Technische Universität Wien

High-performance thermoelectric (TE) materials near room temperature are crucial for cooling and energy harvesting applications. This study reports the outstanding thermoelectric performance of p-type Mn-doped Fe₂VAl Heusler alloy thin films, specifically Fe₂V_0.8Mn_0.2Al, prepared using magnetron sputtering. These films were deposited on insulating oxide substrates to eliminate any spurious contributions from the substrate. Large p-type Seebeck coefficients (S) have been observed for all films, revealing a maximum power factor of 4.26 mWK^-2m^-1 at 300 K. This study revealed thickness-dependent thermoelectric properties, with the highest power factor achieved in the 500 nm film. Films with d = 300 nm and 500 nm exhibit weak ferromagnetism. Hall resistivity measurements evidence an anomalous Hall effect (AHE) for the 300 nm and 500 nm samples. The AHE is strongest for the 500 nm film, consistent with a magnetic enhancement of the Seebeck coefficient and power factor. Additionally, we synthesized Al-rich p-type Fe₂V_0.9Mn_0.1Al_1.5 thin films at room temperature, 200°C, 400°C, and 600°C. The film deposited at 600°C exhibits an exceptional figure of merit ZT _appr ~0.8 and a power factor of 6.7 mW·K^-2·m^-1 at room temperature, which are respectively, 4 times and 1.5 times larger than the best values ever reported for any bulk or thin film p-type Fe₂VAl-based material.

To evaluate the influence of the nature of silane coupling agents on the consistency of dental composites at various temperatures.

Silanes SI 1-4 were synthesized in one single step. They were characterized by ¹H and ¹³C NMR spectroscopy. SI 1-4, as well as 3-methacryloyloxypropyltrimethoxysilane (MPTS), 8-methacryloyloxyoctyltrimethoxysilane (MOTS) and n-dodecyltrimethoxysilane were then used to functionalize a barium aluminum borosilicate glass filler (d₅₀ = 1.0 µm). Silanizations were carried out in cyclohexane in the presence of a catalytic amount of n-propylamine. Each silane was used in an equimolar amount. Composites containing 67 wt% of silanized fillers and packable composites exhibiting a similar consistency at room temperature were subsequently formulated. The consistency of the uncured composites was determined at various temperatures (23 °C, 30 °C, 50 °C and 60 °C) using a texture analyzer. The flexural strength and modulus of the cured composites were assessed according to ISO 4049.

The structure of the silane was shown to strongly influence the consistency of composites. The spacer length between silyl and methacrylate groups, as well as the presence of a urea or a urethane moiety, were demonstrated to be key parameters. Heating of each composite resulted in a drop of the consistency. The decrease was however significantly stronger if coupling agents with long spacers were selected. Especially, the use of SI 3 provided a packable composite which exhibited a packable consistency at 30 °C and flowable consistency at 60 °C. Regarding mechanical properties, it was shown that the coupling agent must be able to copolymerize with the monomers of the organic matrix to obtain high flexural strength and modulus values. The silanization of glass fillers using silanes bearing a long spacer was shown to have an additional advantage: packable composites having a higher filler content, and consequently improved flexural modulus, can be formulated.

The use of filler particles functionalized with silanes containing long alkyl spacers between the silyl and methacrylate moiety is a promising strategy for the development of packable dental composites which exhibit good mechanical properties and a strong drop in consistency upon heating.

This study examines public waste, meaning solid waste generated "on the go" in public spaces such as streets, parks and plazas. Despite containing a high proportion of recyclable materials, this waste stream is frequently overlooked in both academic research and circular waste management strategies. Using Vienna, Austria, as a case study, the research employs Material Flow Analysis (MFA) to systematically assess public waste flows and evaluate five alternative management scenarios. The scenarios include strategies such as enhanced source separation and advanced automated sorting of residual waste, aiming to enhance circular material use in public space. Waste flows were analyzed in detail across 16 sub-fractions, enabling a highly granular and accurate modelling approach. Although public waste represents only 4.5% of municipal solid household waste in Vienna, it contains a high proportion of recyclable materials (65%), much of which is currently not recovered due to a lack of waste separation (in the status quo less than 3% of recyclables are source-separated). Study results show that scenarios involving advanced residual waste sorting achieve the highest overall material recovery, where over 40% of publicly disposed waste is recovered for recycling. However, if additional factors like the quality of recovered materials are taken into account, the performance difference between separate collection and automated residual waste sorting is expected to diminish. This study provides the first detailed modelling of public waste flows and a robust foundation for evidence-based decision-making and future research on economic and environmental impacts.