Material Dispersion Research Articles

Coherent FIR/THz wave generation and steering via surface-emitting thin film lithium niobate waveguides.

Generating narrowband, continuous wave FIR/THz light via difference frequency generation (DFG) remains challenging due to material absorption and dispersion from optical phonons. The relatively new platform of thin film lithium niobate enables high-confinement nonlinear waveguides, reducing device size and potentially improving efficiency. We simulated surface-emitting DFG from 10 to 100 THz in a thin film lithium niobate waveguide with fixed poling period, demonstrating reasonable efficiency and bandwidth. Furthermore, adjusting wavelength and relative phase in an array of these waveguides enables beam steering along two directions. Continuous wave FIR/THz light can be efficiently generated and steered using these integrated devices.

FeCu alloy dispersed N-doped carbon compound material for electrocatalytic naproxen degradation

FeCu alloy dispersed N-doped carbon compound material for electrocatalytic naproxen degradation

Dual-functional trisiloxane as binder additive for high volume expansion Li-ion battery electrodes

Silicon-based anodes for lithium-ion batteries have the inherent advantage of higher capacity. However, the inherent expansion of Si within the anodes during cycling, causing low battery life, has limited its application. Various approaches are being investigated to mitigate the adverse effects, ranging from the patterned deposition of Si, blending silicon materials with graphite active materials, and using modified polymeric binders. Inspired by the super spreading capabilities of siloxane compounds and with an aim to optimize the graphite-SiO composite electrode, this work focuses on tweaking the binder formulation with a trisiloxane-based additive which enables uniform dispersion of active material within the electrode and enhances the wetting of the electrolyte within the electrode. In this work, graphite with 15 wt% silicon monoxide was used as an electrode with trisiloxane-modified binder showing much improved electrochemical performance with better mechanical integrity compared to the benchmark electrode. The cell with modified binder exhibited remarkable cycling stability up to 400 cycles at 0.2 C-rate. A detailed study on the role of the trisiloxane additives on the physicochemical properties of electrode materials has also been elucidated. The prospects of employing these additives for similar high-volume expansion electrodes are also discussed.

Accurate characterization of complex Bloch modes in optical chain waveguides using real-valued computations

This research presents a highly accurate and easy-to-implement method to characterize the complex Bloch modes propagating along optical chain waveguides with three-dimensional (3D) layered geometries and dispersive negative-epsilon material compositions. The technique combines commercial EM solver results with analytical post-processing to avoid iterative complex root estimation on the complex plane. The proposed methodology is based on the real-valued computations that yield the complex Bloch wavevector with superior accuracy even when both radiation and material losses are present. In addition, we introduce a single unit-cell technique to provide the possibility of dense meshing of 3D geometries when available computational resources are limited. To verify our results, two different plasmonic and dielectric case studies are discussed. The obtained results agree well with numerical and experimental results from the literature. Due to its generality, robustness, and high accuracy, the method is beneficial for studying a large variety of waveguide-based nanophotonic components.

Effects of Different Die Metals on the Performance and Friction and Wear of Composite Materials during the Extrusion Process.

Extrusion technology is widely utilized in the rubber processing industry, with the extruder serving as the core equipment. As mixed rubber enters the extruder, it undergoes conveyance and plasticization, ultimately forming specific shapes and dimensions upon extrusion. The extruder head is a crucial component, playing a key role in achieving the final product's required size and shape. Factors such as its structure, materials, and manufacturing processes significantly impact the efficiency, product quality, and sustainability of the extrusion process. However, prolonged operation leads to severe wear of the extruder head, adversely affecting rubber product quality. Additionally, extruder head processing poses challenges, with maintenance and repair being complex procedures. Therefore, exploring a wear-resistant, long-lasting metal material for the extruder head without compromising mixed rubber performance is essential. This study focuses on severely worn extruder head metal materials, comparing wear levels after friction with STELLITE 6 alloy, Hastelloy C-276 alloy, 38CrMoAlA, and tungsten carbide with composite rubber. Results show that compared to the NR/BR composite material after Hastelloy C-276 alloy friction, rubber Payne effect increased by 4.4% (38CrMoAl), 3.2% (STELLITE 6), and 4.6% (tungsten carbide). Similarly, rubber dispersion decreased by 9.4% (38CrMoAl), 4.7% (STELLITE 6), and 9.8% (tungsten carbide). Rolling resistance increased by 18.1% (38CrMoAl), 16% (STELLITE 6), and 23.4% (tungsten carbide). Friction coefficient increased by 3.5% (38CrMoAl), 2.8% (STELLITE 6), and 4.3% (tungsten carbide). Wear volume increased by 39.3% (38CrMoAl), 45.3% (STELLITE 6), and 48.9% (tungsten carbide). Specifically, using Hastelloy C-276 alloy as the extruder head metal material yields the best NR/BR composite material dispersion, highest ten times tear strength, excellent anti-wet skid resistance, and minimum rolling resistance. Conversely, using the other alloys results in varying reductions in the physical and mechanical properties of NR/BR composite materials. This research is crucial for improving rubber product quality and extending extruder head lifespan.

Self‐Responsive Janus Hydrogel with Alternation of Day and Night for Highly Efficient Solar Evaporation

Solar‐driven interfacial evaporation technology offers a promising method for sustainable freshwater production. Hydrogels have emerged as promising materials for interfacial evaporation, as they possess the capability to activate water molecules and lower the enthalpy required for evaporation. However, monolithic hydrogels fail to meet the diverse water content requirements in different evaporation regions. Herein, a thermoresponsive hydrogel (CSAm) capable of spontaneously forming Janus structures under sunlight illumination is designed. CSAm exhibits reversible solar‐induced wetting transition, enabling efficient evaporation with asymmetric wetting properties during the day and self‐cleaning of salts with hydrophilic wetting properties during the night. This transition of Janus structures allows for the regulation of water content distribution within the evaporator, meeting the diverse water content requirements of different evaporation regions. CSAm is composed of a thermoresponsive polymer, poly(N,N‐diethylacrylamide), and a hydrophilic polymer, polyacrylamide, cross‐linked to form a scaffold structure. The uniform dispersion of photothermal material (CuS) within the gel scaffold is achieved using lignosulfonates. This study investigates the Janus structure characteristics, photo/thermoresponsive properties, salt resistance, and evaporation performance. Under 1 sun illumination (1 kW m−2), CSAm exhibits a high evaporation rate of 2.67 kg m−2 h−1 and demonstrates long‐term stability in seawater desalination.

Time-domain modeling of interband transitions in plasmonic systems

Efficient modeling of dispersive materials via time-domain simulations of the Maxwell equations relies on the technique of auxiliary differential equations. In this approach, a material’s frequency-dependent permittivity is represented via a sum of rational functions, e.g., Lorentz poles, and the associated free parameters are determined by fitting to experimental data. In the present work, we present a modified approach for plasmonic materials that requires considerably fewer fit parameters than traditional approaches. Specifically, we consider the underlying microscopic theory and, in the frequency domain, separate the hydrodynamic contributions of the quasi-free electrons in partially filled bands from the interband transitions. As an illustration, we apply our approach to gold and demonstrate how to treat the interband transitions within the effective model via connecting to the underlying electronic band structure, thereby assigning physical meaning to the remaining fit parameters. Finally, we show how to utilize this approach within the technique of auxiliary differential equations. Our approach can be extended to other plasmonic materials and leads to efficient time-domain simulations of plasmonic structures for frequency ranges where interband transitions have to be considered.

Exploring a novel tubular-type modular reactor for solar-driven thermochemical energy storage

Thermochemical energy storage (TCES) has gained extensive attention as a potential solution to address the mismatch between solar thermal energy production and demand. In this study, a novel tubular-type modular TCES reactor is introduced. COMSOL modelling of the system is developed and experimentally validated using a laboratory-scale TCES system. Both types of reactors show similar temperature increases, intensifying with higher inlet relative humidity. Their maximum temperature lifts exceeding 26 °C at 90 % RH. Tubular designs offer better axial flexural strength and dispersion of TCES composite materials compared to plate structures. This property of tubular structures beneficial reducing bed thickness and pressure drop and enhancing equivalent thermal efficiency. Simulations show tubular-type modular reactors reduce pressure drop by 4–5 times compared to plate-type modular reactors, increasing equivalent thermal efficiency by nearly 7% points. Increasing the number of reactor beds and inner tube radius improves equivalent thermal efficiency due to reduced bed thickness and pressure drop. As the number of matrix rows and columns in the reactor bed increases from 2 to 10, bed thickness decreases from 0.058 m to 0.012 m, reducing pressure drop from 845.53 Pa to 38 Pa and increasing equivalent thermal efficiency from 78.82 % to 96.61 %.

FOR THE CALCULATION OF THE PARAMETERS OF THE VIBRATORY CONVEYOR OF THE DRYING INSTALLATION

The article deals with the theory of the movement of material in the vibrating conveyor of a drying installation developed at the National Technical University Dnipro Polytechnic, whose working surface has a stepped shape and the flow of coolant is directed at an angle to the horizontal plane. This constructive solution implements a method of creating a vibrating fluid layer in the working chamber, which significantly increases the drying speed of finely dispersed material. The working surface of the vibratory conveyor is made in the form of a step-shaped grid. Under the action of directional vibration excitation, the material entering drying moves along the grating surface and is blown through the slits with hot air. A feature of the vibro conveyor is the ability to move material with a wide granulometric composition, which includes fractions of grains from micrometers to tens of millimeters. When considering the movement of material along the working surface of the vibratory conveyor, it is possible to distinguish the loading zone and the transportation zone. In the loading area, the material is accepted into transport condition. In the transport zone, the material is subjected to an additional force from the coolant. For the efficient operation of the vibratory conveyor, the speed of movement of the material in the loading and transportation zone must be equal, which requires a comprehensive consideration of this issue. The mode with the separation of the material from the working surface of the vibrating conveyor with the assumption of the absence of air resistance is considered. Differential equations have been compiled and dependencies have been obtained that establish the relationship between the movement parameters of the material in the loading area of the vibrating conveyor, where there is no coolant flow, the angle of inclination of the working surface, width and angle of inclination of the plates forming the surface of the gas distribution grid. The conditions under which the contact of the material particles with the coolant flow is determined. Differential equations of particle motion taking into account the influence of the air flow on it are obtained, and dependences are obtained that determine the height of the gas distribution grid stage, the angle of inclination of the coolant flow to the horizontal plane, the motion parameters of the material particle with the additional effect of the heat carrier pressure on it. Thus, the proposed method of calculation allows obtaining initial data for designing the loading section of the transporting surface and the first stage of the gas distribution grid of the vibrating conveyor of the drying unit, as well as analyzing the influence of design parameters on the movement of a material particle.

STUDY OF THE TECHNOLOGICAL PROCESS OF MECHANICAL DEHYDRATION OF FOOD PRODUCTION WASTE THROUGH MATHEMATICAL MODELING

The separation of wet dispersed materials is becoming an urgent task for the industry of Ukraine and other countries, especially in the food and processing industries. Solving this task can effectively solve the problem of efficient management of wastes such as alcohol grounds, beer grounds, beet pulp, coffee and barley sludge. After separation of the liquid phase from the waste (dewatering), the solid phase can serve as a soil conditioner, a useful additive to agricultural feed, be used as a high-calorie fuel, and have other beneficial uses in both the processing and agricultural industries. After separation of the liquid phase from the waste (dehydration), the solid phase can serve as a useful additive to agricultural feed or be used as a high-calorie fuel. The most promising method of separating wet dispersed waste is mechanical dehydration. This method provides high productivity, low energy consumption, which is hundreds of times less than when using thermal methods to achieve the required moisture level of waste. A promising type of equipment for the mechanical separation of wet dispersed waste is presses with a hydraulic drive. They are characterized by compact size, high energy efficiency and reliability, as well as the possibility of precise regulation of waste processing parameters. The article presents a diagram of an improved and highly efficient installation with a hydraulic drive for the separation of wet dispersed materials. A mathematical model is presented that connects the parameters of the separation process, the design characteristics of the installation and the physical and mechanical properties of the material being processed. The found equations can be used to establish relationships between the working parameters of the processes, the design parameters of the equipment for the efficiency of the proposed bioenergy waste recycling technology.

CHARACTERISTICS OF THE INERTIAL PROPERTIES OF THE DISPERSED MATERIAL

It is noted that in the strength calculations of structural elements of aircraft, among other things, the modes of forced and natural vibrations are taken into account. In this regard, the dynamic properties of the transported cargo are taken into account, which are significantly different for solid and dispersed materials. Considered is a dispersed material located on a platform that performs harmonic oscillations. The main problem in establishing the dynamic properties of a dispersed material is the impossibility of calculating the average coefficient of dynamic friction, since its value is influenced by the interaction of dispersed particles with each other in the entire mass of the material, and not only with the surface of the platform. The description of the dynamic status of a dispersed material in the form of a composition of its unstable and stable statuses provides the key to solving this and similar problems.

Correlation of Efficient Dispersion and Catalytic Performance of Nanocombustion Catalysts in Energetic Materials: A Case Study of the Nanocopper Oxide Catalyst with Superfine Ammonium Perchlorate.

Obviously, the dispersion of nanocatalytic materials has significant influence on their catalytic performance. In this study, an evaluation method for the dispersion of nanomaterials was established according to the different solid UV absorptions of different substances by taking the dispersion of nanocopper oxide (nano-CuO) in superfine ammonium perchlorate (AP) as an example. The nano-CuO/superfine AP composites with different nano-CuO dispersions can be obtained by changing the process parameters, such as varying the grinding method, the grinding strength, and the grinding time. Three replicate experiments were carried out for different composites to derive the average values of absorbance at 212 nm, and the dispersion of nano-CuO in superfine AP was calculated using the difference equation, as the solid UV curves at 210-214 nm were almost identical for each sample, especially at 212 nm. The properties of different samples were tested by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (IR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), differential scanning calorimetry (DSC), and thermogravimetry-mass spectrometry (TG-MS). The results show that the particle size and structure of superfine AP in the composites prepared by different methods were not changed. The XRD and IR techniques in this study were unable to characterize the dispersion of nano-CuO in the composites due to its low content. The dispersion of nano-CuO in the nano-CuO/superfine AP composites was significantly enhanced with the increase of grinding strength and grinding time, and the dispersion of nano-CuO was positively correlated with its catalytic performance, which means that the thermal decomposition performance of different composites improved with the increasing dispersion of nano-CuO. Highly dispersed nano-CuO exhibited a significant catalytic effect on superfine AP in TG-MS. The above conclusions demonstrate the accuracy of the difference equation for evaluating the dispersion of nanomaterials based on solid UV curves, which is expected to be used extensively in evaluating the dispersion of nanocatalytic materials in energetic materials.

Observații cu privire la unele dicționare germano­-române din secolul al XIX-lea

The observations stated in this article focus on the composition of the word lists and the way of organizing the lexical material in some German-Romanian dictionaries from the 19th century. On the one hand, we analyse the role of German-Romanian dictionaries in putting into circulation and popularizing in Romanian a large number of Latin-Romanic neologisms. On the other hand, we focus on their different ways of organizing the dispersed lexical material by the separate registration of the polysemantic, or concentrated word meanings, by including words from an entire lexical family in the same lexicographic article.

Cellulose/nanocarbon composite based multifunctional aerogels for thermal management

Renewable resource-based aerogels have attracted numerous attention due to the requirement on sustainable multifunctional materials for thermal management. A series of cellulose and nanocarbon composite aerogels have been prepared from a blend of carboxylated cellulose nanofibril (CCNF) with carbon nanotube (CNT), graphene oxide (GO), or carbon fiber (CF) using directional freezing method. CCNF/nanocarbon aerogels from bidirectional freezing exhibit higher compression strength due to bridge structures that are induced by temperature gradient horizontally and vertically. Meanwhile, CCNF/carbon aerogels from bidirectional freezing also have thermal conductivity coefficient (λ) as low as 0.0308 W/(m·K), which increases to 0.0388 W/(m·K) after calcination. The dispersed linear carbon materials CF and CNT in CCNF matrix lead to thermoelectric, Joule heating and photothermal performance of CCNF/nanocarbon aerogels, which is also promoted by calcination. The Seebeck coefficient of CCNF/nanocarbon aerogels ranges from 0.027 to 0.067 mV/K and change into 0.037–0.044 mV/K due to the more uniform carbon network formed after high temperature treatment. A 5–15 V input voltage can induce a temperature increase of 62 ∼ 303 °C for composite aerogel after calcination. A laser with 0.3 W power can result in a rapid temperature increase even to 200 °C in seconds for composite aerogel with and without calcination. These kinds of CCNF/nanocarbon based composite aerogels exhibit ability in thermal management, including thermal insulation, thermoelectric, electric and photo induced heating, which are good candidates for multifunctional aerogels.

The influence of air inlet layout on the inner flow field for a vertical turbo air classifier

In this study, the influence of air inlet layout on the flow field distribution and particle movement trajectory for the vertical turbo air classifier are analyzed comparatively using the numerical simulation method. The air inlet layout adjustment can increase the axial velocity and turbulent dissipation rate at the feeding inlet and do not generate the axial negative velocity, which improves powder material pneumatic transportation and dispersion capacity; the air inlet layout adjustment can match the airflow rotation direction with the rotation direction of the rotor cage, which can eliminate the vortices in the rotor cage channel effectively. Moreover, the particle movement time is shortened and fast classification is completed, which can decrease the particle agglomeration probability and weaken the ‘fish-hook’ effect. The optimization scheme of the air inlet layout is Type-BC. In accordance with the numerical simulation results, the calcium carbonate classification experimental results indicate that the classification performance of the classifier is improved using Type-BC.

Topological electromagnetic waves in dispersive and lossy plasma crystals

Topological photonic crystals, which offer topologically protected and back-scattering-immune transport channels, have recently gained significant attention for both scientific and practical reasons. Although most current studies focus on dielectric materials with weak dispersions, this study focuses on topological phases in dispersive materials and presents a numerical study of Chern insulators in gaseous-phase plasma cylinder cells. We develop a numerical framework to address the complex material dispersion arising from the plasma medium and external magnetic fields and identify Chern insulator phases that are experimentally achievable. Using this numerical tool, we also explain the flat bands commonly observed in periodic plasmonic structures, via local resonances, and how edge states change as the edge termination is periodically modified. This work opens up opportunities for exploring band topology in new materials with non-trivial dispersions and has potential radio frequency (RF) applications, ranging from plasma-based lighting to plasma propulsion engines.

Impact craters formed by spinning granular projectiles.

Craters formed by the impact of agglomerated materials are commonly observed in nature, such as asteroids colliding with planets and moons. In this paper, we investigate how the projectile spin and cohesion lead to different crater shapes. For that, we carried out discrete element method computations of spinning granular projectiles impacting onto cohesionless grains for different bonding stresses, initial spins, and initial heights. We found that, as the bonding stresses decrease and the initial spin increases, the projectile's grains spread farther from the collision point, and in consequence, the crater shape becomes flatter, with peaks around the rim and in the center of the crater. Our results shed light on the dispersion of the projectile's material and the different shapes of craters found on Earth and other planetary environments.

On the Interaction of Massive Photons and Mechanical Oscillators in Cavity Optomechanics: Basic Model and Quantization

AbstractThis study investigates the theoretical aspects of the interaction between photons with mass and a mechanical oscillator as drawn within the framework of cavity optomechanics. The study employs Proca theory as the mathematical framework to initially describe the dynamics of massive photons in a Fabry‐Perot cavity with a movable mass, both in classical and quantum scenarios. It quantifies the modifications induced by the nonzero photon mass, considering first‐ and second‐order effects, and derives expressions for the amplification of radiation pressure resulting from the presence of nonzero photon mass. Additionally, it derives the Hamiltonian of the quantum optomechanical system, incorporating the effects of photon mass at first and second order. It anticipates that experimental realization of massive optomechanics can be achieved by utilizing Proca material, which is a spatio‐temporally dispersive material that exhibits behavior equivalent to Proca theory in a vacuum, thus enabling the study of the interaction between massive photons and mechanical systems in cavity‐based optomechanical setups (referred to as massive cavity optomechanics). The study presented here caters to a diverse audience with an interest in the analysis and measurement of interactions among massive objects at the quantum scale.

PVA/essential oil‐based active food packaging films functionalised with halloysite nanotubes and cellulose nanocrystals as filler materials for the shelf‐life extension of papaya fruits

SummaryThis study investigates the development of polyvinyl alcohol (PVA) and essential oil‐based biocomposite films incorporating halloysite nanotubes (HNTs) and cellulose nanocrystals (CNCs) as reinforcement materials for the packaging of papaya fruits to extend their postharvest shelf‐life. The fabrication process involves the dispersion of filler materials within the PVA polymer matrix, followed by the casting of the films using the solvent‐evaporation technique. The CNC isolated from the papaya peel exhibited rod‐like structures that were confirmed in the morphological studies. The films reinforced with HNT and CNC (5 wt%) had enhanced mechanical properties and exhibited a tensile strength of ~64.40 MPa. The findings of the study demonstrate that the fruits packed with biocomposite materials containing HNTs and CNCs as reinforcements and lemongrass essential oil as active material showed better performance when compared to the control. The edible quality and the storage life of the papaya fruits (TSS, firmness and weight loss %) under investigation were extended by 14 days at ambient temperature (25 °C ± 2 °C) and relative humidity (80%–85%), thus improving the postharvest shelf‐life of harvested papayas. Therefore, PVA‐based active packaging film prepared with lemongrass essential oil, HNTs and CNCs has great potential for the preservation of papaya during postharvest storage.

Preparation of mixed-mode weak cation exchange magnetic solid-phase extraction sorbent and its application in the extraction of 21 illicit drugs from wastewater

The detection of illicit drugs in wastewater can effectively monitor and evaluate the trend of illicit drug abuse. A novel mixed-mode cation exchange magnetic sorbent Fe3O4 @poly(ST/DVB/MA-COOH) was prepared and firstly applied as magnetically dispersed solid phase extraction material to efficiently, rapidly, and selectively extract 21 illicit drugs from wastewater. The selectivity of the sorbent was mainly attributed to the electrostatic interaction. The effects of Fe3O4 @poly(ST/DVB/MA-COOH) preparation and extraction conditions on the adsorption performance were thoroughly discussed. Among the 21 illicit drugs, the absolute extraction recovery values for 19 illicit drugs were greater than 80 % and the entire adsorption process could be achieved in one minute. Subsequently, the Fe3O4 @poly(ST/DVB/MA-COOH) sorbent combined with UHPLC-MS/MS was used to establish a quantitative method for the effectively extracted 19 illicit drugs in wastewater. The method had a good determination coefficient in the range of 0.2–200 ng/L and the limits of detection of the method were 0.03–0.67 ng/L. The spiked recovery values were in the range of 87.0–119.6 %. Finally, the method was successfully applied to the detection of 19 illicit drugs in wastewater samples and also compared with the commonly used SPE method. The obtained results indicate that Fe3O4 @poly(ST/DVB/MA-COOH) has great advantages in the detection of illicit drugs in wastewater.