Gesamtliste aus der Hochschulbibliographie

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Sauni Camposano, Yesenia Haydee; Jaekel, Konrad; Riegler, Sascha S.; Matthes, Sebastian; Glaser, Marcus; Peter, Nicolas J.; Vardo, Emina; Bartsch, Heike; Schwaiger, Ruth; Bergmann, Jean Pierre; Gallino, Isabella; Schaaf, Peter
Controlling propagation velocity in Al/Ni reactive multilayer systems by periodic 2D surface structuring. - In: Advanced engineering materials, ISSN 1527-2648, Bd. n/a (2024), n/a, 2302272, S. 1-11

The chemical energy released as heat during the exothermic reaction of reactive multilayer systems has shown potential applications in various technological areas, e.g., in joining applications. However, controlling the heat release rate and the propagation velocity of the reaction is required to enhance their performance in most of these applications. Herein, a method to control the propagation velocity and heat release rate of the system is presented. The sputtering of Al/Ni multilayers on substrates with periodic 2D surface structures promotes the formation of growth defects into the system. This modification in the morphology locally influences the reaction characteristics. Tailoring the number of 2D structures in the substrate enables the control of the velocity and maximum temperature of the propagation front. The morphology of the produced reactive multilayers is investigated before and after reaction using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. In addition, the enthalpy of the system is obtained through calorimetric analysis. The self-sustained and self-propagating reaction of the systems is monitored by a high-speed camera and a high-speed pyrometer, thus revealing the propagation velocity and the temperatures with time resolution in the microsecond regime.
Kirchhoff, Jonas;
Generic observability for port-Hamiltonian descriptor systems. - In: Mathematics of control, signals, and systems, ISSN 1435-568X, Bd. 0 (2024), 0, insges. 43 S.

The present work is a successor of Ilchmann and Kirchhoff (Math Control Signals Syst 33:359-377, 2021., Ilchmann and Kirchhoff (Math Control Signals Syst 35:45-76, 2023. on (relative) generic controllability of unstructured linear differential-algebraic systems and of Ilchmann et al. (Port-Hamiltonian descriptor systems are generically controllable and stabilizable. Submitted to Mathematics of Control, Signals and Systems, 2023. on (relative) generic controllability of port-Hamiltonian descriptor systems. We extend their results to (relative) genericity of observability. For unstructured differential-algebraic systems, criteria for (relative) generic observability are derived from Ilchmann and Kirchhoff (Math Control Signals Syst 35:45-76, 2023. using duality. This is not possible for port-Hamiltonian systems. Hence, we tweak the results of Ilchmann et al. (Port-Hamiltonian descriptor systems are generically controllable and stabilizable. Submitted to Mathematics of Control, Signals and Systems, 2023. and derive similar criteria as for the unstructured case. Additionally, we consider certain rank constraints on the system matrices.
Neitzel, Benedikt; Puch, Florian
Formation of voids due to transitions in permeability and cavity diameter during resin injection processes. - In: AIP conference proceedings, ISSN 1551-7616, Bd. 3012 (2024), 1, 020013, S. 020013-1-020013-9

The specific mechanical properties of fiber reinforced composite components are unmatched, considering their low weight. To optimize the lightweight potential of fiber reinforced composites, fiber volume contents have to be maximized and imperfections must be eliminated. However, during the production of fiber reinforced composite laminates via resin injection processes, the formation of microscopic voids is nearly inevitable. Even low amounts of imperfections can cause significant deteriorations in the mechanical properties of the material. To reduce the number of voids inside composite components, understanding the formation and transport of voids is essential. Numerous renowned models describe said formation of voids in dependence of local flow front conditions during the impregnation of textile preforms with thermoset resins. State of the art are models emphasizing the formation of meso-and microvoids in dependence of the modified capillary number. These models show plausible correlations when applied to unidirectional preforms or fabrics with constant permeability along the direction of flow. However, the formation of voids remains to be investigated at points of transitioning permeability, such as alterations in the setup of layers or abruptly changing cavity diameters. To expand the applicability of the existing models onto preforms with local changes in permeability, an experimental setup for gradually increasing cavity diameter and varying layer setup is introduced. A planar mold with three increasing levels of cavity height is used to induce changes in permeability. The rate of change in permeability is controlled by defining the slope between each level. In this study, injection pressure as well as flow front velocity were optically traced, and material data was measured. Resulting local void volume contents were quantified by calcination. It is demonstrated how alterations of diameter and layup take effect on the resulting local porosity. The observed impact on void formation is put in context to changes in tow permeability due to local differences in fiber volume content. By including the slope dependent rate of change in tow permeability into the existing model for calculation of void formation by GUEROULT ET AL., the accuracy of the model can be increased. Comparing the unaltered model to experimental results, the deviations between calculations and measurements were diminished when using the newly introduced factors. Although the error of prediction is being significantly reduced, calculations are still flawed since additional effects like overflow at level edges need to be considered. This discourse is meant to administer a starting point for considering rates of change in tow permeability into the commonly established use of shape factors of models of void formation.
Moreira, Pedro H. O.; Soydan, Alper K.; Reiprich, Johannes; Isaac, Nishchay Angel; Aliabadian, Bardia; Vernizzi, Guilherme J.; Jacobs, Heiko O.
Patterned liquid micro rails for the transport of micrometer sized chips. - In: Advanced Materials Technologies, ISSN 2365-709X, Bd. n/a (2024), n/a, 2400235, S. 1-11

Transport and alignment of microscopic chips are important steps in microelectronics component integration with common approaches being pick-and-place, microfluidics, parallel transfer and self-assembly. An alternate transport approach of microscopic chips is proposed using patterned liquid micro rails as chaperones. The surface free energy and interfacial free energy minimization of all constituents enable the creation of stable pathways. This allows for chip-attachment to rails, while the liquid layer lubricates chip-sliding. Monorails, digital monorails, and digital birails are investigated for chip movement behavior. Chip position and speed can be controlled using liquid flow in closed chambers. Speeds from 10 to 400 mm s−1 are achieved with translation distances as long as 50 mm. It is discovered that chips can selectively cross rail discontinuities of up to 500 µm, allowing for chip position control through a stop-and-go motion. A programmable liquid rails-based chip conveyor system is demonstrated by transporting diodes to receptor sites where they undergo self-assembly.
Wang, Honglei; Cheng, Pengfei; Wu, Bing; Yan, Yong; Schaaf, Peter; Sofer, Zdeněk; Wang, Dong
2D metal phosphorous trichalcogenides (MPCh3) for sustainable energy storage and conversion: nanoarchitectonics and advanced applications. - In: Advanced functional materials, ISSN 1616-3028, Bd. n/a (2024), n/a, 2407432, S. 1-22

2D metal phosphorous trichalcogenides (MPCh3) have attracted considerable attention in sustainable energy storage and conversion due to their distinct physical and chemical characteristics, such as adjustable energy bandgap, significant specific surface area, and abundant active sites. However, research on 2D MPCh3 primarily focuses on electrocatalysis, and understanding its energy conversion and storage mechanisms remains incomplete. This review comprehensively summarizes recent advancements in energy storage and conversion using 2D MPCh3-based materials of various structures. It begins with a discussion of the distinctive properties and preparation techniques of 2D MPCh3, followed by a focus on the rational design and development of these materials for diverse energy-related applications, including rechargeable batteries, supercapacitors, electrocatalysis, photocatalysis, and desalination. Finally, it outlines the key challenges and prospects for future research on 2D MPCh3 materials.
Vardo, Emina; Sauni Camposano, Yesenia Haydee; Matthes, Sebastian; Glaser, Marcus; Bartsch, Heike; Hildebrand, Jörg; Bergmann, Jean Pierre; Schaaf, Peter
Impact of substrate thickness and surface roughness on Al/Ni multilayer reaction kinetics. - In: Advanced engineering materials, ISSN 1527-2648, Bd. n/a (2024), n/a, 2302269, S. 1-10

Reactive multilayers comprising alternating nanoscale layers of Al and Ni exhibit potential across various applications, including localized heating for welding and joining. Control over reaction properties is pivotal for emerging applications, such as chemical time delays or neutralization of biological or chemical weapons. In this research, insights are offered into the intricate interplay between substrate thickness, surface roughness, and the behavior of Al/Ni reactive multilayers, opening avenues for tailored applications in various domains. To observe this interplay, silica with various thicknesses from 0.4 to 1.6 μm is deposited on polished single-crystalline Si and rough poly-Si base substrates. Additionally, to analyze the impact of varying silica thickness along the sample length on reaction behavior, silica in steplike shape is fabricated. Subsequently, Al/Ni multilayers with 5 μm total thickness and 20 or 50 nm bilayer periodicities are deposited. Reaction velocity and temperature are monitored with a high-speed camera and pyrometer. In the results, it is indicated that silica thickness significantly affects self-propagation in multilayers. The reaction is not self-sustained for silica layers ≤ 0.4 μm, depending on bilayer periodicity and substrate roughness. The velocity increases or decreases based on the direction of reaction propagation, whether it moves upward or downward, in relation to the thickness of silica.
Bartsch, Heike; Kaltwasser, Mahsa; Karimi, Kiana; Müller, Jens
Low insertion loss interposer approach for RF applications based on commercial LTCC tape, alkaline-free glass and printed metallization. - In: Materials research bulletin, Bd. 178 (2024), 112902, S. 1-5

Materials with high RF performance are in increasing demand due to the needs of modern telecommunications. Glass and low-temperature co-fired ceramics (LTCCs) are both interesting candidates for the design of complex signal transmission systems. Glass can be processed in large panels, and has suitable structure dimensions for silicon processing, but its multilayer capability is limited. LTCC is a mature technology for complex multilayer assemblies, but the structure dimensions and conductor line resolution are restricted by the need to use screen printing technology. The approach presented here combines the advantages of both technological domains: a thin glass sheet is bonded with no additional material to a LTCC multilayer ceramic and sintered to form a tight joint. Metallization of the glass is created using printable pastes and electroplating. Two fabrication routes are compared: etching of printed thick film metal layers, and semi-additive structuring. The results of RF measurements show a low attenuation per unit length for both types of metallization, indicating that our approach is a promising one for the integration of heterogeneous systems of RF transmission modules.
Hanson, Kenneth R.; Döring, Nicola; Walter, Roberto
Sex doll specifications versus human body characteristics. - In: Archives of sexual behavior, ISSN 1573-2800, Bd. 0 (2024), 0, insges. 9 S.

Sex dolls have been criticized for reproducing unrealistic expectations about human bodies. Yet precise sex doll measurements are lacking in the literature nor has there been any systematic attempt to determine the extent to which sex dolls exaggerate human characteristics. To address this gap, we compared the specifications of sex dolls marketed in the USA with the characteristics of women and men living in the USA. Specifically, we tested if and to what degree female dolls were slimmer (H1) and male dolls more muscular (H2) than female and male humans, respectively. Furthermore, we tested if and to what degree female dolls’ breasts (H3) and male dolls’ penises (H4) were larger than those of women and men. We also tested if sex dolls’ observed race/ethnicity was more often White than that of the US population (H5). In 2023, we collected the measures of all 757 full-body sex dolls marketed by the US retailer Body measures from the US population were extracted from scientific literature. Descriptive and inferential statistical analyses were performed using R. All hypotheses were fully or partially confirmed, which indicated that sex dolls marketed in the USA are not realistic depictions of the US population but hypergendered (H1, H2), hypersexualized (H3, H4), and racially fetishized (H5). Implications of the lack of realism are discussed.
Alkorta, Manex; Cizek, Rebecca; Néel, Nicolas; Frederiksen, Thomas; Kröger, Jörg
Impact of single-melamine tautomerization on the excitation of molecular vibrations in inelastic electron tunneling spectroscopy. - In: Nano letters, ISSN 1530-6992, Bd. 0 (2024), 0, insges. 7 S.

Vibrational quanta of melamine and its tautomer are analyzed at the single-molecule level on Cu(100) with inelastic electron tunneling spectroscopy. The on-surface tautomerization gives rise to markedly different low-energy vibrational spectra of the isomers, as evidenced by a shift in mode energies and a variation in inelastic cross sections. Spatially resolved spectroscopy reveals the maximum signal strength on an orbital nodal plane, excluding resonant inelastic tunneling as the mechanism underlying the quantum excitations. Decreasing the probe-molecule separation down to the formation of a chemical bond between the melamine amino group and the Cu apex atom of the tip leads to a quenched vibrational spectrum with different excitation energies. Density functional and electron transport calculations reproduce the experimental findings and show that the shift in the quantum energies applies to internal molecular bending modes. The simulations moreover suggest that the bond formation represents an efficient manner of tautomerizing the molecule.
Gizatullin, Bulat; Mattea, Carlos; Stapf, Siegfried; Wissel, Till; Buntkowsky, Gerd
NMR relaxation dispersion of liquids adsorbed on modified surfaces of SBA-15 mesoporous silica. - In: The journal of physical chemistry, ISSN 1932-7455, Bd. 128 (2024), 21, S. 8785-8796

The NMR relaxation dispersion of 1H and 2H nuclei in water and alkanes was studied in mesoporous SBA-15 silica in its native state and with modified internal surfaces. By comparison with silica gel of comparable characteristic pore size, a qualitative agreement of the relaxation dispersion was found. In the absence of detectable amounts of paramagnetic centers, intramolecular relaxation is approximated by the model of Reorientations Mediated by Translational Displacements (RMTD), which assumes rigid molecules diffusing along curved surfaces and experiencing long-term memory of their relative orientation due to their polarity. For all liquids, significant relaxation dispersion is found so that the vanishing polarity of alkanes does not allow the assumption of a negligible surface interaction. The difference in dispersion shape between 1H and 2H nuclei, relaxing by dipolar and quadrupolar mechanisms, respectively, allows the reconstruction of the intermolecular contribution to relaxation, which has not yet been studied systematically in porous media. A model based on the relative contributions of intra- and intermolecular interactions as well as hydrogen exchange with OH- and NH2-groups is presented.