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The coefficient of restitution describes the energy dissipation resulting from particle-particle and particle–surface interactions in solid–fluid flows. The energy loss depends on the mechanical characteristics of the solid phase, therefore, to correctly predict the behavior of these systems it is necessary to use reliable coefficient values based on the properties of the particles. This paper investigated the energy dissipation in particle–surface collisions using 7 types of particles with a wide range of mechanical properties (Young's modulus between 1.38 × 104 and 2.83 × 109 Pa). Three empirical equations have been proposed to calculate the coefficient of restitution based on the impact velocity and the compressional wave velocity. The experimental results presented an inverse relation between the impact velocity and the coefficient of restitution. This effect was more pronounced for less elastic particles. The models presented an accurate fit to the experimental data and statistical analysis showed that the Power model presented the greater capacity to predict the coefficient of restitution from generic data. The experimental results showed the predominant effect of mechanical characteristics on the coefficient of restitution. In addition, the proposed equations are proved to be precise tools for predicting particle coefficients of restitution with a wide range of elasticity modulus at low velocities.

Hydrodynamics in a newly invented bubble-induced inverse gas–liquid-solids three-phase fluidized bed has been studied via both experimental and numerical methods. With experiments in a 3.0 m column of 0.153 m in diameter, four fluidization regimes including a fixed bed regime, a bed expansion regime, a complete fluidization regime, and a freeboard regime have been identified with the increase in the superficial gas velocity. A three-phase Eulerian-Eulerian CFD model was developed to simulate the hydrodynamics in the inverse three-phase fluidized bed and the simulation results have a good agreement with the experimental data. The effects of the particle property and solids loading on the transitions across the flow regimes were numerically studied. A higher solids loading and/or a larger particle density are reported to contribute to an easier fluidization and a faster flow development to the complete fluidization regime. The radial flow structure becomes less uniform with increased inner circulation of the liquid after introducing more bubbles into the column.

Grain breakage is mainly caused by impact and compression load in harvest and processing. At present, the mechanism of grain breakage under loading, especially the statistics of breakage characteristics, is not clear. The analysis of breakage process of single particle provides a foundation for the understanding of breakage mechanisms. This paper aims to examine breakage behaviour of a single rice particle under compression and impact experiments. Firstly, the equivalent diameter (Dp) and moisture content (MC) of rice particles were regarded as important factors that may affect breakage. Then, by performing quasi-static compression and dynamic impact experiments under different values of Dp and MC, the detailed compression failure force, rice strength, breakage modes, breakage probability, and the breakage probability models were analyzed comprehensively. Furthermore, breakage processes of rice particles under these two breakage experiments were compared and discussed. Finally, the Weibull distribution of the compression breakage characteristics, the “non-size effect” of compression and impact breakage, the tensile failure forms, velocity threshold of impact breakage and the close relationship between the breakage characteristics under impact and compression were mainly found. The findings are useful for providing guidance for the revelation of breakage mechanism and optimizing related agricultural equipment design.

Flow of cohesive granular materials with different moisture contents was examined in a four-bladed mixer via the discrete element method (DEM). Firstly, the mixer diameter (D) was increased while keeping the particle diameter (d) constant. It was observed that when the mixer diameter to the particle diameter ratio (D/d) was larger than a certain critical size (D/d ≥ 75), granular flow behaviors and mixing kinetics followed simple scaling relations. For D/d ≥ 75, flow patterns and mixing kinetics were found to be independent of system size, and velocities of particles scaled linearly with the tip speed of the impeller blades and particle diffusivities scaled with the tip speed of the blades and mixer diameter. These results suggest that past a certain system size the flow and mixing of cohesive particles in large-scale units can be predicted from smaller systems. Secondly, system size was kept constant and particle diameter was changed and it was observed that by keeping the Bond number constant (by changing the level of cohesion) the flow behavior and mixing patterns did not change, showing that larger particles can be used to simulate flow of smaller cohesive particles in a bladed mixer by matching the Bond numbers.

The increasing significance of products consisting of elongated particles or fibres along with a lack of understanding flow properties of fibrous bulk solids in processes urge for appropriate test procedures. Therefore, a tensile tester was designed with respect to the special needs in terms of test techniques of those bulk solids. The procedure of tensile strength determination was tested with regard to several possible influencing factors. Following from that, the manner of filling and filling height were identified to have the greatest influence on results. Furthermore, it is shown that the developed load system is capable of improving the repeatability of test results for fibrous bulk solids. Based on the derived standard procedure, systematic tests were carried out on beech and spruce chips in three different fractions each as well as model materials such as polypropylene fibres and differently sized bunches of glass fibres. The biomass materials have been characterised by dynamic image analysis prior to and after experiments resulting in particle size and shape factor distributions. It is found that tensile strength is affected by particle shape, size, roughness and interparticle contact area.

The development of a simple method that perfectly controls the oxidation and aggregation of metallic particles has been performed. In the present work, metallic nickel (Ni) particles were used as a control, and silica-coating of them was performed to control oxidation and aggregation of them. Metallic Ni particles with a particle size of 924.1 ± 315.7 nm were synthesized in water and exposed to air. Nickel(II) acetate tetrahydrate, hydrazine, and poly(sodium 4-styrenesulfonate) were used as the Ni source, reducing reagent, and stabilizer, respectively. Silica-coating of the metallic Ni particles was performed by adding tetraethylorthosilicate/(3-aminopropyl)triethoxysilane/ethanol solution to the metallic Ni particle colloid solution (Ni/SiO2). The uncoated metallic Ni particles and metallic Ni in the Ni/SiO2 particles began to be oxidized while annealing in air to form NiO at 400 and 500 °C, respectively; the oxidation of metallic Ni particles was controlled by the silica coating. The Ni/SiO2 particles prepared and annealed at 100–300 °C showed soft magnetic behavior, and the saturation magnetization of g-Ni was almost comparable to that of bulk metallic Ni. In addition, the Ni/SiO2 particles annealed even at 500 °C still had soft magnetic behavior, which also supported that the oxidation of metallic Ni particles was successfully controlled by the silica coating.

This paper aims to study the influence of particle shape on the shear strength of superellipsoidal particles by Discrete Element Method (DEM) simulations of triaxial tests in 3D. A total of forty-nine types of equiaxed superellipsoidal particles from three evolution paths have been created. The definition of effective porosity has been proposed. Our findings show that both the particle sphericity and roundness affect the shear strength of the superellipsoidal particle system. Under the mutual impact of initial porosity and particle shape, the simulation results of shear strength and volumetric strains present a trend of initially decreasing and subsequently increasing. The microstructure evolution of superellipsoidal particles during the shearing process is observed microscopically. The anisotropy of fabric reveals the mechanism of effective porosity and sphericity influencing the macroscopic shear strength at the particle scale.

Preparing spherical and submicron FeNi particles in a simple, rapid, and harmless process is highly desirable for various applications yet severely challenging. Herein, we successfully synthesized the FeNi particles from their metal salts in a relatively low reduction atmosphere using three types of reduction agent, i.e., ethanol, ethylene glycol, and formic acid, via spray pyrolysis. The reduction agents were tested over a concentration range of 0–30 vol%. The type and concentration of reduction agents show a crucial role in the formation of FeNi particles. At higher concentrations (25 vol%), ethanol and ethylene glycol produced smooth and spherical FeNi particles of submicron size, 284 ± 1.6 and 399 ± 1.5 nm respectively, whereas formic acid produced particles with an irregular and Janus shape comprising FeNi and FeO, with a size of 396 ± 1.5 nm. A plausible metal salt reduction mechanism was proposed for the different reduction agents. The reduction agent type not only influences the reduction degree but also particle morphology during synthesis. This finding opens new opportunities to adjust the FeNi particles with respect to varied purposes by manipulating reduction agents.

Particle size characterization of heterogeneous mixtures is a challenging task, as it is not feasible to assign the measured signals to the individual components. Within this framework, the study proposes a method that applies the working principle of differential centrifugal sedimentation (DCS) in order to simultaneously separate and measure the denser component within a binary material mixture of submicron particles. The method was validated using a model system consisting of polyvinyl chloride (PVC) and diamond particles in a size range of 0.5 – 1.5 µm. The results proved that by applying a proper density gradient fluid, the diamond particles can be selectively analyzed by hindering the sedimentation of the lighter PVC component. Furthermore, a very promising application could be found with respect to wet fine grinding processes in stirred media mills. In fact, the approach was utilized to individually determine the particle size distribution of the grinding media wear within an ultrafine organic product. Despite the low quantity of wear particles, it was possible to separate them from the organic product under appropriate density conditions. The size distributions of both the wear and the product particles were validated with SEM images, confirming the feasibility of the method.

The aim of this work was to examine the impact of equilibrium judgment criteria on adsorption test of samples with different adsorption kinetics and determine how long it takes for different particle size samples to attain equilibrium adsorption data. The adsorption data of coal samples with three different particle sizes was obtained by manometric method at the different time intervals. High pressure CH4 adsorption equilibrium measurements and low pressure N2 and CO2 adsorption measurements were carried out for coal samples of eight various particle sizes. The results demonstrated that both the equilibrium and disequilibrium adsorption data satisfied the Langmuir equation. The Langmuir volume (VL) increased on the equilibrium time increase and it became more remarkable with increasing particle size. The Langmuir pressure (PL) showed an opposite and more obvious trend. When the particle size of the coal sample decreased from 2 to 4 to

Draft tubes have emerged as promising internal devices to overcome the scale up limitations of the spouted bed. Although only a few parameters define draft tubes, the design of these devices is complex and remains a challenging task, as knowledge concerning the gas–solid flow pattern in the spouted bed is required for a proper implementation. Therefore, this study aims to propose a new criterion for the design of draft tubes (nonporous and open-sided) based on the average spout diameter measured by a borescopic technique in conical spouted beds without draft tube. Based on the radial and axial particle velocity profiles, hydrodynamic analysis, and cycle time distributions, the new configurations are compared with those without tube and with conventional draft tubes. The new open-sided tube provides maximum particle velocities of 480.90 ± 14.60 mm/s in the spout and 90.10 ± 4.40 mm/s in the annulus. These values are lower and higher than the particle velocities obtained without draft tube in the spout and annulus regions, respectively, which means it modifies particle residence time in these regions. The new open-sided tube provides a more efficient gas–solid contact than any conventional one, with spouting behaviour being very similar to the configuration without tube (differences in the minimum spouting velocity being in the 2–6% range), which is a key aspect for scale up purposes.

A simplified geometric model of a circular tube with a sedimentary layer is proposed and named as sedimentary duct. Based on h = 1/4d (h is the thickness of sedimentary layer and d is the pipe diameter), the flow field (Re = 40000) and particle distribution (5, 10, 50 μm and St = 0.6, 2.5, 63) in the sedimentary duct are simulated using Large Eddy Simulation (LES) coupled with Lagrange Particle Tracking (LPT) method. As a result, four streamwise eddies are found in the sedimentary duct as distributed in pairs near the corner. The eddy center near ceiling is found to be farther from the corner than that from the floor. Small particles (5 μm, St = 0.6) tend to move with the secondary flow as their upward movements distribute in both sides. Their centripetal movement is near the floor and preferential distribution near the top. For large particles (50 μm, St = 63), it is the drag force that dominates their motion while for medium particles (10 μm, St = 2.5) lift force may have significant influence on their motion. This study is the first work to investigate the characteristics of particle behavior in turbulent sedimentary duct flows.

Particle shape is an important factor that affects particle breakage and the mechanical behaviour of granular materials. This report explored the effect of angularity on the mechanical behaviour of breakable granular materials under triaxial tests. Various angular particles are generated using the quasi-spherical polyhedron method. The angularity α is defined as the mean exterior angle of touching faces in a particle model. A breakable particle is constructed as an aggregate composed of coplanar and glued Voronoi polyhedra. After being prepared under the densest conditions, all assemblies were subjected to triaxial compression until a critical state was reached. The macroscopic characteristics, including the shear strength and dilatancy response, were investigated. Then, particle breakage characteristics, including the extent of particle breakage, breakage pattern and correlation between the particle breakage and energy input, were evaluated. Furthermore, the microscopic characteristics, including the contact force and fabric anisotropy, were examined to probe the microscopic origins of the shear strength. As α increases, the peak shear strength increases first and then remains constant, while the critical shear strength generally increases. Assemblies with larger angularity tend to cause more serious particle breakage. The relative breakage is linearly correlated with α under shear loading. Compared with unbreakable particles, the peak shear strength and the critical volumetric strain decline, and the degree of decline linearly increases with increasing α.

In this work, frictional, cylindrical particle shear flows with different size distributions (monodisperse, binary, Gaussian, uniform) are simulated using the Discrete Element Method (DEM). The influences of particle size distribution and interparticle friction coefficient on the solid phase stresses, bulk friction coefficient, and jamming transition are investigated. In frictional dense flows, shear stresses rise rapidly with the increasing solid volume fraction when jamming occurs. The results suggest that at the jamming volume fraction, stress fluctuation and granular temperature achieve the maximum values, and the rate of the stress increase with increasing solid volume fraction approaches the peak value. Meanwhile, the degree of cylindrical particle alignment approaches a valley value. In the polydisperse flows, the jamming volume fraction exhibits significant dependences on the fraction of the longer particles and the particle size distribution. Two models considering the effect of particle size distribution are discussed for predicting the jamming volume fractions of polydisperse flows with frictional, cylindrical particles.

The discrete element method (DEM) coupled with computational fluid dynamics (CFD) is a powerful tool for exploring the detailed behaviors of dense particle–fluid interaction problems such as fluidized beds. Coarse-graining models have been proposed to decrease the computational cost by increasing the model particle size. In this study, we examine the influence of the model particle size and the spatial resolution on the average size and number of bubbles in coarse-graining DEM-CFD calculations of bubbling fluidized beds. Calculation results indicate that the bubble size is scaled by the model particle size if parameters are following similarity laws defined in a particle scale, as well as the geometric similarity of the whole system is maintained. The usage of coarse spatial resolution increases the bubble size and decreases the number of bubbles. The countervailing influence of the model particle size and the spatial resolution in a practical coarse-graining scenario results in nearly the same bubble size.

An electric virtual impactor with a capability of sampling fine and ultrafine particles was developed and its performance was evaluated both numerically and experimentally. The electric virtual impactor was provided with metallic electrodes, to which electric voltage in the range of 75–9000 V was applied for creating an electric field within the virtual impactor. Particle electric mobility was utilized to sample ultrafine particles at the major outflow section, while particle inertia was employed to collect fine particles at the minor outflow section. Silver nanoparticles with known charge level and Arizona test dust were used to experimentally validate the performance of the electric virtual impactor. Numerical and experimental outcomes agreed well with each other. The upper cutoff size of the electric virtual impactor was fixed at about 2.6 μm, while the lower cutoff size varied from 7 nm to 110 nm depending on the applied electric voltage. As a result, the proposed electric virtual impactor was able to sample both fine and ultrafine particles of a desired particle size range.

Understanding the transportation and deposition (TD) of inhaled aerosol particles in human lung airways is important for health risk assessment and therapeutic efficiency of targeted drug delivery. The particle TD into a human lung depends on lung anatomy, breathing pattern, as well as particle properties. The breathing capacity and lung airway diameters can be reduced by about 10% every 10 years after the age of 50. However, the age-specific particle TD in human lungs, particularly in the aged, has not been well understood in literature. This study investigates the particle TD in the lungs of people aged 50–70 years, using computational fluid dynamics (CFD). A new cutting method that splits the lung model into different sections has been developed as a feasible CFD method to simulate the particle TD in G0 to G14 lung airways. The inhalation of micron scale particles with three diameters (5 μm, 10 μm and 20 μm) and a constant air flow rate in inhalation is considered. It is found that different sized particles are deposited in different generation airways. Nearly 100% of 20 μm particles are deposited in the upper lung airways (G0-G5) and no particles pass through G7. Particles can go into deeper airways as their diameter decreases. When the particle size is decreased to 5 μm, over 48% of particles can pass through G14 and enter the deeper lung airways. An increase in age causes more particles to deposit in the upper airway and fewer particles to enter the deeper airways.

Cooperative behavior displayed by five steel disks falling in a low-density particle bed involves the formation of upward and downward convex configurations, which resembles the flying pattern of a flock of birds. In this study, we focused on overtaking behavior in two falling disks, which causes the cooperative behavior, and we investigated the effects of differences in the disk release time and the initial disk separation distance on the falling behavior of the disks experimentally. Expanded polystyrene (EPS) particles (diameter 5.08 mm, mass 1.45 mg) were used as the bed particles and steel disks (diameter 25.4 mm, thickness 5.22 mm, mass 20.2 g) were used as the falling disks. We released one to five disks with various disk release time differences (0–0.154 s) and initial separation distances (0–100 mm). We recorded the disk falling behavior in the particle bed with a high-speed video camera (500 fps) and analyzed the behavior with image analysis software. Five-disk cooperative behavior similar to that reported in the literature occurred in our experimental setup. In the two-disk experiments, we observed overtaking behavior for an initial separation distance of 10 mm and release time difference of ≤ 0.076 s, and for an initial separation distance of ≤ 60 mm and release time difference of 0.02–0.03 s. The overtaking behavior arose from the decrease in the falling velocity of the first disk released. The EPS particle packing fraction in the area above the disk one disk diameter wide and a quarter of the disk diameter high determined the disk falling velocity. This mechanism was explained by the displacement behavior of EPS particles around the disks as the disks fell.

Vortex chamber fluidized bed (VCFB) is a novel type of fluidized bed which has many advantages compare to conventional fluidized beds due to its high-G operation. Hence, the VCFB can replace the conventional fluidized bed for process intensification. However, particle loss at the initial stage of particle injection from VCFB is an important issue which may prevent the particle bed formation inside the VCFB. Therefore, the quality of the fluidized bed will largely depends upon it. The present work aims to study the particle loss from a VCFB at the beginning of particle injection by varying different conditions such as particle feeding location, number of feeding points and particle diameter. A three-dimensional computational fluid dynamics (CFD) model of the VCFB is developed and the particle loss is studied numerically. It is observed that particle loss is minimal when particles are injected from the rear wall of the vortex chamber. Particle loss increases with increasing the number of particle injection points and particle diameter.

Particle velocity measurement based on cross-correlation algorithm is used widely in various multiphase flow systems. In this study, an optical fiber probe, i.e. Labasys® 100 from MSE Meili was used to systematically compare the qualities of its measured particle velocities in a pair of hydrodynamically distinct regimes, i.e. a fast fluidized bed (FFB) and a bubbling fluidized bed (BFB). Compared to FFBs, the measured particle velocities in BFBs show lower data repeatability, higher percentage of invalid data and higher sensitivity to the selection of the threshold value of maximum cross-correlation coefficient, which corresponds to much lower measurement qualities in this regime. Comparatively, higher measurement qualities were observed in the FFB based on the same evaluating methods. The highest measurement qualities appear in the core region of the riser and under high superficial gas velocities. A matchup relationship between the measurement quality and the shape of the probability density function (PDF) curves of maximum cross-correlation coefficient is found. Narrower PDF curves correspond to higher measurement quality and vice versa.

In this paper the influence of the inlet and outlet configurations of a pseudo-2D fluidized riser on the hydrodynamics (i.e. flow pattern and cluster characteristics) are studied. A detailed comparison between experimental data and full 3D CFD-DEM simulation results is performed. Solids volume fraction and mass flux are characterized and particle clusters are detected in our CFD-DEM simulations and compared to experimental data. It is shown that a correct representation of the outlet is very important for a correct simulation of the solids holdup in the top section of the riser. The core-annulus flow behavior is generally well predicted by the model and cluster characteristics such as cluster occurance and velocity are also in good agreement with experimental data. Finally, an outlook is given for the future use of CFD-DEM simulation approaches to study riser flows.

3D printing has been applied in numerous research fields ranging from biomedical, mechanical engineering and chemistry to material science. 3D printing applications have driven innovations in particle technology, especially through tackling particle-related issues arising from the development of particle-based printing feedstocks across such application areas. Therefore, in this review, established 3D printing processes are described to include their prototyping mechanisms, advantages and limitations. Various particulate systems, including dry and wet systems, as printing feedstock materials are introduced. The main motivation for this paper is to outline the current state of particulate feedstock systems and to attempt to outline future directions for enhancing these particle applications. This paper would be valuable for individuals, researchers and companies who need adequate and comparative information regarding the state of particle applications in the AM industry.

Collisions between particles and the wall covered by a liquid layer play an important role in many different industrial processes (e.g., chemical, pharmaceutical, and transportation). Understanding the rebound motion law of the collision between particles and the wall covered by a liquid layer is vital to ensure the high efficiency of processes such as wet granulation and fluid catalytic cracking. In the present study, we investigated the influence of different collision angles on the liquid bridge geometry, particle motions, particle energy, and other collision details based on the oblique collisions between particles and the target plate covered by a liquid layer. Results showed that the collision angle of particles has a great effect on the liquid bridge geometry. Moreover, the liquid bridge caused by different collision angles initially increases the particle deflection angle difference and then decreases, and this influence gradually increases with the increase of the collision angle. In addition, the collision angle greatly affects the particle’s energy.

To reveal the particle dynamic characteristic in the bend, high-speed particle image velocimetry (PIV) and wavelet transform were used to measure and analyze the particle velocity in a horizontal-vertical pneumatic conveying system. The pressure drop and particle velocity are analyzed to elucidate the macroscopic motion properties of particles in the different radius ratio bend firstly. Then the methods of continuous wavelet transform and one-dimensional discrete orthogonal wavelet transform are used to analyze the particle dynamic characteristic in the different regions of the bend pipe in terms of time–frequency characteristics of particle fluctuation velocity, fluctuation energy distributions of wavelet components, and auto-correlation of various frequencies. The results show that the particles are mainly small-scale motion in the rapidly decreasing region, while the large-scale motion increases in the accelerating region near the inlet and the stable region near the outlet. And the results of the wavelet component show that the acceleration and deceleration of particles in the bend will decrease the proportion of high-frequency fluctuation energy. The auto-correlation coefficient of the high-frequency component decays slower and has a longer period at the critical position of the three regions.

A bi-directional coupling between the Discrete Element Method (DEM) and Population Balance Modelling (PBM) is suggested to model the failure of pharmaceutical tablets under abrasive conditions such as bulk flow of impact. DEM provides the description of kinetics and permits the extraction of collision energy distributions. Representation of the primary shape of the tablets is achieved by using the multi-sphere approach, a rigid assembly of systematically connected spheres to resemble non-spherical shape. Based on the collision energy distribution and the abrasion characteristics of the tablets by solving the PBM equations, the mass loss of tablets according to their mechanical resistance, as well as the fragment size distribution progeny can be computed. For the description of the abrasive failure characteristics, a multi-stage calibration procedure for the empirical breakage kernels of Vogel and Peukert as well as of Ghadiri and Zhang is also applied. The novelty of the presented approach is the bi-directional coupling: tablet and fragment distribution masses are dynamically updated for subsequent time steps in DEM by the particle replacement method according to the stress history of the system. The outcome of this methodology helps to get a deeper understanding of the process-property relationships, to evaluate the effect of any process or geometry modifications in processing operations, such as drum coating, and to reduce the requirements of experimental investigations.

Large contact forces on granules could give rise to undesirable attrition. In a new device, referred to as the Particle Shear and Impact tester, granules are subjected to repeated and sequential impact and shearing, the latter effected by two counter-rotating rollers with differential angular speeds and an adjustable gap between the rollers. This enables the contact force distribution to be varied in order to apply representative contact forces, as experienced in manufacturing plants. Granule flow in the rollers is simulated by Distinct Element Method for several roller gap sizes. The resulting contact force distribution is compared to that from shear cell simulations for representative plant normal stresses (8 to 15 kPa), in order to calibrate the appropriate gap size. The 90th percentile of the contact forces distributions from the two simulations are matched to set the gap size. A roller gap size approximately 3.5 times the 90th percentile of the particle size (based on number distribution) gives a good match of the interparticle contact forces between the rollers and the shear cell. This enables replicating the stresses that granules experience in plants, whether during handling and transport, or during more severe stressing conditions, e.g. compaction or even grinding, thereby assessing attrition or fragmentation propensity of granules.

The cold flow hydrodynamics and segregation characteristics of a binary mixture of high-ash coal and sand have been investigated in a dual fluidized bed (DFB) gasifier. A short riser, maintained in the fast-fluidized bed regime by different combinations of primary and secondary aerations, is used. The influence of fluidization velocities, secondary-to-primary aeration ratio ( φ ), particle mixture properties has been examined on the full-loop pressure profile, solids circulation rate ( G s ), and segregation characteristics. A substantial influence on DFB pressure profiles is observed for the polydisperse binary mixture compared to unary sand particles having a narrow particle size distribution. Coarse particle fractions measured at loop-seal and pot-seal indicates significant segregation in the riser and the BFB, which reduces as fluidization velocities increase. Variations in G s and φ show a minimal impact on particle segregation. No reverse gas bypass is detected for the designed operating parameters through solids recycle valves, namely loop-seal and pot-seal. Except for some discrepancies observed at high superficial velocities and G s , the values of axial solids holdup in the riser yield a reasonable agreement between experiments and a hydrodynamic model based on empirical correlations.

Coccoliths are micro-structured biomineral particles found in cell protective covering layers of coccolithophore species. They are mainly composed of CaCO3 and their individual crystal entities are arranged in such a way that they construct complex and unique structures. This complexity is found down to the individual particle level and appears to have promising properties to offer. This study focuses on the essential step prior to any kind of implementation, which is the recovery of the material. It summarizes cleaning protocols found in literature, compares them for the first time for the same freshly cultivated material and addresses challenges that still need to be overcome. Further, it highlight the advantages and disadvantages of the best cleaning protocols, suggests optimizations with promising results and uses size distribution measurements to analyse the recovery efficiency. To that end, further characterization techniques, new for coccoliths, are introduced and used to improve our current knowledge of the particles behaviour.

For production of electrodes for lithium-ion batteries, conductive carbon black (CB) has to be dispersed within the anode and cathode slurry. A sufficient dispersing degree has to be reached in order to ensure the formation of an adequate conductive network within the electrodes. As intermediate product, CB is dispersed in binder solution, prior to addition of active materials. As binder system on anode side carboxymethylcellulose in water is used, whereas on cathode side polyvinylidene fluoride in N-Methyl-2-pyrrolidone is applied. The conductive carbon slurry facilitates the characterization of the slurry properties, based on changes of CB. The structure and amount of conductive carbon black influences the slurry properties decisively. Viscosity increases with increasing CB content, which affects the shear stress within the mixing process. Rheological properties and particle size distributions are investigated over time while dispersing CB with various tip speeds in a dissolver. Dispersion kinetics are described on behalf of an existing model for tip speed variations. Based on the investigations of rheological changes due to varying amount of CB, an extended model enclosing the CB concentration as variable was developed. Using the extended model, particle sizes for new process parameters can be predicted.

Calcite-core/Mg-calcite (MgxCa1−xCO3)-shell nanorods were synthesized by bubbling CO2 gas into Ca(OH)2 aqueous slurry with Mg2+ doping. The thermal stability of the resulting particles in the forms of aqueous slurry and dry powder was investigated, and the nanorods doped with higher Mg2+ concentrations were found to have excellent thermal stability both in water and air. The microscopic structures of the nanorods were characterized in detail by XRD and TEM, and the Mg-calcite nanoclusters that almost fully covered the particle surface were deduced to be responsible for the improvement of particle morphology stability. Facile fabrication of 1D anisotropic nanoparticles with better thermal stability can widen the industrial application of calcite.

In the framework of the Euler-Euler gas–solid two-fluid model, the particle population balance equation is solved by the direct quadrature method of moment. The dynamic process of ultrafine particle movement and aggregation in an internally circulating fluidized bed is simulated. The distribution of the concentration and velocity of the agglomerates in the flow process is given, and the changes of the moments in the bed are shown. The effects of different breakage coefficients and inlet gas rates on the concentration distribution of agglomerates are compared. The results show that the particle size decreases with the increase of breakage coefficient, and the time required to reach steady fluidization state increases; the higher the inlet velocity, the better the effect of circulating particles in the bed. When there is a certain gas velocity difference between the two sides, the effect of circulating particles in the bed is better.

The aim of present study is to investigate the modification of poor kaolin by boehmite to produce zeolite A via fusion techniques. The processed kaolins containing considerable content of quartz, as a major impurity, were employed, and alkalinity, boehmite content, fusion temperature, and ageing time were changed to achieve zeolite A. Regardless of the starting material composition, the sodium hydroxide/kaolin ratio should be fixed in the range of 2.00–2.33 to delete quartz. Boehmite was added to material mixtures for compensating aluminum deficit followed by thermal treatment at 700, and 800 °C. The presence of boehmite in the precursors is very crucial for the formation of zeolite A. The maximum relative crystallinity was obtained by control of the boehmite/kaolin ratio at the level of 0.26. The zeolite A produced from clay containing illite + kaolinite + pyrophyllite indicated the semi-cubic particles with rounded edges, and lower surface area, 17.5 m2.g−1 while the application of kaolinite-rich clay resulted in the mesoporous product with an average pore size of 8 nm, and larger surface area of about 59.6 m2.g−1.

The particle based Discrete Element Method (DEM) can be applied to examine comminution processes. In this study, a DEM framework has been extended to model particle breakage without mass loss. After a breakage event occurs, spherical particles, as often considered in the DEM, are replaced by size reduced spherical fragments. During the following time steps, the fragments grow to their desired sizes, so that the mass loss can be counterbalanced. Previously defined overlaps with adjacent unbroken and broken particles (fragments) as well as walls are allowed. The breakage model has been realized in a parallelized DEM framework because comminution processes are often attributed to large numbers of particles and by parallelization the computational time can be reduced efficiently. An oedometer (one-dimensional compression in axial direction of a confined particle bed) has been modelled to investigate the parallelization efficiency and the influence of the permitted overlaps during the growth process on the growth duration. A simplified roller mill has been considered to examine the applicability of the breakage procedure considering parallelization. The results show that parallelization reduces computational time considerably. The breakage procedure is suitable to model comminution processes involving even densely packed particle systems and is superior to existing approaches.

Liquid marbles may be traditionally formed by rolling a droplet on a bed of non-wetting particles resulting in encapsulation and stabilisation. Particles used in this process may range from nanometre to millimetre if handled with sufficient care. This method, however, runs the risk of droplet coalescence and is limited to non-wetting particles. Currently there exist some alternative methods of formulation including using electrostatics to either deliver a particle bed to the droplet or pull the droplet to the particles. The former has shown some promise in potential batch processes but is hindered by interparticle forces. Additional production methods include a form of blender, but this has shown to be unable to produce marbles of a narrow size distribution. Once formed, liquid marbles have demonstrated value as potential blood typing devices, as micro-reaction vessels due to the inherent barrier between the internal phase and the substrate whilst maintaining gas permeability, and as contaminant sensors. Liquid marbles also demonstrate a remarkable level of elasticity under compressive force and reduced evaporation rates when compared to bare water droplets, a function of the size and composition of the stabilising particles. In addition to this, liquid marbles have been proposed as actuators. Locomotion may easily be induced in these structures, using electrostatics, sound, magnetism or light depending on the particle/liquid combinations used in formation, and the environment of deployment. This review seeks to present and summarise recent advances in the field of liquid marble manufacture and methods for actuation. We also aim to highlight potential future avenues of further study within this arena.

Based on the significantly different melting points and high oxygen affinities, the fabrication of chromium-based tungsten silicides is restricted to powder metallurgical production routes. To foster particle contacts and diffusion processes between chromium and tungsten, which are known to necessitate long sintering times, mechanical alloying or milling processes prior to sintering are established. Nonetheless, due to spinodal decomposition of Cr and W, the solid solution formation is complex and yet little understood. For this reason, the influence of the mechanical milling time (0–24 h) on the crystal structure and the microstructural properties of hot-pressed 60Cr30W10Si (wt.–%) is examined. In this context, two different powders containing a different tungsten particle size (0.8 and 3 µm) were mechanically alloyed to analyze the impact on the phase formation and the particle distribution in the microstructure. It was shown that mechanical milling supported the mechanical clamping between the particles. However, the increased milling times significantly decreased the crystallite sizes of the particles and fostered the tungsten solubility in the Cr-rich (Cr, W) solid solution formed during sintering, thus supporting the densification.

This study was carried out to assess the contribution of Co and CrC reinforcement particles to Cu main matrix powders by powder metallurgy (P/M) method as well as to mechanical properties, abrasion resistance and microstructure properties. For this purpose, the matrix material Cu powders, Co and CrC reinforcement particles, of which the weight percents are as follows: 5% (2% Co + 3% CrC), 10% (4% Co + 6% CrC) and 15% (6% Co + 9% CrC), were added. The samples were produced by cold pressing at room temperature and 450 MPa pressure, using the P/M method. Microstructure characterization of composite samples was performed by SEM-EDS and XRD analysis. Mechanical characterization of composite samples was carried out by analyzing the data of density determinations, hardness measurements, abrasion resistance tests and tensile tests. As a result of this study, it was observed that as the reinforcement ratio increased, the relative density of the samples decreased while the hardness of the samples increased. As a result of the findings obtained from the analysis of the tensile tests and other tests performed, it was clearly seen that the reinforcement particle ratio of wt. 10% was the optimum reinforcement ratio for this study.

The characteristics of how graphite particles adhere to the walls of high-temperature gas-cooled reactors are very important for analyzing reactor source terms. In the present study, atomic force microscopy (AFM) is used to measure the particle adhesion force and the wall morphology, then Lennard-Jones potential theory and the finite element method (FEM) are coupled to calculate the adhesion force between different particles and rough walls. The obvious deviations between the AFM measurements and the theoretical models are due to the contact hypothesis of a sphere with a smooth flat plane in the latter. The FEM results reveal the formation of maximum adhesion at the pull-off point of the particle and the corresponding stress distribution. For aspherical particles, the local curvature of the particle contact interface is the main factor affecting the adhesion force. In addition, for rough walls, different contact regimes correspond to different adhesion trends. When discrete wall roughness with hemispheres and truncated cones is used, the FEM predictions are closer to the AFM measurements, indicating that roughness dominates the adhesion weakening.

Aiming at the problems of low collection efficiency of fine particulate matter and large area occupied by existing electrostatic precipitators (ESP), a new type of horizontal electrode ESP is proposed. It has the advantages of accelerating turbulent coalescence, increasing the effective dust collecting area and increasing the particle driving speed. The performance of the new type of ESP is systematic studied through simulation and experiment at the same time, and the results matches well. By comparing the dust removal effect of the horizontal electrode ESP and the conventional ESP, it can be concluded that the horizontal electrode ESP has a better dust removal efficiency, and can still maintain a better dust removal effect under high air velocity. The dust removal efficiency of new ESP can reach above 98% under the experimental conditions.

Suppressing the crystallization and plate-like crystallite growth of RE2(OH)4SO4·2H2O compound by low-temperature (~4 °C) precipitation produced an amorphous RE2(OH)3.3(CO3)0.35SO4·2H2O precursor (RE = Gd1-xTbx) that can be decomposed to Gd2O2SO4:Tb and Gd2O2S:Tb green phosphor nanopowders of unimodal size distributions upon calcination in air at 1000 °C (average particle size ~156.9 nm) and in hydrogen at 800 °C (average particle size ~130.2 nm), respectively. The optimal RE3+ concentration for precursor synthesis was determined to be ~0.10 mol/L. Through detailed characterization by XRD, FTIR, DTA/TG, FE-SEM, TEM and particle sizing, the courses of phase/morphology evolution were clarified. Photoluminescence study found that the (Gd0.99Tb0.01)2O2SO4 and (Gd0.98Tb0.02)2O2S representative phosphors have quantum efficiencies of ~16.8% (λex = 275 nm) and 38.5% (λex = 286 nm), fluorescence lifetimes of ~3.70 and 1.75 ms and activation energies for thermal quenching of ~0.552 and 0.385 eV, respectively. The values are remarkably larger than those reported for Gd2O2S:Tb, which are considered to be due to higher purity, better crystallization and fewer luminescence-quenching defects of the product. Particularly, the (Gd0.99Tb0.01)2O2SO4 phosphor has negative thermal quenching up to ~150 °C and can retain over 85% of its room temperature emission intensity at 250 °C, which may enlighten its application in high-power LEDs.

Volume Specific Surface-Area (VSSA) has been identified as a relevant and alternative method to electron microscopy (EM) to determine whether a material is or not a nanomaterial. VSSA is an integral measurement method that provides an indirect representation of particle size. When this conversion into particle diameter is carried out, constituent particles are supposed to be monodisperse, which can be considered far from reality, materials being composed of polydisperse constituent particles. The way particle polydispersion affects the VSSA of a material, and thus the equivalent particle diameter deduced, is investigated in this paper. In particular, the specific case of normally-distributed, spherical constituent particles, is considered. A theoretical study has led to the introduction of a correction polydispersion-based factor. From experimental VSSA data obtained for eight powders covering a range of constituent particle median diameters from 9 to 130 nm, the VSSA-based constituent particle median diameters were compared to the median constituent particle size obtained from electron microscopy analysis, considered as the reference method. Integrating constituent particle polydispersion through the use of the correction factor improves the accuracy of particle size stemming from the VSSA approach, the relative discrepancies being within ±20% from the reference diameter.