High‐Energy X‐Rays: A tool for Advanced Bulk Investigations in Materials Science and Physics

Abstract

High-energy X-rays between 30 keV and 1 MeV, such as provided by modern synchrotron radiation sources as the ESRF and HASYLAB, bear the advantage of high penetration into most materials. Even heavy element compositions can be accessed in their volume. The range of applications is huge and spreads from nuclear spectroscopy to the characterization of metal extrusion under industrial conditions. This article compiles an overview over the most common instrumental diffraction techniques.Modern two-dimensional detectors are used to obtain rapid overviews in reciprocal space. For example, diffuse scattering investigations benefit from the very flat Ewald sphere as compared to low energies, which allow mapping of several Brillouin zones within one single shot. Diffraction profiles from liquids or amorphous materials can be recorded easily. For materials science purposes, whole sets of Debye-Scherrer rings are registered onto the detector, their diameters and eccentricities or their intensity distribution along the rings relating to anisotropic strain or texture measurements, respectively. At this point we stress the resolution of this technique which has to be carefully taken into account when working on a second generation synchrotron source.Energy-dispersive studies of local residual strain can be studied by a dedicated three-circle diffractometer which allows accurately to adjust the scattering angle from a defined gauge volume.Triple axis diffractometry and reciprocal space mapping is introduced and can be employed for highest resolution purposes on single crystal characterization, even under heavy and dense sample environments. Thus, the perfection of single crystals can be mapped and strain fields and superstructures as introduced by the modulation from ultrasonic waves into crystals or epitaxially grown Si/Ge layers can be investigated in detail. Phase transitions as magnetic ordering can be studied directly or through its coupling to the crystal lattice. Time resolved studies are performed stroboscopically from a sub-nanosecond to a second time scale.The combination of these techniques is a strong issue for the construction and development of future instruments.

Effect of laser welding parameters on the austenite and martensite phase fractions of NiTi

“…Owing to the high photon flux of these sources, the beam spot size can be very narrow, while still providing good statistics [11]. Additionally, it is possible to obtain precise control of the beam position, ensuring that the analysed region corresponds entirely to a given region.…”

Monitoring of Heat Treatment Processes by High Energy Synchrotron Radiation

“…4 two diffractograms of the automotive TRIP--steel HCT690T are displayed, which were obtained by diffraction experiments with synchrotron radiation at 100 keV and by Co K α radiation. Though the angular range is necessarily much smaller for the high energy radiation, the large number of detected peaks is obvious, resulting from the much larger part of reciprocal space accessible with 100 keV radiation [18]. Additionally, the peaks are more distinct, for example the {220} fcc peak is clearly separated using synchrotron radiation but hardly distinguishable from the background using Co radiation.…”

“…It should be noted that already for 60 keV photons the penetration depth reaches the millimeter scale. Consequently, macroscopic volumes of sheet steel can be probed [18]. At the HARWI-II beamline used here, photon energies between 60 and 240 keV are available with a (monochromatic) photon flux several orders of magnitude higher than that of laboratory tubes (cf.…”

The role of synchrotron radiation in examining the self-assembly of crystalline nanoporous framework materials: from zeolites and aluminophosphates to metal organic hybrids

“…In particular, a move towards very high energy monochromatic synchrotron X-ray sources has recently been observed in the in situ heterogeneous catalysis community 16,17 and it is likely that this will also occur in the field of CNFM formation studies. Such setups will not only allow the development of larger more realistic autoclave-like sample environments but also give regular access to some of the less well utilized techniques described in Table 1, such as PDF analysis, which requires high measurement statistics over large scattering vectors.…”