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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 49 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , 2D photonic crystal emitter at 1,400°C for thermophotovoltaic energy harvesting(Elsevier, 2025-10-15); ; ; ; Spectrally selective emitters that endure extreme temperatures (exceeding 1,000°C) are vital for thermophotovoltaic energy harvesting. Here, we report a 2D photonic crystal emitter composed of yttria-stabilized zirconia particles on a tungsten mirror, fabricated through a simple and scalable self-assembly process. The emitter demonstrates spectral stability for 2 h and structural stability for 14 h at 1,400°C under high vacuum, with degradation attributed to zirconium nitridation, which is avoided under Ar or forming gas atmospheres. Long-term durability is demonstrated over 6 months and 200 thermal cycles at 1,050°C, effectively mitigating tungsten oxidation. The emitter achieves 52% spectral efficiency for a 0.72 eV photovoltaic band gap. This work offers perspectives on designing and implementing spectrally selective emitters that remain stable at high temperatures and resilient in harsh environments, representing a significant step forward in developing robust thermophotovoltaic energy-harvesting systems.Publicationtype: Journal Article22 29 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Multi-scale structural characterization of ceramic-based photonic glasses for structural colors(2024-12-01); ; ; ; Structural colors arise from selective light interaction with (nano)structures, which give them advantages over pigmented colors such as resistance to fading and possibility to be fabricated out of traditional low-cost and non-toxic materials. Since the color arises from the photonic (nano)structures, different structural features can impact their photonic response and thus, their color. Therefore, the detailed characterization of their structural features is crucial for further improvement of structural colors. In this work, we present a detailed multi-scale structural characterization of ceramic-based photonic glasses by using a combination of high-resolution ptychographic X-ray computed tomography and small angle X-ray scattering. Our results uncover the structure-processing-properties’ relationships of such nanoparticles-based photonic glasses and point out to the need of a review of the structural features used in simulation models concomitantly with the need for further investigations by experimentalists, where we point out exactly which structural features need to be improved.Publicationtype: Journal Article21 53 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Colloidal self-assembly – from controlled deposition to structural colorsPublicationtype: Doctoral Thesis41 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Tailoring disorder and quality of photonic glass templates for structural coloration by particle charge interactions(American Chemical Society (ACS), 2021-04-20); ; ; ; To obtain high-quality homogeneous photonic glass-based structural color films over large areas, it is essential to precisely control the degree of disorder of the spherical particles used and reduce the crack density within the films as much as possible. To tailor the disorder and quality of photonic glasses, a heteroaggregation-based process was developed by employing two oppositely charged equal-sized polystyrene (PS) particle types. The influence of the particle size ratio on the extent of heteroaggregation in the suspension mixes is investigated and correlated with both the morphology and the resultant optical properties of the films. The results show that the oppositely charged particle size ratio within the mix greatly influences the assembled structure in the films, affecting their roughness, crack density, and the coffee-ring formation. To better differentiate the morphology of the films, scanning electron microscopy images of the microstructures were classified by a supervised training of a deep convolutional neural network model to find distinctions that are inaccessible by conventional image analysis methods. Selected compositions were then infiltrated with TiO2 via atomic layer deposition, and after removal of the PS spheres, surfacelated inverse photonic glasses were obtained. Different color impressions and optical properties were obtained depending on the heteroaggregation level and thus the quality of the resultant films. The best results regarding the stability of the films and suppression of coffee-ring formation are obtained with a 35 wt % positively charged over negatively charged particle mix, which yielded enhanced structural coloration associated with improved film quality, tailored by the heteroaggregation fabrication process.Publicationtype: Journal ArticleScopus© Citations 7 127 576 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , A combined compression and indentation study of mechanical metamaterials based on inverse opal coatings(Elsevier, 2020-05-12); ; ; A relatively new class of tailored photonic metamaterials based on the inverse opal (IO) structure shows multifunctionality with exceptional mechanical response due to its periodic porous arch-like structure. Exploiting the smaller is stronger paradigm through varying its pore size and the addition of atomic layer deposition (ALD) films, allow tailorable strength and elastic modulus. Quantification of such properties are achieved through flat punch nanoindentation testing. Results are validated by comparison to microcompression tests, a widely used technique to circumvent the complex stress state normally imposed by indentation, but in the case of high porosity is greatly simplified, approximating uniaxial stress; results from both mechanical loading approaches show strong similarities. All results showed a dependence of strength and elastic modulus on the ratio of the deformation size, i.e., micropillar or flat punch diameter, to the pore size, a trend which is well described by the influence of the boundary conditions of the test method rather than an intrinsic size effect. At larger ratios the values approach a constant value. Furthermore, the mechanical response can be tailored through the deposition of a thin film on the shell structure of the silica IO structures; 34 nm of TiO2 was shown to produce a 10-fold increase in strength and 5-fold increase in elastic modulus.Publicationtype: Journal ArticleScopus© Citations 9 249 292 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , YSZ Hollow Sphere Photonic Glasses: Tailoring Optical Properties for Highly Saturated Non-Iridescent Structural Coloration(2019-09-01); ; ; ; Non-iridescent structural colors can be obtained by the disordered arrangement of monodisperse spheres, a so-called photonic glass (PhG), in which the structure is designed to reflect or transmit light at specific wavelengths depending on the desired color. PhGs are possible alternatives for conventional pigments due to their wide viewing angle, stability against photobleaching, and environment-friendly fabrication. However, structural colors generated by common full-sphere PhGs reported in the literature show only low saturation. The recently developed PhG structure based on yttria-stabilized zirconia (YSZ) hollow spheres displays highly saturated blue structural color for tailored parameters. In this case, structural color originates from a sharp transition in the reflection spectrum generated by the specific design of the YSZ hollow sphere PhG fabricated via co-deposition. Here, a systematic study of the parameters resulting in highly saturated structural color, namely YSZ shell thickness, pore size, and film thickness, is presented. This work shows that by tailoring these parameters, the sharpness, spectral position, and reflectance of the transition can be tuned individually. Based on the gained knowledge, YSZ hollow sphere PhG with tailored optical properties can be easily fabricated.Publicationtype: Journal Article177 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Advancing the fabrication of YSZ-inverse photonic glasses for broadband omnidirectional reflector filmsA single-step and all-colloidal deposition method to fabricate yttrium-stabilized zirconia (YSZ)-inverse photonic glasses with 3 μm pores was developed. The process is based on electrostatic attraction and repulsion in suspension, controlled by surface charge of polystyrene (PS)microspheres and YSZ nanoparticles, used as pore templates and matrix material, respectively. The pH was used as a tool to change surface charges and particle-particle interactions. Photonic glass films with 3 μm pores yielded broadband omnidirectional reflection over the wavelengths of 1–5 μm, relevant for thermal radiation at temperatures around 1200 °C. These highly porous materials maintained their structural stability and reflectance after being annealed at 1200 °C for 120 h.Publicationtype: Journal ArticleScopus© Citations 9 820 475 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Highly selective photonic glass filter for saturated blue structural color(2019-04-02); ; ; ; Angle independent non-absorbing spectral filters are required for many applications such as sunscreens, structural colors, photovoltaics, and radiative cooling. One of the promising and simple to manufacture structures is based on the disordered arrangement of monodisperse spherical particles by self-assembly, also called photonic glasses. So far, reported photonic glasses inherently show poor spectral selectivity with a smooth transition in reflection. No significant improvement is usually expected from particles optimization as the Mie resonances are broad for small dielectric particles with a moderate refractive index. Via Fourier space engineering, we show here that it is, nonetheless, possible to obtain sharp spectral transitions from the synergetic effect of a core-shell geometry of the particles with the short range order of the photonic glass. We apply the developed approach to demonstrate a high color saturation of a non-iridescent blue structural color employing a photonic glass with hollow sphere particles, which features a sharp spectral transition in reflection. The experimental results support the theoretical predictions from the first-order approximation. © 2019 Author(s).Publicationtype: Journal ArticleScopus© Citations 18 339 348