Graphene is becoming an increasingly popular platform for developing high-efficiency hydrogen isotope separation technologies operated at room temperature. However, its performance can be strongly affected by contributions from atomic defects. Understanding the influence of defects on the hydrogen isotope selectivity of graphene is thus imperative but remains elusive. In this work, we investigated the electrically driven proton/deuteron permeation through nitrogen-doped graphene membranes with varying N concentrations and configurations. The results show that N-doping significantly enhances the proton and deuteron permeability of graphene (by one order of magnitude). More importantly, deuterons are found to permeate faster through pyridinic N-containing defects than protons, demonstrating a pronounced inverse kinetic isotope effect (KIE) with kH/kD of 0.75. Conversely, pyrrolic N-containing defects exhibit a normal KIE (kH/kD = 1.56). The exclusive contribution of the pyridinic N to the inverse KIE is confirmed by the reversed KIE factor of the pyridinic N-dominated sample subjected to modification. Theoretical calculations indicate that the explicit dependence of KIE on N configuration originates from the different leading mechanisms of proton/deuteron permeation through these N-containing defects, which is governed by the size and the chemisorption imparted by defects. These findings provide fundamental insights into the correlation between defect characteristics and proton/deuteron transport in graphene, and contribute to developing economical hydrogen isotope separation technologies through the defect engineering of graphene.

The characteristic Raman spectra of UH3 produced at the initial stage of U-H2O corrosion were observed, which provided a direct evidence of the existence of interfacial UH3. The results were further identified and confirmed by the isotopic labeling method and other characterization techniques. The water-formed hydride layer was distributed at the interface of metallic uranium and oxide with several nanometers in thickness via the depth profile analysis. The characterizations of oxidation behavior suggested the interfacial UH3 translated to oxide and acted as a reaction front in the corrosion process. The experimental results supported the hydride-catalyzed corrosion mechanism of wet oxidation.

The radiochemical reaction products of T2/DT-CO system with different tritium pressures were studied in this work. The results show that the pressure of tritium and reactant was the key factor affecting the reaction rate of T2/DT-CO system, and the reaction products were closely related to the initial tritium concentration. Gradual evolution of reaction products including multi-carbon and multi-oxygen organic compounds were jointly affected by tritium decay in reactant molecules and bond breaking of reactant molecules by β-rays released from tritium decay. In addition, the tritium concentration in the deuterium-tritium mixture also affected the reaction products. High tritium concentration was conducive to the formation of multi-oxygen organics, while low tritium concentration was helpful to produce multi-carbon organics.

This study investigates the corrosion products formed on the surface of metallic uranium (U) during H2O corrosion in an open to air system. The results unambiguously reveal the presence of UH3 nanoparticles dispersed in the non-adherent corrosion layers, albeit in small quantities. High-resolution transmission electron microscopy provides an atomic-scale depiction of the coexistent structure of UH3 and UO2, which is described by an innovative “Core (UH3) – Shell (UO2)” model within the corrosion layers. The direct observation of UH3 in this form provides evidence supporting the U-H2O corrosion mechanism postulated to be catalyzed by the interfacial hydrides.

The characteristic Raman spectra of UH3 produced at the initial stage of U-H2O corrosion were observed, which provided direct evidence of the existence of water-formed interfacial UH3. The results were further identified and confirmed using the isotopic labelling method and other characterization techniques. The water-formed hydride layer was distributed at the interface of metallic uranium and oxide exhibiting several nanometers of thickness via the depth profile analysis. The characterizations of oxidation behavior suggested that the interfacial UH3 transformed to oxide and acted as a reaction front in the corrosion process. The experimental results supported the hydride-catalyzed corrosion mechanism of wet oxidation.

Tritium induced radiochemical reaction between hydrogen and carbon monoxide was investigated with the aid of ECR plasma reaction. The results show that long-chain organics such as C4Q10, C5Q12 and C6Q14 were formed in DT-CO mixture without any catalyst, and short-chain organics were the reactants to long-chain organics. CH4, C2H2 and C2H4 were detected in the plasma reaction of hydrogen and carbon monoxide mixture, but no C3+ organics were found. This study revealed that the dominant process of the tritium induced reactions mainly caused by the free radicals produced by β-rays from tritium decay. The fracture of CH bonds promotes the carbon chain growth, while the breakage of CC bonds inhibits the growth of organic carbon chain.

Electrolysis of water is widely used for hydrogen isotope separation and the development of hydrogen evolution reaction (HER) catalysts with high selectivity and activity is of key importance. Herein, we propose single atom catalysts (SACs) as promising catalysts for efficient hydrogen isotope separation. Pt SACs and Pt nanoparticles (NPs) have been fabricated on nanoarray-structured nitrogen-doped graphite foil (NGF) substrate by a polyol reduction method. The as prepared Pt1/NGF electrode exhibits high activity and selectivity toward HER with a low overpotential of 0.022 V at 10 mA·cm−2 and a high separation factor of 6.83 for hydrogen and deuterium separation, much better than Pt NPs counterpart. Density functional theory (DFT) calculations ascribe the high activity and selectivity to the constructed Pt-N2C2 structure. This work develops a new opportunity for the design and application of high-efficiency and stable SACs toward hydrogen isotope separation by electrolysis of water.

The X-ray diffraction spectra of long-time aged LiD/T were examined by a XRD. The lattice constant, grain size and strain were all estimated from the X-ray diffraction patterns. The interface effect on the self-irradiation swelling of lithium tritide was studied by theoretical simulation and experimental observation. The results show that the lattice constant, grain size and strain of LiD/T samples with different self-irradiation aging time fluctuate in different degrees. 3He atoms produced by tritium decay tend to diffuse to the grain boundaries. With the self-irradiation aging time increasing, interface proliferation appears in lithium tritide. In the same selfirradiation aging time, the cracks on the surface of the intact LiD/T sample are easy to widen, while the prefabricated cracks in the sample are not easy to widen. In addition, the accumulation of 3He in the crystal results in the lattice constant growing, and the migration to the grain boundary of 3He leads to the lattice constant contraction. Internal stress leads to grain fragmentation and grain refinement.

Carbon supported single-atom catalysts (SACs) with well-defined active sites and maximum atom utilization efficiency exhibit good activity and selectivity toward a series of electrocatalytic reactions. For the practical applications of SACs, development of facile synthetic methods and analytical techniques is highly useful. Here, single-atom copper has been successfully anchored on sulfur sites of doped graphite foam via an underpotential deposition strategy. By this strategy, the loading amount of Cu SACs can be regulated through tuning the deposition potential, the S contents of the doped graphite foam and the concentration of Cu precursor; moreover, the regulation is perfectly in line with Nernst equation combined with Langmuir adsorption model. Importantly, a stripping voltammetry method is successfully developed for the first time to in-line quantitatively analyze the resultant Cu SACs. Our Cu SACs exhibit remarkable oxygen reduction reaction (ORR) activity with a half-wave potential of 0.862 V (vs RHE) and long-term stability.

Near-equiatomic, multi-component alloys with disordered solid solution phase (DSSP) are associated with outstanding performance in phase stability, mechanical properties and irradiation resistance, and may provide a feasible solution for developing novel uranium-based alloys with better fuel capacity. In this work, we build a machine learning (ML) model of disordered solid solution alloys (DSSAs) based on about 6000 known multicomponent alloys and several materials descriptors to efficiently predict the DSSAs formation ability. To fully optimize the ML model, we develop a multi-algorithm cross-verification approach in combination with the SHapley Additive exPlanations value (SHAP value). We find that the Delta S-C, Lambda, Phi(s), gamma and 1/Omega, corresponding to the former two Hume - Rothery (H - R) rules, are the most important materials descriptors affecting DSSAs formation ability. When the ML model is applied to the 375 uranium-bearing DSSAs, 190 of them are predicted to be the DSSAs never known before. 20 of these alloys were randomly synthesized and characterized. Our predictions are in-line with experiments with 3 inconsistent cases, suggesting that our strategy offers a fast and accurate way to predict novel multi-component alloys with high DSSAs formation ability. These findings shed considerable light on the mapping between the material descriptors and DSSAs formation ability.

The extreme environment in a fusion reactor, namely high thermal load and intense energetic particles, requires the materials to possess high strength and good ductility at high temperature in combination with excellent radiation resistance. Conventional metal tungsten (W) and its alloy cannot satisfy these rigorous requirements, but the discovery of the W-based high-entropy alloys (HEAs) with outstanding properties sheds light on the developments of structural materials. Unique properties of some of these alloys make them promising candidates for engineering applications in fusion reactor beyond conventional W and its alloys. In particular, their strengthening-toughening mechanism has also aroused wide concern. Here, the design, microstructure, mechanical properties and irradiation performance of W-based HEAs are reviewed, and their future prospects are outlined.

In present study, Li4SiO4 ceramics were sequentially irradiated at room temperature using 540 keV He+ and 250 keV H+ with ion fluences of 1 x 1016 ions/cm2 and 1 x 1017 ions/cm2, corresponding to 2.14 displacements per atom (dpa) and 21.4 dpa, respectively. The change of featured structures and the long-term evolution of helium bubbles in irradiated Li4SiO4 were investigated by grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy and transmission electron microscope (TEM). For the as-irradiated Li4SiO4, the results revealed that the lattice parameter and the amorphous fraction increased and the crystallinity decreased with the increasing irradiation dose, and the anionic disordering was the mainly induced damage. When the irradiation dose reached to 21.4 dpa, high-density bubbles with a mean diameter of 1.6 nm were observed in Li4SiO4. The following 480-day aging at room temperature rendered bubble growth due to surface diffusion, which was demonstrated by the fact of an increase in bubble size (mean diameter of 18.4 nm) and a decrease in bubble density. The formation and growth of bubbles could benefit from the presence of amorphous structures and hydrogen atoms. Furthermore, the dynamic evolution of bubbles during annealing at 723 K was monitored by in-situ TEM, and the results indicated that the migration and coalescence mechanism dominated the growth of bubbles in Li4SiO4 under relatively low temperatures.

In nuclear fusion reactor facilities, the multi-confinement system and the air detritiation system (ADS) are very important to prevent tritium leaking to the environment. A high-performance tritium oxidation catalyst is strongly required in the ADS. In this study, the air resistance and catalytic performance of honeycomb detritiation catalysts are investigated. Then, the honeycomb catalysts are applied in a glove-box detritiation system as well as in an ADS, and the detritiation performance is tested with tritium. Honeycomb catalysts have a much lower air resistance and an excellent scale-up effect due to the behavior of laminar flow. Thus, the honeycomb catalyst increases the reaction space velocity by nearly 100 times without decreasing the conversion rate of H2. Even at an extremely low tritium concentration, the honeycomb catalyst transforms tritium over 95% into tritiated water. In short, Pt-loaded honeycomb catalysts have a huge advantage in and broad potential for air detritiation.

The influence of diffusive Nb redistribution on the microstructure and Volta potential of U-5.5Nb alloys thermally aged at 400 degrees C for durations between 1 h and 100 h was investigated and their surfaces were examined post-corrosion using various microscopy techniques. The results demonstrated that Nb-depleted lamellae resulting from Nb redistribution have the lowest Volta potential in the microstructure and are extremely sensitive to pitting, as demonstrated by immersion experiments and potentiometric polarization tests. However, the pitting potential of the aged alloys (205.2 +/- 3.9 mV) did not change with the content of Nb-depleted lamellae.

An ideal carbon support, nanoarray-structured nitrogen-doped graphite foil (NNGF), is facilely prepared via a nitrogen plasma procedure of commercial graphite foil (GFL). After plasma treatment, NNGF owns both the bulk layer of graphite inherited from GFL and surface layer of nanoarray-structured defect-rich N doped carbon. Nanometer-sized NiFe layered double hydroxides (NiFe LDH), as an example, are electrodeposited onto NNGF for direct utilization as an OER electrode. Due to the remained graphite layer, the composite electrode is highly conductive; owing to the strong interaction between N dopants and LDH sheets, the charge transfer is dramatically enhanced; meanwhile the diffusion of liquid reactants and gas products during electrocatalysis is also facilitated by the nanoarray structure. As expected, this hybrid NiFe LDH/NNGF electrode exhibits a low overpotential of 0.191 V at 10 mA cm(-2). Such nanoarray-structured carbon material is promising to be a universal support for other active species (e.g. NiCo LDH).

铀铌合金作为一种重要的核工程材料,因其较高的密度、优异的耐蚀性能和良好的力学性能等特点,被广泛应用于核工业领域.铀铌合金受成分及热处理工艺影响显著,表现出复杂的相转变和组织结构特征,使得铀铌合金耐腐蚀性能及力学性能可在较大范围内获得调控.本文按照“成分/工艺-结构-性能”主线,综述了近年铀铌合金在结构、性能调控方面的研究进展,认为:低温时效机制和杂质控制技术仍是铀铌二元合金研究中需要重点关注的问题;高通量设计、制备及表征手段的出现,为未来铀铌多元合金结构及性能调控研究带来了新的机遇与挑战.

Platinum-based single-atom catalysts (SACs) are among the most promising candidates for the practical applications of electrochemical hydrogen evolution reaction (HER), but their catalytic efficiency remains to be further enhanced. Herein, a well-designed nanoarray-structured nitrogen-doped graphite foil (NNGF) substrate is introduced to support Pt SACs in Pt-N-4 construction (Pt-1/NNGF) for HER. Within NNGF, the constructed nanoarray-structured surficial layer for supporting Pt SACs could enhance the exposure of active sites to the electrolyte and improve the reaction and diffusion kinetics; meanwhile, the retained graphite structures in bulk NNGF provide not only the required electrical conductivity but also the mechanical stability and flexibility. Because of such double-layer structures of NNGF, stable Pt-N-4 construction, and binder-free advantages, the Pt-1/NNGF electrode exhibits a low overpotential of 0.023 V at 10 mA cm(-2) and a small Tafel slope of 29.1 mV dec(-1) as well as an excellent long-term durability.

The exploration of high-performance and low-cost electrocatalysts for catalyzing both hydrogen and oxygen evolution reaction (HER and OER) at high current density is of vital significance for the commercialization of water splitting. Herein, amorphous NiFe phosphides are electrodeposited on 3D nanoarraystructured nitrogen-doped carbon paper (NCP) for direct use as a hybrid electrode toward overall water splitting. The as-prepared NiFe-P/NCP electrode requires only an overpotential of 0.226 and 0.125 V at 50 mA cm(-2) for OER and HER, respectively. In addition, NiFe-P/NCP electrodes are further measured as a catalytic cathode and anode couple (NiFe-P/NCPI INiFe-P/NCP) for overall water splitting, exhibiting a low cell voltage of 1.547 to reach 10 mA cm(-2) as well as a long-term durability. Our work reveals the significance of introducing well-designed substrate and bimetallic active species for enhanced electrochemical performance towards overall water splitting. (C) 2020 Elsevier Ltd. All rights reserved.

Based on the previous study in frontal displacement chromatography (FDC) packed with Pd-Al2O3, two groups of separation experiments were conducted to derive the rules how the two most significant factors, temperature and gas flow rate, to influence the separation performance. Separations of the first group were carried out at the feed gas flow rate of 15 mL/min and temperature of 303-213 K, and the second group at 253 K and 10-100 mL/min, with the identical composition of feedstock ((5 +/- 0.1)%H-2-(5 +/- 0.1)%D-2-(90 +/- 0.1)%Ar). The results indicate the derived rules are consistent with those from references: 1) the rules of temperature effects on separation efficiency lie in two aspects that the lower the temperature is, the larger the thermodynamic separation effect is, and the higher the temperature is, the quicker the hydrogen isotopes exchange dynamics becomes. As to FDC using palladium, 263-213 K will be an appropriate temperature range to have excellent separation performance achieved with the insight into these two aspects. 2) the rule of the influence of gas flow rate basically obeys the van Deemter equation, which means that it does exist an theoretically optimal gas flow rate, (u) over bar (opt), at a certain temperature and for a certain composition of feedstock, and considering the theoretics and efficiency, separations conducted at the gas flow rate of an suitable range that higher than (u) over bar (opt) but less than 10 (u) over bar (opt) can derive good separation performance. The results and discussion have verified the imperative impact of temperature and gas flow rate on the separation performance of this FDC method, and the derived desirable temperature and gas flow rate ranges would supply valuable supports and references for future applications of FDC in hydrogen isotopes separation and tritium recovery in fusion reactors. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.