Synchrotron Radiation Techniques Research Articles

In-situ nanoscale imaging of charge transfer of BiNiO3 under high pressure

Over last decades, both synchrotron radiation techniques and high pressure research have made great progress. Advanced synchrotron capabilities with high spatial resolution, high flux, and high energy resolution provides us many new avenues to conduct advanced high pressure researches. In this talk, we will focus on the new developments of the nanoscale imaging techniques on the pressure induced phase separation in three dimensions. BiNiO3 under goes a charge transfer induced phase transition under high pressure or temperature, which shows excellent colossal negative thermal expansion effect [1]. Co-exist of both high density and low density phases over a wide range pressure or temperature plays the key roles on the negative thermal expansion behavior. We utilized a newly developed X-ray absorption near edge spectroscopy tomography method, and successfully resolved the mixture of high/low pressure phases as a function of pressure at tens of nanometer resolution. By choosing incident x-ray energy near Ni absorption edge, the pressure induced valence transition can be mapped at tens of nanometer scale in 3d, which provides crucial information on the HP-LP phase boundary [2]. As temperature driven grain growth upon heating, we can draw fundamental information on the pressure-induced phase growth mechanism.

Intrinsic antiferromagnetic/insulating phase at manganite surfaces and interfaces

In this work we investigate interfacial effects in bilayer systems integrated by La2/3Sr1/3MnO3 (LSMO) thin films and different capping layers by means of surface-sensitive synchrotron radiation techniques and transport measurements. Our data reveal a complex scenario with a capping-dependent variation of the Mn oxidation state by the interface. However, irrespective of the capping material, an antiferromagnetic/insulating phase is also detected at the interface, which is likely to originate from a preferential occupancy of Mn 3d 3z2−r2 eg orbitals. This phase, which extends approximately to two unit cells, is also observed in uncapped LSMO reference samples, thus pointing to an intrinsic interfacial phase separation phenomenon, probably promoted by the structural disruption and inversion symmetry breaking at the LSMO free surface/interface. These experimental observations strongly suggest that the structural disruption, with its intrinsic inversion symmetry breaking at the LSMO interfaces, plays a major role in the observed depressed magnetotransport properties in manganite-based magnetic tunneling junctions and explains the origin of the so-called dead layer.

Synchrotron Imaging Techniques for Bone and Cartilage Tissue Engineering: Potential, Current Trends, and Future Directions

Biomedical imaging is crucial to the success of bone/cartilage tissue engineering (TE) by providing detailed three-dimensional information on tissue-engineered scaffolds and associated bone/cartilage growth during the healing process. Synchrotron radiation (SR)-based biomedical imaging is an emerging technique for this purpose that has been drawing considerable recent attention. Due to the unique properties of synchrotron light, SR biomedical imaging can provide information that conventional X-ray imaging is not able to capture. SR biomedical imaging techniques notably differ from conventional imaging in both physics and implementation, thus varying with regard to both capability and popularity for biomedical imaging applications. In the earlier decade, synchrotron-based imaging was used in bone/cartilage TE to characterize bone/cartilage scaffolds and tissues as well as the varying degrees of success in reconstruction. However, several key issues should be addressed through research before SR biomedical imaging can be advanced to a noninvasive method for application to live animals and eventually to human patients. This review briefly presents recent developments in this area, focusing on different synchrotron-based biomedical imaging techniques and their advantages and limitations, as well as reported applications to bone and cartilage TE. Key issues and challenges are also identified and discussed along with recommendations for future research.

Double-strand breaks on F98 glioma rat cells induced by minibeam and broad-beam synchrotron radiation therapy

To assess the DNA damage induced by MBRT and BB radiations on glioma cells. The analysis of fluorescent intensity emitted per nucleus was plotted versus DNA content 2 and 17h after irradiations. At around cell-doubling time (17h) after exposures, the remaining DNA radiation damage could be correlated with cellular death. A higher γH2AX IF intensity per cell could be detected 2 and 17h after MBRT when compared with BB. 17h after MBRT, misrepaired damaged cells remained arrested in both G1 and G2 phases. A pronounced G2 phase arrest was detected at 17h after MBRT and BB. However, only after MBRT, a dose-dependent increasing number of damaged cells appeared arrested also in the G1 phase, and a higher amount of cells more prone to undergo apoptosis were detected. The threshold dose required to enhance the effectiveness of both synchrotron radiation techniques was 12Gy.

The magnetic P-T phase diagram of langasite Ba3TaFe3Si2O14 at high hydrostatic pressures up to 38 GPa

The langasite-type crystals with 3d ions are considered as a class of multiferroics in which ferroelectricity can be induced by the magnetic ordering. In this paper, the high-pressure magnetic states of the langasite-type powdered sample Ba3TaFe3Si2O14 have been investigated in a diamond anvil cell by the nuclear forward scattering of synchrotron radiation technique at different temperatures in hydrostatic conditions. In the pressure range of 0 < P < 19.5 GPa, an increase of the Neel temperature TN from 27 to 41 K was observed in the antiferromagnetic phase of the material. At pressures ∼19.5 GPa, a transition to another magnetic phase with huge increase in the Neel temperature to ∼120 K was found. We attribute this change to the structural transition at ∼19.5 GPa which is evidenced by a drastic change of Raman spectra at this pressure. A tentative magnetic P-T phase diagram of Ba3TaFe3Si2O14 is proposed.

Direct Observation of para-Xylylene as the Decomposition Product of the meta-Xylyl Radical Using VUV Synchrotron Radiation

Xylyl (methylbenzyl) radicals are important combustion intermediates, formed in the pyrolysis and oxidation of xylenes and other substituted aromatic fuel additives. We have used VUV synchrotron radiation and imaging photoelectron photoion coincidence (iPEPICO) spectroscopy techniques to identify para-xylylene as the dominant stable C8H8 product arising from thermal decomposition of the meta-xylyl radical. A complex rearrangement from a meta- to a para-substituted aromatic, supported by quantum chemical calculations, can rationalize the observed reaction products. This work provides the first experimental evidence for the pyrolysis products of the meta-xylyl radical and can explain why the decomposition of this radical is considerably slower than that of the ortho and para isomers. This study emphasizes the utility of VUV synchrotron radiation and iPEPICO spectroscopy to tackle the reaction mechanism of combustion-relevant processes.

DIRECT OBSERVATION OF THE SHELL-LIKE STRUCTURE OF SiO2 PARTICLES SYNTHESIZED BY THE MULTISTAGE STÖBER METHOD

Ultramicrotomy was used to prepare a cross-section of shell-like amorphous SiO2 spherical particle synthesized by the multistage Stöber method which allowed performing first direct observations of the hierarchical structure of the SiO2 particle by transmission and scanning electron microscopy. The presence of primary, secondary and tertiary particles forming the inner structure of SiO2 spheres was established. The use of the small angle scattering of neutrons and synchrotron radiation techniques has enabled to define the size of the primary particles, the fractal parameters of their surface and the bulk density of the SiO2 spheres.

Computed Tomography Diffraction-Enhanced Imaging forIn SituVisualization of Tissue Scaffolds Implanted in Cartilage

Long-term in vivo studies on animal models and advances from animal to human studies should rely on noninvasive monitoring methods. Synchrotron radiation (SR)-diffraction enhanced imaging (DEI) has shown great promise as a noninvasive method for visualizing native and/or engineered tissues and bio-microstructures with appreciable details in situ. The objective of this study was to investigate SR-DEI for in situ visualization and characterization of tissue-engineered scaffolds implanted in cartilage. A piglet stifle joint implanted with an engineered scaffold made from poly-ɛ-caprolactone was imaged using SR computed tomography (CT)-DEI at an X-ray energy of 40 keV. For comparison, in situ visualization was also conducted with commonly used SR CT-phase contrast imaging and clinical magnetic resonance imaging techniques. The reconstructed CT-DE images show the implanted scaffold with the structural properties much clearer than those in the CT-PC and MR images. Furthermore, CT-DEI was able to visualize microstructures within the cartilage as well as different soft tissues surrounding the joint. These microstructural details were not recognizable using other imaging techniques. Taken together, the results of this study suggest that CT-DEI can be used for noninvasive visualization and characterization of scaffolds in cartilage, representing an advance in tissue engineering to track the success of tissue scaffolds for cartilage repair.

The application of synchrotron methods in characterizing iron and cobalt Fischer–Tropsch synthesis catalysts

This article reviews the use of synchrotron radiation techniques to confront issues associated with cobalt and iron catalysts. The main areas that are examined include: (1) the application of TPR-XANES and TPR-EXAFS to gain insight into the hydrogen reduction of cobalt catalysts and the carburization of iron catalysts; (2) the impact of promoters on these reduction/carburization rates; (3) the local atomic structure of promoters and its influence on catalyst selectivity; (4) exploring the deactivation of cobalt catalysts; (5) the influence of crystallite size in stabilizing cobalts catalyst against water effects; and (6) temperature effects in alkali promoted iron catalysts in retaining the iron carbide phase against reoxidation by water.

Quantifying Morphological Parameters of the Terminal Branching Units in a Mouse Lung by Phase Contrast Synchrotron Radiation Computed Tomography

An effective technique of phase contrast synchrotron radiation computed tomography was established for the quantitative analysis of the microstructures in the respiratory zone of a mouse lung. Heitzman’s method was adopted for the whole-lung sample preparation, and Canny’s edge detector was used for locating the air-tissue boundaries. This technique revealed detailed morphology of the respiratory zone components, including terminal bronchioles and alveolar sacs, with sufficiently high resolution of 1.74 µm isotropic voxel size. The technique enabled visual inspection of the respiratory zone components and comprehension of their relative positions in three dimensions. To check the method’s feasibility for quantitative imaging, morphological parameters such as diameter, surface area and volume were measured and analyzed for sixteen randomly selected terminal branching units, each consisting of a terminal bronchiole and a pair of succeeding alveolar sacs. The four types of asymmetry ratios concerning alveolar sac mouth diameter, alveolar sac surface area, and alveolar sac volume are measured. This is the first ever finding of the asymmetry ratio for the terminal bronchioles and alveolar sacs, and it is noteworthy that an appreciable degree of branching asymmetry was observed among the alveolar sacs at the terminal end of the airway tree, despite the number of samples was small yet. The series of efficient techniques developed and confirmed in this study, from sample preparation to quantification, is expected to contribute to a wider and exacter application of phase contrast synchrotron radiation computed tomography to a variety of studies.

High-Pressure Measurements of Hydrogen Phase IV Using Synchrotron Infrared Spectroscopy

Phase IV of dense solid hydrogen has been identified by its infrared spectrum using high-pressure synchrotron radiation techniques. The spectrum exhibits a sharp vibron band at higher frequency and lower intensity than that for phase III, indicating the stability of molecular H(2) with decreased intermolecular interactions and charge transfer between molecules. A low-frequency vibron having a strong negative pressure shift indicative of strongly interacting molecules is also observed. The character of the spectrum is consistent with an anisotropic, mixed layer structure related to those recently predicted theoretically. Phase IV was found to be stable from 220 GPa (300 K) to at least 340 GPa (near 200 K), with the I-III-IV triple point located. Infrared transmission observed to the lowest photon energies measured places constraints on the electronic properties of the phase.

Investigation on corrosion behavior of Ni-based alloys in molten fluoride salt using synchrotron radiation techniques

Ni-based alloys have been selected as the structural materials in molten-salt reactors due to their high corrosion resistance and excellent mechanical properties. In this paper, the corrosion behavior of some Ni-based superalloys including Inconel 600, Hastelloy X and Hastelloy C-276 were investigated in molten fluoride salts at 750 °C. Morphology and microstructure of corroded samples were analyzed using scanning electron microscope (SEM), synchrotron radiation X-ray microbeam fluorescence (μ-XRF) and synchrotron radiation X-ray diffraction (SR-XRD) techniques. Results from μ-XRF and SR-XRD show that the main depleted alloying element of Ni-based alloys in molten fluoride salt is Cr. In addition, the results indicate that Mo can enhance the corrosion resistance in molten FLiNaK salts. Among the above three Ni-based alloys, Hastelloy C-276 exhibits the best corrosion resistance in molten fluoride salts 750 °C. Higher-content Mo and lower-content Cr in Hastelloy C-276 alloy were responsible for the better anti-corrosive performance, compared to the other two alloys.

Speciation of major heavy metals in ambient fine particles collected in the atmospheres of Xuanwei, Yunan, a higher lung incidence area in China

Xuan Wei area, Yunnan province of China, has one of the highest lung cancer mortality rates in China. Heavy metals in the aerosol are potential facts that might attribute to the cause of lung cancer, and speciation of heavy metals could play a key role in toxicity of heavy metals. Therefore, we try to reveal speciation of major heavy metals by using of synchrotron radiation techniques in this study. Mass concentration of chemical elements in ambient particles were analyzed by PIXE (Proton induced X-ray emission), and speciation of Cu was investigated by XAFS (X-ray absorption near-edge structure). Our results demonstrated that mass levels of heavy metals ranked as Fe (791.62 ng/m3) >Zn (479.49 ng/m3) >Pb(154.76 ng/m3) >Cu(28.51 ng/m3) >Co (11.79 ng/m3) >Ni (8.20 ng/m3). The Cu speciation in the different size fraction was different. Speciation of Cu in fine particles (PM0.56~0.32) is present as Cu (I), and significant amount of Cu is present as Cu (II) in the ultrafine particles (PM0.1).

Direct evidence of the high strain tolerance of the critical current of DI-BSCCO tapes fabricated by means of the pretensioned lamination technique

A remarkable improvement in the strain dependence of critical current and the mechanical properties of DI-BSCCO-Bi2223 tapes was achieved by means of the pretensioned lamination technique. In order to elucidate the origin of this high performance, the local strain exerted on BSCCO filaments was investigated by means of the synchrotron radiation technique. The relaxation strain Ar was expressed by the sum of thermal strain and tensile strain in the fracture of BSCCO filaments. It was concluded that the central parameter when considering the improvement of strain induced properties is the force free strain exerted on BSCCO filaments together with their own strength.

Doping Effect on High-Pressure Behaviors of Sc,Y-doped AlN Nanoprisms

In situ X-ray diffraction studies of rare-earth metals Sc- and Y-doped AlN nanoprisms were carried out using angle-dispersive synchrotron radiation technique in a diamond anvil cell up to approximately 40 and 35 GPa, respectively. Pressure-induced wurtzite-to-rocksalt phase transitions start at 18.6 and 16.2 GPa and complete at 29.8 and 26.5 GPa, showing lower phase-transition pressures compared with bulk AlN and AlN nanowires while slightly higher than that of AlN nanocrystals. The effects of volume expansion, volume collapse, and crystal defects on phase transition have been discussed. The distinct high-pressure behaviors can be explained in terms of the doping-induced Al vacancy defects along with substitute ions sit at the cation sites, which lead to the distortion of the crystal structure that reduce the structural stability of the doped AlN nanoprisms.

Analyses of heavy metals in sewage and sludge from treatment plants in the cities of Campinas and Jaguariúna, using synchrotron radiation total reflection X-rayfluorescence

A major consequence of accelerated urban and industrial development in the last decades is water pollution. In particular, metal contamination is a significant problem, causing serious changes to the environment and adversely affecting human health. The cities of Campinas and Jaguariúna are inserted in the Campinas Metropolitan Region (CMR), one of the most dynamic regions in the Brazilian economy, accounting for 2.7% of Gross National Product (GNP) and 7.83% of São Paulo State Product—or approximately $ 70.7 billion per year. Besides having a strong economy, the region also presents an infrastructure that provides the development of the entire metropolitan area. Therefore, to study the anthropogenic influences of the cities, the evaluation of the quality of raw and treated effluent and, the sludge generated in sewage treatment plants (STP), especially with regard to heavy metals was performed by Total Reflection X-Ray Fluorescence with Synchrotron Radiation technique. The results were compared with the allowed values established by Brazilian Legislation. For raw and treated effluents collected in Jaguariúna and Campinas city in the Stations of Treatment of Sewage (Camanducaia and Anhumas), Cr presented higher concentrations than the maximum allowed values established by CONAMA 357. However, it is necessary to do other studies to define the fraction of Cr+3 and Cr+6 to compare to the new legislation. The other elements were in agreement with established regulations. For sludge sampled in the same locations, the concentrations of Cr, Cu, Pb, Ni and Zn were compared with the CONAMA 375 and showed values smaller than the maximum allowed values, indicating the possibility to re-use the sludge.

Pencilbeam Irradiation Technique for Whole Brain Radiotherapy: Technical and Biological Challenges in a Small Animal Model

We have conducted the first in-vivo experiments in pencilbeam irradiation, a new synchrotron radiation technique based on the principle of microbeam irradiation, a concept of spatially fractionated high-dose irradiation. In an animal model of adult C57 BL/6J mice we have determined technical and physiological limitations with the present technical setup of the technique. Fifty-eight animals were distributed in eleven experimental groups, ten groups receiving whole brain radiotherapy with arrays of 50 µm wide beams. We have tested peak doses ranging between 172 Gy and 2,298 Gy at 3 mm depth. Animals in five groups received whole brain radiotherapy with a center-to-center (ctc) distance of 200 µm and a peak-to-valley ratio (PVDR) of ∼ 100, in the other five groups the ctc was 400 µm (PVDR ∼ 400). Motor and memory abilities were assessed during a six months observation period following irradiation. The lower dose limit, determined by the technical equipment, was at 172 Gy. The LD50 was about 1,164 Gy for a ctc of 200 µm and higher than 2,298 Gy for a ctc of 400 µm. Age-dependent loss in motor and memory performance was seen in all groups. Better overall performance (close to that of healthy controls) was seen in the groups irradiated with a ctc of 400 µm.

Elemental concentration analysis in prostate tissues using total reflection X-ray fluorescence

Prostate cancer (PCa) currently represents the second most prevalent malignant neoplasia in men, representing 21% of all cancer cases. Benign Prostate Hyperplasia (BPH) is an illness prevailing in men above the age of 50, close to 90% after the age of 80. The prostate presents a high zinc concentration, about 10-fold higher than any other body tissue. In this work, samples of human prostate tissues with cancer, BPH and normal tissue were analyzed utilizing total reflection X-ray fluorescence spectroscopy using synchrotron radiation technique (SR-TXRF) to investigate the differences in the elemental concentrations in these tissues. SR-TXRF analyses were performed at the X-ray fluorescence beamline at Brazilian National Synchrotron Light Laboratory (LNLS), in Campinas, São Paulo. It was possible to determine the concentrations of the following elements: P, S, K, Ca, Fe, Cu, Zn and Rb. By using Mann–Whitney U test it was observed that almost all elements presented concentrations with significant differences (α=0.05) between the groups studied.

Three-Dimensional Damage Evolution Measurement in EB-PVD TBCs Using Synchrotron Laminography

This study provides the first results of three dimensional microstructural evolution analysis of a typical EB-PVD thermal barrier coating subjected to thermal cycling. Results have been obtained using the technique of synchrotron-radiation computed laminography (SRCL), enabling the scanning of samples that are thin but extended in two dimensions. A correlation with quantitative measurements of phase transformation from β-NiAl to γ’-Ni3Al was achieved from 3D images and 2D cross-section analysis. Morphological features of phase transformation and damaged areas within the bond-coat layer obtained by SRCL are discussed.

Identification of four-hydrogen complexes in In-rich InxGa1−xN (x>0.4) alloys using photoluminescence, x-ray absorption, and density functional theory

Postgrowth hydrogen incorporation in In-rich In${}_{x}$Ga${}_{1\ensuremath{-}x}$N ($x>0.4$) alloys strongly modifies the optical and structural properties of the material: A large blueshift of the emission and absorption energies is accompanied by a remarkable broadening of the interatomic-distance distribution, as probed by synchrotron radiation techniques. Both effects vanish at a finite In-concentration value ($x$ \ensuremath{\sim} 0.5). Synergic x-ray absorption measurements and first-principle calculations unveil two different defective species forming upon hydrogenation: one due to the high chemical reactivity of H, the other ascribed to mere lattice damage. In the former species, four H atoms bind to as many N atoms, all nearest-neighbors of a same In atom. The stability of this peculiar complex, which is predicted to behave as a donor, stems from atomic displacements cooperating to reduce local strain.