Showing papers in "International Journal of Smart and Nano Materials in 2014"
TL;DR: Shungite is presented as a natural carbon allotrope of a multilevel fractal structure that is formed by a successive aggregation of reduced graphene oxide nanosheets.
Abstract: Shungite is presented as a natural carbon allotrope of a multilevel fractal structure that is formed by a successive aggregation of ~1 nm reduced graphene oxide nanosheets. Turbostratic stacks of the sheets of ~1.5 nm in thickness and globular composition of the stacks of ~6 nm in size determine the secondary and tertiary levels of the structure. Aggregates of globules of tens of nanometers complete the structure. Molecular theory of graphene oxide, supported by large experience gained by the modern graphene science, has led to the foundation of the suggested presentation. The microscopic view has found a definite confirmation when analyzing the available empirical appearance of shungite. To our knowledge, this is the first time a geological process is described at quantum level.
66 citations
TL;DR: In this article, a bistable spherical cap made of iron carbonyl-infused polydimethylsiloxane is used to actuate a magnetizable structure remotely through permanent magnets.
Abstract: Multistable shells have been proposed for a variety of applications; however, their actuation is almost exclusively addressed through embedded piezoelectric patches. Additional actuation techniques are needed for applications requiring high strains or where remote actuation is desirable. Part of the reason for the lack of research in this area is the absence of appropriate models describing the detailed deformation and energetics of such shells. This work presents a bistable spherical cap made of iron carbonyl-infused polydimethylsiloxane. The magnetizable structure can be actuated remotely through permanent magnets while the transition is recorded with a high-speed camera. Moreover, the experiment is reproduced in a finite element (FE) dynamic model for comparison with the physical observations. High-speed footage of the physical cap inversion together with the FE modeling gives valuable insight on preferable intermediate geometries. Both methods return similar values for the magnetic field strength requ...
54 citations
TL;DR: In this paper, the interfacial thermal transport between graphene nanofiller and polymer matrix at small material length scale is investigated using nonequilibrium molecular dynamics (NEMD) simulations, taking into account the effects of model size and thermal conductivity of graphene.
Abstract: Exploring thermal transport in graphene–polymer nanocomposite is significant to its applications with better thermal properties. Interfacial thermal conductance between graphene and polymer matrix plays a critical role in the improvement of thermal conductivity of graphene–polymer nanocomposite. Unfortunately, it is still challenging to understand the interfacial thermal transport between graphene nanofiller and polymer matrix at small material length scale. To this end, using nonequilibrium molecular dynamics (NEMD) simulations, we investigate the interfacial thermal conductance of graphene–polyethylene (PE) nanocomposite. The influence of functionalization with hydrocarbon chains on the interfacial thermal conductance of graphene–polymer nanocomposites was studied, taking into account the effects of model size and thermal conductivity of graphene. An analytical model is also used to calculate the thermal conductivity of nanocomposite. The results are considered to contribute to the development of new gr...
51 citations
TL;DR: In this paper, carbon nanotube yarn with carboxyl and hydroxyl groups was functionalized using sulfuric and nitric acid solutions in 3:1 volumetric ratio.
Abstract: Carbon nanotube (CNT) yarn was functionalized using sulfuric and nitric acid solutions in 3:1 volumetric ratio. Successful functionalization of CNT yarn with carboxyl and hydroxyl groups (e.g., COOH, COO–, OH, etc.) was confirmed by attenuated total reflectance spectroscopy. X-ray diffraction revealed no significant change to the atomic in-plane alignment in the CNTs; however, the coherent length along the diameter was significantly reduced during functionalization. A morphology change of wavy extensions protruding from the surface was observed after the functionalization treatment. The force required to fracture the yarn remained the same after the functionalization process; however, the linear density was increased (310%). The increase in linear density after functionalization reduced the tenacity. However, the resistivity density product of the CNT yarn was reduced significantly (234%) after functionalization.
49 citations
TL;DR: A simple protocol for the chemical modification of graphene with platinum nanoparticles and its subsequent electroanalytical application toward sensitive and selective determination of arsenic has been described in this article, where the proposed nanostructure showed linearity in the concentration range 10-100 nM with a detection limit of 1.1 nM.
Abstract: A simple protocol for the chemical modification of graphene with platinum nanoparticles and its subsequent electroanalytical application toward sensitive and selective determination of arsenic has been described. Chemical modification was carried out by the simultaneous and sequential chemical reduction of graphene oxide and hexachloroplatinic acid in the presence of ethylene glycol as a mild reducing agent. The synthesized graphene–platinum nanocomposite (Gr–nPt) has been characterized through infrared spectroscopy, x-ray diffraction study, field emission scanning electron microscopy and cyclic voltammetry (CV) techniques. CV and square-wave anodic stripping voltammetry have been used to quantify arsenic. The proposed nanostructure showed linearity in the concentration range 10–100 nM with a detection limit of 1.1 nM. The proposed sensor has been successfully applied to measure trace levels of arsenic present in natural sample matrices like borewell water, polluted lake water, agricultural soil, tomato a...
35 citations
TL;DR: In this article, the authors improved the electromechanical performance of ionic polymer-metal composites by developing high surface area Pd-Pt electrodes and tailoring the ionomer membrane thickness.
Abstract: In this study, we attempt to improve the electromechanical performance of ionic polymer–metal composites (IPMCs) by developing high surface area Pd-Pt electrodes and tailoring the ionomer membrane thickness. With proper electroless plating techniques, a high dispersion of palladium particles is achieved deep in the ionomer membrane, thereby increasing notably the interfacial surface area of electrodes. The membrane thickness is increased using 0.5 and 1 mm thick ionomer films. For comparison, IPMCs with the same ionomer membranes, but conventional Pt electrodes, are also prepared and studied. The electromechanical, mechanoelectrical, electrochemical and mechanical properties of different IPMCs are characterized and discussed. Scanning electron microscopy-energy dispersive X-ray (SEM-EDS) is used to investigate the distribution of deposited electrode metals in the cross section of Pd-Pt IPMCs. Our experiments demonstrate that IPMCs assembled with millimeter thick ionomer membranes and newly developed Pd-Pt...
28 citations
TL;DR: A summary of important experimental findings on the mediation of nanoscale surface topography on the behavior of various cells, as well as the underlying mechanism, is provided.
Abstract: The rapid development of fabrication and processing technologies in the past two decades has enabled researchers to introduce nanoscale features into materials which, interestingly, have been shown to greatly regulate the behavior and fate of biological cells. In particular, important cell responses (such as adhesion, proliferation, differentiation, migration, and filopodial growth) have all been correlated with material nanotopography. Given its great potential, intensive efforts have been made, both experimentally and theoretically, to understand why and how cells respond to nanoscale surface features, and this article reviews recent progress in this field. Specifically, a brief overview on the fabrication and modification techniques to create nanotopography on different materials is given first. After that, a summary of important experimental findings on the mediation of nanoscale surface topography on the behavior of various cells, as well as the underlying mechanism, is provided. Finally, both classi...
27 citations
TL;DR: In this paper, a compression-based piezoelectric energy harvester using a multilayer stack configuration is proposed for civil infrastructure system applications where large compressive loads occur, such as heavily vehicular loading acting on pavements.
Abstract: Over the past few decades, wireless sensor networks have been widely used in the field of structure health monitoring of civil, mechanical, and aerospace systems. Currently, most wireless sensor networks are battery-powered and it is costly and unsustainable for maintenance because of the requirement for frequent battery replacements. As an attempt to address such issue, this article theoretically and experimentally studies a compression-based piezoelectric energy harvester using a multilayer stack configuration, which is suitable for civil infrastructure system applications where large compressive loads occur, such as heavily vehicular loading acting on pavements. In this article, we firstly present analytical and numerical modeling of the piezoelectric multilayer stack under axial compressive loading, which is based on the linear theory of piezoelectricity. A two-degree-of-freedom electromechanical model, considering both the mechanical and electrical aspects of the proposed harvester, was developed to ...
22 citations
TL;DR: In this paper, a study on the mechanical and thermo-mechanical properties of carbon nanotube (CNT) reinforced nanocomposites is presented, where regression formulas were developed to describe the effects of CNT orientation, aspect ratio, and CNT volume fraction.
Abstract: A study on the mechanical and thermo-mechanical properties of carbon nanotube (CNT) reinforced nanocomposites is presented in this article. Mori–Tanaka method is used for modeling the effective stiffness and coefficient of thermal expansion. Regression formulas were developed to describe the effects of CNT orientation, aspect ratio, and CNT volume fraction. Given the statistical distributions of CNT orientations and aspect ratios, the effective properties can be conveniently derived by numerical integration using these formulas.
21 citations
TL;DR: In this paper, a low-temperature SnO2 gas sensor on silicon nanostructures formed by femtosecond laser irradiation was presented, which works at low temperature because of adsorption of gas molecules that trap electrons to the surface of SnO 2.
Abstract: A novel low-temperature SnO2 gas sensor was prepared and studied on silicon nanostructures formed by femtosecond laser irradiation. By applying a bias voltage on the silicon substrate to alter the charge distribution on the surface of the SnO2, carbon monoxide (CO), and ammonia (NH3) gas can be distinguished by the same sensor at room temperature. The experimental results are explained with a mechanism that the sensor works at low temperature because of adsorption of gas molecules that trap electrons to the surface of the SnO2.
18 citations
TL;DR: In this paper, a three-phase nanocomposite of sulfonated polyaniline embedded with single-walled carbon nanotubes (f-SWCNTs) hybridized with freshly prepared zinc oxide (ZnO) nanocrystals has been found to be good luminescent material with tuned emission properties.
Abstract: Functionalized single-walled carbon nanotubes (f-SWCNTs) hybridized with freshly prepared zinc oxide (ZnO) nanocrystals have been found to be good luminescent material with tuned emission properties. A three-phase nanocomposite of sulfonated polyaniline embedded with such SWCNT/ZnO nanostructures has been prepared by a simple solution mixing chemical process and characterized by using high-resolution transmission electron microscopy, X-ray diffractometry, Raman spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The study of UV-visible absorption and photoluminescence spectroscopies reveal that the ternary polymer nanocomposite is a luminescent material with enhanced emission intensity. Also an increase in DC conductivity indicates that the nanocomposite is also a good conductive material, satisfying Mott’s variable range hopping model for a two-dimensional conduction. Such a three-phase nanocomposite may find extensive application in dye-sensitized solar cells, sensors,...
TL;DR: In this article, the effect of viscoelasticity on the electromechanical performance of a dielectric elastomer (DE) balloon was investigated. And the authors showed that the effect on the amplitude and the mean stretch of the DE balloon is independent of the viscoelsensitivity.
Abstract: In this paper, we present a theoretical study about the effect of viscoelasticity on the electromechanical performance of a dielectric elastomer (DE) balloon. The thermodynamic dissipative model is given and the equation of motion is deduced by a free-energy method. It is found that when the balloon is only subject to the pressure or a static voltage, it may reach a state of equilibrium after the viscoelastic relaxation. When the static voltage exceeds a certain value, the balloon will never reach the equilibrium and be in failure eventually. When the voltage is sinusoidal, the balloon will resonate at multiple frequencies. The study result indicates that the natural frequency is independent on the viscoelasticity. However, the presence of viscoelasticity can reduce the amplitude and increase the mean stretch of the DE.
TL;DR: In this paper, the influence of controlling in-flight hot particle characteristics on properties of plasma sprayed nanostructured yttria stabilized zirconia (YSZ) coatings is described.
Abstract: This article describes the influence of controlling in-flight hot particle characteristics on properties of plasma sprayed nanostructured yttria stabilized zirconia (YSZ) coatings. This article depicts dependence of adhesion strength of as-sprayed nanostructured YSZ coatings on particle temperature, velocity and size of the splat prior to impact on the metallic substrate. Particle temperature measurement is based on two-color pyrometry and particle velocities are measured from the length of the particle traces during known exposure times. The microstructure and adhesion strength of as-sprayed nano-YSZ coatings were studied. Field emission scanning electron microscopy results revealed that morphology of coating exhibits bimodal microstructure consisting of nano-zones reinforced in the matrix of fully melted particles. The coating adhesion strength is noticed to be greatly affected by the melting state of agglomerates. Maximum adhesion strength of 42.39 MPa has been experimentally found out by selecting opt...
TL;DR: In this paper, a low-cost miniature humidity sensor with an interdigitated aluminium electrode connected in parallel on a quartz substrate is presented, where the aluminium electrode was covered with a sensitive film of a nanoporous thin film made from novel sol-gel technique.
Abstract: This paper presents a development of a low-cost miniature humidity sensor with an interdigitated aluminium electrode connected in parallel on quartz substrate. Interdigitated capacitive device has been fabricated using the photolithography method. The aluminium electrode was covered with sensitive film of a nanoporous thin film of γ-Al2O3 made from novel sol–gel technique. Nanostructured thin film offers very high surface to volume ratio with distribution of micro pores for moisture detection. Pore morphologies of the film have been studied by field emission electron microscope and X-ray diffraction methods. Impedance measurement of the miniature capacitive humidity sensor toward relative humidity was investigated at room temperature by Agilent 4294A impedance analyzer (Agilent, Santa Clara, CA, USA). The device exhibits short response and recovery times and good repeatability.
TL;DR: In this paper, the authors investigated the thermal performance, energy savings, and financial payback period of passive aerogel Trombe walls applied to the existing UK housing stock using parametric modeling.
Abstract: There is an opportunity to improve the efficiency of passive Trombe walls and active solar air collectors by replacing their conventional glass covers with lightweight polycarbonate panels filled with nanoporous aerogel insulation. This study investigates the thermal performance, energy savings, and financial payback period of passive Aerogel Trombe walls applied to the existing UK housing stock. Using parametric modeling, a series of design guidance tables have been generated, providing estimates of the energy savings and overheating risk associated with applying areas of Trombe wall to four different house types across the UK built to six notional construction standards. Calculated energy savings range from 183 kWh/m2/year for an 8 m2 system retrofitted to a solid walled detached house to 62 kWh/m2/year for a 32 m2 system retrofitted to a super insulated flat. Predicted energy savings from Trombe walls up to 24 m2 are found to exceed the energy savings from external insulation across all house types and...
TL;DR: The advances in magnetorheological (MR) fluids and massive potential applications in the fields of engineering have been described in the book of Norman M. Wereley Magnetorheology: Advances and Applications as mentioned in this paper.
Abstract: A new book of Norman M. Wereley Magnetorheology: Advances and Applications describes the advances in magnetorheological (MR) fluids and massive potential applications in the fields of engineering s...
TL;DR: In this article, the authors demonstrate that by applying short electrical pulses, one could minimize the exposure of the DEAs to high leakage current, which is one of the main mechanisms for electrical breakdown.
Abstract: Dielectric elastomer actuators (DEAs) are a class of artificial muscles capable of large linear strains (well over 100%), and with high energy density, and low cost and weight. One of the most prominent failure modes of a DEA is electrical breakdown, which can damage the device permanently, limiting its deformation capability. Breakdown is also common, since to maximize energy output, devices often operate near the breakdown limit. Elucidating breakdown mechanisms, as well as finding ways to prevent it, are of intense research interest. We show that by applying short electrical pulses, one could minimize the exposure of the DEAs to high leakage current, which is one of the main mechanisms for electrical breakdown. This allows one to operate at significantly higher potentials than the DC breakdown voltage. By applying pulses, we demonstrate up to 81.7% area strain repeatedly, at voltages more than twice the DC breakdown limit, without the risk of failure. The pulsed operation mode of DEAs accommodating hig...
TL;DR: In this paper, high elastic energy density and high efficiency ionic electromechanical actuators were prepared from aligned activated microwave exfoliated graphite oxide (A-aMEGO)/polymer nano-composites.
Abstract: High elastic energy density and high-efficiency ionic electromechanical actuators were prepared from aligned activated microwave exfoliated graphite oxide (A-aMEGO)/polymer nano-composites, and the electromechanical performance was characterized. The elastic modulus and elastic energy density of the ionic actuators can be tuned over a wide range by varying the polymer (poly (vinylidene fluoride/chlorotrifluoroethylene) [P(VDF-CTFE)]) concentration in the nano-composite actuators. The A-aMEGO/P(VDF-CTFE) nano-composite actuators with 35 wt.% of polymer content exhibit an elastic energy density higher than 5 J/cm3 and an electromechanical conversion efficiency higher than 3.5%, induced under 4 V. The results show the promise of high-density highly aligned graphene electrodes for high-performance ionic electromechanical transduction devices.
TL;DR: In this article, aluminum oxide-hydroxide nanofibers are electroadhesively grafted onto glass microfibers, therefore forming a macroscopic assembly of alumina nano-nibers on the second solid in highly organized matter.
Abstract: Aluminum oxide-hydroxide nanofibers, 2 nm in diameter and approximately 250 nm long, are electroadhesively grafted onto glass microfibers, therefore forming a macroscopic assembly of alumina nanofibers on the second solid in highly organized matter. The assembly can be viewed as a straight cylinder with rough surface and charge density of approximately 0.08 C/m2. This creates a significant electric field with negligible screening (ka ≪ 1) in the region close to the surface of the assemblies. This field attracts nano- and micron-size particles from as far as 0.3 mm in less than a few seconds, many orders of magnitude greater than the conventional Derjaguin–Landau–Verwey–Overbeek theory that predicts only nanometer-scale effects arising from the presence of the surface. The strong electric field on the surface is then able to retain particles such as micron-size powdered activated carbon as well as much smaller particles such as fumed silica nanoparticles of 10–15 nm in diameter, viruses, atomically thick s...
TL;DR: In this paper, a carbon hollow cylinder has been synthesized by continuous spray pyrolysis of ferrocene-benzene solution in argon atmosphere, which has been turned into a water filter by closing one end and keeping a small funnel at the other.
Abstract: The present article deals with filtration of seawater to remove sodium chloride (NaCl) using filter made from organized structures of carbon nanotubes (CNTs). The filter consists of hollow carbon cylinder (length ~10 cm, diameter ~1 cm), which is composed of radially aligned CNTs. This carbon hollow cylinder has been synthesized by continuous spray pyrolysis of ferrocene–benzene solution in argon atmosphere. The hollow cylinder has been turned into a water filter by closing one end and keeping a small funnel at the other. Filtration of seawater (Marina Beach, Chennai, India) has been obtained both under the self pressure of seawater column in the hollow cylinder and under the difference of pressure created by enclosing the filter in a vacuum tight container. It has been found that the efficiency of filtration is about two times higher under partial vacuum (~10–2 torr) created on the filtrate (water) side. After filtration of seawater, a deposit in the inner surface of hollow cylinder has been found. This ...
Abstract: Single-walled carbon nanotubes (SWNTs) have been introduced as compliant electrodes for dielectric elastomers (DEs) due to fault tolerance. To acquire a better electrostrictive strain and longer lifetime, it is essential to obtain a certain and uniform width of the SWNT electrode. To ensure uniform width manually, a small flux and longer time are necessary. Moreover, it is difficult to control the width of the electrode for the randomness of manual spraying. Therefore, a new type of automatic spraying process is presented in this paper. The width and homogeneity of the electrode can be easily controlled by certain parameters of the process. Two methods for detecting the homogeneity of the electrode are introduced in this paper: Measurement of surface resistance and luminosity. The coefficient of variation (CV) values detected by the two methods are virtually equal and less than 8%, which shows the feasibility of the detection method and homogeneity of automatic spraying. The speed of automatic spraying is...
TL;DR: In this paper, the effect of the preparation conditions on the structure and morphology of the composites was also addressed through the characterization of selected samples with similar composition prepared by melt compounding.
Abstract: Ethylene copolymers with different polar comonomers, such as vinyl acetate, methyl acrylate, glycidyl methacrylate, and maleic anhydride, were used for the preparation of polymer/clay nanocomposites by statically annealing their mechanical mixtures with different commercial or home-made organically modified montmorillonites containing only one long alkyl tail. The nanostructure of the products was monitored by X-ray diffraction, and the dispersion of the silicate particles within the polymer matrix was qualitatively evaluated through microscopic analyses. The effect of the preparation conditions on the structure and the morphology of the composites was also addressed through the characterization of selected samples with similar composition prepared by melt compounding. In agreement with the findings reported in a previous paper for the composites filled with two-tailed organoclays, intercalation of the copolymer chains within the tighter galleries of the one-tailed clays occurs easily, independent of the ...