Effects of Ga-doping on the microstructure and magnetic properties of MnBi alloys

Yang, Yang,Kim, Jong-Woo,Si, Ping-Zhan,Qian, Hui-Dong,Shin, Yongho,Wang, Xinyou,Park, Jihoon,Li, Oi Lun,Wu, Qiong,Ge, Hongliang,Choi, Chul-Jin Elsevier 2018 JOURNAL OF ALLOYS AND COMPOUNDS Vol.769 No.-

<P><B>Abstract</B></P> <P>The low temperature phase Mn<SUB>55</SUB>Bi<SUB>45-<I>x</I> </SUB>Ga<SUB> <I>x</I> </SUB> (<I>x</I> = 0, 1, 3, 5, and 10) alloys were prepared by induction melting process with subsequent low temperature annealing. The effects of Ga-doping on the crystal structure and magnetic properties of the alloys were systematically studied. The room temperature coercivities of Mn<SUB>55</SUB>Bi<SUB>45-<I>x</I> </SUB>Ga<SUB> <I>x</I> </SUB> after ball milling increased from 1.43 T for <I>x</I> = 0 to 1.66 T for <I>x</I> = 5, while the saturation magnetization decreased from 60.7 Am<SUP>2</SUP>/kg (<I>x</I> = 0) to 45.1 Am<SUP>2</SUP>/kg (<I>x</I> = 5). The maximum energy product (<I>BH</I>)<SUB>max</SUB> of Mn<SUB>55</SUB>Bi<SUB>44</SUB>Ga powders reached 7.87 MGOe. The Curie temperature of the Mn<SUB>55</SUB>Bi<SUB>45-<I>x</I> </SUB>Ga<SUB> <I>x</I> </SUB> alloys increased from 633 K to 658 K with increasing Ga concentration in the range of 0 ≤ <I>x</I> ≤ 5.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Effects of doping Ga on the microstructural and magnetic properties of MnBi alloy. </LI> <LI> The MnBi-Ga powders are achieved by surfactant assisted high energy ball milling. </LI> <LI> The maximum energy produce (<I>BH</I>)<SUB>max</SUB> shows 7.87 MGOe for Mn<SUB>55</SUB>Bi<SUB>44</SUB>Ga sample. </LI> <LI> The coercivity of Mn<SUB>55</SUB>Bi<SUB>40</SUB>Ga<SUB>5</SUB> after ball milling reached 1.66 T at room temperature. </LI> <LI> The elevated curie temperature (<I>T</I> <SUB>c</SUB>) by doping Ga makes it a possible candidate for high temperature applications. </LI> </UL> </P>

Upshift of MnBi magnetic properties via process optimizations

Yang Yang,Jong-Woo Kim,Jihoon Park,Hui-Dong Qian,Jung Tae Lim,Oi Lun Li,Chul-Jin Choi 한국자기학회 2019 한국자기학회 학술연구발표회 논문개요집 Vol.29 No.2

The effects of composition on microstructure and magnetic properties of MnBi alloys

Yang Yang,Yongho Shin,Hui-Dong Qian,Ping-Zhan Si,Jihoon Park,Oi Lun Li,Jong-Woo Kim,Chul-Jin Choi 한국자기학회 2018 한국자기학회 학술연구발표회 논문개요집 Vol.2018 No.11

A New Water Oxidation Catalyst: Lithium Manganese Pyrophosphate with Tunable Mn Valency

Park, Jimin,Kim, Hyunah,Jin, Kyoungsuk,Lee, Byung Ju,Park, Yong-Sun,Kim, Hyungsub,Park, Inchul,Yang, Ki Dong,Jeong, Hui-Yun,Kim, Jongsoon,Hong, Koo Tak,Jang, Ho Won,Kang, Kisuk,Nam, Ki Tae American Chemical Society 2014 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.136 No.11

<P>The development of a water oxidation catalyst has been a demanding challenge for the realization of overall water-splitting systems. Although intensive studies have explored the role of Mn element in water oxidation catalysis, it has been difficult to understand whether the catalytic capability originates mainly from either the Mn arrangement or the Mn valency. In this study, to decouple these two factors and to investigate the role of Mn valency on catalysis, we selected a new pyrophosphate-based Mn compound (Li<SUB>2</SUB>MnP<SUB>2</SUB>O<SUB>7</SUB>), which has not been utilized for water oxidation catalysis to date, as a model system. Due to the monophasic behavior of Li<SUB>2</SUB>MnP<SUB>2</SUB>O<SUB>7</SUB> with delithiation, the Mn valency of Li<SUB>2-<I>x</I></SUB>MnP<SUB>2</SUB>O<SUB>7</SUB> (<I>x</I> = 0.3, 0.5, 1) can be controlled with negligible change in the crystal framework (e.g., volume change ∼1%). Moreover, inductively coupled plasma mass spectrometry, X-ray photoelectron spectroscopy, ex-situ X-ray absorption near-edge structure, galvanostatic charging–discharging, and cyclic voltammetry analysis indicate that Li<SUB>2-<I>x</I></SUB>MnP<SUB>2</SUB>O<SUB>7</SUB> (<I>x</I> = 0.3, 0.5, 1) exhibits high catalytic stability without additional delithiation or phase transformation. Notably, we observed that, as the averaged oxidation state of Mn in Li<SUB>2-<I>x</I></SUB>MnP<SUB>2</SUB>O<SUB>7</SUB> increases from 2 to 3, the catalytic performance is enhanced in the series Li<SUB>2</SUB>MnP<SUB>2</SUB>O<SUB>7</SUB> < Li<SUB>1.7</SUB>MnP<SUB>2</SUB>O<SUB>7</SUB> < Li<SUB>1.5</SUB>MnP<SUB>2</SUB>O<SUB>7</SUB> < LiMnP<SUB>2</SUB>O<SUB>7</SUB>. Moreover, Li<SUB>2</SUB>MnP<SUB>2</SUB>O<SUB>7</SUB> itself exhibits superior catalytic performance compared with MnO or MnO<SUB>2</SUB>. Our study provides valuable guidelines for developing an efficient Mn-based catalyst under neutral conditions with controlled Mn valency and atomic arrangement.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2014/jacsat.2014.136.issue-11/ja410223j/production/images/medium/ja-2013-10223j_0012.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja410223j'>ACS Electronic Supporting Info</A></P>

The effect of Sn substitution on magnetic properties of MnBi

Yang Yang,Jong-Woo Kim,Jihoon Park,Jung Tae Lim,Hui-Dong Qian,Oi Lun Li,Chul-Jin Choi 한국자기학회 2019 한국자기학회 학술연구발표회 논문개요집 Vol.29 No.2

Control of magnetic properties of MnBi by elements doping

Yang Yang,Hui-Dong Qian,Jung Tae Lim,Jihoon Park,Jong-Woo Kim,Chul-Jin Choi 한국자기학회 2020 한국자기학회 학술연구발표회 논문개요집 Vol.30 No.2

Microstructure and Magnetic Properties of Sn added MnBi Bulk Magnets

Yang Yang,Jung Tae Lim,Jihoon Park,Hui-Dong Qian,Oi Lun Li,Jong-Woo Kim,Chul-Jin Choi 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.2

Rare-earth free permanent magnets are current emerging issues of industry for the growing market demands. Among the rare-earth free permanent magnets, MnBi has attracted attention for large magnetocrystalline anisotropy constant (K₁ ≈ 1.6 MJ/m³, at 300 K) and unique positive temperature coefficient of coercivity (Hc). The low-temperature phase (LTP) of MnBi exhibits a saturation magnetization (Ms) of 80 emu/g, and the theoretical maximum energy product (BH)max 17.7 MGOe at room temperature. However, it is a challenge to fabricate MnBi bulk magnets while maintaining the superior magnetic properties of the powder, especially to prevent the reduction of Hc from powder to bulk. The effects of Sn adding on the microstructure and magnetic properties of MnBi bulk magnets have been systematically investigated. As kwon, the pure MnBi bulk magnets are challenging to reach high Hc in previous studies, and a few reference works have been reported about research on fabrication of high Hc MnBi bulks by adding the third element. It was found that the Sn-added MnBi bulk magnets show the increased Hc and the improved squareness, apparently related to restructuring the intergranular phase due to Sn element addition. The Hc of MnBi bulk magnet with 3 wt.% Sn reaches 11.6 kOe, which is 35 % higher than that of the pure MnBi magnet. In the sample of 1 wt.% Sn added MnBi bulk magnet, the Hc was elevated to 10.0 kOe, and the maximum energy product (BH)max was recorded of 7.84 MGOe at room temperature. This makes Sn added MnBi bulk magnet a promising candidate for next-generation rare-earth-free bulk magnets. 〈그림 본문참조〉

Fully Automated Circulating Tumor Cell Isolation Platform with Large-Volume Capacity Based on Lab-on-a-Disc

Park, Jong-Myeon,Kim, Minseok S.,Moon, Hui-Sung,Yoo, Chang Eun,Park, Donghyun,Kim, Yeon Jeong,Han, Kyung-Yeon,Lee, June-Young,Oh, Jin Ho,Kim, Sun Soo,Park, Woong-Yang,Lee, Won-Yong,Huh, Nam American Chemical Society 2014 ANALYTICAL CHEMISTRY - Vol.86 No.8

<P>Full automation with high purity for circulating tumor cell (CTC) isolation has been regarded as a key goal to make CTC analysis a “bench-to-bedside” technology. Here, we have developed a novel centrifugal microfluidic platform that can isolate the rare cells from a large volume of whole blood. To isolate CTCs from whole blood, we introduce a disc device having the biggest sample capacity as well as manipulating blood cells for the first time. The fully automated disc platform could handle 5 mL of blood by designing the blood chamber having a triangular obstacle structure (TOS) with lateral direction. To guarantee high purity that enables molecular analysis with the rare cells, CTCs were bound to the microbeads covered with anti-EpCAM to discriminate density between CTCs and blood cells and the CTCs being heavier than blood cells were only settled under a density gradient medium (DGM) layer. To understand the movement of CTCs under centrifugal force, we performed computational fluid dynamics simulation and found that their major trajectories were the boundary walls of the DGM chamber, thereby optimizing the chamber design. After whole blood was inserted into the blood chamber of the disc platform, size- and density-amplified cancer cells were isolated within 78 min, with minimal contamination as much as approximately 12 leukocytes per milliliter. As a model of molecular analysis toward personalized cancer treatment, we performed epidermal growth factor receptor (EGFR) mutation analysis with HCC827 lung cancer cells and the isolated cells were then successfully detected for the mutation by PCR clamping and direct sequencing.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancham/2014/ancham.2014.86.issue-8/ac403456t/production/images/medium/ac-2013-03456t_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ac403456t'>ACS Electronic Supporting Info</A></P>

Effects of Sn Addition on the Microstructure and Magnetic Properties of MnBi Bulk Magnets

Yang Yang,Jung Tae Lim,Jihoon Park,Hui-Dong Qian,Oi Lun Li,Jong-Woo Kim,Chul-Jin Choi 한국자기학회 2021 한국자기학회 학술연구발표회 논문개요집 Vol.31 No.1

Rare-earth free permanent magnets are current emerging issues of industry for the growing market demands. Among the rare-earth free permanent magnets, MnBi has attracted attention for large magneto crystalline anisotropy constant (K1 ≈ 1.6 MJ/m³, at 300 K) [1] and unique positive temperature coefficient of coercivity (H_c) [2]. The low-temperature phase (LTP) of MnBi exhibits a saturation magnetization (M_s) of 80 emu/g, and the theoretical maximum energy product (BH)_max 17.7 MGOe at room temperature [3]. However, it is a challenge to fabricate MnBi bulk magnets while maintaining the superior magnetic properties of the powder, especially to prevent the reduction of H_c from powder to bulk. The effects of Sn adding on the microstructure and magnetic properties of MnBi bulk magnets have been systematically investigated. As kwon, the pure MnBi bulk magnets are challenging to reach high H_c in previous studies, and a few reference works have been reported about research on fabrication of high H_c MnBi bulks by adding the third element. It was found that the Sn-added MnBi bulk magnets show the increased H_c and the improved squareness, apparently related to restructuring the intergranular phase due to Sn element addition. The H_c of MnBi bulk magnet with 3 wt.% Sn reaches 11.6 kOe, which is 35 % higher than that of the pure MnBi magnet. In the sample of 1 wt.% Sn added MnBi bulk magnet, the H_c was elevated to 10.0 kOe, and the maximum energy product (BH)_max was recorded of 7.84 MGOe at room temperature. This makes Sn added MnBi bulk magnet a promising candidate for next-generation rare-earth-free bulk magnets.

해방 이후 한국인 이름의 특성 및 변천 양상에 대한 사회언어학적 연구

강희숙(Hui-suk, Gang),양명희(Myung-hee, Yang),박동근(Dong-geun, Park) 어문연구학회 2012 어문연구 Vol.73 No.-

본 연구에서는 한국인들이 살아오면서 축적하고 있는 언어문화 가운데 하나로, 한국인 이름의 전형적 특성은 무엇이며, 그러한 특성은 시대별로 어떠한 변화를 겪고 있는가를 파악하기 위하여 해방 이후 시기인 1950년대부터 2000년대까지 50년간에 걸쳐 출생한 한국인 이름의 특성을 사회언어학의 연구 방법론 가운데 하나인 계량적 방법을 통해 분석하였다. 이러한 연구 목적을 수행하기 위하여 본 연구에서는 서울 지역 60,000명, 광주·대전·대구 등 지방 대도시 지역 61,200명, 전라도·충청도·경상도 군 지역 61,200명 등 총 182,400명의 이름을 표본으로, 각 연대별 이름의 특성 및 그 변천 양상을 이름의 어종별 분포, 중복 빈도, 이름의 첫 글자와 끝 글자의 유형, 음절수, 음절말음의 유형 등에 초점을 맞춰 살펴보았다. 연구 결과, 한자어 이름이 차지하는 비중이 압도적으로 높게 나타나되, 한자어 이름은 여성보다 남성이, 고유어나 외래어 이름은 남성보다 여성이 더 높은 비중을 차지하며, 남성은‘영수>성수, 정호>정훈>지훈>지훈>민준’이, 여성은 ‘영숙>미숙>은영>지혜>민지>유진’이 각 연대별로 중복빈도가 가장 높은 전형적인 이름으로 밝혀졌다. 또한, 이름 끝 글자의 경우, 남성은‘수, 호>훈>현>준’이, 여성은 ‘자, 숙, 순, 희, 옥’ 등이 높은 빈도로 사용되다가 1980년대 이후에는‘영’이나‘은’ 같은 글자가 구성요소로 나타나는 가운데,‘희’가 모든 시대에 공통적으로 출현함으로써 가장 오랫동안 여성 이름을 구성하는 요소로 자리 잡고 있음이 확인되었다. 또한, 이름의 음절수를 분석한 결과, 2음절로 이루어진 경우가 98% 이상의 높은 비중을 차지하며, 1음절 이름의 경우는 남성이, 3음절, 4음절 이상의 다음절인 경우는 여성이 훨씬 더 높은 비중을 차지한다는 사실과 함께, 이름의 끝 음절 말음으로 선택되는 음 가운데 가장 높은 비중을 차지하는 것은 ‘ㄴ’이나 ‘모음’이며, 남성은 모음보다는 자음 ‘ㄴ’이, 여성은 ‘ㄴ’보다 모음으로 끝나는 비중이 더 높게 나타난다는 사실이 확인되었다. This study aims to identify what typical characteristics of names for Korean people, one of Korean linguistic cultures, are and what changes they have had. For the study, characteristics of names of Korean people who were born for 50 years from 1950s to 2000s were analysed with a use of qualitative method, one of socio-linguistic methodologies. A total of names of 182,400 persons including 60,000 from the capital area and 61,200 from local areas including Gwangju, Daejeon and Daegu were sampled and analysed with a focus given on distribution of language types, frequency of duplication, types of the first and last letters in the names, the number of syllables, and types of the lat sounds of syllables. As a result, it was discovered that the occupancy rate of Chinese names was overwhelmingly high. More male names were in Chinese than female names. Names of Korean or foreign origin were usually used for females. The names with the highest duplication frequency were‘Yeongsu>Seongsu, Jeongho>Jeonghun>Jihun>Jihun>Minjun for males, and ‘Yeongsuk>Misuk>Eunyeong>Jihye>Minji>Yujin’ for females. The last letters of the names which were frequently used were ‘Su, Ho>Hun>Hyeon>Jun’ for males, and Ja, Suk, Sun, Hui, Ok’ for females. However, since 1980s, letters such as ‘Yeong’ or ‘Eun’ have appeared as components of the names, but 'Hui' has appeared in the most common for such a long time. As a result of analysing the number of syllables in the names, it was discovered that more than 98% were made of two syllables. One syllable names were usually used by male subjects and the names with more than three or four syllables were usually found in female subjects. 'ㄴ' or 'vowels' were most frequently used as the last sounds in the last syllables of the names. ' ㄴ ‘ a consonant, was more used for the last sound of male names and ' vowels ' were more used for the last sound of female names.