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Item type:Publication, Access status: with files , Coupled evaluation of R-curve behaviour and subcritical crack growth: Experimental method and data interpretationThe fracture resistance is a design-relevant and material-specific feature. In ceramic materials, the fracture resistance can increase as a function of the crack length. Such behaviour is beneficial, e.g. in terms of the thermal shock resistance. It is termed R-curve behaviour and reflects the capacity of the material for intrinsic and/or extrinsic toughening during stable crack advance. Another design-relevant material-specific property is the sensitivity towards subcritical crack growth. The latter is a time-dependent phenomenon and commonly estimated by two crack growth parameters. The presented paper aims for a detailed review of sequential fourpoint bending experiments on V-notched beams, which are used to evaluate both phenomena from a single measurement. Three groups of materials (Al2O3, Si3N4, and Lithosil glass) were tested and analysed by this method in order to provide an experimental data background.Publicationtype: Journal Article13 23 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , On the influence of antioxidants and recycled MgO–C source material on the mechanical properties of carbon-bonded magnesia refractories(Wiley, 2026-04-12); ; ; In the present study, the role of recycled source material and the addition of antioxidants to refractory MgO–C material commonly used in the steel industry were addressed from the perspective of fracture mechanics. Initially, the fracture behaviour of the fine grained MgO–C-matrix was assessed by sequential bending experiments (particle sizes <150 μm). Based on this, coarse grained parts with particle sizes up to 7 mm were prepared and characterised in regard to their high-temperature properties, i.e. the refractoriness under load, the thermal expansion behaviour and the Young's modulus as function of the temperature. Four differently designed batches were tested. One batch, consisting of all fresh source materials (MgO and C), served as reference. Furthermore, the additives Al, SiO₂ and TiO₂ were systematically added, and 50% of the source material was replaced by recycled MgO–C from the industry. During the batch production, environmentally friendly fructose, collagen and lignin served as temporary binding agents. It was found that while the addition of recycled MgO–C had a reducing effect on the mechanical properties, the opposite was observed for the addition of antioxidants.Publicationtype: Journal Article11 15 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Area moment of inertia and other physical quantities for special cross-sectional areas of bend specimens(2026-03-04)With regard to materials in nature having extraordinary properties, one focus of our research is nacre-inspired materials. On the basis of 3D-printing, it was possible to prepare tiny bending bars in order to be tested in three-point bending (3PB). However, their cross sections are not rectangular but have a special geometric shape. Therefore, analytical calculations concerning the area moment of inertia and other physical quantities were performed for the correct analysis of the measured data.Publicationtype: Technical Report44 15 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , High-resolution analysis of ordered and disordered isoporous 3D nanostructures using PXCT(Springer, 2026-02-17); ; ; ; Many applications of 3D isoporous (nano)structures rely on the use of liquids flowing through the material. Therefore, a better understanding of the underlying processes and the influence of the structural properties on the fluid flow is of high importance. However, due to the small structure sizes, the analysis of the fluid flow processes is difficult. Using synchrotron radiation-based ptychography X-ray computed tomography (PXCT), ordered and disordered isoporous Al2O3 structures with different nominal pore sizes are investigated and characterized. The detailed, scanned 3D structures are simulated regarding their differences in fluid flow properties. It was found that ordering has only a minor influence on the fluid velocity’s homogeneity compared to the influence of the connection points between the macropores.Publicationtype: Journal Article52 47 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Energy-dependent chemical interface damping induced by 1-decanethiol self-assembled monolayer on Au(111)(Soc., 2026-02-11); ; ; ; The chemical interface damping (CID) effect increases the collision frequency of free electrons in metals by changes to the metal surface. We have now experimentally disentangled the two contributions to CID: induced roughness and direct charge transfer. The latter is an important area of research in photoelectrochemistry with potential applications in light-induced chemical reactions. We present a broadband investigation of the CID effect on Au(111) covered by a self-assembled monolayer of decanethiol. Spectroscopic ellipsometry measurements show a photon-energy-dependent increase of the collision frequency. We observe a constant, photon energy-independent contribution, which is attributed to induced roughness, and a contribution that linearly increases with photon energy from about 1 eV upward, which we attribute to direct charge transfer. The onset of the charge transfer mechanism corresponds to the occupied orbitals of thiols bound to the Au surface, as confirmed by density functional theory calculations.Publicationtype: Journal Article32 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Double-tough and ultra-strong ceramics: leveraging multiscale toughening mechanisms through Bayesian optimization(Elsevier, 2026-01-13); ; ; An optimization-driven approach is presented to create a “double-tough” ceramic. The material features two main toughening mechanisms – crack deflection in a brick-and-mortar microstructure, and transformation toughening in the mortar – and it is engineered to achieve high strength and fracture toughness levels simultaneously. The material design involves high-strength alumina bricks interconnected via a ceria-stabilized zirconia mortar. Given that the design of the optimal material, featuring multiscale toughening mechanisms, typically requires a laborious trial-and-error approach, a Bayesian optimization framework is proposed to streamline and accelerate the experimental campaign. A Gaussian process is used to emulate the material’s mechanical response, and a cost-aware batch Bayesian optimization is implemented to efficiently identify optimal design process parameters, accounting for the cost of experimentally varying them. This approach expedites the optimization of the material’s mechanical properties. As a result, a bio-inspired all-ceramic composite is developed, exhibiting an exceptional balance between bending strength (704MPa) and fracture toughness (13.6MPam<sup>0.5</sup>), along with a stress intensity factor at crack initiation of 6.7MPam<sup>0.5</sup>. The material exhibits significantly higher strength than both nacre-like ceramic composites and transformation-toughened zirconia at comparable toughness levels.Publicationtype: Journal Article22 26 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Die HOOU an der TUHH : Erfahrungen und Erfolge 2025Im Jahr 2025 wurden 9 Projekte im Rahmen der Hamburg Open Online University (HOOU) an der TUHH umgesetzt. Die projektspezifischen Erfahrungen und Erfolge werden in dieser Broschüre zusammenfassend dargestellt.Publicationtype: Text20 15 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Defect migration in supercrystalline nanocomposites(American Chemical Society (ACS), 2025-12-16); ; ; ; Supercrystalline nanocomposites (SCNCs) are nanostructured hybrid materials with a variety of unique functional properties. Given their periodically arranged building blocks, they also offer interesting parallels with crystalline materials. They can be processed in multiple forms and at different scales, and cross-linking their organic ligands via heat treatment leads to a boost of their mechanical properties. This study shows, via X-ray and in situ scanning transmission electron microscopy (STEM) analyses, how each of these processing steps plays a distinct role in the generation, migration, interaction, and healing of supercrystalline defects. Pressing of SCNCs into bulk pellets leads to a distortion of the otherwise fcc superlattice, while emulsion-templated self-assembly yields supraparticles (SPs) with stacking faults and size-dependent symmetries. Heat treatment at the same temperatures as those applied for the organic cross-linking has significant effects on planar defects. Stacking faults migrate and get healed, as also confirmed via molecular dynamics simulations, and intersupercrystalline “grain” boundaries migrate via anisotropic motion of disconnections. These rearrangements of defects at the supercrystalline scale (tens of nanometers) in nanocomposites with high mechanical properties (compressive strength of 100–500 MPa) provide insights into the formation and evolution of ordered assemblies of functionalized nanoparticles.Publicationtype: Journal Article40 13 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Printing photonic-based thermal barrier coatings onto metal alloy(Nature Publishing Group, 2025-12-01); ; ; ; Reflective coatings based on photonic crystals and photonic glasses are usually produced by traditional colloidal self-assembly techniques characterised by limited control over the deposition surface and lengthy processing times. The emergence of Additive Manufacturing combined with Colloidal Assembly (AMCA) has enabled fast and precise deposition of homogeneous photonic structures, whilst circumventing issues such as the undesired coffee-ring effect. However, the application of this technique was limited to flat substrates. This study investigates the AMCA of ceramic-based colloidal structures onto metallic curved surfaces, relevant to the field of thermal barrier coatings (TBCs). Our results demonstrate the homogeneous ceramic-based photonic glass coatings can be AMCA-printed on different substrates only when a conscious surface charge matching between the colloidal particles and the substrates is made. It also demonstrates the importance of controlling the contact angle of the suspension on the substrates and the printing geometry strategy, differing from traditional direct writing. We further demonstrate the versatility of this method by printing highly porous three-dimensional gadolinium zirconate structures onto curved Inconel substrates. These coatings are engineered for their use as reflective “photonic-based” thermal barrier coatings (rTBCs), capable of suppressing both radiative and conductive heat transport. The resultant AMCA-printed Gd2Zr2O7 rTBCs outperform state-of-the-art TBCs in terms of their reflectance properties and provide a reliable thermal protection to the underlying Inconel alloy, lowering its temperature by about 150 °C in a torch experiment.Publicationtype: Journal Article68 23 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Boosting the mechanical strength and photocatalytic activity of 3D-printed titania aerogels by atomic layer deposition and heat treatment(American Chemical Society (ACS), 2025-11-05); ; König, SandraTitania aerogels are highly porous materials optimal for photocatalysis due to their high surface area. Further spatial structuring by 3D printing improves gas diffusion in the aerogel, leading to a higher photocatalytic activity. However, the aerogel’s mechanical properties are reduced in comparison to non-3D printed aerogels. We hereby present an approach based on atomic layer deposition (ALD) of subnanometer-thin TiO2 layers to compensate for that detrimental effect. The ALD-deposited TiO2 consists of amorphous and anatase phase, with the anatase phase likely crystallizing on the aerogel’s crystallites. Nanoindentation measurements confirm that the TiO2 ALD-coatings improve the aerogel’s mechanical properties. Additionally, it enhances the photocatalytic properties of the TiO2 aerogel, which we attribute to the increased interface area and improved interconnection of the nanoparticle network. By further thermal postprocessing, it is possible to fully crystallize the ALD-deposited TiO2, which shows a complementary effect on photocatalytic performance, improving hydrogen evolution rate by more than 1 order of magnitude from 6.35 to 125 μmol g−1 h−1. The combination of 3D structuring of aerogels with ALD coatings demonstrated in this work could be extended in the future to a wide range of materials where the interplay between mechanical and catalytic properties is vital.Publicationtype: Journal Article33 16