• 제목, 요약, 키워드: crystallization

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Recent progress of continuous crystallization

  • Wang, Ting;Lu, Haijiao;Wang, Jingkang;Xiao, Yan;Zhou, Yanan;Bao, Ying;Hao, Hongxun
    • Journal of Industrial and Engineering Chemistry
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    • v.54
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    • pp.14-29
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    • 2017
  • Continuous crystallization has always been a hot topic in industrial crystallization. Many efforts have been made to improve the continuous crystallization, either by designing novel continuous crystallizers or by proposing improved design and operation of conventional continuous crystallizers. Some new models for continuous crystallization processes have also been proposed and tested in recent years. In this work, the development of continuous crystallization in recent years, including novel crystallizers, control strategies, models and some assistive technologies, is summarized. Promising as it is, continuous crystallization is still not as universal as batch crystallization due to the existence of the drawbacks, such as blockage and encrustation. Therefore, further efforts are needed before wider application of continuous crystallization.

Study on the Isothermal Crystallization Behaviors of PEN/TLCP Blends

  • Park, Jong-Ryul;Yoon, Doo-Soo;Lee, Eung-Jae;Bang, Moon-Soo;Choi, Jae-Kon
    • Elastomers and Composites
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    • v.51 no.1
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    • pp.56-62
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    • 2016
  • The isothermal crystallization behaviors of blends of poly(ethylene naphthalate) (PEN) and a thermotropic liquid crystalline polymer (TLCP) were investigated by differential scanning calorimetry (DSC) as functions of crystallization temperature and blend composition. Avrami analyses were applied to obtain information on the crystal growth geometry and the factors controlling the rate of crystallization. The crystallization kinetics of the PEN/TLCP blends followed the Avrami equation up to a high degree of crystallization, regardless of crystallization temperature. The calculated Avrami exponents for PEN/TLCP revealed three-dimensional growth of the crystalline region in each blend. The crystallization rate of each blend increased as the crystallization temperature decreased, and decreased as the TLCP content increased. The crystallization of PEN in the blend was affected by the addition of TLCP, which acts as a nucleating agent.

Enhanced Crystallization of Amorphous Si Using viscous Ni Solution and Microwave Annealing

  • Ahn, Jin-Hyung;Eom, Ji-Hye;Ahn, Byung-Tae
    • Journal of Information Display
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    • v.2 no.2
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    • pp.7-12
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    • 2001
  • A viscous Ni solution was coated over amorphous Si thin film for evenly spread of Ni metal source. The Ni s. prepared by dissolving $NiCl_2$ into IN HCI and mixing with propylene glycol. $NiCl_2$ and Ni were deposited on the amorphous film after oven dry and they enabled to obtain a uniform crystallization. The crystallization using the viscous Ni solution was a Ni-silicide mediated process, the same process used with Ni metal layer. The crystallization temperature was lowered to $480^{\circ}C$ by the synergy effect of silicide-mediated crystallization and microwave-induced crystallization. Lateral crystallization was also enhanced such that the velocity of lateral crystallization by microwave annealing became faster than by furnace annealing.

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액정 고분자와 폴리(에틸렌 테레프탈레이트) 블렌드의 결정화 거동 (Crystallization Behaviors of Liquid Crystalline Polymer/poly(ethylene terephthalate) blends)

  • 방문수
    • 한국산학기술학회논문지
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    • v.7 no.4
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    • pp.559-566
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    • 2006
  • 폴리(에틸렌 테레프탈레이트)와 액정 폴리에스테르의 블렌드를 등온 결정화 거동에 대하여 연구하였다. 블렌드내의 PET의 결정화 거동을 나타내주는 결정화 속도나 결정이 어떤 모양으로 성장하는가에 대한 정보를 얻기위해 Avrami 식을 이용하였다. 블렌드내 PET의 결정화는 결정화온도에 무관하게 높은 결정화도에 이르기까지 Avrami 식에 잘 적용됨을 알 수 있었으며 Avrami 지수값, n이 2를 나타냄으로써 블렌드내의 PET의 결정이 1차원적으로 성장함을 알 수 있었고, 결정화 온도가 높을수록 결정화 속도가 느려짐을 조사 결과 확인하였다.

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Polymer-directed Crystallization of Sibutramine using Cellulose Derivatives

  • Bae, Ha-Rim;Lee, Hye-Seung;Lee, Min-Kyung;Lee, Jong-Hwi
    • Journal of Pharmaceutical Investigation
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    • v.41 no.1
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    • pp.45-50
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    • 2011
  • Nonclassical pathway of crystallization has been utilized to modify the properties and morphologies of inorganic and organic/inorganic materials. In here, the polymer-directed crystallization method has been applied to the pharmaceutical active ingredient to assess the applicability for as a particle engineering tool. The polymer-directed crystallization was successful to modifying the crystal size, habit and morphology, but it was not effective to discover the novel polymorphs of Sibutramine (SB). SB was selected as a model drug and polyacrylic acid (PAA), polyethylene imine (PEI) and chitosan (CHI) were added as a crystallization pathway modifier. SB was crystallized via drowning crystallization using methanol or ethanol as a solvent and water as a non-solvent. The significant interactions between polymer and the drug were confirmed by measuring the solubility of the drug in presence of polymer during the crystallization. The crystal forms of SB are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and optical microscope (OM). The polymer-directed crystallization seems to be able to modify the crystal properties of pharmaceutical active ingredient, which is critical in determining the bioavailability, processability, and stability.

Classification of metals inducing filed aided lateral crystallization (FALC) of amorphous silicon

  • Jae-Bok Lee;Se-Youl Kwon;Duck-Kyun Choi
    • 한국결정성장학회지
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    • v.11 no.4
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    • pp.160-165
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    • 2001
  • The effects of various metals on Field Aided Lateral Crystallization (FALC) behaviors of amorphous silicon (a-Si) were investigated. Under an influence of electric field, metals such s Cu, Ni and Co were found to fasten the lateral crystallization toward a metal-free region, exhibiting a typical FALC behavior while the lateral crystallization of a-Si was not obvious for Pd. However, Au, Al and Cr did not induce the lateral crystallization of a-Si in metal-free region. Such phenomenological differences in various metals were studied in terms of dominant diffusing species (DDS) in the reaction between metal and Si. It was judged that the applied electric field enhanced the crystallization velocity by accelerating the diffusion of metal atoms since the occurrence of lateral crystallization would be strongly dependent on the diffusion of metal atoms than that of Si atoms. Therefore, it was concluded that he only metal-dominant diffusing species in the reaction between metal and Si results in the crystallization of a-Si in metal-free region.

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Crystallization of Amorphous Silicon Films Using Joule Heating

  • Ro, Jae-Sang
    • 한국표면공학회지
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    • v.47 no.1
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    • pp.20-24
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    • 2014
  • Joule heat is generated by applying an electric filed to a conductive layer located beneath or above the amorphous silicon film, and is used to raise the temperature of the silicon film to crystallization temperature. An electric field was applied to an indium tin oxide (ITO) conductive layer to induce Joule heating in order to carry out the crystallization of amorphous silicon. Polycrystalline silicon was produced within the range of a millisecond. To investigate the kinetics of Joule-heating induced crystallization (JIC) solid phase crystallization was conducted using amorphous silicon films deposited by plasma enhanced chemical vapor deposition and using tube furnace in nitrogen ambient. Microscopic and macroscopic uniformity of crystallinity of JIC poly-Si was measured to have better uniformity compared to that of poly-Si produced by other methods such as metal induced crystallization and Excimer laser crystallization.

Effect of sinusoidal Taylor vortex flow on cooling crystallization of L-lysine

  • Nguyen, Anh-Tuan;Kim, Woo-Sik
    • Korean Journal of Chemical Engineering
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    • v.34 no.7
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    • pp.1896-1904
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    • 2017
  • An elliptical Couette-Taylor (ECT) crystallizer with a unique sinusoidal Taylor vortex flow was developed to promote the recovery and size distribution of L-lysine crystals in cooling crystallization. When using the ECT crystallizer, the recovery was enhanced to a maximum of 100% with a mean residence time of only 15 min. When comparing the crystallization efficiency, the recovery and size distribution of the L-lysine crystals in the ECT crystallizer were over 33% and 50% higher, respectively, than those in the conventional MSMPR crystallizer and slightly higher than those in the circular Couette-Taylor (CT) crystallizer. This improved crystallization in the ECT crystallizer was explained in terms of the sinusoidal profile of the Taylor vortex intensity. Plus, since the nucleation and growth processes determine the recovery and crystal size distribution, the mean residence time, inner cylinder rotation speed, and feed concentration were all varied to investigate their influence on the crystallization efficiency.

Rheological properties and crystallization kinetics of polypropylene block copolymer with repeated extrusion

  • Sung Yu-taek;Seo Won Jin;Kim Jong Sung;Kim Woo Nyon;Kwak Dong-Hwan;Hwang Tae-Won
    • Korea-Australia Rheology Journal
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    • v.17 no.1
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    • pp.21-25
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    • 2005
  • Rheological properties and crystallization kinetics of the polypropylene (PP) block copolymer and recycled PP block copolymer were studied by advanced rheometric expansion system (ARES), differential scanning calorimetry (DSC), and optical microscopy. In the study of the dynamic rheology, it is observed that the storage modulus and loss modulus for the PP block copolymer and recycled PP block copolymer did not change with frequency. In the study of the effect of the repeated extrusion on the crystallization rate, half crystallization time of the PP samples was increased with the number of repeated extrusion in isothermal crystallization temperature ($T_c$). From the isothermal crystallization kinetics study, the crystallization rate was decreased with the increase of the number of repeated extrusion. Also, from the result of Avrami plot, the overall crystallization rate constant (K) was decreased with the increase of the number of the repeated extrusion. From the study of the optical microscopy, the size of the spherulite of the PP samples did not change significantly with the number of repeated extrusion. However, it was clearly observed that the number of the spherulite growth sites was decreased with the number of repeated extrusion. From the results of the crystallization rate, isothermal crystallization kinetics, Avrami plots, and optical microscopy, it is suggested that the crystallization rate of the PP block copolymer is decreased with the increase of the number of repeated extrusion.

열시차 분석에 대한 결정화 Kinetics의 응용 (Application of Crystallization Kinetics on Differential Thermal Analysis)

  • 이선우;심광보;오근호
    • 한국세라믹학회지
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    • v.35 no.11
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    • pp.1162-1170
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    • 1998
  • PbO-TiO2-B2O3-BaO 계 유리상에서 PbTiO3의 결정화 메커니즘에 대한 이론적 고찰 및 전자현미경 관찰 그리고 결정화 기구의 열시차 분석에 대한 응용성을 조사하였다. 열시차 분석에 대한 Kissinger 식의 응용은 DTA 분석시 시료내 핵밀도가 변하지 않을 때 적용할 수 있으며, 표면결정화를 유도하기 위해 분말시료를 사용하는 경우도 활성화 에너지를 시료의 결정화 메커니즘에 크게 영향을 받는다. Ozawa 식에 의한 Avrami parameter n은 전자현미경 관찰에 의해 파악된 결정화메커니즘과 잘 일치하고 있었으며, 수정 Kissinger 식은 시료의 결정화 메커니즘을 반영하고 있어 시료의 전처리와 관계없이 참값의 활성화에너지를 구할 수 있다.

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