산화질소 검출용 마이크로 가스센서 제조공정

김정식,윤진호,김범준,Kim, Jung-Sik,Yoon, Jin-Ho,Kim, Bum-Joon 한국재료학회 2013 한국재료학회지 Vol.23 No.6

In this study, a micro gas sensor for $NO_x$ was fabricated using a microelectromechanical system (MEMS) technology and sol-gel process. The membrane and micro heater of the sensor platform were fabricated by a standard MEMS and CMOS technology with minor changes. The sensing electrode and micro heater were designed to have a co-planar structure with a Pt thin film layer. The size of the gas sensor device was about $2mm{\times}2mm$. Indium oxide as a sensing material for the $NO_x$ gas was synthesized by a sol-gel process. The particle size of synthesized $In_2O_3$ was identified as about 50 nm by field emission scanning electron microscopy (FE-SEM). The maximum gas sensitivity of indium oxide, as measured in terms of the relative resistance ($R_s=R_{gas}/R_{air}$), occurred at $300^{\circ}C$ with a value of 8.0 at 1 ppm $NO_2$ gas. The response and recovery times were within 60 seconds and 2 min, respectively. The sensing properties of the $NO_2$ gas showed good linear behavior with an increase of gas concentration. This study confirms that a MEMS-based gas sensor is a potential candidate as an automobile gas sensor with many advantages: small dimension, high sensitivity, short response time and low power consumption.

Pd 촉매금속의 표면형상 변형에 의한 고감도 MEMS 형 마이크로 수소가스 센서 제조공정

김정식,김범준,Kim, Jung-Sik,Kim, Bum-Joon 한국재료학회 2014 한국재료학회지 Vol.24 No.10

In this study, highly sensitive hydrogen micro gas sensors of the multi-layer and micro-heater type were designed and fabricated using the micro electro mechanical system (MEMS) process and palladium catalytic metal. The dimensions of the fabricated hydrogen gas sensor were about $5mm{\times}4mm$ and the sensing layer of palladium metal was deposited in the middle of the device. The sensing palladium films were modified to be nano-honeycomb and nano-hemisphere structures using an anodic aluminum oxide (AAO) template and nano-sized polystyrene beads, respectively. The sensitivities (Rs), which are the ratio of the relative resistance were significantly improved and reached levels of 0.783% and 1.045 % with 2,000 ppm H2 at $70^{\circ}C$ for nano-honeycomb and nano-hemisphere structured Pd films, respectively, on the other hand, the sensitivity was 0.638% for the plain Pd thin film. The improvement of sensitivities for the nano-honeycomb and nano-hemisphere structured Pd films with respect to the plain Pd-thin film was thought to be due to the nanoporous surface topographies of AAO and nano-sized polystyrene beads.

SrAl₂O₄계 축광재료의 습식공정에 의한 나노분말 합성 및 발광특성

김정식,Kim, Jung-Sik 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.8

$Eu^{2+}$ and $Dy^{3+}$ co-doped strontium aluminate, $SrAl_2O_4$ long phosphorescent phoshor was fabricated and its photoluminescence was characterized. The phosphor, $SrAl_2O_4:Eu^{2+},Dy^{3+}$ was synthesized by a coprecipitation in which metal salts of $Sr(NO_3)_2$, $Al(NO_3)_3{\cdot}9H_2O$, were dissolved in $(NH_4)_2CO_3$ solution with adding $Eu(NO_3)_3{\cdot}5H_2O$ and $Dy(NO_3)_3{\cdot}5H_2O$ as a activator and co-activator, respectively. The coprecipitated products were separated from solution, washed, and dried in a vacuum dry oven. The dried powders were then mixed with 3 wt% $B_2O_3$ as a flux and heated at $800{\sim}1400^{\circ}C$ for 3 h under the reducing ambient atmosphere of 95%Ar+$5%H_2$ gases. For the synthesized $SrAl_2O_4:Eu^{2+},Dy^{3+}$, properties of photoluminescence such as emission, excitation and decay time were examined. The emission intensity increased as the annealing temperature increased and showed a maximum peak intensity at 510 nm with a broad band from $400{\sim}650\;nm$. Monitored at 520 nm, the excitation spectrum showed a maximum peak intensity at $315{\sim}320\;nm$ wavelength with a broad band from $200{\sim}500\;nm$ wavelength. The decay time of $SrAl_2O_4:Eu^{2+},Dy^{3+}$ increased as the annealing temperature increased.

연구논문 : TPM 과 RCM 에서의 보전계획 비교

김정식,장중순 ( Jung Sik Kim,Joong Soon Jang ) 한국품질경영학회 1997 품질경영학회지 Vol.25 No.1

염을 이용한 Sr 페라이트의 분말합성과 그의 자성특성

김정식,김시동,Kim, Jung-Sik,Kim, Si-Dong 한국세라믹학회 2005 한국세라믹학회지 Vol.42 No.10

In this study we prepared the Sr-ferrite powders and magnet by a molten salt method using the (NaCl+KCl) salt mixture. Starting materials of $Fe_{2}$$O_{3}$ and Sr$Co_{3}$ were mixed as the molar ratio of 5.70:1, and 0.08 mol$ \% $ $Al_{2}$$O_{3}$, 0.10 mo1$ \% $ Si$O_{2}$ and 0.12 mo1$ \% $ CaO were added as additives. Sr-ferrite powders synthesized at the reaction temperatures of 800$\∼$1200$ ^{\circ}C $ showed the typical M-type hexagonal ferrite phase, and hexagonal plate-like morphology with uniform distribution of 1$\∼$3 $\mu$m particle size. The bulk density of the sintered Sr-ferrite magnet prepared with powders by the molten salt method showed the maximum density of 4.82 g/$cm^{3}$ at the sintering temperature of 1200$^{\circ}C $. The maxima of remanent flux density (Br, 45 emu/g) and coercive force (iHc, 3.75 kOe) occurred at the sintering temperatures of 1150$ ^{\circ}C$ and 1200$^{\circ}C $.

서로 다른 반응경로에 따른 일방향 용융공정된 Y-Ba-Cu-O계 Bulk초전도체의 미세구조 고찰

김정식,김찬중,Kim, Jeong-Sik,Kim, Chan-Jung 한국재료학회 1997 한국재료학회지 Vol.7 No.10

초기 혼합분말을 다르게 사용함으로써 다른 반응경로를 따라 성장된 일방향 집합조직 YB $a_{2}$BaCu $O_{5}$(Y211)형상과 분포가 초기 혼합분말이 달라짐에 따라 상당히 다르게 형성되었다. 여러 반응경로 중에서 $Y_{2}$ $O_{3}$+Y123$\longrightarrow$ $Y_{1.6}$Ba/ sub 2.2/ $O_{y}$와 ( $Y_{2}$ $O_{3}$BaCu $O_{2}$)+Y123$\longrightarrow$ $Y_{1.6}$B $a_{2.3}$C $u_{3.3}$ $O_{y}$반응에 의하여 용융공정된 경우 일방향 집합조직 Y 123 결정 성장이 잘 일어났으며, 특히 Y123의 포정반응 온도 이하의 낮은 온도에서도 결정성장이 일어났다. 또한 Y211입자 미세화가 다른 반응에 의한 용융공정보다 잘 일어났다. 이와같은 서로 다른 반응과정에 의하여 용융공정된 미세구조의 차이점들을 $Y_{2}$ $O_{3}$-BaO-CuO 3원계 상평형도를 이용하여 설명하였다.다.다.다.다.다.다.

DACUM 방법에 의한 건설용 타워크레인 기능사 자격 교육과정 개발연구

김정식,박문선,황욱선,김용수,Kim, Jung-Sik,Park, Moon-Sun,Hwang, Uk-Sun,Kim, Yong-Su 한국건설관리학회 2009 한국건설관리학회 논문집 Vol.4 No.3

본 연구는 기존 타워크레인 운전기능사 시험교과목의 미흡한 부분을 충족시키기 위해 DACUM방법을 활용하여 새로운 교육과정을 제안하고자 실시하였다. 이를 위하여 현행 타워크레인 운전기능사 교육제도 문제점 및 기존교과목을 조사하였으며, 이를 토대로 DACUM방법에 따른 새로운 교과목과 기존 교과목과의 비교분석을 실시하였다. 상기와 같은 목적과 방법에 따라 진행된 본 연구의 결과를 요약하면 다음과 같다: 1) 기존의 타워크레인 운전기능사 교과목은 즉시 건설현장에서 직무를 수행하기 어려운 실정이고 안전관리, 타워크레인 운전시 고장에 대한 교육이 미흡한 것으로 분석되었다. 2) DACUM방법으로 도출된 개선된 교과목은 7개이며 그 사항은 다음과 같다. 이론교과목 5개와 실기교과목 2개로 구성되었으며, 개발 및 제안된 교과목은 타워크레인 운전기능사가 이론과 실기면에서 건축공사현장에 즉시 활용할 수 있을 것으로 분석되었다. The purpose of this study is to suggest new subject to satisfy the lack parts of examination course of the existing driving tower crane certificate by using the DACUM method. For this, problems of education for the existing driving tower crane certificate and the existing subjects are examined and, based on these, comparing analysis of new subjects that follows the DACUM method and the existing subjects are conducted. The results of this study that were progressed following the purpose and method at the above are as follow : 1) It is analyzed that the existing subjects for the driving tower crane certificate could not be applied to construction fields immediately and the education to deal with disorders when driving the tower cranes. 2) The number of the subjects that have been advanced following the DACUM method is seven and those consist of five theoretical subjects and two practical subjects. It is analyzed that the developed and suggested subjects can be used in construction fields when considering the theoretical and practical parts in no time.

(알니코, 사마리움-코발트) 본드자석의 제조 및 자기적 특성연구

김정식,Kim, Jung-Sik 한국전기전자재료학회 2010 전기전자재료학회논문지 Vol.23 No.12

In this study the (Alnico, Sm-Co) bonded magnets were fabricated by mixing the Sm-Co added alnico alloy powders with epoxy resin and binder, appropriately. Also, the hybrid ring magnets of (Alnico, Sm-Co)/Sr-ferrite were fabricated by coupling the Sr-ferrite composite layer with an (Alnico, Sm-Co) magnet. The magnetic properties of (Alnico, Sm-Co) ring magnets were varied with the amount of Sm-Co powders. The addition of Sm-Co powders increased a remanent induction($B_r$) and coercive force($_BH_C$), while decreasing a surface flux density and repulsive distance. The surface flux density and repulsive distance for the (Alnico, Sm-Co) ring magnet increased with a magnetizing voltage up to about 160 V and reached an apparent saturation point. Also, the measurements of temperature and moisture characteristics showed that the surface flux densities of N-S poles and repulsive distance decreased a little within 4% after 10 days passed.

고농도 차아염소산나트륨 발생장치 국산화 개발

김정식,신현수,이은경,정붕익,Kim, Jung Sik,Shin, Hyun Su,Lee, Eun Kyoung,Jung, Bong Ik 대한기계학회 2013 대한기계학회 논문집. Transactions of the KSME. C, 산업기술과 혁신 Vol.1 No.1

본 연구는 정수처리공정에서 사용하는 염소소독으로 취급이 용이하며, 기존 액화염소를 대체할 수 있는 현장발생형 고농도 차아염소산나트륨 발생장치를 국산화 개발하는 것이다. 이 장치는 포화소금물을 이용한 전기화학적 특성으로 고농도(12%)의 차아염소산나트륨을 생성하는 것으로, 저농도(0.8%)의 차아염소산나트륨 발생장치보다 전류효율 38.7 % 높이고, 소금사용량 54.6 %와 클로레이트 함량 97.3%을 저감하는 장치이다. The purpose of this study is to replace existing liquid chlorine with localization of on-site high (12%) sodium hypochlorite generation system. On-site high (12%) sodium hypochlorite generation system is higher the current efficiency of 38.7%, 54.6% reduction of salt consumption, and 97.3% lower rate of chlorate than on-site low (0.8%) sodium hypochlorite generation system.

티타늄 표면조도가 조골세포의 부착 및 분화에 미치는 영향

김정식,이재관,고성희,엄흥식,장범석,Kim, Jung-Sik,Lee, Jae-Kwan,Ko, Sung-Hee,Um, Heung-Sik,Chang, Beom-Seok 대한치주과학회 2005 Journal of Periodontal & Implant Science Vol.35 No.4

The success of an implant is determined by its integration into the tissue surrounding the biomaterial. Surface roughness is considered to influence the behavior of adherent cells. The aim of this in vitro study was to determine the effect of surface roughness on Saos-2 osteoblast-like cells. Titanium disks blasted with 75 ${/mu}m$ aluminum oxide particles and machined titanium disks were prepared. Saos-2 were plated on the disks at a density of 50,000 cells per well in 48-well dishes. After 1 hour, 1 day, 6 days cell numbers were counted. One day, 6 days after plating, alkaline phosphatase(ALPase) activity was determined. Compared to experimental group, the number of cells was significantly higher on control group. The stimulatory effect of surface roughness on ALPase was more pronounced on the experimental group than on control group. These results demonstrate that surface roughness alters proliferation and differentiation of osteoblasts. The results also suggest that implant surface roughness may play a role in determining phenotypic expression of cells.