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The Antarctic Slope Current (ASC) plays a central role in redistributing water masses, sea ice, and tracer properties around the Antarctic margins, and in mediating cross-slope exchanges. While the ASC has historically been understood as a wind-driven circulation, recent studies have highlighted important momentum transfers due to mesoscale eddies and tidal flows. Furthermore, momentum input due to wind stress is transferred through sea ice to the ASC during most of the year, yet previous studies have typically considered the circulations of the ocean and sea ice independently. Thus, it remains unclear how the momentum input from the winds is mediated by sea ice, tidal forcing, and transient eddies in the ocean, and how the resulting momentum transfers serve to structure the ASC. In this study the dynamics of the coupled ocean–sea ice–ASC circulation are investigated using high-resolution process-oriented simulations and interpreted with the aid of a reduced-order model. In almost all simulations considered here, sea ice redistributes almost 100% of the wind stress away from the continental slope, resulting in approximately identical sea ice and ocean surface flows in the core of the ASC in a fully spun-up equilibrium state. This ice–ocean coupling results from suppression of vertical momentum transfer by mesoscale eddies over the continental slope, which allows the sea ice to accelerate the ocean surface flow until the speeds coincide. Tidal acceleration of the along-slope flow exaggerates this effect and may even result in ocean-to-ice momentum transfer. The implications of these findings for along- and across-slope transport of water masses and sea ice around Antarctica are discussed.

The transformations of CO2 molecules into valuable products are of increasing interest due to the negative impact of anthropogenic CO2 emissions on global warming. The CO2-to-methanol hydrogenation is an economically profitable reaction of carbon fixation, but it still steps away from widespread industrialization because of the lack of efficient and selective catalysts. Recently, single-atom alloy (SAA) catalysts have been developed to work remarkably in CO2 hydrogenation reactions. Doping isolated single atoms into metallic catalyst can dramatically alter the catalytic performance of the host. We have performed a screening discovery on Ru and 6 RuX (X = Fe, Co, Ni, Cu, Ir and Pt) SAAs using density functional theory (DFT) computations. We considered 13 possible elementary reactions in 4 possible reaction pathways on Ru and all RuX surfaces. In the computed mechanisms, we found that the formation of *H2COOH and *HCOO intermediates plays a critical role in determining catalysts’ activities. Doping Co and Pt isolated single atoms into Ru surface can thermodynamically and kinetically facilitate these intermediates formation processes, eventually promoting the production of methanol. The combination of weak binding and enhanced charge redistribution on RuCo and RuPt surfaces give them improved catalytic activities over pure Ru. This work will ultimately facilitate the discovery and development of SAAs for CO2 to methanol, serving as guidance to experiments and theoreticians alike.

In this paper, the volatile and char combustion were separated in a high temperature fixed bed reactor. The effects of temperature (700–1300 °C) and oxygen concentration (5%–40%) on volatile-N and char-N, as well as the nitrogen conversion mechanism of three different biomass were studied in O2/CO2 and O2/Ar atmospheres. The results show that the release amount of fuel-NO increases first and then decreases with temperature in both coupled and separated combustion. Nitrogen redistribution caused by the interaction between volatile and char during pyrolysis at high temperatures can affect the final release amount of fuel-NO. Thus, below 1100 °C, the release amount of fuel-NO in coupled combustion is smaller than that in separated combustion, while the opposite trend is shown after 1100 °C. With temperature increasing, the release amount of volatile-NO increases first and then decreases, while the release amount of char-NO decreases continuously. The release amount of volatile-NO in O2/CO2 is less than that in O2/Ar, and the release amount of char-NO also shows the same result at low temperature, and shows the opposite trend at high temperature. With oxygen concentration increasing, the release amount of fuel-NO in coupled and separated combustion, as well as volatile-NO and char-NO increases first and then decreases.

Calcium sulfate (CaSO4) has been verified as a promising oxygen carrier (OC) in the chemical looping combustion (CLC) for its high oxygen capacity, abundant reserve and low cost, but its low reactivity and deleterious sulfur species emission from the side reactions of CaSO4 should be well considered for its wide application in CLC. In order to promote the reactivity of CaSO4 and increase its potential to inhibit the gaseous sulfur emission, a CeO2-enhanced CaSO4 OC mixed OC of core-shell structure was prepared using the combined template synthesis method. Reaction characteristics of the prepared CaSO4-CeO2 mixed OC with a typical lignite was first conducted and systematically investigated, and an improved reactivity of the prepared CaSO4-CeO2 mixed OC was demonstrated than its single component CaSO4 or CeO2 due to the fast transfer and exchange of oxygen from the CaSO4 substrate to coal via the doped CeO2. Furthermore, the solid products formed from the mixed CaSO4-CeO2 OC with the selected coal were collected and analyzed. Especially, evolution and redistribution of the sulfur species of different forms were focused. At the latter reaction stage of YN reaction with the CaSO4-CeO2 mixed OC, the SO2 emitted from the side reactions of CaSO4 was greatly diminished and the doped CeO2 was proven effective to directionally fix the SO2 released to turn into different solid sulfur compounds, which were determined as Ce2O2S, Ce2S3 and Ce2(SO4)3·5H2O and formed through the different pathways. In addition, good regeneration of the reduced CaSO4-CeO2 mixed OC could be reached in spite of the unavoidable interaction between the included minerals in coal and the reduced mixed OC. Overall, the combined template method-made CaSO4-CeO2 mixed OC reported herein was not only endowed with enhanced reactivity for coal conversion, but also owned the potential to directionally fix the gaseous sulfur emission, which is quite applicable as OC for simultaneous decarbonatization and desulfurization in the real CLC process.

Screening of AgNO3/AgStBu solutions in DMF, DMSO and NMP resulted in an isolation of three novel nanosized silver/thiolate complexes with a torus-like {Ag20(StBu)10} core. The structures of [NO3@Ag20(StBu)10(NO3)9(DMF)6] (1) and [NO3@Ag20(tBuS)10(NO3)8(NMP)8][NO3@Ag19(tBuS)10(NO3)8(NMP)6]2(NO3) (2) were studied by SCXRD. The self-assembly process leading to 1 can be switched to a different outcome by Br–, resulting in [Br@Ag16(StBu)8(NO3)5(DMF)3](NO3)2 (3), which is the one of the few genuine host-guest complex in the silver/thiolate systems. Solutions of the individual complexes in CH3CN were studied by HR-ESI-MS techniques, which revealed a dynamic behavior for each complex, driven by a redistribution of the {AgNO3} units. This dynamics results in the appearance of both cationic and anionic species, based on unchanged silver-thiolate cores. Day light causes degradation of 3 with the formation of a composite material based on defective orthorhombic Ag2S with a porous morfology, as observed with SEM technique. Electrocatalytic HER activity of such material was studied.

The present work compares the 2D and 3D distribution of TiB2 particles in a semisolid processed Al-4.5%Cu-5wt.% TiB2 in-situ composite prepared by flux assisted synthesis. The composite was synthesized by the reaction of K2TiF6 and KBF4 salts in molten Al-4.5Cu alloy held at 800 oC for an hour. The extent of distribution of TiB2 particles was investigated using Field Emission Scanning Electron Microscopy (FESEM) and X-ray computed tomography (XCT) to obtain 2Dand 3D images respectively. The studies indicated improved distribution of TiB2 particles after semi-solid forging of composites (at 0.1 volume fraction of liquid and 50% reduction) as compared to as cast composites. The hardness of the semisolid forged composites showed a significant increase and is uniform in all directions. The increase in hardness could be attributed to particle fragmentation and its redistribution in the matrix. Further investigation will be needed to understand the mechanism of redistribution and investigate the mechanical properties of such composites in detail. Copyright © 2016 VBRI Press.

Geological CO $$_2$$ sequestration is an effective approach to mitigate greenhouse gas emissions by permanently trapping CO $$_2$$ in the subsurface. A large portion of injected CO $$_2$$ is trapped by capillary forces in pores and eventually dissolves into the reservoir brine due to convective mixing to achieve permanent entrapment. In regions where convective mixing is slow, non-convective transport can play an important role in redistributing residually trapped CO $$_2$$ , but the mechanisms and timescales for redistribution have yet to be explored thoroughly. In previous work, we have shown that capillary pressure difference among residually trapped gas ganglia can induce Ostwald ripening, thereby redistributing the separate-phase gas through diffusion despite the gas phase remaining trapped over the entire course of equilibration. In this study, we show from a thermodynamic point of view that other natural gradients in geologic formations— hydrostatic pressure, geothermal gradients and capillary heterogeneity—can also redistribute CO $$_2$$ by non-convective transport. Mechanisms for resulting non-convective transport include molecular diffusion, the sedimentation effect and potentially the Soret effect. Results show that hydrostatic pressure dominates redistribution such that the separate-phase gas is transported upward through molecular diffusion and accumulates under the seal at the steady state. A typical timescale for gas phase redistribution is $$10^5$$ years/m; for a 100-m-thick formation, redistribution is complete after $$\sim 10^7$$ years. Although non-convective transport is an extremely slow process, it causes local accumulation of the gas phase and in some settings may remobilize the trapped gas phase.

Although molybdenum disulfide (MoS2)-based materials are generally known as active electrocatalysts for the hydrogen evolution reaction (HER), the inert performance for the oxygen evolution reaction (OER) seriously limits their wide applications in alkaline electrolyzers due to there exists too strong metal-sulfur (M−S) bond in MoS2. Herein, by means of surface reorganization engineering of bimetal Al, Co-doped MoS2 (devoted as AlCo3-MoS2) through in situ substituting partial oxidation, we successfully significantly activate the OER activity of MoS2, which affords a considerably low overpotential of 323 mV at −30 mA cm−2, far lower than those of MoS2, Al-MoS2 and Co-MoS2 catalysts. Essentially, the AlCo3-MoS2 substrate produces lots of M−O (M=Al, Co and Mo) species with oxygen vacancies, which trigger the surface self-reconstruction of pre-catalysts and simultaneously boost the electrocatalytic OER activity. Moreover, benefiting from the moderate M−O species formed on the surface, the redistribution of surface electron states is induced, thus optimizing the adsorption of OH* and OOH* intermediates on metal oxyhydroxides and awakening the OER activity of MoS2.

In this study, a vertical twin-roll cast (TRC) thermal-fluid coupling model was established to determine a suitable roll-casting velocity. A slab of 0.9mm thick roll-cast Al-50 wt.% Si alloy with a two-phase zone width of 473°C was prepared at a velocity of 20m/min for the first time. In addition, the finite element simulation showed that the average heat transfer rate had a positive correlation with the roll-casting velocity. When the roll-casting velocity increased to 20m/min, the average heat transfer rate reached 1260K/s, at which point, the average size of the primary Si was merely 16.5μm. This was a decrease of approximately 90% when compared with the size of alloys cast with conventional methods. After carrying out semi-solid heating, an observation on the distribution of alloy elements identified a novel phenomenon of solute redistribution, i.e., inverse segregation. This inverse segregation process was highly significant in further controlling solute redistribution in the alloy. Additionally, it provided a new concept for improving roll-cast segregation.

Phase-change solvents (PCSs) is a class of chemicals that promises significant cost reductions in post-combustion CO2 capture. However, their use in the design of efficient absorption/desorption processes is challenged by their non-ideal behavior. A generic and flexible model is proposed for the design of phase-change CO2 capture process systems, that enables the effective identification of highly performing flowsheet configurations and recycle stream redistribution policies. The validation of the model using experimental data for the PCS mixture of MAPA/DEEA (3-(Methylamino)-Propylamine/2-(Diethylamino)-Ethanol) indicates only 4% and 0.5% differences in the reboiler duty and in the absorption and desorption temperatures. The novel PCS mixture of S1N/DMCA (N-Cyclohexyl-1,3-Propanediamine/N,N-Dimethylcyclohexylamine) and the PCS MCA (N-methylcyclohexylamine) are used in the optimum design of CO2 capture process units in two industrial cases; a quicklime production plant and a gas-fired power plant. The reboiler duty of S1N/DMCA reaches 2.1 GJ/ton CO2 and the solvent exhibits up to 47% lower operating costs than the conventional MEA (Monoethanolamine), with only 1.7% higher capital costs. The loading of S1N/DMCA reaches up to 1.35 mol CO2/mol of solvent at the exit stream of the phase-separator, whereas this solvent exhibits up to 181% higher CO2 release efficiency than MEA in the desorber. S1N/DMCA is an excellent option for plants with flue gas CO2 concentration as low as 3.5 mol%.

Size reduction can generally enhance the surface reactivity of inorganic nanomaterials. The origin of this nano-effect has been ascribed to ultrasmall size, large specific surface area, or abundant defects, but the most intrinsic electronic-level principles are still not fully understood yet. By combining experimental explorations and mathematical modeling, herein we propose an electronic-level model to reveal the physicochemical nature of size-dependent nanomaterial surface reactivity. Experimentally, we reveal that competitive redistribution of surface atomic orbitals from extended energy band states into localized surface chemical bonds is the critical electronic process of surface chemical interactions, using H2O2-TiO2 chemisorption as a model reaction. Theoretically, we define a concept, orbital potential (G), to describe the electronic feature determining the tendency of orbital redistribution, and deduce a mathematical model to reveal how size modulates surface reactivity. We expose the dual roles of size reduction in enhancing nanomaterial surface reactivity—inversely correlating to orbital potential and amplifying the effects of other structural factors on surface reactivity.

We report a dramatic reduction of operation voltage of a CuO nanowire-based ionization gas sensor due to the crystalline-to-amorphous phase transformation. The structural change is attributed to the ion bombardment and heating effect during the initial discharge, which brings about the formation of abundant nanocrystallites and surface states favoring gaseous ionization. The gas-sensing properties of the CuO nanowire sensor are confirmed by differentiating various types or concentrations of volatile organic compounds diluted in nitrogen, with a low detection limit at the ppm level. Moreover, a sensing mechanism is proposed on the basis of charge redistribution by electron-gas collision related to the specific ionization energy. The insightful study of the electrode microstructure delivers an exploratory investigation to the effect of gas ionization toward the discharge system, which provides new approaches to develop advanced ionization gas sensors.

Lubricant-infused surfaces (LISs) can promote stable dropwise condensation and improve heat transfer rates due to a low nucleation free-energy barrier and high droplet mobility. Topographical differences in the oil surface cause water microdroplets to rigorously self-propel long distances, continuously redistributing the oil film and potentially refreshing the surface for re-nucleation. Using high-speed microscopy, we reveal that during water condensation on LISs, the smallest visible droplets (diameter ~ 1um, qualitatively representing nucleation) predominantly emerge in oil-poor regions due to a smaller thermal activation barrier. Considering the significant heat transfer performance of microdroplets (< 10um) and transient characteristic of microdroplet movement, we compare the apparent nucleation rate density and water collection rate for LISs with oils of different viscosity and a solid hydrophobic surface at a wide range of subcooling temperatures. Generally, the lowest lubricant viscosity leads to the highest nucleation rate density. We characterize the length and frequency of microdroplet movement and attribute the nucleation enhancement primarily to higher droplet mobility and surface refreshing frequency. Interestingly and unexpectedly, hydrophobic surfaces outperform high-viscosity LISs at high subcooling temperatures, but are generally inferior to any of the tested LISs at low temperature differences. To explain the observed non-linearity between LISs and the solid hydrophobic surface, we introduce two dominant regimes that influence the condensation efficiency: mobility-limited and coalescence-limited. Our findings advance the understanding of dynamic water-lubricant interactions and provide new design rationales for choosing surfaces for enhanced dropwise condensation and water collection efficiencies., submitted to Langmuir

Twin engineering is an efficient strategy to improve the photocatalytic activity of semiconductors (e.g., BiVO4). A systematic study that combines theory and experiments is conducted to reveal the underlying enhanced catalytic mechanism of twin-structured BiVO4. The key characteristic of twinned structures is the partial strain introduced by twin boundaries. Lattice distortion introduced by the twin boundaries leads to charge redistribution and built-in electronic fields between the twin boundaries and the bulk. The generated homojunctions possess a staggered band alignment structure, and their band offsets are increased by the Fermi-level pinning effect. The series of homojunctions in twinned structures is beneficial for facilitating charge separation. Additionally, lattice distortion around twin boundaries leads to the broken geometric symmetry of metal-oxygen polyhedrons in twinned crystals. The adsorption energies of adsorbates decrease significantly, resulting in reduction of the overpotential. The reduced overpotential favors acceleration of the oxygen evolution reaction on twinned structures.

Heavily doped n-type Ge crystals are essential for Ge-based electronics and optical applications. In this report, we describe the mechanism of dopant redistribution via out-diffusion and re-evapora...

Advanced materials development, manufacturing, and modeling capabilities for innovative reactor designs support nuclear security and mission-focused science through enhanced technology for safer and more efficient and secure production of nuclear energy. The high temperature moderator material yttrium hydride poses a significant enhancement in small reactor design by thermalizing (slowing down) neutrons and decreasing the required fuel mass for a system. The research presented here supports understanding hydrogen distribution in yttrium hydride through: (1) the development of neutron-based hydrogen imaging and crystallographic characterization that allows us to understand fundamental diffraction behaviors and to observe changes in hydrogen distribution as a function of temperature and (2) subsequent neutron multiplication (reactivity) effects of changes in hydrogen distribution using measurement-based cross sections in a sample microreactor design. The main conclusions from the work are that: (1) hydrogen does not redistribute significantly below temperatures of 800°C in yttrium hydride and (2) hydrogen redistribution affects the reactivity slightly but not significantly.

Ambient atmosphere is critical for the surface/interface chemistry of electrodes that governs the operation and failure in energy storage devices (ESDs). Here, taking an Al/graphite battery as an example, both the relaxation and failure processes in the working graphite electrodes have been dynamically monitored by multiple in situ surface and interface characterization methods within various well-controlled atmospheres. Relaxation effects are manifested by recoverable stage-structure change and electronic relaxation occurring in anhydrous inert atmospheres and O2, which are induced by the anion/cation redistribution within the neighboring graphene layers and have slight influence on the long-term cycling. In contrast, rapid and unrecoverable failure behaviors happen in hydrous atmospheres as shown by the stage-structure degradation and electronic decoupling between guest ions and host graphite, which are caused by the hydrolysis between newly intercalated H2O molecules and intercalants. Consistent with the characterization results, exposure to H2O can cause nearly 100% capacity loss. The methodology and concept adopted in this work to unravel the battery mechanism under ambient conditions are universal and significant to investigate many ESDs.

Though copper is a capable electrocatalyst for the CO2 reduction reaction (CO2RR), it rapidly deactivates to produce mostly hydrogen. A current hypothesis as to why this occurs is that potential-induced morphological restructuring takes place, leading to a redistribution of the facets at the interface resulting in a shift in the catalytic activity to favor the hydrogen evolution reaction over CO2RR. Here, we investigate the veracity of this hypothesis by studying the changes in the voltammetry of various copper surfaces, specifically the three principal orientations and a polycrystalline surface, after being subjected to strongly cathodic conditions. The basal planes were chosen as model catalysts, while polycrystalline copper was included as a means of investigating the overall behavior of defect-rich facets with many low coordination steps and kink sites. We found that all surfaces exhibited (perhaps surprisingly) high stability when subjected to strongly cathodic potentials in a concentrated alkaline electrolyte (10 M NaOH). Proof for morphological stability under CO2RR-representative conditions (60 min at -0.75 V in 0.5 M KHCO3) was obtained from identical location scanning electron microscopy, where the mesoscopic morphology for a nanoparticle-covered copper surface was found unchanged to within the instrument accuracy. Observed changes in voltammetry under such conditions, we found, were not indicative of a redistribution of surface sites but of electrode fouling. Besides impurities, we show that (brief) exposure to oxygen or oxidizing conditions (i.e., 1 min) leads to copper exhibiting changing morphology upon cathodic treatment which, we posit, is ultimately the reason why many groups report the evolution of copper morphology during CO2RR: accidental oxidation/reduction cycles.

Levulinic acid (LA) is one of the substances, which can be obtained from cellulosic biomass via acid hydrolysis and serves as a precursor in the synthesis of gamma-valerolactone (GVL) – platform chemical for so-called valeric fuels. This work is devoted to the study of catalytic conversion of LA to GVL using mono- (Ru) and bimetallic (Ru-Co) catalysts based on ruthenium-containing nanoparticles immobilized in hyper-crosslinked polystyrene (HPS). It was shown that RuO2 nanoparticles are an active phase of HPS-based Ru catalysts, which allow nearly 100 % yield of GVL at 120 °C and 2 MPa of hydrogen partial pressure for the reaction time 60 min. Introduction of cobalt in catalyst composition in a proper amount (Ru-to-Co weight ratio is 30) was found to result in Ru redistribution inside the polymeric support and, in turn, to the increase of reaction rate of LA hydrogenation.

Abstract Conditions for the formation of microconcentration inhomogeneities in Fe–Ni alloys, which can decrease their invar characteristics, are determined. The nickel separation can be reached in the course of short-term annealing as a result of deformation-induced nickel segregation, nickel redistribution between martensite and austenite and between ferrite and austenite as well.

The electronic structures and the character of the electron density redistribution in the palladium complexes with the redox-active ligands in the oxidized and nonoxidized forms are studied by X-ray photoelectron spectroscopy. According to the photoelectron spectroscopic data, the redox-active ligands exist in different oxidation states due to the redox process proceeding “at ligand.” It is shown that the transition from the neutral to oxidized semiquinone form (from [Pd(LMe)2]·2Cl·H2O to [Pd $$\left( {{\text{L}}_{{{\text{Ph}}}}^{{{\text{ISQ}}}}} \right)$$ 2]) occurs in the ligand and involves no palladium ions, and the oxidation state of palladium remains unchanged: Pd(II). A significant difference in the photoelectron spectroscopic characteristics obtained for the oxidized trans-complex at 298 and 153 K indicates a specific electronic lability of this complex.

Two AlxCoCrFeNi (x = 0.75, 1.25) high entropy alloys (HEAs) were prepared and annealed with different temperatures (800, 1000 and 1200 °C) and holding times (2 h, 4 h and 8 h) using furnace cooling. Effects of annealing treatment details on the microstructure and hardness of the HEAs were investigated. It was found that the σ-phase did not form in the Al0.75CoCrFeNi alloy for whatever annealing temperatures or holding times. The σ-phase was produced at 610 °C and dissolved at 930 °C in the Al1.25CoCrFeNi alloy. After dissolution, the σ-phase could reappear when this alloy furnace cooled from higher annealed temperature (1200 °C for 4 h) or longer duration time (1000 °C for 8 h). The reason is that the redistribution of Cr element in the post-holding stage or furnace cooling stage was sufficient to precipitate σ-phase. The formation and dissolution of σ-phase and their influences on the hardness in the HEAs were analyzed and discussed thoroughly.

The field of vibrational polariton chemistry was firmly established in 2016 when a chemical reaction rate at room temperature was modified within a resonantly tuned infrared cavity without externally driving the system. Despite intense efforts by scientists around the world to understand why the reaction rate changes, no convincing theoretical explanation exists. In this perspective, first, we briefly review this seminal experiment, as well as relevant experiments that have since followed that have hinted at the roles of reactant concentration, cavity frequency, and symmetry. Then, we analyze the relevance of leading theories, such as quantum electrodynamics-modified transition rate theories, the photonic solvent cage effect, the impact of dissipation from dark states, bond strengthening via intramolecular vibrational energy redistribution, and collectively enhanced local molecular properties. Finally, we construct a roadmap toward the theory of vibrational polariton chemistry by suggesting experiments to test theories and new paths for theorists. We believe that understanding the importance of the onset of the strong coupling regime, designing experiments to capture changes in reaction pathways, and further developing the theories of cavity-modified intramolecular vibrational energy redistribution and collectively enhanced local molecular properties are crucial next steps. We hope this perspective will be a valuable resource for guiding research in the field of vibrational polariton chemistry.

Model of the impurities redistribution in the surface layer of an alloy under the action of pulsed laser radiation

Good knowledge of the redistribution characteristic of solute elements is essential for the design and the production of new alloying systems. Part I of this series demonstrated the deviations of m...

Chlorpyrifos is an extensively used insecticide in the agriculture worldwide and was often detected in both surface waters and groundwater, posing threats to local residents’ health. Temporal chang...

Complexes that could be switched between two electronic states by external stimuli have attracted much attention for their potential application in molecular devices. However, a realization of such a phenomenon with low-valent main-group element-centered complexes remains challenging. Herein, we report the synthesis of cyclic (alkyl)(amino)silylene (CAASi)-ligated monatomic silicon(0) complexes (silylones). The bis(CAASi)-ligated silylone adopts a π-localized ylidene structure (greenish-black color) in the solid state and a π-delocalized ylidene structure (dark-purple color) in solution that could be reversibly switched upon phase transfer (ylidene [L: → :Si = L ↔ L = Si: ← :L]). The observed remarkable difference in the physical properties of the two isomers is attributed to the balanced steric demand and redox noninnocent character of the CAASi ligand which are altered by the orientation of the two terminal ligands with respect to the Si-Si-Si plane: twisted structure (π-localized ylidene) and planar structure (π-delocalized ylidene). Conversely, the CAASi/CDASi-ligated heteroleptic silylone (CDASi = cyclic dialkylsilylene) only exhibited the twisted π-localized ylidene structure regardless of the phase. The synthesized silylones also proved themselves as monatomic silicon surrogates. Thermolysis of the silylones in the presence of an ethane-1,2-diimine afforded the corresponding diaminosilylenes. Analyses of the products suggested a stepwise mechanism that proceeds via a disilavinylidene intermediate.

Although various cobalt-sulfide-based materials have been reported for the hydrogen evolution reaction, only a few have achieved high activity in both acid and alkaline electrolytes due to the inherent poor conductivity and low active sites. In this work, a heterojunction of cobalt sulfide and Mo2N is designed for efficient hydrogen evolution reactions in both acid and alkaline electrolytes. X-ray photoelectron spectroscopy reveals that Mo-S bonds are formed at the interface between Mo2N and CoS2, which result in the fabricated Mo2N/CoS2 materials exhibiting a considerably enhanced hydrogen evolution reaction activity than the corresponding Mo2N, CoS2, and most reported Mo- and Co-based catalysts in electrolytes of H2SO4 and KOH solutions. Density functional theory calculations suggest that the redistribution of charges occurs at the heterointerface. In addition, the interfacial active sites possess a considerably lower hydrogen adsorption Gibbs free energy than those atoms that are far away from the interface, which is beneficial to the process of hydrogen evolution reaction. This study provides a feasible strategy for designing hetero-based electrocatalysts with a tuned highly active interface.

The paper considers the redistribution of the charge density in a carbon nanotube caused by the adsorption of a lithium atom on it. The effective lithium charges were calculated according to the me...

Density functional theory calculations were applied to investigate LiF decoration of B12N12 cage in terms of the structures and stabilities. Then, the resulted LiF-decorated B12N12 cages were explored to find their capability as hydrogen storage. The DFT results showed that decoration of BN cages is independent of the previously decorated BN bonds. LiF decoration of BN bonds leads to charge redistribution so that charges of the atoms nearest to the decorated bonds change and charges of the other ones remain rather unchanged. Hydrogen prefers to bind to the B atoms that are nearest to the decorated Li. It was revealed that H atoms bind more strongly to B atoms of LiF-decorated B12N12 cages in comparison to pristine B12N12 cage. Two types of hydrogen bonding were formed in B12N12Li4F4 and B12N12Li6F6, binding of hydrogens in a quasi-molecular form to the decorated Li atoms, and also binding of hydrogen in atomic to B atoms. Calculated binding energies showed that binding of hydrogen to the models is an intermediate between physical and chemical adsorption, indicating that the LiF-decorated B12N12 cages are suitable as hydrogen storage materials.

It is shown that a specific nonlinear collective photon–photon interaction occurs in a nanodispersed medium, which corresponds to the transition of the medium in an intense electromagnetic field to an optically dense state, and which in its physical sense can be called the induced coherent interaction of laser fields.

The conditions of energy exchange in two- and three-layer ensembles of charged particles of various sizes in a gravity field are investigated. The processes of the redistribution of stochastic kinetic energy between fractions of particles having different temperatures, as well as the redistribution of stochastic energy over the degrees of freedom are numerically simulated. A semi-empirical approximation is proposed that depends on the temperature of thermal sources and the characteristic frequencies of the system, and describes well the processes of energy exchange in all the cases under consideration.

Abstract Using the Mössbauer spectroscopy and transmission electron microscopy (TEM) methods, the temperature boundary of a strain-induced transformation with the inversion of the direction of nitrogen redistribution is determined in the structure of the FeMn22Cr18N0.83 austenitic steel. Deformation by high pressure torsion in Bridgman anvils below the temperature limit (298 K) leads to an increase in the amount of nitrogen in the interstitial solid solution and deformation above the limit (373 K) leads to a decrease in this value. An increase in the deformation temperature leads to the complete dissolution of the products of cellular decomposition and the formation of submicrocrystalline austenite with secondary nanocrystalline nitrides. Changes in the direction of nitrogen redistribution are explained by the competition between the mechanisms of relaxation of the structure along the paths of dispersion, dissolution of nitrides by dislocation, and decomposition of a solid solution supersaturated with nitrogen.

Novel technical solutions and ideas for increasing the yield of solar and semiconductor grade polycrystalline silicon processes have been analyzed. The predominant polycrystalline silicon technology is currently still the Siemens process including the conversion of technical grade silicon (synthesized by carbon-thermal reduction of quartzites) to trichlorosilane followed by rectification and hydrogen reduction. The cost of product silicon can be cut down by reducing the trichlorosilane synthesis costs through process and equipment improvement. Advantages, drawbacks and production cost reduction methods have been considered with respect to four common trichlorosilane synthesis processes: hydrogen chloride exposure of technical grade silicon (direct chlorination, DC), homogeneous hydration of tetrachlorosilane (conversion), tetrachlorosilane and hydrogen exposure of silicon (hydro chlorination silicon, HC), and catalyzed tetrachlorosilane and dichlorosilane reaction (redistribution of anti-disproportioning reaction). These processes remain in use and are permanently improved. Catalytic processes play an important role on silicon surface, and understanding their mechanisms can help find novel applications and obtain new results. It has been noted that indispensable components of various equipment and process designs are recycling steps and combined processes including active distillation. They provide for the most complete utilization of raw trichlorosilane, increase the process yield and cut down silicon cost.

Whenever T-junctions are used in chemical processes and petroleum industries for two-phase separation, a maldistribution of phases is observed between outlets of the junction. Currently, the regular T-junctions are utilized in the industry due to which equipment downstream faces high liquid carryovers. Unfortunately, downstream equipment is not capable of handling high liquid carryovers and they trip frequently, consequently. This review manuscript summarizes the effect of different factors that influence phase separation in the T-junction. This article refers to the geometrical parameters, phase superficial velocity flow regimes encounter during the separation process, and different side arm modifications. This article is a contribution to this field as it summarizes and concludes all these factors comprehensively, to give a verdict on ways to improve phase separation. It is also recommended that the effect of side arm modifications or combinations must be explored for further understanding.

The redistribution of C and N atoms during cryogenic treatment is crucial for the microstructure evolution and properties of high nitrogen martensitic steel. Here, the distinct redistribution behavior of C and N atoms in a martensitic stainless steel with 0.3 wt% C and 0.5 wt% N after cryogenic treatment were investigated by the atom probe tomography. Carbon clusters begin to form after cryogenic treatment at − 60 °C and gradually increase with the decrease of cryogenic treatment temperature. While Mo–N and Cr–N pairs are homogeneously distributed in the matrix even after cryogenic treatment at −120 °C, and then form enrichment phenomenon when the cryogenic temperature is deeply lowered to − 190 °C. It is found that the distinct redistributions of C and N atoms are associated with the different interaction energy between substitutional atoms and them. The stronger interaction between Cr, Mo atoms and N delays the segregation of N during the cryogenic treatment. Finally, the mechanical properties results confirmed that the deep lower cryogenic treatment is a promising method to improve the hardness and strength in the high nitrogen martensitic stainless steel.

Droplets impacting solid surfaces is ubiquitous in nature and of practical importance in numerous industrial applications. For liquid-repelling applications, rigidity-based asymmetric redistribution and flexibility-based structural oscillation strategies have been proven on artificial surfaces; however, these are limited by strict impacting positioning. Here, we show that the gap between these two strategies can be bridged by a flexibility-patterned design similar to a trampoline park. Such a flexibility-patterned design is realized by three-dimensional projection micro-stereolithography and is shown to enhance liquid repellency in terms of droplet impalement resistance and contact time reduction. This is the first demonstration of the synergistic effect obtained by a hybrid solution that exploits asymmetric redistribution and structural oscillation in liquid-repelling applications, paving the rigidity-flexibility cooperative way of wettability tuning. Also, the flexibility-patterned surface is applied to accelerate liquid evaporation.

Elevated atmospheric CO2 concentration (eCO2) often reduces nitrogen (N) content in rice plants and stimulates tillering. However, there is a general consensus that reduced N would constrain rice tillering. To resolve this contradiction, we investigated N distribution and transcriptomic changes in different rice plant organs after subjecting them to eCO2 and different N application rates. Our results showed that eCO2 significantly promoted rice tillers (by 0.6, 1.1, 1.7, and 2.1 tillers/plant at 0, 75, 150, and 225 kg N ha−1 N application rates, respectively) and more tillers were produced under higher N application rates, confirming that N availability constrained tillering in the early stages of growth. Although N content declined in the leaves (−11.0 to −20.7 mg g−1) and sheaths (−9.8 to −28.8 mg g−1) of rice plants exposed to eCO2, the N content of newly emerged tillers on plants exposed to eCO2 equaled or exceeded the N content of tillers produced under ambient CO2 conditions. Apparently, the redistribution of N within the plant per se was a critical adaptation strategy to the eCO2 condition. Transcriptomic analysis revealed that eCO2 induced less extensive alteration of gene expression than did N application. Most importantly, the expression levels of multiple N‐related transporters and receptors such as nitrate transporter NRT2.3a/b and NRT1.1a/b were differentially regulated in leaf and shoot apical meristem, suggesting that multiple genes were involved in sensing the N signal and transporting N metabolites to adapt to eCO2. The redistribution of N in different organs could be a universal adaptation strategy of terrestrial plants to eCO2.

A general problem when designing functional nanomaterials for energy storage is the lack of control over the stability and reactivity of metastable phases. Using the high-capacity hydrogen storage candidate LiAlH4 as an exemplar, we demonstrate an alternative approach to the thermodynamic stabilization of metastable metal hydrides by coordination to nitrogen binding sites within the nanopores of N-doped CMK-3 carbon (NCMK-3). The resulting LiAlH4@NCMK-3 material releases H2 at temperatures as low as 126 °C with full decomposition below 240 °C, bypassing the usual Li3AlH6 intermediate observed in bulk. Moreover, >80% of LiAlH4 can be regenerated under 100 MPa H2, a feat previously thought to be impossible. Nitrogen sites are critical to these improvements, as no reversibility is observed with undoped CMK-3. Density functional theory predicts a drastically reduced Al-H bond dissociation energy and supports the observed change in the reaction pathway. The calculations also provide a rationale for the solid-state reversibility, which derives from the combined effects of nanoconfinement, Li adatom formation, and charge redistribution between the metal hydride and the host.

In spite of the comprehensive study of the metal-mediated conversion of NO to N2O disclosing the conceivable processes/mechanism in biological and biomimetic studies, in this study, the synthesis cycles and mechanism of NO reduction to N2O triggered by the electronically localized dinuclear {Fe(NO)2}10-{Fe(NO)2}9 dinitrosyl iron complex (DNIC) [Fe(NO)2(μ-bdmap)Fe(NO)2(THF)] (1) (bdmap = 1,3- bis(dimethylamino)-2-propanolate) were investigated in detail. Reductive conversion of NO to N2O triggered by complex 1 in the presence of exogenous ·NO occurs via the simultaneous formation of hyponitrite-bound {[Fe2(NO)4(μ-bdmap)]2(κ4-N2O2)} (2) and [NO2]--bridged [Fe2(NO)4(μ-bdmap)(μ-NO2)] (3) (NO disproportionation yielding N2O and complex 3). EPR/IR spectra, single-crystal X-ray diffraction, and the electrochemical study uncover the reversible redox transformation of {Fe(NO)2}9-{Fe(NO)2}9 [Fe2(NO)4(μ-bdmap)(μ-OC4H8)]+ (7) ↔ {Fe(NO)2}10-{Fe(NO)2}91 ↔ {Fe(NO)2}10-{Fe(NO)2}10 [Fe(NO)2(μ-bdmap)Fe(NO)2]- (6) and characterize the formation of complex 1. Also, the synthesis study and DFT computation feature the detailed mechanism of electronically localized {Fe(NO)2}10-{Fe(NO)2}9 DNIC 1 reducing NO to N2O via the associated hyponitrite-formation and NO-disproportionation pathways. Presumably, the THF-bound {Fe(NO)2}9 unit of electronically localized {Fe(NO)2}10-{Fe(NO)2}9 complex 1 served as an electron buffering reservoir for accommodating electron redistribution, and the {Fe(NO)2}10 unit of complex 1 acted as an electron-transfer channel to drive exogeneous ·NO coordination to yield proposed relay intermediate κ2-N,O-[NO]--bridged [Fe2(NO)4(μ-bdmap)(μ-NO)] (A) for NO reduction to N2O.

International audience; Calcium is an abundant, biocompatible, and environmentally friendly element. The use of organocalcium complexes as catalysts in organic synthesis has had some breakthroughs recently, but the reported reaction types remain limited. On the other hand, hydrosilanes are highly important reagents in organic and polymer syntheses, and redistribution of hydrosilanes through C-Si and SiH bond cleavage and reformation provides a straightforward strategy to diversify the scope of such compounds. Herein, we report the synthesis and structural characterization of two calcium alkyl complexes supported by beta-diketiminato-based tetradentate ligands. These two calcium alkyl complexes react with PhSiH3 to generate calcium hydrido complexes, and the stability of the hydrido complexes depends on the supporting ligands. One calcium alkyl complex efficiently catalyzes the selective redistribution of ArSiH3 or Ar(alkyl)SiH2 to Ar3SiH and SiH4 or Ar-2(alkyl)SiH and alkylSiH(3), respectively. More significantly, this calcium alkyl complex also catalyzes the cross-coupling between the electron-withdrawing substituted Ar(R)SiH2 and the electron-donating substituted Ar'(R)SiH2, producing ArAr'(alkyl)SiH in good yields. The synthesized ArAr'(alkyl)SiH can be readily transferred to other organosilicon compounds such as ArAr'(alkyl)SiX (where X = OH, OEt, NEt2, and CH2SiMe3). DFT investigations are carried out to shed light on the mechanistic aspects of the redistribution of Ph(Me)SiH2 to Ph-2(Me)SiH and reveal the low activation barriers (17-19 kcal/mol) in the catalytic reaction.

Ni0.5Zn0.5Fe2O4 is one of the most versatile and technologically indispensable soft magnetic materials; however, a detailed investigation on the effect of substitution-induced cation redistribution...

The effect of oxygen ion implantation on the physicochemical structure of the surface and the corrosion-electrochemical behavior of high-chromium Fe13Cr steel has been examined by potentiometry, atomic force microscopy, X-ray photoelectron spectroscopy, and microhardness measurements. Ion implantation leads to a significant reduction in corrosion losses. Optimal from the point of surface passivation and, consequently, reduction of corrosion losses of the material is the regime of steel treatment with oxygen ions with a dose of D = 5 × 1016 cm–2, after which the sample demonstrates the most stable behavior during local and general corrosion. It has been shown that the increase in the corrosion resistance of steel is due to the redistribution of elements in the surface layers caused by ion implantation and the intense formation of spinels of variable composition consisting of iron and chromium oxides with different oxidation states. In this case, the microhardness of the surface layers of the steel after ion implantation does not change significantly.