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Compacting a material means applying pressure so that the material itself loses its internal pores. It improves the homogeneity of the material itself and increases its density. The pore structure of compacted clay is also an important factor that affects its mechanical properties, permeability and water absorption. In this study, MX-80 bentonite clay was first compacted into round cakes of different densities and then subjected to tomography image analysis technique using micro-computed tomography (micro-CT) at millimeter scale of accuracy for 1.0–2.0 g/cm3compacted clay (thickness of 0.3 cm bentonite compacted clay). In this paper, we use the latest commercial specifically for scientific visualization, materials science, non-destructive testing, numerical simulation of chromatographic imaging and other functions of a powerful visualization of the image analyzing method.

Exploring the migration behavior of radioactive nuclides in the surrounding rock media of the disposal site is the basis for the safety evaluation of radioactive waste disposal sites. In this study, the column experiment was employed to evaluate the nuclide migration behavior in the surrounding rock medium of a near-surface disposal site in China and to investigate the advection–dispersion behavior of tritium (HTO) and plutonium-238 (238Pu) in highly weathered argillaceous shale with different degree of weathering. A reasonable numerical model was selected to fit the experimental breakthrough curves (BTCs) and obtain relevant migration parameters. The results showed that: (1) the breakthrough curves of HTO and 238Pu in fractured media with varying degrees of weathering exhibited clear “peak forward” and “tail dragging” phenomena; (2) the stream tube model can better fit the BTCs of the nuclides in the highly weathered fractures and obtain the average dispersion coefficient , average distribution coefficient , and other parameters; (3) the two-region non-equilibrium model can better fit the BTCs of the nuclides in the penetrating fractures and weak weathering fractures and obtain the volumetric water content of the mobile liquid region (θm), distribution coefficient (Kd), and other parameters.

In this paper, we establish quantitative Green’s function estimates for some higher-dimensional lattice quasi-periodic (QP) Schrödinger operators. The resonances in the estimates can be described via a pair of symmetric zeros of certain functions and the estimates apply to the sub-exponential-type non-resonance conditions. As the application of quantitative Green’s function estimates, we prove both the arithmetic version of Anderson localization and the finite volume version of ((12−))-Hölder continuity of the integrated density of states (IDS) for such QP Schrödinger operators. This gives an affirmative answer to Bourgain’s problem in Bourgain (2000).

Tree boosting is a widely used machine learning model in many financial fields. Additively homomorphic encryption is an important cryptographic tool used for secure tree boosting in the setting of federated learning. However, homomorphic encryption includes computationally expensive operations. Current frameworks for secure tree boosting are extremely slow. In this article, we propose E-Booster, a novel accelerator for the training of secure tree boosting. E-Booster can fully exploit algorithmic superiority and architectural optimization to achieve unprecedented performance, and to address the obstacle in deploying additively homomorphic encryption in industrial applications. E-Booster has been implemented on an Intel Agilex field-programmable gate array and evaluated on four public datasets. It achieves a 5.1–7.8-times speedup over a CPU with 32 threads for secure tree boosting. To the best of our knowledge, E-Booster is the first additively homomorphic encryption accelerator that can be applied to industrial secure tree boosting.

Strongly correlated electron materials harbor interesting materials physics, such as high-Tcsuperconductivity, colossal magnetoresistance, and metal–insulator transition. These physical properties can be greatly influenced by the dimensionality and geometry of the hosting materials and their interaction strengths with underlying substrates. In a classic strongly correlated oxide vanadium sesquioxide (V2O3), the coexistence of a metal–insulator and paramagnetic-antiferromagnetic transitions at ∼150 K makes this material an excellent platform for exploring basic physics and developing future devices. So far, most studies have been focused on epitaxial thin films in which the strongly coupled substrate has a pronounced effect on V2O3, leading to the observations of intriguing phenomena and physics. In this work, we unveil the kinetics of a metal–insulator transition of V2O3single-crystal sheets at nano and micro scales. We show the presence of triangle-like alternating metal/insulator phase patterns during phase transition, which is drastically different from the epitaxial film. The observation of single-stage metal–insulator transition in V2O3/graphene compared to the multistage in V2O3/SiO2evidence the importance of sheet–substrate coupling. Harnessing the freestanding form of the V2O3sheet, we show that the phase transition of V2O3sheet can generate a large dynamic strain to monolayer MoS2and tune its optical property based on the MoS2/V2O3hybrid structure. The demonstration of the capability in tuning phase transition kinetics and phase patterns using designed hybrid structure of varied sheet–substrate coupling strengths suggests an effective knob in the design and operation of emerging Mott devices.

Layer transfer techniques have been extensively explored for semiconductor device fabrication as a path to reduce costs and to form heterogeneously integrated devices. These techniques entail isolating epitaxial layers from an expensive donor wafer to form freestanding membranes. However, current layer transfer processes are still low-throughput and too expensive to be commercially suitable. Here we report a high-throughput layer transfer technique that can produce multiple compound semiconductor membranes from a single wafer. We directly grow two-dimensional (2D) materials on III–N and III–V substrates using epitaxy tools, which enables a scheme comprised of multiple alternating layers of 2D materials and epilayers that can be formed by a single growth run. Each epilayer in the multistack structure is then harvested by layer-by-layer mechanical exfoliation, producing multiple freestanding membranes from a single wafer without involving time-consuming processes such as sacrificial layer etching or wafer polishing. Moreover, atomic-precision exfoliation at the 2D interface allows for the recycling of the wafers for subsequent membrane production, with the potential for greatly reducing the manufacturing cost.

Background: As an external medicine, policresulen solution didn't get much attention throughout the world. From the paper which had been published yet, there has been no report concerning other unknown impurities in the policresulen solution. Four known components had been identified as well as quantified, however, as long as people’s concern for drug safety increased rapidly, there still remain impurities to be studied. Objective: This paper focuses on the separation and characterization of the impurities in the policresulen solution, which is critical for controlling the production of this drug. Methods: The components and impurities in the policresulen solution were separated and characterized using HPLC coupled with to Q-TOF mass spectrometry. An ACE EXCEL 5 C18-PFP column (4.6 mm×250 mm, 5 μm) was used, and the mobile phases were 0.01 M ammonium acetate solution and methanol. Results: 21 previously unknown impurities were separated and characterized in a policresulen solution, and the structures were proposed based on the MS/MS fragmentation data. Conclusion: Based on the characterization of impurities, this study showed that there remain lots of oligomers in the policresulen solution, apart from four known components. This study could be used for further analytical analysis of the policresulen solution, which could improve the quality control of the policresulen solution and other preparations recommended in pharmacopoeias.

Heterogeneous integration of single-crystal materials offers great opportunities for advanced device platforms and functional systems1. Although substantial efforts have been made to co-integrate active device layers by heteroepitaxy, the mismatch in lattice polarity and lattice constants has been limiting the quality of the grown materials2. Layer transfer methods as an alternative approach, on the other hand, suffer from the limited availability of transferrable materials and transfer-process-related obstacles3. Here, we introduce graphene nanopatterns as an advanced heterointegration platform that allows the creation of a broad spectrum of freestanding single-crystalline membranes with substantially reduced defects, ranging from non-polar materials to polar materials and from low-bandgap to high-bandgap semiconductors. Additionally, we unveil unique mechanisms to substantially reduce crystallographic defects such as misfit dislocations, threading dislocations and antiphase boundaries in lattice- and polarity-mismatched heteroepitaxial systems, owing to the flexibility and chemical inertness of graphene nanopatterns. More importantly, we develop a comprehensive mechanics theory to precisely guide cracks through the graphene layer, and demonstrate the successful exfoliation of any epitaxial overlayers grown on the graphene nanopatterns. Thus, this approach has the potential to revolutionize the heterogeneous integration of dissimilar materials by widening the choice of materials and offering flexibility in designing heterointegrated systems.

Manipulating materials at the atomic scale and assembling them into macroscopic structures with controlled dimensionalities and single-crystal quality are grand scientific challenges. Here, we report a general solvent evaporation method to synthesize large-area uniaxial-oriented growth of free-standing thin films at the liquid–air interface. Crystals nucleate at the solution surface and rotate into the same orientation under electrostatic interaction and then merge as large crystals and grow laterally into a large-area uniform thin film with millimeter-sized grains. The lateral dimension is confined only by the size of containers. The film thickness can be tuned by adjusting solvent evaporation rate (R) and solute diffusivity (D), and a characteristic length, L*∼DR, was derived to estimate the film thickness. Molecular dynamic (MD) simulations reveal a concentration spike at the liquid–air interface during fast solvent evaporation, leading to the lateral growth of thin films. The large-area uniaxial oriented films are demonstrated on both inorganic metal halides and hybrid metal halide perovskites. The solvent evaporation approach and the determination of key parameters enabling film thickness prediction are beneficial to the high throughput and scalable production of single crystal-quality thin film materials under controlled evaporation conditions.

Pyroelectricity describes the generation of electricity by temporal temperature change in polar materials1–3. When free-standing pyroelectric materials approach the 2D crystalline limit, how pyroelectricity behaves remained largely unknown. Here, using three model pyroelectric materials whose bonding characters along the out-of-plane direction vary from van der Waals (In2Se3), quasi-van der Waals (CsBiNb2O7) to ionic/covalent (ZnO), we experimentally show the dimensionality effect on pyroelectricity and the relation between lattice dynamics and pyroelectricity. We find that, for all three materials, when the thickness of free-standing sheets becomes small, their pyroelectric coefficients increase rapidly. We show that the material with chemical bonds along the out-of-plane direction exhibits the greatest dimensionality effect. Experimental observations evidence the possible influence of changed phonon dynamics in crystals with reduced thickness on their pyroelectricity. Our findings should stimulate fundamental study on pyroelectricity in ultra-thin materials and inspire technological development for potential pyroelectric applications in thermal imaging and energy harvesting.

In this work, an attractive malachite leaching agent has been developed for extracting copper from malachite. The possible chemical reaction of malachite in TCA was also analyzed. The effects of the temperature, TCA concentration, average particle size, and stirring speed on malachite dissolution were investigated and a kinetic model was developed to describe the observed effects. It was found that the dissolution rate increases with increasing solution temperature, concentration, and stirring speed, and decreases with increasing mean particle size. The TCA solution can provide H+ions, which facilitates the dissolution reaction. A surface chemical reaction contraction model controls dissolution and the activation energy of the dissolution process was determined to be 43.23 kJ/mol. It was shown that TCA can be used as a leaching agent for effective extraction of copper from malachite.

The topology optimization can be used to obtain preliminary turbomachinery disk designs which meet strength requirement. In order to eliminate enclosed holes which challenge manufacturing processes and to ensure distinct solid-void interface in the optimal result obtained by the topology optimization, a density distribution function is introduced for each element column in the design domain. Then, a parameter in each function is used to determine the disk’s thickness at corresponding radial position by controlling element densities. Once thicknesses at all radial positions are optimized, the shape of disk is thus determined. In this way, the optimization problem can be simplified by using these parameters as design variables. Illustrative examples are carried out to demonstrate the effectiveness of the proposed method in designing both compressor disks and turbine disks in comparison to the software T-Axis Disk and shape optimization method.

Tamusu area is the primary pre-selection site of clayrock disposal repository for high-level radioactive waste (HLW) in China. However, the research on the migration behavior of nuclides in Tamusu clayrock is still in its infancy. For the first time in laboratory, the diffusion behavior of Re(VII) in Tamusu clayrock core was studied by means of through-diffusion method. The effects of pH, ionic strength and humic acid on the diffusion behavior of Re(VII) in clayrock were studied. The effective diffusion coefficient, apparent diffusion coefficient and rock capacity factor value were obtained. All the experimental conditions of Re(VII) diffusion in Tamusu clayrock are compared with other geological samples under the same conditions in literature data. The diffusion mechanism of radionuclide in Tamusu clay is discussed, which can provide experimental data for site selection and safety assessment of high-level radioactive waste repository in China. The experimental results showed an effective application and reference for the countries disposed HLW in mudrocks or clayrocks, such as France, Belgium etc. in Europe. Moreover, this research can provide the original data support for the metallogenic regularity and prospecting prognosis of rare element rhenium in different geological environments.

An effective vaccine is needed to end the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. Here, we assess the preliminary safety, tolerability and immunogenicity data from an ongoing single-center (in Jiangsu province, China), parallel-group, double-blind phase 1 trial of the vaccine candidate BNT162b1 in 144 healthy SARS-CoV-2-naive Chinese participants. These participants are randomized 1:1:1 to receive prime and boost vaccinations of 10 µg or 30 µg BNT162b1 or placebo, given 21 d apart, with equal allocation of younger (aged 18–55 years) and older adults (aged 65–85 years) to each treatment group (ChiCTR2000034825). BNT162b1 encodes the SARS-CoV-2 spike glycoprotein receptor-binding domain (RBD) and is one of several messenger RNA-based vaccine candidates under clinical investigation. Local reactions and systemic events were generally dose dependent, transient and mild to moderate. Fever was the only grade 3 adverse event. BNT162b1 induced robust interferon-γ T cell responses to a peptide pool including the RBD in both younger and older Chinese adults, and geometric mean neutralizing titers reached 2.1-fold (for younger participants) and 1.3-fold (for the older participants) that of a panel of COVID-19 convalescent human sera obtained at least 14 d after positive SARS-CoV-2 polymerase chain reaction test. In summary, BNT162b1 has an acceptable safety profile and produces high levels of humoral and T cell responses in an Asian population.

The adsorption and activation of CO2molecules on the surface of photocatalysts are critical steps to realize efficient solar energy-induced CO2conversion to valuable chemicals. In this work, a defect engineering approach of a high-valence cation Nb-doping into TiO2was developed, which effectively enhanced the adsorption and activation of CO2molecules on the Nb-doped TiO2surface. A highly ordered Nb-doped TiO2nanotube array was prepared by anodization of the Ti–Nb alloy foil and subsequent annealing at 550 °C in air for 2 h for its crystallization. Our sample showed a superior photocatalytic CO2reduction performance under simulated solar illumination. The main CO2reduction product was a higher-energy compound of acetaldehyde, which could be easily transported and stored and used to produce various key chemicals as intermediates. The acetaldehyde production rate was over ∼500 μmol·g–1·h–1with good stability for repeated long-time uses, and it also demonstrated a superior product selectivity to acetaldehyde of over 99%. Our work reveals that the Nb-doped TiO2nanotube array could be a promising candidate with high efficiency and good product selectivity for the photocatalytic CO2reduction with solar energy.

In this paper, the effects of sodium sulfosalicylate on hemimorphite activation were studied. Sulfosalicylic acid ions enhanced the sulfidation-flotation process, which increased the flotation recovery by 49.70%, and after lead ion assisted activation, the flotation recovery subsequently increased by 13.11%. Time-of-flight secondary ion spectrometry (TOF-SIMS) surface analysis revealed that the surface structure of the hemimorphite was greatly damaged by sodium sulfosalicylate, which could promote ZnS film formation for obtaining hemimorphite hydrophobicity. The ZnS film thickness on the hemimorphite surface was approximately 41.78 nm with direct sulfidation. After activating sulfidation, excellent flotation effects were obtained as the ZnS film reached about 418.19 nm. 3D images showed a heterogeneous and homogeneous ZnS film on the hemimorphite surface after direct sulfidation and activating sulfidation, respectively. The X-ray photoelectron spectroscopy (XPS)-based analysis of the substances on the hemimorphite surface further indicated that the atomic concentration of sulfur on the surface of the activating sulfidation hemimorphite nearly double that of the direct sulfidation hemimorphite (1.57% versus 2.38%, respectively). After activating sulfidation, the XPS spectra indicated that a deep complexation reaction occurred with sodium sulfosalicylate on the hemimorphite surface with various elements and significantly influenced elemental distribution on the hemimorphite surface.

The atomic mechanisms of the melting process of gold nanoparticles were investigated by molecular dynamics simulations. Melting under a high heating rate is found to be much different from the near equilibrium melting and is a typical overheating process. The melting begins with the formation of a premelting layer near the surface, and the interface of the solid and premelting layer drives the nucleation of the liquid into the interior of nanoparticles. The high heating rate causes solid–liquid coexistence in a large temperature interval. These imply that the melting process can be controlled effectively by different heating ways.

Supplemental Digital Content is available in the text.

High specific capacity anode materials such as silicon (Si) are increasingly being explored for next-generation, high performance lithium (Li)-ion batteries. In this context, Si films are advantageous compared to Si nanoparticle based anodes since in films the free volume between nanoparticles is eliminated, resulting in very high volumetric energy density. However, Si undergoes volume expansion (contraction) under lithiation (delithiation) of up to 300%. This large volume expansion leads to stress build-up at the interface between the Si film and the current collector, leading to delamination of Si from the surface of the current collector. To prevent this, adhesion promotors (such as chromium interlayers) are often used to strengthen the interface between the Si and the current collector. Here, we show that such approaches are in fact counter-productive and that far better electrochemical stability can be obtained by engineering a van der Waals “slippery” interface between the Si film and the current collector. This can be accomplished by simply coating the current collector surface with graphene sheets. For such an interface, the Si film slips with respect to the current collector under lithiation/delithiation, while retaining electrical contact with the current collector. Molecular dynamics simulations indicate (i) less stress build-up and (ii) less stress “cycling” on a van der Waals slippery substrate as opposed to a fixed interface. Electrochemical testing confirms more stable performance and much higher Coulombic efficiency for Si films deposited on graphene-coated nickel (i.e., slippery interface) as compared to conventional nickel current collectors.

•Provides insights about how individual's aspirin use behaviors were affected by the information they got.•Reveals the interaction effect of information from health provider and internet on patients with different aspirin demand.•Shows the different risks and effectives of using aspirin in primary versus secondary CVD preventions.

In this article, the non-self dual extended Harper’s model with a Liouville frequency is considered. It is shown that the corresponding integrated density of states is $$\frac{1}{2}$$12-Hölder continuous. As an application, the homogeneity of the spectrum is proven.

The brittleness of oxide glasses has dramatically restricted their practical applications as structural materials despite very high theoretical strength. Herein, using molecular dynamics simulations, we show that silica glass prepared by consolidating glassy nanoparticles exhibit remarkable tensile ductility. Because of dangling bonds at surfaces and high contact stresses, the pressure applied for consolidating glassy nanoparticles to achieve ductility is significantly lower than that required to toughen bulk glass via permanent densification. We have identified 5-fold silicon, with a higher propensity to carry out local shear deformation than 4-fold silicon, as the structural origin for the observed tensile ductility. Interestingly, the work hardening effect has been, for the first time, observed in thus-prepared silica glass, with its strength increasing from 4 GPa to ∼7 GPa upon cold work. This is due to stress-assisted relaxation of 5-fold silicon to 4-fold during cold work, analogous to transformation hardening.

Supplemental Digital Content is available in the text.

We report atomistic simulations of the melting of nanocrystalline gold with mean grain sizes from 1.7 to 23 nm. Analysis of the structural changes near melting point at the atomic scale confirms that in the melting process, the solid–liquid interface sweeps rapidly from grain boundary into inner grain as the temperature increases. We find a linear relation between the melting point and the reciprocal grain size for the larger grain size samples, above 7.7 nm, similar to the observations in nanoparticles. However, based on the critical Lindemann ratio, the grain boundaries in these cases should be liquefied at very low temperature (less than 800 K for grain size of 9.7 nm). At a small grain size, this relation between grain size and melting temperature was broken. In particular, at grain sizes below 4 nm, the melting point was found to be approximately constant. It was proposed that the growth and/or merging of grains at low temperature far from melting was contributed to this observation.

We used molecular dynamics simulation to investigate the friction of a single asperity against a rigid substrate, while generating debris. In the low wear regime (i.e., non-linear wear rate dependence on the contact stress, via atom-by-atom attrition), the frictional stress is linearly dependent on the normal stress, without any lubrication effect from the wear debris particles. Both the slope (friction coefficient) and friction at zero normal stress depend strongly on asperity-substrate adhesion. In the high wear regime (i.e., linear wear rate dependence on the contact stress, via plastic flow), the friction-normal stress curves deviate from a linear relation merging toward plastic flow of the single asperity which is independent of the interfacial adhesion. One can further link wear and friction by considering debris generation as chemical reaction, driven by both normal and frictional forces. The coupling between wear and friction can then be quantified by a thermodynamic efficiency of the debris generation. While the efficiency is less than 5% in the low wear regime, indicating poor mechanochemical coupling, it increases with normal stress toward 50% in the high wear regime.

Silicon (Si) shows promise as an anode material in lithium-ion batteries due to its very high specific capacity. However, Si is highly brittle, and in an effort to prevent Si from fracturing, the research community has migrated from the use of Si films to Si nanoparticle based electrodes. However, such a strategy significantly reduces volumetric energy density due to the porosity of Si nanoparticle electrodes. Here we show that contrary to conventional wisdom, Si films can be stabilized by two strategies: (a) anchoring the Si films to a carbon nanotube macrofilm (CNM) current collector and (b) draping the films with a graphene monolayer. After electrochemical cycling, the graphene-coated Si films on CNM resembled a tough mud-cracked surface in which the graphene capping layer suppresses delamination and stabilizes the solid electrolyte interface. The graphene-draped Si films on CNM exhibit long cycle life (>1000 charge/discharge steps) with an average specific capacity of ∼806 mAh g–1. The volumetric capacity averaged over 1000 cycles of charge/discharge is ∼2821 mAh cm–3, which is 2 to 5 times higher than what is reported in the literature for Si nanoparticle based electrodes. The graphene-draped Si anode could also be successfully cycled against commercial cathodes in a full-cell configuration.

BNT162b2, an mRNA vaccine against COVID-19, is being utilised worldwide, but immunogenicity and safety data in Chinese individuals are limited.

Multi-stakeholder alliances – groups of payers, purchasers, providers, and consumers that work together to address local health goals – are frequently used to improve health care quality within communities. Under the Aligning Forces for Quality (AF4Q) initiative, multi-stakeholder alliances were given funding and technical assistance to encourage the use of health information technology (HIT) to improve quality. We investigated whether HIT adoption was greater in AF4Q communities than in other communities.

Commercially available lattices contain various kinds of morphological imperfections which result in great degradation in lattices’ mechanical properties, therefore, to obtain imperfection insensitive lattice structure is obviously a practical research subject. Hierarchical structure materials were found to be a class of promising anti-defect materials. This paper builds hierarchical lattice by adding soft adhesion to lattice’s cell edges and numerical results show that its imperfection sensitivity to missing bars is minor compared with the classic lattice. Soft adhesion with appropriate properties reinforce cell edge’s bending stiffness and thus reduce the bending deformation in lattice caused by missing bars defect, which is confirmed by statistical analysis of normalized node displacements of imperfect lattices under hydrostatic compression and shear loads.

The recent interest and excitement in graphene has also opened up a pandora’s box of other two-dimensional (2D) materials and material combinations which are now beginning to come to the fore. One family of these emerging 2D materials is transition metal dichalcogenides (TMDs). So far there is very limited understanding on the wetting behavior of “monolayer” TMD materials. In this study, we synthesized large-area, continuous monolayer tungsten disulfide (WS2) and molybdenum disulfide (MoS2) films on SiO2/Si substrates by the thermal reduction and sulfurization of WO3and MO3thin films. The monolayer TMD films displayed an advancing water contact angle of ∼83° as compared to ∼90° for the bulk material. We also prepared bilayer and trilayer WS2films and studied the transition of the water contact angle with increasing number of layers. The advancing water contact angle increased to ∼85° for the bilayer and then to ∼90° for the trilayer film. Beyond three layers, there was no significant change in the measured water contact angle. This type of wetting transition indicates that water interacts to some extent with the underlying silica substrate through the monolayer TMD sheet. The experimentally observed wetting transition with numbers of TMD layers lies in-between the predictions of one continuum model that considers only van der Waals attractions and another model that considers only dipole–dipole interactions. We also explored wetting as a function of aging. A clean single-layer WS2film (without airborne contaminants) was shown to be strongly hydrophilic with an advancing water contact angle of ∼70°. However, over time, the sample ages as hydrocarbons and water present in air adsorb onto the clean WS2sheet. After ∼7 days, the aging process is completed and the advancing water contact angle of the aged single-layer WS2film stabilizes at ∼83°. These results suggest that clean (i.e., nonaged) monolayer TMDs are hydrophilic materials. We further show that substitution of sulfur atoms by oxygen in the lattice of aged monolayer WS2and MoS2films can be used to generate well-defined ‘hydrophobic–hydrophilic’ patterns that preferentially accumulate and create microdrop arrays on the surface during water condensation and evaporation experiments.

The influence of temperature on the hydrogen diffusion behavior in X80 pipeline steel during stacking for slow cooling was studied using electrochemical penetration method, the temperature field and the hydrogen diffusion in this pipeline steel during stacking for slow cooling were simulated by ABAQUS finite element method (FEM) software. The results show that in this process there is a reciprocal relationship between the natural logarithm of hydrogen diffusion coefficient and temperature. The cooling rate decreases gradually with the increase of steel plate thickness. The hydrogen content is higher at high temperature (500–400 °C) than that in low temperature region (300–100 °C). The FEM simulation results are consistent with the experimental ones, and the model can be used to predict the hydrogen diffusion behavior in industrial production of X80 pipeline steel.

Sonochemical synthesis and optical property of palm-leaf-like ZnO-Bi 2 O 3 nanocomposite have been reported. The analysis of XRD approves that the nanocomposite material is ZnO-Bi 2 O 3 . The composition of the product has been analysed by XPS and it is concluded that the molecular ratio of Bi 2 O 3 :ZnO is 1:4.6. SEM images show that the morphology of the nanocomposite is stelliform dendrite. The sonication time appears to be a critical parameter for shape determination. Also, the presence of Bi 3+ is vital to the formation of the palm-leaf-like dentrites. Photoluminescence spectra at room temperature of the products show that the synthesised materials possess good optical properties. The mechanism of the dendrite growth has also been discussed.

Abstract

Previous studies of the interaction of water with graphene-coated surfaces have been limited to flat (smooth) surfaces. Here we created a rough surface by nanopatterning and then draped the surface with a single-layer graphene sheet. We found that the ultrasheer graphene drape prevents the penetration of water into the textured surface thereby drastically reducing the contact angle hysteresis (which is a measure of frictional energy dissipation) and preventing the liquid contact line from getting pinned to the substrate. This has important technological implications since the main obstacle to the motion of liquid drops on rough surfaces is contact angle hysteresis and contact line pinning. Graphene drapes could therefore enable enhanced droplet mobility which is required in a wide range of applications in micro and nanofluidics. Compared to polymer coatings that could fill the cavities between the nano/micropores or significantly alter the roughness profile of the substrate, graphene provides the thinnest (i.e., most sheer) and most conformal drape that is imaginable. Despite its extreme thinness, the graphene drape is mechanically robust, chemically stable, and offers high flexibility and resilience which can enable it to reliably drape arbitrarily complex surface topologies. Graphene drapes may therefore provide a hitherto unavailable ability to tailor the dynamic wettability of surfaces for a variety of applications.

We report a novel physicochemical route to produce highly crystalline nitrogen-doped graphene nanoribbons. The technique consists of an abrupt N2gas expansion within the hollow core of nitrogen-doped multiwalled carbon nanotubes (CNx-MWNTs) when exposed to a fast thermal shock. The multiwalled nanotube unzipping mechanism is rationalized using molecular dynamics and density functional theory simulations, which highlight the importance of open-ended nanotubes in promoting the efficient introduction of N2molecules by capillary action within tubes and surface defects, thus triggering an efficient and atomically smooth unzipping. The so-produced nanoribbons could be few-layered (from graphene bilayer onward) and could exhibit both crystalline zigzag and armchair edges. In contrast to methods developed previously, our technique presents various advantages: (1) the tubes are not heavily oxidized; (2) the method yields sharp atomic edges within the resulting nanoribbons; (3) the technique could be scaled up for the bulk production of crystalline nanoribbons from available MWNT sources; and (4) this route could eventually be used to unzip other types of carbon nanotubes or intercalated layered materials such as BN, MoS2, WS2, etc.

Abstract

In this paper, we report a simple, rapid and selective colorimetric visualization of arsenic using unmodified gold nanoparticles (AuNPs) and a phytochelatin-like peptide (γ-Glu-Cys)3-Gly-Arg (denoted as PC3R). Arsenic prevented the peptide from attaching to the surface of AuNPs by coordinating to all the three cysteine residues of PC3R, thus preventing the PC3R-triggered AuNPs aggregation and color change. The present approach is selective to arsenic detection and is much faster and simpler than the conventional analytical methods. The detection limit is 20 nM, which is lower than the World Health Organization's (WHO) standard for drinking water. The feasibility for the detection of arsenic in groundwater has also been demonstrated. This method will be valuable for the design of new types of metal ions sensors and will likely lead to many colorimetric detection applications in environmental monitoring.

This work explores the efficacy of different characterization methods of identification of self-propelled motions of nanomotors out of overwhelming thermal noises. Here a linear catalytic nanomotor swimming in a two-dimensional fluid is investigated using the molecular dynamics simulation method. A model fuel-catalyst reactive force field is designed to produce exothermic decomposition reactions of diatomic fuel molecules into monatomic product molecules, which can be accelerated by the presence of model catalysts. Steady states with constant chemical composition and temperature are achieved by Monte Carlo product-to-reactant conversion operations and a Nose-Hoover thermostat, respectively. The self-propelled autonomous motion of the nanomotor is characterized by the accumulated displacement along the propulsion direction and the mean square displacement analysis. Compared to a control system without catalysts, it is found that, the chemical propulsion affects the linear motion considerably, but has little effect on its overall diffusion behavior due to rotational Brownian motions with a very short relaxation time. However, by confining the rotational degree of freedom, the diffusion of the nanomotor is evidently accelerated by the chemical propulsion. Thus, to characterize the autonomous motion of linear nanomotors, one can either track the trajectory of each nanomotor individually or measure the confined diffusive behavior of nanomotors collectively. The latter method is more appealing to implement experimentally.

To explore the coordination possibilities of fluorene‐based ligands, two manganese(II) complexes with the ligand 9,9‐dibutyl‐9H‐fluorene‐2,7‐carboxylate (L) were synthesized and characterized: [Mn2(L)2(DMF)3]∞(1) and [Mn2(L)2(DMF)]∞(2). X‐ray single‐crystal diffraction analyses show that complex 1has a two‐dimensional (2D) (4,4) structure, whereas complex 2consits of a three‐dimensional (3D) (4,5)‐connected topology framework. The results indicate that the steric bulk of the fluorene ring in H2Lplays an important role in the formations of 1and 2. Additional pyridine‐based ligands govern the formation of the final frameworks of 2. Moreover, the luminescent properties of these complexes were briefly investigated.

Aluminum nitride (AlN) is a popular buffer layer and interlayer. The understanding of how AlN serves as a wetting and fracture‐mitigating layer relies on molecular pictures of the AlN layer and the interfaces. However, molecular dynamics (MD) simulation studies on AlN system, particularly on its wurtzite phase, have been limited. This is because most existing interatomic force fields of AlN target the less common zinc blende phase. Here, we report a new Tersoff‐based AlN force field for its wurtzite structure. This potential has been extensively tested in terms of lattice parameters, bulk modulus, cohesive energy, and heat capacity. In addition, thermal expansion coefficient (TEC) of wurtzite AlN, a key property to precisely model heterostructures, has been calculated using MD method. The value of 2.66 × 10−6K−1calculated at 300 K for TEC is in excellent agreement with the reported experimental value.

Hotspots that form spontaneously during cook-off (a process in which an explosive is annealed) have been observed in 3D molecular dynamics simulations of a model energetic material. Hotspots that are unable to reach a critical radius of ∼1.5 nm self-extinguish, whereas hotspots that exceed the critical radius continue to grow with a radial velocity that becomes supersonic. The value of the critical hotspot radius observed in the simulations is in excellent agreement with that predicted from the Frank-Kamenetskii classical initiation theory. The rate of formation of N2, which includes both hot spot nucleation and growth, displays Arrhenius behavior with respect to the initial annealing temperature with an activation energy of ∼0.5 eV, which is roughly half of that previously determined for thermal decomposition. New equations based on Johnson−Mehl−Avrami−Kolmogorov kinetics are proposed for describing the extent of detonated material that could provide new insight into mechanisms of critical hotspot nucleation.