Zeitschriftenaufsätze ab 2018 bis 2021

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Niu, Wenhui; Xu, Bowen; Li, Fupeng; Hou, Minjie; Ren, Kun; Zhang, Da; Lei, Yong; Yang, Bin; Liang, Feng
Hierarchical mesoporous NiO nanosheet arrays as integrated electrode for hybrid sodium-air batteries. - In: Ceramics international, ISSN 0272-8842, Bd. 49 (2023), 13, S. 21355-21362

Attributed to its environmental friendliness, high theoretical energy density, and abundant sodium resource, rechargeable hybrid sodium-air batteries (HSABs) are expected to become a promising pioneer of the new-generation green energy storage device. However, HSABs suffer from the high voltage gap, low energy conversion efficiency, and poor cycle stability due to the low catalytic activity of catalysts caused by the degradation of polymer binders. Herein, hierarchical mesoporous NiO nanosheet arrays grown on carbon papers (CP) (NiO NACP) were synthesized by a facile and efficient hydrothermal route and calcination process, which acts as an integrated electrode for HSABs. Compared with traditional air electrodes that contain a polymer binder and conductive carbon, the integrated NiO NA@CP electrode prevents the aggregation of catalysts, improves the electronic conductivity by good electric contact and ensures its robust mechanical stability. In addition, NiO NA@CP electrode with the abundant porosity and large specific area offers plenty of active sites and shortens ion transfer length and rapid mass transport in ORR/OER process, leading to excellent oxygen catalytic activities. HSABs with NiO NA@CP electrode show a low overpotential of 0.65 V, a state-of-the-art power density (7.53 mW cm^-2), as well as an excellent cyclability of 170 cycles (over 170 h) at a current density of 0.1 mA cm^-2.

Schiemer, Melanie; Reum, Thomas; Töpfer, Hannes
An efficient modeling approach of 1D-planar metamaterials in the high-frequency regime. - In: Compel, ISSN 2054-5606, Bd. 42 (2023), 3, S. 776-786

Purpose The purpose of this paper is to present an alternative modeling approach in terms of the determination of a physically equivalent circuit model for one-dimensional (1D) planar metamaterials in the high-frequency regime, without a postprocessing optimization procedure. Thereby, an efficient implementation of physical relationships is aimed. Design/methodology/approach In this paper, a method based on quasi-stationary simulations and mathematical conversions to derive the values for a physically equivalent circuit model is proposed. Because the electromagnetic coupling mechanisms are investigated in detail, a simplification for the considered multiconductor transmission line structure is achieved. Findings The results show that the proposed modeling approach is an efficient and physically meaningful alternative to classical full-wave simulation techniques for the investigated inhomogeneous transmission line structure in both the time domain as well as in the frequency domain. In the course of this, the effort is reduced while a comparable accuracy is maintained, whereby specific coupling mechanisms are considered in circuit simulations. Originality/value The process to obtain information about physically interpretable lumped element values for a given structure or to determine a layout for known ones is simplified with the aid of the proposed approach. An advantageous adaption of the presented procedure to other areas of application is well conceivable.

Zhang, Chenglin; Chandan Solanki, Pankaj; Cao, Dawei; Zhao, Huaping; Lei, Yong
Integration of cointercalation and adsorption enabling superior rate performance of carbon anodes for symmetric sodium-ion capacitors. - In: ACS applied materials & interfaces, ISSN 1944-8252, Bd. 15 (2023), 20, S. 24459-24469

Carbon materials have been the most common anodes for sodium-ion storage. However, it is well-known that most carbon materials cannot obtain a satisfactory rate performance because of the sluggish kinetics of large-sized sodium-ion intercalation in ordered carbon layers. Here, we propose an integration of co-intercalation and adsorption instead of conventional simplex-intercalation and adsorption to promote the rate capability of sodium-ion storage in carbon materials. The experiment was demonstrated by using a typical carbon material, reduced graphite oxide (RGO400) in an ether-solvent electrolyte. The ordered and disordered carbon layers efficiently store solvated sodium ions and simplex sodium ions, which endows RGO400 with enhanced reversible capacity (403 mA h g^-1 at 50 mA g^-1 after 100 cycles) and superior rate performance (166 mA h g^-1 at 20 A g^-1). Furthermore, a symmetric sodium-ion capacitor was demonstrated by employing RGO400 as both the anode and cathode. It exhibits a high energy density of 48 W h g^-1 at a very high power density of 10,896 W kg^-1. This work updates the sodium-ion storage mechanism and provides a rational strategy to realize high rate capability for carbon electrode materials.

Schmidt, Kiril; Spaniol, Eric; Trautmann, Marcus; Bergmann, Jean Pierre; Füssel, Uwe
The GMAW process using a two-dimensional arc deflection with AC hot wires. - In: Welding journal, ISSN 0043-2296, Bd. 102 (2023), 4, S. 88-s-96-s

Heat input in gas metal arc welding (GMAW) directly correlates with the applied current. As a result, welding irregularities, such as incomplete fusion and excessive penetration, increase and mechanical properties decrease. One way for adjusting heat input is to use hot wire technology. In this article, a two-dimensional arc deflection in GMAW was presented by simultaneous application of two alternating current (AC) hot wires. It is shown how the positioning of the hot wires and the signal characteristics of the current intensity influenced the deflection pattern and weld quality. It was found that the magnetic fields of the two hot wires overlapped due to the narrow opening between. Therefore, an increased one-dimensional deflection resulted. To obtain a two-dimensional deflection, it was necessary to shield the magnetic fields from each other by means of a ferritic material. By pulsing or phase shifting the current signals, individual deflection patterns were possible. The effect of arc deflection was visualized with high-speed recordings and metallographic investigations. Different deflection patterns were generated to adjust heat input and counteract weld irregularities. The use of hot wire technology allowed an increase in deposition rate by simultaneous improvement of weld quality.

Peng, Xuanran; Liu, Jing; Kang, Yaru; Mao, Xu; Yan, Wei; Wang, Xiaohui; Liu, Kong; Xu, Rui; Yang, Fuhua; Li, Zhaofeng
Coupling of photonic and plasmonic modes for double nanowire cavities. - In: Photonics, ISSN 2304-6732, Bd. 10 (2023), 4, 415, S. 1-11

We analyze the coupling between double nanowire cavities for both photonic modes and plasmonic modes. When the spacing between nanowires reduces, a redshift of the resonant frequency of the symmetric mode and a blueshift of the resonant frequency of the antisymmetric mode are observed. Compared to single nanowire cavity modes, the Q factors of antisymmetric supermodes of double nanowires can be improved by 51% for photonic modes and by 24% for plasmonic modes. The mechanisms of Q factor improvement for photonic modes and plasmonic modes are studied based on the field distribution of radiations from the modes. This paper may contribute to research and applications for double nanowire lasers and nanowire laser arrays.

Meinecke, Stefan; Köster, Felix; Christiansen, Dominik; Lüdge, Kathy; Knorr, Andreas; Selig, Malte
Data-driven forecasting of nonequilibrium solid-state dynamics. - In: Physical review, ISSN 1550-235X, Bd. 107 (2023), 18, S. 184306-1-184306-18

We present a data-driven approach to efficiently approximate nonlinear transient dynamics in solid-state systems. Our proposed machine-learning model combines a dimensionality reduction stage with a nonlinear vector autoregression scheme. We report an outstanding time-series forecasting performance combined with an easy-to-deploy model and an inexpensive training routine. Our results are of great relevance as they have the potential to massively accelerate multiphysics simulation software and thereby guide the future development of solid-state-based technologies.

Stauffenberg, Jaqueline; Reibe, Michael; Krötschl, Anja; Reuter, Christoph; Ortlepp, Ingo; Dontsov, Denis; Hesse, Steffen; Rangelow, Ivo W.; Strehle, Steffen; Manske, Eberhard
Tip-based nanofabrication below 40 nm combined with a nanopositioning machine with a movement range of Ø100 mm. - In: Micro and nano engineering, ISSN 2590-0072, Bd. 19 (2023), 100201, S. 1-5

In this paper, the combination of an advanced nanopositioning technique and a tip-based system, which can be used as an atomic force microscope (AFM) and especially for field emission scanning probe lithography (FESPL) is presented. This is possible through the use of active microcantilevers that allow easy switching between measurement and write modes. The combination of nanopositioning and nanomeasuring machines and tip-based systems overcomes the usual limitations of AFM technology and makes it possible to perform high-precision surface scanning and nanofabrication on wafer sizes up to 4 in. We specifically discuss the potential of nanofabrication via FESPL in combination with the nanofabrication machine (NFM-100). Results are presented, where nanofabrication is demonstrated in form of a spiral path over a total length of 1 mm and the potential of this technique in terms of accuracy is discussed. Furthermore, ten lines were written with a pitch of 100 nm and a linewidth below 40 nm was achieved, which is in principle possible over the entire range of motion.

Konrad, Annika C.; Engert, Veronika; Albrecht, Reyk; Dobel, Christian; Döring, Nicola; Haueisen, Jens; Klimecki, Olga; Sandbothe, Mike; Kanske, Philipp
A multicenter feasibility study on implementing a brief mindful breathing exercise into regular university courses. - In: Scientific reports, ISSN 2045-2322, Bd. 13 (2023), 7908, S. 1-14

Practicing mindfulness is associated with stress reduction and with positive effects in the context of learning and teaching. Although effects on student populations have been studied extensively, there are few studies implementing mindfulness exercises in university courses directly. For this reason, we aimed to investigate whether the use of a brief mindfulness exercise in regular university courses, guided by the lecturers, is feasible and has immediate effects on the students’ mental states. We conducted a preregistered multicenter study with one observational arm, following an ABAB design. In total, N = 325 students from 19 different university courses were included at baseline and n = 101 students at post measurement. Students were recruited by N = 14 lecturers located in six different universities in Germany. Lecturers started their courses either by guiding a brief mindfulness exercise (intervention condition) or as they regularly would, with no such exercise (control condition). In both conditions, the mental states of students and lecturers were assessed. Over the semester, n = 1193 weekly observations from students and n = 160 observations from lecturers were collected. Intervention effects were analyzed with linear mixed-effects models. The brief mindfulness exercise, compared to no such exercise, was associated with lower stress composite scores, higher presence composite scores, higher motivation for the courses, as well as better mood in students. Effects persisted throughout a respective course session. Lecturers also reported positive effects of instructing mindfulness. Implementing a brief mindfulness exercise in regular university teaching sessions is feasible and has positive effects on both students and lecturers.

He, Shijiang; Wang, Zidong; Wang, Zhijie; Lei, Yong
Recent progress and future prospect of novel multi-ion storage devices. - In: Journal of semiconductors, ISSN 2058-6140, Bd. 44 (2023), 4, 040201, S. 1-5

Omidian, Maryam; Brand, Jonathan; Néel, Nicolas; Crampin, Simon; Kröger, Jörg
From a wide band gap to the superconducting proximity effect: Fe on Pb(111). - In: New journal of physics, ISSN 1367-2630, Bd. 25 (2023), 3, 033036, insges. 1-15 S.

Epitaxially grown Fe nanostructures on Pb(111) were studied by low-temperature scanning tunneling microscopy and spectroscopy. The deposited Fe assemblies are classified into two groups according to their electronic behavior close to the Fermi energy. One group exhibits a wide energy gap of 0.7 eV that is independent of the temperature ranging from 5 K to room temperature. These Fe islands indicate the absence of the superconductivity proximity effect in their interior. The other group shows a metallic behavior at the Fermi level. The substrate superconducting phase locally enters into these islands, which is evidenced by a sharp resonance at the Fermi energy presumably signaling Andreev reflection at the magnet-superconductor interface.