In Situ Deformation and Breakage of Silica Particles Inside a SEM

AbstractMechanical properties and particle breakage behavior in the submicron size range are of fundamental importance for many particle related processes and applications. Although many (in situ) studies have been dedicated to materials’ size dependent mechanical characterization, particles as free standing structures have been omitted widely. An important, yet open question is the structure property relationship at small scales. Within this account, the application of a custom built manipulator for particle compression inside a scanning electron microscope (SEM) is presented: Stöber-Fink-Bohn (SFB) particles with mean diameters of 500nm and 1000nm are subjected to heat treatments and their mechanical properties are directly correlated to the internal structure. The as-synthesized SFB particles exhibit a complex and size dependent internal structure. Mechanical properties undermatching the values of fused silica are found and only plastic cracking at large strains is observed: cracks are formed at the surface and propagate in radial direction towards the particle center. Heat treatment leads to densification. The degree of changes is controlled by temperature and treatment time. Starting from initially low values, Young's modulus and hardness are increasing with treatment temperature. Properties of fused silica are approached or even exceeded after a treatment at 1000°C. A significant level of plasticity and high sustained deformations are still found. Whereas small particle show ductile cracking, the heat treated micron sized particles show a brittle behavior. A brittle to ductile transition in the size range of 500 nm to 1000 nm is thus identified

Magneli-Phases in Anatase Strongly Promote Co-Catalyst-Free Photocatalytic Hydrogen Evolution

Magneli phases of titanium dioxide (such as Ti4O7, Ti5O9, etc.) provide electronic properties, namely a stable metallic behavior at room temperature. In this manuscript, we demonstrate that nanoscopic Magneli phases, formed intrinsically in anatase during a thermal aerosol synthesis, can enable significant photocatalytic H2 generation. This without the use of any extrinsic co-catalyst in anatase. Under optimized conditions, mixed phase particles of 30 percent anatase, 25 percent Ti4O7 and 20 percent Ti5O9 are obtained that can provide, under solar light, direct photocatalytic H2 evolution at a rate of 145 micromol h-1 g-1. These anatase particles contain 5-10 nm size inter-grown phases of Ti4O7 and Ti5O9. Key is the metallic band of Ti4O7 that induces a particle internal charge separation and transfer cascade with suitable energetics and favorable dimensions that are highly effective for H2 generation

Rapid fabrication and interface structure of highly faceted epitaxial Ni-Au solid solution nanoparticles on sapphire

Supersaturated Ni-Au solid solution particles were synthesized by rapid solid-state dewetting of bilayer thin films deposited onto c-plane sapphire single-crystals. Rapid thermal annealing above the miscibility gap of the Ni-Au system followed by quenching to room temperature resulted in textured and faceted submicron-sized particles as a function of alloying content in the range of 0-28 at% Au. Morphologically, the observed kinetic crystal shapes are confined by close-packed planes; in addition, high-index facets are identified as a function of alloying content by TEM cross-sectioning and equilibrium crystal shape simulations. All samples exhibit a distinct out-of-plane as well as in-plane texture along densely packed directions. Lattice parameters extracted from independent orthogonal X-ray and electron diffraction techniques prove the formation of a solid solution without tetragonal distortion imposed by the sapphire substrate. At the particle-substrate interface of highly alloyed particles segregation of Au atoms as well as dislocations in stand-off position are found. These observations are in-line with a semi-coherent interface, where Au segregation is triggered by the reduction of the overall strain energy due to: (i) a lower shear modulus on the particle side of the interface, (ii) the shifting of misfit dislocations in stand-off position further away from the stiffer substrate and (iii) a reduction of intrinsic misfit dislocation strain energy on the tensile side. In addition, the mechanical properties of pure and alloyed particles were characterized by in situ compression experiments in the SEM. Typical force-displacement data of defect-free single-crystals were obtained, reaching the theoretical strength of Ni for particles smaller than 400 nm. Alloying changes the mechanical response from an intermittent and discrete plastic flow behavior into a homogeneous deformation regime at large compressive strain

Das Forschungsdatenzentrum der Universität Hamburg

The more recent discussion of research data practices at relevant conferences, workshops and respective publications suggest substantially different foci of problems and solutions in managing data between scientific disciplines. There seems to be a particularly profound gap in natural science and humanities whereas social and life sciences are placed somewhere in between. Indeed data centers tailored to the specific needs of a single discipline (physics, chemistry, climate studies) are numerous in science and tend to be nearly absent for a specific humanities subject. While the former ask for and report solutions on scaling up (larger quantities of data can be run by the same application) and scaling out (larger quantities of data can use the same infrastructure), the latter are concerned with the heterogeneity of relatively small amounts of data (long-tail problem) and a divergence of agreed standards; something we may term as cross scaling. In either case, an efficiency problem has to be solved. On the one hand, huge amounts of data have to be handled within an acceptable time frame, on the other hand, many different applications with diverse functionalities have to be handled with an acceptable number of resources.  We would like to argue here that independent from the discipline either optimization problem should be addressed. Throughout the last decade, we have also observed that projects in science diversify and prefer individualized solutions which additionally hints at increasing data heterogeneity in natural science as well while, at the same time, some humanities projects produce petabytes of data. To show the necessity of a differentiated approach, the research data center of Universität Hamburg is offered as a case in point. The evolution of the center specialized in humanities projects to a research data center offering services for the whole university whereas other disciplinary data centers continue to exist side by side illustrates the entire range of tasks of data stewardship. It includes the continuous development of services while getting more and more involved in natural science projects as well as task sharing and communication with other data institutions. A core asset to understand the requirements of each discipline is a multidisciplinary team. Yet, the main organizing principle of the offered services centers around the stages of the data life cycle (1. data creation and deposit, 2. managing active data, 3. data repositories and archives, 4. data catalog and registries). The interdigitation of these stages is paramount in the long term strategy

Specific effects of Ca2+ ions and molecular structure of β-lactoglobulin interfacial layers that drive macroscopic foam stability

β-Lactoglobulin (BLG) adsorption layers at air–water interfaces were studied in situ with vibrational sum-frequency generation (SFG), tensiometry, surface dilatational rheology and ellipsometry as a function of bulk Ca2+ concentration. The relation between the interfacial molecular structure of adsorbed BLG and the interactions with the supporting electrolyte is additionally addressed on higher length scales along the foam hierarchy – from the ubiquitous air–water interface through thin foam films to macroscopic foam. For concentrations 30 mM Ca2+, micrographs of foam films show clear signatures of aggregates which tend to increase the stability of foam films. Here, the interfacial layers have a higher surface dilatational elasticity. In fact, macroscopic foams formed from BLG dilutions with high Ca2+ concentrations where aggregates and interfacial layers with higher elasticity are found, showed the highest stability with much smaller bubble sizes

The Future is Big Graphs! A Community View on Graph Processing Systems

Graphs are by nature unifying abstractions that can leverage interconnectedness to represent, explore, predict, and explain real- and digital-world phenomena. Although real users and consumers of graph instances and graph workloads understand these abstractions, future problems will require new abstractions and systems. What needs to happen in the next decade for big graph processing to continue to succeed?Comment: 12 pages, 3 figures, collaboration between the large-scale systems and data management communities, work started at the Dagstuhl Seminar 19491 on Big Graph Processing Systems, to be published in the Communications of the AC

Ludwig von Mises and the 'Ordo-Interventionists' More than Just Aggression and Contempt?

This paper explores the four decades of intellectual relationship between the Austrian School economist Ludwig von Mises (1881-1973) and two major representatives of German ordoliberalism, Walter Eucken (1891-1950) and Wilhelm Röpke (1899-1966). The timespan covered starts in the early 1920s and terminates with Röpke's passing in 1966, a period featuring numerous encounters in person and several debates in published works, accompanied by exchange in correspondence. The central goal of the paper is to provide a more nuanced understanding of the reasons for the hostile climate and the confrontation patterns than earlier narratives in secondary literature. A key tool is the technique of embedding the scholarly component of the interactions into a complex network of interpersonal relationships. The four decades are separated into five distinct phases with differently nuanced communication patterns: 1) early socialization echoing the animosities between the Austrian School and the Historical School; 2) initial debates in the 1920s and early 1930s on business cycle theory and policy where seniority and maturity play an important role; 3) clashes on political economy and social philosophy at the Colloque Walter Lippmann in 1938 and during the two initial decades of the Mont Pèlerin Society after 1947; 4) coexistence during the German "economic miracle"; 5) exchanges in the 1960s, including a discussion of archival materials never published before about Mises' only honorary doctorate in economics, awarded to him by the University of Freiburg in 1964. Based on this historical account at the heart of the paper, conjectures are formulated as to why - despite the common ground in the inquiries pursued - the protagonists continuously fail to engage in more fruitful scholarly debates, and hypotheses are formulated about the substantive core at stake. In addition, a critical overview of selected strands within the extensive historiographic literature exploring the Austrian School and ordoliberalism in recent decades is provided, including a specific reading of the concept of neoliberalism

2nd Workshop on Humanities-Centred Artificial Intelligence (CHAI)

AI can support research in the Humanities making it easier and more efficient. It is thus essential that AI practitioners and Humanities scholars take a Humanities-centred approach to the development, deployment and application of AI methods for the Humanities. This entry includes the following presentations from the 2nd CHAI workshop. Hagen Peukert: AI Approaches Overcome Variability Problems In Diachronic Text Analysis: The Case Of Identifying Bound Affixes in Middle English (download presentation 1) Hussein Mohammed, Agnieszka Helman-Ważny: Understanding the Zhangzhung Nyengyu tsakali Collection using Computational Pattern Analysis (download presentation 2) Jens Dörpinghaus: Social Network Analysis and Co-Occurrence: Identifying the Gaps Simon Schiff, Magnus Bender, Ralf Möller: Embodiment of an Agent by a Pepper Robot for Explaining Retrieval Results (download presentation 4 and demo) Haiyan Hu-von Hinüber, Sylvia Melzer: On the Awakening of the Buddhological Epigraphy and Philology from the AI (download presentation 5) The submitted presentations are included in this upload for which permission to publish has been granted. The KI2021 workshop – Humanities-Centred AI was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy - EXC 2176 ’Understanding Written Artefacts: Material, Interaction and Transmission in Manuscript Cultures’, project no. 390893796