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채희백 순천향대학교 기초과학연구소 1995 순천향자연과학연구 논문집 Vol.1 No.1
We measured high temperature thermophysical properties of POCO-AXM-5Q1 graphite which has been used as a reference standard material from NIST(National Institute of Standards and Technology). Thermal diffusivity an specific heat were measured in a temperature range 300∼1400K with laser flash method. Specific heat is modeled by the Debye phonon model. Thermal conductivity can be calculated by the measured specific heat and the measured thermal diffusivity. Electrical conduction and thermal conduction are correlated as the Wiedemann-Frantz law which is modeled with the free electron gas. High temeprature thermal conduction is governed by the phonon-phonon scattering as U-process or N-process. The combined model is fitted to the data and analysed.
채희백,김수호,박훈,홍진수 순천향대학교 기초과학연구소 2000 순천향자연과학연구 논문집 Vol.6 No.2
Reactive pulsed laser deposition(PLD) is used to deposit TiN with varying the substrate temperature and the pressure of N2 gas in the vacuum chamber. The hardness of TiN is very sensitive to the PLD processing parameters. XRD peak is sharp at the lowest N2 pressure 10-4 torr at 450℃ and decreases when the pressure is higher at the same substrate temperature. Nano-indenter is used to measure the hardness of the film from the top surface to the depth of 300 nm. Crystallized film with sharper XRD peak is shown higher hardness. Reactive PLD TIN film is shown 40% inhancemant of the hardness than non-reactive PLD film.
채희백,윤영수,박훈,김수호 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6
In order to enhance biocompatibility, a hydroxyapatite (HA) coating on Ti-6Al-4V is a common implant used in dental and orthopedic procedures. HA coatings were deposited by using a pulsed laser deposition (PLD) technique with a Nd:YAG laser (355 nm) on a Ti-6Al-4V substrate at a low substrate temperature of 300 ℃ in a vacuum without water vapor. The deposited coatings were post-heated for 4 h in air at dierent temperatures (400, 525 and 600 ℃). The crystallinity and the composition were in fluenced by the post-heat treatment. The as-deposited coating was amorphous in phase without a HA structure and the post-heated coating at 400 ℃ showed no significant change in crystallinity. When the coatings were post-heated at 525 and 600 ℃, they were transformed to a highly-crystalline HA phase. The XRD patterns showed almost all the main HA peaks. The phosphate (PO3-4) band and the hydroxyl (OH-) band were observed in the FTIR spectra. The Ca/P ratio was 2.20 and the average adhesion strength between the HA coating and substrate was 30.4 MPa. We obtained crystalline, higher-bonding-strength HA ,films through a post-heat treatment of the as-deposited films.
박세일,채희백 순천향대학교 기초과학연구소 1996 순천향자연과학연구 논문집 Vol.2 No.1
화학증착법으로 합성한 다이아몬드 필름의 비열을 80 - 400 k사이에서 AC Calorimetry를 사용하여 측정하였다. 합성할 때 반응로내의 메탄가스의 농도를 7.5%와 10%로 하였다. 다이아몬드필름내에 주상구조의 낱알경계가 관찰되었다. 열전도도 측정과 광학현미경관찰을 한 결과 point defects, extended defect, dislocation 및 void 등의 불순물이 필름내 존재함이 확인되었다. 이들 defects들은 열에너지 운반자 -포논과 충돌을 일으키는 scattering center가 되며 결정도를 떨어뜨리는 원인이된다. 또한 이들은 결정의 경도를 떨어뜨리게되며 결과적으로 비열을 증가시킨다. 측정된 비열데이터를 디바이모델로 해석하여 디바이온도를 구하였다.
CO 가스 감지 위한 Sb가 첨가된 SnO₂박막 센서의 개발
김창교,채희백 순천향대학교 부설 산업기술연구소 1996 순천향 산업기술연구소논문집 Vol.2 No.1
Two types of thin film SnO2 gas sensors, which are Pd-SnO2-Pt-SiO2-Si and P.-(Sb-SnO2)-Pd-SiO2-Si, were explored. The influence of Sb additives on the gas sensitivity of SnO2 film was investigated. The SEM analysis showed that the surface morphology of the thin film gas sensor is columnar tyre. The temperature dependence of resistance change of SnO2 was examined. The gas sensing characteristics of the devices were investigated. The SnO2 samples doped simultaneously with Pt and Sb show a higher sensitivity to CO than the SnO2 samples doped with Pd. The sensitivity of the SnO2 doped with Pt and Sb to CO gas was 26% at 300℃
DLC(Diamond Like Carbon) Films의 열전도도
채희백,이태기 순천향대학교 기초과학연구소 1997 순천향자연과학연구 논문집 Vol.3 No.1
DLC(Diamond Like Carbon) films were deposited by RF-PACVD(Radio Frequency - Plasma Assited Vapor Deposited) method. Films were deposited by varying negative self bias voltage(bias voltage was 100V, 500V) and the substrate was silicon wafer. Thermal conductivity of DLC film was measured by 3ω-method(quasi steady state method) in a temperature range 77K∼300K. Thermal conductivity of the film which was made at high bias voltage is higher than the film which was made at low bias voltage.
채희백,이수빈,홍진수,김승우 순천향대학교 기초과학연구소 1997 순천향자연과학연구 논문집 Vol.3 No.2
Nd-Yag pulsed laser(210mJ, 6ns) was focused on polymer to make craters in an atmosphere. The size of the crater has a trend to follow the ideal estimation. Laser-firing near the focal point in air could be an energy dissipation of laser and a possible cause of the crater size reduction. Multiple plasma image and normal eruption of the plasma was also studied with photographs.
채희백,정영석,이태기 순천향대학교 기초과학연구소 1997 순천향자연과학연구 논문집 Vol.3 No.2
Nano-sized SiC particles of 1, 10, 20 and 30 vol% were dispersed in a-Si₃N₄ matrix and hot-pressed under the condition of 30 MPa of N₂ at 1850℃. Thermal conductivity of Si₃N₄-SiC nanocomposite was measured between 300 K and 400 K. Si₃N₄-20 vol% SiC showed the lowest thermal conductivity. In growth Si₃N₄, SiC-nano particle could be a nucleation site and dispersion is maximized in the Si₃N₄-matrix when the vol% is 20. More than 20 vol% SiC, SiC particles are located on the Si₃N₄ boundaries. Thus, phonons are scattered well in Si₃N₄-20 vol% SiC with the dispersed SiC and thermal resistance(conductivity) is high(low). Similar behavior was reported in the electricl resistivity and fracture toughness.
채희백,김종철 순천향대학교 기초과학연구소 1997 순천향자연과학연구 논문집 Vol.3 No.1
FIbrous glass board is widely used for the heat-insulation material. Thermal conductivity of these material is low. NIST prepared the cirtified reference material which is used for the comparison and verification of the apparatus for thermal conductivity measurements Guarded hot plate method is used to measure thermal conductivity and the results are compared with NIST data. Heat conduction path has three modes, such as through the fiber glass itself, air between the fiber and by radiation. The apparent thermal conductivity of fiber glass board 1450b is 3.5~4.2x10-2 W/m K in a temperature range from ambient to 345K. It's in agreement with NIST data within ±1.5%.
이상협;배형철;송석태;한찬수;채희백 순천향대학교 기초과학연구소 2010 순천향자연과학연구 논문집 Vol.16 No.2
In order to know how the [2-(2'-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene] (MEH-PPV) layer works in organic light emitting diode, two different types of devices were fabricated, which are MEH-PPV single layer devices and MEH-PPV/tris (8-hydroxy-quinoline)aluminium(Alq3) bilayer devices. On the indium-tin-oxide(ITO) glass anode MEH-PPV layer was first spin-coated, and the Alq3 layer and the aluminium(Al) anode were vapor-deposited sequentially. The devices shows a trend that has lower current, luminous efficiency in case the thickness of the device is larger. Some bilayer devices, however, show more improved performance than other devices of smaller total thickness. This results were discussed on the basis of improved exciton formation resulting from balanced carrier transport.