Rock-ice avalanches in cold high-mountain regions pose severe hazards due to their high mobility,yet the quantitative controls of particle-size ratio and ice content remain insufficiently constrained.This study invest...Rock-ice avalanches in cold high-mountain regions pose severe hazards due to their high mobility,yet the quantitative controls of particle-size ratio and ice content remain insufficiently constrained.This study investigates their coupled effects using inclinedflume experiments and Discrete Element Method(DEM)simulations,covering three gravel sizes(2-5 mm,5-7 mm,7-10 mm)and four ice-content levels(0%,20%,40%,60%).Run-out distance,velocity,energy components,flow regime(Savage number),and segregation indexαwere quantified.Increasing ice content significantly enhances mobility,but with diminishing marginal effectiveness.From 0%to 40%ice content,run-out distance increases by 41%-86%,whereas the additional increase from 40%to 60%contributes only 12%-23%.Particle-size ratio strongly governs segregation intensity.Fine-gravel groups reach segregation indices ofα=0.92-0.98,indicating nearly complete upward migration of ice,whereas medium-gravel and coarse-gravel groups exhibit much weaker segregation,stabilizing atα=0.68-0.74 and 0.60-0.69.Savage number analyses reveal marked flow-regime transitions.At 0%ice content,Savage numbers reach 1.0-1.5,indicating a collisional regime.Increasing ice content suppresses collisionality,with Savage numbers decreasing to 0.03-0.07 at 60%ice content,consistent with dense-regime flow.DEM energy analyses confirm this regime shift:for finegravel mixtures,collision energy decreases by 14%,while sliding-friction energy increases by 33%as ice content increases from 0%to 60%,reflecting enhanced overburden effects imposed by upward-segregated ice layers.Medium and coarse mixtures exhibit weaker or opposite energy-shift patterns,demonstrating strong size dependence.Mechanistically,large particle-size contrasts promote strong segregation and form dense basal rock layers that increase basal friction and reduce mobility.When particle sizes are similar or ice content is high,segregation remains limited,allowing ice to mix into the basal layer,thereby reducing basal friction and enhancing mobility.This research quantitatively demonstrates how composition controls particle spatial distribution,flow regime,and energy dissipation,offering new mechanistic insights into the propagation and deposition behaviors of rock-ice avalanches and improving hazard assessment in vulnerable high-mountain regions.展开更多
Bacterial cells are widely accepted as nucleation sites for calcium carbonate precipitation in biomineralization based on the Microbially Induced Carbonate Precipitation(MICP)process.For MICP-based insitu biotreatment...Bacterial cells are widely accepted as nucleation sites for calcium carbonate precipitation in biomineralization based on the Microbially Induced Carbonate Precipitation(MICP)process.For MICP-based insitu biotreatment,the firstproblem to be solved is how to introduce and retain the bacterial cells in the soil,which involves the migration and retention of bacterial cells during the biogrouting process.Soil particle size,a key factor in determining pore throat size,can have a significanteffect on the migration and retention of bacterial cells in the soil and therefore on biomineralization.To investigate the effect of particle size on the migration and retention of bacterial cells in sand and its biomineralization,two sets of tests were carried out in this study,including percolation tests and sand column treatment tests.Soil urease activity(definedas urease activity per unit mass of soil)and calcium carbonate content of the biomineralized sand were measured to comprehensively assess the migration and retention of bacterial cells in the sand.The results indicate that sands with a particle size smaller than 0.25 mmwould inhibit the migration of bacteria in the sand,resulting in a nonuniform distribution of precipitated calcium carbonate and a low strength enhancement of biomineralization.On the other hand,sands with a particle size larger than 1.18 mm are unfavorable for retaining bacterial cells in the sand,resulting in low calcium conversion efficiency.Meanwhile,particle size would also affect the formation of effective calcium carbonate through interparticle contact number and interparticle pore size,and thus biomineralization.展开更多
Small angle x-ray scattering(SAXS)is an advanced technique for characterizing the particle size distribution(PSD)of nanoparticles.However,the ill-posed nature of inverse problems in SAXS data analysis often reduces th...Small angle x-ray scattering(SAXS)is an advanced technique for characterizing the particle size distribution(PSD)of nanoparticles.However,the ill-posed nature of inverse problems in SAXS data analysis often reduces the accuracy of conventional methods.This article proposes a user-friendly software for PSD analysis,GranuSAS,which employs an algorithm that integrates truncated singular value decomposition(TSVD)with the Chahine method.This approach employs TSVD for data preprocessing,generating a set of initial solutions with noise suppression.A high-quality initial solution is subsequently selected via the L-curve method.This selected candidate solution is then iteratively refined by the Chahine algorithm,enforcing constraints such as non-negativity and improving physical interpretability.Most importantly,GranuSAS employs a parallel architecture that simultaneously yields inversion results from multiple shape models and,by evaluating the accuracy of each model's reconstructed scattering curve,offers a suggestion for model selection in material systems.To systematically validate the accuracy and efficiency of the software,verification was performed using both simulated and experimental datasets.The results demonstrate that the proposed software delivers both satisfactory accuracy and reliable computational efficiency.It provides an easy-to-use and reliable tool for researchers in materials science,helping them fully exploit the potential of SAXS in nanoparticle characterization.展开更多
An A1203p/A1 composite was successfully synthesized using a displacement reaction between 80 wt% A1 and 20 wt% CuO powders at a heating rate of 5 ℃/min. Two different sizes CuO particles were used, and all the experi...An A1203p/A1 composite was successfully synthesized using a displacement reaction between 80 wt% A1 and 20 wt% CuO powders at a heating rate of 5 ℃/min. Two different sizes CuO particles were used, and all the experiments were conducted under an argon atmosphere. To analyze the microstructural evolution during synthesis, the A1-20 wt% CuO samples were heated to the temperatures selected according to the differential scanning calorimetry curve and then immediately quenched with water. The phase composites and microstructure of the water-quenching samples were in- vestigated using X-ray diffraction, optical microscopy, scanning electron microscopy and energy-dispersive spectrometry. The results indicate that the CuO particle size has a significant effect on the microstructural evolution of the samples during the heating stage and on the microstructure of synthesized composites. Smaller CuO particles can decrease the reaction temperature, narrow the reaction temperature range at the different reaction stages during the heating stage and make the size and distribution of in situ A1203 particles more uniform. The reaction between A1 and CuO can be complete as the temperature rises to 900 ℃. The size of the in situ A1203 particles is approximately 5 μm when the size of the CuO particles is less than 6 μm. This sample has a relatively high Rockwell hardness of 60 HRB.展开更多
Developing the railway transport sector is a challenging scientific,economic and social research topic starting with ensuring human security.The main topic that should be developed in that sense is the ballast stabili...Developing the railway transport sector is a challenging scientific,economic and social research topic starting with ensuring human security.The main topic that should be developed in that sense is the ballast stability and dynamical behaviour under external loading and environmental changes.This paper investigates the effect of particle size distribution and normal pressure on the mechanical response of a ballast bed.Grading curves of ballast layers with different sizes are illustrated to discuss their strength behaviour under various strains to deduce the significant effect on the direct shear performance of the ballast layer.Direct shear tests with different Particle Size Distribution(PSD)were reproduced using the Discrete Element Method(DEM).It is noticed that when the number of small-sized ballast increases,the shear strength and the friction angle increase to varying degrees under different normal pressures,with an average increase of 27%and 8%,respectively.When the number of large-sized ballast decreases,the shear strength and the friction angle decrease to varying degrees under different normal pressures,with an average decrease of 6%and 3%,respectively.展开更多
This work used 5CrMnMo steel and titanium carbide(TiC)powders to fabricate particulate metal matrix composites(PMMCS).The composites’microstructure,hardness,and impact toughness were compared with four different tita...This work used 5CrMnMo steel and titanium carbide(TiC)powders to fabricate particulate metal matrix composites(PMMCS).The composites’microstructure,hardness,and impact toughness were compared with four different titanium carbide ceramic particle sizes.The phase composition and microstructure of composites were studied.Vickers hardness and Charpy impact tests were employed to analyze composites’hardness and impact ductility,respectively.The results showed that the four groups of composites are mainly composed of martensite,trace residual austenite,and titanium carbide(undissolved TiC and primary TiC particles).With the growth of the ceramic particle dimension in the composite layer,the number of primary titanium carbide ceramics gradually decreased.When the initial ceramic particle size was small,it tended to generate dendritic primary TiC,and when the particle size was large,it tended to generate polygons and ellipsoids.Furthermore,with the growth of titanium carbide ceramic particle dimension in the composites,the hardness of the composites decreased but the impact toughness of the composites rose first and then descended.When the ceramic particle size was 50-75μm,the composite had the highest hardness,and the impact energy of the composites was the highest,which is 8 J.This was because there were more undissolved titanium carbide ceramics in the composite,and there was a thicker matrix metal between the ceramic particles.展开更多
The increased risk of chronic diseases has led to increasing importance of coarse foods in daily life,but the inclusion of new ingredients has a great degree of influence on the structural characteristics and sensory ...The increased risk of chronic diseases has led to increasing importance of coarse foods in daily life,but the inclusion of new ingredients has a great degree of influence on the structural characteristics and sensory qualities of the food.The effects of five different particle size variations on the physicochemical characteristics,dough,and steamed bread structure of Flaxseed-based milk coproduct(FMC)were investigated.As the particle size decreases,the structure of the dough becomes denser due to an increase in water retention capacity and dissolution capacity,weakening the competition for dough moisture and allowing for an increase in air-holding capacity.The reduction in particle size increased the specific volume of the steamed bread,a decrease in the spread ratio,and an optimization of hardness and elasticity,as well as an increase in consumer acceptance of the FMC steamed bread.However,it is not the smaller the particle size,the higher the quality of steamed bread,appropriate reduction of particle size can improve the quality of steamed bread.In addition,the addition of FMC reduces fat digestion.Therefore,the present study proposes a method to change the particle size of FMC to optimize the quality of the steamed bread and to reduce fat digestibility by adding FMC.展开更多
A feasible criterion was established to determine the lower size limit of raw coal(d_(pRm))for efficient beneficiation in the air-fluidized bed with magnetite particles.The feasibility of using small magnetite particl...A feasible criterion was established to determine the lower size limit of raw coal(d_(pRm))for efficient beneficiation in the air-fluidized bed with magnetite particles.The feasibility of using small magnetite particles to accommodate the fine raw coal was demonstrated from the experimental perspective.The minimum size for the magnetite particles to be fluidized smoothly was clarified as 47.1μm,which corresponded to the border between Geldart-B and-A groups.Since the gangue and coal components in the raw coal were crushed into the same size,d_(pRm)depended on the greater one between d_(pGm)(minimum size required for the gangue particles to sink towards the bottom)and d_(pCm)(minimum size required for the coal particles to float towards the top).dpcm was determined as 259μm by supposing that provided the gangue particles accumulated in the lower half bed,they could be potentially extracted from the bottom.On the other hand,it was observed that the coal particles could always accumulate in the upper half bed.Under such circumstances,dpcm was revealed as 9.8μm since finer coal particles would be blown out by air before the 47.1μm sized magnetite particles became fluidized.Eventually,dpRm was clarified as 259μm,agreeing with the common view that raw coal coarser than 6 mm could be effectively beneficiated in the air-fluidized bed with magnetite particles.Additionally,the difficulty in beneficiating the fine raw coal was revealed to arise more from the remixing of sorted gangue particles than that of separated coal particles.展开更多
High-steep waste dumps in open-pit mines frequently demonstrate complex particle-size distributions and fractal characteristics along their slopes,which have a significant impact on slope stability.This study takes th...High-steep waste dumps in open-pit mines frequently demonstrate complex particle-size distributions and fractal characteristics along their slopes,which have a significant impact on slope stability.This study takes the Dasuji South waste dump in Inner Mongolia as a case to quantify the fractal dimensions of soil-rock mixtures at various slope heights,and to clarify how these fractal properties govern shear strength and deformation behavior under overlying stress,thereby affecting the overall stability of the waste dump slope.Field sampling and laboratory tests were conducted to determine the particle-size composition and fractal dimensions while direct shear tests were conducted and revealed that lower fractal dimensions indicating coarser particle assemblages significantly enhance shear resistance.Complementary PFC_(2)D discrete element simulations demonstrate that slopes composed of lower-fractaldimension materials deform less and contain localized deformation zones,whereas higher-fractal-dimension slopes experience more extensive displacement and a heightened risk of landslides.These findings refine our understanding of the relationship between fractal grain-size distribution and slope stability,providing a robust theoretical basis for improved stability assessment and optimized support strategies in deep open-pit mining waste dumps,and ultimately aiding in more effective disaster prevention within geotechnical engineering.展开更多
Mg-3Gd(wt.%)samples with different initial grain sizes were prepared to evaluate the grain size effect on microstructural evolution during cold rolling and subsequent annealing hardening response.The deformation behav...Mg-3Gd(wt.%)samples with different initial grain sizes were prepared to evaluate the grain size effect on microstructural evolution during cold rolling and subsequent annealing hardening response.The deformation behavior and mechanical response of the as-rolled and annealed samples were systematically investigated by a combination of electron microscopy and microhardness characterization.The results show that the twinning activities were highly suppressed in the fine-grained samples during rolling.Upon increasing the rolling reduction to 40%,ultra-fine grain structures with a volume fraction of∼28%were formed due to the activation of multiple slip systems.Conversely,twinning dominated the early stages of deformation in the coarse-grained samples.After a 10%rolling reduction,numerous twins with a volume fraction of∼23%were formed.Further increasing the rolling reduction to 40%,high-density dislocations were activated and twin structures with a volume fraction of∼36%were formed.The annealing hardening response of deformed samples was effectively enhanced compared to that of the non-deformed samples,which was attributed to the enhanced Gd segregation along grain boundaries,twin boundaries and dislocation cores.Moreover,the grain size and rolling reduction were found to affect the microstructure evolution during annealing,resulting in a notable difference in the annealing hardening response of Mg-3Gd alloy between samples of different grain sizes deformed to different strains.These findings highlight the crucial importance of microstructural and processing parameters in the design of high-strength,cost-effective Mg alloys.展开更多
In this study,an artificial intelligence-based machine vision system was developed for in-line particle size analysis during the pellet layering process.Drug-layered pellets were produced by coating microcrystalline c...In this study,an artificial intelligence-based machine vision system was developed for in-line particle size analysis during the pellet layering process.Drug-layered pellets were produced by coating microcrystalline cellulose cores with an ibuprofen-containing layering liquid until the target drug content was achieved.Drug content increases with pellet size;therefore,particle size monitoring can ensure product safety and quality.The direct imaging system,consisting of a rigid endoscope,a light source,and a high-speed camera,provides real-time information about pellet size and layer uniformity,enabling timely intervention in the case of out-of-spec products.A convolutional neural network-based instance segmentation algorithm was employed to detect particles in focus,ensuring that pellet size could be accurately determined despite the dense flow of the particles.After training the model,the performance of the developed system was assessed by analysing the particle size distribution of pellet cores with variable sizes within the 250 e850 mm size range.The endoscopic system was tested in-line at a larger scale during the drug layering of inert pellet cores.The particle size data acquired in real time with the endoscopic imaging system corresponded with the reference methods,demonstrating the feasibility of the proposed machine vision-based method as a process analytical technology tool for in-line process monitoring.展开更多
Ethanol steam reforming(ESR)represents a promising route for sustainable hydrogen production,leveraging the high hydrogen content,renewability,and logistical advantages of ethanol.Although Ni-based catalysts are leadi...Ethanol steam reforming(ESR)represents a promising route for sustainable hydrogen production,leveraging the high hydrogen content,renewability,and logistical advantages of ethanol.Although Ni-based catalysts are leading non-noble candidates for ESR,their practical deployment is hindered by compromised H_(2) production efficiency and rapid deactivation.In this work,we combined catalyst synthesis,kinetic analysis,and mechanistic investigation to elucidate the effectsof Ni particle size(3-9 nm)on ESR performance of Ni/CeO_(2) catalysts.These Ni/CeO_(2) catalysts were prepared via a citric acid-assisted coprecipitation method,and systematically characterized using complementary techniques,including high-resolution transmission electron microscopy(HRTEM),in situ X-ray photoelectron spectroscopy(XPS),hydrogen temperature-programmed reduction(H_(2)-TPR),Raman spectroscopy,O_(2)/CO chemisorption,and temperature-programmed surface reaction(TPSR)analyses.Mechanistic study revealed that ethanol dehydrogenation to acetaldehyde is the rate-determining step,defining the intrinsic activity of Ni sites,whereas C-C bond cleavage governs H_(2) selectivity in ESR.At smaller Ni sizes(e.g.,3.1 nm),larger CeO_(2) surface was exposed,which promoted acetaldehyde condensation to acetone,and consequently reduced H_(2) production efficiency.The Ni/CeO_(2) catalyst with~5 nm of Ni particles afforded the highest H_(2) yield(66.3%)and outstanding stability by balancing dehydrogenation activity,H_(2) selectivity,and coking resistance.Conversely,larger Ni particles(>6 nm)facilitated methanation reaction and catalyst deactivation.This work reconciles prior inconsistencies in the Ni size effects on ESR and provides guidance for the design of efficient and durable Ni-based catalysts for H_(2) production.展开更多
Determination of the critical state line(CSL)is important to characterize engineering properties of granular soils.Grain size distribution(GSD)has a significant influence on the location of CSL.The influence of partic...Determination of the critical state line(CSL)is important to characterize engineering properties of granular soils.Grain size distribution(GSD)has a significant influence on the location of CSL.The influence of particle breakage on the CSL is mainly attributed to the change in GSD due to particle breakage.However,GSD has not been properly considered in modeling the CSL with influence of particle breakage.This study aims to propose a quantitative model to determine the CSL considering the effect of GSD.We hypothesize that the change of critical state void ratio with respect to GSD is caused by the same mechanism that influences of the change of minimum void ratio with respect to GSD.Consequently,the particle packing model for minimum void ratio proposed by Chang et al.(2017)is extended to predict critical state void ratio.The developed model is validated by experimental results of CSLs for several types of granular materials.Then the evolution of GSD due to particle breakage is incorporated into the model.The model is further evaluated using the experimental results on rockfill material,which illustrates the applicability of the model in predicting CSL for granular material with particle breakage.展开更多
The structural and the size evolution of embedded In nanoparticles in Al synthesized by ion implantation and subsequent annealing are experimentally investigated. The average radius r of In nanoparticles is determined...The structural and the size evolution of embedded In nanoparticles in Al synthesized by ion implantation and subsequent annealing are experimentally investigated. The average radius r of In nanoparticles is determined as a function of annealing time in a temperature range between 423 K and 453 K. The structural transition of In nanoparticles with the crystallographic orientation In （200）[002]｜｜Al （200）[002] is observed to change into In （111）[110]｜｜Al （002）[110] with a critical particle radius between 2.3 nm and 2.6 nm. In addition, the growth of In nanoparticles in the annealing process is evidently governed by the diffusion limited Ostwald ripening. By further analyzing the experimental data, values of diffusion coefficient and activation energy are obtained.展开更多
To clarify the effect of SnO2 particle size on the arc erosion behavior of AgSnO2 contact material, Ag?4%SnO2 (mass fraction) contact materials with different sizes of SnO2 particles were fabricated by powder metallur...To clarify the effect of SnO2 particle size on the arc erosion behavior of AgSnO2 contact material, Ag?4%SnO2 (mass fraction) contact materials with different sizes of SnO2 particles were fabricated by powder metallurgy. The microstructure of Ag?4%SnO2 contact materials was characterized, and the relative density, hardness and electrical conductivity were measured. The arc erosion of Ag?4%SnO2 contact materials was tested, the arc duration and mass loss before and after arc erosion were determined, the surface morphologies and compositions of Ag?4%SnO2 contact materials after arc erosion were characterized, and the arc erosion mechanism of AgSnO2 contact materials was discussed. The results show that fine SnO2 particle is beneficial for the improvement of the relative density and hardness, but decreases the electrical conductivity. With the decrease of SnO2 particle size, Ag?4%SnO2contact material presents shorter arc duration, less mass loss, larger erosion area and shallower arc erosion pits.展开更多
Effects of size distribution (particle size and content of fine fraction (<10μm)) on scheelite flotation were studied using flotation tests and theoretical calculations. The results show that particle size influen...Effects of size distribution (particle size and content of fine fraction (<10μm)) on scheelite flotation were studied using flotation tests and theoretical calculations. The results show that particle size influences the scheelite recovery and the performance of combined reagents. The scheelite recovery is lowered by adding fine particles (<10μm) into the pulp containing coarse particles. Extended DLVO (EDLVO) theory confirms that the fine fractions (<10μm) could interface with the coarse fractions. The interaction energy and fluid forces are relative to the particle size, which might explain why the fine fractions influence the scheelite flotation. The highest recovery of scheelite using combined reagents as collector and optimum ratio of combined reagents were determined by scheelite particle size and reagent performance. However, the optimum adding order was only determined by reagent performance, which has nothing to do with particle size.展开更多
Al2O3p-Al composites were synthesized using an in-situ reaction in the 80%Al-20%CuO （mass fraction） system. The effects of the CuO particle size on the synthesis temperature and microstructure of the composites were...Al2O3p-Al composites were synthesized using an in-situ reaction in the 80%Al-20%CuO （mass fraction） system. The effects of the CuO particle size on the synthesis temperature and microstructure of the composites were investigated by various methods. The results indicate that the CuO particle size has a significant effect on the temperature at which the complete reaction in the Al-CuO system occurs：the temperature is 200 ℃ lower in the Al-CuO system containing CuO particles with sizes less than 6μm than that containing CuO particles with sizes less than 100μm. The interfacial bonding between Al2O3 particles and Al is not complete when the temperature is below a critical value. The morphology of the Al2O3 particles varies from ribbon-like shape to near spherical shape when the temperature is above a critical value. These two critical temperatures are affected by the particle size of CuO, and the critical temperature of the sample containing CuO particles with sizes less than 6μm is 100 ℃ lower than that of the sample containing CuO particles with sizes less than 100μm.展开更多
Application of particle image velocity (PIV) techniques for measuringparticle size distribution and total number in an activation chamber of desulfurization system isintroduced. Watersheld algorithm is used to choose ...Application of particle image velocity (PIV) techniques for measuringparticle size distribution and total number in an activation chamber of desulfurization system isintroduced. Watersheld algorithm is used to choose the suitable initial gray level threshold whichis used to change the gray level images taken by PIV to black and white ones, then every particle inan image is isolated totally. For every isolating particle, its contour is tracked by the edgeenhancement filter function and kept by Freeman s chain code. Based on a set of particle s chincode, its size and size distribution are calculated and sorted. Finally, the experimental data ofcalcium particles and water drops, separately injected into the activation chamber, and the erroranalysis of data are given out.展开更多
This paper presents a method of measuring the particle mean size and dust concentration by small angle near forward light scattering optics and the extinction theory. Its theory is based on Fraunhofer diffraction the...This paper presents a method of measuring the particle mean size and dust concentration by small angle near forward light scattering optics and the extinction theory. Its theory is based on Fraunhofer diffraction theory which is the approximation of Mie scattering within the forward Fraunhofer diffraction lobe, and Rosin Rammler function is introduced to describe the particle size distribution in two phase flow in advance. Compared with the values by the sample weight method, the measurement results have a reasonable agreement. The present work has demonstrated that this method will be probably used to monitor the parameters of two phase flow.展开更多
In order to evaluate the influence of particle size and particle concentration on the coagulation process, two kinds of particle suspensions, nanoparticles and microparticles,were employed to investigate the effect of...In order to evaluate the influence of particle size and particle concentration on the coagulation process, two kinds of particle suspensions, nanoparticles and microparticles,were employed to investigate the effect of particle size on coagulation mechanisms with varying coagulation parameters. Results showed that it is easier for nanoparticles to cause self-aggregation because of Brownian motion, while interception and sedimentation are the mainly physical processes affecting particle transport for microparticles, so they are more stable and disperse more easily. The particle size distribution and particle concentration had distinct influence on the coagulation mechanisms. Under neutral conditions, as the amount of coagulant increased, the coagulation mechanism for nanoparticles changed from charge neutralization to sweep flocculation and the nanoparticles became destabilized, re-stabilized and again destabilized. For microparticles, although the coagulation mechanism was the same as that of nanoparticles, the increased rate of aluminum hydroxide precipitation exceeded the adsorption of incipiently formed soluble alum species, resulting in the disappearance of the re-stabilization zone. Under acidic conditions, Brownian motion dominates for nanoparticles at low particle concentrations, while sweep flocculation is predominant at high particle concentrations. As for microparticles, charge neutralization and sweep flocculation are the mechanisms for low and high particle concentrations respectively.Under alkaline condition, although the mechanisms for both nano-and microparticles are the same, the morphology of flocs and the kinetics of floc formation are different. At low particle concentrations, nanoparticles have larger growth rate and final size of flocs, while at high particle concentrations, nanoparticles have higher fractal dimension and recovery factors.展开更多
基金funded by the Natural Science Foundation of China(Grants No 42277127)。
文摘Rock-ice avalanches in cold high-mountain regions pose severe hazards due to their high mobility,yet the quantitative controls of particle-size ratio and ice content remain insufficiently constrained.This study investigates their coupled effects using inclinedflume experiments and Discrete Element Method(DEM)simulations,covering three gravel sizes(2-5 mm,5-7 mm,7-10 mm)and four ice-content levels(0%,20%,40%,60%).Run-out distance,velocity,energy components,flow regime(Savage number),and segregation indexαwere quantified.Increasing ice content significantly enhances mobility,but with diminishing marginal effectiveness.From 0%to 40%ice content,run-out distance increases by 41%-86%,whereas the additional increase from 40%to 60%contributes only 12%-23%.Particle-size ratio strongly governs segregation intensity.Fine-gravel groups reach segregation indices ofα=0.92-0.98,indicating nearly complete upward migration of ice,whereas medium-gravel and coarse-gravel groups exhibit much weaker segregation,stabilizing atα=0.68-0.74 and 0.60-0.69.Savage number analyses reveal marked flow-regime transitions.At 0%ice content,Savage numbers reach 1.0-1.5,indicating a collisional regime.Increasing ice content suppresses collisionality,with Savage numbers decreasing to 0.03-0.07 at 60%ice content,consistent with dense-regime flow.DEM energy analyses confirm this regime shift:for finegravel mixtures,collision energy decreases by 14%,while sliding-friction energy increases by 33%as ice content increases from 0%to 60%,reflecting enhanced overburden effects imposed by upward-segregated ice layers.Medium and coarse mixtures exhibit weaker or opposite energy-shift patterns,demonstrating strong size dependence.Mechanistically,large particle-size contrasts promote strong segregation and form dense basal rock layers that increase basal friction and reduce mobility.When particle sizes are similar or ice content is high,segregation remains limited,allowing ice to mix into the basal layer,thereby reducing basal friction and enhancing mobility.This research quantitatively demonstrates how composition controls particle spatial distribution,flow regime,and energy dissipation,offering new mechanistic insights into the propagation and deposition behaviors of rock-ice avalanches and improving hazard assessment in vulnerable high-mountain regions.
基金support by the National Natural Science Foundation of China(NSFC)(Grant Nos.52178319,42477160,52338007).
文摘Bacterial cells are widely accepted as nucleation sites for calcium carbonate precipitation in biomineralization based on the Microbially Induced Carbonate Precipitation(MICP)process.For MICP-based insitu biotreatment,the firstproblem to be solved is how to introduce and retain the bacterial cells in the soil,which involves the migration and retention of bacterial cells during the biogrouting process.Soil particle size,a key factor in determining pore throat size,can have a significanteffect on the migration and retention of bacterial cells in the soil and therefore on biomineralization.To investigate the effect of particle size on the migration and retention of bacterial cells in sand and its biomineralization,two sets of tests were carried out in this study,including percolation tests and sand column treatment tests.Soil urease activity(definedas urease activity per unit mass of soil)and calcium carbonate content of the biomineralized sand were measured to comprehensively assess the migration and retention of bacterial cells in the sand.The results indicate that sands with a particle size smaller than 0.25 mmwould inhibit the migration of bacteria in the sand,resulting in a nonuniform distribution of precipitated calcium carbonate and a low strength enhancement of biomineralization.On the other hand,sands with a particle size larger than 1.18 mm are unfavorable for retaining bacterial cells in the sand,resulting in low calcium conversion efficiency.Meanwhile,particle size would also affect the formation of effective calcium carbonate through interparticle contact number and interparticle pore size,and thus biomineralization.
基金Project supported by the Project of the Anhui Provincial Natural Science Foundation(Grant No.2308085MA19)Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA0410401)+2 种基金the National Natural Science Foundation of China(Grant No.52202120)the National Key Research and Development Program of China(Grant No.2023YFA1609800)USTC Research Funds of the Double First-Class Initiative(Grant No.YD2310002013)。
文摘Small angle x-ray scattering(SAXS)is an advanced technique for characterizing the particle size distribution(PSD)of nanoparticles.However,the ill-posed nature of inverse problems in SAXS data analysis often reduces the accuracy of conventional methods.This article proposes a user-friendly software for PSD analysis,GranuSAS,which employs an algorithm that integrates truncated singular value decomposition(TSVD)with the Chahine method.This approach employs TSVD for data preprocessing,generating a set of initial solutions with noise suppression.A high-quality initial solution is subsequently selected via the L-curve method.This selected candidate solution is then iteratively refined by the Chahine algorithm,enforcing constraints such as non-negativity and improving physical interpretability.Most importantly,GranuSAS employs a parallel architecture that simultaneously yields inversion results from multiple shape models and,by evaluating the accuracy of each model's reconstructed scattering curve,offers a suggestion for model selection in material systems.To systematically validate the accuracy and efficiency of the software,verification was performed using both simulated and experimental datasets.The results demonstrate that the proposed software delivers both satisfactory accuracy and reliable computational efficiency.It provides an easy-to-use and reliable tool for researchers in materials science,helping them fully exploit the potential of SAXS in nanoparticle characterization.
基金financially supported by the Inner Mongolia Natural Science Foundation of China (Nos. 2012MS0801 and 2013MS0804)
文摘An A1203p/A1 composite was successfully synthesized using a displacement reaction between 80 wt% A1 and 20 wt% CuO powders at a heating rate of 5 ℃/min. Two different sizes CuO particles were used, and all the experiments were conducted under an argon atmosphere. To analyze the microstructural evolution during synthesis, the A1-20 wt% CuO samples were heated to the temperatures selected according to the differential scanning calorimetry curve and then immediately quenched with water. The phase composites and microstructure of the water-quenching samples were in- vestigated using X-ray diffraction, optical microscopy, scanning electron microscopy and energy-dispersive spectrometry. The results indicate that the CuO particle size has a significant effect on the microstructural evolution of the samples during the heating stage and on the microstructure of synthesized composites. Smaller CuO particles can decrease the reaction temperature, narrow the reaction temperature range at the different reaction stages during the heating stage and make the size and distribution of in situ A1203 particles more uniform. The reaction between A1 and CuO can be complete as the temperature rises to 900 ℃. The size of the in situ A1203 particles is approximately 5 μm when the size of the CuO particles is less than 6 μm. This sample has a relatively high Rockwell hardness of 60 HRB.
基金"PSPC Régions n°2"("Projets Structurants des Pôles de Compétitivitéen région")funded by Conseil Régional Hauts-de-France and BPI.
文摘Developing the railway transport sector is a challenging scientific,economic and social research topic starting with ensuring human security.The main topic that should be developed in that sense is the ballast stability and dynamical behaviour under external loading and environmental changes.This paper investigates the effect of particle size distribution and normal pressure on the mechanical response of a ballast bed.Grading curves of ballast layers with different sizes are illustrated to discuss their strength behaviour under various strains to deduce the significant effect on the direct shear performance of the ballast layer.Direct shear tests with different Particle Size Distribution(PSD)were reproduced using the Discrete Element Method(DEM).It is noticed that when the number of small-sized ballast increases,the shear strength and the friction angle increase to varying degrees under different normal pressures,with an average increase of 27%and 8%,respectively.When the number of large-sized ballast decreases,the shear strength and the friction angle decrease to varying degrees under different normal pressures,with an average decrease of 6%and 3%,respectively.
基金supported by the Equipment Pre-research and Sharing Technology(41423030503)provided funding for this workThe Equipment Pre-research and Sharing Technology(41423030503)funded this work.
文摘This work used 5CrMnMo steel and titanium carbide(TiC)powders to fabricate particulate metal matrix composites(PMMCS).The composites’microstructure,hardness,and impact toughness were compared with four different titanium carbide ceramic particle sizes.The phase composition and microstructure of composites were studied.Vickers hardness and Charpy impact tests were employed to analyze composites’hardness and impact ductility,respectively.The results showed that the four groups of composites are mainly composed of martensite,trace residual austenite,and titanium carbide(undissolved TiC and primary TiC particles).With the growth of the ceramic particle dimension in the composite layer,the number of primary titanium carbide ceramics gradually decreased.When the initial ceramic particle size was small,it tended to generate dendritic primary TiC,and when the particle size was large,it tended to generate polygons and ellipsoids.Furthermore,with the growth of titanium carbide ceramic particle dimension in the composites,the hardness of the composites decreased but the impact toughness of the composites rose first and then descended.When the ceramic particle size was 50-75μm,the composite had the highest hardness,and the impact energy of the composites was the highest,which is 8 J.This was because there were more undissolved titanium carbide ceramics in the composite,and there was a thicker matrix metal between the ceramic particles.
基金support of the National Key Research and Development Program of China(2023YFD2100403)the Agricultural Science and Technology Innovation Program of Chinese Academy of Agricultural Sciences(CAAS-ASTIP-2021-OCRI)+3 种基金the Earmarked Fund for CARS-14the Innovation Group Project of Hubei Province(2023AFA042)the Key Research Projects of Hubei Province(2020BBA045)the Knowledge Innovation Program of Wuhan-Basic Research(3562).
文摘The increased risk of chronic diseases has led to increasing importance of coarse foods in daily life,but the inclusion of new ingredients has a great degree of influence on the structural characteristics and sensory qualities of the food.The effects of five different particle size variations on the physicochemical characteristics,dough,and steamed bread structure of Flaxseed-based milk coproduct(FMC)were investigated.As the particle size decreases,the structure of the dough becomes denser due to an increase in water retention capacity and dissolution capacity,weakening the competition for dough moisture and allowing for an increase in air-holding capacity.The reduction in particle size increased the specific volume of the steamed bread,a decrease in the spread ratio,and an optimization of hardness and elasticity,as well as an increase in consumer acceptance of the FMC steamed bread.However,it is not the smaller the particle size,the higher the quality of steamed bread,appropriate reduction of particle size can improve the quality of steamed bread.In addition,the addition of FMC reduces fat digestion.Therefore,the present study proposes a method to change the particle size of FMC to optimize the quality of the steamed bread and to reduce fat digestibility by adding FMC.
基金supported by Shandong Provincial Natural Science Foundation(ZR2023MB038)Youth Innovation Team Program of Shandong Higher Education Institution(2022KJ156)。
文摘A feasible criterion was established to determine the lower size limit of raw coal(d_(pRm))for efficient beneficiation in the air-fluidized bed with magnetite particles.The feasibility of using small magnetite particles to accommodate the fine raw coal was demonstrated from the experimental perspective.The minimum size for the magnetite particles to be fluidized smoothly was clarified as 47.1μm,which corresponded to the border between Geldart-B and-A groups.Since the gangue and coal components in the raw coal were crushed into the same size,d_(pRm)depended on the greater one between d_(pGm)(minimum size required for the gangue particles to sink towards the bottom)and d_(pCm)(minimum size required for the coal particles to float towards the top).dpcm was determined as 259μm by supposing that provided the gangue particles accumulated in the lower half bed,they could be potentially extracted from the bottom.On the other hand,it was observed that the coal particles could always accumulate in the upper half bed.Under such circumstances,dpcm was revealed as 9.8μm since finer coal particles would be blown out by air before the 47.1μm sized magnetite particles became fluidized.Eventually,dpRm was clarified as 259μm,agreeing with the common view that raw coal coarser than 6 mm could be effectively beneficiated in the air-fluidized bed with magnetite particles.Additionally,the difficulty in beneficiating the fine raw coal was revealed to arise more from the remixing of sorted gangue particles than that of separated coal particles.
基金supported by the National Key Research and Development Program of China(2024YFC2909500)State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering(SDGZ2505)National Natural Science Foundation of China(42377148)。
文摘High-steep waste dumps in open-pit mines frequently demonstrate complex particle-size distributions and fractal characteristics along their slopes,which have a significant impact on slope stability.This study takes the Dasuji South waste dump in Inner Mongolia as a case to quantify the fractal dimensions of soil-rock mixtures at various slope heights,and to clarify how these fractal properties govern shear strength and deformation behavior under overlying stress,thereby affecting the overall stability of the waste dump slope.Field sampling and laboratory tests were conducted to determine the particle-size composition and fractal dimensions while direct shear tests were conducted and revealed that lower fractal dimensions indicating coarser particle assemblages significantly enhance shear resistance.Complementary PFC_(2)D discrete element simulations demonstrate that slopes composed of lower-fractaldimension materials deform less and contain localized deformation zones,whereas higher-fractal-dimension slopes experience more extensive displacement and a heightened risk of landslides.These findings refine our understanding of the relationship between fractal grain-size distribution and slope stability,providing a robust theoretical basis for improved stability assessment and optimized support strategies in deep open-pit mining waste dumps,and ultimately aiding in more effective disaster prevention within geotechnical engineering.
基金financial support from the National Key Research and Development Program of China(No.2021YFB3702101)National Natural Science Foundation of China(No.52130107,52071038)+5 种基金Fundamental Research Funds for the Central Universities(No.2023CDJXY-018)the“111”Project(No.B16007)by the Ministry of Education and the State Administration of Foreign Experts Affairs of Chinasupport to the Norwegian Micro-and Nano-Fabrication Facility,NorFab(No.295864)the Norwegian Laboratory for Mineral and Materials Characterization,MiMaC(No.269842/F50)the RCN INRPART project IntMat(No.309724)the Center for Research based Innovation SFI PhysMet(No.309584).
文摘Mg-3Gd(wt.%)samples with different initial grain sizes were prepared to evaluate the grain size effect on microstructural evolution during cold rolling and subsequent annealing hardening response.The deformation behavior and mechanical response of the as-rolled and annealed samples were systematically investigated by a combination of electron microscopy and microhardness characterization.The results show that the twinning activities were highly suppressed in the fine-grained samples during rolling.Upon increasing the rolling reduction to 40%,ultra-fine grain structures with a volume fraction of∼28%were formed due to the activation of multiple slip systems.Conversely,twinning dominated the early stages of deformation in the coarse-grained samples.After a 10%rolling reduction,numerous twins with a volume fraction of∼23%were formed.Further increasing the rolling reduction to 40%,high-density dislocations were activated and twin structures with a volume fraction of∼36%were formed.The annealing hardening response of deformed samples was effectively enhanced compared to that of the non-deformed samples,which was attributed to the enhanced Gd segregation along grain boundaries,twin boundaries and dislocation cores.Moreover,the grain size and rolling reduction were found to affect the microstructure evolution during annealing,resulting in a notable difference in the annealing hardening response of Mg-3Gd alloy between samples of different grain sizes deformed to different strains.These findings highlight the crucial importance of microstructural and processing parameters in the design of high-strength,cost-effective Mg alloys.
基金Project no.RRF-2.3.1-21-2022-00015 has been implemented with the support provided by the European Unionsupported by the Agency for Credits and Study Grants coordinated by the Romanian Ministry of National Education from the source of the research grant established through the Government Decision no.118/2023+1 种基金supported by the EKÖP-24-3-BME-103 New National Excellence Program of the Ministry for Culture and Innovation from the source of the National,Research,Development and Innovation Fundsupported by the Doctoral Excellence Fellowship Programme(DCEP)is funded by the National Research Development and Innovation Fund of the Ministry of Culture and Innovation and the Budapest University of Technology and Economics,under a grant agreement with the National Research,Development and Innovation Office.
文摘In this study,an artificial intelligence-based machine vision system was developed for in-line particle size analysis during the pellet layering process.Drug-layered pellets were produced by coating microcrystalline cellulose cores with an ibuprofen-containing layering liquid until the target drug content was achieved.Drug content increases with pellet size;therefore,particle size monitoring can ensure product safety and quality.The direct imaging system,consisting of a rigid endoscope,a light source,and a high-speed camera,provides real-time information about pellet size and layer uniformity,enabling timely intervention in the case of out-of-spec products.A convolutional neural network-based instance segmentation algorithm was employed to detect particles in focus,ensuring that pellet size could be accurately determined despite the dense flow of the particles.After training the model,the performance of the developed system was assessed by analysing the particle size distribution of pellet cores with variable sizes within the 250 e850 mm size range.The endoscopic system was tested in-line at a larger scale during the drug layering of inert pellet cores.The particle size data acquired in real time with the endoscopic imaging system corresponded with the reference methods,demonstrating the feasibility of the proposed machine vision-based method as a process analytical technology tool for in-line process monitoring.
基金supported by the National Key Research and Develop-ment Pr0gram of China(Nos.2021YFA1501104 and 2023YFA1506802)the National Natural Science Foundation of China(No.22032001).
文摘Ethanol steam reforming(ESR)represents a promising route for sustainable hydrogen production,leveraging the high hydrogen content,renewability,and logistical advantages of ethanol.Although Ni-based catalysts are leading non-noble candidates for ESR,their practical deployment is hindered by compromised H_(2) production efficiency and rapid deactivation.In this work,we combined catalyst synthesis,kinetic analysis,and mechanistic investigation to elucidate the effectsof Ni particle size(3-9 nm)on ESR performance of Ni/CeO_(2) catalysts.These Ni/CeO_(2) catalysts were prepared via a citric acid-assisted coprecipitation method,and systematically characterized using complementary techniques,including high-resolution transmission electron microscopy(HRTEM),in situ X-ray photoelectron spectroscopy(XPS),hydrogen temperature-programmed reduction(H_(2)-TPR),Raman spectroscopy,O_(2)/CO chemisorption,and temperature-programmed surface reaction(TPSR)analyses.Mechanistic study revealed that ethanol dehydrogenation to acetaldehyde is the rate-determining step,defining the intrinsic activity of Ni sites,whereas C-C bond cleavage governs H_(2) selectivity in ESR.At smaller Ni sizes(e.g.,3.1 nm),larger CeO_(2) surface was exposed,which promoted acetaldehyde condensation to acetone,and consequently reduced H_(2) production efficiency.The Ni/CeO_(2) catalyst with~5 nm of Ni particles afforded the highest H_(2) yield(66.3%)and outstanding stability by balancing dehydrogenation activity,H_(2) selectivity,and coking resistance.Conversely,larger Ni particles(>6 nm)facilitated methanation reaction and catalyst deactivation.This work reconciles prior inconsistencies in the Ni size effects on ESR and provides guidance for the design of efficient and durable Ni-based catalysts for H_(2) production.
基金supported by the National Science Foundation of the United States under a research grant (CMMI-1917238)
文摘Determination of the critical state line(CSL)is important to characterize engineering properties of granular soils.Grain size distribution(GSD)has a significant influence on the location of CSL.The influence of particle breakage on the CSL is mainly attributed to the change in GSD due to particle breakage.However,GSD has not been properly considered in modeling the CSL with influence of particle breakage.This study aims to propose a quantitative model to determine the CSL considering the effect of GSD.We hypothesize that the change of critical state void ratio with respect to GSD is caused by the same mechanism that influences of the change of minimum void ratio with respect to GSD.Consequently,the particle packing model for minimum void ratio proposed by Chang et al.(2017)is extended to predict critical state void ratio.The developed model is validated by experimental results of CSLs for several types of granular materials.Then the evolution of GSD due to particle breakage is incorporated into the model.The model is further evaluated using the experimental results on rockfill material,which illustrates the applicability of the model in predicting CSL for granular material with particle breakage.
基金Project supported by the National Natural Science Foundation of China(Grant No.11505160)the Director Foundation of Institute of Materials,Chinese Academy of Engineering Physics(Grant No.SJZD201406)
文摘The structural and the size evolution of embedded In nanoparticles in Al synthesized by ion implantation and subsequent annealing are experimentally investigated. The average radius r of In nanoparticles is determined as a function of annealing time in a temperature range between 423 K and 453 K. The structural transition of In nanoparticles with the crystallographic orientation In （200）[002]｜｜Al （200）[002] is observed to change into In （111）[110]｜｜Al （002）[110] with a critical particle radius between 2.3 nm and 2.6 nm. In addition, the growth of In nanoparticles in the annealing process is evidently governed by the diffusion limited Ostwald ripening. By further analyzing the experimental data, values of diffusion coefficient and activation energy are obtained.
基金Project(51274163)supported by the National Natural Science Foundation of ChinaProject(13JS076)supported by the Key Laboratory Research Program of Shaanxi Province,China+1 种基金Project(2012KCT-25)supported by the Pivot Innovation Team of Shaanxi Electrical Materials and Infiltration Technique,ChinaProject(2011HBSZS009)supported by the Special Foundation of Key Disciplines,China
文摘To clarify the effect of SnO2 particle size on the arc erosion behavior of AgSnO2 contact material, Ag?4%SnO2 (mass fraction) contact materials with different sizes of SnO2 particles were fabricated by powder metallurgy. The microstructure of Ag?4%SnO2 contact materials was characterized, and the relative density, hardness and electrical conductivity were measured. The arc erosion of Ag?4%SnO2 contact materials was tested, the arc duration and mass loss before and after arc erosion were determined, the surface morphologies and compositions of Ag?4%SnO2 contact materials after arc erosion were characterized, and the arc erosion mechanism of AgSnO2 contact materials was discussed. The results show that fine SnO2 particle is beneficial for the improvement of the relative density and hardness, but decreases the electrical conductivity. With the decrease of SnO2 particle size, Ag?4%SnO2contact material presents shorter arc duration, less mass loss, larger erosion area and shallower arc erosion pits.
基金Project(51074037)supported by the National Natural Science Foundation of China
文摘Effects of size distribution (particle size and content of fine fraction (<10μm)) on scheelite flotation were studied using flotation tests and theoretical calculations. The results show that particle size influences the scheelite recovery and the performance of combined reagents. The scheelite recovery is lowered by adding fine particles (<10μm) into the pulp containing coarse particles. Extended DLVO (EDLVO) theory confirms that the fine fractions (<10μm) could interface with the coarse fractions. The interaction energy and fluid forces are relative to the particle size, which might explain why the fine fractions influence the scheelite flotation. The highest recovery of scheelite using combined reagents as collector and optimum ratio of combined reagents were determined by scheelite particle size and reagent performance. However, the optimum adding order was only determined by reagent performance, which has nothing to do with particle size.
基金Project(2012MS0801)supported by the Natural Science Foundation of Inner Mongolia,China
文摘Al2O3p-Al composites were synthesized using an in-situ reaction in the 80%Al-20%CuO （mass fraction） system. The effects of the CuO particle size on the synthesis temperature and microstructure of the composites were investigated by various methods. The results indicate that the CuO particle size has a significant effect on the temperature at which the complete reaction in the Al-CuO system occurs：the temperature is 200 ℃ lower in the Al-CuO system containing CuO particles with sizes less than 6μm than that containing CuO particles with sizes less than 100μm. The interfacial bonding between Al2O3 particles and Al is not complete when the temperature is below a critical value. The morphology of the Al2O3 particles varies from ribbon-like shape to near spherical shape when the temperature is above a critical value. These two critical temperatures are affected by the particle size of CuO, and the critical temperature of the sample containing CuO particles with sizes less than 6μm is 100 ℃ lower than that of the sample containing CuO particles with sizes less than 100μm.
基金The Special Funds for State Key Projects for Fun- damental Research (G1999022201-04).
文摘Application of particle image velocity (PIV) techniques for measuringparticle size distribution and total number in an activation chamber of desulfurization system isintroduced. Watersheld algorithm is used to choose the suitable initial gray level threshold whichis used to change the gray level images taken by PIV to black and white ones, then every particle inan image is isolated totally. For every isolating particle, its contour is tracked by the edgeenhancement filter function and kept by Freeman s chain code. Based on a set of particle s chincode, its size and size distribution are calculated and sorted. Finally, the experimental data ofcalcium particles and water drops, separately injected into the activation chamber, and the erroranalysis of data are given out.
文摘This paper presents a method of measuring the particle mean size and dust concentration by small angle near forward light scattering optics and the extinction theory. Its theory is based on Fraunhofer diffraction theory which is the approximation of Mie scattering within the forward Fraunhofer diffraction lobe, and Rosin Rammler function is introduced to describe the particle size distribution in two phase flow in advance. Compared with the values by the sample weight method, the measurement results have a reasonable agreement. The present work has demonstrated that this method will be probably used to monitor the parameters of two phase flow.
基金supported by the National Natural Science Foundation of China(No.51808530)
文摘In order to evaluate the influence of particle size and particle concentration on the coagulation process, two kinds of particle suspensions, nanoparticles and microparticles,were employed to investigate the effect of particle size on coagulation mechanisms with varying coagulation parameters. Results showed that it is easier for nanoparticles to cause self-aggregation because of Brownian motion, while interception and sedimentation are the mainly physical processes affecting particle transport for microparticles, so they are more stable and disperse more easily. The particle size distribution and particle concentration had distinct influence on the coagulation mechanisms. Under neutral conditions, as the amount of coagulant increased, the coagulation mechanism for nanoparticles changed from charge neutralization to sweep flocculation and the nanoparticles became destabilized, re-stabilized and again destabilized. For microparticles, although the coagulation mechanism was the same as that of nanoparticles, the increased rate of aluminum hydroxide precipitation exceeded the adsorption of incipiently formed soluble alum species, resulting in the disappearance of the re-stabilization zone. Under acidic conditions, Brownian motion dominates for nanoparticles at low particle concentrations, while sweep flocculation is predominant at high particle concentrations. As for microparticles, charge neutralization and sweep flocculation are the mechanisms for low and high particle concentrations respectively.Under alkaline condition, although the mechanisms for both nano-and microparticles are the same, the morphology of flocs and the kinetics of floc formation are different. At low particle concentrations, nanoparticles have larger growth rate and final size of flocs, while at high particle concentrations, nanoparticles have higher fractal dimension and recovery factors.
