Low-cost fabrication of highly dispersed atomically-thin MoS2 nanosheets with abundant active Mo-terminated edges

In this work,highly dispersed atomically-thin MoS2 nanosheets were fabricated at one thousandth of the commercial cost using sepiolite(SEP)mineral nanofibers as carriers via a microwave hydrothermal method.Atomresolved microscopy revealed the MoS2 nanosheets were only 1–4 atomic layers thick.The Mo atoms anchored on the mineral surface served as nucleation sites for the nanosheet growth.The MoS2 layers were in staggered stacking yielding abundant atomic steps at the nanosheets’edges,where catalytically active molybdenum terminations dominated instead of the inert sulfur atoms commonly reported.DFT calculations disclosed that the bonding of Mo(MoS2)and O(SEP)at the MoS2/sepiolite(MSEP)interface enabled SEP to be a unique support,superior to the other minerals for growing such highly-dispersed ultrathin MoS2 architecture.In a typical photocatalyisis application,the MSEP demonstrated a significantly improved photocatalytic performance for RhB degradation compared with the MoS2 nanosheets assembled microspheres.This work provides an important new strategy for low-cost batch preparation of high quality 2D materials via assembly on mineral materials.

Redistributing Cu species in Cu-SSZ-13 zeolite as NH3-SCR catalyst via a simple ion-exchange

The nature and distribution of Cu species in Cu-SSZ-13 play a vital role in selective catalytic reduction of NO by NH3(NH3-SCR),but existing methods for adjusting the Cu distribution are complex and difficult to control.Herein,we report a simple and effective ion-exchange approach to regulate the Cu distribution in the one-pot synthesized Cu-SSZ-13 that possesses sufficient initial Cu species and thus provides a“natural environment”for adjusting Cu distribution precisely.By using this proposed strategy,a series of Cu-SSZ-13x zeolites with different Cu contents and distributions were obtained.It is shown that the dealumination of the as-synthesized Cu-SSZ-13 during the ion-exchange generates abundant vacant sites in the double six-membered-rings of the SSZ-13 zeolite for relocating Cu2+species and thus allows the redistribution of the Cu species.The catalytic results showed that the ion-exchanged Cu-SSZ-13 zeolites exhibit quite different catalytic performance in NH3-SCR reaction but superior to the parent counterpart.The structure–activity relationship analysis indicates that the redistribution of Cu species rather than other factors(e.g.,crystallinity,chemical composition,and porous structure)is responsible for the improved NH3-SCR performance and SO_(2) and H_(2)O resistance.Our work offers an effective method to precisely adjust the Cu distribution in preparing the industrial SCR catalysts.

Effect of secondary air on NO emission in a 440 t/h circulating fluidized bed boiler based on CPFD method

The 440 t/h circulating fluidized bed boiler was numerically simulated by the Computational Particle Fluid Dynamics(CPFD)method.The combustion characteristics of circulating fluidized bed boiler and the effect of secondary air on NO emission were investigated.The full-scale three-dimensional model of a 440 t/h circulating fluidized bed boiler was established.The rationality of the grid was validated by the experimental data of material layer resistance.The accuracy of the simulation was validated by measuring the temperature of each measuring point in the dense phase area.The combustion conditions in the furnace under different setting modes were simulated.The effects of secondary air rates on NO formation in fluidized bed were predicted.The results show that when the secondary air rate increases to 27%,the proper secondary air rate has a positive effect on the inhibition of NO generation,and the proper strengthening of the central air supply will improve the permeability of the secondary air and make the combustion more uniform and stable.When the secondary air rate increases to 33%,excessive improvement of air classification and central air distribution will affect the stability of circulating fluidized bed operation.Therefore,air classification and strengthening of central air supply can be used together to inhibit the generation of NO.

Graphene coatings for corrosion resistance of nickel and copper in acidic,alkaline and neutral environments

Graphene coatings have been reported to provide impressive corrosion resistance to nickel(Ni)and copper(Cu),because of remarkable characteristics of inertness and impermeablity of graphene.However,as the earlier investigations have generally been carried out in chloride environment,and it is important to understand the performance of graphene coating also in more aggressive environments such as acids and alkali.This study investigated the electrochemical corrosion behaviour of bare and graphene-coated(by chemical vapour deposition(CVD))Ni and Cu in 0.5 M H_(2)SO_(4),0.1 M NaCl and 0.5 M NaOH solutions.Electrochemical tests and post corrosion characterisation revealed the improvement in the corrosion resistance of Ni due to multilayer graphene coating to be similar in the three solutions,i.e.,the robustness of the barrier property of the multilayer graphene is largely unaffected by the aggressiveness of the corrosive environment.However,the improvement in corrosion resistance of bare Ni due to multilayer graphene is considerably greater(nearly 3 orders of magnitude)in the most aggressive of the test solutions(0.5 M H_(2)SO_(4)).The improvement is considerably less in 0.5 M NaOH because bare Ni develops a robust passive layer in highly alkaline solutions.The improvement in corrosion resistance of bare Cu is limited(within an order of magnitude)in the three solutions because Cu develops only 1-2 layers of graphene.

Electrocatalysts development for hydrogen oxidation reaction in alkaline media:From mechanism understanding to materials design

Anion exchange membrane(AEM)fuel cells have gained great attention partially due to the advantage of using non-precious metal as catalysts.However,the reaction kinetics of hydrogen oxidation reaction(HOR)is two orders of magnitude slower in alkaline systems than in acid.To understand the slower kinetics of HOR in base,two major theories have been proposed,such as(1)pH dependent hydrogen binding energy as a major descriptor for HOR;and(2)bifunctional theory based on the contributions of both hydrogen and hydroxide adsorption for HOR in alkaline electrolyte.Here,we discuss the possible HOR mechanisms in alkaline electrolytes with the corresponding change in their Tafel behavior.Apart from the traditional Tafel-Volmer and Heyrovsky-Volmer HOR mechanisms,the recently proposed hydroxide adsorption step is also discussed to illustrate the difference in HOR mechanisms in acid and base.We further summarize the representative works of alkaline HOR catalyst design(e.g.,precious metals,alloy,intermetallic materials,Ni-based alloys,carbides,nitrides,etc.),and briefly describe their fundamental HOR reaction mechanism to emphasize the difference in elementary reaction steps in alkaline medium.The strategy of strengthening local interaction that facilitates both H2 desorption and Hads+OHads recombination is finally proposed for future HOR catalyst design in alkaline environment.

Study on flow characteristics and phase holdup in a slurry bubble column coupled with mild agitation Author links open overlay panel

A pilot-scale experimental setup was constructed to investigate the effect of mild agitation on the bubble characteristics and phase holdup in a slurry bubble column.Mild agitation positively impacts the axial uniform distribution of solid holdup,though it shows insignificant influence on the radial distribution.In homogenous regime,mild agitation promotes the coalescence of bubbles,and the effect becomes stronger with increasing agitator speed.The mild agitation contributes to a decrease in bubble size in heterogeneous flow regime.Mild agitation presents a significant effect on the gas holdup by adjusting the bubble size and bubble motion trajectory.The modification was introduced to predict the gas holdup considering the effects of mild agitation,a necessary consideration for applications requiring mild agitation.This adapted model predicts gas holdup with a maximum error of 12.9%.

Settling behavior of spherical particles in vertical annulus:Experimental study and model development

Coiled tubing(CT)drilling technology offers significant advantages in terms of cost and efficiency for exploitations of unconventional oil and gas resources.However,the development of CT drilling technol-ogy is restricted by cuttings accumulation in the wellbore due to non-rotation of the drill string and limited circulating capacity.Cuttings cleaning becomes more difficult with the wall resistance of pipe-wellbore annulus on the cutting transport.Accurate description of particle transport process in the pipe-wellbore annulus is,therefore,important for improving the wellbore cleanliness.In this study,high-speed cam-era is used to record and analyze the settling process of particles in the transparent annulus filled with power-law fluids.A total of 540 tests were carried out,involving dimensionless diameters of 0.10-0.95 and particle Reynolds Numbers of 0.01-12.97,revealing the effect of the dimensionless diameter and particle Reynolds number on the annulus wall effect,and the wall factor model with an average relative error of2.75%was established.In addition,a dimensionless parameter,Archimedes number,independent of the settling velocity,was introduced to establish an explicit model of the settling velocity of spherical particles in the vertical annulus,with the average relative error of 7.89%.Finally,a calculation example was provided to show how to use the explicit model of settling velocity in annulus.The results of this study are expected to provide guidance for field engineers to improve the wellbore cleanliness of coiled tubing drilling.

Reticular exploration of uranium-based metal-organic frameworks with hexacarboxylate building units

The rational reticular design of metal-organic frameworks(MOFs)from building units of known geometries is essential for enriching the diversity of MOF structures.Unexpected and intriguing structures,however,can also arise from subtle changes in the rigidity/length of organic linkers and/or synthetic conditions.Herein,we report three uranium-based MOF structures—i.e.,NU-135X(X=0,1,2)—synthesized from trigonal planar uranyl nodes and triptycene-based hexacarboxylate ligands with variable arm lengths.A new chiral 3,6-connected nuc net was observed in NU-1350,while the extended versions of the ligand led to 3-fold catenated MOFs(NU-1351 and NU-1352)with rare 3,6-connected cml-c3 nets.The differences in the topology of NU-1350 and NU-1351/NU-1352 could be attributed to the slight distortions of the shorter linker in the former from the ideal trigonal prism geometry to an octahedral geometry when coordinated to the trigonal planar uranyl nodes.

A machine vision tool for facilitating the optimization of large-area perovskite photovoltaics

We report a fast,reliable and non-destructive method for quantifying the homogeneity of perovskite thin films over large areas using machine vision.We adapt existing machine vision algorithms to spatially quantify multiple perovskite film properties(substrate coverage,film thickness,defect density)with pixel resolution from pictures of 25 cm2 samples.Our machine vision tool—called PerovskiteVision—can be combined with an optical model to predict photovoltaic cell and module current density from the perovskite film thickness.We use the measured film properties and predicted device current density to identify a posteriori the process conditions that simultaneously maximize the device performance and the manufacturing throughput for large-area perovskite deposition using gas-knife assisted slot-die coating.PerovskiteVision thus facilitates the transfer of a new deposition process to large-scale photovoltaic module manufacturing.This work shows how machine vision can accelerate slow characterization steps essential for the multi-objective optimization of thin film deposition processes.

Factors affecting production of nonaqueous peracetic acid in tubular packed reactors

The synthesis of nonaqueous peracetic acid inacetone by acetaldehyde oxidation was carried out in atubular packed reactor. The influencing factors of thereacting system including packing material, oxygen carrier,and reactor configuration were investigated. Theresults show that porous materials are inappropriate forperacetic acid synthesis and only non porous materialwith appropriate surface area can provide good peraceticacid selectivity and yield. Among the six kinds of packingmaterial investigated, SA-5118 is the best one. As oxidizinggas, pure oxygen is superior to air. The optimumlength-to-inner diameter ratio of the reactor is about 40.Under the proper reaction conditions, the highest peraceticacid yield of 84.15% and the highest selectivity of93.34% can be achieved which indicates that the novelreacting system is effective and economical for nonaqueousperacetic acid production.

Identification of stable adsorption sites and diffusion paths on nanocluster surfaces:an automated scanning algorithm

The diverse coordination environments on the surfaces of discrete,three-dimensional(3D)nanoclusters contribute significantly to their unique catalytic properties.Identifying the numerous adsorption sites and diffusion paths on these clusters is however tedious and time-consuming,especially for large,asymmetric nanoclusters.Here,we present a simple,automated method for constructing approximate 2D potential energy surfaces for the adsorption of atomic species on the surfaces of 3D nanoclusters with minimal human intervention.These potential energy surfaces fully characterize the important adsorption sites and diffusion paths on the nanocluster surfaces with accuracies similar to current approaches and at comparable computational cost.Our method can treat complex nanoclusters,such as alloy nanoclusters,and accounts for cluster relaxation and adsorbate-induced reconstruction,important for obtaining accurate energetics.Moreover,its highly parallelizable nature is ideal for modern supercomputer architectures.

Capturing 2D van der Waals magnets with high probability for experimental demonstration from materials science literature

2D van der Waals(vdW)magnets have opened intriguing prospects for next-generation spintronic nanodevices.Machine learning techniques and density functional theory calculations enable the discovery of 2D vdW magnets to be accelerated;however,current computational frameworks based on these state-ofthe-art approaches cannot offer probability analysis on whether a 2D vdW magnet can be experimentally demonstrated.Herein,a new framework can be established to overcome this challenge.Via the framework,2D vdW magnets with high probability for experimental demonstration are captured from materials science literature.The key to the successful establishment is the introduction of the theory of mutual information.Historical validation of predictions substantiates the high reliability of the framework.For example,half of the 302D vdW magnets discovered in the literature published prior to 2017 have been experimentally demonstrated in the subsequent years.This framework has the potential to become a revolutionary force for progressing experimental discovery of 2D vdW magnets.

Nanocellulose-based porous materials: Regulation and pathway to commercialization in regenerative medicine

We review the recent progress that have led to the development of porous materials based on cellulose nanostructures found in plants and other resources. In light of the properties that emerge from the chemistry, shape and structural control, we discuss some of the most promising uses of a plant-based material, nanocellulose, in regenerative medicine. Following a brief discussion about the fundamental aspects of self-assembly of nanocellulose precursors, we review the key strategies needed for material synthesis and to adjust the architecture of the materials (using three-dimensional printing, freeze-casted porous materials, and electrospinning) according to their uses in tissue engineering, artificial organs, controlled drug delivery and wound healing systems, among others. For this purpose, we map the structure-property-function relationships of nanocellulose-based porous materials and examine the course of actions that are required to translate innovation from the laboratory to industry. Such efforts require attention to regulatory aspects and market pull. Finally, the key challenges and opportunities in this nascent field are critically reviewed.

Magnetic systems for cancer immunotherapy

Immunotherapy is a rapidly developing area of cancer treatment due to its higher specificity and potential for greater efficacy than traditional therapies.Immune cell modulation through the administration of drugs,proteins,and cells can enhance antitumoral responses through pathways that may be otherwise inhibited in the presence of immunosuppressive tumors.Magnetic systems offer several advantages for improving the performance of immunotherapies,including increased spatiotemporal control over transport,release,and dosing of immunomodulatory drugs within the body,resulting in reduced off-target effects and improved efficacy.Compared to alternative methods for stimulating drug release such as light and pH,magnetic systems enable several distinct methods for programming immune responses.First,we discuss how magnetic hyperthermia can stimulate immune cells and trigger thermoresponsive drug release.Second,we summarize how magnetically targeted delivery of drug carriers can increase the accumulation of drugs in target sites.Third,we review how biomaterials can undergo magnetically driven structural changes to enable remote release of encapsulated drugs.Fourth,we describe the use of magnetic particles for targeted interactions with cellular receptors for promoting antitumor activity.Finally,we discuss translational considerations of these systems,such as toxicity,clinical compatibility,and future opportunities for improving cancer treatment.

Unlocking the door to highly efficient Ag-based nanoparticles catalysts for NaBH4-assisted nitrophenol reduction

Ag-based nano particles(NPs)catalysts have recently attracted in creasi ng atte ntion in NaBH4-assisted n itrophe nol reducti on,especially in 4?n itrophe nol(4?NP)reducti on.Moreover,Ag-based NPs catalysts are con sidered to be very promising for practical applicati ons because of their fascinating advantages,e.g.,easy preparation,relatively low cost and less toxicity,high activity and good stability.Basically,the size and shape of Ag NPs are well known as the key factors for achieving highly efficient catalytic reduction of 4-NP.In this review,three highly efficient Ag-based NPs catalysts(supported Ag NPs,anisotropic Ag NPs and bimetallic Ag NPs)are highlighted for the 4-NP reduction,in eluding the catalytic mecha nism and reactio n rate caused by their adjustments in size and shape.Although high catalytic activity has bee n demonstrated by several Ag-based NPs catalysts,further improvement in the catalytic performance is still desired.In terms of the most recent progress in Ag-based NPs catalysts for 4?NP reduction,this review provides a comprehensive assessment on the material selection,synthesis and catalytic characterizations of these catalysts.Moreover,this review aims to correlate the catalytic performance of Ag-based NPs catalysts with their size and shape,guiding the development of novel cost-effective and high-performance catalysts.

Quantifying defects in thin films using machine vision

The sensitivity of thin-film materials and devices to defects motivates extensive research into the optimization of film morphology.This research could be accelerated by automated experiments that characterize the response of film morphology to synthesis conditions.Optical imaging can resolve morphological defects in thin films and is readily integrated into automated experiments but the large volumes of images produced by such systems require automated analysis.Existing approaches to automatically analyzing film morphologies in optical images require application-specific customization by software experts and are not robust to changes in image content or imaging conditions.Here,we present a versatile convolutional neural network(CNN)for thin-film image analysis which can identify and quantify the extent of a variety of defects and is applicable to multiple materials and imaging conditions.This CNN is readily adapted to new thin-film image analysis tasks and will facilitate the use of imaging in automated thin-film research systems.

Connecting particle sphericity and circularity

Sphericity,a measure of how much a particle’s shape deviates from spherical,is useful as a shape factorwhen characterizing particulate materials.However,particle surface areas,required when determiningthe sphericity,are very difficult to measure.As a result,the circularity,derivable from microscopic views,is often measured instead and assumed to be equal to the sphericity.This paper shows that the twoquantities are generally not equal for simple non-spherical shapes and provides advice on improving theestimation of sphericity from circularity.

A note on a boundary condition for spouted beds

The boundary condition, zero solids pressure at the top of a particle bed of maximum spoutable height, Hm, is shown to eliminate any resort to empiricism in the derivation of the fluid velocity in the annulus of a spouted bed for which both viscous and inertial effects are taken into account. The same boundary condition fails when applied to a spouted bed for which the bed height H 〈 Hm, especially when H 〈 0.8Hm.