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유한요소법에 의한 ZnO 바리스터 동작 시 발생되는 열폭주 현상 해석
장경욱 한국전기전자재료학회 2022 전기전자재료학회논문지 Vol.35 No.4
Since the ZnO varistor is a semiconductor device, the internal thermal distribution during the varistor operation is recognized as an important factor in the performance and deterioration of the varistor. For an optimal varistor structure design, the thermal runaway phenomenon during the varistor operation was interpreted using the Comsol 5.2 analysis program by a finite element analysis. The maximum temperature of the center measured in the cross section of the ZnO varistor was confirmed to increase as the temperature moved from the lower electrode to the center towards the upper electrode up to 572.6 K. The electrodes are thinned so that the influence of the Schottky barrier is not great. The heat gradient balance is determined to be improved when the electrode of the hybrid form is introduced. The thickness, density, pore distribution, impurity uniformity, and particle size of the ZnO varistor are required, and it is determined that the pyrolysis gradient will be improved regardless of the electrode thickness. When these results are applied to design the ZnO varistor, the optimal structure of the ZnO varistor can be obtained.
반응성 액상 소결법으로 제조한 다공성 Mg<sub>3</sub>Sb<sub>2</sub>계 화합물의 열전물성
장경욱,김인기,김일호,Jang, Kyung-Wook,Kim, In-Ki,Kim, Il-Ho 한국재료학회 2015 한국재료학회지 Vol.25 No.2
The porous $Mg_3Sb_2$ based compounds with 60~70% of relative density were prepared by powder compaction at room temperature and reactive liquid phase sintering at 1023 K for 4hrs. The stoichiometric $Mg_3Sb_2$ compounds were synthesized from elemental Sb and Mg powder in the mixing range of 61~63 at% Mg. The increased scattering effect due to the micro-pores reduced the mobility of the charge carrier and the phonon, which caused the electrical conductivity and the thermal conductivity to decrease, respectively. But the scattering effect was greater for the electrical conductivity than for the thermal conductivity. Excess Mg alloyed in the $Mg_3Sb_2$ compounds decreased the electrical conductivity, but had no effect on the thermal conductivity. On the other hand, the large increase of the Seebeck coefficient was the result of a decrease in the charge carrier density due to the excess Mg. Dimensionless figure of merit of the porous $Mg_3Sb_2$ compound reached a maximum value of 0.28 at 61 at% Mg. The obtained value was similar to that of $Mg_3Sb_2$ compounds having little pores.
MWCNT/ZnO 복합체 필름을 이용한 가스센서의 NOX 가스 검출 특성 분석
장경욱,김현수,이원재,박용서 한국전기전자재료학회 2016 전기전자재료학회논문지 Vol.29 No.5
In this study, we fabricated NOX gas sensor by using multi-walled carbon nanotubes(MWCNT)/zinc oxide(ZnO) composite film. Carbon nanotubes (CNTs) have good electronic, chemical-stability, and sensitivity characteristics. And zinc oxide (ZnO) is a wide band gap and large exciton binding energy semiconductor. In particular, gas sensors require characteristics such as high speed, sensitivity, and selectivity. The fabricated gas sensor was used to detect NOX gas for different values of the NOX gas concentrations. The gas sensor that absorbed NOX gas molecules showed a increasing in resistance. The sensitivity of the gas sensor was increased by increasing the gas concentrations. Additionally, while changing the temperature inside the chamber for the MWCNT/ZnO composite film gas sensor, we obtained the sensitivity. And the comparison analysis to ZnO film gas sensor for detecting NOX gas. From the experiment result, we confirmed improvement of NOX gas detection characteristics using the MWCNT/ZnO composite film. 본 연구에서는 우수한 전도 특성과 화학적 안정성을 지녔으며 소형화 및 대량생산이 가능한 카본 나노 튜브(carbon nanotubes, CNT)를 열적 화학 기상 성장법(Thermal Chemical Vapor Deposition)을 통해 제조된, MWCNT (Multi-Walled Carbon Nanotube)와 산화아연(zinc oxide, ZnO)을 이용하여 MWCNT/ZnO 복합체 필름을 제작하였으며, 상온 및 온도 변화에 따른 NOX 가스 검출 특성을 산화아연 가스센서와 비교 분석하였다. 또한, 챔버 내 NOX 가스 농도에 따른 가스센서의 검출 특성을 실험하였다.
GC물질을 코팅한 QCM가스센서의 가스검출 및 열화특성에 관한 연구
장경욱 경원전문대학 2000 論文集 Vol.22 No.-
In recognition of the gases using the quartz crystal microbalance (QCM) coated with the film materials, it is important to obtain the recognition ability of gases, and the stability of film coated above the QCM. Especially, the thickness of film coated above the QCM is decreased according with the using circumstance and time of QCM gas sensor. Therefore, the sensing chararcteristics of film is changed with these. In this paper, we coated the lipid GC materials varing with the blended amount of PVC (Poly Vinyl Chloride) and solution (Tetra Hydrofan:THF) above QCM to obtain the stability of lipid PC film. QCM gas sensors coated with film materials were measured the frequency change in the chamber of stationary gas sensing system injected 1-hexane, ethyl acetate, ethanol and benzene of 20㎕, respectively. Also, we measured the degradation characteristics of QCM gas sensor to show the properties of stability.
웨어러블용 Nylon-Yarn NO<sub>x</sub> 가스 센서의 검출 온도 변화에 따른 열 특성 시뮬레이션
장경욱,Jang, Kyung-Uk 한국전기전자재료학회 2020 전기전자재료학회논문지 Vol.33 No.4
Atmospheric environmental problems have a major impact on human health and lifestyle. In humans, inhalation of nitrogen oxides causes respiratory diseases, such as bronchitis. In this paper, thermal analysis of a gas sensor was carried out to design and fabricate a wearable nylon-yarn gas sensor for the detection of NO<sub>x</sub> gas. In the thermal analysis method, the thermal diffusion process was analyzed while operating the sensors at 40 and 60℃ to secure a temperature range that does not cause thermal runaway due to temperature in the operating environment. Thermal diffusion analysis was performed using the COMSOL software. The thermal analysis results could be useful for analyzing gas adsorption and desorption, as well as the design of gas sensors. The thermal energy diffusion rate increased slightly from 10.05 to 10.1 K/mm as the sensor temperature increased from 40 to 60℃. It was concluded that the sensor could be operated in this temperature range without thermal breakdown.