285 research outputs found
Quantitative investigations of supported metal catalysts by ASAXS
No full textLimits and potentiality of anomalous small-angle X-ray scattering for the investigation of supported metal catalysts are discussed. The different sources of statistical errors are illustrated using two catalysts containing metals with absorption edges at very different energies (Au and Pd). Optimized experimental conditions and measuring strategy are proposed, and data-evaluation methods for obtaining quantitative reliable results are suggested. By this method, Au content as low as 0.2 wt% and Pd content of 3 wt% could be investigated with success. The detection limits for palladium are higher, mainly due to its smaller electronic contrast
Non-specular X-ray scattering from thin films and multilayers with small-angle scattering equipment
No full textWe present measurements of non-specular X-ray scattering from rough interfaces at a dedicated small-angle scattering beamline that allows for very low divergence of the incident beam and therefore for high resolution close to the specularly reflected beam. A two-dimensional detector is used to measure the non-specular intensity both in and out of the plane of reflection. The method is exemplified by an Au single layer, an amorphous Nb/Al2O3 multilayer and an epitaxial GaAs/AlAs superlattice sample
sj-docx-1-cpx-10.1177_21677026221101379 – Supplemental material for Change of Threat Expectancy as Mechanism of Exposure-Based Psychotherapy for Anxiety Disorders: Evidence From 8,484 Exposure Exercises of 605 Patients
No full textSupplemental material, sj-docx-1-cpx-10.1177_21677026221101379 for Change of Threat Expectancy as Mechanism of Exposure-Based Psychotherapy for Anxiety Disorders: Evidence From 8,484 Exposure Exercises of 605 Patients by Andre Pittig, Ingmar Heinig, Stephan Goerigk, Jan Richter, Maike Hollandt, Ulrike Lueken, Paul Pauli, Jürgen Deckert, Tilo Kircher, Benjamin Straube, Peter Neudeck, Katja Koelkebeck, Udo Dannlowski, Volker Arolt, Thomas Fydrich, Lydia Fehm, Andreas Ströhle, Christina Totzeck, Jürgen Margraf, Silvia Schneider, Jürgen Hoyer, Winfried Rief, Michelle G. Craske, Alfons O. Hamm and Hans-Ulrich Wittchen in Clinical Psychological Science</p
Decomposition and nanocrystallization in reactively sputtered amorphous Ta-Si-N thin films
No full textThe nanocrystallization process of reactively sputtered thin amorphous Ta-Si-N films is investigated by anomalous small angle x-ray scattering (ASAXS) and x-ray diffraction (XRD). Changes in the microstructure in Ta40Si14N46 films, density variations in the amorphous matrix, decomposition, formation, and growth of nanocrystals after vacuum anneals at different temperatures in the range between 800 and 1000 degreesC are observed and the results of the different techniques are compared. From a Fourier analysis of ASAXS intensities the nanostructure of the investigated ternary system is derived using a model of hard spheres according to Guinier and Fournet. ASAXS investigations indicate that the noncrystalline samples can be described by a monophase fit and the crystallized samples by a bimodal-phase fit, the latter results being consistent with XRD which identifies TaN and Ta5Si3 phases. Detailed analysis shows that TaN nanograins of approximately 2 nm size develop after a decomposition process. Larger grains of Ta5Si3 are observed in addition to the TaN grains if annealing is performed at temperatures higher than 950 degreesC. The aim of these investigations is to give a generally applicable explanation of the barrier failure mechanism for Ta-Si-N diffusion barriers, which is actually observed at temperatures below the crystallization temperature if the films are used in contact with Cu or Al. (C) 2001 American Institute of Physics
ASAXS study of Au, Pd and Pd-Au catalysis supported on active carbon
No full textAmong the techniques commonly used, small angle X-ray scattering (SAXS) is, in principle, particularly suited for the analysis of nanostructured systems. However, catalysts supported on porous materials are three phase systems (support, voids and metal), so that the resulting spectrum contains more information than a single conventional SAXS measurement allows to extract. The use of synchrotron radiation source allows to circumvent this difficulty and to separate the scattering of the support from the one of metal by taking advantage of the so-called anomalous or resonant behavior of the atomic scattering amplitude of an element near its absorption edge. The results so far obtained on some Au, Pd and Pd-Au samples supported on active carbon are reported here
The Impact of the Turing Number on Quantitative ASAXS Measurements of Ternary Alloys
No full textDuring the last ten years, anomalous small angle x ray scattering ASAXS became a precise quantitative method resolving scattering contributions two or three orders of magnitude smaller compared with the overall small angle scattering, which are related to the so called pure resonant scattering contribution. The technique gives access to the analysis of weak concentration fluctuations in systems undergoing spinodal decomposition, which cannot be resolved by transmission electron microscopy TEM images because these systems are to a large degree homogeneous. In addition to the structural information, precise quantitative information about the different chemical concentrations localized in the nanosized structures of ternary alloys are obtained from these scattering contributions. The application of the Gauss elimination algorithm to the vector equation established by ASAXS measurements at three x ray energies is demonstrated for two ternary alloys, one in the state of spinodal decomposition. The example deals with the quantitative analysis of the resonant invariant RI analysis . From the integrals of the pure resonant scattering contribution, the chemical concentrations in the nanoscaled phases are determined. Moreover the Turing numbers of the vector equation stated by the ASAXS measurement are calculated giving a decisive quantitative measure thereby indicating whether the quantitative parameters obtained from the matrix inversion are significan
Decomposition kinetics in copper-cobalt alloys systems: Applications of small-angle x-ray scattering
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