• Title, Summary, Keyword: crystallization

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Novel Porous Materials Prepared by Repeated Directional Crystallization of Solvent (용매의 반복 방향성 결정화를 통해 제작된 새로운 다공성재료)

  • Kim, Hyun Jin;Lee, Jonghwi
    • Polymer(Korea)
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    • v.39 no.1
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    • pp.151-156
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    • 2015
  • Herein, novel porous structures were fabricated from monomer solutions of dimethylsiloxane and benzene by directional crystallization in twice. First, a honeycomb-like structure was fabricated by $1^{st}$ directional crystallization of solvent. By infiltration of the solution and subsequent $2^{nd}$ directional crystallization, novel structures of different pores in the honeycomb-like structure were fabricated. The porous materials prepared by the repeated directional crystallization have higher indentation modulus and hardness than those of the samples prepared by single directional crystallization. When a higher solution concentration was used in $2^{nd}$ directional crystallization, the maximum increase (indentation modulus: 2140% increase, indentation hardness: 2330% increase) was obtained. On the other hand, porosity and contact angle were lower in the samples from $2^{nd}$ directional crystallization than those from $1^{st}$ directional crystallization. A large decreases was observed, when a relatively high concentration was used in $2^{nd}$ directional crystallization (porosity: 21% decrease, contact angle: 36% decrease).

Crystallization of Amorphous Silicon Films by Field-Aided Lateral Crystallization (FALC) technique at $350^{\circ}C$

  • Park, Kyoung-Wan;Cho, Ki-Taek;Choi, Duck-Kyun
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.548-551
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    • 2002
  • The crystallization of amorphous silicon (a-Si) was achieved using a field aided lateral crystallization (FALC) process at 350 $^{\circ}C$. Under the influence of an electric field, Cu is found to drastically enhance the lateral crystallization velocity of a-Si. When an electric field was applied to the selectively Cu-deposited a-Si film during the heat treatment at temperature as low as 350 $^{\circ}C$, dendrite-shaped crystallization of a-Si progressed toward Cu-free region and the crystallization from negative electrode side toward positive electrode side was accelerated. We identified that 1000${\AA}$ thick a-Si film was completely crystallized by Cu-FALC process at 350 $^{\circ}C$ by TEM analysis.

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Determining an Optimal Low Temperature Polycrystalline Silicon Crystallization Technology of LCD using Patent Map and AHP (특허맵과 AHP를 활용한 최적의 LCD 저온폴리실리콘 결정화 기술 선정)

  • KIM, Kwan Yeoul;Lee, Jang Hee
    • Knowledge Management Research
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    • v.12 no.1
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    • pp.39-52
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    • 2011
  • Many LCD manufacturers continue to develop the technologies of LCD manufacturing processes for the reduction of production cost, power consumption and high-resolution. The LTPS (Low Temperature Polycrystalline Silicon) crystallization technology is important for rearranging the internal structure of liquid crystal grain by adding certain energy to amorphous silicon and turning it into poly-silicon in order to manufacture LCD with better performance. We consider 14 existing technologies of LTPS crystallization in the LCD manufacturing and present an intelligent analysis methodology using patent map and AHP (Analytic Hierarchy Process) analysis for determining an optimal LTPS crystallization technology. By using patent map analysis, we easily understand the development process and mega-trend of LTPS crystallization technologies and their relationship. By using AHP analysis, we evaluate 14 LTPS technologies. Through the use of proposed methodology, we determine the Continuous Wave Laser Lateral Crystallization technology as an optimal one.

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Alternating Magnetic Field Crystallization of Amorphous Si Films

  • Kang, K.H.;Park, S.H.;Lee, S.J.;Nam, S.E.;Kim, H.J.
    • Journal of Information Display
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    • v.4 no.1
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    • pp.34-37
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    • 2003
  • We investigate the solid phase crystallization of amorphous Si films on glass substrates under alternating magnetic field induction. The kinetics of crystallization are found to be greatly enhanced by alternating magnetic field. While complete crystallization takes heat treatment of more than 14 hours at 570$^{\circ}C$, it can be reduced by applying the megnetic field to 20 minutes. It is assumed that the enhancement of crystallization is associated with an electromotive force voltage generated by alternating magnetic field. This electric field applied in the amorphous Si may possibly be the reason for acceleration of the atomic mobility of crystallization through the modification of atomic potentials

Molecular Dynamics Study on External Field Induced Crystallization of Amorphous Argon Structure

  • Park, Seung-Ho;Cho, Sung-San;Lee, Joon-Sik;Choi, Young-Ki;Kwon, Oh-Myoung
    • Journal of Mechanical Science and Technology
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    • v.18 no.11
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    • pp.2042-2048
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    • 2004
  • A molecular dynamics study has been conducted on an external-force-field-induced isothermal crystallization process of amorphous structures as a new low-temperature athermal crystallization process. An external cyclic-force field with a dc bias is imposed on molecules selected randomly in an amorphous-phase of argon. Multiple peaks smoothed out in the radial distribution functions for amorphous states appear very clearly during the crystallization process that cannot be achieved otherwise. When the amorphous material is locally exposed to an external force field, crystallization starts and propagates from the interfacial region and crystallization growth rates can be estimated.

The Substrate Effects on Kinetics and Mechanism of Solid-Phase Crystallization of Amorphous Silicon Thin Films

  • Song, Yoon-Ho;Kang, Seung-Youl;Cho, Kyoung-Ik;Yoo, Hyung-Joun
    • ETRI Journal
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    • v.19 no.1
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    • pp.26-35
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    • 1997
  • The substrate effects on solid-phase crystallization of amorphous silicon (a-Si) films deposited by low-pressure chemical vapor deposition (LPCVD) using $Si_2H_6$ gas have been extensively investigated. The a-Si films were prepared on various substrates, such as thermally oxidized Si wafer ($SiO_2$/Si), quartz and LPCVD-oxide, and annealed at 600$^{\circ}C$ in an $N_2$ ambient for crystallization. The crystallization behavior was found to be strongly dependent on the substrate even though all the silicon films were deposited in amorphous phase. It was first observed that crystallization in a-Si films deposited on the $SiO_2$/Si starts from the interface between the a-Si and the substrate, so called interface-interface-induced crystallization, while random nucleation process dominates on the other substrates. The different kinetics and mechanism of solid-phase crystallization is attributed to the structural disorderness of a-Si films, which is strongly affected by the surface roughness of the substrates.

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Technological Trend of Crystallization Research for Bioproduct Separation (Bioproduct 분리를 위한 결정화 연구 동향)

  • Kim, Woo-Sik;Lee, Eun-Kyu
    • KSBB Journal
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    • v.20 no.3
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    • pp.164-176
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    • 2005
  • In bioengineering field, current academic trends and informations on crystallization technology for bioproduct separation were summarized. It is essential for utilizing the crystallization technology to understand the fundamental phenomena of crystallization of crystal nucleation, crystal growth, crystal agglomeration and population balance for the design of crystallizers. In general, the crystal nucleation that the crystalline solids occur from the solution is analyzed by Gibb's free energy change in the aspect of thermodynamics and in the present paper the crystal nucleation models based on the above thermodynamics are summarized by their key characteristics. The crystal growth and agglomeration, which have been studied over 50 years and are essential phenomena for separation technology, are reviewed from their basic concept to most leading edge trend of researches. In the material and population balances for the designs of crystallization separation process, the analysis of crystallizers is summarized. Thereon, the present review paper will academically contribute the understanding the crystallization phenomena and the design of the crystallization separation process.

Kinetic and thermodynamic characteristics of crystallization of vancomycin

  • Ha, Geon-Soo;Kim, Jin-Hyun
    • Korean Journal of Chemical Engineering
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    • v.34 no.9
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    • pp.2451-2458
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    • 2017
  • We investigated the effect of the major process parameters (crystallization temperature and time) on the efficiency of the vancomycin crystallization process and conducted a kinetic and thermodynamic analysis. The most clear and uniform vancomycin crystals with the highest yield (~98%) were obtained at the optimum crystallization temperature (283 K) and time (1,440 min). The electron microscope, SEM, and XRD analyses showed that intact crystalline vancomycin was obtained when using a crystallization temperature of 283, 288, and 293 K. The kinetic analysis results revealed that the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model was suitable with a high value for $r^2$ (>0.9561) and low value for RMSD (<0.0170). Finally, from the thermodynamic analysis the Gibb's free energy change (${\Delta}G^0$), entropy change (${\Delta}S^0$), and enthalpy change (${\Delta}H^0$) were all negative, indicating that the crystallization process was spontaneous, irreversible, and exothermic.

Enhanced Crystallization of Amorphous Silicon using Electric Field

  • Song, Kyung-Sub;Jun, Seung-Ik;Park, Sang-Hyun;Park, Duck-Kyun
    • Proceedings of the Korea Association of Crystal Growth Conference
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    • pp.243-246
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    • 1997
  • A new technique for low temperature crystallization of amorphous silicon, called field aided lateral crystallization(FALC) was attempted. To demonstrate the concept of FALC, thin layer of nickel(30${\AA}$) was deposited on top of amorphous silicon film and the electric field was applied during the crystallization. The effects of electric field on the crystallization behavior of amorphous silicon film were investigated.

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New Solid-phase Crystallization of Amorphous Silicon by Selective Area Heating

  • Kim, Do-Kyung;Jeong, Woong-Hee;Bae, Jung-Hyeon;Kim, Hyun-Jae
    • Journal of Information Display
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    • v.10 no.3
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    • pp.117-120
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    • 2009
  • A new crystallization method for amorphous silicon, called selective area heating (SAH), was proposed. The purpose of SAH is to improve the reliability of amorphous silicon films with extremely low thermal budgets to the glass substrate. The crystallization time shortened from that of the conventional solid-phase crystallization method. An isolated thin heater for SAH was fabricated on a quartz substrate with a Pt layer. To investigate the crystalline properties, Raman scattering spectra were used. The crystalline transverse optic phonon peak was at about 519 $cm^{-1}$, which shows that the films were crystallized. The effect of the crystallization time on the varying thickness of the $SiO_2$ films was investigated. The crystallization area in the 400nm-thick $SiO_2$ film was larger than those of the $SiO_2$ films with other thicknesses after SAH at 16 W for 2 min. The results show that a $SiO_2$ capping layer acts as storage layer for thermal energy. SAH is thus suggested as a new crystallization method for large-area electronic device applications.