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3-성분 종입자법으로 제조한 저전압 ZnO 바리스터의 발진 전도특성
장경욱,김영천,황석영,김용주,이준웅 한국전기전자재료학회 1996 電氣電子材料學會誌 Vol.9 No.10
In this study, we may be presented the carrier oscillation properties for the low-voltage varistor fabricated by a new method of three composition seed grain, in order to analyze the behavior of carriers at the its equivalent circuit model. The oscillation phenomena of carriers appeared from current-voltage characteristics under knee voltage is shown by the transient flow of nontrapped carriers group in the trap level of intergranular layer, surface state and/or depletion layer. In particularly, current oscillation phenomena is hardly shown in the high electric field. It is that the injected carriers from both electrodes are directly from the conduction band of forward biased ZnO grain through the intergranular layer into the reverse biased ZnO grain, because the trap level in the electric field above the knee voltage is mostly filled.
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.
장경욱 한국전기전자학회 2019 전기전자학회논문지 Vol.23 No.3
In this study, the diffusion process and the thermal energy distribution gradient of the sensor were confirmed by usingthe finite element analysis program (COMSOL) of the mesh method to analyze the thermal diffusion in the wearablefabric (Nylon) + MWCNT gas sensor. To analyze the diffusion process of thermal energy, the structure of the gas sensor was modeled in a two dimensionplane. The proposed modeling was presented with the characteristic value for the component of the sensor, and the gassensor designed using the mesh finite element method (FEM) was proposed and analyzed by suggesting the one-waypartial differential equation in the governing equation to know the degree of thermal energy diffusion and the thermalenergy gradient. In addition, the temperature gradient 10[K/mm] of the anode-cathode electrode layer and the gas detection unit wasinvestigated by suggesting the heat velocity transfer equation. 요 약 본 연구에서는 웨어러블 Fabric (Nylon) + MWCNT 가스센서 내부에서 열확산을 해석하기 위해서 요소해석 프로그램(comsol)을 이용하여 센서 내부에서의 열용량의 확산 과정과 열용량 분포 경도를 확인하였다. 열용량의 확산과정을 해석하기 위해서 가스센서의 구조체에 대하여 이차원으로 모델링을 진행하였으며, 제시된 모델링에대해서 센서 구성 부분에 대한 특성값을 제시하여 메시 요소법(FEM)을 이용하여 설계된 웨어러블 가스센서에 대해서 열용량이 확산되는 정도와 열용량 경도를 구하기 위해서 지배방정식으로 1계 편미분방정식을 제안하여 해석하였으며, 열속도 전달식을 제안하여 전극층과 가스 검출부의 10[K/mm] 온도 경도를 구하였다.
장경욱 경원전문대학 1996 論文集 Vol.18 No.1
This paper may be presented the carrier oscillation properties for the low voltage varistor fabricated by a new method of three-composition seed grain, in order to analyze the behavior of carriers at the its equivalent circuit model. The oscillation phenomena of carriers appeared from current-voltage characteristics under knee voltage is shown by the trasient flow of nontrapped carriers group in the trap level of intergranular layer, surface state and/or depletion layer. However, current oscillation phenomena is hardly shown in the high electric field. The injected carriers from both electrodes are directly flow from the conduction band of forward biased grain through the intergranular layer into the reverse biased grain, because the trap level in the electric field above the knee voltage is mostly filled.
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.
$TiO_2$를 첨가한 산화 아연 바리스터에 대한 열자격전류의 기원
장경욱,이성일,이준웅 한국전기전자재료학회 1993 電氣電子材料學會誌 Vol.6 No.2
ZnO 바리스터의 비선형 전도특성은 입자의 구조로부터 설명할 수 있다. 본 논문에서는 ZnO 바리스터의 입자구조에 트랩된 캐리어를 분석하기 위해서 TSC 측정 기법을 사용하였다. 측정 결과로 부터 네개의 TSC피크를 얻었다. 고온으로 부터 첫번째 두번째와 세번째 TSC피크의 기원은 각각 트랩, 도너 밀도 및 입계층의 트랩으로 나타나고 네번째 피크의 기원은 공핍층에 있는 도너 이온의 탈분극에 의해서 기인하는 것으로 사료된다. .alpha.$_{1}$피크의 활성화 에너지는 약 0.33-1.42eV였다. 또한 바리스터의 예비동작 영역에서의 전도특성은 .alpha.$_{1}$과 .alpha.$_{2}$피크의 값에 지배된다는 것을 확인하였다.