Non-linear analytical modeling of planar compliant mechanisms. - In: Mechanism and machine theory, Bd. 155 (2021), 104067, insges. 15 S.
Compliant mechanisms are state of the art in technical applications, especially in precision engineering. They mostly achieve their motion due to bending-dominated deformation of their compliant segments, i.e. flexure hinges. Accurately analyzing a compliant mechanism in dependence of specific flexure hinges is still a challenging task due to the monolithic design and non-linearities caused by large deflections. Most existing accurate analytical models are restricted to single hinges. Therefore, this paper presents a non-linear analytical approach to calculate the elasto-kinematic properties of arbitrary planar compliant mechanisms. The approach is based on the theory for large deflections of rod-like structures. As a typical example, a compliant parallel four-bar linkage with varying compliant segments is investigated by means of the proposed analytical approach. The motion and deformation behavior are numerically calculated with the use of MATLAB®. It is shown, that the analytical results are in good correlation with FEM-based simulations and measurements of a manufactured prototype. To demonstrate the generality of the proposed method, two further and more complex mechanism examples are considered. As a result, the implemented modeling approach allows an accurate and fast analysis as well as synthesis of manifold planar compliant mechanisms with distributed or concentrated compliance.
https://doi.org/10.1016/j.mechmachtheory.2020.104067
Well-defined nanostructures for electrochemical energy conversion and storage. - In: Advanced energy materials, ISSN 1614-6840, Bd. 11 (2021), 15, 2001537, insges. 53 S.
Electrochemical energy conversion and storage play crucial roles in meeting the increasing demand for renewable, portable, and affordable power supplies for society. The rapid development of nanostructured materials provides an alternative route by virtue of their unique and promising effects emerging at nanoscale. In addition to finding advanced materials, structure design and engineering of electrodes improves the electrochemical performance and the resultant commercial competitivity. Regarding the structural engineering, controlling the geometrical parameters (i.e., size, shape, hetero-architecture, and spatial arrangement) of nanostructures and thus forming well-defined nanostructure (WDN) electrodes have been the central aspects of investigations and practical applications. This review discusses the fundamental aspects and concept of WDNs for energy conversion and storage, with a strong emphasis on illuminating the relationship between the structural characteristics and the resultant electrochemical superiorities. Key strategies for actualizing well-defined features in nanostructures are summarized. Electrocatalysis and photoelectrocatalysis (for energy conversion) as well as metal-ion batteries and supercapacitors (for energy storage) are selected to illustrate the superiorities of WDNs in electrochemical reactions and charge carrier transportation. Finally, conclusions and perspectives regarding future research, development, and applications of WDNs are discussed.
https://doi.org/10.1002/aenm.202001537
Nanoparticle gas phase electrodeposition: fundamentals, fluid dynamics, and deposition kinetics. - In: Journal of aerosol science, ISSN 1879-1964, Bd. 151 (2021), 105652, S. 1-15
This communication uncovers missing fundamental elements and an expanded model of gas phase electrodeposition; a relatively new and in large parts unexplored process, which combines particle generation, transport zone and deposition zone in an interacting setup. The process enables selected area deposition of charged nanoparticles that are dispersed and transported by a carrier gas at atmospheric pressure conditions. Two key parameters have been identified: carrier gas flow rate and spark discharge power. Both parameters affect electrical current carried by charged species, nanoparticle mass, particle size and film morphology. In combination, these values enable to provide an estimate of the gas flow dependent Debye length. Together with Langmuir probe measurements of electric potential and field distribution, the transport can be described and understood. First, the transport of the charged species is dominated by the carrier gas flow. In close proximity, the transport is electric field driven. The transition region is not fixed and correlates with the electric potential profile, which is strongly dependent on the deposition rate. Considering the film morphology, the power of the discharge turns out to be the most relevant parameter. Low spark power combined with low gas flow leads to dendritic film growth. In contrast, higher spark power combined with higher gas flow produces compact layers.
https://doi.org/10.1016/j.jaerosci.2020.105652
Preface magnetic carriers conference 2018. - In: Journal of magnetism and magnetic materials, ISSN 1873-4766, Bd. 494 (2020), 165748
https://doi.org/10.1016/j.jmmm.2019.165748
Active scanning probes in nanostructure fabrication. - In: Design strategies for synthesis and fabrication, (2020), S. 18-1-18-12
Richtiger Name des Verfassers: Mathias Holz
https://dx.doi.org/10.1201/9780367341558-18
Anwendungen der Schwingquarzmethode in der Galvanotechnik. - In: ZVO-Report, (2020), 2, S. 42
Abscheidung von dekorativen Chromschichten mittels niederfrequenter Pulsabscheidung zur Anpassung des optischen Erscheinungsbilds. - In: WOMag, ISSN 2195-5905, Bd. 9 (2020), 6, S. 1-8
Das optische Erscheinungsbild von galvanisch abgeschiedenen Chromschichten ist eines der wichtigsten Kriterien für deren dekorative Anwendung. Für die dekorative Verchromung werden zunehmend Elektrolyte auf Basis von dreiwertigem Chrom als Ersatz für die bisher verwendeten Elektrolyte auf Basis von sechswertigem Chrom eingesetzt. Chrom aus Elektrolyten mit dreiwertigen Chromverbindungen neigt jedoch dazu, bei Dicken über 100 nm einen gelblichen Farbton zu haben, was für die meisten Anwendungen unerwünscht ist. Die Farbverschiebung hängt mit einer Änderung der Oberflächenmorphologie aufgrund des Wachstums der Chromkeime zusammen. Durch die Verwendung von gepulstem Strom mit Einschaltzeiten im Bereich von Sekunden wird das unerwünschte Kornwachstum unterdrückt und die Bildung frischer Kerne begünstigt. Dadurch bilden sich kompakte Chromschichten mit feinerem Gefüge und verbesserten Farbwerten. Ein bläuliches Aussehen und ein hoher Glanz werden bis zu einer Dicke von mehr als 200 nm beibehalten. Basierend auf den Ergebnissen wird eine Kombination aus konstantem und gepulstem Strom vorgeschlagen, die ein ähnliches visuelles Erscheinungsbild ergibt wie nur bei gepulstem Strom, jedoch die angestrebte Schichtdicke in deutlich kürzerer Zeit erreicht.
https://dx.doi.org/10.7395/2020/Leimbach1
Synthesis and characterization of size controlled bimetallic nanosponges. - In: Multifunctional materials, (2020), S. 1-34
Metallic and bimetallic nanosponges with well-defined size and form have attracted increasing attention due to their unique structural properties and their potential for many applications. In this chapter, the recently developed methods for the synthesis and preparation of metallic and bimetallic nanosponges are presented. These methods can be mainly cataloged in two groups: dealloying-based methods and reduction reaction-based methods. Different topographical reconstruction methods for the investigation of their structural properties are then reviewed briefly. The optical properties of the metallic nanosponges are clearly different from those of the solid counterparts due to the tailored disordered structure. The recent advances in the exploration of the distinct linear and non-linear optical properties of the nanosponges are summarized.
https://doi.org/10.1515/9783110345001-001
Left posterior inferior parietal cortex causally supports the retrieval of action knowledge. - In: NeuroImage, ISSN 1095-9572, Bd. 219 (2020), 117041, insges. 11 S.
Conceptual knowledge is central to human cognition. The left posterior inferior parietal lobe (pIPL) is implicated by neuroimaging studies as a multimodal hub representing conceptual knowledge related to various perceptual-motor modalities. However, the causal role of left pIPL in conceptual processing remains unclear. Here, we transiently disrupted left pIPL function with transcranial magnetic stimulation (TMS) to probe its causal relevance for the retrieval of action and sound knowledge. We compared effective TMS over left pIPL with sham TMS, while healthy participants performed three different tasks - lexical decision, action judgment, and sound judgment - on words with a high or low association to actions and sounds. We found that pIPL-TMS selectively impaired action judgments on low sound-low action words. For the first time, we directly related computational simulations of the TMS-induced electrical field to behavioral performance, which revealed that stronger stimulation of left pIPL is associated with worse performance for action but not sound judgments. These results indicate that left pIPL causally supports conceptual processing when action knowledge is task-relevant and cannot be compensated by sound knowledge. Our findings suggest that left pIPL is specialized for the retrieval of action knowledge, challenging the view of left pIPL as a multimodal conceptual hub.
https://doi.org/10.1016/j.neuroimage.2020.117041
Ag-nanoparticles-decorated Ge-nanowhisker grafted on carbon fiber cloth as flexible and effective SERS substrates. - In: ChemistrySelect, ISSN 2365-6549, Bd. 5 (2020), 27, S. 8338-8343
Three-dimensional (3D) flexible surface enhanced Raman scattering (SERS) substrates of silver nanoparticles (Ag-NPs) decorated Germanium nanowhiskers (Ge-NWHKs) grafted on carbon fiber cloth (CFC) (denoted as Ag-NPsGe-NWHKs@CFC) are constructed via chemical vapor deposition growth of high-density Ge-NWHKs on CFC and then assembly of Ag-NPs on the Ge-NWHKs by galvanic displacement. Ordered 3D framework of Ge-NWHKs grafted flexible CFC impels the formation of large amounts of Ag-NPs with homogenous distribution via spontaneous reduction of Ag+ ions. Thus, the Ag-NPs@Ge-NWHKs@CFC SERS substrates present ultra-high sensitivity, good reproducibility, and high flexibility. This SERS sensor has achieved a detection limit of 1 pM for Rhodamine 6G and 0.1 nM for thiram respectively. The as-fabricated SERS substrates show promising potential for applications in rapid detection of trace organic pollutants in the aquatic environment.
https://doi.org/10.1002/slct.202001290