X-ray absorption spectroscopy (XAS) is a well-established element sensitive and nondestructive method to determine both the oxidation state of and the local environment around one given element in materials. One major strength of this technique is that no special sample preparation is usually required, and that it is a bulk sensitive method due to the long-range penetration length of X-rays in matter. It can also be used for studies of chemistry of thin films and surfaces. XAS sensitivity to the local order makes such experimental approach to be useful not only for crystalline materials but also for liquids, gases, or amorphous matter.
Conventionally implemented at beam lines in synchrotron radiation sources, XAS is now also available at laboratory thanks to recent development of laboratory scale spectrometers. The access to such instruments is provided by the Center for X-ray spectroscopy, which counts several spectrometers serving users from both academia and industry through equipment rent for independent users, mail-in services or customary experimental support on request.
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We have several X-ray imaging facilities in the X-ray laboratory providing quantitative 3D tomography data of the sample. Several types and sizes of samples can be imaged. The nanotom (Phoenix|x-ray Systems + Services GmbH) micro-CT scanner enables sub-micrometer resolution with a sample diameter below 20 mm. The maximum sample diameter is 120 mm. The more recent Bruker SkyScan allows slightly smaller samples but has the advantage of relatively easy operation. Complementary synchrotron-based imaging methods can provide imaging resolutions of up to tens of nanometers. More information can be found in our Microtomography blog.
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A grating based X-ray phase-contrast imaging setup (Talbot-Lau interferometer) was recently implemented in the X-ray laboratory. By exploiting scattering and phase shift information of the X-ray wavefield modified by a sample, a 1000-fold increase in soft-tissue contrast can be achieved compared to conventional attenuation based X-ray imaging methods. This method is especially suitable for samples with only small density differences, such as biological samples (soft tissues), polymers and fibre composites. The finalized device will be able to provide quantitative 3D tomographic data of the sample with three different contrast mechanisms: absorption, phase shift (refraction) and dark-field (small angle scattering based).
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X-ray scattering and diffraction can be used non-destructively to study the atomistic level properties of materials, and to determine their crystallinity, crystalline structure and orientation. In this laboratory, one can find a combined wide-angle X-ray scattering (WAXS) and diffraction (XRD) measurement setup capable of measuring various range of samples: i.e., powders, liquids and small, macroscopic solids, films and surfaces, often with very little preparation needed. We conduct a lot of scattering and diffraction measurements in collaboration with different university and industrial facilities.
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Our main experimental synchrotron techniques are inelastic and elastic X-ray scattering, X-ray imaging, as well as X-ray absorption and emission spectroscopies and their related tools such as resonant inelastic X-ray scattering, resonant X-ray emission spectroscopy, and high-energy resolution fluorescence-detected X-ray absorption spetroscopy. We work in close collaboration with synchrotron radiation laboratories worldwide, such as the European Synchrotron (ESRF), MAX IV Laboratory and the Swiss Light Source (SLS). We are also an integral part of the Finnish Synchrotron Radiation Users' Organization (FSRUO).
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