We report a silver-catalyzed hydrogen isotope exchange reaction that enables direct deuteration of quinones and related scaffolds, using readily available D2O as an isotopic source. The homogeneous Ag2SO4 system provides high isotopic enrichment, up to 99%, with excellent regioselectivity across diverse frameworks, including substituted para-naphthoquinones, anthraquinones, coumarins, quinolinones, and chromones. We also developed a heterogeneous version of the same reaction by supporting silver nanoparticles on carbon nanotubes. The nanohybrid catalyst maintains high performance and allows for easy removal of the catalyst from the final product through filtration. The dual homogeneous/heterogeneous approaches pioneer quinone hydrogen isotope exchange, providing practical and straightforward access to isotopologues.

Materials imperfections in Nb-based superconducting quantum circuits-in particular, two-level-system (TLS) defects-are a major source of decoherence, ultimately limiting the performance of quantum computation and sensing. Thus, identifying and understanding the microscopic origin of possible TLS defects in these devices will help develop strategies that eliminate them, which are key to superconducting qubit performance improvement. In this paper, we demonstrate an order-of-magnitude reduction in two-level system losses in three-dimensional superconducting radio frequency (SRF) niobium resonators by a 10-h high vacuum (HV) heat treatment at 650 degrees C, even after exposure to air and high-pressure rinsing (HPR). X-ray photoelectron spectroscopy (XPS) and high-resolution scanning transmission electron microscopy (STEM) reveal an alteration of the native oxide composition regrown after air exposure and HPR and the creation of nanoscale crystalline oxide regions, which correlates with the measured tenfold quality factor enhancement at low fields of the 1.3 GHz niobium resonator. Tunneling spectroscopy measurements show a pronounced proximity effect that further confirms the presence of metallic layers on the niobium surface.

Thanks to species identification and growth interface localization experiments, a mechanism of iron corrosion in liquid UF6 at 80 degrees C was suggested. After an UF6 dissociation step, resulting fluorine (HF, F- or F center dot) was adsorbed at the FeF2 external interface and diffused into the iron fluoride layer via fluorine vacancy. FeF2 grew thus at the FeF2/Fe interface. Two FeF2 growth kinetics were observed depending on the presence or absence of NOxF impurities. Both corrosion rates were controlled by the cathodic reaction and presence of NOxF catalysed it.

This study investigates the use of atomic layer deposition (ALD) to mitigate multipacting phenomena inside superconducting radio frequency cavities used in particle accelerators while preserving high quality factors in the 1010 range. The unique ALD capability to control the film thickness down to the atomic level on arbitrary complex shape objects enables the fine-tuning of TiN film resistivity and total electron emission yield (TEEY) from coupons to devices. This level of control allows us to adequately choose a TiN film thickness that provides both high resistivity to prevent Ohmic losses and a low TEEY to mitigate multipacting for the application of interest. The methodology presented in this work can be scaled to other domains and devices subject to RF fields in vacuum and sensitive to multipacting or electron discharge processes with their own requirements in resistivities and TEEY values.

The results reported here are the first on pure iron corrosion in liquid UF6 at 80 degrees C. Two kinetic behaviours have been observed: one led to micrometric scales (from micron to hundreds of microns after several months) and the other one to hundreds of nanometers for several months. The higher corrosion kinetics resulted in the presence of impurities such as NOxF complexes formed by interaction between the medium and the reactor material. These NOxF catalysed the corrosion reaction leading to a corrosion mechanism controlled by the cathodic reaction rate. Effect of impurities in UF6 coming from experimental conditions or nature of uranium ore should then be systematically and carefully checked. Whatever the corrosion kinetics and the presence of impurities, the nature of the layer was identical: a duplex fluoride scale composed of an iron rich layer, FeF2, and a uranium rich layer evolving over time from U2F9 to UF5.

This study presents the development of a synthesis route for sodium aluminosilicate hydrate (N-A-S-H) gels with various Si/Al ratios carried out at ambient temperature. The synthesis is based on a simple "sol-gel" method, where commercial reactants are used to provide highly reactive Si an Al sources. Comprehensive characterization, including scanning electron microscope-energy-dispersive spectroscopy (SEM-EDS), gas pycnometry, inductively coupled plasma (ICP), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and magic angle spinning (MAS) nuclear magnetic resonance (NMR) (27Al, 23Na, 29Si, and 1H), is employed to verify the morphology, density, chemical composition, long-range order, and local structure of the gels. Our results show that the synthesized gels are pure, amorphous, and homogeneous with Si/Al final ratio ranging from 1.22 to 2.23. Structural analysis of the gels indicates the synthesis of compounds with high degree of geopolymerization, which are representative of N-A-S-H gel formed in sodium-based geopolymers. center dot A new route to synthesize pure sodium aluminosilicate hydrate (N-A-S-H) gels representative of N-A-S-H formed in sodium-based geopolymers is presented.center dot N-A-S-H gels are synthesized at room temperature with various Si/Al ratios.center dot Synthesized gels are amorphous, homogeneous, and well-geopolymerized. image

We report the design, synthesis, and in vitro evaluation of stimuli-responsive nanoscale micelles that can be activated by light to induce a cytotoxic effect. Micelles were assembled from amphiphilic units made of a photoactivatable ferrocenyl linker, connected on one side to a lipophilic chain, and on the other side to a hydrophilic pegylated chain. In vitro experiments indicated that pristine micelles ("off" state) were nontoxic to MCF-7 cancer cells, even at high concentrations, but became potent upon photoactivation ("on" state). The illumination process led to the dissociation of the micelles and the concomitant release of iron species, triggering cytotoxicity.

The influence of cobalt and cobalt–manganese oxide coating thickness on its ability to be a good diffusion barrier against Cr outward diffusion was investigated for stainless steel interconnects (AISI 441) of a solid oxide cell (SOC). The coatings were all synthesized using a DLI-MOCVD (Direct Liquid Injection-Metal Oxide Chemical Vapor Deposition) hot wall reactor. The study shows that a minimum cobalt oxide thickness of 300 nm was needed to be a good diffusion barrier against Cr for the 500-h exposure test. This observation was linked to the Mn concentration reached in the cobalt spinel during exposure. Indeed, during exposure at high temperature, Mn diffused from the substrate into the cobalt coating and transformed cobalt spinel into Co-Mn spinel. Whereas pure cobalt spinel was a good Cr diffusion barrier, cobalt-manganese spinel, Co3-xMnxO4, was not when x > 2. The thickness of the cobalt coatings must be chosen so that the Mn quantity coming into it from diffusion from the substrate does not degrade the protectiveness of the coating.

Polymers are widely used in various sectors of the nuclear industry where they can become contaminated with fission and activation products. The resulting nuclear wastes consist in a mixture of different polymers, which may be classified as long-lived intermediate-level waste (LL-ILW) if they have been in contact with long-lived radionuclides. From their production, polymers will be radio-oxidized. If different type of polymeric materials degrade close to each other, cross-infection can happen and alter the known degradation mechanisms. The objective of this work is to investigate the interaction between the HCl, which mimic polyvinyl chloride (PVC) degradation, and radio-oxidized polypropylene (PP). Polymers are characterized before interaction with HCl: additives are identified in the pristine polypropylene and evolution of the films with dose are evidenced (POH, POOH and CO bonds are increasing with dose). Evolution under HCl exposure of PP and of radio-oxidized PP is followed by different techniques, in situ and ex situ. Upon contact, a rapid evolution of the gases (HCl consumption in addition to CO2, H2O and CO formation) in the reactor is observed for the 15 first hours, followed by a slow evolution. At the molecular level in the polymer, in situ FTIR spectroscopy analyses show a decrease of the POH/POOH broad infrared peak along with the formation of ketone bonds. CCl bonds are also evidenced. Finally, sorption of HCl is shown. Hypotheses on preferred mechanisms are suggested, some of them being evaluated in Part 2 of this article.

Superconducting qubits have arisen as a leading technology platform for quantum computing, which is on the verge of revolutionizing the world's calculation capacities. Nonetheless, the fabrication of computationally reliable qubit circuits requires increasing the quantum coherence lifetimes, which are predominantly limited by the dissipations of two-level system defects present in the thin superconducting film and the adjacent dielectric regions. In this paper, we demonstrate the reduction of two-level system losses in three-dimensional superconducting radio frequency niobium resonators by atomic layer deposition of a 10 nm aluminum oxide Al2O3 thin films, followed by a high vacuum heat treatment at 650 °C for few hours. By probing the effect of several heat treatments on Al2O3-coated niobium samples by x-ray photoelectron spectroscopy plus scanning and conventional high resolution transmission electron microscopy coupled with electron energy loss spectroscopy and energy dispersive spectroscopy, we witness a dissolution of niobium native oxides and the modification of the Al2O3-Nb interface, which correlates with the enhancement of the quality factor at low fields of two 1.3 GHz niobium cavities coated with 10 nm of Al2O3.

Titanium dioxide nanoparticles were combined with carbon nanotubes and gold to develop improved photocatalysts for the production of hydrogen from water. The entangled nature of the nanotubes allowed for the integration of the photoactive hybrid catalyst, as a packed-bed, in a microfluidic photoreactor, and the chips were studied in the photocatalyzed continuous flow production of hydrogen. The combination of titanium dioxide with carbon nanotubes and gold significantly improved hydrogen production due to a synergistic effect between the multi-component system and the stabilization of the active catalytic species. The titanium dioxide/carbon nanotubes/gold system permitted a 2.5-fold increase in hydrogen production, compared to that of titanium dioxide/carbon nanotubes, and a 20-fold increase, compared to that of titanium dioxide.

Homogeneous and heterogeneous U 1-x Ce x O 2 (with 0≤ x≤ 0.25) materials were prepared via wet and dry chemistry routes, respectively before being submitted to dynamic leaching experiments. The feeding solution containing 0.20 mmol.L −1 H 2 O 2 was kept under air and renewed to guarantee the stability of H 2 O 2 during the experiment. Normalized alteration rates were determined from U concentration in the leachates. For homogeneous (U,Ce)O 2 materials, the dissolution rate was divided by a factor of 3 when increasing the Ce content from 0.08 to 0.25. Surface characterizations revealed that studtite precipitated all over UO 2 pellet surface and only on the UO 2 grains of heterogeneous U 0.92 Ce 0.08 O 2 samples. The behaviour of this heterogeneous material was similar to that observed for (U,Pu)O 2 in the same conditions, which revealed the reliability of cerium as a plutonium analogue.

Tuning magnetic and electronic transport properties in spinel oxides requires a faithful description between chemical composition and cation site-occupation. Here this challenge is addressed using Fe3-xCrxO4 thin films grown by oxygen-assisted molecular-beam epitaxy within a wide range of composition (0.0 <= x <= 1.2). Spec-troscopic measurements (e.g., X-ray magnetic circular dichroism), refined by theoretical simulations (e.g., crystal field multiplet), are performed to establish a quantitative link between chromium content, Fe2+/Fe3+ site-occupation and macroscopic physical properties of the layers. It is found that Fe3-xCrxO4 thin films (i) delay the transition from inverse to normal spinel configuration with increasing chromium content and (ii) promote collinear spin structure, at odds with bulk material. As a result, strong antiferromagnetic interactions are pre-served between spins in tetrahedral and octahedral spinel sublattices, so that chromium-rich thin films exhibit Curie temperatures above room temperature and higher magnetization. Electron hopping is also favored by this singular cation distribution and electronic band gap is smaller than expected for these thin films. The cation site-occupation is therefore a key feature to consider for applications of Fe3-xCrxO4 thin films in spintronics and photocatalysis, as it enables manipulation of magnetic properties (Curie temperature and magnetization) and band gap engineering.

The initial stages of oxidation of 9Cr steel in CO 2 , O 2 , CO 2 –O 2 and CO 2 –O 2 –H 2 O is studied by gas phase analysis (GPA) at 550 °C using 13 C 16,16 O 2 , 18,18 O 2 and 2 H 2 16 O isotopic molecules in order to discriminate the reactions of all gas molecules. Protective and non-protective oxide scales are formed on 9Cr steel depending on the exact composition of the gas mixture. In pure CO 2 , 9Cr steel forms a slow growing chromium-rich oxide scale without any carburization. Adding O 2 impurities in CO 2 favors the formation of fast growing iron-rich duplex oxide scale coupled to strong carburization. Adding several % of O 2 in CO 2 favors again the formation of slow growing oxide scale but with different structure and composition than in pure CO 2 . GPA analyses combined with oxide scale analyses demonstrate that the composition and structure of the transient oxide scale formed on 9Cr surface is determined by the rate at which surface adsorbed oxygen atoms are supplied by the gas phase in the first minutes of exposure. The presence of the very oxidizing O 2 molecules in CO 2 increases drastically the surface oxidation rate, favoring formation of a non-protective oxide scale which transmits carbon permitting carburization of the steel. Adding water vapor to a CO 2 gas environment slows carburization. Preferential adsorption of water vapor molecules over CO 2 /CO molecules in the inner oxide scale is proposed to explain this result. A unified mechanism for the formation of the transient oxide scale on 9Cr steel in CO 2 /O 2 /H 2 O gas mixtures is described.

Homogeneous and heterogeneous U 1-x Ce x O 2 (with 0≤ x≤ 0.25) materials were prepared via wet and dry chemistry routes, respectively before being submitted to dynamic leaching experiments. The feeding solution containing 0.20 mmol.L −1 H 2 O 2 was kept under air and renewed to guarantee the stability of H 2 O 2 during the experiment. Normalized alteration rates were determined from U concentration in the leachates. For homogeneous (U,Ce)O 2 materials, the dissolution rate was divided by a factor of 3 when increasing the Ce content from 0.08 to 0.25. Surface characterizations revealed that studtite precipitated all over UO 2 pellet surface and only on the UO 2 grains of heterogeneous U 0.92 Ce 0.08 O 2 samples. The behaviour of this heterogeneous material was similar to that observed for (U,Pu)O 2 in the same conditions, which revealed the reliability of cerium as a plutonium analogue.

In the current paper, we have studied the impact of microwave (2.45 GHz) plasma treatment of submicronic (250-600 nm) tungsten dust, upon tritium gas retention. Herein, the con-ducted experiments have emphasized the role of dust treatments in pure hydrogen gas versus hydrogen plasma, before the tritiation process at different pressures. The obtained tritiated dust was analyzed via room temperature desorption and dissolutions. Additionally, Scanning Electron Microscopy and X-ray Photoelectron Spectroscopy analyses were per-formed to observe the changes induced by the plasma discharge. The results have shown that the Specific Surface Area of dust is enhanced by using microwave hydrogen plasma treatments, resulting in a high tritium gas retention inside the submicronic tungsten dust. & COPY; 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Abstract The initial stages of oxidation of 9Cr steel in CO2, O2, CO2-O2 and CO2-O2-H2O is studied by Gas Phase Analysis (GPA) at 550°C using 13C16,16O2, 18,18O2 and 2H216O isotopic molecules in order to discriminate the reactions of all gas molecules. Protective and non-protective oxide scales are formed on 9Cr steel depending on the exact composition of the gas mixture. In pure CO2, 9Cr steel forms a slow growing chromium rich oxide scale without any carburization. Adding O2 impurities in CO2 favors the formation of fast growing iron rich duplex oxide scale coupled to strong carburization. Adding several % of O2 in CO2 favors again the formation of slow growing oxide scale but with different structure and composition than in pure CO2. GPA analyses combined with oxide scale analyses demonstrate that the composition and structure of the transient oxide scale formed on 9Cr surface is determined by the rate at which surface adsorbed oxygen atoms are supplied by the gas phase in the first minutes of exposure. The presence of the very oxidizing O2 molecules in CO2 increases drastically the surface oxidation rate and favors the formation of non-protective duplex oxide scale against carburization. Adding water vapor to a CO2 gas environment slows carburization. Preferential adsorption of water vapor molecules over CO2/CO molecules in the inner oxide scale is proposed to explain this result. A unified mechanism for the formation of the transient oxide scale on 9Cr steel in CO2/O2/H2O gas mixtures is described.