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X-ray absorption spectroscopy and related techniques
Alojz Kodre, Iztok Arčon, Jana Padežnik Gomilšek, 2004, izvirni znanstveni članek

Opis: In the extensive field of X-ray diagnostic techniques, nowadays mostly implemented on synchrotron X-ray sources, the X-ray absorption methods offer a relatively simple tool for structural analysis of materials. The advantage of the methods is the sensitivity to chemical species and the insensitivity to the long-range order. An overview of various detection techniques is given together with the discussion of accuracy of the method with regard to the spatial resolution and the possible contamination by intra-atomic contributions, the multielectron photoexcitations.
Ključne besede: X-rays, absorption, EXAFS, XANES
Objavljeno: 30.08.2017; Ogledov: 185; Prenosov: 41
.pdf Celotno besedilo (146,75 KB)
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High-resolution X-ray absorption spectrometry of atomic vapors
Andrej Mihelič, Alojz Kodre, Iztok Arčon, Jana Padežnik Gomilšek, 2004, izvirni znanstveni članek

Opis: A measurement of an x-ray absorption spectrum of a monatomic sample yields pure atomic absorption essential for the EXAFS (Extended X-ray Absorption Fine Structure) analysis in cases of a weak structural signal. A construction of an absorption cell to contain vapor sample takes into account specific properties of the investigated element. Metal-vapor absorption cells for the elements K, Zn, Rb, Cd, Cs, and Hg are presented and comments are made on the use of materials and the operating mechanisms of the cells.
Ključne besede: x-ray absorption, atomic vapors, K, Zn, Rb, Cd, Cs, EXAFS
Objavljeno: 18.08.2017; Ogledov: 457; Prenosov: 35
.pdf Celotno besedilo (105,40 KB)
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Structural properties and thermal stability of cobalt- and chromium-doped $α-MnO_2$ nanorods
Romana Cerc Korošec, Polona Umek, Alexandre Gloter, Jana Padežnik Gomilšek, Peter Bukovec, 2017, izvirni znanstveni članek

Opis: $α-MnO_2$ nanorods were synthesized via the hydrothermal decomposition of $KMnO_4$ in an acidic environment in the presence of $Co^{2+}$ and $Cr^{3+}$ ions. Reactions were carried out at three different temperatures: 90, 130 and 170 °C. All prepared samples exhibit a tetragonal $MnO_2$ crystalline phase. SEM–EDS analysis shows that cobalt cations are incorporated to a higher degree into the $MnO_2$ framework than chromium ions, and that the content of the dopant ions decreases with increasing reaction temperature. The oxidation of $Co^{2+}$ to $Co^{3+}$ during the reaction was proved by an XANES study, while EXAFS results confirm that both dopant ions substitute $Mn^{4+}$ in the center of an octahedron. The K/Mn ratio in the doped samples synthesized at 170 °C is significantly lower than in the undoped samples. Analysis of an individual cobalt-doped $α-MnO_2$ nanorod with HAADF-STEM reveals that the distribution of cobalt through the cross-section of the nanorod is uniform. The course of thermal decomposition of the doped nanorods is similar to that of the undoped ones. Dopant ions do not preserve the $MnO_2$ phase at higher temperatures nor do they destabilize the cryptomelane structure.
Ključne besede: $α-MnO_2$, manganese dioxide, doping, EXAFS, nanorods, XANES
Objavljeno: 10.08.2017; Ogledov: 499; Prenosov: 196
.pdf Celotno besedilo (8,24 MB)
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EXAFS and IR analysis of electrochromic $NiO_x$/$NiO_xH_y$ thin films
Jana Padežnik Gomilšek, Romana Cerc Korošec, Peter Bukovec, Alojz Kodre, 2008, izvirni znanstveni članek

Opis: Electrochromic (EC) thin films of $NiO_x$ and $NiO_xH_y$ are prepared by sol-gel method from nickel chloride precursor and deposited onto a suitable substrate by dip-coating technique. The development of the structure with thermal treatment is investigated by EXAFS and IR spectroscopy in two series of films, with high and low concentration of chloride as counter ions. In the former, the predominant structure before thermal treatment is nickel hydroxide. The baking induces condensation, yet with no trace of NiO. In the latter group, colloidal particles are indicated, on which acetate groups are adsorbed or coordinated. At the maximum EC-response the formation of NiO grains is established by EXAFS and IR.
Ključne besede: electrochromism, thin films, nickel oxide, nickel hydroxide, EXAFS
Objavljeno: 18.08.2017; Ogledov: 321; Prenosov: 41
.pdf Celotno besedilo (286,00 KB)
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Specific EXAFS tools in analysis of MoSI nanowires
Alojz Kodre, Jana Padežnik Gomilšek, Iztok Arčon, Anton Meden, Dragan Mihailović, 2006, izvirni znanstveni članek

Opis: The structure of nanowires prepared by vapor synthesis from Mo, S and I is investigated by methods of x-ray diffraction (XRD) and extended x-ray absorption fine structure (EXAFS). Starting with a qualitative model of the structure from XRD, the metrics is introduced with interatomic distances determined from EXAFS. Two specific tools to increase the resolution of EXAFS method are discussed: the reciprocity relation between data from adjacent target atoms, and difference EXAFS from data on samples with small changes in stoichiometry.
Ključne besede: EXAFS, nanowires, molybdenum sulphide-iodide
Objavljeno: 25.08.2017; Ogledov: 204; Prenosov: 47
.pdf Celotno besedilo (365,05 KB)
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