Hierarchically Structured Nb_(2)O_5 Microflowers with Enhanced Capacity and Fast-Charging Capability for Flexible Planar Sodium Ion Micro-Supercapacitors

Planar Na ion micro-supercapacitors(NIMSCs) that offer both high energy density and power density are deemed to a promising class of miniaturized power sources for wearable and portable microelectron-ics. Nevertheless, the development of NIMSCs are hugely impeded by the low capacity and sluggish Na ion kinetics in the negative electrode.Herein, we demonstrate a novel carbon-coated Nb_(2)O_5 microflower with a hierarchical structure composed of vertically intercrossed and porous nanosheets, boosting Na ion storage performance. The unique structural merits, including uniform carbon coating, ultrathin nanosheets and abun-dant pores, endow the Nb_(2)O_5 microflower with highly reversible Na ion storage capacity of 245 mAh g^(-1) at 0.25 C and excellent rate capability.Benefiting from high capacity and fast charging of Nb_(2)O_5 microflower, the planar NIMSCs consisted of Nb_(2)O_5 negative electrode and activated car-bon positive electrode deliver high areal energy density of 60.7 μWh cm^(-2),considerable voltage window of 3.5 V and extraordinary cyclability. Therefore, this work exploits a structural design strategy towards electrode materials for application in NIMSCs, holding great promise for flexible microelectronics.

Electrodeposited 3D hierarchical NiFe microflowers assembled from nanosheets robust for the selective electrooxidation of furfuryl alcohol

A robust and green strategy for the selective upgrading of biomass-derived platform chemicals towards highly valuable products is important for the sustainable development.Herein,the efficient electrocatalytic oxidation of biomass-derived furfuryl alcohol(FFA)into furoic acid(FurAc)catalyzed by the electrodeposited non-precious NiFe microflowers was successfully reached under the low temperature and ambient pressure.The 3D hierarchical NiFe microflowers assembled from ultrathin nanosheets were controllably synthesized by the electrodeposition method and uniformly grown on carbon fiber paper(CFP).Electrochemical analysis confirmed that NiFe nanosheets more preferred in the selective oxidation of FFA(FFAOR)than oxygen evolution reaction(OER).The linear sweep voltammetry(LSV)in FFAOR displayed a clear decrease towards lower potential,resulting in 30 mV reduction of overpotential at 20 mA cm^(-2) compared with that of OER.The optimal catalyst Ni_(1)Fe_(2) nanosheets exhibited the highest selectivity of FurAc(94.0%)and 81.4%conversion of FFA within 3 h.Besides,the influence of various reaction parameters on FFAOR was then explored in details.After that,the reaction pathway was investigated and rationally proposed.The outstanding performance for FFAOR can be ascribed to the unique structure of 3D flower-like NiFe nanosheets and oxygen vacancies,resulting in large exposure of active sites,faster electron transfer and enhanced adsorption of reactants.Our findings highlight a facile and convenient mean with a promising green future,which is promising for processing of various biomass-derived platform chemicals into value-added products.

Porous Graphene Microflowers for High-Performance Microwave Absorption

Graphene has shown great potential in microwave absorption(MA) owing to its high surface area, low density,tunable electrical conductivity and good chemical stability.To fully realize graphenes& MA ability, the microstructure of graphene should be carefully addressed. Here we prepared graphene microflowers(Gmfs) with highly porous structure for high-performance MA filler material. The efficient absorption bandwidth(reflection loss B-10 dB) reaches 5.59 GHz and the minimum reflection loss is up to -42.9 dB, showing significant increment compared with stacked graphene. Such performance is higher than most graphene-based materials in the literature. Besides, the low filling content(10 wt%) and low density(40–50 mg cm^(-3))are beneficial for the practical applications. Without compounding with magnetic materials or conductive polymers,Gmfs show outstanding MA performance with the aid of rational microstructure design. Furthermore, Gmfs exhibit advantages in facile processibility and large-scale production compared with other porous graphene materials including aerogels and foams.

Assembling ZnO Nanorods into Microflowers through a Facile Solution Strategy: Morphology Control and Cathodoluminescence Properties

In this work, flowerlike ZnO micro/nanostructures assembled from nanorods are obtained through a facile hydrothermal route. The experimental results indicated that the as-synthesized ZnO microflowers have an average diameter of 2 μm, composed of nanorods of an average diameter of 200 nm and a tapered morphology.ZnO with other morphologies were also obtained by varying the reaction conditions. Systematical conditiondependent experiments were conducted to reveal the growth mechansim of the microflowers. It is suggested that the zinc source types, solution p H value, and reaction temperature, as well as reaction time are responsible for the variations of ZnO morphology. Luminescence properties of ZnO microflowers were investigated through monitoring different parts of nanorods, showing good optical quality.

The Effect of Repeat Cardiopulmonary bypass on Epicardial Microflow and Graft Flow during Intraoperative Heart Failure

Objective\ The relationship between graft blood flow, epicardial microflow, mean arterial pressure and hemorheologic changes was studied during intraoperative heart failure. Methods\ These parameters were done to evaluate the use of repeated cardiopulmonary bypass support for the intraoperative heart failure following aorto coronary bypass surgery. Included in this study were 10 patients with a mean age of 70 and unstable angina undergoing coronary bypass grafting and suffering from intraoperative heart failure. The epicardiai microflow, graft flow, mean arterial pressure and blood cell filterability were measured. Resluts\ During heart failure, the mean arterial pressure fell by 41%(P<0.01), graft flow by 67%(P<0.01) and epicardialmicroflow by 64%(P<0.01). After 15 to 56 min of assisted cardiopulmonary bypass support, the epicardial microflow and graft flow were partially restored, while red cell and white cell filterability was reduced by 31% and 64% respectively (P<0.01). There were significant correlations between graft flow, epicardial microflow, blood cell filterability and cardiopulmonary bypass time. All patients recovered and were discharged from the hospital.Conclusion\ It is concluded that the use of temporary assisted CPB support to treat intrapoperative heart failure allows the recovery of the myocardium and thereby restores the mean arterial pressure. The recovery of graft flow and epicardial flow occurred to a lesser extent. The CPB support seemed to be suitable for about 60 min probably because of increasing disturbance to the blood cell filterability, graft flow and the epicardial microcirculation.\;

Simple Template-Free Synthesis of Bi₂O₃Microflowers Composed of Nanorods

This paper reports that α-Bi2O3 microflowers can be synthesized by an extremely simple and easy approach of inducing a reaction through the addition of NaOH aqueous solution to a mixed aqueous solution of Bi(NO3)3·5H2O and HNO3 scanning electron microscopy images of the Bi2O3 microflowers indicate that the Bi2O3 nanorods grew radially from the centre of the microflower to form the microflower shape. The findings of this study show that control of the reaction temperature, reaction time, and raw material mixture ratio plays an important role in the formation of α-Bi2O3 microflowers. It is especially revealed that α-Bi2O3 microflowers can be formed at low temperatures with short reaction times. It has thus far been reported that flower-shaped Bi2O3 particles or their precursors can be synthesized by the addition of additives such as organic molecules or certain inorganic ions. The present work reports on the discovery of ways to synthesize flower-shaped Bi2O3 particles without the use of special additives.

Continuous microflow visible-light photocatalytic N-formylation of piperidine and its kinetic study

N-formylation of amines,a class of synthetically important reactions,is typically conducted using metal catalysts that are relatively expensive or not readily available and usually needs harsh conditions to increase the reaction efficiency.Here,an efficient continuous microflow strategy was developed for the gas-liquid visible-light photocatalytic N-formylation of piperidine,which achieved a reaction yield of 82.97%and a selectivity of>99%at 12 min using cheap organic dye photocatalyst under mild reaction conditions.The influence of essential parameters,including light intensity,temperature and equivalents of the gas,additive and photocatalyst,on the reaction yield was systematically studied.Furthermore,kinetic investigations were conducted,exhibiting the dependence of reaction rate and equilibrium yield of N-formylpiperidine on light intensity,temperature and photocatalyst equivalent.The microflow photocatalytic approach established in this work,which realized a markedly higher space-time yield than the conventional batch method(37.9 vs.0.212 mmol h-1 L-1),paves the way for the continuous,green and efficient synthesis of N-formamides.

Nitrogen-doped carbon-coated hollow SnS_(2)/NiS microflowers for high-performance lithium storage

Nitrogen-doped carbon-coated hollow SnS_(2)/NiS(SnS_(2)/NiS@N–C)microflowers were obtained using NiSn(OH)6 nanospheres as the template via a solventthermal method followed by the polydopamine coating and carbonization process.When served as an anode material for lithium-ion batteries,such hollow SnS_(2)/NiS@N–C microflowers exhibited a capacity of 403.5 mAh·g^(−1) at 2.0 A·g^(−1) over 200 cycles and good rate performance.The electrochemical reaction kinetics of this anode was analyzed,and the morphologies and structures of anode materials after the cycling test were characterized.The high stability and good rate performance were mainly due to bimetallic synergy,hollow micro/nanostructure,and nitrogen-doped carbon layers.The revealed excellent electrochemical energy storage properties of hollow SnS_(2)/NiS@N–C microflowers in this study highlight their potential as the anode material.

Solvent regulation strategy of Co-MOF-74 microflower for supercapacitors

Metal-organic frameworks(MOFs)with porous crystal structures have attracted extensive attention in application of energy storage and conversion,owing to their regularity,porosity,large specific surface area,etc.In this work,Co-MOF-74 microflower has been successfully prepared via a controllable solvent regulation strategy.Through modulating the polarity of the solvent,crystals grow in certain preferred orientation and Co-MOF-74 with various morphologies were obtained.Thereinto,the energy storage performance of Co-MOF-74 microflower was measured in both three-electrode system and asymmetric supercapacitor device(specific capacitance of 164.2 F/g at 0.5 A/g in the three-electrode system and 62.5 F/g at 1 A/g in the asymmetric supercapacitor device).This can be attributed to the preferred crystal orientation resulting in a regular and uniform microflower,which is of great significance to electronic interfacial exchange and ion transfer during electrochemical reactions.

壳聚糖微花的制备及影响其形貌的因素

以壳聚糖(chitosan,CS)为原料,在其溶解过程中通过超声和过氧化氢对其进行辅助溶解,之后通过离子交联法,将三聚磷酸钠(sodium tripolyphosphate,TPP)由下而上地注入到CS溶液中,并通过冷冻干燥得到了壳聚糖微花(chitosan microflower,CSMF),并对其进行一系列表征,研究影响其成花的因素。结果发现CSMF粒径在1~2μm;CSMF的傅里叶红外变换光谱在532cm^(-1)出现了磷酸根基团的振动峰;CSMF的晶型由CS的半结晶结构变为了水合多晶型结构;CSMF的X射线光电子能谱结果显示其产生了C—N^(+)键;而热重分析结果显示CSMF的热稳定性较CS稍有降低;并且发现预处理方式、超声时间、CS溶液温度和CS与TPP质量比会影响CSMF的花状结构,而超声功率和过氧化氢添加量不会影响其花状结构,进而推测其成花机理为将原CS降解成在一定分子质量范围内的短长链CS,然后在一定的温度下TPP与降解后相对较长的CS链交联形成微花结构的底座,与降解后相对较短的CS链交联形成纳米片,最后再通过CS结构上面的—NH_(3)^(+)与磷酸根离子之间的相互作用,将纳米片自组装到底座上,进而生成了微花结构。

微通道连续流制备碳量子点的创新实验设计

为探索新工科背景下学科交叉融合的创新教学模式,培养兼具扎实理论基础和实践能力的化工人才,自主设计开发了微通道反应平台用于本科化学工程实验教学中。以牛奶为原料设计连续流制备碳量子点的综合实验平台,通过紫外-可见光分光光度计、傅里叶变换红外光谱仪、透射电子显微镜等对碳量子点的形貌、结构和光学性能进行表征。通过该实验训练,学生能更好地了解微通道技术的原理和应用,掌握相关的实验操作及表征方法。此外,该实验涉及化学、化工、材料、自动化控制等多学科知识交叉融合,能开拓学生视野,培养其创新意识、实践能力与合作精神。

Boron-assisted growth of silica nanowire arrays and silica microflowers for bendable capacitor application

Aligned silica nanowire arrays and silica microflowers were fabricated using boron as the catalyst and under the flow N2 gas. The obtained product had no catalyst contamination. And silica nanowires had long lengths of a few hundreds. The growth of nanowire arrays and microflowers was explained using mechanism. Parallel-plate capacitors using silica nanowire mat as the dielectric were fabricated. The silica nanowire capacitor shows a specific capacitance of 0.24 n F/cm~2 at the frequency of 100 Hz. The capacitor is not monotone changing with the frequency. The measurement of mechanical properties shows that the tunneling current increases along with an increase in bending angle of the capacitor.

Solid-state template-free fabrication of uniform Mo2C microflowers with lithium storage towards Li-ion batteries

Herein,we first report one-step synthesis of uniform Mo2 C microflowers(MCMFs)from low-cost precursors via industrialized solid-state strategy.With fine optimization in precursor ratio and pyrolysis temperatures,the as-fabricated MCMFs are assembled well with interconnected single-crystalline nanosheet subunits.More encouragingly,the resultant MCMFs are further highlighted as a competitive anode with robust and long-duration lithium-storage behaviors towards high-performance Li-ion batteries.

A Unified Gas-Kinetic Scheme for Continuum and Rarefied Flows III:Microflow Simulations

Due to the rapid advances inmicro-electro-mechanical systems(MEMS),the study of microflows becomes increasingly important.Currently,the molecular-based simulation techniques are the most reliable methods for rarefied flow computation,even though these methods face statistical scattering problem in the low speed limit.With discretized particle velocity space,a unified gas-kinetic scheme(UGKS)for entire Knudsen number flow has been constructed recently for flow computation.Contrary to the particle-based direct simulation Monte Carlo(DSMC)method,the unified scheme is a partial differential equation-based modeling method,where the statistical noise is totally removed.But,the common point between the DSMC and UGKS is that both methods are constructed through direct modeling in the discretized space.Due to the multiscale modeling in the unified method,i.e.,the update of both macroscopic flow variables and microscopic gas distribution function,the conventional constraint of time step being less than the particle collision time inmany direct Boltzmann solvers is released here.The numerical tests show that the unified scheme is more efficient than the particle-basedmethods in the low speed rarefied flow computation.Themain purpose of the current study is to validate the accuracy of the unified scheme in the capturing of non-equilibrium flow phenomena.In the continuum and free molecular limits,the gas distribution function used in the unified scheme for the flux evaluation at a cell interface goes to the corresponding Navier-Stokes and free molecular solutions.In the transition regime,the DSMC solution will be used for the validation of UGKS results.This study shows that the unified scheme is indeed a reliable and accurate flow solver for low speed non-equilibrium flows.It not only recovers the DSMC results whenever available,but also provides high resolution results in cases where the DSMC can hardly afford the computational cost.In thermal creep flow simulation,surprising solution,such as the gas flowing from hot to cold regions along the wall surface,is observed for the first time by the unified scheme,which is confirmed later through intensive DSMC computation.

Microflow Simulations via the Lattice Boltzmann Method

The exact solution to the hierarchy of nonlinear lattice Boltzmann kinetic equations,for the stationary planar Couette flow for any Knudsen number was presented by S.Ansumali et al.[Phys.Rev.Lett.,98(2007),124502].In this paper,simulation results at a non-vanishing value of the Knudsen number are compared with the closed-form solutions for the higher-order moments.The order of convergence to the exact solution is also studied.The lattice Boltzmann simulations are in excellent agreement with the exact solution.

Graphene oxide-decorated Fe2（MoO4）3 microflowers as a promising anode for lithium and sodium storage

Mixed transition metal oxides （MTMOs） have received intensive attention as promising anode materials for lithium-ion batteries （LIBs） and sodium-ion batteries （SIBs）. In this work, we demonstrate a facile one-step water-bath method for the preparation of graphene oxide （GO） decorated Fe2（MoO4）3 （FMO） microflower composite （FMO/GO）, in which the FMO is constructed by numerous nanosheets. The resulting FMO/GO exhibits excellent electrochemical performances in both LIBs and SIBs. As the anode material for LIBs, the FMO/GO delivers a high capacity of 1,220 mAh·g^-1 at 200 mA·g^-1 after 50 cycles and a capacity of 685 mAh·g^-1 at a high current density of 10 A·g^-1. As the anode material for SIBs, the FMO/GO shows an initial discharge capacity of 571 mAh·g^-1 at 100 mA·g^-1, maintaining a discharge capacity of 307 mAh·g^-1 after 100 cycles. The promising performance is attributed to the good electrical transport from the intimate contact between FMO and graphene oxide. This work indicates that the FMO/GO composite is a promising anode for high-performance lithium and sodium storage.

Cerium-yttrium binary oxide microflower:synthesis,characterization and catalytic dehydration property

Cerium dioxide has a comparatively lower Ce4+/Ce3+redox pair,which leaves abundant oxygen vacancies on oxide lattice,also making incorporation of foreign ion and subsequent applications feasible and convenient.In this work,a series of cerium-yttrium mixed oxides were prepared by using polyvinylpyrrolidone as major template through sol-gel,which were further employed as catalyst for dehydration of aniline with formic acid into N-phenylformamide.Characterizations reveal that synthetic samples have a variety of morphologies including nanoparticle,microflower,and uniform microrods.The monitoring of particle size,zeta potential,and ultravioletvisible(UV-Vis)of preparative solution indicate that selfassembly of polyvinylpyrrolidone and its subsequent reaction with metal ion determines sample morphology.In catalytic dehydration,all samples show high dehydration efficiencies that are comparable to those from anhydrous Na2SO4 and combination of dicyclohexylcarbodiimide with 4-dimethylaminopyridine and dichloromethane shows better outputs than water.In association with structural analysis,cerium looks more active than yttrium,while yttrium mainly plays as a structure-directing and poreformingagent.Thisstudymaycontributeto micro-/nanofabrication of rare earth composites and their catalytic applications.

挤出式3D打印陶瓷梯度材料动态混合过程数值模拟

针对微流挤出工艺下制备陶瓷梯度材料引起的混合难题,依托混合挤出核心功能部件——多组分主动混合机构,结合理论分析、ANSYS仿真模拟与打印实验,探究了螺杆结构下混料腔内多组分材料混合机制及其规律.首先,对流体流动进行理论分析;其次,对料腔内流体流场进行仿真分析,定义了该工艺下材料混合时间的构成;最后以螺杆转速、材料进给量、进料顺序3个影响因素作为研究对象,通过组分输运模型进行模拟分析,研究了上述3个因素对多材料混合过程的影响及其规律.结果表明:在变径螺杆作用下腔内压力沿着挤出方向阶跃式升高,口模附近迅速泄压;腔内流体速度沿挤出方向递增,在螺槽的左、右底角部位会形成材料滞留区.螺杆转速的变化对内部流体的流动影响大于进给量;通过混合过程模拟结果发现螺杆转速的增加有利于提高平面混合均匀性,对腔内流体的平均停留时间影响不大;增大进料量不仅缩短了混料腔内流体停留时间,还降低了螺杆的轴向混合能力;材料过渡时间随着料腔内高黏度流体体积分数的增加而逐渐增加.最后,打印锯齿形梯度渐变部件,利用MATLAB软件进行图像处理,验证了理论分析与数值模拟研究的合理性与正确性.该研究为了解挤出式3D打印陶瓷梯度材料混合过程的机理奠定了基础,并为后续混料设备的结构改进提供了理论支持.

微流场渗流检测技术在水库渗漏处理中的应用研究

渗漏是影响水库大坝整体安全的关键因素,如何有效的检测水库大坝的渗漏点、渗漏通道和渗漏流速等一直是坝工安全领域研究的热点。针对目前水库大坝渗漏点难以精确定位和对渗漏量测量不准确等问题,阐述了声呐流速测量原理,提出了微流场渗流检测技术,并依托板桥水库实际工程展开应用。通过采用“DB-VI三维流速矢量声纳测量仪”,对板桥水库混凝土溢流坝裂缝渗漏通道进行检测,精细地测量出声波在流体中能量传递的大小与分布,同时,结合水下摄像进行了验证,确认了主要渗漏点的位置,为采取针对性的处理措施提供了依据。

高帧率超声造影在鉴别浅表淋巴结良恶性中的临床价值

目的应用高帧率超声造影观察浅表淋巴结增强均匀性和灌注方向,探讨其鉴别良恶性淋巴结的临床价值。方法选取我院经病理证实的浅表淋巴结异常患者121例(共121枚淋巴结),根据淋巴结大小分为A组37例(最大径0.5~1.0 cm)、B组56例(最大径>1.0~2.0 cm)、C组28例(最大径>2.0 cm),均行常规帧率及高帧率超声造影并保留其对应的动脉期图像,然后启动微血流增强模式,以1/3~1/2倍速播放并留存动态图像,分析两种造影帧率下各组良恶性浅表淋巴结增强均匀性和灌注方向的差异。绘制受试者工作特征(ROC)曲线分析常规帧率及高帧率超声造影鉴别不同大小良恶性浅表淋巴结的诊断效能。结果常规帧率和高帧率超声造影显示121例良恶性浅表淋巴结增强均匀性比较差异均有统计学意义(均χ^(2)=14.546,均P<0.001);常规帧率和高帧率超声造影显示良恶性浅表淋巴结灌注方向比较差异均有统计学意义(χ^(2)=5.160、4.600,均P<0.05)。C组中良恶性浅表淋巴结增强均匀性比较差异有统计学意义(χ^(2)=9.614,P=0.002)。各组中良恶性浅表淋巴结灌注方向比较差异均有统计学意义(均P<0.05)。ROC曲线分析显示,高帧率超声造影及常规帧率超声造影鉴别良恶性浅表淋巴结的曲线下面积(AUC)均分别为0.852、0.740,差异有统计学意义(Z=2.640,P=0.008);其中A、B、C组高帧率超声造影与常规帧率超声造影鉴别良恶性浅表淋巴结的AUC分别为0.817和0.669、0.864和0.732、0.827和0.772。A组两种帧率超声造影的AUC比较差异有统计学意义(Z=2.101,P=0.036),B、C组两种帧率超声造影的AUC比较差异均无统计学意义(Z=1.509、0.797,P=0.131、0.425)。结论高帧率超声造影可以清晰显示良恶性浅表淋巴结的增强均匀性和灌注方向,具有较好的鉴别诊断价值。