• 한국결정성장학회지
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• 제8권1호
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• pp.187-192
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• 1998

일반적으로 재료의 응고조직은 주상정과 등축정 수지상 영역으로 이루어지는데 이것은 제품의 기계적, 물리적 성질과 밀접한 관계를 가지기 때문에 주상정-등축정 천이에 관한 많은 이론적 연구가 행하여지고 있다. 본 연구에서는 J.D. Hunt에 의하여 일방향응고시 주상정앞에서의 핵생성과 결정성장조건을 이용하여 구하여진 해석학적 주상정-등축정 조건식을 바탕으로 응고속도에 따라 변하는 분배계수와 액상선기울기를 적용하여 수정된 조건식을 구하였다. 그리고 Al-Cu합금에 대하여 응고변수인 핵생성수, 핵생성온도, 합금의 조성, 응고속도 온도기울기에 따른 천이현상의 변화를 조사하였다.

• 한국세라믹학회지
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• 제15권3호
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• pp.157-167
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• 1978

The batch compositions and physical properties of slag-ceramics were studied with respect to their formability from the molten state and conditions of nucleation and crystal growth treatment. The selected batch compositions for nucleation and growth studies were slag, 56%; silica sand, 28%; $Na_2O＋MgO$, 8% and $TiO_2＋$chromite, 8%. The optimum nucleation condition was the temperature of 75$0^{\circ}C$ with 6 hrs. holding time and the optimum growth condition was the temperature 975$^{\circ}C$ with zero holding time. The slag-ceramics prepared under the above conditions showed the best developed microtexture. The grown crystals were identified as diopside with the average grain size of 5.7$\mu\textrm{m}$, and the amount of crystal grown were about 53% by weight. The prepared specimens of slag-ceramics showed the microhardness, 793kg/$\textrm{mm}^2$; MOR, 1,050 kg/$\textrm{cm}^2$ and thermal expansion coefficient, $85{\div}10^{-7}$cm/cm/$^{\circ}C$($25^{\circ}C$~$700^{\circ}C$).

• 한국군사과학기술학회지
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• 제13권1호
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• pp.120-125
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• 2010

For application of transparent bulletproof materials, the SLS(soda-lime-silicate) glass was heated by 2-step crystallization. The DTA curve for SLS glass revealed the nucleation and crystal growth temperature at about $575^{\circ}C$ and $675^{\circ}C$, respectively. The crystallized glass was heated at various conditions(temperature, time). As a result, the maximum nucleation and crystal growth rates were $3.8\times10^5/mm^3{\cdot}hr$ at $575^{\circ}C$ and 20.58nm/min at $680^{\circ}C$, respectively. The bending strength, fracture toughness and vickers hardness were 451.7MPa, $0.9388MPa{\cdot}m^{1/2}$, and $693.9H_v$ which were 201%, 31%, and 22% higher than parent glass, respectively. Surface image and transmittance of crystallized SLS glass were analyzed by optical microscopy and UV/VIS/NIR spectrophotometer. Transmittance of crystallized SLS glass at visible-range(200~800nm) was not changed.

• 한국표면공학회지
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• 제32권3호
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• pp.385-388
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• 1999

Electron field emission properties from various CVD diamond films were studied. Diamond films were synthesized by microwave plasma CVD at 1173K and at 673K substrates temperature and pulse microwave plasma CVD at 1173K. B-doped diamond film was synthesized by microwave plasma CVD at 1173K also. Estimation by SEM, both the non-doped diamond film and B-doped diamond film which were synthesized at 1173K substrate temperature were $2~3\mu\textrm{m}$ in diameter and nucleation densities were $10^{8}{\;}numbers/\textrm{cm}^2$ order. The diamond film synthesized at 673K was $0.2\mu\textrm{m}$ in diameter and nucleation densities was 109 numbers/cm2 order. The diamond film synthesized by pulse microwave plasma CVD at 1173K was $0.2\mu\textrm{m}$ in diameter and nucleation density was $10^{9}{\;}numbers/\textrm{cm}^2$ order either. From the result of electron field emission measurement, electron field emission at $20V/\mu\textrm{m}$ from CVD diamond film synthesized by pulse microwave plasma CVD was $37.3\mu\textrm{A}/\textrm{cm}^2$ and the diamond film showed the best field emission property comparison with other CVD diamond.

• 한국재료학회지
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• 제11권12호
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• pp.1074-1079
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• 2001

To study the distribution of boron and the boron effect for nucleation of graphite in high carbon steel, neutron induced autoradiography method is used. High carbon steel is easy to make the graphitization by addition of boron. It is easy to analysis of boron distribution using neutron radiography with neutron fluence of $1.9$\times${\times}10^{13}/cm^2$in the boron added high carbon steel. By the neutron induced autoradiography technique, it was found that the distribution of boron depended on boron content, graphitiging temperature and time. And by the analysis of secondary ion mass spectroscopy (SIMS) and electron probe micro analysis (EPMA), boron or boride were acted at nucleation site of graphite in high carbon steel.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.588-590
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• 2008

The thermal signature of nucleation process is characterized by the induction time, the degree of supercooling, and the equilibrium temperature depression. The initiation of nucleation presents stochastic characteristics. The factors that affect nucleation are mechanical impact, ionic concentration, mineral surface characters, and pore size. Hydrate-bearing sediments behave mechanically like other cemented sediments. The data set has important implications for the calibration and interpretation of geophysical measurements and downhole logs collected in gas hydrate provinces, providing particular insight for the interpretation of P- and S-wave data and resistivity logs. In addition, laboratory formation history and ensuing pore-scale spatial distribution likely have a more pronounced effect on the macroscale mechanical properties of hydrate-bearing sediments

• 한국결정성장학회지
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• 제8권2호
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• pp.227-232
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• 1998

Si, Mo 등을 substrate로 하고 Hot-Filament C.V.D법으로 저압으로 다이아몬드 박막을 생성시킬 때 탄화수소의 부착과정, 핵생성 및 성장을 조사하였다. 특성은 substrate의 종류, 온도, 압력, 유속 및 $CH_4-H_2$가스의 몰분율과 같은 process 변수로 조사하였으며 다이아몬드는 Ra-man spectroscopy로 측정하였다. 특히 다이아몬드 핵생성과 성장은 scratch와 같은 결함이 있는 곳에 발생하였고 표면확산 등이 핵생성 초기단계에서 중요한 역할을 하였다.

• 대한전자공학회논문지
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• 제25권7호
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• pp.759-766
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• 1988

the effect of heat treatment in oxygen ambient on the nucleation and growth of oxidation induced stacking faults(OSF) in n-type(100)silicon wafer has been investigated. The growth of OSF is determind as a function of oxygen concentration in silicon wafer, heat treatment time and temperature, and the activation energy for the growth of OSF can be obtained from the growth kinetics. The activation energies are respectively 2.66 eV for dry oxidation and 2.37 eV for wet oxidation. In this paper, we have also studied the structural feature of OSF with the comparison of optical microscopic morphology and crystalline structure.

• 한국전기전자재료학회논문지
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• 제24권9호
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• pp.766-772
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• 2011

Amorphous Si (a-Si) thin films of $p^+/p^-/n^+$ were deposited on $Si_3N_4$/glass substrate by using a plasma enhanced chemical vapor deposition (PECVD) method. These films were annealed at various temperatures and for various times by using a rapid thermal process (RTP) equipment. This step was added before the main thermal treatment to make the nuclei in the a-Si thin film for reducing the process time of the crystallization. The main heat treatment for the crystallization was performed at the same condition of $600^{\circ}C$/18 h in conventional furnace. The open-circuit voltages ($V_{oc}$) were remained about 450 mV up to the nucleation condition of 16min in the nucleation RTP temperature of $680^{\circ}C$. It meat that the process time for the crystallization step could be reduced by adding the nucleation step without decreasing the electrical property of the thin film Si for the solar cell application.

• 한국결정학회지
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• 제7권1호
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• pp.30-35
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• 1996

수열법에 의해 고온 고압용 autoclave내에서 calcite 단결정을 성장하였으며, 자외-가시영역에서의 투과율 등을 측정하였다. Calcite 단결정 성자에 관해 보고된 광화제로는 6M의 M2CO3(M=K, Rb)와 chloride등이 있는데 강알카리의 경우 성장속도는 크나 autoclave를 백금으로 내장해야 하며 chloride의 경우 자발 핵생성에 의한 성장(spontaneous nucleation and growth)의 경향이 강하여 종자결정위에서 성장하는 것에 비해 autoclave 벽면 위에서 자발 핵생성에 의한 성장이 더 우세한 것으로 알려져 있다. 본 연구에서는 autoclave의 내장재료로 고가의 백금대신 테프론을 사용하고자 성장온도가 테프론의 내온(280℃)에서 NH4Cl을 광화제로 사용하여 calcite 단결정을 성장하였다. 연구결과 NH4Cl 수열용액으로 calcite 단결정을 성장할 때 자발 핵생성을 억제하려면 NaCl 또는 CH3COOH가 소량 첨가된 수열용액에서 온도구배를 6-7℃ 이하로 유지하여 성장하여야 함을 확인하였다. 성장된 calcite의 자외 및 청색 가시영역에서 투과율은 80% 정도로 천연보다 약 10% 높았다.