Good rehydration and flowability are desirable properties of powdered ingredients in food formulations such as instant soups, beverage mixes, and nutritional supplements. Binder-free fluidized bed agglomeration involves spraying a liquid onto a bed of solid particles fluidized by hot air, where the liquid droplets collide with the moving particles, creating sticky zones on their surfaces by local wetting. Spraying water in the fluidized bed facilitates the transition of solids from the glassy to the rubbery state, thus enhancing agglomeration. When two or more particulate materials are processed simultaneously, effective mixing results in the formation of hetero-aggregates. In the present study, two types of maltodextrins, widely used as carriers and bulking agents in food powders, were combined to investigate the influence of fluidization gas temperature and water spray rate on agglomeration and mixing behavior. Three mass ratios of maltodextrin DE6 and DE19 (1:1, 1:2, and 2:1) were examined, each optimized through seven experimental trials. Particle size, composition, moisture content, shape, fractal dimension, porosity, flowability, and rehydration were evaluated. The process successfully produced hetero-aggregates under optimal conditions, ensuring larger particles with target composition and low moisture content. The produced material had elongated and irregular shapes with edges and concavities. Agglomerates were classified as free-flowing powders, capable of faster and more homogeneous dispersion compared to the raw materials. Notably, the system with 1:1 mass ratio achieved instantaneous dissolution, less than 30 s against 15 min for the raw materials. Binder-free agglomeration can tailor particle properties for rapid solubilization and easy handling, underscoring its potential for practical applications in instant food systems and formulations requiring fast reconstitution. This study provides a systematic investigation of how the interplay between fluidization temperature and water spray rate governs hetero-aggregate formation of maltodextrin mixtures under a binder-free process, establishing quantitative relationships between process parameters and agglomerate properties.

Flowability and fluidization quality of bulk solids are closely interlinked and decisive for the processing behavior and homogeneity of product quality in many applications, ranging from fine chemicals to energy generation. In this perspective, we summarize recent advances in the modification of flowability towards the improvement of fluidization quality, with a special focus on cohesive (Geldart-C) particles. Furthermore, open challenges are named, directions are given, and methods (e.g. machine learning and AI) are discussed to address them.

The mixing quality in nanoparticulate systems plays a fundamental role in the functional enhancement of advanced materials. In this study, we evaluate the effectiveness of mixing TiO 2 (rutile) and ZrO 2 (monoclinic) nanopowders using Raman mapping and energy-dispersive X-ray (EDX) spectroscopy within a scanning electron microscope (SEM). Eighteen experiments were carried out in an opposed jet fluidized bed, varying process time, mass ratio, and Laval nozzle back pressure. Raman mapping enabled spatially resolved identification of phases, while SEM/EDX provided high-resolution elemental composition. Both techniques indicated good overall inter-aggregate mixing efficiency, especially at a mass ratio of 1:1, with average Ti atomic fractions close to 0.607. Quantitative comparison showed that Raman micro spectroscopy yielded lower relative deviations from the expected values and required simpler sample preparation, making it a practical choice for assessing mixing homogeneity. Deviations from the expected compositions were more pronounced at other mass ratios (especially 1:2), likely owing to differences in particle size, density, and aggregation tendencies. Finally, in contrast to previous intra-aggregate mixing studies, the current results suggest that inter-aggregate composition tends to stabilize near equimolar proportions regardless of the initial mass ratio, highlighting self-regulating behavior at the macro scale. (c) 2025 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

Nanoparticle powders produced by mixing have applications in catalysis, coatings, and advanced materials, yet they remain challenging owing to the strong cohesive behavior of the constituents. Hetero-aggregates form through hetero-contacts at interfaces between chemically distinct materials, but achieving a uniform distribution of components requires an efficient mixing process. Opposed jet fluidized beds offer a promising approach for overcoming these limitations. In this study, the formulation of titania-zirconia hetero-aggregates was investigated by analyzing process parameters and their impact on the inter- and intra-aggregate mixing quality. The effects of feed composition mass ratios (1:1, 2:1, and 1:2), back pressures of the Laval nozzles (0.5, 2.5, and 5.0 bar), and processing times (1 and 5 min) were evaluated by mapping the Ti atomic fraction. The composition and shape of the hetero-aggregates were investigated. The hetero-aggregates exhibited compositions closely aligned with the expected values, based on the initial masses of the components. Shape analysis revealed star-like, elongated, and irregular structures, with circularity and roundness values of approximately 0.4 and 0.5, respectively. Most hetero-aggregates exhibited porosities between 0.971 and 0.991, indicating highly porous structures with significant void spaces. These findings demonstrate that opposed jet fluidized beds enable control over the composition and morphology of hetero-aggregates, leading to efficient nanoparticle mixing.

Near‐infrared laser sources have the potential to change the process dynamics in laser powder bed fusion of polymers. To take full advantage of the shorter processing laser wavelength, the addition of absorbing additives, such as carbon black nanoparticles, becomes inevitable. Many nanoparticle characteristics can influence the laser‐material interaction, such as quantity, dispersion, and position relative to the polymer matrix, but have not been investigated under processing conditions. Therefore, this study improves the understanding of the optical material properties present in laser powder bed fusion by quantifying the thermo‐optical properties of PA11 powder, melt and solid, additivated with minute amounts of carbon black nanoparticles on the surface and throughout the volume of the particles. Surface‐additivation results in the highest increase in laser attenuation overall and creates a segregated network that acts as a barrier to laser penetration in the molten and solid state. By contrast, the random distribution of agglomerated nanoparticles throughout the particle volume allows most of the laser radiation to pass through. Other nanoparticle effects, such as thermal stabilization and crystal formation, affect the volume‐additivated particles the most. The thermo‐optical results are complemented by analysis of process‐relevant powder, thermal, structural, and compositional material properties.

The stabilization of single-atom catalysts on semiconductor substrates is pivotal for advancing photocatalysis. TiO2, a widely employed photocatalyst, typically stabilizes single atoms at oxygen vacancies-sites that are accessible but prone to agglomeration under illumination. Here, we demonstrate that cation vacancies in Ti-deficient TiO2 nanosheets provide highly stable anchoring sites for Pt single atoms, enabling persistent photocatalytic hydrogen evolution. Ultrathin TiO2 nanosheets with intrinsic Ti4+ vacancies are synthesized via lepidocrocite-type titanate delamination and Pt single atoms are selectively trapped within these vacancies through a simple immersion process. The resulting Pt-decorated nanosheets exhibit superior photocatalytic hydrogen evolution performance, outperforming both Pt nanoparticle-loaded nanosheets and benchmarked Pt single-atom catalysts on P25. Crucially, Pt atoms anchored at Ti4+ vacancies display remarkable resistance to light-induced agglomeration, a key limitation of conventional single-atom photocatalysts. Density functional theory calculations reveal that Pt incorporation into Ti4+ vacancies is highly thermodynamically favorable and optimizes hydrogen adsorption energetics for enhanced catalytic activity. This work highlights the critical role of cation defect engineering in stabilizing single-atom co-catalysts and advancing the efficiency and durability of photocatalytic hydrogen evolution.

A major challenge in the powder bed fusion (PBF) process with polyamides, which are the most commonly used powders, is the handling of already used powder (aged powder). During PBF, polyamide powders undergo chemical ageing, resulting in altered thermal and rheological properties of the feedstock material. Components made from aged powder are of inferior quality. Therefore, aged powder is usually refreshed with new (virgin) powder. Although, a substantial amount of aged powder accumulates over the course of processing. These excess quantities are either employed in other plastic manufacturing processes (downcycling) or, more frequently, disposed. A combined process of solvolysis with subsequent thermally induced liquid-liquid phase separation and polymer crystallisation (TIPS+S) is used to restore the thermal properties and rheological properties of aged polyamide 12 (PA12) and thus to make the powders suitable for PBF again. The degree of solvolysis of the aged PA12 is tuned by reaction temperature or reaction time. A kinetic model allows to determine suitable process parameters for TIPS+S depending on the ageing condition of the feed to match the thermal properties of the recycled PA12 powders to those of PA12 virgin powder. The optimised recycled PA12 powder shows comparable zero shear viscosity, particle size distribution, particle shape and flowability to the virgin material. Specimen built from equally mixed recycled and aged PA12 powder achieved the same mechanical properties like those obtain by PBF of equally mixed virgin and aged powder. Therefore, a closed loop recycling approach is feasible, in which aged PA12 powders from the PBF process are recycled by the proposed TIPS+S process.

Powder bed fusion of polymers with a laser beam (PBF-LB/P) is a layer-based additive manufacturing method that excels in producing functional components of complex geometries. However, the limitation of commercially available materials to mostly polyamides reduces the range of applications for PBF-LB/P-processed parts. Recently, liquid-liquid phase separation and crystallization have been reported as a suitable method to produce poly(butylene terephthalate) (PBT) microparticles of good flowability as a PBF-LB/P feedstock. PBT is an interesting plastic feedstock as its properties allow for an extension of the application of AM-built parts in the automotive and electronics sectors. Starting from PBT feed materials with different molar mass distributions, we investigate the effect of the feed material used in the thermal precipitation process under otherwise identical process parameters on the resulting PBT powder properties. The thermal precipitation process is highly robust with respect to bulk solid properties, such as particle size distribution, particle shape, flowability, and intrinsic properties (crystal structure and melting behavior). These product characteristics are virtually unaffected by the average molar mass of the PBT feed. Melt crystallization is accelerated, while the viscosity decreases with decreasing molecular mass. Once favorable process conditions are defined, which lead to powders with suitable properties, the crystallization kinetics and melt viscosity can be adjusted accordingly without changing the powder properties. Key parameters, which influence part porosity (through melt coalescence), layer adhesion, or the tendency of the material to warp during the PBF-LB/P process, are adjustable to produce a customized starting material.

Herein, we demonstrate the preparation of magnetic polyamide 11 feedstock powders for powder bed fusion (PBF) using liquid-liquid phase separation and crystallization. By adding magnetic nanomaterials during the precipitation process, the particulate additive is incorporated into the polymer matrix. This enables the production of filled systems at single particle level, which is advantageous in terms of the adjustable magnetic strength and homogeneity of the powder. Thermogravimetric analysis is used to determine the additive content and onset temperature of decomposition of composite powders, where additive-enhancement of PA11 powders with magnetic iron oxide nanoparticles showed a positive influence on the thermal stability of the feedstock. Successive analysis of particle size distribution, shape, colour, crystal structure, magnetic properties and thermal properties of the composite powders are carried out and their properties are discussed with respect to the PBF process. A decrease in particle size, width of the thermal process window and isothermal crystallization time can be attributed to the nucleating effect of the magnetic additive. The PBF processability of the composite feedstock is demonstrated by the production of magnetic tensile bar specimens from additive-enhanced PA11 powders with 1wt.-% magnetic iron oxide.

This work systematically investigates the influence of spray parameters on the shape factor descriptors and the fractal dimensions of polymer agglomerates produced by fluidised bed spray agglomeration. Polystyrene primary-particles with sizes <100 mu m (Geldart C/A) are used to investigate the shape formation during the agglomeration process with regard to the spray-parameters, i.e., volume flows of the atomization gas and the binder liquid. As binding agent, a solution of polymethyl-methacrylate in acetone is used. Analysis of the ag-glomerates is carried out using scanning electron microscopy and laser diffraction. Development of agglomerate -size and the distributions of the shape factors circularity, roundness and compactness are monitored by image analysis and correlated with the spray parameters. The calculation of the fractal dimensions with regard to the Sauter mean diameter using the box counting method is performed and compared with the shape factors, resulting in two complementary methods to describe the shape of agglomerates.

Raw data of fragments and corresponding morphological descriptors of green peas after impact comminution in a hammer mill.

Substituting conventional doctor blade- or roller-based powder application methods for laser-based powder bed fusion of polymers (PBF-LB/P) by electrophotographic powder application (EPA) offers significant advantages. In particular, the selective powder deposition enabled by EPA allows high powder efficiency and the possibility to locally adjust part properties during their fabrication. However, defined charging of powder particles is decisive for achieving an accurate selective deposition of powder layers by means of electrophotography. This is the first comprehensive study on the specific triboelectric charge control of polymer particles for their subsequent use in electrophotographic powder application for PBF-LB/P. For this purpose, approaches for charge control of toner particles in the context of digital (2D) printing technologies are adapted and applied to polypropylene (PP) feedstocks for PBF-LB/P. In order to show transferability to other polymers, the charge control method developed in this paper is also applied to polyamide 12 (PA12) high density polyethylene (HDPE) and polystyrene (PS). For successful EPA, unipolar charging of polymer particles is decisive. However, non-functionalized PP shows a strongly bipolar triboelectric charging, which is unsuitable for EPA. The charge control method developed in this work shifts this strongly bipolar triboelectric charging to a unipolar charging. This is achieved by the synergy of both functionalizing the particle surface with charge control agents (CCAs) and choosing suitable carrier particles known from two-component toners. The developed method allows to control crucial parameters of triboelectric charging, namely polarity, amount of charge and resulting surface potential. Furthermore, the presented results provide new insights into the transfer behavior of charged PP particles in an external electric field. Finally, this enables the triboelectric charging mechanism to be used for electrophotographic powder application in PBF-LB/P.

Substituting conventional doctor blade-or roller-based powder application methods for laser-based powder bed fusion of polymers (PBF-LB/P) by electrophotographic powder application (EPA) offers significant advantages. In particular, the selective powder deposition enabled by EPA allows high powder efficiency and the possibility to locally adjust part properties during their fabrication. However, defined charging of powder particles is crucial for achieving an accurate selective deposition of powder layers by means of electrophotography. This is the first comprehensive study on the specific triboelectric charge control of polymer particles for their subsequent use in electrophotographic powder application for PBF-LB/P. For this purpose, approaches for charge control of toner particles in the context of digital (2D) printing technologies are adapted and applied to polypropylene (PP) feedstocks for PBF-LB/P. In order to show transferability to other polymers, the charge control method developed in this paper is also applied to polyamide 12 (PA12) high density polyethylene (HDPE) and polystyrene (PS). For successful EPA, unipolar charging of polymer particles is crucial. However, non-functionalized PP shows a strongly bipolar triboelectric charging, which is unsuitable for EPA. The charge control method developed in this work shifts this strongly bipolar triboelectric charging to a unipolar charging. This is achieved by the synergy of both functionalizing the particle surface with charge control agents (CCAs) and choosing suitable carrier particles known from two-component toners. The developed method allows to control crucial parameters of triboelectric charging, namely polarity, amount of charge and resulting surface potential. Furthermore, the presented results provide new insights into the transfer behavior of charged PP particles in an external electric field. Finally, this enables the triboelectric charging mechanism to be used for electrophotographic powder application in PBF-LB/ P.

Metallic alloy nanoparticles (NPs) exhibit interesting optical, electrical and catalytic properties, dependent on their size, shape and composition. In particular, silver-gold alloy NPs are widely applied as model systems to better understand the syntheses and formation (kinetics) of alloy NPs, as the two elements are fully miscible. Our study targets product design via environmentally friendly synthesis conditions. We use dextran as the reducing and stabilizing agent for the synthesis of homogeneous silver-gold alloy NPs at room temperature. Our approach is a one-pot, low temperature, reaction-controlled, green and scalable synthesis route of well-controlled composition and narrow particle size distribution. The composition over a broad range of molar gold contents is confirmed by scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy (STEM-EDX) measurements and auxiliary inductively coupled plasma-optical emission spectroscopy measurements (ICP-OES). The distributions of the resulting particles in size and composition are obtained from multi-wavelength analytical ultracentrifugation using the optical back coupling method and further confirmed by high-pressure liquid chromatography. Finally, we provide insight into the reaction kinetics during the synthesis, discuss the reaction mechanism and demonstrate possibilities for scale-up by a factor of more than 250 by increasing the reactor volume and NP concentration.

Within this contribution, the incorporation of nanoparticles (SiO2, Al2O3, TiO2) into the matrix of precipitated polyamide particles during thermally induced phase separation (TIPS) is demonstrated. The obtained polymer composite powders are tailored for their application in powder bed fusion (PBF). The flexible process allows to tune and adapt the powder properties to meet specific challenges like narrow particle size distribution, spherical particles, high additive contents and good distribution of the additive within the powder. Thermogravimetric analysis and electron microscopy prove the incorporation of the nano-sized additive into the matrix of the polymer. The influence of the additive material during polymer precipitation on the particle size distribution and shape of the powders is discussed. Thermal properties of the composite powders were assessed by dynamic and isothermal DSC for subsequent Avrami analysis. The observed acceleration of the crystallization kinetics could be attributed to the nucleating effect of the additive. All powders showed an easy-flowing (flow index ffC > 4) behavior. This allowed the deposition of homogeneous powder layers during PBF experiments also at high temperatures. The processability of the composite powders in the PBF process was demonstrated by single layer experiments.

This study presents shape transformation of anisotropic high-performance thermoplastic polyetherketoneketone (PEKK) and carbon fiber reinforced powder composite particles (HT-23) by thermal rounding. The shape transformation is achieved by (partial) melting of the high-temperature thermoplast microparticles. Three different process setups are presented, investigating the impact of the source of heat supply on the resulting shape modification: using a directly heated sheath gas flow, an indirect heat supply through the reactor wall and a combined approach. Regardless of the chosen setup, a modification of the particle shape was observable. The most advantageous shape transformation was observed in the indirect heating approach. In addition, the enhanced shape transformation yields an improved free flow behaviour of the powders, as quantified by ring-shear experiments. Reductions of the unconfined yield strengths of the powders for high consolidation stresses as high as 18 percent for PEKK and 30 percent for the HT-23 are achieved. Thereby, processability of the powder in laser based powder bed fusion is enhanced, extending the range of available (composite) polymer materials.

The feasibility of thermally-induced phase separation and crystallization for the production of semi-crystalline polyetherimide (PEI) microparticles from an amorphous feedstock has been reported recently. Here, we investigate process parameter dependencies for designing and control of particle properties. A stirred autoclave was used to extend the process controllability, as the applied process parameters, e.g., stirring speed and cooling rate, were adjusted. By increasing the stirring speed, the particle size distribution was shifted to larger values (correlation factor ρ = 0.77). Although, the enhanced droplet breakup, induced by the higher stirring speed, led to the formation of smaller particles (ρ = −0.68), broadening the particle size distribution. The cooling rate showed a significant influence on the melting temperature, reducing it with a correlation factor of ρ = −0.77, as confirmed by differential scanning calorimetry. Lower cooling rates led to larger crystalline structures and enhanced the degree of crystallinity. The polymer concentration mainly affected the resulting enthalpy of fusion, as an increased polymer fraction enhanced the latter (correlation factor ρ = 0.96). In addition, the circularity of the particles was positively correlated to the polymer fraction (ρ = 0.88). The structure assessed via X-ray diffraction, was not affected.

This study presents bulk material characterization, especially powder flowability, of eight food powders from six different plants (almond, chestnut, chickpea, coconut, hazelnut and rice). The characterization of the bulk powders includes the particle size distributions, true densities, bulk and tapped densities, as well as the powder porosity and moisture content. The flowability is determined by means of Hausner ratio, Carr's index, flow function by an annular shear cell and dynamic angle of repose. The flowability characteristics are discussed in regard to the bulk powder properties and evaluated for their applicability as some methods could give misleading results for the flowability.

The high demand for an efficient energy supply for various applications facilitates the development of innovative storage technologies like all-solid-state batteries in addition to novel production technologies. Compared to the conventional manufacturing process, additive manufacturing (AM) is a promising technology used for the rapid and cost-effective production of battery components containing separators. However, AM technologies like laser-based powder bed fusion of polymers (PBF-LB/P) have been neglected so far. The present research aims to fill this research gap and outline a novel approach for processing polymers like polyethylene oxide (PEO) and polyvinylidene fluoride (PVDF) into separators using PBF-LB/P. Optimal process parameters for manufacturing PVDF and PEO with PBF-LB/P to generate homogeneous and dense layers represent the key findings of this paper and provide a deeper process understanding. The first proof of concept for producing separator layers by PBF-LB/P in a scalable process is demonstrated as a result.

Nanostructured heteroaggregates provide improved or new functionalities over homoaggregates due to the formation of heterocontacts. For a high number of heterocontacts, intense mixing of the primary particles and their reaggregation is required. This work presents results using the principle of fluidization for formulation of nanostructured heteroaggregates. Intraaggregate mixing of constituents is evaluated by SEM-EDX. The feasibility of two technologies, spouted bed and opposed jet fluidized bed, is demonstrated, also showing the variety of structures that can be achieved by the technologies.