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During twin screw granulation (TSG), small particles, which generally have irregular shapes, agglomerate together to form larger granules with improved properties. However, how particle shape impacts the conveying characteristics during TSG is not explored nor well understood. In this study, a graphic processor units (GPUs) enhanced discrete element method (DEM) is adopted to examine the effect of particle shape on the conveying characteristics in a full scale twin screw granulator for the first time. It is found that TSG with spherical particles has the smallest particle retention number, mean residence time, and power consumption; while for TSG with hexagonal prism (Hexp) shaped particles the largest particle retention number is obtained, and TSG with cubic particles requires the highest power consumption. Furthermore, spherical particles exhibit a flow pattern closer to an ideal plug flow, while cubic particles present a flow pattern approaching a perfect mixing. It is demonstrated that the GPU-enhanced DEM is capable of simulating the complex TSG process in a full-scale twin screw granulator with non-spherical particles.

Effective transport coefficient (ETC) of particulate composites is a crucial parameter in many industrial applications. ETC is subject to many microstructural parameters of the system at different scales. In this work, stochastic reconstruction is applied to study possible microstructure configurations between two selected systems. The initial system is configured to a microstructure with overlapping discs agglomerates of monodisperse diameter D = 12 pixels; the final system is configured to a particulate system of monodisperse diameter D = 1 pixel. Easy but powerful diagrams are presented as a quick design tool. The diagram user only requires the determination of two statistical magnitudes: probability of the neighbor connectivity, and infinite cluster, both statistical functions are detailed in the manuscript. This particulate composite information is defined from microstructure images. Proposed diagrams allow the user to get a position in a “map” that describes how ETC magnitude change according to: 1) size of the agglomerate diameter, 2) phase surface fraction, 3) mono-distributed and poly-distributed configuration, and 4) matrix phase or dispersed phase condition as the conductive phase. The diagram user can immediately obtain a full panorama without solving complex equations, which would let to make decisions about the modification of the geometric structure of the particulate composite. The microstructures studied are delimited to biphasic, isotropic particulate composites. The experimental validation of the diagram's effectiveness with particulate composites from the literature is accomplished.

Objective of this work was to develop a novel method for characterizing real 3D shapes of particles smaller than 20 μm by X-ray microtomography (X-RMT). Multidimensional separation of heterogenous solids through agglomeration in suspension will improve recycling processes as the particle shape and the agglomerate size are used for shape-selective separation. In the present paper we discuss the fundamentals of X-ray tomography and the experimental setup for selective spherical agglomeration in suspension. A specific preparation method of the particulate sample for X-RMT followed by 3D image processing, are essential for the shape analysis expressed as sphericity. We also discuss the limitation of this method due to the so-called Partial Volume Effect and particle clusters in the order of magnitude of X-RMT resolution. As proof of concept, we used a mixture of graphite platelets and spheronized graphite particles for a shape selective-agglomeration in suspension. The remaining fines were analyzed and showed more platelets than in the mixture. This indicates that spheronized particles are preferably bound in the agglomerates. These findings show that, based on the discussed sample preparation and a 3D image analysis in connection with X-RMT, particle shapes of micronized particles can be discriminated.

Segregation of granular materials is often induced by differences in size, density, shape and surface properties. Density and size-induced mixing and segregation of binary mixtures of glass beads and/or resin particles in the FT4 powder rheometer are investigated experimentally using a new FT4 methodology. The proposed methodology allows for quantification of mixing and segregation of components based on a mixing index. It is observed that the mixing index increases with increasing density and size ratio. Variation of flow energy and torque is related to the mixing and segregation of the mixture components, thus demonstrating that the FT4 powder rheometer may be used as a predictive tool for the tendency of mixture components to segregate under various stress conditions. Numerical analysis by DEM shows that for non-cohesive systems mixing and segregation occur by sifting of fines through interstitial gaps formed between coarse particles in the dilated region. For the non-cohesive system, higher blade tip speeds reduce the rate of mixing and minimise the segregation of different-sized components. Increasing the interfacial energy reduces the rate of mixing and alleviates the segregation of particles. For the cohesive systems, mixing occurs by rupture of cohesive fine clusters with the mixing index increasing with increasing blade tip speed owing to the higher shear stresses that break the agglomerates.

International audience; This paper (part II) is devoted to the effect of molecular adsorption on the surface of magnetic iron oxide nanoparticles (IONP) on the enhancement of their (secondary) field-induced agglomeration and magnetic separation. Experimentally, we use Methylene Blue (MB) cationic dye adsorption on citrate-coated maghemite nanoparticles to provoke primary agglomeration of IONP in the absence of the field. The secondary agglomeration is manifested through the appearance of needlelike micron-sized agglomerates in the presence of an applied magnetic field. With the increasing amount of adsorbed MB molecules, the size of the field-induced agglomerates increases and the magnetic separation on a magnetized micropillar becomes more efficient. These effects are mainly governed by the ratio of magnetic-to-thermal energy α, suspension supersaturation Δ0, and Brownian diffusivity Deff of primary agglomerates. The three parameters (α, Δ0, and Deff) are implicitly related to the surface coverage θ of IONP by MB molecules through the hydrodynamic size of primary agglomerates exponentially increasing with θ. Experiments and developed theoretical models allow quantitative evaluation of the θ effect on the efficiency of the secondary agglomeration and magnetic separation.

In this study, Al–CuO nanocomposites were fabricated by sol-gel method. As a contrast, the thermite was prepared by physical mixing at the equivalence ratio of 0.5, 1, 2, respectively. The intermediates and samples as prepared were characterized by SEM and XRD. The exothermic properties of the two samples prepared at different equivalence ratios were tested and the reaction products were characterized by XRD. The SEM results show that the sample prepared by the sol-gel method demonstrates a micron-sized agglomerated sphere formed by a mutual wrapping of Al NPs and CuO NPs, and the particles are evenly distributed in the agglomerate. In addition, when the content of Al powder is seriously insufficient, the heat release of the sample prepared by physical mixing is 1.6 times that of by sol-gel method. With the increase of Al powder content, the exothermic properties of Al/CuO NPs prepared by sol-gel method began to increase significantly compared with physical mixing and the difference is 1.5 times when the equivalence ratio increases to 2. It can be concluded that the reason for this result may be attributed to the different mass transfer modes of components due to the different morphologies of samples.

Due to its industrial applications, the assessment of the explosibility parameters of aluminum powder is essential. However, they strongly depend on the Particle Size Distribution (PSD), which impacts both the rate-limiting step of the combustion mechanism and the radiative transfer. This article describes the influence of the test procedure on the explosion severity of six aluminum samples, having primary particle diameters ranging between 0.04 and 125 μ m . The PSD measured in situ after dispersion in a 20 L sphere differs from those obtained before dispersion, particularly for nanoparticles for which the presence of agglomerates is evidenced. The explosion severity parameters were measured at different turbulence levels by changing the nozzle geometry and ignition delay time. The impact of the injection procedure varies from micron-sized aluminum dust to nanoparticles due to their low inertia. Moreover, if an alternative nozzle could be more appropriate at a lower turbulence level, the rebound nozzle is always the most conservative option for standard test conditions. Finally, the mean particle surface area was identified as an appropriate indicator of the micro/nano scale's explosivity performance. Results suggest that below 3 m 2 / g , the combustion would be diffusion-limited and kinetic-limited otherwise.

The fluidization behaviors of SiO2 nanoparticles with high initial bed heights of 8–24 cm are investigated experimentally. The effects of the initial bed height and the superficial gas velocity on the minimum fluidization velocity, bed heights, axial solid distributions and the agglomerate diameter are discussed. The results show that the minimum fluidization velocity decreases significantly with the increase of the initial bed height. Over 80% of nanoparticles are fluidized at the bottom dense region of the bed under all fluidization conditions. The high bed expansion arises from a significant increase of the upper dilute region of the bed. The mean diameter of agglomerates measured in the dilute region increases with the initial bed height and the superficial gas velocity. There exists a low-frequency mass transfer between the dense and dilute regions of the bed.

Graphene materials, with their distinctively fascinating physicochemical properties, have been receiving great attention as favorable anode materials for use in Li-ion batteries (LIBs). However, the high affinity of graphene nanosheets to restack and agglomerate during electrode assembly reduces the deliverable specific capacity due to the limited available surface area and active sites for Li-ion storage. Furthermore, the high aspect ratio of graphene nanosheets could result in long transport pathways for Li-ions and consequently limiting the rate performance. These drawbacks can be significantly improved via the functionalization of graphene by various heteroatoms and also the formation of porous graphene, adding unique beneficial properties to the inherent characteristics of graphene. Here, a comprehensive review of porous and/or heteroatom doped graphene anode materials for LIBs is presented, which summarizes in detail the main recent literature from their procedure, optimum synthesis parameters, relevant mechanisms, and the obtained morphology/structure to their electrochemical performance as the LIBs anode. Finally, the research gaps are proposed. This review will promote the basic understanding and further development of porous and/or doped graphene materials as anodes for LIBs.

Background Particle breakage deteriorates dairy powder properties and it easily takes place in many processes. However, there currently is a lack of research on dairy powder breakage for understanding and controlling it. The research on particle breakage in other industries is very extensive and thorough, and could act as good reference knowledge for dairy powder breakage research, but at this time there is no review of this useful information. Scope and approach Based on the research done in dairy powder breakage and findings of particle breakage studies of other industries relevant to dairy powder particle properties, this review includes the breakage mechanisms of dairy powders, methods suitable for studying dairy powder breakage, the influence of breakage on powder properties, and influencing factors of dairy powder breakage which also can be considered as controlling factors. Key findings and conclusions Powder breakage significantly affects dairy powder physical properties which in-turn influence powder functionalities, especially the rehydration properties. The extent of agglomerates breakage corresponds to different breakage mechanisms which result in different final particle sizes and particle size distributions. The processing conditions (such as the parameters during dry-mixing, vibration, and pneumatic conveying) and the characteristics of particles (including physical properties and composition) are two main influencing factors that can be considered to control dairy powder breakage. However, there is currently not enough study showing which factors are more effective in controlling breakage. Some single-particle or multi-particle tests can be used to investigate dairy powder breakage and further research on the effectiveness of those controlling factors should be done.

The object of the research is cement samples modified by agglomerates of tungsten carbide nanopowders obtained from carbide waste. The paper considers the influence of tungsten carbide nanopowder on the change in the main cement characteristics (density, water demand, setting time, kinetics of strength gain, compressive strength, bending strength). The optimum additive content in cement materials is 3%. This parameter is estimated by the maximum growth of compressive and flexural strength at all stages of hardening. The effect of WC powder additive on the structure of the cement matrix has been shown. Due to the high dispersibility of WC nanopowder, its particles act as additional crystallization centers, fill in the micropores of the cement stone and create a denser and stronger structure. The results of studying the microstructure of the cement stone with additions of WC powder indirectly confirm the results of strength characteristics. The cement-sand samples with the modifier are found to have a denser crystallized cement-sand stone compared to the control sample (without WC powder addition). The conducted researches have shown perspectivity of application of WC nanoparticles agglomerates as modifying additives for cement materials, which can be used in production of special purpose concrete (hydraulic, radioprotective, etc.). The economic effect of the use of WC nanoadditives obtained from hard-alloy production wastes can be obtained due to a reduction in costs at the stages of construction and operation of structures, buildings, structures based on it.

The paper presents the results of tests of carbon plastic samples consisting of carbon fabric Grafill TR30S-S (Italy) and epoxy resin binder EPR 320 modified by WC tungsten carbide nanopowders in the form of agglomerates. The positive effect of additives on the tensile strength and on the modulus of elasticity at transverse bending of the concentration of additives 1-3% is shown.

A set of theoretical and experimental studies showing the promising application of devices with the rotating electromagnetic field in the technology of processing sludge wastes of metal production is presented in the paper. Regularities of magneto-vibrational layer formation in those devices and parameters of its energy state control are disclosed. There has also a model of agglomerate destruction in the magneto-vibrational layer been proposed, which establishes a connection of agglomerate particle sizes with the strength of magnetic field induction required for its destruction. The results of studies of the process of ferromagnetic particle grinding are presented, factors affecting the degree of grinding are determined. The possibility of forming an ultradisperse fraction during grinding in the rotating electromagnetic field has been experimentally proved. The effect of porousness on the degree of ferromagnetic particle grinding is shown.

The hydrodynamic behavior of cohesive TiO2 nanoparticle agglomerates was studied in a conical fluidized bed. The effects of size, particle polydispersity, and airflow velocity were analyzed in the transition regime from heterogeneous to homogeneous and turbulent fluidization. The simple-agglomerates size was ~25–75 μm with fractal dimensions of ~1.95–2.50. Adhesive CFD-DEM simulations were performed to study the interaction between the simple-agglomerates by combining Mindlin-Dersiewicz and Johnson-Kendall-Roberts (JKR) contact models. The effects of restitution and friction coefficients, probability density function, and coordination number of agglomerates were studied on the particle velocity profiles in the spout and annular zones. The error analysis results showed that bed dynamics is more sensitive to a change in the friction coefficient than in the restitution coefficient. A good agreement between the results was found for friction and restitution coefficients close to one, which is evidence of nearly elastic collisions between TiO2 agglomerates.

Cohesive elongated particles are ubiquitous in some industrial particle and powder processing operations; however, only a few studies investigated the kinematics of such particles using a discrete element method (DEM). Therefore, in this study, a DEM-based model was used to investigate the kinematics of cohesive elongated particles agitated in a vertical axis mixer. A contact-area-proportional model accounting for sphero-cylindrical particle geometry was employed for modeling particle–particle and particle–boundary cohesion. Generally, the flow patterns of the elongated particles in the vertical axis mixer remain stable as the particle cohesion level increases from no cohesion to low cohesion. However, flow pattern differences appear when the particle cohesion level increases to high cohesion, including the formation of large agglomerates, particle adhesion to the drum base and sidewall, and a significant heap height increase owing to the large angle of repose which high cohesion particles could maintain. Overall increasing the particle cohesion level increases the mass flow rate of particles over the blade, emphasizing the importance of particle cohesion of the bed. At the condition of high cohesion, the variation of the flow rate over the blade is significantly higher than that for no cohesion or low cohesion.

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.

Objectives. This paper presents research results on the encapsulation of a fluidized bed of liquid and solid toxic waste containing chemicals with a hazard class of 1–3.Methods. Soils contaminated with hexachlorobenzene and hexachlorocyclohexane were used as the seed material. Ceresin was selected as the encapsulant, which was sprayed onto the fluidized bed through a pneumatic nozzle at a temperature of 135°C. Before the spraying of the ceresin, binders were introduced into the fluidized bed of the seed material through pneumatic nozzles in the form of a melt of high-temperature coal-tar pitch and wastewater containing sodium and arsenic salts as well as heavy metal oxides. The experiments were carried out using a modified GLATT AGT-150 laboratory unit.Results. The results demonstrate that the mechanism for granule formation is a mixed mechanism. The binding of the seed material is carried out by both the pitch and salting out. In this case, the cavities in the agglomerates are partially filled with salt deposits, which increases the strength and integrity of the final product’s structure. Ranges for the process parameter values were established at the point at which there was no unwanted agglomeration in the fluidized bed, and dust formation did not exceed 5%. When the ratio of the bed mass to the mass of ceresin is equal to unity, a moisture-resistant free-flowing product of hazard class 5 is obtained, which is suitable for transportation and long-term storage. The average diameters of the initial particles and encapsulated granules were 0.5 and 1.5 mm, respectively.Conclusions. The present study demonstrates a potential process for the granulation– encapsulation of toxic waste and hazardous substances with a hazard class of 1–3 in a single fluid-bed apparatus, resulting in the formation of a moisture-resistant hazard class-5 granular product suitable for transportation and long-term storage. The results obtained can be used in the development of an industrial large-scale process for encapsulating waste of hazard classes 1–3.

In the present paper, a new approach for detonation nanodiamond (DND) deagglomeration is proposed. DND agglomerates of the size from 20 to 200 nm have been exposed to wet sonication assisted oxidat...

Natural cork (NC) and its agglomerates are renewable materials that could be effective substitutes for non-renewable foams, such as expanded polystyrene (EPS), in the cores of sandwich materials. Although many existing studies have analysed the behaviour of different cork agglomerates under tensile, compression, or shear loads, no studies to date have simultaneously analysed the behaviour of multiple cork materials under all these loads. Therefore, in this study, the behaviour of NC and five cork agglomerates were analysed under tensile, compression and shear loads, and the mechanical and specific properties and the shape of the stress–strain curves were compared with those obtained for five EPS counterparts to analyse the relationship between the mechanical behaviour of the core and the main failure modes of the sandwich. Although EPS exhibited higher specific properties, NC exhibited higher mechanical properties under all the loads. The agglomerates all exhibited lower mechanical properties except for shear strain. Additionally, because no specific standards were available for testing cork products, slightly modified standards for testing other materials were adopted.

Bed particle agglomeration and ash deposition in a 0.2 t/d circulating fluidized bed (CFB) gasifying high sodium Zhundong lignite (ZD) at different air equivalence ratios (ERs) were experimentally investigated. With quartz as bed material in the CFB at 900 °C, ZD within 3 mm in size was fed into the furnace and gasified at ERs 0.73–0.33. Two air-cooled probes were inserted in the furnace chamber (P1) and placed at the cyclone outlet (P2) respectively to simulate ash deposition. The bottom ash (BA), fly ash and ash deposited on probes were collected and analysed by using XRD, SEM-EDS, and an ash fusion analyser. At ER0.73 during gasification, agglomerates of bed particles were observed, since low melting-points sodium silicates sticking the bed particles together. Meanwhile, in the presence of NaFeSi2O6 and sodium silicate, char particles were found to have been coated by quartz and ash particles. Independent temperature-programmed ESEM imaging analysis showed these minerals became molten even at 800 °C, confirming their low melting-points. Agglomeration in BA became even severe as ER decreased, suggesting an aggravated agglomeration tendency. The fly ash mainly composed of calcium sulphate and Na-bearing minerals, whose morphological and mineralogical features were independent of ERs. In addition, ash deposited on P2 under all gasification conditions was found to be rich in Na2SO4. However, the contents of NaCl and unburned carbon increased significantly as ERs decreased. This decreased the sintering tendency of deposited ash but promoted corrosion of the P2 probe tip as observed.

The column bioleaching of copper flotation tailings was comparatively investigated using layered heap construction method (LM), agglomerate heap construction method (AM), and pellets-sintering heap construction method (PM). The bacterial communities of free, attached, weakly-attached, and strongly-attached microbes in the later bioleaching stage were investigated. In AM group, the addition of lump sulphide ore resulted in the low leachate pH, high ferric iron concentration, and rapid microbial adsorption, which obtained the maximum copper extraction (60.1%) compared with LM (54.6%) and PM (43.9%) groups. The relative abundance of dominant genera and microbial communities of different microbiota underwent changes in three heap construction methods. The alpha-diversity indexes of attached, weakly-attached, and strongly-attached microbes were different, while no significant change was observed in free bacteria. The variation of whole bacterial community was significantly associated with solution pH, total iron, and ferric iron concentrations. Pearson correlation analysis and partial least square path model both indicated that attached bacteria made larger contribution to the copper extraction of tailings.

In this work an innovative formulation of bone cement for the treatment of bone tumor and its associated complications has been designed by preparing a new class of Fe3O4–Ag nanostructures, using gallic acid as a reducing agent. The obtained nanoparticles have been introduced in polymethyl methacrylate (PMMA)-based composite cement evaluating the insertion of different amounts and the use of different mixing methods. The morphology, the composition and the antibacterial effect of Fe3O4–Ag nanostructures have been investigated together with the morphology, the composition, the mechanical properties of the nanoparticles-containing composite cements as well as their antibacterial effect. The obtained results revealed a good antimicrobial effect of Fe3O4–Ag nanostructures, a significant influence of their amount and of the used mixing method on the particles dispersion and agglomeration in the PMMA matrix and, as a result, on the mechanical properties. In particular, a better dispersion of nanoparticles was obtained by using the mechanical mixing, reducing the tendency to agglomerate. The increase of nanoparticles amount induced a slight decrease of the mechanical properties; however, the introduction of 10% w/w of Fe3O4–Ag allowed to improve the composites ability to reduce the bacteria adhesion.

This work probes the slurry architecture of a high silicon content electrode slurry with and without low molecular weight polymeric dispersants as a function of shear rate to mimic electrode casting conditions for poly(acrylic acid) (PAA) and lithium neutralized poly(acrylic acid) (LiPAA) based electrodes. Rheology coupled ultra-small angle neutron scattering (rheo-USANS) was used to examine the aggregation and agglomeration behavior of each slurry as well as the overall shape of the aggregates. The addition of dispersant has opposing effects on slurries made with PAA or LiPAA binder. With a dispersant, there are fewer aggregates and agglomerates in the PAA based silicon slurries, while LiPAA based silicon slurries become orders of magnitude more aggregated and agglomerated at all shear rates. The reorganization of the PAA and LiPAA binder in the presence of dispersant leads to a more homogeneous slurry and a more heterogeneous slurry, respectively. This reorganization ripples through to the cast electrode architecture and is reflected in the electrochemical cycling of these electrodes.

Environmental pollution by organic pollutants is a serious concern which may be solved by photocatalytic degradation of pollutants, yet the efficiency of actual photocatalytic materials is limited. For instance, conventional MoS2 nanosheets tend to agglomerate, which hinders the access of pollutants to active sites. To overcome this challenge, we hypothesized that assembling MoS2 nanosheets on a mineral support would improve access to active sites. We synthesized a catalyst made of 3–4 atomic layers of MoS2 nanosheets deposited on tourmaline using a microwave hydrothermal method. Results show that tourmaline occurs as a polyhedron single crystal that supports the epitaxial growth of 2H-MoS2 layers on tourmaline (77 $$\overline{3}$$ ) facets, while an intrinsic rolling up behavior of MoS2 layer from [002] to [106] on the mineral surface accounts for the curly morphology. The pangolin-like MoS2/tourmaline composite degrades rhodamine B much better than the pure MoS2 nanosheets assembled microspheres. This is explained by the reduced thickness of MoS2 nanosheets according to the density functional theory. Overall, our findings represent a new tactic for the cost-effective batch preparation of two-dimensional materials with high catalytic performance.

In Press., [EN]: Ca3Co4O9 + xwt.% TiC (x = 0, 0.25, 0.5, 0.75, and 1.0) polycrystalline thermoelectric ceramics have been prepared through the classical ceramic route. XRD characterization has demonstrated that all samples are mainly composed by the Ca3Co4O9 phase, while microstructural observation has shown that no reaction between both components has been produced. Moreover, TiC particles are well distributed for small additions, and start to agglomerate from 0.75 wt.% content. Density measurements showed that nearly no changes have been produced by TiC addition and nearly the whole porosity appears as open one. Furthermore, electrical resistivity decreases up to 0.75 wt.% addition, increasing for higher content. On the other hand, Seebeck coefficient has been maintained unchanged in all samples. In spite of an irregular behaviour of thermal conductivity with temperature, it tends to decrease when the temperature is raised, displaying the lowest values for the 0.25 wt.% samples. These data led to an increase of about 40% in ZT values at 800 °C for samples with 0.25 wt.% addition, when compared with the pure ones. Finally, linear thermal expansion coefficient is decreased when TiC content is increased, which can be exploited to fit the thermal expansion coefficients of all the components used to build a power generation thermoelectric module., [ES]: Se han preparado cerámicas de composición Ca3Co4O9 + x% en peso de TiC (x = 0, 0,25; 0,5; 0,75, y 1,0) utilizando el método clásico de estado sólido. La caracterización por XRD mostró que la fase termoeléctrica Ca3Co4O9 aparecía como mayoritaria. Las observaciones microestructurales determinaron que no se produce reacción entre esta fase y las partículas de TiC. Estas partículas aparecen bien distribuidas cuando hay pequeñas adiciones y comienzan a aglomerarse a partir del 0,75% en peso. Las medidas de densidad indicaron que este parámetro no se modifica con la adición de TiC y, además, que se produce una porosidad de tipo abierto. La presencia de TiC modifica la resistividad eléctrica de forma que disminuye hasta el 0,75% en peso de TiC, aumentando para contenidos mayores, sin afectar el coeficiente de Seebeck. La conductividad térmica muestra un comportamiento irregular, pero tiende a disminuir al aumentar la temperatura, alcanzando los menores valores en muestras con 0,25% en peso de TiC. Estos resultados llevaron a un aumento del 40% en los valores de ZT a 800 °C en muestras con 0,25% TiC en peso, comparados con los medidos en muestras sin TiC. Finalmente, el coeficiente de dilatación lineal disminuye al aumentar el contenido de TiC, lo que puede utilizarse para ajustar los coeficientes de dilatación de todos los componentes al construir un módulo termoeléctrico de generación de potencia., The authors wish to thank the Gobierno de Aragón-FEDER (Research Group T 54-17R), and the Spanish MINECO (Ministerio de Economía y Competitividad)-FEDER (Project MAT2017-82183-C3-1-R) for financial support. Authors would like to acknowledge the use of Servicio General de Apoyo a la Investigación-SAI, Universidad de Zaragoza.

Mixing of nanoparticle agglomerates in a fluidized bed was investigated by CFD-DEM. A parallel program was used that simultaneously uses the computational resources of GPU and CPU on a single computer. The bed expansion obtained from simulation was compared with experimental and good agreement was observed. Bed expansion in agglomerate particulate fluidization (APF) was 2 to 5 times the initial bed height and final bed expansion in agglomerate bubbling fluidization (ABF) was 1 to 2 times the initial bed height by changing the gas velocity from 2 to 4 and 4 to 8 cm/s for APF and ABF regimes respectively. Gas volume fraction distribution was investigated for both APF and ABF regimes, which showed a more uniform distribution in APF. Increasing the gas velocity led to a more homogenous in the APF bed but it did not change the homogeneity of the ABF bed. Besides, the axial and radial dispersion coefficients in ABF were greater than those in APF. Axial dispersion coefficient varied from 2 × 10−6 to 4 × 10−5 m2/s. Lacey mixing index was investigated in both APF and ABF regimes and it showed that the quality of mixing in ABF was better than APF.

A monodisperse population balance model (MPBM) is developed here that capitalizes on the rapid attainment of the self-preserving size distribution and asymptotic fractal-like structure of agglomerates by coagulation to simulate their evolution with only three equations. Total agglomerate carbon molar, C , number ( N ) and area ( A ) concentrations are tracked. The model accounts for the polydispersity of agglomerates by enhancing their collision frequency by that of their self-preserving size distribution based on the radius of gyration in the free molecular regime. Scaling laws from detailed discrete element modeling (DEM) simulations are used to describe the fractal-like morphology of the agglomerates. The MPBM predicts the evolution of soot f v , N and average mobility and primary particle diameters during surface growth and agglomeration in laminar premixed ethylene flames as well as soot oxidation in a tube reactor within 30% of detailed DEM, sectional population balance simulations and measurements. Thus, when self-preserving size distribution and asymptotic structure of agglomerates are attained, this simple MPBM has unprecedented accuracy and can be readily interfaced with computational fluid dynamic (CFD) to model soot formation in combustion devices or process design and optimization for the synthesis of carbonaceous agglomerate nanoparticles.

The size and the agglomeration state of nanoparticles (NPs) play a very important role in nanoparticle applications due to the effect of the dispersion level of NPs on their toxicity, pharmaceutical activity, and catalytic activity. In this study, a novel two-stage nanoparticle disperser system was proposed. We focused on the effects of the aspect ratio (L/D, length (L) and diameter (D)) of the round jet (a straight pipe) on the nanoparticle size distribution (PSD) and we attempted to explain how the jet wakes induced the NP deagglomeration based on the numerical results. The median diameters, mode diameters, and geometric mean diameters (GMD) of the PSDs that were obtained using the second-stage were significantly smaller than those achieved using the first-stage disperser alone. Overall, the GMD, mode diameters, and median diameters could all reach sub-70 nm, which was approaching close to the NP primary diameter (30–40 nm). The particle sizes decreased with the increasing dimensionless nozzle diameter (D* = D/Dp × 10−3, Dp represents the particle diameter). The increase in L/D for a constant D hardly affected the PSDs but led them to be closer to a standard lognormal distribution. Regarding the NP traveling path and its considerable inertia as it penetrated the Mach disc, these particular field distributions of the jet-wake might explain why the suspended sub-micro NP agglomerates could be highly deagglomerated. Namely, the nano NP agglomerates would suffer the severe shear stress around the Mach disc.

Water in jet fuels is an important concern for the aeronautical industry, especially at freezing temperatures, for which ice-clogging phenomena may occur in the fuel-feeding system, with a risk causing accidents. In this work, ice particles formed from water addition in jet A-1 fuel have been characterized by X-ray Micro-Computed Tomography (μCT) at −18±2 °C. For this purpose, an experimental sampling campaign was conducted in a fuel-icing test bench designed to characterize the properties of aeronautical filters. The samples were conditioned, transported, stored under cold-stable conditions and afterward preserved using a specific cryogenic cell during the X-ray scans. After image processing and analysis, the three dimensional (3D) images allowed us to access the shape complexity of the particles at a resolution of 5 μm. The different samples gave repeatable and coherent results, exhibiting wide size distributions of the ice particles, ranging from 20 to 970 μm with a peak between 100 and 400 μm. The increase of the water content volumetric fraction (C) as well as that of the time by which the ice particles were recirculating in the injection loop (τ), showed tendencies towards wider and smaller size distributions, respectively. The sphericity indexes (ψ) were higher than 0.7 for ~70% of particles, indicating a significant trend to rounded shapes. The mean curvature distributions of the agglomerates showed some displacements towards concave surfaces at high C, and towards convex surfaces at longer τ. This illustrates the occurrence of more complex structures for higher water contents and the “grinding effect” of the recirculating time.

The sintering intensity is an important factor determining techno-economic efficiency of sinter production which provides the blast-furnace process with the main type of agglomerated iron ore raw materials. The charge sintering rate depends on technological parameters of the sintering process. Therefore, a systematic study of sintering technological parameters, which determine its intensity, is of practical and scientific interest. Indicators of the sintering process intensity are considered that assess it from both the mechanical and heat engineering positions. It is shown that in its purest form the sintering process intensity is characterized by the vertical agglomeration rate and combustion intensity of the sintering charge carbon. Two other indexes − the specific productivity for suitable sinter and intensity of heat output in the combustion zone – are less representative for the comparative estimation of sintering intensity, since their values depend on sintered mass strength and thermal effect of carbon combustion respectively. These factors go beyond the essence of the sintering intensity concept. Since content of fines of 5 – 0 mm at different sinter plants is not equal, representative performance comparison of sintering process is possible only taking into account the total amount of fines generated throughout the agglomerate transport path from sinter machine to blast furnace or the results of testing the agglomerate strength in a drum. A comprehensive systematic classification of techniques has been developed to intensify the sintering process based on the material-component principle using four levels of separation – objects, directions, paths and methods in which each subsequent level concretizes and develops the previous one. Its value is universality, which makes it possible to apply a systematization and separation system for almost all already known and future methods of sintering process intensification.

In general, block crystals tend to cake and have poor flowability. Changing the crystal shape to sphericity is useful to overcome those disadvantages. In this work, spherical agglomerates of potass...

This article describes the advances in the design, implementation, and evaluation of efficient algorithms for self-gravity simulations in astronomical agglomerates. Three algorithms are presented and evaluated: the occupied cells method, and two variations of the Barnes–Hut method using an octal and a binary tree. Two scenarios are considered in the evaluation: two agglomerates orbiting each other and a collapsing cube. The results show that the proposed octal tree Barnes–Hut method allows improving the performance of the self-gravity calculation up to 100 times with respect to the occupied cells method, while having good numerical accuracy. The proposed algorithms are efficient and accurate methods for self-gravity simulations in astronomical agglomerates.

The effect of varying amounts of CoAl2O4 inoculant ranging from 0 to 2 wt pct on the microstructure evolution of Inconel 718(IN718) fabricated by selective laser melting (SLM) was evaluated. Characterization of the as-built microstructure revealed that addition of CoAl2O4 resulted in a modest degree of grain refinement with a slight increase in microstructural anisotropy. Increasing the total CoAl2O4 content beyond 0.2 wt pct resulted in severe agglomeration of the non-metallic particles and the formation of slag inclusions measuring up to 100 μm in size present in the as-built microstructure. In addition to large agglomerates, the inoculant was chemically reduced to form a fine dispersion of submicron-sized Al2O3 particles throughout the IN718 matrix. The fine dispersion of oxides significantly hindered grain recrystallization during the post-fabrication heat treatment due to a Zener pinning effect. The findings from this study indicate in order to effectively utilize CoAl2O4 as a grain refining inoculant for additive manufacturing, the process parameters need to be optimized to avoid agglomeration of the non-metallic particles and other process-related defects.

In the present work, nanostructured La2(Zr0·7Ce0.3)2O7/YSZ functionally graded coatings were prepared by applying the atmospheric plasma spraying process. The La2(Zr0·7Ce0.3)2O7 compound was synthesized via the calcination process to get a nanostructured precursor precipitate at 600 °C. Two types of nanostructured functionally graded coatings were applied on the Hastelloy X substrates coated with NiCrAlY and 8YSZ. The agglomerates of La2(Zr0·7Ce0.3)2O7 were then used to apply the type I coating. Type II coating was then applied by the plasma spraying of the heat-treated agglomerates of La2(Zr0·7Ce0.3)2O7. The results of the phase and microstructural analysis showed that a nano-composite microstructure comprising the main phases of lanthanum zirconate with the partial solubility of cerium cation (LZ) and the solid solution of cerium lanthanum zirconate (LC) was formed in both types of coatings. Type II coating was relatively denser; so, it could be considered as a dense nanostructured coating. The results of the oxidation tests also showed that only the type II coating had higher oxidation resistance, as compared to that of the conventional YSZ coating. Parabolic oxidation rate constant of this coating was equal to 0.114 μm2/h. On the other hand, the oxidation rate constant for the type I coating and conventional YSZ coating was measured to be 0.141 μm2/h and 0.147 μm2/h, respectively. In addition, the results of the thermal insulation capability test indicated that the thermal barrier capability of the type I coating was 59% higher than that of the conventional YSZ coating. However, under similar conditions, this percentage was 29% for the type II coating.

Agglomerates are a large cluster of primary particles, which may result in the flaws of the final ceramics. Stereolithography suspensions could pose challenges to identify their coarse agglomerates without modifications to their properties; the suspensions are mostly high turbid and viscous in some cases. Any modifications, such as dilution, can alter the actual degree of agglomeration. In this study, a means to characterize the degree of dispersion was developed using the automated fineness of grind gauge. The fineness of grind gauge was visualized to determine the nature of the trapped agglomerates and their distribution. The resulted agglomerate size distribution was treated mathematically as a power law distribution in a selected region. The power law function was found to describe the degree of dispersion of suspensions, which was associated with the coarse agglomerate distribution behavior.

Fine particles with the size below 1 μm are difficult to be captured with the traditional dust removal devices because of their poor charge capacity and filterability. Using the agglomeration pretreatment can realize the fine particles growth, then facilitating the capture process. In this study, a novel system with the combination of corona discharge and embedded turbulence was put forward. The results showed that the device can agglomerate the smaller particles into bigger ones, and the maximum decrease of number concentration for small particles can reach 40% in the bipolar corona discharge condition. The median diameters of fine particles can be improved by 47% maximumly in the condition of arrangement of turbulence bars and loopholes with a lower flow velocity. The simulated calculation and pilot scale test were conducted and the results were consistent with experimental conclusions.

Hydrogen absorption often induces changes of various properties of rare-earth metals. In this paper, we study the influence of hydrogenation on the structural, magnetic and magnetocaloric properties of high-purity nanocrystalline terbium. Strong (00l) texture present in the parent Tb sample is practically destroyed after the hydrogenation procedure. We observe formation of agglomerates of different sizes and shapes depending on the hydrogen content in the samples. We find traces of β-hydride (TbH2) in the main α-hydride TbHx phase. For TbHx with x = 0.25 and 0.5 at.H/f.u. The effect of hydrogenation on the magnetocaloric properties is studied in magnetic fields up to 9 T. The magnetocaloric effect decreases after hydrogenation. The -ΔSM(T) curves feature a table-like effect in the vicinity of the magnetic phase transitions in magnetic fields exceeding 1 T.

This paper investigated the joint influence of particle crushing and intermediate principal stress coefficient on the macro and micro performances of granular assembles by using 3D discrete element method. The soil particle was modeled by crushable agglomerate. Numerical true triaxial tests with crushable agglomerates were performed. The mechanical behaviors of specimens with unbreakable agglomerates were also tested in this study. The results demonstrated that grain breakage can significantly affect the behaviors of granular soils in both macro and micro scales. Moreover, the present paper also showed that particle breakage did not influence the unique relationship between the intermediate principal stress coefficient b and the deviatoric fabric of strong contacts. This can provide a good basis for developing micro-parameter-based constitutive model considering particle breakage for granular soils.

Oiling out during the crystallization process often generates agglomeration. This research is focused on the control of agglomeration in the antisolvent crystallization of the propylparaben-ethanol-water system in the presence of oiling out, that is, the liquid-liquid phase separation phenomenon. Crystallization trajectories were designed to start from a homogeneous solution with different initial concentrations of propylparaben in ethanol, crossing the liquid-liquid phase separation region in the ternary phase diagram by adding the antisolvent of water. A combination of process analytical technology tools, such as focused beam reflectance measurement, particle visual monitoring, and attenuated total reflectance ultraviolet/visible, enabled the detection of the different stages of the oiling out crystallization process, including the droplet formation of the dispersed phase, prenucleation, nucleation, and crystal growth both in the liquid-liquid phase-separated system and in the homogeneous solution. The crystals tended to form normally at higher initial concentrations of propylparaben while tending to agglomerate at a lower initial concentration. Crystallization experiments were also performed with the addition of sonication, with variation in sonication start time, duration, and power. The results showed that ultrasound could reduce the agglomeration dependent on the initial application time. The mechanism of crystallization and agglomeration in oiling out was discussed.

AlCa75 with equal Ca content was used to replace pure Ca for the preparation of AlSi12 foam in a stable pore structure after foaming for 20 min. The stability mechanism was studied based on the comparison between the macroscopic pore structure evolution and the second phase composition of AlCa75 and pure Ca aluminum foam. It was found that the porosity and average pore size of the AlSi12 foam with AlCa75 were stable without any abnormal large pores, and the foaming stage was prominent. The stability of AlSi12 foam with pure Ca is inferior. After 20 min of foaming, the foam bursts in the center. Combined with the microscopic characteristic analysis, it could see that the second phase produced by AlCa75 is mainly Al2Si2Ca, which can be uniformly dispersed in the matrix. The addition of pure Ca reduces the amount of the second phase and the main phase Al4Ca is easy to agglomerate. The stability mechanism shows that the Al2Si2Ca second phase, formed by AlCa75, demonstrates a better stabilizing effect in different foaming stages. Due to the premature agglomeration caused by Al4Ca and the low content of the second phase, the AlSi12 foam with pure Ca is challenging to long-term stability.

Durability is one of the main obstacles that inhibits the commercialization of polymer electrolyte membrane (PEM) fuel cells for transport applications, in which the microstructure of the catalyst layers (CLs) deteriorates under dynamic loading operation. In this study, CLs’ naturally random porous structure is simplified to be a random three-phase microstructure consisting of ionomers, catalyst agglomerates and pores, and the onset and growth of delamination process between the ionomer and catalyst agglomerate is investigated numerically by considering the catalyst agglomerate as elastic while the ionomer is elasto-viscoplastic, influenced by the cell assembly force arising from the cell clamping and variations in temperature and relative humidity. It is found that increasing clamping stress delays the delamination onset but has marginal effect on delamination propagation. The amplitude of hygrothermal cycles is the dominating factor in delamination and more frequent startup/shutdown of PEM fuel cells alleviates the delamination. Correlation between the rate of plastic strain accumulation in the ionomer and the interface delamination has been observed.

Selective Laser Sintering (SLS) of Titania powders is studied to understand how the initial material properties and the process conditions affect the degree of sintering/melting and the mechanical properties of the semi-3D artefact produced.Five samples with differing particle size were used to explore the feasibility of processing them by SLS. Laser power and scan speed were studied as process variables to assess and quantify the effect of their changes on the properties of product. The measured tensile strength was used in the equation for the strength of the powder’s agglomerates developed by Rumpf, which allowed estimating the size of the sintered necks. The sintering temperature of each powder sample was determined experimentally and used to predict the size of the sintered neck for the different powder grain size using different literature models; these values were then compared with the values obtained from the experiments.

In this research work, the variation in the mechanical and thermal behavior of tungsten (W)-reinforced epoxy resin (EPR) composites by varying the tungsten particulate content has been investigated. The composites were fabricated by manual mixing and specimens containing tungsten particles varying in proportion of 1, 3, 5, 7, and 9 wt. % were synthesized. X-ray diffraction (XRD) analysis of the specimen reveals the presence of epoxy resin and an increasing proportion of W in the prepared specimen. Scanning electron microscopy (SEM) analysis reveals the homogenous distribution of W particulates in the epoxy resin matrix for adding tungsten particulates up to 7 wt. % and further increasing the tungsten content leads to the formation of agglomerates of W particulates. In mechanical characterization, it has been found that the tensile strength shows an improvement of 103%, flexural strength is improved by 129%, and impact strength is improved by 164% for the addition of 7 wt. % of W particulates. In thermal characterization, Thermogravimetry analysis (TGA) shows that the stability in the thermal behavior of the composites increases with the addition of W particulates to the matrix of epoxy resin.

In the present study, AA2024-SiO2np nanocomposites were prepared by the vortex method and effects of SiO2 content on resulting microstructural and mechanical properties were investigated. The results indicate that the addition of 0.5vol% of nanoparticles decreased the size of the dendrite cell intervals by about 16%. The observed mechanical properties exhibited an improvement of about 17, 28, 10, 157, 8 and 13%, in hardness, ultimate tensile strength, yield strength, tensile elongation, flexural and shear strengths, respectively. With more considerable additions of nanoparticles, scanning electron microscopy investigations confirm that there were more significant amounts of nanoparticle agglomerates in the microstructure, which reduced the mechanical properties of 1vol% SiO2np reinforced nanocomposite. The primary strengthening mechanisms evaluated appeared to be the effect of grain refinement (Hall–Petch), Orowan strengthening and the mismatch in coefficient of thermal expansion of the reinforcements and the matrix alloy. Evidence of some agglomerations of nanoparticles was recognized on the tensile fractured surfaces of the nanocomposites.

It is challenging to hydrothermally synthesize solution-processable MoS2, as the strong van der Waals force between MoS2 nanosheets induces self-assembly of agglomerates. Here, we introduce poly(3,...

Aluminum hydride (AlH3) is currently receiving considerable attention due to its potential to replace aluminum (Al) as a new metal fuel in solid propellants. In this study, simultaneous thermogravimetric analysis and differential scanning calorimetry and a laser ignition testing system were used to investigate the thermal oxidation and combustion characteristics of AlH3 and Al. The combustion residues were then analyzed using a scanning electron microscope. Results show that the thermal oxidation processes of both AlH3 and Al contain a mass loss stage and two mass gain stages. After dehydrogenation, AlH3 exhibits a stepwise oxidation behavior that is similar to that of a similar sized Al, but has a much higher mass gain. The combustion process of Al can be divided into three stages, which correspond to the combustion of dispersed Al particles, formation of Al agglomerate and combustion of Al agglomerate, respectively. The combustion flame of AlH3 is significantly different from that of Al, but their microscopic combustion behaviors are very similar. A unique flame delamination phenomenon exists in the early stage of AlH3 flame development. AlH3 has shorter ignition delay times and a larger combustion intensity than Al. The release and combustion of hydrogen changes the combustion environment of the remaining AlH3 particles, leading to the appearance of an OH characteristic peak and increasing the production path of AlO. The morphology of combustion residues shows that the dehydrogenation of AlH3 starts from the particle surface and then gradually expands towards its interior.

La2Ce2O7 (LC), La2Zr2O7 (LZ), and yttria stabilized zirconia (YSZ) nanostructured powders with different agglomerate structures were successfully synthesized via wet-chemical method, and their high-temperature sintering resistance was systematically studied in this paper. Experimental results indicate that the synthesized nanostructured YSZ sample possessed the highest sintering resistance while nanostructured LC sample had the lowest sintering resistance. Theory of sintering process at initial stage was used to analyze experimental results. Sintering abilities of materials were closely related to their surface energy, lattice and grain boundary diffusion coefficients, and powder morphologies. Moreover, intrinsic sintering resistance (ISR) and extrinsic sintering resistance (ESR) were defined to further clarify the experimental results. ISR is determined by surface energy, lattice and grain boundary diffusion coefficients of the material, while ESR is affected by dimensions and density of raw powders. The highest sintering resistance of YSZ originated from dense initial powder with large size, which led to extraordinary ESR of the sample. ISR of LZ was found to be much better than that of YSZ and LC, while ISR values of LC and YSZ were similar. Finally, as ISR ability of thermal barrier coating (TBC) materials can be clarified by studying the corresponding crystalline size evolution, a feasible approach was proposed to compare ISR ability of novel TBC materials.

Composite powders containing TiB2 and ZrB2 particles were successfully prepared through combustion synthesis of (2-x)TiO2–xZrO2–2B2O3–(10 + y)Mg system. Results showed increase in the x-value from 0 to 2 mol and y-value from 0 to 2.5 mol didn't have any considerable impact on reaction front velocity. In the case of TiO2–B2O3–Mg system with stoichiometric composition, agglomerates containing large TiB2 particles with hexagonal plate-like morphology embedded in a MgO matrix were remained after leaching. The addition of 25 wt% excess Mg (y = 2.5) to this mixture resulted in the dissolution of unwanted phases and the formation of pure submicron TiB2 particles. On the contrary, for the ZrO2–B2O3–Mg mixture (x = 2) unreacted ZrO2 remained and a ZrB2/ZrO2 composite powder was acquired. Both TiB2 and ZrB2 particles were only attained at x = 1.5 mol. The addition of 25 wt% excess Mg to this sample had an inverse effect and removed ZrB2 instead of ZrO2. Lastly, a TiB2/ZrO2 composite powder having submicron titanium boride particles was prepared after leaching process. Simultaneous thermal analyses results showed the combustion reaction sequence in the TiO2–ZrO2–B2O3–Mg system involves; dehydration of powders, melting of B2O3, reaction of molten B2O3 with solid Mg, solid-state reaction of TiO2 and Mg and the formation of Ti, partial reaction of ZrO2 with Mg and the formation of Zr and finally, development of TiB2 and ZrB2 through reaction of Ti and Zr with B element.

The impact of agglomerates on solid surfaces occurs inevitably during the processing of granular materials. In this work, numerical simulations of the surface impact of wet agglomerates are carried out by introducing liquid bridge interactions into a soft-sphere DEM model, and the instantaneous impact behaviors are discussed quantitatively at the single particle scale. Results indicate that the impact process usually includes four stages, i.e., compression, expansion, fragmentation, and re-agglomeration. The expanding radius is found to follow an exponential-law with time, and the number of fragments follows a power-law with impact velocity. Due to liquid bridge interactions, chain-like structures are observed beyond the impact, similar to those formed during the impact of dense suspension droplets. Moreover, the impact behaviors can be generally classified into four groups with respect to impact velocity, i.e., minor compression without splashing, severe compression with minor splashing, severe splashing with minor fragmentation, and severe fragmentation.

Metformin hydrochloride is a drug used in the treatment of type 2 diabetes and is administered orally using high-dose tablets. Due to its poor flowability and agglomeration during storage, metformin is commonly processed using an intermediate step such as granulation before the material can be compressed into tablets. Spherical crystallization is a method, which can be used to improve the flowability and tabletability of drugs and excipients. This study set out to create a simple quasi-emulsion solvent-diffusion crystallization method for the highly water-soluble metformin hydrochloride using a single solvent and antisolvent with surfactants so that a direct compression of the material can be realized. Hollow, spherical agglomerates of metformin with good flowability and reduced storage agglomeration were successfully produced using this method. The effect of different surfactants (HPMC, polysorbate 80 and sorbitane monooleate) used to stabilize the transient emulsion during crystallization as well as different system parameters on the morphology, flowability of the particles and storage agglomeration was analyzed.