Influence of carboxylic acids on the performance of trivalent chromium electrolytes for the deposition of functional coatings. - In: Electrochimica acta, ISSN 1873-3859, Bd. 411 (2022), 140054
As a direct consequence of the restrictions on the use of hexavalent chromium compounds, the demand for a suitable replacement has arisen. In this work the electrodeposition of thick chromium layers (>1µm) from a trivalent electrolyte is investigated with the aim to identify an electrolyte composition for the deposition of hard functional coatings. These layers can be used to surface finish tribological components experiencing high wear rates or mechanical stress in applications such as coating printing cylinders, feed rollers or piston rods. The influence of different carboxylic acids (malonic acid, malic acid, glycolic acid) on the deposition has been studied. The effect of current density on the current efficiency was investigated using in-situ microgravimetry. For a technical application the electrolyte containing malonic acid was the most promising one and was further investigated regarding the properties of the deposits, such as surface morphology, crack formation, composition, thickness and hardness, aiming at properties as close as possible to those of hexavalent chromium. In comparison to hexavalent chromium, the layer of trivalent chromium showed the same properties in terms of crack formation, hardness and layer thickness (> 1 µm).
https://doi.org/10.1016/j.electacta.2022.140054
Disentangling faradaic, pseudocapacitive, and capacitive charge storage: a tutorial for the characterization of batteries, supercapacitors, and hybrid systems. - In: Electrochimica acta, ISSN 1873-3859, Bd. 412 (2022), 140072
Today's electrochemical energy storage technologies aim to combine high specific energy and power, as well as long cycle life, into one system to meet increasing demands in performance. These properties, however, are often characteristic of either batteries (high specific energy) or capacitors (high specific power and cyclability). To merge battery- and capacitor-like properties in a hybrid energy storage system, researchers must understand and control the co-existence of multiple charge storage mechanisms. Charge storage mechanisms can be classified as faradaic, capacitive, or pseudocapacitive, where their relative contributions determine the operating principles and electrochemical performance of the system. Hybrid electrochemical energy storage systems can be better understood and analyzed if the primary charge storage mechanism is identified correctly. This tutorial review first defines faradaic and capacitive charge storage mechanisms and then clarifies the definition of pseudocapacitance using a physically intuitive framework. Then, we discuss strategies that enable these charge storage mechanisms to be quantitatively disentangled using common electrochemical techniques. Finally, we outline representative hybrid energy storage systems that combine the electrochemical characteristics of batteries, capacitors and pseudocapacitors. Modern examples are analyzed while step-by-step guides are provided for all mentioned experimental methods in the Supplementary Information.
https://doi.org/10.1016/j.electacta.2022.140072
Nanometer-thick hematite films as photoanodes for solar water splitting. - In: ACS applied nano materials, ISSN 2574-0970, Bd. 5 (2022), 2, S. 2897-2905
Photoelectrochemical (PEC) water splitting is one of the most promising sustainable methods for feasible solar hydrogen production. However, this method is still impractical due to the lack of suitable photoanode materials that are efficient, stable, and cost-effective. Here, we present a surprisingly simple fabrication method for efficient, stable, and cost-effective nanometer-thick hematite films utilizing a rapid, ambient annealing approach. In the oxygen evolution reaction, the fabricated hematite films exhibit a Faradaic efficiency of 99.8% already at 1 V versus the reversible hydrogen electrode (RHE), a real photocurrent density of 2.35 mA cm-2 at 1.23 V versus RHE, and a superior photo-oxidation stability recorded for over 1000 h. Considering the active surface area, the measured photocurrent density is higher than any value achieved so far by hematite and other single-material thin-film photoanodes. Hence, we show for the first time that undoped hematite thin films can compete with doped hematite and other semiconductor materials.
https://doi.org/10.1021/acsanm.2c00095
Localized surface states influence in the photoelectrocatalytic performance of Al doped a-SiC:H based photocathodes. - In: Materials science in semiconductor processing, ISSN 1873-4081, Bd. 143 (2022), 106474, insges. 10 S.
https://doi.org/10.1016/j.mssp.2022.106474
Selective metallization of polymers: surface activation of polybutylene terephthalate (PBT) assisted by picosecond laser pulses. - In: Advanced engineering materials, ISSN 1527-2648, Bd. 24 (2022), 4, 2100933, S. 1-15
https://doi.org/10.1002/adem.202100933
Galvanische Abscheidung von Nickel-Chrom-Legierungsschichten. - In: WOMag, ISSN 2195-5891, Bd. 10 (2021), 10, S. 21-24
TU Ilmenau startet DFG-Projekt zur Optimierung von Lithiumionenbatterien. - In: WOMag, ISSN 2195-5891, Bd. 10 (2021), 7/8, S. 13
Investigation of the contact resistance as a function of the temperature for connectors and wire terminals. - In: 30th International Conference on Electrical Contacts, (2021), S. 202-209
The hardness of coating materials such as tin or gold is temperature-dependent, so the contact area and thus the contact resistance change depending on the temperature. Contact resistance measurements are carried out on hard gold- and tin-coated connector contacts at elevated temperatures. It is shown that the contact resistance decreases significantly with increasing temperature. Tests are also being carried out with solid and stranded copper wires. In addition to the hardness, foreign layers on the copper conductors have a further influence on the contact resistance.
https://doi.org/10.22032/dbt.51522
Simulation verschiedener Hull-Zellen-Geometrien, Teil 1 - spezielle Elektrodengeometrien in 2D und 3D. - In: Galvanotechnik, ISSN 0016-4232, Bd. 112 (2021), 10, S. 1315-1323
Development of a dynamic model of lithium ion battery pack for battery system monitoring algorithms in electric vehicles. - In: 2021 23rd European Conference on Power Electronics and Applications (EPE'21 ECCE Europe), (2021), S. P.1-P.10
The main objective of this paper is to develop an accurate and a self-corrective model for lithium ion battery pack, based on the analysis of properties and performance of equivalent circuit models of pack's cells and the use of artificial neural networks. This model is expected to meet the requirements for improving the accuracy of battery state estimation required for the monitoring algorithms of the battery system in electric vehicles.The use of the neural network will make it possible to adjust and correct modelling deviations and errors in equivalent circuit model parameters by comparing the modelled cells voltage and the measured voltage and generating modified model parameters based on this comparison.The validation experimental results show that the parameters of the modified model contributed to reducing the error rate in the cell voltage by approximately 70-80% of the error rate in the equivalent circuit model voltage.
https://doi.org/10.23919/EPE21ECCEEurope50061.2021.9570709