샆스와 미세 구조 및 화학적 특성

한상욱 한국물리학회 2013 새물리 Vol.63 No.10

페르미 황금률을 (Fermi Golden rule) 이용하여 물질 내 선택된 특정 원소 주위 구조 및 화학적 특성을 결정하는 기법이 샆스 (XAFS, X-ray absorption fine structure) 이다. 샆스는 엑스선의 흡수 특성을 이용하기 때문에 시료의 상태 (고체, 액체, 기체)나, 결정도 (결정체, 비정질), 그리고 형태 (필름, 포일, 가루, 혼합물)와 무관하게 적용 가능하다. 샆스 분석을 통하여 물질을 구성하고 있는 원소의 종류와, 특정 원소의 산화수 및 그 원소 주위의 한곳 구조 특성 (local structural properties)을 결정할 수 있다. 샆스는 매우 폭넓게 다양한 혼합물의 특성을 연구하는데 활용될 수 있지만, 측정된 샆스 데이터로부터 결정적인 정보를 얻기 위하여 매우 정교하고 올바른 측정 및 분석과 절차가 필요하다. 본 논문에서는 샆스 측정을 통하여 정량적으로 한곳 구조 및 화학적인 특성을 결정하는 방법을 체계적으로 논의하였다. XAFS (X-ray absorption fine structure) that is based on the Fermi Golden rule is a local probe to determine local structural and chemical properties around a selected element in a material. XAFS can determine types of atoms, chemical valence states, and local structural properties regardless of phase (solid, liquid, gas),crystanillity (crystal, amorphous), or shape (film, foil, powder,compound). XAFS can be widely used to study various compounds. However, a precise analysis is required to obtain critical information from XAFS. We systematically discussed how to determine local structural and chemical properties from XAFS.

Transformation of zinc-concentrate in surface and subsurface environments: Implications for assessing zinc mobility/toxicity and choosing an optimal remediation strategy

Kwon, Man Jae,Boyanov, Maxim I.,Yang, Jung-Seok,Lee, Seunghak,Hwang, Yun Ho,Lee, Ju Yeon,Mishra, Bhoopesh,Kemner, Kenneth M. Elsevier Applied Science Publishers 2017 Environmental pollution Vol.226 No.-

<P><B>Abstract</B></P> <P>Zinc contamination in near- and sub-surface environments is a serious threat to many ecosystems and to public health. Sufficient understanding of Zn speciation and transport mechanisms is therefore critical to evaluating its risk to the environment and to developing remediation strategies. The geochemical and mineralogical characteristics of contaminated soils in the vicinity of a Zn ore transportation route were thoroughly investigated using a variety of analytical techniques (sequential extraction, XRF, XRD, SEM, and XAFS). Imported Zn-concentrate (ZnS) was deposited in a receiving facility and dispersed over time to the surrounding roadside areas and rice-paddy soils. Subsequent physical and chemical weathering resulted in dispersal into the subsurface. The species identified in the contaminated areas included Zn-sulfide, Zn-carbonate, other O-coordinated Zn-minerals, and Zn species bound to Fe/Mn oxides or clays, as confirmed by XAFS spectroscopy and sequential extraction. The observed transformation from S-coordinated Zn to O-coordinated Zn associated with minerals suggests that this contaminant can change into more soluble and labile forms as a result of weathering. For the purpose of developing a soil washing remediation process, the contaminated samples were extracted with dilute acids. The extraction efficiency increased with the increase of O-coordinated Zn relative to S-coordinated Zn in the sediment. This study demonstrates that improved understanding of Zn speciation in contaminated soils is essential for well-informed decision making regarding metal mobility and toxicity, as well as for choosing an appropriate remediation strategy using soil washing.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Zn-concentrate accumulated in soils transformed to Zn species of various stability. </LI> <LI> Zn species at our site underwent the transformation from Zn sulfides → O-coordinated Zn. </LI> <LI> XAFS/sequential extraction showed a correlation between acid extractability and Zn speciation. </LI> <LI> Metal speciation enables a better assessment of metal mobility/toxicity and the choice of an optimal remediation strategy. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Graphical Abstract. Conceptual model of the apparent physical and geochemical processes controlling surface-subsurface partitioning of Zn in the study area.</P> <P>[DISPLAY OMISSION]</P>

연안저니에서의 석탄회 조립물에 의한 황화수소 제거기구의 해석

김경회(K.H.Kim),이인철(I.C.Lee),日比野忠史(T.Hibino),日比野忠史(S.Hayakawa) 한국해양환경·에너지학회 2013 한국해양환경공학회 학술대회논문집 Vol.2013 No.5

Synthesis and temperature-dependent local structural and electrical properties of VO2 films

Zhenlan Jin,황인희,박창인,Jae-Kuan Son,Sang-Wook Han 한국물리학회 2016 Current Applied Physics Vol.16 No.2

We examine the local structural and electrical properties of VO2 films showing metal-to-insulator transition (MIT) by using in-situ x-ray absorption fine structure (XAFS) measurements at the V K edge and resistance measurements in the temperature range 20e120 C. VO2 films are synthesized on Al2O3 (0001) substrates by DC magnetron sputtering deposition. X-ray diffraction measurements show that the films have b-oriented monoclinic-phase crystals at room temperature. XAFS measurements reveal a local structural transition in the films from the monoclinic (M1) to the rutile (R) phase at ~70 C during their heating; further, temperature-dependent resistance (ReT) measurements showed a sharp MIT in the films at ~75 C. Extended XAFS (EXAFS) measurements reveal non-rigid changes of VeO and VeV bond lengths from the M1 to the R phase via the M2 phase. In-situ EXAFS and ReT measurements show that the synthesized VO2 films act as Mott insulators and that their electrical property change is not proportional to their structural property change at their MIT temperature.

Local structural and Magnetic Properties of Zn1-x MnxTe Semiconductor Films

한상욱,최용대 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.1

We investigated the local structural properties around the Zn and the Mn atoms of Zn1-xMnxTe (ZMT) magnetic semiconductor films (x = 0.16 and 0.27) by using the X-ray absorption fine struc- ture (XAFS). The ZMT lms were synthesized with a hot-wall epitaxy process. The XAFS mea- surements at the Zn K edge revealed that the ZMT films had an ordered zinc-blende structure and that no distinguishable structural disorder existed in any atomic pair independent of the Mn composition ratio. The XAFS analysis at the Mn K edge demonstrated that the Mn ions had a chemical valence state of 2+ and that they were exactly substituted at the Zn site. DC magnetiza- tion measurements from the specimens did not show a ferromagnetic property in the temperature range of 5 ∼ 300 K.

Synthesis and temperature-dependent local structural and electrical properties of VO₂ films

Jin, Z.,Hwang, I.H.,Park, C.I.,Son, J.K.,Han, S.W. Elsevier 2016 Current Applied Physics Vol.16 No.2

<P>We examine the local structural and electrical properties of VO2 films showing metal-to-insulator transition (MIT) by using in-situ x-ray absorption fine structure (XAFS) measurements at the V K edge and resistance measurements in the temperature range 20-120 degrees C. VO2 films are synthesized on Al2O3 (0001) substrates by DC magnetron sputtering deposition. X-ray diffraction measurements show that the films have b-oriented monoclinic-phase crystals at room temperature. XAFS measurements reveal a local structural transition in the films from the monoclinic (M-1) to the rutile (R) phase at similar to 70 degrees C during their heating; further, temperature-dependent resistance (ReT) measurements showed a sharp MIT in the films at similar to 75 degrees C. Extended XAFS (EXAFS) measurements reveal non-rigid changes of V-O and V-V bond lengths from the M-1 to the R phase via the M-2 phase. In-situ EXAFS and R-T measurements show that the synthesized VO2 films act as Mott insulators and that their electrical property change is not proportional to their structural property change at their MIT temperature. (C) 2015 Elsevier B.V. All rights reserved.</P>

Characterization of Elemental Composition and Valence State of Cyclone-collected Aerosol Particles Using EDXRF and XAFS at Three Sites in Japan

Tomoaki Okuda,Weidong Jing,Katsutomo Saito,Takuma Okamoto,Hibiki Saito,Kazuki Sugimoto,Chiharu Nishita-Hara,Keiichiro Hara,Masahiko Hayashi,Shuichi Hasegawa 한국대기환경학회 2022 Asian Journal of Atmospheric Environment (AJAE) Vol.16 No.2

The valence state and concentration of metallic pollutants are important factors contributing to the health effects of respirable particulate matter (PM); however, they have not been well studied. In this study, coarse and fine powder samples of atmospheric PM were collected using a cyclone system at Kanagawa (KO), Saitama (SA), and Fukuoka (FU) in Japan in 2017. Energy dispersive X-ray fluorescence spectroscopy (EDXRF) was used to measure the concentrations of nine metallic elements (Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, and Pb), and X-ray absorption fine structure (XAFS) spectroscopy was used to analyze the valence states of target elements (Cr, Mn, Fe, Cu, and Zn). The EDXRF results indicated that the average contents of Fe, Ti, and Zn were much higher than those of the other six elements in all samples. The XAFS results showed that the major valence states of the elements were Cr(III), Mn(II), Fe(III), Cu(II), and Zn(II). The percentages of Mn(IV), Fe(II), and Cu(0) were higher in KO and SA samples than in FU samples. Mn(0) and Zn(0) were detected in some samples only, and Cu(I) was not detected in any samples. Correlation analysis, principal component analysis, and cluster analysis were performed on the EDXRF and XAFS data of the target elements. The source identification results showed that the sources of metal contaminants in the samples varied considerably between sampling sites and depended on the industrial structure and geographical location of the sampling area. Our findings on the different valence states of the elements may be important for determining the toxicity of PM at different locations.

μXAFS and TEM studies of Fe(III) oxides precipitated on submarine basaltic glass from South Pacific Gyre

Mitsunobu, S.,Suzuki, Y.,Watanabe, K.,Yang, K.,Kim, J.W. Elsevier 2018 Chemical geology Vol.501 No.-

<P><B>Abstract</B></P> <P>In the present study, we investigated secondary products formed on the surface of altered basaltic glass from the sediment-basalt interface by multiple characterizations with EPMA, μXANES, μEXAFS, TEM, and EELS. μXANES and EPMA analyses showed that secondary products with high Fe abundance were precipitated on the surface of basalt glass and that the Fe species in the secondary product was dominantly composed of Fe(III) oxides, hematite, which was also agreeable with EELS result. Characterization by TEM and μEXAFS suggested that the hematite was nanoparticulate with particle size of 10–20 nm. This is the first study showing the occurrence of nanosized hematite as secondary products in altered basaltic glass, although there are many studies on the formation of Fe(III) (hydr)oxides in basalt alteration.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Altered submarine basaltic glass from sediment-basalt interface in South Pacific Gyre </LI> <LI> Micro- and nano-scale characterizations by μXAFS and TEM techniques </LI> <LI> Occurrence of nanosized hematite as secondary products in altered basaltic glass </LI> </UL> </P>

Structural and Optical Properties of Hydrogen-ion-implanted ZnO Nanorods

Y.-B. Lee,C.-H. Kwak,S.-Y. Seo,김선효,C.-I. Park,B.-H. Kim,S.-H. Park,최용대,한상욱 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.61

We investigated the micro-structural and the optical properties of H+-ion-implanted ZnO nanorods by using X-ray absorption fine structure (XAFS) measurements at the Zn K edge and photoluminescence (PL) measurements. Vertically-aligned ZnO nanorods were synthesized using metal-organic chemical-vapor deposition and were vertically implanted with hydrogen ions (H+) at an energy of 90 keV and a total flux of 1016 particles/cm2. Scanning electron microscopy measurements showed no detectable defects existing in the H+-ion-implanted ZnO nanorods. However,transmission electron microscopy measurements revealed that an amorphous phase existed, particularly near the top parts of the nanorods. X-ray diffraction and XAFS measurements provided further evidence that the nanorods had structural defects due to the H+-ion implantation. PL measurements showed that the transition peak intensity of the H+-ion-implanted ZnO nanorods was decreased dramatically due to the ion implantation.

Temperature-dependent magnetic and local structural properties of diamagnetic a-HgI2

여순목,Jae-Kuan Son,Chang-In Park,황인희,Zhenlan Jin,Jang Ho Ha,Sang-Wook Han 한국물리학회 2016 Current Applied Physics Vol.16 No.9

We examined the temperature-dependent magnetic and structural properties of a-HgI2 in the temperature range of 300e400 K using temperature-dependent DC-magnetization, x-ray diffraction (XRD), and x-ray absorption fine structure (XAFS) measurements. DC-magnetization measurements of a-HgI2 single crystals show a sudden reduction of diamagnetic susceptibility for T > 350 K. XRD measurements with Rietveld refinements reveal a small but substantial amount of decrease in disorder in both Hg and I sites above 350 K, with neither a structural transition nor vacancies in the temperature range. XAFS demonstrates a shift of the I K edge for T > 350 K but no changes at the Hg L3 edge. A stronger bonding of Hg-I pairs above 350 K likely affects the electrons in the outermost shells of iodine atoms and enhances the intrinsic paramagnetic properties, thereby producing a reduction in diamagnetism.