The properties of particle ensembles are defined by a complex multidimensional parameter space, namely particle size, shape, surface, structure, composition and their distributions. Macroscopic product properties are a direct result of these disperse particle properties. Therefore, the comprehensive multidimensional characterization of particle ensembles is a key task in any product design. However, the determination of complex property distributions is major challenge. We provide a broad overview of the current tools for multidimensional particle characterization. First, the mathematical handling of multidimensional (nD) property distribution is outlined as a necessary framework for the correct handling of nD particle size distributions (PSDs). Then, well-established techniques as well as recent developments with the potential to extract nD property distributions are reviewed. Ex situ imaging techniques like electron tomography or Raman spectroscopy with AFM co-localization, for instance, provide a resolution on the level of single particles but are limited in terms of sample statistics. A particular focus lies therefore on methods in the gas and the liquid phase, which provide multidimensional particle properties either directly or by a combination of one-dimensional techniques.

Understanding the flowability of cohesive powders at high temperature is of great importance for many industrial applications where these materials are handled at harsh thermal conditions. For instance, the Calcium-Looping (CaL) process, involving the transport, storage and fluidization of limestone powders at high temperature, is being considered nowadays as a promising technology for thermochemical energy storage (TCES) in concentrated solar power plants (CSP). In this context, the High Temperature Seville Powder Tester (HTSPT) is presented in this work as a useful tool to analyze how the flow behavior of cohesive powders changes with temperature. The manuscript reviews the main results obtained so far using this novel apparatus. The change of powder cohesiveness and therefore of powder flowability as depending on temperature, particle size, material properties and nanosilica surface coating is illustrated.

The aerosol particles play a significant role in the environment and human health. They are also increasingly used in medicine (drug carriers), preparation (nanocatalysts) and many other fields. For these applications, the particles have to possess unique properties which arise directly from their structure and topology. Indeed, the functionality of the nanostructure particle is defined through its application, like chromatography, sensors, microelectronics, catalysis, and others. That is the reason why people are more and more interested in manufacturing structured particles. The structured particles are the particles with well-defined topological structure. Examples of such particles are porous particles, hollow particles (with the empty space inside), or multi-component particles with the segregation of components in the particle structure. Such particles usually have very interesting features, e.g. porous particles have a significantly larger surface area than the simple spherical particles with similar volume. The present paper contains a comprehensive review of the numerical simulation methods of the formation of highly ordered structured particles. The most important methods will be described in detail and their fields of application (with specific examples), advantages, limitations and information about their accuracy will be given.

Particle breakage occurs in comminution machines and, inadvertently, in other process equipment during handling as well as in geotechnical applications. For nearly a century, researchers have developed mathematical expressions to describe single-particle breakage having different levels of complexity and abilities to represent it. The work presents and analyses critically a breakage model that has been found to be suitable to describe breakage of brittle materials in association to the discrete element method, either embedded in it as part of particle replacement schemes or coupled to it in microscale population balance models. The energy-based model accounts for variability and size-dependency of fracture energy of particles, weakening when particles are stressed below this value, as well as energy and size-dependent fragment size distributions when particles are stressed beyond it, discriminating between surface and body breakage. The work then further validates the model on the basis of extensive data from impact load cell and drop weight tests. Finally, a discussion of challenges associated to fitting its parameters and on applications is presented.

Inherent challenges regarding the rheological characterization of slurries of elongated particles have necessitated the development of alternatives to standardized rheometers. These methods of measurement, and the associated advances in the quantification of shear and normal stress measurements, are described. Also, recent advances in modeling and predictive capabilities are summarized. During shearing flows, confinement substantially influences the orientation distribution of the particles; this change in the microstructure impacts the rheology, even as the smallest confining dimension exceeds seven particle lengths. The slow development of the orientation distributions renders additional difficulties in evaluating the rheology. Achievements of the measurement methods include a universal shear viscosity as a function of concentration for a wide range of particle lengths to diameters (aspect ratios). The jamming limit (divergence of the viscosity with concentration) of the suspensions has been also shown to scale differently than for spheres. More general dynamics of the suspensions and the additional needs for measurement improvements are discussed.

Dockage and foreign material (DFM) distribution in grain silos is an important factor in managing stored grain. The DFM distribution in grain silos is dictated by the segregation mechanisms of DFM during grain loading. Loading grain into silos from a central spout is a special case of heap flows of granular materials. However, our understanding of heap flows is still evolving, and no models are currently available to predict the dockage and foreign material distribution in grain silos. Based on an extensive literature review, this paper identified the dominant mechanisms of DFM segregations during central spout filling in grain silos and main factors influencing DFM distribution. The DFM distribution patterns were characterized. The experimental methods for analyzing DFM segregations and distribution were also reviewed. The gaps of our knowledge on segregation mechanisms and factors influencing segregation were summarized and future research directions and challenges were discussed.

The synthesis of noble metals and their alloy nanoparticles by laser-induced nucleation is described. Femtosecond laser pulses with an energy on the order of mJ were tightly focused to create an intensity of 10¹⁴ W/cm² or more in an aqueous solution of noble metal ions. The intense laser field generated solvated electrons and hydrogen radicals that have a highly reducing ability, resulting in nucleation through the reduction of the noble metal ions and particle growth through ripening. This laser-induced nucleation method can be performed without any reducing agents. Excess irradiation of chloroauric acid solution led to the formation of a stable colloidal solution of gold nanoparticles without any surfactants. Additionally, the irradiation of a mixed solution of different noble metal ions formed solid–solution alloy nanoparticles, even though these metals were immiscible in the bulk. Moreover, the laser-induced nucleation made it possible to form quinary solid-solution alloy nanoparticles of noble metals. The mechanism of superior catalytic activity found for alloy nanoparticles by using Rh–Pd–Pt solid–solution nanoparticles is discussed in terms of elemental distributions inside the particles.

Recently, various types of functionalized metal oxide nanoparticles have been used for many applications because of their unique chemical and physical properties. To synthesize metal oxide nanoparticles, liquid-phase synthesis techniques have been developed. The production process of metal oxide nanoparticles in aqueous media is extremely complex because the formation, crystal structure, crystallinity, chemical composition, and morphology of the particles are considerably dependent on the preparation conditions (e.g., anion and cation concentrations and species, additives, solution pH, reaction temperature, and reaction time). Accordingly, clarifying these effects is fundamental to accurately understand the formation mechanism of metal oxide nanoparticles to further develop new functionalized nanoparticles. In this review, the influence of anions (Cl⁻, SO₄²⁻, and NO₃⁻) and cations (Ni²⁺, Cu²⁺, and Cr³⁺) on the formation and structure of iron oxide nanoparticles in aqueous media is described.

Li-ion batteries with “nickel” as the main material or the highest ratio material on the cathode or anode electrode have attracted considerable attention. Nickel has high strength and corrosion resistance. Nickel has also been utilized successfully as the cathode and anode materials. The specific capacity and energy and power density of the material increased with increasing nickel content. However, several problems have limited the use of nickel-based Li-ion batteries. Problems such as cation mixing, the properties of nickel, and highly Ni-rich compounds leading to side reactions, influence the electrochemical performance of Li-ion batteries. The morphology is another factor affecting the electrochemical performance. Further studies will be needed to synthesize materials with the desired morphology and determine how the morphology affects the electrochemical performance. In a morphological perspective, extensive morphological adjustments are a pathway to a long and stable life cycle. In this light, nickel-based electrodes are manufactured continuously and will always be considered for next-generation secondary energy storage. The morphology of nickel-based active materials is one of the main factors determining the high-performance of Li-ion batteries.

A variety of dosage forms have been developed in order to achieve effective and safe drug delivery in topical or systemic drug administrations. In this review, formulation research and process issues related to a popular oral dosage form, the tablet, are introduced. Research on oral dosage forms, including orally disintegrating tablets (ODTs) and films (ODFs), which have recently been developed with an aim toward more patient-centric drug therapy, is also introduced. Another trend in recent drug therapy is an increase in the number of large bioactive molecules among the newly developed active pharmaceutical ingredients (APIs). To design dosage forms for these APIs, novel dosage form design and administration routes are required. For this purpose, we have tried to effectively use the polymer-coated liposomes in oral, pulmonary and ophthalmic administration. For example, suitable polymers were introduced for the design of specific administration routes, such as mucoadhesive liposomes for oral administration. The key point in these researches is the particle design for the component particles of final dosage forms, both in the case of coarse powder particle design for formulating solid dosage forms and in the case of colloidal particle design, such as the design of liposomes for peptide drug delivery.

While the formulation of pharmaceuticals as liquids is common practice, powders are associated with enhanced stability, avoidance of the cold chain, lower dosing requirements, and more convenient administration. These are particularly critical for proteins, as they are expensive and complicated to manufacture. Powders also have improved aerosol properties for pulmonary delivery. Conventional techniques for formulating powders include spray-drying, shelf freeze-drying, spray freeze-drying, and spray freezing into liquid, but they produce powders with poor aerosol performance and/or activity due to suboptimal powder properties. Thin-film freezing (TFF) is a new cryogenic technique that can engineer highly porous, brittle, powder matrices with excellent aerosol performance properties and stability. Herein, we describe TFF in comparison to other cryogenic techniques. Physical properties of TFF powders such as morphology, moisture sorption, stability, solubility, and dissolution, as well as aerosol properties are discussed. In addition, factors that significantly affect the physical and aerosol properties of dry powders prepared by TFF, such as solids content, drug loading, solvent system, excipient, and dry powder delivery device, are analyzed. Finally, we provide evidence supporting the applicability of using TFF to prepare dry powder formulations of protein-based pharmaceuticals, enabling their cold chain-free storage as well as efficient pulmonary delivery.

The grain sizes can significantly influence the granular mechano-morphology, and consequently, the macro-scale mechanical response. From a purely geometric viewpoint, changing grain size will affect the volumetric number density of grain-pair interactions as well as the neighborhood geometry. In addition, changing grain size can influence initial stiffness and damage behavior of grain-pair interactions. The granular micromechanics approach (GMA), which provides a paradigm for bridging the grain-scale to continuum models, has the capability of describing the grain size influence in terms of both geometric effects and grain-pair deformation/dissipation effects. Here the GMA based Cauchy-type continuum model is enhanced using simple power laws to simulate the effect of grain size upon the volumetric number density of grain-pair interactions, and the parameters governing grain-pair deformation and dissipation mechanisms. The enhanced model is applied to predict the macroscopic response of cohesive granular solids under conventional triaxial tests. The results show that decreasing grain-sizes can trigger brittle-to-ductile transition in failure. Grain size is found to affect the compression/dilatation behavior as well as the post-peak softening/hardening of granular materials. The macro-scale failure/yield stress is also found to have an inverse relationship with grain-sizes in consonance with what has been reported in the literature.

The simulation of grinding mills with the discrete element method (DEM) has been advancing. First, it emerged as a method for studying charge motion with spherical balls and predicting the power draw of the mill. Subsequently, studies on liner wear, charge motion with ellipsoidal and polyhedral shaped particles simulated with three dimensional DEM followed. Further, the impact energy spectra computed in the DEM algorithm is leading to the development of models for the breakage of brittle particles in mills. The core elements in such simulations are the shape of particles in the mill charge and the power draw of the mill due to operating variables. To advance the field, we present a set of experimental data and the corresponding DEM validation results for a 90 × 13 cm mill. The DEM algorithm uses the volume-overlap method which is more realistic for multifaceted irregular particle collisions. Further, we use the scanned shape of the rock media and multifaceted spherical shape for the grinding media to represent as close as possible the actual charge in the mill. First, we present DEM validation for spherical grinding media-only experiments, rock-only experiments, and a mixture of spherical grinding media and rocks, as well as aluminum cubes only to represent the theme of particle shape. Finally, a discussion of the contact mechanics parameters in the four modes of experiments is given. Since the feed ore to plant scale mills can vary in shape, mill simulations with scanned shape of typical particles are the future for more accurate results.

The central concern in the fabrication of carbon nanotube (CNT) reinforced metal composites is the well balance between uniform dispersion and structural integrity of CNTs. Rapid and uniform self-assembly of CNTs and spherical Aluminum (Al) particles into a core-shell structure is realized by a smart mechanical powder processing. The factors influencing the dispersion uniformity and structural integrity of CNTs during the processing are studied, including the size of Al particles, mixing speed and mixing time. It is revealed that a size of 35 μm is preferred for the Al particles to tear apart the CNT clusters and obtain a uniform dispersion of CNTs on Al surface. Different composite states, CNTs are singly dispersed, thickly wrapped, or embedded in the Al particles, can be obtained by changing the mixing speed. Well coordination between the CNT dispersion homogeneity and structural integrity could be achieved under suitable processing condition. Therefore, it can be adopted as an efficient and intelligent technology to achieve the desired performance in CNT/Al composites.

A workflow for developing a multidimensional, linear correlation between the process conditions during fluidized bed spray granulation and the surface morphology of the resulting granules is presented. Spray coating experiments with Cellets^®500 particles and sodium benzoate solution were performed in a lab-scale fluidized bed varying liquid spray rate, fluidization air flow rate, fluidization air temperature, spray air temperature and spray atomization pressure. To characterize the surface structure, the surface roughness of the coated particles was quantified using confocal laser-scanning microscopy. The roughness was correlated to the process conditions, and the resulting correlation was rigorously analyzed for the importance and co-linearities of the individual process parameters using a principal component analysis. The surface roughness is strongly dependent on the spray rate of the coating solution, the fluidization air temperature and the atomization pressure at the nozzle. In general, wet process conditions and large droplets with a low initial velocity favor the formation of particles with a rough surface structure, while dry conditions and fine droplets with a high velocity result in granules with a smooth and compact coating layer.

The calcium-looping process, relying on the reversible calcination/carbonation of CaCO₃, is one of the most promising solution to perform thermochemical energy storage (TCES) for concentrating solar power (CSP) plants. Indeed, CaO precursors such as limestone can rely on the high energy density, low cost, large availability and nontoxicity. In this work, the study of the sound-assisted carbonation of fine CaO particles (< 50 μm) for TCES-CSP has been furthered. In particular, a kinetic study has been performed to analyze the effect of the particular carbonation conditions to be used in TCES-CSP applications, i.e. involving carbonation under high CO₂ partial pressure and at high temperature. All the experimental tests have been performed in a lab-scale sound-assisted fluidized bed reactor applying high intensity acoustic field with proper frequency (150 dB–120 Hz). The carbonation kinetics has been analyzed by applying a simple kinetic model, able to properly describe the fast (under kinetic control) and slow (under diffusion control) stage of the reaction. In particular, the reaction rate, the intrinsic carbonation kinetic constant and the characteristic product layer thickness have been evaluated, also highlighting their dependence on the temperature between 800 and 845 °C; a value of 49 kJ mol⁻¹ has been obtained for the activation energy. Finally, a good agreement between the conversion-time profiles, evaluated from the applied kinetic models, and the experimental data has been obtained.

Microspheres composed of poly (lactic-co-glycolic acid) (PLGA) were formed in liquid droplets using the electrospray technique. The structure of the microspheres was controlled by changing the electric voltage of the electrospray. PLGA microspheres with porous structures and micro-sized nanocomposite particles comprising PLGA nanosphere aggregates were formed at 5.0–7.0 kV and 2.5–3.5 kV, respectively. The structural change was related to the extent of evaporation of the solvent from the droplets during their flight. When the evaporation was completed in the relatively small droplets, the microspheres with porous structures were formed in the droplets. To study the mechanism, we observed the effects of the electric voltage of the electrospray, PLGA concentration, flight distance of the droplets, and molecular weight of PLGA on the structure of the PLGA particles. The novelty of this study is the analysis of the size and structure of the PLGA microparticles, which were controlled by the electrospray technique. Therefore, this research has important implications for the structural design and preparation of nanocomposite particles.

Nanoparticle synthesis using flow chemistry has the potential to enhance the large-scale accessibility of precision-engineered nanomaterials at lower prices. This goal has been difficult to achieve primarily due to reactor fouling and the lack of efficient reagent mixing encountered, especially in those scaled-up systems. The present study aimed to overcome the two challenges by integrating a liquid-liquid biphasic segmented flow system with static mixing. This strategy was applied to the synthesis of gold nanoparticles (AuNPs) using citrate reduction chemistry. It was demonstrated that reactor fouling was eliminated by implementing the biphasic flow strategy. As a result, the overall mean particle size of the as-synthesized AuNPs was measured to be 15.5 nm with a polydispersity index (PDI) of 0.07, and with the reproducibility of ± 6.4 %. The biphasic flow system achieved a reaction yield of 88.7 ± 1.1 % reliably with a throughput of 60 mL/hour up to 8 hours.