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Nb-1%Zr, Nb-5%Zr 합금에서 Zirconium과 탄소의 상호작용 및 표면분정
박동수,이원식,채건식 慶北大學校 物理化學硏究所 1984 硏究論文集 Vol.5 No.-
Nb-1% Zr, Nb-5% Zr 합금에서 지르코니움과 탄소의 상호작용 및 표면분정현상을 아르곤 이온종을 부착한 Auger 전자분광기로 연구했다. 고순도(99.996%)니오비움 다결정은 대부분의 탄소와 산소로 크게 부식되어 있었으며, 니오비움 다결정 내부에 함유된 탄소의 화학적 결합상태도 탄화물, 석묵 두가지 상태로 나타났다. 고순도 니오비움 다결정에 소량의 지르코니움(1%, 5%)을 첨가해서 만든 Nb-Zr 합금표면은 화학적으로 안정한 지르코니움 탄화물로 덮혀있고, 그 두께가 약 10Å정도임을 Auger분광자료로 밝혀냈고, 여기에 나타난 지르코니움, 탄소는 Nb-Zr 합금에서 표면 분정된 사실도 밝혀냈다. Nb-Zr 합금을 점진적으로 온도를 올려가면서, 지르코니움이 표면 분정된 양을 측정한 결과 지르코니움은 1300℃ 근방에서 산소는 1100℃ 근방에서 가장 많이 표면분정됨을 알았다. 이상의 실험결과로 탄소 산소로 크게 부식되어 있는 니오비움 다결정에 소량의 지르코니움(1%, 5%)를 첨가하므로서 탄소 산소의 부식을 크게 줄일 수 있음을 알았다. Auger electron spectrosopcy has been used in conjunction with argon ion sputtering in a study of the surface segregation and interaction of carbon with zirconium in Nb-Zr alloys. The result of depth profiling with argon ion sputtering showed that the carbon coverage on the Nb-Zr alloy surfaces was significantly more than that on the Nb polycrystalline surface. The dominant part of these carbon and oxygen was due to segregation from the Nb-Zr alloys. The segregation of zirconium to the Nb-Zr alloy surfaces occured at temperature as low as 900℃ with the maximum occurring around 1100℃. While the maximum depths of zirconium and oxygen segregated from the Nb-Zr alloy at temperature 1100℃ were respectively 5Å and 15Å.
Helix-coiled gold nanowires for molecular sensing.
Chae, Weon-Sik,Kim, Eun-Mee,Yu, Hyunung,Jeon, Seokwoo,Jung, Jin-Seung American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.4
<P>Helix-coiled gold nanowires were fabricated by a templating route using unique composite templates consisting of anodic aluminum oxide (AAO) nanotubular membrane and confined mesoporous silica therein. A different degree of confinement energy induces a different degree of helix curvature of confined porous silica nanochannels in an AAO, which works as a hard template for the electrochemical deposition of gold, thereby rationally enabling a different degree of helix curvature of gold nano-replicas. From surface-enhanced Raman scattering experiments, we first found that helix-coiled gold nanowires show more distinctly enhanced molecule sensing efficiency than those from simple smooth gold nanowires, and gold nanowires with the narrower lateral width show more enhanced molecule sensing efficiency than those of thicker width helix nanowires.</P>
Fabrication of 50 to 1000 nm Monodisperse ZnS Colloids
Chae, Weon-Sik,Kershner, Ryan J.,Braun, Paul V. Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.1
Monodisperse ZnS colloidal particles with precisely specified diameters over a broad size range were synthesized by controlled aggregation. Sub-10nm ZnS seed crystals were first nucleated at ambient temperature and then grown at an elevated temperature, which produced large polydisperse colloidal particles. Subsequent rapid thermal quenching and heating processes induced a number of secondary nucleations in addition to growing the large polydisperse microparticles which were finally removed by centrifugation and discarded at the completion of the reaction. The secondary nuclei were then aggregated further at elevated temperatures, resulting in colloidal particles which exhibited a nearly monodisperse size distribution. Particle diameters were controlled over a wide size range from 50 nm to 1 μm. Mie simulations of the experiment extinction spectra determined that the volume fraction of the ZnS is 0.66 in an aggregated colloidal particle and the colloidal particle effective refractive index is approximately 2.0 at 590 nm in water. The surface of the colloidal particles was subsequently coated with silica to produce ZnS@silica core-shell particles.
Effect of Ordered Intermediate Porosity on Ion Transport in Hierarchically Nanoporous Electrodes
Chae, Weon-Sik,Gough, Dara Van,Ham, Sung-Kyoung,Robinson, David B.,Braun, Paul V. American Chemical Society 2012 ACS APPLIED MATERIALS & INTERFACES Vol.4 No.8
<P>The high surface area of nanoporous electrodes makes them promising for use in electrochemical double-layer supercapacitors, desalination and pollution remediation, and drug delivery applications. When designed well and operating near their peak power, their charging rates are limited by ion transport through their long, narrow pores. This can be alleviated by creating pores of intermediate diameter that penetrate the electrode. We have fabricated electrodes featuring these by creating colloidal crystal-templated opals of nanoporous gold formed by dealloying. The resulting electrodes contain a bimodal pore-size distribution, with large pores on the order of several 100 nm and small pores on the order of 10 nm. Electrochemical impedance spectrometry shows that porous gold opals sacrifice some capacitance, but possess a lower internal resistance, when compared to a porous gold electrode with only the smaller-diameter pores. The architectural flexibility of this approach provides a greater ability to design a balance between power density and energy density.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2012/aamick.2012.4.issue-8/am300798j/production/images/medium/am-2012-00798j_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am300798j'>ACS Electronic Supporting Info</A></P>
Fluorescence Modulation of Graphene Quantum Dots Near Structured Silver Nanofilms
Chae, Weon-Sik,Yun, Jungheum,Nam, Sang-Hyeon,Lee, Sang-Geul,Yang, Won-Geun,Yoon, Hyewon,Park, Minsu,Jeon, Seokwoo American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.16
<P>Here, we study the plasmonic metal-enhanced fluorescence properties of blue-emitting graphene quantum dots (GQDs) and green-emitting graphene oxide quantum dots (GOQDs) using fluorescence lifetime imaging microscopy. Reactive ion sputtered silver (Ag) on zinc oxide (ZnO) thin films deposited on silicon (Si) wafers are used as the substrates. The morphology of the sputtered Ag gradually changes from nanoislands, via and elongated network and a continuous film with nanoholes, to a continuous film with increasing sputtering time. The fluorescence properties of GQD and GOQD on the Ag are modulated in terms of the intensities and lifetimes as the morphology of the Ag layers changes. Although both GQD and GOQD show similar fluorescence modulation on the Ag nanofilms, the fluorescence of GQD is enhanced, whereas that of GOQD is quenched due to the charge transfer process from GOQD to ZnO. Moreover, the GQD and GOQD exhibit different fluorescence lifetimes due to the effect of their electronic configurations. The theoretical calculation explains that the fluorescence amplification on the Ag nanofilms can largely be attributed to the enhanced absorption mechanism arising from accumulated optical fields around nanogaps and nanovoids in the Ag nanofilms.</P> [FIG OMISSION]</BR>
Chae, Weon-Sik,Im, Sung-Jae,Lee, Jin-Kyu,Kim, Yong-Rok Korean Chemical Society 2005 Bulletin of the Korean Chemical Society Vol.26 No.3
Free-standing nanoporous alumina membrane microtubes with different shapes (rectangular and cylindrical tubes) and variable dimensions were easily fabricated by direct anodization of the aluminum templates of the specified shapes (strip and wire) and dimensions during the electrochemical reaction.