Layer Of Particles Research Articles

High Energy Physics Applications on Fiber Optic Sensors in Relative Humidity

Our multidisciplinary research group has been conducting studies in recent years on the use of fiber grating-based sensors for relative humidity measurement in the Compact Muon Solenoid (CMS) instrument at CERN in Geneva. In order to monitor low relative humidity (RH) values even in cold temperatures, our multidisciplinary research group has been working to develop near-field fibre optic sensors based on tin dioxide particle layers, in light of the extensive research conducted in the past few years to evaluate the radiation hardness capability of fibre optic technology in high-energy physics settings. Compared to other sensor types, optical fiber sensors provide several advantages. These benefits mostly stem from the characteristics of optical fibers, which include their tiny size, inexpensive, electromagnetic passivity, resistance to high pressure, and resistance to high temperatures. Sensing is the process of measuring variables like temperatures, stress, or angular velocity by examining the characteristics of light. To evaluate the sensors' performance under the circumstances needed for CERN experiments, untried tests in the [0-65] %RH range at various temperatures were conducted. There were other campaigns of progressive irradiation using γ-ionizing radiations. The results obtained show that the suggested technologies have great potential for usage in High Energy Physics (HEP) activities as a reliable and acceptable replacement for commercial hygrometers in the future.

Electrochemical Characterization of Artificial Solid Electrolyte Interphase Developed on Graphite Via ALD

During formation of Li-ion batteries, a ‘natural’ solid electrolyte interphase (SEI) is formed at the anode side by decomposition products of the electrolyte. The properties of the SEI are extremely decisive for the overall battery properties, such as rate capability and cycling stability. However, the SEI formation consumes Li, leading to so called ‘formation losses’ that can make up to 15% of the theoretical energy density of the battery. Several approaches have been presented to overcome formation losses while preserving excellent overall battery properties. Particularly, electrochemical prelithiation and the application of artificial SEIs prior cell assembly are considered to effectively reduced formation losses while improving the interfacial charge transfer properties and increasing cycling stability.Herein, the authors present an innovative approach of applying a multifunctional artificial SEI on anode material powders via consecutive atomic layer deposition (ALD) cycles. As a model system, graphite powder has been chosen to be modified and characterized.The resulting electrodes show substantially improved electrochemical performance in half cells and full cells, regarding initial capacity loss, CE and cycling stability. Furthermore, model electrodes consisting of a single layer of graphite particles were manufactured, which exclude the effects of a typical composite electrode and therefore reveal the intrinsic properties of the active material. Using this approach, the interfacial kinetics and the rate capability are investigated comparatively between pristine and ALD coated electrodes, revealing the impact of the artificial SEI on the materials level.

SiO2 Nanoparticle Coating to Enable Polyethylene-Based Na-Ion Battery Separators

The increasing demand for Li-ion batteries (LIBs), pushed even more by the electrical vehicle industry, has highlighted the concern with the scarcity and uneven distribution of LIB raw materials. Electrochemical energy storage based on alternative chemistries, once properly developed, may provide sufficient energy density to partly supply that demand, reducing the dependence on Li natural reserves. Among the studied chemistries, Na-ion-based storage is currently attracting a lot of research attention. This is partly due to the similarities between Li and Na, which allow for the utilisation of analogous materials and methods already in place for LIBs. However, not every component of LIBs can be directly applied to Na-ion batteries (SIB).[1] This is the case for battery separators, the membranes used to avoid physical contact between the two battery electrodes to prevent short circuiting while conducting ions from one battery pole to the other. Porous polyolefin films, such as polyethylene (PE) and polypropylene (PP), have been successfully used in LIBs, but are not compatible with SIB electrolytes. In the latter case, issues arise from the poor wettability of the separator with the electrolyte, which leads to low ionic conductivity, and creates an uneven flux of ions that can cause cell failure. To address this issue, previous reports have shown that the presence of inorganic oxides such as ZrO2 [2] and SiO2 [3] on polyolefin films can increase the affinity of the separator with commonly used LIB and SIB electrolytes. Moreover, ceramic-modified films also show higher thermal stability and hindered thermal shrinkage, which improves battery safety.In this work, we investigated PE coated with spherical SiO2 particles (designed by Glantreo, Ireland) with different sizes of 85 and 200 nm. The coatings were made by tape casting both sides of a PE film with slurries containing SiO2 particles and a binder. Binder type, SiO2 concentration and SiO2/binder ratio were optimized for each particle size. The obtained films were characterized by scanning electron microscopy and infrared spectroscopy, and were compared regarding their wettability, thermal stability, and ionic conductivity. The films were tested as separators in hard-carbon half-cells with 1 mol/L NaClO4 in either diethylene glycol dimethyl ether (DEGDME) or ethylene carbonate (EC)/ propylene carbonate (PC) electrolyte. With carbonate-based electrolyte, PE has very low wettability and cells short circuit within the first cycle. However, SiO2-PE samples showed higher wettability, which allowed for cycling at low current densities. In DEGDME-based electrolyte, cells with PE separator presented capacity fade, with 50% capacity loss after 250 cycles at 400 mA/g. On the other hand, cells with SiO2-PE separator had stable cycling for more than 300 cycles and no short-circuiting was observed, even when high active mass loading electrodes (8 mg/cm2) were used. These are promising results showing that a surface layer of SiO2 particles can make PE a viable option for SIB separators.

Mesoporous Carbon Supported Catalyst for Heavy Duty Fuel Cells

The interaction between the catalyst and the carbon support is crucial to both the performance and durability of the membrane electrode assembly (MEA) in a polymer electrolyte membrane fuel cell. Local oxygen transport resistance (RO2) has shown to be a significant contributor to the overpotential loss in the catalyst layer.1 Utilizing mesoporous carbon supports has shown to reduce RO2 compared to high surface area carbon and prevent ionomer poisoning of Pt inside the pores.2 Engineered catalyst supports (ECS) synthesized through templated organic precursor provides improved control of resulting carbon morphology.3 This work presents a detailed study of the performance and durability of the ECS supported catalyst. Effect of Pt weight percentage on the carbon support, ionomer loading, and the ionomer type on the catalyst performance and durability is presented. Figure 1 shows the performance at beginning of life (BOL) and end of life (EOL) after 90000 cycles, using US DOE’s electrocatalyst protocol, for MEAs with different ionomer loadings. Polarization curve, Pt accessibility through CO stripping, and RO2 from limiting current will be presented are measured at different intervals between BOL and EOL. Characterization of the Pt particle and catalyst layer structure performed at BOL and EOL will also be presented. This study highlights the value of the morphological and electrochemical evaluation to provide detailed insights into the catalyst and mesoporous carbon support interaction. Acknowledgement This research is supported by Technology Readiness Gross Receipts Tax Credit through New Mexico Legislature. This research is supported by U.S. Department of Energy (DOE) Hydrogen and Fuel Cell Technologies Office, through the Million Mile Fuel Cell Truck Consortium (M2FCT). References 1 Kongkanand, A. et al. Journal of Physical Chemistry Letters, 7, (7), 1127-1137, 2016.2 Ramaswamy, N. et al. Journal of The Electrochemical Society, 167, (6), 064515, 2020.3 Ramaswamy, N. US DOE Hydrogen and Fuel Cells Program: 2020 Annual Merit Review and Peer Evaluation Report, 2020. Figure 1

Study on the differences between non-catalytic and catalytic oxidation of soot based on catalyst CeO2

Exploring the differences between soot non-catalytic and catalytic oxidation process is beneficial to enhance the catalyst performance and soot removal efficiency of catalytic diesel particulate filters. In this paper, the soot samples are pretreated under high temperature conditions at both non-catalytic and catalytic oxidation atmosphere to obtain target pretreated soot samples with different mass loss. Five typical oxidation stages are analyzed with corresponding soot mass loss rate of 15 %, 25 %, 50 %, 70 %, 85 %. The soot physicochemical properties including oxidation activity, porous structure, particle layer, nanostructure, graphitization and functional groups are explored; further, the correlations among these physicochemical properties are analyzed, and three levels of catalytic effect mechanism are proposed based on CeO2 catalyst. This paper helps in understanding the differences of the mechanisms between non-catalytic and catalytic oxidation of soot.

Oxidation differences on Si- versus C-terminated surfaces of SiC during planarization in the fabrication of high-power, high-frequency semiconductor device

Silicon carbide (SiC) wafers have attracted attention as a material for advanced power semiconductor device applications due to their high bandgap and stability at high temperatures and voltages. However, the inherent chemical and mechanical stability of SiC poses significant challenges in the chemical mechanical planarization (CMP) process, an essential step in reducing defects and improving surface flatness. SiC exhibits different mechanical and chemical properties depending on SiC terminal faces, affecting SiC oxidation behavior during the CMP process. Here, we investigate the process of oxide layer formation during the CMP process and how it relates to the SiC terminal faces. The results show that under the same conditions, the C-terminated face (C-face) exhibits higher oxidation reaction kinetics than the Si-terminated face (Si-face), forming an oxide layer of finer particles. Due to the different oxidation kinetic tendencies, the oxide layer formed on the C-face has a higher friction coefficient and more defects than the oxide layer formed on the Si-face. This results in a higher removal rate during CMP for the C-face than the Si-face. Furthermore, by controlling the physicochemical properties of the oxide film, high removal rates can be achieved by friction with the pad alone, without the need for nanoparticle abrasives.

Numerical investigation on a bimodal mixing system of solid–liquid mixture in an industrial mixing cooker

The powder mixing for foods is regarded to be unique because tons of products are manufactured through powder mixing processes in food industries; hence there is no room for doubt about the importance of a better understanding of the mixing mechanism. On the other hand, the powder mixing for foods has not been established so far. In this study, a series of simulations of the powder mixing in a liquid are performed using the discrete element method–computational fluid dynamics method. A monodispersed and bimodal mixing systems are computed to evaluate the effect of the particle density and the mixing shaft obliquity in a particular mixing cooker. The monodispersed system was computed purely for a purpose of reference to compare with the bimodal system. By performing a simulation on a monodispersed and bimodal mixing systems with very small density differences between solids as well as solid and liquid, this study provides significant evidence and novel insights into understanding the mixing mechanism of food products. In the monodispersed mixing system, the particles with the density close to water are revealed to be affected by the diffusive mixing which is due to buoyancy and the drag force. Furthermore, an increase in mixing shaft obliquity is shown to improve mixing performance in the monodispersed mixing system. In the bimodal mixing system the effect of the gravitational force is shown to be extremely important for the efficient powder mixing, even if the density difference is very small as 5%. The heavier particles initially positioned in the upper layer are drawn down into the layer of the lighter particles by gravitational force, facilitating mixing and enhancing efficiency. These are new findings which showed unique particle behaviour in mixing systems. This study provides new insights into the specific powder mixing mechanism in a liquid which are frequently encountered in the food industries.

SPH–DEM modelling of hypervelocity impacts on rubble-pile asteroids

ABSTRACT Investigating the hypervelocity impact process on rubble-pile asteroids is crucial for understanding the formation and evolution of small celestial bodies, and has important implications for planetary defence. In recent years, numerical simulations have been widely used to model asteroid impacts, as a complement to experimental and theoretical approaches. In particular, the hybrid SPH–DEM framework has been introduced to describe the multistage dynamics involving shock propagation and gravitational re-accumulation. However, the tension between modelling accuracy and computational costs poses significant challenges in rubble-pile impact simulations. In this study, we introduce two distinct particle configurations, i.e. multiple layers of similar-sized surface contact particles and a set of different-sized gravity particles, to efficiently describe the large irregular boulders during long-term evolution. Accordingly, the new transition algorithms are implemented to convert the smoothed particle hydrodynamics (SPH) results into the desired discrete-element method (DEM) configurations. With the proposed method, the complexity of contact computation is reduced from $\mathcal {O}(N)$ to $\mathcal {O}(N^{2/3})$, and the gravity computation is accelerated by about one hundred times while maintaining the same level of resolution. The method is then used to simulate the double asteroid redirection test impact on the rubble-pile asteroid Dimorphos. Our numerical simulations have reproduced the observation results regarding momentum transfer and mass ejection. Moreover, we predict that the impact event will form a final crater larger than 45–68 m in diameter and lead to global resurfacing of the target. The renewed surface and fresh interior will be accessible to the upcoming Hera mission, providing new perspectives on the formation and evolution of the rubble-pile binary asteroids.

Differences in structural changes and pathophysiologic effects of low-density lipoproteins upon accumulation of acylhydroperoxy derivatives in their outer phospholipid monolayer or upon chemical modification of apoprotein b-100 by natural dicarbonyl

Nanoparticles of the lipid-transporting system of the organism - low-density lipoproteins (LDL) of blood plasma are easily subjected to free radical peroxidation with formation of their main modified forms - oxidized LDL itself (containing hydroperoxy-acyls in phospholipids of the outer layer of particles) and dicarbonyl-modified LDL (apoprotein B-100 of which was chemically modified by the Maillard reaction). Based on the study of free radical oxidation kinetics of LDL, it was found that the existing in the literature designation “oxidized lipoproteins” is incorrect because it does not reveal the nature of oxidative modification of LDL. It is shown that “atherogenic” LDL (particles of which are actively captured by cultured macrophages) are not the oxidized LDL (in which LOOH-derivatives of phospholipids are formed by enzymatic oxidation of of C-15 lipoxygenase of rabbit reticulocytes), but dicarbonyl-modified LDL. The important role of dicarbonyl-modified LDL in the molecular mechanisms of atherogenesis and endothelial dysfunction is discussed.

Large-scale laboratory investigation of the performance of a novel isolation particle layer for offshore final disposal sites

The complex seabed conditions and ocean environment pose significant challenges to the material selection and construction of bottom liners for offshore final disposal sites. To overcome the challenges, this study proposed a novel isolation particle layer for offshore final disposal sites. The isolation particle was composed by salt-resistant bentonite coating material and cement core material (D10 was 10 mm in core diameter and 2 mm in coating thickness; D20 was 20 mm and 4 mm). Upon immersion in artificial seawater, the isolation particles underwent expansion, leading to the formation of the novel isolation particle layers with low hydraulic conductivity less than 1 × 10-7 cm/s and adsorption of heavy metals in bentonite interlayers. Large column tests showed that both D10 and D20 isolation particle layers exhibited remarkable swelling capacity and low hydraulic conductivity (4.3 × 10-9 cm/s and 2.6 × 10-8 cm/s) under 3 m seawater pressure. During one year of observation, water tank test demonstrated that both isolation particle layers displayed remarkable stability and low hydraulic conductivity of 2.73 × 10-10 cm/s and 8.36 × 10-10 cm/s with load. The maximum adsorption capacities of salt-resistant bentonite were 123.55 mg/g for Pb2+, 60.29 mg/g for Cd2+ and 54.22 mg/g for Cu2+. Both isolation particle layers exhibited a high removal rate of over 95 % for heavy metals in water tank tests. The large-scale laboratory tests indicated the significant potential of the novel isolation particle layer for offshore final disposal sites. Subsequently, a testing ocean site will be selected to further investigate its practical engineering performance.

A pore-level 3D lattice Boltzmann simulation of mass transport and reaction in catalytic particles used for methane synthesis

Three-dimensional lattice Boltzmann (LB) simulations were carried out to investigate the mass transport and reaction inside and around catalytic porous particles used in fluidized beds for the synthesis of methane from biogas (H2/CO mixtures). The 3D internal porous structure of a real particle with a size ∼200 μm was assessed with Synchrotron-based X-ray tomography (XTM). Pore-resolved simulations with a suitable LB model for catalytic reactions in microflows revealed that the preferential diffusion of H2 and the resulting inability of CO to penetrate deep inside the pores led to segregated distributions of the two species, hindering reaction in the downstream parts of the particle and rendering CO the deficient reactant. The implications for practical fluidized beds are that, for specific bed zones with a high dense-phase (solid-phase) volume fraction and a predominant flow direction, CO starvation may occur and may thus limit the methane yields. Subsequent parametric studies of spherical particles with a diameter 2R=150 μm and an artificially generated porosity allowed comparisons of LB results with radially symmetric analytical continuum-model solutions. The LB simulations revealed appreciable angular variations in the CO concentration at the external surface (r=R) and the outer layers of particle, especially at the higher investigated Damköhler numbers, which were however diminished as the core of the particle (r→0) was approached. The large angular variations, in conjunction with the skewed CO distributions towards their lower values, led to LB-computed particle effectiveness factors ∼30% lower than the corresponding analytical solutions.

Influence of Sphericity on Surface Termination of Icosahedral Colloidal Clusters.

Colloids self-organize into icosahedral clusters composed of a Mackay core and an anti-Mackay shell under spherical confinement to minimize the free energy. This study explores the variation of surface arrangements of colloids in icosahedral clusters, focusing on the determining factors behind the surface arrangement. To efficiently assemble particles in emulsion droplets, droplet-to-droplet osmotic extraction from particle-laden droplets to salt-containing droplets is used, where the droplets are microfluidically prepared to guarantee a high size uniformity. The icosahedral clusters are optimally produced during a 24-h consolidation period at a 0.04m salt concentration. The findings reveal an increase in the number of particle layers from 10 to 15 in the icosahedral clusters as the average number of particles increases from 3300 to 11 000. Intriguingly, the number of layers in the anti-Mackay shells, or surface termination, appears to more strongly depend on the sphericity of the clusters than on the deviation in the particle count from an ideal icosahedral cluster. This result suggests that the sphericity of the outermost layer, formed by the late-stage rearrangement of particles to form an anti-Mackay shell near the droplet interface, may play a pivotal role in determining the surface morphology to accommodate a spherical interface.

Superhydrophobic and breathable polydimethylsiloxane/nano-SiO2@polylactic acid electrospun membrane with core-sheath fiber structure

Polylactic acid (PLA) has great potential to replace traditional petroleum-based polymers, especially in membrane production, due to its biocompatibility, degradability, and renewability. However, there are rare reports of superhydrophobic and breathable PLA membranes. In this work, a multifunctional PDMS/SiO2@PLA membrane with superhydrophobicity and breathability was prepared by coaxial electrospinning method to coat the surface of PLA fiber with a thin layer of biocompatible polydimethylsiloxane (PDMS) and nano-silica particles. The prepared membrane has a water contact angle (WCA) of 151.8 ± 1.3° and a water sliding angle (WSA) of 5.7 ± 0.3°. Thanks to its superhydrophobicity, it can support a water column of 195 cm. The membrane has excellent breathability that its water vapor transmission rate is ~14.7 kg·m−2·24 h−1. Moreover, the freezing time of the membrane is 2.25 times longer than that of the original PLA membrane. In addition, it has an oil-water separation efficiency of 99.9 % and a flux of ~12,300 L·m−2·h−1. The overall performance of this multi-functional PDMS/SiO2@PLA membrane is one of the best among the fluorine-free electrospun membranes.

Chemical characteristics, distribution patterns, and source apportionment of particulate elements and inorganic ions in snowpack in Harbin, China

Snowpack, which serves as a natural archive of atmospheric deposition of multiple pollutants, is a practical environmental media that can be used for assessing atmospheric records and input of the pollutants to the surface environments and ecosystems. A total of 29 snowpack samples were collected at 20 sampling sites covering three different functional areas of a major city (Harbin) in Northeast China. Two samples at the “snow layer” and one or two samples at the “particulate layer” were collected at each sampling site in the industrial areas characterized by multi-layer snowpack, and only one sample at the “snow layer” was collected at each sampling site in the cultural and recreational as well as agricultural areas. The snow contents of 31 elements (Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Y, Cd, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Pb) and six major water-soluble inorganic ions (WSIIs, NH4+, K+, Ca2+, NO2−, NO3−, and SO42−) were analyzed. The total mass of the measured elements is dominated (95.8%–99.2%) by crustal elements. Heavy metals only account for 0.77%–4.07% of the total mass of the elements, but are occasionally close to or even above the standard limit in the “Environmental Quality Standards for Surface Water” of China (GB3838-2002). SO42− and Ca2+ are the main anion and cation, accounting for 34.9%–81.1% and 1.43%–29.9%, respectively, of the measured total ions. Total atmospheric deposition of crustal elements and heavy metals is dominated by wet deposition in areas near the petrochemical plant and by dry deposition in areas near the cement plant. Coal combustion, industrial emissions, and traffic-related activities lead to the enrichment of heavy metals in the snowpacks of urban and suburban areas, while coal combustion and biomass burning contribute to pollution in rural areas. The cities and regions situated in the western, northwestern, northern, and northeastern directions from Harbin are potential source regions of these pollutant species.

Effect of Bidispersity on Polymer-Bound Layers of Carbon Black Primary Particles: Combining Large-Scale Simulations and Experiments

Effect of Bidispersity on Polymer-Bound Layers of Carbon Black Primary Particles: Combining Large-Scale Simulations and Experiments

Efficient Fluoride Removal from Aqueous Solution Using Graphene/Ce Composite Supported on Activated Carbon

Background: More than 260 million people worldwide are affected by excess fluoride (F- > 1.5 mg/L) in their drinking water. Fluorosis of the teeth and skeleton, among other health issues, is caused by it. Objective: The aim of this study is to evaluate the fluoride removal from contaminated water using graphene-based new adsorbent material. Method: Graphene (G) was prepared by a facile liquid-phase exfoliation method. CeO2 nanoparticles (NPs) were synthesized by the co-precipitation method. G was treated with CeO2 NPs in a probe sonicator to generate G/Ce material in solution. Finally, the impregnation evaporation process synthesized the G/Ce supported on activated carbon composite (G/Ce/AC). Results: FE-SEM analysis shows that the crumpling and scrolling sheets of G, the nanosized spherical shape of CeO2 NPs and a thick layer of nano-sized spherical particles has built up on the surface of graphene in G/Ce/AC composite. After conversion to G/Ce/AC Composite, the specific surface area of graphene was increased from 3.08 to 485.3621 m2/g. The adsorption of fluoride on G/Ce/AC was investigated using batch systems (effects of pH, contact time, adsorbent dosage and the initial fluoride concentration), adsorption isotherm and kinetic studies. The pseudo-second order was the one that best described the kinetic data, while the Langmuir isotherm best described the equilibrium data with a maximum adsorption capacity equal to 27.9 mg/g. Conclusion: Therefore, the results show that the G/Ce/AC composite was well synthesized and has excellent fluoride adsorption capacity compared to other materials already evaluated for this purpose.

Precise control of discharge of spherical particles by cone valve configuration: Insert – Converging orifice

The effect of the size and shape of the insert (inverted cone, sphere) when placed axially above an orifice on the mass discharge rate (MDR) of monodisperse spherical particles from a cylindrical silo has been investigated through experiments and DEM simulations. MDR characteristics have been measured for various distances between the insert and the orifice.An important practical finding is that, within a specific range of placement distances, the MDR increases by approximately 10% when a conical insert is used, whereas no such effect was observed when a spherical insert was employed.It was observed that, in some cases, a slight increase in friction coefficient leads to an increase in MDR as result of alterations in the initial grain structure, facilitating faster discharge.In a quasi-2D configuration, significant changes in flow rate occur when the thickness exceeds the natural multiple of dp, allowing the next layer of particles to flow.

Layer formation on quartz bed particles during fast pyrolysis of grass

Commercial fast pyrolysis technologies use bed materials, normally natural sand mainly consisting of quartz, acting as circulating heat carrier materials. Nowadays, the commercial conversion of biomass into fast pyrolysis bio-oil (FPBO) is still using ash-lean woody residues as a feedstock since the application of more abundant and possibly cheaper ash-rich agricultural biomass is currently at a significantly lower technology readiness level (TRL). To promote FPBO production from ash-rich biomass, the ash-related issues during the operation process need to be further studied. In the present investigation, the characteristics and formation process of layers formed on quartz bed particles, collected from a bench-scale fast pyrolysis unit based on the rotating cone technology, were studied. Two grass residues, representative of typical Si-K-rich agricultural biomass fuels, were used as feedstocks. Quartz bed particles at different sampling times from startup with fresh bed particles were collected. Scanning Electron Microscopy/Energy-Dispersive Spectroscopy (SEM/EDS) was employed to characterize the layer properties. Bed particle layers exhibited an uneven and discontinuous distribution on the quartz surface. This distribution over bed particles, as well as layer thickness, increased with the operational time. The dominating elements contained in layers were Si, K, Ca, and Cl (excluding O), which resembled that of individual bed ash particles found in the bed samples. In addition, the interpretation of the results was supported by thermodynamic equilibrium calculations. The findings suggest that the process of layer formation was governed by the direct adhesion of non-melted bed ash particles during the fast pyrolysis of grass.

Modeling of a flexible perforated membrane backed by granular materials

It has recently been shown that adding activated carbon particles to the interior of a Helmholtz resonator can improve the resonator's absorption at low frequencies. A similar improvement has been found when a layer of activated carbon partially fills the space behind a finite, tensioned impermeable membrane. In that case, absorption peaks due to the modal response of the tensioned membrane were found to be significantly enhanced in the low frequency range. In the present work, the modeling aspects of the latter work are extended in a number of ways. First, the circular membrane is considered to be both tensioned and flexurally stiff, and further, it is micro-perforated: i.e., it has a finite flow resistance. Secondly, the particle layer behind the membrane is modeled by using a finite difference procedure that accounts for interaction of the particle layer and walls that contain it: i.e., the particle stack itself is allowed to exhibit modal behavior in the radial direction. Finally, the interaction of the membrane nearfield and the particle stack is fully accounted for. It is shown that previously observed behavior can be reproduced, and further that the modal behavior of the particle stack may also enhance the system's absorption.

Phase transition and damping behavior of Al matrix composites reinforced by a NiTi particle layer

Phase transition and damping behavior of Al matrix composites reinforced by a NiTi particle layer