Three-Dimensional Characterization of Dry Particle Coating Structures Originating from the Mechano-fusion Process.

Dry particle coating processes are of key importance for creating functionalized materials. By a change in surface structure, initiated during coating, a surface property change and thus functionalization can be achieved. This study introduces an innovative approach employing 3D X-ray micro-computed tomography (micro-CT) to characterize coated particles, consisting of spherical alumina particles (d50 = 45.64 µm), called hosts, surrounded by spherical polystyrene particles (d50 = 3.5 µm), called guests. The formed structures, hetero-aggregates, are generated by dry particle coating using mechano-fusion (MF). A deeper understanding of the influence of MF process parameters on the coating structures is a crucial step toward tailoring of coating structure, resulting surface property and functionalization. Therefore, the influence of rotational speed, process time, and total mechanical energy input during MF is explored. Leveraging micro-CT data, acquired of coated particles, enables non-stereologically biased and quantitative coating structure analysis. The guest's coating thickness is analyzed using the maximum inscribed sphere and ray method, two different local thickness measurement approaches. Particle-discrete information of the coating structure are available after a proper image processing workflow is implemented. Coating efficiency and guest's neighboring relations (nearest neighbor distance and number of neighbors inside search radius) are evaluated.

Influence of Hydrolyzed Metal Ions and Surfactants on the Phase Transfer of Al2O3, SiO2, and SnO2.

There are various possibilities for changing the surface properties of particles. In this work, the charge reversal on different metal oxides with different electrolytes is investigated and whether this allows a change in wettability due to a subsequent adsorption of surfactants, e.g., sodium dodecyl sulfate (SDS). It is investigated if the materials of the particles differ only by the isoelectric point or if the surface chemistry of the materials has an influence on the charge reversal as well. Furthermore, the adsorption of SDS as an anionic surfactant is examined, which is also characterized by a second charge reversal and related to a sign change of the electrophoretic mobility µe. Finally, it is examined whether the adsorption of the hydrolyzed metal ions and the subsequent adsorption of SDS are effective enough to hydrophobize the particles and allow phase transfer from the aqueous to second nonaqueous liquid phase. In addition, the influence of pH is investigated because the hydrolyzed metal cations are formed only in a certain pH range, which means that the bridge formed between the particle surface and the surfactant works only in a certain pH range, which would allow pH-selective extraction of the particle system into the second nonaqueous liquid phase.

Particle-Bubble Interactions: an Investigation of the Three-Phase Contact Line by Atomic Force Microscopy.

The dynamics of the three-phase contact line during particle-bubble interactions determine the stability of particle-bubble aggregates in flotation. The interaction of particles and sessile gas bubbles can be studied by colloidal probe atomic force microscopy (CP-AFM). This paper demonstrates a method to obtain the contact angle, the position of the three-phase contact line on the particle, and the bubble profile by utilizing the full information contained in AFM force-distance curves, i.e., force and CP-position information as well as the work done to move the three-phase contact line on the CP-particle. The proposed method does not require any assumption of a constant contact angle or a constant opening angle. This is achieved by the combined solution of the particle force balance and an expression for the work required to move the three-phase contact line over the colloid probe. The applicability to AFM force-distance measurements was demonstrated for the interaction of a hydrophobic SiO2 or a hydrophobic Al2O3 colloidal probe particle with sessile gas bubbles having radii between 45 and 80 µm.

Influence of different discharge levels on the mechanical recycling efficiency of lithium-ion batteries.

Prior to the mechanical processing, discharging is necessary to prevent hazards. While the discharging process, different phenomena can occur changing the characteristics of the functional units of LIB. This study reveals the influence on the mechanical recycling and the obtained material when different discharge levels are used for various cells differing in their cell chemistry. It shows that for different cells, for example, copper deposits happen on the cathode as well as active material deposits on the separator foil. These new properties deteriorate the black mass quality and show contamination of the products with other material streams. It is being tested whether established sub-processes are suitable. However, it becomes clear that further recycling steps (e.g. flotation, hydrometallurgy) can be influenced as well as their product quality and element specific yield.

Fast and Efficient Evaluation of the Mass Composition of Shredded Electrodes from Lithium-Ion Batteries Using 2D Imaging.

With the increasing number of electrical devices, especially electric vehicles, the need for efficient recycling processes of electric components is on the rise. Mechanical recycling of lithium-ion batteries includes the comminution of the electrodes and sorting the particle mixtures to achieve the highest possible purities of the individual material components (e.g., copper and aluminum). An important part of recycling is the quantitative determination of the yield and recovery rate, which is required to adapt the processes to different feed materials. Since this is usually done by sorting individual particles manually before determining the mass of each material, we developed a novel method for automating this evaluation process. The method is based on detecting the different material particles in images based on simple thresholding techniques and analyzing the correlation of the area of each material in the field of view to the mass in the previously prepared samples. This can then be applied to further samples to determine their mass composition. Using this automated method, the process is accelerated, the accuracy is improved compared to a human operator, and the cost of the evaluation process is reduced.

From Meso to Macro: Controlling Hierarchical Porosity in Supraparticle Powders.

A drying droplet containing colloidal particles can consolidate into a spherical assembly called a supraparticle. Such supraparticles are inherently porous due to the spaces between the constituent primary particles. Here, the emergent, hierarchical porosity in spray-dried supraparticles is tailored via three distinct strategies acting at different length scales. First, mesopores (<10 nm) are introduced via the primary particles. Second, the interstitial pores are tuned from the meso- (35 nm) to the macro scale (250 nm) by controlling the primary particle size. Third, defined macropores (>100 nm) are introduced via templating polymer particles, which can be selectively removed by calcination. Combining all three strategies creates hierarchical supraparticles with fully tailored pore size distributions. Moreover, another level of the hierarchy is added by fabricating supra-supraparticles, using the supraparticles themselves as building blocks, which provide additional pores with micrometer dimensions. The interconnectivity of the pore networks within all supraparticle types is investigated via detailed textural and tomographic analysis. This work provides a versatile toolbox for designing porous materials with precisely tunable, hierarchical porosity from the meso- (3 nm) to the macroscale (≈10 µm) that can be utilized for applications in catalysis, chromatography, or adsorption.

Comprehensive Characterization of Shredded Lithium-Ion Battery Recycling Material.

Herein we report on an analytical study of dry-shredded lithium-ion battery (LIB) materials with unknown composition. Samples from an industrial recycling process were analyzed concerning the elemental composition and (organic) compound speciation. Deep understanding of the base material for LIB recycling was obtained by identification and analysis of transition metal stoichiometry, current collector metals, base electrolyte and electrolyte additive residues, aging marker molecules and polymer binder fingerprints. For reversed engineering purposes, the main electrode and electrolyte chemistries were traced back to pristine materials. Furthermore, possible lifetime application and accompanied aging was evaluated based on target analysis on characteristic molecules described in literature. With this, the reported analytics provided precious information for value estimation of the undefined spent batteries and enabled tailored recycling process deliberations. The comprehensive feedstock characterization shown in this work paves the way for targeted process control in LIB recycling processes.

PARROT: A Pilot Study on the Open Access Provision of Particle-Discrete Tomographic Datasets.

In the present paper, as part of an interdisciplinary research project (Priority Programme SPP2045), we propose a possible way to design an open access archive for particle-discrete tomographic datasets: the PARROT database (https://parrot.tu-freiberg.de). This archive is the result of a pilot study in the field of particle technology and three use cases are presented for illustrative purposes. Instead of providing a detailed instruction manual, we focus on the methodologies of such an archive. The presented use cases stem from our working group and are intended to demonstrate the advantage of using such an archive with concise and consistent data for potential and ongoing studies. Data and metadata merely serve as examples and need to be adapted for disciplines not concerned here. Since all datasets within the PARROT database and its source code are freely accessible, this study represents a starting point for similar projects.

Influence of cell opening methods on organic solvent removal during pretreatment in lithium-ion battery recycling.

The use and development of lithium-ion batteries (LIBs) are promoting the technological transformation of individual mobility, consumer electronics and electric energy storage. At their end of life, the complex compounds are disposed by different recycling technologies with defined secondary raw material production. The applied depollution temperatures of the process routes influence not only the recycling efficiency but also the process expenditure, design, medium and costs. Different pretreatment strategies in terms of dismantling depth and depollution temperature are existing. Furthermore, manual and mechanical methods for cell opening are distinguished, which together with the depollution leads to a respective organic solvent evaporation. In this contribution to LIB recycling, the influence of different dismantling depths, achieved by manual cell opening, on the thermal depollution of the LIB cells regarding the mass difference originating by organic solvent evaporation are quantified, in order to determine cell and equipment properties for a safe cell opening. As a result, combinations of thermal depollution and manual cell opening are discussed regarding technical and economic feasibility. The process medium and equipment properties for a safe cell opening are determined. Furthermore, recommendations for future industrial LIB waste management are presented.

Electrochemical Stimulation of Water-Oil Interfaces by Nonionic-Cationic Block Copolymer Systems.

Variable interfacial tension could be desirable for many applications. Beyond classical stimuli like temperature, we introduce an electrochemical approach employing polymers. Hence, aqueous solutions of the nonionic-cationic block copolymer poly(ethylene oxide)114-b-poly{[2-(methacryloyloxy)ethyl]diisopropylmethylammonium chloride}171 (i.e., PEO114-b-PDPAEMA171 with a quaternized poly(diisopropylaminoethyl methacrylate) block) were investigated by emerging drop measurements and dynamic light scattering, analyzing the PEO114-b-qPDPAEMA171 impact on the interfacial tension between water and n-decane and its micellar formation in the aqueous bulk phase. Potassium hexacyanoferrates (HCFs) were used as electroactive complexants for the charged block, which convert the bishydrophilic copolymer into amphiphilic species. Interestingly, ferricyanides ([Fe(CN)6]3-) act as stronger complexants than ferrocyanides ([Fe(CN)6]4-), leading to an insoluble qPDPAEMA block in the presence of ferricyanides. Hence, bulk micellization was demonstrated by light scattering. Due to their addressability, in situ redox experiments were performed to trace the interfacial tension under electrochemical control, directly utilizing a drop shape analyzer. Here, the open-circuit potential (OCP) was changed by electrolysis to vary the ratio between ferricyanides and ferrocyanides in the aqueous solution. While a chemical oxidation/reduction is feasible, also an electrochemical oxidation leads to a significant change in the interfacial tension properties. In contrast, a corresponding electrochemical reduction showed only a slight response after converting ferricyanides to ferrocyanides. Atomic force microscopy (AFM) images of the liquid/liquid interface transferred to a solid substrate showed particles that are in accordance with the diameter from light scattering experiments of the bulk phase. In conclusion, the present results could be an important step toward economic switching of interfaces suitable, e.g., for emulsion breakage.

Multiscale Tomographic Analysis for Micron-Sized Particulate Samples.

The three-dimensional characterization of distributed particle properties in the micro- and nanometer range is essential to describe and understand highly specific separation processes in terms of selectivity and yield. Both performance measures play a decisive role in the development and improvement of modern functional materials. In this study, we mixed spherical glass particles (0.4­5.8 µm diameter) with glass fibers (diameter 10 µm, length 18­660 µm) to investigate a borderline case of maximum difference in the aspect ratio and a significant difference in the characteristic length to characterize the system over several size scales. We immobilized the particles within a wax matrix and created sample volumes suitable for computed tomographic (CT) measurements at two different magnification scales (X-ray micro- and nano-CT). Fiber diameter and length could be described well on the basis of the low-resolution micro-CT measurements on the entire sample volume. In contrast, the spherical particle system could only be described with sufficient accuracy by combining micro-CT with high-resolution nano-CT measurements on subvolumes of reduced sample size. We modeled the joint (bivariate) distribution of fiber length and diameter with a parametric copula as a basic example, which is equally suitable for more complex distributions of irregularly shaped particles. This enables us to capture the multidimensional correlation structure of particle systems with statistically representative quantities.

Temperature data during steam pressure filtration in combination with a water insoluble pore liquid.

Data presented in this article focus on the application of steam pressure filtration in combination with a water insoluble pore liquid. The article describes measured temperature profiles during steam pressure filtration within a filter cake. This article is co-submitted to the article 'Steam Pressure Filtration in Combination with a Water Insoluble Pore Liquid' [1] (DOI: 10.1016/j.ces.2020.115782) where the occurring phenomena as well as the interpretation of temperature profiles during steam pressure filtration are explained in detail. The article expands the shown data to other material systems.

Self-constructed automated syringe for preparation of micron-sized particulate samples in x-ray microtomography.

In X-ray microtomography the sample has to meet special requirements regarding (1) mechanical stability (blurring), (2) geometry (FOV - field of view, rotational symmetry) and (3) composition (high attenuating phases). When analyzing micron-sized particulate material (e.g. powders), the particles in the FOV have to be (4) statistically representative and fixation (embedding matrix) becomes a critical issue due to segregation and agglomeration effects. The authors describe a self-constructed, low-cost automated syringe that allows controlling aspiration speed and suctioning volume. The carrier matrix is a wax structure that is shock frozen within a small polymeric tube. With this, the authors could successfully validate the method to determine particle size distributions (PSD). The described method is used in a related study by Ditscherlein et al. (2019). •Low-cost automated syringe constructed with LEGO-parts and automatized with Arduino-microcontroller.•Particle sample embedded within a shock-frozen wax matrix.•Reproducibility successfully demonstrated by determining particle size distributions.

Stochastic Modeling of Multidimensional Particle Properties Using Parametric Copulas.

In this paper, prediction models are proposed which allow the mineralogical characterization of particle systems observed by X-ray micro tomography (XMT). The models are calibrated using 2D image data obtained by a combination of scanning electron microscopy and energy dispersive X-ray spectroscopy in a planar cross-section of the XMT data. To reliably distinguish between different minerals the models are based on multidimensional distributions of certain particle characteristics describing, for example, their size, shape, and texture. These multidimensional distributions are modeled using parametric Archimedean copulas which are able to describe the correlation structure of complex multidimensional distributions with only a few parameters. Furthermore, dimension reduction of the multidimensional vectors of particle characteristics is utilized to make non-parametric approaches such as the computation of distributions via kernel density estimation viable. With the help of such distributions the proposed prediction models are able to distinguish between different types of particles among the entire XMT image.

Crushing of large Li-ion battery cells.

The number of electric and hybrid electric vehicles (EVs and HEVs) as an alternative to internal combustion engines (ICE) has been rapidly growing for the last five years. When the electric cars or their traction batteries reach their end of life (EOL), an efficient recycling (from a material as well as an energetic point of view) is important to ensure sustainability and to close the materials cycle. Combining mechanical processes like crushing, screening and sorting, valuable metals such as copper, steel and aluminium can be recovered. Key to this is a sufficient liberation of components by crushing and grinding. This study focuses on safety issues of mechanical processing and on the correlation between the material composition and the required specific mechanical energy input necessary to break the Li-ion battery cell apart. Investigations on the crushing behaviour of the single components (anode-, cathode- and separator foils as well as housing materials) and entire Li-ion battery cells were done. Measured specific mechanical stress energies for the crushing of complete battery cells are compared to calculated ones. Inputs to the calculation are the measured specific stress energies of the single components comminution. As a result, the comminution can be adjusted and optimized in order to keep up with the rapid development of Li-ion batteries. With respect to the recyclability of Li-Ion battery cells, recommendations for a design appropriate for recycling are made.

Description of Ore Particles from X-Ray Microtomography (XMT) Images, Supported by Scanning Electron Microscope (SEM)-Based Image Analysis.

In this paper, three-dimensional (3D) image data of ore particle systems is investigated. By combining X-ray microtomography with scanning electron microscope (SEM)-based image analysis, additional information about the mineralogical composition from certain planar sections can be gained. For the analysis of tomographic images of particle systems the extraction of single particles is essential. This is performed with a marker-based watershed algorithm and a post-processing step utilizing a neural network to reduce oversegmentation. The results are validated by comparing the 3D particle-wise segmentation empirically with 2D SEM images, which have been obtained with a different imaging process and segmentation algorithm. Finally, a stereological application is shown, in which planar SEM images are embedded into the tomographic 3D image. This allows the estimation of local X-ray attenuation coefficients, which are material-specific quantities, in the entire tomographic image.

Measuring interactions between yeast cells and a micro-sized air bubble via atomic force microscopy.

A method for the determination of interactions between yeast cells and air bubbles using the atomic force microscope was developed, in which a bubble acts as probe on immobilised living cells. The experimental setup and influencing parameters like bubble size, dwell time and maximum contact force on force-distance curves and maximum adhesion forces are explained. Also, interactions between bubble and yeast cells under variation of pH, ethanol concentration, salt concentration, ionic strength and influence of storage time in Yeast Malt Broth and phosphate buffered saline are investigated and discussed.

Coagulation and stabilization of sterically functionalized magnetite nanoparticles in an organic solvent with different technical polymers.

This experimental study deals with the colloidal stability of sterically functionalized magnetite nanoparticles in a low dielectric constant organic solvent with different concentrations of technical grade polymers. Those dispersions are the starting point of a solution and spray drying process chain to synthesize highly filled nanocomposite materials with nanoparticle volume concentrations exceeding 10%. We introduce a thermo gravimetric method together with light extinction and dynamic light scattering measurements to gain quantitative information on the concentration of primary particles and the mechanism of destabilization or stabilization by polymer addition. Poly(vinyl butyral) is found to stabilize the dispersion considerably caused by stronger interactions with the fatty acid coated magnetite particles quantified by means of adsorption measurements. Both poly(methyl methacrylate) as well as two grades of poly(bisphenol A carbonate) are found to destabilize the dispersion due to depletion flocculation over the entire concentration range investigated However there is a significant quantity of a stable fraction of primary nanoparticles in the supernatant after depletion flocculation occurred. This fraction of primary particles is increasing with decreasing polymer concentration. We furthermore point out important concerns and limitations for the composition of and concentrations in such complex colloidal systems for use in industrially relevant processes.

Characterization of magnetic ion-exchange composites for protein separation from biosuspensions.

Downstream processing is a major issue in biotechnological production. A multitude of unit operations with nonsatisfying yield are often used to reach the desired product purity. Direct recovery technologies such as high-gradient magnetic fishing (HGMF) are advantageous because of their ability to separate the desired product in early stages from crude cultivation broths. However, the use of magnetic particles to capture valuable biotechnological products is often linked to the drawback that support particles are expensive and not available in greater quantities. This current work presents new composite magnetic particles that can be used in biotechnology. They are manufactured by a spray drying process. During this process, the nanosized magnetite particles as well as functional ion-exchange nanoparticles are integrated into one particle in which they are linked by a matrix polymer. The production procedure is flexible, scalable, and therefore economical. These particles have good adsorption capacities of up to 85 mg/g adsorbed protein and good binding kinetics. They are resistant to harsh conditions such as short ultrasonic treatment or extreme pHs. In order to test their usefulness in biosuspensions, model proteins were separated using these particles. The anion and cation exchanger particles separated lysozyme (LZ) or BSA from cultivation suspensions. The selectivity of recovery was dependent on other proteins present as is usual for ion-exchange binding mechanisms.

Characterization of protein capacity of nanocation exchanger particles as filling material for functional magnetic beads for bioseparation purposes.

In this study we describe the synthesis and characterization of nanocation exchanger particles (NCEX) as the functional filling material for magnetic beads. Polystyrene NCEX particles were synthesized from styrene via a mini-emulsion polymerization. The coupling of cation exchanger groups was done with chlorosulfuric acid after the polymerization reaction. The NCEX particles have an average diameter of 160-260 nm. Their ion exchange capacity amounts up to 4.58 mval/g. In an adsorption experiment it was possible to adsorb 192 mg lysozyme/g NCEX. Depending on the equilibrium concentration of lysozyme in the bulk solution 70-85% of the attached protein was desorbed. NCEX particles were used to produce magnetic beads with cation exchanger properties. Therefore an innovative production process for the synthesis of magnetic beads from different single components was used. The produced magnetic beads contained 40 wt % NCEX material and showed an ion exchanger capacity of 2 mequiv/g. It was possible to adsorb 75 mg lysozyme/g magnetic beads with a maximum recovery rate of 95%.