Engineering dislocation‐rich plastic zones in ceramics via room‐temperature scratching

In this communication, we demonstrate a simple but powerful method to engineer dislocations into large plastic zones in various single‐crystal ceramic materials via room‐temperature scratching. By using a Brinell indenter with a diameter of 2.5 mm, we successfully produced plastic zones with a width and depth of ∼150 µm in a single scratch track, while the length of the scratch track can be arbitrarily long depending on the sample size. Increasing the number of repetitive scratching cycles increases the dislocation density up to ∼10¹³ m⁻² without visible crack formation. The outlined experimental procedure is showcased on single‐crystal SrTiO₃, MgO, ZnS, and CaF₂ to demonstrate the general applicability of this technique. In light of the increasing research interest in dislocation‐tuned functional and mechanical properties in ceramics, our method will serve as a simple, fast, and robust technique to pave the road for scaling up the required large plastic zones for dislocation engineering in ceramics

Dislocation toughening in single‐crystal KNbO₃

The growing research interest in dislocation‐tuned functionality in ceramics is evident, with the most recent proofs‐of‐concept for enhanced ferroelectric properties, electrical conductivity, and superconductivity via dislocations. In this work, we focus on dislocation‐tuned mechanical properties and demonstrate that, by engineering high dislocation densities (up to 10¹⁴ m⁻²) into KNbO₃ at room temperature, the fracture toughness can be improved by a factor of 2.8. The microstructures, including dislocations and domain walls, are examined by optical microscopy, electron channeling contrast imaging, piezo‐response force microscopy, and transmission electron microscopy methods to shed light on the toughening mechanisms. In addition, high‐temperature (above the Curie temperature of KNbO₃) indentation tests were performed to exclude the influence of ferroelastic toughening, such that the origin of the toughening effect is pinpointed to be dislocations

On the Potential of Multi-objective Automated Algorithm Configuration on Multi-modal Multi-objective Optimisation Problems

The complexity of Multi-Objective (MO) continuous optimisation problems arises from a combination of different characteristics, such as the level of multi-modality. Earlier studies revealed that there is a conflict between solver convergence in objective space and solution set diversity in the decision space, which is especially important in the multi-modal setting. We build on top of this observation and investigate this trade-off in a multi-objective manner by using multi-objective automated algorithm configuration (MO-AAC) on evolutionary multi-objective algorithms (EMOA). Our results show that MO-AAC is able to find configurations that outperform the default configuration as well as configurations found by single-objective AAC in regards to objective space convergence and diversity in decision space, leading to new recommendations for high-performing default settings

Engineering dislocation-rich plastic zones in ceramics via room-temperature scratching

In this communication, we demonstrate a simple but powerful method to engineer dislocations into large plastic zones in various single-crystal ceramic materials via room-temperature scratching. By using a Brinell indenter with a diameter of 2.5 mm, we successfully produced plastic zones with a width and depth of ∼150 μm in a single scratch track, while the length of the scratch track can be arbitrarily long depending on the sample size. Increasing the number of repetitive scratching cycles increases the dislocation density up to ∼1013 m−2 without visible crack formation. The outlined experimental procedure is showcased on single-crystal SrTiO3, MgO, ZnS, and CaF2 to demonstrate the general applicability of this technique. In light of the increasing research interest in dislocation-tuned functional andmechanical properties in ceramics, our method will serve as a simple, fast, and robust technique to pave the road for scaling up the required large plastic zones for dislocation engineering in ceramics

Dislocation toughening in single-crystal KNbO3

The growing research interest in dislocation-tuned functionality in ceramics is evident, with the most recent proofs-of-concept for enhanced ferroelectric properties, electrical conductivity, and superconductivity via dislocations. In this work, we focus on dislocation-tuned mechanical properties and demonstrate that, by engineering high dislocation densities (up to 1014 m−2) into KNbO3 at room temperature, the fracture toughness can be improved by a factor of 2.8. The microstructures, including dislocations and domain walls, are examined by optical microscopy, electron channeling contrast imaging, piezo-response force microscopy, and transmission electron microscopy methods to shed light on the toughening mechanisms. In addition, high-temperature (above the Curie temperature of KNbO3) indentation tests were performed to exclude the influence of ferroelastic toughening, such that the origin of the toughening effect is pinpointed to be dislocations

Schulinspektion als Steuerungsimpuls? Ergebnisse aus Forschungsprojekten

Böhm-Kasper O, Brüsemeister T, Dietrich F, et al., eds. Schulinspektion als Steuerungsimpuls? Ergebnisse aus Forschungsprojekten. Educational Governance. Vol 25. Wiesbaden: Springer VS; 2016

Schulinspektion als Steuerungsimpuls zur Schulentwicklung und seine Realisierungsbedingungen auf einzelschulischer Ebene – Ergebnisse eines triangulativ orientierten Verbundprojekts

Böhm-Kasper O, Brüsemeister T, Dietrich F, et al. Schulinspektion als Steuerungsimpuls zur Schulentwicklung und seine Realisierungsbedingungen auf einzelschulischer Ebene – Ergebnisse eines triangulativ orientierten Verbundprojekts. In: Bundesministerium für Bildung und Forschung, ed. Steuerung im Bildungssystem. Implementation und Wirkung neuer Steuerungsinstrumente im Schulwesen. Bildungsforschung. Vol 43. 2016: 110-136