• Title, Summary, Keyword: crystallization

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Preparation and Crystallization Behavior of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Grafted with Poly(N-vinylpyrrolidone) (Poly(N-vinylpyrrolidone)이 그래프트된 Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) 공중합체의 합성 및 결정화 거동)

  • Wang, Wei;Zhang, Yu;Chen, Yanmo
    • Polymer(Korea)
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    • v.31 no.5
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    • pp.385-392
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    • 2007
  • Poly (N-vinylpyrrolidone) (PVP) groups were grafted onto a poly(3-hydroxybutyrate-co-3-hydroryvalerate) (PHBV) backbone in order to modify its properties and synthesize a novel biocompatible copolymer. The crystallization behavior of PHBV and grafted PHBV was investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). During the cooling-induced crystallization process, the crystallization temperature and the crystallization rate of the grafted PHBV decreased with increasing PVP weight fraction. On the heating scans of all grafted PHBV samples, a new crystallization exothermic peak appeared at almost the same temperature, suggesting the operation of a recrystallization process, while the melting temperature ($T_m$) and the apparent enthalpy of fusion (${\Delta}H_f$) were not affected by graft modification. During the isothermal crystallization process at the same temperature, the presence of side PVP groups decreased the spherulitic growth rate and the spherulitic band spacing with increasing PVP weight fraction in samples.

Crystallization of Poly(vinylidene fluoride)-SiO2 Hybrid Composites Prepared by a Sol-gel Process

  • Cho, Jae Whan;Sul, Kyun Il
    • Fibers and Polymers
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    • v.2 no.3
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    • pp.135-140
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    • 2001
  • Organic-inorganic hybrid composites consisting of poly(vinylidene fluoride) (PVDF) and SiO$_2$ were prepared through a sol-gel process and the crystallization behavior of PVDF in the presence of $SiO_2$ networks was investigated by spectroscopic, thermal and x-ray diffraction measurements. The hybrid composites obtained were relatively transparent, and brittleness increased with increasing content of tetraethoxysilane (TEOS). It was regarded from FT-lR and DSC thermal analyses that at least a certain interaction existed between PVDF molecules and the $SiO_2$ networks. X-ray diffraction measurements showed that all of the hybrid samples had a crystal structure of PVDF ${\gamma}$-phase. Fresh gel prepared from the sol-gel reaction showed a very weak x-ray diffraction peak near 2$\theta$=$21^{\circ}$ due to PVDF crystallization, and Intensity increased grade-ally with time after gelation. The crystallization behavior of PVDF was strongly affected by the amount of $SiO_2$ networks. That is, $SiO_2$ content directly influenced preference and disturbance fur crystallization. In polymer-rich hybrids, $SiO_2$ networks had a favorable effect on the extent of PVDF crystallization. In particular, the maximum portent crystallinity of PVDF occurred at the content of 3.7 wt% $SiO_2$ and was higher than that of pure PVDF. However. beyond about 10 wt% $SiO_2$, the crystallization of PVDF was strongly confined.

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Synthesis and Non-Isothermal Crystallization Behavior of Poly (ethylene-co-1,4-butylene terephthalate)s

  • Jinshu Yu;Deri Zhou;Weimin Chai;Lee, Byeongdu;Le, Seung-Woo;Jinhwan Yoon;Moonhor Ree
    • Macromolecular Research
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    • v.11 no.1
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    • pp.25-35
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    • 2003
  • A series of random poly(ethylene-co-1,4-butylene terephthalate)s (PEBTs), as well as poly(ethylene terephthalate) (PET) and poly(1,4-butylene terephthalate) (PBT), were synthesized by the bulk polycondensation. Their composition, molecular weight, and thermal properties were determined. All the copolymers are crystallizable, regardless of the compositions, which may originate from both even-atomic-numbered ethylene terephthalate and butylenes terephthalate units that undergo inherently crystallization. Non-isothermal crystallization exotherms were measured over the cooling rate of 2.5-20.0 K/min by calorimetry and then analyzed reasonably by the modified Avrami method rather than the Ozawa method. The results suggest that the primary crystallizations in the copolymers and the homopolymers follow a heterogeneous nucleation and spherulitic growth mechanism. However, when the cooling rate increases and the content of comonomer unit (ethylene glycol or 1,4-butylene glycol) increases, the crystallization behavior still becomes deviated slightly from the prediction of the modified Avrami analysis, which is due to the involvement of secondary crystallization and the formation of relatively low crystallinity. Overall, the crystallization rate is accelerated by increasing cooling rate but still depended on the composition. In addition, the activation energy in the non-isothermal crystallization was estimated.

Trend of Crystallization Technology and Large Scale Research for Fabricating Thin Film Transistors of AMOLED Displays (AMOLED 디스플레이의 박막트랜지스터 제작을 위한 결정화 기술 동향 및 대형화 연구)

  • Kim, Kyoung-Bo;Lee, Jongpil;Kim, Moojin;Min, Youngsil
    • Journal of Convergence for Information Technology
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    • v.9 no.5
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    • pp.117-124
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    • 2019
  • This paper discusses recent trends in the fabrication of semiconducting materials among the components of thin film transistors used in AMOLED display. In order to obtain a good semiconductor film, it is necessary to change the amorphous silicon into polycrystalline silicon. There are two ways to use laser and heat. Laser-based methods include sequential lateral solidification (SLS), excimer laser annealing (ELA), and thin-beam directional crystallization (TDX). Solid phase crystallization (SPC), super grain silicon (SGS), metal induced crystallization (MIC) and field aided lateral crystallization (FALC) were crystallized using heat. We will also study research for manufacturing large AMOLED displays.

Effects of crystallization reagent and pH on the sulfide crystallization of Cu and Ni in fluidized bed reactor (유동층 반응기를 이용한 구리와 니켈의 황화물 결정화에 결정화 시약 및 pH가 미치는 영향)

  • Jeong, Eunhoo;Shim, Soojin;Yun, Seong Taek;Hong, Seok Won
    • Journal of Korean Society of Water and Wastewater
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    • v.28 no.2
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    • pp.207-215
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    • 2014
  • Wastewater containing heavy metals such as copper (Cu) and nickel (Ni) is harmful to humans and the environment due to its high toxicity. Crystallization in a fluidized bed reactor (FBR) has recently received significant attention for heavy metal removal and recovery. It is necessary to find optimum reaction conditions to enhance crystallization efficacy. In this study, the effects of crystallization reagent and pH were investigated to maximize crystallization efficacy of Cu-S and Ni-S in a FBR. CaS and $Na_2S{\cdot}9H_2O$ were used as crystallization reagent, and pH were varied in the range of 1 to 7. Additionally, each optimum crystallization condition for Cu and Ni were sequentially employed in two FBRs for their selective removal from the mixture of Cu and Ni. As major results, the crystallization of Cu was most effective in the range of pH 1-2 for both CaS and $Na_2S{\cdot}9H_2O$ reagents. At pH 1, Cu was completely removed within five minutes. Ni showed a superior reactivity with S in $Na_2S{\cdot}9H_2O$ compared to that in CaS at pH 7. When applying each optimum crystallization condition sequentially, only Cu was firstly crystallized at pH 1 with CaS, and then, in the second FBR, the residual Ni was completely removed at pH 7 with $Na_2S{\cdot}9H_2O$. Each crystal recovered from two different FBRs was mainly composed of CuxSy and NiS, respectively. Our results revealed that Cu and Ni can be selectively recovered as reusable resources from the mixture by controlling pH and choosing crystallization reagent accordingly.

Crystallization behavior of ITO thin films sputtered on substrates with and without heating (가열기판 및 비가열 기판에 증착한 ITO 박막의 결정화 거동)

  • Park, Ju-O;Lee, Joon-Hyung;Kim, Jeong-Joo;Cho, Sang-Hee
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.89-92
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    • 2003
  • ITO thin films were deposited by RF-magnetron sputtering method and crystallization behavior of the films with and without external heating as a function of deposition time was examined. X-ray diffraction results indicated an amorphous state of the film when the deposition time is short about 10 min. When the deposition time was increased over 20 min development of crystallization of the films is observed. Because RF-sputtering transfers the high-energy to the growing film by energetic bombardment, it is believed that considerable activation energy for the crystallization of the film has transferred during deposition, which resulted in the crystallization of ITO thin films without external energy supply.

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An In-Situ Optical Study on Silicon Crystallization Process Using an Excimer Laser (Excimer Laser응용 실리콘 결정화 공정에 대한 In-Situ 광학적 연구)

  • Kim, W.J.;Y, C.-Hwan;Park, S.H.;Kim, H.J.
    • Proceedings of the KSME Conference
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    • pp.1407-1411
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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 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 analysis. 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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An Effect on the Solution Crystallization Temperature Difference and Cooling Capacity of the Absorption Chiller by a Solution Cooler in the Absorber (흡수기내 용액 냉각기가 흡수식 냉동기의 용액 결정화 온도차와 냉각 용량에 미치는 효과)

  • Chin, Sung-Min;Lee, Jae-Heon;Jurng, Jong-Soo
    • Proceedings of the KSME Conference
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    • pp.1518-1523
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    • 2003
  • The objective of the present work is to investigate an effect on the solution crystallization temperature difference and the cooling capacity of the absorption chiller by a solution cooler in the absorber. The cooling capacity of the absorption chiller can be higher, with the enhanced performance of the solution heat exchangers. But, because the solution crystallization temperature difference becomes smaller at the absorber inlet, the heat capacity of the solution heat exchangers might be limited by the danger of crystallization, which can cause the serious damages. In this paper, the heat capacity ratio of the solution cooler is defined as the ratio of the heat capacity of the solution cooler to that of the absorber. If it becomes larger in the additional type solution cooler, the solution crystallization temperature difference is augmented and the cooling capacity is also increased.

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Study on Carbon Pick-up in molten iron (I);Effect of Crystallization heat treatment of Carbon-bearing materials on Carbon Pick-up in molten iron (용철(熔鐵)에서의 가탄(加炭)에 관(關)한 연구(硏究)(1);가탄(加炭)에 미치는 탄소재(炭素材)의 결정화열처리(結晶化熱處理)의 영향)

  • Cho, Won-Il;Lee, Jong-Nam
    • Journal of Korea Foundry Society
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    • v.3 no.3
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    • pp.159-166
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    • 1983
  • In order to develope domestic carburizers, the experiment was carried out by applying crystallization heat treatment to domestic anthracites and also to foreign products to compare with domestic anthracites.The present work was mainly concerned with the effect of their degree of crystallization of carbon-bearing materials on carbon pick-up in molten iron.Those effects were evaluated by the measurement of density, chemical composition, specific electric resistivity, and X-ray intensity of carbon-bearing materials. Experimental results thus obtained were summurized as follows. 1. The degree of crystallization of domestic anthracites and foreign products was increased with increasing heat treatment temperature. 2. The more degree of crystallization, the shorter the dissolving time of domestic anthracites in molten iron was obtained, while that of foreign products was remained constant. 3. As the degree of crystallization of domestic anthracites and foreign products was increased, the carbon content as well as carbon recovery in molten iron was increased.

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Crystallization of Ferrite Powder Using Ultrasonic Wave (초음파를 이용한 페라이트 분말의 결정화)

  • 신현창;오재희;이재춘;최승철
    • Journal of the Korean Ceramic Society
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    • v.37 no.2
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    • pp.181-185
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    • 2000
  • A new technique capable of accelerating the crystallization of ferrite powder at low temperature is developed. Effects of the ultrasonic waves on the crystallization were studied for ferrite powders prepared using the co-precipitation method. The crystallization of the ferrite powders exposed to the ultrasonic waves were characterized by the XRD. The amorphous ferrite powders prepared using the co-precipitation method were crystallized as a result of the exposure to the ultrasonic waves for 5h and the crystallization of the ferrite powders became more enhanced in proportion to the time exposed. The ferrite powder exposed to the ultrasonic waves for 25h had higher crystallinity a larger specific surface area than the ferrite powder calcined at 500$^{\circ}C$ for 2h.

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