• 대한기계학회논문집
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• 제19권9호
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• pp.2122-2132
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• 1995

There are some cases which require to grasp the abrasion resistance property in the fields of the high-technology to be required the high specific strength and modulus. In this study, wear test with the various test temperature and velocity were performed in the SiCw/A16061 composite and A16061 matrix using the wear test machine of the ring-on-disc type. As the results, the friction and wear properties by various test temperature and velocity were examined. The worn surface has observed by scanning electron microscope in order to examine the wear mechanism.

• Transactions on Electrical and Electronic Materials
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• 제2권2호
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• pp.32-36
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• 2001

A new solid source for low temperature diffusion into silicon was developed. The source wafer consists of an “active” compound, which is sol-gel prepared phosphosilicate glass-ceramics containing 56% P$_2$O$\sub$5/, embedded in a skeletal foam-like, inert substrate. Phosphorus diffusion from the new solid sources at low temperatures (800-875$^{\circ}C$) produced reprodecible sheet resistances and shallow junctions. From a series of one hour doping runs, the life time of the phosphosilicate source was determined to be over 40 hours. The effective diffusion coefficient of phosphorus into silicon and the corresponding activation energy at 850$^{\circ}C$ were determined to be 7.5${\times}$10$\^$-15/ $\textrm{cm}^2$/sec and ∼3.9 eV, respectively.

• 설비공학논문집
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• 제8권1호
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• pp.1-12
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• 1996

In lots of application to heat exchanger systems, closed two-phase thermosyphons are tilted from a horizontal. If the tilt angle, especially, is less than 30$^{\circ}$, the operational performances of thermosyphon are highly dependent on tilt angle. The present study was conducted to better understand such operational behaviors as mech-anni는 of phase change, and flow patterns inside a tilted thermosyphon. For experiment, an ethanol thermosyphon with a 35% of fill charge rate was designed and manufactured, using a copper tube with a diameter 19mm and a length 1500mm. Through a series of test, the tilt angle was kept constant at each of 4 different values in the range 10~25deg. and the heat supply to the evaporator was stepwisely increased up to 30㎾/$m^2$. When a steady state was established to the thermosyphon for each step of thermal loads, the wall temperature distribution and vapor temperature at the condenser were measured. The wall temperature distributions demonstrated a formation of dry patch in the top end zone of the evaporator, with a values of temperature 20~4$0^{\circ}C$ higher than the wetted surface for a moderate heat flux q≒20㎾/$m^2$. Inspite of the presence of hot dry patch, however, the mean values of boiling heat transfer coefficient at the evaporator wall were still in a good agreement with those predicted by Rohsenow's formula, which was based on nucleate boiling. For the condenser, the wall temperatures were practically uniform, and the measured values of condensation heat transfer coefficient were 1.7 times higher than the predicted values obtained from Nusselt's film condensation theory on tilted plate. Using those two expressions, a correlation was formulated as a function of heat flux and tilt angle, to determine the total thermal resistance of a tilted thermosyphon. The correlation formula showed a good agreement with the experimental data within 20%.

• 한국전기전자재료학회논문지
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• 제27권12호
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• pp.809-814
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• 2014

Spinel thin films were prepared by the spin spray technique to develop new thermal imaging materials annealed at low temperature for uncooled microbolometer applications. The spinel thin films were deposited from $[(Ni_{0.30}Co_{0.33}Mn_{0.37})_{1-x}Cu_x]_3O_4$ ($0.1{\leq}x{\leq}0.2$) solutions and then annealed at $400^{\circ}C$ for 1 h in argon. Effects of Cu content (x) and deposition time on the electrical properties of the annealed films were investigated. With increasing deposition time, the resistivity of the annealed films increased. For the annealed films deposited for 1 min, the resistivity of x=0.15 films was lower than that of x=0.1 films due to the different grain sizes. The high temperature coefficient of resistance (TCR) of the annealed films could be obtained at temperature below $50^{\circ}C$. Typically, the resistivity of $127{\Omega}{\cdot}cm$ and TCR of -5.69%/K at $30^{\circ}C$ were obtained for x=0.1 films with deposition time of 1 min annealed at $400^{\circ}C$ for 1 h in argon.

• 전기학회논문지
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• 제56권9호
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• pp.1602-1608
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• 2007

The composites were fabricated, respectively, using 61[vol.%] SiC-39[vol.%] $TiB_2$ and using 61[vol.%] SiC-39[vol.%] $ZrB_2$ powders with the liquid forming additives of 12[wt%] $Al_2O_3+Y_2O_3$ by hot pressing annealing at $1650[^{\circ}C]$ for 4 hours. Reactions between SiC and transition metal $TiB_2$, $ZrB_2$ were not observed in this microstructure. The result of phase analysis of composites by XRD revealed SiC(6H, 3C), $TiB_2$, $ZrB_2$ and $YAG(Al_5Y_3O_{12})$ crystal phase on the Liquid-Phase-Sintered(LPS) $SiC-TiB_2$, and $SiC-ZrB_2$ composite. $\beta\rightarrow\alpha-SiC$ phase transformation was occurred on the $SiC-TiB_2$ and $SiC-ZrB_2$ composite. The relative density, the flexural strength and Young's modulus showed the highest value of 98.57[%], 249.42[MPa] and 91.64[GPa] in $SiC-ZrB_2$ composite at room temperature respectively. The electrical resistivity showed the lowest value of $7.96{\times}10^{-4}[\Omega{\cdot}cm]$ for $SiC-ZrB_2$ composite at $25[^{\circ}C]$. The electrical resistivity of the $SiC-TiB_2$ and $SiC-ZrB_2$ composite was all positive temperature coefficient resistance (PTCR) in the temperature ranges from $25[^{\circ}C]$ to $700[^{\circ}C]$. The resistance temperature coefficient of composite showed the lowest value of $1.319\times10^{-3}/[^{\circ}C]$ for $SiC-ZrB_2$ composite in the temperature ranges from $100[^{\circ}C]$ to $300[^{\circ}C]$ Compositional design and optimization of processing parameters are key factors for controlling and improving the properties of SiC-based electroconductive ceramic composites.

• 지구물리와물리탐사
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• 제18권3호
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• pp.105-114
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• 2015

상온 상습 환경에서 수포화 암석코어의 전기비저항을 장시간 모니터링 할 수 있는 장치를 구현하였다. 양쪽 금속망 전극에 덧댄 종이필터와 암석코어를 감싼 열수축튜브의 상부 중앙 외피면에 3-채널 펌프로 물을 충분히 공급하면서 전기저항을 측정하면 암석코어의 수포화 상태를 유지하면서 일주일 이상 전기비저항을 모니터링 할 수 있다. 이 장치를 이용하여 흑운모 편마암, 안산암질 응회암, 셰일의 3종류 암석코어의 수포화 전기저항을 9일간 모니터링 한 결과 다음과 같은 2가지 가설을 제시할 수 있었다. 즉, 전기비저항 온도계수의 수렴 속도는 열물성과 관련이 있을 것이라는 것과 건조 저항을 수포화 때의 평균 저항으로 나눈 건조/수포화 저항비는 유효공극률과 상관될 것이라는 것이다. 실제로, 3가지 암석의 건조/수포화 저항비는 각각 48, 705, 2로 나타났고 이때 각각의 유효공극률은 3.7%, 3.3%, 13.0%이었다.

• 센서학회지
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• 제7권5호
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• pp.356-363
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• 1998

유한요소법을 이용한 수치해석의 결과를 바탕으로 실리콘기판위에 스트레스균형이 이루어진 $Si_3N_4$(150 nm)/$SiO_2$(300 nm)/$Si_3N_4$(150 nm) 다이아프램을 증착한 후, 히터의 물질로 Pt를 사용하고, 마이크로머시닝 기술로 뒷면의 실리콘기판을 식각하여 열손실이 개선된 마이크로히터를 제작하였다. 또한, 히터의 온도를 측정하기 위해서 온도센서를 내장하였다. 온도에 따른 온도센서의 저항 값 및 히터의 소비전력을 측정 계산하고, IR thermoviewer로 다이아프램의 열분포를 측정하여, 유한요소법으로 수치해석한 온도분포특성과 비교 분석하였다. 히터의 저항온도계수는 약 $0.00379/^{\circ}C$였고, 약 $300^{\circ}C$의 온도에서 51 mW정도의 전력이 소모되었으며, 히터위의 $SiO_2$층에서의 온도분포는 비교적 균일하였다.

• 한국방재학회 논문집
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• 제1권1호
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• pp.127-138
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• 2001

CFRCs는 고온에서의 우수한 물성에도 불구하고, 연소에 대한 취약한 성질로 인하여 많은 분야에서 사용에 제약을 받고 있다. 그러므로 EFRCs의 연소저항성을 향상시키기 위해서 수 많은 연구가 수행되어지고 있다. 본 연구에서는 고온에서 보다 개선된 물성과 높은 연소저항성을 부여하고, 다른 도포물질과 비교해서 낮은 열팽창계수의 차이를 보이는 탄화규소를 Pack-Cementation 방법으로 4방향성 CFRCs에 도포하였다. 제작된 탄화규소로 도포된 CFRCs는 광학현미경의 관찰을 통하여 도포 메카니즘을 추정하였으며, TGA 시험을 통하여 개선된 연소저항성을 조사하였다. Arc plasma torch 시험을 통하여 고온 연소특성과 거동을 연구하였다. 그 결과로부터 탄화규소로 코팅된 CFRCs의 기계적 강도와 고온 연소특성이 순수한 4방향성 CFRCs에 비해서 개선되었다는 것을 알았다.

• 센서학회지
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• 제12권5호
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• pp.199-204
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• 2003

본 논문에서는 Ta-N 스트레인게이지를 이용한 극한 환경용 세라믹 박막형 압력센서의 제작 및 특성에 관하여 연구하였다. 압력감지부로 Ta-N 스트레인게이지를 사용하였으며, SDB(Si-wafer Direct Bonding)와 전기화학적 식각정지법을 이용하여 매몰 cavity를 가지는 저가격 고수율의 Si 박막 다이어프램을 제작하였다. 또한, 실리콘 박막 다이어프램상에 박막형 스트레인게이지를 형성하여 세라믹 박막형 압력센서를 제작하였다. 제작된 세라믹 박막형 압력 센서는 기존의 스트레인 게이지를 이용한 로드셀에 비해서 온도특성이 우수하고 재현성, 소형화, 집적화 및 저가격화가 가능하기 때문에 고온, 고압 등의 각한 환경에서도 사용이 가능할 것으로 기대된다.

• 한국표면공학회지
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• 제32권1호
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• pp.3-9
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• 1999

Pt thin film of about 7000$\AA$ thickness was deposited on the alumina substrate using DC Magnetron Sputter and the characteristics of the film for temperature sensor were investigated. When film of about 7000$\AA$ thickness was deposited at working gas pressure of $2.0{\times}10^{-3}$torr, sputtering power of 50W, substrate temperature of $350^{\circ}C$(Ts), sheet resistance(Rs), resistivity($\rho$) and temperature coefficient of resistivity(TCR) of the film were respectively 0.39$\Omega$/$\square$, 27.60$\mu\Omega$-cm and $3350 ppm/^{\circ}C$. When the film was annealed at $1000^{\circ}C$ for 240min in hydrogen ambient, Rs, $\rho$ and TCR were respectively 0.236$\Omega$/$\square$, 15.18$\mu\Omega$-cm and 3716 ppm/$3716 ppm/^{\circ}C$. When working gas of 15sccm oxygen and 100sccm Argon were used, Rs, $\rho$ and TCR were respectively 0.335$\Omega$/$\square$, 22.45$\mu\Omega$-cm and $3427 ppm/^{\circ}C$. When the film was annealed at $1000^{\circ}C$ for 240min, Rs, $\rho$and TCR were respectively 0.224/$\Omega$$\square$, 14$\mu\Omega$-cm and $3760 ppm/^{\circ}C$ and the characteristics of the film were much improved.