Enhancement of Electrical Properties of Nanostructured Polysilicon Layers Through Hydrogen Passivation.

PubMed

Zhou, D; Xu, T; Lambert, Y; Cristini-Robbe; Stiévenard, D

2015-12-01

The light absorption of polysilicon planar junctions can be improved using nanostructured top surfaces due to their enhanced light harvesting properties. Nevertheless, associated with the higher surface, the roughness caused by plasma etching and defects located at the grain boundary in polysilicon, the concentration of the recombination centers increases, leading to electrical performance deterioration. In this work, we demonstrate that wet oxidation combined with hydrogen passivation using SiN(x):H are the key technological processes to significantly decrease the surface recombination and improve the electrical properties of nanostructured n(+)-i-p junctions. Nanostructured surface is fabricated by nanosphere lithography in a low-cost and controllable approach. Furthermore, it has been demonstrated that the successive annealing of silicon nitride films has significant effect on the passivation quality, resulting in some improvements on the efficiency of the Si nanostructure-based solar cell device.

Electrostatic cloaking of surface structure for dynamic wetting

NASA Astrophysics Data System (ADS)

Shiomi, Junichiro; Nita, Satoshi; Do-Quang, Minh; Wang, Jiayu; Chen, Yu-Chung; Suzuki, Yuji; Amberg, Gustav

2017-11-01

Dynamic wetting problems are fundamental to the understanding of the interaction between liquids and solids. Even in a superficially simple experimental situation, such as a droplet spreading over a dry surface, the result may depend not only on the liquid properties but also strongly on the substrate-surface properties; even for macroscopically smooth surfaces, the microscopic geometrical roughness can be important. In addition, as surfaces may often be naturally charged, or electric fields are used to manipulate fluids, electric effects are crucial components that influence wetting phenomena. Here we investigate the interplay between electric forces and surface structures in dynamic wetting. While surface microstructures can significantly hinder the spreading, we find that the electrostatics can ``cloak'' the microstructures, i.e. deactivate the hindering. We identify the physics in terms of reduction in contact-line friction, which makes the dynamic wetting inertial force dominant and insensitive to the substrate properties. This work was financially supported in part by, the Japan Society for the Promotion of Science, Swedish Governmental Agency for Innovation Systems, and the Japan Science and Technology Agency.

Study of electrical properties of meridian on human body surface

NASA Astrophysics Data System (ADS)

Wang, Feng; Uematsu, Haruyuki; Otani, Nobuo

2007-12-01

This paper presents the study of the subcutaneous electrical impedance on the human body surface. Measurements of the electrical impedance on five adult male subjects were carried out and analyzed for the possible detection of the acupuncture meridian lines of ancient Chinese medicine on the human body. The distribution of electrical impedance measured at 40 points over the volar side of the right upper limb of the subjects. The results show that electrical impedance varies at different locations of the human body surface, and the locations with lower electrical impedance coincide with the locations where the meridian is believed to exist.

Acoustic wave device using plate modes with surface-parallel displacement

DOEpatents

Martin, Stephen J.; Ricco, Antonio J.

1992-01-01

Solid-state acoustic sensors for monitoring conditions at a surface immersed in a liquid and for monitoring concentrations of species in a liquid and for monitoring electrical properties of a liquid are formed by placing interdigital input and output transducers on a piezoelectric substrate and propagating acoustic plate modes therebetween. The deposition or removal of material on or from, respectively, a thin film in contact with the surface, or changes in the mechanical properties of a thin film in contact with the surface, or changes in the electrical characteristics of the solution, create perturbations in the velocity and attenuation of the acoustic plate modes as a function of these properties or changes in them.

Acoustic wave device using plate modes with surface-parallel displacement

DOEpatents

Martin, S.J.; Ricco, A.J.

1992-05-26

Solid-state acoustic sensors for monitoring conditions at a surface immersed in a liquid and for monitoring concentrations of species in a liquid and for monitoring electrical properties of a liquid are formed by placing interdigital input and output transducers on a piezoelectric substrate and propagating acoustic plate modes there between. The deposition or removal of material on or from, respectively, a thin film in contact with the surface, or changes in the mechanical properties of a thin film in contact with the surface, or changes in the electrical characteristics of the solution, create perturbations in the velocity and attenuation of the acoustic plate modes as a function of these properties or changes in them. 6 figs.

Acoustic wave device using plate modes with surface-parallel displacement

DOEpatents

Martin, S.J.; Ricco, A.J.

1988-04-29

Solid-state acoustic sensors for monitoring conditions at a surface immersed in a liquid and for monitoring concentrations of species in a liquid and for monitoring electrical properties of a liquid are formed by placing interdigital input and output transducers on a piezoelectric substrate and propagating acoustic plate modes therebetween. The deposition or removal of material on or from, respectively, a thin film in contact with the surface, or changes in the mechanical properties of a thin film in contact with the surface, or changes in the electrical characteristics of the solution, create perturbations in the velocity and attenuation of the acoustic plate modes as a function of these properties or changes in them. 6 figs.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Electrical, dielectric and surface wetting properties of multi-walled carbon nanotubes/nylon-6 nanocomposites

NASA Astrophysics Data System (ADS)

Long, Yun-Ze; Li, Meng-Meng; Sui, Wan-Mei; Kong, Qing-Shan; Zhang, Lei

2009-03-01

This paper reports that the multi-walled carbon nanotubes (MWCNT)/nylon-6 (PA6) nanocomposites with different MWCNT loadings have been prepared by a simple melt-compounding method. The electrical, dielectric, and surface wetting properties of the CNT/PA6 composites have been studied. The temperature dependence of the conductivity of the CNT/PA6 composite with 10.0 wt% CNT loading (σRT ~ 10-4 S/cm) are measured, and afterwards a charge-energy-limited tunnelling model (ln σ(T) ~ T-1/2) is found. With increasing CNT weight percentage from 0.0 to 10.0 wt%, the dielectric constant of the CNT/PA6 composites enhances and the dielectric loss tangent increases two orders of magnitude. In addition, water contact angles of the CNT/PA6 composites increase and the composites with CNT loading larger than 2.0 wt% even become hydrophobic. The obtained results indicate that the electrical and surface properties of the composites have been significantly enhanced by the embedded carbon nanotubes.

Materials characterization study of conductive flexible second surface mirrors

NASA Technical Reports Server (NTRS)

Levadou, F.; Bosma, S. J.; Paillous, A.

1981-01-01

The status of prequalification and qualification work on conductive flexible second surface mirrors is described. The basic material is FEP Teflon witn either aluminium or silver vacuum deposited reflectors. The top layer has been made conductive by deposition of layer of a indium oxide. The results of a prequalification program comprised of decontamination, humidity, thermal cycling, thermal shock and vibration tests are presented. Thermo-optical and electrical properties. The results of a prequalification program comprised of decontamination, humidity, thermal cycling, thermal shock and vibration tests are presented. Thermo-optical and electrical properties, the electrostatic behavior of the materials under simulated substorm environment and electrical conductivity at low temperatures are characterized. The effects of simulated ultra violet and particles irradiation on electrical and thermo-optical properties of the materials are also presented.

Evaluation of Fatigue Behavior and Surface Characteristics of Aluminum Alloy 2024 T6 After Electric Discharge Machining

NASA Astrophysics Data System (ADS)

Mehmood, Shahid; Shah, Masood; Pasha, Riffat Asim; Sultan, Amir

2017-10-01

The effect of electric discharge machining (EDM) on surface quality and consequently on the fatigue performance of Al 2024 T6 is investigated. Five levels of discharge current are analyzed, while all other electrical and nonelectrical parameters are kept constant. At each discharge current level, dog-bone specimens are machined by generating a peripheral notch at the center. The fatigue tests are performed on four-point rotating bending machine at room temperature. For comparison purposes, fatigue tests are also performed on the conventionally machined specimens. Linearized SN curves for 95% failure probability and with four different confidence levels (75, 90, 95 and 99%) are plotted for each discharge current level as well as for conventionally machined specimens. These plots show that the electric discharge machined (EDMed) specimens give inferior fatigue behavior as compared to conventionally machined specimen. Moreover, discharge current inversely affects the fatigue life, and this influence is highly pronounced at lower stresses. The EDMed surfaces are characterized by surface properties that could be responsible for change in fatigue life such as surface morphology, surface roughness, white layer thickness, microhardness and residual stresses. It is found that all these surface properties are affected by changing discharge current level. However, change in fatigue life by discharge current could not be associated independently to any single surface property.

Testing and Optimization of Electrically Conductive Spacecraft Coatings

NASA Technical Reports Server (NTRS)

Mell, R. J.; Wertz, G. E.; Edwards, D. L. (Technical Monitor)

2001-01-01

This is the final report discussing the work done for the Space Environments and Effects (SEE) Program. It discusses test chamber design, coating research, and test results on electrically thermal control coatings. These thermal control coatings are being developed to have several orders of magnitude higher electrical conductivity than most available thermal control coatings. Most current coatings tend to have a range in surface resistivity from 1,011 to 1,013 ohms/sq. Historically, spacecraft have had thermal control surfaces composed of dielectric materials of either polymers (paints and metalized films) or glasses (ceramic paints and optical solar reflectors). Very seldom has the thermal control surface of a spacecraft been a metal where the surface would be intrinsically electrically conductive. The poor thermal optical properties of most metals have, in most cases, stopped them from being used as a thermal control surface. Metals low infrared emittance (generally considered poor for thermal control surfaces) and/or solar absorptance, have resulted in the use of various dielectric coatings or films being applied over the substrate materials in order to obtain the required optical properties.

Effect of various electrokinetic treatment regimes on solids surface properties and thermal behavior of oil sediments.

PubMed

Kariminezhad, Esmaeel; Elektorowicz, Maria

2018-04-10

The electrokinetic process has shown its ability to separate the different material phases. However, not much is known about the effect of the electric fields on the surface properties of solids in the oil sediments and their behavior under different electrical regimes. In this study, the effect of four different types of electrical current on the surface properties of oil sediments was investigated, namely constant direct current (CDC), pulsed direct current (PDC), incremental direct current (IDC) and decremental direct current (DDC). X-ray photoelectron spectroscopy (XPS) analyses showed a decrease in the concentration of carbon from 99% in centrifuged samples to 63% on the surface of the solids in the PDC-treated oil sediment. Wettability alteration and contact angle studies showed an enhance in hydrophilicity of the solids following electrokinetic treatment. A significant change in carbon and oxygen-containing functionalities at the surface solids of the DDC-treated sediment was also observed. Thermogravimetric analyses (TGA) confirmed the ability of electrokinetic treatment in separating the phases by shifting the thermogram profiles towards lower temperatures. The findings showed that the electrokinetic process exerts its effect by altering the surface properties of the sediment solids and destabilizing water-in-oil emulsions to facilitate phase separation of this complex waste. Copyright © 2018 Elsevier B.V. All rights reserved.

Thermoelectric Properties of Topological Crystalline Insulator Nanowires

NASA Astrophysics Data System (ADS)

Xu, Enzhi

Bulk lead telluride (PbTe) and its alloy compounds are well-known thermoelectric materials for electric power generation. Tin telluride (SnTe) which has the same rock-salt crystalline structure as PbTe has recently been demonstrated to host unique topological surface states that may favor improved thermoelectric properties. In this thesis work, we studied the thermoelectric properties of single-crystalline nanowires of the SnTe family compounds, i.e. undoped SnTe, PbTe, (Sn,Pb)Te alloy, and In-doped SnTe, all of which were grown by a vapor transport approach. We measured the thermopower S, electrical conductivity sigma and thermal conductivity kappa on each individual nanowire over a temperature range of 25 - 300 K, from which the thermoelectric figures of merit ZTs were determined. In comparison to PbTe nanowires, SnTe and (Sn,Pb)Te has lower thermopower but significantly higher electrical conductivity. Both SnTe and (Sn,Pb)Te nanowires showed enhanced thermopower and suppressed thermal conductivity, compared to their bulk counterparts. The enhancement of thermopower may result from the existence of topological surface states, while the suppression of thermal conductivity may relate to the increased phonon-surface scattering in nanowires. Moreover, indium doping suppresses both electrical and thermal conductivities but enhances thermopower, yielding an improved figure of merit ZT. Our results highlight nanostructuring in combination with alloying or doping as an important approach to enhancing thermoelectric properties. In spite of excellent thermoelectric properties and robust topological surface states, we found that the nanowire surface is subject to fast oxidation. In particular, we demonstrated that exposure of In-doped SnTe nanowires to air leads to surface oxidation within only one minute. Transmission electron microscopy characterization suggests the amorphous nature of the surface, and X-ray photoelectron spectroscopy studies identify the oxide species on nanowire surface. We further developed an effective approach to removing surface oxides by means of argon ion sputtering.

Laser modification of macroscopic properties of metal surface layer

NASA Astrophysics Data System (ADS)

Kostrubiec, Franciszek

1995-03-01

Surface laser treatment of metals comprises a number of diversified technological operations out of which the following can be considered the most common: oxidation and rendering surfaces amorphous, surface hardening of steel, modification of selected physical properties of metal surface layers. In the paper basic results of laser treatment of a group of metals used as base materials for electric contacts have been presented. The aim of the study was to test the usability of laser treatment from the viewpoint of requirements imposed on materials for electric contacts. The results presented in the paper refer to two different surface treatment technologies: (1) modification of infusible metal surface layer: tungsten and molybdenum through laser fusing of their surface layer and its crystallization, and (2) modification of surface layer properties of other metals through laser doping of their surface layer with foreign elements. In the paper a number of results of experimental investigations obtained by the team under the author's supervision are presented.

Fabrication of Superhydrophobic Surfaces with Controllable Electrical Conductivity and Water Adhesion.

PubMed

Ye, Lijun; Guan, Jipeng; Li, Zhixiang; Zhao, Jingxin; Ye, Cuicui; You, Jichun; Li, Yongjin

2017-02-14

A facile and versatile strategy for fabricating superhydrophobic surfaces with controllable electrical conductivity and water adhesion is reported. "Vine-on-fence"-structured and cerebral cortex-like superhydrophobic surfaces are constructed by filtering a suspension of multiwalled carbon nanotubes (MWCNTs), using polyoxymethylene nonwovens as the filter paper. The nonwovens with micro- and nanoporous two-tier structures act as the skeleton, introducing a microscale structure. The MWCNTs act as nanoscale structures, creating hierarchical surface roughness. The surface topography and the electrical conductivity of the superhydrophobic surfaces are controlled by varying the MWCNT loading. The vine-on-fence-structured surfaces exhibit "sticky" superhydrophobicity with high water adhesion. The cerebral cortex-like surfaces exhibit self-cleaning properties with low water adhesion. The as-prepared superhydrophobic surfaces are chemically resistant to acidic and alkaline environments of pH 2-12. They therefore have potential in applications such as droplet-based microreactors and thin-film microextraction. These findings aid our understanding of the role that surface topography plays in the design and fabrication of superhydrophobic surfaces with different water-adhesion properties.

Surface engineering of ferroelectric polymer for the enhanced electrical performance of organic transistor memory

NASA Astrophysics Data System (ADS)

Kim, Do-Kyung; Lee, Gyu-Jeong; Lee, Jae-Hyun; Kim, Min-Hoi; Bae, Jin-Hyuk

2018-05-01

We suggest a viable surface control method to improve the electrical properties of organic nonvolatile memory transistors. For viable surface control, the surface of the ferroelectric insulator in the memory field-effect transistors was modified using a smooth-contact-curing process. For the modification of the ferroelectric polymer, during the curing of the ferroelectric insulators, the smooth surface of a soft elastomer contacts intimately with the ferroelectric surface. This smooth-contact-curing process reduced the surface roughness of the ferroelectric insulator without degrading its ferroelectric properties. The reduced roughness of the ferroelectric insulator increases the mobility of the organic field-effect transistor by approximately eight times, which results in a high memory on–off ratio and a low-voltage reading operation.

Effective electromagnetic properties of microheterogeneous materials with surface phenomena

NASA Astrophysics Data System (ADS)

Levin, Valery; Markov, Mikhail; Mousatov, Aleksandr; Kazatchenko, Elena; Pervago, Evgeny

2017-10-01

In this paper, we present an approach to calculate the complex dielectric permittivity of a micro-heterogeneous medium composed of non-conductive solid inclusions embedded into the conductive liquid continuous host. To take into account the surface effects, we approximate the inclusion by a layered ellipsoid consisting of a dielectric core and an infinitesimally thin outer shell corresponding to an electrical double layer (EDL). To predict the effective complex dielectric permittivity of materials with a high concentration of inclusions, we have modified the Effective Field Method (EFM) for the layered ellipsoidal particles with complex electrical properties. We present the results of complex permittivity calculations for the composites with randomly and parallel oriented ellipsoidal inclusions. To analyze the influence of surface polarization, we have accomplished modeling in a wide frequency range for different existing physic-chemical models of double electrical layer. The results obtained show that the tensor of effective complex permittivity of a micro-heterogeneous medium with surface effects has complicate dependences on the component electrical properties, spatial material texture, and the inclusion shape (ellipsoid aspect ratio) and size. The dispersion of dielectric permittivity corresponds to the frequency dependence for individual inclusion of given size, and does not depend on the inclusion concentration.

Electro-responsive polyelectrolyte-coated surfaces.

PubMed

Sénéchal, V; Saadaoui, H; Rodriguez-Hernandez, J; Drummond, C

2017-07-01

The anchoring of polymer chains at solid surfaces is an efficient way to modify interfacial properties like the stability and rheology of colloidal dispersions, lubrication and biocompatibility. Polyelectrolytes are good candidates for the building of smart materials, as the polyion chain conformation can often be tuned by manipulation of different physico-chemical variables. However, achieving efficient and reversible control of this process represents an important technological challenge. In this regard, the application of an external electrical stimulus on polyelectrolytes seems to be a convenient control strategy, for several reasons. First, it is relatively easy to apply an electric field to the material with adequate spatiotemporal control. In addition, in contrast to chemically induced changes, the molecular response to a changing electric field occurs relatively quickly. If the system is properly designed, this response can then be used to control the magnitude of surface properties. In this work we discuss the effect of an external electric field on the adhesion and lubrication properties of several polyelectrolyte-coated surfaces. The influence of the applied field is investigated at different pH and salt conditions, as the polyelectrolyte conformation is sensitive to these variables. We show that it is possible to fine tune friction and adhesion using relatively low applied fields.

Research on Lessening of Bonding Effects Between the Metallic and Non-Metallic Surfaces Through the Graphite Films Deposited with Pulsed Electrical Discharges Process

NASA Astrophysics Data System (ADS)

Marin, L.; Topala, P.

2017-06-01

The paper presents the results of experimental research on the physics of natural graphite film formation, the establishment of chemical composition and functional properties of the graphite films, formed on metal surfaces, as a result of the action of plasma in the air environment, at a normal pressure, under the electrical discharge in impulse conditions (EDI). The researchings were performed in the frame of doctoral thesis “Research on lessening of the bonding effects between the metallic and nonmetallic surfaces through the graphite films” and aimed to identify the phenomena that occur at the interface metal/ film of graphite, and to identify also the technological applications that it may have the surface treatment for submitting the films of graphite on metallic surfaces achieved through an innovative process of electrical pulsed discharges. After the research works from the PhD theme above mentioned, a number of interesting properties of graphite pellicle have been identified ie reducing of metal surface polarity. This led to drastic decreases for the values of adhesion when bonding of metal surfaces was performed using a structural polyurethane adhesive designed by ICECHIM. Following the thermo-gravimetric analysis, performed of the graphite film obtained by process of electrical pulsed discharges, have been also discovered other interesting properties for this, ie reversible mass additions at specific values of the working temperature Chemical and scanning electron microscopy analysis have revealed that on the metallic surface subjected to electrical pulsed discharges process, outside the graphite film, it is also obtained a series of spatial formation composed of carbon atoms fullerenes type which are responsible for the phenomenon of addition of mass.

Effect of TiO2 nanoparticles doping on structural and electrical properties of PVA: NaBr polymer electrolyte

NASA Astrophysics Data System (ADS)

Sagar, Rohan N.; Ravindrachary, V.; Guruswamy, B.; Hegde, Shreedatta; Mahanthesh, B. K.; Kumari, R. Padma

2018-05-01

The effect of TiO2 nanoparticles on morphology and electrical properties of PVA: NaBr composite films were carried out using various techniques. The pure and TiO2 nanoparticle doped PVA: NaBr composite films were prepared using solvent casting method. The FTIR spectral studies shows that the Ti+ ions of TiO2 interacts with hydroxyl group (OH) of PVA via hydrogen bonding and forms the charge transfer complexes (CTC). These interactions are of inter/intra molecular type and affects the surface morphology as well as the electrical properties of composite films. XRD study shows that the crystallinity of the composite increases with doping level. SEM studies shows that the increase in roughness of the surface of the composite films and uniform dispersion of nanofillers in polymer matrix. Electrical properties are analyzed using impedance analyzer and higher conductivity (10-4Scm-1) is achieved for 5 wt % TiO2 doping concentration.

Magnetic and electrical properties of Martian particles

NASA Technical Reports Server (NTRS)

Olhoeft, G. R.

1991-01-01

The only determinations of the magnetic properties of Martian materials come from experiments on the two Viking Landers. The results suggest Martian soil containing 1 to 10 percent of a highly magnetic phase. Though the magnetic phase mineral was not conclusively identified, the predominate interpretation is that the magnetic phase is probably maghemite. The electrical properties of the surface of Mars were only measured remotely by observations with Earth based radar, microwave radiometry, and inference from radio-occultation of Mars orbiting spacecraft. No direct measurements of electrical properties on Martian materials have been performed.

APOLLO 17 - INFLIGHT Experiment Equipment

NASA Image and Video Library

1972-11-28

S72-53950 (November 1972) --- The transmitter of the Surface Electrical Properties Experiment (S-204) in a deployed configuration. This experiment will be deployed at the Taurus-Littrow landing site by the Apollo 17 crewmen. The purpose of the SEP experiment is to obtain data about the electromagnetic energy transmission, absorption and reflection characteristics of the lunar surface and subsurface for use in the development of a geological model of the upper layers of the moon. The experiment is designed to determine layering in the lunar surface, to search for the presence of water below the surface, and to measure electrical properties of the lunar material in situ.

Comprehensive design of omnidirectional high-performance perovskite solar cells

PubMed Central

Zhang, Yutao; Xuan, Yimin

2016-01-01

The comprehensive design approach is established with coupled optical-electrical simulation for perovskite-based solar cell, which emerged as one of the most promising competitors to silicon solar cell for its low-cost fabrication and high PCE. The selection of structured surface, effect of geometry parameters, incident angle-dependence and polarization-sensitivity are considered in the simulation. The optical modeling is performed via the finite-difference time-domain method whilst the electrical properties are obtained by solving the coupled nonlinear equations of Poisson, continuity, and drift-diffusion equations. The optical and electrical performances of five different structured surfaces are compared to select a best structured surface for perovskite solar cell. The effects of the geometry parameters on the optical and electrical properties of the perovskite cell are analyzed. The results indicate that the light harvesting is obviously enhanced by the structured surface. The electrical performance can be remarkably improved due to the enhanced light harvesting of the designed best structured surface. The angle-dependence for s- and p-polarizations is investigated. The structured surface exhibits omnidirectional behavior and favorable polarization-insensitive feature within a wide incident angle range. Such a comprehensive design approach can highlight the potential of perovskite cell for power conversion in the full daylight. PMID:27405419

Comprehensive design of omnidirectional high-performance perovskite solar cells.

PubMed

Zhang, Yutao; Xuan, Yimin

2016-07-13

The comprehensive design approach is established with coupled optical-electrical simulation for perovskite-based solar cell, which emerged as one of the most promising competitors to silicon solar cell for its low-cost fabrication and high PCE. The selection of structured surface, effect of geometry parameters, incident angle-dependence and polarization-sensitivity are considered in the simulation. The optical modeling is performed via the finite-difference time-domain method whilst the electrical properties are obtained by solving the coupled nonlinear equations of Poisson, continuity, and drift-diffusion equations. The optical and electrical performances of five different structured surfaces are compared to select a best structured surface for perovskite solar cell. The effects of the geometry parameters on the optical and electrical properties of the perovskite cell are analyzed. The results indicate that the light harvesting is obviously enhanced by the structured surface. The electrical performance can be remarkably improved due to the enhanced light harvesting of the designed best structured surface. The angle-dependence for s- and p-polarizations is investigated. The structured surface exhibits omnidirectional behavior and favorable polarization-insensitive feature within a wide incident angle range. Such a comprehensive design approach can highlight the potential of perovskite cell for power conversion in the full daylight.

Morphology, composition and electrical properties of SnO{sub 2}:Cl thin films grown by atomic layer deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Hsyi-En, E-mail: sean@mail.stust.edu.tw; Wen, Chia-Hui; Hsu, Ching-Ming

2016-01-15

Chlorine doped SnO{sub 2} thin films were prepared using atomic layer deposition at temperatures between 300 and 450 °C using SnCl{sub 4} and H{sub 2}O as the reactants. Composition, structure, surface morphology, and electrical properties of the as-deposited films were examined. Results showed that the as-deposited SnO{sub 2} films all exhibited rutile structure with [O]/[Sn] ratios between 1.35 and 1.40. The electrical conductivity was found independent on [O]/[Sn] ratio but dependent on chlorine doping concentration, grain size, and surface morphology. The 300 °C-deposited film performed a higher electrical conductivity of 315 S/cm due to its higher chlorine doping level, larger grain size, andmore » smoother film surface. The existence of Sn{sup 2+} oxidation state was demonstrated to minimize the effects of chlorine on raising the electrical conductivity of films.« less

Modification of surface characteristic and tribo-electric properties of polymers by DBD plasma in atmospheric air

NASA Astrophysics Data System (ADS)

Bekkara, Mohammed Fethi; Dascalescu, Lucien; Benmimoun, Youcef; Zeghloul, Thami; Tilmatine, Amar; Zouzou, Noureddine

2018-01-01

The aim of this paper is to quantify the effects of dielectric barrier discharge (DBD) exposure on the physico-chemical and tribo-electric properties of polymers. The study was conducted in atmospheric air on polypropylene, polyethylene and polyvinyl-chloride. These three types of polymers are widely used in industry. The polymers were characterized by means of an optical profilometer, a fourier-transform infrared (FTIR) spectrometer and an electric charge measurement system. The latter is composed of a Faraday pail connected to an electrometer. The profilometer analyses showed that the DBD plasma treatment has increased the surface roughness of the three polymers. FTIR revealed that oxygen atoms and polar groups were grafted on their surfaces, thereby conferring them a hydrophilic character. The short (2 sec) DBD plasma treatment has considerably improved the electrostatic charge acquired by the polymers during electrostatic tribo-charging, while longer exposures conferred the polymer anti-static properties and decreased its tribo-charging capability. The correlation between the results of the physico-chemical analyses and the tribo-electric behavior has been discussed.

Changes of electrical conductivity of the metal surface layer by the laser alloying with foreign elements

NASA Astrophysics Data System (ADS)

Kostrubiec, Franciszek; Pawlak, Ryszard; Raczynski, Tomasz; Walczak, Maria

1994-09-01

Laser treatment of the surface of materials is of major importance for many fields technology. One of the latest and most significant methods of this treatment is laser alloying consisting of introducing foreign atoms into the metal surface layer during the reaction of laser radiation with the surface. This opens up vast possibilities for the modification of properties of such a layer (obtaining layers of increased microhardness, increased resistance to electroerosion in an electric arc, etc.). Conductivity of the material is a very important parameter in case of conductive materials used for electrical contacts. The paper presents the results of studies on change in electrical conductivity of the surface layer of metals alloyed with a laser. A comparative analysis of conductivity of base metal surface layers prior to and following laser treatment has been performed. Depending on the base metal and the alloying element, optical treatment parameters allowing a required change in the surface layer conductivity have been selected. A very important property of the contact material is its resistance to plastic strain. It affects the real value of contact surface coming into contact and, along with the material conductivity, determines contact resistance and the amount of heat generated in place of contact. These quantities are directly related to the initiation and the course of an arc discharge, hence they also affect resistance to electroerosion. The parameter that reflects plastic properties with loads concentrated on a small surface, as is the case with a reciprocal contact force of two real surfaces with their irregularities being in contact, is microhardness. In the paper, the results of investigations into microhardness of modified surface layers compared with base metal microhardness have been presented.

Imaging of electrical response of NiO x under controlled environment with sub-25-nm resolution

DOE PAGES

Jacobs, Christopher B.; Ievlev, Anton V.; Collins, Liam F.; ...

2016-07-19

The spatially resolved electrical response of rf-sputtered polycrystalline NiO x films composed of 40 nm crystallites was investigated under different relative humidity levels (RH). The topological and electrical properties (surface potential and resistance) were characterized using Kelvin probe force microscopy (KPFM) and conductive scanning probe microscopy at 0%, 50%, and 80% relative humidity with sub 25nm resolution. The surface potential of NiO x decreased by about 180 mV and resistance decreased in a nonlinear fashion by about 2 G when relative humidity was increased from 0% to 80%. The dimensionality of surface features obtained through autocorrelation analysis of topological, surfacemore » potential and resistance maps increased linearly with increased relative humidity as water was adsorbed onto the film surface. Spatially resolved surface potential and resistance of the NiO x films were found to be heterogeneous, with distinct features that grew in size from about 60 nm to 175 nm between 0% and 80% RH levels, respectively. Here, we find that the changes in the heterogeneous character of the NiO films are consistent through the topological, surface potential, and resistance measurements, suggesting that the nanoscale surface potential and resistance properties converge with the mesoscale properties as water is adsorbed onto the NiO x film.« less

Facile Dry Surface Cleaning of Graphene by UV Treatment

NASA Astrophysics Data System (ADS)

Kim, Jin Hong; Haidari, Mohd Musaib; Choi, Jin Sik; Kim, Hakseong; Yu, Young-Jun; Park, Jonghyurk

2018-05-01

Graphene has been considered an ideal material for application in transparent lightweight wearable electronics due to its extraordinary mechanical, optical, and electrical properties originating from its ordered hexagonal carbon atomic lattice in a layer. Precise surface control is critical in maximizing its performance in electronic applications. Graphene grown by chemical vapor deposition is widely used but it produces polymeric residue following wet/chemical transfer process, which strongly affects its intrinsic electrical properties and limits the doping efficiency by adsorption. Here, we introduce a facile dry-cleaning method based on UV irradiation to eliminate the organic residues even after device fabrication. Through surface topography, Raman analysis, and electrical transport measurement characteristics, we confirm that the optimized UV treatment can recover the clean graphene surface and improve graphene-FET performance more effectively than thermal treatment. We propose our UV irradiation method as a systematically controllable and damage-free post process for application in large-area devices.

Effect of oxidation agent on wood biomass in ethylene vinyl acetate conductive polymer: tensile properties, tensile fracture surface and electrical properties

NASA Astrophysics Data System (ADS)

Hanif, M. P. M.; Supri, A. G.; Rozyanty, A. R.; Tan, S. J.

2017-10-01

The wood fiber (WF) type of Pulverised Wood Filler obtained by combustion process at temperature under 700 °C for 3 hours was characterized and coated with ferric chloride (FeCl3) by ethanol solution. Both carbonized wood fiber (CWF) and carbonized wood fiber-ferric chloride (CWF-FeCl3) were used as filler in ethylene vinyl acetate (EVA) conductive polymer. The filler was coated with FeCl3 to enhance the properties of the CWF to achieve progressive mechanical and electrical properties. The CWF and CWF-FeCl3 loading were varied from 2.5 to 10.0 wt%. EVA/CWF and EVA/CWF-FeCl3 conductive polymer were processed by using Brabender Plasticoder at 160 °C with 50 rpm rotor speed for 10 min. The mechanical properties were investigated by tensile testing and the tensile fractured surface of conductive polymers was analyzed by scanning electron microscopy (SEM) analysis. Then, the electrical conductivity of conductive polymer was determined by four-point probe I-V measurement system. The EVA/CWF-FeCl3 conductive polymer showed greater electrical conductivity and tensile strength but lower elongation at break than EVA/CWF conductive polymer. SEM morphology displayed rougher surface between CWF-FeCl3 and EVA phases compared to EVA/CWF conductive polymer.

Effect of surface oxide films on the properties of pulse electric-current sintered metal powders

NASA Astrophysics Data System (ADS)

Xie, Guoqiang; Ohashi, Osamu; Yamaguchi, Norio; Wang, Airu

2003-11-01

Metallic powders with various thermodynamic stability oxide films (Ag, Cu, and Al powders) were sintered using a pulse electric-current sintering (PECS) process. Behavior of oxide films at powder surfaces and their effect on the sintering properties were investigated. The results showed that the sintering properties of metallic powders in the PECS process were subject to the thermodynamic stability of oxide films at particles surfaces. The oxide films at Ag powder surfaces are decomposed during sintering with the contact region between the particles being metal/metal bond. The oxide films at Cu powder surfaces are mainly broken via loading pressure at a low sintering temperature. At a high sintering temperature, they are mainly dissolved in the parent metal, and the contact regions turn into the direct metal/metal bonding. Excellent sintering properties can be received. The oxide films at Al powder surfaces are very stable, and cannot be decomposed and dissolved, but broken by plastic deformation of particles under loading pressure at experimental temperatures. The interface between particles is partially bonded via the direct metal/metal bonding making it difficult to achieve good sintered properties.

Conductivity enhancement of carbon aerogel by modified gelation using self additive

NASA Astrophysics Data System (ADS)

Singh, Ashish; Kohli, D. K.; Bhartiya, Sushmita; Singh, Rashmi; Rajak, Gaurav; Singh, M. K.; Karnal, A. K.

2018-04-01

Carbon aerogels having high surface area and open pore structure are being studied for many electrochemical applications such as fuel cells and super capacitors. Moderate electrical conductivity of resorcinol - formaldehyde (R-F) derived carbon aerogel limits its utility in these applications. The current manuscript briefs about the synthesis of composite carbon aerogel using carbon aerogel itself as additive during gelation of water based carbon aerogel and study the effect on its conductivity and surface properties. The additive carbon aerogel was synthesized and pre-treated at higher temperature to achieve enhancement in conductivity. The composite carbon aerogel (CCA) samples were characterized for surface area properties, morphology, electrical conductivity and specific capacitance. The surface area properties of CCA showed improvement and specific surface area of ˜1798 m2/g with total pore volume of 1.7 cm3/g. was obtained. The electrical conductivity of the composite carbon aerogel with 5 wt % additive showed improvement over the plain carbon aerogel with respective values of 144 S/m and 128 S/m. The specific capacitance evaluated for CA and CCA are 102 and 118 F/g at scan rate of 10mV/s with improvement of ˜16%.

The surface chemical properties of multi-walled carbon nanotubes modified by thermal fluorination for electric double-layer capacitor

NASA Astrophysics Data System (ADS)

Jung, Min-Jung; Jeong, Euigyung; Lee, Young-Seak

2015-08-01

The surfaces of multi-walled carbon nanotubes (MWCNTs) were thermally fluorinated at various temperatures to enhance the electrochemical properties of the MWCNTs for use as electric double-layer capacitor (EDLC) electrodes. The fluorine functional groups were added to the surfaces of the MWCNTs via thermal fluorination. The thermal fluorination exposed the Fe catalyst on MWCNTs, and the specific surface area increased due to etching during the fluorination. The specific capacitances of the thermally fluorinated at 100 °C, MWCNT based electrode increased from 57 to 94 F/g at current densities of 0.2 A/g, respectively. This enhancement in capacitance can be attributed to increased polarization of the thermally fluorinated MWCNT surface, which increased the affinity between the electrode surface and the electrolyte ions.

Electromagnetic properties of material coated surfaces

NASA Technical Reports Server (NTRS)

Beard, L.; Berrie, J.; Burkholder, R.; Dominek, A.; Walton, E.; Wang, N.

1989-01-01

The electromagnetic properties of material coated conducting surfaces were investigated. The coating geometries consist of uniform layers over a planar surface, irregularly shaped formations near edges and randomly positioned, electrically small, irregularly shaped formations over a surface. Techniques to measure the scattered field and constitutive parameters from these geometries were studied. The significance of the scattered field from these geometries warrants further study.

Effects of surface morphology on the optical and electrical properties of Schottky diodes of CBD deposited ZnO nanostructures

NASA Astrophysics Data System (ADS)

Mwankemwa, Benard S.; Akinkuade, Shadrach; Maabong, Kelebogile; Nel, Jackie M.; Diale, Mmantsae

2018-04-01

We report on effect of surface morphology on the optical and electrical properties of chemical bath deposited Zinc oxide (ZnO) nanostructures. ZnO nanostructures were deposited on the seeded conducting indium doped tin oxide substrate positioned in three different directions in the growth solution. Field emission scanning electron microscopy was used to evaluate the morphological properties of the synthesized nanostructures and revealed that the positioning of the substrate in the growth solution affects the surface morphology of the nanostructures. The optical absorbance, photoluminescence and Raman spectroscopy of the resulting nanostructures are discussed. The electrical characterization of the Schottky diode such as barrier height, ideality factor, rectification ratios, reverse saturation current and series resistance were found to depend on the nanostructures morphology. In addition, current transport mechanism in the higher forward bias of the Schottky diode was studied and space charge limited current was found to be the dominant transport mechanism in all samples.

Toward intrinsic graphene surfaces: a systematic study on thermal annealing and wet-chemical treatment of SiO2-supported graphene devices.

PubMed

Cheng, Zengguang; Zhou, Qiaoyu; Wang, Chenxuan; Li, Qiang; Wang, Chen; Fang, Ying

2011-02-09

By combining atomic force microscopy and trans-port measurements, we systematically investigated effects of thermal annealing on surface morphologies and electrical properties of single-layer graphene devices fabricated by electron beam lithography on silicon oxide (SiO(2)) substrates. Thermal treatment above 300 °C in vacuum was required to effectively remove resist residues on graphene surfaces. However, annealing at high temperature was found to concomitantly bring graphene in close contact with SiO(2) substrates and induce increased coupling between them, which leads to heavy hole doping and severe degradation of mobilities in graphene devices. To address this problem, a wet-chemical approach employing chloroform was developed in our study, which was shown to enable both intrinsic surfaces and enhanced electrical properties of graphene devices. Upon the recovery of intrinsic surfaces of graphene, the adsorption and assisted fibrillation of amyloid β-peptide (Aβ1-42) on graphene were electrically measured in real time.

Optical and electrical properties of porous silicon layer formed on the textured surface by electrochemical etching

NASA Astrophysics Data System (ADS)

Weiying, Ou; Lei, Zhao; Hongwei, Diao; Jun, Zhang; Wenjing, Wang

2011-05-01

Porous silicon (PS) layers were formed on textured crystalline silicon by electrochemical etching in HF-based electrolyte. Optical and electrical properties of the TMAH textured surfaces with PS formation are studied. Moreover, the influences of the initial structures and the anodizing time on the optical and electrical properties of the surfaces after PS formation are investigated. The results show that the TMAH textured surfaces with PS formation present a dramatic decrease in reflectance. The longer the anodizing time is, the lower the reflectance. Moreover, an initial surface with bigger pyramids achieved lower reflectance in a short wavelength range. A minimum reflectance of 3.86% at 460 nm is achieved for a short anodizing time of 2 min. Furthermore, the reflectance spectrum of the sample, which was etched in 3 vol.% TMAH for 25 min and then anodized for 20 min, is extremely flat and lies between 3.67% and 6.15% in the wavelength range from 400 to 1040 nm. In addition, for a short anodizing time, a slight increase in the effective carrier lifetime is observed. Our results indicate that PS layers formed on a TMAH textured surface for a short anodization treatment can be used as both broadband antireflection coatings and passivation layers for the application in solar cells.

Influence of processing history on the mechanical properties and electrical resistivity of polycarbonate - multi-walled carbon nanotubes nanocomposites

NASA Astrophysics Data System (ADS)

Choong, Gabriel Y. H.; De Focatiis, Davide S. A.

2015-05-01

In this work we investigate the effects of compounding temperature and secondary melt processing on the mechanical response and electrical behaviour of polycarbonate filled with 3 wt% carbon nanotubes. The nanocomposites were melt compounded in an industrial setting at a range of temperatures, and subsequently injection moulded or compression moulded. The surface hardness, uniaxial tensile properties and electrical resistivity were measured. Secondary melt processing is found to be the dominant process in determining the final mechanical properties and resistivity of these materials.

Neurogenic differentiation of human umbilical cord mesenchymal stem cells on aligned electrospun polypyrrole/polylactide composite nanofibers with electrical stimulation

NASA Astrophysics Data System (ADS)

Zhou, Junfeng; Cheng, Liang; Sun, Xiaodan; Wang, Xiumei; Jin, Shouhong; Li, Junxiang; Wu, Qiong

2016-09-01

Adult central nervous system (CNS) tissue has a limited capacity to recover after trauma or disease. Recent medical cell therapy using polymeric biomaterialloaded stem cells with the capability of differentiation to specific neural population has directed focuses toward the recovery of CNS. Fibers that can provide topographical, biochemical and electrical cues would be attractive for directing the differentiation of stem cells into electro-responsive cells such as neuronal cells. Here we report on the fabrication of an electrospun polypyrrole/polylactide composite nanofiber film that direct or determine the fate of mesenchymal stem cells (MSCs), via combination of aligned surface topography, and electrical stimulation (ES). The surface morphology, mechanical properties and electric properties of the film were characterized. Comparing with that on random surface film, expression of neurofilament-lowest and nestin of human umbilical cord mesenchymal stemcells (huMSCs) cultured on film with aligned surface topography and ES were obviously enhanced. These results suggest that aligned topography combining with ES facilitates the neurogenic differentiation of huMSCs and the aligned conductive film can act as a potential nerve scaffold.

Electro-optic properties of organic nanotubes.

PubMed

Stoylov, Stoyl P; Stoilova-McPhie, Svetla

2011-08-10

In this review article the theoretical and experimental possibilities of applying EO-methods for estimation of the physico-chemical properties of the organic nanotubes (ONTs) are studied. The ONTs are highly organized nanostructures of strongly elongated, anysometric, and hollow cylinders with a size range of 1 nm to 10,000 nm, e.g. in aqueous solutions they could behave as colloid (disperse) particles. They have high interaction ability due to their extremely large curved, rolled-up external surfaces (bilayers of membrane walls) and unique properties because of their specific electric charge distribution and dynamics that make possible the functionalization of their surfaces. Thus they could template guestsubstances such as membrane proteins and protein complexes on the exterior surfaces and in the membrane. We performed our investigations for the case of ONT aqueous colloid suspension. Following our earlier proposition of the general expression for the electro-optic (EO) effect we derived equations for the evaluation of the electric properties of ONT particles such as mechanism of electric polarization and identification of their most important electric Dipole Moments (DM), permanent (pDM) and induced (iDMs). Further we recommend ways for the calculation of their magnitude and direction. Also we evaluated some geometrical properties such as length of the ONT particles and their polydispersity. The knowledge that we provided about the ONT properties may enable us to elucidate and predict their biological activity. Templating biological active ligands (such as membrane proteins and protein complexes) on the inner and outer surfaces as well as in the surface membrane creates their potential usefulness as carrier and deliverer of biopharmaceuticals in bio-nanodevices. The theoretical equations were compared with the experimental data for ONTs such as (lipid) LNT, Tobacco Mosaic Virus (TMV) and microtubules (MT). Comparison of EO methods with other methods used till now shows that the EO methods are faster, not invasive and do not alter the studied particles. Copyright © 2011 Elsevier B.V. All rights reserved.

Electric field theory based approach to search-direction line definition in image segmentation: application to optimal femur-tibia cartilage segmentation in knee-joint 3-D MR

NASA Astrophysics Data System (ADS)

Yin, Y.; Sonka, M.

2010-03-01

A novel method is presented for definition of search lines in a variety of surface segmentation approaches. The method is inspired by properties of electric field direction lines and is applicable to general-purpose n-D shapebased image segmentation tasks. Its utility is demonstrated in graph construction and optimal segmentation of multiple mutually interacting objects. The properties of the electric field-based graph construction guarantee that inter-object graph connecting lines are non-intersecting and inherently covering the entire object-interaction space. When applied to inter-object cross-surface mapping, our approach generates one-to-one and all-to-all vertex correspondent pairs between the regions of mutual interaction. We demonstrate the benefits of the electric field approach in several examples ranging from relatively simple single-surface segmentation to complex multiobject multi-surface segmentation of femur-tibia cartilage. The performance of our approach is demonstrated in 60 MR images from the Osteoarthritis Initiative (OAI), in which our approach achieved a very good performance as judged by surface positioning errors (average of 0.29 and 0.59 mm for signed and unsigned cartilage positioning errors, respectively).

Surface electrical properties experiment. [for Taurus-Littrow region of the moon on Apollo 17

NASA Technical Reports Server (NTRS)

Simmons, G.

1974-01-01

The Surface Electrical Properties Experiment (SEP) was flown to the moon in December 1972 on Apollo 17 and used to explore a portion of the Taurus-Littrow region. SEP used a relatively new technique, termed radio frequency interferometry (RFI). Electromagnetic waves were radiated from two orthogonal, horizontal electric dipole antennas on the surface of the moon at frequencies of 1, 2, 4, 8, 16, and 32 Mhz. The field strength of the EM waves was measured as a function of distance with a receiver mounted on the Lunar Roving Vehicle and using three orthogonal, electrically small, loops. The interference pattern produced by the waves that travelled above the moon's surface and those that travelled below the surface was recorded on magnetic tape. The tape was returned to earth for analysis and interpretation. Several reprints, preprints, and an initial draft of the first publication of the SEP results are included. These documents provide a rather complete account of the details of the theory of the RFI technique, of the terrestrial tests of the technique, and of the present state of our interpretation of the Apollo 17 data.

Influence of binding material of PZT coating on microresonator's electrical and mechanical properties

NASA Astrophysics Data System (ADS)

Janusas, Giedrius; Guobiene, Asta; Palevicius, Arvydas; Brunius, Alfredas; Cekas, Elingas; Baltrusaitis, Valentinas; Sakalys, Rokas

2017-06-01

Microresonators are fundamental components integrated in hosts of MEMS applications: covering the automotive sector, the telecommunication industry, electronic equipment for surface/material characterization and motion sensing, and etc. The aim of this paper is to investigate the mechanical and electrical properties of PZT film fabricated with three binding materials: polyvinyl butyral (PVB), polymethyl methacrylate (PMMA) and polystyrene (PS) and to evaluate applicability in control of microresonators Q factor. Micro particles of PZT powder were mixed with 20% solution of PVB, PMMA and PS in benzyl alcohol. For investigation of mechanical and electrical properties multilayer cantilevers were made. Obtained PZT and polymer paste was screen printed on copper (thickness 40 μm) using polyester monofilament screen meshes (layer thickness 50 μm) and dried for 30 min at 100°C. Electric dipoles of the PZT particles in composite material were aligned using high voltage generator (5 kV) and a custom-made holder. Electric field was held for 30 min. Surfaces of the applied films were investigated by Atomic Force Microscope NanoWizard(R)3 NanoScience. Dynamic and electrical characteristics of the multilayer were investigated using laser triangular displacement sensor LK-G3000. The measured vibration amplitude and generated electrical potential was collected with USB oscilloscope PicoScope 3424. As the results showed, these cantilevers were able to transform mechanical strain energy into electric potential and, v.v. However, roughness of PZT coatings with PMMA and PS were higher, what could be the reason of the worse quality of the top electrode. However, the main advantage of the created composite piezoelectric material is the possibility to apply it on any uniform or non-uniform vibrating surface and to transform low frequency vibrations into electricity.

Surface plasmon resonance and polarization change properties in centrosymmetric nanoright-triangle dimer arrays

NASA Astrophysics Data System (ADS)

Ma, Qilin; Liu, Guangqiang; Chen, Yiqing; Zhao, Qian; Guo, Jing; Yang, Shaosong; Cai, Weiping

2018-03-01

Dimer nanoparticles in a sandwich structure exhibit a large electric-field intensity enhancement. The dispersion relation between the surface plasmon resonance (SPR) and particle size has not been reported yet, owing to the effects of the particle size, shape, materials, etc. A sandwich structure, which contains a nano-right-triangle dimer array, SiO2 spacer, and Au film, is proposed, with a significant electric-field intensity enhancement and polarization-changing properties. The dependence of the peak positions of the two localized surface plasmon resonance (LSPR) modes as a function of the triangle thicknesses is discussed; different trends are observed for the different LSPR modes. We introduce a concept on the rule for LSPR peak position change, which can contribute to a better understanding of the LSPR modes. In addition, centrosymmetric but not axisymmetric structures, which like in our study exhibit surface plasmon polaritons typically show different responses to a different polarization of the incident light. Here, we showed that our centrosymmetric but not axisymmetric structure can change the linearly polarized light into a circularly or elliptically polarized wave, by surface plasmon-induced polarization properties. Far-field distribution maps are used to study the properties of the surface plasmons-induced circular or elliptic polarization wave. These findings could be employed to better understand the surface plasmon-induced polarization properties showed in previous reports and near-field of surface plasmons. These findings could be employed to better understand the near-field of surface plasmons and polarization properties.

Coated carbon nanotube array electrodes

DOEpatents

Ren, Zhifeng; Wen, Jian; Chen, Jinghua; Huang, Zhongping; Wang, Dezhi

2006-12-12

The present invention provides conductive carbon nanotube (CNT) electrode materials comprising aligned CNT substrates coated with an electrically conducting polymer, and the fabrication of electrodes for use in high performance electrical energy storage devices. In particular, the present invention provides conductive CNTs electrode material whose electrical properties render them especially suitable for use in high efficiency rechargeable batteries. The present invention also provides methods for obtaining surface modified conductive CNT electrode materials comprising an array of individual linear, aligned CNTs having a uniform surface coating of an electrically conductive polymer such as polypyrrole, and their use in electrical energy storage devices.

Coated carbon nanotube array electrodes

DOEpatents

Ren, Zhifeng [Newton, MA; Wen, Jian [Newton, MA; Chen, Jinghua [Chestnut Hill, MA; Huang, Zhongping [Belmont, MA; Wang, Dezhi [Wellesley, MA

2008-10-28

The present invention provides conductive carbon nanotube (CNT) electrode materials comprising aligned CNT substrates coated with an electrically conducting polymer, and the fabrication of electrodes for use in high performance electrical energy storage devices. In particular, the present invention provides conductive CNTs electrode material whose electrical properties render them especially suitable for use in high efficiency rechargeable batteries. The present invention also provides methods for obtaining surface modified conductive CNT electrode materials comprising an array of individual linear, aligned CNTs having a uniform surface coating of an electrically conductive polymer such as polypyrrole, and their use in electrical energy storage devices.

Monitoring electrical properties for improving the lithological and hydrological characterization of landslides

NASA Astrophysics Data System (ADS)

Malet, J. P.; Gance, J.; Lajaunie, M.; Gallistl, J.; Denchik, N.; Flores Orozco, A.; Ottowitz, D.; Supper, R.; Sailhac, P.; Gautier, S.; Schmutz, M.

2017-12-01

Imaging water flows in landslides is of critical importance as the distribution of pore-fluid pressures controls the dynamics (acceleration, deceleration) of the material. Detecting and imaging water is a difficult task, not only because of the complex topography and the small dimensions of the geological structures, but also because the landslide material consists of unsaturated porous and heterogeneous fractured media, leading to multi-scale water-flow properties. Further, these properties can change in time, in relation to temperature, rainfall and biological forcings. Electrical properties are relevant proxies of the sub-surface hydrological properties. In order to image water in landslide bodies, we propose to combine multi-frequency electrical and electromagnetic measurements using campaigns or permanent instruments, and surface/boreole investigations, installed on several unstable slopes in France. To evaluate the information gained from electrical properties for different geological conditions, we discuss electrical and electro-magnetic imaging results for data collected at four different landslides located in France (Super-Sauze and La Valette in the South East Alps, Lodève lin the southern border of the Massif Central Massif, and Séchilienne in the North French Alps). Time-lapse electrical DC resistivity observations, complex electrical conductivity (conduction and polarization/chargeability) measured by IP imaging methods, and controlled-source electromagnetic (CS-AMT) methods are discussed. Imaging results demonstrate an improved lithological characterization of the landslide structures (delineation of the sliding planes, identification of the fractures, discrimination of clay lenses with enhanced resolution); further, water infiltration within the soil matrix and/or the fractures is discriminated allowing better modelling of the hydrological regime of the landslides at the slope scale. This research is conducted in the frame of the project HYDROSLIDE - Hydrogeophysical Monitoring of Clay-Rich Landslides funded by the Austrian Science Fund (FWF) and the French Research Agency (ANR).

Numerical modelling of the Luna-Glob lander electric charging on the lunar surface with SPIS-DUST

NASA Astrophysics Data System (ADS)

Kuznetsov, I. A.; Hess, S. L. G.; Zakharov, A. V.; Cipriani, F.; Seran, E.; Popel, S. I.; Lisin, E. A.; Petrov, O. F.; Dolnikov, G. G.; Lyash, A. N.; Kopnin, S. I.

2018-07-01

One of the complicating factors of the future robotic and human lunar landing missions is the influence of the dust. The upper insulating regolith layer is electrically charged by the solar ultraviolet radiation and the flow of solar wind particles. Resulted electric charge and thus surface potential depend on the lunar local time, latitude and the electrical properties of the regolith. Understanding of mechanisms of the dust electric charging, dust levitation and electric charging of a lander on the lunar surface is essential for interpretation of measurements of the instruments of the Luna-Glob lander payload, e.g. the Dust Impact sensor and the Langmuir Probe. One of the tools, which allows simulating the electric charging of the regolith and lander and also the transport and deposition of the dust particles on the lander surface, is the recently developed Spacecraft Plasma Interaction Software toolkit, called the SPIS-DUST. This paper describes the SPIS-DUST numerical simulation of the interaction between the solar wind plasma, ultraviolet radiation, regolith and a lander and presents as result qualitative and quantitative data of charging the surfaces, plasma sheath and its influence on spacecraft sensors, dust dynamics. The model takes into account the geometry of the Luna-Glob lander, the electric properties of materials used on the lander surface, as well as Luna-Glob landing place. Initial conditions are chosen using current theoretical models of formation of dusty plasma exosphere and levitating charged dust particles. Simulation for the three cases (local lunar noon, evening and sunset) showed us the surrounding plasma sheath around the spacecraft which gives a significant potential bias in the spacecraft vicinity. This bias influences on the spacecraft sensors but with SPIS software we can estimate the potential of uninfluenced plasma with the data from the plasma sensors (Langmuir probes). SPIS-DUST modification allows us to get the dust dynamics properties. For our three cases we've obtained the dust densities around the spacecraft and near the surface of the Moon. As another practical result of this work we can count a suggestion of improving of dusty plasma instrument for the next mission: it must be valuable to relocate the plasma sensors to a distant boom at some distance from the spacecraft.

Electrical properties of surface and interface layers of the N- and In-polar undoped and Mg-doped InN layers grown by PA MBE

NASA Astrophysics Data System (ADS)

Komissarova, T. A.; Kampert, E.; Law, J.; Jmerik, V. N.; Paturi, P.; Wang, X.; Yoshikawa, A.; Ivanov, S. V.

2018-01-01

Electrical properties of N-polar undoped and Mg-doped InN layers and In-polar undoped InN layers grown by plasma-assisted molecular beam epitaxy (PA MBE) were studied. Transport parameters of the surface and interface layers were determined from the measurements of the Hall coefficient and resistivity as well as the Shubnikov-de Haas oscillations at magnetic fields up to 60 T. Contributions of the 2D surface, 3D near-interface, and 2D interface layers to the total conductivity of the InN films were defined and discussed to be dependent on InN surface polarity, Mg doping, and PA MBE growth conditions.

Effect of surface roughness of trench sidewalls on electrical properties in 4H-SiC trench MOSFETs

NASA Astrophysics Data System (ADS)

Kutsuki, Katsuhiro; Murakami, Yuki; Watanabe, Yukihiko; Onishi, Toru; Yamamoto, Kensaku; Fujiwara, Hirokazu; Ito, Takahiro

2018-04-01

The effects of the surface roughness of trench sidewalls on electrical properties have been investigated in 4H-SiC trench MOSFETs. The surface roughness of trench sidewalls was well controlled and evaluated by atomic force microscopy. The effective channel mobility at each measurement temperature was analyzed on the basis of the mobility model including optical phonon scattering. The results revealed that surface roughness scattering had a small contribution to channel mobility, and at the arithmetic average roughness in the range of 0.4-1.4 nm, there was no correlation between the experimental surface roughness and the surface roughness scattering mobility. On the other hand, the characteristics of the gate leakage current and constant current stress time-dependent dielectric breakdown tests demonstrated that surface morphology had great impact on the long-term reliability of gate oxides.

Wave tilt sounding of multilayered structures. [for probing of stratified planetary surface electrical properties and thickness

NASA Technical Reports Server (NTRS)

Warne, L.; Jaggard, D. L.; Elachi, C.

1979-01-01

The relationship between the wave tilt and the electrical parameters of a multilayered structure is investigated. Particular emphasis is placed on the inverse problem associated with the sounding planetary surfaces. An inversion technique, based on multifrequency wave tilt, is proposed and demonstrated with several computer models. It is determined that there is close agreement between the electrical parameters used in the models and those in the inversion values.

Effects of Different Surfactants on Structural, Tribological and Electrical Properties of Pulsed Electro-Codeposited Cu-ZrO2 Composite Coatings

NASA Astrophysics Data System (ADS)

Maharana, H. S.; Basu, A.

2018-03-01

Cu-ZrO2 composite coating was synthesized by pulse electrodeposition from an acidic sulfate electrolyte dispersed with nano-sized ZrO2 particles. Effects of different surfactants in different amounts on the codeposition and distribution of ZrO2 particles in the copper matrix, surface-mechanical (hardness and wear) and electrical (conductivity) properties of developed composite coatings have been thoroughly investigated. Sodium dodecyl sulfate (SDS), poly acrylic acid (PAA) and glucose have been added in the electrolyte in different concentrations as anionic, polymeric and nonionic surfactants. Obtained experimental results confirmed that addition of SDS up to 1 g/L improves the amount of codeposited ZrO2 particles in the copper matrix and surface-mechanical properties of the nanocomposite coatings. But, in case of PAA- and glucose-assisted coatings, highest amount of ZrO2 codeposition was observed in 0.5 g/L PAA and 20 g/L glucose-assisted coatings, which in turn affected the mechanical properties. Surface-mechanical properties were found to be affected by coating matrix morphology and crystallographic orientation along with embedded ZrO2 particle content. Electrical conductivity of all the deposits not only depends upon the codeposition of ZrO2 particles in the matrix but also on the microstructure and crystallographic orientation.

Electrical Properties of the V-Defects of Epitaxial HgCdTe

NASA Astrophysics Data System (ADS)

Novikov, V. A.; Grigoryev, D. V.; Bezrodnyy, D. A.; Voitsekhovskii, A. V.; Dvoretsky, S. A.; Mikhailov, N. N.

2017-07-01

The manufacturing process of wide-band-gap matrix photodetector devices and miniaturization of their individual pixels gave rise to increased demands on the material quality and research methods. In the present paper we propose using the methods of atomic-force microscopy to study the local distribution of electrical properties of the V-defects that form in epitaxial films of HgCdTe during their growth process via molecular beam epitaxy. We demonstrate that a complex approach to studying the electrical properties of a predefined region of a V-defect allows one to obtain more detailed information on its properties. Using scanning spreading resistance microscopy, we show that, for a V-defect when the applied bias is increased, the surface area that participates in the process of charge carrier transfer also increases almost linearly. The presence of a potential barrier on the periphery of individual crystal grains that form the V-defect interferes with the flow of current and also affects the distribution of surface potential and capacitive contrast.

Method for making defect-free zone by laser-annealing of doped silicon

DOEpatents

Narayan, Jagdish; White, Clark W.; Young, Rosa T.

1980-01-01

This invention is a method for improving the electrical properties of silicon semiconductor material. The method comprises irradiating a selected surface layer of the semiconductor material with high-power laser pulses characterized by a special combination of wavelength, energy level, and duration. The combination effects melting of the layer without degrading electrical properties, such as minority-carrier diffusion length. The method is applicable to improving the electrical properties of n- and p-type silicon which is to be doped to form an electrical junction therein. Another important application of the method is the virtually complete removal of doping-induced defects from ion-implanted or diffusion-doped silicon substrates.

Modeling of electrical impedance tomography to detect breast cancer by finite volume methods

NASA Astrophysics Data System (ADS)

Ain, K.; Wibowo, R. A.; Soelistiono, S.

2017-05-01

The properties of the electrical impedance of tissue are an interesting study, because changes of the electrical impedance of organs are related to physiological and pathological. Both physiological and pathological properties are strongly associated with disease information. Several experiments shown that the breast cancer has a lower impedance than the normal breast tissue. Thus, the imaging based on impedance can be used as an alternative equipment to detect the breast cancer. This research carries out by modelling of Electrical Impedance Tomography to detect the breast cancer by finite volume methods. The research includes development of a mathematical model of the electric potential field by 2D Finite Volume Method, solving the forward problem and inverse problem by linear reconstruction method. The scanning is done by 16 channel electrode with neighbors method to collect data. The scanning is performed at a frequency of 10 kHz and 100 kHz with three objects numeric includes an anomaly at the surface, an anomaly at the depth and an anomaly at the surface and at depth. The simulation has been successfully to reconstruct image of functional anomalies of the breast cancer at the surface position, the depth position or a combination of surface and the depth.

Realization of MEMS-IC Vertical Integration Utilizing Smart Bumpless Bonding

NASA Astrophysics Data System (ADS)

Shiozaki, Masayoshi; Moriguchi, Makoto; Sasaki, Sho; Oba, Masatoshi

This paper reports fundamental technologies, properties, and new experimental results of SBB (Smart Bumpless Bonding) to realize MEMS-IC vertical integration. Although conventional bonding technologies have had difficulties integrating MEMS and its processing circuit because of their rough bonding surfaces, fragile structures, and thermal restriction, SBB technology realized the vertical integration without thermal treatment, any adhesive materials including bumps, and chemical mechanical polishing. The SBB technology bonds sealing parts for vacuum sealing and electrodes for electrical connection simultaneously as published in previous experimental study. The plasma CVD SiO2 is utilized to realize vacuum sealing as sealing material. And Au projection studs are formed on each electrode and connected electrically between two wafers by compressive plastic deformation and surface activation. In this paper, new experimental results including vacuum sealing properties, electrical improvement, IC bonding results on the described fundamental concept and properties are reported.

Anodizing of High Electrically Stressed Components

DOE Office of Scientific and Technical Information (OSTI.GOV)

Flores, P.; Henderson, D. J.; Good, D. E.

2013-06-01

Anodizing creates an aluminum oxide coating that penetrates into the surface as well as builds above the surface of aluminum creating a very hard ceramic-type coating with good dielectric properties. Over time and use, the electrical carrying components (or spools in this case) experience electrical breakdown, yielding undesirable x-ray dosages or failure. The spool is located in the high vacuum region of a rod pinch diode section of an x-ray producing machine. Machine operators have recorded decreases in x-ray dosages over numerous shots using the reusable spool component, and re-anodizing the interior surface of the spool does not provide themore » expected improvement. A machine operation subject matter expert coated the anodized surface with diffusion pump oil to eliminate electrical breakdown as a temporary fix. It is known that an anodized surface is very porous, and it is because of this porosity that the surface may trap air that becomes a catalyst for electrical breakdown. In this paper we present a solution of mitigating electrical breakdown by oiling. We will also present results of surface anodizing improvements achieved by surface finish preparation and surface sealing. We conclude that oiling the anodized surface and using anodized hot dip sealing processes will have similar results.« less

Investigation of dielectric substrates on electrical and optical performance of wafer-scale graphene using non-contact methods

NASA Astrophysics Data System (ADS)

Wang, Dong; Ning, Jing; Zhang, Jincheng; Guo, Lixin; Hao, Yue

2017-10-01

Here we systemically discussed the influence of dielectric substrates on the surface morphology, electrical and optical performance of transferred graphene. The electrical properties were investigated using a microwave-probing technique without metal-graphene contact. We found that a complex mechanism governed the influence of the surface properties of the dielectric substrates, such as morphology, hydrophilicity, crystallinity, and polarization, on the performance of the graphene. We also found that graphene on r-Al2O3 was more effective for graphene-based devices with a high carrier mobility of ˜5000 cm2 V-1 s-1. This provides a new method to choose the most suitable substrate for fabricating graphene-based devices.

Direct Carbon Fuel Cells: Converting Waste to Electricity

DTIC Science & Technology

2007-09-01

Contained energy DCFC single cell ....................................................................................20 10 Direct Carbon...to convert the chemical energy in solid carbon particles directly to electricity in single cell systems with (an experimentally verified...at the polarized condition. The reactivity of carbon is affected by many properties, such as crystallization , electrical conductivity, surface area

Low damage electrical modification of 4H-SiC via ultrafast laser irradiation

NASA Astrophysics Data System (ADS)

Ahn, Minhyung; Cahyadi, Rico; Wendorf, Joseph; Bowen, Willie; Torralva, Ben; Yalisove, Steven; Phillips, Jamie

2018-04-01

The electrical properties of 4H-SiC under ultrafast laser irradiation in the low fluence regime (<0.50 J/cm2) are presented. The appearance of high spatial frequency laser induced periodic surface structures is observed at a fluence near 0.25 J/cm2 and above, with variability in environments like in air, nitrogen, and a vacuum. In addition to the formation of periodic surface structures, ultrafast laser irradiation results in possible surface oxidation and amorphization of the material. Lateral conductance exhibits orders of magnitude increase, which is attributed to either surface conduction or modification of electrical contact properties, depending on the initial material conductivity. Schottky barrier formation on ultrafast laser irradiated 4H-SiC shows an increase in the barrier height, an increase in the ideality factor, and sub-bandgap photovoltaic responses, suggesting the formation of photo-active point defects. The results suggest that the ultrafast laser irradiation technique provides a means of engineering spatially localized structural and electronic modification of wide bandgap materials such as 4H-SiC with relatively low surface damage via low temperature processing.

Spatially resolved resistance of NiO nanostructures under humid environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobs, Christopher B; Ievlev, Anton; Collins, Liam F

2016-01-01

The spatially resolved electrical response of polycrystalline NiO films composed of 40 nm crystallites was investigated under different relative humidity levels (RH). The topological and electrical properties (surface potential and resistance) were characterized with sub 25nm resolution using Kelvin probe force microscopy (KPFM) and conductive scanning probe microscopy under argon atmosphere at 0%, 50%, and 80% relative humidity. The dimensionality of surface features obtained through autocorrelation analysis of topological maps increased linearly with increased relative humidity, as water was adsorbed onto the film surface. Surface potential decreased from about 280mV to about 100 mV and resistance decreased from about 5more » G to about 3 G , in a nonlinear fashion when relative humidity was increased from 0% to 80%. Spatially resolved surface potential and resistance of the NiO films was found to be heterogeneous throughout the film, with distinct domains that grew in size from about 60 nm to 175 nm at 0% and 80% RH levels, respectively. The heterogeneous character of the topological, surface potential, and resistance properties of the polycrystalline NiO film observed under dry conditions decreased with increased relative humidity, yielding nearly homogeneous surface properties at 80% RH, suggesting that the nanoscale potential and resistance properties converge with the mesoscale properties as water is adsorbed onto the NiO film.« less

Development of micro-four-point probe in a scanning tunneling microscope for in situ electrical transport measurement.

PubMed

Ge, Jian-Feng; Liu, Zhi-Long; Gao, Chun-Lei; Qian, Dong; Liu, Canhua; Jia, Jin-Feng

2015-05-01

Electrons at surface may behave differently from those in bulk of a material. Multi-functional tools are essential in comprehensive studies on a crystal surface. Here, we developed an in situ microscopic four-point probe (4PP) transport measurement system on the basis of a scanning tunneling microscope (STM). In particular, convenient replacement between STM tips and micro-4PPs enables systematic investigations of surface morphology, electronic structure, and electrical transport property of a same sample surface. Performances of the instrument are demonstrated with high-quality STM images, tunneling spectra, and low-noise electrical I-V characteristic curves of a single-layer FeSe film grown on a conductive SrTiO3 surface.

Near surface geophysical techniques on subsoil contamination: laboratory experiments

NASA Astrophysics Data System (ADS)

Capozzoli, Luigi; Giampaolo, Valeria; Rizzo, Enzo

2016-04-01

Hydrocarbons contamination of soil and groundwater has become a serious environmental problem, because of the increasing number of accidental spills caused by human activities. The starting point of any studies is the reconstruction of the conceptual site model. To make valid predictions about the flow pathways following by hydrocarbons compound is necessary to make a correct reconstruction of their characteristics and the environment in which they move. Near-surface geophysical methods, based on the study of electrical and electromagnetic properties, are proved to be very useful in mapping spatial distribution of the organic contaminants in the subsurface. It is well known, in fact, that electrical properties of the porous media are significantly influenced by hydrocarbons because, when contaminants enter the rock matrix, surface reaction occur between the contaminant and the soil grain surface. The main aim of this work is to investigate the capability of near-surface geophysical methods in mapping and monitoring spatial distribution of contaminants in a controlled setting. A laboratory experiment has been performed at the Hydrogeosite Laboratory of CNR-IMAA (Marsico Nuovo, PZ) where a box-sand has been contaminated by diesel. The used contaminant is a LNAPL, added to the sand through a drilled pipe. Contaminant behaviour and its migration paths have been monitored for one year by Electrical Resistivity measurements. In details, a Cross Borehole Electrical Resistivity Tomography techniques were used to characterize the contamination dynamics after a controlled hydrocarbon spillage occurring in the vadose zone. The approach with cross-borehole resistivity imaging provide a great advantage compared to more conventional surface electrical resistivity tomography, due to the high resolution at high depth (obviously depending on the depth of the well instrumented for the acquisition). This method has been shown to provide good information on the distribution of electrical properties of the subsoil at high depths and, in some cases, a detailed assessment of dynamic processes in the subsurface environment (Binley et al., 2002). Our study confirms the link between hydrocarbons contamination and geoelectrical signal and the capability of cross-hole electrical resistivity tomographies to realize a non-invasive characterization of LNAPL contamination of the media. Although, the electrical behaviour is much more complex and the relation with the contaminants depends also by time of investigation.

A corrugated perfect magnetic conductor surface supporting spoof surface magnon polaritons.

PubMed

Liu, Liang-liang; Li, Zhuo; Gu, Chang-qing; Ning, Ping-ping; Xu, Bing-zheng; Niu, Zhen-yi; Zhao, Yong-jiu

2014-05-05

In this paper, we demonstrate that spoof surface magnon polaritons (SSMPs) can propagate along a corrugated perfect magnetic conductor (PMC) surface. From duality theorem, the existence of surface electromagnetic modes on corrugated PMC surfaces are manifest to be transverse electric (TE) mode compared with the transverse magnetic (TM) mode of spoof surface plasmon plaritons (SSPPs) excited on corrugated perfect electric conductor surfaces. Theoretical deduction through modal expansion method and simulation results clearly verify that SSMPs share the same dispersion relationship with the SSPPs. It is worth noting that this metamaterial will have more similar properties and potential applications as the SSPPs in large number of areas.

Effect of geometric configuration on the electrocaloric properties of nanoscale ferroelectric materials

NASA Astrophysics Data System (ADS)

Hou, Xu; Li, Huiyu; Shimada, Takahiro; Kitamura, Takayuki; Wang, Jie

2018-03-01

The electrocaloric properties of ferroelectrics are highly dependent on the domain structure in the materials. For nanoscale ferroelectric materials, the domain structure is greatly influenced by the geometric configuration of the system. Using a real-space phase field model based on the Ginzburg-Landau theory, we investigate the effect of geometric configurations on the electrocaloric properties of nanoscale ferroelectric materials. The ferroelectric hysteresis loops under different temperatures are simulated for the ferroelectric nano-metamaterials with square, honeycomb, and triangular Archimedean geometric configurations. The adiabatic temperature changes (ATCs) for three ferroelectric nano-metamaterials under different electric fields are calculated from the Maxwell relationship based on the hysteresis loops. It is found that the honeycomb specimen exhibits the largest ATC of Δ T = 4.3 °C under a field of 391.8 kV/cm among three geometric configurations, whereas the square specimen has the smallest ATC of Δ T = 2.7 °C under the same electric field. The different electrocaloric properties for three geometric configurations stem from the different domain structures. There are more free surfaces perpendicular to the electric field in the square specimen than the other two specimens, which restrict more polarizations perpendicular to the electric field, resulting in a small ATC. Due to the absence of free surfaces perpendicular to the electric field in the honeycomb specimen, the change of polarization with temperature in the direction of the electric field is more easy and thus leads to a large ATC. The present work suggests a novel approach to obtain the tunable electrocaloric properties in nanoscale ferroelectric materials by designing their geometric configurations.

Tuning oxidation level, electrical conductance and band gap structure on graphene sheets by cyclic atomic layer reduction technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gu, Si-Yong; Hsieh, Chien-Te; Lin, Tzu-Wei

The present work develops an atomic layer reduction (ALR) method to accurately tune oxidation level, electrical conductance, band-gap structure, and photoluminescence (PL) response of graphene oxide (GO) sheets. The ALR route is carried out at 200 °C within ALR cycle number of 10–100. The ALR treatment is capable of striping surface functionalities (e.g., hydroxyl, carbonyl, and carboxylic groups), producing thermally-reduced GO sheets. The ALR cycle number serves as a controlling factor in adjusting the crystalline, surface chemistry, electrical, optical properties of GO sheets. With increasing the ALR cycle number, ALR-GO sheets display a high crystallinity, a low oxidation level, anmore » improved electrical conductivity, a narrow band gap, and a tunable PL response. Finally, on the basis of the results, the ALR technique offers a great potential for accurately tune electrical and optical properties of carbon materials through the cyclic removal of oxygen functionalities, without any complicated thermal and chemical desorption processes.« less

Tuning oxidation level, electrical conductance and band gap structure on graphene sheets by cyclic atomic layer reduction technique

DOE PAGES

Gu, Si-Yong; Hsieh, Chien-Te; Lin, Tzu-Wei; ...

2018-05-12

The present work develops an atomic layer reduction (ALR) method to accurately tune oxidation level, electrical conductance, band-gap structure, and photoluminescence (PL) response of graphene oxide (GO) sheets. The ALR route is carried out at 200 °C within ALR cycle number of 10–100. The ALR treatment is capable of striping surface functionalities (e.g., hydroxyl, carbonyl, and carboxylic groups), producing thermally-reduced GO sheets. The ALR cycle number serves as a controlling factor in adjusting the crystalline, surface chemistry, electrical, optical properties of GO sheets. With increasing the ALR cycle number, ALR-GO sheets display a high crystallinity, a low oxidation level, anmore » improved electrical conductivity, a narrow band gap, and a tunable PL response. Finally, on the basis of the results, the ALR technique offers a great potential for accurately tune electrical and optical properties of carbon materials through the cyclic removal of oxygen functionalities, without any complicated thermal and chemical desorption processes.« less

Scalable fabrication of a hybrid field-effect and acousto-electric device by direct growth of monolayer MoS2/LiNbO3

PubMed Central

Preciado, Edwin; Schülein, Florian J.R.; Nguyen, Ariana E.; Barroso, David; Isarraraz, Miguel; von Son, Gretel; Lu, I-Hsi; Michailow, Wladislaw; Möller, Benjamin; Klee, Velveth; Mann, John; Wixforth, Achim; Bartels, Ludwig; Krenner, Hubert J.

2015-01-01

Lithium niobate is the archetypical ferroelectric material and the substrate of choice for numerous applications including surface acoustic wave radio frequencies devices and integrated optics. It offers a unique combination of substantial piezoelectric and birefringent properties, yet its lack of optical activity and semiconducting transport hamper application in optoelectronics. Here we fabricate and characterize a hybrid MoS2/LiNbO3 acousto-electric device via a scalable route that uses millimetre-scale direct chemical vapour deposition of MoS2 followed by lithographic definition of a field-effect transistor structure on top. The prototypical device exhibits electrical characteristics competitive with MoS2 devices on silicon. Surface acoustic waves excited on the substrate can manipulate and probe the electrical transport in the monolayer device in a contact-free manner. We realize both a sound-driven battery and an acoustic photodetector. Our findings open directions to non-invasive investigation of electrical properties of monolayer films. PMID:26493867

Electrical properties of double layer dielectric structures for space technology

NASA Astrophysics Data System (ADS)

Lian, Anqing

1993-04-01

Polymeric films such as polyimide (PI) and polyethylene terephthalate (PET) are used in space technology as thermal blankets. Thin SiO2 and SiN coatings plasma deposited onto PI and PET surfaces were proposed to protect the blanket materials against the space environment. The electrical properties of this kind of dual layer dielectric structure were investigated to understand the mechanisms for suppressing charge accumulation and flashover. Bulk and surface electrical conductivities of thin single-layer PI and PET samples and of the dual layer SiO2 and SiN combinations with PI and PET were measured in a range of applied electrical fields. The capacitance voltage (CV) technique was used for analyzing charge transport and distribution in the structures. The electric current in the bulk of the SiO2/PI and SiN/PI samples was found to depend on the polarity of the electric field. Other samples did not exhibit any such polarity effect. The polarity dependence is attributed to charge trapping at the PI/plasma deposit interface. The CV characteristics of the Al-PI-SiO2-Si structure confirm that charges which can modify the local electric field can be trapped near the interface. A model is proposed to interpret the properties of the currents in dual layer structures. This model can semi-quantitatively explain all the observed results.

NASA charging analyzer program: A computer tool that can evaluate electrostatic contamination

NASA Technical Reports Server (NTRS)

Stevens, N. J.; Roche, J. C.; Mandell, M. J.

1978-01-01

A computer code, the NASA Charging Analyzer Program (NASCAP), was developed to study the surface charging of bodies subjected to geomagnetic substorm conditions. This program will treat the material properties of a surface in a self-consistent manner and calculate the electric fields in space due to the surface charge. Trajectories of charged particles in this electric field can be computed to determine if these particles enhance surface contamination. A preliminary model of the Spacecraft Charging At The High Altitudes (SCATHA) satellite was developed in the NASCAP code and subjected to a geomagnetic substorm environment to investigate the possibility of electrostatic contamination. The results indicate that differential voltages will exist between the spacecraft ground surfaces and the insulator surfaces. The electric fields from this differential charging can enhance the contamination of spacecraft surfaces.

Electrical properties of dislocations in III-Nitrides

NASA Astrophysics Data System (ADS)

Cavalcoli, D.; Minj, A.; Pandey, S.; Cavallini, A.

2014-02-01

Research on GaN, AlN, InN (III-N) and their alloys is achieving new heights due their high potential applications in photonics and electronics. III-N semiconductors are mostly grown epitaxially on sapphire, and due to the large lattice mismatch and the differences in the thermal expansion coefficients, the structures usually contain many threading dislocations (TDs). While their structural properties have been widely investigated, their electrical characteristics and their role in the transport properties of the devices are still debated. In the present contribution we will show conductive AFM studies of TDs in GaN and Al/In GaN ternary alloys to evidence the role of strain, different surface polarity and composition on their electrical properties. Local I-V curves measured at TDs allowed us to clarify their role in the macroscopic electrical properties (leakage current, mobilities) of III-N based devices. Samples obtained by different growers (AIXTRON, III-V Lab) were studied. The comparison between the results obtained in the different alloys allowed us to understand the role of In and Al on the TDs electrical properties.

Influence of microstructure and surface topography on the electrical conductivity of Cu and Ag thin films obtained by magnetron sputtering

NASA Astrophysics Data System (ADS)

Polonyankin, D. A.; Blesman, A. I.; Postnikov, D. V.

2017-05-01

Conductive thin films formation by copper and silver magnetron sputtering is one of high technological areas for industrial production of solar energy converters, energy-saving coatings, flat panel displays and touch control panels because of their high electrical and optical properties. Surface roughness and porosity, average grain size, internal stresses, orientation and crystal lattice type, the crystallinity degree are the main physical properties of metal films affecting their electrical resistivity and conductivity. Depending on the film thickness, the dominant conduction mechanism can affect bulk conductivity due to the flow of electron gas, and grain boundary conductivity. The present investigation assesses the effect of microstructure and surface topography on the electrical conductivity of magnetron sputtered Cu and Ag thin films using X-ray diffraction analysis, scanning electron and laser interference microscopy. The highest specific conductivity (78.3 MS m-1 and 84.2 MS m-1, respectively, for copper and silver films at the thickness of 350 nm) were obtained with the minimum values of roughness and grain size as well as a high degree of lattice structuredness.

Electrical and fluid transport in consolidated sphere packs

NASA Astrophysics Data System (ADS)

Zhan, Xin; Schwartz, Lawrence M.; Toksöz, M. Nafi

2015-05-01

We calculate geometrical and transport properties (electrical conductivity, permeability, specific surface area, and surface conductivity) of a family of model granular porous media from an image based representation of its microstructure. The models are based on the packing described by Finney and cover a wide range of porosities. Finite difference methods are applied to solve for electrical conductivity and hydraulic permeability. Two image processing methods are used to identify the pore-grain interface and to test correlations linking permeability to electrical conductivity. A three phase conductivity model is developed to compute surface conductivity associated with the grain-pore interface. Our results compare well against empirical models over the entire porosity range studied. We conclude by examining the influence of image resolution on our calculations.

Trade-offs of the opto-electrical properties of a-Si:H solar cells based on MOCVD BZO films.

PubMed

Chen, Ze; Zhang, Xiao-dan; Liang, Jun-hui; Fang, Jia; Liang, Xue-jiao; Sun, Jian; Zhang, De-kun; Chen, Xin-liang; Huang, Qian; Zhao, Ying

2015-01-07

Boron-doped zinc oxide (BZO) films, deposited by metal-organic chemical vapor deposition (MOCVD), have been widely used as front electrodes in thin-film solar cells due to their native pyramidal surface structure, which results in efficient light trapping. This light trapping effect can enhance the short-circuit current density (Jsc) of solar cells. However, nanocracks or voids in the silicon active layer may form when the surface morphology of the BZO is too sharp; this usually leads to degraded electrical properties of the cells, such as open-circuit voltage (Voc) and the fill factor (FF), which in turn decreases efficiency (Eff) [Bailat et al., Photovoltaic Energy Conversion, Conference Record of the 2006 IEEE 4th World Conference on. IEEE, 2006, vol. 2, pp. 1533-1536]. In this paper, an etching and coating method was proposed to modify the sharp "pyramids" on the surface of the BZO films. As a result, an evident enhancement was achieved for these modified, BZO-based cells' Voc, FF, and Eff, although the Jsc exhibited a small decrease. In order to increase the Jsc and maintain the improved electrical properties (Voc, FF) of the cell, a thin BZO coating, deposited by MOCVD, was introduced to coat the sputtering-treated BZO film. Finally, we optimized the trade-off among the Voc, FF, and Jsc, that is, we identified a regime with an increase of the Jsc as well as a further improvement of the other electrical properties.

A Technique for Estimating the Surface Conductivity of Single Molecules

NASA Astrophysics Data System (ADS)

Bau, Haim; Arsenault, Mark; Zhao, Hui; Purohit, Prashant; Goldman, Yale

2007-11-01

When an AC electric field at 2MHz was applied across a small gap between two metal electrodes elevated above a surface, rhodamine-phalloidin-labeled actin filaments were attracted to the gap and became suspended between the two electrodes. The variance of each filament's horizontal, lateral displacement was measured as a function of electric field intensity and position along the filament. The variance significantly decreased as the electric field intensity increased. Hypothesizing that the electric field induces electroosmotic flow around the filament that, in turn, induces drag on the filament, which appears as effective tension, we estimated the tension using a linear, Brownian dynamic model. Based on the tension, we estimated the filament's surface conductivity. Our experimental method provides a novel means for trapping and manipulating biological filaments and for probing the surface conductance and mechanical properties of single polymers.

Global Military Operating Environments (GMOE) Phase I: Linking Natural Environments, International Security, and Military Operations

DTIC Science & Technology

2013-01-30

example from the Negev Desert, Israel, Journal of Geophysical Research, (05 2009): 1. doi: 01/14/2013 5.00 Michael Young, Eric McDonald, Jianting Zhu... radiation (incoming – reflected) x Solar Radiation Eppley Incoming solar radiation x Surface temperature IR Apogee Continuous surface...and electrical properties (dielectric permittivity and electrical conductivity). Additional measurements of solar radiation (four components), air

Tube Failure Mechanisms.

DTIC Science & Technology

studies will be made: ( a ) An investigation of the factors influencing electrical breakdown in a vacuum and across the surface of a dielectric. (b) An...The purpose of this program is to investigate the nature and the principal causes of failures in microwave tubes. In this context, the following...investigation of the various electrical and surface properties of materials commonly used in microwave tubes, i.e., OFHC copper, alumina ceramic, tungsten

A novel material screening platform for nanoporous gold-based neural electrodes

NASA Astrophysics Data System (ADS)

Chapman, Christopher Abbott Reece

Neural-electrical interfaces have emerged in the past decades as a promising modality to facilitate the understanding of the electropathophysiology of neurological disorders as well as the normal functioning of the central nervous system, and enable the treatment of neurological defects through electrical stimulation or electrically-controlled drug delivery. However, chronically implanted electrodes face a myriad of design challenges, including their coupling to neural tissue (biocompatibility), small form factor requirement, and their electrical properties (maintaining a low electrical impedance). Planar electrode materials such as planar platinum and gold experience a large increase in electrical impedance when electrode dimensions are reduced to increase spatial resolution of neural recordings. A decrease in electrode surface area reduces the total capacitance of the electrode double layer resulting in an increase in electrode impedance. This high impedance can reduce the signal amplitude and increase the thermal noise, resulting in degradation of signal-to-noise ratio. Conventionally, this increase in electrical impedance at small electrode dimensions has been mitigated by coatings with rough morphologies such as platinum black, conducting polymers, and titanium nitride. Porous surfaces have high effective surface area enabling low impedance at small electrode dimensions. However, achieving long-term stability of cellular coupling to the electrode surface has remained difficult. Designing electrodes that can physically couple with neurons successfully and maintain low impedance at small electrode dimensions necessitates consideration of novel electrode coatings, such as carbon nanotubes and gold nanopillars. Another promising material, and focus of this proposal, is thin film nanoporous gold (np-Au). Nanoporous gold is a promising material for addressing these limitations because of its inherently large effective surface area allows for lower impedances at small form factors, and its modifiable surface morphology can be used to control cell-electrode coupling. Additionally, thin film nanoporous gold is fabricated by traditional microfabrication methods, and thus can be directly adopted by the current state-of-the-art neural electrode fabrication processes. All these properties make thin film nanoporous gold a promising candidate for use in neural electrode surfaces. This dissertation seeks to characterize both the morphological and the electrical response of neural cells to thin film nanoporous gold morphologies using an in vitro electrode morphology screening platform. The specific aims for this proposal are to: (i) develop a electrode morphology library that displays varying topographies to study structure-property relationships of thin film nanoporous gold and cellular response, (ii) characterize neural cell response to identified nanoporous gold topographies that reduce adverse tissue response in vitro, and (iii) develop an electrophysiology platform to characterize neural coupling to each identified nanoporous gold topography.

Mapping nanometric electronic property changes induced by an aryl diazonium sub-monolayer on HOPG.

PubMed

González, M C R; Carro, P; Vázquez, L; Creus, A H

2016-10-26

The morphology as well as the electric and electronic properties of aryl diazonium, in particular 4-nitrobenzene-diazonium (NBD), films on HOPG surfaces have been studied at the nanoscale level. By controlling the 2,2-diphenyl-1-picrylhydrazyl concentration during the NBD film growth, we have been able to control the thickness of the layer. The implications of NBD submonolayer adsorption on the electrical properties of this system have been analysed through Density Functional Theory (DFT) calculations, Atomic Force (AFM), Electric Force (EFM) and Kelvin Probe Force (KPFM) microscopies. DFT simulations showed that the NBD molecule adsorbs almost perpendicularly to the HOPG surface, which was confirmed experimentally through AFM imaging in the dynamic mode. In addition, DFT calculations showed that the adsorbed NBD has an appreciable dipole moment directed towards the HOPG surface and along the vertical direction of the HOPG surface. The existence of this dipole is the origin of the EFM contrast observed between the NBD-free and NBD-covered regions when a bias of -2 V was applied to the tip. Besides, the KPFM measurements show that the NBD adsorption leads to higher work function values, which is in agreement with the DFT calculations. Noticeably, our studies show that the KPFM signal is sensitive to the partial NBD coverage of the HOPG surface below the monolayer level.

Surface-Controlled Properties of Myosin Studied by Electric Field Modulation.

PubMed

van Zalinge, Harm; Ramsey, Laurence C; Aveyard, Jenny; Persson, Malin; Mansson, Alf; Nicolau, Dan V

2015-08-04

The efficiency of dynamic nanodevices using surface-immobilized protein molecular motors, which have been proposed for diagnostics, drug discovery, and biocomputation, critically depends on the ability to precisely control the motion of motor-propelled, individual cytoskeletal filaments transporting cargo to designated locations. The efficiency of these devices also critically depends on the proper function of the propelling motors, which is controlled by their interaction with the surfaces they are immobilized on. Here we use a microfluidic device to study how the motion of the motile elements, i.e., actin filaments propelled by heavy mero-myosin (HMM) motor fragments immobilized on various surfaces, is altered by the application of electrical loads generated by an external electric field with strengths ranging from 0 to 8 kVm(-1). Because the motility is intimately linked to the function of surface-immobilized motors, the study also showed how the adsorption properties of HMM on various surfaces, such as nitrocellulose (NC), trimethylclorosilane (TMCS), poly(methyl methacrylate) (PMMA), poly(tert-butyl methacrylate) (PtBMA), and poly(butyl methacrylate) (PBMA), can be characterized using an external field. It was found that at an electric field of 5 kVm(-1) the force exerted on the filaments is sufficient to overcome the frictionlike resistive force of the inactive motors. It was also found that the effect of assisting electric fields on the relative increase in the sliding velocity was markedly higher for the TMCS-derivatized surface than for all other polymer-based surfaces. An explanation of this behavior, based on the molecular rigidity of the TMCS-on-glass surfaces as opposed to the flexibility of the polymer-based ones, is considered. To this end, the proposed microfluidic device could be used to select appropriate surfaces for future lab-on-a-chip applications as illustrated here for the almost ideal TMCS surface. Furthermore, the proposed methodology can be used to gain fundamental insights into the functioning of protein molecular motors, such as the force exerted by the motors under different operational conditions.

Parametric study of the physical properties of hydrate-bearing sand, silt, and clay sediments: 1. Electromagnetic properties

USGS Publications Warehouse

Lee, J.Y.; Santamarina, J.C.; Ruppel, C.

2010-01-01

The marked decrease in bulk electrical conductivity of sediments in the presence of gas hydrates has been used to interpret borehole electrical resistivity logs and, to a lesser extent, the results of controlled source electromagnetic surveys to constrain the spatial distribution and predicted concentration of gas hydrate in natural settings. Until now, an exhaustive laboratory data set that could be used to assess the impact of gas hydrate on the electromagnetic properties of different soils (sand, silt, and clay) at different effective stress and with different saturations of hydrate has been lacking. The laboratory results reported here are obtained using a standard geotechnical cell and the hydrate-formed tetrahydrofuran (THF), a liquid that is fully miscible in water and able to produce closely controlled saturations of hydrate from dissolved phase. Both permittivity and electrical conductivity are good indicators of the volume fraction of free water in the sediment, which is in turn dependent on hydrate saturation. Permittivity in the microwave frequency range is particularly predictive of free water content since it is barely affected by ionic concentration, pore structure, and surface conduction. Electrical conductivity (or resistivity) is less reliable for constraining water content or hydrate saturation: In addition to fluid-filled porosity, other factors, such as the ionic concentration of the pore fluid and possibly other conduction effects (e.g., surface conduction in high specific surface soils having low conductivity pore fluid), also influence electrical conductivity.

Electrochemical properties for high surface area and improved electrical conductivity of platinum-embedded porous carbon nanofibers

NASA Astrophysics Data System (ADS)

An, Geon-Hyoung; Ahn, Hyo-Jin; Hong, Woong-Ki

2015-01-01

Four different types of carbon nanofibers (CNFs) for electrical double-layer capacitors (EDLCs), porous and non-porous CNFs with and without Pt metal nanoparticles, are synthesized by an electrospinning method and their performance in electrical double-layer capacitors (EDLCs) is characterized. In particular, the Pt-embedded porous CNFs (PCNFs) exhibit a high specific surface area of 670 m2 g-1, a large mesopore volume of 55.7%, and a low electrical resistance of 1.7 × 103. The synergistic effects of the high specific surface area with a large mesopore volume, and superior electrical conductivity result in an excellent specific capacitance of 130.2 F g-1, a good high-rate performance, superior cycling durability, and high energy density of 16.9-15.4 W h kg-1 for the performance of EDLCs.

Do Membranes Dream of Electric Tubes? Advanced Membranes Using Carbon Nanotube - Polymer Nanocomposites

NASA Astrophysics Data System (ADS)

de Lannoy, Charles-Francois Pedro Claude Karolek Ghislain

Membrane technologies represent an energy efficient, effective solution for treating municipal and commercial waters/wastewaters. Membranes are predominantly polymer-based and despite steady advances in polymeric materials, they continue to suffer from operational problems including biofouling and breakages. This work addresses these two disparate problems by developing novel CNT-polymer nanocomposite materials that contain variously functionalized carbon nanotubes (fCNTs) in low quantities (<0.5wt%). Several strategies have been employed to achieve highly functional CNT-polymer nanocomposite membranes including blend mixing, ionic charge association, and covalent cross-linking with monomer and oligomer constituents. These CNT-polymer nanocomposite membranes were compared to traditional polymer membranes across various properties including increased Young's Modulus, changes in surface hydrophilicity, fine control over molecular weight cut-off and flux, and surface electrical conductivity. Membranes with high surface electrical conductivity were further tested for their anti-biofouling properties. Finally, CNT stability and polymer compatibility were evaluated throughout membrane manufacture, use, and cleaning. The incorporation of CNTs mixed in bulk phase and linked through ionic associations in polymer matrices showed significant (50%) increases in Young's modulus for certain CNT functionalizations and derivatization percent. Membranes formed with high surface electrical conductivity demonstrated almost complete resistance to biofouling (> 95%) in long-term bacterially challenged experiments. CNTs and polymer mixtures that lacked covalent or ionic bonds were susceptible to significant (up to 10%) loss of CNTs during membrane non-solvent gelation and aggressive chemical cleaning treatment. Functionalized carbon nanotubes endow polymer membranes with their unique strength and electrically conductive properties. These added properties were demonstrated to greatly improve membrane operational efficiency and membrane longevity. CNT-polymer nanocomposite membranes offer low-energy, high-efficiency, and long-lifetime alternatives to traditional polymer membranes. With further advances in polymeric nanomaterials, membrane technology has the potential for wide applicability across many fields outside of water filtration and desalination.

Electrical potential modulation of dynamic film properties of aqueous surfactant solutions through a nanogap

NASA Astrophysics Data System (ADS)

Xie, Guoxin; Luo, Jianbin; Liu, Shuhai; Guo, Dan

2011-01-01

The effect of external electrical potentials (EEPs) on aqueous surfactant films nanoconfined in a ball-plate configuration has been investigated by measuring the dynamic film thickness with an interferometer. Experimental results indicate that the film formation properties of the surfactant solutions in the nanogap under applied EEPs are strongly dependent on the interfacial adsorbed surfactant structure. Effective control over the film formation properties by applying EEPs depends on the signs of the charges on the solid surface and the surfactant headgroups, the surfactant concentration, and the magnitude of EEPs. Remarkable alterations of the film formation properties in the nanogap by EEPs can be observed except when the surface charge is the same in sign as the headgroups and the surfactant concentration is above the critical micelle concentration. Mechanisms of these phenomena have been discussed in this work.

LiNbO3 surfaces from a microscopic perspective

NASA Astrophysics Data System (ADS)

Sanna, Simone; Gero Schmidt, Wolf

2017-10-01

A large number of oxides has been investigated in the last twenty years as possible new materials for various applications ranging from opto-electronics to heterogeneous catalysis. In this context, ferroelectric oxides are particularly promising. The electric polarization plays a crucial role at many oxide surfaces, and it largely determines their physical and chemical properties. Ferroelectrics offer in addition the possibility to control/switch the electric polarization and hence the surface chemistry, allowing for the realization of domain-engineered nanoscale devices such as molecular detectors or highly efficient catalysts. Lithium niobate (LiNbO3) is a ferroelectric with a high spontaneous polarization, whose surfaces have a huge and largely unexplored potential. Owing to recent advances in experimental techniques and sample preparation, peculiar and exclusive properties of LiNbO3 surfaces could be demonstrated. For example, water films freeze at different temperatures on differently polarized surfaces, and the chemical etching properties of surfaces with opposite polarization are strongly different. More important, the ferroelectric domain orientation affects temperature dependent surface stabilization mechanisms and molecular adsorption phenomena. Various ab initio theoretical investigations have been performed in order to understand the outcome of these experiments and the origin of the exotic behavior of the lithium niobate surfaces. Thanks to these studies, many aspects of their surface physics and chemistry could be clarified. Yet other puzzling features are still not understood. This review gives a résumé on the present knowledge of lithium niobate surfaces, with a particular view on their microscopic properties, explored in recent years by means of ab initio calculations. Relevant aspects and properties of the surfaces that need further investigation are briefly discussed. The review is concluded with an outlook of challenges and potential payoff for LiNbO3 based applications.

In Vitro Biocompatibility of Si Alloyed Multi-Principal Element Carbide Coatings

PubMed Central

Vladescu, Alina; Titorencu, Irina; Dekhtyar, Yuri; Jinga, Victor; Pruna, Vasile; Balaceanu, Mihai; Dinu, Mihaela; Pana, Iulian; Vendina, Viktorija

2016-01-01

In the current study, we have examined the possibility to improve the biocompatibility of the (TiZrNbTaHf)C through replacement of either Ti or Ta by Si. The coatings were deposited on Si and 316L stainless steel substrates by magnetron sputtering in an Ar+CH4 mixed atmosphere and were examined for elemental composition, chemical bonds, surface topography, surface electrical charge and biocompatible characteristics. The net surface charge was evaluated at nano and macroscopic scale by measuring the electrical potential and work function, respectively. The biocompatible tests comprised determination of cell viability and cell attachment to the coated surface. The deposited coatings had C/(metal+Si) ratios close to unity, while a mixture of metallic carbide, free-carbon and oxidized species formed on the film surface. The coatings’ surfaces were smooth and no influence of surface roughness on electrical charge or biocompatibility was found. The biocompatible characteristics correlated well with the electrical potential/work function, suggesting a significant role of surface charge in improving biocompatibility, particularly cell attachment to coating's surface. Replacement of either Ti or Ta by Si in the (TiZrNbTaHf)C coating led to an enhanced surface electrical charge, as well as to superior biocompatible properties, with best results for the (TiZrNbSiHf)C coating. PMID:27571361

Influence of Microstructure on the Electrical Properties of Heteroepitaxial TiN Films

NASA Astrophysics Data System (ADS)

Xiang, Wenfeng; Liu, Yuan; Zhang, Jiaqi

2018-05-01

Heteroepitaxial TiN films were deposited on Si substrates by pulse laser deposition at different substrate temperature. The microstructure and surface morphology of the films were investigated by X-ray diffraction (θ-2θ scan, ω-scan, and ϕ-scan) and atomic force microscopy. The electrical properties of the prepared TiN films were studied using a physical property measurement system. The experimental results showed that the crystallinity and surface morphology of the TiN films were improved gradually with increasing substrate temperature below 700 °C. Specially, single crystal TiN films were prepared when substrate temperature is above 700 °C; However, the quality of TiN films gradually worsened when the substrate temperature was increased further. The electrical properties of the films were directly correlated to their crystalline quality. At the optimal substrate temperature of 700 °C, the TiN films exhibited the lowest resistivity and highest mobility of 25.7 μΩ cm and 36.1 cm2/V s, respectively. In addition, the mechanism concerning the influence of substrate temperature on the microstructure of TiN films is discussed in detail.

Influence of PZT Coating Thickness and Electrical Pole Alignment on Microresonator Properties.

PubMed

Janusas, Giedrius; Ponelyte, Sigita; Brunius, Alfredas; Guobiene, Asta; Vilkauskas, Andrius; Palevicius, Arvydas

2016-11-10

With increasing technical requirements in the design of microresonators, the development of new techniques for lightweight, simple, and inexpensive components becomes relevant. Lead zirconate titanate (PZT) is a powerful tool in the formation of these components, allowing a self-actuation or self-sensing capability. Different fabrication methods lead to the variation of the properties of the device itself. This research paper covers the fabrication of a novel PZT film and the investigations of its chemical, surface, and dynamic properties when film thickness is varied. A screen-printing technique was used for the formation of smooth films of 60 µm, 68 µm, and 25 µm thickness. A custom-made poling technique was applied to enhance the piezoelectric properties of the designed films. However, poling did not change any compositional or surface characteristics of the films; changes were only seen in the electrical ones. The results showed that a thinner poled PZT film having a chemical composition with the highest amount of copper and zirconium led to better electrical characteristics (generated voltage of 3.5 mV).

Long-term characterization of neural electrodes based on parylene-caulked polydimethylsiloxane substrate.

PubMed

Jeong, Jinmo; Chou, Namsun; Kim, Sohee

2016-06-01

This study investigates the mechanical and long-term electrical properties of parylene-caulked polydimethylsiloxane (PDMS) as a substrate for implantable electrodes. The parylene-caulked PDMS is a structure where particles of parylene fill the porous surface of PDMS. This material is expected to have low water absorption and desirable mechanical properties such as flexibility and elasticity that are beneficial in many biomedical applications. To evaluate the mechanical property and electrical stability of parylene-caulked PDMS for potential in-vivo uses, tensile tests were conducted firstly, which results showed that the mechanical strength of parylene-caulked PDMS was comparable to that of native PDMS. Next, surface electrodes based on parylene-caulked PDMS were fabricated and their impedance was measured in phosphate-buffered saline (PBS) solution at 36.5 °C over seven months. The electrodes based on parylene-caulked PDMS exhibited the improved stability in impedance over time than native PDMS. Thus, with improved electrical stability in wet environment and preserved mechanical properties of PDMS, the electrodes based on parylene-caulked PDMS are expected to be suitable for long-term in-vivo applications.

Effect of pond ash on pen surface properties

USDA-ARS?s Scientific Manuscript database

Maintaining adequate feedlot pen surfaces is expensive. Pond ash (PA), a coal-fired electrical generation by-product, has good support qualities. A study was conducted comparing the performance of pond ash (PA) surfaced pens with soil surface (SS) pens. Four pens of an eight pen series with dimensio...

Simulation of Martian surface conditions and dust transport

NASA Astrophysics Data System (ADS)

Nørnberg, P.; Merrison, J. P.; Finster, K.; Folkmann, F.; Gunnlaugsson, H. P.; Hansen, A.; Jensen, J.; Kinch, K.; Lomstein, B. Aa.; Mugford, R.

2002-11-01

The suspended atmospheric dust which is also found deposited over most of the Martian globe plays an important (possibly vital) role in shaping the surface environment. It affects the weather (solar flux), water transport and possibly also the electrical properties at the surface. The simulation facilities at Aarhus provide excellent tools for studying the properties of this Martian environment. Much can be learned from such simulations, supporting and often inspiring new investigations of the planet. Electrical charging of a Mars analogue dust is being studied within a wind tunnel simulation aerosol. Here electric fields are used to extract dust from suspension. Although preliminary the results indicate that a large fraction of the dust is charged to a high degree, sufficient to dominate adhesion/cohesion processes. A Mars analogue dust layer has been shown to be an excellent trap for moisture, causing increased humidity in the soil below. This allows the possibility for liquid water to be stable close to the surface (less than 10 cm). This is being investigated in an environment simulator where heat and moisture transport can be studied through layers of Mars analogue dust.

Effect of copper phthalocyanine thickness on surface morphology, optical and electrical properties of Au/CuPc/n-Si heterojunction

NASA Astrophysics Data System (ADS)

Reddy, P. R. Sekhar; Janardhanam, V.; Jyothi, I.; Harsha, Cirandur Sri; Reddy, V. Rajagopal; Lee, Sung-Nam; Won, Jonghan; Choi, Chel-Jong

2018-02-01

Effects of the thickness of copper phthalocyanine (CuPc) film (2, 5, 10, 15, 20, 30 and 40 nm) on the surface morphology, optical and electrical properties of Au/CuPc/n-Si heterojunction have been investigated. The optical band gap of CuPc film was increased with increase in the thickness of the CuPc film. The electrical properties of the Au/n-Si Schottky junction and Au/CuPc/n-Si heterojunctions were characterized by current-voltage ( I-V) and capacitance-voltage ( C-V) measurements. The barrier height, ideality factor and series resistance were estimated based on the I-V, Cheung's and Norde's methods. The barrier heights increased with increasing CuPc interlayer thickness up to 15 nm and remained constant for thickness above 20 nm, associated with the incapability of the generated carriers to reach the interface. The discrepancy in the barrier heights obtained from I-V and C-V measurements indicates the presence of barrier inhomogeneity at the interface as evidenced by higher ideality factor values. It can be concluded that the electrical properties of Au/n-Si Schottky junction can be significantly altered with the variation of CuPc thickness as interlayer.

Effect of annealing temperature on the microstructure and optical-electrical properties of Cu-Al-O thin films

NASA Astrophysics Data System (ADS)

Zhang, Y. J.; Liu, Z. T.; Zang, D. Y.; Che, X. S.; Feng, L. P.; Bai, X. X.

2013-12-01

We have successfully prepared Cu-Al-O thin films on silicon (100) and quartz substrates by radio frequency (RF) magnetron sputtering method. The as-deposited Cu-Al-O film is amorphous in nature and post-annealing treatment in argon ambience results in crystallization of the films and the formation of CuAlO2. The annealing temperature plays an important role in the surface morphology, phase constitution and preferred growth orientation of CuAlO2 phase, thus affecting the properties of the film. The film annealed at 900 °C is mainly composed of CuAlO2 phase and shows smooth surface morphology with well-defined grain boundaries, thus exhibiting the optimum optical-electrical properties with electrical resistivity being 79.7 Ω·cm at room temperature and optical transmittance being 80% in visible region. The direct optical band gaps of the films are found in the range of 3.3-3.8 eV depending on the annealing temperature.

Nanoscale electrical property studies of individual GeSi quantum rings by conductive scanning probe microscopy.

PubMed

Lv, Yi; Cui, Jian; Jiang, Zuimin M; Yang, Xinju

2012-11-29

The nanoscale electrical properties of individual self-assembled GeSi quantum rings (QRs) were studied by scanning probe microscopy-based techniques. The surface potential distributions of individual GeSi QRs are obtained by scanning Kelvin microscopy (SKM). Ring-shaped work function distributions are observed, presenting that the QRs' rim has a larger work function than the QRs' central hole. By combining the SKM results with those obtained by conductive atomic force microscopy and scanning capacitance microscopy, the correlations between the surface potential, conductance, and carrier density distributions are revealed, and a possible interpretation for the QRs' conductance distributions is suggested.

Optical and electrical properties of ion beam textured Kapton and Teflon

NASA Technical Reports Server (NTRS)

Mirtich, M. J.; Sovey, J. S.

1977-01-01

An electron bombardment argon ion source was used to ion etch polyimide (Kapton) and fluorinated ethylene, FEP (Teflon). Samples of polyimide and FEP were exposed to (0.5-1.0) keV Ar ions at ion current densities of (1.0-1/8) mA/sq cm for various exposure times. Changes in the optical and electrical properties of the samples were used to characterize the exposure. Spectral reflectance and transmittance measurements were made between 0.33 and 2.16 micron m using an integrating sphere after each exposure. From these measurements, values of solar absorptance were obtained. Total emittance measurements were also recorded for some samples. Surface resistivity was used to determine changes in the electrical conductivity of the etched samples. A scanning electron microscope recorded surface structure after exposure. Spectral optical data, resistivity measurements, calculated absorptance and emittance measurements are presented along with photomicrographs of the surface structure for the various exposures to Ar ions.

Large piezoelectricity in electric-field modified single crystals of SrTiO3

NASA Astrophysics Data System (ADS)

Khanbabaee, B.; Mehner, E.; Richter, C.; Hanzig, J.; Zschornak, M.; Pietsch, U.; Stöcker, H.; Leisegang, T.; Meyer, D. C.; Gorfman, S.

2016-11-01

Defect engineering is an effective and powerful tool to control the existing material properties and produce completely new ones, which are symmetry-forbidden in a defect-free crystal. For example, the application of a static electric field to a single crystal of SrTiO3 forms a strained near-surface layer through the migration of oxygen vacancies out of the area beneath the positively charged electrode. While it was previously shown that this near-surface phase holds pyroelectric properties, which are symmetry-forbidden in centrosymmetric bulk SrTiO3, this paper reports that the same phase is strongly piezoelectric. We demonstrate the piezoelectricity of this phase through stroboscopic time-resolved X-ray diffraction under alternating electric field and show that the effective piezoelectric coefficient d33 ranges between 60 and 100 pC/N. The possible atomistic origins of the piezoelectric activity are discussed as a coupling between the electrostrictive effect and spontaneous polarization of this near-surface phase.

Preliminary Evaluation of Polyarylate Dielectric Films for Cryogenic Applications

NASA Technical Reports Server (NTRS)

Patterson, Richard L.; Hammoud, Ahmad; Fialla, Peter

2002-01-01

Polymeric materials are used extensively on spacecraft and satellites in electrical power and distribution systems, as thermal blankets and optical surface coatings, as well as mechanical support structures. The reliability of these systems when exposed to the harsh environment of space is very critical to the success of the mission and the safety of the crew in manned-flight ventures. In this work, polyarylate films were evaluated for potential use as capacitor dielectrics and wiring insulation for cryogenic applications. Two grades of the film were characterized in terms of their electrical and mechanical properties before and after exposure to liquid nitrogen (-196 C). The electrical characterization consisted of capacitance and dielectric loss measure Cents in the frequency range of 50 Hz to 100 kHz, and volume and surface resistivities. The mechanical measurements performed included changes in tensile (Young's modulus, elongation-at-break, and tensile strength) and structural properties (dimensional change, weight, and surface morphology). The preliminary results, which indicate good stability of the polymer after exposure to liquid nitrogen, are presented and discussed.

Clear, Conductive, Transparent, Flexible Space Durable Composite Films for Electrostatic Charge Mitigation

NASA Technical Reports Server (NTRS)

Watson, Kent A.; Connell, John W.; Delozier, Donavon M.; Smith, Joseph G., Jr.

2004-01-01

Space environmentally durable polymeric films with low color and sufficient electrical conductivity to mitigate electrostatic charge (ESC) build-up have been under investigation as part of a materials development activity. These materials have potential applications on advanced spacecraft, particularly on large, deployable, ultra-light weight Gossamer spacecraft. The approach taken to impart sufficient electrical conductivity into the polymer film while maintaining flexibility is to use single wall carbon nanotubes (SWNTs) as conductive additives. Approaches investigated in our lab involved an in-situ polymerization method, addition of SWNTs to a polymer containing reactive end-groups, and spray coating of polymer surfaces. The work described herein is a summary of the current status of this project. Surface conductivities (measured as surface resistance) in the range sufficient for ESC mitigation were achieved with minimal effects on the physical, thermal, mechanical and optical properties of the films. Additionally, the electrical conductivity was not affected by harsh mechanical manipulation of the films. The chemistry and physical properties of these nanocomposites will be discussed.

Laser-based surface preparation of composite laminates leads to improved electrodes for electrical measurements

NASA Astrophysics Data System (ADS)

Almuhammadi, Khaled; Selvakumaran, Lakshmi; Alfano, Marco; Yang, Yang; Bera, Tushar Kanti; Lubineau, Gilles

2015-12-01

Electrical impedance tomography (EIT) is a low-cost, fast and effective structural health monitoring technique that can be used on carbon fiber reinforced polymers (CFRP). Electrodes are a key component of any EIT system and as such they should feature low resistivity as well as high robustness and reproducibility. Surface preparation is required prior to bonding of electrodes. Currently this task is mostly carried out by traditional sanding. However this is a time consuming procedure which can also induce damage to surface fibers and lead to spurious electrode properties. Here we propose an alternative processing technique based on the use of pulsed laser irradiation. The processing parameters that result in selective removal of the electrically insulating resin with minimum surface fiber damage are identified. A quantitative analysis of the electrical contact resistance is presented and the results are compared with those obtained using sanding.

Variation in the electrical properties of ion beam irradiated cadmium selenate nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chauhan, R. P., E-mail: chauhanrpc@gmail.com; Narula, Chetna; Panchal, Suresh

The key feature of nanowires consists in the pronounced change in properties induced by the low dimensionality and high surface to volume ratio. The study of electrical transport properties of nanowires is important for electronic device applications. Energetic ions create changes, which may be structural or chemical, in a material along their track and these changes might alter the material’s properties. The demand of the modern technology is to understand the effect of radiation on the different properties of the material for its further applications. The present study is on the high-energy Nickel ion beam (160 MeV Ni{sup +12}) induced modificationsmore » in the electrical and structural properties of the cadmium selenate nanowires. An enhancement in the electrical conductivity of irradiated wires was observed as the ion fluence was increased especially in the forward I–V characteristics. The creation of defects by ion irradiation and the synergy of the ions during their passage in the sample with the intrinsic charge carriers may be responsible for the variation in the transport properties of the irradiated nanowires.« less

Influence of the nanotube oxidation on the rheological and electrical properties of CNT/HDPE composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nobile, Maria Rossella, E-mail: mrnobile@unisa.it; Somma, Elvira; Valentino, Olga

Rheological and electrical properties of nanocomposites based on multi-walled carbon nanotubes (MWNTs) and high density polyethylene (HDPE), prepared by melt mixing in a micro-twin screw extruder, have been investigated. The effect of MWNT concentration (0.5 and 2.5 wt %) and nanotube surface treatment (oxidative treatment in a tubular furnace at 500°C for 1 hr in a 95% nitrogen, 5% oxygen atmosphere) has been analyzed. It has been found that the sample conductivity with oxidation of the nanotubes decreases more than 2 orders of magnitude. Scanning electron microscopy showed good adhesion and dispersion of nanotubes in the matrix, independently of themore » surface treatment. Electrical and rheological measurements revealed that the oxidative treatment, causing some reduction of the MWNT quality, decreases the efficiency of the nanotube matrix interaction.« less

Influence of surface error on electromagnetic performance of reflectors based on Zernike polynomials

NASA Astrophysics Data System (ADS)

Li, Tuanjie; Shi, Jiachen; Tang, Yaqiong

2018-04-01

This paper investigates the influence of surface error distribution on the electromagnetic performance of antennas. The normalized Zernike polynomials are used to describe a smooth and continuous deformation surface. Based on the geometrical optics and piecewise linear fitting method, the electrical performance of reflector described by the Zernike polynomials is derived to reveal the relationship between surface error distribution and electromagnetic performance. Then the relation database between surface figure and electric performance is built for ideal and deformed surfaces to realize rapidly calculation of far-field electric performances. The simulation analysis of the influence of Zernike polynomials on the electrical properties for the axis-symmetrical reflector with the axial mode helical antenna as feed is further conducted to verify the correctness of the proposed method. Finally, the influence rules of surface error distribution on electromagnetic performance are summarized. The simulation results show that some terms of Zernike polynomials may decrease the amplitude of main lobe of antenna pattern, and some may reduce the pointing accuracy. This work extracts a new concept for reflector's shape adjustment in manufacturing process.

Method And Apparatus For Two Dimensional Surface Property Analysis Based On Boundary Measurement

DOEpatents

Richardson, John G.

2005-11-15

An apparatus and method for determining properties of a conductive film is disclosed. A plurality of probe locations selected around a periphery of the conductive film define a plurality of measurement lines between each probe location and all other probe locations. Electrical resistance may be measured along each of the measurement lines. A lumped parameter model may be developed based on the measured values of electrical resistance. The lumped parameter model may be used to estimate resistivity at one or more selected locations encompassed by the plurality of probe locations. The resistivity may be extrapolated to other physical properties if the conductive film includes a correlation between resistivity and the other physical properties. A profile of the conductive film may be developed by determining resistivity at a plurality of locations. The conductive film may be applied to a structure such that resistivity may be estimated and profiled for the structure's surface.

Electric Arc and Electrochemical Surface Texturing Technologies

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; Rutledge, Sharon K.; Snyder, Scott A.

1997-01-01

Surface texturing of conductive materials can readily be accomplished by means of a moving electric arc which produces a plasma from the environmental gases as well as from the vaporized substrate and arc electrode materials. As the arc is forced to move across the substrate surface, a condensate from the plasma re-deposits an extremely rough surface which is intimately mixed and attached to the substrate material. The arc textured surfaces produce greatly enhanced thermal emittance and hold potential for use as high temperature radiator surfaces in space, as well as in systems which use radiative heat dissipation such as computer assisted tomography (CAT) scan systems. Electrochemical texturing of titanium alloys can be accomplished by using sodium chloride solutions along with ultrasonic agitation to produce a random distribution of craters on the surface. The crater size and density can be controlled to produce surface craters appropriately sized for direct bone in-growth of orthopaedic implants. Electric arc texturing and electrochemical texturing techniques, surface properties and potential applications will be presented.

Simulations of electrically induced particle structuring on spherical drop surface

NASA Astrophysics Data System (ADS)

Hu, Yi; Vlahovska, Petia; Miksis, Michael

2016-11-01

Recent experiments (Ouriemi and Vlahovska, 2014) show intriguing surface patterns when a uniform electric field is applied to a droplet covered with colloidal particles. Depending on the particle properties and the electrical field intensity, particles organize into an equatorial belt, pole-to-pole chains, or dynamic vortices. Here we present a model to simulate the collective particle dynamics, which accounts for the electrohydrodynamic flow and particle dielectrophoresis due to the non-uniformity of local electrical field. In stronger electric fields, particles are expected to undergo Quincke rotation, inducing rotating clusters through inter-particle hydrodynamical interaction. We discuss how the field intensity influences the width, orientation and periodicity of the particle clusters. Our results provide insight into the various particle assembles discovered in the experiments.

The relationship between the surface composition and electrical properties of corrosion films formed on carbon steel in alkaline sour medium: an XPS and EIS study.

PubMed

Galicia, Policarpo; Batina, Nikola; González, Ignacio

2006-07-27

This work studies the evolution of 1018 carbon steel surfaces during 3-15 day immersion in alkaline sour medium 0.1 M (NH4)2S and 10 ppm CN(-) as (NaCN). During this period of time, surfaces were jointly characterized by electrochemical techniques in situ (electrochemical impedance spectroscopy, EIS) and spectroscopic techniques ex situ (X-ray photoelectron spectroscopy, XPS). The results obtained by these techniques allowed for a description of electrical and chemical properties of the films of corrosion products formed at the 1018 steel surface. There is an interconversion cycle of chemical species that form films of corrosion products whose conversion reactions favor two different types of diffusions inside the films: a chemical diffusion of iron cations and a typical diffusion of atomic hydrogen. These phenomena jointly control the passivity of the interface attacked by the corrosive medium.

Surface-properties relationship in sputtered Ag thin films: Influence of the thickness and the annealing temperature in nitrogen

NASA Astrophysics Data System (ADS)

Guillén, C.; Herrero, J.

2015-01-01

Metal layers with high roughness and electrical conductivity are required as back-reflector electrodes in several optoelectronic devices. The metal layer thickness and the process temperature should be adjusted to reduce the material and energetic costs for the electrode preparation. Here, Ag thin films with thickness ranging from 30 to 200 nm have been deposited by sputtering at room temperature on glass substrates. The structure, morphology, optical and electrical properties of the films have been analyzed in the as-grown conditions and after thermal treatment in flowing nitrogen at various temperatures in the 150-550 °C range. The surface texture has been characterized by the root-mean-square roughness and the correlation length coefficients, which are directly related to the electrical resistivity and the light-scattering parameter (reflectance haze) for the various samples. The increment in the reflectance haze has been used to detect surface agglomeration processes that are found dependent on both the film thickness and the annealing temperature. A good compromise between light-scattering and electrical conductivity has been achieved with 70 nm-thick Ag films after 350 °C heating.

Electrical properties of transparent conductive ATO coatings obtained by spray pyrolysis

NASA Astrophysics Data System (ADS)

Zinchenko, T. O.; Kondrashin, V. I.; Pecherskaya, E. A.; Kozlyakov, A. S.; Nikolaev, K. O.; Shepeleva, J. V.

2017-08-01

Transparent conductive coatings based on thin films of metal oxides have been widely spread in various optoelectronic devices and appliances. It is necessary to determine the influence of preparation conditions on coatings properties for their use in the solution of certain tasks. Thin films of tin dioxide were obtained by the method of spray pyrolysis on glass substrates. Surface resistance and resistivity, concentration and mobility of charge carriers, the conductivity were measured, and the dependences showing the effect of preparation conditions on electrical properties of optically transparent coatings.

Experimental analysis of electrical properties of composite materials

NASA Astrophysics Data System (ADS)

Fiala, L.; Rovnaník, P.; Černý, R.

2017-02-01

Dry cement-based composites are electrically non-conductive materials that behave in electric field like dielectrics. However, a relatively low amount of electrically conductive admixture significantly increases the electrical conductivity which extends applicability of such materials in practice. Therefore, they can be used as self-monitoring sensors controlling development of cracks; as sensors monitoring moisture content or when treated by an external electrical voltage as heat sources used for deicing of material's surface layer. Alkali-activated aluminosilicates (AAA), as competing materials to cement-based materials, are intensively investigated in the present due to their superior durability and environmental impact. Whereas the electrical properties of AAA are similar to those cement-based, they can be enhanced in the same way. In both cases, it is crucial to find a reasonable amount of electrically conductive phase to design composites with a sufficient electrical conductivity at an affordable price. In this paper, electrical properties of composites based on AAA binder and electrically conductive admixture represented by carbon nanotubes (CNT) are investigated. Measurements of electrical properties are carried out by means of 2-probes DC technique on nine types of samples; reference sample without the conductive phase and samples with CNT admixture in amount of 0.1 % - 2.5 % by vol. A significant increase of the electrical conductivity starts from the amount of 0.5 % CNT admixture and in case of 2.5 % CNT is about three orders of magnitude higher compared to the reference sample.

Molecular structures of (3-aminopropyl)trialkoxysilane on hydroxylated barium titanate nanoparticle surfaces induced by different solvents and their effect on electrical properties of barium titanate based polymer nanocomposites

NASA Astrophysics Data System (ADS)

Fan, Yanyan; Wang, Guanyao; Huang, Xingyi; Bu, Jing; Sun, Xiaojin; Jiang, Pingkai

2016-02-01

Surface modification of nanoparticles by grafting silane coupling agents has proven to be a significant approach to improve the interfacial compatibility between inorganic filler and polymer matrix. However, the impact of grafted silane molecular structure after the nanoparticle surface modification, induced by the utilized solvents and the silane alkoxy groups, on the electrical properties of the corresponding nanocomposites, has been seldom investigated. Herein, the silanization on the surface of hydroxylated barium titanate (BT-OH) nanoparticles was introduced by using two kinds of trialkoxysilane, 3-aminopropyltriethoxysilane (AMEO) and 3-aminopropyltrimethoxysilane (AMMO), with different solvents (toluene and ethanol), respectively. Solid-state 13C, 29Si nuclear magnetic resonance (NMR) spectroscopy and high-resolution X-ray photoelectron spectroscopy (XPS) were employed to validate the structure differences of alkoxysilane attachment to the nanoparticles. The effect of alkoxysilane structure attached to the nanoparticle surface on the dielectric properties of the BT based poly(vinylidene fluoride) (PVDF) nanocomposites were investigated. The results reveal that the solvents used for BT nanoparticle surface modification exhibit a significant effect on the breakdown strength of the nanocomposites. Nevertheless, the alkoxy groups of silane show a marginal influence on the dielectric properties of the nanocomposites. These research results provide important insights into the fabrication of advanced polymer nanocomposites for dielectric applications.

On the properties evolution of engineered surfaces of thin reinforced thermoplastic tapes during consolidation

NASA Astrophysics Data System (ADS)

Leon, Angel; Perez, Marta; Barasinski, Anais; Abisset-Chavanne, Emmanuelle; Chinesta, Francisco

2017-12-01

Advanced thermoplastic composite materials look to add functional properties to the mechanical ones, the latter usually ensured by the continuous fibers involved in the composite preforms. For that purpose the use of reinforced thermoplastic resins are being considered. These resins usually integrate manometric particles, with a variety of shapes (rods, spheres, discs, ...) with enhanced functional properties, ensuring for example the increase of thermal or electrical conductivities. However, even when considering adequate particles distribution and orientation in the preforms, forming processes induced properties cannot be ignored and they are particuarly critical at the ply interfaces level, where the degree of intimate contact must be maximized while ensuring equivalent functional properties to the ones existing in the bulk. One possibility for maximizing the intimate contact and at the same time controlling the induced functional anisotropy consists of designing engineered surfaces consolidated by the combined action of temperature and pressure. The combined effect results in a microscopic flow that induces at its turn the evolution of the position and orientation of the particles, and consequently the evolution of the associated properties, e.g. thermal and electrical conductivities. In the present work we address a simplified modeling framework of the functional properties evolution during the consolidation of unidirectional tapes. It combines the squeeze flow modeling, the flow induced microstructural anisotropy and its impact on the thermal and electrical conductivities.

Effects of rutin on the physicochemical properties of skin fibroblasts membrane disruption following UV radiation.

PubMed

Dobrzyńska, Izabela; Gęgotek, Agnieszka; Gajko, Ewelina; Skrzydlewska, Elżbieta; Figaszewski, Zbigniew A

2018-02-25

Human skin provides the body's first line of defense against physical and environmental assaults. This study sought to determine how rutin affects the membrane electrical properties, sialic acid content, and lipid peroxidation levels of fibroblast membranes after disruption by ultraviolet (UV) radiation. Changes in cell function may affect the basal electrical surface properties of cell membranes, and changes can be detected by electrokinetic measurements. The charge density of the fibroblast membrane surface was measured as a function of pH. A four-component equilibrium model was used to describe the interaction between ions in solution and ions on the membrane surface. Agreement was found between experimental and theoretical charge variation curves of fibroblast cells between pH 2.5 and 8. Sialic acid content was determined by Svennerholm's resorcinol method, and lipid peroxidation was estimated by measuring the malondialdehyde level. Compared to untreated cells, ultraviolet A (UVA)- or ultraviolet B (UVB)-treated skin cell membranes exhibited higher concentrations of acidic functional groups and higher average association constants with hydroxyl ions, but lower average association constants with hydrogen ions. Moreover, our results showed that UVA and UVB radiation is associated with increased levels of sialic acid and lipid peroxidation products in fibroblasts. Rutin protected cells from some deleterious UV-associated membrane changes, including changes in electrical properties, oxidative state, and biological functions. Copyright © 2018 Elsevier B.V. All rights reserved.

Energy storage in ferroelectric polymer nanocomposites filled with core-shell structured polymer@BaTiO3 nanoparticles: understanding the role of polymer shells in the interfacial regions.

PubMed

Zhu, Ming; Huang, Xingyi; Yang, Ke; Zhai, Xing; Zhang, Jun; He, Jinliang; Jiang, Pingkai

2014-11-26

The interfacial region plays a critical role in determining the electrical properties and energy storage density of dielectric polymer nanocomposites. However, we still know a little about the effects of electrical properties of the interfacial regions on the electrical properties and energy storage of dielectric polymer nanocomposites. In this work, three types of core-shell structured polymer@BaTiO3 nanoparticles with polymer shells having different electrical properties were used as fillers to prepare ferroelectric polymer nanocomposites. All the polymer@BaTiO3 nanoparticles were prepared by surface-initiated reversible-addition-fragmentation chain transfer (RAFT) polymerization, and the polymer shells were controlled to have the same thickness. The morphology, crystal structure, frequency-dependent dielectric properties, breakdown strength, leakage currents, energy storage capability, and energy storage efficiency of the polymer nanocomposites were investigated. On the other hand, the pure polymers having the same molecular structure as the shells of polymer@BaTiO3 nanoparticles were also prepared by RAFT polymerization, and their electrical properties were provided. Our results show that, to achieve nanocomposites with high discharged energy density, the core-shell nanoparticle filler should simultaneously have high dielectric constant and low electrical conductivity. On the other hand, the breakdown strength of the polymer@BaTiO3-based nanocomposites is highly affected by the electrical properties of the polymer shells. It is believed that the electrical conductivity of the polymer shells should be as low as possible to achieve nanocomposites with high breakdown strength.

Ferrocene Containing Copolymers with Improved Electrostatic Dissipation Properties for Advanced Applications

NASA Technical Reports Server (NTRS)

Smith, T. M.; Nelson, G. L.

2005-01-01

Electrostatic dissipative polymers are used for a variety of functions. Typical methods utilized to transform electrically insulating polymers into either charge dissipative or conductive materials involve incorporating a conductive filler, conductive polymer, oxidizing the surface using plasma, or incorporating surfactants that act as surface wetting agents. Another approach is to synthesize a block copolymer that is expected to result in better electrical properties with minimal impacts to physical, fire, and thermal properties. One such block that can be added into the main chain of polymers is a diol terminated ferrocene oligomer, which is expected to impart electrostatic dissipative properties into the host polymer while concurrently improving the overall fire properties. Previous work with polyurethanes incorporating a ferrocene oligomer into the main chain resulted in much improved fire retardancy. In dealing with electrostatic dissipative materials the important questions are: how easily does the material charge and how quickly can the charge move to ground. One normally describes the materials conductivity, but conductivity only measures the fastest path for an electron not the slowest path. The slowest path is the one of interest, since it is left on the surface and thus can cause discharges. In order to assess ease of charging and decay times corona charge dissipation measurements can accurately assess these properties by introducing a charge on the surface of the material then measuring the surface voltage and the amount of charge deposited. The charge decay curve then will give an indication of a materials electrostatic dissipation properties. Normally, triboelectric testing can be performed, but results vary. Corona charge dissipation results are more repeatable.

Proceedings of the 13th biennial conference on carbon. Extended abstracts and program

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

1977-01-01

Properties of carbon are covered including: mechanical and frictional properties; chemical reactivity and surfaces; aerospace applications; carbonization and graphitization; industrial applications; electrical and thermal properties; biomaterials applications; fibers and composites; nuclear applications; activated carbon and adsorption; advances in carbon characterization; and micromechanics and modeling. (GHT)

Preparation and electrical properties of oil-based magnetic fluids

NASA Astrophysics Data System (ADS)

Sartoratto, P. P. C.; Neto, A. V. S.; Lima, E. C. D.; Rodrigues de Sá, A. L. C.; Morais, P. C.

2005-05-01

This paper describes an improvement in the preparation of magnetic fluids for electrical transformers. The samples are based on surface-coated maghemite nanoparticles dispersed in transformer insulating oil. Colloidal stability at 90°C was higher for oleate-grafted maghemite-based magnetic fluid, whereas decanoate and dodecanoate-grafted samples were very unstable. Electrical properties were evaluated for samples containing 0.80%-0.0040% maghemite volume fractions. Relative permittivity varied from 8.8 to 2.1 and the minimum value of the loss factor was 12% for the most diluted sample. The resistivity falls in the range of 0.7-2.5×1010Ωm, whereas the ac dielectric strength varied from 70to79kV. These physical characteristics reveal remarkable step forward in the properties of the magnetic fluid samples and may result in better operation of electrical transformers.

Surface topography and electrical properties in Sr2FeMoO6 films studied at cryogenic temperatures

NASA Astrophysics Data System (ADS)

Angervo, I.; Saloaro, M.; Mäkelä, J.; Lehtiö, J.-P.; Huhtinen, H.; Paturi, P.

2018-03-01

Pulsed laser deposited Sr2FeMoO6 thin films were investigated for the first time with scanning tunneling microscopy and spectroscopy. The results confirm atomic scale layer growth, with step-terrace structure corresponding to a single lattice cell scale. The spectroscopy research reveals a distribution of local electrical properties linked to structural deformation in the initial thin film layers at the film substrate interface. Significant hole structure giving rise to electrically distinctive regions in thinner film also seems to set a thickness limit for the thinnest films to be used in applications.

Structural and electrochemical properties of nanostructured nickel silicides by reduction and silicification of high-surface-area nickel oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Xiao; Zhang, Bingsen; Li, Chuang

Graphical abstract: Nanostructured nickel silicides have been synthesized by reduction and silification of high-surface-area nickel oxide, and exhibited remarkably like-noble metal property, lower electric resistivity, and ferromagnetism at room temperature. Highlights: Black-Right-Pointing-Pointer NiSi{sub x} have been prepared by reduction and silification of high-surface-area NiO. Black-Right-Pointing-Pointer The structure of nickel silicides changed with increasing reaction temperature. Black-Right-Pointing-Pointer Si doping into nickel changed the magnetic properties of metallic nickel. Black-Right-Pointing-Pointer NiSi{sub x} have remarkably lower electric resistivity and like-noble metal property. -- Abstract: Nanostructured nickel silicides have been prepared by reduction and silicification of high-surface-area nickel oxide (145 m{sup 2} g{sup -1})more » produced via precipitation. The prepared materials were characterized by nitrogen adsorption, X-ray diffraction, thermal analysis, FT-IR spectroscopy, scanning electron microscopy, transmission electron microscopy, magnetic and electrochemical measurements. The nickel silicide formation involves the following sequence: NiO (cubic) {yields} Ni (cubic) {yields} Ni{sub 2}Si (orthorhombic) {yields} NiSi (orthorhombic) {yields} NiSi{sub 2} (cubic), with particles growing from 13.7 to 21.3 nm. The nickel silicides are ferromagnetic at room temperature, and their saturation magnetization values change drastically with the increase of Si content. Nickel silicides have remarkably low electrical resistivity and noble metal-like properties because of a constriction of the Ni d band and an increase of the electronic density of states. The results suggest that such silicides are promising candidates as inexpensive yet functional materials for applications in electrochemistry as well as catalysis.« less

[Stimuli sensitive changes in electrical surface properties of soft membranes: from a synthesized polymer to a biological system].

PubMed

Makino, K

1997-01-01

The electrical surface properties of biological cells have been studied, which provided us with the fundamental knowledge about the cell surface. The change in shape or biological functions of cells may affect the surface properties and can be detected by electrokinetic measurements. Biological cell surfaces are covered with polysaccharide chains, some are charged and some are not. Some polysaccharides produce a hydrogel matrixes under a proper condition. We thus consider it reasonable that cell surface is approximated by a hydrogel surface. Electrophoretic mobility measurements are useful for studying the surface properties of biological cells suspended as colloidal particles in an electrolyte solution. The electro-osmotic velocity measurements on the other hand are advantageous to the study of the surface properties of slab-shaped biological systems such as membranes. This work was started with a hydrogel, as a model material. As a hydrogel, poly(N-isopropylacrylamide) poly(NIPAAm), abbreviated as hereafter, was chosen, because this hydrogel changes its volume depending on temperature. The dependence of the electrophoretic mobility of latex particles covered with poly(NIPAAm) hydrogel layer or of the electro-osmotic mobility on poly(NIPAAm) plate upon temperature and ionic strength of the dispersing medium was well explained with an electrophoretic mobility formula for "soft particles" developed by Ohshima. The electrokinetic measurements and the explanation of data with an electrophoretic mobility formula for "soft particles" give us information about the surface charge density and the "softness" of soft surfaces. On the basis of the findings with hydrogels, we have discussed the relationship between the changes in shape or function of the biological cells and the change in physicochemical surface properties using these measurements. To study the change in physicochemical properties of the cell surface caused by apoptosis, we have measured the electrophoretic mobilities of intact and apoptotic human promyelocytic leukemia cell lines, HL-60RG cells. We have also studied the differences observed in surface properties of malignant lymphosarcoma cell line, RAW117-P, and its variant, RAW117-H10, with a high metastatic property to the liver. In both cases, the cell surfaces became softer by the changes of biological functions. We have applied electrophoresis and electro-osmosis measurements to the study of the electrokinetic surface properties of rat basophilic leukemia cells, RBL cells. It was also found that the surface of Human umbilical vein endothelial cells, HUVEC, is considerably soft as compared with those of other biological cells we have studied before.

Modification of electrical properties of silicon dioxide through intrinsic nano-patterns

NASA Astrophysics Data System (ADS)

Majee, Subimal; Barshilia, Devesh; Banerjee, Debashree; Kumar, Sanjeev; Mishra, Prabhash; Akhtar, Jamil

2018-05-01

The inherent network of nanopores and voids in silicon dioxide (SiO2) is generally undesirable for aspects of film quality, electrical insulation and dielectric performance. However, if we view these pores as natural nano-patterns embedded in a dielectric matrix then that opens up new vistas for exploration. The nano-pattern platform can be used to tailor electrical, optical, magnetic and mechanical properties of the carrier film. In this article we report the tunable electrical properties of thermal SiO2 thin-film achieved through utilization of the metal-nanopore network where the pores are filled with metallic Titanium (Ti). Without any intentional chemical doping, we have shown that the electrical resistivity of the oxide film can be controlled through physical filling up of the intrinsic oxide nanopores with Ti. The electrical resistivity of the composite film remains constant even after complete removal of the metal from the film surface except the pores. Careful morphological, electrical and structural analyses are carried out to establish that the presence of Ti in the nanopores play a crucial role in the observed conductive nature of the nanoporous film.

Magnetic and electrical control of engineered materials

DOEpatents

Schuller, Ivan K.; de La Venta Granda, Jose; Wang, Siming; Ramirez, Gabriel; Erekhinskiy, Mikhail; Sharoni, Amos

2016-08-16

Methods, systems, and devices are disclosed for controlling the magnetic and electrical properties of materials. In one aspect, a multi-layer structure includes a first layer comprising a ferromagnetic or ferrimagnetic material, and a second layer positioned within the multi-layer structure such that a first surface of the first layer is in direct physical contact with a second surface of the second layer. The second layer includes a material that undergoes structural phase transitions and metal-insulator transitions upon experiencing a change in temperature. One or both of the first and second layers are structured to allow a structural phase change associated with the second layer cause a change magnetic properties of the first layer.

Adsorption properties for urokinase on local diatomite surface

NASA Astrophysics Data System (ADS)

Yang, Yuxiang; Zhang, Jianbo; Yang, Weimin; Wu, Jieda; Chen, Rongsan

2003-02-01

In this paper, adsorption isotherm of urokinase on two typical local diatomites were determined at 25 °C and their surface electrical potentials (ζ), isoelectrical point values (IEP) were determined. The properties of diatomites, the relationship among diatomite structure, pore-size distribution, surface ζ and adsorption isotherm were discussed. The adsorption equation of urokinase was calculated from the adsorption isotherm. The adsorption mode of urokinase on diatomite surface was judged by the configuration function α. The relationship between the amount of adsorbed urokinase and IEP value was also discussed.

The effect of a combined low-pressure gas discharge on metal surfaces

NASA Astrophysics Data System (ADS)

Brzhozovskii, B.; Brovkova, M.; Gestrin, S.; Martynov, V.; Zinina, E.

2018-04-01

The properties and effects of a combined gas discharge, obtained by superimposing ultrahigh-frequency electromagnetic and electrostatic fields on the surface of metal products, have been studied. Estimates for the main physical properties characterizing the discharge have been obtained. The paper shows that the properties of a combined discharge essentially depend on the sign of the constant electric potential of the workpiece. In the case of a positive potential, there is a substantial hardening of the metal surface layer. Blanket coating formation, which is a nanocomposite two-phase structure, has been recorded.

Development of Tailorable Electrically Conductive Thermal Control Material Systems

NASA Technical Reports Server (NTRS)

Deshpande, M. S.; Harada, Y.

1997-01-01

The optical characteristics of surfaces on spacecraft are fundamental parameters in controlling its temperature. Passive thermal control coatings with designed solar absorptance and infrared emittance properties have been developed and have been in use for some time. In this total space environment, the coating must be stable and maintain its desired optical properties as well as mechanical properties for the course of the mission lifetime. The mission lifetimes are increasing and in our quest to save weight, newer substrates are being integrated which limit electrical grounding schemes. All of this has added to already existing concerns about spacecraft charging and related spacecraft failures or operational failures. The concern is even greater for thermal control surfaces that are very large. One way of alleviating such concerns is to design new thermal control material systems (TCMS) that can help to mitigate charging via providing charge leakage paths. The objective of this program was to develop two types of passive electrically conductive TCMS. The first was a highly absorbing/emitting black surface and the second was a low (alpha(sub s)/epsilon(sub N)) type white surface. The surface resistance goals for the black absorber was 10(exp 4) to 10(exp 9) Omega/square, and for the white surfaces it was 10(exp 6) to 10(exp 10) Omega/square. Several material system concepts were suggested and evaluated for space environment stability and electrical performance characterization. Our efforts in designing and evaluating these material systems have resulted in several developments. New concepts, pigments and binders have been developed to provide new engineering quality TCMS. Some of these have already found application on space hardware, some are waiting to be recognized by thermal designers, and some require further detailed studies to become state-of-the-art for future space hardware and space structures. Our studies on baseline state-of-the-art materials and conductive concepts have resulted in several important findings that are of interest to all thermal designers and systems integrators.

Properties of carbon composite paper derived from coconut coir as a function of polytetrafluoroethylene content

NASA Astrophysics Data System (ADS)

Destyorini, Fredina; Indriyati; Indayaningsih, Nanik; Prihandoko, Bambang; Zulfia Syahrial, Anne

2018-03-01

The carbon composite papers were produced by utilizing carbon materials from coconut coir. In the present work, carbon composite papers (CCP) were prepared by mixing carbon materials in the form of powder and fibre with polymer (ethylene vinyl acetate and polyethylene glycol) in xylene at 100°C. Then, polytetrafluoroethylene (PTFE) with different content was used to treat the surface of CCP. The properties of PTFE-coated CCP were analysed by means of contact angle measurement, tensile testing, porosity, density, and electrical conductivity measurements. As expected, all CCP’s surfaces treated with PTFE were found to be hydrophobic with contact angle >120° and relatively constant during 60 minutes measurement. Furthermore, water contact angle, density, and mechanical properties of CCP generally increase with increasing PTFE content. However, the porosity and electrical conductivity of CCP decrease slightly as the PTFE content increased from 0 wt% to 30 wt%. Based on the observation and analysis, the optimum PTFE content on CCP was 20 %, in which the mechanical properties and hydrophobicity behaviour were improved significantly, but it was only caused a very small drop in porosity and electrical conductivity

An in vivo study of electrical charge distribution on the bacterial cell wall by atomic force microscopy in vibrating force mode

NASA Astrophysics Data System (ADS)

Marlière, Christian; Dhahri, Samia

2015-05-01

We report an in vivo electromechanical atomic force microscopy (AFM) study of charge distribution on the cell wall of Gram+ Rhodococcus wratislaviensis bacteria, naturally adherent to a glass substrate, under physiological conditions. The method presented in this paper relies on a detailed study of AFM approach/retract curves giving the variation of the interaction force versus distance between the tip and the sample. In addition to classical height and mechanical (as stiffness) data, mapping of local electrical properties, such as bacterial surface charge, was proved to be feasible at a spatial resolution better than a few tens of nanometers. This innovative method relies on the measurement of the cantilever's surface stress through its deflection far from (>10 nm) the repulsive contact zone: the variations of surface stress come from the modification of electrical surface charge of the cantilever (as in classical electrocapillary measurements) likely stemming from its charging during contact of both the tip and the sample electrical double layers. This method offers an important improvement in local electrical and electrochemical measurements at the solid/liquid interface, particularly in high-molarity electrolytes when compared to techniques focused on the direct use of electrostatic force. It thus opens a new way to directly investigate in situ biological electrical surface processes involved in numerous practical applications and fundamental problems such as bacterial adhesion, biofilm formation, microbial fuel cells, etc.We report an in vivo electromechanical atomic force microscopy (AFM) study of charge distribution on the cell wall of Gram+ Rhodococcus wratislaviensis bacteria, naturally adherent to a glass substrate, under physiological conditions. The method presented in this paper relies on a detailed study of AFM approach/retract curves giving the variation of the interaction force versus distance between the tip and the sample. In addition to classical height and mechanical (as stiffness) data, mapping of local electrical properties, such as bacterial surface charge, was proved to be feasible at a spatial resolution better than a few tens of nanometers. This innovative method relies on the measurement of the cantilever's surface stress through its deflection far from (>10 nm) the repulsive contact zone: the variations of surface stress come from the modification of electrical surface charge of the cantilever (as in classical electrocapillary measurements) likely stemming from its charging during contact of both the tip and the sample electrical double layers. This method offers an important improvement in local electrical and electrochemical measurements at the solid/liquid interface, particularly in high-molarity electrolytes when compared to techniques focused on the direct use of electrostatic force. It thus opens a new way to directly investigate in situ biological electrical surface processes involved in numerous practical applications and fundamental problems such as bacterial adhesion, biofilm formation, microbial fuel cells, etc. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00968e

Development of Tailorable Electrically Conductive Thermal Control Material Systems

NASA Technical Reports Server (NTRS)

Deshpande, M. S.; Harada, Y.

1998-01-01

The optical characteristics of surfaces on spacecraft are fundamental parameters in controlling its temperature. Passive thermal control coatings with designed solar absorptance and infrared emittance properties have been developed and been in use for some time. In this total space environment, the coating must be stable and maintain its desired optical properties for the course of the mission lifetime. The mission lifetimes are increasing and in our quest to save weight, newer substrates are being integrated which limit electrical grounding schemes. All of this has already added to the existing concerns about spacecraft charging and related spacecraft failures or operational failures. The concern is even greater for thermal control surfaces that are very large. One way of alleviating such concerns is to design new thermal control material systems (TCMS) that can help to mitigate charging via providing charge leakage paths. The object of this program was to develop two types of passive electrically conductive TCMS.

Dielectric and electrical characteristics of Sr modified Ca1Cu3Ti4O12

NASA Astrophysics Data System (ADS)

Sahu, M.; Choudhary, R. N. P.; Roul, B. K.

2018-05-01

This paper mainly reports on the effect of Sr substitution on dielectric and electrical properties of CaCu3Ti4O12 at different temperature and frequency. Preliminary analysis of X-ray diffraction data of sintered samples confirms the reported cubic structure. Study of surface morphology shows that the surface of the samples contains well-defined and uniformly distributed grains. Some electrical parameters (permittivity, tangent loss and impedance) of the materials were measured and analyzed over a wide range of temperature (25 to 315 °C) and frequency (50 to 2x106 Hz). The ultra high dielectric constant and low energy dissipation have been observed in the said experimental conditions of phase-pure prepared compounds. It is expected that the addition of nano-size compounds or oxide will help to enhance the above properties useful for fabrication of super-capacitor.

Geometrical and Friction Properties of Perennial Grasses and Their Weeds in View of an Electro-Separation Method

NASA Astrophysics Data System (ADS)

Kovalyshyn, Stepan J.; Dadak, Viktor O.; Sokolyk, Vitalij V.; Grundas, Stanisław; Stasiak, Mateusz; Tys, Jerzy

2015-04-01

Many seed mixtures of herbs are difficult to separate. This is confirmed by studies determining the basic geometrical and friction properties of the seeds of perennial grasses and seeds of their weeds. The results show that in most cases the value of their geometrical parameters (length, thickness, and width) and friction properties (friction coefficients for different external surfaces of internal friction coefficients) are substantially similar and differ slightly among each other. This is the evidence that these properties are impractical to use in the process of separation as signs of divisibility. In the paper, a method for electro-separation of seed mixtures of herbs based on the use of complex physical, mechanical properties and electrical components in the separation are presented. The electric field that acts as an additional working body allows considering the surface conditions and biological status of seed mixtures of particles and significantly expands the functionality of the separators. Confirmation of the effectiveness of the proposed method for separation can be seen in the example of purification of red clover and sorrel seeds. By imposition of an electric field on an inclined moving separating plane, we can completely separate weed seeds from the main crop. The results confirm the effectiveness of the electro-separating method.

A comparison of LLDPE-based nanocomposites containing multi-walled carbon nanotubes and graphene

NASA Astrophysics Data System (ADS)

Vasileiou, Alexandros; Docoslis, Aristides; Kontopoulou, Marianna

2015-05-01

Composites of linear-low density polyethylene (LLDPE) with multi-walled carbon nanotubes (MWCNT) and thermally reduced graphene (TRGO) were produced by melt compounding. The composites were compatibilized by grafting aromatic pyridine groups onto the LLDPE backbone. The aromatic moieties established non-covalent π-π interactions with the carbon nanostructures, thus allowing for efficient dispersion, without compromizing their electrical properties. By using identical matrices, it was possible to investigate the effects of filler geometry on the electrical, mechanical and rheological properties of the composites. The 1-D nature and smaller surface area of the MWCNT facilitated their dispersion within the polymer matrix, whereas the graphene agglomerates appeared to breakup through an erosion mechanism. The resulting mixture of aggregates and individual graphene platelets favored lower electrical and rheological percolation thresholds. However the maximum electrical conductivity achieved in the TRGO/LLDPE was lower by about an order of magnitude compared to the MWCNT/LLDPE composites, probably due to residual oxygen in the graphene's structure. TRGO based composites presented higher moduli at the same filler loadings, while elongations at break were comparable. All composites exhibited time-dependent rheological properties, indicative of their tendency to aggregate. A more pronounced increase in viscoelastic properties was noted in the composites containing TRGO, presumably due to the higher surface area of the graphene platelets, and the presence of larger aggregates.

Preparation and properties of electro-conductive fabrics based on polypyrrole: covalent vs. non-covalent attachment

NASA Astrophysics Data System (ADS)

David, N. C.; Anavi, D.; Milanovich, M.; Popowski, Y.; Frid, L.; Amir, E.

2017-10-01

Electro-conductive fabrics were prepared via in situ oxidative polymerization of pyrrole (Py) in the presence of unmodified and chemically modified cotton fabrics. Chemical modification of cotton fabric was achieved by covalent attachment of a bifunctional linker molecule to the surface of the fabric, followed by incorporation of a monomer unit onto the linker. The fabrics were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron spectroscopy, and thermal analysis. Furthermore, the effect of Py concentration on the degree of polypyrrole (PPy) grafting, surface morphology, electrical resistivity, and laundering durability were studied for both types of cotton fabrics. Reductions of several orders of magnitude in surface and volume electrical resistivities were observed for both non-covalently and covalently linked cotton-PPy systems, whereas the effect of covalent pre-treatment of the fabric was stronger at low Py concentration. On the other hand, at higher monomer concentration, the electrical properties and laundering durability of the fabrics we comparable for both unmodified and chemically pre-treated cotton fabrics, indicating that only a small fraction of PPy chains were chemically grafted onto the fabric surface with the majority of the polymer being connected to the fabric through hydrogen bonds.

Role of Electrical Double Layer Structure in Ionic Liquid Gated Devices.

PubMed

Black, Jennifer M; Come, Jeremy; Bi, Sheng; Zhu, Mengyang; Zhao, Wei; Wong, Anthony T; Noh, Joo Hyon; Pudasaini, Pushpa R; Zhang, Pengfei; Okatan, Mahmut Baris; Dai, Sheng; Kalinin, Sergei V; Rack, Philip D; Ward, Thomas Zac; Feng, Guang; Balke, Nina

2017-11-22

Ionic liquid gating of transition metal oxides has enabled new states (magnetic, electronic, metal-insulator), providing fundamental insights into the physics of strongly correlated oxides. However, despite much research activity, little is known about the correlation of the structure of the liquids in contact with the transition metal oxide surface, its evolution with the applied electric potential, and its correlation with the measured electronic properties of the oxide. Here, we investigate the structure of an ionic liquid at a semiconducting oxide interface during the operation of a thin film transistor where the electrical double layer gates the device using experiment and theory. We show that the transition between the ON and OFF states of the amorphous indium gallium zinc oxide transistor is accompanied by a densification and preferential spatial orientation of counterions at the oxide channel surface. This process occurs in three distinct steps, corresponding to ion orientations, and consequently, regimes of different electrical conductivity. The reason for this can be found in the surface charge densities on the oxide surface when different ion arrangements are present. Overall, the field-effect gating process is elucidated in terms of the interfacial ionic liquid structure, and this provides unprecedented insight into the working of a liquid gated transistor linking the nanoscopic structure to the functional properties. This knowledge will enable both new ionic liquid design as well as advanced device concepts.

Role of Electrical Double Layer Structure in Ionic Liquid Gated Devices

DOE PAGES

Black, Jennifer M.; Come, Jeremy; Bi, Sheng; ...

2017-10-24

Ionic liquid gating of transition metal oxides has enabled new states (magnetic, electronic, metal–insulator), providing fundamental insights into the physics of strongly correlated oxides. However, despite much research activity, little is known about the correlation of the structure of the liquids in contact with the transition metal oxide surface, its evolution with the applied electric potential, and its correlation with the measured electronic properties of the oxide. Here, we investigate the structure of an ionic liquid at a semiconducting oxide interface during the operation of a thin film transistor where the electrical double layer gates the device using experiment andmore » theory. We show that the transition between the ON and OFF states of the amorphous indium gallium zinc oxide transistor is accompanied by a densification and preferential spatial orientation of counterions at the oxide channel surface. This process occurs in three distinct steps, corresponding to ion orientations, and consequently, regimes of different electrical conductivity. The reason for this can be found in the surface charge densities on the oxide surface when different ion arrangements are present. Overall, the field-effect gating process is elucidated in terms of the interfacial ionic liquid structure, and this provides unprecedented insight into the working of a liquid gated transistor linking the nanoscopic structure to the functional properties. This knowledge will enable both new ionic liquid design as well as advanced device concepts.« less

Role of Electrical Double Layer Structure in Ionic Liquid Gated Devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Black, Jennifer M.; Come, Jeremy; Bi, Sheng

Ionic liquid gating of transition metal oxides has enabled new states (magnetic, electronic, metal–insulator), providing fundamental insights into the physics of strongly correlated oxides. However, despite much research activity, little is known about the correlation of the structure of the liquids in contact with the transition metal oxide surface, its evolution with the applied electric potential, and its correlation with the measured electronic properties of the oxide. Here, we investigate the structure of an ionic liquid at a semiconducting oxide interface during the operation of a thin film transistor where the electrical double layer gates the device using experiment andmore » theory. We show that the transition between the ON and OFF states of the amorphous indium gallium zinc oxide transistor is accompanied by a densification and preferential spatial orientation of counterions at the oxide channel surface. This process occurs in three distinct steps, corresponding to ion orientations, and consequently, regimes of different electrical conductivity. The reason for this can be found in the surface charge densities on the oxide surface when different ion arrangements are present. Overall, the field-effect gating process is elucidated in terms of the interfacial ionic liquid structure, and this provides unprecedented insight into the working of a liquid gated transistor linking the nanoscopic structure to the functional properties. This knowledge will enable both new ionic liquid design as well as advanced device concepts.« less

A study on prevention of an electric discharge at an extraction electrode of an electron cyclotron resonance ion source for cancer therapy.

PubMed

Kishii, Y; Kawasaki, S; Kitagawa, A; Muramatsu, M; Uchida, T

2014-02-01

A compact ECR ion source has utilized for carbon radiotherapy. In order to increase beam intensity with higher electric field at the extraction electrode and be better ion supply stability for long periods, electric geometry and surface conditions of an extraction electrode have been studied. Focusing attention on black deposited substances on the extraction electrode, which were observed around the extraction electrode after long-term use, the relation between black deposited substances and the electrical insulation property is investigated. The black deposited substances were inspected for the thickness of deposit, surface roughness, structural arrangement examined using Raman spectroscopy, and characteristics of electric discharge in a test bench, which was set up to simulate the ECR ion source.

The Role of Electrical Anisotropy in Modeling and Interpreting Controlled-Source Electromagnetic Responses for Hydraulic Fracture Monitoring

NASA Astrophysics Data System (ADS)

Trevino, S., III; Hickey, M. S.; Everett, M. E.

2017-12-01

Controlled-Source Electromagnetics (CSEM) can be used to monitor the movement and extent of injection fluid during a hydraulic fracture. The response of the fluid to energization by a CSEM source is dependent upon the electrical conductivity difference between the fluid and background geological formation. An important property that must be taken into account when modeling and interpreting CSEM responses is that electrical conductivity may be anisotropic. We study the effect of electrical anisotropy in both the background formation and the fluid-injection zone. First, various properties of the background formation can affect anisotropy including variations in grain size, composition and bedding-plane orientation. In certain formations, such as shale, the horizontal component of the conductivity can be more than an order of magnitude larger than the vertical component. We study this effect by computing differences in surface CSEM responses using the analytic 1-D anisotropic primary solution of a horizontal electric dipole positioned at the surface. Second, during hydraulic fracturing, the injected fluid can create new fractures and infill existing natural fractures. To include the explicit fracture geometry in modeling, a large increase in the number of nodes and computational time is required which may not be feasible. An alternative is to instead model the large-scale fracture geometry as a uniform slab with an appropriate bulk conductivity. Micro-scale fracture geometry may cause preferential fluid propagation in a single direction or plane which can be represented by electrical anisotropy of the slab. To study such effects of bulk anisotropy on CSEM responses we present results from multiple scenarios of surface to surface hydraulic fracture monitoring using 3-D finite element modeling. The model uses Coulomb-gauged potentials to solve Maxwell's equations in the frequency domain and we have updated the code to allow a triaxial electrical conductivity tensor to be specified. By allowing for formation and target electrical anisotropy these modeling results contribute to a better understanding and faster interpretation of field data.

Understanding the adhesion and optical properties of eutectic metal alloys for solution-processed electronics

NASA Astrophysics Data System (ADS)

Kumar, Prashant; Aggarwal, Shantanu; Narayana, Chandrabhas; Narayan, K. S.

2018-02-01

The role of indium in controlling the adhesion and the optical properties of fusible, low- melting alloys is highlighted in this work. The optical activity of indium-alloy/polymer interface is probed using surface-enhanced Raman spectroscopy, which shows a large increase in polymer Raman modes intensity. Signatures of plasmon and chemically enhanced Raman are visible for more than one polymer. Improvement in adhesion is also reflected in their ability to coat conformally onto the polymer surface resulting in a suitable interface for electrical transport. The electrical characteristics of alloy electrodes, which are printed in ambient conditions, are superior when compared to the thermally evaporated aluminum cathodes. Raman and responsivity measurements indicate that indium (In) forms metal/organic hybrid charge-transfer states at the alloy/polymer interface and assumes a decisive role in controlling the mechanical, optical, and electrical properties of these electrodes. Our studies suggest that the indium present in small quantities (˜5 wt. %) can significantly improve the overall performance of the low-temperature printable eutectic alloy electrodes.

Electrical properties of Schottky barrier diodes fabricated on (001) β-Ga2O3 substrates with crystal defects

NASA Astrophysics Data System (ADS)

Oshima, Takayoshi; Hashiguchi, Akihiro; Moribayashi, Tomoya; Koshi, Kimiyoshi; Sasaki, Kohei; Kuramata, Akito; Ueda, Osamu; Oishi, Toshiyuki; Kasu, Makoto

2017-08-01

The electrical properties of Schottky barrier diodes (SBDs) on a (001) β-Ga2O3 substrate were characterized and correlated with wet etching-revealed crystal defects below the corresponding Schottky contacts. The etching process revealed etched grooves and etched pits, indicating the presence of line-shaped voids and small defects near the surface, respectively. The electrical properties (i.e., leakage currents, ideality factor, and barrier height) exhibited almost no correlation with the density of the line-shaped voids. This very weak correlation was reasonable considering the parallel positional relation between the line-shaped voids extending along the [010] direction and the (001) basal plane in which the voids are rarely exposed on the initial surface in contact with the Schottky metals. The distribution of small defects and SBDs with unusually large leakage currents showed similar patterns on the substrate, suggesting that these defects were responsible for the onset of fatal leak paths. These results will encourage studies on crystal defect management of (001) β-Ga2O3 substrates for the fabrication of devices with enhanced performance using these substrates.

The Transport Properties of Activated Carbon Fibers

DOE R&D Accomplishments Database

di Vittorio, S. L.; Dresselhaus, M. S.; Endo, M.; Issi, J-P.; Piraux, L.

1990-07-01

The transport properties of activated isotropic pitch-based carbon fibers with surface area 1000 m{sup 2}/g have been investigated. We report preliminary results on the electrical conductivity, the magnetoresistance, the thermal conductivity and the thermopower of these fibers as a function of temperature. Comparisons are made to transport properties of other disordered carbons.

Laser surface modification of electrically conductive fabrics: Material performance improvement and design effects

NASA Astrophysics Data System (ADS)

Tunakova, Veronika; Hrubosova, Zuzana; Tunak, Maros; Kasparova, Marie; Mullerova, Jana

2018-01-01

Development of lightweight flexible materials for electromagnetic interference shielding has obtained increased attention in recent years particularly for clothing, textiles in-house use and technical applications especially in areas of aircraft, aerospace, automobiles and flexible electronics such as portable electronics and wearable devices. There are many references in the literature concerning development and investigation of electromagnetic shielding lightweight flexible materials especially textile based with different electrically conductive additives. However, only little attention is paid to designing and enhancing the properties of these special fabrics by textile finishing processes. Laser technology applied as a physical treatment method is becoming very popular and can be used in different applications to make improvement and even overcome drawbacks of some of the traditional processes. The main purpose of this study is firstly to analyze the possibilities of transferring design onto the surface of electrically conductive fabrics by laser beam and secondly to study of effect of surface modification degree on performance of conductive fabric including electromagnetic shielding ability and mechanical properties. Woven fabric made of yarns containing 10% of extremely thin stainless steel fiber was used as a conductive substrate.

Electric field effect on the electronic structure of 2D Y2C electride

NASA Astrophysics Data System (ADS)

Oh, Youngtek; Lee, Junsu; Park, Jongho; Kwon, Hyeokshin; Jeon, Insu; Wng Kim, Sung; Kim, Gunn; Park, Seongjun; Hwang, Sung Woo

2018-07-01

Electrides are ionic compounds in which electrons confined in the interstitial spaces serve as anions and are attractive owing to their exotic physical and chemical properties in terms of their low work function and efficient charge-transfer characteristics. Depending on the topology of the anionic electrons, the surface electronic structures of electrides can be significantly altered. In particular, the electronic structures of two-dimensional (2D) electride surfaces are of interest because the localized anionic electrons at the interlayer space can be naturally exposed to cleaved surfaces. In this paper, we report the electronic structure of 2D Y2C electride surface using scanning tunneling microscopy (STM) and first-principles calculations, which reveals that anionic electrons at a cleaved surface are absorbed by the surface and subsequently resurged onto the surface due to an applied electric field. We highlight that the estranged anionic electrons caused by the electric field occupy the slightly shifted crystallographic site compared with a bulk Y2C electride. We also measure the work function of the Y2C single crystal, and it shows a slightly lower value than the calculated one, which appears to be due to the electric field from the STM junction.

Effects of lithium doping on microstructure, electrical properties, and chemical bonds of sol-gel derived NKN thin films

NASA Astrophysics Data System (ADS)

Lin, Chun-Cheng; Chen, Chan-Ching; Weng, Chung-Ming; Chu, Sheng-Yuan; Hong, Cheng-Shong; Tsai, Cheng-Che

2015-02-01

Highly (100/110) oriented lead-free Lix(Na0.5K0.5)1-xNbO3 (LNKN, x = 0, 0.02, 0.04, and 0.06) thin films are fabricated on Pt/Ti/SiO2/Si substrates via a sol-gel processing method. The lithium (Li) dopants modify the microstructure and chemical bonds of the LNKN films, and therefore improve their electrical properties. The optimal values of the remnant polarization (Pr = 14.3 μC/cm2), piezoelectric coefficient (d33 = 48.1 pm/V), and leakage current (<10-5 A/cm2) are obtained for a lithium addition of x = 0.04 (i.e., 4 at. %). The observation results suggest that the superior electrical properties are the result of an improved crystallization, a larger grain size, and a smoother surface morphology. It is shown that the ion transport mechanism is dominated by an Ohmic behavior under low electric fields and the Poole-Frenkel emission effect under high electric fields.

Enhancement of Device Performances in GaN-Based Light-Emitting Diodes Using Nano-Sized Surface Pit.

PubMed

Yeon, Seunghwan; Son, Taejoon; Shin, Dong Su; Jung, Kyung-Young; Park, Jinsub

2015-07-01

We report the improvement in optical and electrical properties of GaN-based green light-emitting diodes (LEDs) with nano-sized etch pits formed by the surface chemical etching. In order to control the density and sizes of etch pits formed on top surface of green LEDs, H3PO4 solution is used as a etchant with different etching time. When the etching time was increased from 0 min to 20 min, both the etch pit size and density were gradually increased. The improvement of extraction efficiency of LEDs using surface etching method can be attributed to the enlarged escape angle of generated photon by roughened p-GaN surface. The finite-difference time-domain (FDTD) simulation results well agreed with experimentally observed results. Moreover, the LED with etched p-GaN surface for 5 min shows the lowest leakage current value and the further increase of etching time resulting in increase of densities of the large-sized etch pit makes the degradation of electrical properties of LEDs.

Simulation of variation of apparent resistivity in resistivity surveys using finite difference modelling with Monte Carlo analysis

NASA Astrophysics Data System (ADS)

Aguirre, E. E.; Karchewski, B.

2017-12-01

DC resistivity surveying is a geophysical method that quantifies the electrical properties of the subsurface of the earth by applying a source current between two electrodes and measuring potential differences between electrodes at known distances from the source. Analytical solutions for a homogeneous half-space and simple subsurface models are well known, as the former is used to define the concept of apparent resistivity. However, in situ properties are heterogeneous meaning that simple analytical models are only an approximation, and ignoring such heterogeneity can lead to misinterpretation of survey results costing time and money. The present study examines the extent to which random variations in electrical properties (i.e. electrical conductivity) affect potential difference readings and therefore apparent resistivities, relative to an assumed homogeneous subsurface model. We simulate the DC resistivity survey using a Finite Difference (FD) approximation of an appropriate simplification of Maxwell's equations implemented in Matlab. Electrical resistivity values at each node in the simulation were defined as random variables with a given mean and variance, and are assumed to follow a log-normal distribution. The Monte Carlo analysis for a given variance of electrical resistivity was performed until the mean and variance in potential difference measured at the surface converged. Finally, we used the simulation results to examine the relationship between variance in resistivity and variation in surface potential difference (or apparent resistivity) relative to a homogeneous half-space model. For relatively low values of standard deviation in the material properties (<10% of mean), we observed a linear correlation between variance of resistivity and variance in apparent resistivity.

Photodetectors using III-V nitrides

DOEpatents

Moustakas, T.D.; Misra, M.

1997-10-14

A photodetector using a III-V nitride and having predetermined electrical properties is disclosed. The photodetector includes a substrate with interdigitated electrodes formed on its surface. The substrate has a sapphire base layer, a buffer layer formed from a III-V nitride and a single crystal III-V nitride film. The three layers are formed by electron cyclotron resonance microwave plasma-assisted molecular beam epitaxy (ECR-assisted MBE). Use of the ECR-assisted MBE process allows control and predetermination of the electrical properties of the photodetector. 24 figs.

Photodetectors using III-V nitrides

DOEpatents

Moustakas, Theodore D.; Misra, Mira

1997-01-01

A photodetector using a III-V nitride and having predetermined electrical properties is disclosed. The photodetector includes a substrate with interdigitated electrodes formed on its surface. The substrate has a sapphire base layer, a buffer layer formed from a III-V nitride and a single crystal III-V nitride film. The three layers are formed by electron cyclotron resonance microwave plasma-assisted molecular beam epitaxy (ECR-assisted MBE). Use of the ECR-assisted MBE process allows control and predetermination of the electrical properties of the photodetector.

Nanoscale Roughness and Morphology Affect the IsoElectric Point of Titania Surfaces

PubMed Central

Borghi, Francesca; Vyas, Varun; Podestà, Alessandro; Milani, Paolo

2013-01-01

We report on the systematic investigation of the role of surface nanoscale roughness and morphology on the charging behaviour of nanostructured titania (TiO2) surfaces in aqueous solutions. IsoElectric Points (IEPs) of surfaces have been characterized by direct measurement of the electrostatic double layer interactions between titania surfaces and the micrometer-sized spherical silica probe of an atomic force microscope in NaCl aqueous electrolyte. The use of a colloidal probe provides well-defined interaction geometry and allows effectively probing the overall effect of nanoscale morphology. By using supersonic cluster beam deposition to fabricate nanostructured titania films, we achieved a quantitative control over the surface morphological parameters. We performed a systematical exploration of the electrical double layer properties in different interaction regimes characterized by different ratios of characteristic nanometric lengths of the system: the surface rms roughness Rq, the correlation length ξ and the Debye length λD. We observed a remarkable reduction by several pH units of IEP on rough nanostructured surfaces, with respect to flat crystalline rutile TiO2. In order to explain the observed behavior of IEP, we consider the roughness-induced self-overlap of the electrical double layers as a potential source of deviation from the trend expected for flat surfaces. PMID:23874708

Investigation of the influence of pretreatment parameters on the surface characteristics of amorphous metal for use in power industry

NASA Astrophysics Data System (ADS)

Nieroda, Jolanta; Rybak, Andrzej; Kmita, Grzegorz; Sitarz, Maciej

2018-05-01

Metallic glasses are metallic materials, which exhibit an amorphous structure. These are mostly three or more component alloys, and some of them are magnetic metals. Materials of this kind are characterized by high electrical resistivity and at the same time exhibit very good magnetic properties (e.g. low-magnetization loss). The above mentioned properties are very useful in electrical engineering industry and this material is more and more popular as a substance for high-efficiency electrical devices production. This industry area is still evolving, and thus even higher efficiency of apparatus based on amorphous material is expected. A raw material must be carefully investigated and characterized before the main production process is started. Presented work contains results of complementary examination of amorphous metal Metglas 2605. Studies involve two ways to obtain clean and oxidized surface with high reactivity, namely degreasing followed by annealing process and plasma treatment. The amorphous metal parameters were examined by means of several techniques: surface free energy (SFE) measurements by sessile drop method, X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and both ex situ and in situ Raman spectroscopy. Additionally, influence of plasma parameters on wetting properties were optimized in systematic way with Design of Experiments (DOE) method. A wide range of used methods allow to fully investigate the amorphous metal material during preliminary preparation of surface. Obtained results provide information about appropriate parameters that should be applied in order to obtain highly reactive surface with functional oxide layer on it.

Vapor-phase polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT) on commercial carbon coated aluminum foil as enhanced electrodes for supercapacitors

NASA Astrophysics Data System (ADS)

Tong, Linyue; Skorenko, Kenneth H.; Faucett, Austin C.; Boyer, Steven M.; Liu, Jian; Mativetsky, Jeffrey M.; Bernier, William E.; Jones, Wayne E.

2015-11-01

Laminar composite electrodes are prepared for application in supercapacitors using a catalyzed vapor-phase polymerization (VPP) of 3,4-ethylenedioxythiophene (EDOT) on the surface of commercial carbon coated aluminum foil. These highly electrically conducting polymer films provide for rapid and stable power storage per gram at room temperature. The chemical composition, surface morphology and electrical properties are characterized by Raman spectroscopy, scanning electron microscopy (SEM), and conducting atomic force microscopy (C-AFM). A series of electrical measurements including cyclic voltammetry (CV), charge-discharge (CD) and electrochemical impedance spectroscopy are also used to evaluate electrical performance. The processing temperature of VPP shows a significant effect on PEDOT morphology, the degree of orientation and its electrical properties. The relatively high temperature leads to high specific area and large conductive domains of PEDOT layer which benefits the capacitive behavior greatly according to the data presented. Since the substrate is already highly conductive, the PEDOT based composite can be used as electrode materials directly without adding current collector. By this simple and efficient process, PEDOT based composites exhibit specific capacitance up to 134 F g-1 with the polymerization temperature of 110 °C.

Effect of nanoholes on the plasmonic properties of star nanostructures

NASA Astrophysics Data System (ADS)

Zhu, Shaoli; Whittaker, Andrew K.; Blakey, Idriss

2011-12-01

The transmission and localized electric field distribution of nanostructures are the most important parameters in the plasmonic field for nano-optics and nanobiosensors. In this paper, we propose a novel nanostructure which may be used for nanobiosensor applications. The effect of nanoholes on the plasmonic properties of star nanostructure was studied via numerical simulation, using the finite-difference time-domain (FDTD) method. In the model, the material type and size of the nanostructures was fixed, but the distance between the monotor and the surface of the nanoholes was varied. For example, nanoholes were located in the center of the nanostructures. The simulation method was as follows. Initially, the wavelength of incident light was varied from 400 to 1200 nm and the transmission spectrum and the electric field distribution were simulated. Then at the resonance wavelength (wavelength where the transmission spectrum has a minimum), the localized electric field distribution was calculated at different distances from the surface of the nanostructures. This study shows that the position of nanoholes has a significant effect on the transmission and localized electric field distribution of star nanostructures. The condition for achieving the maximum localized electric field distribution can be used in nano-optics and nanobiosensors in the future.

Tribological properties of fish scale inspired underwater superoleophobic hierarchical structure in aqueous environment

NASA Astrophysics Data System (ADS)

Lian, Zhongxu; Xu, Jinkai; Wan, Yanling; Li, Yiquan; Yu, Zhanjiang; Liu, Qimeng; Yu, Huadong

2017-10-01

Underwater superoleophobic surfaces are becoming increasingly important in regard to self-cleaning, anti-fouling, oil droplet transportation and water/oil separation. Although a great number of underwater superoleophobic surfaces have been demonstrated, their tribological properties remain impractical for the purposes of real-life applications. Herein, a two-step method of high speed wire electrical discharge machining and boiling water treatment was adopted to fabricate fish scale inspired underwater oil repellent hierarchical structure on an aluminum (Al) alloy 5083 surface. The hierarchical roughness and hydroxyl groups were obtained on the surface, and the surface exhibited the ability to prevent contact with organic fluids when submerged in water. Moreover, the tribological properties of underwater superoleophobic Al surfaces in aqueous environments were analyzed. The average friction coefficient of underwater superoleophobic surfaces was decreased compared with the polished Al surface. We believe that this research will contribute to the engineering application of underwater superoleophobic surfaces in the future.

Design of a hybrid emissivity domestic electric oven

NASA Astrophysics Data System (ADS)

Isik, Ozgur; Onbasioglu, Seyhan Uygur

2017-10-01

In this study, the radiative properties of the surfaces of an electric oven were investigated. Using experimental data related to an oven-like enclosure, a novel combination of surface properties was developed. Three different surface emissivity combinations were analysed experimentally: low-emissivity, high emissivity (black-coated), and hybrid emissivity. The term "hybrid emissivity design" here corresponds to an enclosure with some high emissive and some low-emissive surfaces. The experiments were carried out according to the EN 50304 standard. When a brick (load) was placed in the enclosure, the view factors between its surfaces were calculated with the Monte Carlo method. These and the measured surface temperatures were then used to calculate the radiative heat fluxes on the surfaces of the load. The three different models were compared with respect to energy consumption and baking time. The hybrid model performed best, with the highest radiative heat transfer between the surfaces of the enclosure and the load and minimum heat loss from the cavity. Thus, it was the most efficient model with the lowest energy consumption and the shortest baking time. The recent European Union regulation regarding the energy labelling of domestic ovens was used.

Material Damage System and Method for Determining Same

NASA Technical Reports Server (NTRS)

Okojie, Robert (Inventor)

2017-01-01

A system and method for determining a change in a thickness and temperature of a surface of a material are disclosed herein. The system and the method are usable in a thermal protection system of a space vehicle, such as an aeroshell of a space vehicle. The system and method may incorporate micro electric sensors arranged in a ladder network and capacitor strip sensors. Corrosion or ablation causes a change in an electrical property of the sensors. An amount of or rate of the corrosion or the ablation and a temperature of the material is determined based on the change of the electrical property of the sensors.

Rheological and electrical properties of hybrid nanocomposites of epoxy resins filled with graphite nanoplatelets and carbon black.

PubMed

Truong, Quang-Trung; Lee, Seon-Suk; Lee, Dai-Soo

2011-02-01

Graphite nanoplatelets (GNP) were prepared by microwave irradiation of natural graphites intercalated with ferric chloride in nitromethane (GIC). Intercalated structure of GIC was confirmed by X-ray diffraction patterns. SEM images of GIC after microwave irradiation showed the exfoliation of GIC, the formation of GNPs. Hybrid nanocomposites of bisphenol-A type epoxy resins filled with GNP and a conductive carbon black (CB) were prepared and rheological and electrical properties of the nanocomposites were investigated. Viscosity and electrical surface resistivity of the nanocomposites showed minima at certain mixtures of GNP and CB in the epoxy resins.

Surface electrical properties experiment. Part 2: Theory of radio-frequency interferometry in geophysical subsurface probing

NASA Technical Reports Server (NTRS)

Kong, J. A.; Tsang, L.

1974-01-01

The radiation fields due to a horizontal electric dipole laid on the surface of a stratified medium were calculated using a geometrical optics approximation, a modal approach, and direct numerical integration. The solutions were obtained from the reflection coefficient formulation and written in integral forms. The calculated interference patterns are compared in terms of the usefulness of the methods used to obtain them. Scattering effects are also discussed and all numerical results for anisotropic and isotropic cases are presented.

Programmable and electrically controllable light scattering from surface-polymer stabilized liquid crystals.

PubMed

Bédard-Arcand, Jean-Philippe; Galstian, Tigran

2012-08-01

We report the creation and study of a polarization independent light scattering material system based on surface-polymer stabilized liquid crystals. Originally isotropic cell substrates with thin nonpolymerized reactive mesogen layers are used for the alignment of pure nonreactive nematic liquid crystals. The partial interdiffusion of the two materials followed by the application of orienting external electric and magnetic fields and the photo polymerization of the reactive mesogen allow us the control of electro-optic scattering properties of obtained cells.

The study of the dynamics of erythrocytes under the influence of an external electric field

NASA Astrophysics Data System (ADS)

Mamaeva, Sargylana N.; Maksimov, Georgy V.; Antonov, Stepan R.

2017-11-01

A mathematical model is considered for the determination of the surface charge of an erythrocyte with its shape approximated by a surface of revolution of the second order, and the investigation of the dynamics of erythrocytes under the influence of an external electric field. In the first part of this work, the electrical surface charge of the erythrocyte of the patient was calculated with the assumption that the change in the shape and size of the red blood cells leads to stabilization of the electric field, providing a normal electrostatic repulsion. In the second part of the work, the research results of dynamics of changes in the morphology of erythrocytes under the influence of an external electric field depending on the values of their surface charge and resistance of blood plasma is presented. In the course of the work, the dependence of the surface charge of red blood cells from their shape and size is presented. The determination of the relationship between the value of the charge field and the surface of erythrocytes in norm and in pathology is shown. The dependence of the velocity of the erythrocytes on the characteristics of the external electric field, surface charge of the erythrocyte and properties of the medium is obtained. The results of this study can be applied indirectly to diagnose diseases and to develop recommendations for experimental studies of hemodynamics under the influence of various external physical factors.

Topological defects in electric double layers of ionic liquids at carbon interfaces

DOE PAGES

Black, Jennifer M.; Okatan, Mahmut Baris; Feng, Guang; ...

2015-06-07

The structure and properties of the electrical double layer in ionic liquids is of interest in a wide range of areas including energy storage, catalysis, lubrication, and many more. Theories describing the electrical double layer for ionic liquids have been proposed, however a full molecular level description of the double layer is lacking. To date, studies have been predominantly focused on ion distributions normal to the surface, however the 3D nature of the electrical double layer in ionic liquids requires a full picture of the double layer structure not only normal to the surface, but also in plane. Here wemore » utilize 3D force mapping to probe the in plane structure of an ionic liquid at a graphite interface and report the direct observation of the structure and properties of topological defects. The observation of ion layering at structural defects such as step-edges, reinforced by molecular dynamics simulations, defines the spatial resolution of the method. Observation of defects allows for the establishment of the universality of ionic liquid behavior vs. separation from the carbon surface and to map internal defect structure. In conclusion, these studies offer a universal pathway for probing the internal structure of topological defects in soft condensed matter on the nanometer level in three dimensions.« less

Theoretical models for electrochemical impedance spectroscopy and local ζ-potential of unfolded proteins in nanopores

NASA Astrophysics Data System (ADS)

Vitarelli, Michael J.; Talaga, David S.

2013-09-01

Single solid-state nanopores find increasing use for electrical detection and/or manipulation of macromolecules. These applications exploit the changes in signals due to the geometry and electrical properties of the molecular species found within the nanopore. The sensitivity and resolution of such measurements are also influenced by the geometric and electrical properties of the nanopore. This paper continues the development of an analytical theory to predict the electrochemical impedance spectra of nanopores by including the influence of the presence of an unfolded protein using the variable topology finite Warburg impedance model previously published by the authors. The local excluded volume of, and charges present on, the segment of protein sampled by the nanopore are shown to influence the shape and peak frequency of the electrochemical impedance spectrum. An analytical theory is used to relate the capacitive response of the electrical double layer at the surface of the protein to both the charge density at the protein surface and the more commonly measured zeta potential. Illustrative examples show how the theory predicts that the varying sequential regions of surface charge density and excluded volume dictated by the protein primary structure may allow for an impedance-based approach to identifying unfolded proteins.

Dust environment of an airless object: A phase space study with kinetic models

NASA Astrophysics Data System (ADS)

Kallio, E.; Dyadechkin, S.; Fatemi, S.; Holmström, M.; Futaana, Y.; Wurz, P.; Fernandes, V. A.; Álvarez, F.; Heilimo, J.; Jarvinen, R.; Schmidt, W.; Harri, A.-M.; Barabash, S.; Mäkelä, J.; Porjo, N.; Alho, M.

2016-01-01

The study of dust above the lunar surface is important for both science and technology. Dust particles are electrically charged due to impact of the solar radiation and the solar wind plasma and, therefore, they affect the plasma above the lunar surface. Dust is also a health hazard for crewed missions because micron and sub-micron sized dust particles can be toxic and harmful to the human body. Dust also causes malfunctions in mechanical devices and is therefore a risk for spacecraft and instruments on the lunar surface. Properties of dust particles above the lunar surface are not fully known. However, it can be stated that their large surface area to volume ratio due to their irregular shape, broken chemical bonds on the surface of each dust particle, together with the reduced lunar environment cause the dust particles to be chemically very reactive. One critical unknown factor is the electric field and the electric potential near the lunar surface. We have developed a modelling suite, Dusty Plasma Environments: near-surface characterisation and Modelling (DPEM), to study globally and locally dust environments of the Moon and other airless bodies. The DPEM model combines three independent kinetic models: (1) a 3D hybrid model, where ions are modelled as particles and electrons are modelled as a charged neutralising fluid, (2) a 2D electrostatic Particle-in-Cell (PIC) model where both ions and electrons are treated as particles, and (3) a 3D Monte Carlo (MC) model where dust particles are modelled as test particles. The three models are linked to each other unidirectionally; the hybrid model provides upstream plasma parameters to be used as boundary conditions for the PIC model which generates the surface potential for the MC model. We have used the DPEM model to study properties of dust particles injected from the surface of airless objects such as the Moon, the Martian moon Phobos and the asteroid RQ36. We have performed a (v0, m/q)-phase space study where the property of dust particles at different initial velocity (v0) and initial mass per charge (m/q) ratio were analysed. The study especially identifies regions in the phase space where the electric field within a non-quasineutral plasma region above the surface of the object, the Debye layer, becomes important compared with the gravitational force. Properties of the dust particles in the phase space region where the electric field plays an important role are studied by a 3D Monte Carlo model. The current DPEM modelling suite does not include models of how dust particles are initially injected from the surface. Therefore, the presented phase space study cannot give absolute 3D dust density distributions around the analysed airless objects. For that, an additional emission model is necessary, which determines how many dust particles are emitted at various places on the analysed (v0, m/q)-phase space. However, this study identifies phase space regions where the electric field within the Debye layer plays an important role for dust particles. Overall, the initial results indicate that when a realistic dust emission model is available, the unified lunar based DPEM modelling suite is a powerful tool to study globally and locally the dust environments of airless bodies such as planetary moons, Mercury, asteroids and non-active comets far from the Sun.

Deformation analysis of vesicles in an alternating-current electric field.

PubMed

Tang, Yu-Gang; Liu, Ying; Feng, Xi-Qiao

2014-08-01

In this paper the shape equation for axisymmetric vesicles subjected to an ac electric field is derived on the basis of the liquid-crystal model. The equilibrium morphology of a lipid vesicle is determined by the minimization of its free energy in coupled mechanical and ac electric fields. Besides elastic bending, the effects of the osmotic pressure difference, surface tension, Maxwell pressure, and flexoelectric and dielectric properties of phospholipid membrane as well are taken into account. The influences of elastic bending, osmotic pressure difference, and surface tension on the frequency-dependent behavior of a vesicle membrane in an ac electric field are examined. The singularity of the ac electric field is also investigated. Our theoretical results of vesicle deformation agree well with previous experimental and numerical results. The present study provides insights into the physical mechanisms underpinning the frequency-dependent morphological evolution of vesicles in the electric and mechanical fields.

The physics and chemistry of graphene-on-surfaces.

PubMed

Zhao, Guoke; Li, Xinming; Huang, Meirong; Zhen, Zhen; Zhong, Yujia; Chen, Qiao; Zhao, Xuanliang; He, Yijia; Hu, Ruirui; Yang, Tingting; Zhang, Rujing; Li, Changli; Kong, Jing; Xu, Jian-Bin; Ruoff, Rodney S; Zhu, Hongwei

2017-07-31

Graphene has demonstrated great potential in next-generation electronics due to its unique two-dimensional structure and properties including a zero-gap band structure, high electron mobility, and high electrical and thermal conductivity. The integration of atom-thick graphene into a device always involves its interaction with a supporting substrate by van der Waals forces and other intermolecular forces or even covalent bonding, and this is critical to its real applications. Graphene films on different surfaces are expected to exhibit significant differences in their properties, which lead to changes in their morphology, electronic structure, surface chemistry/physics, and surface/interface states. Therefore, a thorough understanding of the surface/interface properties is of great importance. In this review, we describe the major "graphene-on-surface" structures and examine the roles of their properties and related phenomena in governing the overall performance for specific applications including optoelectronics, surface catalysis, anti-friction and superlubricity, and coatings and composites. Finally, perspectives on the opportunities and challenges of graphene-on-surface systems are discussed.

Surface property detection apparatus and method

DOEpatents

Martens, J.S.; Ginley, D.S.; Hietala, V.M.; Sorensen, N.R.

1995-08-08

Apparatus and method for detecting, determining, and imaging surface resistance corrosion, thin film growth, and oxide formation on the surface of conductors or other electrical surface modification. The invention comprises a modified confocal resonator structure with the sample remote from the radiating mirror. Surface resistance is determined by analyzing and imaging reflected microwaves; imaging reveals anomalies due to surface impurities, non-stoichiometry, and the like, in the surface of the superconductor, conductor, dielectric, or semiconductor. 4 figs.

Membrane on a Chip: A Functional Tethered Lipid Bilayer Membrane on Silicon Oxide Surfaces

PubMed Central

Atanasov, Vladimir; Knorr, Nikolaus; Duran, Randolph S.; Ingebrandt, Sven; Offenhäusser, Andreas; Knoll, Wolfgang; Köper, Ingo

2005-01-01

Tethered membranes have been proven during recent years to be a powerful and flexible biomimetic platform. We reported in a previous article on the design of a new architecture based on the self-assembly of a thiolipid on ultrasmooth gold substrates, which shows extremely good electrical sealing properties as well as functionality of a bilayer membrane. Here, we describe the synthesis of lipids for a more modular design and the adaptation of the linker part to silane chemistry. We were able to form a functional tethered bilayer lipid membrane with good electrical sealing properties covering a silicon oxide surface. We demonstrate the functional incorporation of the ion carrier valinomycin and of the ion channel gramicidin. PMID:16127170

Methods of DNA methylation detection

NASA Technical Reports Server (NTRS)

Maki, Wusi Chen (Inventor); Filanoski, Brian John (Inventor); Mishra, Nirankar (Inventor); Rastogi, Shiva (Inventor)

2010-01-01

The present invention provides for methods of DNA methylation detection. The present invention provides for methods of generating and detecting specific electronic signals that report the methylation status of targeted DNA molecules in biological samples.Two methods are described, direct and indirect detection of methylated DNA molecules in a nano transistor based device. In the direct detection, methylated target DNA molecules are captured on the sensing surface resulting in changes in the electrical properties of a nano transistor. These changes generate detectable electronic signals. In the indirect detection, antibody-DNA conjugates are used to identify methylated DNA molecules. RNA signal molecules are generated through an in vitro transcription process. These RNA molecules are captured on the sensing surface change the electrical properties of nano transistor thereby generating detectable electronic signals.

Analysis of Laser Injection Condition and Electrical Properties in Local BSF for Laser Fired Contact c-Si Solar Cell Applications.

PubMed

Park, Cheolmin; Choi, Gyuho; Balaji, Nagarajan; Ju, Minkyu; Lee, Youn-Jung; Lee, Haeseok; Yi, Junsin

2018-07-01

A crystalline silicon (c-Si) local-back-contact (LBC) solar cell for which a laser-condition-optimized surface-recombination velocity (SRV), a contact resistance (Rc), and local back surface fields (LBSFs) were utilized is reported. The effect of the laser condition on the rear-side electrical properties of the laser-fired LBC solar cell was studied. The Nd:YAG-laser (1064-nm wavelength) power and frequency were varied to obtain LBSF values with a lower contact resistance. A 10-kHz laser power of 44 mW resulted in an Rc of 0.125 ohms with an LBSF thickness of 2.09 μm and a higher open-circuit voltage (VOC) of 642 mV.

Structure-property and composition-property relationships for poly(ethylene terephthalate) surfaces modified by helium plasma-based ion implantation

NASA Astrophysics Data System (ADS)

Tóth, A.; Veres, M.; Kereszturi, K.; Mohai, M.; Bertóti, I.; Szépvölgyi, J.

2011-10-01

The surfaces of untreated and helium plasma-based ion implantation (He PBII) treated poly(ethylene terephthalate) (PET) samples were characterised by reflectance colorimetry, contact angle studies and measurements of surface electrical resistance. The results were related to the structural and compositional data obtained by the authors earlier on parallel samples by XPS and Raman spectroscopy. Inverse correlations between lightness and ID/ IG ratio and between chroma and ID/ IG ratio were obtained, suggesting that the PBII-treated PET samples darken and their colourfulness decreases with the increase of the portion of aromatic sp 2 carbon rings in the chemical structure of the modified layer. Direct correlation between water contact angle and the ID/ IG ratio and inverse correlations between surface energy and ID/ IG ratio and between dispersive component of surface energy and ID/ IG ratio were found, reflecting that surface wettability, surface energy and its dispersive component decrease with the formation of surface structure, characterised again by enhanced portion of aromatic sp 2 carbon rings. The surface electrical resistance decreased with the increase of the surface C-content determined by XPS and also with the increase of the surface concentration of conjugated double bonds, reflected by the increase of the π → π* shake-up satellite of the C 1s peak.

Electrical transport properties of spray deposited transparent conducting ortho-Zn2SnO4 thin films

NASA Astrophysics Data System (ADS)

Ramarajan, R.; Thangaraju, K.; Babu, R. Ramesh; Joseph, D. Paul

2018-04-01

Ortho Zinc Stannate (Zn2SnO4) exhibits excellent electrical and optical properties to serve as alternate transparent electrode in optoelectronic devices. Here we have optimized ortho-Zn2SnO4 thin film by spray pyrolysis method. Deposition was done onto a pre-heated glass substrate at a temperature of 400 °C. The XRD pattern indicated films to be polycrystalline with cubic structure. The surface of films had globular and twisted metal sheet like morphologies. Films were transparent in the visible region with band gap around 3.6 eV. Transport properties were studied by Hall measurements at 300 K. Activation energies were calculated from Arrhenius's plot from temperature dependent electrical measurements and the conduction mechanism is discussed.

Point Defects in Oxides: Tailoring Materials Through Defect Engineering

NASA Astrophysics Data System (ADS)

Tuller, Harry L.; Bishop, Sean R.

2011-08-01

Optimization of electrical, optical, mechanical, and other properties of many advanced, functional materials today relies on precise control of point defects. This article illustrates the progress that has been made in elucidating the often complex equilibria exhibited by many materials by examining two recently well-characterized model systems, TlBr for radiation detection and PrxCe1-xO2-δ, of potential interest in solid-oxide fuel cells. The interplay between material composition, electrical conductivity, and mechanical properties (electrochemomechanics) is discussed, and implications in these relations, for example, enhancing electrical properties through large mechanical strains, are described. The impact of space charge and strain fields at interfaces, particularly important in nanostructure materials, is also emphasized. Key experimental techniques useful in characterizing bulk and surface defects are summarized and reviewed.

Growth of strained Si/relaxed SiGe heterostructures on Si(110) substrates using solid-source molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Arimoto, Keisuke; Nakazawa, Hiroki; Mitsui, Shohei; Utsuyama, Naoto; Yamanaka, Junji; Hara, Kosuke O.; Usami, Noritaka; Nakagawa, Kiyokazu

2017-11-01

A strained Si/relaxed SiGe heterostructure grown on Si(110) substrate is attractive as a platform for high-hole-mobility Si-based electronic devices. To improve the electrical property, a smoother surface is desirable. In this study, we investigated surface morphology and microstructural aspects of strained Si/relaxed SiGe/Si(110) heterostructures grown by solid-source (SS) molecular beam epitaxy (MBE). It was revealed that SSMBE provides a way to grow strained Si/relaxed SiGe heterostructures with smooth surfaces. In addition, it was found that the strain in the SiGe layer of the SSMBE-grown sample is highly anisotropic whereas that of the GSMBE-grown sample is almost biaxially relaxed. Along with the surface morphology, the symmetry in degree of strain relaxation has implications for the electrical property. Results of a calculation shows that anisotropic strain is preferable for device application since it confines holes solely in the strained Si layer where hole mobility is enhanced.

Interrelation of the construction of the metamorphic InAlAs/InGaAs nanoheterostructures with the InAs content in the active layer of 76-100% with their surface morphology and electrical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vasil'evskii, I. S., E-mail: ivasilevskii@mail.ru; Galiev, G. B.; Klimov, E. A.

The influence of the construction of a metamorphic buffer on the surface morphology and electrical properties of InAlAs/InGaAs/InAlAs nanoheterostructures with InAs content in the active layer from 76 to 100% with the use of the GaAs and InP substrates is studied. It is shown that such parameters as the electron mobility and the concentration, as well as the root-mean-square surface roughness, substantially depend on the construction of the metamorphic buffer. It is established experimentally that these parameters largely depend on the maximal local gradient of the lattice constant of the metamorphic buffer in the growth direction of the layers rathermore » than on its average value. It is shown that, with selection of the construction of the metamorphic buffer, it is possible to form nanostructured surfaces with a large-periodic profile.« less

Aligned hierarchical Ag/ZnO nano-heterostructure arrays via electrohydrodynamic nanowire template for enhanced gas-sensing properties.

PubMed

Yin, Zhouping; Wang, Xiaomei; Sun, Fazhe; Tong, Xiaohu; Zhu, Chen; Lv, Qiying; Ye, Dong; Wang, Shuai; Luo, Wei; Huang, YongAn

2017-09-22

Gas sensing performance can be improved significantly by the increase in both the effective gas exposure area and the surface reactivitiy of ZnO nanorods. Here, we propose aligned hierarchical Ag/ZnO nano-heterostructure arrays (h-Ag/ZnO-NAs) via electrohydrodynamic nanowire template, together with a subsequent hydrothermal synthesis and photoreduction reaction. The h-Ag/ZnO-NAs scatter at top for higher specific surface areas with the air, simultaneously contact at root for the electrical conduction. Besides, the ZnO nanorods are uniformly coated with dispersed Ag nanoparticles, resulting in a tremendous enhancement of the surface reactivity. Compared with pure ZnO, such h-Ag/ZnO-NAs exhibit lower electrical resistance and faster responses. Moreover, they demonstrate enhanced NO 2 gas sensing properties. Self-assembly via electrohydrodynamic nanowire template paves a new way for the preparation of high performance gas sensors.

Effects of Electron Beam Irradiation and Thiol Molecule Treatment on the Properties of MoS2 Field Effect Transistors

NASA Astrophysics Data System (ADS)

Choi, Barbara Yuri; Cho, Kyungjune; Pak, Jinsu; Kim, Tae-Young; Kim, Jae-Keun; Shin, Jiwon; Seo, Junseok; Chung, Seungjun; Lee, Takhee

2018-05-01

We investigated the effects of the structural defects intentionally created by electron-beam irradiation with an energy of 30 keV on the electrical properties of monolayer MoS2 field effect transistors (FETs). We observed that the created defects by electron beam irradiation on the MoS2 surface working as trap sites deteriorated the carrier mobility and carrier concentration with increasing the subthreshold swing value and shifting the threshold voltage in MoS2 FETs. The electrical properties of electron-beam irradiated MoS2 FETs were slightly improved by treating the devices with thiol-terminated molecules which presumably passivated the structural defects of MoS2. The results of this study may enhance the understanding of the electrical properties of MoS2 FETs in terms of creating and passivating defect sites.

Synthesis and characterization of novel 4-Tetra-4-Tolylsulfonyl ZnPc thin films for optoelectronic applications

NASA Astrophysics Data System (ADS)

Khalil, Salah; Tazarki, Helmi; Souli, Mehdi; Guasch, Cathy; Jamoussi, Bassem; Kamoun, Najoua

2017-11-01

Novel 4-Tetra-4-Tolylsulfonyl:zinc phthalocyanine and simple zinc phthalocyanine were synthesized. Our materials were grown on glass substrates by spin coating technique. Thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electronic micrograph (SEM), atomic force microscopy (AFM), spectrophotometer and Hall effect measurement. X-ray spectra reveal that 4-Tetra-4-Tolylsulfonyl:zinc phthalocyanine (4T4TS:ZnPc) and zinc phthalocyanine (ZnPc) thin films have a monoclinic crystalline structure in β phase. The surface properties and chemical composition were detailed using XPS measurement. SEM were used to investigate the surface morphology for 4T4TS:ZnPc and ZnPc thin films. Atomic force microscopy images have shown a decrease in surface roughness after substitution. Optical properties were investigated by measuring transmission and reflection spectra. Electrical properties were studied and the different electrical parameters was measured and compared on glass, silicon and tin dioxide substrates by Hall Effect technique. All obtained results indicate an improvement in physical properties of 4T4TS:ZnPc which allows used it in optoelectronic applications.

The Electric Propulsion Interactions Code (EPIC)

NASA Technical Reports Server (NTRS)

Mikellides, I. G.; Mandell, M. J.; Kuharski, R. A.; Davis, V. A.; Gardner, B. M.; Minor, J.

2004-01-01

Science Applications International Corporation is currently developing the Electric Propulsion Interactions Code, EPIC, as part of a project sponsored by the Space Environments and Effects Program at the NASA Marshall Space Flight Center. Now in its second year of development, EPIC is an interactive computer tool that allows the construction of a 3-D spacecraft model, and the assessment of a variety of interactions between its subsystems and the plume from an electric thruster. These interactions may include erosion of surfaces due to sputtering and re-deposition of sputtered materials, surface heating, torque on the spacecraft, and changes in surface properties due to erosion and deposition. This paper describes the overall capability of EPIC and provides an outline of the physics and algorithms that comprise many of its computational modules.

Exploiting the flexibility and the polarization of ferroelectric perovskite surfaces to achieve efficient photochemistry and enantiospecificity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rappe, Andrew

This research project explored the catalytic properties of complex surfaces of functional materials. The PI used first-principles density functional theory (DFT) calculations to explore a tightly integrated set of properties. The physical properties of complex functional materials that influence surface chemistry were explored, including bulk and surface electric dipoles, and surface conductivity. The energetic, compositional, electronic, and chemical properties of the surfaces of these materials were explored in detail, and connections between material properties and chemical reactivity were established. This project led to 28 publications, including Nat. Comm., JACS, 3 PRL, 7 PRB, 2 ACS Nano, 2 Nano Lett., 4more » JPCL, 2 JCP, Chem. Mater., ACS Appl. Mater. Interfaces, Phys. Rev. Appl., and a U.S. Patent on surface catalysts. The key accomplishments in this project involved work in six coordinated areas: pioneering ways to control bulk dipoles in order to dynamically affect catalysis, exploring novel ways of bringing charge to the surface for redox catalysis, nonstoichiometric surfaces offering new sites for heterogeneous catalysis, illustrating how surface catalysis responds to applied pressure, catalytic growth of carbon-based materials, and new computational methods allowing more accurate exploration of molecule-surface interactions« less

Emergence of a Stern Layer from the Incorporation of Hydration Interactions into the Gouy-Chapman Model of the Electrical Double Layer.

PubMed

Brown, Matthew A; Bossa, Guilherme Volpe; May, Sylvio

2015-10-27

In one of the most commonly used phenomenological descriptions of the electrical double layer, a charged solid surface and a diffuse region of mobile ions are separated from each other by a thin charge-depleted Stern layer. The Stern layer acts as a capacitor that improves the classical Gouy-Chapman model by increasing the magnitude of the surface potential and limiting the maximal counterion concentration. We show that very similar Stern-like properties of the diffuse double layer emerge naturally from adding a nonelectrostatic hydration repulsion to the electrostatic Coulomb potential. The interplay of electrostatic attraction and hydration repulsion of the counterions and the surface leads to the formation of a diffuse counterion layer that remains well separated from the surface. In addition, hydration repulsions between the ions limit and control the maximal ion concentration and widen the width of the diffuse double layer. Our mean-field model, which we express in terms of electrostatic and hydration potentials, is physically consistent and conceptually similar to the classical Gouy-Chapman model. It allows the incorporation of ion specificity, accounts for hydration properties of charged surfaces, and predicts Stern layer properties, which we analyze in terms of the effective size of the hydrated counterions.

Electrophoretic Deposition of Cu-SiO2 Coatings by DC and Pulsed DC for Enhanced Surface-Mechanical Properties

NASA Astrophysics Data System (ADS)

Maharana, H. S.; Lakra, Suprabha; Pal, S.; Basu, A.

2016-01-01

The present study explored the possibilities of improvement in the surface-mechanical properties of electrodeposited Cu-SiO2 composite coating and its underlying mechanism. Composite coatings were developed using SiO2-dispersed acidic copper sulfate electrolyte by direct current and pulse-current electro-codeposition techniques with variation of pulse frequencies at a fixed duty cycle. X-ray diffraction analysis of the coatings revealed information regarding the presence of various phases and crystallographic orientations of the deposited Cu matrix. Scanning electron microscopy and energy dispersive x-ray spectroscopy techniques were used to investigate the surface morphology and chemical composition of the coatings, respectively, and it was observed that SiO2 particles were uniformly distributed in the composite coatings. Surface roughness was found to be reduced with the increasing pulse frequency. The Vickers microhardness and ball-on-plate wear study showed improvement in surface-mechanical properties due to the formation of fine Cu matrix, dispersion strengthening due to homogeneously distributed SiO2 particles, and the preferred orientation of the Cu matrix. Marginal decrease in electrical conductivity with the increasing SiO2 content and pulse frequency was observed from the four-probe electrical conductivity measurement technique.

Tailored Surfaces/Assemblies for Molecular Plasmonics and Plasmonic Molecular Electronics.

PubMed

Lacroix, Jean-Christophe; Martin, Pascal; Lacaze, Pierre-Camille

2017-06-12

Molecular plasmonics uses and explores molecule-plasmon interactions on metal nanostructures for spectroscopic, nanophotonic, and nanoelectronic devices. This review focuses on tailored surfaces/assemblies for molecular plasmonics and describes active molecular plasmonic devices in which functional molecules and polymers change their structural, electrical, and/or optical properties in response to external stimuli and that can dynamically tune the plasmonic properties. We also explore an emerging research field combining molecular plasmonics and molecular electronics.

Electrowetting of Weak Polyelectrolyte-Coated Surfaces.

PubMed

Sénéchal, Vincent; Saadaoui, Hassan; Rodriguez-Hernandez, Juan; Drummond, Carlos

2017-05-23

Polymer coatings are commonly used to modify interfacial properties like wettability, lubrication, or biocompatibility. These properties are determined by the conformation of polymer molecules at the interface. Polyelectrolytes are convenient elementary bricks to build smart materials, given that polyion chain conformation is very sensitive to different environmental variables. Here we discuss the effect of an applied electric field on the properties of surfaces coated with poly(acrylic acid) brushes. By combining atomic force microscopy, quartz crystal microbalance, and contact angle experiments, we show that it is possible to precisely tune polyion chain conformation, surface adhesion, and surface wettability using very low applied voltages if the polymer grafting density and environmental conditions (pH and ionic strength) are properly formulated. Our results indicate that the effective ionization degree of the grafted weak polyacid can be finely controlled with the externally applied field, with important consequences for the macroscopic surface properties.

Choice of reconstructed tissue properties affects interpretation of lung EIT images.

PubMed

Grychtol, Bartłomiej; Adler, Andy

2014-06-01

Electrical impedance tomography (EIT) estimates an image of change in electrical properties within a body from stimulations and measurements at surface electrodes. There is significant interest in EIT as a tool to monitor and guide ventilation therapy in mechanically ventilated patients. In lung EIT, the EIT inverse problem is commonly linearized and only changes in electrical properties are reconstructed. Early algorithms reconstructed changes in resistivity, while most recent work using the finite element method reconstructs conductivity. Recently, we demonstrated that EIT images of ventilation can be misleading if the electrical contrasts within the thorax are not taken into account during the image reconstruction process. In this paper, we explore the effect of the choice of the reconstructed electrical properties (resistivity or conductivity) on the resulting EIT images. We show in simulation and experimental data that EIT images reconstructed with the same algorithm but with different parametrizations lead to large and clinically significant differences in the resulting images, which persist even after attempts to eliminate the impact of the parameter choice by recovering volume changes from the EIT images. Since there is no consensus among the most popular reconstruction algorithms and devices regarding the parametrization, this finding has implications for potential clinical use of EIT. We propose a program of research to develop reconstruction techniques that account for both the relationship between air volume and electrical properties of the lung and artefacts introduced by the linearization.

Mechanical, dielectric and surface analysis of hydroxyapatite doped anions for implantations

NASA Astrophysics Data System (ADS)

Helen, S.; Kumar, A. Ruban

2018-04-01

Calcium Phosphate has broad applications in field of medicine and in tissue engineering. In that hydroxyapatite is one of the calcium phosphate similar to bone and teeth mineral phase. The aim of this paper is to improve mechanical property of hydroxyapatite which has less mechanical strength by doping of ions. The ions increase its strength which can be used in various medical applications. Surface property of hydroxyapatite and electrical property of ion doped hydroxyapatite analyzed and shown that it can be used in implantations, coatings.

LaAlO{sub 3}/Si capacitors: Comparison of different molecular beam deposition conditions and their impact on electrical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pelloquin, Sylvain; Baboux, Nicolas; Albertini, David

2013-01-21

A study of the structural and electrical properties of amorphous LaAlO{sub 3} (LAO)/Si thin films fabricated by molecular beam deposition (MBD) is presented. Two substrate preparation procedures have been explored namely a high temperature substrate preparation technique-leading to a step and terraces surface morphology-and a chemical HF-based surface cleaning. The LAO deposition conditions were improved by introducing atomic plasma-prepared oxygen instead of classical molecular O{sub 2} in the chamber. An Au/Ni stack was used as the top electrode for its electrical characteristics. The physico-chemical properties (surface topography, thickness homogeneity, LAO/Si interface quality) and electrical performance (capacitance and current versus voltagemore » and TunA current topography) of the samples were systematically evaluated. Deposition conditions (substrate temperature of 550 Degree-Sign C, oxygen partial pressure settled at 10{sup -6} Torr, and 550 W of power applied to the O{sub 2} plasma) and post-depositions treatments were investigated to optimize the dielectric constant ({kappa}) and leakage currents density (J{sub Gate} at Double-Vertical-Line V{sub Gate} Double-Vertical-Line = Double-Vertical-Line V{sub FB}- 1 Double-Vertical-Line ). In the best reproducible conditions, we obtained a LAO/Si layer with a dielectric constant of 16, an equivalent oxide thickness of 8.7 A, and J{sub Gate} Almost-Equal-To 10{sup -2}A/cm{sup 2}. This confirms the importance of LaAlO{sub 3} as an alternative high-{kappa} for ITRS sub-22 nm technology node.« less

Liquid phase deposition of a space-durable, antistatic SnO₂ coating on Kapton.

PubMed

Gotlib-Vainstein, Katya; Gouzman, Irina; Girshevitz, Olga; Bolker, Asaf; Atar, Nurit; Grossman, Eitan; Sukenik, Chaim N

2015-02-18

Polyimides are widely used in thermal blankets covering the external surfaces of spacecrafts due to their space durability and their thermo-optical properties. However, they are susceptible to atomic oxygen (AO) erosion, the main hazard of low Earth orbit (LEO), and to electrical charging. This work demonstrates that liquid phase deposition (LPD) of 100 nm of tin oxide creates a protective coating on Kapton polyimide that has good adherence and is effective in preventing AO-induced surface erosion and in reducing electrical charging. The as-deposited tin oxide induces no significant changes in the original thermo-optical properties of the polymer and is effective in preventing electrostatic discharge (ESD). The durability of the oxide coating under AO attack was studied using oxygen RF plasma. The AO exposure did not result in any significant changes in surface morphology, thermo-optical, mechanical, and electrical properties of the tin oxide-coated Kapton. The erosion yield of tin oxide-coated Kapton was negligible after exposure to 6.4 × 10(20) O atoms·cm(-2) of LEO equivalent AO fluence, indicating a complete protection of Kapton by the LPD deposited coating. Moreover, the tin oxide coating is flexible enough so that its electrical conductivity stays within the desired range of antistatic materials despite mechanical manipulations. The advantages of liquid phase deposited oxides in terms of their not being line of site limited are well established. We now extend these advantages to coatings that reduce electrostatic discharge while still providing a high level of protection from AO erosion.

Graphene-interfaced electrical biosensor for label-free and sensitive detection of foodborne pathogenic E. coli O157:H7.

PubMed

Pandey, Ashish; Gurbuz, Yasar; Ozguz, Volkan; Niazi, Javed H; Qureshi, Anjum

2017-05-15

E. coli O157:H7 is an enterohemorrhagic bacteria responsible for serious foodborne outbreaks that causes diarrhoea, fever and vomiting in humans. Recent foodborne E. coli outbreaks has left a serious concern to public health. Therefore, there is an increasing demand for a simple, rapid and sensitive method for pathogen detection in contaminated foods. In this study, we developed a label-free electrical biosensor interfaced with graphene for sensitive detection of pathogenic bacteria. This biosensor was fabricated by interfacing graphene with interdigitated microelectrodes of capacitors that were biofunctionalized with E. coli O157:H7 specific antibodies for sensitive pathogenic bacteria detection. Here, graphene nanostructures on the sensor surface provided superior chemical properties such as high carrier mobility and biocompatibility with antibodies and bacteria. The sensors transduced the signal based on changes in dielectric properties (capacitance) through (i) polarization of captured cell-surface charges, (ii) cells' internal bioactivity, (iii) cell-wall's electronegativity or dipole moment and their relaxation and (iv) charge carrier mobility of graphene that modulated the electrical properties once the pathogenic E. coli O157:H7 captured on the sensor surface. Sensitive capacitance changes thus observed with graphene based capacitors were specific to E. coli O157:H7 strain with a sensitivity as low as 10-100 cells/ml. The proposed graphene based electrical biosensor provided advantages of speed, sensitivity, specificity and in-situ bacterial detection with no chemical mediators, represents a versatile approach for detection of a wide variety of other pathogens. Copyright © 2016 Elsevier B.V. All rights reserved.

Nanostructured Gd3+-TiO2 surfaces for self-cleaning application

NASA Astrophysics Data System (ADS)

Saif, M.; El-Molla, S. A.; Aboul-Fotouh, S. M. K.; Ibrahim, M. M.; Ismail, L. F. M.; Dahn, Douglas C.

2014-06-01

Preparation of self-cleaning surfaces based on lanthanide modified titanium dioxide nanoparticles has rarely been reported. In the present work, gadolinium doped titanium dioxide thin films (x mol Gd3+-TiO2 where x = 0.000, 0.005, 0.008, 0.010, 0.020 and 0.030 mol) were synthesized by sol-gel method and deposited using doctor-blade method. These films were characterized by studying their structural, optical and electrical properties. Doping with gadolinium decreases the band gap energy and increase conductivity of thin films. The photo self-cleaning activity in term of quantitative determination of the active oxidative species (rad OH) produced on the thin film surfaces was evaluated using fluorescent probe method. The results show that, the highly active thin film is the 0.020 Gd3+-TiO2. The structural, morphology, optical, electrical and photoactivity properties of Gd3+-TiO2 thin films make it promising surfaces for self-cleaning application. Mineralization of commercial textile dye (Remazol Red RB-133, RR) and durability using 0.020Gd3+-TiO2 film surface was studied.

End-of-Life Optical Property Predictions of White Conductive Thermal Control Coatings through Analysis of On-Orbit and Ground Based Testing Data

NASA Technical Reports Server (NTRS)

Hasegawa, Mark; Freese, Scott; Kauder, Lon; Triolo, Jack

2011-01-01

New system requirements pertaining to thermal optical properties and coating electrical properties are commonly specified on non-low earth orbit missions. An increasing number of projects are specifying coatings with a surface resistivity of less than lE-9 ohm/square to mitigate electrostatic charge buildup events over a range of operational temperatures. There are a limited number of coatings that. meet these electrical property requirements while having flight derived optical properties in representative environments. Goddard Space Flight Center Code 546, Contamination and Thermal Coatings Group has recently explored the variety of electrically conductive white coatings available through domestic vendors to evaluate properties to meet project requirements in a geostationary orbit. The lack of significant flight data in representative environments required the careful selection of samples in ground based tests to establish end of life thermal properties. Attention must be given to the origin and pedigree of samples used on past on-orbit experiments to insure that the present formulations for the materials are similar and will react in similar manner.

Electric organ discharges and near-field spatiotemporal patterns of the electromotive force in a sympatric assemblage of Neotropical electric knifefish.

PubMed

Waddell, Joseph C; Rodríguez-Cattáneo, Alejo; Caputi, Angel A; Crampton, William G R

2016-10-01

Descriptions of the head-to-tail electric organ discharge (ht-EOD) waveform - typically recorded with electrodes at a distance of approximately 1-2 body lengths from the center of the subject - have traditionally been used to characterize species diversity in gymnotiform electric fish. However, even taxa with relatively simple ht-EODs show spatiotemporally complex fields near the body surface that are determined by site-specific electrogenic properties of the electric organ and electric filtering properties of adjacent tissues and skin. In Brachyhypopomus, a pulse-discharging genus in the family Hypopomidae, the regional characteristics of the electric organ and the role that the complex 'near field' plays in communication and/or electrolocation are not well known. Here we describe, compare, and discuss the functional significance of diversity in the ht-EOD waveforms and near-field spatiotemporal patterns of the electromotive force (emf-EODs) among a species-rich sympatric community of Brachyhypopomus from the upper Amazon. Copyright © 2016 Elsevier Ltd. All rights reserved.

Comparison of Three E-Beam Techniques for Electric Field Imaging and Carrier Diffusion Length Measurement on the Same Nanowires.

PubMed

Donatini, F; de Luna Bugallo, Andres; Tchoulfian, Pierre; Chicot, Gauthier; Sartel, Corinne; Sallet, Vincent; Pernot, Julien

2016-05-11

Whereas nanowire (NW)-based devices offer numerous advantages compared to bulk ones, their performances are frequently limited by an incomplete understanding of their properties where surface effect should be carefully considered. Here, we demonstrate the ability to spatially map the electric field and determine the exciton diffusion length in NW by using an electron beam as the single excitation source. This approach is performed on numerous single ZnO NW Schottky diodes whose NW radius vary from 42.5 to 175 nm. The dominant impact of the surface on the NW properties is revealed through the comparison of three different physical quantities recorded on the same NW: electron-beam induced current, cathodoluminescence, and secondary electron signal. Indeed, the space charge region near the Schottky contact exhibits an unusual linear variation with reverse bias whatever the NW radius. On the contrary, the exciton diffusion length is shown to be controlled by the NW radius through surface recombination. This systematic comparison performed on a single ZnO NW demonstrates the power of these complementary techniques in understanding NW properties.

Effects of Pretreatment on the Electronic Properties of Plasma Enhanced Chemical Vapor Deposition Hetero-Epitaxial Graphene Devices

NASA Astrophysics Data System (ADS)

Zhang, Lian-Chang; Shi, Zhi-Wen; Yang, Rong; Huang, Jian

2014-09-01

Quasi-monolayer graphene is successfully grown by the plasma enhanced chemical vapor deposition heteroepitaxial method we reported previously. To measure its electrical properties, the prepared graphene is fabricated into Hall ball shaped devices by the routine micro-fabrication method. However, impurity molecules adsorbed onto the graphene surface will impose considerable doping effects on the one-atom-thick film material. Our experiment demonstrates that pretreatment of the device by heat radiation baking and electrical annealing can dramatically influence the doping state of the graphene and consequently modify the electrical properties. While graphene in the as-fabricated device is highly p-doped, as confirmed by the position of the Dirac point at far more than +60 V, baking treatment at temperatures around 180°C can significantly lower the doping level and reduce the conductivity. The following electrical annealing is much more efficient to desorb the extrinsic molecules, as confirmed by the in situ measurement, and as a result, further modify the doping state and electrical properties of the graphene, causing a considerable drop of the conductivity and a shifting of Dirac point from beyond +60 V to 0 V.

Chemical and electrical passivation of Si(1 1 1) surfaces

NASA Astrophysics Data System (ADS)

Tian, Fangyuan; Yang, Dan; Opila, Robert L.; Teplyakov, Andrew V.

2012-01-01

This paper compares the physical and chemical properties of hydrogen-passivated Si(1 1 1) single crystalline surfaces prepared by two main chemical preparation procedures. The modified RCA cleaning is commonly used to prepare atomically flat stable surfaces that are easily identifiable spectroscopically and are the standard for chemical functionalization of silicon. On the other hand electronic properties of these surfaces are sometimes difficult to control. A much simpler silicon surface preparation procedure includes HF dipping for a short period of time. This procedure yields an atomically rough surface, whose chemical identity is not well-defined. However, the surfaces prepared by this approach often exhibit exceptionally attractive electronic properties as determined by long charge carrier lifetimes. This work utilizes infrared spectroscopy and X-ray photoelectron spectroscopy to investigate chemical modification of the surfaces prepared by these two different procedures with PCl5 (leading to surface chlorination) and with short- and long-alkyl-chain alkenes (1-decene and 1-octodecene, respectively) and follows the electronic properties of the starting surfaces produced by measuring charge-carrier lifetimes.

Correlation between electrical direct current resistivity and plasmonic properties of CMOS compatible titanium nitride thin films.

PubMed

Viarbitskaya, S; Arocas, J; Heintz, O; Colas-Des-Francs, G; Rusakov, D; Koch, U; Leuthold, J; Markey, L; Dereux, A; Weeber, J-C

2018-04-16

Damping distances of surface plasmon polariton modes sustained by different thin titanium nitride (TiN) films are measured at the telecom wavelength of 1.55 μm. The damping distances are correlated to the electrical direct current resistivity of the films sustaining the surface plasmon modes. It is found that TiN/Air surface plasmon mode damping distances drop non-linearly from 40 to 16μm as the resistivity of the layers increases from 28 to 130μΩ.cm, respectively. The relevance of the direct current (dc) electrical resistivity for the characterization of TiN plasmonic properties is investigated in the framework of the Drude model, on the basis of parameters extracted from spectroscopic ellipsometry experiments. By probing a parametric space of realistic values for parameters of the Drude model, we obtain a nearly univocal dependence of the surface plasmon damping distance on the dc resistivity demonstrating the relevance of dc resistivity for the evaluation of the plasmonic performances of TiN at telecom frequencies. Finally, we show that better plasmonic performances are obtained for TiN films featuring a low content of oxygen. For low oxygen content and corresponding low resistivity, we attribute the increase of the surface plasmon damping distances to a lower confinement of the plasmon field into the metal and not to a decrease of the absorption of TiN.

Dielectrics for long term space exposure and spacecraft charging: A briefing

NASA Technical Reports Server (NTRS)

Frederickson, A. R.

1989-01-01

Charging of dielectrics is a bulk, not a surface property. Radiation driven charge stops within the bulk and is not quickly conducted to the surface. Very large electric fields develop in the bulk due to this stopped charge. At space radiation levels, it typically requires hours or days for the internal electric fields to reach steady state. The resulting electric fields are large enough to produce electrical failure within the insulator. This type failure is thought to produce nearly all electric discharge anomalies. Radiation also induces bond breakage, creates reactive radicals, displaces atoms and, in general, severely changes the chemistry of the solid state material. Electric fields can alter this process by reacting with charged species, driving them through the solid. Irradiated polymers often lose as much as a percent of their mass, or more, at exposures typical in space. Very different aging or contaminant emission can be induced by the stopped charge electric fields. These radiation effects are detailed.

Structural and electrical properties of AlN layers grown on silicon by reactive RF magnetron sputtering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bazlov, N., E-mail: n.bazlov@spbu.ru; Pilipenko, N., E-mail: nelly.pilipenko@gmail.com; Vyvenko, O.

2016-06-17

AlN films of different thicknesses were deposited on n-Si (100) substrates by reactive radio frequency (rf) magnetron sputtering. Dependences of structure and electrical properties on thickness of deposited films were researched. The structures of the films were analyzed with scanning electron microscopy (SEM) and with transmitting electron microscopy (TEM). Electrical properties of the films were investigated on Au-AlN-(n-Si) structures by means of current-voltage (I-V), capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) techniques. Electron microscopy investigations had shown that structure and chemical composition of the films were thickness stratified. Near silicon surface layer was amorphous aluminum oxide one contained trapsmore » of positive charges with concentration of about 4 × 10{sup 18} cm{sup −3}. Upper layers were nanocrystalline ones consisted of both wurzite AlN and cubic AlON nanocrystals. They contained traps both positive and negative charges which were situated within 30 nm distance from silicon surface. Surface densities of these traps were about 10{sup 12} cm{sup −2}. Electron traps with activation energies of (0.2 ÷ 0.4) eV and densities of about 10{sup 10} cm{sup −2} were revealed on interface between aluminum oxide layer and silicon substrate. Their densities varied weakly with the film thickness.« less

ESTEC wiring test programme materials related properties

NASA Technical Reports Server (NTRS)

Judd, M. D.

1994-01-01

Electrical wires are considered as EEE parts and are covered within the ESA SCC specification series (ESA SCC 3901/XXX). This specification defines the principal properties of the wires including insulation/lay-up and electrical properties. Some additional space related materials requirements are also included, requirements such as outgassing and silver plating thickness. If a project has additional materials requirements over and above those covered by the relevant SCC specification, then additional testing is required. This is especially true for crewed spacecraft. The following topics are discussed in this context: additional requirements for manned spacecraft; flammability; arc tracking; thermal decomposition; microbial surface growth; and ageing.

Thermoelectric studies of nanoporous thin films with adjusted pore-edge charges

NASA Astrophysics Data System (ADS)

Hao, Qing; Zhao, Hongbo; Xu, Dongchao

2017-03-01

In recent years, nanoporous thin films have been widely studied for thermoelectric applications. High thermoelectric performance is reported for nanoporous Si films, which is attributed to the dramatically reduced lattice thermal conductivity and bulk-like electrical properties. Porous materials can also be used in gas sensing applications by engineering the surface-trapped charges on pore edges. In this work, an analytical model is developed to explore the relationship between the thermoelectric properties and pore-edge charges in a periodic two-dimensional nanoporous material. The presented model can be widely used to analyze the measured electrical properties of general nanoporous thin films and two-dimensional materials.

Electrochemical Deposition Of Conductive Copolymers

NASA Technical Reports Server (NTRS)

Nagasubramanian, Ganesan; Distefano, Salvador; Liang, Ranty H.

1991-01-01

Experiments show electrically conductive films are deposited on glassy carbon or indium tin oxide substrates by electrochemical polymerization of N-{(3-trimethoxy silyl) propyl} pyrrole or copolymerization with pyrrole. Copolymers of monomer I and pyrrole exhibit desired electrical conductivity as well as desired adhesion and other mechanical properties. When fully developed, new copolymerization process useful in making surface films of selectable conductivity.

Beyond the Point Charge: Equipotential Surfaces and Electric Fields of Various Charge Configurations

ERIC Educational Resources Information Center

Phillips, Jeffrey A.; Sanny, Jeff; Berube, David; Hoemke, Anatol

2017-01-01

A laboratory experiment often performed in an introductory electricity and magnetism course involves the mapping of equipotential lines on a conductive sheet between two objects at different potentials. In this article, we describe how we have expanded this experiment so that it can be used to illustrate the electrostatic properties of conductors.…

Electrically Conductive Anodized Aluminum Surfaces

NASA Technical Reports Server (NTRS)

Nguyen, Trung Hung

2006-01-01

Anodized aluminum components can be treated to make them sufficiently electrically conductive to suppress discharges of static electricity. The treatment was conceived as a means of preventing static electric discharges on exterior satin-anodized aluminum (SAA) surfaces of spacecraft without adversely affecting the thermal-control/optical properties of the SAA and without need to apply electrically conductive paints, which eventually peel off in the harsh environment of outer space. The treatment can also be used to impart electrical conductivity to anodized housings of computers, medical electronic instruments, telephoneexchange equipment, and other terrestrial electronic equipment vulnerable to electrostatic discharge. The electrical resistivity of a typical anodized aluminum surface layer lies between 10(exp 11) and 10(exp 13) Omega-cm. To suppress electrostatic discharge, it is necessary to reduce the electrical resistivity significantly - preferably to < or = 10(exp 9) Omega-cm. The present treatment does this. The treatment is a direct electrodeposition process in which the outer anodized surface becomes covered and the pores in the surface filled with a transparent, electrically conductive metal oxide nanocomposite. Filling the pores with the nanocomposite reduces the transverse electrical resistivity and, in the original intended outer-space application, the exterior covering portion of the nanocomposite would afford the requisite electrical contact with the outer-space plasma. The electrical resistivity of the nanocomposite can be tailored to a value between 10(exp 7) and 10(exp 12) Omega-cm. Unlike electrically conductive paint, the nanocomposite becomes an integral part of the anodized aluminum substrate, without need for adhesive bonding material and without risk of subsequent peeling. The electrodeposition process is compatible with commercial anodizing production lines. At present, the electronics industry uses expensive, exotic, electrostaticdischarge- suppressing finishes: examples include silver impregnated anodized, black electroless nickel, black chrome, and black copper. In comparison with these competing finishes, the present nanocomposite finishes are expected to cost 50 to 20 percent less and to last longer.

EFFECT OF IONIC STRENGTH ON ACID-BASE PROPERTIES OF VICINAL WATER

EPA Science Inventory

Surface research over the past 75 years has clearly shown that water under the influence of electrical and magnetic force fields (vicinal water) does not have the same properties as bulk water. Vicinal water is vital in influencing and maintaining the critical spatial and confor...

Effects of functionalization on thermal properties of single-wall and multi-wall carbon nanotube-polymer nanocomposites.

PubMed

Gulotty, Richard; Castellino, Micaela; Jagdale, Pravin; Tagliaferro, Alberto; Balandin, Alexander A

2013-06-25

Carboxylic functionalization (-COOH groups) of carbon nanotubes is known to improve their dispersion properties and increase the electrical conductivity of carbon-nanotube-polymer nanocomposites. We have studied experimentally the effects of this type of functionalization on the thermal conductivity of the nanocomposites. It was found that while even small quantities of carbon nanotubes (~1 wt %) can increase the electrical conductivity, a larger loading fraction (~3 wt %) is required to enhance the thermal conductivity of nanocomposites. Functionalized multi-wall carbon nanotubes performed the best as filler material leading to a simultaneous improvement of the electrical and thermal properties of the composites. Functionalization of the single-wall carbon nanotubes reduced the thermal conductivity enhancement. The observed trends were explained by the fact that while surface functionalization increases the coupling between carbon nanotube and polymer matrix, it also leads to formation of defects, which impede the acoustic phonon transport in the single-wall carbon nanotubes. The obtained results are important for applications of carbon nanotubes and graphene flakes as fillers for improving thermal, electrical and mechanical properties of composites.

Electronic structure and bonding properties of potassium (K) on graphite under external electric field.

NASA Astrophysics Data System (ADS)

Tapia, Alejandro; Canto, Gabriel

2005-03-01

The effect of an external electric field on the potassium (K) adsorption on the graphite surface, are studied by means of first-principles total-energy calculations. The results were obtained with the pseudopotentials LCAO method (SIESTA code) and the Generalized Gradient Approximation (GGA) for the exchange-correlation potential. The structural parameters, bonding properties, and electronic structure of the K-graphite system are studied in the triangular (2x2) overlayer phase as a function of the external electric field magnitude. We find an important change in the K-graphite bonding as a consequence of the charge transfer from the adatom towards the substrate induced by the electric field. The results are discussed in the light of the experimental observed difussion of K into graphite induced by external electric fields. This work was supported by Consejo Nacional de Ciencia y Tecnolog'ia (CONACYT, M'exico) under Grants No. 43830-F and No. 44831-F.

International Congress on Glass XII (in several languages)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Doremus, R H; LaCourse, W C; Mackenzie, J D

1980-01-01

A total of 158 papers are included under nine headings: structure and glass formation; optical properties; electrical and magnetic properties; mechanical properties and relaxation; mass transport; chemical durability and surfaces; nucleation; crystallization; and glass ceramics; processing; and automatic controls. Separate abstracts were prepared for eight papers; four of the remaining papers had been processed previously for the data base. (DLC)

On the influence of various physicochemical properties of the CNTs based implantable devices on the fibroblasts' reaction in vitro.

PubMed

Benko, Aleksandra; Frączek-Szczypta, Aneta; Menaszek, Elżbieta; Wyrwa, Jan; Nocuń, Marek; Błażewicz, Marta

2015-11-01

Coating the material with a layer of carbon nanotubes (CNTs) has been a subject of particular interest for the development of new biomaterials. Such coatings, made of properly selected CNTs, may constitute an implantable electronic device that facilitates tissue regeneration both by specific surface properties and an ability to electrically stimulate the cells. The goal of the presented study was to produce, evaluate physicochemical properties and test the applicability of highly conductible material designed as an implantable electronic device. Two types of CNTs with varying level of oxidation were chosen. The process of coating involved suspension of the material of choice in the diluent followed by the electrophoretic deposition to fabricate layers on the surface of a highly biocompatible metal-titanium. Presented study includes an assessment of the physicochemical properties of the material's surface along with an electrochemical evaluation and in vitro biocompatibility, cytotoxicity and apoptosis studies in contact with the murine fibroblasts (L929) in attempt to answer the question how the chemical composition and CNTs distribution in the layer alters the electrical properties of the sample and whether any of these properties have influenced the overall biocompatibility and stimulated adhesion of fibroblasts. The results indicate that higher level of oxidation of CNTs yielded materials more conductive than the metal they are deposited on. In vitro study revealed that both materials were biocompatible and that the cells were not affected by the amount of the functional group and the morphology of the surface they adhered to.

Graphite pellicles, methods of formation and properties

NASA Astrophysics Data System (ADS)

Topala, P.; Marin, L.; Besliu, V.; Stoicev, P.; Ojegov, A.; Cosovschii, P.

2015-11-01

The paper presents the results of experimental investigations aimed at the establishing the composition and the functional properties of the graphite pellicles formed on the metal surfaces by the action of plasma in the air media at normal pressure applying electrical discharges in impulse (EDI). It shows that they have the same behavior characteristics as fullerene, avoiding the stick effect between metal surfaces and between metal and liquid glass at temperatures of the order of 400-1200 °C.

Effect of deposition temperature on the properties of Al-doped ZnO films prepared by pulsed DC magnetron sputtering for transparent electrodes in thin-film solar cells

NASA Astrophysics Data System (ADS)

Kim, Doo-Soo; Park, Ji-Hyeon; Shin, Beom-Ki; Moon, Kyeong-Ju; Son, Myoungwoo; Ham, Moon-Ho; Lee, Woong; Myoung, Jae-Min

2012-10-01

A simple but scalable approach to the production of surface-textured Al-doped ZnO(AZO) films for low-cost transparent electrode applications in thin-film solar cells is introduced in this study by combining pulsed dc magnetron sputtering (PDMS) with wet etching in sequence. First, structural, electrical, and optical properties of the AZO films prepared by a PDMS were investigated as functions of deposition temperature to obtain transparent electrode films that can be used as indium-free alternative to ITO electrodes. Increase in the deposition temperature to 230 °C accompanied the improvement in crystalline quality and doping efficiency, which enabled the lowest electrical resistivity of 4.16 × 10-4 Ω cm with the carrier concentration of 1.65 × 1021 cm-3 and Hall mobility of 11.3 cm2/V s. The wet etching of the films in a diluted HCl solution resulted in surface roughening via the formation of crater-like structures without significant degradation in the electrical properties, which is responsible for the enhanced light scattering capability required for anti-reflective electrodes in thin film solar cells.

Electrical and optical percolations in PMMA/GNP composite films

NASA Astrophysics Data System (ADS)

Arda, Ertan; Mergen, Ömer Bahadır; Pekcan, Önder

2018-05-01

Effects of graphene nanoplatelet (GNP) addition on the electrical conductivity and optical absorbance of poly(methyl methacrylate)/graphene nanoplatelet (PMMA/GNP) composite films were studied. Optical absorbance and two point probe resistivity techniques were used to determine the variations of the optical and electrical properties of the composites, respectively. Absorbance intensity, A, and surface resistivity, Rs, of the composite films were monitored as a function of GNP mass fraction (M) at room temperature. Absorbance intensity values of the composites were increased and surface resistivity values were decreased by increasing the content of GNP in the composite. Electrical and optical percolation thresholds of composite films were determined as Mσ = 27.5 wt.% and Mop = 26.6 wt.%, respectively. The conductivity and the optical results were attributed to the classical and site percolation theories, respectively. Optical (βop) and electrical (βσ) critical exponents were calculated as 0.40 and 1.71, respectively.

Effect of co-doping process on topography, optical and electrical properties of ZnO nanostructured

NASA Astrophysics Data System (ADS)

Mohamed, R.; Mamat, M. H.; Malek, M. F.; Ismail, A. S.; Yusoff, M. M.; Syamsir, S. A.; Khusaimi, Z.; Rusop, M.

2018-05-01

We investigated of Undoped ZnO and Magnesium (Mg)-Aluminium (Al) co-doped Zinc Oxide (MAZO) nanostructured films were prepared by sol gel spin coating technique. The surface topography was analyzed using Atomic Force Microscopy (AFM). Based on the AFM results, Root Mean Square (RMS) of MAZO films have rougher surface compared to pure ZnO films. The optical and electrical properties of thin film samples were characterized using Uv-Vis spectroscopy and two point probes, current-voltage (I-V) measurements. The transmittance spectra for both thin samples was above 80% in the visible wavelength. The MAZO film shows the highest conductivity compared to pure ZnO films. This result indicates that the improvement of carrier mobility throughout doping process and possibly contribute by extra ion charge.

Electrically conductive nanostructured silver doped zinc oxide (Ag:ZnO) prepared by solution-immersion technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Afaah, A. N., E-mail: afaahabdullah@yahoo.com; Asib, N. A. M., E-mail: amierahasib@yahoo.com; Aadila, A., E-mail: aadilaazizali@gmail.com

2016-07-06

p-type ZnO films have been fabricated on ZnO-seeded glass substrate, using AgNO{sub 3} as a source of silver dopant by facile solution-immersion. Cleaned glass substrate were seeded with ZnO by mist-atomisation, and next the seeded substrates were immersed in Ag:ZnO solution. The effects of Ag doping concentration on the Ag-doped ZnO have been investigated. The substrates were immersed in different concentrations of Ag dopant with variation of 0, 1, 3, 5 and 7 at. %. The surface morphology of the films was characterized by field emission scanning electron microscope (FESEM). In order to investigate the electrical properties, the films weremore » characterized by Current-Voltage (I-V) measurement. FESEM micrographs showed uniform distribution of nanostructured ZnO and Ag:ZnO. Besides, the electrical properties of Ag-doped ZnO were also dependent on the doping concentration. The I-V measurement result indicated the electrical properties of 1 at. % Ag:ZnO thin film owned highest electrical conductivity.« less

Method for the thermal characterization, visualization, and integrity evaluation of conducting material samples or complex structures

DOEpatents

Ortiz, Marcos G.

1992-01-01

A method for modeling a conducting material sample or structure (herein called a system) as at least two regions which comprise an electrical network of resistances, for measuring electric resistance between at least two selected pairs of external leads attached to the surface of the system, wherein at least one external lead is attached to the surface of each of the regions, and, using basic circuit theory, for translating measured resistances into temperatures or thermophysical properties in corresponding regions of the system.

Method for the thermal characterization, visualization, and integrity evaluation of conducting material samples or complex structures

DOEpatents

Ortiz, M.G.

1992-11-24

Disclosed is a method for modeling a conducting material sample or structure (herein called a system) as at least two regions which comprise an electrical network of resistances, for measuring electric resistance between at least two selected pairs of external leads attached to the surface of the system, wherein at least one external lead is attached to the surface of each of the regions, and, using basic circuit theory, for translating measured resistances into temperatures or thermophysical properties in corresponding regions of the system. 16 figs.

Ferroelectrics: A pathway to switchable surface chemistry and catalysis

NASA Astrophysics Data System (ADS)

Kakekhani, Arvin; Ismail-Beigi, Sohrab; Altman, Eric I.

2016-08-01

It has been known for more than six decades that ferroelectricity can affect a material's surface physics and chemistry thereby potentially enhancing its catalytic properties. Ferroelectrics are a class of materials with a switchable electrical polarization that can affect surface stoichiometry and electronic structure and thus adsorption energies and modes; e.g., molecular versus dissociative. Therefore, ferroelectrics may be utilized to achieve switchable surface chemistry whereby surface properties are not fixed but can be dynamically controlled by, for example, applying an external electric field or modulating the temperature. Several important examples of applications of ferroelectric and polar materials in photocatalysis and heterogeneous catalysis are discussed. In photocatalysis, the polarization direction can control band bending at water/ferroelectric and ferroelectric/semiconductor interfaces, thereby facilitating charge separation and transfer to the electrolyte and enhancing photocatalytic activity. For gas-surface interactions, available results suggest that using ferroelectrics to support catalytically active transition metals and oxides is another way to enhance catalytic activity. Finally, the possibility of incorporating ferroelectric switching into the catalytic cycle itself is described. In this scenario, a dynamic collaboration of two polarization states can be used to drive reactions that have been historically challenging to achieve on surfaces with fixed chemical properties (e.g., direct NOx decomposition and the selective partial oxidation of methane). These predictions show that dynamic modulation of the polarization can help overcome some of the fundamental limitations on catalytic activity imposed by the Sabatier principle.

Applications for Electrical Impedance Tomography (EIT) and Electrical Properties of the Human Body.

PubMed

Lymperopoulos, Georgios; Lymperopoulos, Panagiotis; Alikari, Victoria; Dafogianni, Chrisoula; Zyga, Sofia; Margari, Nikoletta

2017-01-01

Electrical Impedance Tomography (EIT) is a promising application that displays changes in conductivity within a body. The basic principle of the method is the repeated measurement of surface voltages of a body, which are a result of rolling injection of known and small-volume sinusoidal AC current to the body through the electrodes attached to its surface. This method finds application in biomedicine, biology and geology. The objective of this paper is to present the applications of Electrical Impedance Tomography, along with the method's capabilities and limitations due to the electrical properties of the human body. For this purpose, investigation of existing literature has been conducted, using electronic databases, PubMed, Google Scholar and IEEE Xplore. In addition, there was a secondary research phase, using paper citations found during the first research phase. It should be noted that Electrical Impedance Tomography finds use in a plethora of medical applications, as the different tissues of the body have different conductivities and dielectric constants. Main applications of EIT include imaging of lung function, diagnosis of pulmonary embolism, detection of tumors in the chest area and diagnosis and distinction of ischemic and hemorrhagic stroke. EIT advantages include portability, low cost and safety, which the method provide, since it is a noninvasive imaging method that does not cause damage to the body. The main disadvantage of the method, which blocks its wider spread, appears in the image composition from the voltage measurements, which are conducted by electrodes placed on the periphery of the body, because the injected currents are affected nonlinearly by the general distribution of the electrical properties of the body. Furthermore, the complex impedance of the skin-electrode interface can be modelled by using a capacitor and two resistor, as a result of skin properties. In conclusion, Electrical Impedance Tomography is a promising method for the development of noninvasive diagnostic medicine, since it is able to provide imaging of the interior of the human body in real time without causing harm or putting the human body in risk.

Calculation of surface potentials at the silica–water interface using molecular dynamics: Challenges and opportunities

NASA Astrophysics Data System (ADS)

Lowe, Benjamin M.; Skylaris, Chris-Kriton; Green, Nicolas G.; Shibuta, Yasushi; Sakata, Toshiya

2018-04-01

Continuum-based methods are important in calculating electrostatic properties of interfacial systems such as the electric field and surface potential but are incapable of providing sufficient insight into a range of fundamentally and technologically important phenomena which occur at atomistic length-scales. In this work a molecular dynamics methodology is presented for interfacial electric field and potential calculations. The silica–water interface was chosen as an example system, which is highly relevant for understanding the response of field-effect transistors sensors (FET sensors). Detailed validation work is presented, followed by the simulated surface charge/surface potential relationship. This showed good agreement with experiment at low surface charge density but at high surface charge density the results highlighted challenges presented by an atomistic definition of the surface potential. This methodology will be used to investigate the effect of surface morphology and biomolecule addition; both factors which are challenging using conventional continuum models.

Self-assembled tunable networks of sticky colloidal particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Demortiere, Arnaud; Snezhko, Oleksiy Alexey; Sapozhnikov, Maksim

Self-assembled tunable networks of microscopic polymer fibers ranging from wavy colloidal "fur" to highly interconnected networks are created from polymer systems and an applied electric field. The networks emerge via dynamic self-assembly in an alternating (ac) electric field from a non-aqueous suspension of "sticky" polymeric colloidal particles with a controlled degree of polymerization. The resulting architectures are tuned by the frequency and amplitude of the electric field and surface properties of the particles.

Counterbalancing of morphology and conductivity of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate based flexible devices.

PubMed

Jang, Woongsik; Ahn, Sunyong; Park, Soyun; Park, Jong Hyeok; Wang, Dong Hwan

2016-12-01

The importance of conductive polymer electrodes with a balance between the morphology and electrical conductivity for flexible organic photovoltaic properties has been demonstrated. Highly transparent PEDOT:PSS anodes with controlled conductivity and surface properties were realized by insertion of dimethyl sulfoxide (DMSO) and a fluorosurfactant (Zonyl) as efficient additives and used for flexible organic photovoltaic cells (OPVs) which are based on a bulk-heterojunction of polythieno[3,4-b]-thiophene-co-benzodithiophene (PTB7):[6,6]phenyl-C 71 -butyric acid methyl ester (PC 71 BM). We investigated the correlation between the electrical properties of PEDOT:PSS electrodes and their influences on the surface morphology of the active materials (PTB7:PC 71 BM). When the device was prepared from the PEDOT:PSS layer functioning as an anode of OPV through an optimized ratio of 5 vol% of DMSO and 0.1 wt% of fluorosurfactant, the devices exhibited improved fill factor (FF) due to the enhanced coverage of PEDOT:PSS films. These results correlate with reduced photoluminescence and increased charge extraction as seen through Raman spectroscopy and electrical analysis, respectively. The conductive polymer electrode with the balance between the morphology and electrical conductivity can be a useful replacement for brittle electrodes such as those made of indium tin oxide (ITO) as they are more resistant to cracking and bending conditions, which will contribute to the long-term operation of flexible devices.

Influence of 400 keV carbon ion implantation on structural, optical and electrical properties of PMMA

NASA Astrophysics Data System (ADS)

Arif, Shafaq; Rafique, M. Shahid; Saleemi, Farhat; Sagheer, Riffat; Naab, Fabian; Toader, Ovidiu; Mahmood, Arshad; Rashid, Rashad; Mahmood, Mazhar

2015-09-01

Ion implantation is a useful technique to modify surface properties of polymers without altering their bulk properties. The objective of this work is to explore the 400 keV C+ ion implantation effects on PMMA at different fluences ranging from 5 × 1013 to 5 × 1015 ions/cm2. The surface topographical examination of irradiated samples has been performed using Atomic Force Microscope (AFM). The structural and chemical modifications in implanted PMMA are examined by Raman and Fourier Infrared Spectroscopy (FTIR) respectively. The effects of carbon ion implantation on optical properties of PMMA are investigated by UV-Visible spectroscopy. The modifications in electrical conductivity have been measured using a four point probe technique. AFM images reveal a decrease in surface roughness of PMMA with an increase in ion fluence from 5 × 1014 to 5 × 1015 ions/cm2. The existence of amorphization and sp2-carbon clusterization has been confirmed by Raman and FTIR spectroscopic analysis. The UV-Visible data shows a prominent red shift in absorption edge as a function of ion fluence. This shift displays a continuous reduction in optical band gap (from 3.13 to 0.66 eV) due to formation of carbon clusters. Moreover, size of carbon clusters and photoconductivity are found to increase with increasing ion fluence. The ion-induced carbonaceous clusters are believed to be responsible for an increase in electrical conductivity of PMMA from (2.14 ± 0.06) × 10-10 (Ω-cm)-1 (pristine) to (0.32 ± 0.01) × 10-5 (Ω-cm)-1 (irradiated sample).

Interpretation of the human skin biotribological behaviour after tape stripping

PubMed Central

Pailler-Mattei, C.; Guerret-Piécourt, C.; Zahouani, H.; Nicoli, S.

2011-01-01

The present study deals with the modification of the human skin biotribological behaviour after tape stripping. The tape-stripping procedure consists in the sequential application and removal of adhesive tapes on the skin surface in order to remove stratum corneum (SC) layers, which electrically charges the skin surface. The skin electric charges generated by tape stripping highly change the skin friction behaviour by increasing the adhesion component of the skin friction coefficient. It has been proposed to rewrite the friction adhesion component as the sum of two terms: the first classical adhesion term depending on the intrinsic shear strength, τ0, and the second term depending on the electric shear strength, τelec. The experimental results allowed to estimate a numerical value of the electric shear strength τelec. Moreover, a plan capacitor model with a dielectric material inside was used to modelize the experimental system. This physical model permitted to evaluate the friction electric force and the electric shear strength values to calculate the skin friction coefficient after the tape stripping. The comparison between the experimental and the theoretical value of the skin friction coefficient after the tape stripping has shown the importance of the electric charges on skin biotribological behaviour. The static electric charges produced by tape stripping on the skin surface are probably able to highly modify the interaction of formulations with the skin surface and their spreading properties. This phenomenon, generally overlooked, should be taken into consideration as it could be involved in alteration of drug absorption. PMID:21227961

Interpretation of the human skin biotribological behaviour after tape stripping.

PubMed

Pailler-Mattei, C; Guerret-Piécourt, C; Zahouani, H; Nicoli, S

2011-07-06

The present study deals with the modification of the human skin biotribological behaviour after tape stripping. The tape-stripping procedure consists in the sequential application and removal of adhesive tapes on the skin surface in order to remove stratum corneum (SC) layers, which electrically charges the skin surface. The skin electric charges generated by tape stripping highly change the skin friction behaviour by increasing the adhesion component of the skin friction coefficient. It has been proposed to rewrite the friction adhesion component as the sum of two terms: the first classical adhesion term depending on the intrinsic shear strength, τ(0), and the second term depending on the electric shear strength, τ(elec). The experimental results allowed to estimate a numerical value of the electric shear strength τ(elec). Moreover, a plan capacitor model with a dielectric material inside was used to modelize the experimental system. This physical model permitted to evaluate the friction electric force and the electric shear strength values to calculate the skin friction coefficient after the tape stripping. The comparison between the experimental and the theoretical value of the skin friction coefficient after the tape stripping has shown the importance of the electric charges on skin biotribological behaviour. The static electric charges produced by tape stripping on the skin surface are probably able to highly modify the interaction of formulations with the skin surface and their spreading properties. This phenomenon, generally overlooked, should be taken into consideration as it could be involved in alteration of drug absorption.

Comparison of the physical, chemical and electrical properties of ALD Al 2 O 3 on c- and m- plane GaN: Comparison of the physical, chemical and electrical properties of ALD Al 2 O 3 on c- and m- plane GaN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wei, D.; Hossain, T.; Nepal, N.

2014-02-01

Our study compares the physical, chemical and electrical properties of Al 2O 3 thin films deposited on gallium polar c- and nonpolar m -plane GaN substrates by atomic layer deposition (ALD). Correlations were sought between the film's structure, composition, and electrical properties. The thickness of the Al 2O 3 films was 19.2 nm as determined from a Si witness sample by spectroscopic ellipsometry. We measured the gate dielectric was slightly aluminum-rich (Al:O=1:1.3) from X-ray photoelectron spectroscopy (XPS) depth profile, and the oxide-semiconductor interface carbon concentration was lower on c -plane GaN. The oxide's surface morphology was similar on both substrates,more » but was smoothest on c -plane GaN as determined by atomic force microscopy (AFM). Circular capacitors (50-300 μm diameter) with Ni/Au (20/100 nm) metal contacts on top of the oxide were created by standard photolithography and e-beam evaporation methods to form metal-oxide-semiconductor capacitors (MOSCAPs). Moreover, the alumina deposited on c -plane GaN showed less hysteresis (0.15 V) than on m -plane GaN (0.24 V) in capacitance-voltage (CV) characteristics, consistent with its better quality of this dielectric as evidenced by negligible carbon contamination and smooth oxide surface. These results demonstrate the promising potential of ALD Al 2O 3 on c -plane GaN, but further optimization of ALD is required to realize the best properties of Al 2O 3 on m -plane GaN.« less

Physical and electrical characterizations of AlGaN/GaN MOS gate stacks with AlGaN surface oxidation treatment

NASA Astrophysics Data System (ADS)

Yamada, Takahiro; Watanabe, Kenta; Nozaki, Mikito; Shih, Hong-An; Nakazawa, Satoshi; Anda, Yoshiharu; Ueda, Tetsuzo; Yoshigoe, Akitaka; Hosoi, Takuji; Shimura, Takayoshi; Watanabe, Heiji

2018-06-01

The impacts of inserting ultrathin oxides into insulator/AlGaN interfaces on their electrical properties were investigated to develop advanced AlGaN/GaN metal–oxide–semiconductor (MOS) gate stacks. For this purpose, the initial thermal oxidation of AlGaN surfaces in oxygen ambient was systematically studied by synchrotron radiation X-ray photoelectron spectroscopy (SR-XPS) and atomic force microscopy (AFM). Our physical characterizations revealed that, when compared with GaN surfaces, aluminum addition promotes the initial oxidation of AlGaN surfaces at temperatures of around 400 °C, followed by smaller grain growth above 850 °C. Electrical measurements of AlGaN/GaN MOS capacitors also showed that, although excessive oxidation treatment of AlGaN surfaces over around 700 °C has an adverse effect, interface passivation with the initial oxidation of the AlGaN surfaces at temperatures ranging from 400 to 500 °C was proven to be beneficial for fabricating high-quality AlGaN/GaN MOS gate stacks.

Effect of different atmospheres on the electrical contact performance of electronic components under fretting wear

NASA Astrophysics Data System (ADS)

Liu, Xin-Long; Cai, Zhen-Bing; Cui, Ye; Liu, Shan-Bang; Xu, Xiao-Jun; Zhu, Min-Hao

2018-04-01

The effects of oxide etch on the surface morphology of metals for industrial application is a common cause of electrical contacts failure, and it has becomes a more severe problem with the miniaturization of modern electronic devices. This study investigated the effects of electrical contact resistance on the contactor under three different atmospheres (oxygen, air, and nitrogen) based on 99.9% copper/pogo pins contacts through fretting experiments. The results showed the minimum and stable electrical contact resistance value when shrouded in the nitrogen environment and with high friction coefficient. The rich oxygen environment promotes the formation of cuprous oxide, thereby the electrical contact resistance increases. Scanning electron microscope microscopy and electron probe microanalysis were used to analyze the morphology and distribution of elements of the wear area, respectively. The surface product between contacts was investigated by x-ray photoelectron spectroscopy analysis to explain the different electrical contact properties of the three tested samples during fretting.

Optical and electrical stability of viral-templated copper sulfide (Cu1.8S) films

NASA Astrophysics Data System (ADS)

Shahriar Zaman, Mohammed; Bernard Grajeda, Gabriel; Haberer, Elaine D.

2014-04-01

The optical and electrical stabilities of viral-templated non-stoichiometric copper sulfide, digenite (Cu1.8S) films were investigated. The films were composed of large agglomerates of randomly aligned Cu1.8S-coated M13 filamentous phage. Free carrier optical absorption associated with localized surface plasmon resonance (LSPR) was observed in the near infrared spectral region, and the films were electrically active, displaying a linear current-voltage relationship. Under ambient conditions, the magnitude of the LSPR absorption increased, following a power law relationship with time, and the electrical resistance of viral-templated films decreased significantly. In contrast, the resistance of films stored under low oxygen, low humidity conditions experienced a smaller reduction in electrical resistance. Changes in optical and electrical film properties under ambient conditions were associated with an increase in free carrier concentration within the copper chalcogenide material due to oxygen exposure. X-ray photoelectron spectroscopy was used to relate this increase in free carrier concentration to compositional changes on the viral-templated material surface.

Al-Coated Conductive Fiber Filters for High-Efficiency Electrostatic Filtration: Effects of Electrical and Fiber Structural Properties.

PubMed

Choi, Dong Yun; An, Eun Jeong; Jung, Soo-Ho; Song, Dong Keun; Oh, Yong Suk; Lee, Hyung Woo; Lee, Hye Moon

2018-04-10

Through the direct decomposition of an Al precursor ink AlH 3 {O(C 4 H 9 ) 2 }, we fabricated an Al-coated conductive fiber filter for the efficient electrostatic removal of airborne particles (>99%) with a low pressure drop (~several Pascals). The effects of the electrical and structural properties of the filters were investigated in terms of collection efficiency, pressure drop, and particle deposition behavior. The collection efficiency did not show a significant correlation with the extent of electrical conductivity, as the filter is electrostatically charged by the metallic Al layers forming electrical networks throughout the fibers. Most of the charged particles were collected via surface filtration by Coulombic interactions; consequently, the filter thickness had little effect on the collection efficiency. Based on simulations of various fiber structures, we found that surface filtration can transition to depth filtration depending on the extent of interfiber distance. Therefore, the effects of structural characteristics on collection efficiency varied depending on the degree of the fiber packing density. This study will offer valuable information pertaining to the development of a conductive metal/polymer composite air filter for an energy-efficient and high-performance electrostatic filtration system.

Could binary mixture of Nd-Ni ions control the electrical behavior of strontium-barium M-type hexaferrite nanoparticles?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iqbal, Muhammad Javed, E-mail: mjiqauchem@yahoo.com; Farooq, Saima

2011-05-15

Research highlights: {yields} Strontium-barium hexaferrites (Sr{sub 0.5}Ba{sub 0.5}Fe{sub 12}O{sub 19}) in single magnetoplumbite phase solid structure are synthesized by the co-precipitation method. {yields} Structural and electrical properties of Nd-Ni substituted ferrites are investigated. {yields} These ferrite materials possess high electrical resistivity (108 {Omega} cm) that is essential to curb the eddy current loss, which is pre-requisite for surface mount devices. -- Abstract: Cationic substitution in M-type hexaferrites is considered to be an important tool for modification of their electrical properties. This work is part of our comprehensive study on the synthesis and characterization of Nd-Ni doped strontium-barium hexaferrite nanomaterials ofmore » nominal composition Sr{sub 0.5}Ba{sub 0.5-x}Nd{sub x}Fe{sub 12-y}Ni{sub y}O{sub 19} (x = 0.00-0.10; y = 0.00-1.00). Doping with this binary mixture modulates the physical and electrical properties of strontium-barium hexaferrite nanoparticles. Structural and electrical properties of the co-precipitated ferrites are investigated using state-of-the-art techniques. The results of X-ray diffraction analysis reveal that the lattice parameters and cell volume are inversely related to the dopant content. Temperature dependent DC-electrical resistivity measurements infer that resistivity of strontium-barium hexaferrites decreases from 1.8 x 10{sup 10} to 2.0 x 10{sup 8} {Omega} cm whereas the drift mobility, dielectric constant and dielectric loss tangent are directly related to the Nd-Ni content. The results of the study demonstrate a relationship between the modulation of electrical properties of substituted ferrites and nature of cations and their lattice site occupancy.« less

Propagation behavior of two transverse surface waves in a three-layer piezoelectric/piezomagnetic structure

NASA Astrophysics Data System (ADS)

Nie, Guoquan; Liu, Jinxi; Liu, Xianglin

2017-10-01

Propagation of transverse surface waves in a three-layer system consisting of a piezoelectric/piezomagnetic (PE/PM) bi-layer bonded on an elastic half-space is theoretically investigated in this paper. Dispersion relations and mode shapes for transverse surface waves are obtained in closed form under electrically open and shorted boundary conditions at the upper surface. Two transverse surface waves related both to Love-type wave and Bleustein-Gulyaev (B-G) type wave propagating in corresponding three-layer structure are discussed through numerically solving the derived dispersion equation. The results show that Love-type wave possesses the property of multiple modes, it can exist all of the values of wavenumber for every selected thickness ratios regardless of the electrical boundary conditions. The presence of PM interlayer makes the phase velocity of Love-type wave decrease. There exist two modes allowing the propagation of B-G type wave under electrically shorted circuit, while only one mode appears in the case of electrically open circuit. The modes of B-G type wave are combinations of partly normal dispersion and partly anomalous dispersion whether the electrically open or shorted. The existence range of mode for electrically open case is greatly related to the thickness ratios, with the thickness of PM interlayer increasing the wavenumber range for existence of B-G type wave quickly shortened. When the thickness ratio is large enough, the wavenumber range of the second mode for electrically shorted circuit is extremely narrow which can be used to remove as an undesired mode. The propagation behaviors and mode shapes of transverse surface waves can be regulated by the modification of the thickness of PM interlayer. The obtained results provide a theoretical prediction and basis for applications of PE-PM composites and acoustic wave devices.

Tailoring Interfacial Properties by Controlling Carbon Nanotube Coating Thickness on Glass Fibers Using Electrophoretic Deposition.

PubMed

Tamrakar, Sandeep; An, Qi; Thostenson, Erik T; Rider, Andrew N; Haque, Bazle Z Gama; Gillespie, John W

2016-01-20

The electrophoretic deposition (EPD) method was used to deposit polyethylenimine (PEI) functionalized multiwall carbon nanotube (CNT) films onto the surface of individual S-2 glass fibers. By varying the processing parameters of EPD following Hamaker's equation, the thickness of the CNT film was controlled over a wide range from 200 nm to 2 μm. The films exhibited low electrical resistance, providing evidence of coating uniformity and consolidation. The effect of the CNT coating on fiber matrix interfacial properties was investigated through microdroplet experiments. Changes in interfacial properties due to application of CNT coatings onto the fiber surface with and without a CNT-modified matrix were studied. A glass fiber with a 2 μm thick CNT coating and the unmodified epoxy matrix showed the highest increase (58%) in interfacial shear strength (IFSS) compared to the baseline. The increase in the IFSS was proportional to CNT film thickness. Failure analysis of the microdroplet specimens indicated higher IFSS was related to fracture morphologies with higher levels of surface roughness. EPD enables the thickness of the CNT coating to be adjusted, facilitating control of fiber/matrix interfacial resistivity. The electrical sensitivity provides the opportunity to fabricate a new class of sizing with tailored interfacial properties and the ability to detect damage initiation.

Characterization and properties of micro- and nanowires of controlled size, composition, and geometry fabricated by electrodeposition and ion-track technology

PubMed Central

2012-01-01

Summary The combination of electrodeposition and polymeric templates created by heavy-ion irradiation followed by chemical track etching provides a large variety of poly- and single-crystalline nanowires of controlled size, geometry, composition, and surface morphology. Recent results obtained by our group on the fabrication, characterization and size-dependent properties of nanowires synthesized by this technique are reviewed, including investigations on electrical resistivity, surface plasmon resonances, and thermal instability. PMID:23365800

Self-organization of multifunctional surfaces--the fingerprints of light on a complex system.

PubMed

Reinhardt, Hendrik; Kim, Hee-Cheol; Pietzonka, Clemens; Kruempelmann, Julia; Harbrecht, Bernd; Roling, Bernhard; Hampp, Norbert

2013-06-25

Nanocomposite patterns and nanotemplates are generated by a single-step bottom-up concept that introduces laser-induced periodic surface structures (LIPSS) as a tool for site-specific reaction control in multicomponent systems. Periodic intensity fluctuations of this photothermal stimulus inflict spatial-selective reorganizations, dewetting scenarios and phase segregations, thus creating regular patterns of anisotropic physicochemical properties that feature attractive optical, electrical, magnetic, and catalytic properties. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

AlGaN/GaN heterostructures with an AlGaN layer grown directly on reactive-ion-etched GaN showing a high electron mobility (>1300 cm2 V-1 s-1)

NASA Astrophysics Data System (ADS)

Yamamoto, Akio; Makino, Shinya; Kanatani, Keito; Kuzuhara, Masaaki

2018-04-01

In this study, the metal-organic-vapor-phase-epitaxial growth behavior and electrical properties of AlGaN/GaN structures prepared by the growth of an AlGaN layer on a reactive-ion-etched (RIE) GaN surface without regrown GaN layers were investigated. The annealing of RIE-GaN surfaces in NH3 + H2 atmosphere, employed immediately before AlGaN growth, was a key process in obtaining a clean GaN surface for AlGaN growth, that is, in obtaining an electron mobility as high as 1350 cm2 V-1 s-1 in a fabricated AlGaN/RIE-GaN structure. High-electron-mobility transistors (HEMTs) were successfully fabricated with AlGaN/RIE-GaN wafers. With decreasing density of dotlike defects observed on the surfaces of AlGaN/RIE-GaN wafers, both two-dimensional electron gas properties of AlGaN/RIE-GaN structures and DC characteristics of HEMTs were markedly improved. Since dotlike defect density was markedly dependent on RIE lot, rather than on growth lot, surface contaminations of GaN during RIE were believed to be responsible for the formation of dotlike defects and, therefore, for the inferior electrical properties.

Polyelectrolyte brushes on dielectric surfaces

NASA Astrophysics Data System (ADS)

Antila, Hanne; Luijten, Erik

When chains of charged polymers are grafted to a solid surface, a polyelectrolyte (PE) brush results. These types of PE assemblies have a wide range of applications ranging from fuel cells and switchable electrodes to drug delivery. Many of these applications stem from the ability of PE brushes to respond to external stimuli: the brush properties can be tuned, for example, by varying electric field, PE grafting density, pH, salt concentration or salt valency. Accordingly, deciphering the brush behavior under different conditions has been a subject of considerable experimental, theoretical, and computational research efforts. However, the effect of the dielectric properties of the substrate on the PE brush has received much less attention. We use coarse-grained molecular dynamics simulations to show how varying the dielectric mismatch between the solvent and the substrate can significantly affect the brush. We demonstrate how tuning this mismatch can either diminish or enhance the effects of other control parameters, such as pH, on the brush properties. Furthermore, we investigate how dielectric properties of the substrate affect the brush, and the ion distribution and mobility within the brush, when the brush is exposed to an electric field.

Multifunctional surface modification of silk fabric via graphene oxide repeatedly coating and chemical reduction method

NASA Astrophysics Data System (ADS)

Cao, Jiliang; Wang, Chaoxia

2017-05-01

Multifunctional silk fabrics with electrical conductive, anti-ultraviolet and water repellent were successfully prepared by surface modification with graphene oxide (GO). The yellow-brown GO deposited on the surface of silk fabric was converted into graphitic black reduced graphene (RGO) by sodium hydrosulfite. The surface properties of silk fabrics were changed by repeatedly RGO coating process, which have been proved by SEM and XPS. The SEM results showed that the RGO sheets were successive form a continuously thin film on the surface of silk fabrics, and the deposition of GO or RGO also can be proved by XPS. The electrical conductivity was tested by electrical surface resistance value of the silk fabric, the surface resistance decreased with increasing of RGO surface modification times, and a low surface resistance value reached to 3.24 KΩ cm-1 after 9 times of modification, indicating the silk obtained excellent conductivity. The UPF value of one time GO modification silk fabric (silk-1RGO) was enhanced significantly to 24.45 in comparison to 10.40 of original silk. The contact angle of RGO coating silk samples was all above of 120°. The durability of RGO coated silk fabrics was tested by laundering. The electrical surface resistance of silk-4RGO (65.74 KΩ cm-1), silk-6RGO (15.54 KΩ cm-1) and silk-8RGO (3.86 KΩ cm-1) fabrics was up to 86.82, 22.30 and 6.57 KΩ cm-1 after 10 times of standard washing, respectively. The UPF value, contact angle and color differences of RGO modified silk fabric slightly changed before and after 10 times of standard washing. Therefore, the washing fastness of electric conduction, anti-ultraviolet and water repellent multifunctional silk fabrics was excellent.

Plasma membrane surface potential: dual effects upon ion uptake and toxicity

USDA-ARS?s Scientific Manuscript database

Electrical properties of plasma membranes (PMs), partially controlled by the ionic composition of the bathing medium, play significant roles in the distribution of ions at the exterior surface of PMs and in the transport of ions across PMs. The effects of coexistent cations (commonly Al3+, Ca2+, Mg...

Reactive molecular dynamics of the initial oxidation stages of Ni111 in pure water: effect of an applied electric field.

PubMed

Assowe, O; Politano, O; Vignal, V; Arnoux, P; Diawara, B; Verners, O; van Duin, A C T

2012-12-06

Corrosion processes occurring in aqueous solutions are critically dependent upon the interaction between the metal electrode and the solvent. In this work, the interaction of a nickel substrate with water molecules has been investigated using reactive force field (ReaxFF) molecular dynamics simulations. This approach was originally developed by van Duin and co-workers to study hydrocarbon chemistry and the catalytic properties of organic compounds. To our knowledge, this method has not previously been used to study the corrosion of nickel. In this work, we studied the interaction of 480 molecules of water (ρ = 0.99 g·cm(-3)) with Ni(111) surfaces at 300 K. The results showed that a water "bilayer" was adsorbed on the nickel surface. In the absence of an applied electric field, no dissociation of water was observed. However, the nickel atoms at the surface were charged positively, whereas the first water layer was charged negatively, indicating the formation of an electric double layer. To study the corrosion of nickel in pure water, we introduced an external electric field between the metal and the solution. The electric field intensity varied between 10 and 20 MeV/cm. The presence of this electric field led to oxidation of the metal surface. The structural and morphological differences associated with the growth of this oxide film in the presence of the electric field were evaluated. The simulated atomic trajectories were used to analyze the atomic displacement during the reactive process. The growth of the oxide scale on the nickel surface was primarily due to the movement of anions toward the interior of the metal substrate and the migration of nickel toward the free surface. We found that increasing the electric field intensity sped up the corrosion of nickel. The results also showed that the oxide film thickness increased linearly with increasing electric field intensity.

Co-adsorption of water and oxygen on GaN: Effects of charge transfer and formation of electron depletion layer.

PubMed

Wang, Qi; Puntambekar, Ajinkya; Chakrapani, Vidhya

2017-09-14

Species from ambient atmosphere such as water and oxygen are known to affect electronic and optical properties of GaN, but the underlying mechanism is not clearly known. In this work, we show through careful measurement of electrical resistivity and photoluminescence intensity under various adsorbates that the presence of oxygen or water vapor alone is not sufficient to induce electron transfer to these species. Rather, the presence of both water and oxygen is necessary to induce electron transfer from GaN that leads to the formation of an electron depletion region on the surface. Exposure to acidic gases decreases n-type conductivity due to increased electron transfer from GaN, while basic gases increase n-type conductivity and PL intensity due to reduced charge transfer from GaN. These changes in the electrical and optical properties, as explained using a new electrochemical framework based on the phenomenon of surface transfer doping, suggest that gases interact with the semiconductor surface through electrochemical reactions occurring in an adsorbed water layer present on the surface.

A New Kinetic Simulation Model with Self-Consistent Calculation of Regolith Layer Charging for Moon-Plasma Interactions

NASA Astrophysics Data System (ADS)

Han, D.; Wang, J.

2015-12-01

The moon-plasma interactions and the resulting surface charging have been subjects of extensive recent investigations. While many particle-in-cell (PIC) based simulation models have been developed, all existing PIC simulation models treat the surface of the Moon as a boundary condition to the plasma flow. In such models, the surface of the Moon is typically limited to simple geometry configurations, the surface floating potential is calculated from a simplified current balance condition, and the electric field inside the regolith layer cannot be resolved. This paper presents a new full particle PIC model to simulate local scale plasma flow and surface charging. A major feature of this new model is that the surface is treated as an "interface" between two mediums rather than a boundary, and the simulation domain includes not only the plasma but also the regolith layer and the bedrock underneath it. There are no limitations on the surface shape. An immersed-finite-element field solver is applied which calculates the regolith surface floating potential and the electric field inside the regolith layer directly from local charge deposition. The material property of the regolith layer is also explicitly included in simulation. This new model is capable of providing a self-consistent solution to the plasma flow field, lunar surface charging, the electric field inside the regolith layer and the bedrock for realistic surface terrain. This new model is applied to simulate lunar surface-plasma interactions and surface charging under various ambient plasma conditions. The focus is on the lunar terminator region, where the combined effects from the low sun elevation angle and the localized plasma wake generated by plasma flow over a rugged terrain can generate strongly differentially charged surfaces and complex dust dynamics. We discuss the effects of the regolith properties and regolith layer charging on the plasma flow field, dust levitation, and dust transport.

Simulations of surface stress effects in nanoscale single crystals

NASA Astrophysics Data System (ADS)

Zadin, V.; Veske, M.; Vigonski, S.; Jansson, V.; Muszinsky, J.; Parviainen, S.; Aabloo, A.; Djurabekova, F.

2018-04-01

Onset of vacuum arcing near a metal surface is often associated with nanoscale asperities, which may dynamically appear due to different processes ongoing in the surface and subsurface layers in the presence of high electric fields. Thermally activated processes, as well as plastic deformation caused by tensile stress due to an applied electric field, are usually not accessible by atomistic simulations because of the long time needed for these processes to occur. On the other hand, finite element methods, able to describe the process of plastic deformations in materials at realistic stresses, do not include surface properties. The latter are particularly important for the problems where the surface plays crucial role in the studied process, as for instance, in the case of plastic deformations at a nanovoid. In the current study by means of molecular dynamics (MD) and finite element simulations we analyse the stress distribution in single crystal copper containing a nanovoid buried deep under the surface. We have developed a methodology to incorporate the surface effects into the solid mechanics framework by utilizing elastic properties of crystals, pre-calculated using MD simulations. The method leads to computationally efficient stress calculations and can be easily implemented in commercially available finite element software, making it an attractive analysis tool.

Acid-base properties of the surface of the α-Al2O3 suspension

NASA Astrophysics Data System (ADS)

Ryazanov, M. A.; Dudkin, B. N.

2009-12-01

The distribution of the acid-base centers on the surface of α-Al2O3 suspension particles was studied by potentiometric titration, and the corresponding p K spectra were constructed. It was inferred that the double electric layer created by the supporting electrolyte substantially affected the screening of the acid-base centers on the particle surface of the suspension.

Acid-functionalized carbon nanofibers for high stability, thermoelectrical and electrochemical properties of nanofluids.

PubMed

Said, Zafar; Allagui, Anis; Abdelkareem, Mohammad Ali; Alawadhi, Hussain; Elsaid, Khaled

2018-06-15

Carbon-based nanofluids are viewed as promising thermal fluids for heat transfer applications. However, other properties, such as electrical conductivity and electrochemical behavior, are usually overlooked and rarely investigated despite their importance for the overall performance characterization of a given application. In this study, we synthesized PAN-based carbon nanofibers (CNF) by electrospinning, and characterized them using electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, and thermogravimetric analysis. Thermoelectrical and electrochemical measurements were carried out on nanofluids. We found that, although CNF nanofluids exhibit good thermal and electrical properties with a negligible corrosive effect, the suspensions tend to sediment within a few days. However, acid treatment of CNF (F-CNF), which resulted in the shortening of the fibers and the appearance of surface-oxygenated species, made F-CNF-based nanofluids exhibit superior stability in water that extended for more than 90 days, with consistent and superior thermal and electrical properties. Copyright © 2018 Elsevier Inc. All rights reserved.

Schumann Resonances on Mars - a Two-layer Ground Case

NASA Astrophysics Data System (ADS)

Kozakiewicz, J.; Kulak, A.; Mlynarczyk, J.

2012-04-01

Schumann resonances (SR) are global resonances of electromagnetic waves in the range of extremely low frequencies (ELF) propagating in a cavity formed by a planetary surface and a lower ionosphere. SR are induced by electrical discharges, which on Earth are associated mainly with lightning. They were predicted by Winfried Otto Schumann in 1952. SR are supposed to occur on Mars, although many properties of the Martian environment are still unknown. One of the most important problems in modeling SR on Mars is to estimate electrical properties of the Martian ground and their influence on ELF waves propagation. The Martian crust is composed mainly of basaltic materials. Water, which causes significant increase in electrical conductivity of rocks, does not exist in liquid state at the surface of Mars. Therefore the Martian ground is believed to be a low conductive one. However, it is possible that some liquid water may be present at various depths below the surface. In our previous study we have developed an analytical model, based on the characteristic electric and magnetic altitudes' formalism, that has allowed us to take into consideration the Martian ground. Using this new model, we found that basaltic ground of low conductivity greatly influenced the SR parameters. In this work, we carried out simulations in order to characterize an influence of vertical changes in ground properties on the parameters of the Martian ground-ionosphere waveguide. We have considered several cases of a two-layer ground, in which the lower layer was of higher conductivity than the upper one. The obtained results indicate how the SR parameters depend on electrical conductivity, permittivity, and depth of the layers. The results also point out the importance of studying SR on Mars and the need for further research in propagation of ELF waves in the Martian environment. SR can be used as a remote sensing tool for exploration of the Martian crust. Furthermore, they can be especially useful for groundwater detection.

Electrochromic properties of polyaniline-coated fiber webs for tissue engineering applications.

PubMed

Beregoi, Mihaela; Busuioc, Cristina; Evanghelidis, Alexandru; Matei, Elena; Iordache, Florin; Radu, Mihaela; Dinischiotu, Anca; Enculescu, Ionut

2016-08-30

By combining the electrospinning method advantages (high surface-to-volume ratio, controlled morphology, varied composition and flexibility for the resulting structures) with the electrical activity of polyaniline, a new core-shell-type material with potential applications in the field of artificial muscles was synthesized. Thus, a poly(methylmethacrylate) solution was electrospun in optimized conditions to obtain randomly oriented polymer fiber webs. Further, a gold layer was sputtered on their surface in order to make them conductive and improve the mechanical properties. The metalized fiber webs were then covered with a PANI layer by in situ electrochemical polymerization starting from aniline and using sulphuric acid as oxidizing agent. By applying a small voltage on PANI-coated fiber webs in the presence of an electrolyte, the oxidation state of PANI changes, which is followed by the device color modification. The morphological, electrical and biological properties of the resulting multilayered material were also investigated. Copyright © 2015 Elsevier B.V. All rights reserved.

Quantitative characterization of surface topography using spectral analysis

NASA Astrophysics Data System (ADS)

Jacobs, Tevis D. B.; Junge, Till; Pastewka, Lars

2017-03-01

Roughness determines many functional properties of surfaces, such as adhesion, friction, and (thermal and electrical) contact conductance. Recent analytical models and simulations enable quantitative prediction of these properties from knowledge of the power spectral density (PSD) of the surface topography. The utility of the PSD is that it contains statistical information that is unbiased by the particular scan size and pixel resolution chosen by the researcher. In this article, we first review the mathematical definition of the PSD, including the one- and two-dimensional cases, and common variations of each. We then discuss strategies for reconstructing an accurate PSD of a surface using topography measurements at different size scales. Finally, we discuss detecting and mitigating artifacts at the smallest scales, and computing upper/lower bounds on functional properties obtained from models. We accompany our discussion with virtual measurements on computer-generated surfaces. This discussion summarizes how to analyze topography measurements to reconstruct a reliable PSD. Analytical models demonstrate the potential for tuning functional properties by rationally tailoring surface topography—however, this potential can only be achieved through the accurate, quantitative reconstruction of the PSDs of real-world surfaces.

Effect of pH on the electrical properties and conducting mechanism of SnO2 nanoparticles

NASA Astrophysics Data System (ADS)

Periathai, R. Sudha; Abarna, S.; Hirankumar, G.; Jeyakumaran, N.; Prithivikumaran, N.

2017-03-01

Semiconductor nanoparticles have attracted more interests because of their size-dependent optical and electrical properties.SnO2 is an oxygen-deficient n-type semiconductor with a wide band gap of 3.6 eV (300 K). It has many remarkable applications as sensors, catalysts, transparent conducting electrodes, anode material for rechargeable Li- ion batteries and optoelectronic devices. In the present work, the role of pH in determining the electrical and dielectric properties of SnO2 nanoparticles has been studied as a function of temperature ranging from Room temperature (RT) to 114 °C in the frequency range of 7 MHz to 50 mHz using impedance spectroscopic technique. The non linear behavior observed in the thermal dependence of the conductance of SnO2 nanoparticles is explained by means of the surface property of SnO2 nanoparticles where proton hopping mechanism is dealt with. Jonscher's power law has been fitted for the conductance spectra and the frequency exponent ("s" value) gives an insight about the ac conducting mechanism. The temperature dependence of electrical relaxation phenomenon in the material has been observed. The complex electric modulus analysis indicates the possibility of hopping conduction mechanism in the system with non-exponential type of conductivity relaxation.

Spectroscopic and Electrochemical Properties of Lithium-Rich LiFePO4 Cathode Synthesized by Solid-State Reaction

NASA Astrophysics Data System (ADS)

Rosaiah, P.; Hussain, O. M.; Zhu, Jinghui; Qiu, Yejun

2017-08-01

Lithium iron phosphate (Li x FePO4) is synthesized by a solid-state reaction method. The structural, electrical and electrochemical properties are studied in detail. It is found that the increment of lithium concentration (up to x = 1.05) does not affect the structure of LiFePO4 but improves its electrical conductivity as well as electrochemical performance. Surface morphological studies exhibited the formation of rod-like nanoparticles with small size. Electric and dielectric properties are also investigated over a frequency range of 1 Hz-1 MHz at different temperatures. The conductivity increased with increasing temperature, which follows the Arrhenius relation with the activation energy of about 0.31 eV. And the electrochemical tests found that the Li1.05FePO4 cathode possessed improved discharge capacity with better cycling performance.

Microwave assisted growth of nanorods vanadium dioxide VO2 (R): structural and electrical properties

NASA Astrophysics Data System (ADS)

Derkaoui, I.; Khenfouch, M.; Mothudi, B. M.; Moloi, S. J.; Zorkani, I.; Jorio, A.; Maaza, M.

2018-03-01

Nanostructured metal oxides have attracted a lot of attention recently owning to their unique structural advantages and demonstrated promising chemical and physical properties for various applications. In this study, we report the structural and electrical properties of vanadium dioxide VO2 (R) prepared via a single reaction microwave (SRC) synthesis. Our results are revealing that the components of VO2 (R) films have a rod-like shape with a uniform size distribution. The nanorods with very smooth and flat surfaces have a typical length of up to 2μm and a width of about several nanometers. The structural investigations reveal the high crystallinity of VO2 (R) ensuring good electrical contact and showing a high conductivity as a function of temperature. This synthesis method provides a new simple route to fabricate one-dimensional nanostructured metal oxides which is suitable for a large field of applications especially for smart windows.

Understanding the low temperature electrical properties of nanocrystalline tin oxide for gas sensor applications

NASA Astrophysics Data System (ADS)

Drake, Christina Hartsell

Nanocrystalline metal/metal oxide is an important class of transparent and electronic materials due to its potential use in many applications, including gas sensors. At the nanoscale, many of the phenomena observed that give nanocrystalline semiconducting oxide enhanced performance as a gas sensor material over other conventional engineering materials is still poorly understood. This study is aimed at understanding the low temperature electrical and chemical properties of nanocrystalline SnO2 that makes it suitable for room temperature gas detectors. Studies were carried out in order to understand how various synthesis methods affect the surfaces on the nano-oxides, interactions of a target gas (in this study hydrogen) with different surface species, and changes in the electrical properties as a function of dopants and grain size. A correlation between the surface reactions and the electrical response of doped nanocrystalline metal-oxide-semiconductors exposed to a reducing gas is established using Fourier Transform Infrared (FTIR) Spectroscopy attached to a specially built custom designed catalytic cell. First principle calculations of oxygen vacancy concentrations from absorbance spectra are presented. FTIR is used for effectively screening of these nanostructures for gas sensing applications. The effect of processing temperature on the microstructural evolution and on the electronic properties of nanocrystalline trivalent doped-SnO 2 is also presented. This study includes the effect of dopants (In and Ce) on the growth of nano-SnO2, as well as their effects on the electronic properties and gas sensor behavior of the nanomaterial at room temperature. Band bending affects are also investigated for this system and are related to enhanced low temperature gas sensing. The role and importance of oxygen vacancies in the electronic and chemical behavior of surface modified nanocrystalline SnO2 are explored in this study. A generalized explanation for the low temperature gas sensor behavior of nanocrystalline oxide is presented that can be generalized to other nano-oxide systems and be useful in specific engineering of other nanomaterials. Deeper understanding of how nano-oxides react chemically and electronically would be extremely beneficial to issues present in current low cost, low temperature sensor technology. Ability to exactly monitor and then engineer the chemistry of nanostructures in the space charge region as well as the surface is also of great significance. Knowledge of the mechanisms responsible for enhanced sensor response in this material system could viably be applied to other material systems for sensor applications.

Tribological and Electrical Properties of Diamond-Like Carbon Films Deposited by Filtered Vacuum Arc Method for Medical Guidewire Application.

PubMed

Kang, Ki-Noh; Jeong, Hyejeong; Lee, Jaehyeong; Park, Yong Seob

2018-09-01

A good medical guidewires are used to introduce stents, catheters, and other medical devices inside the human body. In this study, diamond-like carbon (DLC) film was proposed to solve the poor adhesion problem of guidewire and to improve the tribological performance of guidewire. DLC films were fabricated on Si substrate by using FVA (Filtered Vacuum Arc) method. In this work, the tribological, structural, and electrical properties of the fabricated DLC films with various arc currents were experimentally investigated. All DLC films showed smooth and uniform surface with increasing applied arc current. The rms surface roughness was increased and the value of contact angle on the film surface was decreased with increasing arc current. The hardness and elastic modulus of DLC films were improved, and the resistivity value of DLC films were decreased with increasing arc current. These results are associated with ion bombardment effects by the applied arc current and bias voltage.

Fabrication of (NH4)2S passivated GaAs metal-insulator-semiconductor devices using low-frequency plasma-enhanced chemical vapor deposition

NASA Astrophysics Data System (ADS)

Jaouad, A.; Aimez, V.; Aktik, Ç.; Bellatreche, K.; Souifi, A.

2004-05-01

Metal-insulator-semiconductor (MIS) capacitors were fabricated on n-GaAs(100) substrate using (NH4)2S surface passivation and low-frequency plasma-enhanced chemical vapor deposited silicon nitride as gate insulators. The electrical properties of the fabricated MIS capacitors were analyzed using high-frequency capacitance-voltage and conductance-voltage measurements. The high concentration of hydrogen present during low-frequency plasma deposition of silicon nitride enhances the passivation of GaAs surface, leading to the unpinning of the Fermi level and to a good modulation of the surface potential by gate voltage. The electrical properties of the insulator-semiconductor interface are improved after annealing at 450 °C for 60 s, as a significant reduction of the interface fixed charges and of the interface states density is put into evidence. The minimum interface states density was found to be about 3×1011 cm-2 eV-1, as estimated by the Terman method. .

Defect-free erbium silicide formation using an ultrathin Ni interlayer.

PubMed

Choi, Juyun; Choi, Seongheum; Kang, Yu-Seon; Na, Sekwon; Lee, Hoo-Jeong; Cho, Mann-Ho; Kim, Hyoungsub

2014-08-27

An ultrathin Ni interlayer (∼1 nm) was introduced between a TaN-capped Er film and a Si substrate to prevent the formation of surface defects during thermal Er silicidation. A nickel silicide interfacial layer formed at low temperatures and incurred uniform nucleation and the growth of a subsequently formed erbium silicide film, effectively inhibiting the generation of recessed-type surface defects and improving the surface roughness. As a side effect, the complete transformation of Er to erbium silicide was somewhat delayed, and the electrical contact property at low annealing temperatures was dominated by the nickel silicide phase with a high Schottky barrier height. After high-temperature annealing, the early-formed interfacial layer interacted with the growing erbium silicide, presumably forming an erbium silicide-rich Er-Si-Ni mixture. As a result, the electrical contact property reverted to that of the low-resistive erbium silicide/Si contact case, which warrants a promising source/drain contact application for future high-performance metal-oxide-semiconductor field-effect transistors.

Simultaneous control of thermoelectric properties in p- and n-type materials by electric double-layer gating: New design for thermoelectric device

NASA Astrophysics Data System (ADS)

Takayanagi, Ryohei; Fujii, Takenori; Asamitsu, Atsushi

2015-05-01

We report a novel design of a thermoelectric device that can control the thermoelectric properties of p- and n-type materials simultaneously by electric double-layer gating. Here, p-type Cu2O and n-type ZnO were used as the positive and negative electrodes of the electric double-layer capacitor structure. When a gate voltage was applied between the two electrodes, holes and electrons accumulated on the surfaces of Cu2O and ZnO, respectively. The thermopower was measured by applying a thermal gradient along the accumulated layer on the electrodes. We demonstrate here that the accumulated layers worked as a p-n pair of the thermoelectric device.

Structural, optical, morphological and electrical properties of undoped and Al-doped ZnO thin films prepared using sol—gel dip coating process

NASA Astrophysics Data System (ADS)

Boukhenoufa, N.; Mahamdi, R.; Rechem, D.

2016-11-01

In this work, sol—gel dip-coating technique was used to elaborate ZnO pure and ZnO/Al films. The impact of Al-doped concentration on the structural, optical, surface morphological and electrical properties of the elaborated samples was investigated. It was found that better electrical and optical performances have been obtained for an Al concentration equal to 5%, where the ZnO thin films exhibit a resistivity value equal to 1.64104 Ω·cm. Moreover, highest transparency has been recorded for the same Al concentration value. The obtained results from this investigation make the developed thin film structure a potential candidate for high optoelectronic performance applications.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cho, Byungsu; Samsung Display Co. Ltd., Tangjeong, Chungcheongnam-Do 336-741; Choi, Yonghyuk

We demonstrate an enhanced electrical stability through a Ti oxide (TiO{sub x}) layer on the amorphous InGaZnO (a-IGZO) back-channel; this layer acts as a surface polarity modifier. Ultrathin Ti deposited on the a-IGZO existed as a TiO{sub x} thin film, resulting in oxygen cross-binding with a-IGZO surface. The electrical properties of a-IGZO thin film transistors (TFTs) with TiO{sub x} depend on the surface polarity change and electronic band structure evolution. This result indicates that TiO{sub x} on the back-channel serves as not only a passivation layer protecting the channel from ambient molecules or process variables but also a control layermore » of TFT device parameters.« less

Solvophilic and solvophobic surfaces and non-Coulombic surface interactions in charge regulating electric double layers

NASA Astrophysics Data System (ADS)

Vangara, R.; van Swol, F.; Petsev, D. N.

2018-01-01

The properties of electric double layers are governed by the interface between the substrate and the adjacent electrolyte solution. This interface is involved in chemical, Coulombic, and non-Coulombic (e.g., van der Waals or Lennard-Jones) interactions with all components of the fluid phase. We present a detailed study of these interactions using a classical density functional approach. A particular focus is placed on the non-Coulombic interactions and their effect on the surface chemistry and charge regulation. The solution structure near the charged interface is also analyzed and used to offer a thorough interpretation of established concepts such as the Stern and diffuse ionic layers.

Carbon Redox-Polymer-Gel Hybrid Supercapacitors.

PubMed

Vlad, A; Singh, N; Melinte, S; Gohy, J-F; Ajayan, P M

2016-02-26

Energy storage devices that provide high specific power without compromising on specific energy are highly desirable for many electric-powered applications. Here, we demonstrate that polymer organic radical gel materials support fast bulk-redox charge storage, commensurate to surface double layer ion exchange at carbon electrodes. When integrated with a carbon-based electrical double layer capacitor, nearly ideal electrode properties such as high electrical and ionic conductivity, fast bulk redox and surface charge storage as well as excellent cycling stability are attained. Such hybrid carbon redox-polymer-gel electrodes support unprecedented discharge rate of 1,000C with 50% of the nominal capacity delivered in less than 2 seconds. Devices made with such electrodes hold the potential for battery-scale energy storage while attaining supercapacitor-like power performances.

Model for interface formation and the resulting electrical properties for barium-strontium-titanate films on silicon

NASA Astrophysics Data System (ADS)

Mueller, A. H.; Suvorova, N. A.; Irene, E. A.; Auciello, O.; Schultz, J. A.

2003-04-01

The interface formation between sputtered barium strontium titanate (BST) films and both Si and SiO2 substrate surfaces has been followed using real-time spectroscopic ellipsometry and the mass spectrometry of recoiled ions. In both substrates an intermixed interface layer was observed and subcutaneous Si oxidation occurred. A model for the interface formation is proposed in which the interface includes an SiO2 film on Si, and an intermixed film on which is pure BST. During the deposition of BST the interfaces films were observed to change in time. Electrical characterization of the resulting metal-BST interface capacitors indicates that those samples with SiO2 on the Si surface had the best electrical characteristics.

Sputtered deposited nanocrystalline ZnO films: A correlation between electrical, optical and microstructural properties

NASA Astrophysics Data System (ADS)

Lee, J.; Gao, W.; Li, Z.; Hodgson, M.; Metson, J.; Gong, H.; Pal, U.

2005-05-01

Zinc oxide thin films were prepared by dc (direct current) and rf (radio frequency) magnetron sputtering on glass substrates. ZnO films produced by dc sputtering have a high resistance, while the films produced using rf sputtering are significantly more conductive. While the conductive films have a compact nodular surface morphology, the resistive films have a relatively porous surface with columnar structures in cross section. Compared to the dc sputtered films, rf sputtered films have a microstructure with smaller d spacing, lower internal stress, higher band gap energy and higher density. Dependence of conductivity on the deposition technique and the resulting d spacing , stress, density, band gap, film thickness and Al doping are discussed. Correlations between the electrical conductivity, microstructural parameters and optical properties of the films have been made.

A ‘NanoSuit’ surface shield successfully protects organisms in high vacuum: observations on living organisms in an FE-SEM

PubMed Central

Takaku, Yasuharu; Suzuki, Hiroshi; Ohta, Isao; Tsutsui, Takami; Matsumoto, Haruko; Shimomura, Masatsugu; Hariyama, Takahiko

2015-01-01

Although extremely useful for a wide range of investigations, the field emission scanning electron microscope (FE-SEM) has not allowed researchers to observe living organisms. However, we have recently reported that a simple surface modification consisting of a thin extra layer, termed ‘NanoSuit’, can keep organisms alive in the high vacuum (10−5 to 10−7 Pa) of the SEM. This paper further explores the protective properties of the NanoSuit surface-shield. We found that a NanoSuit formed with the optimum concentration of Tween 20 faithfully preserves the integrity of an organism's surface without interfering with SEM imaging. We also found that electrostatic charging was absent as long as the organisms were alive, even if they had not been coated with electrically conducting materials. This result suggests that living organisms possess their own electrical conductors and/or rely on certain properties of the surface to inhibit charging. The NanoSuit seems to prolong the charge-free condition and increase survival time under vacuum. These findings should encourage the development of more sophisticated observation methods for studying living organisms in an FE-SEM. PMID:25631998

Simulation of electric double-layer capacitors: evaluation of constant potential method

NASA Astrophysics Data System (ADS)

Wang, Zhenxing; Laird, Brian; Yang, Yang; Olmsted, David; Asta, Mark

2014-03-01

Atomistic simulations can play an important role in understanding electric double-layer capacitors (EDLCs) at a molecular level. In such simulations, typically the electrode surface is modeled using fixed surface charges, which ignores the charge fluctuation induced by local fluctuations in the electrolyte solution. In this work we evaluate an explicit treatment of charges, namely constant potential method (CPM)[1], in which the electrode charges are dynamically updated to maintain constant electrode potential. We employ a model system with a graphite electrode and a LiClO4/acetonitrile electrolyte, examined as a function of electrode potential differences. Using various molecular and macroscopic properties as metrics, we compare CPM simulations on this system to results using fixed surface charges. Specifically, results for predicted capacity, electric potential gradient and solvent density profile are identical between the two methods; However, ion density profiles and solvation structure yield significantly different results.

Study of Electrical Contacts and Devices in Advanced Semiconductors

NASA Technical Reports Server (NTRS)

Hall, H. P.; Das, K.; Alterovitz, Samuel (Technical Monitor)

2001-01-01

Research conducted at Tuskegee University concentrates on electrical contacts to GaN films and their characterization with the objective of understanding contact formation and realizing low-resistance metal contacts. Contact properties are known to be strongly related to surface preparation. It appears that the as-received material had a thin oxide film on the surface of the GaN film. Various cleaning treatments were employed in order to render the surface contamination free and removal of the oxide film. Metal films were then deposited by e-beam evaporation. Electrical characteristics of these contacts indicated that the optimal treatment was an organic solvent cleaning followed by etching in buffered oxide solution. Contacts established with Al were observed to be ohmic in nature, whereas Au, Cr, Ti, and Pt exhibit rectifying contacts. Platinum contacts were almost ideal as shown by an ideality factor of 1.02.

Sub-micron elastic property characterization of materials using a near-field scanning optical microscope

NASA Astrophysics Data System (ADS)

Blodgett, David W.; Spicer, James B.

2001-12-01

The ability to characterize the sub-surface mechanical properties of a bulk or thin film material at the sub-micron level has applications in the microelectronics and thin film industries. In the microelectronics industry, with the decrease of line widths and the increase of component densities, sub-surface voids have become increasingly detrimental. Any voids along an integrated circuit (IC) line can lead to improper electrical connections between components and can cause failure of the device. In the thin film industry, the detection of impurities is also important. Any impurities can detract from the film's desired optical, electrical, or mechanical properties. Just as important as the detection of voids and impurities, is the measurement of the elastic properties of a material on the nanometer scale. These elastic measurements provide insight into the microstructural properties of the material. We have been investigating a technique that couples the high-resolution surface imaging capabilities of the apertureless near-field scanning optical microscope (ANSOM) with the sub-surface characterization strengths of high-frequency ultrasound. As an ultrasonic wave propagates, the amplitude decreases due to geometrical spreading, attenuation from absorption, and scattering from discontinuities. Measurement of wave speeds and attenuation provides the information needed to quantify the bulk or surface properties of a material. The arrival of an ultrasonic wave at or along the surface of a material is accompanied with a small surface displacement. Conventional methods for the ultrasound detection rely on either a contact transducer or optical technique (interferometric, beam deflection, etc.). However, each of these methods is limited by the spatial resolution dictated by the detection footprint. As the footprint size increases, variations across the ultrasonic wavefront are effectively averaged, masking the presence of any nanometer-scale sub-surface or surface mechanical property variations. The use of an ANSOM for sensing ultrasonic wave arrivals reduces the detection footprint allowing any nanometer scale variations in the microstructure of a material to be detected. In an ANSOM, the ultrasonic displacement is manifested as perturbations on the near-field signal due to the small variations in the tip-sample caused by the wave arrival. Due to the linear dependence of the near-field signal on tip-sample separation, these perturbations can be interpreted using methods identical to those for conventional ultrasonic techniques. In this paper, we report results using both contact transducer (5 MHz) and laser-generated ultrasound.

Electrochemically induced actuation of liquid metal marbles

NASA Astrophysics Data System (ADS)

Tang, Shi-Yang; Sivan, Vijay; Khoshmanesh, Khashayar; O'Mullane, Anthony P.; Tang, Xinke; Gol, Berrak; Eshtiaghi, Nicky; Lieder, Felix; Petersen, Phred; Mitchell, Arnan; Kalantar-Zadeh, Kourosh

2013-06-01

Controlled actuation of soft objects with functional surfaces in aqueous environments presents opportunities for liquid phase electronics, novel assembled super-structures and unusual mechanical properties. We show the extraordinary electrochemically induced actuation of liquid metal droplets coated with nanoparticles, so-called ``liquid metal marbles''. We demonstrate that nanoparticle coatings of these marbles offer an extra dimension for affecting the bipolar electrochemically induced actuation. The nanoparticles can readily migrate along the surface of liquid metals, upon the application of electric fields, altering the capacitive behaviour and surface tension in a highly asymmetric fashion. Surprising actuation behaviours are observed illustrating that nanoparticle coatings can have a strong effect on the movement of these marbles. This significant novel phenomenon, combined with unique properties of liquid metal marbles, represents an exciting platform for enabling diverse applications that cannot be achieved using rigid metal beads.Controlled actuation of soft objects with functional surfaces in aqueous environments presents opportunities for liquid phase electronics, novel assembled super-structures and unusual mechanical properties. We show the extraordinary electrochemically induced actuation of liquid metal droplets coated with nanoparticles, so-called ``liquid metal marbles''. We demonstrate that nanoparticle coatings of these marbles offer an extra dimension for affecting the bipolar electrochemically induced actuation. The nanoparticles can readily migrate along the surface of liquid metals, upon the application of electric fields, altering the capacitive behaviour and surface tension in a highly asymmetric fashion. Surprising actuation behaviours are observed illustrating that nanoparticle coatings can have a strong effect on the movement of these marbles. This significant novel phenomenon, combined with unique properties of liquid metal marbles, represents an exciting platform for enabling diverse applications that cannot be achieved using rigid metal beads. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00185g

Effect of residual gas on structural, electrical and mechanical properties of niobium films deposited by magnetron sputtering deposition

NASA Astrophysics Data System (ADS)

Wang, Lanruo; Zhong, Yuan; Li, Jinjin; Cao, Wenhui; Zhong, Qing; Wang, Xueshen; Li, Xu

2018-04-01

Magnetron sputtering is an important method in the superconducting thin films deposition. The residual gas inside the vacuum chamber will directly affect the quality of the superconducting films. In this paper, niobium films are deposited by magnetron sputtering under different chamber residual gas conditions. The influence of baking and sputtering process on residual gas are studied as well. Surface morphology, electrical and mechanical properties of the films are analysed. The residual gas analysis result before the sputtering process could be regarded as a reference condition to achieve high quality superconducting thin films.

Apparatus for electroplating particles of small dimension

DOEpatents

Yu, C.M.; Illige, J.D.

1980-09-19

The thickness, uniformity, and surface smoothness requirements for surface coatings of glass microspheres for use as targets for laser fusion research are critical. Because of thier minute size, the microspheres are difficult to manipulate and control in electroplating systems. The electroplating apparatus of the present invention addresses these problems by providing a cathode cell having a cell chamber, a cathode and an anode electrically isolated from each other and connected to an electrical power source. During the plating process, the cathode is controllably vibrated along with solution pulse to maintain the particles in random free motion so as to attain the desired properties.

Role of Defects and Adsorbed Water Film in Influencing the Electrical, Optical and Catalytic Properties of Transition Metal Oxides

NASA Astrophysics Data System (ADS)

Wang, Qi

Transition metal oxides (TMOs) constitute a large group of materials that exhibit a wide range of optical, electrical, electrochemical, dielectric and catalytic properties, and thus making them highly regarded as promising materials for a variety of applications in next generation electronic, optoelectronic, catalytic, photonic, energy storage and energy conversion devices. Some of the unique properties of TMOs are their strong electron-electron correlations that exists between the valence electrons of narrow d- or f-shells and their ability to exist in variety of oxidation states. This gives TMOs an enormous range of fascinating electronic and other physical properties. Many of these remarkable properties of TMOs arises from the complex surface charge transfer processes at the oxide surface/electrochemical redox species interface and non-stoichiometry due to the presence of lattice vacancies that may cause significant perturbation to the electronic structure of the material. Stoichiometry, oxidation state of the metal center and lattice vacancy defects all play important roles in affecting the physical properties, electronic structures, device behavior and other functional properties of TMOs. However, the underlying relationships between them is not clearly known. For instance, the exchange of electrons between adsorbates and defects can lead to the passivation of existing defect states or formation of new defects, both of which affect defect equilibria, and consequently, functional properties. In depth understanding of the role of lattice defects on the electrical, catalytic and optical properties of TMOs is central to further expansion of the technological applications of TMO based devices. The focus of this work is to elucidate the interactions of vacancy defects with various electrochemical adsorbates in TMOs. The ability to directly probe the interactions of vacancy defects with gas and liquid phase species under in-operando conditions is highly desirable to obtain a mechanistic understanding of the charge transfer process. We have developed a spectroscopic technique for studying vacancy defects in TMOs using near-infrared photoluminescence (NIR-PL) spectroscopy and showed that this technique is uniquely suited for studying defect-adsorbate interactions. In this work, a series of studies were carried out to elucidate the underlying structure-defect-property correlations of TMOs and their role in catalyzing electrical and electrochemical properties. In the first study, we report a new type of electrical phase transition in p-type, non-stoichiometric nickel oxide involving a semiconductor-to-insulator-to-metal transition along with the complete change of conductivity from p- to n-type at room temperature induced by electrochemical Li+ intercalation. Direct observation of vacancy-ion interactions using in-situ NIR-PL show that the transition is a result of passivation of native nickel (cationic) vacancy defects and subsequent formation of oxygen (anionic) vacancy defects driven by Li+ insertion into the lattice. X-ray photoemission spectroscopy studies performed to examine the changes in the oxidation states of nickel due to defect interactions support the above conclusions. In the second study, main effects of oxygen vacancy defects on the electronic and optical properties of V2O5 nanowires were studied using in-situ Raman, photoluminescence, absorption, and photoemission spectroscopy. We show that both thermal reduction and electrochemical reduction via Li+ insertion results in the creation of oxygen vacancy defects in the crystal that leads to band filling and an increase in the optical band gap of V2O5 from 1.95 eV to 2.45 eV, an effect known as the Burstein-Moss effect. In the third study, we report a new type of semiconductor-adsorbed water interaction in metal oxides known as "electrochemical surface transfer doping," a phenomenon that has been previously been observed on hydrogen-terminated diamond, carbon nanotube, gallium nitride and zinc oxide. Most TMOs at room temperature are known to be strongly hydrated. We show that an adsorbed water film present on the surface of TMOs facilitates the dissolution of gaseous species and promotes charge transfers at the adsorbed-water/oxide interfaces. Further, we show the role of vacancy defects in enhancing catalytic processes by directly monitoring the charge transfer process between gaseous species and vacancy defects in non-stoichiometric p-type nickel oxide and n-type tungsten oxide using in-situ NIR-PL, electrical resistance, and X-ray photoelectron spectroscopy. We find the importance of adsorbed water and vacancy defects in affecting catalytic, electronic, electrical, and optical changes such as insulator-to-metal transitions and radiative emissions during electrochemical reactions. In addition, we demonstrate that electrochemical surface transfer doping exists in another system, specifically, in gallium nitride, and the presence of this adsorbed water film present on the surface of GaN induces electron transfer from GaN that leads to the formation of an electron depletion region on the surface.

Microwave processed NiMg ferrite: Studies on structural and magnetic properties

NASA Astrophysics Data System (ADS)

Chandra Babu Naidu, K.; Madhuri, W.

2016-12-01

Ferrites are magnetic semiconductors realizing an important role in electrical and electronic circuits where electrical and magnetic property coupling is required. Though ferrite materials are known for a long time, there is a large scope in the improvement of their properties (vice sintering and frequency dependence of electrical and magnetic properties) with the current technological trends. Forth coming technology is aimed at miniaturization and smart gadgets, electrical components like inductors and transformers cannot be included in integrated circuits. These components are incorporated into the circuit as surface mount devices whose fabrication involves low temperature co-firing of ceramics and microwave monolithic integrated circuits technologies. These technologies demand low temperature sinter-ability of ferrites. This article presents low temperature microwave sintered Ni-Mg ferrites of general chemical formula Ni1-xMgxFe2O4 (x=0, 0.2, 0.4, 0.5, 0.6, 0.8, 1) for potential applications as transformer core materials. The series of ferrites are characterized using X-ray diffractometer, scanning electron microscopy, Fourier transform infrared and vibrating sample magnetometer for investigating structural, morphological and magnetic properties respectively. The initial permeability is studied with magnesium content, temperature and frequency in the temperature range of 308 K-873 K and 42 Hz-5 MHz.

Electrical and structural properties of (Pd/Au) Schottky contact to as grown and rapid thermally annealed GaN grown by MBE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nirwal, Varun Singh, E-mail: varun.nirwal30@gmail.com; Singh, Joginder; Gautam, Khyati

2016-05-06

We studied effect of thermally annealed GaN surface on the electrical and structural properties of (Pd/Au) Schottky contact to Ga-polar GaN grown by molecular beam epitaxy on Si substrate. Current voltage (I-V) measurement was used to study electrical properties while X-ray diffraction (XRD) measurement was used to study structural properties. The Schottky barrier height calculated using I-V characteristics was 0.59 eV for (Pd/Au) Schottky contact on as grown GaN, which increased to 0.73 eV for the Schottky contact fabricated on 700 °C annealed GaN film. The reverse bias leakage current at -1 V was also significantly reduced from 6.42×10{sup −5} Amore » to 7.31×10{sup −7} A after annealing. The value of series resistance (Rs) was extracted from Cheung method and the value of R{sub s} decreased from 373 Ω to 172 Ω after annealing. XRD results revealed the formation of gallide phases at the interface of (Pd/Au) and GaN for annealed sample, which could be the reason for improvement in the electrical properties of Schottky contact after annealing.« less

Systems and Methods of Laser Texturing of Material Surfaces and Their Applications

NASA Technical Reports Server (NTRS)

Gupta, Mool C. (Inventor); Nayak, Barada K. (Inventor)

2014-01-01

The surface of a material is textured and by exposing the surface to pulses from an ultrafast laser. The laser treatment causes pillars to form on the treated surface. These pillars provide for greater light absorption. Texturing and crystallization can be carried out as a single step process. The crystallization of the material provides for higher electric conductivity and changes in optical and electronic properties of the material. The method may be performed in vacuum or a gaseous environment. The gaseous environment may aid in texturing and/or modifying physical and chemical properties of the surfaces. This method may be used on various material surfaces, such as semiconductors, metals and their alloys, ceramics, polymers, glasses, composites, as well as crystalline, nanocrystalline, polycrystalline, microcrystalline, and amorphous phases.

The Role of Interfaces in Polyethylene/Metal-Oxide Nanocomposites for Ultrahigh-Voltage Insulating Materials.

PubMed

Pourrahimi, Amir Masoud; Olsson, Richard T; Hedenqvist, Mikael S

2018-01-01

Recent progress in the development of polyethylene/metal-oxide nanocomposites for extruded high-voltage direct-current (HVDC) cables with ultrahigh electric insulation properties is presented. This is a promising technology with the potential of raising the upper voltage limit in today's underground/submarine cables, based on pristine polyethylene, to levels where the loss of energy during electric power transmission becomes low enough to ensure intercontinental electric power transmission. The development of HVDC insulating materials together with the impact of the interface between the particles and the polymer on the nanocomposites electric properties are shown. Important parameters from the atomic to the microlevel, such as interfacial chemistry, interfacial area, and degree of particle dispersion/aggregation, are discussed. This work is placed in perspective with important work by others, and suggested mechanisms for improved insulation using nanoparticles, such as increased charge trap density, adsorption of impurities/ions, and induced particle dipole moments are considered. The effects of the nanoparticles and of their interfacial structures on the mechanical properties and the implications of cavitation on the electric properties are also discussed. Although the main interest in improving the properties of insulating polymers has been on the use of nanoparticles, leading to nanodielectrics, it is pointed out here that larger microscopic hierarchical metal-oxide particles with high surface porosity also impart good insulation properties. The impact of the type of particle and its inherent properties (purity and conductivity) on the nanocomposite dielectric and insulating properties are also discussed based on data obtained by a newly developed technique to directly observe the charge distribution on a nanometer scale in the nanocomposite. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modifying Surface Energy of Graphene via Plasma-Based Chemical Functionalization to Tune Thermal and Electrical Transport at Metal Interfaces.

PubMed

Foley, Brian M; Hernández, Sandra C; Duda, John C; Robinson, Jeremy T; Walton, Scott G; Hopkins, Patrick E

2015-08-12

The high mobility exhibited by both supported and suspended graphene, as well as its large in-plane thermal conductivity, has generated much excitement across a variety of applications. As exciting as these properties are, one of the principal issues inhibiting the development of graphene technologies pertains to difficulties in engineering high-quality metal contacts on graphene. As device dimensions decrease, the thermal and electrical resistance at the metal/graphene interface plays a dominant role in degrading overall performance. Here we demonstrate the use of a low energy, electron-beam plasma to functionalize graphene with oxygen, fluorine, and nitrogen groups, as a method to tune the thermal and electrical transport properties across gold-single layer graphene (Au/SLG) interfaces. We find that while oxygen and nitrogen groups improve the thermal boundary conductance (hK) at the interface, their presence impairs electrical transport leading to increased contact resistance (ρC). Conversely, functionalization with fluorine has no impact on hK, yet ρC decreases with increasing coverage densities. These findings indicate exciting possibilities using plasma-based chemical functionalization to tailor the thermal and electrical transport properties of metal/2D material contacts.

Role of chemical functional groups on thermal and electrical properties of various graphene oxide derivatives: a comparative x-ray photoelectron spectroscopy analysis

NASA Astrophysics Data System (ADS)

Balaji Mohan, Velram; Jakisch, Lothar; Jayaraman, Krishnan; Bhattacharyya, Debes

2018-03-01

In recent years, graphene and its derivatives have become prominent subject matter due to their fascinating combination of properties and potential applications in a number application. While several fundamental studies have been progressed, there is a particular need to understand how different graphene derivatives are influenced in terms of their electrical and thermal conductivities by different functional groups they end up with through their manufacturing and functionalisation methods. This article addresses of the role of different functional groups present of different of reduced graphene oxides (rGO) concerning their electrical and thermal properties, and the results were compared with elemental analyses of functionalised reduced graphene oxide (frGO) and graphene. The results showed that electrical and thermal conductivities of the rGO samples, highly dependent on the presence of residual functional groups from oxidation, reduction and functionalisation processes. The increase in reduction of oxygen, hydroxyl, carboxylic, epoxide moieties and heterocyclic compounds increase the specific surface area of the samples through which the mean electron path has increased. This improved both electrical and thermal conductivities together in all the samples which were highly dependent on the efficiency of different reductant used in this study.

Tools for proximal soil sensing

USDA-ARS?s Scientific Manuscript database

Proximal soil sensing (i.e. near-surface geophysical methods) are used to study soil phenomena across spatial scales. Geophysical methods exploit contrasts in physical properties (dielectric permittivity, apparent electrical conductivity or resistivity, magnetic susceptibility) to indirectly measur...

Influence of electrical properties of treated surface on RF-excited plasma needle at atmospheric pressure

NASA Astrophysics Data System (ADS)

Sakiyama, Y.; Graves, D. B.; Stoffels, E.

2008-05-01

We present a comparison of a finite element analysis of the atmospheric pressure RF-excited plasma needle interacting with different surfaces with corresponding experimental observations of light emission spatial profiles. The gas used is helium with 1 ppm nitrogen as an impurity. The needle has a point-to-plane geometry with a radius of 30 µm at the tip and an inter-electrode gap of 1 mm. We employ a fluid model in two-dimensional axisymmetric coordinates. Our simulation results indicate that the plasma structure strongly depends on the electrical properties of the treated surface as well as the discharge mode. In the lower power corona mode with a dielectric surface, the plasma is confined near the needle tip. As a result, particle fluxes to the dielectric surface are relatively low and follow a Gaussian-like radial profile. In the higher power glow mode with a dielectric surface, the particle fluxes to the surface are orders of magnitude higher and the spatial distribution of the particle fluxes becomes radially more uniform due to a uniform ionization layer just above the treated surface. When a conductive plate replaces the dielectric surface in the glow mode, a quite intense ionization spot appears near the surface closest to the needle tip. Consequently, the particle fluxes to the surface peak near the symmetry axis under these conditions. These simulation results are validated by experimental observation of light emission spatial profiles.

Influence of ion pairing in ionic liquids on electrical double layer structures and surface force using classical density functional approach.

PubMed

Ma, Ke; Forsman, Jan; Woodward, Clifford E

2015-05-07

We explore the influence of ion pairing in room temperature ionic liquids confined by planar electrode surfaces. Using a coarse-grained model for the aromatic ionic liquid [C4MIM(+)][BF4 (-)], we account for an ion pairing component as an equilibrium associating species within a classical density functional theory. We investigated the resulting structure of the electrical double layer as well as the ensuing surface forces and differential capacitance, as a function of the degree of ion association. We found that the short-range structure adjacent to surfaces was remarkably unaffected by the degree of ion pairing, up to several molecular diameters. This was even the case for 100% of ions being paired. The physical implications of ion pairing only become apparent in equilibrium properties that depend upon the long-range screening of charges, such as the asymptotic behaviour of surface forces and the differential capacitance, especially at low surface potential. The effect of ion pairing on capacitance is consistent with their invocation as a source of the anomalous temperature dependence of the latter. This work shows that ion pairing effects on equilibrium properties are subtle and may be difficult to extract directly from simulations.

Effect of Molecule–Surface Reaction Mechanism on the Electronic Characteristics and Photovoltaic Performance of Molecularly Modified Si

PubMed Central

2013-01-01

We report on the passivation properties of molecularly modified, oxide-free Si(111) surfaces. The reaction of 1-alcohol with the H-passivated Si(111) surface can follow two possible paths, nucleophilic substitution (SN) and radical chain reaction (RCR), depending on adsorption conditions. Moderate heating leads to the SN reaction, whereas with UV irradiation RCR dominates, with SN as a secondary path. We show that the site-sensitive SN reaction leads to better electrical passivation, as indicated by smaller surface band bending and a longer lifetime of minority carriers. However, the surface-insensitive RCR reaction leads to more dense monolayers and, therefore, to much better chemical stability, with lasting protection of the Si surface against oxidation. Thus, our study reveals an inherent dissonance between electrical and chemical passivation. Alkoxy monolayers, formed under UV irradiation, benefit, though, from both chemical and electronic passivation because under these conditions both SN and RCR occur. This is reflected in longer minority carrier lifetimes, lower reverse currents in the dark, and improved photovoltaic performance, over what is obtained if only one of the mechanisms operates. These results show how chemical kinetics and reaction paths impact electronic properties at the device level. It further suggests an approach for effective passivation of other semiconductors. PMID:24205409

Electrical properties of dispersions of graphene in mineral oil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monteiro, O. R., E-mail: othon.monteiro@bakerhughes.com

2014-02-03

Dispersions of graphene in mineral oil have been prepared and electrical conductivity and permittivity have been measured. The direct current (DC) conductivity of the dispersions depends on the surface characteristics of the graphene platelets and followed a percolation model with a percolation threshold ranging from 0.05 to 0.1 wt. %. The difference in DC conductivities can be attributed to different states of aggregation of the graphene platelets and to the inter-particle electron transfer, which is affected by the surface radicals. The frequency-dependent conductivity (σ(ω)) and permittivity (ε(ω)) were also measured. The conductivity of dispersions with particle contents much greater than themore » percolation threshold remains constant and equal to the DC conductivity at low frequencies ω with and followed a power-law σ(ω)∝ ω{sup s} dependence at very high frequencies with s≈0.9. For dispersions with graphene concentration near the percolation threshold, a third regime was displayed at intermediate frequencies indicative of interfacial polarization consistent with Maxwell-Wagner effect typically observed in mixtures of two (or more) phases with very distinct electrical and dielectric properties.« less

Coating agents affected toward magnetite nanoparticles properties

NASA Astrophysics Data System (ADS)

Petcharoen, Karat; Sirivat, Anuvat

2012-02-01

Magnetite nanoparticles --MNPs-- are innovative materials used in biological and medical applications. They respond to magnetic field through the superparamagnetic behavior at room temperature. In this study, the MNPs were synthesized via the chemical co-precipitation method using various coating agents. Fatty acids, found naturally in the animal fats, can be used as a coating agent. Oleic acid and hexanoic acid were chosen as the surface modification agents to study the improvement in the suspension of MNPs in water and the magnetite properties. Suspension stability, particle size, and electrical conductivity of MNPs are critically affected by the modification process. The well-dispersed MNPs in water can be improved by the surface modification and the oleic acid coated MNPs possess excellent suspension stability over 1 week. The particle size of MNPs increases up to 40 nm using oleic acid coated MNPs. The electrical conductivity of the smallest particle size is 1.3x10-3 S/cm, which is 5 times higher than that of the largest particle, suggesting potential applications as a biomedical material under both of the electrical and magnetic fields.

Development of functionally-oriented technological processes of electroerosive processing

NASA Astrophysics Data System (ADS)

Syanov, S. Yu

2018-03-01

The stages of the development of functionally oriented technological processes of electroerosive processing from the separation of the surfaces of parts and their service functions to the determination of the parameters of the process of electric erosion, which will provide not only the quality parameters of the surface layer, but also the required operational properties, are described.

Recent Progress on Stability and Passivation of Black Phosphorus.

PubMed

Abate, Yohannes; Akinwande, Deji; Gamage, Sampath; Wang, Han; Snure, Michael; Poudel, Nirakar; Cronin, Stephen B

2018-05-11

From a fundamental science perspective, black phosphorus (BP) is a canonical example of a material that possesses fascinating surface and electronic properties. It has extraordinary in-plane anisotropic electrical, optical, and vibrational states, as well as a tunable band gap. However, instability of the surface due to chemical degradation in ambient conditions remains a major impediment to its prospective applications. Early studies were limited by the degradation of black phosphorous surfaces in air. Recently, several robust strategies have been developed to mitigate these issues, and these novel developments can potentially allow researchers to exploit the extraordinary properties of this material and devices made out of it. Here, the fundamental chemistry of BP degradation and the tremendous progress made to address this issue are extensively reviewed. Device performances of encapsulated BP are also compared with nonencapsulated BP. In addition, BP possesses sensitive anisotropic photophysical surface properties such as excitons, surface plasmons/phonons, and topologically protected and Dirac semi-metallic surface states. Ambient degradation as well as any passivation method used to protect the surface could affect the intrinsic surface properties of BP. These properties and the extent of their modifications by both the degradation and passivation are reviewed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Inspecting the microstructure of electrically active defects at the Ge/GeOx interface

NASA Astrophysics Data System (ADS)

Fanciulli, Marco; Baldovino, Silvia; Molle, Alessandro

2012-02-01

High mobility substrates are important key elements in the development of advanced devices targeting a vast range of functionalities. Among them, Ge showed promising properties promoting it as valid candidate to replace Si in CMOS technology. However, the electrical quality of the Ge/oxide interface is still a problematic issue, in particular for the observed inversion of the n-type Ge surface, attributed to the presence of dangling bonds inducing a severe band bending [1]. In this scenario, the identification of electrically active defects present at the Ge/oxide interface and the capability to passivate or anneal them becomes a mandatory issue aiming at an electrically optimized interface. We report on the application of highly sensitive electrically detected magnetic resonance (EDMR) techniques in the investigation of defects at the interface between Ge and GeO2 (or GeOx), including Ge dangling bonds and defects in the oxide [2]. In particular we will investigate how different surface orientations, e.g. the (001) against the (111) Ge surface, impacts the microstructure of the interface defects. [1] P. Tsipas and A. Dimoulas, Appl. Phys. Lett. 94, 012114 (2009) [2] S. Baldovino, A. Molle, and M. Fanciulli, Appl. Phys. Lett. 96, 222110 (2010)

InGaN/GaN quantum dots as optical probes for the electric field at the GaN/electrolyte interface

NASA Astrophysics Data System (ADS)

Teubert, J.; Koslowski, S.; Lippert, S.; Schäfer, M.; Wallys, J.; Dimitrakopulos, G.; Kehagias, Th.; Komninou, Ph.; Das, A.; Monroy, E.; Eickhoff, M.

2013-08-01

We investigated the electric-field dependence of the photoluminescence-emission properties of InGaN/GaN quantum dot multilayers in contact with an electrolyte. Controlled variations of the surface potential were achieved by the application of external electric fields using the electrolytic Schottky contact and by variation of the solution's pH value. Prior to characterization, a selective electrochemical passivation process was required to suppress leakage currents. The quantum dot luminescence is strongly affected by surface potential variations, i.e., it increases exponentially with cathodic bias and acidic pH values. The results cannot be explained by a modification of intra-dot polarization induced electric fields via the quantum confined Stark effect but are attributed to the suppression/enhancement of non-radiative recombination processes, i.e., mainly hole transfer into the electrolyte. The results establish a link between the photoluminescence intensity and the magnitude of electric fields at the semiconductor/electrolyte interface.

Properties of Lightning Strike Protection Coatings

NASA Astrophysics Data System (ADS)

Gagne, Martin

Composite materials are being increasingly used by many industries. In the case of aerospace companies, those materials are installed on their aircraft to save weight, and thus, fuel costs. These aircraft are lighter, but the loss of electrical conductivity makes aircraft vulnerable to lightning strikes, which hit commercial aircrafts on average once per year. This makes lightning strike protection very important, and while current metallic expanded copper foils offer good protection, they increase the weight of composites. Therefore, under the CRIAQ COMP-502 project, a team of industrial partners and academic researchers are investigating new conductive coatings with the following characteristics: High electromagnetic protection, high mechanical resistance, good environmental protection, manufacturability and moderate cost. The main objectives of this thesis, as part of this project, was to determine the main characteristics, such as electrical and tribomechanical properties, of conductive coatings on composite panels. Their properties were also to be tested after destructive tests such as current injection and environmental testing. Bombardier Aerospace provided the substrate, a composite of carbon fiber reinforced epoxy matrix, and the current commercial product, a surfacing film that includes an expanded copper foil used to compare with the other coatings. The conductive coatings fabricated by the students are: silver nanoparticles inside a binding matrix (PEDOT:PSS or a mix of Epoxy and PEDOT:PSS), silvered carbon nanofibers embedded in the surfacing film, cold sprayed tin, graphene oxide functionalized with silver nanowires, and electroless plated silver. Additionally as part of the project and thesis, magnetron sputtered aluminum coated samples were fabricated. There are three main types of tests to characterize the conductive coatings: electrical, mechanical and environmental. Electrical tests consist of finding the sheet resistance and specific resistivity of conductive coatings. Mechanical tests include adhesion, scratch, hardness and Young's modulus of the coatings. The environmental tests are temperature cycling and salt spray cycling. These basic characteristics were investigated first, but further tests also combine the categories, such as electrical tests before, during and after environmental tests, and the effects on the sample's mechanical properties after high electrical current injections. The electrical properties of the conductive coatings have improved and are very close to that of current expanded metallic foil or within an order of magnitude. The mechanical properties of most of these coatings are also good. They exhibit good adhesion, hardness, and no significant loss of flexion properties after current injections. The environmental tests are more mitigated, with some conductive coatings losing their surface conductivity, others having a small increase in specific resistivity, and some were simply unaffected. Tests such as thermogravimetric analysis, scanning electron microscope analysis of scratch tests, and optical microscope observations are included to provide additional analysis of the results of the conductive coatings. The conductive coatings were characterized and tested as part of the CRIAQ project. Lightning strike tests are required to gather further information on these conductive coatings. The main application for these coatings is for lightning strike protection of aircraft, but they can also be used for ground based lightning strike protection and general electromagnetic shielding.

Hierarchy of adhesion forces in patterns of photoreactive surface layers

NASA Astrophysics Data System (ADS)

Hlawacek, Gregor; Shen, Quan; Teichert, Christian; Lex, Alexandra; Trimmel, Gregor; Kern, Wolfgang

2009-01-01

Precise control of surface properties including electrical characteristics, wettability, and friction is a prerequisite for manufacturing modern organic electronic devices. The successful combination of bottom up approaches for aligning and orienting the molecules and top down techniques to structure the substrate on the nano- and micrometer scale allows the cost efficient fabrication and integration of future organic light emitting diodes and organic thin film transistors. One possibility for the top down patterning of a surface is to utilize different surface free energies or wetting properties of a functional group. Here, we used friction force microscopy (FFM) to reveal chemical patterns inscribed by a photolithographic process into a photosensitive surface layer. FFM allowed the simultaneous visualization of at least three different chemical surface terminations. The underlying mechanism is related to changes in the chemical interaction between probe and film surface.

Interfacial and electrical properties of InGaAs metal-oxide-semiconductor capacitor with TiON/TaON multilayer composite gate dielectric

NASA Astrophysics Data System (ADS)

Wang, L. S.; Xu, J. P.; Liu, L.; Lu, H. H.; Lai, P. T.; Tang, W. M.

2015-03-01

InGaAs metal-oxide-semiconductor (MOS) capacitors with composite gate dielectric consisting of Ti-based oxynitride (TiON)/Ta-based oxynitride (TaON) multilayer are fabricated by RF sputtering. The interfacial and electrical properties of the TiON/TaON/InGaAs and TaON/TiON/InGaAs MOS structures are investigated and compared. Experimental results show that the former exhibits lower interface-state density (1.0 × 1012 cm-2 eV-1 at midgap), smaller gate leakage current (9.5 × 10-5 A/cm2 at a gate voltage of 2 V), larger equivalent dielectric constant (19.8), and higher reliability under electrical stress than the latter. The involved mechanism lies in the fact that the ultrathin TaON interlayer deposited on the sulfur-passivated InGaAs surface can effectively reduce the defective states and thus unpin the Femi level at the TaON/InGaAs interface, improving the electrical properties of the device.

Inspecting Friction Stir Welding using Electromagnetic Probes

NASA Technical Reports Server (NTRS)

Kinchen, David G.

2004-01-01

A report describes the use of advanced electromagnetic probes to measure the dimensions, the spatial distribution of electrical conductivity, and related other properties of friction stir welds (FSWs) between parts made of the same or different aluminum alloy(s). The probes are of the type described in in another Tech Brief. To recapitulate: A probe of this type is essentially an eddy-current probe that includes a primary (driver) winding that meanders and multiple secondary (sensing) windings that meander along the primary winding. Electrical conductivity is commonly used as a measure of heat treatment and tempering of aluminum alloys, but prior to the development of these probes, the inadequate sensitivity and limited accuracy of electrical-conductivity probes precluded such use on FSWs between different aluminum alloys, and the resolution of those probes was inadequate for measurement of FSW dimensions with positions and metallurgical properties. In contrast, the present probes afford adequate accuracy and spatial resolution for the purposes of measuring the dimensions of FSW welds and correlating spatially varying electrical conductivities with metallurgical properties, including surface defects.

Evaluation of physico-mechanical properties of clayey soils using electrical resistivity imaging technique

NASA Astrophysics Data System (ADS)

Kibria, Golam

Resistivity imaging (RI) is a promising approach to obtaining continuous profile of soil subsurface. This method offers simple technique to identify moisture variation and heterogeneity of the investigated area. However, at present, only qualitative information of subsurface can be obtained using RI. A study on the quantification of geotechnical properties has become important for rigorous use of this method in the evaluation of geohazard potential and construction quality control of landfill liner system. Several studies have been performed to describe electrical resistivity of soil as a function of pore fluid conductivity and surface conductance. However, characterization tests on pore water and surface charge are not typically performed in a conventional geotechnical investigation. The overall objective of this study is to develop correlations between geotechnical parameters and electrical resistivity of soil, which would provide a mean to estimate geotechnical properties from RI. As a part of the study, multiple regression analyses were conducted to develop practically applicable models correlating resistivity with influential geotechnical parameters. The soil samples considered in this study were classified as highly plastic clay (CH) and low plasticity clay (CL) according to Unified Soil Classification System (USCS). Based on the physical tests, scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS) analysis, kaolinite was identified as the dominant mineral with some traces of magnesium, calcium, potassium, and iron. Electrical resistivity tests were conducted on compacted clays and undisturbed samples under varied geotechnical conditions. The experimental results indicated that the degree of saturation substantially influenced electrical resistivity. Electrical resistivity decreased as much as 11 times from initial value for the increase of degree of saturation from 23 to 100% in the laboratory tests on compacted clays. In case of undisturbed soil samples, resistivity decreased as much as sixteen fold (49.4 to 3.2 Ohm-m) for an increase of saturation from 31 to 100%. Furthermore, the resistivity results were different for the specimens at a specific degree of saturation because of varied surface activity and isomorphous substitution of clayey soils. In addition to physical properties, compressibility of clays was correlated with electrical conductivity. Based on the investigation, it was determined that the electrical conductivity vs. pressure curves followed similar trends as e vs. logp curves. Multiple linear regression (MLR) models were developed for compacted and undisturbed samples using statistical analysis software SAS (2009). During model development, degree of saturation and CEC were selected as independent variables. The proposed models were validated using experimental results on a different set of samples. Moreover, the applicability of the models in the determination of degrees of saturation was evaluated using field RI tests.

Engineering Topological Surface State of Cr-doped Bi2Se3 under external electric field

NASA Astrophysics Data System (ADS)

Zhang, Jian-Min; Lian, Ruqian; Yang, Yanmin; Xu, Guigui; Zhong, Kehua; Huang, Zhigao

2017-03-01

External electric field control of topological surface states (SSs) is significant for the next generation of condensed matter research and topological quantum devices. Here, we present a first-principles study of the SSs in the magnetic topological insulator (MTI) Cr-doped Bi2Se3 under external electric field. The charge transfer, electric potential, band structure and magnetism of the pure and Cr doped Bi2Se3 film have been investigated. It is found that the competition between charge transfer and spin-orbit coupling (SOC) will lead to an electrically tunable band gap in Bi2Se3 film under external electric field. As Cr atom doped, the charge transfer of Bi2Se3 film under external electric field obviously decreases. Remarkably, the band gap of Cr doped Bi2Se3 film can be greatly engineered by the external electric field due to its special band structure. Furthermore, magnetic coupling of Cr-doped Bi2Se3 could be even mediated via the control of electric field. It is demonstrated that external electric field plays an important role on the electronic and magnetic properties of Cr-doped Bi2Se3 film. Our results may promote the development of electronic and spintronic applications of magnetic topological insulator.

Influence of surface conductivity on the apparent zeta potential of calcite.

PubMed

Li, Shuai; Leroy, Philippe; Heberling, Frank; Devau, Nicolas; Jougnot, Damien; Chiaberge, Christophe

2016-04-15

Zeta potential is a physicochemical parameter of particular importance in describing the surface electrical properties of charged porous media. However, the zeta potential of calcite is still poorly known because of the difficulty to interpret streaming potential experiments. The Helmholtz-Smoluchowski (HS) equation is widely used to estimate the apparent zeta potential from these experiments. However, this equation neglects the influence of surface conductivity on streaming potential. We present streaming potential and electrical conductivity measurements on a calcite powder in contact with an aqueous NaCl electrolyte. Our streaming potential model corrects the apparent zeta potential of calcite by accounting for the influence of surface conductivity and flow regime. We show that the HS equation seriously underestimates the zeta potential of calcite, particularly when the electrolyte is diluted (ionic strength ⩽ 0.01 M) because of calcite surface conductivity. The basic Stern model successfully predicted the corrected zeta potential by assuming that the zeta potential is located at the outer Helmholtz plane, i.e. without considering a stagnant diffuse layer at the calcite-water interface. The surface conductivity of calcite crystals was inferred from electrical conductivity measurements and computed using our basic Stern model. Surface conductivity was also successfully predicted by our surface complexation model. Copyright © 2016 Elsevier Inc. All rights reserved.

Amphotericin B channels in phospholipid membrane-coated nanoporous silicon surfaces: implications for photovoltaic driving of ions across membranes.

PubMed

Yilma, Solomon; Liu, Nangou; Samoylov, Alexander; Lo, Ting; Brinker, C Jeffrey; Vodyanoy, Vitaly

2007-03-15

The antimycotic agent amphotericin B (AmB) functions by forming complexes with sterols to form ion channels that cause membrane leakage. When AmB and cholesterol mixed at 2:1 ratio were incorporated into phospholipid bilayer membranes formed on the tip of patch pipettes, ion channel current fluctuations with characteristic open and closed states were observed. These channels were also functional in phospholipid membranes formed on nanoporous silicon surfaces. Electrophysiological studies of AmB-cholesterol mixtures that were incorporated into phospholipid membranes formed on the surface of nanoporous (6.5 nm pore diameter) silicon plates revealed large conductance ion channels ( approximately 300 pS) with distinct open and closed states. Currents through the AmB-cholesterol channels on nanoporous silicon surfaces can be driven by voltage applied via conventional electrical circuits or by photovoltaic electrical potential entirely generated when the nanoporous silicon surface is illuminated with a narrow laser beam. Electrical recordings made during laser illumination of AmB-cholesterol containing membrane-coated nanoporous silicon surfaces revealed very large conductance ion channels with distinct open and closed states. Our findings indicate that nanoporous silicon surfaces can serve as mediums for ion-channel-based biosensors. The photovoltaic properties of nanoporous silicon surfaces show great promise for making such biosensors addressable via optical technologies.

Effect of Electric Field on the Wetting Behavior of Eutectic Gallium-Indium Alloys in Aqueous Environment

NASA Astrophysics Data System (ADS)

Yuan, Bo; He, Zhi-Zhu; Liu, Jing

2018-02-01

Room-temperature liquid metals have many intriguing properties that have not previously been fully understood. Among them, surface tension behaviors of such metals are especially critical in a group of newly emerging areas such as printed electronics, functional materials and soft machines, etc. This study is dedicated to clarifying the wettability of liquid metals on various substrate surfaces with varied roughness immersed in solutions when subject to an electric field. The contact angles of Ga75.5In24.5 in several typical liquids were comprehensively measured and interpreted, and were revealed to be affected by the components and concentration of the environmental solution. Meanwhile, the roughness of the substrates is also revealed to be an important parameter dominating the process. The dynamic wetting behaviors of liquid metal in aqueous environment under an electric field were quantified. The contact angle values of eutectic gallium-indium alloys (eGaIn) on titanium substrates with different roughness would lead to better electrowetting performances on rougher surfaces. In particular, using an electrical field to control the wetting status of liquid metal with the matching substrate have been illustrated, which would offer a practical way to flexibly control liquid metal-based functional devices working in an aqueous environment. Furthermore, Lippmann-Young's equation reveals the relationship between contact angle and applied voltage, explaining the excellent electrowetting property of eGaIn. The power law, R = αt β , was adopted to characterize the two-stage wetting process of eGaIn under different voltages. In the initial process, β ≈ 1/2 represents the complete wetting law, while the later one, β ≈ 1/10, meets with Tanner's law of a drop spontaneously spreading on a smooth surface.

Optical, electrical, and photovoltaic properties of PbS thin films by anionic and cationic dopants

NASA Astrophysics Data System (ADS)

Cheraghizade, Mohsen; Jamali-Sheini, Farid; Yousefi, Ramin

2017-06-01

Lead sulfide (PbS) thin films were deposited by CVD method to examine the effects of anionic and cationic dopants on optical and electrical properties for photovoltaic applications. XRD diffractograms verified the formation of cubic phase of multicrystalline PbS thin films. FESEM images showed surface morphologies in nano-dimensions (rods and flowers). UV-Vis-NIR spectrum revealed absorbance in the visible and NIR regions for all samples, in which dopants decreased the intensity of absorbance. Se as an anionic dopant for PbS thin films increased electrical resistance, acceptor concentrations, and crystallite defects, and decreased flat-band voltage and depletion width. Finally, photovoltaic measurements indicated that Zn-doped PbS thin film, as a photovoltaic cell, exhibited higher conversion efficiency and external quantum efficiency (EQE).

A knitted glove sensing system with compression strain for finger movements

NASA Astrophysics Data System (ADS)

Ryu, Hochung; Park, Sangki; Park, Jong-Jin; Bae, Jihyun

2018-05-01

Development of a fabric structure strain sensor has received considerable attention due to its broad application in healthcare monitoring and human–machine interfaces. In the knitted textile structure, it is critical to understand the surface structural deformation from a different body motion, inducing the electrical signal characteristics. Here, we report the electromechanical properties of the knitted glove sensing system focusing on the compressive strain behavior. Compared with the electrical response of the tensile strain, the compressive strain shows much higher sensitivity, stability, and linearity via different finger motions. Additionally, the sensor exhibits constant electrical properties after repeated cyclic tests and washing processes. The proposed knitted glove sensing system can be readily extended to a scalable and cost-effective production due to the use of a commercialized manufacturing system.

Gate-tunable gigantic changes in lattice parameters and optical properties in VO2

NASA Astrophysics Data System (ADS)

Nakano, Masaki; Okuyama, Daisuke; Shibuya, Keisuke; Ogawa, Naoki; Hatano, Takafumi; Kawasaki, Masashi; Arima, Taka-Hisa; Iwasa, Yoshihiro; Tokura, Yoshinori

2014-03-01

The field-effect transistor provides an electrical switching function of current flowing through a channel surface by external gate voltage (VG). We recently reported that an electric-double-layer transistor (EDLT) based on vanadium dioxide (VO2) enables electrical switching of the metal-insulator phase transition, where the low-temperature insulating state can be completely switched to the metallic state by application of VG. Here we demonstrate that VO2-EDLT enables electrical switching of lattice parameters and optical properties as well as electrical current. We performed in-situ x-ray diffraction and optical transmission spectroscopy measurements, and found that the c-axis length and the infrared transmittance of VO2 can be significantly modulated by more than 1% and 40%, respectively, by application of VG. We emphasize that these distinguished features originate from the electric-field induced bulk phase transition available with VO2-EDLT. This work was supported by the Japan Society for the Promotion of Science (JSPS) through its ``Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST Program).''

Probing organic field effect transistors in situ during operation using SFG.

PubMed

Ye, Hongke; Abu-Akeel, Ashraf; Huang, Jia; Katz, Howard E; Gracias, David H

2006-05-24

In this communication, we report results obtained using surface-sensitive IR+Visible Sum Frequency Generation (SFG) nonlinear optical spectroscopy on interfaces of organic field effect transistors during operation. We observe remarkable correlations between trends in the surface vibrational spectra and electrical properties of the transistor, with changes in gate voltage (VG). These results suggest that field effects on electronic conduction in thin film organic semiconductor devices are correlated to interfacial nonlinear optical characteristics and point to the possibility of using SFG spectroscopy to monitor electronic properties of OFETs.

Mechanochemical activation and patterning of an adhesive surface toward nanoparticle deposition.

PubMed

Baytekin, H Tarik; Baytekin, Bilge; Huda, Sabil; Yavuz, Zelal; Grzybowski, Bartosz A

2015-02-11

Mechanical pulling of adhesive tape creates radicals on the tape's surface. These radicals are capable of reducing metal salts to the corresponding metal nanoparticles. In this way, the mechanically activated tape can be decorated with various types of nanoparticles, including Au, Ag, Pd, or Cu. While retaining their mechanical properties and remaining "sticky," the tapes can exhibit new properties derived from the presence of metal nanoparticles (e.g., bacteriostaticity, increased electrical conductivity). They can also be patterned with nanoparticles only at selective locations of mechanical activation.

Analysis of ultraviolet exposure effects on the surface properties of epoxy/graphene nanocomposite films on Mylar substrate

NASA Astrophysics Data System (ADS)

Clausi, Marialaura; Santonicola, M. Gabriella; Schirone, Luigi; Laurenzi, Susanna

2017-05-01

In this paper, we present a study of the effects generated by exposure to UV-C radiation on nanocomposite films made of graphene nanoplatelets dispersed in an epoxy matrix. The nanocomposite films, at different nanoparticle size and concentration, were fabricated on Mylar substrate using the spin coating process. The effects of UV-C irradiation on the surface hydrophobicity and on the electrical properties of the epoxy/graphene films were investigated using contact angle measurements and electrical impedance spectroscopy, respectively. According to our results, the UV-C irradiation selectively degrades the polymer matrix of the nanocomposite films, giving rise to more conductive and hydrophobic layers due to exposure of the graphene component of the composite material. The results presented here have important implications in the design of spacecraft components and structures destined for long-term space missions.

Structure of propagating arc in a magneto-hydrodynamic rail plasma actuator

NASA Astrophysics Data System (ADS)

Gray, Miles D.; Choi, Young-Joon; Sirohi, Jayant; Raja, Laxminarayan L.

2016-01-01

The spatio-temporal evolution of a magnetically driven arc in a rail plasma flow actuator has been characterized with high-speed imaging, electrical measurements, and spectroscopy. The arc draws a peak current of ~1 kA. High-speed framing cameras were used to observe the complex arc propagation phenomenon. In particular, the anode and cathode roots were observed to have different modes of transit, which resulted in distinct types of electrode degradation on the anode and cathode surfaces. Observations of the arc electrical properties and induced magnetic fields are used to explain the transit mechanism of the arc. Emission spectroscopy revealed the arc temperature and species composition as a function of transit distance of the arc. The results obtained offer significant insights into the electromagnetic properties of the arc-rail system as well as arc-surface interaction phenomena in a propagating arc.

High-Performance Polyimide Powder Coatings

NASA Technical Reports Server (NTRS)

2008-01-01

Much of the infrastructure at Kennedy Space Center and other NASA sites has been subjected to outside weathering effects for more than 40 years. Because much of this infrastructure has metallic surfaces, considerable effort is continually devoted to developing methods to minimize the effects of corrosion on these surfaces. These efforts are especially intense at KSC, where offshore salt spray and exhaust from Solid Rocket Boosters accelerate corrosion. Coatings of various types have traditionally been the choice for minimizing corrosion, and improved corrosion control methods are constantly being researched. Recent work at KSC on developing an improved method for repairing Kapton (polyimide)-based electrical wire insulation has identified polyimides with much lower melting points than traditional polyimides used for insulation. These lower melting points and the many other outstanding physical properties of polyimides (thermal stability, chemical resistance, and electrical properties) led us to investigate whether they could be used in powder coatings.

Carbon Redox-Polymer-Gel Hybrid Supercapacitors

PubMed Central

Vlad, A.; Singh, N.; Melinte, S.; Gohy, J.-F.; Ajayan, P.M.

2016-01-01

Energy storage devices that provide high specific power without compromising on specific energy are highly desirable for many electric-powered applications. Here, we demonstrate that polymer organic radical gel materials support fast bulk-redox charge storage, commensurate to surface double layer ion exchange at carbon electrodes. When integrated with a carbon-based electrical double layer capacitor, nearly ideal electrode properties such as high electrical and ionic conductivity, fast bulk redox and surface charge storage as well as excellent cycling stability are attained. Such hybrid carbon redox-polymer-gel electrodes support unprecedented discharge rate of 1,000C with 50% of the nominal capacity delivered in less than 2 seconds. Devices made with such electrodes hold the potential for battery-scale energy storage while attaining supercapacitor-like power performances. PMID:26917470

Optical and electrical stability of viral-templated copper sulfide (Cu{sub 1.8}S) films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shahriar Zaman, Mohammed; Bernard Grajeda, Gabriel; Haberer, Elaine D., E-mail: haberer@ucr.edu

The optical and electrical stabilities of viral-templated non-stoichiometric copper sulfide, digenite (Cu{sub 1.8}S) films were investigated. The films were composed of large agglomerates of randomly aligned Cu{sub 1.8}S-coated M13 filamentous phage. Free carrier optical absorption associated with localized surface plasmon resonance (LSPR) was observed in the near infrared spectral region, and the films were electrically active, displaying a linear current-voltage relationship. Under ambient conditions, the magnitude of the LSPR absorption increased, following a power law relationship with time, and the electrical resistance of viral-templated films decreased significantly. In contrast, the resistance of films stored under low oxygen, low humidity conditionsmore » experienced a smaller reduction in electrical resistance. Changes in optical and electrical film properties under ambient conditions were associated with an increase in free carrier concentration within the copper chalcogenide material due to oxygen exposure. X-ray photoelectron spectroscopy was used to relate this increase in free carrier concentration to compositional changes on the viral-templated material surface.« less

POlarized Light Angle Reflectance Instrument I Polarized Incidence (POLAR:I)

NASA Technical Reports Server (NTRS)

Sarto, Anthony W.; Woldemar, Christopher M.; Vanderbilt, V. C.

1989-01-01

The light scattering properties of leaves are used as input data for models which mathematically describe the transport of photons within plant canopies. Polarization measurements may aid in the investigation of these properties. This paper describes an instrument for rapidly determining the bidirectional light scattering properties of leaves illuminated by linearly polarized light. Results for one species, magnolia, show large differences in the bidirectional light scattering properties depending whether or not the electric vector E is parallel to the foliage surface.

Oligonucleotide probes functionalization of nanogap electrodes.

PubMed

Zaffino, Rosa Letizia; Mir, Mònica; Samitier, Josep

2017-11-01

Nanogap electrodes have attracted a lot of consideration as promising platform for molecular electronic and biomolecules detection. This is mainly for their higher aspect ratio, and because their electrical properties are easily accessed by current-voltage measurements. Nevertheless, application of standard current-voltages measurements used to characterize nanogap response, and/or to modify specific nanogap electrodes properties, represents an issue. Since the strength of electrical fields in nanoscaled devices can reach high values, even at low voltages. Here, we analyzed the effects induced by different methods of surface modification of nanogap electrodes, in test-voltage application, employed for the electrical detection of a desoxyribonucleic acid (DNA) target. Nanogap electrodes were functionalized with two antisymmetric oligo-probes designed to have 20 terminal bases complementary to the edges of the target, which after hybridization bridges the nanogap, closing the electrical circuit. Two methods of functionalization were studied for this purpose; a random self-assembling of a mixture of the two oligo-probes (OPs) used in the platform, and a selective method that controls the position of each OP at selected side of nanogap electrodes. We used for this aim, the electrophoretic effect induced on negatively charged probes by the application of an external direct current voltage. The results obtained with both functionalization methods where characterized and compared in terms of electrode surface covering, calculated by using voltammetry analysis. Moreover, we contrasted the electrical detection of a DNA target in the nanogap platform either in site-selective and in randomly assembled nanogap. According to our results, a denser, although not selective surface functionalization, is advantageous for such kind of applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface morphological, structural, electrical and optical properties of GaN-based light-emitting diodes using submicron-scaled Ag islands and ITO thin films

NASA Astrophysics Data System (ADS)

Lee, Young-Woong; Reddy, M. Siva Pratap; Kim, Bo-Myung; Park, Chinho

2018-07-01

An ITO-Ag islands complex as a new transparent conducting electrode (TCE) structure (on the 5 nm-thick p-InGaN/90 nm-thick p-GaN) for achieving high-performance and more reliable GaN-based LEDs were fabricated. A normal LED with a conventional ITO TCE was also compared. The surface morphological, structural, electrical and optical properties of fabricated GaN-based light-emitting diodes using a complex electrode of submicron-scaled Ag islands and ITO thin films are explored by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), current-voltage (I-V) and output power-current (L-I) techniques. Surface morphology investigations revealed Ag islands formed uniformly on the p-InGaN/p-GaN surface during rapid thermal annealing at 400 °C for 1 min in N2 ambient. The ohmic properties and overall device-performance of the suggested contact and device structures were superior to those in the conventional ITO contact and normal ITO LED structures. Based on the results of XRD and XPS measurements, the formation of the intermetallic gallide phases (AgGa) is responsible for better performance characteristics of the ITO-Ag islands device. The significant improvements are described in terms of the conducting bridge influence, highly effective micro-mirror effect, and wider photon window via the roughened structure.

Plasmonic transparent conductors

NASA Astrophysics Data System (ADS)

Liapis, Andreas C.; Sfeir, Matthew Y.; Black, Charles T.

2016-09-01

Many of today's technological applications, such as solar cells, light-emitting diodes, displays, and touch screens, require materials that are simultaneously optically transparent and electrically conducting. Here we explore transparent conductors based on the excitation of surface plasmons in nanostructured metal films. We measure both the optical and electrical properties of films perforated with nanometer-scale features and optimize the design parameters in order to maximize optical transmission without sacrificing electrical conductivity. We demonstrate that plasmonic transparent conductors can out-perform indium tin oxide in terms of both their transparency and their conductivity.

Electrons on a spherical surface: Physical properties and hollow spherical clusters

NASA Astrophysics Data System (ADS)

Cricchio, Dario; Fiordilino, Emilio; Persico, Franco

2012-07-01

We discuss the physical properties of a noninteracting electron gas constrained to a spherical surface. In particular we consider its chemical potentials, its ionization potential, and its electric static polarizability. All these properties are discussed analytically as functions of the number N of electrons. The trends obtained with increasing N are compared with those of the corresponding properties experimentally measured or theoretically evaluated for quasispherical hollow atomic and molecular clusters. Most of the properties investigated display similar trends, characterized by a prominence of shell effects. This leads to the definition of a scale-invariant distribution of magic numbers which follows a power law with critical exponent -0.5. We conclude that our completely mechanistic and analytically tractable model can be useful for the analysis of self-assembling complex systems.

Synergistic effect of topography, surface chemistry and conductivity of the electrospun nanofibrous scaffold on cellular response of PC12 cells.

PubMed

Tian, Lingling; Prabhakaran, Molamma P; Hu, Jue; Chen, Menglin; Besenbacher, Flemming; Ramakrishna, Seeram

2016-09-01

Electrospun nanofibrous nerve implants is a promising therapy for peripheral nerve injury, and its performance can be tailored by chemical cues, topographical features as well as electrical properties. In this paper, a surface modified, electrically conductive, aligned nanofibrous scaffold composed of poly (lactic acid) (PLA) and polypyrrole (Ppy), referred to as o-PLAPpy_A, was fabricated for nerve regeneration. The morphology, surface chemistry and hydrophilicity of nanofibers were characterized by Scanning Electron Microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and water contact angle, respectively. The effects of these nanofibers on neuronal differentiation using PC12 cells were evaluated. A hydrophilic surface was created by Poly-ornithine coating, which was able to provide a better environment for cell attachment, and furthermore aligned fibers were proved to be able to guide PC12 cells grow along the fiber direction and be beneficial for neurite outgrowth. The cellular response of PC12 cells to pulsed electrical stimulation was evaluated by NF 200 and alpha tubulin expression, indicating that electrical stimulation with a voltage of 40mV could enhance the neurite outgrowth. The PC12 cells stimulated with electrical shock showed greater level of neurite outgrowth and smaller cell body size. Moreover, the PC12 cells under electrical stimulation showed better viability. In summary, the o-PLAPpy_A nanofibrous scaffold supported the attachment, proliferation and differentiation of PC12 cells in the absence of electrical stimulation, which could be potential candidate for nerve regeneration applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Diester-containing Zwitterionic Gemini Surfactants with Different Spacer and Its Impact on Micellization Properties and Viscosity of Aqueous Micellar Solution.

PubMed

Patil, Sachin Vasant; Patil, Sanyukta Arun; Pratap, Amit Prabhakar

2016-09-01

A series of diester containing zwitterionic gemini surfactants, N,N-dimethyl-N-alkyl-2-[[hydroxy (alkoxy) phosphinyl]oxy]-alkylammonium designated as C8(-)-S-Cn(+), S = 2 and 3, n = 12, 14 and 16, were synthesized and characterized by instrumental techniques namely FT-IR, (1)H NMR, (13)C NMR, (31)P NMR and Mass spectral studies. These new gemini surfactants further investigated for their various surfactant properties. The critical micelle concentration (cmc) and the effectiveness of surface tension reduction (Πcmc) were determined as a function of surfactant concentration by means of surface tension measurement. Micellization and viscosity properties were investigated by surface tension, electrical conductivity, dye micellization and rheology techniques. The findings of the aqueous surfactant system obtained were impacted by polarity, size and the nature of zwitterions as the surface. The thermodynamic and viscosity properties of these surfactants found to be based on the structures of gemini surfactants.

Partial substitution of Zn Effects on the Structural and Electrical Properties of High Temperature Hg0.95Ag0.05Ba2Ca2Cu3O8+δ Superconductors

NASA Astrophysics Data System (ADS)

Abed, Noor S.; Fathi, Sabah J.; Jassim, Kareem A.; Mahdi, Shatha H.

2018-05-01

The effect of the Ag partial substitution at Hg site in HgOδ layer and Zn partial substitution at Ca site in CaO layer on the structure,Tc,electrical properties, and oxygen content for Hg-1223 have been studied. Bulk polycrystalline Hg1-xAgxBa2Ca2-yZnyCu3O8+δ compound samples with x=0.05 and y=0.0, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3, are synthesized by a solid state reaction process. Structural properties are studied by using X-ray powder pattern, the high temperature phase superconductor (Hg-1223) of the tetragonal structure didn't change with the partial substitution of Zn and Ag ions, lattice parameters c,c/a are established to vary with Ag and Zn- substitution. The surface morphology has been studied by using atomic force microscopes (AFM), showed that all specimens have good crystalline and homogeneous surface. Also give a best nano size value is 75.72 nm at x=0.05 and y=0.3. Four probe technique is used to measure Tc. The Tc were found to be increases from 129 K to 147 K and oxygen content were found to be increases with increasing Zn. In addition, dielectric properties (dielectric constant, dielectric loss factor, and the alternating electrical conductivity) are characterized directly by relating with Ag and Zn concentration.

Multipulse nanosecond laser irradiation of silicon for the investigation of surface morphology and photoelectric properties

NASA Astrophysics Data System (ADS)

Sardar, Maryam; Chen, Jun; Ullah, Zaka; Jelani, Mohsan; Tabassum, Aasma; Cheng, Ju; Sun, Yuxiang; Lu, Jian

2017-12-01

We irradiate the single crystal boron-doped silicon (Si) with different number of laser pulses at constant fluence (7.5 J cm-2) in ambient air using Nd:YAG laser and examine its surface morphology and photoelectric properties in details. The results obtained from optical micrographs reveal the increase in heat affected zone (HAZ) and melted area of laser irradiated Si with increasing number of laser pulses. The SEM micrographs evidence the formation of various surface morphologies like laser induced periodic surface structures, crater, microcracks, clusters, cavities, pores, trapped bubbles, nucleation sites, micro-bumps, redeposited material and micro- and nano-particles on the surface of irradiated Si. The surface profilometry analysis informs that the depth of crater is increased with increase in number of incident laser pulses. The spectroscopic ellipsometry reveals that the multipulse irradiation of Si changes its optical properties (refractive index and extinction coefficient). The current-voltage (I-V) characteristic curves of laser irradiated Si show that although the multipulse laser irradiation produces considerable number of surface defects and damages, the electrical properties of Si are well sustained after the multipulse irradiation. The current findings suggest that the multipulse irradiation can be an effective way to tune the optical properties of Si for the fabrication of wide range of optoelectronic devices.

Development of electrically conductive-superoleophobic micropillars for reducing surface adhesion of oil at low temperatures

NASA Astrophysics Data System (ADS)

Pan, Zihe; Wang, Tianchang; Zhou, Yikang; Zhao, Boxin

2016-12-01

Electrically conductive and superoleophobic micropillars have been developed through the construction of biomimetic micropillars using Ag-filled epoxy composites and the incorporation of FDTS on the micropillar surface. These micropillars are found to be superoleophobic with an oil contact angle of 140°, demonstrating excellent self-cleaning properties. The conductivity of micropillars allows for the Joule-heating effect to actively reduce the adhesion and even unfreeze the frozen oil droplets by passing electrical current. Electrical resistance of the composite micropillars was modulated by two orders of magnitudes by varying the contents of Ag flakes from 45 wt% to 65 wt%. The effectiveness of conductive micropillars for surface un-freezing was investigated by applying DC current to decrease the adhesion strength of frozen oil droplets on surfaces. The results showed a pronounced reduction of frozen oil adhesion force by 60% when the resistance increased from 7.5 Ω to 877 Ω after applying DC current for 2 min. By continuously applying DC current for 3 min, the frozen oil adhesion decreased to 0.05 N, reaching zero when the surface was heated up to -10 °C after applying DC current for 5 min. In contrast, when the droplet was heated up to -5 °C by hot air, there is still a substantial force of adhesion. The research findings demonstrate the use of constructing conductive-superoleophobic composite micropillars at surface for eliminating the frozen oil from surfaces at low temperatures.

Dielectrophoresis-Based Particle Sensor Using Nanoelectrode Arrays

NASA Technical Reports Server (NTRS)

Li, Jun; Cassell, Alan M.; Arumugam, Prabhu U.

2013-01-01

A method has been developed for concentrating, or partly separating, particles of a selected species from a liquid or gas containing these particles, and flowing in a channel. An example of this is to promote an accumulation (and thus concentration) of the selected particle (e.g., biological species such as E. coli, salmonella, anthrax, tobacco mosaic virus or herpes simplex, and non-biological materials such as nano- and microparticles, quantum dots, nanowires, nano - tubes, and other inorganic particles) adjacent to the first surface. Additionally, this method can also determine if the particle species is present in the liquid. This is accomplished by providing an insulating material in an interstitial volume between two or more adjacent nanostructure electrodes. It can also be accomplished by providing a functionalizing substance, located on a selected region of the insulating material surface, which promotes attachment of the selected species particles to the functionalized surface, and measuring a selected electrical property such as electrical impedance, conductance, or capacitance. A time-varying electrical field E, having a root-mean-square intensity of E(sup 2) rms, with a non-zero gradient in a direction transverse to the liquid or fluid flow direction, is produced by a nanostructure electrode array with a very high-magnitude gradient near exposed electrode tips. A dielectrophoretic force causes the selected particles to accumulate near the electrode tips, if the medium and selected particles have substantially different dielectric constants. An insulating material surrounds most of the nanostructure electrodes, and a region of the insulating material surface is functionalized to promote attachment of the selected particle species to the surface. An electrical property value Z(meas) is measured at the functionalized surface, and is compared with a reference value Z(ref) to determine if the selected species particles are attached to the functionalized surface. Some advantages of this innovation are that an array of nanostructure electrodes can provide an electric field intensity gradient that is one or more orders of magnitude greater than the corresponding gradient provided by a conventional microelectrode arrangement, and that, as a result of the high-magnitude field intensity gradients, a nanostructure concentrator can trap particles from high-speed microfluidic flows. This is critical for applications where the entire analysis must be performed in a few minutes

Method for simultaneous measurement of mass loading and fluid property changes using a quartz crystal microbalance

DOEpatents

Granstaff, Victoria E.; Martin, Stephen J.

1993-01-01

A method, using a quartz crystal microbalance, to obtain simultaneous measurement of solid mass accumulation and changes in liquid density-viscosity product. The simultaneous real-time measurements of electrical parameters yields that changes in surface mass can be differentiated from changes in solution properties. Two methods to obtain the admittance/frequency data are employed.

Fabrication of nanoscale to macroscale nickel-multiwall carbon nanotube hybrid materials with tunable material properties

NASA Astrophysics Data System (ADS)

Abdalla, Ahmed M.; Majdi, Tahereh; Ghosh, Suvojit; Puri, Ishwar K.

2016-12-01

To utilize their superior properties, multiwall carbon nanotubes (MWNTs) must be manipulated and aligned end-to-end. We describe a nondestructive method to magnetize MWNTs and provide a means to remotely manipulate them through the electroless deposition of magnetic nickel nanoparticles on their surfaces. The noncovalent bonds between Ni nanoparticles and MWNTs produce a Ni-MWNT hybrid material (NiCH) that is electrically conductive and has an enhanced magnetic susceptibility and elastic modulus. Our experiments show that MWNTs can be plated with Ni for Ni:MWNT weight ratios of γ = 1, 7, 14 and 30, to control the material properties. The phase, atom-level, and morphological information from x-ray diffraction, energy dispersive x-ray spectroscopy, scanning electron microscopy, transmission electron microscopy, dark field STEM, and atomic force microscopy clarify the plating process and reveal the mechanical properties of the synthesized material. Ni metalizes at the surface of the Pd catalyst, forming a continuous wavy layer that encapsulates the MWNT surfaces. Subsequently, Ni acts as an autocatalyst, allowing the plating to continue even after the original Pd catalyst has been completely covered. Raising γ increases the coating layer thickness from 10 to 150 nm, which influences the NiCH magnetic properties and tunes its elastic modulus from 12.5 to 58.7 GPa. The NiCH was used to fabricate Ni-MWNT macrostructures and tune their morphologies by changing the direction of an applied magnetic field. Leveraging the hydrophilic Ni-MWNT outer surface, a water-based conductive ink was created and used to print a conductive path that had an electrical resistivity of 5.9 Ω m, illustrating the potential of this material for printing electronic circuits.

Dust particles investigation for future Russian lunar missions.

NASA Astrophysics Data System (ADS)

Dolnikov, Gennady; Horanyi, Mihaly; Esposito, Francesca; Zakharov, Alexander; Popel, Sergey; Afonin, Valeri; Borisov, Nikolay; Seran, Elena; Godefroy, Michel; Shashkova, Inna; Kuznetsov, Ilya; Lyash, Andrey; Vorobyova, Elena; Petrov, Oleg; Lisin, Evgeny

One of the complicating factors of the future robotic and human lunar landing missions is the influence of the dust. Meteorites bombardment has accompanied by shock-explosive phenomena, disintegration and mix of the lunar soil in depth and on area simultaneously. As a consequence, the lunar soil has undergone melting, physical and chemical transformations. Recently we have the some reemergence for interest of Moon investigation. The prospects in current century declare USA, China, India, and European Union. In Russia also prepare two missions: Luna-Glob and Luna-Resource. Not last part of investigation of Moon surface is reviewing the dust condition near the ground of landers. Studying the properties of lunar dust is important both for scientific purposes to investigation the lunar exosphere component and for the technical safety of lunar robotic and manned missions. The absence of an atmosphere on the Moon's surface is leading to greater compaction and sintering. Properties of regolith and dust particles (density, temperature, composition, etc.) as well as near-surface lunar exosphere depend on solar activity, lunar local time and position of the Moon relative to the Earth's magneto tail. Upper layers of regolith are an insulator, which is charging as a result of solar UV radiation and the constant bombardment of charged particles, creates a charge distribution on the surface of the moon: positive on the illuminated side and negative on the night side. Charge distribution depends on the local lunar time, latitude and the electrical properties of the regolith (the presence of water in the regolith can influence the local distribution of charge). On light side of Moon near surface layer there exists possibility formation dusty plasma system. Altitude of levitation is depending from size of dust particle and Moon latitude. The distribution dust particle by size and altitude has estimated with taking into account photoelectrons, electrons and ions of solar wind, solar emission. Dust analyzer instrument PmL for future Russian lender missons intends for investigation the dynamics of dusty plasma near lunar surface. PmL consist of three blocks: Impact Sensor and two Electric Field Sensors. Dust Experiment goals are: 1) Impact sensor to investigate the dynamics of dust particles near the lunar surface (speed, charge, mass, vectors of a fluxes) a) high speed micrometeorites b) secondary particles after micrometeorites soil bombardment c) levitating dust particles due to electrostatic fields PmL instrument will measure dust particle impulses. In laboratory tests we used - min impulse so as 7•10-11 N•c, by SiO2 dust particles, 20-40 µm with velocity about 0,5 -2,5 m/c, dispersion 0.3, and - max impulse was 10-6 N•c with possibility increased it by particles Pb-Sn 0,7 mm with velocity 1 m/c, dispersion ±0.3. Also Impact Sensor will measure the charge of dust particle as far as 10-15 C ( 1000 electrons). In case the charge and impulse of a dust particle are measured we can obtain velocity and mass of them. 2) Electric field Sensor will measure the value and dynamics of the electric fields the lunar surface. Two Electric Field Sensors both are measured the concentration and temperature of charged particles (electrons, ions, dust particles). Uncertainty of measurements is 10%. Electric Field Sensors contain of Lengmure probe. Using Lengmure probe to dark and light Moon surface we can obtain the energy spectra photoelectrons in different period of time. PmL instrument is developing, working out and manufacturing in IKI. Simultaneously with the PmL dust instrument to study lunar dust it would be very important to use an onboard TV system adjusted for imaging physical properties of dust on the lunar surface (adhesion, albedo, porosity, etc), and to collect dust particles samples from the lunar surface to return these samples to the Earth for measure a number of physic-chemical properties of the lunar dust, e.g. a quantum yield of photoemission, what is very important for modeling physical processes in the lunar exosphere.

Determination of the surface charge density and temperature dependence of purple membrane by electric force microscopy.

PubMed

Du, Huiwen; Li, Denghua; Wang, Yibing; Wang, Chenxuan; Zhang, Dongdong; Yang, Yan-lian; Wang, Chen

2013-08-29

We report here the measurement of the temperature-dependent surface charge density of purple membrane (PM) by using electrostatic force microscopy (EFM). The surface charge density was measured to be 3.4 × 10(5) e/cm(2) at room temperature and reaches the minimum at around 52 °C. The initial decrease of the surface charge density could be attributed to the reduced dipole alignment because of the thermally induced protein mobility in PM. The increase of charge density at higher temperature could be ascribed to the weakened interaction between proteins and the lipids, which leads to the exposure of the charged amino acids. This work could be a benefit to the direct assessment of the structural stability and electric properties of biological membranes at the nanoscale.

Improved interface and electrical properties of atomic layer deposited Al2O3/4H-SiC

NASA Astrophysics Data System (ADS)

Suvanam, Sethu Saveda; Usman, Muhammed; Martin, David; Yazdi, Milad. G.; Linnarsson, Margareta; Tempez, Agnès; Götelid, Mats; Hallén, Anders

2018-03-01

In this paper we demonstrate a process optimization of atomic layer deposited Al2O3 on 4H-SiC resulting in an improved interface and electrical properties. For this purpose the samples have been treated with two pre deposition surface cleaning processes, namely CP1 and CP2. The former is a typical surface cleaning procedure used in SiC processing while the latter have an additional weak RCA1 cleaning step. In addition to the cleaning and deposition, the effects of post dielectric annealing (PDA) at various temperatures in N2O ambient have been investigated. Analyses by scanning electron microscopy show the presence of structural defects on the Al2O3 surface after annealing at 500 and 800 °C. These defects disappear after annealing at 1100 °C, possibly due to densification of the Al2O3 film. Interface analyses have been performed using X-ray photoelectron spectroscopy (XPS) and time-of-flight medium energy ion scattering (ToF MEIS). Both these measurements show the formation of an interfacial SiOx (0 < x < 2) layer for both the CP1 and CP2, displaying an increased thickness for higher temperatures. Furthermore, the quality of the sub-oxide interfacial layer was found to depend on the pre deposition cleaning. In conclusion, an improved interface with better electrical properties is shown for the CP2 sample annealed at 1100 °C, resulting in lower oxide charges, strongly reduced flatband voltage and leakage current, as well as higher breakdown voltage.

3D polarisation speckle as a demonstration of tensor version of the van Cittert-Zernike theorem for stochastic electromagnetic beams

NASA Astrophysics Data System (ADS)

Ma, Ning; Zhao, Juan; Hanson, Steen G.; Takeda, Mitsuo; Wang, Wei

2016-10-01

Laser speckle has received extensive studies of its basic properties and associated applications. In the majority of research on speckle phenomena, the random optical field has been treated as a scalar optical field, and the main interest has been concentrated on their statistical properties and applications of its intensity distribution. Recently, statistical properties of random electric vector fields referred to as Polarization Speckle have come to attract new interest because of their importance in a variety of areas with practical applications such as biomedical optics and optical metrology. Statistical phenomena of random electric vector fields have close relevance to the theories of speckles, polarization and coherence theory. In this paper, we investigate the correlation tensor for stochastic electromagnetic fields modulated by a depolarizer consisting of a rough-surfaced retardation plate. Under the assumption that the microstructure of the scattering surface on the depolarizer is as fine as to be unresolvable in our observation region, we have derived a relationship between the polarization matrix/coherency matrix for the modulated electric fields behind the rough-surfaced retardation plate and the coherence matrix under the free space geometry. This relation is regarded as entirely analogous to the van Cittert-Zernike theorem of classical coherence theory. Within the paraxial approximation as represented by the ABCD-matrix formalism, the three-dimensional structure of the generated polarization speckle is investigated based on the correlation tensor, indicating a typical carrot structure with a much longer axial dimension than the extent in its transverse dimension.

Graphene–Gold Nanoparticles Hybrid—Synthesis, Functionalization, and Application in a Electrochemical and Surface-Enhanced Raman Scattering Biosensor

PubMed Central

Khalil, Ibrahim; Julkapli, Nurhidayatullaili Muhd; Yehye, Wageeh A.; Basirun, Wan Jefrey; Bhargava, Suresh K.

2016-01-01

Graphene is a single-atom-thick two-dimensional carbon nanosheet with outstanding chemical, electrical, material, optical, and physical properties due to its large surface area, high electron mobility, thermal conductivity, and stability. These extraordinary features of graphene make it a key component for different applications in the biosensing and imaging arena. However, the use of graphene alone is correlated with certain limitations, such as irreversible self-agglomerations, less colloidal stability, poor reliability/repeatability, and non-specificity. The addition of gold nanostructures (AuNS) with graphene produces the graphene–AuNS hybrid nanocomposite which minimizes the limitations as well as providing additional synergistic properties, that is, higher effective surface area, catalytic activity, electrical conductivity, water solubility, and biocompatibility. This review focuses on the fundamental features of graphene, the multidimensional synthesis, and multipurpose applications of graphene–Au nanocomposites. The paper highlights the graphene–gold nanoparticle (AuNP) as the platform substrate for the fabrication of electrochemical and surface-enhanced Raman scattering (SERS)-based biosensors in diverse applications as well as SERS-directed bio-imaging, which is considered as an emerging sector for monitoring stem cell differentiation, and detection and treatment of cancer. PMID:28773528

Interfacial structure and electrical properties of ultrathin HfO2 dielectric films on Si substrates by surface sol-gel method

NASA Astrophysics Data System (ADS)

Gong, You-Pin; Li, Ai-Dong; Qian, Xu; Zhao, Chao; Wu, Di

2009-01-01

Ultrathin HfO2 films with about ~3 nm thickness were deposited on n-type (1 0 0) silicon substrates using hafnium chloride (HfCl4) source by the surface sol-gel method and post-deposition annealing (PDA). The interfacial structure and electrical properties of ultrathin HfO2 films were investigated. The HfO2 films show amorphous structures and smooth surface morphologies with a very thin interfacial oxide layer of ~0.5 nm and small surface roughness (~0.45 nm). The 500 °C PDA treatment forms stronger Hf-O bonds, leading to passivated traps, and the interfacial layer is mainly Hf silicate (HfxSiyOz). Equivalent oxide thickness of around 0.84 nm of HfO2/Si has been obtained with a leakage current density of 0.7 A cm-2 at Vfb + 1 V after 500 °C PDA. It was found that the current conduction mechanism of HfO2/Si varied from Schottky-Richardson emission to Fowler-Nordheim tunnelling at an applied higher positive voltage due to the activated partial traps remaining in the ultrathin HfO2 films.

Space Durable Polyimide/Carbon Nanotube Composite Films for Electrostatic Charge Mitigation

NASA Technical Reports Server (NTRS)

Watson, Kent A.; Smith, Joseph G., Jr.; Connell, John W.

2003-01-01

Low color, space environmentally durable polymeric films with sufficient electrical conductivity to mitigate electrostatic charge (ESC) build-up have been under investigation as part of a materials development activity. These materials have potential applications on advanced spacecraft, particularly on large, deployable, ultra-light weight Gossamer spacecraft. The approach taken to impart sufficient electrical conductivity into the polymer film is based on the use of single walled carbon nanotubes (SWNT) as conductive additives. Earlier approaches investigated in our lab involved both an in-situ polymerization approach and addition of SWNT to an oligomer containing reactive end-groups as methods to improve SWNT dispersion. The work described herein is based on the spray coating of a SWNT/solvent dispersion onto the film surface. Two types of polyimides were investigated, one with reactive end groups that can lead to bond formation between the oligomer chain and the SWNT surface and those without reactive end-groups. Surface conductivities (measured as surface resistance) in the range sufficient for ESC mitigation were achieved with minimal effects on the mechanical, optical, thermo-optical properties of the film as compared to the other methods. The chemistry and physical properties of these nanocomposites will be discussed.

Graphene-Gold Nanoparticles Hybrid-Synthesis, Functionalization, and Application in a Electrochemical and Surface-Enhanced Raman Scattering Biosensor.

PubMed

Khalil, Ibrahim; Julkapli, Nurhidayatullaili Muhd; Yehye, Wageeh A; Basirun, Wan Jefrey; Bhargava, Suresh K

2016-05-24

Graphene is a single-atom-thick two-dimensional carbon nanosheet with outstanding chemical, electrical, material, optical, and physical properties due to its large surface area, high electron mobility, thermal conductivity, and stability. These extraordinary features of graphene make it a key component for different applications in the biosensing and imaging arena. However, the use of graphene alone is correlated with certain limitations, such as irreversible self-agglomerations, less colloidal stability, poor reliability/repeatability, and non-specificity. The addition of gold nanostructures (AuNS) with graphene produces the graphene-AuNS hybrid nanocomposite which minimizes the limitations as well as providing additional synergistic properties, that is, higher effective surface area, catalytic activity, electrical conductivity, water solubility, and biocompatibility. This review focuses on the fundamental features of graphene, the multidimensional synthesis, and multipurpose applications of graphene-Au nanocomposites. The paper highlights the graphene-gold nanoparticle (AuNP) as the platform substrate for the fabrication of electrochemical and surface-enhanced Raman scattering (SERS)-based biosensors in diverse applications as well as SERS-directed bio-imaging, which is considered as an emerging sector for monitoring stem cell differentiation, and detection and treatment of cancer.

Optical interferometry study of film formation in lubrication of sliding and/or rolling contacts

NASA Technical Reports Server (NTRS)

Stejskal, E. O.; Cameron, A.

1972-01-01

Seventeen fluids of widely varying physical properties and molecular structure were chosen for study. Film thickness and traction were measured simultaneously in point contacts by interferometry, from which a new theory of traction was proposed. Film thickness was measured in line contacts by interferometry and electrical capacitance to establish correlation between these two methods. An interferometric method for the absolute determination of refractive index in the contact zone was developed and applied to point contact fluid entrapments. Electrical capacitance was used to study the thickness and properties of the soft surface film which sometimes forms near a metal-fluid interface.

Structural and electrical properties of sputter deposited ZnO thin films

NASA Astrophysics Data System (ADS)

Muhammed Shameem P., V.; Mekala, Laxman; Kumar, M. Senthil

2018-05-01

The growth of zinc oxide thin films having different oxygen content was achieved at ambient temperature by reactive dc magnetron sputtering technique and their structural and electrical properties are studied. The structural studies show that the films are polycrystalline with a preferential orientation of the grains along the c-axis [002], which increases with increase in oxygen partial pressure. The grain size and the surface roughness of the zinc oxide films are found to decrease with increasing oxygen partial pressure. It is observed that the resistivity of the zinc oxide films can be tuned from semiconducting to insulating regime by varying the oxygen content.

Effects of Zn-In-Sn elements on the electric properties of magnesium alloy anode materials.

PubMed

Yu, Zhan; Ju, Dongying; Zhao, Hongyang; Hu, Xiaodong

2011-06-01

A new magnesium alloy anode is based on an environmentally friendly electrode that contains none of mercury, lead and chromate, but it can enhance the electric properties of alloy significantly. Magnesium alloy adding eco-friendly elements Zn-In-Sn which was developed by orthogonal design were obtained by two casting methods. The effect of additive elements on performance of electrode material was studied. The effects of elements addition and casting method on electric properties and corrosive properties of Mg-Zn-In-Sn alloys were investigated by using electrochemical measurements, corrosive tests and observation of surface structure. The results show that Mg-Zn-In-Sn alloy anode has higher electromotive force and more stable work potential than that commercial magnesium alloy AZ91. It is suitable for anode material of magnesium battery for its small hydrogen evolution, less self-corrosion rate and easy to shed corrosive offspring off. Copyright © 2011 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.

Electric and Hydraulic Properties of Carbon Felt Immersed in Different Dielectric Liquids

PubMed Central

Kossenko, Alexey; Lugovskoy, Svetlana

2018-01-01

Electroconductive carbon felt (CF) material, having a permeable structure and significant electroconductive surface, is widely used for electrodes in numerous electrochemical applications such as redox flow batteries, fuel cells, electrochemical desalination apparatus, etc. The internal structure of CF is composed of different lengths of carbon filaments bonded together. This structure creates a large number of stochastically oriented and stochastically linked channels that have different lengths and cross sections. Therefore, the CF hydraulic permeability is similar to that of porous media and is determined by the internal empty volume and arrangement of carbon fibers. Its electroconductivity is ensured by the conductivity of the carbon filaments and by the electrical interconnections between fibers. Both of these properties (permeability and electrical conductivity) are extremely important for the efficient functioning of electrochemical devices. However, their influences counter each other during CF compressing. Increasing the stress on a felt element provides supplementary electrical contacts of carbon filaments, which lead to improved electrical conductivity. Thus, the active surface of the felt electrode is increased, which also boosts redox chemical reactions. On the other hand, compressed felt possesses reduced hydrodynamic permeability as a result of a diminished free volume of porous media and intrinsic channels. This causes increasing hydrodynamic expenditures of electrolyte pumping through electrodes and lessened cell (battery) efficiency. The designer of specific electrochemical systems has to take into account both of these properties when selecting the optimal construction for a cell. This article presents the results of measurements and novel approximating expressions of electrical and hydraulic characteristics of a CF during its compression. Since electrical conductivity plays a determining role in providing electrochemical reactions, it was measured in dry conditions and when the CF was immersed in several non-conductive liquids. The choice of such liquids prevented side effects of electrolyte ionic conductivity impact on electrical resistivity of the CF. This gave an opportunity to determine the influences of dielectric parameters of electrolytes to increase or decrease the density of interconnectivity of carbon fibers either between themselves or between them and electrodes. The experiments showed the influence of liquid permittivity on the conductivity of CF, probably by changing the density of fiber interconnections inside the felt. PMID:29690636

Electric and Hydraulic Properties of Carbon Felt Immersed in Different Dielectric Liquids.

PubMed

Kossenko, Alexey; Lugovskoy, Svetlana; Averbukh, Moshe

2018-04-23

Electroconductive carbon felt (CF) material, having a permeable structure and significant electroconductive surface, is widely used for electrodes in numerous electrochemical applications such as redox flow batteries, fuel cells, electrochemical desalination apparatus, etc. The internal structure of CF is composed of different lengths of carbon filaments bonded together. This structure creates a large number of stochastically oriented and stochastically linked channels that have different lengths and cross sections. Therefore, the CF hydraulic permeability is similar to that of porous media and is determined by the internal empty volume and arrangement of carbon fibers. Its electroconductivity is ensured by the conductivity of the carbon filaments and by the electrical interconnections between fibers. Both of these properties (permeability and electrical conductivity) are extremely important for the efficient functioning of electrochemical devices. However, their influences counter each other during CF compressing. Increasing the stress on a felt element provides supplementary electrical contacts of carbon filaments, which lead to improved electrical conductivity. Thus, the active surface of the felt electrode is increased, which also boosts redox chemical reactions. On the other hand, compressed felt possesses reduced hydrodynamic permeability as a result of a diminished free volume of porous media and intrinsic channels. This causes increasing hydrodynamic expenditures of electrolyte pumping through electrodes and lessened cell (battery) efficiency. The designer of specific electrochemical systems has to take into account both of these properties when selecting the optimal construction for a cell. This article presents the results of measurements and novel approximating expressions of electrical and hydraulic characteristics of a CF during its compression. Since electrical conductivity plays a determining role in providing electrochemical reactions, it was measured in dry conditions and when the CF was immersed in several non-conductive liquids. The choice of such liquids prevented side effects of electrolyte ionic conductivity impact on electrical resistivity of the CF. This gave an opportunity to determine the influences of dielectric parameters of electrolytes to increase or decrease the density of interconnectivity of carbon fibers either between themselves or between them and electrodes. The experiments showed the influence of liquid permittivity on the conductivity of CF, probably by changing the density of fiber interconnections inside the felt.

A study of the electrical properties of p-n junctions formed by ion-implantation into gallium arsenide

NASA Technical Reports Server (NTRS)

Lin, A. H.

1972-01-01

In the process of ion implantation, ion beams bombard the surface and create undesirable surface effects. The surface effects were investigated, and surface leakage currents were shown to be reduced by surface treatment. I-V characteristics and C-V measurements were obtained for the Zn-GaAs and Zn-(In,Ga)As junction is considered as a p-i-n heterojunction, without generation-recombination current. The Zn-GaAs junction is considered as a p-n homojunction with appreciable generation-recombination currents.

Apparatus for electroplating particles of small dimension

DOEpatents

Yu, Conrad M.; Illige, John D.

1982-01-01

The thickness, uniformity, and surface smoothness requirements for surface coatings of glass microspheres for use as targets for laser fusion research are critical. Because of their minute size, the microspheres are difficult to manipulate and control in electroplating systems. The electroplating apparatus (10) of the present invention addresses these problems by providing a cathode cell (20) having a cell chamber (22), a cathode (23) and an anode (26) electrically isolated from each other and connected to an electrical power source (24). During the plating process, the cathode (23) is controllably vibrated along with solution pulse to maintain the particles in random free motion so as to attain the desired properties.

Molecular-dynamics simulations of self-assembled monolayers (SAM) on parallel computers

NASA Astrophysics Data System (ADS)

Vemparala, Satyavani

The purpose of this dissertation is to investigate the properties of self-assembled monolayers, particularly alkanethiols and Poly (ethylene glycol) terminated alkanethiols. These simulations are based on realistic interatomic potentials and require scalable and portable multiresolution algorithms implemented on parallel computers. Large-scale molecular dynamics simulations of self-assembled alkanethiol monolayer systems have been carried out using an all-atom model involving a million atoms to investigate their structural properties as a function of temperature, lattice spacing and molecular chain-length. Results show that the alkanethiol chains tilt from the surface normal by a collective angle of 25° along next-nearest neighbor direction at 300K. At 350K the system transforms to a disordered phase characterized by small tilt angle, flexible tilt direction, and random distribution of backbone planes. With increasing lattice spacing, a, the tilt angle increases rapidly from a nearly zero value at a = 4.7A to as high as 34° at a = 5.3A at 300K. We also studied the effect of end groups on the tilt structure of SAM films. We characterized the system with respect to temperature, the alkane chain length, lattice spacing, and the length of the end group. We found that the gauche defects were predominant only in the tails, and the gauche defects increased with the temperature and number of EG units. Effect of electric field on the structure of poly (ethylene glycol) (PEG) terminated alkanethiol self assembled monolayer (SAM) on gold has been studied using parallel molecular dynamics method. An applied electric field triggers a conformational transition from all-trans to a mostly gauche conformation. The polarity of the electric field has a significant effect on the surface structure of PEG leading to a profound effect on the hydrophilicity of the surface. The electric field applied anti-parallel to the surface normal causes a reversible transition to an ordered state in which the oxygen atoms are exposed. On the other hand, an electric field applied in a direction parallel to the surface normal introduces considerable disorder in the system and the oxygen atoms are buried inside.

Subsurface Resistivity Structures in and Around Strike-Slip Faults - Electromagnetic Surveys and Drillings Across Active Faults in Central Japan -

NASA Astrophysics Data System (ADS)

Omura, K.; Ikeda, R.; Iio, Y.; Matsuda, T.

2005-12-01

Electrical resistivity is important property to investigate the structure of active faults. Pore fluid affect seriously the electrical properties of rocks, subsurface electrical resistivity can be an indicator of the existence of fluid and distribution of pores. Fracture zone of fault is expected to have low resistivity due to high porosity and small gain size. Especially, strike-slip type fault has nearly vertical fracture zone and the fracture zone would be detected by an electrical survey across the fault. We performed electromagnetic survey across the strike-slip active faults in central Japan. At the same faults, we also drilled borehole into the fault and did downhole logging in the borehole. We applied MT or CSAMT methods onto 5 faults: Nojima fault which appeared on the surface by the 1995 Great Kobe earthquake (M=7.2), western Nagano Ohtaki area(1984 Nagano-ken seibu earthquake (M=6.8), the fault did not appeared on the surface), Neodani fault which appeared by the 1891 Nobi earthquake (M=8.0), Atera fault which seemed to be dislocated by the 1586 Tensyo earthquake (M=7.9), Gofukuji fault that is considered to have activated about 1200 years ago. The sampling frequencies of electrical and magnetic field were 2 - 1024Hz (10 frequencies) for CSAMT survey and 0.00055 - 384Hz (40 frequencies) for MT survey. The electromagnetic data were processed by standard method and inverted to 2-D resistivity structure along transects of the faults. Results of the survey were compared with downhole electrical logging data and observational descriptions of drilled cores. Fault plane of each fault were recognized as low resistivity region or boundary between relatively low and high resistivity region, except for Gofukuji fault. As for Gofukuji fault, fault was located in relatively high resistivity region. During very long elapsed time from the last earthquake, the properties of fracture zone of Gofukuji fault might changed from low resistivity properties as observed for other faults. Downhole electrical logging data were consistent to values of resistivity estimated by electromagnetic survey for each fault. The existence of relatively low and high resistivity regions in 2-D structure from electromagnetic survey was observed again by downhole logging at the correspondent portion in the borehole. Cores recovered from depthes where the electrical logging showed low resistivity were hardly fractured and altered from host rock which showed high resistivity. Results of electromagnetic survey, downhole electrical logging and observation of drilled cores were consistent to each other. In present case, electromagnetic survey is useful to explore the properties of fault fracture zone. In the further investigations, it is important to explore relationships among features of resistivity structure and geological and geophysical situations of the faults.

Improved optoelectronics properties of ITO-based transparent conductive electrodes with the insertion of Ag/Ni under-layer

NASA Astrophysics Data System (ADS)

Ali, Ahmad Hadi; Abu Bakar, Ahmad Shuhaimi; Hassan, Zainuriah

2014-10-01

ITO-based transparent conductive electrodes (TCE) with Ag/Ni thin metal under-layer were deposited on Si and glass substrates by thermal evaporator and RF magnetron sputtering system. Ceramic ITO with purity of 99.99% and In2O3:SnO2 weight ratio of 90:10 was used as a target at room temperature. Post-deposition annealing was performed on the TCE at moderate temperature of 500 °C, 600 °C and 700 °C under N2 ambient. It was observed that the structural properties, optical transmittance, electrical characteristics and surface morphology were improved significantly after the post-annealing process. Post-annealed ITO/Ag/Ni at 600 °C shows the best quality of TCE with figure-of-merit (FOM) of 1.5 × 10-2 Ω-1 and high optical transmittance of 83% at 470 nm as well as very low electrical resistivity of 4.3 × 10-5 Ω-cm. The crystalline quality and surface morphological plays an important role in determining the quality of the TCE multilayer thin films properties.

Enhanced Flux and Electrochemical Cleaning of Silicate Scaling on Carbon Nanotube-Coated Membrane Distillation Membranes Treating Geothermal Brines.

PubMed

Tang, Li; Iddya, Arpita; Zhu, Xiaobo; Dudchenko, Alexander V; Duan, Wenyan; Turchi, Craig; Vanneste, Johann; Cath, Tzahi Y; Jassby, David

2017-11-08

The desalination of inland brackish groundwater offers the opportunity to provide potable drinking water to residents and industrial cooling water to industries located in arid regions. Geothermal brines are used to generate electricity, but often contain high concentrations of dissolved salt. Here, we demonstrate how the residual heat left in spent geothermal brines can be used to drive a membrane distillation (MD) process and recover desalinated water. Porous polypropylene membranes were coated with a carbon nanotube (CNT)/poly(vinyl alcohol) layer, resulting in composite membranes having a binary structure that combines the hydrophobic properties critical for MD with the hydrophilic and conductive properties of the CNTs. We demonstrate that the addition of the CNT layer increases membrane flux due to enhanced heat transport from the bulk feed to the membrane surface, a result of CNT's high thermal transport properties. Furthermore, we show how hydroxide ion generation, driven by water electrolysis on the electrically conducting membrane surface, can be used to efficiently dissolve silicate scaling that developed during the process of desalinating the geothermal brine, negating the need for chemical cleaning.

EFFECTS OF TRITIUM GAS EXPOSURE ON THE GLASS TRANSITION TEMPERATURE OF EPDM ELASTOMER AND ON THE CONDUCTIVITY OF POLYANILINE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clark, E; Marie Kane, M

2008-12-12

Four formulations of EPDM (ethylene-propylene diene monomer) elastomer were exposed to tritium gas initially at one atmosphere and ambient temperature for between three and four months in closed containers. Material properties that were characterized include density, volume, mass, appearance, flexibility, and dynamic mechanical properties. The glass transition temperature was determined by analysis of the dynamic mechanical property data per ASTM standards. EPDM samples released significant amounts of gas when exposed to tritium, and the glass transition temperature increased by about 3 C. during the exposure. Effects of ultraviolet and gamma irradiation on the surface electrical conductivity of two types ofmore » polyaniline films are also documented as complementary results to planned tritium exposures. Future work will determine the effects of tritium gas exposure on the electrical conductivity of polyaniline films, to demonstrate whether such films can be used as a sensor to detect tritium. Surface conductivity was significantly reduced by irradiation with both gamma rays and ultraviolet light. The results of the gamma and UV experiments will be correlated with the tritium exposure results.« less

Modified rare earth semiconductor oxide as a new nucleotide probe.

PubMed

Shrestha, S; Mills, C E; Lewington, J; Tsang, S C

2006-12-28

Recent rapid developments in biological analysis, medical diagnosis, pharmaceutical industry, and environmental control fuel the urgent need for recognition of particular DNA sequences from samples. Currently, DNA detection techniques use radiochemical, enzymatic, fluorescent, or electrochemiluminescent methods; however, these techniques require costly labeled DNA and highly skilled and cumbersome procedure, which prohibit any in-situ monitoring. Here, we report that hybridization of surface-immobilized single-stranded oligonucleotide on praseodymium oxide (evaluated as a biosensor surface for the first time) with complimentary strands in solution provokes a significant shift of electrical impedance curve. This shift is attributed to a change in electrical characteristics through modification of surface charge of the underlying modified praseodymium oxide upon hybridization with the complementary oligonucelotide strand. On the other hand, using a noncomplementary single strand in solution does not create an equivalent change in the impedance value. This result clearly suggests that a new and simple electrochemical technique based on the change in electrical properties of the modified praseodymium oxide semiconductor surface upon recognition and transduction of a biological event without using labeled species is revealed.

A simple electrical-mechanical model of the heart applied to the study of electrical-mechanical alternans

NASA Technical Reports Server (NTRS)

Clancy, Edward A.; Smith, Joseph M.; Cohen, Richard J.

1991-01-01

Recent evidence has shown that a subtle alternation in the surface ECG (electrical alternans) may be correlated with the susceptibility to ventricular fibrillation. In the present work, the author presents evidence that a mechanical alternation in the heartbeat (mechanical alternans) generally accompanies electrical alternans. A simple finite-element computer model which emulates both the electrical and the mechanical activity of the heart is presented. A pilot animal study is also reported. The computer model and the animal study both found that (1) there exists a regime of combined electrical-mechanical alternans during the transition from a normal rhythm towards a fibrillatory rhythm, (2) the detected degree of alternation is correlated with the relative instability of the rhythm, and (3) the electrical and mechanical alternans may result from a dispersion in local electrical properties leading to a spatial-temporal alternation in the electrical conduction process.

Electrical Conductivity through a Single Atomic Step Measured with the Proximity-Induced Superconducting Pair Correlation

DOE PAGES

Kim, Howon; Lin, Shi -Zeng; Graf, Matthias J.; ...

2016-09-08

Local disordered nanostructures in an atomically thick metallic layer on a semiconducting substrate play significant and decisive roles in transport properties of two-dimensional (2D) conductive systems. We measured the electrical conductivity through a step of monoatomic height in a truly microscopic manner by using as a signal the superconducting pair correlation induced by the proximity effect. The transport property across a step of a one-monolayer Pb surface metallic phase, formed on a Si(111) substrate, was evaluated by inducing the pair correlation around the local defect and measuring its response, i.e., the reduced density of states at the Fermi energy usingmore » scanning tunneling microscopy. We found that the step resistance has a significant contribution to the total resistance on a nominally flat surface. Our study also revealed that steps in the 2D metallic layer terminate the propagation of the pair correlation. Furthermore, superconductivity is enhanced between the first surface step and the superconductor–normal-metal interface by reflectionless tunneling when the step is located within a coherence length.« less

Characterization Of Graphene-Ferroelectric Superlattice Hybrid Devices

NASA Astrophysics Data System (ADS)

Yusuf, Mohammed; Du, Xu; Dawber, Matthew

2013-03-01

Ferroelectric materials possess a spontaneous electrical polarization, which can be controlled by an electric field. A good interface between ferroelectric surface and graphene sheets can introduce a new generation of multifunctional devices, in which the ferroelectric material can be used to control the properties of graphene. In our approach, problems encountered in previous efforts to combine ferroelectric/carbon systems are overcome by the use of artificially layered superlattice materials grown in the form of epitaxial thin films. In these materials the phase transition temperature and dielectric response of the material can be tailored, allowing us to avoid polarization screening by surface absorbates, whilst maintaining an atomically smooth surface and optimal charge doping properties. Using ferroelectric PbTiO3/SrTiO3 superlattices, we have shown ultra-low-voltage operation of graphene field effect devices within +/- 1 V at room temperature. The switching of the graphene field effect transistors is characterized by pronounced resistance hysteresis, suitable for ultra-fast non-volatile electronics. Low temperature characterization confirmed that the coercive field required for the ferroelectric domain switching increases significantly with decreasing temperatures. National Science Foundation (NSF) (grant number 1105202)

Hydrothermal growth of ZnO nanowires on flexible fabric substrates

NASA Astrophysics Data System (ADS)

Hong, Gwang-Wook; Yun, Sang-Ho; Kim, Joo-Hyung

2016-04-01

ZnO nanowires (NWs) would provide significant enhancement in sensitivity due to high surface to volume ratio. We investigated the first methodical study on the quantitative relationship between the process parameters of solution concentration ratio, structure, and physical and properties of ZnO NWs grown on different flexible fabric surfaces. To develop a fundamental following concerning various substrates, we controlled the growth speed of ZnO NWs and nanowires on cotton surface with easy and moderate cost fabrication method. Using ammonium hydroxide as the reactant with zinc nitrate hexahydrate, ZnO NWs layer have been grown on metal layers, instead of seed layer. ZnO NWs fabrication was done on different fabric substrates such as wool, nylon and polypropylene (PP). After the ZnO NWs grown to each substrates, we coated insulating layer with polyurethane (PU) and ethyl cellulose for prevent external intervention. Detailed electrical characterization was subsequently performed to reveal the working characteristics of the hybrid fabric. For electrical verification of fabricated ZnO NWs, we implemented measurement impact test and material properties with FFT analyzer and LCR meter.

Electrical Conductivity through a Single Atomic Step Measured with the Proximity-Induced Superconducting Pair Correlation.

PubMed

Kim, Howon; Lin, Shi-Zeng; Graf, Matthias J; Miyata, Yoshinori; Nagai, Yuki; Kato, Takeo; Hasegawa, Yukio

2016-09-09

Local disordered nanostructures in an atomically thick metallic layer on a semiconducting substrate play significant and decisive roles in transport properties of two-dimensional (2D) conductive systems. We measured the electrical conductivity through a step of monoatomic height in a truly microscopic manner by using as a signal the superconducting pair correlation induced by the proximity effect. The transport property across a step of a one-monolayer Pb surface metallic phase, formed on a Si(111) substrate, was evaluated by inducing the pair correlation around the local defect and measuring its response, i.e., the reduced density of states at the Fermi energy using scanning tunneling microscopy. We found that the step resistance has a significant contribution to the total resistance on a nominally flat surface. Our study also revealed that steps in the 2D metallic layer terminate the propagation of the pair correlation. Superconductivity is enhanced between the first surface step and the superconductor-normal-metal interface by reflectionless tunneling when the step is located within a coherence length.

Improved interfacial and electrical properties of GaAs metal-oxide-semiconductor capacitors with HfTiON as gate dielectric and TaON as passivation interlayer

NASA Astrophysics Data System (ADS)

Wang, L. S.; Xu, J. P.; Zhu, S. Y.; Huang, Y.; Lai, P. T.

2013-08-01

The interfacial and electrical properties of sputtered HfTiON on sulfur-passivated GaAs with or without TaON as interfacial passivation layer (IPL) are investigated. Experimental results show that the GaAs metal-oxide-semiconductor capacitor with HfTiON/TaON stacked gate dielectric annealed at 600 °C exhibits low interface-state density (1.0 × 1012 cm-2 eV-1), small gate leakage current (7.3 × 10-5 A cm-2 at Vg = Vfb + 1 V), small capacitance equivalent thickness (1.65 nm), and large equivalent dielectric constant (26.2). The involved mechanisms lie in the fact that the TaON IPL can effectively block the diffusions of Hf, Ti, and O towards GaAs surface and suppress the formation of interfacial As-As bonds, Ga-/As-oxides, thus unpinning the Femi level at the TaON/GaAs interface and improving the interface quality and electrical properties of the device.

Morphologies and optical and electrical properties of InGaN/GaN micro-square array light-emitting diode chips.

PubMed

Han, Dan; Ma, Shufang; Jia, Zhigang; Liu, Peizhi; Jia, Wei; Shang, Lin; Zhai, Guangmei; Xu, Bingshe

2018-04-10

InGaN/GaN micro-square array light-emitting diode (LED) chips (micro-chips) have been prepared via the focused ion beam (FIB) etching technique, which can not only reduce ohmic contact degradation but also control the aspect ratio precisely in three-dimensional (3D) structure LED (3D-LED) device fabrication. The effects of FIB beam current and micro-square array depth on morphologies and optical and electrical properties of the micro-chips have been studied. Our results show that sidewall surface morphology and optical and electrical properties of the micro-chips degrade with increased beam current. After potassium hydroxide etching with different times, an optimal current-voltage and luminescence performance can be obtained. Combining the results of cathodoluminescence mappings and light output-current characteristics, the light extraction efficiency of the micro-chips is reduced as FIB etch depth increases. The mechanisms of micro-square depth on light extraction have been revealed by 3D finite difference time domain.

Effects of anisotropic surface texture on the performance of ionic polymer-metal composite (IPMC)

NASA Astrophysics Data System (ADS)

He, Qingsong; Yu, Min; Ding, Haitao; Guo, Dongjie; Dai, Zhendong

2010-04-01

Ionic polymer metal composite (IPMC), an electrically activated polymer (EAP), has attracted great attention for the excellent properties such as large deformation, light weight, low noise, flexibility and low driving voltages, which makes the material a possible application as artificial muscle if the output force can be increased. To improve the property, we manufactured the Nafion membrane by casting from liquid solution, modified the surface by sandblasting or polishing, and obtained the isotropic and anisotropic surface texture respectively. The microstructure of the Nafion surface and metal electrode, effects of surface texture on the output force and displacement of IPMC were studied. Results show that the output force of IPMC with the anisotropic surface texture is 2~4 times higher than that with the isotropic surface texture without enormous sacrifice of the displacement. The output force may reach to 6.63gf (Sinusoidal 3.5V and 0.1Hz, length 20mm, width 5mm and thickness 0.66mm), which suggest an effective way to improve the mechanical properties of IPMC.

Integrating surface and borehole geophysics in ground water studies - an example using electromagnetic soundings in south Florida

USGS Publications Warehouse

Paillet, Frederick; Hite, Laura; Carlson, Matthew

1999-01-01

Time domain surface electromagnetic soundings, borehole induction logs, and other borehole logging techniques are used to construct a realistic model for the shallow subsurface hydraulic properties of unconsolidated sediments in south Florida. Induction logs are used to calibrate surface induction soundings in units of pore water salinity by correlating water sample specific electrical conductivity with the electrical conductivity of the formation over the sampled interval for a two‐layered aquifer model. Geophysical logs are also used to show that a constant conductivity layer model is appropriate for the south Florida study. Several physically independent log measurements are used to quantify the dependence of formation electrical conductivity on such parameters as salinity, permeability, and clay mineral fraction. The combined interpretation of electromagnetic soundings and induction logs was verified by logging three validation boreholes, confirming quantitative estimates of formation conductivity and thickness in the upper model layer, and qualitative estimates of conductivity in the lower model layer.

Ionization of Rydberg atoms colliding with a metal surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sjakste, J.; Borisov, A. G.; Gauyacq, J. P.

2006-04-15

We report on a theoretical study of the ionization process of Xe* Rydberg atoms colliding with a metal surface, in the presence of an external electric field. The evolution of the Xe* outer electron is studied by a wave packet propagation approach, allowing to include all dynamical aspects of the collision, in particular nonadiabatic inter-Rydberg transitions. We investigate how the different Xe* Stark states formed in the external field couple together and ionize on the surface and how the different polarizations of the electronic cloud in the Xe* states are reflected in their ionization properties. We show that the presencemore » of the external electric field can significantly perturb the dynamics of the ionization process. Our results account for recent results from Dunning et al. [Nucl. Inst. Meth. B 203, 69 (2003)]. In particular, it is explained how the external electric field present in the experimental procedure of Dunning et al. leads to the apparent absence of a polarization effect in the ionization process.« less

A scanning probe mounted on a field-effect transistor: Characterization of ion damage in Si.

PubMed

Shin, Kumjae; Lee, Hoontaek; Sung, Min; Lee, Sang Hoon; Shin, Hyunjung; Moon, Wonkyu

2017-10-01

We have examined the capabilities of a Tip-On-Gate of Field-Effect Transistor (ToGoFET) probe for characterization of FIB-induced damage in Si surface. A ToGoFET probe is the SPM probe which the Field Effect Transistor(FET) is embedded at the end of a cantilever and a Pt tip was mounted at the gate of FET. The ToGoFET probe can detect the surface electrical properties by measuring source-drain current directly modulated by the charge on the tip. In this study, a Si specimen whose surface was processed with Ga+ ion beam was prepared. Irradiation and implantation with Ga+ ions induce highly localized modifications to the contact potential. The FET embedded on ToGoFET probe detected the surface electric field profile generated by schottky contact between the Pt tip and the sample surface. Experimentally, it was shown that significant differences of electric field due to the contact potential barrier in differently processed specimens were observed using ToGOFET probe. This result shows the potential that the local contact potential difference can be measured by simple working principle with high sensitivity. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fabrication of electrically bistable organic semiconducting/ferroelectric blend films by temperature controlled spin coating.

PubMed

Hu, Jinghang; Zhang, Jianchi; Fu, Zongyuan; Weng, Junhui; Chen, Weibo; Ding, Shijin; Jiang, Yulong; Zhu, Guodong

2015-03-25

Organic semiconducting/ferroelectric blend films attracted much attention due to their electrical bistability and rectification properties and thereof the potential in resistive memory devices. During film deposition from the blend solution, spinodal decomposition induced phase separation, resulting in discrete semiconducting phase whose electrical property could be modulated by the continuous ferroelectric phase. However, blend films processed by common spin coating method showed extremely rough surfaces, even comparable to the film thickness, which caused large electrical leakage and thus compromised the resistive switching performance. To improve film roughness and thus increase the productivity of these resistive devices, we developed temperature controlled spin coating technique to carefully adjust the phase separation process. Here we reported our experimental results from the blend films of ferroelectric poly(vinylidene fluoride-trifluoroethylene (P(VDF-TrFE)) and semiconducting poly(3-hexylthiophene) (P3HT). We conducted a series of experiments at various deposition temperatures ranging from 20 to 90 °C. The resulting films were characterized by AFM, SEM, and VPFM to determine their structure and roughness. Film roughness first decreased and then increased with the increase of deposition temperature. Electrical performance was also characterized and obviously improved insulating property was obtained from the films deposited between 50 and 70 °C. By temperature control during film deposition, it is convenient to efficiently fabricate ferroelectric/semiconducting blend films with good electrical bistability.

Preparation of TiO2/Ag/TiO2 (TAT) multilayer films with optical and electrical properties enhanced by using Cr-added Ag film

NASA Astrophysics Data System (ADS)

Loka, Chadrasekhar; Lee, Kee-Sun

2017-09-01

The dielectric-metal-dielectric tri-layer films have attracted much attention by virtue of their low-cost and high quality device performance as a transparent conductive electrode. Here, we report the deposition of Cr doped Ag films sandwiched between thin TiO2 layers and investigation on the surface microstructure, optical and electrical properties depending on the thickness of the Ag(Cr). The activation energy (1.18 eV) for grain growth of Ag was calculated from the Arrhenius plot using the law Dn -D0n = kt , which was comparable to the bulk diffusion of Ag. This result indicated the grain growth of Ag was effectively retarded by the Cr addition, which was presumed to related with blocking the surface and grain boundary diffusion due to Cr segregation. Based on thermal stability of Cr added Ag film, we deposited TiO2/Ag(Cr)/TiO2 (TAT) multilayer thin films and with a 10 nm thick Ag(Cr), the TAT films showed high optical transmittance in the visible region (94.2%), low electrical resistivity (8.66 × 10-5 Ω cm), and hence the high figure of merit 57.15 × 10-3 Ω-1 was achieved. The high transmittance of the TAT film was believed to be attributed to the low optical loss due to a reduction in the Ag layer thickness, the surface plasmon effect, and the electron scattering reduced by the Ag layer with a low electrical resistivity.

Correlation between morphology, electron band structure, and resistivity of Pb atomic chains on the Si(5 5 3)-Au surface

NASA Astrophysics Data System (ADS)

Jałochowski, M.; Kwapiński, T.; Łukasik, P.; Nita, P.; Kopciuszyński, M.

2016-07-01

Structural and electron transport properties of multiple Pb atomic chains fabricated on the Si(5 5 3)-Au surface are investigated using scanning tunneling spectroscopy, reflection high electron energy diffraction, angular resolved photoemission electron spectroscopy and in situ electrical resistance. The study shows that Pb atomic chains growth modulates the electron band structure of pristine Si(5 5 3)-Au surface and hence changes its sheet resistivity. Strong correlation between chains morphology, electron band structure and electron transport properties is found. To explain experimental findings a theoretical tight-binding model of multiple atomic chains interacting on effective substrate is proposed.

A FEM-based method to determine the complex material properties of piezoelectric disks.

PubMed

Pérez, N; Carbonari, R C; Andrade, M A B; Buiochi, F; Adamowski, J C

2014-08-01

Numerical simulations allow modeling piezoelectric devices and ultrasonic transducers. However, the accuracy in the results is limited by the precise knowledge of the elastic, dielectric and piezoelectric properties of the piezoelectric material. To introduce the energy losses, these properties can be represented by complex numbers, where the real part of the model essentially determines the resonance frequencies and the imaginary part determines the amplitude of each resonant mode. In this work, a method based on the Finite Element Method (FEM) is modified to obtain the imaginary material properties of piezoelectric disks. The material properties are determined from the electrical impedance curve of the disk, which is measured by an impedance analyzer. The method consists in obtaining the material properties that minimize the error between experimental and numerical impedance curves over a wide range of frequencies. The proposed methodology starts with a sensitivity analysis of each parameter, determining the influence of each parameter over a set of resonant modes. Sensitivity results are used to implement a preliminary algorithm approaching the solution in order to avoid the search to be trapped into a local minimum. The method is applied to determine the material properties of a Pz27 disk sample from Ferroperm. The obtained properties are used to calculate the electrical impedance curve of the disk with a Finite Element algorithm, which is compared with the experimental electrical impedance curve. Additionally, the results were validated by comparing the numerical displacement profile with the displacements measured by a laser Doppler vibrometer. The comparison between the numerical and experimental results shows excellent agreement for both electrical impedance curve and for the displacement profile over the disk surface. The agreement between numerical and experimental displacement profiles shows that, although only the electrical impedance curve is considered in the adjustment procedure, the obtained material properties allow simulating the displacement amplitude accurately. Copyright © 2014 Elsevier B.V. All rights reserved.

Impact of defects on the electrical transport, optical properties and failure mechanisms of GaN nanowires.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Armstrong, Andrew M.; Aubry, Sylvie; Shaner, Eric Arthur

2010-09-01

We present the results of a three year LDRD project that focused on understanding the impact of defects on the electrical, optical and thermal properties of GaN-based nanowires (NWs). We describe the development and application of a host of experimental techniques to quantify and understand the physics of defects and thermal transport in GaN NWs. We also present the development of analytical models and computational studies of thermal conductivity in GaN NWs. Finally, we present an atomistic model for GaN NW electrical breakdown supported with experimental evidence. GaN-based nanowires are attractive for applications requiring compact, high-current density devices such asmore » ultraviolet laser arrays. Understanding GaN nanowire failure at high-current density is crucial to developing nanowire (NW) devices. Nanowire device failure is likely more complex than thin film due to the prominence of surface effects and enhanced interaction among point defects. Understanding the impact of surfaces and point defects on nanowire thermal and electrical transport is the first step toward rational control and mitigation of device failure mechanisms. However, investigating defects in GaN NWs is extremely challenging because conventional defect spectroscopy techniques are unsuitable for wide-bandgap nanostructures. To understand NW breakdown, the influence of pre-existing and emergent defects during high current stress on NW properties will be investigated. Acute sensitivity of NW thermal conductivity to point-defect density is expected due to the lack of threading dislocation (TD) gettering sites, and enhanced phonon-surface scattering further inhibits thermal transport. Excess defect creation during Joule heating could further degrade thermal conductivity, producing a viscous cycle culminating in catastrophic breakdown. To investigate these issues, a unique combination of electron microscopy, scanning luminescence and photoconductivity implemented at the nanoscale will be used in concert with sophisticated molecular-dynamics calculations of surface and defect-mediated NW thermal transport. This proposal seeks to elucidate long standing material science questions for GaN while addressing issues critical to realizing reliable GaN NW devices.« less

Analyte concentration at the tip of a nanopipette.

PubMed

Calander, Nils

2009-10-15

Concentration of molecules within the tips of nanopipettes when applying a DC voltage is herein investigated using finite-element simulations. The ion concentrations and fluxes due to diffusion, electro-migration, and electro-osmotic flow, and the electric potential are determined by the simultaneous solution of the Nernst-Planck, Poisson, and Navier-Stokes equations within the water solution containing sodium and chloride ions and negatively charged molecules. The electric potential within the pipette glass wall is at the same time determined by the Poisson equation together with appropriate boundary conditions and accounts for a field effect through the wall. Fixed negative surface charge on both the internal and external glass surfaces of the nanopipette is included together with the field effect through the glass wall to account for the electric double layer and the electro-osmosis. The inclusion of the field effect through the pipette wall is new compared to previous modeling of similar structures and is shown to be crucial for the behavior at the tip. It is demonstrated that the concentration of molecules is a consequence of ionic charge accumulation at the tip screening the electric field, thereby slowing down the electrophoretic motion of the molecules, which is further slowed down or stopped by the oppositely directed electro-osmosis. It is also shown that the trapping is very sensitive to the properties of the molecule, that is, its electrophoretic mobility and diffusion coefficient, the properties of the pipette, the ionic strength of the solution, and the applied electric field.

Effect of Electric Discharge on Properties of Nano-Particulate Catalyst for Plasma-Catalysis.

PubMed

Lee, Chung Jun; Kim, Jip; Kim, Taegyu

2016-02-01

Heterogeneous catalytic processes have been used to produce hydrogen from hydrocarbons. However, high reforming temperature caused serious catalyst deteriorations and low energy efficiency. Recently, a plasma-catalyst hybrid process was used to reduce the reforming temperature and to improve the stability and durability of reforming catalysts. Effect of electric discharges on properties of nanoparticulate catalysts for plasma-catalysis was investigated in the present study. Catalyst-bed porosity was varied by packing catalyst beads with the different size in a reactor. Discharge power and onset voltage of the plasma were measured as the catalyst-bed porosity was varied. The effect of discharge voltage, frequency and voltage waveforms such as the sine, pulse and square was investigated. We found that the optimal porosity of the catalyst-bed exists to maximize the electric discharge. At a low porosity, the electric discharge was unstable to be sustained because the space between catalysts got narrow nearly close to the sheath region. On the other hand, at a high porosity, the electric discharge became weak because the plasma was not sufficient to interact with the surface of catalysts. The discharge power increased as the discharge voltage and frequency increased. The square waveform was more efficient than the sine and pulse one. At a high porosity, however, the effect of the voltage waveform was not considerable because the space between catalysts was too large for plasma to interact with the surface of catalysts.

Matrix of moments of the Legendre polynomials and its application to problems of electrostatics

NASA Astrophysics Data System (ADS)

Savchenko, A. O.

2017-01-01

In this work, properties of the matrix of moments of the Legendre polynomials are presented and proven. In particular, the explicit form of the elements of the matrix inverse to the matrix of moments is found and theorems of the linear combination and orthogonality are proven. On the basis of these properties, the total charge and the dipole moment of a conducting ball in a nonuniform electric field, the charge distribution over the surface of the conducting ball, its multipole moments, and the force acting on a conducting ball situated on the axis of a nonuniform axisymmetric electric field are determined. All assertions are formulated in theorems, the proofs of which are based on the properties of the matrix of moments of the Legendre polynomials.

Effect of polymer residues on the electrical properties of large-area graphene–hexagonal boron nitride planar heterostructures

DOE PAGES

Voyloy, Dimitry; Lassiter, Matthew G.; Sokolov, Alexei P.; ...

2017-06-19

Polymer residue plays an important role in the performance of 2D heterostructured materials. Herein, we study the effect of polymer residual impurities on the electrical properties of graphene–boron nitride planar heterostructures. Large-area graphene (Gr) and hexagonal boron nitride (h-BN) monolayers were synthesized using chemical vapor deposition techniques. Atomic van-der-Waals heterostructure layers based on varied configurations of Gr and h-BN layers were assembled. The average interlayer resistance of the heterojunctions over a 1 cm 2 area for several planar heterostructure configurations was assessed by impedance spectroscopy and modeled by equivalent electrical circuits. As a result, conductive AFM measurements showed that themore » presence of polymer residues on the surface of the Gr and h-BN monolayers resulted in significant resistance deviations over nanoscale regions.« less

Effect of polymer residues on the electrical properties of large-area graphene–hexagonal boron nitride planar heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voyloy, Dimitry; Lassiter, Matthew G.; Sokolov, Alexei P.

Polymer residue plays an important role in the performance of 2D heterostructured materials. Herein, we study the effect of polymer residual impurities on the electrical properties of graphene–boron nitride planar heterostructures. Large-area graphene (Gr) and hexagonal boron nitride (h-BN) monolayers were synthesized using chemical vapor deposition techniques. Atomic van-der-Waals heterostructure layers based on varied configurations of Gr and h-BN layers were assembled. The average interlayer resistance of the heterojunctions over a 1 cm 2 area for several planar heterostructure configurations was assessed by impedance spectroscopy and modeled by equivalent electrical circuits. As a result, conductive AFM measurements showed that themore » presence of polymer residues on the surface of the Gr and h-BN monolayers resulted in significant resistance deviations over nanoscale regions.« less

Characteristics of W Doped Nanocrystalline Carbon Films Prepared by Unbalanced Magnetron Sputtering.

PubMed

Park, Yong Seob; Park, Chul Min; Kim, Nam-Hoon; Kim, Jae-Moon

2016-05-01

Nanocrystalline tungsten doped carbon (WC) films were prepared by unbalanced magnetron sputtering. Tungsten was used as the doping material in carbon thin films with the aim of application as a contact strip in an electric railway. The structural, physical, and electrical properties of the fabricated WC films with various DC bias voltages were investigated. The films had a uniform and smooth surface. Hardness and frication characteristics of the films were improved, and the resistivity and sheet resistance decreased with increasing negative DC bias voltage. These results are associated with the nanocrystalline WC phase and sp(2) clusters in carbon networks increased by ion bombardment enhanced with increasing DC bias voltage. Consequently, the increase of sp(2) clusters containing WC nanocrystalline in the carbon films is attributed to the improvement in the physical and electrical properties.

Electrical properties of fluorine-doped ZnO nanowires formed by biased plasma treatment

NASA Astrophysics Data System (ADS)

Wang, Ying; Chen, Yicong; Song, Xiaomeng; Zhang, Zhipeng; She, Juncong; Deng, Shaozhi; Xu, Ningsheng; Chen, Jun

2018-05-01

Doping is an effective method for tuning electrical properties of zinc oxide nanowires, which are used in nanoelectronic devices. Here, ZnO nanowires were prepared by a thermal oxidation method. Fluorine doping was achieved by a biased plasma treatment, with bias voltages of 100, 200, and 300 V. Transmission electron microscopy indicated that the nanowires treated at bias voltages of 100 and 200 V featured low crystallinity. When the bias voltage was 300 V, the nanowires showed single crystalline structures. Photoluminescence measurements revealed that concentrations of oxygen and surface defects decreased at high bias voltage. X-ray photoelectron spectroscopy suggested that the F content increased as the bias voltage was increased. The conductivity of the as-grown nanowires was less than 103 S/m; the conductivity of the treated nanowires ranged from 1 × 104-5 × 104, 1 × 104-1 × 105, and 1 × 103-2 × 104 S/m for bias voltage treatments at 100, 200, and 300 V, respectively. The conductivity improvements of nanowires formed at bias voltages of 100 and 200 V, were attributed to F-doping, defects and surface states. The conductivity of nanowires treated at 300 V was attributed to the presence of F ions. Thus, we provide a method of improving electrical properties of ZnO nanowires without altering their crystal structure.

Electrical Aspects of Impinging Flames

NASA Astrophysics Data System (ADS)

Chien, Yu-Chien

This dissertation examines the use of electric fields as one mechanism for controlling combustion as flames are partially extinguished when impinging on nearby surfaces. Electrical aspects of flames, specifically, the production of chemi-ions in hydrocarbon flames and the use of convective flows driven by these ions, have been investigated in a wide range of applications in prior work but despite this fairly comprehensive effort to study electrical aspects of combustion, relatively little research has focused on electrical phenomena near flame extinguishment, nor for flames near impingement surfaces. Electrical impinging flames have complex properties under global influences of ion-driven winds and flow field disturbances from the impingement surface. Challenges of measurements when an electric field is applied in the system have limited an understanding of changes to the flame behavior and species concentrations caused by the field. This research initially characterizes the ability of high voltage power supplies to respond on sufficiently short time scales to permit real time electrical flame actuation. The study then characterizes the influence of an electric field on the impinging flame shape, ion current and flow field of the thermal plume associated with the flame. The more significant further examinations can be separated into two parts: 1) the potential for using electric fields to control the release of carbon monoxide (CO) from surface-impinging flames, and 2) an investigation of controlling electrically the heat transfer to a plate on which the flame impinges. Carbon monoxide (CO) results from the incomplete oxidation of hydrocarbon fuels and, while CO can be desirable in some syngas processes, it is usually a dangerous emission from forest fires, gas heaters, gas stoves, or furnaces where insufficient oxygen in the core reaction does not fully oxidize the fuel to carbon dioxide and water. Determining how carbon monoxide is released and how heat transfer from the flame to the plate can be controlled using the electric field are the two main goals of this research. Multiple diagnostic techniques are employed such as OH chemiluminescence to identify the reaction zone, OH PLIF to characterize the location of this radical species, CO released from the flame, IR imaging and OH PLIF thermometry to understand the surface and gas temperature distribution, respectively. The principal finding is that carbon monoxide release from an impinging diffusion flame results from the escape of carbon monoxide created on the fuel side of the flame along the boundary layer near the surface where it avoids oxidation by OH, which sits to the air side of the reaction sheet interface. In addition, the plate proximity to the flame has a stronger influence on the emission of toxic carbon monoxide than does the electric field strength. There is, however, a narrow region of burner to surface distance where the electric field is most effective. The results also show that heat transfer can be spatially concentrated effectively using an electric field driven ion wind, particularly at some burner to surface distances.

Solar energy estimated from geostationary satellites and its application on the energy management system

NASA Astrophysics Data System (ADS)

Nakajima, T. Y.; Takamatsu, T.; Funayama, T.; Yamamoto, Y.; Takenaka, H.; Nakajima, T.; Irie, H.; Higuchi, A.

2017-12-01

Recently, estimating and forecasting the solar radiation in terms of the electric power generation by photovoltaic (PV) systems is needed for the energy management system (EMS). The estimation technique depends on the latest atmospheric sciences. For instance, when one like to estimate solar radiation reached to ground surface, one will focus on the existence of clouds and their properties, because clouds exert an important influence to the radiative transfer. Visible-to-infared imaging radiometer aboard the geostationary satellites, Himawari, GOES, and Meteosat are useful for such objective, since they observe clouds for full disk of the Earth with high temporal frequency and moderately spatial resolution. Estimation of solar radiation at the ground surface from satellite imagery consists of two steps. The first step is retrieval of cloud optical and microphysical properties by use of the multispectral imaging data. Indeed, we retrieve cloud optical thickness, cloud particle sizes, and cloud top height from visible, near-infrared, and thermal infrared wavelength of the satellite imageries, respectively. The second step is the radiative transfer calculation. We will obtain solar radiation reached to the ground surface, using cloud properties retrieved from the first step, and radiative transfer calculations. We have built a system for near-real time estimation of solar radiation for global scale, named the AMATERASS system, under the support of JST (Japan Science and Technology Agency), CREST/EMS (Energy Management System). The AMATERASS dataset has been used for several researches. For example, Waseda University group applied the AMATERASS data in the electric power system, considering accidental blackout in the electric system for local scale. They made it clear that when AMATERASS data exists the chance of electric voltage deviancy is mitigated when the blackout is over. We have supported a solar car race in Australia, named World Solar Challenge (WSC) 2013, 2015, and 2017, by suppling the AMATERASS solar radiation and some meteorological data along the race track, dynamically following the location of the solar car. This experience is important because the era of electric vehicles equippe with PV panels will come soon.

Effect of electrical discharging on formation of nanoporous biocompatible layer on Ti-6Al-4V alloys.

PubMed

Yang, Tzu-Sen; Huang, Mao-Suan; Wang, Mao-Sheng; Lin, Ming-Hong; Tsai, Meng-Yuan; Wang, Pei-Yi Wang

2013-08-01

In this study, the electrical discharge machining (EDM) was formed on the surface of the Ti-6Al-4V (Ti64) specimen. The properties of adhesion and proliferation of MG-63 cells were evaluated the interactions between the EDM-treated layer and cells. The incorporation of oxygen roughened the EDM-treated specimen surface on a microscale, where the nanoscale pores were superimposed. The EDM-treated layer, which can generate the thick anatase TiO2 on the Ti64 surface, afforded a cytocompatible environment. In cell culture, alkaline phosphatase activity and osteocalcin can be dramatically enhanced on the EDM-treated surfaces when compared with the untreated surface. In addition, the increase in peak currents to the EDM functionalization led to enhancement of multiple osteoblast functions. This study reveals that the chemistry and crystallinity of the EDM-treated layer played important roles in affecting osteoblastic responses to the specimens, which provided insight into the development of new biomedical implant surfaces.

Rapid mixing of viscous liquids by electrical coiling

PubMed Central

Kong, Tiantian; Li, Jingmei; Liu, Zhou; Zhou, Zhuolong; Ng, Peter Hon Yu; Wang, Liqiu; Shum, Ho Cheung

2016-01-01

The control for the processing of precursor liquids determines whether the properties and functions of the final material product can be engineered. An inherent challenge of processing viscous liquids arises from their large resistance to deform. Here, we report on the discovery of an electric approach that can significantly contribute to address this challenge. The applied electric force can induce a straight viscous jet to coil, and the resulting coiling characteristics are governed by the electric stress. We demonstrate the promising use of electrical coiling in the rapid and efficient mixing of viscous liquids. Remarkably, the degree of mixing can be precisely adjusted by tuning the applied electric stress. Our approach of controlling the coiling electrically has important implications on applications such as dispensing and printing of resins, printing patterned surfaces and scaffolds, processing of food and generating non-woven fabrics. PMID:26860660

Emulation of Forward-looking Radar Technology for Threat Detection in Rough Terrain Environments: A Scattering and Imaging Study

DTIC Science & Technology

2012-12-01

a) Ground with flat surface; (b) Ground with randomly rough surface, hrms =1.2 cm, lc=14.93 cm; (c) Ground with randomly rough surface, hrms =1.6 cm...horizontal-horizontal (hh)-polarized images for 20 m×10 m scene: (a) Ground with flat surface; (b) Ground with randomly rough surface, hrms =1.2 cm...lc=14.93 cm; (c) Ground with randomly rough surface, hrms =1.6 cm, lc=14.93 cm. Ground electrical properties: εr=6, σd=10 mS/m. Frequency span: 0.3

Developing a tissue-engineered neural-electrical relay using encapsulated neuronal constructs on conducting polymer fibers.

PubMed

Cullen, D Kacy; R Patel, Ankur; Doorish, John F; Smith, Douglas H; Pfister, Bryan J

2008-12-01

Neural-electrical interface platforms are being developed to extracellularly monitor neuronal population activity. Polyaniline-based electrically conducting polymer fibers are attractive substrates for sustained functional interfaces with neurons due to their flexibility, tailored geometry and controlled electro-conductive properties. In this study, we addressed the neurobiological considerations of utilizing small diameter (<400 microm) fibers consisting of a blend of electrically conductive polyaniline and polypropylene (PA-PP) as the backbone of encapsulated tissue-engineered neural-electrical relays. We devised new approaches to promote survival, adhesion and neurite outgrowth of primary dorsal root ganglion neurons on PA-PP fibers. We attained a greater than ten-fold increase in the density of viable neurons on fiber surfaces to approximately 700 neurons mm(-2) by manipulating surrounding surface charges to bias settling neuronal suspensions toward fibers coated with cell-adhesive ligands. This stark increase in neuronal density resulted in robust neuritic extension and network formation directly along the fibers. Additionally, we encapsulated these neuronal networks on PA-PP fibers using agarose to form a protective barrier while potentially facilitating network stability. Following encapsulation, the neuronal networks maintained integrity, high viability (>85%) and intimate adhesion to PA-PP fibers. These efforts accomplished key prerequisites for the establishment of functional electrical interfaces with neuronal populations using small diameter PA-PP fibers-specifically, improved neurocompatibility, high-density neuronal adhesion and neuritic network development directly on fiber surfaces.

Dependence of B1+ and B1- Field Patterns of Surface Coils on the Electrical Properties of the Sample and the MR Operating Frequency.

PubMed

Vaidya, Manushka V; Collins, Christopher M; Sodickson, Daniel K; Brown, Ryan; Wiggins, Graham C; Lattanzi, Riccardo

2016-02-01

In high field MRI, the spatial distribution of the radiofrequency magnetic ( B 1 ) field is usually affected by the presence of the sample. For hardware design and to aid interpretation of experimental results, it is important both to anticipate and to accurately simulate the behavior of these fields. Fields generated by a radiofrequency surface coil were simulated using dyadic Green's functions, or experimentally measured over a range of frequencies inside an object whose electrical properties were varied to illustrate a variety of transmit [Formula: see text] and receive [Formula: see text] field patterns. In this work, we examine how changes in polarization of the field and interference of propagating waves in an object can affect the B 1 spatial distribution. Results are explained conceptually using Maxwell's equations and intuitive illustrations. We demonstrate that the electrical conductivity alters the spatial distribution of distinct polarized components of the field, causing "twisted" transmit and receive field patterns, and asymmetries between [Formula: see text] and [Formula: see text]. Additionally, interference patterns due to wavelength effects are observed at high field in samples with high relative permittivity and near-zero conductivity, but are not present in lossy samples due to the attenuation of propagating EM fields. This work provides a conceptual framework for understanding B 1 spatial distributions for surface coils and can provide guidance for RF engineers.

Investigation on electrical surface modification of waste to energy ash for possible use as an electrode material in microbial fuel cells.

PubMed

Webster, Megan; Lee, Hae Yang; Pepa, Kristi; Winkler, Nathan; Kretzschmar, Ilona; Castaldi, Marco J

2018-03-01

With the world population expected to reach 8.5 billion by 2030, demand for access to electricity and clean water will grow at unprecedented rates. Municipal solid waste combusted at waste to energy (WtE) facilities decreases waste volume and recovers energy, but yields ash as a byproduct, the beneficial uses of which are actively being investigated. Ash is intrinsically hydrophobic, highly oxidized, and exhibits high melting points and low conductivities. The research presented here explores the potential of ash to be used as an electrode material for a microbial fuel cell (MFC). This application requires increased conductivity and hydrophilicity, and a lowered melting point. Three ash samples were investigated. By applying an electric potential in the range 50-125 V across the ash in the presence of water, several key property changes were observed: lower melting point, a color change within the ash, evidence of changes in surface morphologies of ash particles, and completely wetting water-ash contact angles. We analyzed this system using a variety of analytical techniques including sector field inductively coupled plasma mass spectrometry, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, and tensiometry. Ability to make such surface modifications and significant property changes could allow ash to become useful in an application such as an electrode material for a MFC.

Pinus Pinaster surface treatment realized in spatial and temporal afterglow DBD conditions

NASA Astrophysics Data System (ADS)

Lecoq, E.; Clément, F.; Panousis, E.; Loiseau, J.-F.; Held, B.; Castetbon, A.; Guimon, C.

2008-04-01

This experimental work deals with the exposition of Pinus Pinaster wood samples to a DBD afterglow. Electrical parameters like duty cycle and injected energy in the gas are being varied and the modifications induced by the afterglow on the wood are analysed by several macroscopic and microscopic ways like wettability, XPS analyses and also soaking tests of treated wood in a commercial fungicide solution. Soaking tests show that plasma treatment could enhance the absorption of fungicide into the wood. The wettability results point out that the plasma treatment can inflict on the wood different surface properties, making it hydrophilic or hydrophobic, when varying electrical parameters. XPS analyses reveal several chemical modifications like an increase of the O/C ratio and the presence of carboxyl groups on the surface after plasma treatments.

Measuring the Valence of Nanocrystal Surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Owen, Jonathan Scharle

2016-11-30

The goal of this project is to understand and control the interplay between nanocrystal stoichiometry, surface ligand binding and exchange, and the optoelectronic properties of semiconductor nanocrystals in solution and in thin solid films. We pursued three research directions with this goal in mind: 1) We characterized nanocrystal stoichiometry and its influence on the binding of L-type and X-type ligands, including the thermodynamics of binding and the kinetics of ligand exchange. 2) We developed a quantitative understanding of the relationship between surface ligand passivation and photoluminescence quantum yield. 3) We developed methods to replace the organic ligands on the nanocrystalmore » with halide ligands and controllably deposit these nanocrystals into thin films, where electrical measurements were used to investigate the electrical transport and internanocrystal electronic coupling.« less

Method for simultaneous measurement of mass loading and fluid property changes using a quartz crystal microbalance

DOEpatents

Granstaff, V.E.; Martin, S.J.

1993-04-13

A method is described, using a quartz crystal microbalance, to obtain simultaneous measurement of solid mass accumulation and changes in liquid density-viscosity product. The simultaneous real-time measurements of electrical parameters yields that changes in surface mass can be differentiated from changes in solution properties. Two methods to obtain the admittance/frequency data are employed.

Lightning generation in Titan due to the electrical self-polarization properties of Methane

NASA Astrophysics Data System (ADS)

Quintero, A.; Falcón, N.

2009-05-01

We describe an electrical charge process in Titan's thunderclouds, due to the self-polarization properties or pyroelectricity of methane, which increases the internal electric field in thunderclouds and facilitates the charge generation and separation processes. Microphysics that generates lightning flashes is associated with the physical and chemical properties of the local atmosphere, so methane could be the principal agent of the electrical activity because of its great concentration in Titan's atmosphere. Besides, Titan's electrical activity should not be very influenced by Saturn's magnetosphere because lightning occurs at very low altitude above Titan's surface, compared with the greater distance of Saturn's magnetosphere and Titan's troposphere. Using an electrostatic treatment, we calculate the internal electric field of Titan's thunderclouds due to methane's pyroelectrical properties, 7.05×10^11 Vm^-1; and using the telluric capacitor approximation for thunderclouds, we calculate the total charge obtained for a typical Titan thundercloud, 2.67×10^9 C. However, it is not right to use an electrostatic treatment because charge times are very fast due to the large methane concentration in Titan's clouds and the life time of thunderclouds is very low (around 2 hours). We consider a time dependent mechanism, employing common Earth atmospheric approaches, because of the similitude in chemical composition of both atmospheres (mainly nitrogen), so the typical charge of a thundercloud in Titan should reach between 20 C to 40 C, like on Earth. We obtain that lightning occurs with a frequency between 2 and 6 KHz. In Titan's atmosphere, methane concentration is higher than on Earth, and atmospheric electrical activity is stronger, so this model could be consistent with the observed phenomenology.

Investigating interfacial contact configuration and behavior of single-walled carbon nanotube-based nanodevice with atomistic simulations

NASA Astrophysics Data System (ADS)

Cui, Jianlei; Zhang, Jianwei; He, Xiaoqiao; Mei, Xuesong; Wang, Wenjun; Yang, Xinju; Xie, Hui; Yang, Lijun; Wang, Yang

2017-03-01

Carbon nanotubes (CNTs), including single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs), are considered to be the promising candidates for next-generation interconnects with excellent physical and chemical properties ranging from ultrahigh mechanical strength, to electrical properties, to thermal conductivity, to optical properties, etc. To further study the interfacial contact configurations of SWNT-based nanodevice with a 13.56-Å diameter, the corresponding simulations are carried out with the molecular dynamic method. The nanotube collapses dramatically into the surface with the complete collapse on the Au/Ag/graphite electrode surface and slight distortion on the Si/SiO2 substrate surface, respectively. The related dominant mechanism is studied and explained. Meanwhile, the interfacial contact configuration and behavior, depended on other factors, are also analyzed in this article.

On the Dielectric Properties of the Martian-like Surface Sediments

NASA Technical Reports Server (NTRS)

Heggy, E.; Clifford, S. M.; Morris, R. V.; Paillou, P.; Ruffie, G.

2004-01-01

We have undertaken laboratory electromagnetic characterization of the total set of minerals identified by TES on the Martian surface in order to investigate experimentally the dielectric properties of the sediments covering it in the frequency range from 1 to 30 MHz. Volcanic Rocks with a well defined mineralogy and petrology from potential terrestrial analogues sites have also been included in the study. Our primary objective is to evaluate the range of electrical and magnetic losses that may be encountered by the various Radar sounding and imaging experiments dedicated to map the Martian subsurface searching for underground water. The electromagnetic properties of these Mars-like materials will be presented as a function of various geophysical parameters, such as porosity, bulk density and temperature. The secondary objective, is to locate regions were surface dielectric conditions are suitable for subsurface sounding.

Land-ocean contrast on electrical characteristics of lightning discharge derived from satellite optical measurements

NASA Astrophysics Data System (ADS)

Adachi, T.; Said, R.; Cummer, S. A.; Li, J.; Takahashi, Y.; Hsu, R.; Su, H.; Chen, A. B.; Mende, S. B.; Frey, H. U.

2010-12-01

Comparative studies on the electrical properties of oceanic and continental lightning are crucial to elucidate air discharge processes occurring under different conditions. Past studies however have primarily focused on continental lightning because of the limited coverage of ground-based instruments. Recent satellite measurements by FORMOSAT-2/ISUAL provided a new way to survey the global characteristics of lightning and transient luminous events regardless of land and ocean. In this study, we analyze ISUAL/spectrophotometer data to clarify the electrical properties of lightning on a global level. Based on the results obtained by Cummer et al. [2006] and Adachi et al. [2009], the OI-777.4nm emission intensity is used to infer lightning electrical parameters. Results show a clear land-ocean contrast on the parameters of lightning discharge: in oceanic lightning, peak luminosity is 60 % higher and the time scale of return stroke is 30 % shorter. These results suggest higher peak current in oceanic lightning, which is consistent with the fact that elves, EMP-driven phenomena, also tend to occur over the ocean [Chen et al., 2008]. Further analysis of lightning events occurring around the Caribbean Sea shows that the transition-line of lightning electrical properties is precisely located along the coastline. We suggest that the differences in these electrical properties may be due to the boundary conditions (conductivity, surface terrain, etc). In this talk, based on the calibration with NLDN and Duke magnetometer data, current moment change and charge moment change will be globally evaluated using a complete set of the ISUAL-observed lightning events.

Surface morphology and electrochemical studies on polyaniline/CuO nano composites

NASA Astrophysics Data System (ADS)

Ashokkumar, S. P.; Vijeth, H.; Yesappa, L.; Niranjana, M.; Vandana, M.; Basappa, M.; Devendrappa, H.

2018-05-01

An electrochemically synthesized Polyaniline (PANI) and Polyaniline/copper oxide (PCN) nano composite have studied the morphology and electrochemical properties. The composite is characterized by X-ray diffraction (XRD) and surface morphology was studied using FESEM and electrochemical behavior is studied using cyclic voltammetry (CV) technique. The CV curves shows rectangular shaped curve and they have contribution to electrical double layer capacitance (EDCL).

Manipulating Ferroelectrics through Changes in Surface and Interface Properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balke, Nina; Ramesh, Ramamoorthy; Yu, Pu

Ferroelectric materials are used in many applications of modern technologies including information storage, transducers, sensors, tunable capacitors, and other novel device concepts. In many of these applications, the ferroelectric properties, such as switching voltages, piezoelectric constants, or stability of nanodomains, are crucial. For any application, even for material characterization, the material itself needs to be interfaced with electrodes. On the basis of the structural, chemical, and electronic properties of the interfaces, the measured material properties can be determined by the interface. This is also true for surfaces. However, the importance of interfaces and surfaces and their effect on experiments aremore » often neglected, which results in many dramatically different experimental results for nominally identical samples. Therefore, it is crucial to understand the role of the interface and surface properties on internal bias fields and the domain switching process. Here, the nanoscale ferroelectric switching process and the stability of nanodomains for Pb(Zr,Ti)O 3 thin films are investigated by using scanning probe microscopy. Interface and surface properties are modulated through the selection/redesign of electrode materials as well as tuning the surface-near oxygen vacancies, which both can result in changes of the electric fields acting across the sample, and consequently this controls the measured ferroelectric and domain retention properties. By understanding the role of surfaces and interfaces, ferroelectric properties can be tuned to eliminate the problem of asymmetric domain stability by combining the effects of different electrode materials. Lastly, this study forms an important step toward integrating ferroelectric materials in electronic devices.« less

Manipulating Ferroelectrics through Changes in Surface and Interface Properties

DOE PAGES

Balke, Nina; Ramesh, Ramamoorthy; Yu, Pu

2017-10-23

Ferroelectric materials are used in many applications of modern technologies including information storage, transducers, sensors, tunable capacitors, and other novel device concepts. In many of these applications, the ferroelectric properties, such as switching voltages, piezoelectric constants, or stability of nanodomains, are crucial. For any application, even for material characterization, the material itself needs to be interfaced with electrodes. On the basis of the structural, chemical, and electronic properties of the interfaces, the measured material properties can be determined by the interface. This is also true for surfaces. However, the importance of interfaces and surfaces and their effect on experiments aremore » often neglected, which results in many dramatically different experimental results for nominally identical samples. Therefore, it is crucial to understand the role of the interface and surface properties on internal bias fields and the domain switching process. Here, the nanoscale ferroelectric switching process and the stability of nanodomains for Pb(Zr,Ti)O 3 thin films are investigated by using scanning probe microscopy. Interface and surface properties are modulated through the selection/redesign of electrode materials as well as tuning the surface-near oxygen vacancies, which both can result in changes of the electric fields acting across the sample, and consequently this controls the measured ferroelectric and domain retention properties. By understanding the role of surfaces and interfaces, ferroelectric properties can be tuned to eliminate the problem of asymmetric domain stability by combining the effects of different electrode materials. Lastly, this study forms an important step toward integrating ferroelectric materials in electronic devices.« less

Electrical current at micro-/macro-scale of undoped and nitrogen-doped MWPECVD diamond films

NASA Astrophysics Data System (ADS)

Cicala, G.; Velardi, L.; Senesi, G. S.; Picca, R. A.; Cioffi, N.

2017-12-01

Chemical, structural, morphological and micro-/macro-electrical properties of undoped and nitrogen-(N-)doped diamond films are determined by X-ray photoelectron spectroscopy, Raman and photoluminescence spectroscopies, field emission scanning electron microscopy, atomic force microscopy, scanning capacitance microscopy (SCM) and two points technique for I-V characteristics, respectively. The characterization results are very useful to examine and understand the relationship among these properties. The effect of the nitrogen incorporation in diamond films is investigated through the evolution of the chemical, structural, morphological and topographical features and of the electrical behavior. The distribution of the electrical current is first assessed at millimeter scale on the surface of diamond films and then at micrometer scale on small regions in order to establish the sites where the carriers preferentially move. Specifically, the SCM images indicate a non-uniform distribution of carriers on the morphological structures mainly located along the grain boundaries. A good agreement is found by comparing the electrical currents at the micro- and macro-scale. This work aims to highlight phenomena such as photo- and thermionic emission from N-doped diamond useful for microelectronic engineering.

Synthesis and electrical properties of (LiCo 3/5Fe 1/5Mn 1/5)VO 4 ceramics

NASA Astrophysics Data System (ADS)

Ram, Moti

2010-03-01

(LiCo 3/5Fe 1/5Mn 1/5)VO 4 ceramic was synthesized via solution-based chemical method. X-ray diffraction analysis was carried out on the synthesized powder sample at room temperature, which confirms the orthorhombic structure with the lattice parameters of a = 10.3646 (20) Å, b = 3.7926 (20) Å, c = 9.2131 (20) Å. Field emission scanning electron microscopic analysis was carried out on the sintered pellet sample that indicates grains of unequal sizes (˜0.1 to 2 μm) presents average grains size with polydisperse distribution on the surface of the ceramic. Complex impedance spectroscopy (CIS) technique is used for the study of electrical properties. CIS analysis identifies: (i) grain interior, grain boundary and electrode-material interface contributions to electrical response (ii) the presence of temperature dependent electrical relaxation phenomena in the ceramics. Detailed conductivity study indicates that electrical conduction in the material is a thermally activated process. The variation of A.C. conductivity with frequency at different temperatures obeys Jonscher's universal law.

Effect of structural transformation of C+-ion implanted PMMA into quasi-continuous carbonaceous layer on its optical and electrical properties

NASA Astrophysics Data System (ADS)

Arif, Shafaq; Rafique, M. Shahid; Saleemi, Farhat; Sagheer, Riffat

2018-02-01

The samples of Polymethylmethacrylate (PMMA) have been implanted with 500 keV C+-ions at different ion fluences ranging from 9.3 × 1013 to 8.4 × 1014 ions/cm2. The structural modifications are examined by Fourier Transform Infrared and Raman spectral studies. For the investigation of optical, electrical and surface morphological properties of implanted samples UV-Visible spectrometer, four probe apparatus and optical microscope have been employed. The FTIR spectra confirmed the cleavage of chemicals bonds as a consequence of polymer chain scission, whereas, Raman studies revealed the transformation of PMMA structure into quasi-continuous amorphous carbon with increasing ion fluences. A continuous reduction has been observed in the optical band gap of PMMA from 3.16 to 1.42 eV. Moreover, the refractive index, extinction coefficient and electrical conductivity of implanted PMMA are found to be an increasing function of the ion fluence. The micrographic images revealed the signatures of ion-induced defects like cracking, dehydrogenation, stress and swelling on the surface of PMMA. These implanted samples have a potential to be used in the field of optical communications and thin plastic flexible electronics.

Post-Annealing Effects on Surface Morphological, Electrical and Optical Properties of Nanostructured Cr-Doped CdO Thin Films

NASA Astrophysics Data System (ADS)

Hymavathi, B.; Rajesh Kumar, B.; Subba Rao, T.

2018-01-01

Nanostructured Cr-doped CdO thin films were deposited on glass substrates by reactive direct current magnetron sputtering and post-annealed in vacuum from 200°C to 500°C. X-ray diffraction studies confirmed that the films exhibit cubic nature with preferential orientation along the (111) plane. The crystallite size, lattice parameters, unit cell volume and strain in the films were determined from x-ray diffraction analysis. The surface morphology of the films has been characterized by field emission scanning electron microscopy and atomic force microscopy. The electrical properties of the Cr-doped CdO thin films were measured by using a four-probe method and Hall effect system. The lowest electrical resistivity of 2.20 × 10-4 Ω cm and a maximum optical transmittance of 88% have been obtained for the thin films annealed at 500°C. The optical band gap of the films decreased from 2.77 eV to 2.65 eV with the increase of annealing temperature. The optical constants, packing density and porosity of Cr-doped CdO thin films were also evaluated from the transmittance spectra.

Au3+ ion implantation on FTO coated glasses: Effect on structural, electrical, optical and phonon properties

NASA Astrophysics Data System (ADS)

Sahu, Bindu; Dey, Ranajit; Bajpai, P. K.

2017-06-01

Effects of 11.00 MeV Au3+ ions implanted in FTO coated (thickness ≈300 nm) silicate glasses on structural, electrical optical and phonon behavior have been explored. It has been observed that metal clustering near the surface and sub-surface region below glass-FTO interface changes electrical and optical properties significantly. Ion implantation does not affect the crystalline structure of the coated films; however, the unit cell volume decreases with increase in fluence and the tetragonal distortion (c/a ratio) also decreases systematically in the implanted samples. The sheet resistivity of the films increases from 11 × 10-5 ohm-cm (in pristine) to 7.5 × 10-4 ohm-cm for highest ion beam fluence ≈1015 ions/cm2. The optical absorption decreases with increasing fluence whereas, the optical transmittance as well as reflectance increases with increasing fluence. The Raman spectra are observed at ∼530 cm-1 and ∼1103 cm-1 in pristine sample. The broad band at 530 cm-1 shifts towards higher wave number in the irradiated samples. This may be correlated with increased disorder and strain relaxation in the samples as a result of ion beam irradiation.

Nanoporous Gold: Fabrication, Characterization, and Applications

PubMed Central

Seker, Erkin; Reed, Michael L.; Begley, Matthew R.

2009-01-01

Nanoporous gold (np-Au) has intriguing material properties that offer potential benefits for many applications due to its high specific surface area, well-characterized thiol-gold surface chemistry, high electrical conductivity, and reduced stiffness. The research on np-Au has taken place on various fronts, including advanced microfabrication and characterization techniques to probe unusual nanoscale properties and applications spanning from fuel cells to electrochemical sensors. Here, we provide a review of the recent advances in np-Au research, with special emphasis on microfabrication and characterization techniques. We conclude the paper with a brief outline of challenges to overcome in the study of nanoporous metals.

An incremental double-layer capacitance of a planar nano gap and its application in cardiac-troponin T detection.

PubMed

Hsueh, Hsiao-Ting; Lin, Chih-Ting

2016-05-15

Surface potential is one of the most important properties at solid-liquid interfaces. It can be modulated by the voltage applied on the electrode or by the surface properties. Hence, surface potential is a good indicator for surface modifications, such as biomolecular bindings. In this work, we proposed a planar nano-gap structure for surface-potential difference monitoring. Based on the proposed architecture, the variance of surface-potential difference can be determined by electrical double layer capacitance (EDLC) between the nano-gap electrodes. Using cyclic voltammetry method, in this work, we demonstrated a relationship between surface potential and EDLC by chemically modifying surface properties. Finally, we also showed the proposed planar nano-gap device provides the capability for cardiac-troponin T (cTnT) measurements with co-existed 10 µg/ml BSA interference. The detection dynamic range is from 100 pg/ml to 1 µg/ml. Based on experimental results and extrapolation, the detection limit is less than 100 pg/ml in diluted PBS buffer (0.01X PBS). These results demonstrated the planar nano-gap architecture having potentials on biomolecular detection through monitoring of surface-potential variation. Copyright © 2015 Elsevier B.V. All rights reserved.

Roll-to-Roll Manufacturing of Robust Superhydrophobic Coating on Metallic Engineering Materials.

PubMed

Dong, Shuliang; Wang, Zhenlong; Wang, Yukui; Bai, Xuelin; Fu, Yong Qing; Guo, Bin; Tan, Chaoliang; Zhang, Jia; Hu, PingAn

2018-01-17

Creating a robust superhydrophobic surface on the conventional engineering materials at mass production is of great importance for a self-cleaning, anti-icing, nonwetting surface and low flow resistance in industrial applications. Herein, we report a roll-to-roll strategy to create durable and robust superhydrophobic surfaces with designed micro-/nanoscale hierarchical structures on many conventional engineering materials by combining electrical discharge machining and coating of carbon nanoparticles, followed by oil penetration and drying. The treated surface shows good superhydrophobic properties with a static water contact angle of 170 ± 2° and slide angle of 3 ± 1°. The treated surface also exhibits good resilience and maintains the performance after being tested in various harsh conditions, including water flushing for several days, sand abrasion, scratching with sandpapers, and corrosive solution. Significantly, the superhydrophobic surfaces also show a high efficiency of self-cleaning properties even after oil contamination during applications.

Nanosecond pulsed electric field induced changes in cell surface charge density.

PubMed

Dutta, Diganta; Palmer, Xavier-Lewis; Asmar, Anthony; Stacey, Michael; Qian, Shizhi

2017-09-01

This study reports that the surface charge density changes in Jurkat cells with the application of single 60 nanosecond pulse electric fields, using atomic force microscopy. Using an atomic force microscope tip and Jurkat cells on silica in a 0.01M KCl ionic concentration, we were able to measure the interfacial forces, while also predicting surface charge densities of both Jurkat cell and silica surfaces. The most important finding is that the pulsing conditions varyingly reduced the cells' surface charge density. This offers a novel way in which to examine cellular effects of pulsed electric fields that may lead to the identification of unique mechanical responses. Compared to a single low field strength NsPEF (15kV/cm) application, exposure of Jurkat cells to a single high field strength NsPEF (60kV/cm) resulted in a further reduction in charge density and major morphological changes. The structural, physical, and chemical properties of biological cells immensely influence their electrostatic force; we were able to investigate this through the use of atomic force microscopy by measuring the surface forces between the AFM's tip and the Jurkat cells under different pulsing conditions as well as the interfacial forces in ionic concentrations. Copyright © 2017 Elsevier Ltd. All rights reserved.

Influence of electrical resistivity and machining parameters on electrical discharge machining performance of engineering ceramics.

PubMed

Ji, Renjie; Liu, Yonghong; Diao, Ruiqiang; Xu, Chenchen; Li, Xiaopeng; Cai, Baoping; Zhang, Yanzhen

2014-01-01

Engineering ceramics have been widely used in modern industry for their excellent physical and mechanical properties, and they are difficult to machine owing to their high hardness and brittleness. Electrical discharge machining (EDM) is the appropriate process for machining engineering ceramics provided they are electrically conducting. However, the electrical resistivity of the popular engineering ceramics is higher, and there has been no research on the relationship between the EDM parameters and the electrical resistivity of the engineering ceramics. This paper investigates the effects of the electrical resistivity and EDM parameters such as tool polarity, pulse interval, and electrode material, on the ZnO/Al2O3 ceramic's EDM performance, in terms of the material removal rate (MRR), electrode wear ratio (EWR), and surface roughness (SR). The results show that the electrical resistivity and the EDM parameters have the great influence on the EDM performance. The ZnO/Al2O3 ceramic with the electrical resistivity up to 3410 Ω·cm can be effectively machined by EDM with the copper electrode, the negative tool polarity, and the shorter pulse interval. Under most machining conditions, the MRR increases, and the SR decreases with the decrease of electrical resistivity. Moreover, the tool polarity, and pulse interval affect the EWR, respectively, and the electrical resistivity and electrode material have a combined effect on the EWR. Furthermore, the EDM performance of ZnO/Al2O3 ceramic with the electrical resistivity higher than 687 Ω·cm is obviously different from that with the electrical resistivity lower than 687 Ω·cm, when the electrode material changes. The microstructure character analysis of the machined ZnO/Al2O3 ceramic surface shows that the ZnO/Al2O3 ceramic is removed by melting, evaporation and thermal spalling, and the material from the working fluid and the graphite electrode can transfer to the workpiece surface during electrical discharge machining ZnO/Al2O3 ceramic.

Multiferroic properties of microwave sintered PbFe12-xO19-δ

NASA Astrophysics Data System (ADS)

Prathap, S.; Madhuri, W.

2017-05-01

The effect of iron deficiency on the structural, electrical, ferroelectric and magnetic properties of nano PbFe12-xO19-δ (where x=0.0, 0.25, 0.50, 0.75, 1.0) hexaferrites prepared by sol-gel auto combustion and processed by microwaves are investigated. X-ray analysis confirms single phase magneto-plumbite phase formation. The surface morphology is studied from Field Emission Scanning Electron Microscope. Further, optical properties are investigated using Fourier Transform Infrared spectra and UV-visible spectra. AC electrical conductivity is estimated as a function of temperature and frequency in the range of room temperature (RT) to 500 °C and 100 Hz to 5MHz. AC electrical conduction analysis shows that conduction is mainly due to small polaron hopping mechanism. The variation of polarization with applied electric field exhibits hysteresis loop confirming the ferroelectric nature. The initial permeability studies with varying temperature reveals that the Curie transition temperature for the present series is around 400 °C. Variation of initial permeability with frequency ranging from 100 to 5 MHz shows a constant value (except for x=0.0) opening avenues for high frequency applications.

Impact of the Topological Surface State on the Thermoelectric Transport in Sb2Te3 Thin Films.

PubMed

Hinsche, Nicki F; Zastrow, Sebastian; Gooth, Johannes; Pudewill, Laurens; Zierold, Robert; Rittweger, Florian; Rauch, Tomáš; Henk, Jürgen; Nielsch, Kornelius; Mertig, Ingrid

2015-04-28

Ab initio electronic structure calculations based on density functional theory and tight-binding methods for the thermoelectric properties of p-type Sb2Te3 films are presented. The thickness-dependent electrical conductivity and the thermopower are computed in the diffusive limit of transport based on the Boltzmann equation. Contributions of the bulk and the surface to the transport coefficients are separated, which enables to identify a clear impact of the topological surface state on the thermoelectric properties. When the charge carrier concentration is tuned, a crossover between a surface-state-dominant and a Fuchs-Sondheimer transport regime is achieved. The calculations are corroborated by thermoelectric transport measurements on Sb2Te3 films grown by atomic layer deposition.

Electrostatic stabilization of multi-walled carbon nanotubes dispersed in nonaqueous media.

PubMed

Damasceno, João Paulo V; Zarbin, Aldo J G

2018-06-04

Dispersing carbon nanotubes is an easy and low-cost way to manipulate these solids and allows the preparation of more complex materials or devices, so it is fundamental for further uses that these dispersions have controlled properties and high colloidal stability. In this work we report the spontaneous electrical charge build-up in pristine multi-walled carbon nanotubes dispersed in common organic solvents such as chloroform and tetrahydrofuran and the achievement of dispersions stable for long periods without adding passivant agents or functional groups on nanotubes surface. Results from electrokinetics, homo- and heterocoagulation provided macroscopic evidences that carbon nanotubes acquire electric charges after dispersion in some organic liquids and we confirmed this process by measuring in situ Raman spectra of the nanotubes dispersions with higher surface electric potentials. We also show that the signal of electric potential of the dispersions can be predicted by the acid-base behaviour of the dispersing medium, corroborating previously reports for other dispersions of carbon nanomaterials. Copyright © 2018 Elsevier Inc. All rights reserved.

On the origin of the changes in the opto-electrical properties of boron-doped zinc oxide films after plasma surface treatment for thin-film silicon solar cell applications

NASA Astrophysics Data System (ADS)

Le, Anh Huy Tuan; Kim, Youngkuk; Lee, Youn-Jung; Hussain, Shahzada Qamar; Nguyen, Cam Phu Thi; Lee, Jaehyung; Yi, Junsin

2018-03-01

The modification of the steep and sharp valleys on the surface of the boron-doped zinc oxide (BZO) front electrodes by plasma surface treatment is a critical process for avoiding a significant reduction in the electrical performance of thin-film silicon solar cells. In this work, we report the origin of the changes in the electrical and optical properties of the BZO films that occur after this process. On the basis of an analysis of the chemical states, we found an improvement of the carrier concentration along with the treatment time that was mainly due to an increase of the oxygen vacancy. This indicated a deficiency of the oxygen in the BZO films under argon-ion bombardment. The red-shift of the A1 longitudinal optical mode frequency in the Raman spectra that was attributed to the existence of vacancy point defects within the films also strengthened this argument. The significant reduction of the haze ratio as well as the appearance of interference peaks on the transmittance spectra as the treatment time was increased were mainly due to the smoothing of the film surface, which indicated a degradation of the light-scattering capability of the BZO films. We also observed a gain of the visible-region transmittance that was attributed to the decrease of the thickness of the BZO films after the plasma surface treatment, instead of the crystallinity improvement. On the basis of our findings, we have proposed a further design rule of the BZO front electrodes for thin-film silicon solar cell applications.

Significant improvement in the electrical characteristics of Schottky barrier diodes on molecularly modified Gallium Nitride surfaces

NASA Astrophysics Data System (ADS)

Garg, Manjari; Naik, Tejas R.; Pathak, C. S.; Nagarajan, S.; Rao, V. Ramgopal; Singh, R.

2018-04-01

III-Nitride semiconductors face the issue of localized surface states, which causes fermi level pinning and large leakage current at the metal semiconductor interface, thereby degrading the device performance. In this work, we have demonstrated the use of a Self-Assembled Monolayer (SAM) of organic molecules to improve the electrical characteristics of Schottky barrier diodes (SBDs) on n-type Gallium Nitride (n-GaN) epitaxial films. The electrical characteristics of diodes were improved by adsorption of SAM of hydroxyl-phenyl metallated porphyrin organic molecules (Zn-TPPOH) onto the surface of n-GaN. SAM-semiconductor bonding via native oxide on the n-GaN surface was confirmed using X-ray photoelectron spectroscopy measurements. Surface morphology and surface electronic properties were characterized using atomic force microscopy and Kelvin probe force microscopy. Current-voltage characteristics of different metal (Cu, Ni) SBDs on bare n-GaN were compared with those of Cu/Zn-TPPOH/n-GaN and Ni/Zn-TPPOH/n-GaN SBDs. It was found that due to the molecular monolayer, the surface potential of n-GaN was decreased by ˜350 mV. This caused an increase in the Schottky barrier height of Cu and Ni SBDs from 1.13 eV to 1.38 eV and 1.07 eV to 1.22 eV, respectively. In addition to this, the reverse bias leakage current was reduced by 3-4 orders of magnitude for both Cu and Ni SBDs. Such a significant improvement in the electrical performance of the diodes can be very useful for better device functioning.

Simulations of particle structuring driven by electric fields

NASA Astrophysics Data System (ADS)

Hu, Yi; Vlahovska, Petia; Miksis, Michael

2015-11-01

Recent experiments (Ouriemi and Vlahovska, 2014) show intriguing surface patterns when a uniform electric field is applied to a droplet covered with colloidal particles. Depending on the particle properties and the electric field intensity, particles organize into an equatorial belt, pole-to-pole chains, or dynamic vortices. Here we present 3D simulations of the collective particle dynamics, which account for electrohydrodynamic flow and dielectrophoresis of particles. In stronger electric fields, particles are expected to undergo Quincke rotation and impose disturbance to the ambient flow. Transition from ribbon-shaped belt to rotating clusters is observed in the presence of the rotation-induced hydrodynamical interactions. Our results provide insight into the various particle assembles discovered in the experiments.

Materials and Manufacturing Technology Directorate Thermal Sciences and Materials Branch (Overview)

DTIC Science & Technology

2010-09-01

Molecular Mechanics for thermo-mechanical response Materials Characterization • CNT modified durable thermal interface ( DTI ) • MEMS-based RTD micro...stabilization. Surface Characterization by Atomic Force Microscopy: Probing Thermal, Electrical, and Mechanical Properties Heater Current Path Anchor Leg 50 µm

Colloidal Electrolytes and the Critical Micelle Concentration

ERIC Educational Resources Information Center

Knowlton, L. G.

1970-01-01

Describes methods for determining the Critical Micelle Concentration of Colloidal Electrolytes; methods described are: (1) methods based on Colligative Properties, (2) methods based on the Electrical Conductivity of Colloidal Electrolytic Solutions, (3) Dye Method, (4) Dye Solubilization Method, and (5) Surface Tension Method. (BR)

Final thickness reduction and development of Goss texture in C- and Al-free Fe-3%Si-0.1%Mn-0.012%S electrical steel

NASA Astrophysics Data System (ADS)

Oh, Eun Jee; Heo, Nam Hoe; Koo, Yang Mo

2017-11-01

The correlation between final thickness reduction and development of Goss texture has been investigated in a C- and Al-free Fe-3%Si electrical steel. During final annealing, the annealing texture is transited from {110}⊥ND to {100}⊥ND texture with increasing final thickness reduction. This is due to the decrease in primary grain size after pre-annealing with increasing final thickness reduction which accelerates the selective growth rate of the {100} grains at the expense of the other {hkl} grains. At an optimal final thickness reduction of 75.8%, the high magnetic induction of 1.95 Tesla, which arises from the sharp {110}<001> Goss texture and is comparable to that of conventional grain-oriented electrical steels, is obtained from the C- and Al-free Fe-3%Si-0.1%Mn electrical steel. Such a high magnetic property is produced through the surface-energy-induced selective grain growth of the Goss grains under the lower surface-segregated condition of sulfur which makes the surface energy of the {110} plane lowest among the {hkl} planes.

Deformation and electrical properties of magnetic and vertically conductive composites with a chain-of-spheres structure

NASA Astrophysics Data System (ADS)

Choi, Chulmin; Hong, Soonkook; Chen, Li-Han; Liu, Chin-Hung; Choi, Duyoung; Kuru, Cihan; Jin, Sungho

2014-05-01

Vertically anisotropically conductive composites with aligned chain-of-spheres of 20-75 mm Ni particles in an elastomer matrix have been prepared by curing the mixture at 100°C-150°C under an applied magnetic field of ˜300-1000 Oe. The particles are coated with a ˜120 nm thick Au layer for enhanced electrical conductivity. The resultant vertically aligned but laterally isolated columns of conductive particles extend through the whole composite thickness and the end of the Ni columns protrude from the surface, contributing to enhanced electrical contact on the composite surface. The stress-strain curve on compressive deformation exhibits a nonlinear behavior with a rapidly increasing Young's modulus with stress (or pressure). The electrical contact resistance Rc decreases rapidly when the applied pressure is small and then more gradually after the applied pressure reaches 500 psi (˜3.4 MPa), corresponding to a 30% deformation. The directionally conductive elastomer composite material with metal pads and conductive electrodes on the substrate surface can be used as a convenient tactile shear sensor for applications involving artificial limbs, robotic devices, and other visual communication devices such as touch sensitive screens.

Evaluating the electrical discharge machining (EDM) parameters with using carbon nanotubes

NASA Astrophysics Data System (ADS)

Sari, M. M.; Noordin, M. Y.; Brusa, E.

2012-09-01

Electrical discharge machining (EDM) is one of the most accurate non traditional manufacturing processes available for creating tiny apertures, complex or simple shapes and geometries within parts and assemblies. Performance of the EDM process is usually evaluated in terms of surface roughness, existence of cracks, voids and recast layer on the surface of product, after machining. Unfortunately, the high heat generated on the electrically discharged material during the EDM process decreases the quality of products. Carbon nanotubes display unexpected strength and unique electrical and thermal properties. Multi-wall carbon nanotubes are therefore on purpose added to the dielectric used in the EDM process to improve its performance when machining the AISI H13 tool steel, by means of copper electrodes. Some EDM parameters such as material removal rate, electrode wear rate, surface roughness and recast layer are here first evaluated, then compared to the outcome of EDM performed without using nanotubes mixed to the dielectric. Independent variables investigated are pulse on time, peak current and interval time. Experimental evidences show that EDM process operated by mixing multi-wall carbon nanotubes within the dielectric looks more efficient, particularly if machining parameters are set at low pulse of energy.

Modal analysis and cut-off conditions of multichannel surface-acoustic-waveguide structures.

PubMed

Griffel, G; Golan, G; Ruschin, S; Seidman, A; Croitoru, N

1988-01-01

Multichannel guides for surface acoustic waves can improve the efficiency of SAW (surface acoustic-wave) devices significantly. Focusing, steering, and modulating the propagating acoustical modes can be achieved similarly to optical waveguided devices. A general formulation is presented for the analysis of the lateral waveguiding properties of Rayleigh modes in surfaces loaded with deposited strips of different materials. General expressions are obtained for the number of modes and cutoff conditions in these structures. As examples of applications, a simple directional coupler and an electrically controlled coupler are proposed.

Improved Diffraction Efficiency of Polarization-Sensitive Azobenzene-Containing Copolymers in an Electric Field

NASA Astrophysics Data System (ADS)

Davidenko, N. A.; Davidenko, I. I.; Mokrinskaya, E. V.; Pavlov, V. A.; Studzinsky, S. L.; Tarasenko, V. V.; Tonkopieva, L. S.; Chuprina, N. G.

2018-03-01

Recording media for polarization holography based on new azobenzene-containing monomers with octylmethacrylate are created. Their electrophysical and information properties are investigated. Improvement of the diffraction efficiency of holograms in these media in an external electric field formed by charging the free surface of the polymer film in a corona discharge is demonstrated. The diffraction efficiency is improved more in the copolymer, in which the azobenzene fragments possess larger dipole moments.

Estimating the power-law distribution of Earth electrical conductivity from low-frequency, controlled-source electromagnetic responses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beskardes, G. D.; Weiss, Chester J.; Everett, M. E.

Electromagnetic responses reflect the interaction between applied electromagnetic fields and heterogeneous geoelectrical structures. Here by quantifying the relationship between multi-scale electrical properties and the observed electromagnetic response is therefore important for meaningful geologic interpretation. Furthermore, we present here examples of near-surface electromagnetic responses whose spatial fluctuations appear on all length scales, are repeatable and fractally distributed, suggesting that the spatial fluctuations may be considered as “geologic noise”.

Estimating the power-law distribution of Earth electrical conductivity from low-frequency, controlled-source electromagnetic responses

DOE PAGES

Beskardes, G. D.; Weiss, Chester J.; Everett, M. E.

2016-11-30

Electromagnetic responses reflect the interaction between applied electromagnetic fields and heterogeneous geoelectrical structures. Here by quantifying the relationship between multi-scale electrical properties and the observed electromagnetic response is therefore important for meaningful geologic interpretation. Furthermore, we present here examples of near-surface electromagnetic responses whose spatial fluctuations appear on all length scales, are repeatable and fractally distributed, suggesting that the spatial fluctuations may be considered as “geologic noise”.

Selenium nanomaterials: applications in electronics, catalysis and sensors.

PubMed

Chaudhary, Savita; Mehta, S K

2014-02-01

This review provides insights into the synthesis, functionalization, and applications of selenium nanoparticles in electronics, optics, catalysis and sensors. The variation of physicochemical properties such as particle size, surface area, and shape of the selenium nanoparticles and the effect of experimental conditions has also been discussed. An overview has also been provided on the fundamental electrical and optical properties of selenium nanomaterials as well as their utilization in different research fields. The work presents an insight on selenium nanoparticles with interesting properties and their future applications.

Numerical correction of the phase error due to electromagnetic coupling effects in 1D EIT borehole measurements

NASA Astrophysics Data System (ADS)

Zhao, Y.; Zimmermann, E.; Huisman, J. A.; Treichel, A.; Wolters, B.; van Waasen, S.; Kemna, A.

2012-12-01

Spectral Electrical Impedance Tomography (EIT) allows obtaining images of the complex electrical conductivity for a broad frequency range (mHz to kHz). It has recently received increased interest in the field of near-surface geophysics and hydrogeophysics because of the relationships between complex electrical properties and hydrogeological and biogeochemical properties and processes observed in the laboratory with Spectral Induced Polarization (SIP). However, these laboratory results have also indicated that a high phase accuracy is required for surface and borehole EIT measurements because many soils and sediments are only weakly polarizable and show phase angles between 1 and 20 mrad. In the case of borehole EIT measurements, long cables and electrode chains (>10 meters) are typically used, which leads to undesired inductive coupling between the electric loops for current injection and potential measurement and capacitive coupling between the electrically conductive cable shielding and the soil. Depending on the electrical properties of the subsurface and the measured transfer impedances, both coupling effects can cause large phase errors that have typically limited the frequency bandwidth of field EIT measurement to the mHz to Hz range. The aim of this study is i) to develop correction procedures for these coupling effects to extend the applicability of EIT to the kHz range and ii) to validate these corrections using controlled laboratory measurements and field measurements. In order to do so, the inductive coupling effect was modeled using electronic circuit models and the capacitive coupling effect was modeled by integrating discrete capacitances in the electrical forward model describing the EIT measurement process. The correction methods were successfully verified with measurements under controlled conditions in a water-filled rain barrel, where a high phase accuracy of 2 mrad in the frequency range up to 10 kHz was achieved. In a field demonstration using a 25 m borehole chain with 8 electrodes with 1 m electrode separation, the corrections were also applied within a 1D inversion of the borehole EIT measurements. The results show that the correction methods increased the measurement accuracy considerably.

Concentration dependences of the physicochemical properties of a water-acetone system

NASA Astrophysics Data System (ADS)

Fedyaeva, O. A.; Poshelyuzhnaya, E. G.

2017-01-01

Concentration dependences of the UV spectrum, refractive index, specific electrical conductivity, boiling point, pH, surface tension, and heats of dissolution of a water-acetone system on the amount of acetone in the water are studied. It is found that the reversible protolytic interaction of the components occurs in all such solutions, resulting in the formation of hydroxyl and acetonium ions. It is shown that shifts of the equilibrium between the molecules and ions in the solution leads to extreme changes in their electrical properties. It is concluded that the formation of acetone solutions of water is accompanied by heat absorption, while the formation of aqueous solutions of acetone is accompanied by heat release.

Radio-frequency oxygen-plasma-enhanced pulsed laser deposition of IGZO films

NASA Astrophysics Data System (ADS)

Chou, Chia-Man; Lai, Chih-Chang; Chang, Chih-Wei; Wen, Kai-Shin; Hsiao, Vincent K. S.

2017-07-01

We demonstrate the crystalline structures, optical transmittance, surface and cross-sectional morphologies, chemical compositions, and electrical properties of indium gallium zinc oxide (IGZO)-based thin films deposited on glass and silicon substrates through pulsed laser deposition (PLD) incorporated with radio-frequency (r.f.)-generated oxygen plasma. The plasma-enhanced pulsed laser deposition (PEPLD)-based IGZO thin films exhibited a c-axis-aligned crystalline (CAAC) structure, which was attributed to the increase in Zn-O under high oxygen vapor pressure (150 mTorr). High oxygen vapor pressure (150 mTorr) and low r.f. power (10 W) are the optimal deposition conditions for fabricating IGZO thin films with improved electrical properties.

Superhydrophobic surfaces’ influence on streaming current based energy harvester

NASA Astrophysics Data System (ADS)

Fouché, Florent; Dargent, Thomas; Coffinier, Yannick; Treizebré, Anthony; Vlandas, Alexis; Senez, Vincent

2016-11-01

The purpose of this paper is to report the design, fabrication and characterization of silicon-based microfluidic channels with superhydrophobic walls for energy harvesting. We present the fabrication step of silicon based streaming current energy harvester and the nanostructuration of the microchannel walls. We characterize the superhydrophobic properties of the surface in a closed system. Our preliminary results on the electrical characterization of the device show a 43% increase of power harvested with our superhydrophobic surface compared to a planar hydrophobic surface.

Electric double layer at metal oxide surfaces:static properties of the cassiterite-water interface.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vlcek, L.; Zhang, Z.; Machesky, M .L.

2007-03-24

The structure of water at the (110) surface of cassiterite ({alpha}-SnO{sub 2}) at ambient conditions was studied by means of molecular dynamics simulations and X-ray crystal truncation rod experiments and interpreted with the help of the revised MUSIC model of surface protonation. The interactions of the metal oxide in the simulations were described by a recently developed classical force field based on the SPC/E model of water. Two extreme cases of completely hydroxylated and nonhydroxylated surfaces were considered along with a mixed surface with 50% dissociation. To study the dependence of the surface properties on pH, neutral and negatively chargedmore » variants of the surfaces were constructed. Axial and lateral density distributions of water for different types of surfaces were compared to each other and to experimental axial density distributions found by X-ray experiments. Although significant differences were found between the structures of the studied interfaces, the axial distances between Sn and O atoms are very similar and therefore could not be clearly distinguished by the diffraction technique. The explanation of structures observed in the density distributions was provided by a detailed analysis of hydrogen bonding in the interfacial region. It revealed qualitatively different hydrating patterns formed at neutral hydroxylated and nonhydroxylated surfaces and suggested a preference for the dissociative adsorption of water. At negatively charged surfaces, however, the situation can be reversed by the electric field stabilizing a hydrogen bond network similar to that found at the neutral nonhydroxylated surface. Comparison with previously studied rutile ({alpha}-TiO{sub 2}) surfaces provided insight into the differences between the hydration of these two metal oxides, and an important role was ascribed to their different lattice parameters. A link to macroscopic properties was provided by the revised MUSIC surface protonation model. Explicit use of the Sn-O bond lengths based on ab initio calculations and H-bond configurations as inputs led to the prediction of a pH of zero net-proton induced surface charge (pH{sub pzc}) that agrees very well with those determined experimentally (about 4.4 at 298 K).« less

Electric double layer at metal oxide surfaces: Static properties of the cassiterite - Water Interface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vlcek, Lukas; Zhang, Zhan; Machesky, Michael L.

2007-01-01

The structure of water at the (110) surface of cassiterite ({alpha}-SnO{sub 2}) at ambient conditions was studied by means of molecular dynamics simulations and X-ray crystal truncation rod experiments and interpreted with the help of the revised MUSIC model of surface protonation. The interactions of the metal oxide in the simulations were described by a recently developed classical force field based on the SPC/E model of water. Two extreme cases of completely hydroxylated and nonhydroxylated surfaces were considered along with a mixed surface with 50% dissociation. To study the dependence of the surface properties on pH, neutral and negatively chargedmore » variants of the surfaces were constructed. Axial and lateral density distributions of water for different types of surfaces were compared to each other and to experimental axial density distributions found by X-ray experiments. Although significant differences were found between the structures of the studied interfaces, the axial distances between Sn and O atoms are very similar and therefore could not be clearly distinguished by the diffraction technique. The explanation of structures observed in the density distributions was provided by a detailed analysis of hydrogen bonding in the interfacial region. It revealed qualitatively different hydrating patterns formed at neutral hydroxylated and nonhydroxylated surfaces and suggested a preference for the dissociative adsorption of water. At negatively charged surfaces, however, the situation can be reversed by the electric field stabilizing a hydrogen bond network similar to that found at the neutral nonhydroxylated surface. Comparison with previously studied rutile ({alpha}-TiO{sub 2}) surfaces provided insight into the differences between the hydration of these two metal oxides, and an important role was ascribed to their different lattice parameters. A link to macroscopic properties was provided by the revised MUSIC surface protonation model. Explicit use of the Sn-O bond lengths based on ab initio calculations and H-bond configurations as inputs led to the prediction of a pH of zero net-proton induced surface charge (pH{sub pzc}) that agrees very well with those determined experimentally (about 4.4 at 298 K).« less

Electrical Properties of Tholins and Derived Constraints on the Huygens Landing Site Composition at the Surface of Titan

NASA Astrophysics Data System (ADS)

Lethuillier, A.; Le Gall, A.; Hamelin, M.; Caujolle-Bert, S.; Schreiber, F.; Carrasco, N.; Cernogora, G.; Szopa, C.; Brouet, Y.; Simões, F.; Correia, J. J.; Ruffié, G.

2018-04-01

In 2005, the complex permittivity of the surface of Saturn's moon Titan was measured by the PWA-MIP/HASI (Permittivity Wave Altimetry-Mutual Impedance Probe/Huygens Atmospheric Structure Instrument) experiment on board the Huygens probe. The analysis of these measurements was recently refined but could not be interpreted in terms of composition due to the lack of knowledge on the low-frequency/low-temperature electrical properties of Titan's organic material, a likely key ingredient of the surface composition. In order to fill that gap, we developed a dedicated measurement bench and investigated the complex permittivity of analogs of Titan's organic aerosols called "tholins." These laboratory measurements, together with those performed in the microwave domain, are then used to derive constraints on the composition of Titan's first meter below the surface based on both the PWA-MIP/HASI and the Cassini Radar observations. Assuming a ternary mixture of water ice, tholin-like dust and pores (filled or not with liquid methane), we find that at least 10% of water ice and 15% of porosity are required to explain observations. On the other hand, there should be at most 50-60% of organic dust. PWA-MIP/HASI measurements also suggest the presence of a thin conductive superficial layer at the Huygens landing site. Using accurate numerical simulations, we put constraints on the electrical conductivity of this layer as a function of its thickness (e.g., in the range 7-40 nS/m for a 7-mm thick layer). Potential candidates for the composition of this layer are discussed.

Hydroxyapatite Nanowire-Based All-Weather Flexible Electrically Conductive Paper with Superhydrophobic and Flame-Retardant Properties.

PubMed

Chen, Fei-Fei; Zhu, Ying-Jie; Xiong, Zhi-Chao; Dong, Li-Ying; Chen, Feng; Lu, Bing-Qiang; Yang, Ri-Long

2017-11-15

How to survive under various harsh working conditions is a key challenge for flexible electronic devices because their performances are always susceptible to environments. Herein, we demonstrate the novel design and fabrication of a new kind of the all-weather flexible electrically conductive paper based on ultralong hydroxyapatite nanowires (HNs) with unique combination of the superhydrophobic surface, electrothermal effect, and flame retardancy. The superhydrophobic surface with water repellency stabilizes the electrically conductive performance of the paper in water. For example, the electrical current through the superhydrophobic paper onto which water droplets are deposited shows a little change (0.38%), and the electrical performance is steady as well even when the paper is immersed in water for 120 s (just 3.65% change). In addition, the intrinsic electrothermal effect of the electrically conductive paper can efficiently heat the paper to reach a high temperature, for example, 224.25 °C, within 10 s. The synergistic effect between the electrothermal effect and superhydrophobic surface accelerates the melting and removal of ice on the heated electrically conductive paper. Deicing efficiency of the heated superhydrophobic electrically conductive paper is ∼4.5 times that of the unheated superhydrophobic electrically conductive paper and ∼10.4 times that of the heated superhydrophilic paper. More importantly, benefiting from fire-resistant ultralong HNs, thermally stable Ketjen black, and Si-O backbone of poly(dimethylsiloxane), we demonstrate the stable and continuous service of the as-prepared electrically conductive paper in the flame for as long as 7 min. The electrical performance of the electrically conductive paper after flame treatment can maintain as high as 90.60% of the original value. The rational design of the electrically conductive paper with suitable building materials and structure demonstrated here will give an inspiration for the development of new kinds of all-weather flexible electronic devices that can work under harsh conditions.

Soft-Matter Resistive Sensor for Measuring Shear and Pressure Stresses

NASA Astrophysics Data System (ADS)

Tepayotl-Ramirez, Daniel; Roberts, Peter; Majidi, Carmel

2013-03-01

Building on emerging paradigms in soft-matter electronics, we introduce liquid-phase electronic sensors that simultaneously measures elastic pressure and shear deformation. The sensors are com- posed of a sheet of elastomer that is embedded with fluidic channels containing eutectic Gallium- Indium (EGaIn), a metal alloy that is liquid at room temperature. Applying pressure or shear traction to the surface of the surrounding elastomer causes the elastomer to elastically deform and changes the geometry and electrical properties of the embedded liquid-phase circuit elements. We introduce analytic models that predict the electrical response of the sensor to prescribed surface tractions. These models are validated with both Finite Element Analysis (FEA) and experimental measurements.

Understanding Trap Effects on Electrical Treeing Phenomena in EPDM/POSS Composites.

PubMed

Du, Boxue; Su, Jingang; Tian, Meng; Han, Tao; Li, Jin

2018-05-31

POSS (polyhedral oligomeric silsesquioxane) provides an interesting alternative nano-silica and has the potential of superior dielectric properties to restrain electrical degradation. By incorporating POSS into EPDM to suppress electrical tree, one of precursors to dielectric failure, is promising to improve the lifetime of insulation materials. This paper focuses on the electrical treeing phenomena in EPDM/OVPOSS (ethylene propylene diene monomer/octavinyl-POSS) composites based on their physicochemical properties and trap distributions. ATR-IR and SEM characteristics are investigated to observe the chemical structure and physical dispersion of EPDM/OVPOSS composites. Electrical treeing characteristics are studied by the needle-plane electrode, and the trap level distributions are characterized by surface potential decay (SPD) tests. The results show that the 3 wt% EPDM/OVPOSS is more effective to restrain the electrical tree growth than the neat EPDM in this paper. It is indicated that the EPDM/OVPOSS with a filler content of 3 wt% introduces the largest energy level and trap density of deep trapped charges, which suppress the transportation of charge carriers injected from the needle tip and further prevent the degradation of polymer molecules. The polarity effects are obvious during the electrical treeing process, which is dependent on the trap level differences between positive and negative voltage.

Subatomic-scale force vector mapping above a Ge(001) dimer using bimodal atomic force microscopy

NASA Astrophysics Data System (ADS)

Naitoh, Yoshitaka; Turanský, Robert; Brndiar, Ján; Li, Yan Jun; Štich, Ivan; Sugawara, Yasuhiro

2017-07-01

Probing physical quantities on the nanoscale that have directionality, such as magnetic moments, electric dipoles, or the force response of a surface, is essential for characterizing functionalized materials for nanotechnological device applications. Currently, such physical quantities are usually experimentally obtained as scalars. To investigate the physical properties of a surface on the nanoscale in depth, these properties must be measured as vectors. Here we demonstrate a three-force-component detection method, based on multi-frequency atomic force microscopy on the subatomic scale and apply it to a Ge(001)-c(4 × 2) surface. We probed the surface-normal and surface-parallel force components above the surface and their direction-dependent anisotropy and expressed them as a three-dimensional force vector distribution. Access to the atomic-scale force distribution on the surface will enable better understanding of nanoscale surface morphologies, chemical composition and reactions, probing nanostructures via atomic or molecular manipulation, and provide insights into the behaviour of nano-machines on substrates.

Numerical modelling of needle-grid electrodes for negative surface corona charging system

NASA Astrophysics Data System (ADS)

Zhuang, Y.; Chen, G.; Rotaru, M.

2011-08-01

Surface potential decay measurement is a simple and low cost tool to examine electrical properties of insulation materials. During the corona charging stage, a needle-grid electrodes system is often used to achieve uniform charge distribution on the surface of the sample. In this paper, a model using COMSOL Multiphysics has been developed to simulate the gas discharge. A well-known hydrodynamic drift-diffusion model was used. The model consists of a set of continuity equations accounting for the movement, generation and loss of charge carriers (electrons, positive and negative ions) coupled with Poisson's equation to take into account the effect of space and surface charges on the electric field. Four models with the grid electrode in different positions and several mesh sizes are compared with a model that only has the needle electrode. The results for impulse current and surface charge density on the sample clearly show the effect of the extra grid electrode with various positions.

The Charging of Composites in the Space Environment

NASA Technical Reports Server (NTRS)

Czepiela, Steven A.

1997-01-01

Deep dielectric charging and subsequent electrostatic discharge in composite materials used on spacecraft have become greater concerns since composite materials are being used more extensively as main structural components. Deep dielectric charging occurs when high energy particles penetrate and deposit themselves in the insulating material of spacecraft components. These deposited particles induce an electric field in the material, which causes the particles to move and thus changes the electric field. The electric field continues to change until a steady state is reached between the incoming particles from the space environment and the particles moving away due to the electric field. An electrostatic discharge occurs when the electric field is greater than the dielectric strength of the composite material. The goal of the current investigation is to investigate deep dielectric charging in composite materials and ascertain what modifications have to be made to the composite properties to alleviate any breakdown issues. A 1-D model was created. The space environment, which is calculated using the Environmental Workbench software, the composite material properties, and the electric field and voltage boundary conditions are input into the model. The output from the model is the charge density, electric field, and voltage distributions as functions of the depth into the material and time. Analysis using the model show that there should be no deep dielectric charging problem with conductive composites such as carbon fiber/epoxy. With insulating materials such as glass fiber/epoxy, Kevlar, and polymers, there is also no concern of deep dielectric charging problems with average day-to-day particle fluxes. However, problems can arise during geomagnetic substorms and solar particle events where particle flux levels increase by several orders of magnitude, and thus increase the electric field in the material by several orders of magnitude. Therefore, the second part of this investigation was an experimental attempt to measure the continuum electrical properties of a carbon fiber/epoxy composite, and to create a composite with tailorable conductivity without affecting its mechanical properties. The measurement of the conductivity and dielectric strength of carbon fiber/epoxy composites showed that these properties are surface layer dominated and difficult to measure. In the second experimental task, the conductivity of a glass fiber/epoxy composite was increased by 3 orders of magnitude, dielectric constant was increased approximately by a factor of 16, with minimal change to the mechanical properties, by adding conductive carbon black to the epoxy.

Interfacial control of oxygen vacancy doping and electrical conduction in thin film oxide heterostructures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veal, Boyd W.; Kim, Seong Keun; Zapol, Peter

2016-06-10

Oxygen vacancies in proximity to surfaces and heterointerfaces in oxide thin film heterostructures have major effects on properties, resulting, for example, in emergent conduction behaviour, large changes in metal-insulator transition temperatures or enhanced catalytic activity. Here we report the discovery of a means of reversibly controlling the oxygen vacancy concentration and distribution in oxide heterostructures consisting of electronically conducting In2O3 films grown on ionically conducting Y2O3-stabilized ZrO2 substrates. Oxygen ion redistribution across the heterointerface is induced using an applied electric field oriented in the plane of the interface, resulting in controlled oxygen vacancy (and hence electron) doping of the filmmore » and possible orders-of-magnitude enhancement of the film's electrical conduction. The reversible modified behaviour is dependent on interface properties and is attained without cation doping or changes in the gas environment.« less

On the Possibility of Estimation of the Earth Crust's Properties from the Observations of Electric Field of Electrokinetic Origin, Generated by Tidal Deformation within the Fault Zone

NASA Astrophysics Data System (ADS)

Alekseev, D. A.; Gokhberg, M. B.

2018-05-01

A 2-D boundary problem formulation in terms of pore pressure in Biot poroelasticity model is discussed, with application to a vertical contact model mechanically excited by a lunar-solar tidal deformation wave, representing a fault zone structure. A problem parametrization in terms of permeability and Biot's modulus contrasts is proposed and its numerical solution is obtained for a series of models differing in the values of the above parameters. The behavior of pore pressure and its gradient is analyzed. From those, the electric field of the electrokinetic nature is calculated. The possibilities of estimation of the elastic properties and permeability of geological formations from the observations of the horizontal and vertical electric field measured inside the medium and at the earth's surface near the block boundary are discussed.

DNA hybridization sensor based on pentacene thin film transistor.

PubMed

Kim, Jung-Min; Jha, Sandeep Kumar; Chand, Rohit; Lee, Dong-Hoon; Kim, Yong-Sang

2011-01-15

A DNA hybridization sensor using pentacene thin film transistors (TFTs) is an excellent candidate for disposable sensor applications due to their low-cost fabrication process and fast detection. We fabricated pentacene TFTs on glass substrate for the sensing of DNA hybridization. The ss-DNA (polyA/polyT) or ds-DNA (polyA/polyT hybrid) were immobilized directly on the surface of the pentacene, producing a dramatic change in the electrical properties of the devices. The electrical characteristics of devices were studied as a function of DNA immobilization, single-stranded vs. double-stranded DNA, DNA length and concentration. The TFT device was further tested for detection of λ-phage genomic DNA using probe hybridization. Based on these results, we propose that a "label-free" detection technique for DNA hybridization is possible through direct measurement of electrical properties of DNA-immobilized pentacene TFTs. Copyright © 2010 Elsevier B.V. All rights reserved.

Interfacial control of oxygen vacancy doping and electrical conduction in thin film oxide heterostructures

DOE PAGES

Veal, Boyd W.; Kim, Seong Keun; Zapol, Peter; ...

2016-06-10

Oxygen vacancies in proximity to surfaces and heterointerfaces in oxide thin film heterostructures have major effects on properties, resulting, for example, in emergent conduction behavior, large changes in metal-insulator transition temperatures, or enhanced catalytic activity. Here in this paper, we report the discovery of a means of reversibly controlling the oxygen vacancy concentration and distribution in oxide heterostructures consisting of electronically conducting In 2O 3 films grown on ionically conducting Y 2O 3-stabilized ZrO 2 substrates. Oxygen ion redistribution across the heterointerface is induced using an applied electric field oriented in the plane of the interface, resulting in controlled oxygenmore » vacancy (and hence electron) doping of the film and possible orders-of-magnitude enhancement of the film's electrical conduction. The reversible modified behavior is dependent on interface properties and is attained without cation doping or changes in the gas environment.« less

Nitridation of SiO2 for surface passivation

NASA Technical Reports Server (NTRS)

Lai, S. K. C.

1985-01-01

An attempt is made to relate the electrical properties of silicon dioxide film to the process history. A model is proposed to explain some of the observed results. It is shown that with our present knowledge of the dielectric, silicon dioxide film shows a lot of promise for its use in surface passivation, both for its resistance to impurity diffusion and for its resistance to radiation damage effects.

Light Management in Transparent Conducting Oxides by Direct Fabrication of Periodic Surface Arrays

NASA Astrophysics Data System (ADS)

Eckhardt, S.; Sachse, C.; Lasagni, A. F.

Line- and hexagonal-like periodic textures were fabricated on aluminium zinc oxide (AZO) using direct laser interference patterning method. It was found that hexagonally patterned surfaces show a higher performance in both transparency and diffraction properties compared to line-like textured and non-patterned substrates. Furthermore, the electrical resistance of the processed AZO coated substrates remained below the tolerance values for transparent conducting electrodes.

Modeling the Adsorbate Coverage Distribution Over a Multi-Faceted Catalytic Grain in the Presence of an Electric Field: O/Fe from First Principles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bray, Jacob; Hensley, Alyssa J. R.; Collinge, Greg

The impact of an external electric field on the concerted behavior of oxygen over a multi-faceted catalytic Fe grain is determined via the interpolation of ab initio models of oxygen adsorption on Fe(100), Fe(110), and Fe(111) in the presence of an external electric field. The application of both negative and positive electric fields weaken the adsorption strength for oxygen on all three surface facets, with Fe(110) experiencing the greatest effect. Kinetic models of a multi-faceted catalytic Fe grain show that the average oxygen coverage over the grain surface is reduced under the influence of both a negative and positive electricmore » field, which are consistent with phase diagram results at comparable pressures. Furthermore, we show that there is a weak synergistic effect between a Pd promoter and a positive electric field on the oxygen adsorption energy, i.e. the Pd promoter and electric field combination weaken the oxygen adsorption energy to a greater degree than the simple addition of both components separately. In conclusion, the work shows that the application of an applied external electric field may be a useful tool in fine-tuning chemical properties of Fe-based catalysts in hydrodeoxygenation applications.« less

Modeling the Adsorbate Coverage Distribution Over a Multi-Faceted Catalytic Grain in the Presence of an Electric Field: O/Fe from First Principles

DOE PAGES

Bray, Jacob; Hensley, Alyssa J. R.; Collinge, Greg; ...

2018-04-15

The impact of an external electric field on the concerted behavior of oxygen over a multi-faceted catalytic Fe grain is determined via the interpolation of ab initio models of oxygen adsorption on Fe(100), Fe(110), and Fe(111) in the presence of an external electric field. The application of both negative and positive electric fields weaken the adsorption strength for oxygen on all three surface facets, with Fe(110) experiencing the greatest effect. Kinetic models of a multi-faceted catalytic Fe grain show that the average oxygen coverage over the grain surface is reduced under the influence of both a negative and positive electricmore » field, which are consistent with phase diagram results at comparable pressures. Furthermore, we show that there is a weak synergistic effect between a Pd promoter and a positive electric field on the oxygen adsorption energy, i.e. the Pd promoter and electric field combination weaken the oxygen adsorption energy to a greater degree than the simple addition of both components separately. In conclusion, the work shows that the application of an applied external electric field may be a useful tool in fine-tuning chemical properties of Fe-based catalysts in hydrodeoxygenation applications.« less

The structure and properties of a simple model mixture of amphiphilic molecules and ions at a solid surface

NASA Astrophysics Data System (ADS)

Pizio, O.; Sokołowski, S.; Sokołowska, Z.

2014-05-01

We investigate microscopic structure, adsorption, and electric properties of a mixture that consists of amphiphilic molecules and charged hard spheres in contact with uncharged or charged solid surfaces. The amphiphilic molecules are modeled as spheres composed of attractive and repulsive parts. The electrolyte component of the mixture is considered in the framework of the restricted primitive model (RPM). The system is studied using a density functional theory that combines fundamental measure theory for hard sphere mixtures, weighted density approach for inhomogeneous charged hard spheres, and a mean-field approximation to describe anisotropic interactions. Our principal focus is in exploring the effects brought by the presence of ions on the distribution of amphiphilic particles at the wall, as well as the effects of amphiphilic molecules on the electric double layer formed at solid surface. In particular, we have found that under certain thermodynamic conditions a long-range translational and orientational order can develop. The presence of amphiphiles produces changes of the shape of the differential capacitance from symmetric or non-symmetric bell-like to camel-like. Moreover, for some systems the value of the potential of the zero charge is non-zero, in contrast to the RPM at a charged surface.

Insights into the effects of solvent properties in graphene based electric double-layer capacitors with organic electrolytes

NASA Astrophysics Data System (ADS)

Zhang, Shuo; Bo, Zheng; Yang, Huachao; Yang, Jinyuan; Duan, Liangping; Yan, Jianhua; Cen, Kefa

2016-12-01

Organic electrolytes are widely used in electric double-layer capacitors (EDLCs). In this work, the microstructure of planar graphene-based EDLCs with different organic solvents are investigated with molecular dynamics simulations. Results show that an increase of solvent polarity could weaken the accumulation of counter-ions nearby the electrode surface, due to the screen of electrode charges and relatively lower ionic desolvation. It thus suggests that solvents with low polarity could be preferable to yield high EDL capacitance. Meanwhile, the significant effects of the size and structure of solvent molecules are reflected by non-electrostatic molecule-electrode interactions, further influencing the adsorption of solvent molecules on electrode surface. Compared with dimethyl carbonate, γ-butyrolactone, and propylene carbonate, acetonitrile with relatively small-size and linear structure owns weak non-electrostatic interactions, which favors the easy re-orientation of solvent molecules. Moreover, the shift of solvent orientation in surface layer, from parallel orientation to perpendicular orientation relative to the electrode surface, deciphers the solvent twin-peak behavior near negative electrode. The as-obtained insights into the roles of solvent properties on the interplays among particles and electrodes elucidate the solvent influences on the microstructure and capacitive behavior of EDLCs using organic electrolytes.

Ferroelectric polarization effect on surface chemistry and photo-catalytic activity: A review

NASA Astrophysics Data System (ADS)

Khan, M. A.; Nadeem, M. A.; Idriss, H.

2016-03-01

The current efficiency of various photocatalytic processes is limited by the recombination of photogenerated electron-hole pairs in the photocatalyst as well as the back-reaction of intermediate species. This review concentrates on the use of ferroelectric polarization to mitigate electron-hole recombination and back-reactions and therefore improve photochemical reactivity. Ferroelectric materials are considered as wide band gap polarizable semiconductors. Depending on the surface polarization, different regions of the surface experience different extents of band bending and promote different carriers to move to spatially different locations. This can lead to some interesting interactions at the surface such as spatially selective adsorption and surface redox reactions. This introductory review covers the fundamental properties of ferroelectric materials, effect of an internal electric field/polarization on charge carrier separation, effect of the polarization on the surface photochemistry and reviews the work done on the use of these ferroelectric materials for photocatalytic applications such as dye degradation and water splitting. The manipulation of photogenerated charge carriers through an internal electric field/surface polarization is a promising strategy for the design of improved photocatalysts.

Antibacterial properties of Ag-doped hydroxyapatite layers prepared by PLD method

NASA Astrophysics Data System (ADS)

Jelínek, Miroslav; Kocourek, Tomáš; Jurek, Karel; Remsa, Jan; Mikšovský, Jan; Weiserová, Marie; Strnad, Jakub; Luxbacher, Thomas

2010-12-01

Thin hydroxyapatite (HA), silver-doped HA and silver layers were prepared using a pulsed laser deposition method. Doped layers were ablated from silver/HA targets. Amorphous and crystalline films of silver concentrations of 0.06 at.%, 1.2 at.%, 4.4 at.%, 8.3 at.% and 13.7 at.% were synthesized. Topology was studied using scanning electron microscopy and atomic force microscopy. Contact angle and zeta potential measurements were conducted to determine the wettability, surface free energy and electric surface properties. In vivo measurement (using Escherichia coli cells) of antibacterial properties of the HA, silver-doped HA and silver layers was carried out. The best antibacterial results were achieved for silver-doped HA layers of silver concentration higher than 1.2 at.%.

Effect of V/III ratio on the surface morphology and electrical properties of m-plane (10 1 bar 0) GaN homoepitaxial layers

NASA Astrophysics Data System (ADS)

Barry, Ousmane I.; Tanaka, Atsushi; Nagamatsu, Kentaro; Bae, Si-Young; Lekhal, Kaddour; Matsushita, Junya; Deki, Manato; Nitta, Shugo; Honda, Yoshio; Amano, Hiroshi

2017-06-01

We have investigated the effect of V/III ratio on the surface morphology, impurity concentration and electrical properties of m-plane (10 1 bar 0) Gallium Nitride (GaN) homoepitaxial layers. Four-sided pyramidal hillocks are observed on the nominally on-axis m-plane GaN films. Hillocks sizes relatively increase by increasing the V/III ratio. All facets of pyramidal hillocks exhibit well-defined step-terrace features. Secondary ion mass spectrometry depth profiles reveal that carbon impurities decrease by increasing the V/III ratio while the lowest oxygen content is found at an optimized V/III ratio of 900. Vertical Schottky barrier diodes fabricated on the m-GaN samples were characterized. Low leakage current densities of the order of 10-10 A/cm2 at -5 V are obtained at the optimum V/III ratio. Oxygen impurities and screw-component dislocations around hillocks are found to have more detrimental impact on the leakage current mechanism.

Self-Cleaning Microcavity Array for Photovoltaic Modules.

PubMed

Vüllers, Felix; Fritz, Benjamin; Roslizar, Aiman; Striegel, Andreas; Guttmann, Markus; Richards, Bryce S; Hölscher, Hendrik; Gomard, Guillaume; Klampaftis, Efthymios; Kavalenka, Maryna N

2018-01-24

Development of self-cleaning coatings is of great interest for the photovoltaic (PV) industry, as soiling of the modules can significantly reduce their electrical output and increase operational costs. We fabricated flexible polymeric films with novel disordered microcavity array (MCA) topography from fluorinated ethylene propylene (FEP) by hot embossing. Because of their superhydrophobicity with water contact angles above 150° and roll-off angles below 5°, the films possess self-cleaning properties over a wide range of tilt angles, starting at 10°, and contaminant sizes (30-900 μm). Droplets that impact the FEP MCA surface with velocities of the same order of magnitude as that of rain bounce off the surface without impairing its wetting properties. Additionally, the disordered MCA topography of the films enhances the performance of PV devices by improving light incoupling. Optical coupling of the FEP MCA films to a glass-encapsulated multicrystalline silicon solar cell results in 4.6% enhancement of the electrical output compared to that of an uncoated device.

A role for ion implantation in quantum computing

NASA Astrophysics Data System (ADS)

Jamieson, David N.; Prawer, Steven; Andrienko, Igor; Brett, David A.; Millar, Victoria

2001-04-01

We propose to create arrays of phosphorus atoms in silicon for quantum computing using ion implantation. Since the implantation of the ions is essentially random, the yield of usefully spaced atoms is low and therefore some method of registering the passage of a single ion is required. This can be accomplished by implantation of the ions through a thin surface layer consisting of resist. Changes to the chemical and/or electrical properties of the resist will be used to mark the site of the buried ion. For chemical changes, the latent damage will be developed and the atomic force microscope (AFM) used to image the changes in topography. Alternatively, changes in electrical properties (which obviate the need for post-irradiation chemical etching) will be used to register the passage of the ion using scanning tunneling microscopy (STM), the surface current imaging mode of the AFM. We address the central issue of the contrast created by the passage of a single ion through resist layers of PMMA and C 60.

Highly efficient flexible optoelectronic devices using metal nanowire-conducting polymer composite transparent electrode

NASA Astrophysics Data System (ADS)

Jung, Eui Dae; Nam, Yun Seok; Seo, Houn; Lee, Bo Ram; Yu, Jae Choul; Lee, Sang Yun; Kim, Ju-Young; Park, Jang-Ung; Song, Myoung Hoon

2015-09-01

Here, we report a comprehensive analysis of the electrical, optical, mechanical, and surface morphological properties of composite nanostrutures based on silver nanowires (AgNW) and PEDOT:PSS conducting polymer for the use as flexible and transparent electrodes. Compared to ITO or the single material of AgNW or PEDOT:PSS, the AgNW/PEDOT:PSS composite electrode showed high electrical conductivity with a low sheet resistance of 26.8 Ω/sq at 91% transmittance (at 550 nm), improves surface smoothness, and enhances mechanical properties assisted by an amphiphilic fluoro-surfactant. The polymeric light-emitting diodes (PLEDs) and organic solar cells (OSCs) using the AgNW/PEDOT:PSS composite electrode showed higher device performances than those with AgNW and PEDOT:PSS electrodes and excellent flexibility under bending test. These results indicates that the AgNW/PEDOT:PSS composite presented is a good candidate as next-generation transparent elelctrodes for applications into flexible optoelectronic devices. [Figure not available: see fulltext.

Superhydrophobic honeycomb-like cobalt stearate thin films on aluminum with excellent anti-corrosion properties

NASA Astrophysics Data System (ADS)

Xiong, Jiawei; Sarkar, D. K.; Chen, X.-Grant

2017-06-01

Superhydrophobic cobalt stearate thin films with excellent anti-corrosion properties were successfully fabricated on aluminum substrates via electrodeposition process. The water-repellent properties were attributed to the honeycomb-like micro-nano structure as well as low surface energy of cobalt stearate. The correlation between the surface morphology, composition as well as wetting properties and the molar ratio of inorganic cobalt salt (Co(NO3)2) and organic stearic acid (SA) abbreviated as Co/SA, in the electrolyte were studied carefully. The optimum superhydrophobic surface obtained on the electrodeposited cathodic aluminum substrate, in the mixed ethanolic solution with Co/SA molar ratio of 0.2, was found to have a maximum contact angle of 161°. The polarization resistance of superhydrophobic aluminum substrates was calculated as high as 1591 kΩ cm2, which is determined to be two orders of magnitude larger than that of the as-received aluminum substrate as 27 kΩ cm2. Electrochemical impedance spectroscopy (EIS) was also employed to evaluate the corrosion resistance properties of these samples. Furthermore, electrical equivalent circuits (EEC) have been suggested in order to better understand the corrosion phenomena on these surfaces based on the corresponding EIS data.

Electrokinetic properties of polymer colloids

NASA Technical Reports Server (NTRS)

Micale, F. J.; Fuenmayor, D. Y.

1986-01-01

The surface of polymer colloids, especially polystyrene latexes, were modified for the purpose of controlling the electrokinetic properties of the resulting colloids. Achievement required a knowledge of electrical double layer charging mechanism, as a function of the electrolyte conditions, at the polymer/water interface. The experimental approach is to control the recipe formulation in the emulsion polymerization process so as to systematically vary the strong acid group concentration on the surface of the polymer particles. The electrophoretic mobility of these model particles will then be measured as a function of surface group concentration and as a function of electrolyte concentration and type. An effort was also made to evaluate the electrophoretic mobility of polystyrene latexes made in space and to compare the results with latexes made on the ground.

Properties of p-n-junctions formed by a laser irradiation of a surface of n-Cd1-xZnxTe single crystal

NASA Astrophysics Data System (ADS)

Khomyak, V. V.; Ilashchuk, M. I.; Shtepliuk, I. I.

2015-03-01

Photosensitive barrier structures were fabricated by high-power pulsed laser irradiation of a freshly-cleaved surface of п-type bulk Cd1-xZnxTe substrates. Their electrical properties were investigated and discussed. Dominant carrier mechanisms at a forward and a reverse bias in terms of a recombination and tunnel-recombination model were analyzed. At the illumination reaching 100 mW · cm-2, these surface-barrier р-Cd1-хZnхTe/п-Cd1-хZnхTe structures were possessed by the following photoelectric parameters: open-circuit voltage Voc = 0.61 V, short-circuit current Isc = 0.21 mА and fill factor FF = 0.49, respectively.

Functionalization of silicon nanowires by conductive and non-conductive polymers

NASA Astrophysics Data System (ADS)

Belhousse, S.; Tighilt, F.-Z.; Sam, S.; Lasmi, K.; Hamdani, K.; Tahanout, L.; Megherbi, F.; Gabouze, N.

2017-11-01

The work reports on the development of hybrid devices based on silicon nanowires (SiNW) with polymers and the difference obtained when using conductive and non-conductive polymers. SiNW have attracted much attention due to their importance in understanding the fundamental properties at low dimensionality as well as their potential application in nanoscale devices as in field effect transistors, chemical or biological sensors, battery electrodes and photovoltaics. SiNW arrays were formed using metal assisted chemical etching method. This process is simple, fast and allows obtaining a wide range of silicon nanostructures. Hydrogen-passivated SiNW surfaces show relatively poor stability. Surface modification with organic species confers the desired stability and enhances the surface properties. For this reason, this work proposes a covalent grafting of organic material onto SiNW surface. We have chosen a non-conductive polymer polyvinylpyrrolidone (PVP) and conductive polymers polythiophene (PTh) and polypyrrole (PPy), in order to evaluate the electric effect of the polymers on the obtained materials. The hybrid structures were elaborated by the polymerization of the corresponding conjugated monomers by electrochemical route; this electropolymerization offers several advantages such as simplicity and rapidity. SiNW functionalization by conductive polymers has shown to have a huge effect on the electrical mobility. Hybrid surface morphologies were characterized by scanning electron microscopy (SEM), infrared spectroscopy (FTIR-ATR) and contact angle measurements.

Pyroelectricity as a possible mechanism for cell membrane permeabilization.

PubMed

García-Sánchez, Tomás; Muscat, Adeline; Leray, Isabelle; Mir, Lluis M

2018-02-01

The effects of pyroelectricity on cell membrane permeability had never been explored. Pyroelectricity consists in the generation of an electric field in the surface of some materials when a change in temperature is produced. In the present study, tourmaline microparticles, which are known to display pyroelectrical properties, were subjected to different changes in temperature upon exposure to cells in order to induce an electric field at their surface. Then, the changes in the permeability of the cell membrane to a cytotoxic agent (bleomycin) were assessed by a cloning efficacy test. An increase in the permeability of the cell membrane was only detected when tourmaline was subjected to a change in temperature. This suggests that the apparition of an induced pyroelectrical electric field on the material could actually be involved in the observed enhancement of the cell membrane permeability as a result of cell electropermeabilization. Copyright © 2017 Elsevier B.V. All rights reserved.

Bulk and Thin film Properties of Nanoparticle-based Ionic Materials

NASA Astrophysics Data System (ADS)

Fang, Jason

2008-03-01

Nanoparticle-based ionic materials (NIMS) offer exciting opportunities for research at the forefront of science and engineering. NIMS are hybrid particles comprised of a charged oligomeric corona attached to hard, inorganic nanoparticle cores. Because of their hybrid nature, physical properties --rheological, optical, electrical, thermal - of NIMS can be tailored over an unusually wide range by varying geometric and chemical characteristics of the core and canopy and thermodynamic variables such as temperature and volume fraction. On one end of the spectrum are materials with a high core content, which display properties similar to crystalline solids, stiff waxes, and gels. At the opposite extreme are systems that spontaneously form particle-based fluids characterized by transport properties remarkably similar to simple liquids. In this poster I will present our efforts to synthesize NIMS and discuss their bulk and surface properties. In particular I will discuss our work on preparing smart surfaces using NIMS.

Atomic Layer Deposition in Bio-Nanotechnology: A Brief Overview.

PubMed

Bishal, Arghya K; Butt, Arman; Selvaraj, Sathees K; Joshi, Bela; Patel, Sweetu B; Huang, Su; Yang, Bin; Shukohfar, Tolou; Sukotjo, Cortino; Takoudis, Christos G

2015-01-01

Atomic layer deposition (ALD) is a technique increasingly used in nanotechnology and ultrathin film deposition; it is ideal for films in the nanometer and Angstrom length scales. ALD can effectively be used to modify the surface chemistry and functionalization of engineering-related and biologically important surfaces. It can also be used to alter the mechanical, electrical, chemical, and other properties of materials that are increasingly used in biomedical engineering and biological sciences. ALD is a relatively new technique for optimizing materials for use in bio-nanotechnology. Here, after a brief review of the more widely used modes of ALD and a few of its applications in biotechnology, selected results that show the potential of ALD in bio-nanotechnology are presented. ALD seems to be a promising means for tuning the hydrophilicity/hydrophobicity characteristics of biomedical surfaces, forming conformal ultrathin coatings with desirable properties on biomedical substrates with a high aspect ratio, tuning the antibacterial properties of substrate surfaces of interest, and yielding multifunctional biomaterials for medical implants and other devices.

Enhancement in photovoltaic properties of silicon solar cells by surface plasmon effect of palladium nanoparticles

NASA Astrophysics Data System (ADS)

Atyaoui, Malek; Atyaoui, Atef; Khalifa, Marwen; Elyagoubi, Jalel; Dimassi, Wissem; Ezzaouia, Hatem

2016-04-01

This work presents the surface Plasmon effect of Palladium nanoparticles (Pd NPs) on the photovoltaic properties of silicon solar cells. Pd NPs were deposited on the p-type silicon base of the n+/p junction using a chemical deposition method in an aqueous solution containing Palladium (II) Nitrate (PdNO3)2 and Ammonium Hydroxide (NH4OH) followed by a thermal treatment at 500 °C under nitrogen atmosphere. Chemical composition and surface morphology of the treated silicon base were examined by energy dispersive X-ray (EDX) spectroscopy, scanning electronic microscopy (SEM) and Atomic Force Microscopy (AFM). The effect of the deposited Pd NPs on the electrical properties was evaluated by the internal quantum efficiency (IQE) and current-voltage (I-V) measurements. The results indicate that the formation of the Pd NPs is accompanied by an enhanced light absorption and improved photovoltaic parameters.

Bending Properties of Nickel Electrodes for Nickel-Hydrogen Batteries

NASA Technical Reports Server (NTRS)

Lerch, Brad A.; Wilson, Richard M.; Keller, Dennis; Corner, Ralph

1995-01-01

Recent changes in manufacturing have resulted in nickel-hydrogen batteries that fail prematurely by electrical shorting, This failure is believed to be a result of a blistering problem in the nickel electrodes. In this study the bending properties of nickel electrodes are investigated in an attempt to correlate the bending properties of the electrode with its propensity to blister. Nickel electrodes from three different batches of material were tested in both the as-received and impregnated forms. The effects of specimen curvature and position within the electrode on the bending strength were studied, and within-electrode and batch-to-batch variations were addressed. Two color-imaging techniques were employed to differentiate between the phases within the electrodes. These techniques aided in distinguishing the relative amounts of nickel hyroxide surface loading on each electrode, thereby relating surface loading to bend strength. Bend strength was found to increase with the amount of surface loading.

Electrical and material properties of hydrothermally grown single crystal (111) UO2

NASA Astrophysics Data System (ADS)

Dugan, Christina L.; Peterson, George Glenn; Mock, Alyssa; Young, Christopher; Mann, J. Matthew; Nastasi, Michael; Schubert, Mathias; Wang, Lu; Mei, Wai-Ning; Tanabe, Iori; Dowben, Peter A.; Petrosky, James

2018-04-01

The semiconductor and optical properties of UO2 are investigated. The very long drift carrier lifetimes, obtained from current-voltage I( V) and capacitance-voltage C( V) measurements, along with the well-defined optical properties provide little evidence of an abundance of material defects away from the surface region. Schottky barrier formation may be possible, but very much dependent on the choice of contact and surface stoichiometry and we find that Ohmic contacts are in fact favored. Depth resolved photoemission provided evidence of a chemical shift at the surface. Density functional theory, with the Heyd-Scuseria-Ernzerhof (HSE) functional, indicates a band gap of a 2.19 eV and an anti-ferromagnetic ground state. Ellipsometry measurements indicates at UO2 is relatively isotropic with a band gap of approximately 2.0 eV band gap, consistent with theoretical expectations.

Structural, electrical and mechanical properties of selenium doped thallium based high-temperature superconductors

NASA Astrophysics Data System (ADS)

Cavdar, S.; Kol, N.; Koralay, H.; Ozturk, O.; Asikuzun, E.; Tasci, A. T.

2016-01-01

In this study, highly-refined chemical powders were synthesized by having them ready in appropriate stoichiometric proportions with conventional solid state reaction method so that they would produce the superconductor TlPb0.3Sr2Ca1-xSexCu2Oy (x = 0; 0.4; 0.6; 1.0). This study aims to understand effect of the selenium doping on the superconducting, structural and mechanical properties of the aforementioned superconducting material. The effect of the doping rates on the structural and electrical properties of the sample has been identified. Electrical characteristics of the TlPb0.3Sr2Ca1-xSexCu2Oy material were measured using standard four point probe method. Structural characteristics were examined with the powder X-ray diffractometer (XRD) and scanning electron microscope (SEM). Mechanical properties were analyzed with Vickers microhardness measurements on the sample surface. According to the results, it was observed that the reflection comes from the (00l) and parallel planes increased with Se doping. Particle size increases with increasing doping ratio. According to results of the mechanical measurements, all samples exhibit indentation size effect (ISE) behavior. Comparing the obtained results with theoretical studies, it was understood that Hays Kendall approach is the best method in determination of mechanical properties and analyzing microhardness of the materials.

Mechanically Robust 3D Nanostructure Chitosan-Based Hydrogels with Autonomic Self-Healing Properties.

PubMed

Karimi, Ali Reza; Khodadadi, Azam

2016-10-12

Fabrication of hydrogels based on chitosan (CS) with superb self-healing behavior and high mechanical and electrical properties has become a challenging and fascinating topic. Most of the conventional hydrogels lack these properties at the same time. Our objectives in this research were to synthesize, characterize, and evaluate the general properties of chitosan covalently cross-linked with zinc phthalocyanine tetra-aldehyde (ZnPcTa) framework. Our hope was to access an unprecedented self-healable three-dimensional (3D) nanostructure that would harvest the superior mechanical and electrical properties associated with chitosan. The properties of cross-linker such as the structure, steric effect, and rigidity of the molecule played important roles in determining the microstructure and properties of the resulting hydrogels. The tetra-functionalized phthalocyanines favor a dynamic Schiff-base linkage with chitosan to form a 3D porous nanostructure. Based on this strategy, the self-healing ability, as demonstrated by rheological recovery and macroscopic and microscopic observations, is introduced through dynamic covalent Schiff-base linkage between NH 2 groups in CS and benzaldehyde groups at cross-linker ends. The hydrogel was characterized using FT-IR, NMR, UV/vis, and rheological measurements. In addition, cryogenic scanning electron microscopy (cryo-SEM) was employed as a technique to visualize the internal morphology of the hydrogels. Study of the surface morphology of the hydrogel showed a 3D porous nanostructure with uniform morphology. Furthermore, incorporating the conductive nanofillers, such as carbon nanotubes (CNTs), into the structure can modulate the mechanical and electrical properties of the obtained hydrogels. Interestingly, these hydrogel nanocomposites proved to have very good film-forming properties, high modulus and strength, acceptable electrical conductivity, and excellent self-healing properties at neutral pH. Such properties can be finely tuned through variation of the cross-linker and CNT concentration, and as a result these structures are promising candidates for potential applications in various fields of research.

Control of magnetism by electrical charge doping or redox reactions in a surface-oxidized Co thin film with a solid-state capacitor structure

NASA Astrophysics Data System (ADS)

Hirai, T.; Koyama, T.; Chiba, D.

2018-03-01

We have investigated the electric field (EF) effect on magnetism in a Co thin film with a naturally oxidized surface. The EF was applied to the oxidized Co surface through a gate insulator layer made of HfO2, which was formed using atomic layer deposition (ALD). The efficiency of the EF effect on the magnetic anisotropy in the sample with the HfO2 layer deposited at the appropriate temperature for the ALD process was relatively large compared to the previously reported values with an unoxidized Co film. The coercivity promptly and reversibly followed the variation in gate voltage. The modulation of the channel resistance was at most ˜0.02%. In contrast, a dramatic change in the magnetic properties including the large change in the saturation magnetic moment and a much larger EF-induced modulation of the channel resistance (˜10%) were observed in the sample with a HfO2 layer deposited at a temperature far below the appropriate temperature range. The response of these properties to the gate voltage was very slow, suggesting that a redox reaction dominated the EF effect on the magnetism in this sample. The frequency response for the capacitive properties was examined to discuss the difference in the mechanism of the EF effect observed here.

Electrical properties of MIS devices on CdZnTe/HgCdTe

NASA Astrophysics Data System (ADS)

Lee, Tae-Seok; Jeoung, Y. T.; Kim, Hyun Kyu; Kim, Jae Mook; Song, Jinhan; Ann, S. Y.; Lee, Ji Y.; Kim, Young Hun; Kim, Sun-Ung; Park, Mann-Jang; Lee, S. D.; Suh, Sang-Hee

1998-10-01

In this paper, we report the capacitance-voltage (C-V) properties of metal-insulator-semiconductor (MIS) devices on CdTe/HgCdTe by the metalorganic chemical vapor deposition (MOCVD) and CdZnTe/HgCdTe by thermal evaporation. In MOCVD, CdTe layers are directly grown on HgCdTe using the metal organic sources of DMCd and DiPTe. HgCdTe layers are converted to n-type and the carrier concentration, ND is low 1015 cm-3 after Hg-vacancy annealing at 260 degrees Celsius. In thermal evaporation, CdZnTe passivation layers were deposited on HgCdTe surfaces after the surfaces were etched with 0.5 - 2.0% bromine in methanol solution. To investigate the electrical properties of the MIS devices, the C-V measurement is conducted at 80 K and 1 MHz. C-V curve of MIS devices on CdTe/HgCdTe by MOCVD has shown nearly flat band condition and large hysteresis, which is inferred to result from many defects in CdTe layer induced during Hg-vacancy annealing process. A negative flat band voltage (VFB approximately equals -2 V) and a small hysteresis have been observed for MIS devices on CdZnTe/HgCdTe by thermal evaporation. It is inferred that the negative flat band voltage results from residual Te4+ on the surface after etching with bromine in methanol solution.

Synthesis and applications of electrically conducting polymer nanocomposites

NASA Astrophysics Data System (ADS)

Ku, Bon-Cheol

This research focuses on the synthesis and applications of electrically conducting polymer nanocomposites through molecular self-assembly. Two different classes of polymers, polyaniline (PANI) and polyacetylenes have been synthesized by biomimetic catalysis and spontaneous polymerization method. For gas barrier materials, commercially available polymers, poly(allylamine hydrochloride) (PAH) and poly (acrylic acid) (PAA), have also been used and thermally cross-linked. The morphological, optical and electrical properties of amphiphilic polyacetylenes have been studied. Furthermore, barrier properties, permselectivity, pervaporation properties of polyacetylenes/aluminosilicate nanocomposites have been investigated. For processability and electrical properties of carbon nanotube and conducting polymers, substituted ionic polyacetylenes (SIPA) have been covalently incorporated onto single-walled carbon nanotubes (SWNT) using the "grafting-from" technique. In the first study, a nanocomposite film catalyst has been prepared by electrostatic layer-by-layer (ELBL) self-assembly of a polyelectrolyte and a biomimetic catalyst for synthesis of polyaniline. Poly(dimethyl diallylammonium chloride) (PDAC) and hematin have been used as polycation and counter anions, respectively. The absorption spectra by UV-vis-NIR spectroscopy showed that conductive form polyaniline was formed not only as a coating on the surface of the ELBL composites but was also formed in solution. Furthermore, it was found that the reaction rate was affected by pH and concentration of hematin in the multilayers. The feasibility of controlled desorption of hematin molecules from the LBL assembly was explored and demonstrated by changing the pH and hematin concentration. The polymerization rate of aniline in solution was enhanced with decreasing pH of the solutions due to increased desorption of hematin nanoparticles from the multilayers. These ELBL hematin assemblies demonstrated both a way to functionalize surfaces with conductive polyaniline and a potential method of reusability of the catalyst for improved cost effectiveness. For fabrication of multifunctional nanocomposite membranes, (P2EPy-R/Saponite) n on NafionRTM substrate was demonstrated by electrostatic layer-by layer assembly technique. (Abstract shortened by UMI.)

Epitaxial Growth, Surface, and Electronic Properties of Unconventional Semiconductors: RE-V/III-V Nanocomposites and Semiconducting Half Heusler Alloys

DTIC Science & Technology

2014-09-01

with approximately 5 × 1018 Si atoms/cm3 to yield a conductive buffer for STM and photoemsission spectroscopy measurements. On some samples a 3 nm ErAs...where S is the Seebeck coefficient, σ is the electrical conductivity , and κ is the thermal conductivity . Here the electronic information is contained... conductivities (κ = κe + κlat). While the electronic component of thermal conductivity κe is inherently tied to electrical conductivity σ via Wiedemann

Detection of Fatigue Crack in Basalt FRP Laminate Composite Pipe using Electrical Potential Change Method

NASA Astrophysics Data System (ADS)

Altabey, Wael A.; Noori, Mohammed

2017-05-01

Novel modulation electrical potential change (EPC) method for fatigue crack detection in a basalt fibre reinforced polymer (FRP) laminate composite pipe is carried out in this paper. The technique is applied to a laminate pipe with an embedded crack in three layers [0º/90º/0º]s. EPC is applied for evaluating the dielectric properties of basalt FRP pipe by using an electrical capacitance sensor (ECS) to discern damages in the pipe. Twelve electrodes are mounted on the outer surface of the pipe and the changes in the modulation dielectric properties of the piping system are analyzed to detect damages in the pipe. An embedded crack is created by a fatigue internal pressure test. The capacitance values, capacitance change and node potential distribution of ECS electrodes are calculated before and after crack initiates using a finite element method (FEM) by ANSYS and MATLAB, which are combined to simulate sensor characteristics and fatigue behaviour. The crack lengths of the basalt FRP are investigated for various number of cycles to failure for determining crack growth rate. Response surfaces are adopted as a tool for solving inverse problems to estimate crack lengths from the measured electric potential differences of all segments between electrodes to validate the FEM results. The results show that, the good convergence between the FEM and estimated results. Also the results of this study show that the electrical potential difference of the basalt FRP laminate increases during cyclic loading, caused by matrix cracking. The results indicate that the proposed method successfully provides fatigue crack detection for basalt FRP laminate composite pipes.

Multi-frequency electrical and electromagnetic measurements for imaging water flows: application to catchment and landslide hydrology.

NASA Astrophysics Data System (ADS)

Lajaunie, Myriam; Sailhac, Pascal; Malet, Jean-Philippe; Larnier, Hugo; Gance, Julien; Gautier, Stéphanie; Pierret, Marie-Claire

2017-04-01

Imaging water flows in mountainous watersheds is a difficult task, not only because of the topography and the dimensions of the existing structures, but also because the soils and rocks consist of unsaturated porous and heterogeneous fractured media, leading to multi-scale water-flow properties. In addition, these properties can change in time, in relation to temperature, rainfall and biological forcings. Electrical properties are relevant proxies of the subsurface hydrological properties. In order to image water flows, we consider measurements of the complex electrical conductivity (conduction and polarization/chargeability effects) which translate into a frequency dependance of the conductivity at the sample scale. We further discuss the combined use of electromagnetic (CS-AMT) and electric (DC and IP) measurements at the slope scale. The solving of processing, calibration and modelling issues allows the estimation of hydrological properties (i.e. permeability, soil humidity) giving master constraints for slope-scale hydrological modelling. We illustrate the application of these methods for the identification of the hydrological role of weathered structures of granitic catchments (e.g. Strengbach, Vosges mountains, ca. 80 km from Strasbourg, North East France) where new AMT processing has been developed in the AMT dead band to improve DC electrical imaging. We also illustrate the use of these methods to document the seasonal regime of the groundwater of the Lodève landslide (unstable slope located at Pégairolles, foot of the Cévennes mountain, ca. 80 km from Montpellier, South of France) where a new detailed time-lapse DC and IP setup (surface and borehole) is being tested. The works are supported by the research projects HYDROCRISZTO and HYDROSLIDE, and the large infrastructure project CRITEX.

First principles study of size and external electric field effects on the atomic and electronic properties of gallium nitride nanostructures

NASA Astrophysics Data System (ADS)

Yilmaz, Hulusi

A comprehensive density functional theory study of atomic and the electronic properties of wurtzite gallium nitride (GaN) nanostructures with different sizes and shapes is presented and the effect of external electric field on these properties is examined. We show that the atomic and electronic properties of [101¯0] facet single-crystal GaN nanotubes (quasi-1D), nanowires (1D) and nanolayers (2D) are mainly determined by the surface to volume ratio. The shape dependent quantum confinement and strain effects on the atomic and electronic properties of these GaN nanostructures are found to be negligible. Based on this similarity between the atomic and electronic properties of the small size GaN nanostructures, we calculated the atomic and electronic properties of the practical size (28.1 A wall thickness) single-crystal GaN nanotubes through computational much economical GaN nanoslabs (nanolayers). Our results show that, regardless of diameter, hydrogen saturated single-crystal GaN tubes with the wall thickness of 28.1 A are energetically stable and they have a noticeably larger band gap with respect to the band gap of bulk GaN. The band gap of unsaturated single-crystal GaN tubes, on the other hand, is always smaller than the band gap of the wurtzite bulk GaN. In a separate study, we show that a transverse electric field induces a homojunction across the diameter of initially semiconducting GaN single-crystal nanotubes and nanowires. The homojunction arises due to the decreased energy of the electronic states in the higher potential region with respect to the energy of those states in the lower potential region under the transverse electric field. Calculations on single-crystal GaN nanotubes and nanowires of different diameter and wall thickness show that the threshold electric field required for the semiconductor-homojunction induction increases with increasing wall thickness and decreases significantly with increasing diameter.

Geometry effect on electrokinetic flow and ionic conductance in pH-regulated nanochannels

NASA Astrophysics Data System (ADS)

Sadeghi, Morteza; Saidi, Mohammad Hassan; Moosavi, Ali; Sadeghi, Arman

2017-12-01

Semi-analytical solutions are obtained for the electrical potential, electroosmotic velocity, ionic conductance, and surface physicochemical properties associated with long pH-regulated nanochannels of arbitrary but constant cross-sectional area. The effects of electric double layer overlap, multiple ionic species, and surface association/dissociation reactions are all taken into account, assuming low surface potentials. The method of analysis includes series solutions which the pertinent coefficients are obtained by applying the wall boundary conditions using either of the least-squares or point matching techniques. Although the procedure is general enough to be applied to almost any arbitrary cross section, nine nanogeometries including polygonal, trapezoidal, double-trapezoidal, rectangular, elliptical, semi-elliptical, isosceles triangular, rhombic, and isotropically etched profiles are selected for presentation. For the special case of an elliptic cross section, full analytical solutions are also obtained utilizing the Mathieu functions. We show that the geometrical configuration plays a key role in determination of the ionic conductance, surface charge density, electrical potential and velocity fields, and proton enhancement. In this respect, the net electric charge and convective ionic conductance are higher for channels of larger perimeter to area ratio, whereas the opposite is true for the average surface charge density and mean velocity; the geometry impact on the two latest ones, however, vanishes if the background salt concentration is high enough. Moreover, we demonstrate that considering a constant surface potential equal to the average charge-regulated potential provides sufficiently accurate results for smooth geometries such as an ellipse at medium-high aspect ratios but leads to significant errors for geometries having narrow corners such as a triangle.

Electrical and Dielectric Properties of a n-Si Schottky Barrier Diode with Bismuth Titanate Interlayer: Effect of Temperature

NASA Astrophysics Data System (ADS)

Yıldırım, M.; Şahin, C.; Altındal, Ş.; Durmuş, P.

2017-03-01

An Au/Bi4Ti3O12/ n-Si Schottky barrier diode (SBD) was fabricated with a 51 nm Bi4Ti3O12 interfacial layer. Admittance measurements of the fabricated SBD were carried out in the bias voltage ( V) range of -4 V and 6 V. Capacitance ( C) and conductance ( G/ω) measurements were carried out in a wide temperature range of 120-380 K so that temperature effects on electrical and dielectric properties of the SBD were investigated. Main electrical parameters were extracted from reverse bias C -2- V plots. It was found that variance of electrical and dielectric parameters of the SBD with temperature is basically different for low and high temperature regions. A fair number (˜1012 eV-1 cm-2) was obtained for surface states ( N ss); however, N ss first decreased then increased with temperature. This result was associated with increased defects with temperature and higher activation energy in the high temperature region. Dielectric parameters of the SBD were also extracted and the dielectric constant of SBD was found as ˜10 at room temperature. Application of modulus formalism to the admittance data revealed temperature-activated dielectric relaxation at 340 K. Results showed that the temperature has considerable effects on electrical and dielectric properties of Au/Bi4Ti3O12/ n-Si SBD.

Assessment of alterations in the electrical impedance of muscle after experimental nerve injury via finite-element analysis.

PubMed

Wang, Lucy L; Ahad, Mohammad; McEwan, Alistair; Li, Jia; Jafarpoor, Mina; Rutkove, Seward B

2011-06-01

The surface measurement of electrical impedance of muscle, incorporated as the technique of electrical impedance myography (EIM), provides a noninvasive approach for evaluating neuromuscular diseases, including amyotrophic lateral sclerosis. However, the relationship between alterations in surface impedance and the electrical properties of muscle remains uncertain. In order to investigate this further, a group of healthy adult rats, a group of rats two weeks postsciatic crush, and a group of animals six months postcrush underwent EIM of the gastrocnemius-soleus complex. The animals were then killed and the conductivity and permittivity of the extracted muscle measured. Finite-element models based on MRI data were then constructed for each group. The characteristic EIM parameter, 50 kHz phase (±standard error), obtained with surface impedance measurements was 17.3° ± 0.3° for normal animals, 13.8° ± 0.7° for acutely injured animals, and 16.1° ± 0.5° for chronically injured animals. The models predicted parallel changes with phase values of 24.3°, 18.8°, and 21.2° for the normal, acute, and chronic groups, respectively. Other multifrequency impedance parameters showed similar alterations. These results confirm that surface impedance measurements taken in conjunction with anatomical data and finite-element models may offer a noninvasive approach for assessing biophysical alterations in muscle in neuromuscular disease states.

Electric Propulsion Induced Secondary Mass Spectroscopy

NASA Technical Reports Server (NTRS)

Amini, Rashied; Landis, Geoffrey

2012-01-01

A document highlights a means to complement remote spectroscopy while also providing in situ surface samples without a landed system. Historically, most compositional analysis of small body surfaces has been done remotely by analyzing reflection or nuclear spectra. However, neither provides direct measurement that can unambiguously constrain the global surface composition and most importantly, the nature of trace composition and second-phase impurities. Recently, missions such as Deep Space 1 and Dawn have utilized electric propulsion (EP) accelerated, high-energy collimated beam of Xe+ ions to propel deep space missions to their target bodies. The energies of the Xe+ are sufficient to cause sputtering interactions, which eject material from the top microns of a targeted surface. Using a mass spectrometer, the sputtered material can be determined. The sputtering properties of EP exhaust can be used to determine detailed surface composition of atmosphereless bodies by electric propulsion induced secondary mass spectroscopy (EPI-SMS). EPI-SMS operation has three high-level requirements: EP system, mass spectrometer, and altitude of about 10 km. Approximately 1 keV Xe+ has been studied and proven to generate high sputtering yields in metallic substrates. Using these yields, first-order calculations predict that EPI-SMS will yield high signal-to-noise at altitudes greater than 10 km with both electrostatic and Hall thrusters.

Scheming of microwave shielding effectiveness for X band considering functionalized MWNTs/epoxy composites

NASA Astrophysics Data System (ADS)

Bal, S.; Saha, S.

2016-02-01

Present typescript encompasses anextraordinary electrical and mechanical behaviors of carboxylic (-COOH) functionalized multiwall carbon nanotube (MWNTs)/epoxy composites at low wt.% (0,5, 0,75, 1wt.%). Functionalization on the surface of the nanotube assists MWNTs in dispersing it into epoxy polymer in a respectable manner, Fabricated composites are exposed to different characterization techniques in order to examine the overall physical properties, Microwave shielding effectiveness (SE) for X band (8-12 GHz) and the flexural properties have been premeditated to predict the electrical and mechanical performances. It was found that the total SE of the nanocomposites was increased with the positive gradient of MWNT contents, The best result was recorded for 1 wt.% MWNT loading (SE of about 51,72 dB).In addition, incorporation of nanofillers enhanced the flexural modulus, flexural strength and micro-hardness of the resulting composites while comparing with neat epoxy, Nanocomposites with 0,75 wt,% MWNT loading demonstrated an incrementof 101% in modulus than that of neat epoxy, Theincrement in mechanical properties was due to achievement of good dispersion quality, effective bonding between MWNTs and epoxy polymer analyzed by micrographs of fracture surfaces

Enhanced Flux and Electrochemical Cleaning of Silicate Scaling on Carbon Nanotube-Coated Membrane Distillation Membranes Treating Geothermal Brines

DOE PAGES

Tang, Li; Iddya, Arpita; Zhu, Xiaobo; ...

2017-10-13

The desalination of inland brackish groundwater offers the opportunity to provide potable drinking water to residents and industrial cooling water to industries located in arid regions. Geothermal brines are used to generate electricity, but often contain high concentrations of dissolved salt. Here in this paper, we demonstrate how the residual heat left in spent geothermal brines can be used to drive a membrane distillation (MD) process and recover desalinated water. Porous polypropylene membranes were coated with a carbon nanotube (CNT)/poly(vinyl alcohol) layer, resulting in composite membranes having a binary structure that combines the hydrophobic properties critical for MD with themore » hydrophilic and conductive properties of the CNTs. We demonstrate that the addition of the CNT layer increases membrane flux due to enhanced heat transport from the bulk feed to the membrane surface, a result of CNT's high thermal transport properties. Furthermore, we show how hydroxide ion generation, driven by water electrolysis on the electrically conducting membrane surface, can be used to efficiently dissolve silicate scaling that developed during the process of desalinating the geothermal brine, negating the need for chemical cleaning.« less

Effect of Zn on the structural and electrical properties of high temperature HgBa2Ca2Cu3O8+δ superconductor

NASA Astrophysics Data System (ADS)

Omar, Bilal A.; Fathi, Sabah J.; Jassim, Kareem A.

2018-05-01

Bulk polycrystalline HgBa2Ca2-yZnyCu3O8+δ compound samples with y =0.0, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3, are synthesized by a solid state reaction process. Study identifies Zinc partial substitution on superconductivity behavior. Structural properties are studied by using X-ray powder pattern, the high temperature phase superconductor (Hg-1223) of the tetragonal structure didn't change with the partial substitution of Zn ions in Ca site, lattice parameters c, c/a are established to vary Zn-substitution. The surface morphology has been studied by using atomic force microscopes (AFM), showed that all specimens have good crystalline and homogeneous surface. Also give a best nano size value is 83.29 nm at y=0.05. Four probe technique is used to measure Tc. The highest Tc and oxygen content were found to be Tc=132 K for y=0.05 after that, Tc decreases from 132 K to 115 K with increasing Zn. In addition, dielectric properties (dielectric constant, dielectric loss factor, and the alternating electrical conductivity) are characterized directly by relating with Zn concentration.

Enhanced Flux and Electrochemical Cleaning of Silicate Scaling on Carbon Nanotube-Coated Membrane Distillation Membranes Treating Geothermal Brines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Li; Iddya, Arpita; Zhu, Xiaobo

The desalination of inland brackish groundwater offers the opportunity to provide potable drinking water to residents and industrial cooling water to industries located in arid regions. Geothermal brines are used to generate electricity, but often contain high concentrations of dissolved salt. Here in this paper, we demonstrate how the residual heat left in spent geothermal brines can be used to drive a membrane distillation (MD) process and recover desalinated water. Porous polypropylene membranes were coated with a carbon nanotube (CNT)/poly(vinyl alcohol) layer, resulting in composite membranes having a binary structure that combines the hydrophobic properties critical for MD with themore » hydrophilic and conductive properties of the CNTs. We demonstrate that the addition of the CNT layer increases membrane flux due to enhanced heat transport from the bulk feed to the membrane surface, a result of CNT's high thermal transport properties. Furthermore, we show how hydroxide ion generation, driven by water electrolysis on the electrically conducting membrane surface, can be used to efficiently dissolve silicate scaling that developed during the process of desalinating the geothermal brine, negating the need for chemical cleaning.« less

Common Structure in Different Physical Properties: Electrical Conductivity and Surface Waves Phase Velocity

NASA Astrophysics Data System (ADS)

Mandolesi, E.; Jones, A. G.; Roux, E.; Lebedev, S.

2009-12-01

Recently different studies were undertaken on the correlation between diverse geophysical datasets. Magnetotelluric (MT) data are used to map the electrical conductivity structure behind the Earth, but one of the problems in MT method is the lack in resolution in mapping zones beneath a region of high conductivity. Joint inversion of different datasets in which a common structure is recognizable reduces non-uniqueness and may improve the quality of interpretation when different dataset are sensitive to different physical properties with an underlined common structure. A common structure is recognized if the change of physical properties occur at the same spatial locations. Common structure may be recognized in 1D inversion of seismic and MT datasets, and numerous authors show that also 2D common structure may drive to an improvement of inversion quality while dataset are jointly inverted. In this presentation a tool to constrain MT 2D inversion with phase velocity of surface wave seismic data (SW) is proposed and is being developed and tested on synthetic data. Results obtained suggest that a joint inversion scheme could be applied with success along a section profile for which data are compatible with a 2D MT model.

Nonlinear surface waves at ferrite-metamaterial waveguide structure

NASA Astrophysics Data System (ADS)

Hissi, Nour El Houda; Mokhtari, Bouchra; Eddeqaqi, Noureddine Cherkaoui; Shabat, Mohammed Musa; Atangana, Jacques

2016-09-01

A new ferrite slab made of a metamaterial (MTM), surrounded by a nonlinear cover cladding and a ferrite substrate, was shown to support unusual types of electromagnetic surface waves. We impose the boundary conditions to derive the dispersion relation and others necessary to formulate the proposed structure. We analyse the dispersion properties of the nonlinear surface waves and we calculate the associated propagation index and the film-cover interface nonlinearity. In the calculation, several sets of the permeability of the MTM are considered. Results show that the waves behaviour depends on the values of the permeability of the MTM, the thickness of the waveguide and the film-cover interface nonlinearity. It is also shown that the use of the singular solutions to the electric field equation allows to identify several new properties of surface waves which do not exist in conventional waveguide.

Giant thermally-enhanced electrostriction and polar surface phase in L a2M o2O9 oxygen ion conductors

NASA Astrophysics Data System (ADS)

Li, Qian; Lu, Teng; Schiemer, Jason; Laanait, Nouamane; Balke, Nina; Zhang, Zhan; Ren, Yang; Carpenter, Michael A.; Wen, Haidan; Li, Jiangyu; Kalinin, Sergei V.; Liu, Yun

2018-04-01

Ferroelectrics possess spontaneous electric polarization at macroscopic scales which nonetheless imposes strict limitations on the material classes. Recent discoveries of untraditional symmetry-breaking phenomena in reduced material dimensions have indicated feasibilities to extend polar properties to broader types of materials, potentially opening up the freedom for designing materials with hybrid functionalities. Here, we report the unusual electromechanical properties of L a2M o2O9 (LAMOX) oxygen ion conductors, systematically investigated at both bulk and surface length levels. We first observed giant electrostriction effects in L a2M o2O9 bulk ceramics that are thermally enhanced in concert with their low-energy oxygen-vacancy hopping dynamics. Moreover, while no clear bulk polarization was detected, the surface phases of LAMOX were found to be manifestly polar, likely originating from the coupling between the intrinsic structural flexibilities with strain gradients (i.e., flexoelectricity) and/or chemical heterogeneities present in the materials. These findings identify L a2M o2O9 as a promising electromechanical material system and suggest that the flexible structural and chemical configurations in ionically active materials could enable fundamentally different venues to accommodate electric polarization.

Enhancement of mechanical and electrical properties of continuous-fiber-reinforced epoxy composites with stacked graphene

PubMed Central

Shepelev, Olga; Kenig, Samuel

2017-01-01

Impregnation of expandable graphite (EG) after thermal treatment with an epoxy resin containing surface-active agents (SAAs) enhanced the intercalation of epoxy monomer between EG layers and led to further exfoliation of the graphite, resulting in stacks of few graphene layers, so-called “stacked” graphene (SG). This process enabled electrical conductivity of cured epoxy/SG composites at lower percolation thresholds, and improved thermo-mechanical properties were measured with either Kevlar, carbon or glass-fiber-reinforced composites. Several compositions with SAA-modified SG led to higher dynamic moduli especially at high temperatures, reflecting the better wetting ability of the modified nanoparticles. The hydrophilic/hydrophobic nature of the SAA dictates the surface energy balance. More hydrophilic SAAs promoted localization of the SG at the Kevlar/epoxy interface, and morphology seems to be driven by thermodynamics, rather than the kinetic effect of viscosity. This effect was less obvious with carbon or glass fibers, due to the lower surface energy of the carbon fibers or some incompatibility with the glass-fiber sizing. Proper choice of the surfactant and fine-tuning of the crosslink density at the interphase may provide further enhancements in thermo-mechanical behavior. PMID:29046838

Enhancement of mechanical and electrical properties of continuous-fiber-reinforced epoxy composites with stacked graphene.

PubMed

Naveh, Naum; Shepelev, Olga; Kenig, Samuel

2017-01-01

Impregnation of expandable graphite (EG) after thermal treatment with an epoxy resin containing surface-active agents (SAAs) enhanced the intercalation of epoxy monomer between EG layers and led to further exfoliation of the graphite, resulting in stacks of few graphene layers, so-called "stacked" graphene (SG). This process enabled electrical conductivity of cured epoxy/SG composites at lower percolation thresholds, and improved thermo-mechanical properties were measured with either Kevlar, carbon or glass-fiber-reinforced composites. Several compositions with SAA-modified SG led to higher dynamic moduli especially at high temperatures, reflecting the better wetting ability of the modified nanoparticles. The hydrophilic/hydrophobic nature of the SAA dictates the surface energy balance. More hydrophilic SAAs promoted localization of the SG at the Kevlar/epoxy interface, and morphology seems to be driven by thermodynamics, rather than the kinetic effect of viscosity. This effect was less obvious with carbon or glass fibers, due to the lower surface energy of the carbon fibers or some incompatibility with the glass-fiber sizing. Proper choice of the surfactant and fine-tuning of the crosslink density at the interphase may provide further enhancements in thermo-mechanical behavior.

Surface and interface sciences of Li-ion batteries. -Research progress in electrode-electrolyte interface-

NASA Astrophysics Data System (ADS)

Minato, Taketoshi; Abe, Takeshi

2017-12-01

The application potential of Li-ion batteries is growing as demand increases in different fields at various stages in energy systems, in addition to their conventional role as power sources for portable devices. In particular, applications in electric vehicles and renewable energy storage are increasing for Li-ion batteries. For these applications, improvements in battery performance are necessary. The Li-ion battery produces and stores electric power from the electrochemical redox reactions between the electrode materials. The interface between the electrodes and electrolyte strongly affects the battery performance because the charge transfer causing the electrode redox reaction begins at this interface. Understanding of the surface structure, electronic structure, and chemical reactions at the electrode-electrolyte interface is necessary to improve battery performance. However, the interface is located between the electrode and electrolyte materials, hindering the experimental analysis of the interface; thus, the physical properties and chemical processes have remained poorly understood until recently. Investigations of the physical properties and chemical processes at the interface have been performed using advanced surface science techniques. In this review, current knowledge and future research prospects regarding the electrode-electrolyte interface are described for the further development of Li-ion batteries.

PHOBOS Exploration using Two Small Solar Electric Propulsion Spacecraft

NASA Technical Reports Server (NTRS)

Lang, Jared J.; Baker, John D.; Castillo-Rogez, Julie C.; McElrath, Timothy P.; Piacentine, Jamie S.; Snyder, J. Steve

2012-01-01

Primitive bodies are exciting targets for exploration as they provide clues to the early Solar system conditions and dynamical evolution. The two moons of Mars are particularly interesting because of their proximity to an astrobiological target. However, after four decades of Mars exploration, their origin and nature remain enigmatic. In addition, when considering the long-term objectives of the flexible path for the potential human exploration to Mars, Phobos and Deimos present exciting intermediate opportunities without the complication and expense of landing and ascending from the surface. As interest in these targets for the next frontier of human exploration grows, characterization missions designed specifically to examine surface properties, landing environments, and surface mapping prior to human exploration are becoming increasingly important. A precursor mission concept of this sort has been developed using two identical spacecraft designed from low cost, flight proven and certified off-the-shelf component and utilizing Solar Electric Propulsion (SEP) to orbit both targets as secondary payloads launched aboard any NASA or GTO launch. This precursor mission has the potential to address both precursor measurements that are strategic knowledge gaps and decadal science, including soil physical properties at the global and local (human) scale and the search for in situ resources.

Influence of Pore Structure on SIP Properties Deduced from Micro-Scale Modelling

NASA Astrophysics Data System (ADS)

Volkmann, Jan; Klitzsch, Norbert; Wiens, Eugen; Mohnke, Oliver

2010-05-01

In geophysics frequency dependent complex resistivity measurements are called Spectral Induced Polarization (SIP). In other fields this method is known as Impedance Spectroscopy. In the last two decades many empirical relations were proposed which relate the frequency dependent electrical properties of water saturated rocks to structural properties such as pore radius and inner surface area, or to hydraulic conductivity. Unfortunately, these relations are not universal; they apply only for specific rock types and water compositions. In order to quantify the influence of inner rock structure (as well as of electrochemical water and rock properties) on the frequency dependent electrical properties we model the charge transport processes at the pore space using Comsol Multiphysics. In the frequency domain the effect of Induced Polarization (IP) is characterised by a phase shift between a measured electric current and an alternating voltage applied to the ground. A possible origin of this behaviour particularly for nonconducting rock minerals can be seen in the membrane polarization model as proposed by Marshall and Madden. This model describes a system of electrolyte filled pores. Different mobilities of cations and anions in the small pores cause a membrane effect and thus an electrical polarization. We aim to find a more realistic way of modelling the membrane polarization effect than using the simple Marshall and Madden model. The electric double layer, the origin of the Induced Polarization effect, is caused by surface charges located at the electrolyte rock interface. Thus, the EDL as a boundary effect is accounted for by reduced ion mobilities at the inner surface area. The governing equations and boundary conditions for a system of larger and smaller pores with applied voltage are expressed in frequency domain using a time harmonic approach, the electric current is determined to obtain information about amplitude and phase of the complex resistivity. The results are compared to corresponding theoretic and experimental results. The model is applied to study the influence of pore sizes and pore structure as well as of electrolyte properties like ion mobilities and concentrations. We find two characteristic phase minima in the frequency range 1mHz - 100MHz. The dependence of the 'high frequency' minimum (f > 10kHz) on the electrolyte concentration and the dependence of the corresponding relaxation times on variations of the pore geometry are in good agreement with the classical Maxwell-Wagner theory. In contrast to this effective medium approach the simulations confirm the necessity of pore throats to obtain non-vanishing phase values. For large size differences of the smaller and larger pores a second 'low frequency' minimum (f < 10kHz) exists. Its relaxation time mainly depends on the length of the large pores of the system. Furthermore we find a decreasing phase amplitude with increasing electrolyte concentration not predicted by Marshall and Madden and similar models but confirmed by experimental results. This study was conducted within the Transregional Collaborative Research Centre 32 (SFB TR 32; subproject A2), funded by the German Research Foundation (DFG). Present and future studies are supported by the Deutsche Gesellschaft für Erdöl, Erdgas und Kohle e.V. (DGMK).

A new multicomponent salt of imidazole and tetrabromoterepthalic acid: structural, optical, thermal, electrical transport properties and antibacterial activity along with Hirshfeld surface analysis.

PubMed

Dey, Sanjoy Kumar; Saha, Rajat; Singha, Soumen; Biswas, Susobhan; Layek, Animesh; Middya, Somnath; Ray, Partha Pratim; Bandhyopadhyay, Debasis; Kumar, Sanjay

2015-06-05

Herein, we report the structural, optical, thermal and electrical transport properties of a new multicomponent salt (TBTA(2-))·2(IM(+))·(water) [TBTA-IM] of tetrabromoterepthalic acid (TBTA) with imidazole (IM). The crystal structure of TBTA-IM is determined by both the single crystal and powder X-ray diffraction techniques. The structural analysis has revealed that the supramolecular charge assisted O(-)⋯HN(+) hydrogen bonding and Br⋯π interactions play the most vital role in formation of this multicomponent supramolecular assembly. The Hirshfeld surface analysis has been carried out to investigate supramolecular interactions and associated 2D fingerprint plots reveal the relative contribution of these interactions in the crystal structure quantitatively. According to theoretical analysis the HOMO-LUMO energy gap of the salt is 2.92 eV. The salt has been characterized by IR, UV-vis and photoluminescence spectroscopic studies. It shows direct optical transition with band gaps of 4.1 eV, which indicates that the salt is insulating in nature. The photoluminescence spectrum of the salt is significantly different from that of TBTA. Further, a comparative study on the antibacterial activity of the salt with respect to imidazole, Gatifloxacin and Ciprofloxacin has been performed. Moreover, the current-voltage (I-V) characteristic of ITO/TBTA-IM/Al sandwich structure exhibits good rectifying property and the electron tunneling process governs the electrical transport mechanism of the device. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of Sn doping on structural, mechanical, optical and electrical properties of ZnO nanoarrays prepared by sol-gel and hydrothermal process

NASA Astrophysics Data System (ADS)

Agarwal, Manish Baboo; Sharma, Akash; Malaidurai, M.; Thangavel, R.

2018-05-01

Undoped and Sn doped Zinc oxide nanorods were prepared by two step process: initially growth of seed layers by sol-gel spin coating technique and then zinc oxide nanorods by hydrothermal process using the precursors zinc nitrate hexahydrate, hexamine and tin chloride. The effects on the electrical, optical, mechanical and structural properties for various Sn concentrations were studied. The crystalline phase determination from X-ray diffraction (XRD) confirms that Sn doped ZnO nanorods have hexagonal wurtzite structure. The variations of stress and strain with different doping concentration of Sn in ZnO nanorods were studied. The doping effect on electrical properties and optical bandgap is estimated by current voltage characteristics and absorbance spectra respectively. The surface morphology was studied with field emission scanning electron microscope (FESEM), which shows that the formation of hexagonal nanorods arrays with increasing Sn concentration. The calculated value of Young's modulus of elasticity (Y) for all the samples remains same. These results can be used in optoelectronic devices.

Reinforced Thermoplastic Polyimide with Dispersed Functionalized Single Wall Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Lebron-Colon, Marisabel; Meador, Michael A.; Gaier, James R.; Sola, Francisco; Scheiman, Daniel A.; McCorkle, Linda S.

2010-01-01

Molecular pi-complexes were formed from pristine HiPCO single-wall carbon nanotubes (SWCNTs) and 1-pyrene- N-(4- N'-(5-norbornene-2,3-dicarboxyimido)phenyl butanamide, 1. Polyimide films were prepared with these complexes as well as uncomplexed SWCNTs and the effects of nanoadditive addition on mechanical, thermal, and electrical properties of these films were evaluated. Although these properties were enhanced by both nanoadditives, larger increases in tensile strength and thermal and electrical conductivities were obtained when the SWCNT/1 complexes were used. At a loading level of 5.5 wt %, the Tg of the polyimide increased from 169 to 197 C and the storage modulus increased 20-fold (from 142 to 3045 MPa). The addition of 3.5 wt % SWCNT/1 complexes increased the tensile strength of the polyimide from 61.4 to 129 MPa; higher loading levels led to embrittlement and lower tensile strengths. The electrical conductivities (DC surface) of the polyimides increased to 1 x 10(exp -4) Scm(exp -1) (SWCNT/1 complexes loading level of 9 wt %). Details of the preparation of these complexes and their effects on polyimide film properties are discussed.

Dynamic Determination of Some Optical and Electrical Properties of Galena Natural Mineral: Potassium Ethyl Xanthate Solution Interface

NASA Astrophysics Data System (ADS)

Todoran, D.; Todoran, R.; Anitas, E. M.; Szakacs, Zs.

2017-12-01

This paper presents results concerning optical and electrical properties of galena natural mineral and of the interface layer formed between it and the potassium ethyl xanthate solution. The applied experimental method was differential optical reflectance spectroscopy over the UV-Vis/NIR spectral domain. Computations were made using the Kramers-Kronig formalism. Spectral dependencies of the electron loss functions, determined from the reflectance data obtained from the polished mineral surface, display van Hove singularities, leading to the determination of its valence band gap and electron plasma energy. Time dependent measurement of the spectral dispersion of the relative reflectance of the film formed at the interface, using the same computational formalism, leads to the dynamical determination of the spectral variation of its optical and electrical properties. We computed behaviors of the dielectric constant (dielectric permittivity), the dielectric loss function, refractive index and extinction coefficient, effective valence number and of the electron loss functions. The measurements tend to stabilize when the dynamic adsorption-desorption equilibrium is reached at the interface level.

Thermal, Mechanical, and Electrical Properties of Graphene Nanoplatelet/Graphene Oxide/ Polyurethane Hybrid Nanocomposite.

PubMed

Pokharel, Pashupati; Lee, Sang Hyub; Lee, Dai Soo

2015-01-01

Hybrid nanocomposites of polyurethane (PU) were prepared by in-situ polymerization of 4,4'- diphenyl methane diisocyanate (MDI) with mixture of graphene oxide (GO) and graphene nanoplatelet (GNP) dispersed in a poly(tetramethylene ether glycol) (PTMEG). Effects of the fillers, GO and GNP, on the thermal, mechanical, and electrical properties of the nanocomposites of PU were investigated. Sonication of the hybrid of GNP and GO with PTMEG enabled effective dispersion of the fillers in the solution than the sonication of GNP alone. The addition of PTMEG in the solution prevented the GNPs from the restacking during the drying process. It was observed that the electrical conductivity and mechanical property of the nanocomposites based on the hybrid of GO and GNP were superior to the nanocomposite based on GNP alone at the same loading of the filler. At the loading of the 3 wt% hybrid filler in PU, we observed the improvement of Young's modulus -200% and the surface resistivity of 10(9.5) ohm/sq without sacrificing the elongation at break.

Surface oxidation and thermoelectric properties of indium-doped tin telluride nanowires.

PubMed

Li, Zhen; Xu, Enzhi; Losovyj, Yaroslav; Li, Nan; Chen, Aiping; Swartzentruber, Brian; Sinitsyn, Nikolai; Yoo, Jinkyoung; Jia, Quanxi; Zhang, Shixiong

2017-09-14

The recent discovery of excellent thermoelectric properties and topological surface states in SnTe-based compounds has attracted extensive attention in various research areas. Indium doped SnTe is of particular interest because, depending on the doping level, it can either generate resonant states in the bulk valence band leading to enhanced thermoelectric properties, or induce superconductivity that coexists with topological states. Here we report on the vapor deposition of In-doped SnTe nanowires and the study of their surface oxidation and thermoelectric properties. The nanowire growth is assisted by Au catalysts, and their morphologies vary as a function of substrate position and temperature. Transmission electron microscopy characterization reveals the formation of an amorphous surface in single crystalline nanowires. X-ray photoelectron spectroscopy studies suggest that the nanowire surface is composed of In 2 O 3 , SnO 2 , Te and TeO 2 which can be readily removed by argon ion sputtering. Exposure of the cleaned nanowires to atmosphere leads to rapid oxidation of the surface within only one minute. Characterization of electrical conductivity σ, thermopower S, and thermal conductivity κ was performed on the same In-doped nanowire which shows suppressed σ and κ but enhanced S yielding an improved thermoelectric figure of merit ZT compared to the undoped SnTe.

Fundamental Properties of One-Dimensional Zinc Oxide Nanomaterials and Implementations in Various Detection Modes of Enhanced Biosensing

PubMed Central

Hahm, Jong-in

2016-01-01

Recent bioapplications of one-dimensional (1D) zinc oxide (ZnO) nanomaterials, despite the short development period, have shown promising signs as new sensors and assay platforms offering exquisite biomolecular sensitivity and selectivity. The incorporation of 1D ZnO nanomaterials has proven beneficial to various modes of biodetection owing to their inherent properties. The more widely explored electrochemical and electrical approaches tend to capitalize on the reduced physical dimensionality, yielding a high surface-to-volume ratio, as well as on the electrical properties of ZnO. The newer development of the use of 1D ZnO nanomaterials in fluorescence-based biodetection exploits the innate optical property of their high anisotropy. This review considers stimulating research advances made to identify and understand fundamental properties of 1D ZnO nanomaterials, and examines various biosensing modes utilizing them, while focusing on the unique optical properties of individual and ensembles of 1D ZnO nanomaterials specifically pertaining to their bio-optical applications in simple and complex fluorescence assays. PMID:27215822

Mechanical and electro-optical properties of unconventional liquid crystal systems

NASA Astrophysics Data System (ADS)

Liao, Guangxun

Four types of unconventional liquid crystal systems - amphotropic glycolipids; novel bent-core liquid crystals, bent-core liquid crystal and glycolipid mixtures, and colloidal crystal-liquid crystal systems - were studied and characterized by polarizing microscopy, electrical current, digital scanning calorimetry, and dielectric spectroscopy. Thermotropic properties of glycolipids show a number of unusual properties, most notably high (60-120) relative dielectric constants mainly proportional to the number of polar sugar heads. The relaxation of this dielectric mode is found to be governed by the hydrogen bonding between sugar heads. Studies on novel bent-core liquid crystals reveal a new optically isotropic ferroelectric phase, molecular chirality-induced polarity, and transitions between molecular chirality and polarity driven phases. Mixtures of several bent-core substances with nematic, polar SmA and SmC phases, and a simple amphiphilic sugar lipid with SmA mesophase found to obey the well known miscibility rules, i.e. the sugar lipid mixes best with the polar SmA bent-core material. In addition, the chiral sugar lipid was found to induce tilt to the non-tilted polar SmA phase, which represents a new direction among the chirality--polarity--tilt relations. The effects of the surface properties and electric fields were studied on various colloid particles--and liquid crystal systems. It is found that the surface properties (hydrophobicity, roughness, rubbing) of the substrates are important in determining the size and symmetry of colloidal crystals. The director field of the liquid crystal infiltrated in the colloid crystals can be rendered both random and uniform along one of the crystallographic axis. We present the first observations of DC electric-field-induced rotational and translational motion of finite particles in liquid crystals. The electrorotation is essentially identical to the well - known Quincke rotation, which in liquid crystals triggers an additional translational motion at higher fields. Analysis of the electro-rotation and translations provides new ways to probe local rheological properties of liquid crystals.

Electrical and galvanomagnetic properties of nanoporous carbon samples impregnated with bromine

NASA Astrophysics Data System (ADS)

Danishevskii, A. M.; Popov, V. V.; Kyutt, R. N.; Gordeev, S. K.

2013-07-01

Nanoporous carbon samples with a large specific surface area can be filled with heavier elements or their compounds, which makes it possible to investigate the interaction of their electronic subsystems with carbon. One of the elements convenient for filling pores of carbon materials is bromine. Impregnation of nanoporous carbon samples with bromine causes the occurrence of the processes of micropore filling, monolayer adsorption, and intercalation. It has been found that samples impregnated with bromine substantially change their electrical and galvanomagnetic properties, and these changes depend on the structure of the samples. It has been shown that, if in the skeleton of a porous carbon sample there is a fraction of graphite clusters, the impregnation of the sample with bromine increases the concentration of charged carriers (holes). But when the sample has a quasi-amorphous structure, the injection of bromine into the sample leads to the appearance of a certain concentration of electrons in addition to charged mobile holes of the initial sample; i.e., the electrical conductivity becomes bipolar. In the former case, bromine molecules intercalate graphite clusters and, since bromine is an acceptor during intercalation of graphite, the hole concentration in the carbon skeleton network increases. In the latter case, bromine molecules can only be adsorbed on pore walls. As a result, the adsorption interaction between the electron shells of bromine molecules and the carbon surface leads to the formation of a donor layer near the surface and to the generation of electrons in the carbon skeleton network.

Effect of surface charge convection and shape deformation on the dielectrophoretic motion of a liquid drop

NASA Astrophysics Data System (ADS)

Mandal, Shubhadeep; Bandopadhyay, Aditya; Chakraborty, Suman

2016-04-01

The dielectrophoretic motion and shape deformation of a Newtonian liquid drop in an otherwise quiescent Newtonian liquid medium in the presence of an axisymmetric nonuniform dc electric field consisting of uniform and quadrupole components is investigated. The theory put forward by Feng [J. Q. Feng, Phys. Rev. E 54, 4438 (1996), 10.1103/PhysRevE.54.4438] is generalized by incorporating the following two nonlinear effects—surface charge convection and shape deformation—towards determining the drop velocity. This two-way coupled moving boundary problem is solved analytically by considering small values of electric Reynolds number (ratio of charge relaxation time scale to the convection time scale) and electric capillary number (ratio of electrical stress to the surface tension) under the framework of the leaky dielectric model. We focus on investigating the effects of charge convection and shape deformation for different drop-medium combinations. A perfectly conducting drop suspended in a leaky (or perfectly) dielectric medium always deforms to a prolate shape and this kind of shape deformation always augments the dielectrophoretic drop velocity. For a perfectly dielectric drop suspended in a perfectly dielectric medium, the shape deformation leads to either increase (for prolate shape) or decrease (for oblate shape) in the dielectrophoretic drop velocity. Both surface charge convection and shape deformation affect the drop motion for leaky dielectric drops. The combined effect of these can significantly increase or decrease the dielectrophoretic drop velocity depending on the electrohydrodynamic properties of both the liquids and the relative strength of the electric Reynolds number and electric capillary number. Finally, comparison with the existing experiments reveals better agreement with the present theory.

Quantifying Arctic Terrestrial Environment Behaviors Using Geophysical, Point-Scale and Remote Sensing Data

NASA Astrophysics Data System (ADS)

Dafflon, B.; Hubbard, S. S.; Ulrich, C.; Peterson, J. E.; Wu, Y.; Wainwright, H. M.; Gangodagamage, C.; Kholodov, A. L.; Kneafsey, T. J.

2013-12-01

Improvement in parameterizing Arctic process-rich terrestrial models to simulate feedbacks to a changing climate requires advances in estimating the spatiotemporal variations in active layer and permafrost properties - in sufficiently high resolution yet over modeling-relevant scales. As part of the DOE Next-Generation Ecosystem Experiments (NGEE-Arctic), we are developing advanced strategies for imaging the subsurface and for investigating land and subsurface co-variability and dynamics. Our studies include acquisition and integration of various measurements, including point-based, surface-based geophysical, and remote sensing datasets These data have been collected during a series of campaigns at the NGEE Barrow, AK site along transects that traverse a range of hydrological and geomorphological conditions, including low- to high- centered polygons and drained thaw lake basins. In this study, we describe the use of galvanic-coupled electrical resistance tomography (ERT), capacitively-coupled resistivity (CCR) , permafrost cores, above-ground orthophotography, and digital elevation model (DEM) to (1) explore complementary nature and trade-offs between characterization resolution, spatial extent and accuracy of different datasets; (2) develop inversion approaches to quantify permafrost characteristics (such as ice content, ice wedge frequency, and presence of unfrozen deep layer) and (3) identify correspondences between permafrost and land surface properties (such as water inundation, topography, and vegetation). In terms of methods, we developed a 1D-based direct search approach to estimate electrical conductivity distribution while allowing exploration of multiple solutions and prior information in a flexible way. Application of the method to the Barrow datasets reveals the relative information content of each dataset for characterizing permafrost properties, which shows features variability from below one meter length scales to large trends over more than a kilometer. Further, we used Pole- and Kite-based low-altitude aerial photography with inferred DEM, as well as DEM from LiDAR dataset, to quantify land-surface properties and their co-variability with the subsurface properties. Comparison of the above- and below-ground characterization information indicate that while some permafrost characteristics correspond with changes in hydrogeomorphological expressions, others features show more complex linkages with landscape properties. Overall, our results indicate that remote sensing data, point-scale measurements and surface geophysical measurements enable the identification of regional zones having similar relations between subsurface and land surface properties. Identification of such zonation and associated permafrost-land surface properties can be used to guide investigations of carbon cycling processes and for model parameterization.

Potential of electrical resistivity tomography and muon density imaging to study spatio-temporal variations in the sub-surface

NASA Astrophysics Data System (ADS)

Lesparre, Nolwenn; Cabrera, Justo; Courbet, Christelle

2015-04-01

We explore the capacity of electrical resistivity tomography and muon density imaging to detect spatio-temporal variations of the medium surrounding a regional fault crossing the underground platform of Tournemire (Aveyron, France). The studied Cernon fault is sub-vertical and intersects perpendicularly the tunnel of Tournemire and extends to surface. The fault separates clay and limestones layers of the Dogger from limestones layers of the Lias. The Cernon fault presents a thickness of a ten of meters and drives water from an aquifer circulating at the top of the Dogger clay layer to the tunnel. An experiment combining electrical resistivity imaging and muon density imaging was setup taking advantage of the tunnel presence. A specific array of electrodes were set up, adapted for the characterization of the fault. Electrodes were placed along the tunnel as well as at the surface above the tunnel on both sides of the fault in order to acquire data in transmission across the massif to better cover the sounded medium. Electrical resistivity is particularly sensitive to water presence in the medium and thus carry information on the main water flow paths and on the pore space saturation. At the same time a muon sensor was placed in the tunnel under the fault region to detect muons coming from the sky after their crossing of the rock medium. Since the muon flux is attenuated as function of the quantity of matter crossed, muons flux measurements supply information on the medium average density along muons paths. The sensor presents 961 angles of view so measurements performed from one station allows a comparison of the muon flux temporal variations along the fault as well as in the medium surrounding the fault. As the water saturation of the porous medium fluctuates through time the medium density might indeed present sensible variations as shown by gravimetric studies. During the experiment important rainfalls occurred leading variations of the medium properties affecting density and electrical resistivity physical parameters. We show with data sets acquired before and after an important rainfall event how muon density and electrical resistivity imaging may complementary characterize variations of the medium properties. The development of such innovative experiments for hydrogeophysical studies presents then the ability to supply new information on fluid dynamics in the sub-surface.

Carbon Nanotube/Space Durable Polymer Nanocomposite Films for Electrostatic Charge Dissipation

NASA Technical Reports Server (NTRS)

Smith, J. G., Jr.; Watson, K. A.; Thompson, C. M.; Connell, J. W.

2002-01-01

Low solar absorptivity, space environmentally stable polymeric materials possessing sufficient electrical conductivity for electrostatic charge dissipation (ESD) are of interest for potential applications on spacecraft as thin film membranes on antennas, solar sails, large lightweight space optics, and second surface mirrors. One method of imparting electrical conductivity while maintaining low solar absorptivity is through the use of single wall carbon nanotubes (SWNTs). However, SWNTs are difficult to disperse. Several preparative methods were employed to disperse SWNTs into the polymer matrix. Several examples possessed electrical conductivity sufficient for ESD. The chemistry, physical, and mechanical properties of the nanocomposite films will be presented.

Studies into Equine Electrocardiography and Vectorcardiography

PubMed Central

Holmes, J. R.; Alps, B. J.

1967-01-01

Theoretical consideration has been given in two horses to the properties of the electric field created by the equine heart acting as a simple electric generator. The principles of the vectorial theory have been applied to test the validity of application of the dipole concept. The cardiac electric forces, althrough complex in the immediate region of the heart, appear at the body surface in a similar form to those arising from a relatively immobile, single equivalent dipole. The potential value of the technique of vectorcardiography in cardiological investigations is briefly discussed. ImagesFig. 1.Fig. 3.Fig. 5.Fig. 10.Fig. 12.Fig. 13. PMID:17649586

Silicon oxide: a non-innocent surface for molecular electronics and nanoelectronics studies.

PubMed

Yao, Jun; Zhong, Lin; Natelson, Douglas; Tour, James M

2011-02-02

Silicon oxide (SiO(x)) has been widely used in many electronic systems as a supportive and insulating medium. Here, we demonstrate various electrical phenomena such as resistive switching and related nonlinear conduction, current hysteresis, and negative differential resistance intrinsic to a thin layer of SiO(x). These behaviors can largely mimic numerous electrical phenomena observed in molecules and other nanomaterials, suggesting that substantial caution should be paid when studying conduction in electronic systems with SiO(x) as a component. The actual electrical phenomena can be the result of conduction from SiO(x) at a post soft-breakdown state and not the presumed molecular or nanomaterial component. These electrical properties and the underlying mechanisms are discussed in detail.

A review of the surface features and properties, surfactant adsorption and floatability of four key minerals of diasporic bauxite resources.

PubMed

Zhang, Ningning; Nguyen, Anh V; Zhou, Changchun

2018-04-01

Diasporic bauxite represents one of the major aluminum resources. Its upgrading for further processing involves a separation of diaspore (the valuable mineral) from aluminosilicates (the gangue minerals) such as kaolinite, illite, and pyrophyllite. Flotation is one of the most effective ways to realize the upgrading. Since flotation is a physicochemical process based on the difference in the surface hydrophobicity of different components, determining the adsorption characteristics of various flotation surfactants on the mineral surfaces is critical. The surfactant adsorption properties of the minerals, in turn, are controlled by the surface chemistry of the minerals, while the latter is related to the mineral crystal structures. In this paper, we first discuss the crystal structures of the four key minerals of diaspore, kaolinite, illite, and pyrophyllite as well as the broken bonds on their exposed surfaces after grinding. Next, we summarize the surface chemistry properties such as surface wettability and surface electrical properties of the four minerals, and the differences in these properties are explained from the perspective of mineral crystal structures. Then we review the adsorption mechanism and adsorption characteristics of surfactants such as collectors (cationic, anionic, and mixed surfactants), depressants (inorganic and organic), dispersants, and flocculants on these mineral surfaces. The separation of diaspore and aluminosilicates by direct flotation and reverse flotation are reviewed, and the collecting properties of different types of collectors are compared. Furthermore, the abnormal behavior of the cationic flotation of kaolinite is also explained in this section. This review provides a strong theoretical support for the optimization of the upgrading of diaspore bauxite ore by flotation and the early industrialization of the reverse flotation process. Copyright © 2018 Elsevier B.V. All rights reserved.

Modeling the hydrogeophysical response of lake talik evolution

USGS Publications Warehouse

Minsley, Burke J.; Wellman, Tristan; Walvoord, Michelle Ann; Revil, Andre

2014-01-01

Geophysical methods provide valuable information about subsurface permafrost and its relation to dynamic hydrologic systems. Airborne electromagnetic data from interior Alaska are used to map the distribution of permafrost, geological features, surface water, and groundwater. To validate and gain further insight into these field datasets, we also explore the geophysical response to hydrologic simulations of permafrost evolution by implementing a physical property relationship that connects geology, temperature, and ice saturation to changes in electrical properties.