Analytische Chemie
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This paper describes the production and characteristics of the nanoparticle test materials prepared for common use in the collaborative research project NanoChOp (Chemical and optical characterization of nanomaterials in biological systems), in casu suspensions of silica nanoparticles and CdSe/CdS/ZnS quantum dots (QDs). This paper is the first to illustrate how to assess whether nanoparticle test materials meet the requirements of a "reference material" (ISO Guide 30, 2015) or rather those of the recently defined category of "representative test material (RTM)" (ISO/TS 16195, 2013). The NanoChOp test materials were investigated with small-angle X-ray scattering (SAXS), dynamic light scattering (DLS), and centrifugal liquid sedimentation (CLS) to establish whether they complied with the required monomodal particle size distribution. The presence of impurities, aggregates, agglomerates, and viable microorganisms in the suspensions was investigated with DLS, CLS, optical and electron microscopy and via plating on nutrient agar. Suitability of surface functionalization was investigated with attenuated total reflection Fourier transform infrared spectrometry (ATR-FTIR) and via the capacity of the nanoparticles to be fluorescently labeled or to bind antibodies. Between-unit homogeneity and stability were investigated in terms of particle size and zeta potential. This paper shows that only based on the outcome of a detailed characterization process one can raise the status of a test material to RTM or reference material, and how this status depends on its intended use.
Absorptionskantentomographie, auch bekannt als differentielle Tomographie an Kanten, ist ein Verfahren, bei dem ausgenutzt wird, dass sich die Schwächung von Röntgenstrahlen beim Übergang der Photonenenergie über die Absorptionskanten sprunghaft ändert. Die Verwendung von Synchrotronstrahlung ermöglicht die Anwendung der Absorptionskantentomographie für nahezu jedes Element, da sie eine intensive, durchstimmbare Strahlenquelle mit kleiner Bandbreite darstellt. Der Mikrotomographieaufbau der BAM am Elektronenspeicherring BESSY II eignet sich mit einem Energiebereich von 5 keV bis über 60 keV und einer Ortsauflösung besser als 0.5 µm zur differentiellen Tomographie an den K-Kanten der Elemente von Chrom bis zu den Lanthaniden, bei Einbeziehung der L-Kante bis zu Uran.
In dieser Arbeit wird die Absorptionskantentomographie ausgenutzt, um das Gefüge von Legierungen dreidimensional und nichtdestruktiv zu vermessen. Als Beispiel wird eine Legierung zwischen Magnesium, Yttrium und Zink analysiert, die sich gegenüber unlegiertem Magnesium durch größere Festigkeit und geringere Korrosionsanfälligkeit auszeichnet. Der Grund dafür liegt in der Bildung einer kristallographisch hochgeordneten Phase (long period stacking ordered - LPSO) der Legierungsbestandteile, die die Matrix in Form von Fasern durchzieht. Anhand ihres Yttriumgehaltes wird die dreidimensionale Verteilung der LPSO-Phase in der Matrix für verschiedene Proben bestimmt und mit Schnittbildern und Korrosionstests verglichen. Die Absorptionskantentomographie erweist sich als eine geeignete Methode, um die dreidimensionale Mikrostruktur von Legierungen zu charakterisieren.
Absorptionskantentomographie, auch bekannt als differentielle Tomographie an Kanten, ist ein Verfahren, bei dem ausgenutzt wird, dass sich die Schwächung von Röntgenstrahlen beim Übergang der Photonenenergie über die Absorptionskanten sprunghaft ändert. Die Verwendung von Synchrotronstrahlung ermöglicht die Anwendung der Absorptionskantentomographie für nahezu jedes Element, da sie eine intensive, durchstimmbare Strahlenquelle mit kleiner Bandbreite darstellt. Der Mikrotomographieaufbau der BAM am Elektronenspeicherring BESSY II eignet sich mit einem Energiebereich von 5 keV bis über 60 keV und einer Ortsauflösung besser als 0.5 µm zur differentiellen Tomographie an den K-Kanten der Elemente von Chrom bis zu den Lanthaniden, bei Einbeziehung der L-Kante bis zu Uran.
In dieser Arbeit wird die Absorptionskantentomographie ausgenutzt, um das Gefüge von Legierungen dreidimensional und nichtdestruktiv zu vermessen. Als Beispiel wird eine Legierung zwischen Magnesium, Yttrium und Zink analysiert, die sich gegenüber unlegiertem Magnesium durch größere Festigkeit und geringere Korrosionsanfälligkeit auszeichnet. Der Grund dafür liegt in der Bildung einer kristallographisch hochgeordneten Phase (long period stacking ordered - LPSO) der Legierungsbestandteile, die die Matrix in Form von Fasern durchzieht. Anhand ihres Yttriumgehaltes wird die dreidimensionale Verteilung der LPSO-Phase in der Matrix für verschiedene Proben bestimmt und mit Schnittbildern und Korrosionstests verglichen. Die Absorptionskantentomographie erweist sich als eine geeignete Methode, um die dreidimensionale Mikrostruktur von Legierungen zu charakterisieren.
Simulation becomes more and more important in modern CT imaging. It is increasingly used to optimize techniques for complex applications, to support the preparation of written procedures, and for educational purposes. The radiographic simulator aRTist is a modelling tool which simulates X-ray imaging using a hybrid analytical and Monte Carlo method to efficiently model the radiation transport. In addition to the relevant physical effects such as absorption, scattering and fluorescence, simplified fast models are employed to describe the characteristics of the X-ray source and the detector. aRTist is well equipped to model realistic X-ray imaging setups due to the ability to load exported CAD object descriptions. A simple CT scan module is contained in aRTist which allows the simulation of standard (circular cone beam) scanning trajectories.
TomoSynth is a module for aRTist which allows to set up more complex scanning trajectories by attaching geometrical modification functions to the objects in the radiographic scene. In this way, advanced scanning modes can be realized, for instance helical CT as an overlay of a rotation and a linear motion, or laminography as a motion of the source point. In addition to deterministic motion, also random variations can be introduced. By combining random variations with deterministic motion, non-ideal (realistic) CT scan geometries can be simulated, e.g. focal spot drift and mechanical instability of the axis of rotation. The TomoSynth module conveniently allows to construct these scenarios in a graphical interface and provides a preview before starting the (potentially long running) batch job. Therefore, deviations from ideal CT scan trajectories can be easily adjusted which is a necessary step towards uncertainty determination from simulation.
Absorption edge tomography, also known as differential tomography at absorption edges, is a method which exploits the sudden change of the attenuation coefficient, when the photon energy crosses the absorption edge of an element. Synchrotron radiation is the best source for absorption edge tomography, because of its small bandwidth, high intensity and easily adjustable photon energy. The synchrotron beamline BAMline at the synchrotron radiation facility BESSY II in Berlin, which is operated by the Bundesanstalt für Materialforschung und -prüfung (BAM), provides a monochromatized beam in a photon energy range from 5 keV up to 80 keV with a bandwidth of 2%, when the double multilayer monochromator is used. Together with the microtomography setup, this enables differential tomography with submicron resolution at the K edge of the elements from chromium up to the lanthanides, and up to uranium, when the L edges are used as well.
In this work, metal organic frameworks (MOFs) embedded in polymer are characterized using differential tomography. MOFs are microporous structures of metal ions, coordinated by organic linker molecules, that can be used in a broad field of applications, especially in gas storage and catalysis. In this work, polymer embedded MOFs were extruded into filaments, which could be used for 3d-printing to profit from the specific properties of the MOFs in polymeric materials combined with the arbitrary shapes provided by 3d-printing. For the extrusion, different polymer classes like ABS, polyester- and polyetherurethanes, as well as different MOFs (ZIF-8, ZIF-67, HKUST-1) were used to create MOF containing filaments with a nominal diameter of 3.0 mm. Differential tomography at the edges of the Zn, Co, and Cu was then used to find the distribution of the corresponding MOF in the filament and to analyze the shape of the inclusions.
Mechanochemically synthesized metal–organic Framework material HKUST-1 in combination with acrylonitrile butadiene styrene polymer was used to form a polymer metal–organic framework composite material by a simple extruder.
This composite filament was used for 3D printing. Xray diffraction measurements were used to prove the homogeneous distribution of the metal–organic framework in the polymer on a centimeter scale, whereas X-ray Absorption Edge Tomography using a synchrotron radiation source was able to evaluate the 3D distribution of the metal–organic framework material both in the filament and the resultant printed sample with a resolution of a few lm. Our very first data indicate that, apart from a few clusters having significantly higher Cu concentration, HKUST-1 is distributed homogeneously down to the 100 lm length scale in both polymer bulk materials in the form of clusters with a size of a few lm. Absorption Edge Tomography in combination with data fusion also allows for the calculation of the metal–organic framework amount located on the external polymer surface.
Absorption edge tomography is a method which exploits the sudden change of the attenuation coefficient, when the photon energy crosses the absorption edge of an element. The beamline BAM line at BESSY II, which is operated by the Federal Institute for Materials Research and Testing, can provide a monochromatized beam in a photon energy range from 5 keV up to 80 keV with a bandwidth of 2%. Together with the microtomography setup, this enables differential tomography sensitive to any element with N >= 24 (Cr) by using an appropriate K- or L-edge in this range. Here, a polymer filament embedding metal organic framework (MOF) was prepared and used for 3D printing. Absorption edge tomography at the copper K edge was employed to perform a non-destructive 3D characterization of the microstructure of the embedded MOF. Data fusion was then used to determine the size distribution of the embedded MOF.
Absorption edge tomography is a method which exploits the sudden change of the attenuation coefficient, when the photon energy crosses the absorption edge of an element. The beamline BAM line at BESSY II, which is operated by the Federal Institute for Materials Research and Testing, can provide a monochromatized beam in a photon energy range from 5 keV up to 80 keV with a bandwidth of 2%. Together with the microtomography setup, this enables differential tomography sensitive to any element with N >= 24 (Cr) by using an appropriate K- or L-edge in this range. Here, a polymer filament embedding metal organic framework (MOF) was prepared and used for 3D printing. Absorption edge tomography at the copper K edge was employed to perform a non-destructive 3D characterization of the microstructure of the embedded MOF. Data fusion was then used to determine the size distribution of the embedded MOF.
This paper describes a novel methodology for quantitative in-situ moisture measurement without tracking agents using X-ray computed tomography (XCT). The high levels of grey-scale precision required for the measurement of moisture without tracking agents resulted in the need for an additional image calibration procedure to correct for water-related X-ray scattering and for equipment-variability related artefacts arising during in-situ testing. This calibration procedure was developed on the basis of existing principles of XCT image cor-rection. Resulting images of moisture distribution exhibit a high level of agreement with expected material behaviour. This research demonstrated that XCT can be successfully used to measure both moisture-front movement over time and changes in 3D moisture distribution within samples. This approach to moisture measurement lays the groundwork for the planned future investigation of the interaction between cracking induced by varying chemical and mechanical processes and water transport in concrete.
Durch den großflächigen Einsatz der Computertomographie (CT) in unterschiedlichen Industriebereichen steigen auch die Anforderungen an die quantitative Bildanalyse. Subjektive Bildwahrnehmung muss durch objektive Algorithmen ersetzt werden. In diesem Artikel stellt die Bundesanstalt für Materialforschung und -prüfung (BAM), die seit den 1980er Jahren an der Entwicklung der industriellen CT beteiligt ist, anhand ausgewählter Beispiele den aktuellen Stand ihrer Analysemethoden an verschiedenen Anwendungsbeispielen der CT vor.