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Item type:Publication, Access status: with files , Interphase-engineering by atomic layer deposition of nacre-inspired alumina composites(Elsevier, 2026-01-03); ; ; ; Nacre, also known as mother of pearl, is a layered brick-and-mortar structure composed of hard mineral platelets and soft organic protein. Found in the inner shells of certain mollusks, this natural architecture has evolved to optimize mechanical properties for the protection of the organism. The unique structured design of nacre and its exceptional mechanical performance have inspired the development of synthetic nacre-like materials. In this work, we introduce a novel approach for fabricating nacre-inspired ceramic composites using atomic layer deposition (ALD) to engineer the interphase, or “mortar”, between aligned alumina platelets. ALD, known for its sub-nanometer thickness control and conformal coating capabilities, enables uniform tuning of the interphase thickness from 30 nm up to 120 nm, offering a significant advantage in tailoring the mechanical properties of ceramic-ceramic composites. Our results reveal a direct correlation between ALD-deposited aluminum oxide thickness and enhanced mechanical performance, with increased modulus and hardness observed as the mortar thickens. Three-point bending tests further show that flexural strength is maximized with thicker ALD coatings . In situ micromechanical testing reveals crack initiation at surface defects in micro-cantilevers, with cracks effectively deflected by the nacre-inspired architecture. This resultsin an average flexural strength of approximately 400 MPa, achieved without additional heat treatment or sintering. The precision of ALD in creating conformal interphases is critical to the improved structural integrity and performance of the composite, demonstrating its potential asa powerful technique for fabricating high-performance, bio-inspired ceramic composites.Publicationtype: Journal Article40 18 - 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 , Switchable 3D Photonic Crystals Based on the Insulator-to-Metal Transition in VO2(American Chemical Society (ACS), 2024-12-11); ; ; Photonic crystals (PhCs) are optical structures characterized by the spatial modulation of the dielectric function, which results in the formation of a photonic band gap (PBG) in the frequency spectrum. This PBG blocks the propagation of light, enabling filtering, confinement, and manipulation of light. Most of the research in this field has concentrated on static PhCs, which have fixed structural and material parameters, leading to a constant PBG. However, the growing demand for adaptive photonic devices has led to an increased interest in switchable PhCs, where the PBG can be reversibly activated or shifted. Vanadium dioxide (VO2) is particularly notable for its near-room-temperature insulator-to-metal transition (IMT), which is accompanied by significant changes in its optical properties. Here, we demonstrate a fabrication strategy for switchable three-dimensional (3D) PhCs, involving sacrificial templates and a VO2 atomic layer deposition (ALD) process in combination with an accurately controlled annealing procedure. The resulting VO2 inverse opal (IO) PhC achieves substantial control over PBG in the near-infrared (NIR) region. Specifically, the synthesized VO2 IO PhC exhibits PBGs near 1.49 and 1.03 μm in the dielectric and metallic states of the VO2 material, respectively, which can be reversibly switched by adjusting the external temperature. Furthermore, a temperature-dependent switch from a narrow-band NIR reflector to a broad-band absorber is revealed. This work highlights the potential of integrating VO2 into 3D templates in the development of switchable photonics with complex 3D structures, offering a promising avenue for the advancement of photonic devices with adaptable functionalities.Publicationtype: Review Article26 23 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Enhanced Photocatalytic Properties and Photoinduced Crystallization of TiO2–Fe2O3 Inverse Opals Fabricated by Atomic Layer Deposition(American Chemical Society (ACS), 2024-09-03); ; ; ; The use of solar energy for photocatalysis holds great potential for sustainable pollution reduction. Titanium dioxide (TiO2) is a benchmark material, effective under ultraviolet light but limited in visible light utilization, restricting its application in solar-driven photocatalysis. Previous studies have shown that semiconductor heterojunctions and nanostructuring can broaden the TiO2’s photocatalytic spectral range. Semiconductor heterojunctions are interfaces formed between two different semiconductor materials that can be engineered. Especially, type II heterojunctions facilitate charge separation, and they can be obtained by combining TiO2 with, for example, iron(III) oxide (Fe2O3). Nanostructuring in the form of 3D inverse opals (IOs) demonstrated increased TiO2 light absorption efficiency of the material, by tailoring light-matter interactions through their photonic crystal structure and specifically their photonic stopband, which can give rise to a slow photon effect. Such effect is hypothesized to enhance the generation of free charges. This work focuses on the above-described effects simultaneously, through the synthesis of TiO2-Fe2O3 IOs via multilayer atomic layer deposition (ALD) and the characterization of their photocatalytic activities. Our results reveal that the complete functionalization of TiO2 IOs with Fe2O3 increases the photocatalytic activity through the slow photon effect and semiconductor heterojunction formation. We systematically explore the influence of Fe2O3 thickness on photocatalytic performance, and a maximum photocatalytic rate constant of 1.38 ± 0.09 h-1 is observed for a 252 nm template TiO2-Fe2O3 bilayer IO consisting of 16 nm TiO2 and 2 nm Fe2O3. Further tailoring the performance by overcoating with additional TiO2 layers enhances photoinduced crystallization and tunes photocatalytic properties. These findings highlight the potential of TiO2-Fe2O3 IOs for efficient water pollutant removal and the importance of precise nanostructuring and heterojunction engineering in advancing photocatalytic technologies.Publicationtype: Journal Article16 31 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Achieving high-temperature stable structural color through nanostructuring in polymer-derived ceramics(American Chemical Society (ACS), 2024-04-18); ; ; ; Structural colors offer a myriad of advantages over conventional pigment-based colors, which often rely on toxic chemical substances that are prone to UV degradation. To take advantage of these benefits in demanding environments, there is growing interest in producing structural colors from ceramics. Polymer-derived ceramics (PDCs) emerge as a compelling choice, presenting two distinct advantages: their enhanced shape ability in their polymeric state associated with impressive temperature resistance once converted to ceramics. This study pioneers the fabrication of noniridescent structural colors from silicon oxycarbide (SiOC) PDC, enabled by the nanostructuring of an inverse photonic glass within the PDC material. This design, a functionally graded material with an inverse photonic glass (FGM-PhG) structure, leverages the innate light-absorbing properties of SiOC, yielding a vivid structural color that maintains its saturation even in white surroundings. This study elucidates the process−structure−properties relationship for the obtained structural colors by investigating each layer of the functionally graded material(FGM) in a stepwise coating deposition process. To further emphasize the exceptional processing flexibility of PDCs, the three-step process is later transferred to an additive manufacturing approach. Finally, the FGM-PhG structural colors are demonstrated to have remarkable thermal stability up to 1000 °C for 100 h, possibly making them the most thermally stable ceramic structural colors to date.Publicationtype: Journal Article32 65 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Mullite photonic glasses with exceptional thermal stability for novel reflective thermal barrier coatings(Springer, 2023-08); ; ; ; Thermal barrier coatings are essential materials systems for insulating and protecting substrates exposed to high temperatures. In such systems, the heat transfer has three possible paths: conduction, convection and irradiation. The higher the operating temperature, the more important it is to control or protect against the radiative component, since the radiative heat flux becomes non-negligible. The radiation can be controlled by the use of ceramic-based photonic nanostructures, namely photonic crystals and photonic glasses, creating so-called reflective thermal barrier coatings. In this work, mullite inverse photonic glasses (PhG) have been produced by thermally induced reaction on sol–gel-based silica structures coated with nanometric films of Al2O3 by atomic layer deposition. The conversion to mullite was carried out following a two-stage heat-treatment. The pre-annealing associated with the further mullite formation results in an excellent structural stability of these PhGs up to 1500 °C, being able to retain their high reflectivity in the near infrared range. Therefore, this structure can be considered for next-generation reflective thermal barrier coatings. Graphical abstract: [Figure not available: see fulltext.]Publicationtype: Journal ArticleScopus© Citations 1 69 71 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Printing crack‐free microporous structures by combining additive manufacturing with colloidal assembly(Wiley-VCH, 2023-02); ; ; ; To date high printing resolution and scalability, i.e., macroscale component dimensions and fast printing, are incompatible characteristics for additive manufacturing (AM) processes. It is hereby demonstrated that the combination of direct writing as an AM process with colloidal assembly enables the breaching of this processing barrier. By tailoring printing parameters for polystyrene (PS) microparticle-templates, how to avoid coffee ring formation is demonstrated, thus printing uniform single lines and macroscale areas. Moreover, a novel “comb”-strategy is introduced to print macroscale, crack-free colloidal coatings with low viscous colloidal suspensions. The printed templates are transformed into ceramic microporous channels as well as photonic coatings via atomic layer deposition (ALD) and calcination. The obtained structures reveal promising wicking capabilities and broadband reflection in the near-infrared, respectively. This work provides guidelines for printing low viscous colloidal suspensions and highlights the advancements that this printing process offers toward novel applications of colloidal-based printed structures.Publicationtype: Journal ArticleScopus© Citations 2 89 207