Computation of local permeability in granular soils using spatial time domain reflectometer

This letter proposes semi-analytical methods to obtain the local permeability for granular soils based on indirect measurements of the local porosity profile in a large coaxial cell permeameter using spatial time domain reflectometry. The porosity profile is used to obtain the local permeability using the modified Kozeny-Carman and Katz-Thompson equations, which incorporated an effective particle diameter that accounted for particle migration within the permeameter. The profiles of the local permeability obtained from the proposed methods are compared with experimentally obtained permeability distributions using pressure measurements and flow rate. The permeabilities obtained with the proposed methods are comparable with the experimentally obtained permeabilities and are within one order of magnitude deviation, which is an acceptable range for practical applications.

Measuring the free energy of hard-sphere colloidal glasses

Free energy is a key thermodynamic observable that controls the elusive physics of the glass transition. However, measuring the free energy of colloidal glasses from microscopy images is challenging due to the difficulty of measuring the individual particle size in the slightly polydisperse glassy systems. In this paper, we carry out experiments and numerical simulations of colloidal glasses with the aim to find a practical approach to measure the free energy from colloidal particles at mild polydispersity. We propose a novel method which requires only the particle coordinates from a few confocal microscopy snapshots to estimate the average particle diameter and use it as an input for our experimental free energy measurements. We verify our free energy calculations from Cell Theory with the free energy obtained by Thermodynamic Integration. The excellent agreement between the free energies measured using the two methods close to the glass transition packing fraction highlights the dominant role played by \emph{vibrational} entropy in determining a colloidal glass's free energy. Finally, the noticeable free energy difference calculated from uniform and conjectured particle sizes emphasizes the sensitivity on particle free volumes when measuring free energy in the slightly polydisperse colloidal glass.

Novel 3D grid porous Li4Ti5O12 thick electrodes fabricated by 3D printing for high performance lithium-ion batteries

Three-dimensional (3D) grid porous electrodes introduce vertically aligned pores as a convenient path for the transport of lithium-ions (Li-ions), thereby reducing the total transport distance of Li-ions and improving the reaction kinetics. Although there have been other studies focusing on 3D electrodes fabricated by 3D printing, there still exists a gap between electrode design and their electrochemical performance. In this study, we try to bridge this gap through a comprehensive investigation on the effects of various electrode parameters including the electrode porosity, active material particle diameter, electrode electronic conductivity, electrode thickness, line width, and pore size on the electrochemical performance. Both numerical simulations and experimental investigations are conducted to systematically examine these effects. 3D grid porous Li4Ti5O12 (LTO) thick electrodes are fabricated by low temperature direct writing technology and the electrodes with the thickness of 1085 µm and areal mass loading of 39.44 mg·cm−2 are obtained. The electrodes display impressive electrochemical performance with the areal capacity of 5.88 mAh·cm−[email protected] C, areal energy density of 28.95 J·cm−[email protected] C, and areal power density of 8.04 mW·cm−[email protected] C. This study can provide design guidelines for obtaining 3D grid porous electrodes with superior electrochemical performance.

Number concentration dependence of ultrasonic disruption ratio of diameter-sorted microcapsules

The use of ultrasound to destroy microcapsules in microbubble-assisted drug delivery systems (DDS) is of great interest. In the present study, the disruption ratios of capsule clusters were measured by observing and experimentally analyzing microcapsules with polymer shells undergoing disruption by ultrasound. The microcapsules were dispersed in a planar microchamber filled with a gelatin gel and sonicated using 1 MHz focused ultrasound. Different capsule populations were obtained using a filtration technique to modify and control the capsule sizes. The disruption ratio as a function of the concentration of capsules was obtained through image processing of the recorded photomicrographs. We found that the disruption ratio for each population exponentially decreases as the particle number concentration (PNC) increases. The maximum disruption ratio of the diameter-sorted capsules was larger than that of polydispersed capsules. Particularly, for resonant capsule populations, the ratio was more than twice that of polydispersed capsules. Furthermore, the maximum disruption ratio occurred at higher concentrations as the mean particle diameter of the capsule cluster decreased.

Clozapine-Encapsulated Binary Mixed Micelles in Thermosensitive Sol–Gels for Intranasal Administration

(1) Background: Clozapine is the most effective antipsychotic. It is, however, associated with many adverse drug reactions. Nose-to-brain (N2B) delivery offers a promising approach. This study aims to develop clozapine-encapsulated thermosensitive sol–gels for N2B delivery. (2) Methods: Poloxamer 407 and hydroxypropyl methylcellulose were mixed and hydrated with water. Glycerin and carbopol solutions were added to the mixture and stirred overnight at 2–8 °C. Clozapine 0.1% w/w was stirred with polysorbate 20 (PS20) or polysorbate 80 (PS80) at RT (25 °C) before being added to the polymer solution. The final formulation was made to 10 g with water, stirred overnight at 2–8 °C and then adjusted to pH 5.5. (3) Results: Formulations F3 (3% PS20) and F4 (3% PS80) were selected for further evaluation, as their gelation temperatures were near 28 °C. The hydrodynamic particle diameter of clozapine was 18.7 ± 0.2 nm in F3 and 20.0 ± 0.4 nm in F4. The results show a crystallinity change in clozapine to amorphous. Drug release studies showed a 59.1 ± 3.0% (F3) and 53.1 ± 2.7% (F4) clozapine release after 72 h. Clozapine permeated after 8 h was 20.8 ± 3.0% (F3) and 17.8 ± 3.1% (F4). The drug deposition was higher with F4 (144.8 ± 1.4 µg/g) than F3 (110.7 ± 2.7 µg/g). Both sol–gels showed no phase separation after 3 months. (4) Conclusions: Binary PS80-P407 mixed micelles were more thermodynamically stable and rigid due to the higher synergism of both surfactants. However, binary mixed PS20-P407 micelles showed better drug permeation across the nasal mucosa tissue and may be a preferable carrier system for the intranasal administration of clozapine.

ВПЛИВ МЕХАНІЧНОЇ АКТИВАЦІЇ НА РОЗМІРНІ ХАРАКТЕРИСТИКИ ТА ФОРМУ ЧАСТИНОК ГЛИНОПОРОШКІВ РІЗНОГО ТИПУ

Purpose. Determination of the influence of the process of preliminary mechanical activation on the dimensional characteristics and shape of particles of different types of clay powders.Methodology. Clay powders of montmorillonite and palygorskite type were chosen as the objects of research in this work. The process of mechanical activation of clay powders was carried out using a laboratory ball mill. For microanalysis of sample particles, the method of optical polarizing microscopy was used. Morphometric analysis of clay powder particles was performed by image analysis using the ImageJ software. At the same time, the area and perimeter were determined, and the equivalent diameter and also the shape index of the particles of the samples were calculated. The experimental data were statistically processed using the Statistica and Excel software packages.Results. The paper investigates the effect of the process of mechanical activation on the dimensional characteristics and shape of particles of montmorillonite and palygorskite type clay powders. It was found that the decrease in the average values of the equivalent particle diameter in the process of mechanical action (~14–15%) is realized mainly due to the destruction of their largest aggregates. Moreover, the intensity of this process is noticeably higher for clay of the montmorillonite type. It is shown that for both studied samples, the process of mechanical activation leads to an increase in the average values of the particle shape index (~ by 9–10%) and an increase in the uniformity of their distribution by this index.Scientific novelty. Using a detailed morphometric analysis of particles of various types of clay powders, the regularities of the influence of the mechanical activation process on the quantitative statistical characteristics of their distribution over the equivalent diameter and shape index have been established.Practical value. The results obtained will make it possible to reasonably approach the choice of pretreatment methods for clay powders intended for the production of polymer filled nanocomposite materials.

Modeling of optical characteristics of organic solar cells based on poly (3,4-ethylene dioxythiophene): polystyrene sulfonate with incorporated silver nanoparticles

Changing the geometric parameters of the elements of the organic solar cell (OSC) and its components, changes in its optical characteristics such as reflection, absorption and transmission of light were studied. In the simulation, the main elements influencing the change in the characteristics of the OSC were poly (3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT: PSS), poly (3-hexylthiophene): [6,6] phenyl-C61butyric acid methyl ester (P3HT: PCBM) on silver nanoparticles. The dimensions of silver nanoparticles coincide with the thickness of the PEDOT layer (50 nm) in which they are located, the particle diameter is 45 nm, the thickness of the P3HT: PCBM layer has always remained equal to 100 nm. The peak at a wavelength of about 726 nm, when there are silver particles in the OSC, indicates the presence of localized surface plasmon resonance (LPPR), which causes a local amplification of the electromagnetic field near the surface of metal nanoparticles. LPPR induced by silver nanoparticles not only increases the degree of light absorption, but also enhances the degree of exciton dissociation. As a result, photocurrent and overall OSC efficiency can be significantly improved due to LPPR.

Preparation and electrochemical characterization of TiO2 as an anode material for magnesium-ion batteries

Anode on the basis of titanium dioxide powder was made. Its morphological characteristics were investigated using ellipsometry, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). Electrochemical properties were also investigated by cyclic voltammetry. Dispersing, mixing the initial reagents for obtaining homogenized paste and its coating to a substrate, drying and cutting the electrodes were main steps of anode production. The results of ellipsometry, SEM and EDS demonstrated a uniformly distributed layer of about 200 μm thickness with porous structure, particle diameter of 50–80 nm and titanium dioxide content (45.7 %). The XRD data confirmed the active anode matrix formation with a monoclinic crystal lattice corresponding to the modification of titanium dioxide (B) with small anatase inclusions. Electrochemical behavior of the electrode was examined in acetonitrile-based Mg(TFSI)2 solution. Diffusion coefficient (DMg) and the charge transfer rate constant (kct) were determined from cyclic voltammograms 1.54∙10–2 cm2/s and 1.29∙10–4 cm/s, respectively. A two-step electrochemical reaction was revealed by the ratio of the electricity amount consumed in the cathode and anode processes at varying the number of cycles. Small values of polarization resistance (Rp) calculated from cyclic voltammograms indicated rapid diffusion of magnesium ions during intercalation/deintercalation.

Study on Particle Manipulation in a Metal Internal Channel under Acoustic Levitation

In order to study the acoustic levitation and manipulation of micro-particles in the heterogeneous structures inside metal, a test system for internal levitation in three-dimensional space is designed, establishing the 3D motion model of ultrasonic levitation and manipulation of micro-particles. The relationship between levitation force, particle diameter, internal channel size, and transmission thickness is established through the motion manipulation tests of multi-configuration channel levitation micro-particles in components. The results show that the proposed method can realize the following movement of levitation micro-particles at a higher speed and the control of motion accuracy in three-dimensional space. The micro-particles can be reliably suspended and continuously moved inside the components along a predesigned motion trajectory. The results provide an effective and feasible processing scheme for direct processing through the internal spatial structure.

Measurement report: Three years of size-resolved eddy-covariance particle number flux measurements in an urban environment

Size-resolved particle number fluxes in the size range of 10 nm < particle diameter (Dp) < 200 nm were measured over a 3-year period (April 2017–March 2020) using the eddy-covariance technique at an urban site in Berlin, Germany. The observations indicated the site as a net source of particles with a median total particle number flux of FTNC=0.86 × 108 m−2 s−1. The turbulent surface–atmosphere exchange of particles was clearly dominated by ultrafine particles (Dp < 100 nm) with a share of 96 % of total particle number flux (FUFP=0.83 × 108 m−2 s−1). Annual estimates of median FTNC and FUFP slightly decreased by −9.6 % (−8.9 % for FUFP) from the first to the second observation year and a further −5.9 % (−6.1 % for FUFP) from the second to the third year. The annual variation might be due to different reasons such as the variation of flux footprints in the individual years, a slight reduction of traffic intensity in the third year, or a progressive transition of the vehicle fleet towards a higher share of low-emission standards or electric drive. Size-resolved measurements illustrated events of bidirectional fluxes, i.e. simultaneous emission and deposition fluxes within the size spectrum, which occurred more often in spring, late summer, and autumn than in winter. Multi-year observations of size-resolved particle fluxes proved to be important for a deeper understanding of particle exchange processes with the urban surface and the pronounced influence of traffic at this urban site.