• 한국재료학회지
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• 제2권2호
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• pp.101-109
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• 1992

PET(polyethylene terephthalate)는 섬유 및 다방면의 응용분야에 사용되는 상업용 고분자로 알려져 있다. 본 논문에서는 PET를 개질하기 위해 pentanediol의 이성질체인 1,5-pentanediol(1, 5-PD)과 neopentyl glycol(NPG)를 제3 monomer로 도입시켰다. NPG를 도입시킨 경우에는 결정화 속도가 감소하고, 1,5-PD로 개질된 PET는 1,5-PD가 약 10mo1% 첨가될 때가지 결정화 속도가 서서히 증가하였다. 이러한 결과는 NPG의 branch된 methyl기가 고분자 사슬에 표면으로 확산되면서 결정화하는 것을 방해하기 때문이다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.278-279
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• 2005

The crystallization of FePt/MgO(100) magnetic thin films of various thicknesses has been studied using synchrotron x-ray scattering, atomic force microscope, and vibrating sample magnetometer. In film with a 500-${\AA}$-thick, ordered (fct) FePt phase was dominantly crystallized into perpendicular (001) grains keeping the magnetically easy c-axis normal to the film plane during annealing. In film with a 812-${\AA}$-thick, however, longitudinal (110) grains keeping the c-axis parallel to the film plane were grown on top of the perpendicular (001) grains. The behavior of the magnetic properties was consistent with the thickness dependence of the crystallization. We attribute the thickness dependence of the crystallization to the substrate effect, which prefers the growth of the c-axis oriented perpendicular grains near the film/substrate interfacial area.

• 폴리머
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• 제37권1호
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• pp.100-112
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• 2013

현재 일반화되어 있는 pilot scale의 복합체 생산설비에서 용융 삽입법으로 nylon 66/Cloisite 93A 나노복합체의 상용화 가능성을 확인하였으며, nylon 66에 Cloisite 93A 도입으로 인장 및 굴곡응력에 대한 강도와 탄성률이 향상되었고, 형태학적 및 결정화 거동의 분석을 통해 Cloisite 93A 함량, nylon 66 점도 및 그에 따른 결정화 거동이 주요 영향요소임을 확인하였다.

• 열처리공학회지
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• 제31권4호
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• pp.165-170
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• 2018

W, Fe, and carbon powders were mechanical alloyed to produce $W_{35}Fe_{43}C_{22}$ ternary alloy powders containing nanocrystal W embedded within amorphous matrix. When the powder samples were heated to the primary crystallization temperature of $735^{\circ}C$, most parts of their amorphous region were fully crystallized to [W,Fe]-rich $M_6C$ carbides. Interestingly, a little portion of the carbides changes to stoichiometric line compounds ($M_{12}C$ and $W_6Fe_7$) and a solution phase (Fe-rich bcc), and remaining parts of the crystallites were amorphized again. The resulting microstructure was retained even by cyclic heating between room temperature of $1,200^{\circ}C$, and thus we found that the amorphous structure can be irreversibly formed at above glass transition temperature.

• 한국전기전자재료학회논문지
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• 제34권2호
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• pp.99-104
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• 2021

Ion-beam sputtering (IBS) was used to deposit semiconducting IZTO (indium zinc tin oxide) thin films onto heavily-doped Si substrates using a sintered ceramic target with the nominal composition In0.4Zn0.5Sn0.1O1.5, which could work as a channel layer for oxide TFT (oxide thin film transistor) devices. The crystallization behavior and electrical properties were examined for the films in terms of deposition parameters, i.e. target tilt angle and substrate temperature during deposition. The thickness uniformity of the films were examined using a stylus profilometer. The observed difference in electrical properties was not related to the degree of crystallization but to the deposition temperature which affected charge carrier concentration (n), electrical resistivity (ρ), sheet resistance (Rs), and Hall mobility (μH) values of the films.

• 폴리머
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• 제37권3호
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• pp.332-341
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• 2013

H-shaped amphiphilic pentablock copolymers $(PSt)_2-b-PCL-b-PEO-b-PCL-b-(PSt)_2$ was synthesized via chemoenzymatic method by combining enzyme-catalyzed ring-opening polymerization (eROP) of ${\varepsilon}$-caprolactone (${\varepsilon}$-CL) and atom transfer radical polymerization (ATRP) of styrene. By this process, we obtained copolymers with controlled molecular weight and low polydispersity. The structure and composition of the obtained copolymers were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC) and infrared spectroscopy analysis (IR). The crystallization behavior of the copolymers was analyzed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The crystallization behavior of the H-shaped block copolymers demonstrated a PCL dominate crystallization. The self-assembly behavior of the copolymers was investigated in aqueous media. The hydrodynamic diameters of the copolymer micelles in aqueous solution were measured by dynamic light scattering (DLS). The morphology of the copolymer micelles was observed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The hydrodynamic diameters of spherical micelles declined gradually with the increase of the hydrophobic chain lengths of the copolymers. The critical micelle concentration (CMC) values were determined from fluorescence emission, and it was found that the CMCs decreased with an increase of PSt hydrophobic block lengths.

• Elastomers and Composites
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• 제49권1호
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• pp.13-23
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• 2014

본 연구에서는 생체분해성 폴리에스터 계열의 glycolide, L-lactide 및 ${\varepsilon}$-caprolactone 단량체를 이용하여 2단계 중합법에 의한 삼원 공중합체를 제조하여, DSC를 이용한 비등온 결정화 거동을 고찰하였다. 보다 더 정확한 거동을 검토하기 위하여 Avrami 식과 Ozawa 식을 조합하여 비등온 결정화 거동을 고찰하였다. 과냉각도를 분석한 결과 PGCLA21의 값이 가장 큰 값을 보이고 있으며 L-lactide 함량이 증가함에 따라 과냉각도는 증가하는 경향을 보이고 있다. 수정된 Avrami 식을 이용하여 다양한 냉각속도에서 비등온 결정화 거동 결정화 속도 상수는 큰 경향을 보이고 있지 않는 것을 알 수 있었다. Avrami 및 Ozawa 식을 조합하여 특정한 상대적 결정화도에서의 냉각함수를 구한결과 L-lactide 함량이 증가하면서 PGCL과 비교시 결정화 속도를 향상시키는 역할을 하고 있는 것으로 여겨지는 반면 PGCLA41과 PGCLA21을 비교시 L-lactide 함량이 일정 이상 증가시 logF(T) 값이 큰 것을 확인 할 수 있는데 이는 동일한 결정을 얻는데 더 많은 냉각 속도를 필요로 한다는 것을 의미하며 결정화 속도 향상에 부정적인 영향을 미치는 것으로 판단된다.

• 한국재료학회지
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• 제33권2호
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• pp.63-70
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• 2023

In this study, crystallization was effectively suppressed in Al-based metallic glasses (Al-MGs) during pulverization by cryo-milling by applying an extremely low processing temperature and using a surfactant. Before Al-MGs can be used as an additive in Ag paste for solar cells, the particle sizes of the Al-MGs must be reduced by milling. However, during the ball milling process crystallization of the Al-MG is a problem. Once the Al-MG is crystallized, they no longer exhibit glass-like behavior, such as thermoplastic deformation, which is critical to decrease the electrical resistance of the Ag electrode. The main reason for crystallization during the ball milling process is the heat generated by collisions between the particles and the balls, or between the particles. Once the heat reaches the crystallization temperature of the Al-MGs, they start crystallization. Another reason for the crystallization is agglomeration of the particles. If the initially fed particles become severely agglomerated, they coalesce instead of being pulverized during the milling. The coalesced particles experience more collisions and finally crystallize. In this study, the heat generated during milling was suppressed by using cryo-milling with liquid-nitrogen, which was regularly fed into the milling jar. Also, the MG powders were dispersed using a surfactant before milling, so that the problem of agglomeration was resolved. Cryo-milling with the surfactant led to D50 = 10 um after 6 h milling, and we finally achieved a specific contact resistance of 0.22 mΩcm² and electrical resistivity of 2.81 μΩcm using the milled MG particles.

• Korean Chemical Engineering Research
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• 제40권6호
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• pp.659-663
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• 2002

에틸알코올의 첨가로 과포화가 유도되는 NaF 결정화 과정을 수정진동자를 이용하여 측정하였다. 준안정 상태의 NaF 용액에 에틸알코올을 첨가하면 NaF의 용해도가 감소하여 NaF 과포화가 형성되어 결과적으로 NaF 결정이 생성 및 성장한다. NaF 용액의 과포화에서 결정 생성 및 성장하는 변화를 감지하기 위하여 수정진동자의 금전극 표면을 염산시스테아민(cysteamine hydrochloride; 2-mercaptoethylamine hydrochloride)으로 self-assembly하여 수식하여 응용 가능성을 검토하였다. 과포화 과정을 통해 생성된 NaF 결정이 염산시스테아민 표면 위에 흡착되면 흡착된 양에 비례하여 수정진동자 주파수가 변화하기 때문에 주파수 변화를 측정함으로써 간접적으로 NaF 결정과정을 분석할 수 있었다. 알코올의 주입량을 1-5 ml로 변화시킴으로써 용액 중에 형성되는 NaF의 과포화 농도의 수준을 변화시켜 주었으며, 염산시스테아민 박막에 대한 주파수 변화를 분석함으로써 주입량에 따른 NaF 결정화 정도를 해석할 수 있었다. 이들 결과들을 통하여 수정진동자를 이용한 NaF 결정화 과정의 분석이 가능함을 알 수 있었다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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• pp.656-660
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• 2003

We studied the crystallization behavior of LP-CVD a-Si film using UV pulsed laser. With increase in the shot number of irradiation by fixing its energy density, poly-Si film having a large grain size of $0.5 {\mu}m$ was obtained. By analyzing the crystallized Si films using optical analysis such as Raman spectroscopy or AFM technique etc., conspicuous correlation between the grain size and the resultant film properties such as the stress or the roughness has been found. With the increase in the energy density or the shots number of laser, remarkable grain growth occurred following to the roughness formation corresponding to the increase in the tensile stress.