• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1997년도 Proceedings of the 13th KACG Technical Meeting `97 Industrial Crystallization Symposium(ICS)-Doosan Resort, Chunchon, October 30-31, 1997
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• pp.1-5
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• 1997

The growth mechanism of AMT(Ammonium Meta-Tungstate) crystal was interpreted as two-step model. The contribution of the diffusion step increased with the increase of temperature, crystal size, and supersaturation. The crystal size distribution from a batch cooling crystallizer was predicted by the numerical solution of a mathematical model which uses the kinetics of nucleation and crystal growth. Temperature control of a batch crystallizer was studied using Learning control algorithm. The purity of AMT crystal producted in this investigation was above 99.99%.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1998년도 IUMRS-ICEM ABSTRACT BOOK
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• pp.130.4-130
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• 1998

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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• pp.1333-1336
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• 1998

Hydrogenated amorphous silicon(a-Si:H) films which were deposited by plasma enhanced chemical deposition(PECVD) have been recrystallized by the two-step rapid thermal annealing(RTA) employing the halogen lamp. The a-Si:H films evolve hydrogen explosively during the high temperature crystallzation step. In result, the recrystallized polycrystalline silicon(poly-Si) films have poor surface morphology. In order to avoid the hydrogen evolution, the films have undergone the dehydrogenation step prior to the crystallization step Before the RTA process, the active area of thin film transistors (TFT's) was patterned. The prepatterning of the a-Si:H active islands may reduce thermal damage to the glass substrate during the recrystallization. The computer generated simulation shows the heat propagation from the a-Si:H islands into the glass substrate. We have fabricated the poly-Si TFT's on the silicon wafers. The maximun ON/OFF current ratio of the device was over $10^5$.

• Journal of Welding and Joining
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• 제20권5호
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• pp.93-98
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• 2002

The effect of bonding misfit on single crystallization of transient liquid phase (TLP) bonded joints of single crystal superalloy CMSX-2 was investigated using MBF-80 insert metal. The bonding misfit was defined by (100) twist angle (rotating angle) at bonded interface. TLP bonding of specimens was carried out at 1523K for 1.8ks in vacuum. The post-bond heat treatment consisted of the solution and sequential two step aging treatment was conducted in the Ar atmosphere. The crystallographic orientation analysis across the TLP bonded joints was conducted three dimensionally using the electron back scattering pattern (EBSP) method. EBSP analyses f3r the bonded and post bonded heat treated specimens were conducted. All bonded joints had misorientation centering around the bonded interface for as-bonded and post-bond heat treated specimens with rotating angle. The average misorientation angle between both solid phases in bonded interlayer was almost identical to the rotating angle at bonded interface. HRTEM observation revealed that the atom arrangement of both solid phases in bonded interlayer was quite different across the bonded interface. It followed that grain boundary was formed in bonded interface. It was confirmed that epitaxial growth of the solid phase occurred from the base metal substrates during TLP bonding and single crystallization could not be achieved in joints with rotating angle.

• 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.

• Fibers and Polymers
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• 제4권4호
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• pp.156-160
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• 2003

Poly(ethylene 2,6-naphthalate) (PEN)/Poly(ethylene glycol) (PEG) copolymers were synthesized by two step reaction during the melt copolymerization process. The first step was the esterification reaction of dimethyl-2,6-naphthalenedicarbox-ylate (2,6-NDC) and ethylene glycol (EG). The second step was the condensation polymerization of bishydroxyethylnaphthalate (BHEN) and PEG. The copolymers contained 10 mol% of PEG units with different molecular weights. Structures and thermal properties of the copolymers were studied by using $^1{H-NMR}$, DSC, TGA, etc. Especially, while the intrinsic viscosities of PEN/PEG copolymers increased with increasing molecular weights of PEG, but the glass transition temperature, the cold crystallization temperature, and the weight loss temperature of the copolymers decreased with increasing molecular weights of PEG. Consequently, the hydrophilicities by means of contact angle measurement and moisture content of the copolymer films were found to be significantly improved with increasing molecular weights of PEG.

• 한국세라믹학회지
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• 제33권8호
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• pp.855-862
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• 1996

The nucleation and the crystal growth rates of Ge-Se-Te chalcogenide glass by two step heat-treatment and its effect on the mechanical optical properties and water-resistance were determined. The maximum nuclea-tion and crystal growth rate were 2.1$\times$103/mm3 .min at 28$0^{\circ}C$ and 0.4${\mu}{\textrm}{m}$/min at 33$0^{\circ}C$ respectively. When the crystal volume fraction with crystal size $1.5mutextrm{m}$ was about 4% the (hardness and fracture toughness were about 117kg/mm2 and 6.0 MPa.mm1/2)respectively. The weight loss of crystallized glass in water was lower than parent glass($25^{\circ}C$ for 32 hrs : 0.03% 8$0^{\circ}C$ for 16 hrs : 0.1%) as 0.01% at $25^{\circ}C$, 0.03% at 8$0^{\circ}C$ for 16 hrs : 0.1%) at $25^{\circ}C$ 0.03% at 8$0^{\circ}C$ respectively. The IR-transmittance decreased with increasing crystal size and crystal volume fraction. The IR-transmittance of crystallized glass with the crystal size of $1.5mutextrm{m}$ (crystal volume fraction : 4%) presented 56% which was about 4% lower than that of parent glass.

• 한국치위생학회지
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• 제19권1호
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• pp.151-159
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• 2019

Objective: This study aimed to investigate the relation between rinsing time and the change in enamel surface after fluoride application on the enamel surface. Methods: We recruited two sample groups with different mouth rinsing times. While one group rinsed the teeth immediately after applying acidulated phosphate fluoride (APF) gel, the other group rinsed the teeth 30 minutes after APF gel application. In each group, we performed the following four-step experiment: (i) apply APF gel on the teeth, (ii) rinse the teeth, (iii) immerse the teeth in orange juice, and (iv) measure enamel surface microhardness and scan enamel surfaces. Results: The group that rinsed 30 minutes after treatment exhibited greater microhardness than the group that rinsed immediately after fluoride treatment. The former also showed smooth and regular crystallization, whereas the latter showed rough and damaged crystallization and irregular surfaces. Conclusions: Based on these observations, we conclude that delaying the rinsing time improves the dental caries preventive effect of fluoride.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권4호
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• pp.232-238
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• 2000

PZT thin films(3500 ) have been prepared onto $Pt/Ti/SiO_2/Si$ substrates with a RF magnetron sputtering system using PB1.05(Zr0.52,Ti0.48)O3 ceramic target. We used two-step annealing techniques. As the RTA times and temperatures were increased, crystallization of PZT thin films were enhanced. The ferroelectric characteristics of PZT capacitors fabricated at $700^{\circ}C$ for 60 seconds were like these remanent polarization were $12.1 \muC/cm^2$, coercive field were 110 kV/cm, leakage current density were $4.1\times10-7 A/cm^2,\; \varepsilonr=442,$ and remanent polarization were decreased by 22% after 1010 cycles, respectively.

• Applied Science and Convergence Technology
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• 제27권5호
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• pp.105-108
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• 2018

Transparent $TiO_2$ nanotube arrays are successfully prepared by a two-step approach involving electrochemical anodization and RF magnetron sputtering. First, a Ti film is deposited on an FTO substrate by RF magnetron sputtering at room temperature. The morphologies of the Ti film are controlled by the working distance, Ar flow, and DC power. Second, an anodization treatment is electrochemically performed for the formation of nanotube arrays from the deposited Ti film, followed by post-annealing treatment in air for the formation of $TiO_2$ crystallization. The back side of the crystallized $TiO_2$ nanotube arrays is illuminated with solar light to characterize the photoelectrochemical reaction, and their photoelectrochemical properties are investigated. This work provides information on application of a thin film deposited by RF sputtering in the field of photoelectrochemical water splitting.