Universal architecture and defect engineering dual strategy for hierarchical antimony phosphate composite toward fast and durable sodium storage

Antimony(Sb)-ba sed anode materials are feasible candidates for sodium-ion batteries(SIBs) due to their high theoretical specific capacity and excellent electrical conductivity.However,they still suffer from volume distortion,structural collapse,and ionic conduction interruption upon cycling.Herein,a hierarchical array-like nanofiber structure was designed to address these limitations by combining architecture engineering and anion tuning strategy,in which SbPO_(4-x) with oxygen vacancy nanosheet arrays are anchored on the surface of interwoven carbon nanofibers(SbPO_(4-x)@CNFs).In particular,bulky PO_(4)^(3-) anions mitigate the large volume distortion and generate Na_(3)PO_(4) with high ionic conductivity,collectively improving cyclic stability and ionic transport efficiency.The abundant oxygen vacancies substantially boost the intrinsic electronic conductivity of SbPO_4,further accelerating the reaction dynamics.In addition,hierarchical fibrous structures provide abundant active sites,construct efficient conducting networks,and enhance the electron/ion transport capacity.Benefiting from the advanced structural design,the SbPO_(4-x)@CNFs electrodes exhibit outstanding cycling stability(1000 cycles at 1.0 A g^(-1) with capacity decay of 0.05% per cycle) and rapid sodium storage performance(293.8 mA h g^(-1) at 5.0 A g^(-1)).Importantly,systematic in-/ex-situ techniques have revealed the "multi-step conversion-alloying" reaction process and the "battery-capacitor dual-mode" sodium-storage mechanism.This work provides valuable insights into the design of anode materials for advanced SIBs with elevated stability and superior rate performance.

A CLOSED SYSTEM OF EQUATIONS FOR DENSE TWO-PHASE FLOW AND EXPRESSIONS OF SHEARING STRESS OF DISPERSED PHA’E AT A WALL

Inthis paper, each of the two phases in dense two-phase flow is considered as continuous medium and the fundamental equations for two-phase flow arc described in Eulerian form. The generalized constitutive relation of the Bingham fluid is applied to the dispersed phase with the analysis oj physical mechanism of dense two-phase flow. The shearing stress of dispersed phase at a wall is used to give a boundary condition. Then a mathematical model for dense two-phase flow is obtained. In addition, the expressions of shearing stress of dispersed phase at a wall is derived according to the fundamental model of the friclional collision between dispersed-plutse particles and the wall.

Discrete dislocation plasticity analysis of dispersion strengthening in oxide dispersion strengthened(ODS) steels

A discrete dislocation plasticity analysis of dispersion strengthening in oxide dispersion strengthened(ODS) steels was described. Parametric dislocation dynamics(PDD) simulation of the interaction between an edge dislocation and randomly distributed spherical dispersoids(Y2O3) in bcc iron was performed for measuring the influence of the dispersoid distribution on the critical resolved shear stress(CRSS). The dispersoid distribution was made using a method mimicking the Ostwald growth mechanism. Then, an edge dislocation was introduced, and was moved under a constant shear stress condition. The CRSS was extracted from the result of dislocation velocity under constant shear stress using the mobility(linear) relationship between the shear stress and the dislocation velocity. The results suggest that the dispersoid distribution gives a significant influence to the CRSS, and the influence of dislocation dipole, which forms just before finishing up the Orowan looping mechanism, is substantial in determining the CRSS, especially for the interaction with small dispersoids. Therefore, the well-known Orowan equation for determining the CRSS cannot give an accurate estimation, because the influence of the dislocation dipole in the process of the Orowan looping mechanism is not accounted for in the equation.

Two‑Level Biomimetic Designs Enable Intelligent Stress Dispersion for Super‑Foldable C/NiS Nanofiber Free‑Standing Electrode

Due to the lack of in-depth understanding about the folding issues of the electronic materials,it is a huge challenge to pre-pare a super-foldable and highly electrochemical faradic electrode.Here,inspired from from the fully nimble structures of cuit cocoons and cockscomb petals,with two-level biomimetic design,for the first time we prepared a super-foldable and electrochemically functional freestanding cathode,made of C-fiber@NiS-cockscomb(SFCNi).In virtue of its nimble biomi-metic structures,SFCNi can remarkably sustain over 100,000 times,repeated true-folding without composite fibers fracture,functional matters detachment,conductivity degradation,or electrochemical performance change.The main mechanism behind these behaviors was disclosed by Real-time scanning electron microscopy and mechanical simulations,on the folding process.Results unveil that the cockscomb-like NiS with atomic thickness can deform freely due to the need of bending,and the cuit-cocoon-like SFCNi can generate an“ε-shape”folding structure at the crease.Such a smart self-adaptive deforma-tion capability can effectively reduce the effect of stresses and local excessive deformations,so that the chemical bonds can preserve their interaction,and the material won’t fracture.This subtle and exceptional mechanical behavior realizes a super-foldable property.The two-level biomimetic design strategy is a novel method for fabrication of super-foldable composite electrodes and integrated multi-functional super-foldable devices.

Relection of elastic waves at the elastically supported boundary of a couple stress elastic half-space

The relection elastic waves at the elastically supported boundary of a couple stress elastic half-space are studied in this paper. Different from the classical elastic solid, there are three kinds of elastic waves in the couple stress elastic solid, and two of them are dispersive. The boundary conditions of a couple stress elastic half-space include the couple stress vector and the rotation vector which disappear in the classical elastic solids. These boundary conditions are used to obtain a linear algebraic equation set, from which the amplitude ratios of relection waves to the incident wave can be determined. Then, the relection coeficients in terms of energy lux ratios are calculated numerically, and the normal energy lux conservation is used to validate the numerical results. Based on these numerical results,the inluences of the boundary parameters, which relect the mechanical behavior of elastic support, on the relection energy partition are discussed. Both the incident longitudinal wave（the P wave） and incident transverse wave（the SV wave） are considered.

Yield stress measurements and microstructure of colloidal kaolin powders clusterized and dispersed in different liquids

Rheologicat measurements of four colloidal kaolin powders dispersed in water, paraffinic oil and liquid rubber have been done at solid concentration （9 （VS/VL） in the range 8-33%. In quasi-static conditions the yield stress τ° values were derived. An S-shaped relationship between τ° and （9 exists, that allows to evaluate the percolation threshold θc values. In water θc ranges between 29% and 33%, while it is between 17% and 21% in oil and in liquid rubber. In water the microstructure units, i.e. the primary clusters among kaolin crystallites, are denser and bigger than the ones in the two other liquids. Furthermore, in quasistatic condition, the aqueous microstructure units have less tendency to cling together to form a network that can span all over the liquid phase. The different kaolin dispersions at θ equal to 22% are characterized by yield stress ranging between 7.S Pa and 59 Pa in water, 66-250 Pa in oil and 230-770 Pa in liquid rubber. It has been found that for any kaolin types the log τ°/ θ evaluated near to the percolation threshold is a conservative parameter of the three different liquids. These results are useful to design colloidal dispersions with selected microstructure.

Bearing capacity and load transfer mechanism of a static drill rooted nodular pile in soft soil areas

The static drill rooted nodular pile is a new type of pile foundation consisting of precast nodular pile and the surrounding cemented soil.This composite pile has a relatively high bearing capacity and the mud pollution will be largely reduced during the construction process by using this type of pile.In order to investigate the bearing capacity and load transfer mechanism of this pile,a group of experiments were conducted to provide a comparison between this new pile and the bored pile.The axial force of a precast nodular pile was also measured by the strain gauges installed on the pile to analyze the distribution of the axial force of the nodular pile and the skin friction supported by the surrounding soil,then 3D models were built by using the ABAQUS finite element program to investigate the load transfer mechanism of this composite pile in detail.By combining the results of field tests and the finite element method,the outcome showed that the bearing capacity of a static drill rooted nodular pile is higher than the bored pile,and that this composite pile will form a double stress dispersion system which will not only confirm the strength of the pile,but also make the skin friction to be fully mobilized.The settlement of this composite pile is mainly controlled by the precast nodular pile;meanwhile,the nodular pile and the surrounding cemented soil can be considered as deformation compatibility during the loading process.The nodes on the nodular pile play an important role during the load transfer process,the shear strength of the interface between the cemented soil and the soil of the static drill rooted pile is larger than that of the bored pile.

A rheological method for selecting nano-kaolin powder as filler in SBR rubber

This paper shows that the stiffness ofstyrene-butadiene solid rubber with added kaolin powder is related to the yield stress of kaolin dispersion in liquid polybutadiene rubber up to the percolation threshold. For five kinds of kaolin powder, the value of τ° spans the range of 100-430 Pa, while the corresponding compressive elastic constant of SBR varies from 12 to 21 MPa. A relationship between τ° and △E^i^＊/ER^＊ is proposed. Critical examination of these data infers that kaolin powder dispersed in solid rubber matrix acts as an additive which decreases the random movement of the polybutadiene chains. Consequently, dispersions of nano-particles in liquid and in solid SBR are considered to be related, thus leading to a theological method for selecting nano-particles as fillers in solid SBR.