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- 저자 : 함다슬 (검색결과 6 건)
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Tin Microcrystals Synthesized by Thermal Chemical Vapor Deposition in a Hydrogen-Reducing Atmosphere
함다슬,정원,강현철 대한금속·재료학회 2019 대한금속·재료학회지 Vol.57 No.6
We demonstrate a synthetic route to high-quality Sn microcrystals using thermal chemical vapor deposition (CVD) in a hydrogen-reducing atmosphere. During thermal CVD with SnO2 powder, a mixture of Ar and H2 (4%) gases was used as a carrier gas to maintain a hydrogen reduction environment. Hydrogen maintained a reduction environment throughout the thermal CVD process. Samples were prepared at temperatures of 800, 900, and 1000 °C. The structural properties of the Sn microcrystals were determined using synchrotron X-ray diffraction (XRD), transmission electron microscopy, and micro-Raman spectroscopy. In particular, the atomic position order in both the out-of-plane and in-plane directions was determined through high-resolution XRD measurement in a four-circle geometry. We found that at temperatures greater than 800 °C the supersaturation of Sn and O vapors induces the formation of microcrystals by self-assembly process without additional metallic seeds. As determined by the energy dispersive X-ray analysis, oxygen atoms and/or vapor were simultaneously reduced by hydrogen gas, resulting in the formation of Sn crystals rather than Sn oxide crystals. We also found that the Sn microcrystals were mostly strain-free singlecrystalline and of high quality with extremely low mosaicity. The order of the atomic positions in both the out-of-plane and in-plane directions was comparable to that of single-crystalline sapphire.
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Effect of pH on the Structure of Calcium Phosphate Crystals Synthesized using a Hydrothermal Process
함다슬,차수연,강현철,이수용 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.7
We investigated the effect of pH on the structure of calcium phosphate crystals synthesized using a hydrothermal process. The as-prepared samples were characterized by using X-ray diffraction, scanning electron microscopy, energy dispersive X-ray, and transmission electron microscopy analyses. We found that the structure and the shape of the calcium phosphate crystals depended significantly on the pH of the precursor solution. At pH $<$ 6, rectangular disk-shaped dicalcium phosphate anhydrous (DCPA) microcrystals were formed; on the other hand, at pH $>$ 8, hydroxyapatite (HA) nanorods were predominantly formed. This can be explained by a self-setting mechanism associated with the role of hydroxide species during the hydrothermal process. Both DCPA and HA crystals were single crystalline, with preferred orientations along the (001) planes of monoclinic DCPA and hexagonal HA.
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수열합성법을 이용한 산화아연 나노와이어의 에피택시 성장
함다슬,정병언,양명훈,이종관,최영빈,강현철,Ham, Daseul,Jeong, Byeong Eon,Yang, Myeong Hun,Lee, Jong Kwan,Choi, Young Bin,Kang, Hyon Chol 한국전기전자재료학회 2018 전기전자재료학회논문지 Vol.31 No.7
Epitaxial ZnO nanowires (NWs) were synthesized on sapphire (001) substrates using a hydrothermal process. The effects of the pH value of the precursor solution on the structural and optical properties of the resulting NWs was studied. The epitaxial relationship and the domain matching configuration between the sapphire (001) substrate and the as-grown ZnO NWs were determined using synchrotron X-ray diffraction measurements. The (002) plane of $w{\ddot{u}}rtzite$ ZnO NW grows in the surface normal direction parallel to the sapphire (001) direction. However, three types of in-plane domain matching configurations were observed, such as the on-position, $30^{\circ}$-rotated position, and ${\pm}8.5^{\circ}$-rotated position relative to the on-position, which might be attributed to inheriting the in-plane domain configuration of the ZnO seed layer.
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Twenty new records of mycophagous gall midges (Diptera: Cecidomyiidae) from Korea
함다슬,마야숍,배연재 국립생물자원관 2019 Journal of species research Vol.8 No.2
Mycophagous gall midges in the family Cecidomyiidae (Diptera) are poorly known in Korea, with only 14 recorded species. From our sampling throughout South Korea during 2015-2017, we present evidence of the Korean distribution of another 20 species as follows-Lestremiinae: Anarete angusta Mo & Xu, 2009; Micromyinae: Anodontoceras saigusai Yukawa, 1967, Campylomyza appendiculata Jaschhof, 2015, Campylomyza furva Edwards, 1938, Peromyia gotohi Jaschhof, 2001, Peromyia pumila Jaschhof, 2001, and Tekomyia populi Möhn, 1960; Winnertziinae: Leptosyna nervosa (Winnertz), 1852, Winnertzia nigripennis (Kieffer), 1894, and Winnertzia solidaginis Felt, 1907; Porricondylinae: Bryocrypta indubitata Mamaev, 1964, Camptomyia flavocinerea Panelius, 1965, Coccopsilis obscura (Mamaev), 1964, Coccopsilis paneliusi (Yukawa), 1971, Cryptoneurus muscicola (Kieffer), 1896, Dirhiza abludentis (Mamaev), 1998, Divellepidosis separata (Yukawa), 1971, Larimyia lavalis Fedotova & Sidorenko, 2007, Parvovirga latostylata Jaschhof, 2013, and Porricondyla nigripennis (Meigen), 1830.
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다이캐스팅 공정으로 제조한 ADC12 알루미늄 합금의 물성 향상 및 진공 열처리 효과
조지훈,함다슬,오성찬,차수연,강현철,Jo, Jihoon,Ham, Daseul,Oh, Seongchan,Cha, Su Yeon,Kang, Hyon Chol 한국결정성장학회 2021 한국결정성장학회지 Vol.31 No.1
We report structural, mechanical, and thermal properties of diecast ADC12 aluminum alloys characterized using synchrotron X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray (EDX) analysis, thermal conductivity (λ), Vickers hardness (Hv), and stress-strain measurements. We also studied the effect of post-annealing performed in a vacuum atmosphere on the mechanical properties of diecast ADC12 alloys. EDX and XRD results revealed that Al2Cu and AlCu3 grains are formed, well dispersed in Al base and highly crystalline. Ultimate tensile strength (UTS) of 307.9 ± 9.1 MPa and elongation of 2.98 ± 0.62 % were estimated. λ was 129.3 ± 0.27 W/m·K and Hv was approximately 130. Both values were significantly higher than the reported values. At annealing temperatures ranging from 25 to 200℃, UTS and Hv values remained constant, while as the annealing temperature increased to 500℃, these values gradually decreased. This is because stabilization of the microstructure improves toughness and ductility. 최적의 조건에서ADC12 알루미늄 합금을 다이캐스팅 기법으로 제조하여 구조적, 기계적, 열적 성질을 연구하였다. 또한 진공에서 후속 열처리한 ADC12 알루미늄 합금의 기계적 물성 변화를 규명하였다. 방사광 X-선 회절 및 energy dispersive X-선 화학조성 분석법을 통하여 ADC12 합금은 알루미늄 기저에 알루미늄과 구리의 화합물인 Al2Cu 및 AlCu3 상이 결정질 형태로 분포하고 있음을 규명하였다. 대표적인 기계적 물성값인 인장강도와 연신율은 각각 307.9 ± 9.1 MPa와 2.98 ± 0.62 %이다. 기존 보고보다 우수한 열전도도(129.3 ± 0.27 W/m·K)와 비이커스 경도값(Hv = 130)을 나타낸다. 후속 열처리 결과, 200℃까지는 기계적 물성치가 일정하게 유지되었으나, 이후 500℃까지 열처리 온도를 증가시킬 경우에는 인장강도와 비이커스 경도가 점진적으로 감소하였다. 이는 열처리 도중 미세조직이 안정화되면서 인성과 연성이 향상되었기 때문이다.
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