (Mg,Al)TiOn and $\beta$-quartz solid solution and $\alpha$-cordierite crystal, respectively. The crystallization in melted glass with nucleants occurs through bulk crystallization and in case of that without nucleants surface crystallization occurs, while the crystallization in gel is internal crystallization from interface between particles formed after densification.

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Crystallization of amorphous silicon films below $450^{\circ}C$ by FALC ($450^{\circ}C$ 이하에서 FALC 공정에 의한 비정질 실리콘의 결정화)

  • 박경완;유정은;최덕균
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.12 no.4
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    • pp.210-214
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    • 2002
  • The crystallization behavior of amorphous silicon (a-Si) film was investigated by using Cu-field aided lateral crystallization (Cu-FALC) process below $450^{\circ}C$. The lateral crystallization was induced from the Cu deposited region outside of pattern toward the Cu-free region inside of the pattern by applying an electric field during heat treatment. As expected, the lateral crystallization toward Cu-free region proceeded from negative toward positive electrode side. The occurrence of Cu-FALC phenomenon was interpreted in terms of dominant diffusing species in the reaction between Cu and Si. Even at the annealing temperature of $350^{\circ}C$, the large dendrite-shaped branches were formed in the crystallized region and the polarity in the lateral crystallization was clearly observed. Consequently, we could successfully crystallize the a-Si at the temperature as low as $350^{\circ}C$ by an electric field of 30 V/cm with fast crystallization velocity of 12 $\mu$m/h.

Recovery of High Concentrated Phosphates using Powdered Converter Slag in Completely Mixed Phosphorus Crystallization Reactor (완전혼합형 정석탈인반응조에서 미분말 전로슬래그를 이용한 고농도 인의 회수)

  • Kim, Eung-Ho;Yim, Soo-Bin;Jung, Ho-Chan;Lee, Eok-Jae;Cho, Jin-Kyu
    • Journal of Korean Society on Water Environment
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    • v.21 no.1
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    • pp.59-65
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    • 2005
  • A phosphate recovery system from artificial wastewater was developed using a completely mixed phosphorus crystallization reactor, in which powdered converter slag was used as a seeding crystal. In preliminary test, the optimal pH range for meta-stable hydroxyapatite crystallization for high phosphorus concentration was observed to be 6.0 to 7.0, which was different from the conventionally known pH range (8.0~9.5) for effective crystallization in relatively low phosphorus concentration less than 5 mg/L. The average phosphorus removal efficiency in a lab-scaled completely mixed crystallization system for artificial wastewater with about 100 mg/L of average $PO_4-P$ concentration was shown to be 60.9% for 40 days of lapsed time. XRD analysis exhibited that crystalline of hydroxyapatite formed on the surface of seed crystal, which was also observed in SEM analysis. In EDS mapping analysis, composition mole ratio (=Ca/P) of the crystalline was found to be 1.78, indicating the crystalline on the surface of seed crystal is likely to be hydroxyapatite. Particle size distribution analysis showed that average size of seed crystal increased from $28{\mu}m$ up to $50{\mu}m$, suggesting that phosphorus recycling from wastewater with high phosphorus concentration can be successfully obtained by using the phosphorus crystallization recovery system.

Nucleation and Crystal Growth of $\beta$-eucryptite in a Glass of the Molecular Composition Li2O.Al2O3.2SiO2 (Li2O.Al2O3.2SiO2의 조성을 갖는 유리에서 $\beta$-eucryptite의 핵생성 및 결정성장)

  • 이상현;장수진
    • Journal of the Korean Ceramic Society
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    • v.22 no.3
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    • pp.53-59
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    • 1985
  • Nucleation and crystallization of $\beta$-eucryptite in a glass of molecular percentage composition Li2O.Al2O3.2SiO2 are studied. The glasses are made by quenching of the melts from 143$0^{\circ}C$ to room temperature. Heat-treatment for nucleation and crystal growth are caried out at various temperature in the range between 50$0^{\circ}C$ and 80$0^{\circ}C$ with different duration of time. The amounts of crystallization are estimated by the method of x-ray powder diffraction. As the results a time-temperature-transformation relation for crystallization is derived. The maximum rate of crystallization is observed at about 75$0^{\circ}C$ from the T-T-T-curve while the crystallization temperature is detected at 67$0^{\circ}C$ by DTA measurement. The crystallization temperature moved to 62$0^{\circ}C$ by adding 5 weight percents of TiO2 and it moved to 78$0^{\circ}C$ by adding 2 weight percents of V2O5. The crystallization temperature moved to 62$0^{\circ}C$ by adding 5 weight percent of TiO2 it moved to 78$0^{\circ}C$ by adding 2 weight percents of V2O5 The activation energy for crystallization from the pure glass is calculated as 68 Kcal/mol and it varied to 53 Kcal/mol and 110Kcal/mol when 5 weight percents of TiO2 and weight percents of V2O5 are added respectively.

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Separation and Purification of 2,6-Dimethylnaphthalene Present in the Fraction of Light Cycle Oil by Crystallization Operation (결정화조작에 의한 접촉분해경유 유분에 함유된 2,6-디메틸나프탈렌의 분리·정제)

  • Kim, Su Jin
    • Applied Chemistry for Engineering
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    • v.29 no.6
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    • pp.799-804
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    • 2018
  • The separation and purification of 2,6-dimethylnaphthalene (2,6-DMN) present in the light cycle oil (LCO) fraction was investigated by a crystallization operation. Solute crystallization (SC) was performed using LCO fraction and iso-propyl alcohol as a raw material and a SC solvent, respectively. Increasing the operation temperature and volume ratio of the solvent to the raw material (S/F) resulted in improving the purity of 2,6-DMN, whereas the yield decreased. As a result of the crystallization operation in three steps containing the SC using LCO fraction (13.9% 2,6-DMN) and isopropyl alcohol, the re-crystallization 1 (RC 1) using the crystals recovered by SC and methyl acetate, and RC 2 using the crystals recovered by RC 1 and methyl acetate, the crystal with 99.9% 2,6-DMN was recovered with 19.5% yield. Furthermore, the separation and purification process of 2,6-DMN present in the LCO fraction was reevaluated by using the experimental results obtained through each operations of SC, RC 1, and RC 2.

An Optical Study on ELC Process of Amorphous Silicon (비정질 실리콘의 ELC 공정에 대한 광학적 연구)

  • 김우진;윤창환;박승호;김형준
    • Laser Solutions
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    • v.6 no.2
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    • pp.9-17
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    • 2003
  • Due to the heat confinement in the shallow region of the target for a short time scale, pulsed laser annealing has received an increasing interest for the fabrication of poly-Si thin film transistors(TFTs) on glass as a low cost substrate in the flat panel displays. The formation and growth mechanisms of poly silicon(poly-Si) grains in thin films are investigated using an excimer laser crystallization system. To understand the crystallization mechanism, the grain formations are observed by FESEM photography. The optical reflectance and transmittance during the crystallization process are measured using HeNe laser optics. A two-step ELC(Excimer Laser Crystallization) process is applied to enhance the grain formation uniformity.

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Development of Crystallization Distinction Supporting System Using Image Processing

  • Saito, Kanako;Kawabata, Kuniaki;kunimitsu, Satoshi;Asama, Hajime;Mishima, Taketoshi
    • Proceedings of the IEEK Conference
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    • pp.1788-1791
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    • 2002
  • In the post-genome era. it is one of important research subject to Investigate the roles of the proteins in human body based on decoded genome information during Human Genome Project. In order to clarify them. it is necessary to analyze the structure of the protein crystals and their function. ' Crystallization is the beginning stage of protein structure determination process. There are some methods for structural analysis of the proteins, and general one is X-ray structural analysis method. In order to utilize this method for analyzing the protein crystal's structure, artificial protein crystallization is required. However, since artificial crystallizing work takes much time and manpower. the performance against its cost is still low. Therefore. we started to discuss to develop a supporting system for improving efficiency of the crystallization distinction procedure. In this paper, we examine to realize such supporting system for crystallization distinction using image-processing technique and report about our experimental result with many real protein solution images.

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