Zr-Ti based thin-film metallic glasses (TFMGs) constitute promising candidates for biomedical applications. Expected surfaces that are eligible for use inside the body have to gather a high biocompatibility, while preventing bacterial colonization. The objective of this work is to investigate potentialities opened by the innovative ternary Zr-Ti-Ag system. Films were deposited by magnetron cosputtering from independent targets, allowing a wide silver enrichment (10-41 at % Ag). Films were studied regarding their microstructural, mechanical, physicochemical, and biological properties. These properties were discussed in light of the films' composition. This study established that the structure of the films was strongly influenced by their silver content. The expected amorphous structure was obtained between 20 and 36 at % Ag, for which mechanical properties are high, and compatible with a potential biomedical application. Surface is then very smooth, with presence of dispersed micrometric crystallized islets. Evolution of the surface wettability was found to be primarily governed by the film morphology rather than by its chemical composition. Biologically, a pronounced antibacterial activity against both E. coli and S. gordonii was recorded from 25 at % Ag. Such an antibacterial effect was assigned to silver, as demonstrated by tests carried out with synthetic ions-released solutions. Besides, these films also have evidenced a good cytocompatibility toward gingival fibroblasts. These results highlight the key role of composition-controlled microstructure of Zr-Ti-Ag TFMGs, and demonstrate their potential as antibacterial and biocompatible coatings for dental implant applications.

Advanced surfaces combining biocompatibility with antibacterial properties are of prime interest in the biomedical field. In this context, ternary thin film metallic glasses of the Zr-Cu-Ag system with low silver contents (2 and 4 at. %) were deposited by magnetron sputtering and studied regarding their mechanical, microstructural, and antibacterial properties. The effect of further laser texturing of the PVD-deposited films, promoting Laser-Induced Periodic Surface Structures (LIPSSs), was also investigated. Results were then discussed in light of the chemical composition of films on the one hand and on the topographic characteristics of laser-treated surfaces on the other hand. Ternary films exhibited the expected metallic glass structure, with good associated mechanical properties. Besides, the low contents of Ag were sufficient to promote a significant antibacterial action against Escherichia coli, still enhanced by ultrafast laser texturing. Textured areas were also identified as prone to limit bacterial colonization due to the combined effect of the hydrophobic character of the treated surfaces together with a killing contact interaction.

This work addresses the fabrication of transparent glass surfaces with superior water-repellence (i.e., superhydrophobicity), and related functional properties such as omniphobicity, anti-fogging and anti-icing responses. Surfaces have been processed by means of mild femtosecond laser patterning combined with the grafting of fluorinated tethered molecules. Controlling the laser scan and ablation conditions permits the fabrication of under-design grooves with cross and lineal morphologies and separations between 10 and 500 um. These patterns provide a high transparency and repellence to liquids and ice over large areas. The best performance is obtained for cross or parallel line patterned glass with microgrooves separated by 100 um and 15 um depth thanks to 5 laser scanning repetitions. These surfaces present a stable Cassie-Baxter wetting state and very low ice-adhesion strength while keeping up to 80

To produce dense parts using the fused filament fabrication process, a sintering step is required. After debinding, sintering must be perfectly controlled to obtain functional parts by controlling sintering conditions such as temperature and atmosphere. The aim of this work is to propose a detailed study of the densification during sintering of a H13 steel, as a function of both temperature and the nature of the atmosphere, linking it to the final relative density and microstructure. To this end, complementary in situ and ex situ characterisation methods were used to study the densification evolution at the filamentary scale. The influence of environmental sintering conditions was also discussed in terms of porosity dynamics and measured mechanical properties. The results provide a better understanding of sintering and in particular of the operating conditions to be used to obtain functional parts.

One of the main interests of 2D materials is their ability to be assembled with many degrees of freedom for tuning and manipulating excitonic properties. There is a need to understand how the structure of the interfaces between atomic layers influences exciton properties. Here we use cathodoluminescence and time-resolved cathodoluminescence experiments to study how excitons interact with the interface between two twisted hexagonal boron nitride (hBN) crystals with various angles. An efficient capture of free excitons by the interface is demonstrated, which leads to a population of long-lived and interface-localized (2D) excitons. Temperature dependent experiments indicate that for high twist angles, these excitons localized at the interface further undergo a selftrapping. It consists in a distortion of the lattice around the exciton on which the exciton traps itself. Our results suggest that this exciton-interface interaction causes the broad 4-eV optical emission of highly twisted hBN-hBN structures. Exciton self-trapping is finally discussed as a common feature of sp2 hybridized boron nitride polytypes and nanostructures due to the ionic nature of the B-N bond and the small size of their excitons.

Under high electrical current, some materials can emit electromagnetic radiation beyond incandescence. This phenomenon, referred to as electroluminescence, leads to the efficient emission of visible photons and is the basis of domestic lighting devices (for example, light-emitting diodes)1,2. In principle, electroluminescence can lead to mid-infrared emission of confined light-matter excitations called phonon polaritons3,4, resulting from the coupling of photons with crystal lattice vibrations (optical phonons). In particular, phonon polaritons arising in the van der Waals crystal hexagonal boron nitride (hBN) present hyperbolic dispersion, which enhances light-matter coupling5,6. For this reason, electroluminescence of hyperbolic phonon polaritons (HPhPs) has been proposed as an explanation for the peculiar radiative energy transfer within hBN-encapsulated graphene transistors7,8. However, as HPhPs are locally confined, they are inaccessible in the far field, and as such, any hint of electroluminescence has been based on indirect electronic signatures and has yet to be confirmed by direct observation. Here we demonstrate far-field mid-infrared (wavelength approximately 6.5 μm) electroluminescence of HPhPs excited by strongly biased high-mobility graphene within a van der Waals heterostructure, and we quantify the associated radiative energy transfer through the material. The presence of HPhPs is revealed by far-field mid-infrared spectroscopy owing to their elastic scattering at discontinuities in the heterostructure. The resulting radiative flux is quantified by mid-infrared pyrometry of the substrate receiving the energy. This radiative energy transfer is also shown to be reduced in hBN with nanoscale inhomogeneities, demonstrating the central role of the electromagnetic environment in this process.

We present a benchmarking protocol that combines the characterization of boron nitride (BN) crystals and films with the evaluation of the electronic properties of graphene on these substrates. Our study includes hBN crystals grown under different conditions and scalable BN films deposited by either chemical or physical vapor deposition (CVD or PVD). We explore the complete process from boron nitride growth, over its optical characterization by time-resolved cathodoluminescence (TRCL), to the optical and electronic characterization of graphene by Raman spectroscopy after encapsulation and Hall bar processing. Within our benchmarking protocol we achieve a homogeneous electronic performance within each Hall bar device through a fast and reproducible processing routine. We find that a free exciton lifetime of 1 ns measured on as-grown hBN crystals by TRCL is sufficient to achieve high graphene room temperature charge carrier mobilities of 80,000 cm^2/(Vs) at a carrier density of |n| = 10^12 cm^-2, while respective exciton lifetimes around 100 ps yield mobilities up to 30,000 cm^2/(Vs). For scalable PVD-grown BN films, we measure carrier mobilities exceeding 10,000 cm^2/(Vs) which correlates with a graphene Raman 2D peak linewidth of 22 cm^-1. Our work highlights the importance of the Raman 2D linewidth of graphene as a critical metric that effectively assesses the interface quality (i.e. surface roughness) to the BN substrate, which directly affects the charge carrier mobility of graphene. Graphene 2D linewidth analysis is suitable for all BN substrates and is particularly advantageous when TRCL or BN Raman spectroscopy cannot be applied to specific BN materials such as amorphous or thin films. This underlines the superior role of spatially-resolved spectroscopy in the evaluation of BN crystals and films for the use of high-mobility graphene devices.

The in-situ microstructure evolution of a standard black enamel and the stress evolution during thermal treatments are investigated through the deposition of the enamel on a model, inert Si substrate. The sintering of the glass frit by viscous flow results in the formation of pores. The crystallization of the glass frit constituting the enamel has been observed to affect the rheological properties of the enamel, increasing its relative viscosity, and leading to an increase in the stress regeneration temperature during cooling. It was observed that an increase in elastic stress in the enamel during cooling, due to a thermal expansion mismatch between the enamel and the substrate, resulted in the initiation and propagation of cracks when tensile stress reached 170MPa. It was found that viscous flow at high temperatures during subsequent thermal cycles promotes self-healing of previously formed cracks.

We present a novel experimental protocol using Cathodoluminescence measurements as a function of the electron incident energy to study both exciton diffusion in a directional way and surface exciton recombination. Our approach overcomes the challenges of anisotropic diffusion and the limited applicability of existing methods to the bulk counterparts of 2D materials. The protocol is then applied at room and at cryogenic temperatures to four bulk hexagonal boron nitride crystals grown by different synthesis routes. The exciton diffusivity depends on the sample quality but not on the temperature, indicating it is limited by defect scattering even in the best quality crystals. The lower limit for the diffusivity by phonon scattering is 0.2 cm$^{2}$.s$^{-1}$. Diffusion lengths were as much as 570 nm. Finally, the surface recombination velocity exceeds 10$^{5}$ cm$^{2}$.s$^{-1}$, at a level similar to silicon or diamond. This result reveals that surface recombination could strongly limit light-emitting devices based on 2D materials.

Implants and surgical tools are commonly used in the medical field. However, issues including poor osseointegration, rejection, or bacterial contamination may still occasionally occur, causing serious complications susceptible to lead even to the patient death. It is therefore necessary to move toward new alternative advanced surfaces, that may possess both antibacterial properties and improved biocompatibility compared with existing solutions. Metallic glasses may constitute this kind of promising materials, gathering a high physico-chemical resistance combined with outstanding mechanical properties. The first part of this review explores the interest of metallic glasses for biomedical applications, and focuses on their biological properties. Metallic glasses are considered under their two forms: bulk, as well as thin films. The behaviour of these metallic glasses towards micro-organisms (bacteria, cells in particular) is then described. Besides, surface texturing by pulsed laser represents a further degree of freedom to deeply functionalize the metallic glasses’ surface. The induced modifications may not only concern the morphology of the surface, but also its chemistry at a small scale. In this sense, the review demonstrates the importance of such a surface modification on the biological properties, and on the dynamic of cells on these advanced surfaces in particular. Finally, the last part is dedicated to the latest developments of ultrashort laser irradiation of metallic glasses. It is shown how these nano-engineered surfaces can influence the biological behaviour of metallic glasses. Explanations rely on the patterning design on the one hand, on chemistry of the irradiated material on the other hand.

This work reports on the influence of nanoparticle (NP) size distribution and the chemical nature of gold (Au) and/or silver (Ag) NPs in the localized surface plasmon resonance (LSPR) responses. The NPs were produced embedded in a titanium dioxide (TiO2) thin film, deposited by reactive magnetron sputtering technique followed by in-vacuum thermal treatment at 400 degrees C. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) gave quantitative key information in terms of both the size and distribution of the noble metal NPs. The average Feret diameter was 17 nm (sigma = 8) and 55 nm (sigma = 28) for Au/TiO2 and Ag/TiO2 films, respectively, while the Au-Ag/TiO2 film showed intermediate values, with an average size of 22 nm (sigma = 9). HAAD-STEM, complemented by EDX chemical mapping, revealed an unusual formation of cluster structures containing local distributions of bimetallic (alloyed) Au-Ag NPs. The synergetic characteristics and properties of such bimetallic Au-Ag NPs resulted in an outstanding LSPR sensitivity compared to the monometallic counterparts. Furthermore, the analysis of the average nearest neighbor distances (about one order of magnitude lower than counterparts) suggests the existence of plasmonic hotspots relevant to be explored in sensing and surface-enhanced spectroscopies.

Multicracking of a thin brittle layer deposited on a substrate with an intermetallic layer is studied using finite fracture mechanics. Nonlinear implementation of the coupled criterion is used to predict the initiation and successive subdivisions of a periodic network of cracks considering intermetallic layer plasticity and interface debonding. Plasticity has a moderate influence on the cracking kinetics whereas debonding length has a strong influence on the saturation crack spacing. The cracking kinetics predicted numerically is more abrupt than in experiments because of the periodicity assumption, however crack spacing at saturation similar to those measured experimentally are obtained. The tensile strength and critical energy release rate of the thin brittle layer are determined by inverse identification based on the crack density variation as a function of the imposed loading. The proposed approach also enables the accurate determination of the interface critical energy release rate based on the experimentally measured debonding lengths.

Hexagonal boron nitride (hBN) presents valuable intrinsic properties and attracts considerable attention for the development of novel two-dimensional (2D) materials-based technologies. Even though huge efforts have been made to improve the bottom-up synthesis of integrated and high quality hBN, the devices presenting the best performances are still made using hBN exfoliated from bulk crystals. In this context, we explore the Polymer-Derived Ceramics (PDC) route coupled to a high temperature process that produces millimetric and high quality hBN crystals. By investigating the (micro)structure of several samples, we demonstrate that the crystal growth occurs by segregation from a Li3BN2-BN solution upon cooling and from hBN seeds. In particular, we show that crystallization can occur at a temperature as low as 1400 degrees C. Overall, these results show that hBN crystal growth in the Li3BN2-BN system is compatible with conventional flux methods that may be the most promising platform for continuous seeded hBN crystal growth.

This study investigated the redox exsolution of Ni nanoparticles from a nanoporous La0.52Sr0.28Ti0.94Ni0.06O3 perovskite. The characteristics of exsolved Ni nanoparticles including their size, population, and surface concentration were deeply analyzed by environmental scanning electron microscopy (ESEM), transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDX) mapping, and hydrogen temperature-programmed reduction (H2-TPR). Ni exsolution was triggered in hydrogen as early as 400 °C, with the highest catalytic activity for low-temperature CO oxidation achieved after a reduction step at 500 °C, despite only a 10% fraction of Ni exsolved. The activity and stability of exsolved nanoparticles were compared with their impregnated counterparts on a perovskite material with a similar chemical composition (La0.65Sr0.35TiO3) and a comparable specific surface area and Ni loading. After an aging step at 800 °C, the catalytic activity of exsolved Ni nanoparticles at 300 °C was found to be 10 times higher than that of impregnated ones, emphasizing the thermal stability of Ni nanoparticles prepared by redox exsolution.

This work describes crystallization mechanisms in a model ZrCu thin film metallic glass, synthesized through magnetron sputtering. Global-scale characterization techniques, including differential scanning calorimetry and X-ray diffraction, are compared with local-scale characterization obtained through in situ transmission electron microscopy during isothermal heating. This multi-scale approach establishes the crystallization sequence of ZrCu thin film metallic glasses. Furthermore, it highlights the role of oxidation as a nucleation site, initiating the crystallization process. Once initiated, crystallization progresses as a propagating front, scanning and transforming the amorphous matrix. The combination of both global and local approaches yields consistent key thermodynamic values. Additionally, monitoring the advancing crystallization front during in situ high-temperature transmission electron microscopy provides access to crucial kinetic parameters, such as diffusion coefficients.

Flax fibre represents one of the most promising natural components for the development of new innovative highperformance biobased composite materials. Their properties are closely related to the lumen, the central cavity of the fibre, which was only studied, to date, under unrealistic environments as in dry conditions. The objective of the current study is to characterise, at a micrometre-scale, the surface and volume modifications induced by exposure of fibres to humid atmospheres. Different dynamic characterization strategies have shown a significant opening of the hydrated lumen "channel". Values of this opening rate are discussed in the light of potential biases linked to the investigation technique (SEM versus X-ray tomography), and to the adopted acquisition approach (in situ versus ex situ). By eSEM, after a 5 min. exposure to the water-saturated environment for instance, the lumen opening value was measured at 36 +/- 2% for ex-situ hydration of the bundles with a subsequent delamination of the fibre, while it was only 15 +/- 2% when hydration was progressively conducted into the SEM chamber. By microtomography, the lumen swelling for the single fibre was estimated to be within the same order of magnitude, about 7%, after hydration and measurements performed under realistic atmospheric pressure.