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Commissioning and performance of X-ray absorption spectroscopy beamline at the Siam Photon Laboratory
Abstract
We report commissioning results and performance of X-ray absorption spectroscopy (XAS) beamline, BL-8, at the Siam Photon Laboratory. BL-8 has been opened for users since the year 2006. It is tunable by a fixed-exit double crystal monochromator equipped with InSb(111), Si(111), and Ge(220) crystals covering photon energy from 1830 to 9000eV. Thus elemental absorption K-edges of silicon up to copper can be investigated. Other heavier elements may be studied via their L or M edges. The front end is windowless and the beamline is terminated with a Kapton window followed by the XAS station equipped with ionization chambers for transmission-mode measurements. The measured photon flux at sample is approximately 108–1010 photons/s/100mA for the 1mm×10mm beam size. The commissioning XANES spectra of sulfur standards and EXAFS spectra of copper are presented.
... The XAS beamline (BL-8) of the National Synchrotron Research Center (NSRC), Thailand, has been successfully constructed and opened for users since 2006 (Klysubun et al., 2007). Therefore, it is a good opportunity for us to conduct archaeological research using the XAS beamline in Thailand. ...
... The Fe K-edge XANES spectra were measured in the transmission mode using the BL-8 beamline of the National Synchrotron Research Center (NSRC, Thailand). Monochromatized 1.2 GeV SR X-rays, obtained from a Ge (220) doublecrystal monochromator, was used to select the photon energy with a spectral resolution (ΔE/E) of 10-4 ( Klysubun et al., 2007). While scanning the photon energy, the absorption spectrum was measured with 2 ionization chambers located before and after the sample. ...
Dan Kwian, Sukhothai and Ratchaburi pottery clays are economically important pottery clays. They are well known in the Thai ceramic society for making Dan Kwian pottery, Sawankhalok pottery and Dragon jars, respectively. There have been several studies of these pottery clays. However, few of them used statistics to analyze their results. This work is a comparative study of the compositions and properties of these three pottery clays using statistical software to analyze the results. Results show that the major components of these pottery clays are SiO2 and Al2O3. The Modulus of Rupture (MOR) of each pottery clay fired at 700°C are not significantly different. Sukhothai pottery clay fired at 900°C has a higher MOR and bulk density while its porosity, water absorption and apparent specific gravity are less than those of the Dan Kwian and Ratchaburi pottery clays fired at the same temperature. Additionally, the current study developed regression equations for estimating the properties of all pottery clays under study. Finally, it was found that the L*, a*, b* and reflectance spectra of all pottery clays increased when firing temperature was increased from 700 to 900°C.
... The XAS beamline (BL-8) of the National Synchrotron Research Center (NSRC), Thailand, has been successfully constructed and opened for users since 2006 (Klysubun et al., 2007). Therefore, it is a good opportunity for us to conduct archaeological research using the XAS beamline in Thailand. ...
... The Fe K-edge XANES spectra were measured in the transmission mode using the BL-8 beamline of the National Synchrotron Research Center (NSRC, Thailand). Monochromatized 1.2 GeV SR X-rays, obtained from a Ge (220) doublecrystal monochromator, was used to select the photon energy with a spectral resolution (ΔE/E) of 10 -4 (Klysubun et al., 2007). While scanning the photon energy, the absorption spectrum was measured with 2 ionization chambers located before and after the sample. ...
The pottery shards excavated from the Ban Chiang archaeological site a UNESCO world heritage site, Thailand are well known for their distinctive red paint and exquisite designs. The pottery assemblages are found to span 3 periods: Pre-metal, Bronze, and Iron Ages. The aim of this research is to explore the firing techniques used for pottery production during these time spans. X-ray absorption spectroscopy carried out at Beam line 8 (BL-8) of the National Synchrotron Research Center (NSRC), Thailand was used to measure Fe 2+ and Fe 3+ distributions in the pottery. A range of other analytical techniques, including X-ray Diffraction (XRD), X-ray Fluorescence (XRF), Fourier Transform Infrared Spectroscopy (FT-IR), Differential Thermal Analysis (DTA), and Thermal Gravimetric Analysis (TGA) were also used to obtain the chemical compositions and information on changes in the thermal properties of the samples. The Fe K-edge absorption spectra of mixed standard iron compounds and the red clay ceramics fired under control conditions at various temperatures are used as a reference standard to determine the ferric/ferrous ratio in the pottery shards. Results revealed that all Ban Chiang pottery was likely fired under partial reducing conditions, but the firing temperature used was higher in the Pre-metal Age than those in the Bronze and Iron Ages.
... XANES is an advanced characterization technique for the study of sulfur atoms incorporation into the NR film. The sulfur K-edge absorption energy enables to provide information on the two or three coordination shells around the absorbing atom [6]. ...
... The XANES measurements were carried out at the beamline 8 (BL8) using synchrotron radiation from Synchrotron Light Research Institute (SLRI) in Thailand [6], storage ring operated at 1.2 GeV electron beam energy and an electron beam current of about 100 mA. The measurements were performed in a fluorescence mode using a 5-grid ionization Lytle fluorescence detector. ...
In this work, we present the results of sulfur crosslinking and degradation in natural rubber (NR) studied by X-ray absorption near-edge structure spectroscopy (XANES). Sulfur K-edge XANES spectra has been collected and analyzed to provide the geometry and electronic environment of sulfur crosslinks during vulcanization and degradation processes by ozone aging. We found that reversion took place before the onset of oxidative process at the sulfur bridge. Parallel to the oxidative process, the production of cyclic sulfanes took places. This physicochemical properties which were calculated from S K-edge XANES spectra were correlated with the
mechanical of NR films by varying accelerator type. The accelerator zinc diethyldithiocarbamate (ZDEC) gave highest film strength when compared with other accelerators: Ncyclohexylbenzothiazole sulfenamide (CBS), 2,2' dibenzothiazyl disulfide (MBTS), and tetramethylthiuram disulfide (TMTD).
... In this report we will describe the technical specification of BL8 and its XAS station that has not been updated in the literature after the commissioning of TM-mode XAS (Klysubun et al., 2006(Klysubun et al., , 2007. During the last four years major developments have been focused on expanding the photon energy range, implementation of the FY-mode XAS technique in addition to the TM-mode technique, and standardization for improving data quality and throughput of the beamline. ...
... To isolate ultra-highvacuum (UHV; 10 À10 torr) conditions in the front-end section and high-vacuum (HV; 10 À6 torr) conditions in the downstream sections of the beamline, two differential pumping stages, each of which encompasses a small rectangular duct of low vacuum conductance (LVC) and an ion pump (IP) with high pumping speed, were employed, rather than using an ordinary beryllium window, which significantly attenuates synchrotron radiation in the soft X-ray regime. Functional testing of this differential pumping system was reported by Klysubun et al. (2007). It should be noted that, to date, there has never been a failure originating from this vacuum sectioning scheme. ...
Beamline BL8 of the Synchrotron Light Research Institute (Thailand) is routinely operated for X-ray absorption spectroscopy (XAS) in an intermediate photon energy range (1.25-10 keV). The photon energy is scanned by using a double-crystal monochromator, the crystal pair of which can be interchanged among KTP(011), InSb(111), Si(111) and Ge(220). The experimental set-up conveniently facilitates XAS measurements in transmission and fluorescence-yield modes at several K-edges of elements ranging from magnesium to zinc. Instrumentation and specification of the beamline and the XAS station are described, together with the determination of the available photon flux [0.1-6 × 10(10) photon s(-1) (100 mA)(-1)], energy resolution (1-5 × 10(-4)) and stability of photon energy calibration (0.07 eV), representing the beamline performance. Data quality and accuracy of XANES and EXAFS measured at BL8 are compared with those of other well established beamlines. A noted distinction of BL8 is its relatively high sensitivity for studying phosphorous, sulfur and chlorine in diluted systems and its maximum beam size of 14 mm (width) × 1 mm (height), which is suitable for bulk characterization.
... The electronic structure of the SnO 2 sample and the influence of the increasing temperature on the electronic structure properties were studied by the XAS. The data collection process was carried out at room temperatures at the beamline BL8: XAS of SPL [24,25]. The laboratory is the first synchrotron facility of Thailand and serves as a 1.2 GeV synchrotron light source. ...
In this work, tin dioxide (SnO2) thin films were prepared at various substrate temperatures (380–440 °C, in steps of 20 °C) on glass substrates by the Spray Pyrolysis Method. X-ray Diffraction (XRD) measurements revealed that the SnO2 thin films were formed in a tetragonal crystallized structure. The electronic structure of the tin dioxide thin films that were prepared at several substrate temperatures were investigated with the collected X-ray Absorption Spectroscopy (XAS) data. The crystal structure analysis was also supported by the Extended X-ray Absorption Fine Structure (EXAFS) data analysis extracted from the X-ray Absorption Fine Structure (XAFS) data. Unstable crystal behaviors were detected in the samples due to metastable SnO structure formations as a result of phase transitions from the SnO to SnO2 structure during the annealing processes. Clear information on the atomic displacements in the samples as a picture of the crystal mechanism was obtained from the analysis of EXAFS data. The SnO2 thin films were found to exhibit high transmittance (average 90%) in the 400–1100 nm interval. The thickness of the SnO2 thin film (t) and refractive index (n) were calculated from transmittance spectra in the visible region using envelope method. The direct energy band gaps of the films obtained were 4.01–4.09 eV. Atomic force microscope (AFM) measurements were performed in order to investigate the surface roughness of the SnO2 thin films.
... Measurements of Mn K-edge X-ray absorption near edge structure (XANES) spectra of the samples were carried out at the Synchrotron Light Research Institute of Thailand using the X-ray absorption spectroscopy beamline (BL8) [6] to study the changes of Mn oxidation states before and after the treatments. The photon energy was scanned with Ge (220) double-crystal monochromator while the XANES spectra were recorded in fluorescence mode using a 13-channel array germanium detector. ...
Rubellite, one of the most attractive members of the colorful family of tourmalines, has its colors ranging from fine red hues to pinkish and violetish nuances. Some of them are very light while others are so dark that the real hue can only be identified when the stones are held against the light. Fine jewelry-grade rubellites are relatively rare; therefore, color enhancement are normally required on natural samples. In present study, pink tourmaline samples from Mozambique were enhanced using two methodologies, i.e., gamma irradiation and heat treatment. The samples were characterized before and after the color enhancements. Conclusive remarks were drawn upon the modification of their color appearance, optical absorption, and oxidation states of the chromophores. After preparation, the samples were divided into two groups: The first group were irradiated with 400, 500 and 600 kGy of gamma while the second group were heat treated at 350, 450 and 550 °C. After irradiation, the slightly pink tourmaline samples turned saturated pink. The color of heat-treated samples, however, were faded from initially very slightly pink to colorless with increasing temperatures. It was noticed that both gamma irradiation and heat treatment at current conditions did not affect any inclusions in the specimens. FTIR spectra of untreated samples displayed several bands at 3300-3700 cm⁻¹ for OH-stretching, 5200 cm⁻¹ for H2O and 4200–4400 cm⁻¹ for Fe-OH. After both treatments, all bands were decreased, especially, for the OH band. UV–vis-NIR spectra of the untreated samples displayed the absorption band at 520 nm related to Mn³⁺. Upon treatments, this band was increased with peak height depended on the treatment conditions. Mn K-edge x-ray absorption spectra of the samples exhibited the shift of Mn oxidation to a higher number after both treatments.
... XAFS technique in the hard x-ray region can provide useful tools for electronic and crystal structure study. The measurements were performed for Ca K-edge of the LCLZO samples at Beamline-BL8:XAS of Siam Photon Laboratory (SPL) Synchrotron Radiation facility in Nakhon Ratschasima, Thailand [8]. The beamline BL8 operates for the technique x-ray absorption spectroscopy. ...
In this study, calcium doped Li7La3Zr2O12 (LLZO) were synthesized as a candidate for the solid state electrolyte material according to the Li7-2x CaxLa3Zr2O12 (LCLZO) general formula where x has the value “1.0” and also the parent material for the sample series of Li5Ca1- xGaxLa3Zr2O12. Crystal and electronic properties of the LCLZO materials were studied in two steps; Ca²⁺ substitution to Li⁺ coordinations and Ga³⁺ substitution to Ca²⁺ coordinations. Analysis confirmed that a calcium sit in two lithium coordinations, however, the Ca²⁺ doped LCLZO material were determined in tetragonal structure, not cubic, which has lower properties for battery electrolytes. In the second step of the study, with the attempt of the substitution of the Ga³⁺ ions to the Ca²⁺ coordinations, the phase of the tetragonal LCLZO structures changed to cubic LCLZO structure. According to the XAS analysis of the O K-edge spectra, it is determined that oxygen coodinations are the main role player in the samples and cause the formation of the “Li5GaO4” structures with the Ga³⁺ substitution.
... The electronic structure of the SnO 2 sample and the influence of the increasing temperature on the electronic structure properties were studied by the XAS. The data collection process was carried out at room temperatures at the beamline BL8: XAS of SPL [24,25]. The laboratory is the first synchrotron facility of Thailand and serves as a 1.2 GeV synchrotron light source. ...
The aim of the work was preparation of tin oxide thin film and study of investigate the usability of these film in solar cell. To understand the physical properties of SnO2 thin film, in solar cells we examined its optical transmittance and crystal structure. Tin oxide (SnO2) thin film deposited on a commercial microscope glass by spray pyrolysis method were characterized optical measurements. The film is highly transparent in the visible range of the electromagnetic spectrum with an optical transmittance (T%) reaching to values up to 80–96% over 400 nm. Using these data, the optical band gap (Eg), the extinction coefficient k and the refractive index n value were calculated. The XRD analyses indicate that tin oxide thin film is found to have a tetragonal rutile structure. As a result of this work, it can be said that the obtained polycrystalline SnO2 thin film can be used as window layer in solar cells due to its high optical transmittance.
... between solution Zn content and Zn percentage in resulting film). XAFS data were collected at Beamline-BL8:XAS of Siam Photon (SLRI) Synchrotron Radiation facility (Nakhon Ratschasima, Thailand) in fluorescence yield mode (FY) [8,9]. The beamline delivers x-rays between the energy range of 1·25-10 keV. ...
A series of Zn doped copper materials were investigated upon their crystal and electronic structure with the general formula Cu1-xZnx. CuZn alloys were produced via electrodeposition method. Galvanostatic deposition was preferred for the deposition. Crystal properties of the samples were studied via X-ray diffraction (XRD) patterns and supported by the X-ray absorption fine structure spectroscopy (XAFS) data. According to the crystal structure analysis, crystal geometries of the substituted samples were mainly determined in bcc cubic. The study has revealed that, low amount of Zn substitution (0.1M) are inactive in the molecular interplays and treated as an impurity in fcc copper environment. However, higher Zn concentrations (> 0.1 M) have built bcc structure under the influence of the highly overlapped 4p levels wavefunctions of the neighbouring Cu and Zn atoms. Thus, 0.1 M zinc substitution has been determined as a threshold of the phase transition from fcc to the bcc structure.
... X-ray absorption spectroscopy (XAS) spectra of the natural sapphires focused on Ti K-edge using XANES and EXAFS techniques in fluorescence mode were carried out at the XAS BL-8 station, Synchrotron Light Research Institute (SLRI), Thailand. The x-ray beam from the synchrotron radiation has been generated from the bending magnets [8,9]. XAS is a suitable technique applied for gemstone research due to a non-destructive method [10]. ...
Sapphire, an inorganic gem-material in a variety of corundum, mainly consists of alpha-alumina (α-Al2O3) structure. The geological origins of sapphire are related to either basaltic or metamorphic rocks. The causes of the color on sapphire are some trace elements such as Cr, Fe, and Ti. It could be mentioned that Ti atoms have cooperated with Fe atoms for creating the blue color. In this study, X-ray absorption spectroscopy (XAS) technique focused on the x-ray absorption near edge structure (XANES) and the extended x-ray absorption fine structure (EXAFS) is employed to identify the oxidation state of Ti atoms and Ti-O bond length on sapphire samples. The Ti K-edge XANES and EXAFS spectra of natural sapphires were carried out using the 13-channel array germanium detector in fluorescence mode. The XANES spectra showed that the oxidation state of Ti was Ti⁴⁺ regardless of Fe content. Moreover, the Ti-O bond length on a-Al2O3 was equal to the Ti-O bond length on rutile (TiO2) analyzed from the EXAFS spectra. From these results, it could be concluded that the oxidation state of Ti atoms on natural sapphires was Ti⁴⁺ which substitutes Al³⁺ on the sapphire structure.
... To perform detailed crystal structure analysis, additional EXAFS (Extended X-ray Absorption Fine Structure) measurements in the hard x-ray region were performed for Er L 3 -edge and Fe K-edge of the Er x Fe 1-x BO 3 samples. The data were collected at Beamline-BL8:XAS of Siam Photon (SLRI) Synchrotron Radiation facility in Nakhon Ratschasima, Thailand [20,21]. The beamline BL8 operates for X-ray Absorption Spectroscopy, serves a high flux light from a bending magnet and has an energy range from 1.25 keV to 10 keV. ...
Influence of rare earth erbium substitution in the FeBO3 material was investigated on its crystal and electronic properties. Studies were mainly carried by the absorption spectroscopy techniques (XAS) in coordination with the x-ray diffraction (XRD) patterns. Crystal structure properties of the samples were studied by x-ray absorption fine structure spectroscopy (XAFS) technique as a complementary probe of FeBO3 material at the room temperatures (RT). During the study, 4f level of Er was selected as the main playground due to their interesting relations that may yield fruitful physical phenomena in the materials. Besides, 4f-3d interplay were determined to emerge dominant interactions causing phase transitions both in crystal and magnetic structures of the samples. With the increasing Erbium substitutions, interesting electronic and magnetic properties were observed in the samples like; varying electrical resistivity of the samples and related crystal phase transition etc.
... The lengths of LCD1 and LCD2 are 230 mm and inner dimensions are 17 mm (width) Â 8 mm (height) and 19.6 mm (width) Â 8.6 mm (height), respectively. LCD1 and LCD2, installed between the vacuum chambers (BS, FSM3 and XBPM), function as two differential pumping stages (Renier & Draperi, 1997;Klysubun et al., 2007), and thus no beryllium (Be) window, which strongly absorbs lowenergy X-rays, is needed. A polyimide window (PW) (7.5 mm thick) is installed between the DCM chamber and the first ionization chamber of the XAS station. ...
The SUT-NANOTEC-SLRI beamline was constructed in 2012 as the flagship of the SUT-NANOTEC-SLRI Joint Research Facility for Synchrotron Utilization, co-established by Suranaree University of Technology (SUT), National Nanotechnology Center (NANOTEC) and Synchrotron Light Research Institute (SLRI). It is an intermediate-energy X-ray absorption spectroscopy (XAS) beamline at SLRI. The beamline delivers an unfocused monochromatic X-ray beam of tunable photon energy (1.25–10 keV). The maximum normal incident beam size is 13 mm (width) × 1 mm (height) with a photon flux of 3 × 108 to 2 × 1010 photons s−1 (100 mA)−1 varying across photon energies. Details of the beamline and XAS instrumentation are described. To demonstrate the beamline performance, K-edge XANES spectra of MgO, Al2O3, S8, FeS, FeSO4, Cu, Cu2O and CuO, and EXAFS spectra of Cu and CuO,nbsp;are presented.
... Further analysis on the crystal structure were performed by the MAUD software [6]. Also, to support the vague details appeared during the crystal structure analysis, additional EXAFS (Extended X-ray Absorption Fine Structure) measurements were performed for Fe K-edge of the CexFe1-xBO3 samples at Beamline-BL8:XAS of SIAM Photon facility (SLRI) (Nakhon Ratschasima, Thailand) at room temperature in transmission mode [7,8]. Additionally, electronic structure study of the CexFe1-xBO3 compound were performed by the collected X-ray Absorption Near Edge Spectroscopy (XANES) measurements at MAX-Lab synchrotron radiation facility of Lund University in Sweden. ...
Cerium substituted FeBO3 samples were investigated according to their crystal and electronic properties via the general formula CexCuFe1-x BO3. With the doping of the heavy fermion “Cerium”, samples were determined in polycrystallinestructure. With the incressing Ce in the samples, disturbances on the Cu-Fe planes became more clear that supports the formation of geometrically different crystal structures. To obtain the electronic mechanisms in the crystals, X-rayAbsorption Fine StructureSpectroscopy (XAFS) technique were used to study the electronic properties of the samples in coordination with the X-ray diffraction(XRD) patterns. As a result of the analysis, f-levels of the Cerium atoms were determined as the main playground of interplays and strongly correlated electrons of 4f-3d levels were determined to emerge dominant interactions causing phase transitions.
... Zn and Mn L 3,2 -edge and O K-edge XANES data were collected at the beamline I1011 on MAX-Lab in TEY (Total Electron Yield) mode, at room temperature and under ultra high vacuum (UHV) ( $10 À 10 Torr) conditions. The beamline I1011 is located on the ring MAX-II, using an elliptically polarizing undulator and providing soft x-ray with a variable polarization state [13]. ...
... Zn and Mn L 3,2 -edge and O K-edge XANES data were collected at the beamline I1011 on MAX-Lab in TEY (Total Electron Yield) mode, at room temperature and under ultra high vacuum (UHV) ( $10 À 10 Torr) conditions. The beamline I1011 is located on the ring MAX-II, using an elliptically polarizing undulator and providing soft x-ray with a variable polarization state [13]. ...
The change in the crystal and electronic structure properties of wurtzite ZnO nanoparticles was studied according to Mn doping in the powder samples. The investigations were conducted by X-ray Absorption Fine Structure Spectroscopy (XAFS) technique for the samples prepared with different heating and doping processes. Electronic analysis was carried out by the collected data from the X-ray Absorption Near-Edge Structure Spectroscopy (XANES) measurements. Additional crystal structure properties were studied by Extended-XAFS (EXAFS) analysis. Longer heating periods for the undoped wurtzite ZnO samples were determined to own stable crystal geometries. However, for some doped samples, the distortions in the crystal were observed as a result of the low doping amounts of Mn which was treated as an impurity. Besides, the changes in oxygen locations were determined to create defects and distortions in the samples.
... Mainly studies were carried out by X-ray techniques; XRD (X-ray Diffraction) and X-ray Absorption Fine Structure (XAFS) as XANES and EXAFS Spectroscopy. XAFS data were collected at Beamline-BL8:XAS of Siam Photon (SLRI) Synchrotron Radiation facility which is located in the campus area of the Suranaree University of Technology in Nakhon Ratschasima, Thailand [4,5]. This beamline operates for X-ray Absorption Spectroscopy and serves light from a bending magnet and has an energy range of 1.25-10 keV. ...
Crystal and electronic structure properties of bimetallic AgAu and AgCu alloy thin films were investigated by X-ray spectroscopic techniques. The aim of this study is to probe the influence of Au or Cu atoms on the electronic behaviors of Ag ions in bimetallic alloy materials that yields different crystal properties. To identify the mechanisms causing crystal phase transitions, study were supported by the collected EXAFS (Extended X-ray Absorption Fine Structure) data. Crystal structures of both Cu and Au doped bimetallic Ag samples were determined mainly in cubic geometry with “Fm3m” space group. Through the Ag–Au and Ag–Cu molecular interactions during bimetallic alloy formations, highly overlapped electronic levels that supports large molecular band formations were observed with different ionization states. Besides, traces of the d–d interactions in Au rich samples were determined as the main interplay in the broad molecular bond formations. The exact atomic locations and types in the samples were determined by EXAFS studies and supported by the performed calculations with FEFF scientific code.
... Additionally, the periodicity of the oscillations in the region allows us to decide the bond lengths, the amplitudes of the fine structure and provides information about the number of atoms that surround the absorbing atom [6,7]. XAFS data were collected at Beamline-BL8 of Siam Photon (SLRI) Synchrotron Radiation facility in Nakhon Ratschasima, Thailand [8,9]. The beamline operates for X-ray absorption spectroscopy (XANES and XANES) and serves a high flux light from a bending magnet and has an energy range of 1.25-10 keV. ...
... Additionally, the periodicity of the oscillations in the region allows us to decide the bond lengths, the amplitudes of the fine structure and provides information about the number of atoms that surround the absorbing atom [6,7]. XAFS data were collected at Beamline-BL8 of Siam Photon (SLRI) Synchrotron Radiation facility in Nakhon Ratschasima, Thailand [8,9]. The beamline operates for X-ray absorption spectroscopy (XANES and XANES) and serves a high flux light from a bending magnet and has an energy range of 1.25-10 keV. ...
Neodymium substituted TiBO3 samples were investigated according to their crystal, electric and electronic properties. Studies were conducted by X-ray absorption fine structure spectroscopy (XAFS) technique for the samples with different substitutions in the preparation processes. To achieve better crystal structure results during the study, XRD pattern results were supported by extended-XAFS (EXAFS) analysis. The electronic structure analysis were studied by X-ray absorption near-edge structure spectroscopy (XANES) measurements at the room temperatures. Due to the substituted Nd atoms, prominent changes in crystal structure, new crystal geometries for Nd-Ti complexes, phase transitions in the crystals structure were detected according to the increasing Nd substitutions in the samples. In the entire stages of the substitutions, Nd atoms were observed as governing the whole phenomena due to their dominant characteristics in Ti geometries. Besides, electrical resistivity decay was determined in the materials with the increasing amount of Nd substitution.
... XAFS data were collected at Beamline-BL8 of Siam Photon (SLRI) Synchrotron Radiation facility in Nakhon Ratschasima, Thailand [17,18]. The beamline operates for X-ray Absorption Spectroscopy (XANES and XANES) and serves a high flux light from a bending magnet and has an energy range of 1.25 keV to 10 keV. ...
... XANES measurements were carried out at beamline 8 of the Synchrotron Light Research Institute (SLRI) in Thailand [6]. The energy scan was carried out using the Si(111) double crystal monochromator to cover the K-edge of sulfur. ...
The sulfur crosslinking films from Natural Rubber (NR), Carboxylated Stryrene Butadiene Rubber (XSBR) latices, and their blends have been investigated using X-ray absorption near-edge structure spectroscopy (XANES). The film was prepared by casting the latex compound on glass surface and heating at 120oC in a hot air oven for 10 minutes. The sulfur crosslinking density were studied by the XANES. This was done to provide the local geometry and electronic environment of sulfur bonding in the rubber networks. We found that the reversion takes place before the onset of oxidative processes at the sulfur bridges. Parallel to the oxidative processes, the production of cyclic sulfanes takes places. This relationship depends on the rubber compositions.
... Tensile properties were operated at a cross-head speed of 500 mm/min. The XANES measurement was carried out at the beamline 8 of the Synchrotron Light Research Institute (SLRI) in Thailand [6]. The measurements were performed in a fluorescence mode using a 5-grid ionization Lytle fluorescence detector. ...
In this research, natural rubber (NR) was directly mixed with polyethylene (PE) and was compressed at 150 o C. The PE was then separated and migrated to form a thin film on the rubber surface during the vulcanization process. The tensile properties of composite film were rising with increasing the PE contents from 15 to 150 phr as well as the ozone aging properties. The surface topography of the composite film was examined by using scanning electron microscopy (SEM) and was found that the PE form lamellar crystallites on the rubber interface after ozone treatment. The effect of PE on NR cross-linking was also investigated using S K-edge XANES Spectroscopy.
... X-ray absorption spectroscopy (XAS) measurements at the Ti K edge were carried out at in transmission mode using the BL8 beamline at the Siam photon source at the Synchrotron Light Research Institute, (SLRI), Thailand [43]. An incident beam size of 13 mm width by 1 mm height, energy 4900 eV < E < 5300 eV was obtained by Rocking a Ge(220) double crystal monochromator giving and energy resolution of E/E = 3 × 10 −4. ...
Ba0.09Al0.18Ti0.12O0.61 glasses have been produced by aerodynamic levitation and laser heating. Neutron diffraction, x-ray diffraction, x-ray absorption spectroscopy, molecular dynamics simulation, and reverse Monte Carlo refinement methods have been used to obtain a detailed atomistic structural model of the glass. This model has been used to investigate its atomic coordination and network structure. It is found that the Al atoms are almost exclusively fourfold tetrahedrally coordinated to oxygen atoms. In contrast, the Ti atoms coordinate to oxygen atoms in approximately equal numbers of four- and fivefold coordinated sites with a small number of sixfold sites. The results show the presence of some tetrahedral TiO4 structural motifs although the dominant O-Ti-O bond angle occurs at 90∘ . It is found that Al/Ti-O network structure shows strong similarities with other oxide glass forming systems although a first sharp diffraction peak is not observed. The results are used to discuss the unusual properties of the Ba-Al-Ti-O glasses produced under different quenching conditions.
... The in-situ XAS experiments were conducted at Beamline2.2 [20,21] at the Synchrotron Light Research Institute(SLRI) in Thailand. XANES spectra of Fe K-edge (7112 eV) were collected at different states of charge and discharge during battery operation over a voltage range of 1.5-4.8 ...
Li 2 FeSiO 4 (LFS) is one of the most studied materials for use as cathodes in next generation high capacity Li-ion batteries. In this work, high purity and nanosized LFS/C material with the monoclinic crystal structure in P2 1 space group are studied. Structural transformations upon cycling and during relaxation of the high performance LFS/C material are investigated using in situ time resolved X-ray absorption spectroscopy (XAS). Results show that phase transformation involving the present of Fe ion in the Fe4+state when cycling above 4.43 V is responsible for high capacity characteristics in this LFS/C material. The Fe K-edge energy variations during relaxation indicate that local structural and oxidation state of Fe also change. This transient change in local structure of Fe in LFS materials is captured by this technique for the first time.
... The x-ray beam simulated for the bending magnet source was traced through each optic and characterized in terms of photon flux, beam size, beam convergence and energy resolution. As compared to a Ge(220) double crystal monochromator (DCM) used at the beamline BL8 of the SPL [19], higher photon flux can be obtained from a double multilayer monochromator (DMM), which plays a vital role in the high flux applications, for example, XRPD technique, microscopic x-ray fluorescence analysis, small-angle x-ray scattering technique and ...
Physical properties of materials are governed by the temperature and pressure of environment. Because of the advancement in technology, the structural studies under high pressure are interested for finding the desired properties of materials for various kinds of work. Solar energy is one of the most available and clean energy interested by researchers for a long period of time. Among those materials used for solar cell applications, CuInSe2 is an absorber in solar cell (1) in which their high pressure structures are fully investigated here. The equipments that require determining crystal structure of the material are Synchrotron X-rays Diffraction with wavelength 0.4654 o A and DAC (Diamond Anvil Cell). DAC is used to increase the pressure and the diffraction patterns are collected using ADXRD technique. From the diffraction patterns of CuInSe2 at ambient pressure, its crystal structure is tetragonal with space group d
... X-ray absorption near edge structures (XANES) of the samples and standards were measured at the beamline No.8 at the Siam Photon Laboratory [10]. Photon energy of an X-ray beam transported through the beamline was scanned by InSb(111) double crystals equipped in the monochromator. ...
CaSO 4 and (NH 4) 2 SO 4 were used to study the "self-absorption effect" of sulfur K-edge XANES absorption spectra. Further investigations on detector type dependent analytical sensitivities were conducted by using two types of detectors namely Germanium detector (Ged) and Lytle detector (Lyd). This study reported for the first time that sulfur K-edge XANES absorption spectra of PM 10 showed the highest S/N ratios when detected by GeD. In addition, the "grain size effect" plays an important role in analytical sensitivity of sulfur K-edge XANES absorption spectra.
... XANES of the samples and standards were measured at the beamline No.8 at the Siam Photon Laboratory [13]. Photon energy of an Xray beam transported through the beamline was scanned by InSb(111) double crystals equipped in the monochromator. ...
This paper aims to enhance the credibility of applying the sulfur K-edge XANES spectroscopy as an innovative “fingerprint” for characterizing environmental samples. The sensitivities of sulfur K-edge XANES spectra of ten sulfur compound standards detected by two different detectors, namely, Lytle detector (LyD) and Germanium detector (GeD), were studied and compared. Further investigation on “self-absorption” effect revealed that the maximum sensitivities of sulfur K-edge XANES spectra were achieved when diluting sulfur compound standards with boron nitride (BN) at the mixing ratio of 0.1%. The “particle-size” effect on sulfur K-edge XANES spectrum sensitivities was examined by comparing signal-to-noise ratios of total suspended particles (TSP) and particulate matter of less than 10 millionths of a meter
(
PM
10
)
collected at three major cities of Thailand. The analytical results have demonstrated that the signal-to-noise ratios of sulfur K-edge XANES spectra were positively correlated with sulfate content in aerosols and negatively connected with particle sizes. The combination of hierarchical cluster analysis (HCA) and principal component analysis (PCA) has proved that sulfur K-edge XANES spectrum can be used to characterize German terrestrial soils and Andaman coastal sediments. In addition, this study highlighted the capability of sulfur K-edge XANES spectra as an innovative “fingerprint” to distinguish tsunami backwash deposits (TBD) from typical marine sediments (TMS).
... Results of this study could provide additional information on the effect of La 3+ doping on the BaTiO 3 structure. [8]. The double crystal monochromator Ge(220) was used to monochramatized the X-ray beam for the Ti K-edge and Ba L III -edge. ...
La-doped barium titanate (Ba1-xLaxTiO3) is an important electronic ceramic material used in a wide variety of applications including in multilayer capacitor, transducers, ferroelectric thin film memories, and positive temperature coefficient resistor (PTCR). In this work, we investigated the changes of the local atomic structure around barium and titanium ions of Ba1-xLaxTiO3 compounds prepared by solid state reaction using X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). The X-ray Absorption Near-Edge Structure (XANES) spectra at the Ti K-edge (4966 eV) and Ba LIII-edge (5247 eV) were analyzed. Our findings suggest that La3+ doping can modify the degree of covalency of the Ti-O bonds, but cause no change in the BaTiO3 unit cell volume and the atomic coordinate around Ti4+, Ba2+ions.
... The XANES measurement was carried out at the beamline 8 of the Synchrotron Light Research Institute (SLRI) in Thailand [13]. The measurements were performed in a fluorescence mode using a 5-grid ionization Lytle fluorescence detector. ...
Squalene has been used as a model compound for the investigation of sulphur crosslink in the vulcanization process. The effects of the accelerator on the crosslink were deduced from the sulfur K-edge absorption spectra. The majority of the crosslinks for the squalene vulcanized with ZDEC or TMTD is likely disulfidic, while that vulcanized with CBS or MBTS is monosulfidic.
... XANES was performed on the samples, and standards were measured at beam line no. 8 in the Siam Photon Laboratory [17]. Photon energy from an X-ray beam transported through the beam line was scanned by InSb(111) double crystals installed in the monochromator (see Figure 1). ...
This paper focuses on providing new results relating to the impacts of Diurnal variation, Vertical distribution, and Emission source on sulfur K-edge XANES spectrum of aerosol samples. All aerosol samples used in the diurnal variation experiment were preserved using anoxic preservation stainless cylinders (APSCs) and pressure-controlled glove boxes (PCGBs), which were specially designed to prevent oxidation of the sulfur states in PM(10). Further investigation of sulfur K-edge XANES spectra revealed that PM(10) samples were dominated by S(VI), even when preserved in anoxic conditions. The "Emission source effect" on the sulfur oxidation state of PM(10) was examined by comparing sulfur K-edge XANES spectra collected from various emission sources in southern Thailand, while "Vertical distribution effects" on the sulfur oxidation state of PM(10) were made with samples collected from three different altitudes from rooftops of the highest buildings in three major cities in Thailand. The analytical results have demonstrated that neither "Emission source" nor "Vertical distribution" appreciably contribute to the characteristic fingerprint of sulfur K-edge XANES spectrum in PM(10).
In this study, gamma-manganese sulphide (γ-MnS) films were prepared at various thickness and deposition time at a temperature of 50 °C by Chemical Bath Deposition Method (CBD). The characterization of the gamma-MnS films were determined by using the following methods; X-ray Absorption Fine Structure Spectroscopy (XAFS), X-ray diffraction (XRD), optical absorption, Field Emission-Scanning Electron Microscope (FE-SEM), Energy Dispersive X-ray analysis (EDX). The electronic interplay via the coupling between Mn 3d levels and S 2p levels was determined to build up strong molecular bonds containing broad band with hybrid pd levels at low energy levels. The results of the electronic structure analysis were also tested with the absorption spectroscopy calculations and high agreement is reported. XRD analysis revealed that the film deposited for 5 h had amorphous structure and turned to be crystal structure in hexagonal phase with deposition time 10, 15, 20 h due to increasing film thickness value. The optical band gap values were reduced from 3.86 eV to 3.10 eV with increasing film thickness. The average refractive index value of films at visible region were calculated between 1.55 and 2.81 as a function of increment in film thickness. The mobility and resistivity of the films were measured as 8.65–55.76 cm²/Vs and 3.10 × 10⁵–2.39 × 10⁶ Ωcm, respectively, by Hall measurement.
A new X-ray absorption spectroscopy (XAS) beamline is currently under construction at a bending magnet of the National Synchrotron Radiation Centre SOLARIS. The front end of this beamline was installed in April 2020. This beamline has a few outstanding characteristic features: The monochromator is a fixed exit beam Lemmonier type monochromator allowing to cover the pursued energy range (1 keV to ~15 keV) with 3 sets of crystals: KAP (100) + multilayer, InSb (111) and Ge (220). The monochromator is a high vacuum system allowing the change of crystals in less than an hour. In order to minimize absorption of photons no windows will be installed in the beamline down to the monochromator, and just one thin polypropylene window will be used for separating the vacuum of the monochromator from the ionization chambers and the sample chamber. A special differential ion pump will be installed to maintain the pressure difference of four orders of magnitude between the storage ring and the monochromator. As SOLARIS is a low energy machine, the beamline can be built without any radiation safety hutches without exceeding the strict low radiation safety levels. The straightforward design of the beamline without additional optical elements, its compact overall dimensions and an easy to handle monochromator make this beamline especially user friendly. In combination with the characteristics of the 1.5 GeV SOLARIS storage ring this beamline will be specifically attractive for the tender X-ray range, i.e. the K-edges of important elements such as P, S, Si, Al and Mg.
An XAFS study was performed on the electronic and crystal structure properties of LiGa1-xBxO2 (LGO) material in where boron atoms were substituted at the gallium sites. Studies were carried out by the X-ray powder diffraction (XRD) patterns and supported by the Extended-XAFS data. The analysis on the substituted materials revealed interesting mechanisms at the boron sites that preserved the crystal symmetry in the entire bulk. It was determined that, boron atoms do not lie in the Ga sites due to inequivalent ionic radii and formed a crystal LiB3O5, which has the same crystal geometry and space group of the parent LGO. With the presence of the boron atoms on the vicinity of the gallium atoms, tiny shifts on the main edge spectra resulted from the change in the oxidation of the gallium atoms.
Neodymium substituted Li 2 MnO 3 samples were prepared by the solid-state reaction method. The crystal and electronic structure properties of the prepared samples were investigated by x-ray based techniques. According to the analysis, it was determined that Nd atoms did not sit in to the Cr coordinations in Nd substituted samples and built up a different crystal structure. To support the analysis of the crystal structure study of the samples, electronic structure properties of the Nd substituted samples were studied via the collected data by x-ray absorption fine structure (XAFS) spectroscopy from the Mn K-edge. The results of the data analysis revealed that due to the misfit with the ionic radii and also the oxidation states, substituted neodymium atoms built up isolated crystal domains in Li 8 Mn 5 Nd 18 O 39 cubic crystal structure. The symmetry in Mn K-edge absorption data of the sample both in parent Li 2 MnO 3 and Nd substituted samples confirmed that Mn coordinations has not been influenced by the Nd substitution.
The red color of ruby is caused by Cr³⁺ impurities substituting Al³⁺ in Al2O3 structure. The complete substitution of Al³⁺ by Cr³⁺ produces Cr2O3 that has the green color. In this study, we focused on the phase transition of solid solution between corundum (Al2O3) and eskolaite (Cr2O3) mineral series. A series of Al2O3-Cr2O3 samples were prepared by mixing fine powder of Al2O3 and Cr2O3 in various ratios. They were ground together and then recrystallized. The obtained crystals were ground again in powder form for X-ray absorption near edge structure (XANES) measurements to avoid polarization dependence. The measurements were carried out at the Cr K-edge absorption energy using a 13-channel array Ge detector in the fluorescence mode. The XANES spectra showed line-shape transitions for 0.125 to 100% variation of Cr2O3. Significant variations in transitions were found when the Cr2O3 content was between 20% and 80%. With Cr2O3 concentration increasing, the sample colors apparently turned from pink to dark green. CIELAB color index measurements were performed. The variations of line-shape spectra of the Al2O3-Cr2O3 samples were found to be consistent with the CIELAB color index results. This Cr K-edge XANES study could be useful for the research in mineral sciences.
Boron-substituted LiCrO2 battery cathode material samples were investigated by X-ray-based techniques to probe the influence of boron on their crystal and electronic structure properties. Studies were carried on a series of Li-ion battery cathode materials with the general formula LiCr1−xBxO2. Up to 10 pct boron substitution amounts, light boron atoms were determined to sit in Cr coordinations. However, for more substitutions (>10 pct), higher electronegativity of boron was determined to govern the crystal structure by obtaining isolated boron-centered domains and built Li2BO4 structures. Electronic structure studies and further crystal structure analysis were carried by X-ray absorption fine structure technique. In the studied samples, increasing boron concentration in the samples (i.e., >10 pct substitution) were determined to cause a decrease in oxygen bond distances as a result of boron sitting in some chromium locations. As a result of this study, 10 pct boron substitution was determined as a threshold to protect the LiCrO2 crystal structure.
Ion implantation technique has been used for improving the quality of natural ruby. The implantation were performed by using 90 keV N2-ion and 50 keV O-ion beams. Either kind of ion species can eliminate tiny inclusions in the ruby as observed from an optical microscope. The red color of the ruby was intensified after O-ion implantation. N2-ion implantation changes the color of red ruby to be violet-red. UV-Vis and X-ray absorption spectroscopic techniques were employed for investigating the mechanism behind the optical quality improvement of the ruby. The results from both measurement techniques are reported and discussed.
Neodymium-substituted CuFeO2 samples were investigated according to their crystal and electronic properties via the general formula Nd x Cu1−x FeO2. The crystal structure analysis results revealed polycrystalline formations in the sample and a change in crystalline sizes with the substituted heavy fermion “Nd.” Increasing the Nd amount in the sample was determined to cause a disturbance on the Cu-Fe planes that supports the formation of crystal structures with low crystal symmetries such as monoclinic or triclinic geometries. To obtain the background mechanisms of the crystal properties, the X-ray absorption fine structure spectroscopy technique was used to study the electronic properties of the samples. Prominent changes in the crystal structures due to 4f electrons’ contributions from the substituted Nd atoms as the main “role player” in the phase transitions were determined. The Nd atoms were observed as the key element guiding the entire phenomenon as a result of their large size and narrow 4f levels. Also, magnetic properties of the samples were tested at room temperature and without an applied magnetic field by X-ray magnetic circular dichroism study due to previous studies that reported the parent oxide CuFeO2 to have magnetic ordering at T N = 11 K (−262 °C). Except the sample for x = 1.0 (NdFeO3), no magnetic ordering was observed at room temperature; i.e., all of the samples showed paramagnetic behaviors.
Vulcanized rubber materials are useful in our surroundings. However, detail structure and reaction are not revealed even in present. Since squalene molecule possesses some same properties compared with natural rubber, we have prepared the samples of vulcanized squalene at 140 °C for several hours. To understand the vulcanization reaction,sulfur K-edge NEXAFS measurements have been carried out for the vulcanized squalene under liquid phase with He-path system and fluorescence detection mode. Moreover, we have tried curve fitting analysis of NEXAFS spectra. The results indicate that the squalene has been vulcanized by the S8 molecule at 140 °C and the S8 molecule length is shortened from 8 to 5-6 after the vulcanization reaction.
The sol-gel reaction of tetraethoxysilane in natural rubber (NR) latex was conducted to produce in situ silica-filled NR latex, followed by adding sulfur cross-linking reagents to the latex in a liquid state. The latex was cast and subjected to sulfur curing to result in a unique morphology in the NR composite of a flexible film form. The contents of in situ silica filling were controlled up to 35 parts per one hundred rubber by weight. The silica was locally dispersed around rubber particles to give a filler network. This characteristic morphology brought about the composite of good dynamic mechanical properties. Synchrotron X-ray absorption near-edge structure spectroscopy suggested that the sulfidic linkages of the sulfur cross-linked composites were polysulfidic, Sx (x ≥ 2), and a fraction of shorter polysulfidic linkages became larger with the increase of in situ silica. The present observations will be of use for developing a novel in situ silica-filled NR composite prepared in NR latex via liquid-phase soft processing. Copyright © 2011 John Wiley & Sons, Ltd.
To support various applications for high-pressure research in Thailand, an experimental setup for X-ray powder diffraction under high-pressure conditions using synchrotron radiation, which is based on station 9.1 at the Daresbury Synchrotron Radiation Source, is being developed on the bending magnet beamline BL8 at the Siam Photon Laboratory. Monochromatic X-rays with a photon energy of 9 keV are provided by a fixed-exit double crystal monochromator equipped with Ge(220) crystals. In a recent experiment, we could record a complete diffraction pattern of the hexagonal phase of ZnO using an image plate area detector. However, diffraction intensity should be improved by adding focusing optics. In this work, we propose the use of a double multilayer monochromator in combination with a focusing mirror. Results from ray-tracing simulation for the proposed optics will be presented.
The local structure of MgxZn1−xO nanocrystals is studied using synchrotron x-ray absorption near edge structures (XANES) over the full range of composition, from x = 0 to 1. Mg and Zn K-edges XANES measurements allow us to selectively study the local environments around Mg and Zn atoms in these nanocrystalline samples. Our results indicate that, for MgO-ZnO alloys, Zn is highly miscible in the rocksalt domain (i.e., up to ∼50 at. %) while the miscibility of Mg in the wurtzite domain is much less but is still substantial (i.e., up to ∼20 at. %). The simulated XANES spectra, based on first principles methods, are consistent with the observed spectra, confirming our finding. Because it is short-ranged and element-specific, the technique is useful for local structure and crystal phase determination of nanostructures, quantum dots, and mixed-phase alloys in general.
Nickel and nickel–platinum supported on zeolite beta in proton form (Ni/HBEA and NiPt/HBEA) with Ni loading of 1, 3, 5 wt.% and Pt loading of 1 wt.% were prepared by impregnation. Characterization by ex situ X-ray absorption near edge structure (XANES) showed that the oxidation state of Ni in all calcined samples were +2 and reducibility of nickel by hydrogen flow increased with metal loading. At low loading, nickel had a strong interaction with the zeolite and was difficult to reduce. The interaction became weaker as the Ni loading increased, resulting in more agglomeration to larger cluster size which could be reduced more easily. Dependence of Ni reducibility on temperature and time for the mono- and bimetallic samples with 5 wt.% Ni loading was investigated further by in situ XANES. The reducibility in the bimetallic sample was increased with temperature and time, higher than the monometallic one due to the presence of Pt. In addition, the bimetallic sample was best reduced, when investigated in situ, at 350 °C for 60 min.
Yellow and colorless ancient glasses, which were once used to decorate the Temple of the Emerald Buddha, Bangkok, Thailand, around 150 years ago, are studied to unravel the long-lost glass-making recipes and manufacturing techniques. Analyses of chemical compositions, using synchrotron x-ray fluorescence (SRXRF), indicate that the Thai ancient glasses are soda lime silica glasses (60 % SiO2; 10 % Na2O; 10 % CaO) bearing lead oxide between 2–16 %. Iron (1.5–9.4 % Fe2O3) and manganese (1.7 % MnO) are present in larger abundance than the other 3d transition metals detected (0.04–0.2 %). K-edge x-ray absorption near edge spectroscopy (XANES) and extended x-ray absorption fine structure spectroscopy (EXAFS) provide conclusive evidence on the oxidation states of Fe being 3+ and Mn being 2+ and on short-length tetrahedral structures around the cations. This suggests that iron is used as a yellow colorant with manganese as a decolorant. L
3-edge XANES results reveal the oxidation states of lead as 2+. The results from this work provide information crucial for replicating these decorative glasses for the future restoration of the Temple of the Emerald Buddha.
Ethanol pollutant either emitted from ethanol-fueled vehicles at low temperature or released from industries as volatile organic compound (VOC) could be removed by catalytic oxidation. This work investigated adsorption of ethanol on bimetallic catalysts containing Pt with loading of 0.5 wt% and Co, Cu, or Mn with loading of 15 wt% supported on RH-MCM-41 by temperature programmed desorption (ethanol-TPD) and thermogravimetric analysis (ethanol-TGA). Evolution of gases from the ethanol-TPD indicated the role of oxides as potential oxygen supplier in ethanol oxidation. On the monometallic catalyst containing oxides of Co, Cu, and Mn on MCM-41, the oxide of Co was the better oxygen supplier than that of the others to react with the adsorbed ethanol to produce CO2. Furthermore, the bimetallic 0.5Pt–15Co/RH-MCM-41 with cobalt in the form of Co3O4, showed the highest ethanol adsorption and CO2 desorption. Consequently, ethanol oxidation was studied on the bimetallic 0.5Pt–15Co/RH-MCM-41 by in situ infrared spectroscopy in which intermediates and reaction pathways were proposed when ethanol and oxygen were flowed through the cell at various temperatures. Results from the ethanol oxidation in a fixed bed flow reactor showed that the bimetallic catalyst gave lower ethanol conversion than monometallic Pt but seemed to be more stable than the monometallic Pt catalyst.
The catalytic activities of Re–Co/CeO2 bimetallic catalysts for the water gas shift (WGS) reaction were investigated and compared with activities of Co/CeO2. It was found that the rate of WGS reaction over Re–Co/CeO2 bimetallic catalysts was higher than that of a single catalyst of Co on ceria. It seems that Re influences the catalysts and the catalyst performance in several ways. XRD and Raman spectroscopy results indicate that metal oxides were dispersed on ceria surface and H2-chemisorption indicated better dispersion of Co on the ceria surface upon addition of Re. X-ray absorption near edge structure (XANES) spectra of Re–Co/CeO2 indicate that Re promotes the reduction of surface ceria to Ce2O3 and provides oxygen vacancies that facilitate the redox process at the surface. XANES also indicated that electron densities were withdrawn from Co d-state to Re, leading to weaker Co-adsorbate bonds. All of these effects contribute to an increase in the WGS reaction rate.
The catalytic activities of Re–Ni/CeO2 bimetallic catalysts were investigated for the water gas shift reaction in the temperature range of 150–600°C. Re–Ni/CeO2 bimetallic catalysts were prepared by the incipient wetness impregnation method with aqueous solutions of Ni(NO3)2·6H2O and NH4ReO4. The amount of Re was kept constant at 1wt%, while that of Ni was varied at 1.0, 2.5, 5.0, 7.5 and 10.0wt%. The activities of all doped samples were tested in a flow reactor with initial mixed feed gas of 5% CO and 10% H2O. Re–Ni/CeO2 bimetallic catalysts showed a higher rate of WGS reaction than Ni/CeO2 monometallic catalysts. The results from XRD and Raman spectroscopy indicate that doped oxide species were dispersed on the ceria surface and H2 chemisorption indicated better dispersion of Ni on the ceria surface with the addition of Re. X-ray absorption near edge structure (XANES) of the Ce L3 edge indicated that Re promotes the reduction of Ce4+ at the surface and facilitates the WGS redox process. XANES results also indicated movement of electron density from Ni to Re leading to an enhancement of CO adsorption on the Ni active sites. All of these effects contributed to an increase of the WGS reaction rates.
XANES was used as complementary to XRD for the investigation of speciation of Cr in cement clinkers prepared by the co-burning of raw meal blended with Cr2O3. The concentration of Cr in the mixture was 0.1, 0.5, 1.0, 2.0, 5.0, and 10.0 wt%. The mixture was burnt at 1450 °C for 90 min. XANES spectra show that all samples contain Cr6+ species. A similar ratio of different Cr containing compounds was found for all clinkers with a Cr concentration of 2.0 wt% and below. A discrepancy between XANES spectra and the changes in free lime concentration was observed when the Cr concentration increased from 1.0 to 2.0 wt%. Above 2.0 wt%, complicated changes in the XANES spectra were observed with increasing Cr concentration. Different Cr-compounds were formed in all samples, and reduction of free lime content was observed for the sample with a Cr concentration of 10.0 wt%.
Both synthetic and natural α-Al2O3 samples with different Cr concentrations were investigated by XANES. The Cr contents were analyzed using LA-ICP-MS technique prior to this experiment. XANES spectra combined with first principle calculations showed the transformation from α-Al2O3:Cr3+ to α-Al2O3:Cr3+,Cr3+ or α-Cr2O3 as the Cr-Cr content increased. The absorption transformation could be resulted from the change of environment around Cr3+ ions, i.e., the Al-O-Cr bonds decreased while the Cr-O-Cr bonds increased. Significant differences in XANES line shapes observed for synthetic and natural α-Al2O3 samples suggested the differences in local environments around Cr ions in both samples. The XANES line shape of α-Al2O3:Cr3+,Cr3+ or Cr ion pairs corresponded to the Cr content, which was also confirmed by the intensity ratios between N2-line and sideband S of R-lines of photoluminescence spectra.
Optically active organic gas sensors represent a promising molecular sensing device with low power consumption. We report
experimental and computational investigations into the molecular interactions of metal phthalocyanine thin films with alcohol
vapor. In the gas-sensing regime, the interactions of zinc phthalocyanine and alcohol molecules were studied by the Density
Functional Theory (DFT) calculations, in comparison to the x-ray absorption spectroscopy. The DFT results reveal a reversible
charge interaction mechanism between the zinc atom and the oxygen atom in the alcohol OH group, which corresponds to a shift
in the x-ray absorption edge of the zinc atom. In the irreversible interaction regime, the effect of saturated alcohol vapor
on spin-coated zinc phthalocyanine films was studied by the phase contrast microscopy, the optical absorption spectroscopy,
and the transmission electron microscopy. Annealing the spin-coated films in saturated methanol vapor was found to induce
an irreversible structural transformation from an amorphous to a crystalline phase, similar to the effect of a thermal annealing
process. These crystallization processes of the zinc phthalocyanine films were also found to enhance their stability and alcohol
sensing performance.
Synchrotron radiation S K- and L-edge X-ray absorption near-edge structure (XANES) spectra are reported for the cubic, rocksalt (B1) structure sulfides niningerite (MgS), alabandite (MnS), and oldhamite (CaS), and for their solid solutions (Mn,Fe)S and (Mg,Mn)S, and S L-edge XANES spectra are reported also for (Mg,Fe)S solid solutions. Pre-edge features at the S K-edge are attributed to transition of S 1s electrons to the lowest available unoccupied S 3pσ* antibonding states hybridized with metal 3d(eg) states, and at the S L-edge to transition of S 2p electrons to unoccupied S 3sσ*, 4s σ*, and 3d antibonding states hybridized with metal 3d(eg) states, and to a lesser extent 3d(t2g) states. The S K-edge XANES spectra for the solid solutions show a progressive participation of 3d orbitals in metal-S bonding with increase in substitution by Fe in (Mn,Fe)S and (Mg,Fe)S and Mn in (Mg,Mn)S through progressive increase in the area of the pre-edge feature. However, the pre-peak area does not increase linearly in each solid solution series showing that a real change in bulk electronic properties has occurred. Increase in pre-peak area reflects an increase in overall attainability of metal 3d states for hybridization with S 3pσ* antibonding states as proportionally more metal 3d orbitals become available. The S L-edge XANES spectra show progressive evolution of pre-edge features at the L3- and L2- edges (a1 and a2, respectively). Only a2 is present in the S L-edge XANES spectrum of FeS (troilite), and with progressive decrease in Fe content in (Mn,Fe)S and (Mg,Fe)S solid solutions, a1 first appears, then becomes dominant. Since a1 is attributed to transition of S 2p3/2 electrons to S 3sσ* states hybridized with metal 3d(eg) and 3d(t2g) states, this appears to represent an increased contribution from metal-S π-bonding. The results show that the size and position of the pre-edge features to the S K- and L-edges are controlled more by the DOS of hybridized 3d(egβ) and 3d(t2gβ) states and nearest-neighbor coordination of the metal atoms than by the precise coordination of S and the extended structure of the sulfide. The full multiple scattering approach has been applied to the calculation of the S K-edge XANES spectra of MgS, MnS, and CaS. Results are consistent with experimental XANES spectra, especially for the pre-edge features, which are often neglected in such calculations.
IFEFFIT, an interactive program and scriptable library of XAFS algorithms is presented. The core algorithms of AUTOBK and FEFFIT have been combined with general data manipulation and interactive graphics into a single package. IFEFFIT comes with a command-line program that can be run either interactively or in batch-mode. It also provides a library of functions that can be used easily from C or Fortran, as well as high level scripting languages such as Tcl, Perl and Python. Using this library, a Graphical User Interface for rapid 'online' data analysis is demonstrated. IFEFFIT is freely available with an Open Source license. Outside use, development, and contributions are encouraged.
Bitumens exposed to atmospheric conditions undergo various types of weathering including evaporation, biodegradation, abiotic oxidation, and water washing. Sulfur present in bitumens is a good marker of oxidation processes as it is very sensitive to oxidation and exhibits a range of oxidation states from -2 to +6. Sulfur K- and Ledge XANES spectroscopy were applied to the asphaltene extracts of a series of recent geological and archeological bitumens from the Middle East. In all the samples, dibenzothiophene is the major sulfur moiety. In the least altered asphaltene, minor species include disulfide, alkyl sulfide and sulfoxide. The proportion of oxidized sulfur (sulfoxide, sulfone, sulfonate and sulfate) increases with the alteration of the samples, whereas the disulfide and alkyl sulfide content decreases. This work illustrates the interest of XANES spectroscopy as a selective probe for determining sulfur speciation in natural samples, and the complementarity of S K- and L- edge for identifying the oxidized and reduced forms of sulfur respectively.
X-ray absorption near edge structure (XANES) measurements were carried out at the sulfur K-edge of nine sulfanes with the structure RSnR, n = 2–4. The discrete part of the XANES spectra of these sulfanes is expected to be quite similar under the change of the hydrocarbon substituents R. However, significant differences were observed in the energy splitting of the pre-edge resonances as well as in the relative intensities of these features. A linear correlation is observed between the splitting of the sulfur 1s → σ ∗(SC) and 1s → σ ∗(SS) transitions and the SC bond length. Similar correlations are expected for the energy splitting and the SC bond enthalpy and the difference in electronegativity between the sulfur atom and the substituent R. We have carried out MS-X α calculations on the CSS fragment to support the proposed assignment and the parameter dependence of the resonances mentioned above.
in oxidation states. Sulfur occurs in soil both in organic and inorganic forms. However, most of the soil S Sulfur K-edge X-ray absorption spectroscopy (XANES) was used (95%) in temperate and tropical ecosystems is present to identify S oxidation states and assess the impact of land use changes on the amount, form, and distribution of organic S in particle-size in organic forms (Janzen and Ellert, 1998; Saggar et al., separates and their humic substance extracts. Soil samples (0-10 cm) 1998; Solomon et al., 2001a). Knowledge of the specia- were collected from natural forest, tea plantations, and cultivated tion of S in organic materials could, therefore, provide fields at Wushwush and from natural forest, Cupressus plantations a clearer understanding of the amount, form, and bio- and cultivated fields at Munesa sites in Ethiopia. Sulfur XANES geochemical transformations of S in the ecosystem. Our spectra measured directly from the size separates could not be quanti- knowledge of the biogeochemical S cycling is, however, tatively analyzed due to high background noise. However, qualitative severely limited by relatively crude analytical tech- comparison of spectra from size separates and their humic extracts niques used in S measurements and speciation. Most of were very similar and thus provides a characteristic fingerprint of S the present studies on soil organic S are based on a in mineral soils. X-ray absorption near-edge spectroscopy showed the fractionation technique using HI reduction of organic presence of most reduced (sulfides, disulfides, thiols, and thiophenes), intermediate (sulfoxides and sulfonates) and highly oxidized S (ester- S compounds in soil (Tabatabai, 1982; Kowalenko, SO4-S) forms. Sulfur in intermediate oxidation states was dominant 1993a,b). The biochemical characterization of organic (39-50%; where 66-96% of it being sulfonate S) in humic extracts S as ester-SO4-S (HI-reducible S) and C-bonded S has from clay, while highly oxidized S dominated (40-56%) the silt spectra. advanced the understanding of the organic S cycle in Concentrations of C-bonded and ester-SO4-S extracted by the HI soil (e.g., McGill and Cole, 1981; Janzen and Ellert, fractionation did not correlate with those from XANES (ester-SO4-S 1998; Lehmann et al., 2001; Solomon et al., 2001a). How- revealed by XANES vs. HI-fractionation, r 0.23; P 0.001). A ever, this technique is only an indirect method involving major shift following land use changes occurred in the most reduced differential reduction of organic S compounds to H 2S and intermediate S species. Their proportion decreased in the order: and is, therefore, not an entirely satisfactory procedure natural forests plantations cultivated fields. In contrast, highly to directly speciate S within complex organic functional oxidized S increased in the order: natural forests plantations cultivated fields at both sites. Our results indicated that C-bonded S groups. Moreover, this chemical reduction method can- (most reduced and intermediate S) may represent the more labile not identify intermediate oxidation states of S in organic forms of organic S compounds compared with ester-SO4-S. Therefore, matter and consequently almost no information is avail- S K-edge XANES has a significant potential to evaluate the influence able about their turnover rates. Other studies have at- of anthropogenic changes on the nature and distribution of S and to tempted to speciate S into its functional groups using follow its dynamics in terrestrial ecosystems.
A two parallel crystal monochromator to be used in the soft X-ray range with the synchrotron radiation emitted by the A.C.O. storage ring is described. With K.A.P. crystals () the 500–1500 eV energy range can be covered. The measured resolution is 1.5 eV at 1100 eV. The system has been designed to keep fixed in position the emergent beam.
X-ray absorption spectroscopy is aspectroscopic in situ technique whichcombines the high penetration strength inherentto X-rays with the advantages of local probetechniques, such as no need for long rangeorder and the ability to obtain information onselected sites of a given sample only.Consequently, this technique is applicable to abroad variety of scientific questions,including many applications in biological,agricultural and environmental sciences. Thefirst part of this review provides anintroduction to the method, whose applicationto a broad variety of problems is discussed indetail, especially XAS of sulfur in biologicalsystems. In the second part new ideas forfurther experiments using this versatile methodare presented.
X-ray absorption near edge structure (XANES) spectroscopy at the sulfur K-edge was applied to probe the speciation of sulfur of metabolically different sulfur-accumulating bacteria in situ. Fitting the spectra using a least-square fitting routine XANES reveals at least three different forms of sulfur in bacterial sulfur globules. Cyclooctasulfur dominates in the sulfur globules of Beggiatoa alba and the very recently described giant bacterium Thiomargarita namibiensis. A second type of sulfur globules is present in Acidithiobacillus ferrooxidans: here the sulfur occurs as polythionates. In contrast, in purple and green sulfur bacteria the sulfur mainly consists of sulfur chains, irrespective of whether it is accumulated in globules inside or outside the cells. These results indicate that the speciation of sulfur in the sulfur globules reflects the different ecological and physiological properties of different metabolic groups of bacteria.
The solubility of inorganic phosphorus in soils is regulated by surface-adsorbed phosphate or phosphate minerals. The objective of this study was to determine whether different phosphate species of relevance to soils showed distinguishing XAFS spectral features. Phosphorus K-XANES spectra for Fe-phosphates were characterized by a unique pre-edge feature near -3 eV (relative energy) that increased in intensity with increasing mineral crystallinity and was very weak for phosphate adsorbed on goethite. Spectra of Ca-phosphates and a soil sample exhibited a distinct shoulder on the high-energy side of the absorption edge. Spectra of Al-phosphates were characterized by a weak pre-edge feature at -1 eV.
- G Sarret
G. sarret, et al., J. Synchrotron Rad. 6 (1999) 670.
- A Prange
- H Modrow
A. Prange, H. Modrow, Rev. Environ. Sci. Bio/Technol. 1 (2002) 259.
- D Hesterberg
D. Hesterberg, et al., J. Synchrotron Rad. 6 (1999) 636.
- R Chauvistre
R. Chauvistre, et al., Chem. Phys. 223 (1997) 293.
The k 2 -weighted w and Fourier-transformed spectra derived from a K-edge EXAFS spectrum of a copper foil
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ARTICLE IN PRESS
Fig. 5. The k 2 -weighted w and Fourier-transformed spectra derived from a K-edge EXAFS spectrum of a copper foil.
- M Lemonnier
M. Lemonnier, et al., Nucl. Instr. and Meth. 152 (1978) 109.
- A Prange
A. Prange, et al., Microbiology 148 (2002) 267.
- M Newville
M. Newville, J. Synchrotron Rad. 8 (2001) 322.