Fe 및 Ni기 산화물 분산 강화 합금의 연구동향

박천웅,변종민,박종관,김영도,Park, Chun Woong,Byun, Jong Min,Park, Jong Kwan,Kim, Young Do 한국분말야금학회 2016 한국분말재료학회지 (KPMI) Vol.23 No.1

Ni₅Y 합금상이 형성된 Ni계 산화물 분산강화 아토마이징 분말의 밀링 거동 분석

박천웅,변종민,최원준,김영도,Park, Chun Woong,Byun, Jong Min,Choi, Won June,Kim, Young Do 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.2

Ni-based oxide dispersion strengthened (ODS) alloys have a higher usable temperature and better high-temperature mechanical properties than conventional superalloys. They are therefore being explored for applications in various fields such as those of aerospace and gas turbines. In general, ODS alloys are manufactured from alloy powders by mechanical alloying of element powders. However, our research team produces alloy powders in which the $Ni_5Y$ intermetallic phase is formed by an atomizing process. In this study, mechanical alloying was performed using a planetary mill to analyze the milling behavior of Ni-based oxide dispersions strengthened alloy powder in which the $Ni_5Y$ is the intermetallic phase. As the milling time increased, the $Ni_5Y$ intermetallic phase was refined. These results are confirmed by SEM and EPMA analysis on microstructure. In addition, it is confirmed that as the milling increased, the mechanical properties of Ni-based ODS alloy powder improve due to grain refinement by plastic deformation.

변호사의 학벌/학력, 전관 (前官), 그리고 주변화: 대한제국 시기에 등록한 조선인 변호사들의 주변화와 식민지 문화 및 사회자본

박천웅 ( Chun Woong Park ) 법과사회이론학회 2015 법과 사회 Vol.0 No.50

This research paper examines the marginalization of practicing lawyers in colonial Korea 1920-30s. While high-status lawyers are characterized with higher income, practicing law in a large city, stable client relations, low-status lawyers are featured by lower income, practicing law in a small city, unstable client relations. Thus frequent transfers to smaller cities as well as relatively lower income indicate one aspect of lawyer’ marginalization processes. Through analyzing archival data during the colonial period (1910-45) such as lawyer transfer notices on the Japanese Colonial Government Gazette, classified documentations on lawyer registration produced by the colonial government, and an annual income survey of lawyers in Northwestern Korea, I discover that lawyers who reported lower incomes and frequently transferred from larger cities to smaller cities in the 1920-30s were Koreans who had registered circa 1906-10 and practiced law since then. I explain the Korean lawyers’ marginalization process in terms of relatively lower educational background and lack of social networks. With these findings, this paper argues that lawyers with little cultural and social capitals are marginalized in the social structure of the bar.

식민지 조선 변호사의 연결망, 계층화, 협업

박천웅(Chun Woong Park) 한국사회학회 2016 韓國社會學 Vol.50 No.1

이 논문은 1910-23년 사이 조선고등법원 민사 상고 판결록에 나타난 변호사 선임 사례들을 분석하여, 변호사의 민족성이 식민지 조선 변호사 사회 내의 연결망과 계층화에 영향을 미쳤다는 점을 입증하였다. 기존의 연구에서는 비백인, 여성, 비명문대학 출신 변호사들이 백인, 남성, 명문 대학 출신 변호사들의 연결망으로부터 배제되고 사회적으로 높은 지위를 가지는 의뢰인들을 만날 기회가 제약되기 때문에 변호사 사회 내에서 주변화 된다고 설명하였다. 식민지 조선의 일본인 변호사들은 민족성과 자격 조건의 측면에서 주류에 속한다고 할 수 있었지만, 언어 및 문화적 차이로 인하여 조선인 고객과의 접근성에 제약이 있었다. 오히려, 일본에서 법학을 배운 후 조선으로 귀국한 조선인 변호사들이 엘리트 조선인 의뢰인들의 법률적 수요를 충족시켜줄 수 있었다. 조선고등법원에 제기된 민사 상고 사건 판결록에 나타난 변호사들 간의 공동 수임의 사례와 변호사들을 선임한 의뢰인들의 유형을 구분하여, 본 논문은 1) 식민지 조선의 변호사 연결망이 민족성에 의해 구분되었고, 2) 일본인 변호사들이 기업 및 사회 유명인 고객을 유치하는데 조선인 변호사들에 비해 우위에 있었으며, 3) 일본에서 법을 배워 일본어에 능통하였던 소수의 조선인 변호사들에 의해 두 변호사 진영이 매개되었다는 점을 보인다. 식민지 조선에서 변호사들이 민족성에 의해 분절되고 계층화 되었으며 일본에서 법을 배운 일부 조선인만이 일본인 변호사와의 협업이 가능했었다는 이 논문의 발견점은 전문직 사회 내의 차별을 확인하면서 이러한 차별을 희석시킬 제도적 수단이 중심부에서 획득한 문화적 상징적 자본이라는 점을 보여준다. By analyzing the attorney appointments in the lawsuits filed to the High Court of colonial Korea from 1910 through 1923, this research examines how lawyers’ ethnicity segmented, stratified, and bridged the social structure of the bar in colonial Korea under Japan’s rule. Existing literature has suggested that non-whites, female, migrant lawyers are marginalized in the bar due to the exclusions from the circle of mainstream lawyers and from the opportunities to have prestigious clients. While Japanese lawyers were sufficient enough to be considered the mainstream in terms of ethnicity and qualification, nonetheless, cultural and linguistic differentials from Korean elite clients limited them from monopolizing the upper structure of the bar. Instead, some Korean lawyers who had learned law in Japan possibly met the legal demands of the Korean elite clients. I investigated joint-cases in which Koreans and Japanese lawyers worked together from the lawsuit records filed to the High Court of Colonial Korea(1910-23) through using social network analysis methods. I also investigated how lawyers’ ethnicity affected the client type, after classifying the clients recorded in the lawsuits into corporation, social celebrity, and ordinary people. I discovered that: 1) the social networks of lawyers were divided into a Korean group and a Japanese group; 2) Japanese lawyers were more privileged than Koreans in terms of having elite clients; 3) a handful of Korean lawyers who had learned law in Japan possibly joined the mainstream Japanese network. I conclude that while lawyer’s ethnicity segmented and stratified the social structure of the bar in colonial Korea, the proficiency of the Japanese language and a college degree in Japan diluted the effects of stratified division for Korean lawyers.

계면활성제를 이용하여 anatase TiO₂ 나노 입자와 결합된 rutile TiO₂ 분말의 광촉매 특성

변종민,박천웅,김영인,김영도,Byun, Jong Min,Park, Chun Woong,Kim, Young In,Kim, Young Do 한국분말야금학회 2018 한국분말재료학회지 (KPMI) Vol.25 No.3

The coupling of two semiconducting materials is an efficient method to improve photocatalytic activity via the suppression of recombination of electron-hole pairs. In particular, the coupling between two different phases of $TiO_2$, i.e., anatase and rutile, is particularly attractive for photocatalytic activity improvement of rutile $TiO_2$ because these coupled $TiO_2$ powders can retain the benefits of $TiO_2$, one of the best photocatalysts. In this study, anatase $TiO_2$ nanoparticles are synthesized and coupled on the surface of rutile $TiO_2$ powders using a microemulsion method and heat treatment. Triton X-100, as a surfactant, is used to suppress the aggregation of anatase $TiO_2$ nanoparticles and disperse anatase $TiO_2$ nanoparticles uniformly on the surface of rutile $TiO_2$ powders. Rutile $TiO_2$ powders coupled with anatase $TiO_2$ nanoparticles are successfully prepared. Additionally, we compare the photocatalytic activity of these rutile-anatase coupled $TiO_2$ powders under ultraviolet (UV) light and demonstrate that the reason for the improvement of photocatalytic activity is microstructural.

저온 브레이징용 Al-Si-Cu 합금의 Sn 첨가에 따른 융점 및 기계적 특성 변화 연구

김민상,박천웅,변종민,김영도,Kim, Min Sang,Park, Chun Woong,Byun, Jong Min,Kim, Young Do 한국재료학회 2016 한국재료학회지 Vol.26 No.7

For the development of a low-melting point filler metal for brazing aluminum alloy, we analyzed change of melting point and wettability with addition of Sn into Al-20Cu-10Si filler metal. DSC results showed that the addition of 5 wt% Sn into the Al-20Cu-10Si filler metal caused its liquidus temperature to decrease by about 30 oC. In the wettability test, spread area of melted Al-Cu-Si-Sn alloy is increased through the addition of Sn from 1 to 5 wt%. For the measuring of the mechanical properties of the joint region, Al 3003 plate is brazed by Al-20Cu-10Si-5Sn filler metal and the mechanical property is measured by tensile test. The results showed that the tensile strength of the joint region is higher than the tensile strength of Al 3003. Thus, failure occurred in the Al 3003 plate.

란타넘 산화물의 분산을 통해 향상된 파괴인성을 갖는 몰리브데넘 합금의 제조

최원준,박천웅,박정효,김영도,변종민,Choi, Won June,Park, Chun Woong,Park, Jung Hyo,Kim, Young Do,Byun, Jongmin 한국분말재료학회 (*구 분말야금학회) 2019 한국분말재료학회지 (KPMI) Vol.26 No.3

In this study, lanthanum oxide ($La_2O_3$) dispersed molybdenum ($Mo-La_2O_3$) alloys are fabricated using lanthanum nitrate solution and nanosized Mo particles produced by hydrogen reduction of molybdenum oxide. The effect of $La_2O_3$ dispersion in a Mo matrix on the fracture toughness at room temperature is demonstrated through the formation behavior of $La_2O_3$ from the precursor and three-point bending test using a single-edge notched bend specimen. The relative density of the $Mo-0.3La_2O_3$ specimen sintered by pressureless sintering is approximately 99%, and $La_2O_3$ with a size of hundreds of nanometers is uniformly distributed in the Mo matrix. It is also confirmed that the fracture toughness is $19.46MPa{\cdot}m^{1/2}$, an improvement of approximately 40% over the fracture toughness of $13.50MPa{\cdot}m^{1/2}$ on a pure-Mo specimen without $La_2O_3$, and this difference in the fracture toughness occurs because of the changes in fracture mode of the Mo matrix caused by the dispersion of $La_2O_3$.

차세대 초고온 합금인 Mo-Si-B 합금의 연구 동향

최원준,박천웅,박정효,김영도,변종민,Choi, Won June,Park, Chun Woong,Park, Jung Hyo,Kim, Young Do,Byun, Jong Min 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.2

Over the last decade, the next generation's ultra-high-temperature materials as an alternative to Nickel-based superalloys have been highlighted. Ultra-high-temperature materials based on refractory metals are one of several potential candidates. In particular, molybdenum alloys with small amounts of silicon and boron (Mo-Si-B alloys) have superior properties at high temperature. However, research related to Mo-Si-B alloys were mainly conducted by several developed countries but garnered little interest in Korea. Therefore, in this review paper, we introduce the development history of Mo-Si-B alloys briefly and discuss the properties, particularly the mechanical and oxidation properties of Mo-Si-B alloys. We also introduce the latest research trends of Mo-Si-B alloys based on the research paper. Finally, for domestic research related to this field, we explain why Mo-Si-B alloys should be developed and suggest the potential directions for Mo-Si-B alloys research.

탄화 규소가 균일 분산된 규화 몰리브데넘계 복합재의 제조

최원준,박천웅,김영도,변종민,Choi, Won June,Park, Chun Woong,Kim, Young Do,Byun, Jong Min 한국분말야금학회 2018 한국분말재료학회지 (KPMI) Vol.25 No.5

Molybdenum silicide has gained interest for high temperature structural applications. However, poor fracture toughness at room temperatures and low creep resistance at elevated temperatures have hindered its practical applications. This study uses a novel powder metallurgical approach applied to uniformly mixed molybdenum silicide-based composites with silicon carbide. The degree of powder mixing with different ball milling time is also demonstrated by Voronoi diagrams. Core-shell composite powder with Mo nanoparticles as the shell and ${\beta}-SiC$ as the core is prepared via chemical vapor transport. Using this prepared core-shell composite powder, the molybdenum silicide-based composites with uniformly dispersed ${\beta}-SiC$ are fabricated using pressureless sintering. The relative density of the specimens sintered at $1500^{\circ}C$ for 10 h is 97.1%, which is similar to pressure sintering owing to improved sinterability using Mo nanoparticles.

저온 알루미늄 브레이징용 Al-Cu-Si-Sn 합금 설계 및 분말 제조

김희연,박천웅,이원희,김영도,Heeyeon Kim,Chun Woong Park,Won Hee Lee,Young Do Kim 한국분말재료학회 (*구 분말야금학회) 2023 한국분말재료학회지 (KPMI) Vol.30 No.4

This study investigates the melting point and brazing properties of the aluminum (Al)-copper (Cu)-silicon (Si)-tin (Sn) alloy fabricated for low-temperature brazing based on the alloy design. Specifically, the Al-20Cu-10Si-Sn alloy is examined and confirmed to possess a melting point of approximately 520℃. Analysis of the melting point of the alloy based on composition reveals that the melting temperature tends to decrease with increasing Cu and Si content, along with a corresponding decrease as the Sn content rises. This study verifies that the Al-20Cu-10Si-5Sn alloy exhibits high liquidity and favorable mechanical properties for brazing through the joint gap filling test and Vickers hardness measurements. Additionally, a powder fabricated using the Al-20Cu-10Si-5Sn alloy demonstrates a melting point of around 515℃ following melting point analysis. Consequently, it is deemed highly suitable for use as a low-temperature Al brazing material.