Journal articles from 2018

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Oliva Ramírez, Manuel; Wang, Dong; Flock, Dominik; Rico, Víctor; González-Elipe, Agustín R.; Schaaf, Peter
Solid-state dewetting of gold on stochastically periodic SiO2 nanocolumns prepared by oblique angle deposition. - In: ACS applied materials & interfaces, ISSN 1944-8252, Bd. 13 (2021), 9, S. 11385-11395
Im Titel ist "2" tiefgestellt

https://doi.org/10.1021/acsami.0c19327
Hotovy, Ivan; Spieß, Lothar; Mikolasek, Miroslav; Kostic, Ivan; Sojkova, Michaela; Romanus, Henry; Hulman, Martin; Buc, Dalibor; Rehacek, Vlastimil
Layered WS2 thin films prepared by sulfurization of sputtered W films. - In: Applied surface science, Bd. 544 (2021), 148719
Im Titel ist "2" tiefgestellt

We present structural, optical and electrical investigations of layered WS2 films prepared on tungsten. A two-step technique has been used to synthesize layered WS2 films using sulfurization of W films sputtered with thinner (1 and 2 nm) and thicker (14 and 28 nm) thicknesses at 800 ˚C. XRD analysis revealed that the examined films are polycrystalline with texture and have a 2H-WS2 hexagonal microstructure. Using Raman spectroscopy with the 532 nm laser excitation, the presence of E12g and A1g vibration modes was observed and the layered nature of WS2 was confirmed. FE SEM observations showed two different surface morphologies. The samples grown on thinner W films were not compact over the surface and agglomeration of nanosize grains in combination of triangles and flakes was visible. In another group the surface was lamellar and contained plenty of nanorods embedded vertically and/or inclined at different angles to the surface. Layered WS2 films exhibited a direct band gap in the range of 2.1-2.5 eV and they were n-type semiconductors with the sheet resistance in the order of several M at room temperature.



https://doi.org/10.1016/j.apsusc.2020.148719
Yan, Yong; Liu, Chunyue; Jian, Hanwen; Cheng, Xing; Hu, Ting; Wang, Dong; Shang, Lu; Chen, Ge; Schaaf, Peter; Wang, Xiayan; Kan, Erjun; Zhang, Tierui
Substitutionally dispersed high-oxidation CoOx clusters in the lattice of rutile TiO2 triggering efficient Co-Ti cooperative catalytic centers for oxygen evolution reactions. - In: Advanced functional materials, ISSN 1616-3028, Bd. 31 (2021), 9, 2009610, insges. 13 S.
Im Titel sind "x" und "2" tiefgestellt

The development of economical, highly active, and robust electrocatalysts for oxygen evolution reaction (OER) is one of the major obstacles for producing affordable water splitting systems and metal-air batteries. Herein, it is reported that the subnanometric CoOx clusters with high oxidation state substitutionally dispersed in the lattice of rutile TiO2 support (Co-TiO2) can be prepared by a thermally induced phase segregation process. Owing to the strong interaction of CoOx clusters and TiO2 support, Co-TiO2 exhibits both excellent intrinsic activity and durability for OER. The turnover frequency of Co-TiO2 is up to 3.250 s-1 at overpotentials of 350 mV; this value is one of the highest in terms of OER performance among the current Co-based active materials under similar testing conditions; moreover, the OER current density loss is only 6.5% at a constant overpotential of 400 mV for 30 000 s, which is superior to the benchmark Co3O4 and RuO2 catalysts. Mechanism analysis demonstrates that charge transfer occurs between Co sites and their neighboring Ti atoms, triggering the efficient Co-Ti cooperative catalytic centers, in which OH* and O* are preferred to be adsorbed on the bridging sites of Co and Ti with favorable adsorption energy, inducing a lower energy barrier for O2 generation.



https://doi.org/10.1002/adfm.202009610
Chavez, Jhohan; Ziolkowski, Marek; Schorr, Philipp; Spieß, Lothar; Böhm, Valter; Zimmermann, Klaus
A method to approach constant isotropic permeabilities and demagnetization factors of magneto-rheological elastomers. - In: Journal of magnetism and magnetic materials, ISSN 1873-4766, Bd. 527 (2021), 167742

The use of non-conventional materials is nowadays of much interest in scientific community. Magneto-rheological elastomers are hybrid materials, which in presence of magnetic fields state a change in their mechanical properties. They are composed by an elastomeric matrix with embedded magnetic particles. One of the most attractive features of these materials is that as soon as the magnetic field is removed from the material, the original mechanical properties are completely recovered, with negligible differences in comparison to the original state. This paper focuses on the study of magnetic characteristics of these smart materials, such as relative permeability and demagnetizing factors, for samples with different volume concentration of ferromagnetic particles.



https://doi.org/10.1016/j.jmmm.2021.167742
Cheng, Pengfei; Wang, Honglei; Müller, Björn; Müller, Jens; Wang, Dong; Schaaf, Peter
Photo-thermoelectric conversion using black silicon with enhanced light trapping performance far beyond the band edge absorption. - In: ACS applied materials & interfaces, ISSN 1944-8252, Bd. 13 (2021), 1, S. 1818-1826

https://doi.org/10.1021/acsami.0c17279
Schricker, Klaus; Bergmann, Jean Pierre; Hopfeld, Marcus; Spieß, Lothar
Effect of thermoplastic morphology on mechanical properties in laser-assisted joining of polyamide 6 with aluminum. - In: Welding in the world, ISSN 1878-6669, Bd. 65 (2021), 4, S. 699-711

This paper examined the joining zone between semi-crystalline polyamide 6 and aluminum EN AW 6082 in laser-based joining and evaluated the mechanical properties of the joint. The joint tests were carried out in overlap configuration and a characterized in terms of energy per unit length. The mechanical properties were examined to the point of cohesive failure. An increasing energy per unit length resulted in a reduced crosshead displacement in short-term testing and a decreased fatigue strength. Further material testing was carried out locally at various positions within the joining zone. The mechanical properties were correlated with results of a hardness test, thermoplastic morphology, differential scanning calorimetry (DSC), and X-ray diffraction (XRD). By combining the findings with heat-treated samples at elevated temperatures, secondary crystallization was identified and evidenced as a primary effect among the changes in mechanical properties due to the heat treatment of the thermoplastic material.



https://doi.org/10.1007/s40194-020-01048-1
Biele, Lukas; Schaaf, Peter; Schmid, Florian
Method for contact resistance determination of copper during fast temperature changes. - In: Journal of materials science, ISSN 1573-4803, Bd. 56 (2021), 5, S. 3827-3845

https://doi.org/10.1007/s10853-020-05490-w
Wang, Anni; Oliva Ramírez, Manuel; Caplovicova, Maria; Vretenar, Viliam; Böttcher, Julius; Hopfeld, Marcus; Kups, Thomas; Flock, Dominik; Schaaf, Peter
Formation of CuCrCoFeNiO high entropy alloy thin films by rapid thermal processing of Cu/CrNiO/FeCo multilayers. - In: Surface and coatings technology, ISSN 1879-3347, Bd. 405 (2021), 126563

https://doi.org/10.1016/j.surfcoat.2020.126563
Torres, Carlos; Quispe, Roger; Calderón, Noely Z.; Eggert, Lara; Hopfeld, Marcus; Rojas, Christopher; Camargo, Magali K.; Bund, Andreas; Schaaf, Peter; Grieseler, Rolf
Development of the phase composition and the properties of Ti2AlC and Ti3AlC2 MAX-phase thin films - A multilayer approach towards high phase purity. - In: Applied surface science, Bd. 537 (2021), 147864

MAX phase thin films have been synthesized by thermal treatment of a Ti-Al-C multilayer system. The preparation of the multilayer system was carried out via magnetron sputtering. Based on the thickness ratio among the individual nanoscale monolayers (Ti, Al, C), the resulting MAX phase stoichiometry can be controlled. This paper describes the synthesis of both Ti2AlC and Ti3AlC2 MAX phases from the same precursor multilayer system which is composed of a sequence of Ti/Al/C pure elemental single layers with thicknesses of 14, 6, and 3.5 nm, respectively. This sequence is repeated 22 times with a total thickness of around 500 nm. Rapid thermal treatment tests were performed to study the phase development. The Ti2AlC MAX phase forms in a temperature range below 850 ˚C, whereas the Ti3AlC2 MAX phase starts to form at temperatures above 850 ˚C and reaches its highest phase purity at 950 ˚C. The thin film structures were studied by X-ray diffraction and Raman spectroscopy. Furthermore, the electrical and mechanical properties were investigated to gain more insights regarding the phase transformation and their influence on the thin film properties.



https://doi.org/10.1016/j.apsusc.2020.147864
Wang, Dong; Schaaf, Peter
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