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Item type:Publication, Access status: with files , Scalable fabrication and mechanical behaviour of hierarchical porous nickel networksAs the demand for light-weight structural and functional materials grows, the fabrication of hierarchical, high-performance micro- and nano-architectures becomes increasingly important. Here, we present a scalable alloying–dealloying strategy to fabricate porous metal with two- and three-level hierarchical networks (2 L-/3L-HN). By exploiting the vapour pressure difference between Ni and Zn, vapour phase alloying of Ni foam with Zn, followed by vapour phase dealloying of the resulting γ-Zn84Ni16 foam, generates a second hierarchical level, producing 2L-HN Ni or 2L-HN β-Zn50Ni50. Re-alloying 2L-HN β-Zn50Ni50 to 2L-HN γ-Zn84Ni16 via vapour phase alloying while preserving its hierarchical architecture enables chemical dealloying to create a third level of hierarchy at the nanoscale, producing 3L-HN Ni with significantly increased specific surface area. A novel scaling law is proposed to predict the mechanical properties of these hierarchical porous metallic networks as a function of solid fraction, and its validity is supported by compression tests on 2L-HN Ni with varying densities. This work establishes a scalable and versatile route for fabricating multiscale porous metallic networks with light-weight, tunable mechanical performance and high surface area.Publicationtype: Journal Article25 13 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Investigations on the role of support and synthesis procedure for the Rux–Cuy/CNT‐catalysed hydrogenolysis of glycerol to 1,2‐propanediol(Wiley, 2026-07-14); ; ; Tailoring support effects plays an important role for controlling activity and selectivity in heterogeneously catalyzed gas–liquid reactions. Sophisticated carbon supports like single‐ and multiwall carbon nanotubes (CNTs) as well as in house produced Globugraphite were used for the synthesis of bimetallic Ru–Cu catalysts, which were tested in a multibatch reactor setup for the chemical hydrogenolysis of glycerol to 1,2‐propanediol (1,2‐PDO) in aqueous solution. In‐depth characterization using multiple tools like inductively coupled plasma optical emission spectrometry, CHNS‐O analysis, N₂‐physisorption, scanning electron microscopy, transmission electron microscopy, energy‐dispersive X‐ray spectroscopy, powder X‐ray diffraction, H₂‐temperature programmed reduction, laser diffraction, and point of zero charge measurements revealed the dominating effects that the various carbon supports exert on the catalytic performance. The best‐performing catalyst synthesized by wetness impregnation consisted of Ru–Cu₃ nanoparticles (NPs) from mixed RuCl₃ and Cu(NO₃)₂ precursors dispersed on multiwall CNT Baytubes with a productivity of p = 12.74 g₁,₂‐PDO gactive metal ⁻¹ h⁻¹ . Its superior activity combined with high 1,2‐PDO selectivity (S= 75%) can be explained both by the nature of the highly dispersed Ru and Cu NPs showing the lowest reduction peak temperature on entangled tubes of CNT agglomerates demonstrating a high mesopore volume for optimal reactant accessibility and the highest specific surface area of all investigated materials. This lays the foundation for implementing this highly active and selective catalyst in a future SMART reactor for glycerol valorisation.Publicationtype: Journal Article57 40 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Decoupling geometry and surface chemistry in 3D-printed ALD-functionalized porous ceramic channels(American Chemical Society (ACS), 2026-06-29); ; ; Minna, FortuneCapillary-driven transport is traditionally attributed to the static pore geometry and wettability. However, the time-dependent surface energy of metal oxides, amplified by the high surface area of porous media, remains a key yet underexplored aspect. This study introduces a novel manufacturing route capable of decoupling macroscopic geometry from surface chemistry by integrating additive manufacturing combined with colloidal assembly (AMCA) and functionalization by atomic layer deposition (ALD). This approach enables the fabrication of highly porous aluminum(III) oxide (Al2O3) and titanium dioxide (TiO2) ceramic channels after thermal burn-out. Within these structures, the structural and chemical properties are tuned and investigated. Spontaneous imbibition experiments at 0, 6, and 24 h after burn-out reveal a transition from a classical Lucas−Washburn rise to a resistance-limited regime dominated by evaporation and viscous drag. Time-resolved contact-angle measurements revealed that both oxides become superhydrophilic after burn-out and undergo subsequent hydrophobic recovery. Despite TiO2 being intrinsically more hydrophilic, Al2O3 channels consistently exhibited faster imbibition rates and a higher liquid rise. This behavior is attributed to the rapid surface relaxation of Al2O3, which reduces contact-line friction and minimizes pinning at high-energy adsorption sites, thereby enhancing fluid uptake. Macroscopic geometrical variations in printed channels did not affect the imbibition height but scaled linearly with imbibed volume, confirming the successful decoupling of geometric and chemical transport factors. The excellent structural reproducibility of the AMCA-ALD method establishes it as a robust manufacturing platform for programmable capillary transport. This approach provides a general pathway to design porous ceramics with independently engineered geometries and surface chemistries for applications in microfluidics, diagnostics, and catalysis.Publicationtype: Journal Article28 46 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Universal and scalable fabrication of plasmonic nanocrystals for ultrasensitive SERS(ACS, 2026-05-10); ; ; 18 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Functional vanadium oxide nanostructures fabricated via atomic layer deposition: a review(Elsevier, 2026-05-05); ; ; ; Vanadium oxide nanostructures have emerged as a promising material system for a wide range of applications based on their structural, electronic, optical, and catalytic properties. The multiple phases of vanadium oxides, e.g., V2O3, VO2, and V2O5, feature distinct crystal structures and properties which contribute to their versatility. There are several methods to fabricate vanadium oxide nanostructures such as sol-gel synthesis, hydrothermal methods, physical vapor deposition, sputter deposition, chemical vapor deposition, atomic layer deposition (ALD), and solid-state reactions. From those techniques, ALD offers precise control over the conformality, thickness, and composition of thin films leading to unique possibilities for the functionalization of previously prepared nanostructured templates with vanadium oxides. This review summarizes recent advancements in the synthesis of ALD-based vanadium oxide nanostructures focusing on suitable ALD precursors, ALD process conditions, and required post-deposition thermal annealing treatments to transform the as-deposited vanadium oxide films to distinguished crystalline phases. The functional properties of ALD-based vanadium oxide nanostructures in catalysis, electrochemical energy storage, sensors, and stimuli-responsive “smart” devices are presented. Moreover, existing challenges in fabrication and practical application are discussed. Finally, future perspectives on tailoring the properties of ALD-based vanadium oxide nanostructures by adjusting templates, optimizing the vanadium oxide film thickness, or utilizing supercycle ALD processes are outlined, which can pave the way for sustainable applications and “smart” devices.Publicationtype: Review Article49 55 - 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 Article53 48 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , High-resolution electron microscopic investigations on the fatigue behaviour of ultra-high-performance concrete and modelling with bonded-particle model(Springer, 2026); ; ; ; Given the increasing demand for sustainable and lightweight concrete structures, the application of ultra-high-performance concrete (UHPC) has gained significant relevance. However, in contrast to static loading conditions, cyclic loads are more prevalent in real-world scenarios. Despite the superior mechanical properties of UHPC, it may exhibit a different resistance to cyclic loading. Consequently, this study focuses on both experimental and numerical analyses to investigate the primary mechanisms responsible for crack initiation at the meso-, micro-, and nanoscale. Following mechanical fatigue testing, microstructural alterations were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). To extend these findings to the mesoscale, a novel rheological model was developed. The results suggest that fatigue damage originates from nanoscale transformations of ettringite, combined with a densification of the cementitious matrix. Moreover, an increased content of unhydrated cement clinker within the matrix enhances fatigue resistance. At the mesoscale, stress concentrations around aggregate particles intensify with increasing load cycles, propagating into the binder matrix and contributing to further material degradation.Publicationtype: Book Part17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Einfluss der Art grober Gesteinskörnung auf Struktur und Eigenschaften von ultrahochfestem Beton - Abschlussbericht in LangfassungThe addition of coarse aggregate is one possibility to lower the cement content of ultra-high strength concrete (UHPC). Within the research project an UHPC with a maximum grain size of 0.5 mm was varied with 30 vol.-% of coarse aggregate, with a grain size of 5-8 mm. 16 different rock types were added to the fine-grained reference mixture. The rock types cover most of the high strength rocks available in Germany. The rock and the UHPC specimens were examined under different aspects. Both the mechanical behaviour, as the structural and chemical properties were determined. As the main results it can be stated, that not only basalt, but a lot of rock types can be used to produce UHPC, even if the addition of coarse aggregates decrease the strength of all specimens in comparison to the original mixture. Basalt and other fine-grained vulcanic rocks are useful, but also coarse-grained plutonic granite and metamorphic granulite and gneiss. Also with dense sedimentary limestone (Massenkalk), UHPC can be produced. Coarse-grained metamorphic marble, sandstone (also with very high strength), and the sandstone-like greywacke, and metamorphic amphibolite were not successful. Dolomite and the examined quarzite resulted in somehow inconsistent strength values. There is a strong linear correlation of the rock and the UHPC compressive strength. There is no threshod value of the rock strength, resulting in a decrease of the UHPC strength, but the lower the rock strength, the lower is the UHPC strength. A correlation between the typical grain size of the rock and the UHPC strength is not visible. In no case, also with very high spatial analytical resolution, a chemical reaction was visible between the minerals of the rocks and the cement matrix. It seems, that the UHPC ist too dry, after short time, to get chemical reactions between the rock grains and the binder matrix. All rock types were very well embedded in the cement matrix. They are great differences in the coarseness of the grain surfaces. Together with differences in the porosity of the rocks this resulted in effects on UHPC workability.Publicationtype: Report36 9 - 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 Article43 15 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , High-temperature He+ Irradiation of Low-iron-bearing olivine: laboratory simulations of space weathering on Mercury(IOP Publishing, 2025-11-01); ; ; ; Das, Swarna PravaThe surface of Mercury is highly space weathered, and the products of space weathering are different than on the Moon. Here we simulate the interaction of solar wind ions with the surface of Mercury by implanting low-iron-bearing (∼3 wt% Fe) olivine slices with 4 keV He⁺ ions both under ambient conditions and at 450 °C during the irradiation. The sample irradiated under ambient conditions shows a ∼140 nm thick partially amorphous layer on top of the grain with high concentrations of bubbles and cavities. However, the sample irradiated at 450 °C has a 110-140 nm thick polycrystalline layer with 1-5 nm sized nanoparticles of metallic iron and no bubbles or cavities. Mg atoms are preferentially sputtered from the ion-damaged layer present on the sample irradiated under ambient conditions, but no difference in composition is seen between the crystalline olivine and the ion-damaged layer in the sample irradiated at 450 °C. In addition, a thin amorphous film deposited on a micro-electromechanical systems-based chip is heated up to 1200 °C in situ inside a transmission electron microscope for a few milliseconds, and it produced nanoparticles of size 5-30 nm. Our results show that solar wind irradiation of low-iron-bearing olivine in the equatorial regions of Mercury will produce nanoparticles of iron whose sizes will be larger than that on the surface of the Moon and that the size will further increase during impacts of dust particles. Solar-wind-implanted He can diffuse out of regolith grains and can be a source of He observed in the exosphere of Mercury.Publicationtype: Journal Article19 8