Skalenübergreifende Kombination von korrelativen 3D-Mikroskopiemethoden zur Analyse der komplexen 3D-Mikrostruktur poröser Materialien

This thesis constitutes correlative and scale-bridging microscopy studies investigating the complex three dimensional pore space of materials utilized in the fields of catalysis and high temperature Co-base superalloys. The respective micro- and nanostructure is characterized by a combination of X-ray nanotomography (Nano-CT), electron tomography (ET), scanning transmission electron microscopy (STEM) and scanning electron microscopy (SEM). Here, in particular the opportunities of the different methods and contrast mechanisms are exploited to methodologically further develop workflows and strategies for a robust data analysis and interpretation. Overall, three separate studies are presented, unraveling the formation processes and complex structure of supported catalytically active liquid metal solutions (SCALMS), macroporous zeolite particles and oxidized layers of a Co-base superalloy ERBOCo-1. The highly promising SCALMS system demonstrates excellent catalytic properties. The material consists of a macroporous support with embedded low-melting alloy (e.g. Ga-Pd) particles. To unravel the complex pore space and the location of the catalytically active sites, correlative Nano-CT in combination with 360°-ET and analytical transmission electron microscopy (TEM) is applied. The homogenous structure of the porous support network is revealed carrying a statistical distribution of Ga-Pd droplets, which themselves exhibit a nonhomogeneous elemental distribution of Ga and Pd. These findings enable adjustments to the structural and functionality model of SCALMS existing in literature. Macroporous zeolite particles display an hierarchical pore systems with morphological features ranging from the micro- to the nanoscale. Here, the interconnected pore space renders zeolites to be a promising catalysts carrier material system. By combing Nano-CT and 360°-ET, we provide the structure and morphology of single zeolite particles at different states of the synthesis process, enabling a deep insight into pore formation process and its relations to the matrix zeolite material. Investigations of single particles are extended via the large field of view (LFOV) mode of the Nano-CT to larger particle clusters, giving access to better statistics and further to the interparticle pore space and related packing behaviour of those clusters. Co-base superalloys are a promising high-temperature material of which mechanical properties as well as phase stability have been improved over the last decades. Nowadays resistivity against oxidation is of outmost importance. To improve the latter, an in-depth insight into the porosity, pore connectivity and phase formation upon exposure to high temperatures is of great importance. A unique workflow of combining Nano-CT, single-slice focused ion beam (FIB) and SEM imaging combined with energy-dispersive X-ray spectroscopy (EDXS) enables quantification and precise segmentation of the complex pore space and multilayered oxide scales. In all presented topics a main focus of this thesis are advancements in lab-based Nano- CT imaging to find suitable ways of complementing it with other tomography methods. Several examples of correlative Nano- CT and ET are presented, enabling highly precise segmentation and quantitative analysis by ET-informed Nano-CT reconstruction. With Nano-CT experiments primarily being performed in phase contrast (PC) mode, the generated artifacts like halo formation require compensation. This challenge is tackled by a direct correlation of Nano-CT and ET in high angle annular dark-field (HAADF) STEM mode, where in the latter the contrast formation mechanisms are well comprehended and can be consequently utilize to understand and further calibrate the CT image series. In addition, the limits of a singular Nano-CT experiment can be expanded by a multi-ROI “stitching approach”. In this procedure, several partially overlapping neighbouring tilt series are virtually combined into a single sequence taking advantage of the large depth of field (DOF) of the Nano-CT instrument.Diese Arbeit stellt korrelative und skalenübergreifende Mikroskopiestudien dar, die die komplexe dreidimensionale Struktur von porösen Materialien aus den Bereichen Katalyse und Co-Basis Superlegierungen untersuchen. Die vorliegende Mikrostruktur wird durch eine Kombination von Röntgen-Nanotomographie (Nano-CT), Elektronentomographie (ET), Rastertransmissionselektronenmikroskopie (STEM) und Rasterelektronenmikroskopie (REM) charakterisiert. Daher werden drei separate Studien vorgestellt, die die oben genannten Mikroskopietechniken kombinieren, um die Bildungsprozesse und die komplexe Struktur von „supported catalytically active liquid metal solutions“ (SCALMS), makroporösen Zeolithpartikeln und oxidierten Schichten der Co-Basis Superlegierung ERBOCo-1 zu entschlüsseln. Das vielversprechende SCALMS System weist hervorragende katalytische Eigenschaften auf. Das Material besteht aus einem makroporösen Träger mit eingebetteten niedrigschmelzenden Legierungspartikeln (z.B. Ga-Pd). Um die komplexe Porenmorphologie und die Position der katalytisch aktiven Stellen aufzudecken, wird korrelatives Nano- CT in Kombination mit 360°-ET und analytischer Transmissionselektronenmikroskopie (TEM) eingesetzt. Es stellt sich eine homogene Struktur des porösen Trägernetzwerks heraus und die integrierten Ga-Pd-Tröpfchen weisen eine statistische Verteilung im 3D-Volumen und eine inhomogene Elementverteilung von Ga und Pd auf. Daraus ergeben sich Anpassungen an das bereits existierende SCALMS Modell. Makroporöse Zeolithpartikel bestehen aus einem hierarchischen Porensystem mit morphologischen Größen auf mehreren Längenskalen. Das verbundene Porensystem macht Zeolithe zu einem vielversprechenden Katalysator-Trägermaterial. Durch die Kombination von Nano-CT und 360°-ET zur Untersuchung einzelner Zeolithpartikel in verschiedenen Stadien des Syntheseprozesses, wird ein tiefer Einblick in die Porenbildung und die Beziehungen zum Matrix-Zeolithmaterial ermöglicht. Mit der Übertragung der durch die Einzelpartikelanalyse gewonnenen Erkenntnisse auf den Large Field of View (LFOV)-Modus des Nano-CT wird eine erweiterte statistische Relevanz und ein Zugang zum Porenraum zwischen den Partikeln durch Nano-CT größerer Partikelagglomerate erreicht. Co-Basis-Superlegierungen sind ein vielversprechender Hochtemperaturwerkstoff und die mechanischen Eigenschaften sowie die Phasenstabilität wurden in den letzten Jahren verbessert. Ein weiteres wichtiges Thema ist die Untersuchung ihrer Widerstandsfähigkeit gegen Oxidation. Um letzteres zu realisieren, ist es entscheidend, einen tiefen Einblick in die Porosität, die Porenkonzentration und die Phasenbildung bei Einwirkung von hohen Temperaturen zu erhalten. Ein einzigartiger Arbeitsablauf aus der Kombination von Nano-CT und „single slice focused ion beam“ (FIB) und REM-Bildgebung in Kombination mit energiedispersiver Röntgenspektroskopie (EDXS) ermöglicht die Quantifizierung und präzise Segmentierung des komplexen Porenraums und der vielschichtigen Oxidschichten. Ein weiterer Schwerpunkt dieser Arbeit sind Weiterentwicklungen in der laborbasierenden Nano-CT-Bildgebung, um geeignete Möglichkeiten zur Ergänzung mit anderen Tomographieverfahren zu finden. Es werden mehrere Beispiele für korrelative Nano-CT und ET vorgestellt, die eine hochpräzise Segmentierung und quantitative Analyse durch ET-informierte Nano-CT Rekonstruktion ermöglichen. Da Nano- CT-Experimente primär im Phasenkontrast-Modus (PC) durchgeführt werden, müssen die entstehenden Artefakte wie Halo-Bildung kompensiert werden. Dies kann bis zu einem gewissen Grad durch eine direkte Korrelation von Nano-CT und ET im „high angle annular dark-field“ (HAADF) STEM-Modus realisiert werden, wo die Mechanismen der Kontrastbildung bekannt sind. Schließlich können die Grenzen eines einzelnen Nano-CT-Experiments durch den so genannten „Stitching- Ansatz“ erweitert werden. Bei diesem Verfahren werden mehrere, sich teilweise überlappende, benachbarte Kippserien virtuell zu einer einzigen Sequenz zusammengefasst, wobei die große Tiefenschärfe (DOF) des Nano-CT-Geräts ausgenutzt wird

Evaluation of a quality system developed for pharmacy teaching laboratories

Background: The implementation of a quality system improves the educational quality of activities undertaken in a laboratory. Aim: To evaluate the perception of undergraduate pharmacy students and laboratory demonstrators on the quality system implemented in the laboratories of the Department of Pharmacy at the University of Malta. Method: A self-administered questionnaire was developed, psychometrically evaluated and distributed to second, third and fourth year undergraduate pharmacy students and laboratory demonstrators (N=110). Results: Out of a total of 94 questionnaires collected, 91 participants agreed that the implemented quality system is important to carry out procedures correctly and safely in the laboratory and is a helpful educational tool for students to appreciate quality processes in pharmacy (n=84). Ninety two participants agreed that standard operating procedures are an essential aspect of a quality system and are important educational tools for laboratory work (n=73). Conclusion: The implemented laboratory quality system is a valuable educational tool for pharmacy students.peer-reviewe

Fabrication and extreme micromechanics of additive metal microarchitectures

The mechanical performance of metallic metamaterials with 3-dimensional solid frames is typically a combination of the geometrical effect ("architecture") and the characteristic size effects of the base material ("microstructure"). In this study, for the first time, the temperature- and rate-dependent mechanical response of copper microlattices has been investigated. The microlattices were fabricated via a localized electrodeposition in liquid (LEL) process which enables high-precision additive manufacturing of metal at the micro-scale. The metal microlattices possess a unique microstructure with micron sized grains that are rich with randomly oriented growth twins and near-ideal nodal connectivity. Importantly, copper microlattices exhibited unique temperature (-150 and 25 degree C) and strain rate (0.001~100 s-1) dependent deformation behavior during in situ micromechanical testing. Systematic compression tests of fully dense copper micropillars, equivalent in diameter and length to the struts of the microlattice at comparable extreme loading conditions, allow us to investigate the intrinsic deformation mechanism of copper. Combined with the post-mortem microstructural analysis, substantial shifts in deformation mechanisms depending on the temperature and strain rate were revealed. On the one hand, at room temperature (25 degree C), dislocation slip based plastic deformation occurs and leads to a localized deformation of the micropillars. On the other hand, at cryogenic temperature (-150 degree C), mechanical twinning occurs and leads to relatively homogeneous deformation of the micropillars. Based on the intrinsic deformation mechanisms of copper, the temperature and strain rate dependent deformation behavior of microlattices could be explained

A three-year post-graduate Doctorate in Pharmacy course incorporating professional, experiential and research activities : a collaborative innovative approach

Background A three-year post-graduate international Doctorate in Pharmacy collaborative course, was launched by the Department of Pharmacy, University of Malta in collaboration with the College of Pharmacy, University of Illinois at Chicago.Aim and rationale To demonstrate that the professional Doctorate in Pharmacy (i) fits the requirements of a Level 8 degree according to the Bologna process, (ii) helps graduates develop competencies and attributes in proficiency in clinical and professional aspects, (iii) has a research component that provides the right level of abilities to participate in research initiatives and to interpret research outcomes, (iv) enables graduates to obtain leadership characteristics.Approach The unique characteristics of the course were evaluated through an outcomes result-oriented measurement. Leadership aspects were measured through policies and strategies presented by students and graduates.Outcomes i) course is in line with the Bologna declaration, ii) research work shown in the dissertation satisfied competencies required iii) research abilities have been examined through a third party and found to be compliant with acquiring of concepts in the design, carrying out, assessment of outcomes and interpretation of results of the research study carried out by each student, and iv) leadership characteristics were shown by the positions taken up by the graduates and early outcomes from these positions.Conclusion Learning activities enable development of professionals able to merge scientific and practice aspects in the evaluation of innovative therapies, the use of medicines and patient monitoring, and in pharmaceutical policy development and regulation. Leadership positions taken up by graduates point to the acquisition of leadership skills by graduates.Next Steps The authors are happy to extend collaboration for this model to be adapted by other institutions for the curricular development entailed in this programme to enhance and improve an innovative aspect in the evolvement of the pharmacy profession on the international scenario.peer-reviewe

Correlative Laboratory Nano‐CT and 360° Electron Tomography of Macropore Structures in Hierarchical Zeolites

Hierarchical pore structures exhibit morphological features on several length scales, which govern important materials properties in catalysis, such as catalytic activity, diffusivity or selectivity. Correlative tomography offers unique opportunities for a comprehensive and scale‐bridging 3D characterization of such complex pore morphologies, which is crucial to further optimize materials design and synthesis routines. This study explores the capabilities of correlative 360° electron tomography (ET) and lab‐based nano X‐ray computed tomography (Nano‐CT) enabling 3D analyses of volumes of up to (60 µm)³ with down to nm resolution, as demonstrated for zeolite particles with embedded macropores. By first applying the two techniques to the same particle the higher resolution and fidelity of ET are used to improve the segmentation of pore space in the Nano‐CT reconstruction. Extended statistical relevance and access to interparticle pore space are obtained from reconstructions of larger particle agglomerates, using the large‐field‐of‐view mode of the Nano‐CT. The presented correlative approach enables real space analyses of important pore characteristics for comparison with complementary pore characterization techniques. Moreover, by investigating samples from different stages of the synthesis, 360°‐ET and Nano‐CT provide unique insights into the formation mechanism of porous materials, as demonstrated for the steam‐assisted crystallization of the macroporous zeolite particles