Technische Universität Wien

Two-dimensional (2D) layered materials such as transition metal dichalcogenides (e.g., MoS₂, WS₂) and MXenes (e.g., Ti₃C₂T_x), as well as hybrids of these materials are the focus of current research in solid lubrication due to their outstanding performance.Transition metal carbo-chalcogenides (TMCCs), consisting of an MXene core and a TMD-like surface, represent an inherent combination of TMDs and MXenes without the need to construct hybrids out of the individual layers.Due to their layered structure and surface chem., favorable tribol. properties can be expected from these novel materials.Here, multilayer Ta₂S₂C and Nb₂S₂C TMCCs are deposited solely as a powder onto a steel substrate and their tribol. properties under linear sliding against different counterbodies, i.e., Al₂O₃, SiC, 100Cr6, and polytetrafluoroethylene (PTFE) are discussed.Advanced materials characterization techniques are used to detect the presence of TMCCs inside the wear tracks and to reveal their 2D structure within the tribofilm.Finally, d. functional theory (DFT) simulations are used to unravel the easy shearability of TMCCs at the nanoscale.The results demonstrate the great potential of this new 2D material family, which also offers many possibilities for defined tuning of the solid-solid interface.

The shift to renewable energy sources increases the demand for energy storage to balance supply and demand.The call for heat storage solutions is particularly high with heat dominating residential energy needs.Simultaneously, significant industrial waste heat potential could be seasonally stored in reversible chem. reactions using thermochem. energy storage technologies.This study investigates the reversible dehydration of calcium chloride dihydrate which has been recognized as a suitable thermochem. material in prior studies.A new method is introduced by investigating the reaction in a lab-scale batch-type suspension reactor.In the reactor, a mech. stirrer suspends the solid thermochem. material in an inert liquid, to prevent agglomeration of the particles.The investigation involves a parameter variation that includes different suspension media, different mass fractions of the solid reactant, as well as different system pressures during charging.The exptl. investigation renders 40 wt% solid or lower as the most promising mass fraction to avoid agglomeration.Vegetable oils show promising results as suspension media.However, they lack thermal stability in the temperature range of up to 210°C.Mineral oil can ensure thermal and cycle stability.Furthermore, a notable reduction in the dehydration reaction temperatures (176 to 109°C) is observed when the system pressure is decreased down to 50 mbar.The study concludes that calcium chloride dihydrate has the potential to be used for 22 stable charging and discharging cycles in a mineral oil suspension and that lowering the system pressure can reduce the required charging temperature of the system.To further enhance the suspension method, it is essential to focus on mass transfer and foam mitigation during the dehydration reaction.

Objective. Microdosimetry is gaining increasing interest in particle therapy. Thanks to the advancements in microdosimeter technologies and the increasing number of experimental studies carried out in hadron therapy frameworks, it is proving to be a reliable experimental technique for radiation quality characterisation, quality assurance, and radiobiology studies. However, considering the variety of detectors used for microdosimetry, it is important to ensure the consistency of microdosimetric results measured with different types of microdosimeters. Approach. This work presents a novel multi-thickness microdosimeter and a methodology to characterise the radiation quality of a clinical carbon-ion beam. The novel device is a diamond detector made of three sensitive volumes (SVs) of different thicknesses: 2, 6 and 12 µm. The SVs, which operate simultaneously, were accurately aligned and laterally positioned within 3 mm. This alignment allowed for a comparison of the results with a negligible impact of the SVs alignment and their lateral positioning, ensuring the homogeneity of the measured radiation quality. An experimental campaign was carried out at MedAustron using a carbon-ion beam of typical clinical energy (284.7 MeV u−1). Main results. The measurement results allowed for a meticulous interpretation of its radiation quality, highlighting the effect of the SV thickness. The consistency of the microdosimetric spectra measured by detectors of different thicknesses is discussed by critically analysing the spectra and the differences observed. Significance. The methodology presented will be highly valuable for future experiments investigating the effects of the target volume size in radiobiology and could be easily adapted to the other particles employed in hadron therapy for clinical (i.e. protons) and for research purposes (e.g. helium, lithium and oxygen ions).