Fabrication of multi-shell coated silicon nanoparticles via in-situ electroless deposition as high performance anodes for lithium ion batteries

Si-based materials have been extensively studied because of their high theoretical capacity,low working potential,and abundant reserves,but serious initial irreversible capacity loss and poor cyclic performance resulting from large volume change of Si during lithiation and delithiation processes restrict their widespread application.Herein,we report the preparation of multi-shell coated Si(DS-Si)nanocomposites by in-situ electroless deposition method using Si granules as the active materials and copper sulfate as Cu sources.The ratio of Si and Cu was readily tuned by varying the concentration of copper sulfate.The multi-shell(Cu@CuxSi/SiO2)coating on Si surface promotes the formation of robust and dense SEI films and the transportation of electron.Thus,the obtained DS-Si composites exhibit an initial coulombic efficiency of 86.2%,a capacity of 1636 mAh g^-1 after 100 discharge-charge cycles at 840 mA g^-1,and an average charge capacity of 1493 mAh g^-1 at 4200 mA g^-1.This study provides a low-cost and large-scale approach to the preparation of nanostructured Si-metal composites anodes with good electrochemical performance for lithium ion batteries.

Heterostructured Mn_(3)O_(4)-MnS Multi-Shelled Hollow Spheres for Enhanced Polysulfide Regulation in Lithium-Sulfur Batteries

Constructing heterojunctions and hollow multi-shelled structures can render materials with fascinating physicochemical properties,and have been regarded as two promising strategies to overcome the severe shuttling and sluggish kinetics of polysulfide in lithium-sulfur(Li-S)batteries.However,a single strategy can only take limited effect.Modulating catalytic hosts with synergistic effects are urgently desired.Herein,Mn_(3)O_(4)-MnS heterogeneous multi-shelled hollow spheres are meticulously designed by controlled sulfuration of Mn2O3 hollow spheres,and then applied as advanced encapsulation hosts for Li-S batteries.Benefiting from the separated spatial confinement by hollow multi-shelled structure,ample exposed active sites and built-in electric field by heterogeneous interface,and synergistic effects between Mn_(3)O_(4)(strong adsorption)and MnS(fast conversion)components,the assembled battery achieves prominent rate capability and decent cyclability(0.016%decay per cycle at 2 C,1000 cycles).More crucially,satisfactory areal capacity reaches up to 7.1 mAh cm^(-2)even with high sulfur loading(8.0 mg cm^(-2))and lean electrolyte(E/S=4.0 pL mg^(-1))conditions.This work will provide inspiration for the rational design of hollow multi-shelled heterostructure for various electrocatalysis applications.

A 3-Node Co-Rotational Triangular Finite Element for Non-Smooth,Folded and Multi-Shell Laminated Composite Structures

Based on the first-order shear deformation theory,a 3-node co-rotational triangular finite element formulation is developed for large deformation modeling of non-smooth,folded and multi-shell laminated composite structures.The two smaller components of the mid-surface normal vector of shell at a node are defined as nodal rotational variables in the co-rotational local coordinate system.In the global coordinate system,two smaller components of one vector,together with the smallest or second smallest component of another vector,of an orthogonal triad at a node on a non-smooth intersection of plates and/or shells are defined as rotational variables,whereas the two smaller components of the mid-surface normal vector at a node on the smooth part of the plate or shell(away from non-smooth intersections)are defined as rotational variables.All these vectorial rotational variables can be updated in an additive manner during an incremental solution procedure,and thus improve the computational efficiency in the nonlinear solution of these composite shell structures.Due to the commutativity of all nodal variables in calculating of the second derivatives of the local nodal variables with respect to global nodal variables,and the second derivatives of the strain energy functional with respect to local nodal variables,symmetric tangent stiffness matrices in local and global coordinate systems are obtained.To overcome shear locking,the assumed transverse shear strains obtained from the line-integration approach are employed.The reliability and computational accuracy of the present 3-node triangular shell finite element are verified through modeling two patch tests,several smooth and non-smooth laminated composite shells undergoing large displacements and large rotations.

Miniband Formation in GaN/AlN Constant-Total-Effective-Radius Multi-shell Quantum Dots

We study the procedure of miniband formation in CaN/lAIN constant-total-effective-radius multi-shell quantum dots （CTER-MSQDs） by calculating the subband energies. We find a different behavior of the miniband widths and miniband gaps when the number of wells changes. It is shown that with increasing the inner quantum dot radiusRin, the number of minigaps decreases; with increasing the outer quantum dot radius Rout, the number of minigaps increases. We show that in the CTER-MSQDs systems, two kinds of minigaps exist： in the type （i） ones, minigaps increase monotonically when the number of wells increases while in the type （ii） ones, with increasing the number of wells, some of minigaps create, increase, at a critical number of wells decrease and finally vanish. Thus tuning of the m/nigaps and miniband widths in the CTER-MSQDs systems by using the number of wells, inner and outer quantum dot radii Rin and Rout is now possible.

Hollow Multi-shelled Structure Photoelectric Materials: Multiple Shells Bring Novel Properties

Hollow multi-shelled structures(HoMSs)have made significant strides across a wide spectrum of scientific investigations since the inception of the sequential templating approach(STA)in 2009,revealing distinctive temporal-spatial ordering properties.The recent establishment of a mathematical model for STA has not only demystified the formation of concentration waves within the STA process but also extended its relevance to gentler solutionbased systems,thereby broadening the HoMs landscape.Herein,focusing on photoelectric applications,this review first summarizes the unique temporal-spatial ordering features of HoMs.Subsequentially,the greatly enhanced properties of light capture and absorption,exciton separation,and transfer are deeply discussed.Finally,we conclude with a perspective on the potential challenges and burgeoning opportunities that lie ahead in the advancement of HoMs development.

Balanced Polysulfide Containment and Lithium Ion Transport in Lithium-Sulfur Batteries via Nitrogen-doped Carbon Hollow Multi-shelled Structures on Modified Separators

Representing the next-generation technology in lithium-ion batteries,lithium-sulfur(Li-S)batteries offer increased specific energy without relying on scarce metals like nickel and cobalt,but suffer from a low practical specific energy due to poor conductivity and a short lifespan due to the shuttle effect of polysulfides.Balancing the confinement of polysulfides and the transport of lithium ions requires highly elaborate modifiers for separators.Hollow multi-shelled structures(HoMSs)show promise as hierarchical mesostructures for separators,offering multiple shell layers and internal cavities that effectively inhibit polysulfide shuttle.Thoughtful design of these structures is crucial to address these challenges effectively.In this study,nitrogen-doped carbon HoMS(NC HoMS)was created using polymer templates through a precisely controlled polymerization process.Batteries featuring NC HoMS-modified separators exhibit improved capacity and cycling stability in comparison to those utilizing commercial separators.Especially,triple-shelled NC HoMS strikes a balance in polysulfide containment and lithium ion transport.Featuring a sulfur loading of 6.34 mg/cm^(2),the Li-S battery can consistently complete 100 charge-discharge cycles,starting with a discharge capacity of 966.4 mA·h/g with a 75.8%capacity retention rate.NC HoMS holds potential as the separator modifier in addressing the polysulfide shuttle problem and facilitating the Li-ion transportation for advanced Li-S batteries.

Multi-shelled TiO2/Fe2TiO5 heterostructured hollow microspheres for enhanced solar water oxidation

There remains a pressing challenge in the fabrication of superior photocatalysts for light-driven water oxidation.Here,we designed and fabricated heterostructured TiO2/Fe2TiO5 hollow microspheres with single-,double-,closed-double-,triple-,and core-shell structures and different Fe/Ti molar ratios using a facile sequential templating approach.The closed-double-shelled TiO2/Fe2TiO5 hollow microspheres with 35% Fe exhibited the highest oxygen evolution reaction rate up to 375 μmol＆#183;g-1＆#183;h-1 and good stability for 5 h.The high performance can be attributed to the closed-double shell,which had more reactive sites and greater light-harvesting ability,self-supported thin shells with short charge-transfer paths,and a favorable staggered band alignment between the TiO2 and Fe2TiOs.

Understanding formation mechanism of ZnO diatomic chain and multi-shell structure using physical mechanics:Molecular dynamics and first-principle simulations

In this paper,the possibility of the monatomic chain (MC) formation for ZnO material was studied by molecular dynamics (MD) simulation.The process of MC formation and the effects of temperature,strain rate and size were studied extensively.The tensile process can be divided to be five stages and the ZnO diatomic chain (DC) can be found.The MD results show that most atoms in MC came from the original surface of ZnO nanowires (NWs).Temperature and strain rate are two important factors affecting the process,and both high temperature and low strain rate in a certain range would be beneficial to the formation of DC.Moreover,the effects of strain rate and temperature could attribute to the Arrhenius model and the energy release mechanism.Furthermore,multi-shell structure was found for the samples under tensile strain and the layer-layer distance was about 3.Our studies based on density functional theory showed that the most stable structure of ZnO DC was confirmed to be linear,and the I-V curve was also got using ATK.

Multi-shelled CuO microboxes for carbon dioxide reduction to ethylene

The electroreduction of CO2 to valuable chemicals and fuels offers an effective mean for energy storage.Although CO2 has been efficiently converted into C1 products(e.g.,carbon monoxide,formic acid,methane and methanol),its convention into high value-added multicarbon hydrocarbons with high selectivity and activity still remains challenging.Here we demonstrate the formation of multi-shelled CuO microboxes for the efficient and selective electrocatalytic CO2 reduction to C2H4.Such a structure favors the accessibility of catalytically active sites,improves adsorption of reaction intermediate(CO),inhibits the diffusion of produced OH−and promotes C-C coupling reaction.Owing to these unique advantages,the multi-shelled CuO microboxes can effectively convert CO2 into C2H4 with a maximum faradaic efficiency of 51.3%in 0.1 M K2SO4.This work provides an effective way to improve CO2 reduction efficiency via constructing micro-and nanostructures of electrocatalysts.

A versatile ligand-assisted cooperative template method to synthesize multi-shelled mesoporous hollow metal hydroxide and oxide nanospheres as catalytic reactors

Nowadays,multi-shelled mesoporous hollow metal oxide nanospheres have drawn a lot of attention due to their large internal space,nanometer scaled shell thickness,high specific surface area and well-defined mesopores,of which unique nanostructure endows metallic oxides with enhanced properties.In this thesis,we have studied and proposed a versatile ligand-assisted cooperative template method to synthesize multi-shelled mesoporous hollow metal hydroxides and oxides nanospheres,in which silica nanospheres act as sacrificial templates and the coordination interaction between metal ions and surfactant can be cooperatively amplified by using chelating ligand(ascorbic acid)as a co-template.The synthesized metal hydroxides and oxides nanospheres possess stable hollow structure,uniform spherical morphology and tunable diameter from 270 to 690 nm.All the multi-shelled mesoporous hollow metal hydroxide and metal oxide nanospheres exhibit high surface areas(up to 640 m^(2)/g).The obtained Au nanoparticles loaded composited nanospheres exhibit excellent reactivity for solvent-free aerobic oxidation of ethylbenzene with high activity(28.2%)and selectivity(87%).

Multi-shelled α-Fe_2O_3 microspheres for high-rate supercapacitors

Hollow structured metal oxides are extensively studied in energy storage and conversion systems. In this work, we report the fabrication of multi-shelled Fe_2O_3 microspheres with nanospindles assembly on its exterior shell. The β-FeOOH precursor nanospindles were firstly grown on the surface of carbon microspheres to produceβ-FeOOH@carbon composites, which were later converted into multi-shelled Fe_2O_3 microspheres by calcination in air.As electrode material for supercapacitors, the multi-shelled Fe_2O_3 microspheres exhibit high capacity and good rate capability. The electrode delivers the specific capacitances of630 and 510 F g^(-1) at the current densities of 1 and 5 A g^(-1),respectively.

Scalable synthesis of multi-shelled hollow N-doped carbon nanosheet arrays with confined Co/CoP heterostructures from MOFs for pH-universal hydrogen evolution reaction

Developing low-cost but efficient hydrogen evolution reaction(HER)electrocatalysts over whole pH values is a significant but daunting task for the large-scale application of electrochemical hydrogen production.Herein,we develop,for the first time,a scalable MOF-assisted strategy for the fabrication and microstructural optimization of multi-shelled hollow N-doped carbon nanosheet arrays with confined Co/CoP heterostructures on carbon cloth(Co/CoP@NC/CC)for boosting HER performances.The key to this strategy is the step-by-step epitaxial growth of unprecedented multilayer ZIF-L arrays on carbon cloth,which are subsequently pyrolyzed and controllably phosphorized to achieve the precise control over the shell number and nanoarchitectures of the Co/CoP@NC/CC.Impressively,the HER performances can be significantly enhanced by increasing hollow shell number,and the optimal triple-shelled hollow Co/CoP@NC/CC exhibits low overpotentials of 86,78 and 145 mV in acidic,alkaline and neutral media to deliver a current density of 10 mA cm^(-2),respectively,ranking as one of the best Co-based HER electrocatalysts over whole pH values.Further DFT calculations suggest that the Co/CoP heterostructures can effectively boost the cleavage of H–OH to generate protons and optimize the adsorption energy of hydrogen(ΔG_(H*)),which,together with the large electrode/electrolyte interface and accelerated charge/mass transfer of multi-shelled hollow array structure as well as the good conductivity and dispersity,are responsible for the remarkably improved HER performances.This study not only provides a new toolbox for enriching the family of multi-shelled nanoarchitecture materials,but also points out a general and effective route to develop highly efficient self-supported electrode materials for energy-related applications and beyond.

空间分布系列球壳声场耦合与辐射特性研究

针对大深度载人潜器的多球壳组合结构,以水介质中任意空间分布的系列弹性球壳为研究对象,利用球函数平移加法定理,建立计及球壳间声场相互作用的多球壳系统声振耦合模型,计算分析空间分布系列球壳的声场耦合特性及其影响因素。结果表明:声场相互作用将改变球壳模态间耦合关系,使得单阶模态对球壳振动的贡献不再限于单个峰值,进而影响声辐射频谱特征;双球壳系统受激球壳和非受激球壳都产生声辐射,轴向激励情况下,两球壳间存在强声场耦合效应,激励力偏离轴向时,声场耦合效应逐渐减弱;不同尺度球壳组成的双球壳系统扩展了声场有效耦合的频率范围,辐射声场兼具两个球壳的模态特征;多球壳串列布置时,声场耦合效应具有传递作用,多球壳按不同角度分散布置时,辐射声场空间分布则更趋复杂。

微波多腔体外壳导电胶粘接覆铜板失效原因分析与解决

[目的]某微波多腔体外壳(可伐材料)镀镍/金后,在通过导电胶粘接覆铜板时出现导电胶与可伐腔体不浸润、导电胶开裂、覆铜板从可伐腔体外壳上剥离等不良现象。[方法]通过建立故障树,结合能谱分析、水滴试验和剪切力测试,对上述问题的主要影响因素逐一进行分析。[结果]导电胶粘接失效的主要原因是镀金后浸泡金保护剂工艺参数不当,以及转运过程中所用包装盒上的微量硅油沾污了外壳表面。[结论]在导电胶粘接前对微波多腔体外壳进行化学清洗,以及禁用含硅油的包装盒后,未再出现粘接失效现象。

相变材料微胶囊的研究进展

为进一步提高能源利用率,满足当今社会对可持续能源的迫切需求,首先,列举了相变材料微胶囊的芯材和壁材的分类及其选择原则;其次,分析总结了相变材料微胶囊不同制备技术的国内外最新研究进展,重点对比归纳了物理法、化学法以及物理化学法等制备技术的原理、特点及其适用范围;然后,综述了相变材料微胶囊在纺织、医疗、建筑、能源等领域的应用进展并分析总结国内外最新相关研究;最后,针对相变材料微胶囊在生产制备和实际应用中的关键问题,提出其潜在解决方案和优先发展方向,以推进相变材料微胶囊不断向绿色化、多功能化方向深入发展。

纳米多层各向同性弹性球壳的轴对称自由振动

经典连续体力学理论不再适用于具有尺度效应的微纳结构问题求解。运用状态空间方法和非局域弹性理论,建立考虑非局域效应的纳米多层球壳模型,求解了纳米多层球壳的轴对称自由振动问题。分别以不同半径的银、金纳米粒子为例进行计算并与低频拉曼散射实验值进行比较。研究结果表明:取纳米粒子的半径为材料的内特征尺度,各粒子结构自由振动频率的计算值与实验值基本相符。上述力学模型有望应用于超声作用下纳米靶向超声造影剂振动分析或其他纳米多层壳结构振动分析等。

一种铝合金壳体压铸模具设计

通过对壳体零件的结构和成形性分析,重点对模具设计的主要环节进行了详细的分析与研究;分析设计了模具的分型面位置、浇注和排溢系统的结构以及推出机构,采用在侧面厚壁处多点浇口的结构形式;对模具的型芯、型腔做了具体的结构设计,采用型腔在定模、型芯在动模的普通两板式结构形式;并且型芯和型腔部分制作成活动镶件,便于修理、更换,模具结构简单、实用,完全满足模具的设计要求。

前沿科研成果融入水污染控制工程教学——多壳层纳米粒子的制备与高级氧化技术降解四环素

设计了一个多壳层CeO_(2)纳米粒子活化过硫酸盐降解盐酸四环素的水污染控制工程实验。用水热法合成CeO_(2)掺杂的碳微球,然后煅烧得到多壳层CeO_(2)纳米粒子,最后用多壳层CeO_(2)纳米粒子活化过一硫酸盐(PMS)进行盐酸四环素的降解。本实验能够让学生深入了解高级氧化技术的原理,锻炼学生制备纳米粒子和使用仪器设备的能力,认识表征技术,理解多变量实验中控制变量的意义,培养学生的科学素养。

陶瓷封装外壳多表面外观检测机构的设计与应用

由于对陶瓷封装外壳的特殊设计需求以及对批次间一致性要求越来越高,人工质检不再能完全满足要求。针对外壳的外形特点、缺陷特点以及生产特点,通过对融合人工智能(AI)检测技术的封装外壳缺陷自动检测算法的研究,设计了多金、缺金、凹/凸点等关键外观缺陷的检测方案。通过开发多表面缺陷检测机构,实现陶瓷封装外壳多个表面缺陷检测的自动化,保证了多表面缺陷均可检测性。该检测机构搭配不同镜头和多角度光源,提高了机器视觉采集能力。相比人工检测,该检测机构的检测能力较高,并实现效率提升2倍以上。该多表面外观检测机构的应用提高了产品检验质量和检验一致性,实现了人工检测向全自动检测的跨越。

基于位移-速度输入法结构多点激励FPS支座隔震效果研究

受行波效应、相干效应、场地效应的影响,大跨度结构的多点激励地震反应分析非常复杂,且考虑多点激励下对大跨空间网格结构隔震性能的影响是结构工程抗震方向中有重大意义的研究课题。以单层圆柱面大跨度空间网架结构为研究对象,基于直接位移法,应用SAP2000有限元软件建立了多点激励动力反应时程分析模型,进行结构在地震动一致激励和多点激励作用下的动力反应分析计算。结果表明:水平地震动多点激励效应对大跨度空间结构的影响十分显著,需采取使用多点激励输入方式。不设置隔震支座时,多点激励下,支撑柱弯矩与剪力随波速的减小而明显增加,柱顶位移变小,中柱轴力略微上升。基础隔震时,各支撑柱柱顶内力与位移的分配较无隔震时存在差异。边柱的弯矩、剪力及轴力均小于中柱的相应值,但柱顶位移增加明显。柱弯矩减震效率保持在45%~75%,柱剪力减震效率保持在60%~85%;柱顶隔震时,能得到比基础隔震更高的隔震效率,且柱弯矩隔震效率高达90%左右,柱剪力隔震效率保持在85%~90%。柱顶位移显著减小,柱轴力比基础隔震时略有增加。