Centre of Excellence NAMASTE

Achieving macroscale superlubricity with engineering materials is highly desirable for energy conservation, environmental benefits, and longevity of mechanical components. However, attaining superlubricity in aqueous‐lubricated systems with enhanced load‐bearing capacity remains challenging in metallic materials. Herein, nitrogen‐doped graphene quantum dots (NGQDs) as a nano‐additive in aqueous glycerol facilitate macroscale superlubricity between friction pairs of steel and silicon‐doped hydrogenated amorphous carbon (a‐C:H:Si). Superlubricity is observed in boundary‐lubrication regime with a friction coefficient of 0.0055–0.0097 under various sliding conditions. Notably, the wear of the steel counterface (k = 8.51 × 10−9 mm3/Nm) decreased by 47.8%, resulting in a final contact pressure of 206.7 MPa, which exceeds values reported for aqueous‐lubricated systems during superlubricity. The lubrication mechanism reveals that NGQDs' adsorption on the steel‐worn surface, coupled with the tribocatalytic generation of FeNxCy moieties on a‐C:H:Si surface, is crucial for reducing friction. These FeNxCy moieties, with a multitude of active sites, facilitate the subsequent anionic adsorption of pyrrolic‐rich NGQDs. Simultaneously, the formation of amorphous graphitic film, driven by continuous shearing and exfoliation of graphene sheets within the adsorbed NGQDs, contributes to the stability of superlubricity. These findings provide insights into the functional characteristics of NGQDs for achieving superlubricity in aqueous‐lubricated systems, paving the way for future energy‐saving applications.

We present experiments on Slovenian, Croatian and Serbian morphosyntactic annotation and lemmatisation between the former state-of-the-art for these three languages and one of the best performing systems at the CoNLL 2018 shared task, the Stanford NLP neural pipeline. Our experiments show significant improvements in morphosyntactic annotation, especially on categories where either semantic knowledge is needed, available through word embeddings, or where long-range dependencies have to be modelled. On the other hand, on the task of lemmatisation no improvements are obtained with the neural solution, mostly due to the heavy dependence of the task on the lookup in an external lexicon, but also due to obvious room for improvements in the Stanford NLP pipeline’s lemmatisation.

Although the link between the inhalation of nanoparticles and cardiovascular disease is well established, the causal pathway between nanoparticle exposure and increased activity of blood coagulation factors remains unexplained. To initiate coagulation tissue factor bearing epithelial cell membranes should be exposed to blood, on the other side of the less than a micrometre thin air-blood barrier. For the inhaled nanoparticles to promote coagulation, they need to bind lung epithelial-cell membrane parts and relocate them into the blood. To assess this hypothesis, we use advanced microscopy and spectroscopy techniques to show that the nanoparticles wrap themselves with epithelial-cell membranes, leading to the membrane’s disruption. The membrane-wrapped nanoparticles are then observed to freely diffuse across the damaged epithelial cell layer relocating epithelial cell membrane parts over the epithelial layer. Proteomic analysis of the protein content in the nanoparticles wraps/corona finally reveals the presence of the coagulation-initiating factors, supporting the proposed causal link between the inhalation of nanoparticles and cardiovascular disease.

PurposeIn this contribution, the design and integration of a piezoelectric vibrating device into low-temperature, co-fired ceramic (LTCC) structures are presented and discussed. The mechanical vibration of the diaphragm was stimulated with a piezoelectric actuator, which was integrated onto the diaphragm. Three different methods for the integration were designed, fabricated and evaluated.Design/methodology/approachThe vibrating devices were designed as an edge-clamped diaphragm with an integrated piezoelectric actuator at its centre, whose role is to stimulate the vibration of the diaphragm via the converse piezoelectric effect. The design and feasibility study of the vibrating devices was supported by analytical methods and finite-element analyses.FindingsThe benchmarking of the ceramic vibrating devices showed that the thick-film piezoelectric actuator responds weakly in comparison with both the bulk actuators. On the other hand, the thick-film actuator has the lowest dissipation factor and it generates the largest displacement of the diaphragm with the lowest driving voltage. The resonance frequency of the vibrating device with the thick-film actuator is the most sensitive for an applied load (i.e. mass or pressure).Research limitations/implicationsResearch activity includes the design and the fabrication of a piezoelectric vibrating device in the LTCC structure. The research work on the piezoelectric properties of integrated piezoelectric actuators was limited.Practical implicationsPiezoelectric vibrating devices were used as pressure sensors.Originality/valuePiezoelectric vibrating devices could be used not only for pressure sensors but also for other type of sensors and detectors and for microbalances.

The phase evolution, microstructure, and electrical properties of WO 3 ‐doped ZnO–Bi 2 O 3 ‐based varistors were investigated for different amounts x (0 ≤ x ≤ 1.60 mol%) of the dopant. When x was less than 0.40, the dissolved W 6+ in the β‐Bi 2 O 3 acted as a donor in the grain boundaries and reduced the electrical properties of the ZnO varistors. However, when x was 0.40 mol%, which meant an amount of WO 3 equal to that of Bi 2 O 3 , the electrical properties dramatically increased, which means the W 6+ donor effect is removed at the grain boundaries because a new Bi 2 WO 6 phase was formed in the grain‐boundary regions. The Bi 2 WO 6 phase has high oxygen conductivity at high temperatures; it transfers more oxygen to the grain boundaries in order to further enhance the electrical properties. For x values higher than 0.40 (i.e., an addition of WO 3 that is greater than the content of Bi 2 O 3 ), the electrical properties were steadily reduced in comparison to the composition with x = 0.40. This could be explained by the reduced amount of Co, Mn, and Al at the grain boundaries and in the ZnO grains as a result of their incorporation into the ZnWO 4 phase. The electrical properties of the ZnO grains and the grain boundaries were in agreement with the results of the impedance spectroscopy analysis.

Phase‐pure K 0.5 Na 0.5 NbO 3 ( KNN ) fine powders were synthesized via a solid‐state route from a homogeneous solid mixture. A colloidal dispersion comprising a mixed ethanol solution of potassium and sodium acetates and Nb 2 O 5 fine particles was attrition milled and dried carefully to avoid water absorption. Two‐step calcination in air at 450°C and 625°C, each for 3 h, resulted in the phase‐pure KNN powders. The volume‐based median diameter of the final product was ca. 0.8 μm. Starting from the same precursors without dissolving the acetates, the phase‐pure KNN was never achieved even when the two calcination temperatures were increased to 550°C and 700°C, in spite of the same milling conditions. Key issues of eliminating second phases were (i) starting from a wet‐milled mixture with a single solution containing both of the A‐site species, and (ii) repeated wet milling of the reaction mixture to disintegrate reaction‐induced agglomerates. These enabled rapid nuclei growth from chemically interacted precursor prior to calcination, and short diffusion path due to repeated deagglomeration, excluding formation of off‐stoichiometric second phases. All these items were confirmed by different analytical tools, among others, thermo‐gravimetry and differential thermal analysis (TG‐DTA), particle size analyses, and XPS at various reaction stages. On the heating stage microscope, a shrinkage onset was observed at 850°C, that is, 150 K lower than that of conventionally prepared KNN , that is, via a solid‐state synthesis from carbonates by a two‐step calcination at 800°C and 750°C, for 4 h each. No second phase was observed after sintering up to 1100°C.