MobilNachhaltigS: TC Plattling MoMoZeitschriftenartikel
M. Uitz, Michael Sternad, S. Breuer, C. Täubert, T. Traußnig, V. Hennige, I. Hanzu, M. Wilkening
Aging of Tesla's 18650 Lithium-Ion Cells: Correlating Solid-Electrolyte-Interphase Evolution with Fading in Capacity and Power
Journal of The Electrochemical Society, vol. 164, no. 14
2017
DOI: 10.1149/2.0171714jes
Abstract anzeigen
The long-term performance of commercial lithium-ion batteries used in today's electric vehicles is of utmost importance for automotive requirements. Here, we use Tesla's 18650 cells manufactured by Panasonic to elucidate the origins of capacity fading and impedance increase during both calendar and cycle aging. Full cell testing is systematically carried out at three different temperatures (25°C, 40°C, 60°C). The cells are galvanostatically cycled at different C-rates (0.33 C – 1 C) and calendar aging is monitored at 4 different state-of-charges (SOC). Operation at high temperatures turns out to have the largest effect on both the capacity and direct current (DC) impedance. As an example, after 500 cycles at 25°C and 40°C capacity fading is approximately 12%, while at 60°C the fading reaches 22%. Our DC impedance measurements reveal the same trend. Post mortem analysis indicate that aging is strongly related to changes of the solid electrolyte interphase (SEI). Hence, the changes in performance are correlated with the change in composition (and thickness) of the SEI formed. In particular, we quantitatively measure the formation of electrically insulating LiF and find a correlation between overall DC impedance of the cells and lithium fluoride of the SEI.
MobilNachhaltigS: TC Plattling MoMoZeitschriftenartikel
R. Janski, M. Fugger, M. Forster, M. Sorger, A. Dunst, I. Hanzu, Michael Sternad, M. Wilkening
Lithium barrier materials for on-chip Si-based microbatteries
Journal of Materials Science: Materials in Electronics, vol. 28, no. 19, pp. 14605-14614
2017
DOI: 10.1007/s10854-017-7325-4
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The integration of lithium-ion batteries, featuring ultra-high discharge rates, directly into silicon-based semiconductor devices opens unique paths towards the development of new mobile micro-electronics applications. Nevertheless, the small and mobile lithium ions have to be confined within the battery area of the silicon chip, otherwise the nearby fine microelectronics devices will be irreversibly damaged. Hence, a barrier material that blocks Li+ transport from the active components of the battery into the surrounding crystalline Si is needed. Here we evaluated the capability of magnetron sputtered barrier films of nitrides and alloys of refractory metals to prevent lithium ion diffusion and, thus, the formation of Li–Si phases outside the battery area. In order to determine the Li profiles in the barrier layer and in the silicon substrate, time-of-flight secondary ion mass spectroscopy was applied for profiling the first microns. In combination with electrochemical testing it turned out that titanium nitride as well as tantalum nitride barriers are able to significantly block Li ion migration.
GesundF: Angewandte GesundheitswissenschaftenHochschulschrift
Richard Latzel
Entwicklung und Zusammenhang von konditionellen Leistungsfaktoren und Spielleistung im deutschen Nachwuchsleistungs- und Profibasketball
Ausgezeichnet mit dem Publikationspreis des Deutschen Basketball Bundes (DBB)
2017
Abstract anzeigen
Konditionelle Leistungsfaktoren und ihr Einfluss auf die Spielleistung im deutschen Nachwuchsleistungs- und Profibasketball EINLEITUNG: Durch das komplexe Anforderungsprofil des professionellen Basketballs ist die Spielleistung auch von der athletischen Leistungsfähigkeit der Spieler bestimmt. Dennoch konnten bis dato nur wenige Studien eine direkte Verbindung zwischen Athletik und Spielleistung aufzeigen (McGill et al., 2012). Ziel der vorliegenden Arbeit war es daher, den Einfluss von basketballrelevanten konditionellen Fähigkeiten auf Komponenten der Spielleistung im deutschen Nachwuchsleistungs- und Profibasketball zu untersuchen. METHODIK: 89 Spieler der höchsten deutschen Basketball Jugendligen ( JBBL: n=37, Alter: 14,8 ± 0,6 Jahre, Größe: 182,8 ± 7,6 cm, Gewicht: 67,6 ± 12,7 kg; NBBL: n=27, Alter: 17,0 ± 0,8 Jahre, Größe: 192,3 ± 7,8 cm, Gewicht: 80 ± 10,2 kg) sowie der 1. Bundesliga (BBL: n=25, Alter: 26,3 ± 3,6 Jahre, Größe: 196,0 ± 9,5 cm, Gewicht: 101,3 ± 9,8 kg) nahmen jeweils vor einer Saison an einer basketballspezifischen Leistungsdiagnostik teil. Alle Spieler durchliefen Tests der Schnelligkeit (21m-Sprint (23m, s), 10x15m Wiederholungssprinttest (RST, s)), Sprungkraft (No step vertical jump (NSVJ, cm), Maximal- sprung mit Anlauf (MVJ, cm), 30s Wiederholungssprungtest (30s, W/kg)), Agilität (Lane Agility (LA, s), T-Test (MAT, s)) und Ausdauer (YoYo IR1-Test (YoYo-IR1, m)). In der anschließenden Saison wurden ausgesuchte Parameter der Spielleistung erhoben (Anzahl der Spiele und Einsatzzeit, Punkte, Assists, Rebounds, Steals, Blocks, Effektivitätswert). ERGEBNISSE: Bei den JBBL- Spielern korrelierten nahezu alle erhobenen Fitnessdaten signifikant mit einem oder mehreren Merkmalen der Spielleistung (p<0,05), wobei LAT den größten Einfluss auf Einsatzzeit (r=-0,64), Punkte (r=-0,66), Assists (r=-0,64), Steals (r=-0,63) und Effektivitätswert (r=-0,64) hatte. Bei den NBBL-Spielern wiesen NSVJ, MVJ, RST, 23m und LAT ebenfalls einen signifikanten Zusammenhang mit Einsatzzeit, Assists und Steals auf. Bei den Profispielern korrelierten nur noch NSVJ and MVJ signifikant mit Rebounds und LAT signifikant mit Steals. Zudem wurden positionsspezifische Unterschiede festgestellt: in allen untersuchten Altersklassen korrelierten bei den Spielern der Positionen 1-3 vor allem die Leistungen in den Agilitätstests, und bei den Spielern der Positionen 4 und 5 vor allem die Reichhöhen im Standsprung mit den für ihre Positionen wichtigsten Parametern der Spielleistung. Der Vergleich mit der internationalen Leistungsspitze ergab ein insgesamt niedrigeres konditionelles Leistungsniveau des deutschen Nachwuchsleistungs- und Profibasketballs. DISKUSSION: Diese Ergebnisse zeigen, dass im Nachwuchsleistungsbasketball eine hohe allgemeine Fitness die Grundlage hoher Spielleistung bildet, während im Profibasketball vor allem positionsspezifische Aspekte der Fitness einen direkten Einfluss auf ausgesuchte Parameter der Spielleistung nehmen. Dies, und der im internationalen Vergleich niedrigere konditionelle Leistungsstand erweisen, dass das Konditionstraining in der Trainingspraxis des deutschen Nachwuchsleistungs- und Profibasketballs eine deutliche Aufwertung erfahren sollte.
NachhaltigF: Angewandte Naturwissenschaften und WirtschaftsingenieurwesenS: TC Teisnach SensorikZeitschriftenartikel
F. Singer, Maria Kufner
Model based laser-ultrasound determination of hardness gradients of gas-carburized steel
NDT & E International, vol. 88, pp. 24-32
2017
DOI: 10.1016/j.ndteint.2017.02.006
Abstract anzeigen
Gas carburizing is a common industrial process utilized for case hardening of low carbon steels. However, thereis a lack of non-destructive evaluation systems for the measurement of hardness-depth profiles. We propose anovel measurement method for the determination of hardness-depth profiles of two-step gas carburized steelspecimens. The method is based on the measurement of broadband laser excited Rayleigh waves. Rayleighwaves were generated by a pulsed Nd: YAG laser in the thermoelastic regime and measured with a heterodyneMach-Zehnder interferometer in the near-field. From two measurements with different source to receiverdistances the dispersion diagrams were calculated by means of the phase spectral analysis method. In order tosimulate the observed dispersive behavior of the Rayleigh waves,first the two-step gas carburizing process wassimulated using solutions of the diffusion equation. The resulting continuous hardness profile was thendiscretized into up to 100 layers. Thereafter the Rayleigh wave dispersion diagram was calculated from thediscretized stack of layers using a delta-matrix formulation of the Thomson-Haskell transfer matrix method. Inorder to obtain bestfitting hardness profiles, the simulated dispersion diagrams werefitted to measurementswith a curvefitting algorithm. Comparison of the Rayleigh wave inversion method with destructively obtainedVickers hardness profiles shows good quantitative agreement.
NachhaltigF: Angewandte Naturwissenschaften und WirtschaftsingenieurwesenS: TSZ WeißenburgZeitschriftenartikel
Loupos, K., Damigos, Y., Amditis, A., Gerhard, R., Dmitry Rychkov, Wirges, W., Schulze, M., Lenas, S.-A., Chatziandreoglou, C., Malliou, C.M., Tsaoussidis, V., Brady, K., Frankenstein, B.
Structural health monitoring system for bridges based on skin-like sensor
IOP Conference Series: Materials Science and Engineering, vol. 236, no. Proceedings of BESTInfra2017 - Building up Efficient and Sustainable TransportInfrastructure 2017
2017
DOI: 10.1088/1757-899X/236/1/012100
Abstract anzeigen
Structural health monitoring activities are of primal importance for managing transport infrastructure, however most SHM methodologies are based on point-based sensors that have limitations in terms of their spatial positioning requirements, cost of development and measurement range. This paper describes the progress on the SENSKIN EC project whose objective is to develop a dielectric-elastomer and micro-electronics-based sensor, formed from a large highly extensible capacitance sensing membrane supported by advanced microelectronic circuitry, for monitoring transport infrastructure bridges. Such a sensor could provide spatial measurements of strain in excess of 10%. The actual sensor along with the data acquisition module, the communication module and power electronics are all integrated into a compact unit, the SENSKIN device, which is energy-efficient, requires simple signal processing and it is easy to install over various surface types. In terms of communication, SENSKIN devices interact with each other to form the SENSKIN system; a fully distributed and autonomous wireless sensor network that is able to self-monitor. SENSKIN system utilizes Delay-/Disruption-Tolerant Networking technologies to ensure that the strain measurements will be received by the base station even under extreme conditions where normal communications are disrupted. This paper describes the architecture of the SENSKIN system and the development and testing of the first SENSKIN prototype sensor, the data acquisition system, and the communication system.
NachhaltigF: Angewandte Naturwissenschaften und WirtschaftsingenieurwesenS: TSZ WeißenburgZeitschriftenartikel
Wang, J., Dmitry Rychkov, Gerhard, R.
Chemical modification with orthophosphoric acid enhances surface-charge stability on polypropylene electrets
Applied Physics Letters, vol. 110, no. 19
2017
DOI: 10.1063/1.4983348
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The low surface-charge stability of polypropylene (PP) frequently limits its application as an electret material. In this paper, we demonstrate how the treatment of PP-film surfaces with orthophosphoric acid (H3PO4) enhances their charge stability. To discriminate between the effects of chemical modification and thermal treatment, as-received and annealed PP films are used as reference samples. The electret properties of treated and non-treated PP films are characterized with thermally stimulated discharge (TSD) and isothermal surface-potential decay (ISPD) experiments, from which considerable improvement in thermal and temporal charge stability is observed for samples modified with H3PO4. The half-value temperature (T1∕2) observed on TSD curves of chemically treated PP increases to 131 and 145 °C for positive and negative charges, respectively. The enhancement might be attributed to the phosphoric compounds detected on the H3PO4-modified surfaces via attenuated-total-reflection infrared spectroscopy. Deeper surface traps formed at the “foreign” phosphorus-containing structures are able to capture the charges over longer time periods and at higher temperatures, thus leading to significant improvements in the temporal and thermal surface-charge stabilities of PP electrets.
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