Surface Properties Of Particles Research Articles

Multidimensional Separation by Magnetic Seeded Filtration: Theoretical Study

Magnetic seeded filtration (MSF) is a multidimensional solid–liquid separation process capable of fractionating a multimaterial suspension based on particle size and surface properties. It relies on the selective hetero-agglomeration between nonmagnetic target and magnetic seed particles followed by a magnetic separation. Experimental investigations of multimaterial suspensions are challenging and limited. Therefore, a Monte Carlo model for the simulation of hetero-agglomeration processes is developed, validated, and compared to a discrete population balance model. The numerical investigation of both charge-based and hydrophobicity-based separation in an 11-material system, using synthetic agglomeration kernels based on real-world observations, yields results consistent with prior experimental studies and expectations: Although a multidimensional separation is indeed possible, unwanted hetero-agglomeration between target particles results in a reduced selectivity. This effect is more pronounced when separation is based on a dissimilarity rather than a similarity in the separation criterion and emphasizes the advantages of hydrophobicity-based systems. For the first time, 2D grade efficiency functions T(φ,d) are presented for MSF. However, it is shown that these functions strongly depend on the initial state of the suspension, which casts doubt on their general definition for agglomeration-based processes and underlines the importance of a simulation tool like the developed MC model.

Changes of surface properties of sucrose particles during grinding in a cocoa butter-based suspension and their influence on the macroscopic behavior of the suspension

AbstractChocolate mass is a cocoa butter-based suspension, which mainly consists of sugar and cocoa particles dispersed in a continuous lipid phase. During chocolate manufacturing, sugar particles have to be ground to sizes below 25–30 µm. Such a fine grinding is carried out either by five roll refiners or by ball mills. Despite obtaining similar particle size distributions at the end, the grinding procedures result in different chocolate mass properties. The reasons for that are not fully understood, so far. Therefore, changes in particle sizes and surface properties of sucrose particles as well as their interactions with surrounding cocoa butter during the different grinding processes were investigated including atomic force microscopy techniques to characterize local surface states. It was found that especially the alteration of surfaces during continued grinding differed. In the case of roller grinding, surface states became more inhomogeneous and different surfaces states at microscopic level existed in parallel. More homogenous surfaces but with a higher degree of amorphous states were formed during grinding in the ball mill. Variations in macroscopic behavior of the suspension can be explained by the differences in interaction of particles with each other and with the surrounding lipid phase.

Measuring Rolling Friction at the Nanoscale.

Colloidal probe microscopy, a technique whereby a microparticle is affixed at the end of an atomic force microscopy (AFM) cantilever, plays a pivotal role in enabling the measurement of friction at the nanoscale and is of high relevance for applications and fundamental studies alike. However, in conventional experiments, the probe particle is immobilized onto the cantilever, thereby restricting its relative motion against a countersurface to pure sliding. Nonetheless, under many conditions of interest, such as during the processing of particle-based materials, particles are free to roll and slide past each other, calling for the development of techniques capable of measuring rolling friction alongside sliding friction. Here, we present a new methodology to measure lateral forces during rolling contacts based on the adaptation of colloidal probe microscopy. Using two-photon polymerization direct laser writing, we microfabricate holders that can capture microparticles, but allow for their free rotation. Once attached to an AFM cantilever, upon lateral scanning, the holders enable both sliding and rolling contacts between the captured particles and the substrate, depending on the interactions, while simultaneously giving access to normal and lateral force signals. Crucially, by producing particles with optically heterogeneous surfaces, we can accurately detect the presence of rotation during scanning. After introducing the workflow for the fabrication and use of the probes, we provide details on their calibration, investigate the effect of the materials used to fabricate them, and report data on rolling friction as a function of the surface roughness of the probe particles. We firmly believe that our methodology opens up new avenues for the characterization of rolling contacts at the nanoscale, aimed, for instance, at engineering particle surface properties and characterizing functional coatings in terms of their rolling friction.

A mechanism for the stable adhesion of bubbles and particles: The effect of particle surface properties

Shale gas fracturing flowback fluid (FFF) is characterized by complex composition, high generation volume, viscosity, chemical oxygen demand, and suspended solids content, which is harmful to the environment and needs to be reused after treatment. In the previous work, microbubble-enhanced flocculation can effectively treat the microfine particles in FFF by the trapping and bridging functions of microbubbles. The formation of stable bubble-particle adhesion throughout the microbubble-enhanced flocculation process is the key step to achieve efficient solid-liquid separation. In this work, the influence of particle surface interface properties, including surface hydrophobicity and roughness, on the stable adhesion was investigated. The results show that the more hydrophobic and rougher the particle surface is, the lower the three-phase contact (TPC) formation time (from 581 ms to 128 ms) and the number of collisions (from 10 to 4). The shorter TPC formation time and fewer collisions mean the faster the bubble forms a stable adhesion with the particle. The main reasons are the increase of hydrophobic gravitational force and the existence of “pinch” effect. In addition, the addition of surfactant can enhance the stability of the liquid film and weaken the deformation of the bubble, which increases the formation time of TPC. The above results provide a theoretical basis for the treatment of FFF by microbubbles-enhanced flocculation.

Critical attributes of fine excipient materials in carrier-based dry powder inhalation formulations: The particle shape and surface properties

The potential of fine excipient materials to improve the aerodynamic performance of carrier-based dry powder inhalation (DPI) formulations is well acknowledged but not fully elucidated. To improve the understanding of this potential, we studied two fine excipient materials: micronized lactose particles and silica microspheres. Inhalation formulations, each composed of a coarse lactose carrier, one of the two fine excipient materials (0.0–15.0 % w/w), and a spray-dried drug (fluticasone propionate) material (1.5 % w/w) were prepared. The physical structure, the flow behavior, the aerosolization behavior, and the aerodynamic performance of the formulations were studied. The two fine excipient materials similarly occupied carrier surface macropores. However, only the micronized lactose particles formed agglomerates and appeared to increase the tensile strength of the formulations. At 2.5 % w/w, the two fine excipient materials similarly improved drug dispersibility, whereas at higher concentrations, the micronized lactose material was more beneficial than the silica microspheres. The findings suggest that fine excipient materials improve drug dispersibility from carrier-based DPI formulations at low concentrations by filling carrier surface macropores and at high concentrations by forming agglomerates and/or enforcing fluidization. The study emphasizes critical attributes of fine excipient materials in carrier-based DPI formulations.

Factors Influencing Food Powder Flowability

The flowability of food powders is a critical determinant of their processing efficiency, product quality, and overall operational success. This review delves into the intricacies of powder flowability, elucidating the factors that govern it and exploring various methods for its evaluation and enhancement. Particle size and distribution, particle shape, surface properties, moisture content, and storage conditions stand as the key determinants of powder flowability. Finer powders, with their increased interparticle cohesive forces, tend to exhibit poorer flowability. Particle shape also plays a role, with irregular or elongated particles flowing less readily than spherical ones. Surface properties influence interparticle friction, thereby impacting flow behavior. Moisture content significantly affects flowability, as increased moisture can lead to liquid bridge formation, hindering powder movement. Storage temperature, on the other hand, generally enhances powder flow due to reduced interparticle cohesive forces at higher temperatures. This highlights the need to understand the factors influencing food powder flowability and to employ appropriate evaluation strategies for optimizing food powder processing efficiency, product quality, and overall production success.

β-glucan-modified nanoparticles with different particle sizes exhibit different lymphatic targeting efficiencies and adjuvant effects

Particle size and surface properties are crucial for lymphatic drainage (LN), dendritic cell (DC) uptake, DC maturation, and antigen cross-presentation induced by nanovaccine injection, which lead to an effective cell-mediated immune response. However, the manner in which the particle size and surface properties of vaccine carriers such as mesoporous silica nanoparticles (MSNs) affect this immune response is unknown. We prepared 50, 100, and 200 nm of MSNs that adsorbed ovalbumin antigen (OVA) while modifying β-glucan to enhance immunogenicity. The results revealed that these MSNs with different particle sizes were just as efficient in vitro, and MSNs with β-glucan modification demonstrated higher efficacy. However, the in vivo results indicated that MSNs with smaller particle sizes have stronger lymphatic targeting efficiency and a greater ability to promote the maturation of DCs. The results also indicate that β-glucan-modified MSN, with a particle size of ∼100 nm, has a great potential as a vaccine delivery vehicle and immune adjuvant and offers a novel approach for the delivery of multiple therapeutic agents that target other lymph-mediated diseases.

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.

Preparation of Degradable and Transformable Core-Corona-Type Particles that Control Cellular Uptake by Thermal Shape Change.

Particle-cell interactions, such as cellular uptake, vary depending on the particle size, shape, and surface properties. By dynamic control of the physical properties of particles, microparticle-cell interactions can intentionally be altered. Particle degradability is also necessary for their application in the body. In this study, we aimed to prepare degradable core-corona-type particles that are deformed near the body temperature and investigated particle shape-dependent cellular uptake. Degradable and transformable particles consisting of poly(2-methylene-1,3-dioxepane)-co-poly(ethylene glycol) with three-armed poly(ε-caprolactone) (PCL) were prepared. The particle melting point was controlled by the chain length of the three-armed PCL. Particle degradation occurred under both acidic and alkaline conditions via ester group hydrolysis in the polymer backbones. The rod-shaped microparticles prepared by uniaxial stretching at a temperature above the melting point of the core showed less uptake into macrophages than did the spherical microparticles. Therefore, the degradable transformable particles enable macrophage interaction control via stimuli-regulated particle shapes and are expected to be applied as drug delivery carriers that can be decomposed and excreted from the body.

On the behavior of sub-micrometer polystyrene particles subjected to AC insulator-based dielectrophoresis.

Polymer beads, especially polystyrene particles, have been extensively used as model species in insulator-based dielectrophoresis (iDEP) studies. Their use in alternating current iDEP (AC-iDEP) is less explored; however, an assessment in the low-frequency regime (≤10kHz) allows to link surface conduction effects with the surface properties of polymer particles. Here, we provide a case study for various experimental conditions assessing sub-micrometer polystyrene particles with AC-iDEP and link to accepted surface conduction theory to predict and experimentally verify the observed AC-iDEP trapping behavior based on apparent zeta potential and solution conductivity. We find excellent agreement with the theoretical predictions, but also the occurrence of concentration polarization electroosmotic flow under the studied conditions, which have the potential to confound acting dielectrophoresis conditions. Furthermore, we study a case relevant to the assessment of microplastics in human and animal body fluids by mimicking the protein adsorption of high abundant proteins in blood by coating polystyrene beads with bovine serum albumin, a highly abundant protein in blood. Theoretical predictions and experimental observations confirm a difference in observed AC-iDEP behavior between coated and non-coated particles, which might be exploited for future studies of microplastics in blood to assess their exposure to humans and animals.

Preparation and Performance Evaluation of Quaternary Copolymer Sand Control Agent

Summary Sand production is a common problem in petroleum extraction, and the development of water-soluble polymer sand control agents is currently a research hotspot. However, this research does not provide details of the chemical structure and lacks discussions on adsorption and sand control mechanisms. Herein, a new water-soluble polymer sand control agent (PAADD) is reported on; it is a copolymer of 2-acrylamido-2-methylpropane sulfonic acid (AMPS), N-(3-dimethylaminopropyl) methacrylamide (DPM), a functional monomer (DAM) containing ketone groups and self-crosslinking properties, and acrylamide (AM). First, the synthesis conditions of PAADD are optimized, and then its sand control mechanism is explored. Experimental results reveal that PAADD can adsorb on the sand surface through electrostatic attraction and hydrogen bonding and change the surface properties of sand particles, which promotes the aggregation of sand particles and permits good sand control ability. In flow experiments, after the injection of PAADD solution (500 mg/L) into a sandpacked model with a permeability of 500 md, the critical sand production rate of the sandpacked model increased more than 100 times and the permeability damage rate (PDR) was 30–40%.

ФОРМУВАННЯ КОМПОЗИТУ ПРИ ВАРІЮВАННІ ДИСПЕРСНОСТІ НАПОВНЮВАЧА ТА ВИДУ ЗВ’ЯЗУЮЧОГО

The aim of this study was to investigate polymer composites based on andesite of different dispersion as a filler with different types of polymer matrix for further development of production technology. Varying the types and concentration of mineralfillers of different genesis, including volcanic rocks, is one of the ways to modify polymer composite materials. The choice of filler type is an important factor influencing the structure formation and properties of the resulting composite. At the same time, varying the particle size distribution of the filler and its quantitative ratio with the matrix makes it possible to adjust the performance properties of the resulting composite materials within a wide range. In addition, the surface properties of thefiller particles and the chemical nature of the polymer matrix are of great importance. The possibility of expanding the range and increasing the operational reliability of composite materials when using new types of natural raw materials determine therelevance of this research. To achieve this goal, a set of modern methods of physical and chemical analysis and standardised testing of materials was used in the study. The object of the study was composite materials using andesite screenings as a fractionated filler and copolymers as a matrix. Changes in the physical and mechanical properties of the composites were determined by varying the content (55-85 wt.%) and granulometry of the filler and the type of polymeric binder. According to the test results, it is possible to adjust the parameters of the properties of polymer composites, while the range of their changes is as follows: water absorption 2.2-14.9 %, density 1.24-1.96 g/cm3, abrasion 0.005-0.1 g/cm2, elastic modulus 41-83 Pa/mm2, which indicates the prospects of manufacturing and practical use of the obtained wear-resistant composites in construction

Study on dispersion stability of natural brucite in aqueous media

A brucite suspension can absorb sulfur dioxide (SO2). It thereby plays a significant role flue gas desulfurization. However, the dispersion of a natural brucite suspension is low which seriously affects its efficiency for SO2 absorption. The dispersion stability and particle size of the brucite suspension are therefore, particularly important to investigate. The effects of types and dosages of inorganic dispersants on the particle size and dispersion stability of the brucite suspension have been investigated in the present study by performing sedimentation experiments and zeta potential tests. The results showed that the addition of 0.5 wt.% sodium hexametaphosphate (SHMP) had a positive effect on the dispersion stability of brucite in an aqueous medium. The effect of SHMP on the surface properties of the brucite particles was also studied by performing characterizations like scanning electron microscopy (SEM) and infrared spectroscopy (IR), and by using an extended DLVO theory (named after Boris Derjaguin and Lev Landau, Evert Verwey and Theodoor Overbeek). The results showed that SHMP was chemisorbed on the brucite particle surface. It also formed complexes with magnesium ions, and changed the zeta potential of brucite. In addition, calculations based on the extended DLVO theory showed that the sum of the steric hindrance-induced interaction energy, Van-der-Waals energy, and electrostatic energy changed from an unfavorable value to a favorable value with an increase in the particle distance. These results showed that the addition of SHMP could improve the desulphurization effect of the brucite suspension.

Impact of carrier particle surface properties on drug nanoparticle attachment

HypothesisThe stabilization and isolation to dryness of drug nanoparticles has always been a challenge for nano-medicine production. In the past, the use of montmorillonite (MMT) clay carrier particles to adsorb drug nanoparticles and maintain their high surface area to volume ratio after isolation to dryness has proven to be effective. We hypothesise that the distribution of hydrophilic and hydrophobic patches on the clay’s surface as well as its porosity/roughness, hinder the agglomeration of the drug nanoparticles to the extent that they retain their high surface area to volume ratio and display fast dissolution profiles. ExperimentsIn this work, the distribution of hydrophobicity and hydrophilicity, and the porosity/roughness, of the surface of selected silica carrier particles were varied and the impact of these variations on drug nanoparticle attachment to the carrier particle and subsequent dissolution profiles was studied. FindingsThe fastest dissolution profiles at the highest drug nanoparticle loadings were obtained with a periodic mesoporous organosilane carrier particle which had a homogeneous distribution of hydrophobic and hydrophilic surface properties. Carrier particles with rough/porous surfaces and a combination of hydrophobic and hydrophilic patches resulted in nanocomposite powders with faster dissolution behaviour than carrier particles with predominantly either a hydrophobic or hydrophilic surface, or with non-porous/smoother surfaces.

The Relevance of Carbon for Energy Transition: Ways to Assess Its Surface Properties and Standardize Their Characterization

Technical carbon blacks (CB) are well-established materials that gain increasing attraction in the context of electrification and transition towards renewable energy sources. Their availability, low price, and favorable properties (e.g., conductivity, specific surface area) make them ideal candidates as additives in batteries or as support material for electrocatalysts, e.g., in fuel cells [1]. However, due to the vast number of producers and manufacturing processes large variations in their properties can be observed making product quality control difficult.To this end, we report on ways and methods to standardize the characterization of CB materials that are specifically designed for fuel cell and battery applications. By applying analytical centrifugation (AC) and combining it with complementary methods (e.g., electrical conductivity measurements, Boehm titration), we identify parameters like particle size, morphology, and surface properties that are influential for the overall value chain in electrode manufacturing. This helps to minimize the effects of material inherent property fluctuations as well as process-related fluctuations on the final electrochemical performance.Four different CBs were investigated, and their various properties were assessed. Our results show that the degree of graphitization and hence the electrical conductivity in a CB can be correlated with the overall surface basicity. Moreover, these properties can be linked with their dispersibility features on the ink formulation level and studied via liquid phase characterization using Hansen Parameters (Fig. 1) [2]. In brief, the higher the basicity of a CB surface is, the better the interaction with non-polar/mildly polar aprotic solvents becomes. This is especially true when oxygen-containing surface functional groups that cause a higher overall polarity of the material are missing.Figure 1: Hansen interaction space (for polar, disperse and hydrogen bonding interactions) showing the location of various solvents that are used as probe liquids for determining the Hansen Similarity Parameters of the respective CBs in 3D space (a) and 2D representations (b-d).To conclude, we were able to identify differences in CB materials by applying AC-based characterization techniques. Those differences can have a huge impact on the overall process chain of electrode production as they are decisive not only in formulation considerations but also in the subsequent processing steps. In the future, we will focus on closing the process chain and try to apply our characterization routines for an efficient identification of decisive process parameters at every stage of production. Additionally, we want to transfer knowledge gained from lab-scale techniques (e.g., sonication methods) to industrially relevant mixing procedures. By this, we will give electrode manufacturers tools at hand for a fast characterization of feed materials to save costly and lengthy adjustments of processes due to quality fluctuations. An accelerated implementation of green energy solutions is sought by this approach.

On the grain growth of CeO2 nanocrystals in AC/DC electrical fields

Processing of materials using electrical field presents an important research and engineering field. It allows to process materials at less demanding conditions, synthesize new phases and compositions. Herein, nanocrystals of CeO2 were synthetized and grown in-situ under AC and DC electrical fields. Main crystallographic properties like crystallite size, morphology texture and grain boundaries were significantly influenced by the electrical field up to 600 °C. Above this temperature, the thermally driven grain growth hindered the electrical field effect and led to a common behavior, isotropic particle shape and surface properties. This can be linked to the electrical and thermal force competition for the grain boundary development. To our knowledge such comprehensive description of the field effect on the growth of nanocrystals and its limitations has never been reported and can open a new door for processing of nanocrystalline materials.

Aerosol photoemission as a versatile tool for nanoparticle surface investigations: Evaluation of metal oxide formation and surface properties of multi-component particles

Aerosol photoemission as a versatile tool for nanoparticle surface investigations: Evaluation of metal oxide formation and surface properties of multi-component particles

Viscous Sintering of Acid Leached Glass Powders

The process of viscous flow sintering is a phenomenon that is closely linked to the surface properties of the glass particles. In this work, we studied the extreme case of acid-leaching of soda-lime-silicate glass beads of two different particle size distributions and its effects on non-isothermal viscous sintering of powder compacts. Depth profiling of the chemical composition after leaching revealed a near-surface layer depleted in alkali and alkaline earth ions, associated with concurrent hydration as mass loss was detected by thermogravimetry. Heating microscopy showed that acid treatment of glasses shifted the sinter curves to higher temperatures with increasing leaching time. Modelling of the shrinkage with the cluster model predicted a higher viscosity of the altered surface layer, while analysis of the time scales of mass transport of mobile species (Na+, Ca2+ and H2O) during isochronous sintering revealed that diffusion of Na+ can compensate for concentration gradients before sintering begins. Also, exchanged water species can diffuse out of the altered layer, but the depletion of Ca2+ in the altered surface layer persists during the sinter interval, resulting in a glass with higher viscosity, which causes sintering to slow down.

Auto-agglomeration of dry ibuprofen powder under mechanical vibration: Effect of particle morphology and surface properties

This study investigates the effect of ibuprofen particle morphology and surface properties on its tendency to auto-agglomerate. Four diverse particle morphologies were produced by recrystallisation of ibuprofen from solvents with different polarities. The aspect ratio and the polar component of the recrystallised particles decreased as follows: methanol > ethanol > acetonitrile > hexane. The auto-agglomeration process was induced by mechanical vibration and the agglomerate strength was assessed by the Dispersion and Agglomerate Strength indices. Relatively strong agglomerates were detected only in the case of ibuprofen recrystallised from ethanol and acetonitrile, whereas weaker and no agglomerates were formed during mechanical vibration of ibuprofen recrystallised from methanol and hexane, respectively. It was found that tendency of ibuprofen powder to auto-agglomerate was associated with lower tribo-electric charges during mechanical vibration, hypothetically linked to the competitive advantage of electrostatic attraction of high surface polarity particles to the walls of the vibration box which can hinder particle-particle interactions. Crystal surface polarity could be altered by the crystallisation protocol and/or by particle breakage (exposing more crystal facets of high polarity) during mechanical vibration.

[Research Progress on Toxicity of Microplastics in Soil to Terrestrial Plants and Their Degradation Mechanism].

Microplastics(MPs), as a new type of environmental pollutants, have gradually attracted widespread attention since they were introduced by British scientists in 2004. Soil is an important accumulation site for microplastics, which can expand the scope of contamination and accumulate with agricultural practices such as irrigation and tillage. Microplastics in soil cause a variety of toxicities to terrestrial plants. The small particle size, difficult degradation, and strong adsorption capacity bring a challenge to the microplastic pollution treatment of soil. In this study, the toxicity of microplastics to terrestrial plants was reviewed in terms of their direct or indirect toxicity and combined effects with other pollutants, mainly in terms of mechanical injury, induction of oxidative stress, and cytotoxicity and genotoxicity to plants, resulting in plant growth and plant tissue metabolism obstruction. In general, the toxicity of microplastics depended on the polymer type, size, and dose; plant tolerance; and exposure conditions. In addition, the production of secondary microplastics and endogenous contaminants during their degradation in soil enhanced the biotoxicity of microplastics. Further, the physical, chemical, and microbial degradation mechanisms of microplastics were introduced in this study based on the current research. At first, the physical and chemical degradation of microplastics mainly occurred by changing the particle size and surface properties of microplastics and producing intermediates. Then, smaller-sized microplastics and their intermediates could eventually be converted to water and carbon dioxide through physical, chemical, and biological functions. Finally, further prospects regarding soil microplastics were introduced, and we provided information for future improvement and pollution control of microplastics.