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고상법에 의한 100 nm BaTiO<sub>3</sub> 분말의 합성
김정환,정한승,조준엽,홍정오,김영태,허강헌,Kim, Jung-Hwan,Jung, Han-Seong,Cho, Joon-Yeob,Hong, Jeong-Oh,Kim, Young-Tae,Hur, Kang-Heon 한국세라믹학회 2009 한국세라믹학회지 Vol.46 No.2
$BaTiO_3$ powder was synthesized by the solid-state reaction of fine $BaTiO_3$ and $TiO_2$ raw materials. Fine grinding media of 50 and 300 microns were used for obtaining fine particulate mixture of $BaTiO_3$ and $TiO_2$ with high homogeneity. Effect of the size of grinding media on the synthesis mechanism of $BaTiO_3$ was discussed on the basis of the particulate morphology and thermogravimetry data for the mixture powders. By using the finer grinding media, $BaTiO_3$ was formed at the lower temperature and the particle size with the relatively narrower distribution could be obtained. $BaTiO_3$ powder with the average size of 100 nm was synthesized by the solid reaction in vacuum atmosphere.
50μm급 이트리아 안정화 지르코니아 비드의 미세구조 및 마모 조건에 따른 마모율 분석
김정환,윤세중,한병동,안철우,윤운하,최종진,Kim, Jung-Hwan,Yoon, Sae-Jung,Hahn, Byung-Dong,Ahn, Cheol-Woo,Yoon, Woon-Ha,Choi, Jong-Jin 한국재료학회 2019 한국재료학회지 Vol.29 No.4
This study analyzes the mechanical properties, including the attrition rate, of $50{\mu}m$ size yttria-stabilized zirconia (YSZ) beads with different microstructures and high-energy milling conditions. The yttria distribution in the grain and grain-boundary of the fully sintered beads relates closely to Vickers hardness and the attrition rate of the YSZ beads. Grain size, fractured surfaces, and yttrium distribution are analyzed by electronic microscopes. For standardization and a reliable comparison of the attrition rate of zirconia beads with different conditions, Zr content in milled ceramic powder is analyzed and calculated by X-ray Fluorescence Spectrometer(XRF) instead of directly measuring the weight change of milled YSZ beads. The beads with small grain sizes sintered at lower temperature exhibit a higher Vickers hardness and lower attrition rate. The attrition rate of $50{\mu}m$ YSZ beads is measured and compared with the various materials properties of ceramic powders used for high-energy milling. The attrition rate of beads appears to be closely related to the Vickers hardness of ceramic materials used for milling, and demonstrates more than a 10 times higher attrition rate with Alumina(Hv ~1650) powder than $BaTiO_3$ powder (Hv ~315).
폴리프로필렌 글리콜의 표면-보조 레이저 탈착/이온화에서 선형 비행시간 질량분석기의 분해능 개선을 위한 시간 지연 추출법의 응용
김정환,강위경,Kim, Jung Hwan,Kang, Wee Kyung 대한화학회 2000 대한화학회지 Vol.44 No.4
폴리프로필렌 글리콜의 표면-보조 레이저 탈착/이온화를 이용하여 선형 비행시간 질량 분석기에서 시간-지연 추출법이 분해능 개선, 질량-초점 길이 및 기기 퍼짐 효과의 영향을 수치계산과 비교하여 평가해였다. 비행시간 초점영역은 고저압 펄스의 지연 시간에 비례하였고 지연 시간 변화로 질량 초점 영역을 쉽게 조절할 수있었다. 시간 지연 추출법으로 얻어진 질량 스펙트럼의 분해능은 4500으로 연속추출법(20kV)에 비해 7배 정도 개선되었고 △m=2000의 질량-초점길이를 보여주었다. 시간 지연 추출법에서 기기 퍼짐 요인에 의한 분해능 개선의 한계를 계산하였고 5ns의기기 퍼짐 효과에 의해 동위원소 분리 검출은 분자량 2500까지 가능하였다. 시간 지연 추출법을 이용하여 폴리프로필렌 글리콜 분자가 탄고 표면에서 탈착될 때 생성되는 분열체 시리즈를 개선된 고분해능으로 동위원소 분포 수준으로 확인하였으며 분열 경로 규명 및 동위원소 비 질량분석기로의 응용 가능성을 시험하였다. The pulsed-delayed extraction (PDE) in linear time-of-flight mass spectrometer(TOF MS) is characterized on the enhancement of resolution, mass-depth of focus and effect of instrumentahan 2000. The ion signals separate isotopically by up to molecular weight of 2500 in instrumental broadening of 5 ns, which is a good agreement with calculation. The fragmentation paths of PPG can be sug-gested by the isotopica distributions of fragment series produced when PPG desorbed from graphite surface.
새로운 Cyanomethyl-1,3,5-triazine 유도체들의 합성
김정환,김은주,Kim, Jung Hwan,Kim, Un Ju 대한화학회 1996 대한화학회지 Vol.40 No.11
6-Cyanomethyl-1, 3, 5-triazine의 2번과 4번 위치에 amino, n-propylamino, isopropylamino, 및 anilino기가 도입된 새로운 유도체 4들의 합성은 6-chloro-1, 3, 5-triazine 유도체 2'들과 3들을 tert-butyl cyanoacetate로 반응시켜 얻었으며, 6-chloro-1, 3, 5-triazine의 2번과 4번 위치에 amino, n-propylamino, isopropylamino, 및 anilino기가 도입된 유도체 2'들과 3들은 2, 4, 6-trichloro-1, 3, 5-triazine 및 4, 6-dichloro-1, 3, 5-triazine 유도체 2들과 amine 유도체들로부터 합성되었다. New 6-cyanomethyl-1,3,5-triazine derivatives 4 containing amino, n-propylamino, isopropylamino and anilino groups at 2-and 4-position on the 6-cyanomethyl-1,3,5-triazine ring were prepared from 6-chloro-l,3,5-triazine derivatives 2' and 3 with tert-butyl cyanoacetate. The derivatives of 6-chloro-l,3,5-triazine 2' and 3 containing amino, n-propylamino, isopropylamino and anilino groups at 2- and 4-position on the 6-chloro-1,3,5-triazine ring were prepared from 2,4,6-trichloro-1,3,5-triazine as well as 4,6-dichloro-1,3,5-triazine derivatives 2 with amine derivatives.
새로운 2-Quinazolylacetonitrile 유도체들의 합성
김정환,민경수,Kim, Jung Hwan,Min, Kyung Su 대한화학회 2001 대한화학회지 Vol.45 No.6
H-chelate형태의 2-Quinazolylacetonitrile유도체들은 2-cyanomethylquinazoline에 여러가지 친전자체들, 즉, 4-chloroquinazoline, 4-chloro-2-phenylquinazoline, 4,6-dichloropyrinidine, 4,6-dichloro-2-phenylpyrimidine, 4,6-dichloro-5-phenylpyrimidine, 2-chloroauinoxaline,1,3- dichloroisoquinoline, 2,6-dichloropyrazine, 2-chloropyrazine, 4,6-dichloro-2,5-diphenylpyrimidine 등을 반응시켜 얻을 수 있었다. 합성된 H-chelate화합물들은 polymethine계의 발색단 구조를 가지게 된다. 이들 화합물에 대한 구조는 분광학적인 방법으로 분석 확인 하였다. 2-Quinazolylacetonitrile derivatives containing H-chelate have been synthesized from 2-cyanomethylquinazoline using electrophiles such as 4-chloroquinazoline, 4-chloro-2-phenylquinazoline, 4,6-dichloropyrimidine, 4,6-dichloro-2-phenylpyrimidine, 4,6-dichloro-5-phenylpyrimidine, 2-chloroquinoxaline, 1,3-dichloroisoquinoline, 2,6-dichloropyrazine, 2-chloropyrazine and 4,6-dichloro-2,5-diphenylpyrimidine. These H-chelates may serve as a polymethine chromophore system. Structures of the target molecules were identified by spectral methods.
대기 플라즈마 용사공정을 이용한 Cu계 벌크 비정질 금속 코팅의 미세조직 분석과 나노 압입시험을 이용한 상 분석
김정환,강기철,윤상훈,나현택,이창희,Kim, Jung-Hwan,Kang, Ki-Cheol,Yoon, Sang-Hoon,Na, Hyun-Taek,Lee, Chang-Hee 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.6
In this study, Cu-based bulk metallic glass (BMG) coatings were deposited by atmospheric plasma spraying (APS) process with different process conditions (with- and without hydrogen gas). As adding the hydrogen gas, thermal energy in the plasma flame increased and induced difference in the melting state of the Cu-based BMG particles. The microstructure and mechanical properties of the coatings were analyzed using a scanning electron microscope (SEM) with an energy dispersive spectroscopy (EDS) and nano-indentation tester in the light of phase analysis. It was elucidated by the nano-indentation tests that un-melted region was a mainly amorphous phase which showed discrete plasticity observed as the flow serrations on the load.displacement (P - h) curves, and the curves of solidified region showed lower flow serrations as amorphous phase mingled with crystalline phase. Oxides produced during the spraying process had the highest hardness value among the phases and were well mixed with other phases resulted from the increase in melting degree.
초등학교 수학과 ICT 활용 교육에서 스프레드시트를 활용한 교수-학습에 관한 연구
김정환,구정모,한병래,Kim, Jung-Hwan,Gu, Jung-Mo,Han, Byoung-Rae 한국정보교육학회 2009 정보교육학회논문지 Vol.13 No.3
Many current researches are limited in the statistics field, which is a part of mathematics class in the secondary school. Moreover, it's hard to apply to the elementary school since they are written in English. To overcome this limitations, the objectives from the unit that is suitable for using EXCEL in the elementary mathematics lessons are selected in this research. And a problem-based learning model for these lessons would be introduced that it can help students to focus on solving substances of the problems by reducing the time for arithmetic calculation.