Search

The “Fani Maoré” eruption off the coasts of Mayotte has been intensively monitored by applying methods similar to those used for subaerial eruptions. Repeated high-resolution bathymetric surveys and dredging, coupled with petrological analyses of time-constrained samples, allowed tracking the evolution of magma over the whole submarine eruptive sequence. Indeed, after one year of direct ascent (Phase 1), basanitic magma switched to a different pathway that sampled a tephri-phonolitic subcrustal reservoir (Phase 2). Later, the magma pathway shifted again in the crust resulting in a new eruption site located 6 km northwest of the main edifice (Phase 3). The petrological signature of lava flows reveals both an evolution by fractional crystallization and syn-eruptive mixing with a tephri-phonolitic magma.We demonstrate that high-flux eruption of large volumes of basanitic magma from a deep-seated reservoir can interact with shallower reservoirs and remobilize eruptible magma. This has significant hazards implications with respect to the capacity of such large eruptions to reactivate shallow-seated inactive reservoirs from a transcrustal magmatic system that could be located potentially at a distance from the high-flux eruptive site.

Self-doped CuS nanoparticles (NPs) were successfully synthesized via microwave-assisted polyol process to act as co-catalysts to TiO2 nanofiber (NF)-based photoanodes to achieve higher photocurrents on visible light-assisted water electrolysis. The strategy adopted to perform the copper cation sulfidation in polyol allowed us to overcome the challenges associated with the copper cation reactivity and particle size control. The impregnation of the CuS NPs on TiO2 NFs synthesized via hydrothermal corrosion of a metallic Ti support resulted in composites with increased visible and near-infrared light absorption compared to the pristine support. This allows an improved overall efficiency of water oxidation (and consequently hydrogen generation at the Pt counter electrode) in passive electrolyte (pH = 7) even at 0 V bias. These low-cost and easy-to-achieve composite materials represent a promising alternative to those involving highly toxic co-catalysts. [ABSTRACT FROM AUTHOR]

We compared the impact of alumina doping on the structure of Al2O3–SiO2 amorphous thin films and bulk glasses using Raman spectroscopy and x‐ray diffraction. In both thin films and bulk glasses, the addition of Al2O3 is accompanied by an increase in the mean Si–O–T angle and an evolution of the ring statistics with a decrease in the proportion of small rings. We evidenced structural differences between sputtered films and fused bulk glasses. Sputtered Al2O3–SiO2 thin films are about 6%–7% denser than their equivalent Al2O3–SiO2 bulk glasses. This difference is mainly due to a change in ring statistics with the formation of small rings within the sputtered thin films. These structural differences in atomic structural organization highlight the impact of the synthesis conditions and open the door to further investigation of the structure–functional property relationships in sputtered Al2O3–SiO2 thin films. [ABSTRACT FROM AUTHOR]

This study focuses on metal/polymer nanocomposite thin films made by atmospheric pressure Plasma-Enhanced Chemical Vapor Deposition. The aerosol of isopropanol-dissolved tetrachloroauric acid (HAuCl4:3H2O gold salt) is injected in a dielectric barrier discharge to synthesize plasmonic nanocomposite thin films. Argon is used as carrier gas with or without 133 ppm addition of ammonia (NH3) to respectively get or not a Penning mixture. Results show that NH3 largely influences the salt reduction and thin film properties. According to the aerosol characterization, the size distribution at the plasma entrance supports that isopropanol mainly evaporates before injection in the plasma. The salt initially dissolved in each droplet precipitates during evaporation before injection as solid nanoparticles of about 30 nm diameter with eventual traces of solvent. Then, the nanocomposite thins film are studied. Optical properties, as plasmonic resonance, are characterized by UV–visible absorption spectroscopy. The chemical composition is analyzed using X-ray photoelectron spectroscopy and Raman spectroscopy, complemented by X-ray diffraction analysis as well as chemical mapping obtained by Energy dispersive spectroscopy coupled to scanning electron microscopy (SEM) operating in Scanning Transmission Electron Microscopy mode. Additionally, the morphology of the deposits is investigated by atomic force microscopy and SEM, highlighting the influence of NH3 gas on the film nature and therefore its role in the overall deposition process. Finally, optical emission spectroscopy of the plasma gives clue to better understand the effect of NH3. The overall results show that the salt nanoparticles are reduced in the plasma phase leading to non-aggregated metal Au NPs embedded in a carbon-based matrix formed by isopropanol polymerization. The presence of NH3 in the plasma unambiguously decreases the salt reduction and affects the thin film properties, consequently changing their plasmonic response related to the size, concentration, and composition of the embedded NPs. [ABSTRACT FROM AUTHOR]

The chemical synthesis of alloy nanoparticles requires adequate conditions to enable co-reduction instead of separate reduction of the two metal cations. The mechanism of formation of bimetallic cobalt–ruthenium nanoalloys by reducing metal salts in an alcohol medium was explored to draw general rules to extrapolate to other systems. The relative kinetics of the reduction of both metal cations were studied by UV-visible and in situ Quick-X-ray absorption spectroscopies as well as H2 evolution. The addition of Co(II) ions does not influence the reduction kinetics of Ru(III) but adding Ru(III) to a Co(II) solution promotes the reduction of cobalt cations. Indeed, while CoO is formed when reaching the boiling temperature of the solvent for the monometallic system, a direct reduction of Co is observed at this temperature without formation of the oxide for the bimetallic one. The co-reduction of the metal cations results in the formation of bimetallic nanoplatelets, the size of which can be tuned by changing the Ru content. [ABSTRACT FROM AUTHOR]