Arrangement Of Particles Research Articles

Investigation of the atomic-level microstructural evolution of quadruple-fused α/β titanium particles during sintering

The sintering dynamics of binary particles have been extensively studied; however, the sintering behavior of multiparticles still needs further investigation because it plays a key role in many industrial processes and advanced technologies. Herein, we used molecular dynamics simulations to investigate the sintering dynamics of quadruple titanium (Ti) particles. We investigated two particle arrangement configurations of Ti particles, ααββ and αβαβ, at three sintering temperatures (900 K, 1300 K, and 2000 K) to explore the microstructural changes of Ti particles during sintering. Furthermore, we proposed a formula for calculating the fusion ratio of multiple particles. The results show that ααββ-Ti could retain its HCP structure when sintered at 1300 K and 900 K, whereas only BCC-Ti was observed after sintering at high temperatures. The effect of diffusion mechanisms was more substantial at high temperatures, and the higher the sintering temperature, the better the particle fusion effect. In addition to the effect of temperature on atomic migration, different particle arrangement configurations can impact atomic migration.

Peak Wavelength Mapping of Triangular Reflection in Spherical Colloidal Cluster with Icosahedral Symmetry

Spherical colloidal clusters have various types of particle arrangements. Interestingly, one type has an icosahedron symmetry, characterized by the existence of five-fold axes. When the colloidal particle size is comparable to the wavelength of light, icosahedral colloidal clusters exhibit a unique triangular reflection with a specific wavelength, owing to optical interference. In this paper, we report the results of a detailed optical study on the position-dependent peak wavelength within the triangular region. Based on the map of the peak wavelength and spectral shape, we propose a structural model of the icosahedral colloidal cluster and discuss its formation process.

When optical vortex array meets cycloid.

Optical vortex arrays (OVAs) have drawn widespread attention owing to their multiple optical vortices and higher dimensions. However, existing OVAs have not yet been utilized to exploit the synergy effect as an entire system, particularly for manipulating multiple particles. Thus, the functionality of OVA should be explored to respond to application requirements. Hence, this study proposes a functional OVA, called cycloid OVA (COVA), based on a combination of cycloid and phase-shift techniques. By modifying the cycloid equation, multiple structural parameters are designed to modulate the structure of the COVAs. Subsequently, versatile and functional COVAs are experimentally generated and modulated. In particular, COVA executes local dynamic modulation, whereas the entire structure remains unchanged. Further, the optical gears are first designed using two COVAs, which exhibit potential for transferring multiple particles. Essentially, OVA is endowed the characteristics and capacity of the cycloid when they meet. This work provides an alternative scheme to generate OVAs, which will open up advanced applications for the complex manipulation, arrangement and transfer of multiple particles.

Self-Assembled Tetratic Crystals by Orthogonal Colloidal Force.

Bonding simple building blocks to create crystalline materials with design has been sophisticated in the molecular world, but this is still very challenging for anisotropic nanoparticles or colloids, because the particle arrangements, including position and orientation, cannot be manipulated as expected. Here biconcave polystyrene (PS) discs to present a shape self-recognition route are used, which can control both the position and orientation of particles during self-assembly by directional colloidal forces. An unusual but very challenging two-dimensional(2D) open superstructure-tetratic crystal (TC)-is achieved. The optical properties of the 2D TCs are studied by the finite difference time domain method, showing that the PS/Ag binary TC can be used to modulate the polarization state of the incident light, for example, converting the linearly polarized light into left-handed or right-handed circularly polarized light. This work paves an important way for self-assembling many unprecedented crystalline materials.

PECULIARITIES OF STRUCTURAL PHASE TRANSITIONS IN A SELF-ORGANIZING AOT/WATER/ISOPROPYL MYRISTATE SYSTEM UPON INTRODUCTION OF L-LYSINE

New biocompatible microemulsion and liquid-crystalline sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/water/isopropyl myristate systems have been obtained for the delivery of drugs and physiologically active substances. A combination of dynamic light scattering and X-ray diffraction methods has been used to determine their structural and size characteristics. The Primus and SasView software packages have been employed to simulate the shape and arrangement of particles as depending on AOT content. It has been shown that, as the concentration of the surfactant increases, the shape of micelles varies from spherical to cylindrical, and, at high concentrations, a structural phase transition occurs with the formation of a liquid-crystalline phase. The influence of a model bioactive compound, L-lysine, on the size and structure of the system has been studied. It has been revealed that the addition of the amino acids to the samples leads to an increase in the microemulsion droplet size, and, in the case of the liquid-crystalline phase, to the disintegration of the hexagonal packing into individual cylinders. The results obtained can be useful for the analysis of the mechanisms of L-lysine release from the AOT/water/isopropyl myristate transport system.

A Multi-orientation System for Determining Angular Distributions of Shear Wave Velocity in Soil Specimens

Abstract Soils typically have anisotropic mechanical and hydraulic properties due to the micro-scale interactions between particles that are influenced by particle morphology and depositional processes that can lead to particular particle arrangements (i.e., fabric anisotropy) and by imposed loading conditions and history (i.e., stress anisotropy). Experimental assessment of the anisotropy of soil specimens is a challenging feat, typically accomplished using specialized geotechnical testing and imaging equipment. The anisotropy of soil specimens can also be assessed based on measured responses, such as the velocity of propagating shear waves. This paper presents the development of a system that enables the measurement of shear wave velocity (VS) along different orientations and polarization planes using seven pairs of piezoelectric bender elements (BEs) to obtain angular distributions of VS. Specimens of glass beads and angular natural sands were tested in isotropic and one-dimensional (1D) compression to demonstrate the results obtained with the multi-BE system. The experimental results indicate that the effects of fabric and stress anisotropy can be identified by the angular distributions of VS, as well as measurements obtained along different polarization planes (i.e., VS,HH, VS,HV, and VS,VH). The level of anisotropy in soil specimens can be quantified either in terms of ratios of shear wave velocities or of parameters used to fit the angular VS distribution. The results also show that the parameters describing the relationship between VS and mean effective stress depend on the orientation of the propagating wave. The proposed system may enable the nondestructive assessment of soil specimen anisotropy using conventional laboratory equipment, which would complement other sophisticated experimental methods such as X-ray computed tomography and particle-based numerical simulations.

Control Effect of Deposition Processes on Shale Lithofacies and Reservoirs Characteristics in the Eocene Shahejie Formation (Es4s), Dongying Depression, China

The lacustrine fine-grained sedimentary rocks in the upper interval of the fourth member of the Eocene Shahejie Formation (Es4s) in the Dongying Depression are important shale oil exploration targets in Bohai Bay Basin. They are widely distributed and rich in organic matter. In this study, samples were observed under the optical microscope and FESEM, combined with geochemical test and physical property analysis to study the sedimentary characteristics and reservoir characteristics of them. Nine lithofacies are recognized based on the mineral composition, the content of organic matter and the beddings. The middle-high organic laminated calcareous fine-grained sedimentary rocks (LF1) and the middle-high organic laminated mixed fine-grained sedimentary rocks (LF2) resulted from seasonal sediment variations and settled by suspension in the deep lake. The middle-high organic flaggy mixed fine-grained sedimentary rocks (LF3), the middle-high organic flaggy calcareous fine-grained sedimentary rocks (LF4), the middle-high organic massive calcareous fine-grained sedimentary rocks (LF5) and the middle organic massive mixed fine-grained sedimentary rocks (LF6) were formed by redeposition. The low organic massive argillaceous fine-grained sedimentary rocks (LF7), the low organic massive felsic fine-grained sedimentary rocks (LF8) and the low organic massive mixed fine-grained sedimentary rocks (LF9) are affected by the terrigenous input events. The pore structures vary in different beddings which are influenced by the kinds and arrangement of minerals and particles. In the laminated lithofacies, the ink-bottle-shaped pores are dominant. In the flaggy and massive lithofacies, the ink-bottle-shaped pores and the slit-shaped pores coexist. LF1 and LF2 are the best target for shale oil exploration and the LF3, LF4, LF5 and LF6 are the second. The deposition processes control the lithofacies and reservoir characteristics of the fined-grained sedimentary rocks.

Response and prediction of unsaturated permeability of loess to microstructure

The study of water infiltration helps to investigate the pollutants' migration, grasp the mechanism of the water cycle, and correctly evaluate water resources. This paper reveals the mechanism of compacted loess's one-dimensional vertical water infiltration characteristics using a low-cost water infiltration device. In addition, it investigates particle arrangement and pore size distribution characteristics using nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM). The test finding suggests that the loess's early-stage infiltration rate is significant, and the dry density is not related to the infiltration characteristics. With the advance of the wetting front, the infiltration rate decreases under air resistance. The unsaturated permeability decreases with dry density at lower matric suction while unaffected by the dry density at higher matric suction. Moreover, the volume and connectivity of pores mainly control the water infiltration characteristics. Finally, based on the test results, a method for rapidly predicting the unsaturated permeability of loess is proposed. The results of the study help predict contaminant transport and guide groundwater extraction and management.

Adjustment of Micro- and Macroporosity of ß-TCP Scaffolds Using Solid-Stabilized Foams as Bone Replacement.

To enable rapid osteointegration in bioceramic implants and to give them osteoinductive properties, scaffolds with defined micro- and macroporosity are required. Pores or pore networks promote the integration of cells into the implant, facilitating the supply of nutrients and the removal of metabolic products. In this paper, scaffolds are created from ß-tricalciumphosphate (ß-TCP) and in a novel way, where both the micro- and macroporosity are adjusted simultaneously by the addition of pore-forming polymer particles. The particles used are 10-40 wt%, spherical polymer particles of polymethylmethacrylate (PMMA) (Ø = 5 µm) and alternatively polymethylsilsesquioxane (PMSQ) (Ø = 2 µm), added in the course of ß-TCP slurry preparation. The arrangement of hydrophobic polymer particles at the interface of air bubbles was incorporated during slurry preparation and foaming of the slurry. The foam structures remain after sintering and lead to the formation of macro-porosity in the scaffolds. Furthermore, decomposition of the polymer particles during thermal debindering results in the formation of an additional network of interconnecting micropores in the stabilizing structures. It is possible to adjust the porosity easily and quickly in a range of 1.2-140 μm with a relatively low organic fraction. The structures thus prepared showed no cytotoxicity nor negative effects on the biocompatibility.

Homogenized transition conditions for plasmonic metasurfaces

The present study aims to model the optical response of plasmonic metasurfaces made of a periodic arrangement of metallic particles with arbitrary shape and subwavelength dimensions. By combining homogenization with quasistatic plasmonic eigenmode expansion, the metasurface is replaced by a zero-thickness interface associated with frequency-dependent effective susceptibilities. The resulting discontinuities of the fields are responsible for strong interaction with the incoming light at the resonances when the complex permittivity of the metal passes close to the real permittivity of an eigenmode. Our modeling provides a physical picture of resonances in plasmonic metasurfaces, and it allows for a huge decrease in the numerical cost of their computations. In addition, comparisons with direct numerics in two dimensions evidence its predictive force at any incidence, particle shape, and arrangement.

Non-Markovian speedup evolution of a center massive particle in two-dimensional environmental model

A two-dimensional ray model is introduced to realize the non-Markovian speedup evolution of a center massive particle gravitationally coupled to a controllable environment (multilayer arrangement of the massive particles). By controlling the environment, for instance by choosing a judicious mass of the environmental particles or by changing the separation distance of each massive particle, two dynamical crossover behaviors from Markovian to non-Markovian and from no-speedup to speedup are achieved due to the gravitational interactions between the system particle and environmental particles. It is obvious that the critical mass of the environmental particles or the critical separation distance for these two dynamical crossover behaviors restrict each other directly. The larger the value of the mass of the environmental particles is, the smaller the value of the critical separation distance should be requested. In addition, it should be emphasized that the non-Markovian dynamics is the principal physical reason for the speedup evolution of the system massive particle. Particularly, the non-Markovianity of the dynamics process of the system massive particle in the even ray case has better correspondence with the quantum speed limit time than that in the singular ray case.

Prediction of Tail-Off Pressure Peak Anomaly on Small-Scale Rocket Motors

Numerical studies intended to predict solid rocket motors anomalies are the major contributors when developing strategies to both limit expensive fire tests and to investigate and understand the physical phenomena from which anomalies can arise. This paper aims to present a mathematical–physical method to evaluate the pressure peak, namely Friedman Curl, occurring at the tail-off phase of small-scale rocket motors. Such phenomenon is linked to the grain solid particles arrangement (i.e., packing effect); indeed, those particles show a tendency to accumulate at a certain distance from the metallic case, implying a local burn rate increment and a combustion chamber pressure rise close to the tail-off phase. Comparisons between experimental and simulated combustion chamber pressure profiles are outlined to prove the effectiveness of the mathematical–physical approach. Simulations were carried out with an internal ballistic simulation tool developed by the authors of this work.

Improving nanoparticle superlattice stability with deformable polymer gels.

The self-assembly of colloidal nanoparticles into ordered superlattices typically uses dynamic interactions to govern particle crystallization, as these non-permanent bonds prevent the formation of kinetically trapped, disordered aggregates. However, while the use of reversible bonding is critical in the formation of highly ordered particle arrangements, dynamic interactions also inherently make the structures more prone to disassembly or disruption when subjected to different environmental stimuli. Thus, there is typically a trade-off between the ability to initially form an ordered colloidal material and the ability of that material to retain its order under different conditions. Here, we present a method for embedding colloidal nanoparticle superlattices into a polymer gel matrix. This encapsulation strategy physically prevents the nanoparticles from dissociating upon heating, drying, or the introduction of chemicals that would normally disrupt the lattice. However, the use of a gel as the embedding medium still permits further modification of the colloidal nanoparticle lattice by introducing stimuli that deform the gel network (as this deformation in turn alters the nanoparticle lattice structure in a predictable manner). Moreover, encapsulation of the lattice within a gel permits further stabilization into fully solid materials by removing the solvent from the gel or by replacing the solvent with a liquid monomer that can be photopolymerized. This embedding method therefore makes it possible to incorporate ordered colloidal arrays into a polymer matrix as either dynamic or static structures, expanding their potential for use in responsive materials.

Substrated inhomogeneous metasurfaces analysis using interaction constant method

Inhomogeneous metasurfaces as a periodic array of supercells in which each supercell consists of different types of particles are good candidates for increasing the bandwidth in many applications. However, the presence of a substrate is often apparent in many cases; therefore, analyzing substrated inhomogeneous metasurfaces is highly attractive and important. In this paper, an efficient analysis of the plane-wave scattering by inhomogeneous substrated metasurfaces is presented using interaction constant method (ICM). In our proposed method, we calculate the total effective polarizability tensors of inhomogeneous substrated metasurfaces using both the individual polarizabilities of each particle and the closed-form interaction coefficients that relate to the interactions of the particles with each other. Since the interaction constants are calculated analytically, this method is time effective for different arrangements of particles in supercells, and with different array periods. The reflectance and transmittance of different inhomogeneous metasurfaces have been obtained and compared to full-wave simulations by a commercial EM solver, here, and this has confirmed the accuracy of the numerical results of our proposed method. Moreover, in our last example, we present a wideband terahertz absorber, and analyze its structure with our method. It seems that our proposed method is a step forward in the analysis and design of inhomogeneous substrated metasurfaces, for various applications.

Effect of pyrazine in PEDOT:PSS thin films: Structural, optical, optoelectrical, and electrical analysis

The pristine PEDOT:PSS and different weight amounts of pyrazine in PEDOT:PSS thin films were prepared using the doctor-blading technique on a borosilicate glass substrate. The structural, optical, and electrical properties of the effect of pyrazine in PEDOT:PSS thin films were presented for the first time of this admixed solution. More accuracy in the surface of thin films was observed by atomic force microscopy (AFM) which revealed the granular deposits on the film surfaces. Some hill shapes and the distribution of agglomerated grains were also observed on the thin films. The PEDOT:PSS with pyrazine has a preferred orientation to be an orthorhombic crystal structure. The crystallite sizes were reduced from 230.40 nm to 101.81 nm for 30–60 mg pyrazine in the PEDOT:PSS. The energy band gap (Eg) value of pristine PEDOT:PSS is of 3.50 eV with Urbach energy (EU) of 336.10 meV. The alteration Eg values from 3.52 to 3.67 eV was obtained with the estimated EU values in the range of 283.16–324.62 meV depends on various amounts of pyrazine. The linear optical parameters, i.e., the refractive index, optical electronegativity, real/imaginary dielectric constants, extinction coefficient, and optical conductivity were investigated and explained by the changes in the formation, nucleation, growth of clusters, and particle arrangement. As the spectrum increased, the highest χ(1), χ(3), and n2 values were obtained for the 80 mg pyrazine in PEDOT:PSS of 0.110, 2.562 × 10−14 esu, and 6.219 × 10−13 esu, respectively. The electrical conductivity was clearly increased for pyrazine exceeding 40 mg from 1.85 × 102 to 3.84 × 102 S/cm and the figure of merit was in the range of 4.34 × 10−2 to 4.68 × 10−2 Ω−1. Thus, the novelty of this work can show that pyrazine in the range of 40 mg–80 mg is the optimum condition to synthesize non-linear optical (NLO) materials, organic light-emitting diodes (OLEDs), and organic light-emitting transistors (OLETs).

Simulation of a TRISO MiniFuel irradiation experiment with data-informed uncertainty quantification

An irradiation experiment using tristructural isotropic (TRISO) fuel particles and the miniature fuel (MiniFuel) irradiation vehicle was performed in Oak Ridge National Laboratory’s High Flux Isotope Reactor (HFIR) to support development of the Kairos Power fluoride salt–cooled, high-temperature reactor (KP-FHR). This paper describes modeling predictions of temperatures and fuel burnup for the as-built experiment. An uncertainty quantification (UQ) analysis was performed to determine the effect of TRISO particle volume and position on the temperature predictions at various fuel heat generation rates (HGRs). This UQ study utilized fuel kernel position and volume measurements previously collected using X-ray computed tomography (XCT) techniques and Monte Carlo sampling methods to generate fuel compact cases that were then analyzed using a finite element thermal model. The UQ analysis indicated that uncertainty in calculated temperatures caused by varying TRISO particle arrangement is relatively small, even at high fuel HGR. Final predictions of particle temperatures throughout the irradiation are shown to be relevant to KP-FHR normal and off-normal operating conditions and to previous TRISO irradiation experiments. The combination of XCT with UQ analyses will inform post-irradiation examination (PIE) of the irradiated fuel compacts, and these analyses can be used to develop fuel performance models for coated particle fuel forms. Both PIE of separate-effects irradiation data and enhanced fuel performance modeling support accelerated qualification of TRISO fuels for a broad range of advanced reactor applications. The novel approach demonstrated here of measuring TRISO particle configurations with XCT methods and generating representative fuel compacts for finite element modeling and UQ analysis could be leveraged by the broader particle fuel community in the development of other TRISO fuel experiments in which these variables may have a significant impact on key outcomes.

Effect of different arrangements of globe particles on radio frequency heating uniformity: Using black pepper as an example

Different arrangements of stacked globe particles may result in various heating patterns in radio frequency heating. In this study, black pepper particles with an identical diameter (5 mm) and four different arrangements subjected to radio frequency heating were modeled and the heating rate and temperature distribution were compared. The four arrangements were simple cubic, body centered cubic, rhombohedral and face centered cubic. Within different arrangements, as the porosity increased from 0.25 to 0.47, the heating time increased from 500 to 780 s for reaching a target temperature of 70 °C. For heating rates comparison at the sample center and corners, rhombohedral model had the highest R2 (0.9953, 0.9975) and lowest RMSE (1.0709, 0.7642), respectively, among all arrangements. For temperature distribution on the top surface, the highest similarity of heating pattern between simulation and experiment was also found in rhombohedral model with an RMSE of 124.30. Therefore, the optimal prediction results was obtained in an arrangement with the closest porosity to randomly stacked globe particles in experiment. This study verified the importance of porosity and arrangement of particles in RF heating, and expanded the usage of RMSE for modeling accuracy evaluation.

Structure formation processes in fullerene mixtures

Glass formation processes in condensed matter are characterized by some specific short-range order changes in the arrangement of particles (atoms/molecules/ions). So, the short-range structural order in supercooled liquids and glasses is characterized by fivefold symmetry in the arrangement of particles, often referred to as icosahedral (ideal or distorted) short-range order. This article is devoted to the study of local structural features of the supercooled melt of the A20B80 fullerene mixture (where A = C60 and B = C70) obtained under various cooling protocols in order to elucidate the mechanism of formation of the icosahedral short-range order in binary molecular liquids. Comprehensive studies of the properties of a fullerene mixture melt were carried out using large-scale molecular dynamics simulations followed by structural and cluster analysis. The crystallization temperature and the critical glass transition temperature of the system were calculated to be T_m~1439 K and T_c~1238 K, respectively. It has been established that the crystallization of a binary fullerene mixture proceeds according to the polycrystalline scenario with the formation of clusters with fcc and hcp symmetries. It is shown that in a supercooled fullerene mixture, the short-range icosahedral order is formed by an insignificant number of ideal icosahedral clusters and a certain set of distorted icosahedral clusters, the fraction of which remains practically unchanged at temperatures below the critical glass transition temperature. Keywords: molecular dynamics, fullerenes, short-range order, structural ordering.

Процессы структурообразования в фуллереновых смесях

Glass formation processes in condensed matter are characterized by some specific short-range order changes in the arrangement of particles (atoms/molecules/ions). So, the short-range structural order in supercooled liquids and glasses is characterized by fivefold symmetry in the arrangement of particles, often referred to as icosahedral (ideal or distorted) short-range order. This article is devoted to the study of local structural features of the supercooled melt of the A20B80 fullerene mixture (where A = C60 and B = C70) obtained under various cooling protocols in order to elucidate the mechanism of formation of the icosahedral short-range order in binary molecular liquids. Comprehensive studies of the properties of a fullerene mixture melt were carried out using large-scale molecular dynamics simulations followed by structural and cluster analysis. The crystallization temperature and the critical glass transition temperature of the system were calculated to be Tm ≈ 1439 K and Tc ≈ 1238 K, respectively. It has been established that the crystallization of a binary fullerene mixture proceeds according to the polycrystalline scenario with the formation of clusters with fcc and hcp symmetries. It is shown that in a supercooled fullerene mixture, the short-range icosahedral order is formed by an insignificant number of ideal icosahedral clusters and a certain set of distorted icosahedral clusters, the fraction of which remains practically unchanged at temperatures below the critical glass transition temperature.

A novel theoretical method to determine the effective optical properties of high refractive index nanocomposites.

The continuous development of advanced optical devices towards high performance, miniaturization and integration has led to an increasing demand for high refractive index optical materials. Nanocomposites - made from high refractive index inorganic nanoparticles and good processability polymers - combine the advantages of both materials to create a synergistic effect. However, the diversity and complexity of the composites make laboratory preparation less efficient. Therefore, to prepare composites that meet the refractive index requirements, it is essential to predict the effective optical properties at different wavelengths. This study proposes a finite element parametric retrieval (FEPR) method to calculate the effective complex refractive index of nanocomposites (meff). The effects of the ratio of film thickness to particle diameter, particle arrangement, particle volume fraction (fv) and particle diameter (d) on meff are considered. The results demonstrate that changing the spatial arrangement, volume fraction and diameter of the particles can cause changes in the scattering effect of particles or the interaction between the electromagnetic waves and the particles, resulting in changes in the meff. Compared with effective medium theory (EMT), the FEPR method can be used to characterise the meff values in complex cases through finite element parametric modelling. The FEPR method is an efficient and accurate method for predicting the effective optical properties of nanocomposites, and can also be applied to the design and development of materials to discover the factors influencing the properties and variation patterns from large amounts of data, and to obtain predictive models that can guide the design of new materials.