Areal Mass Density Research Articles

A flexible phased array system with low areal mass density

Phased arrays are multiple antenna systems capable of forming and steering beams electronically using constructive and destructive interference between sources. They are employed extensively in radar and communication systems but are typically rigid, bulky and heavy, which limits their use in compact or portable devices and systems. Here, we report a scalable phased array system that is both lightweight and flexible. The array architecture consists of a self-monitoring complementary metal–oxide–semiconductor-based integrated circuit, which is responsible for generating multiple independent phase- and amplitude-controlled signal channels, combined with flexible and collapsible radiating structures. The modular platform, which can be collapsed, rolled and folded, is capable of operating standalone or as a subarray in a larger-scale flexible phased array system. To illustrate the capabilities of the approach, we created a 4 × 4 flexible phased array tile operating at 9.4–10.4 GHz, with a low areal mass density of 0.1 g cm^(−2). We also created a flexible phased array prototype that is powered by photovoltaic cells and intended for use in a wireless space-based solar power transfer array.

Flexible arrays signal change in communications

A flexible phased array that has an areal mass density of only 0.1 g cm–2 could help deliver a new era of lightweight, portable and reconfigurable communication systems.

Dynamic comparison between the cylindrical and quasi-spherical implosions based on thin-shell models

The quasi-spherical electromagnetic implosions are capable of generating hot dense plasmas more efficiently than the cylindrical ones. The dynamic properties of stagnated cylindrical and quasi-spherical shells are compared numerically based on the thin-shell models. The cylindrical implosions are simulated with the zero-dimensional thin-shell model, and the quasi-spherical implosions with the multi-element thin-shell model. The simulated velocity, areal mass density, and areal kinetic energy density of the stagnated quasi-spherical plasma shell increase with the latitude increasing, which is different from the cylindrical case. The kinetic energy densities are optimized for both of stagnated cylindrical and quasi-spherical shells in a quite large span of initial radii and load linear masses. The kinetic energy density in the spherical radiation converter can be over four times as large as that in the cylindrical radiation converter. The numerical results can help optimize quasi-spherical load parameters for Z-pinch driver with peak current of 1.5 MA and rising time of 80 ns, and the method described here is also feasible to optimize load parameters for various-scale Z-pinch drivers.

Cu-Al Composite as the Negative Electrode for Long-life Al-Ion Batteries

Rechargeable Al-ion batteries have attracted great interest due to their advantages in high anode capacity, high safety, etc. However, conventional Al foil negative electrode has critical problems in corrosion and pulverization. Here, we propose a novel Cu-Al composite, which is prepared by a facile electrochemical plating approach, as the negative electrode for addressing above challenges. Remarkably, the plated Cu foil negative electrode delivers excellent stability and long cycle life compared with the Al foil negative electrode, although its thickness and areal mass density are only 30% and ∼76% of that of the Al foil negative electrode, respectively. The essential pulverization problem in bare Al negative electrode would be dramatically reduced attributing to excellent corrosion resistance of Cu foil. Besides, the plated Al is still attached to the Cu foil during repeated charge-discharge processes, resulting in a nearly 100% Coulombic efficiency even after long-term cycling. More importantly, the plated Cu foil negative electrode is convenient for the large-scale practical applications. In view of our results, this work opens an effective approach for configuring low-cost, high energy density, long cycle life and scalable negative electrode of Al-ion batteries.

Diffusive tunneling in an isobaric but non-isothermal fuel-pusher mixture

The hydrodynamic mix of fusion fuel and inert pusher can simultaneously generate smaller fuel pockets and finer pusher layers that separate them. Smaller fuel pockets have greater local Knudsen numbers, which tend to exacerbate the Knudsen layer reactivity reduction. A thinner pusher layer separating the neighboring fuel pockets, on the other hand, can enable the diffusive tunneling of Gamow fuel ions through the pusher layer and hence alleviate the Knudsen layer reactivity degradation. Here, the diffusive tunneling phenomenon describes a random walk process by which the Gamow fuel ions from one fuel pocket can traverse the inert pusher layer to join a neighboring fuel pocket without losing much of their energy. This is made possible by the much slower collisional slowing down rate compared with the pitch angle scattering rate of light fuel ions with heavier pusher ions. In an isobaric target mixture where fuel and pusher segments can have distinct temperatures, due to their different compressibilities, the temperature effect on the critical pusher layer areal density below which diffusive tunneling can occur, which is a property of the hydrodynamic mix, is understood by computing the ion charge state distribution using a collisional radiative model. This information is fed into the collisionality evaluation, enabling a parametric scan of the diffusive tunneling physics in terms of the target pressure, fuel, and pusher temperatures. It is found that when the gold pusher layer has a temperature above 1 keV, the variation of the pusher temperature has little effect on the critical areal mass density below which diffusive tunneling can occur. If the pusher layer is 1 keV or below, the critical areal mass density rises sharply, indicating that for a stronger fuel-pusher temperature disparity, the onset of diffusive tunneling will be at an earlier stage of the hydrodynamic mix when the fuel-pusher mixing structures are of less reduced size.

Oxidative Layer-By-Layer Multilayers Based on Metal Coordination: Influence of Intervening Graphene Oxide Layers.

Layer-by-layer (LbL) fabricated oxidative multilayers consisting of successive layers of inorganic polyphosphate (PP) and Ce(IV) can electrolessly form thin conducting polymer films on their surface. We describe the effect of substituting every second PP layer in the (PP/Ce) multilayers for graphene oxide (GO) as a means of modifying the structure and mechanical properties of these (GO/Ce/PP/Ce) films and enhancing their growth. Both types of LbL films are based on reversible coordinative bonding between the metal ions and the oxygen-bearing groups in PP and GO, instead of purely electrostatic interactions. The GO incorporation leads to the doubling of the areal mass density and to a dry film thickness close to 300 nm after 4 (GO/Ce/PP/Ce) tetralayers. The film roughness increases significantly with thickness. The (PP/Ce) films are soft materials with approximately equal shear storage and loss moduli, but the incorporation of GO doubles the storage modulus. PP displays a marked terminating layer effect and practically eliminates mechanical losses, making the (GO/Ce/PP/Ce) films almost pure soft elastomers. The smoothness of the (PP/Ce) films and the PP-termination effects are attributed to the reversible coordinative bonding. The (GO/Ce/PP/Ce) films oxidize pyrrole and 3,4-ethylenedioxythiophene (EDOT) and form polypyrrole and PEDOT films on their surfaces. These polymer films are considerably thicker than those formed using the (PP/Ce) multilayers with the same nominal amount of cerium layers. The GO sheets interfere with the polymerization reaction and make its kinetics biphasic. The (GO/Ce) multilayers without PP are brittle and thin.

Generation of GeV Electron Beam From a Laser-Plasma Accelerator and Its Prospect as a Desktop Source of Energetic Positrons and Gamma Rays For Applications

Laser wakefield acceleration (LWFA) is a plasma-based electron beam accelerator technology that can deliver electron beams with energies up to several GeVs, depending mainly on the power of the used laser system and the electron injection scheme. Here, we present the results from a GeV electron accelerator with a high reproducibility and a charge up to 30 pC using 110–120-TW laser pulses and by employing the well-established self-truncated ionization injection (STII) mechanism. These electron beams can be further used via bremsstrahlung in high-Z solid materials for the generation of gamma-rays and positron beams, therefore, composing a compact radiation source for various applications. Here, we use the Monte Carlo simulation code “Geant4” for studying the properties of those radiations. As expected, the characteristics of the generated gamma-rays and positron beams showed a strong dependence on the incident electron beam, target material, and thickness. The trend of positrons and gamma-rays energies and yield is shown for different high-Z to low-Z targets with the same areal mass density. Thicknesses of the target material in terms of its radiation length have been varied periodically in order to find the optimal thickness for obtaining the maximum energy and yield of the radiations. A trend can be seen in terms of energy spectra of the gamma-rays and positrons while increasing the thickness of the targets. The amount of radiation yields is also crucial to the choice of appropriate thickness of the target. In addition, this paper provides a brief description of the electrodynamics processes such as bremsstrahlung and electron–positron pair production initiated by LWFA electron beams.

Energetic Radiation From Galactic Cosmic Ray Interactions With Saturn's Main Rings.

Saturn's main rings have an energetic particle and gamma ray photon radiation environment produced by ring interactions of galactic cosmic ray (GCR) protons and heavier ions penetrating the planetary dipolar magnetic field. Accurate models of this radiation environment are important for interpretation of Pioneer 11 and Cassini in situ measurements near the rings and for constraints on radiolytic contributions to neutral gas production and ice chemistry. A GEANT (GEometry ANd Tracking) based simulation is used to model flux spectra of protons, electrons, positrons, charged pions, neutrons, and gamma ray photons emitted from GCR interactions with H2O ice spheres approximating the ring material. Dependent on location in the A to D rings within the planetary magnetic field of Saturn, only GCR protons above respective energies of 20 to 72 GeV can reach the rings without being deflected away by the magnetic field. Calculated differential and integral fluxes from our simulations have good agreement with in situ Pioneer-11 measurements in selected energy channels. The charged particle and neutral radiation measurements are sensitive, respectively, to the sizes and areal mass densities of ring bodies. Computed gamma ray emission fluxes are 8% of our calculated limit for detection from the Earth by the Fermi Large Area Telescope. Addition of charged particle sensors and neutron-photon imaging spectrometers to a future Saturn Ring Observer mission would provide valuable information on the ring mass structure. The present paper provides a foundation for modeling of Pioneer 11 and Cassini radiation measurements across the main rings and future measurements of radiation from the rings.

Density, Elastic Constants, and Thermal Conductivity of Interfacially Polymerized Polyamide Films for Reverse Osmosis Membranes

The thickness, volumetric mass density, longitudinal elastic constant, and thermal conductivity of fully aromatic polyamide reverse osmosis membrane active layers synthesized by interfacial polymerization were measured using a combination of Rutherford backscattering spectrometry, quartz crystal microbalance measurements of areal mass density, optical ellipsometry, atomic force microscopy, picosecond acoustics, and time-domain thermoreflectance (TDTR). A support-free synthesis approach was used to produce smooth three-dimensionally cross-linked polyamide films from m-phenylenediamine (MPD) and trimesoyl chloride (TMC) at a fixed molar ratio of 99:1 MPD:TMC with 0.1–2 wt % MPC and 0.005–0.1 wt % TMC. A novel method to measure the areal mass density of nanoscale polymer films by Rutherford backscattering spectrometry was developed to aid in characterization of the volumetric mass density of the membranes. The volumetric mass density and longitudinal elastic constant of free-standing polyamide films increase...

Silver Nanowire-Based Flexible Transparent Composite Film for Curvature Measurements

A transparent, flexible, and conductive epoxy resin film embedded with silver nanowires is fabricated through a simple process. The effect of silver nanowire areal mass density on the electrical and optical properties of films is investigated. It is found that resistance of the transparent composite film will change regularly during the bending process. The influence mechanism of bending behavior on the electrical property is explored. On the basis of this mechanism, the curvature in the bending process can be acquired immediately by measuring the resistance of the composite film. The high elastic modulus (800 MPa) of the composite film is a benefit for distinguishing the factor of resistance change caused by bending or stretching with low force. Additionally, high stability of the bending detector is demonstrated with 500 repeated bending cycles and a 6-month durability test.

Solution processed silver-nanowire/zinc oxide based transparent conductive electrode for efficient photovoltaic performance

To replace expensive and scarce Indium Tin Oxide (ITO) as transparent conductive electrode (TCE) in solar cell fabrication, low-cost and solution processed metal nanowires can also be used as a TCE due to its higher conductivity and transparency. Despite of its higher conductivity and transparency, bare Silver nanowire (AgNW) film suffers due to its poor adhesion and smaller contact area with lower-lying n-type buffer layer. In this work, percolation network of AgNWs covered with scalable and solution processed ZnO film as transparent conductive electrode (TCE) is demonstrated and utilized for fabrication of CuInGaSe2 thin film solar cell. The concentration of the AgNWs in percolation network is optimized as areal mass density of AgNWs in the TCE. The conductive atomic force microscope studies are done to conclude the enhancement of current collection by covering the AgNW film with solution processed ZnO layer. The AgNW-based TCE with areal mass density of 242 mg/m2, sheet resistance 11 Ω/sq and transmittance 90% exhibited maximum conversion efficiency of 13.4% which is comparable to the efficiency obtained for vacuum based sputter deposited ITO or ZnO as TCE.

(Invited) Imperceptible Graphene Based Electronic Tattoo Sensors

During last decade, there have been advances in wearables with applications in mobile healthcare, athletic, assistive technology, human machine interface and internet of things. However, current wearable sensors and systems have at least one or more of the following drawbacks: they are bulky, expensive, distractive, unsuitable for long term measurement or prone to motion artifact. We present ultrathin graphene based electronic tattoo (GET) sensors with the overall thickness of less than 500 nm. Presented e-tattoo sensors can be laminated on skin like as temporary tattoo and form conformal contact to microscopic texture of the skin. GET is a set of dry sensors with electrode-skin interface impedance comparable to wet gel electrodes that are gold standard in medical applications. Low electrode-skin interface impedance of these e-tattoo sensors results in high signal to noise ratio and high sensing quality. Due to low areal mass density of GET, it attaches to skin without any adhesive or tape, just by Van der Waals force. Presented e-tattoos are both optically and mechanically imperceptible, therefore, they are desirable for applications in prominent areas of appearance such as face. We present the successful demonstration of GET applications for electrocardiography (EEG), electroencephalography (EEG), electromyography (EMG), electrooculography (EOG), skin temperature sensing, skin hydration sensing and human robot interface.

Fabrication of High-Haze Flexible Transparent Conductive PMMA Films Embedded with Silver Nanowires * *Supported by the International S&T Cooperation Program of China under Grant No 2015DFH60240, the Ningbo Municipal Science and Technology Innovative Research Team under Grant No 2016B10005, the Zhejiang Provincial Natural Science Foundation of China under Grant No LY15B050003, and the Ningbo Natural Science Foundation under Grant No

High-haze flexible transparent conductive polymethyl methacrylate (PMMA) films embedded with silver nanowires (AgNWs) are fabricated by a low-cost and simple process. The volatilization rate of the solvent in PMMA solution affects the surface microstructures and morphologies, which results in different haze factors of the composite films. The areal mass density of AgNW shows a significant influence on the optical and electrical properties of composite films. The AgNW/PMMA transparent conductive films with the sheet resistance of 5.5Ωsq −1 exhibit an excellent performance with a high haze factor of 81.0% at 550 nm.

Proton energy behavior by variation of the target density in laser acceleration

Ion acceleration using a laser pulse irradiating a thin disk target is examined using three-dimensional and two-dimensional particle-in-cell simulations. A laser pulse of 620 TW, with an intensity of 5×1021 W/cm2 and a duration of 27 fs, is irradiated on to a double-layer target. Simulations are performed by varying the ion density, i.e., electron density, of the first layer with a fixed areal mass density. It is shown that the obtained proton energy increases dramatically for a certain density of the first layer, which is made of a material having a small mass over charge ratio, “light” material, such as carbon; that is, the Coulomb explosion of the target and radiation pressure acceleration act effectively above a certain density. Moreover, even for the same electron density, the reflection of the laser pulse from the first layer is small for a “light” material.

Surface orientation effects on bending properties of surgical mesh are independent of tensile properties.

Current mechanical testing of surgical mesh focuses primarily on tensile properties even though implanted devices are not subjected to pure tensile loads. Our objective was to determine the flexural (bending) properties of surgical mesh and determine if they correlate with mesh tensile properties. The flexural rigidity values of 11 different surgical mesh designs were determined along three textile directions (machine, cross-machine, and 45° to machine; n = 5 for each) using ASTM D1388-14 while tracking surface orientation. Tensile testing was also performed on the same specimens using ASTM D882-12. Linear regressions were performed to compare mesh flexural rigidity to mesh thickness, areal mass density, filament diameter, ultimate tensile strength, and maximum extension. Of 33 mesh specimen groups, 30 had significant differences in flexural rigidity values when comparing surface orientations (top and bottom). Flexural rigidity and mesh tensile properties also varied with textile direction (machine and cross-machine). There was no strong correlation between the flexural and tensile properties, with mesh thickness having the best overall correlation with flexural rigidity. Currently, surface orientation is not indicated on marketed surgical mesh, and a single mesh may behave differently depending on the direction of loading. The lack of correlation between flexural stiffness and tensile properties indicates the need to examine mesh bending stiffness to provide a more comprehensive understanding of surgical mesh mechanical behaviors. Further investigation is needed to determine if these flexural properties result in the surgical mesh behaving mechanically different depending on implantation direction. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 854-862, 2018.

Multivariate Optimization of Fiber Reinforced Laminate Using Ant Colony Optimization Algorithm

Fiber reinforced laminate design is a challenging problem in the field of composite laminates. It provides us a systematic way to design the laminates of desired properties while conveniently incorporating the thick-ness and mass constraints. In this paper, we pursue the multivariate graphite fiber reinforced laminate design problem using Ant Colony Optimization (ACO) algorithm. Classical lamination theory is used to determine mid-plane strains, curvatures and stresses in individual lamina under applied biaxial loading conditions. The fiber orientations, lamina thickness, number of layers and fiber volume fractions of lamina are considered as the optimization variables. Failure of the lamina is analyzed by Tsai–Wu failure criterion. Objective of the study is to maximize the load carry capacity of the composite laminate structure and minimize the areal mass density under multivariate/multiobjective optimization.

Ultra-thin smart acoustic metasurface for low-frequency sound insulation

Insulating low-frequency sound is a conventional challenge due to the high areal mass required by mass law. In this letter, we propose a smart acoustic metasurface consisting of an ultra-thin aluminum foil bonded with piezoelectric resonators. Numerical and experimental results show that the metasurface can break the conventional mass law of sound insulation by 30 dB in the low frequency regime (<1000 Hz), with an ultra-light areal mass density (<1.6 kg/m2) and an ultra-thin thickness (1000 times smaller than the operating wavelength). The underlying physical mechanism of such extraordinary sound insulation performance is attributed to the infinite effective dynamic mass density produced by the smart resonators. It is also demonstrated that the excellent sound insulation property can be conveniently tuned by simply adjusting the external circuits instead of modifying the structure of the metasurface.

Combined quartz crystal microbalance with dissipation (QCM-D) and generalized ellipsometry (GE) to characterize the deposition of titanium dioxide nanoparticles on model rough surfaces

Measuring the interactions between engineered nanoparticles and natural substrates (e.g. soils and sediments) has been very challenging due to highly heterogeneous and rough natural surfaces. In this study, three-dimensional nanostructured slanted columnar thin films (SCTFs), with well-defined roughness height and spacing, have been used to mimic surface roughness. Interactions between titanium dioxide nanoparticles (TiO2NP), the most extensively manufactured engineered nanomaterials, and SCTF coated surfaces were measured using a quartz crystal microbalance with dissipation monitoring (QCM-D). In parallel, in-situ generalized ellipsometry (GE) was coupled with QCM-D to simultaneously measure the amount of TiO2NP deposited on the surface of SCTF. While GE is insensitive to effects of mechanical water entrapment variations in roughness spaces, we found that the viscoelastic model, a typical QCM-D model analysis approach, overestimates the mass of deposited TiO2NP. This overestimation arises from overlaid frequency changes caused by particle deposition as well as additional water entrapment and partial water displacement upon nanoparticle adsorption. Here, we demonstrate a new approach to model QCM-D data, accounting for both viscoelastic effects and the effects of roughness-retained water. Finally, the porosity of attached TiO2NP layer was determined by coupling the areal mass density determined by QCM-D and independent GE measurements.

Numerical simulations of generation of high-energy ion beams driven by a petawatt femtosecond laser

Abstract This contribution presents results of a Particle-in-Cell simulation of ion beam acceleration via the interaction of a petawatt 25 fs laser pulse of high intensity (up to ~1021 W/cm2) with thin hydrocarbon (CH) and erbium hydride (ErH3) targets of equal areal mass density (of 0.6 g/m2). A special attention is paid to the effect that the laser pulse polarization and the material composition of the target have on the maximum ion energies and the number of high energy (>10 MeV) protons. It is shown that both the mean and the maximum ion energies are higher for the linear polarization than for the circular one. A comparison of the maximum proton energies and the total number of protons generated from the CH and ErH3 targets using a linearly polarized beam is presented. For the ErH3 targets the maximum proton energies are higher and they reach 50 MeV for the laser pulse intensity of 1021 W/cm2. The number of protons with energies higher than 10 MeV is an order of magnitude higher for the ErH3 targets than that for the CH targets.

Axial backlighting of two-wire Z-pinch using an X-pinch as an X-ray source

The axial backlighting of two-wire Z-pinch using an X-pinch as an X-ray source was conducted on PPG-1, a pulsed power generator with a current of 400 kA in amplitude and 100 ns in pulse width. Its time-resolved axial backlighting images are obtained. In the backlighting images all the physical processes similar to those occurring in the early stage of the wire-array Z-pinch are observed, including the expansion of the high-density wire core surrounded by low-density coronal plasmas, the motion of the coronal plasma toward the axis of the wire-array, and the formation of precursor plasma. The areal mass density of the plasma shown in the backlighting images is calibrated with step-wedge filters. And the time-resolved radial distributions of the areal mass density of the plasma from the two-wire Z-pinch are obtained.