Monte Carlo study on abnormal growth of Goss grains in Fe-3%Si steel induced by second-phase particles

The selective abnormal growth of Goss grains in magnetic sheets of Fe-3%Si （grade Hi-B） induced by second-phase particles （AlN and MnS） was studied using a modified Monte Carlo Ports model. The starting microstructures for the simulations were generated from electron backscatter diffraction （EBSD） orientation imaging maps of recrystallized samples. In the simulation, second-phase particles were assumed to be randomly distributed in the initial microstructures and the Zener drag effect of particles on Goss grain boundaries was assumed to be selectively invalid because of the unique properties of Goss grain boundaries. The simulation results suggest that normal growth of the matrix grains stagnates because of the pinning effect of particles on their boundaries. During the onset of abnormal grain growth, some Goss grains with concave boundaries in the initial microstructure grow fast abnormally and other Goss grains with convex boundaries shrink and eventually disappear.

EFFECTS OF DISPERSED SECOND-PHASE PARTICLES ON MIXED CONDUCTORS OF Li_(1+x)V_3O_8(X=0, 1)

The structure and electric properties of the mixed conductors of Li_(1+x)V_3O_8(x=0.1) containing dispersed second-phase α-Al_2O_3 particles have been studied in the paper. The total conductivity of the specimen containing 6m/o α-Al_2O_3 is five or six times as much as that of pure Li_(1+x)V_3O_8 (x=0.1) at room temperature. By the analyses of NMR and ESR, it is known that at low temperature, the transport activation energy of Li^+ ions reduced, the transport frequency of Li^+ ions are speeded up and thus ionic conductivity increased in the specimens containing α-Al_2O_3 particles. At high temperature, diffusion effect of α-Al_2O_3 on electronic transport becomes great, the enhancement of ionic conductivity caused by α-Al_2O_3 doesn't make up the decrease of electronic conductivity caused by the diffusion effect, so that total conductivity of the specimens containing DSPP is lower than that of pure Li_(1+x)V_3O_8(x=0.1). As a result, DSPP mainly increases ionic conductivity of the mixed conductors at room temperature.

Influences of solid particles on the formation of the third phase crud during solvent extraction

The influences of solid particles in leach solution on the formation of the third phase crud during solvent extraction of copper were studied. Analyzed from the point of view of pH value and surface tension, the study results showed that the solid particle is one of the most important contributors for the formation of the third phase crud. During solvent extraction, if the pH value was greater than 2.30, the number of solid particles in the mother solution increased, in which case the possibility of forming the third phase crud could also increase, and the interface tension value might grow in pace with the quantity of the third phase crud.

PREPARATION OF WATERBORNE ULTRAFINE PARTICLES OF EPOXY RESIN BY PHASE INVERSION TECHNIQUE

Waterborne ultrafine particles of epoxy resin were prepared by phase inversion technique. The results of SEM revealed that the particles diameter was in the range of 50 to 100 nm and the effects on amount of water required at phase inversion point were also discussed.

Effect of ECAP processing on distribution of second phase particles,hardness and electrical conductivity of Cu-0.81Cr-0.07Zr alloy

The effect of equal-channel angular pressing(ECAP)processing at room temperature and 300℃on the distribution of the second phase particles and its influence on hardness and electrical conductivity of the commercial Cu-0.81Cr-0.07Zr alloy were investigated.Microstructural characterization indicated that the area fraction of coarse Cr-rich particles decreased after ECAP processing.This reduction was attributed to the Cr dissolution induced by plastic deformation.The electrical conductivity of the alloy decreased by 12%after 4 ECAP passes at room temperature due to the increase of electrons scattering caused by higher Cr content in solid solution and higher density of defects in the matrix.These results were supported by the reduction of the Cu lattice parameter and by the exothermic reactions,during differential scanning calorimetry(DSC)analysis,observed only in the samples subjected to ECAP processing.Aging heat treatment after ECAP processing promoted an additional hardening effect and the complete recuperation of the electrical conductivity,caused by the re-precipitation of the partially dissolved particles.The better combination of hardness(191 HV)and electrical conductivity(83.5%(IACS))was obtained after 4 ECAP passes at room temperature and subsequent aging at 380℃for 1 h.

Approximations of the Scattering Phase Functions of Particles

Based on anomalous diffraction theory and the modified Rayleigh-Debye approximation, a physically realistic model in bridging form is described to approximate the scattering phase function of particles. When compared with the exact method, the bridging technique reported here provides a reasonable approximation to the Mie results over a broader range of angles and size parameters, and it demonstrates the advantage of being computationally economic. In addition, the new phase function model can be essentially extended to other shapes and conveniently used in more complicated scattering and emission problems related to the solutions of the radiative transfer equations.

Phase separation and super diffusion of binary mixtures of active and passive particles

Computer simulations were performed to study the dense mixtures of passive particles and active particles in two dimensions.Two systems with different kinds of passive particles(e.g.,spherical particles and rod-like particles)were considered.At small active forces,the high-density and low-density regions emerge in both systems,indicating a phase separation.At higher active forces,the systems return to a homogeneous state with large fluctuation of particle area in contrast with the thermo-equilibrium state.Structurally,the rod-like particles accumulate loosely due to the shape anisotropy compared with the spherical particles at the high-density region.Moreover,there exists a positive correlation between Voronoi area and velocity of the particles.Additionally,a small number of active particles capably give rise to super-diffusion of passive particles in both systems when the self-propelled force is turned on.

Mssbauer Effect in Ultrafine Particles with Fe-C Solid Solution,γ-Fe and Fe_3C Phases

Ultrafine particles prepared by evaporating pure Fe in CH4 atmosphere using arc-dischargeheating method, were found to consist of Fe-C solid solution, γ-Fe and Fe3C phases. EfFect of annealing temperature on phase transformation and hyperfine interactions has been investigated by Mossbauer spectroscopy, X-ray diffraction (XRD), differential thermal analysis and thermogravimetry (DTA-TG), transmission electron microscopy (TEM), oxygen determination and vibrating sample magnetometer (VSM) measurements. It was observed that phase transformation of γ-Fe to α-Fe occurs during annealing in vacuum. The mechanism causing the change of hyperfine interactions with annealing temperature differs for Fe-C solution and interstitial compounds. DifFerence of hyperfine interactions of Fe-C solid solution in the starting sample and its annealed samples is ascribed to the improvement of activation of interstitial carbon atoms. Stress-relieving in structure of annealed Fe3C particle can result in a weak influence on hyperfine interactions. Parameters fitted to the Mossbauer spectra show the existence of superparamagnetism in all the samples. Absorbed and combined oxygen on particle surface of the starting sample were determined.

Physical information-enhanced graph neural network for predicting phase separation

Although phase separation is a ubiquitous phenomenon, the interactions between multiple components make it difficult to accurately model and predict. In recent years, machine learning has been widely used in physics simulations. Here,we present a physical information-enhanced graph neural network(PIENet) to simulate and predict the evolution of phase separation. The accuracy of our model in predicting particle positions is improved by 40.3% and 51.77% compared with CNN and SVM respectively. Moreover, we design an order parameter based on local density to measure the evolution of phase separation and analyze the systematic changes with different repulsion coefficients and different Schmidt numbers.The results demonstrate that our model can achieve long-term accurate predictions of order parameters without requiring complex handcrafted features. These results prove that graph neural networks can become new tools and methods for predicting the structure and properties of complex physical systems.

A Test Study of 50% Lightning Impulse Breakdown Voltage on Rod-Plane Gap with Two-Phase Mixture of Gas and Solid Particles

A test study on 50% lightning impulse breakdown voltage in two-phase mixture of gas and solid particles has been carried out in a specially designed discharge cabinet. A mechanical sieve is set up for sifting different solid particles into the discharge space uniformly. The lightning impulse voltage according with international electro-technical commission （IEC） standard is applied to the electrodes inside the discharge cabinet by the rule of up-down method in a total of 40 times. The results showed that the 50% lightning impulse breakdown voltage in two-phase mixture of gas and solid particles has its own features and is much different from that in air.

Numerical Simulations of Snow Accumulation in the Bogie Region of a Train Considering Snow Particle Rotation

To investigate the influence of snow particle rotational motion on the accumulation of snow in the bogie region of high-speed trains,an Euler‒Lagrange numerical approach is adopted.The study examines the effects of snow particle diameter and train speed on the ensuing dynamics.It is shown that considering snow particle rotational motion causes significant deviation in the particle trajectories with respect to non-rotating particles.Such a deviation increases with larger snow particle diameters and higher train speeds.The snow accumulation on the overall surface of the bogie increases,and the amount of snow on the vibration reduction device varies greatly.In certain conditions,the amount of accumulated snow can increase by several orders of magnitudes.

EFFECT OF DISPERSED PHASE PARTICLES ON ELECTRICAL CONDUCTION OF PEO-NaSCN

Fast ionic conductors are one kind of solid state material with ionic conductivity as high as that of melten salts or liquid electrolytes.Ionic conductivity is one of the important parameters for characterizing a fast ionic conductor.For a long time materialists and chemists have made great efforts in search of new fast ionic conductors with high ionic conductivity.In view of structure,they have synthesised silver and copper fast ionic conductors with so called open structures.But it is not so successful for searching more applicable alkaline fast ionic conductors.Since polymer has flexibility for making thin film,it concentrates attention on the polymer-alkaline salt complex.Fenton et al.have first reported poly(ethylene oxide) (PEO)-alkaline salt complex.Later on Armard et al.have investigated the electrical property of PEO-NaSCN.

Modeling of Adhesive Particles Using a Combination of the Two-Body Interaction and Phase-Field Methods

Discrete materials such as powders and granular materials have been widely used due to their specific characteristics. The precise evaluation is accordingly becoming important, and various numerical schemes have been developed. However, the interactions among the constituent particles are still difficult to model precisely. Especially, contact conditions, which vary with material properties and circumstances, are difficult to formulate. In this study, a computational model for simulating adhesive particles on contact in a many-particle system is proposed. The interaction between the particles was represented by a two-body repulsive force that depends on the distance between particles and an additional adhesive force at the contact point. A phase-field variable was introduced to express the surface of each particle, and the adhesive force was formulated using the phase-field distribution. As a result, the adhesion of particles was properly expressed. For a mono-particle system, neighboring particles adhered and uniformly aggregated, while for a dual-particle system, several characteristic patterns were obtained depending on the initial arrangement of the particles. Repulsive contact was also considered as a specific case, and the corresponding results were obtained.

Preparation of Composite Particles Made of Biodegradable Polymer and a Few Additives with Phase Separation Followed by Drying-in-Liquid

It was tried to prepare the biodegradable composite particles by the phase separation method followed by the drying-in-liquid method. The composite particles were made of poly-ε-caprolac-tone, quaternary ammonium, carbon black and wax. In the experiment, acetone and water were selected as a good solvent and a poor solvent for poly-ε-caprolactone, quaternary ammonium and wax, respectively. The composite particles were prepared by changing the surfactant species and their concentration, the feeding velocity of water and the weight ratio of poly-ε-caprolactone with larger molecular weight to one with smaller molecular weight. The composite particles with the inner structure in which carbon black, quaternary ammonium and wax were coated well with poly-ε-caprolactone could be prepared by the preparation method presented in this study. The structure and the mean diameter of composite particles were strongly affected by the feeding velocity of water. The higher the feeding velocity of water, the larger the mean diameter of composite particles. The mean diameter was drastically decreased with the surfactant concentration and increased with the added amount of poly-ε-caprolactant with larger molecular weight.

Preparation of Polymer Composite Particles by Phase Separation Followed by Suspension Polymerization

The novel method for preparing the polymer composite particles has been developed. It was tried to prepare polymer composite particles composed of polystyrene and carbon black with the phase separation method followed by suspension polymerization. In order to prepare the polymer composite particles with the more uniform diameter, the styrene monomer droplets containing carbon black were formed with phase separation emulsification in which ethyl alcohol and water were used as the good solvent and the poor solvent for styrene monomer, respectively. In the experiment, the surfactant species and their concentrations, the pouring velocity of water and the weight ratio of carbon black to styrene monomer were mainly changed. Water was poured at the given pouring velocity into ethyl alcohol in which styrene monomer and an initiator were dissolved and carbon black was dispersed beforehand. The spherical polymer composite particles containing carbon black were prepared with Tween 20 and Tween 80 of nonionic surfactants and the irregular polymer composite particles were prepared with PVA, SDS and Kotamine. The diameters of polymer composite particles increased with the pouring velocity of water and with the weight ratio of carbon black to styrene monomer.

Effect of post annealing on phase transformation of Ni-Mn-Ga ferromagnetic shape memory alloy particles prepared by ball milling

The effect of post annealing on the phase transformation of Ni52Mn24Ga24 ferromagnetic shape memory alloy particles prepared by ball milling was studied. Ni52Mn24Ga24 alloy particles at micron scale were prepared successfully by ball milling the crushed bulk alloy. SEM observation reveals that the shape of the as-milled particle is regular polygon and a lot of cracks can be seen at the surface of the particles. For as-milled particles,the widening of characteristic peak can be found in the XRD pattern,and no transformation characterization can be detected by DSC. Post annealing at the elevated temperature will recover the transformation behavior of milled particles to the same level as that of bulk sample. It is shown that with increasing annealing temperature above 400 ℃,Ms decreases and As increases,while the magnetic transition temperature keeps constant. XRD results indicate that the change of grain size of the particles results in such an effect of post annealing.

Identification and Quantification of Non-Spherical Particles

In commercial applications of phase Doppler anemometry (PDA), the effectiveness of non sphericity of particles is present and the response of PDA system deviates from the theoretical prediction. In this paper, the statistic characteristics of PDA signal related to irregular particles is analyzed and a method of statistic classification of irregular particles is proposed.It proves that the parameter of PDA signal for irregular particles is an unbiased estimation for spherical ones, the mean of the phase difference is in direct proportion to the mean diameter of particles and the standard deviation of the phase difference increases linearly with the standard deviation of irregular particles. As an application of the identification of irregular objects, fuzzy patterns and similarities of haemocytes are used to recognize and quantify cell samples.The statistic classification of particles is more significant in practice.

Adaptable "bubble particles" prepared by green aqueous phase reshaping for completely removing odor

Facile and ecofriendly loading of micro/nano function-specific substances to create functional materials is a trend being pursued by researchers.However,current micro/nano particles loading approaches are often hindered by issues such as uneven distribution,unsatisfactory stability and complicate procedure.In this work,we present an aqueous phase reshaping method that only utilizes the moisture to fabricate the"bubble particles",which could perfectly cater to the topography of the substrate.The green preparation of bubble particles adopts an absolutely zero-pollution method,realizing the firm loading of particles on the substrate.Integrating the preparation and loading of particles overcomes the traditional complicate process,while the aqueous phase reshaping ensures uniform and firm loading of the"bubble particles"onto the substrate.Our mechanism demonstrates a significant enhancement in the interface relation after aqueous phase reshaping,with a 121-fold increase in contact surface area achieved by reducing the height by 1μm.Furthermore,we explore for the first time the influence of the nature of the receiving substrate on the interface morphology of particles during electrostatic spraying,which has important guiding significance for the interface relationship of electrostatic spraying and even electrostatic spinning materials.We also screen out the natural antibacterial essential oil linalool as the effective specialized antibacterial agent,which can specifically inhibit the odor-producing Proteus in urine,with an antibacterial rate of up to 100%.Taken together,this simple,ecofriendly method for fabricating functional materials with optimal interface stability appears highly promising for use in various products formed by electrostatic spraying/spinning.

Self-assembly of Binary Particles with Electrostatic and van der Waals Interactions

Nanoparticles with competitive interactions in solution can aggregate into complex structures. In this work, the synergistic self-assembles of binary particles with electrostatic and van der Waals interactions are studied with the particle Langevin dynamics simulation using a simple coarse-grained particle model. Various aggregations such as spherical, stacking-disk and tube structures are observed by varying the particles size and the interaction strength. The aggregation structures are explained with the packing theories of amphiphilic molecules in solution and dibolck copolymers in bulk. When the opposite ions are introduced into solution, the distribution of structures in the phase diagram appears an obvious offset. The simulation result is helpful to deeply understand the formation mechanism of complex nanostructures of multicomponent particles in solution.

Effects of Additive AlCl_3 on Crystal Phase, Particle Size and Microstructural Parameters of Nanocrystalline TiO_2 Prepared by HF-PCVD

Nanocrystalline TiO2 was prepared by high frequency plasma chemical vapor deposition (HF-PCVD). The effects of additive AlCl3 on crystal phase, particle size and microstructurai parameters of TiO2 nanocrystallites were investigated by X-ray diffraction(XRD) and transmission electron microscopy (TEM). The nanocrystallites obtained experimentally are mixture of anatase and rutile, the uniform diameters of particles are about 30 nm. The phase transformation from anatase to rutile was accelerated by AlCl3, and rutile content is increased from 26.7 wt pct to 53.6 wt pct with increasing of addition of AlCl3 from 0.0 wt pct to 5.0 wt pct. The particle size is reduced and the size distribution becomes very narrow. The crystal lattice constants have the trend to decrease, and celi volumes appear as shrinkable.