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To study the effects of the morphology of ZnO particles on the properties of asphalt binder and asphalt mixture, the micro ZnO particles with different morphologies (agglomerate, sphere, rod and flower), whose average size were 2 µm, were made by the homogeneous precipitation and hydrothermal methods. A series of tests, including the softening point, bending beam rheometer (BBR), dynamic shear rheological (DSR), Marshall test, rutting test and so on, were used for evaluating the properties of asphalt binder and asphalt mixture. The analysis of variance (ANOVA) and the maximum relative difference (MRD) were introduced to study the effects of the morphology of ZnO particles on the properties of asphalt binder and asphalt mixture. Finally, the optimal morphology of the ZnO particle was recommended. The results show that the morphology of the ZnO particle has a significant effect on the rutting factor, has an effect on the viscosity in the situation of the dosages of SBS are 0% and 4%, has no effect on the low temperature ability of asphalt binder. In terms of asphalt mixture, the morphology of the ZnO particle has a noticeable effect on the high temperature stability, has an effect on the low temperature ability, has almost no effect on the water stability of asphalt mixture. Furthermore, the rod-like ZnO particles are more conducive to promote the properties of asphalt binder and asphalt mixture. As a result, the rod-like ZnO particle is recommended.

Static electricity has an important effect on gas–solid fluidized bed reactor fluidization performance. In the process of fluidization, electrostatic interaction between particles will obviously accelerate particle agglomerate formation, which consequently reduces the fluidization performance. Pulsed gas flow injection is an efficient method to enhance particle mixing, thereby weakening the occurrence of particle agglomerate. In this study, the two-dimensional hybrid pulsed fluidized bed is established. The flow characteristics are studied by using the coupled CFD-DEM numerical simulation model considering electrostatic effects. Influences of different pulsed frequencies and gas flow ratios on fluidized bed fluidization performance are investigated to obtain the optimal pulsed gas flow condition. Results show that in the presence of static electricity, the bubble generation position is lower, which is conducive to the particle flow. Pulsed gas flow can increase the particle velocity and improve the diffusion ability. The bubble generation time is different at different frequencies, and the frequency of 2.5 Hz has the most obvious effect on the flow characteristics. Different gas flow ratios have significant impacts on the particle movement amplitude. When the pulse gas flow accounts for a large ratio, the particle agglomerate tends to be larger. Therefore, in order to improve the fluidization effect, the ratio of pulsed gas flow to stable gas flow should be appropriately reduced to 0.5 or less.

International audience; In order to extract the most capacity out of Li-ion battery (LIB) active materials, the optimization of the electrodes architectures at the mesoscale is essential. This work focuses on the morphology of the inactive phase (carbon additives and binder) through a 3-D modeling approach based on stochastic generation of electrode mesostructures with realistic LiNi1/3Mn1/3Co1/3O2 particle size distributions. It was found that having the inactive phase as a film spread on the active material results in poorer performance in part due to the loss of active surface area when compared to an agglomerate-like morphology.

In this work, a tapered fluidized bed (TFB) without a distributor for fluidizing carbon nanotube (CNT) was applied for improving the dead zone, blockage, and fracture of distributor, which occurred in actual production. Experiments were performed under different superficial gas velocities, static bed heights, CNT agglomerate size, and positions of pressure probe. To obtain multi-perspective and multi-scale understanding of fluidization dynamics of gas–CNT flow in the TFB without a distributor, the standard deviation, skewness, kurtosis, wavelet decompositions and homogeneous index analysis methods were adopted. Some noticeable phenomena were observed. Particle movements including inter-particle, gas–particle and particle–wall dominate dynamic characteristics. The amplitudes of pressure fluctuations of coarse agglomerated multi-walled CNT were more sensitive to the gas velocity than that of fine agglomerated multi-walled CNT. The sensitively of energy contribution of the meso- and macro-structures was that the sensitivity of the measured position was less than the sensitivity of the energy contribution by the changes of particle size, and the sensitivity of the energy contribution by the changes of particle size was less than the energy contribution by the changes of gas velocity. The fluidization quality of coarse agglomerated multi-walled CNT was better than that of fine agglomerated multi-walled CNT, which was verified by the skewness and wavelet analysis.

In the electrochemical process, Pt nanoparticles (NPs) in Pt-based catalysts usually agglomerate due to Oswald ripening or lack of restraint, ultimately resulting in reduction of the active sites and catalytic efficiency. How to uniformly disperse and firmly fix Pt NPs on carbon matrix with suitable particle size for catalysis is still a big challenge. Herein, to prevent the agglomeration and shedding of Pt NPs, Ni species is introduced and are evenly dispersed in the surface of carbon matrix in the form of Ni-N-C active sites (Ni ZIF-NC). The Ni sites can be used to anchor Pt NPs, and then effectively limit the further growth and agglomeration of Pt NPs during the reaction process. Compared with commercial Pt/C catalyst, Pt@Ni ZIF-NC, with ultralow Pt loading (7 wt%) and ideal particle size (2.3 nm), not only increases the active center, but also promotes the catalysis kinetics, greatly improving the ORR and HER catalytic activity. Under acidic conditions, its half-wave potential (0.902 V) is superior to commercial Pt/C (0.861 V), and the mass activity (0.38 A per mg Pt) at 0.9 V is 4.7 times that of Pt/C (0.08 A per mg Pt). Besides, it also shows outstanding HER performance. At 20 and 30 mV, its mass activity is even 2 and 6 times that of Pt/C, respectively. Whether it is under ORR or HER conditions, it still shows excellent durability. These undoubtedly indicate the realization of dual-functional catalysts with low-Pt and high-efficiency properties.

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.

The two stage technology of porous carbonaceous material obtaining via pyrolysis in inert medium with subsequent activation by steam is well-known. While steam could be a suitable substance for pyrolysis as well, the single-staged technology for waste tires recycling is yet to be developed. A comparative analysis of the characteristics of the carbonaceous materials obtained by the single-staged steam pyrolysis of waste tires was carried out, which could provide theoretical background for development of such technology. The steam pyrolysis was performed in a tubular reactor in an overheated steam medium (500 °C with 5 kg/h mass flow rate). The technical characteristics of the obtained samples were evaluated in context of their potential for further application as absorbent and raw material for the rubber production according to Chemical Abstracts Service No. 1333-86-4. The composition and physical-chemical properties of the obtained samples were studied using BET and thermogravimetric analysis, atomic emission, transmission and scanning electron microscopies, Raman, X-ray diffraction and photoelectron spectroscopies. The results revealed that the structure and properties of all obtained carbonaceous material samples were similar. The samples consisted of amorphous carbon (with a disordered graphite lattice) and contained a significant amount of metal oxides. According to experimental data, zinc was present in the form of ZnO with a binding energy of 1022.4 eV, while sulfur was observed in the form of sulfide and oxysulfide with binding energies of 161.8 and 163.2 eV, respectively. According to electron microscopy, the morphology of samples was represented by a set of spherical agglomerates comprising nanosized particles. According to the BET analysis of the samples, the specific surface area was varieb in range between 52.0 and 66.0 m2/g, the pore volume values were within a range of 0.53-0.87 cm3/g while the average pore size was varied from 412 to 527 A.

Float polishing (FP) is a non-contact polishing method in which a thin layer of fluid is maintained between the workpiece and precision lap by hydrodynamic pressure effect. While it is known to consistently produce atomically flat surfaces with little or no sub-surface damage, the characteristics of polishing fluid flow and material removal have not been studied in-depth. In this research, the underlying mechanism in FP is investigated by means of computational fluid dynamics (CFD) and molecular dynamics (MD) simulation. It is revealed that a fluid gap few microns in height is generated by the wedge effect of slurry. The near wall flow condition is further investigated by direct observation and tracing of cavitation bubbles. Abrasive particle trajectory tracing is carried out with a well calibrated CFD model, and suggests that single abrasive particles move almost parallel to the workpiece surface at a relative speed of around 0.5 mm/s. Next, single abrasive particle interactions with the surface of a Ni crystal are simulated by MD to predict the required conditions in terms of kinetic energy for effective smoothing of the surface. Finally, it is concluded that the material removal mechanism in FP is dependent on a minimum size of nano-abrasive agglomerates of several 100 nm, and the existence of two types of smoothing phenomena: atomic removal and atomic transfer.

In this paper, equilibrium molecular dynamic simulations were used to calculate the thermal conductivity of Cu-Ar nanofluid with various initial aggregation structures at different volume fractions. The microscopic mechanism of the effect of nanoparticle agglomerate aggregation mode on the thermal conductivity of nanofluids was analyzed. Results showed that the particle size is the key factor to determine the aggregation structure of nanoparticles. The enhancement efficiency of diffusion-limited aggregation on the thermal conductivity of nanofluids was found to be greater than that of reaction-limited aggregation, and the effect of different aggregation structures on the diffusion coefficient of nanofluidic systems may be one of the potential mechanisms affecting the thermal conductivity of nanofluids.

ZnO nanoparticles were synthesized from C. sativum adopting green synthesis. Optical property of ZnO particles thus obtained was studied by UV spectral data, size of the particles was determined from XRD studies and morphology established from SEM micrographs. XRD data revealed the hexagonal wurtzite structure of the ZnO sample, size of the particles was about 74 nm obtained from Scherrer equation. ZnO particles appear as an agglomerate of nanoflakes. Investigation of gas sensing property establishes that the material exhibits excellent sensing performances including high gas response, good selectivity, fast response/recovery time.

Gas bubble distribution is considered one of the most critical factors affecting the Industrial Fluid Coking™ process since it influences the formation of wet agglomerates that causes fouling in the stripper section. A multi-phase Eulerian–Eulerian two-fluid method (TFM) coupled with the kinetic theory of the granular flow (KTGF) was used to investigate the hydrodynamics of a bubbling fluidized bed; the goal is to increase the flow of gas bubbles into the first half of the jet cavity formed when liquid is sprayed into the fluidized bed, thus reducing the formation of wet agglomerates. The numerical simulations under different superficial gas velocities, different gas distributor geometries, and different gas distributor inclined angles were carried out. The results showed that the predicted bubble distributions at the injection level under the lab and commercial operating conditions are similar although the particles and gases are different under those two operating conditions. More gas bubbles can be directed to the first half of the jet cavity by either increasing the gas superficial velocity (directing around 20% more gas to the specified area) or using the proposed new gas distributor (directing around 30% more gas to the specified area). The effect of the inlet gas distributor configuration on the bubble distribution is much more substantial when the inclined angle of the gas distributor is large.

In this paper, Al2O3–TiC/ZL101 composites were fabricated via in-situ reaction process with TiO2, Al, graphite and ZL101 powders. Microstructure characteristics, formation mechanism of reinforcements, thermodynamic calculation of reaction, hardness and tribological behavior of the composites were investigated in detail. The distribution of Al2O3 and TiC precipitates changes from agglomerate to relative uniform with the content rise of strengthening phases. Al2O3 precipitates are irregular spherical with the average size of 3–5 μm. The shape of TiC particles is cube or polygon and the size is about 2–4 μm. The thermodynamic calculation of reactants further proves the reinforcements formation, which is consistent with the microstructure observation and X-ray diffraction result. The formation mechanism of TiC and Al2O3 mainly is by diffusion and precipitation. The microhardness and wear performance of composites remarkably improve, friction coefficient and wear weitgh loss decrease with the content rise of TiC and Al2O3 phases. The microhardness of C3 composite increases from 93HV to 162HV, the friction coefficient (FC) and weight loss decrease from 1.15 and 0.128g to 0.43 and 0.066g compared with the ZL101 alloy. C3 composite has the best wear property for the highest hardness, the lowest FC and weight loss. Microstructure refinement, uniform dispersion of TiC and Al2O3 precipitates and the strong interfacial adhesion between reinforcements and matrix are attributed to the better wear performance of composites. The wear surface morphology shows that the wear mechanism of ZL101 alloy is mainly adhesive wear while the wear style of the composites is abrasive wear.

A CFD-DEM coupled with a cohesive contact model is developed for simulation of a Wurster fluidized bed with heat and mass transfer. First, the water evaporation and cohesive contact sub-models are tested, respectively. Second, a Wurster fluidized bed with heating, drying, and wet particle fluidization is simulated. Results show that the particle temperature in the bottom and draft tube rises faster than that in the annular region, which leads to the probability density distribution of the particle temperature presents two peaks. The circulation pattern also has a significant effect on particle drying. Under conditions with a small amount of liquid injection, the water evaporates immediately and the particles are fluidized normally. Increasing the liquid injection rate, the stability of the particle circulation decreases. Under conditions with significant particle cohesion, large agglomerates are formed and the fluidization breaks down. The current study provides an effective method for studying hydrodynamics of Wurster fluidized beds with simultaneous processes of heating, drying, and wet particle fluidization.

The present study evaluates elastic and inelastic contact forces in predicting the fluidization characteristics of irregularly shaped Titania nanoparticle agglomerates in a bench-scale conical fluidized bed. At first, experiments were performed to identify the mutual effects of gas velocity and agglomerate size on the instantaneous pressure, bed pressure drop and bed expansion ratio. Rigid complex-agglomerates (∼100−200 μm) were mainly formed in the partially fluidized regime, while soft simple-agglomerates (∼20−70 μm) were primarily formed in the spouting regime. The simulations were performed through the CFD-DEM approach. The error analysis of results in the partially fluidized regime revealed that the combination of Hertz-Mindlin and Johnson-Kendall-Roberts (HM + JKR) model led to a better prediction of the bed pressure drop and bed expansion ratio than the spring-dashpot (LSD) model. In the transition flow regime, the Hysteretic model led to better results of the instantaneous pressure values than those proposed for other flow regimes. In the spouting flow regime, the HM and Thornton models led to over-estimation of bed pressure drop when compared to the LSD model. The comparative results of this study provide promising new insights into the collision mechanism of polydisperse agglomerates in different flow regimes for industrial aspects.

The chemical agglomeration technology can effectively remove fine particles during coking coal loading and unloading. Aiming at the traditional agglomerator has the high price and secondary pollution problems, the new method of viscosifying fine particles was established. The fine particles were contacted with the soap solution through the cyclone circumfluence to increase viscosifying and agglomerate. The regulation and control of uniform humidification of whole particles were studied, and the relations among humidification, agglomeration, dust suppression and agglomeration conditions of fine particles were discussed. By establishing the agglomeration model and mechanical model, the influence of agglomeration on the force and velocity distribution of particles was analyzed based on CFD. The results showed that the soap solution has a strong effect on agglomeration of particle size less than 0.5 mm. The adsorption and flocculation of the polymer chain in the soap can promote the agglomeration of the fine particles. In the area of vortex formed by swirling air, with the mass addition ratio of soap powder increases from 5% to 15%, the coating efficiency of fine particles increases from 82% to 96%. The agglomeration results show that the average concentration of the fine particles decreases by nearly 20% finally.

A survey of cadmium plated field return hardware showed ubiquitous cadmium whisker growth. The most worn and debris-covered hardware showed the densest whisker growth. Whiskers were often found growing in agglomerates of nodules and whiskers. The hardware was rinsed with alcohol to transfer whiskers and debris from the hardware to a flat stub. Fifty whiskers were studied individually by scanning electron microscopy (SEM), including energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD). Most of the whiskers were single crystal, though three were found to contain grain boundaries at kinks. The whiskers ranged from 5 to 600 μm in length and 80 pct showed a < $$\overline{1 }$$ 2 $$\overline{1 }$$ 0> type growth direction. This growth direction facilitates the development of low energy side faces of the whisker, (0001) and {1010}.

High-resolution transmission electron microscopy (HRTEM) was used to observe the soot particles emitted from gasoline direct injection (GDI) engine equipped with metallic particulate filter (GPF). The changes of microscopic morphology and structure of the soot particles at pre-GPF and post-GPF were studied at a fixed speed of 1500 r/min and 25 %, 50 % 75 % and 100 % load, respectively. Furthermore, the micro-parameters of the primary particles that make up the soot particles were analyzed. The results show that the primary particles are approximately spherical, and agglomerate to form irregular shapes such as chains, branches and rings. The load and GPF have no significant influence on the microscopic morphology of the soot particles, the fractal dimension of soot particles at both ends of the GPF increases with the increase of load. Under the experimental conditions of the engine, most primary particles consisting of the soot particles are “shell-core” structure; The fringe length, tortuosity and interlayer spacing of the primary particles at pre- and post-GPF are monomodal. Among them, the average fringe length increases with the increase of load, while both the average tortuosity and average interlayer spacing change the opposite. These indicated that the degree of graphitization of the soot particle increases with the increasing load. Load and GPF only affect the micro-structure parameters of the primary particles and have no effect on its distribution.

We describe an in situ facile synthetic approach to prepare carbon quantum dot (CQD) fluorescent markers (FMs) for polyethylene (PE) in the presence of agglomerated silica nanoparticles (SiO2 NPs) under mild reaction conditions. First SiO2 NPs, prepared by the Stöber method, were dispersed in toluene. This dispersion was added to a PE solution in toluene. After heating (either in air or under Ar) a fluorescent mixture was obtained. After drying, PE films were obtained by compression molding, which showed strong blue fluorescence, attributed to CQDs. SiO2 NPs loading values varied between 0.5 and 4 wt %. Subsequent to isolation, the fluorescent CQDs were characterized by TEM, UV-vis, and fluorescence spectroscopy. TEM imaging unveiled a lattice spacing value of 0.21 nm of the isolated fluorescent particles which is typical for (100) graphite plane lattice spacing in CQDs. UV spectroscopy and fluorescence measurements show characteristic absorption and excitation spectra for the aromatic core and oxidized surface defects typically observed for CQDs. The emission maximum for PE/CQD samples increased from 394 to 408 nm when the reaction temperature was decreased from 110 to 90 °C, which is attributed to increasing oxygen content in the reaction mixture upon decreasing the reaction temperature. When the reaction was performed under Ar, the PE/CQD samples emitted in the ultraviolet region (286 nm). Finally, we demonstrated that PE samples marked with CQDs can be easily visually identified upon irradiating with 367 nm light. Thus, the marked PE can be used, for example, as a labeling ingredient in master batches for component identification and in recycling.

Aluminum powder can increase the specific impulse and improve the combustion performance of a solid propellant; however, agglomeration can result in the loss of two-phase flow, a decrease in specific impulse of the propellant, and an increase in the thermal protection pressure of the motor structure. This study employs digital inline holography, which offers the advantage of non-contact three-dimensional measurements, to investigate the agglomeration particle size near the burning surface. This study aims to quantitatively analyze these particle size data to determine the effects of pressure, ammonium perchlorate particle size, coarse and fine ammonium perchlorate content ratio, and aluminum particle size on the agglomeration particle size distribution. The experimental results indicate that increasing the pressure from 0.1 MPa to 0.8 MPa reduces the average particle diameter of agglomeration by at least 9.6%, results in a more concentrated agglomeration particle size distribution, and decreases the volume and number proportion of agglomeration by approximately 7% and 17%, respectively. Furthermore, when the particle size of ammonium perchlorate decreases from 250 μm to 90 μm, the agglomeration particle size distribution becomes more concentrated, the average diameter of agglomeration decreases by at least 37.4%, and the number and volume proportion of agglomeration decrease by approximately 13% and 44%, respectively. The ratio of coarse and fine ammonium perchlorate content has a nonlinear effect on agglomeration. When this ratio is 0.6, the average agglomerate diameter decreases by at least 16%, the agglomeration particle size distribution is more concentrated than that the ratio is 0.39 and 1.29, and the agglomeration number and volume fraction decrease by more than 6% and 32%, respectively. Moreover, decreasing the initial aluminum particle size from 30 μm to 15 μm reduces the average agglomeration particle diameter by more than 21.6%, results in a more concentrated agglomeration particle size distribution, however, increases the number and volume proportion of agglomeration by approximately 17% and 8%, respectively. The conclusions of this study are expected to be significantly helpful in optimizing propellant formulation, reducing the particle size of aluminum agglomeration, and improving the combustion performance of propellants.

The size distribution and morphology evolution of the initial agglomerates on the burning surface of aluminized composite propellants have a strong influence on the agglomeration mechanism and size of condensed products. However, most previous research has focused on the establishment of size prediction models, and research on other characteristics of initial agglomerates is still lacking. The characteristics of the size distribution and evolution of the morphology of the initial agglomerates are investigated in this study. Analysis of the size distribution of the initial agglomerates shows that the distribution is regular in the stable combustion stage, and the agglomerates in this stage show weak agglomeration. The morphologies of the initial agglomerates are found to comprise coral-like structures composed of small alumina particles with strong fluidity in Stage (a), in which the effect of accumulation is dominant. In Stage (b), the initial agglomerates exhibit a relatively stable form of a ‘spherical structure + coral-like bond’, and the effects of accumulation and combustion are in dynamic equilibrium. In Stage (c), the initial agglomerates are spherical with an oxidation cap, and this stage is dominated by combustion. Through analysis of the characteristics of the size distribution and morphology evolution of the initial agglomerates, the agglomeration mechanism of aluminum particles on the burning surface is further clarified, which provides the foundation for further research.

Актуальность исследования обусловлена отсутствием эффективных методов и средств борьбы с загрязнением атмосферы субмикронными частицами размером менее 2,5 мкм. Применяемое для этих целей ультразвуковое воздействие не позволяет обеспечить степень укрупнения дисперсных частиц, достаточную для их осаждения или улавливания существующим газоочистным оборудованием. Как показывают экспериментальные исследования, даже при максимальном уровне звукового давления (при превышении которого инициируется обратный процесс - диспергирование капель или разрушении агломератов частиц) эффективность ультразвуковой коагуляции оказывается недостаточной, особенно при малой счетной концентрации частиц. Это обуславливает необходимость выявление новых физических эффектов и разработки новых способов воздействия, повышающих эффективность коагуляции тонкодисперсных частиц. Цель: разработка способа для повышения эффективности ультразвуковой коагуляции частиц размером менее 2,5 мкм за счет формирования вихревых акустических течений в тонком воздушном промежутке между излучателем и отражателем и создание устройства для его практической реализации. Результаты. Предложен новый способ и устройство для очистки газов от дисперсных частиц размером менее 2,5 мкм за счет увеличения времени ультразвукового воздействия на каждую частичку и создания зон локального увеличения концентрации субмикронных частиц. Это обеспечивается за счет формирования вихревых потоков между излучающей (в виде изгибно-колеблющегося диска) и отражающей поверхностями. Локальная зона повышенной концентрации частиц формируется в периферийной области вихря за счет дрейфа частиц под действием центробежных сил из центральной области вихря к его периферии. Предложенный способ обеспечивает повышение эффективности с 13 до 50 %, в зависимости от исходной концентрации дисперсных частиц. The relevance of the research is caused by the lack of effective methods and means of combating atmospheric pollution with particles less than 2,5 microns in size. The ultrasonic effect used for these purposes does not allow ensuring the degree of coarsening of dispersed particles sufficient for their sedimentation or capture by the existing gas cleaning equipment. Experimental studies show that even at the maximum sound pressure level (above which the reverse process - the dispersion of drops or the destruction of particle agglomerates - is initiated), the efficiency of ultrasonic coagulation is insufficient, especially at a low counting concentration of particles. This necessitates the identification of new physical effects and the development of new methods of ultrasonic exposure, providing an increase in the efficiency of coagulation of fine particles. The main aim: development of a method for increasing the efficiency of ultrasonic coagulation of particles less than 2,5 microns in size due to emerging vortex acoustic flows in a thin air gap between the emitter and the reflector and a device for its implementation. Results. The authors have proposed a new method and device for cleaning gases from dispersed particles less than 2,5 microns in size by increasing the time of ultrasonic action on each particle and creating zones of local increase in the concentration of fine and submicron particles. This is provided by the formation of vortex flows between the emitting (in the form of a flexural-vibrating disk) and the reflecting surfaces. A local zone of increased concentration of particles is formed in the peripheral region of the vortex, due to the drift of particles under the action of centrifugal particles from the central region of the vortex to its periphery. The proposed method provides the increase in efficiency from 13 to 50 %, depending on the initial concentration of dispersed particles.

The effect of iron carbon agglomerates (ICA) on the reduction of pellet (or sinter) is very important to the smelting efficiency of BF. In this paper, the effect of addition amount of ICA on the re...

Nickel (Ni) nanoparticles (NPs) prepared through vapor-phase synthesis (VPS) are preferred for multilayer ceramic capacitor electrodes due to their high purity and crystallinity advantages. Agglomerated Ni NPs are usually generated using VPS but are undesirable because they cause various problems such as low packing density and electrical shorts. This study proposes the use of coating-assisted chemical vapor synthesis (CVS) for agglomerate inhibition using NaCl or KCl as a coating agent. We have found that the agglomeration ratio, 34.40%, for conventional CVS, can be reduced to 4.80% in the proposed method by in-flight coating with KCl at 900 °C by image analysis using field-emission scanning electron microscopy. Furthermore, the X-ray diffraction and X-ray fluorescence analyses confirm that the NaCl and KCl coating agent can be removed by washing with distilled water. We believe that this coating process can be used to inhibit the formation of agglomerates during the CVS of Ni NPs.

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.

Hydrodynamics of fluidization of hydrophilic titanium nanoparticles with vibration was investigated through pressure fluctuations using recurrence quantification analysis. The bed expansion revealed that the bed operates in the ABF regime. The standard deviation of the pressure fluctuations indicated that vibration reduces the minimum fluidization velocity. Hydrodynamic structures were defined using the wavelet transform analysis of pressure fluctuations and the effect of vibration was investigated through the energy of the pressure signal and the recurrence analysis. It was shown that the agglomerates have the most impact on the fluidization of the nanoparticles and vibration has a significant effect on this structure. Using the energy of the signal and recurrence analysis, characteristics of the vibration on the fluidization were defined. The energy of finer structures is higher in the vibrated bed, indicating a more stochastic pattern in this case. The recurrence rate showed the dynamic behavior of formation and breakage of agglomerates in the bed.

Photocurable systems are used in solid freeform fabrication by vat photopolymerization. This process requires a photopolymerization reaction to form layers selectively. The light interaction with the reactive medium results in scattering and absorption governing cure depth. This is further modeled in Jacob's equation. This study examined the cure depth model for alumina and silver suspensions as a function of compositional variables and energy dose. It included studying the effect of agglomeration, which showed that the cure depth reduces with fewer coarse agglomerates. Furthermore, in highly dispersed systems, the role of particle sizes, solid contents, refractive indices, and extinction coefficients were examined. The key results show that the cure depth has a proportional relationship with particle size. It is also independent of solid content for systems with smaller refractive index differences and extinction coefficients, which was explained through depth attenuation and critical energy dose.

With the advantages of high power density, long cycle life, and fast charging, supercapacitor has become a research hotspot in recent decades. Graphene is considered as an ideal electrode material for supercapacitors because of its special electrical and mechanical properties. In order to prepare graphene that can be used as supercapacitor electrode materials, various methods are proposed, among which hydrothermal method is mostly used, but graphene prepared using this method always agglomerates seriously and rarely have pores that might be helpful for the increase of electrochemical performance. Therefore, sodium alginate, which has strong hydrogen bonding with graphene oxide and might be helpful to optimize the structure of graphene in the reduction process, should be considered. In this paper, by optimizing the ratio of reducing agent and graphene oxide in hydrothermal reaction, two samples that exhibit better performance were obtained. On this basis, sodium alginate was added in the process of hydrothermal reduction of graphene oxide, and the effect of it on the structure and properties of graphene was explored. The results demonstrate that pore structure is formed and the rate performance is improved obviously by adding sodium alginate.

Investigation of the parameters affecting the agglomeration process of nanoparticles and its morphology is a challenging research problem. In recent years, various computer simulation methods are d...

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.

Since agglomerates in catalyst inks affect the catalyst layers (CL) and membrane electrode assemblies (MEA) of proton exchange membrane fuel cell (PEMFC), it is important to study the connection among catalyst agglomerates, CL structure, and MEA performance. This study investigates the effect of Pt/GC catalyst agglomerates on the morphology and permeability of the CL by modulating the properties of the catalyst ink in two different ways. Additionally, MEA was further electrochemically tested to understand the relationship between the catalyst agglomerates and MEA performance. The result shows that High-pressure homogenization is more effective than mechanical shear mixing in dispersing the agglomerates in catalyst inks. However, the excessive homogenization pressure produced larger agglomerated particles, probably because more effective dispersion caused by higher homogenization pressure supplies new chain carriers for polymerization and higher temperature caused by higher homogenization pressure. Moreover, the surface of the CL fabricated in inks prepared by a homogenizer is more uniform, neat, and hydrophilic. But the number of secondary pores in the catalyst layer decreases at excessive homogeneous pressure, and the water permeability becomes poor, which in turn result in lower performance and higher mass transfer resistance. The electrochemical performance test results showed that the MEA with a relatively hydrophobic CL had a performance of 0.707 V at 1000 mA cm−2, which was 30 mV higher than that with a relatively hydrophilic CL. This study provides insights for better tuning the properties of catalyst ink, CL morphology, and permeability to obtain better performance of MEA.

This paper highlights the relationship between changes in structural and morphological features, electronic structure and exanging of time mechanical treatment at microbraker (MBT). Scaning electron microscopy revealed a change in the morphological features of nanoscale powders. From the comparison of SEM images of 0.8SiO2/0.2Al2О3 mixture before and after MBT, it is established that due to MBT, the agglomerates of the initial components are simultaneously crushed with perfect mixing particles of oxides between each other and the formation of new agglomerates with a denser structure. The increase in processing time leads to an increase in the density of the nanocomposite. The effect of time of mechanical treatment on the structural parameters and phase composition of mixtures of silicon dioxide and titanium were studied using the method of X-ray structural analysis. The established agglomeration is accompanied by a change in the lattice parameter c with a change in the regions of coherent scattering of crystalline Al2О3. Ultra-soft X-ray emission spectroscopy was used to study the distribution of Op-, Sisd- and Alsd- valence electrons in 0.8SiO2/0.2Al2О3 powder mixtures after the different time of mechanicall treatment. An increase in atomic charges has been measured and can be explained by the transfer of electrons from Si and Al to O atoms in split Opπ-binding states.

During agglomeration in the nozzle zone of spray dryers, dry particles are forced to collide with drying droplets. These collisions ideally form agglomerates with improved flowability and reconstitution properties. However, the interactions of feed parameters on the collision outcomes are unclear. This study examines the influence of a varied total solid content of the feed solution on agglomerate formation in a pilot plant spray dryer. An increase in total solid content (TS) from 30 to 50% TS (w/w) resulted in an increase in porosity of the primary particles, whereby particle size development was reasoned by this effect. Agglomerate porosity increased but agglomerate size increased more due to a changed particle viscosity. By adding a marker powder, it was found that higher total solid contents resulted in less coalescence of the agglomerates. The counter-current air classification in the drying chamber affected the agglomerate properties such as size, density and shape.

The ionomer state in the catalyst ink of a proton exchange membrane fuel cell (PEMFC) plays a critical role in the formation of the catalyst/ionomer interface on the catalyst layer (CL). In this study, the effect of ionomer dispersion state on catalyst ink dispersion and the construction of a reasonable CL was investigated. The study of catalyst inks revealed that the dispersion of n-propanol (NPA) -ionomer dispersion or sonication could effectively reduce the catalyst particle size in inks. For shear-dispersion and homogenizer-dispersion inks, the catalyst particle size was reduced from 6.17 nm to 5.12 nm and from 5.12 nm to 4.67 nm, respectively. The ionomer dispersion was capable of significantly reducing the size of agglomerates in the ink, which resulted in a reduction in the particle size of agglomerates on the surface of the cathode CL and an improvement in its flatness. The pore size distributions of the MEA cathode catalyst layers showed that water bath ultrasonic treatment of the ionomer could result in a more reasonable pore structure for the catalyst layer. The single-cell test revealed that changing the ionomer's dispersion state could significantly increase the fuel cell's output voltage to 0.707 V at 1000 mA cm−2, and the cell's power density to 1028 mW cm−2 at 2000 mA cm−2.

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.

Micromotors are fascinating objects that are able to move autonomously and perform various complex tasks related to drug delivery, chemical processes, and environmental remediation. Among the types of micromotors, droplet-based micromotors are characterized by a wide range of functional properties related to the capability of encapsulation and deformation and the possibility of using them as microreactors. Relevant problems of micromotor utilization in the chemical processes include intensification of mixing and locomotion of passive objects. In this paper, the technique for preparation of superfast active droplets, which can be used as micromotors for effective locomotion of passive droplets in the oil-in-water emulsion, is demonstrated. The possibility of passive droplet locomotion in the emulsion is determined by a relation between the diameters of active and passive droplets. If the diameter of active droplets is larger than the diameter of passive droplets, the agglomerates form spontaneously in the emulsion and move in a straight line. In the case of the opposite relation between diameters, the agglomerates consisting of active and passive droplets rotate intensively. This makes it impossible to move the passive droplets to a given distance. Such micromotors can achieve unprecedentedly high velocities of motion and can be used to intensify mixing on the microscales.

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.

Arrays of nanowires can be fabricated by template synthesis for use as active substrates for surface-enhanced Raman spectroscopy. When the substrates dry during the manufacturing process, nanowires agglomerate on the surface. At a certain height of nanowires, only their ends stick together, which is necessary for the efficient formation of hot spots on substrates for surface-enhanced Raman spectroscopy. Sticking together at a given height of nanowires is determined by the equilibrium of the elastic energy of their bending and the energy of formation of a unit of free surface.

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.

Gd2(WO4)3 and Gd2(WO4)3:0.5% Tm3+, 10% Yb3+ nanopowders have been prepared by the Pechini method and solid-state sintering. According to X-ray diffraction results, the materials prepared by the Pechini method are more uniform in phase composition. Optimal synthesis conditions were defined: t = 900°C and τ = 1 h for Gd2(WO4)3 and t = 950°C and τ = 3 h for Gd2(WO4)3:0.5% Tm3+, 10% Yb3+. The surface morphology of the materials has been studied by scanning electron microscopy. The samples prepared by solid-state sintering have been found to be highly agglomerated, and large agglomerates have been shown to persist even after ultrasonic processing. The average size of the doped and undoped nanoparticles prepared by the Pechini method has been determined to be 44.0 and 47.6 nm, respectively. Luminescence spectra of Gd2(WO4)3:0.5% Tm3+, 10% Yb3+ were measured and compared the intensities of the Tm3+ 1G4 → 3H6, 1G4 → 3F4, 3F1,2→3H6, and 3H4 → 3H6 radiative transitions in the materials prepared by both methods. The data obtained in this study demonstrate that the Pechini process is a preferable and promising method for the synthesis of Gd2(WO4)3 and Gd2(WO4)3:Tm3+,Yb3+ nanopowders.

Carbothermal reduction-nitridation method is an effective means for synthesizing Si3N4 powder. Herein, spherical monodisperse silica was used as silicon source. The effects of reaction temperature, nitrogen flow rate and Si3N4 seeds content on the products were studied. It was found that high-purity α-Si3N4 (>99.0 wt%) was synthesized from C/SiO2 = 3:1 at 1400 °C, reaction time of 6 h and nitrogen flow rate of 800 ml/min. The powder, with an average size of 0.5 μm, showed good dispersity and regular morphology because spherical monodisperse silica could be completely coated with carbon. The more contact sites between SiO2 and C, the higher concentration of SiO(g) would be produced in the initial stage. It also indicated that the nucleation rate of α-Si3N4 increased, thereby inhibiting the formation of an agglomerate phase and suppressing the grain growth of α-Si3N4. Furthermore, higher nitriding temperature and Si3N4 seeds content both decreased the grain size and increased β-Si3N4 content. The forming mechanism of non-agglomerated and submicron-sized α-Si3N4 was clarified.

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.